RU2501842C1 - Method for dearomatisation of gasoline fraction - pyrolysis material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of dearomatising a gasoline fraction - pyrolysis material, which involves extraction of aromatic hydrocarbons from a gasoline fraction at 62-180°C, obtaining a raffinate with low content of aromatic hyrocarbons, wherein the selective solvent used is a mixture containing 50-65 wt % N-methylpyrrolidone, 30-45% triethylene glycol, 3-7 wt % water.

EFFECT: low content of aromatic hydrocarbons in the gasoline fraction.

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Description

The invention relates to the oil refining and petrochemical industries, in particular to a method for extraction dearomatization of raw pyrolysis.

A known method of extraction of aromatic hydrocarbons from mixtures with non-aromatic hydrocarbons using triethylene glycol [see Prince GI Beetrich, A. A. Gail, D. Lempe and others. Separation of hydrocarbons using selective solvents. - L .: Chemistry, 1987. - p.153], the disadvantages of which are low selectivity and dissolving ability, leading to an increase in the multiplicity of the solvent to the raw material (7-15: 1 wt.) And an increase in the temperature of extraction (over 150 ° C), low thermal stability, high solvent toxicity.

The closest technical solution to the present invention is a method for the extraction of aromatic hydrocarbons, which use a mixture of triethylene glycol with low molecular weight alcohols containing from 2 to 4 carbon atoms [see RF patent N 2202529, 2003].

The disadvantage of this extraction method is the insufficient selectivity of triethylene glycol mixed with low molecular weight alcohols, significant differences in the boiling points of triethylene glycol (T _bp = 285 ° C) and low molecular weight alcohols (for example, for methanol T _bp = 64.7 ° C, for ethanol T _bp = 78.3 ° C), it is necessary to maintain a constant composition of the solvent during its regeneration, in addition, low molecular weight alcohols can form azeotropic mixtures with alkanes, cycloalkanes, benzene, toluene, which also complicates the regeneration process solvent.

The technical task is to obtain a gasoline fraction with a low content of aromatic hydrocarbons used in the pyrolysis process.

The technical result is a decrease in the content of aromatic hydrocarbons in the gasoline fraction - raw materials of pyrolysis.

It is achieved in that a mixture containing 50-65 wt.% N-methylpyrrolidone, 30-45 wt.% Triethylene glycol, 3-7 wt.% Water is used as a selective solvent.

Studies of the process of extraction dearomatization of aromatic hydrocarbons from a gasoline fraction of 62-180 ° C of the Astrakhan gas condensate with N-methylpyrrolidone (NMP), triethylene glycol (TEG) and mixtures with different ratios of these solvents (the concentration of NMP in the mixture was changed from 0 to 100 wt.%) Showed the effectiveness of the proposed mixture.

By mixing NMP, which has a high dissolving power, and TEG, which exhibits high selectivity with respect to an aromatic hydrocarbon, it is possible to obtain a gasoline fraction with a low content of aromatic hydrocarbons.

The proposed method was carried out as follows: in a sealed container equipped with a stirrer, 50-100 g of a gasoline fraction of 62-180 ° C containing 28.3 wt.% Aromatic hydrocarbons and 50-100 g of a solvent containing 50-65 wt. NMP, 30-45 wt.% TEG, 3-7 wt.% Water, with a ratio of solvent to raw materials from 1: 1 to 2: 1. The contents of the container were thermostated at 30–40 ° С with vigorous stirring for 10–15 min, and then settled for 30–40 min. After settling, the raffinate (upper layer) and extract (lower layer) phases were separated. In a sealed container equipped with a stirrer, the raffinate phase was loaded, which was repeatedly washed with distilled water at a temperature of 70 ° C. After which the watered solvent was removed, the raffinate was dried over calcium chloride, filtered and weighed. The aromatic hydrocarbon content in the raffinate was determined by gas-liquid chromatography.

Example 1

In a sealed container with a stirrer, 50 g of a gasoline fraction of 62-180 ° C containing 28.3 wt.% Aromatic hydrocarbons and 50 g of a solvent containing 57 wt.% NMP, 38 wt.% TEG and 5 wt.% Water were loaded. At 40 ° C, the mixture was stirred vigorously for 15 minutes and 30 minutes. In a sealed container equipped with a stirrer, the raffinate phase was loaded, which was repeatedly washed with distilled water at a temperature of 70 ° C. After which the watered solvent was removed, the raffinate was dried over calcium chloride, filtered and weighed. Received 38.8 g of raffinate containing 5.9 wt.% Aromatic hydrocarbons. The degree of extraction of aromatic hydrocarbons amounted to 79 wt.% From the content in the original gasoline fraction.

Example 2

The process was carried out in five thermostatically controlled sealed containers equipped with a stirrer. The first container was charged with 50 g of the gasoline fraction 62-180 ° C containing 28.3 wt.% Aromatic hydrocarbons and 100 g of solvent containing 60 wt.% NMP, 35 wt.% TEG and 5 wt.% Water. At 40 ° C, the mixture was vigorously stirred for 15 minutes and settled for 30 minutes. After settling, the raffinate and extract phases were separated. The obtained extract phase is treated with a fresh portion of the feed, and the raffinate phase in the second container with a fresh portion of the solvent. The process was continued until the final extract phase in the first tank and the final raffinate phase in the fifth tank were obtained. In a sealed container equipped with a stirrer, the raffinate phase was loaded, which was repeatedly washed with distilled water at a temperature of 70 ° C. After which the watered solvent was removed, the raffinate was dried over calcium chloride, and filtered. A fifth stage raffinate was obtained containing 2.6% by weight of aromatic hydrocarbons. The degree of extraction of aromatic hydrocarbons amounted to 90.8 wt.% From the content in the original gasoline fraction.

Table 1 presents the results of single-stage and multi-stage extraction. As can be seen from the table, with single-stage extraction, the maximum degree of extraction was 79.2 wt.%, The minimum content of aromatic hydrocarbons in the extract was 5.9 wt.%. An increase in the number of extraction stages to five made it possible to increase the degree of extraction to 90.8 wt.%, And reduce the aromatic hydrocarbon content in the raffinate to 2.6 wt.%.

Due to the high extraction ability of the mixture containing 50-65 wt.% NMP, 30-45 wt.% TEG, 3-7 wt.% Water, it was possible to reduce the process temperature to 30-40 ° C, the ratio of the solvent to the feed to 1 -2: 1, get a raffinate with a low content of aromatic hydrocarbons even during single-stage extraction.

Positive effect. A decrease in the content of aromatic hydrocarbons in the pyrolysis feedstock contributes to an increase in ethylene yield during the pyrolysis of gasoline fractions. The proposed method also allows to obtain a concentrate of aromatic hydrocarbons, which can be used as raw materials for petrochemical industries. Moreover, the use of the proposed solvent mixture does not require changes to the well-known scheme of the process of extraction of aromatic hydrocarbons from gasoline fractions.

Table 1. The composition of the solvent, wt.% Multiplicity of solvent: raw materials Temperature ° C The degree of extraction of Ar. HC ³ , wt.% Contents Ar. HC ³ in the raw material of pyrolysis, wt.% NMP ¹ TEG ² water Before extraction After extraction Single stage extraction - one hundred - 1: 1 40 48,4 28.3 14.6 fifty 45 5 1: 1 40 76.0 28.3 6.8 55 40 5 1: 1 40 79.2 28.3 5.9 60 35 5 1: 1 40 78.8 28.3 6.0 65 thirty 5 1: 1 40 79.2 28.3 5.9 one hundred - - 1: 1 40 52.7 28.3 13,4 Five step extraction - one hundred - 2: 1 40 58.3 28.3 11.8 fifty 45 5 2: 1 40 88.3 28.3 3.3 55 40 5 2: 1 40 90.8 28.3 2.6 60 35 5 2: 1 40 90.8 28.3 2.6 65 thirty 5 2: 1 40 90.1 28.3 2,8 one hundred - - 2: 1 40 63.6 28.3 10.3 1 - N-methylpyrrolidone 2 - triethylene glycol 3 - aromatic hydrocarbons

Information sources

1. G.I. Beetrich, A. A. Gaile, D. Lempe and others. Separation of hydrocarbons using selective solvents. - L .: Chemistry, 1987 .-- 192 p.

2. RF patent N 2202529, IPC С07С 7/10. Grushova. E.I., Kuchuk. A.V. / Method for the extraction of aromatic hydrocarbons, publ. 04/20/2003 g. (Prototype).

Claims (1)

A method of dearomatization of a gasoline fraction — a pyrolysis feedstock, including extraction of aromatic hydrocarbons from a gasoline fraction of 62-180 ° C., preparation of a low aromatic hydrocarbon raffinate, characterized in that a mixture containing 50-65 wt.% N-methylpyrrolidone is used as a selective solvent 30-45 wt.% Triethylene glycol, 3-7 wt.% Water.