Effects of Methane and Ethane on the Heterogeneous Production of Water from Hydrogen and Oxygen over Platinum in Stagnation Flow

The effects of CH4 and C2H6 on the catalytic production of water from hydrogen-rich mixtures are investigated in a stagnation flow reactor using a combination of experimental and numerical methods. The analytical treatment assesses the accuracy of a detailed elementary reaction mechanism recently proposed for partial oxidation of ethane in short-contact-time reactors. Both CH4 and C2H6 inhibit the heterogeneous water-forming chemistry, as evidenced by a strong correlation between the net water production, light-off temperature, and mole fraction of hydrocarbon in the reactor. The effects of C2H6 on Pt are more pronounced than those of CH4, due to its propensity for forming carbonaceous overlayers on the catalyst surface. A general kinetic mechanism used successfully to describe partial oxidation of C2H6 over Pt-impregnated monoliths could not reproduce the experimental observations. Discrepancies between model chemistry and experiment reveal possible avenues for the improvement of the mechanism.