Method for producing aromatic nitrile compound and method for producing carbonic acid ester

Abstract

A method for producing an aromatic nitrile compound is provided by which the aromatic nitrile compound can be selectively obtained in high yield in a shortened reaction time using an aromatic amide compound and which can inhibit the formation of by-products.　The above-mentioned problem was solved by the following method for producing an aromatic nitrile compound.　The method for producing an aromatic nitrile compound includes a dehydration reaction in which an aromatic amide compound is dehydrated. The dehydration reaction includes a contact step in which the aromatic amide compound and a diluent are brought into contact with a catalyst in a gas phase. In the contact step, the temperature at which the aromatic amide compound and the diluent are brought into contact with the catalyst is 300°C or higher.

Description

Method for producing aromatic nitrile compounds and method for producing carbonate esters

[0001] The present invention relates to a method for producing an aromatic nitrile compound, which includes a step of dehydrating an aromatic amide compound in a vapor phase, and a method for producing a carbonate ester.

[0002] Carbonate ester is carbonate CO(OH) ２ It is a general term for compounds in which one or both of the two hydrogen atoms in the above group are substituted with an alkyl group or an aryl group, and has the structure RO-C(=O)-OR' (R and R' represent a saturated hydrocarbon group or an unsaturated hydrocarbon group).

[0003] Carbonate esters are extremely useful compounds, used as additives in gasoline to improve octane numbers, diesel fuel additives to reduce particles in exhaust gases, and as alkylating agents, carbonylating agents, and solvents in the synthesis of resins and organic compounds such as polycarbonates, urethanes, pharmaceuticals, and agricultural chemicals, as well as raw materials for electrolytes in lithium-ion batteries, lubricating oil raw materials, and oxygen scavengers to prevent rust in boiler piping.

[0004] Known conventional methods for producing carbonate esters include, for example, a step of reacting water, which is produced as a by-product in the reaction of alcohol with carbon dioxide, with a nitrile compound (see, for example, Patent Documents 1 and 2). These methods for producing carbonate esters also include a step of dehydrating an amide compound produced from water and the nitrile compound to regenerate the nitrile compound.

[0005] Such conventional methods for producing carbonate esters do not necessarily allow selective regeneration of nitrile compounds in a short time and in high yield, making it difficult to efficiently produce the target carbonate ester compound.

[0006] Patent Document 1: WO2015 / 099053 Patent Document 2: WO2020 / 022416

[0007] A main object of the present invention is to provide a method for producing an aromatic nitrile compound, which can selectively produce an aromatic nitrile compound in a high yield while shortening the reaction time using an aromatic amide compound and can suppress the generation of by-products. Another object of the present invention is to realize an efficient method for producing a carbonate ester by applying such a method for producing an aromatic nitrile compound.

[0008] The present inventors have investigated a method for producing an aromatic nitrile compound by dehydrating an aromatic amide compound, and have found that when an aromatic amide compound and a diluent are brought into contact with a catalyst at high temperature in the gas phase, the reaction rate can be significantly improved and the reaction time can be shortened, while the generation of by-products can be suppressed and the target compound can be selectively obtained in high yield.

[0009] According to the present invention, the regeneration rate of an aromatic amide compound to an aromatic nitrile compound by a dehydration reaction can be improved. Furthermore, in the method of the present invention for producing a carbonate ester from carbon dioxide and an alcohol, which incorporates such a dehydration reaction step, excellent effects such as efficient production of a carbonate ester have been confirmed.

[0010] The present invention includes, for example, the following: [1] A method for producing an aromatic nitrile compound, comprising a dehydration reaction for dehydrating an aromatic amide compound, wherein the dehydration reaction includes a contacting step of contacting the aromatic amide compound and a diluent with a catalyst in a gas phase, and wherein the temperature at which the aromatic amide compound and the diluent are contacted with the catalyst in the contacting step is 300°C or higher. [2] A method for producing an aromatic nitrile compound according to the above [1], wherein the diluent contains at least one of a solvent and an inert gas. [3] A method for producing an aromatic nitrile compound according to the above [2], wherein the solvent contains at least an aromatic compound. [4] A method for producing an aromatic nitrile compound according to the above [3], wherein the aromatic compound is represented by the following formula (1): (In formula (1), R １are each independently selected from an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkoxy group having 1 to 10 carbon atoms which may have a substituent, an aryl group having 6 to 30 carbon atoms which may have a substituent, and an aryloxy group having 6 to 30 carbon atoms which may have a substituent, and a is an integer from 1 to 6. [5] A method for producing an aromatic nitrile compound according to any of [3] and [4] above, for example [3] above, wherein the aromatic compound has one or two aromatic rings and one or more groups selected from an alkyl group, an alkoxy group, and an aryloxy group. [6] A method for producing an aromatic nitrile compound according to any of [3] to [5] above, for example [3] above, wherein the aromatic compound has a spontaneous ignition temperature of 300°C or higher. [7] A method for producing an aromatic nitrile compound according to any of [3] to [6] above, for example [3] above, wherein the aromatic compound includes at least one of 1,3,5-trimethylbenzene, p-cymene, phenyl ether, and anisole. [8] The method for producing an aromatic nitrile compound according to any one of [1] to [5] above, for example, [1] above, wherein the pressure of the reaction system in the contacting step is 101.3 kPa or less. [9] The method for producing an aromatic nitrile compound according to any one of [1] to [8] above, for example, [1] above, wherein the aromatic amide compound comprises at least a heteroaryl amide compound, and the aromatic nitrile compound comprises at least a heteroaryl nitrile compound.

[10] The method for producing an aromatic nitrile compound according to [9] above, wherein the heteroaryl amide compound comprises 2-picolinamide, and the heteroaryl nitrile compound comprises 2-cyanopyridine.

[11] The method for producing an aromatic nitrile compound according to any one of [1] to

[10] above, for example, [1] above, wherein a vaporized inert gas is used in the contacting step.

[12] The method for producing an aromatic nitrile compound according to any one of [3] to

[11] above, for example,

[11] above, wherein the inert gas comprises at least nitrogen gas.

[13] The method for producing an aromatic nitrile compound according to any one of [1] to

[12] above, for example, [1] above, wherein the catalyst comprises an alkali metal.

[14] The method for producing an aromatic nitrile compound according to any one of the above [2] to

[13] , for example, the above [2], wherein the solvent is compatible with the aromatic amide compound.

[15] The method for producing an aromatic nitrile compound according to any one of the above [1] to

[14] , for example, the above [1], wherein the catalytic contact time of the aromatic amide compound in the gas phase is 0.001 seconds or more and less than 10 seconds.

[0011]

[16] A method for producing a carbonate ester, comprising: a first reaction step including a carbonate ester production reaction in which an alcohol and carbon dioxide are reacted in the presence of an aromatic nitrile compound to produce a carbonate ester and water, and a hydration reaction in which the produced water is hydrated with the aromatic nitrile compound to produce an aromatic amide compound; and a second reaction step in which, after separating the aromatic amide compound from the reaction system of the first reaction step, an aromatic amide compound is regenerated from the aromatic amide compound by a dehydration reaction comprising the contact step described in any one of [1] to

[15] above, wherein at least a portion of the aromatic nitrile compound regenerated in the second reaction step is used in the first reaction step.

[17] A method for producing a carbonate ester according to

[16] above, wherein a catalyst containing cerium oxide is used in the carbonate ester production reaction.

[18] A method for producing a carbonate ester according to

[16] above, wherein the alcohol includes an alcohol having 1 to 6 carbon atoms.

[0012] According to the present invention, it is possible to efficiently produce (regenerate) aromatic nitrile compounds, such as cyanopyridines, from aromatic amide compounds, such as pyridinecarboxamides (picolinamide, nicotinamide, etc.) and benzamides. That is, in the dehydration reaction of the aromatic amide compound for the regeneration, the generation of by-products can be suppressed, the target compound can be selectively obtained in high yield, and the reaction rate can be improved. Therefore, according to the present invention, the reaction time for the dehydration reaction to regenerate the aromatic nitrile compound can be significantly shortened compared to conventional methods. Furthermore, in the dehydration step using a gas-phase reaction at high temperatures, the reaction vessel can be made smaller than in conventional dehydration steps of amide compounds using a liquid-phase reaction or a gas-phase reaction at lower temperatures. Therefore, according to the present invention, it is possible to easily industrialize the process of regenerating the corresponding aromatic nitrile compound from an aromatic amide compound. Furthermore, according to the present invention, by producing an aromatic nitrile compound as described above, an efficient method for producing a carbonate ester can also be realized.

[0013] 1 is an example of an apparatus for producing a carbonate ester. 2 is a diagram schematically illustrating an apparatus for producing an aromatic nitrile compound in an example where a solvent is used. 3 is a diagram schematically illustrating an apparatus for producing an aromatic nitrile compound in an example where an inert gas is used. 4 is a diagram showing the relationship between the reaction temperature and the yield of an aromatic nitrile compound (2-cyanopyridine (2-CP)) in the dehydration reaction in an example and a comparative example where a solvent is used. 5 is a diagram showing the relationship between the reaction temperature and the by-product production rate of pyridine (Py) in the dehydration reaction in an example and a comparative example where a solvent is used.

[0014] Preferred embodiments of the present invention will be described in detail below.

[0015] <1. Method for Producing Aromatic Nitrile Compound> In the method for producing an aromatic nitrile compound of the present invention, an aromatic amide compound, for example, pyridinecarboxamide (2-pyridinecarboxamide, 3-pyridinecarboxamide, or 4-pyridinecarboxamide), is dehydrated in a gas phase to convert it into an aromatic nitrile compound such as cyanopyridine. That is, the method for producing an aromatic nitrile compound of the present invention involves, for example, a contact step in which an aromatic amide compound is brought into contact with a catalyst supported on a basic metal oxide in a gas phase at high temperature, thereby causing a dehydration reaction to occur and producing an aromatic nitrile compound.

[0016]

[0017] (Reaction Substrate) Examples of aromatic amide compounds used in the method for producing an aromatic nitrile compound include amide compounds having an aromatic hydrocarbon ring such as a benzene ring, a naphthalene ring, or an anthracene ring, or a heteroaryl ring. Among these aromatic amide compounds, those having a heteroaryl ring, i.e., heteroaryl amide compounds, are preferably used. Examples of heteroaryl amide compounds include amide compounds having a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a furan ring, a thiophene ring, an imidazole ring, a pyrazole ring, or an oxazole ring. Preferred examples of heteroaryl amide compounds include those having a pyridine ring, such as the above-mentioned pyridinecarboxamides (2-pyridinecarboxamide, 3-pyridinecarboxamide, and 4-pyridinecarboxamide). As is clear from the above reaction formula, the aromatic nitrile compound produced by the production method of the present invention is a product of a dehydration reaction corresponding to the above-mentioned aromatic amide compound. Therefore, specific examples of aromatic nitrile compounds that can be produced by the production method of the present invention include heteroaryl nitrile compounds. Preferred specific examples of the heteroaryl nitrile compound include those having a pyridine ring, such as cyanopyridines (2-cyanopyridine, 3-cyanopyridine, and 4-cyanopyridine).

[0018] (Catalyst) The catalyst used in the dehydration reaction of the present invention preferably contains an oxide of an alkali metal (K, Li, Na, Rb, Cs). In particular, it is preferable to use a catalyst containing an oxide of at least one of Na, K, Rb, and Cs (cesium) as the catalyst used in the reaction. Furthermore, while a substance that is generally used as a catalyst support can be used as the support for the catalyst, after examining various supports, it has been found that a support such as SiO ２ , and ZrO ２ It is preferable to include any one of the following.

[0019] The catalyst used in the dehydration reaction of the present invention can be produced by the following method, for example. ２ In this case, commercially available powder or spherical SiO ２ It is preferable to use a granular material having a particle size of, for example, 4.0 mm or less so that the active metal can be uniformly supported, and to remove moisture, to carry out preliminary calcination in air, for example, at 700°C for about 1 hour. ２ There are various types of catalysts, but catalysts with a larger specific surface area are preferred because they can disperse the active metals more highly and improve the yield of aromatic nitrile compounds. ２ However, the specific surface area of ​​the catalyst after preparation is preferably SiO ２ and the interaction with the active metal, etc. ２ In this case, the specific surface area of ​​the catalyst after production may be less than 150 m ２ The metal oxide serving as the active species can be supported by an impregnation method such as an incipient wetness method or an evaporation-to-dryness method.

[0020] The metal salt that serves as the catalyst precursor may be water-soluble, and in the case of an alkali metal, various compounds such as carbonates, hydrogen carbonates, chlorides, nitrates, silicates, etc. The catalyst can be used by impregnating a carrier with an aqueous solution of a basic metal precursor, followed by drying and calcination. The calcination temperature varies depending on the precursor used, but is preferably 400 to 600°C.

[0021] Furthermore, the catalyst used in the present invention is SiO ２ , ZrO ２ A catalyst in which only one or more alkali metal oxides are supported on a carrier made of one or two of the above is preferred, but it may contain inevitable impurities other than the above elements that are mixed in during the catalyst production process, etc. However, it is desirable to avoid the mixing of impurities as much as possible.

[0022] The catalyst used in the present invention, in which a metal oxide serving as an active species is supported on a carrier, may be in the form of either a powder or a molded body, and in the case of a molded body, it may be in any shape such as a sphere, pellet, cylinder, ring, wheel, granule, etc. The catalyst may also be used by being fixed to a support structure such as a honeycomb.

[0023] While there are no limitations on the size of the carrier, when a spherical carrier is used, the average diameter of the catalyst particles (carrier diameter) is preferably within the range of 0.01 to 8.0 mm, more preferably 0.03 to 6.0 mm, and even more preferably 0.05 to 5.0 mm. Thus, by using a catalyst with a carrier diameter relatively larger than the average diameter of catalyst particles (carrier diameter) used in a liquid-phase reaction, a flow path for the reactant in a gas-phase reaction can be secured, ensuring a high space velocity. However, when a fluidized bed is used in a gas-phase reaction, a catalyst with a relatively small particle size is preferred so that the catalyst can be stirred with a small gas flow rate. When a fixed bed is used in a gas-phase reaction, a relatively large particle size and shape are preferred so that pressure loss is minimized. The carrier diameter, i.e., the average diameter of the catalyst particles, refers to the average diameter of the entire catalyst particle, including the active component of the catalyst and the carrier. The catalyst carrier diameter is a value measured based on a sieving method, such as the general rules for sieving test methods specified in JIS Z8815.

[0024] The amount of catalyst supported may be set as appropriate, and the amount of active species such as alkali metal oxides supported in terms of metal, based on the total catalyst weight, is preferably 0.05 to 2.0 mmol / g, more preferably 0.10 to 1.5 mmol / g, and even more preferably 0.30 to 1.0 mmol / g. The amount of catalyst used during the reaction may also be set as appropriate.

[0025] (Reaction Method and Reaction Vessel) In the method for producing an aromatic nitrile compound of the present invention, it is preferable to use a gas-phase reaction in which a gaseous or mist-like amide compound is passed through a catalyst layer together with a diluent, and for example, a fixed-bed or fluidized-bed gas-phase reaction apparatus can be applied. In this manner, in the contact step in which an aromatic amide compound is brought into contact with a catalyst in the gas phase, it is preferable to use an aromatic amide compound in a completely vaporized state, but it is also possible to use an aromatic amide compound in a state in which liquid droplets (mist) are partially contained in the gas.

[0026] The method for producing an aromatic nitrile compound is desirably carried out while removing by-product water produced by a dehydration reaction. As a result of extensive studies by the present inventors, it has been found that, for example, by attaching a vaporization chamber to the top of a reaction tube containing a catalyst, adding an aromatic amide compound dropwise to the vaporization chamber, and passing the amide compound in a gas phase through a catalyst layer in a short period of time, it is possible to increase the amount of aromatic nitrile compound produced and suppress the production of by-products.

[0027] (Diluent) In the above-described dehydration reaction, it is preferable to use a diluent. In particular, it is preferable to use at least one of an inert gas and a solvent, which will be described in detail later, as the diluent in the dehydration reaction. The diluent is primarily used to reduce the frequency of contact between the water produced when the aromatic amide compound is vaporized and reacted with the catalyst and the unreacted aromatic amide compound or the aromatic nitrile compound, which is the reaction product, and to reduce the production of by-products such as pyridine. Therefore, an inert gas can also be used as the diluent. Furthermore, if the diluent is compatible with the aromatic amide compound in the liquid phase, it can be mixed with a diluent compatible with the aromatic amide compound in advance in the step of vaporizing the aromatic amide compound, and then delivered as a liquid to prevent blockages due to precipitation of the aromatic amide compound. That is, the diluent may be an inert gas or a liquid that is not compatible with the aromatic amide compound to be subjected to the dehydration reaction, although a compatible liquid is more preferable. A diluent that is compatible with an aromatic amide compound in the liquid phase is not only a diluent that can be mixed with an aromatic amide compound in any ratio, but also a diluent that can dissolve the target aromatic amide compound only up to a predetermined solubility, and includes a diluent in an amount that can dissolve the aromatic amide compound to a concentration that is equal to or less than the upper limit of the solubility at a predetermined temperature.

[0028] (Inert Gas) As described above, in the dehydration reaction, it is preferable to contact an inert gas in a gas phase with the catalyst together with the aromatic amide compound. That is, the inert gas is used in the dehydration reaction in a vaporized state. Specific examples of the inert gas used in the dehydration reaction include nitrogen gas and rare gases such as helium and argon, and nitrogen gas is preferably used. The flow rate of the inert gas and the like will be described later.

[0029] (Solvent) In the above-described dehydration reaction, it is preferable to use a solvent. In particular, as described above, in the step of vaporizing an aromatic amide compound, by previously mixing the aromatic amide compound with a solvent compatible with the aromatic amide compound and then feeding the mixture, it is possible to prevent clogging problems due to precipitation of the aromatic amide compound. That is, the solvent is preferably one that is compatible with the aromatic amide compound that is the target of the dehydration reaction. A solvent that is compatible with an aromatic amide compound is not only a solvent that can be mixed with the aromatic amide compound in any ratio, but also a solvent that can dissolve the target aromatic amide compound only up to a predetermined solubility, and includes an amount of solvent that can dissolve the aromatic amide compound to a concentration not exceeding the upper limit of the solubility at a predetermined temperature.

[0030] The solvent preferably contains at least an aromatic compound, and the aromatic compound preferably used is one represented by the following formula (1): In formula (1), R １ are each independently selected from an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkoxy group having 1 to 10 carbon atoms which may have a substituent, an aryl group having 6 to 30 carbon atoms which may have a substituent, and an aryloxy group having 6 to 30 carbon atoms which may have a substituent.

[0031] R in formula (1) １ is preferably an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkoxy group having 1 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent. １ is more preferably any one of an alkyl group having 1 to 4 carbon atoms which may have a substituent, an alkoxy group having 1 to 3 carbon atoms which may have a substituent, and an aryl group having 6 to 12 carbon atoms which may have a substituent, and even more preferably any one of an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 or 2 carbon atoms which may have a substituent, and an aryl group having 6 to 8 carbon atoms which may have a substituent. In formula (1), a is an integer of 1 to 6, and a is preferably an integer of 1 to 4, and more preferably an integer of 1 to 3.

[0032] Examples of the substituent include a halogen atom, a hydroxy group, a carboxy group, a cyano group, an amide group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms. The number of carbon atoms in the general formula (1) is the total number of carbon atoms, including the number of carbon atoms in the substituent.

[0033] The aromatic compound as a solvent preferably has one or two aromatic rings and one or more selected from alkyl groups, alkoxy groups, and aryloxy groups, more preferably a total of 1 to 3 alkyl and / or alkoxy groups. The aromatic compound also preferably has a plurality of aromatic rings, such as two, linked by ether bonds, for example, benzene rings.

[0034] The aromatic compound solvent used in the dehydration reaction preferably includes, for example, at least one of 1,3,5-trimethylbenzene, p-cymene, phenyl ether, and anisole. Other specific examples of the solvent include aromatic compounds such as pyridine compounds, ketone compounds, ether compounds, ester compounds, and alcohols. The aforementioned aromatic compounds are preferably used. Examples of pyridine compounds as solvents, i.e., compounds having a pyridine skeleton, include 2-alkylpyridines, 3-alkylpyridines, and 4-alkylpyridines, such as 4-methylpyridine and pyridine. In particular, in dehydration reactions in which pyridine may be produced as a by-product, using a pyridine compound as a solvent under suitable conditions can eliminate the need for a step of removing the main by-product, pyridine. Examples of ketone compounds as solvents include cyclic ketone compounds such as cyclopentanone and cyclohexane, and acetone.

[0035] It is preferable to use a solvent consisting of only one or more substances selected from the above-mentioned compounds as the solvent for the dehydration reaction, but a mixed solvent further containing other compounds may also be used.

[0036] The solvent is preferably vaporized together with the aromatic amide compound and used in the dehydration reaction (contact step). Thus, it is preferable to use a solvent that is vaporized and used in the dehydration reaction. Furthermore, since the solvent is used in the dehydration reaction, which is performed at high temperatures, as will be described in detail below, it is preferable that the solvent, which is preferably an aromatic compound, has a high spontaneous ignition temperature. For example, the solvent preferably has a spontaneous ignition temperature of 300°C or higher, 340°C or higher, 380°C or higher, or 400°C or higher, more preferably 430°C or higher or 450°C or higher, even more preferably 470°C or higher or 500°C or higher, and particularly preferably 550°C or higher. The boiling point of the solvent, which is preferably an aromatic compound, is not particularly limited, but the boiling point at atmospheric pressure is, for example, 20°C or higher to 300°C or lower, preferably 80°C or higher to 250°C or lower, and more preferably 110°C or higher to 200°C or lower.

[0037] (Conditions for dehydration reaction including contacting step) As described above, the method for producing an aromatic nitrile compound has a contacting step in which an aromatic amide compound is contacted with a catalyst in a gas phase in a dehydration reaction. In the contacting step, the temperature at which the aromatic amide compound and a diluent such as a solvent are contacted with the catalyst is, for example, 285°C or higher, and preferably 300°C or higher. The contact temperature is more preferably 300°C or higher and 550°C or lower, even more preferably 320°C or higher and 520°C or lower, and particularly preferably 350°C or higher and 490°C or lower. The temperature at which the aromatic amide compound or the like is contacted with the catalyst is, for example, the temperature in the vicinity of the catalyst layer in a reaction tube (reaction vessel) in which the catalyst is fixed, as will be described later.

[0038] The catalytic contact time of the aromatic amide compound in the contact step, and the catalytic contact time of the mixed gas of the gaseous composition when an inert gas, a solvent, etc. is contained together with the aromatic amide compound, is preferably 0.001 seconds or more, or 0.005 seconds or more, for example, 0.01 seconds or more and less than 10 seconds. The catalytic contact time is more preferably 0.1 seconds or more and less than 5 seconds, and even more preferably 0.5 seconds or more and less than 2 seconds. The catalytic contact time is the average time for the aromatic amide compound gas or the mixed gas to pass through the catalyst layer, and is calculated as follows: catalytic contact time (seconds) = catalyst layer height in reactor (cm) ÷ gas linear velocity in reactor (cm / second).

[0039] In the contact step, the molar ratio of the flow rate of the aromatic amide compound to the flow rate of the gaseous composition is preferably 1:0 to 1:200, more preferably 1:1 to 1:100, and even more preferably 1:1 to 1:20. The space velocity (SV) of all gaseous components in the contact step is 1,000 to 50,000 (h －１ ), more preferably 1,500 to 30,000 (h －１ ), and more preferably 2,000 to 25,000 (h －１ When the contact step is carried out under reduced pressure, the space velocity (SV) of all gas components is 1,000 to 1,000,000 (h －１ ), more preferably 1,500 to 700,000 (h －１ ), and more preferably 1,900 to 504,000 (h －１ )

[0040] The dehydration reaction can be carried out under a pressure ranging from elevated pressure (e.g., 506.5 kPa) to atmospheric pressure (101.3 kPa) or reduced pressure (e.g., 101.3 to 1.0 kPa, 101.3 to 1.0 kPa to 0.1 kPa), but is not particularly limited thereto. It is preferable to carry out the dehydration reaction under reduced pressure. The reaction pressure in the dehydration reaction is preferably 101.3 kPa or less, more preferably 90 kPa to 1.0 kPa or 80 kPa to 5.0 kPa, even more preferably 70 kPa to 10 kPa or 60 kPa to 20 kPa, and particularly preferably 50 kPa to 30 kPa.

[0041] It is also preferable to dehydrate the aromatic amide compound in a liquid state before vaporization. When using molecular sieves as a dehydrating agent, there are no particular limitations on the type or shape, but for example, those with generally high water absorption such as 3A, 4A, and 5A, in spherical or pellet form, can be used. For example, Zeolum manufactured by Tosoh Corporation can be suitably used.

[0042] (Examples of by-products in dehydration reactions)

[0043] In the dehydration reaction of an aromatic amide compound, pyridine is thought to be produced as a by-product via the aromatic carboxylic acid due to the decomposition of the aromatic amide compound as described above. However, the reaction solution after the dehydration reaction using the contact step of the present invention contains almost no by-products such as pyridine shown in the above formula.

[0044] <2. Method for Producing Carbonate Ester Using Aromatic Nitrile Compound> In the regeneration of an aromatic amide compound to an aromatic nitrile compound by dehydration reaction, the provision of a gas-phase contact step has enabled a significant improvement in the reaction rate and a significant reduction in the reaction time. This has enabled a significant improvement in the regeneration rate of an aromatic amide compound to an aromatic nitrile compound by dehydration reaction and a significant reduction in the CO 2 production rate using an aromatic nitrile compound. ２It has become possible to balance the reaction rate and the rate of synthesis of carbonate ester from alcohol, and these reactions can be established as a series of commercial processes. Based on this, the present inventors have applied this knowledge to the production of carbonate esters, and have conceived the production method of carbonate esters described below.

[0045] (First Reaction Step) In the first reaction step of the method for producing a carbonate ester of the present invention, for example, CeO ２ The present invention includes a reaction in which an alcohol is directly reacted with carbon dioxide in the presence of a solid catalyst containing, for example, cerium oxide and an aromatic nitrile compound to produce a carbonate ester (carbonate ester production reaction).

[0046] In this process, when an alcohol and carbon dioxide are reacted, water is also produced in addition to a carbonate ester. However, an aromatic amide compound is produced by a hydration reaction between the aromatic nitrile compound present in the reaction system and the produced water, and the produced water can be removed or reduced from the reaction system. In this way, by efficiently removing water from the reaction system, it is possible to promote the production of a carbonate ester. For example, as shown in the following formula:

[0047]

[0048] (Alcohol) Here, the alcohol may be any alcohol selected from one or more of primary alcohols, secondary alcohols, and tertiary alcohols. For example, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, allyl alcohol, 2-methyl-1-propanol, cyclohexanemethanol, benzyl alcohol, ethylene glycol, 1,2-propanediol, and 1,3-propanediol are preferred because they provide a high product yield and a fast reaction rate. The carbonate esters produced in this step are dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, diheptyl carbonate, dioctyl carbonate, dinonane carbonate, diallyl carbonate, di-2-methyl-propyl carbonate, dicyclohexanemethyl carbonate, dibenzyl carbonate, ethylene carbonate, 1,2-propylene carbonate, and 1,3-propylene carbonate, respectively. Furthermore, in the first reaction step, it is preferable to use an alcohol having 1 to 6 carbon atoms, and it is more preferable to use an alcohol having 2 to 4 carbon atoms. In particular, when the resulting carbonate ester is used as a raw material for diaryl carbonate, it is preferable to adjust the carbon number of the alcohol to fall within the above-mentioned range. Furthermore, it is preferable to use a monohydric or dihydric alcohol in the first reaction step.

[0049] (Carbonate Ester Production Catalyst) In the first reaction step for producing a carbonate ester, CeO ２ and ZrO ２ It is preferable to use either one or both of the solid catalysts. For example, CeO ２ Chisel, ZrO ２ Only CeO ２ and ZrO ２ or a mixture of CeO ２ and ZrO ２ Solid solutions and composite oxides of these are preferred, and CeO ２ It is preferable to use only CeO ２ and ZrO ２ The solid solutions and composite oxides of CeO ２ and ZrO２ The mixing ratio is basically 50:50, but the mixing ratio can be set as appropriate.

[0050] Here, the catalyst used in the first reaction step may be in the form of either a powder or a molded body, and in the case of a molded body, it may be in any shape such as a sphere, pellet, cylinder, ring, wheel, or granule.

[0051] (Carbon dioxide) The carbon dioxide used in the present invention is not only that prepared as an industrial gas, but also that separated and recovered from exhaust gases from factories manufacturing various products, steel mills, power plants, etc.

[0052] (Solvent in Carbonate Ester Production Reaction) In the carbonate ester production reaction, it is preferable to use a solvent having a boiling point higher than that of the amide compound to be produced. More preferably, the solvent in the carbonate ester production reaction contains at least one of dialkylbenzene, alkylnaphthalene, and diphenylbenzene. Specific examples include barrel process oil B28AN and barrel process oil B30 (manufactured by Matsumura Oil Co., Ltd.), which contain components such as dialkylbenzene, alkylnaphthalene, and diphenylbenzene.

[0053] (Distillation Separation) After the reaction, the main product, the carbonate ester, the by-product, the aromatic amide compound, the unreacted aromatic nitrile compound, CeO ２ The solid catalyst can be separated by distillation to recover the product.

[0054] (Second Reaction Step) Next, the second reaction step in the present invention will be described. In the second reaction step, the aromatic amide compound produced as a by-product in the first reaction step is preferably separated from the system after the carbonate ester production reaction, and then subjected to a dehydration reaction to produce an aromatic nitrile compound. The second reaction step corresponds to the above-mentioned method for producing an aromatic nitrile compound. That is, in the second reaction step for producing a carbonate ester, an aromatic nitrile compound is produced from an aromatic amide compound by the method described in the above-mentioned section on the method for producing an aromatic nitrile compound, thereby allowing the aromatic nitrile compound to be regenerated. Therefore, details of the second reaction step will be omitted.

[0055] (Reuse of aromatic nitrile compound) The aromatic nitrile compound regenerated in the second reaction step can be reused in the first reaction step (hydration reaction).

[0056] According to the present invention, as described above, by carrying out the dehydration reaction of an aromatic amide compound in a gas phase, it is possible to efficiently regenerate an aromatic nitrile compound from the aromatic amide compound while suppressing the generation of by-products. Furthermore, for example, by fixing a catalyst in a reaction tube, the step of solid-liquid separation of the catalyst is not required, and the recovery of the aromatic nitrile compound is also facilitated. As described above, the present invention makes it possible to selectively regenerate an aromatic nitrile compound from an aromatic amide compound, and to proceed with a series of reactions while separating each component only by distillation separation without solid-liquid separation of the catalyst, thereby realizing an efficient process as described in detail below.

[0057] 3. Carbonate Ester Production Apparatus Next, the carbonate ester production apparatus used in the present invention will be described in more detail below with reference to specific examples. Figure 1 shows an example of a suitable facility.

[0058] (First Reaction Step) In the first reaction step, raw materials, alcohol (1-propanol (PrOH); liquid phase), 2-cyanopyridine (2-CP; liquid phase), and carbon dioxide (CO ２; liquid phase, which may be supplied via a booster pump) is fed to the raw material feed pipe 31, CO ２ Collection tower top CO ２ Transfer piping (CO ２ CO at the top of the recovery tower ２ The raw material mixture is continuously supplied to the carbonic acid ester recovery tower via a top liquid transfer pipe (liquid transfer pipe on the top side of the carbonic acid ester recovery tower) 15, a carbonic acid ester recovery tower top liquid transfer pipe (liquid transfer pipe on the top side of the carbonic acid ester recovery tower) 19, and an amide separation tower top liquid transfer pipe (liquid transfer pipe on the top side of the amide separation tower) 21. ２ and ZrO ２ Dipropyl carbonate (DPrC) is synthesized by circulating the reaction mixture between a fixed-bed flow-type carbonate ester reactor 2 (first reaction section) in which a solid catalyst (solid phase) such as either one or both of the above is fixed to a support material and a buffer tank 1 via first and second reaction liquid circulation pipes 11 and 12 using a pump (not shown). The reaction liquid containing DPrC is continuously extracted from the second reaction liquid circulation pipe 12 in an amount equal to the amount of raw material supplied to the buffer tank 1, recovered via pipe 13, and sent to the DPrC recovery step. PrOH and CO ２ are recovered from the reaction liquid and are transferred to the carbonic acid ester recovery tower overhead liquid transfer pipe 19 and CO ２ Collection tower top CO ２ It can be reused by transferring it to buffer tank 1 via transfer pipe 15. As 2-cyanopyridine, for example, new 2-cyanopyridine is used at the start of the reaction, but 2-cyanopyridine regenerated from 2-picolinamide in amide separation column 6 may be separated and purified, and transferred to buffer tank 1 via amide separation column top liquid transfer pipe 21, for reuse.

[0059] For example, CeO ２ and ZrO ２ As the apparatus for directly synthesizing a carbonate ester (carbonate reactor 2) using the above as a solid catalyst, any of a batch reactor, a semi-batch reactor, a continuous tank reactor, and a flow reactor such as a tubular reactor may be used. However, a fixed bed reactor is preferred because if the catalyst is fixed in the reactor, there is no need to filter and separate the catalyst.

[0060] (Reaction Solution Temperature) The reaction solution temperature in the carbonate ester reactor 2 is preferably 50 to 300°C. When the reaction solution temperature is below 50°C, the reaction rate is low, and both the carbonate ester synthesis reaction and the hydration reaction with 2-cyanopyridine hardly proceed, resulting in low carbonate ester productivity. When the reaction solution temperature exceeds 300°C, the reaction rate of each reaction increases, but decomposition or modification of the carbonate ester is likely to occur, and aromatic amide compounds such as 2-picolinamide are more likely to react with alcohol, resulting in a low carbonate ester yield. The reaction solution temperature is more preferably 100 to 150°C. However, since the ideal reaction solution temperature is likely to vary depending on the type and amount of solid catalyst and the amounts and ratios of raw materials (alcohol, 2-cyanopyridine), it is desirable to set optimal conditions appropriately. Furthermore, since the preferred reaction solution temperature is 100 to 150°C, it is desirable to preheat the raw materials (alcohol, 2-cyanopyridine, etc.) with steam or the like upstream of the carbonate ester reactor.

[0061] (Reaction Pressure) The reaction pressure in the carbonate ester reactor 2 is preferably 0.1 to 20 MPa (absolute pressure). If the reaction pressure is less than 0.1 MPa (absolute pressure), a pressure reducing device is required, which not only makes the equipment complicated and costly, but also requires power energy to reduce the pressure, resulting in poor energy efficiency. If the reaction pressure exceeds 20 MPa, the hydration reaction with 2-cyanopyridine does not proceed easily, resulting in poor yield of carbonate ester, and also requires power energy to increase the pressure, resulting in poor energy efficiency. From the viewpoint of increasing the yield of carbonate ester, the reaction pressure is more preferably 0.5 to 15 MPa (absolute pressure), and even more preferably 1.0 to 10 MPa (absolute pressure).

[0062] (Amount of aromatic nitrile compound (2-cyanopyridine, etc.)) For aromatic nitrile compounds such as 2-cyanopyridine used in the hydration reaction, the amount of the raw material alcohol and CO ２It is preferable to use a molar amount of 0.1 to 5 times the theoretical molar amount of water produced as a by-product in the reaction with CO. It is preferable to introduce the compound into the reactor before the reaction. More preferably, the molar amount of the aromatic nitrile compound such as 2-cyanopyridine is 0.1 to 5 times the theoretical molar amount of the raw material alcohol and CO. ２ The molar amount of the aromatic nitrile compound such as 2-cyanopyridine is preferably 0.2 to 3 times, and more preferably 0.3 to 1.5 times, the theoretical molar amount of water by-produced in the reaction with the solid catalyst. If the molar amount of the aromatic nitrile compound such as 2-cyanopyridine is too small, the amount of 2-cyanopyridine and the like that contributes to the hydration reaction may be small, which may result in a poor yield of carbonate ester. On the other hand, introducing an aromatic nitrile compound such as 2-cyanopyridine in an excessive molar amount compared to the starting alcohol is undesirable because it increases side reactions such as 2-cyanopyridine. Furthermore, the ideal amount of alcohol and 2-cyanopyridine relative to the solid catalyst is thought to vary depending on the type and amount of the solid catalyst, the type of alcohol, and the ratio to 2-cyanopyridine, so it is desirable to appropriately set optimal conditions.

[0063] (Separation of Reaction Products) The reaction products are preferably all separated by distillation. After the reaction in the carbonate ester reactor 2, the reaction liquid 13 is ２ It is sent to recovery tower 3 and CO ２ From the bottom of the recovery tower 3, CO ２ Recovery column: A mixture of PrOH, DPrC, 2-cyanopyridine, and 2-picolinamide is recovered through the column bottom liquid transfer pipe 14, and CO ２ From the top of recovery tower 3, CO ２ Collection tower top CO ２ CO ２ The recovered CO ２ is sent to a buffer tank 1 and recycled to the reaction in a carbonate ester reactor 2.

[0064] CO ２ The mixture recovered from the recovery tower 3 is CO ２The resulting mixture is sent to the dehydrating agent separation column 4 via the recovery column bottom liquid transfer pipe 14, and a mixture of 2-cyanopyridine and 2-picolinamide is recovered from the bottom of the dehydrating agent separation column 4 via the dehydrating agent separation column bottom liquid transfer pipe 16, while PrOH and DPrC are recovered from the top of the dehydrating agent separation column 4 via the dehydrating agent separation column top liquid transfer pipe 17.

[0065] The mixture recovered from the bottom of the dehydrating agent separation column 4 is sent to the amide separation column 6 via the dehydrating agent separation column bottom liquid transfer pipe 16, and 2-picolinamide (20) is recovered from the bottom of the amide separation column 6, and 2-cyanopyridine is recovered from the top of the amide separation column 6. The recovered 2-cyanopyridine is sent to the buffer tank 1 via the amide separation column top liquid transfer pipe 21 and recycled for the reaction in the carbonate ester reactor 2.

[0066] PrOH and DPrC recovered from the top of the dehydrating agent separation column 4 are sent to the carbonate ester recovery column 5 via a dehydrating agent separation column top liquid transfer pipe 17, DPrC is recovered from the bottom of the carbonate ester recovery column 5 via a carbonate ester recovery column bottom liquid transfer pipe 18, and PrOH is recovered from the top of the carbonate ester recovery column 5 via a carbonate ester recovery column top liquid transfer pipe 19. The recovered PrOH is sent to a buffer tank 1 and recycled for the reaction in the carbonate ester reactor 2.

[0067] (Second Reaction Step) In the second reaction step, 2-cyanopyridine is produced by a dehydration reaction of 2-picolinamide in nitrile regeneration gas-phase reactor 8. 2-Picolinamide recovered in amide separation column 6 is transferred to vaporizer 7 through amide separation column bottom liquid transfer pipe 20, where it is mixed with an inert gas, preferably nitrogen or the like, and further heated to near the boiling point of the amide compound to form a gas or a gas-droplet mixture, which is transferred to nitrile regeneration gas-phase reactor 8 through vaporizer-nitrile regeneration gas-phase reactor connecting pipe 22. The type of vaporizer 7 that vaporizes the amide compound and the like is not particularly limited, and any of an ejector-type vaporizer, a contact vaporizer, a bubbling device, or the like may be used.

[0068] In the nitrile compound production apparatus (nitrile regeneration gas-phase reactor 8) used in the present invention, a catalyst supported on a basic metal oxide is contacted in the gas phase with 2-picolinamide and an inert gas, preferably nitrogen, etc., to cause a dehydration reaction of 2-picolinamide. This dehydration reaction produces 2-cyanopyridine. When transporting the amide compound, the amide compound can be dissolved in a transfer solvent and then transported to prevent clogging. When using an amide transfer solvent, it is preferable to vaporize the solvent together with the amide to carry out the nitrile regeneration gas-phase reaction. In this case, solvent vapor can be used instead of an inert gas.

[0069] The type of the nitrile regeneration gas-phase reactor 8 is not particularly limited, and a gas-phase reaction in which a gaseous or mist-like amide compound is passed through a catalyst layer together with an inert gas or the like is preferred, and a gas-phase reaction apparatus such as a fixed bed or a fluidized bed can be applied. In this way, in order to bring 2-picolinamide into contact with a catalyst or the like in the gas phase and efficiently cause the dehydration reaction to proceed, the various reaction conditions described above for the above-mentioned dehydration reaction or the reaction conditions described in the Examples section below can be appropriately adopted.

[0070] The mixed gas containing 2-cyanopyridine is transferred from the gas phase reactor 8 to the H ２ Transfer to O separation device 9. ２ Water and nitrogen gas are separated from the mixed gas in the O separation device 9, and the recovered 2-cyanopyridine and 2-picolinamide are mixed with H ２ O separation device H is transferred via high boiling point transfer pipe 24 ２ The 2-picolinamide is transferred from O separation device 9 to amide separation column 6. 2-Picolinamide is recovered from the bottom of amide separation column 6 via amide separation column bottom liquid transfer pipe 20 and transferred to vaporization device 7, and 2-cyanopyridine is recovered from the top of amide separation column 6. The recovered 2-cyanopyridine is sent to buffer tank 1 via amide separation column top liquid transfer pipe 21 and recycled for the reaction in carbonate ester reactor 2.

[0071] Furthermore, H ２ The nitrogen gas and water separated in the O separator 9 are mixed with H ２O separation device N ２ Send it to the recovery device 10, ２ The water is separated in the recovery device 10 and nitrogen gas is recovered. ２ The water separated in the recovery device 10 is ２ The water is sent to the outside of the carbonic acid ester unit through the recovery unit water transfer pipe 26. ２ The nitrogen gas recovered by the recovery device 10 is N ２ Recovery device N ２ By transferring the amide compound to the vaporizer 7 via the transfer pipe 27, it can be used in a gas phase reaction. When a solvent is used to transfer the amide compound, a separate process for recovering the solvent can be provided, and the solvent can be reused for transferring the amide compound. ２ O separation device 9 and N ２ The type of the recovery device 10 is not particularly limited, and any type of device such as a cooling device or a membrane separation device may be used.

[0072] As described above, in the present invention, not only can dehydration of an amide compound proceed through a contact step in the gas phase, but also the reaction product and the compound to be recycled can be separated by distillation or the like without the need for solid-liquid separation. Therefore, according to the present invention, it is possible to efficiently produce a carbonate ester with fewer production steps while simplifying the apparatus.

[0073] EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. First, examples and comparative examples of the method for producing cyanopyridine will be described.

[0074] Example 1 (Example using a solvent as a diluent) SiO as a carrier ２ (Fuji Silysia Chemical, CARiACT, G-6 (carrier diameter 0.010 mm)) was pre-baked at 700°C for 1 hour. Then, in order to support Cs as an alkali metal, CsNO was added so that the final Cs metal support amount was 0.5 mmol / g. ３ (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of SiO ２ Then, it was dried at 110°C for 6 hours and calcined at 500°C for 3 hours to form Cs ２ O / SiO ２A catalyst was obtained. The catalyst produced by the above-mentioned method was packed into a reaction tube 36 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm (see FIG. 2). Furthermore, a vaporization chamber 33 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm, and packed with Raschig rings, was installed immediately above the reaction tube 36.

[0075] 203 g of 2-picolinamide (2-PA) was heated and mixed with 200 g of 1,3,5-trimethylbenzene (transfer solvent) in a 140°C oil bath, and the resulting mixed solution of 2-PA and 1,3,5-trimethylbenzene was transferred to raw material container 30. Vaporization chamber 33 and reaction tube 36, connected to raw material container 30, were heated in tubular furnaces 34 and 35 (see FIG. 2). The outlet piping of reaction tube 36 was maintained at 180°C. A dry ice / methanol cooling trap container 37 and a trap container 38 were installed to recover the reactants. The outlet piping of trap container 38 was connected to a vacuum pump 39, and the vaporization chamber 33 and reaction tube 36 were depressurized to 40 kPa. After the temperatures of the vaporization chamber and reaction tube stabilized at 337°C, plunger pump 32 was started, and the reaction was carried out for the time shown in the column for catalyst contact time in Table 1 below.

[0076] Examples 2 to 10 and Comparative Examples 1 to 7 The dehydration reaction of 2-picolinamide was carried out in the same manner as in Example 1, using the same reaction apparatus as in Example 1, except that the reaction conditions were changed as shown in Table 1 below.

[0077] The conditions for the above-mentioned catalytic reaction (dehydration reaction) are as shown in Table 1. After the reaction was completed, the reaction product was recovered and analyzed by GC-FID.

[0078] The analytical conditions for the results of the catalytic reaction (dehydration reaction) are as follows: [Analysis conditions] (GC-FID) Shimadzu GC-2014, column: TC-17 (length 30 m, inner diameter 0.25 mm ID, liquid phase film thickness 0.25 μm), vaporization chamber temperature: 250° C., detector: 250° C., carrier N ２ Pressure: 175 kPa, column flow rate: 10.3 mL / min, split ratio: 5.0 Temperature program: [Hold at 40 ° C for 10 min] → [Heat to 250 ° C at 12 ° C / min] → [Hold at 250 ° C for 5 min]

[0079] [24-hour yield per 1 g of catalyst (mmol / 24 hr g)] = (amount of product recovered after 24 hours of reaction (mmol)) / (amount of catalyst (g)) [space velocity: SV (hr －１ ) ]=(Gas volume passing through the catalyst layer (L hr －１ )) / (amount of catalyst (L)) Gas amount: total gas volume of nitrogen, 2-PA, and solvent (L·hr －１ ) [Catalyst filling height (height of catalyst layer in reactor)]: height of catalyst filled in the reaction tube (cm) [Catalyst contact time (sec)] = [Catalyst filling height (cm)] / [Linear velocity (gas linear velocity in reactor) (cm / sec)]

[0080] [Catalyst Carrier Diameter] The catalyst carrier diameter is a value measured based on the general rules of the sieving test method specified in JIS Z 8815 by sieving method.

[0081] [Spontaneous Ignition Temperature of Solvent] The spontaneous ignition temperatures of the solvents used in the examples and comparative examples are measured values ​​or literature values. The measured spontaneous ignition temperatures are measured by an ignition point test in accordance with ASTM E659-15.

[0082] [Temperature of Vaporization Chamber / Reaction Tube and Reaction Temperature (Contact Temperature)] The temperatures of the vaporization chamber / reaction tube and the reaction temperature in the dehydration reaction were measured by inserting a sheath tube made of SUS316 with a built-in thermometer from the bottom of the reaction tube exemplified as reaction tube 36 in the schematic diagrams of the reaction apparatus in Figures 2 and 3 to a position just below the catalyst layer. That is, the temperature just below the catalyst layer was measured, and the temperature before the raw materials were passed through was taken as the temperature of the vaporization chamber / reaction tube, and the temperature after the raw materials were passed through was taken as the reaction temperature (contact temperature).

[0083] [Detection of Unknown Component] When a compound whose molecular structure could not be determined (unknown component) was detected by the measurement method for the product of the contact reaction (dehydration reaction) described in the above [Analysis Conditions] column, it was marked as "Yes", and when no unknown component was detected, it was marked as "No".

[0084]

[0085] Example 11 (Example using a solvent as a diluent) SiO as a carrier ２(Fuji Silysia Chemical, CARiACT, G-6 (carrier diameter 0.010 mm)) was pre-baked at 700°C for 1 hour. Then, in order to support Cs as an alkali metal, CsNO was added so that the final Cs metal support amount was 0.5 mmol / g. ３ (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of SiO ２ Then, it was dried at 110°C for 6 hours and calcined at 500°C for 3 hours to form Cs ２ O / SiO ２ A catalyst was obtained. The catalyst produced by the above-mentioned method was packed into a reaction tube 36 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm (see FIG. 2). Furthermore, a vaporization chamber 33 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm, and packed with Raschig rings, was installed immediately above the reaction tube 36.

[0086] 170 g of 2-picolinamide (2-PA) was heated and mixed with 187 g of p-cymene (transfer solvent) in a 140°C oil bath, and the resulting mixed solution of 2-PA and p-cymene was transferred to raw material container 30. Vaporization chamber 33 and reaction tube 36, connected to raw material container 30, were heated in tubular furnaces 34 and 35 (see FIG. 2). The outlet piping of reaction tube 36 was maintained at 180°C. A dry ice / methanol cooling trap container 37 and a trap container 38 were installed to recover the reactants. The outlet piping of trap container 38 was connected to a vacuum pump 39, and the vaporization chamber 33 and reaction tube 36 were depressurized to 40 kPa. After the temperatures of the vaporization chamber and reaction tube stabilized at 382°C, plunger pump 32 was started, and the reaction was carried out for the time shown in the column for catalyst contact time in Table 2 below.

[0087] Examples 12 to 13 and Comparative Examples 8 to 15 The same reaction apparatus as in Example 11 was used, but the reaction conditions were changed as shown in Table 2 below, and the dehydration reaction of 2-picolinamide was carried out in the same manner as in Example 11.

[0088] Example 14 SiO as a support ２(Fuji Silysia Chemical, CARiACT, G-6 (carrier diameter 0.010 mm)) was pre-baked at 700°C for 1 hour. Then, in order to support K (potassium) as an alkali metal, KNO was added so that the final amount of K metal supported was 0.5 mmol / g. ３ (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of SiO ２ After that, it was dried at 110°C for 6 hours and calcined at 500°C for 3 hours. ２ O / SiO ２ A catalyst was obtained. The catalyst produced by the above-mentioned method was packed into a SUS316 reactor tube 36 with an inner diameter of 10.8 mm and a length of 35 cm (see Figure 2). Furthermore, a vaporization chamber 33 made of SUS316 with an inner diameter of 10.8 mm and a length of 35 cm and packed with Raschig rings was installed directly above the reactor tube 6. 203 g of 2-picolinamide (2-PA) was heated and mixed with 1,3,5-trimethylbenzene (200 g) as a transfer solvent in an oil bath at 140°C, and the resulting mixed solution of 2-PA and 1,3,5-trimethylbenzene was transferred to the raw material container 30. The vaporization chamber 33 and the reactor tube 36, which were connected to the raw material container 30, were heated to 511.2°C in tubular furnaces 34 and 35 (see Figure 2). The outlet piping of the reactor tube 36 was maintained at 180°C. To recover the reactants, a dry ice / methanol cooled trap vessel 37 and a trap vessel 38 were installed. The outlet piping of the trap vessel 38 was connected to a vacuum pump 39, and the vaporization chamber 33 and the reaction tube 36 were depressurized to 40 (KPa). After the temperature of the catalyst layer stabilized, the plunger pump 32 was started, and the reaction was carried out for the time shown in the column of catalyst contact time in Table 2 below. Example 15 SiO as a carrier ２ (Fuji Silysia Chemical, CARiACT, G-6 (carrier diameter 0.010 mm)) was pre-baked at 700°C for 1 hour. Then, in order to support Na as an alkali metal, NaNO was added so that the final amount of supported Na metal was 0.5 mmol / g. ３ (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of SiO ２ Then, it was dried at 110°C for 6 hours and calcined at 500°C for 3 hours to remove Na. ２ O / SiO ２A catalyst was obtained. The catalyst produced by the above-mentioned method was packed into a reaction tube 36 made of SUS316 and having an inner diameter of 10.8 mm and a length of 35 cm (see FIG. 2). Furthermore, a vaporization chamber 33 made of SUS316 and having an inner diameter of 10.8 mm and a length of 35 cm and packed with Raschig rings was installed directly above the reaction tube 36. Using the same reaction apparatus as in Example 14, the dehydration reaction of 2-picolinamide was carried out in the same manner as in Example 14, except that the reaction conditions other than the catalyst were changed as shown in Table 2 below.

[0089] Example 16 (Example using inert gas (nitrogen gas) as diluent) SiO as carrier ２ (Fuji Silysia Chemical, CARiACT, Q-6 (carrier diameter: 0.075 to 0.15 mm)) was pre-baked at 700°C for 1 hour. Then, in order to support Cs as an alkali metal, CsNO was added so that the final Cs metal support amount was 0.5 mmol / g. ３ (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare an aqueous solution of SiO ２ Then, it was dried at 110°C for 6 hours and calcined at 500°C for 3 hours to form Cs ２ O / SiO ２ A catalyst was obtained. The catalyst produced by the above-mentioned method was packed into a reaction tube 36 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm (see FIG. 3). Furthermore, a vaporization chamber 33 made of SUS316, having an inner diameter of 10.8 mm and a length of 35 cm, packed with Raschig rings, was installed immediately above the reaction tube 36.

[0090] 100 g of 2-picolinamide (2-PA) was dissolved in an oil bath at 140°C, and the 2-PA was transferred to the raw material container 30 without using a solvent. The vaporization chamber 33 and the reaction tube 36 connected to the raw material container 30 were heated in tubular furnaces 34 and 35 (see Figure 3). The outlet piping of the reaction tube 36 was maintained at 180°C. A dry ice / methanol cooling trap container 37 and a trap container 38 were installed to recover the reactants. The outlet of the trap container 38 was open to the atmosphere. After the temperatures of the vaporization chamber and the reaction tube stabilized at 516°C, the plunger pump 32 was started, and nitrogen gas was simultaneously introduced as a diluent. The reaction was carried out for the time shown in the column for catalyst contact time in Table 2 below.

[0091] Comparative Example 16 Using the same reaction apparatus as in Example 16, the dehydration reaction of 2-picolinamide was carried out in the same manner as in Example 16, except that the reaction conditions were changed as shown in Table 2 below.

[0092]

[0093] As is clear from the results of the Examples and Comparative Examples, the higher the reaction temperature in the gas-phase dehydration reaction, the more the yield of aromatic nitrile compounds improved and the more the by-product pyridine was suppressed (see Tables 1 and 2 above, and Figures 4 and 5). In some Examples, a relatively large amount of by-products was produced, but the yield of aromatic nitrile compounds was high, and so all Examples were evaluated as being good overall.

[0094] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0095] 30 Raw material container 32 Plunger pump 33 Vaporization chamber 34 Heat medium double tube / tubular furnace 35 Heat medium double tube / tubular furnace / mantle heater 36 Reaction tube 37 Cooling trap container 38 Trap container 39 Vacuum pump 40 Nitrogen introduction line

Claims

1. A method for producing an aromatic nitrile compound, comprising a dehydration reaction for dehydrating an aromatic amide compound, the dehydration reaction having a contacting step of contacting the aromatic amide compound and a diluent with a catalyst in a gas phase, the temperature at which the aromatic amide compound and the diluent are contacted with the catalyst in the contacting step is 300°C or higher.

2. The method for producing an aromatic nitrile compound according to claim 1, wherein the diluent contains at least one of a solvent and an inert gas.

3. The method for producing an aromatic nitrile compound according to claim 2, wherein the solvent contains at least an aromatic compound.

4. The method for producing an aromatic nitrile compound according to claim 3, wherein the aromatic compound is represented by the following formula (1): (In formula (1), R １ are each independently selected from an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkoxy group having 1 to 10 carbon atoms which may have a substituent, an aryl group having 6 to 30 carbon atoms which may have a substituent, and an aryloxy group having 6 to 30 carbon atoms which may have a substituent, and a is an integer from 1 to 6.

5. The method for producing an aromatic nitrile compound according to claim 3, wherein the aromatic compound has one or two aromatic rings and one or more groups selected from an alkyl group, an alkoxy group and an aryloxy group.

6. The method for producing an aromatic nitrile compound according to claim 3, wherein the aromatic compound has a spontaneous ignition temperature of 300° C. or higher.

7. The method for producing an aromatic nitrile compound according to claim 3, wherein the aromatic compound includes at least one of 1,3,5-trimethylbenzene, p-cymene, phenyl ether and anisole.

8. The method for producing an aromatic nitrile compound according to claim 1, wherein the pressure of the reaction system in the contact step is 101.3 kPa or less.

9. The method for producing an aromatic nitrile compound according to claim 1, wherein the aromatic amide compound comprises at least a heteroaryl amide compound, and the aromatic nitrile compound comprises at least a heteroaryl nitrile compound.

10. The method for producing an aromatic nitrile compound according to claim 9, wherein the heteroaryl amide compound comprises 2-picolinamide, and the heteroaryl nitrile compound comprises 2-cyanopyridine.

11. The method for producing an aromatic nitrile compound according to claim 1, wherein a vaporized inert gas is used in the contact step.

12. The method for producing an aromatic nitrile compound according to claim 11, wherein the inert gas contains at least nitrogen gas.

13. The method for producing an aromatic nitrile compound according to claim 1, wherein the catalyst contains an alkali metal.

14. The method for producing an aromatic nitrile compound according to claim 1, wherein the solvent is compatible with the aromatic amide compound.

15. The method for producing an aromatic nitrile compound according to claim 1, wherein the catalytic contact time of the aromatic amide compound in the gas phase is 0.001 seconds or more and less than 10 seconds.

16. A method for producing a carbonate ester, comprising: a first reaction step including a carbonate ester production reaction in which an alcohol is reacted with carbon dioxide in the presence of an aromatic nitrile compound to produce a carbonate ester and water, and a hydration reaction in which the produced water is hydrated with the aromatic nitrile compound to produce an aromatic amide compound; and a second reaction step in which, after separating the aromatic amide compound from the reaction system of the first reaction step, an aromatic amide compound is regenerated from the aromatic amide compound by a dehydration reaction having a contact step according to any one of claims 1 to 15, wherein at least a portion of the aromatic nitrile compound regenerated in the second reaction step is used in the first reaction step.

17. The method for producing a carbonate ester according to claim 16, wherein a catalyst containing cerium oxide is used in the carbonate ester production reaction.

18. The method for producing a carbonate ester according to claim 16, wherein the alcohol includes an alcohol having 1 to 6 carbon atoms.

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