Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 6

Lately, side products of oil processing and coal liquefaction, i.e., asphaltenes, have been extensively investigated. The data regarding the macromolecular structure and morphological characteristics of asphaltene aggregates were mainly acquired in the area of petrochemical technologies. It is known that the concentration of asphaltenes in solution and the presence of additives of various chemical nature have an effect on the structure of asphaltene associates. The data about the formation of planar asphaltene associates and condensed graphite-like structures are of particular interest. In connection with the optimizing of conditions for anodic mass graphitization, coal tar pitch asphaltenes (β-fraction) were investigated. Coal tars with high contents of β-fraction proved themselves in the best way as efficient binders upon thermal treatment of the anodic mass. The present work investigated structural characteristics of macromolecules of medium-temperature coal tar pitch (CTP) using a set of physicochemical methods. The method of selectively soluble groups was used to isolate β-fraction asphaltenes; toluene and hexane were utilised as selective solvents. In order to form asphaltene films, a 0.01 % solution of asphaltenes in toluene was selected. It was demonstrated that structural fragments of CTP asphaltene molecules contained mainly condensed compounds with a number of rings of 3–7. These species contained C11 alkyl substituents and larger the content of which could not be practically determined. Therefore the structure of CTP asphaltene molecules could be described by the Speight model. The coke residue of CTP asphaltenes is characterised by the presence of crystallites from naphthenoaromatic layers. These structures are comprised of subunits of 7–8 layers, with a size of 20–25 Å, graphite-like; an interlayer distance of 3.42 Å.