Peer-Reviewed Journal Details
Mandatory Fields
Ryder, A.G.
2004
May
Applied Spectroscopy
Time-resolved fluorescence spectroscopic study of crude petroleum oils: Influence of chemical composition
Published
()
Optional Fields
fluorescence lifetime petroleum oils APT gravity alkane aromatic asphaltene sulfur polar HYDROCARBON FLUID INCLUSIONS LASER FLUOROSENSOR LIFETIME DECAY SYSTEM
58
613
623
The fluorescence of crude petroleum oils is sensitive to changes in chemical composition and many different fluorescence methods have been used to characterize crude oils. The use of fluorescence lifetimes to quantitatively characterize oil composition has practical advantages over steady-state measurements, but there have been comparatively few studies in which the lifetime behavior is correlated with gross chemical compositional data. In this study, the fluorescence lifetimes for a series of 23 crude petroleum oils with American Petroleum Institute (API) gravities of between 10 and 50 were measured at several emission wavelengths (450-785 nm) using a 380 nm light emitting diode (LED) excitation source. It was found that the intensity average fluorescence lifetime (tau) at any emission wavelength does not correlate well with either API gravity or aromatic concentration. However, it was found that tau is strongly negatively correlated with both the polar and sulfur concentrations and positively correlated with the corrected alkane concentration. This indicates that the fluorescence behavior of crude petroleum oils is governed primarily by the concentration of quenching species. All the strong lifetime-concentration correlations are nonlinear and show a high degree of scatter, especially for medium to light oils with APT gravities of between 25 and 40. The degree of scatter is greatest for oils where the concentrations (wt %) of the polar fraction is similar to10 +/- 4%, the asphaltene component is similar to1 +/- 0.5%, and sulfur is 0.5 +/- 0.4%. This large degree of scatter precludes the use of average fluorescence lifetime data obtained with 380 nm excitation for the accurate prediction of the common chemical compositional parameters of crude petroleum oils.
Grant Details
This work was assisted by an Enterprise Ireland Research Innovation Fund Grant (IF/2001/061), a Millennium Research Grant from the National University of Ireland–Galway, and by the National Centre for Biomedical Engineering Science as part of Higher Education Authority’s Programme for Research in Third Level Institutions.
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