Detailed Spatially Resolved Gas-Phase Investigations of CO ₂ Methanation on a Ni/SiO ₂ Catalyst: Insights into the Reaction Pathway and Efficient Kinetic Parameter Estimation

Spatially resolved gas-phase investigations of the CO2 methanation reaction were performed with a spray-pyrolyzed Ni/SiO2 catalyst in a tubular fixed-bed reactor over a broad range of reaction conditions, with particular focus on the formation of the intermediate product CO. The resulting 24 axially resolved concentration and temperature profiles (about 4000 data points) were used to parametrize a Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic model for the rWGS and consecutive CO methanation reactions linked mechanistically via chemisorbed CO. We show that spatially resolved reactors have proven highly effective for kinetic studies involving reaction networks and intermediates, as axial temperature gradients, reactant conversion, and the effects of reactant ratio and product formation are inherently captured within a spatial profile. This reduces the need for extensive experimental series usually required utilizing differential fixed-bed laboratory reactors. Overall, the work demonstrates the efficiency and methodological value of spatially resolved reactors as an appealing tool for deriving reaction kinetics in heterogeneous catalysis.