Methane Partial Oxidation Catalyzed by Platinum and Rhodium in a High-Temperature Stagnation Flow Reactor

A series of measurements investigating the partial oxidation chemistry of methane and oxygen over platinum and rhodium foils was performed in a stagnation flow reactor at a pressure of 30 Torr. Products from the reactions on the catalytic substrates were quantitatively analyzed via mass spectrometry for consumption of the reactants, methane and oxygen, and for production of hydrogen, carbon monoxide, carbon dioxide, and water. Reactivity for fractional methane conversion, along with hydrogen and carbon monoxide selectivities versus water and carbon dioxide, respectively, were determined over a temperature range of 700−1350 °C. Three reactant stoichiometries were investigated, corresponding to methane-to-oxygen equivalence ratios of 3, 4, and 6. The results highlight differences in the behavior of the two metals over a range of conditions. In general agreement with earlier work, rhodium seems to exhibit greater reactivity. At low temperatures, heavy coking was observed on platinum over time, and rhodium exhibited a susceptibility to deactivation at lean equivalence ratios.