JP2717992B2 - Membrane separation of mixed vapor of organic matter and water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the vaporization of organic substances such as alcohol compounds, ester compounds, ketone compounds, and ether compounds using a gas separation membrane made of a condensation type high molecular polymer. The present invention relates to a gas separation method for continuously and stably removing steam and the like from a mixed steam of water and steam.

[Description of Prior Art]

Recently, using an aromatic polyimide gas separation membrane,
A vapor permeation separation method (dehydration method) for separating water vapor from a mixed vapor of organic matter and water has been proposed in Japanese Patent Application Laid-Open No. 63-267415.

It is well known that the driving force when dewatering a mixed vapor of organic matter and water by a vapor permeation separation method is a partial pressure difference between water vapor inside and outside a separation membrane. Accordingly, a method is generally proposed in which the supply steam pressure is increased and the difference in steam partial pressure is increased by reducing the secondary side (permeation side of the separation membrane) to a high level so as to increase the steam permeation rate. Have been.

However, conventionally, regardless of the composition of the raw material vapor, the raw material vapor is supplied to the membrane at a constant vapor pressure and a constant vapor temperature. There is a problem that the life of the gas separation membrane is shortened and the frequency of replacing the gas separation membrane is increased.

In the dehydration method using a gas separation membrane, even if the vapor pressure is increased in order to increase the permeation rate of water vapor, the condensation polymer is deteriorated by water vapor or the like (hydrolysis, etc.).
As a result, the life of the gas separation membrane is shortened. Therefore, there is an urgent need for a method capable of performing a gas separation operation at a high permeation rate while maintaining the life of the gas separation membrane long.

[Problems to be solved]

The present invention provides a method of dehydrating a mixed vapor of organic matter and water by a vapor permeation separation method using a gas separation membrane made of a condensed high molecular polymer. It is an object of the present invention to provide a method capable of continuously performing a gas separation operation for a long period of time without reducing the life.

[Means to solve the problem]

According to the present invention, the temperature (T) of the mixed vapor of organic matter and water is set to 70.
℃ or more and the pressure (P) of the mixed steam is above normal pressure
A mixed vapor having a temperature of 297 cmHg or less and a temperature (T) and a pressure (P) satisfying the following formula (I) is brought into contact with a gas separation membrane made of a condensed polymer, and The present invention relates to a membrane separation method for a mixed vapor of an organic substance and water, wherein dehydration is continuously performed for 3000 hours or more by a vapor permeable membrane separation method using a separation membrane.

[Where a is the mole fraction of H ₂ O in the mixed vapor, P is the total pressure of the mixed vapor (cmHg), and T is the temperature of the mixed vapor (゜ K). The gas separation membrane used in the present invention can selectively permeate water from a mixed vapor of organic substances containing water, and is made of a condensation polymer. Any type of gas separation membrane may be used, for example, an asymmetric gas separation membrane (flat membrane, spiral type membrane, hollow fiber membrane) made of a condensation polymer, a porous membrane, a composite membrane, and the like. Can be mentioned.

Examples of the condensation polymer include cellulose acetate, polysilicon, polyamide, polysulfone, and polyimide.

In particular, as a condensation polymer, aromatic polyimide is excellent in heat resistance, solvent resistance, water vapor permeation rate, and the like. A separation membrane (asymmetric hollow fiber membrane) can be preferably used.

As the hollow fiber membrane made of the aromatic polyimide, an organic solvent obtained by polymerizing (and imidizing) an acid component such as aromatic tetracarboxylic acid or an acid dianhydride thereof and an aromatic diamine component is used. Using a solution of a soluble aromatic polyamic acid (or aromatic polyimide), a hollow fiber membrane for gas separation having an asymmetric structure formed by a wet film formation method using a coagulation liquid (a homogeneous layer or a dense layer on the surface, A hollow fiber membrane with an integral porous layer inside), or a thin, homogeneous layer of aromatic polyimide formed on the outer surface of a porous hollow fiber membrane of an appropriate material using an aromatic polyimide solution A hollow fiber membrane which is a composite hollow fiber membrane obtained and has sufficient gas separation performance for water vapor can be suitably mentioned.

As the acid component, 3,3 ', 4,4'- or 2,3,3',
4'-biphenyltetracarboxylic acid or its acid dianhydride, or biphenyltetracarboxylic acids such as lower alcohol ester of those acids, 3,3 ', 4,4'-benzophenonetetracarboxylic acid or its acid dianhydride Or a benzophenone tetracarboxylic acid such as a lower alcohol ester of the acid, and a pyromellitic acid such as pyromellitic acid or an acid dianhydride or a lower alcohol ester of the acid.

Further, as the aromatic diamine component, 4,4′-
Diaminodiphenyl ether, 3,4'-diaminodiphenylether, diaminodiphenylethers such as 3,3'-diaminodiphenylether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane,
Diaminodiphenylalkanes such as 2,2-bis (4-aminophenyl) propane and 2,2-bis (3-aminophenyl) propane, 4,4′-diaminodiphenylsulfone,
Diaminosulfones such as 3,4'-diaminodiphenylsulfone; di (aminophenoxy) benzenes such as 1,4-bis (4-aminophenoxy) benzene and 1,3-bis (4-aminophenoxy) benzene; , 2-bis [4-
(4-aminophenoxy) phenyl] propane, 2,2-
Di (aminophenoxyphenyl) propanes such as bis [4- (3-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] Aromatic diamine compounds having 2 to 4 benzene rings, such as di (aminophenoxyphenyl) sulfones such as sulfone, can be suitably mentioned.

As the aromatic diamine component, o-tolidine, o-, m- or p-phenylenediamine, 3,5-
It is also possible to use an aromatic diamine compound having one benzene ring or an aromatic ring such as diaminobenzoic acid and 2,6-diaminopyridine.

As the aromatic polyimide, an aromatic tetracarboxylic acid component containing 50 to 100% by mole, particularly 80 to 100% by mole of biphenyltetocarboxylic acid, and an aromatic compound having 2 to 4 benzene rings in 80% by mole. The soluble aromatic polyimide obtained by polymerization and imidization from the aromatic diamine component contained above has excellent solubility in a phenolic solvent, and a stable spin dope solution can be prepared. It is most suitable from the point of production of a hollow fiber membrane such as its excellent spinnability.

The gas separation membrane used in the present invention is, for example, using a solution of the above-mentioned soluble aromatic polyimide as a dope solution for film formation, extruding from a hollow fiber spinning nozzle to form a hollow fiber thin film of the dope solution. Formed, and then formed into a hollow fiber membrane by a wet film forming method in which the hollow fiber body of the dope solution is brought into contact with a coagulating liquid to coagulate, and further subjected to a heat treatment to form a gas separation hollow made of aromatic polyimide. It can be manufactured as a yarn membrane.

The gas separation membrane used in the present invention is selected according to the “gas permeation rate ratio of water vapor and ethanol (PH ₂ O / PCH ₃ CH ₂ OH)” measured and calculated by the gas permeation test method described below. The permeability (gas separation degree) is preferably 80 or more, particularly 100 or more, and more preferably about 110 to 10,000.

The gas separation membrane has a water vapor permeation rate of 100 ° C. (PH ₂ O: according to a gas permeation test method described later) of about 1 × 10
^-5 cm ³ / cm ² · sec · cmHg or more, especially about 1 × 10 ^{-4 to} 5 × 1
It is preferably about 0 ^-2 cm ³ / cm ² · sec · cmHg.

In the present invention, for example, as shown in FIG. 1, a specific gas separation membrane (a yarn bundle element of an aromatic polyimide hollow fiber membrane shown in FIG. 2) 2 is built in a sealed container 6 for gas separation. Gas separation is performed using the fixed gas separation device 1.

The sealed container 6 communicates with the gas permeable side (inside of the hollow fiber) of the gas separation membrane forming the yarn bundle element 2 of the hollow fiber membrane.
Discharge port (permeate vapor discharge port) 5 ”,“ Substitution gas (purge gas) or source gas supply port (mixed vapor supply port)
3 "and a" container gas or non-permeate gas discharge port (non-permeate vapor discharge port) 4 ".

As shown in FIG. 2, a yarn bundle element of a hollow fiber membrane made of an aromatic polyimide or the like in the gas separation device has an elastomer resin, an acrylate resin, an epoxy resin, a phenol resin at both ends of the yarn bundle. A suitable thermosetting resin such as a resin is solidified by a disk-shaped resin wall 7 or 7 'formed by solidifying the resin into a yarn bundle element 2 of a hollow fiber membrane. In the yarn bundle element 2 of the yarn membrane, it is only necessary that each hollow fiber membrane penetrates the resin wall and opens outward.

In the gas separation device, the yarn bundle element may be a first bundle.
As shown in the figure, the resin walls 7 and 7 'may be hermetically fixed and integrally fixed to the inner wall of the sealed container 6 using an adhesive or the like, if necessary.

In the method of the present invention, for example, an organic-water mixed vapor is heated at a temperature of 70 ° C.
Hg or more and 297 cmHg or less and the gas separation device 1 having a built-in gas separation membrane (a yarn bundle element 2 of a hollow fiber membrane) made of a condensed high-molecular polymer under a condition that satisfies the above-described formula I. The mixed vapor is continuously supplied from the mixed gas supply port 3, and the mixed vapor is caused to flow along the gas supply side (outside) of each hollow fiber membrane of the yarn bundle element. To the inside of the hollow fiber membrane which is maintained under reduced pressure (particularly under reduced pressure of 1 to 300 torr) or purged by a purge gas.
The permeated vapor containing water vapor as a main component is selectively permeated, and the permeated vapor is discharged from the permeated vapor outlet 5 (under reduced pressure or with a purge gas) to remove moisture, while permeating each hollow fiber membrane. The non-permeate vapor (non-permeate gas with reduced moisture) is discharged from the non-permeate vapor discharge port 4 to continuously dehydrate the organic-water mixture vapor supplied by the membrane separation method for a long time. (3000 hours or more).

The organic substance in the mixed vapor used in the method of the present invention has a boiling point of 200 ° C or less, particularly 150 ° C or less,
An organic compound that is liquid at normal temperature (25 ° C.) is preferable.

In the present invention, the above-mentioned mixed vapor of organic matter and water is
The temperature of the mixed vapor (T) is 70 ° C. or more, the pressure (P) of the mixed vapor is normal pressure or more and 297 cmHg or less, and the temperature (T) and the pressure (P) satisfy the above-mentioned formula (I). In order to satisfy the above, it is possible to contact the gas separation membrane made of a condensation type high molecular polymer, in order to achieve a long life of the gas separation membrane, and to increase the permeation rate of selectively permeated moisture. Of particular importance industrially to maintain.

That is, when dewatering is performed by bringing the mixed vapor into contact with the gas separation membrane under the above-described conditions, the amount of water taken into the polymer by the polymer forming the gas separation membrane can be suppressed to a considerably small level. As a result, the hydrolysis of the polymer is suppressed, so that the degree of separation of the gas separation membrane is prevented from rapidly decreasing in a short period of time, and the permeation rate of water vapor in the gas separation membrane is practical. It is maintained at a high level for a long time.

Examples of the above organic substances include methanol, ethanol, isopropanol, n-butanol, sec-butanol, tert-butanol, aliphatic alcohols such as ethylene glycol, alicyclic alcohols such as cyclohexanol, and aromatic compounds such as benzyl alcohol. Organic carboxylic acids such as alcohol, formic acid, acetic acid, propionic acid and butyric acid; organic carboxylic esters such as butyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; cyclic ethers such as tetrahydrofuran and dioxane; and dibutylamine and aniline Organic amines.

In the mixed vapor of organic matter and water, the mixed vapor supplied to the gas separation membrane preferably has a molar fraction (a) of water in the vapor of about 0.01 to 0.96, particularly about 0.05 to 0.95.

〔Example〕

In this example, the organic substance-water mixed vapor dehydration test was carried out by using a gas separation device shown in FIG. 1 which incorporates a yarn bundle element of a hollow fiber membrane made of aromatic polyimide, and an organic substance containing water vapor (ethanol). While supplying the mixed vapor to the gas separation device, the inside of the hollow fiber membrane is depressurized by a vacuum pump and maintained at a reduced pressure of about 300 torr, and the permeated vapor that has passed through the hollow fiber membrane is dried ice-ethanol trap, and The non-permeate gas that did not permeate through the hollow fiber membrane was cooled with cold water,
Each of them is condensed and collected, and the amount of the collected substances is measured and their composition is analyzed by gas chromatography, whereby the water vapor transmission rate [PH ₂ O; cm ³ (S
TP) / cm ² · sec · cmHg], permeation rate of ethanol (PC ₂ H
₅ OH; cm ³ (STP) / cm ² · sec · cmHg] and the degree of separation of the hollow fiber membrane were calculated. The degree of separation was calculated by the following formula II.

Separation degree α = PH ₂ O / PC ₂ H ₅ OH (II) Example 1 A tetracarboxylic acid component consisting only of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 1,4-bis (4
(Aminophenoxy) benzene, and an aromatic diamine component composed of 60 mol% of 4,4'-diaminodiphenyl ether are uniformly dissolved in a melt of a halogenated phenol and polymerized and imidized at a high temperature. The aromatic polyimide solution was extruded from a hollow fiber spinning nozzle, and was coagulated with a low-temperature coagulating liquid to spin a hollow fiber. An asymmetric hollow fiber membrane made of polyimide ”was prepared.

Bundling the above 10 hollow fiber membranes, bonding both ends of the fiber bundle with epoxy resin and curing to form a resin wall, cutting the resin wall portion and opening each hollow fiber membrane to manufacture Thread bundle element (effective length for gas separation: 8cm)
Was prepared, and the yarn bundle element was placed in a sealed container and sealed and fixed to produce a gas separation device of the type schematically shown in FIG.

The above gas separation device was connected to a test facility. First, the inside of the hollow fiber membrane was depressurized to 300 mmHg, and then the total pressure 186 heated to 180 ° C. was supplied from the mixed steam supply port 3 of the gas separation device.
A water / ethanol mixed vapor of cmHg (40% by weight is ethanol; mole fraction of water: 0.798) is supplied along the outside of the hollow fiber membrane (yarn bundle element 2) in the gas separator, A dehydration operation for removing water from the mixed steam is performed at 5000
Performed continuously for hours.

In the above formula I, when the values (a = 0.798, T = 453 ° K, and P = 186 cmHg), which are the conditions of the mixed steam in the dehydrating operation of Example 1, are included, the left side is 2.17. Yes, and the right side is 2.29, which satisfies Formula I.

In the dehydration operation, the amounts of the permeated vapor and the non-permeated vapor and the composition of the collected matter were analyzed, and the changes in the water vapor transmission rate and the degree of separation were calculated over a long period of time, and Table 1 shows the results.

Examples 2 to 3 and Comparative Examples 1 to 2 The same procedure as in Example 1 was performed except that the composition, pressure, and temperature of the mixed vapor of the organic substance and water supplied to the gas separation device were changed as shown in Table 1. The dehydration operation was performed for a long time.

 Table 1 shows the results.

Example 4 A dehydration operation was carried out in the same manner as in Example 1 except that the mixed vapor of water / isopropanol was supplied to the gas separation device while changing the composition, pressure, and temperature shown in Table 1.

 Table 1 shows the results.

[Effects of the present invention] The membrane separation method of the present invention is applied to a case where a mixed vapor of organic matter and water is supplied to a gas separation membrane made of a condensed high-molecular polymer to perform a dehydration operation for a long time. The water-containing mixed vapor supplied to the gas separation membrane is supplied to the gas separation membrane under specific conditions, and the dehydration operation is performed by a membrane separation method, whereby the long-term life of the gas separation membrane is continuously reduced without substantially reducing the long-term life of the gas separation membrane. It is an industrially effective method that can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an example of a gas separation device used in the membrane separation method of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a yarn bundle element of a gas separation membrane (hollow fiber membrane) made of a condensation type polymer incorporated in a gas separation device used in the membrane separation method of the present invention. 1: gas separation device, 2: yarn bundle element, 3: mixed steam supply port, 4: non-permeated steam outlet, 5: permeated steam outlet, 6: sealed container.

Claims (1)

(57) [Claims] 1. The temperature (T) of a mixed vapor of organic matter and water is 70 ° C.
And the pressure (P) of the mixed steam should be equal to or higher than normal pressure.
A mixed vapor having a pressure of 7 cmHg or less and a temperature (T) and a pressure (P) satisfying the following formula (I) is brought into contact with a gas separation membrane made of a condensed high-molecular polymer to obtain the gas. A membrane separation method for a mixed vapor of organic matter and water, wherein dehydration is continuously performed for 3000 hours or more by a vapor permeable membrane separation method using a separation membrane. [Where a is the mole fraction of H ₂ O in the mixed vapor, P is the total pressure of the mixed vapor (cmHg), and T is the temperature of the mixed vapor (゜ K). ]