Hydrogenolysis of ethane, propane, n-butane, and neopentane on the (111) and (110)-(1 times 2) surfaces of iridium

摘要: The hydrogenolysis of ethane, propane, n-butane, and neopentane has been investigated on the (111) (110)-(1{times}2) single-crystalline surfaces iridium at reactant partial pressures between 0.2 5.0 Torr hydrocarbon 20 500 hydrogen for surface temperatures from 400 to 700 K. A coupled high-pressure reactor-ultrahigh vacuum analysis chamber was employed, which permitted both measurement specific rates reaction in situ pre- postreaction characterization. Both apparent kinetics (activation energies preexponential factors) dependence (apparent orders) were examined detail. Postreaction by Auger electron spectroscopy indicated presence a submonolayer carbonaceous residue, coverage nearly identical essentially independent conditions, i.e. temperature pressures. Titration these residues with produced only methane all cases, suggesting that residue plays role spectator. mechanistic model involving rate-limiting, irreversible, unimolecular C-C bond cleavage step employed describe variations activity selectivity temperaturemore » kinetic parameters implicated this model, represent combinations rate coefficients several elementary reactions, have found be consistent expected values factors contributing reactions. This is applied data describes different compounds. 71 refs., 17 figs., 5 tabs.« less