Evolution of high–performance Fischer-Tropsch synthesis catalyst and its catalytic properties during industrial operation

The changes in the activity and structure of a high-performance Fischer-Tropsch synthesis catalyst during operation on a pilot plant in a 14 mm diameter reaction tube of a 6-meter Fischer-Tropsch reactor were studied. Heat was removed by water on the equilibrium line and by intensive heat removal due to a «water-water vapor» phase transition. The initial catalyst, the catalyst from the overheating zone (in case of violation of the process mode) and the normal operating temperature region were studied using a number of physicochemical methods (physical nitrogen sorption, helium pycnometry; electron microscopy, thermogravimetric analysis). It was shown that the leading synthesis reduced cobalt-containing component of the catalyst is deactivated due to carbonization and blocking with high-molecular products (waxes). During normal operation of the lower layers, highly dispersed carbon is formed from the gas phase and the porous system of granules changes with a decrease (in the overheating zone) in the true density. Partial reduction of cobalt oxide on the surface of flaked graphite to a metallic state during thermolysis of the catalyst precursor was detected. The cobalt particles of 20-50 Å in size obtained during catalyst activation can, due to surface diffusion and coalescence, produce clusters of 200-300 Å in size during further operation.