Several studies in the literature have reported that nickel particle size is closely linked with carbon deposition during hydrocarbon steam reforming. Previous work in our group using Ni/CZO catalysts for isooctane autothermal reforming has shown that high nickel loadings lead to high rates of carbon deposition. Catalysts with the smallest particle sizes, as measured by H₂ chemisorption, showed very low carbon deposition. Nickel particle size and loading were inseparable in the series of catalysts studied, however, and the effect of particle size, if any, could not be clearly determined.

The goal of this work was to better understand how variables such as the support preparation technique, calcination temperature, nickel precursor, and calcination atmosphere affect the final nickel dispersion. The hope is that armed with this information we can synthesize a series of reforming catalysts wherein the only variable is nickel particle size to better examine its effect on carbon deposition.

Calcination under air yielded higher nickel dispersions than calcination under nitrogen or reducing atmospheres. The nickel precursor had little effect on dispersion, as both nickel nitrate and nickel acetate gave similar results. Calcination of the support at high temperature prior to impregnation also gave generally higher dispersions. Several samples retained high support surface area after calcination to 900 °C under non-oxidizing atmospheres. Despite this retention of surface area, these samples had very low nickel dispersions. Nickel dispersion appears to decrease linearly with increasing calcination temperature after impregnation under all atmospheres, although the rate of decrease appears to vary.