Role of Vanadylporphyrins in the Flocculation and Sedimentation of Asphaltenes of Heavy Oils with High Vanadium Content

Abstract

Extraction by N,N-dimethylformamide with further column chromatography allowed obtaining concentrate of vanadylporphyrins from asphaltenes of heavy sulfurous oils with high vanadium content. The prevailing types of vanadylporphyrins, their ratio, and molecular mass distribution were determined. The influence of obtained vanadylporphyrin concentrates on the stability of asphaltenes in the system “solvent/precipitator” was investigated. Kinetic studies using UV–vis spectroscopy have revealed that an increase in the content of vanadylporphyrins in asphaltenes leads to acceleration of their deposition from solution and destabilization of colloidal systems.

Redox activity of nickel and vanadium porphyrins: a possible mechanism behind petroleum genesis and maturation?

“…16 There is a recent growing consensus on the fact that vanadium and nickel porphyrins are essentially detected with asphaltene aggregates, which may also be linked to the increase in the viscosity of the crude and gives rise to aggregation phenomena, even if this behavior is not yet fully dened. 17 This preferential positioning of the porphyrins of nickel and vanadium does not seem to be intuitive, which suggests that privileged physicochemical interactions exist.…”

High-Field (3.4 T) ENDOR Investigation of Asphaltenes in Native Oil and Vanadyl Complexes by Asphaltene Adsorption on Alumina Surface

“…While the EPR spectra either in X-or W-band do not reveal the changes caused by adsorption of oil asphaltenes on the surface of γ-alumina, a perceptible difference in 1 H ENDOR spectra and appearance of 27 Al ENDOR spectra are obtained. High-frequency EPR/ENDOR allows resolving the anisotropy of the magnetic properties of stable vanadyl complexes being a part of asphaltenes and, therefore, is orientationselective for the space structure of VP complexes.…”

“…For the adsorbed samples, we also have observed 27 Al Mims ENDOR spectra. Figure 9 shows for the Q10 sample at T = 10 K at the magnetic field B 1 which corresponds to the maximal ESE signal (see Figure 4) to enhance the signal-to-noise ratio.…”

“…It also gives a key why the observed by 1 H ENDOR changes are practically not revealed by EPR-the changes are minimal and are hidden under the broadening of the EPR lines either in X-or W-band ranges. We did not manage to obtain 27 Al Mims ENDOR for B 0 = B 2 . It might be connected with just the lower signal-tonoise ratio in the EPR spectrum compared to B 1 (Figures 4 and 5), and therefore, no deep conclusions from that fact are done in this work.…”

“…It is common knowledge that intermolecular interactions, such as hydrogen bonding, dipole−dipole interactions, and π − π stacking, in asphaltenes lead to aggregation into nanoaggregates in the bulk oil phase and the formation of elastic films at organic−aqueous interfaces although the basic asphaltene structure and mechanism of aggregation continue to be debated [2,17,25]. The relationship between petroporphyrins and asphaltenes is largely unexplored [1,4,[26][27][28].…”