Aqueous-phase hydrogenolysis of glucose to value-added chemicals and biofuels: A comparative study of active metals

Glucose is the most abundant platform molecule of biomass in nature. High value-added chemicals and liquid fuels can be obtained by selectively breaking C-C/C-O bonds and removing surplus oxygen in glucose. This article focuses on glucose hydrogenolysis over a wide variety of transition metal catalysts (Cu/C, Ni/C, Pt/C, Pd/C, Ru/C, Rh/C, Ir/C). Liquid and gas phase after reaction mainly contain three types of products such as polyols, alkanes, furans. Many value-added chemicals and liquid fuels were obtained, such as sorbitol, 1,2-propanediol, ethylene glycol, 2,5-dimethylfuran, 2,5-dimethyltetrahydrofuran, hexane, etc. Different metal catalysts showed different selectivities to these products. Typically, at hydrogenation conditions of 453 K and 4.0 MPa, glucose was largely converted to C-1 products over the Ru/C catalyst. Pd/C selectively converted glucose into C-2 and C-3 products. C-6 products were most selective over Pt/C. The hydrogenation/hydrogenolysis capabilities of different metals for C-C and C-O bonds, the endocyclic C=C and C-O-C bonds are also quite different. For example, Pt/C provides the weakest hydrogenolysis activity to C-O and C-C bonds. Ru/C possesses the highest activity to C-C and C-O bond cleavage. Meanwhile, it is most active for C-O-C bond hydrogenation in glucose at low temperature. Cu/C exhibits the weakest endocyclic C=C bond hydrogenation activity in furan ring. The reaction pathway of glucose hydrogenolysis over different metal catalysts was also outlined. (C) 2014 Elsevier Ltd. All rights reserved.