New One-Pot Catalytic Pathway to Convert Cellulose to Glucose and HMF, an Intermediate for Fuels and Chemicals
09 June 2009
Hydrolysis product yield from cellulose using single and paired CuCl2 /CrCl2 catalysts. Zhang et. al. Click to enlarge. |
Researchers at the Department of Energy’s Pacific Northwest National Laboratory have developed a catalytic pathway for the rapid conversion of cellulose to sugars and further to 5-hydroxymethylfurfural (HMF)—a versatile intermediate for chemicals and fuels.
In 2007, the PNNL team had reported developing a catalytic system to efficiently convert glucose to HMF. (Earlier post.) However, for such a process to be commercially sustainable in large quantities, cellulosic biomass must be able to be used as the feedstock. The bottleneck has been the decrystallization of cellulose followed by hydrolytic cleavage. The new work addresses that issue.
PNNL scientist David King presented the work on 8 June at the North American Meeting of the Catalysis Society. A pair of metal chlorides (CuCl2 and CrCl2) dissolved in an ionic liquid (1-ethyl-3-methylimidazolium chloride ([EMIM]Cl)) at temperatures of 80-120°C collectively catalyze the single-step process of converting cellulose to HMF with an unrefined 96% purity among recoverable products (at 55.4 ±4.0% HMF yield).
The paired CuCl2/CrCl2 catalysts in the ionic liquid solvent show high activity for hydrolytic cellulose depolymerization. The product selectivity can be tuned by simply varying the CuCl2/CrCl2 ratio.
Cellulose depolymerization occurs at a rate that is about one order of magnitude faster than conventional acid-catalyzed hydrolysis. In contrast, single-metal chlorides at the same total loading showed considerably less activity under similar conditions.
After extractive separation of HMF from the solvent, the catalytic performance of recovered [EMIM]Cl and the catalysts was maintained in repeated uses.
Resources
Y. Su, H.M. Brown, X. Huang, X.-d. Zhou, J.E. Amonette, Z.C. Zhang, Single-Step Conversion of Cellulose to 5-Hydroxymethylfurfural (HMF), a Versatile Platform Chemical, Applied Catalysis A, General (2008), doi: 10.1016/j.apcata.2009.04.002
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