JP2003192655A - Method for producing glycinonitrile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially excellent method for producing glycinonitrile, with which a reaction of glycolonitrile of an intermediate product is efficiently completed, unreacted cyamic acid and formaldehyde are not remained and the glycinonitrile synthesis reaction is carried out by a reaction using glycolonitrile as a raw material. <P>SOLUTION: This method for producing glycinonitrile comprises producing glycolonitrile from formaldehyde and cyamic acid in the presence of water as solvent as a first process and producing glycinonitrile from the obtained aqueous solution of glycolonitrile and ammonia as a second process. In the production, a combination of a flow type cyamic acid absorption tank with a stirring tank and a tubular reactor of liquid seal flow type is used as the reactor type of the first process. An alkali metal water-soluble salt in the weight ratio of the metal to raw material cyamic acid of 50-600 ppm is added as the catalyst to the reaction. A combination of a flow type cyamic acid absorption tank with a stirring tank and a tubular reactor of a liquid seal flow type is used as the reactor of the second process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing glycinonitrile, which is a compound useful as a synthetic raw material for amino acids such as glycine, pharmaceuticals, and agricultural chemicals, and more specifically, as a first step in the presence of an aqueous solvent, The present invention relates to an industrially improved method for producing a consistent production method of producing glycolonitrile from formaldehyde and hydrocyanic acid and producing glycinonitrile from the glycolonitrile and ammonia as a second step.

[0002]

2. Description of the Related Art A method for producing formaldehyde cyanohydrin (glycolonitrile) from formaldehyde and hydrocyanic acid in the presence of a water solvent is well known. Further, a method of producing glycinonitrile from glycolonitrile and ammonia in the presence of a water solvent is also well known. However, the reactions in both steps have the following problems, and there is no example in which it is proposed to carry out both steps in a consistent flow reaction.

It is known that the first step, the glycolonitrile synthesis reaction, is greatly affected by the pH of the reaction system, the reaction temperature and the reaction time. That is, the glycolonitrile produced is unstable and is likely to be colored or decomposed. In addition, if unreacted hydrocyanic acid remains without completing the reaction, further promote the coloring and decomposition of the product glycolonitrile due to the coloring of the reaction liquid due to the polymerization of hydrocyanic acid and the influence of the temperature rise due to the heat of polymerization. Is concerned.

As a conventional technique for dealing with the above-mentioned problem of glycolonitrile synthesis reaction, Japanese Patent Application Laid-Open No. 51-100027 discloses sulfur dioxide when adjusting the pH of the reaction system to 1.5 to 2.0. It is disclosed that by using, it is possible to suppress coloring and decomposition reaction of glycolonitrile. Further, in Japanese Patent Laid-Open No. 53-68725, p.
H was adjusted to 4 to 5 and adjusted to 20 in the presence of acidic sulfite ion.
It is reported to carry out the reaction at a reaction temperature of ~ 30 ° C. In addition, Japanese Patent Publication No. 7-30004 discloses a method of carrying out the reaction in the presence of a catalytic amount of sodium acetate at a pH of 4.8 to 6.0 and a reaction temperature of 15 to 30 ° C. Further, in JP-A-6-135923, the preferable ranges of pH (P) and reaction temperature (T) of the reaction system are as follows.
A method for carrying out a glycolonitrile synthesis reaction with T × P of 155 to 240 has been reported.

Also in the glycinonitrile synthesis reaction in the second step, since the product glycinonitrile produced is unstable, in order to suppress its deterioration and coloration,
Reaction conditions and separation conditions from excess ammonia,
Ammonia recovery method is said to be an issue.

In order to solve the problem of the glycinonitrile synthesis reaction, in JP-B-59-28543, α-amino is prepared by reacting an excess amount of ammonia with cyanohydrin supplied in a gaseous state in an aqueous solution. In the method for producing nitrile, a method has been proposed in which the reaction is carried out in a tank reactor with stirring, and the obtained reaction solution is passed through a pipe reactor to substantially complete the reaction. Further, in Japanese Patent Publication No. 56-8023, a tubular reactor is used in which glycolonitrile and ammonia are used in a molar ratio of ammonia / glycolonitrile of 5 to 20 and the flow in the reactor is a piston flow. , A method of reacting in a temperature range of 80 to 150 ° C. has been reported. Also, Japanese Patent No. 26
Japanese Patent No. 42466 discloses a method for producing aminoacetonitrile from glycolonitrile and ammonia, in which formic acid and sulfite or formic acid and acidic sulfite are present in the reaction system.

However, in the methods listed above,
There is a problem to be solved for each process described below, and in order to consistently industrially carry out the first process and the second process, it can be said that it is disadvantageous to use the conventional technique as it is. Absent.

When the first step and the second step are carried out successively, iminodiacetonitrile and a coloring component obtained by polymerization of hydrocyanic acid are produced as byproducts which are industrial problems during the synthesis of glycinonitrile. It is known that there is. For example, according to Japanese Patent Laid-Open No. 4-193854, it is reported that when a stoichiometric amount or less of ammonia is added to glycolonitrile, glycinonitrile and glycolonitrile react with each other, and iminodiacetonitrile is by-produced. ing. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 3-86856 reports that iminodiacetonitrile is preferably synthesized by reacting ammonia with formaldehyde and reacting it with hydrocyanic acid. That is, it is known that in the glycolonitrile synthesis reaction, if unreacted formaldehyde is present, iminodiacetonitrile is easily by-produced via the latter path.

Actually, as a problem in the first step of the synthesis reaction of glycolonitrile, for example, JP-A-51-1 is used.
According to the method of Japanese Patent No. 00027, the conversion rate of hydrocyanic acid remained at 88.1% and a large amount of hydrocyanic acid remained while the reaction time was 6 hours using 2 stirred tank reactors. Are listed. On the other hand, the conversion rate of formaldehyde reaches only 89% even if the reaction is carried out with an excess of hydrocyanic acid, and it is carried out in a situation where both unreacted hydrocyanic acid and formaldehyde remain.

According to the method of JP-A-53-68725, although there is no description about the reactor according to the example, the conversion rate of hydrocyanic acid is 9 while the reaction time takes 4 hours.
It is only 6%, and the selectivity for glycolonitrile based on hydrocyanic acid is only 92%. Further, the formaldehyde conversion rate was only 97%, and it is clear that unreacted hydrocyanic acid and formaldehyde remain in the reaction product.

In the method disclosed in JP-A-6-135923, it is proposed that the relationship between temperature and pH in the reaction zone is defined and the product thereof is set to 155 to 240. However, according to that example, the proposed reaction temperature and pH
However, the conversion rate of hydrocyanic acid was 92% while the reaction time was 2 hours, and the selectivity of glycolonitrile was based on hydrocyanic acid. Is as low as 89%. on the other hand,
The formaldehyde conversion rate remained at 94% despite the execution of the system in which excess hydrocyanic acid was used, and it is clear from this that unreacted hydrocyanic acid and formaldehyde remain.
Further, in the case of producing glycinonitrile by a consistent distribution reaction, there is no description about disadvantages in using such glycolonitrile as a raw material.

In the method described in Japanese Patent Publication No. 7-30004, a method for removing residual hydrocyanic acid is also mentioned, and the description is given on the assumption that hydrocyanic acid remains. Moreover, no description about the reaction method is found in the specification, and the examples are only batch reaction examples.

In the prior art of these first steps, although the hydrocyanic acid is carried out in a slightly excess system, when it is carried out in a flow reaction system which is industrially advantageous, the hydrocyanic acid conversion rate is, of course,
The formaldehyde conversion rate did not reach 100%, and the selectivity for glycolonitrile based on hydrocyanic acid remained around 90%. This means that unreacted hydrocyanic acid,
It suggests the presence of formaldehyde and hydrocyanic acid conversion product (presumed to be a polymer or a hydrolyzate).

Next, in the second step, glycolonitrile is converted into glycinonitrile by reacting with ammonia. The problem of this second step is, for example, Japanese Patent Publication Sho 59
According to the embodiment of the method disclosed in Japanese Patent Publication No. 28543,
It can be mentioned that the conversion of glycolonitrile reaches 100%, but the yield of glycinonitrile is only 93%. However, there is no description about the cause and impurities, and no description about the composition of the aqueous solution of glycolonitrile as a raw material is found.

According to the method of Japanese Patent Publication No. 56-8023,
According to the example, while carrying out the ammonia / glycolonitrile molar ratio at 15 and a large excess of ammonia, as much as 3% of by-product of hydrocyanic acid due to the reverse reaction is observed. Further, 1% or more of glycolonitrile remains, and the yield and selectivity of glycinonitrile are low. Moreover, ammonia is in a large excess, which is disadvantageous in the recovery of ammonia. Moreover, the presence of hydrocyanic acid poses a serious problem that induces coloring of the product liquid.

According to the method of Japanese Patent No. 2642466,
According to that example, there is only an example of a semi-batch reaction system,
In addition, the yield of glycinonitrile is only 96%.
Also in this example, there is no description about the cause or other impurities.

When the target product is glycinonitrile as in the present invention, considering the stability of the product, glycolonitrile produced from hydrocyanic acid and formaldehyde is
The amination reaction should be promptly carried out in one reactor to convert it into glycinonitrile. However, because of the above-mentioned problems, there is no example in the related art in which the cyanohydrination reaction and the amination reaction were studied and evaluated consistently.

Further, when the first step is carried out in a stirred tank flow reactor as seen in the prior art, the residence time distribution is large and excessive retention of the reaction liquid and short pass of the reaction raw material are unavoidable. Therefore, excessive retention is industrially disadvantageous because decomposition reaction of glycolonitrile and color modification easily occur.
The short path of the raw material makes it impossible to complete the reaction efficiently, and unreacted hydrocyanic acid and formaldehyde remain. Therefore, when the product of the first step is supplied as a raw material for the amination (glycinonitrile synthesis) reaction of the second step in a single reaction using the conventional technique, a large amount of impurities are produced as a by-product, which is an industrial problem. It has to be said that it is extremely disadvantageous in implementing it.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing glycinonitrile capable of continuously carrying out the first step and the second step. further,
The present invention provides a method for producing glycolonitrile and glycinonitrile in good yield in each step without producing by-products from the first step affecting the second step as described above. To aim.

[0020]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have invented the following method for producing glycinonitrile. That is, the present invention is the following (1) to (4).

(1) In the method for producing glycinonitrile, in the presence of a water solvent, as a first step, a combination of a stirring tank flow system cyanide absorption tank and a liquid ring flow system tubular reactor is used, A water-soluble salt of an alkali metal as a catalyst is used in a weight ratio of 50 to 600 ppm as a metal relative to raw material hydrocyanic acid.
Addition to produce a glycolonitrile solution from formaldehyde and hydrocyanic acid, and then, as the second step, using a combination of a stirring tank flow system ammonia absorption tank and a liquid ring flow system tubular reactor, the glycolonitrile aqueous solution A method for producing glycinonitrile, which comprises reacting with ammonia as it is to produce glycinonitrile.

(2) The average residence time in the liquid ring flow type tubular reactor of the first step is in the range of 10 to 60 minutes,
And the reaction temperature of the said reactor is 35-75 degreeC, The manufacturing method of glycinonitrile as described in said (1) characterized by the above-mentioned.

(3) The water-soluble salt of the alkali metal is
The method for producing glycinonitrile according to (1) or (2) above, which is a hydroxide of an alkali metal.

(4) In the stirring tank flow type ammonia absorption tank of the second step, ammonia is supplied in a gaseous state, the molar ratio of ammonia to glycolonitrile is in the range of 3 to 10, and the reaction The temperature is 15 to 60 ° C., the reaction temperature in the liquid ring flow type tubular reactor of the second step is 40 to 70 ° C., and the reaction pressure is a pressure at which the dissolved ammonia is not vaporized. The method for producing glycinonitrile according to any one of (1) to (3), which is characterized.

According to the study by the present inventors, when it is attempted to carry out two steps of cyanohydrin synthesis reaction and amination reaction from glycinonitrile using hydrocyanic acid, formaldehyde and ammonia as raw materials, the first step is performed. It was revealed that the problem of by-products greatly affects the second step. Furthermore, according to the study by the present inventors, when unreacted formaldehyde and hydrocyanic acid coexist in the aqueous glycolonitrile solution which is the product of the first step, the following reaction occurs in the reaction with ammonia in the second step. It was found that there are problems such as classification into. This has revealed that the yield of the product glycinonitrile, and thus the yield of glycine, which is the main use of glycinonitrile, decreases.

First, iminodiacetonitrile is by-produced. Iminodiacetonitrile, which is a secondary amine, has a path that is a byproduct of glycolonitrile and glycinonitrile, and a path that is generated by forming hexamethylenetetramine from formaldehyde and ammonia, and further by reacting with hydrocyanic acid. If at least one of formaldehyde and hydrocyanic acid remains in the aqueous nitrile solution, the latter pass increases the by-product of iminodiacetonitrile.

Secondly, unreacted formaldehyde easily reacts with an amine to produce a so-called Schiff base such as methyleneglycinonitrile and its polymer.

Thirdly, the excessive amount of unreacted hydrocyanic acid remaining causes the polymerization of hydrocyanic acid, which leads to a by-product of the coloring polymer, which lowers the yield and increases the coloring of the product liquid.

In the conventionally proposed method for producing glycolonitrile from hydrocyanic acid and formaldehyde, since the reaction cannot be completed, both hydrocyanic acid and formaldehyde remained unreacted as described above. To use the reaction product from this stage as it is as the raw material for the second step,
The above first to third problems are included. Therefore, not only attention has not been paid so far to the method of producing a consistent flow reaction method from glycolonitrile to glycinonitrile, but also about the great influence of the reaction results in the first step on the second step. None of the examples shown
There was no

In order to avoid the above first to third problems,
The inventors of the present invention invented the manufacturing methods (1) to (4),
With a simple reaction control method, complete conversion of hydrocyanic acid or formaldehyde in the first step can be achieved in a shorter time.
Therefore, it became possible to suppress the side reaction of glycolonitrile due to excessive retention. This makes it possible to provide uncolored glycolonitrile as a raw material for the second step with a high yield and a high selectivity and an extremely small amount of unreacted hydrocyanic acid or formaldehyde as a by-product. As a result, in the second step, glycinonitrile can be obtained in high yield, high purity, and without coloring.

In the method of the present invention, by defining a reaction system, a catalyst, and the amount of addition thereof, which have not been heretofore proposed, it is possible to first produce glycolonitrile of high yield, high purity and uncolored. It has become possible. As a result, this glycolonitrile reaction solution can be supplied as it is to the glycinonitrile reactor which is the second step, and it becomes possible to significantly suppress the by-production of iminodiacetonitrile. In addition, the by-product of impurities (Schiff base) derived from formaldehyde can be suppressed, and when it is carried out with an excess of formaldehyde, coloring due to unreacted hydrocyanic acid can be significantly suppressed. Particularly when the reaction is carried out in an equimolar amount, which is a preferable condition as described below,
All the above first to third problems can be solved.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. First, formaldehyde, which is a reaction raw material in the present invention, can be usually supplied as formalin. Formalin usually contains a trace amount of formic acid, and its pH is in the range of 2.5-4. In addition, in formalin, usually 3-10w of methanol is used as a stabilizer.
However, in the present invention, those containing these impurities and stabilizers can be used as they are.

The hydrocyanic acid, which is a reaction raw material in the present invention, can be supplied in any form such as gas, liquid, and aqueous solution. Industrially produced hydrocyanic acid is generally added with a stabilizer such as sulfurous acid and sulfuric acid, but as the hydrocyanic acid in the present invention, a general stabilizer-containing product can be used as it is. In the cyanide absorption tank of the stirring tank flow system in the first step, formalin may be allowed to absorb hydrocyanic acid, or pure water may be absorbed in pure water in the hydrocyanic acid absorption tank to form an aqueous solution of hydrocyanic acid and then at the inlet of the tubular reactor. It may be mixed with formalin.

The supply molar ratio of hydrocyanic acid to formaldehyde in the present invention is usually in the range of 0.95 to 1.05 with respect to hydrocyanic acid. Preferably 0.9
8 to 1.0, which is a slightly excess system of hydrocyanic acid, and more preferably
React in equimolar amounts. The reason is as follows.

That is, unreacted formaldehyde reacts with ammonia to form hexamethylenetetramine in the step of converting into glycinonitrile, which is the second step, and reacts with glycinonitrile to give methyleneglycinonitrile. Will be converted. On the other hand, unreacted hydrocyanic acid is known to be easily polymerized in an aqueous solution, and eventually converted into a coloring substance, which causes coloring of the reaction liquid. In addition, according to the study by the present inventors, when unreacted hydrocyanic acid and formaldehyde are present in the reaction solution of the first step, formaldehyde and ammonia are reacted when ammonia and glycolonitrile are reacted in the second step. From the above, it was confirmed that the above-mentioned hexamethylenetetramine was produced, and further, iminodiacetonitrile was by-produced by the reaction with hydrocyanic acid. Therefore, it is preferable to completely convert at least one of formaldehyde and hydrocyanic acid, and it is more preferable to carry out the reaction in an equal amount to complete the reaction.

In the present invention, as the catalyst of the first step,
A water soluble salt of the alkali metal is added. As the water-soluble salt, alkali metal hydroxides, halides, sulfites, acidic sulfites, sulfates, formates and the like are used.
The alkali metal hydroxide, sulfite or formate is preferable, and sodium hydroxide or potassium hydroxide is more preferable. These catalysts may be previously prepared as an aqueous solution and added to the cyanide absorption water or formalin in the cyanide absorption tank, or formalin at the inlet of the tubular reactor,
It is also possible to mix three kinds of aqueous solution of hydrocyanic acid and aqueous solution of catalyst.

The amount of catalyst added in the first step in the present invention is
If it is too small, a sufficient reaction rate cannot be obtained, and it is difficult to complete the reaction within a predetermined reaction time. On the other hand, when the amount is excessive, the produced glycolonitrile tends to be deteriorated or colored. Therefore, the addition amount is in the range of 50 to 600 ppm, preferably in the range of 100 to 400 ppm, and more preferably in the range of 200 to 300 ppm as a weight ratio with respect to the amount of cyanide supplied as metal.

The reactor type in the glycolonitrile synthesis reaction which is the first step in the present invention is as follows: A cyanide absorption tank of a stirring tank flow system is provided as a first stage (first stage) reactor, and a second stage (second stage) reaction. As a vessel, a liquid ring distribution type tubular reactor is used. In the first-stage stirring tank flow system hydrocyanic acid absorption tank, hydrocyanic acid may be absorbed in formalin as described later, and the reaction may be carried out at the same time, or after pure water is absorbed into hydrocyanic acid aqueous solution, It may be mixed with formalin at the inlet of the tubular reactor. A liquid ring flow type tubular reactor is used for the second stage (second stage) reactor. The reactor type is generally a plug flow.
It is called a tubular flow reactor, which is a reactor type in which the flow velocity distribution of the fluid flowing in the tube is uniform and the short pass and excessive retention of the raw material liquid are suppressed. In the present invention, the reaction can be completed extremely efficiently by using the reactor as the latter stage reactor (finisher reactor) of the reaction between hydrocyanic acid and formaldehyde, which is the first step. It becomes possible to completely consume at least one of

The reaction time in the first step in the present invention, that is, the average residence time, is a balance between the amount of catalyst added and the reaction temperature. However, when the time is short, the reaction is difficult to complete, and when the time is long, the product glycol is produced. There is concern about the modified coloring of ronitrile.
Min, and the range of 10 to 60 minutes in the second-stage liquid ring flow type tubular reactor. Preferably, each residence time is 20-
50 minutes, more preferably, the residence time in the first stage cyanide absorption tank is in the range of 10 to 30 minutes, and the residence time in the second stage tubular reactor is in the range of 20 to 40 minutes. .

The reaction temperature of the first step in the present invention is a balance with the above-mentioned catalyst addition amount and reaction time, but in the first-stage reactor which is a cyanide absorption tank of a stirring tank flow system, absorption of hydrocyanic acid is carried out. In order to accelerate and suppress the polymerization of hydrocyanic acid, for example, in the case where only hydrocyanic acid is absorbed into water in the first-stage reactor to form a hydrocyanic acid aqueous solution, the temperature is in the range of 10 to 50 ° C. When formaldehyde, a catalyst, and hydrocyanic acid are mixed in the first-stage reactor (that is, when a cyanohydrin synthesis reaction is to be carried out), there is a trade-off with the reaction rate, and preferably in the range of 35 to 70 ° C. Yes, and more preferably in the range of 40 to 70 ° C. The reaction temperature in the liquid ring flow type tubular reactor which is the second stage reactor of the first step is in the range of 35 to 75 ° C, preferably 40 to 70 ° C.
More preferably, it is in the range of 45 to 60 ° C.

The operating pressure of the first step in the present invention is a pressure system which allows the reaction solution to maintain a liquid state.
Although it depends on the temperature in the reactor, it is usually 0.1 to
The range is 1.0 MPa / G (/ G means gauge pressure).

In the present invention, the pH at the entrance of the first step reactor (at the time when the aqueous solutions of hydrocyanic acid, formaldehyde and the catalyst are mixed) is the formic acid in the raw material formalin (generated by the Kanitzaro reaction equilibrium. For example, Wako Pure It is secondarily determined by the amount of the chemical reagent grade formaldehyde solution of 400 ppm or less), the amount of sulfurous acid and sulfuric acid contained in the raw material hydrocyanic acid as a general stabilizer, and the amount of the catalyst added. It is a thing. for that reason,
The reaction conditions of the present invention are not particularly specified, but are usually in the range of 2 to 6. The optimum pH is in balance with the reaction temperature, but at a high pH, it is not preferable because it causes a problem in stability of hydrocyanic acid and glycolonitrile and causes color modification. On the other hand, at low pH, it takes time to complete the reaction, and therefore, it is preferably 3 to 5
Is the range.

Reaction temperature and pH of reaction system in the first step
And the reaction temperature of the first step is T ° C., p in the reaction system is
When H is P, the product of T and P (T × P) is 70 to 450
Is preferred, and more preferably 70-150 or 250-450.

The reactor type in the glycinonitrile synthesis reaction, which is the second step in the present invention, is such that an ammonia absorption tank of a stirring tank flow system is provided as a third stage (first stage) reactor, and a fourth stage (second stage) reaction is carried out. As the vessel, a reactor type provided with a liquid ring flow type tubular reactor is used. In the third-stage stirring tank flow system ammonia absorption tank, ammonia is supplied in a gaseous state. In the fourth stage (rear stage) tubular reactor,
It is carried out as a liquid ring reaction under an operating pressure that does not vaporize the ammonia absorbed in the stirring tank. As in the case of the first step, by using a liquid ring flow type tubular reactor as the fourth stage (second stage) reactor, it is possible to suppress the short path and excessive retention of the raw material liquid, and efficiently It is possible to complete the reaction and suppress the modified coloring of the product glycinonitrile.

The molar ratio of ammonia to glycolonitrile (ammonia / glycolonitrile molar ratio) in the second step in the present invention is the ammonia pressure in the reactor (ammonia absorption tank) of the third stage stirred tank flow system. Depends on the temperature and the solubility of ammonia. In general, when the ammonia / glycolonitrile molar ratio is low, the reverse reaction occurs, or the yield is reduced due to the by-production of iminodiacetonitrile. On the contrary, when the molar ratio is high, the load of recovering and recycling ammonia is high. Therefore, it is usually in the range of 3 to 10. It is preferably in the range of 4 to 8, and more preferably in the range of 5 to 7. When ammonia is added to the reactor, it is preferable to supply it in a gaseous state because it can be easily recovered and reused.

In the second step of the present invention, the reaction temperature of the third-stage ammonia absorption tank needs to be cooled because the absorption of ammonia is accompanied by heat generation. Further, a predetermined ammonia / glycolonitrile molar ratio is set. In order to achieve it, it is usually 15 to 60 ° C., although it is a balance with the operating pressure. It is preferably in the range of 20 to 40 ° C, and more preferably in the range of 20 to 30 ° C. The reaction temperature in the fourth stage liquid ring flow type tubular reactor is in the range of 40 to 70 ° C., preferably 40 to 60 ° C., and more preferably, although it is in consideration of the residence time. It is in the range of 45 to 55 ° C. If the temperature is too low, it is difficult to complete the reaction.On the contrary, if the temperature is too high, glycolonitrile by-product due to the reverse reaction, by-product of iminodiacetonitrile, and denaturing coloring of glycinonitrile are likely to occur. is there.

The reaction pressure in the second step in the present invention is
In the third stage ammonia absorption tank, it is usually in the range of 0.1 to 1.0 MPa / G, although it is a balance with the operating temperature in order to achieve a predetermined ammonia / glycolonitrile molar ratio. The range is preferably 0.15 to 0.8 MPa / G, and more preferably 0.2 to 0.6 MPa / G.
Is the range. Although the reaction pressure in the fourth stage liquid ring flow type tubular reactor is a balance with the reaction temperature, it is carried out at a pressure at which the dissolved ammonia in the third stage reactor is not vaporized. Usually, it is in the range of 0.15 to 1.2 MPa / G, preferably in the range of 0.2 to 0.9 MPa / G, and more preferably in the range of 0.3 to 0.7 MPa / G.

The reaction time of the second step in the present invention, that is, the average residence time is a balance with the reaction temperature,
If the time is short, it is difficult to complete the reaction, and if the time is long, there is concern that the product glycinonitrile may be modified and colored. Therefore, the ammonia absorption tank in the third stage is 10 to 60 minutes, and the tubular reactor in the fourth stage is 3
It is in the range of 0 to 90 minutes. Preferably, the residence time in the third stage ammonia absorption tank is in the range of 20 to 40 minutes, and
The residence time in the fourth stage tubular reactor is in the range of 40 to 80 minutes, more preferably the residence time in the third stage ammonia absorption tank is in the range of 25 to 35 minutes, and the fourth stage tube The residence time in the mold flow reactor is in the range of 50 to 70 minutes.

The present invention will be described below with reference to examples.
The present invention is not limited to these examples, and various changes and modifications can be made without changing the gist of the invention.

[0050]

Example 1 Using the reactor shown in FIG. 1, a glycinonitrile synthesis continuous flow reaction was carried out under the following reaction conditions.
In FIG. 1, a reactor 1 is a jacket-type stainless steel autoclave having an inner volume of 100 mL equipped with a stirrer, and is a stirrer tank type hydrogen cyanide absorption tank in the first step of the present invention. In this reactor 1, pure water and hydrocyanic acid are supplied to form a hydrocyanic acid aqueous solution. Then, the pump P-3 operates so as to keep the hold-up at 30 mL by the operation of the attached liquid level gauge,
The aqueous solution of hydrocyanic acid is sent to the reactor 2. Separately, pump P-4
And P-5, the Wako Pure Chemicals Reagent special grade formaldehyde solution and the sodium hydroxide aqueous solution are supplied and mixed at the inlet of the reactor 2. Here, as shown in Table 1 below, the weight ratio of the metal in sodium hydroxide to the raw material hydrocyanic acid was 288 ppm. Reactor 2 has an internal volume of 60 mL
The jacket-type serpentine tube type reactor according to the present invention, which is the liquid ring distribution type tubular reactor according to the present invention. Warm water was circulated in the jacket of the reactor 2. A back pressure valve was installed at the outlet of the reactor 2 to maintain the system internal pressure at 0.5 MPa / G. Here, the reactor 1 is merely an aqueous solution of hydrocyanic acid, and the cyanohydrination reaction is performed in the reactor 2 to produce glycolonitrile. At this time, the pH of the reactor 2 inlet liquid was 3.2, and the temperature of the reactor 2 was 45 ° C. That is, pH, P and temperature T ° C. in the first step reaction zone
The product of was T × P = 144.

Next, as the third stage of the second step, the reactor 2
The outlet product glycolonitrile aqueous solution from the back pressure valve is introduced into the reactor 3. The reactor 3 has an internal volume 2 equipped with a stirrer.
It is a jacket type stainless steel autoclave of 00 mL, and is an ammonia absorption tank of the stirring tank flow system in the present invention. Ammonia gas is introduced into the liquid from another supply port of the reactor 3. The gas pressure of ammonia was set to 0.22 MPa / G by the pressure reducing valve, and the pressure of the reactor 3 was maintained. Cooling water was circulated in the jacket of the reactor 3 to remove heat of ammonia absorption.

As in the fourth step of the second step, reactor 3
Hold up 110m by the operation of the liquid level gauge attached to the
The pump P-6 operates so as to maintain L, and the liquid in the reactor 3 is sent to the reactor 4. The reactor 4 is a jacket-type tubular reactor, which is the liquid ring flow type tubular reactor referred to in the present invention. Hot water is circulated in the jacket of the reactor 4 to keep the inside of the reactor at a predetermined temperature, and the liquid is introduced from below the reactor. A back pressure valve is installed at the outlet of the reactor 4 to reduce the system internal pressure to 0.
It was maintained at 4 MPa / G. In the reactors 3 and 4, an amination reaction is performed to produce glycinonitrile. A product tank was provided at the outlet of the back pressure valve of the reactor 4, and the product glycinonitrile aqueous solution was stored in the product tank kept in a nitrogen atmosphere.

To evaluate the process of the present invention, reactor 2
A sampling line was provided at the outlets of 4 and 4. From this line, after the reaction was started and after 3 hours had passed, the reaction liquids of the first and second steps were respectively sampled and subjected to composition analysis and absorbance analysis. The results of reaction conditions and reaction results in each step are shown in Table 1 below.

[0054]

[Table 1]

As is clear from the evaluation results of this example,
According to the method of the present invention, the yield of glycolonitrile in the reactor 2 is 99.47%, and it has become possible to complete the reaction in the first step extremely efficiently. further,
It was found that glycinonitrile in the second step had a high yield of 98.16% and was obtained without coloring.

[0056]

Example 2 In Example 2, glycinonitrile was produced in the same manner as in Example 1 except that a different lot of hydrocyanic acid was used as a raw material, and the reaction results were evaluated in the same manner. The pH of the inlet liquid of the reactor 2 at this time was 5.6. That is, the product of pH, P and temperature T ° C. in the first step reaction zone is T × P = 2
It became 52.

The reaction results in Example 2 were as follows. First step (reactor 2 outlet) Glycolonitrile yield = 99.6% Reaction liquid color index = 0.008 Second step (reactor 4 outlet) Glycinonitrile yield = 98.26 Glycolonitrile yield = 0.33 Yield of iminodiacetonitrile = 1.41 Color of reaction solution = 0.033

As is clear from the reaction results of this example,
According to the method of the present invention, P × T at the first process entrance
No. 252, it was possible to obtain uncolored glycolonitrile in a high yield in the first step. Furthermore, in the second step as well, it was possible to obtain uncolored glycinonitrile in high yield. According to the method of the present invention, the pH in the first step
However, it was found that glycinonitrile can be obtained in a stable and high yield even if it changes depending on the contents of stabilizers (sulfurous acid, sulfuric acid, etc.) in formic acid and hydrocyanic acid in the raw material formalin.

[0059]

Comparative Example 1 In this Comparative Example, as shown in the reactor diagram in FIG. 2, the liquid ring flow type tubular reactor of the reactor 2 in Example 1 was removed, and the reactor 1 was the same as the reactor 3. Type of stirring tank flow system 400mL autoclave, raw material formalin (Wako Pure Chemicals reagent special grade formaldehyde solution) also used in reactor 1
To supply to. Prussic acid was previously prepared as an aqueous solution in a tank and supplied to the reactor 1. The hold-up of the reactor 1 was 200 mL, and the residence time was about 90 minutes. Further, pure water was supplied to the reactor 1 instead of the sodium hydroxide aqueous solution of the catalyst. That is, the first step was a CSTR 1 tank reaction system in which no catalyst was added. The reaction conditions and results in this comparative example are shown in Table 2 below. At this time, the pH at the inlet of the reactor 1 was 2.8, and the temperature inside the tank of the reactor 1 was set to 65 ° C. That is, the pH in the reaction zone of the first step,
The product of P and temperature T ° C. was T × P = 182.

[0060]

[Table 2]

According to this comparative example, it is not suitable to complete the cyanohydrination reaction when the catalyst does not exist and the first step reactor is a stirred tank flow type tank reactor. Do you get it. Moreover, in the second step using the raw material from the first step as it is, the by-product of iminodiacetonitrile increases, the glycinonitrile yield decreases, and in addition, in order to increase the conversion rate. It was found that the reaction time must be long and the coloring of glycinonitrile will proceed.

[0062]

EFFECTS OF THE INVENTION According to the present invention, by using a reaction system, a catalyst, and the amount of addition thereof, which have not been heretofore proposed, it is possible to obtain a high yield, high purity and no coloring by a simple reaction control method. It becomes possible to produce glycolonitrile.
Furthermore, by feeding this glycolonitrile reaction solution as it is to the glycinonitrile reactor, which is the second step, the by-product of iminodiacetonitrile, the by-product of formaldehyde-derived impurities (Schiff base), and unreacted hydrocyanic acid are caused. It is possible to remarkably suppress the coloring, and it is possible to produce high-purity, high-purity and uncolored glycinonitrile.

[Brief description of drawings]

FIG. 1 is a diagram of a reactor used in Example 1.

FIG. 2 is a diagram of a reaction apparatus used in Comparative Example 1.

[Explanation of symbols]

P-1 to P-6 pumps

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4H006 AA02 AC52 AC54 BA02 BA29                       BC10 BC11 BE06 BE14 QN00                 4H039 CA70 CA71 CF30 CG10

Claims (4)

[Claims] 1. A method for producing glycinonitrile, which comprises:
In the presence of a water solvent, as the first step, using a combination of a cyanide absorption tank of a stirring tank flow system and a liquid ring flow system tubular reactor, a water-soluble salt of an alkali metal as a catalyst, By adding 50 to 600 ppm in weight ratio, a glycolonitrile solution is produced from formaldehyde and hydrocyanic acid, and subsequently, as a second step, a combination of an ammonia absorption tank of a stirring tank flow system and a liquid ring flow system tubular reactor is used, A method for producing glycinonitrile, characterized in that the aqueous glycolonitrile solution is directly reacted with ammonia to produce glycinonitrile. 2. The average residence time in the liquid ring flow type tubular reactor in the first step is in the range of 10 to 60 minutes, and
The method for producing glycinonitrile according to claim 1, wherein the reaction temperature of the reactor is in the range of 35 to 75 ° C. 3. The method for producing glycinonitrile according to claim 1, wherein the water-soluble salt of alkali metal is a hydroxide of alkali metal. 4. The ammonia absorption tank of the stirring tank flow system of the second step, wherein ammonia is supplied in a gaseous state, and the molar ratio of ammonia to glycolonitrile is 3.
The reaction temperature is 15 to 60 ° C., the reaction temperature in the liquid ring flow type tubular reactor of the second step is 40 to 70 ° C., and the reaction pressure is dissolved ammonia. Is a pressure at which vaporization does not occur, The method for producing glycinonitrile according to any one of claims 1 to 3, wherein