**4. Conclusion**

**Yield, %**

ing adsorbed on the silica gel.

Residue on a column

**VR A-1 A-2 AR-1 AR-2**

VR and A-1, the vanadium concentration is about five times higher than the nickel concentration. In this way, a potential share of nickel porphyrins for the selected HPRs can be about

During extraction, the most part of HPRs is transformed into an insoluble finely divided black product. As a result of sulfuric acid exposure, the composition is greatly altered primarily because of newly formed sulfonic and sulfoxide groups, which is represented by the absorption growth in the area of 1030 cm−1 and 1200–1400 cm−1 in IR bands as compared to initial objects. The yield of primary porphyrin extracts for the selected HPRs varies within 6.9–12.9% equivalent to the weight of the initial oil stock (**Table 5**). The maximum extract yield is found for AR-2 where the vanadium and nickel concentration are also maximal. For AR-1, rather high yield of the primary extract is also found; however, the vanadium and nickel concentrations are relatively low. Thus, the total concentration of vanadium and nickel in HPRs is no determinant for forecasting the yield of porphyrin extracts in case of sulfuric acid extraction.

Based on absorption spectra analysis in the visible band, there are metal-free porphyrins found in all obtained extracts with simultaneous dissipation of characteristic absorption bands of vanadyl and nickel porphyrins, which testify demetallization of metal porphyrins during extraction. To characterize porphyrins in obtained extracts, adsorption chromato-

The results of adsorption chromatographic separation of primary porphyrin extracts (**Table 5**) show that about 70–75% include various oil-like and resin-like fractions containing no porphyrins, with some part of them not eluted by the recommended solvent mixture and remain-

A comparative analysis of IR spectra allowed identifying that oil-like and resin-like fractions have the same structural and group composition as resins and oils obtained when analyzing the composition of initial HPRs. The results of chromatographic separation of primary extracts show that the share of porphyrin fractions is 13.0–24.2%. The absorption spectrum analysis

10–20% of the vanadium porphyrin concentration.

164 Phthalocyanines and Some Current Applications

9.7 10.3 11.2 11.8 11.4

Primary extract 7.6 6.8 8.5 11.7 13.1 Rhodo + DPEP 3.7 2.7 3.1 2.3 4.2 ETIO 5.9 6.9 5.6 2.7 7.1 ETIO + Phyllo 3.2 7.1 6.5 1.9 2.9 Phyllo 2.3 2.1 1.7 6.1 10.0 Oil-like 50.0 43.6 54.1 49.0 46.4 Resin-like 25.2 27.3 19.3 27.2 18.0

graphic separation was used with further analysis of electronic spectra.

**Table 5.** Yield of fractions after column chromatography of primary porphyrinic extracts.

It has been found that extraction of metal porphyrins by polar solvents from a solution of asphaltenes or heavy oil residues in aromatic solvents allows increasing the level of extraction of metal porphyrins into the extract due to the destruction of aggregates of metal porphyrins and asphaltenes as compared to the direct extraction of asphaltenes or residues. In asphaltene extraction by polar solvents, the DMF appeared to be the best extractant. In the DMF extract from asphaltenes of heavy petroleum with increased vanadium concentration, vanadyl asphaltenes of etio- and DPEP-types were primarily found. The maximum distribution of the molecular weight for both types is found in vanadyl porphyrin homotype C31 containing nine carbon atoms in alkyl substitutes.

Using sulfuric acid for porphyrin extraction allows producing highly concentrated extracts of demetalated porphyrins without the need for preliminary concentration. The analysis of porphyrin fractions obtained after chromatographic separation of the primary extract of asphaltenes shows predominantly etio- and phyllo-types of porphyrins and smaller concentrations of rhodo- and DPEP-types. Only etio- and phyllo-types of porphyrins were found in resin extracts. In asphaltene extraction, it was found that less than 75% of vanadium is extracted to the extract. In this way, some part of vanadyl porphyrins rigidly bound by a σ-linkage with polycondensed structures of asphaltenes is not extracted by using extraction methods which may be a restriction for petroleum demetallization processes. The concentration of porphyrins when switching from clean asphaltenes and resins to heavy residues is almost indiscernible, which allows proving the selectivity of the sulfuric acid extraction method. This is why the sedimentary extraction method can be used in analyzing oil objects in order to obtain additional information for the composition of metal porphyrins.
