JP2021134411A - Method for producing ammonium persulfate - Google Patents

Abstract

To provide a method for producing ammonium persulfate with high efficiency while preventing quality of a material to be used as a barrier membrane from being degraded.SOLUTION: A method for producing ammonium persulfate by electrolyzing an ammonium sulfate includes the steps of: supplying an ammonium sulfate solution as an anode-side raw material; supplying, as a cathode-side raw material, at least one selected from an ammonium sulfate solution, an ammonium hydroxide solution, and 0.001-1 wt.% of sulfuric acid solution, where an amount of acid-dissociatable hydrogen ions derived from an acid is less than 1.0 mol relative to a charge transfer amount of 1.0 mol; and generating ammonium persulfate on an anode side and ammonia on a cathode side by performing electrolysis using an electrolysis cell partitioned with a cation-exchange membrane, wherein a fiber-reinforced cation-exchange membrane is used as the cation-exchange membrane.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing ammonium persulfate using an aqueous solution of ammonium sulfate as a raw material, and more particularly to a method for producing ammonium persulfate capable of co-producing ammonia at the same time as producing ammonium persulfate.

Ammonium sulfate, also called ammonium sulfate, was once synthesized as a target product, but is now mainly produced as a by-product in the production process of organic compounds such as caprolactam, laurolactam, acrylonitrile or methyl methacrylate, and the coke production process by carbonization of coal. Things are in circulation. For the above organic compounds, it has been desired to develop a manufacturing method that does not produce ammonium sulfate as a by-product, but since the process of manufacturing these compounds is complicated and it is not easy to convert from the existing manufacturing method, many ammonium sulfates are still used. The current situation is that it is a by-product.
Since the by-produced ammonium sulfate contains about 20% of ammonia nitrogen, it can be used as a fertilizer, and most of the by-produced ammonium sulfate in the above-mentioned steps has been used as a fertilizer.

On the other hand, ammonium persulfate is widely and industrially used mainly in applications such as polymerization initiators for emulsion polymerization, oxidative bleaching agents, and copper etching agents. A method of using the above-mentioned ammonium sulfate for producing such ammonium persulfate has been studied, and a method of electrolyzing ammonium sulfate is known as such a method.

For example, Patent Document 1 and Patent Document 2 disclose a method for producing ammonium persulfate, which uses ammonium sulfate as an anode-side raw material and sulfuric acid as a cathode-side raw material. In such a production method, all the electrolytic reactions on the cathode side are reactions in which hydrogen ions derived from sulfuric acid receive electrons to generate hydrogen gas, as shown in the following reaction formula (1). Since the electrolytic solution on the cathode side after electrolysis contains ammonium sulfate and sulfuric acid, it can be used as a raw material on the anode side after being neutralized with ammonia.
_{^{2H + + 2e - → H 2}} (1)
In the above production method, ammonium sulfate is used as the raw material on the anode side, but since the electrolytic solution on the cathode side is reused as the raw material on the anode side after electrolysis, it is not possible to use a large amount of ammonium sulfate produced as a by-product in excess. rice field. In addition, it was necessary to use ammonia and sulfuric acid as raw materials.

On the other hand, Patent Document 3 discloses a method for producing ammonium persulfate, which uses an aqueous solution of ammonium sulfate as a raw material on the anode side and a raw material in which the amount of hydrogen ions that can be acid dissociated is controlled to a specific amount or less as a raw material on the cathode side. There is. When the amount of hydrogen ions that can be acid dissociated from the cathode side raw material is controlled to a specific amount or less, the above reaction formula (1) is prioritized for the electrolytic reaction on the cathode side as long as hydrogen ions derived from sulfuric acid are present in the cathode solution. Hydrogen is generated as a cathode-side product. However, after the acid-derived hydrogen ion deficiency, the following reaction formula (2) is prioritized, so that ammonia is produced as a cathode-side product. According to such a method for producing ammonium persulfate, ammonia, which is relatively more expensive than ammonium sulfate, can be co-produced. The cathode-side product liquid after electrolysis containing ammonia can be used in a lactam manufacturing process or the like.
^{_{2NH 4 + + 2e - → 2NH}} 3 + H 2 (2)
In the methods described in Patent Document 1 and Patent Document 2, sulfuric acid is supplied to the cathode side raw material at any time, the generated ammonia is neutralized, and then the raw material is supplied again, which is relatively more expensive than ammonium sulfate. Is impossible to recover.

Japanese Unexamined Patent Publication No. 11-293484 Japanese Patent No. 5570627 International Publication No. 2018/131493

However, in the method for producing ammonium persulfate as disclosed in Patent Document 3, since a cation exchange membrane that has not been reinforced is used as the diaphragm, the life of the diaphragm is short and continuous operation for a long period of time becomes difficult. Is a concern.

In view of the above circumstances, it is an object of the present invention to provide a method for producing ammonium persulfate capable of co-producing ammonia, which can suppress deterioration of the material used as a diaphragm and can produce ammonium persulfate with high efficiency. ..

In order to solve the above problems, each aspect of the present invention adopts the following configuration.
(1) A method for producing ammonium persulfate by electrolyzing ammonium sulfate.
The process of supplying an aqueous solution of ammonium sulfate as a raw material on the anode side,
As a raw material on the cathode side, an aqueous solution of ammonium sulfate, an aqueous solution of ammonium hydroxide, and an aqueous solution of 0.001 to 1% by weight of sulfuric acid having an acid-derived acid dissociable hydrogen ion amount of less than 1.0 mol with respect to an amount of charge transfer of 1.0 mol. The process of supplying at least one selected from
It has a step of electrolyzing using an electrolytic cell separated by a cation exchange membrane to generate ammonium persulfate on the anode side and at least ammonia on the cathode side.
A method for producing ammonium persulfate, which uses a fiber-reinforced cation exchange membrane as the cation exchange membrane.
(2) The method for producing ammonium persulfate according to (1), wherein the fiber-reinforced cation exchange membrane has a hydrophilic layer on at least one surface.
(3) The method for producing ammonium persulfate according to (1) or (2), wherein the fiber-reinforced cation exchange membrane has a single layer having an ion exchange function.
(4) The method for producing ammonium persulfate according to any one of (1) to (3), which uses a solid platinum electrode as an anode.
(5) The method for producing ammonium persulfate according to (4), wherein the solid platinum electrode is formed by welding solid platinum onto a metal substrate.
(6) The method for producing ammonium persulfate according to (5), wherein the welding is spot welding.
(7) The method for producing ammonium persulfate according to (6), wherein the number of welding points of the spot welding on the metal substrate is 25 points / dm ^{2 or more.}
(8) The method for producing ammonium persulfate according to any one of (1) to (3), which uses a platinum clad electrode as an anode.

According to the present invention, in the method for producing ammonium persulfate capable of co-producing ammonia, deterioration of the material used as a diaphragm can be suppressed, and ammonium persulfate can be produced with high efficiency.

FIG. 1 is a schematic view showing an embodiment of the method for producing ammonium persulfate of the present invention. FIG. 2 is an embodiment of the method for producing ammonium persulfate of the present invention, and is a schematic view when a buffer tank is used.

Hereinafter, the present invention will be described in more detail together with embodiments.
The method for producing ammonium persulfate according to the embodiment of the present invention is a method for producing ammonium persulfate by electrolyzing ammonium sulfate, and includes the following steps.
The process of supplying an aqueous solution of ammonium sulfate as a raw material on the anode side,
As a cathode-side raw material, an aqueous solution of ammonium sulfate, an aqueous solution of ammonium hydroxide, and an aqueous solution of 0.001 to 1% by weight of sulfuric acid having an acid-derived acid dissociable hydrogen ion amount of less than 1.0 mol with respect to a charge transfer amount of 1.0 mol. The process of supplying at least one selected from
A step of electrolyzing using an electrolytic cell separated by a cation exchange membrane to generate ammonium persulfate on the anode side and at least ammonia on the cathode side.
A fiber-reinforced cation exchange membrane is used as the cation exchange membrane.

An aqueous ammonium sulfate solution is used as the anode-side raw material.
The concentration of ammonium sulfate in the ammonium sulfate aqueous solution is not particularly limited, but it is preferable to contain ammonium ions in an amount of charge transfer or more, and from the viewpoint of improving productivity in the electrolytic reaction, 30% by weight or more is more preferable, and 35% by weight or more is further preferable. preferable. The concentration of ammonium sulfate is preferably 45% by weight or less from the viewpoint of suppressing the precipitation of ammonium sulfate crystals in the system. In the present specification, the charge transfer amount (mol) is a value obtained by energizing current (A) × energizing time (s) / Faraday constant (A · s / mol), and is supplied from the cathode side of the power supply device. , The number of electrons transferred to the anode side of the power supply device through the electrolytic reaction.

Further, the anode-side raw material may contain a raw material other than the ammonium sulfate aqueous solution. Examples of the raw material other than the aqueous solution of ammonium sulfate include an acid such as sulfuric acid, a base such as ammonium hydroxide, and a water-soluble solid such as a polarization agent. The polarization agent is not particularly limited as long as it is advantageous for producing a known persulfate, but guanidine, guanidine salt, thiocyanate, cyanide, cyanate, fluoride and the like are preferable. The polarization agent is more preferably guanidine or a guanidine salt from the viewpoint of improving current efficiency. Examples of the guanidine salt include guanidine sulfamate, guanidine nitrate, guanidine sulfate, guanidine phosphate, guanidine carbonate and the like. The concentration of the polarization agent in the anode-side raw material is preferably 0.01% by weight or more from the viewpoint of improving current efficiency. Further, since the polarization agent itself is also decomposed by an electrolytic reaction, the concentration of the polarization agent is preferably 1% by weight or less, more preferably 0.05% by weight or less, from the viewpoint of economy.

The raw materials on the cathode side are an aqueous solution of ammonium sulfate, an aqueous solution of ammonium hydroxide, and an aqueous solution of 0.001 to 1% by weight of sulfuric acid, in which the amount of hydrogen ions derived from the acid that can be dissociated from the acid is less than 1.0 mol with respect to the amount of charge transfer of 1.0 mol. Includes at least one selected from. The amount of hydrogen ions that can be dissociated from an acid is less than 1.0 mol with respect to 1.0 mol of charge transfer, which means that when an electrolytic reaction is carried out up to 1.0 mol of charge transfer, the cathode side raw material supplied to the reaction is carried out. However, it contains less than 1.0 mol of acid-derived hydrogen ions to be subjected to the cathode reaction. The amount of hydrogen ions is preferably less than 0.95 mol from the viewpoint of more efficiently co-producing ammonia on the cathode side. The cathode-side raw material may be a mixture of two or more of the above aqueous solutions.

As the cathode side raw material, at least one of an aqueous solution of ammonium sulfate and an aqueous solution of ammonium hydroxide is preferably used, and an aqueous solution of ammonium sulfate is more preferable. Since these aqueous solutions contain an electrolyte, the electrical resistance can be reduced. In addition, since these aqueous solutions contain ions common to the ions contained in the raw material on the anode side across the diaphragm and do not have hydrogen ions derived from sulfuric acid used for the cathodic reaction, the amount of by-product of ammonia should be increased. Is possible. In addition, since the acid (sulfuric acid) may be corrosive to the cathode material, the electrolytic device, and the subsequent process, it is preferable not to use the acid from the viewpoint of material selection on the cathode side.

The concentration of the raw material on the cathode side is not particularly limited, but when an aqueous ammonium sulfate solution is used, for example, the ammonium sulfate concentration in the aqueous ammonium sulfate solution is preferably 30% by weight or more, more preferably 35% by weight or more, from the viewpoint of improving productivity in the electrolytic reaction. preferable. Further, the concentration is preferably 45% by weight or less from the viewpoint of suppressing the precipitation of ammonium sulfate crystals in the system. The cathode-side raw material may contain other acids, bases, water-soluble salts, and additives such as a polarization agent as long as the effects of the present invention are not impaired.

The electrolytic cell used in the embodiment of the present invention is not particularly limited. As the electrolytic cell, for example, an electrolytic cell separated into an anode chamber and a cathode chamber by a diaphragm can be used. As for the structure of the electrolytic cell, for example, a box-shaped electrolytic cell or a filter press type electrolytic cell can be used. Further, during the electrolytic reaction, a buffer tank may be provided separately from the electrolytic cell, or the electrolytic solution may be circulated between the buffer tank and the electrolytic cell. By providing a buffer tank, it becomes easy to appropriately remove impurities and dehydrate the electrolytic solution after the reaction on each electrode side and then resupply it to the electrolytic cell as a raw material, so that a continuous electrolytic reaction can be performed. It will be easy.

A fiber-reinforced cation exchange membrane is used as the diaphragm that separates the anode chamber and the cathode chamber of the electrolytic cell. The cation exchange membrane is a membrane having an ion exchange function, and specifically, a membrane having a porous ion exchange polymer layer capable of selectively permeating cations. By using such a cation exchange membrane as a diaphragm, it is possible to inhibit the migration of anions generated in the anode chamber to the cathode chamber.

Since the cation exchange membrane is reinforced with fibers, it is possible to suppress breakage and deformation of the cation exchange membrane. When a cation exchange membrane that is not reinforced with fibers is used as a diaphragm, the membrane is likely to swell or contract due to the electrolytic solution, and the membrane is likely to be deformed or broken after long-term electrolysis. In particular, when ammonia is generated on the cathode side, the cation exchange membrane tends to shrink under basic conditions, so that deformation due to shrinkage of the cation exchange membrane occurs compared to the case where hydrogen is generated by the conventional production method. Since it is considered that breakage is likely to occur, it is necessary to reinforce the fibers in order to suppress the deterioration of the cation exchange membrane. When the cation exchange membrane is fiber-reinforced, the reinforcing fibers are inactive with respect to the electrolytic solution and have high mechanical strength, so that swelling and contraction of the membrane can be suppressed. In addition, the presence of reinforcing fibers having high mechanical strength can suppress deformation and breakage of the cation exchange membrane, and the cation exchange membrane is less likely to deteriorate. This facilitates continuous electrolytic reaction for a long period of time.

The form of the fiber reinforcement is not particularly limited, but from the viewpoint of suppressing the interference of charge transfer in the ion exchange polymer layer, the reinforcing fibers are provided so as to be orthogonal to the film thickness direction, and the reinforcing fibers are provided in the film thickness direction. A form that does not exist continuously is preferable. The material of the fiber is not particularly limited, but Teflon (registered trademark) is preferably used from the viewpoint of being inert to the electrolytic solution and having high mechanical strength.

The fiber-reinforced cation exchange membrane preferably has a hydrophilic layer on at least one surface, and more preferably has a hydrophilic layer on both sides. The hydrophilic layer refers to a hydrophilic layer having a certain thickness, and is clearly distinguished from the hydrophilic treatment in which isopropyl alcohol or the like is dropped on the surface of a cation exchange membrane to alter the surface of the membrane. Will be done. Further, the hydrophilic layer is a porous layer through which ions can pass but does not have an ion exchange function.
Examples of the hydrophilic layer include coat layers formed on both sides of the ion exchange polymer layer by coating the hydrophilic polymer.

Since the fiber-reinforced cation exchange membrane has a hydrophilic layer on the surface, it is possible to prevent the gas generated during the electrolytic reaction from adhering to the diaphragm. By suppressing the adhesion of gas to the diaphragm, it is possible to prevent the movement of ions through the diaphragm from being suppressed, and it is possible to suppress an increase in the applied voltage and a decrease in current efficiency during electrolysis, so that it is efficient. Electrolysis can be performed. Further, unlike the hydrophilic treatment in which the film surface is denatured, the effect of the hydrophilic layer can be exhibited for a long period of time even when an electrolytic reaction is carried out for a long period of time.

The fiber-reinforced cation exchange membrane having an ion exchange function (ion exchange polymer layer) is preferably a single layer. When the ion exchange polymer layer is a single layer, it means that it is composed of only one kind of layer. For example, the case of a single layer and the case of two or more layers can be distinguished by the difference in ion exchange capacity due to the difference in the type and amount of ion exchange groups. The type and amount of ion exchange groups can be measured by, for example, elemental analysis or infrared spectroscopy (FT-IR). Since the ion exchange polymer layer is a single layer, it is possible to reduce the applied voltage during the electrolytic reaction. It is considered that the reason for this is that when the ion exchange polymer layer is a single layer, resistance at the contact portion due to connection or adhesion between the ion exchange polymer layers, which occurs in the case of multiple layers, is unlikely to occur.

Examples of the polymer constituting the ion exchange polymer layer include a fluorine-based polymer in which an ion exchange group is introduced at the end of the polymer. As the fluorine-based polymer, polytetrafluoroethylene (PTFE) and perfluorosulfonate ethoxypropyl vinyl ether (PSEPVE) are preferably used from the viewpoint of chemical resistance and ionic conductivity, and a polymer obtained by copolymerizing these is used. May be good. The ion exchange group introduced into the polymer terminal is preferably a sulfonic acid group from the viewpoint of strong acidity and hydrophilicity. As the fiber-reinforced cation exchange membrane in which the ion exchange polymer layer is a fluorine-based polymer, Nafion (registered trademarks) 324 and 551 are preferably used from the viewpoint of satisfying the above-mentioned functions.

As the anode, it is preferable to use a conductive diamond electrode or an electrode containing a platinum group metal. Among the above electrodes, an electrode containing a platinum group metal is more preferable, an electrode containing platinum as a platinum group metal is further preferable, and an electrode in which platinum is exposed on the electrode surface (hereinafter referred to as "platinum electrode") is used. It is even more preferable to use it.

The conductive diamond electrode is generally more expensive than the platinum electrode, and it is preferable to use the platinum electrode from the viewpoint of cost, especially when a large electrolytic cell is used. However, in the conventional method for producing ammonium persulfate which does not co-produce ammonia, when electrolysis is performed using a cation exchange membrane, a conductive diamond electrode is often used because higher current efficiency can be obtained than when a platinum electrode is used. ing. On the other hand, in the method for producing ammonium persulfate coexisting with ammonia, such as the production method according to the embodiment of the present invention, it was found that a platinum electrode can also obtain a current efficiency equal to or higher than that of the conductive diamond electrode. .. As described above, the platinum electrode can be preferably used not only from the viewpoint of cost but also from the viewpoint of current efficiency.

As the platinum electrode, a solid platinum electrode in which solid platinum and a metal base material are bonded, a platinum clad electrode using a clad steel in which platinum and a metal base material are pressure-bonded, and platinum as a metal base material. Examples thereof include plated platinum-plated electrodes. The metal constituting the metal base material is not particularly limited, but from the viewpoint of corrosion resistance of the electrolytic solution, a metal having a passivation film on the surface is preferable, and titanium is more preferable. The metal base material is used to provide rigidity while ensuring the electrical conductivity required as an electrode.
Among the above electrodes, it is preferable to use a solid platinum electrode or a platinum clad electrode, and from the viewpoint of current efficiency, it is more preferable to use a solid platinum electrode. On the other hand, from the viewpoint of economy, it is more preferable to use a platinum clad electrode. By using a solid platinum electrode or a platinum clad electrode, it becomes easy to improve the current efficiency during electrolysis. The reason for this is not clear, but in a solid platinum electrode or a platinum clad electrode, the crystal structure of platinum is more likely to be maintained without being destroyed on the electrode surface, as compared with a platinum-plated electrode or the like. This is considered to contribute to the improvement of current efficiency. When a solid platinum electrode or a platinum clad electrode is used, the current efficiency can be significantly improved as compared with the case where a platinum-plated electrode is used.

When solid platinum whose base material and platinum are not bonded by crimping or plating is used for the anode, it is preferable to bond the solid platinum to the metal base material and use it as a solid platinum electrode. Examples of the method for adhering solid platinum to a metal base material include adhesion by welding and adhesion by an adhesive. Among these bonding methods, welding by welding is preferable, welding methods such as seam welding and spot welding are more preferable, and spot welding is more preferable. By using the above-mentioned preferable bonding method, it is possible to minimize the destruction of the crystal structure of platinum during welding and to secure a sufficient conductive surface. As a result, the electrical resistance between the solid platinum and the metal base material can be suppressed to a low level.

The number of spot welding points on the metal substrate ^{is preferably 25 points / dm 2} or more, and more preferably 80 points / dm ² or more. When the number of welding points is equal to or greater than the above value, the bonding area between the solid platinum and the metal base material becomes sufficient, and an increase in electrical resistance can be suppressed. Further, the upper limit of the number of welding points is not particularly limited, and is determined by cost and physical restrictions.

The current density of the anode ^{is preferably 20 A / dm 2} or more, and more preferably 40 A / dm ² or more. When the current density is in the above range, the electrolysis efficiency is improved and the production efficiency is improved, so that the size of the electrolyzer can be made smaller. The current density of the anode is preferably 500A / dm ² or less, 80A / dm ² or less is more preferable. When the current density is in the above range, an increase in the applied voltage during the electrolytic reaction can be suppressed, which is preferable from an economical point of view.

Lead, zirconium, platinum, nickel, and stainless steel can be used as the metal constituting the cathode. Among the above, from the viewpoint of corrosion resistance, a metal that forms a passivation film on the surface is preferable, or SUS (stainless steel) 316 is more preferable.
The shape of the cathode is not particularly limited, but it is preferable that the wetted area with respect to the electrode weight is large in order to improve the electrolysis efficiency, and it is more preferable to use a metal processed into a wire mesh as the electrode.
The temperature inside the electrolytic cell is preferably maintained at 40 ° C. or lower. When the temperature in the electrolytic cell is 40 ° C. or lower, the reaction of decomposition of salts in the electrolytic cell can be suitably suppressed.

By adopting the production method according to the embodiment of the present invention, it is possible to produce ammonium persulfate with high efficiency while suppressing deterioration of the diaphragm. Under the preferred conditions in the embodiment of the present invention, for example, when the energization time is 2 hours, ammonium persulfate can be produced with a current efficiency of 80% or more, more preferably a current efficiency of 85% or more, still more preferably 90%. As described above, ammonium persulfate can be produced. The upper limit of current efficiency is theoretically 100%. Here, the current efficiency (%) is a value represented by (generated persulfate ion (mol) × 2) / energization amount (F) × 100, and is generated with respect to the energization amount at the time of electrolysis and the energization amount. It is obtained by using the value obtained by converting the amount of ammonium persulfate obtained in terms of the amount of persulfate ion (mol).

When the energization time is 10 hours, the current efficiency is preferably 60% or more, more preferably 65% or more, still more preferably 70% or more. When the current efficiency is within the above range, it can be judged that high current efficiency can be maintained for a long period of time, and it can be said that ammonium persulfate can be produced with high efficiency for a long period of time while suppressing deterioration of the diaphragm.

When the electrolytic reaction is carried out with the anode chamber filled with the anode-side electrolytic solution, persulfate ions are generated in the anode-side electrolytic solution. Ammonium persulfate can be precipitated by supplying the anode-side product liquid in which persulfate ions are generated to, for example, a crystallization tank and evaporating the water content until the solubility becomes lower than that of the prior art. The ammonium persulfate slurry obtained after crystallization can be separated into ammonium persulfate crystals and a crystallization mother liquor by a solid-liquid separator such as a centrifuge. The obtained ammonium persulfate crystals can be dried and commercialized using a powder dryer. In addition, the mother liquor after crystallization can be re-supplied to the process as an anode-side raw material.

In the cathode chamber, as the electrolytic reaction progresses, cations corresponding to the amount of charge transfer and water molecules hydrated with cations move from the anode to the cathode side, and the amount of liquid increases. Therefore, during continuous operation, continuous operation is possible by dehydrating the amount corresponding to this increase from the cathode side product liquid and supplying it to the cathode side again. The method of dehydrating the water that has moved to the cathode side is not particularly limited, but dehydration by evaporation concentration or membrane separation is preferable. Regarding the amount of dehydration, it is preferable to dehydrate by a certain amount or more with respect to the amount of charge transfer, and when the cathode side product liquid contains a salt or the like, the amount of dehydration is preferably equal to or less than the amount in which crystals are precipitated by dehydration. The amount of dehydration per 1 mol of charge transfer is preferably 20 g or more, more preferably 30 g or more. The amount of dehydration is preferably 90 g or less, more preferably 80 g or less. The water obtained by dehydration contains ammonia. This water can be used in a step of producing caprolactam and ammonium sulfate by mixing (neutralizing) it with caprolactam sulfate as, for example, aqueous ammonia.

When the cathode side product liquid is dehydrated and electrolysis is continued while supplying it to the cathode side again, hydrogen ions and ammonium ions corresponding to the amount of charge transfer move from the anode to the cathode side. Therefore, ammonium hydroxide (ammonia-containing water) is generated in the mixed gas of hydrogen and ammonia and / or the product liquid in the gas produced on the cathode side of the cathode chamber. The hydrogen / ammonia mixed gas generated on the cathode side can be separated by a commonly used ammonia gas separation method, for example, deep cold separation or compression separation.

The separated hydrogen gas can be refined and compressed by using a pressure fluctuation adsorption method or the like, and can be used as a fuel for a hydrogenation process in the organic chemical industry or a fuel cell.

In the method for producing ammonium persulfate according to the embodiment of the present invention, ammonium sulfate produced as a by-product in the above-mentioned production steps of lactam, acrylonitrile, methyl methacrylate and the like and the coke production process by carbonization of coal can be used as a raw material. .. At this time, impurities other than ammonium sulfate may be contained in the by-products containing ammonium sulfate in various steps. Depending on the components and contents of these impurities, a side reaction may occur and the current efficiency in the manufacturing process of ammonium persulfate may be lowered. In such a case, it is preferable to purify the impurities in ammonium sulfate in advance to reduce the components that reduce the current efficiency before supplying the ammonium persulfate to the ammonium persulfate production process. As a method for producing impurities in ammonium sulfate, for example, a method of chelating an inorganic substance is preferable.

As a specific example of the method for producing ammonium persulfate according to the embodiment of the present invention, FIG. 1 shows an example in which an aqueous solution of ammonium sulfate (ammonium sulfate) is used as both the anode side raw material and the cathode side raw material. _{In FIG. 1, reference numeral 1 denotes an electrolytic cell, and an aqueous ammonium sulfate aqueous solution ((NH 4} ) ₂ ) produced as an anode-side raw material in the anode-side 2 of the electrolytic cell 1, for example, in the lactam manufacturing process as another manufacturing step 4. SO ₄ ) aq is supplied. As the anodic reaction, as in the prior art, sulfate ions react (consume) to generate persulfate ions as described below.
2SO ₄ ^2- → S ₂ O ₈ ^2- + 2e ⁻

As the dissolved ion on the anode side 2,
Before electrolysis: NH ₄ ⁺ , SO ₄ ^2- = ammonium sulfate aqueous solution After electrolysis: NH ₄ ⁺ , S ₂ O ₈ ^2- = ammonium persulfate aqueous solution, ammonium ions migrate to the cathode side, and ammonium persulfate aqueous solution is generated. go. This anode-side product is concentrated and crystallized and separated into a crystallizing mother liquor and crystals, and the crystals can be commercialized as a salt of ammonium persulfate by, for example, a powder dryer. The crystallization mother liquor can be resupplied to the process as an anode-side raw material.

On the other hand, on the cathode side 3, when an aqueous solution of ammonium sulfate is used as a raw material, an aqueous solution containing ammonium sulfate is supplied, and in the cathode reaction, hydrogen ions of the reaction source are absent or scarce. Reacts to produce ammonia and hydrogen. When there is an acid on the cathode side, hydrogen ions derived from the acid react (consume) as shown in the reaction formula below, and hydrogen gas is generated.
^{_{2NH 4 + + 2e - → 2NH}} 3 + H 2
2H ^{+ +} 2e ^- → _{H 2}
By electrolysis, hydrogen ions, ammonium ions, and water molecules hydrated by these ions, which correspond to the amount of charge transfer, move from the anode side to the cathode side.

Further, FIG. 2 illustrates a case where electrolysis is performed while circulating the liquid between the buffer tank and the electrolytic cell, and the cathode side product liquid is dehydrated and then supplied to the cathode side again. In FIG. 2, 11 indicates an electrolytic cell, and an aqueous ammonium sulfate solution ((NH ₄ ) ₂ SO ₄ ) aq circulates as an anode-side raw material on the anode-side 12 of the electrolytic cell 11 via the anode-side buffer tank 16. Supplied. As the anodic reaction, as in the prior art, sulfate ions react (consume) to generate persulfate ions, and an aqueous ammonium persulfate solution is produced. This anode-side product is concentrated and crystallized and separated into a crystallizing mother liquor and crystals, and the crystals can be commercialized as a salt of ammonium persulfate by, for example, a powder dryer. The crystallization mother liquor can be resupplied to the process as an anode-side raw material.

On the other hand, on the cathode side 13, an ammonium sulfate aqueous solution containing ammonium sulfate is circulated and supplied as a cathode side raw material via the cathode side buffer tank 17, and as a cathode reaction, hydrogen ions of the reaction source are absent or scarce. Ammonium ions migrating from the anode react with each other to generate ammonia and hydrogen. Further, when there is an acid on the cathode side, hydrogen ions derived from the acid react (consume) as in the above reaction formula, and hydrogen gas is generated.
Due to electrolysis, hydrogen ions, ammonium ions corresponding to the amount of charge transfer and water molecules hydrated to these ions move from the anode to the cathode side, and the amount of liquid on the cathode side 13 increases, so that the cathode side buffer tank 17 In, the increase equivalent amount is dehydrated from the cathode side product liquid and supplied to the cathode side 13 again.
As described above, on the cathode side, continuous operation can be easily performed, and ammonium persulfate can be produced with high efficiency without supplying an additional raw material to the cathode.

Hereinafter, the present invention will be specifically described with reference to Examples. The present invention is not limited to these examples.

(Example 1)
Regarding the electrolytic cell, as the cation exchange membrane used as the diaphragm, Nafion (registered trademark) 551 (manufactured by The Chemours Company), which contains reinforcing fibers and has hydrophilic coatings on both surfaces, was used. A wire mesh-like platinum clad electrode prepared by using a clad steel obtained by crimping platinum to a titanium metal base material was used as an anode, and a wire mesh-like SUS316 electrode was used as a cathode. An aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40% by weight ammonium sulfate aqueous solution was supplied to the anode side buffer tank as an anode side raw material in an amount of 5008 g, and the anode side buffer tank and the electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 5010 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 10 hours was 16.8 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 1.40 mol of ammonium persulfate was produced in 2 hours of energization time and 5.30 mol of ammonium persulfate in 10 hours, and the current efficiencies were 83% and 63%, respectively. From the gas produced on the cathode side during electrolysis, hydrogen and ammonia corresponding to the electrolytic reaction were generated, and the generated amounts were 17 g of hydrogen and 286 g of ammonia, respectively.

(Example 2)
Except for using Nafion (registered trademark) 324 (manufactured by The Chemours Company), which contains reinforcing fibers in the cation exchange membrane used as the diaphragm and has two ion exchange polymer layers, the experimental equipment such as the electrolytic cell is used. It was the same as in Example 1. As an anode-side raw material, 5010 g of an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40 wt% ammonium sulfate aqueous solution was supplied to the anode-side buffer tank, and the anode-side buffer tank and the electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 5035 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 10 hours was 16.8 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 1.38 mol of ammonium persulfate was produced in 2 hours of energization time and 5.25 mol of ammonium persulfate in 10 hours, and the current efficiencies were 82% and 63%, respectively. From the gas produced on the cathode side during electrolysis, the generation of hydrogen and ammonia equivalent to the electrolytic reaction was observed.

(Comparative Example 1)
Experiments on electrolytic cells, etc., except that Nafion (registered trademark) 117, which has a single ion exchange polymer layer, no reinforcing fibers, and no hydrophilic coating, was used for the cation exchange membrane used as the diaphragm. The apparatus was the same as in Example 1. As an anode-side raw material, 5006 g of an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40 wt% ammonium sulfate aqueous solution was supplied to the anode-side buffer tank, and the anode-side buffer tank and the electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 5002 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the cathode-side buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 10 hours was 16.8 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 1.34 mol of ammonium persulfate was produced in 2 hours of energization time and 4.88 mol of ammonium persulfate in 10 hours, and the current efficiencies were 80% and 58%, respectively. From the gas produced on the cathode side during electrolysis, the generation of hydrogen and ammonia equivalent to the electrolytic reaction was observed.

(Example 3)
As the anode, a solid platinum electrode made by spot-welding 80 mesh wire mesh solid platinum onto expanded metal, which is a titanium metal base material, at a welding point of 81 points / dm ² was used, but in an electrolytic cell, etc. The experimental apparatus was the same as in Example 1. As an anode-side raw material, an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40 wt% ammonium sulfate aqueous solution was supplied to a 5000 g anode-side buffer tank, and the anode-side buffer tank and electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 5000 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the cathode-side buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 10 hours was 16.8 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 1.42 mol of ammonium persulfate was produced in 2 hours of energization time and 6.14 mol of ammonium persulfate in 10 hours, and the current efficiencies were 85% and 73%, respectively. The average voltage of the electrolytic cell was 7.78V. From the gas produced on the cathode side during electrolysis, the generation of hydrogen and ammonia equivalent to the electrolytic reaction was observed.

(Example 4)
As the anode, an experimental device such as an electrolytic cell was used in Example 1 except that a solid platinum electrode in which 80 mesh wire mesh-like solid platinum was spot-welded on titanium expanded metal at a welding point of 25 points / dm ^{2 was used.} It was the same as. As an anode-side raw material, an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40 wt% ammonium sulfate aqueous solution was supplied to the anode-side buffer tank in an amount of 5008 g, and the anode-side buffer tank and the electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 5001 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the cathode-side buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 10 hours was 16.8 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 1.49 mol of ammonium persulfate was produced in 2 hours of energization time and 6.14 mol of ammonium persulfate in 10 hours, and the current efficiencies were 89% and 73%, respectively. The average voltage of the electrolytic cell was 9.28V. From the gas produced on the cathode side during electrolysis, the generation of hydrogen and ammonia equivalent to the electrolytic reaction was observed.

(Comparative Example 2)
Experimental equipment such as an electrolytic cell is an example except that Nafion (registered trademark) 117 (manufactured by The Chemours Company) is used as a diaphragm and a wire mesh-plated platinum electrode obtained by plating a titanium metal base material with platinum as an anode is used. It was the same as 1. As an anode-side raw material, 6000 g of an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40 wt% ammonium sulfate aqueous solution was supplied to the anode-side buffer tank, and the anode-side buffer tank and the electrolytic cell (anode) were supplied at a flow rate of 1 L / min. The liquid was circulated between the chambers). As a cathode-side raw material, 6000 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode-side buffer tank, and the liquid was circulated between the cathode-side buffer tank and the electrolytic cell (cathode chamber) at a flow rate of 1 L / min. Electrolysis was performed by energizing with an anode current density of 45 A / dm ^2. The amount of charge transfer after electrolysis for 4 hours was 6.72 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 0.88 mol of ammonium persulfate was produced in 2 hours of energization time and 1.62 mol of ammonium persulfate in 4 hours, and the current efficiencies were 52% and 48%, respectively. The average voltage of the electrolytic cell was 6.7V. From the gas produced on the cathode side during electrolysis, the generation of hydrogen and ammonia equivalent to the electrolytic reaction was observed.

(Example 5)
Using an electrolytic cell using Nafion (registered trademark) 551 (manufactured by Chemers) as the diaphragm, 80 mesh wire mesh solid platinum was spot welded ^{to the titanium wire mesh base material at 100 points / dm 2 as the anode.} An electrode made of SUS316, which has an 80-mesh wire mesh shape, was used as a cathode. As a raw material on the anode side, 464 g of an aqueous solution prepared by adding 0.03% by weight of guanidine sulfamate as a polarization agent to a 40% by weight ammonium sulfate aqueous solution was supplied to the anode chamber. The amount of substance of each ion is 3.02 mol of ammonium ion and 1.51 mol of sulfate ion. As a cathode-side raw material, 411 g of a 40 wt% ammonium sulfate aqueous solution was supplied to the cathode chamber. After the supply, the anode current density was set to 45 A / dm ^{2 and the} current was applied to perform electrolysis. The amount of charge transfer after electrolysis for 8 hours was 1.34 mol. After energization, the concentration of ammonium persulfate in the obtained anode-side product was measured by titration. On the anode side, 0.236 mol of ammonium persulfate was produced in 3 hours of electrolysis time and 0.60 mol of ammonium persulfate in 8 hours, and the current efficiencies were 94% and 89%, respectively. Further, hydrogen and ammonia corresponding to the electrolytic reaction were generated from the cathode-side generated gas during the electrolysis, and the generated amounts were 23 g of ammonia and 1 g of hydrogen, respectively.

In Examples 1 to 5, the fiber-reinforced cation exchange membrane was used as the diaphragm, so that the energization time was 8 hours as compared with Comparative Examples 1 and 2 in which the fiber-reinforced cation exchange membrane was used. High current efficiency was obtained even in the case of 10 hours or 10 hours, and high current efficiency was maintained for a long period of time. Further, in Examples 3 to 5, a solid platinum electrode obtained by welding a solid platinum and a metal base material by spot welding with a number of welding points of 25 points / dm ^{2 or more was used as the anode, whereby a higher current was obtained.} Highly efficient results were obtained, and the maintenance rate was also high. Further, in Example 5, the fiber-reinforced cation exchange membrane has hydrophilic layers on both surfaces, the ion exchange polymer layer is a single layer, and the number of welding points is 100 points / dm ^{2 as an anode.} By using a solid platinum electrode obtained by welding a solid platinum and a metal base material by spot welding, the results with particularly high current efficiency and maintenance rate were obtained.

According to the present invention, in a method for producing ammonium persulfate capable of co-producing ammonia, ammonium persulfate can be produced with high efficiency while suppressing deterioration of the material used as a diaphragm, providing an industrially advantageous production process for ammonium persulfate. can.

1, 11 Electrolytic cell 2, 12 Anode side 3, 13 Cathode side 4 Other manufacturing process 16 Anode side buffer tank 17 Cathode side buffer tank

Claims (8)

It is a method of producing ammonium persulfate by electrolyzing ammonium sulfate.
The process of supplying an aqueous solution of ammonium sulfate as a raw material on the anode side,
As a raw material on the cathode side, an aqueous solution of ammonium sulfate, an aqueous solution of ammonium hydroxide, and an aqueous solution of 0.001 to 1% by weight of sulfuric acid having an acid-derived acid dissociable hydrogen ion amount of less than 1.0 mol with respect to an amount of charge transfer of 1.0 mol. The process of supplying at least one selected from
It has a step of electrolyzing using an electrolytic cell separated by a cation exchange membrane to generate ammonium persulfate on the anode side and at least ammonia on the cathode side.
A method for producing ammonium persulfate, which uses a fiber-reinforced cation exchange membrane as the cation exchange membrane. The method for producing ammonium persulfate according to claim 1, wherein the fiber-reinforced cation exchange membrane has a hydrophilic layer on at least one surface. The method for producing ammonium persulfate according to claim 1 or 2, wherein the fiber-reinforced cation exchange membrane has a single layer having an ion exchange function. The method for producing ammonium persulfate according to any one of claims 1 to 3, wherein a solid platinum electrode is used as an anode. The method for producing ammonium persulfate according to claim 4, wherein the solid platinum electrode is formed by welding solid platinum onto a metal substrate. The method for producing ammonium persulfate according to claim 5, wherein the welding is spot welding. The method for producing ammonium persulfate according to claim 6, wherein the number of welding points of the spot welding on the metal substrate is 25 points / dm ^{2 or more.} The method for producing ammonium persulfate according to any one of claims 1 to 3, wherein a platinum clad electrode is used as the anode.

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