Heterogeneous selective oxidation of formaldehyde on oxide catalysts: In situ FTIR study of formaldehyde surface species on a V-Ti-O catalyst and oxygen effect

The interaction of formaldehyde with a highly selective V-Ti-O catalyst for the oxidation of formaldehyde to formic acid is studied by Fourier-transfo rm infrared (FTIR) spectroscopy at 70-200 degrees C. In a flow of formaldeh yde/oxygen mixture and in a mixture without oxygen at optimal temperatures for formic acid formation (100-140 degrees C), methoxy groups and other oxy genates are formed in small amounts. These are two bidentate formates and c ovalently bound monodentate formate. The fact that similar oxygenates are o bserved independently of the presence of oxygen in the reaction mixture sug gests the participation of the catalyst oxygen in their formation. Oxygen a ccelerates the desorption of bidentate formates. Bidentate formates of one type decompose in a flow of air at 100-150 degrees C, and bidentate formate s of the other type decompose at 170-200 degrees C.