JPS63310844A - Production of 2-chloropropionic acid - Google Patents

Abstract

PURPOSE:To facilitate control of oxidation rate and efficiently obtain the titled compound in high selectivity and purity under environment with hardly any corrosion, by oxidizing 2-chloropionaldehyde in the liquid phase with an O2- containing gas, etc., using a specific catalyst. CONSTITUTION:2-Chloropropionaldehyde expressed by formula I is oxidized in the liquid phase with O2 or an O2-containing gas in the presence of at least one metallic compound catalyst selected from titanium compounds, such as TiO2, zirconium compounds, such as ZrO2, and hafnium compounds, such as HfCl4, in a solvent, preferably acetic acid, etc., preferably at 20-120 deg.C, especially preferably at 40-80 deg.C normally under <=100kg/cm<2> O2 partial pressure to afford the aimed compound expressed by formula II useful as an intermediate for producing industrial chemicals and agricultural chemicals. Furthermore, the high-purity aimed compound without containing impurities, such as monochloroacetic acid, can be produced by oxidation using a batch reactor according to the above-mentioned method.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to the production of 2-chloropropionic acid, which is useful as an intermediate for the production of industrial chemicals and agricultural chemicals, using the following reaction formula (1). The present invention relates to a method for producing 2-chloropropionaldehyde by oxidation.

(Prior art and problems to be solved by the invention) 2-Chloropropionic acid has been produced industrially by chlorination of propionic acid according to the following reaction formula (2). It has been manufactured. However, in this method, half of the chlorine consumed is directed to the by-product of hydrogen chloride, as is clear from the equation.
2-chloropropionic acid produced by this method is economically unfavorable in terms of chlorine utilization.
In addition to unreacted propionic acid as impurities, it is difficult to achieve a purity of 95% or higher because it usually contains several % of dichloro compounds such as further chlorinated 2,2-dichloropropionic acid. Since it is difficult to separate 2-chloropropionic acid from 2-chloropropionic acid by simple distillation, it is difficult to obtain highly pure 2-chloropropionic acid using this production method.

As one method for solving these problems, a method for producing 2-chloropropionic acid by oxidizing 2-chloropropionaldehyde is proposed in JP-A-62-96446. Here, 2-chloropropionaldehyde is treated 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 iron compounds, cobalt compounds, nickel compounds, manganese compounds, copper compounds, and cerium compounds. A method for producing 2-chloropropionic acid by oxidation is disclosed. 2- used as raw material in this method
Chloropropionaldehyde is disclosed in, for example, JP-A-61-1
26046, it can be produced by reaction of vinyl chloride with synthesis gas in the presence of rhodium and a base.

This method is an effective method for solving the problems in the conventional 2-chloropropionic acid production methods mentioned above, and is especially effective for producing 2-chloropropionic acid on a relatively large scale using a flow reactor. This is a suitable method for synthesis. In general, when conducting such oxidation reactions industrially, a distribution reaction system is better for carrying out the reaction on a large scale, but when carrying out the reaction on a relatively small scale, it is better to use a batch reaction system, which reduces production costs. It is advantageous from an aspect. However, when producing 2-chloropropionic acid on a small scale using a batch oxidation reactor, the oxidation catalyst made of these metal compounds used in the method shown in JP-A No. 62-96446 has a high Because it is active, oxidation reactions proceed all at once,
It has been found that there are problems in that it is difficult to remove the reaction heat and control the reaction temperature, resulting in loss of selectivity and deactivation of the catalyst in a short period of time. In particular, if the reaction temperature is not strictly maintained within a preferred range, monochloroacetic acid will be produced as a by-product. The amount is at most 1 to 2%, but since the boiling point of monochloroacetic acid is close to that of 2-chloropropionic acid, it is difficult to separate it by distillation.
In order to produce chloropropionic acid, it is preferable to suppress this by-product to below the detection limit. This problem is less important when the reaction is carried out on a large scale using a flow-through type oxidation reactor because the heat of reaction can be removed efficiently.
This method is not suitable for producing 2-chloropropionic acid on a relatively small scale.

One way to solve this problem is to lower the concentration of the catalyst used, but if the catalyst concentration is extremely low, the reaction will stop immediately due to trace amounts of by-products or contamination with catalyst poisoning substances, resulting in a decrease in productivity. .

In addition, lowering the reaction temperature and oxygen partial pressure may be considered in order to control the oxidation reaction rate, but these methods significantly lengthen the induction period of the oxidation reaction, resulting in a decrease in productivity. Furthermore, the use of extremely low catalyst concentrations and low reaction temperatures promotes the formation of peracids and adducts of peracids and aldehydes, which poses a serious problem in ensuring operational safety.

An object of the present invention is to provide a method for efficiently producing 2-chloropropionic acid in a less corrosive environment.

(Means and effects for solving the problems) The present inventors have conducted research to solve these problems and found that when oxidizing 2-chloropropionaldehyde, titanium compounds, zirconium compounds or The inventors have discovered that the above-mentioned problems can be solved by using a metal compound such as a hafnium compound, and have completed the present invention.

That is, the present invention is characterized in that 2-chloropropionaldehyde is oxidized with oxygen or an oxygen-containing gas in the liquid phase in the presence of at least one metal compound catalyst selected from the group consisting of titanium compounds, zirconium compounds, and hafnium compounds. This is a method for producing 2-chloropropionic acid.

Typical examples of these titanium compounds, zirconium compounds, and hafnium compounds include oxides, hydroxides, mineral salts, carboxylates, and carbonates of these metals.

More specifically, examples of titanium compounds include -titanium oxide, titanium dioxide, titanous titanium sulfate, di-titanium sulfate, titanium trichloride, titanium tetrachloride, potassium titanium oxalate, potassium titanium tartrate, etc. ,other than this,
Organic titanium compounds such as titanium isoproboxite are also mentioned as preferred examples of titanium compounds.

Further, examples of the zirconium compound include zirconium dioxide, zirconium hydroxide, zirconium sulfate, zirconium chloride, zirconium oxychloride, zirconium oxynitrate, zirconium oxyacetate, basic zirconium carbonate, and the like.

Examples of hafnium compounds include hafnium oxide and hafnium chloride.

Among these compounds, titanium compounds or zirconium compounds are particularly excellent in terms of effects and are preferably used.

These compounds may be used alone or in a mixture of two or more. Further, these compounds can be used in powder or crystal form, but it is also preferable to use them in a form dissolved in 2-chloropropionic acid or 2-chloropropionaldehyde. The amount of these compounds used is usually 0.001% to 10% by weight in the liquid phase, preferably 0.01%. At temperatures below 20°C, the oxidation reaction rate is slow and industrially unfavorable. At temperatures above 120°C, dehydrochlorination of 2-chloropropionaldehyde and 2-chloropropionic acid, etc. Side reactions become significant and the yield of 2-chloropropionic acid decreases, as does the purity. For these reasons, 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 heat generated by oxidation and obtain good reaction results, it is preferable to carry out 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, and butyric acid; Other examples include dimethyl sulfoxide, sulfolane, acetone, etc. Also, the use of the product 2-chloropropionic acid makes it possible to omit the step of separating the product and solvent after the oxidation reaction. More preferably, the concentration of 2-chloropropionaldehyde in these solvents is usually 1 to 50% by weight,
A range of 5-15% is sometimes 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 it reduces the reaction rate.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. As the oxygen-containing gas, air is generally preferred, but a mixed gas of oxygen and nitrogen is also similarly preferred.

The pressure of these oxygen-containing gases is preferably 0.2 kg/cff1 or more, particularly 5 kg/cij or more 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 not industrially preferable to make the pressure too high, so the oxygen partial pressure is usually set within a range of 100 kg/c- or less.

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

Example 1 69.4 g of 2-chloropropionaldehyde was placed in a stainless steel autoclave with an internal volume of 5N equipped with a stirring device.
(0.75 mol), 950 g of acetic acid as a reaction solvent, and 5.0 g of titanium dioxide (Tilt) as an oxidation catalyst were charged. Add to this a mixed gas of oxygen and nitrogen (1:1).
was pressurized to 100 kg/c4, and the reaction was carried out at 50''C in a hot water bath with stirring for 8 hours.During the reaction, oxygen was constantly supplied from a cylinder, and the pressure inside the autoclave was kept at 1.
00 kg/C1a Niho ivy.

The reaction proceeds mildly with almost no Pjl1 phase, temperature control is extremely easy, and the temperature is within ± the set value.
The reaction temperature could be kept constant within the range of l''C.

After the reaction was completed, the autoclave was cooled, the pressure was released, the contents were taken out, and the contents were analyzed by gas chromatography. As a result of analysis, the conversion rate of 2-chloropropionaldehyde was 86.5%, and the conversion rate of 2-chloropropionic acid was 86.5%. The selectivity to was 99.1%.

Furthermore, no by-product of monochloroacetic acid was observed in the reaction solution.

Comparative Example 1 2-chloropropionaldehyde was oxidized in the same manner as in Example 1, except that 5.0 g of cobalt acetate (tetrahydrate) was used instead of titanium dioxide as a catalyst.

Due to the temperature change inside the reactor, the reaction has an induction period of about 20 minutes, after which the reaction progresses rapidly and temperature control is no longer possible, and the reaction temperature rises to 135°C and then gradually decreases to the set value. I understand.

Analysis of the reaction solution after completion of the reaction revealed that the conversion rate of 2-chloropropionaldehyde was 95.2% and the selectivity to 2-chloropropionic acid was 96.3%. Furthermore, 1.8% of monochloroacetic acid as a by-product was observed in the solution after the reaction.

Examples 2 to 5 2-
Oxidation of chloropropionaldehyde was carried out. The results are shown in Table-1.

In addition, in any case, the reaction temperature is ±1 relative to the set value.
The reaction temperature could be easily controlled within ℃, and no by-product of monochloroacetic acid was observed in the solution after the reaction.

(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, almost no 2,2-dichloropropionic acid is detected in the obtained 2-chloropropionic acid.Furthermore, the oxidation rate is lower than that of the oxidation method of 2-chloropropionaldehyde that has been copied so far. Control can be performed easily. Furthermore, even under such easy-to-control oxidation conditions, the induction period of the reaction is short, and there is almost no peracid by-product.Especially, the method of the present invention allows the use of a batch reactor. This oxidation makes it possible to produce highly pure 2-chloropropionic acid that does not contain impurities such as monochloroacetic acid.

Claims (2)

[Claims] (1) 2-chloropropionaldehyde is oxidized with oxygen or an oxygen-containing gas in the liquid phase in the presence of at least one metal compound catalyst selected from the group consisting of titanium compounds, zirconium compounds, and hafnium compounds. - A method for producing chloropropionic acid. (2) The method according to claim 1, wherein the oxidation is carried out within a temperature range of 40 to 80°C.