The method of separation of aromatic hydrocarbons from mixtures thereof with non-aromatic

 

(57) Abstract:

The invention can be used in the refining and petrochemical industries. Describes a way of separating aromatic hydrocarbons from mixtures with non-aromatic hydrocarbons by liquid extraction or extractive distillation selective extractant on the basis of glycol, water and solvent. As a solvent with a high solubility, a mixture of monometallic of oligoarticular General formula CH3O(CH2CH2O)mN, where m is an integer of 2 to 8, average molecular weight 175 - 190. The technical result - the expansion of raw materials extractive agents with high selectivity and capacity in relation to aromatic hydrocarbons, hydrolytic and thermal stability characterized by availability. 1 C.p. f-crystals, 1 table.

The invention relates to a method of separation of aromatic hydrocarbons from mixtures thereof with non-aromatic methods liquid extraction or extractive rectificatio and can be used in the refining and petrochemical industries.

In the industry to highlight aromati the in compositions with a solvent, having high dissolving ability, which improves the efficiency of the extraction process (Bittrich, J., Gail A. A., Lempa D. and other hydrocarbon Separation using selective solvents. L.: Chemistry 1987. - 192 S.).

The known method using as extractant mixtures of N-methylpyrrolidone with mono-, di - and triethylene glycol (Bursian N. R. and other Isomerization and separation methods alkylaromatic hydrocarbon, C8- M.: Tsniiteneftehim, 1983. - 56 S.; Ed. St. USSR N 341784 C 07 C 15/02, Appl. 19.10.70,; Ed. St. USSR N 1616883 C 07 C 7/10, Appl. 21.09.88). With a good capacity in relation to aromatic hydrocarbons, N-organic insufficiently selective. In addition, N-organic the most expensive of which are used in industry selective solvents.

A known method of using as a solvent a mixture of diethylene glycol with carbonyl-containing compounds, in particular esters of diethylene glycol and carboxylic acids with the number of atoms of C1-C2(Ed. mon. USSR N 499255 C 07 C 7/10, Appl. 03.01.74 year). These compounds exhibit high solvent capacity combined with sufficient selectivity. However, the disadvantages of this method of extraction is essigny substances occurs already at room temperature.

The closest to this invention to the technical essence and the achieved result is a way of separating aromatic hydrocarbons from non-aromatic mixtures by selective solvent extraction with a solvent-based glycol, water and simple ether glycol (Ed. mon. USSR N 827469, C 07 C 7/10, Appl. 20.07.79).

In this way the selective solvent is a mixture of nanometrology or monoethylene ether of triethylene glycol 35 to 65 wt.%, water 0.2 - 7.5 wt.% with diethylene glycol. The main disadvantage of this method is the lack of raw materials used for production of the extractant - clean monometallic or monotropic ethers of triethylene glycol. The production on an industrial scale at present is not due to high capital and energy costs in obtaining the target product, which prevents wide industrial application of the proposed extractants.

The authors set themselves the task of expanding the resource base of the extracting agent with high selectivity and capacity in relation to aromatic hydrocarbons, hydrolytic and thermal stability characterized by availability.

Osteopaticheskii by solvent extraction or extractive distillation selective extractant, contains glycol, water and a solvent with high solubility.

As the solvent having high dissolving ability use a mixture of oligohalob - monometallic esters of oligoarticular (SMOG), the General formula CH3O(CH2CH2O)mH, where m is an integer of 2 to 8, average molecular weight 175 - 190, of the following composition, wt.%:

CH3O(CH2CH2O)2H - 2 - 10 (MK)

CH3O(CH2CH2O)3H - 35 - 55 (MAAG)

CH3O(CH2CH2O)4H - 20 - 35 (MAAG)

CH3O(CH2CH2O)5H - 9 - 15 (MAAG)

CH3O(CH2CH2O)6H - 2 - 8 (MAAG)

CH3O(CH2CH2O)7H - 0,5 - 5 (MAAG)

CH3O(CH2CH2O)8H - 0,01 - 2 (MAAG)

Effective utilization COULD diethylene glycol, as well as with mono - or triethylene glycol.

Able has the following physicochemical characteristics:

Indicator - Norm

1. Boiling point,oC - 230 - 270

2. Freezing point,oC (-60) - (-68)

3. The viscosity at +20oC, cSt - 7 - 8,5

4. Viscosity at -40oC, cSt - 450 - 550

5. Surface tension, 25oC, mn/m - 35,2 - 35,8

6. Density, awn relative to the aromatic hydrocarbon, C6-C8, neorganicheskoi mixed with it, as well as glycols and water already at room temperature. However, in its pure form COULD not sufficiently selective. For the extraction of aromatic hydrocarbons from mixtures with non-aromatic used in conjunction with glycols and water, receiving a favorable combination of high selectivity and solvent ability. The proposed extractant allows you to get vysokoavtomatizirovannyh extract with a good solution that provides a high degree of purity emitted from an extract of individual aromatic hydrocarbons.

By changing the component ratio of the mixed solvent can be adjusted within wide limits as solvent capacity and selectivity of the extractants. This makes it possible to work on different raw materials to achieve the same extraction of aromatic hydrocarbons required purity without increasing the ratio of solvent to raw materials.

The fluctuation of the composition of SMOG in the specified concentration range does not affect its extracting features and properties of the mixed solvent with glycol and water.

The proximity of the physico-chemical properties, including boiling point and COULD glenegedale extractant.

Due to the low vapor pressure under the conditions of transportation, storage and processing COULD not danger of acute poisoning by inhalation. The effect on a living organism refers to hazardous substances to the 4th class of danger according to GOST 12.1.007-76.

COULD the mixed extractant with glycols, related to the 3rd class of hazard, reduces their toxicity and the extent of harmful effects on the body.

The rate of freezing temperature in combination with low-temperature viscosity solves the problem of storage and transportation of the extractant in the low temperature conditions of Siberia and the Far North. Furthermore, the presence of slightly alkaline environment of the extractant inhibits the auto-oxidation, increases its thermal-oxidative stability and imparts corrosion passivity, which eliminates corrosion of valves and piping and makes the extractant stable during prolonged storage.

The mixture of esters obtained by joining ethylene oxide to methanol or its lower esters at a molar ratio of methanol to ethylene oxide of 1:2,5 - 3,5, pressure 5 to 20 ATM and a temperature of 85 - 155oC in the presence of basic catalysts - alcoholate or hydroxide of slowest and obtaining the target product in the VAT stream.

The process of getting ABLE characterized by high product yield with 99.6 - 99.8 per cent, technological simplicity of design and low energy consumption. The production of SMOG is conducted on a massive scale, providing the wide availability of proposed based extractants.

Examples 1 to 8. The table presents data on examples 1 to 8, characterized the extraction of aromatic hydrocarbons systems benzene-hexane and toluene-heptane solvent COULD be used in the compositions with glycol and water.

Single-stage extraction is carried out according to the following scheme. A mixture of aromatic hydrocarbons thermostatic and mixed with double the quantity of extractant for 20 to 30 minutes. Then hold the assertion to full transparency phases, after which they are divided by a common way.

Analysis of the extract and raffinates parts spend chromatographic method.

In examples 1, 4, 5, 6 COULD use, content, wt.%: MK-5,91; MEAG-46,24; MEAG-30,08; MEAG-11,71; MEAG-BR4.61; MEAG-1,44.

In the examples 2,3,10,7 for extraction COULD apply to the content, wt.%: MK-11,24; MEAG-44,75; MEAG-25,4; MEAG-12,3; MEAG-4,87; MEAG-1,43.

In the examples 8,9 composition COULD, wt.%: MK-3,62; MEAG-48,49; ME THE P>oC is subjected to the hydrocarbon feedstock with a total content of aromatic hydrocarbons 40 wt.%, including benzene - 20, toluene - 18, xylene - 2, the rest hexane..

As extractant used a mixed solvent containing, by weight. %: MIGHT 28, water - 6, DAG - 66. Conditions for extraction of examples 1 to 8. The extract and the raffinate with the content of aromatic hydrocarbons 83,1 wt.% and 37.8 wt.% respectively. The distribution coefficient of aromatic hydrocarbons - of) 0.157; the separation factor of 8.0; the degree of extraction - 30,4%.

Example 10. A hydrocarbon mixture containing 35 wt.% benzene and 65 wt.% hexane, separated by means of extractive distillation using as solvent a mixture of SMOG is 47.5 wt.%; Deg is 47.5 wt.%, water - 5.0 wt.%. Aromatic hydrocarbons extract on the column efficiency 20 theoretical plates, at atmospheric pressure, the weight ratio of solvent to raw materials 6: 1 and reflux the number equal to 0. In the process of extractive distillation get hexane with a concentration of 99.7%, the concentration of the selected benzene > 99%.

1. The method of separation of aromatic hydrocarbons from mixtures with non-aromatic hydrocarbons by solvent extraction Alvorada ability characterized in that the solvent with a high solubility, a mixture of monometallic esters of oligoarticular General formula CH3O(CH2CH2O)mH, where m is an integer of 2 to 8, average molecular weight 175 - 190.

2. The method according to p. 1, characterized in that a mixture of monometallic esters of oligoarticular the following composition, wt.%:

CH3O(CH2CH2O)2H - 2 - 10

CH3O(CH2CH2O)3H - 35 - 55

CH3O(CH2CH2O)4H - 20 - 35

CH3O(CH2CH2O)5H - 9 - 15

CH3O(CH2CH2O)6H - 2 - 8

CH3O(CH2CH2O)7H - 0,5 - 5

CH3O(CH2CH2O)8H - 0,01 - 2

 

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