JP2003221389A - Method for producing aqueous solution containing piperazine biscarbodithioate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial method for safely and efficiently producing an aqueous solution containing piperazine-N,N'-biscarbodithioate, more excellent in properties than that obtained by a conventional method. <P>SOLUTION: This method comprises the step of alternatingly adding an aqueous alkali solution and carbon disulfide to thermally molten hydrous or anhydrous piperazine or to an aqueous hydrous piperazine solution to react them together or the step of simultaneously and continuously adding an aqueous alkali solution and carbon dioxide to it to react them together. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to piperazine-N,
The present invention relates to a method for producing an aqueous solution containing N'-biscarbodithioate, and particularly to a method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate in a high concentration,
Further, the present invention relates to an aqueous solution containing piperazine-N, N′-biscarbodithioate having a low content of thiocarbonate as a by-product, and a heavy metal fixing agent using the aqueous solution.

[0002]

2. Description of the Related Art Conventionally, when treating incinerated ash discharged from an incineration plant for municipal waste, industrial waste, etc., fly ash collected by an electric dust collector or the like from flue gas, factory contaminated wastewater, etc. In order to prevent or suppress the release of harmful heavy metals such as lead, mercury, chromium, cadmium, arsenic, and selenium contained in fly ash into the environment, the heavy metals contained in these should be mixed with fly ash. A heavy metal fixing agent that is firmly fixed and insoluble in rainwater is used. As a useful compound applied to such a heavy metal fixing agent, piperazine biscarbodithioate has been known.

As a method for producing piperazine biscarbodithioate, by mixing piperazine, an aqueous solution of potassium hydroxide and water under a nitrogen atmosphere, carbon disulfide is added dropwise while stirring at 40 ° C. to react with each other. % Aqueous solution of potassium piperazine carbodithioate or 40% aqueous solution of sodium piperazine carbodithioate is known (for example, refer to Patent Document 1).

Further, there is known a method for producing a 40% potassium piperazine biscarbodithioate aqueous solution by mixing and dissolving water, potassium hydroxide and piperazine, and then dropwise adding and reacting carbon disulfide at 35 ° C. in a nitrogen atmosphere. (See, for example, Patent Document 2).

[0005]

[Patent Document 1] JP-A-8-224560

[Patent Document 2] Japanese Unexamined Patent Publication No. 8-269434

[0006]

In producing such piperazine biscarbodithioate, piperazine anhydride is used as a raw material. Since piperazine anhydride is a solid at room temperature, it is used in a powder state. Has been done. However, in the case of industrially manufacturing on a large scale, if piperazine is charged in a powder state into a reaction tank, entrainment of gas in the atmosphere with the powder of piperazine is unavoidable, and in addition, the solid is sublimable. Therefore, if it is carried out in the air, there is a possibility that a dust explosion may be caused due to the entrapped oxygen. Also, piperazine reacts with carbon dioxide in the air to produce carbonate,
Because it is oxidized by oxygen in the air and colored,
Careful attention was required in its handling. for that reason,
It was handled under a nitrogen atmosphere, but handling all powders in a nitrogen atmosphere requires expensive equipment.
There was a problem that the system had to be open when the powder was loaded.

On the other hand, the carbon disulfide used in the reaction has a low flash point and ignition point, and must be shielded from oxygen to carry out the reaction. When carbon disulfide is dropped into an aqueous solution to react, It has been necessary to remove oxygen existing in the aqueous solution in advance, and careful attention has been paid to replacing oxygen in the aqueous solution with nitrogen by nitrogen bubbling or the like. Moreover, when piperazine is handled as a powder, it is more difficult to remove oxygen due to an increased chance of oxygen entrapment. When handling such a dangerous substance, not only a large-scale device for preventing the danger but also an obstacle to automation and continuation of the manufacturing process has been hindered.

When piperazine is mixed with a metal hydroxide or an aqueous solution thereof in the presence of solvent water, crystals of piperazine are precipitated or the viscosity of the aqueous solution is increased, which makes stirring difficult. There was a problem. In particular, when producing an aqueous solution containing a high concentration of piperazine biscarbodithioate, precipitation of crystals of piperazine from an aqueous solution in which a metal hydroxide is dissolved at a high concentration or an increase in the viscosity of the aqueous solution is remarkable. It was In this case, if the reaction temperature is maintained at 40 ° C or higher, precipitation of piperazine crystals and increase in viscosity of the aqueous solution can be avoided, but when the reaction is carried out in the glass-lined reaction tank, the reaction tank is not corroded. It was necessary to avoid heating to 40 ° C. or higher so that the temperature would not rise.

INDUSTRIAL APPLICABILITY The present invention does not require a safe and large-scale apparatus in the industrial production of an aqueous solution containing piperazine, which has a risk of dust explosion, and piperazine biscarbodithioate as a raw material of carbon disulfide. It facilitates the handling of these raw materials, enables automation and continuous production processes,
It can be produced efficiently, and further, the precipitation of crystals of piperazine from a strong alkaline aqueous solution and the increase in viscosity of the reaction solution are prevented, and heating of a strong alkaline substance at 40 ° C. or higher is avoided to avoid piperazine-N, N. It is an object of the present invention to provide a method for producing an aqueous solution containing a'-biscarbodithioate salt.

[0010]

The present inventors have found that piperazine hydrate has stability in comparison with anhydrous piperazine,
In addition, while the melting point of piperazine anhydrous is about 104 ° C., the melting point of piperazine hydrate (eg, hexahydrate is 4
4 ° C. dihydrate, about 50 ° C.) is relatively low, and piperazine is heated and melted with piperazine hydrate, or
By using it as a liquid such as an aqueous solution of piperazine anhydride or piperazine hydrate, the danger of dust explosion is eliminated, and by devising the method of charging the raw material, the raw material can be charged without heating the reaction system to high temperature. The inventors have found that an aqueous solution containing piperazine-N, N'-biscarbodithioate can be obtained, which suppresses the precipitation of crystals and the increase in viscosity and has few impurities, and has completed the present invention.

That is, the present invention comprises (1) a step of alternately adding an alkaline aqueous solution and carbon disulfide to a heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate, and reacting them. A method for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate, which is characterized in that (2) heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate, A method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate, which comprises a step of simultaneously and continuously reacting an alkaline aqueous solution and carbon disulfide, and Start the addition of the alkaline aqueous solution and the required amount of carbon disulfide at the same time, and set the alkaline aqueous solution addition time longer than the carbon disulfide addition time. Piperazine according to, characterized in that simultaneous continuous addition of an aqueous solution and carbon disulfide (2) -
Method for producing aqueous solution containing N, N′-biscarbodithioate, (4) Addition of required amount of carbon disulfide is started prior to addition of required amount of alkaline aqueous solution, and addition of the alkaline aqueous solution is completed. The time is set at the same time as or after the end of the addition of the carbon disulfide, and the continuous addition is performed simultaneously. The production of an aqueous solution containing piperazine-N, N′-biscarbodithioate according to (2). Regarding the method.

(5) The ratio of the total number of moles of carbon disulfide to the total number of moles of alkali in the aqueous alkali solution added to the heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate. , Piperazine-N, N′-biscarbodithioate salt, which comprises a step of adding a necessary amount of carbon disulfide and a necessary amount of an alkaline aqueous solution so as to be in the range of 0.8 to 1.5. (6) Heat-melted piperazine hydrate, or the total number of moles of carbon disulfide added to an aqueous solution of piperazine anhydride or piperazine hydrate and the total amount of alkali in an alkaline aqueous solution. The molar ratio is 1.0 to 1.3
The method for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate according to (5), characterized in that

(7) Carbon disulfide was added to an aqueous solution of heat-melted piperazine hydrate, piperazine anhydride or piperazine hydrate in an amount of 1 to 10% by weight based on the total amount of carbon disulfide used in the reaction. A method for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate, characterized in that an aqueous alkali solution is added after or at the same time, and then the remaining total amount of carbon disulfide is added.
(8) The method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate according to any one of (1) to (7), wherein the alkaline aqueous solution is an aqueous solution of metal hydroxide. (9) Piperazine-N, N'-biscarbodithioate as an aqueous solution containing 20% by weight to 60% by weight of piperazine-N, The present invention relates to a method for producing an aqueous solution containing N'-biscarbodithioate.

(10) Piperazine-N, N'-biscarbodithioic acid characterized by using a heat-melted piperazine hydrate or an aqueous solution of piperazine anhydride or piperazine hydrate, an aqueous alkali solution, and carbon disulfide. A method for producing an aqueous solution containing a salt, comprising: (11) a wavelength of 50
Piperazine having an absorption intensity in the visible light absorption spectrum at 0 nm of 0.05 or less.
Regarding an aqueous solution containing N, N'-biscarbodithioate, (12) piperazine-N, N'-bis, characterized in that the absorption intensity in a visible light absorption spectrum at a wavelength of 500 nm is 0.05 or less. A heavy metal fixing agent whose main component is an aqueous solution containing a carbodithioate, (1
3) An aqueous solution containing piperazine-N, N'-biscarbodithioate obtained by the production method according to any one of (1) to (10) or piperazine-N, N 'according to (11). -A heavy metal fixing agent characterized by further adding an alkaline aqueous solution to an aqueous solution containing a biscarbodithioate, (14) piperazine, an alkaline aqueous solution,
And carbon disulfide are reacted in a glass-lined or resin-lined reaction tank, and a method for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Piperazine-N, N'-of the present invention
The method for producing an aqueous solution containing a biscarbodithioate salt is
The heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate, an alkaline aqueous solution, as long as it has a step of reacting by alternately adding carbon disulfide, it is not particularly limited Absent.

The piperazine hydrate used in the present invention is
It contains water of crystallization in piperazine, has a lower melting point than anhydrous products, has good stability, and is easy to handle. The number of water of crystallization contained is not particularly limited, but preferably represents a positive number in the range of 1 to 6, and depending on the structure, 2.5 hydrate or the like is also possible. Piperazine hydrate can be melted by heating or dissolved in water to be used as a liquid state such as an aqueous solution. When piperazine hydrate is used in the liquid state,
It is possible to eliminate the entrainment of oxygen into the reaction system that occurs when it is supplied to the reaction tank as a solid or powder, and once the reaction system is placed in a nitrogen atmosphere at the time of supplying the raw materials, carbon disulfide described below is used. It is not necessary to replace the reaction system with nitrogen before the reaction with, and the handling becomes easy. When the piperazine hydrate is used by melting, it may be heated to a temperature at which it melts or higher, and a specific heating temperature may be in the range of 45 ° C to 80 ° C. If the heating temperature is 80 ° C. or higher, excessive heating causes energy loss and is not preferable. The melted liquid piperazine can be charged directly into the reaction tank, which improves the operability in production. Further, piperazine hydrate is readily soluble in water, and piperazine hydrate can be used as an aqueous solution having a desired concentration in place of molten piperazine hydrate.

The piperazine anhydride used in the present invention can be used in place of piperazine hydrate, but it is preferably dissolved in water and used as an aqueous solution. Since the melting point of piperazine anhydride is about 104 ° C., it is not preferable to use it by melting it because the reaction system becomes hot.

The alkaline aqueous solution used in the present invention is not particularly limited, but when the aqueous solution obtained by the production method of the present invention is used as a heavy metal fixing agent, it is preferably an aqueous solution of an alkali metal hydroxide. Specific examples of such alkali metal hydroxides include potassium hydroxide, sodium hydroxide and lithium hydroxide. The concentration of the aqueous alkali solution such as the aqueous solution of alkali metal hydroxide used is not particularly limited, and can be appropriately adjusted and used depending on the desired concentration of the aqueous solution of piperazine biscarbodithioic acid. For example, when producing a high-concentration piperazine biscarbodithioate, the concentration of the aqueous alkali solution is preferably in the range of 11 to 52% by weight, more preferably 20 to 50% by weight. The amount of alkali used in the reaction of the present invention is relative to piperazine hydrate, etc.
The range of 1.8 to 2.2 molar equivalents is preferable, and the range of 1.0 to 1.2 molar equivalents is preferable with respect to the carbon disulfide used. Further, as will be described later, when the alkali is added to stabilize the produced piperazine biscarbodithioic acid aqueous solution, the amount can be set in consideration of the amount to be added in advance.

The reaction of the piperazine hydrate or piperazine anhydride of the present invention with carbon disulfide is preferably carried out at 25 to 50 ° C. In particular, the boiling point of carbon disulfide is 46 ° C. It is preferable that carbon sulfide is not vaporized, and it is preferable to carry out at 30 ° C to 40 ° C. Further, the reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen because carbon disulfide is flammable. In the present invention, carbon disulfide is preferably used in the range of 1.8 to 2.2 molar equivalents with respect to piperazine hydrate or piperazine anhydride. When it is 1.8 molar equivalents or less, a large amount of piperazine as a raw material remains, and when it is 2.2 equivalents or more, excess carbon disulfide remains in the aqueous solution, which causes a problem of odor during use.

As the reaction solvent used in the present invention, water is mainly used, but a water-soluble solvent such as a lower alcohol may be appropriately used in combination so long as a carbodithioate salt is not precipitated. The amount of the solvent such as water used can be appropriately selected depending on the intended concentration of the aqueous solution.

The method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate according to the present invention is a method in which the above-mentioned hot-melt piperazine hydrate or an aqueous solution of piperazine hydrate or piperazine anhydride is treated with an alkali. It is characterized in that an aqueous solution and carbon disulfide are added alternately to carry out the reaction. It is possible to prevent the reaction solution from becoming strongly alkaline, to prevent the precipitation of piperazine crystals, and to prevent the reaction solution from becoming highly viscous, so that stirring can be easily performed. The alkaline aqueous solution and the carbon disulfide may be added by any method as long as they are added alternately, and can be added by dropping, injection by a pump, or the like. Further, the number of times of alternate addition, the amount of addition, etc. are not limited, but, for example, it may be divided into 2 to 20 times and added alternately. Further, the addition amount to be divided and added may be an evenly divided amount, but it may be small at first and gradually increased. For example, an alkaline aqueous solution and carbon disulfide are added in an amount of 10 wt% and 1
It can be divided into 0% by weight, 20% by weight, 60% by weight, etc. and added alternately. The addition time of the alkaline aqueous solution and carbon disulfide is not particularly limited, but it is preferable to set it so as to prevent the precipitation of piperazine crystals and prevent the reaction solution from becoming highly viscous.

By carrying out the reaction as described above, it is possible to prevent precipitation of the piperazine salt and increase in the viscosity of the solution without raising the temperature. Therefore, the reaction should be carried out within the range of 30 to 40 ° C. You can This makes it possible to use a glass-lined or resin-lined reaction tank without having to consider the erosion of glass and resin. It is possible to use a corrosion resistant metal reaction tank such as stainless steel, but a trace amount of iron is eluted and piperazine-
It is more preferable to use a glass-lined or resin-lined reaction tank because it may react with N, N′-biscarbodithioate to form a black precipitate. The resin used in the reaction tank of the resin lining in the present invention,
Although not particularly limited, specifically, fluororesin, polyethylene, polypropylene, polyvinyl chloride,
Examples thereof include epoxy resin, furan resin, phenol resin, polyalloy, and the like.

The method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate according to the present invention is characterized in that an alkaline aqueous solution and carbon disulfide are continuously added simultaneously to react. In addition, the term “simultaneous” here means that not only the addition of the alkaline aqueous solution and the carbon disulfide is performed at the same time, but also the operation of adding the both in the reaction system is not performed at the same time, and there is a considerable interval between the two. Means to be done without side dishes.

Further, in the present invention, the term "continuous" includes not only the operation of adding at intervals, but also the case of carrying out all the adding operations except the case of performing the adding operation at a considerable interval. For example, it is possible to exemplify the case where the dropping is performed from the dropping device at a constant interval, and the operation of adding a constant amount of the alkaline aqueous solution or carbon disulfide by the adding device is repeated without a considerable interval. The added amount does not have to be constant, and may change with time. Also,
Any addition method may be used, and it may be added by dropping, injection with a pump, or the like.

In the present invention, the addition time of the alkaline aqueous solution and carbon disulfide is not particularly limited, and for example, the dropping rate can be adjusted according to the addition amount so that the addition is completed at the same time. Further, it is similar to the above case that it is preferable to set so as to prevent the precipitation of crystals of piperazine and prevent the reaction solution from becoming highly viscous.

Particularly, in the present invention, the addition of the required amount of the alkaline aqueous solution and the required amount of the carbon disulfide is started at the same time, and the alkaline aqueous solution addition time is set longer than the carbon disulfide addition time so that the alkaline aqueous solution and the carbon disulfide are added. It is preferable to continuously add them simultaneously. In the present invention, the addition of the required amount of carbon disulfide is started before the addition of the required amount of the alkaline aqueous solution, and the end time of the addition of the alkaline aqueous solution is set at the same time as or after the end of the addition of the carbon disulfide. It is preferable to continuously add them simultaneously. By setting the addition time as described above, the production of thiocarbonate as a by-product can be suppressed as much as possible.

The significance of setting the addition time as described above is as follows.
By allowing carbon disulfide to exist in excess in the reaction system and consuming the alkali as a carbodithioate salt so that the alkali does not remain in the reaction system, it is possible to obtain by the reaction between the alkali and carbon disulfide. It is to suppress the by-product of thiocarbonate. Therefore, in order to further suppress the by-product of thiocarbonate, the total amount of carbon disulfide added to the molten liquid or the aqueous solution of piperazine hydrate or an aqueous solution of piperazine anhydride or piperazine hydrate that has been melted by heating is suppressed. Required amount so that the ratio of the number of moles and the total number of moles of the alkali aqueous solution added to the melt or the aqueous solution is in the range of 0.8 to 1.5, preferably 1.0 to 1.3. It is preferable to control the addition of carbon disulfide and the required amount of the alkaline aqueous solution. When the ratio is less than 0.8, the alkali becomes excessive and thiocarbonate is easily produced as a by-product.
Even in the case of 1.5 or more, carbon disulfide easily reacts with the alkaline aqueous solution, and thiocarbonate is easily produced as a by-product. Further, in the method of carrying out the reaction by controlling the molar ratio of the amount of alkali addition and the amount of carbon disulfide added, the addition method is not particularly limited, for example, simultaneous continuous addition, even if alternate addition I do not care.

Further, the method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate of the present invention comprises reacting with a hot-melt piperazine hydrate or an aqueous solution of piperazine hydrate or piperazine anhydride. After adding a part of the carbon disulfide used for the above, an aqueous alkali solution is added and stirred, and then the remaining carbon disulfide is added, or heat-melted piperazine hydrate or piperazine hydrate or piperazine anhydrous is added. To the aqueous solution of the substance, a part of carbon disulfide used in the reaction and an alkaline aqueous solution are simultaneously added and stirred,
After that, the remaining carbon disulfide is added. In this way, when mixing an aqueous alkaline solution with piperazine hydrate or piperazine anhydride, a part of carbon disulfide used in the reaction is added in advance, or at the same time, to prevent precipitation of crystals of piperazine, The reaction solution can be prevented from becoming highly viscous, and stirring can be easily performed. At the same time as the alkaline aqueous solution,
Alternatively, the amount of carbon disulfide added to the piperazine hydrate or the like prior to this is preferably 1 to 10% by weight based on the total amount of carbon disulfide used in the reaction. If it is less than 1% by weight, the effect is not sufficient and 10
Even if it is used in an amount of more than 1% by weight, the effect does not change significantly.

In the present invention, the remaining carbon disulfide may be added and reacted immediately after mixing piperazine hydrate or piperazine anhydride with an aqueous alkali solution. Alternatively, after aging the reaction, the reaction may be performed by adding. You may do it.

The end point of the reaction is determined by confirming the time when the carbon disulfide dispersed in the aqueous solution disappears by NMR and the like, but after the reaction is completed, unreacted carbon disulfide is removed from the aqueous solution. Therefore, it is desirable to perform bubbling with nitrogen. Since unreacted carbon disulfide is separated from the aqueous solution under heating conditions, it is desirable to remove it from the beginning. After the reaction is completed, the aqueous solution is adjusted to pH 10
The above storage is preferable because generation of carbon disulfide can be suppressed during the storage period. PH of the aqueous solution of the reaction product
To store as 10 or more, 0.01 to 200 mol of piperazine-N, N'-biscarbodithioate can be added such as alkali metal hydroxide and various amines.

Piperazine-N, obtained according to the invention,
The aqueous solution containing the N'-biscarbodithioate can be used as a heavy metal fixing agent by directly adding the reaction solution or by adding an additive as necessary. Piperazine-N, N 'in aqueous solution when used as a heavy metal fixative
-The biscarbodithioate concentration is preferably in the range of 20-60% by weight.

Piperazine obtained by the method of the present invention
The aqueous solution containing N, N′-biscarbodithioate has an absorption intensity in the visible light absorption spectrum at a wavelength of 500 nm of 0.05 or less, a low content of thiocarbonate, and is used as a heavy metal fixing agent. The amount of carbon disulfide generated can be suppressed.

The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

Example 1 A 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser, and two dropping funnels was charged with 393 g of water under a nitrogen stream.
108 g of anhydrous piperazine was charged and dissolved, and then the liquid temperature was 35 ° C.
I chose Thereafter, under stirring, 309 g of a 48% potassium hydroxide aqueous solution and 190 g of carbon disulfide were alternately added in a 4-part charge as shown in Table 1. Reaction temperature 35 ° C
Then, the stirring was easy without increasing the viscosity of the liquid. Then, after the carbon disulfide suspended in the reaction solution disappears,
The temperature was raised from 35 ° C to 40 ° C and the mixture was stirred for 2 hours to react unreacted carbon disulfide. Then, nitrogen was bubbled for 5 minutes in order to remove the remaining traces of carbon disulfide. The yield of this reaction was 99.2%. The content of potassium piperazine-N, N′-biscarbodithioate in the obtained synthetic solution was measured, and it was found to be 39.4% by weight.

[0035]

[Table 1]

Example 2 In a 1 L 4-necked flask equipped with a stirrer, a thermometer, and two dropping funnels, 393 g of water and 108 g of anhydrous piperazine hydrate.
Was charged under a nitrogen stream, and after dissolution, the liquid temperature was set to 35 ° C. Then, under stirring, 30% 48% aqueous potassium hydroxide solution 30
9 g and 190 g of carbon disulfide were continuously added dropwise at a reaction temperature of 35 ° C. for 6 hours. The stirring was easy without increasing the viscosity of the liquid. The reaction proceeded rapidly, and carbon disulfide was hardly suspended in the aqueous solution. After the dropping was completed, the temperature was raised from 35 ° C to 40 ° C and the mixture was stirred for 2 hours. Then, nitrogen was bubbled for 5 minutes in order to remove the remaining traces of carbon disulfide. The yield of this reaction is 99.3%
Met. Piperazine-N, N'- in the obtained synthetic solution
As a result of measuring the content of potassium biscarbodithioate, 3
It was 9.1% by weight.

Example 3 A 500 mL four-necked flask equipped with a stirrer, a condenser, a thermometer, and two dropping funnels was charged with water 1 under a nitrogen stream.
40 g was charged, 122 g (0.62 mol) of piperazine hexahydrate melted at 55 ° C. was added, and the temperature of the aqueous solution was adjusted to 35
It was set to ° C. With stirring, 5 g of carbon disulfide (0.0658
Mol, 5% by weight of the total amount charged), and further 48%
144 g (1.23 mol) of aqueous potassium hydroxide solution was added. After the addition, the temperature of the mixture was 33 ° C., and the mixture could be easily stirred without increasing the viscosity of the liquid. Further, 90 g of carbon disulfide was added dropwise at 35 to 40 ° C. Also at this time, no particular increase in the viscosity of the liquid was observed. After the carbon disulfide suspended in the reaction solution disappeared, the mixture was stirred at 40 ° C. for 2 hours. Then, the reaction solution was bubbled with nitrogen gas to obtain 498 g of potassium piperazine-N, N′-biscarbodithioate aqueous solution (yield 99.4%, salt content 39.4% by weight).

Example 4 780 g of water was charged into a 5 L four-necked flask equipped with a stirrer, a condenser, a thermometer, and two dropping funnels, and the temperature was 55 ° C.
598 g (3.08 mol) of piperazine hexahydrate melted in (3) was added, and the temperature of the aqueous solution was set to 40 ° C. Then, under stirring, 715 g of 48% potassium hydroxide aqueous solution and 468 g of carbon disulfide were separately prepared in a dropping funnel, and the dropping time of the potassium hydroxide aqueous solution was 10.5 hours,
The dropping speed was adjusted so that the dropping time of carbon disulfide was 10 hours, and the dropping was started at the same time. Reaction temperature is almost 4
The temperature was maintained at 0 ° C., the viscosity of the liquid did not increase, and the stirring was easy. In addition, potassium hydroxide added to the reaction solution,
The change with time of the total number of moles of carbon disulfide is shown in FIG. After the dropping was completed, the mixture was further stirred at 40 ° C. for 2 hours. Then, nitrogen was bubbled for 5 minutes in order to remove the remaining traces of carbon disulfide. The yield of this reaction is 99.8.
%Met. Piperazine-N, N 'in the obtained synthetic solution
-Results of measuring the content of potassium biscarbodithioate,
It was 39.1% by weight. Further, it can be seen from FIG. 1 that the ratio of the total number of moles of carbon disulfide and potassium hydroxide added to the reaction solution is always in the range of 1.0 to 1.3.

Example 5 Reaction was carried out in the same manner as in Example 4 except that only carbon disulfide was added dropwise for 30 minutes, and then the addition time of the aqueous potassium hydroxide solution was set to 10 hours. When an aqueous solution of potassium hydroxide was added dropwise, white crystals were precipitated, and the white crystals disappeared when the amount of the added potassium hydroxide was almost equivalent to carbon disulfide. As a result, an aqueous solution containing the same piperazine-N, N′-biscarbodithioate potassium as in Example 4 could be obtained. From the above, it was found that when the production was performed using this method, the addition of the potassium hydroxide aqueous solution could be adjusted with the disappearance of white crystals as a guide.

Example 6 683.9 g of water was charged into a 2 L four-necked flask equipped with a stirrer, a condenser, a thermometer, and two dropping funnels.
68% concentrated piperazine melted at 0 ° C (equivalent to dihydrate)
317.9 g (2.50 mol) was added and the temperature of the aqueous solution was set to 40 ° C. Then, under stirring, 576 g of 48% potassium hydroxide aqueous solution and 381 g of carbon disulfide were separately prepared in a dropping funnel, and the dropping time of the potassium hydroxide aqueous solution was 4 hours and the dropping time of carbon disulfide was 3.5 hours. The dropping rate was adjusted so as to be equal to, and the dropping was started at the same time.
The reaction temperature remained at about 40 ° C., and the stirring of the liquid was easy without increasing the viscosity of the liquid. After the carbon disulfide suspended in the reaction solution disappeared, the mixture was further stirred at 40 ° C. for 2 hours. Then, nitrogen was bubbled for 5 minutes in order to remove the remaining traces of carbon disulfide. The yield of this reaction is 99.6%.
Met. Piperazine-N, N'- in the obtained synthetic solution
As a result of measuring the content of potassium biscarbodithioate, 3
It was 9.3% by weight. Then, 41 g of 48% aqueous potassium hydroxide solution was added as an excess alkali component,
Used as a heavy metal fixing agent. After the heavy metal fixing agent was stored at 40 ° C. for 3 months, the odor of carbon disulfide was measured, but no odor was observed. Further, there was no change in the hue of the aqueous solution, and no formation of potassium thiocarbonate was observed.

Comparative Example 1 64 g of piperazine anhydride was charged into a 500 mL four-necked flask equipped with a stirrer, a condenser, a thermometer, and a dropping funnel, and then water at 25 ° C. was added and stirred to give a cloudy slurry. 48% potassium hydroxide aqueous solution 153g
Was added to bring the liquid temperature to 35 ° C., but the viscosity was extremely high and stirring could not be continued, so the reaction was interrupted.

Comparative Example 2 In a 1 L 4-necked flask equipped with a stirrer, condenser, thermometer and dropping funnel, 393 g of water and anhydrous piperazine 10 were added.
8 g was charged, and after dissolution, the liquid temperature was set to 35 ° C. After this,
309 g of 48% potassium hydroxide aqueous solution was added. Crystals of piperazine were deposited, the viscosity of the liquid increased, and stirring became difficult. Then, 190 g of carbon disulfide was added dropwise from the dropping funnel over 6 hours. As the carbon disulfide was dropped, the viscosity of the reaction solution gradually decreased, and stirring became possible.
After the carbon disulfide suspended in the reaction solution disappeared, the mixture was further stirred at 40 ° C. for 2 hours. Then, nitrogen was bubbled for 5 minutes in order to remove the remaining traces of carbon disulfide. The yield of the synthetic solution obtained by this reaction was 99.8%. As a result of measuring the content of piperazine-N, N′-biscarbodithioate potassium in the obtained synthetic solution, 39.
It was 1% by weight.

Example 7 Absorbance of visible light absorption spectrum at a wavelength of 500 of aqueous solutions containing potassium piperazine-N, N'-biscarbodithioate obtained in Examples 1-2, Examples 4-5 and Comparative Example 2. Was measured. The results are summarized in Table 2. Further, 1 wt% of potassium hydroxide was added to the aqueous solution containing potassium piperazine-N, N′-biscarbodithioate obtained in Examples 1 and 2 and Examples 4 to 5, and further, if necessary. Then, the amount of piperazine shown in Table 2 was added to prepare a heavy metal fixing agent. Generation of carbon disulfide and ammonia after mixing with fly ash was measured by the following method using the heavy metal fixing agent prepared as described above. The results are shown in Table 2.
Are shown together.

Example 8 100 g of stalker furnace fly ash was put in a 2 L capacity tetrabac, and after removing the air inside, 1 L of air was hydrated with a syringe to the above aqueous solution of piperazine-N, N'-biscarbodithioate. 5 g of a heavy metal fixing agent added with 1.0% by weight of potassium and 30 g of water are injected in this order. The mixture was kneaded by hand with Tetrabac for 5 minutes, and allowed to stand in a warm bath at 60 ° C. for 30 minutes, and then the generated gas was measured with a detector tube (for carbon disulfide, for ammonia) manufactured by Castec. After the measurement, the air in the tetra bag was removed, 1 L of air was injected, and the gas was left standing at room temperature for 1 day and the generated gas was measured again.

[0045]

[Table 2]

The absorbance of an aqueous solution containing potassium piperazine-N, N'-biscarbodithioate produced by the method of the present invention is 0.05 or less, and when mixed with fly ash, carbon disulfide, While the generation of ammonia is small, the aqueous solution of Comparative Example 2 prepared by the conventional manufacturing method is
When mixed with fly ash, a large amount of carbon disulfide was generated, which was a problem in work. Also, depending on the stirring speed during manufacturing,
It was found that there was a difference in absorbance.

[0047]

As described above, according to the method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate of the present invention, the danger of dust explosion and the like can be prevented and safely performed. Therefore, an aqueous solution containing piperazine-N, N′-biscarbodithioate can be efficiently produced. Further, even when the temperature is 40 ° C. or lower, in the mixing of piperazine and metal hydroxide, it is possible to prevent precipitation of crystals of piperazine or increase of viscosity of the liquid from the mixed solution containing a high concentration of piperazine, so that it is strongly alkaline. A glass lining or resin lining reaction tank, which is difficult to use under heating conditions, can also be preferably used. Furthermore, since an aqueous solution containing piperazine-N, N'-biscarbodithioate in a high concentration can be produced, the production cost can be kept low.
Also, piperazine-N, N 'produced by the method of the present invention.
-Heavy metal fixing agents that are mainly composed of an aqueous solution containing biscarbodithioate generate less carbon disulfide when fly ash is mixed, and are safer in operation than those produced by conventional manufacturing methods. Is.

[Brief description of drawings]

FIG. 1 shows the change with time in the total number of moles of carbon disulfide and potassium hydroxide added to a reaction solution in Example 4.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiharu Ozaki             950 Fujisawa, Nakago Village, Nakacervation District, Niigata Prefecture Japan             Soda Co., Ltd. Nihongi Factory, Production Engineering Laboratory

Claims (14)

[Claims] 1. A heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate,
Piperazine-N, comprising a step of alternately adding an alkaline aqueous solution and carbon disulfide to react with each other.
A method for producing an aqueous solution containing N'-biscarbodithioate. 2. A heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate,
Piperazine-N, characterized by having a step of simultaneously and continuously reacting an aqueous alkaline solution and carbon disulfide.
A method for producing an aqueous solution containing N'-biscarbodithioate. 3. An alkaline aqueous solution and a carbon disulfide are simultaneously added continuously by starting the addition of the required amount of the alkaline aqueous solution and the required amount of the carbon disulfide at the same time, and setting the alkaline aqueous solution addition time longer than the carbon disulfide addition time. The method for producing an aqueous solution containing the piperazine-N, N′-biscarbodithioate salt according to claim 2. 4. The addition of the required amount of carbon disulfide is started before the addition of the required amount of the alkaline aqueous solution, and the end of the addition of the alkaline aqueous solution is set at the same time as or after the end of the addition of the carbon disulfide. The method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate according to claim 2, characterized in that it is added simultaneously and continuously. 5. A heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate,
The required amount of carbon disulfide and the required amount of the alkaline aqueous solution are such that the ratio of the total number of moles of added carbon disulfide and the total number of moles of the alkali in the aqueous alkaline solution is in the range of 0.8 to 1.5. A process for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate, which comprises the step of adding 6. The ratio of the total number of moles of carbon disulfide added to the heat-melted piperazine hydrate or an aqueous solution of piperazine anhydride or piperazine hydrate to the total number of moles of alkali in the alkaline aqueous solution is: Piperazine-N according to claim 5, characterized in that it is in the range of 1.0 to 1.3.
A method for producing an aqueous solution containing N'-biscarbodithioate. 7. A heat-melted piperazine hydrate, or an aqueous solution of piperazine anhydride or piperazine hydrate,
1 to 10 wt% of carbon disulfide is added to the total amount of carbon disulfide used in the reaction, or an aqueous alkali solution is added at the same time, and then the remaining total amount of carbon disulfide is added. A method for producing an aqueous solution containing piperazine-N, N'-biscarbodithioate. 8. The method for producing an aqueous solution containing piperazine-N, N′-biscarbodithioate as claimed in claim 1, wherein the alkaline aqueous solution is an aqueous solution of a metal hydroxide. . 9. The piperazine-N, N according to claim 1, which is an aqueous solution containing 20% by weight to 60% by weight of piperazine-N, N'-biscarbodithioate. A method for producing an aqueous solution containing a'-biscarbodithioate. 10. A piperazine-N, N′-biscarbodithioate salt characterized by using a heat-melted piperazine hydrate or an aqueous solution of piperazine anhydride or piperazine hydrate, an aqueous alkali solution, and carbon disulfide. A method for producing an aqueous solution containing. 11. An aqueous solution containing piperazine-N, N′-biscarbodithioate, which has an absorption intensity in a visible light absorption spectrum at a wavelength of 500 nm of 0.05 or less. 12. A heavy metal containing an aqueous solution containing piperazine-N, N′-biscarbodithioate as a main component, which has an absorption intensity in a visible light absorption spectrum at a wavelength of 500 nm of 0.05 or less. Fixative. 13. An aqueous solution containing the piperazine-N, N′-biscarbodithioate obtained by the production method according to claim 1, or the piperazine-N, N according to claim 11. A heavy metal fixing agent characterized by further adding an alkaline aqueous solution to an aqueous solution containing a'-biscarbodithioate. 14. A piperazine, characterized in that piperazine, an aqueous alkaline solution, and carbon disulfide are reacted in a glass-lined or resin-lined reaction tank.
A method for producing an aqueous solution containing N, N'-biscarbodithioate.