Activity enhancement of carbon nanofiber-based catalysts for CO2 methanation by mechanochemical synthesis

Carbon nanofibers (CNFs) modified with CeO 2 were employed as support for the synthesis of Ni catalysts for the CO 2 methanation reaction. Two different preparation methods were investigated: incipient wetness impregnation and mechanochemical synthesis. The catalysts were tested at atmospheric pressure under a wide range of temperatures (200 – 600 °C) using a stoichiometric ratio of undiluted H 2 /CO 2 and a flow to weight ratio of 600 NL h −1 g Ni −1 . The results showed that the Ni-CeO 2 /CNF catalyst prepared by mechanochemical synthesis showed higher CO 2 conversion and CH 4 selectivity at low temperatures than the one prepared via traditional method. This was attributed to smaller Ni crystallites and to the higher quantity of Ce 3+ sites exposed by the milling process. Stress test carried out at 450 °C showed that the activity and the reaction mechanism remained stable for at least 50 h. • Comparison between incipient wetness impregnation and mechanochemical synthesis. • Ball milling increased the oxygen vacancies concentration, improving CO 2 activation. • 73 % of CO 2 conversion with a 95 % of methane selectivity obtained at 450 °C • High stability of the catalyst prepared via ball milling.