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

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.