Alkaline Earth Metal Aluminate Support for Selective Oxidative Coupling of Methane

• Published in: ChemCatChem 2024-06, Vol.16 (12), p.n/a
• Main Authors: Wei, Zenghao, Movick, William J., Obata, Keisuke, Yu, Yuhang, Takanabe, Kazuhiro
• Format: Article
• Language: English
• Subjects: alkali metal tungstate; alkaline earth metal aluminate; Alkaline earth metals; Aluminates; Catalysts; Coupling; Densification; Ethane; High pressure; high surface area; Metal oxides; Methane; Oxidation; oxidative coupling of methane; Selectivity; Silicon dioxide; support; Vapor phases
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202301706

The oxidative coupling of methane (OCM) provides a direct route to transform methane into higher value products. The alkali metal tungstate catalysts have demonstrated high selectivity towards C2 products, ethane (C2H6) and ethylene (C2H4). However, the severe sintering of the SiO2 support limits the reaction rate requiring active site densification to compete with unselective gas phase combustion reaction especially at high pressure operations. This work studies alkaline earth metal oxides as supports for K2WO4 catalysts to maintain comparatively high surface area under OCM conditions. Among Mg, Ca, and Sr aluminates, the K2WO4/MgAl2O4 catalyst exhibited the highest C2 yields. To achieve high C2 product selectivity, a relatively large loading of K2WO4 (20 wt %) was required likely to cover the unselective surface sites of MgAl2O4 support. The catalyst further showed high levels of stability when utilized at high pressures (0.9 MPa) for over 60 h, without any change in product selectivity. The Mn/K2WO4/MgAl2O4 showed multifold higher CH4 conversion rate, compared with the SiO2 counterpart. The findings showcase the potential of the MgAl2O4 support as a viable candidate for alkali metal tungstate catalysts for OCM, which introduces high density of active components in given volume in the reactor, which induces high contribution of the catalyst relative to the pure gas phase oxidation. Utilizing MgAl2O4 as a support for Mn‐doped K2WO4 catalysts to maintain high surface area under the harsh reaction conditions of OCM, to get high CH4 conversion rata, compared with commonly used SiO2 support.