THE FISCHER-TROPSCH SYNTHESIS WITH A MECHANICAL MIXTURE OF A COBALT CATALYST AND A COPPER-BASED WATER GAS SHIFT CATALYST

The feasibility of using a mechanical mixture of a CO/MgO/SiO2 Fischer-Tropsch catalyst and a Cu-ZnO/Al2O3 water gas shift (WGS) catalyst for hydrocarbon synthesis in a slurry reactor has been established. Such a mixture can combine the superior product distribution from cobalt with the high activity for the WGS reaction characteristic of iron. Weight ratios of Co/MgO/SiO2 to Cu-ZnO/Al2O3 of 0.27 and 0.51 for the two catalysts were studied at 240-degrees-C, 0.79 MPa, and in situ H-2/CO ratios between 0.8 and 3.0. Each catalyst mixture showed stable Fischer-Tropsch activity for about 400 h on stream at a level comparable to the cobalt catalyst operating alone. The Cu-ZnO/Al2O3 catalyst exhibited a very slow loss of activity under these conditions, but when operated alone it was stable in a slurry reactor at 200-220-degrees-C, 0.79-1.48 MPa, and H-2/CO in situ ratios between 1.0 and 2.0. The presence of the water gas shift catalyst did not affect the long-term stability of the primary Fischer-Tropsch selectivity but did increase the extent of secondary reactions, such as I-alkene hydrogenation and isomerization.