Mesoporous bimetallic PdCl 2-CuCl 2 catalysts for dimethyl carbonate synthesis by vapor phase oxidative carbonylation of methanol

Abstract

Dimethyl carbonate (DMC) synthesis reaction by oxidative carbonylation of methanol has been studied in a flow reaction system at atmospheric pressure in the presence of quaternary ammonium salt (QAS)-promoted bimetallic PdCl 2-CuCl 2 catalyst system supported on mesoporous HMS silica. The effects of the various QAS promoters, the promoter doping level and the Cu/Pd mole ratio were investigated, as well as the reaction conditions on the catalytic reactivates. The results showed that the tetrabutylammonium bromide (TBAB) promoted PdCl 2-CuCl 2/HMS catalyst system has the best catalytic performance. The characterization of PdCl 2-CuCl 2-TBAB/HMS catalysts was performed by means of BET, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The essential role of TBAB promoter is to facilitate the Pd(0)/Pd(II) and Cu(II)/Cu(I) redox processes. The formation of substantial amounts of surface stabilized cuprous species on the bimetallic HMS catalysts may account for the significant enhancement of the catalytic performance in DMC synthesis.