Lewis酸碱催化氨基甲酸甲酯和甲醇合成碳酸二甲酯

以反应釜为评价装置,考察了不同种类的Lewis酸和Lewis碱催化剂对氨基甲酸甲酯(MC)和甲醇反应合成碳酸二甲酯的催化活性。在Lewis酸系列催化剂中,ZnCl2具有最佳的催化活性,ZnCl2能与MC的酰胺基上的氮原子配位,从而高效地活化MC;在Lewis碱系列催化剂中,CaO具有最高的催化活性,能稳定甲醇中的甲氧基负离子,从而高效地活化甲醇。在相同条件下,ZnCl2的催化活性高于CaO。二者的混合物能同时活化两个反应底物而起到协同作用,达到最佳的催化效果。在反应温度为180℃、反应时间为10h、甲醇和MC的摩尔比为20∶1的条件下,当MC用量为7.5g时,以0.5gZnCl2和0.5gCaO的混合物为催化剂,MC的转化率为58.5%,碳酸二甲酯的收率可达42.0%。

Synthesis of Dimethyl Carbonate from Methyl Carbamate and Methanol by Lewis Acid-Base Catalysis

Synthesis of dimethyl carbonate from methyl carbamate(MC)and methanol by Lewis acid and Lewis base catalysis were studied in a batch reactor.Among the Lewis acids,zinc chloride was the best which was able to effectively activate basic substrate methyl carbamate by coordination with nitrogen atom of amide.Among the Lewis bases,calcium oxide was the best which was able to effectively activate acid substrate methanol by stabilizing methoxy anion.Under same reaction conditions,the activity of zinc chloride was better than that of calcium oxide.The mixture of the two as catalyst showed synergistic effect in activating both methyl carbamate and methanol at the same time.Under the reaction conditions:180 ℃,10 h,mole ratio of methanol to MC 20 ∶ 1,MC dosage 7.5 g,and mixture of 0.5 g zinc chloride and 0.5 g calcium oxide as catalyst,conversion of MC was 58.5% and yield to dimethyl carbonate was 42.0%.