Investigation of the physico-chemical implications of the hydrogen presence during H2-assisted catalytic combustion of methane using Pd(10 wt.%)/γ-Al2O3 catalyst

The influence of the presence of H2 on the physico-chemical properties of a Pd(10 wt.%)/γ-Al2O3 catalyst was investigated. Catalysts were treated under methane combustion conditions with various amounts of H2 in the feed. Samples obtained were characterized by BET, CO-chemisorption, XRD, XPS and/or ToF-SIMS techniques. The effect of H2 is essentially to sinter the palladium phase and to help remove surface chlorine coming from the palladium precursor. In presence of low amounts of H2, O migration phenomena are suggested to occur to maintain the surface of the palladium particles in an oxidized state while, as the H2 concentration increases, metallic palladium progressively forms in the bulk. Above a threshold value, the H2 concentration becomes too high, metallic palladium is formed on the surface.