KR810001286B1 - Process for electrolytic dimerization of alkyl pyridinium salt - Google Patents

Abstract

N,N'-disubstituted tetrahydro-4,4'-bipyridyls were prepared by the electrolytic coupling of the corresponding N-substituted pyridinium salts. An aq. soln. of the pyridinium salt was passed into the cathode chamber of an electrolysis cell, where the bipyridyl was formed on the surface of the cathode. The aq. soln, was then passed to an extractor connected to the electrolysis cell, where it was extd. with an org. solvent, and the aq. phase was recycled to the electrolysis cell. Yields of <= 96.4 % of N,N'-dimethyltetrahydro-4,4'-bipyridyl were obtained.

Description

Electrolytic Dimerization of N-alkylpyridinium Salts

1 is a diagram showing one embodiment of the method of the present invention using a two-ch electrolytic cell.

2 is a view showing a circulating method of a comparative example in which a liquid catholyte and an organic solvent are simply mixed and the resulting suspension is circulated.

3 shows one embodiment of the method of the invention using a three chamber electrolyzer.

4 shows another form of the method of the present invention using a two chamber electrolyzer and the anolyte is also circulated.

5 is a diagram of the same series in more detail of the method of the invention as shown in FIG.

6 is a graph of the current efficiency with respect to the electricity supply ratio described later with respect to Comparative Example and Example (1) showing the current loss due to the generation of hydrogen gas.

The present invention relates to a process for the preparation of N, N'-2 substituted tetrahydro-4,4'-bipyridyl, and more specifically, to the corresponding N-substituted pyridinium salts by electrolytic dimerization thereof. A method for the metered preparation of, N'-2 substituted tetrahydro-4,4'-bipyridyl.

N, N'-2 substituted 4,4'-bipyridylium salts prepared by oxidizing N, N'-2 substituted tetrahydro-4,4'-bipyridyl are known to be highly effective preparations.

This compound is usually prepared by quaternization of 4,4'-bipyridyl and an organic oxidizing agent such as quinone or tetrahydro-4,4'-bipyridyl substituted with N, N'-2. It can be obtained in high yield by oxidation with an inorganic oxyacid anhydride such as SO ₂ .

The main object of the present invention is to prepare N, N'-2 substituted 4,4'-bipyridyllium, which is useful as a starting compound, N, N'-2 substituted tetrahydro-4,4'-bipyridyl. To provide an excellent method for manufacturing.

The technique for producing N, N'-2 substituted tetrahydro-4,4'-bipyridyl (hereinafter referred to as dimer) by electrolytic reduction of N-substituted pyridinium salt (hereinafter referred to as monomer salt) Became known.

It is also known that electrolytic reduction is carried out in the presence of a water-insoluble organic solvent in order to prevent accumulation of products in the electrolytic cell in the electrolysis of aqueous solutions of monomer salts.

For example, Japanese Patent Application Publication 1974-186 discloses that an oily product formed on the surface of an electrode is decomposed and removed by a water-insoluble organic solvent, so that the reaction proceeds effectively.

However, when the inventor examined the method of Japanese Patent Application Publication No. 1974-186 by the use of electrolytic method, it was found that a substance of unknown composition was decomposed on the surface of the electrode, and the current efficiency of forming a dimer was rapidly decreased. I found it impossible to continue. Although the water-insoluble organic solvent has been decomposed and the dimer formed on the surface of the electrode has been somewhat removed, the dimer decomposed in the solvent always tries to contact the surface of the electrode and any unwanted side reactions occur after the formation of the dimer and The effect of dimer removal on the surface was found to be inherently drastic.

As a result of extensive investigation, it is a useful method to prepare N, N'-2 substituted tetrahydro-4,4'-bipyridyl by electrolytic dimerization of the corresponding N-substituted pyridinium salt in industrial structure, and the present inventors It has been found that the novel method eliminates the above-mentioned drawbacks and that the electrolytic reaction can safely continue for a long time.

More specifically according to the present invention, there is provided a method for preparing N, N'-2 substituted tetrahydro-4,4'-bipyridyl by electrolytic dimerization of the corresponding N-substituted pyridinium salt, which method Characterized by the following steps.

(1) A catholyte containing N-substituted pyridinium salt flows through an electrolytic cell having a positive electrode and a negative electrode, and at least one partition wall is disposed between the positive electrode and the negative electrode in the negative electrode chamber so that the above-described electrolytic cell has a transfer passage and a supply passage. Connected to an extractor placed outside the electrolytic cell through a purifying passage consisting of N, N'-2 substituted tetrahydro-4 corresponding to the N-substituted pyridinium salt on the surface of the cathode when a current flows between the cathode and the anode. 4'-bipyridyl is formed and sometimes transfers the bipyridyl from the cathode surface to the catholyte flowing through the electrolytic cell,

(2) Transfer the catholyte containing bipyridyl to the extractor through the transfer passage, and contact the extractor with the catholyte containing bipyridyl together with the water-insoluble organic solvent to extract the bipyridyl in the organic solvent. .

(3) separating the liquid phase produced from the produced organic phase,

(4) supply the liquid phase separated along the back of the electrolytic cell through the supply passage,

(5) Repeat steps (1) (2) (3) and (4) continuously.

The process of the invention is carried out continuously or step by step during the feeding of starting materials such as monomer salts or by a continuous process.

According to the method of the present invention, contacting the resulting dimer with the surface of the negative electrode can be remarkably suppressed and effectively prevents occurrence of subsequent side reactions of the resulting dimer.

Therefore, according to the method of the present invention, it is possible to stably continue the electrolytic reaction for a long time. It is believed that the removal of the oily product formed on the surface of the electrode in the catholyte in the method of the present invention is mainly due to the shear force generated by the rapid flow of the catholyte. It is also believed that the solubility of oily products in water increases with the function of the N-substituted pyridinium salts as surfactants.

Other objects, features and advantages of the present invention will become apparent to those skilled in the art to be described in the following.

Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

1 shows an exemplary embodiment of the method of the present invention.

In FIG. 1, (1) shows an electrolytic cell comprising a cathode chamber (2), an anode chamber (3), a partition wall (4), a cathode (5) and an anode (6), and (7) and (7 '). ) Denote supply and transfer paths respectively, which cooperate with each other to form a circulation path.

(8) and (9) represent a catholyte circulation apparatus and an extractor, respectively, and (10) and (11) represent an organic phase and a liquid phase, respectively.

Water-insoluble organic solvents that dissolve water and dimers are added to the extractor, and a predetermined amount of monomer is dissolved in the liquid phase. This liquid phase containing monomer salt (hereinafter referred to as catholyte solution or simply catholyte solution) is continuously supplied to the cathode chamber 2 through the supply passage 7 by the catholyte circulation device 8. This catholyte is continuously discharged from the outlet of the cathode chamber and returned to the extractor 9 through the transfer passage 7 '.

While the catholyte circulates in this manner, a predetermined voltage flows between the anode and the cathode and a corresponding current flows between the two electrodes, and when the catholyte flows through the cathode chamber, some of the monomer salts decompose in the catholyte and undergo electrolysis. Will receive. Although the resulting dimer has the property of adhering to the metal surface nationwide, catholyte flows heavily along the surface of the electrode metal, and the dimer is easily removed from the surface of the electrode. Dimer is transferred to the extractor with catholyte.

In the extractor, the dimer is extracted with the extractant. The monomers in the catholyte gradually convert to dimers while the electrical work steps are repeated continuously.

When the linear velocity of the catholyte flowing along the surface of the cathode is too low, the removal efficiency of the product at the cathode surface is low and the electrolysis efficiency is low because the product decomposes at the cathode surface.

The linear velocity of the catholyte required for effectively causing electrolysis is changed depending on the amount of electricity supplied, and it is preferable that the catholyte flows at a linear velocity of at least 0.1 m / sec when the electrolysis is performed at a current density of 0.1-40 A dm ² .

The upper limit of the linear velocity is not particularly a critical point but is particularly 10 m / sec. Catholyte flow is technically possible at linear velocities above 10 m / sec, but it is not recommended to use too high linear velocities. This is because an increase in the liquid pressure at the inlet of the electrolyzer requires not only an electrolyzer, such as a partition wall, which encloses the high pressure, but also requires the use of a high pressure circulating pump, and the electrolytic operation is saturated at a certain linear velocity. Suitable line speeds are generally in the range of 0.3-5 m / sec.

Extractant solvents are sometimes broken down in catholyte. The amount of extractant contained in the catholyte varies depending on the type of solvent used, but smaller amounts of solvent contained yield better results.

It is noteworthy that extractants having a water solubility of 0.1-5% are used in the present invention without incident. However, when an organic solvent is used that decomposes in the catholyte at a concentration greater than 10% by weight, the results obtained are extremely different. The reason is considered as follows. The reaction product is decomposed and contains at least the average concentration in the extraction and after extraction the catholyte is recycled to the electrolyzer in the extractor. However, when a solvent having a high solubility in water is used, the solubility of the reaction product in the catholyte becomes higher and a large amount of the reaction product is contained in the catholyte to supply the electrolyzer in the extractor. Thus, a significant amount of reaction product is always present on the surface of the electrode.

Therefore, unwanted side reactions of the reaction product occur continuously and the by-products are decomposed at the surface of the electrode and the surface conditions of the electrode are disadvantageous.

Specifically, as described above, the partition wall 4 not only allows the negative ions of the monomer to enter the positive electrode room so that the negative ions are removed from the catholyte, but also prevents the diffusion of the dimers generated in the positive electrode chamber so as to prevent the reaction product from contacting the positive electrode. prevent.

Suitable monomer salts electrolytically dimerized in the process of the invention include N-methylpyridinium salts, N-ethylpyridinium salts, Nn- and -iso-propylpyridinium salts, Nn-, -iso-, -sec- and N- (C ₁ -C ₅ ) alkylpyridinium salts such as -tert-butylpyridinium salt, Nn-, -iso, -sec active- and -tert-amylpyridinium salt.

The method of the present invention is a case where a halogen atom, a C ₁ -C ₅ alkyl group, a hydroxyl group or an amino group is an N- (C ₁ -C ₅ ) alkylpyridinium salt having a substitution bond in a pyridine nucleus such as electrolytic dimerization. Can be applied.

Examples of the anions of the N-alkylpyridinium salt described above include chlorine ion, cancel ion, iodide, fluorine ion, sulfate group, benzenesulfonate group, C ₁ -C ₃₀ alkylsulfonate group, trifluoromethane-sulfonite group, Methyl sulfate group, benzoate group, acetate group, citrate group, lactate group, fumarate group, maleate group, maleate group, salicylate group, succinate group, trichloroacetate group, phosphate group, cyanide group, thiocyanate Group, nitrate group, carbonate group, fluorosil mocate group, tetrafluoroborate group and the like.

Halide ions, such as chlorine and cancelling ions, sulfate groups and methylsulfonate groups, are particularly suitable as anions.

For example, N-methylpyridinium chloride is prepared by reaction between pyridine and methyl chloride. The N-methylpyridinium salt having another anion as described above is prepared by adsorbing it to a cation exchange resin and treating it with an acid having the anion described above by recovering the generated N-methylpyridinium salt.

Such N-substituted pyridinium is supplied to the catholyte in the form of a powder or an aqueous solution.

The purity of the starting monomer salt is preferably as high as possible. Electrolysis is adversely affected if the impurities such as methanol and the aromatic nitro compound reacted with the formed N, N'-2 substituted tetrahydro-4,4'-bipyridyl are combined with the starting monomer salt.

Organic solvents used as extraction solvents for carrying out the process of the invention are, for example, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-tecan, isopentane, isohexane, isoheptane Saturated branched hydrocarbons such as isooctane, petroleum ether, gasoline and kerosine: cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cyclohexene and 1,3-cyclohexadiene; Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, propylbenzene, methylethylbenzene, styrene, cumene, hemimelitene, pseudocumene and mesitylene; Halogenated aromatic compounds such as chlorobenzene, dichlorobenzene, chlorotoluene, bromogenene and fluorobenzene; Aromatic amines such as aniline, N-methylaniline, N-ethylaniline, dimethylaniline, diethylaniline, toluidine and chloroaniline; Aromatic cyano compounds such as benzonitrile; Ethers such as diethyl ester, diisopropylethyl, di-n-butylethane, di-n-hexylether, methylphenylether, ethylphenylethyl, ethbenzylether, furan and 2-methylfuran; Water-insoluble alcohols having 4 or more carbon atoms such as butyl alcohol, amyl alcohol, heptanol and hexanol and amines such as triethylamine and triamylamine. They are used alone or in combination.

These organic solvents have dimer degradability and are insoluble in water. Therefore some of them are used as extractant. Aromatic hydrocarbons such as toluene, xylene and ethylbenzene, halogenated aromatic compounds such as chlorobenzene, and saturated branched chain hydrocarbons such as n-hexane and isooctane in these organic solvents are suitable.

As used herein, the term water-insoluble means that the solvent is only dissolved at a concentration of 10% by weight or less even if the solvent is insoluble or dissolved.

In the present invention, the extraction is a rotary disc contactor, Cross Counter type centrifugal extractor, Packed towers, sprayed tau, perforated plate towers, baffle towers ) And any known liquid-liquid extractor such as mixed-precipitator (mlxer-settlers).

The electrode materials used to practice the method of the present invention are as follows.

As a cathode, an alloy containing at least one of these metals, such as lead, mercury, copper, and a main component, that is, a metal having high hydrogen overvoltage, such as a lead-tetriumium alloy, a lead-silver alloy, a lead-tin alloy, and a lead-copper alloy Substances are used.

As anodes, electroconductive materials are used in view of the corrosive action of electrodes such as platinum, carbon, nickel, titanium and stainless steel.

The surface condition of the negative electrode is one of the particularly important factors in the present invention.

To achieve good results it is necessary to keep the cathode surface clean and flat at all times.

When the requirements of the surface conditions of the electrode are not satisfied, the electricity supplied tends to be consumed mostly for hydrogen generation. Therefore, close attention should be paid to the electrode surface conditions.

As partition walls for dividing the electrolytic cell, inorganic membranes such as asbestos membranes and glass filters; Porous organic membrane ion exchange resin membranes made of polymerized compounds such as vertical plates, cellulose acetate, polyacrylonitrile and polytetrafluoroethylene are used. However, in the present invention, an ion exchange resin membrane having high selectivity for the kind of ions is particularly suitable. The advantage of using an ion exchange resin membrane in the product i.e. dimer is that it is decomposed by the action of Cl ₂ or O ₂ formed by anodization of the anion (Cl or SO ₄ ) of the N-substituted pyridinium salt, for example. The anion species which can be completely prevented and gradually accumulate in the cathode chamber by continuous electrolysis can be easily removed outside the dimerization reaction zone.

Moreover, the use of ion exchange resin membranes can prevent adverse impurities contained in the starting monomer salts from being present in the electrolytic dimerization zone.

In the case of the ion exchange resin membrane used for carrying out the method of the present invention, the type and number of ion exchange resin membranes are two or more, and the combination thereof depends on various conditions such as the number and purity of the starting monomer salt.

Usually, satisfactory results are obtained by using 1-3 of the ion exchange resin membrane.

When an electrolytic cell is divided by two ion exchange membranes and divided into a cathode chamber, an anode chamber and an intermediate chamber, the electrolyte solution of each chamber is separately circulated and the electrolyte concentration in each electrolyte solution is determined by removing the decomposed electrolyte solution or adding a new electrolyte solution. It is constantly adjusted to some level. For example, an anion exchange resin membrane and a cation exchange resin membrane are disposed on the cathode side and the anode side, respectively, and an N-substituted pyridinium salt is supplied to the catholyte and accumulated therein, while an anion, chlorine ion, of the N-substituted pyridinium salt is accumulated therein. N, N'-2 substituted tetrahydro-4,4'-bipyridyl formed by electrolytic dimerization and electrically transferred to the intermediate chamber through this anion exchange resin membrane is removed out of the reaction zone by extraction.

Meanwhile, an alkaline electrolyte such as caustic soda is used for the anolyte, alkali metal ions such as sodium ions are transferred to the intermediate chamber through the cation exchange resin membrane, and the hydroxide ions are oxidized at the anode to generate oxygen.

In the intermediate chamber, for example, sodium ions react with chlorine ions to form NaCl. Therefore, the concentration of NaCl liquid in the intermediate chamber is continuously increased by electrolysis.

Therefore, it is better to replace the chamber fluid with water little by little and remove NaCl to keep NaCl concentration constant.

On the other hand, NaOH in the anolyte is consumed, so NaOH may be supplied to the anolyte little by little.

Examples of the electrolyte used to carry out the method of the present invention include hydroxides such as NaOH, KOH, LiOH, and NH ₄ OH; Lithium chloride, Lithium chloride, Lithium fluoride, Lithium sulfate, Lithium phosphate, Potassium sulfate, Potassium phosphate, Sodium chloride, Sodium bromide, Sodium fluoride, Sodium sulfate, Sodium phosphate, Calcium chloride, Calcium bromide, Metal salts such as copper sulfate, aluminum sulfate and sodium nitrate; ammonium salts such as ammonium chloride and ammonium sulfate.

They are used alone or in combination. NaOH, NaCl and sodium sulfate in these electrolytes are most suitable.

While variations of the method can be envisaged with the use of ion exchange resin membranes, many factors, such as current efficiency and resistance of the ion exchange resin membranes to the gases generated, have important influences on the practice of the method of the present invention. I think.

In the above electrolysis, specific examples of the electrolytic dimerization of the present invention are as follows.

According to this specific description, there is provided a method for preparing N, N'-2 substituted tetrahydro-4,4'-bipyridyl by electrolytic dimerization of the corresponding N-substituted pyridinium salt, Characterized by stages.

(1) A catholyte containing N-substituted pyridinium flows through an electrolytic cell having an anode and a cathode disposed opposite to each other, and the cation exchange resin membrane on the anode side and the anion exchange resin membrane on the cathode side are in contact with each other. The anode, cathode, cation exchange resin membrane and anion exchange resin membrane, which are arranged parallel to the anode and cathode and are essentially parallel to the inner wall of the electrolytic cell, have an anode chamber, and the intermediate chamber and cathode chamber in the electrolytic cell include a transfer passage and a supply passage. A N, N'-2 substituted tetrahydro- corresponding to an N-substituted pyridinium salt on the surface of the anode, connected to the electrolytic bath with an extractor disposed outside the electrolytic cell through a circulation passage and current flowing between the anode and cathode. 4,4'-bipyridyl is formed and sometimes migrates from the surface of the cathode to the catholyte flowing through the electrolytic cell.

(2) Catholyte containing electric bipyridyl is conveyed to the extractor via a transfer passage, and catholyte containing electric bipyridyl is contacted with water-insoluble organic solvent in the extractor to make electric bipyridyl in the electric organic solvent. Extract

(3) separating the generated liquid phase from the produced organic phase,

(4) The liquid phase separated along the back of the electrolytic cell is supplied through the supply passage,

(5) Repeat steps (1) (2) (3) and (4) continuously, catholyte constantly supplied with N-substituted pyridinium salt and anode chamber constantly supplied with alkali and N-substituted The salts formed in the intermediate chamber by neutralization between the anions of the pyridinium salts are transferred in the negative chamber and the positive ions of the electric alkali transferred from the anode chamber are constantly transferred in the electrical intermediate chamber.

More specifically, the present invention is implemented according to the system shown in FIG. In FIG. 5, 42, 43, 44, 45, 46, and 47 represent an electrolytic cell, a mixer, a settling tank, a catholyte reservoir, an intermediate chamber liquid reservoir, and an anolyte reservoir, respectively, and 48,49, 50, 51, and 52, respectively, are alkalis. Inlet, middle chamber liquid outlet, water inlet, extractant inlet and product outlet.

The anode chamber 52 is connected in series with the anolyte storage tank 47 and rotates the circulation pump through the circulation passage. The intermediate chamber 54 is connected in series with the intermediate liquid reservoir 46 and rotates the circulation pump through the circulation passage. In these arrangements, the electrolyte in the anode chamber and the intermediate chamber is circulated separately and completely electrolyzed.

The catholyte remaining in the cathode chamber 55 is extracted from the mixer 51, extracted and separated from the settling tank 44, recycled through the catholyte tank 45, and enters the cathode chamber 55. A portion of the extract is recycled to the mixer 51 and the remainder of the extract is continuously recovered at the product outlet 52. N-substituted pyridinium salt is continuously supplied from the N-substituted pyridinium salt inlet 56 to the catholyte reservoir 45 while alkali is continuously supplied from the alkali inlet 48 to the anolyte reservoir 47. The brine solution formed in the intermediate chamber is continuously recovered from the intermediate chamber liquid storage tank 46, thereby satisfying the needs of the mass balance.

The flow of each electrolyte passing through the anode chamber 53, the intermediate chamber 54 and the cathode chamber 55 becomes rather uniform. Therefore, the flow of the electrolyte solution in each chamber described above is suitably controlled by the optimum conditions of selection of openings, numbers, sizes, shapes, and arrangements at the liquid inlet and the liquid outlet of each chamber.

The case where N-methylpyridinium chloride aqueous solution is used as the catholyte to more specifically carry out the electrodimerization of the present invention will be explained by the method of the examples in more detail. In aqueous solution, the N-methylpyridinium cation gives electrons to the surface of the cathode and is dimerized to produce N, N'-2 dimethyl tetrahydro-4,4'-bipyridyl. Bipyridyl is almost insoluble in water and tends to adhere to the surface of the cathode, which is effectively moved from the cathode by circulating flow through the cathode chamber and introduced into the extractor with catholyte, whereby the bipyridyl in the extraction solvent Extracted.

The concentration of N-methylpyridinium clyde in the catholyte is kept constant by the continuous supply of fresh N-methylpyridinium chloride in an amount corresponding to the concentration of N-methylpyridinium cations consumed. Anions of N-methylpyridinium chloride, mainly chlorine ions, are transported through the anion exchange resin membrane to the intermediate chamber where it is reacted with alkali metal cations migrated in the anode chamber to form salts. Since the concentration of salt in the chamber is gradually increased by continuous electrolysis, the concentration is preferably kept constant by continuously replacing the chamber liquid with water. As is apparent from the above, chlorine ions do not reach the anode, so that no chlorine molecules are formed.

Although a cation exchange resin membrane having high resistance to chlorine molecules is disposed on the anode side, no damage to the membrane occurs.

Alkali metal cations of the alkali supplied to the positive electrode are oxidized at the positive electrode to produce oxygen while the cations are transferred to the intermediate chamber through the cation exchange resin membrane. Since the cation exchange resin membrane having a high resistance to oxygen in the generator state is disposed on the anode side, no damage to the membrane occurs.

Since the N-substituted pyridinium salt is more directly supplied to the catholyte, the concentration of the N-substituted pyridinium salt in the catholyte is arbitrarily increased to a high level, such as 1 ml / 1 or more, so that the electrical resistance of the cathode chamber is Developmental decomposition is performed at high current densities because the reduced and limiting current densities in the cation exchange resin membranes are lower compared to that in the anion exchange resin membranes and do not determine the rate of electrolysis. Another advantage of the continuous continuous supply of N-substituted pyridinium salts to the catholyte residue is that there is no passage of N-substituted pyridinium cations through the cation exchange resin membrane, the membrane voltage is controlled to a low level and the cost of electrolysis is reduced, The current efficiency increases in the preparation of N'-2 substituted tetrahydro-4,4'-bipyridyl.

When the electrolytic dimerization of N-substituted pyridinium salts is carried out according to more specificity, the mixing of ions of different types of ions, for example N-substituted pyridinium cations and other electrolytes such as sodium ions, may be carried out in some anode chambers, intermediate chambers. And in the cathode chamber.

Therefore, separation and removal of each electrolytic product can be easily performed.

As described above, in electrolytic dimerization of N-substituted pyridinium salts according to more specific, high yield preparations of N, N'-2 substituted tetrahydro-4,4'-bipyridyl are obtained as well as stable and continuous The operation proceeds for a long time without any degradation of the ion exchange membrane.

In the case where the process of the present invention is carried out on an industrial scale, the starting monomer salt is continuously supplied to the catholyte and is continuously recovered when the reaction product is decomposed in the extraction solvent and the operation of electrolytic dimerization is continued stably for a long time.

The invention will be explained in more detail in accordance with the following examples and is not intended to limit the scope of the invention.

[Comparative Example]

An electrolytic cell comprising a lead plate and a stirring tank having an effective electrode area of 2 cm x 20 cm as a cathode and a platinum gauze as an anode is connected via a circulation passage via a circulation pump as shown in FIG. In FIG. 2, reference numerals 12 and 13 denote electrolyzers and agitating tanks, reference numerals 14 and 14 'denote circulation passages, and reference numerals 15 and 16 denote circulation pumps and agitators, respectively.

Into the stirring tank 13, 300 ml of containing cores containing 0.1 mol of N-methyl pyridinium chloride and 300 ml of diethyl ether were added. While the soy liquor is stirred vigorously with the stirrer 16 to uniformly disperse, the dispersion liquid is circulated through the circulation passages 14 and 14 'by the circulation pump 15 in the electrolytic cell and the stirring tank 13 and the electrolytic cell 12 It is circulated at a linear speed of 0.5m / sec in between.

While this circulation is maintained, a current of 2.8 A flows between the electrodes.

Within minutes from the start of the current supply, the total solid accumulates on the surface of the electrode and hydrogen evolution becomes significant. It was found that 82% of the total amount of electricity supplied was consumed for hydrogen evolution when the electrolysis was continued for 5 hours.

Example 1

An electrolytic cell containing a platinum gauze as the positive electrode and a lead plate having an effective electrode area of 2 cm x 20 cm as the negative electrode comprises an anion exchange resin membrane commercially available under the trade name AclpexA-101 (manufactured by Ashhi Kasei Kogyo KK, Japan) on the positive electrode side. The cathode chamber having a 4 mm width in the electrolytic cell divided by a cation exchange resin membrane commercially available under the trade name of Nafion # 415 (US DuPont Company) on the cathode side; A cathode chamber having a mm is provided. This electrolyzer is connected to the extractor and the liquid reservoir, as shown in FIG. In Fig. 3, reference numerals 17, 18, 19, 20, 21 and 22 denote electrolyzer, anode chamber, intermediate chamber, cathode chamber, anion exchange resin membrane and cation exchange resin membrane, respectively, and reference numerals 23, 24, 25, 26 and 27, respectively. Denote extractor, extraction solvent, catholyte, anolyte reservoir and intermediate chamber liquid reservoir respectively. Reference numerals 28, 29 and 30 denote liquid circulation pumps.

500 ml of 1 N N-methyl pyridinium sulfate aqueous solution was added to the intermediate chamber liquid storage tank 27, and 300 ml of 0.1 N N-methyl pyridinium sulfate aqueous solution and 300 ml of n-hexane were introduced into the extractor 23. Further, 1N aqueous sodium sulfate solution is added to the anolyte storage tank 26. These aqueous solutions are circulated to circulation pumps 28, 29 and 30. The reaction product is removed from the catholyte by extraction in the extractor and circulated only in the lower layer liquid phase in the cathode chamber at a linear velocity of 0.5 m / sec.

The linear velocity of the anolyte and intermediate chamber liquid is 0.1 m / sec in the anode chamber and the intermediate chamber, respectively.

During this circulation of the anolyte, chamber liquid and catholyte, a current of 7 A / dm ² flows between the electrodes. The pH of the catholyte is about 7 after the start of supply of current, but becomes about 13 in a few minutes, and the pH value does not change until the end of the electrolysis.

The voltage between the electrodes is about 10V at the start of the electrolysis but gradually decreases to 7.8V at the end of the electrolysis. All n-hexane layers in the extractor were replaced with 300 ml of fresh n-hexane 5 hours after the start of the electrolysis while the starting monomer salt solution was continuously fed to the intermediate chamber and the electrolysis continued for another 5 hours.

After completion of the electrolysis, the resulting dimer decomposed in n-hexane is analyzed by nuclear magnetic resonance (NMR) analyzer JNM-PMx60 (trade name of NMR apparatus manufactured and sold by Nippon Denshi Co., Ltd.). It was found that 61.7% of the total electricity supplied was used for dimer formation. It was found that 37.4% of the total amount of electricity supplied (in the amount of hydrogen generated during electrolysis) was consumed for hydrogen evolution.

This example was compared with the above comparative example with respect to current efficiency and the results are shown in FIG.

In Figure 6, the term "electricity supply ratio" means the actual amount of electricity supplied (in%) taken against the theoretical electricity required for the electrolytic dimerization of all monomer salts introduced at the start of electrolysis, and the theoretical quantity is estimated at 100%. It became.

Example 2

Electrolysis using the same electrolysis system as used in Example (1) was carried out in the same manner as in Example (1) using N-methylpyridinium chloride instead of N-methyl pydinium sulphate. .

59.4% of the total amount of electricity supplied was used for dimerization and 39.2% of the total amount of electricity supplied was spent on hydrogen evolution.

Example 3

In the same system as used in Example (1), the cation exchange resin membrane “Nafion # 415” was used as a membrane for dividing the anode chamber and the intermediate chamber, and the anion exchange resin membrane “Aciplex A-101” used the intermediate chamber and the cathode chamber. It was used as a membrane to partition. As a starting monomer, an aqueous 1NN-methylpyridinium chloride solution is fed directly to the cathode chamber. 300 ml of 1NN-methyl pyridinium chloride and 300 ml of diethyl ether were put into the extractor 23, and 300 ml of 1N sodium sulfate solution was put into the anolyte reservoir 26 and the intermediate chamber liquid reservoir 27, respectively.

These solutions were circulated by circulation pumps 28, 29 and 30 and electrolysis was carried out in the same manner as described in Example (1). The amount of dimer obtained by electrolysis for 10 hours corresponded to 58.6 of the total amount of electricity supplied and the amount of electricity consumed for hydrogen evolution was 41.0% of the total amount of electricity supplied.

Example 4

An electrolytic cell containing a platinum gauze as cathode and a lead plate having an effective electrode area of 2 cm x 20 cm as a cathode was divided into a cation exchange resin membrane, Naficn # 415, having an anode chamber and a cathode chamber, each connected to an anolyte reservoir and extractor, respectively. And placed outside the electrolyzer as shown in FIG.

In Fig. 4, reference numerals 31, 32, 33 and 34 denote electrolyzers, cation exchange resin membranes, anode chambers and cathode chambers, respectively, and reference numerals 35, 36, 37, 38 and 39 denote extractors, extraction solvents, catholyte and anodes, respectively. Indicates a liquid reservoir and an anolyte. Reference numerals 40 and 41 denote liquid circulation pumps.

500 ml of 1 NN-methyl pyridinium sulfate aqueous solution was added to the anolyte storage tank 38, and 300 ml of 0.1 NN-methyl pyridinium sulfate aqueous solution and 300 ml of n-hexane were put into the extractor 35. The anolyte is circulated between the anolyte reservoir and the anode chamber by a circulation pump 40 at 0.1 m / sec linear velocity in the anode chamber and the catholyte is circulated by a circulation pump 41 at 0.5 m / sec linear velocity in the cathode chamber. Circulated between the extractor and the cathode chamber. While the liquid is thus circulated, a current of 2.8 A flows between the electrodes. After initiation of current supply, N-methyl pyridinium sulfate is continuously supplied in small portions to the anolyte reservoir to replenish spent monomer salts and contain dimers. Recover 100 mL of hexane-100 and replace with 100 mL of fresh n-hexane every 2 hours after the start of electrolysis.

Electrolysis continued for 10 hours.

After electrolysis is completed, dimers decomposed and contained in n-hexane are analyzed using an analytical device.

It was found that 62.4% of the total electricity supplied was used for dimer formation and 37.1% of the total electricity supplied was spent on hydrogen evolution.

Example 5

With reference to FIG. 5, an electrolyzer comprising an alloy plate composed mainly of Pb and containing 0.5 wt% of tellurium as a cathode having a platinum gauze as an anode and an effective electrode area of 2 cm x 20 cm is an anion exchange resin film on the cathode side. (A) Aplex (A-101) and an anode-exchange membrane (Nafion # 415) on the anode side, the cathode chamber 55 having a seal width of 1 mm, an intermediate chamber 54 having a seal width of 15 mm, and an anode having a seal width of 4 mm. It is provided with a thread.

These chambers were each connected to an extractor or to a liquid reservoir via a circulation passage via a circulation pump as shown in FIG.

A 300 mol Nacl aqueous solution having a concentration of 1 mol / l, 300 ml of a 1N NaOH aqueous solution and 600 ml of an N-methylpyridinium chloride aqueous solution having a concentration of 1 mol / l were prepared in an intermediate chamber liquid reservoir (46), an anolyte reservoir (47), and a negative electrode. It puts into the liquid storage tank 45, respectively.

These aqueous solutions are circulated by a circulation pump such that the linear velocity is 0.1 m / sec in the middle chamber 54, 0.1 m / sec in the anode chamber 53 and 0.8 m / sec in the cathode chamber, respectively.

As shown in FIG. 5, 1500 ml of toluene was introduced into the upper layer of the settling tank 44 and circulated between the settling tank 44 and the mixer 43 at 100 speed by the extraction solvent-circulating pump.

While the solution is thus circulated, current flows between the electrodes at a current density of 10 A / dm ² . Over time, N-methyl pyridinium chloride in the catholyte is gradually converted to N, N'-dimethyl tetrahydro-4,4'-bipyridyl which is transferred to the extraction solvent. Thus, an aqueous solution of N methylpyridinium chloride having a concentration of 3.1 mol / l is continuously supplied to the catholyte reservoir so that the concentration of N-methylpyridinium chloride in the catholyte is maintained at 1 mol / l.

Meanwhile, 5N NaOH aqueous solution is supplied little by little to the anolyte storage tank so that the anolyte pH is maintained at about 13. Therefore, NaCl is formed and gradually accumulates in the chamber, and the chamber liquid is gradually replaced with pure water in the chamber liquid reservoir to maintain the concentration of Nacl at 1 mol / l.

Electrolysis continues for 150 hours under the conditions described above. It was found that 8% of the total electricity supplied was spent on hydrogen evolution and 90.2% was used to form N, N'-dimethyl tetrahydro-4,4'-bipyridyl.

Example 6

An electrolytic cell comprising a platinum-precipitated titanium plate as an anode and a copper plate as a cathode was divided by an anion exchange resin membrane (Aciplex A-101) on the cathode side and a cation exchange resin membrane (Nafion # 415) on the anode side. A thread and an anode chamber are provided. The electrode area is 40dm ² . The electrolyzer was connected to the extractor via a liquid circulation pump via a liquid circulation passage.

600 ml of diethyl ether was added to the extractor.

1 L of 1N aqueous sodium sulfate solution and 1.5 L of 1N NaCl aqueous solution were added to the anolyte reservoir and the intermediate chamber liquid reservoir, respectively.

In the same manner as in the previous example, these solutions were each circulated so that the linear velocity was 0.5 m / sec in each chamber.

700 ml of an aqueous solution of N-methylpyridinium chloride having a concentration of 9.4% by weight was added to the extractor and circulated by a circulation pump such that the linear velocity of the solution was 0.7 m / sec in the cathode chamber.

While all solution is circulated in this way, current flows between the two electrodes at a current density of 20 A / dm ² .

A 2N NaOH aqueous solution is continuously supplied to the anode chamber at a rate of 119 gr / hr and the NaCl aqueous solution is returned to the middle chamber at a constant rate while water is supplied so that the concentration of the solution is maintained at an initial level and is fully electrolyzed.

Electrolysis is continued for 8 hours under the above conditions. The conversion of N-methylpyridinium chloride introduced is 67.3% and 36.0% of the total electricity supplied is used for the formation of N, N'-dimethyl tetrahydro-4,4'-bipyridyl. The amount of electricity consumed for hydrogen evolution is 42.5% of the average supplied electricity and is fully electrolyzed.

The electrode was not electrolytically corroded at all.

Example 7

When platinum-plate titanium gauze is used as the positive electrode and combines an alloy plate of about 0.5% by weight of tellurium, the strength is increased and used as the negative electrode.

Effective electrode area of lead alloy plate is 2cmx20cm

Combine the electrolyzer in the box. Anion exchange resin membrane "Aciplex A-101" was placed on the cathode side, and cation exchange resin membrane "Nafion # 415" was placed on the anode side. The actual width of the cathode chamber, the actual width of the intermediate chamber, and the actual width of the anode chamber were 1 mm, 15 mm, and 4 mm, respectively.

A pair of inlets and outlets were formed in the annular holes having a diameter of 6 mm in the electrolyte, respectively, on each side of the electrolytic cell, ie, on the transverse sides of the cathode and anode chambers, and on the top and bottom of the intermediate chamber. This electrolyzer was coupled to a system as shown in FIG. 5 and electrolysis was carried out under the following conditions.

The linear velocity of the circulating electrolyte was about 0.5 m / sec in the cathode chamber and about 0.1 m / sec in the intermediate chamber and anode chamber. The amount of electrolyte added to each liquid storage tank was 300 ml. N-methyl pyridinium chloride is decomposed in an anode chamber at a concentration of 11 mol / l, NaCl is decomposed in an intermediate chamber liquid at a concentration of mol / l, and NaOH is decomposed in an anode chamber at a concentration of 1 mol / l. After the electrolysis is completed, N-methylpyridinium chloride and NaOH are supplied to the catholyte and the anolyte at about 0.2 mol / hr, respectively, to maintain the above-mentioned concentration. An aqueous solution of NaCl is recovered in the chamber liquid reservoir at a rate of about 0.2 mol / hr by the amount of Nacl and water is supplied instead. While the electrolyte solution is thus exchanged, current flows between the two electrodes at a current density of 20 A / dm ² . It was found that when electrolysis continued for 4 hours under the above conditions, 20.3% of the total amount of electricity supplied was consumed for hydrogen evolution. This percentage was gradually increased with continuous electrolysis and when the electrolysis continued for 26.5 hours, the percentage was found to increase by about 40%.

1.5 L of toluene was used as an extraction solvent. No fresh toluene was supplied continuously, but the extraction solvent was circulated at a rate of 100 ml / min between the settling tank and the mixer of the mixer-settling type extractor by a circulation pump.

The stirrer of the mixer was rotated at about 500 rpm. At each time difference of 4 hours, 8.5 hours, 15 hours, 18 hours and 26.5 hours after the start of electrolysis, the electrolysis operation was suspended and all toluene solutions were replaced with fresh toluene.

Of course, at the end of the electrolysis the toluene solution was recovered and not replaced with fresh toluene. The amount of N, N'-dimethyl tetrahydro-4,4'-bipyridyl formed at each time difference was determined using a nuclear magnetic resonance analyzer. It was found that the amounts formed at each time difference were 0.416 mol, 0.49 mol, 0.45 mol, 0.441 mol and 0.638 mol, respectively.

These amounts of N, N'-dimethyltetrahydro-4,4'-bipyridyl formed were 69.7% of the amount of electricity supplied to the formation of N, N'-dimethyltetrahydro-4,4'-bipyridyl, respectively. , 73.0%, 67.1%, 59.1% and 50.3%.

The total amount of N-methylpyridinium chloride supplied to the catholyte at the start of electrolysis and completion of electrolysis was 5.566 mol and the amount of N-methylpyridinium chloride remaining in the catholyte after the completion of electrolysis was 0.519 mol. The total amount of electricity supplied is 2.537 parads.

Thus it was found that 61.6% of the total amount of electricity supplied was used for the formation of N, N'-dimethyltetrahydro-4,4'-bipyridyl.

Example 8

An electrolytic cell containing a platinum gauze as a positive electrode and a lead plate having a convex electrode area of 2 cm x 20 cm as a negative electrode was used for the anion exchange resin membrane ＂, AciplexA-101＂ on the positive electrode side and the cation exchange resin membrane on the negative electrode ＂Nafion # 415＂. And an anode chamber having a yarn width of 4 mm, an intermediate chamber having a yarn width of 15 mm, and a cathode chamber having a yarn width of 1 mm. The electrolyzer was connected to the extractor and the liquid reservoir as shown in FIG.

300 ml of an aqueous solution containing 1 mol / l of NaCl is introduced into the intermediate chamber liquid storage tank 27, and 300 ml of an aqueous solution containing 0.5 mol / l of NaOH is injected into the anolyte storage tank 26.

600 mol of an aqueous solution containing 1.5 L of diethyl ether and 0.2 mol / L of N-methylpyridinium chromide was introduced into the extractor 23.

Each aqueous solution was circulated by circulation pumps 29, 30 and 28, respectively. Only the liquid phase of the lower layer in the extractor was circulated at a linear velocity of 0.5 m / sec in the cathode chamber. The linear velocities of the anolyte and intermediate chamber liquids were 0.1 m / sec in the anode chamber and the intermediate chamber, respectively.

While the anolyte, intermediate liquid and catholyte are circulated in this manner, a current of 20 A / dm 2 flows between the electrodes.

The voltage between the electrodes was about 18V at the start of electrolysis but dropped about 11V after one hour. At 2 hours after the start of electrolysis, the voltage stabilized at about 9.5V. N-methylpyridinium chloride was fed little by little into the catholyte so that their concentration was maintained at 0.2 mol / l in the catholyte. NaOH was added little by little to the anolyte solution so that the pH value of the anolyte solution was maintained at about 13.

When the concentration of N2N'-dimethyltetrahydro-4,4'-bipyridyl in diethyl ether was 0.3 milli mol / g, all diethyl ether solutions in the extractor were recovered and replaced with fresh diethyl ether.

About 20% of the total electricity supplied was spent on hydrogen evolution. Electrolysis continued further. The amount of hydrogen generated gradually increased over the course of the electrolysis time. Thirty percent of the total electricity supplied 50 hours after the start of electrolysis was consumed for hydrogen evolution.

As a result of the electrolysis for 2.5 hours, 2.435 mol of N, N'-dimethyltetrahydro-4,4'-bipyridyl is obtained as 5.05 mol of N-methylpyridinium chromide.

This yield is as high as 96.4% of theory. 75.6% of the total electricity supplied was used later.

After completion of the electrolysis, the electrolytic cell was decomposed. A small amount of brown sludge-like material deposited on the surface of the cathode, but this can be easily removed by washing with water.

The surface of the cathode was cleaned and then tested under a microscope, but no alteration or loss of the cathode due to corrosion was observed.

Claims (1)

In preparing N, N'-disubstituted tetrahydro-4,4'-bipyridyl by electrolytic dimerization of N-substituted pyridinium salt, an aqueous catholyte containing N-substituted pyridinium salt is used as a positive electrode and a negative electrode. And an electrolyzer consisting of at least one partition wall disposed between the anode and the cathode, which is connected to an extractor disposed outside the electrolyzer and a circulation passage consisting of a transfer passage and a pore passage, with a linear velocity of 0.1 m / sec. By supplying the above, N, N'-disubstituted tetrahydro-4,4'-bipyridyl salt is formed on the surface of the cathode and removed into the aqueous catholyte solution and the aqueous catholyte containing the bipyridyl salt is transferred to the feed passage. And transfer the bipyridyl to the organic phase by contacting the water-insoluble organic solvent through the extractor, separating the aqueous phase from the organic phase, recycling only the separated aqueous phase to the electrolytic cell through the feed passage and continuing the step. Electrolytic N- alkyl pyridinium salts, characterized by the second amount repeats speech.

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