Dimethyl carbonate synthesis by oxidative carbonylation with CuBr₃L₂ catalyst

A new type of CuBr₃L₂ complex catalyst for dimethyl carbonate (DMC) synthesis by oxidative carbonylation of methanol in liquid-phase was reported. The complex catalysts were characterized by means of XPS and EPR. The results showed that the introduction of complexing agent tetrabuthylammonium bromide (L) can promote the substantial formation of Cu(I) species for DMC synthesis. With the method of orthogonal experiment, the process conditions (temperature, concentration of catalyst, pressure and reaction time, etc.) were examined. The results indicated that under the optimum conditions (temperature 373-383 K, pressure 3.0-3.5 MPa, reaction time 4-6 h, concentration of catalyst in methanol 0.15-0.20 g/mL), the conversion rate of methanol could reach 23% and the selectivity of DMC could exceed 95%. The reaction kinetics with CuBr₃L₂ complex catalyst for DMC synthesis was investigated. The kinetic equation and parameters were obtained. The results showed that the reaction of methanol oxidative carbonylation to DMC by the catalyst was an second order reaction approximately. The reaction rate constant (K_p) was related to reaction temperature and mass concentration of catalyst, and K_p was directly proportional to the square of mass concentration of catalyst. It was indicated that high temperature and pressure were unfavorable to the main reaction and caused the decrease of DMC selectivity.