JPS6044398B2 - Method for producing dimethyl higher dibasic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel industrial method for producing dimethyl higher dibasic acid.

More specifically, the present invention relates to a method for producing dimethyl higher dibasic acid by cross-Kolbe electrocondensation of monomethyl adipate or monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms. Dimethyl higher dibasic acid has an extremely wide range of uses as a raw material for perfumes, various polymers, plasticizers, etc.

In particular, dimethyl brazilate, dimethyl benotadecanioate, and dimethyl thapsinate are extremely useful as raw materials for producing ethylene brasilate and cyclopentadecanone, which are extremely important as musk fragrances. Current methods and conventionally proposed methods for producing higher dibasic acids and their esters will be described using the above-mentioned brassylic acid, pentadecanoic acid, thapsic acid, and their esters as examples.

Brassylic acid and its esters are produced by a method in which erucic acid contained in rapeseed oil is oxidized with ozone or permanganic acid.

However, this method has problems in that the yield of the oxidation reaction is low, various compounds are produced by the reaction, it is difficult to purify the desired product, and the purity is low.
Furthermore, the following methods have been proposed as methods for synthesizing brazilic acid.

A method of adding diethyl malonate to methyl undecylenate using ditertiarybutyl peroxide and then hydrolyzing the product [Kirkiacharian,
Berdj: Bull. Soc, Chim, Fr, (
5), 1797 (1971)]. Method of heating and reacting ethyl 11-bromoundecanoate and ethyl cyanacetate in dimethylformamide, then hydrolyzing and decarboxylating the product [DUdirK) 2, A. A. Izv
．． Akad. Nauk, SSSR, Ser, Khim,
1974(6), 1421-1423].

A method of heating 2-ethoxycarbonylcyclododecanone with sodium hydroxide in diethylene glycol and then making it acidic [Japanese Patent Publication No. 46-34406].

6, by reacting 2,7-methylenebiscyclohexanone with peracid in the presence of an alkali carbonate salt in a halogenated organic solvent.
6''-methylenebis(6-hexanolide), and then heat-treated with pressurized hydrogen in the presence of a metal catalyst and an acid catalyst in an alcohol solvent (JP-A-55-113741).

However, these methods are not necessarily satisfactory as industrial methods because raw materials are difficult to obtain and expensive and highly dangerous peroxides must be used in the reaction. Furthermore, various production methods have been proposed for pentadecanedioic acid and its esters.

For example, the acid chloride of glutaric acid monomethyl ester and α
, dioxoester is obtained from a cadmium compound made from ω-dibromopentane, and after saponification, WO
Method of performing If-Kishner reduction [A. Kre
uchhurlasJ. A. C. S. ,75,3339(
1953)], using ustiric acid obtained by hydrolyzing ustiradinic acid with an alkali in methanol, treating this with lead tetraacetate in glacial acetic acid to obtain an aldehydic acid, which was oxidized with hydrogen peroxide in an aqueous alkaline solution. (U.S. Pat. No. 2,717,266), diethyl undecylenylmalonate is prepared from undecylenic acid by a known method. A method of adding hydrogen bromide to this in toluene to obtain diethyl 11-promoundecylmalonate, reacting this with diethyl malonate in the presence of sodium alcoholate, and then hydrolyzing and decarboxylating it (especially Publication No. 32-103n), 1
5,16-dihydro. Oxidation of ethyl xylignocerate with sodium periodate yields ω-oxotridecane-1
- a process in which carboxylic acid is obtained and oxidized with potassium permanganate in acetone (German Patent No. 1187600); alleutic acid is treated with hydrogen bromide in acetic acid to produce 9,10,16-tribromopalmitine; An acid was obtained, which was methyl esterified and treated with zinc dust in methanol to obtain methyl ω-bromohexadecenoate, which was treated in acetic acid with sodium acetate dissolved, and then reduced and saponified to give ω- There are methods such as a method of obtaining hydroxypalmitic acid and oxidizing it (Indian Patent No. 65543). However, all of these methods have problems such as extremely long reaction steps, use of special reagents, and low yields, and cannot be said to be satisfactory as industrial production methods. The following methods have also been proposed for producing thapsic acid diester.

For example, a method for producing synchlohexanone by ring-opening dimerization using Fenton's reagent in the presence of butadiene [CMC Publication 1 Hangetsu Line Fine Chemicals Jl97 Detailed August 1 issue] or electrolytic condensation of azelaic acid monoester. Method [Special Publication Shohaichi No. 11116 KOv
sman, E. P. :Fraidlln, G. N. :T
arkhamOv,G. A. (VSSR)Electr
Osint. MOnOmerOv. 49-73 (198
0)] etc. have been proposed. The former method using Fenton's reagent has the problem that many types of products are produced and the desired product is not the main product, and cannot be said to be sufficient as an industrial production method. Even in the latter electrolytic condensation method,
The former document requires separation into an anode chamber and a cathode chamber using a cation exchange membrane, and states that the water concentration in the anolyte is 30 to 4%, making the electrolyzer complex. There seems to be a problem that the current efficiency is low. The latter document also states that a polymeric film that is difficult to dissolve in water and methanol was formed on the anode, and that the film became thicker as electrolysis progressed and was observed with the naked eye. In any case, the method of electrolytic condensation of dicarboxylic acid monoesters having a large number of carbon atoms still has many problems and cannot be said to be a sufficient method for industrial production. Recently, various fermentation methods have been proposed to convert n-alkanes or monocarboxylic acids into dibasic acids using yeast.

However, this fermentation method also has a low yield and is still not sufficient as an industrial method. In view of the above circumstances, the present inventors have developed an industrially advantageous manufacturing method that can solve all the problems of the various methods proposed to date for manufacturing higher dibasic acid diesters. We conducted intensive research to provide the following.

As a result, monomethyl adipate, which has a relatively small number of carbon atoms, was selected as the dicarboxylic acid monoester, and monomethyl adipate was used at a ratio of at least twice the molar amount of monomethyl dicarboxylate having 8 to 11 carbon atoms, and both were mixed in batches. By cross-Kolbe electrolytic condensation, the current efficiency and selectivity are maintained high, the electrolytic sliding voltage is maintained low, and the monomethyl dicarboxylate having 8 to 11 carbon atoms in the electrolyte becomes 1% by weight or less. It has become possible to conduct electrolytic condensation up to 100%, and it has become possible to industrially produce dimethyl dibasic acid with great advantage. In addition, when monomethyl glutarate is selected as monomethyl dicarboxylate, the number of carbon atoms is limited to the case where monomethyl glutarate is produced from glutaric anhydride and methanol and does not contain glutaric anhydride and/or glutaric acid. 8-1
The same effect as when monomethyl adipate is selected can be obtained by batch-wise cross-Kolbe electrolytic condensation of the two by using 1 mole or more of monomethyl dicarboxylate. That is, in the present invention, a mixed acid of monomethyl adipate and monomethyl dicarboxylate having 8 to 11 carbon atoms is mixed in a methanol solution containing an alkali metal salt thereof, and the water concentration in the methanol solution is adjusted to 0.1.
5 to 3.5% by weight, and batchwise electrolytic condensation of monomethyl adipate to monomethyl dicarboxylate having 8 to 11 carbon atoms in a molar ratio of 2 times or more, or glutaric anhydride and/or glutaric acid. It is characterized in that electrolytic condensation is carried out in the same manner as in the case of monomethyl adipate using an acid-free mixed acid of monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms.

The electrolytic condensation reaction of the present invention can be considered as follows.

That is, as mentioned in the production method for thapsic acid diester, various higher dibasic acids can be produced by Kolbe electrocondensation of dicarboxylic acid monoesters having a relatively large number of carbon atoms, or by cross-Kolbe electrocondensation of various dicarboxylic acid monoesters. One would expect that a diester would be obtained. However, as mentioned above, there are many problems with the conventionally proposed method of electrolytically condensing dicarboxylic acid monoesters having a relatively large number of carbon atoms. In addition, the present inventors previously published a detailed industrial technique for producing dimethyl sebacate from monomethyl adipate, which has a relatively small number of carbon atoms, in Japanese Patent Application Laid-Open No. -1
5267 dirt, JP-A-55-158285, JP-A-56
Comparative Example 4 shows the knowledge obtained by applying this technique to monomethyl azelaate, which has a large number of carbon atoms, although it was disclosed in Japanese Patent No. 44782. Looking at these results, there are problems with the high voltage, poor yield and current efficiency, and a large amount of unreacted monomethyl azelaate remaining.Furthermore, a thin polymer film was also observed on the anode surface. , it can be said that there are problems in simply applying the method proposed by the present inventors. The same can be said of the cross-Kolbe electrolytic condensation reaction of different dicarboxylic acid monoesters having a relatively large number of carbon atoms. Although the cause of this is not clear, one possible factor is that a polymeric substance adheres to the surface of the anode. The adhesion of this polymeric substance onto the anode surface can be extremely reduced by the invention. This reduction in the adhesion of polymeric substances is thought to be due to the effect of preventing the formation of polymeric substances, but monomethyl dicarboxylate with a small number of carbon atoms, especially monomethyl adipate, glutaric anhydride, and/or glutaric acid-free glutaric acid The present inventors have confirmed that monomethyl acid has the effect of partially dissolving the generated polymeric substance, and it is thought that this is due to the effect of dissolving the polymeric substance. The first feature of the present invention is that one dicarboxylic acid monoester in the cross-Kolbe electrolytic condensation is a dicarboxylic acid monoester with a small number of carbon atoms, in particular, monomethyl adipate, glutaric anhydride, and/or glutaric acid-free monomethyl glutarate. ” to choose.

Monomethyl adipate can be produced by a common production method, that is, monomethylation of adipic acid, but monomethyl glutarate can also be produced by such a common production method and subjected to cross-Kolbe electrolysis. Then, as shown in Comparative Example 11, the electrolysis results may be worse than in the case of Kolbe electrolysis using monomethyl dicarboxylate alone having a large number of carbon atoms. The reason for this is that when monomethyl glutarate is separated from a three-component system of glutaric acid, monomethyl glutarate, and dimethyl glutarate by distillation, some of the lutaric acid remaining at the bottom of the distillation is dehydrated to produce glutaric anhydride. However, since this glutaric anhydride is distilled out together with water during distillation, the glutaric acid produced by the re-reaction of glutaric anhydride and water will be mixed into the distilled monomethyl glutarate. In addition, since glutaric anhydride and monomethyl glutarate, which contains a portion of glutaric acid, cannot be purified sufficiently even by redistillation, it is possible to prevent some glutaric anhydride and glutaric acid from being mixed into monomethyl glutarate. It is conceivable that these mixed components have an adverse effect on electrolytic condensation. Therefore, in order to produce monomethyl glutarate that is free from glutaric anhydride or glutaric acid, it is necessary to adopt a special production method. That is, glutaric acid anhydride or monomethyl glutarate that does not contain glutaric acid can only be produced by first heating and dehydrating glutaric acid to produce glutaric anhydride, and then reacting this with methanol to produce monomethyl glutarate. It becomes possible to do so. Another feature of the present invention is that monomethyl adipate or monomethyl glutarate has 8 carbon atoms.
It is to use at least twice the mole of monomethyl dicarboxylate of ~11.

That is, the electrolytic condensation reaction of the present invention is greatly influenced by the molar ratio of monomethyl adipate or monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms. Tables 1 and 3 show that the molar proportions of monomethyl adipate and monomethyl azelaate or monomethyl undecanoate were varied, and the amount of monomethyl adipate in the electrolytic solution was varied. This figure shows the results of batchwise electrolytic condensation until the concentration reached 0.1% by weight or more. From this result, the following can be said. Comparative Examples 1-3 and 8-9. As shown in the above, even if electrolysis is carried out in batches until the concentration of monomethyl adipate in the electrolytic solution becomes 0.1% by weight or less, a considerable amount of monomethyl dicarboxylate having 8 to 11 carbon atoms still remains in the electrolytic solution. Also, although the selectivity has not deteriorated much, the current efficiency is quite high. It has gotten worse, and the average sliding voltage has become quite high. Furthermore, if the concentration of monomethyl dicarboxylate having 8 to 11 carbon atoms remaining in the electrolytic solution was further reduced by further electrolysis, the electrolytic sliding voltage would become even more rapid as shown in Comparative Examples 5 and 10. At the same time, the current efficiency further decreases, and even the selectivity deteriorates. To avoid this, the number of carbon atoms in the electrolyte is 8 to 1.
If the electrolysis is terminated with a considerable amount of dimethyl dicarboxylate remaining in No. 1, the advantages of the batch electrolysis method are largely lost. That is, it is necessary to separate monomethyl dicarboxylate having 8 to 11 carbon atoms in the purification process, but it is extremely difficult to separate it by distillation from the product dimethyl dibasic acid, so the separation equipment is complicated. Further, problems arise such as part of the monomethyl dicarboxylic acid being lost during separation, or insufficient separation resulting in a decrease in the purity of the product dimethyl dibasic acid. On the other hand, when monomethyl adipate is used in a molar ratio of at least twice that of monomethyl dicarboxylate having 8 to 11 carbon atoms, these problems are significantly improved.
Furthermore, when monomethyl adipate is used in a molar ratio of 5 times or more, the situation is improved to almost the same as in the case of electrolysis using monomethyl adipate alone. Although the present invention is characterized by batch electrolysis, if one does not mind the complexity of the separation operation of the raw material monomethyl dicarboxylate and the product dimethyl dicarboxylate in the electrolyte purification process, It is possible to carry out continuous electrolysis in which electrolytic condensation is carried out while maintaining a constant concentration of .

That is, the method of adsorbing and separating the raw material monomethyl dicarboxylate onto an anion exchange resin proposed by the present inventors (
JP-A-15267 Publication, U.S. Patent No. 423731
7)).
It goes without saying that this method can also be applied to separating monomethyl dicarboxylate having 8 to 11 carbon atoms remaining in the batch electrolysis described above. In the present invention, dimethyl sebacate or dimethyl suberate is always obtained as one of the products, and this substance is extremely important industrially as a raw material for plasticizers, lubricating oils, nylon, adhesives, etc.

Further, the amount of each product produced can be controlled by changing the molar ratio of the raw materials monomethyl adipate or monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms in the reaction. However, if monomethyl adipate or monomethyl glutarate is used in too large a quantity, the amount of the desired dimethyl higher dibasic acid produced will be small and problems will arise in separation. It is preferable that the amount used is 50 times or less by mole or less relative to monomethyl dicarboxylate. Next, details of producing dimethyl higher dibasic acid from monomethyl adipate and monomethyl dicarboxylate having 8 to 11 carbon atoms will be described.

Monomethyl adipate and monomethyl dicarboxylate having 8 to 11 carbon atoms, which are used as raw materials, can be obtained by esterifying adipic acid and dicarboxylic acid having 8 to 11 carbon atoms, respectively, by a conventional method.

Industrially, it is preferable to use a strongly acidic cation exchange resin as the esterification catalyst. The strongly acidic cation exchange resin used as a catalyst is a polystyrene resin having a sulfonic acid group, and may have a gel type structure or a porous type structure. Also, regarding how to use resin,
In order to carry out the esterification reaction continuously and to effectively exert the function of the ion exchange resin, it is necessary to use it as a fixed bed. Furthermore, if a strongly acidic cation exchange resin is used continuously for a long period of time, the amount of metal ions adsorbed to the resin will increase, and the resin's esterification catalytic ability will gradually decrease. How to play,
For example, reuse becomes possible by regenerating with a nitric acid aqueous solution. For this reason, it is preferable to separately perform the adsorption of metal ions and the esterification reaction using separate ion exchange resins. Regarding the reaction temperature in a fixed bed filled with a strongly acidic cation exchange resin, a higher temperature is more efficient from the point of view of reaction rate, but considering the heat resistance of the resin, a temperature of 60' is practically recommended.
C to 90°C is preferred.

When a raw material liquid is passed through a fixed bed filled with a strongly acidic cation exchange resin, it is undesirable for dicarboxylic acid to precipitate from the raw material liquid at the operating temperature of the fixed bed. In order to prevent precipitation of dicarboxylic acid from the raw material solution, solvents such as methanol, water, and dimethyl dicarboxylate must be maintained at a certain amount or more. This is undesirable because it is necessary to remove the solvent during the separation and purification process. Therefore,
In order to prevent precipitation of adipic acid from the raw material solution without using too much solvent, it is necessary to compensate for the lack of solvent in the raw material solution by partially circulating the effluent from the fixed bed. Become. The amount of circulation of the effluent from the fixed bed cannot be determined because it varies depending on the amount of dicarboxylic acid and solvent in the raw material liquid and the operating temperature of the fixed bed, but it is necessary to ensure that the dicarboxylic acid does not precipitate from the raw material liquid. Good to have. Further, the flow rate of the raw material solution through the fixed bed is not particularly limited, but it is preferably set to such an extent that the esterification reaction within the fixed bed proceeds to near equilibrium. The solution in which electrolytic condensation is carried out is a methanol solution containing the raw materials monomethyl adipate, monomethyl dicarboxylate having 8 to 11 carbon atoms, and their neutralized salts, and the product dimethyl dicarboxylate and other by-products. May contain.

Electrolytic condensation is basically carried out batchwise in consideration of separation and purification of the product in subsequent steps. Furthermore, it is preferable to conduct electrolytic condensation until the total concentration of monomethyl adipate and monomethyl dicarboxylate having 8 to 11 carbon atoms in the electrolytic solution becomes 1% by weight or less at the end of electrolysis. Further, as the electrolytic method, any of the following methods may be used. That is, one method is to charge a certain amount of monomethyl dicarboxylate at the start of electrolysis and conduct the electrolysis completely batchwise until the total concentration of monomethyl dicarboxylate in the electrolytic solution becomes below a certain concentration. Another method is to charge a certain amount of monomethyl of both dicarboxylic acids at the start of electrolysis, and add the remainder continuously during electrolytic condensation, and then the total concentration of monomethyl of both dicarboxylic acids in the electrolyte becomes below a certain concentration. This is a batchwise method. Of the two electrolytic methods, the latter method is preferable in terms of voltage. In the case of the latter electrolytic method, monomethyl adipate has 8 carbon atoms.
The molar ratio of -11 to monomethyl dicarboxylate does not necessarily have to be kept at twice the mole or more during electrolytic condensation, but it is sufficient to keep it at twice the mole or more as a whole. However, it is not preferable to extremely lower the molar ratio of monomethyl adipate to monomethyl dicarboxylate having 8 to 11 carbon atoms at the final stage of electrolysis because a large amount of monomethyl dicarboxylate having 8 to 11 carbon atoms will remain. Regarding the water concentration in the methanol solution during electrolytic condensation, as shown in Examples and Comparative Examples 6 and 7, if the water concentration during electrolytic condensation is extremely reduced, the current efficiency becomes extremely poor. If the concentration exceeds 3.5% by weight, the selectivity and current efficiency will also deteriorate.

) Therefore, in order to maintain high selectivity and current efficiency, it is necessary to maintain the water concentration in the range of 0.15 to 3.5% by weight. The mixed acid of monomethyl adipate, monomethyl dicarboxylate having 8 to 11 carbon atoms, and monomethyl dicarboxylate having 8 to 11 carbon atoms to be charged during electrolytic condensation is 10 to
Used at 5% saliva volume.

If the concentration is higher than 5% by weight, the voltage will be high, and if the concentration is lower than 1% by weight, the volumetric efficiency will be poor, and the current efficiency will also be poor.

In order to increase the conductivity of the solution during electrolytic condensation in the present invention, hydroxides, carbonates, bicarbonates, methylates, ethylates or amines of lithium, potassium, sodium are used as neutralizing bases. However, amines are oxidized at the anode and accelerate the consumption of the anode, and the use of lithium compounds deteriorates current efficiency. Therefore, it is desirable to use hydroxides, carbonates, bicarbonates, and methylates of sodium and potassium. Further, the degree of neutralization (defined as the molar proportion of the mixed acid to be neutralized with a base) during the preparation of the mixed acid of monomethyl adipate and monomethyl dicarboxylate having 8 to 11 carbon atoms is preferably 2 to 50 mol%. . Neutralization degree is 2
If the concentration is less than mol %, the voltage will be high, and if the concentration is higher than 50 mol %, the current efficiency will be low. The current cell used may be one commonly used in organic electrolytic reactions, as long as it is capable of passing the electrolytic solution between the two electrodes at a high flow rate. For example, an electrolytic cell has a cathode plate and an anode plate facing each other in parallel, with a polypropylene plate between the two electrodes defining the electrode spacing. This polypropylene plate has an opening in the center so that the electrolyte can flow therethrough. The current-carrying area of the electrode is determined by the size of this opening, and the electrode spacing is determined by the thickness of this plate. The electrolytic solution enters through a supply port provided in the electrolytic cell, undergoes a reaction while passing between the two electrodes, exits through an outlet port, and is circulated to the electrolyte tank.
As for the electrode materials used in electrolytic condensation, platinum, rhodium, ruthenium, iridium, etc. are used alone or in an alloy for the anode, and are usually used for plating, and titanium, ruthenium, and iridium are used for the plating substrate. etc. are used.

The cathode preferably has a low hydrogen overvoltage, but is not particularly limited, and platinum, iron, stainless steel, titanium, etc. can be used. The flow rate of the electrolytic solution in the electrolytic cell is preferably 1 to 4 m/sec.

If the flow rate is less than 1 m/sec, the current efficiency will be low, and if the flow rate is faster than 4 m/sec, the pressure loss within the electrolytic cell will increase.

The spacing between the electrodes is 0.5~3Tn! n is preferred. 0.5W
If it is less than R, the pressure loss in the electrolytic cell will increase, and if it is wider than 3, the voltage will increase.

The current density is preferably 5 to 4 QA1d, and if it is less than 5A1d, the current efficiency becomes low. The temperature of the electrolyte is 45-65
°C is preferred. If the temperature is lower than 45° C., the current efficiency will be low and the voltage will be high, and in some cases, products will precipitate.
Temperatures higher than 65°C are limited by the boiling point of the electrolyte.

The purification and separation of the product from the electrolytic solution after the completion of electrolytic condensation is carried out using the method previously proposed by the present inventors for producing dimethyl sebacate by electrolytically condensing monomethyl adipate alone (Japanese Patent Application Laid-open No. 55-1979-1). Publication No. 158285 and JP-A-56-447
This can be carried out in substantially the same manner as in Japanese Patent No. 82).

That is, one method is to add water to the electrolytic solution and then remove methanol to separate it into two oil and water layers.The product is purified by distillation from the oil layer, and the raw material monomethyl adipate and the water layer are purified by distillation from the oil layer. This is a method in which monomethyl dicarboxylate having 8 to 11 carbon atoms is added, water is removed by evaporation, and the alkali metal salts thereof are collected and recycled. Furthermore, when the electrolytic condensation conditions are limited as follows, that is, the water concentration in the electrolyte is 0.6 to 3.
5% by weight, and monomethyl adipate and carbon number 8
When the concentration of the alkali metal salt of the mixed acid monomethyl dicarboxylate in ~11 in the electrolyte is 1% by weight or more and 3 parts by weight or less based on the water in the electrolyte, methanol is simply removed from the electrolyte. It is also possible to separate the oil and water into two layers, distill and purify the product from the oil layer, and collect and recycle the aqueous layer as it is. In this method, it is more preferable to further limit the electrolytic condensation conditions. In other words, considering the purity of dimethyl higher dibasic acid, when it is separated into two oil-water layers, in order to minimize the distribution of the alkali metal salt of the mixed acid in the oil layer, the alkali of the mixed acid relative to the water in the electrolytic solution must be More preferably, the amount of metal salt is 2 parts by weight or less. In addition, in this method, the amount of alkali metal salt in the mixed acid is limited as much as possible, so the voltage is slightly higher. Therefore, as mentioned earlier, it is preferable to adopt an electrolysis method that is preferable in terms of lowering the voltage, that is, a method in which a certain amount of monomethyl dicarboxylate is charged at the start of electrolysis, and the remainder is added continuously during electrolytic condensation. is extremely effective, and it is more preferable that the weight ratio of both monomethyls charged in advance and the remainder be in the range of 2:8 to 8:2. Next, details of the separation and purification method will be described.

The latter method does not include the two operations of the former method: adding water during methanol removal and removing water from the aqueous layer after methanol removal. Therefore, details of the former method will be described below. In the step of removing methanol, methanol is removed after or while adding water to the electrolytic solution. Water may be added in advance before the electrolyte is fed to the methanol distillation column, or it may be directly fed to the methanol distillation column. The amount of water to be added should be such that when methanol is removed to a low concentration, the alkali metal salt of the mixed acid will not precipitate at the bottom of the methanol distillation column, but it is usually 0.5% of the alkali metal salt of the mixed acid. ~5 parts by weight is preferred. If it is less than 0.5 parts by weight, the amount of methanol remaining in the residual liquid after methanol removal will be large, and if it is more than 5 parts by weight, there is a possibility that hydrolysis of the ester moiety will occur.

Methanol removal in the methanol distillation column is carried out under normal pressure. It is desirable that the methanol concentration in the residual liquid after methanol removal be as low as possible from the viewpoint of suppressing the distribution of the alkali metal salt of the mixed acid to the oil layer after the next two-layer separation. It is sufficient if it is less than % by weight,
More preferably, it is 3% by weight or less. In addition, during methanol distillation, the temperature at the bottom of the methanol distillation column is over 800C, and if the residual liquid after methanol removal stays at the bottom of the column for a long time, hydrolysis of the ester portion will occur, so the residence time is It is better to keep the residence time as short as possible, but it is sufficient if the residence time is within 2 hours. In the step of separating the product dimethyl higher dibasic acid and the alkali metal salt of the mixed acid, the residual liquid after methanol removal is cooled and left to stand to separate into an oil layer and an aqueous layer.

As mentioned earlier, if methanol remaining in the residual liquid after methanol removal exceeds 6% by weight, it will be distributed to the oil layer, although this will depend on the amount of alkali metal salt in the mixed acid and water. As the amount of alkali metal salt in the liquid mixture increases, the separation of oil and water also deteriorates. Furthermore, the vertical relationship between oil and water after standing still varies depending on the amount of the alkali metal salt of the mixed acid and water, but if the remaining methanol concentration is high, the oil layer becomes the lower layer. Therefore, it is necessary to avoid residual methanol concentration near the boundary region where the oil-water layer reverses. In the step of purifying dimethyl higher dibasic acid, the separated oil layer may be purified by distillation using a conventional method.

In the process of recovering the alkali metal salt of the mixed acid and circulating it to electrolytic condensation, monomethyl adipate and/or monomethyl dicarboxylate having 8 to 11 carbon atoms are added in advance to the separated aqueous layer, and then water is removed by evaporation. Since precipitation of the alkali metal salt of the mixed acid does not occur, it becomes possible to freely adjust the water concentration in the residual liquid.

Therefore, the amount of water in the entire second step can be adjusted very easily. For monomethyl adipate and/or monomethyl dicarboxylate having 8 to 11 carbon atoms to be added to the aqueous layer in advance, raw materials used for electrolytic reaction can be used, and the amount is determined by removing as much water as possible from the residual liquid. It is sufficient that the alkali metal salt of the mixed acid does not precipitate, and if the amount is too large, the capacity of the water evaporator increases, so from an industrial perspective, it is usually preferably 1 to W parts by weight based on the amount of the alkali metal salt of the mixed acid. Further, when water is removed by evaporation, it is desirable that the residence time of the liquid in the evaporator be as short as possible in order to prevent denaturation due to heating, but from an industrial perspective, it is sufficient that the residence time of the liquid is as short as possible. Furthermore, when evaporated, a small amount of monomethyl adipate and/or monomethyl dicarboxylate having 8 to 11 carbon atoms is mixed in with water, so the entrained monomethyl adipate and/or dicarboxylic acid having 8 to 11 carbon atoms Preferably, a column is provided for recovering the monomethyl acid. In addition, when the amount of alkali metal salt of the mixed acid circulating in the electrolytic condensation process is small, generally when the concentration in the prepared charged electrolyte is 4.5% by weight or less, water from the aqueous layer is After the removal has been carried out in advance to a saturated aqueous solution of the alkali metal salt of the mixed acid, monomethyl adipate and/or
Alternatively, it can also be carried out by adding monomethyl dicarboxylate having 8 to 11 carbon atoms.

Next, one embodiment of a method for producing dimethyl higher dibasic acid from monomethyl adipate and monomethyl tadicarboxylate having 8 to 11 carbon atoms will be described with reference to a flow sheet shown in the drawings.

To explain the first step, 2 is a dissolution tank, and dicarboxylic acid and methanol are supplied to the tank 2 from the supply port 1, and are removed from the upper O part of the distillation column 5, the upper part of the distillation column 7, the lower part of the distillation column 8, and the dissolution tank 2. Methanol and water, dimethyl dicarboxylate, dicarboxylic acid, monomethyl dicarboxylate, and a portion of the reaction liquid extracted from ports 9 are circulated. Dicarboxylic acid is dissolved in the dissolution tank 2 and is supplied to the upper part of the ion exchange resin tower 3 as a raw material liquid. In the ion exchange resin column 3, part of the adsorption and esterification reaction of trace amounts of metal ions in the raw material liquid takes place, and the liquid from which metal ions have been removed is extracted from the lower part of the ion exchange resin column 3, and the ions are removed. It is sent to the upper part of the exchange resin tower 4. Within the ion exchange resin tower 4, an esterification reaction is mainly performed. The resin in the ion-exchange resin tower 3 needs to be regenerated by a general regeneration method, for example, using a nitric acid aqueous solution, when metal ions leak out from the lower part of the tower at a certain concentration or more. Ion exchange resin tower 4
The ester reaction liquid is extracted from the lower part of the ester, a portion of which is circulated through the extraction port 9 to the dissolution tank 2, and a portion of which is sent to the distillation column 5. In the distillation column 5, methanol and water are distilled off, and the residual liquid is extracted from the lower part of the column 5 and sent to the distillation column 6. Methanol and water extracted from the upper part of the distillation column 5 are circulated to the dissolution tank 2. Water and low-boiling by-products are distilled off in the distillation column 6, and the residual liquid is extracted from the lower part of the column 6 and transferred to the distillation column 7.
sent to. In the distillation column 7, dimethyl dicarboxylate is distilled off, and the residual liquid is extracted from the lower part of the column 7 and sent to the distillation column 8. Dimethyl dicarboxylate distilled off from the upper part of the distillation column 7 is circulated to the dissolution tank 2. Monomethyl dicarboxylate is obtained from the upper part of the distillation column 8, and a residual liquid containing dicarboxylic acid and monomethyl dicarboxylate is extracted from the lower part of the column and circulated to the dissolution tank 2. The monomethyl dicarboxylate obtained from the upper part of the distillation column 8 is sent to the next second step.
To explain the second step, 10 is an electrolytic solution tank, and monomethyl adipine triate and monomethyl dicarboxylate having 8 to 11 carbon atoms obtained in the first step are supplied to the tank 10, and the upper part of the distillation column 12 and the recovery A mixed acid solution containing methanol and an alkali metal salt of the mixed acid extracted from the lower part of the column 19 is circulated.

The solution charged in the electrolytic solution tank 10 is circulated between the three electrolytic tanks 11 and electrolytic condensation is performed therebetween. When the electrolytic condensation is completed, the electrolytic solution is extracted from the electrolytic solution tank 10, water extracted from the upper part of the recovery tower 19 is supplied to the electrolytic solution from the supply port 20, and the water-containing electrolytic solution is transferred to the distillation column. Sent to 12F. In the distillation column 12, methanol is distilled off and circulated to the electrolyte tank, and the residual liquid is extracted from the lower part of the column 12 and sent to a decanter 13. In the decanter 13, the oil layer is left standing and separated into two layers, and the oil layer is sent to the distillation column 14, and the water tank contains the monomethyl adipate and/or monomethyl dicarboxylate having 8 to 11 carbon atoms obtained in the first step. Monomethyl dicarboxylate having 8 to 11 carbon atoms is supplied from the supply port 21 and then sent to the lower part of the evaporator 18. While water is evaporated in the evaporator 18, the water evaporated from the upper part of the evaporator 18 and the residual liquid are mixed. is sent to the recovery tower 19. Water is extracted from the upper part of the recovery tower 19 and circulated to the supply port 20. The alkali metal salt of the mixed acid is extracted from the lower part of the recovery tower 19 as a solution of the mixed acid,
It is circulated to the electrolyte tank 10. On the other hand, in the distillation column 14, low-boiling point impurities are distilled off, and the residual liquid is sent to the distillation column 15. In the distillation column 15, dimethyl sebacate is obtained from the upper part of the column, and the residual liquid is sent to the distillation column 16. In the distillation column 16, higher dimethyl dibasic acid with the next highest boiling point is obtained from the upper part of the column, the residual liquid is sent to the evaporator 17, and higher dimethyl dibasic acid with the highest boiling point is obtained from the upper part of the column. High boiling point impurities are extracted from the lower part of the evaporator 17. In addition, in the electrolytic condensation reaction of the second step, the water concentration in the electrolyte is set to 0.6 to 3.
5% by weight, and monomethyl adipate and carbon number 8
When the concentration of the alkali metal salt of the mixed acid of monomethyl dicarboxylate of ~11 in the electrolytic solution is limited to 1% by weight or more and 3 parts by weight or less relative to the water in the electrolytic solution, the drawing of the second step The parts surrounded by broken lines, the supply of water at the supply port 20 and the supply of monomethyl dicarboxylate at the supply port 21 are not necessarily necessary, and the aqueous layer in the decanter 13 can be directly circulated to the electrolyte tank 10.

Next, details of producing dimethyl higher dibasic acid from monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms will be described.

The monomethyl dicarboxylate having 8 to 11 carbon atoms to be used can be obtained by the method described above.

On the other hand, monomethyl glutarate must be obtained by the reaction of glutaric anhydride and methanol as described above.

The glutaric anhydride used in this reaction is prepared using glutaric acid without a solvent or at a temperature of 150°C or higher. In the presence of an inert solvent with S, α, at 150 to 270°C under reduced pressure or normal pressure.
, preferably by thermal dehydration at 200 to 25 CfC. In this case, in the absence of a solvent, it is possible to completely dehydrate by slightly reducing the pressure, while in the presence of a solvent, a slight excess of solvent is used to remove water together with the solvent for complete dehydration, and then the obtained anhydride is purified by distillation. preferable. If dehydration is incomplete, dehydration will progress further during distillation purification of glutaric anhydride, and water will also be distilled out along with glutaric anhydride, resulting in some glutaric acid being generated in the purified glutaric anhydride. This is undesirable because it gets mixed in. Next, in the reaction of glutaric anhydride and methanol, it is desirable to use a slight excess of methanol, preferably methanol in an amount equal to or more than 3 times the molar amount relative to glutaric anhydride.

If methanol is used in excess, a portion of glutaric acid will be produced by the trace amount of water contained in methanol, which is not preferable. The reaction may be carried out at a temperature of 40° C. or higher and lower than the reflux temperature of methanol between 2 and 1 C@, and there is no need to use a catalyst. After the reaction is complete, monomethyl glutarate may be purified by distillation, but during distillation purification, a small portion of monomethyl glutarate changes to glutaric acid and dimethyl glutarate, and a very small amount remains in the distilled monomethyl glutarate. Since glutaric anhydride may be mixed in, it is desirable to subject the reaction solution to electrolytic condensation as a methanol solution of monomethyl glutarate as it is. In addition, glutaric anhydride is produced in the same manner as in the case of glutaric acid alone, using mixed dicarboxylic acids of succinic acid, glutaric acid, and adipic acid, which are produced as by-products when industrially producing adipic acid, as raw materials. You can also do this.

The electrolytic condensation reaction using monomethyl glutarate and monomethyl dicarboxylate having 8 to 11 carbon atoms obtained as described above and the separation and purification of the product after the reaction are carried out using monomethyl adipate as described above. It was done in the same way.

As detailed above, the method of the present invention has the following advantages over conventional methods and various other proposed methods.

First, raw materials are extremely easy to obtain and are inexpensive. Furthermore, no special chemicals or chemicals that pose safety issues are used. Second, the desired product can be obtained with extremely high yield and high current efficiency. That is, it is extremely easy to purify the target product from the reaction product, and it is possible to obtain a product of high purity. Examples 1 to 3, Comparative Examples 1 to 4, Reference Example 1 Monomethyl adipate was obtained as follows.

That is, adipic acid 33! Weight %, dimethyl adipate 3
2.3% by weight, monomethyl adipate3. Lime weight %, methanol 12. Seed amount % and water 18. 1 part by weight of a liquid consisting of 1% heel weight and 20% adipic acid. Heel weight %, dimethyl adipate 2
2. A mixture of 4.2 parts by weight of a liquid consisting of 37.0% by weight of monomethyl adipate, 3.6% by weight of methanol, and 16.1% by weight of water was used as the raw material liquid flowing into the ion exchange resin column. It was prepared as follows. Next, 100 ml (water standard) of strongly acidic cation exchange resin Amperlite 200C (manufactured by Rohm & Haas Co., Ltd., trade name) regenerated into H-type was replaced with water and packed into a column (inner diameter 15 wtφ x 1000 mh with 1 jacket). Then, hot water at 80'C was passed through the jacket.

Next, the raw material liquid 2k9 flowing into the ion-exchange resin tower, which has been heated to 80'C in advance, is passed through downward flow for separation. The solution was passed through an ion exchange resin column at V4, and 400 g of the effluent was removed as an initial stream, and the remaining solution was sampled as a reaction solution.
Analysis of the reaction solution by gas chromatography revealed that it contained 37.1% by weight of monomethyl adipate and 22.4% by weight of dimethyl adipate. Monomethyl adipate was separated and purified from this reaction solution by distillation. . Monomethyl azelaate was obtained as follows.

That is, azelaic acid 33. Weight %, dimethyl azelaate 29. Seed amount%, monomethyl azelaate 0.9% by weight
, other dicarboxylic acids 10.3% by weight, methanol 10%
．． 1 part by weight of a liquid consisting of 16.5% by weight of azelaic acid and 16.5% by weight of azelaic acid and 19.2% by weight of dimethyl azelaate.
% by weight, monomethyl azelaate 31.9% by weight, other dicarboxylic acids 14.4% by weight, methanol 3. Capacity%
and water13. A mixture of 4.5 parts by weight of a liquid consisting of 1.5% by weight was prepared as a raw material to be fed into the ion exchange resin column.
This raw material liquid was passed through an ion exchange resin column in exactly the same manner as in the case of producing monomethyl adipate. Monomethyl azelaate in the obtained reaction solution was 32. The amount of dimethyl azelaate was 19.1% by weight. Monomethyl azelaate was separated and purified from this reaction solution by distillation. An electrolytic condensation reaction was carried out using monomethyl adipate and monomethyl azelaate produced as described above.

That is, put monomethyl adipate and/or monomethyl azelaate in the amount shown in Table 1 into an electrolyte tank,
Next, add potassium hydroxide so that the degree of neutralization of the carboxylic acid becomes 8%, then add methanol, and finally add the water concentration in the charging solution to 3. Water was added to make the weight %. This prepared solution was circulated to the electrolytic cell. The electrolytic cell is 1.0CT1t for both poles.
×1(1)o, the cathode is a titanium plate with a thickness of 2T, and the anode is a titanium plate with a thickness of 2Tn1. A titanium plate plated with 4 micron platinum is used, and the current carrying area between the two electrodes is 1.
A polyethylene plate with a thickness of 1 piece with openings was placed so that the electrode spacing was 1T so that the size was maintained at 0cm x 100C7n.
It was defined as 1n.

The electrolytic cell used had a liquid supply port and a liquid outlet. The liquid was flowed between the two electrodes at a flow rate of 2 ml/sec, and the current density was set to 20
In A1dd, electrolysis was carried out while maintaining the temperature of the liquid at 50 to 57C. Electrolysis was carried out while sampling the electrolytic solution and measuring the remaining amount of monomethyl adipate by gas chromatography analysis, and the end of electrolysis was determined when the concentration became 0.1% by weight or less.

After the electrolysis was completed, each component in the electrolyte was measured by gas chromatography analysis. The results are shown in Table 1. Note that the selectivity and current efficiency were calculated assuming that the neutralization of monomethyl adipate and monomethyl azelaate with potassium hydroxide was carried out at the charged molar ratio of each carboxylic acid. The degree of neutralization of carboxylic acid in a prepared electrolytic solution is expressed by the following formula. Further, the current efficiency was determined on the assumption that 1 mole of each product was produced from the amount of electricity of 2 Faradays.

The formulas for calculating the selectivity and Tokamatsu efficiency are as follows. The same procedure was carried out in the subsequent Examples and Comparative Examples.

Comparative Example 5 Electrolytic condensation was carried out in exactly the same manner as in Comparative Example 1. Even when the concentration of monomethyl adipate in the solution became 0.1% by weight or less, electrolytic condensation was continued.

From that point on, the voltage began to rise, and when the voltage reached 60V, the electrolysis was terminated. The results are shown in Table 1.
Example 4 Using the same electrolytic device as in Example 1, 235 g of monomethyl adipate, 5 g of monomethyl azelaate, was added to the electrolyte tank.
Add 9 g of methanol and 579 g of methanol, then add potassium hydroxide so that the degree of neutralization of the carboxylic acid is 10%, and finally the water concentration in the liquid is 1. Water was added to adjust the heel weight%.

The charging molar ratio of monomethyl adipate to monomethyl azelaate was 5:1. Next, increase the current density to 11AI
dr! The conditions were the same as in Example 1 except for changing the volume to 1, and a mixed solution of 92 g of monomethyl adipate and monomethyl azelate Z momme (mole ratio of monomethyl adipate/monomethyl azelaate was 511) was added to the electrolyte tank. 5. Electrolytic condensation was carried out while continuously supplying the solution. Furthermore, 2. Electrolytic condensation between C@ was continued. The voltage is 6.8-6.
It was 6V. The amount of liquid after the electrolysis was completed was 900 g, and the concentration of each component in the liquid was measured using a gas chromatograph, and the results showed that dimethyl sebacate was 17. The saliva content was 6.5% by weight of dimethyl brassylate, 0.8% by weight of dimethyl thapsinate, and 0.6% by weight of residual monomethyl azelaate. Also, the water concentration is 1.9% by weight
It was hot. The selectivity and current efficiency of each electrocondensation product are shown in Table 2. Next, electrolytic condensation reaction was repeated to obtain electrolytic solution 10k9.

After adding 0.73 kg of water to this electrolytic solution, it was continuously supplied to the middle stage of the distillation column, and the temperature of the bottom of the column was adjusted to 10°C under normal pressure. I pulled it out. The average residence time at the bottom of the distillation column was 1 hour, and the average methanol concentration in the liquid extracted from the bottom of the column was 1.1% by weight. The liquid extracted from the bottom of the tower was cooled and separated into two layers using a decanter. The oil layer is 2.37k9
The potassium salt of the mixed acid of monomethyl adipate and monomethyl azelaate was present in this oil layer at a ratio of 5:1, and was distributed in an amount of 0.01% by weight. The oil layer was further distilled to separate dimethyl sebacate, dimethyl brassylate, and dimethyl thapsinate. The aqueous layer had a concentration of 1.40k9, and after adding 1.33k9 of monomethyl adipate to the aqueous layer, water was evaporated at 125°C under normal pressure in an evaporator. The residence time of the liquid in the evaporator is 3 minutes,
After water evaporation, the water concentration in the monomethyl adipate solution containing potassium salts of monomethyl adipate and monomethyl azelaate was 7.2% by weight. This liquid was collected and reused for the electrolytic condensation reaction. Example 5 Using the same electrolytic apparatus as in Example 1, 289 g of monomethyl adipate, 1 monomethyl azelaate, and 664 g of methanol were placed in an electrolyte tank, and then potassium hydroxide was added so that the degree of neutralization of the carboxylic acid was 10%. was added, and finally water was added so that the water concentration in the liquid was 3.3% by weight.

Next, the conditions were the same as in Example 1 except that the current density was changed to 11 AIdrft, and electrolytic condensation was carried out while 107 g of monomethyl adipate was continuously supplied to the electrolyte tank for 5 hours to supply monomethyl adipate. After this, electrolytic condensation was carried out for 2.7 hours until the concentration of both monomethyl adipate and monomethyl azelaate in the electrolytic solution became 0.1% by weight or less. Voltage is 6.7~
It was 6.4V. The amount of liquid after completion of electrolysis was 1026 g, and the concentration of each component in the liquid was measured using a gas chromatograph, and the results showed that dimethyl sebacate was 19.1% by weight, dimethyl brassylate was 3.7% by weight, and tapsin was 19.1% by weight. Dimethyl acid was 0.3% by weight. The results are shown in Table 2. Next, electrolytic condensation was repeated to obtain 10 kg of electrolyte.

This electrolytic solution was continuously supplied to the middle stage of the distillation column, and the temperature at the bottom of the column was brought to 10°C under normal pressure, and methanol was continuously extracted from the top of the column and an oil-water mixture from the bottom of the column. The average residence time at the bottom of the distillation column was 1 hour, and the average methanol concentration in the liquid extracted from the bottom of the column was 1.5%. The liquid extracted from the bottom of the column was cooled and separated into two layers of oil and water in a decanter. The oil layer is 2.99k9,
Assuming that the potassium salts of monomethyl adipate and monomethyl azelaate are present in the charged proportions at the start of electrolysis, 0. It was distributed in μs weight %. Dimethyl sebacate, dimethyl brassylate, and dimethyl thapsinate were separated from the oil layer by distillation and purification. The aqueous layer weighed 0.72 kg, and the concentration of potassium salts of monomethyl adipate and monomethyl azelaate was 5% by weight, and was recovered as it was and reused in the electrolytic condensation reaction). Example 6 Using the same electrolytic apparatus as in Example 1, 548 g of monomethyl adipate and monomethyl azelaate and 4 expanded methanol were added to the electrolyte tank, and then the degree of neutralization of carboxylic acid was adjusted to 1.
Sodium hydroxide was added so that the concentration was 0%, and finally water was added so that the water concentration in the liquid was 2.5% by weight.

The molar ratio of monomethyl adipate to monomethyl azelaate was 1(7)1. Then the current density is 1Q
Electrolysis was carried out under the same conditions as in Example 1 except that A and 1d were changed.

7. Until the concentration of both monomethyl adipate and monomethyl azelaate in the electrolyte becomes 0.1% by weight or less.
Electrolysis was carried out for 7 hours. The voltage varied from 7.7V to civilian 8V. The amount of liquid after electrolytic condensation was 883g, and the concentration of each component in the liquid was 19.5g for dimethyl sebacate. % seeds, dimethyl brassylate was 4.3% by weight and dimethyl thapsinate was 0.2% by weight. The selectivity and current efficiency of each electrocondensation product are shown in Table 2. Example 7 The amount of monomethyl azelate in Example 6 was 15 g.
Electrolysis was carried out in the same manner as in Example 6 except that r' was changed to 7.1.
I went for a full time.

The voltage varied from 7.5V to 5.7V. The amount of liquid after the electrolysis was completed was 856 g, and the concentrations of each component in the liquid were 21.1% by weight for dimethyl sebacate and 1.5% by weight for dimethyl brassylate. The slag weight is %, and dimethyl thapsinate is 0.
It was less than 0.05% by weight. The selectivity and current efficiency of each product are shown in Table 2. Comparative Example 6 Electrolytic condensation was carried out in the same manner as in Example 6 except that the water concentration in the charging solution was changed to 4.5% by weight.

Electrolysis time is 9.0 bridges, voltage is 7.5-5.6V
changed to. The amount of liquid after electrolytic condensation was 878 g, and the concentration of each component in the liquid was 17.4% by weight for dimethyl sebacate and 3.5% by weight for dimethyl brassylate. The amount of dimethyl thapsinate was 0.2% by weight. The selectivity and current efficiency of each electrocondensation product are shown in Table 2. Comparative Example 7 In Example 6, the alkali to neutralize the mixed acid was sodium hydroxide (9.9gh) and sodium methylate (13.9gh).
4g, and the water concentration in the preparation liquid was 0.10% by weight.
Electrolytic condensation was carried out in exactly the same manner as in Example 6, except that .

Although electrolytic condensation was continued for 1 hour, almost no electrolytic condensation product was produced.

Examples 8 to 1 Comparative Examples 8 and 9 Monomethyl adipate and monomethyl undecanoate were produced in the same manner as in Example 1 using a strongly acidic cation exchange resin as an esterification catalyst.

Next, electrolytic condensation was performed using monomethyl adipate and monomethyl undecanoate. The electrolytic condensation was carried out in the same manner as in Example 1 except that monomethyl azelaate was changed to monomethyl undecanoate. The results are shown in Table 3. Comparative Example 10 Electrolytic condensation was carried out in exactly the same manner as in Comparative Example 4, and electrolytic condensation was continued even when the concentration of monomethyl adipate in the electrolytic solution became 0.1% by weight or less.

From that point on, the voltage began to rise, and when the voltage reached 60V, the electrolysis was terminated. The results are shown in Table 3. Example 11 Monomethyl adipate and monomethyl suberate were obtained by esterifying adipic acid and suberic acid, respectively, using a strongly acidic cation exchange resin as an esterification catalyst.

Next, electrolytic condensation was performed using monomethyl adipate and monomethyl suberate.

The electrolytic condensation was carried out in exactly the same manner as in Example 1 except that monomethyl azelate was changed to monomethyl suberate. The results are shown below. Example 12 Monomethyl adipate and monomethyl sebacate were obtained by esterifying adipic acid and sebacic acid, respectively, using a strongly acidic cation exchange resin as an esterification catalyst.

Next, using the same electrolytic device as in Example 1, monomethyl adipate, monomethyl sebacate, and methanol were placed in an electrolyte tank, and then sodium hydroxide was added so that the degree of neutralization of the carboxylic acid was 10%. Finally, the water concentration in the liquid is 2
．． It was adjusted to have a weight of %.

Then the current density is 10AIdT! Electrolysis was carried out under the same conditions as in Example 1, except for changing to 1. The results are shown below. Example 13 Adipic acid 13.3% by weight, glutaric acid 63.7% by weight
, succinic acid 23. An acid mixture containing 200 TaH
The water was removed by heating to a temperature of 230-250° C. under reduced pressure of 100 g.

Then, the temperature was lowered and the pressure was reduced to 15 TInHg.
Succinic anhydride is removed at a temperature of 40-145 °C, 160 °C
Glutaric anhydride was obtained at a temperature of ~165°C. 228 g of glutaric anhydride and 72 g of methanol were reacted at 55° C. for 5 hours. The above monomethyl glutarate and monomethyl sebacate 2, which are reaction products with methanol, are placed in the electrolyte tank.
16g and methanol 604g, then potassium hydroxide was added so that the degree of neutralization of the acid mixture was 8%, and finally the water content in the solution was reduced to 3. Adjusted to match the amount of sleep.

The thus obtained prepared solution was circulated to the electrolytic cell. Electrolysis was performed in the same manner as in Example 1.

The electrolysis time was between 4.7 and the voltage was between 13.5 and 10.
It changed to 2V. The amount of liquid after electrolysis is 1021 g, and the concentration of each component in the liquid is 10.
The slag weight is %, and dimethyl brassylate is 11. % of heel weight, and dimethyl octadecanoate was 3.9% by weight.
The remaining unreacted monomethyl sebacate was 0. Heel volume% was hot. Table 4 shows the selectivity and current efficiency of each electrolytic condensation product. Example 14 5 parts by weight of decalin were added to 1 part by weight of glutaric acid and heated under reflux, and the produced water was continuously extracted from the system together with a small amount of decalin to carry out a dehydration reaction.

After sufficient dehydration reaction, decalin is removed by distillation,
Glutaric anhydride was then obtained by distillation. 167 g of the obtained glutaric anhydride and 59 g of methanol were reacted at 55° C. for 4 hours to obtain monomethyl glutarate. This monomethyl glutarate and monomethyl sebacate (63 g) and methanol (568 g) were placed in an electrolytic solution tank, and finally water was added so that the water concentration in the solution was 2.0% by weight. Potassium hydroxide was then added to bring the degree of neutralization to 10%. Next, monomethyl glutarate and monomethyl sebacate 24, which were obtained in the same manner as described above using 66 gr of glutaric anhydride and 23 gr of methanol, were set to the same conditions as in Example 1 except that the current density was changed to 11A1dTTt.
Electrolytic condensation was carried out while continuously supplying a mixed solution with g (monomethyl glutarate/monomethyl sebacate molar ratio: 511) to the electrolyte tank for 5.0 hours. Further 2. The bridge electrolytic condensation was continued. The voltage was 7.1-6.9V. The amount of liquid after the electrolysis was completed was 903 g, and the concentrations of each component in the liquid were 13.6% by weight for dimethyl suberate, 6.3% by weight for dimethyl brassylate, and 0.0% for dimethyl octadecanoate. It was 7% by weight. The remaining unreacted monomethyl sebacate was 0. The weight was %. Table 4 shows the selectivity and current efficiency of each electrolytic condensation product. Glutaric acid 119 was added to the four-necked flask of Comparative Example 114e.
g1 dimethyl glutarate 566g1 methanol 458g
and 409 g of water were added, and then 300 mt of strongly acidic cation exchange resin Amperlite 200C (manufactured by Rohm & Haas, trade name) which had been regenerated into H-form was substituted with methanol, water was sufficiently removed, and the mixture was added. The mixture was heated under reflux for 6 hours while stirring thoroughly. catalyst, methanol,
After removing water, dimethyl glutarate 25
9 g and 250 g of monomethyl glutarate were obtained. Monomethyl glutarate is 133 at a reduced pressure of 3-4 TIrmHg.
Obtained at a temperature of ~135°C. Then, the obtained monomethyl glutarate was heated under a reduced pressure of 50 to 100 TnmHg to
Heated at 230°C for 1 hour and then redistilled at 160-165°C under vacuum of 15 wmHg. 292 g of monomethyl glutarate in the electrolyte tank 21 g of monomethyl sebacate
6 g of methanol and 615 g of methanol were added, then potassium hydroxide was added so that the degree of neutralization of the acid mixture was 8%, and then the water content in the solution was adjusted to 2.5% by weight.

Electrolytic condensation was carried out in exactly the same manner as in Example 1 for 5.01 hours.

The voltage varied from 15.0V to 12.2V. j The amount of liquid after electrolysis is 1022 g, and the concentration of each component in the liquid is 7.5 g. Heel weight%, dimethyl brassylate is 9. The amount of dimethyl octadecanoate was 3.2% by weight. The amount of unreacted monomethyl sebacate remaining was 1.7% by weight. Table 4 shows the selectivity and current efficiency of each electrolytic condensation product. BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a flow sheet of one embodiment of the method of the invention.

In the figure, 1 is a supply port, 2 is a dissolution tank, 3, 4 are ion exchange resin columns, 5, 6, 7, 8 are distillation columns, 9 is an extraction port, 10
11 is an electrolyte tank, 11 is an electrolytic cell, 12 is a distillation column, 13 is a decanter, 14, 15, and 16 are distillation columns, 17 and 18 are evaporators, and 19 is a recovery column.

Claims (1)

[Claims] 1 A mixed acid of monomethyl adipate or glutaric anhydride and/or monomethyl glutarate not containing glutaric acid and monomethyl dicarboxylate having 8 to 11 carbon atoms is added to the methanol solution containing the alkali metal salt thereof. The water concentration in the mixture was maintained at 0.15 to 3.5% by weight, and monomethyl adipate or glutaric anhydride and/or
Alternatively, a method for producing dimethyl higher dibasic acid 2, which is characterized in that monomethyl glutarate, which does not contain glutaric acid, is electrolytically condensed batchwise in a molar ratio of at least twice that of monomethyl dicarboxylate having 8 to 11 carbon atoms. A mixed acid of monomethyl adipate or glutaric anhydride and/or monomethyl glutarate not containing glutaric acid and monomethyl dicarboxylate having 8 to 11 carbon atoms is added to a methanol solution containing an alkali metal salt thereof. The water concentration is maintained at 0.15 to 3.5% by weight, and monomethyl adipate or glutaric anhydride and/or monomethyl glutarate containing no glutaric acid is added in 2 times the mole relative to monomethyl dicarboxylate having 8 to 11 carbon atoms. A method for producing dimethyl higher dibasic acid, which comprises performing batchwise electrolytic condensation at the above ratio, and then recovering the alkali metal salt of the mixed acid from the electrolytic condensation solution and recycling it to the electrocondensation reaction.