Cyclohexanedione crystallization purification method

Abstract

The invention belongs to the technical field of recrystallization, and particularly relates to a method for crystallizing and purifying cyclohexanedione. And adding an organic solvent into the crude cyclohexanedione, heating, desolventizing under negative pressure, carrying water under negative pressure by using the organic solvent, preserving heat, filtering, adding a poor solvent into the filtrate, cooling, crystallizing, and centrifuging to obtain the cyclohexanedione. The purity of the cyclohexanedione product obtained through the recrystallization method is 98% or above, the yield is 96% or above, the waste water treatment amount is reduced, cyclohexanedione does not need to be recycled from waste water, the used solvent can be recycled, the production cost is greatly reduced, the process is simple, and the good industrial application value is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of recrystallization, and in particular relates to a method for crystallizing and purifying cyclohexanedione. Background Art

[0002] 1,3-Cyclohexanedione is an important chemical raw material. It can be used to prepare the cardiovascular and cerebrovascular disease and hypertension specific drug carvedilol and the antiemetic drug anthracensetron. It is also an intermediate for the herbicides mesotrione, tembotrione and mesotrione. It can also be used in the synthesis of many other organic compounds.

[0003] At present, there are two main synthesis processes for 1,3-cyclohexanedione. CN 111302909 A discloses a method for preparing 1,3-cyclohexanedione, in which resorcinol is subjected to high-pressure hydrogenation to obtain sodium salt of cyclohexanedione, and 1,3-cyclohexanedione and acidified mother liquor are obtained by acidification and crystallization. The acidified mother liquor is complexed, and the 1,3-cyclohexanedione product is obtained by multiple extractions, concentration, and crystallization. CN 115703700 A discloses a method for condensation of acetobutyric acid ester, in which acetoacetic acid ester and acrylate are used as raw materials in the presence of an organic solvent, an addition product is obtained by Michael addition reaction, the addition reaction liquid and a cyclizing agent undergo Claisen cyclization reaction to obtain a cyclization product, and then the 1,3-cyclohexanedione product is obtained by decarboxylation, esterification, acidification, and refining. Compared with the hydrogenation method of resorcinol, this process has simple reaction conditions, high safety, does not use metal catalysts, and reduces the cost of raw materials.

[0004] In the current production, acetone and acrylate are used as raw materials to produce 1,3-cyclohexanedione by intermittent method. This route first obtains the addition product 5-oxohexanoic acid methyl ester through Michael addition reaction, and then the addition reaction liquid is subjected to Claisen cyclization, acidification and purification to obtain 1,3-cyclohexanedione product.

[0005] Both synthesis methods have the same post-processing crystallization method. The crystallization process currently used mainly involves adding acid dropwise to an aqueous solution of 1,3-cyclohexanedione sodium salt, cooling the solution to 0-5°C, growing crystals, and centrifuging the solution.

[0006] Patent CN1275922C transfers a 50°C sodium salt aqueous solution into a container, adds concentrated hydrochloric acid dropwise with stirring, acidifies at room temperature, cools the reaction solution to 0-5°C, and crystallizes, filters, and dries.

[0007] Patent CN106083545 A The acidification step is divided into two stages. The first stage is to add hydrochloric acid dropwise, and the temperature is controlled at 20-25°C; the second stage is to cool and crystallize, and the temperature drops from 20°C to 5-10°C.

[0008] Patent CN110818540A adds hydrochloric acid dropwise to a sodium salt aqueous solution, controls the reaction temperature at 25-30°C, and ends at a pH of 2-2.5, cools to 0-5°C, keeps warm for 5-6 hours, and then acidifies and rearranges, and then centrifuges and dries.

[0009] However, the main problem of the existing process is that the crude cyclohexanedione obtained by acidification crystallization contains more salt, and the purity of cyclohexanedione after direct drying is often low, only 85% to 90%, and further recrystallization with water is required to obtain cyclohexanedione with higher purity. However, when recrystallization is carried out with water, more cyclohexanedione is dissolved in water and needs to be further recovered. The process is relatively cumbersome, and the amount of wastewater that needs to be treated increases, which increases the cost. Therefore, further optimizing the recrystallization process is an urgent problem to be solved. Summary of the invention

[0010] In view of the problems existing in the existing recrystallization process of cyclohexanedione, the object of the present invention is to provide a method for crystallizing and purifying cyclohexanedione.

[0011] To achieve the above object, the technical solution adopted by the present invention is:

[0012] A method for purifying cyclohexanedione by crystallization comprises the following steps: adding an organic solvent to crude cyclohexanedione, heating it, desolventizing it under negative pressure, using the organic solvent to carry water under negative pressure, and then keeping the temperature and filtering it; adding a poor solvent to the filtrate, cooling it for crystallization, and centrifuging it to obtain purified cyclohexanedione.

[0013] The mother liquor is centrifuged to desolventize and recover the organic solvent for recycling.

[0014] The cyclohexanedione may be 1,2-cyclohexanedione, 1,3-cyclohexanedione or 1,4-cyclohexanedione.

[0015] Furthermore, after adding a poor solvent, the filtrate is cooled to 0-10°C at a rate of 5-20°C / h, and then kept warm for 0.5-2.0h for crystallization, and centrifuged to obtain cyclohexanedione.

[0016] Preferably, after adding a poor solvent, the filtrate is cooled to 0-4°C at a rate of 10-15°C / h, then kept warm for 0.5-2.0h for crystallization, and centrifuged to obtain cyclohexanedione.

[0017] The organic solvent is one or more of chloroform, dichloromethane, ethylene dichloride, methyl isobutyl ketone, methyl tert-butyl ketone, and ethyl acetate, preferably methyl isobutyl ketone or ethylene dichloride.

[0018] The poor solvent is one or more of benzene, toluene, xylene, n-hexane, cyclohexane, and n-heptane, preferably n-hexane or toluene.

[0019] The amount of the organic solvent is 2.0 to 7.0 times, preferably 2.5 to 4.0 times, of the crude cyclohexanedione.

[0020] The negative pressure desolventizing has a pressure of -0.08 MPa to -0.1 MPa, preferably -0.085 MPa to -0.1 MPa.

[0021] The ratio of the organic solvent to the poor solvent is 0.5:1 to 4:1, preferably 1:1 to 2:1.

[0022] The temperature at which the organic solvent is added to the crude cyclohexanedione is 30 to 70°C, preferably 35 to 50°C.

[0023] The organic solvent is charged with water under negative pressure and then kept warm for 0.5 to 2.0 hours, preferably 0.5 to 1.0 hours, before filtering.

[0024] The present invention has the following significant advantages:

[0025] The purity of the cyclohexanedione product obtained by the recrystallization method of the present invention is above 98%, and the yield is also above 96%, which reduces the amount of wastewater treatment, does not need to consider the recovery of cyclohexanedione from the wastewater again, and the used solvent can also be recycled, which greatly reduces the production cost, and the process is relatively simple, and has good industrial application value.

[0026] The method of the invention improves the sticky wall-binding state of the material in the crystallization process, effectively removes water and sodium chloride in crude cyclohexanedione, so that cyclohexanedione meets commercial requirements, and the used solvent can be recycled, which is beneficial to the green industrialization of cyclohexanedione. DETAILED DESCRIPTION

[0027] In order to better understand the technical solution of the present invention, the above contents of the present invention are further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples.

[0028] Example 1

[0029] Preparation of cyclohexanedione:

[0030] Add 2400g of cyclohexanedione sodium salt aqueous solution, add 1024g of 30% hydrochloric acid dropwise, control the temperature of adding hydrochloric acid at 25-30°C, the pH value after acidification is 2-2.5, cool to 0°C, keep warm for 1h, and then centrifuge to obtain 1011.2g of cyclohexanedione with a content of 70.2%, a moisture content of 21.5%, and a sodium chloride content of 5.7%.

[0031] Example 2

[0032] 100 g of wet-base cyclohexane obtained in Example 1 was added, 250 g of methyl isobutyl ketone was added, the negative pressure was brought to -0.095 MPa, the solvent was refluxed at 40 ° C, 20 g of water was separated from the separator, and after being kept at 40 ° C for 30 min, it was filtered while hot to filter out insoluble matter, 250 g of n-hexane was added to the filtrate, and the temperature was slowly cooled to 0 ° C at a cooling rate of 10 ° C / h. The temperature was kept for 30 min and centrifuged to obtain 71.9 g of cyclohexane, with a content of 98.1%, a yield of 96.9%, 0.31% sodium chloride, and 0.12% moisture.

[0033] Example 3

[0034] 100 g of wet-base cyclohexanedione obtained in Example 1 was added, 250 g of methyl isobutyl ketone was added, the mixture was desolventized and refluxed at 40 ° C with negative pressure to -0.095 MPa, 20 g of water was separated from the separator, and the mixture was kept warm at 40 ° C for 30 min, filtered while hot, insoluble matter was filtered out, 250 g of toluene was added to the filtrate, and the mixture was slowly cooled to 0 ° C, the cooling rate was controlled at about 10 ° C / h, and the mixture was kept warm for 30 min. 68.6 g of cyclohexanedione was obtained by centrifugation, with a content of 98.7%, a yield of 97.5%, 0.36% sodium chloride, and 0.20% moisture.

[0035] Example 4

[0036] 100 g of cyclohexanedione obtained in Example 1 was added, 400 g of methyl isobutyl ketone was added, the negative pressure was brought to -0.095 MPa, the solvent was refluxed at 40 ° C, 20 g of water was separated from the separator, and the insoluble matter was filtered out after being kept at 40 ° C for 30 min. 200 g of toluene was added to the filtrate, and the temperature was slowly lowered at a cooling rate of about 10 ° C / h, cooled to 0 ° C, kept warm for 30 min, and centrifuged to obtain 70.0 g of cyclohexanedione, with a content of 99.1%, a yield of 98.1%, 0.23% sodium chloride, and 0.11% moisture.

[0037] Example 5

[0038] 100 g of wet-base cyclohexane obtained in Example 1 was added, 400 g of ethylene dichloride was added, the negative pressure was brought to -0.085 MPa, the solvent was refluxed at 35 ° C, 20 g of water was separated from the separator, the temperature was raised to 40 ° C and kept warm for 30 min, and then filtered while hot to remove insoluble matter. 200 g of toluene was added to the filtrate, and the temperature was slowly cooled to 0 ° C. The cooling rate was controlled at 10 ° C / h, and the temperature was kept for 30 min. 70.1 g of cyclohexanedione was obtained by centrifugation, with a content of 99.1%, a yield of 98.3%, 0.30% sodium chloride, and 0.10% moisture.

[0039] Example 6

[0040] 100 g of wet-base cyclohexane obtained in Example 1 was added, 250 g of dichloromethane was added, the negative pressure was brought to -0.085 MPa, the solvent was refluxed at 35 ° C, 20 g of water was separated from the separator, and after being kept at 40 ° C for 30 min, it was filtered while hot to filter out insoluble matter, and the filtrate was cooled after adding 250 g of n-hexane, and slowly cooled to 0 ° C, the cooling rate was 10 ° C / h, and the temperature was kept for 30 min. 68.8 g of cyclohexane was obtained by centrifugation, the content was 98.2%, the yield was 96.4%, it contained 0.6% sodium chloride, and the moisture content was 0.18%.

[0041] Comparative Example 1

[0042] The difference from Example 5 is that the amount of toluene added to the filtrate is changed to 100 g, and the other conditions are the same as those of Example 5. After centrifugation, 60.2 g of cyclohexanedione is obtained, with a content of 99.1%, a yield of 84.4%, 0.25% sodium chloride, and 0.13% moisture. The result cannot achieve the effect of Example 5.

[0043] Comparative Example 2

[0044] The difference from Example 5 is that the amount of methyl isobutyl ketone added is changed to 500 g, and the other conditions are the same as those of Example 5. After centrifugation, 58.8 g of cyclohexanedione is obtained, with a content of 99.3%, a yield of 82.4%, 0.15% sodium chloride, and 0.10% moisture. The result cannot achieve the effect of Example 5.

[0045] Comparative Example 3

[0046] The difference from Example 5 is that the vacuum degree of the system is changed to -0.080 MPa, resulting in a reflux temperature of the system of 70°C. The other conditions are the same as those of Example 5. After centrifugation, 54.4 g of cyclohexanedione is obtained, with a content of 93.1%, a yield of 76.2%, 0.25% sodium chloride, and 0.10% moisture. The result cannot achieve the effect of Example 5.

[0047] Comparative Example 4

[0048] The difference from Example 5 is that the cooling rate is changed to 25°C / h, and the other conditions are the same as those of Example 5. After centrifugation, 70.2 g of cyclohexanedione is obtained, with a content of 89.1%, a yield of 98.2%, 0.23% sodium chloride, and 0.11% moisture. The result cannot achieve the effect of Example 5.

[0049] It can be seen from the above embodiments and comparative examples that the present invention simply and effectively removes water and sodium chloride in crude cyclohexanedione by controlling important condition parameters in the recrystallization and purification process, solves the problem that the material is easily solidified during the crystallization process of cyclohexanedione, improves the material state during the crystallization process, and avoids equipment damage; at the same time, the purity and yield of cyclohexanedione are also guaranteed. Comparative Example 1 reduces the amount of cyclohexanedione precipitation due to the reduction of the amount of poor solvent added, and the cyclohexanedione yield decreases greatly; Comparative Example 2 changes the amount of organic solvent added, which increases the dissolution of cyclohexanedione and impurities in the organic solvent, reduces the amount of precipitation during the cyclohexanedione crystallization process, and also reduces the precipitation of impurities. Although the cyclohexanedione content is increased, the yield is greatly reduced; In addition, Comparative Example 3 changes the vacuum degree, which leads to a high reflux temperature of the system solvent, so that cyclohexanedione is decomposed at high temperature, and impurities such as 4-acetylbutyric acid are produced, thereby causing low purity and low yield; Comparative Example 4 increases the crystallization cooling rate of cyclohexanedione, and the crystallization process cyclohexanedione precipitation rate is fast, and the material has violent precipitation and solidification phenomena, resulting in low purity and low yield of cyclohexanedione. Therefore, the cyclohexanedione obtained by the recrystallization method of the present invention has a high purity, more than 98%, and a yield of 96%, which avoids the recovery of cyclohexanedione from water.

[0050] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for crystallizing and purifying cyclohexanedione, characterized in that: An organic solvent is added to the crude cyclohexanedione to increase the temperature, desolventize under negative pressure, and water is carried out by the organic solvent under negative pressure, and then the temperature is kept and filtered. After adding a poor solvent to the filtrate, the temperature is lowered and crystallized, and the cyclohexanedione is obtained by centrifugation.

2. The method according to claim 1, characterized in that After adding a poor solvent, the filtrate is cooled to 0-10°C at a rate of 5-20°C / h, then kept warm for 0.5-2.0h for crystallization, and centrifuged to obtain cyclohexanedione.

3. The method according to claim 1, characterized in that The organic solvent is one or more of chloroform, dichloromethane, dichloroethane, methyl isobutyl ketone, methyl tert-butyl ketone and ethyl acetate.

4. The method according to claim 1, characterized in that The poor solvent is one or more of benzene, toluene, xylene, n-hexane, cyclohexane and n-heptane.

5. The method according to claim 1, characterized in that The amount of the organic solvent is 2.0-7.0 times that of the crude cyclohexanedione.

6. The method according to claim 1, characterized in that The negative pressure desolventizing has a pressure of -0.08MPa to -0.1MPa.

7. The method according to claim 1, characterized in that The usage ratio of organic solvent to poor solvent is 0.5:1 to 4:

1.

8. The method according to claim 1, characterized in that Add an organic solvent to the crude cyclohexanedione and raise the temperature to 30-70°C.

9. The method according to claim 1, characterized in that: The organic solvent is carried with water under negative pressure and kept warm for 0.5 to 2.0 hours before filtering.