JP2009242306A - Process for producing carbonic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a process for industrially advantageously producing a carbonic ester from carbon dioxide and an alcohol with the use of a catalyst comprising a metallic compound or a metallic compound and an acidic compound and an organic dehydrating agent as a continuous process. <P>SOLUTION: In the process for producing a carbonic ester from carbon dioxide and an alcohol in the presence of a catalyst comprising a metallic compound or a metallic compound and an acidic compound and an organic dehydrating agent, an acetal having a reaction equilibrium constant with water at a reaction temperature of 5.0×10<SP>3</SP>to 1.0×10<SP>6</SP>and a difference in the boiling point between itself and the carbonic ester formed of not less than 10°C is used as the organic dehydrating agent. In this reaction, a reaction mixture comprising the organic dehydrating agent and a water reaction product is obtained, and from this reaction mixture, a distillate having the carbonic ester as the main component is separated, and the organic dehydrating agent and the water reaction product in the residual fluid are dehydrated to regenerate the organic dehydrating agent, and the regenerated organic dehydrating agent is recycled to the reaction step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a carbonate by reacting carbon dioxide and alcohol with a metal compound or a catalyst containing a metal compound and an acidic compound in the presence of an organic dehydrating agent.

  Carbonic acid esters are useful compounds as polycarbonate raw materials, lithium battery electrolytes, gasoline additives for improving octane number, alkylating agents in various reactions, carbonylating agents, and the like.

  As a conventional method for producing a carbonate ester, there is known a method for producing a carbonate ester by reacting phosgene with a carbonylating agent, an alcohol such as methanol or ethanol, or phenol, and it is produced on an industrial scale. ing. However, this method uses phosgene, which is extremely toxic and corrosive, so care must be taken in handling such as transportation and storage, maintenance of production facilities, waste disposal, ensuring worker safety, etc. Was costly.

Therefore, a method for producing a carbonate ester without using phosgene is desired, and various methods have been studied.
Examples of carbonic acid ester production methods that do not use phosgene include oxidative carbonylation in which carbon monoxide is used as a carbonylating agent to react with alcohol and oxygen, a method in which oxirane and carbon dioxide are reacted, a method in which urea and alcohol are reacted, and the like. Is known (see Non-Patent Document 1).
In addition, Itakura et al. Of the present inventor have found a method of using an alcohol as a substrate in a method for producing a carbonate ester by using a cyclopentadienyl-based metal catalyst. When producing dimethyl carbonate or diethyl carbonate, which are industrially important carbonates, by this method, methanol or ethanol is used as the alcohol.

Since the esterification reaction for producing the carbonate ester is an equilibrium reaction, it is necessary to discharge water produced as a by-product during the reaction out of the reaction system in order to advance the reaction.
As a method of removing by-product water out of the system, water is removed by a chemical engineering technique such as reactive distillation (see Patent Document 1), or water is used by reaction or adsorption in the presence of a dehydrating agent. And the like (see Patent Documents 2 and 3).

  However, when the alcohol used for the reaction is a lower alcohol such as methanol or ethanol, there is a drawback that the lower alcohol itself is discharged out of the system together with the product in the reactive distillation. In addition, a large amount of energy is required for the distillation operation.

  For this reason, when lower alcohol is used as a reaction substrate, it is preferable to remove by-product water by coexisting a dehydrating agent.

  Conventionally, in the production of carbonic acid ester using alcohol as a substrate, as a dehydrating agent, a method using molecular sieve (Patent Document 2), benzaldehyde dimethyl acetal, acetaldehyde dimethyl acetal, formaldehyde dimethyl acetal, acetone dimethyl acetal, acetone diethyl acetal, Acetone dibenzyl acetal, diethyl ketone dimethyl acetal, benzophenone dimethyl acetal, benzyl phenyl ketone dimethyl acetal, cyclohexanone dimethyl acetal, acetophenone dimethyl acetal, 2,2-dimethoxy-2-phenylacetophenone, 4,4-dimethoxy-2,5-cyclo Acetas such as hexadiene-1-one acetal and dimethylacetamide diethyl acetal Organic compound of a dehydrating agent such as Le method using an (organic dehydrating agent) (Patent Documents 3 and 4) have been disclosed.

Of these, the method using acetal as a dehydrating agent is an industrially continuous process because it is difficult to separate the produced carbonic acid ester from the dehydrating agent acetal or the dehydrating performance is insufficient. This reaction was not necessarily appropriate.
Patent No. 2049036 JP 2001-247519 A JP 2005-145939 A JP 2008-24593 A Ullmann's Encyclopedia Of Industrial Chemistry, 6th Edition, Vol.6 P427-455 (2003)

  An object of the present invention is to provide a method for industrially advantageously producing a carbonate ester from carbon dioxide and alcohol using a catalyst comprising a metal compound or a metal compound and an acidic compound and an organic dehydrating agent. . Furthermore, it aims at providing the practical method which can perform manufacture of such carbonate ester as a continuous process.

  As a result of studying to solve the above-mentioned problems, the present inventors have dehydrated carbon dioxide and alcohol in the production reaction of carbonate ester in a method of industrially producing carbonate ester using a metal compound and an organic dehydrating agent. As an organic dehydrating agent used as an agent, the reaction efficiency can be increased by using an organic dehydrating agent, and the product can be easily separated from the carbonate ester product by distillation. In the process of regenerating the organic dehydrating agent and water reaction product by-produced during the production of organic dehydrating agent, it was found that the organic dehydrating agent can be easily regenerated by using another organic dehydrating agent, and the present invention was completed. I came to let you.

That is, the first gist of the present invention is a method for producing a carbonate by reacting carbon dioxide and alcohol with a metal compound or a catalyst containing a metal compound and an acidic compound in the presence of an organic dehydrating agent. The organic dehydrating agent is an acetal having a reaction equilibrium constant with water at the reaction temperature of 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ and a difference in boiling point from the produced carbonate of 10 ° C. or more. A feature of the carbonated ester production method.

The second gist of the present invention resides in a method for producing a carbonate ester comprising at least the following steps (a) to (d).
(A) The reaction equilibrium constant between carbon dioxide and alcohol, a catalyst containing a metal compound or a metal compound and an acidic compound, and water at the reaction temperature is 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ , The reaction is carried out in the presence of an organic dehydrating agent made of acetal having a boiling point difference of 10 ° C. or higher with respect to the produced carbonic acid ester, and a reaction product of the carbonic acid ester and the organic dehydrating agent with water (“organic dehydrating agent / water reactant” To obtain a reaction mixture containing "."
(B) A step of separating a fraction containing carbonate ester as a main component from the reaction mixture of step (b) to obtain a residual liquid.
(C) A step of regenerating the organic dehydrating agent by dehydrating the organic dehydrating agent / water reaction product in the residual liquid in the step (b).
(D) A step of circulating the organic dehydrating agent regenerated in step (c) to step (b).

  The third gist of the present invention is the carbonic acid according to claim 1 or 2, wherein the organic dehydrating agent is 2,2-dimethoxyheptane and / or 2,2-dimethoxy-4-methylpentane. The production method of the ester.

  The fourth gist of the present invention is to regenerate the organic dehydrating agent (referred to as “reactive organic dehydrating agent”) / water reaction product into the residual liquid into the organic dehydrating agent for reaction and the organic dehydrating agent for reaction. The method for producing a carbonic acid ester according to claim 2 or 3, wherein the method is carried out by adding an organic dehydrating agent for regeneration different from the organic dehydrating agent for reaction, which can be separated from the water reactant by distillation, Exist.

  The fifth gist of the present invention resides in the method for producing a carbonate ester according to any one of claims 1 to 4, wherein the alcohol is methanol and the carbonate ester is dimethyl carbonate. .

  According to the present invention, in a method for producing a carbonic ester by reacting carbon dioxide and alcohol in the presence of a metal compound or a catalyst containing a metal compound and an acidic compound, an acetal having specific properties is used as a dehydrating agent. The reaction efficiency can be increased, and the product carbonate can be easily separated from the product by distillation, so that a highly pure carbonate can be produced industrially advantageously.

  Moreover, the organic dehydrating agent can be easily regenerated from another organic dehydrating agent from the organic dehydrating agent / water reaction product by-produced during the production of the carbonic acid ester using such an organic dehydrating agent. The production of carbonate ester can be performed as a continuous process.

  Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

The carbonic acid ester production method of the present invention comprises the step of reacting carbon dioxide and alcohol in the presence of a metal compound or a catalyst containing a metal compound and an acidic compound and an organic dehydrating agent. The reaction equilibrium constant with water at the reaction temperature of the production reaction is 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ , and an acetal having a boiling point difference of 10 ° C. or more with respect to the produced carbonate is used. .

<CO2>
In the present invention, carbon dioxide as a raw material is not particularly limited as long as it does not contain a substance that deactivates the catalyst. Carbon dioxide is industrially produced by separation and purification from gases containing a large amount of carbon dioxide, such as lime furnace gas, coke heavy oil combustion gas, naphtha cracking gas, and crude oil cracking gas. There are no particular restrictions on the method or origin.

  The purity of carbon dioxide is not necessarily high purity, and may be diluted with an inert gas such as nitrogen. However, when diluted with an inert gas, the capacity of the carbonate production apparatus is increased. Since it is necessary, it is preferable that carbon dioxide used as a raw material has high purity, and the purity is desirably 95% or more, preferably 99% or more, and more preferably 99.9% or more.

<Alcohol>
On the other hand, the alcohol is not particularly limited, and alkyl alcohols such as methanol, ethanol and propanol, aralkyl alcohols such as benzyl alcohol, and the like are used.
Of these, when dimethyl carbonate is produced as the carbonate ester, methanol is used as the alcohol.

<Catalyst>
As the catalyst, a metal compound or a catalyst containing a metal compound and an acidic compound is used.

(Metal compound)
As the metal compound, an organic metal alkoxide, an organic metal oxide, or an inorganic metal oxide is used.
The organometallic alkoxide compound is not particularly limited as long as it has catalytic activity for the formation reaction of the carbonate ester of the present invention, and specifically, for example, lithium, sodium, potassium, rubidium, cesium and the like. Alkali metals, alkaline earth metals such as beryllium, magnesium, calcium, strontium and barium, metals such as titanium, tin, zirconium, iron, cobalt, nickel and niobium, and alkoxy groups such as methoxy, ethoxy and propoxy And organometallic alkoxides in combination with allyloxy groups such as phenoxy groups. In addition to the above substituents, alkyl groups such as methyl, ethyl, and propyl groups, and aryl groups such as phenyl groups may be included, and halogens such as fluorine, chlorine, and bromine are included. It may be a thing.
These organometallic alkoxides may be synthesized and isolated in advance, or those produced in the reaction system by the reaction of the corresponding metal halide and other alkali metal alkoxides may be used as they are. May be.

  Said organometallic alkoxide may be used individually by 1 type, and may be used in combination of 2 or more type, For example, the usage-amount is the range (0.01-100 mol% with respect to raw material alcohol) ( In the case of using two or more kinds, the total).

  As the organometallic oxide, for example, at least one metal element selected from the group consisting of a group 4A element (for example, titanium) and a group 4B element (for example, tin) in the short-period type periodic table is one or more. The thing couple | bonded with the alkyl group or the aryl group, and oxygen is mentioned. More specifically, dibutyltin oxide or the like is preferably used.

  The above organic metal oxides may be used alone or in combination of two or more, but the amount used is, for example, in the range of 0.01 to 100 mol% with respect to the raw material alcohol. (The total when two or more types are used).

  Specific examples of inorganic metal oxides include basic oxides such as alkaline earth metals (for example, see JP-A-6-48993), zirconium oxides, titanium oxides, and oxides (for example, JP No. 63-41432), alumina having a pseudoboehmite structure (for example, US Pat. No. 6,207,785), oxide of Group 3B metal of the periodic table (for example, see JP-A-6-211751), or porous Silica or the like is used.

  Said inorganic metal oxide may be used individually by 1 type, and may be used in combination of 2 or more type. As a method of combining two or more kinds of inorganic metal oxides, they may be simply mixed or used as a composite oxide. The usage-amount of an inorganic metal oxide can be made into the range of 0.1-1000 weight% with respect to raw material alcohol (when using 2 or more types, it is the sum total), for example.

  Note that any two or more of the above organometallic alkoxides, organometallic oxides, and inorganic metal oxides may be used in combination.

(Acidic compounds)
The acidic compound is not particularly limited as long as it has catalytic activity in the production reaction of the carbonic acid ester of the present invention, and specifically, Lewis acid or Brensted acid is preferably used. As the Lewis acid, metal triflate, metal halide, Lewis acidic metal oxide and the like are used. In addition, examples of Brensted acid include sulfuric acid, ammonium salt, organic sulfonic acid, heteropoly acid, acidic ion exchange resin, Brensted acidic metal oxide, and the like. Of these, ammonium triflate is preferably used as the ammonium salt, and more specifically diphenylammonium triflate is particularly preferably used.

  These acidic compounds may be used singly or in combination of two or more, but are usually used in combination with the above metal compound, for example, 0% with respect to the above metal compound catalyst. It can be used in the range of 0.001 to 100 mol% (in the case of using two or more kinds in total).

(Usage form)
In the method for producing a carbonic acid ester of the present invention, the above catalyst components can be used singly or in combination of two or more or used on a carrier by a method known per se. Can do. For example, the above metal compounds can be used alone or as a plurality of homogeneous catalysts, or the above acidic compounds can be further added thereto. Moreover, what prepared the said metal compound as a solid catalyst, and carry | supported the said acidic compound on this etc. can be used preferably. Examples of the acidic compound supported on the metal compound include MoO ₃ , WO ₃ , Nb ₂ O ₅ , SO ₄ ²⁻ , PO ₄ ^{3− and the} like.

(Organic dehydrating agent)
In the method for producing a carbonate ester of the present invention, the reaction is further performed in the presence of an organic dehydrating agent having specific properties.

As this organic dehydrating agent, the reaction equilibrium constant with water at the reaction temperature of the carbonate ester production reaction of the present invention is 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ , and the difference in boiling point from the carbonate ester to be produced Is acetal having a temperature of 10 ° C. or higher (hereinafter sometimes referred to as “reactive organic dehydrating agent”). The acetal of the organic dehydrating agent may be an enol ether in equilibrium with the acetal in the reaction system of the present invention. However, the enol ether becomes an acetal in the presence of an alcohol and is used as the dehydrating agent in the present invention. Works. Therefore, enol ether can also be used as a raw material for the acetal that is the organic dehydrating agent of the present invention.

Here, the “reaction equilibrium constant with water at the reaction temperature” can be determined by the following equation, for example.
Reaction equilibrium constant = ketone concentration x alcohol concentration squared ÷ acetal concentration ÷ water concentration

  Further, the difference in boiling point between the organic dehydrating agent for reaction and the carbonate ester produced means the difference in boiling point at the pressure at which the organic dehydrating agent and carbonate ester are separated by distillation.

In the present invention, the technical significance of using an acetal having the above properties as the organic dehydrating agent for reaction is as follows.
That is, by using as a dehydrating agent an acetal having a reaction equilibrium constant with water at the reaction temperature of the carbonate ester formation reaction in the present invention of 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ , the carbonate standard of carbonate ester The yield is 40% or more, and the organic dehydrating agent after the reaction described below can be regenerated. When this equilibrium constant is less than 5.0 × 10 ³ , an industrially practical reaction yield cannot be obtained, and when the equilibrium constant exceeds 1.0 × 10 ⁶ , the reaction yield of carbonate ester is Although improved, there is a problem that the dehydrating agent cannot be recycled because the reaction to regenerate the aldehyde or ketone produced as the organic dehydrating agent / water product for reaction into the acetal as the dehydrating agent does not proceed.

  Further, by using an acetal having a boiling point difference of 10 ° C. or higher with respect to the produced carbonate ester, there is an effect that separation from the produced carbonate ester can be easily performed by distillation or the like. The boiling point difference between the carbonic acid ester and impurity components other than the carbonic acid ester and acetal contained therein (specifically, ketone, enol ether, etc.) is preferably 10 ° C. or more. When the difference between these boiling points is less than 10 ° C., separation and purification by distillation becomes difficult, which is not preferable. When an organic dehydrating agent having a boiling point difference of less than 10 ° C. is used, it is necessary to install a distillation column having a large number of theoretical plates in the distillation step for separating the carbonate after the reaction, and the reflux ratio must be increased. It is economically disadvantageous. Since the larger the boiling point difference is, the easier the distillation separation is. Therefore, the boiling point difference is preferably 20 ° C. or more, and particularly preferably 40 ° C. or more. However, this boiling point difference is usually 100 ° C. or less. The same applies to the boiling point of impurities.

  As such an acetal, for example, 2,2-dimethoxyheptane, 2,2-dimethoxy-4-methylpentane and the like are preferably used. These may be used individually by 1 type, and 2 or more types may be mixed and used for them in arbitrary ratios.

  The amount of acetal used in the organic dehydrating agent for reaction can be appropriately selected according to the equilibrium constant of the acetal used.

<Reaction conditions>
In the carbonate ester production method of the present invention, the reaction conditions are preferably a pressure of 1 to 40 MPa, a temperature of 150 to 250 ° C., and a reaction time of about 6 to 60 hours, but are not limited thereto.

<Continuous process>
In the carbonate ester production method of the present invention, the carbonate ester production reaction can also be carried out continuously. Such a continuous process includes at least the following steps (a) to (d).

(A) The reaction equilibrium constant between carbon dioxide and alcohol, a metal compound or a catalyst containing a metal compound and an acidic compound, and water at the reaction temperature is 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ The reaction is carried out in the presence of an organic dehydrating agent composed of acetal having a boiling point difference of 10 ° C. or higher with respect to the produced carbonic acid ester, and a reaction product of the carbonic acid ester and the organic dehydrating agent with water (“organic dehydrating agent / water reaction”). A step of obtaining a reaction mixture containing the product.
(B) A step of separating a fraction containing carbonate ester as a main component from the reaction mixture of step (b) to obtain a residual liquid.
(C) A step of regenerating the organic dehydrating agent by dehydrating the organic dehydrating agent / water reaction product in the residual liquid in the step (b).
(D) A step of circulating the organic dehydrating agent regenerated in step (c) to step (b).

(Process (I): Carbonate ester production process)
About process (I), it can carry out similarly to the manufacturing method of the carbonate ester mentioned above. The reaction mixture obtained in this step contains at least the produced carbonate ester and the organic dehydrating agent / water reactant for reaction. In the next step (b), the reaction mixture obtained in the step (ii) separates a fraction mainly composed of a carbonate ester from here to obtain a residual liquid.

  Here, the “reactive organic dehydrating agent / water reactant” is a compound produced by the reaction of the organic dehydrating agent for reaction with water, specifically, a ketone or a product produced by the reaction of acetal and water. Aldechte.

(Process (b): Carbonate ester fractionation process)
As a method for separating the fraction mainly composed of carbonate from the reaction mixture containing the carbonate obtained in step (a) and the reaction organic dehydrating agent / water reactant, a known method is appropriately selected. For example, the following methods can be mentioned.

  First, it is preferable to perform separation after removing unreacted carbon dioxide from the reaction system in step (ii) and reducing the pressure. The unreacted carbon dioxide removed here can be reused by returning to the carbonic acid ester production step of step (ii), but it is necessary to compress again at that time, so it was removed in a state where the pressure was as high as possible. This is preferable because the amount of energy used to compress carbon dioxide can be reduced.

  The method for separating the target carbonate from the reaction mixture after removing carbon dioxide is not particularly limited, but is highly practical because it can be industrially separated by distillation. The method for separating by distillation is not particularly limited as long as the carbonate content of the separated fraction is 90% or more. A carbonate ester fraction having a high purity (for example, 95% or more) can also be obtained by a plurality of distillations. Further purification (eg, 98% or more) can be achieved by further purification (distillation, crystallization, etc.) depending on the application.

  Carbonate esters isolated in this way, such as dimethyl carbonate, are used as raw materials for polycarbonate production, lithium battery electrolytes, gasoline additives for improving octane number, alkylating agents in various reactions, and carbonylating agents. The

  In this fractionation step, it is also preferable to perform two-stage distillation. Specifically, after removing carbon dioxide gas from the reaction system, the reaction mixture is subjected to vacuum distillation, simple distillation or rectification, etc. , Separating the catalyst components. Thereafter, this residual liquid is further fractionated by the above method to obtain a carbonate ester. By using such a method, the separated catalyst component can be regenerated by an appropriate method, and returned to the carbonic ester production step of step (A) and used again. Examples of the method for regenerating the separated catalyst component include the method described in JP-A-2006-83065.

  In this way, the residual liquid after separating the fraction mainly composed of carbonate ester is a step of regenerating the organic dehydrating agent for reaction from the organic dehydrating agent for reaction and water reactant in the residual liquid ( C).

(Process (c): Organic dehydrating agent regeneration process for reaction)
There is no particular restriction on the method for regenerating the organic dehydrating agent for reaction by dehydrating the organic dehydrating agent for reaction / water reactant in the residual liquid obtained in step (b), but the organic dehydrating agent for reaction / water Organic dehydrating agent that is different from organic dehydrating agent for reaction, organic dehydrating agent for reaction and organic dehydrating agent for reaction, and water reactant can be separated by distillation (hereinafter referred to as “regenerating organic dehydrating agent”) Is used for dehydration.

  Here, it is preferable that the organic dehydrating agent for regeneration to be used has a boiling point difference of 10 ° C. or higher with respect to the organic dehydrating agent for reaction and its water reaction product because it is easily separated by distillation. Here, the “boiling point difference” means a difference in boiling points at a pressure at which the organic dehydrating agent for reaction or the organic dehydrating agent for reaction / water reactant and the organic dehydrating agent for regeneration are separated by distillation. The larger the difference in boiling points is, the easier the distillation separation is, so 20 ° C. or higher is preferable. However, this boiling point difference is usually 100 ° C. or less.

  Such a regenerating organic dehydrating agent is not particularly limited, and specifically, 2,2-dimethoxypropane, cyclohexanone acetal, anise acetal and the like are preferably used.

  Regeneration of the organic dehydrating agent for reaction by such an organic dehydrating agent for regeneration is performed by adding the organic dehydrating agent for reaction in the residual liquid (reactive organic dehydrating agent / water reaction in the residual liquid) to the residual liquid in the above step (b). The total amount of organic dehydrating agent for reaction and organic dehydrating agent for reaction corresponding to the product is added to the organic dehydrating agent for regeneration in an amount of about 0.1 to 10 times by weight to remove continuously generated acetone. The reaction can be performed by reaction distillation.

  The organic dehydrating agent for reaction regenerated by the above regeneration reaction is separated by an operation such as distillation as necessary, and is recycled to the step (a).

(Process (d): Organic dehydrating agent circulation process for reaction)
When recycling the organic dehydrating agent for reaction regenerated in step (c) to the carbonic acid ester production step of step (a), the regenerated organic dehydrating agent for reaction is purified by an operation such as distillation as necessary. Also good. The purity of the organic dehydrating agent for reaction to be recycled can be determined as appropriate, but it is preferable to increase the purity to 50% or more, more preferably 80%, and to recycle it.
In addition, when the reaction organic dehydrating agent recycled in the step (a) is less than the necessary amount of the reaction organic dehydrating agent in the step (a), a new organic dehydrating agent for reaction is appropriately replenished.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.

[Example 1]
(1) Organic dehydrating agent for reaction: 2,2-dimethoxy-4-methylpentane (reaction equilibrium constant with water at 180 ° C. = 1.5 × 10 ⁵ , boiling point difference with dimethyl carbonate at atmospheric pressure = 60 )) In a 500 ml eggplant type flask containing a stirrer in an argon gas atmosphere, 187 ml of special grade methyl isobutyl ketone (manufactured by Wako Pure Chemical Industries, Ltd., 1.5 mol) and 186 ml of special grade trimethyl orthoformate as an organic dehydrating agent (Wako Pure Chemical Industries, Ltd., 1.7 mol) and montmorillonite K10 10 g (Sigma Aldrich Japan) were charged and heated to 80 ° C. while stirring at 1500 rpm with an apparatus using Dean Stark and Jim Roth. Then, the produced methyl formate is boiled and removed by Dean Stark, and methyl formate is no longer produced In was heated at 80 ℃. The reaction mixture was filtered with a Kiriyama funnel made of Kiriyama funnel with filter paper No5B for Kiriyama funnel to separate the reaction solution and montmorillonite K10, and then the reaction solution was distilled under reduced pressure using a distillation apparatus, and 2,2-dimethoxy-4- Methyl pentane (boiling point: 61-63 ° C. at a pressure of 8 kPa) was obtained in a yield of 56%.

(2) an acidic compound: Synthesis of diphenyl ammonium triflate ^{_{(Ph 2 N + H 2 ·}} -OSO 2 CF 3)
After charging 1.7 g of diphenylamine (made by Wako Pure Chemical Industries, Ltd., special grade, 10 mmol) and 20 ml of special grade toluene (made by Wako Pure Chemical Industries, Ltd.) into a 50 ml volume eggplant type flask containing a stir bar at 1500 rpm. While stirring, 0.88 ml of special grade trifluoromethanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd., 10 mmol) was slowly added dropwise, followed by stirring at room temperature for 15 minutes. After distilling off toluene from the obtained white suspension under reduced pressure, white solid diphenylammonium triflate was washed with 100 ml of special grade hexane (manufactured by Wako Pure Chemical Industries, Ltd.), and Kiriyama was laid with filter paper No5B for Kiriyama funnel. Diphenylammonium triflate and hexane were separated by filtration with a Kiriyama funnel manufactured by Seisakusho, and then dried under reduced pressure to obtain diphenylammonium triflate in a yield of 99%.

(3) Synthesis and purification of dimethyl carbonate Under a nitrogen gas atmosphere, in a 2 L autoclave equipped with a stirrer, 400 ml of special grade methanol (manufactured by Wako Pure Chemical Industries, Ltd., 10 mol), the above organic dehydrating agent (1) 2,2-dimethoxy-4-methylpentane (dimethylacetal of methyl isobutyl ketone) synthesized in 730 g (5 mol), dibutyltin dimethoxide 59 g (manufactured by Sigma-Aldrich Japan, purity 99%, 0.2 mol), and acidic compound After adding 6.4 g (20 mmol) of diphenylammonium triflate synthesized in (2) above, liquefied carbon dioxide (manufactured by Showa Carbonic Acid Co., Ltd., purity 99.99%) was added to pressurize and seal to 6 MPa. .
Thereafter, the inside of the autoclave was heated to 180 ° C. while being stirred at 1500 rpm, and further charged with carbon dioxide to increase the internal pressure to 30 MPa, and then reacted for 24 hours. Thereafter, the content was cooled to 10 ° C. and the pressure was reduced to normal pressure to release the remaining carbon dioxide to obtain a dimethyl carbonate-containing liquid.
This dimethyl carbonate-containing liquid was analyzed by gas chromatography (GC-2010 gas chromatography manufactured by Shimadzu Corporation, column: TC-1 manufactured by GL Sciences Inc.) (analysis conditions: injector: 300 ° C., detector: 330 ° C. Column: maintained at 40 ° C. for 10 minutes, then heated at 10 ° C. for 1 minute and maintained at 310 ° C. for 10 minutes). The dimethyl carbonate yield based on methanol was 60%.

Since the obtained dimethyl carbonate-containing liquid contains dibutyltin dimethoxide and diphenylammonium triflate as catalyst components, dimethyl carbonate-containing liquid containing no catalyst component was obtained by distillation under reduced pressure at 20 torr.
In addition to dimethyl carbonate having a boiling point of 90 ° C., this dimethyl carbonate-containing liquid contains methanol having a boiling point of 65 ° C., methyl isobutyl ketone having a boiling point of 116 ° C., and 2,2-dimethyl-4-methylpentane having a boiling point of 150 ° C. It was.

  In order to separate and purify dimethyl carbonate from this solution, a distillation column packed with a regular packing equivalent to 10 theoretical plates (Sulzer Lab Packing) was used. Distillation was carried out under the condition of flowing out from the top of the column to obtain a dimethyl carbonate mixed solution of 59 wt% methanol and 40 wt% dimethyl carbonate. The dimethyl carbonate mixture was further distilled at 10 atm and a reflux ratio of 10 to obtain 103 g of dimethyl carbonate having a purity of 95%.

(4) Regeneration and recycling of organic dehydrating agent The distillation residue obtained by distilling and separating the dimethyl carbonate mixed solution in (3) above contains methyl isobutyl ketone and 2,2-dimethoxy-4-methylpentane. 2,2-dimethoxypropane (acetone dimethyl acetal) was added to the distillation residue to regenerate the dehydrating agent.
260 g (2.5 mol) of 2,2-dimethoxypropane (manufactured by Wako Pure Chemical Industries, Ltd.) and 3.2 g (10 mmol) of diphenylammonium triflate synthesized in (2) above were added to the distillation residue, and atmospheric pressure and reflux 2,2-dimethoxy-4-methyl containing 0.7% by weight of methyl isobutyl ketone from the bottom of the column at a ratio of 1 and a bottom temperature of 173 ° C. while removing the produced acetone from the top of the distillation column. 418 g of pentane was obtained.

Using 2,2-dimethoxy-4-methylpentane regenerated in this manner, the dimethyl carbonate formation reaction was performed again. By repeating the same operation as in (3) above, dimethyl carbonate could be produced in the same yield.
The results are shown in Table 1.

[Example 2]
(1) Synthesis of organic dehydrating agent for reaction: 2,2-dimethoxyheptane (reaction equilibrium constant with water at 180 ° C. = 7.0 × 10 ³ , boiling point difference with dimethyl carbonate at atmospheric pressure = 84 ° C.) Instead of methyl isobutyl ketone, 2,2-dimethoxyheptane (boiling point: boiling point: as in (1) of Example 1) except that 210 ml of special grade 2-heptanone (manufactured by Wako Pure Chemical Industries, Ltd., 1.5 mol) was used. A pressure of 1.9 kPa and 63 to 65 ° C.) was obtained with a yield of 83%.

(2) Synthesis and purification of dimethyl carbonate 800 g (5 mol) of 2,2-dimethoxyheptane (dimethylacetal of 2-heptanone) synthesized in the above (1) was used instead of 2,2-dimethoxy-4-methylpentane. Then, the same reaction as in Example 1 (3) was carried out, and dimethyl carbonate having a boiling point of 90 ° C., methanol having a boiling point of 65 ° C., 2-heptanone having a boiling point of 151 ° C., and 2,2-dimethoxyheptane having a boiling point of 174 ° C. The contained dimethyl carbonate-containing liquid was obtained. With respect to this dimethyl carbonate-containing solution, the yield of methanol-based dimethyl carbonate was determined by the same analysis method as in Example 1, and was found to be 50%.
This dimethyl carbonate-containing liquid was distilled in a distillation column packed with a regular packing equivalent to 10 theoretical plates (Lab Pack made by Sulzer), as in (3) of Example 1, under conditions of atmospheric pressure and reflux ratio 1. Distillation was carried out under the condition that 80% of dimethyl carbonate flows out from the top of the column to obtain a dimethyl carbonate mixed solution of 64% by weight of methanol and 36% by weight of dimethyl carbonate. To obtain 91 g of dimethyl carbonate having a purity of 95%.

(3) Regeneration and recycling of organic dehydrating agent The distillation residue obtained by distilling and separating the dimethyl carbonate mixed solution in (2) above contains methyl isobutyl ketone and 2,2-dimethoxyheptane. 2,2-dimethoxypropane (manufactured by Wako Pure Chemical Industries, Ltd.) 260 g (2.5 mol) and diphenylammonium triflate 3.2 g (10 mmol) synthesized in (2) of Example 1 were added, and atmospheric pressure and reflux were added. 2,2-dimethoxy-4-methyl containing 0.7% by weight of methyl isobutyl ketone from the bottom of the column at a ratio of 1 and a bottom temperature of 173 ° C. while removing the produced acetone from the top of the distillation column. 418 g of pentane was obtained.

Using the 2,2-dimethoxyheptane regenerated in this way, the dimethyl carbonate formation reaction of (2) above was performed again. By repeating the same operation, dimethyl carbonate could be produced with the same yield.
The results are shown in Table 1.

[Comparative Example 1]
(1) Synthesis of comparative organic dehydrating agent: 1,1-dimethoxycyclohexane (reaction equilibrium constant with water at 180 ° C. = 4.4 × 10 ³ , boiling point difference with dimethyl carbonate at atmospheric pressure = 84 ° C.) Instead of methyl isobutyl ketone, 1,1-dimethoxycyclohexane (boiling point: pressure 6) was used in the same manner as in (1) of Example 1 except that 150 ml of special grade cyclohexanone (manufactured by Wako Pure Chemical Industries, Ltd., 1.5 mol) was used. 0.7-kPa at 82-84 ° C.) with a yield of 64%.

(2) Synthesis and purification of dimethyl carbonate In place of 2,2-dimethoxy-4-methylpentane, 720 g (5 mol) of 1,1-dimethoxycyclohexane (dimethylacetal of cyclohexanone) synthesized in the above (1) was used. The same reaction as in Example 1 (3) was carried out, and contained dimethyl carbonate having a boiling point of 90 ° C., methanol having a boiling point of 65 ° C., cyclohexanone having a boiling point of 155 ° C., and 1,1-dimethoxycyclohexane having a boiling point of 174 ° C. A dimethyl carbonate-containing liquid was obtained. With respect to this dimethyl carbonate-containing liquid, the yield of methanol-based dimethyl carbonate was determined by the same analysis method as in Example 1, and found to be 21%.
This dimethyl carbonate-containing liquid was distilled in a distillation column packed with a regular packing equivalent to 10 theoretical plates (Lab Pack made by Sulzer), as in (3) of Example 1, under conditions of atmospheric pressure and reflux ratio 1. Distillation was carried out under the condition that 90% of dimethyl carbonate flows out from the top of the column to obtain a dimethyl carbonate mixed solution of 81% by weight of methanol and 19% by weight of dimethyl carbonate. Distillation was performed so that the methanol concentration at the bottom of the column was 99% by weight at a reflux ratio of 50, and the column top distillate was further distilled at 10 atm and a reflux ratio of 1 to obtain 37 g of dimethyl carbonate having a purity of 95%.

  In this comparative example, 1,1-dimethoxycyclohexane used as a dehydrating agent has low reactivity with water, so that the production efficiency of dimethyl carbonate is lower than that in Example 1.

[Comparative Example 2]
(1) Comparative organic dehydrating agent: 2,2-dimethoxypropane (reaction equilibrium constant with water at 180 ° C. = 7.6 × 10 ⁴ , boiling point difference with dimethyl carbonate at atmospheric pressure = 7 ° C.) Synthesis and Purification of Dimethyl Carbonate Under a nitrogen gas atmosphere, in a 2 L autoclave equipped with a stirrer, 400 ml of special grade methanol (manufactured by Wako Pure Chemical Industries, Ltd., 10 mol), 520 g of 2,2-dimethoxypropane as an organic dehydrating agent ( 5 mol), 59 g of dibutyltin dimethoxide (manufactured by Sigma-Aldrich Japan, purity 99%, 0.2 mol) and 6.4 g (20 mmol) of diphenylammonium triflate synthesized in Example 1 (2) as an acidic compound. By adding liquefied carbon dioxide (Showa Carbonic Acid Co., Ltd., purity 99.99%) It was sealed.
Thereafter, the inside of the autoclave was heated to 180 ° C. while being stirred at 1500 rpm, and further charged with carbon dioxide to increase the internal pressure to 30 MPa, and then reacted for 24 hours. Thereafter, the contents were cooled to 0 ° C., and the pressure was reduced to normal pressure to release the remaining carbon dioxide to obtain a dimethyl carbonate-containing liquid. With respect to this dimethyl carbonate-containing liquid, the yield of dimethyl carbonate based on methanol was determined by the same analysis method as in Example 1, and it was 40%.

Since the obtained dimethyl carbonate-containing liquid contains dibutyltin dimethoxide and diphenylammonium triflate as catalyst components, dimethyl carbonate-containing liquid containing no catalyst component was obtained by distillation under reduced pressure at 100 Torr.
This dimethyl carbonate-containing liquid contains dimethyl carbonate having a boiling point of 90 ° C., methanol having a boiling point of 65 ° C., acetone having a boiling point of 56 ° C., and 2,2-dimethoxypropane having a boiling point of 83 ° C.
In order to separate and purify dimethyl carbonate from this solution, distillation was carried out under conditions of atmospheric pressure and a reflux ratio of 5 in a distillation column packed with a regular packing (lab packing made by Sulzer) equivalent to 10 theoretical plates. In this composition, since the boiling point of dimethyl carbonate is the highest, when distillation separation is performed under the condition that 90% of dimethyl carbonate is recovered from the bottom of the column, the top composition is 12% by weight of dimethyl carbonate, 36% by weight of methanol, 48% by weight of acetone, When 2,2-dimethoxypropane is 4% by weight, the bottom composition is 33% by weight of dimethyl carbonate, 33% by weight of methanol, 8% by weight of acetone, and 27% by weight of 2,2-dimethoxypropane. %, 35% of acetone and 96% of 2,2-dimethoxypropane remained at the bottom of the column. That is, when the bottom temperature of the distillation tower was raised, it was found that a large amount of dimethyl carbonate originally desired to remain on the bottom of the tower other than 2,2-dimethoxypropane was separated at the top.
Thus, since 2,2-dimethoxypropane, which is a dehydrating agent, could not be separated well by azeotropic distillation, the dimethyl carbonate production reaction could not be performed again.

  The results of Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in Table 1.

Claims (5)

In the method for producing carbonic acid ester by reacting carbon dioxide and alcohol with a metal compound or a catalyst containing a metal compound and an acidic compound in the presence of an organic dehydrating agent,
The organic dehydrating agent is an acetal having a reaction equilibrium constant with water at the reaction temperature of 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ and having a boiling point difference of 10 ° C. or more with respect to the produced carbonate. A process for producing a carbonic ester characterized by the above. The manufacturing method of the carbonate ester characterized by including the process of following (a)-(d) at least.
(A) The reaction equilibrium constant between carbon dioxide and alcohol, a catalyst containing a metal compound or a metal compound and an acidic compound, and water at the reaction temperature is 5.0 × 10 ^{3 to} 1.0 × 10 ⁶ , The reaction is carried out in the presence of an organic dehydrating agent made of acetal having a boiling point difference of 10 ° C. or higher with respect to the produced carbonic acid ester, and a reaction product of the carbonic acid ester and the organic dehydrating agent with water (“organic dehydrating agent / water reactant” To obtain a reaction mixture containing "."
(B) A step of separating a fraction containing carbonate ester as a main component from the reaction mixture of step (b) to obtain a residual liquid.
(C) A step of regenerating the organic dehydrating agent by dehydrating the organic dehydrating agent / water reaction product in the residual liquid in the step (b).
(D) A step of circulating the organic dehydrating agent regenerated in step (c) to step (b).   The method for producing a carbonate ester according to claim 1 or 2, wherein the organic dehydrating agent is 2,2-dimethoxyheptane and / or 2,2-dimethoxy-4-methylpentane.   Regeneration of the organic dehydrating agent (referred to as “reactive organic dehydrating agent”) / water reactant can be separated into the residual liquid by distillation from the reactive organic dehydrating agent and the reactive organic dehydrating agent / water reactant. The method for producing a carbonic acid ester according to claim 2 or 3, wherein the organic dehydrating agent for regeneration is different from the organic dehydrating agent for reaction.   The method for producing a carbonate ester according to any one of claims 1 to 4, wherein the alcohol is methanol and the carbonate ester is dimethyl carbonate.