Reaction Characteristics of Ni-Based Catalyst Supported by Al₂O₃ in a Fluidized Bed for CO₂ Methanation

CO₂ methanation is a promising technology to store renewable energy by converting carbon dioxide with green hydrogen into methane, which is known as power to gas (PtG). In this study, CO₂ methanation performance of a Ni/Al₂O₃ catalyst was investigated in a bubbling fluidized bed (BFB) and the axial gas concentration, temperature, and CO₂ conversion were densely analyzed. Moreover, a modified reaction kinetic model was proposed, and the results were compared with experimental data. The bed temperature increased by 11 °C from 340 °C to 351 °C within the first 30 mm of the fluidized bed. The CO₂ conversion was approximately 90% within 50 mm from the bottom of the reactor and was maintained above this height. The Ni/Al₂O₃ catalyst exhibited the highest CO₂ conversion (95%) at 320 °C. Using a simple plug-flow reactor model, three optimized kinetic modification factors (1.5094, 0.0238, and 0.2466) were used to fit the experimental data. The hydrodynamic effects significantly influenced the chemical reaction kinetics of the BFB.