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

Abstract

BackgroundIn 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 is characterized by various techniques such as XRD, FTIR, XPS, TPR, BET surface area, and FESEM, and the support effect of the prepared catalysts in the OCM reaction is evaluated.ResultsThe XPS results show 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 oC is higher than Mn‐Na2WO4/γ‐Al2O3 and Mn‐Na2WO4/γ‐Al2O3‐SiO2 catalysts, but with increasing temperature is reduced. At 850 oC, the amount of O2‐ in the treated Mn‐Na2WO4/γ‐Al2O3 catalyst is higher than in 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 oC.This article is protected by copyright. All rights reserved.