Cr modified TiO ₂-loaded MCM-41 catalysts for UV-light driven photodegradation of diethyl sulfide and ethanol

Gas-phase photocatalytic oxidation (PCO) and adsorption of diethyl sulfide and ethanol in a batch reactor using Cr-modified TiO ₂-loaded MCM-41 silica and commercial TiO ₂ as photocatalysts were studied with in situ FTIR method. Mesoporous molecular sieves MCM-41 modified with Cr were synthesized by hydrothermal method; Si:Cr atomic ratio was 80:1 or 20:1. Final deposition of 25% TiO ₂ was conducted by sol-gel method using titanium isopropoxide as a precursor. Adsorption measurements in a static reactor were used to estimate the Langmuir isotherm parameters (monolayer capacity and adsorption constant). Photooxidation experiments under UV irradiation demonstrated that TiO ₂ loading on Cr-MCM-41 improve its activity in diethyl sulfide removal but decelerated the CO ₂ formation. On the contrary, the rate of ethanol oxidation increased strongly as a result of TiO ₂ loading and the highest activity was observed for 25% TiO ₂/MCM-41 photocatalyst without chromium. Sulfate species were detected on the TiO ₂ surface after complete diethyl sulfide oxidation. Water and CO ₂ were identified as the final products whereas acetaldehyde and CO were identified as by-products of ethanol photocatalytic oxidation. Visible light activity was not detected for TiO ₂/MCM-41 and TiO ₂/Cr-MCM-41 photocatalysts in oxidation of gas phase diethyl sulfide and ethanol.