Synthesis of furfural from d-xylose and corncob with chromium chloride as catalyst in biphasic system

Article abstract of DOI:10.14233/ajchem.2014.17333

An efficient process was developed for the conversion of D-xylose into furfural with chromium chloride as catalyst in a biphasic system. The optimal furfural yield of 38.76 % was obtained in the following reaction conditions: reaction temperature 140 °C, reaction time 1 h and the catalyst loading 2 mmol. Sodium chloride used as co-catalyst was found to affect the furfural yield. A higher furfural yield of 52.55 % was achieved in the presence of 3 g of sodium chloride when using chromium chloride catalyst for the dehydration of D-xylose into furfural. The CrCl3·6H₂O-NaCl catalytic system could be recycled and its stable activity was showed after three successive runs. Moreover, this work also provided useful information for the production of furfural from biomass. The furfural yield of 23.88 % was achieved when corncob used as starting materials.

Full text of DOI:10.14233/ajchem.2014.17333

Asian Journal of Chemistry; Vol. 26, No. 6 (2014), 1717-1720
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17333
Synthesis of Furfural from D-Xylose and Corncob with
Chromium Chloride as Catalyst in Biphasic System†
1
1,2,*
2
2
YE ZHANG , MINGQIANG CHEN , JUN WANG and QINGSONG HU
1
2
School of Earth Science and Environmental Engineering, Anhui University of Science and Technology, Huainan 232001, P.R. China
School of Chemical Engineering, Anhui University of Science and Technology, Huainan 232001, P.R. China
*
Corresponding author: Fax: +86 554 6668742; E-mail: mqchen@aust.edu.cn
Published online: 10 March 2014;
AJC-14875
An efficient process was developed for the conversion of D-xylose into furfural with chromium chloride as catalyst in a biphasic system.
The optimal furfural yield of 38.76 % was obtained in the following reaction conditions: reaction temperature 140 ºC, reaction time 1 h
and the catalyst loading 2 mmol. Sodium chloride used as co-catalyst was found to affect the furfural yield. A higher furfural yield of
52.55 % was achieved in the presence of 3 g of sodium chloride when using chromium chloride catalyst for the dehydration of D-xylose
into furfural. The CrCl ·6H O-NaCl catalytic system could be recycled and its stable activity was showed after three successive runs.
3
2
Moreover, this work also provided useful information for the production of furfural from biomass. The furfural yield of 23.88 % was
achieved when corncob used as starting materials.
Keywords: D-Xylose, Furfural, Hydrolysis reaction, Chromium chloride, Co-catalyst, Biphasic system.
hydrolysis and subsequent dehydration of the obtained pentose
using mineral acids as catalyst in aqueous media. However,
the mineral acids are limited for corrosion, safety problems
INTRODUCTION
With petroleum resources declining and environmental
5
6
concerns rising, the production of energy and chemicals from
renewable biomass has become an intense topic of applied and
basic research. Especially, the production of furfural becomes
one of the focal point of comprehensive utilization of biomass
resource. Furfural, containing a furan ring and an aldehyde
group, is envisaged as a potential platform chemical for the
and critical reaction conditions.Additionally, H PO
3
4
, HCOOH
7
COOH used as catalyst were reported. Recently, chlo-
and CH
3
rides in ionic liquid used as catalysts for furfural production is
becoming a hot topic. Binder studied the production of furfural
from xylose in 1-butyl-3-methylimidazolium chloride
3
([BMIM]Cl) using CrCl as a catalyst and achieved an furfural
1
8
biofuels, bio-based chemicals and biopolymer industries .
yield of 56 % by holding the system at 100 ºC for 4 h . In
subsequent studies, zhang reported a considerable furfural
Furfural is mainly used as a solvent for the refining of lubri-
cating oils and diesel fuels and as an intermediate chemical in
the manufacturing of industrial solvents, such as tetrahydrofuran
3 2
yield of 84.8 % from xylan by usingAlCl ·6H O in [BMIM]Cl
9
under microwave heating at 170 ºC for 10 s . Although ideal
furfural yields from xylose or xylan have been obtained, the
cost of proposed system is expensive. In addition, the ionic
liquid will produced passivation effect in the sugar dehydration
(
THF), 2-methyltetrahydrofuran (2-MTHF), furfural alcohols,
etc. Other furan derivatives that can be produced from furfural
like furan, 2-methylfuran (MF) are reported as promising biofuel
component. In addition, 2,5-furandicarboxylic acid (FDCA)
has been identified by the US Department of Energy as one of
1
0-12
process . Therefore, a relatively inexpensive, low-toxicity,
high-speed and high-yield system is still necessary. Water has
been proposed as green and ideal reaction solvent. In pure
water, xylose dehydration is generally nonselective, leading
to many by-products besides furfural. To overcome side reactions,
the application of biphasic system (using organic solvents as
extraction solvent) has recently been proposed. In this study,
2
-4
1
2 top value-added chemicals .
Furfural production is based on the chemical conversion
of monosaccharide (xylose). Industrial furfural production is
based on the pentosan-containing lignocellulosic materials
(
corncob, wheat straw, rice straw, oat hulls and bagasse)
†Presented at The 7th International Conference on Multi-functional Materials and Applications, held on 22-24 November 2013, Anhui
University of Science & Technology, Huainan, Anhui Province, P.R. China

1
718 Zhang et al.
Asian J. Chem.
a one-pot production of furfural from xylose over CrCl ·6H
3
2
O
six different metal chlorides (CrCl ·6H
3
2 3 2
O, AlCl ·6H O,
catalyst in toluene/water solvent was reported. The effects of
reaction temperature, reaction time, catalyst loading and NaCl
loading were investigated to optimize the process.
CuCl ·2H O, FeCl , CoCl ·6H O, ZnCl ) and the results were
2
2
2
3
2
2
summarized in Table-1. Compared to the absence of catalyst,
all six metal chlorides could promote the conversion of D-
xylose into furfural. Only CrCl
The yield of 38.76 % was achieved within 1 h while the conver-
sion of xylose was 92.07 %. Other catalysts, such as ZnCl
CoCl ·6H O, had no obvious catalytic activities in the conver-
sion of xylose and gave the furfural yields less than 1 %. How-
ever, when FeCl , CuCl ·2H O, AlCl ·6H O were used, the
3 2
·6H O showed superior results.
EXPERIMENTAL
2
,
D-Xylose (98 %), furfural, phloroglucinol were purchased
from Aladdin. Toluene and hydrochloric acid were obtained
from Huainan Chemical Reagent Co. Ltd. and glacial acetic
2
2
3
2
2
3
2
acid, NaCl, CrCl ·6H
3
2 3 2 2 2 3
O, AlCl ·6H O, CuCl ·2H O, FeCl ,
furfural yield was improved to a certain degree, with final
furfural yield ranging from 3.77-15.74 % and conversion of
CoCl ·6H O, ZnCl were purchased from Sinopharm Chemical
2
2
2
Reagent Co. Ltd. All the reagents were used as received.
Conversion of D-xylose: The conversion of D-xylose was
performed in a homemade small reactor. In a typical experi-
ment, a reactor was charged with D-xylose (0.75 g, 5 mmol),
3 2
xylose ranging from 48.36-71.57 %. In short, CrCl ·6H O was
found to be much more effective for conversion of xylose.
This result might be because that stronger Lewis acidity of
3+
Cr not only lowered the barrier of the isomerization of xylose
to xylulose, but also accelerated the dehydration of xylulose
3 2
CrCl ·6H O (0.533 g, 2 mmol), NaCl (3 g), water (20 mL) and
toluene (20 mL). Then closed and paced into the oil bath after
the temperature of thermostatic oil bath rose to the reaction
temperature and kept constant and zero time was taken. All
solutions were mixed at the maximum constant rate using a
magnetic stirrer during the reaction to prevent hot spots. The
reactor was pressurized because of the vapor pressure of the
solution at the reaction temperature used. At the end of the
reaction, the reactor was removed from the oil bath and cooled
to room temperature by flowing cold water.At last, the aqueous
and organic phases were separated, diluted before the analysis.
Analytical methods: The furfural obtained from D-xylose
was detected and quantified by Select Ion Method (SIM) using
a DB-17column (GC-MS, QP5050A). Helium was used as
carrier gas at a flow rate of 1.3 mL/min and the initial column
temperature was 80 ºC for 3 min, followed with a ramp of 10
ºC/min to final temperature of 180 ºC. The temperature of
injection port and detector port were both 200 ºC. Under these
conditions, furfural had a retention time of 3.7 min. The concen-
tration of D-xylose in hydrolyzate was determined by colori-
3 2
to furfural. Thus, the CrCl ·6H O was selected for further
14
assessments .
TABLE-1
EFFECT OF DIFFERENT CATALYSTS ON FURFURAL
a
YIELD AND CONVERSION OF XYLOSE
Entry
Catalyst
No catalyst
CrCl ·6H O
Conversion of xylose (%) Furfural yield (%)
1
2
3
4
5
6
7
4.56
0.07
38.76
15.74
6.76
3.77
0.57
0.54
92.07
71.57
48.36
55.35
17.02
15.02
3
2
AlCl ·6H O
3
2
FeCl3
CuCl ·2H O
2
2
ZnCl2
CoCl ·6H O
2
2
a
Reaction conditions: 5 mmol xylose, 2 mmol catalyst, 20 mL H O, 20
2
mL toluene, 140 ºC, 1 h.
Effect of reaction temperature on conversion of D-
xylose: The reaction conditions were optimized by studying
the effect of reaction temperature, reaction time and the catalyst
loading and NaCl loading on D-xylose conversion and furfural
yield, the results were shown in Table-2.
13
metric method . Firstly, weighed 5 g phloroglucinol reagent
into a 250 mL Erlenmeyer flask and then added 100 mL glacial
acetic acid and 6 mL hydrochloride acid. Make sure the
phloroglucinol reagent completely dissolved. Secondly,
pipetted the 1 mL diluted hydrolyzate into test tube, added 5
mL phloroglucinol solvent and then put them into boiling water
bath for 8 min. At last, the samples were estimated based on
the absorbance at 554 nm using ultraviolet-visible spectro-
photometer. All concentrations of D-xylose and furfural were
calculated based on standard curves constructed by using
authentic samples. All analyses were performed duplicate.
Calculation: The furfural yield and conversion of D-
xylose were calculated by following equations:
Initially, the reaction temperature varied from 100 to 180 ºC
with other conditions remained unchanged (Table-2, entry 1-
5
). The D-xylose conversion increased from 17.7 to 99.13 %
with the reaction temperature increasing, but the furfural yield
at the different reaction temperature was more subtle. The
furfural yield increased from 1.42 to 38.76 by increasing the
reaction temperature from 100 to 140 ºC, then decreased to
2
9.69 and 11.67 % at the temperature of 160 and 180 ºC,
respectively. Fig. 1 showed the furfural yields as a function of
D-xylose conversion at different reaction temperatures. It was
suggested that the dehydration of D-xylose into furfural can
be divided into three stages based on the reaction temperatures.
In the first stage (between 100 and 120 ºC), only a small part
of D-xylose was converted into furfural, with a conversion
rate of 0.28. In the second stage (between 120 and 140 ºC),
the conversion rate increased to 0.61. In the third stage (between
140 and 180 ºC), with D-xylose conversion further increasing,
the furfural yield decreased, for side reactions (cross and
polymerization) causing the loss of furfural during the higher
Moles of furfural producted
Furfural yield =
×100 %
Initial moles of xylose

Moles of xylose unreacted 
Initial moles of xylose
Conversion of xylose = 1−

×100 %



RESULTS AND DISCUSSION
15
temperature . Our results showed that 140 ºC was the best
reaction temperature for the CrCl ·6H O catalyzed conversion
of D-xylose to furfural in toluene/water biphasic system.
Effect of catalyst variation on the conversion of D-
3
2
xylose: In preliminary experiments, D-xylose was treated with

Vol. 26, No. 6 (2014)
Synthesis of Furfural from D-Xylose and Corncob with Chromium Chloride 1719
TABLE-2
VARIATION OF REACTION PARAMETERS IN
CONVERSION OF D-XYLOSE INTO FURFURAL
4
0
0
Reaction time (min)
C
a
A 20
B 40
C 60
D 90
E 120
D
Catalyst Reaction Reaction Conversion Furfural
loading
Entry
temp.
(ºC)
time
(min)
of xylose
(%)
yield
(%)
B
3
(mmol)
1
2
3
4
5
6
7
8
9
2
2
2
2
2
2
2
2
2
2
1
2
3
4
5
100
120
140
160
180
140
140
140
140
140
140
140
140
140
140
60
60
60
60
60
20
40
60
90
120
60
60
60
60
60
17.70
42.45
92.07
99.46
99.13
77.22
88.67
92.07
93.87
97.45
90.69
92.07
99.57
99.47
99.57
1.42
8.44
E
A
38.76
29.69
11.67
20.11
31.06
38.76
35.51
25.83
35.87
38.76
38.56
37.61
36.34
20
10
10
11
12
13
14
15
0
20
40
60
80
100
Xylose conversion (%)
Fig. 2. Furfural yield to D-xylose conversion at different reaction times
a
Effect of catalyst loading on conversion of D-xylose:
Reaction conditions: 5 mmol xylose, 20 mL H O, 20 mL toluene.
2
The effect of catalyst loading was presented in Table-2 (entry
11-15) and the relationship between furfural yield and D-xylose
conversion at different catalyst loading was displayed in Fig. 3.
The results indicated that D-xylose conversion and furfural
yield significantly increased when the catalyst was less than 2
mmol, the furfural yield achieved the maximum value of
4
3
2
1
0
0
0
0
0
Reaction temperature (°C)
C
A 100
B 120
C 140
D 160
E 180
D
38.76 % at the catalyst loading of 2 mmol. However, as the
catalyst loading beyond the 2 mmol, the furfural yield gradually
16
decreased for side reactions converting furfural to humin .
The optimal catalyst loading was 2 mmol.
E
B
Catalyst loading (mmol)
39
38
37
36
A 1
B 2
C 3
D 4
E 5
B
C
A
20
40
60
80
100
Xylose conversion (%)
Fig. 1. Furfural yield to D-xylose conversion at different reaction tempe-
ratures
D
E
Effect of reaction time on conversion of D-xylose: The
reaction time varied from 20 to 120 min (Table-2, entry 6-10)
while the other reaction conditions were kept constant. In the
first 20 min, the D-xylose conversion and furfural yield were
A
77.22 and 20.11 %, respectively. For longer reaction time, the
D-xylose conversion and furfural yield were both increased.
The maximum value of furfural yield was obtained at 1 h.
After 1 h, the furfural yield began to drop but the D-xylose
conversion continued to rise slowly. Fig. 2 showed the relation-
ship between the D-xylose conversion and furfural yield at
different reaction times. The rate of conversion of D-xylose
into furfural was different at different reaction times. In the
first stage (0-20 min), the rate was the lowest (0.26), while in
the second stage (20-40 min), the generation rate increased to
85
90
95
Xylose conversion (%)
100
Fig. 3. Furfural yield plotted as a function of D-xylose conversion at different
catalyst loading
Effect of NaCl loading on conversion of D-xylose: The
effect of salt has been suggested to enhance the partition coeffi-
17
cient of furfural in organic phase . Further studies were done
to optimize the efficiency. Different amounts of NaCl were
added to the aqueous phase (Table-3). The results showed that
the furfural yield achieved to 52.55 % with 3 g NaCl for 1 h at
140 ºC. Compared to the absence of NaCl, the furfural yield
increased 35.58 %. However, a further increasing in the NaCl
loading did not result in better furfural yield, presumably due
to furfural dehydration. Finally, the catalytic stability of
0
.95 and then to 2.26 in the third stage between 40 and 60
min. In the fourth stage (60-120 min), the furfural yield started
to decrease while the D-xylose was further increased and a
linear relationship between D-xylose conversion and furfural
yield was observed. It was suggested that 1 h was the optimum
reaction time at 140 ºC.

1
720 Zhang et al.
Asian J. Chem.
TABLE-3
EFFECT OF NaCl LOADING ON FURFURAL
YIELD AND CONVERSION OF XYLOSE
Conclusion
In this study, a new catalytic system based on the catalyst
CrCl ·6H O with NaCl as co-catalyst has been established for
a
3
2
NaCl loading
Conversion of
xylose (%)
Furfural yiled
(%)
Entry
(
g)
0
1
2
3
4
5
3
3
the efficient conversion of D-xylose into furfural.An excellent
furfural yield of 52.55 % was achieved in following conditions:
reaction temperature 140 ºC, reaction time 1 h, catalyst loading
1
2
3
4
5
6
92.07
95.57
98.48
98.66
97.16
94.95
98.57
97.98
38.76
44.43
47.61
52.55
50.52
48.55
52.88
51.52
2
mmol, NaCl loading 3 g, toluene 20 mL and water 20 mL.
The catalytic system could reuse without significant activity
loss. In addition, when corncob was used as start materials, a
furfural yield of 23.88 % was also obtained.
b
7
c
8
a
ACKNOWLEDGEMENTS
Reaction condition: 5 mmol xylose, 2 mmol CrCl ·6H O, 20 mL H O,
3
2
2
b
0 mL toluene, 140 ºC, 1 h. Entry 7 used recycled CrCl ·6H O-NaCl
2
catalytic system after the fresh catalyst system has been used one time.
3 2
This research was carried out with support of the National
Natural Science Foundation of China (Grant No. 21376007),
the National Key Technology R&D Program of China (Grant
No. 2014BAD02B03) , the Key Project of Fund of Education
Department ofAnhui Province(KJ2012A084) and the Colleges
Natural Science Foundation ofAnhui Educational Committee
of China (Grant No. KJ2013Z074).
c
Entry 8 used recycled CrCl ·6H O-NaCl catalytic system after the
3
2
fresh catalyst system has been used two times.
3 2
CrCl ·6H O-NaCl catalyst system in the biphasic system were
investigated (Table-3, entry 7-8). The results showed that the
furfural yield in toluene reached a steady value for reusing
two times without reducing the catalytic activity of catalyst.
So the NaCl can be used as co-catalyst to increase the furfural
selection.
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mL H O, 20 mL toluene, 140 ºC, 1 h.
2
(
4