C2 selectivity enhancement in oxidative coupling of methane over microwave-irradiated catalysts

The oxidative coupling of methane over Li/MgO and BaBiO_{3 - x} catalysts irradiated by microwaves and classically heated is reported. Enhanced selectivities in C₂⁺ products are observed at lower temperatures under microwave conditions, especially with the Li/MgO catalyst.

The complex permittivity measurements of BaBiO_{3 - x} show that the regeneration of the active oxygen species on the surface is lower under microwave irradiation than classical heating. X-ray diffraction analyses of the catalyst before and after catalytic reaction, when it is classically heated and when it is heated by microwave irradiation, corroborate these results. Therefore, the CH₃^? carbanions are less oxidated at the catalyst surface under microwave irradiation.

On the other hand, the quenching of the output gas probably decreases the oxidation of CH°₃ radicals in the gas phase when the Li/MgO catalyst is irradiated by microwaves. The quenching of the output gas is a unique consequence of microwave irradiation which heats the catalyst without heating the wall of the reactor.