The Intrinsic Kinetics Of Methane Steame Reforming Over A Commercial Ni/α-Al₂O₃ Catalyst

Nature gas not only is one of important environmentally benign energy source, but also a stock for the production of hydrogen and synthesis gas. Methane steam reforming is the crucial reaction used to synthesize ammonia, methanol and hydrogen in industrial scale.Intrinsic kinetics of methane stream reforming over a commercial Ni/α-Al2O3 catalyst was investigated in this work.The equilibrium constants of the methane steam reforming reaction system were calculated. Experimental work was carried out in a tubal differential reactor over a wide range of operation parameters. It was show that the formation of carbon dioxide is much faster than that of carbon monoxide at lower temperature. It suggests that the reaction, CH4+2H2O=CO2+4H2, probably dominates methane steam reforming at the conditions of lower temperature. However, both carbon monoxide and carbon dioxide are primary reaction products. These facts imply that the reactions CH4+CO2=2CO+2H2 , CH4+H2O=CO+3H2 or H2+CO2=CO+H2O take place simultaneously. Base on the effect of reaction temperature on the selectivity, it can be expected that the selectivity of carbon dioxide will decrease with increasing the reaction temperature. Five possible reaction models describing the kinetic behaviour of the reaction network were considered, applying the methods of parameter estimation and model discrimination, a satisfactory intrinsic model for methane reforming over the catalyst used in this study was determined. The formation rates of carbon monoxide and carbon dioxide increase with raising the partial pressures of methane, and carbon dioxide (for the formation of CO) or water gas (the formation of CO2). Good agreement was obtained between the experimental data and results predicted by the rate equations. The intrinsic kinetic equations established are as follow:This set of kinetic models gives a reasonable representation of the experimental data, and also predicts a detail product distribution of methane steam reforming. Combining the model with a differential balances of mass and heat, and the transfer in the catalyst pellet. It can be model an industrial reactor and simulate its operation performance.