The University of Toledo
The University of Toledo Digital Repository
Theses and Dissertations
2015
Conversion of cellulose from plant biomass to and
its derivatives in ionic liquid media
Siamak Alipour
University of Toledo
Follow this and additional works at: http://utdr.utoledo.edu/theses-dissertations
Recommended Citation
Alipour, Siamak, "Conversion of cellulose from plant biomass to and its derivatives in ionic liquid media" (2015). Theses and
Dissertations. 1825.
http://utdr.utoledo.edu/theses-dissertations/1825
This Dissertation is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses
and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's
About page.
A Dissertation
entitled
Conversion of Cellulose from Plant Biomass to 5-(hydroxymethyl)furfural (HMF) and its
Derivatives in Ionic Liquid Media
by
Siamak Alipour
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the
Doctor of Philosophy Degree in Engineering
_________________________________________
Dr. Sasidhar Varanasi, Committee Chair
_________________________________________
Dr. Sridhar Viamajala, Committee Member
_________________________________________
Dr. Patricia Relue, Committee Member
_________________________________________
Dr. Ashok Kumar, Committee Member
_________________________________________
Dr. Kana Yamamoto, Committee Member
_________________________________________
Dr. Patricia R. Komuniecki, Dean
College of Graduate Studies
The University of Toledo
May 2015
Copyright 2015, Siamak Alipour
This document is copyrighted material. Under copyright law, no parts of this document
may be reproduced without the expressed permission of the author.
An Abstract of
Conversion of Cellulose from Plant Biomass to 5-(hydroxymethyl)furfural (HMF) and its
Derivatives in Ionic Liquid Media
by
Siamak Alipour
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the
Doctor of Philosophy Degree in Engineering
The University of Toledo
May 2015
In this study, the main goal is introducing a new method for the production of 5(hydroxymethyl)furfural (HMF) and its derivatives. I propose an integrated process with
low energy input for high-yield production of hydroxymethyl furfural (HMF) from
glucose in biomass hydrolysates. Due to the prevalent recognition that HMF is a versatile
platform molecule for fuels and chemicals, there is a critical need for economically viable
technologies for its production from biomass hydrolysates. Previous attempts to generate
HMF in aqueous media (either from untreated biomass or from hydrolysates) have not
resulted in high yields due to loss of product to humins and inability to prevent hydrolysis
of HMF to levulinic and formic acids. Although biomass hydrolysates typically contain
glucose, it is now broadly recognized that the best yields can be obtained by dehydration
of the corresponding keto-isomer, fructose, and by executing the reactions in non aqueous
reaction media (e.g. DMSO and ionic liquids (ILs)). The challenge then, for costeffective and high-yield HMF production, is to devise a cohesive pathway to efficiently
transfer glucose from biomass hydrolysate into the non-aqueous reaction media; produce
iii
HMF in high yield; and isolate it for downstream processing, all with low energy input
and recycling of process streams.
The technology addresses this challenge and we propose a hybrid enzyme- and
chemo-catalytic process that first converts hydrolysate glucose to its more reactive ketose
form and subsequently integrates with a downstream catalytic dehydration step that
achieves high yields of HMF. The conversion of hydrolysate glucose to fructose and its
near-complete recovery is accomplished through a novel enzyme-based simultaneousisomerization-and-reactive-extraction (SIRE) process. The recovered fructose is then
dehydrated to HMF in an acidic ionic liquid (IL) reaction medium and simultaneously
extracted into low-boiling tetrahydrofuran (THF) solvent to prevent side reactions,
increase process yields and facilitate easy product recovery. Conversion of fructose to
HMF in IL-media results in superior yields than in aqueous solutions and also occurs at
mild operating conditions (IL rxn T ~ 50 °C; aqueous rxn T >160 °C). Finally, a key
feature of this technology is that it permits recycling and reuse of the catalysts, solvents
and reaction media. This method also is proven to be an ideal pathway to produce furfural
and HMF simultaneously from mixed C5 and C6 sugars stream. In addition, for the
important HMF derivatives namely 5-ethoxy methyl furfural (EMF), levulinic acid and 5acetoxymethyl furfural (AMF) production this method has modified and successfully
applied.
iv
To my beloved Parents, Hengameh and Babak
for their love, support and patience
Acknowledgements
I would like to sincerely thank my family for their endless support. My wife,
parents and brother have encouraged me enormously during my PhD journey. Without
their helps my dreams would not be achieved. They were always beside me in any
situation that I faced.
I would like to thank my advisor Prof., Sasidhar Varanasi for his scientific
support, useful hints and patience. Without his considerations my PhD achievement was
not possible. I would also like to thank my PhD committee Drs. Sridhar Viamajala,
Patricia Relue, Ashok Kumar and Kana Yamamoto for their recommendations and
Chemical and Environmental Engineering Department support throughout my PhD.
My Colleagues and lab mates have helped me a lot during my experiments; I
would like to express my gratitude to them especially to Brook, Heng, Bin and Peng.
Also I want to appreciate my best friend, Nima Mansouri, helps and supports.
v
Table of Contents
Abstract ......................................................................................................................... iii
Acknowledgements .........................................................................................................v
Table of Contents .......................................................................................................... vi
List of Tables................................................................................................................. xi
List of Figures .............................................................................................................. xii
1 Introduction ..................................................................................................................1
1-1 Preview ..................................................................................................................... 1
1-2 Dissertation outline .................................................................................................. 5
2 High Yield 5-Hydroxymethylfurfural Production from Biomass Sugar at Facile
Reaction Conditions: a Hybrid Enzyme- and Chemo-Catalytic Technology .....................8
2.1 Introduction .............................................................................................................. 8
2.2 Materials and Methods .......................................................................................... 12
2.2.1 Chemicals and Materials .......................................................................... 12
2.2.2 Preparation of saccharified biomass hydrolysate.................................... 13
2.2.3 Simultaneous-isomerization-and-reactive-extraction (SIRE) and backextraction (BE) ................................................................................................... 13
vi
2.2.4 Fructose conversion to HMF in IL reaction media ................................. 14
3.2.5 Fructose and xylulose conversion to HMF and furfural in IL reaction
media ................................................................................................................... 15
2.2.6 Analytical methods ................................................................................... 15
2.3 Results and Discussion .......................................................................................... 16
2.3.1 Step 1 – Simultaneous-isomerization-and-reactive-extraction (SIRE) . 16
2.3.2 Step 2 – Back-extraction (BE) of fructose from the organic phase ....... 18
2.3.3 Step 3 – Dehydration of fructose to HMF. .............................................. 22
2.3.4 Biomass Hydrolysate ................................................................................ 26
2.3.5 IL Reusability ............................................................................................ 26
2.3.6 Fructose Loading ...................................................................................... 28
2.3.7 Mixed fructose and xylulose stream ........................................................ 29
2.4 Conclusion .............................................................................................................. 30
3 High Yield Biomass Hydrolysate Conversion to 5- (ethoxymethyl)furfural ................. 31
3.1 Introduction ............................................................................................................ 31
3.2 Materials and Methods .......................................................................................... 34
3.2.1 Chemicals and Materials .......................................................................... 34
3.2.2 Fructose conversion to EMF in IL media ................................................ 34
3.2.3 Glucose conversion to EMF in IL media ................................................ 35
3.2.4 Analytical methods ................................................................................... 35
3.3 Results and discussions ......................................................................................... 36
3.3.1 Reaction Kinetics data .............................................................................. 37
3.3.2 Temperature effect on the products yield ................................................ 38
vii
3.3.3 Ethanol loading effect on the products yield ........................................... 39
3.3.4 Fructose loading effect on the products yield ......................................... 40
3.3.5 IL reusability ............................................................................................. 41
3.3.6 Glucose conversion to EMF ..................................................................... 42
3.4 Conclusion .............................................................................................................. 44
4 Facile Production and in-situ Esterification of HMF from Biomass Sugars in Ionic
Liquid Media ................................................................................................................. 45
4.1 Introduction ............................................................................................................ 45
4.2 Materials and Methods .......................................................................................... 48
4.2.1 Chemicals and Materials .......................................................................... 48
4.2.2 Experimental procedure............................................................................ 48
4.2.3 Analytical Procedures ............................................................................... 49
4.3 Results and Discussion .......................................................................................... 50
4.3.1 Effect of acetic acid loading on the final furan yield .............................. 50
4.3.2 H2SO4 loading influence on final furan yield ......................................... 51
4.3.3 Temperature effects on furan yield .......................................................... 52
4.3.4 Effect of fructose loading on final furan yield ........................................ 56
4.3.5 IL recycling ............................................................................................... 57
4.3.6 Extracting Solvent efficiency ................................................................... 58
4.3.7 Effects of modifications to the reactants and IL reaction medium ........ 59
4.4 Conclusion .............................................................................................................. 64
5 Levulinic acid Production in High from Biomass Hydrolysate sugar by Implementing
SIRE-BE Technique ...................................................................................................... 65
viii
5.1 Introduction ............................................................................................................. 65
5.2 Materials and Methods .......................................................................................... 68
5.2.1 Chemicals and Materials .......................................................................... 68
5.2.2 Fructose conversion to Levulinic acid ..................................................... 68
5.2.3 Glucose conversion to Levulinic acid ..................................................... 69
5.2.4 Analytical methods ................................................................................... 69
5.3 Results and Discussion .......................................................................................... 70
5.3.1 Acid catalyst loading effect on the levulinic acid yield in the aqueous
media ................................................................................................................... 70
5.3.2 Reaction duration effect on the levulinic acid yield in the aqueous
media ................................................................................................................... 71
5.3.3 Temperature effect on the levulinic acid yield in the aqueous media ... 72
5.3.4 Fructose loading effect on the levulinic acid yield in the aqueous media
............................................................................................................................. 74
5.3.5 Glucose conversion to the levulinic acid in the aqueous media ............ 76
5.3.6 Levulinic acid production in the [BMIM-SO3]HSO4 and DI water
mixture ................................................................................................................ 77
5.3.7 [BMIM-SO3]HSO4 loadings effect on the levulinic acid yield ............. 78
5.3.8 Levulinic acid kinetic data in the [BMIM-SO3]HSO4 and DI water
mixture ................................................................................................................ 79
5.3.9 Temperature effect on the levulinic acid yield in the [BMIM-SO3]HSO4
and DI water mixture ......................................................................................... 80
ix
5.3.10 Fructose loading effect on the levulinic acid yield in the [BMIMSO3]HSO4 and DI water mixture ...................................................................... 81
5.3.11 Ionic liquid reusability ............................................................................ 82
5.3.12 Ionic liquids replacement effect on the levulinic acid yield ................ 83
5.4 Conclusion .............................................................................................................. 85
6 Conclusion, Alternative Approaches and Suggestions for Future Works ..................... 86
6.1 Conclusion .............................................................................................................. 86
6.2 Alternative implementations of SIRE-BE technique and suggestions ............... 87
References ..................................................................................................................... 93
x
List of Tables
2.1
IL screening for selective back-extraction of fructose from the organic solvent . . 20
2.2
Fructose dehydration to HMF in [EMIM]HSO4 media ....................................... 25
2.3
Results for dehydration of mixed ketoses back-extracted into [EMIM]HSO4 ..... 30
4.1
Comparison the total furan yield between dehydration and in-situ esterification
system and only dehydration reaction ................................................................. 56
4.2
Furan yield in the modified experiments............................................................. 61
4.3
Furan yield in the different IL ............................................................................ 63
5.1
Glucose conversion to LA and HMF .................................................................. 77
xi
List of Figures
1-1
HMF as a building Block ..................................................................................... 4
2-1
Schematic representation of the three-step process for production of HMF from
the biomass sugar glucose. ................................................................................. 12
2-2
Effect of boronic acid to sugar mole ratio on sugar extraction and ketose
selectivity for SIRE. ........................................................................................... 18
2-3
Schematic diagram of the 4 stage SIRE followed by BE with the summary of
results for a 30 g/l (~165mM) aqueous glucose stream ....................................... 22
2-4
Summary of SIRE-BE results for biomass hydrolysate ....................................... 26
2-5
HMF yield with repeated reuse of the IL dehydration media .............................. 27
2-6
HMF yield as a function of the initial fructose loading ....................................... 28
2-7
Process schematic for furans production from biomass hydrolysate sugars
(glucose and xylose) by the SIRE-BE-Dehydration-in-IL approach .................... 29
3-1
The block box diagram of the biomass conversion to value added products ........ 36
3-2
Kinetic data of Fructose conversion, EMF, HMF and EL yield ........................... 38
3-3
Ethanol loading effect on fructose conversion and products yield . ...................... 40
3-4
Fructose loading effect on fructose conversion and products yield ...................... 41
3-5
[EMIM]HSO4 reusability results........................................................................ 42
xii
3-6
Glucose conversion to EMF, LE and HMF results .............................................. 44
4-1
Effects of acetic acid loading on final furan yield ............................................... 51
4-2
Influence of H2SO4 loading on final furan yield ................................................. 52
4-3
Fructose, HMF, and AMF content (mole % relative to initial moles of sugar)
versus time at (a) 80°C (b) 100°C (c) 117°C....................................................... 55
4-4
Reaction pathway for fructose dehydration and in-situ HMF esterification ......... 55
4-5
Effect of fructose loading on final furan yield .................................................... 57
4-6
Reusability of [EMIM]Cl results ........................................................................ 58
4-7
Solvents extraction efficiency comparison.......................................................... 59
4-8
Effects of glucose and fructose on the products yield ......................................... 62
5-1
Acid catalyst concentration effects on fructose conversion, LA and HMF yield .. 71
5-2
Reaction duration effect on fructose conversion, LA and HMF yield .................. 72
5-3
Temperature effect on the fructose conversion, and LA and HMF yield ............. 74
5-4
Fructose loading effects on LA and HMF yield .................................................. 76
5-5
[BIMIM-SO3]HSO4 weight percent effects on LA yield .................................... 79
5-6
Kinetic data of fructose conversion and LA yield in IL aqueous mixture ............ 80
5-7
Temperature effect on fructose conversion and LA yield in IL aqueous mixture 81
5-8
Fructose loading effect on LA yield in IL aqueous mixture ................................ 82
5-9
IL aqueous mixture reusability results ................................................................ 83
5-10
Fructose conversion, LA and HMF yield in different ILs.................................... 85
6-1
Schematic diagram for the alternative reactor configuration ............................... 89
6-2
DMSO weight percent effects on HMF yield ..................................................... 91
xiii
Chapter 1
Introduction
1-1 Preview
The steady growth of world energy consumption, energy security, diminishing fossil
fuel resources, and environmental impact require the usage of renewable alternative
energy resources [1,2]. Solar energy, wind energy, hydropower, geothermal energy and
biomass are major renewable alternative energy resources [3]. Among these energy
resources, biomass is the only one that is based on carbon, while others are suitable to
produce electrical energy. Based on the constituent biopolymers, biomass could be
classified into lignocellulosic and non-ligneous biomass. Lignocellulosic biomass is the
most abundant class of biomass: agricultural residue (e.g. wheat straw, sugarcane
bagasse, corn stover), forest products (hardwood and softwood), and dedicated crops
(switchgrass, salix) [4] are examples of lignocellulosic materials that can be used as
renewable sources of energy. Non-ligneous biomass are lignin-deficient feedstocks
include micro- or macro-algae, oleaginous feedstocks, bacteria, fungi, etc. [5, 6].
1
Initially edible biomass such as corn or cane sugar were studied and used for the
production of chemicals and biofuels. However, this usage can cause shortages in these
food sources. As a result, it will increase food prices and raises the food versus fuel
debate. Such issues have driven researchers to develop technologies to process non-edible
biomass (e.g., lignocellulosic biomass) to produce biofuel and chemicals sustainably
without affecting food supplies. In addition, lignocellulosic biomass has two important
advantages over edible biomass feedstocks: it is more abundant and can be grown faster
and at lower costs as well [7].
Lignocellulosic biomass is composed of cellulose (40–50%), hemicellulose (25–
35%), and lignin (15–20%) [8]. Cellulose is a polymer of glucose units linked via βglycosidic bonds, and is typically embedded as crystalline fibrils within the complex of
lignin/hemicellulose matrix, which makes it largely inaccessible to hydrolysis in
untreated biomass. Since the cellulose is the major part of the lignocellulosic biomass, its
transformation to chemical and fuels is essential to build a sustainable chain of products.
The hemicellulose fraction of lignocellulosic biomass is also an amorphous polymer that
is comprised of up to five different sugar monomers: D-xylose, L-arabinose, D-galactose,
D-glucose, and D-mannose; xylose is the most abundant among these sugars [8-9]. The
last part of the lignocellulosic biomass, lignin, is a cross-linked polymer network of
methoxylated phenylpropane structures, that included coniferyl alcohol, sinapyl alcohol,
and coumaryl alcohol [10-11].
Production of chemicals and fuels from lignocellulosic biomass feedstock requires
various innovative approaches and multistep processes due to its high degree of chemical
and structural complexity. In general, the biomass is first fractionated into its major
2
components, and the individual components are then converted into suitable products
[12]. The lignocellulosic biomass has a very rigid structure to protect it in nature; its
fractionation, accordingly, requires a special pretreatment followed by hydrolysis. The
pretreatment can include physical (e.g. milling, comminuting) and chemical (e.g. acid or
base hydrolysis) methods. Following the pretreatment step, the hydrolysis of crystalline
cellulose is affected via enzyme hydrolysis. The resulting sugars can then be converted to
value-added compounds through conventional chemical and/or biochemical routes. This
approach is popularly referred to as “the sugar platform.”
The following seven petro-chemical compounds: toluene, benzene, xylene, 1,3butadiene, propylene, ethane, and methane form the “platform chemicals” in a traditional
petroleum refinery based approach for manufacturing high-value chemicals [13]. In an
analogous bio-refinery based approach to chemicals and fuels, carbohydrate-derived
sugars, and lignin-derived phenolics would serve as starting compounds that can be
converted to a different set of “platform-molecules” [14]. One such class of platform
molecules are furans obtained via dehydration of C6 and C5 sugars. They are important
building blocks that can be further processed to produce solvents and fuels. For instance,
5-hydroxymethyl-furfural (HMF), furfural, and 2, 5-furan-di-carboxylic acid are
mentioned in the DOE top 10 list of platform chemicals [15], and in a recent update by
Bozell et. al. [16], these were included in the 10+4 list as well.
3
Figure 1-1: HMF as a building Block [17]
Figure 1-1 presents some of the important compounds that can be produced from
HMF. In view of these important chemical and material precursors that can result from
HMF, finding pathways that economically produce HMF from cellulose in high yields is
the crucial first step in bio-refining and is the principal objective of this thesis.
The recent discovery that cellulose can be dissolved in some ILs [18-20] opened
the possibility for using these ILs as reaction media for cellulose-derived chemicals and
materials. For instance, cellulose, which is insoluble in aqueous media, requires
heterogeneous reaction conditions and the use of cellulase enzyme cocktails to affect its
hydrolysis to glucose in water. In contrast, depolymerization/hydrolysis of cellulose in
presence of mineral acid catalysts becomes feasible in ILs under homogeneous reaction
conditions, as ILs are able to dissolve appreciable amounts of cellulose. Here, the
4
hydrolysis of β (1→4) glycosidic linkages is catalyzed by the protons. Different solid
acids (Amberlyst, Nafion, alumina, sulfonated zircona, and zeolithes) have also been
shown to hydrolyze both microcrystalline cellulose or α-cellulose in the IL butyl-methyl
imadazolium chloride, [BMIM]Cl [21-22]. In addition, some preliminary investigations
on dehydration of the monosaccharaides to furans was also reported in IL media, In these
reactions, the acidity of the IL medium [23] and its water content [24] play an important
role. In most of these early studies, the furan yields were low and the reaction conditions
were rather severe.
In the present work, it has been proposed to exploit the unique reaction
environment offered by the ILs to produce furans and furan-derived compounds from
major biomass sugars, namely, glucose (six-carbon sugar) and xylose (five-carbon sugar).
Several innovative strategies are proposed to maximize product yields, while conducting
the involved reaction steps under facile conditions. Strategies for recovering and reusing
the reaction media are also proposed. Overall, the objective of this Dissertation is to
develop technologies that can make large scale production of furans and furan-derived
compounds from biomass sugars economically viable.
1-2 Dissertation outline
In order to gain the goals of this work, HMF and its derivatives production have
studied in detail. The investigation results are presented in the separate chapters for each
component. Consequently the dissertation is organized as follows:
5

In the first chapter the introduction has provided. The importance of topic and
motivation for this study are highlighted in this section. Also the pathway for the
aim of the dissertation is provided.

The second chapter presents a complete image of simultaneous isomerization and
reactive extraction (SIRE) - back extraction (BE) and dehydration process. This
chapter includes the process mechanism description and data of HMF production
form biomass hydrolysate. Besides, chapter two shows the results of
implementing SIRE-BE- Dehydration process for simultaneous HMF and furfural
production from a mixed xylose and glucose stream. In order to obtain optimum
conditions for this method different operating parameters have investigated in
detail.

Chapter three illustrates the results of modifications in SIRE-BE-Dehydration
process to produce 5-ethoxy methyl furfural (EMF) from C6 sugars. The data also
present EMF, EL, and HMF yields changes due to variations in the different
parameters such as temperature, reactants loading, reaction duration etc.

Chapter four includes the one-pot 5-acetoxy methyl furfural (AMF) production
from C6 sugars. Prepared data provide the effects of reactants and catalyst
loading, reaction temperature and duration, different reaction media, and various
precursors on the AMF yield. Besides reusability of reaction media and extracting
organic solvent efficiency has shown.

Chapter five demonstrates the results of levulinic acid preparation from biomass
hydrolysate. The results provide optimum operating conditions (e. g. temperature,
6
reaction duration, catalysts and reactants loadings). In addition, in order to
produce levulinic acid in high yield various reaction media has investigated.

Chapter six provides the conclusions, alternative approaches and comments for
future studies.
7
Chapter 2
High Yield 5-Hydroxymethylfurfural Production from
Biomass Sugar at Facile Reaction Conditions: a Hybrid
Enzyme- and Chemo-Catalytic Technology
2.1 Introduction
Lignocellulosic biomass can serve as a sustainable feedstock for producing liquid
transportation fuels and chemical and material precursors, augmenting petroleum
resources in this role. Pretreatment processes and saccharification depolymerize the
biomass cellulose and hemicellulose to produce monomeric sugars. These carbohydratederived sugars are the starting compounds for conversion into a diverse set of “platformmolecules” [15,16] such as furans. The furan 5-(hydroxymethyl)furfural (HMF) produced
from dehydration of glucose is an important intermediate. Hydrodeoxygenation of HMF
condensation products provide “drop-in” liquid transportation fuels [25-30], while
hydrogenation products e.g. dimethylfuran and dimethyl-tetrahydrofuran, are good fuel
additives [31-34]. Furan dicarboxylic acid (FDCA) obtained from catalytic oxidation of
8
HMF is a viable replacement for terephthalic acid – the petrochemical precursor for PET
plastic [35].
Since HMF is formed via acid-catalyzed sugar-dehydration reactions, aqueous
phase hydrothermal conversion of untreated lignocellulosic feedstocks or saccharified
hydrolysates has naturally received the most attention [17]. However, these processes are
generally considered unviable due to high energy demand of the processes (up to 220°C),
low carbon efficiency (< 60%) due to char/humin formation, and HMF rehydration to
levulinic acid and formic acid [17, 36]. For example, the Biofine process produces
levulinic acid (from cellulose) and furfural (from hemicellulose) but not HMF [36]. In
addition to relatively low yields, the products are dilute and require energy-intensive
product recovery steps [37].
From several recent studies with pure sugars, two themes have consistently
emerged. The first is that due to the very stable nature of the glucose ring structure, high
reaction temperatures are required to offset side-reactions and increase HMF yield.
Glucose’s keto-isomer fructose gives much higher HMF yields and at relatively milder
reaction conditions [38-41]. However, if HMF is to be produced from biomass
feedstocks, it is imperative that its conversion be achieved starting from glucose
produced via saccharification. Isomerization of glucose to fructose is thus the necessary
first step for efficient HMF production. Unfortunately, this isomerization reaction is
plagued by an unfavorable aldose to ketose ratio at equilibrium (~1:1). At present, the
absence of cost-effective methods for achieving high fructose yields is a barrier to using
this more-suitable isomer for HMF production [38].
9
The second emergent theme is that non-aqueous reaction media stabilize HMF
and prevent its further conversion to levulinic and formic acids (with the accompanying
loss of carbon efficiency) and cross-condensation to humins. This has been substantiated
in several investigations showing high HMF yield from fructose dehydration in solutions
of water and polar organics (DMSO, sulfolane, N-methylpyrrolidone, γ-valerolactone,
tetrahydrofuran, and dimethyl acetamide) containing mineral or solid-acid catalysts [34,
40-47]. Dehydration of fructose in acidic ILs have also shown comparable HMF
productivity [48], with the additional advantage of milder reaction temperatures (≤50°C)
[49] relative to polar organic media (>100°C) [46]. Adoption of non-aqueous reaction
media, in particular ILs, for HMF production is to-date hindered by a lack of effective
strategies for getting biomass sugars into the reaction media, isolating the HMF product,
and recovering the reaction medium for reuse.
In this chapter, a cohesive pathway is presented to efficiently transfer glucose
from biomass hydrolysate into a non-aqueous reaction medium as fructose; produce HMF
in high yield; and isolate the HMF for downstream processing. The three main steps for
this process as envisioned in Figure 2-1 have low energy input and recyclable process
streams. We have implemented a simultaneous-isomerization-and-reactive extraction
(SIRE) process to convert glucose to fructose and overcome the unfavorable aldose-toketose transformation equilibrium [50,51]. Reactive-extraction of fructose into an
immiscible organic phase (octanol) is achieved through selective binding with the
lipophilic aryl boronic acid (ABA) napthalene-2-boronic acid (N2B). Fructose is
recovered in a nearly-pure, concentrated form by back-extraction (BE) into an immiscible
acidic IL reaction medium ([EMIM]HSO4). Fructose dehydration is conducted in the IL
10
at 50°C with in situ extraction into tetrahydrofuran (THF). Evaporation of the low-boiling
point THF (nbp 66°C) can be used to recover the HMF in an energy-efficient manner.
This scheme permits recycle of the organic extraction phase, the IL, and THF, with all
steps operating at <70ºC and at ambient pressure.
This process has also been implemented with biomass hydrolysate produced from
dilute-acid pretreatment of corn stover. Due to the specificity of the reactive-extraction
and differences in partitioning capacities between the three media, impurities from the
hydrolysate do not transfer into the IL reaction media. Hence, the process has the
potential for implementation with hydrolysates derived through diverse methods. SIREBE is also well-suited for concentrating (>5 fold) dilute hydrolysates through use of low
organic-to-hydrolysate (in SIRE) and IL-to-organic (in BE) volume ratios [50]. Thus,
energy-intense evaporation methods for concentrating sugar streams are avoided.
Besides, the feasibility of converting the mixed glucose and xylose stream by the
implementing proposed process has studied.
11
Step 1: Simultaneous isomerization of
glucose and reactive-extraction (SIRE)
of fructose to organic phase
Step 2: Back-extraction (BE)
of fructose from organic
phase to ionic liquid (IL)
Step 3: Dehydration of
fructose to HMF with
in situ extraction
organic phase
recycle
immobilized
GXI column
F
GF
Low bp organic
organic w/ ABA
F-ABA
fructose-rich
organic
F-ABA
pH 8.5
T = 60 °C
F
Acidic IL
T = 50 °C
HMF
F  HMF
T = 50 °C
fructose-rich IL
aqueous
glucose
solution
IL recycle
sugar-depleted
medium
fluid flow path
add/withdraw material at a specific time
Figure 2-1: Schematic representation of the three-step process for production of HMF from the
biomass sugar glucose. Glucose is isomerized to fructose using immobilized glucose/xylose
isomerase (GXI), and the fructose is selectively-extracted into an organic phase via complexation
with a lipophilic aryl boronic acid (ABA). The fructose-rich organic phase releases fructose when
contacted with an acidic ionic liquid (IL) reaction media. Fructose is dehydrated to HMF and
simultaneously extracted into an immiscible organic to increase HMF yield. The dotted arrows
represent addition/removal of the media at a specified time in the process; the solid arrows
indicate continuous recirculation of the process stream during a batch experiment.
2.2 Materials and Methods
2.2.1 Chemicals and Materials
Glucose, fructose, HMF,
xylose,
furfural,
sec-butylphenol, sec-butanol,
tetrahydrofuran (THF), phosphotungstic acid hydrate (12-TPA), Aliquat® 336, sodium
acetate and napthalene-2-boronic acid (N2B) were purchased from Sigma Aldrich Co.
(St. Louis, MO). All ionic liquids (ILs) ─ 1-ethyl-3-methylimidazolium chloride
([EMIM]Cl,
98%
([EMIM]CH3SO4,
([EMIM]HSO4,
purity),
97%
95%
1-butyl-3-methylimidazolium
purity),
1-ethyl-3-methylimidazolium
purity),
and
12
methyl
sulfate
hydrogen
sulfate
1-ethyl-3-methylimidazolium
trifluoromethanesulfonate ([EMIM]TFO, 98% purity) ─ were also purchased from Sigma
Aldrich Co. Wet Amberlyst 15 (Acros Organic Co., Geel, Belgium) and Amberlyst 70
(Dow Chemical Co., Midland, MI) were used as received. Immobilized xylose isomerase
(Gensweet® IGI, GXI) and Spezyme CP were a kind gift from Genencor International
(Rochester, NY); Novozyme 188 (Novozyme Corp., Denmark) was purchased from
Sigma-Aldrich. All other chemicals and solvents were purchased from Thermo Fisher
Scientific Inc. (Pittsburgh, PA).
2.2.2 Preparation of saccharified biomass hydrolysate
Dilute acid pre-treated corn stover biomass was received from NREL (Golden,
CO). The solids-containing slurry (predominantly cellulose and lignin) was washed twice
with DI water, and the solids were separated by filtration with Whatman® type 42 ashless
filter paper. For saccharification, 160 g of wet biomass was added to 500 ml of 50 mM
sodium acetate buffer in DI water and the pH was adjusted to 4.8 with HCl. Two
saccharification enzymes cocktails were added, 15 FPU/g glucan of Spezyme CP and 30
CBU/g glucan of Novozyme 188, and the slurry was mixed continuously at 200 rpm in a
shaker/incubator and 50 °C for 72 hr. The biomass hydrolysate was separated from the
remaining solids by centrifugation at 5000 rpm for 10 min followed by filtration with
Whatman® type 42 ashless filter paper. The hydrolysate was stored at 4°C until use for
SIRE-BE.
2.2.3 Simultaneous-isomerization-and-reactive-extraction (SIRE) and backextraction (BE)
The SIRE-BE method was used to produce a high purity, concentrated solution of
fructose from glucose at high yield. To conduct the SIRE step, a 165 mM (30g/l) glucose
13
solution was prepared, either by mixing pure glucose or diluting biomass hydrolysate in
50 mM sodium phosphate buffer, buffered to pH 8.5. The glucose solution was
isomerized overnight with 4.5g/l GXI to reach an equilibrium conversion of glucose to
fructose (~45%). The aqueous glucose/fructose solution was contacted with an
immiscible octanol phase containing 165 mM N2B and 412.5 mM Aliquat® 336 for 3 hrs
to preferentially extract fructose from the solution and drive the isomerization towards
more fructose formation. All steps in SIRE were conducted at 60°C and NaOH was
added as needed to keep the pH at 8.5. After SIRE was complete, organic and aqueous
phases were separated by centrifugation at 5000 rpm for 10 min. To recover and
concentrate the extracted fructose, the organic phase was contacted with a reduced
volume of IL (IL-to-organic volume ratio <1). The organic phase and IL were separated
by centrifugation at 5000 rpm for 10 min. The fructose-rich IL was used as the reaction
phase for fructose dehydration.
Results from the SIRE process are reported as:
Fructose in the organic phase
Fructose and glucose in the organic phase
Sugar in the organic phase
Initial sugar in the aqueous phase
Fructose extraction selectivity =
Sugar extraction efficiency =
2.2.4 Fructose conversion to HMF in IL reaction media
Dehydration of fructose to HMF was conducted in an IL reaction mixture
composed of 1000 mg [EMIM]HSO4, fructose (2-20 wt% fructose to IL), and acid
catalysts. The reaction media (~1 ml total volume) was added to a 25×90 mm glass vial.
In experiments where HCl was used as the acid catalyst and the amount of fructose was
varied, the molar ratio of HCl to fructose was held constant at 0.55. In experiments with
in situ product extraction, 12 ml of an organic solvent (THF or MIBK) was also added to
14
the reaction vial. To initiate dehydration, a magnetic stir bar was added to the vial, and
the vial was capped and placed in an oil bath on a stirring hotplate with the temperature
set at either 50 or 100°C. After a specified reaction period, the vial was rapidly cooled by
ice-water bath to quench the reaction, and the phases were separated by centrifugation at
5000 rpm for 10 min. The IL and organic phase compositions were analyzed by high
performance liquid chromatography (HPLC) and gas chromatography (GC) as described
in the following section.
3.2.5 Fructose and xylulose conversion to HMF and furfural in IL reaction media
Simultaneous dehydration of Ketoses to furans was conducted in an IL reaction
mixture composed of 1000 mg [EMIM]HSO4, fructose (10 wt% fructose to IL), xylulose
(3 wt% fructose to IL) and HCl as the acid catalysts. The experimental protocol has used
for this experiment is similar to the pervious section. Also fructose and xylulose were
prepared from glucose and xylose as described in section 2.2.3.
2.2.6 Analytical methods
Calibration standards for glucose, fructose, xylose, xylulose, furfural and HMF
were prepared in deionized water. Calibration standards and IL reaction media samples,
diluted with water as needed, were analyzed by HPLC using an Agilent 1100 HPLC
system equipped with a refractive index detector (RID). Two Shodex SH1011 columns
(300×8 mm, from Showa Denko K.K, Japan) in series were used for analysis of the
sugars and HMF. A mobile phase of 5 mM H2SO4 was run at 0.6 ml/min; the column and
RID detector temperatures used were 50°C and 35°C, respectively, for optimal peak
resolution and detection. For HMF quantification in THF, HPLC with an Agilent Zorbax
SB-C18 reverse-phase column was used with a UV detector. The mobile phase used was
15
a 1:4 v/v methanol:water (pH=2 with H2SO4) solution at a flow rate of 0.7 ml/min, and
the column temperature was 35°C. The concentration of HMF in MIBK was analyzed by
GC on a Shimadzu 2010 chromatograph with an RTX®-Biodiesel column (15m×0.32
mm I.D.) using a flame ionization detector (FID). The oven temperature was
programmed for a 1 min hold at 60°C followed by a 10 °C/min ramp to 300°C. Helium
was used as the carrier gas at a flow rate of 1.0 ml/min. The injector was used in split
mode; the injector and the detector temperature were 300°C.
2.3 Results and Discussion
As mentioned before, the proposed process consists of three steps that will be
described in this section with experimental results provided for each step. In addition to
pure sugar data the process performance on biomass hydrolysate is also presented.
2.3.1 Step 1 – Simultaneous-isomerization-and-reactive-extraction (SIRE)
In order for SIRE to be effective, it must be conducted at a pH suitable for both
isomerization and reactive-extraction. In our implementation, a glucose solution at pH 8.5
was first isomerized by the GXI enzyme which catalyzes the isomerization of glucose to
fructose. The partially-isomerized sugar solution was contacted with an immiscible
organic phase of octanol containing the lipophilic boronic acid N2B and a quaternary
ammonium salt Aliquat® 336 to promote the extraction of fructose from the aqueous to
the organic phase. These components have been previously demonstrated to be effective
in SIRE for xylose isomerization to xylulose [50].
To understand how the combination of N2B and Aliquat® 336 promotes fructose
extraction, it should be noted that ABAs form esters with sugar in a pH-dependent and
16
reversible manner. At high pH (> 8.5), lipophilic ABAs exist predominantly in their
conjugate-base form (ABA-) at the organic-aqueous interface. The conjugate-base is able
to bind with sugar to form a tetragonal ester (ABAS -) which accumulates at the interface.
Addition of a lipophilic quaternary ammonium salt (Q+Cl-) such as Aliquat® 336 to the
organic phase makes it possible to dissolve the negatively charged ABA in the organic
phase. Ion pair formation between the lipophilic ammonium cation (Q +) and the ABAS yields neutral (Q+)(ABAS-), which is soluble in the organic phase. The net result of the
esterification of fructose with the ABA and ion-pair formation is extraction of sugar from
the aqueous phase to the organic phase. Due to the selective complexation and extraction
of fructose from the aqueous phase, additional glucose isomerizes to restore the
fructose/glucose equilibrium. The isomerization of glucose and extraction of fructose to
the organic phase continues until the binding of fructose to the ABA reaches equilibrium.
The mole ratios of N2B to sugars and Aliquat® 336 to N2B are important factors that can
affect sugar extraction and sugar selectivity. As shown in Figure 2-2 increasing the mole
ratio of N2B to sugars will increases the fructose and glucose extraction, but will also
reduce fructose selectivity. For Aliquat® 336 to N2B mole ratios greater than 1.5, the
sugar extraction and fructose selectivity are comparable. Since any glucose that extracts
is lost in downstream processing, operation conditions were chosen that maximize sugar
extraction with very high fructose selectivity.
17
100
Sugar extraction efficiency or
Fructose extraction selectivity, %
90
80
A:N2B 0.5
A:N2B 1.5
A:N2B 2
A:N2B 2.5
70
60
50
40
30
20
10
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
N2B:Sugar mole ratio
Figure 2-2: Effect of boronic acid to sugar mole ratio on sugar extraction (closed symbols) and
ketose selectivity (open symbols) for SIRE. N2B in the organic phase was 165 mM; glucose in
the aqueous phase was 30 g/l (166.7 mM). The volumes of the two phases were adjusted to
achieve different N2B to sugar mole ratios. The concentration of Aliquat® 336 was in the organic
phase was varied to test several different molar ratios to N2B (A:N2B) as shown in the legend.
Results shown are for equilibrium isomerization and extraction data in individual experiments
[These data are prepared by help of Peng Zhang].
2.3.2 Step 2 – Back-extraction (BE) of fructose from the organic phase
2.3.2.1 BE media selection
The stability of the sugar-ABA ester is reduced at low pH. Thus, by contacting the
sugar-laden organic phase with an immiscible, acidic solvent, the ABA reverts to its
uncharged acid form and fructose is back-extracted into the low pH solvent. In our
18
experiments, the back-extraction (BE) of fructose is accomplished by contacting the
organic phase with an acidic ionic liquid (IL). In evaluating candidate ionic liquids for
fructose back-extraction and its dehydration in this process, three primary requirements
were considered. First, the IL be immiscible with the organic phase used for SIRE. The
IL must also be capable of extracting the sugar from the organic phase during the backextraction phase. Finally, the IL must be a suitable medium for the efficient dehydration
of fructose to HMF
In general, imidazolium-based ILs have been preferred for dehydration reactions,
with [EMIM]Cl and [EMIM]HSO4 reported as very suitable reaction media for fructose
dehydration at low temperatures [48,52]. Table 2-1 summarizes the evaluation of four
imidazolium based ILs for octanol immiscibility and fructose extraction efficiency. Only
[EMIM]HSO4 and [EMIM]TFO were immiscible with octanol, making them candidates
for fructose extraction and subsequent dehydration. In evaluating their ability to extract
sugar from the organic phase, [EMIM]HSO4 was able to back-extract all of the sugar,
while [EMIM]TFO was only able to strip 50%. As such, [EMIM]HSO4 was used as the
medium for all subsequent BE and fructose dehydration experiments. At room
temperature, where dehydration is insignificant, 92% of fructose recovery was observed
with overnight BE. Since dehydration readily occur at 60°C, the time used for BE of
fructose must be limited to prevent extraction of HMF into the organic phase. When 165
mM N2B is used for SIRE, a 5 min contact between organic phase and IL for BE results
in 84% BE efficacy at 60°C.
19
Table 2.1: IL screening for selective back-extraction of fructose from the organic solvent.
Suitable ILs must be immiscible with octanol and facilitate selective fructose extraction. A 30
mM glucose solution was pre-isomerized and used for SIRE with an octanol phase containing 30
mM N2B and 75 mM Aliquat® 336. After SIRE reacted equilibrium, the sugar in the organic
phase was back-extracted using a volume ratio of the organic phase to IL of 2:1. The fructose
back-extracted is the percentage of fructose in the organic phase that was recovered into the ionic
liquid.
*
Ionic liquid
Immiscible with
octanol?
Fructose backextracted (%)
[BMIM]CH3SO4
No
NA*
[EMIM]Cl
No
NA*
[EMIM]HSO4
Yes
100
[EMIM]TFO
Yes
50**
Not applicable due to solvent/IL miscibility; ** 50 mM HCl added
2.3.2.2 SIRE-BE validation
After selecting an appropriate organic phase composition for SIRE and
[EMIM]HSO4 for fructose BE, the complete SIRE-BE process was tested with a 30 g/l
glucose solution. In order to increase the extraction of fructose with N2B under the
conditions required for high fructose selectivity, the aqueous phase was subjected to four
sequential stages of SIRE to increase fructose isomerization and recovery as illustrated in
Figure 2-3. In each stage, a fresh volume of the organic phase was contacted with the
aqueous sugar isomerization phase in a volume ratio that produced sugar extraction
efficiency of 60% and fructose extraction selectivity of 90%. The net results of the SIREBE process for production of fructose from the 30g/l glucose solution are shown in
20
Figure 2-3. For glucose isomerization under these conditions without reactive extraction,
fructose yield is around 45%. However, the 4-stage SIRE results in a shift in the overall
isomerization of glucose to fructose from 45% to 89%. After 4 stages, 97% of the initial
sugar is transferred to the organic phase; 90% of this sugar is fructose. After completing
the SIRE steps, sugar was back extracted to the [EMIM]HSO4. The organic phase to IL
volume ratio adjusted such that the fructose concentration in the IL media would be ~10
wt% (g fructose/ g IL) in the [EMIM]HSO4. The SIRE-BE process is able to produce,
purify, and concentrate fructose from a glucose solution with minimal energy inputs (all
steps are conducted at 60°C). An additional benefit of using SIRE-BE to transfer sugar to
the IL for dehydration is that glucose (and fructose) in the aqueous phase after SIRE can
be recycled to the feed inlet for reprocessing unlike, other approaches in which the
isomerization and dehydration occur in a single vessel [53].
21
Figure 2-3: Schematic diagram of the 4 stage SIRE followed by BE with the summary of results
for a 30 g/l (~165 mM) aqueous glucose stream contacted with octanol containing 165 mM N2B
and 412.5 mM Aliquat® 336. These data show results for multi-stage extraction of fructose
during SIRE and the concentration of sugar during the BE step. The aqueous phase (1) was preisomerized to equilibrium (2) prior to four sequential stages of SIRE, each with 3 hr contact
between the organic and aqueous phases. The molar ratio of N2B to sugar in each stage of SIRE
was adjusted to achieve optimal sugar extraction and fructose selectivity by changing the organic
phase volume. N2B to sugar molar ratios used were as follows: Stage I (streams 2 & 10) – 1:1;
Stage II (streams 3 & 11) – 2:1; Stage III (streams 4 & 12) – 3:1; and Stage IV (streams 5 & 13)
3.5:1.
2.3.3 Step 3 – Dehydration of fructose to HMF.
Fructose dehydration to HMF was conducted under a variety of different
conditions using 10 wt% fructose. Dehydration was accomplished at low temperatures
(50 or 100°C) and some experiments included the addition of a dehydration catalyst
and/or an immiscible organic media for in situ HMF extraction from the IL reaction
22
medium. The results of these experiments are summarized in Table 2-2. Runs 1-3 are the
baseline results for HMF yield for [EMIM]HSO4 and fructose at 50°C. The HMF yield
increases from 25% to 30% with increased reaction time of 180 min to 540 min.
However, this extended reaction time is difficult to justify given the marginal
improvement in the yield. As an alternate method to increase HMF yield, an organic
solvent immiscible with the IL was used to achieve in situ HMF extraction. Y. PaganTorres et al. [39] have used sec-butyl phenol (SBP) for HMF extraction from aqueous
media; it has also proven viable for extraction of furfural from aqueous media [51].
However, SBP is not suitable here as it is miscible with [EMIM]HSO4. Two proven
HMF extraction solvents [54,55] that are immiscible with [EMIM]HSO4 - THF and
MIBK - were tested for their ability to increase HMF yield in IL. As shown in runs 4 and
5, the benefit was comparable to that achieved with the extended 9 hr dehydration time.
Another means to increase the HMF yield is the addition of solid and mineral acid
catalysts to the reaction system. The addition of 12-TPA (run 6) provided no
improvement over in situ extraction into THF (run 4), but Amberlyst 15 addition
increased HMF yield to 47% (runs 7 and 8). These solid acid catalysts, while being easily
recovered, did not catalyze the dehydration as efficiently as HCl (runs 10 and 11) at this
temperature (HMF yield of 68% with THF). For the aqueous phase HCl-catalyzed
dehydration of C5 sugars to furfural, addition of NaCl has been reported to further
increase furan yield [56,57]. As shown in runs 12 and 13, addition of 0.7 M NaCl resulted
in a 10-12% increase in HMF yield over HCl alone, with in situ extraction of HMF into
THF achieving an 80% HMF yield.
23
From a product recovery standpoint, THF is attractive as its normal boiling point
(66°C) allows its economical separation from HMF by evaporation. To determine if in
situ HMF extraction under a higher reaction temperature could significantly improve
HMF yield, a higher boiling point solvent was needed. MIBK was used for this purpose.
In comparing runs 11 and 15 with in situ extraction and HCl as the catalyst, the increased
reaction temperature resulted in a 10% increase in HMF yield and a significant reduction
in reaction time. Addition of NaCl produced a slight increase in HMF yield from 78 to
83% (see runs 15 & 16); however, this is only a 3% increase in yield as compared to in
situ THF extraction at 50°C using HCl with NaCl (run 13). Performance of solid acid
catalysts are improved at 100°C (runs 17-20) but still results in lower HMF yield than the
combination of HCl/NaCl.
Although [EMIM]TFO was not effective in extracting fructose from the octanol
phase during back-extraction, dehydration was performed in this IL to compare its
performance to [EMIM]HSO4 as a reaction medium. As shown in runs 15 and 21, HMF
yield in [EMIM]HSO4 was nearly double that in [EMIM]TFO under the same
experimental conditions. Thus, selection of the IL is crucial for both fructose extraction
and dehydration.
24
Table 2.2: Fructose dehydration to HMF in [EMIM]HSO4 media. All experiments were conducted with
1000 mg [EMIM]HSO4 and 100 mg fructose. For experiments with in situ HMF extraction, 12 ml of
organic solvent were used. Total HMF yield includes HMF in both the IL and solvent phases.
Run
Catalyst
In situ
extraction
solvent
Reaction
conditions
Total HMF
yield
(mol %)
1
-
-
50 °C, 180 min
25
2
-
-
50 °C, 360 min
28
3
-
-
50 °C, 540 min
30
4
-
THF
50 °C, 180 min
30
5
-
MIBK
50 °C, 180 min
30
6
12-TPA (50 mg)
THF
50 °C, 180 min
31
7
Amberlyst 15 (50 mg)
THF
50 °C, 180 min
41
8
Amberlyst 15 (50 mg)
THF
50 °C, 360 min
47
9
Amberlyst 15 (100 mg)
THF
50 °C, 180 min
46
10
0.42 mM HCl
-
50 °C, 180 min
64
11
0.42 mM HCl
THF
50 °C, 180 min
68
12
0.42 mM HCl; 0.7 M NaCl
-
50 °C, 180 min
74
13
0.42 mM HCl; 0.7 M NaCl
THF
50 °C, 180 min
80
14*
3.4 M HCl; 0.7 M NaCl
THF
50 °C, 180 min
80
15
0.42 mM HCl
MIBK
100 °C, 30 min
78
16
0.42 mM HCl; 0.7 M NaCl
MIBK
100 °C, 30 min
83
17
Amberlyst 15 (50 mg)
-
100 °C, 75 min
58
18
Amberlyst 15 (50 mg)
MIBK
100 °C, 75 min
72
19
12-TPA (50 mg)
MIBK
100 °C, 180 min
60
20
Amberlyst 70 (50 mg)
MIBK
100 °C, 75 min
65
21**
0.42 mM HCl
MIBK
100 °C, 30 min
40
*Dehydration conducted on the fructose from BE step. **[EMIM]TFO used instead of [EMIM]HSO4
25
2.3.4 Biomass Hydrolysate
In addition to pure sugar, the feasibility of using saccharified biomass hydrolysate
as a feed for the SIRE-BE process was also evaluated. Glucose-rich biomass hydrolysate
was produced by enzymatic saccharification of the solids remaining after dilute acid
pretreatment of corn stover. Results for SIRE-BE are shown in Figure 2-4. When
compared to the results for pure glucose (Table 2-2 and Figure 2-3), the fructose
extraction selectivity, sugar extraction efficiency, the total fructose yield, and HMF yield
are very comparable.
1.14 g/l G1
9.26 g/l F1
0.17 g/l G
1.47 g/l F
0.45 g/l G
0.43 g/l F
Figure 2-4: Summary of SIRE-BE results for biomass hydrolysate produced from corn
stover. Biomass hydrolysate was diluted to 165 mM glucose to allow comparison of the SIREBE-Dehydration results to those of pure glucose in Figure 2-3. Experimental conditions used for
SIRE were the same as describe in Figure 2-3. Dehydration conditions are those described in
Table 2-2 for Run 13.
2.3.5 IL Reusability
Due to the costs associated with an ionic liquid reaction phase, it is highly
appropriate to determine if the IL reaction media can be reused for multiple cycles of
26
back-extraction and dehydration. If so, conversion of glucose to fructose to HMF could
be implemented in a semi-continuous process with the IL phase as a closed loop as
shown in Figure 2-1. To assess IL reusability, fructose was back-extracted into the IL
reaction media, and the mixture was held at 50°C for 180 min for dehydration with THF
used for in situ HMF extraction. After the reaction, the THF/HMF phase was removed,
and the IL/HCl media was used for two additional rounds of BE and dehydration. Results
of repeated dehydration in the recycled IL, reported as HMF yield, are shown in Figure 25. No reduction in HMF yield was observed after 3 cycles of dehydration, with recycling
of the [EMIM]HSO4/HCl reaction media.
100
HMF yield , mol %
90
80
70
60
50
40
30
20
10
0
1
2
Run number
3
Figure 2-5: HMF yield with repeated reuse of the IL dehydration media. Dehydration was
conducted in 1000 mg [EMIM]HSO4 and 10 wt% fructose loading with 0.42 mM HCl as a
catalyst at 50°C for 180 min and 12 ml of THF for in situ extraction (Table 2, Run 11); fructose
conversion was 100%. Following phase separation, the IL phase was contacted with an additional
10 ml of THF to extract residual HMF and minimize carryover to the next reaction cycle; no
HMF was detected in the IL at the end of Run 3. HMF yield is based on HMF extracted into the
combined 22 ml of THF.
27
2.3.6 Fructose Loading
Since both the IL and HCl serve as catalysts for the dehydration reaction, we
investigated the effect of the fructose loading in the IL on the overall HMF yield. These
experiments were conducted with in situ extraction of HMF into THF at 50°C for 180
min. The yields of HMF achieved are shown in Figure 2-6. These results indicate that for
fructose loadings up to 10 wt% the HMF yield is unchanged. When, the loading was
increased from 10 to 20 wt % a reduction in HMF yield from 80% to 74% was observed.
Figure 2-6: HMF yield as a function of the initial fructose loading. Dehydration was conducted in
1000 mg [EMIM]HSO4 with 0.42 mM HCl and 0.7 mM NaCl as a catalyst at 50°C for 180 min.
The volume of THF used for in situ extraction of HMF was scaled at 1.2 ml THF per 1 wt%
fructose based on the initial fructose loading in the IL. Fructose conversion was 100% in each
experiment. The HMF yield is based on the combined content in both the IL and THF phases.
28
2.3.7 Mixed fructose and xylulose stream
Based on the biomass pretreatment method the biomass hydrolysate contains the
mixture of xylose and glucose. Thus it is important to investigate the feasibility of
implementing our state of the art SIRE-BE-Dehydration process for simultaneous
conversion of biomass sugars (glucose and xylose) to HMF and furfural with facile
reaction conditions. The process conceptual schematic is shown in Figure 2-7. Described
principle for single sugar (glucose) conversion to furan (HMF) is also valid for this case.
STEP 1
Simultaneous isomerization &
reactive extraction (SIRE)
of biomass sugars (50-60 oC)
Biomass hydrolysate
with added XI pellets
STEP 2
Back extraction (BE) of
ketose sugars into IL
reaction media
organic
w/ ABA
STEP 3
Dehydration with
in situ furan
extraction (50 oC)
acidic ionic liquid (IL)
low bp
organic (THF)
Glucose
Fructose
Fructose
HMF HMF
Xylose
Xylulose
Xylulose
Furfural Furfural
Figure 2-7: Process schematic for furans production
from biomass HMF
hydrolysate
sugars
F 92%
79%
HMF
79%
Cumulative molar yields:
Xu 94%
(glucose and xylose) by the SIRE-BE-Dehydration-in-IL
approach.
Fur 82%
Fur 82%
The three steps of the SIRE-BE-dehydration process have successfully implemented
at laboratory scale employing the system schematically depicted in Figure 2-1. Starting
feed was glucose- and xylose-rich streams. Each stream was subjected to SIRE to
generate organic phases containing ketose sugar that were subsequently back-extracted
into [EMIM]HSO4 (containing HCl and NaCl) by contacting the phases for 10 min to
obtain at 10 wt% fructose or a 3 wt% xylulose solution (Table 2-3, column 1) in IL.
These ketose sugars were dehydrated with in situ extraction into THF which resulted in
high isolated yields of HMF and furfural.
29
Table 2-3: Results for dehydration of mixed ketoses back-extracted into [EMIM]HSO4. The
ketoses were produced from SIRE performed on dilute acid pretreated corn stover biomass
hydrolysate received from NREL. The dehydration was conducted with in situ extraction into
THF at 50°C.
Ketose loading in IL,
wt% (g ketose/g IL)
10 wt% fructose
3 wt% xylulose
Catalyst
0.42 mM HCl; 0.7 M
NaCl
2.45 mM HCl; 0.7 M
NaCl
Reaction conditions
Furan yield, mol%
50 °C, 180 min
86 (HMF)
50 °C, 180 min
88 (Furfural)
2.4 Conclusion
Our process innovations overcome several key technical barriers in the pathway
to furan production. The unfavorable aldose-to-ketose transformation equilibrium is
overcome through reactive-extraction of the ketose sugars into an immiscible organic
phase through selective binding with ABA. The hurdle for efficient transfer of
hydrolysate sugars into a non-aqueous reaction medium is overcome through backextraction of the isomerized and concentrated sugars into [EMIM]HSO4. Finally, the
economically-viable isolation of furan from the reaction medium is accomplished through
in-situ extraction of furans from IL into THF.
30
Chapter 3
High Yield Biomass Hydrolysate Conversion to 5(ethoxymethyl)furfural
3.1 Introduction
During the past century crude-oil has been used as a resource for production of
bulk-chemicals and transportation fuels. Due to declining fossil resources, steady growth
of demand for fuels and chemicals, environmental impact and political issues associated
with fossil resources, it is necessary to replace this important energy source with
alternative sustainable resources. Lignocellulosic biomass proves to be a viable
alternative for production of transportation fuels and chemicals based on its abundant
availability (production rate (10×1011 tons per year)) and high carbon content. In order to
synthesize required products from biomass, first the carbohydrates of biomass should be
converted to one of the several “building block” molecules [15]. 5-(hydroxymethyl)
furfural (HMF) is a promising “platform molecule” and its important role has been
highlighted in the recent reviews [16,17].
31
HMF is a versatile compound which is formed by acid-catalyzed dehydration of
C6 sugars. Apart from its important role in the synthesis of renewable plastics, it has been
reported as a fuel additive or transportation fuel precursor. For instance, HMF has been
hydrogenated to 2,5-dimethylfuran which can be used as octane booster [33]. In another
pathway, HMF was subjected to aldol condensation reaction; then, the resulting C9-C15
molecules were hydrogenated to produce diesel-range fuels [27,58]. Recently 5(ethoxymethyl) furfural (EMF), product of HMF etherification with ethanol, has been
reported as a diesel fuel additive [59]. EMF as fuel additive has promising properties: it
has high energy density [60]; its production does not require hydrogenation, and its
presence in the blend in the diesel engine has decreased fine particulate and SO x emission
[61]. In addition, EMF has low toxicity concerns since it has been used as a flavoring
agent in beverage industries [31]. Ethyl levulinate (EL) is, often, produced during EMF
synthesis as a byproduct. EL also has been reported as a diesel fuel additive [62].
Different acid catalysts have been reported that catalyzed HMF conversion to
EMF in high yield [63-65]. Considering that fructose dehydration to HMF is also
conducted in presence of acid catalysts, different research groups have studied one-pot
fructose conversion to EMF. For instance, Brown et. al. [66] have used fructose as the
feed with ion-exchange resin as acid catalyst to produce EMF, but selectivity was low.
Bing and co-workers have used [MIMBS]3PW12O40 [67], Wang and co-workers [68]
have conducted fructose conversion to EMF in presence of phosophotungstic acid
catalyst, moreover cellulose sulfuric acid catalyst has been reported as a bio-supported
solid acid catalyst [69] to produce EMF from fructose. Balakrishnan et. al. [31] have
studied the performance of different solid and mineral acid catalysts along with the role
32
of other parameters on the conversion of fructose or HMF to EMF, and proposed a
possible reaction pathway. Kraus and Guney [70] also have conducted one-pot fructose
conversion to EMF in acid functionalized ionic liquid. Although these groups have
reported promising results, to make the EMF production process economically feasible,
glucose should be used as the feed, since glucose is the most abundant C6 sugar produced
via depolymerization of biomass carbohydrates with a much lower price compared to
fructose. In this regard, some efforts have been made to produce EMF directly from
glucose. Abu-Omar’s group [71] has used AlCl3 as an acid catalyst and conducted onepot glucose conversion to EMF at high temperature (> 130°C). Liu et al [72] also used
AlCl3; however, they conducted the reaction at different conditions: a lower temperature
(100°C) and longer reaction duration. Unfortunately the reported EMF yields are low,
less than 40 mol%. Riisager and co-workers [73] have used sulfonic acid functionalized
ionic liquid; however, the glucose was converted to ethyl D-glucopyranoside in the IL
medium. A completely different approach for EMF production was suggested by Mascal
et. al. [74-76]. In the first step, they have converted C6 sugars or cellulose directly to 5(chloromethyl) furfural (CMF). Then, in presence of ethanol, the Cl atom in the CMF
was replaced by an ethoxy group to produce EMF and HCl. Despite high reported EMF
yields, this method has not scaled up due to some concerns, such as the recyclability of
produced acid (HCl) and the effects of non- reacted halides on the automobile fuel system
[31].
Here in we report a novel approach to synthesize EMF in high yield from biomass
hydrolysate glucose. This approach takes advantage of the previously described
Simultaneous-Isomerization-and-Reactive-Extraction
33
(SIRE)
followed
by
Back-
Extraction (BE) approach to convert glucose (in biomass hydrolysate) to a concentrated
fructose-solution in IL; Dehydration of fructose to HMF, with in-situ etherification of
HMF to EMF, is achieved by conducting the sequential reactions in the [EMIM]HSO4
medium in presence of ethanol and an acid catalyst. Different reaction parameters have
been investigated to establish optimum conditions.
3.2 Materials and Methods
3.2.1 Chemicals and Materials
Fructose, glucose, HMF, ethanol, EMF, EL, and 1-ethyl-3-methylimidazolium
hydrogen sulfate ([EMIM]HSO4, 95% purity), were purchased from Sigma Aldrich Co.
(St. Louis, MO). All other chemicals and solvents were used as received from Thermo
Fisher Scientific Inc. (Pittsburgh, PA).
3.2.2 Fructose conversion to EMF in IL media
Fructose conversion to EMF and EL was conducted in a reaction mixture
composed of 1g ([EMIM]HSO4, 0.5-2 ml ethanol, fructose (10 wt% fructose to IL) and
HCl as the acid catalyst with molar ratio of HCl to fructose held constant at 0.55. The
reaction media was added to a 38×20 mm glass vial. To initiate dehydration, a magnetic
stir bar was added to the vial, and the vial was capped and placed in an oil bath on a
stirring hotplate with the temperature set at the desired value. After a specified reaction
period, the vial was rapidly cooled by ice-water bath to quench the reaction. The IL phase
compositions were analyzed by high performance liquid chromatography (HPLC). EL
was extracted by toluene and analyzed by gas chromatography (GC).
34
3.2.3 Glucose conversion to EMF in IL media
Glucose (pure or from biomass hydrolysate) was converted to fructose by
implementing the SRE-BE process. Described procedure in chapter 2 was followed in
this regard, and then fructose was converted to EMF as mentioned in the previous
section.
3.2.4 Analytical methods
Calibration standards for fructose, HMF, and EMF were prepared in deionized
water. IL reaction media samples, diluted with water as needed, and calibration standards
were analyzed by HPLC using an Agilent 1100 HPLC system equipped with a refractive
index detector (RID). A single Shodex SH1011 column (300×8 mm, from Showa Denko
K.K, Japan) was used for analysis of the sugar, HMF and levulinic acid. A mobile phase
of 5 mM H2SO4 was run at 0.6 ml/min; the column and RID detector were maintained at
65°C and 35°C, respectively, for optimal peak resolution and detection. The
concentration of EL in toluene was determined by GC on a Shimadzu 2010
chromatograph with an RTX®-Biodiesel column (15m×0.32 mm I.D.) using a flame
ionization detector (FID). The oven temperature was programmed for a 1 min hold at
60°C followed by a 10 °C/min ramp to 300°C. Helium was used as the carrier gas at a
flow rate of 1.0 ml/min. The injector was used in split mode; the injector and the detector
temperature was 300°C. All the experiments were repeated at least two times and the
reported results are the average of these multiple runs; the standard deviation was less
than 2% among different runs.
35
3.3 Results and discussions
The block box diagram of the developed process for converting biomass
hydrolysate sugar (Glucose) to EMF and EL is presented in Figure 3-1. Briefly, in the
first step of the process, acid pretreated biomass is saccharified to release sugar. In the
second step by implementing SIRE-BE method glucose from biomass hydrolysate is
isomerized to fructose and selectively extracted to an immiscible organic phase. Then,
fructose is back extracted into [EMIM]HSO4. Finally, in presence of ethanol, fructose
dehydration to HMF and simultaneous HMF etherification to EMF is conducted in the IL.
Isolation of the products from reaction media can perform via fractional distillation due
to the large differences in the boiling points of ethanol (78°C), HMF (116°C), EMF
(254°C), EL (203°C) and [EMIM]HSO4 (bp >350°C). In order to determine the optimum
operating conditions for the proposed process, we first investigate different parameters
effects on the fructose dehydration to HMF and in-situ HMF etherification to EMF and
then by merging the obtained results with the provided data in chapter 2, the optimum
parameters will be established for the process.
Biomass
Saccharification
Fructose
Dehydration
& HMF
Etherification
SIRE-BE
SIRE-BE
EMF
Products
Separation
Figure 3-1: The block box diagram of the biomass conversion to value added products
36
EL
HMF
3.3.1 Reaction Kinetics data
Figure 3-2 presents the kinetic data at temperature levels of 80°C, 90°C and
100°C for fructose dehydration to HMF and in-situ conversion of HMF to EMF via
etherification reaction with ethanol. Data demonstrate that at these temperatures almost
all of the fructose is consumed within the first thirty minutes beyond this time, the
dominant reaction is the etherification of HMF to the EMF, as seen by the continuous
drop in HMF concentration and increase in EMF concentration. In addition the results
show that at higher temperature the reactions kinetic are faster and EMF has produced
sooner. The yield kinetics of EMF and EL display the behavior typical of final products
in a reactions-in-series case, i.e., they increase steadily with time.
100
80 °C
90
Yield/Conversion
80
70
60
50
40
30
20
Fructose Conversion
10
0
HMF Yield
0
30
60
90
120
Time (min)
37
150
180
EMF Yield
EL Yield
100
90 °C
90
Yield/Conversion
80
70
60
50
40
30
20
Fructose Conversion
10
0
HMF Yield
0
30
60
90
120
Time (min)
150
180
EMF Yield
EL Yield
100
90
100 °C
Yield/Conversion
80
70
60
50
40
30
Fructose Conversion
20
HMF Yield
10
0
0
30
60
90
120
Time (min)
150
180
EMF Yield
EL Yield
Figure 3-2: Kinetic data of Fructose conversion, EMF, HMF, EL yield at 80°C, 90°C and
100°C, 1g [EMIM]HSO4, 2ml ethanol, 100mg fructose, 0.36 mmol HCl as acid catalyst
3.3.2 Temperature effect on the products yield
The results presented in the Figure 3-2 show the temperature effect on the
products distribution. Comparing the products yield at these temperature levels show that
38
at the lowest temperature (80°C) HMF yield is higher than EMF even after continuing the
reaction for 180 min. At 90°C EMF yield is higher than HMF; however there are
significant amount of HMF available which has not converted. The results also indicate
that by increasing temperature to 100°C the majority of HMF will be converted to EMF
and EL. In another words, although fructose has disappeared very fast even at 80°C,
higher temperature is required to completely convert HMF to EMF. Despite different
product distributions, the total product yield remains almost constant at all of the
temperatures.
3.3.3 Ethanol loading effect on the products yield
In addition, we also studied the effect of different amounts of ethanol (as a nonlimiting reactant) on the yields of products and their distribution. The presented results in
Figure 3-3 demonstrate that at low ethanol loading (mole ratio of ethanol to fructose: 15)
the total products yield is lower compared to highest ethanol loading (mole ratio of
ethanol to fructose: 60).
39
100
Yield/Conversion
80
HMF Yield
60
EL Yield
40
EMF Yıeld
Total Product Yield
20
0
Fructose Conversion
15
30
60
Ethanol to fructose mole ratio
Figure 3-3: Ethanol loading effect on fructose conversion and products yield. 1g [EMIM]HSO4,
100mg fructose, 100°C, 2hr, 0.36 mmol HCl as acid catalyst
3.3.4 Fructose loading effect on the products yield
The influence of the fructose initial concentration on the EMF, EL and HMF yield
is investigated. The experiment with 10% fructose to IL mass ratio (referred to as the
original experiment) is repeated at 7%, 15% and 20% initial fructose loadings. The
results demonstrated in Figure 3-4 indicate that there are not any appreciable changes in
the total products yield.
40
100
Yield/Conversion
80
HMF Yield
60
EL yield
40
EMF Yield
Total Product Yield
20
0
Fructose conversion
7
10
15
Fructose (wt%)
20
Figure 3-4: Fructose loading effect on fructose conversion and products yield. 1g [EMIM]HSO4,
100°C, 2hr, Ethanol mole ratio to fructose:60, HCl mole ratio to fructose:0.55
3.3.5 IL reusability
In order to investigate the reusability of the [EMIM]HSO4, the fructose
dehydration and in-situ HMF etherification reaction has repeated for three consecutive
cycle. The results presented in Figure 3-5 show that the total products yield remains
constant and proves the feasibility of IL recycling.
41
90
Yield (mol%)
75
60
45
Total Product Yield
30
15
0
1
2
Cycle Number
3
Figure 3-5: [EMIM]HSO4 reusability results. reaction condition in each run: 2ml ethanol 1g
[EMIM]HSO4, 100mg fructose, 100°C, 120min, 0.036 mmol HCl as acid catalyst, Total products
yield is summation of EMF, HMF and LE yield
3.3.6 Glucose conversion to EMF
The main object of this chapter is providing a pathway that converts biomass
hydrolysate sugar to EMF. Therefore, first glucose is prepared from biomass hydrolysate
solution, then SIRE-BE process implemented to convert glucose to fructose in high yield,
finally EMF and EL are produced from fructose dehydration and in-situ HMF
etherification in [EMIM]HSO4 and ethanol mixture. The results of glucose conversion to
EMF by applying this technique for two different feed cases: a) pure glucose and b)
glucose from biomass hydrolysate solution are presented in Figure 3-6. The glucose
isomerizations to fructose yield and fructose back extraction efficiency are similar to the
reported data in chapter 2 and have not presented here. EMF, EL, and HMF yield are
similar for two cases which prove the advantage of the SIRE-BE process that can use
42
glucose from saccharified biomass hydrolysate solution without any demand for
purification process.
Although glucose usage as the feed is the main advantage of the proposed
process, comparing products yield in Figure 3-2 and 3-6 shows that higher yield has
reported while fructose has used. This lost can be attributed to presence of small amount
of octanol which remains on top of the [EMIM]HSO4 phase after BE step and contributes
in the etherification reaction with HMF, consequently decreases the EMF yield. This
phenomenon is proven by adding different amount of octanol to the reaction media
containing [EMIM]HSO4, ethanol, HCl, and fructose. The EMF yield decreases from
63% to 53% and 43% as the octanol increases in the range of zero to 250µl and 500µl
respectively. It is worth noting that the produced ether from HMF and octanol does not
express as a carbon lost to undesired side products. Since, Gruter and co-worker from
Furanix Technologies [77] have studied HMF etherification in presence of different
alcohols (included ethanol, isobutanol and octanol) and reported that the mixture of
produced ethers can be used as fuel additives.
43
50
Yield (mol%)
40
30
Pure Glucose
20
Biomass Hydrolysate
10
0
HMF
EMF
Products
EL
Figure 3-6: Glucose conversion to EMF, LE and HMF results
3.4 Conclusion
A new approach is developed for the converting glucose from biomass
hydrolysate in high yields to ethoxymethyl furfural (EMF). The new approach couples a
novel SIRE-BE technology that provides a path for transferring glucose in the form of
concentrated fructose into an IL medium, with the unique traits offered by [EMIM]HSO4
media in affecting fructose conversion to EMF under facile conditions. In addition to
EMF, a smaller quantity of EL is also produced. The total product yield, defined as
(EMF+EL+HMF) yields, in excess of 87% is possible while using fructose as the feed.
Of this 66% is EMF, 12% is EL and 9% is HMF. Various parameters effects on the
products yield have investigated and optimum conditions determined.
44
Chapter 4
Facile Production and in-situ Esterification of HMF
from Biomass Sugars in Ionic Liquid Media
4.1 Introduction
Fossil fuels have been used as energy and chemical source for several decades.
However, this source is finite, has security concerns and imposes great impact on climate
changes by CO2 emission. To overcome these issues a new sustainable energy source
should be used. Biomass is the answer for these demands since it is the most abundant
(1.0 × 1011 ton per year global production) renewable resources [78]. To build a chain
from biomass to fuel and chemical precursor, the crucial step is converting sugars
prepared from biomass to components called “building blocks”. Among these 5(hydroxymethyl)furfural (HMF) is an important one since it provides a bridge between
carbohydrate chemistry and mineral oil-based industrial organic chemistry [79].
Typically, the starting point for producing biomass-based HMF is the glucose-rich
hydrolysates obtained through pretreatment and enzyme hydrolysis of the biomass. It
45
would be ideal if the glucose in the hydrolysate could be dehydrated directly in the
aqueous phase itself to HMF. While Bronstead acid catalyzed dehydration of glucose has
been investigated, the product yield is low due to HMF rehydration to levulinic and
formic acid and in particular, humin formation and loss of sugar results from cross
condensation of HMF with sugar and/or resinification of HMF in aqueous environment.
Changing reaction media from aqueous to others that stabilize HMF such as DMSO or insitu extraction of HMF into an immiscible organic phase, i.e., biphasic system has been
reported [40].
HMF is a very important intermediate building block, however almost it is not
used as a final product. In addition, it is rather unstable under the conditions that it forms.
Thus it is interesting to find out the applications of HMF derivatives, especially those
derivatives that can be produce in-situ. Simultaneous HMF production and conversion to
more stable form in the reaction medium can avoid the need for in-situ extraction of
HMF. Furthermore, if the resulting compound is less hydrophilic compared to HMF, it
can be more completely extracted into a low-boiling point organic solvent to reduce
isolation costs and extraction can be carried out after the reaction under room temperature
condition which lower the operating cost. Beside, this strategy will increase the total
yield of sugar conversion to furans compared to the case that only HMF is produced in
single phase reactor, since HMF contribution in the undesired side reactions will be
prevented.
A distinguished example for this approach is HMF production by sugar
dehydration in IL media and in-situ esterification to 5-acetoxymethylfurfural (AMF) with
acetic acid, since AMF is more stable compared to HMF. It can be used as the 2, 546
furandicarboxylic acid (FDCA) precursor and easily extracted from reaction media.
Partenheimer and Grushin [80] have recognized AMF during HMF oxidation to 2, 5diformylfuran (DFF) and FDCA as a byproduct and Furanix Technologies [81] results
have proved that at a provided temperature and pressure AMF oxidation to FDCA occurs
in high yield. It is worth noting that FDCA has broad range of applications, thus its
important role in the bio-refinery has highlighted by in the DOE report [15] and recent
update by Bozell et. al. [16]. For instance, based on the Gandini and co-workers [82]
FDCA can take place of the terephtalic acid in the manufacture of polyethylenterphatalate
(PET). The other polymeric applications of FDCA are the preparation of furanic modified
amine based curatives for polyesters, hybrid epoxy and urea-urethanes [83], and as
polyester polyols in production of corrosion and flame resistance coating [84].
The goal of this chapter is introducing a new pathway that conducts simultaneous
sugar dehydration and HMF esterification in IL media in presences of Bronsted acid
catalysts. Due to novelty in the HMF ester application and lack of the knowledge related
to its production, a deep investigation on parameters affecting AMF production in IL
media is required. Thus, we will investigate different IL media, reaction conditions
(temperature, time etc.), reactant loading, and acid catalyst concentrations to optimize
AMF production yield. In addition the feasibility of modification for this new pathway
will be explored.
47
4.2 Materials and Methods
4.2.1 Chemicals and Materials
Glucose,
Fructose,
HMF,
AMF,
1-ethyl-3-methylimidazolium
chloride
([EMIM]Cl), 1-ethyl-3-methylimidazolium hydrogen sulfate ([EMIM]HSO4), 1-ethyl-3methylimidazolium trifluoromethanesulfonate ([EMIM]TFO), acetic acid, and acetic
anhydride were purchased from Sigma Aldrich Co. (St. Louis, MO, USA). Methyl
isobutyl ketone (MIBK), tetrahydrofuran (THF), and other chemicals were prepared from
Thermo Fisher Scientific Inc. (Pittsburgh, PA, USA) and were used as received
4.2.2 Experimental procedure
The sugar dehydration to HMF and its in-situ esterification to AMF was
conducted in IL medium in a single-pot arrangement. In a standard experiment, 1000 mg
of [EMIM]Cl, 100 mg fructose, 0.16 mmole acid catalyst (H2SO4), and 35 mmole acetic
acid were loaded into 25×90 mm glass vials. The vials were capped and heated in an oil
bath over a hot plate, while constantly stirring the contents of each vial using a magnetic
stirrer. After rapidly raising the temperature of the reaction mixture to 80oC (~ 3min), the
reaction was allowed to proceed for a pre-specified time period, at which time the vial
was cooled to room temperature and the immiscible organic solvent, MIBK, was added to
the reaction mixture in a 8:1 (v/v) (in case of [EMIM]Cl) or 3:1 (v/v) (in case of
[EMIM]HSO4) proportion. Following the addition of an organic solvent, the vials were
sealed and the two phases were vigorously stirred together for 10 minutes to selectively
extract AMF and HMF from the IL medium. Next, the vials were centrifuged at 5000
rpm for 10 minutes to separate the organic and IL phases.
48
4.2.3 Analytical Procedures
The organic phase was analyzed using GC while the IL phase was analyzed by
HPLC. The products in the organic phase, in addition to external standards of HMF and
AMF, were analyzed using a Shimadzu 2010 Gas Chromatograph with an RTX®Biodiesel column (15m×0.32mm I.D.) and a Flame Ionization Detector (FID). The
injector was used in a split mode; the injector temperature was set at 250°C. The detector
temperature was set at 300°C. The oven temperature was programmed as follows: hold
for 1 min at 60°C and ramp up to 300°C at 10 °C/min. Helium was used as the carrier gas
at flow rate of 1.0 ml/min.
The high performance liquid chromatography (HPLC) was used to analyze the IL
phase. The analysis was carried out using an Agilent 1100 HPLC with a Shodex SH1011
column (300×8 mm from Showa Denko K. K, Japan) using a refractive index detector
(RID). During the HPLC analysis, column temperature was maintained at 65°C, and the
mobile phase employed was 5 mM H2SO4 at a flow rate of 0.55 ml/min.
Based on the measured quantities of the HMF and AMF, the yields for these
compounds are defined as follows:
HMF yield (mol%) = (moles of HMF in the organic and IL phases)×100/ initial
moles of fructose in the IL
AMF yield (mol%) = (moles of AMF in the organic and IL phases)×100/ initial moles of
fructose in the IL
Total furans yield (mol%) = (moles of (HMF + AMF) in the organic and IL phases)×100/
initial moles of fructose in the IL
49
4.3 Results and Discussion
4.3.1 Effect of acetic acid loading on the final furan yield
As noted in the Introduction, addition of acetic acid to the IL medium is expected
to facilitate the in-situ esterification of HMF (produced via fructose dehydration) to
AMF, thereby reducing the participation of HMF in undesirable side reactions that lead to
loss of furan. Figure 4-1 shows the effect of acetic acid loading on the HMF, AMF and
total furans yields. As shown in the figure, raising the acetic acid to fructose mole ratio
not only affects the conversion of HMF to AMF as expected but also leads to an
improvement in the total furans yield, confirming that in-situ esterification strategy
mitigates the loss of HMF to side-reactions. As seen in Figure 4-1, the total furans yield
goes up significantly as the acetic acid to fructose mole ratio is raised at a fixed initial
fructose loading, The total furans yield reaches 80%, at an acetic acid to fructose mole
ratio of 64, in contrast to the 60% yield of HMF seen in the base case with no acetic acid.
In addition, most of these furans (about 80%) will be in the form of AMF, which is a
more desirable starting chemical for producing furan dicraboxylic acid (FDCA).
Increasing, acetic acid loading beyond a mole ratio of 64 does not lead to any additional
improvement in AMF or total furans yield. Thus, the mole ratio of acetic acid to fructose
of 64 is considered the optimum and was used in all the other experiments. Using
stoichiometric excess of acetic acid in the reaction medium also has other advantages:
acetic acid dissolves in [EMIM]Cl in all proportions forming a homogenous solution that
has a much lower viscosity compared to the neat IL; consequently, not only the energy
requirements for mixing are reduced but also more rapid reaction kinetics are ensured.
50
Also, after isolating the furans into an IL-immiscible organic solvent following the
completion of the reaction, most of the acetic acid will be left behind in the IL and can be
reused in subsequent runs, along with the recycled IL medium thus making the process
cost effective.
Figure 4-1: Effects of acetic acid loading on final furan yield; Reaction conditions: 1000 mg
[EMIM]Cl 100 mg fructose, mole ratio of H2SO4 to sugar:0.28, Reaction duration:6hrs,
temperature:80°C
4.3.2 H2SO4 loading influence on final furan yield
In general esterification reaction is conducted in presence of an acid catalyst; in
addition fructose dehydration to HMF is catalyzed by an acid catalyst. Thus H2SO4 is
chosen as a low price acid catalyst for this study. The H2SO4 loading effects on AMF and
HMF yields are demonstrated in Figure 4-2. The results indicate that increasing H2SO4
mole ratio to fructose mole from 0.07 to 0.28 improves the AMF yield significantly.
However, further addition of H2SO4 slightly decreases the total furan yield due to HMF
51
contribution in side reactions. Moreover, when dehydration was carried out, with no in
situ esterification (data not shown), we observed about 60% yield of HMF at H 2SO4 to
fructose mole ratio of 0.22. Thus, in-situ esterification does not significantly increase
H2SO4 requirement.
Figure 4-2: Influence of H2SO4 loading on final furan yield, Reaction conditions: 1000 mg
[EMIM]Cl, 100 mg fructose, mole ratio of acetic acid to sugar:64, Reaction time:6hrs,
temperature:80°C
4.3.3 Temperature effects on furan yield
The one-pot fructose dehydration to HMF and its in-situ esterification to AMF
have been investigated at three different temperatures (80, 100, & 117°C). The results
shown in Figure 4-3 present a typical behavior of two reactions in series, in which
fructose concentration rapidly decreases, HMF concentration first increases then reaches
52
a maximum finally decreases, and AMF concentration steadily increases. This reaction
pathway is shown in Figure 4-4.
Figure 4-3 a demonstrates that at the 80°C almost all of the fructose is consumed
within the first thirty minutes at which time the concentration of HMF reaches its
maximum. Beyond the first thirty minutes, the dominant reaction is the esterification of
HMF to the AMF, as seen by the continuous drop in HMF concentration and increase in
AMF concentration. The fact that the total furans (HMF + AMF) is not decreasing over
this period indicates that there is no loss of furan to rehydration to levulinic acid or
humins. At the end of the reaction, we are seeing a total furans yield of 80% of which
almost 60% is AMF yield and the remaining is HMF yield. Comparing the total furans
yield in this system with the similar case that only fructose dehydrates to HMF was
conducted (see Table 4-1 run 1), indicates 20% increase in the total furan yield. That
means in-situ esterification prevents HMF lost in undesired side reactions.
In addition, the kinetic studies are repeated at two higher temperatures (Figure 4-3
b and c). While the kinetics, as expected, is faster, the total furans yield is slightly lower,
indicating that higher temperatures are not preferred. The highest AMF yield at 100°C
and 117°C are 56.5% and 54.6% respectively. Runs 2 and 3 in Table 4-1 compare the
total furan yield for simultaneous dehydration and esterification with the identical cases
that only dehydration were conducted at these temperature (100°C and 117°C). Results
indicates that in-situ esterification raise total furan yield up 20% for these experiments.
53
(a)
(b)
54
(c)
Figure 4-3: Fructose, HMF and AMF content (mole % relative to initial moles of sugar) versus
time at (a)80°C (b)100°C (c)117°C; Reactant :1000 mg [EMIM]Cl, 100 mg fructose, mole ratio
of acetic acid to sugar:64, mole ratio of H2SO4 to sugar:0.28
Figure 4-4: Reaction pathway for fructose dehydration and in-situ HMF esterification
55
Table 4.1: Comparison the total furans yield between dehydration and in-situ esterification
system and only dehydration reaction (total furans yield= AMF yield + HMF yield)
Temperature
Total furans yield at dehydration
HMF yield at
(°C)
& in-situ esterification (mol%)*
dehydration (mol%) **
360
80
80
60
2
180
100
75
55
3
120
117
72
49
Run
Time (min)
1
*
Reactants amount are identical with reported one in Figure 3.
Reactants: 1000 mg [EMIM]Cl 100 mg fructose, mole ratio of H2SO4 to sugar: 0.22.
**
4.3.4 Effect of fructose loading on final furan yield
The influence of the fructose initial concentration on the AMF and HMF yields is
demonstrated in Figure 4-5. The experiment with 10% fructose to IL mass ratio (referred
to as the original experiment) is repeated at two other initial fructose loadings: one at half
the original loading, and the other at double the initial loading. We did not observe any
appreciable change in the total yield of HMF or AMF. This is an advantage of IL medium
compared to aqueous phase in fructose dehydration reaction. Since increasing fructose
loading from 4.5wt% to 18wt% raise losses from 20% to 35% of sugar to humins [85].
This result is in parallel with X. Qi et.al. [86] findings that in the IL media fructose initial
concentration has not a negative effect on the HMF yield in the fructose dehydration
reaction.
56
Figure 4-5: Effect of fructose loading on final furan yield, reaction conditions: 1000 mg
[EMIM]Cl, mole ratio of acetic acid to sugar:64, mole ratio of H 2SO4 to sugar:0.28, Reaction
time:6 hrs, temperature:80°C
4.3.5 IL recycling
After in-situ esterification, the furans can be completely extracted from IL
medium into an organic solvent such as MIBK or THF at room temperature, and IL will
be reused for next dehydration and esterification reactions. Removal of acetic acid and
H2SO4 from the IL medium is not necessary as they are the required components of the
reaction mixture, when the IL medium is reused. In order to test this idea, first
simultaneous dehydration and esterification were conducted, then furans separated from
IL by MIBK, then reactions repeated with the residual IL medium for a second time. The
results of these experiments presented in Figure 4-6 prove the feasibility of the IL
recycling. In addition, as shown esterification of IL is not compromised in the second
run.
57
90
80
Yield (mol%)
70
AMF
60
50
HMF
40
30
Total
20
10
0
1
2
Cycle number
Figure 4-6: Reusability of [EMIM]Cl results, total yield is summation of AMF and HMF yields,
reaction conditions: 1000 mg [EMIM]Cl, 100 mg fructose, mole ratio of acetic acid to sugar:64,
mole ratio of H2SO4 to sugar:0.28, Reaction time:6 hrs, temperature:80°C
4.3.6 Extracting Solvent efficiency
MIBK have been reported as a reaction medium in the HMF oxidation to FDA
[87] and FDCA [88]. Thus in this study we also have used that as an extracting solvent
despite its high normal boiling point. In addition, it is possible to use THF (normal
boiling point 66°C) in order to save energy while separating and isolating AMF (normal
boiling point 122°C) from reaction media and THF. The extraction efficiency of THF is
96% which is higher than 85% for MIBK (see Figure 4-7). Thus in a case that pure AMF
is required, THF is more desired solvent compared to MIBK due to its better performance
and low energy demand for separation.
58
Figure 4-7: Solvents extraction efficiency comparison, reaction conditions: 1000 mg [EMIM]Cl,
100 mg fructose, mole ratio of acetic acid to sugar:64, mole ratio of H 2SO4 to sugar:0.28, 16 ml
organic solvent, Reaction time:6 hrs, temperature:80°C, extraction efficiency (%) defied as
[AMF(organic)]/( [AMF(organic)] + [AMF(IL)] ×100
4.3.7 Effects of modifications to the reactants and IL reaction medium
In an attempt to improve the yield of total furans, several changes to the basic
experimental protocol (used with the data discussed in the previous sections) were
considered. The results of these modifications to the original dehydration and in-situ
esterification experiment are tabulated in Tables 4-2 and 4-3. Case 1 in the Table 4-2 is
the base case (i.e., the results of the original experiment to which other experiments will
be compared). The first considered change was replacing acetic acid with acetic
anhydride. The rationale for this modification is the expectation that the water molecules
generated during the dehydration of sugar to HMF as well as the esterification of HMF to
AMF will be used in converting acetic anhydride to acetic acid, and are thus removed
from the reaction medium, as they are formed. The removal of water molecules can
59
eliminate the rehydration of furans and also shift esterification reaction equilibrium
toward more AMF production. The results of this experiment are presented as case 2 in
Table 4-2. Unfortunately, it appears that the very few moles of water generated by the
dehydration and esterification reactions were not enough to convert sufficient moles of
acetic anhydride to acetic acid to derive the expected benefit. Indeed, AMF yield of 32%
seen in case 2 was lower compared to case 1 (60%). This loss of yield is likely due to the
unavailability of adequate amounts of acetic acid for converting HMF to AMF. In the
absence of this in-situ esterification, the accumulated HMF is likely to participate in
undesired side reactions leading to the formation of humins and loss of total furan yield.
Indeed, in case 2 significantly higher amount of humins production was observed with a
dramatically reduced HMF yield.
It have been reported that inorganic salts such as NaCl have positive effects in the
production of furfural from xylose [59,60,89]. For instance, Marcotullio et. al. [59] has
shown 81 % yield for furfural from xylose in the 50 mM HCl aqueous solution. Rong and
co-worker [60] have presented the 83% yield of furfural form xylose in the biphasic
system in presence of acid catalyst. In addition, Binder and Raines [45] have described
that halide salts particularly Iodine and Bromine improve the HMF production yield from
fructose or glucose in the DMA and presence of acid catalyst (H 2SO4 and CrCl3
respectively). Based on these reports, it can be inferred that the addition of NaCl to the IL
medium can improve furan yields. This strategy can be particularly valuable as NaCl,
similar to IL, is a non-volatile component of the reaction medium and could easily be
recycled. Thus, small amounts of NaCl (see Table 4-2) were included in the reaction
medium to investigate the catalytic effect of NaCl on the furans yield. (The amount of
60
NaCl that could be used is limited by the solubility of NaCl in the IL medium). The result
(Case 3) indicates that the AMF yield is improved (~ 5%) compared to the original
experiment.
Table 4.2: Furan yield in the modified experiments
HMF yield
(mol%)
Total Furans
Yield
(mol%)
Case
Feed
Additive
AMF yield
(mol%)
1
FructoseAcetic acid
-
60
20
80
-
32
3
35
NaCl
63
20
83
2
FructoseAcetic
anhydride
3
FructoseAcetic acid
Reactant amounts: 1000 mg [EMIM]Cl, 100 mg fructose, mole ratio of acetic acid or acetic anhydride to
sugar:64, mole ratio of H2SO4 to sugar:0.28, Reaction time:6 hrs, temperature:80°C,
*
NaCl mass ratio to [EMIM]Cl mass:3%.
Fructose is an attractive C6 sugar as a feed compared to glucose for HMF
production since its dehydration rate to HMF is higher and has better selectivity [85].
However, glucose advantages as a feed are its more availability and lower price. C.
Zhang group [48] have introduced CrCl2 as a catalyst that in the [EMIM]Cl converts
glucose to HMF in high yield. Therefore glucose was used as the feed to conduct one-pot
dehydration and in-situ esterification. However, the furans yield was very lower
compared to case that fructose used as the feed (Figure 4-8). These data indicate that onepot glucose conversion to AMF and HNF has not produce furans in high yield and it is
required to implement the SIRE-BE process that first isomerize glucose to fructose in
61
high yield, then separate sugars, and finally use fructose as the feed for dehydration and
in-situ esterification.
Figure 4-8: Effects of glucose and fructose on the products yield, reaction conditions: 1000 mg
[EMIM]Cl, 100 mg sugar , mole ratio of acetic acid to sugar:64, mole ratio of H2SO4 to sugar:
0.28, in the case of glucose 0.05 mmole CrCl2 added and reaction time:3hrs, temperature:100°C
The AMF and HMF extraction from [EMIM]Cl and acetic acid reaction medium
requires addition of significant amount of immiscible organic solvent such as MIBK. In
order to address this issue the feasibility of the [EMIM]Cl replacement with other ILs
namely [EMIM]HSO4 and [EMIM]TFO have been studied. Fructose dehydration to
HMF and simultaneously HMF production and esterification in [EMIM]HSO4 and
[EMIM]TFO results are summarized in the Table 4-3. In the neat ILs, fructose
dehydration to HMF yields are 45mol% and 37mol% in the [EMIM]HSO4 and
[EMIM]TFO respectively. Besides, AMF and HMF yield are 46mol% and 24mol% in
62
[EMIM]HSO4 and in [EMIM]TFO AMF and HMF yield are 40mol% and 8mol%
respectively in fructose dehydration to HMF and in-situ HMF esterification to AMF
reactions. The results indicate that furans yield are different in each IL, however
implementing the in-situ esterification will increase the total furans yield because of
preventing HMF contribution in undesired side reactions. Although, the total furans yield
is lower in [EMIM]HSO4 compared to [EMIM]Cl, the required amount of solvent for
products extraction from [EMIM]HSO4 is 37.5% of [EMIM]Cl.
Table 4.3: Furan yield in the different IL.
case
IL
Feed
AMF
yield
(mol %)
HMF
yield
(mol %)
Total Furans
Yield
(mol %)
1
[EMIM]HSO4
Fructose
-
45
45
2
[EMIM]HSO4
FructoseAcetic acid
46
24
70
3
[EMIM]TFO
Fructose
-
37
37
4
[EMIM]TFO
FructoseAcetic acid
40
8
48
Reactant amounts: 1000 mg IL, 100 mg fructose, mole ratio of acetic acid to sugar: 64,
mole ratio of H2SO4 to sugar: 0.28
63
4.4 Conclusion
In summary we have studied the one-pot fructose dehydration and in-situ HMF
esterification to AMF in presence of acetic acid. The reaction was conducted in facile
conditions (80ºC and 6hrs) in [EMIM]Cl. At the end of reaction the AMF and HMF yield
are 60% and 20% respectively. Comparing this total furans yield with a HMF yield in a
case that only fructose dehydrated shows that up to 20% increase in the furans yield.
Although at 100ºC and 117ºC reaction duration is shorter (180 and 120 min respectively),
the total furans yield are lower (75% and 72% respectively) compared to 80ºC. Besides,
optimum loading of non-limiting reactant (acetic acid) and acid catalysts (H2SO4) were
determined to be 64 (ratio of acetic acid to fructose) and 0.28 (mole ratio of H 2SO4 to
fructose). The [EMIM]Cl provides a reaction medium that increasing fructose loading up
to 20% ( mass ratio of fructose to IL ) has not negative effects on furans yield. Our results
also shows that [EMIM]Cl can be recycled and reused. Furthermore, the products
extraction efficiency was compared for two an immiscible organic solvent (THF or
MIBK) at room temperature. The results indicate that addition of NaCl with reactant
improves the total furans yield up to 83% that makes the process more economically
feasible. Acetic anhydride was used to enhance the products yield. However, due to large
HMF losses in side reactions the total furans yield is lower compared to case that acetic
acid was used. Moreover, fructose replacement with glucose was resulted in low AMF
and HMF yield. [EMIM]HSO4 and [EMIM]TFO were also studied in order to find an IL
that demands lower amount of immiscible organic solvent for AMF and HMF separation
and isolation. The results indicate that [EMIM]HSO4 is a proper replacement for
[EMIM]Cl in this regard.
64
Chapter 5
Levulinic acid Production in High from Biomass
Hydrolysate sugar by Implementing SIRE-BE
Technique
5.1 Introduction
In the past century, we were very dependent on the fossil fuel resources for the
production of fuels and chemicals. However, for the future, it is vital to find a sustainable
alternative energy resource, considering the increasing demand for energy due to growth
in world population, declining finite fossil resources, and adverse environmental impact
of fossil fuels. Biomass has the potential to provide the ideal solution for this problem.
Over 150 billion tons of biomass is produced per year, and biomass is the only renewable
resource containing carbon that can be used in the production of liquid hydrocarbon fuels
and chemicals [90].
It is well-known that in petro-refineries a few “building-block” chemicals, namely
benzene, toluene, xylene (BTX), ethylene, propylene, and butadiene form the starting
65
points for the production of a wide variety of value-added products. Bozel and Peterson,
in a highly-celebrated DOE report [15], proposed that a similar “platform-molecule”
approach could be very fruitful in valorizing biomass as well to fuels and high-value
products. These platform molecules are derived from the major components of biomass,
i.e., cellulose, hemicellulose and lignin. As per this report [15] and its recent update [16],
levulinic acid is one of the important platform molecules that can be derived from
biomass carbohydrates.
Levulinic acid is a short chain fatty acid that possesses an acidic carboxyl group
and a ketone carbonyl group that gives the opportunity to produce a broad range of
products such as fuels, fuel additives, resins, and solvents [15,16,90,91]. Several research
groups have investigated the role of levulinic acid as a fuel precursor, with very
promising results. For instance levulinic acid can be used as a feedstock to produce γ–
valero lactone (GVL) [92-94]. It has been shown that GVL has potential to be used as a
replacement of ethanol in the gasoline-ethanol blends or fuel additives [95]. Dumesic’s
group has reported an integrated catalytic process that produces liquid alkenes from GVL
[96]. Lane and co-workers [97] have converted GVL to “valeric biofuels” through
multistage hydrogenation and esterification reactions. In addition, it has been shown that
levulinate ester can be used as diesel additive [65]. Recently, Mascal et. al. [98] have
proposed a novel method to produce branched C7-C10 gasoline-like hydrocarbons from
hydrodeoxygenation of the angelica lactone dimer. Angelica lactone is intermolecular
dehydration product of levulinic acid. Another pathway of levulinic acid conversion to
fuel is hydrogenation to methyl-tetrahydrofuran (MTHF) [99] which has been approved
66
as P Series type fuel [10]. Also, thermal deoxygenation of levulinic acid with formic acid
salt has been reported as a method to produce fuel [100,101].
In light of these promising preliminary studies, there is significant interest in
developing technologies for producing levulinic acid in high yields from biomass
carbohydrates in a cost-effective manner. While there is presently no commercial process
for producing levulinic acid, Biofine Process [102] is one of the early technologies
proposed for levulinic acid production from the biomass. In this process, energy-intensive
two-step approach is employed for the direct conversion of biomass. Despite high
levulinic acid yield achievements due to huge energy requirement for levulinic acid
production, separation and purification; this process has not implemented in a large scale
[103]. Also, production of levulinic acid from pure cellulose or glucose, in acidic reaction
media, was investigated in the literature. In these “one-pot synthesis” processes, acid
catalyzes multiple reaction-steps: first it promotes the hydrolytic depolymerization of
cellulose to its glucose monomers, second it catalyzes the dehydration of glucose to the
corresponding furan, and finally it promotes the rehydration of the furan to produce
levulinic and formic acids. Based on the available data, one-pot production of levulinic
acid from cellulose or sugars demands high temperatures and relatively high pressures, in
addition to large amounts of acid catalyst [90,104]. These requirements prevent scale-up
of these technologies due to high operating costs, issues associated with levulinic acid
purification, and environmental issues related to the disposal of large quantities of acid
catalyst [37].
In this chapter, we propose a new approach for levulinic acid production in high
yield from glucose in biomass hydrolysate. The approach involves transferring glucose
67
from biomass hydrolysate into an acid aqueous medium in the form of a concentrated
fructose solution using the previously-described SIRE-BE process. The concentrated
fructose is then converted to levulinic acid in high yields under facile reaction conditions.
The proposed technique successfully addresses most of the draw-backs plaguing the
existing methods of levulinic acid production from glucose.
5.2 Materials and Methods
5.2.1 Chemicals and Materials
Fructose, glucose, HMF, levulinic acid, 1-ethyl-3-methylimidazolium hydrogen
sulfate
([EMIM]HSO4,
95%
purity),
and
1-ethyl-3-methylimidazolium
trifluoromethanesulfonate ([EMIM]TFO, 98% purity) were purchased from Sigma
Aldrich Co. (St. Louis, MO). 1-(4-sulfobutyl)-3-methyl imidazolium hydrogen sulfate
([BIMIM-SO3]HSO4 98% purity) was used as received from Solvonic (Toulouse,
France). All other chemicals and solvents were prepared from Thermo Fisher Scientific
Inc. (Pittsburgh, PA).
5.2.2 Fructose conversion to Levulinic acid
Fructose conversion to levulinic acid was conducted in two different reaction
media namely low pH aqueous medium and mixture of ([BIMIM-SO3]HSO4 and DI
water. The IL and DI water mixture was composed of [BIMIM-SO3]HSO4 and DI water
(determined value of weight percent have used) in addition to fructose (2-15 wt%
fructose to IL). The reaction media (~1 ml total volume) was added to a 38×20 mm glass
vial. To initiate dehydration of the sugar and subsequent break down of the furan formed
to levulinic acid, a magnetic stir bar was added to the vial, and the vial was capped and
placed in an oil bath on a stirring hotplate with the temperature set at a pre-specified
68
value. After a specified reaction period, the vial was rapidly cooled by ice-water bath to
quench the reaction. Humins were separated by centrifugation at 5000 rpm for 10 min. In
the case that the low pH aqueous phase was used as the reaction medium, the same
protocol was applied and a specified amount of HCl added to provide required acidity in
the solution. Compositions in the IL and aqueous phases were analyzed by high
performance liquid chromatography (HPLC).
5.2.3 Glucose conversion to Levulinic acid
Glucose from biomass hydrolysate isomerized in high yield to fructose by
implementing the SIRE-BE process. Then the concentrated fructose stream has converted
to levulinic acid in the low pH aqueous media as described in the previous section. The
details of the experimental protocols of SIRE-BE approach is provided in the chapter 2.
5.2.4 Analytical methods
Calibration standards for fructose, HMF, and levulinic acid were prepared in DI
water. Reaction media samples, diluted with water as needed, and calibration standards
were analyzed by HPLC using an Agilent 1100 HPLC system equipped with a refractive
index detector (RID). A single Shodex SH1011 column (300×8 mm, from Showa Denko
K.K, Japan) was used for analysis of the sugar, HMF and levulinic acid. A mobile phase
of 5 mM H2SO4 was run at 0.6 ml/min; the column and RID detector temperatures used
were 65°C and 35°C respectively, for optimal peak resolution and detection. All the
experiments were repeated at least two times and the reported results are the average of
these multiple runs; the standard deviation was less than 2% among different runs.
69
Based on the measured quantity of the levulinic acid, HMF and fructose the yields
and conversion for this compound is defined as follows:
Levulinic acid yield (mol%) = (moles of produced levulinic acid) / initial moles of
fructose × 100
HMF yield (mol%) = (moles of produced HMF) / initial moles of fructose ×100
Fructose conversion (%) = (initial moles of fructose - final moles of fructose) / initial
moles of fructose × 100
5.3 Results and Discussion
In the proposed levulinic acid production from biomass hydrolysate process, an
essential step is fructose conversion to levulinic acid. As already noted, in an acidcatalyzed aqueous environment fructose first undergoes dehydration to form HMF. The
formed HMF participates in the rehydration reaction with water molecules and produces
levulinic and formic acids. Thus, to maximize levulinic acid yield produced from fructose
different parameters have to be considered and investigated.
5.3.1 Acid catalyst loading effect on the levulinic acid yield in the aqueous media
Figure 5-1 shows the effect of HCl concentration in the reaction medium on the
levulinic acid yield. The results indicate that as the HCl concentration is raised from
0.5M to 2M, levulinic acid yield dramatically improves, and almost all of the fructose is
converted (>95%) at an acid concentration of 2M. Also, major portion of the reacted
fructose is converted to levulinic acid and HMF, as indicated by the yields of these
compounds.
70
Yield/Conversion
100
Fructose Conversion
90
LA Yield
80
HMF Yield
70
60
50
40
30
20
10
0
0
0.5
1
1.5
HCl concentration (M)
2
Figure 5-1: Acid catalyst concentration effect on fructose conversion, LA and HMF yield,
95°C, 90 min, fructose loading 9 wt%
5.3.2 Reaction duration effect on the levulinic acid yield in the aqueous media
After establishing that near-to-complete fructose conversion takes place in about
90 minutes at 2M HCl concentration and 95°C, we explored whether the rehydration of
the HMF to levulinic acid continues beyond 90 minutes, by allowing the reaction to
proceed up to 180 minutes. Figure 5-2 shows that when the reaction is allowed to proceed
till 120 minutes, fructose is completely converted, and levulinic acid and HMF yields
reach 60% and 5%, respectively. Further continuing the reactions consume the entire
HMF and increase levulinic acid yield slightly.
71
100
90
Yield/Conversion
80
70
60
50
Fructose Conversion
40
LA Yield
30
HMF Yield
20
10
0
0
30
60
90
120
Time (min)
150
180
Figure 5-2: Reaction duration effect on fructose conversion, LA and HMF yield, 95°C,
HCl concentration 2M, fructose loading 9wt%
5.3.3 Temperature effect on the levulinic acid yield in the aqueous media
In order to evaluate the effect of reaction temperature on fructose conversion,
HMF and levulinic acid yield the experiment is conducted at different temperatures
included: 85°C, 105°C and 115°C. Results displayed in Figure 5-3 indicate that lowering
the reaction temperature from 95°C to 85°C dramatically reduces the levulinic acid yield.
For instance, comparing levulinic acids yield at 120 minutes for these two temperatures
present yield reduction from 60mol% to 20mol%. In addition at lower temperature
(85°C) HMF amount which is not converted is significant. Although at 85°C complete
fructose and HMF conversion take very long time, at 105°C and 115°C as expected the
kinetic are much faster. These results are in agreement with Girisuta et. al. [105] finding
that C6 sugars conversion to levulinic acid exhibit a high sensitivity toward reaction
temperature.
72
100
85 °C
90
Yield/Conversion
80
70
60
50
40
30
20
Fructose Conversion
10
0
LA Yield
0
45
90
135 180 225 270 315 360
Time (min)
100
HMF Yield
105 °C
90
Yıeld/Conversion
80
70
60
50
40
30
20
Fructose Conversion
10
0
LA Yıeid
0
15
30
45 60 75
Time (min)
73
90
105 120
HMF Yield
100
115 °C
90
Yield/Conversion
80
70
60
50
40
30
20
10
0
Fructose Conversion
0
15
30
Time (min)
45
60
LA Yield
HMF Yield
Figure 5-3: Temperature effect on the fructose conversion, LA and HMF yield, HCl concentration
2M, fructose loading 9 wt%
5.3.4 Fructose loading effect on the levulinic acid yield in the aqueous media
As mentioned, cellulose has also been used as the substrate for levulinic acid
production due to its lower price compared to sugars. Since cellulose, unlike sugars, does
not dissolve in water, the reaction medium is heterogeneous. Here the acid catalyst helps
the hydrolytic saccharification of cellulose to glucose which subsequently undergoes
dehydration to HMF and further conversion to levulinic acid. In most studies involving
cellulose, cellulose loading in the reaction medium was deliberately kept low (< 5wt %)
to avoid high glucose concentrations as HMF is known to participate in crosscondensation reactions with the glucose, leading to loss in HMF yield, and hence in
levulinic acid yield. However, such low sugar concentrations would imply extremely low
concentration of the final product (levulinic acid) in the reaction medium (~ 1wt%).
Isolating levulinic acid from these extremely dilute aqueous solutions through
74
evaporative schemes is usually cost-prohibitive. For instance, in the well-known Biofine
process [102], the biomass loading is less than 5wt% which results in final levulinic acid
concentrations of about 1wt% at the end of the process. The cost of evaporating the
enormous amount of water to recover levulinic acid is very detrimental to the process
economics and remains a major obstacle in scaling up this process [103]. While
distillation is an energy-intensive separation, as the concentration of levulinic acid in the
reaction mixture increases, the separation costs will decrease exponentially. Therefore, it
is imperative that processes that can accommodate higher sugar loadings in the reaction
media be developed. In this regard, processes that use fructose as the starting sugar are
more likely to be economically viable, as the product loss to cross-condensation reactions
is not as high at the reactions conditions necessary with fructose. The main advantage of
the modified SIRE-BE process is that it is possible, using this approach, to achieve high
fructose loadings in the reaction medium even when the starting biomass hydrolysates are
dilute in sugar concentrations. As shown in Figure 5-4, levulinic acid can be produced at
appreciable yields up to fructose loadings of 18wt%, which would imply a 6 fold increase
in the levulinic acid concentration in the final reaction mixture compared to Biofine
process.
75
100
Yield/Conversion
80
60
Fructose Conversion
40
HMF Yield
LA Yield
20
0
9
13.5
18
27
Fructose wt%
36
Figure 5-4: Fructose loading effects on LA and HMF yield, 95°C, 2hrs
5.3.5 Glucose conversion to the levulinic acid in the aqueous media
Although the one-pot fructose conversion to levulinic acid shows remarkable
results, glucose as the feed is more desired compared to fructose due to its lower price
and availability. However, as mentioned in the introduction section one-pot glucose
conversion to levulinic acid is impractical. Here in we report a state of art technique to
overcome the issues. In this method, SIRE-BE process is coupled with one-pot fructose
conversion to levulinic acid. Generally in this pathway the SIRE-BE process is
implemented to prepare a concentrated stream of fructose from glucose, then fructose
transferred to acidic aqueous solution. Finally HMF formation and its in-situ rehydration
are conducted in a way that promotes the highest levulinic acid yield. The SIRE-BE
mechanism and performance are depicted in details in chapter 2. The results of glucose
conversion to levulinic acid are summarized in Table 5-1.
76
Table 5.1: Glucose conversion to LA and HMF
Glucose
Fructose dehydration and in-situ HMF rehydration yield**
conversion to
Feed
Fructose yield
Conversion (%)
*
(mol%)
Glucose
89
100
*
**
HMF Yield
LA Yield
(mol%)
(mol%)
5
60
Reaction condition: see chapter 2
Reaction condition: 95°C, 2hrs, HCl concentration 2M, fructose loading 9wt%
5.3.6 Levulinic acid production in the [BMIM-SO3]HSO4 and DI water mixture
While mineral acids are effective catalysts for producing levulinic acid from
biomass carbohydrates, they pose a number of operational problems. It is not easy to
recover the soluble acid catalysts at the end of the process; the problem is compounded
by the fact that the product of the reaction is also an acid. Disposal of process streams
containing unrecovered acid can lead to health and environmental hazards due to their
corrosive nature. In summary, additional costs associated with acid catalyst recovery,
treatment (neutralization), and disposal make processes based on soluble acid catalysts
economically less feasible. The use of solid acid catalyst such as amberlyst 70 can
alleviate the catalyst separation problem [106]. However, as was observed by Dumesic’s
group, maintaining the catalyst performance at high level required periodic regeneration
of the catalyst; the catalyst gradually lost its activity within four cycles of reuse.
Therefore, development of catalytic approaches that are not hindered by these issues is
desirable. In this regard, our SIRE-BE approach provides a novel alternative. As has
77
already been observed, in this approach, the low pH medium used for back extracting the
ketose sugar from the organic phase serves dual roles: (1) provides the driving force
needed to strip the ketose from the organic phase, and (2) provides the acid catalyst
necessary for promoting the conversion of the ketose sugar to levulinic acid. We
observed that aqueous mixtures of the task specific IL, 1-(4-sulfobutyl)-3-methyl
imidazolium hydrogen sulfate [BMIM-SO3]HSO4 provides uniquely suitable media in
this context. The mixtures are not only very effective in back-extracting ketose from the
organic phase (following SIRE) but also are able to affect conversion of fructose to
levulinic acid without the need of an additional acid catalyst in the medium. This
represents a significant advantage as the issues with the catalyst recovery are eliminated
in this process. Thus different parameters effects on levulinic acid yield are investigated
in this reaction media.
5.3.7 [BMIM-SO3]HSO4 loadings effect on the levulinic acid yield
Figure 5-5 presents fructose conversion to levulinic acid with various weight
percent of [BMIM-SO3]HSO4 in the aqueous media for two different fructose loading
(2.5 and 9 wt%). The results indicates that increasing the IL weight percent from 25wt%
to 75wt% in the reaction media dramatically increases the levulinic acid yield in the both
fructose loadings; however, further addition of IL beyond 75wt% decreases the product
yield. These results constitute successful demonstration of the unique role of aqueous and
[BMIM-SO3]HSO4 mixtures in levulinic acid production.
78
80
LA Yield (mol%)
70
60
50
40
2.5 wt%
30
9 wt%
20
10
0
25
50
75
95
IL wt%
Figure 5-5: [BIMIM-SO3]HSO4 weight percent effect on levulinic acid yield, 95°C, 1hr,
bars represent levulinic acid yield for 2.5 wt% (black) and 9 wt% (white) fructose loading in the
reaction media
5.3.8 Levulinic acid kinetic data in the [BMIM-SO3]HSO4 and DI water mixture
The kinetics of levulinic acid production from fructose in [BIMIM-SO3]HSO4
and water mixture (75wt% IL) are presented in Figure 5-6. The levulinic acid reaches its
maximum yield at 60 minutes and fructose is completely converted to reaction
intermediates by 15 min; indicating that the reaction kinetics in the IL-water mixture are
significantly faster than in acidic aqueous media. The shorter reaction duration at this
temperature, it will decrease the volume of the reactor required and benefit the overall
process economy.
79
100
Yield/Conversion
80
60
LA Yield
40
Fructose Conversion
20
0
0
15
30
45 60 75
Time (min)
90
105 120
Figure 5-6: Kinetic data of fructose conversion and levulinic acid yield in IL and DI
water mixture, [BIMIM-SO3]HSO4 loading 75wt%, 95°C, fructose loading 2.5wt%
5.3.9 Temperature effect on the levulinic acid yield in the [BMIM-SO3]HSO4 and DI
water mixture
Figure 5-7 shows the levulinic acid yield at different temperatures (80, 85, 90 and
95°C) in the IL-water reaction medium. The results indicate that at lowest temperature
(80°C) significant amount of HMF has remained in the reaction medium and levulinic
acid yield is moderate. By raising the temperature to 95°C the levulinic acid yield has
increased and HMF yield decreased significantly. It is worth noting that the combined
HMF and levulinic acid yield (total products yield) have stayed constant over whole
temperature range.
80
100
Yield/Conversiom
80
60
Fructsoe Conversion
40
HMF Yield
LA Yield
20
0
80
85
90
Temperature (C)
95
Figure 5-7: Temperature effect on fructose conversion and levulinic acid yield in IL
aqueous mixture, [BIMIM-SO3]HSO4 loading 75wt%, fructose loading 2.5wt%
5.3.10 Fructose loading effect on the levulinic acid yield in the [BMIM-SO3]HSO4
and DI water mixture
From an economic view point high feed loading benefits the process and makes it
more viable. Thus, it is of interest to evaluate the effect of fructose loading on levulinic
acid yield. It was shown in the second chapter that fructose loading does not have as
much a negative effect in IL media as in aqueous media on the furan yield, since IL can
stabilize the furan. However, in the aqueous media furan yield drops dramatically by
increasing fructose loading [85]. In this system, the reaction medium is, by necessity, a
mixture of IL and water. Hence, we expect, with this system, a behavior that is between
these two limits. As seen in Figure 5-8, although levulinic acid yield drops, it is not
drastically reduced with higher fructose loadings.
81
80
LA Yield (mol%)
70
60
50
40
30
20
10
0
2.5
5
9
15
Fructose wt%
Figure 5-8: Fructose loading effect on levulinic acid yield in IL aqueous mixture,
[BIMI-SO3]HSO4 loading 75wt%, 95°C, 1hr, fructose loading 2.5wt%
5.3.11 Ionic liquid reusability
In order to investigate the IL and DI water mixture reusability, the one-pot
fructose conversion to levulinic acid conducted in three consecutive cycles. The results
presented in Figure 5-9 proves the [BIMIM-SO3]HSO4 and DI water mixture reusability.
82
100
90
Yield/Conversion
80
70
60
50
Fructsoe Conversion
40
LA Yield
30
20
10
0
1
2
run number
3
Figure 5-9: IL aqueous mixture reusability results, [BIMI-SO3]HSO4 loading 75wt%,
95°C, 1hr, fructose loading 2.5wt%
5.3.12 Ionic liquids replacement effect on the levulinic acid yield
In the second chapter it was shown that [EMIM]HSO4, [EMIM]TFO and
[BIMIM-SO3]HSO4 can be used in the back extraction step of SIRE-BE process to
recover fructose from the organic phase to the IL medium. Thus, the fructose conversion,
HMF and levulinic acid yield were compared for similar operating conditions in these ILs
to find out which IL provides the best levulinic acid yield among them. Since IL acidity
is expected to catalyze the fructose conversion to levulinic acid reactions, extraneous acid
catalyst was not added to the reaction medium. In the [EMIM]TFO and DI water mixture
(75wt% IL) as the reaction medium negligible amount of the HMF and levulinic acid are
produced. Also, 43% of the fructose is converted (Figure 5-10 a) to undesired sideproducts. This trend became even worse by increasing the fructose loading from 2.5wt%
to 5wt% (Figure 5-10 b). In the [EMIM]HSO4 and DI water mixture (75wt% IL) higher
83
amounts of fructose is converted (66%), but the major product was HMF (its yield is 55
mol%), with a small loss to undesired side products. In this case the levulinic acid yield
was dramatically low (less than 5 mol%). Besides, in the same [EMIM]HSO4 and DI
water mixture by doubling the fructose loading from 2.5wt% to 5wt%, the fructose
conversion decreases; as a result the HMF yield reduces from 55 mol% to 45 mol% and
levulinic acid amount become completely negligible. The results indicate that the
[BIMIM-SO3]HSO4 mixture with water (75wt% IL) is the preferred medium among
these ILs for this process due to high levulinic acid yield.
100
(a)
Yield/Conversion
80
60
Fructose Conversion
HMF Yield
40
LA Yield
20
0
[EMIM]TFO
[EMIM]HSO4
IL
[BMIMSO3]HSO4
84
100
(b)
Yield/Conversion
80
60
Fructose Conversion
HMF Yield
40
LA Yield
20
0
[EMIM]TFO
[EMIM]HSO4
IL
[BMIMSO3]HSO4
Figure 5-10: Fructose conversion, levulinic acid and HMF yields in different ILs, IL loading
75wt%, reaction condition 95°C, 1hr, fructose loading (a) 2.5wt% (b) 5wt%
5.4 Conclusion
To summarize, in this chapter we develop a novel multistep method that converts
biomass sugar (glucose) to levulinic acid at high yield. In the first step of the process,
SIRE, glucose is efficiently isomerized in high yield to fructose, while it is being
simultaneously extracted in to an organic solvent; then, in the next step, the organic phase
is contacted with a low pH aqueous solution or [BIMIM-SO3]HSO4 mixture with DI
water (75 wt % IL) to back extract fructose. Finally, fructose is dehydrated to HMF and
HMF simultaneously converted to levulinic acid. The major advantage of this process is
the facile reaction conditions that reduce energy inputs; also, in this technology process
streams can be recycled relatively easily as there is no externally added acid catalyst in
the reaction medium, which benefits the process economy.
85
Chapter 6
Conclusion, Alternative Approaches and Suggestions
for Future Works
6.1 Conclusion
In this study, a novel method is presented for the production of 5(hydroxymethyl)furfural HMF from the biomass sugar glucose at high conversion (80%
of theoretical) under facile reaction conditions. The method consists of three sequential
steps. In the first step of this process, glucose is simultaneously isomerized to fructose
and selectively- and reactively-extracted into an organic phase via complexation with an
organophilic boronic acid. In the second step, fructose is recovered and concentrated
from the organic solvent by back-extraction into an ionic liquid medium. In the third and
final step, fructose is dehydrated at 50°C for 3hr to produce HMF in high yield. We
achieved comparable results for this process with biomass hydrolysate produced from
dilute acid pretreatment of corn stover and pure glucose at equal initial glucose
concentrations. Four ILs were tested due to their recognized performance as dehydration
86
media. However, only one - [EMIM]HSO4 - was immiscible with the organic solvent and
effective at back-extracting sugar from the organic solvent. The effectiveness of
Amberlyst15, Amberlyst70, 12-TPA, and HCl as dehydration catalysts in the IL phase
was also tested, as was in situ extraction of HMF into an immiscible organic phase during
dehydration. Our results indicate that HMF production can be achieved with initial
fructose to IL loadings of up to 20wt% with little loss of HMF yield. Besides, this method
has been used to simultaneously produce HMF and furfural from mixed fructose and
xylulose streams.
Based on the provided data in the former chapters it has been shown that by
implementing and modifying Simultaneous Isomerization and Reactive Extraction
(SIRE), Back Extraction (BE) and Dehydration technique we could use glucose in pure
state or for the first time from sacchrified biomass hydrolysate solution as the feed for
EMF, EL, LA, and formic acid production. This gain eliminates the glucose separation
and purification steps. Consequently the overall process cost will reduce dramatically and
make the proposed process economically viable. In addition, in this study various ionic
liquid has been used successfully as the reaction media for fructose dehydration and/or
in-situ HMF etherification, esterification, and rehydration. In order to obtain optimum
operating conditions different parameters have investigated and introduced for each
compound.
6.2 Alternative implementations of SIRE-BE technique and suggestions
Considering the mentioned benefits make it clear that how vital is the SIRE-BE
concept in developing the Bio-Refinery. Therefore it is crucial to investigate some of the
87
problems that may negatively affect the introduced process and propose solutions for
them. The first issue is the solubility of the octanol in the water. We find out that octanol
has very small solubility in the water (2 mg/kg water). Even this small quantity in a large
scale can hurt the process economic due to octanol loss. One suggestion to eliminate this
problem can be implementing high molecular weight alcohol such as C14 or C16 long
chain alcohols instead of octanol. However, even these alcohols have very low solubility
in the water. Besides, very small amount of the Aliquat® 336 dissolution in the water has
an environmental risk that can prevent large scale application of the process. In addition,
due to solubility of important ionic liquids such as [EMIM]Cl or SYPHOS 106 in the
octanol, IL selection choices are very limited. Therefore, the opportunities for using these
ILs in producing HMF and its derivatives by this method will reduce.
In order to address these issues we should propose another contact configuration
for Phenyl Boronic Acid (PBA) components in the SIRE-BE process. We suggest using
the immobilized PBA particles in a fixed bed type reactor instead of octanol containing
PBA and Aliquat® 336 which eliminates organic phase role in the process. In this case
initially the aqueous inlet feed containing biomass hydrolysate C5 and C6 sugars will
circulate in a system as depicted in Figure 6-1. In the Immobilized XI reactor aldoses
isomerizes to ketoses and reach the equilibrium state, then the solution feed will pass
through the immobilized BPA reactor. In this reactor ketoses preferably will be bonded to
the PBA particles and aldoses will remain and be the main constituent of the leaving
solution at the end of cycle. This cyclic process will be continued until the aldoses
isomerization to ketoses yield approaches to a determined value. Then in the BE step,
back extracting solvent which can be an acidic ionic liquid or mixture of an acidified
88
ionic liquid and organic solvent will pass through the immobilized BPA reactor and
extract ketoses. After extracting ketoses, desired reaction such as fructose dehydration
and HMF etherification, rehydration, or esterification can conduct in the back extracted
media. This successful modification can solve the octanol carry over issue in addition to
aqueous phase contamination risk by releasing Aliquat® 336.
Besides it is possible to use any solvent included [EMIM]Cl or SYPHOS 106 as
the back extraction solvent in the BE step. Since the new configuration removes the
organic phase and required contact step between that and back extracting solvent in the
BE.
Immobilized XI reactor
Immobilized PBA reactor
Figure 6-1: Schematic diagram for the alternative reactor configuration
Another important issue in the proposed SIRE-BE-Dehydration process is the
application of ionic liquid. Although the ionic liquids show an extra ordinary
performance in the proposed process, the ionic liquids are expensive, viscous and hard to
handle. In order to overcome these obstacles and take the advantage of the ionic liquids,
89
we suggest using mixture of ionic liquid and organic solvents such as DMSO, DMI etc.
instead of neat ionic liquids. We believe that partial ionic liquid replacement with organic
solvent will solve the problems. For instance, the mixture viscosity will be very low
compared to neat IL. Thus, the processing cost will decrease. Also, organic solvent such
as DMSO are much cheaper which reduces the capital cost of the process. Consequently,
the process will be more economically desirable. In order to prove the feasibility of
partial [EMIM]HSO4 replacement with DMSO we have conducted fructose dehydration
in [EMIM]HSO4 and DMSO mixture. Figure 6-2 shows different weight percent
replacement of [EMIM]HSO4 by DMSO. The results indicate that increasing the DMSO
weight percent from 30% to 70% will increases HMF yield from 64mol% to 70mol%
respectively since HMF degradation in the side reactions is prevented. Furthermore,
simultaneous extraction of HMF with MIBK in [EMIM]HSO4 and DMSO mixture have
been studied. The results demonstrate an increase in the HMF yield. In addition,
[EMIM]HSO4 and DMSO mixture (70wt% DMSO) extraction efficiency is 12% higher
compared to biphasic systems consist of [EMIM]HSO4 and MIBK.
90
80
HMF Yield (mol%)
70
60
without MIBK
50
40
with MIBK
30
20
10
0
0
10
20
30
40
50
60
70
80
DMSO wt%
Figure 6-2: DMSO weight percent effects on HMF yield (1000 mg reaction media, 100 mg
Fructose, 100°C, 0.31 mmol HCl, reaction duration 30 min, MIBK if used 12 ml)
In this chapter, different aspects of SIRE-BE dehydration has discussed and a new
configuration has introduced to overcome the mentioned issues. For the future studies
we believe the essential experiments should include proving the new configuration
process by providing experimental data and then optimizing its operating parameters.
In addition we want to emphasis on the importance of PBA in the SIRE-BEDehydration process. In order to obtain higher level performance form PBAs, the
future experiments should explore the new PBA compounds with higher
complexation capacity in addition to higher selectivity towards ketoses. Final
suggestion for future experiment is investigating the feasibility of conducting HMF
oxidation reaction in the organic solvents (such as THF) or one-pot HMF production
and oxidation reactions. Due to the fact that HMF oxidation derivatives have various
91
applications and their production in parallel with the SIRE-BE- Dehydration process
will support the Bio-Refinery concept.
92
References
[1] J. Cheng, Biomass to Renewable Energy Processes, CRC press, Taylor& Francis
Group, 2010.
[2] D.M. Mousdale, Introduction to biofuels, Taylor & Francis Group, 2010.
[3] A. Demirbas, Pyrolysis Mechanism of Biomass Materials. Energy Sources, Part A:
Recovery, Utilization, and Environmental Effects, 2009, 31, 1186-1193.
[4] A. V. Bridgwater, D. Meier and D. Radlein, An overview of fast pyrolysis of biomass,
Organic Geochemistry, 1999, 30, 1479-1493.
[5] L. E. Graham, M. J. Graham, and W. L. Wilcox, Algae, Second ed. Benjamin
Cumming/Pearson, 2009.
[6] L. A. Johnson, P. J. White and R. Galloway, Soybeans: chemistry, production,
processing, and utilization. AOCS Press, 2008.
[7] D. L. Klass, in Biomass for the Renewable Energy and Fuels, Encyclopedia of
Energy, ed. C. J. Cleveland, Elsevier, London, 2004.
[8] C. E. Wyman, B. E. Dale, R. T. Elander, M. Holtzapple, M. R. Ladisch and Y. Y.
Lee, Coordinated development of leading biomass pretreatment technologies,
Bioresource Technology, 2005, 96, 1959–1966.
93
[9] L. R. Lynd, J. H. Cushman, R. J. Nichols and C. E. Wyman, Fuel ethanol from
cellulosic biomass, Science, 1991, 251, 1318–1323.
[10] G. W. Huber, S. Iborra and A. Corma, Synthesis of Transportation Fuels from
Biomass: Chemistry, Catalysts, and Engineering, Chemical Reviews, 2006, 106, 40444098.
[11] F. S. Chakar and A. J. Ragauskas, Review of current and future softwood kraft lignin
process chemistry, Industrial Crops and Production, 2004, 20, 131–141.
[12] J. C. Serrano-Ruiz and James A. Dumesic, Catalytic routes for the conversion of
biomass into liquid hydrocarbon transportation fuels, Energy and Environmental Science,
2011, 4, 83-99.
[13] A. Boisen, T. B. Christensen, W. Fu, Y. Y. Gorbanev, T. S. Hansen, J. S. Jensen, S.
K. Klitgaard, S. Pedersen, A. Riisager, T. Ståhlberg, and J. M. Woodley, Process
integration for the conversion of glucose to 2,5-furandicarboxylic acid, Chemical
Engineering Research and Design, 2009, 87, 1318-1327.
[14] www.chemistryinnovation.co.uk/FROPTOP.
[15] T. Werpy and G. Petersen, Top Value Added Chemicals from Biomass Vol. IResults of Screening for Potential Candidates from Sugars and Synthesis Gas, NREL/TP510-35523; National Renewable Energy Laboratory: Golden, CO, 2004.
[16] J. J. Bozell and G. R. Petersen, Technology development for the production of
biobased products from biorefinery carbohydrates—the US Department of Energy’s “Top
10” revisited, Green Chemistry, 2010, 12, 539-554.
94
[17] R.-J. van Putten, J. C. van der Waal, E. de Jong, C. B. Rasrendra, H. J. Heeres, and J.
G. de Vries, Hydroxymethylfurfural, A Versatile Platform Chemical Made from
Renewable Resources, Chemical Reviews, 2013, 113, 1499−1597.
[18] R. P. Swatloski, R. D. Rogers and J. D. Holbrey, Dissolution and processing of
cellulose using ionic liquids, WO, 2003, 029329.
[19] R. P. Swatloski, S. K. Spear, J. D. Holbrey and R. D. Rogers, Dissolution of
Cellulose with Ionic Liquids, Journal of the American Chemical Society, 2002, 124,
4974-4975.
[20] U. Vagt, in Handbook of Green Chemistry: Green Solvents, Vol. 6— Ionic Liquids,
ed. P. Wasserscheid and A. Stark, Wiley-VCH, 2010, p. 115.
[21] H. Olivier-Bourbigou, L. Magna, and D. Morvan, Ionic liquids and catalysis: Recent
progress from knowledge to applications, Applied Catalysis A: General 2010, 1, 1–56.
[22] C. Li, Q. Wang and Z. K. Zhao, Acid in ionic liquid: An efficient system for
hydrolysis of lignocellulose, Green Chemistry, 2008, 10, 177-182.
[23] L. Vanoye, M. Fanselow, J. D. Holbrey, M. P. Atkins and K. R. Seddon, Kinetic
model for the hydrolysis of lignocellulosic biomass in the ionic liquid, 1-ethyl-3-methylimidazolium chloride, Green Chemistry, 2009, 11, 390-396.
[24] J. B. Binder and R. T. Raines, Fermentable sugars by chemical hydrolysis of
biomass, Proceeding of National Academy of Science of the USA, 2010, 107, 4516-4521.
[25] A. Corma, O. dela Torre and M. Renz, Production of high quality diesel from
cellulose and hemicellulose by the Sylvan process: catalysts and process variables,
Energy & Environmental Science, 2012, 5, 6328-6344.
95
[26] A. Corma, O. dela Torre and M. Renz, High-Quality Diesel from Hexose- and
Pentose-Derived Biomass Platform Molecules, ChemSusChem, 2011, 4, 1574-1577.
[27] G. W. Huber, J. N. Chheda, C. J. Barrett and J. A. Dumesic, Production of Liquid
Alkanes by Aqueous-Phase Processing of Biomass-Derived Carbohydrates, Science,
2005, 308, 1446-1450.
[28] W. Shen, G. A. Tompsett, K. D. Hammond, R. Xing, F. Dogan, C. P. Grey, W. C.
Conner Jr, S. M. Auerbach and G. W. Huber, Liquid phase aldol condensation reactions
with MgO–ZrO2 and shape-selective nitrogen-substituted NaY, Applied Catalysis A:
General, 2011, 392, 57-68.
[29] R. M. West, Z. Y. Liu, M. Peter, C. A. Gärtner and J. A. Dumesic, Carbon–carbon
bond formation for biomass-derived furfurals and ketones by aldol condensation in a
biphasic system, Journal of Molecular Catalysis A: Chemical, 2008, 296, 18-27.
[30] J. Yang, N. Li, G. Li, W. Wang, A. Wang, X. Wang, Y. Cong and T. Zhang,
Solvent-Free Synthesis of C10 and C11 Branched Alkanes from Furfural and Methyl
Isobutyl Ketone, ChemSusChem, 2013, 6, 1149-1152.
[31] M. Balakrishnan, E. R. Sacia and A. T. Bell, Etherification and reductive
etherification
of
5-(hydroxymethyl)furfural:
5-(alkoxymethyl)furfurals
and
2,5-
bis(alkoxymethyl)furans as potential bio-diesel candidates, Green Chemistry, 2012, 14,
1626-1634.
[32] M. Chidambaram and A. T. Bell, A two-step approach for the catalytic conversion of
glucose to 2,5-dimethylfuran in ionic liquids, Green Chemistry, 2010, 12, 1253-1262.
96
[33] Y. Román-Leshkov, Christopher J. Barrett, Zhen Y. Liu and James A. Dumesic,
Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates, Nature,
2007, 447, 982-985.
[34] X. Tong, Y. Ma and Y. Li, Biomass into chemicals: Conversion of sugars to furan
derivatives by catalytic processes, Applied Catalysis A: General, 2010, 385, 1-13.
[35] B. Saha, D. Gupta, M. M. Abu-Omar, A. Modak and A. Bhaumik, Porphyrin-based
porous organic polymer-supported iron(III) catalyst for efficient aerobic oxidation of 5hydroxymethyl-furfural into 2,5-furandicarboxylic acid, Journal of Catalysis, 2013, 299,
316-320.
[36] D. J. Hayes, S. Fitzpatrick, M. H. B. Hayes and J. R. H. Ross, in BiorefineriesIndustrial Processes and Products (Wiley-VCH Verlag GmbH, 2008), pp. 139-164.
[37] R. Weingarten, W. C. Conner and G. W. Huber, Production of levulinic acid from
cellulose by hydrothermal decompositioncombined with aqueous phase dehydration with
a solid acid catalyst Energy & Environmental Science, 2012, 5, 7559-7574.
[38] E. Nikolla, Y. Román-Leshkov, M. Moliner and M. E. Davis, “One-Pot” Synthesis
of 5-(Hydroxymethyl)furfural from Carbohydrates using Tin-Beta Zeolite ACS Catalysis,
2011, 1, 408-410.
[39] Y. J. Pagán-Torres, T. Wang, J. M. R. Gallo, B. H. Shanks and J. A. Dumesic,
Production of 5-Hydroxymethylfurfural from Glucose Using a Combination of Lewis and
Brønsted Acid Catalysts in Water in a Biphasic Reactor with an Alkylphenol Solvent,
ACS Catalysis, 2012, 2, 930-934.
97
[40] Y. Román-Leshkov, J. N. Chheda and J. A. Dumesic, Phase Modifiers Promote
Efficient Production of Hydroxymethylfurfural from Fructose, Science, 2006, 312, 19331937.
[41] K.-i. Seri, Y. Inoue and H. Ishida, Catalytic Activity of Lanthanide(III) Ions for the
Dehydration of Hexose to 5-Hydroxymethyl-2-furaldehyde in Water, Bulletin of the
Chemical Society of Japan, 2001, 74, 1145-1150.
[42] B. R. Caes and R. T. Raines, Conversion of Fructose into 5-(Hydroxymethyl)furfural
in Sulfolane, ChemSusChem, 2011, 4, 353-356.
[43] R. M. Musau and R. M. Munavu, The preparation of 5-hydroxymethyl-2furaldehyde (HMF) from d-fructose in the presence of DMSO, Biomass, 1987, 13, 67-74.
[44] J. M. R. Gallo, D. M. Alonso, M. A. Mellmer and J. A. Dumesic, Production and
upgrading of 5-hydroxymethylfurfural using heterogeneous catalysts and biomassderived solvents, Green Chemistry, 2013, 15, 85-90.
[45] J. B. Binder and R. T. Raines, Simple Chemical Transformation of Lignocellulosic
Biomass into Furans for Fuels and Chemicals, Journal of the American Chemical Society,
2009, 131, 1979-1985.
[46] J. P. Lange, E. van der Heide, J. van Buijtenen and R. Price, Furfural—A Promising
Platform for Lignocellulosic Biofuels, ChemSusChem, 2012, 5, 150-166.
[47] A. Takagaki, M. Ohara, S. Nishimura and K. Ebitani, A one-pot reaction for
biorefinery: combination of solid acid and base catalysts for direct production of 5hydroxymethylfurfural from saccharides, Chemical Communications, 2009, 41, 62766278.
98
[48] H. Zhao, J. E. Holladay, H. Brown and Z. C. Zhang, Metal Chlorides in Ionic Liquid
Solvents Convert Sugars to 5-Hydroxymethylfurfural, Science, 2007, 316, 1597-1600.
[49] L. Lai and Y. Zhang, The Effect of Imidazolium Ionic Liquid on the Dehydration of
Fructose to 5-Hydroxymethylfurfural, and a Room Temperature Catalytic System,
ChemSusChem, 2010, 3, 1257-1259.
[50] B. Li, P. Relue and S. Varanasi, Simultaneous isomerization and reactive extraction
of biomass sugars for high yield production of ketose sugars, Green Chemistry, 2012, 14,
2436-2444.
[51] B. Li, S. Varanasi and P. Relue, High yield aldose–ketose transformation for
isolation and facile conversion of biomass sugar to furan, Green Chemistry, 2013, 15,
2149-2157.
[52] S. Lima, P. Neves, M. M. Antunes, M. Pillinger, N. Ignatyev and A. A. Valente,
Conversion of mono/di/polysaccharides into furan compounds using 1-alkyl-3methylimidazolium ionic liquids Applied Catalysis A General, 2009, 363, 93-99.
[53] V. Choudhary, S. H. Mushrif, C. Ho, A. Anderko, V. Nikolakis, N. S. Marinkovic,
A. I. Frenkel, S. I. Sandler and D. G. Vlachos, Insights into the Interplay of Lewis and
Brønsted
Acid
Catalysts
in
Glucose
and
Fructose
Conversion
to
5-
(Hydroxymethyl)furfural and Levulinic Acid in Aqueous Media, Journal of the American
Chemical Society, 2013, 135, 3997-4006.
[54] Y. Román-Leshkov and J. A. Dumesic, Solvent Effects on Fructose Dehydration to
5-Hydroxymethylfurfural in Biphasic Systems Saturated with Inorganic Salts, Topics in
Catalysis, 2009, 52, 297-303.
[55] A. C. Cope, Production and recovery of furans, US Patent, 1959, 2917520 A
99
[56] G. Marcotullio and W. De Jong, Chloride ions enhance furfural formation from Dxylose in dilute aqueous acidic solutions, Green Chemistry, 2010, 12, 1739-1746.
[57] C. Rong, X. Ding, Y. Zhu, Y. Li, L. Wang, Y. Qu, X. Ma and Z. Wang, Production
of furfural from xylose at atmospheric pressure by dilute sulfuric acid and inorganic salts,
Carbohydrate Research, 2012, 350, 77-80.
[58] C. J. Barrett, J. N. Chheda, G. W. Huber and J. A. Dumesic, Single-reactor process
for sequential aldol-condensation and hydrogenation of biomass-derived compounds in
water, Applied Catalysis B: Environmental, 2006, 66, 111–118.
[59] G. J. M. Gruter and F. Dautzenberg, Method for the synthesis of 5alkoxymethylfurfural ethers and their use, European Patent, 2007, 1834950 A1.
[60] M. Mascal, and E. B. Nikitin, Direct high-yield conversion of cellulose into biofuel,
Angew. Chem., Int. Ed. 2008, 47, 7924-7926.
[61] G. J. M. Gruter and F. Dautzenberg, Method for the synthesis of 5hydroxymethylfurfural ethers and their use, U.S. Patent, 2011, 0082304 A1.
[62] S. W. Fitzpatrick, The Biofine technology: A "bio-refinery" concept based on
thermochemical conversion of cellulosic biomass, ACS Symposium, 2006, 921, 271–287.
[63] P. Neves, M. M. Antunes, P. A. Russo, J. P. Abrantes, S. Lima, A. Fernandes, M.
Pillinger, S. M. Rocha, M. F. Ribeiro, and A. A. Valent, Production of biomass-derived
furanic ethers and levulinate esters using heterogeneous acid catalysts, Green Chemistry,
2013, 15, 3367-3376.
[64] P. Che, F. Lu, J. Zhang, Y. Huang, X. Nie, J. Gao, and J. Xu, Catalytic selective
etherification of hydroxyl groups in 5-hydroxymethylfurfural over H4SiW12O40/MCM-41
nanospheres for liquid fuel production, Bioresource Technology, 2012, 119, 433-436.
100
[65] P. Lanzafame, D.M. Temi, S. Perathonera, G. Centi, A. Macario, A. Aloise, and G.
Giordano, Etherification of 5-hydroxymethyl-2-furfural (HMF) with ethanol to biodiesel
components using mesoporous solid acidic catalysts, Catalysis Today, 2011, 175, 435–
441.
[66] D.W. Brown, A.J. Floyd, R.G. Kinsman, and Y. Roshan-Ali, Dehydration reactions
of fructose in non-aqueous media, Journal of Chemical Technology and Biotechnology,
1982, 32, 920–924.
[67] L. Bing, Z. Zhang and K. Deng, Efficient One-Pot Synthesis of 5(Ethoxymethyl)furfural from Fructose Catalyzed by a Novel Solid Catalyst, Industrial
and Engineering Chemistry Research, 2012, 51, 15331–15336.
[68] H. G. Wang, T. Deng, Y. Wang, Y. Qi, X. Hou, and Y. Zhu, Efficient catalytic
system for the conversion of fructose into 5-ethoxymethylfurfural, Bioresource
Technology, 2013, 136, 394-400.
[69] B. Lu, Z. Zhang, and K. Huang, Cellulose sulfuric acid as a bio-supported and
recyclable solid acid catalyst for the synthesis of 5-hydroxymethylfurfural and 5ethoxymethylfurfural from fructose, Cellulose, 2013, 20, 2081-2089.
[70] G. A. Kraus and T. Guney, A direct synthesis of 5-alkoxymethylfurfural ethers from
fructose via sulfonic acid-functionalized ionic liquids, Green Chemistry, 2012, 14, 1593.
[71] Y. Yanga, C. Hu, and M. M. Abu-Omar, Conversion of glucose into furans in the
presence of AlCl3 in an ethanol–water solvent system, Bioresource Technology, 2012,
190–194.
[72] B. Liu, Z. Zhang, K. Huang, and Z. Fang, Efficient conversion of carbohydrates into
5-ethoxymethylfurfural in ethanol catalyzed by AlCl3, Fuel, 2013, 113, 625–631.
101
[73] Sh. Saravanamurugan, O. N. Van Buu, and A. Riisager, Conversion of Mono- and
Disaccharides to Ethyl Levulinate and Ethyl Pyranoside with Sulfonic AcidFunctionalized Ionic Liquids, ChemSusChem, 2011, 6, 723–726.
[74] M. Mascal and E. B. Nikitin, Dramatic Advancements in the Saccharide to 5(Chloromethyl)furfural Conversion Reaction, ChemSusChem, 2009, 2, 859–861.
[75] M. Mascal and E. B. Nikitin, Towards the Efficient, Total Glycan Utilization of
Biomass, ChemSusChem, 2009, 2, 423–426.
[76] M. Mascal and E. B. Nikitin, High-yield conversion of plant biomass into the key
value-added feedstocks 5-(hydroxymethyl)furfural, levulinic acid, and levulinic esters via
5-(chloromethyl)furfural, Green Chemistry, 2010, 12, 370–373.
[77] G. J. M. Gruter and L. E. Manzar, Hydroxy methyl furfural ethers from sugars or
HMF and mixed alcohols, US Patent, 2010, 0058650.
[78] Z. Zhang and Z. K. Zhao, Microwave-assisted conversion of lignocellulosic biomass
into furans in ionic liquid, Bioresource Technology, 2010, 101, 1111-1114.
[79] M. E. Zakrzewska, E. Bogel-Lukasik, and R. Bogel-Lukasik, Ionic Liquid-Mediated
Formation of 5-HydroxymethylfurfuralsA Promising Biomass-Derived Building Block,
Chemical Reviews, 2011, 111, 397-417.
[80] W. Partenheimer and V. V. Grushin, Synthesis of 2,5-Diformylfuran and Furan-2,5Dicarboxylic
Acid
by
Catalytic
Air-Oxidation
of
5-Hydroxymethylfurfural.
Unexpectedly Selective Aerobic Oxidation of Benzyl Alcohol to Benzaldehyde with
Metal Bromide, Catalysts Advanced Synthesis & Catalysis 2001, 343, 102-111.
102
[81] C. M. de Diego, M. Adrianus Dam, G. J. M. Gruter, Method for the preparation of
2,5-furandicarboxylic acid and for the preparation of the dialkyl ester of 2,5furandicarboxylic acid, US Patent, 2012, 0271060.
[82] C. Moreau, M. N. Belgacem, and A. Gandini, Recent Catalytic Advances in the
Chemistry of Substituted Furans from Carbohydrates and in the Ensuing Polymers,
Topics in Catalysis, 2004, 27, 11-30.
[83] H. P. Benecke, A.W. Kawczak, D. B. Garbark, Reaction product of aromatic
diamine with 2,5-dicarboxylic furan; for polyureas, polyurethanes elastomers; chain
extransion; reaction injection molding; controlling cure time, US Patent, 2008, 0207847.
[84] J. L. King, A. W. Kawczak, H. P. Benecke, K. P. Mitchell, M.C. Clingerman,
Polyester Polyols Derived From 2,5-Furandicarboxylic Acid, and Method, US Patent,
2008, 81883.
[85] B.F. M. Kuster, 5-Hydroxymethylfurfural (HMF). A Review Focusing on its
Manufacture, Starch, 1990, 42, 314-321.
[86] X. Qi, M. Watanabe, T. M. Aida, and R. L. Smith, Jr, Efficient process for
conversion of fructose to 5-hydroxymethylfurfural with ionic liquids, Green Chemistry,
2009, 11, 1327-1331.
[87] C. Carlini, P. Patrono, A. M. R. Galletti, G. Sbrana, and V. Zima, Selective
oxidation of 5-hydroxymethyl-2-furaldehyde to furan-2,5-dicarboxaldehyde by catalytic
systems based on vanadyl phosphate, Applied Catalysis A: General, 2005, 289, 197-204.
[88] C. Moreau, R. Durand, C. Pourcheron, and D. Tichit, Selective oxidation of 5hydroxymethylfurfural to 2,5-furan-dicarboxaldehyde in the presence of titania supported
vanadia catalysts, Studies in Surface Science and Catalysis, 1997, 108, 399-406.
103
[89] C. Liu and C. Wayman, The enhancement of xylose monomer and xylotriose
degradation by inorganic salts in aqueous solutions at 180°C, Carbohydrate Research,
2006, 341, 2550-2556.
[90] D. W. Rackemann and W. O. S. Doherty, The conversion of lignocellulosics to
levulinic acid Biofuels, Bioproducts and Biorefining, 2011, 5, 198–214.
[91] D. M. Alonso, S. G. Wettstein, J. Q. Bond, T. W. Root, and J. A. Dumesic,
Production of Biofuels from Cellulose and Corn Stover Using Alkylphenol Solvents,
ChemSusChem, 2011, 4, 1078-1081.
[92] H. Heeres, R. Handana, D. Chunai, C. Borromeus Rasrendra, B. Girisuta and H. Jan
Heeres, Combined dehydration/(transfer)-hydrogenation of C6-sugars (D-glucose and Dfructose) to γ-valerolactone using ruthenium catalysts, Green Chemistry, 2009, 11, 1247–
1255.
[93] L. Deng, Y. Zhao, J. Li, Y. Fu, B. Liao and Q.-X. Guo, Conversion of Levulinic
Acid
and
Formic
Acid
into
γ-Valerolactone
over
Heterogeneous
Catalysts,
ChemSusChem, 2010, 3, 1172–1175.
[94] D. J. Braden, C. A. Henao, J. Heltzel, C. C. Maravelias and J. A. Dumesic,
Production of liquid hydrocarbon fuels by catalytic conversion of biomass-derived
levulinic acid, Green Chemistry, 2011, 13, 1755–1765.
[95] J. J. Bozell, Connecting Biomass and Petroleum Processing with a Chemical Bridge,
Science, 2010, 329, 522–523.
[96] J. Q. Bond, D. M. Alonso, D. Wang, R. M. West and J. A. Dumesic, Integrated
Catalytic Conversion of γ-Valerolactone to Liquid Alkenes for Transportation Fuels,
Science, 2010, 327, 1110–1114.
104
[97] J.-P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus, L. Clarke and H. Gosselink,
Valeric Biofuels: A Platform of Cellulosic Transportation Fuels, Angew. Chem., Int. Ed.,
2010, 49, 4479–4483.
[98] M. Mascal, S. Dutta, and I. Gandarias, Hydrodeoxygenation of the Angelica Lactone
Dimer, a Cellulose-Based Feedstock: Simple, High-Yield Synthesis of Branched C7–C10
Gasoline-like Hydrocarbons, Angew. Chem. Int. Ed. 2014, 53, 1854 –1857.
[99] D. C. Elliott and J. G. Frye, Oxopentanoic acid, catalytic hydrogenation and ring
opening and withdrawal a hydrogenated product, US Patent, 1999, 5883266.
[100] T. J. Schwartz, A. R. P. van Heiningen and M. C. Wheeler, Energy densification of
levulinic acid by thermal deoxygenation, Green Chemistry, 2010, 12, 1353– 1356.
[101] P. A. Case, A. R. P. van Heiningen and M. C. Wheeler, Liquid hydrocarbon fuels
from cellulosic feedstocks via thermal deoxygenation of levulinic acid and formic acid
salt mixtures, Green Chemistry, 2012, 14, 85–89.
[102] S. W. Fitzpatrick, Production of levulinic acid from carbohydrate-containing
materials, US Patent, 1997, 5608105.
[103] Commercialization of Biofine Technology for levulinic acid production from paper
sludge, Final Technical Report for DOE, BioMetics, Inc., 2002.
[104] B. Girisuta, PhD thesis, University of Groningen, 2007.
[105] B. Girisuta, L. P. B. M. Janssen and H. J. Heeres, A kinetic study on the
decomposition of 5-hydroxymethylfurfural into levulinic acid, Green Chemistry, 2006, 8,
701-709.
105
[106] D. M. Alonso, J. Marcel, R. Gallo, M. A. Mellmer, S. G. Wettstein and J. A.
Dumesic, Direct conversion of cellulose to levulinic acid and gamma-valerolactone using
solid acid catalysts, Catalysis Science and Technology, 2013, 3, 927-931.
106