The formation of diethyl ether via the reaction of iodoethane with atomic oxygen on the Ag(110) surface

The reactions of iodoethane (ICH2CH3) on clean and oxygen-covered Ag(110) s urfaces were investigated using temperarure-programmed desorption (TPD) and high-resolution electron energy-loss spectroscopy (HREELS). Iodoethane ads orbs dissociatively at 150 K to produce surface ethyl groups on both clean and oxygen-covered Ag(110) surfaces. The ethyl species couple to form butan e on both surfaces, with the desorption peak maximum located between 218 an d 238 K, depending on the ethyl coverage. In addition to butane, a number o f oxidation products including diethyl ether, ethanol, acetaldehyde, surfac e acetate, ethylene, carbon dioxide and water were formed on the oxygen-dos ed AE(110) surface. Diethyl ether was the major oxygenate produced at all e thyl:oxygen ratios, and the peak temperature for ether evolution varied fro m 220 to 266 K depending on the relative coverages of these reactants. The total combustion products, CO2 and H2O were primarily formed at low ethyl c overages in the presence of excess oxygen. The formation of ethylene near 2 40 K probably involves an oxygen-assisted dehydrogenation pathway since eth ylene is not formed from ethyl groups on the clean surface. Acetaldehyde an d ethanol evolve coincidentally with a peak centered at 270-280 K, and are attributed to the reactions of surface ethoxide species. The surface acetat e which decomposes near 620 K is formed from subsequent reactions of acetal dehyde with oxygen atoms. The addition of ethyl to oxygen to form surface e thoxides was verified by HREELS results. The yields of all products exhibit ed a strong dependence on the relative coverages of ethyl and oxygen. (C) 1 999 Elsevier Science B.V. All rights reserved.