The Determination of Hydroxyl Groups in Coal by Fourier Transform Infrared and 13C NMR Spectroscopy

Abstract

Fourier transform infrared spectroscopy and solid state 13C NMR spectroscopy have been used to measure the hydroxyl groups in coal. The methodology depends upon measuring the intensities of bands and resonances assigned to the products of acetylation reactions. In the infrared three separate bands, assigned to acetylated phenolic OH, alkyl OH, and NH groups, can be identified. In NMR, we used the methoxy carbon to determine the total OH. Spectroscopic measurements demonstrate that not only does the total OH content of coals but also the individual types of OH groups vary systematically as a function of rank. The proportion of phenolic to alkyl OH is approximately constant for the coals used in this study.