Controlling Factors in Deoxygenation Kinetics and Selectivity: Reactions of Ethylene Oxide on Mo(110)

Article abstract of DOI:10.1021/ja00198a008

Ethylene oxide intramolecularly eliminates ethylene directly into the gas phase at 200 K (E_aca.12 kcal/mol) during reaction on Mo(110) with 70percent efficiency as shown by temperature-programmed reaction and X-ray photoelectron spectroscopy.Atomic oxygen, a product of this reaction, increases the rate of ethylene formation by slowing the kinetics for the competing nonselective decomposition pathway which accounts for the other 30percent of reaction of chemisorbed ethylene oxide.The nonselective decomposition products of reaction are gaseous dihydrogen, surface carbon, and oxygen.At high ethylene oxide exposures, a small amount of molecular desorption is also observed at 150 K.Deposition of an atomic oxygen overlayer(θ₀ ca 0.27) on Mo(110) prior to reaction enhances the selectivity of ethyle formation reaction to 90percent.Reaction saturation is controlled by the buildup of hydrocarbon fragments on clean Mo(110) and by oxygen site blocking on the oxygen precovered surface as shown by isothermal reaction spectroscopy.Carbon-heteroatom bond strength correlates with the temperature of ethylene formation in comparing reaction of ethylene oxide to that of the sulfur-containing analogue, ethylene sulfide, on Mo(110).