Keggin heteropolyacid H3PW12O40 supported on different oxides for catalytic and catalytic photo-assisted propene hydration

Abstract

Catalytic and catalytic photo-assisted hydration of propene to form 2-propanol in gas–solid regime at atmospheric pressure and 85 °C were carried out by using a heteropolyacid (POM) supported on different oxides. Binary materials were prepared by impregnation of H₃PW₁₂O₄₀ on different commercial and home prepared supports (TiO₂, SiO₂, WO₃, ZrO₂, ZnO, Al₂O₃). Some of the composites were active both for catalytic and catalytic photo-assisted reactions. The Keggin type POM was completely and partially degraded, when supported on ZnO and Al₂O₃, respectively, and these binary solids always resulted as inactive for both catalytic and catalytic photo-assisted reactions. The supported Keggin POM species played a key role both for the catalytic and the photo-assisted catalytic reactions, due to their strong acidity and ability to form strong oxidant species under UV irradiation, respectively. The contemporary presence of heat and UV light improved the activity of almost all POM supported materials. All materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM), diffuse reflectance spectroscopy (DRS), determination of the conduction and valence band energy by photovoltage measurements, Fourier transform infrared spectroscopy (FTIR), NH₃-TPD experiments and time resolved microwave conductivity (TRMC).