JPS62274086A - Electrolytic anion substitution method - Google Patents

Abstract

PURPOSE:To improve the durability of diaphragms in an electrolytic cell used to synthesize amino acid by an electrolytic ion substitution method and to develop an electrolytic anion substitution method by which superior efficiency is attained, by using F-contg. anion exchange membranes each having a specified structure as the diaphragms. CONSTITUTION:When amino acid is synthesized by an electrolytic anion substitution method using ion exchange membranes, an electrolytic cell 1 is divided into an anode chamber 6, an intermediate chamber 7 and a cathode chamber 8 with anion exchange membranes 2, 3, the anode 4 of Pt or the like and the cathode 5 of Fe or the like are placed in the anode and cathode chambers 6, 8, respectively, and hydrochloric acid and sodium hydroxide are fed to the anode and cathode chambers 6, 8, respectively. Electrolysis is then carried out at 50A/dm<2> current density to obtain an amino acid soln. by the substitution of OH<-> for Cl<-> in the intermediate chamber 7. An F- contg. anion exchange membrane represented by formula I and having quat. ammonium groups represented by formula II or IV is used as the anion exchange membrane 2. An F-contg. anion exchange membrane represented by the formula I and having quat. ammonium groups represented by formula III is used as the anion exchange membrane 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrolytic ion replacement method for replacing anion species in an aqueous solution containing ions with other anion species using an ion exchange membrane electrolysis method. For more details,
This invention relates to an electrolytic anion replacement method using a fluorine-based anion exchange membrane with a special structure as a diaphragm. .

Although the method of the present invention can be used in various fields, it is particularly effective in the field of synthesis of organic and inorganic compounds.

[Prior art]

In the field of amino acid synthesis, amino acids are synthesized from a hydrochloric acid solution containing amino acids obtained by hydrolyzing proteins with concentrated hydrochloric acid. During this process, the amino acid salt rI! In order to obtain an amino acid from a solution, there are generally well known methods such as neutralizing with an alkali and removing the resulting salt by electrodialysis, or contacting with an OH-type anion exchange resin.

However, the neutralization-electrodialysis method has problems such as generating salt waste liquid and requiring complicated process control for electrodialysis, and the ion exchange resin method has been pointed out to have problems such as resin regeneration waste liquid. ing.

Similar problems also exist in the field of amine synthesis.

In amine synthesis, there is a process in which a hydrochloric acid solution of an amine is neutralized with a large amount of alkali, and the resulting salt is separated by electrodialysis or crystallization. The cost of the alkali used in this process accounts for a significant portion of the amine production cost, and the electrodialysis and crystallization steps require complicated process control.

Furthermore, similar processes exist in the field of synthesis of high purity metal oxides. Wet synthesis of high-purity metal oxides generally requires a process in which the metal is dissolved in a strong acid solution, a large amount of alkali is added thereto, and the metal hydroxide is precipitated. This process also generates a large amount of salt waste, and also insoluble ions (e.g., Na) in the metal hydroxide.
, Hso, 0Lso, 2-, etc.) is difficult to sufficiently remove, and they remain as impurities in the finally obtained metal oxide.

These processes all have a common problem in that they either neutralize a strong acid solution of the necessary substance with a large amount of alkali or use an ion exchange resin method.

In recent years, an electrolytic ion replacement method has been proposed for the gold component 'tfK of the amino acid and has attracted attention. (For example, JP-A-58
-55577) In this process, the anode and cathode are separated by several hydrocarbon-based anion exchange membranes, an amino acid hydrochloric acid solution is supplied to the intermediate chamber between the anion exchange membranes, and one anion This is a method in which C2- ions are permeated and removed by an exchange membrane, and OH- ions are permeated and supplied from the other anion exchange membrane.

The electrode reaction is a reaction that generates chlorine gas and hydrogen gas, which can be synthesized to recover hydrochloric acid necessary for protein hydrolysis.

Although in principle this process does not generate unnecessary waste and is an extremely useful method, it does have some important problems.

This is a problem of durability of hydrocarbon-based anion exchange membranes.

Hydrocarbon-based anion exchange membranes are generally strong acids.

It has poor durability in strong alkali and high temperature areas, and it has almost no durability under strong oxidizing substances such as chlorine gas, and it can be used for a short period of about a few weeks. The membrane may collapse.

Therefore, using a conventional hydrocarbon-based anion exchange membrane,
If such a process were to be carried out, the anion exchange membrane would have to be replaced frequently, resulting in poor economic efficiency of the process itself.

As mentioned above, although the electrolytic anion replacement method using ion-exchange membrane electrolysis is a well-known technology and there is an extremely high demand for its practical application as an industrial process, there are process limitations. Due to the conditions and many problems that need to be solved, it has not yet been established as a satisfactory industrial process.

[Object of the present invention]

An object of the present invention is to eliminate the drawbacks of conventional electrolytic anion replacement methods using ion exchange membranes and to provide an efficient and economical electrolytic anion replacement method.

[Means for solving problems]

The present inventors have conducted intensive studies regarding the electrolytic anion replacement method using ion exchange membranes, and in particular regarding anion exchange membranes, which have been a problem in the past, and have developed a fluorine-based anion exchange membrane with a special structure. We have discovered that this membrane exhibits extremely excellent properties, and furthermore, by electrolytic operation using a fluorine-based anion exchange membrane with this special structure, it is possible to realize an alternative electrolytic anion replacement method that can be applied to a variety of processes. This discovery led to the completion of the present invention.

The fluorine-based anion exchange membrane having a special structure used in the present invention refers to an element-based anion exchange membrane made of a copolymer of repeating units represented by the following general formula. .

Furthermore, the fluorine-based anion exchange membrane used in the present invention has a fourth
As the group containing a quaternary ammonium group, it is desirable to use a fluorine-based anion exchange membrane having a group containing a quaternary ammonium group represented by the following general formula, the following general formula, or the following general formula.

Specific examples of these fluorine-based anion exchange membranes include polymer membranes having the following structure.

1P, C-0F Shun Ha ■ 0 horses 'IPsO-01F number CII! Q IF-OF.

C Horse ■ LiA + Shima Yu ← Be 0 Horse 01F 吋p: 1 + o % posted ← -01F, OF increase + Yu Yu ¥ Yu 7 Exchange capacity of the fluorine-based anion exchange membrane having a special structure used in the present invention is α16 meq/9・Dry resin~A
Orneq/9.Dry resin can be used, but preferably, rL5 meq/9.Dry resin to 2.8 meq/9.Dry resin is used.

If the exchange capacity is less than the above range, the resistance of the membrane will be high and the electrolytic voltage will rise, leading to an increase in electricity costs.If the exchange capacity exceeds the above range, problems such as swelling and collapse of the membrane will occur. This becomes a cause of interfering with stable electrolytic reversal.

The thickness of the fluorine-based anion exchange membrane used in the present invention is usually 4
It can be used in the range of 0μ to 500μ, but preferably 1
Those in the range of 00μ to 50Qμ are used. 1 more
A reinforcing material can also be introduced into the fluorine-based anion exchange membrane used in the present invention in order to increase the strength of the membrane.

The fluorine-based anion exchange membrane with the above-mentioned special structure exhibits excellent heat resistance, acid resistance, alkali resistance, and oxidation resistance. By electrolytic operation using an anion exchange membrane, it is possible to realize an efficient electrolytic anion replacement method that can be applied to various processes.

A diagram of the principle of the present invention is shown in FIG.

FIG. 1 shows amino acid (AA) as one example of the present invention.
A hydrochloric acid solution of C1-
An example of substitution with an ionic OH- ion is shown.

1 is an electrolytic cell, 2.3 is each anion exchange membrane (AM) 14
is an anode, 5 is a cathode, 6 is an anode chamber, and 7 is an intermediate chamber.

8 is a cathode chamber. ``An amino acid hydrochloric acid solution (AA-HOI) is supplied to the intermediate chamber 7, hydrochloric acid is supplied to the anode chamber 6, and a sodium hydroxide solution is supplied to the cathode chamber 8.

When the electrolytic reaction is started, chlorine gas is generated from the 5JA electrode 4 and hydrogen gas is generated from the cathode 5. In the intermediate chamber 7 , Ol- ions move to the anode chamber 6 through the anion exchange membrane 2 , and OH'''' ions move from the cathode chamber 8 to the intermediate chamber 7 through the anion exchange membrane 5 .

As a result of the above, in the intermediate chamber 7, the 01- ion is the OH- ion K11l! Finally, an amino acid solution is obtained.

In such processes, anion exchange membranes are exposed to harsh conditions of acidic solutions, alkaline solutions, and oxidizing solutions containing chlorine gas.

Under such harsh conditions, conventional hydrocarbon-based anion exchange membranes have poor durability and are practically difficult to implement as an industrial process, but the special membrane used in the present invention Due to the excellent durability of the fluorine-based anion exchange membrane having this structure, the electrolytic anion replacement method can be established as an industrial process.

All of the fluorine-based anion exchange membranes used in the present invention exhibit extremely excellent acid resistance. However, when the anion exchange membrane 2 in FIG. 1 comes into contact with an oxidizing solution as well as an acidic solution, Among the structures of fluorine anion exchange membranes, fluoride has particularly excellent oxidation resistance.

[The group containing the quaternary ammonium group of the fluorine-based anion exchange membrane has the following general formula, where 2 is a halogen anion] or the quaternary ammonium group of the fluorine-based anion exchange membrane. It is desirable to use an anion exchange membrane in which the group containing is represented by the following general formula,
In addition, when the anion exchange membrane 5 in FIG. 1 comes into contact with an alkaline solution as well as an acid solution, the quaternary ammonium group of the fluorine anion exchange membrane is used as a fluorine anion exchange membrane with particularly excellent alkali resistance. It is preferable to use an anion exchange membrane in which the group containing the following formula is represented by the following general formula.

Note that the fluorine-based anion exchange membrane with a special structure used in the present invention has 1. Shapes such as a flat membrane shape, a cylindrical shape, and a tube shape can also be used.

Conventionally known electrode materials can be used as the anode and cathode of the electrolytic cell used in the present invention. Materials are selected appropriately.

Such an electrode material is used as an anode, for example, T1°Ta
, Zn, Nb, etc. on the surface of a corrosion-resistant base material such as Pt, or.

An anode coated with a platinum group metal such as Rh and/or an oxide of a platinum group metal is used, and the cathode is made of 1Fa, Ni
A cathode made of a metal such as , Ou, or an alloy thereof, or whose surface is coated with a material 1 exhibiting a low overvoltage (for example, Raney 12, Kel, etc.) can be used.

In the ion exchange membrane electrolysis method of the present invention, the electrolytic cell usually consists of three chambers: an anode chamber, an intermediate chamber, and a cathode chamber, but it is also possible to select a multi-chamber type other than three chambers. It is also possible to implement efficient electrolysis methods using cells.

Furthermore, in the ion exchange membrane electrolysis method of the present invention, the electrolysis temperature can range from room temperature to 100° C., and the current density can usually be carried out in the range of 50 A/dn/or less.

[Effects of the present invention]

As described above, by using a fluorine-based anion exchange membrane having a special structure, an efficient electrolytic anion replacement method can be realized as an industrial process.

Although the method of the present invention can be used in various fields, it is particularly of extremely high industrial value in the field of synthesis of organic and inorganic compounds.

〔Example〕

Examples will be described below, but the present invention is not limited thereto.

Example 1 An electrolytic anion was exchanged to obtain a glycine solution from a hydrochloric acid solution containing glycine using an ion exchange membrane electrolysis method.

The electrolytic cell is a 3-chamber wall cell as shown in Figure 1, and T is used as the anode.
1 of 1xpanded M@ta1 on the base material 1aK
An electrode coated with t-oxide is used, and the Ex of N1 is used as the electrode.
Panned Metal was used. The area of each electrode is (L 56 c1m', anode, distance between anodes is 71J
And so.

In order to separate the IIJA electrode chamber and the intermediate chamber, a fluorine-based anion exchange membrane (exchange volume: 1.10me) having the following structure -4or,oy,Y(ay,cp)-
q/9 dry resin, film thickness 140μ) was used as an anion exchange membrane to separate the cathode chamber and the anode chamber. Ion exchange membrane (exchange capacity 1.00me
q/9 dry resin, film thickness 130μ) was used.

2N Hat is supplied to the anode chamber, 2N NaOH is supplied to the cathode chamber, and 2! 1101/L of an equimolar solution of glycine in hydrochloric acid was supplied and circulated. When electrolysis was carried out at room temperature with a current density of 20A/am, the electrolysis voltage was 4.9μ.As the electrolysis continued, the glycine hydrochloric acid solution changed to a glycine solution, but at the same time, the glycine solution in the intermediate chamber changed to a glycine solution. As the pH value increases and approaches the isoelectric point, the conductivity decreases.Therefore, the electrolytic voltage increases.

When the electrolysis voltage exceeded 8V, the 01-ion removal rate of the Koshin chamber where electrolysis was stopped, that is, the electrolytic anion replacement rate was 96.
%, 1! The flow efficiency was 55%. Also, p of the intermediate chamber solution
H is 2.6, indicating that the glycine solution is near the isoelectric point.

Furthermore, when the amount of glycine in the anode and cathode chambers after electrolysis was measured, it was almost zero, indicating that almost no glycine leaked into the anode and cathode chambers.

Note that the current efficiency of 55% is due to the occurrence of back migration of H ions passing through the fluorine-based anion exchange membrane.

Example 2. Comparative Example 1 An amino acid hydrochloric acid solution containing about 20% mixed amino acids and about 16% hydrochloric acid solution was prepared by adding 1.5 times the molar amount of hydrochloric acid to the mole containing glutelin. . 10 tons of this solution was subjected to a continuous electrolysis test for 10 days under the same conditions as in Example 1 using the same three-chamber electrolytic cell as in Example 1.

The amount of hydrochloric acid in 10 to be supplied to the first intermediate chamber is 01''''
The amount of ions is about 44 mol, and the amount of current is about 64F.

As a result of the 10-day electrolysis test, the amount of hydrochloric acid in 10 supplied to the intermediate chamber decreased by about 4 molK in terms of 01-ion amount.

Therefore, the electrolytic anion replacement rate is approximately 91%.

Anion Exchange Membrane During the 10 day test, the electrolytic voltage gradually increased from an initial 4.8V but never exceeded 8V.

On the other hand, as Comparative Example 1, 7. Using a hydrocarbon-based anion-exchange membrane instead of an elementary-based anion-exchange membrane,
An electrolytic test was conducted in the same manner as in Example 1, and the electrolytic voltage was 4.4 V at the beginning, but as the electrolysis time progressed, the electrolytic voltage gradually increased and reached 107 or more on the 7th day.
The next day, the membrane was cracked.

This caused contamination of the liquid in each chamber, making it impossible to continue electrolysis.

Reference Example Table 1 shows the results of a durability test of a fluorine-based anion exchange membrane and a hydrocarbon-based anion exchange membrane having a special structure used in the present invention.

The durability is evaluated by immersing the membrane in each solution for a certain period of time, then measuring the electrical resistance in a 1 mol/L sodium chloride aqueous solution. I did it.

As is clear from the table, it has a special structure used in the present invention)
, element-based anion exchange membranes exhibit superior durability compared to hydrocarbon-based anion exchange membranes.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an example of the electrolysis process of the present invention. 1. Electrolytic cell 2. Fluorine anion exchange membrane 5. Fluorine anion exchange membrane 4. @ Electrode S Cathode & anode chamber l Intermediate chamber & Cathode chamber

Claims (6)

[Claims] (1) As an ion exchange membrane, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. q is a positive number, and its ratio p/q is 2-16. Y is a quaternary ammonium group] The electrolytic chamber is divided using a fluorine-based anion exchange membrane made of a copolymer of repeating units represented by the following formula, an aqueous solution containing ions is supplied, and the electrolysis is carried out by ion exchange membrane electrolysis. An electrolytic anion replacement method characterized by replacing anion species in an aqueous solution with other anion species. (2) Groups containing quaternary ammonium groups in fluorine-based anion exchange membranes include the following general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ [R^1, R^2, R^3 are lower alkyl groups (but ,
(R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain) Z^■ is a halogen anion] Claim 1 using an anion exchange membrane represented by Method described. (3) Groups containing quaternary ammonium groups in fluorine-based anion exchange membranes include the following general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ [R^1, R^2, R^3 are lower alkyl groups (but ,
R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) R^4 is a hydrogen atom or a lower alkyl group Z is a halogen ion] The method according to claim 1, using an anion exchange membrane represented by the following formula. (4) As a group containing a quaternary ammonium group in a fluorine-based anion exchange membrane, there are the following general formula ▲ mathematical formula, chemical formula, table, etc. ▼ [R^1, R^2, R^3 are lower alkyl groups ( however,
R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) R^4 and R^5 are hydrogen atoms or lower alkyl group Z is
Halogen anion a is an integer of 3 to 7.] The method according to claim 1, using an anion exchange membrane represented by: (5) As a membrane in contact with an oxidizing solution, the group containing a quaternary ammonium group of a fluorine-based anion exchange membrane has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R^1, R^2, R^3 is a lower alkyl group (however,
R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) Z^■ is a halogen anion] Or, the group containing the quaternary ammonium group of the fluorine-based anion exchange membrane is the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [R^1, R^2, R^3 is a lower alkyl group (however,
R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) R^4 and R^5 are hydrogen atoms or lower alkyl group Z is
Halogen anion a is an integer of 3 to 7.] The method according to claim 1, using an anion exchange membrane represented by: (6) As a membrane in contact with an alkaline solution, the group containing the quaternary ammonium group of the fluorine-based anion exchange membrane has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R^1, R^2, R ^3 is a lower alkyl group (however,
R^1 and R^2 may be combined to form a tetramethylene chain or a pentamethylene chain. ) R^4 is a hydrogen atom or a lower alkyl group Z is a halogen ion] The method according to claim 1, using an anion exchange membrane represented by the following formula.