Origin of vinylic C-H bond activation in the combustion of alkenes on palladium: an HREELS study of propene on Pd(100)-p(2x2)-O

[摘要] While the mechanism of many reactions with oxygen on Ag(110) can be successfully predicted according to the gas-phase acidity of the reacting molecule, recent temperature-programmed reaction spectroscopic study of propene reactions with oxygen on Pd(100) reveals that the most reactive C-H bond is the vinylic rather than the most acidic, allylic, C-H bond. Using vibrational spectroscopy it is found that two forms of propene species exist on the surface al 130 K: a pi-bonded stale and a di-sigma-bonded state. The former desorbs molecularly upon heating, while the latter undergoes combustion. In the di-sigma-bonded state, the sp(3) rehybridization strongly reduces the acidity from its gas-phase value, rendering the methyl hydrogens unreactive. The mechanism for the combustion of propene is proposed. (C) 1997 Elsevier Science B.V.

[发布日期] 1997-11-26

[关键词] combustion;electron energy-loss spectroscopy;oxidation;oxygen;palladium;propene;reaction mechanism;single crystal surface