JPS5943551B2 - Method for producing 4-butanolides - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing 4-butanolides from acrylic acid esters and aldehydes, and particularly to a method for producing 4-butanolides by electrolytic reduction coupling reaction.

The 4-butanolides referred to in the present invention refer to 4-butanolide, that is, γ-butyrolactone and its monosubstituted product at the 41-position.

4-Butanolides, especially 4-alkyl-4-butanolides, have a unique aroma and are used as flavoring agents for foods and cosmetics, as well as being useful as intermediates in the production of fragrances, medicines, agricultural chemicals, etc. .

For example, 4-n-propyl-4-butanolide has a coumarin-like aroma, and 4-n-hexyl-4-butanolide has a nutty aroma when concentrated, and a peach-like aroma when diluted. Each of these is known as a fragrance. The following methods have been proposed for producing 4-butanolides by electrolytic reduction coupling reaction of acrylic esters and aldehydes.

That is, using dimethylformamide as a solvent, aldehyde,
A method of electrolytically reducing a mixture of acrylic acid esters and trimethylthalolsilane in a homogeneous system using a lead electrode ["Te
trahedrOnLettersL Volume 21 No. 502
9-5032 pages (1980)] and a method of coupling a mixture of engineered tananal and propanal with an arylate ester in an aqueous potassium phosphate solution using a graphite electrode activated with mercury [Zh.Org.Kh
lmJl Volume 11, No. 9, Pages 1984-1985 (1975)]. In the former, electrolysis is performed in a homogeneous system, but generally when electrolysis is performed in a homogeneous system, three types of solvents are used: water-protic solvent, water-protic polar solvent, and aprotic polar solvent. Conceivable.

As a result of various studies on electrolytic reduction coupling reactions in a homogeneous system, the present inventors obtained the following findings as disclosed in Japanese Patent Application No. 155746/1982. That is, it was confirmed that the current efficiency was extremely low in water-protic solvent. Although the reason for this is not well understood, it is thought that one of the causes is that a part of the aldehyde undergoes acetalization and hemiacetalization by the solvent. Furthermore, in the case of water and aprotic polar carrier, the selectivity of 4-butanolide based on aldehyde is extremely low. In this case, it is thought that the action of hydroxyl ions, which are thought to be slightly generated by the electrolysis of water, is enhanced by the aprotic polar solvent, causing an undesirable side reaction for the aldehyde. Therefore, in order to perform electrolysis in a homogeneous system while maintaining both high yield and current efficiency, it is necessary to use an aprotic polar solvent alone, taking into consideration the compatibility with water and the solubility of the conductive supporting salt. used in
In addition, it seems necessary to use a special reagent such as trimethylchlorosilane. However, it is necessary to use an expensive propellant such as dimethylformamide, and it is necessary to use trimethylchlorosilane in an equimolar amount to the aldehyde. There are problems such as the need to be careful in handling as it is hydrolyzed. On the other hand, in the latter case, it is difficult to manufacture the electrodes used, and the carbon electrode lacks mechanical strength, so it may break or crack when attached to a filter press type battery case, which is usually used industrially. There are drawbacks such as the need to solve the pollution problem caused by the use of mercury. Furthermore, this method has the disadvantage that 4-butanolide is obtained as a mixture of 4-methyl-4-butanolide and 4-ethyl-4-butanolide, making separation and purification complicated. The present inventors have conducted intensive research to overcome various drawbacks of the conventional production method of 4-butanolides and to develop a method that can be easily implemented industrially. In a tank, using a specific inorganic salt as a supporting electrolyte, in the presence of a conductive substance having a phase transfer catalyst function, in an aqueous emulsion state, the concentration of acrylic acid ester is increased to a set level or higher, and the pH in the p aqueous phase is set. It has been found that 4-butanolide can be easily produced with extremely high yield and high current efficiency using a simplified apparatus by electrolytic reduction.

The present invention was made based on the above-mentioned knowledge, and it is possible to produce 4-butanolides in high yield and with high current efficiency under mild conditions without using expensive additives or additives that require careful handling. , the product can be easily isolated, the cathode has strong mechanical strength and is non-toxic, and the conductive material can be easily separated and recovered using a simplified device. The object of the present invention is to provide an industrially advantageous method for producing 4-butanolides.

The method for producing 4-butanolides of the present invention that achieves the above object uses a mixture of acrylic ester and aldehyde as a cathode, lead or a lead alloy, cadmium, as an anode,
A single-chamber electrolyzer made of iron or iron alloys, lead or lead alloys,
In the presence of an electrically conductive substance selected from the group consisting of an inorganic salt containing a phosphate, a quaternary ammonium salt, and a quaternary phosphonium salt, or having at least one kind of phase transfer catalyst function,
It is characterized in that electrolytic reduction is carried out in the aqueous emulsion state, with the acrylic acid ester concentration in the aqueous emulsion being 1.0% by weight or more, and the pH in the aqueous phase being in the range of 6 to 9.

The reaction of the present invention proceeds roughly according to the following reaction formula.

υ-1几υ11 (R in the formula is a substituted or unsubstituted alkyl group, aryl group, aralkyl group, alkenyl group, or alkynyl group, R
' is an alkyl group.

) The essence of the present invention is to perform the electrolytic reaction shown above in a single-chamber electrolyzer, and simply achieving high current efficiency and high yield does not achieve the objective; it is necessary to suppress hydrogen generation. This can only be achieved by preventing the formation of explosive gas mixtures.

Therefore, by using an inorganic salt and a conductive substance having a phase transfer catalytic function, the pH of the aqueous phase of the aqueous emulsion is adjusted to a set range, and the acrylic acid ester in the aqueous emulsion is raised to a set concentration or higher. 3
It is necessary to combine two characteristics. In the present invention, this reaction is carried out in an aqueous emulsion state, that is,
It is necessary to carry out the process in a heterogeneous phase consisting of an aqueous phase and an organic phase.

In this case, the pH in the aqueous phase has an important meaning in the present invention. That is, it is necessary to adjust the pH in the aqueous phase to a range of 6 to 9. In an acidic region with a pH of 6 or lower and an alkaline region with a pH of 9 or higher, acrylic esters and aldehydes become unstable, side reactions occur, and the reaction rate of 4-butanolides based on acrylic esters and aldehydes decreases. Especially PH6
In the following acidic range, the amount of propionate ester produced increases and the reaction yield based on acrylic ester decreases. Also, electrode wear increases. The aqueous phase of the aqueous emulsion mainly contains phosphates and conductive substances having a phase transfer catalytic function, and these influence the pH, especially the phosphates. In order to bring the pH of the aqueous layer into the range of 6 to 9, it is necessary to bring the phosphate, ie, the alkali metal salt of phosphoric acid, to pH 6 to 9. In order to adjust the pH of the alkali metal salt of phosphoric acid to 6 to 9, neutralize the phosphoric acid or dihydrogen phosphate with an alkali, or neutralize the alkali metal hydroxide or monohydrogen phosphate with phosphoric acid. Must. The inorganic salt used in the present invention is a phosphate alone or a mixture of a phosphate and a borate.

However, as described below, when sulfate ions are used as anions for quaternary ammonium salts and quaternary phosphonium salts, these sulfates are mainly dissolved in the aqueous phase, so some sulfate ions are present in the aqueous phase. I will do it. That is,
Of course, there is no problem even if some inorganic sulfate is present. Electrode wear is reduced when using a mixture of phosphate and borate. The cations of the inorganic salt used in the present invention include, for example, alkali metal cations such as sodium, potassium, lithium, cesium and rubidium, and ammonium ions, with sodium and potassium being preferred for economical reasons. There is no particular restriction on the amount of inorganic salt used, as long as the electrical resistance of the emulsion is not extremely high and electrolysis can be carried out smoothly, and the concentration in the aqueous phase is usually 1.
It is used in a range of 30% by weight.

The aldehyde used in the present invention is not particularly limited, but from an industrial standpoint, aliphatic aldehydes having 2 to 13 carbon atoms are preferred, and saturated linear aldehydes are more preferred. For example, propanal, butanal, pentanal,
These include hexanal, heptanal, octanal, and nonanal. In the present invention, the yield is significantly improved by carrying out electrolysis in an aqueous emulsion state using an inorganic salt and a conductive substance having a phase transfer catalytic function, such as a quaternary ammonium salt or a quaternary phosphonium salt, respectively. The degree of effectiveness of the quaternary ammonium salt and quaternary phosphonium salt used in the present invention differs depending on the type thereof.

Furthermore, the degree of effectiveness of quaternary ammonium salts and quaternary phosphonium salts also differs depending on the type of aldehyde.
That is, in the case of an aldehyde having 2 to 4 carbon atoms, it is preferable to use a quaternary ammonium salt and a quaternary phosphonium salt in which the total number of carbon atoms in the general formula described below is 10 or more and 25 or less. When it is less than 10 and more than 25, current efficiency and reaction yield decrease.

In the case of an aldehyde having 5 to 13 carbon atoms, it is preferable to use one in which the total number of carbon atoms in the general formula described below is 10 or more and 20 or less, and it is more preferable to use one in which the total number of carbon atoms is 16. When the total number of carbon atoms is 10 or less and 20 or more, current efficiency and reaction yield decrease. The quaternary ammonium salt and quaternary phosphonium salt described above have the general formula (quaternary ammonium salt), (quaternary phosphonium salt) (Rl in the formula
, R2, R3 and R4 are the same or different alkyl groups or aralkyl groups, the total number of carbon atoms in these groups is 10 to 25, X is an acid group, n is an integer, and This value corresponds to the valence of the ion.

) is a compound represented by

In the quaternary ammonium salt and quaternary phosphonium salt, Rl, R2, R3 and R4 are generally alkyl groups selected from the group consisting of methyl group, ethyl group, propyl group, butyl group, and amyl group. Among these, one in which at least three of Rl, R2, R3 and R4 are an alkyl group having 3 or more carbon atoms is more preferred.
In particular, in the case of an aldehyde having 5 to 13 carbon atoms, it is preferable that all the alkyl groups are butyl groups. These include, for example, tetra(n or IsO)-propyl, tetra(n or IsO)-butyl, tetra(n or IsO)-propyl, tetra(n or IsO)-butyl,
Examples include ammonium salts and phosphonium salts of sO)-amyl, ethyltripropyl, ethyltributyl, and ethylpropyldibutyl. The amount of quaternary ammonium salt and quaternary phosphonium salt in the aqueous layer of the aqueous emulsion may be 0.01% by weight or more, preferably 0.1% by weight or more and 5% by weight or less.

If the amount of quaternary ammonium salt and quaternary phosphonium salt is too small, current efficiency and reaction yield will decrease. As the counteranion X (same as X shown in the general formula) of the quaternary ammonium salt or quaternary phosphonium salt, for example, phosphate ion, sulfate ion, halogen ion, etc. are used, but among these, Phosphate ions are preferred.

Sulfate ions, halogen ions, etc. cause a slight decrease in reaction yield and current efficiency. Among these, halogen ions are undesirable because they have the problem of increasing electrode wear. As the acrylic ester used in the present invention, lower alkyl esters of acrylic acid are preferred from the viewpoint of solubility in water, and acrylic methyl ester (hereinafter abbreviated as methyl acrylate) is more inexpensive and industrially easily available.

) is most preferred. In the present invention, the concentration of acrylic ester in the electrolytic solution needs to be 1.0% by weight or more, and more preferably 1.5% by weight or more.

If it is less than 1.0% by weight, a large amount of hydrogen gas is generated, which not only reduces the current efficiency but also creates explosive atmosphere with the oxygen gas generated at the anode, which is unfavorable from a safety standpoint.

If it is 1.0% by weight or more and 1.5% by weight or less, hydrogen gas will be generated, but by diluting it with a small amount of inert gas such as nitrogen gas, it is possible to prevent the generation of explosive gas and perform electrolysis. .

When the content is 1.5% by weight or more, hydrogen gas is hardly generated and electrolysis can be carried out without problems.

Methods for increasing the concentration of acrylic ester in the electrolytic solution to a set concentration or higher include a batch method in which electrolysis is started from a high concentration and reaches the set concentration, or a continuous method in which acrylic ester is continuously added and maintained at the set concentration. be.

The cathode material used in the present invention is lead or an alloy containing lead as a main component, cadmium, etc., but it does not cause pollution problems, has sufficient mechanical strength, and can be used in a bipolar filter press type battery case. It is preferable to use lead or a lead alloy containing lead as a main component, which can continue stable operation for a long period of time even when used for.

Examples of lead alloys include hard lead containing antimony, lead-tin alloy, and the like. Examples of the anode material used in the present invention include iron or an iron alloy containing iron as a main component, lead or a lead alloy containing lead as a main component, and preferably iron or an iron alloy containing iron as a main component.

Examples of iron alloys include carbon steel and stainless steel. Lead or lead alloys containing lead as a main component are subject to significant wear.
The electrolytic cell used in the present invention is a single-chamber electrolytic cell using the anode and cathode described above. As a single electrolytic cell, there are, for example, a filter press type, a tank type, etc., but the filter press type is preferable from an industrial perspective. To explain in detail about the filter press type, a cathode plate and an anode plate are opposed in parallel, and there is a polypropylene plate between the two electrodes that defines the electrode spacing, and the electrolyte flows through the center of this polypropylene plate. The electrolytic cell has an aperture in the plate, and the current-carrying area of the electrode is determined by the size of the aperture, and the distance between the electrodes is determined by the thickness of the plate. The electrolyte contains substances derived from the reactants such as acrylic esters and aldehydes, and their electrolyzed products such as 4-butanolide, adipate diethyl, propionate esters, and alcohol, as well as water and water to increase conductivity. It is a mixture of electrically conductive substances and exists as a two-phase system of an organic phase and an aqueous phase.
In some cases, it is also possible to add an acrylic acid ester polymerization inhibitor, and emulsifiers and the like may be used to stabilize the emulsion, and solvents may be added as long as they do not adversely affect emulsion formation. Although it is possible to add these additives or solvents, it is usually preferable to perform electrolysis without using these additives or solvents. The molar ratio of aldehyde to acrylic ester in the electrolytic solution is preferably 1 to 10 from the viewpoint of yield, and more preferably 1 to 5 from the viewpoint of product separation.
is preferred.

The volume ratio of the organic phase in the emulsion to the total emulsion is preferably 0.5 or less in view of ease of product separation.

The temperature during electrolysis may be any temperature as long as it is below the boiling point of the electrolytic solution, but it is usually 20 to 60°C, especially 20°C to prevent thermal denaturation of the aldehyde and acrylic ester.
0 to 40°C is preferred.

The current density on the cathode surface is 1A/Dml to 50A.
/d〆 is preferable. 1A/DW? If it is less than 501 Iy/d, the productivity decreases and electrodes with a wide area are required, and if it is more than 501 Iy/d, heat generation due to liquid resistance is severe and it is not practical.

Normally, it is carried out at 5 to 20 A/d. The electrolytic reaction solution is
It is desirable that the aqueous phase and the organic phase be supplied onto the cathode surface in a finely suspended state; therefore, in a tank-type electrolytic cell, it is necessary to stir the electrolyte thoroughly; In a filter press type electrolytic cell, the flow linear velocity of the electrolytic reaction solution is preferably at least a velocity at which an emulsion is sufficiently formed, and is usually 100 to 400 (7
It is carried out in the range of L/sec. In the present invention, the electrolytic reaction solution is generally treated as follows.

That is, first, the electrolytic reaction solution is separated into two phases, an organic phase and an aqueous phase, and then the conductive substance distributed in the organic phase is extracted with a small amount of water. The organic phase is then distilled, first to remove low-boiling by-products such as alcohol, then to recover unreacted raw materials, and then to obtain the product. On the other hand, as for the aqueous phase, after removing low-boiling by-products such as alcohol by steaming, the remaining liquid containing the conductive substance is recycled and reused as the aqueous phase of the electrolyte. In the method of the present invention, products can be separated very easily through such treatment, and conductive substances can also be recovered very easily. The advantages of the present invention are listed below.

1) Using a specific inorganic salt as a supporting electrolyte, in the presence of a conductive substance with a phase transfer catalyst function, in an aqueous emulsion state, increase the concentration of acrylic acid ester to a set level or higher, and set the pH in the aqueous phase to perform electrolytic reduction. By doing so, a single-chamber electrolytic cell with simplified equipment does not require the conventionally used electrolytic cell separated into a cathode chamber and anode chamber and an anolyte, and without using expensive reagents. , 4-butanolides can be obtained with extremely high current efficiency and excellent selectivity.

Furthermore, adipic acid ester, which is partially produced as a by-product, is also extremely important industrially. 2) Product separation is extremely easy.

In other words, by simply allowing the emulsion to leave the electrolytic cell, it can be separated into an organic phase mainly composed of acrylic acid ester, aldehyde, and 4-butanolide, and an aqueous phase mainly composed of water and a conductive substance. can be easily separated. The product can be easily isolated and purified by removing only this organic phase and distilling it. In this distillation, unlike in a homogeneous system, there is no need to distill and recover a large amount of solvent, and the utility costs are extremely low. After the electrolytic solution is separated into two phases, the aqueous phase can be subjected to subsequent electrolysis as it is after some treatment. 3) The conductive substance in 4-butanolide can be easily separated and recovered.

That is, as described in 2) above, the organic phase and the aqueous phase can be easily separated, and the conductive substance in the organic phase can be separated and recovered very easily by extraction with water. As described above, the present invention has great significance in that it provides a very advantageous industrial process for producing 4-butanolides from acrylic esters and aldehydes.

Next, Examples will be shown to further specifically explain the present invention. Note that the selectivity and current efficiency were calculated using the following formula. Selectivity of 4-butanolides based on acrylic ester J7S~-▼νl~-''4 based on aldehyde
- Selectivity of butanolides Selectivity of adipic acid ester based on acrylic acid ester However, the current efficiency was determined on the assumption that 1 mole of the product is produced from the amount of electricity of 2 Farads.

Example 1 16.3y of potassium hydroxide was dissolved in water, 13.7g of a 50% aqueous solution of tetra-n-butylammonium phosphate was added thereto, the pH of this aqueous solution was adjusted to 7 with phosphoric acid, and then 60.29 g of butanal and 24.0 g of methyl acrylate were added, and water was added so that the total liquid volume was 6009 g.

This solution was charged into an electrolyte tank and circulated to the electrolytic cell. Both electrodes of the electrolytic cell have a current-carrying area of 2CTn x 30C71L, and the cathode has a thickness of 4mT1. The lead plate and the anode are made of a carbon steel plate with a thickness of 2 mm, and the current carrying area between the two electrodes is 2.

0cm x 30? A 2 mm thick polyethylene plate with openings was placed so that the electrodes were held at a distance of 2 m77.
! stipulated.

The electrolytic cell used had a liquid supply port and a liquid outlet. The liquid was flowed between the electrodes at 2 m/sec, and the current density was 10 A/Dm2.
Next, electrolysis was carried out while maintaining the temperature of the liquid at 25 to 30°C. In addition, at the same time as the electrolytic reaction started, methyl acrylate and butanal were added to the electrolyte tank at 11.09/Hr and 7.
79/Nr was added continuously, and the reaction was stopped after 6 hours. When the hydrogen gas concentration in the gas generated during the electrolytic reaction was measured, it was 0.
．． It was 1/v% or less. After stopping the electrolytic reaction, the electrolyte was analyzed using gas chromatography, and the concentration of methyl acrylate was 3.49% by weight, which was 4% by weight based on methyl acrylate.
- Selectivity of n-propyl-4-butanolide 80.2%,
Selectivity of dimethyl adipate 1.1 (f), selectivity of 4-n-propyl-4-butanolide based on butanal 95
．． The current efficiency of 8% and 4-n-propyl-4-butanolide was 91.1%. Example: 2 cathodes with a thickness of 2m77 instead of a lead plate! Other than using a cadmium plate, a lead plate with a thickness of 4 mm instead of a carbon steel plate for the anode, and a 50% aqueous solution of tetra-n-amylammonium phosphate in place of tetra-n-butylammonium phosphate, 16.19 was carried out. An electrolytic reaction was carried out in the same manner as in Example 1.

When the hydrogen gas concentration in the gas generated during the electrolytic reaction was measured, it was found to be 0.1 v/v % or less. After the electrolytic reaction was completed, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 5.34% by weight, and the selectivity of 4-n-propyl-4-butanolide based on methyl acrylate was 91.2.
%, selectivity of dimethyl adipate 1.0% Selectivity of 4-n-propyl-4-butanolide based on butanal 86.
0%, the current efficiency of 4-n-propyl-4-butanolide was 83.0%.

Example 3 Example 1 except that a 50% aqueous solution of tetra-n-butyl ammonium sulfate (14.29 g) was used instead of tetra-n-butylammonium phosphate.
An electrolytic reaction was carried out in the same manner.

When the hydrogen gas concentration in the gas generated during the electrolytic reaction was measured, it was 0.1 v/% or less. After the electrolytic reaction was completed, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 4.37% by weight, and the selectivity for 4-n-propyl-4-butanolide was 81.2% based on methyl acrylate.
, selectivity of dimethyl adipate 1.0%, selectivity of 4-n-propyl-4-butanolide based on butanal 88.
0%, the current efficiency of 4-n-propyl-4-butanolide was 83.5%. Example 4 An electrolytic reaction was carried out in the same manner as in Example 1, except that the amount of methyl acrylate charged was changed from 24.0 f1 to 89, and the amount of butanal was changed from 60.29 to 20.1 g.

As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction,
The maximum value was 2.0v/%, and the average value was 1.8v/v%. After the electrolytic reaction was completed, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 1.33% by weight, and the selectivity of 4-n-propyl-4-butanolide was 80.5% based on methyl acrylate. Selectivity of dimethyl adipate 1.2%, 4-n-propyl-4 based on butanal
-Selectivity of butanolide 95.2%, 4-n-propyl-
The current efficiency of 4-butanolide was 90.2%. Example 5 An electrolytic reaction was carried out in the same manner as in Example 1, except that 14.2% of a 50% aqueous solution of tetra-n-butylphosphonium phosphate was used instead of tetra-n-butylammonium phosphate.

The result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction was 0.
．． It was 1v/% or less. After the electrolytic reaction was completed, the electrolyte was analyzed using gas chromatography, and the concentration of methyl acrylate was 3.59% by weight, which was 4-4% based on methyl acrylate.
Selectivity of n-propyl-4-butanolide 81.0%, selectivity of dimethyl adipate 1.0%, selectivity of 4-n-propyl-4-butanolide based on butanal 95.3%
, the current efficiency of 4-n-propyl-4-butanolide is 91
．． It was 0%. Example 6 46.89% of potassium dihydrogen phosphate and 16.39% of potassium hydroxide with a purity of 85% were dissolved in water, and tetra-n-
50% aqueous solution of butylammonium phosphate13.
7 g was added, and the pH of this aqueous solution was adjusted to 7 with phosphoric acid. Next, 95.59 heptanal and 24.09 methyl acrylate were added, and water was added so that the total liquid volume was 6009.

This solution was charged into an electrolyte tank and circulated to the electrolytic cell. The same electrolytic cell as in Example 1 was used, and the electrolytic reaction was carried out under the same electrolytic reaction conditions as in Example 1. Further, at the same time as the start of the electrolytic reaction, methyl acrylate and heptanal were continuously added to the electrolyte tank at a rate of 10.19/Hrl and 3.39/Hrl, respectively, and the electrolytic reaction was stopped after 6 hours. As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction, it was found to be 0.4/% or less. After stopping the electrolytic reaction, the electrolyte was analyzed using gas chromatography, and the concentration of methyl acrylate was 3.
27% by weight, selectivity of 4-n-hexyl-4-butanolide based on methyl acrylate 62.0%, selectivity of dimethyl adipate 30.1%, 4-n- based on heptanal
Hexyl-4-butanolide selectivity 78.5%, 4-n
-Hexyl-4-butanolide had a current efficiency of 65.2%. Example 7 The amount of methyl acrylate in the preparation was changed from 24.0g to 8.09g.
An electrolytic reaction was carried out in the same manner as in Example 6 except that heptanal was changed from 95,59 to 31.8y.

As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction,
The maximum value was 2.6 v/v%, and the average value was 2.1 v/v%. After the electrolytic reaction was completed, the electrolyte was analyzed using gas chromatography, and the concentration of methyl acrylate was 1.2% by weight.
, selectivity of 4-n-hexyl-4-butanolide based on methyl acrylate 61.9%, selectivity of dimethyl adipate 30.2%, 4-n-hexyl- based on heptanal
The selectivity for 4-butanolide was 78.7%, and the current efficiency for 4-n-hexyl-4-butanolide was 64.3%.
Example 8 41.39 g of sodium dihydrogen phosphate, 9.9 g of sodium hydroxide, and 12.09 g of sodium tetraborate were dissolved in water, and 12.39 g of a 50% aqueous solution of ethyl tri-n-butylammonium phosphate was added thereto. The pH of this aqueous solution was adjusted to 7 with phosphoric acid, and then heptanal 95
．． 59, add 24.09 methyl acrylate and the total liquid volume is 6
Water was added so that it became 009.

This solution was subjected to an electrolytic reaction in the same manner as in Example 6. As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction, it was found to be 0.
．． It was 3v/v% or less. After stopping the electrolytic reaction, the electrolyte was analyzed by gas chromatography, and the concentration of methyl acrylate was 3.27% by weight, which was 4% by weight based on methyl acrylate.
-n-hexyl-4-butanolide selectivity 57.0%,
Selectivity of dimethyl adipate 21.5%, selectivity of 4-n-hexyl-4-butanolide based on heptanal 72
．． 0%, the current efficiency of 4-n-hexyl-4-butanolide is 60. It was 0%. Example 9 50% of tetra-n-butylphosphonium phosphate instead of tetra-n-butylammonium phosphate
An electrolytic reaction was carried out in the same manner as in Example 6, except that 1442 g of the % aqueous solution was used.

As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction,
It was below 0.4v/v%. After the electrolytic reaction was completed, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 3.34% by weight, and the selectivity of 4-n-hexyl-4-butanolide based on methyl acrylate was 63.1.
%, the selectivity of dimethyl adipate is 29.2%, the selectivity of 4-n-hexyl-4-butanolide based on hepcunar is 79.1%, and the current efficiency of 4-n-hexyl-4-butanolide is 65.8%. It was hot. Comparative Example 46.8y of potassium dihydrogen phosphate was dissolved in water, and 50% of tetra-n-butylammonium phosphate was added to the solution.
Aqueous solution 13.79, heptanal 95.5f! , 24.09% of methyl acrylate was added and water was added to make the total liquid volume 6009% (the pH in the aqueous phase was 4.2).

Claims (1)

[Claims] 1. Phosphate in a single chamber electrolytic cell consisting of a mixture of acrylic acid ester and aldehyde as a cathode, lead or a lead alloy, cadmium, and iron or an iron alloy, lead or a lead alloy as an anode. In an aqueous emulsion state, in the presence of an electrically conductive substance having a phase transfer catalytic function selected from the group consisting of an inorganic salt containing an inorganic salt, a quaternary ammonium salt, and a quaternary phosphonium salt, the acrylic acid in the aqueous emulsion is The acid ester concentration is 1.0% by weight or more, and the pH in the aqueous phase is
4 characterized in that electrolytic reduction is carried out in the range of 6 to 9.
- A method for producing butanolides. 2. The method according to claim 1, wherein the cathode is lead or a lead alloy, and the anode is iron or an iron alloy. 3. The method according to claim 1, wherein the phosphate is an alkali metal salt of phosphoric acid. 4. The method according to claim 3, wherein the alkali metals are sodium and potassium. 5 Acrylic acid ester concentration in aqueous emulsion is 1
．． The method according to claim 1, wherein the content is 5% by weight or more. 6. The method according to claim 1, wherein the aldehyde is an aliphatic aldehyde having 2 to 13 carbon atoms. 7 The aldehyde is an aliphatic aldehyde with 2 to 3 carbon atoms, and the quaternary ammonium salt and quaternary phosphonium salt have the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (Quaternary ammonium salt) (Quaternary phosphonium salt) (
In the formula, R^1, R^2, R^3 and R^4 are the same or different alkyl groups or aralkyl groups, and the total number of carbon atoms in these groups is 10 to 25, and X is an acid n is an integer and corresponds to the ionic valence of X. ) The method according to claim 1, wherein the compound is a compound represented by: 8. Claim 7, in which R^1, R^2, R^3 and R^4 in the general formula are all alkyl groups, and the total number of carbon atoms in these alkyl groups is 14 to 20. Method described. 9 The aldehyde is an aliphatic aldehyde with 5 or more carbon atoms, and the quaternary ammonium salt and quaternary phosphonium salt have the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R^1, R^2, R^3 and R^4 are the same or different alkyl groups or aralkyl groups, and the total number of carbon atoms in these groups is 10 to 20, and
is an acid group, and n is an integer corresponding to the ionic valence of X. ) The method according to claim 1, wherein the compound is a compound represented by: 10. The method according to claim 9, wherein R^1, R^2, R^3 and R^4 in the general formula are all alkyl groups. 11. The method according to claim 10, wherein all the alkyl groups are butyl groups. 12. The method according to claims 7 and 9, wherein X in the general formula is a unit corresponding to a monovalent phosphate ion. 13. The method according to claims 7 and 9, wherein the concentration of the quaternary ammonium salt in the aqueous layer of the aqueous emulsion is 0.01% by weight or more and 5% by weight or less. 14. The method according to claim 1, wherein the acrylic ester is a lower alkyl ester of acrylic acid. 15. The method according to claim 14, wherein the lower alkyl ester of acrylic acid is methyl acrylate.