Progresses of coal liquefaction catalysts in Japan

Research and development of catalysts and their performances for coal liquefaction are reviewed, enphasizing the contribution of recent 20 years from Japan. A variety of iron based catalysts were extensively examined to define the pyrrhotite as the active species produced in the liquefaction process. Synthetic pyrite, synthesized hydroxy ferric oxide, finely ground pyrite and limonite have been applied in the process development of coal liquefaction. Iron impregnation onto coal particles using waste water was examined also in a continuous-dow reactor. Finer particles were found to reduce significantly the amount of the catalyst to obtain the same oil yield. Usefulness of such catalysts is proved in the continuous operation of a large scale pilot plant. Iron, iron-nickel, and iron-molybdenum sulfides were found to be active catalysts when they are supported on nano-particles of carbon. Catalysts for recovery and repeated use and for selective aromatic ring opening are under current research.