PHOTOCATALYTIC OXIDATION OF PROPAN-2-OL BY SEMICONDUCTOR ZEOLITE COMPOSITES

The photocatalytic oxidation of liquid propan-2-ol to propanone has been investigated using semiconductor-zeolite composites consisting of either CdS or TiO2 in Y zeolite. CdS-based composites were prepared by cation exchange with Cd2+ followed by sulfidation with either Na2S or H2S, whereas TiO2-based composite was prepared by Ti(OEt)4 impregnation followed by hydrolysis and calcination. Rate measurements at 303 K were made to assess how the activity of CdS-based material depended on reaction conditions; differences from CdS supported on gamma-Al2O3 are ascribed to smaller CdS particles and the higher adsorption potential of the zeolite matrix for O2 and H2O. However, rate measurements under standard conditions over the temperature range 283-308 K yielded the same activation energies as for CdS and TiO2 supported on gamma-Al2O3, 53 +/- 2 kJ mol-1 for CdS-based catalysts and 21 +/- 1 kJ mol-1 for TiO2-based catalysts. It follows that the physico-chemical properties of the semiconductor control the activation energy, whereas the zeolite matrix is responsible for controlling semiconductor particle size during preparation and modifying the effective reaction conditions through adsorption.