Chromatographic Isolation of Petroleum Vanadyl Porphyrins Using Sulfocationites as Sorbents

A comparative analysis of the composition of vanadyl porphyrins isolated from heavy oil using two different sulfocationites has been carried out. As a source of vanadyl porphyrins, heavy oil of Volga-Ural basin characterized by a high vanadium content was used. The N,N-dimethylformamide extract of asphaltenes was derived from this oil and subjected for isolation of primary vanadyl porphyrin concentrate on a SiO2 column, which was then chromatographically purified with sulfocationite by our improved method. Strongly acidic cation-exchange resin and asphaltene sulfocationite recently developed in our laboratory were used as sulfocationites. According to ultraviolet visible spectroscopy, both sulfocationites showed excellent applicability for purification, providing isolation of a broad (>50%) fraction of vanadyl porphyrins with higher spectral purity compared to results of conventional methods. Results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis showed that composition of isolated vanadyl porphyrins depends upon the chemical nature of sulfocationite. Despite the same range of vanadyl porphyrin homologues (C-26-C-40, with maximum falling on C-32) isolated by both sulfocationites, purification with asphaltene.sulfocationite resulted in a 1.4-fold decrease in the content of the most abundant DPEP type of vanadyl porphyrins, with a corresponding 1.1-1.9-fold increase in the content of the rest of the types. It was also established that, when purification is accomplished, a significant part of the same vanadyl porphyrins still remains in the column, which can be explained by their associations with non-porphyrin components of the oil.