Influence of Ni Chemical States on the Partial Oxidation Mechanism of Methane: An Energetics Analysis
- 化学化工－已发表论文 
An energetics analysis of the possible elementary steps involved in the partial oxidation of methane (POM) over different chemical states of Ni was carried out using the unity bond index-quadratic exponential potential (UBI-QEP) method. The results show that the rate determining step for the partial oxidation mechanism of methane is related to the chemical state of the Ni. Over reduced Ni the rate determining step for CO formation is the association of surface CH(3) species with surface O species. Over a partial positive charged Ni surface the rate determining step is that methane dissociates into the CH(x)O species with the assistance of oxygen. Over the reduced and partial positive charged Ni sites in coexistence, however, the rate determining step depends on the competition between the formation of surface CH(3) species and the recombination of surface CH(3) species with surface O species. This competition is related to the chemical states of the Ni sites. If the partial positive charged Ni sites are predominant on the surface, the recombination of surface C species with surface O species and the recombination of surface H atom species favor CO and H(2) formation because of decreasing barriers. The surface CH(x) species does not dissociate easily and surface carbon deposition is significantly inhibited.