JPH04226934A - Purification of 2-chloropropionic acid - Google Patents

Abstract

PURPOSE:To recover high-purity 2-chloropropionic acid by separating and purifying crude 2-chloropropionic acid. CONSTITUTION:When crude 2-chloropropionic acid contains a dichloro isomer as an impurity, the crude 2-chloropropionic acid is preheated at 130-180 deg.C in the presence of a metal compound and when does not contain the dichloro isomer, the crude 2-chloropropionic acid is previously concentrated or coarsely purified at <=160 deg.C, and then the metal compound is separated and removed at <=160 deg.C and carried out a final purification of 2-chloropropionic acid to give a high-quality product.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to a method for obtaining highly pure α-CPA by purifying crude 2-chloropropionic acid (hereinafter referred to as α-CPA) or a solution containing crude α-CPA.

0002

BACKGROUND OF THE INVENTION α-CPA is used as an intermediate for various chemicals such as lactic acid and alanine, agricultural chemicals, and pharmaceuticals. In addition, in recent years, there has been a strong demand for high purity products in racemic resolution and the like.

α-CPA is industrially produced by chlorination of propionic acid. That is, the following reaction formula, CH3CH2COOH + Cl2 →
It is carried out using CH3CHClCOOH + HCl (2), but in addition to unreacted propionic acid as impurities, it usually contains on the order of several percent of further chlorinated dichloro compounds such as 2,2-dichloropropionic acid. It has been considered difficult to produce products with a purity of 99% or more by weight using conventional methods. The dichlor compound referred to here is a chlorine compound of propionic acid in which two hydrogens are replaced with chlorine, and 2,2-dichloropropionic acid generally accounts for the majority. The boiling point of such a dichlor compound is very close to that of α-CPA, and it is difficult to separate and remove it by normal distillation operations. In addition, no industrially good means of separation has been found for other methods.

[0004] Therefore, even α-CPA currently manufactured as a high-purity product has a purity of about 98 to 99% by weight, and α-CPA with a purity of 99% by weight or more can be obtained by chlorinating propionic acid. is not manufactured.

Furthermore, recently, high purity α-CPL of 99% by weight or more has been obtained by oxidizing 2-chloropropionaldehyde (hereinafter referred to as α-CPL) with oxygen or oxygen-containing gas in the liquid phase in the presence of a metal compound catalyst. C.P.
A method for manufacturing A has also been proposed (Japanese Patent Laid-Open No. 1983-1996)
446).

α-CP is produced by liquid phase oxidation reaction of α-CPL.
The manufacturing method for A is based on the reaction formula CH3CHClCHO + 1/2O2 →
CH3CHClCOOH (1). The raw material α-CPL is, for example, disclosed in JP-A-61-1
26046, by the reaction of vinyl chloride with synthesis gas in the presence of rhodium and a base. Therefore, there is no use of chlorine, and there is almost no by-product of dichlor which is difficult to separate, making it possible to produce α-CPA with a purity of 99% by weight or more.

[0007]

As a method for separating and removing dichlor compounds, an azeotropic distillation method using an aliphatic hydrocarbon as an azeotropic agent is disclosed in JP-A-58014-1987. However, even in this method, the added azeotropic agent and α
The difference in the boiling points of the azeotrope formed between -CPA and the dichloride is not so large. Therefore, in order to obtain high-purity α-CPA, the number of stages and energy required for the distillation column become extremely large, and a process for separating and recovering the entrainer is also required.

Furthermore, FR2582645 describes a method in which a hydrogenation reaction is carried out in the presence of a metal catalyst such as palladium, rhodium or ruthenium to convert dichloroform, which is difficult to separate, into propionic acid with a low boiling point, which is then purified by distillation. Disclosed. However, this method not only requires hydrogen, but also produces hydrogen chloride as a by-product along with propionic acid, which is undesirable from the standpoint of equipment corrosion.

On the other hand, in the method of producing high-purity α-CPA by liquid phase oxidation of α-CPL, the reaction solution contains unreacted α-CPL, reaction by-products, catalyst, solvent, etc. However, if ordinary distillation was used as a purification method, colorless and transparent α-CPA could not be obtained, probably due to the poor thermal stability of α-CPA, and there was a large loss of quality during purification. There was a problem.

The purpose of the present invention is to solve the various problems in the purification process as described above, and to obtain highly pure α-C through simple operations.
The object of the present invention is to provide a purification method for obtaining PA.

[0011]

[Means for Solving the Problems] As a result of intensive study on these problems, the present inventors have completed the following invention.

That is, the α-CPA purification method of the present invention heat-treats a crude α-CPA solution containing a metal compound,
Thereafter, the metal compound is separated and removed at a temperature of 160° C. or lower, and then α-CPA is finally purified and recovered.

[0013] In the present invention, the crude α-CPA solution is
α-CPA or an α-CPA-containing solution containing as an impurity a chlorinated product of propionic acid in which two hydrogens are replaced with chlorine after a chlorination reaction of propionic acid, or α-C
It is a reaction solution obtained by liquid phase oxidation of PL with oxygen or oxygen-containing gas. The bottom is oxidized.

In the case of the former crude α-CPA solution, the higher the heat treatment temperature, the more the dichlor compound deteriorates, but excessively high temperatures lead to the deterioration of α-CPA itself. Moreover, if the temperature is too low, the modification efficiency of the dichlor compound will decrease. Therefore, the heat treatment temperature is 110°C or higher, preferably 1
A range of 30°C to 180°C is preferable. In addition, the heat treatment time is determined as appropriate since the amount of metal compound varies depending on the heat treatment temperature, but in reality, the equipment cost and α-CPA required for the product are determined accordingly.
The most economical conditions are adopted, taking into account the purity of the product and the amount of loss during the purification process.

α- obtained by oxidation reaction of α-CPL
CPA and α-CPA-containing solutions originally contain almost no dichloride, but although unidentified impurities with high boiling points increase slightly due to this heat treatment operation, unidentified impurities with boiling points relatively close to α-CPA are This significant decrease was confirmed by gas chromatography analysis.

Purification operations include recovery and removal of various low-boiling point substances, solvent recovery, removal of metal compounds, and removal of high-boiling point compounds, but generally a distillation method is used in which substances with low boiling points are separated sequentially. It is.

The oxidation reaction of α-CPL is usually carried out in the absence of a solvent or in a carboxylic acid such as acetic acid, propionic acid, butyric acid, dimethyl sulfoxide, sulfolane, etc., and the product α-CPA is also used as a solvent. In the case of the reaction solution for liquid phase oxidation of α-CPL that contains almost no dichloride,
The generated α-CPA is constantly heated in the presence of metal compounds until the final purification stage. Such heating operations in the presence of metal compounds promote dechlorination and high boiling of α-CPA. become. Although this phenomenon can be observed even at temperatures of about 100°C, it generally becomes noticeable at high temperatures of 130°C or higher, particularly 150°C or higher. Therefore,
After such a heating operation, the reaction solution showed phenomena such as a rapid increase in the amount of propionic acid and coloring to blackish brown, and the purified α-C
PA also shows pale yellow or purple coloration, and a colorless and transparent product cannot be obtained.

As described above, long-term heating in the presence of a metal compound in an oxidation reaction at a high temperature of 130° C. or higher, especially 150° C. or higher is not desirable, but if the heating operation is performed for a short time, It won't have a big impact. Therefore, although the heating time largely depends on the temperature and the amount of metal compound, it is generally preferable that the heating time is within 1 hour in total in the range of 130 to 150°C. Also,
Heating at a temperature of 150° C. or higher, particularly 160° C. or higher is best avoided as much as possible, since it greatly affects the rapid increase of propionic acid and the turning of the reaction solution into blackish brown.

As described above, heating operations in the presence of metal compounds lead to an increase in the amount of purification loss of α-CPA, and furthermore, the distilled α-CPA becomes colored, making it difficult to obtain the required colorless and transparent product. I can't. That is, in the final distillation purification operation under conditions where metal compounds are not separated and removed, yellow or purple coloration is observed in the distilled α-CPA not only at high temperatures but also at low temperatures below 130°C. It is impossible to obtain a colorless and transparent liquid.

Therefore, in the method of the present invention, at least α-C
By separating and removing the metal compound before final purification of PA, it became possible to produce highly pure, colorless and transparent α-CPA. In addition, for solutions containing almost no dichloride, the maximum heating temperature in the presence of metal compounds should be 160°C or lower, preferably 150°C or lower to reduce the loss of α-CPA deterioration during the purification process. It is also possible to do so.

[0021] In the separation of metal compounds, the maximum temperature reached is 16
It may be carried out before the temperature reaches 0°C, preferably 150°C. Therefore, it is possible to separate the metal compound directly from the reaction solution, but in reality, the most economical method is adopted after considering the energy requirements, amount of loss due to alteration of α-CPA, equipment costs, etc. . For example, when performing an oxidation reaction in an acetic acid solvent and performing distillation purification, it is preferable to separate and recover the solvent, then separate the metal compound, and then perform high-level purification of α-CPA. This means that the boiling point of acetic acid is α-C
Because it is lower than PA, if metal compounds are separated early, acetic acid, which is used in large quantities, will have to be vaporized twice.
This is because it is uneconomical in terms of energy and equipment costs. In addition, as a method for separating metal compounds, a method using a thin film evaporator which has a short contact time and almost no temperature rise due to liquid depth, a method of extraction and separation at a temperature of 150° C. or lower, etc. are suitably used.

The metal compound used is at least one metal compound selected from the group consisting of iron compounds, cobalt compounds, nickel compounds, manganese compounds, copper compounds, cerium compounds, and molybdenum compounds, mineral acid salts, carboxylic acid It is often used as a soluble salt.

More specifically, iron compounds include divalent or trivalent iron compounds such as ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate, and ferric nitrate. Mineral acid salts of iron, divalent or trivalent iron carboxylates such as ferrous acetate, ferric acetate, ferrous benzoate, and ferric oxalate are preferably used, and iron α- CPA salts are also commonly used. In addition, ferric hydroxide, ferric oxide, etc. can also be used.

[0024] As the cobalt compound, cobalt chloride,
Cobalt mineral salts such as cobalt sulfate and cobalt nitrate,
Cobalt carboxylates such as cobalt acetate, cobalt formate, cobalt oxalate, and cobalt naphthenate are preferred, and α-CPA salts of cobalt are also often used. In addition, cobalt hydroxide, cobalt oxide, basic cobalt carbonate, etc. can also be used.

[0025] As the nickel compound, nickel chloride,
Mineral acid salts of nickel such as nickel bromide, nickel iodide, nickel sulfate, and nickel nitrate, and carboxylic acid salts of nickel such as nickel acetate, nickel formate, nickel oxalate, and nickel benzoate are preferred;
CPA salts are also commonly used. In addition, nickel carbonate,
Nickel hydroxide, nickel oxide, etc. can also be used.

[0026] As the manganese compound, manganese chloride,
Manganese mineral salts such as manganese sulfate and manganese nitrate,
Manganese carboxylates such as manganese acetate, manganese formate, manganese benzoate, and manganese naphthenate are preferred, and α-CPA salts of manganese are also often used. In addition, manganese dioxide or manganese carbonate may also be used.

[0027] Copper compounds include monovalent or divalent mineral acid salts such as cuprous chloride, cupric chloride, copper sulfate, and copper nitrate;
Divalent copper carboxylates such as copper acetate, copper formate, copper citrate, and copper naphthenate are preferably used;
PA salts are also commonly used. In addition to these, cuprous oxide, cupric oxide, cupric hydroxide, copper carbonate, etc. can also be used.

Examples of cerium compounds include trivalent or tetravalent mineral acid salts of cerium such as cerous chloride, cerous sulfate, ceric sulfate, and cerous nitrate, cerous acetate, and ceric acetate. Trivalent or tetravalent cerium carboxylates such as cerium carboxylates are preferably used, and cerium α-CPA salts are also often used. In addition,
Ceric oxide, cerous carbonate, etc. can also be used.

Examples of molybdenum compounds include mineral acid salts of divalent, trivalent or pentavalent molybdenum such as molybdenum dichloride, molybdenum trichloride and molybdenum pentachloride, and pentavalent molybdenum salts such as molybdenum acetate and molybdenum naphthenate. Carboxylate salts are preferably used, and α-CPA salts of molybdenum are also often used.

These metal compounds may be used alone or in combination of two or more. There is no particular restriction on the amount used, but a larger amount is better from the viewpoint of the modification efficiency of the dichlor compound. Generally, in consideration of handleability and economical efficiency, it is preferable to contain metal in a range of 0.01% to 10% by weight based on α-CPA.

[0031] Through these operations, the dichlor compound, which is difficult to separate, changes in quality and changes into low-boiling point substances and high-boiling point substances such as propionic acid and acetic acid, which are easy to separate by distillation, and also changes into α-CPA itself. ing. Furthermore, it has been confirmed that other impurities other than the dichlor compound, which have boiling points close to that of α-CPA, are also reduced over time by this treatment. Therefore, after this heat treatment, not only the amount of impurities such as dichlor compound is significantly reduced compared to before the treatment, but also α
-The yield of CPA will also be improved.

The α-CPA or α-CPA-containing solution thus obtained is purified by a method such as distillation to produce highly pure α-CPA. In this case, by performing this heat treatment, the target to be separated is converted from the dichloride, which has a boiling point very close to that of α-CPA, to substances with a large boiling point difference such as propionic acid, acetic acid, and high-boiling substances, and is not separated using ordinary distillation. It can be easily purified by manipulation. The conditions for the distillation operation are not particularly limited, but the number of theoretical plates may be about 3 to 20, and the reflux ratio is 0.1 to 3.
It is enough. As described above, it is possible to produce α-CPA with a higher purity than ever before even by a simple ordinary distillation purification operation without adding an entrainer.

[0033]

[Example] The present invention will be explained in detail with reference to Examples. In addition, the following example shows an example of the present invention,
It is not intended to limit the scope of the invention.

Example 1 (Synthesis of α-CPA) 85% by weight α-CPL was dissolved in acetic acid to prepare a 10% by weight α-CPL solution. In this solution, cobalt acetate and iron salt of α-CPA were dissolved at 4 and 40 ppm by weight in metal terms, respectively, and the solution was continuously supplied to a 1 liter autoclave equipped with a stirrer and heated to 50°C.
, air oxidation reaction was carried out under a pressure of 80 kg/cm2G. The resulting reaction solution contained 6% by weight of α in addition to acetic acid.
-CPA, 5% by weight of α-CPL, 2% by weight of water and some low-boiling impurities and high-boiling impurities such as catalyst.

(Separation of low boiling point substances) This reaction solution was evaporated and separated by 85% of the acetic acid using a 10 liter rotary evaporator. The final oil bath temperature was 84°C.

Next, distillation purification was carried out continuously in a 40-stage glass Oldershaw distillation column to remove low-boiling substances such as residual acetic acid and water. The temperature and average residence time of the bottom liquid at this time were 124° C. and 6 hours, and the bottom liquid was colored blackish brown. In addition, the propionic acid concentration in the distillate and bottom liquid is 2% of that of the feed liquid, respectively.
．． 2 times and 1.4 times, and it was confirmed that the increase was due to heating during distillation.

(Catalyst Separation and Final Purification) This bottom liquid was continuously supplied to a thin film evaporator equipped with a stirrer to separate the catalyst. The maximum temperature of the heating medium was 160°C, and the distillate was colored yellow. Subsequently, this distillate was subjected to high-level purification of α-CPA in a batch manner using the Oldershaw distillation apparatus described above. Bottom temperature is 125
The temperature was started at 150°C and finally increased to 150°C. Also,
The reflux ratio was also operated in the range of 0.5 to 1.5. The first distillate is 1
After removing 0% by weight, the receiver was replaced and α-CPA
When continuously distilled, a colorless and transparent distillate was obtained. When the obtained distillate was analyzed by gas chromatography, it was confirmed that high purity α-CPA of 99.6% by weight was obtained.

Example 2 α
- CPA was purified.

The degree of coloration of the distillation column bottom liquid during the removal of low-boiling substances in the Oldershaw distillation column was much lower than that in Example 1. Furthermore, the production of propionic acid due to heating during distillation was extremely small, and almost no propionic acid was detected in the bottom liquid. Furthermore, in the final batch distillation purification, a colorless and transparent distillate was obtained by distilling and removing only 5% of the initial distillate, and the purity was also 9.
It was 9.7% by weight.

Comparative Example 1 α was prepared in the same manner as in Example 1 except that the catalyst was not separated.
- CPA was purified. In the final distillation purification,
Although 10% by weight of the initial distillate was removed by distillation at a reflux ratio of 0.5, the color of the distillate was pale purple, and the purity was as low as 99.0% by weight or less. In addition, the reflux ratio was set to 2.0 and distillation was carried out continuously until the distillation rate reached 40% by weight, but although the color of the distillate became slightly lighter, the coloring did not disappear. The purity was also 99.4% by weight, which was lower than that of Example 1.

Example 3 In a 50 ml glass container, 30 g of α-CPA containing 3.3% by weight of dichloride, 0.06 g of cobalt acetate, and 0.6 g of iron salt of α-CPA were placed. I sealed it tightly. The container was placed in a silicone oil bath heated to 150° C. and heat-treated for a predetermined period of time.

As shown in Table 1, the results confirmed a decrease in dichloride and an increase in low-boiling impurities mainly propionic acid and acetic acid, non-volatile residue, etc., and α-
It was also confirmed that CPA increased slightly. Thus, after 5 hours of heat treatment, the dichlor compound was reduced to nearly one-fourth of the amount before heat treatment, and after 10 hours, it was reduced to less than one-tenth.

Example 4 α-CPA having the same composition as in Example 3 was heat-treated in the same manner as in Example 3 except that the temperature of the silicone oil bath was set to 130°C. The results are shown in Table 1.

As can be seen from Table 1, as in Example 3, a decrease in dichloride and an increase in low-boiling point impurities such as propionic acid and acetic acid, as well as non-volatile residues, etc., were confirmed, and α-CPA slightly increased. It was also confirmed that After 10 hours of heat treatment, the dichlor compound had been reduced to less than half.

Example 5 In a 1-liter glass flask equipped with a stirrer and a condenser, 700 grams of α-CPA having the same composition as in Example 3, 1.4 grams of cobalt acetate, and 1 liter of iron salt of α-CPA were added.
4 grams were added and heat treated in an oil bath at 150°C for 5 hours. The dichloride content after heat treatment is 0.
There was a large decrease of 8% by weight.

After separating the catalyst from the heat-treated α-CPA solution at 160°C in a glass thin film evaporator, the α-CPA solution was heated to 10 plates.
It was purified by distillation using a stage Oldershaw distillation column. Distillation was carried out batchwise at a reflux ratio of 1. 5 as the first distillate
After removing the weight% by distillation, replace the distillate receiver,
Distillates with distillation rates ranging from 5 to 90% were collected. Composition analysis by gas chromatography revealed that α-
The CPA purity was extremely high at 99.5% by weight.

Comparative Example 2 α-CPA was heat-treated in the same manner as in Example 3 except that no metal compound was added. The results are shown in Table 2.

As can be seen from Table 2, almost no decrease in the dichlor compound was observed even after 10 hours of heat treatment.

Comparative Example 3 α-CPA was heat treated in the same manner as in Example 3 except that the heat treatment temperature was 100°C. Table 2 shows the results.
Shown below.

As can be seen from Table 2, almost no decrease in the dichlor compound was observed even after 10 hours of heat treatment.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

Effects of the Invention By purifying α-CPA according to the method of the present invention, α-CPA with a purity of 99% by weight or more, which has not been previously available, can be obtained industrially in good yield.

Claims (20)

[Claims] Claim 1: A purification method for recovering 2-chloropropionic acid in high purity from a crude 2-chloropropionic acid solution containing a metal compound, the method comprising: separating and removing the metal compound at a temperature of 160°C or lower; - A method for purifying 2-chloropropionic acid, which comprises finally purifying and recovering chloropropionic acid. Claim 2: The crude 2-chloropropionic acid solution is
- It is obtained by liquid-phase oxidation of chloropropionaldehyde with oxygen or oxygen-containing gas, and is concentrated or roughly purified before removing metal compounds under conditions where the maximum temperature does not exceed 160°C. The purification method according to claim 1, which is carried out. 3. The purification method according to claim 2, wherein the metal compound is at least one metal compound selected from the group consisting of iron compounds, cobalt compounds, nickel compounds, manganese compounds, copper compounds, cerium compounds, and molybdenum compounds. 4. The purification method according to claim 3, wherein the metal compound is a soluble salt. 5. The purification method according to claim 4, wherein the soluble salt is at least one salt selected from the group consisting of acetate, naphthenate and 2-chloropropionate. 6. The purification method according to claim 2, wherein the concentration or crude purification is carried out at a temperature not exceeding 150°C. 7. The purification method according to claim 2, wherein the concentration or rough purification is performed at a temperature of 130° C. or lower. Claim 8: Concentration or crude purification at 130-150°C
The purification method according to claim 2, characterized in that the purification is carried out at a temperature range of 1 hour or less. 9. The purification method according to claim 2, wherein the amount of the metal compound used is 0.01 to 10% by weight of the metal based on the 2-chloropropionic acid. 10. The purification method according to claim 2, wherein the separation and removal of the metal compound is carried out by thin film evaporation. 11. The purification method according to claim 2, wherein the separation and removal of the metal compound is carried out by extraction and separation at 150° C. or lower. 12. The crude 2-chloropropionic acid solution is
2-chloropropionic acid or a 2-chloropropionic acid-containing solution containing as an impurity a chlorinated product of propionic acid in which two hydrogens obtained by chlorination of propionic acid are replaced with chlorine. The purification method according to claim 1, wherein the heat treatment is performed in advance in the presence of a metal compound. 13. The metal compound is an iron compound, a cobalt compound, a nickel compound, a manganese compound, a copper compound,
Claim 12 is at least one metal compound selected from the group consisting of cerium compounds and molybdenum compounds.
Purification method as described. 14. The purification method according to claim 13, wherein the metal compound is a soluble salt. 15. The purification method according to claim 14, wherein the soluble salt is at least one salt selected from the group consisting of acetate, naphthenate, and 2-chloropropionate. 16. The purification method according to claim 12, wherein the temperature of the heat treatment is 110° C. or higher. 17. The temperature of the heat treatment is 130 to 180°C.
The purification method according to claim 12, wherein the purification method is within the range of 18. The purification method according to claim 12, wherein the separation and removal of the metal compound is carried out by thin film evaporation. 19. The purification method according to claim 12, wherein the separation and removal of the metal compound is carried out by extraction and separation at 150° C. or lower. 20. The amount of the metal compound used is 0.01 to 10% by weight of the metal relative to 2-chloropropionic acid.
The purification method according to claim 12.