Abstract
Hybrid materials have been prepared by impregnation of the heteropolyacid H3PW12O40 on commercial TiO2. The polyoxometalates (POM) amount deposited was 15, 30, 50 and 70% with respect to the weight of the TiO2 support. Moreover two samples containing a POM amount of 15, and 50% with respect to the weight of SiO2 were also prepared for the sake of comparison. All prepared samples were efficient catalysts for the hydration of propene to 2-propanol in gas–solid regime at atmospheric pressure and at temperatures ranging between 50 and 85°C. The study carried out on the hybrid TiO2 based materials evidenced that, as far as the catalytic activity is concerned, exists an optimum in the amount of POM. Notably the contemporary presence of heat and UV light improved the activity of the POM/TiO2 and POM/SiO2 materials, although POM/TiO2 showed better catalytic and catalytic photo-assisted activity than POM/SiO2. POM species played a key role in both the catalytic and photo-assisted catalytic reactions, due to its surface acidity and ability to form strong oxidant species under UV irradiation. The presence of TiO2 under UV irradiation improved the heteropolyacid performance supplying conduction band electrons to the POM.
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