Nickel/Zirconia-Catalyzed CO ₂ Methanation in Differential and Integral Fixed-Bed Reactors: Experimental and Computational Fluid Dynamics Studies

Isothermal conditions and a chemical-kinetics-limited rate should be maintained when measuring the reaction rates of gases on solid catalysts. However, in highly exothermic reactions─such as the Sabatier reaction─temperature variations within the catalyst bed make it challenging to achieve isothermality. In this study, temperature changes in a Ni/ZrO2 catalyst bed were minimized using α-Al2O3 diluent and high gas hourly space velocities (GHSVs) to achieve low feed gas conversion (differential conditions: 0.9 MPa; 523–873 K; GHSV = 7600–30,000 L/h/g cat). The temperature profile within the catalyst bed was obtained by coupling a previously reported kinetic model with three-dimensional computational fluid dynamics (CFD) simulations. Experiments were also conducted under integral conditions at low GHSVs, resulting in high conversion rates and heat release. CFD simulations accurately reproduced the experimental feed gas conversion and temperature, suggesting that the CFD-simulation-guided kinetic parameters appropriately predicted the methanation characteristics at practically relevant high conversion rates.