A post-treatment method for oxime ether solutions

Abstract

The application provides a post-treatment method of oxime ether solution, and belongs to the technical field of post-treatment of organic synthesis. The post-treatment method comprises the following steps: filtering a butanone oxime methyl ether solution generated in a reaction to obtain a filtrate; adding an acid into the filtrate, adjusting the pH value of the filtrate to 5.0-7.0, and then stirring to obtain a neutralized solution; performing a freezing treatment on the neutralized solution to obtain a frozen solution; and filtering the frozen solution by using a pervaporation membrane to obtain a post-treated oxime ether solution. Through the synergistic effect of neutralizing alkalinity, low-temperature inhibition of reaction activity and efficient dehydration, the generation of by-products butanone and dangerous chemicals methylamine and methylhydrazine can be significantly reduced, the yield and purity of the oxime ether are improved, the safety and environmental risks are reduced, and the method is suitable for the synthesis of downstream products such as methoxylamine hydrochloride.

Description

Technical Field

[0001] This invention relates to the field of post-processing technology in organic synthesis, and more particularly to a post-processing method for oxime ether solutions. Background Technology

[0002] Oxime ethers are an important class of organic synthesis intermediates, widely used in pesticides, pharmaceuticals, and fine chemicals. For example, methyl ethyl ketone oxime, a key intermediate, can be hydrolyzed to prepare methoxyamine hydrochloride, which is an important raw material for the synthesis of antibiotics and herbicides. With the development of green chemical engineering technologies, the efficient synthesis and purification techniques of oxime ethers have become a research hotspot.

[0003] While the haloalkanes method is widely used in the industrial production of oxime ethers, the trace amounts of water and sodium hydroxide remaining in the system after the reaction can induce hydrolysis and other side reactions in the oxime ether during subsequent storage and processing. This not only reduces the yield but also generates hazardous substances such as methylamine, posing a serious threat to safe production and product quality. Furthermore, because the boiling points of the oxime ether are extremely close to those of water, traditional distillation separation faces technical bottlenecks of low efficiency and high energy consumption.

[0004] Therefore, there is an urgent need to develop a new and efficient method for the dehydration and stabilization of oxime ether solutions. Summary of the Invention

[0005] The purpose of this invention is to address the problems of high production of byproducts (butanone, methylamine, methylhydrazine, N-hydroxy-N-methylmethylamine, etc.) and poor safety and low yield caused by residual alkalinity and moisture in oxime ether solutions in the prior art, and to provide a post-treatment method for oxime ether solutions.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a post-treatment method for oxime ether solutions, comprising the following steps: 1) The butanone oxime methyl ether solution generated in the reaction was filtered to obtain the filtrate; 2) Add acid to the filtrate, adjust the pH of the filtrate to 5.0~7.0, and then stir to obtain a neutralized solution; 3) Freeze the neutralized solution to obtain a frozen solution; 4) The freezing solution was filtered using a pervaporation membrane to obtain a post-treated oxime ether solution.

[0007] Preferably, the butanone oxime methyl ether solution is generated by reacting chloromethane, butanone oxime, and sodium hydroxide in a solvent.

[0008] Preferably, filtration is performed within 1-2 hours after the reaction to produce the butanone oxime methyl ether solution. Filtration is used to remove solid impurities, including sodium chloride and excess sodium hydroxide.

[0009] Preferably, the filtration in step 1) is vacuum filtration or pressurized filtration, and the filtration medium is a ceramic filter membrane or a polypropylene filter cloth.

[0010] Preferably, the acid in step 2) is one or more of hydrochloric acid, citric acid and acetic acid; the stirring time is 25-35 min.

[0011] Preferably, the freezing temperature in step 3) is -25~0℃, and the freezing time is 1~3h.

[0012] Preferably, the permeation side pressure of the pervaporation membrane in step 4) is 100~2000Pa, and the filtration temperature is 20~40℃.

[0013] Preferably, the water content of the post-treatment oxime ether solution in step 4) is ≤0.1wt%.

[0014] The beneficial effects of this invention are: 1) This invention optimizes the post-processing steps, combining neutralization, freezing, and membrane separation technologies to specifically inhibit the alkaline hydrolysis of oxime ethers. Its core principle is as follows: acid neutralization eliminates the catalytic effect of residual alkali; freezing lowers the reaction activation energy to suppress side reaction rates; and membrane separation efficiently removes water to reduce the hydrolysis medium. The synergistic effect of these three technologies significantly reduces byproduct formation and improves product stability. Simultaneously, it simplifies subsequent purification processes, reduces costs and risks, and has promising prospects for industrial application.

[0015] 2) This invention, through the synergistic effect of neutralizing alkalinity, inhibiting reactivity at low temperature and efficient dehydration, can significantly reduce the generation of by-products methyl ketone and hazardous chemicals methylamine and methylhydrazine, improve the yield and purity of oxime ethers, reduce safety and environmental risks, and is applicable to the synthesis of downstream products such as methoxyamine hydrochloride. Detailed Implementation

[0016] This invention provides a post-treatment method for oxime ether solutions, comprising the following steps: 1) The butanone oxime methyl ether solution generated in the reaction was filtered to obtain the filtrate; 2) Add acid to the filtrate, adjust the pH of the filtrate to 5.0~7.0, and then stir to obtain a neutralized solution; 3) Freeze the neutralized solution to obtain a frozen solution; 4) The freezing solution was filtered using a pervaporation membrane to obtain a post-treated oxime ether solution.

[0017] In this invention, the butanone oxime methyl ether solution is generated by reacting chloromethane, butanone oxime, and sodium hydroxide in a solvent; the solvent is preferably one or more of dimethyl sulfoxide, tetrabutylammonium bromide, ethylbenzene, o-xylene, n-hexane, tert-butanol, methanol, diethylene glycol dimethyl ether, butanone, ethylene glycol dimethyl ether, and 1,3-dimethyl-2-imidazolinone.

[0018] In this invention, filtration is performed within 1 to 2 hours after the reaction to generate the butanone oxime methyl ether solution, preferably within 1.5 hours. The filtration is used to remove solid impurities, including sodium chloride and excess sodium hydroxide.

[0019] In this invention, the filtration in step 1) is preferably vacuum filtration or pressurized filtration, and the filtration medium is preferably a ceramic filter membrane or a polypropylene filter cloth.

[0020] In this invention, the acid in step 2) is preferably one or more of hydrochloric acid, citric acid and acetic acid; the stirring time is preferably 25-35 min, more preferably 27-32 min, and even more preferably 30 min.

[0021] In this invention, the acid added in step 2) is used to neutralize the residual alkali.

[0022] In this invention, the freezing temperature in step 3) is preferably -25~0℃, more preferably -20~-10℃, and even more preferably -15℃, and the freezing time is preferably 1~3h, more preferably 1.5~2.5h, and even more preferably 2h.

[0023] In this invention, the permeation side pressure of the pervaporation membrane in step 4) is preferably 100~2000Pa, more preferably 200~1000Pa, and even more preferably 500~800Pa. The filtration temperature is preferably 20~40℃, more preferably 25~35℃, and even more preferably 30℃.

[0024] In this invention, a pervaporation membrane is used to remove water from the freezing solution.

[0025] In this invention, the water content of the post-treatment oxime ether solution in step 4) is preferably ≤0.1wt%, more preferably ≤0.05wt%, and even more preferably ≤0.02wt%.

[0026] This invention involves immediately filtering, precisely adjusting the pH, and cryogenically freezing the oxime ether solution after the reaction of the methyl ethyl ketone (MEK) oxime methyl ether solution. This suppresses the alkaline catalytic environment at the source, significantly reducing oxime ether hydrolysis and side reactions. Then, a pervaporation membrane is used for efficient dehydration of the oxime ether solution. This membrane technology is independent of the differences in boiling points of the components, utilizing the membrane's preferential selectivity for water molecules to achieve efficient separation of oxime ethers with boiling points close to water. The two methods work synergistically to ensure both the reaction safety and separation economy of the system.

[0027] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0028] In the examples and comparative examples, the preparation method of the butanone oxime methyl ether reaction solution was as follows: 87.2 g (1 mol) of butanone oxime, 200 mL of tert-butanol, and 60 g (1.5 mol) of sodium hydroxide were added to a 2 L high-pressure reactor. After sealing, 60 g (1.2 mol) of chloromethane was introduced, and the reaction was carried out at 10 °C for 3 h to obtain the butanone oxime methyl ether reaction solution.

[0029] Example 1

[0030] Within 1 hour after the reaction to produce methyl ethyl ketone oxime ether was completed, the solution was filtered under reduced pressure for 30 minutes using a 0.2 μm ceramic membrane at a vacuum of -0.085 MPa to remove sodium chloride and excess sodium hydroxide solids, yielding 300 mL of filtrate. 3 wt% hydrochloric acid was added dropwise to the filtrate to adjust the pH to 6.0, and the mixture was stirred for 30 minutes to obtain a neutralized solution. The neutralized solution was then transferred to a -20°C environment for freezing for 2 hours. After freezing, the solution was filtered through a polyvinyl alcohol (PVA) membrane (PVA membrane separation layer pore size less than 2 nm) at an osmotic pressure of 800 Pa and a temperature of 30°C to obtain the post-treated oxime ether solution.

[0031] Example 2

[0032] Within 1.5 hours after the reaction to produce methyl ethyl ketone oxime ether was completed, the solution was filtered under reduced pressure for 30 minutes using a 0.2 μm ceramic membrane at a vacuum of -0.085 MPa to remove sodium chloride and excess sodium hydroxide solids, yielding 300 mL of filtrate. 3 wt% acetic acid was added dropwise to the filtrate to adjust the pH to 5.5, and the mixture was stirred for 30 minutes to obtain a neutralized solution. The neutralized solution was then transferred to a -15°C environment for freezing for 2 hours. After freezing, the solution was filtered through a polyvinyl alcohol (PVA) membrane (PVA membrane separation layer pore size less than 2 nm) at an osmotic pressure of 600 Pa and a temperature of 35°C to obtain the post-treated oxime ether solution.

[0033] Example 3

[0034] Within 1 hour after the reaction solution containing methyl ethyl ketone oxime was completed, the solution was filtered under reduced pressure for 30 minutes using a 0.2 μm polypropylene filter cloth at a vacuum degree of -0.085 MPa to remove sodium chloride and excess sodium hydroxide solids, yielding 300 mL of filtrate. 4 wt% hydrochloric acid was added dropwise to the filtrate to adjust the pH to 6.5, and the solution was stirred for 30 minutes to obtain a neutralized solution. The neutralized solution was then transferred to a -22°C environment for freezing for 1.5 hours. After freezing, the solution was filtered through a polyvinyl alcohol (PVA) membrane (PVA membrane separation layer pore size less than 2 nm) at an osmotic pressure of 200 Pa and a temperature of 25°C to obtain a post-treated oxime ether solution.

[0035] Comparative Example 1

[0036] The pervaporation membrane filtration step in Example 1 is omitted.

[0037] Comparative Example 2

[0038] The freezing process of Example 1 is omitted, and the neutralized solution is directly filtered through a pervaporation membrane at 1.0 MPa and 30°C.

[0039] Comparative Example 3

[0040] The freezing process and the pervaporation membrane filtration process of Example 1 are omitted.

[0041] Comparative Example 4

[0042] The step of adding hydrochloric acid to adjust the pH value in Example 1 is omitted. 300 mL of filtrate is directly transferred to a -20°C environment for freezing treatment for 2 h. After freezing, the solution is filtered through a pervaporation membrane at 1.0 MPa and 30°C.

[0043] Comparative Example 5

[0044] The steps of adding hydrochloric acid to adjust the pH value and filtering through a pervaporation membrane in Example 1 are omitted. 300 mL of filtrate is directly transferred to a -20 °C environment for freezing treatment for 2 h.

[0045] Comparative Example 6

[0046] The steps of adding hydrochloric acid to adjust the pH value and freezing treatment in Example 1 are omitted. 300 mL of filtrate is directly filtered through a pervaporation membrane under a permeation pressure of 600 Pa and a temperature of 30 °C.

[0047] Comparative Example 7

[0048] Within 1 hour after the reaction to generate methyl ethyl ketone oxime was completed, sodium chloride and excess sodium hydroxide solids were removed by vacuum filtration using a 0.2 μm ceramic filter membrane to obtain 300 mL of filtrate; the steps of adding hydrochloric acid to adjust the pH value, freezing treatment and pervaporation membrane filtration in Example 1 were omitted.

[0049] Samples of the butanone oxime methyl ether reaction solution (before treatment) and the post-treatment oxime ether solution (after treatment) of Example 1 and Comparative Examples 1-7 were taken respectively. The water content, methylamine content, methylhydrazine content and butanone content in the butanone oxime methyl ether reaction solution and the post-treatment oxime ether solution were detected by gas chromatography. The results are shown in Table 1.

[0050] Table 1. Detection results of Example 1 and Comparative Examples 1-7

[0051] The above embodiments demonstrate that by optimizing the post-processing technology, the present invention can effectively suppress side reactions, significantly improve the purity and yield of oxime ethers, reduce safety and environmental risks, and is suitable for industrial applications.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A post-treatment method for oxime ether solutions, characterized in that, Includes the following steps: 1) The butanone oxime methyl ether solution generated in the reaction was filtered to obtain the filtrate; 2) Add acid to the filtrate, adjust the pH of the filtrate to 5.0~7.0, and then stir to obtain a neutralized solution; 3) Freeze the neutralized solution to obtain a frozen solution; 4) The freezing solution was filtered using a pervaporation membrane to obtain a post-treated oxime ether solution.

2. The post-processing method according to claim 1, characterized in that, The methyl ether solution of butanone oxime is produced by reacting chloromethane, butanone oxime, and sodium hydroxide in a solvent.

3. The post-processing method according to claim 1 or 2, characterized in that, The reaction is completed within 1-2 hours after the formation of the butanone oxime methyl ether solution. The filtration is used to remove solid impurities, including sodium chloride and excess sodium hydroxide.

4. The post-processing method according to claim 3, characterized in that, Step 1) The filtration is vacuum filtration or pressure filtration, and the filtration medium is a ceramic filter membrane or a polypropylene filter cloth.

5. The post-processing method according to claim 1, characterized in that, Step 2) The acid is one or more of hydrochloric acid, citric acid and acetic acid; the stirring time is 25~35 minutes.

6. The post-processing method according to claim 1 or 5, characterized in that, Step 3) The freezing temperature is -25~0℃, and the freezing time is 1~3h.

7. The post-processing method according to claim 6, characterized in that, Step 4) The pervaporation membrane has a permeation side pressure of 100~2000Pa and a filtration temperature of 20~40℃.

8. The post-processing method according to claim 7, characterized in that, Step 4) The water content of the post-treatment oxime ether solution is ≤0.1wt%.

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