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

The combined use of O2 and CO2 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/SiO2, under a wide range of inlet O2 and CO2 concentrations. The overall impact of CO2 was found to depend on the operating conditions and the catalyst used. At O2‐rich conditions, a negative effect of CO2 was observed on C2 selectivity. At O2‐lean conditions, a positive effect of CO2 on both catalysts was observed, likely originating from an enhanced dehydrogenation of C2H6 to C2H4 and limited deep oxidation of the involving hydrocarbons and reaction intermediates. The behavior induced by CO2 is attributed to its mild oxidizing ability and interactions with the catalysts. The enhanced dehydrogenation of C2H6 was observed and confirmed by specific tests with a CO2 and C2H6 feed. Well‐controlled CO2 addition improved the value of the OCM product mixture, mainly due to a 9 % increase in C2H4 and a 19 % increase in CO selectivity, resulting in a 25 % reduction of CO2 at the outlet over the La−Sr/CaO catalyst. These findings provide new insight into the CO2 effect on OCM and the data to translate this research into OCM process alternatives. [ABSTRACT FROM AUTHOR]