Comparison between catalytic and catalytic photo-assisted propene hydration by using supported heteropolyacid

Abstract

Hybrid materials have been prepared by impregnation of the heteropolyacid H 3PW 12O 40 on commercial TiO 2. The polyoxometalates (POM) amount deposited was 15, 30, 50 and 70% with respect to the weight of the TiO 2 support. Moreover two samples containing a POM amount of 15, and 50% with respect to the weight of SiO 2 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 TiO 2 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/TiO 2 and POM/SiO 2 materials, although POM/TiO 2 showed better catalytic and catalytic photo-assisted activity than POM/SiO 2. 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 TiO 2 under UV irradiation improved the heteropolyacid performance supplying conduction band electrons to the POM.