Infrared Spectroscopic Study of the Influence of Oxygen in Coal on the Plastic Stage of the Coking Process

摘要

The method of sample preparation which yields a thin film, free from any support material, for the spectroscopic examination of coals, their oxidized and carbonized products, proved to be an improvement on the mineral-oil mull, the pressed alkali-halide disc and the multiple internal reflection techniques for semi-quantitative work, both in terms of ease of sample preparation and quality of spectra obtained. A lack of knowledge about the film thickness limited the method's use in quantitative work. Spectral investigations showed that when a coal is oxidized, the major changes in the coal structure involve a loss of aliphatic C-H linkages which is accompanied by an increase in hydroxyl and carboxyl groups. On further carbonization, the loss of aliphatic C-H bonds continues, but the hydroxyl and carboxyl groups start to be removed; the major changes occur during the period in which the coal is in the so-called fluid range. This behavior is consistent with hydroxyl groups introduced into coal with oxidation undergoing condensation reactions to produce ether linkages which can bridge coal lamellae, thus reducing their mobility with respect to each other. Unfortunately, however, a combination of factors (involving the nature of the coal structure), and also the basis of infrared spectrometry, preclude the detection of any resultant ether linkages by conventional infrared spectroscopic methods. (ERA citation 05:021570)