JPH01233257A - Production of 2-chloropropionic acid - Google Patents

Abstract

PURPOSE:To obtain the title compound useful as an industrial chemical at relatively low temperature in short time and high purity under circumference of reduced corrosion, by oxidizing 2-chloropropionaldehyde with oxygen in the presence of a specific amount of metal compounds in liquid phase. CONSTITUTION:For example, 2-chloropropionaldehyde expressed by formula I is oxidized with oxygen or oxygen-containing gas in the presence of an iron compound (e.g., iron (II) chloride or iron (III) chloride) of 0.01-100mg based on 1mol of the above-mentioned compound and vanadium compound (e.g., vanadium trioxide), cobalt compound [e.g., cobalt (II) acetate (4 hydrate)] or chromium compound [e.g., chromium (III) oxide ] of 0.01-1times mol based on atomic ratio in a liquid phase to provide 2-chloropropionic acid expressed by formula II. The oxidation reaction is preferably carried out in the range of 20-120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to the production of 2-chloropropionaldehyde by oxidizing 2-chloropropionaldehyde according to the following reaction formula (1).
- A method for producing chloropropionic acid.

2-Chloropropionic acid is a compound that has a wide range of uses as an intermediate for the production of industrial chemicals and pesticides.

(Problems to be solved by conventional technology and invention) 2-
Chloropropionic acid is industrially produced by chlorination of propionic acid according to the following reaction formula (2). However, in this method, as is clear from the equation, half of the chlorine consumed is directed to the by-product of hydrogen chloride, which is economically unfavorable in terms of the utilization rate of chlorine. Since it contains unreacted chlorine and various impurities, its utility value is low, and it also has the disadvantage of requiring alkali for neutralization when disposed of. In addition, the 2-chloropropionic acid obtained by this method usually contains several percent of dichloro compounds such as 2,2-dichloropropionic acid, which is further chlorinated, in addition to unreacted propionic acid as impurities. It is difficult to achieve a purity of 95% or higher, especially since these dichlor compounds are difficult to separate from 2-chloropropionic acid by simple distillation.
When chloropropionic acid is required, it has the disadvantage of requiring complicated operations such as, for example, first converting it into methyl ester, subjecting it to precision distillation, and then separating methanol after hydrolysis. Furthermore, this chlorination reaction of propionic acid has other problems, such as requiring expensive materials for the equipment to handle highly corrosive hydrogen chloride and placing a heavy burden on the maintenance of the equipment.

As one method for solving these problems, the present inventors have proposed the following method of producing 2-chloropropionic acid by oxidizing 2-chloropropionaldehyde. That is, 2-chloropropionaldehyde shown in JP-A No. 62-96446 was converted into an iron compound,
Production of 2-chloropropionic acid by oxidation with oxygen or oxygen-containing gas in the liquid phase in the presence of at least one metal compound selected from the group consisting of cobalt compounds, nickel compounds, manganese compounds, copper compounds and cerium compounds. It's a method.

The raw material 2-chloropropionaldehyde can be produced, for example, by the reaction of vinyl chloride and synthesis gas in the presence of rhodium and a base, as disclosed by the present inventors in JP-A-61-126046.

This method is an effective method for solving the problems in the conventional method for producing 2-chloropropionic acid mentioned above, and is particularly effective in producing 2-chloropropionic acid with higher purity than the conventional method. This is a suitable way to do so. However, if even higher purity 2-chloropropionic acid is required, these methods produce small amounts of impurities such as acetic acid, propionic acid, or monochloroacetic acid through side reactions, so these byproducts must be removed. Requires a removal process. However, among these by-products, monochloroacetic acid in particular has a boiling point close to that of 2-chloropropionic acid;
It has been found that separation by distillation requires a distillation column with an extremely large number of plates, resulting in an expensive production method. Such high purity 2
-Chloropropionic acid is used in the biochemical industry and as a raw material for optical resolution of 2-chloropropionic acid.

(Means for Solving the Problem) The present inventors have researched a solution to this problem and found that the oxidation of 2-chloropropionaldehyde is carried out using an appropriate amount of an iron compound catalyst and an appropriate ratio of a vanadium compound. The present invention was based on the discovery that when carried out in the presence of a multi-component catalyst containing a combination of chromium, cobalt compounds, or chromium compounds, the reaction proceeds at a relatively low temperature, resulting in extremely low by-products of impurities such as monochloroacetic acid. I ended up completing it.

That is, in the present invention, 2-chloropropionaldehyde is (1) 0.2-chloropropionaldehyde per mole of 2-chloropropionaldehyde.
Oxygen or oxygen in the liquid phase in the presence of an iron compound containing 01ag atoms to 1oomg atoms, and (2) a vanadium compound, cobalt compound, or chromium compound in an amount of 0.001 to 1 times the atomic ratio to the iron compound. This is a method for producing 2-chloropropionic acid, which is characterized by oxidizing with a contained gas.

The iron compounds used in the method of the present invention include divalent or trivalent iron mineral salts such as ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, and ferric nitrate, and acetic acid. Preferred are organic acid salts of divalent or trivalent iron such as ferrous, ferric acetate, ferrous benzoate, and ferrous oxalate. Iron etc. can also be used. Further, 2-chloropropionate of divalent or trivalent iron is also mentioned as an example of a preferable iron compound.

On the other hand, examples of vanadium compounds include vanadium compounds such as vanadium dioxide, vanadium pentoxide, vanadium trichloride, vanadium oxytrichloride, vanadium oxytrichloride, vanadium oxynitrate, vanadium oxysulfate, and vanadium oxyoxalate.

In addition, as an example of a cobalt compound, cobalt acetate (■
) (tetrahydrate), cobalt (n) acetylacetonate, cobalt CDI) acetylacetonate, cobal benzoate) (If), basic cobal carbonate) (I[), cobal chloride) (II), water M Cobalt oxide (■), cobalt oxide (■), cobalt naphthenate, cobalt nitrate (n) (
hexahydrate), cobal oxalate) (n), cobal sulfate) (I
I) Cobalt compounds such as heptahydrate.

Furthermore, examples of chromium compounds include chromium oxide (■),
Chromium oxide (■), chromium naphthenate, chromium chloride (■
), chromium chloride (■), chromium (I [[) acetylacetonate, basic chromium carbonate (■), chromium iodide (■)
, chromium nitrate (I[[), and chromium sulfate (I[[)).

In the method of the present invention, the amount of these compounds used is important. The iron compound is usually preferably used in an amount of 0.0001 mg atom to 200 g atom, particularly preferably 0.01 mg atom to 10 kg atom, per mole of 2-chloropropionaldehyde as a raw material. Although the reaction proceeds even if the amount is less than this lower limit, the reaction rate becomes slow and the by-product of peracid increases, resulting in poor selectivity and unfavorable safety results.

Furthermore, even if an amount of the catalyst is used in an amount exceeding this upper limit, the effect will not be improved any further, and problems in handling may occur, which is not preferable. Further, the amount of vanadium compound, cobalt compound, or chromium compound used in the method of the present invention is o in atomic ratio with respect to the iron compound used as a catalyst.
, ooot ~ 5 times, particularly preferably o, ooi ~ 1 times. If the amount is below this lower limit, the effect will be small;
If the characteristics of the present invention are not utilized, and the amount exceeds this upper limit, the required amount of the vanadium compound, cobalt compound, or chromium compound becomes large, which is not economically preferable.

In the method of the present invention, it is preferable to oxidize 2-chloropropionaldehyde at a temperature in the range of 20 to 120°C; temperatures below 20°C are unfavorable industrially because the oxidation reaction rate is slow. Furthermore, at temperatures above 120"C, side reactions such as dehydrochlorination of 2-chloropropionaldehyde and 2-chloropropionic acid become significant, resulting in a decrease in the yield and purity of 2-chloropropionic acid. For this reason, the temperature used is more preferably in the range of 40 to 80°C.

In the method of the present invention, oxidation proceeds satisfactorily even in the absence of a solvent, but in order to efficiently remove the heat generated by oxidation and obtain good reaction results, it is preferable to carry out the oxidation in the presence of a solvent. As such a solvent, any solvent can be used as long as it does not cause deterioration or side reactions under oxidation reaction conditions. Preferred examples include carboxylic acids such as acetic acid, propionic acid, butyric acid, and also dimethyl sulfoxide, sulfolane, acetone, and the like. Further, the use of the product 2-chloropropionic acid is more preferable since it makes it possible to omit the step of separating the product and the solvent after the oxidation reaction, and 2-chloropropionaldehyde in these solvents. The concentration is usually 1 to 50% by weight.
In particular, a range of 5 to 30% by weight is preferably used.

In this oxidation of 2-chloropropionaldehyde,
Water contamination from raw materials and solvents is often seen,
The coexistence of water in the reaction system is undesirable because the reaction rate decreases. However, in the method of the present invention, it is not necessary to completely remove water in the reaction system, and usually 10% by weight of water is added to the liquid phase.
If the amount is particularly preferably 3% by weight or less, oxidation will proceed sufficiently.

In the method of the invention, oxygen or an oxygen-containing gas is used as the oxidizing agent. Air is most commonly used as the oxygen-containing gas. The pressure of these oxygen-containing gases is preferably 0.2 kg/cj or more, particularly 5 kg/cj in terms of oxygen partial pressure in the reaction system.

Although it is not necessary to set a particular upper limit on the oxygen partial pressure, it is industrially undesirable to make the pressure too high, so the oxygen partial pressure is usually carried out within a range of 100 kg/aa or less.

(Example) Below, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 7.4 g of 2-chloropropionaldehyde was placed in a 70 d stainless steel autoclave equipped with a stirring device.
(80 mmol), 50 g of acetic acid as a reaction solvent, and ferrous sulfate (heptahydrate) (FeSOa4H) as an oxidation catalyst.
50 mg (0.18 mmol) of vanadium dioxide (VzOi) and 7 mg (0.05 mmol) of vanadium dioxide (VzOi) were charged. Air was pressurized to 75 kg/d, and the reaction was carried out at 45°C for 1.5 hours in a hot water bath with stirring.As the reaction progressed, the pressure decreased, so oxygen was supplied from a cylinder. The pressure was kept at 75 kg/CIi.

After the reaction was completed, the autoclave was cooled, the pressure was released, the contents were taken out, and the results of gas chromatography analysis showed that the conversion rate of 2-chloropropionaldehyde was 98.4%, converting it to 2-chloropropionic acid. The selectivity was 99.5% or more. Further, by-products such as acetic acid and monochloroacetic acid were not observed in the reaction solution.

Comparative Example 1 In the method of Example 1, ferrous sulfate 5 was used as an oxidation catalyst.
Oxidation of 2-chloropropionaldehyde was performed in the same manner except that 1 g of 0 ff was used.

Analysis of the reaction solution after completion of the reaction revealed that the conversion rate of 2-chloropropionaldehyde was 65.2% and the selectivity to 2-chloropropionic acid was 99.5% or more.

Comparative Example 2 2-chloropropionaldehyde was oxidized in the same manner as in Example 1 except that 7 mg of vanadium dioxide was used as the oxidation catalyst.

Analysis of the reaction solution after completion of the reaction revealed that the conversion rate of 2-chloropropionaldehyde was 41.2% and the selectivity to 2-chloropropionic acid was 99.5% or more.

Example 2 Oxidation was carried out in the same manner as in Example 1 except that 25 mg (0.1 mmol) of cobalt acetate (■) (tetrahydrate) was used instead of 7 mg of vanadium trioxide and the reaction temperature was 50 °C. I did it. As a result, reaction results were obtained in which the conversion rate of 2-chloropropionaldehyde was 96.6% and the selectivity to 2-chloropropionic acid was 99.5% or more.

Example 3 In Example 1, ferrous oxalate (dihydrate) 50 tag (0,28
The same method was used except that chromium oxide (n[) 9 vag (0.06 mmol) was used instead of 7 mg of vanadium dioxide and the reaction was carried out at an air pressure of 50 Kg/cd. As a result, the conversion rate of 2-chloropropionaldehyde was 97.8%, and the conversion rate of 2-chloropropionaldehyde was 97.8%.
A reaction result with a selectivity to t-propionic acid of 99.5% or more was obtained.

(Effects of the Invention) According to the method of the present invention, 2-chloropropionic acid can be industrially produced in an environment with less corrosion than the conventional chlorination method of propionic acid. In addition, 2,2-dichloropropionic acid is hardly detected in the obtained 2-chloropropionic acid, and furthermore, compared to the oxidation method of 2-chloropropionaldehyde that has been proposed so far, it is possible to oxidize 2-chloropropionic acid at a lower temperature. Since oxidation can be performed, there are very few by-product impurities, resulting in highly pure 2
- It becomes possible to easily obtain chloropropionic acid.

Furthermore, compared to the oxidation methods of 2-chloropropionaldehyde proposed so far, a faster reaction rate can be obtained at the same temperature, so the reaction time can be shortened, and as a result, side reactions are also avoided. As this decreases, productivity per reactor increases.

Claims (1)

[Scope of Claims] 1 2-chloropropionaldehyde (1) 0.0% per mole of 2-chloropropionaldehyde.
(2) a vanadium compound, a cobalt compound, or a chromium compound in an amount of 0.001 to 1 times the atomic ratio to the iron compound in the presence of oxygen or oxygen in the liquid phase. A method for producing 2-chloropropionic acid, which comprises oxidizing with a gas contained therein.