STUDY OF THE PYROLYSIS OF GAS CONDENSATES FROM FIELDS IN THE TOMSK REGION

S. I. SMOLYANINOV, A. V. KRAVTSOV, V. A. KUZNETSOVA, M. D. MEDVEDEV

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

The study of the group and individual hydrocarbon composition of gas condensates from the Myldzhino, Luginets, Severo-Vasyugan, and Kazan fields, located in the territory of Tomsk Oblast, showed that they are of a methane-naphthene character with an insignificant content of aromatic hydrocarbons (not more than 4% based on condensate). In physicochemical properties and hydrocarbon composition, all the gas condensates studied are practically identical.

In the gasoline fractions, paraffinic hydrocarbons predominate, with a significant content among them of alkanes of normal structure. The amount of naphthenic hydrocarbons is 18–34% and decreases with increasing boiling temperature of the distillate [1]. This characteristic of these fuels makes it possible to regard them as valuable feedstock for pyrolysis for the purpose of obtaining lower olefins.

We investigated the pyrolysis process of the fraction b.p.–62°C of Luginets gas condensate as a typical representative of condensates from fields in Tomsk Oblast. The group composition of this fraction is given in Table 1.

Table 1

Individual composition of the fraction of Luginets gas condensate
b.p.–62°C

We studied the influence of external conditions—temperature, contact time, and degree of dilution of the feedstock with steam—on the yield and composition of the pyrolysis products. Experimentally, the optimal conditions for obtaining maximum yields of ethylene and propylene were found. The pyrolysis process was carried out at temperatures of 725–850°C and at various contact times from 0.2 to 1.6 sec. The experimental results are summarized in Table 2.

It is seen from Table 2 that the highest ethylene yield (32.8 wt.% based on the initial feedstock) is achieved at \(t = 825^\circ\mathrm{C}\) and a contact time of 0.74 sec. The maximum propylene yield (12.5 wt.% based on the initial feedstock) was obtained at a pyrolysis temperature of 800°C and a contact time of 0.7 sec. The coke yield at temperatures of 725, 750, 800, 825, 850°C, and also at

Table 2

Effect of temperature and contact time on the individual composition of the pyrolysis gas (fraction from b.p. to 62°C, from Luginets gas condensate)

Yields of individual components in the raw gas, wt. %

at different contact times is fairly considerable and ranges between 1–2 wt.% based on the feedstock. The sum of the unsaturated hydrocarbons C₂H₄ and C₃H₆ passes through a maximum at all temperatures studied and at different contact times. This can be explained by the fact that ethylene and propylene are intermediate products in the pyrolysis process [2].

It is known that dilution of the feedstock with steam promotes an increase in the yield of the target products [3] and a decrease in the amount of tar and coke formed. To assess the effect of dilution of the feedstock with steam on the yield of pyrolysis products, we carried out experiments with 10, 20, 30, 40, 50, and 60% steam feed at \(t = 825^\circ\mathrm{C}\). The feedstock feed rate was the same throughout all experiments and was 1.5 ml/min. Data on the yield and composition of the pyrolysis gas are given in Table 3.

Table 3

Yield and composition of pyrolysis components upon dilution of the feedstock with steam
(in wt.% based on the initial feedstock)

The ethylene yield reaches a maximum at 40% dilution of the feedstock with steam and amounts to 36.4 wt.% based on the feedstock; that of propylene—at 10% dilution—and amounts to 19.4%. Coke formation under these pyrolysis conditions is insignificant. With further dilution (60%), the yield of the target products decreases markedly. This can apparently be explained by insufficient superheating of the steam and by temperature fluctuations in the reactor zone.

Conclusions

1. A study was carried out of the pyrolysis process of the fraction from the initial boiling point to 62°C of the Luginets gas condensate field in the Tomsk Region.

2. The optimum conditions for obtaining the target products were identified—temperature, contact time, and degree of dilution of the feedstock with steam.

3. On the basis of the group hydrocarbon composition of the pyrolysis gas, it was established that the fraction from the initial boiling point to 62°C of the Luginets condensate is a good feedstock for obtaining ethylene and propylene.

References

1. N. M. Smolyaninova, K. K. Stramkovskaya, L. N. Ponomareva, V. A. Kuznetsova, M. E. Shlykova. Study of the hydrocarbon composition of gas condensates from the Myldzhinskoye field. Problems of Chemistry. Scientific Notes of the Tomsk State Pedagogical Institute. No. 26, 1969.

2. R. Z. Magaril. Mechanism and Kinetics of Homogeneous Thermal Transformations of Hydrocarbons. Moscow, “Khimiya,” 1970.

3. P. I. Lukyanov, A. G. Basistov. Pyrolysis of Petroleum Feedstock. Moscow, State Scientific and Technical Publishing House for Petroleum and Mining-Fuel Literature, 1962.