碱性氧化物催化氨基甲酸乙酯与乙醇合成碳酸二乙酯

在釜式反应器中,以碱性氧化物为催化剂,对尿素与乙醇合成碳酸二乙酯(DEC)的决速步骤氨基甲酸乙酯(EC)与乙醇反应合成DEC进行了活性测试,并采用CO2-TPD方法表征了催化剂的碱性质,研究了碱性氧化物的碱性质与催化活性的关系,同时考察了反应温度、反应时间和催化剂用量对DEC合成反应的影响。实验结果表明,CaO具有最佳的催化活性,这是因为CaO表面具有最强的碱性位;以CaO为催化剂合成DEC的最佳反应条件为:EC 0.1 g、乙醇1.0 mol、反应温度190℃、反应时间9 h、催化剂用量1.0 g;在此条件下,EC转化率为40.7%,DEC收率为20.8%。表征结果显示,碱性氧化物的碱强度是影响其催化活性的重要因素,其表面碱性位可与乙醇中的羟基作用释放Hδ+,从而活化乙醇,促进DEC的合成。

Synthesis of Diethyl Carbonate from Ethyl Carbamate and Ethanol over Basic Oxide Catalysts

The synthesis of diethyl carbonate(DEC) from ethyl carbamate(EC) and ethanol over basic oxide catalysts was studied in a batch reactor,which was a rate-determining step for the reaction of urea and ethanol.The basicities of the catalysts were measured by means of CO2-TPD and the relationship between the catalyst performances and the basicities was studied.The effects of reaction temperature,reaction time and catalyst dosage on the synthesis were investigated.The catalytic performance of CaO among the used basic oxides was the best due to its strongest basicity.Under the optimal reaction conditions:EC 0.1 g,ethanol 1.0 mol,reaction temperature 190 ℃,reaction time 9 h and CaO catalyst dosage 1.0 g,EC conversion was 40.7% and DEC yield was 20.8%.The characterization results showed that,the surface base sites could activate ethanol through the abstraction of Hδ +,which could promote the DEC synthesis.