Improvement of Catalytic Activity of Ce-MFI-Supported Pd Catalysts for Low-Temperature Methane Oxidation by Creation of Concerted Active Sites

Ce-containing MFI-type zeolite (Ce-MFI)-supported Pd catalysts modified by a second metal were prepared and applied to low-temperature oxidative coupling of methane reactions. Screening of various second metal species revealed that the combination of Pd and Co supported on Ce-MFI positively affected the catalytic performance and that the C2H6 yield was improved compared with that for the control Ce-MFI-supported Pd catalyst. This benefit would arise from the creation of new active sites by the proximate Pd and Co species on Ce-MFI, as suggested by high-angle angular dark -field scanning transmission electron microscopy with energy-dispersive X-ray spec-troscopy, X-ray photoelectron spectroscopy, and H-2-temperature-programmed reduction measurements. In addition, the highly dispersed Ce species in Ce-MFI, which were generated via the mechanochemical method, contributed to the creation of catalytically active sites, i.e., concerted Ce, Pd, and Co species.