The slurry of Tanito Harum coal (Indonesia) was rapidly heated up by the preheater of 1t/d Process Supporting Unit (PSU). The behaviour of coal macerals in initial stage of coal liquefaction has been investigated with petrographic analysis. Consequently, the relationship between the vitrinite reflectance of heated coal and products yield, residence time in preheater and H/C atomic ratio of toluene insoluble can be recognized. A fraction of coal maceral selectively reacted in the initial stage of coal liquefaction. The progress of coal liquefaction at preheating process was dependent on temperature and residence time of preheater.
