One-pot selective conversion of hemicellulose (Xylan) to xylitol under mild conditions

Article abstract of DOI:10.1002/cssc.201200290

Something from nothing: Hemicellulose is selectively converted into valuable xylitol via a mild hydrogen transfer reaction, with a xylitol yield above 80%. Instead of using high-pressure H₂, isopropanol is used as hydrogen source in the presence of a Ru/C catalyst. Furthermore, a selective step-by-step conversion of hemicellulose and cellulose to different polyols in a one-pot process is described. Copyright

Full text of DOI:10.1002/cssc.201200290

DOI: 10.1002/cssc.201200290
One-Pot Selective Conversion of Hemicellulose (Xylan) to Xylitol under Mild
Conditions
[
a]
Guangshun Yi and Yugen Zhang*
The conversion from biomass to value-added bulky chemicals
has attracted increasing attention due to its renewable source
urgency to develop a cost-efficient and green chemical process
for the transformation.
[
1,2]
and the depletion of fossil-fuel resources.
Xylitol, a five-
The main challenge for the current industrial process of xyli-
tol production is the multi-step operation and the high-pres-
sure hydrogenation reaction process. In contrast to the less de-
carbon sugar alcohol with high sweetening power, was listed
in the top 11 high-value chemicals from biomass by the US De-
[
3]
[12]
partment of Energy. Compared to white sugar (sucrose), it is
veloped hemicellulose hydrolysis/hydrogenation process, the
[
4]
1
.2 times sweeter and contains 40% less calories. It is safe for
process for cellulose hydrolysis/hydrogenation has been widely
[13]
diabetics and is approved for use in food by many countries
and organizations including the U.S. Food and Drug Adminis-
studied and well documented. Most of the protocols report-
ed in literature employ the use of acids/transition metal cata-
lysts or bifunctional catalysts for the cellulose hydrolysis/hydro-
[
5]
tration, the European Union, and the World Health Organiza-
[
6]
[14]
tion.
genation under high pressures of hydrogen gas. Recently,
[15]
Industrially, xylitol is produced by the reduction of pure
xylose, obtained from acidic hydrolysis of xylan-containing
Fukuoka et al. reported an alternative protocol by using al-
cohol as hydrogen source, with a hydrogen transfer reaction to
convert cellulose to sorbitol and mannitol. The reaction condi-
tions included the treatment of cellulose at a temperature of
1908C for 18 h, generating a maximum yield of sorbitol and
mannitol of ~45%. Inspired by this work, herein, we have de-
veloped a one-pot process for the selective catalytic conver-
sion of hemicellulose to xylitol via a hydrogen transfer reac-
tion. Xylitol of high purity was produced with a yield of >80%
under mild conditions (1408C, 3 h). Instead of using the high-
[
7]
products such as hardwoods or corn cobs. This process con-
tains multiple steps, including the production of xylose by acid
decomposition of xylan-containing natural products, concen-
trating the hydrolysis solution to remove impurities, catalytic
hydrogenation of xylose to xylitol under high-pressure H gas
2
(up to 50 atm) at elevated temperatures, and the consequent
purification and isolation. This entire chemical process is labori-
ous, cost- and energy-intensive and environmentally unfriendly.
The final yield of xylitol obtained from such a process only cor-
responds to about 50–60% of xylan present in the raw materi-
[7,10c,16]
pressure H gas currently utilized by industrial processes,
2
isopropanol was used as the hydrogen source in the presence
of Ru/C catalyst. This one-pot simple process converts hemicel-
lulose into xylitol in high yields under mild reaction conditions
and represents a cost- and energy-efficient method. The reac-
tion is illustrated in Scheme 1.
[
8]
als. All these factors have contributed to the higher cost of
xylitol compared to sugar and the consequently smaller share
[
9]
in the huge market.
Intensive research has been initiated for economically viable
and eco-friendly alternative strategies for the production of xy-
The reaction conditions were optimized to pursue high cata-
lyst and engineering efficiency. Firstly, it was found that the re-
[
8–10]
litol.
However, most of the research activities have focused
on the bioconversion of xylose
that has been obtained by the
hydrolysis of xylan-containing
products to xylitol by employing
specific microbial strains for
fermentation.
A
considerable
number of bacteria, fungi and
yeasts were found to produce
[
10d,11]
xylitol from xylose.
Despite
all these efforts, such methods
have not yet been able to re-
place the current chemical proc-
Scheme 1. One-pot transfer hydrogenation of xylan to xylitol in isopropanol.
[
9a]
ess. Consequently, there is an
action temperature is crucial to the yield of xylitol production.
As shown in Figure 1, the xylitol yield increased almost linearly
with the increase in temperature, in the range of 1008C to
[
a] Dr. G. S. Yi, Dr. Y. G. Zhang
Institute of Bioengineering and Nanotechnology
3
1 Biopolis Way, The Nanos
1408C, in which a higher xylitol yield was obtained with higher
Singapore 138669 (Singapore)
Fax: (+65)6478-9080
E-mail: ygzhang@ibn.a-star.edu.sg
temperature. At 1408C and 1508C, the xylitol yield reached
a plateau, and beyond a reaction temperature of 1508C, the
yield of xylitol decreased. In addition, the conversion of hemi-
cellulose was also increased as the reaction temperature in-
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201200290.
ChemSusChem 0000, 00, 1 – 5
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
1
&
ÞÞ
These are not the final page numbers!

[
a]
Table 1. Effect of the water-to-isopropanol ratio on the xylitol yield.
Entry
Water [mL]
Iso-PrOH [mL]
Xylitol [mg (%)]
1
2
3
4
5
6
7
8
7
6
4
2
1
0
0
1
2
4
6
7
8
8.62 (11.1)
61.4 (78.7)
62.8 (80.5)
64.8 (83.0)
62.8 (80.5)
46.8 (60.0)
9.84 (12.6)
[
a] Reaction conditions: 75 mg hemicellulose, 25 mg Ru/C, water, isopro-
2 4
panol, 7 mL H SO , in 10 mL Teflon-lined hydrothermal reactor, 1408C for
3
h.
Figure 1. Production yield of xylitol vs. reaction temperature. Reaction condi-
tions: 75 mg hemicellulose (xylan, 0.513 mmol d-xylose units), 25 mg Ru/C
change in the xylitol yield was observed. This tolerance to
a broad range of solvent composition is important for practical
(
4
2.4 mol%), 4 mL water, 4 mL isopropanol, 7 mL H
9.2 mol% H ), in 10 mL Teflon-lined hydrothermal reactor for 14 h.
2
SO
4
(0.126 mmol,
[17]
+
applications, as well as for solvent recycling. In fact, a reac-
tion with a larger scale (375 mg hemicellulose) was carried out
under the same conditions in a 50 mL Teflon-lined hydrother-
mal reactor and 313.3 mg of isolated xylitol (80.3%) was ob-
creased, but reached a plateau at 1208C. The reaction temper-
ature was then fixed at 1408C for the subsequent experiments.
Kinetic studies showed that the reaction was almost com-
plete in 3 h, with a high xylitol yield of 83% (Figure 2). The xyli-
tol yield remained stable at about the same value for reaction
[17]
tained. Reaction with recycled isopropanol was also carried
out with the standard reaction procedure without any detri-
ment to the reaction yield, as 81.8% yield of xylitol was
obtained.
In the current one-pot system, the detailed process includes
a two-step cascade reaction. The first step is acid-catalyzed
hemicellulose hydrolysis to xylose, followed by a Ru-catalyzed
transfer hydrogenation reaction to convert xylose to xylitol.
Although different types of acid additives have been used in
[1,13d,18]
biomass hydrolysis,
we found that a small amount of
H SO4 is crucial to convert hemicellulose to xylitol in our
2
system. Without acidic additives the xylitol yield is only 5.7%,
as shown in Figure 3. As a small amount of acid was added,
the xylitol yield significantly increased. Moreover, the xylitol
yield reached a maximum as 7 ml of 96% H SO (equal to
2
4
+
0
.17% w/w, 49.2 mol% H ) was applied, as shown in Figure 3.
An excess amount of acid led to a decrease in the xylitol yield.
The optimized conditions with 7 ml of 96% H SO in 8 mL of
2
4
mixture solvent (pH~2) for the reaction at 1408C is compara-
ble to the extremely low acid (ELA) conditions (a system with
pH 2.2, for reaction at >2008C) defined by the National Re-
Figure 2. Production yield of xylitol vs. reaction time at 1408C. Reaction con-
ditions: 75 mg hemicellulose, 25 mg Ru/C, 4 mL water, 4 mL isopropanol,
7
2 4
mL H SO , in 10 mL Teflon-lined hydrothermal reactor.
times varying from 3 to 8 h but started to decline slightly as
the reaction time was extended beyond 8 h.
In our reaction system, a mixture of water and isopropanol
was employed as solvent. Water plays an important role in the
hydrolysis of hemicellulose to the d-xylose monomer, and the
isopropanol provides the hydrogen source for the transfer hy-
drogenation reduction of xylose to xylitol in the presence of
[
15]
the Ru/C catalyst. In our system, the ratio of water and iso-
propanol was also optimized, as shown in Table 1. In the case
of pure water or pure isopropanol as solvent, only a small
amount of xylitol was formed. However, when a water and iso-
propanol mixture was used as solvent, the yield of xylitol was
significantly increased. Table 1 shows that if the ratio of water
to isopropanol was in the range from 7:1 to 1:3, no significant
Figure 3. Production yield of xylitol vs. the amount of H
added. Reaction conditions: 75 mg hemicellulose, Ru/C, 4 mL water, 4 mL
2 4
SO and catalyst
isopropanol, H
3 h.
2 4
SO , in 10 mL Teflon-lined hydrothermal reactor, 1408C for
&2
&
www.chemsuschem.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemSusChem 0000, 00, 1 – 5
ÝÝ
These are not the final page numbers!

[
19]
newable Energy Laboratory (USA). It could be considered as
a green technology, since the corrosive characteristics of ELA
are close to those of neutral aqueous reactions and the stan-
dard-grade stainless steel equipment can be used instead of
when the catalyst was reused for five consecutive runs. After
five rounds of reaction, the Ru/C catalyst was also character-
ized by TEM (Supporting Information, Figure S1), and no obvi-
ous changes were observed for the morphology and particle
size of the Ru nanoparticles when compared to the fresh cata-
lyst. This result indicates that the current reaction conditions
are rather mild and that the Ru/C catalyst is stable and recycla-
ble under these process conditions.
[
19]
high-nickel alloys.
Other acids were also screened in this process. An equiva-
lent amount of HCl was used to replace H SO , and to our sur-
2
4
prise, only a negligible amount of xylitol was detected. Instead,
a high yield of xylose was observed, indicating that hemicellu-
lose has been hydrolyzed into xylose, but under HCl condi-
tions, xylose was not able to further convert to xylitol. This
The reaction pathway for this process is rather straightfor-
ward. Hemicellulose is first hydrolyzed into xylose under acidic
conditions. Following with that, xylose is converted to xylitol
by Ru catalyzed hydrogen transfer reaction (Scheme 1). During
this hydrogen transfer process, 1.8% of isopropanol
(0.94 mmol) was converted to acetone, which is more than
two times the yield of xylitol (64.8 mg, 0.426 mmol). This
Figure was much lower than the hydrogen transfer from cellu-
lose to sorbitol and mannitol as reported by Fukuoka et al
À
may be due to the existence of Cl ions that quenched the ac-
tivity of the Ru/C catalyst in the transfer hydrogenation step,
[
16a]
as reported by Fukuoka et al.
When H SO was used, almost
2 4
all the xylose was converted to xylitol. We also ran experiments
using an equivalent amount of solid acid (Amberlyst-15), and
the resulting xylitol yield was 36.1%. When the amount of Am-
berlyst-15 was doubled, the yield of xylitol reached 47.9%.
Further increments in the amount of solid acid led to a de-
crease in xylitol yield, as shown in Table S1 of the Supporting
Information.
[15]
(22 times),
indicating the milder reaction conditions and
higher hydrogen transfer efficiency in our reaction.
Hemicellulose is the second-most common polysaccharide
in nature and represents about 20–35% of lignocellulosic bio-
mass, while cellulose and lignin makes up the remaining per-
centage. It is well known that both hemicellulose and cellulose
Ruthenium supported on active carbon (Ru/C, Aldrich,
5
wt%) was selected as catalyst. To test the optimimal catalyst
[19]
loading, a set of reactions were conducted, as shown in
Figure 3. Without the Ru catalyst, negligible xylitol was detect-
ed, and xylose was observed instead. When the catalyst load-
ing was increased, the xylitol yield increased steadily and
reached a maximum at a catalyst loading of 15 mg. Further in-
creases in the amount of catalyst to 20 mg and 25 mg resulted
in small increments in the xylitol yield. As comparison, other
heterogeneous catalysts, such as Pd/C and Raney nickel, were
also tested in this reaction. However, no catalytic activity was
observed for either the Pd/C or Raney nickel catalysts (Sup-
porting Information, Table S2).
can be hydrolyzed under different acidic conditions.
The
mild conditions applied in our one-pot conversion of hemicel-
lulose to xylitol provide an interesting opportunity for the se-
lective conversion of hemicellulose, over cellulose or lignin in
[20]
raw biomass. To test the selectivity of hemicellulose over cel-
lulose, 75 mg of mixture (37.5 mg hemicellulose and 37.5 mg
cellulose) was put into the reactor and kept at 1408C for 3 h.
To our delight, the hemicellulose was efficiently converted to
xylitol in more than 80% yield, while the cellulose remained
unreacted (100% recovered). Cellulose was not hydrolyzed
under these conditions, mainly due to its robust crystal struc-
ture. Inspired by this result, a one-pot step-by-step selective
conversion of hemicellulose and cellulose in raw biomass to
polyols process is proposed, as shown in Scheme 2.
To test the durability of the Ru/C catalyst, it was recovered
by centrifugation after the first reaction cycle. The recycled cat-
alyst was directly used in the next reaction run. As shown in
Figure 4, the Ru/C catalyst demonstrated excellent recyclability
in this reaction. There is no significant deactivation observed
Sugarcane bagasse is abundant waste biomass and has bal-
anced components of both hemicellulose and cellulose (~25%
hemicellulose, ~42% cellulose with lignin in the remaining per-
[21]
centage.). It was selected as an example of a raw-material
feedstock to demonstrate the one-pot selective conversion
process proposed in Scheme 2. In the initial test, 75 mg of sug-
arcane bagasse was treated in a reactor, under standard condi-
tions for 3 h. Trace amounts of xylitol was detected in the reac-
Figure 4. Durability of Ru/C catalyst. Reaction conditions: 75 mg hemicellu-
lose, 25 mg Ru/C, 4 mL water, 4 mL isopropanol, 7 mL H
lined hydrothermal reactor, 1408C for 3 h.
2
SO
4
, in 10 mL Teflon-
Scheme 2. One-pot step-by-step selective conversion of sugarcane bagasse
to different products.
ChemSusChem 0000, 00, 1 – 5
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org
&
3
&
ÞÞ
These are not the final page numbers!

tion system and xylose was detected as the major product.
A possible reason for the minimal conversion to xylitol includes
the buffering capacity of the extraneous lignin in the lignocel-
lulosic biomass for acids, which would hinder the hydrolysis
hemicellulose, 25 mg Ru/C catalyst, 4 mL water, 4 mL isopropanol,
and 7 mL of H SO , and the reactor was purged with N before seal-
ing. The reactor was heated to 1408C in a silicon-oil bath and was
2
4
2
maintained at this temperature for 3 h with magnetic stirring
(600 rpm). After the reaction, the reactor was left to cool on its
[
19]
process. We subsequently doubled the reaction time to 6 h.
At this stage, 15.4 mg (80.4%) xylitol (containing a small
own.
[
10c]
amount of arabinitol)
was obtained and almost no xylose
remained. Most importantly, there was only a negligible
amount (<1%) of sorbitol/mannitol products observed in the
first step of the reaction (Supporting Information, Table S3), in-
dicating the high selectivity of the first step of the reaction to-
wards hemicellulose. Lignin was also extracted into the isopro-
panol/water phase and it was precipitated as the isopropanol
Product analysis
After reaction, the reaction mixture was separated by filtration. The
remaining solid (Ru/C catalyst and the unreacted hemicellulose)
were dried and weighed after washing with water. The xylitol yield
was analyzed by using a sugar analyzer (DKK-TOA Corporation,
Japan. Model: SU-300) and was further confirmed with isolated
yield (Supporting Information). The sugar analyzer was operated in
[
22]
was removed in vacuo. 4 mL water, 4 mL isopropanol, 7 ml
sugar alcohol mode, with a xylitol standard solution for calibration.
H SO were then added to the residual solids (57.7 mg, includ-
2
4
À1
Testing conditions: mobile phase: 200 mm NaOH, 0.5 mLmin
39.98C.
,
ing cellulose and solid Ru/C catalyst) and the mixture was
[
23]
heated to 2458C for 12 h, resulting in sorbitol and mannitol
yields of 21.1% (Supporting Information, Table S3). Although
this system is less efficient for the transformation of cellulose
to the corresponding polyols, it demonstrated the excellent
possibility for the one-step separation of the three main com-
ponents of plant biomass by the selective conversion of hemi-
cellulose to xylitol, with the conversion of the remaining cellu-
lose to related polyols in one pot under mild conditions.
Characterization
1
13
The xylitol product was characterized by H and C NMR (Bruker
AV-400). The Ru/C catalyst was characterized by TEM (FEI Tecnai
F20). NMR and TEM spectra are in the Supporting Information (Fig-
ures S1 and S2).
In summary, a one-pot catalytic conversion of hemicellulose
(
xylan) to xylitol via a hydrogen transfer reaction was devel- Acknowledgements
oped. Xylitol of high purity was produced with a yield of
80% under mild conditions (1408C, 3 h). Instead of using
>
This work was supported by the Institute of Bioengineering and
Nanotechnology (Biomedical Research Council), Biomass-to-
Chemicals program (Science and Engineering Research Council),
Agency for Science, Technology and Research, Singapore.
high-pressure H gas similar to current industry processes, iso-
2
propanol was used as the hydrogen source in the presence of
a Ru/C catalyst. Furthermore, a selective step-by-step conver-
sion of hemicellulose and cellulose to different polyols in
a one-pot process was also developed. With this process, sug-
arcane bagasse was converted into xylitol, sorbitol and manni-
tol, and lignin. This method not only improves on the current
industry process for xylitol synthesis, with a simple, one-pot
process with mild conditions and higher resultant yields, it also
provides new insight in the conversion of biomass in a more
efficient and complete way.
Keywords: carbohydrates
·
heterogeneous catalysis
·
hydrogen transfer · renewable resources · ruthenium
[
1] Selected reviews: a) Special issue in Science: Sustainability and Energy,
Science 2007, 315, 781–813; b) A. M. Ruppert, K. Weinberg, R. Palkovits,
Angew. Chem. 2012, 124, 2614–2654; Angew. Chem. Int. Ed. 2012, 51,
2564–2601; c) J. N. Chheda, G. W. Huber, J. A. Dumesic, Angew. Chem.
2
007, 119, 7298–7318; Angew. Chem. Int. Ed. 2007, 46, 7164–7183;
d) G. W. Huber, A. Corma, Angew. Chem. 2007, 119, 7320–7338; Angew.
Chem. Int. Ed. 2007, 46, 7184–7201; e) B. Kamm, Angew. Chem. 2007,
119, 5146–5149; Angew. Chem. Int. Ed. 2007, 46, 5056–5058; f) J. O.
Metzger, Angew. Chem. 2006, 118, 710–713; Angew. Chem. Int. Ed.
2006, 45, 696–698; g) O. Inderwildi, D. King, Energy Environ. Sci. 2009,
Experimental Section
Materials
2
4
, 343–346; h) Y. G. Zhang, J. Y. G. Chan, Energy Environ. Sci. 2010, 3,
08–417; i) J. J. Bozell, G. R. Petesen, Green Chem. 2010, 12, 539–544;
Hemicellulose (Beechwood xylan) was purchased from Sigma–Al-
drich (96.6% purity, containing 6.5 wt% physisorbed water). The
hemicellulose was used directly without any pre-treatment. Sugar-
cane bagasse was ball-milled for 1 h. d-Xylose (ꢀ99%), xylitol
j) N. Li, G. W. Huber, J. Catal. 2010, 270, 48–59.
[2] a) E. L. Kunkes, D. A. Simonetti, R. M. West, J. C. Serrano-Ruiz, C. A. Gart-
ner, J. A. Dumesic, Science 2008, 322, 417–421; b) Y. Gen, Y. G. Zhang,
J. Y. Ying, Angew. Chem. 2008, 120, 9485–9488; Angew. Chem. Int. Ed.
(
ꢀ99%), Ru/C (5 wt% metal), Amberlyst-15 resin, and cellulose
2
008, 47, 9345–9348; c) J. Y. G. Chan, Y. G. Zhang, ChemSusChem 2009,
were purchased from Sigma–Aldrich. Isopropanol (HPLC grade)
was from J. T. Baker. Sulfuric acid (95–97%), hydrochloric acid
2, 731–734; d) C. H. Christensen, J. Rass-Hansen, C. C. Marsden, E. Taarn-
ing, K. Egeblad, ChemSusChem 2008, 1, 283–289; e) M. Stçcker, Angew.
Chem. 2008, 120, 9340–9351; Angew. Chem. Int. Ed. 2008, 47, 9200–
(
37%), Pd/C, and Raney nickel were purchased from Merck and
used as received.
9
211; f) P. Gallezot, Green Chem. 2007, 9, 295–302; g) N. Ji, T. Zhang, M.
Zheng, A. Wang, H. Wang, X. Wang, J. G. Chen, Angew. Chem. 2008, 120,
638–8641; Angew. Chem. Int. Ed. 2008, 47, 8510–8513; h) L. Lai, Y. G.
8
General reaction procedure
Zhang, ChemSusChem 2010, 3, 1257–1260; i) M. S. Holm, S. Saravana-
murugan, E. Taarning, Science 2010, 328, 602–605; j) M. X. Tan, L. Zhao,
Y. G. Zhang, Biomass Bioenergy 2011, 35, 1367–1370; k) T. D. Matson, K.
Barta, A. V. Iretskii, P. C. Ford, J. Am. Chem. Soc. 2011, 133, 14090–
The conversion of hemicellulose was conducted in a 10 mL Teflon-
lined hydrothermal reactor. The reactor was charged with 75 mg
&4
&
www.chemsuschem.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemSusChem 0000, 00, 1 – 5
ÝÝ
These are not the final page numbers!

1
6
4097; l) Z. Lin, D. Yu, Y. N. Sum, Y. G. Zhang, ChemSusChem 2012, 5,
25–628.
boers, H. Schepers, F. De Clippel, C. J. Gommes, B. Goderis, P. A. Jacobs,
B. F. Sels, Green Chem. 2010, 12, 1560–1563; c) J. Geboers, S. Van de
Vyver, K. Carpentiek, K. De Blochouse, T. Vosch, P. Jacobs, B. F. Sels,
Chem. Commun. 2010, 46, 3577–3579; d) S. Van de Vyver, J. Geboers, M.
Dusselier, H. Schepers, T. Vosch, L. Zhang, G. van Tendeloo, P. A. Jacobs,
B. F. Sels, ChemSusChem 2010, 3, 698; e) V. Jollet, F. Chambon, F. Rata-
boul, A. Cabiac, C. Pinel, E. Guillon, N. Essayem, Top. Catal. 2010, 53,
1254–1257; f) W. Deng, M. Liu, X. Tan, Q. Zhang, Y. Wang, J. Catal. 2010,
271, 22–32; g) L. N. Ding, A. Q. Wang, M. Y. Zheng, T. Zhang, Chem-
SusChem 2010, 3, 818–821.
[
[
3] http://www.osti.gov/bridge/purl.cover.jsp?purl=/926125-eeUkhS/.
4] a) J. Wisniak, M. Hershkow, R. Leibowit, S. Stein, Ind. Eng. Chem. Res.
1
5] US Code of Federal Regulations: 21 CFR 101.80, http://www.accessda-
ta.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.80.
6] WHO Technical report Series, 1983. 696, 23–24.
7] H. Buckl, R. Fahn, C. E. Hofstadt, US Patent 3980719, 1974.
8] X. Chen, Z.-H. Jiang, S. Chen, W. Qin, Int. J. Biol. Sci. 2010, 6, 834–844.
9] a) R. S. Prakasham, R. S. Rao, P. J. Hobbs, Curr. Trends Biotechnol. Pharm.
974, 13, 75–79; b) A. Emodi, Food Technol. 1978, 32, 28–31.
[
[
[
[
[
[15] H. Kobayashi, H. Matsuhashi, T. Komanoya, K. Hara, A. Fukuoka, Chem.
Commun. 2011, 47, 2366–2368.
2
009, 3, 8–36; b) R. S. Rao, C. P. Jyothi, R. S. Prakasham, P. N. Sarma, L. V.
Rao, Bioresour. Technol. 2006, 97, 1974–1978.
10] a) T. B. Granstrçm, M. Leisola, Agro Food Ind. Hi-Tech 2009, 20, 32–35;
[16] a) H. Kobayashi, Y. Ito, T. Komanoya, Y. Hosaka, P. L. Dhepe, K. Kasai, K.
Hara, A. Fukuoka, Green Chem. 2011, 13, 326–333; b) J. Geboers, S. Van
de Vyver, K. Carpentier, P. Jacobs, B. Sels, Chem. Commun. 2011, 47,
5590–5592.
[
b) T. B. Granstrçm, K. Izumori, M. Leisola, Appl. Microbiol. Biotechnol.
2007, 74, 277–281; c) H. M. Baudel, C. A. M. de Abreu, C. Z. Zaror, J.
Chem. Technol. Biotechnol. 2005, 80, 230–233; d) C. Guo, C. Zhao, P. He,
D. Lu, A. Shen, N. Jiang, J. Appl. Microbiol. 2006, 101, 1096–1104;
e) N. U. Nair, H. Zhao, Metab. Eng. 2010, 12, 462–468.
[17] L. Lai, Y. G. Zhang, ChemSusChem 2011, 4, 1745–1748.
[18] M. A. Harmer, A. Fan, A. Liauw, R. K. Kumar, Chem. Commun. 2009,
6610–6612.
[
[
11] O. Akinterinwa, R. Khankal, P. C. Cirino, Curr. Opin. Biotechnol. 2008, 19,
[19] J. S. Kim, Y. Y. Lee, R. W. Torget, Appl. Biochem. Biotechnol. 2001, 91–93,
331–340.
[20] T. vom Stein, P. M. Grande, H. Kayser, F. Sibilla, W. Leitner, P. D. de Maria,
Green Chem. 2011, 13, 1772–1777.
[21] a) M. Brienzo, A. F. Siqueira, A. M. F. Milagres, Biochem. Eng. J. 2009, 46,
199–204; b) R. de Freitas Branco, J. C. dos Santos, S. S. da Silva, Biomass
Bioenergy 2011, 35, 3241–3246.
[22] B. C. Saha, J. Ind. Microbiol. Biotechnol. 2003, 30, 279–291.
[23] C. Luo, S. Wang, H. Liu, Angew. Chem. 2007, 119, 7780–7783; Angew.
Chem. Int. Ed. 2007, 46, 7636–7639.
461–467.
12] a) F. M. Gꢁrio, C. Fonseca, F. Carvalheiro, L. C. Duarte, S. Marques, R.
Bogel-Łukasik, Bioresour. Technol. 2010, 101, 4775–4800; b) R. Palkovits,
K. Tajvidi, J. Procelewska, R. Rinaldi, A. Ruppert, Green Chem. 2010, 12,
972–978.
[
13] Selected recent Reviews, see: a) S. Van de Vyver, J. Geboers, P. A. Jacobs,
B. F. Sels, ChemCatChem 2011, 3, 82; b) J. Geboers, S. Van de Vyver, R.
Ooms, B. O. de Beeck, P. A. Jacobs, B. F. Sels, Catal. Sci. Technol. 2011, 1,
714–726; c) P. Gallezot, Top. Catal. 2010, 53, 1209–1213; d) R. Rinaldi, F.
Schꢂth, ChemSusChem 2009, 2, 1096–1107; e) D. A. Simonetti, J. A. Du-
mesic, Catal. Rev. Sci. Eng. 2009, 2, 610–626; f) P. Gallezot, Chem-
SusChem 2008, 1, 734–737; g) G. W. Huber, S. Iborra, A. Corma, Chem.
Rev. 2006, 106, 4044–4098.
[14] a) A. Fukuoka, P. L. Dhepe, Angew. Chem. 2006, 118, 5285–5287; Angew.
Received: April 26, 2012
Chem. Int. Ed. 2006, 45, 5161–5163; b) S. Van de Vyver, L. Peng, J. Ge-
Published online on && &&, 2012
ChemSusChem 0000, 00, 1 – 5
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org
&
5
&
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
G. S. Yi, Y. G. Zhang*
Something from nothing: Hemicellu-
lose is selectively converted into valu-
able xylitol via a mild hydrogen transfer
reaction, with a xylitol yield above 80%.
&& – &&
One-Pot Selective Conversion of
Hemicellulose (Xylan) to Xylitol under
Mild Conditions
Instead of using high-pressure H , iso-
2
propanol is used as hydrogen source in
the presence of a Ru/C catalyst. Further-
more, a selective step-by-step conver-
sion of hemicellulose and cellulose to
different polyols in a one-pot process is
described.
&6
&
www.chemsuschem.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemSusChem 0000, 00, 1 – 5
ÝÝ
These are not the final page numbers!