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Abstract The complex structure of the catalytic active phase, and surface‐gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na₂WO₄/SiO₂catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H₂‐TPR, TAP and steady‐state kinetics) experiments, that the long speculated crystalline Na₂WO₄active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na‐WO_xsites. Kinetic analysis via temporal analysis of products (TAP) and steady‐state OCM reaction studies demonstrate that (i) surface Na‐WO_xsites are responsible for selectively activating CH₄to C₂H_xand over‐oxidizing CH_yto CO and (ii) molten Na₂WO₄phase is mainly responsible for over‐oxidation of CH₄to CO₂and also assists in oxidative dehydrogenation of C₂H₆to C₂H₄. These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na₂WO₄/SiO₂catalysts.