固体碱催化剂上碳酸甲乙酯的洁净合成

制备了氧化镁、氧化钙及镁铝复合金属氧化物3种固体碱催化剂，对不同温度下3种催化剂上碳酸二甲酯与碳酸二乙酯酯交换合成碳酸甲乙酯反应的催化性能进行了考察，并推测了固体碱催化剂上碳酸二甲酯与碳酸二乙酯酯交换合成碳酸甲乙酯的反应机理．结果表明，镁铝复合金属氧化物对该反应具有最优的催化活性，在回流温度下、反应时间为4h、碳酸二甲酯与碳酸二乙酯摩尔比为1：1的条件下，碳酸甲乙酯收率可达45．8％．采用X射线衍射，CO2程序升温脱附对催化剂进行表征．X射线衍射谱图显示镁铝复合金属氧化物中以MgO、Al2O3晶相为主，同时存在少量的MgAl2O4物种．CO2程序升温脱附曲线表明酯交换反应主要在弱碱活性住上进行．

Clean Synthesis of Ethyl Methyl Carbonate over Solid Alkali Catalysts

The Mg-Al composite oxide, MgO and CaO catalysts were synthesized and their catalytic properties for the transesterification reaction to synthesize ethyl methyl carbonate from dimethyl carbonate and diethyl carbonate were evaluated at different temperatures respectively. And a possible mechanism for the investigated reaction over solid alkal catalysts was proposed. The results indicate that Mg-Al composite oxide possesses the best catalytic activity for the title reaction: Under the reaction conditions of refluxing temperature, reaction time 4 h and molar ratio of dimethyl carbonate to diethyl carbonate 1:1, the yield of ethyl methyl carbonate reached 45.8%. The catalysts were characterized by means of X-ray diffraction( XRD) , CO2-temperature programmed desorption(CO2-TPD). XRD analysis shows that in the Mg-Al composite oxide catalyst, MgO and Al2O3 are the main crystal phases with a little MgAl2O4 species. The CO2-TPD curves reveal that the weak alkali sites are mainly responsible for the transesterification reaction.