Mechanistic Investigation of Dimethyl Carbonate Synthesis Over Palladium Chloride Catalyst

The production of dimethyl carbonate (DMC) from CO and methyl nitrite (MN) is of great industrial interest for chemicals upgrading. As one of the most efficient catalysts, PdCl₂ based catalyst has been widely investigated and been verified to be highly selective toward DMC yielding. However, the underlying mechanism is unclear so far. Herein, we identified the active sites and corresponding reaction pathway on PdCl₂ (140) surface by the density functional theory (DFT) calculations, combining with X-ray absorption fine structure (XAFS) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements. The dissociation of MN resulted in the construction of Cl vacancies on PdCl₂ (140) surface, which are the specific sites for DMC formation. On the other hand, the continuous loss of Cl induced the reduction of PdCl₂ to Pd, leading to changed pathway of reaction and decreased yield of DMC. These insights highlighted the importance of Cl-balance in PdCl₂ based catalyst system, which determined the final products of CO oxidative esterification.