INFRARED STUDIES OF THE MECHANISM OF METHANOL DECOMPOSITION ON CU SIO2/

The mechanism of methanol decomposition on silica-supported Cu has bee n investigated by means of infrared spectroscopy and temperature-progr ammed desorption spectroscopy. Infrared spectra taken during both isot hermal and temperature-programmed experiments reveal the following spe cies: methanol, methoxy groups, formaldehyde, methylenebis(oxy) groups , and formate groups. The only products observed during temperature-pr ogrammed decomposition are formaldehyde, carbon dioxide, hydrogen, and water. The ratio of hydrogen to carbon dioxide is 0.5 indicating that both products are formed by the decomposition of formate groups on th e surface of copper. A mechanism for methanol decomposition is propose d, based on the sequence of species observed during temperature-progra mmed infrared (TPD-LR) experiments. Simulations of the TPD-IR experime nts based on the proposed scheme provide an accurate representation of the observed variations in the concentrations of adsorbed species. (C ) 1994 Academic Press, Inc.