Authors: Z.R. Ismagilov, N.S. Zakharov, S.A. Sozinov

Title of the article: Electron paramagnetic resonance study of coal tar and coal pitch by line shape analysis

Year: 2022, Issue: 6, Pages: 67-74

Branch of knowledge: 2.6.12. Chemical technology of fuel and high-energy substances

Index UDK: 547.024, 543.429.22.

DOI: 10.26730/1999-4125-2022-6-67-74

Abstract: In this work, the method of electron paramagnetic resonance (EPR) was used to study the radical structure in the series: coal tar, coal tar pitch, α-fraction of coal tar pitch. It was shown that in the presented series there is an increase in the concentration of paramagnetic centers, which is associated with the elimination (breaking of bonds by the homolytic mechanism) of hydrogen atoms and aliphatic fragments from conjugated aromatic systems as a result of fractionation. In this case, the linewidths of the EPR spectra of coal tar and coal tar pitch practically coincide (~2.4±0.1 G) and differ significantly from the linewidth of the α-fraction of coal tar pitch (5.5 G), which is associated with a significant proportion of dipole–dipole interactions between radicals in the sample. The obtained experimental EPR spectra were simulated using the program for simulating EPR spectra EasySpin in Matlab. The experimentally obtained spectral lines are satisfactorily described in the simulator using the Lorentz and Gaussian functions with several spin packets. The conducted studies have shown that, unlike coal tar pitch, the pitch and α-fraction contain radicals bound by dipole-dipole interaction. At the same time, in coal tar pitch, the main type of such bound radicals are radicals of an aliphatic nature, and in its α-fraction, aromatic. It has also been shown that the α-fraction of coal tar pitch contains a smaller amount of aliphatic radicals.

Key words: coal tar pitch α-fraction electron spin resonance line shape analysis EasySpin radicals

Receiving date: 25.11.2022

Approval date: 16.12.2022

Publication date: 27.12.2022

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