DE2830144C2 - Process for the production of sebacic acid from adipic acid - Google Patents

Description

The invention relates to a process for the production of sebacic acid from adipic acid by electrolytic Condensation of monomethyl adipate.

Electrochemical condensation retardations of carboxylic acids are commonly called the Kolbe reaction and for example by H. Kolbe in Ann. 69

2CHjOOC (CH ₂ ) ₄ COCr

- 2nd

In the usual procedures, the individual stages can be carried out as follows, for example: Monomethyl adipate is produced by the half-esterification of adipic acid with methanol in the absence of a Catalyst or prepared in the presence of an acid catalyst (Japanese Patent Laid-Open 00 024/74). The electrolytic condensation of monomethyl adipate takes place by dissolving monomethyl adipate in a methanol solution and electrolysis of the partially with an alkali, e.g. B. Potassium Hydroxide,

(1849) 257 and A.C. Brown in Ann. 261 (1891) 107 described. An example of the Kolbe reaction is the production of dimethyl sebacate from monomethyl adipate The reaction at the anode can be represented by the following equation:

For the large-scale production of sebacic acid from adipic acid, the following three steps must be carried out be performed:

1) In the first stage, monomethyl adipate is formed.

2) In the second stage, dimethyl sebacate is made from monomethyl adipate by electrolytic condensation and separating and purifying dimethyl sebacate from the electrolytic solution containing dimethyl sebacate

3) In the third stage, sebacic acid is formed.

CH ₃ OOC (CH ₂ ) SCOOCh ₃ + 2CO ₂

45 neutralized solution to form an electrolyte solution, ζ. B. a methanol solution containing monomethyl adipate and its alkali salt, dimethyl sebacate and trace amounts of by-products such as dimethyl adipate, methyl n-valerate, methyl α> -hydroxyvalerate, methyl allyl acetate, and subsequent separation of the electrolysis product in the electrolyte solution from the monomethyl adipate used and its alkali salt Dimethyl sebacate by extraction (US Pat. No. 3,896,011). Sebacic acid is obtained by hydrolysis of the dimethyl sebacate separated and purified in this way in the presence of an acid catalyst (US Pat. No. 3,896,011).

The major deficiency lies in the large-scale production of sebacic acid by the usual process in the second stage, in which the dimethyl sebacate from the electrolyte solution containing the dimethyl sebacate is separated. The separation of the dimethyl sebacate from the electrolyte solution containing the dimethyl sebacate can be done by methods such as distillation, crystallization, extraction '. The separation by distillation however, has the disadvantage that dimethyl sebacate and monomethyl adipate are obtained as an azeotropic mixture, see above

that it is not expedient to carry out the separation by distillation. In the crystallization process must be operated at a low temperature, so that there is a disadvantage that contamination unavoidable with monomethyl adipate and its alkali salt during the crystallization of dimethyl sebacate Therefore, an extrative separation process is used in which water, hexane or heptane is used Electrolyte solution is added. When using water as the extractant, this method has However, there is the disadvantage that a large amount of water must be used and the separation of the oil layer and the water layer after extraction due to a very small difference in the specific gravity of the two layers is very difficult. The use of an organic solvent such as n-heptane as the Extractant has the disadvantage that inevitably more than an insignificant amount of monomethyl adipate passes into the n-heptane layer According to the latest process, which is described in US-PS 38 96 011, the separation of high purity dimethyl sebacate is successful using a relatively small amount of an extractant, namely with the addition of an organic solvent that the Dimethyl sebacate dissolves, but does not dissolve water, along with water for electrolyte solution and separation after carried out a certain contact time. But even with the latest method mentioned above, there are the problems of the usual procedures not fundamentally solved. The reintroduction of water and jo an organic solvent in the system is inevitable, and more than a moderate amount of one Extraction solvent is required to separate high purity dimethyl sebacate. These are the Disadvantages of the latter method. r>

In an effort to eliminate the disadvantages of the conventional methods, it has now been found that Monomethyl adipate separated in the electrolyte solution by adsorption on an anion exchanger, an alkali salt of monomethyl adipate by extraction with an extremely small amount of water or by adsorption on a cation exchanger as alkali metal ions separated and also easily adsorbed on the anion exchanger monomethyl adipate Methanol or water present in the system · * ■ "> can be regenerated and the alkali metal ions adsorbed on the cation exchanger easily through Monomethyl adipate and / or a methanol solution containing monomethyl adipate present in the system can be regenerated. As a result, it has become possible to use dimethyl sebacate from monomethyl adipate and its alkali salt can be easily separated and highly pure dimethyl sebacate can be obtained without a organic solvent and water are reintroduced into the system or with some> 5 Only a very small amount of water is introduced into the system.

The invention accordingly provides a process according to claim 1. Preferred embodiments are subject of the dependent claims 2 to 6. The invention to be described below with reference to the drawings.

F i g. 1 shows a flow diagram of a for carrying out the first step a) according to the invention appropriate procedure; b5

Figure 2 graphically illustrates the relationship between iron ion concentration or cyclopentanone concentration in the reaction solution and the time in the first stage a) of the process according to the invention described in Example 5 and Example 6;

F i g. Figure 3 shows a flow diagram of a for carrying out steps b) and c) according to the invention suitable method, the removal of methanol from the electrolyte solution, treatment with Water and the treatment with an anion exchanger in the fixed bed are carried out in this order will;

F i g. FIG. 4 shows a flow sheet for carrying out steps b) and c) of the method according to FIG Invention suitable method in which a treatment with a cation exchanger in a fixed bed followed by a gradual anion exchange treatment;

F i g. 5 shows a method suitable for carrying out steps b) and c) according to the invention, at that the cation exchange treatment and the anion exchange treatment are carried out at the same time.

The first stage of the process according to the invention, in which monomethyl adipate is formed by the half-esterification of adipic acid, is described in detail below.

In general, a solution containing adipic acid and methanol is sufficient as exhaust material. To the Suppressing formation of dimethyl adipate and preferentially forming monomethyl adipate is preferred used as a starting material, a solution containing 1 mole of adipic acid, 0.2 to 2 moles of dimethyl adipate, 0.5 to Contains 5 moles of methanol and 1 to 10 moles of water.

The reaction can be carried out using an acid catalyst, for example a mineral acid such as Sulfuric acid, hydrochloric acid or nitric acid or an organic sulfonic acid, e.g. B. p-toluenesulfonic acid, be performed. In this case, the reaction conditions are not subject to any particular limitation, however, the reaction is preferably carried out under a pressure of 0.98 bar or more and at a temperature carried out at 50 ° C or more. The reaction can also be carried out in the absence of a catalyst will. In this case, preferably at high temperatures under pressure, e.g. B. under a pressure of 1.96 to 4.7 bar, and a temperature of 120 to 200 ° C worked. It is preferred to take the reaction Carry out use of a strongly acidic cation exchange resin as the acidic catalyst. In this Case has the use of a strongly acidic cation exchange resin versus the use of a mineral acid or an organic sulfonic acid as Catalyst a disadvantage in terms of the catalytic activity, but the advantage in terms of Corrosion of the reactor and the separation of the reaction product from the catalyst. Furthermore, the Using a catalyst is definitely disadvantageous compared to working without a catalyst, but be advantageous from the standpoint of the reaction conditions and the formation of by-products.

When working without a catalyst, the reaction must be carried out at high temperatures under pressure for a long time. Further, when the production of monomethyl adipate is carried out on an industrial scale for a long time under these conditions, the formation of cyclopentanone as a by-product increases as shown by curve A in FIG. 2 shows. The formation of high-boiling compounds as by-products also increases. This by-product formation is caused by trace amounts of metal *

ions, especially iron ions, that are released from the reactor itself into the reaction solution by the reaction taking strict conditions, e.g. B. at high temperatures under pressure, are released and as a catalyst with the formation of cyclopentanone and high-boiling compounds are effective. In the It is common practice to use unreacted adipic acid during the large-scale production of monomethyl adipate Separate purification of the monomethyl adipate and return it to the starting solution. In such a Case also shows that metal ions not only come from the reactor, but also from a still released during the purification of the monomethyl adipate. Taking these facts into account is a mode of operation in which the strongly acidic cation exchange resin acts as a catalyst in the large-scale production of monomethyl adipate is used most advantageously.

Examples of suitable strongly acidic cation exchange resins are polystyrene resins, e.g. B. styrene-divinylbenzene copolymers, which contain sulfonic acid groups and either a gel structure or a pore structure exhibit. For the continuous implementation of the esterification reaction and for effective utilization Due to the activity of the cation exchange resin, the resin must be used as a fixed bed. If that strong acidic cation exchange resin is used continuously for a long time, takes place gradually Decrease in the catalytic activity of the resin during esterification due to an increase in the amount of am Resin adsorbed metal ions instead. In such a case, the cation exchange resin can after a usual, widely used procedures, e.g. B. by regeneration with aqueous nitric acid solution, regenerated and reused.

As to the reaction temperature in the filled with the strongly acidic cation exchange resin packed bed, so higher temperatures from the standpoint of reaction rate are more effective, however, in consideration of heat resistance of the resin is at a temperature of 12O ⁰ C or less, especially of 90 "C or less, preferable However, since a longer reaction time is required if the reaction temperature is too low, a temperature of 60 ° to 90 ° C. is preferred in practice

On the other hand, when the solution used as the starting material by the strongly acidic Cation exchange resin filled fixed bed is passed, a separation of adipic acid from the as Starting material used solution at the operating temperature of the fixed bed is unfavorable. The deposition of adipic acid from the starting solution can be prevented if the amounts of the solvent such as methanol, water and dimethyl adipate are kept above a certain minimum amount. the However, the use of solvents in large excess is inexpedient as a result of the necessity Removal of the solvents during the separation of the monomethyl adipate from the reaction solution and his purification. To prevent the excretion of adipic acid from the starting solution without the use of a to prevent large excess of solvent, must therefore a deficit of the solvent in the starting solution by recycling part of the Expiration from the fixed bed can be supplemented. The circulated amount of the runoff from the fixed bed is different depending on the amounts of adipic acid and solvents in the starting solution

sung as well as the temperature of the fixed bed and cannot be limited, but it is sufficient to to avoid the separation of adipic acid from the starting solution. Furthermore, the flow rate is subject the starting solution through the fixed bed is not particularly limited, but the flow rate is preferably chosen so that the esterification reaction in the fixed bed to almost equilibrium can run.

An example of the method for producing monomethyl adipate using a stark acidic cation exchange resin as a catalyst is described below with reference to the method shown in FIG. 1 shown flow chart. Adipic acid and methanol are poured into a dissolution vessel 1 an inlet 7 introduced. Methanol and water removed from the distillation column 4 overhead are, dimethyl adipate and water, which are removed from the distillation column 5 overhead, Adipic acid and monomethyl adipate taken from the bottom of the distillation column 6 and a Part of the reaction solution drawn off from an outlet opening 8 is circulated into the dissolution vessel 1 returned. Adipic acid is dissolved in the dissolution vessel 1 and at the top of the Abandoned ion exchange resin column 2 as the starting solution. Find in column 2 the ion exchange resin Adsorption of trace amounts of metal ions and part of the esterification reaction take place. From the foot of the Ion exchange column 2, the liquid from which the metal ions have been removed is removed and abandoned on top of the ion exchange resin column 3, in which the esterification reaction mainly takes place. The resin in the ion exchange column 2 must after a conventional regeneration process, for example regenerated using an aqueous nitric acid solution if the allowable concentration of the metal ions in the liquid which is withdrawn from the ion exchange column 2 is exceeded will. Since the adsorption of metal ions and the esterification reaction are separated using two ion exchange resin columns are carried out, the regulation of the ion exchange column is very easy. From the foot of the ion exchange column 3 is the The esterification reaction solution is drawn off and partly through the discharge line 8 to the dissolution vessel 1 returned and partly led to the distillation column 4. The concentrations of cyclopentanone and Iron ion in the esterification reaction solution with the passage of time can be kept very low, like that Curves C and Din F i g. 2 show. In the distillation column 4, methanol and water are distilled off, and the liquid residue is removed from the bottom of column 4 withdrawn and applied to the distillation column 5 The methanol and the water, which from the Distillation column 4 pass overhead, are returned to the dissolution vessel 1 in the distillation column 5 dimethyl adipate and water are distilled off. The liquid residue is off the bottom the column 5 withdrawn and given to the distillation column 6. The dimethyl adipate and the Water withdrawn from the top of the distillation column 5 is separated into two layers After some of the water has been removed through the discharge line 9, the residue is returned to the dissolution vessel 1. Monomethyl adipate is released from the Obtained head of the distillation column 6, and the liquid containing adipic acid and monomethyl adipate

ge residue is withdrawn from the column as bottom product and returned to dissolution vessel 1.

The production of dimethyl sebacate by electrolytic Condensation in the second stage b) of the process according to the invention from that in the first The monomethyl adipate obtained at the stage is described in detail below.

The electrolyte solution to be used in electrolytic condensation contains monomethyl adipate and its neutralized salt, dimethyl sebacate and methanol.

As for the water concentration in the electrolytic solution, is the relationship between water concentration and current efficiency, water concentration and product yield known (e.g. from Journal of Applied Chemistry (U.S.S.R.) 38 (1956) 1776). To the current yield and to keep the product yield high, the water concentration must be 5% by volume or less be lowered. It is also assumed that the maximum current efficiency and material efficiency achieved can be achieved by lowering the water concentration as much as possible. However, it was surprising found that an extreme lowering of the water concentration the current yield after a Number of attempts rather reduced. As Table 3 in Example 13 shows, the current yield drops considerably, when the water concentration in the electrolyte solution falls below 0.15% by weight. On the other hand it was found that at a water concentration of more than 5.0% by weight the current yield and the product yield also sink. In order to keep the current yield and the product yield high, the The water concentration in the electrolyte solution must be kept in the range from 0.15 to 3.0% by weight.

In order to increase the electrical conductivity of the electrolyte solution, hydroxides, Carbonates. Bicarbonates, methylates and ethylates of sodium, potassium or lithium or amines are used will. However, since an amine is oxidized on the anode to accelerate the consumption of the anode and the use of a lithium compound lowers the current yield, hydroxides are preferred, Carbonates, bicarbonates or methyls of Uses sodium or potassium.

The degree of neutralization of the monomethyl adipate (defined as the molar amount for the neutralization of the Monomethyl adipate with a base) is preferably 10 to 60 mol%, in particular 20 to 50 mol%. If the degree of neutralization is less than 10 mol%, the voltage increases, and above 60 Mol% decreases the current yield.

The concentration of dimethyl sebacate in the electrolyte solution is preferably 5 to 40% by weight, in particular 10 to 30% by weight. If the concentration is below 5% by weight, the current efficiency is low, while at a concentration of more than 40% by weight, the tension increases (US Pat. No. 3,896,011).

Any electrolysis cells commonly used for organic electrolytic reactions and to pass an electrolyte solution between two electrodes at a high flow rate ability are suitable for the purposes of the invention. For example, an electrolysis cell that has a Cathode plate and an anode plate aligned parallel to it and one between the electrodes arranged polyethylene plate to determine the distance between the two electrodes included. The polyethylene plate has in its central part an opening zone for the passage of the electrolyte solution. The area of the electrodes through which current flows is dependent on the area of the opening zone and depending on the thickness of the polyethylene sheet

^r i electrode spacing determined. The electrolyte solution is introduced through an inlet opening of the electrolysis cell, passed between the two electrodes while the reaction is being brought about, and after leaving the cell through an outlet to one

ι ti electrolyte solution container returned.

As materials for the electrodes, platinum, rhodium, ruthenium, iridium can be used alone or as an alloy can be used for the anode. These metals are generally galvanized using

! ι dung of titanium, tantalum used as a substrate. as Cathodes are preferred with low hydrogen overvoltage, but the cathode is not necessarily limited to that. Platinum, iron, stainless steel, titanium can be used as the cathode.

: ii The flow rate of the electrolyte solution in the electrolysis cell is preferably 1 to 4 m / second, in particular 1 to 3 m / second. if the flow velocity is less than 1 m / second, the current yield decreases, while with flow

_ '■> ming speeds of more than 4 m / second the Pressure loss in the electrolysis cell is greater (US-PS 38 96 011).

The distance between the electrodes is preferably 0.5 to 3 mm, in particular 0.5 to 2 mm.

jo If the distance is less than 0.5 mm, the Pressure loss in the electrolysis cell is greater, while at a distance of more than 3 mm the voltage increases (US-PS 38 96 011).

The current density is preferably 5 to

;> 40 A / dm ² , especially 10 to 30 A / dm ² . If the current density is less than 5 A / dm ² , the current yield drops (US Pat. No. 3,896,011).

The temperature of the electrolyte solution is preferably 45 to 65.degree. C., in particular 50 to ^60.degree. C. If

w the temperature is lower than 45 ° C, the will decrease

Current efficiency and the voltage increases. Temperatures above 65 ^° C. are limited by the boiling point of the electrolyte solution (US Pat. No. 3,896,011).

The separation of the dimethyl sebacate in stage c)

• »ι from the solution containing the dimethyl sebacate, the in the above-described electrolytic condensation in the second stage of the process according to the invention, and the purification of the dimethyl sebacate is detailed below

, π described.

To obtain dimethyl sebacate from a rviethanol solution of the electrolyte solution, the rvionomeihyiadipat and its metal salt. Dimethyl sebacate and trace amounts of other by-products contain the the electrolytic condensation are formed, the following stages are necessary: a stage for Removal of the methanol by distillation, a step to separate the alkali metal salt from monomethyl adipate or alkali metal ions and a step for

bo separation of monomethyl adipate

The monomethyl adipate is separated from the electrolyte solution by treatment with a Anion exchanger.

For the anion exchange treatment, various

b5 different anion exchangers are used, however, an anion exchange resin is used in practice preferred. Strongly basic anion exchange resins with quaternary-

Ren ammonium groups as exchange groups, weakly or moderately strong base anion exchange resins with primary to tertiary amine groups as exchange groups. When methanol or hot water used as regenerants in the manner discussed below are weak or medium strength basic anion exchange resins technically advantageous, taking into account the Regeneration efficiency and heat resistance Of the resins, anion exchange resins of the tertiary amine type are particularly preferred. at Use of methanol as a regenerant can use strongly basic anion exchange resins Pyridinium groups as exchange groups in addition to weakly or moderately basic anion exchange resins are advantageously used technically.

When using weakly basic, moderately strongly basic anion exchange resins or anion exchange resins with pyridinium groups alone as the anion exchange resin or when using a such anion exchange resin together with a cation exchange resin as a mixed bed in the As explained below, the amount of methanol present must be kept as low as possible because the presence of methanol prevents the adsorption of monomethyl adipate on the anion exchange resin. In general, the concentration of the methanol in the fixed bed of the ion exchange resin supplied solution and in the remaining in the fixed bed. Solution at 5 wt% or less held. Therefore, in this case, the methanol must be removed from the electrolytic solution prior to the anion exchange treatment removed.

As a regenerating agent for the anion exchange resins, water or a hydrophilic organic solvent, e.g. B. methanol, ethanol, acetone and tetrahydrofuran can be used. A suitable regenerant on an industrial scale is methanol or heated water in the case of the treatment in combination with the water treatment and methanol in the case of the treatment in combination with the cation exchange treatment. The use of methanol is particularly preferred, since the methanol removed from the electrolyte solution can advantageously be used here. For regeneration, higher temperatures are preferred from the standpoint of the regeneration efficiency, but lower temperatures are preferable from the standpoint of the boiling points of the regenerants and the heat resistance of the resins. In general, preference is given to using methanol from room temperature to 60 ^° C. or hot water from 80 ^{° C.} to 90 ^° C. as a regenerant for weakly or moderately basic anion exchange resins. When using strongly basic anion exchange resins with quaternary ammonium groups as exchange groups, methanol from room temperature to 40 ^° C. is preferably used as the regenerant.

The next step is the separation of the alkali metal salt from monomethyl adipate or water treatment or cation exchange treatment of alkali metal ions is carried out.

The water treatment can be carried out before or after the anion exchange treatment or at the same time as you carried out using a fixed bed filled with an anion exchanger as the extraction column will. In either case, there will be the effect of extracting the alkali salt of monomethyl adipate by the water layer not changed, but the anion exchange treatment after the water treatment is dated Preferred from the standpoint of adsorption of the monomethyl adipate on the anion exchanger. Further must for separation an added aqueous solution in two layers during the water treatment, the methanol removed prior to water treatment. Therefore, the removal of methanol from the

ίο electrolyte solution, the water treatment and the anion exchange treatment in practice it is preferably carried out one after the other in this order. The one used for the extraction treatment with water The amount of water is sufficient if two layers are separated after the oil and water layers have been mixed can be, but are generally preferably 5 to 50 wt .-% water, based on the Weight of the electrolyte solution after removal of the methanol, used.

The cation exchange treatment in which only alkali metal ions are absorbed by an alkali salt be separated from monomethyl adipate to release the monomethyl adipate, is preferably before carried out the anion exchange treatment or

2S should at least concurrently with the anion exchange treatment be performed. Various cation exchangers can be used for the cation exchange treatment may be used, but a cation exchange resin is preferably used in practice applies when the cation exchange treatment is carried out alone. When the cation exchange treatment is carried out simultaneously with the anion exchange treatment, a mixed bed may advantageously be used from a cation exchange resin and an anion

ii exchange resin or preferably an amphoteric ion exchange resin having cation exchange groups and anion exchange groups can be used. There the presence of methanol hardly affects the effect of the cation exchange treatment

4 »the removal of the methanol in contrast to the aforementioned water treatment at any time during the cation exchange treatment be made.

The cation exchange resins used for the cation exchange treatment are not subject to any particular one Limitation, however, are weakly acidic or moderately acidic cation exchange resins in view on the regeneration efficiency technically advantageous if monomethyl adipate and / or a

w a solution of monomethyl adipate in methanol can be used as a regenerant. Of this are cation exchange resins of the acrylic acid type taking into account the exchangeability or iminodiacetic acid type from the weakly acidic ones

ο cation exchange resins and cation exchange resins of the phosphonic acid type preferred by the moderately acidic cation exchange resins

As a means of regenerating the cation exchange resins Monomethyl adipate and / or an aqueous solution or a hydrophilic organic solution are suitable Solvents such as methanol, ethanol, acetone, tetrahydrofuran, the monomethyl adipate contains of these are monomethyl adipate and / or a monomethyl adipate containing methanol solution technically preferred when the cation exchange resin together A mixed bed with the anion exchange resin used must be used as a regenerant Monomethyl adipate and methanol in that order

can be used as the regeneration of the cation exchange resin and the regeneration of the anion exchange resin can be carried out at the same time have to. Even with the use of methanol alone, the regeneration of the cation exchange resin is also achieved possible because monomethyl adipate is desorbed by regeneration of the anion exchange resin, forming a methanol solution of monomethyl adipate. As monomethyl adipate, this can be added to the Electrolytic reaction used starting material can be used. Containing as monomethyl adipate The drain from the regeneration of the anion exchange resin, and as a methanol solution, is suitable Methanol can be used as the methanol separated from the electrolyte solution so that it does not it is necessary to introduce a new regenerant into the system. The regeneration is from From the point of view of the efficiency of the regeneration, preferably carried out at higher temperatures, however, usually taking into account the boiling temperature of the regenerant and the Heat resistance of the resin worked at a temperature in the range from room temperature to 60 ° C.

The amphoteric ion exchange resin, which in the case is used to carry out the cation exchange treatment and the anion exchange treatment at the same time is not subject to any particular limitation. However, when using methanol as a regenerant is used, is preferably an amphoteric ion exchange resin, the weakly basic or contains moderately basic functional groups and weakly acidic functional groups, from the standpoint the efficiency of the regeneration is used. As weakly basic or moderately basic functional parts Primary to tertiary amines groups come in question, however, from the standpoint of interchangeability tertiary amines are preferably used. Functional groups come as weakly acidic functional groups Acrylic acid and methacrylic acid groups in question, but functional acrylic acid groups are from Interchangeability point of view preferred. Therefore, an amphoteric ion exchange resin, the tertiary Contains amine groups and functional acrylic acid groups, technically particularly preferred The quantitative ratio weakly basic or moderately strong basic functional groups to weakly acidic functional groups can be changed at will. The most favorable proportion will depend on the amount of monomethyl adipate and the amount of alkali metal ions that are added to adsorb and remove are selected.

If monomethyl adipate and alkali metal ions on the amphoteric ion exchange resin, the weakly basic or contains moderately basic functional groups and weakly acidic functional groups, to be adsorbed, the presence of methanol can cause the adsorption of monomethyl adipate prevent the weakly basic or moderately strong basic functional groups. To monomethyl adipate and to adsorb and separate alkali metal ions at the same time, therefore, the existing The amount of methanol should be kept as low as possible. In general, the methanol concentration is preferred in the solution placed on the fixed bed filled with the amphoteric ion exchange resin is abandoned, and adjusted in the remaining solution in the fixed bed to less than 5 wt .-% Therefore should in this case remove the methanol from

the electrolyte solution "before the supply to the fixed bed be made.

Suitable agents for regenerating the amphoteric ion exchange resin are water and hydrophilic ones organic solvents such as methanol, ethanol, acetone, tetrahydrofuran. Of this, methanol is in the industrial practice is preferred because the methanol removed from the electrolyte solution can be used can. From the standpoint of regeneration efficiency, regeneration temperatures are elevated preferable, however, the regeneration is done taking into account the boiling point of the regenerant and the heat resistance of the resin in general, preferably at one temperature carried out between room temperature and 60 ° C.

If the removal of menhanol is carried out before the ion exchange of anions and cations and methanol is used for the regeneration of the ion exchange resin, the im Regenerating agent remaining after the regeneration of the ion exchange resin be driven out. As a means for expelling the methanol, water or organic compounds, which have no affinity for water and are not adsorbed on the resin, e.g. B. dimethyl adipate and Dimethyl sebacate can be used. For large-scale production, taking into account the Post-treatments an electrolyte solution preferably made of methanol, monomethyl adiphate and be Metal salt have been removed. When performing the anion exchange treatment in combination with the Water treatment, water can be used as a solution to drive off.

The method for separating dimethyl sebacate from the electrolyte solution containing dimethyl sebacate and for the purification of the dimethyl sebacate is described below with reference to the flow sheets, in which the substitution stage, in which a regenerant solution in an ion exchange column remains, is omitted.

F i g. Figure 3 shows a flow sheet showing the water treatment and the anion exchange treatment in one Fixed bed illustrated as an example The electrolyte solution is placed between an electrolyte solution container 11 and an electrolysis cell 12 circulated. A part of the electrolyte solution in the electrolysis cell 12 is drawn off and fed to a distillation column 13. In the distillation column Ϊ3 is methanol removed while the remaining solution from the bottom of the column 13 is fed to a mixer 14. Water is fed in through inlet 15 and mixed with the remaining solution with sufficient stirring The mixture is then fed to a decanter 16 from the top of the Decanter 16, an oil layer containing dimethyl sebacate and monomethyl adipate is pulled off and Abandoned on top of the anion exchange resin column 17. In the column 17 is monomethyl adipate on Resin adsorbed and a solution containing dimethyl sebacate as the main component from the base of the Column 17 withdrawn. Highly pure dimethyl sebacate is obtained by further distillation. That by distillation Methanol passing over at the top of the distillation column 13 reaches the bottom of the anion exchange resin column 17 to recover the monomethyl adipate adsorbed on the resin, and then becomes in the circuit to the electrolyte solution container 11 for the Use returned to the Elektroivse reaction Vom

Bottom of the decanter 16 becomes an aqueous layer containing an alkali metal salt of monomethyl adipate contains, withdrawn a The aqueous layer is in the evaporator 18 in water and the Alkalisaiz of Monomethyl adipate separated The water is reused for extraction, and the alkali salt of Monomethyl adipate is returned to the electrolyte solution tank 11 to be used in the electrolysis reaction to be used.

F i g. 4 shows a flow chart and illustrates one Embodiment of the cation exchange treatment on a fixed bed and the anion exchange treatment on a fixed bed, with the cation exchange treatment stepwise before the anion exchange treatment is made. The electrolyte solution is between an electrolyte solution container 11 and an electrolysis cell 12 out in circulation. Part of the electrolyte solution in the electrolysis cell 12 is withdrawn and placed on top of a cation exchange resin column 23. In the column 23 are the Alkali metal ions are adsorbed on the resin, and the electrolytic solution from which the alkali metal ions have been removed is withdrawn from the lower end of the column 23 and applied to a distillation column 24. In the Distillation column 24 removes methanol. The remaining solution is from the bottom of the Column 24 withdrawn and placed on top of an anion exchange resin column 25. In column 25 monomethyl adipate is adsorbed on the resin, and a solution that is the main component dimethyl sebacate contains, is withdrawn from the foot of the column 25. Further distillation results in high purity Obtained dimethyl sebacate. The methanol passing over at the top of the distillation column 24 becomes at the bottom abandoned the anion exchange resin column 25 in order to remove the monomethyl adipate adsorbed on the resin in the column recovered, and withdrawn from the top of column 25. The base of the cation exchange resin column 23 apart from the monomethyl adipate, the amount of which is found in the electrolysis reaction corresponds to the amount consumed, fed through an inlet 26. In addition, the from the top of the anion exchange resin column 25 withdrawn methanol solution containing monomethyl adipate supplied, whereupon the on Resin adsorbed alkali metal ions in the solution can be recovered. A methanol solution that Menomethyl adipate and its alkali metal salt is withdrawn from the top of the column 23 and into the Electrolyte solution container 11 returned as an insert for the electrolysis reaction.

Fig. 5 shows a flow diagram, which as an example Embodiment of the cation exchange treatment on a fixed bed and the anion exchange treatment illustrated on a fixed bed with simultaneous implementation of both treatments. The electrolyte solution is circulated between an electrolyte solution container 11 and an electrolytic cell 12. A Part of the electrolyte solution in the electrolysis cell 12 is drawn off and transferred to a distillation column 33 given up. In the distillation column 33, methanol is removed. The remaining solution is from The bottom of the column 33 is withdrawn and placed on top of an ion exchange resin column 34. In the Ion exchange resin column 34 becomes monomethyl adipate and alkali metal ions on the amphoteric ion exchange resin adsorbed. A solution that contains dimethyl sebacate as its main component is from The foot of the column 34 is withdrawn. Through more

Highly pure dimethyl sebacate is obtained by distillation. The overflowing at the top of the distillation column 33 Methanol is fed to the foot of the ion exchange resin column 34, in which monomethyl adipate and alkali metal ions, adsorbed on the resin can be recovered in methanol. The monomethyl adipate and its alkali salt-containing methanol solution is withdrawn from the top of the column 34 and into the Electrolyte solution container 11 returned as an insert for the electrolysis reaction

There, as the later exemplary embodiments show, the ion exchange resin again after the regeneration Is adsorptive, the ion exchange columns can of course be operated continuously.

As already mentioned, the invention enables the separation of dimethyl sebacate from the electrolyte solution without simultaneous separation of monomethyl adipate and its alkali salt by a combination of the water treatment and the anion exchange treatment or by a combination of the cation exchange treatment and the anion exchange treatment in the separation of dimethyl sebacate from the electrolyte solution containing the dimethyl sebacate. Furthermore, by-products such as dimethyl adipate, methyl nvalerate, methyl aj-hydroxyl valerate, methyl allyl acetate, which are separated off with the dimethyl sebacate, can be separated off, for example by distillation. In contrast to conventional extraction processes in which a considerable amount of water and an organic solvent not present in the system are used to obtain high-purity dimethyl sebacate, the method according to the invention enables the production of extremely high-purity dimethyl sebacate without an organic solvent and water in the system or to be introduced, by making only a very small wat ^r nienge introduced into the system in order to extract an alkali metal salt of monomethyl adipate.

The hydrolysis of the separated and purified dimethyl sebacate in the second stage to form Sebacic acid in step d) of the process according to the invention is described in detail below.

As an embodiment of the hydrolysis reaction, the continuous reaction is disadvantageous. The batch Carrying out the reaction has the economic advantage that the reaction cannot be carried out without mixing converted materials such as monomethyl sebacate to perfection and the quality of the sebacic acid is increased.

The hydrolysis reaction can be carried out using a mineral acid such as nitric acid, sulfuric acid and hydrochloric acid or an organic sulfonic acid such as p-toluenesulfonic acid can be carried out as a catalyst. From the standpoint of corrosion of the materials of the reactor and the rate of reaction will preferably nitric acid is used as the catalyst. In this case, when dimethyl sebacate can be a aqueous acid catalyst solution with a concentration of 10 to 30% by weight in an amount which is lower is as the amount equivalent to the solubility of the sebacic acid in the aqueous acid catalyst solution at the hydrolysis temperature corresponds, added and the hydrolysis is carried out with removal of methanol, the Hydrolysis can be completed in a very short time. It is also possible to carry out the hydrolysis reaction, by first using water and then an aqueous nitric acid solution. In this! "All can hydrolysis using water that

in 4 times the weight of the dimethyl sebacate or added in a larger size, 2 to 5 Hours at a temperature of 220 ° to 280 ° C under a pressure of 34.3 to 49 bar and the hydrolysis using the aqueous nitric acid solution at a nitric acid concentration of 12 to 25 % By weight 0.5 to 1.5 hours at a temperature of 80 ° to 100 ° C. About the speed To increase the hydrolysis reaction, the hydrolysis reaction with the addition of sebacic acid, which formed as a reaction product, to the system for removing that formed by the reaction Methanol can be carried out of the system. This process has over that with nitric acid Process carried out as a catalyst has the disadvantage that the reaction rate is not very high, however, the process has numerous advantages: The reaction can take place at a relatively low temperature carried out and completed in one stage, while the reaction rate over one certain height is maintained. The separation of the catalyst from the sebacic acid formed is easy, and the methanol is not changed. When using nitric acid as a catalyst, the in reacts the reaction solution formed methanol with nitric acid to form methyl nitrate. This cannot can be completely prevented even if the methanol is removed from the system during the reaction. Furthermore, if the first half of the reaction is carried out without a catalyst, there is sebacic acid formed slightly or heavily discolored. When this reaction is carried out at high temperatures and high pressures becomes, the discoloration of the reaction product increases significantly. Taking into account the above mentioned factors is the method in which sebacic acid is added to the reaction system and the as a result, methanol formed is removed from the reaction system during the hydrolysis, for the industrial scale Production of sebacic acid by hydrolysis of dimethyl sebacate is particularly preferred.

The effect of adding sebacic acid to accelerate the hydrolysis reaction is in the first Half of the reaction in which two layers, i.e. H. a dimethyl sebacate layer and a water layer are present, considerable. As can be seen later in Table 3, as the amount of sebacic acid added increases, the The time until the reaction solution becomes uniform is shorter and the reaction is accelerated. But through Addition of excess sebacic acid worsens the volumetric efficiency of the reactor, is the sebacic acid in large-scale production in an amount of 1 to 20 wt .-%, based on the weight of the dimethyl sebacate, added.

To accelerate the hydrolysis reaction in a way other than by adding sebacic acid to the The methanol formed by the hydrolysis is continuously evaporated from the system System removed and at the same time continuously replenished the water removed together with the methanol. Furthermore, this mode of operation enables the reaction to be guided to completion. The removal of Methanol can occur immediately after the reaction, however the effect is in the second half of the Reaction in which the reaction solution is in the steady state and not as in the first half of the reaction in two layers, namely as a dimethyl sebacate layer and as a water layer, d. H. as an uneven solution is present, stronger. In addition, if the methanol is removed in the first half of the reaction, will in addition, a considerable amount of dimethyl sebacate is distilled off together with the methanol, so that it it is necessary to separate and recover the distilled dimethyl sebacate. Considering Due to these factors, the methanol is preferably removed in the second half of the reaction Evaporation of methanol from the system is removed at the same time water Removing a lot larger amounts of methanol and water by evaporation is admittedly from the standpoint of the reaction rate advantageous, however, by removing too large amounts of methanol and water the expenditure on thermal energy is greater. Therefore, it is generally preferred to be 2 to 6 parts by weight Methanol and water per part by weight of the dimethyl sebacate used are removed. A higher water concentration in the reaction solution is advantageous from the standpoint of the reaction rate, however a lower concentration is preferable from the standpoint of the volumetric efficiency of the reactor. In general, the water concentration during the hydrolysis reaction is preferably in Maintained range from 10 to 75% by weight.

. '"> Higher reaction temperatures are from the standpoint the rate of reaction is advantageous, but higher reaction temperatures require higher reaction pressures and also cause discoloration of the reaction product. In particular, a

i »Reaction temperature above? 20 ° C a considerable Causes discoloration of the reaction product. In the first half of the reaction in which the reaction solution is uneven, the influence of the reaction temperature is very great, as will be shown in the later

r> Table 5 below show and the reaction rate is very low at temperatures below 180 ° C. In the second half of the reaction, in which the If the reaction solution is uniform, the influence of the reaction temperature is slight, above 150.degree there is almost no difference. Taking these facts into account, the reaction becomes preferable in the first half of the reaction, during which the reaction solution is non-uniform, at a temperature from 180 ° to 220 ° C and in the second half of the ϊ reaction, in which the reaction solution is uniform, at carried out at a temperature of 150 ° to 220 ° C.

A specific embodiment of a process for the hydrolysis of dimethyl sebacate with the addition of Sebacic acid to the reaction system and removal of

w methanol formed during the reaction the system is described below as an example.

Be in a batch operated reactor

Dimethyl sebacate, sebacic acid and water are added, whereupon the hydrolysis is started. The reactor

ν-, is heated until the reaction solution becomes homogeneous. Once the reaction solution is homogeneous, the methanol and water are continuously removed from the reactor by evaporation, while at the same time the water, which is removed along with the methanol,

bo is continuously supplemented to provide the response To lead to perfection. The withdrawn from the reactor aqueous solution containing the methanol is in a Abandoned distillation column, from which methanol passes overhead and is obtained while from

tv> foot of the column water withdrawn and continuously is fed to the reactor. After the reaction, activated charcoal is added to the reactor to decolorize the reaction solution, whereupon the aqueous solution, the

Contains activated carbon and sebacic acid, from the reactor is removed and placed on a filter. After filtering off the activated carbon, it becomes the sebacic acid containing aqueous solution fed to an evaporator, in which the water is evaporated and recovered and in this way sebacic acid is obtained.

The invention is further illustrated by the following examples. In these examples, all are related Quantities in percent and parts by weight, unless otherwise stated.

example 1

As a starting material, a solution was prepared that contained 34.7% adipic acid, 373% dimethyl adipate, 15.2% Methanol and 12.8% water contained a strongly acidic cation exchange resin which regenerates to the Η-type (100 ml based on water) was substituted with water and transferred to a jacketed column of 15 mm inside diameter and 1000 mm length filled water of 80 ° C was through the jacket 1 kg of the starting solution, preheated to 80 ° C., was passed through the column at a space flow rate from 31 / hour passed through the column from top to bottom A first discharge of 400 g was the first electricity to be tapped. A sample was taken from the rest of the drain as a reaction solution. Analysis by gas chromatography revealed that the reaction solution was 32.0% monomethyl adipate and 35.1% Dimethyl adipate contained The separation of the monomethyl adipate from the reaction solution and its purification were made by distillation.

An electrolyte solution for electrolytic condensation was made by dissolving monomethyl adipate, obtained by the half-esterification of adipic acid, potassium hydroxide and dimethyl sebacate in Methanol prepared in such amounts that the solution is 4% monomethyl adipate, 4.6% potassium salt of Contained monomethyl adipai, 20% dimethyl sebacate and 0.5% water in methanol. 2 kg of the electrolyte solution were placed in an electrolyte solution container and introduced into an electrolysis cell. In the electrolysis cell there was one between the cathode and anode Had current passage area of 1.5 χ 100 cm, one

1 mm thick polyethylene plate, which had an opening zone of such a size that the current passage area 1.5 100 cm, arranged so that the distance to each electrode was 1 mm. The cathode consisted of a titanium plate of 2 mm thickness and the anode of a titanium plate of 2 mm thickness, which with a 2 μm thick platinum layer was plated. the The electrolysis cell was provided with an inlet and an outlet for the electrolyte solution. The electrolysis was at a flow rate of the electrolyte solution between the two electrodes of

2 m / second, a current density of 10 A / dm ² and at a temperature of the electrolyte solution of 55 ° C. with continuous replenishment of the monomethyl adipate consumed in the course of the electrolysis for 3 hours. The cell voltage was 7.8 V. After the electrolysis, it was confirmed by gas chromatography that dimethyl sebacate was formed as a product. The current efficiency was 67.8% and the product yield was 80.9%.

The electrolyte solution obtained by the electrolytic condensation consisted of a methanol solution which contained 4% monomethyl adipate, 4.6% potassium salt of monomethyl adipate, 24% dimethyl sebacate and, as by-products, dimethyl adipate, methyl n-valerate, methyl uJ-hydroxyvalerate, methyl allyl acetate in trace amounts was removed from the electrolyte solution by distillation so that the methanol concentration was lowered to 25% .

To 250 g of the electrolytic solution from which methanol had been removed, 25 g of water was added. That The mixture was stirred at room temperature. Then the solution separated into two layers. the The upper oil layer contained dimethyl sebacate and monomethyl adipate, while the lower layer contained an aqueous one Layer was made up of the potassium salt of monomethyl adipate

The methanol concentration of the oil layer was 1.5%.

100 ml (based on water) of a weakly basic anion exchange resin were then added of the tertiary amine type regenerated to the OH type with the electrolyte solution substituted, from which methanol, monomethyl adipate and its potassium salt had been removed, and into one jacketed column was filled with an internal diameter of 15 mm and a length of 1000 mm. 200 g the oil layer from which methanol and the potassium salt of monomethyl adipate had been removed were removed from up and down through the anion exchange column with a space velocity of 1.0 / 1 / hour. at Passed room temperature The amount of drain in which the concentration of monomethyl adipate 0.05% or less (this concentration is defined as the concentration of monomethyl adipate

jo at the breakthrough point), was 165 g and the breakthrough capacity was 0.71 milliequivalent / cm ³ resin. The breakthrough capacity of the monomethyl adipate was determined according to the following equation:

Breakthrough capacitance =

M _A V _A llQ0-C _A )

1000.

Here, Wa is the amount run off up to the breakthrough point (g), Wb is the amount of solution that replaces the resin (g), C _{A is} the concentration of monomethyl adipate in the starting solution applied to the anion exchange column (%), Ma is the molecular weight of monomethyl adipate and V _{A is} the Resin volume (based on water) (ml). (The breakthrough capacity was also determined for other anion exchange treatments in the manner described above.) Through the jacket of the anion exchange column

warm water of 60 ⁰ C was passed continuously.

Through the anion exchange resin column, 250 ml

so methanol, which was ^{preheated to 60 0} C, from bottom to top in a flow rate of 1.5 1 / hour. passed to drive off the solution remaining in the anion exchange resin column and to desorb the monomethyl adipate adsorbed on the resin. The amount of monomethyl adipate obtained in the discharge was 17 g, corresponding to a yield of 81%. The yield in% was calculated according to the following equation:

Yield in% =

W _r - W,

100.

Here, Wc stands for the amount of monomethyl adipate obtained in the process (in g), Wo for the amount of monomethyl adipate in the solution remaining in the anion exchange column (in g) and Wn the amount of monomethyl adipate adsorbed on the resin (in g). (The% yields given below for other anion exchange treatments were found in the

in the same manner as described above) The anion exchange column was then brought to room temperature cooled, whereupon 150 g of the electrolyte solution, from the methanol, monomethyl adipate i'nd its potassium salt had been removed, from bottom to top at room temperature in a flow rate of 1.5 l / Hrs. Passed through the anion exchange column to convert the Drive out methanol. The methanol concentration in the effluent was lowered to 43% by weight.

The above-mentioned layer, made up of the methanol and the potassium salt of monomethyl adipate had been removed, was added in an amount of 200 g of up to down at room temperature at a rate of 1.01 / hour. again through the anion exchange column directed. The amount which flowed out to the breakpoint of monomethyl adipate was 166 g. the Breakthrough capacity was 0.72 milliequivalents / ml Resin.

In the adsorption step and readsorption step of the anion exchange treatment, the purity was Dimethyl sebacate in the up to the break point of monomethyl adipate from the anion exchange resin column runoff 99.9% or more. The purity of the dimethyl bacats was determined as follows Calculated equation:

Purity =

■ 100.

Herein, Cb is the monomethyl adipate concentration and Cc is the dimethyl sebacate concentration. The analysis of the monomethyl adipate and dimethyl sebacate was carried out by gas chromatography. The separation of the dimethyl sebacate from the effluent which flowed out of the anion exchange resin column up to the breakthrough point of monomethyl adipate and the purification of the dimethyl sebacate were carried out by distillation.

A mixture of 190 g of dimethyl sebacate separated and purified from the electrolytic solution obtained by the electrolytic condensation, 9 g of sebacic acid and 200 g of water was placed in a 1 liter autoclave. The reaction was carried out at a temperature of 18O ⁰ C with vigorous stirring. The reaction solution was initially not homogeneous, but became homogeneous after 3.0 hours, calculated from the start of the reaction. As soon as the reaction solution became homogeneous, the continuous removal of methanol and water from the autoclave was started. At the same time, the water removed with the methanol was continuously replenished by adding water to the autoclave. Under these conditions, the reaction was continued for an additional 5 hours. A total of 640 g of water and methanol were removed and a total of 660 g of water were added to make up. During the reaction, the internal pressure of the autoclave was 6.87 to 8.83 bar. The conversion due to the hydrolysis was 99.3 mol% after the reaction. The conversion by hydrolysis was calculated as the ratio of the number of moles of sebacic acid formed to the number of moles of dimethyl sebacate used.

Example 2

From a used as starting material solution (solution A) 56.3% adipic acid, 20.1% of dimethyl adipate, 12.1% methanol and 11.4% water, adipic acid was deposited at a temperature below 90 ⁰ C. The solution A was placed in an autoclave and heated for 4 hours at 150 ⁰ C to effect the reaction, wherein a Reaküonslösung (solution B) was obtained. Solution B consisted of 21.6% adipic acid, 38.0% monomethyl adipate, 203% dimethyl adipate, 4.4% methanol and 15.6% water. A mixture of 1 part of solution A and 4 parts of solution B was prepared as a starting material for application to an ion exchange resin column

The mixture consisted of 28.5% adipic acid, 30.4% monomethyl adipate, 20.1% dimethyl adipate, 5.9% methanol and 14.8% water at a dissolution temperature of the adipic acid of 73 ° C
Then, 100 cm ³ (relative to water) of a strongly acidic cation exchange resin had been regenerated to Η type, substituted with water, and mm in a jacketed column having an inner diameter of 15 and a length of 1000 mm filled Hot water of 80 ⁰ C was passed through the mantle. Subsequently, 2 kg of preheated to 80 ⁰ C starting solution from top to bottom at a flow rate of 8 l / h. passed through the ion exchange resin column. A first effluent of 400 g was removed as the first stream. The remainder of the effluent as a reaction solution was sampled. Analysis by gas chromatography revealed that the reaction solution contained 39.5% monomethyl adipate and 20.1% dimethyl adipate. The separation of the monomethyl adipate from the reaction solution and its purification

juices were made by distillation.

An electrolytic solution for electrolytic condensation was prepared by using monomethyl adipate, the had been made by half-esterification of adipic acid, sodium methylate and dimethyl sebacate in

j3 methanol were dissolved in such amounts that the Solution contained 4.5% of the sodium salt of monomethyl adipate and 20% dimethyl sebacate in methanol. the electrolytic condensation was carried out in the manner described in Example 1, except that the

ίο water concentration in the electrolyte solution Addition of water to the electrolyte solution was kept at 1.51%. The voltage of the electrolysis cell was 7.8 V. After the electrolysis, the yield of dimethyl sebacate was determined by gas chromatography The current efficiency was 66.5% and the product yield was 79.3%. By the electrolytic Condensation was obtained as an electrolyte solution, a methanol solution containing 4% monomethyl adipate, 4.5% des Sodium salt of monomethyl adipate, 24% dimethyl

) o sebacate and trace amounts of by-products such as dimethyl adipate, methyl n-valerate, methyl-co-hydroxyvalerai, Contained methyl allyl acetate. The electrolyte solution was converted to methanol by distillation except for one 2.5% concentration removed.

To 250 g of the electrolytic solution from which methanol had been removed, 25 g of water was added. That Mixture was stirred at room temperature. Then the solution separated into two layers, viz an upper layer of oil containing dimethyl sebacate and mono-

bo methyl adipate, and a lower layer of water, which contained the sodium salt of monomethyl adipate.

The methanol concentration in the oil layer was 1.5%.

The anion exchange treatment was carried out in the manner described in Example 1, but using changed the regeneration temperature of 60 ° C to 3O ^0. The following results were obtained:

1) During the adsorption process, the amount of runoff that had flowed out was up to the breakthrough point of monomethyl adipate 166 g. The breakthrough capacity was 0.72 milliequivalents / ml Resin. The purity of the dimethyl sebacate in the drain was 99.9% or more.

2) During the regeneration, the amount of monomethyl adipate recovered in the drain was 16 g. This corresponds to a recovery of 70%.

3) During the readsorption process, the amount of up to the breakthrough point was Monomethyl adipate effluent was 158 g and the breakthrough capacity was 0.66 milliequivalents / ml Resin. The dimethyl sebacate in the effluent had a purity of 99.9% or more.

The separation of dimethyl sebacate from the up to the breakthrough point of monomethyl adipate from the Anion exchange resin column and the purification of the dimethyl sebacate were carried out by distillation.

A mixture of 80% dimethyl sebacate separated and purified from the electrolytic solution obtained by the electrolytic condensation, 2% sebacic acid and 18% water was placed in an amount of 400 g in a 1 liter autoclave. The reaction was carried out at a temperature of 180 ^° C. with vigorous stirring. After 3.7 hours from the start of the reaction, the reaction solution became homogeneous. The second half of the reaction after the formation of a homogeneous reaction solution was carried out in the manner described in Example 1. The total amount of methanol and water withdrawn by distillation until the end of the reaction was 920 g and the total amount of water added was 970 g. The conversion by hydrolysis after the reaction was 98.9 mol%.

Example 3

Using a three-necked flask fitted with a thermometer, condenser, and stirrer, a Reaction solution containing 146 g of adipic acid, 32 g of methanol, 36 g of water and 50 mg-equivalents of nitric acid , heated under reflux for 6 hours at normal pressure, an oil bath being used for heating. After the reaction, analysis by gas chromatography revealed that the resulting solution was 114 g of monomethyl adipate and contained 24.5 g of dimethyl adipate. The monomethyl adipate was distilled from the obtained solution separated and purified

The electrolytic condensation was carried out in the manner described in Example 2, but using sodium carbonate instead of sodium methylate and monomethyl adipate obtained by half-esterification of adipic acid as the neutral salt group. The voltage of the electrolysis cell was 7JB V, the current yield 67.2% and the product yield 80.2%.

From that obtained by electrolytic condensation Electrolyte solution, the removal of methanol and the separation of the sodium salt from Monomethyl adipate by extraction into a layer of water in the manner described in Example 1.

Subsequently, 100 cm ³ (based on water) of a weakly basic anion exchange resin of the tertiary amine type, which had been regenerated to the OH type, were substituted with water and filled into a jacketed column with an internal diameter of 15 mm and a length of 1000 mm. 195 g of the oil layer, from which methanol and the sodium salt of monomethyl adipate had been removed, were poured from top to bottom at room temperature at a flow rate of 1.01 / hour. passed through the anion exchange resin column. The drain separated into two layers, a top oil layer containing dimethyl sebacate and one

ίο lower water layer. The runoff amount of the oil layer which flowed out up to the breakdown point of monomethyl adipate was 100 g and the breakdown capacity was 0.73 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the oil layer had a purity of 99.9% or

π more.

The expulsion of the solution remaining in the anion exchange resin column and the desorption of the am Resin adsorbed monomethyl adipate was done in the manner described in Example 1. The amount of im

The monomethyl adipate obtained in the outflow was 17 g corresponding to a yield of 80%.

After cooling the anion exchange resin column to room temperature, 150 ml of water were added Room temperature from bottom to top through the

2Ί anion exchange column with a flow rate of 1.5 1 / hour. passed to drive off the methanol. The methanol concentration in the effluent was decreased to 0.1%.

Then 195 g of the oil layer from the

3d methanol and the sodium salt of monomethyl adipate had been removed at room temperature with a flow rate of 1.01 / hour. again from the top to passed through the anion exchange resin column at the bottom. The process was divided into two layers, an upper one

The oil layer containing dimethyl sebacate and a lower layer of water. The amount of oil that had flowed out up to the breakdown point of monomethyl adipate was 101 g and the breakdown capacity was 0.73 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in

w of the oil layer sculptural a purity of 99.9% or more, the separation of dimethyl sebacate from the up to the break through point of monomethyl from the anion exchange resin column leaked process and purification of the Dimethylsebacats were

4i distillation carried out.

100 g of dimethyl sebacate were placed in a 2 l glass vessel separated from the electrolyte solution obtained by the electrolytic capacitor and cleaned had been, and given 1.5 kg of an 18% aqueous nitric acid solution and at normal pressure heated with vigorous stirring for 3 hours with removal of methanol by distillation on the reflux condenser to carry out the hydrolysis. The conversion by hydrolysis after the reaction was 99, i Mol%. The methanol concentration during hydrolysis was kept at 0.03% or less. the Sebacic acid formed by the hydrolysis was dissolved in the reaction solution and did not separate out.

B e i s ρ i e 1 4

A mixture of 146 g of adipic acid, 96 g methanol 54 g water and 139 g of dimethyl adipate was added to Einei autoclave and reacted for 2 hours under vigorous stirring at a temperature of 150 ⁰ C. After the reaction, the analysis was by Gaschro chromatography that 112 g of monomethyl had been formed. The separation of the Monomethyladi

pats from the reaction solution and its purification were carried out by distillation.

The electrolytic condensation was carried out in the manner described in Example 2, but using of sodium carbonate instead of sodium methylate as a neutral salt group using N-ionomethyl adipate, which is obtained by half-esterification of Adipic acid was obtained. The voltage of the electrolysis cell was 7.8 V, the Stroke yield 67.0% and the product yield 79.8%. ic

The separation of dimethyl sebacate from the electrolyte solution obtained by the electrolytic condensation was carried out in the manner described in Example 3. was "> water nii_'hi 50 ^& C 90 ⁰ C but betru ¹⁷ and hot water as the regenerating means 90 ^r C instead of methanol from bf / 'C uses the following, but the temperature of the guided through dci coat the anion exchange column. Results were obtained:

1) During the adsorption process, the flow amount of up to the break through point of leaked oil monomethyl layer 102 g and the breakthrough capacity was 0.75 milliequivalents / cm ^J resin. The dimethyl sebacate in the oil layer had a purity of 99.9% or more.

2) During the regeneration, 16 g of Monomethyiadipai were in the process corresponding to one recovery gained by 70%.

3) During the adsorption, the amount of the oil layer leaked up to the breakpoint of monomethyl adipate was 89 g. The breakdown capacity was 0.65 milliequivalents / cm ^{3 of} resin. The dimethyl sebacate in the oil layer had a purity of 99.9% or more ^; '

The dimethyl sebacate was made from the anion exchange column to the breakthrough point Drainage from the 4i> which has flowed out of monomethyl adipate Anion exchange column separated by distillation and purified by distillation.

The hydrolysis of dimethyl sebacate separated and purified from the electrolytic solution obtained by the electrolytic condensation, t; was carried out in the manner described in Example 1.

Example 5

Monomethyl g was half-esterification of adipic acid by following the procedure whose flow diagram in F i. 1 is shown.

Entry 7 gave 13.8 kg / hour. Adipic acid and 3.0 kg / hour. Methanol introduced into the dissolution vessel 1, methanol and water withdrawn from the top of the distillation column 4, dimethyl adipate and water withdrawn from the top of the distillation column 5, adipic acid and monomethyl adipate withdrawn from the bottom of the distillation column 6, and a Part of the reaction solution withdrawn from the outlet 8 was circulated. The dissolution vessel was heated to 8O ⁰ C, and a raw material solution was kg in an amount of 240 / hr. taken from the vessel 1 t, 5 and placed on top of the ion exchange resin column 2. The starting material solution had the following composition: 28.0% adipic acid, 203% dimethyl adipate, 30.8% monomethyl adipate, 5.7% methanol, 14.9% water and 0.3% cyclopentanone. The ion exchange column 2 was filled with 15 l of strongly acidic cation exchange resin which had been regenerated to the Η type. The raw material solution was passed through the column at 8O ⁰ C. The resin in the ion exchange column 2 was regenerated once with aqueous in-nitric acid solution after continuous operation for 200 hours. The effluent flowing out of the ion exchange column 2 at the bottom was applied to the ion exchange column 3. The ion exchange column 3 was filled with 601 strongly acidic cation exchange resin which had been regenerated to the Η type. The effluent from the bottom of lonenaustauscherkolonne 2 flow was passed through the column 3 while it was maintained at 8O ⁰ C. From the bottom of the ion exchange column 3, the reaction solution was in an amount of 240 kg / hour. deducted. A quarter of the solution was applied to the distillation column 4, while 3/4 of the solution was drawn off through the draw-off line 8 and returned to the dissolution vessel 1. The reaction solution withdrawn from the foot of the ion exchange column 3 had the following composition: 22.0% adipic acid, 20.2% dimethyl adipate, 37.0% monomethyl adipate, 4.3% methanol, 15.7% water and 0.3% cyclopentanone. The changes in the concentration of iron ion and cyclopentanone in the solution withdrawn from the ion exchange column 3 over time are given in Table 1 and in FIG. 2 shown. In Fig. 2, the curve C the Cyclopenlanonkonzentration and the curve D represents the iron ion concentration. In the distillation column 4, the temperature was held at ground level at 14O ⁰ C under atmospheric pressure. Methanol and water, which were distilled off at the top of the column, were fed to the dissolving vessel 1, while the remaining solution was drawn off from the bottom of the column and applied to the distillation column 5. In the distillation column 5, the temperature at the bottom was kept at 200 ^° C. under reduced pressure (26.6 mbar). Dimethyl adipate and water were abdcstilüert from the column overhead. Dimethyl adipate and water withdrawn from the top of the distillation column 5 were separated into two layers. The water was discharged from the discharge line 9 in an amount of 2.0 kg / hour, while the remaining solution was returned to the dissolving vessel 1. A solution which contained adipic acid and monomethyl adipate was drawn off from the bottom of the distillation column 5 and applied to the distillation column 6. In the column 6, the temperature at the bottom was kept at 210 ^° C. under reduced pressure (26.6 mbar). Monomethyl adipate was from the top of the column in an amount of 15 kg / hour. withdrawn to form an electrolytic solution for electrolytic condensation. A solution containing adipic acid and monomethyl adipate was withdrawn from the foot of the distillation column 6 and returned to the dissolution vessel I.

The individual devices were made from the following materials:

Dissolution vessel 1 SUS 304

Ion exchange columns 2 and 3 SUS 304 Distillation column 4 SUS 304

Distillation column 5 SUS 316

Distillation column 6: reboiler made of titanium and evaporator unit made of SUS 316

Tabel

Time.
Hours.

Concentralization

from

Cyclopentanone,

Concentration of

Iron ion, ppm

50
100
150
200

0.3 0.3 0.3 0.3

Using monomethyl adipate obtained by half-esterification of adipic acid electrolytic condensation was carried out in the manner described in Example 1.

The electrolyte solution obtained by the electrolytic condensation was removed of methanol and the separation of the potassium salt of monomethyl adipate by extraction to the water layer in the manner described in Example 1.

In the next step, 100 cm ³ (based on water) of a strongly basic anion exchange resin of the pyridinium type, which had been regenerated to the OH type, with the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, substituted and converted into a Filled column with an internal diameter of 12 mm and a length of 1500 mm. Then 400 g of the oil layer from which methanol and the potassium salt of monomethyl adipate had been removed were poured from top to bottom at room temperature at a flow rate of 1.01 / hour. passed through the anion exchange resin column. The amount of the effluent flowing out to the breakthrough point of monomethyl alcohol was 218 g and the breakthrough capacity was 1.10 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the effluent had a purity of 99.9% or more.

The expulsion of the in the anion exchange resin column remaining solution and the desorption of the monomethyladiapts adsorbed on the resin were transferred to the In Example 1 described manner carried out, but not the expulsion and regeneration temperatures mentioned in Example 1, but room temperature was used. The one in the process The recovered amount of the monomethyl adipate was 24 g, corresponding to a yield of 78%.

The methanol remaining in the anion exchange resin column was converted to that described in Example 1 Expelled wisely.

Then 400 g of the oil layer from which the methanol and the potassium salt of monomethyl adipate had been removed were again from top to bottom at room temperature at a flow rate of 1.0 1 / hour. passed through the anion exchange resin column to the breakpoint of monomethyl adipate. The amount of effluent flowed out was 203 g. The breakthrough capacity was 0.99 milliequivalents / ml resin. The dimethyl sebacate in the effluent had a purity of 993% or more. The dimethyl sebacate was separated from the effluent flowing out of the anion exchange resin column up to the break-through point of monomethyl adipate by distillation and purified by distillation

The dimethyl sebacate produced by the electrolytic solution obtained by electrolytic condensation had been separated and purified, was on hydrolyzed in the manner described in Example 1.

Example 6

The production of monomethyl adipate by half-esterification of adipic acid was carried out in the manner described in Example 5, but using a reactor 2 instead of the ion exchange resin columns 2 and 3 (FIG. 1) and the circulation of part of the reaction solution withdrawn from the discharge line 8 to the dissolution vessel 1 was omitted. The reactor was operated under the following conditions: A starting corn solution was fed from the dissolving vessel 1 in an amount of 60 kg / hour. led to reactor 2. The esterification reaction was carried out in reactor 2 at a temperature of 180 ^° C. and an average residence time of 5 hours. The starting material solution had the following composition 20 hours after the start of the reaction: 45.5% adipic acid, 20.3% dimethyl adipate, 10.8% monomethyl adipate, 9.3% methanol. 12.3% water and 0.8% cyclopentanone. From the reactor 2, the reaction solution was in an amount of 60 kg / hour. deducted. This solution had the following composition: 21.7% adipic acid, 20.0% dimethyl adipate, 37.2% monomethyl adipate, 4.3% methanol. 15.6% water and 0.9% cyclopentanone. The changes with the lapse of time in the concentrations of cyclopentanone and iron ion in the reaction solution withdrawn from the reactor 2 are shown in Table 2 and are represented by curves /. and S in FIG. 2 shown.

Table 2 concentration concentration / hurry. from de ·. Hours. Cyclopentanone. Exertions. ppm 0.9 15th 20th 1.2 20th 50 2.0 40 KX) 3.2 70 150 4.0 105 200

The reactor 2 was made of stainless steel SUS 316, while the dissolving vessel 1 and the Distillation columns 4, 5 and 6 made of the same materials as those described in Example 5

-, ρ attempt were made.

using monomethyl adipate. obtained by the half-esterification of adipic acid had been. electrolytic condensation was carried out in the manner described in Example 1.

Then 100 cm ³ (based on water) of a weakly acidic cation exchange resin of the acrylic acid type, which was regenerated to the Η-type, substituted with methanol and filled into a jacketed column of 12 mm inside diameter and 1500 mm length. Then 500 g of the electrolytic Condensation obtained electrolyte solution at room temperature and a flow rate of 1.5 1 / hour. passed through the cation exchange resin column from top to bottom . The drainage amount below a potassium ion concentration of 50 ppm, which is defined as the potassium ion concentration at the breakthrough point, was 360 g. The breakthrough capacity was 0.71 milaqurvalent / cm ³ resin. In this case

the breakdown capacitance was calculated using the equation described in Example 1 in which Monomethyl adipate has been replaced by the potassium ion. (The values given later for other cation exchange treatments were calculated using the same method.)

While warm water of 55 ° C was passed through the jacket of the cation exchange column, were then 200 g of monomethyl adipate and 150 g of methanol, both of which were preheated to 55 ° C., in this Sequence from bottom to top with a flow rate of 1.5 1 / hour. through the cation exchange column passed to drive off the solution remaining in the cation exchange resin column and to desorb the potassium ions adsorbed on the resin. The amount of potassium ions obtained in the process was 2.1 g corresponding to a recovery of 45%. In this case the percentage recovery was using the equation described in Example 1 in which monomethyl adipate is replaced by the Potassium ion was replaced, calculated. (The values given below for other cation exchange treatments were calculated using the same method.)

After cooling the cation exchange resin column to room temperature, 500 g of the electrolyte solution were again from the bottom to the top at room temperature and a flow rate of 1.51 / hour. passed through the cation exchange column. The amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 290 g and the breakthrough capacity was 0.55 milliequivalent / cm ^{3 of} resin.

Then, methanol was distilled from the electrolytic solution from which potassium ions had been removed were removed except for a methanol concentration in the remaining solution of 2.5%.

Subsequently, 100 cm ³ (based on water) of a weakly basic tertiary amine type anion exchange resin which had been regenerated to the OH type was substituted with the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, and encased Column of 12 mm inner diameter and 1500 mm length filled. Then, 200 g of a mixture, which had been removed by adding 100 g of the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, to 100 g of the electrolyte solution from which potassium ions and methanol were removed from top to bottom at room temperature and a flow rate of 1.01 / hour. passed through the anion exchange column. The amount of the effluent which had flowed out up to the breakthrough point of monomethyl adipate was 175 g and the breakthrough capacity was 0.71 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the effluent had a purity of 99.9% or more.

The expulsion of the solution remaining in the anion exchange resin column and the desorption of the monomethyl adipate adsorbed on the resin were carried out in the manner described in Example 1. The amount of monomethyl adipate recovered in the effluent was 16 g, corresponding to a recovery of 81%. The methanol was then stripped from the anion exchange resin column in the manner described in Example 1.

Then, 200 g of the previously prepared mixture of the electrolyte solution from which potassium ions and methanol had been removed and the electrolyte solution from which methanol, monomethyladipal and its potassium salt had been removed, at room temperature and a flow rate of 1.01 / hour. again from top to bottom through the

■ 'Anion exchange resin column passed. The amount of effluent flowed to the monomethyl adipate break-through point was 177 g and the break-through capacity was 0.72 miliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the effluent had a purity of

κι 99.9% or more.

The dimethyl sebacate was made from the to the breakthrough point of monomethyl adipate from the Anion-exchange resin column, the effluent which has flowed out, is separated off by distillation and removed by distillation

i ~ 'cleaned. The potassium ion was determined by atomic absorption analysis analyzed.

The hydrolysis of the Dimethyisebacais produced by the electrolyte solution obtained by electrolytic condensation had been separated and purified,

2 ”became in the manner described in Example 1 carried out.

Example 7

The experiment described in Example 1 was

2Ί repeated, but the separation of dimethyl sebacate from the electrolyte solution obtained by the electrolytic condensation was carried out under the following conditions:
As a regeneration agent for the cation exchange

3 <) shear resin were 200 g of a methanol solution containing 10% Containing monomethyl adipate and 150 g of methanol, instead of 200 g of monomethyl adipate and 150 g of methanol, used in the experiment described in Example 6 was used. With the exception of

π use of the aforementioned regenerant the experiment was carried out in the manner described in Example 6.

In the operations carried out in the cation exchange column, the following results were obtained

4 »received:

1) During the adsorption process, the amount that flowed out up to the breakthrough point of the potassium ion was Amount of drain 355 g and the through-

■ f 3 fracture capacity 0.70 milliequivalent / cm ³ resin.

2) During the regeneration, the amount of the potassium ion recovered in the drain was 2.0 g corresponding to a recovery of 42%.

3) During the readsorption, the amount run off up to the breakthrough point of the potassium ion was 275 g and the breakthrough capacity was 0.51 milliequivalent / cm ^{3 of} resin.

Example 8

i; The experiment described in Example 1 was repeated, but the separation of dimethyl sebacate from the electrolyte solution obtained by the electrolytic condensation was carried out under the following conditions :

Methanol was so far distilled off from the electrolyte solution that the methanol concentration in the remaining solution was £ 2%.

Then, 100 cm ³ (based on water) of a weakly acidic cation exchange resin of the imi nodiacetic acid type which had been converted to the HCl type were substituted with the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, and placed in a jacketed column

with an inner diameter of 12 mm and a length of 1500 mm. Through the cation exchange resin column, 700 g of a mixture, which was prepared by adding 41 μg of the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, to 290 g of the electrolyte solution from which methanol had been removed, was prepared from top to bottom was at room temperature and a flow rate of 1.5 1 / hour. directed. The amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 442 g and the breakthrough capacity was 0.87 milliequivalent / cm ^{3 of} resin.

While warm water of 55 ° C was passed through the jacket of the cation exchange column, were 100 g of monomethyl adipate, 200 g of a methanol solution containing 10% monomethyl adipate, and 150 g Methanol, all of which had been preheated to 55 ° C., in this order from bottom to top a flow rate of 1.5 1 / hour. through the cation exchange resin column passed, whereby the solution remaining in the cation exchange resin column is driven off and the potassium ions adsorbed on the resin were desorbed. The one won in the process The amount of potassium ion was 2.7 g, corresponding to a recovery of 48%.

After cooling the cation exchange column to room temperature, 150 g of the electrolyte solution, from which methanol, monomethyl adipate and its potassium salt had been removed, from bottom to above at room temperature and a flow rate of 1.5 1 / hour. through the cation exchange resin column passed to the remaining solution of the regenerant to drive out. The methanol concentration in the effluent was lowered to 4.5%.

Subsequently, 700 g of a mixture prepared from the electrolyte solution from which methanol had been removed and the electrolyte solution from which methanol, monomethyl adipate and its alkali salt had been removed in the manner described above was prepared at room temperature and a flow rate of 1.5 1 / hour passed through the cation exchange resin column from top to bottom. The amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 330 g and the breakthrough capacity was 0.61 milliequivalent / cm ^{3 of} resin.

Then, a weakly basic tertiary amine type anion exchange resin which had been regenerated to the OH type was charged in a column in the manner described in Example 1. 400 g of the effluent which had flowed out of the cation exchange resin column up to the breakthrough point of the potassium ion were passed through the anion exchange resin column in the manner described in Example 1. The amount of runoff that had flowed out to the breakpoint of monomethyl adipate was 225 g and the breakdown capacity was 0.72 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the effluent had a purity of 99.9% or more.

In the manner described in Example 1, the solution remaining in the anion exchange resin column became driven out and the monomethyl adipate adsorbed on the resin is desorbed. The amount of the Monomethyl adipate was 18 g corresponding to a recovery of 79%.

After the regenerant solution remaining in the anion exchange resin column had been driven off in the manner described in Example 1, 300 g of the effluent which had flowed out of the cation exchange column up to the breakthrough point of the potassium ion were passed through the anion exchange resin column again , 71 milliequivalent / cm ³ resin. The dimethyl sebacate in the effluent had a purity of 99.9% or more.

The dimethyl sebacate was made from the to the breakthrough point of monomethyl adipate from the

κι anion exchange resin column, the effluent which has flowed out is separated off by distillation and by distillation cleaned.

Example 9

The experiment described in Example 1 was repeated, but with the separation of the dimethyl sebacate of the electrolytic solution obtained by the electrolytic condensation among the following Conditions was carried out:

2Ii the one in example! The experiment described in 8 was repeated, but the pretreatment of the weakly acidic anion exchange resin of the iminodiacetic acid type was carried out under the following conditions:

That by de pretreatment in the NaOH type transferred ion exchange resin was substituted with water and placed in a jacketed column of 12 mm Filled inside diameter and 1500 mm in length. While warm water of 55 ° C through the mantle

jo was passed, a preheated to 55 ° C 16% aqueous solution of monomethyl adipate at a rate of 1.51 / hour. in an amount which corresponded to 15 times the amount of the resin (based on water), passed through the column from top to bottom, the sodium ion adsorbed on the resin being desorbed. While still warm water was passed through the jacket of the column, was preheated to 55 ⁰ C methanol from top to bottom at a rate of 1.5 1 / h. in a crowd

• »ι · which corresponded to 15 times the amount of resin through which Column passed, whereby the monomethyl adipate adsorbed on the resin was desorbed. Then it became Replaced methanol in the column with water.

The cation exchange treatment had the following results:

1) During the adsorption, the amount of drainage flowed out up to the breakdown point of the potassium ion was 403 g and the breakdown capacity was 0.78 milliequivalent / cm ^{3 of} resin.

2) During the regeneration, the amount of the potassium ion recovered in the drain was 3.2 g corresponding to a recovery of 59%.

3) During the readsorption, the amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 373 g and the breakthrough capacity was 0.71 milliequivalent / cm ^{3 of} resin.

Example 10

bo The experiment described in Example 1 was repeated except that the dimethyl sebacate is different from that obtained by the electrolytic condensation Electrolyte solution was separated as follows:

The experiment described in Example 8 was carried out

to wieHerholt, but with a moderately acidic Phosphonic acid type cation exchange resin regenerated to Η type in place of the weakly acidic cation exchange resin from the imi-

nodiacetic acid type which had been converted to HCl type was used. The treatments in the Cation exchange column the following results were obtained:

1) During the adsorption, the amount of effluent flowed out to the breakdown point of the potassium ion was 575 g and the breakdown capacity was 1.18 milliequivalents / cm ^{3 of} resin.

2) During the regeneration, the amount of the potassium ion recovered in the drain was 4.4 g corresponding to a recovery of 52%.

3) During the readsorption, the amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 532 g and the breakthrough capacity was 1.08 milliequivalents / cm ^{3 of} resin.

Example 11

The experiment described in Example 1 was repeated, but with the separation of dimethyl sebacate carried out from the electrolytic solution obtained by the electrolytic condensation in the following manner became:

The amphoteric ion exchange resin used was a resin which had been prepared by suspension polymerization of acrylic acid, chloromethylated styrene and divinylbenzene and treatment of the copolymer formed with diethylamine. The exchange capacity of the amino group was 0.87 milliequivalent / cm ³ resin and that of the carboxyl group was 0.84 milliequivalent / cm ³ resin.

From the above-mentioned electrolyte solution, methanol was converted to a concentration of 2.5% distilled off. 300% of the electrolytic solution from which methanol was removed in this way became Given 600 g of the electrolyte solution, from which methanol, monomethyl adipate and its potassium salt have been removed were, 900 g of a starting solution for the ion exchange column were obtained.

Then 150 cm ³ (based on water) of the amphoteric ion exchange resin converted into the NaOH type were substituted with water and filled into a jacketed column with an internal diameter of 12 mm and a length of 1500 mm.

While warm water of 55 ° C through the jacket of lonenaustauscherkolonne was conducted, were 1500 g of a 16% aqueous Monomethyladipatlösung, which was preheated to 55 ⁰ C, at a flow rate of 1.51 / hr. passed from bottom to top through the ion exchange column in order to desorb the sodium ion adsorbed on the resin. Then, while warm water at 55 ° C was still being passed through the jacket of the ion exchange column, 1500 r.il methanol, which had been preheated to 55 ° C, was added at a flow rate of 1.51 / hour. passed from bottom to top through the ion exchange column in order to desorb the monomethyl adipate adsorbed on the resin.

After cooling the ion exchange column to room temperature, 225 g of the electrolyte solution, from which methanol, monomethyl adipate and its potassium salt had been removed at room temperature with a flow rate of 1.5 1 / hour. from bottom to top through the ion exchange column passed to drive off methanol. The methanol concentration in the effluent was lowered to 4.5%.

Through the ion exchange column, which is treated with the amphoteric in the manner described above Ion exchange resin was filled, 900 g of the pretreated starting solution were from top to bottom at room temperature and a flow rate of 1.01 / hour. directed The amount of expiration of the Solution in which the potassium ion concentration is 50 ppm or less and the monomethyl adipate concentration 0.05% or less was 249 g. The solution in which the monomethyl adipate concentration more than 0.05% and the potassium ion concentration 50 ppm or

ίο was less, expired in an amount of 329 g. The breakthrough capacity of monomethyl adipate was 0.41 milliequivalent / cm ³ resin. The dimethyl sebacai in the solution which flowed out to the breakpoint of monomethyl adipate had a purity of 99.9%

i> or more. The breakthrough capacity of the potassium ion was 0.30 milliequivalent / cm ³ resin. The breakdown capacitance was calculated according to the following equation:

Breakthrough capacity

(W _r -

1 * ^ (100- Q)

• 1000.

Here, Wf denotes the amount of runoff (g) that has flowed out up to the breakthrough point, IVc denotes the amount of

2ϊ solution which substitutes the resin (g), Cd the concentration of monomethyl adipate (including the potassium salt of monomethyl adipate) or the concentration of the potassium ion in the starting solution fed to the ion exchange column (%), Cf the difference

κι between the total concentrations of monomethyl adipate and its potassium salt in the starting solution fed to the ion exchange column and the Total concentrations of monomethyl adipate and its potassium salt in the up to the breakthrough point

i-, outflow (° / o), Vb the resin volume (based on water (cm ³ )) and Mb the molecular weight of monomethyl adipate or potassium.

Then, while warm water of 55 ° C was passed through the jacket of the ion exchange column was, 375 ml of methanol, which was preheated to 55 ° C, to bottom up at one flow rate from 1.51 / hour passed through the ion exchange column to that in the ion exchange resin column To drive off remaining solution and the monomethyl adipate and the potassium ions which are adsorbed on the resin were to desorb. The amount of monomethyl adipate (including potassium salt of monomethyl adipate) was 20 g, corresponding to a recovery of 72%. The one in the process

^The amount of potassium ion recovered was 2.7%, corresponding to a recovery of 51%. The% recovery was calculated according to the following equation:

Amount recovered in% = -— · 100.

Herein, Wn means the amount of monomethyl adipate (including the potassium salt) recovered in the effluent

bo of monomethyl adipate) or potassium ion (g), W / the amount of monomethyl adipate (including the potassium salt of monomethyl adipate) or potassium ion in the solution remaining in the ion exchange resin column (g) and VV / the amount adsorbed on the resin

s of monomethyl adipate or potassium ion (g).

After cooling the ion exchange column to room temperature, 225 g of the electrolyte solution, from the methanol, monomethyl adipate and its potassium

salt had been removed from bottom to top at room temperature with a flow rate from 1.5 i / h through the ion exchange column passed to drive off the methanol. The methanol concentration in the effluent was lowered to 4.5%.

Subsequently, 900 g of the solution used in the ion exchange column, which had been prepared from the electrolyte solution from which methanol had been removed and the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed, were again prepared at room temperature and a flow rate of 1.01 / hour passed through the ion exchange column from top to bottom. The amount of monomethyl adipate which had flowed out up to the breakthrough point was 245 g and the breakthrough capacity was 0.40 milliequivalent / cm ^{3 of} resin. The amount of runoff that had flowed out to the point of breakthrough of the potassium ion was 322 g and the breakthrough capacity was 0.29 milliequivalent / cm ^{3 of} resin. The dimethyl sebacate in the effluent flowed out to the breakpoint of monomethyl adipate had a purity of 99.9% or more.

The dimethyl sebacate was made from the to the breakthrough point of monomethyl adipate from the The outflow which has flowed out from the ion exchange column is separated off by distillation and purified by distillation.

Example 12

The experiment described in Example 1 was repeated, but with the separation of dimethyl sebacate from the electrolytic solution obtained by the electrolytic condensation under the following conditions was carried out:

Methanol was evolved from the electrolyte solution to a methanol concentration of 2.5% in the remaining one Solution distilled off. To 300 g of the electrolyte solution from which methanol was removed in this way, 600 g of the electrolyte solution were added, from the methanol, monomethyl adipate and its sodium salt had been removed, 900 g of a feed solution for the ion exchange column being obtained.

Then 50 cm ³ (based on water) of a moderately acidic cation exchange resin of the phosphonic acid type regenerated to the Η-type and 150 cm ³ (based on water) of a weakly basic anion exchange resin of the tertiary amine type that had been regenerated to the OH type, sufficiently mixed and substituted with the electrolyte solution from which methanol, monomethyl adipate and its potassium salt had been removed and filled into a jacketed column of 12 mm inside diameter and 2000 mm length. Then 900 g of the previously prepared feed solution at room temperature and a flow rate of 1.01 / hour. passed from top to bottom through the ion exchange column containing the mixed bed. The drained amount in which the monomethyl adipate concentration was 0.05% or less and the potassium ion concentration was 50 ppm or less was 254 g. The amount of the drain in which the monomethyl adipate concentration was more than 0.05% and the potassium ion concentration was 50 ppm or less was 9 g. The breakthrough capacity of monomethyl adipate was 0.50 milliequivalent / cm ³ and the breakthrough capacity of the potassium ion was 0.26 milliequivalent / cm ³ resin. The dimethyl sebacate in the effluent flowed out to the breakpoint of monomethyl adipate had a purity of 99.9% or more. The breakthrough capacity was calculated in the manner described in Example 11

While warm water of 55 ° C was passed through the jacket of the ion exchange column, were "> 200 g of monomethyl adipate and 300 ml of methanol, both of which were preheated to 55 ° C, in that order with a flow rate of 1.5 1 / hour. from bottom to top through the ion exchange column passed to the in the ion exchange resin column

ίο expel remaining solution and the monomethyl adipate and desorb the potassium ion adsorbed on the resin. The one recovered in the process The amount of potassium ion was 3 g, corresponding to a recovery of 56%. The recovery in% was calculated in the manner described in Example 11, however, the recovery of monomethyl adipate was not determined in%.

After cooling the ion exchange column to room temperature, 300 g of the electrolyte solution, from which methanol, monomethyl adipate and its potassium salt had been removed at room temperature with a flow rate of 1.51 / hour. from passed down through the ion exchange column to drive off the methanol. The methanol concentration in the process was reduced to 4.5%.

Then 900 g of the feed solution, which had previously been removed from the electrolyte solution, from the methanol and from the electrolyte solution from which methanol, monomethyl adipate and its potassium salt were removed in which had been produced, at room temperature with a flow rate of 1.0 1 / hour. again passed from top to bottom through the ion exchange resin column. The amount of up to Breakthrough point of monomethyl adipate flowed out

j ") a drainage was 252 g and the breakthrough capacity 0.49 milliequivalent / cm ^{3 of} resin. The amount of drainage flowed out up to the breakthrough point of the potassium ion was 261 g and the breakthrough capacity was 0.25 milliequivalent / cm ³ resin. The dimethyl sebacate in the

■ 40 to the breakpoint of the monomethyl adipate The effluent had a purity of 99.9% or more.

The dimethyl sebacate was made from the to the breakthrough point of monomethyl adipate from the j ion exchange column, the effluent which has flowed out is separated off by distillation and purified by distillation.

Example 13

The experiment described in Example 2 was repeated, but with others, in Table 3 mentioned water concentration in the electrolyte solution during the electrolytic condensation of the through Half-esterification of adipic acid obtained monomethyl adipate was worked. The results are in Table 3 mentioned.

Table 3

Ver water Current- 0.4 Product- Tension. search concentrate yield, 67.3 bulging c. V 60 No. tration,
% "/» 67.9 % 1 0.12 66.5 - 5.9 2 0.15 66.4 80.6 7.5 65 3 0.85 56.3 80.7 7.8 4th 1.51 79.3 7.8 5 3.05 81.4 7.5 6th 3.56 71.1 7.6

Example 14

The experiment described in Example I was repeated, but the hydrolysis of the dimethyl sebacate, that from the electrolytic condensation The electrolyte solution obtained had been separated and purified, was carried out as follows:

A mixture containing dimethyl sebacate, sebacic acid and water in the amounts shown in Table 4 was placed in a 1 liter autoctave. The reaction was ui.ter vigorous stirring at 180 ⁰ C performed the first non-homogeneous reaction solution became homogeneous as the reaction proceeds. From the point in time

From when the reaction solution became homogeneous, methanol and water were continuously passed through Distillation removed from the autoclave while at the same time that removed along with the methanol Continuously replenish water; became. The reaction was carried out for an additional 5 hours In the reaction, the internal pressure in the autoclave was 6.87 to 8.83 bar. The to form a homogeneous solution required time, the total amount of methanol and water distilled off by the end of the reaction, the total amount of water supplied and the conversion in the hydrolysis are shown in Table 4.

Table 4 Application quantities, g
Dimethyl sebacin
sebacal acid 0 water Required
Zeil to
Formation of a
homogeneous
Solution. Stü. total quantity
to distill off
temp methanol
and water,
G All in all
fed
Water,
G sales
by
Hydro
lysis,
Mol% attempt
No. 200 9 200 6.4 6 OK 655 99 ,! 1 190 18th 200 3.0 640 660 99.3 2 180 53 200 2.4 595 610 99.5 3 140 Example 15 200 1.0 510 535 99.4 4th io the by Was distilled off at the end of the reaction,

The experiment described in Example 1 was repeated, but the hydrolysis of the dimethyl sebacate, separated from the electrolyte solution obtained by the electrolytic condensation and cleaned, was carried out as follows:

400 g of a solution were placed in a 1 l autoclave given, which contained 48% dimethyl sebacate, 2% sebacic acid and 50% water. The first half of the reaction was carried out with vigorous stirring at the temperature given in Table 5 until the reaction solution became homogeneous. From the time when the reaction solution became homogeneous, the reaction temperature was adjusted to 160 "C and the Reaction carried out for a further 5 hours while methanol and water were continuously discharged from the autoclave were distilled off and at the same time the water removed with the methanol was continuously replenished became. The total amount of methanol and water was 680 g. During the second half of the reaction the internal pressure in the autoclave was 4.9 to 5.89 bar.

The reaction temperature during the first half of the reaction until a homogeneous The time required for the solution and the conversion in the hydrolysis are given in Table 5 below.

Table 5

attempt Rcaklion For education sales No. temperature a homo in the in the very solution Hydro 1st half required lysis, the reaction, Time, Mol% C. Sld. 1 160 12.5 99.2 2 120 3.1 99.4 3 200 1.9 99.3

For this purpose 3 sheets of drawing paper

Claims (6)

Patent claims: 1. A process for the preparation of sebacic acid from adipic acid, wherein one a) the adipic acid is converted into the monomethyladipic acid ester with methanol, b) a mixture of the monomethyl adipate obtained from its alkali salt and from dimethyl sebacate subjected to electrolysis in methanolic solution,. c) the monomethyl adipate from the electrolysis solution and separating its alkali salt, and d) the dimethyl sebacate is hydrolyzed to sebacic acid in the presence of an acid catalyst and the methanol formed by the hydrolysis is removed from the system during the hydrolysis, characterized in that one
in step c) either after removing the methanol from the electrolysis solution, the alkali salt of the monomethyl adipate is extracted with water or the alkali metal ions are removed before or after the removal of the methanol from the electrolysis solution with the aid of a weak or medium-strength cation exchanger fixed bed, and then the monomethyl adipate separates from the alkali-free mixture, which should contain a maximum of 5 wt .-% methanol, with the help of a weak, medium-strength or pyridinium group-containing fixed anion exchanger bed, iu and in stage d) optionally the dimethyl sebacate in the presence of 1-20% by weight of sebacic acid hydrolyzed 2. The method according to claim 1, characterized in that that the alkali salt of monomethyl adipate with 5-50 wt .-% water, based on the Weight of the electrolyte solution, extracted. 3. The method according to claim 1, characterized in that the monomethyl adipate with a Anion exchanger containing tertiary amino groups is removed 4. The method according to claim 1, characterized in that the alkali metal ions with the help a cation exchanger fixed bed, which with monomethyl adipate and / or a monomethyl adipate containing methanol solution has been regenerated and the monomethyl adipate is removed with the help an anion exchanger fixed bed that has been regenerated with methanol or warm water, separates 5. The method according to claim 1 to 4, characterized in that the separation stage c) with an electrolysis solution carried out in the stage a) has been obtained by passing adipic acid, methanol and water over a fixed bed filled with a strongly acidic cation exchanger. 6. The method according to claim 1 to 5, characterized in that the separation stage c) with an electrolysis solution carried out in the stage b) by electrolytic condensation of the monomethyl adipate in 0.15-3.0% by weight of water containing electrolyte solution has been obtained.