Analysis of aromatic fractions of low-temperature coal tars with the use of synchronous luminescence technique

The qualitative analysis by synchronous luminescence technique was performed on aromatic fractions of primary tars obtained from humic and sapropelic coals (from Upper Silesia Basin). The synchronous luminescence technique, called also the technique of spectral fractionation, consists in the record of a spectrum at the constant difference between the positions of emission and excitation monochromators (Dl). This difference is calculated as a result of subtraction of effective emission and excitation wavelengths characterising compounds identified in investigated mixture. In relation with conventional luminescence technique, giving broad, low resolved bands in the conditions of ambient temperature, the synchronous luminescence technique enables to obtain well resolved and simplified spectra that facilitate the identification of individual components of the mixture. The application of this technique to analysis of aromatic fractions composition of primary tars from coals of various genesis and technological properties (sapropelic and humic coals) has shown a general similarity of composition with predomination of aromatic compounds containing 2-4 condensed rings. In the sample derived from sapropelic coal, a markedly higher intensity of bands is observed, attributed to aromatics of lower condensation degree (2-3 condensed rings), in relation with the bands of aromatics with higher intensity (3-4 condensed rings). The reverse relation is observed for sample from humic coal. In both analysed samples, a series of the following individual compounds has been identified from groups of aromatics: naphthalenes, acenaphthenes, benzofluorenes, anthracenes, pyrenes, and benz(a)anthracenes. Smaller amounts of benz(a)pyrenes, benz(ghi)perylene, and 3, 4-9, 10-dibenzopyrene were also encountered. The technique of synchronous luminescence made possible, therefore, the identification of individual components of complex mixture of aromatic compounds in coal derived products. This technique is thus of great value for the characteristics of aromatic compounds in thermolysis products of coal, in the cognitive aspect, as well as in monitoring of environment.