A precipitated iron Fischer-Tropsch catalyst for synthesis gas conversion to liquid fuels

Abstract

A precipitated iron Fischer-Tropsch (F-T) catalyst with nominal composition 100 Fe/3 Cu/4 K/16 SiO 2 (in parts by weight) was tested in a stirred tank slurry reactor. The performance of this catalyst (activity and selectivity) under baseline activation (H 2 reduction at 240°C for 2 h) and process conditions (260°C, 1.48 MPa, 1.4 Nl/g-cat/h, H 2 /CO = 2/3) was found to be comparable to that of the best state-of-the-art iron F-T catalysts. In this study the repeatability of performance was demonstrated by performing multiple tests of the catalyst from the same preparation batch, whereas reproducibility of catalyst preparation procedure was demonstrated in tests of the catalyst from different batches. Catalyst productivity (i.e. reactor space-time-yield) was increased by 40% (relative to baseline process conditions) by increasing reaction pressure from 1.48 MPa to 2.17 MPa, while simultaneously increasing gas space velocity in order to maintain a constant contact time in the reactor. The intrinsic activity of the catalyst was increased up to 75% through the use of different pretreatment procedures. The catalyst productivity in run SA-2186 at 260°C, 2.17 MPa, 3.4 Nl/g-cat/h and H 2 /CO = 2/3 was 0.86 (g hydrocarbons/g-Fe/h) at syngas conversion of 79%, methane selectivity of 3% (weight percent of total hydrocarbons produced) and C 5 + hydrocarbon selectivity of 83 wt%. This represents a 75% increase in catalyst productivity relative to Rheinpreussen's slurry bubble column reactor. The yield of liquid and wax hydrocarbons in different tests of our catalyst was 80-89%, and the Anderson-Schulz-Flory parameter was 0.92-0.94 (high alpha catalyst). This catalyst is ideally suited for production of high quality diesel fuels via hydrocracking of the F-T wax product.