Effect of the cobalt-precursor on the reactivity of cobalt-based Fischer-Tropsch catalysts supported on stabilized alumina

This study investigates the effect of the cobalt precursor (nitrate and acetate) on the catalytic performance in the Fischer-Tropsch synthesis of catalysts supported on stabilized CoAl2O4/Al2O3 pellets. The catalysts are prepared via multi-steps of impregnation of the support with aqueous solutions of cobalt nitrate or acetate followed by calcination in air. The dispersion of the Co3O4 particles obtained via exothermic decomposition of acetate increases if each impregnation is followed by calcination. In fact, halving the calcinations leads to Co3O4 particles even bigger than those formed from cobalt-nitrate. A worsening of the catalytic performances is observed when the Co-acetate catalysts are tested in the FTS. Such a result is explained on the basis of Co0 particles size effect. Pt improves the catalysts reducibility regardless of the Co-precursor. The metallic surface area of the Pt-promoted Co-nitrate catalyst is higher than that of the corresponding Co-acetate catalyst, thus resulting in improved catalytic performances.