TITLE: Methane Activation by Metals and Semiconductors. Molecular Orbital Theory. Annual Report September 1987-August 1988.

AUTHOR: A. B. Anderson.

INST.  AUTHOR: Case Western Reserve Univ., Cleveland, OH. Dept. of Chemistry.

SPONSOR: Gas Research Inst., Chicago, IL.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Other [GRI],  Sep 88,  66p.

NTIS ORDER NO.: PB89-131163/INW

ABSTRACT:

An atom superposition and electron delocalization molecular orbital study has been made of a CHn and CO reactions over coordinatively unsaturated Mo(IV) edge cations in MoS2. Coupling to C2H6 and C2H5(a) proceed with high barriers. CH2(a) coupling to strongly adsorbed ethylene proceeds with a lower barrier, and hydrogenation to ethane is possible. CO binds relatively weakly to 5-fold coordinated Mo and strongly to 4-fold coordinated sites. Over two such sites, CO easily tilts to a di-Sigma bridging orientation and dissociates with a low barrier. In the Fischer-Tropsch process hydrogenation to CH3(ads) and H2O(g) is expected.  CO inserts into the Mo-CH3 bond with a low barrier, and subsequent hydrogenations to form C2H6+H2O or CH3CH2OH are favorable. It is proposed that the selectivity toward alcohol formation over alkali-doped MoS2 (the DOW process) may stem from the ability of the alkali cations to stabilize alkoxy intermediates. A second molecular orbital study shows AlN behaves similarly to MgO toward CH4. Stoichiometric AlN is inactive. CH4 is activated by surface N(2-) hole sites, forming surface HN(2-) and methyl radicals.

REPORT  NUMBER: GRI 88/0280

CONTRACT  NUMBER: GRI-5086-260-1327