Hydrogen production at low temperature from methane on cerium and nickel based mixed oxides.

Communication oraleInternational audiencePartial oxidation of methane (POM) to synthesis gas, CO + H2, has been investigated between 50°C and 700°C as a function of the metal loading over cerium and nickel based CeNiXOY catalysts. At high temperature, 700°C, a H2 yield of 100 % is obtained. At 200°C, an interesting yield of 34 % is reached with a stable methane conversion of 53 % and a H2 selectivity of 64 %, only when the solid is previously in-situ treated in H2 at 200°C. The activated in H2 solids are catalytic hydrogen reservoirs with the presence of hydride species. Different physico-chemical techniques have been used to characterize the structural, dispersion and reduction properties of the solids. Depending on the composition, a solid solution and/or a highly dispersed nickel oxide on ceria can be obtained. Ion sputtering followed by XPS analysis has been very useful for estimating the size of small NiO clusters present in the compounds. The active nickel species are found to belong to small clusters and/or to solid solution. Correlations among the species present in the solid, and catalytic performances are discussed, an active site based on the formation of anionic vacancies and a mechanism involving a heterolytic abstraction of a hydride species from methane are proposed