Direct synthesis of diethyl carbonate (DEC) by oxidative carbonylation of ethanol offers a prospective "green chemistry" strategy to eliminate the phosgene used in the traditional preparation processes. PdCl2/Cu-HMS catalyst has been investigated, which demonstrated excellent selectivity to DEC by oxidative carbonylation of ethanol in the gas-phase reaction. The Si/Cu molar ratio of mesoporous Cu-HMS supports showed a remarkable effect on catalytic activities. An optimized Si/Cu molar ratio existed for catalytic performance, which was about 50/1. From XPS, ICP, XRD, nitrogen physisorption and IR characterization and analysis, it could be concluded that copper species incorporated into HMS frame and was highly dispersed in the frame of silica. The catalytic performances of PdCl2/Cu-HMS were related with both Cu content in the Cu-HMS and the order degree of mesoporous structure for Cu-HMS. (C) 2010 Elsevier B.V. All rights reserved.