K/KCC-1催化碳酸二甲酯和乙醇酯交换合成碳酸甲乙酯

Synthesis of methyl ethyl carbonate by transesterification of Dimethyl carbonate and ethanol catalyzed using K/KCC-1

摘要:

采用水热合成法制备树突纤维状二氧化硅（KCC-1）载体，以乙酸钾为前驱体，采用等体积浸渍法制备了不同负载量的固体碱催化剂K/KCC-1。通过XRD、FTIR、BET、CO2-TPD和SEM对K/KCC-1材料的晶型、孔道结构、碱性特征、形貌等进行了表征，评价了催化剂对碳酸二甲酯（DMC）和乙醇酯交换合成碳酸甲乙酯（EMC）的催化性能。结果表明K/KCC-1催化剂均具有两种碱性位，分别是由K-O-Si提供的弱碱性位和由K2CO3提供的中强碱性位，且随着K负载量的增加，弱碱性位点逐渐下降，中强碱性位点逐渐增强，催化剂的反应活性增强。K负载量不超过0.9的K/KCC-1仍保持KCC-1的树突纤维结构，使得反应物分子能够轻松的扩散到活性位点上。0.9K/KCC-1具有最高的催化活性，在反应温度为80 ℃、反应时间为5 h、DMC与乙醇的摩尔比为4:1、催化剂用量为DMC的5%的最佳反应条件下，DMC转化率为91.0%，EMC选择性为95.5%。

Abstract:

The dendritic fibrous silica (KCC-1) was prepared by hydrothermal synthesis, and solid base catalyst K/KCC-1 with different loading was prepared by equal volume impregnation with potassium acetate as precursor. The crystal morphology, pore structure and basic characteristics of K/KCC-1 material were characterized by XRD, FTIR, BET, CO2-TPD and SEM etc. The transesterification performance of dimethyl carbonate (DMC) and ethanol to methyl ethyl carbonate (EMC) was evaluated. The results indicate that the K/KCC-1 catalyst has two types of basic sites, the weak basic sites provided by K-O-Si and the medium strong basic sites provided by K2CO3. With the increase of K loading, the weak basic sites gradually decrease, and the medium strong basic sites gradually increase, enhancing the reaction activity of transesterification. K/KCC-1 with a K loading of no more than 0.9 still maintains the dendritic fiber structure of KCC-1, allowing the reactant molecules to easily diffuse to the Active site. 0.9K/KCC-1 has the highest catalytic activity. Under the optimal reaction conditions of reaction temperature of 80 oC, reaction time of 5 hours, molar ratio of DMC to ethanol of 4:1, and catalyst dosage of 5% of DMC, the conversion rate of DMC is 91.0%, and the EMC selectivity is 95.5%.