RAIRS AND TPD STUDY OF METHYL FORMATE, ETHYL FORMATE, AND METHYL ACETATE ON NI(111)

The thermal chemistry of methyl formate, ethyl formate, and methyl acetate on Ni(111) was studied using infrared reflection absorption spectroscopy and temperature programmed desorption. The principal molecular decomposition products in each case were CO and H-2. Methane and acetaldehyde were also formed from ethyl formate. For each of the three molecules, adsorption occurred through the interaction of the carbonyl lone pair with the metal. The orientation of the molecular plane, in each case, was approximately perpendicular to the surface. The molecular surface decomposition species were detected by RAIRS. Methoxy species were formed from methyl formate and methyl acetate. Ethoxy was produced by ethyl formate. Evidence was obtained for the formation of a stable acetyl species during the decomposition of methyl acetate. The decomposition of methyl acetate occurred above 170 K whereas the other two esters began to decompose at approximately 140 K. This study shows that the adsorption induced shifts in the infrared spectra of esters are similar to those which occur on the formation of ester-Lewis acid adducts.