Angewandte
Chemie
2
4 h. The sample was calcined in O at 673 K for 2 h and reduced in H2
2
at 673 K for 2 h to give Pt/g-Al O (Pt 2.5wt%). Ru/HUSY catalysts
2
3
were prepared by the various methods given in the Supporting
Information.
A typical procedure: cellulose (Merck, Avicel, microcrystalline,
0
.16 g), Pt/g-Al O (0.068 g), water (20 mL) and a stirring bar were
2 3
charged in a stainless-steel autoclave (Taiatsu TPR2, 30 mL). Three-
fold scale-up reactions were also performed in an MMJ-100 reactor
(OM Lab-Tech). The autoclave was heated at 463 K for 24 h after
pressurization with H2 to 5 MPa at RT. After the reaction, the
reaction mixture was centrifuged and the filtered solution was
analyzed by HPLC (Shimadzu LC10ATVP, RI detector, Shim-pack
SPR-Ca column (250 7.8 mm), mobile phase: water). Sorbitol and
mannitol were characterized by LC–MS (Shimadzu LCMS-2010 A).
The yield of sugar alcohols was calculated as follows: yield (%) =
(mol of sorbitol and mannitol)/(mol of C H O unit in charged
Figure 2. Hydrolysis of cellulose into glucose by support materials.
Reaction conditions: cellulose (0.16 g), catalyst (0.068 g), water
6
10
5
cellulose) 100. Initial ratio of substrate/catalyst (S/C) was 110 (S =
mol of C H O , C = gatom of bulk metal).
(
20 mL), initial H pressure atRT =5 MPa, 463 K, 24 h. The yields are
2
6
10
5
based on the number of moles of the initial C H O unitin cellulose.
6
10
5
HZSM-5=H form of zeolite Socony mobil, HY=H form of Y zeolite,
FSM-16=folded sheets of mesoporous material, HMOR=H form of
moredenite.
Received: May 15, 2006
Published online: July 6, 2006
Keywords: carbohydrates · catalysts ·
.
heterogeneous catalysis · reduction · water
small amount of glucose was formed with yields of less than
4
%, thus indicating that the metal promotes the hydrolysis of
cellulose. Hence, it is suggested that the acid sites for the
hydrolysis of cellulose are generated in situ from H2 in
[
1] D. L. Klass, Biomass for Renewable Energy, Fuels, and Chem-
icals, Academic Press, San Diego, 1998.
[
17]
addition to the acidic surface sites intrinsic in the support.
[2] H. Danner, R. Braun, Chem. Soc. Rev. 1999, 28, 395 – 405.
[
3] US Department of Energy, EnergyEfficiencyand Renewable
Energy, Top Value Added Chemicals From Biomass, Vol. 1:
In this mechanism, H is dissociatively adsorbed on the metal
2
surface and the hydrogen species reversibly spill over onto the
support surface. The acidic sites catalyze the hydrolysis of
cellulose to glucose, and the C=O group in glucose is readily
“
Results of Screening for Potential Candidates from Sugars and
Synthesis Gas” http://eereweb.ee.doe.gov/biomass/pdfs/
5523.pdf, 2004.
3
reduced by Pt or Ru with H to form sorbitol (Scheme 1). The
2
[4] L. T. Fan, M. M. Gharpuray, Y.-H. Lee, Cellulose Hydrolysis,
Springer, Berlin, 1987.
[5] H. A. Krässig, Cellulose—Structure, Accessibilityand Reactivity ,
Gordon and Breach Science Publishers, Yverdon, 1993.
former hydrolysis is a rate-determining step because the
reduction of glucose gave an almost stoichiometric amount of
sorbitol over the Pt or Ru catalysts.
[
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6] Y. P. Zhang, L. R. Lynd, Biotechnol. Bioeng. 2004, 88, 797 – 824.
7] W. S. Mok, M. J. Antal, G. Varhergyi, Ind. Eng. Chem. Res. 1992,
The maximum yield was not improved when the reaction
was carried out over 72 hours (see the Supporting Informa-
tion). This finding implies that the further degradation of
cellulose was restricted as a result of its robust structure.
Previous reports on the hydrolysis of cellulose recognized that
the factors that control the conversion of cellulose are
crystallinity, degree of polymerization, availability of chain
31, 94 – 100.
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8] M. Ishida, K. Otsuka, S. Takenaka, I. Yamanaka, J. Chem.
Technol. Biotechnol. 2005, 80, 281 – 284.
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[
[
[
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[
6]
Catal. Lett. 2005, 102, 163 – 169.
ends, and fraction of accessible bonds. These factors play a
significant role in our reactions, in which both substrate and
catalyst are solid.
11] P. Gallezot, P. J. Cerino, B. Blanc, G. Flꢀche, P. Fuertes,J. Catal.
1994, 146, 93 – 102.
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2000, 69, 339 – 343.
As described above, we have demonstrated for the first
time that supported metal catalysts can convert cellulose into
sugar alcohols by an environmentally friendly process. This
green process opens new opportunities for the use of
abundant and inexpensive cellulose as a chemical feedstock
with heterogeneous catalysis.
[13] G. W. Huber, J. W. Shabaker, J. A. Dumesic, Science 2003, 300,
075 – 2077.
2
[14] R. R. Davda, J. A. Dumesic, Chem. Commun. 2004, 36 – 37.
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17] H. Hattori, T. Shishido, Catal. Surv. Jpn. 1997, 1, 205 – 213.
Experimental Section
Support materials and metal precursors are summarized in the
Supporting Information. The supports were dried under vacuum
(
[
ca. 0.1 Pa) at 423 K for 1 h. Typically, an aqueous solution of
Pt(H) Cl ]·xH O (5 mL, 15 mg) was added to a mixture of g-Al O
3
2
6
2
2
(Nishio, A-11, 200 mg) and water (20 mL). The reaction mixture was
stirred for 15 h, evaporated to dryness, and dried under vacuum for
Angew. Chem. Int. Ed. 2006, 45, 5161 –5163
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5163