Vacuum-Freeze Drying Assist for the Fabrication of a Nickel-Aluminium Catalyst and Its Effects on the Structure-Reactivity in the Catalytic Dry Reforming of Methane

In this study, a co-precipitation coupled with vacuum-freeze drying (VFD) method was adopted to fabricate a highly mesoporous nickel-aluminium catalyst (VFD-cat). VFD-cat with uniform smaller pore size and a larger BET surface area were obtained than the catalysts prepared following the conventional thermal evaporation drying method (TED-cat). In addition, the VFD method helps to improve the dispersion of precursors, which then enhances the strong metal-support interactions (MSI) of VFD-cat via forming substoichiometric NiAl2O4 spinel. Characterization showed that the average nickel particle size on the VFD-cat was smaller than that of the TED-cat, attributed to the confinement effects of MSI. At 800 °C, the VFD-cat exhibited higher stability during the long-term dry reforming of methane (DRM) test. It was found that the coke formation on spent VFD-cat, especially for the ordered carbon species, was significantly eliminated as compared with TED-cat after the stability test. This strategy offers a facile way to develop DRM catalysts with highly mesoporous and MSI, enhancing the catalytic stability and coke resistance of the nickel-aluminium catalyst. Using an ice scaffold-assisted vacuum-freeze drying method, pore structure was protected and precursor Al(OH)3 was anchored on the surface of Ni(OH)2 during the drying stage, which then avoided the aggregation of the NiO-NiO during the calcination stage. This strategy offers a facile way to develop DRM catalysts with highly mesoporous and strong metal support interaction, enhancing the catalytic stability and coke resistance.