DE2003560A1 - Process for the separation of ethylbenzene from hydrocarbon mixtures - Google Patents

Description

Patent attorney Dipl.-Phys. Gerhard Liedl 8 Munich 22 Steinsdorfstr. 21-22 Tel. 298462

B 4504

JAPAN. GAS-CHEMICAL COMPAiTY, Inc., No. 1-1-2, Uchisaiwai-cho, Chiyödä-ku, IDKI O / Japan

Process for separating ethylbenzene from hydrocarbon mixtures η

The invention relates to a process for separating ethylbenzene from a hydrocarbon mixture which contains ethylbenzene and at least one isomer of xylene. In particular, the invention relates to a process for the separation of ethylbenzene in high purity and in high yields from a mixture of xylenes and ethylbenzene.

Br.P / Ho 009831/1936

It is known that XyIo! Mixtures obtained from the residue a catalytically reformed or thermally cracked petroleum fraction have been obtained, contain xylene isomers, e.g. m-xylene, o-xylene and p-xylene and ethylbenzene. Of the The ethylbenzene content of these mixtures is generally 5-30 MdHs. It is also known that one is significant There is a demand for ethylbenzene as a raw material for the production of styrene. Ethylbenzene can be obtained from the xylene mixture separated by fractionation, since ethylbenzene is the lowest boiling component of the mixture. However, since the boiling point of ethylbenzene is very close to the boiling points of the xylene isomers, it is essential for the separation of the ethylbenzene from the xylene mixture by fractionation necessary, a very high column with more than 100 plates and with a reflux ratio greater than 100 to use. However, it is even with this hyperfractionation very difficult to obtain an ethylbenzene in the high purity that it is for the production of styrene suitable is.

Ethylbenzene can also be extracted from the xylene mixture be separated. The extractants used are hydrogen fluoride and boron trifluoride. This procedure is based on the differences in the basicity of the individual components. The separation is going through allows the differences in affinity of the individual components to the hydrogen fluoride-boron trifluoride extractant. Since ethylbenzene has a smaller basicity than the xylene isomers, ethylbenzene remains in the raffinate phase during the xylene isoiners go into the extract phase when a Xylene mixture, which contains practically no ethylbenzene, is returned to the extract outlet. The for

⁴⁵⁰⁴ .0 09831/1936

ORIGINAL INSPECTED

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The substances used in the extraction separation process hydrogen fluoride and boron trifluoride are among the strongest acids. It is also known that they are effective as Friedel-Crafts catalysts and catalyze side reactions. It is known that aromatic hydrocarbons with side chains can enter into disproportionation reactions and transalkylation reactions. In particular, ethylbenzene has a high reactivity. It tends very easy to disproportion and transalkylation Λ portioning, which are shown in the following formula:

2EB - * B + DEB

EBι ■ + X - ^> B + EX

EB means ethylbenzene, B benzene, DEB diethylbenzene, X xylenes and EX ethy! Xylenes. The separation of the Äthy! Benzene by extraction of the xylene isomers using hydrogen fluoride-boron trifluoride as extractant gewöhn3.ich leads to losses of ethylbenzene and XyIolen ₀ They occur by the disproportionation and transalkylation. E is therefore very difficult to obtain similar ethylbenzene in high purity.

It is evident, however, that the extraction separation process, the hydrogen fluoride boron trifluoride used as the extractant, the fractionation process by far is superior. However, the extraction separation process will not yet used industrially because the side reactions, of ethylbenzene are undesirable.

It has now been found that the disproportionation and / or transalkylation reactions aee ethylbenzene, which were previously regarded as inevitable when ethylbenzene

00 983 1/193 6 '

4504 · ^;

■ ..- QSiT ^ i * \ - ^ ν, Ο- ORfQfNAL INSPECTED

2ÜÜ3560

by extraction from the XyIo! isomers using was separated from hydrogen fluoride boron trifluoride as an extractant in high purity, completely suppressed can be if a saturated aliphatic or alicyclic Hydrocarbon with at least one tertiary carbon atom in the molecule is used as a diluent

_ will.

The inventive method for separating ethylbenzene from a hydrocarbon device from ethylbenzene and at least one aylene isomer. -esrtfeairfri in-which the mixture with an extractant made from hydrogen fluoride and boron trifluoride is treated, wherein the xylene isomers are extracted into the extract phase, while the ethylbenzene in the raffinate phase remains is characterized by that a saturated aliphatic or alicyclic hydrocarbon with at least one tertiary carbon atom is used as a diluent.

Wk Pig · 1 is a simplified flow diagram of a plant which is suitable for the continuous implementation of the process according to the invention.

Those to be used according to the invention as diluents Compounds inhibit the dispersion and transalkylation reactions of ethylbenzene. They must be stable in the presence of hydrogen fluoride and boron trifluoride. Furthermore, it is necessary that they can be easily removed from the ethylbenzene by distillation. A saturated hydrocarbon with 4-7 carbon atoms in the molecule and with at least one tertiary hydrocarbon is suitable as a diluent. Suitable

009831/1936

4504

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n@tph.aaie is a solution of ethylbenzene in the saturated hydrocarbon. Ithy! Benzene can be separated off therefrom in a simple manner by distillation. The xylene isomers <e _a which have a higher basicity than ethylbenzene »are extracted into the Eactrafctphase in iOna an HF-IF ^ -XyIoIisoraere-Koaplex»

W The starting material, from the ethylbene sol in high purity

can be separated is a mixture of! thy! benzene and at least one xyIoI isomer * This & emiseh fcanm further condensed aromatic hydrocarbons «tmö / or Bo lyalky! Aromatics, which are different from the diols, contain. In the Jtusgaiigsroaterial there can also be saturated There are aliphatic or alicyclic hydrocarbons, while unsaturated ones are undesirable fabrics »

The Fig. 1 di «nt to the further Teraoaschaullctoaaag ü-ea erfim procedure - Im I ¹ Ig. 1 becomes a

eatholds, In the middle part Shark information 1 given · hydrogen fluoride «ta

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0139831/193 «

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tion of a liquid-liquid countercurrent extraction using a hydrocarbon phase and a fluorohydrogen phase are suitable. Can be used, for example, Füllkörperkotonnen, columns with perforated plates, extraction devices with devices for mechanical mixing, extraction apparatus with mixing and settling zones, ie so-called mixer-settler, etc.. M

According to the method according to the invention are among suitable Conditions readily obtained the following results when ethylbenzene in the countercurrent extraction process is separated from xylene mixtures, consisting of $ 20 Compose ethylbenzene, 40 $ p- and o-xylene and 40 $ m-xylene: '· ■■' "'·" ■ ··· .. ■

Ethylbenzene concentration in <, the
Raffinate phase (ethylbenzene / total aromatic hydrocarbons) more than $ 99

Ethylbenzene concentration in the (|

Extract phase (ethylbenzene / total aromatic hydrocarbons) less than 0.5 $

Loss of ethylbenzene through diöpro- '"■■■ ·' · ■ '*'" · '■''■■■' -_ ^ '

porting or transalkylation * ". ^ ₁ ?:; ■ '.-, ■;

and the like (Verlusli an Athylbehzol / auge- ^{; ί} '· "- ■" ^! ·

gebene8 Ätliy ^benzene):; '"''" less than ■ 5 $ * *'

It ^ was ίοϊη '"equipped with a stirrer! ·" ExtraktIonssh-7 · -. appkrat · ini1; -3Ö0 "ml. vörwersdet» j & retiesen ·. Extraktionsappara'ti ^;

⁰ ° ^{9 8 3 d}

i 5 J, '■ *' ·

2 over over 3 over 6 over

0.79 mol of ethylbenzene, 0.08 mol of p-xylene, 0.08 mol of o-xylene and 0.36 mol of methylcyclopentane (purity higher than $ 99.0) were added as diluents. The extraction apparatus was then cooled to ^{0 ° C.} 4.1 mol of purified, anhydrous hydrogen fluoride were then added. While mixing the contents of the extractor was to -25 ⁰ C Removing m cooled. 0.25 mol of boron trifluoride were introduced into the extractor from a boron trifluoride measuring tank. The measuring tank was connected to the extraction apparatus by a pipe which had a valve. Boron trifluoride dissolved in hydrogen fluoride with evolution of heat. The temperature of the extractor was adjusted so that it was -20 ⁰ C. The operating pressure in the extractor was 1.5 kg / cm. It is about atmospheric pressure.

15 minutes after the addition of boron trifluoride, the mixing was stopped and the mixture was allowed to stand. Samples were taken from the extract phase and the raffinate phase. These were examined by gas chromatography. P The results are shown in Table 1.

Example 2

The experiment was carried out as described in Example 1, with the exception that a mixture of n-hexane and methylcyclopentane (methylcyclopentane content: 40 mol- #) was used as a diluent. The results are also shown in Table 1.

Comparative example 1

The experiment was carried out as described in Example 1, but with the exception that η-hexane as a diluent

^ ...-.-. 0-0 9 8 3-1 / 1936

- ORIGINAL INSPECTED

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* Me results are also in Table t reproduced »,

HF Tabel 1 Comparison
example 1 example 1 Example 2 Feed' n-hexane (Mole) MGP ⁺ 4.00 EB 4.10 4.00 0.24 P-X 0.25 0.25 .. " 0.36 o-I 0.22 Raf. Phase
(Mol M 0.36 0.15 0.79 EB 0.79 0.79 0.08 P-X 0.08 0.08 0.08 m-X 0.08 O ₀ OS o * IC 86.27 Extr. Phase
(Mol ⁰ A) 88.98 88.45 9.50 W. 6.90 7.18 -, - - 4.23 4 »37 . 55.23 . 50 »99 49.85 21.28; Π, 05 t7, O3 5.39 2.1 ^ 3.54 20.01 29.77 2Sb54

tilt

: üüJo60

Raffinate Extract Raffinate Extract Raffinate Extract

product
iüail 0 , 36 0.00 0.36 0.00 0 , 36 0.00 Thinning 0 , 01 0.00 0.01 0.00 0 , 08 0.02 tion
middle 0 , 67 0.08 0.63 0.07 0 , 50 0.04 B. 0 , 05 0.03 0.05 0.02 0 , 06 0.02 EB _ 0.00 0.01 0.00 p-X m-X

o-X 0.03 0.04- 0.03 0.04 0.02 0.02 DEB - 0.00 0.00 0.01 0.02 0.10

EB recovery
% 94.9 88.7 68.3

Note: Basis of the values given for the composition the raffinate and extract phases are the aromatic hydrocarbons,

⁺ MGP: methylcyclopentane.
Examples 3-7

Mixtures with the composition shown in Table 2 were introduced into a 250 ml extractor. At a temperature of -2O ⁰ C calculated amounts of boron trifluoride were blown into the mixtures. At this temperature, the mixtures were stirred for 20 minutes. Then the entire amount of the mixtures was poured into water. Samples were taken and analyzed by gas chromatography. The results are shown in Table 2 .

009831/193 «

2uÜ3b6U

3 Table 2 5 6th 7th Example no. 4th feed
(Mole) 5.00 5.40 5.05 5.20, HP. 0.32 5.30 0.32 0.30 0.31 BP, i-hexane 0.32 MCH MOP ^; C g mixture ⁴ " Dilution
middle , -0.12 i-pentane 0.12 0.12 0.04 0.39 0.12 0.39 0.39 0.39 EB 0.01 0.39 0.01 0.01 0.01 p-x 0.01 product
(Mole #) 28.98 22.86 22.39 24.17 Dilution8-
middle 12.18 19.09 5.42 0.61 1.22 B; ■ -. 48.21 10.41 63.54 72.97 70.45 EB 2.74 55.68 2.84 3.34 3.03 P-X 7.80 3.16 5.09 0.53 0.78 DEB 70.7 11.58 85.8 98.5 97.2 EB return
winnung # 71.7

Note: The Cg mixture is a mixture .aus 58, ι 21.4 $ methylcyclopentane and 19.8 $ methylpentane,

n-hexane,

The amount added was expressed as methylcyclopentane plus methylpentane calculated. The amount of n-hexane (no tertiary carbon atom) was not included in the calculation.

00 98 3

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Comparative examples 2-7

The mixtures with the composition shown in Table 3 were as described in Examples 3 to 7 treated. The following results were obtained:

Table 3

Comparative example 2 3 4 5 6 7

No.

feed
(Mole)

HF 5.70 4.86 4.40 5.35 5.45 5.40

0.34 0.34 0.26 0.32 0.33 0.32

Diluent n-Hep- η-He- n ~ Ven ·? Gyo- Ben- Neo-

tan xan tan lohezol hexane

xan

0.12 0.12 0.12 0.12 0.12 0.12

EB 0.39 0.39 0.39 0.39 0.39 0.39

p-X 0.01 0.01 0.01 0.01 0.01 0.01

product
(Mol f )

Diluent 25.41 27.10 20.37 21.76 22.23

B 25.13 15.93 20.51 20.33 39.23 21.62

EB 28.50 42.12 35.32 32.57 37.58 27.51

P-X 2.04 2.24 2.40 2.37 2.88 2.24

DEB 18.89 12.56 21.31 22.92 20.12 26.40

EB recovery $ 39.3 59.7 45.8 43.0 48.3 36.4

4504

0 0 9 8 3 1/19 3 6

ORIGINAL INSPECTED

Comparative Examples 8 and 9

The devices with the composition shown in Table 4 were treated in the same way as described in Examples 3-7, with the exception that no diluent was used. In Comparative Example 9, the extraction at -30 ⁰ C was carried out. The results are shown in Table 4.

■ '■ ■ ■ ·. ι

Table 4 .

Comparative Example No. "8 9 ·

9.00 8 _f 90

0.54 0.53

0.57 0.57

0.12 0.12 ..

Temperature -20 ⁰ C. -30 ⁰ C

feed (Mole) HF. EB P-X

Raffinate phase
composition
(Mole j>) 21.79 ;., B. 63.97 · 11.97 EB 12.01 74.93 P-X ■ .. ·. 2.23 9.11 DEB 3.99 Extract phase
composition 18.21 - B. 34.24 11.59 EB. 20.94 45.01 P-X. -. 26.63 23.72 DEB 00 983 1/19 36 19.68 4504

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Raffinate Extract Raffinate Extract

Product (mole) 0 , 08 0 63.2 , 07 0 , 04 75 0 4th , 04 B. 0 , 23 0 , 13 0 , 26 0 , 17th EB 0 , 04 0 , 08 0 , 03 0 , 09 P-X 0 , 01 0 , 10 0 , 01 0 , 07 DEB ΕίΒ return winnung </ o Example 8

In a rotary disc contactor with 50 actual plates, ethylbenzene was separated from a xylene mixture using a hexane mixture containing 30% methylcyclopentane as a diluent. The extraction was atm at -20 ⁰ G and under a pressure of 3.5 and carried out a residence time of 30 Hinuten. The results are shown in Table 5.

Table 5

Dosage (moles / hour)

Loading
kung Back
flow
X Thinning
tion
middle Extra
functional
middle Raffinate extract benzene 0 0 0.5 0 toluene 0.1 0.1 0.1 0.1 EB 22.5 0.1 21.5 0.1 P-X 16.5 11.1 0.1 27.5 m-X 48.9 32.8 0 81.7

4504

009831/1936

ORlOlNAi INSPECTED

;: 00 3 6

o-X 12.1 8.1 0 20.2

HC Hö-. '

here as

C ₉ 0 0 0 0.4

saturated HC 0 0. 96.5

HP - BP, - -

, 7 96 2 O, 3 963 0, 1 962, 9 86 0, 1 86 6th

4504.

00983 1/1936 ° ^R ' ^ÖiNAI - "PECTED

Claims (1)

2Ü03560 Claims / Α process for separating ethylbenzene from a Koh-ÜÜenwasser mixture of ethylbenzene and at least one xylene isomer by subjecting the mixture is treated with an extraction agent of hydrogen fluoride and boron trifluoride, wherein the xylene isomers are hiert into the extract phase extra- Wk * while the ethylbenzene in the raffinate phase, characterized in that a saturated aliphatic or alicyclic hydrocarbon with at least one tertiary carbon atom is used as a diluent, 2. The method according to claim 1, characterized in that the diluent has 4-7 carbon atoms in the molecule, 3 «Method according to claim 1 or 2, characterized in that that the amount of diluent is 2.5-500 moles per 100 moles of ethylbenzene in the xylene mixture, amounts to. 4. The method according to claim 1 to 3, characterized in that the diluent is isohexane, isopentane, methylcyclohexane, Methylcyclopentane, mixtures thereof and Geraische with η-hexane can be used. 5. The method according to claim 1 to 4, characterized in that that the amount of boron trifluoride used is 50-300 moles per 80 moles of xylenes that are in the xylene mixture that is used as the starting material is used. 4504 009831/1936 β. Process according to Claims 1 to 5, characterized in that the reflux xyloIraenge in the last part of the extractor 40-400 moles per 80 moles of xylenes seen in the starting xylene mixture are located, amounts to 7t method according to claim 1 to 6, characterized in that that the dwell time in the extractor is less than an hour amounts to. . | 8. The method according to claim 1 to 7, characterized in that that the starting mixture is essentially free of unsaturated Compounds, excluding aromatics, is. 9. The method according to claim 1 to 8, characterized in that the extraction is carried out at a temperature in the range from -5O ⁰ C to + 2O ⁰ C and under a pressure of 1 to 20 kg / cm. 10. The method according to claims 1 to 9, characterized in that that the extraction is continuous by the countercurrent process is carried out by treating the starting material with the extractant. 00983 1/1936 Blank page