Research on synergistic effect in transesterification reaction catalyzed by Salen-AlCl/n-Bu_4NBr system

Dimethyl carbonate(DMC) has extensive applications as an environmentally benign chemicals.It is mainly synthesized by oxidative carbonylation of methanol(non-phosgene route) or phosgenation of methanol(phosgene route),but both routes involve the use of poisonous or corrosive phosgene or carbon monoxide.DMC is also mildly synthesized by transesterification.The catalytic behavior of Salen-Al complex in ethylene carbonate and methanol transesterification for synthesis of dimethyl carbonate were investigated.A synergistic effect between SalenAlCl and n-Bu_4NBr is discovered.The results show that Salen-AlCl/n-Bu_4NBr system is not only a good catalyst for cyclic addition reaction of CO_2 and ethylene oxide but also effective for transesterification reaction of ethylene carbonate and methanol.The optimal reaction conditions are 120 ℃,2 h,n(MeOH)∶n(PC)=8∶1 and 0.4% of molar fraction(catalyst).