FROM COAL TO CHAR

The evolution of coal into char through a hydroconversion process is studied in this paper. The coals used were Spanish low-rank and bituminous coals. The hydroconversion process was performed in the absence of solvent and at increasing severity conditions: pressure from 5 to 10 MPa, and temperatures from 300-degrees to 400-degrees-C. When the hydrogenations were catalyzed, ammonium heptamolybdate was used as catalyst precursor, using the coal as catalytic support. Several analytical techniques were applied to the obtained chars to find some of the changes undergone by the unconverted part of the coal. According to the results, except for the most reactive coals, a development of microporosity is observed in the first stages of char formation in the absence of catalyst, up to 350-degrees-C for the subbituminous coals and 400-degrees-C for bituminous ones. In general, an increase in network crosslinking with increasing severity conditions is observed.