It has been known that fine particles of pyrite are easily oxidized in the atmosphere. In this paper, the transformation of chemical structure of pyrite which was oxidized under various conditions are discussed in relation to the catalytic activity for coal liquefaction. A surface oxidation of pyrite resulted in a lower coal conversion for brown coal liquefaction.It was found that the finely divided particles of pyrite pulverized in the process solvent has a good liquefaction activity, even if the keeping for a long time.
