Mo-promoted Pd/NaY catalyst for indirect oxidative carbonylation of methanol to dimethyl carbonate

A chlorine-free catalyst consisting of zeolite Y modified with Pd (Pd/NaY) catalyst has been prepared and used in the indirect oxidative carbonylation of methanol to dimethyl carbonate (DMC). The activity and stability of the catalyst were further improved by introducing molybdenum into Pd/NaY using a top-down approach (Pd-Mo/NaY catalyst). The Pd-Mo/NaY catalyst exhibited higher stability compared to the Pd/NaY. A high CO conversion of 97% and DMC selectivity of 80% during a 30-hour catalytic test for the Pd-Mo/NaY were obtained. Furthermore, the incorporation of Mo was found to partially heal the silanols and hinder the aggregation of Pd in the Pd-Mo/NaY catalyst. The interactions between Mo and Pd increased the amount of active Pd²⁺ species and enhanced the adsorption of CO reactant on the Pd-Mo/NaY catalyst. The key reaction intermediate of COOCH₃* was captured by in situ diffuse reflectance infrared Fourier transform spectroscopy. The stabilization of active Pd²⁺ species contributed to the enhanced catalytic activity of the Pd-Mo/NaY catalyst in the indirect oxidative carbonylation of methanol to DMC reaction.