Effect of preheating on chemical structure and infrared spectra of Yanzhou coal

The results of thermosolvolysis experiments performed on a high volatile bituminous coal from Yanzhou, China are described. The coal was preheated in a vacuum at temperatures between 250 and 400 °C, after which the soluble materials were extracted with chloroform, l.r. spectra of the preheated coal, the chloroform extract, and the residue after extraction were measured and compared. The extraction yield passed through a maximum for a preheating temperature near the plastic softening point of the coal. As the preheating temperature was increased, the aromaticity of the coal and its residue after extraction increased markedly. The aromaticity of the extract appeared to increase slightly and the methylene-methyl ratio of the extract dropped significantly near the softening temperature. The ester content of the extract was reduced to almost zero on preheating the coal, presumably because of decarboxylation during preheating.