The investigation of oxygen species in silicalite-1 supported MnOx-Na2WO4 catalyst towards efficient oxidative coupling of methane

Abstract

The oxidative coupling of methane (OCM) as a promising single-step method towards olefins has attracted significant attention in efficient methane conversion and utilization. Here, we report a promising porous MnOx-Na2WO4/S-1 catalyst. The microporous silicalite-1 support ensures a uniform distribution of the elements Na, W and Mn on the catalyst surface, resulting in more active sites. In addition, the catalyst with weakly bonded and easily reduced lattice oxygen favors the generation of oxygen defect sites on the MnOx, further promoting the formation of electrophilic species (peroxide and superoxide). Hence, a high ratio of (O2- + O-)/O2- was achieved to boost the OCM performance. Furthermore, the MnOx-Na2WO4 catalyst supported by S-1 exhibited the ability to inhibit the loss of active components. As a result, an excellent C2 yield of 24.2% was achieved at 760 ℃ for OCM, accompanied by 43.1% CH4 conversion and 56.2% C2 selectivity. Moreover, the catalyst exhibited excellent stability without any deactivation in 50 hours.