LAUSR

Abstract The effects of the harsh conditions achieved when operating the Fischer-Tropsch synthesis at high conversion on the activity and selectivity of Pt-Co/Al2O3 were studied in a slurry bed reactor at T = 220 °C, P = 20 bar, with a feed simulating synthesis gas generated by air-blown gasification (H2: CO: N2 = 4:2:6). The rate of CO consumption decreased with increasing conversion. Decreasing the space velocity and thus increasing the CO conversion was found to have slight effect on CO2 selectivity until a conversion of CO of 75%, after which a strong increase was observed. The production of CO2 raised the H2/CO ratio within the reactor resulting in a large increase in methane selectivity. An increase in CO conversion resulted in a decrease in chain growth probability and C5+ selectivity. The link between the change in the methane selectivity, chain growth probability and C5+ selectivity and the presence of carbonaceous species on the surface is explored.