INFLUENCE OF THE POROUS NATURE OF COALS ON MO-CATALYZED HYDROGENATIONKINETICS

Mo-catalysed hydrogenation processes of four coals, ranked between lig nite B and high volatile bituminous coals, are studied. Ammonium hepta molybdate was used as a catalyst precursor. Hydrogenations were carrie d out at 300, 350 and 400 degrees C at a hydrogen pressure of 10 MPa, with reaction times ranging from 5 to 30 min. The maximum rate of the process, related to the textural characteristics of the coal, was calc ulated from the relationship between the conversion time and the react ion time. The results indicate that at 300 degrees C the catalyst is n ot active and the reaction mainly depends on the efficiency of the mas s transfer process and thus on the coal macropore volume. At higher te mperatures, however, the process takes place catalytically and in this case the catalytic activity is influenced by the coal surface.