Effect of support on methane decomposition for hydrogen production over cobalt catalysts

• Type of support (Al2O3, Nb2O5 and SiO2) affected CH4 decomposition on Co catalyst.
• Cobalt particle size and its interaction with the support played a key role.
• Co/SiO2 reduced at 500 °C was the best catalyst with conversion of 0.27% CH4/mgCo.
• Co/Nb2O5 reduced at 500 °C completely inhibited the reaction due to SMSI effect.
• There was an optimum particle size for the production of carbon filaments.

Cobalt catalysts were tested in methane decomposition reaction at 450 °C to evaluate their catalytic properties in non-oxidative methane conversion for hydrogen production via accumulation of carbon. Silica, alumina and niobia supported cobalt catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), H2 chemisorption and BET surface area measurements. The nature of the support strongly influenced this process. The high initial activity of Co/Al2O3 catalyst reduced at 500 °C lead to a large formation of carbon deposits and consequent catalysts deactivation. For Co/SiO2, the activity increased with reaction time due to reduction of cobalt oxide particles that were not reduced during the reduction pretreatment, and this effect was more pronounced for the reduction at 300 °C. Co/SiO2 reduced at 500 °C was the best catalysts for methane decomposition. For Co/Nb2O5, the Nb2OX species partially covered cobalt particles even for reduced catalysts at low temperature (300 °C) and this effect completely inhibited the reaction after high-temperature reduction (500 °C).