Spark Discharge and Dielectric Barrier Discharge Plasma Catalysis for the Nonoxidative Coupling of Methane to Ethylene with Pd Atomically Dispersed Pd-Cu/γ-Al2O3-R Catalyst

Methane valorization is important for climate change mitigation and sustainable carbon utilization, but conventional nonoxidative coupling of methane (NOCM) suffers from the high activation barrier of CH 4 , limited product selectivity, and rapid coking-induced deactivation. Herein, we develop a spark discharge−dielectric barrier discharge (DBD) coupled plasma-catalytic system for the selective conversion of high-concentration methane to ethylene. Spark discharge first activates CH 4 and preferentially converts it to C 2 H 2 , while a downstream catalyst bed, maintained at 100−130 ° C by residual discharge heat, enables acetylene semihydrogenation to C 2 H 4 . A coupled DBD unit is further introduced for in situ carbon removal and catalyst regeneration. Among the tested catalysts, impregnation−reduction-derived 0.1Pd-5Cu/γ-Al 2 O 3 -R with atomically dispersed Pd exhibited the best performance, achieving 72.38% CH 4 conversion, 72.19% C 2 H 4 selectivity, 92.48% acetylene-based C 2 H 4 selectivity, and a C 2 H 4 space-time yield of 69.97 mmol·g· −1 ·h −1 at 36.2 kJ·L −1 . With DBD-assisted regeneration, efficient NOCM operation was maintained for 630 min. Mechanistic analyses associate the enhanced ethylene selectivity with highly dispersed Pd sites and their electronic modulation by predominantly low-valent Cu species, which suppress overhydrogenation and facilitate ethylene desorption.