Catalytic hydrotreatment of heavy liquids prepared from coals of different rank

Heavy liquids prepared from a bituminous, a sub-bituminous and a brown coal were hydrotreated with commercial and titania-supported nickel-molybdenum catalysts to examine the reactivity and selectivity of the catalysis in relation to catalyst structure and catalytic functions. Liquids from the sub-bituminous and the brown coals behaved very similarly in the depolymerization scheme of conversion from preasphaltene to asphaltene, where the titania-supported catalysts exhibited preferential activity for the preasphaltene fraction with only limited conversion of the asphaltene fraction. The commercial catalyst showed no preferential selectivity in spite of the similar reaction scheme. Preasphaltene from the bituminous coal behaved in a contrasting manner on both catalysts, requiring the ring-opening reaction as deduced from the structural analyses in the same conversion without any preference for asphaltene. The effect of solvent composition was examined in some tests in order to improve conversion.