Study of the Structure of Cobalt-Containing Catalysts Synthesized under Subcritical Conditions

Abstract

A physicochemical study of cobalt-containing (10 wt %) silica-supported Fischer–Tropsch catalysts was carried out. The catalysts were obtained under subcritical conditions (T = 200°C, P = 8 MPa) using water (T_c = 374.1°C, P_c = 22.1 MPa) and propanol-2 (T_c = 235.6°C, P_c = 5.8 MPa). The obtained samples were compared with a 10 wt % Co/SiO₂ catalyst prepared by incipient-wetness impregnation. Comparison of the properties of catalysts in the liquid-phase Fischer–Tropsch synthesis showed that the sample prepared in subcritical water was the most active and selective to aliphatic C₆–C₇ hydrocarbons. This sample is characterized by a high surface area (131.7 m²/g), a uniform distribution of particles in the active phase with an average size of 5 nm and higher accessibility of cobalt species for reagents. According to XPS data, the composition of catalyst active phase is mainly represented by two compounds: Co(OH)₂ and Co₃O₄.