Characterization of pentane-solubles from low rank coal extract

Abstract

The structural characterization by FT-i.r. and 1H n.m.r. spectroscopy of the pentane-soluble fraction of a toluene extract from a Spanish low rank coal has been performed. The pentane-solubles have been fractionated on deactivated SiO 2 by sequential elution with hexane, benzene and tetrahydrofuran. The structural parameters calculated for these fractions indicate branched and cyclic alkanes on the aromatic units, and the number of aromatic rings and rings containing ring-joining methylene and heteroatoms appears to be between 1 and 5. Benzene and THF eluates showed the presence of hydroxyl and carbonyl groups. A comparison with the pentane-solubles from BF 3-phenol depolymerized lignite was made to evaluate the influence of this process on the nature of the soluble products. The pentane solubles of lignite extract have a more aliphatic and less polar character than the same fraction of chemically depolymerized lignite, which contains a maximum of four aliphatic carbon atoms in the average molecule of its benzene and tetrahydrofuran eluates.