Application of electron spin resonance and electronic spectroscopy to the characterization of vanadium species in petroleum fractions

Dickson, Frank E.; Petrakis, L.

doi:10.1021/ac60344a049

Cited by 37 publications

(22 citation statements)

References 5 publications

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“…EPR spectra of asphaltenes show the signals of paramagnetic VO 2+ cations in porphyrin or non-porphyrin structures [21][22][23][24][25] and of organic free radicals, which are the focus of interest in the present study. Owing to the lack of hyperfine structure the only structural parameters are g-factors, lineshapes and linewidths.…”

Section: Electron Paramagnetic Resonance Spectroscopymentioning

confidence: 99%

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

et al. 1998

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The paramagnetic species nature of different geological o¡ asphaltenes are discussed on the basis of Electron Paramagnetic Resonance (EPR) results. Free organic radicals are present in petroleum asphaltenes but their molecular nature is poorly known owing to the multiplicity of their molecular structures which causes the appearance of a single unresolved EPR signal with a linewidth of 4-6 Gauss. In spite of the poorly resolved signals the microwave power dependence of EPR line intensities gives some insights into the nature of the aromatic rings condensation. More aromatic asphaltenes show higher saturation power of the EPR lines: this fact has been explained by a spin exchange mechanism between n-n electronic clouds of adjacent molecules, supported also by some XRD evidences. Moreover, asphaltenes in argon (not paramagnetic gas) show a maximum intensity at much lower microwave power than in oxygen atmosphere (paramagnetic gas); besides, the differences in the saturation behavior for the different asphaltenes are much more evident in oxygen atmosphere. This phenomenon is suggested to be a consequence of a weak spatial complex between aromatic moieties and oxygen molecules that deeply contribute to the relaxation pathway. Synchronous fluorescence spectroscopy confirms the difference in the size of aromatic cores in asphaltenes molecules as supposed on the basis of the saturation mechanism of EPR line intensities.

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Section: Electron Paramagnetic Resonance Spectroscopymentioning

confidence: 99%

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

et al. 1998

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“…The experimental parameter used in this identification is ∆ (chemical shift), which expresses chemical changes. This is calculated from the spectroscopic factors Dickson & Petrakis, 1974). The different values obtained experimentally for the ∆ parameter represent structural differences in the distribution of the ligands around the VO 2+ in complexes.…”

Section: Crude Oil By Eprmentioning

confidence: 99%

“…The chemical shift obtained for Brazilian oil was ∆g 0 = 21.6, indicating that this oil contains vanadyl in the porphyrin and non-porphyrin structures. Based on literature data (Dickson & Petrakis, 1974), it is possible to suggest that vanadyl in Brazilian oil has VO(N4), VO(NS3), VO(N2S2) and VO(N3S2) as possible environments.…”

Section: Specimen G-factormentioning

confidence: 99%

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Crude Oil by EPR

Piccinato¹,

Guedes²,

Mauro³

2012

Crude Oil Emulsions- Composition Stability and Characterization

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“…The other coordination :site on the calcium is taken with a TEA fragment (this adds m/z of 189 to the free acid parent fragment). -[NiTEAr (7) m/ z 2Q.6 -(caTEAj+…”

Section: Positive Ion Fast Atom Bombardment (Fab+} Alass Spectroscopimentioning

confidence: 99%

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

Fish

Reynolds

Gallegos

1987

ACS Symposium Series

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Application of electron spin resonance and electronic spectroscopy to the characterization of vanadium species in petroleum fractions

Cited by 37 publications

References 5 publications

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

Crude Oil by EPR

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

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