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Title of article :
Photochemical weathering study of Brazilian petroleum by EPR spectroscopy
Author/Authors :
Carmen Lu?sa Barbosa Guedes، نويسنده , , Eduardo Di Mauro، نويسنده , , Valdemir Antunes، نويسنده , , Antonio Salvio Mangrich، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2003
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Abstract :
The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals characteristic of free radical, vanadyl (VO2+) and iron III ion (Fe3+). The value of g=2.0045±0.0001 corresponds to free radical species with a peak-to-peak line width ΔH=4.64±0.03 G. The g spectroscopic factor suggests the presence of free radicals in aromatic systems containing carbon, nitrogen and oxygen. Δgo (chemical shift)=21.6±0.1 determined for the VO2+ species characterizes porphyrin and non-porphyrin (with sulfur) complexes in asphaltenes of the crude oil. The species observed with g=2.16±0.01 corresponds to Fe3+ in Fe2O3, and therefore is not part of the molecular structure of the oil under study. The photochemical weathering of Brazilian oil as a film over seawater was monitored by EPR. After 100 h of solar irradiation the line width of the radical decreased by 10.6%, indicating rearrangement among radicals. The Δgo value for VO2+ in the irradiated oil decreased to 19.5±0.1, characterizing degradation of porphyrin systems. Solar irradiation promotes the partial destruction of the asphaltenic fraction of the oil.
Keywords :
EPR , free radicals , Asphaltenes , Photodegradation , Petroleum , Vanadyl
Journal title :
Marine Chemistry
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Link To Document :