JPS6116255B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently obtaining high-purity hexachloroacetone when producing hexachloroacetone by reacting acetone with chlorine. Hexachloroacetone is hydrolyzed under basic conditions to give trichloroacetic acid and chloroform, and is useful as an intermediate for medicines, agricultural chemicals, etc. Hexafluoroacetone can also be produced by replacing chlorine with fluorine. It is an industrially important compound. Relatively many methods for synthesizing hexachloroacetone by chlorination of acetone are known; for example, P.
Fritsch, Ann. 279, 318 (1894), U.S. Patent No. 2199934 (1940), HCCheng, Z.
Although it is described in Physik.Chem.B volume 24, page 308 (1934), these are not efficient methods because the reaction time is long or the yield of hexachloroacetone is low. As an improved method of these, T. Ambrus, Rev.
Chim. vol. 14(9), pp. 506-508 (1963), and U.S. Patent No. 3265740 (1966), etc. are relatively recent.
It has been submitted. The former method involves co-current contact reaction of acetone and chlorine in a 1:3 (molar ratio) at 80 to 90°C in a packed Raschchilling column to obtain low chlorinated acetone mainly consisting of trichloride.
Hexachloroacetone is obtained by reacting excess chlorine with an activated carbon catalyst at ~160°C. The latter method involves reacting pyridine-doped acetone with 2 equivalents of chlorine in the gas phase to obtain less chlorinated acetone, which is then reacted with chlorine in the liquid phase in the presence of a catalytic amount of pyridine to produce hexachloroacetone. I am getting . In both of these methods, the step of obtaining low chlorinated acetone is carried out in the gas phase, so loss of unreacted acetone with high vapor pressure is inevitable, and in the former method, a considerable excess of chlorine is required in the step of obtaining hexachloroacetone. In the latter method, when the amount of pyridine used as a catalyst in the second step of converting to hexachloroacetone is small, 1,1,
Compared to other chlorinated acetones, 1-trichloroacetone has the disadvantage that it is less susceptible to catalytic effects and remains unreacted. In the improved method described in JP-A No. 49-24909, the reaction is carried out in three stages, in which the reaction is carried out at a low temperature in the initial stage where the degree of chlorination is low, and then the reaction is carried out in the presence of an organic base such as pyridine or its salt. The reaction is carried out by heating until a 3 to 4.5 chloride is obtained, and thereafter the reaction is carried out with chlorine in the coexistence of the above-mentioned organic base or its salt under heating and light irradiation. According to this method, the reaction proceeds in a relatively short time and at low temperature, but there is a high possibility that side reactions will occur due to contact between hydrogen chloride and acetone in the liquid phase in the early process, and light irradiation in the late process. This method has disadvantages such as complicated maintenance and management of the equipment, and is not necessarily an industrially advantageous method. In view of the above-mentioned current state of the hexachloroacetone production method, the present inventors have made extensive studies to provide a more efficient method, and as a result, we have determined that low chlorinated acetone can be used as a single phosphine catalyst (excluding triphenylphosphine). Alternatively, it was discovered that high-purity hexachloroacetone can be obtained in high yield by introducing chlorine while heating in the presence of a mixed catalyst of phosphine and an organic base, thereby achieving the present invention. This is what I did. In this specification, phosphine refers to monophenylphosphine, diphenylphosphine, dimethylphenylphosphine, triethylphosphine, tris(4-methylphenyl)phosphine, tri-
We define n-butylphosphine, tri-n-octylphosphine and triphenylphosphine, and organic base to mean pyridine, quinoline, n-tributylamine, n-trioctylamine. These organic bases have relatively high boiling points and are thermally stable compounds. In the present invention, when producing hexachloroacetone by the reaction of acetone and chlorine, in the step of obtaining low chlorinated acetone, one pair of acetone and chlorine is combined in order to avoid the production of by-products such as mesityl oxide and holone. A cocurrent catalytic reaction is carried out in the gas phase at 70 to 100°C in the range of 2 to 1 to 3 (molar ratio), and the generated 1.6 to 1.8 chlorinated acetone is converted to an organic solvent at 25 to 80°C in a subsequent absorption reactor. 2 by absorption and further reaction with excess chlorine.
~2.5 chlorinated acetone is obtained. A small amount of phosphine (excluding triphenylphosphine) alone or a combination catalyst of phosphine and an organic base such as an amine is added to this low chlorinated acetone for 60 minutes.
Almost stoichiometric amount of chlorine is blown in at ~150°C to complete the reaction and obtain hexachloroacetone. At this time, there is no problem in adding a catalyst to the organic solvent used as an absorbent from the initial stage of obtaining low chlorinated acetone. In the present invention, the reaction proceeds even with phosphine (excluding triphenylphosphine) as a single catalyst, but by adding some organic base,
It was found that the reaction could be efficiently terminated even if the amount of catalyst was reduced. In other words, when using a phosphine (excluding triphenylphosphine) catalyst alone, a small amount of catalyst results in a large amount of pentachloroacetone remaining, whereas when using an organic base catalyst such as pyridine alone, 1,1,1-trichloro Although there was a large amount of acetone remaining, it was found that pentachloroacetone and 1,1,1-trichloroacetone could be efficiently reduced by combining the two. The amount of catalyst added is 0.1 if phosphine is used alone.
~5.0 mol%, preferably 0.2-1.0 mol%, and when phosphine and an organic base are combined, both are 0.05-2.0 mol%, preferably
0.1-0.5 mol% is suitable. Any organic solvent that absorbs low chlorinated acetone may be used as long as it does not affect chlorination, has a low vapor pressure, and can be easily separated from the hexachloroacetone produced. It is easy to use low chlorinated acetone. In addition, carbon tetrachloride, chlorobenzene,
Trichlorotrifluoroethane and the like can also be used. This absorbent may be used in an amount of 10 to 100 mol %, preferably 20 to 50 mol %, based on the generated low chlorinated acetone. By using this absorbent, it is possible to moderate the temperature of the reflux condenser installed at the upper part of the absorption reactor, which has the advantage of improving the capture efficiency of low chlorinated acetone and further increasing the chlorine reaction rate. The contact time in the gas phase reaction between chlorine and acetone in the initial reaction can be set over a fairly wide range due to the compensating effect of further chlorination reaction in the subsequent absorption reactor, and can range from 5 to 20 seconds. It is. In the reaction at this stage, it is necessary to bring chlorine and acetone into gas-gas contact in order to avoid side reactions, and the temperature range is preferably 70 to 100°C. The temperature of the absorption reactor was set at 25°C to suppress the loss of organic matter and further increase the chlorine reaction rate.
~80°C is preferred. In the latter stage of converting the low chlorinated acetone thus obtained into hexachloroacetone, the reaction temperature is set at 60°C or higher, and the reaction is terminated by increasing the temperature sequentially to 150°C, but depending on the amount of catalyst. It is sufficient to raise the temperature to 140℃. As for the method of adding the catalyst, when a solid substance such as tris(4-methylphenyl)phosphine is used, it can be dissolved in low chlorinated acetone, and a liquid such as tri-n-butyl-phosphine can be added as it is. When combined with organic bases, both may be added from the beginning or may be added separately as appropriate. Water in the reaction system has a poisoning effect on phosphine and is also undesirable for corrosion of the reaction equipment, so it should be avoided as much as possible, but if water is less than 0.25% by weight based on acetone, the reaction will not proceed. There is no problem with progress. Regarding the amount of chlorine introduced, the reaction proceeds almost quantitatively in the initial stage, and by adjusting the rate of chlorine introduction in the latter stage, the reaction can be completed by suppressing the loss of chlorine, so the approximately theoretical amount is sufficient. be. This reaction can be carried out either batchwise or continuously. Example 1 A glass reaction tube (diameter 21 mm, length
270 mm) through a vaporizer, add 0.3 mol of acetone/
At the same time, 0.9 mol/hour of chlorine (molar ratio 1:2.5) was introduced, and the temperature inside the reactor was maintained at 70-80°C by heating with an electric heater to carry out a cocurrent catalytic reaction. The outlet of the reactor is connected to a 500 ml four-neck flask containing 150 g (0.57 mol) of hexachloroacetone and equipped with a -5 to 0°C reflux condenser at the top, and the temperature of the hexachloroacetone is brought to 50 to 70°C. hold and react for 2 hours
It took 47 minutes (amount of acetone introduced was 1.0 mol). The degree of chlorination of the hypochlorinated acetone produced here was 2.5 as a result of hydrogen chloride produced as a by-product and quantitative determination by gas chromatography. 0.4 g of tri-n-butylphosphine (0.2 mol% based on the acetone charged) was added to this reaction solution collected in hexachloroacetone, and the reaction temperature was adjusted to 60°C.
The temperature was gradually increased from 0.degree. C. to 146.degree. C., and hot hydrogen was fed at a flow rate of 1.0 mol/hour to carry out the reaction for 3.7 hours to obtain pale yellow crude hexachloroacetone. The purity of the crude hexachloroacetone produced was 95.4% as determined by gas chromatography, and the other products were 0.2% of 1.1,1-trichloroacetone.
%, and pentachloroacetone was 4.4%. The overall yield was 91.2% excluding the hexachloroacetone used as a solvent and the catalyst. Comparative Examples 1 and 2 100g of hexachloroacetone as an absorbent
The reaction was carried out in the same manner as in Example 1 except that 0.38 mol of quinoline and pyridine were used as catalysts instead of tri-n-butylphosphine. Table 1 shows the results of the reactions used.

[Table] In the table, TCA indicates trichloroacetone, PCA indicates pentachloroacetone, and HCA indicates hexachloroacetone. Example 2 1 mole of chlorinated acetone with a degree of chlorination of 2.3 was obtained in the same manner as in Example 1, and diphenylphosphine was added to this.
1.12g (0.6 mol%) was added, and 4.4 mol of chlorine was introduced and reacted at 70 to 169°C for 5 hours and 45 minutes. purity
96.1% colorless transparent hexachloroacetone 90.2
% yield. Examples 3, 4, 5, 6, 7, 8 Low chlorinated acetone with a degree of chlorination of 2.5 was obtained in the same manner as in Example 1 except that 100 g of hexachloroacetone was used as an absorbent, and triphenylphosphine was used as a catalyst. and quinoline or pyridine, tri-n-butylphosphine and quinoline or pyridine, tri-n-butylphosphine and tri-n-butylamine, and diphenylphosphine and quinoline. was used. The results are shown in Table 2.

[Table] In the table, TBP represents tri-n-butylphosphine, TBA represents tri-n-butylamine, and DPP represents diphenylphosphine.

Claims (1)

[Claims] 1. Reacting an average of 2 to 2.5 chlorinated acetones with chlorine while heating in the presence of a catalyst consisting of phosphine (excluding triphenylphosphine) alone or a mixture of phosphine and an organic base. A method for producing hexachloroacetone, characterized by: 2 Acetone and chlorine are brought into contact reaction in the gas phase at 70 to 100°C, and the generated average 1.6 to 1.8 chlorinated acetone is absorbed into an organic solvent, and further reacted with excess chlorine to form an average of 2 to 2.5 chlorinated acetone. ,
A method for producing hexachloroacetone, which comprises reacting this product with chlorine while heating in the presence of a catalyst consisting of phosphine alone or a mixture of phosphine and an organic base.