THE POTENTIAL OF HYDROPYROLYSIS AS A ROUTE FOR COAL-LIQUEFACTION

The use of sulphided molybdenum (Mo) as a dispersed catalyst enables t ar yields of approximately 60% daf coal to be achieved for bituminous coals (80-83% dmmf C) in fixed-bed hydropyrolysis using relatively low -severity conditions. Sulphur-containing Mo precursors, such as ammoni um dioxydithiomolybdate are the most effective, Mo concentrations of 0 .2% being required to achieve maximum tar yield. Ion-exchange preparat ion procedures offer the potential of improving catalyst dispersions, and concentrations as low as 0.02% are effective when Mo is ion-exchan ged onto coals coated with hydrous titanium oxides. Iron sulphides are much less effective than in direct liquefaction because of the higher heating rates used in hydropyrolysis. Low-rank coals can yield up to 50% tar without catalyst, and improvements in yield on catalyst additi on are considerably less than for bituminous coals. Exinite has a posi tive synergistic effect on vitrinite conversion in catalytic hydropyro lysis for one of the bituminous coals investigated.