Hydroliquefaction of low-sulfur Australian coals (Wandoan and Yallourn) was studied using iron carbonyl complexes as catalyst. The addition of Fe(CO)
5 (2.8 wt% Fe of coal) increased coal conversion from 48.6 to 85.2% for Wandoan coal, and from 36.7 to 69.7% for Yallourn coal in 1-methylnaphthalene at 425°C under an initial hydrogen pressure of 50 kg cm
?2. When molecular sulfur was added to iron carbonyls (Fe(CO)
5, Fe
2(CO)
9 and Fe
3(CO)
12), higher coal converions ( > 92%) and higher oil yields (>46%) were obtained, along with an increase in the amount of hydrogen transferred to coal from the gas phase (0.2 to 2.8%, d.a.f. coal basis). In the liquefaction studies using a hydrogen donor solvent, tetralin, Fe(CO)
5S catalyst increased the amount of hydrogen absorbed from the gaseous phase and decreased the amount of naphthalene dehydrogenated from tetralin. The direct hydrogen transfer reaction from molecular hydrogen to coal fragment radicals seems to be a major reaction pathway. Organic sulfur compounds, dimethyldisulfide and benzothiophene, and inorganic FeS
2 and NiS were found to be good sulfur sources to Fe(CO)
5. From X-ray diffraction analyses of liquefaction residues, it is concluded that Fe(CO)
5 was converted into pyrrhotite (Fe
1?xS) when sulfur was present, but into Fe
3O
4 in the absence of sulfur.
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