Elvira G. Tazeeva

Features of the composition of vanadyl porphyrins in the crude extract of asphaltenes of heavy oil with high vanadium content

ABSTRACT 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.

Vanadium and paramagnetic vanadyl complexes content in asphaltenes of heavy oils of various productive sediments

ABSTRACT Using the atomic absorption spectrometry and electronic paramagnetic resonance techniques, we have investigated the features of vanadium and vanadyl complexes content in asphaltenes of heavy oils of Permian and Carboniferous productive sediments in the Volga-Ural oil and gas basin deposits. The investigation has been carried out using the heavy oils example, where the asphaltene content ranges from 5.1 to 21.2 wt%, and vanadium content varies in the range of 0.009–0.165 wt%. The specificity of asphaltene–vanadium relationship has been found for heavy oils of various productive sediments. It has been demonstrated that vanadium and vanadyl complexes content in asphaltenes of heavy oils in separate productive sediments varies in the certain range limits.

Structural-group composition and properties of heavy oil asphaltenes modified with sulfuric acid

ABSTRACT Details of the change of structural-group composition of heavy oil asphaltenes modified with sulfuric acid and oleum depending on the process conditions have been determined. The effect of the amount and concentration of sulfuric acid, exposure time, and elevated pressure has been evaluated. The formation of sulfo-, sulfono-, phenolic hydroxyl, carboxylic, and carbonyl functional groups has been detected in Fourier transform infrared (FTIR) spectra for the obtained sulfonated asphaltenes. Spectral coefficients have been calculated for asphaltenes and products of their sulfonation according to the main absorption bands in FT-IR spectra. Analysis of spectral coefficients has indicated the relationship of the fraction of newly formed functional groups in sulfonated asphaltenes and process conditions of sulfuric acid modification. The obtained sulfonated asphaltenes have been analyzed as sulfocationites with the evaluation of sorption capacity. It has been shown that the successive modification of heavy oil asphaltenes with sulfuric acid and oleum gives sulfocationite with the static exchange capacity of 3.39 meq/g. The relationship of spectral coefficients and sorption characteristics of sulfonated asphaltenes has been determined.

Thermal stability and sorption properties of asphaltene sulfocathionites

Abstract Using simultaneous thermogravimetry and differential scanning calorimetry, thermal stability and possible phase transitions of asphaltene sulfocationites and native asphaltenes have been evaluated; the kinetic characteristics of heating have been determined, namely, onset temperature of decomposition, stages of decomposition, and temperature ranges of stability. It has been determined that asphaltene sulfocationites retain structural-group features (IR spectroscopy method) and sorption characteristics while heating up to 350 °C.

Relationship of Light Absorption and Vanadium Content in Asphaltenes and Resins of Heavy Oils

Abstract The relationship of the light absorption of asphaltenes and resins with vanadium content has been investigated on the example of heavy oils of various deposits. In the oils of various deposits in Permian and Carboniferous producing complexes of Volga–Ural oil-and-gas bearing basin, the asphaltene content varies from 5.3 to 21.2 wt %, while the vanadium content is from 0.009 to 0.165 wt %. It has been shown that there is a direct correlation of the light absorption of asphaltenes and vanadium content with the correlation coefficient of higher than 0.96 in the case of each producing complex. There is also a direct relationship between the light absorption of resins and vanadium content in the HOs under study with the correlation coefficient of higher than 0.92 in the case of each producing complex.

Distribution of vanadium and vanadyl porphyrins during fractionation of resins of heavy sulfurous oils

ABSTRACT Features of the content and distribution of vanadium and vanadyl porphyrins in the fractions of resins, which were obtained by separation using column chromatography on silica, have been studied on heavy sulfurous oils of various deposits of the Volga–Ural basin (Russia). The difference of the vanadium and vanadyl porphyrin contents in the fractions of oils of various production complexes has been shown. Features of structural–group composition and predominant types of vanadyl porphyrins in the fractions of resins have been determined.