Photocatalytic decomposition of acetaldehyde over TiO2/SiO2 catalyst

To establish a promising method for the purification of air containing vola tile organic compounds, photocatalytic decompositions of gaseous acetaldehy de over TiO2 deposited on porous silica. (TiO2/SiO2 catalyst) and over a pl atinized TiO2/SiO2 catalyst (Pt-TiO2/SiO2 catalyst) have been investigated including the capture of intermediates on the catalyst surface and regenera tion of the deactivated catalyst by heating. Results of kinetic analysis sh ow that these photocatalytic decompositions obey Langmuir-Hinshelwood kinet ics. A comparison between the amounts of acetaldehyde decomposed and CO2 pr oduced reveals that about 10 % of acetaldehyde is missing. From the observa tion of the photocatalyst surface before and alter the reaction by FT-IR sp ectroscopy, 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 depo sition 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 multifunctiona l reaction process for air purification, in which volatile organic compound s are photocatalytically decomposed The harmful intermediates, formed durin g the reaction are partly adsorbed on the porous catalyst, remain in the re actor system, and together with deposited coke-like substances are converte d into CO2 by heat treatment of the catalyst. The catalyst is thus regenera ted (C) 1999 Elsevier Science Ltd. All rights reserved.