Highly Active and Stable Ni–SiO2 Prepared by a Complex-Decomposition Method for Pressurized Carbon Dioxide Reforming of Methane

Abstract

A series of Ni–SiO2 catalysts was synthesized by the complex-decomposition method using different amino acids as complexing agents and fuels and nickel nitrate and tetraethoxysilane as precursors of Ni and SiO2, respectively. For comparison, ammonium hydroxide and acetic acid were also used as complexing agents and fuels. Characterization by XRD, TEM, and N2 adsorption–desorption at low temperature indicated that the structural and textural properties of the Ni–SiO2 catalysts were strongly dependent on the complexing agent used. The dispersion of metallic Ni was increased by optimizing the complexing agent used. As revealed from H2-TPR patterns, Ni–SiO2 exhibited significantly different interactions between Ni and SiO2, the extent of which was influenced by the complexing agent used. The Ni–SiO2 catalysts were comparatively evaluated for carbon dioxide reforming of methane (CDR) under the following conditions: CH4/CO2 = 1.0, T = 750 °C, GHSV = 53200 mL·g–1·h–1, and P = 1.0 atm. The results indicate that the Ni–SiO2 materials prepared with glycine, alanine, serine, threonine, valine, and proline exhibited much higher activity and stability for CDR under atmospheric conditions than those prepared with lysine, acetic acid, and ammonium hydroxide. Moreover, the Ni–SiO2 material prepared with glycine was also tested at elevated pressures of 5.0 and 10.0 atm. The effect of pressure on the CDR performance was investigated. Importantly, a highly active and stable Ni–SiO2 material for pressurized CDR was obtained by tailoring the structure of Ni–SiO2 and adjusting the interactions between Ni and SiO2 by selecting the complexing agent. Thus, the main factors determining catalyst activity and stability for CDR were clearly revealed.