EVIDENCE FOR CHARGE-TRANSFER COMPLEXES IN HIGH-VOLATILE BITUMINOUS COAL

Solvent-induced association of high-volatile bituminous coal and its extracts is observed on soaking in organic solvents and results in a decrease in pyridine extractability. Medium- and low-volatile bituminous coals dissociate with the same treatment. In the work reported here, the intermolecular interaction responsible for the solvent-induced association was investigated using solvent treatment and elemental and spectroscopic analysis. The results implied that interactions other than van der Waals' forces and hydrogen bonds cause this association. A charge-transfer interaction is consistent with all results obtained and is proposed to be a relatively strong secondary force in high-volatile bituminous coal and to bring about the observed solvent-induced association.