关键词: 磷钨酸 , 缩合反应 , 溶胶-胶凝 , 固体酸

Abstract: Silica-supported H3PW12O40 (e.g. PW12/SiO2) catalysts were prepared in the sol-gel method to solve the problems of H3PW12O40 such as low surface area, difficult separation, and reuse. The catalysts were characterized by XRD and N2-adsorption, their catalytic performance for the condensation of benzaldehyde with glycerol evaluated. The effects of calcination temperature of catalyst, PW12 loading, catalyst dosage and reaction time were investigated. The results show that PW12/SiO2(550 ℃) solid acid have a mean grain size of 20.9~26.4 nm which are typically amorphous. The nanoparticles have high catalytic activity and stability for synthesizing benzaldehyde glycerol acetals. The optimum conditions are as follows: the catalyst calcination temperature is 550 ℃, PW12 loading (mass fraction ) is 10%, the catalyst dosage is 0.5 g, n(benzaldehyde)∶n(glycerol)=1∶1.1, the volume of toluene is 15 mL, the reaction time is 2.0 h. Under these conditions, the conversion of benzaldehyde is 99.2%. Obviouslyy, the unique structure of the Keggin anions and surface acid center and the high specific surface area and the pseudoliquid phase of PW12/SiO2 play an important role in the condensation of benzaldehyde with glycerol.

Key words: H3PW12O40 , Condensation , Sol-gel , Solid acid