Hydrocarbon fractions, analysis

Bonaga, G. and Giumanini, A. G. (1986). Chemical composition of chestnut honey Analysis of the hydrocarbon fraction. J. Apicult. Res. 25,113-120. 

Compositional analysis shows a decrease in the percentage of polar compounds in the oils with increasing residence time (see Table II). The decrease in polar content is substantiated by a lower sulphur content and results in a lower viscosity (see Table II). The oil becomes more aromatic, as shown by n.m.r. spectroscopy (see Table II), with increasing time at temperature, while the molecular weights showed little change. G.l.c. analysis of the saturate hydrocarbon fractions from elution chromatography indicated little change in the saturates with residence time. 

Once the sample preparation is complete, there are several approaches to the analysis of petroleum constituents in the water and soil (1) leachability or toxicity of the sample, (2) the amounts of total petroleum hydrocarbons in the sample, (3) petroleum group analysis, and (4) fractional analysis of the sample. These methods measure different petroleum constituents that might be present in petroleum-contaminated environmental media. 

Weisman, W. 1998. Analysis of Petroleum Hydrocarbons in Environmental Media. Total Petroleum Hydrocarbons Criteria Working Group Series, Vol. 1. Amherst Scientific Publishers, Amherst, MA.(See also Vol. 2, Composition of Petroleum Mixtures, 1998 Vol. 3, Selection of Representation Total Petroleum Hydrocarbons Fractions Based on Fate and Transport Considerations, 1997 Vol. 4, Development of Fraction-Specific Reference Doses and Reference Concentrations for Total Petroleum Hydrocarbons, 1997 and Vol. 5, Human Health Risk-Based Evaluation of Petroleum Contaminated Sites, Implementation of the Working Group Approach, 1999.)... 

Hydrocarbon composition is also determined by mass spectrometry, a technique that has seen wide use for hydrocarbon-type analysis of naphtha and gasoline (ASTM D2789) as well as for the identification of hydrocarbon constituents in higher-boiling naphtha fractions (ASTM D2425). 

PODanalysis analychem A precision laboratory distillation procedure used to separate low-boiling hydrocarbon fractions quantitatively for analytical purposes. Also known as Podblelnlak analysis. pe o de 3,nal 3 S3s )... 

The determination of the exact composition of feed and product streams is also receiving attention. By precision fractionation in the laboratory, often at 100 plus plates and reflux ratios of equal magnitude, narrow boiling fractions are obtained that are further resolved by separation procedures such as azeotropic distillation, extractive distillation, chromatography, solvent extraction, and crystallization. In addition, the instrumental methods of analysis are increasing our information on the composition of complex hydrocarbon fractions. 

The development of a commercial mass spectrometer and its application to hydrocarbon gas analysis by the method of Washburn et al. (63) made gas analysis rapid, economical, and, what is even more important, inspired a confidence in the results of routine hydrocarbon gas analysis which was badly lacking. A complex gaseous mixture comprising the atmospheric gases, carbon monoxide, and Ci to C6 hydrocarbons required more than 20 hours of applied time by the previous methods of low temperature fractional distillation coupled with chemical absorption methods. With the mass spectrometer such an analysis is completed in 2 hours or less, about 15 minutes of which is consumed in the... 

The brief discussion above shows the difficulty of a straightforward paleoenvironmental assessment based on OSC. Their occurrence seems not to be related to any special type of environment on the contrary, they are widespread. However, several of the encountered compounds cannot be related chemotaxonomically to specific biological contributions yet, because information on the lipid composition of appropriate organisms is still scant. Nevertheless, it is clear that much information is contained in the extractable OSC, information which is not evident when only the aliphatic hydrocarbon fraction is investigated. Furthermore, high-molecular-weight sulfur species not directly amenable to GC-MS analysis is another source of information, but chemical treatment (desulfurization) is required for its disclosure. 

With the demonstration of supercritical fluid extraction, an obvious extension would be to extract or dissolve the compounds of interest into the supercritical fluid before analysis with SFC.(6) This would be analogous to the case in HPLC, where the mobile phase solvent is commonly used for dissolving the sample. The work described here will employ a system capable of extracting materials with a supercritical fluid and introducing a known volume of this extract onto the column for analysis via SFC. Detection of the separated materials will be by on-line UV spectroscopy and infrared spectrometry. The optimized SFE/SFC system has been used to study selected nonvolatile coal-derived products. The work reported here involved the aliphatic and aromatic hydrocarbon fractions from this residuum material. Residua at several times were taken from the reactor and examined which provided some insight into the effects of catalyst decay on the products produced in a pilot plant operation. 

An external standard method is used when the standard is analyzed on a separate chromatogram from the sample. Quantitation is based on a comparison of the peak area/height (HPLC or GC) of the sample to that of the reference standard for the analyte of interest. The external standard method is more appropriate for samples with a single target analyte and narrow concentration range, where there is a simple sampling procedure, and for the analysis of hydrocarbon fractions. The calculation requires an accurate extract final volume and constant injection size. The peak area of an analyte is compared with that from a standard or standard curve and corrected for volume ... 

Although most of the oils tested in this study show a similar solubility behavior, significant differences can occur, depending on the composition of the oils with respect to their hydrocarbon fraction and the chemical nature and the amount of additives. With the specifications given by the producers like density and viscosity at standard conditions (see Table 1) no correlation could be found to the experimental data. Further information about the composition is hardly available and an exact analysis is not only undesired but also nearly impossible. This lack of information also makes phase equilibrium calculations to be not very useful for the correlation or prediction of these solubility data. In every single case the solubility has to be determined experimentally. 

Hydrocarbon Class Analysis. The hydrocarbon class or type separation of the pentane-soluble fraction was performed on a silica gel-alumina column according... 

Table II. Total Analysis of Hydrocarbon Fractions of Athabasca Oil...

The classical silica gel chromatographic method for determination of percent olefins in shale oils was studied and found wanting, mainly because of cross-contamination from high levels of olefins and heteroatom-containing compounds. This paper describes a new hydroboration/oxidation procedure for olefins, and reports its use in hydrocarbon-type analysis of both whole shale oils and distillate fractions. Percent composition values for three whole oils ranged as follows saturates, 13-26 olefins, 16-20 aromatics, 5-14 polar compounds, 41S2. A discussion of IR analysis for relative amounts of specific olefin types such as terminal, internal trans, and methylene structures is included. 

Work in the area of hydrocarbon-type analysis, i.e. saturate, olefin, and aromatic, has been conducted at the Laramie Energy Research Center (LERC) for over two decades. During this time, a significant portion of the eflFort has been directed towards the quantification and characterization of the various types of olefins found in Green River Formation shale oils and their distillate fractions (1-9). 

The saturate and aromatic hydrocarbons were separated from the alcohols by elution chromatography on alumina deactivated with 3.8% water in a ratio of 5 g of alumina to 1 g of oil, by successive elutions with (1) 30 mL of cyclohexane and (2) 50 mL of 2% benzene in cyclohexane. The alcohols were recovered for future analysis by washing the column with 100 mL of ethyl ether. The solvent was removed from the hydrocarbon fraction and the yield of saturates plus aromatics calculated back to the neutral oil. The percentage of olefins was determined by difference. The percentage of aromatic material was determined as the difference between the saturates and aromatics from the hydroboration and the saturates from acid absorption. 

Further confirmation of the surface nature of Grignard formation is the observation that when THF-ds and diethyl ether-djo were used as solvent only 28% and 6% deuterium, respectively, were found in the hydrocarbon fraction of the reaction . The source of hydrogen atoms is the disproportionation of the surface radicals. Moreover, the yield of hydrocarbons from reaction in THF is only 1.0-1.5 % whereas in diethyl ether the yield is 20%. This is in accord with the greater solvating power of THF which removes the metal organic species from the surface of the magnesium. Recent XPS analysis of the Grignard formation reaction is consistent with the surface nature of the reaction . 

---