JP2888392B2 - Method for producing acrylonitrile dimer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a linear dimer of 1,4-dicyanobutene by dimerization of acrylonitrile.
The present invention relates to a novel continuous production method for obtaining dinitrile by a method for producing dimer of acrylonitrile for producing 4-dicyanobutadiene and adiponitrile. A novel carboxylic acid β-cyanoethyl ester formed simultaneously in the dimerization reaction is converted to acrylonitrile and carboxylic acid and circulated to the dimerization reaction to increase the selectivity of the acrylonitrile dimer, which is industrially advantageous. It provides a simple process. The obtained dinitrile is an intermediate of hexamethylenediamine as a raw material of nylon-66 and an intermediate of a rust inhibitor and a rubber vulcanization accelerator.

[0002]

2. Description of the Related Art Conventionally, a method for producing 1,4-dicyanobutenes and adiponitrile from acrylonitrile using a ruthenium catalyst has been described in A.I. Misono, et a
1, Bull. Chem. Soc. Jpn. , 40 (1
967) 931 and is well known. This is a method of dimerizing acrylonitrile in the presence of hydrogen using a ruthenium catalyst. It is disclosed that the reaction of this method does not cause acrylonitrile dimerization at all when hydrogen is not added, and the acrylonitrile dimerization proceeds only when the reaction is performed in a hydrogen atmosphere.

However, when the above-mentioned reaction is carried out in a hydrogen atmosphere, the acrylonitrile dimerization and the acrylonitrile hydrogenation reaction occur simultaneously, and a large amount of propionitrile is produced as a by-product. Therefore, in order to improve the selectivity of this dimerization reaction, it is necessary to convert propionitrile to acrylonitrile by a dehydrogenation reaction, but this reaction also has low selectivity and catalytic activity, so that propionitrile cannot be used. The industrialization of the process for reconversion to acrylonitrile has disadvantages which are disadvantageous.

Japanese Patent Publication No. 44-24585, Japanese Patent Publication No. 45-
No. 4048 and JP-B-54-12450 disclose that the selectivity of acrylonitrile linear dimer was improved. In the production method, the selectivity of the acrylonitrile linear dimer is 55 to 67%. However, since the reaction is carried out in the presence of hydrogen, the ratio of propionitrile is 33 to 4%.
Since it was formed with a selectivity of 5% and the amount of by-products of propionitrile was large, it was not an industrially advantageous method for producing an acrylonitrile linear dimer.

In Japanese Patent Publication No. 54-12450, dimerization is carried out in the presence of hydrogen, using an inorganic ruthenium derivative, ruthenium carboxylate or a ruthenium complex as a catalyst, and performing dimerization from the group consisting of lead, zinc, cadmium, tin, iron and manganese. The dimerization reaction is promoted by the coexistence of a metal carboxylate of the selected element. Even in the method for producing an acrylonitrile linear dimer according to this known technique, there is a problem that production of propionitrile is inevitable because hydrogen is used.

[0006] According to Japanese Patent Publication No. 51-146420, acrylonitrile is converted to 300 to 6 in the absence of hydrogen.
It discloses that at a reaction temperature of 00 ° C., it can be dimerized to C ₆ dinitrile using a ruthenium catalyst. However, also in this method, when the amount of by-product propionitrile is small, the conversion of acrylonitrile is low and about several percent. When the conversion of acrylonitrile is high, the by-product of propionitrile increases. , C6 dinitrile. In addition, the resulting dinitrile has a problem that a mixture of a linear dimer and a branched dimer is generated, and the selectivity of a target linear dimer is low.

[0007] Therefore, the above-mentioned conventional method for producing a linear acrylonitrile dimer has a problem that a large amount of by-products such as propionitrile which cannot be easily converted into acrylonitrile raw materials is produced. There was a disadvantage. An object of the present invention is to produce a linear dimer of acrylonitrile without producing a large amount of by-products such as propionitrile that cannot be easily converted to acrylonitrile in the production of acrylonitrile dimer. Is to provide a process.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a process for producing a dimer of acrylonitrile which produces linear dimers of 1,4-dicyanobutene, 1,4-dicyanobutadiene and adiponitrile by dimerization of acrylonitrile. Using a ruthenium compound as a catalyst without using a large amount of hydrogen, in the presence of a carboxylic acid, perform a dimerization reaction without generating a large amount of propionitrile, and simultaneously form a carboxylic acid β- formed in the dimerization reaction. Provided is a process for continuously producing acrylonitrile dimer, which can effectively carry out production of acrylonitrile dimer on an industrial scale by converting cyanoethyl ester to acrylonitrile and carboxylic acid and circulating the dimerization reaction. It is.

The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, in the dimerization reaction of acrylonitrile, using a ruthenium compound as a catalyst without the presence of a large amount of hydrogen, and in the presence of carboxylic acid, It has been found that by performing a dimerization reaction, by-products of propionitrile can be greatly suppressed. Further, they found that the carboxylic acid β-cyanoethyl ester by-produced in this reaction was an adduct of carboxylic acid and acrylonitrile and could be converted to acrylonitrile as a raw material with high selectivity, and the converted acrylonitrile and carboxylic acid were again subjected to a dimerization reaction. It became possible to circulate it to For this reason, they have found that the selectivity of acrylonitrile linear dimer can be greatly improved, and have completed the invention relating to a novel industrial continuous process which is very advantageous for the production of acrylonitrile linear dimer. .

The carboxylic acid β-cyanoethyl ester is
It is represented by the following general formula.

Embedded image (In the formula, R is hydrogen or a saturated or unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group or an aromatic hydrocarbon group.)

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a process for producing an acrylonitrile dimer which produces 1,4-dicyanobutene, 1,4-dicyanobutadiene and adiponitrile as linear dimers by dimerization of acrylonitrile. (A). A dimerization reaction step in which acrylonitrile is introduced into an acrylonitrile dimerization reactor, a carboxylic acid and a ruthenium compound are introduced, a dimerization reaction is performed, and a reaction product containing an acrylonitrile dimer is obtained.

(B). The reaction product in the dimerization reaction step is led, and unreacted acrylonitrile, unreacted carboxylic acid, product propionitrile, carboxylic acid β-cyanoethyl ester and acrylonitrile dimer are separated and separated in the separation step, respectively. The obtained acrylonitrile and carboxylic acid are recycled to the dimerization reaction step and supplied as a raw material, and the separated carboxylic acid β-cyanoethyl ester is supplied to the next step of the carboxylic acid β-cyanoethyl ester conversion reaction step, Separation process to separate the acrylonitrile dimer as the reaction target product formed in the dimerization reaction

(C). The carboxylic acid β-cyanoethyl ester derived from the separation step is subjected to a conversion reaction of the carboxylic acid β-cyanoethyl ester by heating without a catalyst or with addition of a catalyst, and acrylonitrile and carboxylic acid are obtained. The present invention relates to a method for producing an acrylonitrile dimer, which comprises a conversion reaction step in which the acid is separated and supplied to the dimerization reaction step by circulation.

Although the conventionally known method for dimerizing acrylonitrile requires a hydrogen atmosphere, the present invention does not require hydrogen in the method for dimerizing acrylonitrile in the presence of a carboxylic acid as described above. The reaction is characteristic. In a reaction atmosphere that uses a large amount of hydrogen, if it is mixed with air, the explosion range is wide.For safe operation, the reaction operation is complicated, and airtightness is required for safety. The fact that hydrogen is not used in large quantities on an industrial scale simplifies the equipment and is very advantageous for safe operation.

Next, each step of the present invention will be described in detail below. Dimerization reaction stepIn the dimerization reaction step in the present invention, acrylonitrile, ruthenium compound, and carboxylic acid are continuously introduced into the dimerization reactor, and a predetermined reaction temperature and reaction pressure are set in an air atmosphere or an inert gas atmosphere. It is preferable to carry out the dimerization reaction for a predetermined reaction time while holding.

As the conditions for the acrylonitrile dimerization reaction, the reaction temperature is preferably from 70 to 220 ° C., particularly preferably from 100 to 180 ° C. If the reaction temperature is too low, the reaction rate is slow and too high. This is not preferable because the deactivation of the catalyst is accelerated. Reaction pressure is 50mmHg
The reaction can be performed under an arbitrary pressure from a reduced pressure of 100 kg / cm ² to a pressure of 100 kg / cm ² . The reaction time depends on the temperature,
Although it depends on the catalyst, it is preferably 0.1 to 10 hours.

Although it is not necessary to use a solvent, a solvent such as nitrile, ether, hydrocarbon, amide, halogenated hydrocarbon and ester can also be used for performing a mild reaction. Although it may be in the presence of air, it is preferable to use an inert gas such as nitrogen, carbon dioxide, or argon gas in order to avoid an explosive atmosphere for safety.

The ruthenium compound used as a catalyst in the wood invention is an inorganic ruthenium derivative, ruthenium carboxylate or a coordination compound having ruthenium as a central atom, such as ruthenium chloride, ruthenium bromide, ruthenium iodide, Inorganic ruthenium derivatives such as ruthenium sulfate and ruthenium nitrate, ruthenium acetate, ruthenium propionate, ruthenium butanoate, ruthenium pentanate, ruthenium hexanoate, ruthenium stearate, ruthenium naphthenate, ruthenium oxalate,
Ruthenium carboxylate such as ruthenium succinate, Ru
Coordination compounds having ruthenium as the central atom, such as Cl ₂ (acrylonitrile) ₃ , RuCl ₂ (triphenylphosphine) ₃ , and RuCl ₂ (triphenylphosphine) 4, can be used. These ruthenium compounds may be used alone or in combination of a plurality of compounds.

In the present invention, a base and / or a reducing agent may be used in combination with the ruthenium compound. As the base to be used, sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, sodium acetate, sodium propionate, sodium methoxide, sodium ethoxide, ammonia, methyl Examples include amine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, aniline, methylaniline, dimethylaniline, ethylaniline, dimethylaniline and the like.

Preferred examples of the reducing agent include trimethylstannane, triethylstannane, tri-n-propylstannane, tri-n-butylstannane, triphenylstannane, di-n-propylstannane, and di-n-propylstannane. -N-
Butylstannane, diphenylstannane, trimethylgermane, triethylgermane, tri-n-propylgermane, sodium hydride, sodium borohydride, lithium borohydride, lithium aluminum hydride, metal sodium, metal magnesium, metal zinc, etc. No.

The amount of the ruthenium compound used in the catalyst used in the present invention is 0.001 to 1 with respect to acrylonitrile.
It is preferred to use 0 mol%. When a base and / or a reducing agent are used in combination, the amount of the base added is
When the amount is small, the effect of addition is small, and when the amount is large, the amount of dimer produced is reduced due to loss of acrylonitrile. It is preferable that the amount is such that the molar ratio is obtained. The reducing agent is used in an amount of suitably 0.05 to 30 times, preferably 0.1 to 20 times the mole of the ruthenium compound used.

As the organic acid used in the present invention,
Suitable are organic carboxylic acids having 1 to 20, preferably 1 to 15 carbon atoms, optimally acetic acid, propionic acid, methylpropionic acid, dimethylpropionic acid,
It is preferable to use butanoic acid, methylbutanoic acid, ethylbutanoic acid, dimethylbutanoic acid, pentanoic acid, hexanoic acid and the like. These carboxylic acids may be added alone or as a mixture of a plurality of compounds. The carboxylic acid is used in an amount of 0.0 to acrylonitrile used.
It is preferably used in a proportion of 1 to 100 moles, preferably 0.05 to 10 moles. If the amount of the carboxylic acid is too small, the dimer formation rate is slow, and if it is too large, the acrylonitrile concentration is decreased and the dimer formation rate is undesirably reduced. The reaction may be a continuous flow type reaction method of a tube type reaction system or a tank type reaction system, or a batch type reaction method.

Unreacted Product Separation Step The reaction product obtained in the dimerization reaction step is composed of acrylonitrile dimer, unreacted acrylonitrile and unreacted carboxylic acid, propionitrile, carboxylic acid β-cyanoethyl ester And low polymer content,
The reaction product obtained in the dimerization reaction step is derived and, for example, separated in the unreacted substance separation step to separate unreacted acrylonitrile and unreacted carboxylic acid and propionitrile from the reaction product. The unreacted acrylonitrile and carboxylic acid separated in this step are circulated and supplied again to the dimerization reaction step as raw materials.

As a separation unit operation in the unreacted material separation step, a distillation operation is preferable, and unreacted acrylonitrile and carboxylic acid are mixed with propionitrile by a side reaction.
Acrylonitrile dimer of target product, carboxylic acid β-
Comparing the vapor pressure with cyanoethyl ester and low polymer, unreacted acrylonitrile and carboxylic acid and propionitrile by-product clearly form light boiling components, so the reaction product obtained in the dimerization reaction step The unreacted acrylonitrile and carboxylic acid are separated from the unreacted acrylonitrile and carboxylic acid by distillation as a light boiling component by distillation, and the separated unreacted acrylonitrile and carboxylic acid are recycled to the raw material and reused. In addition, propionitrile as a by-product separated as a light boiling component is taken out of the system and discarded.

On the other hand, the acrylonitrile dimer, the carboxylic acid β-cyanoethyl ester and the low polymer, which are the target products, are preferably separated from the residue from which the light boiling point has been substantially removed as a high boiling point. It is desirable to select a perforated plate tower, a packed tower, a tray tower, and a bubble tower as the rectification tower for the distillation operation to be separated. As the distillation operation, continuous distillation is preferable, but batch distillation may be used.

The process for separating the high-boiling components substantially comprises the following two separation processes. That is, the carboxylic acid β-cyanoethyl ester is separated, and the acrylonitrile dimer of the target product is separated from the product separation step to be supplied to the next conversion step and the high boiling point of the residue excluding the carboxylic acid β-cyanoethyl ester. And a dimer separation step.

The high-boiling fraction obtained in the above-mentioned unreacted product separation step contains the target product acrylonitrile dimer (containing linear dimer 1,4-dicyanobutene, 1,4-dicyanobutadiene and adiponitrile). ), Carboxylic acid β-
Since it contains a cyanoethyl ester, a low polymer and the ruthenium catalyst used in the dimerization reaction step, it is desirable to carry out a separation operation by a distillation unit operation in order to separate each component. In order to carry out separation by distillation, since the above-mentioned components form a polymer at a high temperature, it is preferable to prevent the formation of a polymer by performing the separation by vacuum distillation which can be separated at a low temperature.

Product Separation Step In the case of distillation under reduced pressure, the carboxylic acid β-cyanoethyl ester is separated as the first component from the high boiling point of the above components from the gas-liquid equilibrium. Separated and supplied to the conversion reaction step.

Next, the high-boiling fraction obtained from the bottom of the column contains the target product acrylonitrile dimer, low polymer, and the ruthenium catalyst used in the dimerization reaction step. Vacuum distillation is carried out in a high-boiling distillation column, but batch distillation is preferred since multicomponent acrylonitrile dimer is separated. The target product acrylonitrile dimer is obtained from the top of the column.

The distillation residue from which the acrylonitrile dimer of the target product has been substantially sufficiently removed in the high-boiling distillation column is removed from the bottom of the column. Since the residue from the bottom of the column contains a low polymer produced as a by-product and the ruthenium catalyst used in the dimerization reaction step, it is desirable to carry out the treatment in the ruthenium catalyst recovery step to recover ruthenium.

Conversion reaction step The carboxylic acid β-cyanoethyl ester obtained in the unreacted substance separation step is introduced into this step, and a conversion reaction is carried out by the following reaction to obtain acrylonitrile and carboxylic acid, followed by a dimerization reaction step. As raw material. In the conversion reaction step, acrylonitrile and a carboxylic acid are produced by heating the carboxylic acid β-cyanoethyl ester without a catalyst or in the presence of a catalyst.

The conversion reaction of carboxylic acid β-cyanoethyl ester can be generally represented by the following reaction formula.

Embedded image (In the formula, R is hydrogen or a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group or an aromatic hydrocarbon group.) That is, in the dimerization reaction of the present invention, This is a very useful method for simultaneously producing acrylonitrile and a carboxylic acid with high selectivity by heating the resulting carboxylic acid β-cyanoethyl ester without a catalyst or in the presence of a catalyst.

The catalyst used in the conversion reaction of the carboxylic acid β-cyanoethyl ester is a ruthenium compound, a copper compound, a silver compound, a cobalt compound, a mercury compound, a lead compound, and a nickel compound. Propionic acid, butanoic acid, pentanoic acid, hexanoic acid, stearic acid, naphthenic acid, oxalic acid, succinic acid,
Coordination with these metals as central atoms such as organic carboxylate having 1 to 20 carbon atoms such as adipic acid and benzoic acid, inorganic acid salts such as halides, sulfates and nitrates, acetylacetonate and tertiary phosphine complex Compound, methoxide,
Alkoxides such as ethoxide, oxides, hydroxides,
These are simple metals. These catalysts may be used alone or as a mixture of a plurality of compounds.

The reaction method in this step is carried out by heating in the absence or presence of a catalyst to produce acrylonitrile and carboxylic acid from carboxylic acid β-cyanoethyl ester. When the catalyst is added, the amount added is suitably 10 mol% or less, and preferably 5 mol% or less. If the addition amount is large, the catalyst efficiency is not good.

The reaction temperature is suitably from 40 to 300 ° C, preferably from 60 to 250 ° C. The reaction pressure is
The reaction can be performed under any pressure from a reduced pressure of 50 mmHg to a pressure of 100 kg / cm ² . The reaction time in this step depends on the type of catalyst, amount of catalyst used, reaction temperature,
Depending on the pressure and stirring conditions, preferably 0.0
The reaction time is from 1 to 50 hours, and preferably from 0.01 to 10 hours from the viewpoint of economic productivity.

In this step, a solvent may be used.
It is not necessary to use it. Although not particularly necessary, for example, aromatic hydrocarbons, aliphatic or alicyclic hydrocarbons,
Ethers and nitriles can be used as the reaction solvent.

The reaction can be carried out in a closed system, but it is preferable to carry out the reaction while separating acrylonitrile and carboxylic acid formed. The produced acrylonitrile and carboxylic acid are circulated and reused as raw materials for the dimerization reaction. In this case, the residue contains by-product low polymer and catalyst (when a catalyst is used),
It is desirable to perform the treatment in the catalyst recovery step to recover the catalyst.

When β-cyanoethyl carboxylate is reacted under the above reaction conditions and the reaction is carried out while separating the produced acrylonitrile and carboxylic acid, a reactive distillation apparatus may be used as the reaction apparatus for simultaneously performing the reaction and the separation. preferable. The reactive distillation apparatus is installed with a reaction section at the bottom to allow sufficient reaction residence time, and the reaction mode is self-flowing of a tube-type reaction system or a tank-type reaction system so that the reaction section can be sufficiently heated. A batch-type reaction method is also preferable.

Acrylonitrile and carboxylic acid are separated from the reaction product, and the separated acrylonitrile and carboxylic acid are recycled to the raw material for the dimerization reaction and reused.
The rectification section of the reactive distillation device is a perforated plate tower, packed tower, tray tower,
It is desirable to choose a bubble bell tower. The residue obtained by separating acrylonitrile and carboxylic acid in the rectification section is intermittently taken out from the bottom of the column, and is further subjected to a substantial reaction in a batch-type reactive distillation apparatus. Since it contains the polymer and the catalyst used in the reaction step (when a catalyst is used), it is desirable to perform the treatment in the catalyst recovery step to recover the catalyst.

Next, the manufacturing method of the present invention will be described with reference to FIG. FIG. 1 is a manufacturing process showing one embodiment of the present invention, and does not limit the present invention. Raw materials of acrylonitrile, carboxylic acid and ruthenium catalyst are mixed at a predetermined ratio and supplied from a line 7. At this time, acrylonitrile and carboxylic acid separated and recovered from the pipe 11 derived from the unreacted material separation step, the pipe 16 derived from the conversion reaction step, and the pipe 21 derived from the batch separation step are also mixed and reacted in the line 8. The raw materials are prepared so as to have a mixing ratio of the liquid. The prepared raw material liquid is introduced into the dimerization reaction step 1 to perform a dimerization reaction.

After the reaction, the reaction product of the dimerization reaction is introduced into the unreacted product separation step 2 via a conduit 9, acrylonitrile and carboxylic acid are separated from the reaction product by a distillation unit operation, and the dimerization reaction step is conducted via a conduit 11. Used for circulation. In addition, propionitrile, a by-product of the reaction,
It is separated as light boiling by the operation of the distillation unit, taken out of the system through the conduit 10 and discarded. The target product acrylonitrile dimer, carboxylic acid β-cyanoethyl ester and low polymer obtained as a high-boiling component are led out through the conduit 12 and subjected to high boiling in the product separation step 3 and the dimer separation step 6. Separate the fractions into their components. First, product separation step 3
Then, the carboxylic acid β-cyanoethyl ester is first separated as a high boiling point by a distillation unit operation and is led out through a conduit 13.

In the dimer separation step 6, the product separation step 3
The acrylonitrile dimer of the desired product is separated from the high boiling point obtained by the conduit 18 from the bottom of the distillation column. Since the high boiling point obtained by the conduit 18 contains the acrylonitrile dimer of the desired product, a low-polymerized by-product and a ruthenium catalyst, the acrylonitrile dimer is separated from the top of the column by distillation under reduced pressure. As a result, an acrylonitrile dimer as a target product can be obtained. Since the high-boiling component from the bottom of the column contains a low-polymerized product and a ruthenium catalyst which are by-produced, it is desirable to take out the same through the conduit 20 and treat it in a ruthenium catalyst recovery step to recover ruthenium.

The carboxylic acid β-cyanoethyl ester separated by the conduit 13 is directly introduced into the conversion reaction step 4 in the case of a non-catalytic conversion reaction, but when a catalyst is used, the required amount of the catalyst is supplied through the conduit 14. It is mixed and introduced into the conversion reaction step 4. In the conversion reaction step 4, carboxylic acid β-cyanoethyl ester is converted to obtain acrylonitrile and carboxylic acid.

The acrylonitrile and carboxylic acid obtained by the conversion reaction are led out through a conduit 16 and recycled to the dimerization reaction step. The reaction concentrate is intermittently taken out from the bottom of the conversion reaction operation through the conduit 15 and further substantially reacted in the batch separation step 5. The obtained acrylonitrile and carboxylic acid are intermittently led out through the conduit 21. Mix into conduit 16. Since the residue taken out from the conduit 17 from the bottom of the tower contains the low-polymerized by-product and the catalyst used in the reaction step (when a catalyst is used), the residue is treated in the catalyst recovery step to recover the catalyst. .

[0045]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Example 1 In FIG. 1, the following raw material composition and ruthenium acetate as a catalyst for the dimerization reaction were introduced into the dimerization reaction step 1 through a conduit 8 to carry out the reaction. Acrylic nitrile 1500
Parts, 500 parts of acetic acid and 13 parts of ruthenium acetate are fed per hour from the conduit 8 to the dimerization reaction step 1. The dimerization reaction is carried out under a nitrogen atmosphere with stirring at a reaction temperature of 150 ° C. and a reaction gauge pressure of 5 kg / cm. ^The reaction was carried out at ^{2 for} 6 hours. The composition of the reaction solution after 6 hours of the reaction was analyzed by gas chromatography. As a result, 1200 parts of unreacted acrylonitrile, 1,4-dicyanobutene,
It contained 156 parts of a linear dimer of 1,4-dicyanobutadiene and adiponitrile, 9 parts of propionitrile, 249 parts of β-cyanoethyl acetate, 368 parts of acetic acid and 18 parts of a low polymer.

As for the dimerization reaction results, the conversion of acrylonitrile was 20%, the selectivity of linear dimer was 52%, and β
-Selectivity for cyanoethyl acetate was 39%, selectivity for propionitrile was 3%. The formula for calculating the selectivity is
It was represented by the following equations 1, 2, and 3.

[0047]

(Equation 1)

[0048]

(Equation 2)

[0049]

(Equation 3)

The above-mentioned dimerization reaction product is introduced into the unreacted product separation step 2 through the conduit 9 and unreacted acrylonitrile 1200
Parts, 368 parts of unreacted acetic acid, and 9 parts of by-product propionitrile were separated per hour by distillation. The distillation was performed under the following atmospheric distillation conditions. The temperature at the bottom of the distillation column was 83 to 125 ° C. to substantially separate the following components. Acrylonitrile 78 ° C./760 mmHg Propionitrile 97 ° C./760 mmHg Acetic acid 118 ° C./760 mmHg Acrylonitrile and acetic acid were separated from the reaction product by a distillation unit operation, and were circulated to the dimerization reaction step via conduit 11. In addition, propionitrile, a by-product of the reaction, was separated as a low-boiling component by the above-mentioned distillation unit operation, and was taken out of the system through the conduit 10.

In the product separation step 3 and the dimer separation step 6 in which the high boiling point of the distillation residue in the unreacted matter separation step 2 was led out through the conduit 12, the high boiling point was separated into each component. First, in a product separation step 3, β-cyanoethyl acetate having a high boiling point and a high vapor pressure was separated by a distillation unit operation.
Distillation conditions were the following vacuum distillation conditions. The distillation was carried out at a bottom temperature of 125 ° C. to substantially separate the following components. 249 parts of β-cyanoethyl acetate
Separated at 10 ° C./25 mmHg. Next, the high-boiling residue was introduced into the dimer separation step 6 from the conduit 18 and separated by distillation under the following distillation conditions. 1,4-dicyanobutene, 1,4-
156 parts of a linear dimer of dicyanobutadiene and adiponitrile were separated from the top of a vacuum distillation column at 165 to 185 ° C./30 mmHg. Since the residue from the bottom of the column contains a low-polymerized by-product and the ruthenium catalyst used in the reaction step, the residue was treated in the ruthenium catalyst recovery step.

In the product separation step 3, 249 parts of the separated β-cyanoethyl acetate were led out through the conduit 13 and 0.9 part of ruthenium acetate was added through the conduit 14 and introduced into the conversion reaction step 4 to carry out the reaction. The conversion reaction conditions are as follows: after the conversion reaction at a reaction temperature of 170 ° C. and a residence time of 2.0 hours,
114 parts of acrylonitrile and 130 parts of acetic acid were obtained, and were recycled to the dimerization reaction step via the conduit 16. The reaction concentrate is intermittently withdrawn from the bottom of the conversion reaction operation through the conduit 15, and further substantially reacted in the batch separation step 5. The distillate is recovered from the conduit 21 and from the bottom through the conduit 17. The removed residue contains the low-polymerized by-product and the catalyst used in the reaction step (when a catalyst is used).
Processing is performed in the catalyst recovery step to recover the catalyst.

The conversion of β-cyanoethyl acetate was 100% and the selectivity for acrylonitrile was 98%. The formula for calculating the reaction result is as follows:
5

[0054]

(Equation 4)

[0055]

(Equation 5)

The equations for calculating the total reaction results were represented by Equations 6 and 7. The total conversion of acrylonitrile is 12.
4%, and the selectivity of the linear dimer was 83.9%.

[0057]

(Equation 6)

[0058]

(Equation 7)

Example 2 In the attached FIG. 1, ruthenium propionate was introduced into the dimerization reaction step 1 as a catalyst for the following raw material composition and dimerization reaction from the conduit 8 to carry out the reaction. Acrylic nitrile 1
Components of 500 parts, 500 parts of propionic acid and 15 parts of ruthenium propionate are supplied to the dimerization reaction step 1 from a conduit 8 per hour, and the dimerization reaction is carried out under a nitrogen atmosphere with stirring at a reaction temperature of 150 ° C. and a reaction gauge pressure. The reaction was performed at 5 kg / cm ^{2 for a} reaction residence time of 6 hours. The composition of the reaction solution after 6 hours of the reaction was analyzed by gas chromatography. as a result,
The reaction solution contained 1200 parts of unreacted acrylonitrile, 1,
174 parts of a linear dimer of 4-dicyanobutene, 1,4-dicyanobutadiene and adiponitrile, 9 parts of propionitrile, 237 parts of β-cyanoethylpropionate,
It contained 362 parts of propionic acid and 18 parts of a low polymer.

As for the dimerization reaction results, the conversion of acrylonitrile was 20%, the selectivity of linear dimer was 58%, and β
-Selectivity for cyanoethyl propionate was 33%, selectivity for propionitrile was 3%. The calculation formula of the selectivity was represented by the following formulas 1, 2, and 3.

The dimerization reaction product is introduced into the unreacted product separation step 2 through the conduit 9 and unreacted acrylonitrile 1200
Parts, 362 parts of unreacted propionic acid, and 9 parts of by-product propionitrile were separated per hour by distillation. The distillation was performed under the following atmospheric distillation conditions. The temperature at the bottom of the distillation column was 83 to 148 ° C. to substantially separate the following components. Acrylonitrile 78 ° C./760 mmHg Proponitrile 97 ° C./760 mmHg Propionic acid 141 ° C./760 mmHg Acrylonitrile and propionic acid were separated from the reaction product by a distillation unit operation, and the resulting product was recycled to the dimerization reaction step through the conduit 11. In addition, propionitrile, a by-product of the reaction, was separated as a low-boiling component by the above-mentioned distillation unit operation, and was taken out of the system through the conduit 10.

In the product separation step 3 and the dimer separation step 6 in which the high boiling point of the distillation residue in the separation step 2 was led out through the conduit 12, the high boiling point was separated into each component. First, in the product separation step 3, β-cyanoethylpropionate having a high vapor pressure and a high boiling point was separated by a distillation unit operation. Distillation conditions were the following vacuum distillation conditions. The distillation was carried out at a bottom temperature of 125 ° C. to substantially separate the following components. 237 parts of β-cyanoethyl propionate
Separated at 14 ° C./25 mmHg. Next, the high-boiling residue was introduced into the dimer separation step 6 from the conduit 18 and separated by distillation under the following distillation conditions. 1,4-dicyanobutene, 1,4-
174 parts of a linear dimer of dicyanobutadiene and adiponitrile were separated from the top of a vacuum distillation column at 165 to 185 ° C./30 mmHg. Since the high-boiling fraction from the bottom of the column contains the low-polymerized by-product and the ruthenium catalyst used in the reaction step, it was treated in the ruthenium catalyst recovery step.

In the product separation step 3, 237 parts of the separated β-cyanoethyl propionate were led out through a conduit 13, and 4 parts of copper acetate and 2 parts of metallic copper were added to the β-cyanoethyl propionate through a conduit 14, It was introduced into conversion reaction step 4 and reacted. The reaction conditions are as follows:
After conversion at 2.0 ° C. and a residence time of 2.0 hours, 96 parts of acrylonitrile and 134 parts of propionic acid were obtained.
And used in the dimerization reaction step. The reaction concentrate is
From the bottom of the conversion reaction operation, it is intermittently taken out from the conduit 15 and further reacted substantially in the batch separation step 5. The distillate is recovered from the conduit 21 and the residue taken out from the bottom into the residue taken out from the conduit 17. Contains a low polymer produced as a by-product and the catalyst used in the reaction step (when a catalyst is used), and is treated in the catalyst recovery step to recover the catalyst.

The conversion of β-cyanoethylpropionate was such that the conversion was 100% and the selectivity for acrylonitrile was 97%. The formula for calculating the reaction results was represented by Formulas 4 and 5.

Formulas for calculating the total reaction results were represented by Equations 6 and 7. Expressing the overall results, the conversion was 13.6% and the selectivity for the linear dimer was 85%.

[Brief description of the drawings]

FIG. 1 is a process chart according to an embodiment of the production of acrylonitrile dimer.

[Explanation of symbols]

 Reference Signs List 1 dimerization reaction step 2 unreacted substance separation step 3 product separation step 4 conversion reaction step 5 batch separation step 6 dimer separation step 7 to 21

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 253/30 C07C 255/09

Claims (1)

(57) [Claims] 1. A process for producing an acrylonitrile dimer which produces 1,4-dicyanobutene, 1,4-dicyanobutadiene and adiponitrile as linear dimers by dimerization of acrylonitrile, comprising the steps of (a). A dimerization reaction step in which acrylonitrile is introduced into a acrylonitrile dimerization reactor, a carboxylic acid and a ruthenium compound are introduced, and a dimerization reaction is performed to obtain a reaction product containing an acrylonitrile dimer (b). The reaction product in the dimerization reaction step is led, and unreacted acrylonitrile, unreacted carboxylic acid, product propionitrile, carboxylic acid β-cyanoethyl ester and acrylonitrile dimer are separated and separated in the separation step, respectively. Acrylonitrile and carboxylic acid are recycled to the dimerization reaction step and supplied as raw materials,
The separated carboxylic acid β-cyanoethyl ester is supplied to the carboxylic acid β-cyanoethyl ester conversion reaction step in the next step, and a separation step of separating acrylonitrile dimer as a reaction target product generated in the dimerization reaction ( c). The carboxylic acid β-cyanoethyl ester derived from the separation step is subjected to a conversion reaction of the carboxylic acid β-cyanoethyl ester by heating without adding a catalyst or a catalyst, and acrylonitrile and carboxylic acid are obtained. A method for producing an acrylonitrile dimer, comprising a conversion reaction step in which an acid is circulated and supplied to each of the dimerization reaction steps.