The Microstructure of Cobalt Silica Gel Catalyst in the Presence of Al2O3 Additive

The physico-chemical characteristics and microstructure of cobalt silica gel catalysts with an Al2O3 additive (up to 10%) for the synthesis of hydrocarbons by the Fischer–Tropsch method are studied using a set of methods including X-ray diffraction, BET, IR spectroscopy, and temperature-programmed reduction of H2, as well as scanning and transmission electron microscopy. Phases with a spinel structure, Со3О4, CoAl2O4, and solid solutions on their basis are identified in the samples. The addition of Al2O3 changes the degree of heterogeneity and the orientation of the cobalt crystallites in the oxide and reduced forms of the catalysts. Addition of 1% Al2O3 stabilizes Со3О4 in the spinel form with a structure close to the normal one and promotes the formation of cobalt with a unimodal distribution of particles with an average size of 8 nm. The catalyst is characterized by maximum activity and selectivity with respect to C5+ carbons.