Novel Bimetallic Dispersed Catalysts for Temperature-Programmed Coal Liquefaction

Coal liquefaction involves cleavage of methylene and dimethylene and ethertype bridges connecting polycyclic aromatic units. The selected compounds for model coal liquefaction reactions are 4-( 1-naphthylmethy1)bibenzyl (NMBB) and several oxygen-containing compounds. This report mainly describes the synthesis and screening of selected iron and molybdenum compounds as precursors of dispersed catalysts for hydrocracking of NMBB and oxygen-containing compounds. Experiments using NMBB were carried out at 400 *C for 30 min. under 6.9 MPa H2 pressure. All catalyst precursors converted NMBB predominately into naphthalene and 4methylbibenzyl. Small amounts of secondary products were formed by hydrogenation, isomerization and fragmentation of the primary products. Generally, ferrocene demonstrated very low activity as catalyst. Even sulfur addition did not increase activity. Hydrated iron sulfate FeSO4 x 7 H2O gave similar conversion like ferrocene. However, in an experiment with added sulfur, only iron sulfate became a more active catalyst. The same effect was observed in an reaction of CuZr2P3012 with added sulfur. The total sulfur concentration in the latter experiment was 3.4 wt %. In order to clarify the effect of sulfur alone on model compound conversion, NMBB was treated with sulfur in concentrations of 1.2 to 3.4 wt %, corresponding to conditions present in catalytic runs with sulfur. It was found that increasing sulfur concentrations lead to higher NMBB conversion. Furthermore, sulfur had a permanent influence on the reactor walls. It reacted with the transition metals in the steel to form a microscopic black iron sulfide layer on the surface, which could not be removed mechanically. Non catalytic runs after experiments with added sulfur yielded higher conversion than a normal run with a new reactor. This "wall effect" can be reduced by treating sulfided reactors with 6 N HCl for 5 min. and subsequent immersing into a base bath over night. However, repeated cleaning operations after sulfur runs leach out steel components in the reactors and shorten their life span considerably. The objective of the work on oxygen-compounds is to investigate the utility of highly dispersed catalysts, from organometallic precursors, in the removal of heteroatom functionality from the products of a reaction performed under liquifaction conditions. The bimetallic catalytic precursor CoMo-T2 exhibited a sizable increase in the yield of non0-containing products, compared to the run using a standard inorganic catalyst precursor (ATTM) or a non-catalytic reaction. For the runs of both dinaphthylether and xanthene, total conversions at 4OOOC in the presence of the bemetallic precursor, CoMo-T2, are much higher than those with standard monometallic precursor A'ITM. The lower reactivity of the model compounds dinapthyl ether @NE) and xanthene, relative to anthrone, under liquefaction conditions, assists to accentuate the superior bond cleavage capability of the bimetallic catalyst. The low yield of 0-containing products, without sacrificing high conversion, may indicate a selectivity toward preferential C-0 bond cleavage (i.e. removal of oxygen functionality). Catalvtic Hvdrocrackine of NMBB over Dispersed C-