Effect of milling on the formation of chi-alumina from gibbsite and its application as cobalt catalyst support

Abstract

To investigate the effect of milling on formation X-alumina from gibbsite and its application as cobalt catalyst support. Fine gibbsite (d50=13µm) was milled in an attrition mill for 12 and 24 h and calcined at different temperatures in the range of 350 to 600℃. Pure X-alumina was obtained at 350℃ for the 24h-milled fine gibbsite. Without milling, the obtained alumina normally contained the mixed phases between γ and X-phase alumina. The rate constant (k) for phase transformation increased as the particle size of fine gibbsite decreased. For CO hydrogenation, X-alumina prepared from the above-mentioned method, solvothermal method, and γ-Al2O3 were used as support for cobalt catalyst. At initial conditions, the cobalt on X-alumina prepared from fine gibbsite showed higher catalytic activity than other catalysts. However, the cobalt on X-solvothermal performed higher activity at steady state conditions. It was due to stronger interaction between cobalt particles and support as well as more stable cobalt particles on the surface, which was observed by TPR and TEM. Additionally, the catalytic activity of both of Co/X-Al2O3 was higher than that of Co/γ-Al2O3.