4 Conclusion
We investigated the catalytic performance of Cu-MOR catalysts, prepared
by ion-exchange and wetness impregnation, for plasma-catalytic DOMtM in
CH4/O2 plasma. The Cu-MOR IE-3 catalyst,
synthesized through ion-exchange, demonstrates the most favorable
catalytic outcomes, with 7.9% CH4 conversion and 51%
CH3OH selectivity. Conversely, the Cu-MOR catalysts
prepared by wetness impregnation exhibit tendencies towards
over-oxidation of CH4 to CO and CO2,
particularly for the catalysts with higher loadings. The combination of
our catalyst characterizations reveals that ion exchange predominantly
leads to the formation of
zeolite-confined
Cu2+ species within Cu-MOR, whereas wetness
impregnation primarily yields CuO particles. Specifically,
zeolite-confined Cu2+ species function as the active
sites for plasma-catalytic DOMtM, while the presence of CuO clusters and
particles proves detrimental to DOMtM. instead facilitating
over-oxidation reactions leading to CO and CO2production. Finally, the surface species on the catalyst, detected byin-situ FTIR, further corroborate the pivotal role of
zeolite-confined Cu2+ species in plasma-catalytic
DOMtM.