Petroleum vanadium complex concentrations

Other metalloporphyrins can also be found in Nature, though they do not seem to perform any vital physiological function. For example, the copper(II) complex of uroporphyrin-III (Table 1) occurs in high concentrations in the wing feathers of Turacus indicus, and is the source of most commercial samples of uroporphyrin-III. Chlorophyll degradation products, as the nickel and vanadium complexes, are found in oil shales and as a troublesome contaminant in crude petroleum oils. 

Some of the metallic constituents were somewhat soluble in the propane-oil portion, but all tended to be concentrated in the asphaltic portion. Although vanadium (0.02% by weight in the original crude petroleum) was present in all fractions, the greater part was found in the cyclohexane and benzene fractions. From the similarity of the absorption spectra of the vanadium concentrates from petroleum and those of synthetic vanadium porphyrin complexes, Skinner arrived at the conclusion that vanadium compounds from the petroleum of the Santa Maria Valley Field in California exist as porphyrin complexes. Additional metallic constituents were detected by Skinner as these became concentrated in the various solvent fractions, including aluminum, titanium, calcium, and molybdenum. 

The first two of these compounds occur at sufficiently high concentrations in some crudes to enable production of them from petroleum. Benzonitrile has also been detected [6]. Much of the trace metal content of petroleums, in particular vanadium and nickel, is present in association with petroporphy-rins, which are polycyclic pyrroles closely related in structure to the hemes and chlorophylls. These materials are examples of the more complex nitrogen heterocycles to be found in petroleum. These particular heterocycles with their complexed metal atoms contribute much to our present knowledge of the original biogenesis of the petroleum hydrocarbons [6]. 

Vanadium has an abundance in Nature of about 0.02%. It is widely spread but there are few concentrated deposits. Important minerals are patronite (a complex sulfide), vanadinite [Pb5(V04)3Cl], and carnotite [K(U02)V04.> fH20]. The last of these is more important as a uranium ore, but the vanadium is usually recovered as well. Vanadium also occurs widely in certain petroleums, notably those from Venezuela, and it can be isolated from them as oxovanadium(iv) porphyrins.1 V2Os is recovered from flue dusts after combustion. 

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