The role of Li₂CO₃ promoter and steam in increasing C₂H₄/C₂H₆ selectivity in chemical looping oxidative coupling of CH₄ over Mn-Na₂WO₄/support catalysts

Abstract

The main challenge in the oxidative coupling of methane to C₂H₆/C₂H₄ (C₂-hydrocarbons) lies in the low selectivity to the desired products due to their high reactivity to form carbon oxides. Herein, we report that the selectivity in chemical looping oxidative coupling of methane over supported Mn-Na₂WO₄-based catalysts can be significantly increased by catalyst promotion with Li₂CO₃ and performing the reaction with co-fed steam. The selectivity reaches 89% (about 60% C₂H₄ selectivity) at a methane conversion of 19%. The best-performing catalyst showed durable within 90 reaction/reoxidation cycles. With the aid of sophisticated catalyst characterization studies combined with temporal analysis of products, the origins of the enhancing effects of the promoter and steam have been elucidated and can be applied for the development of selective catalysts in various alkane oxidation reactions.

Graphical abstract

Keywords

chemical looping / oxidative coupling of methane / C₂ selectivity / oxygen species / Li₂CO₃ / Mn-Na₂WO₄

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