Oxidative carbonylation of methanol to dimethyl carbonate over CuCl/SiO 2–TiO 2 catalysts prepared by microwave heating: The effect of support composition

Abstract

Copper(I) chloride catalysts with a loading of 20 wt%, supported on silica–titania mixed oxides with Si/Ti ratios of 1, 5, 10 and 50 were prepared by conventional and microwave heating methods and tested in the oxidative carbonylation of methanol to dimethyl carbonate (DMC). X-ray diffraction (XRD), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) were used to examine the bulk and surface properties of the CuCl/SiO 2–TiO 2 catalysts. Quantum-chemical calculations were performed to explore the interaction of CuCl with the silica–titania support. Microwave heating showed some significant advantages over the conventional heating method, with markedly reduced preparation temperature and time, and provided improved catalytic activity in the oxidative carbonylation of methanol. The catalytic behavior of CuCl/SiO 2–TiO 2 in the test reaction studied was strongly dependent on the support composition. Incorporation of tetrahedral Ti(IV) species into the silica matrix could enhance the interaction of copper species with the oxide support. The improved catalytic performance of CuCl/SiO 2–TiO 2 in the DMC synthesis can be understood by the existence of the strong coordination interactions between the Cu + centers of CuCl and the bridging oxygen atoms at the Si–O–Ti bonds in the silica–titania support.