阅读说明：本技术 碳酸酯的制造方法 (Method for producing carbonate ester ) 是由 原田英文 矶部刚彦 刘红玉 新开洋介 梅津僚太郎 于 2019-01-08 设计创作，主要内容包括：本发明实现了一种抑制副产物的生成并且通过简易的工序以高的收率制造碳酸酯的方法,例如制造脂肪族碳酸酯的方法。上述的课题通过如下的碳酸酯的制造方法得到解决,该碳酸酯的制造方法包括在芳香族腈化合物和催化剂的存在下使醇与二氧化碳反应的碳酸酯生成反应,其中,碳酸酯生成反应所使用的醇中的水的含量为0.10质量％以下。(The present invention realizes a method for producing a carbonate ester, for example, an aliphatic carbonate ester, in a high yield by a simple process while suppressing the production of by-products. The above-mentioned problems are solved by a method for producing a carbonic ester, which comprises a carbonic ester formation reaction in which an alcohol is reacted with carbon dioxide in the presence of an aromatic nitrile compound and a catalyst, wherein the water content in the alcohol used in the carbonic ester formation reaction is 0.10% by mass or less.)

1. A method for producing a carbonate ester, characterized by:

comprising a carbonate formation reaction of reacting an alcohol with carbon dioxide in the presence of an aromatic nitrile compound and a catalyst,

the content of water in the alcohol used in the carbonate formation reaction is 0.10 mass% or less.

2. The method for producing a carbonate ester according to claim 1, wherein:

the pressure in the carbonate formation reaction is 0.6MPa or more.

3. The method for producing a carbonate according to any one of claims 1 or 2, characterized in that: the reaction temperature in the carbonate formation reaction is 110 ℃ to 160 ℃.

4. The method for producing a carbonate according to any one of claims 1 to 3, characterized in that: the molar ratio of the aromatic nitrile compound to the alcohol is 1: 1 to 1: 10.

5. The method for producing a carbonate according to any one of claims 1 to 4, wherein: the mole ratio of the catalyst, the aromatic nitrile compound and the alcohol is catalyst: aromatic nitrile compound: alcohol: 1: 100: 200 to 0.5: 100: 600.

6. The method for producing a carbonate according to any one of claims 1 to 5, wherein: the aromatic nitrile compound comprises 2-cyanopyridine.

7. The method for producing a carbonate according to any one of claims 1 to 6, wherein: the catalyst comprises CeO₂。

8. The method for producing a carbonate according to any one of claims 1 to 7, characterized in that: the alcohol contains an aliphatic alcohol, and at least an aliphatic carbonate is produced as the carbonate.

9. The method for producing a carbonate according to any one of claims 1 to 8, characterized in that: the aliphatic alcohol is represented by the following formula (1),

R-OH……(1)

in the formula (1), R represents a linear or branched saturated aliphatic alkyl group having 1 to 10 carbon atoms which may have a substituent.

10. The method for producing a carbonate according to claim 9, wherein:

r in the formula (1) is a saturated aliphatic alkyl group with 1-4 carbon atoms.

11. The method for producing a carbonate according to any one of claims 8 to 10, wherein: the aliphatic alcohol comprises 1-propanol.

12. The method for producing a carbonate according to any one of claims 1 to 11, wherein: further comprising at least one of the following first alcohol dehydration step and second alcohol dehydration step,

a first alcohol dehydration step of dehydrating the alcohol before use in the carbonate formation reaction,

a second alcohol dehydration step of dehydrating the alcohol used in the carbonate formation reaction to reuse the alcohol.

13. The method for producing a carbonate according to any one of claims 1 to 12, characterized in that: the method further comprises a regeneration step of: dehydrating the aromatic nitrile compound with an aromatic amide compound produced by hydration of water produced in the carbonate production reaction, and regenerating the aromatic nitrile compound.

14. The method for producing a carbonate according to any one of claims 1 to 13, characterized in that: the method further comprises a management process, wherein the management process comprises the following steps: keeping the water content in the alcohol below 0.10 mass% and keeping the alcohol.

Technical Field

The present invention relates to a method for producing a carbonate ester such as an aliphatic carbonate ester.

Background

The carbonate being CO (OH) carbonate₂A general term for the compounds in which 1 OR 2 hydrogen atoms among the 2 hydrogen atoms in (a) are substituted with an alkyl group OR an aryl group has a structure of RO — C (═ O) -OR '(R, R' represents a saturated hydrocarbon group OR an unsaturated hydrocarbon group).

Carbonates are very useful compounds for use as additives such as gasoline additives for increasing octane number and diesel fuel additives for reducing particulates in exhaust gas, as well as alkylating agents, carbonylating agents, solvents, and the like in the synthesis of resin-organic compounds such as polycarbonates, polyurethanes, pharmaceuticals and agricultural chemicals, as electrolyte solutions for lithium ion batteries, lubricating oil raw materials, and raw materials for deoxidizers for rust prevention in boiler pipes.

As a method for producing a carbonate ester, a method for directly synthesizing a carbonate ester from an alcohol and carbon dioxide using an heterogeneous catalyst is also known. In this method, it has been studied to greatly improve the amount and rate of production of a carbonate ester by using an aromatic nitrile compound such as 2-cyanopyridine or benzonitrile as a hydrating agent in order to increase the amount of the produced carbonate ester, and to facilitate and increase the reaction rate at a pressure close to normal pressure (see patent documents 1 and 2). However, there is a problem that the amount and rate of production of the carbonate do not always reach satisfactory levels.

Disclosure of Invention

Problems to be solved by the invention

In view of the problems of the prior art, an object of the present invention is to realize a method for producing a carbonate ester, for example, an aliphatic carbonate ester, in a high yield by a simple process while suppressing the production of by-products.

Means for solving the problems

In order to solve the above problems, the present inventors have studied a method for producing a carbonate by reacting an alcohol with carbon dioxide in the presence of an aromatic nitrile compound. Further, the inventors have studied the reaction conditions and found that the generation of by-products can be suppressed by suppressing the amount of water contained in the alcohol or 2-cyanopyridine used as the raw material in the carbonate ester-forming reaction, and a carbonate ester as the target compound can be selectively produced with a high yield.

In the present invention, the aromatic nitrile compound is regenerated into the aromatic nitrile compound by the dehydration reaction of the aromatic amide compound produced by hydration, and a carbonate ester can be produced more efficiently. The gist of the present invention is as follows.

[1] A process for producing a carbonate ester, which comprises reacting an alcohol with carbon dioxide in the presence of an aromatic nitrile compound and a catalyst to produce a carbonate ester,

the content of water in the alcohol used in the carbonate formation reaction is 0.10% by mass or less.

[2] The process for producing a carbonic ester according to the above [1], wherein the pressure in the carbonic ester-forming reaction is 0.6MPa or more.

[3] The process for producing a carbonate ester according to any one of the above [1] and [2], wherein the reaction temperature in the carbonate ester-forming reaction is 110 ℃ to 160 ℃.

[4] The method for producing a carbonate ester according to any one of [1] to [3], wherein the molar ratio of the aromatic nitrile compound to the alcohol is aromatic nitrile compound: alcohol: 1: 10.

[5] The process according to any one of [1] to [4], wherein the molar ratio of the catalyst to the aromatic nitrile compound to the alcohol is from 1: 100: 200 to 0.5: 100: 600.

[6] The method for producing a carbonate ester according to any one of the above [1] to [5], wherein the aromatic nitrile compound contains 2-cyanopyridine.

[7]As described above [1]～[6]The method for producing carbonate according to any of the above, wherein the catalyst contains CeO₂。

[8] The method for producing a carbonate ester according to any one of the above [1] to [7], wherein the alcohol contains an aliphatic alcohol, and at least an aliphatic carbonate ester is produced as the carbonate ester.

[9] The method for producing a carbonate ester according to any one of the above [1] to [8], wherein the aliphatic alcohol is represented by the following formula (1).

R-OH……(1)

[ in the formula (1), R represents a linear or branched saturated aliphatic alkyl group having 1 to 10 carbon atoms which may have a substituent. ]

[10] The process for producing a carbonate ester according to the above [9], wherein R in the formula (1) is a saturated aliphatic alkyl group having 1 to 4 carbon atoms.

[11] The method for producing a carbonate ester according to any one of the above [8] to [10], wherein the aliphatic alcohol contains 1-propanol.

[12] The method for producing carbonic acid esters according to any one of the above [1] to [11], further comprising at least one of the following first alcohol dehydration step and second alcohol dehydration step,

a first alcohol dehydration step of dehydrating the alcohol before use in the carbonate formation reaction,

a second glycol dehydration step of dehydrating the alcohol used in the carbonate formation reaction to reuse the alcohol.

[13] The method for producing a carbonic ester according to any one of the above [1] to [12], further comprising a regeneration step of: the aromatic nitrile compound is dehydrated from the aromatic amide compound produced by hydration of water produced in the carbonate production reaction, and the aromatic nitrile compound is regenerated.

[14] The method for producing a carbonic ester according to any one of the above [1] to [13], further comprising a management step of: the alcohol is preserved while maintaining the water content in the alcohol at 0.10 mass% or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the amount of water in the alcohol used for producing the carbonate ester is reduced, whereby the generation of by-products can be suppressed, and the carbonate ester as the target compound can be selectively produced with a high yield. In addition, according to the present invention, the activity of the catalyst can be sufficiently recovered and reused. As will be described in detail later, the yield of carbonate ester can be increased and the process for producing carbonate ester can be simplified by adjusting the types of the cleaning alcohol and the alcohol used for producing carbonate ester.

As described above, according to the present invention, it is possible to realize a highly efficient method for producing a carbonate ester, in which the yield of the desired carbonate ester is high and the production of by-products is suppressed.

Drawings

FIG. 1 shows an example of an apparatus for producing a carbonate.

Fig. 2 is a diagram showing states of respective substances in respective steps of the manufacturing apparatus of fig. 1.

FIG. 3 is a graph showing the yield of carbonate in a carbonate formation reaction in which the reaction pressure is varied.

FIG. 4 is a graph showing the production rate of by-products in the carbonate production reaction in which the reaction pressure is varied.

FIG. 5 is a graph showing the yields of carbonates in carbonate-forming reactions in which the ratios of alcohol and aromatic nitrile compound as raw materials are different.

FIG. 6 is a graph showing the production rates of by-products in carbonate production reactions in which the ratios of an alcohol and an aromatic nitrile compound as raw materials are different.

FIG. 7 is a graph showing the yield of carbonate in the carbonate formation reaction by varying the reaction temperature.

FIG. 8 is a graph showing the amounts of by-products produced in a carbonate-producing reaction in which the reaction temperature is varied.

FIG. 9 is a graph showing the yield of carbonate in a carbonate-forming reaction in which the reaction pressure is varied under reaction conditions in which the ratio of the aromatic nitrile compound to the alcohol is different from that in the reaction of the results shown in FIG. 3.

FIG. 10 is a graph showing the rate of formation of by-products in a carbonate-forming reaction in which the reaction pressure is varied under reaction conditions in which the ratio of the aromatic nitrile compound to the alcohol is different from that in the reaction of the results shown in FIG. 3.

FIG. 11 is a graph showing the yield of carbonate in a carbonate formation reaction in which the reaction pressure is varied under reaction conditions in which the amount of catalyst used is different from that in the reaction of the results shown in FIG. 9.

FIG. 12 is a graph showing the rate of formation of by-products in a carbonate-forming reaction in which the reaction pressure is varied under reaction conditions in which the amount of catalyst used is different from that in the reaction of the results shown in FIG. 10.

FIG. 13 is a graph showing the change with time in the amount of carbonate formed in the carbonate formation reaction between the case of using an alcohol having a large water content and the case of using an alcohol having a small water content.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In the present specification and the drawings, the same reference numerals are used for components having substantially the same functional configuration, and thus, redundant description is omitted.

< 1. Process for producing carbonate ester

The method for producing a carbonate ester of the present invention includes a carbonate ester-forming reaction for forming a carbonate ester from carbon dioxide and an alcohol. In the carbonate formation reaction, an aliphatic carbonate is formed using, for example, an aliphatic alcohol as the alcohol. The method for producing a carbonate will be described below.

(carbonate formation reaction)

The process for the production of the carbonates of the invention comprises the synthesis of the carbonates by the methods described inContaining CeO₂A step of obtaining a carbonate by a reaction (carbonate formation reaction) in which an alcohol and carbon dioxide are directly reacted in the presence of a solid catalyst such as cerium oxide. In the carbonate formation reaction, propanol (PrOH: e.g., 1-propanol) is used to obtain dipropyl carbonate (O ═ C (OPr))₂: specific examples of DPrC) are represented by the following formula (2).

(alcohol in the carbonate formation reaction)

The alcohol used in the carbonate production reaction is preferably an aliphatic alcohol. The aliphatic alcohol may be any of primary, secondary and tertiary alcohols, or may be a mixture of one or two or more of these. The alcohol used in the carbonate formation reaction is not limited to an aliphatic alcohol.

For example, in the R — OH of the formula (1), R is preferably any of an aromatic group which may include a phenyl group, a benzyl group, an aryl group having a plurality of rings (may be a condensed ring), or the like and which may have a substituent such as a halogen, and a linear or branched saturated aliphatic alkyl group having 1 to 10 carbon atoms which may have a substituent such as a halogen, and the alcohol of the formula (1) is more preferably an aliphatic alcohol as described above. The number of carbon atoms of R in the formula (1) is preferably 1 to 8, preferably 1 to 6, preferably 1 to 4, and particularly preferably 2 to 4 when R is an aliphatic group. When R is an aromatic group, the number of carbon atoms of R in formula (1) is preferably 6 to 24, more preferably 6 to 20, and still more preferably 6 to 16.

The aliphatic alcohol may be any of saturated and unsaturated aliphatic alkyl groups as R in the formula (1), and may have, for example, 3 or less unsaturated bonds, but is preferably a saturated aliphatic alkyl group. That is, R in the formula (1) is preferably a saturated aliphatic alkyl group having 1 to 8 carbon atoms, more preferably a saturated aliphatic alkyl group having 1 to 6 carbon atoms, and particularly preferably a saturated aliphatic alkyl group having 1 to 4 carbon atoms.

Specific examples of the aliphatic alcohol as a raw material for the carbonate formation reaction include methanol, ethanol, 1-propanol, isopropanol (2-propanol), 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, allyl alcohol, 2-methyl-1-propanol, cyclohexanemethanol, ethylene glycol, 1, 2-propylene glycol, and 1, 3-propylene glycol, and when these alcohols are used, the yield of the product is high and the reaction rate is high, which is preferable. When the above-mentioned alcohol is used, the produced carbonates are dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, dipentyl carbonate, dihexyl carbonate, diheptyl carbonate, dioctyl carbonate, dinonyl carbonate, diaryl carbonate, di-2-methyl-propyl carbonate, dicyclohexylmethyl carbonate, dibenzyl carbonate, ethylene carbonate, 1, 2-propylene carbonate, and 1, 3-propylene carbonate, respectively.

Among the above-mentioned specific examples, propanol or butanol, particularly 1-propanol (n-propanol), is preferably used.

When a carbonate obtained by a carbonate formation reaction is used as a raw material for a diaryl carbonate, among the above specific examples, an alcohol having 1 to 6 carbon atoms is preferable, and an alcohol having 1 to 4 carbon atoms is more preferable.

(amount of water in alcohol used in carbonate formation reaction)

In the carbonate production reaction, an alcohol having a water content of 0.10 mass% or less as an impurity is used as a raw material. The water content of the alcohol used in the carbonate formation reaction is preferably 0.09% by mass or less, more preferably 0.08% by mass or less, still more preferably 0.07% by mass or less, for example, 0.064% by mass or less, and particularly preferably 0.05% by mass or less.

If the carbonate formation reaction continues for a relatively long time, water as a by-product which is not completely removed and water content of the raw material to be replenished increase, or water in the raw material tends to gradually increase due to absorption of water in the atmosphere by the raw material stored in a tank or the like. Therefore, in order to maintain the reaction conditions well over a long period of time, it is preferable to suppress the amount of water contained in the alcohol used in the carbonate formation reaction and the 2-cyanopyridine as the dehydrating agent. In particular, the amount of alcohol used is larger than that of the dehydrating solvent, and the alcohol is consumed in the reaction and needs to be gradually replenished, and therefore, it is desirable to control the amount of water. The water content of the alcohol at the time of starting the reaction is preferably 0.04% by mass or less, more preferably 0.02% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.005% by mass or less.

Further, when the water content of the alcohol used in the carbonate formation reaction exceeds 0.14%, the yield of the carbonate as the target compound tends to decrease and the amount of by-products tends to increase, and therefore, it is desirable that the water content in the alcohol is at least 0.14% or less.

(dehydration step of alcohol)

The alcohol having a relatively high water content is preferably used in the carbonate formation reaction after dehydration. Therefore, in the carbonate production reaction, it is preferable to employ not only a step of dehydrating the alcohol before use (first alcohol dehydration step) which may include a supplementary alcohol, but also a step of dehydrating the alcohol stored in, for example, a tank (second alcohol dehydration step) in order to reuse the alcohol which has been used in the carbonate production reaction.

In these dehydration steps, a method such as fractional distillation in a distillation column may be used in addition to a drying agent such as a molecular sieve, calcium oxide, activated anhydrous calcium sulfate, magnesium oxide, magnesium sulfate, anhydrous potassium carbonate, or silica gel. In the second glycol dehydration step, it is preferable to provide a dehydration tank or dehydration line filled with a dehydrating agent separately from the reaction system such as a tank for storing alcohol, and to circulate the alcohol in the dehydration tank or dehydration line to perform dehydration. By reusing the alcohol whose water content has been reduced in this manner, the reaction apparatus can be continuously operated over a long period of time, and a carbonate can be produced at a high yield.

(alcohol control step)

In order to reliably suppress the amount of water in the alcohol used in the carbonate formation reaction, it is preferable to appropriately measure the amount of water and store the alcohol. When alcohol is stored, it is preferable to store the alcohol while controlling the water content so that the water content does not exceed a predetermined reference value, for example, 0.10 mass%. By controlling the water content in the alcohol to be 0.10 mass% or less in this way, the alcohol can be used in the carbonate production reaction while the water content is reliably suppressed to a predetermined level or less.

In the control step, the water content of the alcohol used for the carbonate formation reaction is preferably maintained at 0.09 mass% or less. The water content of the alcohol is more preferably maintained at 0.08 mass% or less, still more preferably at 0.07 mass% or less, for example, at 0.064 mass% or less, and particularly preferably at 0.05 mass% or less by the control step.

(catalyst for production of carbonate)

In the carbonate formation reaction, CeO is preferably contained as an active ingredient₂The catalyst of (1). In addition, CeO can be used₂Other components also containing ZrO₂、ReO₂、NiO、Al₂O₃、Y₂O₃And the like. The catalyst used in the carbonate formation reaction preferably contains only CeO, for example₂Or containing CeO₂And ZrO₂Mixture of (5), CeO₂And ZrO₂The solid catalyst containing only CeO is particularly preferably used₂A solid catalyst as an active ingredient. In addition, CeO₂And ZrO₂In the solid solution or composite oxide of (4), CeO is substantially contained₂And ZrO₂The mixing ratio of (3) was 50: 50, but the mixing ratio can be changed as appropriate.

The catalyst used in the carbonate formation reaction may be in the form of a powder or a molded body. If activity is considered, the catalyst is preferably in the form of a powder. On the other hand, in consideration of the filtration and separation steps, the catalyst is preferably a shaped body, and in the case of the shaped body, the catalyst may be spherical, granular, cylindrical, cyclic, wheel-shaped, granular, or the like.

Further, CeO to be used as an active ingredient may be used as the catalyst₂And a catalyst obtained by supporting the same on a carrier. For example, SiO supported on a carrier as an active ingredient can be used₂、ZrO₂、Al₂O₃、TiO₂Activated carbon and zeolite, etcCatalyst of any 1 or 2.

The average particle size of the catalyst is preferably 0.01 to 200. mu.m, more preferably 1 to 100. mu.m, and particularly preferably 5 to 50 μm. In addition, the specific surface area of the catalyst is preferably 50 to 200m²A concentration of 70 to 200m is more preferable²A specific preferred range is 100 to 200m²/g。

The numerical ranges of the average particle diameter and the specific surface area are those concerning the content of substantially only CeO₂Etc., for example, 99 wt% or more of the particles of the active ingredient, when the catalyst includes a support or a molded body, is not a range with respect to the particle diameter and specific surface area of the particles including the support or the molded body. In the catalyst comprising the support or the shaped body, it is preferable that the particles of the active ingredient used in the production of the catalyst have an average particle diameter and a specific surface area within the above ranges.

In addition, when the catalyst contains components other than the active component, for example, components such as a carrier and a molded body, the catalyst preferably contains at least 50 wt% or more of the active component, more preferably at least 70 wt% or more of the active component, and particularly preferably at least 90 wt% or more of the active component.

(carbon dioxide)

Carbon dioxide used in the carbonate production reaction may be carbon dioxide produced as an industrial gas, or carbon dioxide separated and recovered from exhaust gas from a plant, an iron plant, a power plant, or the like, which produces various products.

(aromatic nitrile Compound)

Examples of the aromatic nitrile compound used in the carbonate formation reaction include 2-cyanopyridine (2-CP), cyanopyrazine, and benzonitrile. Among these, 2-cyanopyridine is particularly preferable.

(use of solvent in carbonate formation reaction)

In the carbonate production reaction, the catalyst is in the form of a powder, and therefore the catalyst and the reaction system can be easily separated by filtration or the like. Therefore, solid-liquid separation by distillation is not required, and the use of a solvent is not required. In this way, the components of the reaction system required can be minimized by not using a solvent in the carbonate production reaction and the method for producing a carbonate including the carbonate production reaction. However, a solvent may be used in the carbonate formation reaction. For example, the solvent used in the carbonate formation reaction may be any of dialkylbenzene, alkylnaphthalene, diphenylbenzene, and the like.

(hydration step)

As shown in the above formula (2), when alcohol and carbon dioxide are reacted in the carbonate formation reaction, water is also formed together with the carbonate. Therefore, in order to efficiently produce a carbonate by the equilibrium reaction of the formula (2), it is preferable to remove water from the reaction system. Therefore, it is preferable to add a nitrile compound, preferably an aromatic nitrile compound, to the reaction system, to produce an amide compound by hydration reaction with water, and to remove the produced water from the reaction system.

Thus, if a hydration step of hydrating an aromatic nitrile compound with water as a by-product to produce an aromatic amide compound is employed, the formation of a carbonate can be promoted by efficiently removing water from the reaction system. For example, as shown in the following formula (3).

(Process for regenerating aromatic nitrile Compound)

As shown in the above formula (3), an aromatic amide compound is produced as a by-product as a result of the hydration step. It is preferable that the aromatic amide compound by-produced in this manner is separated from the system after the carbonate production reaction, and then dehydrated to regenerate the aromatic nitrile compound. The regenerated aromatic nitrile compound can be reused in the hydration reaction described above.

As a method for producing (regenerating) the aromatic nitrile compound, for example, a method comprising C_S2A method using a reaction represented by the following formula (4) which is carried out in the presence of a catalyst of a basic metal oxide such as O and a predetermined solvent. In this reaction, 2-picolinamide as an aromatic amide compound is converted into an aromatic nitrile by a dehydration reactionThe compound is 2-cyanopyridine.

The catalyst used in the dehydration reaction of the present invention contains an oxide of an alkali metal (K, Li, Na, Rb, Cs) which is basic. In particular, as the catalyst used in the above reaction, a catalyst containing at least one oxide of Na, K, Rb and Cs (cesium) is preferably used. In addition, as the carrier of the catalyst, a carrier which is generally used as a carrier of a catalyst can be used, but as a result of research on various carriers, it is possible to preferably use a carrier supported on SiO₂、ZrO₂Any one of 1 or 2.

Further, if the above-mentioned carbonate formation reaction is continued, the activity of the catalyst is lowered. Therefore, the used catalyst may be separated and recovered, and then regenerated. As a method for regenerating the catalyst, for example, a method in which a catalyst used for a certain period or longer is separated from the reaction system as a crude catalyst, and a cleaning step and a firing step are performed using a cleaning liquid such as a cleaning alcohol can be employed. As the cleaning alcohol, it is preferable to use the same alcohol as the alcohol used in the carbonate formation reaction.

(pressure in the carbonate formation reaction)

The reaction pressure for producing a carbonate is preferably 0.6MPa (absolute pressure) or more. When the reaction pressure is set to 0.6MPa (absolute pressure) or more, the carbonate ester as the target compound can be obtained in a high yield, and the occurrence of by-products can be suppressed. On the other hand, when the reaction pressure is set to be low, a pressure reducing device is required, which not only complicates the equipment and increases the cost, but also requires power energy for pressure reduction, and thus energy efficiency is poor.

The upper limit of the reaction pressure may be set to, for example, about 20MPa (absolute pressure), preferably 10MPa or less, and more preferably 8MPa or less. If the reaction pressure is too high, the hydration reaction of the aromatic nitrile compound may be difficult to proceed, and the yield of the carbonate may be reduced.

As described above, the pressure in the carbonate production reaction is preferably set to be in the range of 0.6 to 8MPa (absolute pressure), more preferably 1.0 to 6.0MPa, and still more preferably 2.0 to 4.0 MPa.

(reaction temperature for producing carbonate)

The reaction temperature (temperature of the reaction solution) in the carbonate formation reaction can be adjusted within a range of about 50 to 300 ℃, and is preferably in a range of 110 ℃ to 160 ℃. When the reaction temperature is too low, the reaction rate tends to be low, the carbonate synthesis reaction and the hydration reaction of the aromatic nitrile compound tend to be difficult to proceed, and the productivity of the carbonate tends to be low. When the reaction temperature is too high, the reaction rate of each reaction becomes high, but the yield of the carbonate tends to be low because decomposition and denaturation of the carbonate, the above-mentioned side reaction of 2-picolinamide with alcohol, and the like are likely to occur. The reaction temperature is more preferably 100 to 150 ℃.

As described above, the temperature in the carbonate formation reaction is preferably set in the range of 110 ℃ to 160 ℃, more preferably 120 ℃ to 155 ℃, still more preferably 125 ℃ to 150 ℃, and particularly preferably 130 ℃ to 145 ℃.

Further, the preferable reaction temperature is considered to vary depending on the kind and amount of the solid catalyst, the amount and ratio of the raw materials (alcohol and aromatic nitrile compound), and therefore, it is desirable to appropriately set the optimum conditions. Further, since the preferable reaction temperature is 110 to 160 ℃, it is desirable to preheat the raw material (alcohol, aromatic nitrile compound) with steam or the like before use in the carbonate reaction.

(ratio of component in carbonate formation reaction)

In the carbonate production reaction, the molar ratio of the aromatic nitrile compound to the alcohol is preferably 1: 1 to 1: 10. The ratio of aromatic nitrile compound to alcohol (mole ratio) is more preferably 1: 1 to 1: 8, and particularly preferably 1: 2 to 1: 6.

The molar ratio of the catalyst to the aromatic nitrile compound to the alcohol is preferably 1: 100: 200 to 0.5: 100: 600. The ratio of the catalyst to the aromatic nitrile compound is more preferably 0.9: 100: 300 to 0.6: 100: 500, and particularly preferably 0.8: 100: 400 to 0.7: 100: 500.

In this case, the molar ratio of the catalyst to the aromatic nitrile compound is preferably 10 to 0.05: 100, and more preferably 1 to 0.5: 100. Further, the molar ratio of the catalyst to the alcohol is preferably 1: 10 to 1: 1200, and more preferably 1: 200 to 1: 1200. By adjusting the ratio of the components in the carbonate production reaction to be within the above range, the yield of carbonate can be improved and the production of by-products can be suppressed.

< 2. apparatus for producing carbonate ester

Next, a manufacturing apparatus used in the present invention will be described in more detail by exemplifying specific examples below. FIG. 1 shows an example of an apparatus suitable for producing a carbonate ester. Fig. 2 is a view schematically showing the states of the respective substances in the respective steps in the present facility in fig. 1.

(carbonate formation reaction)

Alcohol (1-propanol (PrOH); liquid phase), 2-cyanopyridine (2-CP; liquid phase), and carbon dioxide (CO) supplied via booster pump 15₂(ii) a Gas phase) or the like is supplied from the buffer tank 1 to be filled with the CeO-containing liquid₂A solid catalyst (solid phase) as a main component in the reaction tube 2. In the reaction tube 2 to which these components are supplied, a carbonate-forming reaction proceeds. Further, the 2-cyanopyridine is used as a new product at the start of the reaction, but it is also possible to reuse the 2-cyanopyridine 27 (gas phase) separated and purified in the dehydrating solvent separation column 6 and the 2-cyanopyridine 31 (liquid phase) purified in the water separation column 8 and regenerated from 2-picolinamide.

In the direct synthesis apparatus for a carbonate shown in FIG. 1, any of flow-through reactors such as a batch reactor, a semi-batch reactor, a continuous tank reactor and a tubular reactor may be used.

The reaction temperature (reaction liquid temperature) in the reaction tube 2 is preferably 50 to 300 ℃, and more preferably 100 to 160 ℃. The reaction pressure in the reaction tube 2 is, for example, 0.1 to 20MPa (absolute pressure), preferably 0.6 to 8 MPa.

CeO used for carbonate formation in carbonate reaction tube 2₂After the catalyst activity is lowered when the catalyst is used for a certain period of time or longer, PrOH36 for cleaning is supplied to the reaction tube 2 to remove catalyst poison for the purpose of catalyst regeneration. Thereafter, the crude PrOH37 containing catalyst poison due to the cleaning of the reaction tube 2 was purified by the PrOH distillation column 9, and the purified PrOH38 was returned to the PrOH tank 10.

In addition, the PrOH tank 10 is externally supplemented with PrOH34 of the reaction raw material. A dehydration tank (neither shown) filled with a dehydrating agent is connected to the PrOH tank 10, and water in PrOH fed from the PrOH tank 10 to the dehydration tank is removed. The thus purified PrOH36 is returned to the PrOH tank 10 and supplied to the reaction tube 2.

The water content in PrOH stored in PrOH tank 10 is preferably measured periodically, for example, and is managed to be an upper limit value, for example, 0.10 wt% or less, which is a management standard of the water content.

The reaction solution 17 after the reaction is sent from the reaction tube 2 to the buffer tank 1. A reaction liquid 18 containing dipropyl carbonate (DPrC) as a target compound produced in the reaction tube 2 is sent from the buffer tank 1 to the low boiling fractionation column 3. CO recovery from overhead of low boiling fractionation column 3₂19. PrOH and DPrC. CO 2₂19 with newly added CO ₂40 together from CO₂Tank 11 is sent to booster pump 15 and used for the carbonate-forming reaction.

Further, the mixture 21 recovered from the low boiling point fractionation column 3, that is, the mixture 12 of 2-cyanopyridine and 2-picolinamide is sent to the dehydrating solvent separation column 6, 2-picolinamide 28 is recovered from the bottom of the dehydrating solvent separation column, and 2-cyanopyridine 27 is recovered from the top of the column. The recovered 2-cyanopyridine 27 is recycled to the reaction tube 2 via the 2-CP tank 13 and the buffer tank 1.

PrOH and DPrC20 recovered from the top of the low boiling substance separation column 3 are sent to an alcohol (PrOH) recovery column 4, crude DPrC (crude dipropyl carbonate) 23 is recovered from the bottom of the alcohol recovery column 4, and crude DPrC23 is sent to a DPrC (dipropyl carbonate) purification column 5. On the other hand, PrOH22 was recovered from the top of the alcohol recovery column 4. The recovered PrOH is recycled to the reaction tube 2 via the PrOH tank 10.

In the DPrC purification column 5, the crude DPrC23 is purified, and the obtained purified DPrC24 is recovered as a final target compound. On the other hand, impurities and the like are discarded as the scrap 25.

The 2-picolinamide (2-PA; 28) recovered in the dehydrating solvent separation column 6 is used for the regeneration of 2-cyanopyridine and transferred to the nitrile regeneration reactor 7. In the nitrile regeneration reactor 7, in the presence of Cs₂The catalyst of O and the solvent of diphenyl ether (DPE) are used for regenerating 2-cyanopyridine (2-CP) through the dehydration reaction of 2-picolinamide.

The 2-cyanopyridine 29 may be recovered from the water separation column 7 during the reaction, or may be directly distilled and recovered after the completion of the reaction. The recovered 2-cyanopyridine 29 is sent to the water separation column 8 together with a part of the solvent DPE. The 2-cyanopyridine 31 purified and recovered in the water separation column 8 is sent to the reaction tube 2 via the 2-CP tank 13 or the like, and reused for the production of a carbonic acid ester. On the other hand, the solvent DPE30 recovered in the water separation column 8 was recycled to the nitrile regeneration reactor 7.

In the above-described embodiment of the present invention, when PrOH38 as an alcohol used in the production of dipropyl carbonate (DPrC) as a carbonate and PrOH34 newly supplied to the reaction system are dehydrated in the PrOH tank 10, dipropyl carbonate (DPrC) can be selectively obtained in a high yield.