DE1645709A1 - Process for the production of aromatic hydrocarbons from hydrocarbon mixtures by selective extraction - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG

Our reference: 0.Z. 25 306 Bk / Hi Ludwigshäfen am Rhein, December 18, 1967

Process for the production of aromatic hydrocarbons from hydrocarbon mixtures by selective extraction

The invention is a method for. Extraction of aromatic hydrocarbons from Kohlenwassersto.ffgemi- see ^v by selective extraction with piperazines.

It is known that hydrocarbon mixtures are made from paraffinic and aromatic components exist, with the help of solvents in paraffin-rich raffinates and aromatic-rich Decompose extracts. Suitable solvents are, for. B. 1 ^ -Butyrolactone, ΪΤ-Alkylpyrrolidone and N-Hydroxyalkylpyrrolidone, Oxazolidone ,. Morpholine and its / derivatives, Tetramethylsulfonalkanedinitriles, propylene carbonate, dicarboxamides and di- or triethylene glycols into consideration.

With the help of these solvents, the aromatic components in the extract should be enriched as high as possible. Another desirable property of a suitable solvent ^N is its resistance to hydrolytic influences under the extraction conditions. This is especially true when water is added to the solvent. In addition, the -ve-r-

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used solvents as low a viscosity as possible to have. However, with regard to these conditions, the solvents mentioned so far do not yet meet those used in technology they made demands.

In addition to aromatics and paraffins, the starting hydrocarbons commonly used in technology often contain considerable amounts Amounts of olefins and / or faphthenes, "so that the solvent for the extraction of the aromatics and their recovery high selectivity in high purity, d. h * at. good dissolving power for aromatics a high separating power must also have for olefins and naphthenes. In many cases, must therefore because of insufficient selectivity of the extractant the starting hydrocarbon before the aromatics are burned off mixture to saturate the unsaturated compounds be selectively hydrogenated. This process step means however, an additional effort.

P It is already from the German Auslegeschrift 1 250 04-0 ' known to use SF-substituted piperazines as extractants use. However, the piperazines mentioned have the disadvantage that they do not combine all desirable properties, such as selectivity, resistance to hydrolysis, low viscosity and suitable boiling range.

. It has now been found that aromatic hydrocarbons can be mixed "from hydrocarbons, the paraffins and optionally ... ->. ..;

■. ■■. ■■■ ".- '' ■ -. ■ ■■ '.._. 3 _ ■' ■ - ■■ -" ■■.

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Contain olefins and / or naphthenes by treating with fciperazines as extractants, according to known extraction processes wins more advantageously than before if you use piperazine derivatives of the general formula

.GH ₉ - CH ₉

X- JT "- .. N-I

in which X is a formyl or acetyl radical and R is is a lower alkyl radical, used as an extractant.

The new extractants have the advantage that they are a have good selectivity and also counter-hydrolytic influences are persistent. Furthermore, because of their physical constants for each, they are common in the art Extraction process can be used. In addition, they also have a good separating power for aromatics from olefins, so that a previous ^ hydrogenation of the starting mixture is not necessary is.

Preferred aromatic hydrocarbons which can be obtained by the process of the invention are mono- or binuclear aromatic hydrocarbons with six-membered aromatic rings, the aliphatic hydrocarbon radicals

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with 1 to 4 carbon atoms as substituents. The process has proven to be particularly effective for the production of mononuclear aromatic hydrocarbons containing up to 3 Have alkyl groups with 1 to 3 carbon atoms. Special The production of benzene * and toluene is of technical importance Obtained xylenes. Suitable aromatic hydrocarbons are for example benzene, toluene, o-xylene, p-xylene, ethylbenzene, i-propylbenzene, p-diisopropylbenzene or styrene.

As starting mixtures, the said aromatic hydrocarbons contain, crude oil distillation cuts such as straight-run gasoline, reformed gasoline, diesel oil, Gas oils, lubricating oils or by known petrochemical processes available hydrocarbon mixtures, such as mineral spirits, pyrolysis gasoline or Schwelbezine in embossing, which can contain olefins or naphthenes in addition to paraffinic hydrocarbons. Starting mixtures containing 3 to 60% by weight are particularly suitable contain aromatic hydrocarbons.

Piperazine derivatives are generally used as extractants formula

CHg - GH 2 \ 2 Ii-R X-N \ CHg - GH

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in which X is a formyl or acetyl radical and R is a means lower AlkyXrest is used. Particularly suitable Piperazines of the above formula have turned out to be in

stands*
X denotes the formyl radical and R denotes an alkyl radical having 1 to 4 carbon atoms, in particular having 1 to 2 carbon atoms. Suitable starting materials are, for example, N-formyl-H'-methylpiperazine, IT-formyl-II'-ethylpiperazine, H-IOrmyl-N'-isopropylpiperazine, II-acetyl-N'-methylpiperazine, H-acetyl-ϊΡ ethylpiperazine or 1-acetyl -iP-butylpiperazine. L-Formyl-U'-methylpiperazine has achieved particular industrial importance.

The piperazine derivatives can be used in pure form or as mixtures with one another and in mixtures with other extractants, such as tetramethyl sulfone, di- or triethylene glycols. The mixtures used as extractants preferably contain more than 60, in particular more than 80% by weight of the piperazines mentioned, based on the total mixture. The addition of ethylene glycol -si, in particular with 10 to 40% by weight of ethylene glycol, based on the piperazines used, has proven to be particularly advantageous 5 to 25% by weight of water, in particular 5 to 15% by weight of water, based on the extractant used or the extractant mixture, a. .. "■ - ..

The process is possible both at normal pressure and at

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higher pressure, ζ. B. up to 5 at, feasible. But you can also work at reduced pressure. In general, temperatures from 0 0 to the boiling point of the solvent are used. Usually one leads z. B1 the liquid-pluid extraction at room temperature or slightly elevated temperature, in particular 30 to 60 ⁰ C, through.

Purely for the extraction of aromatic hydrocarbons

All known per se come to the method _{according to the invention}

W '-

Working methods for the decomposition of hydrocarbons with the help of selective solvents are being considered. In addition to liquid-liquid extraction or countercurrent distribution, the methods of extractive distillation or countercurrent washing can also be used. It can also be useful to combine these working methods. In order to obtain pure aromatics, it is advantageous in the case of Plüssig-Plüssig extraction to work with a backflow, for example on aromatics. Since the aromatics and the piperazines in W are generally completely miscible with each other, the extractant advantageously so much water is added that a Misehungslücke occurs. It can also be useful, with a return flow of another connection, z. B. a hydrocarbon _; from a suitable boiling point to .work. But you can also put water or another solvent in the separation apparatus and generate the return flow within the Iqlonne itself. As so-called auxiliary solvents, it is advantageous to use aliphatic hydrocarbons, such as

■ ■ ■ ■ ■ i_ ^: γ «."

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Propane, butane, pentane or isooctane.

The parts specified in the following example are optional parts. They behave on the clearing parts like kilograms stt, Iilter; ,. :: _; . . "\\:. -, ...

^: ' ' - ^ - i -.:■■-■ -Example ■ ' ^:: _ ". ■:" ■ - "■

A mixture consisting of 50 parts of n-flexan, 60 parts of cyclohexane, 10 parts of cyclohexene and .30 parts of bengol in an amount of 200 parts per hour is introduced into the middle of a 3 m long sieve tray column Parts of N-formyl-IT ¹ -methylpiperazine, which contains 10% by weight of water, and 400 parts of isooctane per hour are added at the lower end of the column. To improve the extraction effect, the liquid column is set in pulsing motion. The extraction temperature is 40 °. At the upper end of the column, a raffinate is drawn off which contains less than 1% of benzene. The extract drawn off in the lower part of the column has the following composition after the isooctane and the extraction medium have been separated off:

Benzene 99.8% by weight, cyclohexene 0.1% by weight, cyclohexane 0.1% by weight, Hexane 0.05

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Claims (1)

- 8 - O.Z. 25th Claim Process for the production of aromatic hydrocarbons; from hydrocarbon mixtures which contain paraffins and optionally olefins and / or naphthenes, by treatment with piperazines as extraction agents, according to known extraction processes, characterized in that piperazine derivatives of the general formula ₂ - CH ₂
XN ■ NO CH ₂ - CH ₂ in which X denotes a pormyl or acetyl radical and R denotes is a lower alkyl radical, used as an extractant. * Badische Anilin- & Soda-Fabrik AG 009832/1754