Mechanism of methane partial oxidation over SiO₂-supported Nickel catalyst

The partial oxidation reaction of methane over reduced 10wt% Ni/Si0₂ catalyst was studied at 600, 650 and 700ºC by means of pulse and bond-order conservation Morse-potential (BOC-MP) methods. In the oxidation reaction of surface carbon deposited on the catalyst, it was observed that the product selectivity was subject to the reaction temperature and the selectivity of CO was increased with raising temperature when the molar ratio of surface carbon to oxygen was above one. In the reaction of CH₄/0₂, the same trend between CO selectivity and reaction temperature was also observed, implying that the partial oxidation of methane to syngas follows the pyrolysis mechanism under the reaction conditions. The BOC-MP calculation on the elementary reaction steps over Ni(111) surface indicates that the direct dissociation of CH₄ without the involvement of surface oxygen is more likely to occur and the formation of CO from CH(s) occurs more readily than from C(s).