Adsorption of acetic acids has been studied by FT-IR on a series of ad
sorbents, known as good catalysts for the selective hydrogenation of c
arboxylic acids to corresponding aldehydes: SnO2, TiO2, Pt/SnO2, Pt/Ti
O2. Very similar adsorbed species are observed by FT-IR with all menti
oned catalysts. The catalysts differ mainly by their behaviour upon in
creasing temperature program. The strongly bound unidentate or the bid
entate, bound to the oxide, are the possible intermediates of the cata
lytic reaction to acetaldehyde.