摘要
合成了Dawson型磷钼酸和钒取代磷钼酸,用UV-Vis、IR和XRD表征了结构,用pH计考察了在不同介质中的酸性.以苯乙酮和醇的缩合反应作为探针反应,考察了磷钼酸中钒含量、磷钼酸用量及醇用量等因素对磷钼酸催化性能的影响.结果表明,钒取代钼后使Dawson型磷钼酸在有机介质中的酸性减弱.当H6P2Mo18O62∶苯乙酮∶乙二醇的物质的量比为6∶1000∶2000,回流反应6 h时,缩酮收率为89.2%.在合成缩酮的反应中,磷钼酸的"假液相"性使其催化活性明显增强,但随着钒取代数增加,钒取代磷钼酸的催化性能减弱;醇分子的空间位阻增大,磷钼酸的催化活性也降低.
Dawson type molybdophosphoric acid and vanadium-substituted molybdophosphoric acids have been syn- thesized and characterized with UV-Vis, IR, XRD and their acidities were investigated in different media using pH meter. The condensation of acetophenone to ketal which has been synthesized from acetophenone and ethylene glycolas has been as a probe reaction to study the effects of vanadium-substituted molybdophosphoric acids with different amount vanadium atoms, amounts of catalyst and ethylene glycol. The results showed that the yields of the acetophenone ethylene glycol got up to 89.2 % when the molar ratio of H6P2Mo18O62 to acetophenone to ethylene glycol was 6： 1000： 2000 after 6 h reflux reaction. The acidities of Dawson-type molybdophosphoric acids were decreased after the molybdenum atoms were substituted by vanadium atoms in the organic mediums. The condensations of acetophenone with alcohols were markedly accelerated by the ＂pseudoliquid phase＂ of the molybdophosphoric acid. The catalytic activities of the vanadium-substituted molybdophoric acids were decreased with the increasing of the amounts of vanadium atom in the molecules, and the yields of ketal were decreased with increasing of the spatial baffle of the alcohols.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2009年第6期511-516,共6页
Journal of Molecular Catalysis(China)
关键词
DAWSON
磷钼酸
缩合
催化
Dawson
Molybdophosphorie acid
Condensation
Catalysis
