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

Graphical CeO 2 /γ-Al 2 O 3 , Pd/CeO 2 , and Pd/CeO 2 /γ-Al 2 O 3 were used for catalyzing low-concentration CH 4 oxidation . γ-Al 2 O 3 can efficiently promote CH 4 oxidation on Pd/CeO 2 and the formation of bicarbonate that is easily gasified to CO 2 . CeO 2 /γ-Al 2 O 3 , Pd/CeO 2 , and Pd/CeO 2 /γ-Al 2 O 3 were used for catalyzing low-concentration CH 4 oxidation. It was found that nano-sized Pd could obviously promote CH 4 oxidation on CeO 2 /γ-Al 2 O 3 . The interaction between Pd and CeO 2 on γ-Al 2 O 3 resulted in higher ratios of Ce 3+ /(Ce 3+ +Ce 4+ ), Pd 2+ /(Pd 2+ +Pd δ+ ), and O ads /(O ads +O latt ), those benefited the formation of more oxygen vacancies and surface reactive oxygen species for CH 4 oxidation. γ-Al 2 O 3 not only supplied a high surface area and enhanced Pd/CeO 2 dispersion on γ-Al 2 O 3 , but also simulated the formation of bicarbonate, where bicarbonate is easier to gasify to CO 2 than bidentate carbonate that formed on Pd/CeO 2 . Operando diffuse reflectance infrared Fourier transform spectroscopy-mass spectrometer analysis results showed that CH 4 oxidation could occur at a temperature as low as 180 °C due to the reaction with surface reactive OH, this reaction was also accompanied by the formation of bicarbonate. The mechanism of CH 4 oxidation promoted by bicarbonate formation on γ-Al 2 O 3 was proposed.