KR0175309B1 - Process for preparing epsilon-caprolactone - Google Patents

Abstract

The present invention is a process for preparing ε-caprolactone using a percarboxylic acid solution and cyclohexanone obtained by oxidizing a rainy season carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst, 1-1.5 mol per mole of cyclohexanone in the reaction system. Percarboxylic acid, 0.012 mol or less of hydrogen peroxide, and 0.04 mol or less of boric acid catalyst are supplied, and the said cyclohexanone and said percarboxylic acid are made to react, and it is related with the manufacturing method which forms (epsilon) -capropaktone.

Description

Method for producing ε-caprolactone

Figure 1 illustrates the steps of preparing the percarboxylic acid solution used to practice the present invention, forming the ε-caprolactone (preparing the initial ε-caprolactone solution) and purifying the initial ε-caprolactone solution. It is an example of a manufacturing flue chart showing the steps to

* Explanation of symbols for main parts of the drawings

1: glass reactor 2: reactor

3: supply line 4: supply line

5: discharge line 6: supply line

7: supply line 8: supply line

9: reboiler 10: discharge line

11: supply line 12: reboiler

13: discharge line 14: discharge line

A: distillation tube B: reflux condenser

C: distillation tube D: distillation tube

The present invention is a method for producing (epsilon) -caprolactone effectively (in high yield) while almost suppressing the formation of by-products, and a percarboxylic acid solution obtained by oxidizing an organic carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst. And cyclohexanone are supplied into the reaction system, and the hydrogen peroxide and the boric acid catalyst are made to be in a smaller ratio, while the reaction method of the present invention relates to a production method for achieving a myth reaction of percarboxylic acid and cyclohexanone in the reaction system.

Since the reaction mixture containing ε-caprolactone obtained above does not actually contain by-products, high purity ε-caprolactone can be easily obtained by a conventional purification process such as distillation.

In the known art, it is known to produce ε-caprolactone by reacting cyclohexanone with percarboxylic acid such as peracetic acid, perpropionic acid (Baeyer-Villiger oxidation reaction). However, since various by-products such as adipic acid and 5-hexenoic acid are formed in the conventional manufacturing process, it is extremely important to carry out purification to separate high purity ε-caprolactone from the reaction mixture containing ε-caprolactone. It is difficult and ε-caprolactone containing such byproducts adversely affects the production of polymers such as polyesterols and polyurethanes.

Various techniques are proposed as a purification method for separating ε-caprolactone from the reaction mixture containing ε-caprolactone obtained by the above-mentioned manufacturing process. For example,

(1) A method of distilling a low boiling point component of an initial epsilon -caprolactone produced by reacting cyclohexanone with a percarboxylic acid solution by a first distillation apparatus, followed by distillation of the product by a second distillation apparatus. (Japanese Patent Publication Nos. 34677/1981 and 42684/1982)

(2) After distilling off the low boiling point component from the reaction mixture obtained by oxidizing cyclohexanone, an inert gas is injected into the condenser of the second distillation tube to suppress the condensation of water. (Japanese Patent Publication No. 59238/1985)

(3) A method of treating initial [epsilon] -caprolactone with an acid sulfite-type anion exchange resin (Japanese Patent Publication No. 16435/1985).

However, these techniques require complex purification processes or by-products (impurities) that are often inseparable by stagnation operations such as distillation operations in the manufacturing process, so these methods can be used to remove ε-caprolactone containing such impurities. There is a problem that can not be applied to the reaction mixture containing.

In recent years, in the preparation of percarboxylic acid used for the oxidation reaction of cyclohexanone, a boric acid catalyst which forms a small amount of by-product in the production of ε-caprolactone is used in place of a strong acid catalyst such as sulfuric acid, and the resulting percarboxylic acid Used for the preparation of solution [epsilon] -carboxylic acid.

In particular, Japanese Patent Laid-Open Nos. 150681/1982 and 124781/1983 have proposed methods for producing stable epsilon -caprolactone by oxidizing cyclohexanone with percarboxylic acid having 2-4 carbon atoms. This method uses carboxylic acid and hydrogen peroxide in the form of an initial percarboxylic acid solution obtained by reacting them in the presence of a boric acid catalyst, and also produces a stable ε-caprolactone solution while continuing to remove water under azeotropic conditions. That's how.

In this conventional method, a weak acid such as boric acid is used, so that less by-products are produced in the preparation of ε-caprolactone compared to when using a strong acid catalyst. However, this method is sufficiently satisfactory because a large amount of low boiling point components such as oxycaproic acid and high boiling point components such as 1,4-caprolactone, 5-hexenoic acid, ethyl propionoxycaproate and ethyl oxycaproate are still formed as by-products. It's unpleasant.

Therefore, in order to industrially produce ε-caprolactone by using percarboxylic acid and cyclohexanone, a manufacturing process that can substantially suppress the amount of by-products, which are undesirable products for purification, has been very necessary.

An object of the present invention is to provide an industrial production method capable of producing ε-caprolactone in high yield without forming by-products (impurities) that are difficult to be separated by purification such as distillation.

The present invention relates to a method for producing ε-caprolactone using a percarboxylic acid solution and cyclohexanone obtained by oxidizing an organic carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst. The present invention relates to a method for producing ε-caprolactone by supplying 1-1.5 mol of carboxylic acid, 0.012 mol or less of hydrogen peroxide, 0.04 mol or less of boric acid catalyst, and reacting the cyclohexanone with the percarboxylic acid in a reaction system.

In the following, important points of the present invention will be described in detail.

In the production process of the present invention, first, using the percarboxylic acid solution and cyclohexanone, it is fed into the oxidation reaction system of cyclohexanone as follows.

(a) The proportion of percarboxylic acid used is 1-1.5 moles, preferably about 1.05-1.4 moles, in particular about 1.1-1.3 moles per mole of said cyclohexanone.

(b) The proportion of hydrogen peroxide used is as low as 0.012 moles or less (preferably about 0.001-0.01 moles) per mole of cyclohexanone.

(c) The proportion of boric acid catalyst used is as low as 0.04 mol or less (preferably 0.001-0.03 mol, more preferably 0.0005-0.018 mol) per mol of the cyclohexanone.

By-products increase when the amount of percarboxylic acid used is less than 1 mole per mole of cyclohexanone or more than 1.5 moles. Moreover, by-products are also increased if the amount of hydrogen peroxide and boric acid catalyst used exceeds the above amount.

Cyclohexanone used in the preparation of the present invention is a compound which contains impurities or impurities that are difficult to separate in the purification of ε-caprolactone, preferably 95% (% by weight) or more, in particular 98% (weight). %) Is a high-purity compound corresponding to cyclohexanone.

In the production process of the present invention, in the oxidation reaction system of cyclohexanone, phosphate, phosphate ester, picolinic acid, dipicolinic acid, picolinic acid and picoline and rotidine can be used to prevent the decomposition loss of percarboxylic acid due to a small amount of metal. Small amounts of stabilizers, such as pyridine derivatives, are preferably contained.

The percarboxylic acid solution used in the preparation of the present invention is a percarboxylic acid solution such as peracetic acid, perpropionic acid and perbutyric acid obtained by oxidizing organic carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst.

The proportion of percarboxylic acid formed by oxidizing organic carboxylic acids such as acetic acid, propionic acid and butyric acid is 5-40% (% by weight), especially 10-30% (% by weight), and the proportion of hydrogen peroxide contained is Less than about 0,01 moles per mole of carboxylic acid, in particular about 0.001-0.008 moles, and the proportion of boric acid catalyst contained (calculated for orthoboric acid) is less than or equal to 0.03 moles per mole of said percarboxylic acid, in particular about 0.005-0.02 Small enough to drive Therefore, each component can be mixed at the above mixing ratio, and the mixture used in the oxidation reaction of cyclohexanone can be easily prepared.

In the above-mentioned percarboxylic acid solution, organic carboxylic acid contains 10-70% (weight ratio), particularly 20-65% (weight ratio), and furthermore, organic solvent is 5-60% (weight ratio), especially 10-55% ( Weight ratio).

The organic carboxylic acid is preferably aliphatic carboxylic acid, most preferably propionic acid, from which perpropionic acid suitable for use in the oxidation of cyclohexanone is obtained.

The organic solvent is a saturated aliphatic monohydric alcohol having 1-5 carbon atoms such as methanol, ethanol, 1-propanol, micro-propanol, 1-butanol, iso-butanol and 1-pentanol, acetic acid, propionic acid and butyric acid Said aliphatic carboxylic acid lower alkyl esters derived from the same aliphatic carboxylic acid, especially lower alcohols having 1-3 carbon atoms and propionic acid lower alkyl esters derived from propionic acid (eg ethyl propiotate).

Said boric acid catalyst is said orthoboric acid and metaboric acid.

The process for preparing the percarboxylic acid solution used in the production process of the present invention is the above industrial process for producing a percarboxylic acid solution having the composition, wherein the organic carboxylic acid such as propionic acid and hydrogen peroxide together with water to form a heterogeneous azeotropic mixture In organic solvents such as propionic acid lower alkyl esters that can form, in the presence of boric acid catalysts such as orthoboric acid and metaboric acid, water is reacted at temperatures of 30-100 ° C., in particular 50-80 ° C., and water introduced together with hydrogen peroxide during the course of the reaction. The water produced during the reaction is continuously removed by azeotropic distillation using an azeotropic distillation tube attached to a condenser and a decanter, thereby producing percarboxylic acid such as perpropionic acid.

As described above, percarboxylic acid solutions containing small amounts of hydrogen peroxide and boric acid that can be suitably used in the manufacturing process of the present invention can be easily obtained, and reaction mixtures containing perpropionic acid do not need to purify the percarboxylic acid solution. It can be used for the oxidation of cyclohexanone, which is the following procedure.

In the process of preparing the percarboxylic acid solution, the hydrogen peroxide is preferably supplied in the form of an aqueous solution containing 30-70% (% by weight) of hydrogen peroxide. The molar ratio of organic carboxylic acid to hydrogen peroxide used is not particularly limited, but in order to effectively react hydrogen peroxide, the molar ratio of organic carboxylic acid (organic carboxylic acid / hydrogen peroxide) to hydrogen peroxide initially used is preferably 1.4-6, in particular 1.5. -5. Furthermore, the amount of catalyst added is preferably 0.03 moles or less, in particular 0.005-0,02 moles per mole of hydrogen peroxide initially supplied into the reaction system.

In the preparation of the above percarboxylic acid solution, the amount of organic solvent, such as the carboxylic acid alkyl ester, used is by weight based on the total amount of water introduced during the reaction with water introduced with hydrogen peroxide for effective azeotropic distillation of water present in the reaction system. 0.3-15 times is preferable.

Furthermore, as mentioned above, for example, azeotropic distillation of the organic solvent and water with condensers and decanters, as mentioned above, may be used during the preparation of the percarboxylic acid solution. The azeotropic distillation in the tube and the distillate concentrated by the condenser are introduced into the decanter and separated by decantation into an organic phase and an aqueous phase. Only the organic phase is refluxed in an azeotropic distillation tube and azeotropic dehydration is continued until there is little separation into the aqueous phase.

In the process of preparing the percarboxylic acid solution, the reaction pressure may vary depending on the composition of the reaction system and the selected temperature, but preferably 10-300 mmHg reduced pressure.

In the production process of the present invention, ε-caprolactone is subjected to 1-8 hours at a reaction temperature of 30-80 ° C, particularly preferably 40-70 ° C, using a mixture for the oxidation reaction of cyclohexanone prepared as described above. It is preferable to effectively prepare ε-caprolactone by oxidizing cyclohexanone in a mixture with the above percarboxylic acid with a reaction time of 2-5 hours which is particularly preferred to form.

If the above reaction time is too long, it becomes a large factor of the reaction in which unwanted by-products are produced in the purification of ε-caprolactone, thereby causing a decrease in the yield of ε-caprolactone and an increase in the production of impurities.

In the production process of the present invention, epsilon -caprolactone can be prepared with excellent reproducibility and high yield. That is, it can be produced with a conversion rate of at least 97% based on the cyclohexanone used in the oxidation reaction, at least 99% selectivity based on the consumed cyclohexanone, and at least 99.5% selectivity based on the spent percarboxylic acid. Ε-caprolactone containing by-products (impurities) can be obtained.

The purification step of separating ε-caprolactone from the oxidation reaction mixture obtained by the production process of the present invention is conventionally performed using the initial ε-caprolactone solution (oxidation reaction mixture) obtained in the step of oxidizing the cyclohexanone. It may be carried out by a phosphorous distillation process.

The above distillation process is carried out by removing low boiling point components such as, for example, percarboxylic acid, carboxylic acid and carboxylic acid alkyl ester in the first distillation and distillation of [epsilon] -caprolactone by a second distillation tube. In order to reduce the losses caused by the decomposition of the peroxide and to prevent pyrolysis of ε-caprolactone, this procedure is preferably carried out under reduced pressure of about 1-100 mmHg. In the above distillation process, it is preferable that the distillation apparatus uses a device of a type suitable for distilling heat sensitive materials such as a thin layer evaporator and a falling film evaporator.

Therefore, since the oxidation reaction mixture obtained by the production process of the present invention contains a very small amount of by-products in the oxidation reaction, the oxidation reaction mixture is purified by the above distillation method under reduced pressure with almost no cause of decomposition by distillation, and thus high purity Ε-caprolactone can be easily obtained.

Furthermore, in the production process of the present invention, epsilon -caprolactone can be produced continuously or discontinuously.

The invention is explained in more detail in the following examples and comparative examples.

In each of the Examples and Comparative Examples, the concentrations of hydrogen peroxide and perpropionic acid were determined by cerium sulfate titration and thiosulfate titration, respectively, and the amounts of ε-caprolactone, propionic acid and ethyl propionate were quantified by gas chromatography. .

Example 1

ε-caprolactone is usually produced by the production flue chart shown in FIG.

[Production of Perpropionic Acid Solution]

In a 2-liter glass reactor 1 with distillation tube A with 20 sheets of Oldershaw plate and reflux condenser B with a settler.

The solution containing was filled from feed line 3.

Subsequently, the reactor 1 is immersed in an oil bath, heated to 100 ° C, and the solution is heated to the boiling point while refluxing and stirring under reduced pressure of 60 mmHg. Then 60% by weight of hydrogen peroxide is added over feed line 4 over 30 minutes until the total amount is 107.4 g. The temperature of reactor 1 is about 65 ° C., and the organic phase in which the heterogeneous azeotrope is concentrated is recycled from reflux condenser B having a precipitation framework. On the one hand, the concentrated aqueous phase is withdrawn continuously from discharge line 5 of reflux condenser B with a settler. The propionic acid and hydrogen peroxide are reacted until the aqueous phase is hardly separated by the reflux condenser B with the above settler, and then stops applying heat to the reactor 1 to complete the reaction. Thus, 686.7 g of perpropionic acid solution was prepared. The reaction requires 4 hours from the start of adding hydrogen peroxide.

The perpropionic acid solution obtained from the bottom of reactor 1 has the following composition (% by weight).

The conversion of hydrogen peroxide is 99.5% and the selectivity to perpropionic acid is 95.0%.

[Preparation of Initial ε-Caprolactone Solution]

Next, 650 g of percarboxylic acid solution (perpropionic acid: 1.70 mol) obtained as described above in a 1 liter glass reactor with a jacket attached to a heat transfer circulation tank (not shown) designed to control the temperature of the reflux condenser and reaction mixture. ) Was filled through feed line 6.

As a result, the perpropionic acid solution in Reactor 2 was heated to 50 ° C. with stirring, and a total amount of 138.7 g (1.414 mol) of cyclohexanone was added over feed line 7 over 30 minutes. While maintaining the temperature at 50 ° C., the mixture was allowed to react for 3 hours from the starting point of cyclohexanone, and then the mixture was cooled to room temperature to prepare 786.3 g of an initial ε-caprolactone solution.

The obtained initial epsilon -caprolactone solution has the following composition (weight%).

The conversion of cyclohexanone is 98.1% and the selectivity to ε-caprolactone is 99.8%. The conversion of propionic acid is 82.1%, and the senility to ε-caprolactone is 99.5%.

[Purification of Initial ε-Caprolactone Solution]

The initial ε-caprolactone solution was fed through feed line 8 at a rate of 260 g / hour in distillation tube C, attached to a thin layer evaporator such as reboiler 9 (filler height: 495 mm) and operated under a pressure of 10 mm Hg. Filled in succession.

The low boiling point component was discharged at a rate of 207.1 g / hour through reflux line 10 of distillation tube C at a reflux rate of 0.25, and the concentrated initial ε-caprolactone was discharged at a rate of 52.9 g / hour. Drained from the bottom.

Furthermore, in distillation tube D operated under a pressure of 10 mmHg and attached to a thin layer evaporator (with 10 sheets of Aldershow plate) such as reboiler 12, the initial ε-caprolactone was continuously supplied at a rate of 75 g / hour. Filled through line 11.

In distillation tube D, epsilon -caprolactone was continuously withdrawn at discharge line 13 at a rate of 72.0 g / hour while refluxing at a reflux rate of 0.2. The high boiling point component was then discharged through the discharge line 14 at the bottom of the reboiler 12.

The purity of the epsilon caprolactone obtained by such an operation was 99,9%, which was a satisfactory purity of the product. (Total amount of low boiling point components such as δ-valerolactone and oxycaproic acid: 0.04% or less (wt%), total amount of high boiling point components such as 5-hexenoic acid, ethylpropionoxycaproate and ethyl oxycaproate: 0.05 %Below)

Example 2 (Comparative Example 1)

670.4 g of perpropionic acid was prepared in the same manner as in Example 1 except that the amount of orthoboric acid used was changed from 1.6 g to 6.4 g. The reaction time required 2.5 hours from the point where hydrogen peroxide was added.

The obtained perpropionic acid solution has the following composition (weight%).

The hydrogen peroxide conversion was 99.0% and the selectivity to perpropionic acid was 96.0%.

Next, except that 632.8 g of percarboxylic acid solution (perpropionic acid: 1.70 mole) and 139.0 g (1.417 mole) of cyclohexanone obtained with the initial epsilon -caprolactone solution were prepared in the same manner as in Example 1. 767.1 g of the resultant initial epsilon -caprolactone solution was prepared without additives, and had the following composition (% by weight).

The conversion of cyclohexanone is 98.0% and the selectivity to ε-caprolactone is 94.6%. The conversion of perpropionic acid is 81.8% and the selectivity to ε-caprolactone is 94.2%.

Furthermore, this initial epsilon -caprolactone was refine | purified by the method similar to Example 1, and it obtained epsilon -caprolactone.

The purity of ε-caprolactone was 99.6% (% by weight), which was not a satisfactory product. (Low boiling point component: about 0.08% (wt%), high boiling point component: 0.25% (wt%))

Example 3 (Comparative Example 2)

680.1 g of perpropionic acid solution was prepared in the same manner as in Example 1, except that the reaction time was changed to 3 hours and 15 minutes in the preparation of perpropionic acid solution. At the time of finishing the said reaction, the aqueous phase was separated lightly through the discharge line 5 in the reflux condenser B with a settler.

Perpropionic acid obtained from the bottom of reactor 1. The solution has the following composition (% by weight).

The conversion of hydrogen peroxide is 95.5% and the selectivity for perpropionic acid is 95.3%.

Next, an initial ε-caprolactone solution was prepared in the same manner as in Example 1, except that 651.9 g of the percarboxylic acid solution (perpropionic acid: 1.65 mol) and 134.9 g (1.375 mol) of cyclohexanone were used. . The resulting initial ε-caprolactone solution weighs 783.3 g and has the following composition (% by weight).

The conversion of cyclohexanone is 99,0% and the selectivity to ε-caprolactone is 95.3%. The perpropionic acid conversion is 76.3%.

Furthermore, this initial (epsilon) -caprolactone solution was refine | purified by the method similar to Example 1, and caprolactone was obtained. The purity of the epsilon caprolactone was 99.2%, which was not a satisfactory product (low boiling point component: 0.35% (wt%), high boiling point component: 0.35 (wt%)).

As described above, the manufacturing process of the present invention is an excellent industrial process for producing ε-caprolactone in high yield while suppressing the formation of by-products (impurities) that are problematic for purification, and is mixed based on cyclohexanone. The reaction mixture is prepared by mixing the cyclohexanone and percarboxylic acid solution by limiting the ratio of percarboxylic acid within a specific range, controlling the ratio of hydrogen peroxide and the ratio of mixed boric acid catalyst based on cyclohexanone to be smaller. The cyclohexanone and the percarboxylic acid can be reacted within, and ε-caprolactone having a purity of at least 99.8% can be easily obtained from the resulting oxidation reaction mixture.

Claims (18)

A process for preparing ε-caprolactone using a percarboxylic acid solution and cyclohexanone obtained by oxidizing an organic carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst, wherein 1-1.5 mole per mole of cyclohexanone is added in the reaction system. A method for producing ε-caprolactone by supplying carboxylic acid, 0.012 mol or less hydrogen peroxide and 0.04 mol or less boric acid catalyst to react the cyclohexanone with the percarboxylic acid. The method according to claim 1, wherein the amount of percarboxylic acid used is about 1.05-1.4 mol per mole of cyclohexanone. 3. A process according to claim 2 wherein the amount of said pecarboxylic acid is about 1.1-1.3 moles per mole of said cyclohexanone. The production method according to claim 1, wherein the amount of hydrogen peroxide used is 0.001-0.01 mol per mol of cyclohexanone. The production method according to claim 1, wherein the amount of said boric acid catalyst used is 0.001-0.03 mol per mol of said cyclohexanone. The manufacturing method of Claim 5 whose usage-amount of said boric acid catalyst is 0.005-0.018 mol per mol of said cyclohexanone. The process of claim 1 wherein the reaction temperature is in the range of 30-80 ° C. 3. The process of claim 7 wherein the reaction temperature is in the range of 40-70 ° C. 9. The process according to claim 1, wherein the reaction time is in the range of 1-8 hours. The method of claim 9, wherein the reaction time is in the range of 2-5 hours. The method of claim 1 wherein the reaction pressure is in the range of 1-100 mm Hg. The method according to claim 1, wherein the percarboxylic acid is perpropionic acid. The production method according to claim 1, wherein the percarboxylic acid further contains an organic solvent. The process according to claim 13, wherein said organic solvent is a lower alkyl ester of aliphatic carboxylic acid. 15. The process of claim 14 wherein said organic solvent is a lower alkyl ester of propionic acid. The process according to claim 15, wherein said organic solvent is methyl propionate. The production method according to claim 1, wherein the reaction further contains a stabilizer. 18. The method of claim 17, wherein said stabilizer is at least one compound selected from the group of phosphates, phosphate esters, picolinic acid, dipicolinic acid, picoline and lutidine.