Catalytic Decarbonylation of Dimethyl Oxalate to Dimethyl Carbonate on Halogen-Modified Alkali Metal Carbonates in a Fixed-Bed Reactor

The activated carbon (AC) supported alkali carbonate catalysts were investigated for dimethyl oxalate (DMO) decarbonylation to dimethyl carbonate (DMC) in a fixed-bed reactor. Among the tested catalysts, K2CO3 supported on AC demonstrated superior performance. Systematic optimization of the preparation conditions identified 200 °C and 20 wt% as the optimal calcination temperature and K2CO3 loading, respectively, achieving the highest DMO conversion and DMC selectivity. The introduction of KBr as a modifier provided a marked improvement, enhancing DMC selectivity from 83.10% to 89.19%. However, during a 20 h stability test, the 10%KBr + 20%K2CO3/AC catalyst exhibited a gradual decline in DMC selectivity. This deactivation is attributed to the leaching of KBr and the formation of potassium oxalate (K2C2O4) via DMO hydrolysis, which is triggered by trace water in the feedstock. Consequently, the trace amount of water in the feedstock would influence both the DMO conversion and DMC selectivity.