尿素醇解法合成碳酸乙烯酯

在干燥碱式碳酸锌催化剂的作用下，以尿素和乙二醇（EG）为原料合成碳酸乙烯酯（EC）。重点考察了催化剂用量、原料配比、反应温度、反应时间对反应结果的影响。并通过GC-MS、FTIR和XRD分析，初步探索了反应机理以及碱式碳酸锌的作用机理。结果表明：当催化剂用量为尿素质量的6%，原料配比n（EG）∶n（尿素）=1∶1，反应温度160℃，反应时间3h，反应压力为0.01MPa时，碳酸乙烯酯收率达到91.64%。尿素和乙二醇合成碳酸乙烯酯的反应中，尿素首先分解生成异氰酸，异氰酸再与乙二醇反应生成中间产物2-羟乙基氨基甲酸酯（2-HEC），最后2-羟乙基氨基甲酸酯脱氨环化生成碳酸乙烯酯。所用碱式碳酸锌催化剂中存在Zn₄CO₃（OH）₆·H₂O和ZnO两种晶相，且以ZnO为主活性组分，两种晶相的协同作用提高了反应收率。

Synthesis of ethylene carbonate by urea alcoholysis

The synthesis of ethylene carbonate from urea and ethylene glycol as raw materials over basic zinc carbonate. The influence of reaction conditions such as the amount of catalyst,raw material ratio,reaction temperature and reaction time on the reaction was discussed in detail. And the mechanism of reaction and the effect of basic zinc carbonate were preliminarily explored by using GC-MS,FTIR and XRD. The results showed that the yield of EC could reach 91.64% under the optimum reaction conditions:the catalyst concentration 6% (based on the mass of urea),n(EG):n(urea)=1:1,the reaction time 3h,and the reaction temperature 160℃,and 0.01MPa of pressure. In this reaction,urea decomposed to isocyanic acid in the first step. Then,isocyanic acid reacted with ethylene glycol to produce the intermediate product 2-hydroxyethyl carbamate (2-HEC). 2-HEC deaminized and cyclized to produce EC. Two crystal phases of Zn₄CO₃(OH)₆·H₂O and ZnO exist in the catalyst,in which ZnO acted as the main active component. The synergistic effect of the two crystal phases improved the yield of EC.