Investigation of the Nature of Free Radicals in Petroleum Asphaltenes and Related Substances by Electron Spin Resonance.

Electron Paramagnetic Resonance Study of Thermal Alteration of Kerogen in Deep-Sea Sediments by Still Intrusion

“…The narrowing of line widths and the decrease of g value as the sample locations approach the heat pocket caused by the sill are consistent with the results of earlier studies on kerogen in natural environments (Hwang and Pusey, 1973), asphaltene (Yen et al, 1962), and coal (Austen et al, 1965). The unusual broading of EPR spectral lines similar to that seen in the sample about 250 cm above the sill was reported by Baker (1975), but the obliteration of EPR spectra as observed in the samples immediately above and below the sill has not been previously reported.…”

“…The unusual broading of EPR spectral lines similar to that seen in the sample about 250 cm above the sill was reported by Baker (1975), but the obliteration of EPR spectra as observed in the samples immediately above and below the sill has not been previously reported. The study of petroleum asphaltene by Yen et al (1962) shows that heating up to 460°C only causes narrowing of line widths and increases rather than decreases spin concentrations. Total elimination of free radicals did not occur in coal maceral up to 750°C (Austen et al, 1965).…”

Electron spin resonance of sedimentary humic acids in relation to their aromatic character

“…However, the possibility that metal-organic com plexes give rise to the ESR signal seems very remote in the samples because two of them have actually no ash ( YEN et al (1962) at tributed the origin of the paramagnetism of petroleum asphaltenes to broken carbon bonds or imperfections in the aromatic network. On the basis of the above consideration, it seems likely that the free radicals in sedimentary humic acids are (1) semiquinone radicals in a condensed ring system or (2) radicals of carbon and nitrogen in the molecule.…”

Crude Oil by EPR

“…These are overlapped in the same magnetic field range (Fig. 5a), being the very intense central line associated with organic free radical Yen et al, 1962) (Fig. 5b).…”

“…The g-factor determined for the free radical signal in Arabian and Colombian petroleum was 2.0033±0.0001 and 2.0030±0.0001, respectively. One possible interpretation for the g-factor values observed corresponds to neutral radicals of carbon or nitrogen (Yen et al, 1962). Thus, Arabian crude oil should have a lower percentage of aromatic carbon than Colombian crude oil, in which the percentage of heteroatoms should be higher.…”