摘要
采用共沉淀法制备了一种棒状MgO(MgO-P)作为催化剂用于催化草酸二甲酯(DMO)和乙醇酯交换合成草酸二乙酯(DEO)反应。当MgO-P占DMO的2.0%(质量分数),DMO和乙醇的物质的量之比为1:10时,70℃下反应2 h后,DMO转化率可达97.7%,对应DEO选择性可达57.7%。催化剂重复使用5次后,DMO转化率和DEO选择性分别降低至80.5%和21.2%,重复使用后的催化剂经焙烧再生后可恢复活性。通过X射线衍射、N_(2)吸/脱附和CO_(2)程序升温脱附法等表征了催化剂结构,并结合催化性能系统讨论了固体催化剂在酯交换法合成DEO反应中的构效关系。结果表明,固体催化剂表面中强碱性位是DMO酯交换合成DEO的活性位,并据此提出了催化剂表面酯交换反应机理,MgO结构中O^(2-)作为碱性位可以极化乙醇分子中羟基氢,生成的乙氧基阴离子可以通过亲核进攻DMO中的羰基碳而引发酯交换反应。
Rod-shaped MgO(MgO-P)was prepared by coprecipitation method and used as catalyst for the transesterification of dimethyl oxalate(DMO)with ethanol to diethyl oxalate(DEO).The results show that the DMO conversion can reach 97.7%,corresponding selectivity to the DEO of 57.7%,when MgO-P accounted for 2.0%(mass fraction)of DMO,the molar ratio of DMO and ethanol is 1:10,and after 2 h of reaction at 70℃,and the DMO conversion and DEO selectivity decrease from 95.8%and 56.0%to 80.5%and 21.2%after five cycles,respectively.The used catalyst can be easily regenerated by a simple calcination process.The structureactivity relationship of solid catalysts for this transesterification reaction was systematically discussed based on the results of catalytic performance and various characterization techniques,such as X-ray diffraction,N_(2) adsorption/desorption and CO_(2) temperatureprogrammed desorption.It is found that the medium strength basic sites on the catalyst surface are the active sites for the synthesis of DEO through transesterification of DMO with ethanol,and the mechanism for the transesterification of dimethyl oxalate with ethanol to diethyl oxalate was also proposed that hydroxyl hydrogen in alcohol was firstly polarized by O^(2-)in MgO as the basic site of the catalyst,then the generating ethoxy anion would nucleophillic attack the carbon atom in the carbonyl group of DMC to initiate the transesterification reaction.
作者
陈芳菊
冯俊
李进
李红力
魏忠
宋晓玲
王自庆
CHEN Fangju;FENG Jun;LI Jin;LI Hongli;WEI Zhong;SONG Xiaoling;WANG Ziqing(Corps Key Laboratory of Green Chemical Processes,School of Chemistry and Chemical Engineering,Shihezi University,Shihezi 832000,Xinjiang,China;Xinjiang Tianye(Group)Co.,Ltd.,Shihezi 832000,Xinjiang,China)
出处
《天然气化工—C1化学与化工》
CAS
北大核心
2022年第4期138-144,共7页
Natural Gas Chemical Industry
基金
新疆生产建设兵团强青科技创新骨干人才项目(2021CB031)
石河子大学高层次人才科研启动经费(RCZK2018C25)。
关键词
酯交换反应
草酸二甲酯
MgO催化剂
草酸二乙酯
transesterification reaction
dimethyl oxalate
magnesium oxide catalyst
diethyl oxalate
