Development of a Kinetic Model for CO2 Methanation over an Optimized Glass-Fiber Ni/SiO2 Catalyst

This study optimizes the nickel content in a glass-fiber catalyst (GFC) synthesized via pulsed surface thermal synthesis, investigates the stability of Ni/GFC, and develops a kinetic model for the CO2 methanation reaction. The activity and selectivity of Ni/GFC in CO2 methanation increase with Ni loading in the 2-5 wt.% range; further increasing the Ni content does not enhance activity. During the initial stage of long-term tests, 5%Ni/GFC exhibits a slight (~4%) deactivation before stabilizing, demonstrating high overall catalyst stability. Using experimental data obtained over a wide range of temperatures (200-400 °C), gas hourly space velocities (2300-11500 h-1), and H2/CO2 feed ratios (0.5-10) on 10%Ni/GFC, a comparative analysis of fifteen kinetic models of varying complexity is performed. A power-law model accounting for adsorption inhibition by CO2 and H2 and incorporating thermodynamic reversibility is selected. The model describes product concentrations with an acceptable average error (1.8 vol.%) and high parameter reliability. The observed activation energy (88 kJ/mol) aligns with literature values for Ni-catalyzed CO2 methanation. This model is suitable for engineering applications in the scale-up and optimization of CO2 methanation processes using Ni/GFC catalysts.