JPS6134415B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an industrially and economically advantageous method for producing β-trifluoromethylpyridines by fluorinating β-trichloromethylpyridines in the gas phase in the presence of a catalyst. β-trifluoromethylpyridines (hereinafter referred to as β-
TFP (abbreviated as TFP) is a compound useful as a raw material for agricultural chemicals such as herbicides, insecticides, and fungicides, as well as dyes and medicines, and its industrial value has recently attracted attention. However, β-trichloromethylpyridines (hereinafter referred to as β-trichloromethylpyridines), which are the raw materials for β-TFP,
(abbreviated as TCP), there have been manufacturing problems, so very little research has been done in the past on the method of manufacturing β-TFP from β-TCP, and of course, the industrial manufacturing technology has not been established. do not have. The present inventors, who had been conducting research on the fluorination of β-TCP, discovered that β-TCP can be fluorinated in the presence of a specific catalyst.
The method of the present invention was completed based on the knowledge that when TCP is reacted with hydrogen fluoride, the fluorination reaction progresses smoothly and β-TFP is produced in good yield. That is, the present invention provides a method in which a compound of the general formula

[Formula] (where n is an integer of 1 to 3) β-trichloromethylpyridine and anhydrous hydrogen fluoride
General formula characterized by reaction in gas phase at 200-700℃

This is a method for producing β-trifluoromethylpyridines represented by the formula: (where n is as described above). In the method of the present invention, β used as a raw material
-TCP includes the 2-, 5-, and 6-positions of the pyridine ring.
Compounds having chlorine atoms as substituents at positions such as -, 2, 6-, 5, 6-, and 2, 5, 6-positions, such as 2-chloro-3-trichloromethylpyridine, 2-chloro -5-trichloromethylpyridine, 3-chloro-5-trichloromethylpyridine, 2,3-dichloro-5-trichloromethylpyridine, 2,6-dichloro-3-trichloromethylpyridine, 2,5,6-trichloro-3 -trichloromethylpyridine, etc., and mixtures thereof. Among these, especially 6-position substituted products, 2.6-
Substituted products and substituted products at 5 and 6 positions are useful as raw materials for herbicides or insecticides. The metal fluoride of chromium, iron or nickel used in the method of the present invention is hydrated chromium trifluoride ( _CrF3 .
3H ₂ O), hydrated ferrous fluoride (FeF ₂ 8H ₂ O), hydrated nickel fluoride (NiF ₂ 3H ₂ O), etc. Ammonium fluoride compounds include ammonium fluoride. , acidic ammonium fluoride, and the like. Although the mixing ratio of these catalysts cannot be determined unconditionally depending on the reaction conditions, it is usually 3 to 20 moles of ammonium fluorine compound per mole of metal fluoride. This blended catalyst is mixed with a carrier such as activated carbon or activated alumina, and the polymerization ratio of the blended catalyst and carrier is usually 1:5 to 1:5.
Used in 10 mixed states. In industrial implementation,
The mixture of the blended catalyst and activated carbon may be formed into particles or pellets of appropriate size and may be present as a fixed bed or a fluidized bed. Furthermore, the reaction efficiency can be increased by allowing chlorine gas to exist in the reaction zone. In the method of the present invention, the raw material β-TCP is vaporized as it is or once dissolved in an inert solvent and then vaporized, and anhydrous hydrogen fluoride is vaporized as it is and introduced into the reactor. Note that it is desirable to preheat β-TCP to around its boiling point or reaction temperature, usually around 300°C, before introducing it into the reactor. Examples of the above-mentioned inert solvent include carbon tetrachloride,
Chloroform, methylene chloride, F-112
( _CFCl2.CFCl2 ), halogenated hydrocarbons such _as F-113 ( _CF2Cl.CFCl2 ), and aromatic hydrocarbons such as benzene and _toluene . When an inert solvent is used, the ratio of β-TCP to solvent may generally be about 1 to 10 moles, preferably about 3 to 5 moles, of the inert solvent per mole of β-TCP. The amount of anhydrous hydrogen fluoride to be supplied to β-TCP is generally about 3 to 15 moles, preferably about 4 to 12 moles, and more preferably about 5 to 9 moles per mole of β-TCP. The reaction between β-TCP and anhydrous hydrogen fluoride is usually 200~
The temperature is 700°C, preferably 300-500°C. The residence time of the reaction mixture in the reaction zone is usually between 1 and 100
It is about seconds, preferably about 2 to 20 seconds. After the above reaction is completed, gaseous substances containing fluorinated products mainly composed of β-TFP, unreacted hydrogen fluoride, by-product hydrochloric acid gas, and inert solvent are discharged from the reactor. However, β-TFP is collected as a liquid mixture through appropriate cooling and condensation equipment, and is isolated as a highly pure product through ordinary purification processes such as extraction, distillation, and crystallization. It can be obtained with a yield of more than 80%. Examples of β-TFP obtained by the method of the present invention include 2-chloro-3-trifluoromethylpyridine, 2-chloro-5-trifluoromethylpyridine, 3-chloro-5-trifluoromethylpyridine, 2. Examples include 3-dichloro-5-trifluoromethylpyridine, 2,6-dichloro-3-trifluoromethylpyridine, 2,5,6-trichloro-3-trifluoromethylpyridine, and mixtures thereof. In addition to the above β-TFP, the fluorinated products discharged from the reactor also contain compounds in which one or two of the chlorine atoms in the trichloromethyl group of β-TCP have been replaced with fluorine atoms, as intermediate products. However, these are separated and recovered together with unreacted raw materials and inert solvents.
It can be recycled to the reaction zone. Example 1 A stainless steel reaction tube with an inner diameter of 42 mm and a length of 1250 mm was used as the reaction section, and a distance of 250 mm from the inlet of the reaction section was used.
was used as the catalyst filling part. On the other hand, for anhydrous hydrogen fluoride as a preheating part, the inner diameter is 20 mm.
mm, using a stainless steel preheating tube with a length of 500 mm,
A heat-resistant glass (Pyrex) preheating tube with an inner diameter of 30 mm and a length of 500 mm was used for β-TCP. The reaction tube and preheating tube were covered with an electric heater and heat insulating material and installed at an angle so that the temperature could be controlled from the outside. Hydrated chromium trifluoride (CrF _{3.3H 2} O) 0.02 mol,
A uniform mixture of powder containing 0.1 mol of acidic ammonium fluoride (NH ₄ .HF) and 0.1 mol of ammonium fluoride (NF ₄ F) and 40 g of granular activated carbon was placed in the catalyst filling section. The reaction tube was heated to 350°C, anhydrous hydrogen fluoride was passed through it at 1g/min for 2 hours, and 277g (1.2 mol) of 2-chloro-5-trichloromethylpyridine and 554g (3.6 mol) of carbon tetrachloride were preheated to 300°C. ) and 192 g (9.6 mol) of anhydrous hydrogen fluoride were fed at an almost constant flow rate over 65 minutes to carry out a gas phase reaction at 350°C. The residence time of the reaction mixture in the reaction tube was about 9 seconds. The gas discharged from the reaction tube was condensed through a water washing tower and an alkali washing tower. The condensate was separated, washed with water, dried over sodium sulfate, and carbon tetrachloride was distilled off under reduced pressure to obtain 242 g of an oil. Analysis of this oil by temperature-rising gas chromatography revealed that the target product, 2-chloro-5-trifluoromethylpyridine, accounted for 94% of the recovered organic matter, and the yield after distillation and purification was 89.5%. It was hot. In addition, the distillation residue contained 20% of 2-chloro-5-fluorodichloromethylpyridine and 2-chloro-5-fluorodichloromethylpyridine as intermediate products.
It contained 67% of -chlorodifluoromethylpyridine, and further contained 3.8% of unreacted 2-chloro-5-trichloromethylpyridine. Example 2 The reaction was carried out in the same manner as in Example 1 except that 0.02 mole of hydrated chromium trifluoride was changed to 0.02 mole of hydrated ferrous fluoride (FeF ₂ .8H ₂ O) to obtain the target product. 2-chloro-5-trifluoromethylpyridine was obtained with a production rate of 93% and a yield of 86.5%. Note that 4% of 2-chloro-5-chlorodifluoromethylpyridine was produced as an intermediate product. Example 3 The reaction was carried out in the same manner as in Example 1 except that 0.02 mole of hydrated chromium trifluoride was changed to 0.02 mole of hydrated nickel fluoride (NiF _{2.3H 2} O) to obtain the target product. 2-chloro-5-trifluoromethylpyridine was obtained with a production rate of 85% and a yield of 80.1%. Note that 10% of 2-chloro-5-chlorodifluoromethylpyridine was produced as an intermediate product.

Claims (1)

[Claims] 1. In the presence of a catalyst consisting of a fluoride of at least one metal element selected from the group consisting of chromium, iron and nickel and an ammonium fluorine compound, n is an integer of 1 to 3) and anhydrous hydrogen fluoride.
A method for producing β-trifluoromethylpyridines represented by the general formula [Formula] (wherein n is as described above), characterized by carrying out the reaction in a gas phase at 200 to 700°C.