The intrinsic kinetics of methane steam reforming over a nickel-based catalyst in a micro fluidized bed reaction system

Methane steam reforming (MSR) is studied experimentally and numerically. The intrinsic kinetics of the reaction are determined using a micro fluidized bed with a catalyst containing more than 50 wt % NiO/α-Al₂O₃. Intrinsic kinetic models are developed for parallel and serial reaction mechanisms, but the parallel mechanism is found to better match the experimental data. The activation energies for CO and CO₂ formation are 81.69 kJ/mol and 59.38 kJ/mol, respectively, and the pre-exponential factors are 316.6 mol/(g h kPa^0.85) and 0.00263 mol/(g h kPa^3.1), respectively. As the reaction temperature increases, the rate of CO formation increases and that of CO₂ decreases. At 800 °C, almost all the CH₄ is converted to CO and H₂, and the methane conversion rate (X_CH4), the hydrogen production rate (Y_H2), and the CO selectivity (S_CO) are 92.28%, 3.34, and 0.99, respectively. The effects of the steam-to-carbon ratio (S/C), inlet velocity, and preheating temperature at different reaction temperatures are simulated using the FLUENT software package. As S/C increases, X_CH4 and Y_H2 increase, but S_CO decreases. The higher the reaction temperature, the less S/C promotes X_CH4 and Y_H2. When the reaction temperature is 700 °C and the inlet velocity is 0.2 m/s (residence time is 0.5 s), X_CH4 is above 95%, and changes in the inlet velocity strongly influence the formation of CO. With increasing preheating temperature, X_CH4, Y_H2, and S_CO all increase gradually.