摘要
合成了不同形貌的ZnO样品,将其作为催化剂用于催化草酸二甲酯(DMO)和无水乙醇(EtOH)酯交换法合成草酸二乙酯(DEO)反应。采用XRD、N_(2)低温物理吸附、XPS、SEM和CO_(2)-TPD对催化剂进行了表征,讨论了ZnO形貌与其催化活性之间的构效关系,考察了反应条件对DMO转化率和DEO选择性的影响,并探究了催化剂重复使用后失活的原因和反应动力学。结果表明,DMO与无水乙醇的酯交换反应活性与ZnO形貌密切相关,其中,花状微球ZnO(ZnO-f)的催化活性最高,在最优条件下〔DMO 1.18 g、n(EtOH)∶n(DMO)=12∶1、ZnO-f用量为DMO质量的2.0%、反应温度80℃、反应时间120 min〕,DMO转化率和DEO选择性分别为99.8%和75.8%。催化剂循环使用4次后,DEO选择性降至25.7%,Zn(OH)_(2)的生成导致总碱性位数量急剧下降和氧空位的丧失是催化剂失活的原因。DMO和无水乙醇在ZnO-f表面的酯交换反应活化能为35.6 kJ/mol,ZnO-f表面存在的丰富中强碱性位活化了DMO和无水乙醇酯交换反应,强碱性位的存在则会抑制该反应的进行。
ZnO samples,synthesized with different morphologies and characterized by XRD,N2 low temperature physical adsorption,XPS,SEM and CO_(2)-TPD,were employed as catalysts for the synthesis of diethyl oxalate(DEO)from transesterification between dimethyl oxalate(DMO)and ethanol(EtOH).The structure-activity relationship between ZnO morphology and its catalytic performance was analyzed,while the influence of reaction conditions on DMO conversion and DEO selectivity were investigated.Moreover,the catalyst deactivation after repeated use and the reaction kinetics were explored.The results showed that the catalytic activity of ZnO samples was closely related to their morphologies,with the flower-like ZnO(ZnO-f)exhibiting the best performance.The DMO conversion rate and DEO selectivity over ZnO-f catalysis reached 99.8%and 75.8%,respectively,under the optimal reaction conditions of DMO 1.18 g,n(EtOH)∶n(DMO)=12∶1,ZnO-f dosage 2.0%of the mass of DMO,reaction temperature 80℃,and reaction time of 120 min.The DEO selectivity decreased to 25.7%after four cycles of ZnO catalyst,respectively.The deactivation of the catalyst was attributed to the formation of Zn(OH)_(2)phase leading to a sharp decrease in the total number of basic sites and the loss of oxygen vacancies.The transesterification of DMO with ethanol over ZnO-f catalyst displayed an activation energy of 35.6 kJ/mol,and the abundant medium basic sites over ZnO-f contributed to its excellent catalytic activity in the transesterification reaction of DMO with ethanol,while the presence of strong basic sites would inhibit the progress of the reaction.
作者
李红力
陈芳菊
王自庆
王培贤
魏忠
宋晓玲
LI Hongli;CHEN Fangju;WANG Ziqi;WANG Peixian;WEI Zhong;SONG Xiaoling(School of Chemistry and Chemical Engineering,Key Laboratory for Green Process of Chemical Engineering of Xinjiang Bingtuan,Shihezi University,Shihezi 832001,Xinjiang,China;Xinjiang Tianye(Group)Co.,Ltd.,Shihezi 832001,Xinjiang,China)
出处
《精细化工》
EI
CAS
CSCD
北大核心
2024年第9期1987-1995,共9页
Fine Chemicals
基金
新疆生产建设兵团强青科技创新领军人才计划项目(2021CB031)
新疆生产建设兵团区域创新引导计划项目(2022BB003)。
关键词
草酸二甲酯
酯交换
催化剂
形貌
花状微球ZnO
草酸二乙酯
dimethyl oxalate
ester exchange
catalysts
morphology
flower-like ZnO microspheres
diethyl oxalate
