DE2049104A1 - Process for the production of potassium p-hydroxybenzoate - Google Patents

Description

Case MC - 2
1 A - 201

Mitsubishi Chemical Industries Limited, Tokyo, Japan

Process for the production of potassium phydroxybenzoate

The invention relates to a process for the preparation of potassium p-hydroxybenzoate by reacting potassium phenate and carbon dioxide at elevated temperature.

p-Hydroxybenzoic acid is of great importance as a starting material for fibers of the polyester-ether type and also as an additive for the division of copolyesters, it has been implemented so far made of alkali phenolate and carbon dioxide under high pressure, initially alkali p-hydroxybenzoate accrues, to which then the precipitation of p-hydroxybenzoic acid Hydrochloric acid, sulfuric acid or acetic acid must be added. This procedure is called the Colbe-Schmidt procedure known.

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However, this method has several disadvantages. Of the main disadvantage is that a starting material in the solid state "reacted at high temperatures and high pressure and mixed with the carbon dioxide. This makes the process conditions very difficult. In addition, it has been very difficult or impossible to operate this conventional process in a continuous system. Accordingly, this method has heretofore been exclusive applied in batch operation.

The object of the present invention is therefore to provide a method to create ren for the production of potassium p-hydroxybenzoate, which can be carried out easily, reproducibly and with high yields and which can be used for batch operation as well as for continuous operation.

This object is achieved in that the Reaction in a single-phase, liquid reaction medium Potassium phenol at, phenol and an auxiliary smediuin carried out is, the auxiliary medium under the Heaktionsbedingungen is inert, is miscible with phenol and im is essentially immiscible.

The method according to the invention has the essential advantage that it can be carried out easily and without cumbersome mixing processes can be and leads in high yields to an extremely pure product, which can be implemented immediately can, e.g. to oopolyesters or to polyester-ether material. Furthermore, the continuous one is also successful with such a method Operation easily.

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^BATH

Ss is essential for the inventive method that the liquid single-phase system consists of potassium phenolate, phenol and an auxiliary medium which is miscible with phenol, however, essentially immiscible with potassium phenate and, on the other hand, miscible with the mixture of potassium phenate and Phenol.

The auxiliary medium miscible with the mixture of potassium phenolate and phenol should be liquid under normal conditions, but at least under the reaction conditions, and be stable under the reaction conditions and under the conditions of the formation of potassium phenolate from phenol and potassium hydroxide with separation of water. The auxiliary medium should not or not substantially dissolve potassium phenolate, but it should be miscible with phenol in almost any ratio. Preferred auxiliary media are, for example, aromatic hydrocarbons, such as, for example, alkylbenzene, for example xylene, trimethylbenzene; Alkylnaphthalene, for example ^ - or β -methylnaphthalene, dimethylnaphthalene and diphenyl; aromatic ethers such as diphenyl ether; aromatic halides such as polychlorodiphenyl. Among the aromatic halides, aromatic chlorides and aromatic bromides are preferred.

JSs can also use aliphatic hydrocarbons as an auxiliary medium be used. Here, too, it must of course be required that the aliphatic hydrocarbon which can be used as an auxiliary medium able to form a single liquid phase with potassium phenolate and phenol. When carrying out the invention Process on an industrial scale must be required that the auxiliary medium; is cheap. Of course you can too Mixtures of the substances mentioned which can be used as auxiliary media come into use. Thus, in general, mixtures of aromatic hydrocarbons and / or aliphatic

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EAD ORiGfNAL

20491

table hydrocarbons and / or other derivatives Use of "

The ratio of potassium phenol, phenol and the auxiliary medium should be "selected so that a single liquid phase is formed under the reaction conditions". The amount of Potassium phenolate should generally be chosen to be quite high, so that the size of the apparatus can be kept within limits can. If sodium phenolate is reacted with carbon dioxide in a similar reaction, a high proportion is obtained of sodium salicylate. Accordingly, should "in the invention Process the alkali phenolate essentially from potassium phenolate exist.

In the process of the present invention, the amount of auxiliary medium is usually 0.2 to 20 parts by weight based on 1 part by weight of potassium phenol and the required amount of phenol is usually 0.1 to 45 mol based on 1 mole of potassium phenol. If an aromatic compound such as alkylbenzene, alkylnaphthalene or diphenyl is used as the auxiliary medium, the amount of auxiliary medium is usually 2 to 20 parts by weight, preferably 3 to 8 parts by weight, based on 1 part by weight of potassium phenolate. If the amount of auxiliary medium is relatively small, the addition of a larger amount of phenol is necessary, which leads to an increase in the side reactions. If the amount of the auxiliary medium is relatively large, the concentration of the potassium phenate becomes too low for the reaction to be carried out on an industrial scale. If an aromatic compound is used as the auxiliary medium, the amount of phenol added can be smaller. It is in this case usually 0 _f 5-3 »Ö mol, preferably 1.0 to 2.5 mol, based on 1 mol Kaliumphenolät. Higher concentrations of phenol can also be used. However, this often leads to lifting reactions, especially the formation of potassium salicylate. Therefore it is not preferable to have a large over-

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finally add phenol. However, it is required enough Add phenol to obtain a single liquid solution phase of potassium phenolate, phenol and auxiliary medium. On the other hand, if no phenol is added, the amount is of potassium salicylate, which is formed via a side reaction, is also relatively high. If an aliphatic medium is used as the auxiliary medium Hydrocarbon is used, the amount of phenol required to realize a single liquid phase must be higher, such as about 1 to 40 moles relative to 1 mol potassium phenolate. In contrast, the amount of auxiliary medium be quite low, such as about 0.2 to .5 parts by weight, based on 1 part by weight of potassium phenolate.

If the reaction repair is too low or too high, a relatively large amount of potassium salicylate is formed in a subsequent reaction. Accordingly, it is preferred to more than 200 ° G, preferably to more than
heat up to about 220 to 250 ° C.

200 ° G, preferably to more than 220 ° C and in particular to

The salicylate yield is directly proportional to the carbon dioxide pressure; However, the yield of p-hydroxybenzoate is more than 60 "/ <> * at a pressure of 2 to 20 kg / cm. At atmospheric pressure, the yield of p-hydroxybenzoate is quite low a yield of more than 60 percent by weight of potassium p-hydroxybenzoate is achieved _o

Under the preferred conditions given, potassium hydroxybenzoate can be obtained in a purity of about 99% and in a yield of more than 60 % , and the side reaction with the formation of salicylate can be suppressed. In the following, a method will be described to produce the only liquid solution phase of potassium phenolate, phenol and auxiliary medium. By mixing the auxiliary medium and potassium phenolate, a slurry is initially obtained, since potassium phenolate does not dissolve in the auxiliary medium. If then gradually

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Phenol to this suspension of potassium phenolate in auxiliary medium is given, the potassium phenate becomes in the phenol dissolved. Two liquid phases are formed, namely an auxiliary medium phase and a phenol-potassium phenolate phase. If more phenol is added to the two liquid phases, a single liquid phase is ultimately obtained Phase of potassium benzolate, phenol and auxiliary medium.

As stated, can thus be the only liquid solution phase made of potassium phenolate, auxiliary medium and phenol, by first making a slurry of potassium phenolate

ψ produces in auxiliary medium and then adds suitable amounts of phenol, which depend on the type of auxiliary medium, the amount of the same and the temperature. For example, "can be used as auxiliary medium a mixture of 50 fo β -Methylnaphtalin, 25 fi oOMethylnaphtalin and 25 ° rf dimethylnaphthalene in various amounts of the potassium phenolate are admixed. In each jail there is a suspension of potassium phenate in the auxiliary medium. In the subsequent gradual addition of phenol to the slurry, two liquid phases are initially formed in each case only liquid

b phase off. In another embodiment, phenol is gradually added to a slurry of 15 ° potassium i and ^σ 85 / ο Alky! Benzene with stirring at 220 ° 0th If more than 2.2 mol of phenol are added to 1 mol of potassium phenolate, a single liquid phase is formed, whereby a state with two liquid phases is passed through first. In another example, phenol is gradually added to a slurry of 15 i "potassium phenolate and $ 85 of light mineral oil with stirring at 220 ° 0th Once on 1 mol of phenolate more than 6.7 mol

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Phenol come, arises after passing through a Zweiphasenflüswigkeit a single liquid phase one _o

Potassium phenate is generally produced by neutralizing phenol with potassium hydroxide. That is why what is so gained contains Ealium pheiiolate moisture. However, it is important to "■■ -" " that one in the preparation of the only liquid solution phase Ealiumphenolate anhydrous is used because the moisture causes the formation of a single liquid phase of Ealiumphenolate, Phenol and auxiliary medium prevented. It also decomposes oich the formed Ealium-p-hydroxybenzoate with the formation of Potassium carbonate if there is moisture in the reaction system or the Ealium p-hydroxybenzoate does not even form. Since potassium plienolate is hygroscopic, it must be the same for the production of anhydrous potassium phenolate to quite high Temperatures are heated. On the other hand, anhydrous decomposes Ealium phenolate readily in the presence of air. Therefore requires the dehydration of potassium plienolate a careful and comprehensive way of working «,

3s, however, it has been found that the drainage of Potassium phenolate can easily be carried out by azeotropic distillation in the presence of the inert auxiliary medium. In these In the event, a suspension of potassium phenolate arises in the Auxiliary medium. In a modified procedure one can Disperse moisture-containing potassium phenate in the auxiliary medium and add a suitable amount of Phaiol, whereupon a mixture of water, phenol and auxiliary medium is distilled off azeotropically to dehydrate the potassium phenolate. At the bottom of the distillation column or tower the only liquid solution phase of potassium phenolate, phenol and auxiliary medium is obtained.

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As noted above, the only liquid solution phase composed of potassium phenolate, phenol and auxiliary medium can be added by adding an appropriate amount of phenol to the mixture of anhydrous potassium phenate and the auxiliary medium. at an industrial process an appropriate amount of Pheiol added to the suspension of potassium phenolate in the auxiliary medium, which is dehydrated by azeotropic distillation of the mixture containing moisture. From an economic point of view, a mixture of potassium phenolate, Phenol and auxiliary medium are distilled azeotropically.

To produce potassium p-hydroxybenzoate, carbon dioxide becomes the only liquid at a temperature of 220 to 250 ° C Solution phase introduced. The reaction temperature depends in each case on the specific type of auxiliary medium, the amount of phenol and the carbon dioxide pressure. The reaction temperature is not limited to the specified range, the carbon dioxide pressure generally ranges from two to twenty atmospheres. However, it is not limited to this area.

That resulting from the reaction of potassium phenolate and carbon dioxide Potassium p-hydroxybenzoate does not dissolve in the auxiliary medium or in phenol. Therefore, the resulting potassium phydroxybenzoate falls as a precipitate. Accordingly, the solid potassium p-hydroxybenzoate can be easily prepared by conventional methods Separation, such as obtained by filtration. Pure p-hydroxybenzoic acid can be obtained by removing the precipitate dissolves of potassium p-hydroxybenzoate in water and separates it out again by adding acid. To dissolve the received Potassium p-hydroxybeiizoats in water, can do that with a The high temperature product is first cooled and then poured into water, as is the case with the conventional one

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Process for the production of p-hydroxybenzoate in a gas-phase gas phase reaction system happens. According to the present invention, however, it is preferred that the obtained one High temperature product without prior cooling. In water or in an aqueous solution of chewing p-hydroxybenzoate to bring in. There is less decomposition of the end product and the way of working is simplified. p-II-hydroxybenzoic acid can also be obtained by adding Yfesser to the mixture of reaction products, potassium p-hydroxybenzoate is then dissolved to separate p-hydroxybenzoic acid introduced an acid. The separated oil phase contains the phenol, which is used to produce the only one liquid phase was added, as well as an additional amount of phenol, which was generated as a by-product. Also contains the oil phase potassium phenolate.

The method according to the invention has the essential advantage that a continuous procedure in the reaction of potassium phenate with carbon dioxide can be achieved. Included it is particularly advantageous that the introduction of the raw materials can be accomplished uniformly and easily, and that dehydration and reaction in one simple device can be carried out. Furthermore, the degree of implementation of carbon dioxide with potassium phenolate very high if one according to the invention works with a single liquid phase. In addition, the degree of conversion of the potassium is very high and the amount of potassium used can be reduced, since almost all of the end product is made from the monocallum salt the hydroxybenzoic acid.

In the following, the invention is explained in more detail with the aid of exemplary embodiments.

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2043104

example 1

In an autoclave, which is provided with a stirrer and a ventilation channel, 22.9 kg of phenol, 6.97 kg of a 43.3 ^ strength potassium hydroxide solution and 48.2 kg of an inert auxiliary medium are placed, which consists of 50 fo 2-methylnaphthalene , 25 fo d -methylnaphthalene and 25 $ dimethylnaphthalene. The starting components are mixed and dehydrated by azeotropic distillation. The mixture turns into a single liquid solution phase when the temperature during the azeotropic distillation reaches a value of 230 ° 0. The solution then has the following composition: 7.93 kg of potassium phenolate, 9.15 kg of phenol and 35.6 kg of the auxiliary medium and less than 0.04 percent by weight of moisture.

The single-phase liquid solution obtained is 240 ° 0 with carbon dioxide of 10 kg / cm reacted for one hour. The compartment of the reaction is added to the cooled contents of the autoclave added water with stirring and the mixture is until separated the aqueous phase left to stand.

The aqueous phase contains 5.30 kg of p-hydroxybenzoic acid and fe 0.11 kg salicylic acid, calculated in the acid form. The yield is $ 64.3.

Example 2

In a 1 1 glass autoclave with a. An aqueous solution of 75 g of potassium phenate, which was concentrated ^{to 88 σ} /> at 180 ° G, is added to the stirrer. In addition, 400 g of a xylene mixture and 112 g of phenol are added to the autoclave under pressure. The Miuchun ^ · is dehydrated by azeotropic distillation under heating at a pressure of 3 to 10 kg / cra ^£ - G. As soon as the temperature of the azeotropic distillation reaches a value of 230 ° C, a single-phase liquid solution is formed. Dieoe a

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BATH ORIGINAL -1 '-

Pliasige liquid solution has the following composition: 66.1 g of potassium phenolate, 94 g of phenol and 330 g of xylene. The received Solution is at 230 ° 0 for one hour with Koh-

p O

Lendioxyd implemented with 5 kg / cm (total pressure 1.2.5 kg / cm). After the reaction, 200 ecm of water are added to the cooled The contents of the Autoclaveη are added with stirring and the mixture is left to stand until the aqueous phase has separated off. The aqueous phase contains 69 g of p-hydroxybenzoic acid and 1.1 g of salicylic acid, calculated in the acid form. The yield is 65, *.

Example 3

A mixture of 50 f 'f> -Methylnaphtalin, 25 $ οι -Methylnaphtalin and 25 ft Dimetliylnaplitalin is used as inert auxiliary medium. The inert auxiliary medium is admixed with 23 percent by weight phenol and passed through a preheater into a distillation tower at a rate of 100 kg / h. Simultaneously, a 48 sequence potassium hydroxide solution is introduced into the distillation tower through the preheater at a rate of 11.7 kg / hour. In the distillation tower, the temperature of the solution at the bottom is kept at 240 ° C. From the top of the distillation tower, water containing phenol and the auxiliary medium is distilled off. On the other hand, at the bottom of the distillation tower, the single-phase liquid solution of anhydrous potassium phenate is obtained at a rate of 101.2 kg / h. The solution has the following composition: 13 percent by weight of potassium pheiiolate, 13 percent by weight of phenol and 74 percent by weight of the auxiliary medium _{or the like}

The solution obtained is in an autoclave with an effective Volume of 100 1 given, which is equipped with a stirrer. At 240 ° C in the presence of a carbon dioxide

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pressure of 10 kg / cm carried out the reaction with carbon dioxide. After cooling the product obtained to 150 by using a heat exchanger, the product is in Water dissolved and separated at 30 kg / h. The aqueous phase contains potassium hydroxybenzoate and a small amount Phenol.

The phenol is removed by countercurrent extraction using xylene and the hydroxybenzoic acid is separated from the potassium p-hydroxybenzoate by adding an acid to the aqueous solution. The p-hydroxybenzoic acid is obtained at a rate of 8.28 kg / h, while salicylic acid is obtained at a rate of 0.17 kg / h. The yield is 61.2 fo.

The separated oil phase contains 14 percent by weight phenol » More phenol is added to this oil phase so that it contains 23 percent by weight phenol. Then the oil phase becomes again returned to the cycle.

Example 4

ψ A slurry of 66 g of potassium phenolate and 330 g of an inactive or inert auxiliary medium consisting of alkylbenals is placed in a 1 liter autoclave equipped with a stirrer. 94 g of phenol are then added to the slurry and the whole is heated to 235 ° C. so that a single phase liquid solution is formed. Carbon dioxide is introduced into the autoclave for one hour at a pressure of 5 kg / cm and caused to react. After the reaction, the product obtained is cooled and, while stirring, 200 ecm / '/ water are added. Then the two resulting phases wound separately »

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The aqueous P-has'e is extracted twice with 50 ecm benzene, around. to remove the phenol. Then 50 g of 35% hydrochloric acid are added added and the crystallizing p-hydroxybenzoe-. acid is separated off * The precipitate is filtered off at 10 ° G and washed with a small amount of water and dried. The crystal mass obtained weighs 42 g and contains 98 percent by weight p-hydroxybenzoic acid and 2 percent by weight salicylic acid. · ■ "

Example 5 "" - - "■

The procedure according to Example 4 is repeated, with instead the 330 g of alkylbehzol and 330 g of methylnaphthalene as an inert auxiliary medium can be used. The crystal mass obtained weighs 41 g and contains 97 percent by weight of p-hydroxybenzoic acid and 3 percent by weight salicylic acid.

Example 6 "'

In one with a stirrer and gas inlet port and an outlet port Equipped autoclaves with a capacity of 2 contain 94 g of phenol and 112 g of a 50% aqueous potassium hydroxide solution given. With the outlet nozzle open, the whole thing is heated to 180 ° C, with about 56 g of barrels evaporating. Then 420 g of a mixture of diphenyl ether and diphenyl (Dausum A, trade name) are introduced into the autoclave, so that a suspension arises. The slurry is on 240 ° 0, with about 18 g of water together with about 20 g of a mixture of diphenyl ether and diphenyl in the dehydration the Aufaohlemmung be distilled off.

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The Aurtoelav is then heated to 170 ° O u'iid! "- 188- gf ^ aiM ·: ιΐ Phenol are added. After heating to 240 ^{O <} O, carbon dioxide is released under a pressure of 5 kg / cm introduced "lüadl · ''--''- i the reaction is carried out for one hour '■;"The'' - ^ r-- ■ · '- ·' held product"'is cooled after the reaction has ended " ^r % lid:''-··> 400 ecm of water are added.'^;'UmgerühiH ^ unii''''*' is then left to stand for phase separation.

The aqueous phase is extracted three times with 50 ecm of benzene and 100 g of 35% hydrochloric acid are used to separate out a crisis stall meal added. The Kristallmas'se will be-i ^! 1O ^ C ab-; filtered and washed with a small amount of water and dried. The crystal mass obtained weighs 79 g and contains 99 percent by weight of p-hydroxybenzoic acid and 1 percent by weight of salicylic acid. * "'° ^;; ''

Example 7 '' ■■ '· ■ · '> · ■ ■ ■ '.- ■ .-. ι.: ': -,

The distillate mix obtained in the azeotropic distillation from the first distillation tower. ag, namely a mixture of 100 parts by weight of light mineral oil (boiling point 25 (Jbis' 300 ° C), 72 parts by weight of phenol 'and 2 parts by weight of water "' fc is introduced into a distillation tower at a rate of 12.3 kg / h wherein the temperature is maintained at the bottom of the tower by means of a Yorheizgerätes to 240 ° C _o Further, in this distillation tower phenol kg at a rate of 13.7 / h and a 48 ^ $ aqueous solution of potassium hydroxide at a speed of 1 ' 1.7 kg / h. All these components are mixed. At the top of the tower, water with a small amount of phenol and mineral oil is distilled off, while a single-phase liquid solution remains at the bottom of the tower, which contains 44.6 percent by weight of potassium phenolate .6 percent by weight phenol and 10.8 percent by weight mineral oil. This mixture is withdrawn at a rate of 29 »6 kg / h

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In a reactor with 100 1 effective volume, which .- ο is equipped with a stirrer, the obtained single-phase liquid solution at a rate of 29.6 kg / h and light mineral oil at a speed of 71.5 kg / h introduced and "reacts at 240 ° G, the carbon dioxide pressure is kept at 10 kg / cm.

The reaction product obtained was treated as in Example 3, p-Hji-droxybenzoic acid being obtained at a rate of 8.83 kg / h and salicylic acid at a rate of 0.14 kg / h. λ

The yield of p-II-hydroxybenzoic acid, based on potassium phenolate, is 64.7 mol fo and the yield of salicylic acid is 1 mol i *. The separated oil phase contains light mineral oil, phenol and water. This oil phase is subjected to a two-stage distillation, with v / ater being removed at the top of the first distillation tower and the light mineral oil being removed at the bottom of the second distillation tower and phenol at the top of the second distillation tower. The phenol obtained and the light mineral oil obtained are returned to the reaction cycle. The distillate mixture obtained in the first reaction tower is returned to the cycle as raw material

Example 8

A mixture of 100 parts by weight of dioctyl ether and 12 parts by weight Phenol is fed into a distillation tower according to Example 3 at a rate of 26.1 kg / h for dehydration introduced. At the same time phenol at a rate of 26.1 kg / h and a 48 $ solution (aqueous) of potassium hydroxide introduced at a rate of 11.7 kg / h.

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All components are mixed together. A single-phase liquid solution is produced at a rate of 38.5 kg / h. of 34.3 percent by weight of potassium phenolate, 46.0 percent by weight of phenol and 19.7 percent by weight of dfoctyl ether. received, ... _s

The obtained single-phase liquid. Solution is with a Ge .. _{; v} , flow rate of 38.5 kg / h in a reactor with 100 1 effec- _:

tive volume., At the same time, dietary ether, with; .., * introduced at a rate of 63.4 kg / h. The reactor is with a. Equipped with stirrer. The reaction is

^ Temperature conducted from 240 ° C and the carbon dioxide pressure is maintained ^w at 10 kg / cm '". The reaction product obtained is treated in the same manner as in Example 2, using p-hydroxybenzoic h at a rate of 8.71 kg / and salicylic acid at a rate of 0.19 kg / h, the yield of p-hydroxybenzoic acid based on potassium phenate is 63.1 mol fo and the yield of salicylic acid is 1.4 mol ^c / o.

A portion of the separated oil phase is recycled as raw material back into the circuit and the rest of the oil phase is subjected to distillation to Dioktyläher and phenol ■ to separate from one another, which respectively in the reactor are recycled to the Rohma-P terialquelle _0th

The following is intended to illustrate the advantages of the present invention explained by test:

Under a pressure of 10 kg / cm standing on carbon dioxide is a schlemmung of potassium phenolate and .the auxiliary smed ium consisting of 50% ^ -Methylnaphtalin, 25 f "qI -Methylnaphtalin and 25 fo dimethylnaphthalene at 240 ° C for one hour, reacted . The yield of p-hydroxybenzoic acid is $ 52.

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At IiBPECTED

Claims (1)

ΡΑΪ EF TA IT SPB ΐϊ QR I. it) procedure. zttr Berc-t ^ lltang von- Ealittn ^ ph ^ 'droxybenzoat by uranium netun-g' from Eäüiiünph @ iiöiat and carbon dioxide at -higher temperature _f d ¹ a du r σ h ge fc e η η ζ ο i oh η et ^; _tl that the etafctiön is carried out in a single-phase fliiösipen Eeaktion: ^ i-iediutii from iCaliu (.! phe.nol & t |, phenol and an auxiliary medium; ^ wob @ i the egg if smediun ur-ter the,! e-Aktionäbedineungen inert iatj rn Can be isolated with phenol and is essentially immiscible with potassium phenolate * 2 ») method n-aoti Anspidöh H ^ thereby ^ e Iz & η η ζ ¹ ei ο h η et ■ _t that the reaction Ewisöhen irohlenfliöx.yd Uöd the Röaktionsrnedium kontimrisrlier, carried out v / irü * 3 ») Ancestors according to one of claims 1 or 2 * d · -: ·. by geke η η Μ eich ή et ^ that the action is carried out at a temperature of 22 ° to ?. $ 0 ^Ö 0 and preferably at a pressure of 2 bic 20 atmospheres _; 4 ») Verfahfsii ftaeh elilim the Ärtöprüehe 1 to 3t characterized känhgeiöhh g © £ t _f daÖ the single phase liquid" produced liäktionsfflidiüm * _# ird by Ivaliumphenolaf ! fiÄBtillatiön in Oögönwai't des and then Phtilol admits * 5 ») ancestors close to one of the claims 1 to 31 thereby g e fc θ η h fe e I ö h η e t j that the single-phase reactions medium is produced »by making a rit-cliun ^ from ittiliu phenolate | Phenol and auxiliary medium with azeotropic distillation freed from weighing content * BAD ORIGINAL t <) 9 325/220 A "" ■■ ■ ^ 60) Method according to one of claims 1 to 5, characterized -characterized that the in the reaction of KaliuBip.her.ol at reaction mixture produced with carbon dioxide Loat high temperature in water or ir. an aqueous solution is washed in by EaliuK-p-hydroyvbenzoate. 7o) Method according to one of claims 1 ■ to 6, characterized in that G e ic. e η η ν, calibrates that the reaction is continuously dui'chgeff.üirt by adding a mixture of potassium cyanide, phenol and auxiliary medium for denydration and the formation of a single-phase solution of potassium phenolate, auxiliary medium and phenol in one Brings in the distillation tower, v; ona.ch the single-phase reaction medium is reacted with carbon dioxide under pressure and at increased temperature, and whereupon the reaction product is finally mixed with water, v ^ obei eich αερ 'potassium p-hydroxybenaoate formed in the Vaoeer i) Hase dissolves and an oil phase containing the excess phenol and the auxiliary medium separates, which is returned to the reaction cycle. 1 0 ·, j 2 ;, / ■>■> η /. . ^{8AD CRIGINAI} -