Vanadium petroporphyrins

Magnetic susceptibility measurement on a Boscan (SR) vanadium petroporphyrin extract indicates Curie-Weiss dependence. V-V interaction or... 

Mogollon, L. Rodriguez, R. Larrota, W., et al., Biocatalytic removal of nickel and vanadium from petroporphyrins and asphaltenes. Appl Biochem Biotechnol, 1998. 70-72 pp. 765-777. 

Rosscup, R. J. and Bowman, J., 1967, Thermal Stabilities of Vanadium and Petroporphyrins Preprints of the Division of Petroleum Chemistry, American Chemical Society, Vol. 12, 77 pp. 

The organic materials extracted from a number of domestic tar sands contain various amounts of vanadium and nickel, sometimes in substantial quantities. Metalloporphyrin complexes of these two metals have been detected in some outcrop and shallow core samples. If these porphyrins are indigenous petroporphyrins, it is evident that these compounds can survive weathering processes. 

Comparison of the uv-visible absorption spectra of these fractions (Figure 2) with the spectra of known vanadium chlorin, phylloerythrin and DPEP complexes (7) suggested that two (samples 422 and 4422) with absorption maxima at 600 nm were probably vanadium phylloerythrin complexes. These two fractions do not appear to be identical to the rhodo-type petroporphyrins with an absorption maximum at 590 nm isolated by Millson et. al. (8) and discussed in detail by Baker et. al. (9) because of the significant difference in the absorption spectra. One fraction (sample 630) may be a vanadium chlorin derivative, while the absorption spectra of the remaining four fractions (samples 3, 61, 421 and 441) were typical vanadium porphyrin spectra with maxima at 412, 538 and 575 nm. For these samples the ratios of the intensities of the 575 and 538 nm bands were in the range 1.15-1.20 which are consistent with the ratios... 

In these petroporphyrins he identified vanadium as well as iron. He established the well-known chemical association between chlorophyll in marine plants and the process of petroleum formation. It was not until 1948 that the second major metallic components in nickel were established. In the intervening years, a number of investigators have found that petroporphyrins are concentrated in the gas oil, resin and asphaltene fractions. " Baker, et at. determined the yields of petroporphyrins from a number of asphaltenes of native crudes and other bituminous materials. Data of ten sources of crude oil as well as tar sands, oil shale and gilsonite are listed in Table 1.3. 

The greater lability toward vanadium removal and porphyrin destruction for the vanadyl petroporphyrins over the synthetic vanadyl porphyrins is a fortunate circumstance. This difference can be rationalized based upon structural differences of the porphyrins involved. Phyllo-type petroporphyrins all contain a cyclopentane ring, fused to one of the pyrrole rings with the methine carbon one of the units of the carbo-cyclic structure. Etio- and rhodo-type petroporphyrins appear to have alkyl substitution at one or more methine positions, as based upon nmr spectral data. Should all petroporphyrins have a carbon substituent on one or more methine carbons, the carbonium ion formed by the reaction would tend to have more charge localization on those methine carbons. These ions are a more stable species by an order of magnitude over those porphyrins without methine substitution. 

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