Broadened Pulse-Step Change−Isotopic Sharp Pulse Analysis of the Mechanism of Methane Partial Oxidation to Synthesis Gas

The mechanism of the partial oxidation of CH 4 was studied by a transient response analysis of a broadened pulse combined with either a step change or a sharp isotopic pulse. Over the unreduced NiO/SiO 2 catalyst, the reaction between CH 4 and O 2 occurs via the Eley−Rideal mechanism, CH 4 in the gas phase (or weakly adsorbed) reacting with O 2 in the adsorbed state. In contrast, over the reduced NiO/SiO 2 catalyst, the reaction takes place by a Langmuir−Hinshelwood mechanism, CH 4 and O 2 reacting in the adsorbed states. In addition, isotopic pulses of 18 O 2 revealed that over the reduced catalyst lattice oxygen is formed and reduced by the carbon species; hence, on the reduced catalyst a dynamic redox process occurs.