The Combined Effect of the Oxidizing Agent and its Concentration on the Oxidative Coupling of Methane

Abstract The combined use of O 2 and CO 2 as oxidizing agents in the oxidative coupling of methane (OCM) has been assessed over two representative OCM catalysts, i. e., La−Sr/CaO and NaMnW/SiO 2 , under a wide range of inlet O 2 and CO 2 concentrations. The overall impact of CO 2 was found to depend on the operating conditions and the catalyst used. At O 2 ‐rich conditions, a negative effect of CO 2 was observed on C 2 selectivity. At O 2 ‐lean conditions, a positive effect of CO 2 on both catalysts was observed, likely originating from an enhanced dehydrogenation of C 2 H 6 to C 2 H 4 and limited deep oxidation of the involving hydrocarbons and reaction intermediates. The behavior induced by CO 2 is attributed to its mild oxidizing ability and interactions with the catalysts. The enhanced dehydrogenation of C 2 H 6 was observed and confirmed by specific tests with a CO 2 and C 2 H 6 feed. Well‐controlled CO 2 addition improved the value of the OCM product mixture, mainly due to a 9 % increase in C 2 H 4 and a 19 % increase in CO selectivity, resulting in a 25 % reduction of CO 2 at the outlet over the La−Sr/CaO catalyst. These findings provide new insight into the CO 2 effect on OCM and the data to translate this research into OCM process alternatives.