IR Spectroscopy of Sapropelic Coal

Abstract

The kerogen structure of sapropelic coal from various sources is studied by IR spectroscopy. Eight coal samples are chosen. The samples are prepared for analysis by crushing to particle size <0.2 mm and 6-h extraction by the Grefe method using a 1 : 1 alcohol–benzene mixture. High-ash samples are subsequently demineralized by means of concentrated hydrochloric and hydrofluoric acids. The coal spectra include characteristic absorption bands corresponding to aromatic structures with long alkyl chains. The aromatic index fa calculated from the IR data correlates almost linearly with the quality of the sapropelic coal—specifically, the yield of volatiles, the bound carbon, and the H/C atomic ratio.