Immobilizing heteropolyacids on zirconia-modified silica as catalysts for oleochemistry transesterification and esterification reactions
Immobilizing heteropolyacids on zirconia-modified silica as catalysts for oleochemistry transesterification and esterification reactions
复制标题
DOI：
10.1016/j.jcat.2014.09.016
复制
发表时间：
2014-12
影响因子：
7.3
通讯作者：
M. Kuzminska;T. Kovalchuk;R. Backov;E. Gaigneaux
中科院分区：
文献类型：
--
作者：
M. Kuzminska;T. Kovalchuk;R. Backov;E. Gaigneaux
提出了一种化学固定化Keggin杂多酸的新方法。将H3PW12O40、H4SiW12O40和H3PMo12O40固定在丁氧锆接枝的二氧化硅上。该固定化方法促进了HPA与载体之间的强相互作用，使HPA的分散度达到25wt.%，从而增加了酸中心的密度。该催化剂对硬脂酸甲酯与正丁醇的酯交换反应和油酸与三羟甲基丙烷的酯化反应具有较高的催化活性。我们证明，与固定化H3PMo12O40相反，H3PW12O40和H4SiW12O40催化剂在非极性油酸介质中对浸出是稳定的。从HPA载体与非极性介质的相互作用强度出发，讨论了如何避开非极性介质中的淋溶。载体与H3PW12O40(或H4SiW12O40)之间较强的相互作用(即较好的抗浸出能力)是由于与Zr-O-Mo相比，Zr和W之间的电负性差较小，且Zr-O-W键的极化率较低。
A new method of chemical immobilization of Keggin heteropolyacids (HPAs) was suggested. H3PW12O40, H4SiW12O40, and H3PMo12O40were immobilized on the silica which was previously grafted with zirconium butoxide. The immobilization method promoted strong interaction HPA-support and yielded 25 wt.% of well-dispersed HPAs, so increasing the density of acid sites. The catalysts were active in the reaction of transesterification of methyl stearate with n-butanol and esterification of oleic acid with trimethylolpropane. We demonstrate that, contrary to the immobilized H3PMo12O40, the H3PW12O40and H4SiW12O40-based catalysts are stable toward leaching in a non-polar oleic acid medium. A discussion on circumventing the leaching in non-polar versus polar media is proposed in terms of interaction strength HPA-support. The stronger interaction (i.e., better resistance for leaching) between the support and H3PW12O40(or H4SiW12O40) is referred to the lower difference of electronegativity between Zr and W and the lower polarizability of the bonds Zr–O–W compared to Zr–O–Mo.