JP2649706B2 - Pervaporation separation method of organic mixture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-resistant asymmetric mixture of an organic compound solution, such as an organic solvent solution in which an organic compound (organic compound) is dissolved, made of a specific soluble aromatic polyimide. Direct contact with the asymmetric separation membrane, at least one organic substance in the organic substance mixture is selectively permeated and permeated through the asymmetric separation membrane, thereby selectively permeating the asymmetric separation membrane. The present invention relates to a pervaporation separation method (pervaporation method) of an organic substance mixed liquid for separating and recovering the organic substance as a vapor.

[Description of Prior Art]

Conventionally, as a method of separating the organic mixture into each component,
Distillation methods are known. However, in the distillation method, it has been extremely difficult to separate an azeotropic mixture, a near-boiling mixture, and an organic compound which is liable to undergo a chemical change by heat.

In order to solve these problems, a method of separating using a separation membrane has been studied. In the method of concentrating and separating an organic substance aqueous solution using a separation membrane, for the concentration of some low-concentration organic substance aqueous solutions, a specific liquid component is selected by the difference in osmotic pressure by bringing the organic substance aqueous solution into contact with the separation membrane. Reverse osmosis, which allows the permeation to occur, has been used. However, since the reverse osmosis method needs to apply a pressure higher than the osmotic pressure of the separated solution, it cannot be applied to a high-concentration aqueous solution of an organic substance having a high osmotic pressure. is there.

Recently, a pervaporation method (pervaporation method) is attracting attention as a new separation method using a separation membrane as a method for separating an organic substance mixture different from a conventional separation method. In this pervaporation method, an organic substance mixture to be separated is supplied in a liquid state to one side (supply side) of a selectively permeable separation membrane, and the separated liquid is brought into direct contact with the supply side of the separation membrane. The other side (permeate side) of the membrane is brought into a vacuum or reduced pressure state. As a result, substances that selectively permeate from the supply side to the permeate side of the separation membrane are taken out in gaseous form, and the organic substance mixture is concentrated. This is a method for separating organic matter.

Many proposals have been made for the aforementioned pervaporation method.

For example, a benzene-cyclohexane mixed solution, or
The separation of a benzene-hexane mixed solution is described in
JP-A-52-111888 exemplifies a separation method using an ionomer polymer membrane, and JP-A-59-30441 exemplifies a separation method using a polyamide membrane.

However, in a known method for separating an organic substance mixture,
The separation membrane used in the pervaporation method has a low permeation rate, or has only a selective separation property such that at least one organic substance in the organic substance mixture cannot be sufficiently permeated selectively. The problem is that the separation membrane used in the known pervaporation method does not have sufficient heat resistance or solvent resistance, and the separation of various organic mixed liquids by the pervaporation method is industrially required. It was extremely difficult to perform for a long time.

[Problems to be solved]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently and selectively pervaporate at least one organic substance from an organic substance mixture in a pervaporation method of an organic substance mixture using an asymmetric separation membrane without the disadvantages of known pervaporation methods. An object of the present invention is to provide a pervaporation separation method which can be separated by a method and can be carried out industrially for a long period of time.

[Means for solving the problem]

The present invention relates to an aromatic tetracarboxylic acid component containing at least 70 mol% of biphenyltetracarboxylic acids, and 9,10-
The content of di (aminophenyl) anthracenes is 15 mol%
On one surface of a heat-resistant asymmetric separation membrane comprising a soluble aromatic polyimide obtained from an aromatic diamine component, which is an aromatic diamine compound having an aromatic diamine compound having a few benzene rings, with the balance being higher. By directly contacting the organic substance mixture, at least one organic substance in the organic substance mixture is selectively permeated and permeated through the asymmetric separation membrane, so that the organic substance permeating the asymmetric separation membrane is removed. The present invention relates to a method for pervaporation and separation of an organic mixed liquid, which is characterized in that the separation is performed as vapor.

Hereinafter, each requirement of the present invention will be described in more detail.

The soluble aromatic polyimide forming the asymmetric separation membrane used in the pervaporation separation method of the present invention comprises: (A) biphenyltetracarboxylic acids, preferably 70 mol% or more, based on the total aromatic tetracarboxylic acid component, preferably Is 80
(B) (a) a content of 9,10-di (aminophenyl) anthracenes of 15 mol with respect to the total aromatic diamine component; %, Preferably 25 to 100 mol%, and (b) the remainder of the aromatic diamine component has a benzene ring of 2 to 3 mol%.
A high-molecular-weight aromatic polyimide obtained by polymerization and imidation from an aromatic diamine component, which is an aromatic diamine compound having one, and soluble in a phenolic organic solvent and the like.

The aromatic polyimide, for example, an aromatic tetracarboxylic acid component, an aromatic diamine component, uniformly dissolved in a phenolic organic solvent, the solution is about 150 to 2
Heating to a high temperature of 50 ° C. or reacting at a low temperature of about 10 to 100 ° C. in the presence of an imidizing agent to polymerize and imidize both components in the solution Can be.

As the biphenyltetracarboxylic acids, 2,3,
3 ', 4'- or 3,3,4,4'-biphenyltetracarboxylic acid or an acid dianhydride thereof, or a salt or lower alcohol ester of the acid.

As the aromatic tetracarboxylic acids, in particular, 2,2
3,3 ', 4'- or 3,3', 4,4'-biphenyltetracarboxylic dianhydride is preferred for producing aromatic polyimides.

In the present invention, the 9,10-di (aminophenyl) anthracenes are represented by the general formula Any aromatic diamine compound represented by

Examples of the 9,10-di (aminophenyl) anthracene include 9,10-bis (4-aminophenyl) anthracene, 9,10-bis (3-aminophenyl) anthracene,
9- (4-aminophenyl) -10- (3-aminophenyl) anthracene and the like can be mentioned.

The aromatic tetracarboxylic acid component is, together with biphenyltetracarboxylic acids, pyromellitic acid or its acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane or its acid dianhydride, bis ( 3,4-dicarboxyphenyl) methane or its acid dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic acid or its acid dianhydride, or 3,3', 4,4'-diphenyl ether Tetracarboxylic acid or its dianhydride may be used in a small proportion.

In the method for producing an aromatic polyimide, when the content ratio of biphenyltetocarboxylic acids in the tetracarboxylic acid component is too small, the obtained aromatic polyimide has low solubility in a phenolic organic solvent. In addition, it is not preferable because an asymmetric separation membrane having a stable quality cannot be manufactured, or the obtained asymmetric separation membrane has poor separation performance in a pervaporation method.

"Aromatic diamine compound having 2-3 benzene rings" used together with 9,10-di (aminophenyl) anthracene in the above-mentioned method for producing an aromatic polyimide.
As 4,4'-diaminodiphenyl ether, 3,4 '
Diaminodiphenyl ethers such as diaminodiphenyl ether, o-dianisidine, o-tolidine, m-
Diaminobiphenyls such as trizine, diaminodiphenylthioethers, diaminodiphenylsulfones,
Aromatic diamine compounds having two benzene rings such as diaminodibenzothiophenes, diaminothioxanthenes, diaminodiphenylalkanes (methane or propane), or bis (aminophenoxy) benzenes, bis (aminophenyl) benzenes Aromatic diamine compounds having three benzene rings.

Note that the aromatic diamine component is m-phenylenediamine, phenylenediamine such as p-phenylenediamine, 3,5-diaminobenzoic acid, 2,4-diaminobenzoic acid,
"Aromatic diamine compounds having one benzene ring" such as diaminobenzoic acids such as esterified products of benzoic acid may be contained in a small proportion (10 mol% or less).

In the present invention, particularly when an aromatic tetracarboxylic acid component containing 70 mol or more of 3,3 ', 4,4'-biphenyltetralacarboxylic acid is used, 9,10-di (aminophenyl) Anthracenes with a content of more than 15 mol% and less than 90 mol%, especially 20 to 80 mol%
A soluble aromatic polyimide obtained by polymerization and imidization using an aromatic diamine component which is an aromatic diamine compound containing 2 to 3 benzene rings, the remainder being contained in a mole% ratio. It is preferable to use a heat-resistant asymmetric separation membrane.

The above-mentioned asymmetric separation membrane made of the aromatic polyimide used in the present invention uses a phenol-based solvent solution of the aromatic polyimide to form a thin film (flat membrane,
Hollow fiber) is formed by a casting method, an extrusion method, or the like,
Then, the thin film can be manufactured by a wet film forming method in which the thin film is brought into contact with a relatively low-temperature coagulating liquid to solidify the thin film to form a flat membrane-shaped or hollow fiber-shaped asymmetric separation membrane. It can be produced by a conventionally known film forming method as described in JP-A-56-21602 and JP-A-56-157435.

In the above-mentioned method for producing an asymmetric separation membrane, the asymmetric separation membrane produced by a wet membrane formation method may be a suitable organic solvent (for example, lower alcohols such as methanol, ethanol, propanol and butanol, and n-hexane). , N
-Washed with an aliphatic or alicyclic hydrocarbon solvent such as heptane, octane, cyclohexane and the like, further dried sufficiently, and further, under an atmosphere of a gas such as nitrogen and air, at about 150 to 420 ° C, especially It is appropriate to perform heat treatment at a temperature of 180 to 400 ° C. for about 0.1 to 5 hours.

The asymmetric separation membrane used in the present invention has a permeation rate Q of an organic substance that selectively permeates when a permeation vapor separation is performed using an organic substance mixed solution, and is about 0.1 kg / m ² · Hr or more, particularly It is preferably about 0.2 to 5 kg / m ² · Hr, and the separation performance (separation coefficient α) of permeated organic matter and non-permeated organic matter is 5 or more, particularly preferably 10 to 6000.

The pervaporation separation method of the present invention comprises the steps of: (a) supplying an organic compound mixed solution to a separation membrane module in which the above-described asymmetric separation membrane (flat membrane, hollow fiber) made of aromatic polyimide is incorporated; Contacting the organic mixture directly with the supply side of the asymmetric separation membrane in the separation membrane module; and (b) flowing a carrier gas (sweep gas), if necessary, through the permeate side of the asymmetric separation membrane. Alternatively, or at least one type of organic substance is selected from the supplied organic substance mixed liquid via the asymmetric separation membrane from the supplied organic substance mixed solution by connecting to a decompression pump or the like installed outside the separation membrane module. (C) Finally, the permeation through the separation membrane is prevented from the non-permeate side (supply side) of the asymmetric separation membrane to the outside of the separation membrane module. The concentrated remaining organic matter solution is taken out and recovered, and at the same time, the permeated vapor (permeate) of the organic matter selectively permeating the separation membrane from the permeate side of the asymmetric separation membrane to the outside of the separation membrane module. ) Is taken out, and if necessary, the permeated vapor (permeate) is cooled, condensed and recovered.

In the present invention, the temperature of the organic mixture supplied to the separation membrane module is preferably about 0 to 120 ° C, particularly preferably about 20 to 100 ° C.

In the separation method of the present invention, the pressure applied to the separation method is generally set such that the pressure on the permeation side of the separation membrane is lower than the pressure on the supply side, and the pressure on the supply side is atmospheric pressure to 60 kg / cm ² , preferably It is preferable that the pressure be from atmospheric pressure to 30 kg / cm ² .

The permeate side of the asymmetric separation membrane in the separation membrane module may be swept gas or reduced pressure when performing permeation vaporization separation of the organic substance mixture. It is sufficient that the pressure is lower than the atmospheric pressure, and it is particularly preferable that the pressure is reduced to about 200 Torr or less, more preferably 100 Torr or less.

As the organic substance mixture to which the method of permeating and vaporizing the organic substance mixture in the present invention can be applied, there are various combinations of organic substances, but, for example, each organic substance has an azeotropic point and cannot be separated by a normal distillation method. This is particularly effective in the case of a mixture of organic substances and a mixture of organic substances which are very difficult to be separated by distillation because their boiling points are close to each other.

Further, all of the organic substance mixed solution may be uniformly dissolved in each other, or a part of the organic substance mixed solution may be separated and suspended in excess of the solubility. However, the mixed liquid containing an organic substance needs to be liquid under the conditions of temperature and pressure when performing pervaporation separation in the mixed state.

As a mixture of organic substances having an azeotropic point, for example,
Benzene / cyclohexane, benzene / normal hexane, methanol / acetone, benzene / methanol, acetone / chloroform (trichloromethane), ethanol / cyclohexane, butanol / cyclohexane, chloroform / normal hexane, ethanol / benzene, ethanol / toluene, xylene isomer mixture Liquid and the like.

Examples of the organic mixture having a boiling point difference of about 20 ° C. or less, particularly 10 ° C. or less, and boiling points close to each other include, for example, ethylbenzene / styrene, parachloroethylbenzene / parachlorostyrene, and toluene / methylcyclohexane. , Butadiene / butenes, butadiene / butanes, and normal butene-1 / isobutene.
The above-mentioned organic mixture can be applied not only to the two-component mixture as described above, but also to a multi-component mixture of three or more components.

In the pervaporation separation method of the present invention, the composition ratio of the organic substance mixture is not particularly limited, and an organic substance mixture of an arbitrary ratio can be separated or concentrated.

The structure, type, and the like of the separation membrane module are not particularly limited. For example, although not particularly limited, a plate-and-frame module, a spiral module, a hollow fiber membrane module, and the like can be used. Is preferred.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples relating to the pervaporation separation method of the present invention.

In Examples and Comparative Examples, the permeation rate Q and the separation coefficient α were determined by cooling and condensing the vaporized components that had passed through the membrane, collecting the weight, measuring the weight, adding an internal standard solution to the condensate, and measuring the TCD. -The weight ratio of the organic substances X and Y was measured by gas chromatography, and calculated by the following formula.

In Reference Examples, the abbreviations of the compounds used for the aromatic tetracarboxylic acid component and the aromatic diamine component are shown below.

(Aromatic tetracarboxylic acid component)

s-BPDA; 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride a-BPDA; 2,3,3', 4'-biphenyltetracarboxylic dianhydride ETDA; 3,3 ', 4 , 4'-Diphenylethertetracarboxylic dianhydride [aromatic diamine compound] ADA; 9,10-bis (4-aminophenyl) anthracene DADE; 4,4'-diaminodiphenylether Reference Examples 1-3 shown in Table 1 Polymerization and imidization are carried out in an organic polar solvent of paraclophenol at a polymerization temperature and a polymerization time shown in Table 1 using substantially equimolar amounts of an acid component having a charge ratio (composition mol%) and a diamine component. An aromatic polyimide solution was prepared.

Table 1 shows the polymer concentration and solution viscosity (rotational viscosity at 100 ° C .; poise) of each aromatic polyimide solution produced as described above.

Using the aromatic polyimide solution obtained as described above, a hollow fiber spinning nozzle is used to form a hollow fiber through a gas into a coagulating liquid (aqueous alcohol solution, 0 ° C.) having the composition shown in Table 1. After extruding the body and performing a semi-dry wet film forming method of forming a hollow fiber by drawing the hollow fiber at a take-up speed of 10 m / min, washing with an alcohol and an aliphatic hydrocarbon, drying and drying were performed. At a heat treatment temperature of 30 minutes to produce an asymmetric hollow fiber separation membrane made of an aromatic polyimide having a shape (inner diameter and thickness of a hollow fiber) shown in Table 1.

Examples 1 to 5 A bundle of four asymmetric hollow fiber separation membranes having a length of 7.5 cm manufactured in each Reference Example was formed into a bundle, and one end of the bundle was sealed with an epoxy resin. A hollow fiber bundle element is created, and the hollow fiber bundle element is installed in a container having an inlet for supplying an organic mixture, an outlet for unpermeate, and an outlet for permeate, and a separation membrane module. Manufactured.

An organic substance mixture having the composition and temperature shown in Table 2 is supplied to the separation membrane module, and the inside of the hollow fiber of the hollow fiber element in the separation membrane module is permeated and vaporized under a reduced pressure of 3 Torr or less. The material vapor was cooled and collected.

Table 2 shows the permeation rate Q and the separation coefficient α of each organic substance in the pervaporation.

Example 6 The asymmetric hollow fiber separation membrane produced in Reference Example 2 (1) was
A immersion treatment was performed at 150 ° C. for 20 hours in a treatment solvent composed of a mixture of benzene and cyclohexane (weight ratio: 1: 1).

Each asymmetric hollow fiber separation membrane subjected to the above treatment
After drying for 20 hours, a separation membrane module was manufactured in the same manner as in Example 1, and the separation performance of each separation membrane module in an organic substance mixture shown in Table 2 was measured.

 Table 2 shows the results.

Comparative Reference Example 1 60 mmol of pyromellitic dianhydride, 60 mmol of 4,4'-diaminodiphenyl ether and 200 g of N-methyl-2-pyrrolidone were placed in a three-neck separable flask, and nitrogen gas was passed therethrough. A polymerization reaction was carried out at 20 ° C. for 10 hours with stirring to produce a polyamic acid, and further, 200 g of N-methyl-2-pyrrolidone was added to the reaction solution.
27 g of pyridine and 35 g of acetic anhydride were added, and the temperature was gradually raised to 80 ° C. with vigorous stirring, and maintained at 80 ° C. for 1 hour to imidize the polymer to precipitate polyimide. Further, ethanol was added to the reaction solution to completely precipitate the polymer, and the polymer was separated by filtration.
Drying under reduced pressure gave a polyimide powder.

This polyimide powder was treated with p-chlorophenol, N-
Methyl-2-pyrrolidone or N, N-dimethylacetamide, respectively, the mixture was heated,
Tried to dissolve the polyimide powder in the above solvent,
Substantially no solution of the polyimide could be prepared.

Therefore, an asymmetric separation membrane could not be produced from the aromatic polyimide obtained by using the above pyromellitic dianhydride.

Comparative Reference Examples 2 to 4, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine (Comparative Reference Example 2), 2,5-
Using dimethyl-paraphenylenediamine (Comparative Reference Example 3) or 2,6-diaminopyridine (Comparative Reference Example 4) in equimolar amounts and in the same manner as in Example 1, paraclophenol in an organic polar solvent, Polymerization was carried out at a polymerization temperature of 180 ° C. for 6 hours, and aromatic polyimides were precipitated.
These aromatic polyimide powders did not substantially dissolve in any of the organic solvents, and a uniform polymer solution could not be prepared.

Comparative Example 1 Aromatic polyimide (General Electric,
10 parts by weight (Ultem), 40 parts by weight of N-methyl-2-pyrrolidone, and 50 parts by weight of tetrahydrofuran were put into a separable flask and stirred to prepare a uniform polymer solution.

The polymer solution was cast on a smooth glass plate with a doctor knife to a thickness of 0.2 mm.
After immersion for a time, an asymmetric separation membrane was formed. Finally, the asymmetric separation membrane was peeled off from the glass plate and dried at 30 ° C. to produce an asymmetric separation membrane.

The above-mentioned asymmetric separation membrane was subjected to a pervaporation method to separate an organic substance mixture containing equivalent amounts of chloroform and n-hexane.

The asymmetric separation membrane was swollen by the organic mixture and the stable separation performance could not be measured.

(Operation and effect of the present invention)

Since the separation method of the present invention is a separation method related to a pervaporation method using an asymmetric separation membrane made of a specific aromatic polyimide, it can be used for separating and concentrating a mixture of various organic substances, and It can be used for a wide range of organic compound liquids, and has sufficient heat resistance, water resistance,
Since a specific polyimide asymmetric membrane having solvent resistance and durability and high separation performance is used, stable separation by pervaporation can be performed for a long time.

Claims (1)

(57) [Claims] (1) 70% by mole of biphenyltetracarboxylic acid
The content of the aromatic tetracarboxylic acid component contained above and 9,10-di (aminophenyl) anthracene is 15
Of a heat-resistant asymmetric separation membrane comprising a soluble aromatic polyimide obtained from an aromatic diamine component which is an aromatic diamine compound which is an aromatic diamine compound having an aromatic diamine compound having two to three benzene rings, with the balance being greater than 2 mol%. On one side, an organic substance mixture is brought into direct contact, and at least one organic substance in the organic substance mixture selectively permeates the asymmetric separation membrane.
A permeation and vaporization separation method of an organic substance mixture, wherein the organic substance having passed through the asymmetric separation membrane is separated as vapor by being permeated.