CATALYSIS AND CHARACTERIZATION OF PD NAY FOR DIMETHYL CARBONATE SYNTHESIS FROM METHYL NITRITE AND CO/

A vapor phase synthesis of dimethyl carbonate (DMC) from carbon monoxi de and methyl nitrite (MN) has been carried out over Pd/NaY catalysts at 383 K, DMC was produced in a good yield. The selectivity to DMC was >85% on the basis of consumed CO or MN. The by-products were dimethyl oxalate, CO2, N2O, methyl formate and dimethoxymethane. The catalytic properties of Pd/NaY were investigated as a function of Pd content an d calcination temperature. It was found that 1 wt.% Pd/NaY calcined at 473 K in air was the. optimum catalyst for the present DMC synthesis. The oxidation state and dispersion of Pd in the Pd/NaY catalysts were characterized by EXAFS and XPS. It was revealed that Pd(NH3)(4)(2+) i n 1 wt.% Pd/NaY changed into Pd metal clusters during the catalytic re action. Pd metal clusters/NaY showed a stable activity for the DMC syn thesis even after 700 h. These results suggest that the cage structure of NaY and anchoring effects of protons suppress Pd metal sintering a nd stabilize very small Pd metal clusters (Pd-13) in the zeolite cages during the reaction.