Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 6

A comprehensive study of the functional and group compositions of hexane-insoluble coal-tar pitch asphaltenes was carried out by chemical elemental analysis, nuclear magnetic resonance (NMR), infrared spectroscopy (IRS), and thermal analysis, and gas chromatography in combination with mass spectrometry. It was shown that the hydrocarbon skeleton of an average hypothetical asphaltene macromolecule can be considered as a set of condensed aromatic nuclei of the re-condensed type containing 7 rings, which have alkyl substituents and connecting bridges, consisting of 2 carbon atoms on average. Moreover, the structure contains one S, N, or O atom on average per 500, 50, or 167 carbon atoms, respectively, and one hydrogen atom per 2 carbon atoms. The ratio of various structural units in the powder of asphaltenes is as follows: there are 4-5 N- and 1.3-1.7 O-containing structures per one S-containing structure. Sulphur atoms are present in thiophene-like, thermally stable fragments of the structure, and pass into the coke residue without decomposition. Oxygen is in thermally unstable carboxyl and phenolic groups decomposing with the evolution of CO₂, as well as in aromatic esters passing into the coke residue. The data obtained using different methods are in good agreement with each other and will allow modeling the structural unit of coal tar-pitch asphaltene macromolecule.