Estudo da fotodegradação de petróleo por ressonância paramagnética eletrônica

AUTOR(ES)

Marcos Cesar Ramoni

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

25/02/2007

RESUMO

Paramagnetic species have been found in the Brazilian Petroleum (BP) and Arabian Light (AL) by means of EPR, before and after irradiation. Two oil samples are of the AL petroleum, a crude oil called ‘Total Arabian’ (TA) and an other sample distilled at 260oC, called ‘Partial Arabian’ (PA). The BP was used in the crude form without treatment. Three oil samples were irradiated by polychromatic light in the UV-visible (Hg lamp) and monochromatic light at 632 nm (He-Ne laser). The EPR spectrum to each sample exhibits typical signal of free radical and VO2+. The spin hamiltonian parameters were determined to the paramagnetic species before and after irradiation. The signal of the free radical has g=2.0046 in the BP and g=2.0053 in the AL due to high percentage of aromatics in Brazilian oil. This aromaticity also explains the narrow linewidth of the free radical in the Brazilian oil. Otherwise, PA being much more viscous than the other two samples caused an increase in the radical linewidth by dipolar interaction. The g values suggest carbon and nitrogen in the radical. These same values indicate that the percentage of sulphur-containing radicals for the Arabian oil is higher than in the Brazilian oil. Irradiation in the UV-visible destroyed the aromatics; this increased the g value and the linewidth of the free radical signal in the Brazilian oil. Irradiation of the Arabian petroleum by laser at 632 nm caused modification in the molecular structure, reducing the g value. The signal of VO2+ showed ? g0=22.8, indicating vanadyl porphyrin in studied oils. When these petroleum were irradiated in the UV-visible arose values of ? g0=12.6, corresponding to the vanadyl non-porphyrin complexes containing sulphur ligand. When the oils were irradiated at 632 nm these values increased significantly (? g0=39.0) indicating the presence of vanadyl non-porphyrin containing oxygen ligand.

ASSUNTO(S)

espectroscopia de laser espectroscopia de infravermelho laser spectroscopy infrared spectrometry

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