Thermal extraction of bituminous coal with petroleum-derived solvents

A U.K. bituminous coal (84.1 wt.% C; 5.2 wt.% H; 7.2 wt.% O) has been coprocessed with a set of five petroleum residues of varied composition. The aim of the work was to test the feasibility of replacing a coal-derived solvent with a petroleum-derived solvent in the first, extraction, stage. The petroleum solvents used consisted of two atmospheric and three vacuum residues with widely varying structural properties. The optimum reaction conditions for the solubilization of coal with these residues was determined. The coal/petroleum interaction was enhanced by a high carbon aromaticity in the petroleum residue, but no simple correlations between the solvent structure and extraction efficiency have as yet been identified.