EFFECT OF CATALYST PRECURSORS ON COAL REACTIVITY IN CATALYTIC HYDROPYROLYSIS

The use of dispersed sulphided molybdenum and hydrous titanium oxide (HTO) catalysts enable tar yields in excess of 60% daf coal to be obtained for bituminous coals in fixed-bed hydropyrolysis using relatively mild conditions. However, it was found that a key difference between hydropyrolysis and batchwise hydrogenation is that the active form of the catalyst must be formed at a lower temperature in hydropyrolysis in order to be effective because of the much higher heating rates used. Thus, ammonium dioxydithiomolybdate which decomposes to form a sulphided Mo compound below 250-degrees-C and Pd-exchanged HTO, where the Pd is reduced below 100-degrees-C, have been found to be particularly effective (approximately 0.2%. Mo required to achieve maximum conversion). Molybdenum naphthenates and iron sulphides are much less effective in hydropyrolysis than in direct liquefaction because the active phases (MoS2 and pyrrhotite) are not appreciably formed below about 400-degrees-C. Preliminary results indicate that low concentrations of Mo (about 0.02%) have considerable activity when ion-exchanged onto HTO-coated coals.