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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 phosphomolybdic acid and vanadium-substituted phosphomolybdic acid were synthesized and their structures were characterized by UV-Vis, IR and XRD. The acidity in different media was investigated by pH meter. The condensation reaction of acetophenone and alcohol was used as probe The effects of vanadium content, phosphomolybdic acid content, alcohol content and other factors on the catalytic activity of phosphomolybdic acid were investigated.The results showed that the acidity of Dawson phosphomolybdic acid in organic medium was weakened after vanadium was substituted for molybdenum. When the molar ratio of H6P2Mo18O62: acetophenone: ethylene glycol is 6:1000:2000 and the reaction time is 6 h, the ketal yield is 89.2% .In the reaction of synthesizing ketal, However, as the substitution number of vanadium increases, the catalytic activity of vanadium-substituted phosphomolybdic acid decreases. The steric hindrance of alcohol molecules increases, and the catalytic activity of phosphomolybdic acid also decreases.