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

Abstract

Carbon nanofibers (CNFs) modified with CeO₂ were employed as support for the synthesis of Ni catalysts for the CO₂ 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 H₂/CO₂ and a flow to weight ratio of 600 NL h⁻¹ g_Ni⁻¹. The results showed that the Ni-CeO₂/CNF catalyst prepared by mechanochemical synthesis showed higher CO₂ conversion and CH₄ selectivity at low temperatures than the one prepared via traditional method. This was attributed to smaller Ni crystallites and to the higher quantity of Ce³⁺ 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.