DE2404560C3 - Process for the production of sebacic acid - Google Patents

Description

The invention relates to a process for the production of sebacic acid by electrolytic condensation a methanolic solution of monomethyl adipate and an alkali salt of monomethyl adipate, the Solution passed through an electrolysis cell, the dimethyl sebacate formed from the reaction mixture separated and then subjected to hydrolysis.

The reaction of the electrochemical condensation of carboxylic acids is generally called the "Kolbe reaction" This reaction is referred to e.g. B. in the references H. Kolbe, Ann. 69, 257 (1849) and A.C. Brown, Ann., 261, 107 (1891). as Typical example of this reaction can be an electrolytic process for the production of dimethyl sebacate from monomethyl adipate. Monomethyl adipate is produced in such a way that Adipic acid is reacted with methanol. When carrying out this electrolytic reaction will be Monomethyl adipate dissolved in methanol and part of the adipate is removed by alkali, e.g. B. Sodium Hydroxide, neutralized. The methanol solution thus formed contains monomethyl adipate and its alkali salt at the same time before. If one considers the molar amounts of the monomethyl adipate and its alkali salt as A (MoI) and B (mole) sets, then is

A + B

x 100 (mol%)

2CH ₁ OuC (CH ₂ I ₄ COO

-2e

defined as the "degree of neutralization α" of the above-mentioned methanol solution electrolytic solution is subjected to electrolysis, then hydrogen is formed at the cathode and decarboxylation and dimerization occur at the anode. The anode reaction is caused by the given the following equation:

CHiOOC (CH _- -KCOOCH, + 2CO _;

In the conventional practice, it has been considered necessary in order to obtain a high electric current efficiency. ^: To keep the 2n degree of neutralization α of the monomethyl adipate at a low value. So z. As described in Japanese patent application 37564/71, for example, that it is essential to maintain a degree of neutralization α below 20 mol%. In the known process, however, the low degree of neutralization of the monomethyl adipate means that the electrolysis must be carried out with a fairly high voltage.

It would therefore be advantageous to carry out this electrolytic conversion on an industrial scale to achieve high power output even if the electrolysis voltage can be kept low.

The invention is therefore based on the object of an improved method for electrolytic production of sebacic acid of the type described at the outset available, in which a very high electrical Current output can be achieved without the electrolysis voltage being kept at high values must become.

The invention relates to a process for the production of sebacic acid by electrolytic condensation of a methanolic solution of monomethyl adipate and an alkali salt of monomethyl adipate, the solution being passed through an electrolytic cell, the dimethyl sebacate formed being separated from the reaction mixture and then subjected to hydrolysis, which is thereby marked is that a concentration of dimethyl sebacate of 5 to 40% by weight is maintained in the solution and the solution is passed through the electrolysis cell at a flow rate of 2 $ to 4.0 rii / sec.

By the measure according to the invention, the flow rate of the electrolysis solution in the Setting the electrolytic cell to a value of at least 2.5 m / sec can result in an unexpectedly high electrical current output can be achieved and the voltage of the electrolytic cell can be constant at a very low value. This beneficial effect is only marginally due to the degree of re-orientation influenced and even with higher neutralization

■ degrees of jo nition can be achieved by the implementation; n; t high power output and can be carried out at low cell voltage

To carry out the process on an industrial scale, an electrolytic cell with a corresponding Size required, the internal pressure of the cell being determined by its volume and structure. So is it z. B. in the case of an electrolytic cell, the cathode and anode plates arranged in parallel owns between which the electrolytic solution

to flows, which are commonly used for organic electrolytic Reactions are used, expediently if the process is carried out on an industrial scale becomes that the electrolytic solution flow channel is in the range of 50 to 200 cm The electrolytic solution flow channel is larger, then the internal pressure of the cell becomes higher and it occurs

2. B _{1 has} the disadvantage that the current output is reduced.

Since according to the invention the electrolytic solution between the cathode and anode plates with a Flow rate of at least 2.5 m / sec passed the electrolytic condensation of monomethyl adipate with a high electrical current output despite an increase in the internal pressure of the electrolytic cell

As a known measure for separating the electrolytically formed dimethyl sebacate from the resulting electrolytic solution can be used as examples

distillation, crystallization and extraction are named. However, the distillation has the Disadvantage that the dimethyl sebacate and the monomethyl adipate form an azeotropic mixture, which does not is separable. Furthermore, lie in the crystallization method such disadvantages e.g. B. suggest that the operation should be carried out at low temperature and that inclusion of the monomethyl adipate in the resulting crystals cannot be avoided. In the case of the traction rivet, when water is used as the extraction solvent, it is necessary to to use this in a huge amount. In general, the water should be in an amount of Use at least three parts per part of the remaining liquid after removal of the Methanol from the electrolytic solution remains because the difference of the specific continues Weight between the extracted water layer and the oil layer is extremely low, it is very difficult to to separate the two layers from each other. In the event that an organic solvent such as n-heptane, as Extraction solution section! is used, a Entrainment of a certain amount of M ^ nomethyladipat in the n-heptane layer cannot be avoided, so that it is impossible to separate only the dimethyl sebacate as a product. As from the previous What can be seen is in the step of separating the dimethyl sebacate from the electrolytic solution the most important problem is the separation from the starting monomethyl adipate.

In contrast, when, be water and an organic solvent which can dissolve the dimethyl sebacate, but which is insoluble in water simultaneously added to the dimethyl-containing electrolytic solution tion by electrolytic capacitors is formed of a monomethyl in methanol, or if such an organic Solvent is added to the electrolytic solution to form two layers, and when water is added to the organic solvent layer, so that water is also present in the organic solvent at the same time. the system separates into a water and organic solvent layer, with the dimethyl sebacate dissolving in the organic solvent layer. This allows dimethyl sebacate to be obtained, which is free from monomethyl adipate. The impurities contained in the dimethyl sebacate can according to the requirements, for. B. can be removed by distillation.

The hydrolysis of the dimethyl sebacate with a mineral acid to form sebacic acid is carried out according to the conventional procedure carried out in such a way that water in an amount of at least 4 Parts by weight per part by weight of the dimethyl sebacate layer before acid hydrolysis is added to make modifications of the methanol and the sebacic acid formed by hydrolysis, and that the hydrolysis reaction One of these hydrolysis processes is carried out at temperatures above 100 ° C. under increased pressure however, involves expensive steps, which leads to great disadvantages when the process is im technical scale is carried out.

It has been found that when dimethyl sebacate becomes an aqueous solution of a mineral acid in the presence of dimethyl sebacate in a smaller amount than is the saturation solubility of sebacic acid in the corresponds to said mineral acid solution, is added and if the hydrolysis with removal of the methanol formed by the reaction carries out, the hydrolysis can be completed very easily.

The production of sebacic acid from adipic acid can according to the invention with great advantages in the be carried out on an industrial scale.

The invention is explained in more detail with reference to the accompanying drawings. It shows

F i g. 1 is a graph showing the relationship between the internal pressure of the electrolytic cell and the represents electrical power output or power output,

Fig.2 is a diagram showing the relationship of Liquid velocity in the electrolytic cell to the electrical current output or current yield, the internal pressure of the electrolytic cell and the electrolytic cell voltage, and

Fig.3 is a flow sheet showing an embodiment of the present invention. Reference numerals 1, 2 and 4 denote a tank for electrolytic Solution, a ·? electrolytic cell and an extraction column.

Monomethyl adipate used in the process of Invention used as a starting material is made from adipic acid and methanol. At this Esterification reaction, it is preferred that i.i dem Reaction Mixture Water in an amount of at least 1 mole per mole in the reaction mixture Adipic acid present

About the relationship between the concentration of dimethyl sebacate and the electric current output and to determine the cell voltage, the following investigations were carried out

Various electrolytic solutions were prepared by neutralizing a methanol solution of monomethyl adipate and dimethyl sebacate with sodium hydroxide so that the concentration of monomethyl adipate was 20% by weight and the degree of neutralization a. Was 30 mol%, with the concentration of the dimethyl sebacate being varied as shown in Table I. Either a cathode plate or an anode plate had an energized area of 2 cm 50 cm. The cathode consisted of a SUS-27 steel plate with a thickness of 2 mm. The anode was composed of a Titanplat ^f e with a thickness of 2 mm which had been plated with platinum in a thickness of 2 μm. A polyethylene plate with a thickness of 2 μπι, which was perforated. that the area subjected to current was 2 cm × 50 cm was placed between the two electrodes, the electrode spacing being set to 2 mm. The electrolytic cell used had inlet and outlet openings for the electrolytic solution. The electrolytic solution was passed through both electrodes with a liquid velocity of 2 m / sec and a current density of 20 A / dm ² . The temperature of the electrolytic solution at the cell outlet was kept at 55 ° C. Electrolysis was carried out for 10 hours under the above-mentioned conditions while removing part of the electrolytic solution; and methanol, monomethyl adipate and sodium monomethyl adipate were supplied so that the concentration of dimethyl sebacate was always kept at the prescribed value. The results obtained are shown in Table I, from which it can be seen that high electric current performance can be obtained when the concentration of dimethyl sebacate in the electrolytic solution is at least 5% by weight

the fact that if the concentration of dimethyl sebacate is too high, the cell voltage increases becomes required that the concentration of dimethyl sebacate in the electrolytic solution is in the range of 5 up to 40% by weight.

Table 1

Conc Yield to Electric Cell tration of Dimethylse Power line tension Dimethyl bacat slung sebacat in the electrolyte tables solution (Ow .-%) (%) (%) (Volt) 2 80.2 74.8 8.2 87.3 80.1 9.8 10 89.6 84.6 12.2 20th 91.6 90.4 14.5 30th 92.0 91.2 17.4 40 91.8 90.5 21.2

The above experiments were repeated in the same way, except that the concentration of dimethyl sebacate was kept at 20 wt .-% and that the degree of neutralization α according to Table II was varied. The results obtained are shown in Table II, from which it can be seen that when the degree of neutralization "goes up to about 60 mol%, the electrical current conduction in one almost can be kept constant high and, if the degree of neutralization exceeds 60 mol%, the electric power is gradually lowered. It will also be seen that when the Degree of neutralization «of monomethyl adipate is higher than 20 mol%, the cell voltage is almost is kept constant low.

• 40

Table Il Yield to Electric Cell Neutral Dimethylse Power line tension degree of sation a bacat stung from mono methyl adipate (%) (%) (Volt) (Mol%) 90.7 89.8 31.4 5 91.9 91.0 24.3 10 91.5 90.2 17.7 20th ^ 1.6 90.4 14.5 30th 91.8 90.9 14.0 40 90.6 894 13.8 60 78.4 86.1 13.6 70 71.8 80.7 13.7 80

50

From the results given in Tables I and II it can be seen that when the concentration of dimethyl sebacate in the electrolytic solution at least 5 wt .-%, preferably 5 to 40 Wt%. and the degree of neutralization <x of the monomethyl adipate at least 20 Moi-%, preferably 20 to 60 Mo! -%, a high electric current output can be obtained in electrolysis and electrolysis can be carried out at a low cell voltage.

60 A neutralizing base is used to increase the electrical conductivity of the electrolytic solution. Examples of such a neutralization base are hydroxides, carbonates, methylates and ethylates of lithium, sodium and potassium, as well as ammonia, dimethylamine, trimethylamine, ethylamine or ethanolamine.

Methanol is the most preferred reaction solvent, but ethanol * isopropanol, Ethylene glycol, dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, acetonitrile, Propionitrile, tetrahydrofuran and water either alone or as a component of a mixed solvent be used.

The use of an electrolytic cell with a certain size is required to take Use the above-mentioned electrolytic solution to carry out the electrolysis on an industrial scale. The internal pressure of the electrolytic cell used is determined by its volume and structure the cell. In an electrolytic cell, like the one usually used for organic electrolysis reactions used are the cathode and anode plates arranged parallel to each other and an electrolytic solution will flow between the two electrodes calmly. When electrolysis on an industrial scale using such a conventional cell is carried out, then it is desirable that the flow passage of the electrolytic solution in the Range from 50 to 200 cm. However, when the electrolytic solution flow passage closes is long, the internal pressure of the electrolytic cell is increased, thereby causing an undesirable decrease the electrical power output is conditioned. The relationship between the internal pressure of the electrical Cell and electrical current output has long been known results of experiments to illustrate This relationship has been carried out are listed below

An electrolytic solution containing 20% by weight monomethyl adipate and 20% by weight dimethyl sebacate, remainder Contained methanol, in which the degree of neutralization «of the monomethyl adipate with potassium hydroxide was 30 mol% was at an electrolytic solution temperature of 55 ° C and at a flow rate of the electrolytic solution was electrolyzed at 1 m / sec for 2 hours using an electrolytic cell This cell had an electrolytic solution flow passage of 100 cm in length and a width of 10 cm and an electrode spacing of 2 mm. In Table III are those obtained Results compiled:

Table III Yield art
Dimethyl sebacate
(%) Electric
Power output
(%) pressure
(bar) 74
72
67
61 66
50
37
31 1.12
1.17
1.24
1.27

From the above results, it can be seen that an increase in the internal pressure is the electrolytic Cell leads to a strong reduction in the electrical current output

To increase the inner end of the electrolytic To prevent cell, it has already been tried to reduce the flow rate of the electrolytic cell Solution to decrease or the distance between the To widen electrodes. However, these attempts were unsuccessful »If that is The flow rate of the electrolytic solution is decreased, then the internal pressure becomes the electrolytic cell, but at the same time the electrical current output is also reduced. if on the other hand, the distance between the electrodes is widened, then the further disadvantage is in purchase to take that electric hvuck in the electric cell is increased.

According to the invention, further experiments are now carried out in order to investigate the relationship between the internal pressure (p) of the electrolytic cell and the electrical current output (η) with regard to different liquid velocities (LV) of the electrolytic solution. The results obtained are shown in FIG. As ilsruuS hsrvor ^ sHl, ksnn ⁱ .vsnn, the liquid velocity, that is, the flow velocity, of the electrolytic solution is increased, even if the internal pressure of the cell is high, the electric current output is maintained at a high value, hardly being influenced by the internal pressure of the cell will. Results of experiments in which the relationship between the liquid velocity (LV) of the electrolytic solution, the internal pressure (p) of the electrolytic cell, the electrical current output (η) and the voltage (V) of the electrolytic cell were examined, the external pressure being of the cell was held at 1 atm are summarized in Figure 2. From this it can be seen that. Although the internal pressure of the electrolytic cell increases with an increase in the flow rate of the electrolytic solution, if the flow rate of the electrolytic solution is kept at a value of at least 2.5 m / sec, a high electric current output can be obtained and the voltage of the electrolytic cell decreases can be kept at a very low value. If the flow rate of the electrolytic solution in the electrolytic cell is set to at least 2.5 m / sec, according to the invention 2.5 to 4 m / sec, then the electrolysis can be carried out with an unexpectedly high current output and with a very low voltage of the electrolytic cell will.

Any electrolytic cells can thus be used in the method according to the invention which are conventionally used for organic electrolytic reactions, provided they have such a structure that the electrolytic solution between the electrodes is so high Flow rate, as indicated above, can flow through. So it is B. possible a To use electrolytic cell, the cathode and anode plates arranged in parallel and a Polyethylene sheet placed between the electrodes to define the electrode spacing, In the middle part of the polyethylene plate a hole is perforated so that the electrolytic Solution can flow. In this cell, the area subjected to current is determined by its size Hole, and the electrode spacing is defined by the thickness of the polyethylene plate. The electrolytic Solution is supplied from an inlet opening. A Tefl of the electrolytic solution is supplied during the Run through the distance between the electrodes. Then electrolytic solution of Eiltei the outlet port removed and returned to the tank of the electrolytic solution.

As materials for the anode, for. B. platinum, ruthenium rhodium, palladium, gold and alloys of which can be used. In general, these metals are plated onto a substrate, e.g. B. off Titanium, tantalum and iron are used.

A material with a low hydrogen overvoltage is preferably used as the material for the cathode is used, but the type of cathode material is not particularly critical in the method of the invention. Preferably platinum, iron, nickel and stainless steel can be used.

It is preferred that the distance between the cathode and the anode be in the range of 1 to 3 mm. In general, it is appropriate that the length of the electrolytic solution flow passage be in the range of 50 to 200 cm. It is advisable that the temperature of the electrolyte solution should be higher than 1; 40 ° C, but it should be lower than the boiling point of the electrolytic solution. The current density is not particularly critical in the process of the invention, although it is generally preferred to carry out the electrolysis at a current density of 20 to 40 A / dm ² .

The dimethyl sebacate produced in this way must be separated from the electrolytic solution will. This separation should now be based on the flow diagram of FIG. 3 are described in more detail. In In Fig. 3, 1 denotes an electrolytic solution tank. The electrolytic solution becomes one circulating electrolytic cell 2 The electrolytic solution obtained is a methanolic solution, the monomethyl adipate, dimethyl sebacate and lesser amounts of by-products such as dimethyl adipate. Methyl n-valerate. Methyl-to-hydroxyvalerate and Methylallyl acetate contains Part of the electrolytic solution is withdrawn and methanol is added to the Removed distillation column 3, while the remainder is introduced into an extraction column 4. At the The method of the invention can remove the electrolytic solution without removing the methanol be sent to the extraction column 4. An organic solvent is supplied from a feed inlet 5 introduced and the lower part of the extraction column 4 together with the electrolytic Solution fed. The feed inlet 5 for the organic solvent can also be at a other place than the point as indicated in F i g. 3 is shown. z. B. in the middle or lower part of the extraction column. It can be all organic ■ Solvents are used that can dissolve dimethyl sebacate and that are insoluble in water, however becomes the use of η-hexane, n-heptane, n-octane. Cyclohexane, isooctane preferred The organic solvent layer which contains the dimethyl sebacate and which is overflowed from the top of the extraction column 4 introduced into distillation column 7 where the organic solvent feed from the feed inlet 5 is distilled and used again for extraction. From the bottom part of the column 7, a liquid is obtained which consists mainly of dimethyl sebacate According to the respective requirements, it becomes one another (not shown) distillation column fed to optionally a dimethyl sebacate product

with higher purity. From the bottom part of the extraction column 4 is an aqueous solution removed, which contains monomethyladipal and its alkali salt. This becomes the distillation column 8 where water is distilled off from the top of the column and used again for extraction. Monomethyl adipate and its alkali salt are taken from the bottom part of the column 8, into the tank of the electrolytic Recirculated solution and used for the electrolysis reaction. The water and the organic solvent are used for extraction in quantities sufficient to produce an organic Layer and an aqueous layer. Generally the water is used in an amount from 0.2 to 2 parts by weight per part by weight of the electrolytic solution to be extracted is used and that organic solvent is used in an amount of 0.2 to 2 parts by weight per part by weight of the electrolytic Solution used. In the method of the invention, it is also possible to carry out the extraction in the manner 20 make that an organic solvent is added to the electrolytic solution to be extracted there to form two layers, the organic solvent layer is removed, water is added to it and performing the extraction in the simultaneous presence of water and the organic solvent. Below are experimental results on the extraction of dimethyl sebacate from the electrolytic Solution described.

A melhanol solution was used as the electrolytic solution used, the 30 wt .-% dimethyl sebacate, 20 wt .-% monomethyl adipate, 9 wt .-% sodium monomethyl adipate and smaller amounts of such by-products as dimethyl adipate, methyl-n-valerianate, Methyl w-hydroxyvalerate and methyl allyl acetate. contained. The methanol was then removed from this electrolytic solution by distillation 500 g of water became 100 g of the remaining liquid and the mixture was stirred at room temperature, thereby forming two layers. the upper oil layer mainly contained dimethyl sebacate and monomethyl adipate. The lower aqueous layer Mainly contained monomethyl adipate and its sodium salt. The ratios (C1 / C2) of the concentrations (Ci) of monomethyl adipate and dimethyl adipate in the upper layer to the concentrations (Cj) these substances in the lower layer were determined. The results obtained are shown in Table IV The above procedures were repeated in the same manner, with the substitution of so Water 500 g of n-heptane were used. In this case the upper n-heptane layer contained dimethyl sebacate and monomethyl adipate. The lower layer mainly contained monomethyl adipate and its sodium salt. The results obtained are summarized in Table IV:

Table IV

solvent

Water n-heptane

water
and n- heptane

Mono- 7.3 0.06 0.03

methyl-

adipate

Dimethyl 45.1 1.2 123

sebacat

Purity (%) 75.6 89.8 99.1

60

65 As can be seen from the above results, in the extraction with an organic solvent, even if countercurrent extraction is carried out with an increased number of stages, a certain amount of monomethyladipai is inevitably contained in the organic solvent layer and it is impossible to obtain the dimethyl sebacate with high purity.

However, as can be seen from the results, the addition of water and n-heptane zl 100 g of the festive liquid left after removal of the methanol and stirring the mixture Room temperature to separate it into two layers and are also given in Table IV are put together, the upper n-heptane layer contains only dimethyl sebacate alone and the lower The aqueous layer contains mainly monomethyladipal and its sodium salt. It can be seen that if Water and an organic solvent dimethyl sebacate can dissolve and is uniösüch in water, can be used in combination for the extraction, Very high purity dimethyl sebacate using a small amount of the extraction solvent can be obtained by, for example, countercurrent extraction.

In the results of Table IV, the purity was determined from the concentration (Cs) of dimethyl sebacate and the concentration (Ca) of monomethyl adipate in the upper layer according to the following Equation determines:

Purity (%) = Cs / (Cs + Ca) χ 100

As can be seen from the results in Table IV, when water and an organic solvent, the dimethyl sebacate can dissolve and is insoluble in water. in the extraction stage simultaneously are present, the dimethyl sebacate from the electrolytic solution without entrainment of monomethyl adipate be separated and by-products contained in the separated dimethyl sebacate, ζ. Β Dimethyl adipate, methyl n-vslerianate, methyl-co-hydroxyvalerate and methylallylacetate, kann.i easily, e.g. B. by distillation, are separated from the dimethyl sebacate.

The dimethyl sebacate thus separated becomes sebacic acid using a mineral acid hydrolyzed. In connection with this hydrolysis, it has been found that this measure is very advantageous can be carried out if the reaction conditions are properly controlled. In particular, was found that in the hydrolysis of dimethyl sebacate with a mineral acid when the hydrolysis takes place Removal of the methanol formed in the reaction from the reaction system is carried out, the Hydrolysis can be very accelerated and that it progresses very rapidly if, however, the hydrolysis is carried out in such a way that only that Methanol is removed from the reaction system, then unreacted dimethyl sebacate and monomethyl sebacate become precipitated crystals of sebacic acid taken with and it takes a long period of time to complete the hydrolysis reaction. As a result of research, it has been found that when Dimethyisebacai becomes a aqueous solution of a mineral acid is added in an amount that does not exceed the amount, which of the saturation solubility of sebacic acid in the aqueous mineral acid solution at the hydrolysis temperature

Il

falur corresponds, and the hydrolysis unte ¹ / removal of the methanol is carried out, the Hydrolysereakiion can be completed in a very short period.

The hydrolysis of dimethyl sebacate to sebacic acid can thus be carried out in a simple manner within a short period of time Period can be effected by adding dimethyl sebacate to an aqueous solution of a mineral acid in «Is added in a specific amount and the hydrolysis takes place with removal of the methanol.

When dimethyl sebacate is added to an aqueous solution of a mineral acid in an amount equivalent to does not exceed the amount, soft the saturation solubility of the sebacic acid in the aqueous Mineral acid solution, then the entire Sebacic acid, which is formed by the hydrolysis, dissolved in the aqueous mineral acid solution and not in Precipitated in the form of crystals. Therefore, the hydrolysis reaction can be carried out easily, without unreacted Dimethyisebacai or Monomethyl sebacate is introduced into the sebacic acid. If the hydrolysis with removal of the Reaction of methanol formed from the reaction system is carried out, then the hydrolysis reaction can be carried out can be accelerated and modification of the methanol with the mineral acid can be effectively avoided will. The removal of the methanol can, for. B. be effected by distillation. It is preferred that the methanol concentration in the liquid to be hydrolyzed is low. Iv .: general she will kept below 0.1 wt .-%.

As the mineral acid, nitric acid is preferred, but sulfuric acid, hydrochloric acid and the like can also be used. It is preferred that the acid concentration be in the range of 10 to 30% by weight. The hydrolysis is preferably carried out at a temperature of at least 90 ⁰ C of at least 100 ⁰ C. performed. In general, the hydrolysis is carried out at a temperature of 100 to 12O ⁰ C.

The invention can achieve the following effects:

1. In the electrolytic condensation of monomethyl adipate and its alkali salt in one Methanol solution for the production of dimethyl sebacate in the electrolyte at one concentration from 5 to 40 wt% enables the dimethyl sebacate to have a high current conduction to manufacture.

2. In the electrolytic condensation of monomethyl adipate and its alkali salt in one methanolic solution by passing the electrolytic solution through an electrolytic It becomes possible to use cells with a liquid velocity of at least 2.5 to 4.0 m / sec made the dimethyl sebacate with a low electrolytic cell voltage and at a high one to produce electrical power.

Thus it is possible according to the invention. Sebacic acid to obtain from adipic acid in a technically advantageous manner.

example 1

10 kg of a methanol solution which contained 20% by weight of monomethyl adipate, which had been neutralized with sodium hydroxide to a neutralization rate c <30 h / loi-Qfa , and 20% by weight of dimethyl sebacate, were used as the electrolytic solution in a tank for the electrolytic solution stored and circulated in an electic cell.

Both electrodes of the cell had a current-applied area of 2 cm × 50 cm. The cathode consisted of a SUS-27 plate with a thickness of 2 mm. The anode consisted of a Tifnplaue with p.in a thickness of 2 mm, which was plated with platinum in a thickness of 2 μm. A polyethylene sheet with a Thickness of 2 mm, which was perforated so that the

ίο the area subjected to current was 2 cm 50 cm, was inserted between the electrodes in order to define the electrode spacing as 2 mm. The electrolytic cell had inlet and outlet ports for the electrolytic solution, and the electrolytic solution was passed between both electrodes at a liquid velocity of 2 m / sec. The electrolysis was carried out at a current density of 20 A / dm ² and an electrolyte solution temperature of 55 ° C. for 10 hours. The concentration of the dimethyl sebacate in the oil solution which was taken after the electrolysis reaction was determined by gas chromatography. The yield was calculated. The results shown in Table V were obtained. The above procedures would be repeated in the same manner, varying the type of base used for neutralization. The results shown in Table V were obtained.

Table V

base 35 LiOH Today Electric Cell NaOH to Dimethyi- Power line tension ■ »o KOH sebacat stung Well, (M ( ⁰ O) (Volt) NH-. 9 "! 8 92.6 14.1 91.7 90.9 14.5 91.3 90.5 14.4 89.8 88.5 16.0 91.7 90.8 13.3

Example 2

The Kolbe synthesis reaction was carried out under the same conditions as in Example 1, wherein if sodium hydroxide was used as the neutralization base, the degree of neutralization α to 30 M01-% was set and the current density was varied according to Table VI. The results obtained are in Table VI compiled:

Table VI Yield to Electric Time Current density Dimethyl Power line tension sebacat stung (M (Volt) (A / crn ^) 85.6 84.4 9.0 5 90.5 89.5 10.1 10 91, p 90.9 14.5 20th 91.8 90.5 18.6 30th 91.7 90.5 23.6 40

Example 3

The Kolbe synthesis reaction was be! the same Conditions carried out as in Example 1, using sodium hydroxide as the neutralization base and the concentration of the monomethyl adipate was varied according to Table VII. The results obtained are summarized in Table VII:

Table VII yield current Cell Conc of dimethyl power tension tration of sebacat Monomethyl adipate (%) (%) (Volt) l weight%) 89.4 88.3 15.8 ίΟ 91.8 90.9 14.5 20th 91.9 90.5 12.8 30th 91.2 90.8 11.0 40 90.5 90 ί ! 4.2 in Example 4

5 kg of a solution containing 30% by weight of monomethyl adipate, which was neutralized with sodium hydroxide to a degree of neutralization α of 40 mol%, and 25% by weight Dimethyl sebacate containing residual methanol were used as an electrolytic solution in a tank for electrolytic Solution stored and circulated in an electrolytic cell.

The cathode consisted of a titanium plate with a thickness of 2 mm. The anode consisted of a titanium plate with a thickness of 2 mm. on the 3 μιπ platinum had been plated. Both electrodes cut a current-applied area of 1 cm χ 150 cm. In between a polyester plate was arranged, which was perforated in this way. that it had the above-mentioned energized area to define the electrode gap to be 3 mm. The electrolytic cell had inlet and outlet ports for the electrolytic solution. The electrolytic solution was allowed to flow between the electrodes at a liquid velocity of 3 mm / sec. The electrolysis was carried out at a current density of 25 A / dm ² and an electrolytic solution temperature of 60 ° C. at the outlet of the cell. The mean internal pressure of the electrolytic cell was 1.29 bar and the electrolytic cell voltage was 17 volts.

After the completion of the electrolytic reaction, the amount of dimethyl sebacate formed was determined by gas chromatography certainly. The electric power output was found to be 83%.

Example 5

Using 5 kg of an electrolytic solution containing 40% by weight of monomethyl adipate. that with Sodium hydroxide had been neutralized to a degree of neutralization * of 10 mol%. and 20% by weight Dimethyl sebacate, the remainder containing methanol, was the electrolysis for 2 hours under the conditions of Example 4 carried out, with the exception that the flow rate of the electrolytic solution, the length the flow passage of the electronic solution and the electrode distance to 4 tti / sec, 100 cm and 2 mm have been modified. The internal pressure of the electrolytic cell was 1.45 bar. The electrolytic Cell voltage was 17 volts.

The amount of dimethyl sebacate formed was determined by gas chromatography found that the electric power output was 88%.

Example 6

Using 5 kg of an electrolytic

ίο solution containing 10 wt .-% monomethyl adipate, which with Sodium hydroxide to a degree of neutralization α of 50 mol% had been neutralized and 30% by weight of dimethyl sebacate, the remainder containing methanol, was the Electrolysis carried out under the same conditions as in Example 5, with the exception that the The flow rate of the electrolytic solution in the cell was changed to 2.5 m / sec. Of the The internal pressure of the electrolytic cell was 1.23 bar.

The electrolytic cell voltage was 14 volts

The amount of dimethyl sebacate formed was

determined by gas chromatography

found that the power output was 81%.

Example 7

An electrolytic solution containing 15.5% by weight of monomethyl adipate, 73% by weight of potassium monomethyl adipate, 22.1% by weight of dimethyl sebacate and 2.5% by weight of other by-products, the remainder being methanol, was removed from an electrolytic cell without removal of the methanol is taken from the electrolytic solution. Then 100 g of water and 100 g of cyclohexane, η-hexane, n-heptane or isooctane were added to 200 g of the electrolytic solution thus taken out, and the mixture was ^{stirred at 40 °} C. to separate it into two layers. The results given in Table VIII were obtained in the same way as in connection with Table IV:

Table VIII Cyclo Organic solvent n-IIeptane Iso- octane C ₁ / C: hexane n-IIexane 0.09 0.08 0.07 0.09 8.7 Monomethyl 14.3 adipate IU 10.7 97.9 Dimethyl 98.3 scbacal 98.3 97.9 ⁵⁰ purity! "») Example 8

The extraction was carried out using a countercurrent extraction column with an inner diameter of 35 mm and a column length of 1200 mm. An electrolytic solution containing 12.7% by weight of monomethyl adipate. 5.2% by weight potassium monomethyl adipate. 19.5% by weight of dimethyl sebacate and to 2.4% of other by-products. Residual methanol was extracted. A mixture of 1 part by weight of the above electrolytic solution and '/? Part by weight of cyclohexane was fed in from the bottom part of the extension column at a rate of 5 m / h with stirring using a velocity wedge. Water was mi (a Geschwindigkeil of 1 m / sec is supplied from the head part of the Exiräktionskolönne. In this way a Gcgenstrom ^j extraction was carried out at room temperature,

The concentration of dimethyl sebacate in the cyclohexane layer from the lower part of the column drained was 22.8%. However, the concentration of monomethyl adipate was less than 0.01% by weight. the Concentration of dimethyl sebacate in the aqueous layer taken from the lower part of the column was 2.1 wt%, but the concentration of monomethyl adipate was 8.9 wt%.

From the above results, it can be seen that when water and cyclohrxane are used as the extraction solvent the dimethyl sebacate separated only with considerable contamination by monomethyl adipate can be.

Water was removed from the aqueous layer by distillation and the remaining liquid became returned to the electrolytic solution tank and subjected to electrolysis.

Example 9

Methanol was removed by distillation from an electrolytic solution containing 20.4% by weight Dimethyl sebacate, 10.0% by weight monomethyl adipate, 3.5% by weight potassium monomethyl adipate and 3.5% by weight contained other by-products, the remainder being methanol. Then 500 g of n-heptane was added to 500 g of the remaining liquid and the mixture was at Stirred at room temperature to separate it into two layers. The upper n-heptane layer contained 25.8% by weight of dimethyl sebacate and 1.6% by weight of monomethyl adipate. Then 100 g of water was added to 100 g of this n-heptane layer and the mixture was stirred to separate it into two layers. The upper n-heptane layer contained 253% by weight Dimethyl sebacate and less than 0.01 wt% monomethyl adipal. The lower aqueous layer contained 1.9% by weight monomethyl adipate and less than 0.01 % W / w dimethyl sebacate. From these results it can be seen that in this example the dimethyl sebacate could be effectively separated from the monomethyl adipate.

The lower layer obtained in the first extraction stage was an oil layer. the 41.4% by weight Monomethyl adipate. 233 wt% dimethyl sebacate. 19.6% by weight of n-heptane and potassium monoethyl adipate ent held. After removing the n-heptane from the oil layer the remaining liquid was returned to the tank for the electrolytic solution by distillation and subjected to electrolysis.

Example 10

A 2 l glass jar was filled with 100 g of dimethyl sebacate. formed by electrolysis. and 1.5 kg of an aqueous solution containing 18% by weight of nitric acid contained, loaded. The resulting mixture was vigorously stirred and refluxed at atmospheric pressure boiled In this way, hydrolysis was carried out for 3 hours, whereby that by the hydrolysis reacted ; i (removed in methanol formed by distillation wtir'le. At the time of the termination of the reaction the hydrolysis rate is 99.9 mol%. The methanol concentration in the resulting liquid kept below 0.03 wt .-%. The by hydrolysis The sebacic acid formed was dissolved in the reaction mixture and it was not precipitated,

Example Il

Using 100 g of dimethyl sebacaf formed by electrolysis and 1 kg of an aqueous solution containing 24% by weight of nitric acid, the hydrolysis was carried out for 5 hours. for a long time carried out in the same manner as in Example 10. The degree of hydrolysis obtained was 97.2 mol- ⁰ A. The methanol concentration in the resulting liquid was kept below 0.03% by weight. All of the sebacic acid formed was dissolved in the reaction mixture without deposits

Example 12

Using 100 g of dimethyl sebacate formed by electrolysis and 1 kg of an aqueous one Solution containing 18% by weight nitric acid

. the hydrolysis was carried out in the same manner as in Example 10. The degree of hydrolysis obtained was 94.8 mol- ⁰ zo. The methanol concentration of the resulting liquid was 0.05% by weight. All of the sebacic acid formed was dissolved in the reaction medium

The liquid thus formed was cooled to room temperature, whereby sebacic acid crystals were precipitated. These were separated off by filtration, washed with 100 g of water and dissolved in 200 g of water at 130 ^° C. under a pressure of 2.6 bar in order to undertake recrystallization. The resulting crystals were separated by filtration, washed with 100 g of water and then dried, whereby 85 g of pure sebacic acid having a melting point of 134 ° C was obtained.

Example 13

A mixture of 1 mol adipic acid, 5 mol water. 5 moles of methanol and 0.2 moles of dimethyl adipate was used in Atmospheric pressure reacted for 5 hours to form monomethyl adipate. The reaction mixture was distilled and the dimethyl adipate was separated

10 kg of a melhanol solution. the 20% by weight monomethyl adipate, which has been neutralized with potassium hydroxide to a degree of neutralization of 30 mol% containing 20% by weight of dimethyl sebacate and 2% by weight of other by-products were placed in a tank for the given electrolytic solution and electrolyzed.

Both electrodes of the electrolytic cell had a current-applied area of 2 cm 100 cm. The cathode consisted of a SUS steel plate with a thickness of 2 mm. The anode consisted of a titanium plate with a thickness of 2 mm. those with 2 μΐπ Was platinum plated. A sheet of polyethylene with a thickness of 2 mm. which was so perforated. that she is a had a live area of 2 cm 100 cm, was arranged between the two electrodes around the

ίο to define electrode spacing of 2 mm. The electrolytic The cell had inlet and outlet openings for the electrolytic solution. The electrolytic solution was / was allowed to flow between both electrodes at a flow rate of 3 m / sec.

The electrolysis was carried out at a current density of 20 A / dnv at an electrolytic solution temperature of 55 ^ C at the outlet of the cell. With removal of part of the electrolytic solution and supply of fresh methanol. Monomethyl adipat and its potassium salt / in such a way that the above composition of the electrolytic Solution was always maintained, the electrolysis was 49 hours long; hamlet led, the amount of formed Dimethyjsebacals was by Gaschrorria-

lography determined. It emerged from this that the electrical slfomleisiung 85.7% and did dent removal of the Product was 89.2%. During the electrolysis, the minimum cell spacing was 13.3 full.

That was in the removed electrolytic solution Dimethyl sebacate in a concentration of 21% by weight. The concentration of the monomethyl adipate was 18% by weight. The degree of neutralization was 27 mol%. In the same way as in example 8 described, 10 kg of this removed electrolytic solution were subjected to a countercurrent extraction, in order to separate the dimethyl sebacate from it. In the extracted cyclohexane layer, the Dimethyl sebacate concentration 23% by weight and the monomethyl adipate concentration was less than 0.01 Wt%.

The cyclohexane solution thus obtained was subjected to fractional distillation to low-boiling components such as cyclohexane, methanol, water, methyl-n-va] erianaζ methyl-ca-hydroxyvalerianate, Methyl allyl acetate and dimethyl adipate, to be removed

nen. Then, the dimethyl sebacate was distilled off and purified. The amount of the thus recovered Dimethyl sebacate was 1.4 kg. The product had a purity of more than 99.9% and a melting point of 26.4 ° C

Using 0.5 kg of dimethyl sebacate, the was formed by electrolysis in the above manner, and 1.5 kg of 25% nitric acid became the hydrolysis was carried out in the same manner as in Example 10 for 4 hours. At the time of termination of the reaction, the degree of hydrolysis was higher than 99 ^ mol% and the methanol concentration of the resultant Liquid was 0.01 wt%. The reaction liquid thus formed became in the same Way as in Example 12 subjected to crystallization, whereby 0.41 kg of pure sebacic acid with a Melting point of 134 ° C were obtained.

For this. 1 sheet of drawings

Claims (1)

Claim: Process for the production of sebacic acid by electrolytic condensation of a methanolic Solution of monomethyl adipate and an alkali salt of monomethyl adipate, the solution being passed through an electrolytic cell, the dimethyl sebacate formed separated from the reaction mixture and is then subjected to hydrolysis, characterized in that in the solution maintains a concentration of dimethyl sebacate of 5 to 40 wt .-% and the solution with a flow rate of 2 ^ 5 to Passes 4.0 m / sec through the electrolysis cell