Method for purifying trifluoromethylpyridines

Abstract

The present invention relates to a method for purifying a compound represented by the formula (I), the method including treating a mixture containing the compound represented by the formula (I) and a compound represented by the formula (II) with an aqueous solution of a basic compound. ##STR00001##
where, in the formula (I), R.sup.1 represents a hydrogen atom or a chlorine atom; in the formula (II), R.sup.2, R.sup.3 and R.sup.4 are the same or different from each other and represent a hydrogen, a chlorine atom or a fluorine atom independently, at least one of R.sup.3 and R.sup.4 represent a chlorine atom or a fluorine atom, and, in the case where R.sup.3 represents a chlorine atom, R.sup.4 represents a chlorine atom or a fluorine atom.

Claims

1. A method for purifying a compound represented by the formula (I) comprising, treating a mixture containing the compound represented by the formula (I): ##STR00015## where R.sup.1 represents a hydrogen atom or a chlorine atom, and a compound represented by the formula (II): ##STR00016## where R.sup.2, R.sup.3 and R.sup.4 are the same or different from each other and represent a hydrogen, a chlorine atom or a fluorine atom independently, at least one of R.sup.3 and R.sup.4 represent a chlorine atom or a fluorine atom, and, in the case where R.sup.3 represents a chlorine atom, R.sup.4 represents a chlorine atom or a fluorine atom, with an aqueous solution of a basic compound, wherein the concentration of the basic compound in the aqueous solution of the basic compound is from 40 to 50% by mass, and the treatment with the aqueous solution of the basic compound is performed at 60 to 110 C.

2. The purification method according to claim 1, wherein the compound represented by the formula (I) is represented by the formula (Ia): ##STR00017##

3. The purification method according to claim 1, wherein the compound represented by the formula (I) is represented by the formula (Ib): ##STR00018##

4. The purification method according to claim 1, wherein, in the formula (II), R.sup.2 and R.sup.4 are the same or different from each other and represent a hydrogen or a chlorine atom independently, and R.sup.3 represents a fluorine atom.

5. The purification method according to claim 1, to react with chlorine and/or anhydrous hydrogen fluoride in a vapor phase in the presence of a catalyst containing a halide of at least one metal element selected from the group consisting of aluminum, chromium, iron, nickel, manganese and cobalt, and a diluent.

6. The purification method according to claim 1, wherein the basic compound is an alkali metal hydroxide.

7. The purification method according to claim 1, wherein the mixture containing the compound represented by the formula (I) and the compound represented by the formula (II) is obtained by allowing a compound represented by the formula (A): ##STR00019## where Ws are the same or different from each other and represent a hydrogen, a fluorine atom or a chlorine atom independently, and X, Y and Z are the same or different from each other and represent a hydrogen or a chlorine atom independently, the treatment with the aqueous solution of the basic compound is performed at 60 to 110 C.

Description

EXAMPLES

(1) The following describes Examples of the present invention but the invention should not be construed as being limited thereto.

(2) The abbreviations used in the following Examples are as follows.

(3) DCTF: 2,3-dichloro-5-trifluoromethylpyridine

(4) DCFTF: 2,5-dichloro-6-fluoro-3-hifluoromethylpyridine

(5) 56CFTF: 5-chloro-6-fluoro-3-trifluoromethylpyridine

(6) CTF: 2-chloro-5-trifluoromethylpyridine

(7) 26CFTF: 2-chloro-6-fluoro-3-trifluoromethylpyridine

(8) 2-CTF: 2-chloro-3-trifluoromethylpyridine

(9) 2,6-DCTF: 2,6-dichloro-3-trifluoromethylpyridine

(10) 256TCTF: 2,5,6-trichloro-3-trifluoromethylpyridine

(11) NaOH: sodium hydroxide

(12) GC: gas chromatography

(13) HPLC: high performance liquid chromatography

Purification Example 1

(14) A crude DCTF mixture (7,500 kg (5 m.sup.3)) was charged into a jacketed tank (10 m.sup.3) equipped with a stirrer made of SUS. Next, a 48% by mass aqueous NaOH solution (300 kg) which corresponds to 4% by mass relative to the mass of the crude DCTF mixture was charged. Then, the whole was heated and stirred at 80 C. for 8 hours.

(15) After confirming that the peak area ratio (Peak area %) of DCFTF was 0.1 PA % or less by GC analysis under the following measurement conditions, warm water (3,750 kg) at 60 C. was charged and followed by stirring for 30 minutes. The mixture was cooled to 50 C. and allowed to stand for 30 minutes, and liquid separation was conducted to obtain purified DCTF.

(16) The term crude DCTF mixture means a mixture containing DCTF, DCFTF and 56CFTF.

Purification Example 2

(17) A crude DCTF mixture (7,500 kg (5 m.sup.3)) was charged into a jacketed tank (10 m.sup.3) equipped with a stirrer made of SUS. Next, a 48% by mass aqueous NaOH solution (450 kg) which corresponds to 6% by mass relative to the mass of the crude DCTF mixture was charged. Then, the whole was heated and stirred at 80 C. for 5 hours.

(18) After confirming that the peak area ratio of DCFTF was 0.1 PA % or less by GC analysis under the following measurement conditions, post treatment was performed in accordance with Purification Example 1 to obtain purified DCTF.

Purification Example 3

(19) A crude DCTF mixture (7,500 kg (5 m.sup.3)) was charged into a jacketed tank (10 m.sup.3) equipped with a stirrer made of SUS. Next, a 48% by mass aqueous NaOH solution (450 kg), which corresponds to 6% by mass relative to the mass of the crude DCTF mixture, was charged. Then, the whole was heated and stirred at 90 C. for 2 hours.

(20) After confirming that the peak area ratio of DCFTF was 0.1 PA % or less by GC analysis under the following measurement conditions, post treatment was performed in accordance with Purification Example 1 to obtain purified DCTF.

Purification Example 4

(21) A crude DCTF mixture (150 g) was charged into a reactor equipped with a stirrer. Next, a 48% by mass aqueous NaOH solution which corresponds to 12.5% by mass relative to the mass of the crude DCTF mixture was charged. Then, the whole was heated and stirred at 80 C. for 11 hours.

(22) After confirming that the peak area ratio of DCFTF was 0.1 PA % or less by GC analysis under the following measurement conditions, post treatment was performed in accordance with Purification Example 1 to obtain purified DCTF.

(23) The results of the GC analysis for purification examples 1 to 4 are shown in Table 1. The measurement conditions of GC were as follows.

(24) Column: 3.2 mm ID3.1 mL 10% silicon OV-101 chromosorb WHP 80 to 100 mesh or its equivalent

(25) Carrier: dichloromethane

(26) Column temperature: 100 C.

(27) Flow rate: about 140 kPa

(28) Detector: FID

(29) TABLE-US-00001 TABLE 1 Before treatment After treatment with aqueous with aqueous Purification NaOH solution (PA %) NaOH solution (PA %) Example DCTF DCFTF 56CFTF DCTF DCFTF 56CFTF 1 70.42 0.26 1.61 72.08 0.02 0.52 2 63.75 0.52 1.88 65.13 0.01 0.22 3 64.53 0.17 0.83 64.87 0.01 0.15 4 98.58 0.89 99.71 0

Purification Example 5

(30) A crude CTF mixture (300 g, CTF: 98 PA % or more) was charged into a round bottom flask (1 L), and then a 25% by mass aqueous solution of NaOH (15 g) which corresponds to 5% by mass relative to the mass of the crude CTF mixture was charged. The mixture was heated and stirred at 100 C. for 15 minutes.

(31) As a result of analysis by HPLC under the following measurement conditions, the peak area ratio of 26CFTF in the crude CTF mixture was 0.307 PA %, but after the treatment, was halved to 0.167 PA %. In order to control the peak area ratio of 26CFTF to 0.1 PA % or less, the treatment time may be further prolonged.

(32) The term crude CTF mixture means a mixture containing CTF and 26 CFTF.

(33) Moreover, the measurement conditions of HPLC were as follows.

(34) Column: Cosmosil-5C18ARII or its equivalent

(35) Column temperature: equivalent to 40 C.

(36) Carrier: Acetonitrile: Water (10 mM H.sub.3PO.sub.4)=60:40

(37) Flow rate: 1.2 mL/min

(38) Detection: UV (254 nm)

Production Examples of CTF and DCTF

Production Example (1)

(39) As a reactor, an Inconel-made vertical reaction tube having a catalyst fluidized bed whose reaction portion had an inner diameter of 97.1 mm and a height of 1,570 mm was installed, which connected with two Inconel-made preheating tubes having an inner diameter of 30 mm and a length of 1,000 mm was used for raw materials and an inert diluent, and the reaction tube and the preheating tubes were covered with an electric heater and a heat-insulating material so that temperature could be controlled.

(40) One obtained by impregnating 2.2 kg of aluminum trifluoride having a particle diameter of 105 to 250 m with 277 g of anhydrous ferric chloride was placed in the catalyst packing part and heated to 200 C., and an anhydrous hydrogen fluoride was introduced at a rate of 2.3 L/minute for 1 hour to activate the catalyst.

(41) The reactor was heated to 400 C., -picoline and nitrogen gas were introduced through the preheating tube so as to be rates of 6.8 g/minute and 9.9 L/minute, respectively, as a mixed gas of about 200 C. and chlorine gas and anhydrous hydrogen fluoride were introduced through a preheating tube so as to be rates of 7.4 L/minute and 7.4 L/minute, respectively, as a mixed gas of about 200 C. They were allowed to react for about 30 hours. During the time, the activated catalyst was continuously supplied and discharged at a rate of 300 g/hour. The residence time of the reaction mixture in the tube was about 3.4 seconds.

(42) A gas discharged from the reactor was allowed to pass through a water-washing column and an alkali-washing column, a condensation product was separated and neutralized with an aqueous ammonia solution, and 19.11 kg of an oily substance was obtained by steam distillation. The oily substance contains about 1 PA % of DCFTF and about 2 PA % of 56 CFTF.

(43) The oily substance was distilled to obtain 1.53 kg of a first fraction containing -trifluoromethylpyridine as a main component, 9.56 kg of a main fraction containing CTF as a main component, and 7.62 kg of a post fraction. The post fraction contained 3.7 PA % of CTF, 14.5 PA % of 2-CTF, 47.7 PA % of 2,6-DCTF and 34.1 PA % of others.

Production Example (2)

(44) In the above Production Example (1), the reaction was carried out in the same manner except that -picoline, -trifluoromethylpyridine, chlorine gas and anhydrous hydrogen fluoride were introduced at rates of 4.6 g/minute, 3.4 g/minute, 5.8 L/minute, and 5 L/minute, respectively. The residence time of the reaction mixture was about 4 seconds and the reaction was continuously carried out for about 8 hours. The reaction product was similarly post-treated to obtain 5.47 kg of an oily substance.

(45) The main composition of this oily substance was 8.2 PA % of -trifluoromethylpyridine, 57.8 PA % of CTF, 9.5 PA % of 2-CTF, 16.1 PA % of DCTF and 8.4 PA % of others.

(46) By distilling the oily substance, a fraction containing CTF as a main component can be obtained.

Production Example (3)

(47) As a reactor, one where the reaction portion was an Inconel-made vertical reaction tube having a catalyst fluidized bed having an inner diameter of 30 mm and a height of 500 mm, which connected with two Inconel-made preheating tubes having an inner diameter of 20 mm and a length of 300 mm, and these were covered with an electric heater and a heat insulating material so that temperature could be controlled, was used.

(48) One (60 g) obtained by mixing a solution in which 24 g of ferric chloride was dissolved in 200 ml of ethanol and 120 g of active carbon (80 to 200 meshes) and then drying them was introduced into the catalyst packing part of the reactor and heated to about 200 C. Then, chlorine gas was introduced so as to be a rate of 1.3 L/minute for about 3 hours to activate the catalyst.

(49) A mixed gas of CTF and nitrogen gas were preheated to about 200 to 250 C. and introduced through one preheating tube so that the rate of the former be 0.5 g/minute and the rate of the latter be 1.0 L/minute into the reaction tube. Also, a mixed gas of chlorine gas and nitrogen gas preheated to the same temperature was introduced through another preheating tube so that the rate of the former be 0.25 L/minute and the rate of the latter be 0.6 L/minute into the reaction tube. They were allowed to react at 250 C. for about 4 hours.

(50) A gas discharged from the reactor was allowed to pass through a water-washing column and an alkali-washing column and condensed, and an oily substance was separated and collected and, after washed with water, dried over sodium sulfate to obtain 110 g of an oily substance.

(51) The main composition of this oily substance was 74.1 PA % of DCTF, 7.1 PA % of 256TCTF, 16.0 PA % of CTF, and 2.7 PA % of others.

(52) By distilling the oily substance, a fraction containing DCTF as a main component can be obtained.

(53) While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The present application is based on Japanese Patent Application No. 2017-74229 filed on Apr. 4, 2017, and the contents are incorporated herein by reference.