The Effect of Metal Dispersion on Ni/Al2O3 Wax Hydrofining Catalyst

Abstract

Positron annihilation spectroscopy for chemical analysis (PASCA), powder x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to study the effect of calcination temperature on active metal dispersion of wax hydrofining catalyst. The experimental results showed that, with the increase of calcination temperature, the metal Ni and the support Al2O3 interaction became weaker. When calcination temperature reached 280°C, Ni(NO3)2 began to decompose and the inhibition effect of NO3 − began to diminish. At 380°C, Ni(NO3)2 was almost decomposed, and NiO still had a high dispersion on the catalyst surface. At 440°C or higher, Ni(NO3)2 was completely decomposed, and to some extent, NiO aggregated on the catalyst surface in the form of noncrystalline clusters (atomic clusters). The most suitable calcination temperature in the experiment for the catalyst Ni/Al2O3 was 440°C or a little higher.