Silicon–nickel intermetallic compounds supported on silica as a highly efficient catalyst for CO methanation

Abstract

Silicon–nickel intermetallic compounds (IMCs) supported on silica (Si–Ni/SiO₂), as a highly efficient catalyst for CO methanation, have been prepared by direct silicification of Ni/SiO₂ with silane at relatively low temperature in a fluidized bed reactor. The as-prepared materials were characterized by X-ray diffraction, transmission electron microscopy, in situ FT-IR of CO adsorption, and H₂-temperature programmed reduction-mass spectrometry (TPR-MS) of CO. The results indicate that uniform NiSi_x nanoparticles with about 3–4 nm are evenly dispersed on silica. The combined in situ FTIR and TPR-MS results suggest that the Si–Ni/SiO₂ catalysts afforded high activity in CO methanation, promoting the formation of CH₄ at ca. 240 °C. The catalytic hydrogenation of CO on Si–Ni/SiO₂ was investigated in a fixed-bed reactor at GHSVs 48 000 mL h⁻¹ g⁻¹ under 1 atm in the temperature interval 200–600 °C. In the higher temperature reaction region (500–600 °C), it is notable that the Si–Ni/SiO₂ catalysts present high activity for CO methanation as compared to the Ni/SiO₂ catalyst. More importantly, the Si–Ni/SiO₂-350 catalyst containing thermally stabile Si–Ni IMCs shows significantly higher resistance to the sintering of Ni particles. Raman characterization of the spent materials qualitatively shows that carbon deposition observed on the conventional Ni/SiO₂ catalyst is much higher than that of the used Si–Ni/SiO₂-350. It is proposed that small amounts of silicon interacting with Ni atoms selectively prevent the adsorption of resilient carbon species.