WO2016068062A1

WO2016068062A1 - Method for producing acetonitrile

Info

Publication number: WO2016068062A1
Application number: PCT/JP2015/080064
Authority: WO
Inventors: 健啓飯塚; 義和高松
Original assignee: 旭化成ケミカルズ株式会社
Priority date: 2014-10-31
Filing date: 2015-10-26
Publication date: 2016-05-06
Also published as: JPWO2016068062A1; CN107074749A; CN107074749B; JP6391703B2

Abstract

A method for producing acetonitrile by performing a gas-phase reaction step for obtaining water-containing crude acetonitrile by subjecting acetic acid and ammonia to a gas-phase reaction while in the presence of a catalyst containing a solid acid catalyst, and a refining step for obtaining an acetonitrile product by refining the water-containing crude acetonitrile, wherein the water content in the water-containing crude acetonitrile is 47 mass% or more relative to 100 mass% of the water-containing crude acetonitrile, and the toluene content therein is 1 mass ppm or higher relative to 100 mass% of the acetonitrile.

Description

Acetonitrile production method

The present invention relates to a method for producing acetonitrile.

Acetonitrile is used as a solvent for chemical reaction, particularly a solvent used for synthesis and purification of pharmaceutical intermediates, a mobile phase solvent for high performance liquid chromatography, and the like. Recently, acetonitrile is also used as a solvent for DNA synthesis and a solvent for purification, a solvent for organic EL material synthesis, and a solvent for washing electronic components.

Particularly, acetonitrile used as a solvent for high performance liquid chromatography needs to have no ultraviolet absorption at a wavelength of 200 to 400 nm so that the ultraviolet absorption does not become a background. Conventionally, such acetonitrile has been obtained by purifying crude acetonitrile.

At present, commercially available acetonitrile is mainly crude acetonitrile obtained as a by-product in the production of acrylonitrile or methacrylonitrile by catalytic ammoxidation reaction of propylene or isobutene, ammonia and oxygen. , Recovered and purified.

On the other hand, as a method for directly producing acetonitrile, a method for producing acetonitrile by reacting acetic acid and ammonia in the gas phase in the presence of a catalyst is also known, and a method for producing crude acetonitrile, which replaces the above-mentioned method for producing crude acetonitrile as a by-product, is also known. (See, for example, Patent Documents 1 and 2). The reaction formula of this production method is as follows. The crude acetonitrile obtained by this reaction may include produced acetonitrile, unreacted acetic acid and ammonia, and produced water.
CH ₃ COOH + NH ₃ → CH ₃ CN + 2H ₂ O

For example, in Patent Document 1, in a method for producing acetonitrile by reacting acetic acid and ammonia in the gas phase in the presence of a catalyst, the reaction product gas is brought into contact with a strong acid to recover acetonitrile as an aqueous solution. A method is disclosed in which ammonia forms a salt with a strong acid to prevent the formation and precipitation of ammonium carbonate. Therefore, in Patent Document 1, it is presumed that carbon dioxide and acetone by-products due to acetic acid decarboxylation reaction represented by the following formula are problematic, but there is no description of by-products produced by the reaction, and high purity. There are no problems in purifying to acetonitrile.
2CH ₃ COOH → CH ₃ COCH ₃ + CO ₂ + H ₂ O

Patent Document 2 discloses that in a method for producing nitrile from carboxylic acid and ammonia using various zeolite catalysts, the molar ratio of ammonia / carboxylic acid is set to 1/1 to 10/1, and H-ZSM-5 is used as the catalyst. , NaY, a zeolite such as H-mordenite, SAPO-40, silica alumina, etc., a reaction temperature of 300 to 500 ° C., and a WHSV of liquid product basis of 0.4 h ⁻¹ are disclosed. According to the example of Patent Document 2, although the yield is disclosed as 100%, the amount of catalyst is large, and it is not assumed to be industrially implemented. Moreover, there is no description about a trace by-product substance, and the problem at the time of refine | purifying to highly purified acetonitrile is not shown.

Japanese Patent No. 51733897 Indian Patent No. 187529

The present inventors produced acetonitrile by a gas phase reaction of acetic acid and ammonia by the method described in the prior art document in the presence of a solid acid catalyst having excellent reaction results and catalyst life. As a result, a phenomenon that is not mentioned at all in the conventional method, that is, hydrated crude acetonitrile to be produced, acetone, methyl ethyl ketone, ethylene, propylene, butene; nitrile compounds such as acrylonitrile and propionitrile; benzene, toluene, xylene, etc. It was found that aromatic compounds of the above; pyridines and the like are contained as trace by-product impurities.

Among these impurities, aromatic compounds such as toluene are known to be substances that greatly affect ultraviolet absorption in the wavelength region of 200 nm. Further, among aromatic compounds, toluene having a boiling point with acetonitrile and estimated to cause distillation separation from azeotropic composition formation has a wavelength of 200 nm even when only 1.0 mass ppm is present with respect to acetonitrile. In this case, the absorbance of UV absorption increases at 0.3 or higher. Therefore, even if it is a very small amount, the by-product of toluene and its purification become a major issue for acetonitrile product quality.

However, the methods described in Patent Documents 1 and 2 have not been studied at all with respect to trace by-product impurities and do not pose such a problem. For example, Patent Document 1 has proposed a method in which an acetic acid raw material is dissolved in an aromatic hydrocarbon and supplied as a solvent.

In addition, in order to purify the hydrated crude acetonitrile obtained by the gas phase reaction into high-purity acetonitrile used in the above-described solvent and cleaning agent, it is necessary to produce it through a plurality of purification steps. Therefore, if the gas phase reaction step is carried out without controlling the amount of water, the purification step becomes complicated, and there is a problem that the cost is greatly increased due to an increase in energy consumption used for purification.

The present invention has been made in view of the above-mentioned problems, and the energy consumption used for the purification of hydrous crude acetonitrile obtained by the gas phase reaction of acetic acid and ammonia using a solid acid catalyst is small, and the purification equipment and purification It aims at providing the manufacturing method of acetonitrile which a process is also simple. In addition, acetonitrile thus obtained is a solvent for chemical reaction, particularly a solvent for synthesizing and purifying pharmaceutical intermediates, or a mobile phase solvent for high-performance liquid chromatography, a solvent for DNA synthesis, and a solvent for purification. It can be suitably used as a solvent for synthesizing organic EL materials or a cleaning solvent for electronic components.

As a result of intensive investigations to solve the above problems, the present inventors have solved the above problems by using a predetermined catalyst and controlling the water content of hydrous crude acetonitrile in the gas phase reaction. The present inventors have found that this can be done and have completed the present invention.

That is, the present invention is as follows.
[1]
A gas phase reaction step in which acetic acid and ammonia are subjected to a gas phase reaction in the presence of a solid acid catalyst to obtain hydrous crude acetonitrile;
Purifying the water-containing crude acetonitrile to obtain a product acetonitrile,
In the hydrous crude acetonitrile,
The water content is 47% by mass or more with respect to 100% by mass of the hydrous crude acetonitrile, and the toluene content is 1 mass ppm or more with respect to 100% by mass of acetonitrile.
A method for producing acetonitrile.
[2]
The method for producing acetonitrile according to [1] above, wherein the solid acid catalyst is an intermediate pore size zeolite.
[3]
The purification step comprises
Separating the ammonia from the hydrated crude acetonitrile to obtain a crude acetonitrile; and
The method for producing acetonitrile according to [1] or [2] above, comprising a dehydration step of separating water from the crude acetonitrile to obtain dehydrated acetonitrile.
[4]
The method for producing acetonitrile according to any one of [1] to [3] above, wherein the toluene content in the product acetonitrile is less than 1.0 mass ppm with respect to 100 mass% of acetonitrile.
[5]
The method for producing acetonitrile according to any one of [1] to [4] above, wherein the acetic acid is an aqueous solution containing 10 to 40% by mass of water.
[6]
The method for producing acetonitrile according to any one of [1] to [5] above, wherein, in the gas phase reaction step, WHSV is 0.5 to 20 h ⁻¹ .
[7]
The method for producing acetonitrile according to any one of items [2] to [6], wherein the intermediate pore size zeolite comprises ZSM-5 type zeolite.
[8]
Acetonitrile produced by the method for producing acetonitrile according to any one of [1] to [7] above.

According to the present invention, there is provided a method for producing acetonitrile in which the amount of energy used for purification of hydrous crude acetonitrile obtained by gas phase reaction of acetic acid and ammonia using a solid acid catalyst is small, and the purification equipment and the purification process are simple. Can be provided. In addition, acetonitrile thus obtained is a solvent for chemical reaction, particularly a solvent for synthesizing and purifying pharmaceutical intermediates, or a mobile phase solvent for high-performance liquid chromatography, a solvent for DNA synthesis, and a solvent for purification. It can be suitably used as a solvent for synthesizing organic EL materials or a cleaning solvent for electronic components.

Hereinafter, the embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications are possible without departing from the scope of the present invention. It is. Note that the expression “A to B” in a numerical range indicates a numerical range of “A or more and B or less” unless otherwise specified.

[Method for producing acetonitrile]
The method for producing acetonitrile according to the present embodiment comprises a gas phase reaction step of obtaining acetic acid and ammonia in a gas phase reaction in the presence of a solid acid catalyst to obtain hydrous crude acetonitrile, and purifying the hydrous crude acetonitrile to obtain product acetonitrile. And a purification step to obtain, wherein the water content of the water-containing crude acetonitrile is 47% by mass or more with respect to 100% by mass of the water-containing crude acetonitrile, and the content of toluene is 100% by mass of acetonitrile. 1 mass ppm or more.

According to this embodiment, by using a solid acid catalyst, it is possible to perform a gas phase reaction with high activity and high yield and stably over a long period of time. In addition, since toluene, which is a by-product in the system using the catalyst, can be easily removed in the purification process, high-purity acetonitrile can be obtained with a small amount of energy consumption and simple purification equipment and purification process. Obtainable.

[Gas phase reaction process]
The gas phase reaction step is a step in which acetic acid and ammonia are reacted in the gas phase in the presence of a solid acid catalyst to obtain hydrous crude acetonitrile. Specifically, it can be carried out by bringing gas-phase contact between acetic acid, ammonia and a catalyst at a predetermined temperature in a reactor filled with a solid acid catalyst, but is not particularly limited.

(material)
Acetic acid and ammonia as raw materials for the gas phase reaction are not particularly limited, and those produced from various chemical synthesis methods can be used. Acetic acid and ammonia are not necessarily highly pure, and may be industrial grade. For example, acetic acid aqueous solution generally used industrially can be used as acetic acid.

The water content of the acetic acid aqueous solution is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 18% by mass or more. Moreover, the content of water in the acetic acid aqueous solution is preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less. When the content of water in the acetic acid aqueous solution is 10% by mass or more, the separation efficiency of impurities (such as toluene) from the hydrated crude acetonitrile tends to be further improved. Moreover, when the content of water in the acetic acid aqueous solution is 40% by mass or more, the gas phase reaction efficiency is further improved, and the energy efficiency regarding the separation of water from hydrous crude acetonitrile or crude acetonitrile tends to be further improved. In addition, although the melting point of acetic acid having a moisture content of 0% by mass is about 17 ° C., the melting point of acetic acid having a moisture content of 40% by mass is reduced to about −27 ° C. It is advantageous if it is carried out automatically. The water content of acetic acid means the weight fraction of water contained in acetic acid based on JIS-K-1351.

(Solid acid catalyst)
The solid acid catalyst used in the present embodiment is not particularly limited as long as it is a solid having a Bronsted acid point, and a conventionally known catalyst is used. For example, clay minerals such as kaolin; What impregnated and carried acids, such as sulfuric acid and phosphoric acid: Acid type ion exchange resin; Zeolites, such as a medium pore diameter zeolite; Active aluminas; Aluminum phosphates; Mesoporous silica alumina etc. are mentioned.

Among these solid acid catalysts, zeolites such as a catalyst containing an intermediate pore size zeolite and activated aluminas are preferable, and a catalyst containing an intermediate pore size zeolite is more preferable. By using such a solid acid catalyst, the effect of this embodiment can be exhibited more effectively.

(Catalyst containing medium pore size zeolite)
The catalyst containing the intermediate pore size zeolite will be described below. “Zeolite” is a general term for crystalline porous aluminosilicates. Zeolite has (SiO ₄ ) ^4- and (AlO ₄ ) ^5- having a tetrahedral structure as basic structural units, and these are three-dimensionally connected to form crystals. Moreover, metallosilicates in which trivalent or tetravalent elements other than aluminum ions are incorporated in the silicate skeleton are also included in the zeolite. Zeolite is diverse in structure and composition, so it is classified differently from various viewpoints such as structure code, formation process, mineralogy, pore size, pore dimension, aluminum concentration, other cation concentration and structural elements. (See Zeolite Science and Engineering, Yoshio Ono and Kenaki Yashima / Edition, Kodansha Scientific). Various framework type codes are defined by the International Zeolite Society (IZA).

(Intermediate pore size zeolite)
Here, the “medium pore diameter zeolite” means a pore diameter range of a small pore diameter zeolite represented by A-type zeolite and a large pore diameter zeolite represented by mordenite, X-type or Y-type zeolite. Means a zeolite having a pore diameter in the middle of the above-mentioned pore diameter, and means, for example, a zeolite having a 10-membered oxygen ring in its crystal structure. The pore diameter of the medium pore diameter zeolite is preferably 5 to 6.5 mm.

(Structure of intermediate pore size zeolite)
The structure of the intermediate pore diameter zeolite is not particularly limited. For example, in the framework type code (FTC) defined by the International Society of Zeolite (IZA), AEL, EUO, FER, HEU, MEL, MFI, NES, TON, And a structure represented by WEI or the like. Among these, an intermediate pore size zeolite having a structure represented by MFI is preferable. Specific examples of the intermediate pore size zeolite having a structure represented by MFI include ZSM-5 type zeolite. By using such an intermediate pore size zeolite, the catalytic activity tends to be further improved.

In addition, as an intermediate pore size zeolite, a metallo in which a part of aluminum (Al) atoms constituting the zeolite skeleton is substituted with an element such as gallium (Ga), iron (Fe), boron (B), chromium (Cr), etc. It is also possible to use aluminosilicates or metallosilicates in which all the aluminum atoms constituting the zeolite skeleton are substituted with the above elements.

(Silica / alumina ratio)
The silica / alumina ratio (molar ratio, the same shall apply hereinafter) of the medium pore diameter zeolite is preferably 20 to 1000, more preferably 20 to 500, and still more preferably 20 to 300. When the silica / alumina ratio is 20 or more, the stability as a catalyst tends to be further improved. Further, when the silica / alumina ratio is within the above range, the catalytic activity tends to be further improved. The silica / alumina ratio of the zeolite can be determined by a known method, for example, by completely dissolving the zeolite in an alkaline aqueous solution and analyzing the resulting solution by plasma emission spectroscopy. The silica / alumina ratio in the case where the intermediate pore diameter zeolite is a metalloaluminosilicate or a metallosilicate is obtained by converting the amount of aluminum atoms substituted by the above elements into the number of moles of Al ₂ O ₃ (alumina). Calculated.

(Method for preparing catalyst containing intermediate pore size zeolite)
A method for preparing the catalyst containing the intermediate pore size zeolite is not particularly limited, and a known method can be used. The intermediate pore size zeolite can be changed in composition after hydrothermal synthesis by modification such as ion exchange, dealumination treatment, impregnation and loading. In the present embodiment, it is preferable that at least a part of the ion exchange site of the intermediate pore size zeolite is exchanged with protons. By using a catalyst containing such an intermediate pore size zeolite, the catalytic activity tends to be further improved.

(Method of forming catalyst containing intermediate pore size zeolite)
The shape of the catalyst containing the intermediate pore diameter zeolite may be powdery or granular, and can be formed into a molded body that has been molded into a suitable shape according to a process such as a gas phase reaction step. The method for forming the catalyst containing the intermediate pore size zeolite is not particularly limited, and a known method can be used. Specifically, a method of spray drying a catalyst precursor, a method of compression molding a catalyst component, and a method of extrusion molding of a catalyst component can be mentioned. In these molding methods, a binder or a diluent for molding (matrix) may be used. The binder and the diluent for molding are not particularly limited, and examples thereof include porous refractory inorganic oxides such as alumina, silica, zirconia, titania, kaolin, diatomaceous earth, and clay. These may be used individually by 1 type, or may use 2 or more types together. Commercially available binders and diluents for molding may be used, or they may be synthesized by a conventional method. When the catalyst containing the intermediate pore size zeolite is molded using a binder, the mass ratio of the intermediate pore size zeolite / (binder and diluent for molding) is preferably 10/90 to 90/10, and more It is preferably 20/80 to 80/20.

(Activated aluminas)
Next, the activated alumina will be described below. Although it does not specifically limit as activated alumina, For example, commercially available activated alumina is mentioned. The shape of the activated alumina may be powdery or granular, and can be made suitable according to a process such as a gas phase reaction step.

(Reactor)
The reactor used in the gas phase reaction step is not particularly limited, and examples thereof include a fixed bed reactor, a fluidized bed reactor, and a moving bed reactor. As the reaction system, either a batch system or a flow system can be used, but a flow system is preferable in consideration of productivity. Note that the description in the present specification does not preclude changes in reaction conditions that can be easily adjusted by those skilled in the art.

When filling the reactor with the solid acid catalyst, in order to keep the temperature distribution of the catalyst layer small, particulates inert to the reaction, such as quartz sand and ceramic balls, may be mixed with the catalyst and packed. . In this case, there is no particular limitation on the amount of granular material inert to the reaction such as quartz sand. In addition, it is preferable that this granular material is a particle size comparable as a catalyst from a uniform mixing property with a catalyst.

In addition, since the gas phase reaction is an endothermic reaction, it is preferable to provide a heat supply mechanism in order to control the desired reaction temperature. For example, when it is industrially carried out on a fixed bed, it is conceivable to employ a multi-tubular shell and tube reactor. Further, the reaction substrate (reaction raw material) may be divided and supplied to the reactor for the purpose of dispersing the endotherm accompanying the reaction.

(Molar ratio of ammonia / acetic acid)
In the gas phase reaction step, the molar ratio of ammonia / acetic acid supplied to the reactor is preferably 1.0 or more, more preferably 1.0 to 1.5, and still more preferably 1.1 to 1. 5. When the ammonia / acetic acid molar ratio is 1.0 or more, the reaction efficiency tends to be further improved. Further, when the ammonia / acetic acid molar ratio is 1.5 or less, the energy consumption for separating and removing ammonia from hydrous crude acetonitrile described later tends to be further reduced in the purification step.

(WHSV (weight space velocity))
WHSV (weight space velocity) is the weight of the raw material flowing per hour with respect to the weight of the catalyst charged in the reactor, and can be determined by the following equation.
WHSV [h ⁻¹ ] = feed weight per hour [g / h] / catalyst filling weight [g]

Here, the “catalyst filling weight” means the filling weight of the solid acid catalyst into the reactor in the present embodiment. When the solid acid catalyst is a molded body, the binder or molding material constituting the molded body is used. It is a reactor filling weight of the whole molded object containing a diluent. In addition, the above-mentioned inert particulate matter is not included in the catalyst filling weight. Here, the “raw material weight” is the total weight of the raw material flowing to the reactor, and the “raw material” includes the diluent described later in addition to acetic acid or an acetic acid aqueous solution and ammonia as raw materials in the present embodiment. It is.

WHSV can be adjusted as appropriate in consideration of productivity, catalyst life, and reaction yield. For example, the WHSV in the vapor phase reaction step, preferably 0.5 ~ ^{50h -1,} more preferably 0.5 ~ ^{20h -1,} more preferably from 0.5 ~ ^{10h -1.} When WHSV is 0.5 h ⁻¹ or more, the amount of catalyst necessary to obtain a constant production amount can be reduced, the reactor can be made compact, and byproducts of undesirable by-products such as acetone and toluene can be reduced. There is a tendency that the raw material can be suppressed and the purification load on high-purity acetonitrile can be further reduced. Further, when WHSV is 50 h ⁻¹ or less, the conversion of acetic acid tends to be further improved, and the selectivity of acetonitrile tends to be further improved.

(Diluent)
In the gas phase reaction step, a diluent may be used in addition to acetic acid and ammonia. The diluent is not particularly limited, and examples thereof include helium, argon, nitrogen, water, paraffinic hydrocarbon gases, and Examples thereof include gases inert to the reaction, such as a mixture thereof. Of these, nitrogen and water are preferred. As the diluent, impurities contained in the reaction raw material may be used as they are, or a separately prepared diluent may be mixed with the reaction raw material and used. The diluent may be mixed with the reaction raw material before entering the reactor, or may be supplied to the reactor separately from the reaction raw material. In addition, for the purpose of adjusting the water content of hydrous crude acetonitrile described later, water may be mixed with hydrous crude acetonitrile produced by a gas phase reaction of acetic acid and ammonia as a diluent for purification.

(Reaction temperature)
The reaction temperature of the gas phase reaction is preferably 250 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 350 ° C. or higher. The reaction temperature of the gas phase reaction is preferably 600 ° C. or lower, more preferably 550 ° C. or lower, and further preferably 520 ° C. or lower. When the reaction temperature is 250 ° C. or higher, the reaction yield tends to be further improved. Moreover, when reaction temperature is 600 degrees C or less, it exists in the tendency which can suppress the production | generation of a by-product more and can also suppress deterioration of a catalyst. In addition, since the gas phase reaction in this embodiment is a dehydration reaction (endothermic reaction), it is preferable to install a heat source in the reactor in order to control the inside of the reactor to a desired reaction temperature. For example, when a gas phase reaction is industrially carried out in a fixed bed reactor, it is conceivable to use a multi-tubular shell and tube reactor.

(Reaction pressure)
The reaction pressure of the gas phase reaction is advantageously low in terms of the reaction equilibrium of the gas phase reaction of the present embodiment, but the reaction rate increases if the pressure is high. Accordingly, it is a balance between the equilibrium conversion rate and the reaction rate, preferably normal pressure to 0.3 MPaG (gauge pressure, the same shall apply hereinafter), more preferably 0.03 to 0.25 MPaG, and still more preferably 0. .05 to 0.20 MPaG.

(Hydrous crude acetonitrile)
“Water-containing crude acetonitrile” includes 10% by mass to 70% by mass of acetonitrile and 30% by mass to 90% by mass of water, in addition to 0% by mass to 60% by mass of impurities. Is a composition that may comprise Examples of the impurities include, but are not limited to, ammonia, acetic acid, acetamide, and acetone.

The content of water in the hydrous crude acetonitrile is preferably 47% by mass or more, more preferably 50% by mass or more, and further preferably 52% by mass or more with respect to 100% by mass of the hydrous crude acetonitrile. The water content in the hydrous crude acetonitrile is preferably 90% by mass or less, more preferably 60% by mass or less, and further preferably 58% by mass or less, with respect to 100% by mass of the hydrous crude acetonitrile. is there. When the content of water in the hydrous crude acetonitrile is 47% by mass or more, in the purification step described later, aromatic compounds such as hydrous crude acetonitrile or toluene in the crude acetonitrile tend to be more efficiently removed simultaneously with ammonia. is there. Moreover, when the content of water in the hydrated crude acetonitrile is 90% by mass or less, the hydrated crude acetonitrile or water in the crude acetonitrile tends to be more efficiently removed in the purification step described later. The water content in the hydrous crude acetonitrile may be adjusted by mixing water as a diluent with respect to the hydrous crude acetonitrile obtained by the gas phase reaction. In this case, the content of water in the hydrous crude acetonitrile is determined by taking into account the weight of the mixed water.

The content of toluene in the hydrous crude acetonitrile obtained by the gas phase reaction is influenced by the reaction conditions, but is preferably 1 to 1000 ppm by mass, more preferably 1 to 100% by mass of acetonitrile. It is ˜500 mass ppm, more preferably 1 to 100 mass ppm. Even if the content of toluene in the hydrous crude acetonitrile is within the above range, the production method of the present embodiment can sufficiently remove toluene. In addition, content of toluene in hydrous crude acetonitrile can be measured by the method as described in an Example.

[Purification process]
The purification step is a step of purifying hydrous crude acetonitrile to obtain product acetonitrile. The step included in the purification step is not particularly limited as long as it is configured to remove water, ammonia and other impurities from the hydrous crude acetonitrile, and examples thereof include a concentration step and a dehydration step.

(Concentration process)
The concentration step is a step in which ammonia is separated from hydrous crude acetonitrile to obtain crude acetonitrile. Although it does not specifically limit as a separation method of ammonia, For example, the method of using a distillation column is mentioned. Here, “crude acetonitrile” is acetonitrile obtained by removing most of the ammonia from water-containing crude acetonitrile and concentrating, and mainly contains 50% by mass or more and less than 75% by mass of acetonitrile, and 25% by mass or more and 50% by mass. % Or less water and other impurities.

By carrying out the concentration step before the dehydration step described later, toluene in the water-containing crude acetonitrile can be efficiently removed simultaneously with ammonia. In particular, as the content of water in the hydrous crude acetonitrile used for purification increases, this effect tends to be improved.

(Dehydration process)
The dehydration step is a step in which water is separated from crude acetonitrile to obtain dehydrated acetonitrile. The method for separating water is not particularly limited, and examples thereof include a method of adding alkali to crude acetonitrile and performing extraction dehydration. Although it does not specifically limit as an alkali which can be used, For example, caustic soda is mentioned. The amount of alkali used can be appropriately adjusted depending on the water content in the crude acetonitrile, and is preferably 10 to 90% by mass, more preferably 30 to 60% by mass, based on the water content of the crude acetonitrile. %. The extraction temperature is preferably 5 to 60 ° C, more preferably 10 to 35 ° C.

The extraction dehydration method is not particularly limited, but for example, a method using a continuous countercurrent contact tower is preferable. The packing for the continuous countercurrent contact tower is not particularly limited, but for example, Raschig ring, Lessing ring, Pole ring, Berle saddle, Interlock saddle, Terralet packing, Dixon ring, McMahon packing are preferable, and regular packing is Although not particularly limited, for example, a mesh-structured packing is preferable.

(Dehydrated acetonitrile)
Here, “dehydrated acetonitrile” is a mixture that may contain 75% by mass or more and 99% by mass or less of acetonitrile, 0% by mass or more and less than 25% by mass of water, and other impurities.

(Other processes)
The refinement | purification process may have other processes, such as a low boiling point removal process and a high boiling point removal process. The low boiling point removal step and the high boiling point removal step are steps for removing a low boiling component below the boiling point of acetonitrile and a high boiling component above the boiling point of acetonitrile from dehydrated acetonitrile to obtain a product acetonitrile described later. Although it does not specifically limit as a low boiling point removal method and a high boiling point removal method, For example, the method of using a distillation column is mentioned.
In addition, water-containing crude acetonitrile is a known method for distillation purification of crude acetonitrile obtained as a by-product when producing acrylonitrile or methacrylonitrile by the catalytic ammoxidation reaction of propylene or isobutene with ammonia and molecular oxygen. It is also possible to purify in the same manner as above or according to the distillation purification method. The conventional techniques to be referred to are not particularly limited, and examples thereof include Japanese Patent Application Laid-Open No. 55-153757, Japanese Patent No. 3104312 and WO 2013/146609.

The product acetonitrile can be obtained through the above purification step.

(Product acetonitrile)
“Product acetonitrile” refers to acetonitrile having an acetonitrile content of more than 99% by mass and an impurity content other than acetonitrile of less than 1% by mass. The content of acetonitrile contained in the product acetonitrile is preferably 99.5% by mass or more and 100% by mass or less, more preferably 99.9% by mass or more and 100% by mass or less, and further preferably 99.99% by mass. It is 100 mass% or less.

(Toluene content in product acetonitrile)
The content of toluene in the product acetonitrile is preferably less than 1.0 ppm by mass, more preferably 0.5 ppm by mass or less, and even more preferably 0.1 ppm by mass or less with respect to 100% by mass of acetonitrile. More preferably, it is less than 0.1 mass ppm. The lower limit of the content of toluene contained in the product acetonitrile is not particularly limited, but is preferably not more than the detection limit, and more preferably 0% by mass with respect to 100% by mass of acetonitrile. When the content of toluene in the product acetonitrile is within the above range, higher quality acetonitrile is obtained.

Moreover, the absorbance of ultraviolet absorption at a wavelength of 200 nm of the product acetonitrile is preferably 0.3 or less, more preferably 0.25 or less, and further preferably 0.2 or less. Further, the lower limit of the absorbance of ultraviolet absorption at a wavelength of 200 nm of the product acetonitrile is not particularly limited, and it is preferably as low as possible, more preferably 0. The absorbance of ultraviolet absorption at a wavelength of 200 nm is an indicator of the content of the aromatic compound in the product acetonitrile. From this point of view, when the absorbance of ultraviolet absorption at a wavelength of 200 nm of the product acetonitrile is within the above range, higher quality acetonitrile is obtained.

[Acetonitrile]
The acetonitrile of this embodiment is obtained by the above production method. Acetonitrile thus obtained is a solvent for chemical reaction, particularly a pharmaceutical intermediate synthesis solvent, a purification solvent, a mobile phase solvent for high performance liquid chromatography, a DNA synthesis solvent and a purification solvent, and an organic EL material. It can be suitably used as a solvent for synthesis or as a cleaning solvent for electronic parts. In addition, acetonitrile of this embodiment is synonymous with product acetonitrile.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Example 1]
<Production of acetonitrile>
Production experiment of hydrous crude acetonitrile by gas phase reaction of acetic acid and ammonia using extrusion catalyst (MFI-30 / Al ₂ O ₃ = 80/20) of H-ZSM-5 zeolite manufactured by JGC Catalysts & Chemicals Co., Ltd. Went. A flow-type fixed bed reactor was used for the reaction. A SUS reaction tube having an inner diameter of 21.2 mm was charged with 73.3 g of the catalyst. The catalyst layer height was 340 mm. An acetic acid aqueous solution (80% acetic acid aqueous solution) having a water content of 20% by mass and ammonia were supplied to the reaction tube.

The raw material composition was ammonia / acetic acid = 1.3 (molar ratio), the reaction raw material WHSV (weight space velocity) was 3.88 h ⁻¹ , the reaction temperature was 440 ° C., and the reaction pressure was 0.11 MPaG. The reaction temperature was the average temperature of the catalyst layer. The reaction product gas flowing out from the reaction tube was cooled and condensed by a cooler connected to the lower part of the reaction tube to obtain a solution of hydrous crude acetonitrile. The reaction was continued for 200 hours, and water-containing crude acetonitrile was appropriately sampled, and composition analysis was performed by gas chromatography (“GC2010” manufactured by Shimadzu Corporation). The composition analysis was performed under the following conditions (the same applies hereinafter).
・ Equipment: “GC2010” manufactured by Shimadzu Corporation
・ Column: “HP-INNOWAX” manufactured by Agilent Technologies
・ Detector: TCD
Column temperature: 60 ° C. (1 minute hold) → 100 ° C. (temperature increase rate 10 ° C./min)→180° C. (temperature increase rate 20 ° C./min)
・ Injection temperature: 200 ℃
-Detector temperature: 200 ° C
Carrier gas: helium

The results of analyzing the composition of hydrous crude acetonitrile after 120 hours and 200 hours under the above conditions were as follows.
Elapsed time (h) 120 200
Acetic acid conversion (mol%) 98.8 98.9
Acetonitrile yield (mol%) 97.8 98.0
(Hydrous crude acetonitrile composition)
Ammonia (mass%) 5.5 5.4
Water (mass%) 51.9 52.0
Acetonitrile (mass%) 41.4 41.5
Acetic acid (mass%) 0.7 0.7
Acetone (mass%) 0.2 0.2
Acetamide (mass%) 0.2 0.2

In the gas phase reaction, a side reaction in which equimolar amounts of acetone and carbon dioxide are generated from 2 mol of acetic acid shown in the following reaction formula occurs. In this example, only hydrous crude acetonitrile is analyzed by gas chromatography, and carbon dioxide that does not dissolve in hydrous crude acetonitrile cannot be analyzed. Therefore, the production amount of carbon dioxide was estimated from the production amount of acetone detected by the analysis, and the conversion rate (mol%) of acetic acid and the yield (mol%) of acetonitrile were obtained.
2CH ₃ COOH → CH ₃ COCH ₃ + CO ₂ + H ₂ O

Further, among the impurities contained in the obtained hydrous crude acetonitrile, the content of toluene was separately analyzed in detail by gas chromatography and found to be 20 ppm by mass with respect to 100% by mass of acetonitrile. In addition, the detailed analysis of toluene content was implemented on condition of the following (same below).
・ Device: “GC-17A” manufactured by Shimadzu Corporation
・ Column: “HP-5” manufactured by Agilent Technologies, Inc.
・ Detector: FID
Column temperature: 50 ° C. (3 minutes hold) → 200 ° C. (temperature increase rate 10 ° C./min)
・ Injection temperature: 250 ℃
-Detector temperature: 250 ° C
・ Carrier gas: Nitrogen

Next, the water-containing crude acetonitrile was purified by distillation according to the following procedure to obtain a product acetonitrile.

Procedure 1: Acetonitrile concentration tower assumed experiment-1
A glass old show distillation column having 20 plates was used, and atmospheric crude continuous distillation of hydrous crude acetonitrile was performed under a reflux ratio of 20 conditions, and the ammonia gas recovered from the top of the column was cooled and recovered. The composition of the obtained ammonia solution was as follows.
(Ammonia solution composition)
Ammonia (mass%) 92.8
Acetonitrile (mass%) 5.1
Acetone (mass%) 1.9
Toluene (mass%) 0.02

Procedure 2: Acetonitrile concentration tower assumption experiment-2
The water-containing crude acetonitrile solution obtained by removing ammonia in the acetonitrile concentration tower assumption experiment-1 was redistilled in the same distillation tower, and the gas recovered from the top of the tower was cooled and recovered. The composition of the obtained crude acetonitrile was as follows.
(Crude acetonitrile composition)
Ammonia (mass%) 0.03
Water (mass%) 34.62
Acetonitrile (mass%) 64.57
Acetic acid (mass%) 0.66
Acetone (mass%) 0.12

When toluene in crude acetonitrile was analyzed by gas chromatography and gas chromatography mass spectrometry (GC-MS), it was found to be below the detection limit of gas chromatography (less than 0.1 ppm by mass with respect to 100% by mass of acetonitrile). It was. GC-MS was analyzed under the following conditions (the same applies hereinafter).
・ Apparatus: “HP-6890 / 5973N” manufactured by Agilent Technologies, Inc.
・ Column: “HP-INNOWAX” manufactured by Agilent Technologies
Oven temperature: 40 ° C. (5 minutes hold) → 200 ° C. (temperature increase rate 10 ° C./min)
・ Injection temperature: 200 ℃
・ Interface temperature: 240 ℃
Carrier gas: helium

Procedure 3: Dehydration tower assumption experiment In order to make the water content in crude acetonitrile below an azeotropic composition, it extracted and dehydrated by adding an alkali. That is, dehydrated acetonitrile having a water content of 5% by mass or less was obtained by countercurrent contact with a 48% sodium hydroxide aqueous solution by a Dixon packing packed tower.

Procedure 4: Low-boiling, high-boiling separation column Using a glass Oldershaw distillation column having 50 stages, by carrying out continuous atmospheric distillation of dehydrated acetonitrile twice under the condition of a reflux ratio of 15, Removal of high-boiling substances and purification were performed to obtain a product acetonitrile.

When toluene in this product acetonitrile was analyzed by gas chromatography, it was below the gas chromatography detection limit (less than 0.1 mass ppm with respect to 100 mass% of acetonitrile).

[Example 2]
A gas phase reaction was performed in the same manner as in Example 1 except that acetic acid having a water content of 8% by mass was used instead of the acetic acid aqueous solution having a water content of 20% by mass. Hydrous crude acetonitrile was collected after 120 hours had passed since the start of the gas phase reaction, and the composition was analyzed by gas chromatography. The results were as follows. The water content of the reaction product liquid was about 47% by mass. The reaction was continued for 120 hours to obtain hydrous crude acetonitrile.
Elapsed time (h) 120
Acetic acid conversion (mol%) 98.7
Acetonitrile yield (mol%) 97.7
(Hydrous crude acetonitrile composition)
Ammonia (mass%) 6.0
Water (mass%) 47.0
Acetonitrile (mass%) 45.6
Acetic acid (mass%) 0.9
Acetone (mass%) 0.2
Acetamide (mass%) 0.2

Further, among the impurities contained in the obtained hydrous crude acetonitrile, the content of toluene was separately separately analyzed in detail by gas chromatography, whereby it was 19 ppm by mass with respect to 100% by mass of acetonitrile.

Subsequently, distillation purification of the obtained hydrous crude acetonitrile was performed in the same manner as in Example 1. The composition of crude acetonitrile obtained by cooling and recovering the gas recovered from the top of the acetonitrile concentration tower assumed experiment-2 was as follows.
(Crude acetonitrile composition)
Ammonia (mass%) 0.05
Water (mass%) 34.80
Acetonitrile (mass%) 64.25
Acetic acid (mass%) 0.73
Acetone (mass%) 0.17

As a result of detailed gas chromatography analysis of toluene in crude acetonitrile, it was 0.1 mass ppm with respect to 100 mass% of acetonitrile. Furthermore, when toluene in the product acetonitrile obtained by the same operation as in Example 1 was analyzed by gas chromatography, it was below the gas chromatography detection limit (less than 0.1 ppm by mass with respect to 100% by mass of acetonitrile). there were.

From this example, by setting the water content of the hydrous crude acetonitrile obtained by the gas phase reaction of acetic acid and ammonia to 47 to 60% by mass, toluene contained in the hydrous crude acetonitrile can be separated by a very general distillation separation method. It was found that concentrated acetonitrile can be obtained by simple removal. As a result, by purifying the concentrated acetonitrile by a known purification method, it is possible to obtain acetonitrile obtained by a gas phase reaction of acetic acid and ammonia using an intermediate pore size zeolite as a catalyst, or high-purity acetonitrile not containing toluene. I understand.

[Comparative Example 1]
A gas phase reaction was performed in the same manner as in Example 1 except that acetic acid having a moisture content of 0% by mass was used instead of the acetic acid aqueous solution having a moisture content of 20% by mass. Water-containing crude acetonitrile was recovered after 11.0 hours had passed since the start of the gas phase reaction, and composition analysis was performed by gas chromatography. The results were as follows. The water content of the reaction product liquid was about 43% by mass. The reaction was continued for 120 hours to obtain hydrous crude acetonitrile.
Elapsed time (h) 11.0
Acetic acid conversion (mol%) 98.6
Acetonitrile yield (mol%) 98.0
(Hydrous crude acetonitrile composition)
Ammonia (mass%) 6.4
Water (mass%) 43.3
Acetonitrile (mass%) 49.1
Acetic acid (mass%) 0.7
Acetone (mass%) 0.2
Acetamide (mass%) 0.3

Further, among the impurities contained in the obtained hydrous crude acetonitrile, the content of toluene was separately analyzed in detail by gas chromatography and found to be 21 ppm by mass with respect to 100% by mass of acetonitrile.

Subsequently, distillation purification of the obtained hydrous crude acetonitrile was performed in the same manner as in Example 1. The composition of crude acetonitrile obtained by cooling and recovering the gas recovered from the top of the acetonitrile concentration tower assumed experiment-2 was as follows.
(Crude acetonitrile composition)
Ammonia (mass%) 0.10
Water (mass%) 34.41
Acetonitrile (mass%) 64.51
Acetic acid (mass%) 0.80
Acetone (mass%) 0.17

Detailed gas chromatography analysis of toluene in the crude acetonitrile revealed that it was 1.3 ppm by mass with respect to 100% by mass of acetonitrile. Furthermore, when toluene in the product acetonitrile obtained by the same operation as in Example 1 was analyzed by gas chromatography, it was 1.1 mass ppm with respect to 100 mass% of acetonitrile.

From this comparative example, when the water content of the hydrous crude acetonitrile obtained by the gas phase reaction between acetic acid and ammonia is less than 47% by mass, it is not suitable to separate and purify the toluene contained in the hydrous crude acetonitrile with an acetonitrile concentration tower. Therefore, it has been found that it cannot be easily removed by a known general distillation separation method.

[Example 3]
Product acetonitrile was produced in the same manner as in Example 1 using water-containing crude acetonitrile having the following composition in which water was added to the water-containing crude acetonitrile obtained at the reactor outlet of Comparative Example 1 and the water content was increased to 52% by mass. .
(Hydrous crude acetonitrile composition)
Ammonia (mass%) 5.4
Water (mass%) 52.0
Acetonitrile (mass%) 41.5
Acetic acid (mass%) 0.6
Acetone (mass%) 0.2
Acetamide (mass%) 0.3

When toluene in the obtained product acetonitrile was analyzed by gas chromatography, it was less than the detection limit (0.1 mass ppm) with respect to 100 mass% of acetonitrile.

[Examples 4 to 6]
As a catalyst, compression molded crushing catalyst of H-beta type zeolite powder (silica / alumina = 25) from JGC Universal Co., Ltd. zeolite sample kit (8-40 mesh classification, hereinafter also referred to as “H-β”), Sumitomo Activated alumina KHD-46 (hereinafter also referred to as “KHD”) manufactured by Chemical Co., Ltd., ZSM-5 type zeolite-containing catalyst of zeolite sample kit manufactured by JGC Universal Co., Ltd. (H-MFI zeolite / alumina molding, silica / alumina = 40 , Hereinafter also referred to as “MFI”), a gas phase reaction of acetic acid and ammonia was performed to produce hydrous crude acetonitrile.

A flow-type fixed bed reactor was used for the reaction. A quartz glass reaction tube having an inner diameter of 20 mm was filled with 10 g of the catalyst. The catalyst layer height was 48 mm. Acetic acid and ammonia having a water content of 20% by mass were supplied to the reaction tube. The raw material composition was ammonia / acetic acid = 1.3 (molar ratio), the reaction raw material WHSV (weight space velocity) was 2.0 h ⁻¹ , the reaction temperature was 424 to 433 ° C., and the reaction pressure was normal pressure. The reaction temperature was the average temperature of the catalyst layer. The reaction product gas flowing out of the reaction tube was cooled and condensed by a cooler connected to the lower part of the reaction tube to obtain hydrous crude acetonitrile. Water-containing crude acetonitrile was sampled and composition analysis was performed by gas chromatography. The results were as follows.
Example 4 Example 5 Example 6
Catalyst H-β KHD MFI
Conversion rate of acetic acid (mol%) 86.4 98.8 96.4
Acetonitrile yield (mol%) 83.1 85.4 96.0
(Hydrous crude acetonitrile composition)
Ammonia (mass%) 5.9 5.2 5.8
Water (mass%) 52.9 51.4 51.3
Acetonitrile (mass%) 31.9 38.3 40.6
Acetic acid (mass%) 7.7 0.8 1.8
Acetone (mass%) 0.1 4.1 0.1
Acetamide (mass%) 1.6 0.3 0.5

Further, among the impurities contained in the hydrous crude acetonitrile obtained in Examples 4 to 6, the content of toluene was separately analyzed in detail by gas chromatography. As a result, it was found that the content was 1 ppm by mass or more with respect to 100% by mass of acetonitrile. there were. Using this hydrous crude acetonitrile, product acetonitrile was produced in the same manner as in Example 1. As a result, when toluene in this product acetonitrile was analyzed by gas chromatography, it was below the gas chromatography detection limit (less than 0.1 mass ppm with respect to 100 mass% of acetonitrile).

This application is based on a Japanese patent application (Japanese Patent Application No. 2014-223300) filed with the Japan Patent Office on October 31, 2014, the contents of which are incorporated herein by reference.

According to the present invention, in the production of acetonitrile by the gas phase reaction of acetic acid and ammonia, the energy consumption used for the purification of the hydrous crude acetonitrile produced by the gas phase reaction is small, and the purification equipment and the process are simple. Process can be realized. Therefore, while minimizing the increase in cost, ultraviolet light at a wavelength of 200 nm is low in toluene content for applications such as solvents used in the synthesis and purification of pharmaceutical intermediates and solvents for high performance liquid chromatography. The present invention has industrial applicability as a method for providing a method for producing high-purity acetonitrile with low absorbance of absorption.

Claims

A gas phase reaction step in which acetic acid and ammonia are subjected to a gas phase reaction in the presence of a solid acid catalyst to obtain hydrous crude acetonitrile;
Purifying the water-containing crude acetonitrile to obtain a product acetonitrile,
In the hydrous crude acetonitrile,
The water content is 47% by mass or more with respect to 100% by mass of the hydrous crude acetonitrile, and the toluene content is 1 mass ppm or more with respect to 100% by mass of acetonitrile.
A method for producing acetonitrile.
The method for producing acetonitrile according to claim 1, wherein the solid acid catalyst is an intermediate pore size zeolite.
The purification step comprises
Separating the ammonia from the hydrated crude acetonitrile to obtain a crude acetonitrile; and
The method for producing acetonitrile according to claim 1, further comprising a dehydration step of separating water from the crude acetonitrile to obtain dehydrated acetonitrile.
The method for producing acetonitrile according to any one of claims 1 to 3, wherein a toluene content in the product acetonitrile is less than 1.0 mass ppm with respect to 100 mass% of acetonitrile.
The method for producing acetonitrile according to any one of claims 1 to 4, wherein the acetic acid is an aqueous solution containing 10 to 40% by mass of water.
The method for producing acetonitrile according to any one of claims 1 to 5, wherein in the gas phase reaction step, WHSV (raw material supply amount per hour / catalyst filling amount) is 0.5 to 20 h- 1 .
The method for producing acetonitrile according to any one of claims 2 to 6, wherein the intermediate pore size zeolite comprises ZSM-5 type zeolite.
Acetonitrile produced by the method for producing acetonitrile according to any one of claims 1 to 7.