Barbara Pilawa1, Andrzej B. Wieckowski2, Marek Lewandowski3
1 Department of Biochemistry and Biophysics, Faculty of Pharmacy, Silesian Medical Academy, Narcyzow 1, 41-200 Sosnowiec, Poland,
2 Institute of Physics, Faculty of Mathematics, Physics and Technology, Pedagogical University, pl. Slowianski 6, 65-069 Zielona Gora, Poland, and - Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17/19, 60-179 Poznan, Poland,
3 Institute of Coal Chemistry, Polish Academy of Sciences, Sowinskiego 5, 44-102 Gliwice, Poland
Evolution of paramagnetic centres of Polish medium-rank coal (85.6 wt% C), its macerals: exinite, vitrinite and inertinite, and petrographically complex samples during thermal decomposition at 300-650ºC was studied by electron paramagnetic resonance in the X-band (9.3 GHz). The total concentration of paramagnetic centres in the coal, exinite and vitrinite heated at 650ºC is higher than for the samples heated at 300ºC. The concentration decreases with temperature for inertinite. There exist four groups of paramagnetic centres with different linewidths of EPR signals in the coal. Two types of paramagnetic centres were detected in inertinite. Three component lines were observed in the EPR spectra of the other samples. The most active in the process of the thermal decomposition are paramagnetic centres with broad Gauss and Lorentz lines. Comparison of the changes in the paramagnetic centres system of the heated pure macerals and the complex coal samples indicates strong interactions between individual macerals during the thermal decomposition.