Furfural

An Entry Point of Lignocellulose in Biorefineries to Produce Renewable Chemicals, Polymers, and Biofuels

Manuel López Granados, David Martín Alonso

• Publisher: WSPC (EUROPE)
• Year: 2018
• ISBN:
  9781786344885
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

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There is a wide consensus that furfural, a renewable commodity currently obtained from lignocellulosic agro-residues with a production volume of around 300 kTon per year, is a key feedstock for leveraging lignocellulosic residues in future biorefineries. Several chemicals are already being manufactured from furfural due to its advantageous production cost. Furthermore, a vast number of others are also technically viable, to produce from oil.

This book compiles the vast existing information into relevant stages of transformations of furfural as renewable chemicals, biofuels and bioresins focusing on the relevant chemical and engineering aspects of processes to obtain them, including reactors and catalysis. It offers essential information for improving the economic and environmental viability of current commercial applications and upcoming future applications.

It should be of particular interests to graduate and advanced undergraduate students, as well as, engineers and academic researchers alike who are working in the field.

--> Contents:

• Preface
• About the Authors
• Chemistry of Furfural and Furanic Derivatives (Jesús Hidalgo-Carrillo, Alberto Marinas and Francisco J Urbano)
• Past, Current Situation and Future Technologies of Furfural Production (David Martín Alonso and Gianluca Marcotullio)
• Renewable Chemicals, Biofuels and Resins from Furfural:
  • Furfuryl Alcohol and Derivatives (Pedro Maireles-Torres and Pedro L Arias)
  • Tetrahydrofurfuryl Alcohol and Derivatives (Pedro Maireles-Torres and Pedro L Arias)
  • Catalytic Transformations of Furfural and Its Derived Compounds into Pentanediols (Sibao Liu, Masazumi Tamura, Yoshinao Nakagawa and Keiichi Tomishige)
  • 2-Methyl Furan and Derived Biofuels (Manuel López Granados, Inaki Gandarias, Iker Obregón and Pedro L Arias)
  • 2-Methyl Tetrahydrofuran (MTHF) and Its Use as Biofuel (Iker Obregón, Inaki Gandarias and Pedro L Arias)
  • Cyclopentanone and Its Derived Biofuel (Manuel López Granados)
  • Levulinic Acid and γ-Valerolactone (Rafael Mariscal and David Martín Alonso)
  • Amination of Furfural (Pedro Maireles-Torres and Pedro L Arias)
  • On the Oxidation of Furfural to Furoic Acid (Michela Signoretto and Federica Menegazzo)
  • Furan, Tetrahydrofuran and Other Furan-Derived Chemicals (Francisco Vila, Manuel Ojeda and Manuel López Granados)
  • Catalytic Oxidation of Furfural to C 4 Diacids-Anhydrides and Furanones (Manuel López Granados)
  • Biofuels and Chemicals from Furfural Condensation Reactions (Irantzu Sádaba and Manuel López Granados)
  • Fuel Additives by Furfural Acetalisation with Glycerol (Manuel López Granados)
  • Furanic Resins and Polymers (Thomas J Schwartz and Sikander H Hakim)
• Future Prospects and Main Challenges (Manuel López Granados and David Martín Alonso)
• Introduction to Chemical Reactors (José Miguel Campos-Martín)
• Introduction to Electrochemistry (María Retuerto and Sergio Rojas)

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--> Readership: Undergraduate and graduate students and academic and industrial researchers interested in the chemical transformations of furfural, biorefinery, biomass, biofuels, renewable chemicals. -->
Furfural;Biorefinery;Biomass;Biofuels;Renewable Chemicals0 Key Features:

• The first chapter is devoted to revising the organic chemistry and reactivity of furanic compounds
• Introduction to chemical reactors and electrochemistry as concepts are included as annexes, to help readers understand the subjects, as they are both frequently citied throughtout the book

Chapter 1

Chemistry of Furfural and Furanic Derivatives

Jesús Hidalgo-Carrillo, Alberto Marinas and Francisco J. Urbano^∗

Departamento de Química Orgánica,
Universidad de Córdoba, Campus de Rabanales,
Edificio Marie Curie, E-14071 Córdoba, España

^∗Corresponding author: [email protected]

1.1.Introduction

Furfural (C₅H₄O₂) and its derivatives have come to prominence within the last years as a source of renewable compounds with high applicability to different fields such as fuels and biochemical production. It is one of the top value-added chemicals that can be produced from biomass. As it will be shown in other chapters of this book, furfural is a natural precursor to a range of furan-based chemicals and solvents such as methyltetrahydrofuran, tetrahydrofuran, tetrahydrofurfuryl alcohol and furoic acid, among others. Thus, compounds derived from furfural are used as plastics, in the pharmaceutical industries, as agricultural fungicides or nematocides, lubricants, resins, bleaching agents, food and beverage additives, wood modifiers or book preservatives, among other uses.

This increase in the interest in these compounds is due to the flexibility in the production of furfural from biomass residues, being one of the top high value-added value products that can be obtained from residues of biomass [1, 2].

Table 1.1.Physical properties of main furan derivatives (adapted from Ref. [3]).

The principal physical properties of furfural and its main derivatives are shown in Table 1.1 [3]. The applications of products derived from furfural are multiple, Table 1.2 showing some of their main applications, as well as their synthetic route based on furfural. Further details will be given in Chapter 3.

Due to the two chemical functionalities present — aldehyde group and aromatic ring — furfural can undergo typical aldehyde reactions, such as nucleophilic additions, condensation reactions, oxidations or reductions, as well as others associated to the furan ring such as electrophilic aromatic substitution or hydrogenation.

The purpose of this chapter is to give an overview of furfural chemical reactivity based on the organic chemistry fundamentals, intending to help the reader to understand the multiple possible reactions that furfural has in function of the different functionalities of the molecule: the aromatic ring and the carbonyl group.

1.2.Furan and furan derivatives

1.2.1.Furan structure, physical properties and synthesis

Furan is a heterocyclic organic compound consisting of a fivemembered aromatic ring with four carbon atoms and an oxygen atom. It is a colorless, highly volatile and flammable liquid with a low-temperature boiling point (Table 1.1). It is slightly soluble in water but readily soluble in common organic solvents such as alcohol, ether or acetone.

Table 1.2.Applications and synthetic procedure of the main furfural derivatives (adapted from Ref. [3]).

Derivative	Process reaction	Utilization
Furfural	Xylosans dehydration	Natural precursor to a range of furan-based chemicals and solvents
Furan	Furfural catalytic decarbonylation	Production of tetrahydrofuran and acetylfuran
Furfuryl alcohol	Furfural catalytic hydrogenation	Production of resins and tetrahydrofurfuryl alcohol; intermediate in fragrances production, lysine and vitamin C
Tetrahydrofurfuryl alcohol	Furfural catalytic hydrogenation	Solvent
2-Methylfuran	Furfural and 5-methylfurfural decarbonylation	Solvent and monomer
Furoic acid	Furfural oxidation	Synthesis of pharmaceuticals and perfumes

1.2.1.1.Furan aromaticity

According to Huckel’s rule, furan is aromatic because it is a flat ring having a six (4n + 2) delocalized π electrons system. Thus, the four carbon atoms and oxygen have sp₂ hybridization, with an atomic p_z orbital perpendicular to the plane of the ring. Each carbon atom brings a p_z electron to the aromatic system, while the oxygen atom provides one of the lone pairs it possesses. The oxygen atom thus retains one of the lone electron pairs placed in a sp₂ hybrid orbital oriented away from the aromatic ring, but in the same plane as this one (Figure 1.1).

Furan has an aromatic resonance stabilization energy of 14.8 kcal·mol⁻¹, energy which is lower than that of thiophene (18.6 kcal·mol⁻¹) and pyrrole (20.6 kcal·mol⁻¹). In other words, the aromatic character of furan is less marked than that of thiophene or pyrrole [4].

Figure 1.1.Structure of furan.

The oxygen atom of furan has an electrodonating mesomeric effect (+M), associated with the ability to delocalize its lone electron pairs. Moreover, it also has an inductive effect (−I) that is evident in the displacement towards the oxygen of the constituent electrons of the C–O bond due to the greater electronegativity of the oxygen.

Although both effects are globally opposed, oxygen exerts a net electron-donating effect, as a consequence of the mesomeric effect being greater than the inductive one (+M > −I). Thus, the oxygen atom provides an additional electron density to the ring, which results in electron density values greater than 1 for each carbon atom.

As previously mentioned, furan as well as its homologs (thiophene and pyrrole) is a surplus π system due to the distribution of six π electrons delocalized in five atoms. This results in a greater electron density in the cycle than in its benzene analogues. This accounts for the higher reactivity of furan in electrophilic aromatic substitution, as compared to benzene.

On the other hand, contrary to the simple six elements aromatic rings, only one of its resonance structures is neutral, whereas the other forms exist as zwitterions (Figure 1.2). As result, although these charged forms contribute a minority to the resonance hybrid, the chemistry of furan will be partly that of the aromatic compounds and partly that of the dienes.

Figure 1.2.Resonance structures for furan. Structures II–V are zwitterionic.

1.2.1.2.Furan synthesis

Furan can be obtained by the Paal–Knorr synthesis, consisting in the dehydration of a 1,4-dicarbonyl compound by P₂O₅ or sulfuric acid (Figure 1.3(a)). However, at present, the main industrial process to obtain furan is decarbonylation of furfural using palladium or nickel catalysts (Figure 1.3(b)), by the copper-catalyzed oxidation of butadiene (Figure 1.3(c)) or by decarboxylation through oxidation with Ag₂O to furoic acid and subsequent elimination of CO₂ on copper catalysts (Figure 1.3(d)).

1.2.2.Furan and furan derivatives reactivity

As stated above, furan has an aromatic character that is associated to its electrophilic aromatic substitution reactivity, although as a result of charged resonance structures, it also behaves, in part, as a diene. Therefore, when establishing the reactivity of the furan ring, we must take into account both aspects.

1.2.2.1.Electrophilic aromatic s...

Table of contents

• Cover Page
• Title
• Copyright
• Preface
• About the Authors
• Contents
• Chapter 1 Chemistry of Furfural and Furanic Derivatives
• Chapter 2 Past, Current Situation and Future Technologies of Furfural Production
• Chapter 3 Renewable Chemicals, Biofuels and Resins from Furfural
• Chapter 3.1 Furfuryl Alcohol and Derivatives
• Chapter 3.2 Tetrahydrofurfuryl Alcohol and Derivatives
• Chapter 3.3 Catalytic Transformations of Furfural and its Derived Compounds into Pentanediols
• Chapter 3.4 2-Methyl Furan and Derived Biofuels
• Chapter 3.5 2-Methyl Tetrahydrofuran (MTHF) and its Use as Biofuel
• Chapter 3.6 Cyclopentanone and its Derived Biofuels
• Chapter 3.7 Levulinic Acid and γ-Valerolactone
• Chapter 3.8 Amination of Furfural
• Chapter 3.9 On the Oxidation of Furfural to Furoic Acid
• Chapter 3.10 Furan, Tetrahydrofuran and Other Furan-derived Chemicals
• Chapter 3.11 Catalytic Oxidation of Furfural to C4 Diacids-anhydrides and Furanones
• Chapter 3.12 Biofuels and Chemicals from Furfural Condensation Reactions
• Chapter 3.13 Fuel Additives by Furfural Acetalization with Glycerol
• Chapter 3.14 Furanic Resins and Polymers
• Chapter 4 Future Prospects and Main Challenges
• Annex 1 Introduction to Chemical Reactors
• Annex 2 Introduction to Electrochemistry
• Index