Iron-Based Catalysts Supported on Carbon Nanoparticles of Hollow Structure for Coal Liquefaction

Recent studies have shown that NiMo catalysts supported on carbon nanoparticles (Ketjen Black: KB) are very effective for the conversion of low-rank coals to oil; however, because of the high cost of Mo, lower cost alternative metals are desired. This study describes the preparation and use of iron-based catalysts having performances very similar to those of NiMo/KB-based catalysts. The iron-based catalysts were prepared by impregnating soluble iron salts onto KB. Coal liquefaction studies were conducted at 450 °C, 60 min, 15 MPa H2 pressure, using solvent (tetralin)/coal/catalyst weight ratios of 1.5/1/0.03. Of the various iron salts investigated, catalysts prepared from iron(II) fumarate (Fe 15 wt % supported on KB) gave the highest oil yield (60%) in the liquefaction of Tanitoharum coal. This yield was similar to that obtained in experiments using 12 times as much Fe in the form of synthetic iron pyrite but was still less effective than the NiMo/KB catalyst. Using 3 times as much Fe fumarate/KB catalyst increased the oil yield to ca. 70% which was comparable to that achieved by NiMo/KB catalyst. Addition of Mo (2 wt %) or Ni (10 wt %) to the Fe/KB catalyst increased the oil yield to ca. 70% with the same weight of catalyst. Comparisons of the hydrogenation and hydrocracking activities of Fe-based KB catalysts and NiMo/KB catalysts for the conversion of coal macromolecules are discussed.