Oxidative Carbonylation for Dimethyl Carbonate Synthesis in Gaseous Phase over Supported Palladium Catalysts

The deactivation mechanism of the supported palladium catalyst for oxidative carbonylation of dimethyl carbonate synthesis from methanol in gaseous phase was studied according to the catalytic reaction behaviors and the XPS spectra for Pd species before and after the reaction. The effects of HCl on the suppression of Pd catalyst deactivation and the regeneration of deactivated catalyst were investigated. It was revealed that the primary reason for the catalyst deactivation was the loss of chlorine, which led to Pd~0 formation from Pd~(2+) at the PdCl_2/C catalyst and led to CuCl or Cu formation from CuCl_2 at the PdCl_2-CuCl_2/C catalyst. Although the presence of HCl during the reaction can delay the catalyst deactivation and promote the deactivated catalyst regeneration, it cannot regenerate the deactivated catalyst completely.