Fluorescence rejection in Raman spectra of Syncrude Sweet Blend distillation fractions

Four techniques for the reduction or elimination of fluorescence from Raman spectra of Syncrude process samples were examined in this study. These methods are based on the retrieval of Raman bands from differential, or derivative spectra. Differential data were generated by subtracting similar spect...

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Bibliographic Details
Published in:Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2005-11, Vol.62 (1), p.582-591
Main Authors: Michaelian, Kirk H., Yuan, Hongqi, Hall, Robert H., Bulmer, J. Tim
Format: Article
Language:English
Subjects:
Distillation fractions
Fluorescence rejection
Hydrocarbons - analysis
Hydrocarbons - chemistry
Hydrocarbons, Aromatic - analysis
Petroleum - analysis
Raman
Sensitivity and Specificity
Spectrometry, Fluorescence
Spectrum Analysis, Raman
Thermodynamics
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Summary:Four techniques for the reduction or elimination of fluorescence from Raman spectra of Syncrude process samples were examined in this study. These methods are based on the retrieval of Raman bands from differential, or derivative spectra. Differential data were generated by subtracting similar spectra of a given sample obtained in three ways: (a) shifted detection utilizing an array detector and two successive spectrometer settings; (b) shifted excitation (dispersive Raman) where the two spectra are recorded using neighbouring laser lines and ordinary photon counting; (c) shifted excitation (FT-Raman) in which the laser frequency is changed in software before acquisition of the second spectrum. In addition to these differential techniques, derivative spectra were acquired directly with a dispersive Raman system by modulating the wavelength during scanning. These fluorescence rejection methods were applied to two groups of Syncrude Sweet Blend distillation fractions. For light gas oils (boiling range, 195–343 °C) the ratio of monocyclic and bicyclic aromatic species was determined and bands due to aliphatic CH n groups were characterized. Heavy gas oils (343–524 °C) yielded bands that allowed quantitation of monocyclic, bicyclic and total aromatic groups. Bands due to aliphatics were also identified for the heavy gas oils. These results constitute a significant advance compared to the information obtainable using conventional dispersive and FT-Raman spectroscopy for the analysis of hydrocarbon distillation fractions.
ISSN:1386-1425
DOI:10.1016/j.saa.2005.01.022