JP4604531B2 - A method for producing cyclic carbonates and oxetanes. - Google Patents

Description

  The present invention relates to a method for producing cyclic carbonates and oxetanes from a triol compound such as 1,1,1-trimethylolalkane and dimethyl carbonate, for example. In particular, the present invention is a method for producing cyclic carbonates by selectively extracting methanol produced as a by-product from the reaction system through a gas separation membrane, and further producing oxetanes by decarboxylating the produced cyclic carbonate. Regarding the method. Oxetanes are useful compounds as materials for photocationic curable resins.

In Patent Document 1, dimethyl carbonate is used as a carbonating agent, and a triol compound is carbonated while extracting by-product methanol to produce a cyclic carbonate, and then the produced cyclic carbonate is decarboxylated to obtain oxetanes. A method is disclosed. In this method, methanol produced as a by-product is continuously extracted (distilled) out of the reaction system together with azeotropic dimethyl carbonate by distillation, and the raw material, particularly dimethyl carbonate, is continuously or While supplying intermittently, it was carbonated to produce cyclic carbonates, and then the produced cyclic carbonate was decarboxylated to obtain oxetanes. There was no disclosure about selectively separating methanol produced as a by-product through a gas separation membrane and extracting it from the reaction system.
JP-A-11-12261

  An object of the present invention is to propose an improved method for producing cyclic carbonates and further oxetanes from a triol compound and dimethyl carbonate while selectively separating by-product methanol by a gas separation membrane and extracting it from the reaction system. And

The present invention relates to a method for producing cyclic carbonates, characterized in that triol compound and dimethyl carbonate are reacted while selectively removing methanol as a by-product using a gas separation membrane, in particular, triol compound and dimethyl carbonate. From the reaction mixture in the presence of a catalyst, a mixed vapor containing methanol as a by-product and dimethyl carbonate as a raw material is generated, and the mixed vapor is brought into contact with a gas separation membrane to selectively permeate methanol. The method relates to a method for producing cyclic carbonates characterized in that non-permeated dimethyl carbonate is returned to the reaction mixture. In addition, the triol compound is 1,1,1-trimethylolalkane, and the permeation rate ratio of methanol vapor to dimethyl carbonate vapor at 120 ° C. (P ′ _MeOH / P ′ _DMC ) of the gas separation membrane is 2 or more. The permeation rate (P ′ _MeOH ) of methanol vapor at 120 ° C. of the gas separation membrane is 1 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg or more, and the gas separation membrane is made of parachlorophenol. It is an asymmetric polyimide hollow fiber membrane which does not melt | dissolve, It is related with the manufacturing method of the said cyclic carbonate characterized by the above-mentioned.

  Furthermore, this invention relates to the manufacturing method of oxetane characterized by manufacturing cyclic carbonates with one of the said manufacturing methods, and then decarboxylating this cyclic carbonate.

  In the present invention, methanol is selectively extracted out of the reaction system, and dimethyl carbonate selectively remains in the reaction system. For this reason, cyclic carbonates and oxetanes can be obtained in high yield without additional supply of raw materials, particularly dimethyl carbonate. Furthermore, the methanol extracted out of the reaction system has a high purity of 80% by weight or more, particularly 85% by weight or more, and can be easily recovered and reused.

  The present invention is characterized in that a triol compound and dimethyl carbonate are reacted while selectively extracting methanol as a by-product through a gas separation membrane. In the present invention, preferably, a mixed vapor containing methanol and by-product dimethyl carbonate is generated from a reaction mixture obtained by reacting a triol compound and dimethyl carbonate in the presence of a catalyst, and the mixed vapor is It is brought into contact with the gas separation membrane and selectively permeated with methanol to be extracted out of the reaction system, while the non-permeated highly concentrated dimethyl carbonate vapor is condensed and returned to the reaction mixture.

  In the present invention, the triol compound is carbonated using dimethyl carbonate as a carbonating agent. Examples of the triol compound include 1,1,1-trimethylolalkanes (wherein the alkane has 2 to 6 carbon atoms) such as 1,1,1-trimethylolethane and 1,1,1-trimethylolpropane. 1,2,6-hexanetriol, 1,2,4-butanetriol and the like are preferably used.

  As a catalyst for this reaction, for example, an alkali metal compound, an alkaline earth metal compound, a nitrogen-containing basic compound, a metal element belonging to groups 2B, 3A, 3B, 4A, and 4B of the periodic table, or a compound thereof is usually used. The catalyst used in the transesterification reaction is preferably used. At least one of these catalysts is used in an amount of 0.00001 to 0.1 mol, preferably 0.00005 to 0.01 mol, more preferably 0.0001 to 0.05 mol, relative to 1 mol of the triol compound. .

  Examples of the alkali metal compound include alkali metal alcoholates (lithium methylate, sodium methylate, potassium methylate, etc.), alkali metal carbonates (lithium carbonate, sodium carbonate, potassium carbonate, etc.), and alkali metal water. An oxide (lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.) is mentioned. Examples of the alkaline earth metal compound include an alkaline earth metal alcoholate (magnesium methylate, etc.), an alkaline earth metal carbonate (magnesium carbonate, etc.), and an alkaline earth metal hydroxide (magnesium hydroxide). Etc.). Examples of the nitrogen-containing basic compound include aliphatic tertiary amines (such as triethylamine and tributylamine) and aliphatic ammonium salts (such as tetramethylammonium bromide and tetrabutylammonium bromide).

  Examples of the metal element belonging to Group 2B of the periodic table or a compound thereof include zinc carbonate and zinc oxide. Examples of the metal element belonging to Group 3A of the periodic table or a compound thereof include yttrium oxide and yttrium carbonate. Examples of the metal element belonging to Group 3B of the periodic table or a compound thereof include boric acid, boric acid esters (such as trimethyl borate), basic aluminum nitrate, and triethoxyaluminum. Examples of the metal element belonging to Group 4A of the periodic table or compounds thereof include zirconium compounds (zirconium acetylacetonate, zirconocene, etc.), titanium compounds (tetrabutoxy titanium, titanium tetrachloride, etc.), and the like. Examples of metal elements belonging to Group 4B of the periodic table or compounds thereof include tin compounds (tetraphenyltin, dibutyltin oxide, etc.), lead compounds (tetrabutyllead, diphenoxylead, etc.), and the like.

  In the present invention, although dimethyl carbonate is not limited, it is used in an amount of about 0.5 to 3 mol, particularly 0.8 to 2 mol, usually 1 to 1.4 mol, relative to 1 mol of the triol compound. When dimethyl carbonate is excessive, by-products in which the produced cyclic carbonate is further carbonated may increase, and the yield of the cyclic carbonate may decrease. On the other hand, when the amount of dimethyl carbonate becomes too small, the polymerization of the triol compound or the generated cyclic carbonate proceeds, so that the yield of the cyclic carbonate decreases.

  In the carbonation reaction, the reaction temperature is 50 to 200 ° C, preferably 70 to 150 ° C, more preferably 80 to 130 ° C, and particularly preferably 85 to 120 ° C. The pressure during the reaction is preferably set in the range of 0.1 to 1 MPa corresponding to the reaction temperature, and the atmosphere during the reaction is preferably an inert gas atmosphere such as nitrogen. The reaction time (corresponding to the residence time when the reaction is carried out continuously) varies depending on the reaction temperature and the amount of catalyst, but is preferably in the range of 1 to 10 hours.

  In the present invention, the reaction is carried out while selectively extracting methanol produced as a by-product in the carbonation reaction out of the reaction system by the gas separation membrane. Specifically, a mixed vapor containing byproduct methanol and dimethyl carbonate is generated from the reaction mixture. It is not possible to generate only methanol vapor. The mixed vapor is easily generated under the above reaction conditions. This mixed vapor is brought into contact with the surface of the gas separation membrane. While the mixed vapor is in contact with the gas separation membrane, the methanol vapor selectively permeates the gas separation membrane and moves to the permeate side of the membrane due to the partial pressure difference between the methanol vapors on both sides of the gas separation membrane. It is pulled out of the system. Dimethyl carbonate vapor does not easily pass through the membrane even when it comes into contact with the gas separation membrane, and remains on the non-permeating side of the membrane, that is, in the reaction system. In the present invention, the dimethyl carbonate vapor remaining on the non-permeating side of the membrane is preferably cooled and condensed and returned to the reaction mixture.

In the present invention, in order to allow methanol vapor to selectively permeate and extract with good separation efficiency by contacting the mixed vapor with a gas separation membrane, the methanol vapor has a high selective permeability to dimethyl carbonate vapor and a methanol vapor permeation rate. It is preferable to use a high gas separation membrane and to increase the effective membrane area of the gas separation membrane.
Furthermore, the partial pressure of methanol vapor contacting the gas separation membrane can be increased by making the reaction system a pressurized system, or the permeation side of the gas separation membrane can be reduced to reduce the partial pressure difference between the methanol vapors on both sides of the gas separation membrane. In addition, a gas other than methanol (for example, air, nitrogen gas, etc.) is allowed to flow as a sweep gas on the permeation side of the gas separation membrane, and the permeated methanol vapor can be forcibly swept from the permeation side of the gas separation membrane. Is preferred. Furthermore, it is suitable for improving the separation efficiency that the reaction is performed using a reactor equipped with a distillation column and the mixed vapor is distilled to an azeotropic composition in the distillation column and then brought into contact with the gas separation membrane. Furthermore, in the present invention, before bringing the mixed vapor into contact with the gas separation membrane, it is preferable to superheat at about 2-3 ° C. or more, preferably 5 ° C. or more in order to maintain the separation efficiency of the gas separation membrane. .

  In the present invention, the carbonation reaction is carried out batchwise or continuously. When the production scale is large, a continuous reaction (a method in which a triol compound, dimethyl carbonate and a catalyst are continuously supplied, methanol is continuously extracted, and a reaction solution is continuously extracted) is particularly preferable.

  A solvent is not particularly required in the carbonation reaction, but there is no problem in using it as long as it is inert in the reaction system. When the solvent has a low boiling point and is vaporized together with methanol and contained in the mixed vapor, a solvent that is more difficult to permeate the gas separation membrane than the dimethyl carbonate vapor is preferable.

  The gas separation membrane used in the present invention is not particularly limited as long as it selectively permeates methanol vapor with respect to dimethyl carbonate vapor. For example, polymer films such as polyimide, polycarbonate, polysulfone, polyetherimide, polyamideimide, films obtained by heat-treating these polymer films, partially carbonized films or carbon films obtained by heat-treating polymer films, ceramics A film or the like can be preferably used. These films may be uniform films, asymmetric films, or composite films. Furthermore, the form of the membrane may be any of a hollow fiber membrane, a flat membrane, a spiral membrane and the like.

The gas separation membrane used in the present invention has a ratio of the permeation rate of methanol vapor to the permeation rate of dimethyl carbonate vapor at 120 ° C. (P ′ _MeOH / P ′ _DMC ) of 2 or more, particularly 3 or more, and further 4 or more. Is preferred. When the ratio of the permeation rate of methanol vapor to the permeation rate of dimethyl carbonate vapor (P ′ _MeOH / P ′ _DMC ) is less than 2, when a by-product methanol is extracted from the reaction system of the carbonation reaction, a considerable amount of dimethyl carbonate Since the carbonate vapor is also discharged out of the reaction system at the same time, it is difficult to obtain the effect of the present invention. The gas separation membrane used in the present invention is more suitable as the ratio of the methanol vapor permeation rate to the dimethyl carbonate vapor permeation rate (P ′ _MeOH / P ′ _DMC ) is larger. It is difficult to get easily.

The gas separation membrane used in the present invention has a methanol vapor permeation rate ( _P′MeOH ) at 120 ° C. of 1 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg or more, particularly 5 × 10 ⁻⁵ cm. ³ (STP) / cm ² · sec · cmHg is preferred. The gas separation membrane used in the present invention is more suitable as the methanol vapor permeation rate (P ′ _MeOH ) is larger. Usually, 100 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg is used. It is difficult to easily get beyond.

  Furthermore, the gas separation membrane used in the present invention preferably has good solvent resistance against organic solvents such as methanol and dimethyl carbonate. If the solvent resistance of the gas separation membrane is low, the gas separation performance deteriorates due to organic vapor such as methanol or dimethyl carbonate, so that it cannot be suitably used. In the present invention, a gas separation membrane that can be particularly preferably used is a gas separation obtained by heat-treating a gas separation membrane made of a polymer such as polyimide to make it infusible (specifically, insolubilized in parachlorophenol). It is a membrane. A gas separation membrane having a solvent resistance higher than that which does not dissolve in parachlorophenol can be suitably used in the present invention because the gas separation performance is not deteriorated by an organic vapor such as methanol or dimethyl carbonate.

  In the gas separation membrane, a hollow fiber membrane is generally preferable because it is easy to increase the effective membrane area, and further comprises an extremely thin skin layer (uniform layer) and a porous layer for increasing the gas permeation rate. Asymmetric membranes are preferred. In the present invention, an asymmetric hollow fiber gas separation membrane obtained by heat-treating an asymmetric hollow fiber gas separation membrane made of polyimide having a substituent as a gas separation membrane to be infusible (specifically, insolubilized in parachlorophenol) is used. It can be used suitably. This asymmetric hollow fiber gas separation membrane has good organic solvent resistance and excellent methanol permselectivity. Hereinafter, an asymmetric polyimide hollow fiber gas separation membrane that is not particularly soluble in parachlorophenol, which is particularly preferred in the present invention, will be described.

  The asymmetric polyimide hollow fiber gas separation membrane that does not dissolve in parachlorophenol in the present invention specifically has solvent resistance that does not dissolve even when immersed in parachlorophenol at 50 ° C. for 30 minutes. In this gas separation membrane, a polyimide having a substituent is used to form an asymmetric hollow fiber membrane, and then the polyimide skeleton and the asymmetric structure of the asymmetric hollow fiber membrane are retained, and the substituent is decomposed, desorbed or crosslinked. It can obtain suitably by heat-processing on the temperature conditions of what is called infusible. This heat treatment not only improves solvent resistance, but also improves separation performance such as permeation rate and permeation rate ratio for organic vapor. Furthermore, since the asymmetric structure is retained and the polyimide skeleton is retained to maintain the mechanical strength before the heat treatment, it is a practical gas separation membrane for separating and recovering organic vapor.

  The glass transition temperature of the polyimide having a substituent that forms the gas separation membrane before the heat treatment must be higher than the so-called infusibilization temperature at which the substituent decomposes and desorbs or crosslinks. The temperature at which the substituent is decomposed and eliminated or crosslinked is 250 ° C. or higher, preferably 380 ° C. or higher, and the glass transition temperature of the polyimide is similarly 250 ° C. or higher, preferably 380 ° C. or higher. When the temperature of the polyimide exceeds 450 ° C., the bond forming the main chain starts to decompose, and at a higher temperature, the polyimide ring decomposes and carbonization proceeds. Therefore, the substituent decomposes and desorbs at a temperature of 450 ° C. or less. Is preferred.

  Preferable examples of the polyimide having the substituent include aromatic polyimides having a polyimide unit represented by the following chemical formula (1).

［ここで、Ａは芳香族テトラカルボン酸からカルボン酸基を除いた４価の残基である。また、Ｂは芳香族ジアミンのアミノ基を除く２価の残基であって、下記化学式（２）〜化学式（７）で示される。］

[Here, A is a tetravalent residue obtained by removing a carboxylic acid group from an aromatic tetracarboxylic acid. B is a divalent residue excluding the amino group of the aromatic diamine, and is represented by the following chemical formulas (2) to (7). ]

［ここで、Ｒ１〜Ｒ４は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R4 are substituents, and at least one of these substituents is an SO ₃ H group, an SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

［ここで、Ｒ１〜Ｒ８は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R8 are substituents, and at least one of these substituents is SO ₃ H group, SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

［ここで、Ｒ１〜Ｒ８は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R8 are substituents, and at least one of these substituents is SO ₃ H group, SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

［ここで、Ｒ１〜Ｒ８は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R8 are substituents, and at least one of these substituents is SO ₃ H group, SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

［ここで、Ｒ１〜Ｒ６は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R6 are substituents, and at least one of these substituents is SO ₃ H group, SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

［ここで、Ｒ１〜Ｒ８は置換基であって、これら置換基のうち少なくとも一つは、ＳＯ_３Ｈ基、ＳＯ_３ＨＮＬ_１Ｌ_２Ｌ_３基（Ｌ_１、Ｌ_２、Ｌ_３は、それぞれ独立に、水素原子又はアルキル基である）、カルボキシル基、水酸基、ハロゲン基、アルキル基、アルコキシ基、及び、アリールオキシ基からなる群から選ばれるいずれかの基であり、その他は水素原子である。］

[Wherein R1 to R8 are substituents, and at least one of these substituents is SO ₃ H group, SO ₃ HNL ₁ L ₂ L ₃ group (L ₁ , L ₂ , L ₃ are respectively Independently a hydrogen atom or an alkyl group), a group selected from the group consisting of a carboxyl group, a hydroxyl group, a halogen group, an alkyl group, an alkoxy group, and an aryloxy group, and the others are hydrogen atoms . ]

  Specific examples of A include 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3,3 ′, 4′-biphenyltetracarboxylic acid, and 2,2 ′, 3,3′-biphenyltetracarboxylic acid. The carboxylic acid group is removed from tetracarboxylic acids such as acid, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 1,4,5,8-naphthalenetetracarboxylic acid and pyromellitic acid. A valent residue can be preferably mentioned. In the present invention, A is 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3,3 ′, 4′-biphenyltetracarboxylic acid, 2,2 ′, 3,3′-biphenyltetracarboxylic acid. Particularly preferred is a tetravalent residue obtained by removing a carboxylic acid group from the tetracarboxylic acid.

  Specific examples of B include 1,3-diaminobenzene-4-sulfonic acid and its triethylammonium salt, 1,3-diaminobenzene-4,6-disulfonic acid and its triethylammonium salt, 3,5-diaminobenzoic acid 2,5-dichloro-p-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2-trifluoromethyl-p-phenylenediamine, benzidine-2,2′-disulfonic acid and its triethylammonium salt, 2 , 2 ′, 5,5′-tetrachlorobenzidine, 3,3′-dihydroxybenzidine, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-di (trifluoromethyl) -4, 4′-diaminodiphenyl, o-dianisidine, 3,3′-dicarboxy-4,4′-diaminobiphenyl, , 3 ′, 5,5′-tetrabromo-6,6′-dimethylbenzidine, 3,3′-dimethyl-4,4′-diaminodiphenylsulfone, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,8-dimethyl-3,7-diaminodibenzo Preferable examples include divalent residues excluding amino groups from diamines such as thiophene-5,5-dioxide, 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid and triethylammonium salt thereof.

The substituent of the polyimide having the substituent must be decomposed and eliminated at a temperature lower than the glass transition temperature of the polyimide. Specifically, the SO ₃ H group, triethylammonium sulfonate, tributyl sulfonate SO ₃ HNL ₁ L ₂ L ₃ group such as ammonium (L ₁ , L ₂ and L ₃ are each independently a hydrogen atom or an alkyl group), carboxyl group, hydroxyl group, halogen group such as Cl and Br, C Are preferably an alkyl group having 1 to 3, an alkoxy group having 1 to 3 C, an aryloxy group such as phenoxy, a trifluoromethyl group, and the like.

  The asymmetric polyimide hollow fiber gas separation membrane that does not dissolve in parachlorophenol that can be suitably used in the present invention has a skin layer thickness of 10 to 200 nm and a porous layer thickness of 20 to 200 μm. preferable. If the thickness of the skin layer is less than 10 nm, it is difficult to produce, and if it exceeds 200 nm, the gas permeation rate decreases, which is not preferable. On the other hand, if the porous layer is less than 20 μm, the mechanical strength becomes small and impractical, and if it exceeds 200 μm, the permeation rate of the porous gas becomes small.

  The asymmetric polyimide hollow fiber gas separation membrane that does not dissolve in parachlorophenol that can be suitably used in the present invention is formed by first forming an asymmetric polyimide hollow fiber gas separation membrane with a polyimide having a substituent, and then the asymmetric polyimide hollow fiber separation membrane. Can be suitably obtained by a method of heat-treating under a temperature condition in which the asymmetric structure is maintained and the substituent is decomposed / desorbed or cross-linked so as to be infusible. Hereinafter, the manufacturing method will be described.

  Approximately equimolar amounts of an aromatic tetracarboxylic acid compound such as tetracarboxylic dianhydride and an aromatic diamine compound are dissolved in a solvent such as phenol and heated at a reaction temperature of 100 to 250 ° C, preferably 130 to 200 ° C. Then, polymerization imidization is carried out while removing water or alcohol to be eliminated. At the reaction temperature, the polycondensation reaction and the imidization reaction proceed to obtain a polyimide solution dissolved in a phenolic solvent in one step. The reaction time is about 10 to 60 hours. At that time, the amount of aromatic tetracarboxylic acid compound and aromatic diamine compound used in the solvent is such that the concentration of polyimide in the solvent is 5 to 50% by weight, particularly when the polymerization solution is used directly for the production of hollow fiber membranes and the like. The concentration is preferably 10 to 40% by weight, more preferably 12 to 25% by weight, and the rotational viscosity (measured at 100 ° C.) of the polymerization solution is preferably 10 to 8000 poise, particularly preferably 100 to 3000 poise. . If the rotational viscosity is too high or too low, spinning and film formation become difficult, which is not preferable. The solvent used for the polymerization imidation of the polyimide is preferably a phenol solvent such as phenol, catechol or parachlorophenol, particularly parachlorophenol, which has good solubility and handleability.

  The polyimide asymmetric hollow fiber gas separation membrane has a dope made of a polyimide solution obtained by polymerization imidization from a hollow fiber spinning nozzle at a spinning nozzle discharge temperature of 60 to 150 ° C., and a rotational viscosity at that temperature of 10 After extruding a dope solution of 10000 poise in a dry air or nitrogen gas atmosphere to form a hollow fiber-shaped molded product, the hollow fiber-shaped molded product was kept with an alcohol solvent or water maintained at a temperature of -10 to 60 ° C. It can be suitably obtained by conducting it in a mixed solvent with an alcohol solvent, solidifying it, washing with an alcohol solvent and an aliphatic hydrocarbon solvent, and drying.

  The asymmetric hollow fiber gas separation membrane made of polyimide having a substituent thus obtained is then heat-treated. The heat treatment may be performed in an inert gas atmosphere such as nitrogen gas, but since so-called infusibilization accompanied by decomposition / desorption or cross-linking of substituents can be performed efficiently, in a gas atmosphere containing oxygen, particularly in the air. Is preferred. The heat treatment is less than the glass transition temperature of the polyimide constituting the asymmetric hollow fiber gas separation membrane and 450 ° C. or lower in order to maintain the polyimide skeleton, and higher than the temperature at which the substituent is decomposed, desorbed or cross-linked to become infusible. Must be carried out in the temperature range. This temperature range is determined by the polyimide and its substituents. The temperature at which the substituent is decomposed / desorbed or crosslinked can be confirmed by pyrolysis gas chromatography / mass spectrometry or thermogravimetric mass spectrometry, or can be estimated by weight reduction or thermomechanical analysis by thermogravimetric analysis. Usually, it is 250-450 degreeC, Preferably it is 380-450 degreeC. The heat treatment may be either a batch type or a continuous type, and the overheat treatment time is not particularly limited, but is preferably 0.01 to 10 hours, particularly 0.1 to 2 hours from the viewpoint of treatment efficiency.

  The heat-treated asymmetric polyimide hollow fiber gas separation membrane substantially retains the polyimide skeleton and the asymmetric structure of the asymmetric polyimide hollow fiber gas separation membrane before heating. Further, it is infusibilized by decomposing / eliminating substituents or crosslinking. As a result, for example, parachlorophenol does not dissolve in the solvent that showed solubility before the heat treatment (solvent resistance is improved), and further, the organic vapor separation performance can be achieved by this heat treatment. Improved to.

  The carbonation reaction of the present invention will be described with reference to the schematic diagram of an example of the production apparatus of the present invention shown in FIG. A raw material triol compound, dimethyl carbonate, a catalyst and, if necessary, a solvent are added to a reaction tank 1 equipped with a heating means and a stirring means, and stirred while heating to a predetermined temperature. A mixed vapor containing methanol vapor and dimethyl carbonate vapor by-produced from the reaction mixture is generated, superheated by the heating device 2, and introduced into the gas separation membrane device 3. The permeation side of the gas separation membrane of the gas separation device 3 is decompressed by the vacuum pump 4. In the gas separation membrane device 3, the mixed vapor contacts the gas separation membrane, and methanol vapor selectively permeates the membrane. On the permeate side of the membrane, methanol vapor becomes highly concentrated and is condensed by the cooling device 5 and recovered in a recovery container 6 equipped with cooling means. The mixed vapor flowing on the non-permeate side of the membrane has a high concentration of dimethyl carbonate, and is condensed by the cooling device 7 and returned to the reaction tank 1 by the pump 9 through the buffer tank 8 provided with cooling means.

  Next, the decarboxylation reaction of the cyclic carbonate obtained by the carbonation reaction will be described. This reaction may be carried out by adding the necessary means to the production apparatus of FIG. 1 and continuing in the same production apparatus, or the reaction solution obtained by the carbonation reaction may be transferred to another production apparatus. You can go. In any case, since the reaction solution obtained by the carbonation reaction contains dimethyl carbonate and a small amount of methanol in addition to the produced cyclic carbonate, these low-boiling compounds are removed by distillation or the like prior to the next decarboxylation. It is preferable to keep it. If dimethyl carbonate remains, it is not preferred because the cyclic carbonate of the produced cyclic carbonate and the polymerization reaction proceed to cause a decrease in the yield of the target product.

  In the decarboxylation of the cyclic carbonate, the above carbonated reaction solution in which the low boiling point compound is removed in the presence of a catalyst used in the carbonation is 100 to 300 ° C, preferably 150 to 250 ° C, more preferably 170 to 220. Done by heating to ° C. Carbon dioxide generated during the reaction is released out of the system. At this time, the catalyst used in the carbonation may be newly added within the above-mentioned catalyst concentration, but the catalyst used in the carbonation remaining in the carbonation reaction solution can obtain a sufficient speed. it can. Moreover, the pressure at the time of reaction is not particularly limited, but is preferably in the range of 0.01 to 1 MPa for operation. The atmosphere during the reaction is preferably an inert gas atmosphere such as nitrogen. In the decarboxylation, an inert solvent (particularly a high boiling point solvent) can be used as in the case of the carbonation. After completion of the reaction, high-purity oxetane is separated by distillation. It is also one of preferred embodiments of the present invention to obtain oxetane by performing distillation simultaneously with decarboxylation.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Abbreviations used in the following examples will be described.
s-BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 6FDA: 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride PMDA: pyromellitic dianhydride Product TSN: 2,8-dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide TCB: 2,2 ′, 5,5′-tetrachlorobenzidine MeOH: methanol DMC: dimethyl carbonate

The measurement method used in the following examples will be described.
(Measurement of gas separation performance for mixed steam)
Preparation of measurement hollow fiber membrane element: 10 hollow fiber membranes are bundled and cut to form a hollow fiber membrane bundle, and one end of the yarn bundle is fixed with an epoxy resin so that the end of the hollow fiber is opened, The other end was fixed with an epoxy resin so that the end of the hollow fiber was closed, and a hollow fiber membrane element for measurement having an effective length of 7.5 cm and an effective membrane area of 9.4 cm ² was manufactured.
Measurement of gas separation performance: A description will be given with reference to a schematic diagram (FIG. 2) of a gas separation membrane performance measuring apparatus. A flask 11 equipped with a heating device is charged with methanol and dimethyl carbonate at a predetermined mixing ratio so that the molar composition ratio of methanol and dimethyl carbonate in the generated mixed vapor is 7: 3, and heated with the heating device. The mixed organic vapor was generated. This mixed organic vapor was superheated by a heating device 12 for superheating to be a mixed organic vapor having an atmospheric pressure of 120 ° C., cooled and liquefied by a cooling device 15, and circulated to the flask 11. During this time, the measuring hollow fiber membrane element is not incorporated in the measuring device. The built-in part is sealed. After the preparation of the mixed organic vapor was continued for 2 hours or more, the mixed organic vapor was analyzed to confirm that the molar composition ratio of methanol to dimethyl carbonate was 7: 3. Thereafter, the measurement hollow fiber membrane element 10 is incorporated into the gas separation membrane performance measuring apparatus as shown in FIG. 2, and the permeation side (inside) of the hollow fiber membrane of the element is maintained at a reduced pressure of 0.0007 MPa by the vacuum pump 13. Gas separation started. After continuing the gas separation for 30 minutes or more as a running-in operation, the permeated gas obtained from the permeation side of the measurement hollow fiber membrane element 10 was led to the dry ice-methanol trap 14 for 30 minutes and collected as a condensate. While calculating | requiring the weight of the collected condensate, the density | concentration of each component was measured by the gas chromatography analysis method, and the quantity of each component of the permeate | transmitted organic vapor | steam was calculated | required. From the obtained amount of each organic vapor component, the transmission rate and the transmission rate ratio of each organic vapor component were calculated. The amount of methanol and dimethyl carbonate charged was a sufficient amount such that the charged mixing ratio did not substantially change during this measurement.

(Measurement of solvent resistance)
After three hollow fiber membranes cut to a length of 2 cm were completely immersed in 20 ml of parachlorophenol adjusted to a temperature of 50 ° C. and held for 30 minutes, the hollow fiber membranes were taken out and visually observed. Observed. In the case of dissolution during immersion, “x” indicates that the hollow fiber membrane shape is maintained but swelling is observed, and “Δ” indicates that no change is observed.

[Reference Example 1]
A gas separation membrane was produced as follows.
(Preparation of polyimide solution having substituents)
0.0315 mol s-BPDA, 0.0280 mol 6FDA, 0.0105 mol PMDA, 0.0355 mol TSN, and 0.0355 mol TCB together with 215 g of parachlorophenol, heating device and agitator Weigh in a separable flask equipped with a nitrogen gas inlet tube and a discharge tube, conduct a polymerization imidization reaction at a temperature of 170 ° C. for 15 hours with stirring in a nitrogen gas atmosphere, and dissolve in parachlorophenol A polyimide solution having a substituent with a polyimide concentration of 17% by weight was prepared.

(Production of asymmetric hollow fiber membrane made of polyimide having substituents)
This solution was filtered through a 400 mesh stainless steel wire mesh to obtain a dope for spinning. This dope is charged into a spinning device equipped with a hollow fiber spinning nozzle (circular opening outer diameter: 1000 μm, circular opening slit width: 200 μm, core opening outer diameter: 400 μm), and hollow fiber spinning nozzle. The hollow fiber-shaped molded product is then discharged into a primary coagulation bath at a temperature of 0 ° C. composed of a 70 wt% aqueous ethanol solution, and a secondary coagulation bath (coagulation solution) provided with a pair of guide rolls. The solidification was completed by reciprocating between guide rolls in a 70 wt% ethanol aqueous solution (temperature: 0 ° C.), and the wet asymmetric hollow fiber membrane was wound around a bobbin. The take-up speed was 10 m / min. This asymmetric hollow fiber membrane was thoroughly washed in ethanol, and then the ethanol was replaced with isooctane, and then isooctane was evaporated and dried at 100 ° C. to obtain an asymmetric hollow fiber membrane composed of a polyimide having a substituent.

(Production and performance of infusibilized asymmetric hollow fiber gas separation membrane)
The asymmetric hollow fiber membrane composed of the polyimide having the substituent is heat-treated in an air atmosphere oven at a temperature of 400 ° C. for 30 minutes to obtain an asymmetric gas separation membrane having an outer diameter of about 400 μm and an inner diameter of about 200 μm. Obtained. The obtained infusible asymmetric gas separation membrane has solvent resistance and characteristics of the gas separation membrane. The solvent resistance is ○, and the permeation rate of methanol vapor (P ′ _MeOH ) is 11.3 × 10 ⁻⁵ cm ³ (STP ) / Cm ² · sec · cmHg, and the ratio of the permeation rate of methanol vapor to dimethyl carbonate vapor (P ′ _MeOH / P ′ _DMC ) was 10.6.

[Example 1]
A gas separation membrane device 3 composed of an infusible asymmetric hollow fiber gas separation membrane produced in Reference Example 1 and having an effective membrane area of 1370 cm ² was incorporated into the reaction apparatus as shown in FIG. Here, 1 is a reaction tank that can be heated and stirred, 2 is a heating means for superheating, 4 is a vacuum pump, 5 is a cooling device for cooling and condensing and trapping the permeated methanol vapor, 6 A recovery container having a cooling means, 7 is a cooling device for cooling and condensing the mixed vapor after methanol vapor is selectively removed, and refluxing it to the flask, 8 is a buffer tank having the cooling means, and 9 is a liquid It is a pump. Reference numeral 3 denotes a gas separation membrane device, in which a hollow fiber inner space and a hollow fiber outer space of the hollow fiber gas separation membrane are separated with a hollow fiber separation membrane interposed therebetween, and the hollow fiber inner space is interposed via a cooling device 5. The hollow fiber outer space is connected to the reaction system so that the pressure is reduced by communicating with the vacuum pump 4, and the mixed steam generated in the reaction tank 1 is superheated by the heating means 2 and then the hollow fiber is separated. It is placed in contact with the outer surface of the membrane.

  3 mol of trimethylolpropane, 4.2 mol of dimethyl carbonate (1.4 times mol with respect to trimethylolpropane), and 0.0015 mol of potassium carbonate as a catalyst are charged into the reaction vessel 1, and the temperature of the reaction mixture is stirred. The temperature was raised to 85 ° C. The inside of the reaction tank 1 was an atmosphere of nitrogen gas at atmospheric pressure, and the permeation side of the gas separation membrane was decompressed to 0.0007 MPa by a vacuum pump. As the reaction progressed, the by-produced methanol vapor selectively permeated through the gas separation membrane, and was liquefied by the cooling device 5 and recovered in the recovery container 6 equipped with cooling means. The mixed vapor flowing on the non-permeate side of the separation membrane has a high concentration of dimethyl carbonate, and is condensed by the cooling device 7 and returned to the reaction tank 1 by the pump 9 through the buffer tank 8 provided with cooling means. . Moreover, although the temperature of the reaction liquid mixture rose gradually, it adjusted so that it might not exceed 120 degreeC. Since the reflux of dimethyl carbonate disappeared after 8 hours of reaction, the reaction was terminated. In a recovery container 6 equipped with a cooling means during the reaction, 216 g of a mixed solution consisting of 88% by weight of methanol and 12% by weight of dimethyl carbonate was recovered from gas chromatography analysis.

The reaction liquid in the reaction tank 1 was cooled and transferred to an evaporator, and low boiling point components (MeOH, DMC, etc.) were almost distilled off at 100 ° C. and about 0.004 MPa. Then, it heated up in order to return to normal pressure and to decarboxylate. Foaming (CO ₂ gas generation) started from about 150 ° C., but the temperature was kept at 200 ° C. to 220 ° C. until the reaction was completed so as not to bump. After the decarboxylation reaction is completed, the reaction mixture is distilled under a reduced pressure of 0.001 to 0.005 MPa using a distillation apparatus to obtain 2.95 mol of 3-ethyl-3-hydroxymethyloxetane having a purity of 99% or more (trimethylol). 98.3 mol% relative to propane).

[Example 2]
The same operation as in Example 1 was performed except that 3.9 mol of dimethyl carbonate (1.3 times mol of trimethylolpropane) was used.
In a collection container 6 equipped with a cooling means during the reaction, 215 g of a mixed solution consisting of 87% by weight of methanol and 13% by weight of dimethyl carbonate was collected.
Next, as a result of decarboxylation in the same manner as in Example 1, 2.92 mol of 3-ethyl-3-hydroxymethyloxetane having a purity of 99% or more (97.3 mol% with respect to trimethylolpropane) was obtained.

Example 3
The same operation as in Example 1 was performed except that 3.6 mol of dimethyl carbonate (1.2 times mol with respect to trimethylolpropane) was used.
In a recovery container 6 equipped with a cooling means during the reaction, 209 g of a mixed solution consisting of 89% by weight of methanol and 11% by weight of dimethyl carbonate was recovered.
Subsequently, as a result of decarboxylation in the same manner as in Example 1, 2.90 mol of 3-ethyl-3-hydroxymethyloxetane having a purity of 99% or more (96.7 mol% based on trimethylolpropane) was obtained.

  The present invention is an improved method for producing cyclic carbonates and further oxetanes from a triol compound and dimethyl carbonate, and cyclic carbonates and oxetanes can be obtained in a high yield even when a relatively small amount of dimethyl carbonate is used. . Furthermore, the methanol extracted out of the reaction system has a high purity and can be easily recovered and reused.

The schematic diagram for demonstrating the outline of an example of the manufacturing apparatus used by this invention Schematic schematic diagram of an apparatus for measuring the gas separation performance of a gas separation membrane

Explanation of symbols

1: Reaction tank provided with heating means and stirring means 2: Heating means for superheating mixed steam 3: Gas separation membrane device 4: Vacuum pump 5: Cooling device 6: Recovery container 7 with cooling means: Cooling Apparatus 8: Buffer tank provided with cooling means 9: Liquid pump 10: Gas separation membrane apparatus 11: Heatable and stirred flask 12: Heating apparatus 13 for superheating mixed vapor 13: Vacuum pump 14: Cooling apparatus (trap)
15: Cooling device 16: Side pipe opening

Claims (5)

From the reaction mixture in which the triol compound and dimethyl carbonate are reacted in the presence of a catalyst, a mixed vapor containing by-produced methanol and the raw material dimethyl carbonate is generated, and the mixed vapor is methanol to dimethyl carbonate vapor at 120 ° C. It is characterized in that it is brought into contact with a gas separation membrane having a vapor permeation rate ratio (P ′ _MeOH / P ′ _DMC ) of 2 or more to selectively permeate and extract methanol, and non-permeated dimethyl carbonate is returned to the reaction mixture. A method for producing cyclic carbonates.   The method for producing a cyclic carbonate according to claim 1, wherein the triol compound is 1,1,1-trimethylolalkane. The permeation rate of methanol vapor (P ′ _MeOH ) at 120 ° C. of the gas separation membrane is 1 × 10 ⁻⁵ cm ³ (STP) / cm ² · sec · cmHg or more. The manufacturing method of cyclic carbonate in any one.   The method for producing cyclic carbonates according to claim 3, wherein the gas separation membrane is an asymmetric polyimide hollow fiber membrane that does not dissolve in parachlorophenol.   The manufacturing method of the oxetane characterized by manufacturing cyclic carbonates with the manufacturing method in any one of the said Claims 1-4, and then decarboxylating this cyclic carbonate.

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