JPH06172283A - Production of alpha-hydroxyisobutyric acid amide - Google Patents

Abstract

PURPOSE:To produce the subject compound in high purity on an industrial scale at a low cost by continuously hydrating acetone cyanhydrin in the presence of a Mn oxide catalyst, thermally decomposing the produced solution of alpha-hydroxyisobutyric acid amide and distilling out the formed acetone and cyanic acid. CONSTITUTION:A reactor is charged with acetone and 2% aqueous solution of sodium hydroxide. Liquid cyanic acid is poured into the reactor while keeping the temperature of the reactor at 20 deg.C and made to react with the reactants. The pH of the liquid is adjusted to 3.0 by adding sulfuric acid and the unreacted cyanic acid and acetone are distilled away under reduced pressure to obtain acetone cyanhydrin. The obtained acetone cyanhydrin 1 is continuously supplied to a hydration reactor 4 charged with a manganese oxide catalyst such as manganese dioxide powder and water 2 and subjected to hydration reaction at 60 deg.C. The produced alpha-hydroxyisobutyric acid amide solution 5 flowed out of the reactor 4 is transferred to a thermal decomposition reactor 6 and retained in the reactor at 80-100 deg.C for 2-30hr. Acetone and cyanic acid formed by the decomposition of acetone cyanhydrin are distilled out and the mixed gas 7 is separated and recovered by a distillation column to obtain the objective compound 11 on an industrial scale at a low cost.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying α-hydroxyisobutyric acid amide (hereinafter abbreviated as HAM), more specifically, acetone cyanohydrin (hereinafter abbreviated as ACH), and water. H obtained by continuously reacting in the liquid phase
The present invention relates to a method for purifying an AM product solution.

[0002]

2. Description of the Related Art Conventionally, as disclosed in British Patent No. 1,351,530, amide compounds have been used to continuously supply a nitrile compound and water to a fixed bed reactor of a manganese dioxide catalyst, It is produced by concentrating the amide compound solution obtained by the hydration reaction to an appropriate concentration with a concentrator, crystallizing it in a crystallizing tank, and collecting the amide compound crystals with a centrifuge.

By the way, even in the continuous production method of HAM by hydration of ACH, the above-mentioned production method is meaningful as a basic step, but from the concentration of the amide compound solution to the separation of the crystals in this method. However, it is insufficient as a method for purifying HAM, which is one of the amide compounds.

That is, British Patent No. 1,351,530
It is disclosed that the unreacted nitrile compound having good thermal stability is recovered from the amide compound solution without being decomposed and is recycled to the hydration reactor. However, with ACH, which is a nitrile compound having a high boiling point and poor thermal stability, it is impossible to recover ACH without decomposing it as in this method. It is well known that ACH generally has poor stability and is easily decomposed as its liquidity changes from weakly acidic to alkaline. However, the stability of ACH in an HAM aqueous solution containing several% of ACH, its decomposition conditions, and the appropriate conditions for recovering it are not known at all. If the unreacted ACH is not separated or removed in the HAM production liquid by the hydration reaction of ACH, or if the separation is insufficient, toxic ACH remains in the HAM crystals along with water in the subsequent HAM crystallization step. It is very dangerous for security.

Also, in general, the desired reaction is converted to 100% conversion.
When the reaction is completed at mol%, it is not necessary to recover the unreacted raw material, but the time required to actually complete the reaction at 100 mol% is approximately 2 to 3 times or more the time required for the conversion of 50 to 60 mol%. Become. Therefore, the productivity of the reactor at a conversion rate of 100 mol% is less than half of the conversion rate of 50 to 60 mol%, and it is very important to recover the unreacted raw material at the medium conversion rate, which has the highest productivity of the reactor. Become. As described above, in the industrial continuous production of HAM by hydration of ACH, the separation and removal of unreacted ACH in the HAM production liquid and its recovery are major problems.

[0006]

In order to solve these problems, the present inventors have decided to solve the problem of H flowing out from the hydration reactor.
The present invention has been found to be effective by a method in which unreacted ACH in the AM product solution is heat-treated at a high temperature and the decomposition by-product is separated by distillation together with acetone.

That is, according to the present invention, acetone cyanohydrin and water are continuously supplied to a reactor of a manganese oxide catalyst to cause a hydration reaction, and an α-hydroxyisobutyric acid amide product liquid flowing out from the reactor is heated. It is introduced into the decomposition reactor, and the α-hydroxyisobutyric acid amide product solution is introduced into the decomposition reactor.
It is a method for producing an α-hydroxyisobutyric acid amide, which is characterized in that it is retained at a temperature of 0 to 100 ° C. for 2 to 30 hours to distill off the acetone cyanohydrin-decomposed acetone and hydrocyanic acid.

The manganese oxide used in the present invention may be either anhydrous or hydrated. The manganese oxide can be produced by a known method, for example, a method of reducing a 7-valent manganese compound in a neutral to alkaline region at 20 to 100 ° C (Zeit. Anorg. Allg. Chem., 309, p. 1 to 32 and p. .12
1 to 150 (1961)), a method of treating potassium permanganate and manganese sulfate under acidic conditions (Biochem. J., 50 , p.43, (19
51) and J. Chem. Soc., 1953 , p. 2189, (1953).
), A method of reducing a 7-valent manganese salt with hydrohalic acid (Japanese Patent Laid-Open No. 63-57535), and a method of electrolytically oxidizing an aqueous solution of manganese sulfate. In particular, manganese dioxide prepared from permanganate and manganese sulfate in the presence of sulfuric acid, and
Electrolytic manganese dioxide is preferred. The catalyst is usually used as a powder of suitable particle size.

The amount of water used in the present invention is AC.
It is usually 1 mol or more, preferably 2 to 20 mol, relative to 1 mol of H.
The molar amount is particularly preferably 4 to 10 mol. As the reaction solvent, in addition to water, a solvent inert to the reaction can be newly used. For example, JP-A-52-222 (US Pat. No. 4,
Acetone disclosed in No. 018,829) is preferably used. The amount of acetone is usually 1 mol of ACH
It is preferable to use it in the range of 0.1 to 6.0 mol.

The temperature of the hydration reaction in the present invention is usually 1
0 to 150 ° C, preferably 20 to 100 ° C, particularly preferably
It is in the range of 30-80 ° C. If this temperature is below 10 ° C,
The activity of the catalyst is low and not practical. On the other hand, if the temperature exceeds 150 ° C., the catalytic activity is high but the HAM yield is drastically reduced, which is not preferable.

The hydration reactor used in the present invention includes:
It is a fixed bed type catalytic reactor or a suspension type catalytic reactor. The fixed bed reactor is a cylindrical container filled with a manganese dioxide catalyst molded into an appropriate size and shape. When a suspension type reactor is used, the catalyst concentration in the catalyst solution is not particularly limited, but it is usually 2% by weight or more, preferably 5 to 50% by weight. The feed rate of the raw material liquid to the suspension reactor is 0.05 to 1.1 ACH per 1 part by weight of the catalyst and 1 hour.
It is preferable that the ratio is 0 part by weight. This suspension type reactor is operated so as to maximize the catalytic activity, and the suspended catalyst having a small particle size is prevented from flowing out of the system.
The outlet of the M product solution from the reactor is equipped with a filter made of metal or glass.

The hydration reactor according to the present invention is usually connected in series with not only one but two or three in order to maximize the conversion of ACH. However, in the present invention, the HAM production liquid from the hydration reactor is introduced into the following thermal decomposition reactor, and unreacted ACH is almost entirely thermally decomposed and can be recovered as a decomposition by-product. The conversion rate of ACH in the hydration reactor can be freely set. However, from the viewpoint of HAM productivity in the hydration reactor, the conversion rate of ACH is usually set in the range of 10 to 90 mol%, preferably 20 to 80 mol%.

The HAM production liquid flowing out from the hydration reactor contains a trace amount of hydrocyanic acid in addition to unreacted ACH and reaction solvent acetone. Conventionally, this HAM production liquid is processed in a distillation column in order to remove and recover low boiling substances such as acetone and hydrocyanic acid therein. The operating conditions of the distillation column are such that the pressure at the top of the distillation column is 200 to 760 Torr and the temperature is 20 to 57 ° C., and the HAM aqueous solution is obtained from the bottom of the distillation column by this operation. However, in this distillation operation, in the HAM production liquid,
Unreacted ACH is not decomposed and most of it remains in the HAM aqueous solution from the bottom. Therefore, in order to solve this problem, in the present invention, a pyrolysis reaction operation for decomposing unreacted ACH into acetone and hydrocyanic acid is newly added, and this is combined with distillation operation to optimize the pyrolysis / distillation operation. It was In the present invention, the bottom liquid obtained by the conventional distillation operation can be introduced into the following thermal decomposition reactor, but the HAM product liquid flowing out from the hydration reactor is directly introduced into the thermal decomposition reactor, It is preferable in terms of equipment that the acetone is distilled off and the unreacted ACH is decomposed and distilled off at the same time.

The apparatus used for the thermal decomposition / distillation operation of the present invention is a thermal decomposition reactor for thermally decomposing ACH contained in the HAM product solution, and acetone and ACH decomposition by-products and water are separated by distillation. It consists of a distillation column for.
These may be provided separately or may be integrated. The thermal decomposition reactor is agitated so that the content liquid is uniform, and the inside of the system is kept at atmospheric pressure, preferably, so that acetone and hydrocyanic acid, which are by-products during the thermal decomposition, can be rapidly removed. Depressurize.

As an operating condition for the thermal decomposition / distillation, it is preferable that the inside of the thermal decomposition reactor is maintained at a temperature of 60 to 110 ° C. and a pressure of 100 to 1200 Torr, preferably 80 to 100 ° C. and a pressure of 100 to 760 Torr. If this temperature is lower than 80 ° C, it takes a very long time to decompose and distill off ACH even at a low pressure of about 100 Torr. If the temperature exceeds 100 ° C, the decomposition of ACH and the removal of the decomposition by-products will be completed in a short time, so there will be no problem in operation, but the amount of water to be distilled or refluxed will be large, and the thermal efficiency will be high. It is not desirable in terms of The HAM product liquid is continuously introduced into the pyrolysis reactor, and the flow rate thereof depends on the internal volume of the pyrolysis reactor, actually, the residence time of the liquid. The residence time varies depending on the temperature and pressure in the pyrolysis reactor, but is usually 1 hour or longer, preferably 2 to 30 hours. If it is less than 1 hour, the decomposition rate of ACH is low, which is not preferable.
No significant improvement in decomposition rate is observed. The purified HAM aqueous solution flowing out from the thermal decomposition reactor is further concentrated according to a conventional method,
Crystals of HAM can be obtained by crystallization and centrifugation.

Representative steps of the present invention will be described below with reference to FIG. ACH1 and water 2, which are raw materials for the hydration reaction, and acetone 3, which is a reaction solvent, are continuously supplied to the hydration reactor 4. The HAM production liquid 5 is introduced into the thermal decomposition reactor 6 through the internal filter of the hydration reactor 4.
A mixed gas 7 consisting of acetone coexisting in the hydration reaction, acetone and hydrocyanic acid by-produced by the decomposition of ACH, and water enters the distillation column 8 from the thermal decomposition reactor 6. Water is separated in the distillation column 8, the remaining acetone and hydrocyanic acid rise as gas, are condensed into a liquid in the condenser 9, and are recovered as the acetone / hydrocyanic acid mixed liquid 10. The acetone / hydrocyanic acid mixture 10 is returned to the original ACH manufacturing process. On the other hand, from the pyrolysis reactor 6 the target purified HA
An M aqueous solution 11 is obtained.

[0017]

EXAMPLES The present invention will be described in detail below with reference to production examples and examples. Here, "%" is based on weight, unless otherwise specified. In the production examples, HAM is supplied to the catalyst in order to evaluate the effect of the present invention more quickly.
The so-called high load of the catalyst was used to increase the amount of CH. The liquid concentrations of ACH, acetone and HAM were measured by liquid chromatography, and the concentration of hydrocyanic acid was measured by silver nitrate titration.

Production Example-Preparation of ACH Acetone was added to a reactor (glass round bottom flask, content 2 lit; reflux condenser, stirrer, thermometer and liquid introduction part).
Charge 80g and 10g of 2% sodium hydroxide solution,
284 g of liquid hydrocyanic acid was injected while maintaining the temperature. After the reaction
Sulfuric acid was added to adjust the pH of the solution to 3.0. Next, unreacted hydrocyanic acid and acetone were distilled off under reduced pressure to obtain 843 g of 99.8% ACH.

Production of HAM (continuous hydration reaction, high load of catalyst) Suspension type reactor (glass round bottom flask, internal capacity 500 ml)
A glass stirring bar, a mercury thermometer, a raw material supply port, and a liquid outlet equipped with a glass ball filter) are charged with 50 g of electrolytic manganese dioxide powder catalyst and 300 g of water, and then the internal temperature is raised to 60 ° C. , Kept at this temperature with stirring. Next, using the ACH obtained above, an acetone aqueous solution of 17.1% ACH (ACH: acetone: water = 1: 1.5: 18 molar ratio) was continuously supplied to the reactor at a flow rate of 37 g / hr by a metering pump. did. Keep the temperature in the reactor at 58-62 ℃,
Also, adjust the liquid volume in the reactor to the range of 290-310 ml,
It was operated continuously for one week. The concentration of each component in the obtained HAM-producing solution is as follows, as an average value for one week. ACH ... 11.5%, Acetone ... 18.4%, HAM ... 5.
Therefore, the ACH conversion was 33 mol%, the HAM selectivity was 78 mol%, and the hydrocyanic acid selectivity was 22 mol%.

Example In a pyrolysis reactor (capacity 500 ml) equipped with a distillation column (theoretical plate number = 3), 25 to 500 ml of the HAM product solution obtained above was added.
It was supplied at a flow rate of / hr. Table 1 (Table 1) shows the relationship between the pressure, temperature and liquid retention time of the thermal decomposition reactor and the ACH concentration and ACH decomposition rate of the outlet liquid. The residence time of the liquid was determined by the amount of liquid in the reactor and the flow rate of the inlet liquid, and the ACH decomposition rate was determined by the following formula. ACH decomposition rate (%) = {(inlet ACH flow rate-outlet ACH
Flow rate) / (inlet ACH flow rate)} x 100

[0021]

[Table 1]

[0022]

INDUSTRIAL APPLICABILITY The present invention is to introduce a HAM product solution from a hydration reactor into a thermal decomposition reactor in an industrial continuous production method of HAM by hydration reaction of ACH using a conventional manganese oxide catalyst. As a result, almost all unreacted ACH is decomposed and removed, and a toxic ACH-free purified HAM aqueous solution can be obtained, which in turn makes it possible to obtain high-purity HAM crystals, as well as the ACH conversion rate in the hydration reactor. This is a very effective method because you can freely set.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a typical HAM illustrating the present invention.

[Explanation of symbols]

 1; ACH 2; water 3; acetone 4; hydration reactor 5; HAM production liquid 6; thermal decomposition reactor 7; mixed gas 8; distillation column 9; condenser 10; acetone / hydrocyanic acid mixed liquid 11; pure HAM aqueous solution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kanemitsu Miyama 1900, Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Shinji Tokuno, 1900, Togo, Mobara-shi, Chiba Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A manganese oxide catalyst reactor is continuously supplied with acetone cyanohydrin and water for hydration reaction,
The α-hydroxyisobutyric acid amide product liquid flowing out of the reactor is introduced into the thermal decomposition reactor, and the α-hydroxyisobutyric acid amide product liquid is introduced into the thermal decomposition reactor at 80 to 100 ° C. for 2 to 30 ° C.
Α, which is characterized in that it is allowed to stay in the range of time to distill off the acetone and cyanic acid from which acetone cyanohydrin is decomposed.
-Method for producing hydroxyisobutyric acid amide.