Nickel/Zirconia-Catalyzed\nCO<sub>2</sub> Methanation\nin Differential and Integral Fixed-Bed Reactors: Experimental and\nComputational Fluid Dynamics Studies

Isothermal conditions and a chemical-kinetics-limited\nrate should\nbe maintained when measuring the reaction rates of gases on solid\ncatalysts. However, in highly exothermic reactionssuch as\nthe Sabatier reactiontemperature variations within the catalyst\nbed make it challenging to achieve isothermality. In this study, temperature\nchanges in a Ni/ZrO<sub>2</sub> catalyst bed were minimized using\nα-Al<sub>2</sub>O<sub>3</sub> diluent and high gas hourly space\nvelocities (GHSVs) to achieve low feed gas conversion (differential\nconditions: 0.9 MPa; 523–873 K; GHSV = 7600–30,000 L/h/g\ncat). The temperature profile within the catalyst bed was obtained\nby coupling a previously reported kinetic model with three-dimensional\ncomputational fluid dynamics (CFD) simulations. Experiments were also\nconducted under integral conditions at low GHSVs, resulting in high\nconversion rates and heat release. CFD simulations accurately reproduced\nthe experimental feed gas conversion and temperature, suggesting that\nthe CFD-simulation-guided kinetic parameters appropriately predicted\nthe methanation characteristics at practically relevant high conversion\nrates.