A Comparative Analysis of the Solubility of Asphaltene Fractions with Addition of Petroleum Vanadyl Porphyrins

High-vanadium heavy oil asphaltenes were fractionated by a sequential precipitation method. Using FT-IR spectroscopy, elemental analysis, and optical spectroscopy, the differences in the compositions of the asphaltene fractions were thoroughly investigated. To isolate and purify vanadyl porphyrins (VPs) from the asphaltenes, extraction with N , N -dimethylformamide (DMF) followed by two-step column chromatography on silica gel and sulfocationite was employed. The effects of VPs on the solubility of the asphaltene fractions were evaluated based on optical density variations in the solvent/precipitant system in a kinetic mode. It was found that, in most cases, adding petroleum VPs to toluene solutions of asphaltene fractions decreases the solubility of these fractions. The highest effect of VPs on the solubility of the asphaltene fractions was observed for samples with a high concentration of polar heteroatom groups and low aromaticity.