FTIR study of adsorption and reactions of methyl formate on powdered TiO2

Adsorption, thermochemistry, and photochemistry of methyl formate on powdered TiO2 have been studied by Fourier-transformed infrared spectroscopy. Methyl formate is adsorbed on the TiO2 surface in two forms. One is molecularly adsorbed methyl formate showing a red-shifted carbonyl stretching. The other is a structure-reorganized species showing absorption bands at 2841, 2866, and 2942 cm(-1) in the CHx stretching region. An orthoester-type intermediate is proposed to explain the observed infrared absorption bands. In the thermal reactions, all the detected carbon-containing gas products are derived from CH3O(a) and HCOO(a), which are generated as surface intermediates in the process of methyl formate decomposition. In methyl formate photochemistry, both O-2 and TiO2 are essential. The origins of the gas products relating to the adsorbed species are also discussed. (C) 1999 Academic Press.