A Facile Strategy to Fabricate High-Performance Ni/SiO₂ Nanocomposite Catalysts for Dry Reforming of Methane

This work proposes a facile route to fabricate Ni/SiO2 nanocomposite catalysts for dry reforming of methane, in which the hydrolysis and condensation of tetraethyl orthosilicate starts and then proceeds around the in situ-formed nickel hydroxide colloids that are stabilized by cetyltrimethylammonium bromide during precipitation using ammonium hydroxide. The average size of Ni nanoparticles (NPs) embedded in a macroporous silica matrix monotonically increases as the initial Ni2+ concentration increases from 0.05 to 0.2 M in the precipitation step, and it is around 6 nm when the latter is 0.2 M. At 750 °C and 1 atm, the reverse water gas shift reaction appears to be more important on small Ni particles than on large ones, and reforming stability over large particles (6 nm) is higher than that of small ones (4 and 4.9 nm). The reforming catalyst with the largest Ni NPs exhibits excellent stability at a weight hourly space velocity of 60 L gcat–1 h–1: methane conversion maintains at ∼88% and H2/CO molar ratio marginally fluctuates around 0.97 during the 100 h of continuous operation. After the stability test, the size of Ni NPs slightly increases but the pattern of spatial confinement remains intact. Moreover, the amount of catalytic coke in the spent catalyst is around 0.18 wt %. However, no carbonaceous materials are detected in the spent one by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Thus, the proposed method may be used to prepare other nickel-based catalysts for hydrocarbon catalytic transformations involving sintering and/or coking.