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Updated: Oct 26, 2025

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na2 WO4 /SiO2
Sagar Sourav1,2, Yixiao Wang1, Daniyal Kiani2
1Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA.
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 Na2 WO4 /SiO2 catalysts. 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 Na2 WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2 Hx and over-oxidizing CHy to CO and (ii) molten Na2 WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2 H6 to C2 H4 . These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2 WO4 /SiO2 catalysts.
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