It is shown that FT-IR spectroscopy permits discrimination to be made between methoxy (methanol) and formate species adsorbed on ZnAl 2O 4 and CuZnAl 2O 4 catalysts. These species were found to be less stable on copper than on ZnAl 2O 4. The presence of reduced copper promotes methanol transformation into formates and then into C0 2: (i) FT-IR results show that copper formate formation from methanol adsorption occurs even at room temperature and that surface oxygen ion participates in its formation; (ii) chemical trapping experiments demonstrate that increasing copper percentage destabilizes formate species, while TPD experiments correlatively indicate an accelerated transformation of formate into CO 2. Formyl species are detected by chemical trapping only at the end of the reaction and are therefore assumed not to participate in the decomposition reaction.