Characterization and comparison of vanadyl and nickel compounds in heavy crude petroleums and asphaltenes by reverse-phase and size-exclusion liquid chromatography/graphite furnace atomic absorption spectrometry

Development of a chromatographic methodology for the separation and quantification of V, Ni and S compounds in petroleum products

“…However, they can also be linked or trapped in other types of macromolecular networks [2]. Several groups have isolated [8][9][10] and determined the structure of free porphyrins from geological sources (e.g., crude oils, oils shales, and coal) [11][12][13][14][15]. Those porphyrins were free bases or metal complexes,particularly involving Ni and V as V=O.…”

“…Solubility parameters have been demonstrated to have great potential to characterizethe solubility and other properties of petroleum and fossil solids and liquids both experimentally and theoretically [16][17][18][19]. Several authors have reportedthat the metallocompounds of V and Ni become separated from each other during the process of isolation with pyridine/water extracts [8]. Therefore, examining these compounds without interference from each other has been impossible.…”

Molecular Characterization of Nickel and Vanadium Nonporphyrin Compounds Found in Heavy Crude Petroleums and Bitumens

“…The same spectral characteristics were observed in the Wilmington moderate polar fraction indicating vanadyl petroporphyrins. RS-UV-vis examination of these moderate polar fractions also indicated the presence of vanadyl pet.roporphyrins by the appearance of the distinctive 408 nm Soret band (1,2).…”

“…These pyridine/water extracts were separated by RP-HPLC into three fractions based on polarity, and the fractions were monitored by element specific detection (GFAA) and UV-vis spectroscopy (2). Most of the nickel-containing compounds eluted in the most polar fractions.…”

Characterization of asphaltenes from Cold Lake heavy oil: variations in chemical structure and composition with molecular size

“…Approximately 80% of all the petroporphyrins detected were contained in fraction 5. Other studies (3,11,12,38,39,48) using extracted petroporphyrin fractions have also reported that vanadium petroporphyrins occurred in a narrow, low molecular-weight band cor---responding to the 800 molecuar weight polystyr&e standard. The fact that low porphyrin concentrations were found in the high molecular-weight fractions suggests that porphyrins are not involved in geothermal chemical reactions such as polymerization or aromatization.…”