Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5425758 | Surface Science | 2006 | 12 Pages |
The chemistry of ethylene adsorbed on a thin MoAl layer grown in ultrahigh vacuum on a thin alumina film is studied using a combination of temperature-programmed desorption and X-ray, Auger and reflection absorption infrared spectroscopies. Both di-Ï-bonded and a small proportion of Ï-bonded ethylene are found, where the di-Ï-bonded ethylene has a Ï/Ï parameter of â¼0.8 and a heat of adsorption of â¼70 kJ/mol. The ethylene self-hydrogenates to yield ethane and a small amount of methane is detected. The surface hydrogenation activation energy of di-Ï-bonded ethylene is â¼65 kJ/mol, while the Ï-bonded species hydrogenates more easily. Adsorbed ethyl species grafted onto the surface by decomposing ethyl iodide predominantly undergo β-hydride elimination to yield ethylene. Ethyl species hydrogenate to ethane at a lower temperature than does di-Ï-bonded ethylene implying that addition of hydrogen to adsorbed ethylene is slower than the rate of ethyl hydrogenation.