多孔二氧化硅负载硅钨酸催化合成柠檬酸三丁酯

Catalytic synthesis of tri-butyl citrate with H_4SiW_(12)O_(40)/SiO_2

以硅酸钠为硅源,十六烷基三甲基溴化铵为模板剂,采用溶胶–凝胶法合成了负载型硅钨酸/二氧化硅(STA/SiO2)催化剂,并采用红外光谱、氮吸附-脱附、热重对其结构和性质进行了表征。结果表明,所制备的硅钨酸/二氧化硅同时具有微孔和介孔结构,且硅钨酸负载后热稳定性有所提高。以柠檬酸三丁酯的合成作为探针反应,考察了制备催化剂时溶液pH值、硅钨酸负载量对催化剂催化性能的影响。结果表明在pH为9,硅钨酸负载量为50%时,制备的硅钨酸/二氧化硅具有较好的催化活性和重复使用性,该催化剂初次使用时,柠檬酸的转化率在300min可达到89.09%,重复使用6次,柠檬酸的转化率在300min仍可达到86.86%。通过对反应动力学进行研究,发现柠檬酸三丁酯的合成反应为一级反应。

A series of silicon tungsten heteropoly acid immobilized on porous silica catalysts（ STA/SiO2 ） were synthesized by sol-gel synthesis method with sodium meta-silicate as silica source,CTAB as template. Their structures were characterized by IR,N2 adsorp-tion-desorption and TGA-DSC. The results showed that micro-and meso-porous STA/SiO2 catalysts with good thermal stability were synthesized. The effect of pH value,loading amount of silicon tungsten heteropoly acid on the catalytic activities of STA/SiO2 in tri-butyl citrate synthesis were also studied. The results showed that the STA/SiO2 which was synthesized at pH value 9,the loading a-mount of silicon tungsten hetero-poly acid 50%has good catalytic activity and reusability. The conversion of citric acid reaches 89. 09%in 300 min when STA/SiO2 is first used,and it still remains 86. 86%when it is reused six times. The tri-butyl citrate syn-thesis reaction is first order reaction according to the analysis of chemical kinetics.