Investigation of the kinetics of methanation of a post-coelectrolysis mixture on a Ni/CZP oxide catalyst

The use of synthetic natural gas (SNG) as a plug-and-play fuel coming from renewables can help to overcome the limitations given by the intermittency of renewable energy. A way to implement the production of SNG pass through the co-electrolysis of CO₂ to a mixture of hydrogen, carbon monoxide and carbon dioxide, steam and small amounts of methane, followed by CO and CO₂ methanation. The presence of different reactants and processes requires the comprehension and quantification of the kinetics of the reactions involved with the aim of optimizing methanation. In this work a kinetic model that considers both the direct CO₂ methanation and the indirect RWGS + CO methanation pathways has been developed over a Ni(10 %wt)/Ce_0.33Zr_0.63Pr_0.04O₂. The kinetic study made it possible to understand the influence of the reactants and products on the reactions through the calculation of reaction rates. This allowed to test, by linearization, the models found in the literature and their adjustment permitted to calculate sixteen kinetic parameters (activation energies, heats of adsorption and pre-exponential factors) present in the rate laws of methanation of CO₂, CO and the Reverse Water Gas Shift reaction. The models then made it possible to simulate the evolution of partial flow rates in an isothermal plug flow reactor and were compared to experimental data.