CS200504B2 - Process for the separation of diolefines and aromatic hydrocarbons - Google Patents

Abstract

The novel solvent for the separation of hydrocarbons by extractive distillation, by gas-liquid scrubbing or by liquid-liquid scrubbing contains N-methyl-morpholin-3-one. The solvent can be used as a mixture with water and/or other organic solvents, for example ethylene glycol. The novel solvent is used above all for the separation of diolefins from mixtures containing them, and also for the separation of olefinic hydrocarbons from mixtures containing them, and likewise for the separation of aromatic hydrocarbons from mixtures containing them.

Description

(54) Method for separating diolefins and aromatic hydrocarbons

The invention relates to a process for separating diolefins and aromatic hydrocarbons.

In particular the invention relates to a process for the separation of diolefins such as butadiene and isoprene and _t from the mixture of hydrocarbons with 4-5 carbon atoms, and aromatic hydrocarbons such as styrene, benzene, toluene and xylenes, alone or in mixture with others, of a mixture of hydrocarbons with 6-8 carbon carbon by liquid-liquid extraction distillation or liquid-liquid extraction.

When separating hydrocarbons from hydrocarbon mixtures by extractive distillation or liquid-liquid extraction, the possibility of using heterocyclic compounds as extraction solvents is known.

Czechoslovak Patent Nos. 166,679,167,866, 167,923, and 152,477 disclose the extraction of aromatic hydrocarbons using N-formylmorpholines as e-extraction solvents.

When evaluating these compounds for industrial use, various aspects must be considered, such as selectivity, transportability, stability, ease of synthesis, toxicity, vapor pressure, specific gravity, boiling point, melting point and others.

It has been found that N-methylmorpholin-3-one is a compound which generally satisfactorily satisfies all of these requirements and has improved selectivity over the above-mentioned extraction solvent together with a natural dissolution capacity and a considerably reduced (in fact almost zero) tendency to hydrolysis when used in conjunction with water.

The principle of a process for separating diolefins such as butadiene and isoprene from a mixture of hydrocarbons such as styrene, benzene, toluene and xylenes, alone or in combination with others, from a mixture of 6 to 8 carbon atoms by extraction distillation or liquid-liquid extraction according to the invention consists characterized in that the separation is carried out in extraction distillation columns having a number of trays in the range of 20 to 80, at a pressure at the top of the column of 9.8 to 490 kPa and at the bottom of the column of 40 to 150 ° C, and N-methylmorpholin-3-one.

In particular, N-methylmorpholin-3-one can be used either alone or in admixture with water up to 20 wt. % and / or with another organic solvent, such as ethylene glycol, to < 20 wt. %.

The solvent according to the invention can also be used advantageously for separating mixtures of saturated olefinic or aromatic hydrocarbons from mixtures or also for separating a single olefinic or aromatic hydrocarbon from mixtures of olefins, saturated hydrocarbons and diolefins or from mixtures of aromatic hydrocarbons.

. The following examples illustrate the invention without limiting it in any way.

Example 1

According to Figure 1, a stream of the following composition is fed to the extraction distillation column 9 via line 1: isoprene

Isopentan

1- pentene

2-methhlil-butene norm. pentane trans 2-pentene 2-isopentene 2-methyl-4-but-1-ene

1,3-ογΜορ6-ηάίθη itopropeylacetylun

282.0 mol / h

13.2 mol / h

39.7 moles / h

67.3 moles / h

120.1 mol / h

29.4 moles / h

18.1 moles / h

11.3 mol / h

1.7 mol / h

0.1 mol / h

The working conditions are as follows:

hydrostatic pressure 107 kPa

L / D 0,9 number of floors 65

The same column was fed via a 2500 kg / h N-methylmorpholin-4-one / water mixture in a ratio of 94: 6,

The following composition is discharged from the top (line 3):

Isoprene

1- pentene

2-Methyl-1-butane standard methyl-2-pentene cis-2-pentene

5.6 mol / h

13.2 mol / h

39.7 moles / h

67.3 moles / h

120.1 mol / h

29.4 moles / h

11.1 moles / h moles / h

The stream leaving the bottom of the column 9 (line 4) is fed to a second extraction purification column 10, together with a flow of 60 kg / h of the above solvent (line 5).

The column 10 is operated under the following conditions:

hydrostatic pressure 107 kPa

L / D 0.9 number of floors 75

From the column head, a stream of isoprene of a purity of more than 99% per second is discharged through line 6 and, in particular, contains:

isoprene, 270.8 mol / h

2-methyl-b-butene 0.3 mol / h

While the more polar hydrocarbons (1,3-cyclopentadiene and itopropenylacutyl) are removed from the side line 7 in the gas phase, a hydrocarbon-free solvent is obtained from the bottom through line 8 and circulated into the above-mentioned extraction distillation column 9 and 10,

Example 2

Referring to FIG. 1, it is fed to the extraction distillation column 9 via line 11. kg / h of the following composition:

saturated hydrocarbons with carbon atoms otophthic hydrocarbons with carbon atoms

1,3-butadiene acetylene Compound (as vinylacetylene) by mass,% by mass,% by mass,%

1,0.00 ppm

The operating conditions are as follows: hydrostatic pressure 392 kPa

L / D 0,9 number of floors ⁷⁰

The same column is fed via line 2 with 10 kg / h of a mixture of N-methyl-1-morpholin-3-one and water in a ratio of 93: 7,

A stream (0.65 kg / h), which mainly contains saturated and olefinic hydrocarbons, is discharged from the top of the column (line 3),

The stream emerging from the bottom of the column 9 through line 4 is sent to the second extraction column 10, together with a stream of 2 kg / h of the above solvent (line 5).

Separation in column 10 is performed after. the following conditions:

hydrostatic pressure 117 kPa

L / D 0,9 number of floors 80

A 0.34 kg / h 1,3-butadiene stream of greater than 99% purity and containing about 20 ppm of acetone compounds is discharged from the top of the column through line 6,

From the side pipe 7, acetone hydrocarbons are removed in the gas phase together with 0.01 kg of butadiene per. hour, while it is drained from the bottom through a pipe. 8, the hydrocarbon-free solvent is circulated into the above extraction columns 9 and 10.

Example 1 a d 3

Referring to Figure 2, a stream of reformed gasoline is fed into the extraction column 8 via line 1:

benzene 1.50 kg / h toluene 2.00 kg00 xylenes 3.50 kg ^ non-aromatic substances 3.00 kg0h.

The working conditions are as follows:

hydrostatic pressure 107 kPa

L / D 0.7 number of floors 55

Db of the same column was fed through a line of 30 kg / h of a mixture of N - [(1-methyl-1-morpholin-3-yl) -one and monoethane-glycol in a 95: 5 ratio by weight,

From the top of the column, a 3.05 kg / h stream is discharged, which mainly contains all non-aromatic hydrocarbons fed to the same column 8.

The product from the bottom of the column is passed through line 4 to the stripper column 9, which operates under the following conditions:

hydrostatic pressure 19.6 kPa

L / D 0,2 number of floors 25

A stream of aromatic hydrocarbons having a preselected amount of saturated compounds is obtained from the top of the column via line 5, while a solvent is obtained from the bottom and recirculated to the column 8.

The distillation of the stream obtained from the bottom of the column 8 can also be carried out in two stages, as shown in Fig. 3.

In this case, the same product is fed from the bottom of the column through line 4 to the first stripper column 9, which operates under the following conditions:

hydrostatic pressure

L / D number of floors

107 kPa

0.2

From the top of the column, a stream having a specified content of saturated compounds is obtained via line 5 and which contains:

benzene 1.49 kg / h toluene 1.99 kg / h xylenes 0.47 kg / h

A stream is discharged from the bottom through line 6 and fed to a second stripper column 10 which operates under the following conditions:

pressure 19.6 kPa

L / D 0.1 number of trays 15 • While the xylene stream of the previously selected specification (3.03 kg / h) is withdrawn from the top of the column through line 7, the solvent is removed from the bottom and recirculated to column 8.

The working conditions are as follows:

hydrostatic pressure 118 kPa

L / D 5 number of floors 80

The same column is fed via a line 2 of 1,300 kg / h of a mixture of N-methylmorpholin-3-one and water in a ratio of 96: 4 by weight.

From the top of the column, water and a stream of organic refined mixture are discharged through line 3:

C8 saturated and olefinic hydrocarbons o-xylene m-xylene and n-xylene ethylbenzene styrene

3.5 kg / h

16.9 kg / h

1 to ^CT / h

8 ^ 6 kg / l

0.3 kg / h

This stream is fed to a distributor 11 to separate the water (line 17) from the refined mixture (line 16).

A stream is discharged from the bottom via line 4 and fed to the extraction column 10 together with a stream of 150 kg / h of the above solvent. The separation in this column is carried out under the following conditions:

hydrostatic pressure 21 kPa

L / D 2.5 number of floors 60

From the top of the column, a stream 6 containing o-xylene and styrene which is recirculated to the column 9 is removed from the column head, while a stream is discharged from the bottom through the line 7, which is fed to the stripper column 12.

This stripper column operates under the following conditions:

hydrostatic pressure 25 kPa number of floors 30

A stream is discharged from the top of the column and fed to manifold 13. Through line 8, styrene having a purity greater than 99.8% is obtained.

Solvent is removed from the bottom of the same column and after mixing in the mixer 15 with tempered water from lines 17 and 18 is allowed to be recirculated.

Example 4

Example 5

According to Figure 4, a stream of 100 kg / h of the fraction having the following composition is fed into the extraction distillation column via line 1:

saturated and olefinic hydrocarbons with 8 carbon atoms 3.5% o-xylene 17.0% m-xylene and p-xylene 43.1% ethylbenzene 8.6 ° / o styrene 27.8%

According to Fig. 5, a stream (1 kg / h) of the following composition is fed to the scrubbing column gas-liquid 9:

saturated hydrocarbons having 4 carbon atoms of about 20 wt. % olefinic hydrocarbons having 4 carbon atoms of about 45 wt. % ·

The working conditions are as follows:

hydrostatic pressure 490 kPa number of floors 40

About 8.5 kg / h of a 94: 6 mixture of N-methylmorpholin-3-one and water in mass were fed into the same column via line 2.

From the top of the column, a stream of gas containing substantially saturated a. olefinic hydrocarbons, while the stream from the bottom of the column is sent via line 4 to the stripper column 10.

The column 10 is operated under the following conditions:.

hydrostatic pressure 539 kPa number of floors 45

A gaseous stream of 4-carbon olefins and 1,3-butadiene is recirculated to the column via line 5 and recirculated to the column.

9, while a stream 6 is discharged from the bottom of the column to a second stripper 11. This column operates under the following conditions:

hydrostatic pressure 107 kPa number of floors 30

The gaseous stream is discharged from the top of the column to the compressor 12. After condensation. is obtained from line 8 according to specification about 0.35 kg / h

1,3-butadiene containing saturated and olefinic compounds (purity greater than 99,5% by weight), while. line 7 recirculates the fractions. of the above column stream

10.

Ze. at the bottom of the column 11 a solvent is obtained which:. shall be reused in column 9.

Example 6

According to FIG. 6 gasoline is used as feed (line 1). . of the following composition:

benzene 15 wt. % toluene! 25 wt. % Xylenes 25 wt. % saturated hydrocarbons 35 wt. %

This stream is fed to a liquid-liquid 14 extraction column having 60 trays at a rate. flow rate 5 kg / h. 13 kg / h of a 95: 5 mixture of N-methylmorpholm-3-one and water in mass are fed through line 13, and the column is maintained at 40-45 ° C (hydrostatic pressure about 196 kPa).

From the top of the column, a stream is discharged through line 3, which is mainly composed of the saturated compounds present in the original batch.

The extract emerging from the bottom of the column is fed to the top of the column 15 (hydrostatic pressure about 117 kPa, number of trays = 30).

The stream from the top of the column 15 is passed through a line 5 to two successive stages 17 and 18, where it coheses. A condensate stream above 120 ° C is passed through line 6 and mixed into the feed. while the current discharged through line 7 is recirculated. to the base of the liquid-liquid extractor 14.

Current drawn from. at the bottom of column 15 is passed through line 8 to column 16 (hydrostatic pressure = 117 kPa, 30 plates).

A gas is discharged from the top of the column, which is distributed in the distributor 9. 3.05 kg / h of a stream of aromatic hydrocarbons having a flow rate is removed via line 10. specified content of saturated compounds, while. ze. the bottom of the manifold. 9, the aqueous stream is discharged, which is reported in part as a return flow. flow to the same column 16 (1.5 kg / h) and partially recirculated to the column. 14 (0.7 kg / h). Solvent removed from. the bottom of column 10 is reused. in the same liquid-liquid extractor.

Example 1 a d 7

According to FIG. charge (pipe 1) reformed gasoline of the following composition:

benzene 4wt% toluene 15 fuels / xylenes 20 210101% saturated hydrocarbons 61 6ϊη (Λ. ·%

This stream is fed to a first liquid-liquid extraction column 12 having 40 trays at a flow rate of 100 kg / h. 250 kg / h of N-methylmorpholin-3-one is fed through line 5 while 40 kg / h of pentane is fed through line 10 to the same column, the extractor is maintained at 25 [deg.] C. (hydrostatic pressure is 0.294 MPa).

The current from the column head via line 2 is sent to. a distillation column 13, while from the top of the column the pentene is recovered via line 8, which is returned to the extractor; from the bottom, about 61.3 kg / h of stream is substantially discharged through line 9 containing substantially the saturated hydrocarbons contained in the original feed. piping 1).

Current. from the bottom of the extractor 12, a second liquid-liquid extractor 14 is sent along with 220 kg / h of pentane through line 11. This column has 20 trays and operates at 25 degrees Celsius and 0.196. MPa. '

The stream discharged from the top of the column via line 4 is sent to the distillation. column 15. While. out of this head. The column is obtained via line 6 with pentane, which is required for. 38.7 kg / h of a mixture of benzene, toluene and xylene having the indicated percentage of saturated compounds is discharged from the bottom via line 7.

From the bottom of the other ^one of the extractor solvent is obtained, which is used in the extractor 12th.

Example 8

Referring to FIG. 8, a stream of the same composition as in Example 1 is fed to the liquid-liquid extraction column.

Also 150 < RTI ID = 0.0 > kg / h < / RTI >

A stream is discharged from the top of the column through line 2 which, after distilling off the solvent contained therein (the operation not shown in the figure) is composed of:.

isoprene . 8.4 mol / h isopentan ' 13.2 moles / h 1-pentene 39.7 moles / h 2-methyl-1-butone «* 7 Q K U> U1U1U / 11 n-pentah 120.1 mol / h trans 2-pentene 29.4 mol / h cis 2-pentene 18.1 moles / h 2-methyl-2-butone 10.8 mol / h Current discharged from bottom 3 is led into the stripper column 13 (hydro- static pressure 147 kPa, 30 floors).

From the column head, a stream of olefins and isoprene is removed via line 4. which is recirculated to ¹ e-xtractor, while from the bottom a line 5 is discharged through a line 5 and fed to a second stripper column 14 (hydrostatic pressure 117 kPa, 20 plates, L / D = 0.2).

From line 6, isoprene is obtained having an indicated content of olefins and saturated compounds, which is fed to an extraction column 11 where polar hydrocarbons are removed, while line 7 yields the solvent required for column 12 work.

The column 12 is operated under the following conditions:

hydrostatic pressure 107 kPa

L / D 0.9 number of floors 75

A stream of isoprene of a purity of more than 99% is discharged from the top of the column through line 8, containing in particular:

isoprene 268.0 mol / h

2-methyl-2-butene 0.5 mol / h

While the most polar hydrocarbons (1,3-cyclopentadiene and isopropylacetylene) are removed in the vapor phase through the side line 9, the hydrocarbon-free solvent is removed from the bottom 10 via line 10 and is then reused in the same column 11.

Example 9

According to FIG. 5, a stream of the following composition is introduced into the scrubbing column gas-liquid 9:

n-butane isobutane b-concrete trans 2-butene cis 2-butene b, 3-aueadene

89.5 mol / h

22.4 moles / h

285.2 moles / h

117.6 moles / h

91.0 mol / h

6.8 mol / h

The working conditions are as follows:

hydrostatic pressure 490 kPa number of floors 40

The same column is fed via line 2;

1,200 kg / h of a mixture of N-methylmorpholin-3-one and water in weight ratio 93: 7.

The stream from the bottom of this column is sent via line 4 to the first stripper column, while a gaseous stream containing:

norm. butane 87.7 mol / h isobutane 22.4 mol / h

5.7 mol / h

The operating conditions of the column 10 are as follows:

hydrostatic pressure number of floors

539 kPa

From the top of the column, a gaseous stream of 4-carbon olefins and saturated hydrocarbons is discharged and recirculated to the column 9, while a stream is discharged from the bottom via line 6 and fed to the second stripper column 11.

This column operates under the following conditions:

hydrostatic pressure number of floors

107 kPa

The gaseous stream is fed to the compressor 12. After condensation, a stream comprising:

norm. butone 1.8 mol / h b-uutene 279.5 mol / h trans 2-butene 117.6 mol / h cis 2-butene 91.0 mol / h b, u-bueadene 6.8 mol / h.

A portion of the above-mentioned stream to the compressor is recirculated through line 7 to column 10.

A solvent is obtained from the bottom of column 11 which is reused in column 9.

In the above examples, the abbreviation L / D means reflux ratio; L is the portion of the condensed vapor that recirculates from the condenser to the top of the column, and D is the remaining portion of the condensed vapor that is discharged from the condenser. The term "required specification" and the like means that the compounds have an analytical composition that must meet customer requirements or certain standards.

Claims (3)

P ft E D Μ E T A process for separating diolefins, such as butadiene and isoprene, from mixtures of C 4 -C 5 hydrocarbons and aromatic hydrocarbons, such as styrene, toluene and xylenes, alone or in admixture with other C 6 -C 8 hydrocarbons by distillation or liquid extraction, a liquid characterized in that the separation is carried out in extraction distillation columns having a number of trays in the range of 20 to 80, at a head pressure of 9.8 to 1.0 490 kPa and a temperature at . , bottom, column, 40 to 150 degrees Celsius, and N-methylmorpholin-3-one is used as solvent. · 2. The process according to claim 1, wherein the solvent is N-methylmorpholin-3-one in admixture with water and / or ethylene glycol. 3. The process according to claim 1, wherein the water and / or ethylene glycol is contained in 20 wt. %.