INVESTIGATION OF THE CARBON STRUCTURE OF COAL THERMAL SOLVOLYSIS PRODUCTS BY RAMAN SPECTROSCOPY

DOI: 10.6060/ivkkt.20256811.7219

This work is devoted to the study by Raman spectroscopy of the features of the structural organization of molecular fragments in products of thermal solvolysis of coal in hydrocarbon solvents. The samples were obtained by dissolving GZhR grade coal in an environment of high-boiling fractions of hydrocarbon residues from coal and oil refining at a moderate temperature of 380 °C, without the use of hydrogen and catalysts. The solvent series included coal tar of high-temperature coking of coal, anthracene fraction of coal tar, heavy gas oil of catalytic cracking of petroleum raw materials and a mixture of coal tar with heavy gas oil of catalytic cracking. Pitch sampels were obtained by vacuum distillation of distillate fractions from the products of thermal dissolution. The macromolecular carbon structure of the thermal dissolution products and pitch samples was characterized by Raman spectroscopy. The calculation and analysis of the main numerical characteristics of the structure of the obtained products are performed: the degree of graphitization, the measure of sample disorder, and the size of crystallites in the basic plane of carbon atoms. It has been established that the obtained samples represent a complex carbon matrix with graphite-like fragments included in its composition. Products obtained in a solvent environment of coal origin are characterized by an increased proportion of ordered graphite structures compared to products obtained in an petroleum solvent. For pitch products, there was an increase in the degree of graphitization compared with thermal dissolution products, while the indicator characterizing the measure of disorder decreased, which allowed us to conclude that more ordered graphite structures were formed in pitch products. A correlation has been established between the indicators of the ordering of structured carbon fragments according to Raman spectroscopy data and the characteristics of the molecular structure of products obtained by FTIR-spectroscopy. Products characterized by higher aromaticity and a lower degree of substitution of aromatic rings according to FTIR data show a higgher degree of graphitization and a lower degree of disorder according to Raman spectroscopy.