Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 3

The composition and structure of nitrogenous bases of the resins of bituminous oil from the Ashalchinskoye deposit of Tatarstan are investigated using a complex of analytical methods including elemental and functional analyses, determination of molecular masses, 1H NMR spectroscopy, structural group analysis, gas chromatography, and mass spectrometry. The nitrogen bases of the resins in oil are analysed before and after their thermal treatment at 450 °C for 30 min in the inert medium. It is established that the nitrogenous bases of the initial resins and "secondary" maltenes are represented by high and low molecular weight compounds. High molecular weight bases prevail in both cases, though their proportion in "secondary" maltenes is much lower. Thermally transformed bases are characterised by lower average molecular weights. This is due to the destruction of alkyl and naphthenic moieties proceeding in the course of thermolysis and resulting in the changes in their structure and the formation of lower molecular weight compounds. As revealed by means of structural group analysis, the mean molecules of a significant part of high molecular weight bases of the "secondary" maltenes are more aromatic due to a decrease in the number of naphthenic cycles and in the number of paraffin carbon atoms in their structural blocks. Low molecular weight bases differ from those of the initial resins in a higher number of naphthenic cycles in the structural blocks of their mean molecules. Alkyl-substituted quinolines and benzoquinolines, naphthoquinolines, naphtho[2,1,8-def]quinolines, thiophenoquinolines, and benzothiophenoquinolines have been identified among the major compounds of initial resins and "secondary" maltenes. The maximum in their distribution falls on alkylbenzoquinolines. The bases of "secondary" maltenes are characterized by a higher relative content of alkylquinolines and alkylthiophenoquinolines. A distinctive feature of the bases of "secondary" maltenes is also an increased proportion of structures with a lower number of carbon atoms in alkyl substituents.