Catalytic conversion of cellulose into levulinic acid by a sulfonated chloromethyl polystyrene solid acid catalyst

Article abstract of DOI:10.1002/cctc.201300956

A novel solid acid catalyst, sulfonated chloromethyl polystyrene (CP) resin (CP-SO₃H-1.69), was synthesized by partially substituting chlorine groups (-Cl) of CP resin with sulfonic group(-SO₃H). This new type solid acid contains not only acid sites, but also cellulose-binding sites (-Cl). A high yield of levulinic acid up to 65.5 % was obtained by converting microcrystalline cellulose over CP-SO₃H-1.69. The high catalytic activity of CP-SO₃H-1.69 was attributed to high amount of sulfonic group and chlorine on the catalyst, which is essential to keep the catalyst with great affinity to substrate. Resin-ating results: The chloromethyl polystyrene resin based solid acid CP-SO₃H-1.69 with a high amount of catalytic sites (-SO₃H) was designed and synthesized. Levulinic acid was obtained in 33 % yield by hydrolyzing microcrystalline cellulose over CP-SO ₃H-1.69 in water. Levulinic acid was achieved in a high yield of 65 % with 90wt % γ-valerolactone/10wt % water as the reaction medium.

Full text of DOI:10.1002/cctc.201300956

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DOI: 10.1002/cctc.201300956
Catalytic Conversion of Cellulose into Levulinic Acid by
a Sulfonated Chloromethyl Polystyrene Solid Acid Catalyst
Yong Zuo, Ying Zhang,* and Yao Fu[a]
A novel solid acid catalyst, sulfonated chloromethyl polystyr-
ene (CP) resin (CP-SO3H-1.69), was synthesized by partially sub-
stituting chlorine groups (ÀCl) of CP resin with sulfonic
group(ÀSO3H). This new type solid acid contains not only acid
sites, but also cellulose-binding sites (ÀCl). A high yield of levu-
linic acid up to 65.5% was obtained by converting microcrys-
talline cellulose over CP-SO3H-1.69. The high catalytic activity
of CP-SO3H-1.69 was attributed to high amount of sulfonic
group and chlorine on the catalyst, which is essential to keep
the catalyst with great affinity to substrate.
a hydrogenation product of LA, can be converted into liquid
alkenes ranging from C8 to C24, which could serve as fuel
blendstocks.[39]
Mineral acids, including H2SO4,[37,38,40–47] HCl,[48–51] and
HBr,[52,53] are used as homogeneous catalysts to produce LA
from biomass feedstocks. Among these catalytic systems, in
the Biofine process developed by Biofine Renewables LLC ex-
hibits excellent performance in the production of LA (0.5 kg LA
per kg cellulose).[46,47] The Biofine process is clearly a relatively
economic process for the production of LA. However, this pro-
cess also has some disadvantages because of the use of sulfu-
ric acid, and these disadvantages include the corrosion of
equipment, environmental pollution, difficulties in the separa-
tion of products, and difficulties in the recovery/reuse of the
catalyst.
As the major component of plant biomass and nongrain feed-
stock, cellulose is extensively considered as an ideal raw mate-
rial for the future for the production of biofuels and chemi-
cals.[1] Cellulose is composed of glucose monomer units con-
nected through b-1,4-glycosidic bonds and has a recalcitrant
structure as a result of the existence of large amounts of intra-
and intermolecular hydrogen bonds among the chains of cellu-
lose. These strong bonds provide researchers with a great chal-
lenge on how to effectively convert cellulose into some useful
compounds.[2] In recent years, many catalytic systems, includ-
ing ionic liquids,[3–5] aqueous media,[6,7] biphasic media,[8–10] and
sub- and supercritical fluids,[11,12] have been developed, and
various cellulose degradation products such as glucose[13–17]
5-hydroxymethylfurfural (HMF),[18–20] levulinic acid (LA),[21–23]
5-chloromethylfurfural,[24,25] ethylene glycol,[26–28] propylene
glycol,[29] and sugar alcohols[30–32] have been obtained. Without
underestimating the value of other cellulose degradation prod-
ucts, LA production from cellulose has received significant at-
tention owing to the fact that LA not only has high chemical
reactivity, which makes it suitable for the production of various
organic chemicals, but it also has the potential to serve as
a chemical intermediate in the production of biofuels through
existing petrochemical technologies. For example, in combina-
tion with phenol, LA is a starting material in the synthesis of
diphenolic acid, which has great potential to replace bispheno-
l A.[33,34] Furthermore, some fuel additives such as levulinic
esters,[35] methyltetrahydrofuran (MTHF),[36] and valeric
esters[37,38] can be synthesized from LA. g-Valerolactone (GVL),
To overcome the disadvantages brought by the use of min-
eral acids, some solid acid catalysts were developed in recent
years.[54–57] Wang et al. developed an aqueous catalytic system
for the production of LA from cellulose by using sulfated TiO2
as a catalyst. LA was obtained in 38% yield under the optimal
conditions.[58] Lai et al. designed and synthesized a novel mag-
netic solid acid by modifying sulfonated mesoporous silica
with magnetic iron oxide particles.[22] LA was obtained in 45%
yield by treating amorphous cellulose with magnetic solid acid
at 1508C. Van de Vyver et al. used sulfonated hyperbranched
poly(arylene oxindole)s to hydrolyze ball-milled cellulose into
LA in a yield of 25% at 1708C over 3 h.[59] More recently, Wein-
garten et al. developed a process consisting of two reaction
steps to produce LA from cellulose.[21] Cellulose was first con-
verted into water-soluble compounds, including HMF and glu-
cose, by a noncatalytic hydrothermal decomposition method,
and then the generated water-soluble compounds were fur-
ther converted over Amberlyst 70 to provide LA in 28% yield.
There are many other solid catalysts that are used to produce
LA, including Nafion SAC-13,[60] MCM-20, MCM-41,[61] and
Y-type zeolites.[62]
In this paper, a novel solid acid catalyst with a large amount
of catalytic sites (ÀSO3H) was synthesized by using chlorometh-
yl polystyrene (CP) resin as a catalyst support to hydrolyze mi-
crocrystalline cellulose. The CP resin is a chloromethylation
product of polystyrene–DVB, which is a kind of polymer made
from styrene with divinylbenzene (DVB) as a cross-linking
agent. As shown in Scheme 1, thiourea, the precursor of the
sulfonic group, was introduced to the CP resin by partially sub-
stituting the chlorine atoms of the CP resin. The benzylthiol CP
resin (CP-SH) was obtained by treating the thiourea-substitut-
ed CP resin with 1 n NaOH solution, followed by washing with
water, protonation with 2 n sulfuric acid, and again washing
with water. The final solid acid catalyst CP-SO3H-x (x represents
[a] Y. Zuo, Prof. Y. Zhang, Prof. Dr. Y. Fu
Anhui Province Key Laboratory of Biomass Clean Energy
Department of Chemistry
University of Science and Technology of China
Hefei 230026 (China)
Fax: (+86)551-360-6689
E-mail: zhzhying@ustc.edu.cn
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201300956.
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Scheme 1. Synthesis route to CP-SO3H-x catalysts.
the amount of sulfonic groups, mmolgÀ1) was obtained by oxi-
dizing the mercapto group of CP-SH with 30% H2O2. A detailed
preparation method is given in the Supporting Information.
Thiourea was selected as the precursor of the sulfonic group
as a result of its excellent nucleophilicity, which allows easy
control of the amount of sulfonic groups on the catalyst. For
example, CP-SO3H-1.69 was achieved by treating the CP resin
with an approximate 0.3 stoichiometric amount of thiourea for
0.5 h, such that 39% of the chlorine of the CP resin was substi-
tuted. CP-SO3H-x with different amounts of sulfuric groups
could be synthesized by controlling the reaction conditions. It
was reported that the chloromethyl moiety on the surface of
the catalyst, as an electronegative group, has the ability to
adsorb the oligosaccharides to the catalyst as a result of the
hydrogen bonds that are formed between the chlorine atoms
of the catalyst and the hydroxy groups of cellulose.[17] There-
fore, maintaining a sufficient amount of chlorine and catalytic
sites (ÀSO3H) on the catalyst is essential to synthesize a catalyst
with high catalytic activity.
Figure 1. Temperature dependence of cellobiose conversion by CP-SO3H-
1.69; reaction conditions: cellobiose (100 mg), catalyst (200 mg), water
(2 mL), 5 h.
the result was consistent with the result obtained from theo-
retical calculations (Figure S8 in the Supporting Information).
Cellobiose is a soluble disaccharide consisting of two glu-
cose units linked through a b-1,4-glycosidic bond as cellulose.
As a start, it is a good model compound for cellulose to be
used to evaluate the catalytic activity of CP-SO3H-x. The cata-
lyst tested was CP-SO3H-1.69. Figure 1 shows the temperature
dependence of cellobiose conversion by this catalyst. Cello-
biose was nearly completely converted into glucose (98%)
with small amounts of HMF (0.9%) and LA (0.8%) at 1508C,
which indicates that CP-SO3H-1.69 is active for the cleavage of
b-1,4-glycosidic bond. The yield of LA increased dramatically
from 0.8 to 11% as the temperature was increased from 150 to
1608C, and this was accompanied by a decrease in the yield of
glucose from 98 to 74%, whereas the yield of HMF remained
nearly unchanged. At the same time, all of the generated
humins were deposited on the catalyst, as the reaction solu-
tion was clear, but the color of the catalyst turned from light
yellow to black. The yield of LA further increased to 36.9% by
increasing the temperature to 1708C, and the yield of glucose
decreased to 29.5%. However, the yield of LA did not increase
further at the higher temperature of 1808C, and the yields ob-
tained for both glucose and HMF at 1808C were almost identi-
cal to those obtained at 1708C, which indicates that the cata-
lyst became severely deactivated beyond 1708C. To prove this
point more intuitively, hydrolysis of cellobiose was conducted
at 1708C with a prolonged reaction time of 10 h, and the yield
of levulinic acid increased slightly to 38.2%, whereas the yield
of glucose decreased to 21.2%. Then, to overcome the prob-
lem of catalyst deactivation, the catalyst loading was increased
to supply more active sites. With an increase in the catalyst
loading to 300 mg and an increase in the reaction time to
10 h, LA was obtained in 45.3% yield, and the conversion of
generated glucose from the hydrolysis of cellobiose increased
to 98% at 1708C.
Modification of the functional groups on the CP resin based
catalyst was verified by Fourier transform infrared spectroscopy
(FTIR). The fixation of thiourea on the CP resin was verified by
the broad bands at approximately 3435 (ÀNH2) and 1680 cmÀ1
(ÀC=NH) and a decrease in the intensity of the chloromethyl
band at 1264 cmÀ1 (Figures S1 and S2 in the Supporting Infor-
mation). The IR spectrum of CP-SH is shown in Figure S2 (see
the Supporting Information), and the weak absorption band
observed at 2560 cmÀ1 is characteristic of the mercapto group
(Figure S3 in the Supporting Information). The absorption
À
band at 1039 cmÀ1 is associated with the SO3 stretching
mode in the sulfonic group (Figure S4 in the Supporting Infor-
mation). To further ensure that all of the sulfur in the catalyst
existed in the form of sulfonic acid, X-ray photoelectron spec-
troscopy (XPS) analysis of the samples, including the thiourea-
substituted CP resin and CP-SO3H-1.69, was conducted. As
shown in Figure S6, all of the sulfur in the thiourea-substituted
CP resin is present in the low valence state (164.35 eV). In con-
trast, after oxidation by hydrogen peroxide, all of the sulfur is
present in the high valence state (168.53 eV), and this demon-
strates that all of the mercapto groups were completely oxi-
dized to sulfonic groups (Figure S7 in the Supporting Informa-
tion). The amount of sulfonic groups on CP-SO3H-x was calcu-
lated on the basis of the sulfur content in the catalyst, which
was determined by elemental analysis. Acid–base titration was
also conducted to determine the amount of sulfonic groups
(Table S1 in the Supporting Information). The chlorine content
on the catalyst was analyzed by X-ray fluorescence (XRF), and
To verify whether CP-SO3H-1.69 had affinity to oligosacchar-
ides, adsorption experiments were conducted with cellobiose
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Figure 3. Photograph of hydrolyzing microcrystalline cellulose over CP-SO3H-
1.69 at 160 (left) and 1708C (right).
*
Figure 2. Adsorption curves of cellobiose on CP-SO3H-1.69 ( ) and CP-SO3H-
&
3.06 ( ); reaction conditions: cellobiose (100 mg), catalyst (100 mg), water
(1 mL), room temperature.
calculated on the basis of the weight of unreacted cellulose.
However, upon conducting the reaction at 1708C, a clear solu-
tion was obtained with a 33% yield of LA (Table 1, entry 2),
and the color of the catalyst changed to black. The contrast of
entries 1 and 2 is shown in Figure 3. It can be seen that the
color of the catalyst was light brown if a large amount of cellu-
lose remained unconverted, whereas the catalyst was black if
cellulose was completely converted; this indicates that the
color change of the catalyst was a result of the generated
humins. To verify whether the chloride group on the catalyst
was of great importance in the conversion of cellulose, CP-
SO3H-3.06 was used to hydrolyze cellulose under the same re-
action conditions. It was found that only 11% of cellulose was
converted and 5% of LA (Table 1, entry 3) was obtained, which
demonstrated that retaining a sufficient amount of chlorine in
the catalyst was essential to keep the CP-SO3H-x catalyst active
for the conversion of cellulose into LA. Catalysts with different
SO3H/Cl ratios were also synthesized for cellulose conversion at
1708C, and CP-SO3H-1.69 exhibited the best catalytic per-
formance (Table S3 in the Supporting Information). Besides cel-
lobiose and cellulose, glucose and sucrose (Table 1, entries 4
and 5), two common carbohydrates, could also be converted
into LA efficiently by CP-SO3H-1.69 with yields of 44 and 48%
in aqueous solution, respectively. Recently, Dumesic and co-
workers found that a mixed sol-
as a substrate at room temperature. As shown in Figure 2, ap-
proximately 13% of cellobiose was adsorbed to CP-SO3H-1.69
over less than 0.5 h. This result is in good agreement with the
work reported by Shuai and Pan.[17] CP-SO3H-3.06 was synthe-
sized and studied in the same adsorption experiment under
the same reaction conditions (the FTIR spectrum of CP-SO3H-
3.06 is given in Figure S5). As shown in Figure 2, only approxi-
mately 2% of cellobiose was adsorbed to CP-SO3H-3.06 as
a result of the fact that 75% of the chlorine atoms on the CP
resin was substituted by sulfonic groups. Therefore, keeping
a sufficient amount of chloride groups on the catalyst is essen-
tial to maintain its ability to adsorb cellobiose.
Then, microcrystalline cellulose was selected to further test
the catalytic activity of CP-SO3H-1.69. Scanning electron micro-
scope (SEM), X-ray diffraction (XRD) and gel permeation chro-
matography (GPC) tests were conducted to determine the par-
ticle size, crystallinity, and degree of polymerization of cellulose
(see Figures S10–12 in the Supporting Information). As shown
in Table 1, it was found that most of the cellulose was not con-
verted, and only 5.4% of LA and less than 1% of HMF (Table 1,
entry 1) were detected upon performing the reaction at 1608C.
Unreacted cellulose was easily separated from the catalytic
system by dropper, and then the conversion of cellulose was
vent composed of 90 wt% GVL
Table 1. Hydrolysis of microcrystalline cellulose, glucose, and sucrose by CP-SO3H-1.69.[a]
and 10 wt% water was a great
reaction medium for the produc-
tion of LA from cellulose by
using solid acid catalysts.[63]
Substrate
T [8C]
Conv. [%]
Yield [mol%]
HMF
glucose
LA
4.7
33.1
5.3
44.2
48.5
65.5
1
2
3
4
5
6
cellulose
cellulose
cellulose
glucose
sucrose
160
170
170
170
170
170
10.2
100
11.3
100
100
100
0.8
2.1
ND[b]
ND[b]
ND[b]
ND[b]
0.5
0.8
0.9
0.8
0.7
ND[b]
Therefore,
a
90 wt% GVL/
10 wt% water solution was used
as a reaction medium to hydro-
lyze cellulose over CP-SO3H-1.69
and a high 65% yield of LA was
achieved (Table 1, entry 6). The
high yield of LA was attributed
to the fact that GVL could solu-
cellulose
[a] Reaction conditions: Substrate (100 mg); 10 h; water (2 mL, for entries 1–5) or 90 wt% GVL/10 wt% water
(2 mL, for entry 6); CP-SO3H-1.69 (for entries 1, 2, and 4–6) or CP-SO3H-3.06 (for entry 3), entries 1–3=500 mg,
entries 4–6=300 mg. [b] ND=not detected.
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ure S9 in the Supporting Information). To determine whether
the pore of the catalyst was unplugged, nitrogen adsorption/
desorption isotherms were measured to detect the surface
area, average pore size, and pore volume of the catalysts
(Table S2 in the Supporting Information). No clear changes oc-
curred for any of the above three parameters values before
catalysis and after regeneration, which demonstrates that all of
the humins were removed in this regeneration process. The
catalytic activity of the used catalyst was nearly fully recov-
ered: the yields of LA and glucose were 43 and 3%, respective-
ly. Then, the regeneration process was conducted again to
remove the newly formed humins on the catalyst before it was
recycled again. A result nearly identical to that in the first run
was obtained. These results revealed that the loss of catalytic
activity of the used catalyst was mainly caused by the humins
deposited on the catalyst.
Figure 4. Hydrolysis of cellobiose by fresh CP-SO3H-1.69 (1), used CP-SO3H-
1.69 (2), regenerated CP-SO3H-1.69 (2+H2O2), and again regenerated CP-
SO3H-1.69 (3+H2O2); reaction conditions: catalyst (300 mg), cellobiose
(100 mg), 10 h, 1708C.
In summary, a novel CP resin-based solid-acid catalyst was
synthesized by partially substituting the chlorine atoms of the
CP resin with sulfonic groups. The amount of sulfonic groups
on the catalyst was tunable. In addition, the sulfonic groups,
as Brønsted acid sites, were strong enough in water, as it was
introduced to the catalyst support through steady covalent
bonding. The CP-SO3H-1.69 catalyst effectively converted mi-
crocrystalline cellulose directly into LA in 33% yield in an aque-
ous system at an initial cellulose concentration of 4.8 wt%, and
a high 65% yield of LA was achieved by using 90 wt% GVL/
10 wt% water as the reaction medium. Although the catalyst
was severely deactivated after the reaction, its activity could
be nearly fully recovered simply by stirring the used catalyst in
28.5 wt% H2O2 at 358C overnight. This work presented a new
method to prepare solid acid catalysts. We not only concen-
trated on how to anchor enough acid sites to the catalyst sup-
port, but we also concentrated on choosing the right catalyst
support to ensure easy access of cellulose to the catalytic site
of the catalyst. Future work is needed to find simpler acid site
fixation methods to simplify the preparation process of the
catalyst. In addition, other solid materials with the ability to
adsorb cellulose could be used to prepare solid acid catalysts.
bilize cellulose and, therefore, improve the interaction between
cellulose and the solid acid catalyst.[64]
A recycling experiment of CP-SO3H-1.69 was performed by
hydrolysis of cellobiose. The used CP-SO3H-1.69 catalyst was
easily separated from the catalytic system by filtration, washed
with deionized water (pH of filtrate was 6), and dried at 808C
overnight before it was used in the next run. As seen in
Figure 4, the yield of LA decreased severely from 45 to 12%
with a 62% yield of glucose, which revealed that the catalyst
was deactivated in the hydrolysis of cellobiose. There are two
possible reasons leading to the loss of catalytic activity of
CP-SO3H-1.69:
1) The sulfonic group on the catalyst was leached into the re-
action medium
2) The generated humins that were deposited onto the cata-
lyst resulted in catalyst deactivation.
On the basis of inductively coupled plasma (ICP) spectrosco-
py, only less than 1% of the sulfonic groups was leached into
the reaction medium during the reaction. Therefore, the loss of
catalytic activity of CP-SO3H-1.69 was not mainly caused by sul-
fonic group leaching. With respect to the second reason, a re-
generation process, therefore, was required to remove the
humins deposited onto the catalyst before it was recycled. Re-
cently, Dumesic and co-workers reported an effective regenera-
tion method to remove humins from solid acid catalysts that
could not be calcined at elevated temperatures.[63] The key
procedure of removing humins was to wash the used catalyst
overnight with a H2O2 solution (28.5 wt%) at room tempera-
ture. We raised the temperature of the H2O2 solution to 358C
because of the fact that relatively more humins were generat-
ed and deposited on CP-SO3H-1.69 in our catalytic system than
that reported by Dumesic and co-workers.[63] To our delight,
the humins deposited on the catalyst were removed, and the
color of the used catalyst turned from black to yellow (see Fig-
Experimental Section
All hydrolysis experiments were performed in thick-walled glass
tubes (15 mL, Synthware Glass). The reaction mixture was heated
to the desired temperature by immersion in a thermostatically con-
trolled oil bath under magnetic stirring at 400 rpm.
Acknowledgements
The authors are grateful to the National Basic Research Program
of China (2012CB215305, 2013CB228103), the National Natural
Science Foundation of China (21172209), the Chinese Academy of
Science, and the Fundamental Research Funds for the Central
Universities for the financial support.
Keywords: biomass · cellulose hydrolysis · levulinic acid · solid
acid · sustainable chemistry
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[1] G. W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106, 4044–4098.
[2] A. J. Ragauskas, C. K. Williams, B. H. Davison, G. Britovsek, J. Cairney,
C. A. Eckert, W. J. Frederick, J. P. Hallett, D. J. Leak, C. L. Liotta, J. R. Mie-
lenz, R. Murphy, R. Templer, T. Tschaplinski, Science 2006, 311, 484–489.
[3] F. R. Tao, H. L. Song, L. J. Chou, ChemSusChem 2010, 3, 1298–1303.
[4] M. E. Zakrzewska, E. Bogel-Łukasik, R. Bogel-Łukasik, Energy Fuels 2010,
24, 737–745.
[5] I. T. Horvꢁth, Green Chem. 2008, 10, 1024–1028.
[6] A. Cabiac, E. Guillon, F. Chambon, C. Pinel, F. Rataboul, N. Essayem,
Appl. Catal. A 2011, 402, 1–10.
[33] S. Van de Vyver, J. Geboers, S. Helsen, F. Yu, J. Thomas, M. Smet, W.
Dehaen, B. F. Sels, Chem. Commun. 2012, 48, 3497.
[34] S. Van de Vyver, S. Helsen, J. Geboers, F. Yu, J. Thomas, M. Smet, W.
Dehaen, Y. Romꢁn-Leshkov, I. Hermans, B. F. Sels, ACS Catal. 2012, 2,
2700–2704.
[35] S. W. Fitzpatrick, ACS Symp. Ser. 2006, 921, 271–287.
[36] D. C. Elliott, J. G. Frye, US Pat. 5883266, 1999.
[37] J. -P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus, L. Clarke, H. Gosse-
link, Angew. Chem. 2010, 122, 4581–4585.
[38] J. -P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus, L. Clarke, H. Gosse-
link, Angew. Chem. Int. Ed. 2010, 49,4479–4483.
[39] J. Q. Bond, D. M. Alonso, D. Wang, R. M. West, J. A. Dumesic, Science
2010, 327, 1110 – 1114.
[7] M. Hara, Energy Environ. Sci. 2010, 3, 601–607.
[8] A. I. Torres, P. Daoutidis, M. Tsapatsis, Energy Environ. Sci. 2010, 3, 1560–
1572.
[9] J. N. Chheda, Y. Romꢁn-Leshkov, J. A. Dumesic, Green Chem. 2007, 9,
342–350.
[40] B. Girisuta, L. Janssen, H. J. Heeres, Ind. Eng. Chem. Res. 2007, 46, 1696–
1708.
[10] Y. Romꢁn-Leshkov, J. N. Chheda, J. A. Dumesic, Science 2006, 312, 1933–
1937.
[41] B. Girisuta, PhD thesis, University of Groningen, The Netherlands, 2007.
[42] J. C. Serrano-Ruiz, D. J. Braden, R. M. West, J. A. Dumesic, Appl. Catal. B
2010, 100, 184–189.
[43] ꢂ. Szabolcs, M. Molnꢁr, G. Dibꢃ, L. T. Mika, Green Chem. 2013, 15, 439–
445.
[44] Q. Fang, M. A. Hanna, Bioresour. Technol. 2002, 81, 187–192.
[45] A. A. Efremov, G. G. Pervyshina, B. N. Kuznetsov, Chem. Nat. Compd.
1998, 34, 182–185.
[11] M. Bicker, J. Hirth, H. Vogel, Green Chem. 2003, 5, 280–284.
[12] F. Jin, H. Enomoto, Energy Environ. Sci. 2011, 4, 382–397.
[13] S. Van de Vyver, L. Peng, J. Geboers, H. Schepers, F. de Clippel, C. J.
Gommes, B. Goderis, P. A. Jacobs, B. F. Sels, Green Chem. 2010, 12,
1560–1563.
[14] D. M. Lai, L. Deng, J. Li, B. Liao, Q. X. Guo, Y. Fu, ChemSusChem 2011, 4,
55–58.
[46] S. W. Fitzpatrick, US Pat. 4897497, 1990.
[15] S. Suganuma, K. Nakajima, M. Kitano, D. Yamaguchi, H. Kato, S. Hayashi,
M. Hara, J. Am. Chem. Soc. 2008, 130, 12787–12793.
[16] A. Onda, T. Ochi, K. Yanagisawa, Green Chem. 2008, 10, 1033–1037.
[17] L. Shuai, X. Pan, Energy Environ. Sci. 2012, 5, 6889–6894.
[18] B. Kim, J. Jeong, D. Lee, S. Kim, H.-J. Yoon, Y.-S. Lee, J. K. Cho, Green
Chem. 2011, 13, 1503–1506.
[47] S. W. Fitzpatrick, US Pat. 5608105, 1997.
[48] J. Shen, C. E. Wyman, AIChE J. 2012, 58, 236–246.
[49] L. F. Yan, N. K. Yang, H. Pang, B. Liao, Clean Soil Air Water 2008, 36, 158–
163.
[50] J. Horvat, B. Klaic, B. Metelko, V. Sunjic, Tetrahedron Lett. 1985, 26,
2111–2114.
[19] R. Huang, W. Qi, R. Su, Z. He, Chem. Commun. 2010, 46, 1115 – 1117.
[20] S. Dutta, S. De, A. K. Patra, M. Sasidharan, A. Bhaumik, B. Saha, Appl.
Catal. A 2011, 409–410, 133–139.
[21] R. Weingarten, W. C. Conner, Jr., G. W. Huber, Energy Environ. Sci. 2012,
5, 7559–7574.
[51] B. F. McKenzie, Org. Synth. 1929, 9, 50–51.
[52] J. Y. Cha, M. A. Hanna, Ind. Crops Prod. 2002, 16, 109–118.
[53] I. F. Wiggins, Adv. Carbohydr. Chem. 1950, 4, 306–314.
[54] S. Van de Vyver, J. Geboers, P. A. Jacobs, B. F. Sels, ChemCatChem 2011,
3, 82–94.
[22] D.-M. Lai, L. Deng, Q. X. Guo, Y. Fu, Energy Environ. Sci. 2011, 4, 3552–
3557.
[55] J. A. Geboers, S. Van de Vyver, R. Ooms, B. Op de Beeck, P. A. Jacobs,
B. F. Sels, Catal. Sci. Technol. 2011, 1, 714–726.
[23] H. Lin, J. Strull, Y. Liu, Z. Karmiol, K. Plank, Z. Guo, L. Yang, Energy Envi-
ron. Sci. 2012, 5, 9773–9777.
[24] M. Mascal, E. B. Nikitin, Angew. Chem. 2008, 120, 8042–8044; Angew.
Chem. Int. Ed. 2008, 47, 7924–7926.
[25] M. Mascal, E. B. Nikitin, ChemSusChem 2009, 2, 859–861.
[26] M. Y. Zheng, A. Q. Wang, N. Ji, J. F. Pang, X. D. Wang, T. Zhang, ChemSu-
sChem 2010, 3, 63–66.
[27] N. Ji, T. Zhang, M. Y. Zheng, A. Q. Wang, H. Wang, X. D. Wang, Y. Y. Shu,
A. L. Stottlemyer, J. G. G. Chen, Catal. Today 2009, 147, 77–85.
[28] N. Ji, T. Zhang, M. Y. Zheng, A. Q. Wang, H. Wang, X. D. Wang, J. G. G.
Chen, Angew. Chem. 2008, 120, 8638–8641; Angew. Chem. Int. Ed. 2008,
47, 8510–8513.
[56] H. Kobayashi, H. Ohta, A. Fukuoka, Catal. Sci. Technol. 2012, 2, 869–883.
[57] D. M. Alonso, S. G. Wettstein, J. A. Dumesic, Chem. Soc. Rev. 2012, 41,
8075–8098.
[58] P. Wang, S. Zhan, H. Yu, Adv. Mater. Res. 2010, 96, 183–187.
[59] S. Van de Vyver, J. Thomas, J. Geboers, S. Keyzer, M. Smet, W. Dehaen,
P. A. Jacobs, B. F. Sels, Energy Environ. Sci. 2011, 4, 3601–3610.
[60] J. Hegner, K. C. Pereira, B. DeBoef, B. L. Lucht, Tetrahedron Lett. 2010, 51,
2356–2358.
[61] K. Lourvanij, G. L. Rorrer, J. Chem. Technol. Biotechnol. 1997, 69, 35–44.
[62] J. Jow, G. L. Rorrer, M. C. Hawley, D. T. A. Lamport, Biomass 1987, 14,
185–194.
[63] D. M. Alonso, J. M. R. Gallo, M. A. Mellmer, S. G. Wettstein, J. A. Dumesic,
Catal. Sci. Technol. 2013, 3, 927–931.
[29] Y. Liu, C. Luo, H. C. Liu, Angew. Chem. 2012, 124, 3303–3307; Angew.
Chem. Int. Ed. 2012, 51, 3249–3253.
[30] J. Geboers, S. Van de Vyver, K. Carpentier, P. Jacobs, B. Sels, Chem.
Commun. 2011, 47, 5590–5592.
[64] S. G. Wettstein, D. M. Alonso, Y. Chong, J. A. Dumesic, Energy Environ.
Sci. 2012, 5, 8199–8203.
[31] S. Van de Vyver, J. Geboers, W. Schutyser, M. Dusselier, P. Eloy, E. Dornez,
J. W. Seo, C. M. Courtin, E. M. Gaigneaux, P. A. Jacobs, B. F. Sels, ChemSu-
sChem 2012, 5, 1549–1558.
[32] B. Op de Beeck, J. Geboers, S. Van de Vyver, J. Van Lishout, J. Snelders,
W. J. J. Huijgen, C. M. Courtin, P. A. Jacobs, B. F. Sels, ChemSusChem
2013, 6, 199–208.
Received: November 8, 2013
Revised: December 24, 2013
Published online on February 4, 2014
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ChemCatChem 2014, 6, 753 – 757 757