Structural analysis of quinoline and pyridine extracts of coals

Abstract

Various ranks of coals were extracted in an autoclave with quinoline at 350–380°C for 1–4 h. More than 50% of bituminous coals were dissolved, and almost 100% of Japanese bituminous coals in particular were dissolved. These quinoline extracts were further extracted by shaking with pyridine at room temperature for 8 h and the extraction yield attained a maximum of 85%. NMR spectra of these extracts were recorded using deuteroquinoline and deuteropyridine as solvent. The structural indices calculated from the observed spectra showed a good agreement between quinoline extracts and pyridine extracts, which indicates that the coal structure is almost homogeneous. The aromatic ring number in structural units varied from 1–2 in younger coals to 5 in coking coals. f a increased from 0.7 for younger coals to 0.9 for coking coals. The aliphatic carbon number per structural unit increased from younger to older coals, but foreign coals had smaller values than Japanese coals, which corresponds well with higher values of H/C in Japanese coals.