Optimisation of bimetallic Co-Ni supported catalysts for oxidation of methane in natural gas vehicles

This work deals with the extensive study of supported bimetallic Co-Ni catalysts for the complete oxidation of methane. The simultaneous incorporation of nickel and cobalt was found to enhance the redox properties by favouring the formation of nickel cobaltite-like species and partially inhibiting the interaction between Co3O4 and alumina. In turn, this resulted in an increase of the amount of Co3+ cations in the catalysts, which led to a more notable presence of active lattice oxygen species in the samples. When the nickel loading was increased, the generation of less active NiO was observed. The improvement of the redox properties resulted in a promotion of the specific reaction rate and a shift of around 50 °C in the T50 value over the bimetallic catalysts. The most active catalyst (25Co-5Ni) was found to be relatively stable during prolonged operation times, but suffered an appreciable and irreversible deactivation in the presence of water vapour.