Comparison of Fractionation Methods for the Structural Characterization of Petroleum Residues (original) (raw)
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Chromatographic separations enabling the structural characterisation of heavy petroleum residues
Fuel, 2003
Two petroleum residues from European crudes have been fractionated using solvent (heptane) separation and column chromatography. The residues and the separated fractions have been characterised by size exclusion chromatography (SEC) and by UV-fluorescence spectroscopy (UV-F). Matrix assisted laser desorption/ionisation-mass spectrometry of the whole residues and the heptane insoluble fractions indicated that the bulk of the residues covered the mass range m/z 300-2000, while the heptane insolubles (1-2% of the whole) contained material in the mass range from about m/z 300 to 10 000. The upper mass ranges indicated by SEC using polystyrene standards were higher; the earliest eluting material from both distillation residues eluted at times corresponding to polystyrene standards of MMs above 1.85 million u. Possible reasons for the different observations are given. Data from UV-F suggests that the heptane solubility separation method was the most successful for the separation of the largest molecular mass and also probably the most polar materials in these residues. However, all three fractionation methods produced similar trends, showing greater polarity of the fractions to correlate with increasing molecular mass. The shift of maximum intensity of fluorescence towards longer wavelengths (in UV-fluorescence) with increasing molecular size, as indicated by SEC, strongly suggests that the fluorescing molecules are large rather than aggregates of small molecules. Differences in comparison with American petroleum residues can be observed.
Bulletin of the Chemical Society of Ethiopia, 2007
Samples of light, medium and heavy Nigerian crude oils and petroleum products including diesel oil, engine oil (SAE 40) and gasoline (PMS) have been separated into four fractions of saturates, monoaromatics, diaromatics and polyaromatics by elution liquid chromatography. The fractions obtained were analysed using IR and UV-visible spectrophotometry. The infrared data confirmed the presence of methyl and methylene groups in the saturate fractions of the crude oils and petroleum products. The C=C stretching vibrations and C-H out of plane bending vibration of aromatics were also found in the mono-, di-and polyaromatics fractions. The characteristic UV spectra of alkyl benzenes and naphthalenes were observed in the monoaromatic and diaromatic fractions, respectively. The spectra of the polyaromatic fractions indicate the presence of anthracenes and phenanthrenes.
Samples of light, medium and heavy Nigerian crude oils and petroleum products including diesel oil, engine oil (SAE 40) and gasoline (PMS) have been separated into four fractions of saturates, monoaromatics, diaromatics and polyaromatics by elution liquid chromatography. The fractions obtained were analysed using IR and UV-visible spectrophotometry. The infrared data confirmed the presence of methyl and methylene groups in the saturate fractions of the crude oils and petroleum products. The C=C stretching vibrations and C-H out of plane bending vibration of aromatics were also found in the mono-, di-and polyaromatics fractions. The characteristic UV spectra of alkyl benzenes and naphthalenes were observed in the monoaromatic and diaromatic fractions, respectively. The spectra of the polyaromatic fractions indicate the presence of anthracenes and phenanthrenes.
Fuel, 2018
Molecular profiling of crude oil is a tremendous challenge due to its inherent complexity. An accurate molecular fingerprint of a crude oil may facilitate rational design of crude oil recovery efforts, such as enhanced oil recovery, improve the efficiencies of the refining processes, and enable a better assessment of the value of the crude oil. Herein, a new approach (Distillation Precipitation Fractionation Mass Spectrometry (DPF-MS) method) is introduced for the molecular level characterization of crude oil. This method involves the separation of crude oil into six fractions followed by high-resolution mass spectral analysis optimized for each individual fraction. The separation methods are distillation, precipitation, and fractionation in an auto column followed by solid phase extraction. Initially, the fractions were examined by using Fourier transform infrared spectroscopy to determine the bulk chemical nature of each individual fraction, such as the extent of aromaticity, degree of polarity, etc. Based on this bulk information, model compounds representative of compounds in each fraction were selected and employed to develop the optimal high-resolution mass spectrometric analysis method for each fraction. An especially important aspect of this work was the optimization of the ionization method separately for each fraction by using appropriate model compounds so that most compounds in each fraction are ionized at approximately the same efficiency to generate only one type of stable ions (either molecular ions, protonated molecules or cations formed by hydride abstraction) containing the intact analyte molecule. This allows the DPF
Oil & Gas Science and Technology - Revue de l'IFP, 2008
-Les fractions solubles dans le pentane et le toluène d'un résidu pétrolier et de trois échantillons de goudron de charbons par chromatographie d'exclusion stérique et par spectroscopie de fluorescence-Un résidu pétrolier de distillation atmosphérique ainsi que trois échantillons de goudron issus des pyrolyses de différents charbons sont séparés en sept fractions par chromatographie liquide sur gel de silice. Les solvants utilisés successivement sont : le pentane, le toluène, l'acétonitrile, la pyridine, la 1-methyl-2-pyrrolidinone (NMP) et l'eau permettant l'obtention de 7 fractions. Les fractions obtenues pour chacun des quatre échantillons sont ensuite comparées par chromatographie d'exclusion stérique (SEC) au moyen d'NMP comme éluant, puis par spectroscopie de fluorescence. Cet article traite uniquement le cas des fractions solubles dans le pentane et le toluène, car étant les moins polaires. D'après les analyses SEC, la taille des molécules aromatiques entre les premières fractions solubles dans le pentane et celles solubles dans le toluène augmente. Ainsi, les fractions du résidu pétrolier possèdent des molécules de plus grande taille que celles extraites, par le même solvant, pour les différents goudrons. Les trois échantillons de goudrons montrent des différences significatives, indiquant que la température de pyrolyse joue un rôle important sur la taille des molécules. Les résultats de spectroscopie, en solution NMP, montrent également de grandes différences entre le résidu pétrolier et les trois goudrons, de même que ces trois derniers sont différents entre eux. En général, les fractions du résidu pétrolier contiennent de plus petits groupes aromatiques que les fractions liquides issues du charbon. Ces fractions de faible polarité, contenant des éléments exclus par la colonne chromatographique, ont peu de chance d'être des agrégats de molécules polaires.
Journal of Chemical & Engineering Data, 2010
Molecular distillation is presented as an alternative technique for the separation of petroleum residues. The technique was used to obtain 13 heavy petroleum cuts from three atmospheric residues (ARs) at 673.15 K and above. The cuts present initial and final boiling points between (673.15 and 951.15) K. To evaluate the efficiency of the technique, chemical characterization of residues and distillate cuts, which included SARA fractionation, 13 C NMR, elemental composition, and density and viscosity analysis, was performed. In addition, extended true boiling point curves of crude oils by simulated distillation and by molecular distillation were compared. An increase in the viscosity and in the density was observed in all cuts with an increased molecular distillation temperature. Such behavior demonstrates that highly polar components that have a high structural complexity, such as resins and asphaltenes, are concentrated at the higher temperatures of the process. A sensitivity analysis of these two properties, together with the temperature, showed that viscosity and density decreased with increased temperature. On the other hand, the thermal expansion coefficient values obtained were equivalent to those reported in literature for petroleum products. Furthermore, a complete characterization of crude oils was made using the molecular distillation process to extend the true boiling point (TBP) curves.
Journal of Chromatographic Science, 1999
Direct application of the fluorescence response enhancement (derived from the interaction of the berberine cation with saturated hydrocarbons) to petrochemical analysis is achieved. Hydrocarbon types are successfully determined in middle (gasoil) and heavy (lubricants, vis-breaking fuel, heavy oil) petroleum distillates with adequate precision and sensitivity. The novelty of this method resides in the fact that a single fluorescence scanning is only needed for the determination of saturates and aromatics in the same chromatogram. In spite of their chemical inertness, saturated hydrocarbons can be quantitatively determined using thin-layer chromatographic densitometry. The fluorescent response depends on the alkane structure. A reliable analysis depends on the adequate choice of variables that influence fluorescence response, precision, and sensitivity: sample load, application volume, beam size, and impregnation conditions (berberine concentration and impregnation time). Sensitivity of the analysis can be tailored to a certain extent through control of the last parameter. The quantitative results agree with those provided using other well-established techniques in the petrochemical industry. Reproduction (photocopying) of editorial content of this journal is prohibited without publisher's permission.