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

Journal Article · Wed Jun 10 00:00:00 EDT 2015 · Surface Science

DOI:https://doi.org/10.1016/j.susc.2015.06.003· OSTI ID:1212370

Dong, Yujung ^[1]; Brooks, John D. ^[1]; Chen, Tsung-Liang ^[2]; Mullins, David R. ^[2]; Cox, David F. ^[1]

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1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The reaction of iodomethane on the nearly stoichiometric α-Cr₂O₃₍0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is first 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 then 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 β-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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725; FG02-97ER14751
• OSTI ID: 1212370
• Alternate ID(s): OSTI ID: 1244746
• Journal Information: Surface Science, Vol. 641; ISSN 0039-6028
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Cr2O3
methyl iodide
XPS
TPD
dehydrogenation