The effect of atomic S/Fe ratio of various natural pyrite catalysts on the liquefaction of Taiheiyo coal has been investigated. The catalytic activity of pyrites was compared on the basis of the exothermic peak temperature and differential pressure in a high-pressure DTA analysis. The exothermic peak temperatures of pyrites with the atomic S/Fe ratio of 1.87 to 1.97 were lower than those with the ratio of 1.99 to 2.04. The latter contained more Na2O, K2O, CaO and MgO and these oxides were considered to inhibit the liquefaction. On the other hand, the results of 500 ml autoclave experiments showed that the liquefaction with the pyrites which were more active in the DTA analysis produced somewhat higher yield of asphaltene. However, the conversion and oil yield were not related to the catalytic activity in the DTA analysis. They might be affected by the contents of SiO2 and Al2O3 in the pyrites.
