Influence of the metal/metal oxide redox cycle on the catalytic activity of methane oxidation over Pd and Ni doped hydroxyapatite

The methane oxidation reaction was investigated over Pd and Ni doped hydroxyapatite (HAP) catalysts. All catalysts were evaluated in both their reduced and oxidised forms, and the behaviour of the metals in the reaction was investigated. The obtained results demonstrated that the reaction proceeds through a redox cycle between metal oxide and reduced metal, however more stable catalysts with higher conversions were observed when the catalysts were pre-treated in oxygen. After CH4 oxidation, all the samples were tested towards coke formation using TGA analysis; results showed that all the catalysts were resistant to the coking process under the conditions studied.