Evolution of High-Performance Fischer–Tropsch Synthesis Catalyst and Its Catalytic Properties during Pilot Operation

Abstract— Changes in activity and structure of a high-performance Fischer–Tropsch synthesis catalyst during its operation in a pilot plant with a 14 mm diameter reaction tube of a 6-meter Fischer–Tropsch reactor were investigated. Heat was removed by water at equilibrium line and by intensive heat removal due to the water–water vapor phase transition. A initial catalyst, a catalyst from overheating zone (during process mode violations), and normal operation temperature ranges were studied with physicochemical methods (nitrogen physical sorption, helium pycnometry, electron microscopy, and thermogravimetric analysis). It was shown that the reduced cobalt-containing component of the catalyst is deactivated because of carbonization and blocking by high-molecular products (waxes). Highly dispersed carbon is formed from the gas phase, and the porous system of granules changes with a decrease in true density (in the overheating zone) during normal operation of lower layers. Partial reduction of cobalt oxide on the surface of flake graphite to a metallic state was observed during thermolysis of the catalyst precursor. Cobalt particles of 20–50 Å formed during catalyst activation can give clusters of 200–300 Å during further operation through surface diffusion and coalescence.