JPS6033902B2 - Method for producing γ,γ-dimethylbutyrolactone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing y,y-dimethylbutyrolactone by electrolytically reducing acetone and acrylic ester.

-Dimethylbutyrolactone has useful uses as a starting material for perfumes, pharmaceuticals, and the like.

The conventional technology for producing y, dimethylbutyrolactone by electrolytically reducing acetone and acrylic acid ester is as follows:
The following methods have been proposed.

That is, {1' method of electrolytic reduction using mercury at the cathode. [
J. org. chem-, 37, 2357 (1972
) and Electrochimica Acta. ,22,
271, (1977)] ■ Electrolytic reduction method using lead as a cathode in the coexistence of trimethylchlorosilane (Tetra
hedron skin rt. , 5029 (1979)) [3}
The present inventors previously proposed a method of electrolytic reduction using lead as the cathode and regulating the current density, electrolysis temperature, and acrylic acid ester concentration in the presence of a supporting electrolyte (Japanese Patent Laid-Open No. 57-288
3 Publication, Tokubatsu Publication No. 57-98683), etc. Method '1} uses mercury as the cathode, so
AFroling, Recu
il, 93, 47 (1974)], organic mercury compounds are produced as a creation organism, and separation operations are difficult, and there are also serious problems in terms of pollution. In addition, this organic mercury compound is not suitable for industrial electrolytic reactions because it precipitates on the surface of the mercury electrode when the flow rate of the electrolytic solution is low. Method (2) has been studied as a method for obtaining the target product in good yield in the case of the reaction between higher ketones and acrylic acid esters, where the electrolyte is non-uniform. However, this method uses dimethylformamide as a solvent and requires the coexistence of trimethylchlorosilane, an expensive reagent, so it cannot be said to be an industrially advantageous production method. '
The three methods are industrially advantageous manufacturing methods that solve the problems of the prior art (1) and (2), but these electrolytic cells, including (1' and A complicated device is required to separate the chamber and anode chamber. Also,■
When an electrolytic reaction is carried out in a single-chamber electrolytic cell using the electrolytic solution produced by the above production method, a significant amount of hydrogen gas is generated, and it cannot be said to be an industrial production method from a safety standpoint. The present inventors have conducted extensive research to overcome the various drawbacks of conventional manufacturing methods and to develop a method that can be easily implemented industrially. By using a specific inorganic salt in the electrolytic solution, raising the concentration of acrylic acid ester in the electrolytic solution to a predetermined concentration or higher, and limiting the pH to a certain range, electrolytic reduction can be carried out with a simplified device in extremely high yield and high yield. We have discovered that dimethylbutyrolactone can be easily produced with current efficiency.

The present invention has been made based on the above-mentioned findings, and can be used in industrial applications using electrodes that do not cause pollution problems, under mild conditions without using expensive additives, and with a simplified device. It is an object of the present invention to provide a method for producing y,y-dimethylbutyrolactone that is advantageous in terms of its properties. The method for producing y,y-dimethylbutyrolactone of the present invention which achieves the above object is to use a mixture of acrylic acid ester and acetone from lead or a lead alloy, cadmium as a cathode, and iron or an iron alloy, lead or a lead alloy as an anode. This single-chamber electrolytic cell uses an inorganic salt with phosphate ions as the supporting electrolyte, and the acrylic acid ester concentration in the electrolyte is 1.0.
It is characterized in that electrolytic reduction is carried out at a concentration of at least % by weight and at a pH within the range of 6 to 9 in the electrolytic solution. The essence of the present invention is to carry out the electrolytic reduction reaction of acetone and acrylic acid ester in a single-chamber electrolytic cell. Electrolytic reactions can be carried out in a one-chamber electrolytic cell. Therefore, it is necessary to combine three characteristics: use an inorganic salt containing phosphate ions, increase the concentration of acrylic acid ester in the electrolyte to a set level or higher, and limit the pH of the electrolyte to a certain range. . In the present invention, the pH in the electrolyte needs to be in the range of 6 to 9.

In acidic conditions with a pH of 6 or less and alkaline conditions with a pH of 9 or more, the reaction yield of y,y-dimethylbutyrolactone based on acrylic acid ester decreases. Furthermore, especially at a pH of 6 or less, hydrogen generation increases and the reaction yield based on acrylic acid ester also decreases significantly. In the present invention, it is necessary to use an inorganic salt having phosphate ions as the conductive substance.

This inorganic salt influences the pH mentioned above. pH 6~
In order to have a pH in the range of 9, it is necessary to adjust the pH of the inorganic salt having phosphate ions, that is, the alkali metal salt of phosphoric acid, to 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 cations of the inorganic salts having phosphate ions 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.

The amount of inorganic salt used is not particularly limited as long as the electrical resistance of the electrolytic solution is not extremely high and electrolysis can be carried out smoothly, and it is usually used within the range of 1 to 30% by weight.

As the acrylic acid ester used in the present invention, lower alkyl esters of acrylic acid are preferable from the viewpoint of solubility in water, and methyl acrylic ester (hereinafter abbreviated as methyl acrylate) is preferable because it is inexpensive and industrially easily available.

) is most preferred. In the present invention, the concentration of acrylic acid 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 lowers the current efficiency but also creates an explosive odor 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 Sogetsujima 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 acid 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 acid ester is continuously added and maintained at the set concentration. be.

The amount of acetone used is 0.5% by weight in the electrolyte.
It is fine if it contains more than 0.5%, but due to the precipitation of inorganic salts, etc.
It is preferably at least 2% by weight and at most 2% by weight.

The electrolytic solution contains substances derived from the reactants such as acrylate ester, acetone, and their electrolyzed products such as y,y-dimethylbutyrolactone, adipate ester, and alcohol, as well as water and a substance derived from the reactants to increase conductivity. It is a mixture of conductive substances. This electrolyte may be either homogeneous or heterogeneous. In some cases, it is also possible to add an acrylic acid ester polymerization inhibitor. The cathode materials used in the present invention include lead, lead alloys containing lead as a main component, cadmium, etc., but they do not cause pollution problems, have sufficient mechanical strength, and can be used for bipolar filter press type electrolysis. 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 in a tank. Examples of lead alloys include hard lead containing antimony and lead-tin alloys. Examples of anode materials used in the present invention include iron or iron alloys containing iron as a main component, lead or lead alloys containing lead as a main component, etc.
Preferably, it is 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.

Examples of the single-chamber electrolytic cell include a filter press type and a tank type, but the filter press type is preferred from an industrial perspective. For more details about the filter press type,
A cathode plate and an anode plate are arranged in parallel to each other, and a polypropylene plate is used to define the electrode spacing between the two electrodes, and a barrier hole is provided in the center of the polypropylene plate to allow the electrolyte to flow. The current-carrying area of the electrode is determined by the size of the opening, and the electrode spacing is determined by the thickness of the plate. The temperature during the electrolytic reaction may be any temperature as long as it is below the boiling point of the electrolytic solution, but is usually preferably 20 to 60 oC in order to prevent thermal denaturation of the acrylic ester. For the current density on the cathode surface, IA/d pillow ~5
0A/d is preferable.

If it is less than IA/d, productivity decreases and a wide area electrode is required, and if it is more than 50 A/d, heat generation due to liquid resistance is severe and it is not practical. Normally, it is carried out at 2 to 30 A/d. After the electrolytic reaction, in a filter press type electrolytic cell, the liquid is passed through the electrolytic cell at a flow linear velocity of usually 100 to 400 cm/sec. In a tank-type electrolytic cell, it is necessary to sufficiently stir the electrolytic reaction solution in order to renew the solution on the electrode surface. In the present invention, the electrolytic reaction solution is generally treated as follows.

That is, first, acetone is removed from the electrolytic reaction solution by distillation,
Next, the deacetonized electrolyte is separated into two phases, an organic phase and an aqueous phase. After separation, the organic phase is purified by distillation. First, low-boiling byproducts such as alcohol are removed, then unreacted raw materials are recovered, and then a product is obtained. On the other hand, as for the aqueous phase, after low-boiling byproducts such as alcohol are removed by distillation, 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, increasing the concentration of acrylic acid ester in the electrolyte to a set concentration or higher, and increasing the p of the electrolyte to
By setting H and performing electrolytic reduction, an expensive single-chamber electrolytic cell with simplified equipment does not require the conventionally used electrolytic cell and anode cell separated into cathode and anode chambers. Y,dimethylbutyrolactone can be obtained with extremely high current efficiency and excellent selection rate without using reagents or the like.

2. Separation of the product is extremely easy.

That is, after removing acetone in the electrolyte by distillation,
It can be easily separated into an organic phase containing dimethylbutyrolactone and acrylic acid ester as main components and an aqueous phase containing water and a conductive substance as main components by a simple operation such as shaking. The product can be easily isolated by removing only this organic phase and distilling it. In this distillation, there is no need to distill and recover a large amount of solvent as in conventional homogeneous systems, and the utility costs are extremely low. 3. The conductive substances in the electrolyte can be easily separated and recovered and reused.

That is, as mentioned in 2 above, the organic phase and the aqueous phase can be easily separated, and the conductive substance is distributed only in the aqueous phase, so if the aqueous phase is slightly treated, it can be separated and recovered very easily and reused. .
As described above, the present invention has great significance in that it provides a very advantageous industrial process for producing y,y-dimethylbutyrolactone from acetone and acrylate ester.

Next, Examples and Comparative 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 y,y-dimethylbutyrolactone based on acrylic acid ester Number of moles of produced Y,y-dimethylbutyrolactone X.

〇 [%] Number of moles of acrylic acid ester consumed Current efficiency = Number of moles of z,y-dimethylbutyrolactone produced x 2x,oo [%] Amount of current (in faraday units) However, current efficiency is 2 faradays of electricity The amount was determined assuming that 1 mole of product was produced.

Example 1 Potassium dihydrogen phosphate 46.8% and potassium hydroxide with a purity of 85% 16.3% were dissolved in water, the pH of this aqueous solution was adjusted to about 7 with phosphoric acid, and then acetone was added to 48.6%. evening,
24.0 g of methyl acrylate was added and water was added to make a total liquid volume of 600 g.

This solution was charged into an electrolyte tank and circulated to the electrolytic cell. The electrolytic cell had a current-carrying area of 2 arcs x 30 cm for both electrodes, the cathode was a lead plate with a thickness of 4, the anode was a carbon steel plate with a thickness of 2 willow, and the current-carrying area between the two electrodes was 2.0 cm x 30 cm. A polyethylene plate having a thickness of 2 and having an opening was placed so that the electrodes were held on the 2nd side, thereby defining the electrode spacing on the 2nd side.

The electrolytic cell used had a liquid supply port and a liquid outlet. The electrolyte was flowed between the electrodes at a rate of 2/sec, and the current density was 10 A/d.
Electrolysis was carried out on the pillow while maintaining the temperature of the liquid at 25 to 30q0. Also, at the same time as the electrolytic reaction started, methyl acrylate and acetone were added to the electrolyte tank at 7.8 hours/hour and 4 hours, respectively.
The addition was continued at 0 evening/hr, and the electrolytic reaction was stopped after 6 hours. 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 stopped, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 3.65% by weight, and the selectivity of dimethylbutyrolactone was 72% based on methyl acrylate.
The current efficiency of y,y-dimethylbutyrolactone is 58.2
%Met. Example 2 The cathode was a cadmium plate with a thickness of 2 ribs instead of a lead plate, the anode was a 6 gold plate with a thickness of 4 ribs instead of a carbon steel plate, and the potassium dihydrogen phosphate used in the preparation was replaced with 4 sodium dihydrogen phosphate.
On 1.3 days, an electrolytic reaction was carried out in the same manner as in Example 1 except that 11.6 days of sodium hydroxide was used instead of potassium hydroxide.

As a result of analyzing the hydrogen gas concentration in the gas generated during the electrolytic reaction,
It was 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 3.65% by weight, and the selectivity of dimethylbutyrolactone was 71.7% based on methyl acrylate.
The current efficiency was 58.0%. Example 3 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 24.02 to 8.0 and acetone from 48.6 to 16.2.

As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction,
The maximum value was 3.0 V/V%, and the average value was 2.4 V/V%. After the electrolytic reaction was completed, the electrolytic solution was analyzed by gas chromatography, and the concentration of methyl acrylate was 1.3% by weight, and the selectivity of y,y-dimethylbutyrolactone based on methyl acrylate was 72.1%. , the current efficiency is 57.5
%Met. Example 4 The amount of potassium dihydrogen phosphate charged was changed from 46.8 to 9.
An electrolytic reaction was carried out in the same manner as in Example 1, except that the amount of potassium hydroxide with a purity of 85% was changed from 16.3 days to 3.3 days.

As a result of measuring the hydrogen gas concentration in the gas generated during the electrolytic reaction,
It was 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 3.6% by weight, and the selectivity of y,y-dimethylbutyrolactone based on methyl acrylate was 71.5%.
The current efficiency was %. Comparative Example IJ A preparation solution in which 46.8 g of potassium dihydrogen phosphate was dissolved in water, 48.6 g of acetone and 24.0 g of methyl acrylate were added to this, and water was added to make a total liquid volume of 600 g. (
When the electrolytic reaction was started in the same manner as in Example 1 except that the pH of the charging solution was 4.2, the hydrogen gas concentration in the generated gas was 17 V/V% after 30 minutes, and after 1 hour. exceeded 30V/V%.

Claims (1)

[Claims] 1. A mixture of acrylic ester and acetone is used in a single-chamber electrolytic cell consisting of lead or a lead alloy, cadmium as a cathode, and iron or an iron alloy, lead or a lead alloy as an anode, and phosphoric acid is used as a supporting electrolyte. γ, characterized in that electrolytic reduction is carried out using an inorganic salt having ions, setting the concentration of acrylic acid ester in the electrolytic solution to 1.0% by weight or more, and setting the pH of the electrolytic solution in the range of 6 to 9. , a method for producing γ-dimethylbutyrolactone. 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 inorganic salt having phosphate ions is an alkali metal salt of phosphoric acid. 4. The method according to claim 3, wherein the alkali metals are sodium and potassium. 5. The method according to claim 1, wherein the acrylic ester is a lower alkyl ester of acrylic acid. 6. The method according to claim 5, wherein the lower alkyl ester of acrylic acid is methyl acrylate. 7 Acrylic acid ester concentration in electrolyte is 1.5% by weight
The method according to claim 1, which is the above.