Table 2 Properties and catalytic activity of HPA in combination with
Ru/C in the hydrogenolysis of sprucea
funded by the Excellence Initiative by the German federal
and state governments to promote science and research at
German universities. We thank Mr A. Deege and Ms H.
Hinrichs for HPLC analyses.
Conversionb,c Yield
(%)
Yield
c,d
C4–C6 (%) C1–C3 (%)
c,d
Entry Catalyst
10
11
H4[Si(W3O10)4] 100
H3[P(W3O10)4] 87
64.9
42.0
7.7
5.2
Notes and references
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500 mg spruce chips without pretreatment: 10 ml water, 100 mg
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5%Ru/C, 500 mg HPA, 433 K, 50 bar H2 (298 K), 5 h. See ESIz
c
Conversion and yield were calculated assuming 45% cellulose and
d
30% hemicellulose, calculated as 75% cellulose (ESIz). Based on
theoretical stoichiometric coefficients (ESIz).
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becomes an important issue. Compared to mineral acids, the
lower concentration of HPA would result in reduced salt
formation upon neutralization. Besides, HPAs may be
precipitated via ion exchange with larger cations, e.g. K+,
Cs+ and NH4+, or in certain cases even extracted to allow
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solid catalysts would be advantageous. Ion exchange resins
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their external surface resembling to some extent p-TSA.
Interestingly, they allow reasonable conversion of cellulose,
but suffer from degradation under reaction conditions
accompanied by leaching of acid sites. Hence, little selectivity
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HPAs were supported on silica following ref. 21 and zinc
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pronounced leaching of active species, while ZnPW showed
little activity and only 23.8% conversion. Nevertheless,
optimization of solid acids improving catalyst–support
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The concept of hydrogenolysis of cellulose combining HPAs
and Ru/C is not only applicable to pure cellulose but could be
transferred to spruce as wooden feedstock (Table 2). Assuming
the cellulose and hemicellulose fraction of spruce to be about
45 and 30%, respectively, SiW allowed complete conversion of
these fractions. Again, C4–C6 sugar alcohols present the main
products with up to 65% yield in only 5 h reaction time at
160 1C. Besides, small amounts of C1–C3 polyols including
glycerol, PG, EG and methanol were formed (ESIz).
16 Based on conversion XCellulose and yield of liquid phase products
YL, carbon efficiency EC = YLX
ꢁ1
In conclusion, we have shown that heteropoly acids
combined with supported Ru catalysts allow direct trans-
formation of cellulose into sugar alcohols with a yield of 81%
and above 90% carbon efficiency. Additionally, this approach
may even be applied to wooden feedstocks and yields of sugar
alcohols of 65% could be reached starting from spruce.
.
Cellulose
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We would like to thank Robert-Bosch Foundation for
financial support. This work was performed as part of the
Cluster of Excellence ‘‘Tailor-Made Fuels from Biomass’’,
c
578 Chem. Commun., 2011, 47, 576–578
This journal is The Royal Society of Chemistry 2011