Efficient and stable catalysts for the synthesis of dimethyl carbonate by carbonylation of methyl nitrite applying the starch-coated activated carbon as a support

Abstract

For the synthesis of dimethyl carbonate (DMC) by carbonylation of methyl nitrite (MN), the lack of efficient and stable catalysts is a crucial factor limiting the application of this technology. It is well known that the physical structure and surface physicochemical properties of a support affect the sintering resistance, catalytic activity and selectivity of a catalyst. Hence, the catalytic performance of the catalyst can be effectively improved by modifying the support. Herein, a series of starch-coated catalysts (Pd–Cu/AC@SX, X = 3, 4, and 5) were prepared and applied for the synthesis of DMC. Among them, the catalyst modified with a concentration of 4 wt% of starch (Pd–Cu/AC@S4) performed the best with a weight time yield of DMC (WTY_DMC) of 1450 g kg_cat⁻¹ h⁻¹, the DMC selectivity based on CO (S_DMC/CO) up to 100%, and the CO conversion to DMC (C_CO) of 53.5%, which improved by nearly 40% compared to the original catalyst. The characterization results showed that the increase in Lewis acidity and the content of Cu²⁺ helped in maintaining the long-term presence of Pd²⁺, the active center of the reaction, which was a key factor for improving the stability. Besides, the increase in the specific surface area and effective pore volume of the micropores of the support improves the selectivity of the catalyst and the dispersion of the metals (Pd²⁺ and Cu²⁺), which is the main reason for the increase in catalytic activity. Eventually, the starch-coated catalysts exhibited excellent catalytic performance. This work puts forward a new idea for the modification of activated carbon supports, and provides an efficient catalyst for the carbonylation of MN to DMC.