Catalytic performances in methane combustion over Pd nanoparticles supported on pure silica zeolites with different structures

Catalytic combustion of CH4 to CO2 and H2O was studied over Pd nanoparticles supported on different siliceous zeolites (MFI, BEA and CHA) with γ-Al2O3 as the reference support, and it was found that as supports, zeolites exert remarkable influence on the catalytic performance of methane oxidation, with the Pd catalyst (1 wt% loading) supported by siliceous MFI (ZSM-5-Si) presenting the highest activity. Over the exceptional catalyst, a complete conversion of methane can be achieved at around 380 °C, which is about 120 °C lower than the temperature needed for the Pd nanoparticles supported on γ-Al2O3 (Pd/γ-Al2O3), one of the best catalysts for the methane combustion. Physicochemical characterizations including X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), temperature programmed desorption of methane (CH4-TPD) and temperature programmed reduction of methane (CH4-TPR) techniques were used to acquire an idea what is behind the discrepancy in the catalytic performances of methane combustion over these Pd-based catalysts. Based on these results, it is proposed that the different methane adsorption and the oxygen migration capability are mainly related to the difference in the catalytic performances of methane combustion over these catalysts. Among these factors, the difference in the methane adsorption is critical for the different catalytic performances, as evidenced by the kinetic measurements.