Cr modified TiO2-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 TiO2-loaded MCM-41 silica and commercial TiO2 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% TiO2 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 TiO2 loading on Cr-MCM-41 improve its activity in diethyl sulfide removal but decelerated the CO2 formation. On the contrary, the rate of ethanol oxidation increased strongly as a result of TiO2 loading and the highest activity was observed for 25% TiO2/MCM-41 photocatalyst without chromium. Sulfate species were detected on the TiO2 surface after complete diethyl sulfide oxidation. Water and CO2 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 TiO2/MCM-41 and TiO2/Cr-MCM-41 photocatalysts in oxidation of gas phase diethyl sulfide and ethanol.

► TiO2/Cr-MCM-41 purifies air from vapors of diethyl sulfide and ethanol.
► The best Si to Cr ratio was 80 for air purification rate and completeness.
► TiO2/MCM-41 without Cr was most active for ethanol vapor photooxidation.
► TiO2 Degussa P25 was superior to Hombifine N for diethyl sulfide vapors oxidation.
► The composites did not exhibit activity under visible light in gas phase.