JPH05271143A - Production of cyclohexanone - Google Patents

Abstract

PURPOSE:To obtain cyclohexanone by subjecting an oxidation-reactional mixture containing cyclohexanol and cyclohexanone obtained by oxidation of cyclohexane to a specific alkali treatment to remove hexahydrobenzaldehyde and distillation. CONSTITUTION:An oxidation reactional mixture containing cyclohexanol and cyclohexanone obtained by oxidation of cyclohexane is mixed with an aqueous solution of an alkali to carry out the primary alkali treatment. Then the mixture is divided into an oil phase and a water phase. Preferably, unreacted cyclohexane is distilled from the oil phase. 20-5000ppm alkali is added to the oil phase when the unreacted cyclohexane is not subjected to separation by distillation and 10-2000ppm alkali compound is added to the oil phase when subjected to separation by distillation and the oil phase is subjected to the secondary alkali treatment at 60-150 deg.C. Finally, cyclohexanone is subjected to separation by distillation from the oil phase subjected to secondary alkali treatment. Thereby, high-quality cyclohexanone from which hexahydrobenzaldehyde of one of impurities is removed is obtained. This compound is useful as a producing raw material of high-quality caprolactam.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for treating an oxidation reaction mixture containing cyclohexanol and cyclohexanone obtained by oxidation of cyclohexane.

[0002]

It is known to prepare cyclohexane with molecular oxygen in the presence of a boric acid compound or a cobalt catalyst, etc., to produce a mixture containing cyclohexanol and cyclohexanone. In this method, many by-products are produced in addition to the desired product. Examples of the by-products include carboxylic acids, alcohols, aldehydes, ketones, ethers, esters and hydrocarbons.
Of these, water-soluble carboxylic acids, lower alcohols and the like can be removed by water extraction, and carboxylic acids and esters can also be saponified and removed in an alkaline aqueous solution. And most of the remaining by-products can be removed by the distillation process.

Further, cyclohexanone (boiling point: 156.5 ° C.) and cyclohexanol (boiling point: 161.0 ° C.), which are difficult to separate even in the above steps, and components very close to the boiling point, for example, butylcyclohexyl ether, n-pentylcyclohexane. It is possible to remove most of cyclohexyl acetate, hexahydrobenzaldehyde, etc. by adopting a specific distillation step (Japanese Patent Application No. 2-91639).

[0004]

However, it is difficult to completely remove impurities having a boiling point close to that of cyclohexanone or cyclohexanol even by the method of Japanese Patent Application No. 2-91639 described above, and a very small amount is contained in the product of cyclohexanone. The inclusion of impurities was unavoidable.

[0005]

Cyclohexanone is industrially general as a raw material for producing caprolactam. That is, after reacting cyclohexanone with hydroxylamine to convert into cyclohexanone oxime,
Caprolactam is produced through the Beckmann rearrangement reaction.

The present inventors have conducted many years of research on the production process from cyclohexane to caprolactam, but hexahydrobenzaldehyde, which is one of the trace impurities in cyclohexanone, remains in the subsequent reaction process, It was found that hexahedrobenzamide was formed at the time of Beckmann rearrangement, and the compound was one of the factors that deteriorate the quality of the product caprolactam. Specifically, the amount of volatile base in the product caprolactam (VB
It has been confirmed that the amount) is increased by the remaining hexahydrobenzamide and affects the appearance, strength, etc. of the fiber product made from caprolactam. Therefore, as a result of extensive studies on means for sufficiently removing hexahydrobenzaldehyde in cyclohexanone, it was found that hexahydrobenzaldehyde in a reaction mixture containing cyclohexanol and cyclohexane can be removed by a specific alkali treatment, and the present invention was reached. ..

That is, the first invention of the present application is a step of mixing an oxidation reaction mixture containing cyclohexanol and cyclohexanone obtained by the oxidation of cyclohexanone with an alkaline aqueous solution and subjecting the mixture to a primary alkali treatment, and a mixture treated with the primary alkali. A step of separating into an oil phase and an aqueous phase, a step of adding an alkali compound of 20 to 5000 ppm to the oil phase and subjecting the oil phase to a secondary alkali treatment at a temperature of 60 to 150 ° C., a secondary alkali treatment A step of distilling and separating cyclohexanone from the obtained oil phase, and a method for producing cyclohexanone, characterized in that each step is treated.

The second invention of the present application is a step of mixing an oxidation reaction mixture containing cyclohexanol and cyclohexanone obtained by the oxidation of cyclohexane with an alkaline aqueous solution and subjecting the mixture to a primary alkali treatment, and a mixture treated with a primary alkali. To separate the oil phase and the aqueous phase, the step of separating the unreacted cyclohexane contained in the oil phase from the oil phase by distillation, the remaining oil phase separated cyclohexane to the oil phase 10-2000ppm of alkaline compound is added,
And a step of performing secondary alkali treatment at a temperature of 60 to 150 ° C., and a step of distilling and separating cyclohexanone from the oil phase subjected to the secondary alkali treatment.

The present invention will be described in detail below. The oxidation reaction mixture containing cyclohexanol and cyclohexanone in the present invention is a mixture obtained by liquid phase oxidation of cyclohexane with molecular oxygen.
When the oxidation reaction is carried out in the presence of a boric acid compound,
It is a mixture obtained by hydrolyzing the mixture after the completion of the oxidation reaction and then separating the aqueous phase containing the boric acid compound. The main components of this mixture are unreacted cyclohexane, the target products cyclohexanol and cyclohexanone, and by-products such as esters and carboxylic acids. The content ratio of these is usually 85 to 95% by weight of unreacted cyclohexane, 4 to 13% by weight of the target product, and 1 to 2% by weight of by-products.

In the first invention, as the first step, the oxidation reaction mixture containing cyclohexanol and cyclohexanone is mixed with an alkaline aqueous solution to carry out a primary alkaline treatment. By this step, impurities such as esters in the oxidation reaction mixture are saponified, and carboxylic acids and alkali salts are extracted and removed into an aqueous phase.

The alkali compound used in the alkaline aqueous solution is usually a caustic alkali such as caustic soda and potassium hydroxide, but an alkali carbonate such as sodium carbonate and potassium carbonate may be used in combination. It is also possible to carry out a multi-step treatment in which the first step is a treatment with an alkali carbonate aqueous solution and the second step is a treatment with a caustic alkaline aqueous solution. The alkali concentration in the aqueous alkali solution is usually 0.1 to 40% by weight,
It is preferably 1 to 30% by weight. The amount of the caustic aqueous solution used is usually 0.5 to 10 of the ester component in the oil phase.
It is selected in the range of a weight amount, preferably 1 to 5 weight amounts. The conditions of the primary alkali treatment are usually 50 to 95 ° C., preferably 70 to 90 ° C., and usually 0.1.
~ 2 hours, preferably 0.2-0.5 hours. When the treatment temperature is low, the saponification reaction becomes slow, and when the treatment temperature is high, a part of the target product, cyclohexanone, is lost due to the condensation reaction. It is desirable to select the conditions.

In the second step of the first invention, the mixture treated with the primary alkali is separated into an oil phase and an aqueous phase. Since the alkaline component remains on the aqueous phase side and a small amount of the oil phase component is mixed in, the aqueous phase can be reused for the primary alkaline treatment in the first step. Further, since some water-soluble impurities remain on the oil phase side as well, it is preferable to completely remove the water-soluble impurities by further mixing and washing the oil phase with pure water for liquid separation.

When such water washing is carried out, the alkali concentration of the oil phase after liquid separation usually remains at only a few ppm or less. In the third step of the first invention, in the oil phase separated in the second step,
An alkaline compound of 20 to 5000 ppm is added to the oil phase, and a secondary alkaline treatment is performed at a temperature of 60 to 150 ° C. By the secondary alkali treatment, hexahydrobenzaldehyde, which is a by-product that could not be sufficiently removed by the primary alkali treatment, is decomposed by a condensation reaction or the like, and as a result, hexahydrobenzaldehyde in cyclohexanone can be almost completely removed. ..

As the method of the secondary alkali treatment, the same alkali compound as that used in the primary alkali treatment, as it is or in the form of a solution, is added to the oil phase and 20 times to the oil phase.
~ 5000 ppm, preferably 100-2000 ppm
At a concentration of 60 to 150 ° C., preferably 100 to
At 130 ° C, usually 0.2 to 4 hours, preferably 0.5 to
Heat treatment for 3 hours. If the temperature of the heat treatment or the alkali concentration is higher than the above range, the decrease in the yield due to the condensation reaction of cyclohexanone becomes a problem. On the other hand, if they are lower than the range, the progress of the decomposition of hexahydrobenzaldehyde becomes slow, which is preferable. Absent.

The above-mentioned secondary alkali treatment may be carried out while distilling and separating unreacted cyclohexane contained in the oil phase. Specifically, the oil phase was introduced into the bottom of the distillation column, a predetermined amount of alkali compound was added, and the bottom temperature was adjusted to 60
Set the condition in the range of ~ 150 ℃, cyclohexanone,
Cyclohexane having a lower boiling point and by-products having a lower boiling point may be distilled off from cyclohexanol. When such a method is adopted, the total amount of the alkali compounds to be added is an amount corresponding to 20 to 2000 ppm with respect to the oil phase before distillation. May be added in.

In the fourth step of the first invention, cyclohexanone is separated and recovered by distillation by a known method. As a known distillation method, components such as unreacted cyclohexane having a lower boiling point than cyclohexanone are distilled off in the first distillation column, while the bottom liquid is supplied to the second distillation column for distillation. A general method is to distill out most of cyclohexanone in the second distillation column and separate and recover it. The bottom liquid of the second distillation column is supplied to the third distillation column and further distilled to distill cyclohexanol and the remaining cyclohexanone, and cyclohexanol in the distillate is dehydrogenated to give cyclohexanone. And can be circulated to the first distillation column.

The above operating conditions of the distillation column are all such that the column top pressure is 20 to 500 Torr, preferably the first and the second.
The pressure is sequentially reduced in the second and third order. The column top temperature is usually controlled in the range of 50 to 150 ° C. according to the column top pressure. Further, as described above, when the method of performing the secondary alkali treatment of the fourth step while distilling off cyclohexane by distillation is performed, the separation of cyclohexane in the first distillation column described above in the fourth step is omitted. Will be.

Next, the second invention will be described. The first step and the second step of the second invention are common to the first invention. In the second invention, in the third step, unreacted cyclohexane contained in the oil phase is separated by distillation under the same conditions as the above-mentioned distillation conditions for separating cyclohexane. In the fourth step, the remaining oil phase from which cyclohexane has been separated is added to the oil phase in an amount of 10 to 2000 ppm, preferably 50
〜1000ppm of alkaline compound is added, 60〜1
At a temperature of 50 ° C, preferably 100-130 ° C, usually
Secondary alkali treatment is performed for 0.2 to 4 hours, preferably 0.5 to 3 hours. Then, as a fifth step, the cyclohexanone is recovered from the secondary alkali-treated oil phase by distillation under the same conditions as the above-mentioned distillation conditions for separating cyclohexanone.

[0019]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the description of the examples as long as the gist thereof is not exceeded. Example 1 Cyclohexane was subjected to liquid-phase oxidation with molecular oxygen in the presence of boric acid, and then hydrolyzed to separate an aqueous phase, and the following composition was obtained (determined by gas chromatography).

[0020]

[Table 1] 100 parts / hr of the oxidation reaction mixture of 10 parts by weight of a 10 wt% sodium carbonate aqueous solution are mixed and continuously mixed with stirring at a temperature of 85 ° C. for an average residence time of 20 minutes,
Then, the mixture after the treatment was separated by allowing it to separate into an oil phase and an aqueous phase. When the oil phase components recovered here were analyzed, they had the following composition.

[0021]

[Table 2]

After adding 200 ppm of caustic soda to the oil phase, it was supplied to the first distillation column to distill off cyclohexane (first distillation column conditions: column bottom temperature 120 ° C., column top temperature 60.
C, tower top pressure 400 Torr). At this time, the amount of hexahydrobenzaldehyde in the bottom liquid after distillation was 1 ppm.
It was below (below the detection limit). Then, the bottom liquid of the second
It was supplied to a distillation column, and purified cyclohexanone was distilled off and recovered from the top of the column. (Conditions for the second distillation column: bottom temperature 110 ° C.,
Tower top temperature 70 ° C., tower top pressure 50 Torr).

Comparative Example 1 Example 1 except that no caustic soda was added in Example 1.
It carried out similarly to. 90 ppm of hexahydrobenzaldehyde was contained in the recovered cyclohexanone.

Reference Example Cyclohexanone obtained from Example 1 and Comparative Example 1 was reacted with hydroxylamine sulfate by a conventional method to convert into cyclohexanone oxime, which was then catalytically reacted with sulfuric acid to produce caprolactam by Beckmann rearrangement reaction. .. The amount of volatile base (VB amount) in the obtained caprolactam product was 5 ppm when the cyclohexanone of Example 1 was used, and 15 ppm when the cyclohexanone of Comparative Example 1 was used. The amount of VB was quantified by the titration method.

Comparative Example 1, Examples 2 to 4 The saponified oil phase of Example 1 was distilled under the conditions of the first distillation column of Example 1 to distill off cyclohexane.
The amount of caustic soda shown in Table 1 was added to the bottom liquid after distillation, and the mixture was kept at 120 ° C. for 2 hours under normal pressure and stirring. The results of measuring the amount of hexahydrobenzaldehyde in each liquid at this time are shown in Table 1. Further, the liquid was further distilled under the conditions of the second distillation column of Example 1,
It was confirmed that most of hexahydrobenzaldehyde was distilled together with cyclohexanone.

[0026]

[Table 3]

[0027]

According to the method of the present invention, high-quality cyclohexanone containing a small amount of hexahydrobenzaldehyde, which is one of the impurities, can be obtained. The cyclohexanone is suitable as a raw material for producing high quality caprolactam.

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[Procedure amendment]

[Submission date] May 7, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The present inventors have conducted many years of research on the production process from cyclohexane to caprolactam, but hexahydrobenzaldehyde, which is one of the trace impurities in cyclohexanone, remains in the subsequent reaction process, It was found that hexahydrobenzamide was formed at the time of Beckmann rearrangement, and the compound was one of the factors that deteriorate the quality of the product caprolactam. Specifically, the amount of volatile base in the product caprolactam (VB
It has been confirmed that the amount) increases due to the remaining hexahydrobenzamide and affects the appearance, strength and the like of the fiber product made from caprolactam. Therefore, as a result of intensive studies on means for sufficiently removing hexahydrobenzaldehyde in cyclohexanone, it was found that hexahydrobenzaldehyde in a reaction mixture containing cyclohexanol and cyclohexane can be removed by a specific alkali treatment, and the present invention was reached. .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020]

[Table 1] 100 parts / hr of the oxidation reaction mixture of Example 1 was mixed with 20 parts / hr of a 1.5 wt% aqueous sodium hydroxide solution, and the mixture was stirred at 85 ° C.
A mixing treatment was continuously performed at the temperature of 20 ° C. for an average residence time of 20 minutes, and then the mixture after the treatment was allowed to stand and separate to separate into an oil phase and an aqueous phase. When the oil phase components recovered here were analyzed, they had the following composition.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location // C07C 27/12 310 8827-4H (72) Inventor Yu Kanda 1-1 Kurosaki Shiroishi, Hachiman Nishi-ku, Kitakyushu, Fukuoka No. Mitsubishi Kasei Kurosaki Factory

Claims (3)

[Claims] 1. A step of mixing an oxidation reaction mixture containing cyclohexanol and cyclohexanone obtained by the oxidation of cyclohexane with an alkaline aqueous solution and subjecting the mixture to a primary alkali treatment, and the mixture treated with the primary alkali into an oil phase and an aqueous phase. A step of separating the liquid phase into the oil phase, a step of adding 20 to 5000 ppm of an alkali compound to the oil phase, and a second alkali treatment at a temperature of 60 to 150 ° C., a cyclohexanone from the oil phase subjected to the second alkali treatment A process for producing cyclohexanone, characterized in that the process is carried out in each step of: 2. The production method according to claim 1, wherein the secondary alkali treatment of is carried out while distilling and separating unreacted cyclohexane contained in the oil phase. 3. A step of mixing an oxidation reaction mixture containing cyclohexanol and cyclohexanone obtained by the oxidation of cyclohexane with an alkaline aqueous solution and subjecting the mixture to a primary alkali treatment, and the mixture treated with the primary alkali to an oil phase and an aqueous phase. And a step of separating into unreacted cyclohexane contained in the oil phase from the oil phase, a step of distilling and separating unreacted cyclohexane contained in the oil phase, and 10 to 2000 ppm of an alkali compound with respect to the oil phase. And add
A method for producing cyclohexanone, which comprises performing a secondary alkali treatment at a temperature of 60 to 150 ° C., a step of distilling and separating cyclohexanone from the oil phase subjected to the secondary alkali treatment, and a step of performing each treatment.