Photocatalytic oxidation of propan-2-ol by semiconductor–zeolite composites

Abstract

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 γ-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 γ-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.