Synthesis of Dimethyl Carbonate by Oxidative Carbonylation with CuBr_3L_2 Catalyst

A novel type of CuBr3L2 complex catalyst for dimethyl carbonate (DMC) synthesis by oxidative carbonylation of methanol in liquid-phase was reported. The results show that under the reaction conditions of temperature 373~383 K, pressure 3.5 MPa, reaction time 4~6 h and the mass concentration of the proposed catalyst in methanol 0.15~0.20 g·mL-1, the conversion rate of methanol can be maintained around 23%~25% and the selectivity of DMC is about 96%~98%. The catalyst proposed has a stable catalytic activity and can be used repeatedly at least 5 recycles. The complex catalysts prepared were characterized by XPS and EPR, and the results indicate that the introduction of complexing agent tetrabuthylammonium bromide (L) can promote the substantial formation of Cu(Ⅰ) species for DMC synthesis. The synthesis reaction mechanism was studied, and the reaction kinetics with CuBr3L2 complex catalyst for DCM synthesis was investigated. The reaction kinetic equation and parameters of the equation were obtained. The results show that the reaction of methanol oxidative carbonylation to DMC by the complex catalyst proposed is an approximate second order reaction, and the reaction rate constant, Kp, is related to reaction temperature and is directly proportional to the square of the mass concentration of catalyst. The experiments also show that high reaction temperature and pressure are unfavorable to the main reaction and will cause the decrease of DMC selectivity.