Catalysis of coal hydroliquefaction by synthetic iron catalysts

The following synthetic iron catalyst precursors were investigated: FeOOH and FeOOH-Al₂O₃ (90:10 wt%) co-precipitated by ammonia, washed and dried either in an oven or by spray-drying, and Fe₂O₃ prepared by flame decomposition of FeCl₃ in the gas phase. These catalyst precursors were sulphided in situ by CS₂ during the hydroliquefaction of a highly volatile bituminous coal. An increasing catalytic activity of the iron sulphide was observed as its particle size decreases down to a very low value (0.05 μm), compared to 2–3 μm and to ? 5 μm. Al₂O₃ did not act as an efficient promoter, even if it gives rise to a decrease of the iron sulphide crystallite size. Diffusional limitations and/or plugging by carbonaceous or mineral solids could result in a low efficiency of the iron sulphide crystallites which lie inside one iron catalyst particle. The above cited flame method, allowing the preparation of pure or doped Fe₂O₃ with particle size even less than 0.05 μm, is worthwhile for further work in coal hydroliquefaction catalysis, where the catalyst acts as Fe_1?xS.