STUDY OF AROMATIC HYDROCARBONS IN KEROSENE FRACTIONS OF SAMOTLOR CRUDE OIL

N. M. SMOLYANINOVA, G. B. NEMIROVSKAYA, V. D. PUTINTSEVA

(Presented by the Scientific-Methodological Seminar of the Organic Departments)

With the development of petroleum-refining processes and jet technology, the importance of relatively high-boiling (kerosene–gas-oil and higher-molecular) petroleum fractions has increased. In this connection, interest has recently grown in studying the chemical composition of these fractions.

The aim of the present work was to isolate aromatic hydrocarbons from kerosene distillates (200–250°C and 250–300°C) of Samotlor crude oil and to study their composition.

The characteristics of the fractions studied are given in Table 1.

The structural groups of aromatic hydrocarbons were isolated from the indicated fractions by adsorption on silica gel according to the VNII NP method [1].

Table 1

Characteristics of kerosene fractions of Samotlor crude oil

Aromatic hydrocarbons of group 1 \((1.49 < n_D^{20} < 1.53)\), containing predominantly alkylbenzenes, were subjected to repeated chromatography on fine-pored silica gel of the ASM grade in order to free them from impurities of paraffin–naphthenic hydrocarbons and to obtain narrower fractions by refractive index \((\Delta n_D 0.001 \div 0.004)\).

The separation was carried out on a column 1.5 m long, with a ratio between the product and silica gel of \(1:20\). A 15-ml fraction was collected in each receiver. Desorption was carried out with petroleum ether \((t_{\text{boil}} 40\text{–}70^\circ\mathrm{C})\) and benzene.

After removal of the solvent, the narrow fractions were dissolved in isooctane and analyzed by UV spectroscopy. Absorption spectra were recorded on an SF-4 spectrophotometer in the near ultraviolet region \((240\text{–}280\ \mathrm{m}\mu)\), characteristic of substituted benzenes. The spectrograms were interpreted by the method described in the works of A. V. Topchiev et al. [2, 3], according to which the position of the absorption maxima in the spectra of alkylbenzenes of a definite type of substitution remains constant.

To study hydrocarbons of the naphthalene series, we used an accelerated picrate method; for this purpose the kerosene fraction was preliminarily distilled, with cuts collected over the boiling ranges, °C [5–9]: 180–210, 210–235, 235–270, 270–310. Each of the fractions was treated with dry picric acid according to the procedure of E. S. Pokrovskaya [4].

On the basis of the melting points of the picrates obtained, and additionally on the basis of their color, a conclusion was drawn regarding the presence in the kerosene fraction of particular hydrocarbons of the naphthalene series. Identification of the hydrocarbons was carried out on the basis of extensive literature material concerning the properties of naphthalene homologs.

Figures 1 and 2 show the spectra of narrow fractions.

Table 2 presents the results of interpretation of the ultraviolet spectra. It is apparent from the table that in the kerosene fraction of Samotlor

Fig. 1. UV spectra of narrow aromatic fractions of the 200–250°C cut

Fig. 2. UV spectra of narrow aromatic fractions of the 250–300°C cut

Table 2

Composition of mononuclear aromatics of kerosene fractions of Samotlor crude oil

of the crude oil, the mononuclear aromatics include: monoalkylbenzenes—by the shoulder or maximum at 256 and 260 mμ; dialkylbenzenes—by the maxima at 264 and 272 mμ; trialkylbenzenes, predominantly with substitution types 1,2,3 and 1,3,5 (maxima at 270 and 272 mμ); and 1,2,3,4-tetraalkylbenzene (268 and 277 mμ).

It should be noted, however, that such determination of the structural subgroups of benzene hydrocarbons is of a very approximate character.

When comparing the composition of the alkylbenzenes in the 200–250°C and 250–300°C distillates, attention is drawn to the fact that the former contains mono-, di-, tri-, and tetraalkylbenzenes, whereas in the latter there are mainly monoalkylbenzenes. This is apparently connected with an increase in the length of the hydrocarbon chain of the side substituent in the aromatic nucleus as the boiling temperature of the fraction increases.

The composition of bicyclic aromatic hydrocarbons is presented in Table 3. It can be seen that, according to the picrate method, the kerosene

Table 3

Composition of bicyclic aromatic hydrocarbons
according to the picrate method

distillate of Samotlor crude oil contains mono-, di-, and trimethyl derivatives of naphthalene.

When the data obtained on the composition of the mononuclear aromatics are compared with analogous studies by V. T. Sklyar and A. P. Lizogub [10], A. V. Topchiev [2], M. M. Kusakov et al. [3], and the data on the composition of deriv-

of aqueous naphthalene—with the studies of E. S. Pokrovskaya and S. S. Nametkin [4–9], it may be concluded that, in terms of the composition of aromatic hydrocarbons, the kerosene fraction of Samotlor crude oil differs little from the oils of other fields studied in this same region.

REFERENCES

1. Methods for the Study of Crude Oils and Petroleum Products. Gostoptekhizdat, 1955.

2. A. V. Topchiev, L. M. Rozenberg, M. M. Kusakov, L. V. Shishkina. Izv. AN SSSR, Otd. khim. nauk, 9, 1109, 1956.

3. M. M. Kusakov, S. S. Nifontova, E. S. Pokrovskaya, L. M. Rozenberg, A. V. Topchiev, M. V. Shishkina. Proceedings of the 10th All-Union Conference on Spectroscopy, 1, 321. Lviv, Lviv University Press, 1957.

4. E. S. Pokrovskaya. Trudy In-ta nefti AN SSSR, 4, 47, 1954.

5. S. S. Nametkina, E. S. Pokrovskaya, T. G. Stepanova. DAN SSSR, 73, 715, 1950.

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10. V. G. Sklyar, A. P. Lizogub. Izv. AN SSSR. Seriya fiziki, 23, 10, 1256, 1959.