JPH0737436B2 - Method for producing carbodihydrazide - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing carbodihydrazide, and more particularly to a method for efficiently producing high quality carbodihydrazide.

[0002]

BACKGROUND OF THE INVENTION Carbodihydrazide is a substance useful as an oxygen scavenger for boilers and is generally produced by reacting a dialkyl carbonate with hydrazine hydrate (Japanese Patent Publication No. 61-28664) or urea and water. Method for producing by reacting added hydrazine (West German Patent No. 21
No. 12398) is known.

[0003]

However, the dialkyl carbonate used in the former method is relatively expensive, and various improvements are necessary in order to obtain a high-purity product by this method. It was not satisfactory. On the other hand, in the latter method, since the reaction rate is small, the reaction time is extremely long, and the quality of the carbodihydrazide obtained at the same time is low, so that it cannot be carried out as a practical method.

Therefore, it is an object of the present invention to provide a method for producing a high-quality carbodihydrazide which is efficient in a short time and can be used practically, while using hydrazine hydrate and inexpensive urea as raw materials.

[0005]

According to the present invention, when urea and hydrazine hydrate are reacted to produce carbodihydrazide, urea and hydrazine hydrate are added in an amount of 120 to 19
The reaction was carried out at 0 ° C., and the carbodihydrazide produced in the presence of semicarbazide as a reaction intermediate was separated and recovered from the reaction mixture, and at least a part of the recovered mother liquor containing semicarbazide was recycled to the reaction system and the remaining recovery was performed. There is provided a method for producing carbodihydrazide, which comprises recovering hydrated hydrazine from mother liquor and reusing it.

[0006]

The reaction between urea and hydrazine hydrate proceeds sequentially as follows.

[0007]

[Chemical 1]

[0008]

[Chemical 2]

[0009]

[Chemical 3]

In the carbodihydrazide formation reaction, "Chemical formula 1" proceeds extremely fast, whereas the carbodihydrazide formation "Chemical formula 2" reaction is extremely slow,
It controls the overall speed. The carbodihydrazide thus formed is hydrolyzed to a carbazine acid hydrazine salt as is clear from the reaction formula of "Chemical Formula 3", and thus the sequential reaction of "Chemical Formula 1" to "Chemical Formula 3" is completed. As a result, the yield of carbodihydrazide deteriorates.

In the present invention, the reaction of "Chemical Formula 3" is controlled, that is, carbodihydrazide is separated at the time when it is formed in the reaction of "Chemical Formula 2", and the hydrolysis of carbodihydrazide and the by-product of impurities are suppressed. Then, the objective is to efficiently produce high quality carbodihydrazide.

The above-mentioned sequential reactions "Chemical formula 1" to "Chemical formula 3" are
When the carbodihydrazide is formed in "Chemical Formula 2", the unreacted hydrazine hydrate, semicarbazide and the like remain unreacted in the reaction mother liquor in the reaction system after the separation. In the present invention, in order to efficiently generate carbodihydrazide, a part of the reaction mother liquor is recycled to the next reaction, and further hydrated hydrazine as a raw material of carbodihydrazide is recovered from the remaining reaction mother liquor,
By reusing it as a raw material for the next generation reaction, it is possible to improve the overall yield and efficiently produce carbodihydrazide.

In the present invention, the reaction temperature is 120 to 1
Carrying out at 90 ° C. is important for industrially producing carbodihydrazide. By carrying out the reaction at this temperature, the hydrolysis of carbodihydrazide can be suppressed while maintaining the reaction rate for practical use.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 is a flow chart for explaining a preferred embodiment of the method for producing carbodihydrazide of the present invention.

In this preferred embodiment, a basic reaction consisting only of virgin urea and hydrated hydrazine is first carried out before carrying out the steps shown in the flow chart. Regarding this basic reaction, (a) the reaction is stopped when carbodihydrazide is produced, (b) the carbodihydrazide produced from the reaction mixture is separated and recovered, and (c) a part of the recovered mother liquor after the carbodihydrazide is separated from the next time. (D) Distilled and recovered hydrated hydrazine from the remaining recovered mother liquor, and then (e) Recovered hydrated hydrazine and virgin hydrated hydrazine and hydrated hydrazine and urea of virgin. , And the mother liquor for separation and recovery for recycling of the previous reaction is subjected to the second reaction at 120 to 190 ° C., and similarly the above steps (a) to (e) are sequentially repeated to produce carbodihydrazide.

Both the basic reaction and the second and subsequent reactions are carried out at 120 to 190 ° C., especially 1
It is carried out at a temperature of 25 to 180 ° C., and the reaction pressure is 1
The pressure is preferably higher than the vapor pressure of hydrazine hydrate at 20 to 190 ° C.

In the reaction system, the ratio of urea to hydrazine hydrate is preferably in the range of 1: 3 to 1:10, particularly 1: 3 to 1: 7 in the basic reaction, and after the second reaction. In the reaction, it is desirable to set the molar ratio represented by the following formula "Equation 1" within the range of 3 to 10, particularly 3 to 7.

[0018]

[Equation 1] In the formula, HH is the total number of moles of hydrated hydrazine newly charged in the reactor and hydrated hydrazine in the recycled mother liquor, SC
Is the number of moles of semicarbazide in the recycled mother liquor, U is the number of moles of virgin urea newly charged in the reactor, CDH
Represents the number of moles of carbodihydrazide in the recycled mother liquor. Therefore, prepare anew from this formula
The amount of hydrazine hydrate and virgin urea can be determined.

Further, this recycled mother liquor is a separated mother liquor after separating carbodihydrazide from the reaction liquid as described later, and in this separated mother liquor, hydrated hydrazine, semicarbazide, carbodihydrazide which could not be separated, etc. Since the reaction raw material and the target substance are contained, the total amount of the separated mother liquor is 100% or less and 90% or less, especially 50 to 90
It is preferable to supply it to the next reaction at a recycling rate of%, since the yield with respect to the total raw materials used can be improved.

The carbodihydrazide can be separated from the reaction mixture by cooling the reaction mixture to 30 ° C. or lower, preferably 20 ° C. or lower, and separating the crystallized crystals to obtain a purity of 98.
% Or more carbodihydrazide crystals can be obtained. This carbodihydrazide crystal can be put to practical use without any special purification. Further, if necessary, it can be further purified by a simple recrystallization.

When carbodihydrazide, semicarbazide and by-products are heated in an aqueous solution or an aqueous hydrazine solution, the hydrazide group is hydrolyzed to recover the hydrated hydrazine. Therefore, the hydrated hydrazine can be obtained by hydrolyzing the remaining separated mother liquor that has not been recycled in the next reaction in the presence of strong alkaline to which sodium hydroxide has been added. In the present invention, carbodihydrazide, semicarbazide and the like are completely hydrolyzed by heating under reflux with a 20% sodium hydroxide aqueous solution for 3 hours to obtain hydrated hydrazine and sodium carbonate.
By distilling and collecting hydrazine hydrate among them, the yield with respect to the total used raw materials can be improved.

In the present invention, in order to control the reaction of "Chemical Formula 3" in the reaction formulas of "Chemical Formula 1" to "Chemical Formula 3", carbozidohydrazide is frequently added at the time when carbazidohydrazide is formed. Need to be separated.

When stopping the reaction, the standard varies depending on the reaction conditions such as reaction temperature and reaction pressure.
In the actual reaction, a pre-experimental reaction was performed in which a constant molar ratio and a constant reaction temperature were set, and the reaction time at which the amount of urea consumed in the above range was measured in advance, Can be used as a guide for stopping the reaction. Further, in this reaction, the reaction rate can be determined by the amount of ammonia generated during the reaction.

[0024]

【Example】

Example 1 Urea 42 was added to a 500 ml capacity autoclave equipped with a stirrer.
g and 175 g of 100% hydrated hydrazine, 1.2
The temperature was raised from room temperature to 150 ° C. over time. 150 ° C
The reaction was carried out for 2 hours while maintaining the temperature. The pressure after the reaction was 13 kg / cm ^ 2. Thereafter, the mixture was cooled to 20 ° C., and the crystallized carbodihydrazide crystals were separated by filtration and dried. The weight of the carbodihydrazide obtained was 31.5.
g (yield to urea: 50.0%), purity 9
The melting point was 9.79% and the melting point was 153.4 ° C, which was satisfactory in terms of quality.

Example 2 Urea 42 was added to a 500 ml capacity autoclave equipped with a stirrer.
g, 100 g of 100% hydrated hydrazine, and 125 g of the separated mother liquor obtained in Example 1 (mother liquor recycling rate: 75%) were charged. The separated mother liquors were hydrazine hydrate, hydrazine carbazate salt, semicarbazide, carbodihydrazide and water 63.9%, 2.0%, 5.4% and 10.6, respectively.
%, 18.1%. Example 1
Carbodihydrazide thus obtained was 46.5 g (yield based on urea: 73.8%), had a purity of 99.67% and a melting point of 155.7 ° C. It was possible.

Example 3 The reaction temperature was increased to 170 by the same method as described in Example 1.
The reaction was carried out by changing the temperature to ° C. While keeping the temperature at 170 ℃,
The reaction was carried out for 45 minutes. The pressure at the end of the reaction is 23 kg /
It became cm ^ 2. The weight of the obtained carbodihydrazide was 31.9 g (yield based on urea was 50.6%), the purity was 99.57%, and the melting point was 154.0 ° C., which was satisfactory in terms of quality.

Example 4 Urea 42 was added to an autoclave equipped with a stirrer and having a capacity of 500 ml.
g and 100% hydrated hydrazine 122.5 g, Example 2
83 g of separated mother liquor obtained in step (mother liquor recycling rate 50
%) Was charged. The separated mother liquors were hydrated hydrazine, hydrazine carbazate, semicarbazide, carbodihydrazide, and water at 63.6%, 1.8%, 3.4%, and 1%, respectively.
It was composed of 1.9% and 19.3%. The reaction was carried out in the same manner as in Example 2, and the obtained carbodihydrazide was 42.2 g (the yield based on urea was 67.0).
%), The purity was 99.92%, and the melting point was 155.9 ° C., which was satisfactory in terms of quality.

Comparative Example In a 1000 ml capacity three-necked flask equipped with a thermometer, a reflux condenser and a stirrer, 240 g (4 mol) of urea and 100 g of urea were added.
%, And hydrazine hydrate (600 g, 12 mol) were refluxed at a charging temperature of 115 to 120 ° C. The reaction rate was 90% after 50 hours by measuring the amount of generated ammonia. Then, it cooled to 20 degreeC, the crystallized crystal was separated by filtration, and was dried. The obtained carbodihydrazide crystals were 234.7 g (yield 65.2% based on urea), the purity was 86.5% and the melting point was 141 ° C., and the quality was extremely poor.

[0029]

According to the present invention, in the production of carbodihydrazide, the carbodihydrazide formed in the coexistence of semicarbazide as the reaction intermediate is separated and recovered from the reaction mixture, and the reaction of the above-mentioned "Chemical formula 1" is performed. Carrying out only a part of the reaction of "Chemical formula 2" to regulate the reaction rate based on urea to a low level, and further recycling the reaction mother liquor to the next reaction, the reaction rate can be increased and high-quality carbohydrate It has become possible to efficiently produce dihydrazide without wasting used raw materials.

[Brief description of drawings]

FIG. 1 is a flow chart showing steps of a reaction after a basic reaction in a method for producing carbodihydrazide.

Claims (7)

[Claims] 1. A by reacting urea with hydrazine hydrate, in producing the carbodihydrazide, by reacting urea with hydrazine hydrate at 120 to 190 ° C., a reaction intermediate
Carbodihydrazide formed in the coexistence of all semicarbazides is separated and recovered from the reaction mixture, at least a part of the recovered mother liquor containing semicarbazide is recycled to the reaction system, and hydrated hydrazine is recovered from the remaining recovered mother liquor, and recovered. A method for producing carbodihydrazide, which is characterized by being used. 2. The method according to claim 1, wherein the molar ratio of the charged urea and the charged hydrazine hydrate in the basic reaction is in the range of 1: 3 to 1:10. 3. The method according to claim 1, wherein the reaction pressure is higher than the vapor pressure of hydrazine hydrate at a reaction temperature of 120 to 190 ° C. 4. The method according to claim 1, wherein the carbodihydrazide is separated and recovered by cooling the reaction mixture to 0 to 20 ° C. for crystallization and separation. 5. The method according to claim 1, wherein the separated hydrazine hydrate is separated and recovered by adding sodium hydroxide to the recovered mother liquor, thermally decomposing it, and then recovering it by distillation. 6. The method according to claim 1, wherein the recycling rate of the recovered mother liquor to be recycled in the next reaction is 90% or less of the recovered mother liquor. 7. When urea is reacted with hydrazine hydrate to produce carbodihydrazide, urea is reacted with hydrazine hydrate at 120 to 190 ° C. as a basic reaction,
(a) The reaction is stopped when carbodihydrazide is produced, (b) The produced carbodihydrazide is separated and recovered from the reaction mixture, and (c) A part of the recovered mother liquor after separation of carbodihydrazide is directly supplied to the next reaction. (D) Distillation and recovery of hydrated hydrazine from the remaining recovered mother liquor, and then (e) Urea of hydrated hydrazine and virgin consisting of recovered hydrated hydrazine and hydrated hydrazine of virgin, and the above ( The recovered mother liquor for recycling obtained in c) is reacted at 120 to 190 ° C., and then (a) to (e) above.
A method for producing carbodihydrazide, which comprises sequentially repeating the above steps.