水滑石/氯化锌催化Knoevenagel缩合反应

Knoevenagel condensation reaction catalyzed by hydrotalcite/zinc chloride

浸渍法制备水滑石负载氯化锌(LDH/ZnCl_(2))催化剂,使用傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、比表面积(BET)、热重分析(TG)对催化剂进行表征。结果表明:在FT-IR中LDH/ZnCl_(2)出现LDH骨架特征吸收峰和ZnCl_(2)特征吸收峰,SEM图中LDH/ZnCl_(2)的表面比LDH表面粗糙,可以辅证ZnCl_(2)负载到LDH上;BET测试结果表明LDH的比表面积为2.0143 m^(2)·g^(-1),LDH/ZnCl_(2)的比表面积为0.8577 m^(2)·g^(-1),二者相比,LDH/ZnCl_(2)的比表面积有所减小。还研究了LDH/ZnCl_(2)在Knoevenagel缩合反应中的催化性能,考察原料摩尔比、溶剂、催化剂用量、反应时间对产率的影响。实验结果表明:室温下,乙醇作溶剂,n(苯甲醛)∶n(丙二腈)=1∶1,催化剂用量为醛用量(质量)的5%,反应时间为15 min,产率为97.5%,催化多种芳香醛化合物与丙二腈反应,产物3a~3h产率为86.2~97.5%,催化剂重复使用3次仍具有较好的催化效果,产率为88.4%。

The hydrotalcite-supported zinc chloride(LDH/ZnCl_(2))catalyst was prepared by the staining method,and the catalyst was characterized by FT-IR,SEM,BET,and TG.The results showed that in FT-IR,LDH/ZnCl_(2) had the characteristic absorption peak of LDH framework and the characteristic absorption peak of ZnCl_(2).The surface of LDH/ZnCl_(2) in the SEM image was rougher than that of LDH,indicating that ZnCl_(2) was loaded on LDH;BET test results showed that the specific surface area of LDH was 2.0143 m^(2)·g^(-1),and the specific surface area of LDH/ZnCl_(2) was 0.8577 m^(2)·g^(-1).Compared with the two,the specific surface area of LDH/ZnCl_(2) was reduced.The catalytic performance of LDH/ZnCl_(2) in the Knoevenagel condensation reaction,the influence of the molar ratio of raw materials,the solvent,the amount of catalyst,and the reaction time on the yield were investigated.The experimental results showed that at room temperature,ethanol was used as a solvent,n(benzaldehyde)∶n(malononitrile)=1∶1,the amount of catalyst was 5%of the amount of aldehyde,the reaction time was 15 minutes,the yield was 97.5%.When catalyzed the reaction of various aromatic aldehydes with malononitrile,the yields of product 3a~3h was 86.2~97.5%.The catalyst was reused for 3 times and still had good catalytic effect,and the yield was 88.4%.