Support effect of Mn/Na2WO4‐based catalysts in oxidative coupling of methane

Abstract

AbstractBACKGROUNDIn this work, the supported Mn‐Na2WO4/γ‐Al2O3, Mn‐Na2WO4/γ‐Al2O3‐TiO2 and Mn‐Na2WO4/ γ‐Al2O3‐SiO2 catalysts were prepared using the dry impregnation procedure and tested for suitability to the oxidative coupling of methane (OCM) reaction. The synthesized catalyst was characterized by various techniques such as X‐ray diffraction (XRD), Fourier transform infrared (FTIR), X‐ray photon spectroscopy (XPS), temperature‐programmed reduction (TPR), Brunauer–Emmett–Teller (BET) surface area and field emission scanning electron microscopy (FESEM), and the support effect of the prepared catalysts in the OCM reaction was evaluated.RESULTSThe XPS results showed that the tetrahedral WO42− phase is presented in all prepared catalysts and it is expected that the presence of this phase is correlated with high OCM activity. The XPS results show that the amount of O2− in the treated Mn‐Na2WO4/γ‐Al2O3‐TiO2 catalyst at 800 °C is higher than that in the Mn‐Na2WO4/γ‐Al2O3 and Mn‐Na2WO4/γ‐Al2O3‐SiO2 catalysts, but is reduced with increasing temperature. At 850 °C, the amount of O2− in the treated Mn‐Na2WO4/γ‐Al2O3 catalyst is higher than in the Mn‐Na2WO4/γ‐Al2O3‐TiO2 and Mn‐Na2WO4/γ‐Al2O3‐SiO2catalysts.CONCLUSIONThe results show that the MnSiO3 and MnTiO3 sites may deliver a much easier Mn2+↔Mn3+ cycle than the MnAl2O4 and MnWO4 sites at low temperatures, and may play a principal role in enhancing the catalyst activity in the OCM reaction at 800 °C. © 2023 Society of Chemical Industry (SCI).