Exploring the Promotion of γ-Al2O3 on Pd/CeO2-Catalyzed Low-Concentration Methane Oxidation Using Operando DRIFTS-MS

CeO2/gamma-Al2O3, Pd/CeO2, and Pd/CeO2/gamma-Al2O3 were used for catalyzing low-concentration CH4 oxidation. It was found that nano-sized Pd could obviously promote CH4 oxidation on CeO2/gamma-Al2O3. The interaction between Pd and CeO2 on gamma-Al2O3 resulted in higher ratios of Ce3+/(Ce3++Ce4+), Pd2+/(Pd2++Pd delta+), and O-ads/(O-ads+O-latt), those benefited the formation of more oxygen vacancies and surface reactive oxygen species for CH4 oxidation. gamma-Al2O3 not only supplied a high surface area and enhanced Pd/CeO2 dispersion on gamma-Al2O3, but also simulated the formation of bicarbonate, where bicarbonate is easier to gasify to CO2 than bidentate carbonate that formed on Pd/CeO2. Operando diffuse reflectance infrared Fourier transform spectroscopy-mass spectrometer analysis results showed that CH4 oxidation could occur at a temperature as low as 180 degrees C due to the reaction with surface reactive OH, this reaction was also accompanied by the formation of bicarbonate. The mechanism of CH4 oxidation promoted by bicarbonate formation on gamma-Al2O3 was proposed.

Automated summary

CeO2/gamma-Al2O3, Pd/CeO2, and Pd/CeO2/gamma-Al2O3 were used for catalyzing low-concentration CH4 oxidation. It was found that nano-sized Pd could significantly enhance CH4 oxidation on CeO2/gamma-Al2O3, due to the interaction between Pd and CeO2 on gamma-Al2O3, which resulted in the formation of more oxygen vacancies and surface reactive oxygen species. Furthermore, gamma-Al2O3 facilitated the formation of bicarbonate, which promoted the gasification of bicarbonate to CO2 and enhanced CH4 oxidation.