JPH06256238A - Production of phenol methyl ethyl ketone - Google Patents

Abstract

PURPOSE:To obtain a compound having high-quality to sufficiently satisfy the JIS specifications by oxidizing sec-butylbenzene and decomposing with an acidic catalyst while recycling the unreacted component, by-products, etc., of each step effectively into the reaction system. CONSTITUTION:Phenol and methyl ethyl ketone are produced from sec- butylbenzene. In the above process, the see-butylbenzene is oxidized to form an oxidation reaction liquid composed mainly of sec-butylbenzene hydroperoxide. The reaction liquid is concentrated by distillation to obtain the above peroxide as the bottom and the distillate is recycled to the oxidation step. The bottom is decomposed into phenol and methyl ethyl ketone by contacting with an acidic catalyst. The decomposition liquid is neutralized with an alkali and separated into an oil layer and a water layer and a part of the water layer is recycled to the neutralizing step. The oil layer is distilled to obtain phenol as the bottom liquid and methyl ethyl ketone as the distillate. The distillate is washed with an alkali to remove the impurities. The product is neutralized, dehydrated and distilled to recover methyl ethyl ketone and the column top distillate is recycled to the alkali washing step.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing phenol and methyl ethyl ketone. More specifically, the present invention relates to a method for producing phenol and methyl ethyl ketone starting from sec-butylbenzene.

[0002]

2. Description of the Related Art Se-butylbenzene is oxidized to se.
A technique is known in which c-butylbenzene hydroperoxide is used, and then the sec-butylbenzene hydroperoxide is decomposed with sulfuric acid to give phenol and methyl ethyl ketone (Japanese Patent Laid-Open No. 8080524).

[0003]

By the way, as one of the quality standards required for methyl ethyl ketone, purity and discoloration of potassium permanganate are defined (JI.
SK 8900). However, the methyl ethyl ketone obtained by the above technique has a problem that it is difficult to satisfy the standards of the purity and the color fading property of potassium permanganate. The following methods are known as methods for purifying methyl ethyl ketone. JP-B-45-41205 discloses a method in which t-butanol which forms an azeotrope with methyl ethyl ketone is decomposed into isobutylene using a zeolite catalyst and then separated. Further, Japanese Patent Publication No. 57-35167 discloses a technique for improving the discoloration of potassium permanganate by contacting crude methyl ethyl ketone with hydrogen in the presence of a catalyst containing rhodium or platinum. Furthermore, Japanese Examined Japanese Patent Publication No. 47-3332
Japanese Unexamined Patent Publication (Kokai) No. 3 discloses a method of removing aldehydes in methyl ethyl ketone by forming an acid alkali metal sulfite or an adduct with alkali metal sulfite.
However, when these methods are applied to a technique for obtaining phenol and methyl ethyl ketone using sec-butylbenzene as a starting material, there is a problem that the purification effect is insufficient.

In view of the current situation, the problem to be solved by the present invention is to oxidize sec-butylbenzene to produce sec.
-Butylbenzene hydroperoxide, then a method for producing phenol and methylethylketone by decomposing the sec-butylbenzene hydroperoxide with an acidic catalyst to give phenol and methylethylketone, which is of high quality and sufficiently satisfies JIS standards. Another object of the present invention is to provide a method for producing phenol and methyl ethyl ketone capable of obtaining methyl ethyl ketone.

[0005]

The present inventors have examined in detail the factors affecting the purity of methyl ethyl ketone and the fading property of potassium permanganate. As a result, those affecting the purity are phenol, sec-butylbenzene, carboxylic acids and carboxylic acid esters, water,
It was found that ethanol and acetone, and unsaturated ketones and aldehydes have an effect on the fading property of potassium permanganate. Further, the present inventor studied the method for efficiently removing such a specific impurity, and arrived at the present invention.

That is, the present invention relates to a method for producing phenol and methyl ethyl ketone using sec-butylbenzene as a starting material, and relates to a method for producing phenol and methyl ethyl ketone characterized by including the following steps. Oxidation step: sec-butylbenzene is oxidized to sec-
Step of obtaining an oxidation reaction liquid containing butylbenzene hydroperoxide as a main component Concentration step: The oxidation reaction liquid is concentrated by distillation to obtain a bottom liquid containing sec-butylbenzene hydroperoxide as a main component from the tower bottom, A process of obtaining a distillate mainly containing sec-butylbenzene from the top and recycling the distillate to an oxidation process Decomposition process: By contacting the bottom liquid of the concentration process with an acidic catalyst, sec-butylbenzene hydro Step of decomposing peroxide into phenol and methyl ethyl ketone First neutralization step: Decomposition liquid obtained in the decomposition step is neutralized with an alkaline aqueous solution, separated into an oil layer and an aqueous layer, and a part of the aqueous layer is re-neutralized step Process for recycling to: 1st distillation process: The oil layer obtained in the 1st neutralization process is subjected to distillation, and a bottom liquid containing methyl as a main component and methyl ethyl Step of Obtaining Distillate Containing Ketone as Main Component Alkaline Washing Step: Carboxylic acid, carboxylic acid ester, unsaturated ketone and aldehyde by washing the distillate obtained in the first distillation step with an alkaline aqueous solution. Step of removing the second species Neutralization step: Step of neutralizing the oil layer after alkali washing First purification step: Step of dehydrating the oil layer obtained in the second neutralization step Second purification step: In the first purification step A step of distilling the obtained bottom liquid to recover methyl ethyl ketone and recycling the top liquid to the alkali washing step again.

The details will be described below. The oxidation step of the present invention is a step of oxidizing sec-butylbenzene to obtain an oxidation reaction liquid containing sec-butylbenzene hydroperoxide as a main component, and is performed, for example, as follows.
That is, liquid sec-butylbenzene is added to 90-1
A sec-butylbenzene hydroperoxide is obtained by contacting with an oxygen-containing gas at a temperature of 50 ° C. and a pressure of 1 to 10 kg / cm ² G.

In the concentration step of the present invention, the oxidation reaction liquid is concentrated by distillation to obtain a column bottom liquid containing sec-butylbenzene hydroperoxide as a main component from the column bottom, and sec-butylbenzene is mainly collected from the column top. This is a step of obtaining a distillate as a component. The distillation conditions in the concentration step may be set so that a bottom liquid containing sec-butylbenzene hydroperoxide as a main component and a distillate containing sec-butylbenzene as a main component can be obtained. Temperature 50-150 ° C, overhead pressure 1-200 torr
Can be given.

The decomposition step of the present invention is a step of decomposing sec-butylbenzene hydroperoxide into phenol and methyl ethyl ketone by contacting the bottom liquid in the concentration step with an acidic catalyst. As an acidic catalyst,
Sulfuric acid, sulfuric anhydride, perchloric acid, phosphoric acid, etc. are used.
The amount of the acidic catalyst used is usually 0.01 to 1 wt%,
The temperature is usually in the range of 50 to 100 ° C.

The first neutralization step of the present invention is to neutralize the decomposition liquid obtained in the decomposition step with an aqueous alkaline solution to separate an oil layer and an aqueous layer, and recycle a part of the aqueous layer to the neutralization step again. It is a process to do. As the alkali used for neutralization, hydroxides such as sodium, potassium and lithium,
Carbonate, bicarbonate and the like can be used. The amount of alkali used is an amount sufficient to maintain the pH of the aqueous layer at usually 5 to 11, preferably 6 to 10. The temperature is preferably room temperature to 90 ° C., and the oil layer / water layer weight ratio is preferably 0.5 to 5. In the neutralization step, it is sufficient that the liquid layer to be neutralized and the alkaline aqueous solution are sufficiently brought into contact with each other, and then the oil layer and the aqueous layer can be separated. For example, a tank equipped with a stirrer, a line mixer, a pipe mixer or the like is used. In the first neutralization step, in order to reduce the amount of waste water, a part of the water layer used in the neutralization step is recycled and used again in the neutralization step. As a result, the salt concentration in the neutralization step increases, but it is usually preferable to maintain the salt concentration at 1 to 30 wt%. The oil layer obtained in the first neutralization step is sent to the next first distillation step, while a part of the water layer is discarded.

The first distillation step of the present invention means that the decomposition liquid obtained in the first neutralization step is subjected to distillation to obtain a bottom liquid containing phenol as a main component and a distillate containing methyl ethyl ketone as a main component. It is a process of obtaining. The distillation conditions include, for example, a column bottom temperature of 150 to 200 ° C. and a pressure of atmospheric pressure to 500 torr. Further, sec- in the first distillation feed raw material
In order to prevent the leakage of butylbenzene to the distillation side,
It is preferable to increase the concentration of methyl ethyl ketone in the distillation column feed material. For example, a part of the methyl ethyl ketone obtained in the below-mentioned third distillation step can be recycled and fed to the first distillation column.

In the alkali washing step of the present invention, the distillate obtained in the first distillation step is washed with an alkaline aqueous solution to remove carboxylic acids, carboxylic acid esters, unsaturated ketones and aldehydes. It is a process. As the alkali, hydroxides, carbonates, bicarbonates of sodium, potassium, lithium and the like can be used. The amount of the alkali used is such that the pH of the oil layer in the alkali washing step is usually 7 or more, preferably 10 to 14, more preferably 13
It should be ~ 14. If the pH of the oil layer is too low, the removal of carboxylic acids, carboxylic acid esters, unsaturated ketones and aldehydes will be insufficient. The alkali is preferably used as an aqueous solution, and its concentration is 10
˜48% by weight is preferred. The weight ratio of oil layer / water layer in the alkali washing step is 0.5 to 10, preferably 0.5 to
It is 4. Between the oil layer / water layer weight ratio in the alkaline washing step and the pH of the oil layer and the conversion rate of isobutyraldehyde, which adversely affects the discoloration of potassium permanganate,
There is a close relationship. That is, if the pH is the same, the smaller the oil layer / water layer weight ratio is, the larger the conversion of isobutyraldehyde is. If the oil layer / water layer weight ratio is the same, the larger pH is the isobutyraldehyde. The conversion rate increases. Therefore, it is possible to efficiently convert and remove isobutyraldehyde by setting the weight ratio of the oil layer / water layer to be small and setting the pH to be large within the range permitted by the volume efficiency. In the alkali washing step, it is sufficient that the oil layer to be washed and the alkaline aqueous solution are sufficiently brought into contact with each other to sufficiently react, and then the oil layer and the water layer can be separated, and for example, a tank equipped with a stirrer is used. More preferably, a continuous kneading tank equipped with a plurality of stirrers or a reactor of liquid extractor type is used.

The alkali cleaning step is a particularly important step in the present invention. That is, substantially all of the carboxylic acids, carboxylic acid esters and unsaturated ketones contained in the distillate obtained in the first distillation step, and most of the aldehydes are removed in this alkali washing step, Carboxylic acids, carboxylic acid esters, and unsaturated ketones can each be about 0.1 ppm by weight or less, and aldehydes can be about 10 ppm by weight or less. At this time, in this alkali washing step, it is sufficient to reduce the aldehydes to about 400 ppm by weight, and the aldehydes can be separated to a level satisfying the potassium permanganate discoloration test in the third distillation step described later. Incidentally, the carboxylic acid is mainly acetic acid and formic acid, which causes a problem of corrosion of the manufacturing apparatus. The carboxylic acid esters are mainly ethyl acetate and ethyl formate, and in particular, ethyl acetate has a problem that it cannot be sufficiently removed only by distillation.
Unsaturated ketones are mainly methyl vinyl ketones, and methyl ethyl ketone containing even 1 ppm by weight thereof does not satisfy the potassium permanganate discoloration test. Further, methyl vinyl ketone has a boiling point difference of only 2 ° C. from methyl ethyl ketone, and is economically difficult to separate by distillation. Aldehydes are mainly acetaldehyde and isobutyraldehyde, of which isobutyraldehyde has a boiling point close to that of methyl ethyl ketone and cannot be economically sufficiently separated only by distillation.
Only about 50 ppm by weight of isobutyraldehyde does not satisfy the potassium permanganate discoloration test of methyl ethyl ketone. Furthermore, 3-methyl-3-buten-2-one is newly produced from methyl ethyl ketone and formaldehyde in the alkali washing step. 3-methyl-3
-Buten-2-one does not satisfy the potassium permanganate discoloration test of methyl ethyl ketone even if it is present in an amount of only 2 ppm by weight, but it can be separated in the second purification step after washing with alkali.

The second neutralization step of the present invention is a step of neutralizing the oil layer after alkali cleaning. Specifically, the oil layer after alkaline cleaning is neutralized with a sulfuric acid aqueous solution to separate the oil layer and the water layer. It is a process. In the subsequent second distillation step, when the oil layer after alkali cleaning is distilled, the pH of the oil layer is important.
In alkaline washing, an aldol-condensation type dimer adduct is produced from methyl ethyl ketone and impurity isobutyraldehyde. This dimer adduct undergoes a reverse decomposition reaction in the alkaline region where the pH is 10 or more during the second distillation, regenerates isobutyraldehyde, and increases isobutyraldehyde in the initial distillate fraction. . This isobutyraldehyde is a potassium permanganate color fading substance as described above. Moreover, in the batch distillation, the recovery of the initial fraction is recognized and the recovery rate is lowered, and the yield is deteriorated in the continuous distillation, so that the yield of methyl ethyl ketone which passes the JIS standard is reduced,
It is a substance that wants to suppress the reverse decomposition reaction. On the other hand, if the pH is in the neutral or acidic range of 7 or less, the reverse decomposition reaction hardly occurs and isobutyraldehyde is not mixed in the distillate. Therefore, when distilling the oil layer after washing with alkali, it is possible to prevent the inclusion of isobutyraldehyde by neutralizing it before the distillation.

As the acid used for neutralization, sulfuric acid, hydrochloric acid, nitric acid, etc. can be used. The amount of the acid used is an amount sufficient to maintain the pH of the aqueous layer at usually 7 or lower, preferably 6 to 4. The temperature is from room temperature to 90 ° C, preferably 60
-80 ° C, and the oil layer / water layer weight ratio is preferably 0.5-4. The neutralization step is sufficient if the liquid layer to be neutralized and the acid aqueous solution are sufficiently contacted, and then the oil layer and the aqueous layer can be separated,
For example, a tank equipped with a stirrer, a line mixer, a pipe mixer or the like is used.

In the second neutralization step, in order to reduce the amount of waste water, it is preferable to recycle a part of the water layer used in the neutralization step again in the neutralization step. as a result,
Although the salt concentration in the second neutralization step increases, it is usually 0.5 to 15
It is preferred to maintain a salt concentration of wt%, preferably 2-10 wt%.

Further, in the present invention, it is preferable to interpose between the second neutralization step and the second distillation step a water washing step for washing the oil layer obtained in the second neutralization step with water. The temperature for washing with water is room temperature to 90 ° C, preferably 60 to 80
C., and the weight ratio of oil layer / water layer is preferably 1 to 4. In the water washing step, it is sufficient that the oil layer to be washed and the washing water are sufficiently brought into contact with each other, and then the oil layer and the water layer can be separated, and for example, a tank equipped with a stirrer, a line mixer, a pipe mixer or the like is used. By using such a water washing step, precipitation / accumulation of various salts in the subsequent distillation column can be prevented, and stable long-term operation becomes possible.

The first refining step of the present invention is a step of dehydrating the oil layer obtained in the second neutralization step. Specifically, in the step of adding a third substance called an entrainer to the oil layer obtained in the second neutralization step and carrying out a heterophasic azeotropic distillation to remove a mixed liquid of water and a light boiling component from the top of the column. is there. The light-boiling component is a light-boiling component for methyl ethyl ketone and contains acetone and ethanol. As the entrainer, a component that causes liquid-liquid phase separation with water and causes a lighter boiling than methyl ethyl ketone or a minimum azeotrope with methyl ethyl ketone can be used. Specific examples include hexane, cyclohexane, and heptane.

Regarding the removal of water from methyl ethyl ketone, ^two columns, a high pressure distillation column of about 5 to ²⁰ kg / cm ² and a distillation column near atmospheric pressure, are used to remove methyl ethyl ketone from the bottom of the high pressure column to the bottom of the low pressure column. The method of obtaining water from each of these (hereinafter referred to as the high pressure method) is industrially adopted. However, the methyl ethyl ketone in this process contains hydrophilic light-boiling components including acetone and ethanol, and in this high-pressure method, these light-boiling components accumulate at the top of the column. The light boiling component can be removed by purging a part of the overhead liquid, but if the concentration of the light boiling component becomes too high, the liquid-liquid phase separation will not occur and the concentration cannot be increased. As a result, the purge amount becomes large, so it is practically difficult to adopt the high pressure method in this process.

There is known an example of carrying out heterophasic azeotropic distillation using an entrainer in dehydration of methyl ethyl ketone (Japanese Patent Laid-Open No. 166205/1984, unclaimed), and this method enables dehydration in methyl ethyl ketone. It is stated that there is. In the first refining step of the present invention, azeotropic distillation is carried out using an entrainer to remove not only dehydration but also light boiling impurities from methyl ethyl ketone containing acetone and ethanol contained in the oil layer in a simultaneously dissolved form. There are features. As the entrainer, hexane, cyclohexane and heptane are preferable, and hexane is more preferable. The distillation conditions for the first purification are:
For example, the tower bottom temperature is 85 ° C., the pressure is normal pressure to 20 kg / cm ^2.
Distillation can be mentioned. The water content of the oil layer is 10 by this distillation.
It is dehydrated from wt% to 300 wtppm, and 80 to 90% of acetone and ethanol can be removed.

The second purification step of the present invention is a step of distilling the bottom liquid obtained in the first purification process to recover methyl ethyl ketone and recycling the top liquid again to the alkali washing step. A preferable specific example of the second purification step is a second purification step including the following second distillation step and third distillation step.

Second distillation step: a step of distilling the bottom liquid obtained in the first refining step to remove a tar component containing 3-methyl-3-buten-2-one as a bottom liquid Third distillation Step: a step of distilling the overhead liquid obtained in the second distillation step to recover methyl ethyl ketone and recycling the overhead liquid to the alkali washing step again

The second distillation step is a step of distilling the bottom liquid obtained in the first refining process to remove the tar component containing 3-methyl-3-buten-2-one as the bottom liquid. is there. In the bottom liquid obtained in the first purification step, the tar component containing the aldol condensate of 3-methyl-3-buten-2-one and methyl ethyl ketone, aldehydes, and unsaturated ketones generated in the alkali washing step is contained. Exists. Especially 3-
Methyl-3-buten-2-one is a potassium permanganate fading substance, and must be kept at 1 wtppm or less according to JIS.
Does not meet the standard. It can be removed to 1 ppm by weight or less by the main distillation, the tar content can be completely removed, the purity of methyl ethyl ketone can be improved, and the potassium permanganate fading substance can be removed. The distillation conditions include atmospheric distillation at a bottom temperature of 85 to 125 ° C., and the bottom liquid is removed as waste oil outside the system. In the bottom liquid, a dimer of methyl ethyl ketone produced in the alkali washing step is present, and it is highly likely that the addition reaction is stopped without dehydration. When the concentration is increased and the alkali washing is performed again, methyl ethyl ketone is restored due to the reversible reaction. Therefore, the bottom liquid of the second distillation step may be partially recycled to the alkali washing step again.

The third distillation step is a step in which the overhead liquid obtained in the second distillation step is distilled to recover methyl ethyl ketone, and the overhead liquid is recycled to the alkali washing step again. The overhead liquid obtained in the second distillation step was completely removed from impurities heavier than methyl ethyl ketone, but was not completely removed in the first purification step including aldehydes which were not completely removed in the alkali washing step. Impurities that are lighter than methyl ethyl ketone, including incomplete acetone, ethanol, and water, are present. In the third distillation step, the light-boiling impurities are removed, and methyl ethyl ketone satisfying the JIS standard can be separated and recovered. Isobutyraldehyde was removed to below the target concentration, all potassium permanganate fading substances could be removed, and the fading test passed. For example, the distillation conditions include atmospheric distillation at a bottom temperature of 82 ° C. Further, the overhead liquid containing isobutyraldehyde is recycled to the alkali washing step. At that time, methyl ethyl ketone leaked to the top of the column can be recovered, and impurities lighter than methyl ethyl ketone are removed to the outside of the system as the top liquid of the first purification step through the alkali washing step and the second neutralization step. .

According to the present invention described above, phenol,
The content of carboxylic acids, carboxylic esters, unsaturated ketones, aldehydes, light boiling components of ethanol and acetone, and water together with sec-butylbenzene is extremely low, and JI concerning purity and potassium permanganate fading property
It is possible to obtain methyl ethyl ketone that sufficiently satisfies the S standard.

[0026]

EXAMPLES Next, the present invention will be described with reference to examples. Example 1 An oil layer liquid in the first neutralization step containing 26.1% of methyl ethyl ketone, 24.4% of sec-butylbenzene and 33.5% of phenol was carried out as follows. 184 kg of the oil layer liquid was distilled under atmospheric pressure at a tower bottom temperature of 177 ° C. to obtain 54.4 kg of a distillate containing 89.0% of methyl ethyl ketone and 119.70 kg of a bottom liquid containing 49.3% of phenol. Next, 50 kg of a 20 wt% sodium hydroxide aqueous solution was added to 50 kg of the distillate, and the mixture was stirred at 70 ° C. for 2 hours to carry out alkali washing. Ethyl formate, ethyl acetate and methyl vinyl ketone were not detected, and they were 200 weight ppm of 3-methyl-3-buten-2-one, 0.04 weight% of isobutyraldehyde, and about 1 weight% of tar content. Next, 20.4 kg of oil layer after alkali cleaning was added with 5.1 k of 8% sodium sulfate water.
Then, 0.05 kg of a 10 wt% sulfuric acid aqueous solution was added, and the mixture was stirred at 70 ° C. for 5 minutes to adjust the pH to 7. Further, 10.4 kg of water was added to the neutralized oil layer, and the mixture was stirred at 70 ° C. for 10 minutes to carry out a water washing step. Water content of the oil layer liquid washed with water is 10
% By weight, 0.16% by weight of acetone, 0.27 of ethanol
% By weight, 0.04% by weight of isobutyraldehyde, 0.02% by weight of 3-methyl-3-buten-2-one, about 1% by weight of tar content. This oil layer liquid was first subjected to atmospheric distillation by adding hexane (column bottom temperature: 85 ° C.) to obtain a water content of 290 wt ppm, acetone of 0.01 wt%, ethanol of 0.0
2% by weight of bottom liquid was obtained. Further atmospheric distillation (column bottom temperature 85
Up to 125 ° C.) 3-methyl-3-buten-2-one,
The tar content is completely removed, and the distillate is distilled under atmospheric pressure (column bottom temperature 8
At 2 ° C., 99.9982% by weight of methyl ethyl ketone was obtained as a side cut solution. This methyl ethyl ketone also satisfied the JIS standard regarding the discoloration of potassium permanganate.

[0027]

As described above, according to the present invention, s
A method for producing phenol and methyl ethyl ketone using ec-butylbenzene as a starting material, which is capable of obtaining high quality methyl ethyl ketone that sufficiently satisfies JIS standards for purity and potassium permanganate fading property. Could provide a way.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C07C 39/04 8930-4H 45/53 45/80 49/10 7188-4H // C07B 61/00 300 (72) Inventor Masaaki Toma 5-1 Anezaki Kaigan, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd. (72) Inventor Hirooki Nagaoka 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Co., Ltd.

Claims (4)

[Claims] 1. A method for producing phenol and methyl ethyl ketone using sec-butylbenzene as a starting material, which comprises the following steps. Oxidation step: sec-butylbenzene is oxidized to sec-
Step of obtaining an oxidation reaction liquid containing butylbenzene hydroperoxide as a main component Concentration step: The oxidation reaction liquid is concentrated by distillation to obtain a bottom liquid containing sec-butylbenzene hydroperoxide as a main component from the tower bottom, A process of obtaining a distillate mainly containing sec-butylbenzene from the top and recycling the distillate to an oxidation process Decomposition process: By contacting the bottom liquid of the concentration process with an acidic catalyst, sec-butylbenzene hydro Step of decomposing peroxide into phenol and methyl ethyl ketone First neutralization step: Decomposition liquid obtained in the decomposition step is neutralized with an alkaline aqueous solution, separated into an oil layer and an aqueous layer, and a part of the aqueous layer is re-neutralized step Process for recycling to: 1st distillation process: The oil layer obtained in the 1st neutralization process is subjected to distillation, and a bottom liquid containing methyl as a main component and methyl ethyl Step of Obtaining Distillate Containing Ketone as Main Component Alkaline Washing Step: Carboxylic acid, carboxylic acid ester, unsaturated ketone and aldehyde by washing the distillate obtained in the first distillation step with an alkaline aqueous solution. Step of removing the second species Neutralization step: Step of neutralizing the oil layer after alkali washing First purification step: Step of dehydrating the oil layer obtained in the second neutralization step Second purification step: In the first purification step A step of distilling the obtained bottom liquid to recover methyl ethyl ketone and recycling the top liquid to the alkali washing step again. 2. The method according to claim 1, wherein the following step is interposed between the second neutralization step and the first purification step. Washing step: a step of washing the oil layer obtained in the second neutralization step 3. In the first refining step, a third substance serving as an entrainer is added to the oil layer obtained in the second neutralization step and distilled to remove a mixed solution containing water, acetone and ethanol from the top of the column. Process 4. The method according to claim 1, wherein the second purification step is a step including the following steps. Second distillation step: a step of distilling the bottom liquid obtained in the first purification step to remove a tar component containing 3-methyl-3-buten-2-one as a bottom liquid Third distillation step: 2 Step of distilling the overhead liquid obtained in the distillation step to recover methyl ethyl ketone and recycling the overhead liquid to the alkali washing step again