JP2007210980A - Method for recovering ethyl acetate from ethyl acetate/methyl ethyl ketone mixture system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for economically and efficiently recovering ethyl acetate in high purity and at a low total acid value from a solvent mixture containing at least ethyl acetate and methyl ethyl ketone without causing the hydrolysis of the ethyl acetate. <P>SOLUTION: This method for recovering ethyl acetate from ethyl acetate/methyl ethyl ketone mixture system comprises bringing a hydroxylamine salt into contact with a weak base to produce the free hydroxylamine, bringing the produced free hydroxylamine into contact with the methyl ethyl ketone in the solvent mixture to react the methyl ethyl ketone with the free hydroxylamine, thereby converting into methyl ethyl ketoxime, and then distilling the organic phase containing the methyl ethyl ketoxime and the ethyl acetate to separate the ethyl acetate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for recovering ethyl acetate from a mixed system of ethyl acetate and methyl ethyl ketone, and in particular, effectively removes high-purity ethyl acetate from a solvent mixture containing at least ethyl acetate and methyl ethyl ketone, such as a waste solvent. It relates to a method that can be recovered.

  In recent years, it has been strongly demanded to separate and recover useful components from solvent mixtures containing multiple components, such as waste solvents emitted during industrial activities, from the viewpoint of recycling effective resources and environmental conservation. It has become like this.

  By the way, as a method for separating and recovering a solvent component from a solvent mixture composed of a plurality of components, distillation is generally used. However, when at least ethyl acetate and methyl ethyl ketone are included as the solvent components of the solvent mixture, the physical properties of these ethyl acetate and methyl ethyl ketone are very similar, and therefore, by a normal distillation operation utilizing the difference in boiling points, It has been difficult to separate and purify by operations such as azeotropic distillation and extractive distillation, in which three components are added to cause a difference in boiling point for distillation. Thus, various methods for separating and recovering ethyl acetate from a solvent mixture of ethyl acetate and methyl ethyl ketone have been studied.

  For example, in Japanese Translation of PCT International Publication No. 2004-536880, methyl ethyl ketone in a solvent mixture containing ethyl acetate and methyl ethyl ketone is converted to 2-butanol by contacting with hydrogen in the presence of a selective hydrogen conversion catalyst. A method has been proposed for recovering ethyl acetate by feeding a solvent mixture containing ethyl acetate and 2-butanol to a distillation column and operating at a pressure below 1 bar absolute. However, such a method requires a hydrogenation reaction step under a high pressure condition and a distillation step under a reduced pressure condition, which is problematic in terms of cost.

  Japanese Patent Laid-Open No. 4-266847 discloses a method for removing carbonyl impurities from esters such as methyl acetate, by reacting the esters with carbonyl impurities to produce water-soluble nitrogen-containing derivatives of carbonyls. By adding an amino compound to react and separating the organic ester phase and the aqueous derivative phase from the resulting reaction product, the resulting ester phase is distilled to further remove heavy impurities. A method for purifying esters such as methyl acetate containing carbonyl impurities is disclosed.

  And, as an amino compound that reacts with carbonyls to form a water-soluble nitrogen-containing derivative, the use of hydroxylamine has been clarified, but such hydroxylamine gradually decomposes, Industrially, it will be supplied as an acid salt. Therefore, a methyl acetate stream containing carbonyl impurities is contacted with the hydroxylamine salt and then free hydroxylamine is obtained in which a base such as potassium hydroxide, sodium hydroxide or lithium hydroxide is used. A technique for processing is adopted.

However, when a strong base such as potassium hydroxide is used, the pH of the system rises and hydrolysis of the esters is promoted. Further, as described above, when a base is directly mixed into the system. When the method is applied to the solvent mixture containing at least ethyl acetate and methyl ethyl ketone, since the pH of the system is locally increased and hydrolysis of the esters is further promoted. There was a problem that the collected ethyl acetate was mixed with acetic acid and ethanol generated by hydrolysis of ethyl acetate. In such a case, it is necessary to further remove ethanol, and since a small amount of acetic acid remains in the ethyl acetate after distillation, the total acid value of ethyl acetate becomes high and the quality is reduced. There was also a problem. Such ethyl acetate having a high total acid value has a low utility value as a solvent such as thinner.
Special table 2004-536880 gazette JP-A-4-266847

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is to induce hydrolysis of ethyl acetate from a solvent mixture containing at least ethyl acetate and methyl ethyl ketone. It is another object of the present invention to provide a method for economically and efficiently recovering ethyl acetate having a high purity and a low total acid value.

  And in order to solve the above-mentioned problem or the problem grasped from the description of the entire specification, the present invention can be suitably implemented in various aspects as listed below. Each aspect described in can be employed in any combination. It should be noted that the aspects and technical features of the present invention are not limited to those described below, and can be recognized based on the entire description of the present specification and the inventive idea disclosed therein. Should be understood.

(1) A method for separating and recovering ethyl acetate from a solvent mixture containing at least ethyl acetate and methyl ethyl ketone, wherein free hydroxylamine is produced by contact with a hydroxylamine salt and a weak base, while the produced free amine is produced. Hydroxylamine is contacted with methyl ethyl ketone in the solvent mixture and the methyl ethyl ketone is reacted with free hydroxylamine to convert it to methyl ethyl ketoxime, followed by distillation of the organic phase containing ethyl acetate with such methyl ethyl ketoxime, A method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system, characterized by separating ethyl acetate.

(2) The aqueous solution of the weak base is mixed with the aqueous solution of the hydroxylamine salt to form an aqueous solution of the free hydroxylamine, and the aqueous solution of free hydroxylamine is mixed with the solvent mixture. Acetic acid from the ethyl acetate / methyl ethyl ketone mixed system according to the aspect (1), wherein a reaction product containing the methyl ethyl ketoxime is formed, and the organic phase is taken out by phase separation of the reaction product. Ethyl recovery method.

(3) The method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system according to the above aspect (1) or (2), wherein the weak base is an inorganic alkali having a buffering action.

(4) The inorganic alkali is at least one selected from the group consisting of carbonates of alkali metals and alkaline earth metals, such as sodium carbonate, potassium carbonate, magnesium carbonate, and calcium carbonate. The method for recovering ethyl acetate from the ethyl acetate / methyl ethyl ketone mixed system according to the aspect (3).

(5) The temperature of the reaction system between the methyl ethyl ketone and the free hydroxylamine is controlled so as not to exceed 40 ° C. The ethyl acetate / ethyl acetate according to any one of the above aspects (1) to (4), A method for recovering ethyl acetate from a methyl ethyl ketone mixed system.

(6) The free hydroxylamine aqueous solution is used in a volume of 0.3 to 2 times the volume of the solvent mixture, according to any one of the above aspects (2) to (5), Of ethyl acetate from ethyl acetate / methyl ethyl ketone mixed system.

(7) The ethyl acetate according to any one of the above aspects (1) to (6), wherein the hydroxylamine salt is used in an amount of 0.4 to 0.6 times equivalent to the methyl ethyl ketone. / Recovery method of ethyl acetate from methyl ethyl ketone mixed system.

(8) The weak acetate is used in an amount of 1 to 1.5 times equivalent to the hydroxylamine salt, and the ethyl acetate / in any one of the above aspects (1) to (7) A method for recovering ethyl acetate from a methyl ethyl ketone mixed system.

  As described above, in the present invention, when methyl ethyl ketone in a solvent mixture containing at least ethyl acetate and methyl ethyl ketone is contacted with free hydroxylamine to convert it to methyl ethyl ketoxime, such free hydroxylamine is converted to hydroxylamine. By generating the salt by contact with a weak base, the pH of the system is increased by the base and the hydrolysis of ethyl acetate is prevented from being promoted, and thus ethanol generated by such hydrolysis is removed. There is no need for any additional process, and the problem that the total acid value of the collected ethyl acetate becomes high due to a small amount of acetic acid contained in the ethyl acetate after distillation is avoided, and there is no risk of quality deterioration. It was possible to demonstrate such features.

  Accordingly, since the ethyl acetate recovered in this way has a low total acid value and high purity, it can be suitably used as various solvents such as thinner. On the other hand, the obtained methyl ethyl ketoxime Can be effectively used as an anti-skinning agent for oil-based paints, a blocking agent for electrodeposition paints, a curing agent raw material for silicone rubber, and the like.

  Also, according to the second aspect of the present invention, an aqueous solution of a hydroxyl base is mixed with an aqueous solution of a weak base to form an aqueous solution of free hydroxylamine, and the aqueous solution of free hydroxylamine is ethyl acetate-methylethylketone. By mixing with a solvent mixture, there is an advantage that the pH of the system can be prevented from being raised by a base, and thus hydrolysis of ethyl acetate in the solvent mixture can be further advantageously suppressed. .

  Furthermore, according to the third aspect of the present invention, the pH of the system can be maintained from neutral to weakly acidic during the oximation reaction of methyl ethyl ketone by using an inorganic alkali having a buffering action as a weak base. It is possible to exhibit the characteristic that it can suppress the hydrolysis of ethyl acetate more advantageously.

  In addition, in the method for recovering ethyl acetate from the ethyl acetate / methyl ethyl ketone mixed system according to the present invention, according to the above fourth aspect of the present invention, the inorganic alkali is sodium carbonate, potassium carbonate, magnesium carbonate, and carbonic acid. By using at least one selected from the group consisting of carbonates of alkali metals and alkaline earth metals, such as calcium, and according to the fifth aspect, the reaction system of methyl ethyl ketone and free hydroxylamine exceeds 40 ° C. In accordance with the sixth to eighth aspects, by controlling the temperature further, the volume of free hydroxylamine aqueous solution relative to the volume of the solvent mixture, the amount of hydroxylamine salt relative to methyl ethyl ketone, the amount of weak base relative to the amount of hydroxylamine salt By setting the Features will become what may be further advantageously exhibited a.

  By the way, in the present invention, the solvent mixture to be separated and recovered is a solvent mixture containing at least ethyl acetate and methyl ethyl ketone. However, such a solvent mixture is particularly limited in the present invention. Rather, in general, waste solvents and the like used in various applications including ethyl acetate and methyl ethyl ketone are targeted. Further, the blending ratio of ethyl acetate and methyl ethyl ketone in the solvent mixture is not particularly limited as long as these two components are mixed. Furthermore, in addition to ethyl acetate and methyl ethyl ketone as described above, various components such as various additives and contaminants may be added to, or contained in such a solvent mixture. There is no problem.

  In order to separate and recover ethyl acetate from the solvent mixture as described above according to the present invention, first, methyl ethyl ketone in the solvent mixture is converted to methyl ethyl ketoxime. That is, in the present invention, the oximation reaction represented by the following reaction formula (I) is allowed to proceed.

  In short, when free hydroxylamine is brought into contact with the solvent mixture, methyl ethyl ketone in the solvent mixture is converted into methyl ethyl ketoxime according to the oximation reaction represented by the above reaction formula (I).

  Here, the free hydroxylamine which causes such an oximation reaction is industrially supplied as a hydroxylamine salt from the viewpoint of stability and safety. Here, examples of the hydroxylamine salt that can be used include hydroxylamine sulfate, hydroxylamine hydrochloride, hydroxylamine phosphate, and the like. Generally, hydroxylamine sulfate is used.

  Moreover, in the ethyl acetate recovery method according to the present invention, advantageously, such a hydroxylamine salt is 0.4 to 0.6 times equivalent, preferably 0.8, to the methyl ethyl ketone in the solvent mixture. It will be used in the range of 41-0.5 times equivalent. When the amount of hydroxylamine salt used is less than the above range, there is a problem that the amount of unreacted methyl ethyl ketone is increased and the purity of the recovered ethyl acetate is lowered. Since unreacted hydroxylamine remains in the reaction system, there is a problem that it is not preferable from the viewpoint of safety.

  In the method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system according to the present invention, free hydroxylamine is generated by contacting the hydroxylamine salt as described above with a weak base. However, it has a great feature.

  That is, in this way, by using a weak base as the base to be contacted with the hydroxylamine salt, the pH of the system in which such a base is mixed is increased, and the hydrolysis of ethyl acetate in the solvent mixture is accelerated. It can be advantageously prevented that it is impregnated, and it can be advantageously suppressed that the reaction product obtained after the oximation reaction is mixed with acetic acid and ethanol produced by the hydrolysis of ethyl acetate. Because it will be. Therefore, there is no particular need for an additional step for removing such ethanol, and a small amount of acetic acid is contained in ethyl acetate separated and recovered by distillation of the reaction product. Such an increase in the total acid value of the recovered ethyl acetate can be advantageously prevented, so that high purity ethyl acetate having a low total acid value is effectively and economically effective. It can be recovered.

  The ethyl acetate recovered in this manner can be effectively used as various solvents such as thinner. Further, even in the case of methyl ethyl ketoxime converted from methyl ethyl ketone by the oximation reaction as described above, since the total acid value is low and high purity methyl ethyl ketoxime can be recovered, such methyl ethyl ketoxime is oily. It can be effectively used as an anti-skinning agent for coatings, a blocking agent for electrodeposition coatings, a curing agent raw material for silicone rubber, and the like, and thus generation of waste can be advantageously suppressed.

  On the other hand, when a strong base is used as a base for generating free hydroxylamine from a hydroxylamine salt, as described above, the release of hydroxylamine is fast, and such a base is mixed. This is not preferable because the pH of the system is increased and the hydrolysis of ethyl acetate in the solvent mixture is accelerated.

  And according to this invention, the inorganic base which has a buffering effect is used advantageously as a weak base used in order to produce | generate free hydroxylamine from a hydroxylamine salt. By using an inorganic alkali having such a buffering action, the pH of the system during the oximation reaction of methyl ethyl ketone can be maintained from neutral to weakly acidic, and thus more advantageous. It is possible to suppress the hydrolysis of ethyl acetate in the solvent mixture.

  Here, examples of such inorganic alkali include alkali metal and alkaline earth metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, and strontium carbonate. In particular, sodium carbonate, potassium carbonate, magnesium carbonate, and calcium carbonate are preferably used. Furthermore, when calcium carbonate is used, the salt produced as a by-product of the neutralization reaction becomes calcium sulfate that is insoluble in water. Therefore, as described later, when a hydroxylamine salt and / or a weak base is used as an aqueous solution. Can be easily separated from water after completion of the reaction, and the recovered water can be used again for the dissolution of hydroxylamine salt or weak base. There is an advantage that the occurrence of can be advantageously suppressed.

  Furthermore, in the method for recovering ethyl acetate according to the present invention, advantageously, the weak base is in the range of 1 to 1.5 times equivalent, preferably 1 to 1.2 times equivalent to the hydroxylamine salt. Will be used. When the amount is less than the above range, hydroxylamine is not completely liberated, and there is a problem that an efficient reaction cannot be sufficiently expected. When the amount is more than the above range, the amount of weak base becomes excessive, There is a problem that the pH of the system rises and hydrolysis of ethyl acetate is promoted, which is not preferable.

  Note that, when such a hydroxylamine salt and a weak base are brought into contact with each other to produce free hydroxylamine, it is generally desirable to mix the hydroxylamine salt and the weak base as aqueous solutions, respectively. Here, as the water used, for example, an aqueous medium such as tap water, distilled water, ion-exchanged water, or other appropriate aqueous solution can be used.

  Here, in the ethyl acetate recovery method according to the present invention, an aqueous solution of hydroxylamine salt is advantageously used at a concentration of 5 to 60% by weight, preferably 10 to 50% by weight. If the concentration is lower than the above concentration, an efficient reaction cannot be expected and the amount of ethyl acetate dissolved in the aqueous phase for recovery increases, so that the recovery rate may decrease, Since the amount of the water phase increases and the amount of water to be treated as wastewater increases, there is a problem that it is not economically preferable. When the concentration is higher than the above-mentioned concentration, a hydroxylamine salt is precipitated, which is not preferable for the reaction. There is a problem.

  Moreover, in the ethyl acetate recovery method according to the present invention, an aqueous solution of a weak base is advantageously used at a concentration of 5 to 30% by weight, preferably 10 to 20% by weight. When the concentration is lower than the above-mentioned concentration, an efficient reaction cannot be expected. As described above, problems such as a decrease in recovery rate due to an increase in the amount of ethyl acetate dissolved in the aqueous phase and a problem such as an increase in the amount of waste water. When the concentration is higher than the above-described concentration, the weak base is not uniformly dissolved, and an efficient reaction may not be expected. Depending on the type of weak base used, the weak base may not be completely dissolved, but there is no problem in the present invention even if it is used in a suspended state.

  In contacting the hydroxylamine salt and the weak base, and further contacting the solvent mixture, no special method is required. For example, the hydroxylamine salt and the weak base can be contacted in any order according to a conventionally known method. After mixing the amine salt into the solvent mixture, the weak base is added thereto to convert the hydroxylamine salt in the solvent mixture to free hydroxylamine, or the weak base is mixed into the solvent mixture and then added to the hydroxyl mixture. Although it can be easily obtained by adding an amine salt to form free hydroxylamine, it is preferable to form a free hydroxylamine by mixing a weak base with the hydroxylamine salt. After freezing, the free hydroxylamine is removed from the solvent. So that allowed to mix in compounds.

  Thus, by first generating free hydroxylamine and then mixing such free hydroxylamine into the solvent mixture, it is advantageously avoided that the pH of the solvent mixture system is increased by the weak base. Therefore, hydrolysis of ethyl acetate in the solvent mixture can be suppressed, and therefore, without any additional step for removing ethanol generated by hydrolysis of such ethyl acetate, It can be more advantageously avoided that acetic acid, which is the other component produced by hydrolysis, is mixed into ethyl acetate and the total acid value of the recovered ethyl acetate is increased. The ethyl acetate recovered in this way is highly pure and has a low total acid value, so that it can be effectively used as various solvents.

  Therefore, in the method for recovering ethyl acetate according to the present invention, as described above, a hydroxylamine salt and a weak base are each preferably used as an aqueous solution, and the aqueous solution of free hydroxylamine obtained by mixing these aqueous solutions. Is mixed with the solvent mixture. Here, the free aqueous hydroxylamine solution varies depending on the amount of the hydroxylamine salt used in the present invention and the type and amount of the weak base, but is generally 0.3 to 2 times the volume of the solvent mixture, preferably 0.5. It will be used at ˜1 times capacity. As described above, if the amount exceeds the above amount, there are problems such as a decrease in recovery due to an increase in the amount of ethyl acetate dissolved in the aqueous phase, an increase in the amount of waste water, and the like. Then, there is a problem that the hydroxylamine salt and the weak base are not uniformly dissolved and an efficient reaction cannot be expected.

  In this way, when free hydroxylamine is brought into contact with methyl ethyl ketone in the solvent mixture, such methyl ethyl ketone is converted into methyl ethyl ketoxime according to the above reaction formula (I), but the recovery of ethyl acetate according to the present invention is performed. In the method, the temperature of the reaction system is preferably controlled so that the reaction between methyl ethyl ketone and free hydroxylamine can proceed without exceeding 40 ° C. For example, as described above, when a free hydroxylamine aqueous solution is obtained from an aqueous hydroxylamine salt solution and an aqueous solution of a weak base, and the free hydroxylamine aqueous solution is mixed with a solvent mixture, the temperature of the reaction system is 40 due to heat generated by the reaction. The aqueous solution can be dropped while adjusting the dropping flow rate of the aqueous solution or adjusting the temperature of the reaction system so as not to exceed ℃. Here, when the temperature exceeds 40 ° C., there is a problem that the decomposition of hydroxylamine is promoted, and there is also a problem that it is not preferable from the viewpoint of safety.

  And an organic phase will be taken out from the reaction product obtained as mentioned above. Here, when the hydroxylamine salt and / or weak base is mixed as an aqueous solution into the solvent mixture, or when free hydroxylamine is mixed as an aqueous solution into the solvent mixture, the organic phase is separated by phase separation of the reaction product. Will be taken out.

  Thereafter, the extracted organic phase is distilled. At that time, the distillation technique and distillation apparatus are not particularly limited. For example, the distillation technique may be atmospheric distillation or vacuum distillation, and any conventionally known technique is employed. Moreover, even if it exists in a distillation apparatus, all well-known various distillation apparatuses, such as a continuous type and a batch type, can be employ | adopted.

  Thus, when the distillation operation is performed, in the reaction product containing methyl ethyl ketoxime and ethyl acetate, prior to the evaporation of methyl ethyl ketoxime, ethyl acetate having a lower boiling point than methyl ethyl ketoxime evaporates from the reaction system. Then, ethyl acetate is taken out.

  The conditions for separating and recovering ethyl acetate by distillation are not particularly limited, but after refluxing at a temperature about the boiling point of ethyl acetate for about 10 minutes to 2 hours, the ethyl acetate is isolated by distillation. In this way, it becomes possible to recover ethyl acetate with higher purity.

  According to the method for separating and recovering ethyl acetate from the ethyl acetate / methyl ethyl ketone mixed system according to the present invention as described above, acetic acid and ethanol are generated by the hydrolysis of ethyl acetate in the solvent mixture, and the ethanol is removed. High-purity ethyl acetate can be effectively used without the need for an additional step for the production of the product and the increase in the total acid value of ethyl acetate recovered by acetic acid mixed in ethyl acetate. And it can be recovered economically. The ethyl acetate recovered in this manner can be effectively used as various solvents such as thinner. Furthermore, even in the case of methyl ethyl ketoxime converted from methyl ethyl ketone remaining after the recovery of ethyl acetate, the total acid value is low and a high purity is obtained, so that it can be used effectively industrially. is there.

  Hereinafter, some examples of the present invention will be shown and the present invention will be more specifically clarified, but the present invention is not limited by the description of such examples. It goes without saying. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. It should be understood that improvements can be made.

  First, as a solvent mixture containing at least ethyl acetate and methyl ethyl ketone, a solvent mixture 1 and a solvent mixture 2 having the compositions shown in Table 1 below were prepared.

Example 1
As shown in Table 2 below, an aqueous solution obtained by dissolving 56.4 g of hydroxylamine sulfate, which is 0.5 times equivalent to methyl ethyl ketone in the solvent mixture, in 131.7 g of ion-exchanged water. And an aqueous solution obtained by dissolving 36.5 g of sodium carbonate in 145.8 g of ion-exchanged water, which is 1.0 times equivalent to the hydroxylamine sulfate, to obtain free hydroxylamine An aqueous solution was obtained.

  Next, 501 g of the solvent mixture 1 prepared above was put into a 1000 ml volume flask equipped with a magnetic stirrer, and the free hydroxylamine aqueous solution prepared as described above was slowly dropped and stirred for about 60 minutes. . At this time, the temperature was adjusted so that the temperature of the reaction system did not exceed 40 ° C. Thereafter, stirring was stopped, and 496 g of the upper organic phase out of the two phases separated into an aqueous phase and an organic phase was recovered using a separatory funnel.

  Moreover, what was shown by FIG. 1 was prepared as a distillation apparatus. In FIG. 1, A is a container for storing a solvent mixture to be subjected to a distillation operation, and here, a 1000 ml capacity flask (distillation can) is adopted. B is a rectifying column. Here, three rectifying columns having an inner diameter of 10 mm filled with a 6 mm square McMahon packing are attached in series in the vertical direction. Further, C is a cooling pipe that liquefies the vapor generated in the flask A. D is a ball valve operated by a reflux ratio timer, and when the ball valve is opened, the evaporant is stored in the receiver G via the branch pipe E and the cooling pipe F. It is configured. In the distillation apparatus shown in FIG. 1, first, the flask A is heated by heating means such as a mantle heater, so that the liquid stored in the flask A becomes vapor. The vapor generated in the flask A is repeatedly subjected to gas-liquid heat exchange by the rectification column B, and gradually rises in the rectification column B. Thereafter, the steam rising to the cooling pipe C is liquefied by the cooling pipe C, and is stored in the receiver G through the branch pipe E and the cooling pipe F while the ball valve D is opened. Yes.

Then, the organic phase recovered as described above is put into a 1000 ml capacity flask A, attached to the lower part of the rectifying column B of the distillation apparatus shown in FIG. 1, heated until the solvent boils, The mixture was refluxed for 30 minutes, and then distillation was started. After the distillation is completed, the distillate is fractionated, the recovery rate is calculated, the purity of the distillate is confirmed by gas chromatography, and the total acid value is determined by automatic acid titration. Apparatus: It confirmed using COM-1500 (made by Hiranuma Sangyo). And the obtained recovery rate, purity, and total acid value were combined with following Table 2, and were shown. The recovery rate was calculated using the following formula.
Recovery rate (%) = [recovered amount (g)] / [charge amount of solvent mixture (g)] × 100

Gas chromatography conditions are as follows.
Equipment: GC-14B (manufactured by Shimadzu Corporation)
Column: Capillary column (CBP1-M50-025)
Stationary phase liquid methyl silicone
Stationary phase liquid thickness 0.25μm
Column material Ultra high purity silica
Column inner diameter 0.22mm
Column length 50m
Carrier gas: helium
Flow rate 2ml / min
Pressure 150kPa
Detector: Hydrogen flame ionization detector (FID)
Hydrogen pressure 50kPa
Air pressure 50kPa
Column temperature: 50 ° C. (1 minute hold) → 5 ° C./minute temperature rise → 145 ° C. (5 minute hold)
Inlet temperature: 200 ° C
Detector temperature: 200 ° C
Sample volume: 0.2 μl (split ratio 1/50)
Designated sensitivity: 10 ^-2
Quantification method: Corrected area percentage method

-Example 2-
Example 1 was repeated except that calcium carbonate was used as a base for generating free hydroxylamine from hydroxylamine sulfate. The obtained results are shown in Table 2 below.

-Example 3-
The same procedure as in Example 1 was conducted except that the amount of hydroxylamine sulfate added was 0.41 times equivalent to methyl ethyl ketone. The obtained results are shown in Table 2 below.

Example 4
The same procedure as in Example 1 was performed except that the amount of weak base added to generate free hydroxylamine from hydroxylamine sulfate was 1.1 times equivalent to that of hydroxylamine sulfate. The obtained results are shown in Table 2 below.

-Example 5
Example 1 was repeated except that the solvent mixture 2 was used as the solvent mixture. The obtained results are shown in Table 2 below.

-Example 6
Example 5 was repeated except that calcium carbonate was used as a base for generating free hydroxylamine from hydroxylamine sulfate. The obtained results are shown in Table 2 below.

-Comparative Example 1-
Example 1 was repeated except that sodium hydroxide was used in an amount twice as much as that of hydroxylamine sulfate as a base for generating free hydroxylamine from hydroxylamine sulfate. The obtained results are shown in Table 2 below.

  As is clear from the results in Table 2, in Comparative Example 1 in which sodium hydroxide, which is a strong base, was used as a base for generating free hydroxylamine from hydroxylamine sulfate, it was released from hydroxylamine sulfate. Compared to Examples 1 to 6 in which a weak base was used as a base for generating hydroxylamine, the total acid value of recovered ethyl acetate and recovered methyl ethyl ketoxime was high. On the other hand, in Examples 1 to 6 where a weak base was used as a base for generating free hydroxylamine from hydroxylamine sulfate, the total acid values of the recovered ethyl acetate and methylethylketoxime were low, The purity and recovery rate of the recovered ethyl acetate and methyl ethyl ketoxime were also comparable to those of Comparative Example 1.

It is a schematic explanatory drawing of the distillation apparatus used in the Example.

Explanation of symbols

A: Distillation can B: Rectification tower C: Cooling pipe D: Ball valve E: Branch pipe F: Cooling pipe G: Receiver

Claims (8)

  A method of separating and recovering ethyl acetate from a solvent mixture containing at least ethyl acetate and methyl ethyl ketone, wherein free hydroxylamine is produced by contact with a hydroxylamine salt and a weak base. The methyl ethyl ketone in the solvent mixture is contacted and reacted with free hydroxylamine to convert the methyl ethyl ketone to methyl ethyl ketoxime, and then the organic phase containing ethyl acetate is distilled together with the methyl ethyl ketoxime to obtain ethyl acetate. A method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system characterized by separating.   The aqueous solution of the weak amine is mixed with the aqueous solution of the hydroxylamine salt to form an aqueous solution of the free hydroxylamine, and the aqueous solution of free hydroxylamine is mixed with the solvent mixture, thereby the methylethylketoxime. The method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system according to claim 1, wherein a reaction product containing is formed, and the organic phase is taken out by phase separation of the reaction product.   The method for recovering ethyl acetate from an ethyl acetate / methyl ethyl ketone mixed system according to claim 1 or 2, wherein the weak base is an inorganic alkali having a buffering action.   4. The inorganic alkali is at least one selected from the group consisting of carbonates of alkali metals and alkaline earth metals, such as sodium carbonate, potassium carbonate, magnesium carbonate, and calcium carbonate. For recovery of ethyl acetate from the ethyl acetate / methyl ethyl ketone mixed system described in 1).   The temperature of the reaction system of the methyl ethyl ketone and the free hydroxylamine is controlled so as not to exceed 40 ° C. The ethyl acetate / methyl ethyl ketone mixed system according to any one of claims 1 to 4, A method for recovering ethyl acetate.   The ethyl acetate / methyl ethyl ketone according to any one of claims 2 to 5, wherein the free hydroxylamine aqueous solution is used in a volume of 0.3 to 2 times the volume of the solvent mixture. Recovery method of ethyl acetate from the mixed system.   The ethylamine / methyl ethyl ketone mixed system according to any one of claims 1 to 6, wherein the hydroxylamine salt is used in an amount of 0.4 to 0.6 times equivalent to the methyl ethyl ketone. Of recovering ethyl acetate. The ethyl acetate / methyl ethyl ketone mixed system according to any one of claims 1 to 7, wherein the weak base is used in an amount of 1 to 1.5 times equivalent to the hydroxylamine salt. A method for recovering ethyl acetate.