Sustainable Production of Biofuels Using Intensified Processes 3031132157, 9783031132155

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Green Energy and Technology

Juan Gabriel Segovia-Hernández · Eduardo Sanchez-Ramirez · Heriberto Alcocer-Garcia · Ana Gabriela Romero-Garcia · Juan Jose Quiroz-Ramirez

Sustainable Production of Biofuels Using Intensified Processes

Green Energy and Technology

Climate change, environmental impact and the limited natural resources urge scientific research and novel technical solutions. The monograph series Green Energy and Technology serves as a publishing platform for scientific and technological approaches to “green”—i.e. environmentally friendly and sustainable—technologies. While a focus lies on energy and power supply, it also covers “green” solutions in industrial engineering and engineering design. Green Energy and Technology addresses researchers, advanced students, technical consultants as well as decision makers in industries and politics. Hence, the level of presentation spans from instructional to highly technical. **Indexed in Scopus**. **Indexed in Ei Compendex**.

Juan Gabriel Segovia-Hernández · Eduardo Sanchez-Ramirez · Heriberto Alcocer-Garcia · Ana Gabriela Romero-Garcia · Juan José Quiroz-Ramirez

Sustainable Production of Biofuels Using Intensified Processes

Juan Gabriel Segovia-Hernández Chemical Engineering Department University of Guanajuato Guanajuato, Guanajuato, Mexico

Eduardo Sanchez-Ramirez Chemical Engineering Department University of Guanajuato Guanajuato, Mexico

Heriberto Alcocer-Garcia Chemical Engineering Department University of Guanajuato Guanajuato, Mexico

Ana Gabriela Romero-Garcia Chemical Engineering Department University of Guanajuato Guanajuato, Mexico

Juan José Quiroz-Ramirez CIATEC Guanajuato, Mexico

ISSN 1865-3529 ISSN 1865-3537 (electronic) Green Energy and Technology ISBN 978-3-031-13215-5 ISBN 978-3-031-13216-2 (eBook) https://doi.org/10.1007/978-3-031-13216-2 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To my family and all the people who have supported me unconditionally along the way to achieve my goals. —Juan Gabriel Segovia-Hernández To my beloved wife and parents —Eduardo Sanchez-Ramirez To my family —Juan José Quiroz-Ramirez To my beloved parents and brother, who have always been my unconditional support. You are my greatest inspiration to continue working to achieve my goals. Thank you for always being by my side —Ana Gabriela Romero-Garcia To my family and friends. Especially to my wife for supporting me to achieve my goals. —Heriberto Alcocer-Garcia

Preface

Biofuel may refer to any form of fuel derived from biomass, and accordingly, its application can be in household energy, for electricity generation, or in the transport sector. The term biofuel in this book specifically refers to those biomass-derived fuels that can be used in the transport sector such as bioethanol, biodiesel, biobutanol, among others. Currently, bioethanol and biodiesel account for more than 90% of global biofuel use. The European Union is promoting the use of biofuels, primarily due to the savings of greenhouse gas emissions that biofuels can potentially offer. Biofuels can diversify the offer of transport fuel and are a way to raise energy selfsufficiency, diversify the production sites, and strengthen the internal agriculture of a country. Lastly, they are suitable, in many cases, for being used in current power trains and fuel infrastructures. Biomass is an attractive energy source for several reasons. First, it is renewable as long as it is properly managed, and second, it is also more evenly distributed over the earth’s surface than finite energy sources and may be exploited using more environmentally friendly technologies. Biomass provides the opportunity for increased local, regional, and national energy self-sufficiency across the globe. The energy in biomass can be accessed by turning the raw materials, or feedstocks, into a usable form. Transportation fuels are made from biomass through biochemical or thermochemical processes. Therefore, for the production of biofuels to be sustainable and economically competitive with an oil refinery, it must present low energy consumption, low operating costs, low environmental impacts, inherent safety, and good dynamic behavior in the design and operation of all equipment. For this reason, it is essential to implement strategies that aim to achieve these key objectives in the design of a biorefinery that produces liquid biofuels. Increasing awareness for energy sustainability, environmental concerns, new and unconventional feedstocks, as well as recent advances in process optimization has sparked a renewed interest in process intensification (PI). PI aims to drastically reduce the energy consumption and processing cost of the chemical processes by utilizing the synergy between multifunctional phenomena at different time and spatial scales and enhancing the mass, heat, and momentum transfer rates. There has been significant growth in the field of PI over the past

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decades that featured both successful industrial applications and increased research interest in academia. This book highlights the importance of process intensification in the production of biofuels and discusses the required interdisciplinary approach to accomplish it. Authors outline intensified processes and current challenges in the production of biofuels at different levels. This book presents an overview of important ideas addressed within methodologies proposed for designing intensified processes. Guanajuato, Mexico

Juan Gabriel Segovia-Hernández Eduardo Sanchez-Ramirez Heriberto Alcocer-Garcia Ana Gabriela Romero-Garcia Juan José Quiroz-Ramirez

Contents

1

Biofuels: Historical Development and Their Role in Today’s Society . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Historical Development of Biofuels . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Biofuels: A Key Component for Society Development . . . . . . . . . . 1.3 Conclusions and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 5 6 7

2

Process Intensification and Circular Economy . . . . . . . . . . . . . . . . . . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Biorefineries and Sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Biorefineries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Biofuels Towards Sustainability . . . . . . . . . . . . . . . . . . . . . . . 2.3 Green Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Twelve Principles of Green Chemistry . . . . . . . . . . . . . . . . . 2.3.2 Green Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Intensified Processes to Produce Biofuels . . . . . . . . . . . . . . . . . . . . . 2.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 9 13 13 14 16 17 18 20 21 21

3

Bioethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Bioethanol: Chemical Properties, Uses and Applications . . . . . . . . 3.2 Feedstock for Bioethanol Production . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Overall Process for Bioethanol Production . . . . . . . . . . . . . . . . . . . . 3.3.1 Pretreatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 Detoxification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 Separation and Purification of Bioethanol . . . . . . . . . . . . . . . 3.4 Process Intensification Applied to Produce Bioethanol . . . . . . . . . . 3.5 Ethyl Acetate a Promising Biofuel . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Overall Process for Bioethanol Production . . . . . . . . . . . . . .

25 25 27 28 30 32 32 35 35 36 41 42

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3.5.2 Process Intensification Applied to Produce Bioethanol Ethyl Acetate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Conclusions and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

45 47 47

Biobutanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Biobutanol: Chemical Properties, Uses and Applications . . . . . . . . 4.2 Butanol as a Substitute for Conventional Fuel . . . . . . . . . . . . . . . . . 4.3 Clostridial Species Involved in Biobutanol Production . . . . . . . . . . 4.4 Feedstock for Biobutanol Production . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Biomass Based on Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Biomass Derived from Lignocellulosic Materials . . . . . . . . 4.4.3 Biomass Derived from Algae . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Overall Process for Biobutanol Production . . . . . . . . . . . . . . . . . . . . 4.5.1 Pretreatment and Hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Issues Associated with ABE Fermentation . . . . . . . . . . . . . . 4.6 Process Intensification Applied to Butanol Production . . . . . . . . . . 4.6.1 Process Intensification in the Reactive Zone . . . . . . . . . . . . 4.6.2 Process Intensification Applied to the Downstream Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Conclusions and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 51 53 55 56 57 58 59 60 60 66 66 66

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2,3-Butanediol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 2,3-Butanediol: Chemical Properties, Uses and Applications . . . . . 5.2 Production of 2,3-BD from Fossil and Renewable Sources . . . . . . . 5.2.1 Microorganisms Useful in the Production of 2,3-BD . . . . . 5.3 Feedstock for 2,3-BD Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Non-renewable Raw Materials . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Renewable Feedstock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Process Intensification Applied to 2,3-BD Production . . . . . . . . . . . 5.5 Process Intensification Applied to 2,3-BD Recovery . . . . . . . . . . . . 5.6 Conclusions and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

91 91 94 95 98 98 100 101 102 106 106

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Methyl-Ethyl Ketone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Methyl-Ethyl Ketone: Chemical Properties, Uses and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Overall Process for MEK Production . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Overall Process for MEK Production . . . . . . . . . . . . . . . . . . 6.2.2 Process Intensification Applied to MEK Production . . . . . . 6.3 MEK Purification Using an Intensive Separation Process . . . . . . . . 6.4 Conclusion and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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111 114 115 118 124 128 128

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Biojet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Biojet: Chemical Properties, Uses and Applications . . . . . . . . . . . . 7.2 Overall Process for Biojet Production . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Process Intensification Applied to Produce Biojet . . . . . . . . . . . . . . 7.3.1 Feedstock for Biojet Production . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Pretreatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 Feedstock Planning Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.4 Process Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Process Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 Objective Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Stochastic Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1 Feedstock Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2 Optimization of Ethanol Process . . . . . . . . . . . . . . . . . . . . . . 7.5.3 Optimization of Biojet Fuel Process . . . . . . . . . . . . . . . . . . . 7.5.4 Minimum Selling Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

131 131 135 136 137 137 137 138 142 142 145 146 146 149 154 155 158 159

8

Ethyl Levulinate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Ethyl Levulinate: General Characteristics, Uses and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Ethyl Levulinate as Fuel Additive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Esterification in Ethyl Levulinate Production . . . . . . . . . . . . . . . . . . 8.3.1 Homogeneous Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Heterogeneous Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Routes for EL Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1 Synthesis of EL from LA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Synthesis of EL from FAL . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.3 Synthesis of EL from Chloromethyl Furfural (CMF) . . . . . 8.4.4 Synthesis of EL from Monosaccharides and Polysaccharides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Process Intensification Applied to Ethyl Levulinate Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.1 Kinetics Models for Ethyl Levulinate Production . . . . . . . . 8.5.2 Optimization and Sustainability Analysis . . . . . . . . . . . . . . . 8.6 Conclusions and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2,5-Dimethylfuran . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 2,5-Dimethylfuran: Chemical Properties, Uses and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Overall Process for DMF Production . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.1 DMF Production Technologies that Use Molecular Hydrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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163 164 166 167 167 168 169 169 171 171 176 177 180 183 184

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9.2.2 DMF Production Technologies that Use Chemical Hydrogen Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Process Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Biorefinery to Produces DMF from the HMF . . . . . . . . . . . . . . . . . . 9.5 Challenges and Opportunities in Process Intensification . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

194 195 195 198 200

10 The Challenge of Biofuel: Energy Generation for a Sustainable Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Chapter 1

Biofuels: Historical Development and Their Role in Today’s Society

Abstract Have you ever imagined what life would be like without energy sources? What would the growth of civilizations have been like without fuel? How would we live today if we did not have technological developments in energy? This and other questions may arise when thinking about the development of fuels to generate energy. Currently talking about fuels is a very daily topic, about which we do not ask ourselves its origin and the evolution that these have had in history. Thought history, the human being has searched for ways of putting energy to work for them. Due to growing population, human has been looking for faster, easier, and more efficient ways to produce energy. However, for years the human being has made excessive use of existing resources, causing them to be depleted at present. Likewise, the pollution generated using these resources is also causing considerable damage to the environment at a global level. For these reasons, there is a growth in the use of alternative energy sources to reduce pollution and meet their energy needs. In this chapter will describe the origin and historical evolution of biofuels. The social, political and environmental context that originated the need for their scientific and technological development. The biofuels with the greatest demand and potential to replace fossil fuels in the medium term will be briefly described.

1.1 Historical Development of Biofuels The history of biofuels is as old as the origin of human civilizations. Biofuels refer to plant biomass and the refined products to be combusted for energy (heat and light). Similar to fossil fuels, biofuels exist in solid, liquid, and gaseous forms [1]. Throughout history, technologies have been used and developed for the best use of biofuels, whether solid, liquid, or gaseous. Figure 1.1 shows the important stages in the use of Biofuels throughout history. The first biofuel used was the wood and other plant material, it is not clear when human being started the controlled use of fired for heat and light. Nevertheless, archaeologists identified charred animal bones and stone tools in wood ash in Wonderwerk Cave of Kuruman Hills in South Africa, providing evidence of controlled fire © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_1

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1 Biofuels: Historical Development and Their …

Fig. 1.1 Important stages in the use of biofuels throughout history

use by prehistoric “mankind” creatures one million years ago [2]. At first, wood was burned for warming, light, and cooking. Then the heat from fired was used to transform materials or change its form to make them more useful, this is the case of metals. Before nineteenth century, the wood continues being used as the primary fuel for cooking and heating. The first liquid biofuel used of which there is a record was the use of vegetable oil. This was used as fuel for ceramic lamps in ancient Egypt. Emphasizing the use of olive, castor, and rapeseed oils. Vegetable oil and animal fats were widely used in oil lamps for lighting before the invention of gas lights and electric lights in late eighteenth century, but for making biodiesel it did not occur until 1930s [3]. Back to 3000 B.C., human beings started to use charcoal (which is formed by the slow pyrolysis of wood) in metallurgy to smelt ores for copper and iron. Charcoal was the designated governmental fuel for cooking and heating in China’s Tang Dynasty in 700 A.D. During 1931–1960 in China and the World War II in Europe when gasoline was scarce, many automobiles were powered by wood gas, a mixture of

1.1 Historical Development of Biofuels

3

carbon monoxide and hydrogen generated by partially burning charcoal in a gasifier [1]. Nowadays, charcoal is still a valuable product used for cooking as a barbeque briquette. As well it is used for heating, air and water purification, art drawing, and steel-making. As human population increased over the time, the dependence on fuels increased as well. During this transition, fossil fuels played a significant role in society and for the development of new technologies. Coal had been used since the second millennium B.C., but its potential used had not been discovered by that time. Around 1760 A.D. it was found that coal can be used as a powerful source of energy, and with this began a new stage in the history, the Industrial Revolution. The industrial revolution marked the beginning of a new era in the use and exploitation of fuels. During the initial stages of industrial revolution, biofuels powered the first lamps and internal combustion engines. The shift from biofuels to petroleum products like kerosene and gasoline as the primary fuel source took place in the 1860s for oil lamps and in the twentieth century for automotive fuels [4]. Coal continued to be used in great quantities until the twentieth century. In the 1800s, biofuels were available primarily for lighting purposes. For those times, another biofuel that gained strength at the beginning of the nineteenth century was bioethanol. Although the production of alcohol by fermentation dates to the beginning of civilizations before Christ, alcohol was used only as a drink and not for fuel. By 1860, thousands of distilleries produced tens of millions of gallons of alcohol per year for lighting in the USA and Europe [5]. Years later the United States government imposed a tax per gallon of alcohol. This meant an increase in the cost of alcohol as fuel, so that the use of biofuels was overshadowed due to high costs, causing significant growth in the petroleum industry. Backing on time, biogas was used since the beginning on the tenth century B.C. to prepare warm bath water. In the beginning of 1800, it was discovered that flammable gas from cattle manure ponds was methane. Years later, around 1859, it was constructed the first recorded anaerobic digestion plant for biogas production in India [6]. Nevertheless, different studies were carried out to study anaerobic digestion as a science and select best anaerobic bacteria and digestion conditions for promoting methane production. Meanwhile in Europe, there was not competition between the use of bioethanol and petroleum as a fuel due to there were no taxes for the ethanol industry. Some countries like Germany and France, wanted to find alternatives to fossil fuels. Before World War I, Germany created the first largescale biofuels industry in the world, by using potatoes to produce bioethanol. Studies in biofuels continued demonstrating that bioethanol could be produced from any vegetable matter that could be fermented. During the nineteenth century there developed some forms of internal combustion engine. In 1893 the German engineer Rudolf Diesel invented the compression-ignited diesel engine. He conducted several tests with vegetable oil fuels, with the aim that farmers could produce their own fuel. Based on this idea, in 1900 the French company Otto demonstrated a diesel engine powered by peanut oil [1]. However, attention to the development of vegetable oil-based fuels has been overshadowed by the high availability and low price of gasoline and diesel.

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1 Biofuels: Historical Development and Their …

Around 1890 till 1914, some countries governments such as Germany, France and England were worried about the longevity of oil reserves and the unpredictable nature of oil supplies [7]. Due to this uncertainty, in Europe and the United States the farmers were encouraged to produce alcohol once again in Europe and US congress lifted alcohol tax in 1906. Moreover, at the beginning of the twentieth century, engineers were evaluating the advantages of ethanol against gasoline. As a result, it was found that ethanol could be used in both high and low compression engines, while gasoline could be used just in low compression engine. Between 1907 and 1909, the US Department of Agriculture conducted more than 2000 engine and fuel tests concluding that “a gallon of alcohol will develop substantially the same power in an internal combustion engine as a gallon of gasoline, due to superior operating efficiency” [4]. This efficiency was later denominated as the “octane” rating. Meanwhile, between the years of 1900 and 1930 more than 30 nations began with a “biofuels program” by promoting the use of biofuels and push the growth of agriculture. Tropical countries like Brazil and Philippines developed new markets for sugar cane. Among with the successful growing of biofuel application, the first generation biorefineries occurred in Brazil [8]. Therefore, the number of distilleries in Brazil producing fuel-grade ethanol increased. Meanwhile in Cuba, it was produced ethanol as an additive for gasoline. The World War II brings innovation in biofuels, German fuel production was derived from non-petroleum sources, while the allies had plenty of oil for the war effort [9]. By that time, the use of alcohol as fuel was a question of necessity, leaving behind the question of costs and efficiency. There was reported the use of different kinds of vegetables oils such as: nuts, tea leaves, cotton and cabbage seed. In China and India, where food was scare, it began to be used alcohol blends. As the war was ended, cheap imported oil was once more readily available and alcohol blends were marketed sporadically. Around those years, different nations wanted to push forward the biofuels production. By 1952 this idea was abandoned due to the increasing availability of cheap oil from the Middle East [4]. Therefore, most of the alternative biofuel programs around the world had been abandoned as far too costly in comparison. After World War II, oil became in the main fuel globally. For more than twenty-five five years the world was totally dependent on oil from the Middle East. This situation changed in 1973, due to the war between countries in the Middle East. Generating an energy crisis at international level, giving the opportunity to look again at biofuels as an alternative to the use of oil as a fuel. Energy crisis spurred a widespread search for alternative energy sources. Around the same time, Brazilian bioethanol production from sugarcane began to increase. While in the USA, bioethanol production from corn for blending with gasoline gain interest for research. During the 80’s most unleaded gasoline in the USA, was made using a petroleum refining process called “severe reforming”, which boosted the levels of benzene, toluene and xylene compounds from 25% to as high as 40% of the fuel [10]. High levels of these carcinogenic compounds in fuels worried environmental policy markets. When these aromatic chemicals were burned in car engines, they not only

1.2 Biofuels: A Key Component for Society Development

5

emitted carcinogens and toxics into the air but highly volatile, photo-reactive chemicals that contributed to urban smog as well. By 1990, the USA Government created the Clean Air Act and empower the Environmental Protection Agency in order to find alternatives to set the increasing environmental problem. The cleaner alternative was that fuels would contain a class of octane boosting compounds such as methanol, ethanol and natural gas [4]. Which contain lower concentrations of aromatic compounds when burned, and reformulated gasoline blends. These “oxygenates” compounds raised gasoline’s oxygen content, promoted more thorough combustion of fuel, reduced pollution and at the same time raised octane. After the growing development of the biofuel program in the USA, where they used corn to produce biofuels, the question began to be stronger: Is it correct to use food crops for the production of fuels? It was till 2007, that Jean Zigler a special rapporteur for food rights, accuses biofuels production from food crops as a “crime against humanity” [11, 12]. The fuel or food issue, becomes a complex situation worldwide arising the idea that the technologies advances should be capable to use agricultural waste to produce fuels. In this way, the goal was to put food and human needs first, local development including fuels second and fuel exports third. For mor than a century, researchers has been concerned about how to evite scarcity of food and develop biofuels from non-food materials. Around the early twentieth century, information about the use of cellulose as a feedstock for biofuels production began to increase. As the years went by, the biofuels potential of cellulose, the most abundant organic material on earth, was a recurrent theme in scientific literature [4]. Nowadays, due to the impact of biofuels on climate change, food rights and sustainability. There is the necessity to develop optimal and sustainable systems that can be capable to produce remarkable results.

1.2 Biofuels: A Key Component for Society Development Through history, it is possible to understand the importance that biofuels have had from the development of the first civilizations to the present. Research into biofuels has progressed considerably in the last century, focusing in the fields of agriculture, transport and chemical engineering. Nowadays, due to the increasing concerns about global climate change, energy security, high oil prices, and declining oil reserves it has been prompted a shift toward biofuels as a feasible and renewable alternative to fossil fuels. The history of development and research in the area of biofuels has always been affected by political and economic issues. Such factors continue to influence biofuel decisions worldwide. Currently, despite considering the use of biofuels as an alternative to solve the environmental problems mentioned above. It is important to consider the environmental, economic, political, and social implications of using these. Consequently, the government of a country faces a difficult trilemma: how to stimulate the growth of the biofuel industry while protecting food security and preserving environmental sustainability simultaneously [13]. To understand the situation, it can be said that

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1 Biofuels: Historical Development and Their …

the direct competition effect, will lead the scarcity of certain food crops that are the feedstock for biofuel production. This situation will push the prices up for these inputs and therefore the increase of both food and energy markets. The increment in cost production will applied not only for those that are direct inputs but also for those that are close substitutes. The indirect competition effect further exacerbates increased food prices due to the reallocation of land from food to biofuels: as land becomes scarce to produce agricultural commodities, it leads to a lowered supply of certain foods, which then creates excess demand for food, ultimately creating upward pressure on food prices [14]. The increment in food prices can be translated as a direct issue of food security. By rising the food prices not only the economies of less developed countries will be treated. Consequently, people in low-income regions and food-deficit countries are more vulnerable to the issue of food security than the ones in developing countries. About the environmental implications, the rapid development of biofuels can lead to serious degradation of agricultural land [15]. By clearing native ecosystems to release land for rapid biofuel production it has been proved that there is an increment in carbon dioxide emissions by burning or decomposing biomass and oxidizing humus. If so, then it will undoubtedly suppress any greenhouse gas benefits of biofuels for decades or even centuries to come [16]. Overall, the global development and utilization of biofuels will continue to increase, in order to maximize the potential of biofuels it is necessary enhance the existing technologies for biofuels production. Nowadays, the current global biofuel production needs to be sustained at a 10% output growth rate per year until 2030 to meet the goals of sustainable development scenarios (SDS). Furthermore, transport biofuel consumption needs to almost triple by 2030 to be on track with the SDS. Unfortunately, the world transport biofuel production increased by only 6% until 2019, and at this stage, only a 3% annual production growth is anticipated over the next 5 years [15].

1.3 Conclusions and Perspectives In this chapter, a summary of how biofuels have evolved over the years was shown. The story about the use of biofuels is as old as the origin of man. Since the beginning of humanity, biofuels have been of vital importance for the development of civilizations. Throughout history, it is possible to observe that research and development in biofuels has been affected according to political, social and economic issues. Nowadays, these factors continue to set the pace of development in the area of biofuels. In order to increase biofuels production, several international biofuels trades have been created, enhancing economic welfare internationally. As well, it is needed to enhance policies to promote biofuel trades and to enhance the production of the next-generation biofuel. As well there is an imperative necessity to seek for improve the existence technologies or develop new once that allow human being to enhance biofuels production and position them as an alternative or substitutes for the predominant fuels.

References

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References 1. M. Guo, W. Song, J. Buhain, Bioenergy and biofuels: history, status, and perspective. Renew. Sustain. Energy Rev. 42, 712–725 (2015). https://doi.org/10.1016/j.rser.2014.10.013 2. F. Berna, P. Goldberg, L.K. Horwitz, J. Brink, S. Holt, M. Bamford, M. Chazan, Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proc. Natl. Acad. Sci. 109, E1215–E1220 (2012). https://doi.org/10. 1073/pnas.1117620109 3. J. Thomson, ed., The scot who lit the world: the story of William Murdoch, in Inventor of Gas Lighting, 1st ed. (Janet Thomson, Glasgow, 2003) 4. B.P. Singh, Biofuel Crops: Production, Physiology and Genetics (CABI, 2013) 5. J.K. Brachvogel, C.J. Thatcher, M.H. Märcker, Industrial Alcohol, Its Manufacture and Uses: A Practical Treatise Based on Dr. Max Maercker’s “Introduction to Distillation” (Munn, 1907) 6. S.E. Nayono, Anaerobic Digestion of Organic Solid Waste for Energy Production (KIT Scientific Publishing, 2010). 7. C.L. Cummins, Internal Fire (Society of Automotive Engineers, Warrendale, PA, 1989) 8. R. Hatti-Kaul, Biorefineries—a path to sustainability? Crop Sci. 50, S-152–S-156 (2010). https://doi.org/10.2135/cropsci2009.10.0563 9. P.M. Gustav Egloff, V. ARSDELL, Substitute fuels as a war economy. Chem. Eng. News Archive. 20, 649–659 (1942). https://doi.org/10.1021/cen-v020n010.p649 10. F. Lyman, The Gassing of America. Washington Post (1990). https://www.washingtonpost. com/archive/lifestyle/1990/04/13/the-gassing-of-america/bce94f4d-c8a1-47e5-8c9c-d0a6be fd8b80/. Accessed 2 June 2022 11. Biofuels, Crime Against Humanity (2007). http://news.bbc.co.uk/1/hi/world/americas/706506 1.stm. Accessed 2 June 2022 12. K. Kleiner, The backlash against biofuels. Nat. Clim Change 1, 9–11 (2008). https://doi.org/ 10.1038/climate.2007.71 13. X. Wang, M.K. Lim, Y. Ouyang, Food-energy-environment trilemma: policy impacts on farmland use and biofuel industry development. Energy Econ. 67, 35–48 (2017). https://doi.org/10. 1016/j.eneco.2017.05.021 14. R. Luque, J.C. Lovett, B. Datta, J. Clancy, J.M. Campelo, A.A. Romero, Biodiesel as feasible petrol fuel replacement: a multidisciplinary overview. Energy Environ. Sci. 3, 1706–1721 (2010). https://doi.org/10.1039/C0EE00085J 15. B. Datta, An economic analysis of biofuels: policies, trade, and employment opportunities (Chapter 1), in Handbook of Biofuels, ed. by S. Sahay (Academic Press, 2022), pp. 3–29. https://doi.org/10.1016/B978-0-12-822810-4.00001-4 16. J. Fargione, J. Hill, D. Tilman, S. Polasky, P. Hawthorne, Land clearing and the biofuel carbon debt. Science 319, 1235–1238 (2008). https://doi.org/10.1126/science.1152747

Chapter 2

Process Intensification and Circular Economy

Abstract Process intensification is a valuable strategy to enhance the performance of production processes. It may allow reductions in costs and environmental impact, and enhancements in terms of operability and safety. Although the PI philosophy and methodology have a relatively long history in the scientific field, the ideas of this philosophy fit well with the current trends of sustainability and circular economy; since both ideas, in short, seek the reduction of resource use, the reduction of waste, and the continuous and circular use of raw materials. To ensure the sustainability of biofuel purification, it is important to develop processes with low environmental impact, which can also be allowed through the development of intensified technologies. This chapter presents how the intensification of processes is directly related to sustainability, circular economy, and the principles of green chemistry. Finally, a summary of the intensified technologies for obtaining liquid biofuels is shown.

2.1 Introduction Relationship between industry and environment is crucial for industrial business performance. Environmental impacts have incrementally increased pressure on industrial businesses. Looking back to the beginning of the industrial revolution, mass production of goods was enabled by new manufacturing methods resulting in products with high availability and low costs. Consequently, due to new consumer societies and staggering growth in industrial activity, emissions to environment, solid waste generation and landfill have become increasingly severe [1]. In addition, due to a growing world population and especially strong middle-class growth the demand for resources is expected to rise rapidly indicating a rising consumption of natural resources. Since planet earth’s resources are limited the requirements of exponential economic and population growth cannot be met [2]. In this scenario, it is not only the challenge of environmental pollution that is becoming acute but the challenge of global resource scarcity as well. These circumstances confront manufacturing industry to simultaneously cope with the pressure of environmental regulations,

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_2

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challenges of resource price volatility and risks in resource supply, in addition to their daily business. The concept of circularity, especially in terms of closed material loops, is not a concept of novelty originating from recent developments, but has been emerging now and then throughout the history: Before the industrial revolution, i.e. in times of craftsmanship and hand production methods, waste as unwanted or unusable material was virtually unknown [3]. The circular economy (CE) has received increasing attention from policymakers globally as a concept that can support the goals of reducing overconsumption of natural resources while delivering economic benefits [1]. A recent meta-definition which is based on an analysis of 114 definitions of the term reads: “A [CE] describes an economic system that is based on business models which replace the ‘end-of-life’ concept with reducing, alternatively reusing, [and] recycling […] materials in production/distribution and consumption processes, […], with the aim to accomplish sustainable development, which implies creating environmental quality, economic prosperity and social equity, to the benefit of current and future generations” [4]. In this context, the need for the chemical industry to develop processes which are more sustainable or eco-efficient has never been so vital [5]. The successful delivery of green, sustainable chemical technologies at industrial scale will inevitably require the development of innovative processing and engineering technologies that can transform industrial processes in a fundamental and radical fashion [5]. To achieve a rapid design and implementation of process design in a CE context, process intensification (PI) can be a promising approach to develop more sustainable processes. The definition of PI has thus evolved from the simplistic statement of ‘the physical miniaturization of process equipment while retaining throughput and performance’ [6] to the all-encompassing definition ‘the development of innovative apparatus and techniques that offer drastic improvements in chemical manufacturing and processing, substantially decreasing equipment volume, energy consumption, or waste formation, and ultimately leading to cheaper, safer, sustainable technologies’ [7]. Several other definitions with slight variations on the generic theme of innovative technologies for greater efficiency have since emerged [8]. The reduction in scale implied by intensification has many desirable consequences for chemical engineering operations. First, the lower mass- and heat-transfer resistances enabled by the reduced path lengths of the diffusion/conduction interfaces, coupled with more intense fluid dynamics in active enhancement equipment, allow reactions to proceed at their inherent rates. By the same token, the more rapid mixing environment afforded by the low reaction volumes should enable conversion and selectivity to be maximized. Residence times of the order of minutes and seconds may be substituted for the hour-scale processing times associated with large conventional batch operations, with beneficial consequences for energy consumption and process safety. PI covers a wide range of processing equipment types and methodologies, as aptly illustrated in Fig. 2.1 [9]. Many of the equipment types classed as ‘intensified technologies’ have long been implemented in the chemical industry, such as compact heat exchangers, structured packed columns, and static mixers. More recent developments include the spinning disc reactor (SDR), oscillatory baffled reactor, loop reactor, spinning tube-in-tube

Fig. 2.1 Classification of PI equipment and methods. Reproduced from [9] with permission of American Institute of Chemical Engineers copyright (2000)

2.1 Introduction 11

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reactor, heat-exchange reactor, microchannel reactor and so on. Lately, it has become increasingly important for the chemical processing industries not only to remain cost competitive but to do so in an environmentally friendly or ‘green’ manner. It is fitting, therefore, that many of the processes based on the PI philosophy also enable clean technology to be practiced. For instance, high selectivity operations in intensified reactors will on their own reduce or ideally eliminate the formation of unwanted byproducts. Combining such intensified reactors with renewable energy sources such as solar energy would give even greater impetus to achieving these green processing targets [5]. Ponce-Ortega et al. [10] defined PI as any activity aiming at the following five outcomes: (a) smaller equipment size for a given throughput; (b) higher throughput for a given equipment size or a given process; (c) less hold up in equipment or less inventory in process for the same throughput; (d) less usage of utility materials and feedstock for a given throughput, and (e) higher performance for given unit size. This definition regarded PI as an extension of process integration activities. Based on this, they summarized the potential benefits of PI activities as realizing cheaper, safer, more energy-efficient, and/or more environmentally friendly processes through innovation while valuing customers through just-in-time manufacturing. Process intensification can be accomplished from different perspectives integrating/hybridizing various levels of abstraction [11]: • Integration of known unit operations: hybrid reaction-reaction, reactionseparation, or separation-separation systems. • Integration of functions: incorporate new functionality into a known operation based on the bioprocess limitations. • Integration of phenomena: identify target key phenomena to accomplish biotransformation and customize the bioprocess design to put them together. Yong et al. [12] have summarized the future trends of the sustainable development of energy systems in three main areas: (i) higher efficiency and waste reduction of biofuel production, (ii) CO2 removal and conversion, and (iii) process integration. Concerning process integration, Nemet et al. [13] have noted that the scope of PI is becoming much wider, considering the integration of not only heat and power but also water, safety, and other aspects of processes. To date, most of the research in biorefineries focus on the conversion or pretreatment aspects, whereas the real cost of biorefineries remains in the downstream processing, which can account for up to 60–80% of the total cost production [14, 15]. In this sense, biorefineries can become viable and sustainable only by using intensified separations that allow the low-cost and high-volume production of biofuels. In addition to the biomass conversion processes, separation and purification of the biomass components and the products streams and their full integration with the overall process is of utmost importance. In many instances, this can be the single biggest factor influencing the overall success and commercialization of biorefineries. Given the significance and importance of this area, separation and purifications technologies and their applications in the production of liquid biofuels is the focus of this chapter. This chapter highlights the importance of process intensification in the purification of liquid biofuels

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(bioethanol, biobutanol, biodiesel, and biojet fuel) and discusses the required interdisciplinary approach to accomplish it. We outline intensified separation technologies reported in the literature and current challenges of processes intensification in the purification of those liquid biofuels at different levels. We present an overview of important ideas addressed within methodologies proposed for designing intensified processes.

2.2 Biorefineries and Sustainability A key driver to satisfy the energy and material demand of the society sustainably is the implementation of the bioeconomy, which is based on renewable bio-based resources to produce materials and energy [16]. It has been estimated that 50% of the products in current use can be obtained through bioprocessing [17]. Different motivations for policy and research to speed the transition towards the bioeconomy are, e.g., the policy goals of climate change mitigation, energy security, the circular economy concept, rural development, and reindustrialization, as well as stimulation of innovation and technology development. Biorefining is a main element in the framework of the emerging bioeconomy as the broad spectrum of biomass resources offers great opportunities for a wide-ranging product portfolio to satisfy the different needs of society [16]. Therefore, biorefining approaches must be applied. Such approaches help to cover future demands for chemicals, materials, transportation fuels, power, and heat.

2.2.1 Biorefineries Biomass is defined as any organic matter that is available on a renewable basis, including dedicated energy crops and tree, agricultural food and feed crop residues, aquatic plants, wood and wood residues, animal wastes, and other materials [18]. Biomass must be sustainably produced and used as efficiently as possible [16]. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and value-added chemicals from biomass. The biorefinery concept is analogous to today’s crude oil refinery, which produce multiple fuels and products from petroleum. Biorefinery term refers to the conversion of biomass feedstock into a host of valuable chemicals and energy with minimal waste and emissions. Furthermore, many different newly advanced biorefineries are under development. The main characteristics of a biorefinery are: • The coupled generation of energy (e.g., gaseous, or liquid biofuels) and materials (e.g., chemicals, food, and feed). • A combination of several process steps (e.g., mechanical processes such as pressing, and thermochemical processes such as gasification). • The use of different raw materials from both virgin and residual sources.

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An aim of the biorefinery is furthermore to use all the synergies for a sustainable and efficient production, to maximize or optimize the economic, environmental, and social benefits. The future expected growth of the biofuel market and the development of new production processes for biofuels make it necessary to develop new integrated biorefineries. Biomass conversion plants will require similar plant concepts as today’s chemical plants or today’s refining of crude oil. The integration of new biorefinery concepts into existing industrial complexes has interesting prospects, e.g., to reduce the capital costs of the biofuel production facilities and thus to reduce the costs of the chemical and energy products produced. Raw biomaterial availability and how to transform it into energy and higher value products requires bioprocessing toward a circular economy [11]. Therefore, combining higher value products with higher heating value fuels production and employing any combination of conversion technologies has the greatest potential for making fuels, chemicals, and materials, and power from biomass competitive [19]. Obtaining modern biofuels, biopower, and bioproducts from biomass can be realized only in the integrated biorefineries. Biorefineries too will use only those technology platforms that are most cost-effective for converting a certain type of biomass into a certain collection of desired end products [19]. The sustainability of a biorefinery depends on the comprehensive utilization of the biomass feedstock to give a diverse product portfolio. This would only be possible with an optimal mix of processes [20]. A full realization of the utilization potential of any biomass resource often requires a complex set of operations. Besides the actual chemical transformation steps, a multitude of physical processes is involved in the raw material pretreatment as well as in the separation of intermediates and products [21]. Therefore, for a biorefinery to be sustainable and economically competitive with an oil refinery, it must present low energy consumption, low operating costs, low environmental impacts, inherent safety, and good dynamic behavior in the design and operation of all equipment. For this reason, it is essential to implement strategies that aim to achieve these key objectives in the design of a biorefinery that produces liquid biofuels [22].

2.2.2 Biofuels Towards Sustainability The present energy system is unsustainable due to issues environmental, economic, and geopolitical concerns that have implications for the future. Bioenergy is one of the most important components to mitigate greenhouse gas emissions and substitute of fossil fuels [23–25]. Renewable energy is one of the most efficient ways to achieve sustainable development. Plants use photosynthesis to convert solar energy into chemical energy. It is stored in the form of oils, carbohydrates, proteins, etc. This plant energy is converted to biofuels. Hence biofuels are primarily a form of solar energy. For biofuels to succeed at replacing large quantities of petroleum fuel, the feedstock availability needs to be as high as possible [26]. There is an urgent need to design integrated biorefineries that are capable of producing transportation fuels and chemicals.

2.2 Biorefineries and Sustainability Table 2.1 Availability of modern transportation fuels [26]

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Fuel type

Availability Current

Future

Gasoline

Excellent

Moderate-poor

Bioethanol

Moderate

Excellent

Biodiesel

Moderate

Excellent

Compressed natural gas

Excellent

Moderate

Hydrogen for fuel cells

Poor

Excellent

The recovery of liquid biofuels for transport from bio renewable raw materials has become a promising alternative for the future. The main transportation fuels that can be obtained from biomass using different processes are sugar ethanol, cellulosic ethanol, grain ethanol, biodiesel, pyrolysis liquids, green diesel, green gasoline, butanol, methanol, syngas liquids, biohydrogen, algae diesel, algae jet fuel, and hydrocarbons [26]. Renewable liquid biofuels for transportation have recently attracted huge attention in different countries all over the world because of its renewability, sustainability, common availability, regional development, rural manufacturing jobs, reduction of greenhouse gas emissions, and its biodegradability [27–29]. Table 2.1 shows the availability of modern transportation fuels. Transportation fuels and petroleum fuelled, biorenewable fuelled (ReFueled), and biorenewable electricity (ReElectrity) powered vehicles are given in Fig. 2.2. The term biofuel or biorenewable fuel (refuel) is referred to as solid, liquid, or gaseous fuels that are predominantly produced from biomass [30–37]. Liquid biofuels being considered world over all into the following categories: (a) Bio-alcohols [38–41], (b) Vegetable oils [42, 43] and biodiesels [44–46]; and (c) Biocrude and synthetic oils [35, 47–49]. Biofuels are important because they replace petroleum fuels. It is expected that the demand for biofuels will rise in the future. Biofuels are generally considered as offering many priorities, including sustainability, reduction of greenhouse gas emissions, regional development, social structure and agriculture, security of supply [50]. Biofuels among other sources of renewable energy is drawing interest as alternative to fossil diesel. With an increasing number of governments now supporting this cause in the form of mandates and other policy initiatives the biofuel industry is poised to grow at a phenomenal rate. Policy drivers for biorenewable liquid biofuels have attracted in rural development and economic opportunities for developing countries [51]. Lignocellulosic material can be converted into liquid fuels by three primary routes, as shown in Fig. 2.3, including syngas production by gasification, bio-oil production by pyrolysis or liquefaction, or hydrolysis of biomass to produce sugar monomer units. Synthesis gas can be used to produce hydrocarbons (diesel or gasoline), methanol, and other fuels [26]. Bio-oils must be upgraded if they are to be used as transportation fuels. Transportation fuels such as ethanol, gasoline, and diesel fuel can be produced from sugar and associated lignin intermediates. Another method of producing biofuels is to grow

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Fig. 2.2 Transportation fuels and petroleum fuelled, biorenewable fuelled (ReFueled), and biorenewable electricity (ReElectrity) powered vehicles

energy crops which have high energy density structures that are easily converted into liquid fuels such as vegetable oils or hydrocarbon-producing plants [53]. Biomass and biofuels appear to hold the key for supplying the basic needs of our societies for the sustainable production of liquid transportation fuels and chemicals without compromising the needs of future generations. A major twenty-first century goal for academia, industry, and government should be the emergence of efficient and economical utilization of biomass resources [53].

2.3 Green Chemistry Green chemistry, also known as sustainable chemistry, is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. Green chemistry applies across the life cycle of a chemical product, including its design, manufacture, and use’ [54]. Green chemistry can be seen as a tool by which sustainable development can be achieved. The application of green chemistry is relevant to social, environmental, and economic concerns. The achievement of sustainable development will require action

2.3 Green Chemistry

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Fig. 2.3 Strategies for production of fuels from lignocellulosic biomass adapted from Huber and Dumesic [52]

by the international community, national governments, commercial and noncommercial organizations, and individuals from a wide variety of disciplines. Acknowledgement of sustainable development has been taken forward into policy by many governments, including European [55], Chinese [56] and American [57].

2.3.1 Twelve Principles of Green Chemistry Clean chemical technology is not a new field; rather, it is a thought process at the design stage of any synthesis using new and existing tools and knowledge. To better illustrate this, the pioneers of this field suggested a range of foundations for the design of more benign chemistry. The first of these is Anastas ‘Twelve Principles of Green Chemistry’ [58]: 1. 2.

Prevention: It is better to prevent waste than to treat or clean up waste after it has been created. Atom Economy: Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.

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3.

Less Hazardous Chemical Synthesis: Wherever practical, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment. 4. Design for Safer Chemicals: Chemical products should be designed for the desired function while minimizing their toxicity. 5. Safer Solvents and Auxiliaries: The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous where necessary. 6. Design for Energy Efficiency: The energy requirements of chemical processes should be noted for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure. 7. Use of Renewable Feedstocks: A raw material or feedstock should be renewable rather than depleting whenever technically and economically practical. 8. Reduction of Derivatives: Unnecessary derivatization (e.g., use of blocking groups, protection/deprotection, temporary modification of physical/chemical processes) should be minimized or avoided, if possible, because such steps require additional reagents, energy use and generate waste. 9. Catalysis: Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. 10. Design for Degradation: Chemical products should be designed so that at the end of their function they break down into innocuous degradation products that do not persist in the environment. 11. Real-time Analysis for Pollution Prevention: Analytical methodologies need to be further developed to allow for real-time in-process monitoring and control prior to the formation of hazardous substances. 12. Inherently Safer Chemistry for Accident Prevention: Substances and the forms of substances used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fire.

2.3.2 Green Metrics After having made an improvement in a chemical process, it is important to be able to evaluate the change. In doing so, a tangible element or benefit of the new technology can be seen, which is likely to help work communication and can potentially facilitate transfer to industry. The problem observed is that the more accurate and universally applicable the metric devised, the more complex and unemployable it becomes. A good metric must be clearly defined, simple, measurable, objective rather than subjective and must ultimately drive the desired behavior [12]. In this section a number of established metrics for measuring green improvements are discussed.

2.3 Green Chemistry

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Effective Mass Yield Effective mass yield is defined as the percentage of the mass of the desired product relative to the mass of all nonbenign materials used in its synthesis [59], Eq. (2.1): E f f ecti ve mass yield (%) =

Mass o f pr oducts × 100 Mass o f nonbengin r eagents

(2.1)

This metric requires a more detailed definition of what is meant by “benign substance”. Since it is defined as: ‘those by-products, reagents or solvents that do not have any associated environmental risk, for example, water, low-concentration saline solution, diluted ethanol, autoclaved cell mass, etc.’ [59]. This definition leaves the metric open to criticism, as all substances have some degree of environmental risk or impact associated with them (which is a subjective term). Carbon Efficiency This metric is a good simplification for use in the pharmaceutical industry as it considers the stoichiometry of reactants and products. Furthermore, it is of interest to the pharmaceutical industry, where development of carbon skeletons is essential. Car bon E f f iciency (%) =

Amount o f car bon in pr oduct × 100 (2.2) T otal car bon present in reagents

Atom Economy Atom economy was designed in a different way to the other metrics; most were designed to measure the improvement made, while Trost [60] designed atom economy as a method by which organic chemists would pursue ‘greener’ chemistry. The simple definition of atom economy is a calculation of how much of the reactants remain in the final product. For a generic multistage reaction, the atom economy is as follows: A+B →C C+D→E E+F→G Atom Economy (%) =

M.W. A

(2.3)

M.W.G × 100 + M.W. B + M.W. D + M.W. F

The drawback of atom economy is that assumptions must be made. However, it is useful because a low atom economy at the design stage of a reaction prior to entry into the laboratory can drive the formulation of a cleaner synthetic strategy [5].

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Reaction Mass Efficiency The reaction mass efficiency considers atom economy, yield, and stoichiometry. E f f iciency (%) =

Mass o f pr oduct × 100 Mass o f A + Mass o f B

(2.4)

Like carbon efficiency, this measure shows the ‘cleanness’ of a reaction but not of a process: for example, neither metric considers waste produced. These metrics might thus present a rearrangement as ‘very green’ but would fail to address any solvent, work up and energy issues arising [5]. Environmental (E) Factor The first general metric for green chemistry remains one of the best. Roger Sheldon’s [61] E-factor can be made as complex and thorough or as simple as required. Assumptions concerning solvent and other factors can be made, or a total analysis can be performed. The E-factor calculation is defined by the ratio of the mass of waste per unit of product. Equation (2.5) shows this mathematically: E-Factor =

T otal waste (kg) Pr oduct (kg)

(2.5)

2.4 Intensified Processes to Produce Biofuels Increasing awareness for energy sustainability, environmental concerns, new and unconventional feedstocks, as well as recent advances in process optimization have sparked a renewed interest in process intensification (PI) [19]. PI aims to drastically reduce the energy consumption and processing cost of the chemical processes by utilizing the synergy between multifunctional phenomena at a different time and spatial scales and enhancing the mass, heat, and momentum transfer rates. There has been significant growth in the field of process intensification over the past decades that featured both successful industrial applications and increased research interest in academia [22, 24]. Therefore, using intensified technologies for the production and separation of liquid biofuels, it is possible to obtain sustainable processes within a circular economy framework. Several intensified technologies used for the production and/or purification of liquid biofuels have been reported. Some examples are shown in Table 2.2.

References

21

Table 2.2 Intensified processes for biofuels production Intensified technology

Biocombustible

References

Extractive distillation

Bioethanol

[62, 63]

Thermally coupled extractive distillation

Bioethanol

[64]

Extractive dividing wall column

Bioethanol

[65, 66]

Pressure-swing distillation

Bioethanol

[67]

Extraction/extractive distillation

Bioethanol

[68]

Reactive distillation columns

Bioethanol

[69]

Distillation and hybrid liquid–liquid extraction

Biobutanol

[70]

Thermally coupled distillation

Biobutanol

[71, 72]

Dividing wall column

Biobutanol

[73, 74]

Decanters and distillation columns

Biobutanol

[75]

Reactive distillation columns

Biojet

[76]

Thermally coupled distillation

Biojet

[77]

2.5 Conclusions Given the future scarcity of fossil fuels, the sustainable production of biofuels should be explored, so that their production can be brought to industrial levels. Through the implementation of the intensification of processes, the reduction in costs and environmental impact and improvements in operability and safety are sought. To ensure that new intensified processes are a better alternative to conventional processes, metrics that focus on achieving the goals of the green chemistry principles must be used. Sustainability metrics must be incorporated from the design stage. When several metrics are integrated simultaneously, it becomes a complex problem, which must be solved through optimization techniques. Although there are already reported works on the use of intensified processes for the production and purification of biofuels, the search for new processes that reduce the production costs of biofuels must continue. The design of processes must adhere to the needs of today’s world, which is why the metrics to be evaluated through the design stage must be adapted in order to satisfy the criteria of sustainability and circular economy.

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Chapter 3

Bioethanol

Abstract Climate change is one of the worst environmental problems worldwide related with CO2 emissions. As is known the burning of fossil fuels has led to everincreasing levels of greenhouse pollution associated with global warming (Venkata Mohan et al., Bioresour Technol 99:59–67 (2008)). Due to environmental problems, the seek for sustainable alternatives of fuels has become mandatory, having as the most promising alternative the use of biomass as an energy source as well to decrease CO2 emissions. There are several biofuels that can be obtained from biomass, highlighting the bioethanol as a promising renewable and sustainable fuel for tackling today’s global energy crisis and the worsening environment quality. Bioethanol has been recognized as a potential replacement to fossil fuel-based energy, and it can overcome the issue of exhaustion of energy sources and reduce the environmental pollution. Compared to fossil fuels, using bioethanol could reduce more than 80% of carbon emissions (Qiao and Lü, in Advances in 2nd generation of bioethanol production. Woodhead Publishing, Sawston, pp 213–227 (2021) [1]). This chapter aims to show an overview of bioethanol production focusing on the production of bioethanol through lignocellulosic biomass. The traditional feedstock for bioethanol production, its conventional production process highlighting two steps, the biomass pretreatment and separation process. As well due to the necessity of enhance the process it is shown some proposals for intensified processes to produce bioethanol.

3.1 Bioethanol: Chemical Properties, Uses and Applications Biofuels made from biomass provides a renewable alternative to fossil fuels in the transport sector. Bioethanol is remarked as one of the most ideal substitutes for gasoline on land transport vehicles. With molecular formula C2 H5 OH, bioethanol is also known as ethyl alcohol. As physical characteristics is a biodegradable transparent and colorless liquid with low toxicity [2]. As well due to its physicochemical characteristics, presented in Table 3.1, as a fuel bioethanol offers some advantages. For example, it is reported that bioethanol has a higher-octane content of 110 in comparison with gasoline with 87. Due to its higher oxygen content allows cleaner © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_3

25

26 Table 3.1 Physicochemical properties of bioethanol [5]

3 Bioethanol Property

Unit

Value

Molecular weigh

kg/kmol

46

Density at 15 °C

kg/l

0.80–0.82

Oxygen content

mass %

34.7

Cetane number

–

5.8

Octane number

–

110

Latent heat of vaporization

MJ/kg

0.91

Lower calorific value

MJ/kg

26.7

Flash point

K

286.15

Autoignition temperature

K

286.15

combustion reducing up to 80% CO2 emission compared to fossil fuels [1], as well it is biodegradable and does not contain aromatics, olefins, and diolefin [3]. Moreover, bioethanol can also be used in different industries such as chemical, food, cosmetic, medicine, etc.; due to its capability of dissolving both polar, hydrophilic, nonpolar, and hydrophobic compounds [4]. It is also reported that bioethanol can be used as raw material to produce other chemical products such as ethylene, methane, butanol, etc. Despite the advantages, bioethanol has some disadvantages to take into consideration during its production. It is miscible with water forming an azeotropic mixture increasing energetic requirements during the distillation process and therefore operation costs. As well it has a lower heating value and lowers energy density, which leads to higher fuel consumption rate when compared with conventional fossil fuels. Bioethanol it can be used as a versatile raw material in various industries, such as the pharmaceutical industry, the cosmetic industry, the chemical industry (as a compound of starting in the synthesis of various products) and it is an excellent solvent, antifreeze, and disinfectant. Nevertheless, bioethanol is mostly used in the transport sector as a constituent of mixture with gasoline or as octane. Bioethanol is mixed with gasoline at the volume fractions of 5, 10 and 85%. A total of 85% bioethanol by volume can only be used in flexible fuel vehicles, while mixtures of 5 and 10% by volume can be used without any engine modifications. In 2016 the global bioethanol production was 100.2 billion L. The annual production of bioethanol is constantly increasing, by 2024 it is estimated an increase of almost 134.5 billion L both in production and consumption worldwide [6]. Figure 3.1 shows global prediction ethanol production (inner circle) and consumption (outer circle) by country or region by 2024. Together, the United States and Brazil produce around 70% of the world’s bioethanol. The vast majority of U.S. bioethanol is produced from corn, while Brazil primarily uses sugarcane. In 1975, a study showed the trend of gasoline replacement by ethanol, in that moment ethanol production as fuel was zero. Around 2003, this amount reached about 30 billion L. The most significant increase was in the United States. On the other hand, Europe did not show much interest in replacing gasoline with ethanol due to its

3.2 Feedstock for Bioethanol Production

27

Fig. 3.1 Predictions of the world bioethanol production (inner circle) and consumption (outer circle) by 2024 [6]

economic policies. Nowadays, the United States produces about 19 billion L a year, and Brazil alone more than 12 billion L. Europe with about 500 million L and Asia with 400 million L [7]. Moreover, the complexity and costs in the bioethanol production processes partly explain the reason why fuel bioethanol is not yet a replacement option for petroleum-derived fuels. To be competitive, and find economic acceptance, the cost for bioconversion of biomass into liquid fuel must be lower than the current gasoline prices [8]; however, there is still a wide margin to reduce the cost of converting biomass in bioethanol.

3.2 Feedstock for Bioethanol Production Bioethanol can be produced from the fermentation of different types of feedstocks which contains sugars. As is shown in Fig. 3.2, feedstock for bioethanol production can be classified into 3 different categories. It is possible to see that Bioethanol can be produced from a variety pf feedstock. According to Fig. 3.2, first generation bioethanol includes food crops such as rice, wheat, barley, potato, corn, sugarcane, and vegetable oil (soybean oil, sunflower oil, olive oil, canola oil, mustard oil) [9]. Due to the kind of feedstock in some countries

28

3 Bioethanol

Fig. 3.2 Feedstock classification for bioethanol production

the use as a raw material for fuels conflicts since that increases food costs. About the second generation bioethanol, the main feedstock includes mainly forest residue, woody biomass, herbaceous biomass, etc.; nonfood crops; municipal solid waste; and animal fat [9]. The second generation have some advantages over the first generation, for instance the feedstock is not entering in conflict with food production due to the use of wastes, as well it produces lower CO2 emissions. Despite, this advantage second generation have lower sugar concentration for producing bioethanol compared to first generation. So, this will directly impact production costs and operational difficulties. In Table 3.2 it is shown a list of lignocellulosic wastes with the technical description for bioethanol production. The third-generation bioethanol considers algal biomass as the feedstock. Thirdgeneration bioethanol is considered as a promising alternative due to their advantages over first- and second-generation bioethanol. For instance, microalgae can be cultivated on marginal land with a water environment, a low cost of cultivation, a high conversion efficiency, and a high energy density [10].

3.3 Overall Process for Bioethanol Production The conventional bioethanol production can be carried out via anaerobic fermentation by using microorganisms as biocatalyst. This reaction involves the conversion of sugar into bioethanol using ethanogenic microorganisms. According to De Blasio there are several proposals of technologies for bioethanol production according to the available feedstock [11]. So according to the feedstock, the selection of the technology for the biomass conversion into bioethanol will change. It means, bioethanol production route changes based on the feedstock nature as is shown in Fig. 3.3.

3.3 Overall Process for Bioethanol Production

29

Table 3.2 Lignocellulosic waste with the technical description for bioethanol production [8] Lignocellulosic waste

Process description

Wheat straw

Bioethanol is obtained by subcritical water pretreatment (extraction at 220.5 °C; extraction time, 22.0 min) combined with separate high solid (15%) hydrolysis and fermentation. Separate hydrolysis and fermentation

Whole plant cassava

Bioethanol obtained by hydrothermal pretreatment (180 °C; 2 MPa; 60 min) followed by fermentation of integrated cellulosic C5 sugar and starch from whole plant cassava, in a simultaneous saccharification and fermentation method. Simultaneous saccharification and fermentation

Wheat and rye stillages

Microwave-assisted pretreatment with dilute acid of wheat and rye stillages to produce >156 mg/g glucose at microwave power of 300 W (15 min, 54 PSI in 24 h process), while after 48 h of fermentation using S. cerevisiae, 20 g/L of bioethanol was obtained

Cotton stalk

Cotton stalk was pretreated in organosolv and hydrothermal processes, followed by pre-hydrolysis using 80 FPU/g cellulose (at 50 °C, at pH 5.0, for 6 h). 15 mg yeast per gram of dry pretreated cotton stalk allowed to carry out the fermentation process at 30 °C with an initial pH 5.0. By this, 47.0 g/L bioethanol were obtained

Sugarcane bagasse

Sugarcane bagasse was pretreated by hydrodynamic cavitation to assist alkaline-hydrogen under optimized conditions, e.g., 0.29 M of NaOH, and 0.78% (v/v) of H2 O2 (9.95 min process time at 3 bar inlet pressure). Doing so, 95.4% digestion of the cellulosic fraction was achieved. Cellulase enzyme was used for hydrolysis, followed by fermentation with Scheffersomyces stipitis NRRL-Y7124. Hence, 31.50 g/L of bioethanol were produced

Rice straw

Maximum glucose yield of 93.6% was obtained using CO2 -incorporated ammonia explosion pretreatment, under optimized conditions: 14.3% ammonia, 2.2 MPa CO2 , at 165.1 °C for 69.8 min residence time. 97% bioethanol were obtained by simultaneous saccharification and fermentation method (simultaneous saccharification and fermentation)

In the case of sugary feedstocks such as sugarcane and sweet sorghum, sugar juice is extracted from the feedstocks, then fermented in the presence of a suitable microorganism to produce ethanol and distilled to separate ethanol. In contrast to the sugary feedstocks, corn and other starchy crops first undergo enzymatic hydrolysis to produce sugar. The sugar is then fermented to produce ethanol. The lignocellulosic biomass lignin along with cellulose and hemicellulose forms a rigid structure that needs various pretreatment techniques to deconstruct the structure. Pretreatment removes lignin and hemicellulose from the lignocellulosic structure while also decreasing crystallinity and increasing the porous surface area, which is favorable for hydrolysis [12]. Despite of the different advances in technologies for bioethanol production, the production of bioethanol from lignocellulosic biomass is an attractive alternative since lignocellulosic raw materials do not compete with food crops and are less

30

3 Bioethanol

Fig. 3.3 Bioethanol production route according to the type of feedstock

expensive than conventional agricultural raw materials [11]. Moreover, from all the biomasses shown, lignocellulose is the most abundant. The biological conversion of various materials with a high lignocellulosic content (forest and agricultural residues, or lignocellulosic crops) offers numerous environmental benefits. Production of second-generation bioethanol takes advantage of a large variety of non-edible agricultural and industrial lignocellulosic wastes. The production of bioethanol from lignocellulosic biomass involves a series of stages such as pretreatment, enzymatic hydrolysis, detoxification, sugar fermentation, recovery, and purification of bioethanol. In Fig. 3.4 it is presented a general scheme for bioethanol production from lignocellulosic biomass.

3.3.1 Pretreatment Bioethanol production from lignocellulosic materials requires an additional pretreatment process before the saccharification and fermentation processes. The pretreatment is an important step to obtain the sugars that will be potentially ferment in the subsequent process. Typically, pretreatment is an expensive step, which represents almost 40% of the total production cost [13]. The selection of the appropriated technology for the pretreatment will depends on the properties of the feedstock. As is shown in Table 3.3, pretreatment technologies can be classified into biological, physical, chemical, and physico-chemical pretreatments, according to the different forces or energy consumed in the pretreatment process. About the chemical pretreatment, excessive use of chemicals is considered environmentally unfriendly. On the

Fig. 3.4 General scheme representation for bioethanol production from lignocellulosic biomass

3.3 Overall Process for Bioethanol Production 31

32

3 Bioethanol

other hand, biological pretreatment is environmentally friendly and works under mild conditions, but the use of microbes for pretreatment is still not the preferred choice for bioethanol production, because of its poor performance (it releases less cellulose), low rate, and multiple products formed (lignin and phenolic compounds), which inhibit the microbial activity [14].

3.3.2 Hydrolysis During the enzymatic hydrolysis, the cellulosic material is converted into glucose molecules by enzymes called cellulases. This treatment breaks down the lignin structure and disrupts the crystalline structure of cellulose [16]. The saccharification process aims to convert cellulose into glucose using enzymatic hydrolysis. In addition to the benefits of sugars from cellulose, there is great interest in other sugars such as pentoses (derived from hemicellulose), which lead to the use of enzymes that act on said substances, for example with xylanases and xylase.

3.3.3 Fermentation The fermentation is a process that can simply be defined as a chemical change caused by the action of microorganisms. Where the activity of some microorganisms that process sugars guide it to produce alcohol in the form of bioethanol, carbon dioxide and ATP molecules that the microorganisms themselves consume in their anaerobic cellular energy metabolism. For the fermentation process there are two key components: the microorganism and the substrate. In the meantime, the selection of microorganisms for fermentation depends on the composition of fermentable sugars. Fungi Saccharomyces cerevisiae and bacteria Zymomonas mobilis are the most used microorganisms in bioethanol production. Both microbes enabale high ethanol yields, high ethanol tolerance, and ferment a wide range of hexoses and disaccharides. Z. mobilis is considered superior as it produces less biomass, but none of them is capable to ferment pentoses [17]. About the production of lignocellulosic bioethanol, there has been studied different configurations for fermentation, but there are three fundamental routes can be distinguished. The first route is through the separate processes of hydrolysis and fermentation (SHF), the second is the simultaneous saccharification and fermentation (SSF) and the third one is the consolidate bioprocessing (CBP) [18]. SHF involves independent hydrolysis and fermentation reaction in different reactions unit. The benefit of SHF is that both enzymatic saccharification and fermentation steps are allowed to be carried out independently at suitable temperature that eventually optimized the performance of the respective saccharifying enzyme and fermenting microorganisms. SSF has always been tested in comparison study with SHF for bioethanol production, as both methods are closely similar in terms of process flow.

3.3 Overall Process for Bioethanol Production

33

Table 3.3 Pretreatment technologies for bioethanol production from lignocellulosic waste [15] Classification

Method

Description

Biological pretreatment

Fungal

Employ microorganisms mainly brown, white, and soft-rot fungi which degrade lignin and hemicelulose. Use of: Phanerochaete chrysosporium, Ceriporia lacerata, Cyathus stercolerus, Ceriporiopsis subvermispora, Pycnoporus cinnarbarinus and Pleurotus ostreaus

Physical pretreatments Mechanical comminution

Chemical pretreatments

Reduction of particle size and cristallinity of lignocellulosic in order to increase the specific surface and reduce the degree of polymerization Mechanical methods can be divided into chipping, grinding or milling

Extrusion

The materials are subjected to heating, mixing and shearing, resulting in physical and chemical modifications during the passage through the extruder

Alkali pretreatments

Growth cellulose digestibility and they are more effective for lignin solubilization, exhibiting insignificant cellulose and hemicellulose solubilization than acid or hydrothermal processes

Acid pretreatment

Solubilize the hemicellulose fraction of the biomass and to make the cellulose more accessible to enzymes. This type of pretreatments can be performed with concentrated or diluted acid, but utilization of concentrated acid is less attractive for ethanol production due to the formation of inhibiting compounds

Ozonolysis

Ozone is a powerful oxidant that shows high delignification efficiency. This lignin removal increases the yield in following enzymatic hydrolysis (continued)

34

3 Bioethanol

Table 3.3 (continued) Classification

Physico-chemical pretreatments

Method

Description

Organosolv

Is a pulping technique that uses an organic solvent to solubilize lignin and hemicellulose. Numerous organic or aqueous solvent mixtures can be utilized, including methanol, ethanol, acetone, ethylene glycol and tetrahydrofurfuryl alcohol, to solubilize lignin and provide treated cellulose suitable for enzymatic hydrolysis

Steam explosion: SO2 -steam explosion

It is a hydrothermal pretreatment in which the biomass is subjected to pressurized steam for a period ranging from seconds to several minutes, and then suddenly depressurized. This pretreatment combines mechanical forces and chemical effects due to the hydrolysis

Liquid hot water

Is an hydrothermal treatment which does not require rapid decompression and does not employ any catalyst or chemicals. Pressure is applied to maintain water in the liquid state at elevated temperatures (160–240 °C) and provoke alterations in the structure of the lignocellulose. The objective of the liquid hot water is to solubilize mainly the hemicellulose, to make the cellulose more accessible and to avoid the formation of inhibitors

Ammonia fiber explosion (AFEX)

Biomass is treated with liquid anhydrous ammonia at temperatures between 60 and 100 °C and high pressure for a variable period of time. The pressure is then released, resulting in a rapid expansion of the ammonia gas that causes swelling and physical disruption of biomass fibers and partial decrystallization of cellulose

Wet oxidation

Employs oxygen or air as catalyst. It permits reactor operation at comparatively low temperatures and short reactor times (continued)

3.3 Overall Process for Bioethanol Production

35

Table 3.3 (continued) Classification

Method

Description

Microwave pretreatment

Pretreatments were carried out by immersing the biomass in dilute chemical reagents and exposing the slurry to microwave radiation for residence times ranging from 5 to 20 min

During SSF, both hydrolysis and fermentation steps are carried out simultaneously in the same reactor vessel [19]. The significant advantage of doing SSF is that the released sugar will be instantly consumed by the fermenting cells, hence indirectly prevented cellulase inhibition due to high concentration of sugar accumulated. About the CBP, this operational strategy integrated mechanical, chemical, and biological process in an effective way to reduce bioethanol production cost by eliminating few processing steps including pretreatment and hydrolysis. In CBP, all of the four steps in the conversion of pre-treated biomass to bioethanol are combined into one and was carried out by a single species or a co-culture microorganisms [20]. For this approach, it required the microorganisms that has capability to excrete cellulose hydrolysis enzyme to breakdown the polysaccharide into monomeric sugars and produced bioethanol by the fermenting microorganisms itself [21].

3.3.4 Detoxification The purpose of detoxification is to eliminate substances that could be tentatively formed during the submission of raw material to pretreatment and enzymatic hydrolysis, which are toxic and inhibitory in fermentation. These substances are typically created due to the high temperatures and acidic conditions in which the previous stages develop. These substances are usually grouped into three categories: furan derivatives, low molecular weight aliphatic acids and phenolic derivatives. There is a range of possibilities to carry out detoxification, and these are classified according to the type of substances and actions that constitute them. The classification of techniques for detoxification are: physical, chemical, and biological methods.

3.3.5 Separation and Purification of Bioethanol The principal problem in the production of bioethanol is the high energy cost involved in its separation. During the fermentation stage large quantities of fermentation broth are obtained with low concentrations of alcohol so it is necessary to eliminate excess water. The conventional technology for bioethanol recovery incudes three stages: (1)

36

3 Bioethanol

Conventional distillation of dilute ethanol to a concentration close to its azeotropic point (95.57 wt.%); (2) extractive or azeotropic distillation using a third component to break up the azeotrope and remove the remaining water. For bioethanol-water extractive distillation, ethylene glycol continues to be the most widely used solvent and (3) Conventional distillation to recover the solvent component and reuse it in the process. Separation process is the biggest challenge during the bioethanol production because the separation implies the consumption of 50–80% of the total energy required in the entire bioethanol production process. In this way there is the necessity to improve separation techniques related to bioethanol production. Therefore, there are some proposals to modify the conventional process into intensified processes resulting an economically option to enhance bioethanol production.

3.4 Process Intensification Applied to Produce Bioethanol As it was mentioned above, in order to bioethanol be competitive against gasoline, and find economic acceptance, it is necessary to reduce the cost of converting biomass in bioethanol. One of the biggest challenges in bioethanol production, is during the recovery and purification process. The mixture of bioethanol water forms an azeotrope, which is why the separation to obtain pure bioethanol and break the azeotrope entails high energy consumption during the conventional distillation process. In order to enhance the separation and reduce energy consumption it is proposed to applied process intensification. That means, to make any process modification achieving higher efficiency, lower expenses, more environmentally friendly operation, size reduction, or any combination of the above. Some examples of process intensification in distillation are membrane distillation, HiGee distillation, cyclic distillation, dividing wall column (DWC), and dividing wall extractive distillation and Petlyuk systems [23]. In order to intensify the conventional extractive distillation process, Errico and Rong proposed a methodology with consist in four steps. (1) Identification of the corresponding simple column, (2) Definition of the sequences thermodynamically, (3) Definition of thermodynamically equivalent sequences and (4) Generation of lateral flow sequences [24]. To exemplify each stage, the specific modifications will be presented taking as a base configuration shown in Fig. 3.5. • Identification of the corresponding simple column According to Fig. 3.5, in the first column the heavier feed component is separated, sending the lighter components as feed flow to the second column. In the second column the bioethanol is obtained as distillate and finally in the third column the solvent is recovered. To understand the modifications of the reference configuration, each section of the column was designated with the number. Due to the existence of recyclable streams, Sects. 3.1 and 3.3 needs to be modify of the reference setup.

3.4 Process Intensification Applied to Produce Bioethanol

37

Fig. 3.5 Reference configuration

• Definition of the sequences thermodynamically It is possible to replace one or more heat exchangers associated with liquid–vapor interconnections as is shown in Fig. 3.6. For the extractive distillation, the presence of the solvent stream and the recyclables could give a preliminary indication of the applicability of a particular configuration. Assuming the liquid stream from the second to the first column is essentially made up of the high-boiling solvent. This restricts the maximum purity obtainable for the water stream, so no positive improvements should be expected from these settings. • Definition of thermodynamically equivalent sequences It is possible to create corresponding equivalent thermodynamic configurations by moving a column section that provides the common reflux ratio or boiling vapor between two consecutive columns. Figure 3.7 shows the methodology of section movements and a possible recombination of the thermally coupled configuration. • Generation of lateral flow sequences

Fig. 3.6 Energy integration from liquid-vapor interconnections

Fig. 3.7 Equivalent thermodynamically configuration

38 3 Bioethanol

3.4 Process Intensification Applied to Produce Bioethanol

39

Single column sections of thermodynamically equivalent sequences can be supplemented with lateral liquid or vapor extraction or even thermal coupling. By following the steps mentioned above, Segovia-Hernández et al. reports that it is possible to obtain series of designs that claim to be economically superior to conventional bioethanol purification processes and with sustainability benefits [25]. Some of these results are summarized in Table 3.4. Based on the designs presented in Table 3.4, Segovia-Hernández et al. presents an analysis comparing the different alternatives of intensified processes in order to find Table 3.4 Proposed thermodynamically equivalent configurations for extractive distillation process for bioethanol production [25] Sequence

Description

Sequence dual columns (SDC)

Consists of a prefractionator followed by the extractive distillation column with a side stream. In the extractive column, bioethanol is obtained in the upper part, the solvent is recovered in the lower part and the side stream of steam contains a mixture of water and bioethanol, which is recycled to the prefractionator

Sequence three-column separation with liquid (STCL)

Consists of a prefractionator, in which the water and bioethanol mixture is partially separated until a purity close to the azeotrope is reached, followed by an extractive distillation column where, using an extractive agent, almost pure bioethanol is obtained in the upper section of the column. Finally, the solvent is recovered in the last column of the sequence. In the upper section of the solvent recovery column, a liquid water–ethanol mixture is obtained, which is recycled to the prefractionator

Scheme

(continued)

40

3 Bioethanol

Table 3.4 (continued) Sequence

Description

Sequence three-column separation with vapor (STCV)

This bioethanol-water mixture configuration is obtained in the upper part of the solvent recovery column in the vapor phase

Dividing wall column with liquid (DWCL)

A configuration in which a liquid stream containing water and bioethanol is recycled to the first column; ethanol is obtained as a distillate from the main column, while solvent is recovered in the bottoms

Dividing wall column with vapor (DWCV)

A configuration similar to the previous one, but the recycled ethanol -water mixture is obtained in the vapor phase

Scheme

the best design to produce bioethanol. The different configurations were simulated in Aspen Plus. The analysis was taking into consider the minimization of the annualized total cost and energetic requirements. In order to have a comparative analysis of the performance of the different proposal designs it was considered a feed flow of 1,694,240 kmol/h of a bioethanol–water mixture containing 5% mol of bioethanol. As well it was considered ethylene glycol as solvent, with a solvent to feed ratio of 0.87 for all cases. Table 3.5 shows the objective functions obtained for the scheme proposed in Table 3.4. Globally the DWCL and DWCV are good options due to the reduction of energy requirements and capital cost. Likewise, the SDC configuration can be a good option

3.5 Ethyl Acetate a Promising Biofuel

41

Table 3.5 Objective functions for the proposed configurations using ethylene glycol as solvent [25] SDC

STCL

STCV

DWCL

DWCV

Condenser duty (MJ)

13,867.78 14,692.75 13,935.74 14,294.95 14,294.95

Reboiler duty (MJ)

17,650.55 18,426.33 17,668.4

Total energy (MJ)

31,518.33 33,119.08 31,604.14 32,315.83 31,709.3

Annualized capital cost (k$/year) 107.8 Solvent makeup (kmol/h)

0.62

18,020.88 17,414.35

132.8

133.1

102.3

102.6

0.004

0.004

0.004

0.004

regarding energy consumption and capital costs. However, it is the configuration that presents the biggest use of solvent due to the side stream. Using this type of setup can be convenient as it can be assessed as a difference between energy and capital costs saved compared to traditional sequences and increased solvent consumption.

3.5 Ethyl Acetate a Promising Biofuel Bioethanol can be used for the synthesis of various important products in the chemical industry such as: acetaldehyde, acetic acid, acetic anhydride, ethyl acetate, ethyl lactate, ethyl tert-butyl ether, ethylene, ethylene glycol, ethylene-propylene-diene monomer, polyethylene and polyethylene glycol [26]. Ethyl acetate has interesting properties as a biofuel, and although other chemical routes to ethyl acetate are being evaluated, the main method used by manufacturers involves the esterification of ethanol and acetic acid in the presence of a catalyst [27]. Ethyl acetate is an organic solvent of moderate polarity with versatile industrial applications. Another prospective application is the biodiesel production from vegetable oil; here, triglycerides are transformed to fatty acid ethyl esters in a lipasecatalyzed transesterification reaction with ethyl acetate as an acyl acceptor instead of methanol [28–31]. Although being an irritant and intoxicant at higher concentrations, ethyl acetate is less toxic to humans compared to many other solvents. Ethyl acetate is an environmentally friendly compound since the ester is easily degraded by bacteria [32] and is regarded as a non-persistent pollutant of the atmosphere [33]. The addition of ethyl acetate to ethanol-gasoline blends creates lots of advantages including: increasing in water tolerance (WT), prevention of phase separation (PST), increasing octane rating (RON, MON), decreasing vapor pressure (VP) and vapor lock index values (VLI). Table 3.6 shows the improvements in these properties [27]. Ethyl acetate causes increase in the area formed due to azeotrope formation but approximately do not affect 50% of volume of fuel. These advantages encourage the use of ethyl acetate as a potential ethanol-gasoline stabilizer or as extender.

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3 Bioethanol

Table 3.6 Effect of ethyl acetate content on the properties of fuel blend contains 15 vol% of ethanol [27] Blend component

Blend composition, vol% E0

E15

E15/3EA

E15/6EA

E15/9EA

E15/12EA

Hydrocarbon gasolina

100

85

82

79

76

73

Ethanol

0

15

15

15

15

15

Ethyl acetate

0

0

3

6

9

12

Total

100

100

100

100

100

100

VP, psi

9.58

9.7

9.59

9.56

9.37

9.28

E70, vol%

27

56

60

60

59

57

VLI

849

1088

1088

1079

1073

1066.8

Oxidation stability, min

>378

>378

>378

>378

>378

>378

1ª

1a

1ª

1a

Corrosivity

1ª

1ª

RON

84.55

89.1

90.4

91.5

92.7

93.8

MON

78.45

81.2

83.1

84.7

85.8

87.4

(T + M)/2

81.5

WT, vol% @25 °C PST, °C

85.5

86.7

88.1

89.3

90.6

0.84

1.01

1.12

1.34

1.6

−12

−20

−20

−20

−20

1a

With a corrosivity within category . It means, responses are noted following up to 3 minutes exposure and up to 1 hour observation.

3.5.1 Overall Process for Bioethanol Production At the commercial scale, many chemical approaches for EtAc synthesis have been established, employing both fossil-based and bio-based raw materials (Table 3.7). EtAc is primarily created through the liquid or vapor phase esterification of acetic acid and ethanol (1), acetylation of ethylene (2), and ethanol dehydrogenation (3). Table 3.7 includes the routes as well. The presence of ethylene in the olefin acetylation (route 2) process, as well as the generation of hydrogen in the Tishchenko pathway (route 3), as well as the high circumstances of both processes, have a detrimental impact on their safety indicators. Even though both routes have excellent atom economy and hydrogen co-produced in the second route might be of interest, this diminishes the beingness of these pathways. Direct esterification (route 1) has the lowest atom economy of the three reactions, but it has the lowest value of the safety indicator, making it the most benign chemical pathway, according to Srinivasan et al. [34]. Furthermore, among the chemical pathways listed in Table 3.7, direct esterification of bio-based acetic acid and ethanol appears to be the most cost-effective option as well as the one with the lowest global warming potential [35]. Even though Fisher esterification to EtAc is a well-known example in academia for teaching basic ideas in chemical reaction engineering and thermochemistry, this system is currently being studied.

3.5 Ethyl Acetate a Promising Biofuel Table 3.7 Industrial chemical routes for ethyl acetate production

43

Chemical route

Reaction

1

CH3 CH2 OH + CH3 COOH ↔ CH3 COOCH2 CH3 + H2 O

2

CH2 = CH2 + CH3 COOH → CH3 COOCH2 CH3

3

2CH3 CH2 OH → CH3 COOCH2 CH3 + 2H2

Kinetic Models Using acid catalysts, a vast number of kinetic investigations on Fisher esterification to EtAc have been published. Because it is more active than most commercial homogeneous (e.g., p-toluene sulfonic acid, Methanesulfonic acid) and heterogeneous (e.g., ion exchange resins) catalysts, H2 SO4 has long been employed as a catalyst. In commercial applications, H2 SO4 loadings vary from 0.2 to 1 wt% of the reactive mixture. However, there are certain drawbacks to utilizing H2 SO4 , such as product darkening, equipment corrosion, the need for neutralization, and the inability to reuse and recycle the catalyst. Even though these drawbacks are removed when solid catalysts are used, it has been discovered that nearly noncommercial heterogeneous catalysts, such as resins, enhance reaction rates to EtAc faster than sulfuric acid under the same operating conditions and acid equivalent loadings. Table 3.8 shows an overview of reaction rate expressions reported for several catalysts, along with the relevant parameters. Only publications using concentrationbased or molar fraction-based kinetics are mentioned since certain kinetic expressions have been generated using other thermodynamic models than the one chosen here (activity-based kinetics [36, 37]). Exclusions were made for expressions that did not have a record of experimental validation [38]. Figure 3.8 shows a diagram of the traditional continuous EtAc production process. The esterification reaction is carried out in a stirred tank reactor (Rx) at 80 °C with a 200-min residence period, where excess HAc is employed to bias the reaction towards ester formation. To extract EtAc from the remaining HAc, the reactor’s output stream is sent to the major distillation column (DC). In a decanter, the distillate from the main column is chilled and mixed with clean water to cause phase separation. The organic phase from the decanter is refined in a recovery column (RC) to yield pure EtAc in the bottoms, which contains EtAc in excess of 90% by weight. The recovery column’s distillate is returned to the main column once more (DC). An azeotropic distillation column (AD) that employs EtAc as an entrainer is commonly used to collect unreacted HAc and recycle it back to the reactor, however it is not mentioned in [44]. The organic phase is reintroduced to the primary column after the distillate from the azeotropic column, which contains mostly H2 O and EtAc, is cooled to activate phase separation. In addition to the process’s complexity and high energy consumption, raw materials and product are lost in the watery outlet streams.

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3 Bioethanol

Table 3.8 Kinetic expressions for acetic acid–ethanol esterification with different catalyst Catalyst

Rate k1 k c c3 c4

H2 SO4

r 1 = k 1 c1 c2 −

HCl

r 1 = k 1 c1 c2 − k 2 c3 c4

Amberlyst 35 wet

Amberlyst 36

Auto cat

References

k1 =

[39]

  (4.195ck + 0.08815)exp 6500.1 T

n = m = 0.5, p = q = 1, T = 100 °C   r = m cat (k1 cHAc cEtOH − k1 = 1.24 × 109 − 6105.6 T k−1 cEtAc cH2O )   5692.1 8 k−1 = 1.34 × 10 − T   r= k+ = 131137exp 57960 RT wcat (k + c H Ac cEtOH −   k−1 cEtAc cH2 O ) k− = 81389 exp − 60550 RT   r = k 1 c1 c2 − k 2 c3 c4 k1 = 0.485 exp − 59774 RT   k2 = 0.123 exp − 59774 RT −E

Auto cat

Parameters

r = Ae RT



c A cB −

c E cw ke

[40] [41]

[42]

[39]



A = 4.85 × 102 E = 14300 cal/mol ke = 4

[43]

Fig. 3.8 Conventional production process-adapted from Kirk–Othmer [44] and completed (dotted line) with water-acid azetropic distillation column for acid recovery and recycle

3.5 Ethyl Acetate a Promising Biofuel

45

3.5.2 Process Intensification Applied to Produce Bioethanol Ethyl Acetate In recent years, different processing technologies applied to ethyl acetate production have been reported, most of which focus on a process intensification approach. Notwithstanding the proposed technologies have claimed to be cost-effective and environmentally friendly, no sustainability assessment of such technologies has been carried out. Furthermore, as there is room for future processes development by introducing more complexity during process intensification, there is need for also including the sustainability evaluation in the early stages of the process synthesis. Benefits of process intensification are associated with the enhanced safety, space and waste reductions, energy savings, higher efficiency and productivity, and consequently better economic and environmental performance. From a general point of view, the thermodynamic approach for process intensification consists of energy integration of streams, stages, or operations, to replace the required amount of heating and/or cooling provided with utilities. The functional domain deals with the integration of two or more operations or technologies within a single unit. This is the case of hybrid and reactive separations such as reactive distillation. The group by Hernandez et al. [45–47] conducted a series of studies on the reactive dividing wall column. They used the reaction of ethanol and acetic acid esterification to form ethyl acetate as the system and carried out the steady and dynamic simulation. They found that the reactive dividing wall column could achieve the set point value in both temperature control loops. The implementation, start up and operation of a dividing wall distillation column to carry out the production of ethyl acetate were reported in the paper by DelgadoDelgado et al. [48]. The results predicted by simulation are in agreement with the data registered during the experimental tests and corroborated by gas chromatography. These results validate previous process simulation studies about design and control of these systems. Production of high-purity ethyl acetate is studied using reactive distillation in the work by Tavan and Hosseini [49]. A new configuration of a RD process is proposed dividing a single RD column into two separate columns namely, RD and rectifier. Impacts of three parameters, including reactant flow rate, reaction trays, and feedinlet location on the temperature profile and component compositions in the columns are investigated to achieve an optimum condition of the process in terms of energy demand. The simulation results show that ratio of reactants near the stoichiometric values with a small amount of ethanol lead to the industrial specification output results. Additionally, it is found that with increasing the reaction stage number, the residence time, and the reaction conversion increase. An assessment of different intensified processes for ethyl acetate production by direct esterification was performed by Santaella et al. [50]. After the selection and validation of the adequate thermodynamic and kinetic models, a comparison among different reported processing technologies (i.e., conventional, reactive distillation,

46

3 Bioethanol

reactive distillation with pressure swing, dividing wall column with reactive reboiler), and a novel proposed configuration using a reactive dividing wall column was carried out (Fig. 3.9). Specifications of raw materials and products used as constrains during simulations were defined according with market requirements. To perform a fair assessment among different alternatives, each process was optimized using a mixed strategy of sensitivity analysis coupled with sequential quadratic programming algorithm. Total annual cost was selected as the optimization variable. According with results, the reactive dividing Wall column configuration proposed ends up being the more energy efficient and cost effective (46% energy and 26% cost savings compared with the traditional process) and it is characterized by the best sustainability indicators. Xie et al. [51] used the heterogeneous catalysts—iron exchange resins— Amberlyst15 and proposed a novel catalyst loading method for the production f ethyl acetate using reactive distillation. Firstly, the reliability of the model of the simulation was verified by the experimental study on the change of liquid split ratio and reflux ratio. After that, the four-column model was established in Aspen Plus to analyze the effects of the amount of azeotropic agent, reflux ratio and acetic acid concentration. Finally, for a fair comparison, the economic analysis was conducted between traditional reactive distillation column and reactive distillation wall column. The results showed that reactive distillation wall column can save 34.7% of total operating costs and 18.5% of TAC. He et al. [52] explicates the preparation of ethyl acetate via esterification of acetic acid and ethanol over brønsted acid ionic liquid (1-Butyl-3-methylimidazolium hydrogen sulfate, [BMIM]HSO4 ) as catalyst. A novel reactive distillation flowsheet for ethyl acetate production using [BMIM]HSO4 was designed and performed by Aspen Plus. The optimal conditions of catalyst dosage, plate number, feed position, feed molar ratio, liquid holdup and reflux ratio for reactive distillation process were obtained by taking the ethyl acetate concentration in product stream as objective function and was found with maximum content of 90.44 wt.% with less than

Fig. 3.9 Proposed reactive dividing wall column configuration

References

47

3% deviation. Keeping the high yield, this approach can provide a feasible reactive distillation process design for ethyl acetate production using [BMIM]HSO4 as high-activity catalyst and can be envisaged as an alternative route for the industrial production of ethyl acetate.

3.6 Conclusions and Perspectives In this chapter it was presented a recompilation of information about bioethanol production. It is possible to see that bioethanol production has been increase developing new alternatives to make bioethanol competitive against gasoline. These new alternatives gives the possibility to obtain bioethanol with high purity and to achieve low cost. Moreover, it is important to continue in the research for more alternatives due to the extended varieties of raw materials that can be used to produce bioethanol. As we could see, is a need to have more development in this topic because according to the feedstock there is not just a single route for production. Every step included in bioethanol production represents different variable for research. Pre-teatment itself represents a huge opportunity area to improvement, as well fermentation in order to seek the best choices of microorganisms or enzymes according to the reaction rates and bioethanol conversion. In this case we focus the report into bioethanol extractive distillation from lignocellulosic biomass. For this case we try to summaries the efforts on research in order to enhance the bioethanol process production. Despite the advantages in intensification process, it is possible to see that conventional distillation process is still the most used technology on industrial level. To promote a stronger potential for its industrial implementation, it is necessary to understand property the operation and control properties of the intensified processes.

References 1. Z. Qiao, X. Lü, Chapter 10—Industrial bioethanol production: status and bottlenecks, in Advances in 2nd Generation of Bioethanol Production, ed. by X. Lü (Woodhead Publishing, Sawston, 2021), pp. 213–227 2. D. Rutz, R. Janssen, Biofuel Technology Handbook (2007) 3. L. Chen, K. Gao, C. Zhang, W. Lang, Alternative fuels for IC engines and jet engines and comparison of their gaseous and particulate matter emissions (Chapter 2), in Adv. ed. by A.K. Azad, M. Rasul (Woodhead Publishing, Biofuels, 2019), pp. 17–64 4. X. Wang, X. Lü, More than biofuels: use ethanol as chemical feedstock (Chapter 3), in Advances in 2nd Generation of Bioethanol Production, ed. by X. Lü (Woodhead Publishing, 2021), pp. 31–51 5. L.S. Khuong, N.W.M. Zulkifli, H.H. Masjuki, E.N. Mohamad, A. Arslan, M.H. Mosarof, A. Azham, A review on the effect of bioethanol dilution on the properties and performance of automotive lubricants in gasoline engines. RSC Adv. 6, 66847–66869 (2016) 6. A. Buši´c, N. Mardetko, S. Kundas, G. Morzak, H. Belskaya, M. Ivanˇci´c Šantek, D. Komes, S. Novak, B. Šantek, Bioethanol production from renewable raw materials and its separation and purification: a review. Food Technol. Biotechnol. 56, 289–311 (2018)

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7. R. Kaviani, Use bioethanol as a clean and cost-effective fuel. J. Eng. Indus. Res. 3, 147–152 (2022) 8. K.A. Subramanian, S.K. Singal, M. Saxena, S. Singhal, Utilization of liquid biofuels in automotive diesel engines: an Indian perspective. Biomass Bioener. 29, 65–72 (2005) 9. A.K. Azad, M.G. Rasul, M.M.K. Khan, S.C. Sharma, M.A. Hazrat, Prospect of biofuels as an alternative transport fuel in Australia. Renew. Sustain. Energy Rev. 43, 331–351 (2015) 10. S.A. Jambo, R. Abdulla, S.H. Mohd Azhar, H. Marbawi, J.A. Gansau, P. Ravindra, A review on third generation bioethanol feedstock. Renew. Sustain. Energy Rev. 65, 756–769 (2016) 11. C. De Blasio, Processes of bioethanol production, in Fundam. Fundamentals of Biofuels Engineering and Technology, ed. by C. De Blasio (Springer International Publishing, Cham, 2019), pp. 233–252 12. C.E. Wyman, B.E. Dale, R.T. Elander, M. Holtzapple, M.R. Ladisch, Y.Y. Lee, Coordinated development of leading biomass pretreatment technologies. Bioresour. Technol. 96, 1959–1966 (2005) 13. A.W. Bhutto, K. Qureshi, K. Harijan, R. Abro, T. Abbas, A.A. Bazmi, S. Karim, G. Yu, Insight into progress in pre-treatment of lignocellulosic biomass. Energy 122, 724–745 (2017) 14. E. Ximenes, Y. Kim, N. Mosier, B. Dien, M. Ladisch, Inhibition of cellulases by phenols. Enzyme Microb. Technol. 46, 170–176 (2010) 15. P. Alvira, E. Tomás-Pejó, M. Ballesteros, M.J. Negro, Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review. Bioresour. Technol. 101, 4851–4861 (2010) 16. A.R. Mankar, A. Pandey, A. Modak, K.K. Pant, Pretreatment of lignocellulosic biomass: a review on recent advances. Bioresour. Technol. 334, 125235 (2021) 17. J.R. Melendez, B. Mátyás, S. Hena, D.A. Lowy, A. El Salous, Perspectives in the production of bioethanol: a review of sustainable methods, technologies, and bioprocesses. Renew. Sustain. Energy Rev. 160, 112260 (2022) 18. M.A. Kassim, T.K. Meng, R. Kamaludin, A.H. Hussain, N.A. Bukhari, Bioprocessing of sustainable renewable biomass for bioethanol production (Chapter 9), in Value-Chain Biofuels. ed. by S. Yusup, N.A. Rashidi (Elsevier, 2022), pp. 195–234 19. B. Erdei, B. Frankó, M. Galbe, G. Zacchi, Separate hydrolysis and co-fermentation for improved xylose utilization in integrated ethanol production from wheat meal and wheat straw. Biotechnol. Biofuels. 5, 12 (2012) 20. D.G. Olson, J.E. McBride, A. Joe Shaw, L.R. Lynd, Recent progress in consolidated bioprocessing. Curr. Opin. Biotechnol. 23, 396–405 (2012) 21. R. Koppram, F. Nielsen, E. Albers, A. Lambert, S. Wännström, L. Welin, G. Zacchi, L. Olsson, Simultaneous saccharification and co-fermentation for bioethanol production using corncobs at lab, PDU and demo scales. Biotechnol. Biofuels. 6, 2 (2013) 22. Z. Szitkai, Z. Lelkes, E. Rev, Z. Fonyo, Optimization of hybrid ethanol dehydration systems. Chem. Eng. Process. Process Intensif. 41, 631–646 (2002) 23. C.E. Torres-Ortega, C. Ramírez-Márquez, E. Sánchez-Ramírez, J.J. Quiroz-Ramírez, J.G. Segovia-Hernandez, B.-G. Rong, Effects of intensification on process features and control properties of lignocellulosic bioethanol separation and dehydration systems. Chem. Eng. Process. Process Intensif. 128, 188–198 (2018) 24. M. Errico, B.-G. Rong, Synthesis of new separation processes for bioethanol production by extractive distillation. Sep. Purif. Technol. 96, 58–67 (2012) 25. J.G. Segovia-Hernández, E. Sánchez-Ramírez, C. Ramírez-Márquez, G. Contreras-Zarazúa, Bioethanol (Chapter 4), in Improvements in Bio-Based Building Blocks Production Through Process Intensification and Sustainability Concepts. ed. by J.G. Segovia-Hernández, E. Sánchez-Ramírez, C. Ramírez-Márquez, G. Contreras-Zarazúa (Elsevier, Amsterdam, 2022), pp. 33–60 26. M. Amine, E.N. Awad, V. Ibrahim, Y. Barakat, Effect of ethyl acetate addition on phase stability, octane number and volatility criteria of ethanol-gasoline blends. Egypt. J. Petrol. 27, 567–572 (2018)

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27. E.Y. Kenig, H. Bäder, A. Górak, B. Beßling, T. Adrian, H. Schoenmakers, Investigation of ethyl acetate reactive distillation process. Chem. Eng. Sci. 56, 6185–6193 (2001) 28. S.-J. Kim, S.-M. Jung, Y.-C. Park, K. Park, Lipase catalyzed transesterification of soybean oil using ethyl acetate, an alternative acyl acceptor. Biotechnol. Bioproces. Eng. 12, 441–445 (2007) 29. M.K. Modi, J. Reddy, B. Rao, R. Prasad, Lipase-mediated conversion of vegetable oils into biodiesel using ethyl acetate as acyl acceptor. Bioresour. Technol. 98, 1260–1264 (2007) 30. S. Uthoff, D. Bröker, A. Steinbüchel, Current state and perspectives of producing biodiesel-like compounds by biotechnology. Biotechnol. Appl. Microbiol. 2, 551–565 (2009) 31. A. Röttig, L. Wenning, D. Bröker, A. Steinbüchel, Fatty acid alkyl esters: perspectives for production of alternative biofuels. Appl. Microbiol. Biotechnol. 85, 1713–1733 32. S.-C.J. Hwang, C.-M. Lee, H.-C. Lee, H. Pua, Biofiltration of waste gases containing both ethyl acetate and toluene using different combinations of bacterial cultures. J. Biotechnol. 105, 83–94 (2003) 33. C. Löser, T. Urit, T. Bley, Perspectives for the biotechnological production of ethyl acetate by yeasts. Appl. Microbiol. Biotechnol. 98, 5397–5415 (2014) 34. R. Srinivasan, N.T.J.P.S. Nhan, A statistical approach for evaluating inherent benign-ness of chemical process routes in early design stages. Process Saf. Environ. Protect. 86, 163–174 (2008) 35. N.T. Hong Thuy, Y. Kikuchi, H. Sugiyama, M. Noda, M Hirao, Techno-economic and environmental assessment of bioethanol-based chemical process: a case study on ethyl acetate. Environ. Prog. Sustain. Energy . 30, 675–684 (2011) 36. P. Seferlis, J Grievink, Optimal design and sensitivity analysis of reactive distillation units using collocation models. Ind. Eng. Chem. Res. 40, 1673–1685 (2001) 37. A. Orjuela, A.J. Yanez, A. Santhanakrishnan, C.T. Lira, D. Miller, Kinetics of mixed succinic acid/acetic acid esterification with Amberlyst 70 ion exchange resin as catalyst. Chem. Eng. J. 188, 98–107 (2012) 38. L.S. Balasubramhanya, F. Doyle, Nonlinear model-based control of a batch reactive distillation column. IFAC Proc. Vol. 10, 209–218 (2000) 39. K. Alejski, F. Duprat, Dynamic simulation of the multicomponent reactive distillation. Chem. Eng. Sci. 51, 4237–4252 (1996) 40. J.M. Smith, Chemical engineering kinetics3d ed., McGraw-Hill, New York, (1981) 41. I.-K. Lai, Y.-C. Liu, C.-C. Yu, M.-J. Lee, H.-P. Huang, Production of high-purity ethyl acetate using reactive distillation: experimental and start-up procedure. Chem. Eng. Process. Process Intensif. 47, 1831–1843 (2008) 42. H. Tian, H. Zheng, Z. Huang, T. Qiu, Y. Wu, Novel procedure for coproduction of ethyl acetate and n-butyl acetate by reactive distillation. Ind. Eng. Chem. Res.51, 5535–5541 (2012) 43. H. Arnikar, T. Rao, A. Bodhe, A gas chromatographic study of the kinetics of the uncatalysed esterification of acetic acid by ethanol. J. Chromatogr. A. 47, 265–268 (1970) 44. K.S.J.J.W. SuSlick, S.N. York, Kirk-Othmer encyclopedia of chemical technology. J. Wiley 26, (1998) 517–541 45. F.O. Barroso-Muñoz, M.D. López-Ramírez, J.G. Díaz-Muñoz, S. Hernández, J.G. SegoviaHernández, H. Hernández-Escoto, R.H.C. Torres, Thermodynamic analysis and hydrodynamic behavior of a reactive dividing wall distillation column, in The 9th International Conference on Chemical & Process Engineering, Rome, Italy, 2009 46. S. Hernández, R. Sandoval-Vergara, F.O. Barroso-Muñoz, R. Murrieta-Dueñas, H. HernándezEscoto, J.G. Segovia-Hernández, V. Rico-Ramirez, Reactive dividing wall distillation columns: simulation and implementation in a pilot plant. Chem. Eng. Process. 48, 250–258 (2009) 47. R. Sandoval-Vergara, F.O. Barroso-Muñoz, H. Hernández-Escoto, J.G. Segovia-Hernández, S. Hernández, V. Rico-Ramírez, Implementation of a Reactive Dividing Wall Distillation Column in a Pilot Plant, Computer Aided Chemical Engineering (Elsevier, Amsterdam, 2008), pp. 229– 234 48. R. Delgado-Delgado, S. Hernández, F.O. Barroso-Muñoz, J.G. Segovia-Hernández, A. CastroMontoya, From simulation studies to experimental tests in a reactive dividing wall distillation column. Chem. Eng. Res. Des. 90, 855–862 (2012)

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Chapter 4

Biobutanol

Abstract Butanol is an organic chemical that is mostly employed as a solvent in a variety of industries. The growing need to mitigate the climatic effects of fossilbased compounds has fueled study into this compound’s potential as a biofuel. This chapter will go through the history of butanol as a biofuel, as well as the present demand for it and the whole biofuel production process. The traditional feedstocks for butanol production, the feedstock to butanol transformation process, and certain butanol purification techniques will all be reviewed. The implementation of process intensification measures that have resulted in enhanced yields in the two primary regions of the process, the reactive stage, and the separation section, will be emphasized. Finally, existing potential niches in the overall process will be addressed, allowing the renewable feedstock process to directly compete with the conventional process.

4.1 Biobutanol: Chemical Properties, Uses and Applications Butanol and its isomers have a four-carbon structure, which can be either linear or branched. Alcohol characteristics are affected by changes in the structural topology of molecules as well as the position of the functional group OH. Table 4.1 summarizes the physicochemical properties of butanol and its isomers in general [1]. The uses of the various isomers are comparable, according to Table 4.1. Furthermore, oil and biomass can be used to make all isomers. N-butanol, in particular, offers the finest properties for usage as a liquid fuel or as a fuel additive. Table 4.2 lists some of the most important features of gasoline, diesel, ethanol, and n-butanol [1, 2]. The Energy Information Administration (EIA) estimates that global energy consumption would grow by roughly 56% in 2040 compared to 2010. Shenbagamuthuraman et al. [3] found that gasoline and other liquid fuels are the most common energy sources for transportation, despite a minor decrease in total transportation energy consumption from 96% in 2012 to 88% in 2040. Countries like the United © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_4

51

52

4 Biobutanol

Table 4.1 Butanol Isomers, topology, and its uses Isomer

Main uses

1-butanol (n-butanol)

Paint thinners, plasticizers, hydraulic braking fluid, cosmetics, and gasoline additives are all examples of solvents

2-butanol

Paint remover, solvent, and domestic cleaning agent

Iso-butanol

Remove Ink component, Solvent and Additive, Gasoline Additive

Tert-butanol

Solvent, industrial solvent, MTBE, ETBE intermediate

Table 4.2 Properties of conventional fossil fuels and some alcohols Molecular formula

Gasoline

Diesel

Methanol

Ethanol

n-Butanol

C4 –C12

C12 –C25

CH3 OH

C2 H5 OH

C4 H9 OH

Molecular weight

111.19

198.4

32.04

46.06

74.11

Cetane number

0–10

40–55

99

> 99

Sum formula

6.1 Methyl-Ethyl Ketone: Chemical Properties, Uses and Applications

113

including MEK, are downstream products of crude oil, fluctuations in crude oil and its downstream derivatives can have a direct impact on market profitability. Crude prices have plummeted in recent years, significantly impacting overall revenues. Furthermore, according to data published by the US Energy Information Administration in 2016, decreased crude oil prices led in increasing stocks of the product, with net inventory growing to 1.72 million barrels per day [3]. MEK’s physicochemical properties are the focus of the primary regulations. MEK’s vapor, for example, is heavier than air and soluble in water and other organic solvents. They can form explosive mixes with oxygen when their concentrations are between 1.4 and 11% (or air). It has the ability to spread across vast distances and hence has the potential to ignite from afar [4]. In terms of human toxicity, the quantity of MEK at which no harmful effects are seen (threshold limit value) has been stated to be 200 ppm in 8 h and up to 300 ppm for short exposures of 15 min. When exposed to 220 ppm MEK for 4 h, 143 participants felt headache, sore throat, nausea, and overall discomfort, according to a study published by the Center for Occupational Health and Safety. MEK’s neurotoxic effects, on the other hand, have been thoroughly researched [5, 6]. Methyl Ethyl Ketone can be created in two ways: a synthetic approach derived from compounds obtained during oil refining, and a natural process involving microorganisms and renewable raw resources. Both options will be discussed further down. Paints and coatings emerged as the most popular application segment, with a CAGR of 4.4% predicted from 2016 to 2024. Increased construction spending, combined with the rapid growth of the vehicle sector in Asia Pacific and the Middle East, has resulted in increased demand for paints and coatings. Specialty, aqueous, powder, and solvent-borne coatings are among the paints and coatings available. The high demand for powder coatings in the automotive and electronics industries has boosted product consumption in this application segment dramatically. From 2016 to 2024, the adhesives and printing ink industries are predicted to develop significantly [3]. The packaging and publishing industries’ growing demand for printing inks is projected to increase the MEK market in this area. Because of its features, such as quick drying and greater adhesion with surfaces including metals, plastics, and glass, the product is widely utilized and is a preferred solvent in the printing business. Over the next six years, developments in end-user industries such as pharmaceuticals, food processing, and cosmetics are predicted to drive volumes in printing inks application. High-resolution printing is possible with MEK solvent-based inks used in these industries. Newspapers, labels, commercial printing, and books are some of the other important uses for printing inks [3]. In 2015, Asia Pacific led the worldwide industry, accounting for over 55% of global demand. High demand from the printing inks sector in rising countries such as China, India, Indonesia, and Thailand is driving regional volumes. Due to rising demand for adhesives and printing inks from residential and commercial building constructions, the area is likely to maintain its dominance over the forecast period. Furthermore, rising urbanization, particularly in China and India, is expected to have a beneficial impact on the adhesives sector in APAC, pushing the regional market.

114

6 Methyl-Ethyl Ketone

Over the projection period, the Middle East and Africa market is expected to grow at a substantial CAGR of 4.4%. The construction industry’s rapid rise in the Gulf countries, such as the United Arab Emirates, Saudi Arabia, Qatar, and others, is expected to drive product demand over the forecast period. Furthermore, the region’s industrialization is said to be driving market expansion [3]. Manufacturers are either engaged in raw material production or consume the end product, therefore the global is concentrated in nature and demonstrates a high degree of integration across the value chain. This enables them to achieve economies of scale and expand their business in order to increase earnings. ExxonMobil, Maruzen Petrochemicals, Shell Chemicals, Arkema S.A, Sasol Solvents, and Petro China are among the major producers. In their production plant in Japan, Maruzen Petrochemicals implemented a new distillation technology dubbed SUPERHIDIC to save around 40% of energy use and produce a cost-effective product. The final products are either distributed by major manufacturers through their own distribution channels or outsourced to independent providers. Xilan Chemicals, Sigma-Aldrich, SherwinWilliams, Wicks Aircraft Supply, and LP Chemicals are some of the major suppliers in the value chain. Because the market is price sensitive, product differentiation is expected to be the most important business strategy for beating the competition and gaining a competitive edge [3].

6.2 Overall Process for MEK Production 1,3-Butadiene is a probable intermediate chemical for hydrocarbon processing (1,3BD). 2,3-BD is made by fermenting industrial waste from the steel and biomass sectors, such as molasses, cereal mash, starch, wheat, sulfite liquor, and maize starch, with a range of microbes including Aerobacter aerogenes. However, the petrochemical method has proven to be the most prevalent and economically viable option thus far. As demonstrated in Fig. 6.1, steam cracking is commonly employed to create 1,3-BD. BD is a by-product of the steam cracking process used to make ethylene. The equivalent feedstocks (C2–C4, naphtha, and oil) are cracked at around 850 °C. Hydrogen, ethylene, propylene, butadiene, and olefin are produced in a steam-cracking furnace and then passed through a quencher, compressor, and dryer. During this process, the hydrocarbons with more than four carbons (C-5 and higher components) are removed, and the 1,3-BD is refined by extractive distillation. One or two extractive distillations are commonly used to remove the C4 raffinates and vinyl acetylene. The main stream then generates the BD to extract the methyl acetylene using a fractionator [7].

Fig. 6.1 Conventional process to manufacture 1,3-BD

6.2 Overall Process for MEK Production

115

Fig. 6.2 Conventional process to manufacture MEK

Butylene hydration, synthesis of secondary butyl alcohol (SBA), and dehydration of SBA are presented in Fig. 6.2 as a commercial technique to producing MEK. Butylene is made from petroleum cracking on a large scale. SBA can be made via acid-catalyzed hydration of 1-butene and 2-butene. At roughly 250 °C, a 75% solution of H2 SO4 is used in the hydration process; specifically, 1-butene/2-butene is reacted in a reactor and then transported to a distillation column to separate the non-reactants from 2-butanol. In addition, the SBA is moved to a distillation column that is intermittent. The dehydrated SBA is dehydrated, and the MEK is produced [8]. As already stated, traditional MEK production entails potentially hazardous operational circumstances. Furthermore, due to the nature of the process, there is an obvious reliance on petroleum derivatives. Beyond generating a conceivable product, there is an unhealthy dependence on oil and the consequences of its use from an environmental standpoint.

6.2.1 Overall Process for MEK Production Because it can create 2,3-BD (2,3-Butanediol) at a high concentration, 2,3-BD synthesis is an appealing microbial fermentation [9, 10]. Pyruvate can be converted to 2,3-BD by a variety of microorganisms. Jansen et al. [11] used Klebsiella oxytoca ATCC 8724 to ferment media containing 50 g/L of xylose in a 7 L batch fermenter and produced a butanediol concentration of 12.63 g/L. When different xylose concentrations ranging from 5 to 150 g/L were utilized, a maximum butanediol productivity of 1.35 g/L/h was attained with a starting xylose concentration of 100 g/L. Using K. oxytoca ATCC 8724, Qureshi and Cheryan [12] obtained a butanediol yield of 0.5 g/g of glucose and a maximum butanediol concentration of 84.2 g/L. The concentration of butanediol achieved in two-step feed batch fermentation was 85.5 g/L [13]. Under batch fermentation conditions, a final butanediol concentration of 95.5 g/L was obtained with a yield and productivity of 0.48 g/g of glucose and 1.71 g/L/h utilizing K. oxytoca ME-UD-3 and a two-stage agitation speed control technique. In the late log phase/stationary phase of fermentation, 2,3-BD is synthesized. 3 Dehydration over an acid catalyst can further convert 2,3-BD generated by microbial fermentation to MEK. Tran and Chambers, for example, have already proposed a hybrid method [14]. The chemistry of diol dehydration to a number of compounds has been thoroughly investigated and reviewed [15–17]. There are fewer studies explicitly looking at 2,3-BD. Tran and Chambers investigated the dehydration of fermentative 2,3-BD over alumina and silica alumina catalysts containing sulfonic acid. High conversion and selectivity were reported by these researchers, but they

116

6 Methyl-Ethyl Ketone

also noted catalyst deactivation, which they attributed to the loss of sulfonic acid groups. Emerson and colleagues utilized sulfuric acid to dehydrate 2,3-BD to MEK in a few studies and fermentation broth in others. Emerson et al. [17] found that MEK could be made from fermentation broth, but that the reaction rate was much slower. Dehydration is the direct route to MEK after 2,3-BD has been produced. Figure 6.3 depicts the reaction pathways of 2,3-BD dehydration to an amorphous calcium phosphate (a-CP) catalyst [8]. The major MEK product IS produced by 2,3-BD dehydration, whereas 2-Methylpropanal and 3-Buten-2-ol are by-products. The first mechanism demonstrates a common rearrangement, which is the translation of a 1,3-hydride to MEK or a 1,3-methyl to 2-MPA. The second process describes a sequential 1,2elimination of H2 O containing 3B2 OL (3-Buten-2-ol). BD is formed after another dehydration.

Fig. 6.3 2,3-BD dehydration process; solid line for main reaction and dashed lines for minor reactions

6.2 Overall Process for MEK Production

117

The majority of 2,3-BD dehydration research focuses on dehydration catalyst conduction or reaction circumstances that provide high yields of the desired products, such as BD, MEK, and 3B2OL, using a specific catalyst [8, 18, 19]. Makshina et al. [20] examined research on 2,3-BD dehydration to 1.3-BD (1,3butanediol) and MEK using various catalysts, whereas [21] detailed research on 1,3-BD using biuma-derived C4 alcohols, including butanediol dehydration to nonsaturated alcohols [21]. The dehydration of 2,3-BD to 1,3-BD and MEK has been studied since the 1940s. Bourns and Nicholls [30], metal and earth oxides [22– 24], zeolites [25–27], sulfonic acid group perfluorinated resin [26], heteropolyacids. Molnár et al. [25] using SiO2 supported in CsH2 PO4 , these researchers were able to achieve a better selectivity of 1.3-BD (> 90%) [28]. The majority of the techniques, such as 1,3-BD, MEK, and 3B2 OL, are centered on catalytic dehydration or reaction conditions that produce large yields.

6.2.1.1

Kinetic Equations to Produce MEK

Following are the reactions that determine the primary pathway of 2,3-BD dehydration: r1

C4 H10 O2 → C4 H8 O + H2 (2,3-BDO) (3B2OL)

(6.1)

r2

C4 H8 O → C4 H6 + H2 O (3B2OL) (1,3-BD)

(6.2)

r3

C4 H10 O2 → C4 H8 O + H2 O (2,3-BDO) (MEK)

(6.3)

r4

C4 H10 O2 → C4 H8O + H2 O (2,3-BDO) (2MPL)

(6.4)

Due to the fact that it is a power-law reaction, the kinetic reaction can be simplified as follows:    1 −E i 1 (6.5) − ki = k Tr e f,i exp R T Tr e f Table 6.2 shows the approximate power-law characteristics for the kinect system. This kinetic data set was utilized to gain a better understanding of the kinetics of MEK generation from 2,3-BD in both standard and enhanced production schemes. In the lines that follow, both scenarios will be discussed. The knowledge gained about the kinetics of MEK synthesis is an enormously essential factor in the intensification of methods for MEK manufacturing. Figure 6.6 depicts a hypothetical reaction network including the a-CP catalyst, based on experimental findings. The

118 Table 6.2 Estimated kinetic parameters of the power-law model [8]

6 Methyl-Ethyl Ketone Model parameter

Value

E1 (J/mol)

2.33E+05

E2 (J/mol)

2.82E+05

E3 (J/mol)

1.93E+05

E4 (J/mol)

1.66E+05

KTref,1 (mol(1−n1) m3(n1−1) s−1 )

7.45E−04

(mol(1−n1) m3(n1−1) s−1 )

4.41E−04

kTref,3 (mol(1−n1) m3(n1−1) s−1 )

6.64E−04

kTref,4 (mol(1−n1) m3(n1−1) s−1 )

1.27E−04

n1 , n3 , n4

1.87E−02

n2

1.46E−01

kTref,2

suggested reaction network is built on a theoretical foundation [18]. The primary products of 2,3-BD dehydration can be depicted as a collection of two parallel paths (1,3-BD, MEK, 3B2OL, 2MPN). The first is a traditional rearrangement mechanism that involves a 1,3-hydride shift that leads to MEK or a 1,2-methyl shift that leads to 2MPN. The second path involves successive 1,2-removal of water, which results in the synthesis of 3B2OL after the first dehydration and 1,3-BD after the second [29]. Because the total amount of minor butene isomers and heavy compounds classified as impurities in all trials is less than 0.3 wt%, and the kinetic model is considerably simplified by ignoring impurities, impurities are not included in the reaction products of this analysis.

6.2.2 Process Intensification Applied to MEK Production Direct fermentation can create MEK, although with a yield of around 0.004 gMEK/gglucose, it performs poorly [5]. Intermediate with 2,3-butanediol is a possible alternative to MEK (2,3-BD). Surprisingly, on this path, the output of 2,3-BD via fermentation is close to the theoretical limit of 0.5 g2,3-BD/gglucose [21, 30]. Song et al. [31] suggested an alternative to the creation and purification of MEK from 2,3-BD in an intriguing review. They proposed a reactor-based development scheme, followed by a series of separation columns and decanters, totaling 10 separation units and a reactor in their concept (see Fig. 6.4). The majority of separation devices are distillation columns. Table 6.3 shows the general characteristics of the design in Fig. 6.4, as stated by Song et al. [31]. An alternative to enhancing a system is to intensify the process (PI). Reduced equipment size, enhanced process performance, reduced stock of equipment, reduced utility and raw material usage, and increased process equipment efficiency are the

6.2 Overall Process for MEK Production

119

Fig. 6.4 Production of MEK in a two-step process by Song et al. [31]

Table 6.3 General parameters of process route of Fig. 6.7 Description

V100 V200 V300 V301 V302 V400 V500 V501

V502

Number of stages

5

5

20

80

56

10

30

62

16

Pressure (kg/sqcmg)

1.4

3.9

3.5

3.8

3.5

1.5

1.1

−0.35 −0.3

Feed temperature (°C)

180

90

38.5

38

44.4

42.2

56.9

106

72.2

85

Overhead temperature (°C) 51

38

40.6

42.1

40.8

94.1

52.8

69

Bottom temperature (°C)

80

128

138

44.4

44.1

131.1 106

72.2

175

Heat duty (MMKcal/h)

–

–

0.76

2.16

0.93

1.72

2.67

0.65

2.25

five qualities that constitute PI [26]. This technique has been effectively established in various circumstances where chemical reactions involve, for example, reactive distillation, in which even the reactor works as a separation mechanism, so the intensification of the processes allows conversion and phase balance limits to be abolished. The effects of RD have been documented in a variety of ways and in distinct case studies. Souza et al. [32], for example, found that the purity of triacetin produced using this approach was significantly higher than that achieved using the old method. When processing methyl acetate, Pöpken et al. [33] observed a reduction in energy consumption, enhanced selectivity, and conversion. Capital cost and energy cost savings of up to 20% have been claimed in some circumstances when reactive distillation has been used [34]. The use of reactive distillation in biofuel production has not been ruled out, but it is primarily for the creation of biodiesel. For example, Kiss et al. [35] proposed manufacturing biodiesel with

120

6 Methyl-Ethyl Ketone

numerous heterogeneous catalysts (niobic acid, sulfated zirconia, sulfated titania, and sulfate tin oxide). The usage of the RD enhanced response time, increased efficiency, and reduced the size of the equipment, resulting in cheaper capital expenditures. Other authors [36, 37] showed improvements in productivity and cost of production for biodiesel production. RD is very desirable in systems where some chemical and phase conditions coexist [38]. It is critical, according to Shah et al. [39], to assess the viability of such a procedure before making a formal proposal for reactive distillation. In this case, the analysis should be accompanied by recommendations that all of these criteria be met, highlighting (i) the presence of more than one element, (ii) the existence of a correlation between the reaction and temperature separation, (iii) operating pressure and temperature are not near the critical area of the components in question, and (iv) component volatility. Using a 1000 kg/h 2,3-BD feed stream as a starting point Based on the previous study published by Song et al. [31], Torres-Vinces et al. [40] proposed an intensified alternative to create MEK (see Fig. 6.6). The number of decanters evaluated by Song et al. [31], which results in many waste streams, is reasonable in the reference situation of Fig. 6.7. The reason for this design is that purifying the system is thermodynamically difficult. There are four azeotropic components: three heterogeneous components between 1,3-BD and H2 O, MEK-H2 O and 2MPL-H2 O, and one homogeneous component between 3B2OL and H2 O (see Fig. 6.5). Because this method requires a lot of energy, traditional columns aren’t usually the best option for azeotropic separations.

Fig. 6.5 Quaternary maps (mole basis) of the components coming from reactive distillation

Fig. 6.6 Novel intensified proposals for MEK production

6.2 Overall Process for MEK Production 121

Fig. 6.7 Pure distillation alternatives for MEK purification: scheme S1, scheme S2, scheme S3, and scheme S4

122 6 Methyl-Ethyl Ketone

6.2 Overall Process for MEK Production

123

Two intensified alternatives were provided as a result of their research. A reactive distillation column and an extractive distillation column served as the foundation for both amplified alternatives. Following an extensive investigation and many simulators testing, glycerol was determined to be the ideal solvent for use in the extractive distillation column. Because 99.5% wt is the lowest purity to be considered as fuel, both enhanced alternatives achieve a recovery constraint of at least 98% wt for all components and a purity constraint of 99.5% wt for MEK, 99% wt for 3-Buten-2-ol, 99% wt for 2MPL, 99% for 1,3-butadiene, and 99.99% for glycerol (26.2% for MEK). The sole topological difference between the two suggestions is that in scheme A, purification occurs directly after the extractive distillation column, whereas in plan B, it occurs after the extractive distillation column. To assess all options, the initial efficiency metric was energy usage. The main goal of these operations is to calculate the amount of energy expended in MJ/KgMEK units. Furthermore, because MEK will be utilized in spark-ignition motors, a comparison of the amount of energy expended and produced for MEK ignition would be fascinating. The second and third efficiency indices were the eco-indicator 99 (EI99) and CO2 emissions. As a result, Tables 6.4 and 6.5 indicate the primary design parameters for those two intensified options. For MEK, the RD column had a 99.86% conversion rate and a 44% selectivity. The effluent from the reactor was purified using an extractive distillation column and three standard columns (in both direct and indirect arrangement after extractive column). After evaluating the direct strategy, the most promising energy demand was 2790 kcal/kgMEK (11.6 MJ/kgMEK) (Scheme A). Scheme A reported 7.07 tonCO2 /h in terms of greenhouse gas emissions’ environmental impact. Although this technique can be thought of as an intensified MEK production scheme, it can also be thought of as an intensified MEK production and separation scheme. It should be noted that a reactive distillation column is employed in the production process, as well as enhanced technology for the separation of the effluent that results from it, Table 6.4 Design parameters for intensified alternative A RD

ED

C1

C2

C3

Number of stages

80

50

80

46

30

Reactive stages

10–80

–

–

–

–

Solvent (kg h−1 )

–

400

–

–

–

Reflux ratio

2.95

0.5

5.488

4.712

0.039

Feed stage

76

5, 46

23

25

14

Operative pressure (kPa)

101.353

101.353

101.353

101.353

101.353

Distillate flowrate (kg h−1 )

999

770

270

437.6

230

Reboiler duty (kcal h−1 )

485,962

130,535

184,390

256,145

161,765

CO2 emissions (ton

h−1 )

Eco-Ind (points year−1 )

7.07 1.825E+06

124

6 Methyl-Ethyl Ketone

Table 6.5 Design parameters for intensified alternative B Number of stages

RD

EC

C1

C2

C3

80

50

56

50

30

Reactive stages

10–80

–

–

–

–

Solvent (kg h−1 )

–

400

–

–

–

Reflux ratio

2.95

0.5

14.1

7.01

0.039

Feed stage

76

5, 46

5

5

23

Operative pressure (kPa)

101.353

101.353

101.353

101.353

101.353

Distillate flowrate (kg h−1 )

999

770

706.65

270.65

230

485,962

130,535

1,130,280

229,264

161,765

Reboiler duty (kcal

h−1 )

CO2 emissions (ton h−1 ) Eco-Ind (points year−1 )

13.42 4.75E+06

an extractive distillation column. Separation schemes for purifying the effluent from the 2,3-BD dehydration process will be explored in the following section.

6.3 MEK Purification Using an Intensive Separation Process Despite relatively good yields for 2,3-BD fermentation and subsequent dehydration, the downstream process has yet to be thoroughly investigated. Furthermore, byproducts such as isobutyraldehyde (2MPL) and 2,3-BD, both of which have considerable participation in the food sector and biosynthesis of isobutanol, are valuable products that may boost the value of the bio-based refinery for the production of MEK [41]. 2,3-BD can be used in a variety of ways. It can be used as an intermediary in the manufacturing of rubber, for example. Because of its low freezing point, it can be utilized as an antifreeze component. 2,3-BD has also shown promise in the production of fumigants, fragrances and inks, explosives, and suppressants. Isobutyraldehyde (2MPL), on the other hand, is employed as a component in the production of perfumes and tastes. It’s also utilized as a starting material for plasticizers, isobutyric acid, and isobutanol [42]. Despite the above-mentioned favorable thermodynamic features, MEK purification remains difficult due to the presence of two azeotropes in the MEK/2MPL/2,3-BD/Water mixture (see Fig. 6.5). Because of the oil-based approach utilized to create MEK, ideas that adequately assess a MEK/IBA/2,3-BD/water mixture are rare. Although certain approaches to MEK purification are known, the purification method does not cover the mixture purified in this study. Furthermore, in the quaternary mixture, they are mixtures that are not thermodynamically complex. Smetana et al. [43], for example, used a membrane method to purify MEK-water; on the other hand, Lloyd [44] patented a

6.3 MEK Purification Using an Intensive Separation Process

125

purification process for the MEK-Ethyl acetate blend. Murphy [45] took a similar technique to this combination. Penner et al. [46] recently provided the conceptual design of four solutions for purifying the MEK/2MPL/2,3-BD/Water combination, but it is based on the complete idea on distillation columns and decanters. It does not, however, imply a rigorous design strategy based on consistent target functions and recovery and purity restrictions. Distillation is, as always, the primary choice for this tough separation. Sánchez-Ramírez et al. [47] proposed an improved method for MEK purification in a recent study. The overall ratio is 65% MEK, 18$ wt, 10% wt, 3% wt, and 7% wt (see Table 6.6), which is a fairly normal dehydration reactor outflow [14, 48] (Fig. 6.7). Sánchez-Ramírez et al. [47] propose an intensified hybrid approach that starts with a liquid–liquid extraction column and uses p-xylene as the solvent. The usage of this liquid–liquid extraction column aids in the separation of azeotropes created by different substances in the feed stream. Intensified processes can be seen in hybrid systems. Hybrid technologies that combine liquid–liquid extraction and distillation columns have been shown to reduce worldwide downstream energy usage. The fact that the liquid–liquid extraction (LLE) column helps to break down the thermodynamic connections between the components and so reduces the energy required is the fundamental rationale for the reduction in energy requirements. The alternatives in Figs. 6.7 and 6.8 were tested using various performance metrics to determine the improvement that can be obtained with the enhanced plan. Four objective functions were examined together and in early design stages in a multiobjective optimization framework: total annual cost (TAC), eco-indicator 99 (EI99), intrinsic process safety (IR), and condition number as an indicator of process controllability. The major goal was to reduce the size of all four objective functions as Table 6.6 Design parameters and performance indexes for the intensified scheme LLE 10

Number of stages Reflux ratio

C2

C3

C4

C5

33

45

45

54

3.483

0.529

16.636

5.01

Feed stage

1, 10

4

27

5

23

Column diameter (m)

1.455

1.285

1.407

1.544

1.098

101.353

101.353

101.353

101.353

101.353

Operative pressure (kPa) Distillate flowrate (kmol

h−1 )

111.997

123.297

19.193

12.9292

Condenser duty (kW)

5776

1693

3191

694

Reboiler duty (kW)

6354

4125

3202

727

η (%)

32.56

TAC ($ year−1 )

7,903,251

Eco-Ind (points year−1 )

1,338,593

Condition number

88,121

IR (Probability year−1 )

0.0014087

126

6 Methyl-Ethyl Ketone

Fig. 6.8 Intensified alternatives for the MEK purification

much as possible. This study uses a hybrid stochastic optimization technique called Differential Evolution with Tabu List to optimize the scenario in question (DETL). Sánchez-Ramírez et al. [47] found that the majority of the methods provided in Fig. 6.9 were not feasible. That example, only scheme S2 of the four schemes examined in Fig. 6.9 is capable of producing designs with high purities and recoveries. On the surface, the schemes appear to be similar; yet the placement of decanters makes a significant difference. When there are three phases, the decanter’s job is to help separate them. The decanter, however, is not always capable of entirely separating these three phases due to the component’s ratio. As shown in Fig. 6.9, we use the mixture as an example to purify MEK before entering the decanter. In the quaternary diagram, the mixture of scheme S2 is the closest to the binary mixture MEK-WATER (binary ax MEK-water). That is to say, column C1 is crucial in the separation of the mix. The schemes S1, S3, and S4 try to remove as much water as possible from the azeotropic zone and send it to the bottom of the column, whereas the S2 sends only 2,3-BD. Figure 6.9 depicts the difference between schemes S1, S3, and S4 and why high recoveries are impossible to achieve, while Fig. 6.8 depicts a complete mass balance for the most promising design. It was feasible to find the design parameters that allow minimizing the goal functions after analyzing the low feasibility of traditional schemes using the Pareto fronts analysis. Tables 6.6 and 6.7 lists the primary design factors as well as the objective functions. Following the optimization procedure, all separation systems produced quite intriguing results. The most promising method, an LLE-based hybrid technique, was the sole means to rejuvenate and purify the entire food mix. In comparison to pure and non-energy-sustainable distillation systems, the hybrid technique boosts energy use, energy advantage, and thermodynamic performance. Furthermore, significant

6.3 MEK Purification Using an Intensive Separation Process

127

Fig. 6.9 Sensitivity analysis for C1 and first decanter in schemes S1, S3 and S4

Table 6.7 Objective function for pure distillation schemes TAC ($

year−1 )

S1

S2

S3

S4

104,719,750

31,011,553 153,136,510 4,435,273

Hybrid-intensified 7,903,251

Eco-Ind (points 2,993,581,413 14,669,116 16,200,579 year−1 )

891,801,275 1,338,593

Condition number

3.8

3.99

4.78

147.5

88,121

IR (probability year−1 )

0.00167156

0.0013323

0.00133414

0.00166587

0.0014087

energy savings were obtained, as evidenced by TAC, EI99, and IR efficiency metrics. The percentage of modifications to the other systems in relation to the intensified system is difficult to determine due to the qualitative nature of the condition number. However, it is clear that there is sufficient motivation to build a stable control mechanism for the enhanced system that is both cost-effective and environmentally friendly. Furthermore, the current relationship between several design possibilities and objective functions, such as the reflux ratio and heat responsibilities, may be known. This meant that existing economic, environmental, controllability, and security objectives might be satisfied by utilizing zone inclinations and possibilities to develop separation options.

128

6 Methyl-Ethyl Ketone

6.4 Conclusion and Perspectives Several increased MEK production alternatives were demonstrated throughout this chapter. Given the nature of the 2,3-BD MEK production process, numerous process intensification techniques can be used in both the reaction and separation zones. In the reaction section, the use of a reactive distillation column resulted in a significant reduction in energy usage as compared to the standard manufacturing option. Improvements in numerous indicators were obtained when only the separation section was approximated using an intensified hybrid approach. Total yearly cost, eco-indicator 99, intrinsic safety, and condition number, cost, environmental impact, safety, and controllability indicators, all improved significantly with the intensified system. Currently, the process of producing MEK from petroleum derivatives is the most extensively employed. The manufacture of 2,3-BD, on the other hand, is necessary in order to establish a production process from renewable raw materials. In other words, the fermentation process that produces 2,3-BD is the limiting factor for MEK generation from biomass. It’s apparent that MEK production will skyrocket once this fermentation technique becomes more productive. On the other hand, the catalytic process involved in the dehydrogenation of 2,3BD to MEK is a key factor to improve. Although the use of a reactive distillation column improves yields significantly, research into various catalytic methods can result in even better yields and conversions to MEK.

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Chapter 7

Biojet

Abstract In recent years, the production and consumption of fossil jet fuel have increased as a consequence of a rise in the number of passengers and goods transported by air. In an economic context still dependent on scarce oil, this represents a problem as well as the inherent environmental impact throughout the life cycle of this fuel. Given this, a promising solution is the use of biojet fuel as renewable aviation fuel. In a framework of circular economy, the use of lignocellulosic biomass in the form of sugar-rich crop residues allows the production of alcohols necessary to obtain biojet fuel. Besides, the tools provided by process intensification make it possible to design a sustainable process with low environmental impact and capable to achieve energy savings. The goal of this work was to design an intensified process to produce biojet fuel from Mexican lignocellulosic biomass having alcohols as intermediates.

7.1 Biojet: Chemical Properties, Uses and Applications Biojet fuel has become a key element in the aviation industry’s strategy to reduce operating costs and environmental impacts. This jet fuel must meet ASTM International specifications and potentially be a 100% drop-in replacement for current petroleum jet fuel. The main challenges for the technology pathway are conceptual intensified process design, process economics, and life-cycle assessment of greenhouse gas emissions. Although the feedstock price and availability and energy intensity of the process are significant barriers, biomass-derived jet fuel has the potential to replace a significant portion of conventional jet fuel [1]. It is important to highlight those studies on the intensification of the biojet fuel production-purification process is an area little explored and with large areas of opportunity. Few studies have been reported to date. Dodecane is a product that has received increased commercial interest quite recently as a possible surrogate for kerosene-based fuels such as Jet-A, S-8, and other conventional aviation fuels. The possibility of using reactive distillation for dodecane production. Preliminary results suggested that that reactive distillation presents an excellent opportunity to produce dodecane. This means an opportunity © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_7

131

132

7 Biojet

to intensify intermediate zones in the biojet fuel production process and thus generate more sustainable and economical. Jet fuel is the most widely used fuel in the aviation sector, it is a kerosene-type fuel from petroleum intermediate distillate, suitable for most turbine-powered aircraft [2]. Jet fuel is made up of a mixture of hydrocarbons whose carbon number is between 8 and 16 carbons, belonging mostly to the class of paraffins and naphthenes, being the proportion of these hydrocarbons in the fuel what determines the properties of this [3]. Table 7.1 presents some of the hydrocarbons present in jet fuel. One of the main properties of jet fuel is its freezing point, which is −40 °C and plays a vital role in aircraft, since the fuel must remain fluid even at the low temperatures experienced during flight. On the other hand, the boiling point that goes from 205 to 300 °C is of great importance since the fuel is used as a hydraulic fluid in the engine control systems, absorbing the excess heat generated by combustion., so it must resist high temperatures without degrading [3]. As of 2008, the aviation industry has defined various mechanisms to mitigate climate change and reduce its environmental impact, with the use of sustainable aviation fuels being one of its main mechanisms. The term SAF is the main term used in the aviation industry to refer to sustainable aviation fuels, although terms such as alternative jet fuel, alternative sustainable fuel, renewable jet fuel or biofuel express the same meaning. Biofuel has practically the same physical and chemical properties as conventional jet fuel, and its use is currently supported up to 50% in mixture with conventional Table 7.1 Main hydrocarbons in jet fuel [3] Hydrocarbon

Formula

Hydrocarbon type

Boiling point (°C)

Freezing point (°C)

n-Octane

C8 H18

n-Paraffin

125.7

− 56.8

2-Metilheptano

C8 H18

Isoparaffin

117.6

− 109.0

1-Methyl-ethylcyclopentan

C8 H16

Naphthene

121.5

− 143.8

Ethylcyclohexane

C8 H16

Naphthene

131.8

− 111.3

o-Xylene

C8 H10

Aromatic

144.4

− 25.2

p-Xylene

C8 H10

Aromatic

138.4

+ 13.3

Cis-Decalin

C10 H18

Naphthene

195.8

− 43

Tetraline

C10 H12

Aromatic

207.6

− 35.8

Naphthalene

C10 H8

Aromatic

217.9

+ 80.3

n-Dodecane

C12 H26

n-Paraffin

216.3

− 9.6

2-Methylundecane

C12 H26

Isoparaffin

210.0

− 46.8

1-Ethylnaphthalene

C12 H12

Aromatic

258.3

− 13.8

n-Hexylbenzene

C12 H18

Aromatic

226.1

− 61.0

n-Hexadecane

C16 H34

n-Paraffin

286.9

+ 18.2

2-Methylpentadecane

C16 H34

Isoparaffin

281.6

− 7.0

n-Decylbenzene

C16 H26

Aromatic

297.9

− 14.4

7.1 Biojet: Chemical Properties, Uses and Applications Table 7.2 Specifications for the jet fuel/biofuel blend [4]

133

Property

Specification ASTM D7566-11

Total acidity (mg KOH/g)

0.1, máx

Aromatics (%vol.)

25, máx (8 mín)

Total sulphur (%peso)

0.3, máx

Distillation temperature 10% recovery (°C)

205, máx

20% recovery (°C)

–

50% recovery (°C)

− (15, mín)

90% recovery (°C)

− (40, mín)

Boiling endpoint (°C)

300, máx

Flash point (°C)

38, mín

Freezing point (°C)

− 47

Viscosity @ −20 °C (cSt)

8, máx

Net heat of combustion (MJ/kg)

42.8, mín

Density @ 15 °C

(kg/m3 )

775–840

jet fuel. Specifications such as the ASTM D7566-11 standard presented in Table 7.2 seek to confine the properties of the jet fuel/biojet fuel blend within an acceptable range to control its quality, ensure reliable performance, and control the variability inherent in biofuel production. Despite the global situation created by COVID-19, slow-growing demand for jet fuel is expected as a result of the global economic recovery. This occurs in a context where the price of fossil fuels rises while petroleum is increasingly scarce. Additionally, the production and consumption of jet fuel are one of the causes of the continuous elevation of greenhouse gasses (GHGs) which contributes to global warming. The aviation sector is one of the GHGs sources that grows faster, at a rate of 5.7% per year [5], and it is responsible of 1.9% of such emissions [6]. In 2018, this contribution augmented to 2.4% [5, 7]. Mainly motivated by the increase in jet fuel prices and its inherent environmental impact, the production of biomass-based alternative fuels in a framework of circular economy emerges as a promissory solution to the dependence of many countries on fossil fuels and to the effects of global warming. In this context, one of the liquid fuels that has gained attention as a substitute of conventional jet fuel is the biojet fuel [8]. Different routes of production for biojet fuel offer diverse advantages and disadvantages. Oil-based biojet fuel has been widely produced and several low-cost technologies have been tested successfully. The most popular are the hydroprocessing of esters and fatty acids (HEFA), the catalytic hydrothermolysis (CH), and the hydroprocessing to depolymerized cellulosic jet (HDCJ) [9–12]. However, the raw material for the oil path has proven not to be entirely sustainable. In this regard, there is a shortage of arable land for oilseeds and, if available, they compete with land for food crops.

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In the particular case of Jatropha curcas crops, although they are capable to grow in diverse agroclimatic conditions, they are accompanied by variations in important parameters such as seed yield, oil content, and nutrient requirements, which critically affects the economic viability of plantations [13, 14]. In addition, it contradicts the principles of the circular economy since oil crops do not arise as a by-product but as a parent feedstock. A route that has not been explored as much as the oil route is that of alcohols. Alcohols can be produced from lignocellulosic biomass, which is considered as the major promising renewable resource, since it is largely available around the world and allow avoiding the food versus fuel conflict related to the use of edible crops. The full recycling and reuse of agro-industrial lignocellulosic wastes contribute to the circular economy since this renewable resource can be used again and again to generate valuable and marketable products, replacing the exhaustible fossil-based resources [1]. Through processes of pretreatment, saccharification, and fermentation, agroindustrial lignocellulosic wastes can be converted into short and long-chain alcohols. Particularly interesting is the upgrading of lignocellulose into bioethanol. Its continuous growing up as a green and cheap alternative source to the petrochemical fuels, being the most common and utilized liquid biofuel, bioethanol is receiving great attention thanks to the development of technology conversion that improves its platform widely [1]. Through stages of dehydration to produce ethylene, oligomerization, and hydrogenation, biojet fuel can be easily obtained from bioethanol. This upgrade is known as the alcohol-to-jet process (ATJ). The whole conversion process from lignocellulosic biomass to biojet fuel through alcohols presents several areas of opportunity to reduce capital and operative costs and environmental impact. One of the strategies to obtain a process that meets these requirements—this is, sustainable—comes from process intensification, which refers to a set of tools capable of achieving dramatic improvements in manufacturing and processing by substantially decreasing equipment size, waste production, and energy consumption which leads to smaller, cleaner, and more energy-efficient processes [15]. This process also faces challenges. A critical step is related to the raw material, its temporal nature and annual variability of biomass supply. Most biomass sources are vegetal material which needs to be planted, cultivated, and harvested through a growth cycle. Additionally, it is reported that the time and frequency of the harvest can affect the yields of energy crops, so it would be necessary to carefully plan and schedule the production to guarantee the quantity and quality of the biomass supply [16]. To date, no work addressing the design and optimization of biojet fuel production from lignocellulosic alcohols under sustainability criteria has been published. This work aims to present an optimized process design to produce biojet fuel from ethanol through the ATJ process in an economical and environmentally friendly way, taking Mexican agro-industrial lignocellulosic biomass as feedstock to accomplish the goals of the circular economy.

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135

7.2 Overall Process for Biojet Production The overall process of biojet fuel production with alcohols as intermediates requires the processing of lignocellulosic biomass to produce such alcohols. The general scheme of alcohols production from lignocellulosic agro-industrial waste involves four steps (Fig. 7.1): the pretreatment of biomass, to break down cell walls into cellulose and hemicellulose, and to remove lignin; hydrolysis (or saccharification) of biomass; the fermentation of produced monosaccharides (pentoses and hexoses) to alcohols by the action of yeasts, bacteria, or other appropriate organisms; and the purification of the alcohol [17]. Once the alcohols have been obtained, they are sent to the ATJ process to be upgraded to biojet fuel. The core of the ATJ process is a concept developed to bridge the gap between alcohols that can easily be produced from renewable resources and the high-quality hydrocarbon fuels needed in aircraft turbines. This process is based on three catalytic reactions: dehydration of alcohol, oligomerization of olefins, and hydrogenation, followed by separation of the synthetic paraffin product in the jet fuel range, as shown in Fig. 7.2. The residual cuts are used as products in the order of gasoline and diesel [19]. Short-chain alcohols such as ethanol, n-butanol, and isobutanol have been of particular interest as raw materials and can be produced from lignocellulosic biomass or waste. The first renewable aviation fuel approved by ASTM D7566 was biojet fuel derived from isobutanol, allowing mixtures of up to 30% with conventional jet fuel. On the other hand, ethanol has recently been approved as a raw material allowing the biojet fuel produced from it to be mixed with conventional jet fuel up to 50% [20]. Despite the production of lignocellulosic ethanol is still unprofitable, and it is difficult to predict when its cost will be reduced to the level of first-generation ethanol, advantage can be taken by considering its production in the framework of an integrated biorefinery to obtain naphtha, gasoline, diesel, and heavy oils among other value-added products [9, 21, 22]. In the case of ethanol, its maximum use in most gasoline-powered vehicles as an additive is in mixtures of 10–15%, which creates a barrier to achieve its market penetration as an additive for gasoline. This, coupled with advances in production efficiency and diversification of the raw material, would result in excess production of ethanol at competitive prices and be available to produce

Fig. 7.1 Conversion process from biomass to ethanol [17, 18]

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Fig. 7.2 Alcohol-to-jet process

a wide range of platform fuels and chemicals. Therefore, its transformation into biojet fuel presents an area of opportunity to achieve greater profitability of alcohol [19, 20]. Another area of opportunity concerns to the purification of ethanol from fermentation broths. Extractive distillation for ethanol presents relatively high costs and, despite this disadvantage, remains as the main choice in the case of large-scale ethanol production. Since ethanol purification zone has been widely studied, high costs and elevated energy consumption have been demonstrated. For this reason, a first approach on the path to sustainability is its intensification. By intensifying this zone, economic and environmental improvements can be achieved, and a safer, energy-efficient, cleaner, cheaper, and greener process can be obtained as various authors have reported [23–25]. Taking into account the previous considerations regarding the use of lignocellulosic agro-industrial waste and process intensification to decrease total costs and environmental impact, the whole process design is addressed to obtain biojet fuel more sustainably, within the framework of the circular economy.

7.3 Process Intensification Applied to Produce Biojet To create a feasible market of biojet fuel in Mexico, it is necessary to meet a demand of at least 5.5% conventional jet fuel with biojet fuel [26], which equals 258 million l. The production of biojet fuel from ethanol involves a series of steps that implicates the production of ethanol from lignocellulosic biomass. The availability of biomass limits the whole process, making it necessary to consider the temporality of the crops and, therefore, of their waste generated within the planning of the feedstock. To satisfy the demand of biojet fuel during a period, more than one feedstock has to be considered. Also, to leverage the number of available pretreatment technologies and their ability to break biomass, more than one pretreatment is necessary. The planning of the feedstock and the diverse combination of feedstocks and pretreatments make it possible to organize the process within a superstructure scheme.

7.3 Process Intensification Applied to Produce Biojet

137

7.3.1 Feedstock for Biojet Production Based on the information provided by the Servicio de Información Agroalimentaria y Pesquera and by SAGARPA [27], sugarcane bagasse and corn stover were selected as feedstocks, as they were the most abundant biomasses in Mexico during 2018. Additionally, sugarcane bagasse and corn stover can be potential substrates for ethanol production since they have high sugar content and are renewable, cheap, and readily available feedstocks [28, 29]. The process was developed to obtain the necessary sugars from these biomasses to produce ethanol. Table 7.3 shows the composition of cellulose, hemicellulose, and lignin on a dry basis, as well as the percentage of moisture of the biomasses in Mexico.

7.3.2 Pretreatment The selection of possible pretreatments was carried based on the evaluation made by Conde-Mejía et al. [37] taking as selection criteria the cost of energy consumed in the operation per ton of dry biomass and the cost of energy per gallon of bioethanol produced reported in their work. In this respect, the most economical alternatives were pretreatment by steam explosion and dilute sulfuric acid.

7.3.3 Feedstock Planning Design To take into account the availability of crops and, therefore, of agricultural waste, planning was designed, whose variables were part of the subsequent optimization process. The design was distributed as shown in Fig. 7.3 for each month of the year. In Fig. 7.3, X represents the amount of cellulosic sugar obtained from sugarcane bagasse, Y represents the fraction of sugars from sugarcane bagasse pretreated by steam explosion, and Z represents the fraction of sugars from corn stover pretreated by steam explosion. Table 7.3 Feedstock composition in dry basis (wt%) [30] Feedstock

Cellulose

Hemicellulose

Lignin

Ash

Moisture

Sugarcane bagasse

41

21

23

1.2

50

Corn stover

36

19

20

2.0

20

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Fig. 7.3 Definition of planning variables

7.3.4 Process Modeling Ethanol is not a single-use intermediate, but it can be employed as a building block for fuels and diverse chemicals [31], so that the ethanol can compete with biojet fuel in case that its production is not necessary. For this reason, the whole process was modeled separately in two parts: the first part consisted of obtaining ethanol from lignocellulosic biomass. The second part concerned the production of biojet fuel from ethanol. Besides, according to a modular manufacturing scheme, this allows to locate the plant of ethanol near to harvest sites and the plant of biojet fuel near to the airports thus reducing supply chain costs, increasing the flexibility of the whole process, and allowing the production network can react to dynamic supply and demand developments [32–35]. Ethanol Process Design The process of obtaining ethanol from lignocellulosic biomass was designed under a superstructure scheme that took into account the two biomasses and the two pretreatments previously selected. Reactor modeling was performed by adjusting experimental data to polynomial equations. This was made in Minitab 19 by employing the “Fit regression model” tool. The experimental data on pretreatment and enzymatic hydrolysis from the literature were sought to be homogeneous in terms of the type of biomass used and the pretreatment applied to allow comparison of the performance of the four reaction trains, that is, what is the economic and environmental impact of processing sugarcane bagasse against corn stover using steam explosion against diluted acid pretreatment. In the case of fermentation, this homogeneity in the data was not necessary, due to the fermenters process liquid streams with glucose independently of the solid biomass type, unlike previous reaction steps where experimental data did depend on the type of biomass.

7.3 Process Intensification Applied to Produce Biojet

139

Reactors in this process were modeled in Microsoft Excel, while the purification of ethanol was modeled in Aspen Plus 8.8. Both were connected through macros from Visual Basic. Model equations for reaction steps are described below. • Pretreatment modeling In this equipment, the next reactions were carried: C6 H10 O5 + H2 O → C6 H12 O6

(7.1)

C5 H8 O4 + H2 O → C5 H10 O5

(7.2)

As a result of the data fit, the next equation was obtained: 2 X r ecov = AT p + Bt p + C S% + DTP2 + Et p2 + F S% + GT p t p 2 + H T p S% + I t p S% + J T p t p S% + K S% T p + L T p3

(7.3)

where: Tp tp S% X recov

temperature inside reactor (°C) pretreatment residence time (min) sulfuric acid percentage recovered fraction of glucan or xylan in pretreated solid.

• Enzymatic hydrolysis modeling In this equipment, the next reaction was carried at 50 °C [36]: C6 H10 O5 + H2 O → C6 H12 O6

(7.4)

As a result of the data fit, the next equation was obtained: X G,H = Ac E + Bth + Cc2E + Dth2 + Ec E th + Fc3E + Gth3 + H c2E th + I c E th2

(7.5)

where: cE enzyme concentration (FPU/g glucan) th hydrolysis residence time (h) X G,H conversion fraction from glucan to glucose during enzymatic hydrolysis. • Fermentation modeling In this equipment, the next reaction was carried at 32 °C [37, 38]: C6 H12 O6 → 2C2 H6 O + 2CO2

(7.6)

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As a result of the data fit, the next equation was obtained: X G,F = AcG + Bt F + CcG2 + Dt F2 + EcG t F + FcG3 + Gt F3 + H cG t F2

(7.7)

where cG glucose concentration at reactor inlet (g/L) tF fermentation residence time (h) X G,F conversion fraction from glucose to ethanol during fermentation • Ethanol purification modeling Ethanol separation modeling was carried by selecting an extractive distillation sequence with glycerol as entrainer, and taking into account equipment costs and energy requirements [39]. The desired purity was 99.5% wt or more since this is the required purity for ethanol to improve physicochemical properties of biojet fuel [9, 12]. This process was modeled and simulated in Aspen Plus 8.8, and NRTL was selected as a thermodynamic model due to the presence of non-idealities in the ethanol/water mixture [40]. The RADFRAC module with Kettle-type reboiler and total condenser was used, and the total number of stages, the feed stages, the distillate/feed ratio, the reflux ratio, and the diameter of the columns were varied. To meet sustainability goals, this zone was intensified. The intensification of ethanol separation has been widely studied, and improvements in energy efficiency, costs savings, and environmental impact have been successfully demonstrated [23– 25, 40, 41]. In this respect, a column sequence with vapor side stream (Fig. 7.4a) and a column sequence of dividing wall (DWC) (Fig. 7.4b) were proposed as intensified schemes. This last configuration can be modeled as a thermally coupled column configuration (or Petlyuk column) (Fig. 7.4c), which is thermodynamically equivalent when there is no transfer energy through the dividing wall [23, 42]. Since Aspen Plus 8.8 does not have a specific block for the DWC column, this was modeled as a Petlyuk column. As in the conventional sequence, the NRTL model was used with the RADFRAC module and varying the total number of stages, the feed stages, the distillate/feed ratio, the reflux ratio, and the diameter of the columns. Biojet Fuel Process Design For the ATJ process, the design and data proposed by Byogy Renewables [43] was employed. Similarly, the simulation was carried in Aspen Plus 8.8, making use of the ENRTL-RK model due to the presence of electrolytic species in some zones of the process. The operational conditions of the reactors, as well as the block employed in Aspen Plus and their specifications, are given in Table 7.4. For those reactions whose conversion is specified, the reference component is written in bold. At the final step, the jet fuel distillation was modeled in a RADFRAC block with a Kettle-type reboiler and total condenser, varying the total number of stages, the feed stages, the distillate flowrate, the reflux ratio, and the diameter of the column.

7.3 Process Intensification Applied to Produce Biojet

141

Fig. 7.4 Intensified schemes: a column with vapor side stream; b dividing wall column (DWC); c DWC modeled as thermally coupled column sequence

Table 7.4 Operational conditions for reactors in ethanol-biojet process [43] Stage

Block in Aspen

Reaction

P (bar)

T (°C)

Specification

Dehydration

RStoic

C2 H5 OH → C2 H4 + H2 O

8–14

320–500

Conversion 0.988

Oligomerization

RYield

–

40–55

350–470

Yield

Hydrogenation

RYield

–

8–15

145–240

Yield

Reforming

Dry

REquil

CH4 + H2 O → CO + 3H2 CH4 + CO2 → 2CO + 2H2

17–25

640–900

Temperature approach 400 °C

Steam (HTS)

RStoic

CO + H2 O → CO2 + H2

15–20

340–520

Conversion 0.9

Steam (LTS)

RStoic

CO + H2 O → CO2 + H2

11–20

175–250

Conversion 0.9

As could be seen, the anterior superstructure, along with the ATJ process, is modeled with highly non-linear and potentially non-convex equations. Besides, the existence of degrees of freedom allows solving the design problem as an optimization problem. Finally, the superstructure to be optimized is shown in Fig. 7.5. As mentioned before, the reaction zone in the biomass-ethanol process was modeled in Microsoft Excel and the purification zone, as well as the entire ethanol-biojet process, was modeled in Aspen Plus. It is important to mention that this block diagram is not

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Fig. 7.5 Complete superstructure for biojet fuel production process

unique but it is going to be subjected to all possible combinations within the solution superstructure.

7.4 Process Optimization Obeying the model of circular economy, the search for apropriate technologies to convert lignocellulosic biomass into biojet fuel, as well as the design and operation parameters that maximize savings and minimize environmental impact turn the design problem into a multi-optimization problem. When these two objectives are met, a sustainable process can be obtained, this is, a most profitable and greener process.

7.4.1 Objective Functions To assess the sustainability of the process in economic and environmental terms, the total annual cost (TAC) and eco-indicator-99 (EI99) were selected as objective functions for both processes, whose benefits have been foregrounded by several studies since they are adequate indicators of the sustainability of a process and are in accordance with the criteria of the circular economy [41, 44–47]. Likewise, for the production process of ethanol, the annual production of alcohol was included to satisfy a demand of 5.5% of conventional jet fuel in Mexico with biojet fuel [26].

7.4 Process Optimization

143

These are expressed in Eq. 7.8:    Min(T AC, E I 99) Fobj X→ = Max(Et O H ) s.t. y→k ≥ x→k

(7.8)

Tables 7.5 and 7.6 show detailed information about the decision variables involved in each operation for both biomass-ethanol process and ethanol-jet process. The letter “d” indicates that the variable is discrete, and the letter “c” indicates that the variable is continuous. The meaning of X, Y, and Z are the same as in Fig. 7.3. In the Purification column, A, B, and C refer to conventional extractive distillation, vapor side stream scheme, and dividing wall scheme, respectively. In total, 132 continuous and 21 discrete variables were counted for biomass-ethanol process. For ethanol-biojet process, 25 continuous and 5 discrete variables were also counted. Total Annual Cost (TAC) The total annual cost (TAC) allows quantifying the economic performance of a process when it is under development. It stands out as an indicator of the economy of the process since it is based not only on the product but on the characteristics of the process for informational and comparative purposes [44]. The total cost objective function includes the operating costs for heating and cooling utilities, as well as the capital costs of the equipment [48]. In addition, Quiroz-Ramírez et al. [47] include, within the operating costs, the cost of electricity and supplies. The objective function of total annual cost is calculated according to Eq. 7.9:   T AC $USD/kg =

n

CT M i tri

i=1

+

m j=1

Cut j

Fk

(7.9)

where C TM represents the total cost of the i-module, C ut is the cost of j-utility, t ri is the payback period, and F k is the reference flow. Ecoindicator-99 The ecoindicator-99 is a quantitative index proposed as part of the methodology of the same name for life cycle analysis [49]. This methodology contemplates the life of a product from the origins of the raw material, during its process, and in its degradation. It is based on the use of standard ecological indicators, which are numbers that express the total environmental load of a product or process. The larger the indicator, the greater the environmental impact [44]. This methodology is divided into three impact categories: human health, ecosystem quality, and resource depletion. It is calculated according to Eq. 7.10:    E I 99(ecopts/kg) =

b

d

k∈K

Fk

δd ωd βb αb,k

(7.10)

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Table 7.5 Decision variables on biomass–ethanol process Variable

Planning

SB–SE

SB-DA

CS-SE

CS-DA

Purification A

B

C

1c

1c

1c

Number of stages

3d

2d

3d

Feed stage

3d

2d

2d

Solvent stage

1d

1d

1d

Reflux ratio

3c

2c

2c

Distillate/feed ratio

3c

2c

2c

Diameter

3c

2c

3c

Solvent/feed ratio

1c

1c

1c

Cellulose amount

12c

X

12c

Y

12c

Z

12c

Temperature

8c

8c

8c

8c

Pressure

1c

1c

1c

1c

Residence time

3c

3c

3c

3c

Acid concentration

1c

Enzyme conc

1c

1c

1c 1c

1c

Side stream stage

3d

Interconnection flowrate

2c

Total

48c

13c

14c

13c

14c

11c 7d

8c 5d

11c 9d

where βb is the total amount of chemical b released per unit of reference flow due to direct emissions, αb,k is the damage caused in category k per unit of chemical b released to the environment, ωd is a weighting factor for damage in categories d, and δd is the normalization factor for damage of category d. The unit of measurement employed for EI99 is the ecopoint, where 1 ecopoint represents one-thousandth of the annual environmental load of an average European inhabitant [41, 44].

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145

Table 7.6 Decision variables on ethanol-biojet process Variable

Reforming

Dehydration

Oligomerization

Hydrogenation

Distillation

Pressure

6c

2c

1c

1c

1c

Temperature

6c

2c

1c

1c

No. of stages

2d

Feed stage

1d

Reflux

1c

Distillate

1c

Side stream flowrates

2d 2c

Diameter Total

12c

4c

2c

2c

5c 5d

7.4.2 Stochastic Optimization In terms of mathematical optimization methods, deterministic and stochastic methods can be used to solve high-dimensional, non-linear problems within a complex search space. On the one hand, deterministic methods require the calculation of first and/or second derivatives of the objective function and its constraints equations. Besides, these methods are strongly dependent on the initial solution chosen in the search for the optimal solution. On the other hand, stochastic methods have the advantage of not requiring the manipulation of the mathematical structure of the objective function and its constraints, allowing to employ the equations in their explicit form and not requiring an initial feasible point. One of the stochastic methods that have shown to be able to solve highly non-linear and potentially non-convex problems is Differential Evolution with Tabu List [50]. Differential Evolution with Tabu List The stochastic optimization method of Differential Evolution with Tabu List (DETL) [51] stands out among other stochastic methods for its robustness, that is, its ability to locate the global optimum regardless of the parameters of the problem, its small number of evaluations of the target function, and its efficiency in terms of computation times. DETL method showed that the use of some concepts of the metaheuristic tabu can improve the performance of the Differential Evolution algorithm. Particularly, the Tabu List is used to avoid the revisit of search space by keeping a record of recently visited points, which can avoid unnecessary function evaluations. This is what provides to the method its high time efficiency [50–53]. The proper functionality of this technique has been proven when applied to intensified systems of separation and reactive distillation [45, 50, 54–57]. The algorithm is shown in Fig. 7.6 and works as follows: each individual is represented as a vector of decision variables becoming part of an initial random population

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of NP individuals generated within the limits of the decision variables. Then, the value of target functions and constraints is calculated for each individual in the initial population. The tabu list is filled with 50% of the individuals in the initial population, and the initial individuals are identified as target individuals (i). Subsequently, one test individual is generated for each target individual by mutation and crossover of three random individuals from the initial/current/parental population. Elements of the mutant vector compete with those of the target vector with a Cr probability of generating a test vector. At this point a tabu check is implemented: if the test individual is close to any individual in the tabu list for a specified distance (Tr taboo ratio) it is rejected without calculating the objective functions and constraints. This will happen until the test individual is far away from any individual on the tabu list. Next, the euclidean distance between the test individual and each individual in the tabu list in the decision variable space to accept the test individual is calculated. Then, objective functions and constraints are calculated for the temporarily accepted test individual. After generating test individuals for all target individuals in the current population, if necessary, an undivided classification of current and combined offspring populations is performed followed by the calculation of the agglomeration distance to select the next generation individuals. Thus, the best NP individuals are used as the population in the subsequent generation [58]. Implementation of the Optimization Algorithm The stochastic optimization method was implemented using a hybrid platform that incorporated Microsoft Excel and Aspen Plus 8.8. In it, a vector of decision variables is sent to Microsoft Excel by using a dynamic data exchange with COM technology. In Microsoft Excel, such values are attributed to process variables required by Aspen Plus 8.8. Once the simulation is completed, Aspen Plus returns the resulting vector to Microsoft Excel. Finally, Microsoft Excel analyzes the values of the objective function and proposes new values of the decision variables according to the stochastic optimization method [41]. This type of tool, illustrated in Fig. 7.7, has been successfully applied to process design and optimization [41, 46, 47, 59]. Optimization was carried out separately for ethanol and biojet fuel production processes. The parameters required by the method and recommended by SánchezRamírez et al. [54] are reported in Table 7.7.

7.5 Results and Discussion 7.5.1 Feedstock Planning Figure 7.8 shows the annual amount of sugarcane bagasse and corn stover that are pretreated by steam explosion and dilute acid and required to produce the optimal flow of ethanol. In total, 8,357,524 t/year of sugarcane bagasse are required, of which 46%

7.5 Results and Discussion

Fig. 7.6 Multiobjective optimization algorithm by Differential evolution with tabu list

147

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Fig. 7.7 Hybrid platform for DETL stochastic optimization

Table 7.7 Parameters of the optimization method Population size

Number of generations

Tabu list size

Crossover probability

Mutation probability

Tabu ratio

120

1000

60

0.9

0.3

0.0001

is sent to steam explosion and 54% to acid pretreatment; and 408,970 t/year of corn stover, of which 28% is subjected to steam explosion and 72% to acid pretreatment. It is observed that, in the optimal, the requirement of sugarcane bagasse is much greater than that of corn stover. This is explained by the fact that it is more expensive to process corn stover in reaction trains involving both pretreatments. Thus, the optimization method compensates this effect by raising the requirements for sugarcane bagasse. The same observation applies to ecoindicator-99. The processing of corn stover by both routes results in a greater environmental impact in contrast to sugarcane bagasse. Again, to minimize this effect the method is oriented to choose the sugarcane bagasse as the most appropriate feedstock. In addition, sugarcane bagasse

Fig. 7.8 Annual biomass requirement in steam explosion and dilute acid processes

7.5 Results and Discussion

149

Fig. 7.9 Annual feedstock planning

Table 7.8 Yield (kg ethanol/kg dry biomass)

Sugarcane bagasse

Corn stover

Steam explosion

14.70

14.80

Diluted acid

16.13

17.05

has a higher content of hexoses sugars, and its cost is lower than that of corn stubble, so the optimization method tends to choose it as the best feedstock. Figure 7.9 shows the distribution of the raw material during the year. It can be observed a tendency for the optimization method to choose sugarcane bagasse processed with diluted acid. This is attributed to the bagasse/acid combination offering better performance with a low TAC and EI99 as shown in Table 7.8.

7.5.2 Optimization of Ethanol Process Figure 7.12 shows the Pareto front for the optimization of the ethanol production process without taking into account the separation sequence. It is important to note that at the zone with maximum ethanol production and minimum TAC and EI99, sustainability criteria are met, obtaining a greener, cleaner and cheaper process. It shows that the maximum production was achieved at 79,894 kg/h (679,100 ton/year) with a purity greater than 99.5% by weight, at a minimum TAC of 0.656 USD/kg ethanol and a minimum EI99 of 0.414 ecopoints/kg ethanol. The trend observed in Fig. 7.10 is typical of a multi-objective optimization in which the objective functions are maximized and minimized. In this case, more ethanol production is expected to demand larger equipment and more energy and feedstock, which becomes an increase in the total annual cost. Simultaneously, an increase in the eco-indicator is expected due to the environmental impact caused by the requirements of electricity, water, steam, steel, and feedstock.

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Fig. 7.10 Pareto front for biomass–ethanol process (no separation sequence). Blue and green dots represent the TAC and the EI99, respectively

Figure 7.11 shows the Pareto front for optimal ethanol production, according to Fig. 7.10. There is a clear compromise between the objective economic and environmental impact functions for the conventional and intensified separation sequences. It can be observed that for the conventional sequence (A) a minimum TAC and EI99 of 1.295 USD/kg ethanol and 0.4716 ecopoints/kg ethanol were achieved, respectively. On the other hand, the column sequence with vapor side stream (B) obtained an optimal of 1.223 USD/kg ethanol and 0.4635 ecopoints/kg ethanol. This represents a reduction of 5.56% in the TAC and 1.72% in the ecoindicator compared to the conventional sequence. Finally, with the dividing wall column sequence (C) a TAC of 1230 USD/kg ethanol and an EI99 of 0.4578 ecopoints/kg ethanol were obtained. Finally, the dividing wall scheme achieved a saving of 5.02% in the TAC and a decrease of 2.92% in the ecoindicator concerning the conventional sequence. An interesting observation lies in the Pareto front of sequence C. Between the C2 and C3 designs, the difference between the ecoindicators is in the order of 10–4 , while the difference between the TACs is 0.014. That is, the difference from the EI99 is not significant enough to rule out the C3 design as better than the B2 design. However, from a utopian point of view, the optimal design of sequence C is around point C2 (Table 7.9). It is observed that the most economical configuration is the column sequence with vapor side stream (B). However, from the environmental point of view, the sequence with dividing wall column (C) is the best alternative. Figure 7.12 shows how the amount of solvent is the most influential factor in the operational costs of distillation sequences. It contributes about 75% to the total cost of each separation sequence. It is also noted that sequence B uses less solvent than sequence C, which is why it is the most economical option. This can be attributed to the reduction in the thermal

7.5 Results and Discussion

151

Fig. 7.11 Pareto front for biomass–ethanol process (with separation sequence)

Fig. 7.12 TAC analysis for separation sequences at the optimal point

Table 7.9 Shows a summary of the optimal objective functions of conventional and intensified processes

TAC (USD/kg ethanol)

A

B

C

1.295

1.223

1.230

5.56

5.02

0.4716

0.4635

0.4578

1.72

2.92

% Reduction EI99 (pts/kg ethanol) % Reduction

load in the dividing wall column which, to achieve the desired purity, is compensated with a greater amount of solvent, as will be discussed below. Continuing with Fig. 7.11, it is observed that in all three cases the total annual cost decreases as the eco-indicator increases. To know the reason for this behavior, three designs are considered in each sequence and analyzed according to their design parameters. These are shown in Tables 7.10, 7.11, and 7.12 for sequences A, B, and C, respectively. It is observed that, for the three schemes, the duty is increased with the reflux ratio, which is a behavior common to distillation processes. Comparing the data reported in these tables with Fig. 7.13, it is observed that designs with a higher

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Table 7.10 Design parameters of conventional sequence Column 1

Column 2

Column 3

Reflux ratio

A1

A2

A3

1.678

1.712

1.878

Diameter

0.705

0.609

0.911

Duty (MW)

160.27

160.65

163.97

Solvent/Feed ratio

0.720

0.589

0.564

Reflux ratio

0.320

0.466

0.501

Diameter

0.855

0.806

0.797

Duty (MW)

28.97

30.86

31.42

Reflux ratio

0.106

0.122

0.125

Diameter

0.848

0.999

0.988

Duty (MW)

9.48

8.68

8.30

Total duty (MW)

198.72

200.19

203.69

TAC

1.403

1.296

1.278

EI99

0.4711

0.4717

0.4728

Table 7.11 Design parameters for sequence with vapor side stream column Column 1

Column 2

B1

B2

B3

Reflux ratio

1.660

1.660

1.654

Diameter

0.755

0.761

0.745

Duty (MW)

160.661

160.684

158.577

Solvent/Feed ratio

0.573

0.504

0.504

Reflux ratio

0.508

0.691

0.713

Diameter

0.991

0.966

0.991

Duty (MW)

40.198

43.155

43.180

Total duty (MW)

200.86

203.84

201.76

TAC

1.280

1.224

1.222

EI99

0.4625

0.4636

0.4681

ecoindicator tend to operate with higher reflux ratios, higher duties, and, therefore, higher amounts of steam, which contributes increasing the EI99. This is because steam generation involves the burning of fossil fuels, which directly influences the eco-indicator as shown in Fig. 7.13. As mentioned above, the amount of solvent, shown as the solvent/feed ratio, decreases as the thermal load of the second column increases, possibly as compensation to achieve the desired ethanol purity. This effect is observed in sequences A, B, and C. In the case of sequence B, the solvent ratio stabilizes at the lowest cost, as seen in Fig. 7.14. Finally, sequence B2 was selected as the optimal and the rest of the process was designed based on the results obtained by this configuration.

7.5 Results and Discussion

153

Table 7.12 Design parameters for dividing wall column Column 1

Column 2

C1

C2

C3

Reflux ratio

1.660

1.659

1.654

Diameter

0.755

0.739

0.802

Duty (MW)

160.661

160.674

158.286

Solvent/feed ratio

0.626

0.522

0.503

Reflux ratio

0.515

0.697

0.798

Diameter

1.215

0.983

0.927

Duty (MW)

18.722

20.730

22.410

Total duty (MW)

179.383

181.403

180.695

TAC

1.316

1.230

1.215

EI99

0.4572

0.4579

0.4586

Fig. 7.13 Ecoindicator-99 analysis for reaction–separation sequence B

Fig. 7.14 Analysis of the total annual cost for the process with vapor side stream (sequence B)

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7.5.3 Optimization of Biojet Fuel Process Figure 7.15 shows the Pareto front for optimization of the biojet fuel production process from ethanol. In this case, a minimum TAC of 0.275 USD/kg biojet fuel and a minimum EI99 of 70.18 ecopoints/kg biojet fuel were achieved. This ecoindicator value is attributed to the greater environmental impact inherent in the presence of hydrocarbons in the process. Finally, this design is capable of producing 224,206 t/year (266,912 m3 /year) of biojet fuel, which meets a 5.72% demand for conventional jet fuel in Mexico. It should be noted that the objective functions do not show a significant variation along the Pareto front, so that any point would represent equivalent designs, that is, it is a flexible design since, despite the change in operating conditions, economic and environmental indicators do not vary substantially. However, an analysis of the ecoindicator reveals that the main source of environmental impact is the flow of processed hydrocarbons in the areas of dehydration, oligomerisation, distillation, and hydrogenation, as shown in Fig. 7.16 for the optimal point. This is why, unlike the biomass-ethanol process, high ecoindicators are presented. In terms of total annual cost, the largest contribution is attributed to the costs of heating utilities, which account for about 75% of operating costs and 50% of the TAC. Taking the three points indicated on the Pareto front and breaking down its costs in Fig. 7.17 it is possible to observe that the decrease in the TAC is rather attributed to a reduction in the cost of equipment and the heating utilities. In the end, the complete process flow diagram is shown in Fig. 7.18. It can be observed that the vapor side stream column configuration is implemented. Also, the optimal design and operating conditions that maximize ethanol production and minimize TAC and EI99 are specified.

Fig. 7.15 Pareto front for ethanol–biojet fuel process

7.5 Results and Discussion

155

Fig. 7.16 Ecoindicator-99 analysis for ethanol–biojet fuel process

Fig. 7.17 TAC analysis for the ethanol–biojet fuel process

7.5.4 Minimum Selling Price The various factors that affect the economic and environmental performance of both process modules, biomass–ethanol and ethanol–biojet fuel have been analyzed. It has been observed that the lower annual costs are presented with high ecoindicators. Under these circumstances, the information provided by the Pareto fronts is not enough to know how profitable a design is if the minimum selling price of biofuel for such a design is not known. In this section, an analysis of the sales price of biojet fuel is performed based on the different designs of the biomass–ethanol process and taking the three points indicated on the Pareto front for the production of biojet fuel, in Fig. 7.19.

3 896.03 kg/h Heavy oils

21.65 MW

Stage 43

6 878.19 kg/h Diesel

Stage 4

26 377.16 kg/h Biojet fuel

-23.49 MW

1.013 bar 191.75 °C 7.8 min 114.5 m3

6.29 bar 160.7 °C 16.8 min 36.5 m3

1.013 bar 188.1 °C 11 min 413 m3

6 662.65 kg/h Lights

Acid solution 27 006.02 kg/h 0.1032% H 2SO 4

27 006.02 kg/h to dilute acid

Saturated steam 2 164.24 kg/h

10 317.42 kg/h to steam explosion

Acid solution 258 171.41 kg/h 0.8005% H 2SO 4

258 171.41 kg/h to dilute acid

6.76 bar 163.5 °C 6 min 143 m3

Water 505 342.7 kg/h

Height: 26.82 m

Diameter: 1.061 m

Reflux ratio: 27.16

Feed stage: 45

46 stages

1.683 bar

8.58 FPU/g cellulose

Pretreated solid 23 771.01 kg/h

1.013 bar 50 °C 33 h 19 290 m3

1.013 bar 50 °C 59.75 h 5 310 m3

1 bar 50 °C 93 h 39 404 m3

1.013 bar 50 °C 94 h 39 952 m3

43 814.00 kg/h Paraffins

Water 55 428.78 kg/h

Pre-hydrolysis liquor 29 924.64 kg/h

28.25 FPU/g cellulose

Pretreated solid 8 704.33 kg/h

Water 20 310.10 kg/h

Pre-hydrolysis liquor 3 655.01 kg/h

14.79 FPU/g cellulose

Pretreated solid 211 247.46 kg/h

Water 492 596.98 kg/h

Pre-hydrolysis liquor 303 028.69 kg/h

13.70 FPU/g cellulose

Pretreated solid 216 575.44 kg/h

52.90 bar 408.21 °C 3.04 m3

2.98 kg/h Water 0.47 kg/h CO 81.4 kg/h CO 2

43 714.10 kg/h Olefins

Oligomerization

8.89 bar 237.30 °C 4.90 m3

Fermented liquid 90 393.55 kg/h

1.013 bar 35 °C 23.6 h 2451.3 m3

Fermented liquid 25 332.71 kg/h

1.013 bar 35 °C 23.7 h 709.5 m3

Fermented liquid 806 817.76 kg/h

1.013 bar 35 °C 23.8 h 17 230 m3

Fermented liquid 595 649.48 kg/h

1.013 bar 35 °C 23.9 h 17 300 m3

Hydrogenation

Hydrolyzed solid 14 111.14 kg/h

Hydrolysis liquor 65 125.55 kg/h

Hydrolyzed solid 5 801.19 kg/h

Hydrolysis liquor 23 213.24 kg/h

Hydrolyzed solid 151 295.98 kg/h

Hydrolysis liquor 552 862.24 kg/h

Hydrolyzed solid 156 447.59 kg/h

Hydrolysis liquor 565 470.56 kg/h

15.02 kg/h H 2

13.80 bar 232.28 °C 0.5235 m3

Low temperature shift reactor

33 545.69 kg/h Water

14.71 kg/h H 2 5.71 kg/h Water 4.72 kg/h CO 74.73 kg/h CO 2

43 642.28 kg/h Ethylene

5.26% Ethanol 91.78% Water 1.00% Glucose 1.96% Xylose

Fermentation broth 1 518 193.5 kg/h

Fig. 7.18 Process flow diagram with optimal configuration for biomass–ethanol–biojet fuel process

Corn stover 37 323.44 kg/h Dry basis

Sugarcane bagasse 476 701.11 kg/h Dry basis

Saturated steam 59 116.66 kg/h

Pre-hydrolysis liquor 60 720.61 kg/h

1.013 bar

19.30 bar 364.85 °C 0.4730 m3

High temperature shift reactor

Height: 29.87 m

Diameter: 0.761 m

D/F 0.0662

Reflux ratio: 1.66

Feed stage: 24

51 stages

Feed stage: 48

Height: 38.40 m

Diameter: 0.966 m

D/F 0.9242

Reflux ratio: 0.691

22.79 bar 915.61 °C 0.7356 m3

Steam reforming

96.86% Water 1.06% Glucose 2.08% Xylose

11.65 kg/h H 2 33.02 kg/h Water 47.18 kg/h CO 8.01 kg/h CO2

10.77 bar 418.61 °C 232.8 m3

Dehydration

160.68 MW

1.013 bar 64 stages

1 431 194.57 kg/h

91.8% Ethanol 8.2% Water

86 998.93 kg/h

-62.0 MW

78.6 °C Stage 6

Glycerol 43 812.66 kg/h

6 551.87 kg/h

99.99% Glycerol

43 801.32 kg/h

99.75% Water

29.97 kg/h CH 4

69.93 kg/h Steam

135.95 kg/h Steam

79 840.35 kg/h Ethanol

43.155 MW

Vapor side stage 63

99.53% Ethanol

80 217.38 kg/h

-32.2 MW

To Biojet Fuel Process

218 529.7 kg/h to steam explosion

156 7 Biojet

7.5 Results and Discussion

157

Fig. 7.19 Minimum selling price of biojet fuel for designs a D1, b D2, and c D3 of the ethanol–biojet fuel process

Figure 7.19 shows the sales prices of biojet fuel for the various scenarios presented. Note that lower sales prices were achieved with both intensified processes, B and C. However, it is necessary to make some observations. On the one hand, between the designs B2 and C2, the one with the lowest selling price is B2. This coincides with the Pareto fronts shown in Fig. 7.11, in which the design with vapor side stream column exhibits the lowest TAC. On the other hand, globally the design C3 exhibits the lowest selling prices. This is associated with the fact that this design has the lowest TAC of those presented in Fig. 7.11. However, as mentioned previously, from a utopian point of view the design C2 is optimal. In addition, although the design C3 has the lowest selling price, it is not yet profitable, which will be discussed later. Figure 7.19b, which corresponds to the optimum point of the ethanol–biojet fuel process, shows that the lower sales prices between the optimal A2, B2 and C2 were achieved with the design B2. This behavior was expected as the lowest TAC was obtained with this design. At the optimum point B2–D2 the minimum selling price was USD 1.653/l. The sale price of conventional jet fuel in Mexico in 2020 was USD 0.414/l of jet fuel. This is an indicator that the entire process is not profitable since the minimum selling price of biojet fuel is four times higher than the selling price of fossil jet fuel. The amount of the solvent contributed greatly to this, as mentioned in the TAC analysis as mentioned in Sect. 7.5.2. One way to reduce this cost is to integrate glycerol into extractive distillation as a by-product of a biodiesel biorefinery. This would avoid the purchase of the solvent and, within the framework of a biorefinery,

158

7 Biojet

it would be fed to the process as a by-product of a previous process. In this sense, the glycerol obtained from the production of biodiesel has a price between 0.09 and 0.20 USD/kg, while the glycerol obtained by other routes has a price between 0.60 and 0.91 USD/kg [60].

7.6 Conclusions An intensified process of biojet fuel production was designed by the route of alcohols produced from lignocellulosic biomass. By simulating the process, it was found that it is capable of producing 266,912 m3 per year of biofuel, an amount that satisfies 5.72% of the national demand for conventional jet fuel in Mexico and is greater than the production needed by 2024 estimated by SENER (2017) and Cluster Bioturbosina CEMIE-Bio (2015). The anterior result was achieved with solutions capable to meet sustainable criteria. With the intensification of the ethanol purification process, it was observed that the most economically feasible configuration was that of a column with a vapor side stream. This achieved savings of 5.56% in the TAC and a 1.72% reduction in the EI99. In contrast, the configuration with dividing wall column achieved a greater reduction in the ecoindicator, of 2.92%; and lower savings in the TAC, of 5.02%. It was identified that the cost of the solvent contributed to 75% of the total annual cost of each purification sequence. Analysis of the amount of solvent involved in each configuration revealed that the column scheme with vapor side stream used less solvent than the dividing wall column scheme. It is important to mention that the scheme with a dividing wall column did not present significant changes in the EI99 and that design C3 presented a better economic and environmental performance than design B2. However, from a utopian point of view the optimal design is in the vicinity of point C2. Regarding the ethanol–biojet fuel process, the high values of the ecoindicator were related to the inherent environmental impact caused by the presence of hydrocarbons in each of the operations of the process. Finally, the design with the lowest selling price corresponded to the scheme with vapor side stream column. This resulted in 1.653 USD/l of biojet fuel. However, this was not lower than the sale price of conventional jet fuel in Mexico (0.414 USD/l), so the entire process is not profitable. To make the process profitable, some actions are recommended. The integration of hydrolysis and fermentation into a single equipment is planned. In addition, the results obtained for intensified separation sequences show a considerable reduction in the ecoindicator. This same effect is expected to be observed when implementing intensified systems in the ethanol–biojet fuel module, which, as observed, has a high environmental impact. Similarly, this innovation would reduce the capital costs of this section. Regarding the profitability of the process, it is recommended to lower the sales price of biojet fuel not only by implementing intensification strategies in both

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41. M. Errico, E. Sanchez-Ramirez, J.J. Quiroz-Ramìrez, J.G. Segovia-Hernandez, B.G. Rong, Synthesis and design of new hybrid configurations for biobutanol purification. Comput. Chem. Eng. 84, 482–492 (2016) 42. F.B. Petlyuk, V.M. Platonov, D.M. Slavinskii, Thermodynamically optimal method for separating multicomponent mixtures. Int. Chem. Eng. 5, 555–561 (1965) 43. Department of the Air Force, Technical Memorandum for Analysis of Biofuels from Byogy Renewables, Memorandum (Department of the Air Force, USA, 2011) 44. A.G. Romero-García, O.A. Prado-Rubio, G. Contreras-Zarazúa, C. Ramírez-Márquez, J.H. Ramírez-Prado, J.G. Segovia-Hernández, Simultaneous design and controllability optimization for the reaction zone for furfural bioproduction. Ind. Eng. Chem. Res. 59, 15990–16003 (2020) 45. G. Contreras-Zarazúa, E. Sánchez-Ramírez, J.A. Vázquez-Castillo, J.M. Ponce-Ortega, M. Errico, A.A. Kiss, J.G. Segovia-Hernández, Inherently safer design and optimization of intensified separation processes for furfural production. Ind. Eng. Chem. Res. 58, 6105–6120 (2019) 46. E. Sánchez-Ramírez, J.J. Quiroz-Ramírez, J.G. Segovia-Hernández, S. Hernández, J.M. PonceOrtega, Economic and environmental optimization of the biobutanol purification process. Clean Technol. Environ. Policy 18, 395–411 (2016) 47. J.J. Quiroz-Ramírez, E. Sánchez-Ramírez, J.G. Segovia-Hernández, S. Hernández, J.M. PonceOrtega, Optimal selection of feedstock for biobutanol production considering economic and environmental aspects. Sustain. Chem. Eng. 5, 4018–4030 (2017) 48. L.A. López-Maldonado, J.M. Ponce-Ortega, J.G. Segovia-Hernández, Multiobjective synthesis of heat exchanger networks minimizing the total annual cost and the environmental impact. Appl. Therm. Eng. 31, 1099–1113 (2011) 49. M. Goedkoop, R. Spriensma, The eco-indicator 99. A damage oriented for life cycle impact assessment, in Methodology Report and Manual for Designers (PRé Consultants, Amersfoort, 2001) 50. H. Alcocer-García, J.G. Segovia-Hernández, O.A. Prado-Rubio, E. Sánchez-Ramírez, J.J. Quiroz-Ramírez, Multi-objective optimization of intensified processes for the purification of levulinic acid involving economic and environmental objectives. Chem. Eng. Process. 136, 123–137 (2019) 51. M. Srinivas, G.P. Rangaiah, Differential evolution with Tabu list for global optimization and its application to phase equilibrium and parameter estimation problems. Ind. Eng. Chem. Res. 46, 3410–3421 (2007) 52. A. Bonilla-Petriciolet, G.P. Rangaiah, J.G. Segovia-Hernández, Evaluation of stochastic global optimization methods for modeling vapor–liquid equilibrium data. Fluid Phase Equilib. 287, 111–125 (2010) 53. A. Bonilla-Petriciolet, G.P. Rangaiah, J.G. Segovia-Hernández, Constrained and unconstrained Gibbs free energy minimization in reactive systems using genetic algorithm and differential evolution with tabu list. Fluid Phase Equilib. 300, 120–134 (2011) 54. E. Sánchez-Ramírez, J.J. Quiroz-Ramírez, C. Ramírez-Márquez, G. Contreras-Zarazúa, J.G. Segovia-Hernández, A. Bonilla-Petriciolet, Optimization of intensified separation processes using differential evolution with Tabu list, in Differential Evolution in Chemical Engineering. Developments and Applications. ed. by P.G. Rangaiah, S. Sharma (World Scientific, Singapore, 2017), pp. 260–288 55. C.L. Salas-Aguilar, A. Bonilla-Petriciolet, J.E. Jaime-Leal, Optimización multi-objetivo del desempeño y consumo energético de procesos de destilación intensificados para sistemas cuaternarios. Afinidad: Revista de química teórica y aplicada 75, 119–130 (2018) 56. E. Sánchez-Ramírez, J.J. Quiroz-Ramírez, J.G. Segovia-Hernández, Synthesis, Design and optimization of schemes to produce 2,3-butanediol considering economic, environmental and safety issues, in Proceedings of the 29th European Symposium on Computer Aided Process Engineering, ed. by A.A. Kiss, R. Lakerveld, L. Öskan (Elsevier, Eindhoven, 2019) 57. J.A. Vázquez-Castillo, G. Contreras-Zarazúa, J.G. Segovia-Hernández, A.A. Kiss, Optimally designed reactive distillation processes for eco-efficient production of ethyl levulinate. J. Chem. Technol. Biotechnol. 94, 2131–2140 (2019)

162

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58. G. Contreras-Zarazúa, J.A. Vázquez-Castillo, C. Ramírez-Márquez, J.G. Segovia-Hernández, J.R. Alcántara-Ávila, Multi-objective optimization involving cost and control properties in reactive distillation processes to produce diphenyl carbonate. Comput. Chem. Eng. 105, 185– 196 (2017) 59. C. Ramírez-Márquez, G. Contreras-Zarazúa, M. Martín, J.G. Segovia-Hernández, Safety, economic, and environmental optimization applied to three processes for the production of solar-grade silicon. Sustain. Chem. Eng. 7, 5355–5366 (2019) 60. C.J.A. Mota, B. Peres-Pinto, A.L. De-Lima, Glycerol: A Versatile Renewable Feedstock for the Chemical Industry (Springer, Berlin, 2017)

Chapter 8

Ethyl Levulinate

Abstract Ethyl levulinate is a versatile chemical feedstock with numerous potential industrial applications. EL can be used up to 5 wt% as the diesel miscible biofuel directly in regular diesel car engines. This chapter describes the production of ethyl levulinate, one of the most important levulinic acid derivatives due to its potential use as a fuel additive and precursor to various chemicals. In this sense, general characteristics and data on this compound, its current production, market, growth prospects and applications are addressed. In addition, recent advances in the production of ethyl levulinate through process intensification were discussed.

8.1 Ethyl Levulinate: General Characteristics, Uses and Applications Ethyl levulinate (EL) is an organic compound with molecular formula C7 H12 O3 , and it is one of the 12 most promising biochemical platforms derived from biomass, according to the US National Renewable Energy and Energy Department [1]. EL and 2-methyltetrahydrofuran (MTHF) are considered the most important derivatives of levulinic acid, due to their potential as fuel additives [2]. Previous research has found that using ethyl levulinate as a fuel additive can significantly reduce pollutants and environmental effect [3]. The potential for ethyl levulinate to be used as a fuel additive in diesel blending has attracted interest in recent years. However, ethyl levulinate has recently been used to produce medicines such as calcium levulinate, which is used for both mineral supplements and tuberculosis pretreatments. EL is also being considered as a possible substitute for valencene in the production of fragrances and fruity, sweet, and floral flavors [2]. In Table 8.1 some of the physical and chemical properties of EL are tabulated, which further elucidate the importance of EL as a fuel additive. In relation to the current ethyl levulinate markets, since EL is a product derived from levulinic acid, its potential markets are even further limited. In this sense, Grand View Research (GVR) (2016) estimated that global ethyl levulinate market demand was 32.4 tons in 2014 and is expected to reach 49.1 tons by 2022, growing at a CAGR © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_8

163

164

8 Ethyl Levulinate

Table 8.1 Physical and chemical properties of EL Property

Value

Property

Value

Chemical formule

C7 H12 O3

References

Mass

144.08

Molecular weight

144.17

Density (at STP)

1012.4 kg/m3

[4]

O2 content

33 wt%

[5]

Boiling point

479.15 K

[6]

Melting point

< 213.15 K

[7]

Flash point

364.15 K

[8]

mm2 /s

References

Cloud point

194.15 K

[9]

Kinematic viscosity

1.50

Lower heating value

24.8 MJ/L

[10]

RVP psi

< 0.01

[11]

Solubility in watera

12.5 wt%

[12]

Heat of vaporizationb

306.7 kJ/kg

[10]

4.690 kPa

[13]

Vapor pressure a

[9]

b

At 293.15 K, At 298.15 K

of 5.3% from 2015 to 2022. The global ethyl levulinate market had a value of USD 8.8 million, also in the period between 2015 and 2022, a growing about 3–3.6% is expected, which means that for 2026 the ethyl levulinate market reaches the USD 14 million [14]. Currently, ethyl levulinate market is at elementary and nascent status due to due to its recent production technology, for this reason its production is dominated by a few numbers of companies such as GFBiochemicals Ltd, Vigon International Inc., Ernesto Ventós, SA among others [15, 16]. It is expected that, as demand for levulinic acid grows and the industry matures, production costs will decrease because of advances in the manufacturing process, economies of scale achieved by manufacturers, and increased acceptance of this product across sectors [14]. Finally, it is important to highlight, that according with different sources the current levulinic acid market is dominated by the Asia-Pacific Region, which represents about 30% of the total levulinic acid market in 2014 [16]. Also, it is expected that this region has the one of the fastest growing demands of ethyl levulinate, due to the continuous growing of some sectors such as the fragrance, food, and fertilizer industries, as well as other nascent industries in China and India [14, 16]. In this sense the Fig. 8.1 shows the market growth rate by region for the period 2020–2025, please note that the norther America region is considered as other important EL market.

8.2 Ethyl Levulinate as Fuel Additive Ethyl levulinate has an energy density of 31.2 MJ/L (energy density of gasoline is 44.4 MJ/kg), much superior to that of ethanol (24 MJ/L). EL has a high flash point of 90 °C, attributable to its low volatility as prescribed by a boiling point of 206 °C. Due

8.2 Ethyl Levulinate as Fuel Additive

165

Fig. 8.1 Market growth rate of ethyl levulinate demand by region from 2020 to 2025 [16]

to its high oxygen content and high boiling point, ethyl levulinate has been originally espoused as a suitable oxygenate additive for diesel fuels to reduce soot formation [17]. EL has a freezing point of −79 °C, this ameliorates biodiesel properties which are negatively affected by cold weather, such as cloud point, pour point, and cold filter plugging point [9]. However, ethyl levulinate has a cetane rating of less than 10, and therefore mixtures with high levels of ethyl levulinate require the addition of a cetane-treating additive [18]. The most studied diesel blend with levulinic acid esters is a low-smoke formulation developed by Biofine and Texaco that uses ethyl levulinate as an oxygenate additive. Their blend consists of 20% ethyl levulinate, 1% co-additive and 79% diesel and can be used in regular diesel engines [19]. Have been reported successful engine tests of various blends of ethyl levulinate, and ethyl levulinate/n-butanol with a diesel fuel, showing marginal increases in brake specific fuel consumption and marginal effect on the emission of unburned hydrocarbons for 10 vol% ethyl levulinate mixtures with a road diesel [20]. In a direct injection compression ignition engine, studied a series of oxygenated fuel components both as neat fuels, and as 30 vol% blends with n-heptane. They noted a reduction in overall particulate mass when using ethyl levulinate as a fuel component, but also noted increase in the overall number of particulate particles [21]. Ethyl levulinate properties such as low cetane number, reactivity, and miscibility may favor its use as a gasoline additive than as a diesel additive [17]. Christensen et al. [10] also noted that the use of ethyl levulinate (at 3.7 wt% oxygen, ∼5.9 mol% ethyl levulinate) as a gasoline extender gives favorable attributes over other possible oxygenated additives, including ethanol and propanol, by; lowering the volatility of the fuel; increasing blended octane numbers by ∼15. Tian et al. [22] found that ethyl levulinate has a higher anti knock propensity than gasoline. This suggests that ethyl levulinate would be better placed as a gasoline additive.

166

8 Ethyl Levulinate

8.3 Esterification in Ethyl Levulinate Production To produce ethyl levulinate, levulinic acid (LA) must be esterified with ethanol (ET) [23]. This reaction is limited by equilibrium and, therefore, to attain high levels of conversion of levulinic acid, the reverse reaction must be minimized by either removing water as the reaction occurs, which is littered with several complications, or by forcing the forward reaction by using an excess amount of ethanol [24]. The plausible reaction mechanism of catalytic LA esterification with ethanol in the presence of HPW/Zr catalyst can be described by several steps as exhibited in Fig. 8.2. The reaction proceeds according to the mechanism proposed previously [25–27]. Once levulinic acid is produced, it was then esterified with ethanol to produce ethyl levulinate. In contrast to the first reaction, which has not been thoroughly studied, this second reaction has been intensively investigated. Some studies focusing on this reaction have been conducted and reported [2]. The esterification process can be sped up by the presence of a homogeneous or heterogeneous catalyst [23]. Examples of commonly used catalysts for esterification are zeolites, which are solid crystalline microporous materials that have a large surface area and strong acid sites [29], and heteropoly acids, which exist in a variety of structures and are known for their high Brønsted acidity compared to other catalyst [30]. Both types of catalysts have several attractive properties such as their easily adjustable acidity, simple recycling process, economic potential, and environmental friendliness [31].

Fig. 8.2 Reaction mechanism of LA esterification with ethanol for EL production [28]

8.3 Esterification in Ethyl Levulinate Production

167

8.3.1 Homogeneous Catalysis Homogeneous catalysts were readily used in esterification reactions in the past, but there is little research specifically dealing with ethyl levulinate production using homogeneous catalysts [32]. The most common homogeneous catalysts are HCl, H3 PO4 , and H2 SO4 . Their initial appeal was due to the fact that with their use, high yields could be attained in short reaction times [33] but they have major downsides, which have led to their disuse. Homogeneous catalysts cannot be recycled, cause equipment corrosion, produce large amounts of wastewater, and are difficult to handle [24, 34]. These aspects led to a preference for heterogeneous catalysts.

8.3.2 Heterogeneous Catalysis There is a wide variety of heterogeneous catalysts available, and studies have shown that one of the important aspects of heterogeneous catalysts is their structure which affects their acid site density. Structures with smaller pores make it more difficult for larger molecules to access the catalytic sites and, therefore, potential catalysts must be selected taking into account this restriction [33]. Several studies analyzed the effectiveness of a variety of heterogeneous catalysts in the production of ethyl levulinate from levulinic acid (Table 8.2). For instance, one study found that the zeolite structure influences the esterification of levulinic acid with ethanol more than its acidity, leading to the conclusion that pore channels have a significant impact on catalytic activity [35, 36]. This is due to a fast deactivation related to the building up of coke when molecules cannot leave the catalytic pores, and so catalytic activity of traditional zeolite crystals is defined by mass transfer limitations [37]. Other possible catalysts are heteropoly acids (HPA), which are often considered the preferred category of solid catalysts [8]. Although they have advantages over homogeneous catalysts in relation to their cost, environmental impact, and equipment corrosion, they also have several disadvantages when compared to other heterogeneous options. HPA are highly soluble in water and other polar solvents, and bulk HPA have a low specific area, which hinders their use as efficient and effective catalysts when dealing with large molecules [40]. Other studies found that the use of hydrothermal carbon materials (HTC) as heterogeneous catalysts was also effective. HTC are an attractive option as catalysts in biomass-based processes because HTC are biomass-derived and, therefore, would contribute further to the development of greener processes [34]. Several esterification processes using HPA and HTC are summarized in Table 8.2. Another carbon material that can be used as catalysts are sulfonated carbon nanotubes [36]. However, this material is not recyclable and when used for esterification of levulinic acid with ethanol, it presented lower specific catalytic activity than Amberlyst-15, an ion-exchange sulfonic resin [36]. Sulfated oxides can also be

168

8 Ethyl Levulinate

Table 8.2 Summary of conversion (C) and selectivity (S) data of processes for synthesis of ethyl levulinate from levulinic acid and ethanol, including catalyst loading on weight basis (CL), temperature (T ), residence time (τ ), the molar ratio of levulinic acid to ethanol (LA:ET ) and reference (REF)

a

Catalyst

Catalyst type

C (%) S (%) CL a (%) T (°C) T (h) LA:ET References

None

None

60

n.a

n.a

250

1.5

1:1

[38]

DTPA/DH-ZSM-597 Zeolite

94

100

15

78

4.0

1:8

[24]

DH-ZSM-5

Zeolite

95

100

13

120

7.0

1:8

[39]

Wells–Dawson Bulk HPA

Heteropoly acid

93

100

15.5

78

10

1:5

[40]

H4 SiW12 O40 -SiOa

Heteropoly acid

75

89

20

75

1:19.4

[31]

HTC-Glu-S

Hydrothermal 92 carbon

93

5.0

60

1.0

1:5

[34]

Zr-SBA-15

Hydrothermal 79 carbon

n.a

5.0

70

24

1:10

[33]

Amberlyst-15

Sulfonated resin

n.a

2.5

70

5.0

1:5

[35]

54

This process requires the use of a solvent, cyclohexane, on a molar ratio of 5:2 to ethanol

used as catalysts, and investigators found that Amberlyst-15 is the most attractive option from those studied [35].

8.4 Routes for EL Synthesis EL production involves the reaction of a biomass-derived substrate through an esterification reaction in the presence of an acid catalyst. EL could be produced by aqueous sugars obtained from biomass pretreatment [41]. The prominent routes to produce EL are shown in Fig. 8.3. To get hexose sugars, raw biomass is delignified to release the cellulose, which on de-polymerization yields glucose. On isomerization followed by dehydration, glucose is converted into fructose and hydroxymethyl furfural (HMF) [42]. In presence of an acid catalyst, on ring-opening, HMF is transformed into LA (Fig. 8.3). On further esterification by ethanol, LA is converted into EL. In an alternate route, glucose could be reacted in the presence of HCl to yield chloromethyl furfural (CMF) which on subsequent ethanolysis produces EL. Acid catalyzed isomerization and dehydration of pentose sugars such as xylose yield xylulose followed by conversion into furfural as shown in Fig. 8.3. On subsequent hydrogenation, furfuryl alcohol (FAL) is formed, which on ethanolysis is suggested to produce EL. Since both pentose and hexose sugars can be converted to EL, a more direct process is suggested via ethanolysis of lignocellulosic biomass. In principle, it is possible to produce EL from any intermediate of hexoses and pentose by replacing the hydrolysis reaction

8.4 Routes for EL Synthesis

169

Fig. 8.3 Routes to produce EL

to an ethanolysis process. However, LA and FAL are most preferred substrates for EL synthesis. Following section provides an insight into the mechanistic pathways and elaborates on the properties of applied catalysts.

8.4.1 Synthesis of EL from LA LA is listed as one of the top 12 building block chemicals derived from biomass as identified by the department of energy, United States in the year 2004 [1] and in the revised list of top 10 chemicals, in the year 2010 [43]. Acidic functionality of LA was observed to undergo esterification reaction with alcohols at room temperature in both catalyzed and un-catalyzed environments [44]. A list of catalysts which have been used for this reaction is summarized [45] in Table 8.3. The reaction rate in the un-catalyzed environment is observed to be slower compared to the acid catalyzed reaction.

8.4.2 Synthesis of EL from FAL Compared to the hexose route, where C6 precursors are converted into EL, pentose route starting with a C5 sugar molecule is more efficient in terms of atom economy [53]. Pentose sugars obtained from hemicellulosic pentosan are traditionally used to produce furfural. On metal catalyzed hydrogenation, furfural is converted into FAL which may serve as a precursor to EL synthesis. About 62% of the total furfural

170

8 Ethyl Levulinate

Table 8.3 Catalytic materials, reaction conditions and EL yield of the LA ethanolysis S. No.

Feed

Process conditions

EtOH to LA molar ratio

Catalyst

EL yield (mol %) T (°C)

References

t (min)

1

06:01

No catalyst

78

300

3.5

[44]

2

05:01

p-toluene sulfonic acid

–

7 days

15.4

[46]

3

01:01

N-methyl-2-pyrrolidonium (NMP) derived Br8nsted acidic ionic liquid

25

1080

> 50.0

[47]

4

64:01:00

Wells–Dawson HPA

78

600

76

[40]

5

64:01:00

Keggin HPA

78

600

93

[40]

6

16:01

Keggin HPA/SiO2

75

360

67

[31]

7

08:01

(DTPA-HPA)/desilicated HZSM-5

76

240

94

[24]

8

08:01

Desilicated HZSM-5

130

300

95

[39]

9

08:01

Micro-meso-HZ-5

130

300

95

[48]

10

06:01

H-BEA (beta zeolite)

78

300

39

[44]

11

05:01

SnO2

70

300

> 6.0

[35]

12

05:01

Sulfated SnO2

70

300

44

[35]

13

05:01

Sulfated TiO2

70

300

40

[35]

14

05:01

Sulfated Nb2 O5

70

300

> 14.0

[35]

15

10:01

Sulfated ZrO2

70

600

27.5

[33]

16

10:01

Sulfated Si-doped ZrO2

70

600

77.5

[33]

17

1.5:1

Sulfated ZrO2 modified TiO2 nano rods

120

120

81.2

[49]

18

2.5:1

Sulfated ZrO2 /TiO2

105

180

90.4

[50]

19

10:01

Sulfated meso-Zr-SBA-15

70

1500

≈ 80.0

[33]

20

4.9:1

Pr-SO3 H-SBA-15 (propyl-sulfonic acid functionalized mesoporous silica)

117

120

≈ 100

[51]

21

05:01

Sulfonated carbon nanotube 70

300

> 50.0

[36]

22

15:01

Zr containing MOFs

480

> 95.0

[52]

78

produced (280,000 MT) worldwide is used for the production of FAL [54]. In addition, esterification reaction of LA to yield EL, leads to difficult product separation in aqueous phase. An alternate route involving ethanolysis of FAL is being explored which has generated renewed interest in EL synthesis, wherein high yield (> 90%) of the levulinate product is reported [55]. EL produced can be upgraded to γ-valerolactone (GVL) [56] and this route, in-terms of obtained high yield, shows

8.4 Routes for EL Synthesis

171

merit over the direct LA conversion to GVL. Besides alkyl levulinates, side products and intermediates are known to be formed in this ethanolysis reaction affecting the selectivity. A significant decrease in EL yield was observed on adding water to the reaction solvent. For example, the reaction conducted with the catalyst, Amberlyst15, in a 20% ethanol and 80% heptane mixture produced 87.7% EL which was reduced to 66.9% in a reaction mixture of 90% ethanol and 10% water [57]. Table 8.4 shows the acid catalysts employed for FAL conversion to EL, reaction conditions employed and obtained EL yield.

8.4.3 Synthesis of EL from Chloromethyl Furfural (CMF) In addition to existing substrates, recently developed technologies for EL production from novel substrates such as CMF have been explored for producing EL [68]. For instance, Breeden et al. [69] have demonstrated significant production of CMF (more than 70% yield) from HMF, glucose and inulin, at 80 °C in less than 15 min [70]. Mascal et al. [70] have successfully obtained 84.7% EL yield from CMF at 160 °C in a relatively short period of time (30 min) [71]. The authors have demonstrated the feasibility of an integrated process to produce EL directly from biomass and seed oil via CMF route [70]. Liu et al. [72] have utilized DFT calculations, to suggest that the reaction proceed via the de-chlorination of CMF to produce 5-ethoxymethyl furfural (EOMF) as the intermediate. At room temperature the intermediate is obtained as the stable product with high yield [71]. However, at elevated temperature (> 100 °C), on subsequent ethanolysis the CMF is converted to EL.

8.4.4 Synthesis of EL from Monosaccharides and Polysaccharides Direct ethanolysis of biomass-derived monosaccharides (glucose, fructose, xylose etc.) and polysaccharides (sucrose, maltose, cellulose etc.) to produce EL in high yield could form the ultimate process for producing fuels and chemicals directly from lignocellulosic biomass. In principle, the ethanolysis reaction could be directly applied to a starchy or woody biomass such as pine wood and wheat straw. Tables 8.5 and 8.6 presents a list of monosaccharides and polysaccharides which have been utilized as substrate for direct EL synthesis via the ethanolysis reaction. Fructose is reported to produce a significantly higher yield on a variety of acid catalysts as compared to other monosaccharides (glucose, mannose etc.).

Al(OTf)3

16

110

120 110

H2 SO4

AlCl3

14

120

90

110

110

110

120

120

15

p-TSA

N-(bis(dimethylamino)methylene)-4-sulfobutan-1-aminium hydrogensulfate ([BsTmG][HSO4 ])

10

13

110

1,3-bis(3-sulfopropyl)-1H-imidazol-3-ium hydrogensulfate [(HSO3 -p)2Im][HSO4 ]

9

1-(4-sulfobutyl) pyridinium hydrogensulfate ([BsPy]-[HSO4 ])

1-methyl-3-(4-sulfobutyl)-1H-imidazol-3-ium hydrogensulfate [BMIm-SH][HSO4 ])

8

Benzenesulfonic acid

3-butyl-1-methyl-1H-imidazol-3-ium hydrogensulfate [BMIm][HSO4 ]

7

11

Propylsulfonic acid functionalized ethane-bridged organosilica hollow nanosphere

6

12

110

Sulfonated activated carbon

5

125 110

Purolite-500

Sulfonated carbon silica composites

3

90

4

125

DOWEX resin

Amberlyst-15

1

T (o C)

Catalyst

Process conditions

2

S. No.

Table 8.4 Catalytic materials, reaction conditions and EL yield of the FAL ethanolysis

180

180

360

360

90

120

120

120

120

120

120

360

1440

10–150

90

10–150

t (min)

~ 67.0

~ 74.0

92.5

94.6

92.5

93

93

95.0

~ 92.0

~ 34.0

84.9

89.6

86

~ 80.0

87.7

~ 60.0

EL yield (mol %)

[62]

[62]

[59]

[59]

[57]

[61]

[61]

[61]

[61]

[61]

[60]

[59]

[53]

[58]

[57]

[58]

(continued)

References

172 8 Ethyl Levulinate

200

SO4 2− /TiO2

Hierarchical zeolite HZ-5

ZSM-5

Hβ-Zeolite

Alumina containing mesoporous TUD-1 (Al-TUD-1-4), Si/Al=21

22

23

24

25

26 140

120

120

139

200

SO4 2− /ZrO2

21

120 140

HPA-ZrO2

Zr-Aluminum oxide

19

20

70

110

AlBr3

Fe(III) acetlyacetone

17

T (o C)

Catalyst

Process conditions

18

S. No.

Table 8.4 (continued)

1440

360

360

240

150

150

1440

360

210–240

180

t (min)

80

82.6

85.8

73

68.3

64.3

80

48

95

< 70.0

EL yield (mol %)

[67]

[59]

[59]

[66]

[65]

[65]

[64]

[59]

[63]

[62]

References

8.4 Routes for EL Synthesis 173

150

160

Glucose

17 AlCl3 .6H2 O

180

H2 SO4 + USY zeolite

Glucose

16

200 180

Sulfated ZrO2 USY zeolite

Glucose

Glucose

230

150

14

Hybrid zirconia zeolite catalyst

K-HPA (H3 PW12 O40 )

160

230

140

130

120

120

140

140

140

140

T (o C)

15

Glucose

13

TiO2

Fructose

Glucose

11

12

H-USY zeolite

Fructose

10

HPA (H3 PW12 O40 ) Hybrid HY zeolite

Fructose

HPA (H3 PW12 O40 )

Fructose

Fructose

7

poly (p-styrenesulfonic acid)-grafted carbon nanotubes (CNT-PSSA)

8

Fructose

6

Amberlyst-15

Sulfonated SBA-15

1-methyl-3-(4-sulfobutyl) imidazolium bis((trifluoromethyl)sulfonyl) amide ([BMIm-SO3 H][NTf2 ])

N,N,N-triethyl-4-sulfobutan-ammonium hydrogensulfate ([NEt3B-SO3 H][HSO4 ])

1-methyl-3-(4-sulfobutyl) imidazolium methane sulfonate ([BMIm-SO3 H][OMs])

Catalyst

Process conditions

9

Fructose

Fructose

3

Fructose

Fructose

2

4

Fructose

1

5

Substrate

S. No.

Table 8.5 Catalytic materials, reaction conditions and EL yield of the monosaccharides ethanolysis

15

120

30

180

360

120

180

1200

180

130

90

1440

1440

1440

1440

1440

1440

t (min)

93

51.4

~ 40.0

~ 25.0

21.9

14.5

71

40

52.8

37

~ 25.0

84

73

~ 70.0

77

74

67

EL yield (mol%)

(continued)

[84]

[83]

[82]

[81]

[77]

[80]

[79]

[78]

[77]

[76]

[75]

[74]

[74]

[29]

[73]

[73]

[73]

References

174 8 Ethyl Levulinate

Sorbose

20 H-USY zeolite

H-USY zeolite H-USY zeolite

Ethyl-D-glucopyronosi de (EDGP)

Mannose

18

Catalyst

Process conditions

19

Substrate

S. No.

Table 8.5 (continued)

160

160

160

T (o C)

1200

1200

1200

t (min)

35

44

41

EL yield (mol%)

[78]

[78]

[78]

References

8.4 Routes for EL Synthesis 175

176

8 Ethyl Levulinate

Table 8.6 Catalytic materials, reaction conditions and EL yield of the polysaccharides ethanolysis S. No.

Substrate

1

Sucrose

2

Sucrose

Process conditions

EL yield (mol%)

References

t (min)

1-methyl-3-(4-sulfobutyl) 140 imidazolium bis((trifluoromethyl)sulfonyl) amide ([BMIm-SO3 H][NTf2])

1440

43

[73]

[3.2H]3 (PW12 O40 )2 (IL POM) 120

720

45

[163]

Catalyst

T (o C)

3

Sucrose

Sulfonated SBA-15

140

1440

35

[75]

4

Sucrose

H-USY zeolite

160

1200

35

[78]

5

Sucrose

Hybrid zirconia HY zeolite

230

360

23.2

[77]

6

Maltose

Amberlyst-70

175

120

~ 20.0

[85]

7

Raffinose

Amberlyst-70

175

120

~ 20.0

[85]

8

Maltose

H-USY zeolite

160

1200

47

[78]

9

Cellubiose

H-USY zeolite

200

1440

44

[78]

10

Inulin

H-USY zeolite

200

1200

39

[78]

11

Inulin

K-HPA (H3 PW12 O40 )

150

120

52.3

[80]

12

Inulin

[3.2H]3 (PW12 O40 )2 (IL POM) 120

720

67

[86]

13

Cellulose

H4 SiW12 O40

205

30

27

[87]

14

Cellulose

K-HPA (H3 PW12 O40 )

220

120

14.8

[77]

15

Cellulose

1-(1-propylsulfonic)-3-methyl imidazolium chloride IL

170

720

38.5

[88]

16

Pine wood

H2 SO4

145

120

44.4

[89]

17

Wheat straw

H2 SO4

183

36

51.0

[90]

18

Furfural residue

H2 SO4 + USY zeolite

219

107

51.2

[83]

8.5 Process Intensification Applied to Ethyl Levulinate Production Nowadays, the production of ethyl levulinate is dominated by a few numbers of companies, however there is not information related with the current technology used to produce LA. Despite this lack of information one of the most promising technologies to produce ethyl levulinate is the reactive distillation RD, where two different operations the reaction and separation are carried out in a single equipment. The use of reactive distillation in the production EL has attracted the attention in recent years because it allows to overcome the equilibrium conversion limitation. In this sense, the first record in a reactive column applied to ethyl levulinate production was proposed by Novita et al. [91]. Figure 8.4 lustrates the reactive distillation process proposed by Novita et al. [91].

8.5 Process Intensification Applied to Ethyl Levulinate Production

177

Fig. 8.4 Conventional reactive distillation process proposed by Novita et al. [91]

Please note, that the process proposed by Novita et al. [91] consist of 3 different columns, the first column is the reactive column, it has 51 stages, and the ethanol is the limiting reactive. In this column 100 kmol/h are fed join to 126 kmol/h of levulinic acid, which corresponds to 100 kmol/h of fresh levulinic acid feed and 26 kmol/h from the recirculation stream, this column has an energy requirement of 3.68 Gcal/h. The second column (RC-1) is a prefractionation column, the aim of this unit is separate the water from the other products, it has 10 stages and a bergy consumption of 2.37 gcal/h. Finally, the third column (RC.2) separates the ethyl levulinate from the unreacted levulinic acid with a purity 99.5% mol basis. This unit has 17 equilibrium stages and anergy consumption of 1.72 G cal/h. As aforementioned the reactive distillation is considered the most feasible process to process ethyl levulinate because it can overcome all the equilibrium limitation associated in esterification reactions. Although reactive distillation is already an intensified process, it can still be improved by increasing the intensification even further. In this sense, the thermally coupled columns as heat integration could be a feasible option for improving the production of EL by reactive distillation. The first work of intensification applied to the reactive distillation of EL was proposed by Novita et al. [91], they proposed three intensified reactive distillation options using as based case the conventional arrangement shown in Fig. 8.4, their intensified option consist in a thermally coupled reactive distillation (TCRD), a reactive distillation with heat integration (RDHI) and a hybrid with heat integration and thermally coupling (THRD). Subsequently, Vazquez-Castillo et al. [92] proposed an additional intensified option which consists of reactive distillation column followed by a dividing wall column (PDWC). These intensified purposes are shown in the Fig. 8.5.

8.5.1 Kinetics Models for Ethyl Levulinate Production As aforementioned, the ethyl levulinate can be produced using different pathways and catalysts, consequently there are different kinetic model to express chemical kinetics

Fig. 8.5 Intensified reactive distillation processes foe ethyl levulinate production

178 8 Ethyl Levulinate

8.5 Process Intensification Applied to Ethyl Levulinate Production

179

in the production of ethyl levulinate. However, the esterification of levulinic acid with ethanol to produce ethyl levulinate stand up over other routes owing to this reaction can be effortless implemented and at the same time the esterification is cheaper than other pathways, despite its equilibrium limitations, which can be overcome using reactive distillation schemes [91]. The reversible esterification reaction to process ethyl levulinate using Amberlyst™ proposed by Tsai [93] is showed in Eq. 8.1 k1

C5 H8 O3 + C2 H5 OH  C7 H12 O3 + H2 O k2

A

B

C

(8.1)

D

where, A = Levulinic acid; B = Ethanol; C = Ethyl levulinate, and D = Water. Although the esterification reaction is carried out on a solid catalyst, the load of said catalyst is so small that the reaction can be modeled as nonidealquasi-homogeneous model [93]. Therefore, the kinetic model of reversible rection can be expressed as an elementary reaction as follows:   aC a D −r A = k1 a A a B − Ka

(8.2)

where, K a is the equilibrium constant, which can be expressed as the ratio among the specific reaction rates or concentrations of the forward and reverse reactions: Ka =

Cc C D K1 = K2 C AC B

(8.3)

The specific reaction rate k1 and k2 using the Arrhenius equation as follows:  k1 = A f exp 

−E 0, f RT

−E 0,r k2 = Ar exp RT

 (8.4)  (8.5)

Table 8.7 shows the kinetic parameters for ethyl levulinate production using Amberlyst proposed by Tsai [93]. Table 8.7 Kinetic parameters for ethyl levulinate production using Amberlyst

Parameter

Value

Af (mol/s kg)

0.0133 × 107

Ar (mol/s kg)

3.077 × 103

E f (kJ/mol)

37.79

E r (kJ/mol)

36.91

180

8 Ethyl Levulinate

8.5.2 Optimization and Sustainability Analysis In this sense, in order to determine the best intensified option Vazquez-Castillo et al. [92] proposed a simultaneous design and optimization of the aforementioned intensified option. They used the differential evolution with tabu list optimization method, and they considered the total annual cost (TAC) Eco indicator 99 (EI99) and Individual risk (EI99) as metrics to quantify the performance of different options. To calculate the TAC the method published by Guthrie [94] was used, which was modified by Ulrich [95] where the cost estimate of a plant is made separated from industrial units, and the use of equations published by Turton et al. [96], that a cost approximation of the process is carried out using Eq. 8.6, that is: n T AC =

C T M,i  + Cut, j m j=1 n

i=1

(8.6)

where TAC is the total annual cost, CTM is the capital cost of the plant, n is the total number of individual units, m is the payblack period, and Cut is the cost of the services, respectively. The Individual Risk (IR) as metric to evaluate the safety of processes separation alternatives. The IR represents the likelihood of injury or decease for a person located at certain distance from the epicenter of an accident [97]. It is important to mention that IR is not a function of the number of people exposed to an accident, owing to it quantifies the damage based on the distance between the accident and the person [98, 99]. Mathematically, the individual risk is expressed as the occurrence frequency of an incident, multiplied by its probability of affectation. Therefore, the IR can be calculated by Eq. 8.7. IR =



f i Px,y

(8.7)

where f i is the occurrence frequency of incident i, and Px, y is the probability of affectation caused by the incident i. The individual risk is calculated by a Quantitative Risk Analysis (QRA). The QRA is a methodology that identifies and quantifies the consequences of potential incidents. This method performs a classification of the potential incidents in two main categories: continuous releases and instantaneous releases. A continuous release is produced by a rupture on a pipeline or a partial rupture of a process equipment, which provokes a continuous leak of matter. In contrast, an instantaneous release consists of a catastrophic rupture of a process equipment, generating the total loss of matter from the process equipment. With the aim of identifying the potential continuous and instantaneous release incidents a Hazard and Operability study (HAZOP) was applied to these distillation processes [99]. This is a common method used in the chemical industry, which is based on deviations of operative conditions. Specific information about this methodology is

8.5 Process Intensification Applied to Ethyl Levulinate Production

181

given by the Center for Chemical Process Safety (CCPS) [99]. Based on the HAZOP analysis Unconfined Vapor Cloud Explosion (UVCE), Boiling Liquid Expanding Vapor Explosion (BLEVE) flash fire and toxic releases have been identified as the potential instantaneous releases incidents, whereas jet fire, flash fire and toxic release were identified as likely continuous release incidents. It is important to mention that the occurrence frequencies of the accidents (fi) were taken from CCPS [99]. These frequencies correspond to typical occurrence frequencies for distillation columns. The eco-indicator 99 is one of the best eco-indicators to quantify the environmental impact since its evaluation is based on the life cycle. Its first uses were focused on the construction area [100, 101]. In the EI99 methodology, 11 impact categories are considered aggregated into three major damages categories: human health, ecosystem quality, and resources depletion. It was quantified following the procedure proposed by Goedkoop and Spriensma [102] as reported in Eq. 8.8: E I 99 =

 b

d

δd ωd βb αb,k

(8.8)

k∈K

where βb represents the total amount of chemical b released per unit of reference flow due to direct emissions, ∝b,k is the damage caused in category k per unit of chemical b released to the environment, δd is a weighting factor for damage in category d, and ωd is the normalization factor for damage of category d. The scale is chosen in such a way that the value of 1 Pt is representative for one-thousandth of the yearly environmental load of one average European inhabitant. In this work, for ecoindicator 99 calculation the impact of three factors was considered as most important in the LA downstream processing: steam (used in column reboiler), electricity (used for pumping) and steel (to build distillation columns and accessories). The values for those three factors are summarized in the manual reported by Goedkoop and Sprinsma [102], also are shown in Table 8.8. Table 8.8 Unit eco-indicator used to measure the eco-indicator 99 in both case studies Impact category

Steel (points/kg)

Steam (points/kg)

Electricity (points/kWh)

Carcinogenic

6.320E−03

1.180E−04

4.360E−04

Climate change

1.310E−02

1.600E−03

3.610E−06

Ionizing radiation

4.510E−04

1.130E−03

8.240E−04

Ozone depletion

4.550E−06

2.100E−06

1.210E−04

Respiratory effects

8.010E−02

7.870E−07

1.350E−06

Acidification

2.710E−03

1.210E−02

2.810E−04

Ecotoxicity

7.450E−02

2.800E−03

1.670E−04

Land occupation

3.730E−03

8.580E−05

4.680E−04

Fossil fuels

5.930E−02

1.250E−02

1.200E−03

Mineral extraction

7.420E−02

8.820E−06

5.700E−06

182

8 Ethyl Levulinate

Mathematically, the optimiation problem proposed by Vazques-Castillo et al. [92] can be expressed as follows: min Z {T AC, EC O99, I R) n n    i=1 C T M,i Cut, j + δd ωd βb αb,k + f i Px,y + = m j=1 b d k∈K Subject to : yi Pc ≥ xi Pc wi Fc ≥ u Fc

(8.9)

(8.10)

The decision variables used for the optimization of the RD processes are a combination of discrete and continuous variables, as listed in Table 8.9. The purity constraints for ethyl levulinate and water were defined as 99.5 and 99.5 mol %, whereas the molar flow rate was set at least 99.5 kmol/h for both ethyl levulinate and water in their respective streams. The results obtained by Vazquez-Castillo et al. [92] are shown by the Pareto Front in Fig. 8.6. The utopian point methodology was used to select the solution with the best trade off between the objectives for each pareto front. Their results indicate that that the thermally coupled reactive distillation (TCRD) process has the lowest energy use (1.667 MJ/kg EL) with major energy savings (9.6–54.3% lower than other RD processes), reduced environmental impact (5.7–51% lower ECO 99 index value) and similar process safety (less than 2% difference as compared to other RD processes considered). Thus, the TCRD process is suggested as the best process alternative to produce ethyl levulinate, although there is room for further selection of other feasible RD processes where other tradeoffs among the indicators may be devised. These result contrast with the results obtained by Novita et al. [91]. The contrasts are explained by the fact that the implementation of a multi-objective optimization algorithm needs some adjustments to the rigorous process simulation: e.g. for the THRD process, the withdrawal side stage number and the side molar flow rate in the first separation column are both variables subject to optimization, while an additional constraint was added for the minimum temperature difference (driving force of 10 K) as it was found that only a fraction of the condenser energy of RC-2 was feasible to be utilized. In case of the RDHI sequence, a liquid stream enters the top of the RC-2 column while a vapor stream leaves the top via a heat exchanger, the heat duty of which is the heat that is subtracted from the heat duty of the reboiler of the reactive column. Based on the overall comparison, the TCRD process is the most appealing to be implemented in the EL production, having the lowest specific energy requirements (1.667 MJ/kg EL) and an annual cost of utilities of only $ 30.35 per ton of EL produced, as well as lowest CO2 emissions (110.4 kg/ton EL) due to thermal coupling.

8.6 Conclusions and Perspectives

183

Table 8.9 Discrete and continuous decision variables for the optimized RD processes CRDP

Decision variables

TCRD

RDHI

THRD

PDWC

Cont Disc Cont Disc Disc Disc Cont Disc Cont Disc Number of stages, RDC

X

X

X

X

X

X

Number of reactive stages

X

X

X

X

X

X

Heat duty of RDC, kW Distillate flow, kmol

h−1

Diameter of RDC, m

X X

X

X

X

X

X

X

X

Number of stages, RC-1

X

Feed stage, RC-1 Reflux ratio of RC-1

X

X X

X

X

X

X

X

X

X

X

Interlinking flow, kmol h−1

X

X

Bottom flow of RC-1, kmol X h−1

X

X

Diameter of RC-1, m

X

X

X

Withdrawal side stage

X

X

Side flow, kmol h−1

X

X

X X

X X

X

Number of stages, RC-2

X

X

X

X

Feed stage, RC-2

X

X

X

X

Reflux ratio of RC-2 Bottom flow, kmol h−1

X

X X X

X

X

Heat duty of RC-2, kW

X

X

Diameter of RC-2, m

X

X

Total number of variables

15

15

X X X X

X

X X

13

17

16

8.6 Conclusions and Perspectives Important aspects, data, production routes and advances on the production of ethyl levulinate were addressed in this chapter. The production of ethyl levulinate from levulinic acid has gained strength in recent years, due to advances in the production of this precursor. The biobased additives market is increasing with a clear growth trend. Therefore, alternatives must continue to be sought that guarantee the sustainable production of ethyl levulinate. In this sense, the first works to produce ethyl levulinate were presented, where they use reactive distillation. Although these works mark a starting point for the intensification of the ethyl levulinate production process, the development of new technologies must continue.

184

8 Ethyl Levulinate

Fig. 8.6 Pareto front for the intensified ethyl levulinate reactive distillation

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Chapter 9

2,5-Dimethylfuran

Abstract 2,5-Dimethylfuran became an attractive biofuel candidate after a new production method using biomass as feedstock was published in the early 2000s. It has an energy density 40% greater than that of ethanol, making it comparable to gasoline. It is also chemically stable and, being insoluble in water, does not absorb moisture from the atmosphere. Recent tests in a single-cylinder gasoline engine found that the thermal efficiency of burning dimethylfuran is similar to that of gasoline. Also, it has a similar heat of vaporization to gasoline; therefore, it may have less cold start problems compared to bioethanol. Overall, from the point of view of physicochemical properties, 2,5-Dimethylfuran is a promising gasoline alternative, with some aspects better than those of gasoline. Challenges and opportunities arise in process intensification to be able to design sustainable biorefineries that can produce it from lignocellulosic biomass in an economically profitable way.

9.1 2,5-Dimethylfuran: Chemical Properties, Uses and Applications Bioethanol, the only successfully commercialized gasoline alternative so far, is produced on a large scale and used mostly in low blend forms. The combustion of ethanol is proven to be clean, robust, and easy to be integrated into conventional petrol vehicles; however, there are several drawbacks of using bioethanol: high production cost during the distillation process, possible contamination by atmospheric water, low energy density, and high volatility. The search for a new renewable gasoline alternative remains a high priority for fuel researchers [1]. 2,5-Dimethylfuran (DMF) is a heterocyclic compound with the formula (CH3 )2 C4 H2 O. A derivative of furan, this simple compound is a potential biofuel, being derivable from cellulose. DMF has a number of attractions as a biofuel [2]. DMF became an attractive biofuel candidate after a new production method using biomass as feedstock was published in the early 2000s [3, 4]. For chemicals to be used in conventional internal combustion systems, they should exhibit certain physicochemical properties that are similar to or comparable to conventional fuels. It has an energy density 40% greater than © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_9

191

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9 2,5-Dimethylfuran

that of ethanol, making it comparable to gasoline. It is also chemically stable and, being insoluble in water, does not absorb moisture from the atmosphere. Evaporating dimethylfuran during the production process also requires around one third less energy than the evaporation of ethanol although it has a boiling point some 14 °C higher, at 92 °C, compared to 78 °C for ethanol. The ability to efficiently and rapidly produce dimethylfuran from fructose, found in fruit and some root vegetables, or from glucose, which can be derived from starch and cellulose—all widely available in nature—adds to the attraction of dimethylfuran, although safety issues must be examined. Bioethanol and biodiesel are currently the leading liquid biofuels [1]. The stoichiometric air/fuel ratio of dimethylfuran is 10.72, compared to ethanol at 8.95 and gasoline at 14.56. This means that burning dimethylfuran requires approximately 33% less air than the same quantity of gasoline, but approximately 20% more air than the same quantity of ethanol. The calorific value of liquid dimethylfuran is 33.7 MJ/kg, compared to 26.9 MJ/kg for ethanol and 43.2 MJ/kg for gasoline. The research octane number (RON) of dimethylfuran is 119. The latent heat of vaporization at 20 °C is 31.91 kJ/mol. Recent tests in a single-cylinder gasoline engine found that the thermal efficiency of burning dimethylfuran is similar to that of gasoline [5]. Comparing the physicochemical properties of DMF with gasoline provides insights into the feasibility of using DMF in current internal combustion engines (see Table 9.1). Table 9.1 shows that DMF has a RON of 101.3 and an MON of 88.1, both of which are above the minimum limits of the regulations in Europe [1]. Compared to those of gasoline, the MON of and the RON of DMF is higher. Therefore, it can be expected that the antiknock ranking is as follows: DMF > gasoline. DMF is an oxygenated hydrocarbon with a gravimetric oxygen content of 17%, making it highly competitive in reducing engine-out emissions. In terms of vehicle-out total hydrocarbon, carbon monoxide and nitro oxide emissions, the advantages of using DMF are lessened. However, particle emissions, one of the most significant challenges in direct-injection spark-ignition vehicles, will be reduced if oxygenated fuels such as DMF is used. A high density of DMF partially makes the volumetric LHV of DMF close to that of Table 9.1 Properties of DMF and gasoline [1]

Gasoline

DMF

Molecular weight (MW; g/mol)

NA

96

O2 (wt %)

16.67

2

Lower heating value (LHV; MJ/kg)

42.9

32.89

Air–fuel ratio (AFR; kg/kg)

14.46

10.72

Research octane number (RON)

96.8

101.3

Motor octane number (MON)

85.7

88.1

ΔHvap (kJ/kg at 298 K)

373

332

Density (kg/l)

0.7446

0.8897

Water solubility (g/l)

Negligible

2.3

9.2 Overall Process for DMF Production

193

gasoline. For a tank topped up with gasoline and DMF, the rank of vehicle mileage range is as follows: gasoline > DMF. DMF has a similar heat of vaporization (ΔHvap) to gasoline; therefore, it may have less cold start problems compared to bioethanol. Overall, from the point of view of physicochemical properties, DMF is a promising gasoline alternative, with some aspects better than those of gasoline. Compared to ethanol and n-butanol, DMF has a lot of superiorities. However, potential issues for the direct usage of DMF in engine still exist which are listed as follows: (a) DMF has high energy density tan ethanol and butanol, but lower than gasoline and diesel. To reach the same engine performance, the utilization of DMF as fuel for gasoline or diesel engine requires fuel-rate increases which lead to the load-increase of the oil supply system. (b) The molecular structure of DMF, including C=C doublé bond and ring enol ether, has great potential to generate the soot precursor during combustion. (c) DMF’s toxicity and impact on the environment and its combustion products need to be further studied [2].

9.2 Overall Process for DMF Production Global energy shortages and environment pollutions have urged scientists to develop a new generation of technologies that can cheaply synthesize biofuels from renewable biomass [6]. The second-generation biofuels must be established in usage of sustainable chemical products and produced through modern and mature chemical technologies such as pyrolysis, Fischer–Tropsch synthesis, or a catalytic process, all of which can produce complex molecules or transform materials into sustainable biofuels. The conversion of lignocellulose into DMF involves multistep processes (Fig. 9.1): (a) pretreatment and hydrolysis of lignocellulose to glucose, (b) catalytic isomerization and dehydration of glucose to 5-hydroxymethylfurfural (HMF), and (c) catalytic hydrodeoxygenation (HDO) of HMF to DMF [7].

9.2.1 DMF Production Technologies that Use Molecular Hydrogen A process to produce DMF was first disclosed by Morikawa in 1980 [8]. In a twostep process, HMF was reduced to 2-methylfurfural alcohol (MFA) using hydrazine followed by HDO using Pd/C and cyclohexene as a hydrogen source to produce 27% DMF at 80 °C. Since then, this technology was not explored until recently when the potential of DMF as a sustainable high-octane biofuel was established, and several researchers have started to develop catalytic routes to produce DMF selectively.

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9 2,5-Dimethylfuran

Fig. 9.1 Process steps for DMF production from lignocellulosic biomass

Roman-Leshkov et al. [3] prepared a CuRu/C catalyst that produced 71% DMF and 16% other products under batch conditions in 1-butanol at 220 °C and 6.8 bar H2 over 10 h.

9.2.2 DMF Production Technologies that Use Chemical Hydrogen Reagents DMF production that involves the catalytic HDO of pure HMF and carbohydrate derived HMF has been investigated with hydrogen generated in situ from chemical hydrogen reagents or by catalytic transfer hydrogenation. Chang et al. [9] used formic acid as a source of hydrogen and a Ru/C nanoparticulate catalyst for the conversion of HMF, fructose, and lignocellulose. Yang and Sen [10] used HMF as a substrate to produce 37% DMF, 43% 5-(formyloxymethyl) furfural (FMF), and 3% levulinic acid (LA) in THF. The advantage of this reaction is that it did not produce the ring saturated product 2,5-dimethyltetrahydrofuran, as observed for reactions conducted with H2 under high-pressure and high temperature conditions. Although the new development in the biomass conversion technology helps pave the way for the mass production of DMF as a new generation biofuel, there are some issues that remain unresolved. One of the issues is that the aforementioned production methods involve two complicated vessels. A single-vessel reactor with a multicomponent catalytic system is favorable for simplifying the production process and for reducing its cost. Chang et al. [9] developed synthesis of DMF by using a single-vessel, multicomponent catalytic system. [DMA]+ [CH3 SO3 ]− (DMA is short form for N-N-dimethylacetamide) was used as a catalyst for the hydrolysis and dehydration of untreated biomass into HMF, and a Ru/C catalyst was used as the catalyst for converting HMF to DMF. Lignocellulosic biomass substrates, such as sugarcane, bagasse, and agar, were used as feedstocks. Fructose was also used as a feedstock, and formic acid was used as catalyst instead of [DMA]+ [CH3 SO3 ]− .The best yield from this method was only 14.3%; much lower than the yield achieved by a

9.4 Biorefinery to Produces DMF from the HMF

195

two-vessel system used by the researcher mentioned earlier. Therefore, the efficiency of single-vessel reactors still requires further investigation.

9.3 Process Economy Although the process economy of most of the reported DMF production methods is not known, Roman-Leshkov et al. [3] reported a detailed cost analysis using an Aspen Plus model based on a two-step integrated process in which fructose solution is first dehydrated with HCl in a biphasic solvent. The organic phase of the resultant HMF solution that contains 58% HMF is then flashed from the aqueous-organic separator to remove excess butanol. The vapor phase through the vaporizer was fed into a plug-flow tubular reactor in which hydrogen was added for the conversion of HMF to DMF in the presence of CuRu/C catalyst. The catalyst needed regeneration after every 10 cycles, which involved treatment of the deactivated catalyst under H2 flow (40 mL/min) at 220 °C for 2 h. Frequent regeneration of the catalyst required additional processing equipment as well as excess catalyst. Based on a 96.6 t per day production target for DMF, $121.9 million capital cost estimate for the base case scenario, and $36.4 million catalyst cost for the first charge with replacement costs of $258 500 every two years, the minimum selling price for DMF is calculated at $7.63 per gallon. The calculated cost obtained by using the Aspen Plus model is very high compared to that obtained for a similar scale corn ethanol production ($2.3 per gallon) or cellulosic ethanol [11].

9.4 Biorefinery to Produces DMF from the HMF The techno-economic feasibility of biorefineries based on processes for producing HMF and DMF from fructose as proposed by Roman-Leshkov et al. [3] is presented in this section. The analysis considers two types of biorefineries: one that produces HMF from fructose in a bi-phasic reactor with an acid catalyst in wáter and a low boiling point solvent (butanol) and a second refinery that build on the first case but also produces DMF from the HMF using a copper–ruthenium catalyst. Block diagram of DMF production process based on published literature [12] is shown in Fig. 9.2. Figure 9.2 shows the process block diagram with simulated mass balances of DMF production from fructose via HMF. The HMF is produced in a biphasic reactor in Area 100. CSTR products are partially separated in Area 200. HMF in the organic rich phase is then flashed to remove excess butanol, and the remaining stream is vaporized at 220 °C and 1.72 MPa in Area 300. The vapor is then sent to a PFTR where hydrogen is added for the conversion of HMF to DMF in presence of CuRu/C catalyst. The process uses a 3-train PFTR reactor configuration with one on-stream reactor, one in regeneration and one on standby. The reactor is operated at 100%

Fig. 9.2 DMF production process block diagram

196 9 2,5-Dimethylfuran

9.4 Biorefinery to Produces DMF from the HMF

197

Table 9.2 Feed and product flow rates for DMF production [12] Raw materials

Flow rate (t/day)

Products

Flow rate (t/day)

Purity (%)

Fructose

300

DMF

96.60

97.74

Butanol

0.95

Levulinic acid

38.01

87.77

HCl

3.74

Byproducts

50.38

96.25

Water

782.1

Wastewater

907.8

H2

5.57

conversion of HMF. An unidentified byproduct is also produced in the reactor. DMF is separated in Area 400 via a flash separation and subsequent distillation. The bottom stream from the distillation column in Area 400 is further distilled in Area 600 where byproduct, butanol and water are separated and recycled. The aqueous stream from Area 200 is evaporated and distilled in Area 500 to separate levulinic acid, fructose, butanol, and water. Fructose, water, and butanol are recycled to the process. The feed and product flowrates of major components in the DMF production process are shown in Table 9.2. The process uses 300 t/day of pure fructose and 5.57 t/day of hydrogen as feedstock. Additional makeup chemicals are HCl (used as catalyst), NaCl (applied to enhance HMF partitioning between aqueous and organic solvent phases) and butanol (added to extract HMF from aqueous phase in the CSTR). The product and byproduct flow rates are obtained as 96.6 (98% pure) t/day, 38 (88% pure) t/day and 50.4 (96% pure) t/day of DMF, levulinic acid and unidentified byproduct, respectively. Total installed equipment cost for the base case scenario is estimated as $121.9 million (excluding catalyst cost). The costliest areas are Area 400 (24% of total installed equipment cost) and Area 500 (46% of total installed equipment cost). In Area 400, DMF is purified through a series of distillation columns. In Area 500, fructose is recovered and levulinic acid is purified (to a purity of 87.8%) through evaporators and distillation columns. Both areas use several condensers and reboilers. The process requires a copper–ruthenium (Cu–Ru/C) catalyst system. The total catalyst cost for 3 reactors is estimated as $36.4 million/charge which is approximately a third of the total installed equipment cost. The process has two major drawbacks. Firstly, the process requires H2 to convert HMF to DMF. This limits the process to colocation with excess hydrogen producing plants or on a hydrogen pipeline. Significant hydrogen use also reduces the renewable energy content of the DMF product since most hydrogen is currently produced from petroleum resources. If other biorefinery processes produced excess hydrogen then it could be effectively utilized in the DMF production module, otherwise the process would need to generate hydrogen within its battery limit which would require additional capital cost and increase the MSP of DMF. Secondly, the process uses NaCl to enhance extraction of HMF from aqueous phase to organic butanol phase in the biphasic CSTR. NaCl introduces uncertainties in the downstream process performance. Removal of NaCl to a significantly low

198

9 2,5-Dimethylfuran

level is cost intensive. It would be interesting to investigate alternative organic phase and improved operating conditions that could eliminate NaCl usage. For economic analysis, if it assumes that all the 18.2 Ml/year (4.8 million gal/year) of DMF could be recovered, then the MSP could be reduced to $1.36/l ($5.14/gal) which would be a substantial cost reduction. Hence, along with lower reactor yields, process loss is a major bottleneck in implementation of this process. The theoretical maximum for this conversion is 590.5 l/t (156 gal/t) of fructose which translates to 88.6 Ml/year (23.4 million gal/year) of DMF at the assumed scale. If theoretical yields were obtained in the current process, the MSP for DMF reduces to $0.9/l ($3.4/gal). Following our earlier assumption of 2000 t/day biomass processing facility, the maximum yield from this conversion will be around 53.4 l/t (14.1 gal/t) of biomass. This value is quite low for fuel use as compared to corn ethanol yield of 398 l/t (105 gal/t) of corn or even cellulosic ethanol with estimated yield of 310 l/t (82 gal/t) of biomass. Fructose feedstock cost contributes 47% to the MSP of DMF. A 20% change in the fructose price results in a 9.3% change in the MSP. The largescale availability of inexpensive fructose is also a bottleneck for this process, which can be addressed through studies for fructose production from cellulosic sources. In this process 75% of inlet fructose is converted in the CSTR and it is assumed that the remaining fructose is recycled after separation from products. However, there is uncertainty regarding the stability of fructose under the reaction and separation conditions. It is possible that fructose may degrade to other compounds thus further decreasing yields. Given the high capital costs, the purchased equipment cost has a significant impact on the MSP of DMF. A 20% change in purchased equipment cost results in a 9% change in the MSP. Currently the inlet HMF concentration in the PFTR is maintained as 10% w/w (upper limit of the published experimental data) and H2 fed is at a rate that is 10 times more than the stoichiometric requirement. In summary, the process for conversion of HMF to DMF uses an expensive Cu–Ru/C catalyst. The catalyst performance at the present level of development does not seem viable for commercial application of DMF as a fuel. Development of less expensive and effective catalysts with lower rare metal composition is essential for fuel applications. In addition, the low yields of DMF as compared to other alternative fuels from biomass, can make it unfeasible to pursue DMF solely for fuel applications. To benefit from synergies in a biorefinery it is imperative that new processes be developed which utilize byproducts like levulinic acid generated in this process to produce useful products.

9.5 Challenges and Opportunities in Process Intensification Process intensification (PI) has demonstrated the potential to significantly improve process efficiency and safety while reducing cost [13, 14], in fact, PI derives from the necessity of substantially improving the performance of process plants [15], moreover, several authors agreed that PI strategies are broader than process integration

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[16] and there play a major role in achieving the desired improvements in process synthesis [17, 18]. Below are some areas of opportunity, which according to the PI, can improve the DMF production process. DMF is a promising biomass-derived renewable fuel candidate that has ideal fuel properties such as a high-octane value, high energy density, low oxygen content, and low water miscibility. Among several process steps for the conversion of carbohydrate-containing biomass into DMF, the last step that involves the catalytic hydrodeoxygenation of 5-hydroxymethylfurfural plays a critical role to ensure a high yield and selectivity of DMF. If we consider only the fuel application, the nature of the catalysts and additives are also important for the formation of analogous molecules that have fuel properties, such as 2,5dimethyltetrahydrofuran, 2-methylfuran, methyltetrahydrofuran, 2-methylfurfural alcohol, and 5-methyltetrahydrofurfural alcohol, so that expensive separation from byproducts can be avoided. On the catalyst development front, it has been shown that bifunctional catalysts that contain a hydrogenation metal as well as a deoxygenation component are more effective for highly selective DMF production. Among the reported bifunctional catalysts, CuRu/C, Ru/Co3 O4 , and Pd/C/ZnCl2 are the most promising and give DMF yields in the range of 71–93%. A potential drawback of the Ru/Co3 O4 material is that the catalyst loading is high (40 wt% based on the substrate weight). Similarly, a high loading of Ru metal in the CuRu catalyst and its use in high concentration (30 wt% catalyst with respect to the starting substrate) shows an unfavorable economy of the two-step process for DMF production that involves the CuRu/Ccatalyzed hydrodeoxygenation of 5-hydroxymethylfurfural to DMF, in which the minimum selling price for DMF is significantly higher than that of conventional fuel. Sensitivity analysis identifies several critical factors that contribute to such a high production cost. Although some of these factors are governed by the market supply and demand, especially raw material and capital costs, the parameters that can be controlled to minimize the DMF production cost include improvement of DMF yields, minimization of catalyst loading, and easy separation of DMF from the product stream. In this context, a high yield of DMF using 10 wt% Pd/C/ZnCl2 catalyst that contains approximately 4 wt% Pd loading is beneficial because this catalyst is stable and recyclable. Furthermore, the expensive separation of DMF from the product stream is not necessary as other over hydrogenation products present in small amounts also have fuel properties. The product stream can be separated easily from low-boiling-point THF solvent in a cost-effective manner. However, the initial investment for the catalyst may be similar or slightly higher because of the high cost of Pd metal. It is important to understand the mechanistic role of the Lewis acid as well as to gain an insight into the effect of pore structure so that more effective bifunctional catalysts can be designed to make this alternate process economically practical. The further upgrading of DMF to p-xylene (pX) is a relatively new research direction, which is seen as a breakthrough approach to minimize dependence on petroleum. The two-step process for the conversion of DMF to pX involves a [4 + 2] cyclization of DMF with ethylene in the presence of a Brønsted acidic catalyst

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followed by the aromatization of 1,4-dimethyl-7-oxabicyclo [3, 4, 4] hept-2-ene intermediate to pX. In the case of the solid-acid-catalyzed cyclization, the acid density and pore size of the catalysts have a significant influence on the overall yield and selectivity of the desired pX product.

References 1. M. Boot, Biofuels from Lignocellulosic Biomass: Innovations Beyond Bioethanol (Wiley, Hoboken, 2016) 2. Y. Qian, L. Zhu, Y. Wang, X. Lu, Recent progress in the development of biofuel 2, 5-dimethylfuran. Renew. Sust. Energ. Rev. 41, 633–646 (2015) 3. Y. Román-Leshkov, C.J. Barrett, Z.Y. Liu, J.A. Dumesic, Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates. Nature 447, 982–985 (2007) 4. H. Zhao, J.E. Holladay, H. Brown, Z.C. Zhang, Metal chlorides in ionic liquid solvents convert sugars to 5-hydroxymethylfurfural. 316, 1597–1600 (2007) 5. K. Alexandrino, Comprehensive review of the impact of 2, 5-Dimethylfuran and 2-Methylfuran on soot emissions: experiments in diesel engines and at laboratory-scale. Energy Fuels 34, 6598–6623 (2020) 6. S. Atsumi, T. Hanai, J.C. Liao, Non-fermentative pathways for synthesis of branched-chain higher alcohols as biofuels. Nature 451, 86–89 (2008) 7. B. Saha, M.M. Abu-Omar, Economics, and perspectives for 2, 5-dimethylfuran production from biomass-derived intermediates. Chem. Sus. Chem. 8, 1133–1142 (2015) 8. S. Morikawa, Reduction of 5-hydroxymethylfurfural. Noguchi Kenkyusho Jiho 23, 39–44 (1980) 9. C. Chang, G. Xu, W. Zhu, J. Bai, S. Fang, One-pot production of a liquid biofuel candidate— ethyl levulinate from glucose and furfural residues using a combination of extremely low sulfuric acid and zeolite USY. Fuel 140, 365–370 (2015) 10. W. Yang, A. Sen, Direct catalytic synthesis of 5-methylfurfural from biomass-derived carbohydrates. Chem. Sus. Chem. 4, 349–352 (2011) 11. L. Tao, A. Aden, The economics of current and future biofuels, in Biofuels, ed. by D. Tomes, P. Lakshmanan, D. Songstad (Springer, Berlin, 2011), pp. 37–69 12. F.K. Kazi, A.D. Patel, J.C. Serrano-Ruiz, J.A. Dumesic, R.P. Anex, Techno-economic analysis of dimethylfuran (DMF) and hydroxymethylfurfural (HMF) production from pure fructose in catalytic processes. Chem. Eng. J. 169, 329–338 (2011) 13. F.J. Keil, Process intensification. Rev. Chem. Eng. 34, 135–200 (2018) 14. P. Lutze, R. Gani, J.M. Woodley, Process intensification: a perspective on process synthesis. Chem. Eng. Process. 49, 547–558 (2010) 15. J.A. Moulijn, A. Stankiewicz, J. Grievink, A. Górak, Process intensification and process systems engineering: a friendly symbiosis. Chem. Eng. Process. 32, 3–11 (2008) 16. J.M. Ponce-Ortega, M.M. Al-Thubaiti, M.M. El-Halwagi, Process intensification: new understanding and systematic approach. Chem. Eng. Process. 53, 63–75 (2012) 17. I. Abdulrahman, V. Máša, S.Y. Teng, Process intensification in the oil and gas industry: a technological framework. Chem. Eng. Process. 159, 108208 (2021) 18. P. Lutze, D.K. Babi, J.M. Woodley, R. Gani, Phenomena based methodology for process synthesis incorporating process intensification. Ind. Eng. Chem. Res. 52, 7127–7144 (2013)

Chapter 10

The Challenge of Biofuel: Energy Generation for a Sustainable Future

There is a clear need to transition energy dependence from fossil fuels to renewable energy sources to address the unprecedented pace of climate change due to the accumulation of greenhouse gases (GHGs) in the atmosphere. Overwhelming evidence has shown that human activity is the major driver of climate change and that its consequences are impacting food production, migration patterns, economic, and political stability on a global scale. In the US alone, 6.677 Gt of GHG were emitted in 2018 with the largest fractions being attributed to transportation (28%), electricity generation (27%), industry (22%), commercial and residential applications (12%), and agriculture (10%) [1]. As all these activities are largely dependent on fossil fuels, technological advances and diversification of alternative energy sources hold promise to significantly reduce carbon emissions and alleviate climate change. Today, with environmental policies pushing for a reduction of GHG emission, aided by recent advances in biofuel production, using intensified process, have become viable and sustainable surrogates for petroleum-based fuels. A key interest in developing or expanding biofuel production and use is the environmental benefits, including the potential to reduce emissions, such as greenhouse gases. An estimated 25% of manmade global carbon dioxide (CO2 ) emissions, a leading GHG, comes from road transport. Global road transport has grown rapidly over the past 50 years and is projected to continue to increase, especially in middleincome countries experiencing rapid economic growth, middle-class expansion, and urbanization. Both biofuels and gasoline give off CO2 when burned. Biofuels are theoretically carbon neutral, releasing CO2 recently absorbed from the atmosphere by the crops used to produce them. Gasoline and other fossil fuels add to the CO2 supply in the atmosphere by giving off CO2 absorbed and trapped in plant material millions of years ago. The advantage of biofuels is less clear in a “life-cycle” analysis that examines not just combustion, but the production and processing of the feedstock into fuel. Most studies indicate that the net energy balance of biofuels is positive (energy output is greater than energy input), but estimates vary widely. Net balances are small for corn ethanol and more significant for biodiesel from soybeans © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 J. G. Segovia-Hernández et al., Sustainable Production of Biofuels Using Intensified Processes, Green Energy and Technology, https://doi.org/10.1007/978-3-031-13216-2_10

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and ethanol from sugarcane and from cellulose. The biofuel with the highest net energy balance reduces GHG the most when compared with that for gasoline [2]. Technological advances and efficiency gains—higher biomass yields per acre and more gallons of biofuel per ton of biomass—could steadily reduce the economic cost and environmental impacts of biofuel production. Biofuel production will likely be most profitable and environmentally benign in tropical areas where growing seasons are longer, per acre biofuel yields are higher, and fuel and other input costs are lower. For example, Brazil uses bagasse, which is a byproduct from sugar production to power ethanol distilleries, whereas the United States uses natural gas or coal. The future of global biofuels will depend on their profitability, which depends on a number of interrelated factors. Key to this will be high oil prices: 6 years of steadily rising oil prices have provided economic support for alternative fuels, unlike previous periods when oil prices spiked and then fell rapidly, undercutting the profitability of nascent alternative fuel programs. On the other hand, the sector’s profitability has been negatively affected by rising feedstock prices (corn and vegetable oil, not sugar), which account for a very large share of biofuel cost of production. For this commodity-dependent industry, government support to reduce profit uncertainty has been a common theme in the U.S., Brazil, and the EU, where biofuel production has been most significant. Biofuels will most likely be part of a portfolio of solutions to high oil prices, including conservation and the use of other alternative fuels. The role of biofuels in global fuel supplies is likely to remain modest because of its land intensity. In the U.S., replacing all current gasoline consumption with ethanol would require more land in corn production than is presently in all agricultural production. Technology will be central to boosting the role of biofuels. If the energy of widely available, cellulose materials could be economically harnessed around the world, biofuel yields per acre could more than double, reducing land requirements significantly [3]. One of the main focuses of this book is the future of the production of several liquid biofuels. As noted throughout this book, this clearly defines the grand challenge in the production and purification of liquid biofuels, which is the production of more fuels but with significantly lower carbon emissions, minimum energy consumption, and economic profitability. An important relationship exists between the design and operation of upstream catalysis units and downstream separation systems. Producing more liquid biofuels with lower carbon emissions will require energy-efficient capacity additions. Advanced separations play a significant role in this regard. First, advanced separations such as membranes and adsorption are thermodynamically advantaged relative to traditional separations such as distillation and absorption. However, traditional separation systems provide fundamental advantages in terms of product purity and recovery, as equilibrium stages can be added with minimal additional energy costs whereas the advanced separation systems often require substantial additional energy inputs for each new stage. Beyond energy, there are capital cost scaling advantages inherent in distillation column design and construction. However, limits exist on column diameters and hydrodynamics, and these limitations contribute to the inflexibility of throughput expansion for distillation. These factors suggest that the

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path forward involves the hybridization of existing separations technology with incremental capacity additions in the form of advanced separations systems [3]. Process Intensification seems to be one of the most viable strategies for the generation of advanced separation systems that allow the production and purification of biofuels sustainably. Process intensification is a rapidly growing area within chemical engineering, and one of the key unit operations thought to intensify chemical processes is the reactive separator (e.g., a membrane reactor, reactive distillation, reactive L-L extraction). These all-in-one operations have advantages in certain applications such as breaking equilibrium limitations and a smaller overall footprint. On the other hand, is the current investment in agricultural and forest lands in the developing world a “global land grab”? From a global perspective, foreign companies and governments are sweeping up large tracts of land across for everything from food crops to biofuel plantations to projects for carbon sequestration. For critics, such efforts are little more than a renewal of colonialism. Yet, at the local level, land deals are often ad hoc and tentative, and do not resemble a coordinated, controlled seizure of land. In many cases protracted land negotiations and lengthy court cases have stalled investment. Companies have rarely coordinated efforts, with negotiations generally isolated and often secretive. Many projects remain in pilot phases, and at least for some, companies have been unable to plant any crops at all [4]. Resistance to these projects equally lacks a united voice. The views of government officials, local elites, and villagers are mixed on the value of attracting external investors to rural areas, and views on biofuels are divided across multiple identity and interest lines. Some are keen to attract investment, create jobs, and increase the income-generation from land; others, however, fear the loss of local control and worry about the marginalization of smallholders and pastoralist groups. Some developing countries have developed large tracts of land for biofuel feedstocks—most notably for sugarcane-based bioethanol in Brazil. Most, however, are experiencing stalled projects and ongoing battles over land and development. Particularly in sub-Saharan Africa, the outcomes so far have largely been lose-lose: communities and environmentalists perceive a loss of control over land and ecosystems, and corporations and developers have yet to turn a significant profit. Moreover, this is not a case of a few deals gone wrong, but rather appears to be a systemic pattern of unresolved struggles over land acquisition and development paths. In this paper, we aim to make sense of these ongoing, cyclical, and unresolved struggles. Drawing on the geographic and anthropological literature on mapping and counter-mapping, we unpack the ways in which various actors are making and responding to claims, paying particular attention to how the representation of space is being used as a strategic tool. Competing maps and surveys, and control over access to them, are providing some opportunities for more powerful actors—especially biofuel companies in conjunction with national or local elites—to gain an upper hand in negotiations. Similar outcomes are occurring elsewhere, and the overall result does indeed look, from a distance, like a global land grab. Yet, close up, research show that the politics of mapmaking is complicating negotiations over territory and resources, making the processes of acquiring land for commercial agriculture and resisting such projects more difficult.

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Various parties are using maps and surveys to claim legal or traditional rights, bolster land claims, and mask or ignore existing uses and users. Moreover, unclear, or missing maps, and understandings of space through landmark-based rather than quantified, gridded land areas, create an equally, if not more, difficult problem: all parties end up less able to control land negotiation processes [4]. In situations of uncertainty and unequal knowledge about land, as the political ecology literature draws out well, more powerful actors tend to determine social and environmental outcomes. Consolidating the knowledge of mapped and “unmapped” land can provide an opportunity to mask unofficial land uses and claims as well as gain control of land labeled as “empty” and “unproductive.” The political economy of both domestic and (especially) transnational investments require companies to seek some level of security in negotiations and land acquisitions, which, in cases of such unclear land transfer processes, remains elusive. Before determining the potential role that biofuels can play by 2030 and to recommend appropriate policies for the development of biofuels, it is important to assess the quantity and structure of future energy demand for transport, and the underlying data for mobility and economic growth [5]. The main points to note are the following forecasts for the period from 2000 to 2030: ● An average annual growth of 0.6% for primary energy (0.9% for final energy), compared to 2.4% increase for gross domestic product (GDP). ● An increase in dependency on energy imports, from 47.1% in 2000 to 67.5% in 2030; ● Freight transport growing at an annual average of 2.1%. Road traffic will gain significantly in terms of market share, mainly at the expense of rail. In 2030, road traffic will account for 77.4% of freight transport services, compared to 69.0% in 2000. ● Personal transport growing at an annual average value of 1.5%, distinctly lower than the growth in GDP. The strongest increase is forecast for aviation, which will double its share to 10.8% and will account for 16% of the overall energy demand of the transport sector in 2030. However, private cars and motorcycles will by far remain the most important means for personal transport, with a market share of 75.8% in 2030, compared to 77.7% in 2000. ● The largest increase in fuel use for transport in absolute terms is expected to be for trucks and buses. After 2010 the fuel demand by trucks is forecast to even exceed that for passenger cars and motorcycles. According to the above study, liquid hydrocarbon fuels will dominate the market by 2030, and diesel will increase its proportion at the expense of gasoline. As a result, there would be a deficit of produced diesel compared to demand and an overcapacity of gasoline production. There will also be a need for kerosene, mainly for aviation. User acceptance of biofuels is paramount. Ideally, users should not notice the difference between conventional and biofuels, nor should they be required to extensively modify their existing vehicles or perform new routines when using biofuels (although future vehicles will have to employ new technology). Storage, distribution, and sales logistics are also important issues. For the private motorist market (cars), it is a benefit

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if the biofuels are compatible with existing logistics systems. For commercial vehicles, particularly truck and bus fleets, separate (dedicated) fuel distribution systems are already common. For commercial vehicles, overall economics will largely dictate how the fuel distribution is organized. In any case, existing infrastructure investments will be in use for their full economical lifetime, even with new fuels being introduced to the market. It seems likely that large-scale biofuel penetration is only possible if the existing engine technologies can be utilized. Ideally, future biofuels could be used as blends to gasoline, diesel or natural gas, or as neat products. Also alternating between biofuels, conventional fuels and blends should be possible. In the period to 2030 it is expected that the regulated exhaust gas emissions (NOx, CO, HC, particulates) will be further reduced in steps to reach near-zero emissions, with vehicle emissions stable over the vehicle’s life. High quality of the fuel is an important enabler to comply with stringent emission regulations. Emission standards (and other vehicle standards) should preferably be based on global technical regulations with relatively minor regional adaptations. Fuel quality must therefore be compatible with this reality on a global basis. In parallel, energy consumption/emission of greenhouse gases should be reduced significantly due to legislation, incentives and increased cost-effectiveness of the transportation means. Examining these new global food system realities through the lens of scenarios for biofuel supply and demand indicates that, if current policies and investment trends continue, real world prices of most cereals, foods and crops are projected to increase in the future. Growth in demand for meat, milk, biofuels, and growing scarcity in water supplies are projected to put pressure on agricultural prices and strain land and water resources further. Climate change will have negative impacts on agricultural production in much of the world. Rising prices and poor progress on food security are not, however, inevitable. Policy reforms and increased investment in agricultural research, irrigation infrastructure, and rural roads, can reduce hunger and poverty and to impact on productivity and prices of biofuels [6]. The challenge is to increase substantially the production of biofuels by using intensified processes and technologies that are both competitive and sustainable. To achieve this, it will be necessary, while supporting the implementation of currently available biofuels, to promote the transition towards second and third generation biofuels, which will be produced from a wider range of feedstock, do not compete with the food chain, and will help to reduce costs of “saved” CO2 . Fuels from biomass, therefore, have a high potential to reduce greenhouse gas emissions, and hence are an important means to fulfil road transport CO2 emissions targets. They can be a reliable fuel source, which can gradually reduce the dependence on oil imports, and, if further developed, can constitute part of a strategic reserve. Notwithstanding the fact that biomass in electricity has the greatest greenhouse gas benefits and biomass in heating is cheapest, transport biofuels have the highest employment intensity and provide the only renewable alternative for existing vehicles. The use of biomass should be promoted in all three sectors. At least up to 2010, there will be no major competition for raw material: biofuels rely mainly on agricultural crops while electricity and heating rely mainly on wood and wastes.

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Finally, the COVID19 pandemic caused a drop of 8.5% in global transport fuel use in 2020 concerning the previous year due to restrictions on people’s movements and disruption in trade logistics around the globe. Consequently, biofuel use fell by 8.7% in 2020 concerning 2019. Once the new normal (post-pandemic) is installed, global biofuel use is expected to grow in the next 10 years. Blending mandates (mixtures fuels-biofuels) are expected to evolve over the projection period for some emerging economies. However, the projection is expected to remain below the E20 goal the government seeks to achieve by 2030. Global biofuel production will continue to be supplied predominantly by traditional feedstock [7]. The major risks and uncertainties for the future development of the biofuels sector are related to the policy environment and oil prices. Policy uncertainty includes changes in mandate levels, enforcement mechanisms, investment in non-traditional biofuel feedstock, tax exemptions and subsidies for biofuels and fossil fuels, and electric vehicles technology and policies for its promotion. In general, new intensified alternatives for biofuel liquid separation should be studied on a consistent and comprehensive basis for accurate comparison. Developing hybrid processes and intensified technologies will help pave a sustainable path for biofuel production, given that due to the drop in demand due to the COVID19 pandemic, once the new post-pandemic normality is achieved, an increase in the production of liquid biofuels will be necessary to cover in different industrial and automotive sectors. In summary, in the global process to produce biofuels, two relevant stages generally participate: reaction and separation. The most important challenge to highlight is to increase production, due to the limitations of the reaction where microorganisms participate, or low yields where they do not participate (chemical reactions). These low yields in the production of biofuels spread throughout the entire process, impacting energy consumption and costs of the separation processes. All this causes the low economic profitability of the processes and the high prices of biofuels. Right at this point, process intensification has an arduous task to solve. Furthermore, as observed throughout this chapter, the production of biofuels also depends on climatological factors, the production of agricultural biomass or organic waste, political factors, taxes, etc., among many others. Therefore, a joint effort between technology (intensification of processes), agriculture, use of natural resources and political aspects will allow profitability and viability in the generation of biofuels in the future.

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