| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 64973 | Journal of Molecular Catalysis A: Chemical | 2015 | 11 Pages |
•Intermediates of acetone photo-oxidation were identified by FTIR spectroscopy.•Identified surface species in the photo-oxidation of several organic compounds.•Initial acetone coverage determines rate of photo-oxidation and surface species.•Acetates and formates are key photo-oxidation intermediates.•Carbonates/bi-carbonates accumulate on the TiO2 surface during photo-oxidation.
In situ transmission infrared spectroscopy was used to investigate the photo-oxidation of acetone on a commercial, oxidized TiO2 (P25) powder catalyst under UV irradiation at ambient temperature, in the absence and presence of gas phase O2. The photochemistry of a number of organic molecules (2-butanone, methanol and acetic acid,) under the same conditions was also studied in order to identify reaction intermediates and products formed in the photo-oxidation of acetone. Under anaerobic conditions (in the absence of gas phase oxygen) limited extent of photo-oxidation of acetone took place on the oxidized TiO2 sample. In the presence of O2 in the gas phase, however, acetone was completely converted to acetates and formates, and ultimately CO2. The initial step in the sequence of photo-induced reactions is the ejection of a methyl radical, resulting in the formation of surface acetates (from the acetyl group) and formates (from the methyl radicals). Acetate ions are also converted to formates, that, in turn, photo-oxidized to CO2. Under the experimental conditions applied the accumulation of carbonates and bicarbonates were observed on the TiO2 surface as the photo-oxidation of acetone proceeded (this was also observed during the course of photo-oxidation of all the other organics studied here). When the initial radical ejection step produced hydrocarbons containing more than one C atoms (as in the case in 2-butanone and mesytil oxide), the formation of aldehydes on the catalyst surface was also observed as a result of secondary reactions.
Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (147 K)Download as PowerPoint slideSurface species formed in the UV photo-oxidation of acetone on a commercial TiO2 powder were identified. After fast methyl radical ejection, the formed carboxylates slowly decompose to CO2, while surface carbonates/bicarbonates accumulate on the TiO2 surface.
