Remarkable catalytic synergism of alumina, metal salt and solvent for conversion of biomass sugars to furan compounds

Article abstract of DOI:10.1016/j.apcata.2017.01.004

Catalytic conversion of sugars to furan compounds has become an important field in the research area of chemicals production from biomass. Here, a remarkable synergism of transition metal salt, alumina and solvent effectively converted glucose to 5-hydroxymethylfurfural (HMF). Studies showed that the alumina participates in glucose to fructose isomerization, while metal salt and DMSO solvent promote fructose dehydration to HMF. This system can work for upto 50?wt% concentration of substrate giving 52% HMF yield. This system can also convert different hexose (including disaccharides and starch) sugars to HMF and pentose sugars to furfural. In terms of HMF yield and stability, this system showed tolerance to the presence of water (upto 15?wt%). Further, oxidized products of HMF showed high solubility in DMSO (45?wt% for 2,5-diformylfuran and 55?wt% for 2,5-furandicarboxylic acid), and they were precipitated out when water was added. These studies promise this sytem as efficient for production of HMF and its further conversions.

Full text of DOI:10.1016/j.apcata.2017.01.004

Accepted Manuscript
Title: Remarkable catalytic synergism of alumina, metal salt
and solvent for conversion of biomass sugars to furan
compounds
Author: <ce:author id="aut0005"
author-id="S0926860X17300042-
5b29e22ecd27983e97f4c142065b00ed"> Gajula
Sampath<ce:author id="aut0010"
author-id="S0926860X17300042-
f0344fb6d9fe5054403f82ca768a8c63"> Kannan
Srinivasan
PII:
S0926-860X(17)30004-2
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2017.01.004
APCATA 16115
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24-12-2016
6-1-2017
Please cite this article as: Gajula Sampath, Kannan Srinivasan, Remarkable
catalytic synergism of alumina, metal salt and solvent for conversion
of biomass sugars to furan compounds, Applied Catalysis A, General
http://dx.doi.org/10.1016/j.apcata.2017.01.004
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Remarkable catalytic synergism of alumina, metal salt and solvent for conversion of
biomass sugars to furan compounds
Gajula Sampath and Kannan Srinivasan*
Inorganic Materials and Catalysis Division, CSIR-Central Salt and Marine Chemicals
Research Institute, Council of Scientific and Industrial Research (CSIR), GB Marg,
Bhavnagar - 364 002, India
Academy of Scientific and Innovative Research, Central Salt and Marine Chemicals Research
Institute, GB Marg, Bhavnagar-364 002, India
*Manuscript Correspondence:
Prof. Dr. Kannan Srinivasan
Inorganic Materials and Catalysis Division
CSIR-Central Salt and Marine Chemicals Research Institute
Council of Scientific and Industrial Research (CSIR)
Bhavnagar - 364 002
India
Tel: +91-278-2567760 Ext. 7030
FAX: +91-278-2567562
E-mail: skannan@csmcri.org ; kanhem1@yahoo.com
Graphical abstract
1

Highlights:
 Metal salt, alumina, and DMSO together synergistically converted glucose to HMF
 Alumina isomerizes glucose to fructose, and CuCl2 & DMSO convert fructose to
HMF
 The system can work for up to 50 wt% concentrations and for different sugars
 System can tolerate water, and promises the use of industrial sugar syrups
Abstract
Catalytic conversion of sugars to furan compounds has become an important field in
the research area of chemicals production from biomass. Here, a remarkable synergism of
transition metal salt, alumina and solvent effectively converted glucose to 5-
hydroxymethylfurfural (HMF). Studies showed that the alumina participates in glucose to
fructose isomerization, while metal salt and DMSO solvent promote fructose dehydration to
HMF. This system can work for upto 50 wt% concentration of substrate giving 52% HMF
yield. This system can also convert different hexose (including disaccharides and starch)
sugars to HMF and pentose sugars to furfural. In terms of HMF yield and stability, this
system showed tolerance to the presence of water (upto 15 wt%). Further, oxidized products
of HMF showed high solubility in DMSO (45 wt% for 2,5-diformylfuran and 55 wt% for 2,5-
furandicarboxylic acid), and they were precipitated out when water was added. These studies
promise this sytem as efficient for production of HMF and its further conversions.
Keywords
5-Hydroxymethylfurfural, Dimethylsulphoxide, Synergism, Alumina, Isomerization,
Dehydration
1. Introduction
With diminishing petroleum resources and increasing concerns on its utilization, it
became necessary to look for alternative renewable sources. Besides considering renewables
like solar, wind and H2, “biomass” has its own potential for the production of organic
chemicals that are necessary for our daily life [1]. Among the various platform molecules
2

derivable from biomass, 5-hydroxymethylfurfural (HMF) is a promising intermediate
obtained by acid-catalyzed dehydration of sugar part of the biomass like cellulose and starch.
HMF has diverse applications, as a raw material, such as solvents (e.g. 2,5-dimethylfuran and
2,5-dimethyltetrahydrofuran), polymer precursors (2,5-furandicarboxylic acid (FDCA), 2,5-
diformylfuran (DFF)), fuel additives and for several value-added chemicals [2].
For HMF production, the mostly used substrate is fructose owing to its ease of
selective conversion. However, for practical application, it is necessary to use abundant
glucose as a substrate which can be produced commercially with more than 90% yield by
acid or enzymatic hydrolysis of starch and cellulose which is the most abundant organic
material on Earth. It is worth mentioning here that most of the catalysts used for fructose
dehydration to HMF did not work efficiently for glucose [3]. This was also evidenced when
sucrose was used as substrate wherein only the fructose part was converted to HMF leaving
behind the unconverted glucose [4].
Recently direct conversion of glucose to HMF using chromium salts in ionic liquid
systems (ILs) was reported [5]. The inhibition in HMF selectivity by other metal salts was
due to lack of glucose to fructose isomerization that led to multiple paths forming other
products including mannose, 1,6-anhydroglucose, etc. Many other catalytic systems were also
tried like combination of solid catalysts (Amberlyst-15 as Brønsted acid and hydrotalcite as
Brønsted base catalysts in N,N-dimethylformamide (DMF) with 3 wt% glucose concentration
[6], Amberlyst-70 Brønsted acid Sn-based materials as Lewis acid with 2 wt% glucose), and
2-
2-
as well as bifunctional catalysts (SO4 /ZrO2-TiO2 in a biphasic solvent and SO4 /ZrO2-Al2O3
in dimethylsulphoxide (DMSO) (5 wt% glucose, 423 K) [7]. Recently, updated reviews
covered many catalysts and solvent systems used in the production of HMF and other furan
derivatives [8-10]. In overall, carbohydrate processing to HMF with current systems is
expected to be expensive, have limitations on working at higher concentration of sugars and
devoid of green quotient due to the proficient use of toxic and corrosive catalysts. It is also
necessary that additional processes and catalysts are needed for the subsequent valorisation of
HMF through cascade operations that demand the avoidance of separation and purification
problems [11]. Hence, integrated multistep reaction systems with components that work at
high substrate concentration, low cost, less toxic, easy-to-handle catalysts and solvents which
can be used for subsequent steps without the necessity of separation are desirable.
Normally in chemical reactions, solvents play some important roles. In literature,
DMSO was used as a co-solvent along with ionic liquids or water to improve the HMF yield
[12]. It was observed that it can acts as a promoter or catalyst in the conversion of sugars
3

[13]. Further, it interacts strongly with HMF through solvation, and thereby restricts the
contact of HMF with intermediates and water molecules, preventing the undesired side
reactions [14]. Also, owing to its high solubility for sugars including starch, and the product
HMF, it is possible to conduct reaction even at high substrate concentrations.
In ILs, only Cr-salts showed good selectivity to HMF from glucose, whereas other
salts which gave similar yields from fructose were non-selective when glucose was used at
similar conversions [5]. In another study, various metal salts were tested wherein CuCl2
showed higher selectivity of HMF from fructose while very little selectivity from glucose
compared to CrCl2 while FeCl3 did not show any conversion of glucose [15]. However, it
would be advantageous if Cu and Fe compounds are used which are less toxic, abundant and
also would assist in further steps like oxidation or reduction [16-18]. Lewis acid catalysts are
known for catalysing the isomerization, and Al-based catalysts were reported for
isomerization of glucose to fructose [19]. Among them alumina is a cheap, abundant and
heterogeneous Lewis acid catalyst.
With a hypothesis on the cooperative activity of transition metal salts (FeCl3 or
CuCl2), Al2O3 and DMSO, we combined them with an endeavour for the selective conversion
of glucose to HMF, studied the reactions for up to 50 wt% of substrate concentration.
2. Experimental
2.1 Materials
Alumina (active neutral-150mesh), L-Rhamnose (monohydrate), D-(-)-Arabinose,
[BMIM]Cl (>98%), furfural (>99%) and HMF (>98%) were purchased from Sigma-Aldrich.
D-(+)-Cellobiose (>98%), D-(+)-Galactose (>98%) and D-(+)-Xylose (>98%) were
purchased from Alfa-Aesar. Sucrose (AR), Glucose (Dextrose anhydrous), DMSO (AR), and
DMF (AR) were purchased from sd-fine Chemicals, India.
2.2 Reaction procedure
Reactions were carried out in a 25 ml round bottomed screw cap tube with magnetic
stirring in a preheated oil bath (on Schott hot plate) set at reaction temperature. For a typical
reaction, first 3 g of solvent was taken in a reactor tube and was pre-heated until the desired
reaction temperature was achieved. Then 0.9 g of substrate (30wt%), and catalysts were
added and stirred at 800 rpm for a specified reaction time. The weight percentage of substrate
indicated is with respect to the amount of solvent [(substrate/solvent) x 100]. After the
4

reaction, tube was taken out and cooled to room temperature. The reaction mixture samples
were stored in a refrigerator at 4 oC before the analysis.
2.3 Analytical methods
Quantification of reactant and products was done with X-bridge amide column using
UHPLC (Shimadzu-Nexera) system linearly connected to Photo diode array (PDA) and
evaporative light scattering detector (ELSD) detectors. Sample for analysis was prepared by
diluting the reaction mixture in water, followed by filtering through a 0.25 µm pore-size
syringe filter. Acetonitrile-water mixture of 0.2 wt% triethylamine was used as mobile phase
°
at 1 ml/min flow rate and keeping the column temperature at 35 C. The method was set with
constant change of the mobile phase mixture from 80:20 to 60:40 that reached in 13 min and
then a constant ratio of 80:20 was maintained for 7 min to stabilize to the initial ratio for the
analysis of the next sample. The sugars were quantified using ELSD (conditions: spray
o
o
chamber (SC) temperature 20 C, drift tube (DT) temperature 45 C and N2 carrier pressure
50 psi). HMF and furfural were quantified by PDA detector at 284 and 260 nm respectively.
Quantification was done based on calibration method using standards.
For all the compounds, standard solutions were made and calibration graphs were
drawn for computing the conversion and yield. After plotting the calibration graphs, and
getting the amount of substance, the following equations were used for calculation.
2.4 Catalyst characterization
Recyclability of alumina was checked by separating the alumina after reaction by
centrifugation, then washing twice with DMSO and used for the reaction by taking fresh
o
DMSO, CuCl2 and substrate. After 4th use, alumina was calcined at 550 C for 6 h and used
for next cycle.
For determination of carbon content on used alumina after each use, the alumina was
washed two times with 2 ml of DMSO, and then 3 times with 5 ml of MeOH, followed by
drying in oven. Carbon content was determined by CHNS elemental analysis using
Elementor’s Vario Microcube instrument.
5

To analyse the acid sites on alumina of both fresh and the calcined form of used
catalyst, pyridine adsorption followed by Diffuse reflectance infrared Fourier transform
(DRIFT) spectroscopic technique analysis was carried out and compared with literature data
[20, 21]. Alumina samples of study were first taken on a watch glass along with 25 ml of
pyridine in a beaker, together were put in a vacuum desiccator, applied vacuum and kept for 1
h. Then pyridine was removed and the physically adsorbed pyridine on sample was removed
by applying vacuum two times. Then DRIFT analysis of the pyridine-adsorbed samples was
conducted using DRIFT spectroscopic investigations were carried out using a Nicolet 5PC
spectrometer equipped with a COLLECTOR II diffuse reflectance mirror system and a high-
temperature DRIFT spectroscopic cell (Spectra-Tech Inc.) at various temperatures (25, 150,
o
o
250, 350 and 450 C). The data received at 150 C showed clear bands, hence the acidity of
all the samples was compared by using this data.
For the determination of pore volume of alumina samples, the washed sample was
o
first dried in oven at 100 C for 2 h. After cooling to room temperature, water was slowly
added dropwise until the powder becomes completely wet by capillary action through the
pores. The pore volume was determined by measuring the increase in the weight of the
sample.
3. Results and discussion
3.1 Catalytic synergism
°
Initially reactions were studied at 80 C with 30 wt% glucose in DMSO solvent using
CuCl2 and alumina as catalysts separately. As shown in Table 1, independently both the
catalysts did not give any HMF yield from glucose, and on the contrary the combination of
these two catalysts formed HMF. It was also observed that in the presence of only alumina,
formation of fructose from glucose was observed, whereas it was not observed in the absence
of alumina or in the presence of CuCl2. It indicates that the alumina is participating in glucose
to fructose isomerization. Mechanistically, both, the ring opening of cyclic form of glucose
(glucopyranose) and the ring-closing of the open-chain form of fructose into fructofuranose
form in the process of isomerization are caused by the hydrogen shift, a reversible reaction as
reported in literature [22]. The individual roles of DMSO and CuCl2 in the conversion of
glucose to HMF were checked by comparing their activity by taking both glucose and
fructose as substrate individually (Table 1). The results indicate that, unlike from glucose,
HMF is formed from fructose in presence of DMSO without any catalyst added. However, In
6

the presence of CuCl2, the yield of HMF increased further. But in the presence of alumina,
both the conversion of fructose and yield of HMF decreased, which may be due to the
reversible isomerization of fructose to glucose. But when CuCl2 is added along with alumina,
conversion of both glucose and fructose increased, which indicates that CuCl2 is promoting
the conversion of sugar towards dehydration step. It was also observed that CuCl2 is
promoting the conversion of fructose towards HMF formation. Thus, the synergic effect of
both CuCl2 and Al2O3 plays a significant role in the conversion of glucose to HMF (Scheme
1).
The yield of HMF from glucose further increased to 56% within short period of time
o
(3 h) by increasing the reaction temperature to 120 C (Table 2, entry 3). In literature,
hydrotalcites were reported for the isomerization of glucose to fructose and was also used in
combination with Amberlyst-15 for direct one-pot conversion of glucose to HMF where
Amberlyst-15 participates in fructose dehydration to HMF [6]. Along this line, Lewis acidic
CuCl2 was combined with Brønsted basic hydrotalcite (MgAl3-CO3-HT); however, this
combination did not show any synergism (Table 2, entry 2). The role of alumina was further
confirmed by conducting the reaction in water medium at similar conditions which resulted in
glucose to fructose isomerization only. In water, although conversion is low (11%), the
selectivity to fructose is very high (>95%) with alumina compared to many other
isomerization catalysts reported [19].
Variation in anion of metal salt was checked by taking CuII salts of different anions
2-
-
(SO4 , NO3 and Cl-). A slightly higher yield was observed with chloride salt (Figure 1),
which is due to the additional influence of chloride ion as reported in literature [23]. The
chlorides of different transition metals with alumina were tested and the activity order is CuII
> FeIII ≈ CrIII > NiII > CoII > ZnII (Table 2). Cu, Fe, and Cr salts showed similarly activity. The
combination of CuCl2 and alumina was tested for the reaction in other solvents which are
commonly reported for this reaction. [BMIm]Cl supported this catalytic combination similar
to the DMSO for the yield of HMF (Figure 2). But water and DMF solvents were inactive for
HMF yield.
DMSO or IL, alumina, and metal salt are all together synergistically working as a
catalytic system, and in the absence of any one of these components, the yield of HMF is
poor.
3.2 HMF synthesis from other substrates
The combination of CuCl2, alumina, and DMSO was applied for other sugar
7

substrates also. This catalytic system successfully converted fructose, galactose, cellobiose
and sucrose into HMF (Table 3). Also, it converted pentose sugars to furfural. As this system
is non-Brønsted acidic in nature, it did not hydrolyze the starch polymer to glucose and hence
no further conversion to HMF was observed (Table 3, entry 6). However, by adding small
amount of Brønsted acid (0.02 mmol H2SO4), the reaction was initiated upon glucan polymer
hydrolysis and 26% yield of HMF was achieved (Table 3, entry 7). The added acid alone was
ineffective to produce HMF (Table 3, entry 8). On the other hand, without adding any acid,
disaccharides (sucrose and cellobiose) were converted into HMF with similar yields as that of
their monomers (Table 3, entry 4 and 5).
3.3 Reaction kinetics and stability of HMF
Kinetic experiments under similar conditions revealed that, upon increasing the
°
reaction temperature from 100 to 120 C, the required time to get maximum HMF yield
°
decreased by 6 times, and by increasing from 120 to 140 C the required time decreased by 3
times. However, irrespective of the temperature, the maximum achievable yield was same
(56±2%). The reaction was scaled up to 10 times of substrate, solvent and catalysts (9 g
glucose, 30 g DMSO, 3 g alumina, 0.5 mmol CuCl2) under the similar conditions as
o
mentioned in Table 2, Entry 3 (120 C, 3 h), and no change in HMF yield (56%) was
observed. Reaction at higher glucose concentration (50 wt% with respect to DMSO) was
°
carried out at 140 C. The HMF yield is 52% indicating no significant loss in the efficiency
this catalytic system even at high substrate concentration. The lesser yields for this reaction,
in particular at high sugar concentration, are common due to unidentified side-products [5],
humins and soluble polymers formation by reaction intermediates [24]. We propose that the
yields can be further improved by using appropriate co-solvents.
Normally, the presence of water decreases the HMF yield as HMF is less stable at
higher temperatures and in aqueous medium [25]. To examine the negative influence,
deliberate addition of water to the solvent was performed. Yield of HMF from glucose did
not decrease with up to 15 wt% of water in DMSO (Table 3, Entry 1). This may be due to the
holding of water molecules by DMSO to a certain limit (here 15 wt%) to avoid the contact of
water with intermediates and products. This result is encouraging as this catalytic system is
amenable when the real industrial aqueous sugar syrups are used. Here, the stability of HMF
in the reaction system was assessed by first taking 100 mg of HMF in 3 g DMSO and stirred
°
at 120 C for 3 h. To that, 200 L water was added and stirred for 2 h. After that 0.3 g
8

alumina and 0.1 mmol CuCl2 were added and stirred for another 2 h. No variation in HMF
content was noted in all these cases indicating its stability under the reaction conditions. The
stability HMF is due to its strong interaction with DMSO that further avoids the contact of
HMF with reactant, intermediates, and water as reported in literature [14]. In literature it was
also was reported that metal salts enhance the stability of HMF [5]. The limit in maximum
yield of HMF may be due to high reactivity of HMF with reaction intermediates which leads
to polymerization [24].
3.4 Recyclability of alumina
After the reaction, the alumina was recovered by centrifugation and tested for its
o
recycle efficiency by adding along with fresh CuCl2 under the optimized conditions (120 C
using 30 wt% glucose). A gradual decrease in the yield of HMF with reuse of alumina was
observed over four cycles (Table 4). It is due to blocking of active sites of alumina by
condensed polymers formed during the reaction. This reason was supported by the increase in
the intensity of brown color as supported from carbon content on the alumina with recycles
(3.2 to 3.5 from 1st to 4th use) measured by CHNS analysis and the color change of alumina
from white to brown after first use and gradual increase in intensity of brown color upon
recycles (Table 4). DMSO or MeOH washings could not remove the adsorbed polymers;
°
however, upon calcination at 550 C for 6 h turned the color to white indicating the removal
of polymers, and the catalytic activity was nearly restored, giving 48% yield.
Pyridine adsorption studies with DRIFT spectroscopy analysis was carried out for
both fresh alumina, alumina used up to 4th cycle, and calcined form of used alumina samples.
Fresh alumina showed the bands at 1542, 1650 and 1485 cm-1 which indicate Bronsted
acidity and a band at 1446cm-l region which indicates Lewis acidity (Fig. 3). On the contrary,
used alumina showed no such bands indicating the acid sites were blocked due to deposition
of polymeric products. However, upon calcination of the used alumina, the corresponding
bands of the acid sites reappeared indicating that the catalytic sites were regained by the
removal of polymers. The absence of shift in these bands for both the samples indicates that
there is no change in nature and strength of acid sites. However when the bands
corresponding to the Lewis and Bronsted acid sites were compared, a change in the ratio of
these sites upon calcination was observed. This could probably due to a decrease in number
of hydroxyl groups upon calcination. This change is probably be responsible for the variation
in the HMF yield.
9

The pore volume analysis was assessed for the alumina samples to see any textural
variations occur upon reuses or calcination. All the samples showed similar pore volume in
the range of 0.73±0.02 ml/g (Table 4) which showed insignificant change in structural
porosity upon recycles and upon calcination, suggesting that the porosity is not a factor for
this variation in activity.
3.5 Scope for the conversion of HMF to DFF or FDCA
It was reported that the solubility of FDCA and DFF in both water and acetic acid
medium was very low (around 0.1 wt%) [26]. Although, FDCA solubility can be improved in
aqueous basic medium, it involves neutralization of acid groups on FDCA. Here, we checked
separately the solubility of these compounds in DMSO, and it showed a significant solubility
for both FDCA (55 wt%) and DFF (45 wt%). It is worth mentioning here that DMSO is
explored as a solvent for the oxidation of HMF to DFF and FDCA in literature [16]. Further
we checked the separation possibility of these compounds from DMSO by adding water to
the product mixture. Just by adding small amount of water (20 wt%), both DFF and FDCA
precipitated out from solvent as white solid (Figure 4). Thus, albeit having the problem in
separating HMF from DMSO [27], the very high solubility of FDCA and DFF in DMSO and
separation (by adding water) will allow one to use this solvent for further reactions of HMF at
high concentrations.
The factors like, high stability of HMF, separation possibility for oxidized furan
derivatives from DMSO, redox catalytic nature of metal compounds and cooperative nature
of alumina create newer opportunities to study subsequent reactions in one-pot leading to
commercially useful products [28]. We believe this system can be improved further through
detailed investigations like using co-solvents & co-catalysts, reaction optimization, chemical
engineering, modification of catalysts, etc.
4. Conclusions
The synergism of a metal salt, alumina and DMSO was observed for the efficient
conversion of glucose to HMF in high yields even at high glucose concentration (52% HMF
yield at 50 wt% concentration of glucose in DMSO solvent with combination of CuCl2 and
alumina). The activity studies showed that the alumina participates in glucose to fructose
isomerization, while CuCl2 & DMSO involve in fructose dehydration to HMF. This catalytic
system can convert various hexose and pentose sugars to HMF and furfural respectively. The
tolerance of this system to the presence of water for up to 15% allows the use of industrial
10

sugar solutions. The high solubility of FDCA (55 wt%) and DFF (45 wt%) in DMSO and
their precipitation by adding water gives an opportunity for this system to be used for further
conversions of HMF. Further investigations of the system might assist in improving the
performance of this system.
Acknowledgements
CSIR-CSMCRI Communication No. 028/2015. Authors thank CSIR, New Delhi for
financial support under the project OLP-0031. G.S. thanks University Grants Commission,
New Delhi for a Senior Research Fellowship. The authors thank Analytical Division and
Centralized Instrument Facility for instrumental support.
11

References
[1] P.N.R. Vennestrøm, C.M. Osmundsen, C.H. Christensen, E. Taarning, Angew. Chem.
Int. Ed. 50 (2011) 10502-10509.
[2] C. Moreaua, M. N. Belgacemb, A. Gandini, Topics Catal. 27 (2004) 1-4.
[3] A.A. Rosatella, S.P. Simeonov, R.F.M. Frade, C.A.M. Afonso, Green Chem. 13 (2011)
754-793.
[4] C. Carlini, M. Giuttari, A.M.R. Galletti, G. Sbrana, T. Armaroli, G. Busca, Appl. Catal.
A: Gen. 183 (1999) 295-302.
[5] H. Zhao, J.E. Holladay, H. Brown, Z.C. Zhang, Science 316 (2007) 1597-1600.
[6] J. Tuteja, S. Nishimura, K. Ebitani, Bull. Chem. Soc. Japan 85 (2012) 275-281.
[7] J. Zhang, L. Lin, S. Liu, Energy Fuels 26 (2012) 4560-4567.
[8] R.J. van Putten, J.C. van der Waal, E. de Jong, C.B. Rasrendra, H.J. Heeres, J.G. de
Vries, Chem. rev. 113 (2013) 1499-1597.
[9] T. Wang, M.W. Nolte, B.H. Shanks, Green Chem. 16 (2014) 548-572.
[10] S.P. Teong, G. Yi, Y. Zhang, Green Chem. 16 (2014) 2015-2026.
[11] A.I. Torres, P. Daoutidis, M. Tsapatsis, Energy Environ. Sci. 3 (2010) 1560-1572.
[12] Q. Bao, K. Qiao, D. Tomida, C. Yokoyama, Catal. Commun. 9 (2008) 1383-1388.
[13] A.S. Amarasekara, L.D. Williams, C.C. Ebede, Carbohydr. Res. 343 (2008) 3021-3024.
[14] G. Tsilomelekis, T.R. Josephson, V. Nikolakis, S. Caratzoulas, ChemSusChem 7 (2014)
117-126.
[15] E.A. Pidko, V. Degirmenci, E.J.M. Hensen, ChemCatChem 4 (2012) 1263-1271.
[16] G.A. Halliday, R.J. Young, V.V. Grushin, Org. Lett., 5 (2003) 2003-2005.
[17] L. Ngoc-Thuc, P. Lakshmanan, K. Cho, Y. Han, H. Kim, Appl. Catal. A:Gen, 464
(2013) 305-312.
[18] Y. Liu, M.A. Mellmer, D.M. Alonso, J.A. Dumesic, ChemSusChem 8 (2015) 3983-
3986.
[19] A.A. Marianou, C.M. Michailof, A. Pineda, E.F. Iliopoulou, K.S. Triantafyllidis, A.A.
Lappas, ChemCatChem 8 (2016) 1100-1110.
[20] E.P. Parry, J. Catal. 2 (1963) 371-379.
[21] C.B. J. Billingham, J. Yarwood, Clay Minerals 31 (1996) 513-522.
[22] V. Choudhary, A.B. Pinar, R.F. Lobo, D.G. Vlachos, S.I. Sandler, ChemSusChem 6
(2013) 2369-2376.
[23] J.B. Binder, R.T. Raines, J. Am. Chem. Soc. 131 (2009) 1979–1985.
12

[24] X. Hu, S. Kadarwati, S. Wang, Y. Song, M.D.M. Hasan, C.Z. Li, Fuel Process.
Technol. 137 (2015) 212-219.
[25] G. Tsilomelekis, M.J. Orella, Z. Lin, Z. Cheng, W. Zheng, V. Nikolakis, D.G. Vlachos,
Green Chem. 18 (2016) 1983-1993.
[26] M.A. Lilga, R.T. Hallen, M. Gray, Topics Catal. 53 (2010) 1264-1269.
[27] J. Wang, J. Ren, X. Liu, G. Lu, Y. Wang, Aiche Journal 59 (2013) 2558-2566.
[28] Y. Roman-Leshkov, C.J. Barrett, Z.Y. Liu, J.A. Dumesic, Nature 447 (2007) 982-985.
13

Figure Captions:
Anion variation study of CuII salts with alumina (0.9 g glucose (30 wt%), 0.3 g
Figure 1
Al2O3, 0.05 mmol copper salt, 3 g DMSO, 120 °C, and 3 h)
Solvent variation study (0.9 g glucose (30 wt%), 0.3 g Al2O3, 0.05 mmol CuCl2, 3
g solvent, 120 °C, and 3 h)
Figure 2
Pyridine adsorption DRIFT-IR spectra of fresh alumina and calcined used alumina
The separation of FDCA or DFF from DMSO
Figure 3
Figure 4
Scheme 1
Conversion of glucose to HMF in DMSO with alumina and metal salt
14

Fig.1
15

Fig.2
16

Fig.3
17

Fig.4
18

Scheme.1
19

Table 1 Glucose/fructose conversion to HMF with different catalyst components
Catalyst
No catalyst
CuCl2
Glucose conv. HMF yield Fructose yield
5
0
0
0
9
0
72
19
0
Al2O3
0
CuCl2+Al2O3 62
20
Fructose conv. HMF yield Glucose yield
Blank
CuCl2
Al2O3
72
38
61
0
0
0
0
0
100
30
CuCl2+Al2O3 83
42
o
0.9 g substrate (30 wt%), 3 g solvent, 80 C, 18 h; Amount of Al2O3 is 0.3 g, CuCl2 is 0.05
mmol
Table 2 Glucose to HMF over different catalytic combinations
Entry Metal salt 2nd catalyst HMF yield
(0.1mmol) (0.3 g)
(%)
[a]
1
2
3
4
5
6
7
8
9
CuCl2
CuCl2
CuCl2
FeCl3
CrCl3
NiCl2
CoCl2
MnCl2
ZnCl2
-
09
Hydrotalcite 0
Al2O3
Al2O3
Al2O3
Al2O3
Al2O3
Al2O3
Al2O3
56
51
49
35
30
21
13
°
0.9 g glucose (30 wt%), 3 g DMSO solvent, 120 C, 3 h. [a]higher amount of CuCl2 (0.6
mmol) was used
20

Table 3 Production of HMF and furfural from different substrates[a]
Entry Substrate
HMF yield
1
2
3
4
5
6
7
8
Glucose[b]
Fructose
Galactose
Cellobiose
Sucrose
Starch[c]
Starch[d]
Starch[d][e]
Pentoses
Rhamnose
Xylose
57
67
33
52
64
0
26
3
Furfural yield
9
31
20
21
10
11
Arabinose
[a]0.9 g substrate (30 wt%), 0.3 g Al2O3, 0.05 mmol CuCl2, 3 g DMSO, 120 °C, 3 h; [b]0.45 g
water was added; [c]20 mg water was added to initiate hydrolysis; [d]20 L 1M H2SO4 (0.02
mmol of H2SO4) was added; [e]without Al2O3 and CuCl2 added
Table 4 Recyclability of alumina
Reuse of Glucose
HMF
Alumina Carbon content
Pore volume
alumina
conversion yield
(%)
after use on alumina after (ml/g)
use (wt%)
0.74
Fresh
alumina
1st use
100
90
59
21
3.2
3.3
0.75
0.75
2nd use
3rd use
4th use
88
15
08
48
3.4
3.5
0.70
0.71
0.74
89
100
After
calcination
0.9 g glucose (30 wt%), 0.3 g alumina, 0.05 mmol CuCl2, 3 g DMSO solvent, 120 °C, 5 h.
21