Photocatalytic decomposition of acetaldehyde over TiO2/SiO2 catalyst

To establish a promising method for the purification of air containing volatile organic compounds, photocatalytic decompositions of gaseous acetaldehyde over TiO2 deposited on porous silica. (TiO2/SiO2 catalyst) and over a platinized TiO2/SiO2 catalyst (Pt-TiO2/SiO2 catalyst) have been investigated including the capture of intermediates on the catalyst surface and regeneration of the deactivated catalyst by heating. Results of kinetic analysis show that these photocatalytic decompositions obey Langmuir-Hinshelwood kinetics. A comparison between the amounts of acetaldehyde decomposed and CO2 produced reveals that about 10 % of acetaldehyde is missing. From the observation of the photocatalyst surface before and alter the reaction by FT-IR spectroscopy, we conclude that this is due to the adsorption of intermediates such as formic acid and acetic acid on the porous catalyst as well as deposition of coke-like substances. When the Pt-TiO2/SiO2 catalyst is heated to a temperature above 473 K, these substances can be removed and discharged as CO2. A series of results obtained in the present work suggests that the use of a Pt-TiO2/SiO2 catalyst will enable us to construct a multifunctional reaction process for air purification, in which volatile organic compounds are photocatalytically decomposed The harmful intermediates, formed during the reaction are partly adsorbed on the porous catalyst, remain in the reactor system, and together with deposited coke-like substances are converted into CO2 by heat treatment of the catalyst. The catalyst is thus regenerated (C) 1999 Elsevier Science Ltd. All rights reserved.