MASS-SPECTROMETRIC AND CHEMOMETRIC STUDIES OF THERMOPLASTIC PROPERTIES OF COALS .3. OPTICAL ANISOTROPY AND ISOTROPY OF CARBONIZED COALS

The aim of the study was to find coal pyrolysates that contribute to the formation of the optically anisotropic phase during carbonization and those which form isotropic char. Twenty-seven coals (the same as already studied in parts 1 and 2) were analyzed. Two sets of data were obtained for each coal: (i) pyrolysis-field ionization mass spectra of vacuum pyrolysates formed on heating coals to 600 degrees C at 10(-4) Pa and (ii) the content of optically anisotropic phase in a coal sample carbonized to 600 degrees C under atmospheric pressure. Correlation analysis was applied to evaluate the quantitative links between the two sets of data. Additionally, the previously obtained set of Gieseler thermoplastic properties of the coals were included in this evaluation. The analysis resulted in the selection of two groups (An and Is) of vacuum pyrolysates. Group An consists of aromatic and partially hydrogenated aromatic hydrocarbons; the higher their content in coals the higher is the content of anisotropic phase on carbonization. Group Is consists of oxygen and nitrogen compounds as well as some aromatic hydrocarbons. The higher its content, the higher is the content of isotropic char in the carbonized coals. Significant correlations also exist between anisotropy content and the Gieseler temperatures of maximum fluidity and resolidification. It has been concluded that group An pyrolysates are inert in intermolecular condensation and are fusible and capable of forming liquid droplets in a wide temperature range in contrast to the group Is pyrolysates which undergo polymerization and condensation at temperatures corresponding to the temperatures of their generation. The direct link between capabilities of coals to develop thermoplasticity and to form anisotropic phase lies in the fact that the two phenomena are generated by the same species.