| High conversions of subbituminous coal to liquid or soluble products were obtained by treatment with large amounts of zinc chloride together with tetralin at temperatures below those of coal pyrolysis. Treatments were carried out in a stirred batch reactor at 250 to 325(DEGREES)C for durations of 10 to 120 min with hydrogen at 3.5 MPa total pressure. The extent of conversion was determined by solvent extractions with cyclohexane, toluene, and pyridine, and products were characterized by elemental analysis, gel permeation chromatography, proton nuclear magnetic resonance, and oxygen functional group analysis. The conversions to soluble products reached 50% solubility in cyclohexane and 85% in pyridine for treatment at 300(DEGREES)C. This conversion increased with increasing temperature and duration of treatment, and was accompanied by progressive reductions in molecular weight as well as by elimination of oxygen (especially ether oxygen) in coal. This behavior, along with the increase in product aromaticity with increasing conversion, indicates a mechanism involving ZnCl(,2)-catalyzed cleavage of crosslinking bonds in the coal. Recombination of the resulting reactive species is prevented by ZnCl(,2)-catalyzed transfer of hydrogen from the tetralin, coal products, and reactor atmosphere, and by alkylation of the tetralin. |
