Synergistic effect between copper and different metal oxides in the selective hydrogenolysis of glucose

Abstract

Copper catalysts have been extensively applied in saccharide hydrogenolysis for their high selectivity to C–O bond cleavage. The hydrogenolysis of glucose contains many reaction procedures, which need the synergistic effect of different active sites. A series of Cu catalysts supported on metal oxides with different surface physicochemical properties were prepared. The metal oxide supports not only influence the properties of Cu, such as dispersion and the electronic state, but also affect the activity of C–C and C–O bond cleavage in glucose. Furthermore, the coordination of a large amount of Lewis acid sites and hydrogenation sites on a Cu/γ-Al₂O₃ catalyst can promote C–C and C–O bond cleavage, leading to the selective conversion of glucose to glycol (selectivity of 66.6%). A Cu/MgO catalyst with a large amount of basic sites and metal sites could accelerate the retro-aldol condensation and isomerization reactions simultaneously, resulting in the main products of C₂, C₃, and C₄ polyols. A study of the synergistic effect between other transition metals and γ-Al₂O₃ showed that Pd had high activity for central C–C bond cleavage in glucose. Ru provided extremely strong activity for C–C bond cleavage at the terminal of the carbon chain in glucose, with the main product being methane (selectivity of 66.4%).