JP4595804B2 - Method for producing cyclohexanone oxime - Google Patents

Description

  The present invention relates to a method for producing cyclohexanone oxime. Cyclohexanone oxime is useful as a raw material for ε-caprolactam and as a raw material for nylon 6.

  As one method for producing cyclohexanone oxime, a method is known in which cyclohexanone is ammoximation-treated with hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst (see, for example, Patent Documents 1 to 3). With respect to a method for recovering cyclohexanone oxime from the reaction solution obtained by the ammoximation reaction, for example, Patent Document 1 discloses that the ammoximation reaction is performed using water as a reaction solvent, and toluene is removed from the reaction solution after catalyst filtration. Discloses a method for extracting cyclohexanone oxime. In Patent Document 3, the above-mentioned ammoximation reaction is performed using a mixed solvent of t-butyl alcohol and water as a reaction solvent, and the reaction liquid after catalyst separation is distilled to remove unreacted ammonia and water-containing t-butyl. A method is disclosed in which after the alcohol is distilled off, cyclohexanone oxime is extracted from the bottoms with toluene, and then the extract is distilled to distill off the toluene, and cyclohexanone oxime is recovered as bottoms.

JP-A-62-59256 JP-A-6-49015 Japanese Patent Laid-Open No. 6-92922

  However, in the above conventional method, the thermal stability of the recovered cyclohexanone oxime is not necessarily sufficient.For example, when stored or transported in a heated and melted state, it is vaporized for further distillation purification or vapor phase Beckmann rearrangement reaction. In some cases, problems such as the occurrence of tar content, and yield and quality degradation may occur.

  Therefore, the present inventors conducted extensive research for the purpose of developing a method capable of advantageously recovering cyclohexanone oxime having excellent thermal stability in the above method for producing cyclohexanone oxime by an ammoximation reaction. After carrying out the reaction, the reaction solution was subjected to a series of steps consisting of predetermined distillation, extraction and washing, and it was found that the above object could be achieved and the present invention was completed.

That is, the present invention includes the following steps (1) to (6),
(1) Reaction step: a step of reacting cyclohexanone, hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst to obtain a reaction solution containing cyclohexanone oxime, water, unreacted ammonia and unreacted cyclohexanone,
(2) First distillation step: A step of distilling the reaction liquid obtained in step (1) to distill ammonia to obtain a bottom liquid containing cyclohexanone oxime, water, and cyclohexanone.
(3) Extraction step: a step of separating the bottoms obtained in step (2) with an organic solvent, and then separating the organic layer and the aqueous layer;
(4) Washing step: a step of mixing the organic layer obtained in step (3) with water and then separating it into an organic layer and an aqueous layer;
(5) Second distillation step: a step of distilling the organic layer obtained in step (4) to distill an organic solvent and water to obtain a bottoms containing cyclohexanone oxime and cyclohexanone,
(6) Third distillation step: a step of distilling the bottoms obtained in step (5) to distill cyclohexanone to obtain bottoms containing cyclohexanone oxime,
The manufacturing method of the cyclohexanone oxime comprised from these is provided.

  In this production method, it is desirable to recycle the ammonia distilled in the first distillation step (2) as the ammonia used in the reaction step (1). The organic solvent distilled in the second distillation step (5) is desirably recycled as the organic solvent used in the extraction step (3), and the water distilled in the second distillation step (5) It is desirable to recycle as water used in the washing step (4). Furthermore, it is desirable to recycle the cyclohexanone distilled in the third distillation step (6) as the cyclohexanone used in the reaction step (1).

  In addition, the washing step (4) comprises mixing the organic layer obtained in the extraction step (3) with an aqueous solution containing a base, and then separating the organic layer and the aqueous layer into a first washing step (4a), It is desirable that the organic layer obtained in the first washing step (4a) is composed of a second washing step (4b) in which the organic layer is mixed with water substantially free of a base and then separated into an organic layer and an aqueous layer. . At this time, as the aqueous solution containing the base used in the first washing step (4a), a mixture of the aqueous layer obtained in the second washing step (4b) with the base can be recycled, As water substantially free of the base used in the washing step (4b), the water distilled in the second distillation step (5) can be recycled.

  According to the present invention, cyclohexanone oxime having excellent thermal stability can be advantageously produced.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The process for producing cyclohexanone oxime according to the present invention comprises a reaction step (1) in which cyclohexanone is ammoximation-reacted with hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst; First distillation step (2) for obtaining a cyclohexanone oxime / water mixture, an extraction step (3) for extracting cyclohexanone oxime from a cyclohexanone oxime / water mixture with an organic solvent, and a washing step for washing the cyclohexanone oxime extract with water (4) ), Distilling the organic solvent from the washed cyclohexanone oxime extract to obtain a crude cyclohexanone oxime as a bottom liquid (5), and distilling off residual cyclohexanone from the crude cyclohexanone oxime to a bottom liquid. As purified cyclohexanone oxime It is those composed of a series of steps in the third distillation step to obtain (6). Here, all of these steps may be performed continuously, a part may be performed continuously, a part may be performed batchwise, or all may be performed batchwise, From the viewpoint of the productivity of cyclohexanone oxime and the thermal stability or quality of the obtained cyclohexanone oxime, it is preferable to carry out all of them continuously.

  FIG. 1 is a flowchart schematically showing an example of a continuous production process of cyclohexanone oxime according to the present invention. That is, first, a predetermined amount of the reaction liquid in which the catalyst is dispersed is retained in the reactor 1, and cyclohexanone 11, hydrogen peroxide 12, ammonia 13 and, if necessary, a solvent and the like are supplied to the reaction liquid, while approximately the same amount as these raw materials. The ammoximation reaction is performed by extracting the reaction solution 14 [reaction step (1)]. Here, in extracting the reaction solution 14, it is preferable to extract only the liquid phase through a filter or the like so that the catalyst stays in the reactor 1. When extracting the catalyst together, a step of separating the catalyst from the extracted reaction solution 14 is required, and supply of the catalyst to the reactor 1 is also required. The catalyst concentration is usually 1 to 200 g / L as the weight per volume of the reaction solution (catalyst + liquid phase), although depending on the activity and reaction conditions. Further, as the reactor 1, it is preferable to use a glass-lined one or a stainless steel one from the viewpoint of preventing the decomposition of hydrogen peroxide.

  The usage-amount of hydrogen peroxide is 0.5-3 mol times normally with respect to cyclohexanone, Preferably it is 0.5-1.5 mol times. Moreover, the usage-amount of ammonia is 1 mol times or more normally with respect to cyclohexanone, Preferably it is 1.5 mol times or more. Here, ammonia is used in excess of cyclohexanone and hydrogen peroxide so as to remain in the reaction solution, thereby increasing the conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime.

  Preferable examples of the reaction solvent that can be used include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, s-butyl alcohol, t-butyl alcohol, and t-amyl alcohol. Water or a mixed solvent thereof can be used.

  The reaction temperature is usually 50 to 120 ° C, preferably 70 to 100 ° C. The reaction is preferably carried out under pressure in order to increase the solubility of ammonia in the reaction solution.

The reaction solution 14 thus obtained contains, in theory, the product cyclohexanone oxime as well as water produced twice as much as cyclohexanone (C ₆ H ₁₀ O + NH ₃ + H ₂ O ₂ → C ₆ H ₁₀ NOH + 2H ₂ O). Moreover, since about 10 to 70 weight% of aqueous solution is normally used as hydrogen peroxide, the water for that amount is also included. Furthermore, unreacted ammonia is contained by using ammonia excessively as described above. Further, since it is difficult to completely react cyclohexanone, unreacted cyclohexanone is also included.

  Therefore, next, the reaction liquid 14 containing cyclohexanone oxime, water, ammonia and cyclohexanone is introduced into the first distillation column 2 and distilled to recover ammonia as a fraction 15 and cyclohexanone oxime as a bottoms 16. To obtain a mixture of water and cyclohexanone [first distillation step (2)]. This distillation is usually carried out at normal pressure, but may be carried out under pressure or under reduced pressure if necessary.

  The ammonia recovered as the fraction 15 is preferably recycled to the reactor 1. When an organic solvent is used in the reaction step (1), that is, when an organic solvent is supplied to the reactor 1, the organic solvent is contained in the reaction liquid 14 and introduced into the first distillation column 2. This is also preferably recovered as a fraction 15 and recycled to the reactor 1. In order to recycle the organic solvent to the reactor 1, the organic solvent used in the reaction step (1) needs to have a lower boiling point than that of cyclohexanone oxime. Depending on the type of organic solvent, water is entrained and distilled due to its azeotropic composition and the like, and this water may be recycled to the reactor 1 together. For example, if t-butyl alcohol is distilled in a state containing about 12 to 18% by weight of water, the water-containing t-butyl alcohol may be recycled to the reactor 1. In addition, ammonia is usually recycled to the reactor 1 using a compressor in a gas state, but cooled to a low temperature under pressure, dissolved in an organic solvent or a water-containing organic solvent, and recycled to the reactor 1 as a solution. May be.

  The bottoms 16 extracted from the first distillation column 2 is introduced into the extractor 3, mixed with the organic solvent 17, and then the organic layer 18 obtained by extracting cyclohexanone oxime and cyclohexanone in the bottoms 16 with the organic solvent. And the aqueous layer 19 that is the extraction residual liquid [extraction step (3)]. The organic solvent 17 for extraction needs to be able to be separated from water, have a cyclohexanone oxime solubility, and have a lower boiling point than that of cyclohexanone oxime. Preferred examples thereof include aromatic hydrocarbon solvents such as toluene, alicyclic hydrocarbon solvents such as cyclohexane, aliphatic hydrocarbon solvents such as hexane and heptane, diisopropyl ether and t-butylmethyl. Examples include ethers such as ethers and esters such as ethyl acetate, among which hydrocarbon solvents such as toluene, cyclohexane and heptane are preferable, and aromatic hydrocarbon solvents such as toluene are particularly preferable. The usage-amount of the organic solvent 17 is 0.1-2 weight times normally with respect to the cyclohexanone oxime in the bottoms 16, and preferably 0.3-1 weight times. The extraction temperature is usually selected in the range from room temperature to the boiling point of the organic solvent 17, and is preferably 40 to 90 ° C. In addition, as the extractor 3, a multi-stage extractable one may be used, or a so-called mixer-settler type in which a mixing part and a liquid separation part are separated may be used in one stage or multiple stages.

  The organic layer 18 from the extractor 3 is introduced into the cleaning device 4, mixed with water 20, and then an organic layer 21 obtained by removing impurities from the organic layer 18 by washing with water, and an aqueous layer formed by dissolving these impurities in water. [Washing step (4)]. Examples of the impurities include ammonium nitrate and ammonium nitrite that can be by-produced in the reaction step (1). The amount of water 20 used for washing is usually 0.05 to 1 times the weight of cyclohexanone oxime in the organic layer 18, and the washing temperature is usually 40 to 90 ° C. In addition, as the washer 4, one that can perform multi-stage extraction may be used as in the case of the extractor 3, or a so-called mixer-settler type with a mixing part and a liquid separation part separated may be used in one stage or multiple stages. Also good.

  By introducing the organic layer 21 from the cleaning device 4 into the second distillation column 5 and distilling it, the organic solvent in the organic layer 21 can be recovered as a fraction 23, and as a bottoms 24, A crude cyclohexanone oxime containing the unreacted cyclohexanone can be obtained [second distillation step (5)]. At that time, water contained in a dissolved or dispersed state in the organic layer 21 is recovered as a fraction 23 together with the organic solvent. This distillation is usually carried out at normal pressure to slightly reduced pressure depending on the boiling point of the organic solvent.

  The organic solvent and water recovered as the fraction 23 are desirably recycled as the extraction organic solvent 17 introduced into the extractor 3 and the washing water 20 introduced into the washer 4, respectively. Specifically, the organic solvent and water recovered as the fraction 23 are introduced into the separator 7 and separated into the organic layer 17 and the aqueous layer 20, and the organic layer 17 is introduced into the extractor 3. What is necessary is just to introduce the water layer 20 into the cleaning device 4.

  By introducing the crude cyclohexanone oxime extracted as the bottoms 24 of the second distillation column 5 into the third distillation column 6 and distilling it, the cyclohexanone can be recovered as the fraction 25 and the bottoms 26, a purified cyclohexanone oxime from which cyclohexanone is removed or reduced can be obtained [third distillation step (6)]. This distillation is usually performed at a temperature of 140 ° C. or lower under a reduced pressure of 10 kPa or lower. The purified cyclohexanone oxime thus obtained is excellent in thermal stability and can be suitably used as a raw material for gas phase Beckmann rearrangement. From the viewpoint of suppressing side reactions in the gas phase Beckmann rearrangement, it is preferable to adjust the distillation conditions so that the concentration of cyclohexanone in the purified cyclohexanone oxime is 1% by weight or less, preferably 0.5% by weight or less.

  The cyclohexanone recovered as the fraction 25 is preferably recycled to the reactor 1. In addition, if accumulation of impurities in the fraction 25 becomes remarkable due to long-term operation or the like, at least a part may be purified by rectification or the like.

  In order to further enhance the thermal stability of the purified cyclohexanone oxime obtained by the above process, the washing step (4) is devised. Specifically, the washing step (4) is changed to the first washing step with an aqueous solution containing a base ( 4a) and the second washing step (4b) with normal water substantially free of base (so-called distilled water, deionized water, purified water, etc.) are advantageous. At this time, the aqueous solution containing the base used in the first washing step (4a) is prepared by mixing the aqueous layer generated in the second washing step (4b) with the base, thereby washing step (4). The amount of the water layer generated as a whole can be reduced. Moreover, the water which is a fraction of a 2nd distillation process can be used as water which does not contain the base used by a 2nd washing | cleaning process (4b) substantially.

  Furthermore, in order to reduce the loss of cyclohexanone oxime in the above process, cyclohexanone oxime that can be contained in a trace amount in the aqueous layer discharged in the extraction step (3) and the aqueous layer discharged in the washing step (4) is reduced. It is desirable to extract and recover with an organic solvent. The organic solvent used here can be the same as that used in the extraction step (3). Therefore, it is desirable that the organic solvent for use in the extraction step (3) is first used for recovering a trace amount of cyclohexanone oxime from the aqueous layer and then used in the extraction step (3). The cyclohexanone oxime is preferably recovered by multistage extraction.

  FIG. 2 is a flowchart schematically showing an example of the above-described two-step cleaning and cyclohexanone oxime recovery, and the portion surrounded by a broken line in FIG. 1 can be replaced with the flowchart of FIG.

  That is, first, regarding the above-described two-stage cleaning, the organic layer 18 from the extractor 3 is introduced into the first cleaner 4a, mixed with the aqueous solution 20a containing the base, and then separated into the organic layer 21a and the aqueous layer 22a. [First cleaning step (4a)]. Here, examples of the base contained in the aqueous solution 20a include alkali metal hydroxides, carbonates, ammonia and the like, and the concentration in the aqueous solution 20a is usually 0.01 to 2N, preferably 0.05. ~ 0.5N. The washing temperature is preferably 60 to 90 ° C., and the amount of the aqueous solution 20a containing the base is preferably 0.2 to 2 times by weight with respect to the cyclohexanone oxime in the organic layer 18. Next, the organic layer 21a from the first washer 4a is introduced into the second washer 4b, mixed with water 20b substantially free of base, and then separated into an organic layer 21b and an aqueous layer 22b [first Two washing steps (4b)]. And the organic layer 21b is introduce | transduced into the 2nd distillation column 5, and distillation is performed. The aqueous layer 22b is mixed with a base or an aqueous solution 27 thereof, and this mixed liquid is recycled as an aqueous solution 20a containing a base introduced into the first cleaning device 4a. The water layer 20 from the fraction 23 of the second distillation column 5 can be used as the water 20b substantially free of base introduced into the second washer 4b.

  Next, regarding the cyclohexanone oxime recovery described above, the aqueous layer 19 from the extractor 3 and the aqueous layer 22a from the first cleaning device 4a are introduced into the recovery device 8 and mixed with the organic solvent 17, and then the aqueous layer 19 and water A small amount of cyclohexanone oxime in the layer 22a is separated into an organic layer 28 obtained by extraction with the organic solvent 17 and an aqueous layer 29 as an extraction residual liquid. The organic layer 28 is introduced into the extractor 3 and used as an organic solvent for extracting cyclohexanone oxime from the bottoms 16 of the first distillation column 2. Moreover, the water layer 29 is processed as waste water. As the organic solvent 17 introduced into the collector 8, the organic layer 17 from the fraction 23 of the second distillation column 5 can be used. In addition, as the extractor 3 and the washer 4, the recoverer 8 may be a multistage extractable one, or a so-called mixer-settler type in which the mixing part and the liquid separation part are separated from one stage to the other. It may be used in multiple stages.

  Further, in order to recover cyclohexanone oxime that can be contained in a trace amount in the aqueous layer discharged in the washing step (4), the aqueous layer is taken as cyclohexanone oxime / water which is the bottoms of the first distillation step (2). It is also advantageous to subject it to the extraction step (3) together with the mixed solution. At this time, if this extraction step (3) is performed by multi-stage extraction, the aqueous layer discharged from the extraction step (3) can be made substantially free of cyclohexanone oxime and need no recovery treatment. It is advantageous.

  Examples of the present invention are shown below, but the present invention is not limited thereto. In the examples,% representing the content is based on weight unless otherwise specified.

Example 1
The following steps and thermal stability tests were carried out by applying the cleaning and recovery operation shown in FIG. 2 to the continuous production process shown in FIG.

[Reaction step (1)]
A reaction liquid in which a titanosilicate catalyst is dispersed is retained in a stirring tank type reactor 1, and cyclohexanone 11, 60% hydrogen peroxide solution 12, ammonia 13 and 15% water-containing t-butyl alcohol are supplied into the reaction solution. However, by extracting the reaction solution 14 through a filter, cyclohexanone / hydrogen peroxide / ammonia / water / t-butyl alcohol = 1 / 1.1 / 1.8 / 4.29 / 4.0 mole supplied. The reaction was performed at a temperature of 85 ° C. under a pressure ratio of 0.25 MPa (gauge pressure). Nitrogen gas produced as a by-product in the reaction was removed from the system, and the accompanying ammonia gas was absorbed into water and recovered. The component concentration in the obtained reaction liquid 14 was cyclohexanone oxime 20.89%, water 21.69%, ammonia 2.30%, cyclohexanone 0.09%, and t-butyl alcohol 55.03%.

[First distillation step (2)]
The reaction liquid 14 extracted from the reactor 1 is introduced into the first distillation tower 2 together with the ammonia-absorbed water, and distilled at a temperature of 83 ° C. at 50 kPa (gauge pressure). Butyl alcohol was recovered, and a mixture of 46.23% cyclohexanone oxime, 53.45% water, and 0.205% cyclohexanone was obtained as bottoms 16. The fraction 15 was used as a part of ammonia fed to the reactor 1 and 15% water-containing t-butyl alcohol.

[Extraction step (3)]
The bottoms 16 from the first distillation column 2 and toluene 28 having the same weight as the cyclohexanone oxime contained in the bottoms 16 were introduced into the extractor 3 and stirred at about 72 ° C. Separated into layer 18 and aqueous layer 19.

[First cleaning step (4a)]
The toluene layer 18 from the extractor 3 and the 0.1N sodium hydroxide aqueous solution 20a having the same weight as the cyclohexanone oxime contained in the toluene layer 18 are introduced into the first washer 4a and stirred at about 72 ° C. After that, it was separated into a toluene layer 21a and an aqueous layer 22a.

[Second cleaning step (4b)]
The toluene layer 21a from the first washer 4a and the water 20b having the same weight as the cyclohexanone oxime contained in the toluene layer 21a were introduced into the second washer 4b and stirred at about 72 ° C. And separated into a toluene layer 21b and an aqueous layer 22b. Sodium hydroxide was added to the aqueous layer 22b to prepare a 0.1N sodium hydroxide aqueous solution, which was used as a 0.1N sodium hydroxide aqueous solution 20a introduced into the first washer 4a.

[Oxime recovery process]
The aqueous layer 19 from the extractor 3 and the aqueous layer 22a from the first washing device 4a are mixed, the mixed aqueous layer and toluene 17 are introduced into the collector 8 and stirred at about 72 ° C., and then the toluene layer 28 and an aqueous layer 29 were separated. The toluene layer 28 was used as toluene 28 introduced into the extractor 3.

[Second distillation step (5)]
The toluene layer 21b from the second washer 4b is introduced into the second distillation column 5, and distilled at a temperature of 107 ° C. under a reduced pressure of 30 kPa. As a fraction 23, a mixture of toluene and water is recovered and taken out. As a liquid 24, crude cyclohexanone oxime having a purity of 98.13% containing 0.54% of cyclohexanone was obtained. The fraction 23 was introduced into the separator 7 and separated into the toluene layer 17 and the aqueous layer 20 at about 35 ° C. The toluene layer 17 was used as toluene 17 introduced into the recovery device 8, and the aqueous layer 20 was used as water 20b introduced into the second cleaning device 4b.

[Third distillation step (6)]
The bottoms 24 from the second distillation column 5 is introduced into the third distillation column 6 and distilled at a temperature of 120 ° C. under a reduced pressure of 4 kPa, and cyclohexanone is recovered as a fraction 25 to obtain a bottoms 26. A purified cyclohexanone oxime having a purity of 99.70% containing 0.02% of cyclohexanone was obtained. The fraction 25 was used as part of the cyclohexanone fed to the reactor 1.

[Thermal stability test]
The purified cyclohexanone oxime obtained as bottoms 26 was distilled under reduced pressure at a pressure of 15 torr (2 kPa) at a temperature of 120 ° C. until no distillation was observed. To 0.01% (tar amount before heat treatment). Further, the cyclohexanone oxime was heat-treated at 200 ° C. for 5 hours under a nitrogen stream and then distilled under reduced pressure in the same manner as described above. As a result, the amount of the remaining tar was 0.54% with respect to the distillation charge ( Tar amount after heat treatment). The amount of tar increased by the heat treatment was 0.53%.

Comparative Example 1
The reaction step (1) and the first distillation step (2) were performed in the same manner as in Example 1. Ammonium sulfate is added to the bottoms 16 from the first distillation column 2 and oil-water separation is performed to obtain cyclohexanone oxime having a purity of 96.8% containing 0.11% cyclohexanone and 2.7% water as an organic layer. It was. The obtained cyclohexanone oxime was subjected to a thermal stability test in the same manner as in Example 1. As a result, the tar amount before the heat treatment was 0.21%, the tar amount after the heat treatment was 15%, and the heat treatment was performed. The increase in tar due to was 14.79%.

Comparative Example 2
The reaction step (1), the first distillation step (2), the extraction step (3), the first washing step (4a), and the second washing step (4b) were performed in the same manner as in Example 1. The toluene layer 21b from the second washer 4b was batch-concentrated at a temperature of 104 to 108 ° C. for 16 hours under a reduced pressure of 65 to 30 kPa, and a purity of 99.1 containing 0.66% of cyclohexanone as a bottoms. % Cyclohexanone oxime was obtained. The obtained cyclohexanone oxime was subjected to a thermal stability test in the same manner as in Example 1. As a result, the tar amount before the heat treatment was 0.07%, and the tar amount after the heat treatment was 7.1%. The amount of tar increased by the heat treatment was 7.03%.

It is a flowchart which shows typically the example of the continuous manufacturing process of the cyclohexanone oxime by this invention. It is a flowchart which shows typically the example which performs washing | cleaning process (4) in two steps including base washing | cleaning, and collect | recovers cyclohexanone oximes from the aqueous layer of extraction process (3) and washing | cleaning process (4).

Explanation of symbols

1 …… Reactor,
2 …… First distillation column,
3 …… Extractor,
4 …… Washer,
4a ... first washer,
4b ... second washer,
5 …… Second distillation column,
6 …… Third distillation column,
7 …… Separator,
8 …… collector,
11 ... cyclohexanone,
12 …… hydrogen peroxide,
13 ... Ammonia,
17 …… Organic solvent,
20 ... water,
24 ... Crude cyclohexanone oxime,
26 ... Purified cyclohexanone oxime.

Claims (7)

The following steps (1) to (6),
(1) Reaction step: a step of reacting cyclohexanone, hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst to obtain a reaction solution containing cyclohexanone oxime, water, unreacted ammonia and unreacted cyclohexanone,
(2) First distillation step: A step of distilling the reaction liquid obtained in step (1) to distill ammonia to obtain a bottom liquid containing cyclohexanone oxime, water, and cyclohexanone.
(3) Extraction step: a step of separating the bottoms obtained in step (2) with an organic solvent, and then separating the organic layer and the aqueous layer;
(4a) first washing step: a step of mixing the organic layer obtained in step (3) with an aqueous solution containing a base, and then separating the organic layer and the aqueous layer;
(4b) Second washing step: a step of mixing the organic layer obtained in step (4a) with water not containing a base, and then separating the organic layer and the aqueous layer;
(5) Second distillation step: a step of distilling the organic layer obtained in step (4 b ), distilling the organic solvent and water, and obtaining a bottom liquid containing cyclohexanone oxime and cyclohexanone,
(6) Third distillation step: distilling the bottoms obtained in step (5) to distill cyclohexanone , including bottoms containing cyclohexanone oxime and containing cyclohexanone at a concentration of 0.5% by weight or less. Obtaining a liquid;
A process for producing cyclohexanone oxime, comprising:   The method according to claim 1, wherein the organic solvent used in the step (3) is selected from a hydrocarbon solvent, an ether solvent and an ester solvent.   The method according to claim 1 or 2, wherein the ammonia distilled in step (2) is recycled to step (1).   The method according to claim 1, wherein the organic solvent distilled in the step (5) is recycled to the step (3). The method according to any one of claims 1 to 4, wherein the water distilled in the step (5) is recycled to the step ( 4b ). The cyclohexanone distilled in step (6) is recycled to step (1).
The method in any one of. The aqueous layer obtained in step (4b) is mixed with a base, and an aqueous solution containing the obtained base is added to step (4a).
The method according to any one of claims 1 to 6, which is recycled to (1).

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