Photocatalytic oxidation of aldehydes: Byproduct identification and reaction pathway

The byproducts and reaction pathway of gas phase photocatalytic oxidation (PCO) of butyraldehyde, propionaldehyde and acetaldehyde over aerogel TiO2 under weak black light were studied by means of liquid nitrogen trapping, water extraction, mass spectrometry and carbon balance. Aldehydes were photocatalytically oxidized to corresponding acids, shorter carbon-chain aldehydes, carbon dioxide and water. The so-generated acids were further oxidized to shorter carbon-chain aldehydes, carbon dioxide, and water. Other side reactions were suppressed. The reaction pathway we found can be explained in a straightforward manner with active O* as well as hydroxyl group as the major oxidants.