JP2005289851A - Preparation method of polycarboxylic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method of a polycarboxylic ester wherein no ammonium sulfate is produced as a by product, by removing ammonia from a reaction system, wherein the ammonia is produced as a by product from a polyvalent nitrile compound having at least two nitrile groups within a molecule. <P>SOLUTION: In the preparation method of the polycarboxylic ester, the polycarboxylic ester is obtained by reacting the polyvalent nitrile compound having at least two nitrile groups within a molecule, water and a lower alcohol in the presence of a catalyst and removing the resulting ammonia from the reaction system. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a method for producing a polyvalent carboxylic acid ester. More specifically, in the present invention, a polyvalent nitrile compound having at least two nitrile groups in the molecule, water, and a lower alcohol are reacted in the presence of a catalyst, and the produced ammonia is removed from the reaction system. It is related with the manufacturing method of polyhydric carboxylic acid ester characterized by obtaining polyhydric carboxylic acid ester by removing.

As a production method for obtaining a polyvalent ester compound from a polyvalent nitrile compound, conventionally, hydrolysis is performed using a strong acid or a strong base compound to produce a polyvalent carboxylic acid, which is then reacted with an alcohol to form a polyvalent ester compound. Although the method of converting is performed, there exists a problem which requires a multistep process.
A method of reacting a nitrile compound and an alcohol using a catalyst and isolating an imino ether intermediate, followed by hydrolysis with a basic catalyst or an acidic catalyst to obtain an ester is known. There is a problem that requires a multi-step process.

  As a method for producing a polyvalent carboxylic acid ester, a method in which a nitrile group is changed to an ester using sulfuric acid in an equivalent amount or more together with water and a lower alcohol is disclosed. For example, in Patent Document 1, 1,2,4-butanetricarboxylic acid triester is obtained by reacting 1,2,4-butanetricarbonitrile with an equivalent amount or more of sulfuric acid in the presence of alcohol and water. . In order to increase the reactivity of the nitrile group, it is necessary to use a strong acid called sulfuric acid. For this reason, by-product ammonia and sulfuric acid react to form a stable sulfuric acid ammonium salt. The problem is that the equivalent amount of sulfuric acid ammonium salt is by-produced, and that it is a waste process. The problem is that it is impossible to recover and reuse ammonia from sulfuric acid ammonium salt because a large amount of energy is required. However, there is a problem that a reactor equipment that can resist corrosion by concentrated sulfuric acid is necessary.

As an esterification method capable of avoiding by-product formation of ammonium salt and allowing it to be liberated out of the system as ammonia, Patent Document 2 discloses that β-- without using sulfuric acid and in the presence of a catalyst such as zinc borate. While removing ammonia produced as a by-product by introducing nitrogen saturated with water together with water and ethanol, ethoxypropionitrile was reacted at 35 atm and 200 ° C. for 3 hours to obtain β-ethoxypropionic acid. A method for conversion to the ethyl ester is disclosed. However, it is possible to efficiently remove ammonia generated from the system by using a polyvalent nitrile compound or by extracting a vapor from the gas phase while introducing a solvent used as a reaction solvent into the reaction solution. It is not described that the yield of is improved.
JP-A-11-116528 Japanese Patent Publication No. 47-12337

  The object of the present invention is to remove the produced ammonia from a polyvalent nitrile compound having at least two or more nitrile groups in the molecule outside the reaction system, thereby avoiding the production of sulfate ammonium salt as a by-product. It is to provide a method for producing a carboxylic acid ester.

The present inventors react a polyvalent nitrile compound having at least two or more nitrile groups in the molecule, water, and a lower alcohol in the presence of a catalyst, and remove generated ammonia from the reaction system. Thus, it was found that a polyvalent carboxylic acid ester characterized by obtaining a polyvalent carboxylic acid ester can be produced, and the present invention has been completed.
That is, the present invention is as follows.
(1) A polyvalent nitrile compound having at least two nitrile groups in the molecule, water, and a lower alcohol are reacted in the presence of a catalyst, and the produced ammonia is removed from the reaction system to A method for producing a polyvalent carboxylic acid ester, comprising obtaining a polyvalent carboxylic acid ester.
(2) The method for producing a polyvalent carboxylic acid ester according to the above (1), wherein the polyvalent nitrile compound contains 1,3,6-hexanetricarbonitrile as a main component.
(3) The polyvalent carboxylic acid according to (1) or (2), wherein the catalyst is one or more compounds selected from a metal selected from copper and zinc, and a salt thereof. Ester production method.
(4) The above description (1) to (3), wherein the removal of ammonia from the system is to extract vapor from the gas phase while introducing a solvent used as a reaction solvent into the reaction solution. This is a method for producing a polyvalent carboxylic acid ester.

  By reacting a polyvalent nitrile compound having at least two or more nitrile groups in the molecule, water, and a lower alcohol in the presence of a catalyst, and removing formed ammonia out of the reaction system, a sulfate ammonium salt It is possible to provide a method for producing a polyvalent carboxylic acid ester without accompanying by-product.

Hereinafter, the present invention will be described in detail.
The polyvalent nitrile compound having at least two or more nitrile groups in the molecule of the present invention is preferably any compound such as an aliphatic nitrile, an aromatic nitrile, a heterocyclic nitrile, and specifically, for example, adiponitrile. , Suberonitrile, sebacononitrile, dodecanedinitrile, butanetricarbonitrile, hexanetricarbonitrile, phthalonitrile, isophthalonitrile, terephthalonitrile, and the like. Adiponitrile, 1,2,4-butanetricarbonitrile, 1,3 , 6-hexanetricarbonitrile, 3-cyanomethyl-1,5-pentanedicarbonitrile and the like are more preferable. These may be a mixture of two or more. Particularly preferred is 1,3,6-hexanetricarbonitrile. Further, in the present invention, since the purification by distillation after converting the polyvalent nitrile compound to the ester compound is easy, a mixture containing at least 30% by mass of these polyvalent nitrile compounds, preferably at least 50% by mass As mentioned above, More preferably, it can also be used preferably also when it is a mixture containing at least 70 mass% or more.

The structure of 1,3,6-hexanetricarbonitrile used in the present invention is represented by the formula (1).
[Chemical 1]
_{NC-CH 2 CH 2 CH-} CH 2 CH 2 CH 2 -CN (1)
｜
CN

The lower alcohol used in the present invention is preferably a linear or branched lower aliphatic alcohol having 1 to 8 carbon atoms, for example, an aliphatic alcohol such as methanol, ethanol, n-propanol, isopropanol, or butanol. A mixture of these may be used.
The amount of alcohol added is at least 1 equivalent, preferably 5 to 20 equivalents, relative to the nitrile group. The amount of water added is at least 1 equivalent, preferably 1.5 to 5 equivalents relative to the nitrile group.
With such addition amounts of alcohol and water, the required reaction rate can be obtained, and the recovery energy of unreacted alcohol and water in distillation of the ester compound after the esterification reaction can be reduced.
It is also preferable to add other solvents other than alcohol and water as long as they do not inhibit the reaction.

The catalyst of the present invention is copper, zinc metal or a salt thereof, preferably copper, zinc metal powder, halide (eg, chloride, bromide, iodide, fluoride), nitrate, hydroxide, acetic acid. Such as salt. The addition amount of the catalyst is 0.01 mol% or more, preferably 0.1 to 100 mol%, more preferably 1 to 30 mol% with respect to the nitrile group.
With such an added amount of catalyst, it is possible to obtain a required reaction rate and reduce the amount of ester compound remaining in the distillation kettle when the ester compound after the esterification reaction is purified by distillation. Well, it can be distilled off at the top of the distillation column.
The catalyst after the reaction is preferably reused for the next reaction after the ester is distilled off from the reaction solution.

The reaction of the present invention is preferably carried out at a temperature of 150 to 250 ° C. and a pressure of 0.5 to 10 MPa.
Under such conditions, it is possible to obtain a required reaction rate and to achieve high selectivity in which side reactions such as decarboxylation are suppressed.
Ammonia is by-produced as the reaction proceeds, and it is necessary to remove this ammonia from the system continuously or intermittently in order to increase the yield and selectivity of the reaction.
As a method for removing generated ammonia, since the boiling point of ammonia is low, it is possible to extract the reaction solution from the reaction system by using an inert gas, and an inert gas that does not participate in the reaction, such as nitrogen. Although it is preferable to introduce the reaction gas into the reaction system by removing air, air, carbon dioxide, etc. from the reaction system, the solvent vapor is extracted from the gas phase while introducing the solvent used as the reaction solvent into the reaction solution. It is a more preferable method to remove the ammonia produced by this process out of the system.

This is because the affinity of the reaction solvent and by-product ammonia is higher than that of the inert gas, and by-product ammonia can be efficiently extracted from the reaction system. It is considered that the tendency of rate-determining ammonia extraction in the case of introduction can be close to that of reaction-determination in the case of solvent vapor extraction.
In addition, if the solvent used as a reaction solvent is not introduced into the reaction solution when removing the reaction solvent vapor out of the system in order to remove by-product ammonia from the reaction solution, the amount of vapor extraction increases. First, it is necessary to charge a large amount of reaction solvent to the charged trinitrile, so that a reactor with a large size must be used, and 2) the amount of solvent is reduced, thereby reducing the amount of solvent in the reaction solution. In order to improve the concentration of the trinitrile substrate and the catalyst and raise concerns about their precipitation, etc., it is necessary to supplement the reaction solvent with the amount of extracted steam, and the solvent used as the reaction solvent is introduced into the reaction solution. .

Although the solvent is withdrawn as a vapor, in the reaction temperature condition of the present invention, the lower aliphatic alcohol that is the reaction solvent or the lower alcohol containing water is heated to a temperature higher than the boiling point at normal pressure. The lower aliphatic alcohol which is a reaction solvent or the lower alcohol containing water has a vapor pressure sufficient for extraction and can be easily distilled as a vapor.
It is also preferable that the extracted reaction solvent vapor is provided with a distillation column and the solvent vapor is extracted after concentrating the ammonia concentration. It is also preferable to combine these methods.
Distilled ammonia can be effectively used as a resource in industry through treatments such as concentration and purification by known methods.

  By the production method of the present invention, a polyvalent nitrile compound having at least two or more nitrile groups in the molecule, water, and a lower alcohol are reacted in the presence of a catalyst, and the produced ammonia is removed from the reaction system. This makes it possible to obtain a polyvalent carboxylic acid ester without the by-product of a sulfuric ammonium salt, which is industrially useful. The esters of 1,3,6-hexanetricarboxylic acid obtained by the production method of the present invention are organic synthetic intermediates, alkyd resins, polyamides, polyimides, polyester resins, plasticizer raw materials, etc., powder paints, polyester fibers and fibers It is used in the field of improving agents and is industrially useful.

Hereinafter, the present invention will be described specifically by way of examples.
The measuring method used in the present invention is as follows.
[Measurement method of trinitrile]
The purity of the trinitrile mixture is determined by measurement by gas chromatography (FID) and gel permeation chromatography (hereinafter referred to as GPC). The content of the high molecular weight polymer of tetramer or higher of acrylonitrile contained in the trinitrile mixture is determined by GPC. The hue is obtained from UV measurement by a transmission method. Each measurement is performed with the following apparatus and conditions.

<Gas chromatography measurement method>
Equipment: GC-14B manufactured by Shimadzu Corporation
Column: GL Science Inc. Capillary column
TC-1 (0.25 mm ID, length 30 m)
Carrier gas: He
Detection: FID
Column temperature condition: 120 ° C. to 200 ° C. at 20 ° C./min,
After holding for 5 minutes, the temperature was raised to 250 ° C. at 10 ° C./min and held for 10 minutes.
Sample dissolution solvent: acetone

<GPC measurement method>
Analysis is performed by dissolving 2.0 mg of each compound with 2.0 g of tetrahydrofuran, filtering through a 0.5 μm filter, and developing and detecting under the following conditions.
Measuring device: HLC-8120GPC manufactured by Tosoh Corporation
Detector: RI
Developing solution: Tetrahydrofuran Developing solution flow rate: 1.0 mL / min
Column: One TSKgel (trademark) GMH _HR- N manufactured by Tosoh Corporation and two G1000H _XL installed in series Column temperature: 40 ° C.

[Measurement method of triester]
Measurement was performed in the same manner as in the above <Gas chromatography measurement method>.

"Production Example 1"
In the single electrolytic cell, a lead alloy having an energization surface of 1 cm × 90 cm was used as a cathode, carbon steel having the same energization surface was used as an anode, and the anode and the cathode were kept at an interval of 2 mm. The electrolytic solution forms an emulsion with 10 parts by mass of an oil phase and 90 parts by mass of an aqueous phase. The composition of the aqueous phase is 2.0% by mass of acrylonitrile, 10% by mass of K ₂ HPO ₄ , and K ₂ B ₄ O. _{7 An} aqueous solution containing 3% by mass, 0.3% by mass of ethyltributylammonium ethyl sulfate, and some adiponitrile, propionitrile, and 1,3,6-hexanecarbonitrile. The pH was adjusted to 8 with phosphoric acid. did. The oil phase is in equilibrium with the aqueous phase, and its composition is 28% by mass of acrylonitrile and 62% by mass of adiponitrile.

This emulsion was circulated and supplied to a single electrolytic cell so that the linear velocity was 1 m / sec on the electrolysis surface, and electrolysis was performed at a current density of 20 A / dm ² and 50 ° C. Simultaneously with the start of electrolysis, the iminodiacetic acid type chelate resin (Lewatit TP207, Trademark) K ⁺ type 200CC in which the aqueous phase of the emulsion sent from the electrolyte tank to the oil / water separator was kept at 50 ° C. Then, the treatment was started at a rate of 6 CC / AH and circulated to the electrolyte tank.
At the same time, the oil phase was continuously extracted, acrylonitrile and water were continuously added so as to maintain the electrolyte solution composition, and ethyltributylammonium ethylsulfuric acid extracted after being dissolved in the oil phase was added as needed.

As a result of conducting electrolysis for 2000 hours in this way, the initial electrolysis voltage was stable at 3.9 V, the hydrogen contained in the generated gas was 0.16 vol% at the end of electrolysis, and the consumption rate of the cathode was 0.8. The anode consumption rate was 21 mg / AH, 0.23 mg / AH, and there was no uneven anode corrosion. The yield of adiponitrile relative to the consumed acrylonitrile was 90%, and the yield of 1,3,6-hexanetricarbonitrile was 7.5%.
Next, the oil phase obtained by the above electrolysis was collected, subjected to water extraction treatment, acrylonitrile, propionitrile and water were distilled off, and then adiponitrile was removed by vacuum distillation. The adiponitrile in this residue was 11.5% by mass.

The removal of adiponitrile from this residual liquid was carried out by batch distillation of a fraction containing adiponitrile as a main component using a vacuum-coated distillation column having a diameter of 32 mmφ and 5 actual stages, and a top temperature of 120 mm at a vacuum of 2.0 mmHg. A distillation residue was obtained by first-cutting a fraction up to ˜210 ° C.
This distillation residue was 4.0% by mass of adiponitrile, 84.5% by mass of 1,3,6-hexanetricarbonitrile, 5.0% by mass of 3-cyanomethyl-1,5-dicyanopentane, and high molecular weight product 6. It was a brown colored nitrile mixture mainly composed of 5% by mass of a trinitrile compound.

"Example 1"
64.0 g of the brown nitrile mixture of Production Example 1, 5.4 g of zinc nitrate hexahydrate, 384 g of methanol and 22 g of water were charged into an autoclave equipped with a stirrer and reacted at a reaction temperature of 200 ° C. for 8 hours. Nitrogen gas saturated with water at room temperature was introduced at a rate of 1 L / min, and ammonia produced was continuously removed from the pressure holding device while maintaining the reaction pressure at 6 MPa.
After cooling to room temperature, the reaction solution was concentrated to distill off methanol and water. The obtained concentrated liquid was put into a 200 mL reaction flask, and distilled through a column filled with SUS 6 mmφ × 5 mm Dixon packing 5 cm long. Under a pressure of 6 mmHg and a distillation temperature of 160 ° C., 12.3 g (yield 14%) of a fraction of 1,3,6-hexanetricarboxylic acid trimethyl ester was obtained. As a result of analysis by gas chromatography, the purity was 99.1%.
In this way, a polyvalent carboxylic acid ester was obtained without the by-product of a sulfuric ammonium salt.

"Example 2"
80.5 g of the brown nitrile mixture of Production Example 1, 44.5 g of zinc nitrate hexahydrate, 24.3 g of water, and 405 g of methanol were charged into a 1.2 L-autoclave with a stirrer, and after nitrogen substitution, the reaction temperature was raised to 200 ° C. Warm up. After reacting at 200 ° C. for 1 hour, a mixed solvent of 95% by mass methanol-5% by mass water was heated and introduced at the bottom of the autoclave at 200 g / hr, and the vapor was removed from the gas phase at 200 g / hr. The reaction was stopped 4 hours after the start of the introduction of the mixed solvent, and after cooling, the contents were taken out, the reaction solution was concentrated, and methanol and water were distilled off. The obtained concentrated liquid was put into a 200 mL reaction flask, and distilled through a column filled with SUS 6 mmφ × 5 mm Dixon packing 5 cm long. 46 g (yield 42%) of 1,3,6-hexanetricarboxylic acid trimethyl ester was obtained at a distillation temperature of 160 ° C. under a pressure of 6 mmHg. As a result of analysis by gas chromatography, the purity was 99.0%.
By distilling ammonia out of the system together with the reaction solvent, the conversion rate to the ester can be improved as compared with ammonia distilling by introducing an inert gas. In this way, a polyvalent carboxylic acid ester was obtained without the by-product of a sulfuric ammonium salt.

"Example 3"
In the implementation of the esterification step of Example 1, 384 g of methanol and 22 g of water were charged into an autoclave equipped with a stirrer to the distillation residue obtained by distilling off the generated 1,3,6-hexanetricarboxylic acid trimethyl ester. The reaction was carried out at 200 ° C. for 8 hours. Nitrogen gas saturated with water at room temperature was introduced at a rate of 1 L / min, and ammonia produced was continuously removed from the pressure holding device while maintaining the reaction pressure at 6 MPa.
After cooling to room temperature, the reaction solution was concentrated to distill off methanol and water. The obtained concentrated liquid was put into a 200 mL reaction flask, and distilled through a column filled with SUS 6 mmφ × 5 mm Dixon packing 5 cm long. A fraction of 10.3 g of 1,3,6-hexanetricarboxylic acid trimethyl ester was obtained at a distillation temperature of 160 ° C. under a pressure of 6 mmHg (yield 12%). As a result of analysis by gas chromatography, the purity was 98.7%.
Thus, the distillation residue remaining when the ester is purified by distillation can be recycled for the next esterification reaction.

"Comparative Example 1"
In the esterification step of Example 2, after raising the temperature to 200 ° C., the reaction was allowed to proceed for 2 hours without introducing a mixed solvent of 95% by mass methanol-5% by mass water and withdrawing vapor from the gas phase. . As a result of extracting a part of the inner solution from the sampling line and analyzing it by gas chromatography, it was not possible to detect the formation of triesters.
Thus, in order to obtain a triester, it was necessary to extract ammonia.

  By the production method of the present invention, a polyvalent nitrile compound having at least two nitrile groups in the molecule, water, and a lower alcohol are reacted in the presence of a catalyst, and the produced ammonia is removed from the reaction system. By doing so, it becomes possible to obtain a polyvalent carboxylic acid ester without the by-product of a sulfuric ammonium salt, which is industrially useful. The esters of 1,3,6-hexanetricarboxylic acid obtained by the production method of the present invention are organic synthetic intermediates, alkyd resins, polyamides, polyimides, polyester resins, plasticizer raw materials, etc., powder paints, polyester fibers and fibers It is used in the field of improving agents and is industrially useful.

Claims (4)

By reacting a polyvalent nitrile compound having at least two or more nitrile groups in the molecule, water, and a lower alcohol in the presence of a catalyst, and removing generated ammonia from the reaction system, a polyvalent carboxylic acid is obtained. A method for producing a polyvalent carboxylic acid ester, comprising obtaining an ester. 2. The method for producing a polyvalent carboxylic acid ester according to claim 1, wherein the polyvalent nitrile compound contains 1,3,6-hexanetricarbonitrile as a main component. The method for producing a polyvalent carboxylic acid ester according to claim 1 or 2, wherein the catalyst is one or two or more compounds selected from a metal selected from copper and zinc, and a salt thereof. The polyvalent carboxylic acid ester according to any one of claims 1 to 3, wherein the ammonia is removed from the system by removing vapor from the gas phase while introducing a solvent used as a reaction solvent into the reaction solution. Production method.