Carbon Spheres Prepared by Hydrothermal SynthesisA Support for Bimetallic Iron Cobalt Fischer-Tropsch Catalysts

Carbon spheres (CSs) synthesised by the hydrothermal approach were explored as a model support material for a bimetallic Fe-Co Fischer-Tropsch (FT) catalyst. The CSs were characterised by N-2 adsorption-desorption, thermogravimetric analysis, FTIR spectroscopy and powder XRD. If annealed at 900 degrees C for 4h, the CSs exhibited an improved surface area, thermal stability and crystallinity. A series of Fe-Co bimetallic FT catalysts supported on the annealed CSs were prepared by co-precipitation. A variety of Fe-to-Co ratios were used with the total metal loadings maintained at 10%. Catalyst reducibility studies were performed by H-2 temperature-programmed reduction and insitu powder XRD. Catalysts with a Fe/Co ratio of 5:5 (w/w) showed Co-Fe alloy formation upon reduction at >450 degrees C. Interestingly, the presence of this alloy did not correlate with high C5+ selectivities during FT synthesis; rather the Co-rich/Fe-poor catalyst gave the best selectivity. The CSs allowed the metal-metal interactions in the bimetallic systems to be monitored because of the weak interaction of the metals with the support.