Three nanoscale iron-based catalyst precursors were tested to determine their effect on the conversion of a subbituminous coal. The results of this study indicate that each of the precursors, superfine iran oxide, Fe7C3, and Fe1-xS, exhibited very similar activity and selectivity with only minor variations. However, the hydrogenation activities of the three catalysts were very different. This was related to the particle size and surface area of the precursor, rather than its phase. The insensitivity to phase was probably due to the rapid transformation of the precursor surface, where the catalytic reaction occurs, to a similar structure in each case. The increase in hydrogen consumption without corresponding increases in conversion indicates that bond cleavage, rather than availability of labile hydrogen, was the rate limiting step in the coal liquefaction reaction.