title: Fluorescence rejection in Raman spectra of Syncrude Sweet Blend distillation fractions.
abstract: 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 degrees 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 degrees 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.
authors.affiliation: Natural Resources Canada, CANMET Energy Technology Centre-Devon, 1 Oil Patch Drive, Suite A202, Devon, Alta., Canada T9G 1A8. michaeli@nrcan.gc.ca
authors.forename: Kirk H
authors.initials: KH
authors.lastname: Michaelian
authors.forename: Hongqi
authors.initials: H
authors.lastname: Yuan
authors.forename: Robert H
authors.initials: RH
authors.lastname: Hall
authors.forename: J Tim
authors.initials: JT
authors.lastname: Bulmer
mesh_terms: D006838:Hydrocarbons / Q000032:analysis* / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000032:analysis; D010578:Petroleum / Q000032:analysis*; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics
chemical_list: D006838:Hydrocarbons; D006841:Hydrocarbons, Aromatic; D010578:Petroleum