FT-Raman and photoacoustic infrared spectroscopy of syncrude light gas oil distillation fractions

Abstract

FT-Raman and photoacoustic (PA) infrared spectra of 12 distillation fractions derived from Syncrude light gas oil (LGO), which has a boiling range from 195 to 343 degrees C, were analyzed in detail in this study. In the fingerprint region (200-1800 cm(-1)) most of the information is obtained from the FT-Raman spectra, which display 36 bands that are assignable to various alkyl or aryl functional groups. Monocyclic, bicyclic and tricyclic aromatics in the 12 fractions were also characterized using Raman bands in this region. The corresponding section of the infrared spectra is much simpler, displaying a relatively small number of bands due to either aromatic or aliphatic CH(n) (n=1, 2 or 3) groups. The Cz.sbnd;H stretching region in both FT-Raman and PA infrared spectra of the LGO distillation fractions was curve-fitted according to procedures established in previous investigations of Syncrude samples with various boiling ranges. The PA spectra of the LGO fractions were also analyzed using an accepted integration strategy that requires no a priori assumptions with regard to the number of constituent bands or their shapes. The curve-fitting results show that the frequencies of the 11 Raman and eight infrared bands used to model the aliphatic ( approximately 2775-3000 cm(-1)) parts of the respective spectra decrease systematically as the median boiling points of the LGO fractions increase. These band positions are consistent with those determined in earlier studies of other distillation fractions. Both curve fitting and integration show that the abundance of CH(2) groups increases at the expense of CH(3) groups as the boiling points of the fractions increase within the LGO region.

Vibrational Spectroscopy and Thermophysical Properties of Ultralow Sulfur Diesel—Alternative Fuel Binary Blends

“…The symmetric and asymmetric stretching bands do not exhibit like behavior in the spectra of any of these three samples, making conclusions similar to those in the previous paragraph impossible. In fact, the latter type of situation is fairly common in Raman and infrared spectra of various hydrocarbon fuels. , Notwithstanding this result, it is readily apparent that the spectra of AF3 and AF4 in this figure are practically identicala finding reminiscent of the relationships among the thermophysical properties of these two fuels in Figure . Thus, the Raman spectra confirm that the AFs fall into three groups: (a) AF1, (b) AF2, and (c) AF3 and AF4.…”

“…Survey Raman spectra of AFs 5, 10, 15 and 20 as well as ULSD are presented in Figure 2.As might be expected, these spectra are generally similar to those obtained previously in our laboratory for middle distillate fuels as well as numerous distillation fractions and process samples. 12,13 The prominent features at about 1375, 1450, and 2800−3000 cm −1 are mostly due to alkyl (CH 2 and CH 3 ) groups. At lower wavenumbers several weaker bands signify the presence of various well-known functional groups.…”

“…Similar assignments of these aromatic bands in Raman spectra of distillation fractions were discussed in our previous work. 12,13 At higher wavenumbers, the C−H stretching region provides additional important information: the spectra of AF3 and AF4 are very similar to each other but distinct from those for AF1 and AF2. The existence of a weak band near 3050 cm −1 affirms the presence of aromatic CH groups in AF2 and ULSD.…”

“…Lorentzian band shapes were assumed for convenience in this calculation. This seven-band model is based on the curve-fitting strategies utilized previously in our laboratory for light and heavy gas oil distillation fractions. , The fitted bands (locations rounded to the nearest wavenumber) are assigned to CH n stretching vibration types according to the values given previously: 2849 cm –1 , CH 2 symmetric; 2868 cm –1 , CH 3 symmetric; 2893 cm –1 , CH; 2913 and 2932 cm –1 , CH 2 asymmetric; 2958 cm –1 , CH 3 asymmetric. The much weaker aromatic CH band is located at 3048 cm –1 .…”

Application of infrared photoacoustic spectroscopy in catalysis

“…It has to be underline the applications of the discussed technique for the investigation of industrial materials or studies having an influence on the industrial production [64]. Those studies covers an analysis of coatings [65,66], rapid determination of limestone in lime products [67], spectra of distillation fractions derived from syncrude heavy gas oil [68], light gas oil [69], post-extraction oil sand [70]. Yang and Simms [71] have compared PA, diffuse reflectance (DR) and transmission IR spectra of the studied carbon fibres.…”