Insights into the role of Mo in boosting CHx* oxidation for CO2 methane reforming

Abstract

CH_x* oxidation is one of the most vital routes to alleviate the carbon deposition problem of CO₂ reforming of methane (DRM) reaction. Whereas, little experimental evidence has been observed on NiMo catalysts where the CH_x* oxidation was dominant over its dissociation reaction. Herein, to experimentally unveil the CH_x* oxidation route of NiMo catalysts, we design three catalysts with different particle sizes and structures. Among them, Mo/Niphy@SiO₂ core shell catalyst demonstrated the dominant CH_x* oxidation route over its dissociation based on in-situ diffuse reflectance infrared Fourier transform spectroscopy experiments. This was attributed to the confinement effect of SiO₂ and the formation of Ni–Mo alloy, inhibiting the CH_x* dissociation reaction. It exhibited relatively stable CH₄ and CO₂ conversions (77 % and 75 % respectively) within 180 h. By contrast, on Mo/Niphy catalyst which has a big Ni size, CH_x* was mainly dissociated to C* and oxidized to CO which further underwent a disproportion reaction to produce CO₂ and C*, leading to the severe carbon deposition and unstable DRM performance. The strategy to unveil the dominant role of CH_x* oxidation via design catalysts with different sizes and structures sheds light on the study of reaction mechanism of other reactions.