Hydrogen production from ethanol in presence of water over cerium and nickel mixed oxides

Hydrogen production from ethanol in the presence of water (H2O/C2H5OH = 3) was investigated over cerium nickel CeNixOy (0 < x ≤ 5) mixed oxide catalysts. The influence of different parameters was analysed, such as reaction temperature, Ni content and in situ pre-treatment in H2. While an ethanol conversion of 100% is reached at 400 °C, a stable activity i.e. ethanol conversion and H2 selectivity can be obtained at very low temperature (200 °C) when the solid is previously in situ treated in H2 in a temperature range between 200 and 300 °C. After such a treatment, the solids studied are hydrogen reservoirs, called oxyhydrides, with the presence of hydrogen species of hydride nature in the anionic vacancies of the solid. Different physicochemical techniques were used to characterize the catalysts. Depending on the composition and metal loading, a solid solution and/or a highly dispersed nickel oxide in ceria can be obtained. Correlations among the species present in the solid, and the 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 ethanol are proposed.