A.1 Appendix A Characterization of Slurry Phase Iron Catalysts for Fischer-Tropsch synthesis

To whom all correspondence should be addressed ‡ The study of Iron Fischer-Tropsch Catalysts by conventional powder X-ray diffraction (XRD) methods is complicated by the multiplicity of phases present ("-Fe, various iron carbides, FeCx magnetite, FeO) and by peak overlap in the diffraction patterns arising from these phases. This has3 4 led to the consensus that activity for Fischer-Tropsch (F-T) synthesis does not correlate with the bulk composition ofthe iron catalyst, as seen by XRD. As we show in this paper, some of the problems associated with sample analysis of the working F-T catalyst originate with the difficulty in preserving the microstructures and composition intact, as the sample is prepared for analysis. In this paper, we present analysis of iron F-T catalysts from a stirred tank reactor where samples have been removed under inert atmosphere and care was taken to preserve the catalyst constituents intact. By using XRD with Quantitative Rietveld Structure Refinement (QRSR) analysis, we c n construct a comprehensive picture of the working catalyst. These results permit us to explain the activation and deactivation of Fe F-T catalysts and to understand the role of activation method; e.g., CO vs. H. We conclude that,2 in its most active form, the Fe catalyst in a slurry reactor consists of,!-carbide (FeC) and alpha-iron7 3 ("-Fe), while the P-carbide, which is also present, appears to be less active. Further work is necessary to elucidate the relative roles of these phases for Iron F-T catalyst activity. Our results also show that Soxhlet extraction, a commonly used procedure to remove the wax from a catalyst, can cause changes in catalyst phase composition