The potential of hydropyrolysis as a route for coal liquefaction

Abstract

The use of sulphided molybdenum (Mo) as a dispersed catalyst enables tar yields of ∼ 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 ammonium dioxydithiomolybdate are the most effective, Mo concentrations 0-2% being required to achieve maximum tar yield. Ion-exchange preparation procedures offer the potential of improving catalyst dispersions, and concentrations as low as 0-02% are effective when Mo is ion-exchanged 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 addition are considerably less than bituminous coals