Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr2O3(0001)

SURFACE SCIENCE

卷:641

Article

Dong, Yujung¹  Brooks, John D.¹  Chen, Tsung-Liang²  Mullins, David R.²  Cox, David F.¹ 

[1] Virginia Polytech Inst & State Univ, Dept Chem Engn, Blacksburg, VA 24061 USA

[2] Oak Ridge Natl Lab, Div Chem Sci, Oak Ridge, TN 37831 USA

关键词: Cr2O3;    Methyl iodide;    XPS;    TPD;    Dehydrogenation;   

DOI  :  10.1016/j.susc.2015.06.003

来源: Elsevier

【 摘 要 】

The reaction of iodomethane on the nearly stoichiometric alpha-Cr2O3(0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is initiated by the dissociation of iodomethane into surface methyl fragments, -CH3, and iodine adatoms. Methyl fragments bound at surface Cr cation sites undergo a rate-limiting dehydrogenation reaction to methylene, = CH2. The methylene intermediates formed from methyl dehydrogenation can undergo coupling reactions to produce ethylene via two principle reaction pathways: (1) direct coupling of methylene and (2) methylene insertion into the methyl surface bond to form surface ethyl groups which undergo beta-H elimination to produce ethylene. The liberated hydrogen also combines with methyl groups to form methane. Iodine adatoms from the dissociation of iodomethane deactivate the surface by simple site blocking of the surface Cr3+ cations. (C) 2015 Elsevier B.V. All rights reserved.

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