Deactivation of a Commercial Co–Al2O3/SiO2 Catalyst in Fischer–Tropsch Synthesis under High-Pressure and Gas Recycling Conditions

Results of a study of the synthesis of hydrocarbons (HC) from CO and H2 in the presence of a commercial Co–Al2O3/SiO2 catalyst at 6.0 MPa and a reaction gas recycle ratio of 2.2–6.0 for 1000 h have been described. Under these conditions, the catalyst deactivation rate depends on the selectivity for synthetic C35+ long-chain HCs (SLCHCs). An increase in the SLCHC content in the products from 27.6 to 39.8% leads to a threefold increase in the catalyst deactivation rate. With an increase in the recycle ratio from 2.2 to 6.0 at a pressure of 6.0 MPa, the olefin content in the synthesis products increases. An increase in temperature leads to a shift of the selectivity toward HCs with a shorter chain. The viscosity of LCHCs condensed in the pores decreases owing to their dilution with lighter HCs, which contributes to an increase in the number of accessible active sites of the catalyst and facilitates catalyst regeneration.