838
Published on the web July 3, 2010
One-pot Formation of Furfural from Xylose via Isomerization and Successive
Dehydration Reactions over Heterogeneous Acid and Base Catalysts
³
Atsushi Takagaki, Mika Ohara, Shun Nishimura, and Kohki Ebitani*
School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292
(Received April 21, 2010; CL-100386; E-mail: ebitani@jaist.ac.jp)
An efficient furfural formation from xylose, a major pentose
OH
O
O
O
HO
O
Dehydration
Isomerization
OH
OH
OH
in hemicellulose of biomass, was demonstrated using a pair of
solid acid and base in one-pot. High furfural yield was obtained
in polar aprotic solvents including N,N-dimethylformamide
using Amberlyst-15 and hydrotalcite under moderate conditions.
This efficient production of furfural was performed via aldose-
ketose isomerization of xylose to xylulose by solid base and
successive dehydration of xylulose to furfural by solid acid.
OH
- 3H2O
OH
OH
Xylulose
Furfural
Xylose
OH
HO
OH
HO
O
Dehydration
Isomerization
O
HO
O
O
OH
OH
OH
- 3H2O
OH
OH
OH
Fructose
5-(Hydroxymethyl)furfural
Glucose
Production of chemicals and fuels from renewable resources
has received considerable attention.1,2 Lignocellulosic biomass,
the most abundant biomass consists of cellulose (ca. 35-50%),
hemicelluloses (ca. 25-30%), and lignin (ca. 15-30%).1,2
Xylose, a major pentose, is involved as a form of xylan in
hemicelluloses. Furan derivatives such as 5-(hydroxymethyl)-
furfural (HMF) and furfural have great potentials as important
platforms for a variety of chemicals including plastics, poly-
mers, and pharmaceuticals.3-6 They can be obtained by
dehydration of monosaccharides of hexoses (glucose and
fructose) and pentose (xylose). Efficient synthesis of furfural
from xylose is strongly desirable as well as HMF synthesis from
hexoses including glucose and fructose.
Figure 1. Possible reaction schemes for furfural formation via
aldose-ketose isomerization and successive dehydration.
benefits, including avoidance of isolation and purification of
intermediate compounds, which saves time, energy, and sol-
vent.16-20
Here, we demonstrated an efficient production of furfural
from xylose using a combination of solid acid and base catalysts
in one-pot under moderate conditions. To our best knowledge,
this is first example of furfural production from xylose via
xylulose formation as an intermediate.
Heterogeneous acid catalysts have been examined for
dehydration of xylose to furfural because of these advantages
including easy separation, nontoxicity, and recyclability. H-
mordenite and H-Y faujasite were found to exhibit dehydration
at 433 K in water-methyl isobutyl ketone or water-toluene
solution by Moreau et al.7 Valente et al. have investigated the
dehydration using a variety of solid acid catalysts including
sulfonic acid appended porous silicas,8 porous niobium sili-
cates,9 metal oxide nanosheets,10 heteropolyacids,11 sulfated
zirconia,12 and delaminated zeolites13 in water-toluene biphase
systems. Although good yield of furfural was obtained (<47%),
these reactions were performed at high temperature (433 K) and
the dehydration mechanism still remains unknown.
In contrast, it is well known that aldoses such as glucose
and mannose can be transformed into corresponding ketoses
such as fructose by base-catalyzed isomerization.14 We have
very recently demonstrated that a pair of Amberlyst-15 as a solid
acid and hydrotalcite as a base catalyst afforded efficient
production from 5-(hydroxymethyl)furfural (HMF) of hexoses
including glucose, sucrose, and cellobiose.15 This one-pot
reaction involves aldose-ketose isomerization by base and
successive dehydration of ketose (fructose) by acid. Because
xylose is an aldopentose, this one-pot system seems to be
applicable for furfural formation from xylose as well as 5-
(hydroxymethyl)furfural formation from glucose as shown in
Figure 1, although there are no reports of xylulose as an
important intermediate for furfural formation. One-pot reaction
using heterogeneous catalysts afford environmentally-friendly
The reaction was typically performed using 0.1 g of solid
acid catalyst and/or 0.2 g of solid base catalyst, 0.1 g of substrate
(xylose) and 3 mL of N,N-dimethylformamide at 353-403 K for
3 h.21 The experiments were carried out in a Schlenk tube
attached with reflux condenser under an N2 atmosphere. The
conversions and yields were estimated using high-performance
liquid chromatography (HPLC) (Waters) with an Aminex HPX-
87H column from Bio-Rad Laboratories, Inc. Samples were
diluted with water before HPLC measurement. The products
were analyzed using a refractive index (RI) detector. The
analysis conditions were set as follows: eluent, 10 mM H2SO4;
flow rate, 0.5 mL min¹1; column temperature, 323 K. For
separation of xylose and xylulose, a Shodex Asahipak NH2P-
50 4E column (eluent; water:acetonitrile = 25:75) was used.
Table 1 shows furfural formation from xylose (pentose)
using solid acid and/or base catalysts at 373 K for 3 h. The
individual use of Amberlyst-15 gave 51% xylose conversion,
but negligible yield and poor selectivity of furfural as a desired
product (below 1%) (Entry 1). In the presence of hydrotalcite,
no production of furfural was observed (Entry 2). An efficient
production of furfural was obtained in the presence of
Amberlyst-15 and hydrotalcite (Entry 3). 42% furfural selectiv-
ity at high xylose conversion (57%) has been achieved using
0.1 g of Amberlyst-15 and 0.1 g of hydrotalcite in N,N-
dimethylformamide at 373 K for 3 h, much higher than those
of para-toluenesulfonic acid (p-TsOH¢nH2O) (Entry 6) and
sulfuric acid (Entry 7). This clearly indicates that one-pot
reaction using a combination of solid acid and base is a powerful
Chem. Lett. 2010, 39, 838-840
© 2010 The Chemical Society of Japan