Effect of mixed γ- and χ-crystalline phases in nanocrystalline Al2O3 on the dispersion of cobalt on Al2O3

This paper reports the results of a study into the effect of mixed γ and crystalline phases in Al2O3 on the characteristics and catalytic activities for CO hydrogenation of Co/Al2O3 catalysts. The catalysts were characterized by X-ray diffraction, N2 physisorption, transmission electron microscopy, and H2 chemisorption. Increasing Co loading from 5 to 20 wt% for the mixed phase Al2O3-supported Co catalysts resulted in a constant increase in both the number of cobalt metal active sites and the hydrogenation activities. However, for those supported on γ-Al2O3, Co dispersion increased up to 15 wt%Co and declined at 20 wt%Co loading. It is suggested that the spherical-shape like morphology of the χ-phase Al2O3 prevented agglomeration of Co particles, especially at high Co loadings.