Methane oxidation by lattice oxygen of CeNbO4+δ

The reactivity of methane with lattice oxygen of cerium niobate, CeNbO4+δ, was studied by temperature-programmed reduction (TPR) in dry CH4 flow at 523–1073 K. Phase transformations and reduction of cerium niobate at 900–1023 K lead to a massive release of hyperstoichiometric oxygen, in amounts determined by the intermediate-temperature phase composition dependent on thermal history. In this temperature range, CH4–TPR shows prevailing formation of carbon monoxide and steam, suggesting that the synthesis gas generation occurs in parallel with extensive oxidation of H2 on the cerium niobate surface. At 1073 K when δ → 0, the reaction of methane with CeNbO4+δ selectively yields synthesis gas with H2/CO ratio close to two.