Sol–gel method for synthesis of Mn–Na2WO4/SiO2 catalyst for methane oxidative coupling

• A novel sol–gel method was developed for preparing the Mn–Na2WO4/SiO2 catalyst for OCM application.
• The best OCM performance was achieved under very desired low methane-to-oxygen ratio and low nitrogen dilution.
• The sol–gel made catalyst provides 5–15% higher C2-selectivity than the wetness impregnated catalyst.
• The proposed preparation method can be efficiently exploited for activating a ceramic membrane.

In this experimental study, a novel sol–gel method was developed to synthesize a 1.9%Mn–5%Na2WO4/SiO2 catalyst for oxidative coupling of methane (OCM) reactions. The performance of the synthesized catalyst was investigated in fixed-bed and porous packed-bed membrane reactors. Particularly, the effects of operating temperature, methane-to-oxygen ratio and nitrogen dilution on the performance of this catalyst were investigated. It was observed that for high values of methane conversion, the sol–gel Mn–Na2WO4/SiO2 catalyst provides 5–15% higher selectivity toward the desired products (C2: C2H4 + C2H6) than the Mn–Na2WO4/SiO2 catalyst prepared by the incipient wetness impregnation method. It was also observed that for a similar set of experiments, the C2-selectivity of the sol–gel catalyst is affected relatively less by the variation of methane-to-oxygen ratio. As a result, this catalyst can be exploited under the low methane-to-oxygen feed ratio which provides an efficient performance in both the OCM reactor and the OCM process scale. The best observed performance of the sol–gel catalyst in the packed-bed membrane reactor is 78% C2-selectivity, 64% ethylene-selectivity and 24.2% C2-yield under 20% nitrogen dilution.

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