Trends in the vanadium and nickel concentrations in asphaltenes of heavy oils from different oilfields, in which the total content of these metals vary from 0.0049 to 0.1795 wt %, have been studied....

Features of changes in the content of nickel and vanadium in heavy oils and their asphaltenes are shown for various fields of Volga-Ural region (Russia). The change in the content of vanadyl complexes in the studied asphaltenes upon increase of vanadium content was demonstrated. Several polar solvents (acetone, N,N-dimethylformamide, isopropanol, acetonitrile) are compared as extractants to obtain crude extracts of vanadyl porphyrins from asphaltenes with vanadium content of 0.44 wt%. The opportunity of more efficient extraction of vanadyl porphyrins from asphaltenes is shown by deposition extraction method, particularly when using N,N-dimethylformamide. Absorption spectra and matrix-assisted laser desorption/ionization (MALDI) mass spectra of the extracts obtained were analyzed. For extracts with maximum content of vanadyl porphyrins, the presence of mainly etio- and deoxophylloerythroetioporphyrins was revealed. It was shown that proportion of etio-type vanadyl porphyrins does not exceed 75% of the amount of porphyrins of DPEP-type. A maximum of molecular weight distribution in both types falls on a homologue of vanadyl porphyrin C₃₁ containing nine carbon atoms in the alkyl substituents.

The features of the distribution of vanadium and nickel between asphaltenes and resins have been revealed using heavy oils from Tatarstan and Samara oblast oilfields as an example. It has been shown that depending on the V and Ni content in asphaltenes and resins, heavy oils of different productive plays are divided into two separate groups. An increase in the V or Ni content of heavy oils is accompanied by an increase in the concentration of the respective metal in asphaltenes and resins. The intervals of variation in the V and Ni content of asphaltenes and resins of the oils attributed to each group have been determined. As the V concentration in asphaltenes increases, the V/Ni ratio also increases, a feature that is not characteristic of resins.

Chemical aging of BND 40/60 bitumen in the presence of an oxidation inhibitor under the conditions of heating in a thin film at 163°C for 5, 10, 15, and 20 h was studied. An increase in the asphaltene content, associated with the new formation of a colloid-unstable high-molecular-weight fraction A1 of increased aromaticity, was observed to a lesser extent than in the straight bitumen.