Pd Supported on ZSM-5 with different ratios of Si/Al as catalysts for direct catalytic decomposition of methane

Hydrogen and filamentous carbon have been produced by direct catalytic decomposition of methane. ZSM-5 Zeolite with ratios of Si/Al (25, 140, and 750) was used as a support in 0.5 wt% Pd/ZSM-5 catalysts. Fresh and spent Pd/ZSM-5 catalysts were characterized by XRD, SEM, TGA and CHN analyses. The hydrogen formation rates for the catalysts were Pd/ZSM-5 (25) < Pd/ZSM-5 (140) < Pd/ZSM-5 (750). The CHN analysis showed wt% of the carbon that was deposited, over the catalysts, during the reaction run to be 15.6, 17.1, and 34.3 for Pd/ZSM-5 (25), Pd/ZSM-5 (140), and Pd/ZSM-5 (750), respectively. The SEM images revealed that filamentous carbon was produced. It appears that the zeolite support in different Si/Al ratios led to form different sizes of palladium particles and palladium dispersion over ZSM-5 support. It is suggested that the catalyst activity be ascribed to the palladium particles size and its dispersion over ZSM-5.