Several Canadian coals were analysed by FT-i.r. The technique is applicable to both the organic and inorganic part of the coal. The method by which the spectra can be subtracted one from the other, allows the distinguishing of one coal from another by characteristic functional groups. The high resolution of the resultant spectra clearly differentiate between the substance extracted by solvents, the unextracted coal material and the original coal itself. The technique has been used to show that the quinoline extract of bituminous coal contains an adduct in which some quinoline is chemically bound to the extracted coal substance. This adduct cannot be removed by washing the extract with HCl at a pH of 2.
(Keywords: lT4.r.; coal; extracts of coal)
The infrared spectrum has been used to characterize the functional groups in a particular substance. For coal it was first used by Cannon and Sutherland'. As molecules increase in complexity, or when a mixture of different substances is present, it becomes more difficult to interpret the spectrum because of the partial or even complete overlapping of characteristic bands. Nevertheless, the identification of certain strong bands, that correspond to definite atomic groupings, is nearly always possible. It is difficult to arrive at conclusions about the precise nature of the structural formula, however, some of these uncertainties can be resolved with the resolution of the spectra and an increase in the signal intensity.
The main benefits of FT-i.r. are in the areas of sensitivity, superior signal/noise ratio, high speed of operation, energy throughput, long term precision and the availability of powerful data manipulation facilities. Due to these advantages, FT-i.r. has found increasing use in coal research. The technique has been used for elucidation of coal structure2-4 and for the structural variations brought about by the oxidation of coa15g6 or the carbonization of solvent refined coal'.
This paper reports the use of FT-i.r. for characterization. A range of Canadian coals was studied. FT-i.r. spectroscopy was used to differentiate one coal from another and to distinguish between concentrations of the functional groups.
EXPERIMENTAL
Coals
Three Canadian coals and one American coal were used in the study. The detailed ultimate and proximate analysis of these coals is given in