Thermal Decomposition of Coal-related Aromatic Compounds in Hydrogen-donating Solvent

In order to elucidate the reaction mechanism of coal dissolution in the hydrogen-donating solvent, twenty aromatic compounds related to coal were treated at 450 °C in the presence of tetralin. Diphenylmethane and bibenzyl slowly decomposed giving alkylbenzenes almost quantitatively. Diphenylmethanol and benzophenone were hydrogenated to diphenylmethane, and benzyl phenyl ketone to a mixture of diphenylmethane and bibenzyl. Diphenyl ether and dibenzofuran are very stable, di-2-naphthyl ether decomposing slowly and benzyl phenyl ether or dibenzyl ether very rapidly. The conversion of aromatic compounds by thermolysis can be correlated as a function of bond dissociation energy. The bond rupture of coal-related polynuclear aromatic compounds at 450 °C was concluded to occur mainly at methylene or ether structures. Addition of phenolic compounds or quinoline is very effective for the decomposition of di-2-naphthyl ether. The effect of phenolic compounds and quinoline on the thermal decomposition of aromatic ether was discussed on the basis of stabilization of transition state due to solvation.