Steam reforming of methane over Ni catalysts prepared from hydrotalcite-type precursors: Catalytic activity and reaction kinetics

Ni/Mg–Al catalysts derived from hydrotalcite-type precursors were prepared by a co-precipitation technique and applied to steam reforming of methane. By comparison with Ni/γ-Al2O3 and Ni/α-Al2O3 catalysts prepared by incipient wetness impregnation, the Ni/Mg–Al catalyst presented much higher activity as a result of higher specific surface area and better Ni dispersion. The Ni/Mg–Al catalyst with a Ni/Mg/Al molar ratio of 0.5:2.5:1 exhibited the highest activity for steam methane reforming and was selected for kinetic investigation. With external and internal diffusion limitations eliminated, kinetic experiments were carried out at atmospheric pressure and over a temperature range of 823–973 K. The results demonstrated that the overall conversion of CH4 and the conversion of CH4 to CO2 were strongly influenced by reaction temperature, residence time of reactants as well as molar ratio of steam to methane. A classical Langmuir–Hinshelwood kinetic model proposed by Xu and Froment (1989) fitted the experimental data with excellent agreement. The estimated adsorption parameters were consistent thermodynamically.

Graphical abstractA Ni0.50/Mg2.50Al catalyst derived from a hydrotalcite-type precursor exhibits high activity and stability as a result of high specific surface area and good Ni dispersion. The kinetic study over the catalyst shows that a Langmuir–Hinshelwood kinetic model is thermodynamically consistent and describes the experimental data very well, with the average relative errors for the overall conversion of CH4 and the conversion of CH4 to CO2 over the range of experimental conditions being 6.3% and 5.6%, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide