Method for separating and recycling kung-fu acid intermediate

Abstract

The invention relates to a separation and recovery method for a kung-fu acid intermediate. A cyclization compound can be recovered by adding an extracting agent into a cyclization reaction material. The method is simple to operate, time-saving and labor-saving, the extracting agent and the cyclization compound can be recycled step by step in a simple distillation manner subsequently, the extracting agent can be repeatedly used, the cyclization compound can be directly used for preparing the kung fu acid in the next reaction step, the discharge amount of three wastes is greatly reduced, and industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to the field of post-treatment of organic intermediate synthesis, and in particular to a method for separating and recovering kung fu acid intermediates. Background Art

[0002] The synthesis method of Kung Fu acid reported in the literature is to use methyl benzoate and 1,1,1-trifluorotrichloroethane as raw materials, and prepare it through four steps of addition, cyclization, saponification, and acidification to form salts.

[0003] After the above-mentioned cyclization reaction is completed and the solvent is distilled, there are a large number of extremely fine inorganic salt particles (usually sodium chloride or potassium chloride) and a certain concentration of DMF or DMAC remaining in the reaction system, forming an emulsified mixture, as well as a large amount of tar. Because the concentration of the three wastes is too high, it cannot be directly processed. It is usually necessary to add a large amount of water to dilute and then process to remove the salt (sodium chloride generated by the reaction) and impurities (mainly residual solvent DMF or DMAC and a small amount of other impurities) in the reactants, because the presence of salt and impurities will have an adverse effect on the next step of hydrolysis, saponification and acidification reaction. In this operation, the amount of wastewater generated by washing salt is large, which increases the discharge of the three wastes in disguised form and increases the processing cost. When the brine is transferred, the high concentration of salt is easy to block the pipeline, which seriously affects the production cycle and reduces production efficiency.

[0004] In the prior art CN112125794A, after the organic solvent is removed by distillation in the cyclization reaction, solid-liquid separation is achieved by high-speed centrifugation to separate and remove inorganic salt particles in the distillation concentrate, and the organic solvent is further removed from the mother liquor after distillation separation to obtain a cyclized compound. This solution uses a flat plate sedimentation centrifuge for solid-liquid separation, which requires two distillation operations, has high equipment and maintenance requirements, high production costs, long processing time, and low production efficiency.

[0005] The existing post-processing operation of the cyclization reaction is inefficient and has high production costs. Therefore, it is necessary to simplify the separation and recovery method of the intermediate of the cyclization reaction of kung fu acid to reduce unnecessary energy and material losses and labor costs. Summary of the invention

[0006] The purpose of the present invention is to provide a method for separating and recovering an intermediate of kung fu acid, which can separate and recover the intermediate of kung fu acid cyclization reaction at low cost and high efficiency.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for separating and recovering a gongfu acid intermediate comprises the following steps: using 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoic acid methyl ester as a substrate, carrying out a cyclization reaction to obtain a cyclization reaction liquid, distilling and recovering the solvent, adding an extractant to the remaining reaction material to recover the cyclized compound, and filtering and recovering the salt.

[0009] Wherein, the extractant is selected from a polar, low-boiling-point organic solvent, and the water content is less than 1%;

[0010] Further, it is selected from a polar organic solvent having a boiling point of 50-130°C;

[0011] Further, methanol, ethanol, ethyl acetate, methyl isobutyl ketone and dioxane are preferred.

[0012] Wherein, the amount of the extractant used is 2-5 times, more preferably 2-3 times, of the cyclization reaction solution by weight.

[0013] The temperature for extracting and recovering the cyclocomplex is 20-80°C, more preferably 40-60°C.

[0014] Wherein, the solvent for the cyclization reaction is selected from any one or more of DMF, DMAC and tert-butyl alcohol.

[0015] Furthermore, before distilling and recovering the solvent, the pH of the system is adjusted to be weakly acidic, preferably pH=3-5.

[0016] Furthermore, the extraction layer can be separated from the extractant and the cyclocomplex by distillation, wherein the extractant can be reused and the cyclocomplex can be directly used in the next reaction.

[0017] Furthermore, the separated salt is washed 1-3 times with an extractant and then recovered, and the washed organic layer is combined into an extractant-cyclized compound system.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] In the prior art, after the cyclization reaction is completed, the solvent is roughly distilled off, and then a large amount of water is added. After stratification, washing, and recovery, salt is obtained. A large amount of residual salt-containing wastewater is directly discharged. The cyclized compound is dehydrated by molecular sieve and then distilled and recovered. The amount of wastewater generated by washing salt is large, and the wastewater contains solvents such as DMF, which is harmful to the environment. When the brine is transferred, the salt concentration is too high and it is easy to block the pipeline, which seriously affects the production cycle.

[0020] The invention recovers the cyclocompound by adding a specific extractant, which is simple to operate, saves time and labor, and subsequently the extractant and the cyclocompound can be recovered step by step by a simple distillation method. The extractant can be reused, and the cyclocompound can be directly used in the next step reaction to prepare kung fu acid.

[0021] Furthermore, the inorganic salts formed in the reaction can be recovered and comprehensively utilized by centrifugation or filtration without adding a large amount of water for dilution, which greatly reduces the generation of wastewater in the cyclization reaction and reduces the possibility of brine clogging the pipeline, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the reaction process of Example 1 of the present invention

[0023] Figure 2 The reaction equipment of Example 1 of the present invention DETAILED DESCRIPTION

[0024] In order to better understand the essence of the present invention, the contents of the present invention are further illustrated in conjunction with the embodiments below, but they cannot be regarded as limiting the present invention. The following description is only used to explain the present invention. Any modifications, substitutions or improvements made without departing from the spirit and principles of the present invention are all within the scope of protection required by the present invention.

[0025] Example 1

[0026] The cyclization reaction kettle was charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoic acid methyl ester (hereinafter referred to as adduct) were charged at low temperature, and the reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0027] The cyclization reaction liquid was transferred to a solvent distillation kettle, and a dilute acid was added to adjust the pH of the system to 3-5. The temperature was controlled to distill at normal pressure to recover 2457 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol was completed, 1976 kg of DMF was recovered by vacuum distillation. After the distillation of DMF was completed, the temperature was lowered by 40-60 ° C. 5000 kg of methanol was added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate was distilled to recover 4920 kg of methanol, and 1666 kg of cyclocompounds were obtained by further distillation. The three-in-one salt was dried to obtain white sodium chloride salt as a by-product.

[0028] The atomic utilization rate in the reaction reaches 98%, and basically no three wastes are generated, which is in line with the green production concept and is conducive to industrial production.

[0029] Example 2

[0030] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0031] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2460 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1968 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 6000 kg of ethanol is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 5808 kg of ethanol, and 1660 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0032] The atomic utilization rate in the reaction reaches 98%, and basically no three wastes are generated, which is in line with the green production concept and is conducive to industrial production.

[0033] Example 3

[0034] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0035] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2453 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1970 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60°C. 5300 kg of ethyl acetate is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 5251 kg of ethyl acetate, and 1653 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0036] The atomic utilization rate in the reaction reaches 98%, and basically no three wastes are generated, which is in line with the green production concept and is conducive to industrial production.

[0037] Example 4

[0038] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0039] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2449 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1959 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60°C. 5600 kg of methyl isobutyl ketone is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 5550 kg of ethyl acetate, and 1659 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0040] The atomic utilization rate in the reaction reaches 98%, and basically no three wastes are generated, which is in line with the green production concept and is conducive to industrial production.

[0041] Example 5

[0042] First application:

[0043] The cyclization reaction kettle was charged with 2000 kg of DMF recovered in Example 1-4 and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct were charged at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0044] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2456 kg of tert-butanol solvent. After the distillation of tert-butanol is completed, 1954 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 5000 kg of methanol (methanol recovered from Example 1 and a portion of methanol is added) is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; 4911 kg of methanol is recovered by distillation of the filtrate, and 1652 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0045] Second application:

[0046] The cyclization reaction kettle was charged with 2000 kg of DMF recovered in Example 1-4 and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct were charged at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0047] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2450 kg of tert-butanol solvent. After the distillation of tert-butanol is completed, 1944 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 5000 kg of methanol (recovered from the methanol used for the first time and a part of methanol is added) is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 4911 kg of methanol, and 1657 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0048] Third application:

[0049] The cyclization reaction kettle was charged with 2000 kg of DMF recovered in Example 1-4 and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct were charged at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0050] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2449 kg of tert-butanol solvent. After the distillation of tert-butanol is completed, 1959 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 5000 kg of methanol (recovered from the methanol used for the second time and a part of methanol is added) is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 4916 kg of methanol, and 1649 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0051] Fourth application:

[0052] The cyclization reaction kettle was charged with 2000 kg of DMF recovered in Example 1-4 and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct were charged at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0053] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2454 kg of tert-butanol solvent. After the distillation of tert-butanol is completed, 1960 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 5000 kg of methanol (recovered from the methanol used for the third time and a part of methanol is added) is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 4904 kg of methanol, and 1657 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0054] Fifth application:

[0055] The cyclization reaction kettle was charged with 2000 kg of DMF recovered in Example 1-4 and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct were charged at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0056] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2455 kg of tert-butanol solvent. After the distillation of tert-butanol is completed, 1964 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60 ° C. 5000 kg of methanol (recovered from the methanol used for the fourth time and a part of methanol is added) is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 4915 kg of methanol, and 1663 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0057] The atomic utilization rate in the reaction reaches 98%, and basically no three wastes are generated, which is in line with the green production concept and is conducive to industrial production.

[0058] Comparative Example 1

[0059] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0060] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2456 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1962 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60°C. 7000 kg of tetrahydrofuran is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 4791 kg of tetrahydrofuran, and 1502 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0061] The extractant tetrahydrofuran in the reaction easily absorbs water, resulting in too high water content in the system. The water in the extractant dissolves salt, and the salt content is too high when the extractant is distilled, which blocks the pipeline. In addition, the amount of the extractant tetrahydrofuran used in the reaction is too high. After the extraction process is completed, the distillation of the solvent takes a long time, the solvent loss is large, the reaction consumes a lot of energy, and the economy is poor, which is not conducive to industrial production.

[0062] Comparative Example 2

[0063] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0064] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2444 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1955 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60°C. 6700 kg of dichloroethane is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate is distilled to recover 5462 kg of dichloroethane, and 1490 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0065] The water content of the extractant in the reaction is too high, the water in the extractant dissolves salt, the salt content is too high when the extractant is distilled, and the pipeline is blocked. In addition, the amount of dichloroethane used in the reaction is too large, and the density of the extractant is relatively large, which is not conducive to the sedimentation and stratification of the salt and is not conducive to industrial production.

[0066] Comparative Example 3

[0067] The cyclization reaction kettle is charged with 2000 kg of DMF and 2500 kg of tert-butanol, and sodium tert-butoxide and 2000 kg of adduct are charged at low temperature. The reaction is terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0068] The cyclization reaction liquid is transferred to a solvent distillation kettle, and a dilute acid is added to adjust the pH of the system to 3-5. The temperature is controlled to distill at normal pressure to recover 2444 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol is completed, 1956 kg of DMF is recovered by vacuum distillation. After the distillation of DMF is completed, the temperature is lowered by 40-60°C. 5000 kg of ethylene glycol is added to the system for salt precipitation, and then transferred to the three-in-one for filtration; 4074 kg of ethylene glycol is recovered by distillation of the filtrate, and 1533 kg of cyclocompound is obtained by further distillation. The three-in-one salt is dried to obtain white sodium chloride salt as a by-product.

[0069] The boiling point of the extractant in the reaction is too high, resulting in incomplete distillation of the extractant. The residual solvent will affect the subsequent saponification reaction, which is not conducive to industrial production.

[0070] Comparative Example 4

[0071] 2000 kg of DMF and 2500 kg of tert-butanol were added to the cyclization reaction kettle, and sodium tert-butoxide and 2000 kg of adduct were added at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0072] The cyclization reaction liquid was transferred to a solvent distillation kettle, the pH of the system was adjusted to 7-8, and the temperature was controlled to distill at normal pressure to recover 2458 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol was completed, 1961 kg of DMF was recovered by vacuum distillation. After the distillation of DMF was completed, the temperature was lowered by 40-60°C. 5000 kg of methanol was added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate was distilled to recover 4790 kg of methanol, and 1581 kg of cyclocompound was obtained by further distillation. The three-in-one salt was dried to obtain white sodium chloride salt as a by-product.

[0073] The pH of the reaction system before extraction is weakly alkaline, the reaction salt precipitation time is increased, and the emulsion layer in the product becomes more, which is not conducive to product separation and is not suitable for industrial production.

[0074] Comparative Example 5

[0075] 2000 kg of DMF and 2500 kg of tert-butanol were added to the cyclization reaction kettle, and sodium tert-butoxide and 2000 kg of adduct were added at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0076] The cyclization reaction liquid was transferred to the solvent distillation kettle, the system pH was adjusted to 10-11, and the temperature was controlled to distill at normal pressure to recover 2463 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol was completed, 1958 kg of DMF was recovered by vacuum distillation. After the distillation of DMF was completed, the temperature was lowered by 40-60°C. 5000 kg of methanol was added to the system for salt precipitation, and then transferred to the three-in-one for filtration; the filtrate was distilled to recover 4715 kg of methanol, and 1492 kg of cyclocompound was obtained by further distillation. The three-in-one salt was dried to obtain white sodium chloride salt as a by-product.

[0077] The pH of the reaction system is too high before extraction, the reaction salt precipitation time is increased, and the emulsion layer in the product becomes more, which is not conducive to product separation and is not suitable for industrial production.

[0078] Comparative Example 6

[0079] 2000 kg of DMF and 2500 kg of tert-butanol were added to the cyclization reaction kettle, and sodium tert-butoxide and 2000 kg of adduct were added at low temperature. The reaction was terminated by keeping the temperature for 0.5-1 h to obtain a cyclization reaction liquid.

[0080] The cyclization reaction liquid was transferred to a solvent distillation kettle, and a dilute acid was added to adjust the pH of the system to 3-5. The temperature was controlled to distill at normal pressure to recover 2463 kg of tert-butyl alcohol solvent. After the distillation of tert-butyl alcohol was completed, 1958 kg of DMF was recovered by vacuum distillation. After the distillation of DMF was completed, the temperature was lowered by 40-60° C. Water was added for washing to remove salt. After the water layer was separated, the kettle residue was dried and transferred to the cyclized product distillation kettle and then continued to distill to obtain 1379 kg of cyclized compound.

[0081] A large amount of water is added to wash the salt during the reaction, which increases the discharge of the three wastes. If the salt is directly filtered without adding water, the produced salt will clog the pipeline and be difficult to filter. The material transferred to the cyclization product distillation kettle has a large viscosity and the material transfer is slow. After being transferred to the cyclization product distillation kettle, distillation is continued to obtain a cyclized compound.

[0082] For the convenience of comparison, the data of the extraction agent selection and post-treatment in the embodiments and comparative examples are listed in the following Table 1.

[0083] Table 1 Summary of Examples

[0084]

[0085] It can be seen from Examples 1-5 and Comparative Examples 1-5 that the technical solution of the present invention is related to the selection of the extractant and the water content of the extractant, as well as the pH of the extraction reaction system.

[0086] Among them, as shown in Examples 1-5 and Comparative Example 6, when a specific organic solvent is selected as the extractant, the extractant and the cyclocompound can be recovered step by step by simple distillation, which is simple to operate, saving time and labor. Further, as shown in Example 5, the extractant selected by the present invention can be reused.

[0087] When a polar low-boiling organic solvent is selected as an extractant, as shown in Examples 1-4, the extraction effect should be selected according to the polarity of the extractant, and when a high-boiling organic solvent is selected, see Comparative Example 3, the extractant is difficult to remove. Further, the water content of the extractant will affect the extraction effect. As shown in Examples 1-4 and Comparative Example 1-2, when the water content of the extractant is less than 1%, the salt cannot be dissolved in the extractant, and the salt content is low when the extractant is distilled, and it is not easy to block the pipeline. When the water content of the extractant is greater than 1%, the water in the extractant dissolves the salt, and the salt content is too high when the extractant is distilled, which blocks the pipeline and is not conducive to industrial production. In addition, the pH of the extraction reaction system will also affect the extraction effect. As shown in Examples 1-5 and Comparative Examples 4-5, when the pH of the extraction reaction system is weakly acidic, preferably pH=3-5, it is conducive to shortening the reaction and improving the reaction efficiency. When the pH of the extraction reaction system is neutral and weakly alkaline, the reaction salt precipitation time increases, and the emulsified layer in the product becomes more, which is not conducive to product separation and is not suitable for industrial production.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for separating and recovering a gongfu acid intermediate, comprising the following steps: The method uses 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoic acid methyl ester as a substrate, performs a cyclization reaction, obtains a cyclization reaction liquid, and distills to recover the solvent. The method is characterized in that an extractant is added to the remaining reaction material to recover the cyclized compound, and the salt is filtered to recover the salt.

2. The method according to claim 1, characterized in that The extractant is selected from polar low-boiling point organic solvents, and its water content is less than 1%.

3. The method according to claim 2, characterized in that The boiling point of the polar low-boiling-point organic solvent is 50-130°C.

4. The method according to claim 3, characterized in that The polar low-boiling point organic solvent is selected from any one or more of methanol, ethanol, ethyl acetate, methyl isobutyl ketone and dioxane.

5. The method according to claim 1, characterized in that The amount of the extractant used is 2-5 times, more preferably 2-3 times, of the cyclization reaction solution by weight.

6. The method according to claim 1, characterized in that The temperature for extracting and recovering the cyclic compound is 20-80°C, more preferably 40-60°C.

7. The method according to claim 1, characterized in that The pH of the cyclization reaction solution is adjusted to be weakly acidic, and then distilled and recovered.

8. The method according to claim 7, characterized in that The cyclization reaction liquid is adjusted to a pH value of 3-5, and then distilled and recovered.

9. The method according to claim 1, characterized in that The solvent for the cyclization reaction is selected from any one or more of DMF, DMAC and tert-butyl alcohol.

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