Li掺杂CeO_(2)固体碱催化甘油酯交换合成碳酸甘油酯

Synthesis of glycerol carbonate by transesterification of glycerol catalyzed by Li doped CeO_(2)solid base

针对由甘油制备碳酸甘油酯的酯交换法中催化剂制备方法复杂、活性组分易流失等问题,采用一锅法制备了Li掺杂CeO_(2)固体碱催化剂。对催化剂进行了X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、BET、X射线光电子能谱(XPS)、CO_(2)程序升温脱附(CO_(2)-TPD)等表征。以甘油转化率和碳酸甘油酯产率为指标,对催化剂进行了筛选,并采用单因素实验对甘油酯交换合成碳酸甘油酯的工艺条件进行了优化,同时考察了催化剂的重复使用性能。结果表明:Li与CeO_(2)之间能够产生协同作用,Li的掺杂能够明显增加CeO_(2)的中强碱活性位点;Li、Ce与柠檬酸物质的量比为0.3∶1∶1时,催化剂催化活性最好;甘油酯交换合成碳酸甘油酯的最优反应条件为反应温度100℃、反应时间2.0 h、催化剂用量为甘油质量的1%、甘油与碳酸二甲酯物质的量比1∶2,在此条件下甘油转化率为90.16%,碳酸甘油酯收率为90.04%;催化剂在重复使用5次后活性无明显下降。采用一锅法制备的Li掺杂CeO_(2)固体碱催化剂具有良好的催化性能,可用于催化甘油酯交换合成碳酸甘油酯。

Aiming at the problems of complex preparation method and easy loss of active components of catalyst in the transesterification method of preparing glycerol carbonate from glycerol,Li doped CeO_(2)solid base catalyst was prepared by one pot method.The catalyst was characterized by XRD,SEM,TEM,BET,XPS and CO_(2)-TPD.With conversion rate of glycerol and yield of glycerol carbonate as indexes,the catalyst was screened and the conditions of transesterification of glycerol to prepare glycerol carbonate were optimized by single factor experiment.The reusability of the catalyst was investigated.The results showed that there was a synergistic effect between Li and CeO_(2),and Li doping could significantly increase the medium and strong base sites of CeO_(2).When molar ratio of Li,Ce and citric acid was 0.3:1:1,the catalyst had the best activity.The optimal reaction conditions were obtained as follows:reaction temperature 100℃,reaction time 2.0 h,catalyst dosage 1%of glycerol mass,and molar ratio of glycerol to dimethyl carbonate 1:2.Under these conditions,the conversion rate of glycerol was 90.16%and the yield of glycerol carbonate was 90.04%,and the activity of the catalyst did not decrease significantly after reused for five times.Li doped CeO,solid base catalyst prepared by one pot method has good catalytic performance,and can be used to catalyze synthesis of glyceryl carbonate by transesterification of glycerol.