Bulletin of the Tomsk Order of the October Revolution and Order of the Red Banner of Labor Polytechnic Institute named after Kirov

Vol. 237

1975

Study of the Individual Hydrocarbon Composition of Gasoline Fractions of Oils from Certain Fields in the Tomsk Region

S. I. Khoroshko, N. M. Smolyaninova

(Submitted by the scientific-methodological seminar of the Faculty of Chemical Technology)

The broad development and diversity of syntheses based on petroleum raw material, chiefly on the basis of individual hydrocarbons contained in oil or obtained from it, have made the question of studying the individual hydrocarbon composition of oil and the products of its processing one of the urgent problems of modern science and technology. Of all the methods used to solve this problem, the most progressive, in our view, is gas-liquid chromatography, which makes it possible to analyze a hydrocarbon mixture rapidly and accurately.

A large number of works are known that are devoted to studying the individual composition of gasolines from various oils using simple packed columns. By using various liquid phases and selecting the optimum experimental conditions, it is possible successfully to separate and identify the majority of hydrocarbons included in gasoline fractions.

However, the columns mentioned have comparatively low efficiency and therefore cannot ensure complete separation of all components of light petroleum distillates. In this connection, the picture of the individual composition of gasolines obtained when they are analyzed on packed columns is not complete.

Recently, capillary columns have begun to be used in chromatographic analysis; they have very high efficiency (more than 100,000 theoretical plates) and therefore make it possible to obtain much more accurate results.

Taking the above into account, we investigated gasolines (end point—122°C) from oils of the Sovetskoe, Sobolinoe, Sredne-Nyrolskoe, Poludennoe, and Olenye fields of the Tomsk Region. The work was carried out with fractions with end points of 60°C, 60–95°C, and 95–122°C, obtained by rectification of the oil on a standard ARN-2 apparatus, whose separating capacity was 15–20 theoretical plates.

The fractions were studied on a modified Khrom-2 chromatograph with a flame-ionization detector. A copper capillary 100–200 m long and with an internal diameter of 0.5 mm was used as the column. The stationary liquid phase (vacuum oil—VM-4), dissolved in benzene, was applied by forcing the solution through the capillary. Nitrogen served as the carrier gas.

The column of the instrument operated under isothermal conditions, and each fraction was analyzed at several temperatures. This necessitated—

Table 1

Individual hydrocarbon composition of gasoline fractions investigated by us
from b.p. to 122°C of the oils studied

Hydrocarbon content in the fraction b.p.–122°C, wt. %

Continuation of Table 1

Continuation of Table 1

Conventional designations: B — butane, G — hexane, Pg — heptane, D — di, M — methyl, P — pentane, T — tri, Ts — cyclo, E — ethyl.

* Hydrocarbons having higher boiling points and found in this fraction owing to the appreciable relative volatility of their nonaromatic hydrocarbons; therefore, they are given in the sum.

It was established that a change in temperature changes the order of elution of individual hydrocarbons, and some components that emerge as a single peak at a given temperature could be separated at another.

The optimal temperature for separating the i.b.p.–60°C and 60–95°C fractions is 35°C. 2-Methylpentane with cyclopentane and 2,4-dimethylpentane with cyclohexane, which were not separated at this temperature, were separated at 95°C. The 95–122°C fraction was analyzed at temperatures of 35, 50, and 95°C. The analysis time for each fraction averaged 30–45 minutes.

Qualitative identification was carried out according to the Kovats retention indices determined for the given temperatures.

The chromatograms were calculated quantitatively by the method of internal normalization: “\(h \tau\)” (\(h\) is the peak height of the given component, \(\tau\) is its retention time), using correction coefficients.

The results of the analysis are presented in Table 1.

As can be seen from the table, all the gasolines studied differ very little from one another in qualitative composition and differ, sometimes considerably, in the quantitative content of certain hydrocarbons. This is apparently also due to the fact that, in the process of petroleum formation, the hydrocarbons passed through identical or similar stages of transformation processes, which differed in the intensity with which the reactions proceeded.

Conclusions

1. A study was carried out of the individual hydrocarbon composition of eight samples of straight-run gasolines (i.b.p.–122°C) obtained from oils of the Sovetskoye, Sobolinoye, Sredne-Nyurolskoye, Olenye, and Poludennoye fields of the Tomsk Region.

2. A great variety of hydrocarbons of all classes was found in the gasolines, among which paraffinic hydrocarbons markedly predominate.

3. From 74 to 77 individual hydrocarbons were found in the gasoline fractions studied.