Abstract:

Ni/SiC methanation catalysts were prepared by an incipient wetness impregnation method. Effects of the oxidation extent of the SiC surface on low-temperature activity and high-temperature stability of the catalysts were investigated. Samples were characterized by thermogravimetry and differential scanning calorimetry, N₂ adsorption-desorption, Fourier transform infrared spectra, temperature-programmed desorption of NH₃, X-ray diffraction, temperature-programmed reduction of H₂ and H₂ chemisorption. The surface area and nickel dispersion of the catalysts decreased with increasing oxidation temperature of the SiC supports, while both reducibility and stability of the catalysts increased. The Ni/SiC catalyst with the unoxidized SiC support showed the poorest high-temperature stability probably because of the weak anchorage of Ni particles to the support. The Ni/SiC samples prepared on the SiC supports oxidized at 500 and 700℃ had better low-temperature activity and high-temperature stability, which was because Ni particles were well dispersed on and strongly anchored to these properly oxidized supports. The Ni/SiC catalyst with the SiC support oxidized at 900℃ showed the worst low-temperature activity because of the larger Ni particles caused by the less active oxide layer due to the overoxidation of the support.

Key words: Methanation, Silicon carbide, Surface oxidation, Nickel, High-temperature stability