Nano- and Biocatalysts for Biodiesel Production E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Reviews recent advances in catalytic biodiesel synthesis, highlighting various nanocatalysts and nano(bio)catalysts developed for effective biodiesel production Nano- and Biocatalysts for Biodiesel Production delivers an essential reference for academic and industrial researchers in biomass valorization and biofuel industries. The book covers both nanocatalysts and biocatalysts, bridging the gap between homogenous and heterogenous catalysis. Readers will learn about the techno-economical and environmental aspects of biodiesel production using different feedstocks and catalysts. They will also discover how nano(bio)catalysts can be used as effective alternatives to conventional catalysts in biodiesel production due to their unique properties, including reusability, high activation energy and rate of reaction, easy recovery, and recyclability. Readers will benefit from the inclusion of: * Introductions to CaO nanocatalysts, zeolite nanocatalysts, titanium dioxide-based nanocatalysts and zinc-based in biodiesel production * An exploration of carbon-based heterogeneous nanocatalysts for the production of biodiesel * Practical discussions of bio-based nano catalysts for biodiesel production and the application of nanoporous materials as heterogeneous catalysts for biodiesel production * An analysis of the techno-economical considerations of biodiesel production using different feedstocks Nano- and Biocatalysts for Biodiesel Production focuses on recent advances in the field and offers a complete and informative guide for academic researchers and industrial scientists working in the fields of biofuels and bioenergy, catalysis, biotechnology, bioengineering, nanotechnology, and materials science.
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Veröffentlichungsjahr: 2021
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Table of Contents
Cover
Title Page
Copyright
Preface
List of Contributors
1 Biodiesel: Different Feedstocks, Conventional Methods, and Factors Affecting its Production
1.1 Introduction
1.2 Different Feedstocks for Biodiesel Production
1.3 Conventional Methods of Biodiesel Production
1.4 Catalysts Used in Biodiesel Production
1.5 Effects of Different Factors on Biodiesel Production Yield
1.6 Physical Properties of Biodiesel
1.7 Conclusions
References
2 Nano(Bio)Catalysts: An Effective Tool to Utilize Waste Cooking Oil for the Biodiesel Production
2.1 Introduction
2.2 Waste Cooking Oils
2.3 Pretreatment of WCOs
2.4 Transesterification Process
2.5 Enzymatic Biocatalysts
2.6 Enzyme Immobilization Techniques
2.7 Physical Methods
2.8 Chemical Methods
2.9 Conclusions
References
3 A Review on the Use of Bio/Nanostructured Heterogeneous Catalysts in Biodiesel Production
3.1 Introduction
3.2 Use of Micro‐ and Nanostructured Heterogeneous Catalysts in Biodiesel Production
3.3 Enzymatic Catalysis
3.4 Conclusions
References
4 Calcium‐Based Nanocatalysts in Biodiesel Production
4.1 Introduction
4.2 Nanocatalysts
4.3 CaO‐Based Nanocatalysts for Biodiesel Production
4.4 Effects of Different Parameters on Biodiesel Production
4.5 Reusability and Leaching of Nanocatalysts
4.6 Conclusions
References
5 Titanium Dioxide‐Based Nanocatalysts in Biodiesel Production
5.1 Introduction
5.2 Natural Occurrences of Titania
5.3 Precursors Used for the Synthesis of TiO
2
NPs
5.4 Methods for the Synthesis of TiO
2
NPs
5.5 Methods for the Synthesis of TiO
2
‐Based Nanocatalysts
5.6 TiO
2
‐Based Nanocatalysts for Biodiesel Production
5.7 Other TiO
2
Nanocomposite Catalysts
5.8 Conclusion
References
6 Zinc‐Based Nanocatalysts in Biodiesel Production
6.1 Introduction
6.2 Feedstocks Used for Biodiesel Production
6.3 Conventional Methods of Biodiesel Production
6.4 Nanotechnology in Biodiesel Production
6.5 Zinc‐Based Nanocatalysts in Biodiesel Production
6.6 Conclusions
References
7 Carbon‐Based Nanocatalysts in Biodiesel Production
7.1 Introduction
7.2 Feedstocks Used for Biodiesel Production
7.3 Conventional Heterogeneous Catalysts
7.4 Carbon‐Based Heterogeneous Nanocatalysts
7.5 Conclusions
References
8 Functionalized Magnetic Nanocatalysts in Biodiesel Production
8.1 Introduction
8.2 Relevance of Heterogeneous Catalysis in Biodiesel Production
8.3 Surface Modification and Functionalization of NPs
8.4 Applications of Functionalized Magnetic Nanocatalysts in Biodiesel Production
8.5 Conclusions
References
9 Bio‐Based Catalysts in Biodiesel Production
9.1 Introduction
9.2 Biodiesel: A Potential Source of Renewable Energy
9.3 Homogeneous Catalysis in Biodiesel Production
9.4 Heterogeneous Catalysis in Biodiesel Production
9.5 Catalyst Supports
9.6 Heterogeneous Bio‐Based Acid Catalysts
9.7 Synthesis of Bio‐Based Solid Acid Catalysts
9.8 Magnetic Bio‐Based Catalysts for Biodiesel Production
9.9 Characterization of Bio‐Based Catalysts
9.10 Reaction Parameters Affecting Biodiesel Production
9.11 Conclusions
References
10 Heterogeneous Nanocatalytic Conversion of Waste to Biodiesel
10.1 Introduction
10.2 Role of Catalysts in Biodiesel Production
10.3 Feedstocks for Biodiesel Production
10.4 Biodiesel Production Process
10.5 Variables Affecting Transesterification
10.6 Heterogeneous Nanocatalysts for Biodiesel Production
10.7 Characterization of Nanoparticles Used for Biodiesel Production
10.8 Influence of Nanoparticle Properties on Biodiesel Production
10.9 Safety Issues Around the Application of Nanocatalysts in Biodiesel Production
10.10 Future Perspectives
10.11 Conclusions
References
11 Application of Rare Earth Cation‐Exchanged Nanozeolite as a Support for the Immobilization of Fungal Lipase and their Use in Biodiesel Production
11.1 Introduction
11.2 Case Study
11.3 Conclusions
References
12 Lipase‐Immobilized Magnetic Nanoparticles: Promising Nanobiocatalysts for Biodiesel Production
12.1 Introduction
12.2 Transesterification for Biodiesel Production
12.3 Advantages of Using Magnetic Nanobiocatalysts
12.4 Synthesis of Nanobiocatalysts
12.5 Techniques for the Characterization of Nanobiocatalysts
12.6 Transesterification Using Magnetic Nanobiocatalysts
12.7 Factors Affecting Enzymatic Transesterification
12.8 Conclusions
References
13 Technoeconomic Analysis of Biodiesel Production Using Different Feedstocks
13.1 Introduction
13.2 Biodiesel Production Technologies
13.3 Feedstock Types for Biodiesel Production
13.4 Technical Performance Evaluation of Biodiesel Production
13.5 Economic Performance Evaluation of the Biodiesel Production Process
13.6 Conclusions
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Biodiesel production from vegetable oils in the presence of HACs (N...
Table 1.2 Biodiesel production from WCOs in the presence of different catalys...
Table 1.3 Biodiesel production from animal fats in the presence of different ...
Table 1.4 Biodiesel production from microalga oils in the presence of differe...
Table 1.5 Biodiesel production from different oils using homogeneous alkali a...
Table 1.6 Biodiesel production from different oils using heterogeneous acidic...
Table 1.7 Biodiesel production from different oils in the presence of enzymat...
Table 1.8 Summary of biodiesel production yield from different oil sources in...
Table 1.9 Advantages and disadvantages of various types of catalysts.
Table 1.10 Standard values of some important physical properties of diesel fu...
Chapter 2
Table 2.1 Chemical compositions of a WCO (Asli et al. 2012).
Table 2.2 Different types of bacterial and fungal lipases used for the transe...
Table 2.3 Different types of lipase immobilization techniques and their respe...
Chapter 4
Table 4.1 Methods of synthesis and properties of different CaO‐based nanocata...
Table 4.2 Synthesis of CaO nanocatalyst from different waste materials and th...
Table 4.3 Synthesis of CaO nanocatalyst supported by different alkaline metal...
Chapter 5
Table 5.1 Different plants, their parts and precursors for the synthesis of T...
Table 5.2 Types of microbes and TiO
2
precursors used to achieve the nanosize ...
Table 5.3 Comparative appraisal of the performance of TiO
2
‐based nanocatalyst...
Chapter 6
Table 6.1 Important edible and non‐edible oils used for biodiesel production.
Table 6.2 Different Zn‐based nanocatalysts used in the production of biodiese...
Chapter 7
Table 7.1 Some important carbon‐based nanocatalysts used in biodiesel product...
Chapter 9
Table 9.1 Compositions of different types of oil palm biomass.
Table 9.2 Key milestones in the industrial development of biodiesel (Lin et a...
Table 9.3 General properties of PFAD feedstocks.
Table 9.4 Carbonization and activation conditions of different types of bioma...
Table 9.5 Functional group characterization of biochar using FT‐IR.
Table 9.6 Bio‐based catalysts used for biodiesel production.
Chapter 10
Table 10.1 Different types of feedstock used for biodiesel production.
Table 10.2 Fatty acid composition profile of few feedstocks used for biodiese...
Table 10.3 Summary of nanocatalysts and operating conditions for biodiesel pr...
Chapter 11
Table 11.1 Amounts of lipases immobilized, enzymatic activities, and FAEE yie...
Chapter 12
Table 12.1 Lipases immobilized on different magnetic nanosupports for biodies...
Chapter 13
Table 13.1 Flash point values of biodiesel fuels from different feedstock typ...
Table 13.2 Cold filter plugging point (CFPP) values of biodiesel fuels from d...
Table 13.3 Cetane numbers of biodiesel fuels from different feedstock types (...
Table 13.4 Viscosities of biodiesel fuels from different feedstock types (Yaş...
Table 13.5 Oxidation stabilities of biodiesel fuels from different feedstock ...
Table 13.6 Most important biodiesel quality standards around the world (Barab...
Table 13.7 Cost estimation classes and their respective primary and secondary...
List of Illustrations
Chapter 1
Figure 1.1 Percentages of various oil sources used in biodiesel production....
Chapter 2
Figure 2.1 Global energy supply from different types of energy sources.
Figure 2.2 General transesterification reaction.
Figure 2.3 Three‐step transesterification reactions for biodiesel production...
Figure 2.4 Typical process design of the transesterification reaction for bi...
Figure 2.5 Typical process design of the transesterification reaction for bi...
Figure 2.6 Physical and chemical methods for enzyme immobilization.
Figure 2.7 Representation of (a) physical entrapment of lipase and (b) chemi...
Figure 2.8 Different types of covalent bond formation between substratum and...
Figure 2.9 Schematic representation of covalent bonding of lipase on polydop...
Chapter 5
Figure 5.1 (a) Crystalline structure of rutile. (b) Fine powder of rutile.
Figure 5.2 (a) Crystalline structure anatase. (b) Image of anatase.
Figure 5.3 (a) Crystalline structure of rhombic brookite. (b) Image of rhomb...
Figure 5.4 (a) Structure of kaolinite clay. (b) Image of clay.
Figure 5.5 (a) Image of ilmenites. (b) Structure of ilmenites.
Figure 5.6 Schematic presentation of different isotopes of TiCl
4
and their r...
Figure 5.7 Schematic illustration of biological synthesis of NPs.
Chapter 6
Figure 6.1 Schematic illustration of the general procedure of biodiesel prod...
Figure 6.2 Design for the ideal process of enzymatic biodiesel production.
Chapter 7
Figure 7.1 Different types of heterogeneous catalysts used in transesterific...
Chapter 8
Figure 8.1 Schematic diagram of the advantages of magnetic nanocatalysis ove...
Scheme 8.1 Transesterification reaction for biodiesel production.
Figure 8.2 Preparation strategy of a hydrophobic hybrid of HPA‐functionalize...
Figure 8.3 (a) TEM image and (b) FESEM images of SO
3
H‐PGMA‐MNPs.
Figure 8.4 Biodiesel production by oleic acid esterification using a Zr‐CMC‐...
Figure 8.5 Synthesis of a super‐magnetic SO
4
/Fe‐Al‐TiO
2
catalyst.
Figure 8.6 Synthesis of silica‐coated TBD‐functionalized ferrite MNPs.
Figure 8.7 Synthesis of TBD‐ and TMG‐functionalized magnetic silica‐coated a...
Figure 8.8 Synthesis of FCHC‐SO
3
H MNPs.
Figure 8.9 (a–c) FESEM images and (d–f) TEM images of recycled catalyst afte...
Figure 8.10 Synthesis of IL‐SiO
2
‐Fe
3
O
4
MNPs.
Figure 8.11 Synthesis of DAIL‐Fe
3
O
4
@NH
2
‐MIL‐88B(Fe) MNPs.
Figure 8.12 Synthesis of core–shell‐structured MOF‐coated basic IL‐functiona...
Chapter 9
Figure 9.1 Biomass wastes from palm oil mills: (a) empty fruit bunches (EFB)...
Figure 9.2 Prices of RBD, CPO, and PFAD oil (Kapor et al. 2017).
Figure 9.3 (a) General esterification reaction of fatty acids. (b) General t...
Figure 9.4 Reaction mechanism for a homogeneous base‐catalyzed transesterifi...
Figure 9.5 Reaction mechanism for acid‐catalyzed homogeneous transesterifica...
Figure 9.6 Reaction mechanism for acid‐catalyzed esterification (Liu et al. ...
Chapter 10
Figure 10.1 Mechanism of acid transesterification.
Figure 10.2 Mechanism of alkali (base)‐catalyzed reaction.
Chapter 11
Figure 11.1 Transesterification of triglycerides with alcohol.
Figure 11.2 Mechanism of lipase in transesterification.
Figure 11.3 Nanozeolite MFI.
Figure 11.4 XRD patterns of as‐made Nano‐FAU/Na and its ion‐exchanged deriva...
Figure 11.5 SEM, TEM, and AFM of as‐made Nano‐FAU/Na.
Figure 11.6 FT‐IR of as‐made Nano‐FAU/Na and its ion‐exchanged derivatives w...
Figure 11.7 Structures from
T. lanuginosus
and
R. miehei
lipases in closed c...
Chapter 12
Figure 12.1 Methods of transesterification based on different catalysts.
Chapter 13
Figure 13.1 Schematics indicating (a) esterification reaction and (b) transe...
Guide
Cover
Table of Contents
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Nano‐ and Biocatalysts for Biodiesel Production
Edited by
Avinash P. Ingle
Biotechnology Centre
Department of Agricultural Botany
Dr. Panjabrao Deshmukh Krishi Vidyapeeth
Akola, Maharashtra
India
This edition first published 2021
© 2021 by John Wiley & Sons Ltd. All rights reserved.
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ISBN: 978‐1‐119‐73000‐2
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Preface
The ever increasing population and global industrialization considerably increase the energy demand. The petroleum‐based fuels (fossil fuels), coal, natural gas, nuclear, and hydropower are the major energy sources currently available for use. However, the utilization of these energies exerts several negative impacts on the environment including issues like global warming, greenhouse gas emission, depletion of fossil fuel reserves, etc. Environmental pollution due to release of various particulate matters and contaminants exerts hazardous effects on human health. Therefore, it is an urgent need to search renewable and sustainable alternative energy sources having novel features like biodegradability, ecofriendly nature, low toxicity, and economical viability. These features are usually possessed by biofuels like biodiesel. Since last few decades, biodiesel has attracted a great deal of attention from scientific as well as a political community due to their many advantages over petroleum diesel like a significant reduction in greenhouse gas emissions, non‐sulfur emissions, non‐particulate matter pollutants, possess very low toxicity, biodegradable nature, and renewability.
Although technologies for industrial production of biodiesel are already developed, these conventional technologies reported to have some drawbacks because those are energy and labor‐intensive, expensive, time consuming, required high amount of water, etc. In this context, scientists are looking towards nanotechnology as a new hope because it has potential to revolutionize different areas of research as well as life. Recent studies, already confirmed that nanomaterials having a size in the range of 1‐100 nm play a crucial role in different processes (i.e. esterification and transesterification) used for biodiesel production. Nanomaterials exhibit novel and outstanding properties including strong catalytic activity due to its minute size. To date, various nanomaterials have been investigated and employed as nano and nanobiocatalysts in enhanced biodiesel production from various renewable sources like vegetable oils, microbial oils, waste cooking oils, animal fats, waste materials, etc. Considering these facts, the editor attempted to discuss the recent advances and role of different nanocatalysts, biocatalysts and nanobiocatalysts in biodiesel production through this book.
In this book, there are total 13 chapters, which are broadly focused on the recent advances and the role of different nano and biocatalysts for the production of biodiesel through esterification and transesterification. Chapter 1 is an introductory chapter, it mainly focused on important feedstocks used for the production of biodiesel. In addition, it also emphasized on various conventional methods commonly employed and different factors affecting the industrial production of biodiesel. Chapter 2 is based on role of different nano(bio)catalysts in the production of biodiesel using waste cooking oil. It also highlighted on the issues of waste cooking oil disposal and its management through their use as important feedstock for biodiesel production. Authors also described the processes for the development of nano(bio)catalysts via different enzyme immobilization techniques. In Chapter 3 authors reviewed the role of different bio/nano structured heterogeneous catalysts in biodiesel production. Chapter 4 specifically focused on the role of calcium oxide nanocatalysts in the production of biodiesel because it is revealed that among different nanocatalysts, metal oxide‐based nanocatalysts showed better catalytic performances as far as transesterification approach is concerned. In the similar line, Chapter 5 discusses the role of titanium di‐oxide nanocatalysts in biodiesel production. In addition, authors also described the different precursors commonly employed in synthesis of titanium di‐oxide nanoparticles and different synthesis methods. Chapter 6 deals with recent advances in the synthesis of zinc‐based nanocatalysts and their effective applications in biodiesel production. Moreover, this chapter briefly highlighted about the different common feedstocks used for the production of biodiesel and conventional approaches routinely in practice for industrial production of biodiesel. Chapter 7 examines the applications of another important kind of nanocatalysts i.e. carbon‐based heterogeneous nanocatalysts for the production of biodiesel. Chapter 8 emphasizes on one of the most important category of nanocatalysts (functionalized magnetic nanocatalysts) in biodiesel production. In recent past, scientific community working in this fields focusing on the use of magnetic nanocatalysts for rapid and economically viable production of biodiesel. The main advantage of using functionalized magnetic nanocatalysts is they can be easily recovered due to their strong magnetic nature and reuse for multiple times making the down‐stream processing easy and cost‐effective. Chapter 9 is about the application of bio‐based nanocatalysts for biodiesel production. Chapter 10 is dedicated to the use of various heterogeneous nanocatalysts in the conversion of waste to biodiesel. It discussed about the effectiveness of heterogeneous nanocatalysts over other conventional catalysts. Chapter 11 focused on application of rare‐earth cation exchanged nanozeolite as a support for the immobilization of fungal lipase and their use in biodiesel production. Nanozeolites are considered to be one of the most suitable support for the immobilization of enzymes commonly employed in biodiesel production because these kind of supports provides high stability to enzymes and protects it from inactivations. Chapter 12 emphasizes on application of lipase immobilized magnetic nanoparticles as promising nanobiocatalysts in biodiesel production. This chapters briefly discussed about various techniques used for enzyme immobilization of lipase on magnetic nanoparticles and their advantages over other catalysts as far as biodiesel production in concerned. Final chapter 13 is focused on the most important and relevant aspects i.e. techno‐economical analysis of biodiesel production using different feedstocks. The techno‐economical analysis of any products is of utmost important from industrial point of view. This is the only analysis which help to run the industry smoothly.
Overall, this book covers very informative chapters written by one or more specialists, experts in the concerned topic. In this way, I would like to offer a very rich guide for researchers in this field, undergraduate or graduate students of various disciplines like biotechnology, nanotechnology, biofuel sectors, biorefining fields, etc. and allied subjects. In addition, this book is useful for people working in various biorefining industries, regulatory bodies, and energy related organizations.
I would like to thank all the contributors for their outstanding efforts to provide state‐of‐the‐art information on the subject matter of their respective chapters. Their efforts will certainly enhance and update the knowledge of the readers about the role of nanotechnology in general and nano(bio)catalysts in particular for biodiesel production. I also thank everyone in the Wiley team for their constant help and constructive suggestions particularly to Higginbotham Sarah (Senior Editor), Stefanie, Nivetha, and other team members. I am also thankful to Science and Engineering Research Board (SERB), Department of Science and Technology, Government of India, New Delhi for providing financial assistance in the form of “Ramanujan Fellowship”.
I hope that the book will be useful for all the readers to find the required information on the latest research and advances in the field of biorefinery and biofuel industries.
Avinash P. Ingle
List of Contributors
Mary Adejoke Ajala
Department of Chemical Engineering
University of Ilorin
Ilorin, Kwara State
Nigeria
Elijah Olawale Ajala
Department of Chemical Engineering
University of Ilorin
Ilorin, Kwara State
Nigeria
Shehu‐Ibrahim Akinfalabi
Institute of Advanced Technology
University Putra Malaysia
Serdang
Malaysia
Rahul Bhagat
Department of Biotechnology
Government Institute of Science
Aurangabad, Maharashtra
India
Nilutpal Bhuyan
Department of Energy
Tezpur University
Assam
India
Neelam Bora
Department of Energy
Tezpur University
Assam
India
Manash J. Borah
Department of Energy
Tezpur University
Assam
India
Dhanapati Deka
Department of Energy
Tezpur University
Assam
India
Fábio Rogério de Moraes
Physics Department
São Paulo State University – UNESP
São Paulo
Brazil
Adriano de Vasconcellos
Physics Department
São Paulo State University – UNESP
São Paulo
Brazil
Hossein Esmaeili
Department of Chemical Engineering
Bushehr Branch
Islamic Azad University
Bushehr
Iran
Rushikesh Fopase
Bio‐Interface & Environmental Engineering Lab, Department of Biosciences and Bioengineering
Indian Institute of Technology Guwahati
Guwahati
India
Shemelis Nigatu Gebremariam
Hawassa University
Wondo Genet College of Forestry and Natural Resources
Shashemene
Ethiopia
João Gomes
CERENA – Center for Natural Resources and Instituto Superior Técnico
Lisbon University
Lisbon
Portugal
Chemical Engineering Department
Instituto Superior de Engenharia de Lisboa
Lisbon Polytechnic, Lisbon
Portugal
Guilherme de Paula Guarnieri
Physics Department
São Paulo State University – UNESP
São Paulo
Brazil
Indarchand Gupta
Department of Biotechnology
Government Institute of Science
Aurangabad, Maharashtra
India
Naeemah A. Ibrahim
Institute of Advanced Technology
University Putra Malaysia
Serdang
Malaysia
Avinash P. Ingle
Biotechnology Centre
Department of Agricultural Botany
Dr. Panjabrao Deshmukh Krishi Vidyapeeth
Akola
Maharashtra
India
Rupam Kataki
Department of Energy
Tezpur University
Assam
India
Jorge Marchetti
Faculty of Sciences and Technology
Norwegian University of Life Sciences
Ås, Norway
Archit Mohapatra
Gujarat Biotechnology Research Centre
Gandhinagar, Gujarat
India
Hamid Mukhtar
Institute of Industrial Biotechnology
Government College University
Lahore
Pakistan
Muhammad Waseem Mumtaz
Department of Chemistry
University of Gujrat
Gujrat
Pakistan
José Geraldo Nery
Physics Department
São Paulo State University – UNESP
São Paulo
Brazil
Chawalit Ngamcharussrivichai
Center of Excellence in Catalysis for Bioenergy and Renewable Chemicals (CBRC), Faculty of Science
Chulalongkorn University
Pathumwan
Thailand
Center of Excellence on Petrochemical and Materials Technology (PETROMAT)
Chulalongkorn University
Pathumwan
Thailand
Harris Panakkal
Department of Biotechnology
Government Institute of Science
Aurangabad, Maharashtra
India
Lalit M. Pandey
Bio‐Interface & Environmental Engineering Lab, Department of Biosciences and Bioengineering
Indian Institute of Technology Guwahati
Guwahati
India
Priti R. Pandit
Gujarat Biotechnology Research Centre
Gandhinagar, Gujarat
India
Jaime Puna
CERENA – Center for Natural Resources and Instituto Superior Técnico
Lisbon University
Lisbon
Portugal
Chemical Engineering Department
Instituto Superior de Engenharia de Lisboa
Lisbon Polytechnic, Lisbon
Portugal
Kalyani Rajkumari
Department of Chemistry
National Institute of Technology Silchar
India
Department of Chemistry
C.V. Raman Global University
Bhubaneswar
India
Umer Rashid
Institute of Advanced Technology
University Putra Malaysia
Serdang
Malaysia
Lalthazuala Rokhum
Department of Chemistry
National Institute of Technology Silchar
India
Department of Chemistry
University of Cambridge
Cambridge, UK
Dipanka Saikia
Department of Energy
Tezpur University
Assam
India
Harvis Bamidele Saka
Department of Chemical Engineering
University of Ilorin
Ilorin, Kwara State
Nigeria
Samuel Santos
CERENA – Center for Natural Resources and
Instituto Superior Técnico, Lisbon University
Lisbon
Portugal
Swati Sharma
Bio‐Interface & Environmental Engineering Lab, Department of Biosciences and Bioengineering
Indian Institute of Technology Guwahati
Guwahati
India
Sajad Tamjidi
Department of Chemical Engineering
Bushehr Branch
Islamic Azad University
Bushehr
Iran
Tooba Touqeer
Department of Chemistry
University of Gujrat
Gujrat
Pakistan
1Biodiesel: Different Feedstocks, Conventional Methods, and Factors Affecting its Production
Hossein Esmaeili1 and Sajad Tamjidi2
1Department of Chemical Engineering, Bushehr Branch, Islamic Azad University, Bushehr, Iran
2Department of Chemical Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran
1.1 Introduction
Fossil fuels are a non‐renewable source of energy whose reserves are limited, and they take millions of years to develop (Banković–Ilić et al. 2014). The widespread use of petroleum derivatives in recent decades has led to energy crisis, global climate change, environmental pollution, and many medical problems, such as cardiovascular diseases and cancers (Dhiraj and Mangesh 2012). Collectively, all these concerns, along with others like global warming and greenhouse gas emissions, have spurred the search for alternative fuels (e.g., biohydrogen, biodiesel, bioethanol, biomethanol, biogas, natural gas, and bioelectricity) that have relatively less adverse impacts on and greater compatibility with the environment (Demirbas 2004; Nascimento et al. 2011; Fahd et al. 2014). According to a report presented by the International Energy Agency (IEA), by 2035, world energy consumption will increase by 33% (International Energy Agency 2013), and it is anticipated that 40% of the growth will come from renewable sources. Among the renewable energies, biodiesel has recently experienced significant developments thanks to its outstanding advantages, including higher cetane number (CN), nontoxicity, and higher flashpoint compared with fossil fuels (Liu et al. 2010; Hasheminejad et al. 2011). Biodiesel is a biofuel with properties closely mimicking those of diesel, but without unfavorable contents such as nitrogen, sulfur, and polycyclic aromatics. This renewable biofuel is a mono‐alkyl esters of long‐chain fatty acids that is produced from vegetable oil, waste edible oil (WEO), waste cooking oil (WCO), waste non‐edible oil, animal fats, and microorganisms such as algae, fungi, and bacteria (Kralova and Sjoblom 2010; Nabi and Hoque 2008).
There are four primary methods of biodiesel production: blending, microemulsion, thermal cracking (pyrolysis), and transesterification. Among these, the transesterification reaction is the most commonly used for the conversion of oils into biodiesel, because the fuel produced by this method has been found to be highly compatible with conventional diesel engines. Direct use of the vegetable oil‐derived biodiesel damages such engines due to the high viscosity of the oil (Ramli et al. 2017). The most common short‐chain alcohols used for this purpose include methanol and ethanol; thanks to its lower price, methanol is the economic alcohol of choice (Ramadhas et al. 2005). Also, removal and recovery of methanol from the final product (biodiesel) is easier than for other alcohols (Allah and Alexandru 2016).
There are three kinds of catalysts commonly used for this process: alkaline, acidic, and enzymatic. Acidic and alkaline catalysts come in both homogeneous and heterogeneous types. Homogeneous alkaline catalysts (HACs) like NaOH and KOH have some disadvantages, including corrosion problems, nonrecyclability, and the production of a large amount of waste, while heterogeneous catalysts have several advantages, including appropriate recyclability, no requirement for a washing step, and higher efficiency in biodiesel production compared to homogeneous ones. However, enzymatic catalysts also have several limitations, including a low reaction rate, high cost of the enzymes, and deactivation of the catalyst, especially when used in industry (Lin et al. 2011; Talha and Sulaiman 2016). Given these limitations, the use of nanocatalysts for biodiesel production has been extensively increased in recent years. Nanocatalysts have several outstanding advantages, including reusability, high catalytic activity, high surface area, and high efficiency (Ambat et al. 2019; Seffati et al. 2020). Apart from the catalyst, there are several other factors that affect the efficiency of biodiesel production. These mainly include reaction time, reaction temperature, alcohol to oil molar ratio, type and concentration of catalyst, stirring rate, and feedstock (oil) used (Verma and Sharma 2016).
Biodiesel is a long‐chain fatty‐acid methyl ester (FAME) derived by the reaction between alcohol, oil, and an appropriate catalyst (Pasupulety et al. 2013). In the conventional process, the oil reacts with the alcohol (methanol, ethanol, propanol, or butanol) in the presence of a catalyst (alkaline, acidic, or enzymatic catalyst) to produce a FAME (biodiesel) as the main product and glycerin as a byproduct (Sundus et al. 2017). According to the United States Environmental Protection Agency (US EPA), the use of biodiesel in a vehicle's engine decreases the emission of hydrocarbon (HC) (about 70%) and of carbon monoxide and particulate matter (50%) compared to diesel fuel, but increases that of NOx (about 10%) (Geller and Goodrum 2004). Phosphorus is another hazardous gas present in diesel that can harm the catalytic part of the control system in the vehicle engine. Therefore, the concentration of phosphorus in the oil must be controlled in order to protect the system. Also, the presence of sulfur can damage the catalytic converter and emission control system. At present, the sulfur content in commercial biodiesel is nearly zero, which is one of its main advantages compared to petro‐diesel (Chen et al. 2018). Moreover, the presence of water in the oil causes hydrolysis of triglyceride to free fatty acid (FFA) and therefore leads to soap formation. If water concentration in the oil is more than 0.05 wt%, water must be removed (Chen et al. 2018). Deposition of metals such as calcium, magnesium, sodium, and potassium can further cause a lot of problems in vehicle engines (Balasubramaniyan 2016).
The aim of this chapter is to discuss the various feedstocks (i.e. oil sources) available (e.g. vegetable oil, microalga oil, animal fat, and waste oil) and their conversion in biodiesel using different conventional heterogeneous catalysts. In addition, recent advances and the application and impact of heterogeneous nanocatalysts on biodiesel production are briefly discussed, and the impact of various reaction parameters such as temperature, reaction time, catalyst content, and alcohol to oil ratio on the transesterification reaction is described. Special focus is given to the physical properties of biodiesel, including pour point, flash point, kinematic viscosity, CN, density, acid number, cloud point, and K + Na + Mg + Ca concentration, and their comparison with international standards.
1.2 Different Feedstocks for Biodiesel Production
More than 70% of the cost of biodiesel production is related to the raw materials. Biodiesel and petro‐diesel cost about 3.03 and 2.46 US$/gal, respectively (Chen et al. 2018). In the literature, a number of different feedstocks are commonly used for biodiesel production, including vegetable oils, WEOs, animal fats, and microalga oil (Channi et al. 2016).
1.2.1 Vegetable Sources
The vegetable oils used to produce biodiesel can be either edible or non‐edible. More than 95% of the biodiesel produced in the world is produced from edible oil, which is easily obtained from the agricultural industries. However, large‐scale production of edible oil‐derived biodiesel may have a negative effect on human life, because it leads to reduction of food supply (Gui et al. 2008). The most common edible oil sources used for biodiesel production include sunflower oil (Visser et al. 2011), rapeseed oil, peanut oil, sesame oil, rice oil, coconut oil (Karmakar et al. 2010), soybean oil, corn oil (Alptekin and Canakci 2008), and hazelnut oil (Sanli and Canakci 2008).
In contrast to edible oil, non‐edible oils can't be consumed by humans, because of the presence of toxic compounds in these sources (Gui et al. 2008). Common examples are palm oil (Salamatinia et al. 2013), jatropha oil (Pramanik 2003), cottonseed oil (Nabi et al. 2009), castor oil (Visser et al. 2011), Moringa oleifera seed oil (Ogbunugafor et al. 2011), neem oil, jojoba oil, and sea mango (Gui et al. 2008). Castor oil may be the best option for biodiesel production because it does not require heat and energy, which are necessary for other sources of vegetable oil (Manan 2013).
Currently, edible oils are in use in several countries, leading to increases in their cost, and hence the cost of the biodiesel produced. In this context, it is economically more efficient to use non‐edible oils (Karmakar et al. 2010). Table 1.1 shows the biodiesel conversion yield (BCY) of different vegetable oils used in the presence of HACs, such as KOH and NaOH. The yield of biodiesel production is calculated through Eq. (1.1), proposed by Seffati et al. (2019):
Table 1.1 Biodiesel production from vegetable oils in the presence of HACs (NaOH and KOH).
Oil source
Catalyst type
BCY (%)
References
Jojoba oil
KOH
83.5
Bouaid et al. (
2007
)
Rapeseed oil
KOH
97
Jazie et al. (
2012
)
Rapeseed oil
NaOH
92
Jazie et al. (
2012
)
Peanut oil
KOH
95
Jazie et al. (
2012
)
Peanut oil
NaOH
88
Jazie et al. (
2012
)
Jatropha curcas
oil
NaOH
98
Chitra et al. (
2005
)
Jatropha curcas
oil
NaOH
90
Berchmans and Hirata (
2008
)
Jatropha curcas
oil
KOH
95
Patil and Deng (
2009
)
Jatropha curcas
oil
KOH
99
Syam et al. (
2009
)
Jatropha curcas
oil
KOH
93
Sahoo and Das (
2009
)
Jatropha curcas
oil
KOH
99
Tiwari et al. (
2007
)
Rapeseed oil
KOH
96
Rashid and Anwar (
2008
)
Sunflower oil
NaOH
97.1
Winayanuwattikun et al. (
2008
)
Peanut oil
NaOH
89
Winayanuwattikun et al. (
2008
)
Corn oil
KOH
96
Winayanuwattikun et al. (
2008
)
Camelina oil
KOH
97.9
Frohlich and Rice (
2005
)
Canola oil
KOH
95
Winayanuwattikun et al. (
2008
)
Cotton oil
NaOH
96.9
Winayanuwattikun et al. (
2008
)
Pumpkin oil
NaOH
97.5
Winayanuwattikun et al. (
2008
)
Jatropha curcas
oil
NaOH
98
Winayanuwattikun et al. (
2008
)
Pongamia pinnata
oil
KOH
98
Sahoo and Das (
2009
)
1.2.2 Waste Oils
WEOs are oil‐based substances containing animal or vegetable matter that can be used for the preparation of food or in cooking but are not suitable for consumption by human beings. The amount of WEO produced in any country around the world is large, varying depending on the quantity of edible oil consumed. More than 15 million tons of WEO are produced annually around the globe, mainly by countries like China (4.5 million tons), Malaysia (0.5 million tons), the United States (10 million tons), Taiwan (0.07 million tons), Canada (0.12 million tons), and Japan (0.45–0.57 million tons), as well as European nations (0.7–1 million tons) (Gui et al. 2008). This oil source can be converted to biodiesel via catalytic and noncatalytic reaction (supercritical transesterification process) (Gui et al. 2008). The disposal of WEOs and WCOs is a major problem as they can pollute the environment. Developed countries have adopted policies that penalize the disposal of WEOs or WCOs via water drainage. Biodiesel production may thus be the best approach to their disposal, being economically viable and efficient. Information on diesel demand and the availability of WCOs in different countries shows that WCO‐derived biodiesel may not be sufficient to completely replace petro‐diesel. However, a significant amount of biodiesel can be produced from WCOs, helping reduce dependency on oil‐based fuel. The amount of WCO produced in any one country varies according to the utilization of vegetable oil (Kulkarni and Dalai 2006).
It is well investigated that WEO or WCO can be used as a low‐cost feedstock for the production of biodiesel. However, due to the presence of particulate contaminants and impurities in WCOs, biodiesel produced from these sources shows relatively high values of pour point and cloud point. Therefore, pretreatment or modification of such oils is essential prior to their use for biodiesel production. This can be achieved using particular chemical processes (Ghanei et al. 2014). According to Allah and Alexandru (2016), the overall cost involved in the production of biodiesel using WCOs is comparatively less than that with vegetable oils and diesel fuel. Table 1.2 shows the BCY of biodiesel production from WCOs in the presence of different catalysts.
Table 1.2 Biodiesel production from WCOs in the presence of different catalysts.
Catalyst
Temp (°C)
Alcohol to oil ratio
Amount of catalyst (wt%)
Time (h)
BCY (%)
References
KOH
57.31
9.05
0.99
1.28
96.33
Dhingra et al. (
2016
)
CaO
50
8 : l
1
1.5
96
Degfie et al. (
2019
)
Ba/CaO
65
6 : 1
3
3
88
Balakrishnan et al. (
2013
)
Copper/zinc oxide
55
8 : 1
12
0.833
97.71
Gurunathan and Ravi (
2015
)
4Mn–6Zr/CaO
80
15 : 1
3
3
92.1
Mansir et al. (
2018
)
MgO
65
24 : 1
2
1
93.3
Ashok et al. (
2018
)
Calcium diglyceroxide
60
9 : 1
1
0.5
93.5
Gupta et al. (
2015
)
KOH/clinoptilolite
65
2.25 : 1
8.1
0.223
97.45
Mohadesi et al. (
2020
)
SO
4
/Fe‐Al‐TiO
2
90
10 : 1
3
2.5
96
Gardy et al. (
2018
)
Butyl‐methyl imidazolium hydrogensulfate
160
15 : 1
5
1
95.65
Ullah et al. (
2015
)
Waste eggshell
65
9 : 1
5
2.75
87.8
Peng et al. (
2018
)
NaOH
69.37
16.7 : 1
4.571
7.08
94.6
Leung and Guo (
2006
)
KOH
94
1.5
1
6 : 1
60
Foroutan et al. (
2018a
)
NaOH
85
1.5
1
6 : 1
60
Foroutan et al. (
2018b
)
NaOH
88.8
0.33
1.1
7 : 1
60
Lam et al. (
2010
)
KOH
87
2
6
9 : 1
87
Lam et al. (
2010
)
H
2
SO
4
99
4
41.8
245 : 1
70
Lam et al. (
2010
)
1.2.3 Animal Fats
The oils obtained from animal fats are another kind of non‐edible oil used for biodiesel production. The important animal fats that are used as sources of these oils include chicken fat (Seffati et al. 2019), goat fat (Chakraborty and Sahu 2014), duck fat (Liu and Wang 2013), mutton fat (Mutreja et al. 2011), and lamb, cow, and pork fats (Banković–Ilić et al. 2014). Among these, goat and mutton fat are the most preferentially used feedstocks for biodiesel production. The total population of goats in the world is around 861.9 million, of which 514.4 million are in Asia (Hassan et al. 2016). The global sheep population is 1078.2 million and that in Asia is 452.3 million, which is about 42% of the world total (Aziz 2010). Therefore, these two sources of feedstocks can be used as an important oil source for biodiesel production in Asia. The final cost of biodiesel produced from raw oils (e.g. vegetable oils) is comparatively higher than that of petroleum‐derived fuels because the cost of feedstock (i.e. the oil) represents about 70–90% of the total expense of biodiesel production (Zhang et al. 2003; Dorado et al. 2006). However, the cost of biodiesel production can be decreased by using non‐edible oils such as waste oils and animal fats. Figure 1.1 shows the shares of different sources of oil in biodiesel production. As can be seen, the most common sources of biodiesel production are vegetable oils, such as soybean and palm oil, which are used in about 50% of all biodiesel produced globally, while less than 20% of biodiesel is produced by means of animal fats (Gnanaprakasam et al. 2013). Moreover, Table 1.3 shows the BCY of different animal fats in the presence of acidic and base catalysts.
Figure 1.1 Percentages of various oil sources used in biodiesel production.
Table 1.3 Biodiesel production from animal fats in the presence of different catalysts.
Oil source
Catalyst type
BCY (%)
References
Tallow oil
H
2
SO
4
98.28
Bhatti et al. (
2008
)
Nile tilapia oil
KOH
98.2
Santos et al. (
2010
)
Poultry oil
H
2
SO
4
99.72
Bhatti et al. (
2008
)
Beef tallow
KOH
90.8
Banković–Ilić et al. (
2014
)
Pork lard
KOH
91.4
Banković–Ilić et al. (
2014
)
Mutton fat
KOH
78.3
Banković–Ilić et al. (
2014
)
Chicken fat
H
2
SO
4
99
Banković–Ilić et al. (
2014
)
Goat tallow
NaOH
96
Esmaeili and Foroutan (
2018
)
Goat tallow
KOH
98
Esmaeili and Foroutan (
2018
)
Goat fat
MgO
93.12
Rasouli and Esmaeili (
2019
)
Chicken fat
CaO
94.4
Keihani et al. (
2018
)
Chicken fat
CaO
75.4
Awaluddin et al. (
2010
)
1.2.4 Microalga Oil
The high oil contents present in microalgae make them a promising source of oil for biodiesel production. The cost of microalga oil is less than or equal to that of animal and vegetable oils (Chen et al. 2018). Microalgae seem to be the only biodiesel source with the potential to entirely replace fossil diesel. They contain high amounts of oil that can be converted to biodiesel and have a higher capability to produce it compared to other feedstocks such as soybean, corn, canola, coconut, jatropha, and palm oil (Chisti 2007) Moreover, microalgae generate many different types of HCs, lipids, and other compounds that are required to produce biodiesel. They have large productivity and an affordable cost (Chisti 2007; Chen et al. 2018).
The capability of some feedstocks for biodiesel production has been studied, and the results show that microalga oil can replace other oil sources (Chen et al. 2018). Chlorella protothecoides (Chen et al. 2012), Nannochloropsis oculate, Phaeodactylum tricornutum, Scenedesmus dimorphus (Islam et al. 2013), Chlorella emersonii, Chlorella salina, and Chlorella vulgaris (Talebi et al. 2013) are some microalgae that show high capability for biodiesel production. Table 1.4 provides a comparison between different microalga oils.
Table 1.4 Biodiesel production from microalga oils in the presence of different catalysts.
Oil source
Catalyst type
Temp. (°C)
Time (h)
Catalyst conc. (wt%)
Alcohol to oil ratio
BCY (%)
References
Chlorella protothecoides
KOH
68
1.33
0.75
6 : 1
98.6
Yaşar and Altun (
2018
)
Spirulina maxima
KOH
65
0.33
0.75
9 : 1
86.1
Rahman et al. (
2017
)
Nannochloropsis
sp.
Ca(OCH
3
)
2
80
3
3
30 : 1
99
Teo et al. (
2016
)
Microalga oil
CaO
55
—
2
9 : 1
96.3
Siva and Marimuthu (
2015
)
Chlorella pyrenoidosa
biomass
Sulfuric acid
120
3
—
—
92.5
Cao et al. (
2013
)
Neochloris oleoabundans
ultrasonic‐assisted H
2
SO
4
—
—
—
—
98
Singh et al. (
2017
)
Neochloris oleoabundans
H
2
SO
4
and NaOH two‐step transesterification process
65
1
10
—
91
Singh et al. (
2017
)
Microalga oil
K‐Pumice
60
2
10
18 : 1
77
Cercado et al. (
2017
)
Chlorella
sp.
H
2
SO
4
23
8
115
—
79.9
Ehimen et al. (
2010
)
Microalga oil
NaOH
60
0.2
2
12 : 1
85
Cercado et al. (
2018
)
Microalga oil
KOH
60
0.2
3
12 : 1
85
Cercado et al. (
2018
)
Microalga oil
LiOH
60
0.2
5
12 : 1
55
Cercado et al. (
2018
)
1.3 Conventional Methods of Biodiesel Production
Direct use of animal fats and vegetable oils (edible and non‐edible), as well as other sources for biodiesel production, is not practical because of the high viscosity and reactiveness of unsaturated HCs. Several methods have been proposed and routinely used to reduce the kinematic viscosity of oils in order to reach the required quality for use in diesel engines, including direct use and mixing, pyrolysis, microemulsion, and transesterification. Among them, the transesterification method is most commonly applied, due to its high BCY (Kirubakaran and Arul Mozhi Selvan 2018; Wahlund et al. 2004).
1.3.1 Microemulsion
According to the International Union of Pure and Applied Chemistry (IUPAC), a microemulsion is a thermodynamically stable system developed upon dispersion of water in oil or oil in water in the presence of surfactant particles, in which one phase is continuous and the other is dispersed in the continuous phase with a size between 0.001 and 0.15 μm (Esmaeili et al. 2014, 2018). The biodiesel produced by this method has a proper CN. The alcohols used are methanol, ethanol, and 1‐butanol. The use of alcohol can reduce the fuel viscosity and improve separation of oils and alkyl nitrate; in addition, alcohol can also increase the CN of the fuel (Kirubakaran and Arul Mozhi Selvan 2018; Gebremariam and Marchetti 2017). The microemulsion method is simple and environmentally friendly, as it produces very small amounts of pollutants. However, it requires high temperatures and expensive devices, and the purity of the biodiesel produced is low (Lin et al. 2011).
1.3.2 Pyrolysis or Thermal Cracking
In pyrolysis, or thermal cracking, chemical changes are applied using heat in the presence of air or nitrogen (Yaman 2004). Several studies have been performed on the thermal cracking of oils to obtained diesel fuel as end product. Thermal decomposition of oil results in the production of several groups of components, including the alkanes, alkenes, alkadienes, carboxylic acids, and aromatics. Different types of vegetable and plant oils undergo different structural changes after thermal decomposition. The biodiesel produced exhibits a low viscosity and a high CN compared to vegetable oil. The process has some disadvantages, including low volatility, high viscosity, and stability against its own simplicity (Lin et al. 2011). In general, the biodiesel produced through microemulsion and thermal cracking methods demonstrates comparatively low CN, leading to incomplete combustion, which makes the approach nonconvenient (Lin et al. 2011; Abbaszaadeh et al. 2012).
1.3.3 Transesterification
Among all proposed methods, the transesterification reaction is the most reliable and effective for biodiesel production on both experimental and industrial scales, because it requires low temperature and pressure and a comparatively short reaction time. It has a high conversion yield and is a simple conversion process (Gebremariam and Marchetti 2017; Lin et al. 2011).
The transesterification process is the reaction between an oil and an alcohol in the presence of an appropriate catalyst to produce methyl ester (biodiesel) and glycerol. The role of the catalyst in this process is to speed up the reaction. After the reaction, the viscosity of oil reduces, while maintaining its heating value. The alcohols used are mostly methanol, ethanol, propanol, and butanol, particularly the former two; methanol is most commonly used to produce biodiesel because of its low cost and comparatively high reactivity, and because it results in the production of FAMEs with higher volatility in comparison to the fatty‐acid ethyl esters (FAEEs). The viscosity of FAEEs is slightly higher than that of FAMEs, but their pour point and cloud point are slightly lower (Seffati et al. 2020; Foroutan et al. 2020). Though the transesterification process is reversible, the process efficiency is affected by several factors, including the reactant ratio, catalyst content, and reaction conditions (Demirbas 2008). Furthermore, the use of more methanol results in more biodiesel production, but excess use leads to higher costs. Usually, catalysts are used to increase the yield and rate of the reaction; these may be alkaline, acidic, or enzymatic, with the alkaline catalysts leading to a faster reaction than the acidic catalysts (Bozbas 2008; Canakci 2007).
1.4 Catalysts Used in Biodiesel Production
The catalysts used for biodiesel production are classified into four groups: homogeneous catalysts, heterogeneous catalysts, enzymatic catalysts, and nanocatalysts (Narasimharao et al. 2007). These will be briefly discussed in this section.
1.4.1 Homogeneous Catalysts
1.4.1.1 Homogeneous Alkaline Catalysts
At industrial scale, biodiesel is usually produced using HACs such as potassium hydroxide (KOH) and sodium hydroxide (NaOH). These types of catalysts are used in industrial applications for many reasons. The reports available show that the reaction rate in the presence of an alkaline catalyst is about 4000‐fold faster than that using an acidic catalyst, though this type of catalyst is limited to vegetable‐derived oils with FFA concentration less than 6 wt%. If an oil (e.g. WEO) contains FFA higher than 6 wt%, an alkaline catalyst cannot be an appropriate option as it may react with the FFA to produce soap, which is undesirable, as it can deactivate the alkaline catalyst, affecting the biodiesel production yield (Esmaeili and Foroutan 2018; Kulkarni and Dalai 2006).
1.4.1.2 Homogeneous Acidic Catalysts
When the FFA content in oil is high, liquid acidic catalysts can be used. Two important acidic catalysts are commonly employed: sulfuric acid and chloric acid. However, while these catalysts have several advantages, they also have some disadvantages, including a comparatively low reaction rate, the need for high reaction temperatures, high alcohol to oil ratios, catalyst separation, and corrosion issues. Other acidic catalysts like HCl, H3PO4, and organic sulfonate acids can also be used to produce biodiesel (Jacobson et al. 2008). The key parameters for an acidic catalyst are the protonation (generation of positive charges) of the carbonyl group on the triglycerides and the alcohol, which attacks the positive‐charged carbon atom to form a tetrahedral intermediate (Demirbas 2008; Koberg and Gedanken 2013; Aransiola et al. 2014).
Table 1.5 shows the BCYs of various oil sources using homogeneous acidic and alkaline catalysts.
Table 1.5 Biodiesel production from different oils using homogeneous alkali and acidic catalysts.
Oil source
Catalyst type
Temp. (°C)
Time (h)
Catalyst conc. (wt%)
Alcohol to oil ratio
BCY (%)
References
Jojoba oil
KOH
25
—
1.35
—
83.5
Bouaid et al. (
2007
)
Peanut oil
KOH
60
1.5
0.5
6 : 1
95
Jazie et al. (
2012
)
Peanut oil
NaOH
60
1.5
0.5
6 : 1
88
Jazie et al. (
2012
)
Rapeseed oil
KOH
60
1.5
1
6 : 1
97
Jazie et al. (
2012
)
Rapeseed oil
NaOH
60
1.5
1
6 : 1
92
Jazie et al. (
2012
)
Microalga oil
LiOH
60
0.2
5
12 : 1
55
Cercado et al. (
2018
)
Chicken fat
H
2
SO
4
50
24
—
30 : 1
99.72
Bhatti et al. (
2008
)
Mutton fat
H
2
SO
4
60
24
—
30 : 1
98.28
Bhatti et al. (
2008
)
Cotton seed oil
Phosphoric Acid
120
10
5
10 : 1
99.79
Dholakiya (
2012
)
1.4.2 Heterogeneous Catalysts
1.4.2.1 Heterogeneous Alkaline Catalysts
Heterogeneous catalysts are superior to homogeneous catalysts because they allow easy separation of the biodiesel and byproducts like glycerol. They also entail lower production costs and are environmentally friendly (Seffati et al. 2019; Saoud 2018). Oxides and derivatives of alkaline metals (e.g. Ba, Mg, Ca, Be, Sr, and Ra) have been studied by several researchers. Among them, Mg and Sr oxides have been extensively applied as catalysts for biodiesel production due to their desirable heterogeneous nature (Rasouli and Esmaeili 2019; Yoo et al. 2010). In addition, waste materials can be used to produce heterogeneous catalysts. Several materials, such as eggshell, mollusk shell, and bone, can be used to produce heterogeneous alkaline catalysts like calcium oxide (CaO). They also help manage the problem of waste materials, which is an important concern. The CaO produced from waste materials offers great potential as a catalyst in the production of biodiesel and has been widely studied (Keihani et al. 2018; Foroutan et al. 2020; Chakraborty and Sahu 2014).
1.4.2.2 Heterogeneous Acid Catalysts
The transesterification reaction of fats and oils in the presence of HACs such as NaOH, NaOMe, KOH, and KOMe has several problems resulting from large amounts of FFA. Though these catalysts can be applied to produce biodiesel, a large amount of methanol and catalyst is consumed. Also, homogeneous acid catalysts such as H2SO4, HCl, and H3PO4 have less BCY than the HACs, and they require higher temperatures, methanol to oil ratios, pressures, and catalyst contents to produce biodiesel with an adequate BCY. Heterogeneous acid catalysts can be easily used in a packed bed continuous flow reactor: one of their main advantages. Also, the use of heterogeneous acid catalysts enables easy separation and purification of the product and reduces waste production (Boey et al. 2013; Melero et al. 2009). Recent research looking for new catalysts has demonstrated that heterogeneous acidic catalysts such as zirconium oxide (ZrO2) and cationic resins show great potential for replacing the liquid homogeneous acidic catalysts (Jacobson et al. 2008).
Table 1.6 shows the BCYs of various oil sources using heterogeneous acidic and alkali catalysts.
Table 1.6 Biodiesel production from different oils using heterogeneous acidic and alkaline catalysts.
Oil source
Catalyst type
Temp. (°C)
Time (h)
Catalyst conc. (wt%)
Alcohol to oil ratio
BCY (%)
References
Nannochloropsis
sp.
Ca(OCH
3
)
2
80
3
3
30 : 1
99
Teo et al. (
2016
)
Microalga oil
K‐Pumice
60
2
10
18 : 1
77
Cercado et al. (
2017
)
Waste cooking oil
KOH/clinoptilolite
65
0.223
8.1
2.25 : 1
97.45
Mohadesi et al. (
2020
)
Waste cooking oil
Ba/CaO
65
3
3
6 : 1
88
Balakrishnan et al. (
2013
)
Waste cooking oil
Copper/zinc oxide
55
0.833
12
8 : 1
97.71
Gurunathan and Ravi (
2015
)
Waste cooking oil
4Mn‐6Zr/CaO
80
3
3
15 : 1
92.1
Mansir et al. (
2018
)
Waste cooking oil
Calcium diglyceroxide
60
0.5
1
9 : 1
93.5
Gupta et al. (
2015
)
Waste cooking oil
Waste eggshell
65
2.75
5
9 : 1
87.8
Peng et al. (
2018
)
Waste cooking oil
SO
4
/Fe‐Al‐TiO
2
90
2.5
3
10 : 1
96
Gardy et al. (
2018
)
Waste cooking oil
Butyl‐methyl imidazolium hydrogen sulfate
160
1
5
15 : 1
95.65
Ullah et al. (
2015
)
1.4.3 Enzymatic Catalysts
The transesterification reaction using enzymatic catalysts has some advantages. The reaction in the presence of enzymatic catalysts occurs without formation of soap and continues free of purification, washing, and neutralization problems. Also, the transesterification reaction can be carried out under normal conditions, and this catalyst has no problem with oils containing large amounts of FFA (Shahid and Jamal 2011). Other advantages include low energy usage, reusability of the catalyst, and zero wastage of water (Norjannah et al. 2016). However, these catalysts are expensive and require long reaction times (about 12–24 hours), which limits their application (Norjannah et al. 2016; Shahid and Jamal 2011). The lipase enzyme is mostly used for converting oil to biodiesel (triacylglycerol acylhydrolase) (Arumugam and Ponnusami 2017; Norjannah et al. 2016). Lipases can be derived from different sources, such as yeast (Candida parapsilosis, Candida deformans, Candida quercitrusa, Candida antarctica, Geotrichum candidum, Pichia burtonii, Pichia xylosa, Saccharomyces lipolytica, and Pichia sivicola), bacteria (e.g. Pseudomonas aeruginosa, Chromobacterium viscosum, Bacillus subtilis, Aeromonas hydrophilia, Staphylococcus canosus, Staphylococcus aureus, Burkholderia glumae, and Achromobacter lipolyticum), and fungi (e.g. Alternaria brassicicola, Streptomyces exfoliates, Rhizopus chinensis, Mucor miehei, Aspergillus niger, and Rhizopus oryzae) (Norjannah et al. 2016). The enzymatic transesterification process for biodiesel production occurs via the ping‐pong bi‐bi mechanism, whereby substrates react to generate products via formation of a substrate–enzyme intermediate. Mechanisms have three steps: (i) alcoholysis of monoglycerides, diglycerides, and triglycerides (glycerides) into fatty acid alkyl ester; (ii) hydrolysis (converting glycerides into FFA) followed by esterification (converting FFA into esters); and (iii) simultaneous reactions of hydrolysis and alcoholysis following esterification (Norjannah et al. 2016).
Table 1.7 shows the BCYs of various oil sources using enzymatic catalysts.
1.4.4 Nanocatalysts
Biodiesel production using the transesterification reaction in the presence of acidic or alkaline catalysts is associated with some problems, like long ester formation and reaction completion times. Moreover, these catalysts are not reusable and form stable emulsions that make ester separation more difficult (Seffati et al. 2019, 2020). In recent years, the use of nanocatalysts has significantly increased due to their improved characteristics compared with other conventional catalysts (Tamjidi et al. 2019; Tamjidi and Esmaeili 2019
