Overcoming the conversion-selectivity trade-off in plasma catalytic conversion of methane to ethylene.

Abstract

Non-thermal plasma (NTP) is a promising approach for activating methane at room temperature, enabling its direct conversion to ethylene under mild conditions. However, the high energy consumption and the trade-off between methane conversion and ethylene selectivity limit its industrial application. Herein, we report a pure-silica self-pillared pentasil (SPP) zeolite catalyst that enables efficient methane conversion to ethylene under non-thermal plasma activation at room temperature. This plasma-catalytic system achieves an exceptional ethylene selectivity of 58.8% with an energy yield of 52 mmol/MJ at atmospheric pressure. Mechanistic studies reveal that isolated hydroxyl groups on the self-pillared pentasil catalyst stabilize gaseous methyl radicals, promoting carbon-carbon coupling and methane dissociation. The confined plasma between catalyst granules selectively suppresses further hydrogenation and methylation of the key C₂H₅ intermediate, thereby achieving high ethylene selectivity. By systematically adjusting boundary conditions, an ethylene yield of 40% is achieved, surpassing the benchmarks of both plasma and thermal catalytic processes.