Catalytic combustion of methane over palladium exchanged zeolites

Palladium cation exchanged zeolites (ZSM-5, mordenite and ferrierite) were studied as catalysts for methane combustion. Pd-zeolites showed much higher activities than PdO/Al₂O₃. For comparable palladium loadings, PdO/Al₂O₃ requires a reaction temperature of ca. 70–80°C higher than Pd-ZSM-5 for conversions between 50–100%. The catalytic activity of Pd-ZSM-5 seems to be related to its reducibility. Temperature-programmed reduction experiments with carbon monoxide showed a lower reduction temperature (ca. 157°C) for Pd-ZSM-5 than for PdO/Al₂O₃ (225°C). Further, the positioning of the palladium by ion exchange offers a highly dispersed form of Pd^II supported on the high surface area zeolite.