JPH01283397A - Method for electrolytic fluorination - Google Patents

Abstract

PURPOSE:To obtain a completely fluorinated trialkylamine having a large number of carbon atoms in high yield by electrolytically fluorinating a mixture of a trialkylamine having a relatively large number of carbon atoms and a trialkylamine having a relatively small number of carbon atoms. CONSTITUTION:A mixture of a 15-24C trialkylamine and a 3-14C trialkylamine is charged in an electrolytic cell having an anode and a cathode along with hydrogen fluoride, and a current is applied between both electrodes. The electrode is appropriately made of nickel or its alloy. The electrolysis is appropriately performed at about -15-20 deg.C, about 0.1-5A/dm<2> current density, and about 4-9V cell voltage. The content of the trialkylamine having a small number of carbon atoms in the mixture is preferably controlled to about 10-90wt.%, or especially to about 20-70%. As a result, the trialkyamine having a large number of carbon atoms is completely fluorinated, and the fluorinated trialkyamine can be easily separated and recovered in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrolytic fluorination method for electrochemically fluorinating trialkylamines.

(Prior Art and Problems to be Solved by the Invention) Electrolytic fluorination is well known as a method for complete fluorination of organic compounds. This method has the advantage that a fully fluorinated product corresponding to the raw organic compound can be obtained in one step. On the other hand, a large amount of decomposition products of raw materials are produced as by-products,
Since the incompletely fluorinated product is mixed into the fully fluorinated product, the yield of the desired fully fluorinated product is not fully satisfactory.

In fact, the present inventors performed electrolytic fluorination of trialkylamines with a relatively large number of carbon atoms, such as tripentylamine and trihexylamine, and were able to obtain the desired perfluorotripentylamine. There wasn't.

(Means for Solving the Problems) Therefore, the present inventors have attempted to improve the yield of the target fully fluorinated product in the electrolytic fluorination method of trialkylamine having a relatively large number of carbon atoms. I have been doing research for this purpose. As a result, by electrolytically fluorinating the trialkylamine with a relatively small number of carbon atoms mixed with the above-mentioned trialkylamine with a relatively large number of carbon atoms,
It has been found that a fully fluorinated trialkylamine having a relatively large number of carbon atoms can be obtained in high yield.

That is, the present invention is an electrolytic fluorination method characterized by electrolytically fluorinating a mixture of a trialkylamine having 15 to 24 carbon atoms and a trialkylamine having 3 to 14 carbon atoms.

In the present invention, the number of carbon atoms to be electrolytically fluorinated is 15.
-24 trialkylamine is a compound in which the total number of carbon atoms in three alkyl groups is in the range of 15 to 24 without any restriction. Specific examples include tripentyl, trihexylamine, dipentylhexylamine, pentyldihexylamine, trihebutylamine, and trioctylamine. On the other hand, as the trialkylamine having 3 to 14 carbon atoms, a compound in which the total number of carbon atoms of three alkyl groups is in the range of 3 to 14 can be used without any restriction. Specific examples include trimethylamine, triethylamine, tripropylamine, tributylamine, diethylpropylamine, ethyldipropylamine, diethylbutylamine, ethyldibutylamine, dipropylbutylamine, propyldibutylamine, and the like.

When the above-mentioned trialkylamine having 15 to 24 carbon atoms is tripentylamine or trihexylamine, triethylamine, tripropylamine or tributylamine may be mixed as the trialkylamine having 3 to 14 carbon atoms. is preferably employed from the viewpoint of the yield of perfluorotripentylamine or perfluorotrihexylamine.

The mixing amount of the trialkylamine having 3 to 14 carbon atoms is in the range of 10 to 90% by weight, and further 20 to 70% by weight, considering the yield of the trialkylamine having 15 to 24 carbon atoms. It is preferable.

For the electrolytic fluorination of the present invention, known methods can be employed without any limitations. Specifically, hydrogen fluoride and an organic compound are supplied to an electrolytic cell equipped with an anode and a cathode, and electricity is applied between the anode and the cathode. As the anode, nickel or its alloy is usually used, and as the cathode, in addition to nickel or its alloy, iron, stainless steel, copper, etc. are used. Further, in addition to the above-mentioned cathode materials that can be used as they are, fluororesin can also be used for the electrolytic cell. The distance between the anode and cathode mentioned above is generally 0.
．． It is preferable to set it as about 5-511.

Electrolysis conditions may be selected appropriately from known ranges, but usually the temperature is -15 to 20°C and the current density is 0.1 to 5 A/dm.
”, a sliding voltage in the range of 4 to 9 V is adopted.From the viewpoint of improving current efficiency and stabilizing the sliding voltage, stirring or circulation of the electrolytic bath, or blowing inert gas into the electrolytic bath, etc. It is preferable to do so.

In addition, the concentration of iron in the electrolytic bath solution is set to 1'5'ppm or less,
Furthermore, it is preferable to set it to 0.3 ppm or less. In this case, the iron concentration is the total concentration of iron atoms contained in iron ions and iron compounds in the electrolytic bath solution.

(Effects) According to the method of the present invention, the yield of a fully fluorinated trialkylamine having 15 to 24 carbon atoms is improved. In addition, trialkylamines having 3 to 14 carbon atoms are fluorinated together with trialkylamines having 15 to 24 carbon atoms, but the latter fully fluorinated product can be easily separated from the former fully fluorinated product. It is. Therefore, the present invention is a preferred method for co-producing a fully fluorinated trialkylamine having 15 to 24 carbon atoms and a fully fluorinated trialkylamine having 3 to 14 carbon atoms.

Example 1 Electrolytic fluorination was carried out as follows by changing the composition of the mixture of trihexylamine and tributylamine as raw materials. A nickel electrolytic cell with a diameter of 10 cm and a height of 20 cm and a nickel circulation tank (capacity 41) having a reflux condenser (-45° C.) at the top were used. The cathode and anode were composed of a total of 15 nickel plates (65 mm x 120 mm, thickness 111) arranged alternately with a distance of about 311 between the electrodes. 3.5 ff of anhydrous hydrogen fluoride and 250 g of a raw material mixture having the composition shown in Table 1 are supplied to the circulation tank, and this mixed solution is flowed between the electrodes from the bottom of the electrolytic tank at a rate of 10 β/min using a pump, and Electrolysis was started while the overflow was returned to the circulation tank again. Gradually increase the current value 5
After 0 hours, electrolysis was carried out at a constant current of 33A. The electrolytic bath and circulation bath are externally cooled to bring the temperature in the electrolytic bath to about 10%.
It was kept at ℃. During the reaction, fluorinated water was continuously replenished so as to maintain a substantially constant amount of electrolytic bath solution. Immediately after the start of electrolysis, the feed of the raw material mixture was started and continued while maintaining a steady state of the concentration of total amines (including amines fluorinated to various degrees) in the electrolytic bath solution at about 15% by weight. I drove. Note that the perfluoro compound produced and precipitated was intermittently extracted from the lower part of the electrolytic cell, its amount was measured, and its composition was determined by gas chromatography. The electrolytic voltage during continuous operation was in the range of 5.7 to 6.0 . In addition, the iron ion concentration in the electrolyte is O, i pp
It was managed so that it was less than m. The influence of the composition of the raw material mixture on the electrolytic fluorination reaction is as shown in Table 1. Table 1 also shows the results of a similar experiment using trihexylamine alone as a comparative example.

1st Table Water The case where all the supplied trihexylamine was converted to perfluorotrihexylamine was defined as 100%.

Example 2 Mixed raw material of tripentylamine and tributylamine,
Electrolytic fluorination of a mixed raw material of tripentylamine and tripropylamine (1:1 by weight in each case) was carried out in the same manner as in Example 1. The results are shown in Table 2. Table 2 also shows the results of a similar experiment using tripentylamine alone as a comparative example. In addition, the electrolysis voltage during continuous operation is 5.65 to 5 in all cases.
．． 85v range, and the iron concentration in the electrolytic bath solution is 0.1
It was controlled to be below ppm.

Table 2 * The case where all of the supplied tripentylamine was converted to perfluorotripentylamine was defined as 100%.

Claims (1)

[Claims] (1) An electrolytic fluorination method characterized by electrolytically fluorinating a mixture of a trialkylamine having 15 to 24 carbon atoms and a trialkylamine having 3 to 14 carbon atoms.