JPS5952712B2 - Electrolytic dimerization method of N-substituted pyridinium salts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic method for electrolytically quantifying N-substituted pyridinium salts to produce N-N'-disubstituted tetrahydro-4,4'-bipyridyls.

N-N'-disubstituted 4,4'-bipyridinium salts obtained by oxidizing N-N'-disubstituted tetrahydro-4,4'-bipyridyl are known as extremely useful herbicides.

The present inventors proposed an electrolytic cell comprising an electrolytic cell having at least one diaphragm in advance, and an extractor installed outside the electrolytic cell and connected by a circulation passage so that an aqueous catholyte can be circulated. Using a device, the products formed on the cathode surface of the electrolytic cell are drained by a flow of aqueous catholyte, transferred through a circulation passage to an extraction device, and brought into contact with a water-immiscible organic solvent to perform aqueous catholyte electrolysis. The N-substituted pyridinium salt is extracted by extracting the products contained in the liquid into an organic solvent, feeding the separated aqueous catholyte into the electrolytic cell again through the circulation path, and repeating these operations continuously. Effectively N-N'-
A method for converting di-substituted tetrahydro-4,4'-bipyridyl was proposed. The main object of the present invention is to provide a structure of an electrolytic cell that can be suitably used in the above method.

There are various possible structures for electrolytic cells that can be used when carrying out the above electrolytic method, but according to the results of studies by the present inventors, there are various structures of electrolytic cells that can be used in practice due to various problems. It has become clear that this is extremely limited. For example, when a non-selective membrane such as an asbestos plate or a glass filter plastic porous membrane is used as the diaphragm, hydrogen ions generated at the anode enter the cathode chamber through the diaphragm and decompose the products generated at the cathode, which is preferable. do not have. To prevent this, when the anolyte is neutralized with an alkali such as sodium hydroxide, sodium ions move through the diaphragm to the catholyte chamber and accumulate in the catholyte, which must be removed from the catholyte. First, it requires a separation device for that purpose, which has the drawback that the electrolysis device becomes complicated.
Also, when a cation exchange resin membrane is used as a diaphragm,
In addition to all the same problems as described above, when the counter anion of the N-substituted pyridinium salt is a chlorine ion, the N-substituted pyridinium cation may be chemically degraded by the chlorine molecules generated at the anode. I understand. Next, when an anion exchange resin membrane is used as a diaphragm, acid is generated at the anode, but because the anion exchange resin membrane has a high hydrogen ion transfer number, some of the generated hydrogen ions pass through the membrane and reach the cathode. The mixture is moved to a chamber and the N-N''-disubstituted tetrahydro-4.4''-bipyridyl formed at the cathode is decomposed.

Furthermore, oxygen is generated at the anode, deteriorating the anion exchange resin membrane, and making long-term continuous operation impossible. As above,
When a single diaphragm is used, no matter what kind of diaphragm is used, each has its own drawbacks, and it has been found that it is difficult to electrolyze N-substituted pyridinium salts efficiently for a long period of time. Ta.

Therefore, another object of the present invention is to prevent electrochemical corrosion or deterioration of the constituent members of an electrolytic cell, to continuously supply raw materials, and to easily remove products from the system without decomposing them. It is an object of the present invention to provide a method for electrolyzing N-monosubstituted pyridinium salts, which can be operated stably for a long period of time and can be extracted. In the electrolytic dimerization method of N-substituted pyridinium according to the present invention, an anion exchange resin membrane is placed on the cathode side of a pair of opposing electrode plates (or nets), and a cation exchange resin membrane is placed on the anode side of the electrode plates (or nets). A cathode chamber, an intermediate chamber, and an anode chamber are arranged parallel to the net and so that the membranes do not touch each other, and surrounded by each electrode plate (or net) and each ion exchange resin membrane. The method is characterized in that an N-substituted pyridinium salt is supplied to the chamber, an alkali is supplied to the anode chamber, and electrolysis is carried out while removing the salt from the intermediate chamber.

Examples of N-mono-substituted pyridinium salts to which the present invention can be applied include lower alkyl-substituted pyridinium salts such as N-methylpyridinium salt, N-ethylpyridinium salt, N-propylpyridinium salt, and N-isopropylpyridinium salt. N-N''-disubstituted tetrahydro-4,4''-bipyridyl can be produced in very good yields.

Examples of the counter anion of the N-substituted pyridinium salt include chloride ion, bromide ion, iodine ion, sulfate group, nitrate group, phosphate group, cyanide ion, borohydrofluoride group, trifluoromethanesulfonic acid group, benzenesulfonic acid group,
Those that provide water-soluble salts, such as benzoic acid, citric acid, hydrofluoric acid, maleic acid, and methyl sulfate, are preferred.

Among the above-mentioned anion species, chloride ions and sulfate radicals are most preferred for manufacturing or cost reasons. N-substituted pyridinium salts having various anions described above can be obtained by, for example, reacting pyridine with methyl chloride to form N-methylpyridinium chloride, adsorbing it on a cation exchange resin, and recovering it using any of the acids mentioned above. By doing so, N-methylpyridinium salts each having a corresponding counter anion are obtained. In carrying out the present invention, examples of the alkali to be supplied to the anode include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide, and sodium carbonate.

An example of an electrolytic cell that can be used in carrying out the present invention will be explained based on the drawings.

Figure 1 shows a box-type electrolytic cell, where 1 is a cathode plate,
2 is an anode plate, 3 is an anion exchange resin membrane, 4 is a cation exchange resin membrane, 5 is a cathode chamber, 6 is an intermediate chamber, 7 is an anode chamber, 8 is a catholyte inlet, 9 is an intermediate chamber liquid inlet, 10 is the anolyte inlet, 1
1 is a catholyte outlet, 12 is an intermediate chamber liquid outlet, 13 is an anolyte outlet, 14 is a cathode terminal, and 15 is an anode terminal. It is best for the electrolytic cell to be box-shaped for design and handling reasons.
It is also possible to have a shape such as a cylinder or an annular shape.

Electrode materials that can be used in the present invention include, as an anode, metals and inorganic materials that have conductivity and are resistant to anolyte and anolyte products, such as platinum, copper, iron, stainless steel, and carbon. In addition, as the cathode, materials such as lead, mercury tin, copper, and alloys mainly composed of these components, which have a large hydrogen overvoltage, are selected.

The electrodes are conveniently plate-shaped, but mesh- or cloth-shaped electrodes can also be used to increase the electrode area. Further, as the ion exchange resin that can be used in the present invention, any existing products can be used, and as the cation exchange resin membrane, for example, Asahi Kasei Corporation's Unflex K-101. Manufactured by DuPont, Nafyon #415, Neosebta CL-25T, manufactured by Tokuyama Soda Kogyo Co., Ltd., Selemion C, manufactured by Asahi Glass Industries, Ltd.
MV, etc., and as an anion exchange resin membrane, Unflex A-101. manufactured by Asahi Kasei Corporation. Examples include AV-4T manufactured by Tokuyama Soda Kogyo Co., Ltd. and Selemion AMV manufactured by Asahi Glass Industries Co., Ltd.

The electrolytic method of N-monosubstituted pyridinium according to the present invention will fully demonstrate its effectiveness when incorporated into the electrolytic system previously proposed by the present inventors. Figure 2 shows a specific example of the electrolytic method of the present invention.
This is what I did.

In the figure, 16 is an electrolytic cell, 17 is an extractor, 18 is a separation tank, 19 is a catholyte reservoir, 20 is an intermediate chamber reservoir, 21 is an anolyte reservoir, 22 is an alkali injection port, 23 is an intermediate chamber fluid outlet, 24
25 is a water supply port, 25 is an extraction solvent supply port, and 26 is a product outlet 1. The anode chamber 27 and the intermediate chamber 28 are each individually connected in series with a circulation passage, a liquid reservoir 21, 20, and a circulation pump, and each electrolyte is circulated during the electrolysis time. Further, the catholyte that has left the cathode chamber 29 is transferred to an extractor 17.
After the product is extracted in step 1, it is separated into an extraction solvent and a catholyte in a separation tank 18. A part of the extraction solvent is circulated to the extractor 17, and a part is continuously extracted from the product outlet 26. It will be done.

The catholyte is also recycled to the cathode chamber 29 via the catholyte reservoir 19 . The material balance can be balanced by supplying N-substituted pyridinium from the cathode diode reservoir 1'' (raw material supply port 30 and extracting it as a salt aqueous solution from the intermediate chamber reservoir 20.Anode chamber 27, intermediate chamber 28. It is preferable that the flow of each electrolytic solution flowing through the shade 9 is uniform, and it is preferable to control the flow in each chamber by changing the number, size, shape, arrangement, etc. of the liquid inlet and liquid outlet of each chamber. Good. When electrolysis is performed using this electrolysis system, for example, if an aqueous N-methylpyridinium chloride solution is used as the catholyte, the N-methylpyridinium cations in the aqueous solution are given electrons on the cathode surface and dimerized. , N-N″-dimethyltetrahydro 4
・4″-Bipyridyl.

The bipyridyl is almost insoluble in water and adheres to the electrode surface, but is removed from the electrode by the circulating water flow in the cathode chamber, and is carried along with the catholyte to an extractor, where it is transferred to an extraction solvent. . By continuously supplying an amount equivalent to the consumed N-methylpyridinium cation, the N-
The concentration of methylpyridinium is kept constant. The chlorine ion, which is the counteranion of N-methylpyridinium, passes through the anion exchange resin membrane and moves to the intermediate chamber, and reacts with the alkali metal cation transferred from the anode chamber to form a salt.
As the electrolysis continues, the salt concentration in the intermediate chamber gradually increases, so it is desirable to replace the intermediate chamber liquid with water and keep the concentration constant. As is clear from the above, since chlorine anions do not reach the anode, chlorine molecules are not generated, and since a cation exchange resin membrane that is resistant to chlorine molecules is placed on the anode side, No deterioration of the membrane occurs.

Furthermore, the alkali metal cations of the alkali supplied to the anode chamber pass through the cation exchange resin membrane to the intermediate chamber, and the hydroxide ions are oxidized at the anode to generate oxygen. Since a cation exchange resin membrane that is resistant to water is placed, the membrane will not deteriorate as well.
Furthermore, in the present invention, by directly supplying the N-substituted pyridinium salt to the catholyte, the concentration of the N-substituted pyridinium salt in the catholyte can be arbitrarily set to a high concentration of, for example, 1 mol/l or more. At the same time, the limiting current density of the cation exchange resin membrane, which has a smaller limiting current density than the anion exchange resin membrane, is not rate-limiting, making it possible to perform high current density electrolysis. .

Furthermore, the advantage of supplying the N-substituted pyridinium salt directly to the cathode is that there is no process in which the N-substituted pyridinium cation, which has a large electrical resistance, passes through the cation exchange resin membrane, so the membrane voltage can be kept low. It is possible to reduce the electrolysis cost and to improve the current efficiency for producing N-N''-disubstituted tetrahydro-4,4''-bipyridyl.

When the N-substituted pyridinium salt is electrolyzed by the electrolysis method of the present invention, no mixing of ionic species occurs in any of the anode chamber, the intermediate chamber, and the cathode chamber. other electrolyte cations,
For example, there is no mixing of sodium ions, etc., and it is extremely easy to separate or take out various electrolytic products.

As described above, when N-substituted pyridinium salt is electrolyzed by the electrolysis method of the present invention, N.N''-disubstituted tetrahydro-4,4''-bipyridyl can be produced in high yield, and the electrode It is possible to operate stably and continuously for a long period of time without deteriorating the ion exchange resin membrane or the like.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 In an electrolytic cell with a platinum wire mesh as an anode and an alloy plate made mainly of lead with an effective electrode area of 2 cm x 20 cm and 0.5% by weight of tellurium added as a cathode, the cathode side was made by Asahi Kasei Corporation. , Anflex A-101 (anion exchange resin membrane), the anode side is partitioned by Nafyon #415 membrane (cation exchange resin membrane) made by Dupont, each cell thickness is 1 mm.
As shown in FIG. connected by a circulation passage.

300 ml of an aqueous sodium chloride solution with a concentration of 1 mol/l is placed in the intermediate chamber liquid reservoir 20. 300 ml of 1N aqueous sodium hydroxide solution is placed in the anolyte reservoir 21. 1 mol/l (7) in catholyte reservoir 19
600ml of N-methylpyridinium chloride was charged, and the aqueous solution was transferred to the anode chamber 27 using a circulation pump.
Intermediate chamber 28 is 0.1m/Sec, cathode chamber 29 is 0.8m
It was circulated at a speed of /Sec.

As shown in the drawing, 1500 g of toluene was added to the rise of the static tank 18.
m1 and extractor 17 using the extraction solvent circulation pump.
and was circulated at a speed of 100 ml/min.

While each electrolyte was being circulated, a current of 10 A/Dm2 was started to flow between the electrodes. N-methylpyridinium chloride in the catholyte is converted to N-N''-dimethyltetrahydro-4,4''-bipyridyl over time and moves into the extraction solvent, so N-methylpyridinium in the catholyte To maintain the chloride concentration at 1 mol/l, the concentration was 3.1 mol/l.
1 of solution was continuously supplied to the catholyte reservoir. Further, a 5N aqueous sodium hydroxide solution was continuously supplied little by little so that the pH of the anolyte was maintained at about 13. Furthermore, since sodium chloride accumulated in the intermediate chamber liquid, the intermediate chamber liquid was gradually replaced with pure water to maintain the concentration at 1 mol/1. 15
After 0 hours of electrolysis, it was found that 8.9% of the total current was consumed to generate hydrogen, and 90.2% was consumed to generate N-N''-dimethyltetrahydro-4,4''-bipyridyl. Ta.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a box-type electrolytic cell used in the method of the present invention,
FIG. 2 is a process explanatory diagram of the present invention.

Claims (1)

[Claims] 1 Arrange an anion exchange resin membrane on the cathode side of a pair of opposing electrode plates (or nets) and a cation exchange resin membrane on the anode side parallel to the electrode plates (or nets) so that the membranes do not touch each other. A cathode chamber, an intermediate chamber, and an anode chamber each surrounded by an electrode plate (or mesh) and each ion exchange resin membrane are provided, and an N-substituted pyridinium salt is supplied to the cathode chamber and an alkali is supplied to the anode chamber, 1. A method for electrolytic dimerization of N-substituted pyridinium salts, characterized in that electrolysis is carried out while removing salt from an intermediate chamber.