Comparative Study of Resins and Asphaltenes of Heavy Oils as Sources for Obtaining Pure Vanadyl Porphyrins by the Sulfocationite-Based Chromatographic Method

Abstract

The resins and asphaltenes of three heavy oils differing in origin (Permian and Carboniferous) and vanadium content (0.025–0.165 wt %) have been studied as sources for isolation of spectrally pure vanadyl porphyrins by sulfocationite-based chromatographic method developed by us recently. This method consists of removing the low polar nonporphyrin components from the resins or DMF extract of asphaltenes on SiO2-column followed by chromatographic isolation of vanadyl porphyrins on the sulfocationite. The asphaltenes were revealed to be a more promising source of vanadyl porphyrins because they possess ≥5 times higher content of vanadium, provide better accumulation of vanadyl porphyrins during deposition extraction by N,N-dimethylformamide, and are less contaminated by low polar nonporphyrin compounds capable of coeluting with vanadyl porphyrins through the sulfocationite column. According to matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, DPEP vanadyl porphyrins were found to be the most abundant type for all studied samples (34.1–54.5%). Rhodo vanadyl porphyrins belong to minor components (3.3–8.7% for each subtype) while Etio and Di-DPEP types take the intermediate position (9.8–28.7%). The resins and asphaltenes of the same oil showed significant difference in the group composition of purified vanadyl porphyrins. For the resins, a ∼1.3-fold decreased content of DPEP vanadyl porphyrins was found, which was compensated by a ∼1.5- and/or ∼1.8-fold increase in the content of Etio and Rhodo vanadyl porphyrins, respectively. However, this change in the composition of vanadyl porphyrins is not accompanied by a notable change of their average molecular weight despite the fact that increased concentration of more substituted (i.e., more hydrophobic) vanadyl porphyrins could be expected for less polar resins. This fact was interpreted in favor of association of vanadyl porphyrins with nonporphyrin components of the oil.

Complexes of Transition Metals with Petroleum Porphyrin Ligands: Preparation and Evaluation of Catalytic Ability

“…The identification of the synthesized metalloporphyrins by their UV-Vis spectra is possible for nickel porphyrins only, because they, along with vanadyl porphyrins, are the minor petroleum components and were already described in the literature. The absorption maxima in the UV-Vis spectra of the nickel petroporphyrins (λ max = 392, 512, 553 nm) synthesized in the present work coincide with the literature values within ±2 nm [17,20,21], which excludes any doubts as to the product composition. Complexes with such metals as Mn 2+ , Cu 2+ , and Zn 2+ were also identified among fossil porphyrins [22,23].…”

Quantifying Crude Oil Contamination in Sand and Soil by EPR Spectroscopy

“…While by no means all types of oil contain significant amounts of free radicals, most heavy oils have indeed been found to show an EPR signal [34]; see also [35][36][37][38][39] for more recent studies on oil composition. It is commonly assumed that radicals are located in the large polycyclic aromatic hydrocarbons (PAHs), predominantly in asphaltenes, but possibly also in resins [40]. By definition, asphaltenes and resins are characterized by their respective solubility in n-heptane (although other solvents are used in the literature), i.e.…”

Impact of Asphaltenes on the Adsorption Behavior of Petroleum Vanadyl Porphyrins: Kinetic and Thermodynamic Aspects

“…We showed in ref that purification effectiveness of the sulfocationite greatly depends on the degree of enrichment of the primary concentrate with VPs. The higher the VP content in the primary concentrate, the lower the consumption of the sulfocationite adsorbent and the higher the spectral purity of VPs yielded.…”

“…To date, column chromatography still remains to be the most powerful tool for petroporphyrin purification. Chromatographic purification is usually employed for either native asphaltenes , or their polar extracts. − This fact is caused by the accumulation of petroporphyrins in the asphaltene fraction during oil fractionation . Recovery of the polar extract of asphaltenes using acetone or N , N ′-dimethylformamide (DMF) provides an even larger accumulation of petroporphyrins before their chromatographic purification.…”

“…However, the abovementioned enriching approaches are insufficient to prepare pure petroporphyrins in one stage of chromatographic purification due to the extremely complex composition of polar petroleum fractions. This circumstance has forced researchers either to perform multistage chromatographic purification using conventional adsorbents such as silica gel or aluminum oxide or to develop alternative stationary phases exhibiting increased selectivity toward petroporphyrins. ,− …”