Individual Hydrocarbon Composition of Gasoline Fractions from Some West Siberian Crude Oils
Abstract Generated abstract
This study examines the individual hydrocarbon composition of gasoline fractions boiling from the initial boiling point to 150°C in four Western Siberian crude oils from the Samotlor, Yuzhno-Cheremshanskoye, Klyuchevskoye, and Ozernoye fields. Fractions obtained by precise rectification were analyzed by gas-liquid chromatography, with additional separation of the 125 to 150°C cut into aromatic and paraffin-naphthenic portions. The analysis identified 134 components in each crude and showed that paraffinic hydrocarbons exceed 50% of the gasoline fractions, with varying proportions of normal and isoalkanes, substantial naphthenic content, and comparatively low aromatic content. The work also reports regularities in the distribution of monomethyl paraffins and naphthenic isomers, contributing data relevant to the geochemical characterization of light hydrocarbons in these crudes.
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INDIVIDUAL HYDROCARBON COMPOSITION OF GASOLINE FRACTIONS OF CERTAIN CRUDES OF WESTERN SIBERIA
V. A. KUZNETSOVA, S. I. KHOROSHKO
(Presented at the scientific-methodological seminar of the organic departments of the Chemical-Technological Faculty)
The discovery of new oil fields in Western Siberia has brought to the fore the problem of a thorough study of their material composition.
The present work is devoted to the study of the individual hydrocarbon composition of gasoline fractions (initial boiling point—150°C) of three crudes from fields of Tomsk Oblast (Yuzhno-Cheremshanskoye, Klyuchevskoye, Ozernoye) and of the largest field in Western Siberia, the Samotlor field, located in Tomsk Oblast. The analysis was carried out by gas-liquid chromatography according to the procedure proposed by A. A. Petrov and co-workers [1, 2, 3].
For the study, fractions of initial boiling point—110°C and 125–150°C were taken, obtained on a precise rectification column with an efficiency of 50 theoretical plates. The 125–150°C fraction was subjected to preliminary separation on silica gel into aromatic and paraffin-naphthenic parts. Chromatography of the indicated fractions was carried out on a copper capillary column 100 m long and with an internal diameter of 0.5 mm; the stationary phase was squalane; the carrier gas was nitrogen. The column temperature was varied from 30 to 106°C.
In all, 134 components were identified in the fraction from the initial boiling point to 150°C of each crude. The table gives the detailed group composition of the fraction under study. It should be noted that there is a high content of paraffinic hydrocarbons (more than 50% of the gasoline), among which normal and isoparaffins are present in approximately equal amounts for the Samotlor and Ozernoye crudes; for the crudes of the Yuzhno-Cheremshanskoye and Klyuchevskoye fields a certain predominance of isostructures is observed (31.02% versus 26.82%, and 33.76% versus 25.92%, respectively). It was found that the distribution of monomethyl derivatives of paraffinic hydrocarbons containing an even number of carbon atoms in the molecule differs substantially from the distribution of those with an odd number of atoms. Hydrocarbons with an odd number of carbon atoms have the methyl group predominantly at the second carbon atom, while those with an even number of atoms have it at the third carbon atom.
The indicated regularity is not observed only for 2-methyloctanes and 3-methyloctanes of the gasolines of the three crudes, from which it may be assumed that such a distribution of methyloctanes is a consequence of the similarity of the structures of the original organic matter, and not the action of secondary or catalytic processes.
Table 1a
Detailed group hydrocarbon composition of the gasoline fraction from IBP to 150°C
| Hydrocarbon group | Content in the fraction, wt. % | Content in the fraction, wt. % | Content in the fraction, wt. % | Content in the fraction, wt. % |
|---|---|---|---|---|
| Samotlor | Yuzhno-Cheremshanskoe | Klyuchevskoe | Ozernoe | |
| 1. Paraffinic hydrocarbons, including: | 62.78 | 54.84 | 59.08 | 55.84 |
| n-alkanes; | 31.62 | 26.82 | 25.92 | 27.12 |
| a) with one tertiary carbon atom | 31.16 | 31.02 | 33.76 | 28.71 |
| b) with two » » | 23.18 | 21.92 | 24.97 | 21.17 |
| c) with three » » | 6.83 | 7.30 | 8.35 | 5.83 |
| d) with one tertiary and one quaternary carbon atom | 0.18 | 0.45 | 0.24 | 0.17 |
| e) with one quaternary carbon atom | 0.29 | 0.56 | 0.65 | 0.46 |
| 2. Naphthenic hydrocarbons, including: | 31.18 | 36.28 | 36.54 | 39.06 |
| a) cyclohexanes | 11.98 | 16.12 | 13.30 | 20.23 |
| b) cyclopentanes | 19.20 | 20.16 | 23.24 | 14.83 |
| 3. Aromatic hydrocarbons | 2.99 | 5.07 | 2.16 | 4.12 |
| 4. Unidentified | 3.05 | 0.81 | 1.61 | 1.60 |
Cyclanes in the fractions studied consist of cyclopentanes and cyclohexanes, with cyclopentanes predominating (the exception is the gasoline from the lake oil). A significant predominance of methylcyclopentane over the other isomers was noted.
The content of monosubstituted naphthenes decreases as the alkyl radicals lengthen. In the \(C_7\) fraction, the relative concentration of hydrocarbons decreases in the series: MCP > 1,2-DMCP > 1,3-DMCP > Et. CP > 1,1-DMCP.
Among the cyclohexanes, a definite regularity is observed in the distribution of individual hydrocarbons: 1,3-DMCH > 1,4-DMCH > 1,2-DMCH.
Conclusions
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The individual hydrocarbon composition of gasolines from 4 fields of Western Siberia has been studied.
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Geochemical regularities in the distribution of light hydrocarbons have been established.
LITERATURE
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Bryanskaya E. K., Olenina Z. K., Petrov A. A. Collection “Methods for the Analysis of Organic Compounds of Petroleum, Their Mixtures, and Derivatives.” Issue 2, 7, 1962.
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Bryanskaya E. K., Zakharenko V. A., Petrov A. A. “Neftekhimiya.” Vol. VI, No. 5, 11, 1966.
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Olenina Z. K., Petrov A. A. “Neftekhimiya.” Vol. IV, No. 1, 71, 1969.