JPS62136226A - Gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain a membrane suitable as a gas separation membrane simple to prepare, excellent in stability and separability and capable of adsorbing and desorbing gas at room temp., by supporting a Schiff base metal complex by a porous polymer support membrane. CONSTITUTION:For example, an org. or inorg. porous membrane having pores with a pore size of 20Angstrom -0.1mum and a thickness of 10-300mum is used as a porous polymer support membrane. A Schiff base metal complex is supported by said porous polymer support membrane by coating or impregnation. A support amount may be within range of about 0.01-5mg/cm<2>. A Schiff base ligand has a structure formed from alpha-diketone, beta-diketone, salicylaldehyde or substituted salicylaldehyde and amine, diamine or triamine by dehydro- condensation. As a core metal, a low valency transition metal such as Co, Fe, Cu, Ni, Mn, Cr or Zn is used. This membrane can be suitably used in the concn. of oxygen.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a gas separation membrane, and more particularly to a gas separation membrane for selectively separating oxygen, carbon oxide, or nitrogen oxide gases, and for separating oxygen or nitrogen gas from air. This invention relates to a gas separation membrane that can be used for selective separation, etc.

[Prior art]

As a gas separation technique, the cryogenic method is the most common, and a typical example is cryogenic separation of oxygen or nitrogen from air.

However, since the deep cooling method consumes a lot of energy, it is thought that energy-saving methods, such as methods that utilize selective adsorption or permeation of gases, will be used in the future.

On the other hand, it has been known for a long time that Schiff base metal complexes absorb certain gases, especially oxygen, and several attempts have been made to utilize this property as oxygen absorbers, oxygen storage agents, or gas separation agents. ing.

For example, there is a method in which a metal complex containing a Schiff base cobalt complex is made into a solution and impregnated into a thin film to function as an oxygen carrier and used as a so-called liquid film (Japanese Patent Laid-Open No. 59-12707).

However, in a liquid film, the solvent in the film gradually evaporates as gas permeates therethrough, so there is a drawback that the life of the film is shortened.

In addition, Schiff base metal complexes change into dinuclear complexes, which easily causes deterioration of gas absorption ability, and gas adsorption requires low temperatures, while gas desorption requires heating and high vacuum. There was a problem that the operation was complicated.

As a solution to this drawback, a method has been proposed in which a certain type of functional group is introduced into a Schiff base metal complex and the complex is made into a polymer by copolymerization (Japanese Patent Laid-Open No. 54-38287).

However, this method has the disadvantage that when polymerized, the active sites are surrounded by inert parts, resulting in a decrease in gas adsorption rate and gas adsorption rate.

Therefore, in order to obtain practical gas adsorbents and separation agents, it has been considered to make thin films, but a durable and homogeneous thin film has not been obtained to date.

Therefore, it can be said that it is currently extremely difficult to utilize Schiff base metal complexes as practical gas adsorbents, storage agents, or gas separation agents.

By the way, it is no exaggeration to say that silicone rubber permeable membranes are the only gas separation membranes currently in practical use.

This permeable membrane has a small oxygen/nitrogen separation coefficient of 2 to 2.5, but an acid S permeation coefficient of 1 x 10 to 1 x -? 10cJ-cm/cA ・sec ・c+++II
It is used to take large values of g.

Attention should be paid to the unit of transmission coefficient here.

That is, since the above value is a permeability coefficient calculated per 1 cm of film thickness, the actual amount of gas permeation increases as the film thickness becomes thinner.

For example, the amount of oxygen permeation when the film thickness is 1 μm is currently:
Efforts continue to make films as thin and defect-free as possible.

In addition to silicone rubber, many other membrane materials are being considered, including oxygen/nitrogen separation coefficients (Poyo/PIJL).
Although some membranes with large ) have been made, most have the drawback of extremely low oxygen permeability coefficients.

Recently, membranes using polyphenylchloroacetylene or polymers having tertiary amino groups, which are comparable to silicone rubber systems, have been produced, but they are still not satisfactory in terms of separation coefficient, membrane stability, etc.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and provides a gas separation membrane that has a large oxygen/nitrogen separation coefficient and oxygen permeability coefficient, is easy to manufacture, has excellent stability, and is highly practical. The purpose is to provide

[Structure of the invention]

The gas separation membrane of the present invention that achieves the above object is characterized in that a Schiff base metal complex is supported on a porous polymer support membrane.

The porous polymer support membrane in the present invention can be an organic porous membrane or an inorganic porous membrane, as long as it has pores of usually 20 to 0.1 µm, preferably 30 to 100 pores. Almost any polymeric membrane can be used as the support membrane, preferably organic porous membranes such as polysulfone membrane, polypropylene membrane, polyacrylonitrile membrane, polycarbonate membrane, polyamide membrane, polyvinyl chloride membrane, etc. can be mentioned.

Further, the thickness of such a film is generally 10 μm to 300 μm.
am, preferably 30 um - 150 am.

Such porous polymer supported membranes are produced by melting the above-mentioned polymeric material in a solvent, casting it onto a glass plate, etc., and coagulating it in some kind of solvent, often water or an aqueous solution. It is manufactured by a conversion method, a method in which a molten polymer is spread into a membrane and then stretched, or a method in which holes are made in a homogeneous polymer using a neutron beam or the like.

Further, the Schiff base used in the present invention is a Schiff base having a structure formed by dehydration condensation of a ketone such as a diketone, a keto acid ester, a ketoamine, or a ketoalcohol, and an amine such as an amine, a diamine, or a triamine. , preferably α-diketone, β-diketone,
It is a Schiff base with a structure formed by dehydration condensation from salicylaldehyde or substituted salicylaldehyde and an amine, diamine, or triamine.

Such Schiff bases are easily produced by reacting ketones and amines in the presence of a solvent according to a conventional method.

Examples of ketones and amines used in the present invention are shown below.

Ketones: salicylaldehyde, nuclear substituted products of salicylaldehyde (substituents: methoxy, ethoxy, propoxy,
butoxy, phenoxy, halogen and nitro), o-
Hydroxyacetophenone, a nuclear substituted product of O-hydroxyacetophenone (the substituents are the same as above), o-hydroxypropiophenone, a nuclear substituted product of O-hydroxypropiophenone (the substituents are the same as above), O-hydroxybenzophenone, 0 -Nuclear substituted product of hydroxybenzophenone (
Substituents are the same as above), diacetyl, acetylacetone,
Benzoylacetone, nuclear substituted product of benzoylacetone (
The substituents are the same as above), trifluoroacetylacetone, hexafluoroacetylacetone, trifluoroacetylacetaldehyde, etc.

Amines: ethylenediamine, 1.2-propanediamine, 1.3-propanediamine, 1.2-cyclohexanediamine, O-phenylene diamine, nuclear substituted product of O-phenylene diamine (substituents are the same as above), ammonia,
Butylamine, diethylenetriamine (bisaminoethyleamine), dipropylenetriamine (bisaminopropylamine), propylamine, ethylamine, methylamine, hydroxylamine, etc.

In addition, in the present invention, the central metal of the Schiff base metal complex is usually cobalt, iron, copper, nickel, manganese,
A low valence transition metal selected from the group consisting of chromium and zinc, preferably cobalt and iron.

Since such a metal complex is produced by mixing a metal salt and a Schiff base in solution, it is essential that the metal salt used is soluble.

For this reason, the counteranion and solvent of the metal salt are not particularly limited, but must be selected so as to make the metal salt soluble.

Specifically, metal salts include organic carboxylates, nitrates,
Chlorides, bromides, diketone complexes, etc., and solvents include lower alcohols such as methanol and ethanol, lower ethers such as diethyl ether, tetrahydrofuran, and dioxane, and lower halogens such as chloroform, dichloromethane, bromoform, and chlorobenzenate. Hydrocarbons, acetonitrile, propionitrile,
Lower nitriles such as benzonitrile, and lower acid amides such as dimethylformamide and dimethylacetamide are commonly used.

If the metal salt or Schiff base is not completely dissolved and there are insoluble substances, it is preferable to separate and use a clear Schiff base metal complex solution using, for example, a filter paper or a microfilter.

In the field of complex chemistry, in order to speed up the formation of Schiff base complexes, 1 to 2
An equivalent amount of alkali, such as sodium hydroxide or potassium hydroxide solution, is added, and the present invention may also optionally include the addition of such an alkali to promote complex formation.

Next, in the present invention, the gas separation membrane has a Schiff base metal complex supported on the above-mentioned porous polymer support membrane to produce a composite membrane.

As a supporting method, a method of applying a Schiff base metal complex solution to a porous polymer support membrane or a method of impregnating a porous polymer support membrane with a Schiff base solution is adopted.

Such coating and impregnation methods are not particularly limited, and commonly used methods are usually adopted, but in order to firmly support the support film on the Schiff base metal complex, a small amount of formalin may be applied to the support film. It can also be mixed into the impregnating solution.

Further, in order to make the coating uniform, a spinner or the like may be used as is commonly used.

Alternatively, a solution in which only the Schiff base is dissolved is applied to the support membrane, or the support membrane is impregnated with this solution, and then the support membrane is impregnated with a solution of a metal salt to transform the Schiff base on the membrane into a metal complex. The gas separation membrane of the present invention can also be produced by a method in which a Schiff base metal complex is uniformly dispersed and melted in a solution doped with a polymer, and a thin film is drawn from the resulting melt.

Further, in order to make the coating uniform, a spinner or the like may be used as is commonly used.

The amount of Schiff base total bending complex supported on the support membrane is usually 0.
．． 01 to 5 mg/cj, preferably 0.2
~'1 mg/aA.

After coating or dipping, the film is dried, but the drying conditions are not particularly limited, and any conventional drying method can be used as appropriate.

Examples include heating drying at 50 to 100°C, drying under reduced pressure, or heating drying under reduced pressure.

In particular, heating drying under reduced pressure often changes the pore size of the support membrane, making it possible to obtain a more effective composite membrane.

〔Effect of the invention〕

As described above, the gas separation membrane of the present invention has a Schiff base supported on a porous polymer membrane, so it is easy to manufacture, has excellent stability and separation coefficient, and has excellent adsorption and desorption at room temperature. A possible membrane is provided.

Therefore, the membrane of the present invention can be suitably used for gas separation.

Examples of the present invention will be described below.

〔Example〕

Example 1 Schiff base of the formula shown below [bis(3-methoxysalicylidene)ethylenediamine, hereinafter referred to as 3-MeO-sal
Abbreviated as en 1 67mg 10n/! To this solution, 10 nl of an ethanol solution in which 13 mg of cobalt acetate was dissolved was added and mixed to prepare a Schiff base cobalt complex solution Co (3-MeO-salen).

This complex solution was applied to a polysulfone membrane (manufactured by Millipore, USA,
(trade name: PTGC), and after being left for 10 minutes, excess liquid on the film was shaken off using a rotating disk.

Furthermore, Co (3-MeO-salen) was applied again,
The excess liquid was shaken off using a spinner.

This crotch was placed in a constant temperature dryer and dried at 50° C. for 1 hour.

The membrane taken out from the dryer was air-cooled to room temperature and then used as a gas separation membrane.

The amount of complex applied on the membrane surface was 0.51 mg/cal.

When the gas permeation performance of this membrane was measured, it was found to be 1.40 x 10 cd/cnl-cmHg for nitrogen gas.
-s and for oxygen gas, 4.20 x IM
/ ad・cmHg-s, the number of isolated cases is 3.0,
It was found that it is possible to produce oxygen-enriched air with this membrane.

Example 2 Schiff base [bis(benzoylacetone)] shown in the following formula
-〇-phenylenediimine (hereinafter abbreviated as bzacoph) 200mg was dissolved in 10mA of ethanol, and 10mA of an ethanol solution in which 60mg of cobalt acetate was dissolved was added to this solution and mixed to prepare a Schiff base cobalt complex. did.

This solution was applied onto the polysulfone membrane, left to stand for 10 minutes, and then the excess liquid was shaken off using a spinner.The above complex solution was further applied, and after left to stand for 10 minutes, the excess liquid was shaken off.

This membrane was placed in a dryer and heated at 50° C. for 1 hour, and the membrane taken out from the dryer was air-cooled and then used as a sample.

The amount of cobalt complex on the membrane surface is 1.53mg/cII!
Met.

When the gas permeation performance of this membrane was measured, it was found to be 3.5 X l0CIII/c+a-cmH for nitrogen gas.
g-s, and for oxygen gas, 10.5X10c
J/ant·cmHg-s, and the separation factor was 3.0.

When air was passed through this membrane at an operating pressure of 3 kg/cnl, oxygen-enriched air with an oxygen concentration of 30.4% and a nitrogen concentration of 69.6% was obtained.

Example 3 Co-bzacoph cleaved in the same manner as Example 2
The scarlet solution was applied onto the polysulfone membrane, and after being left for one hour, the excess liquid on the membrane was shaken off with a spinner.

This membrane was placed in a dryer and heated at 55°C for 2 hours. The membrane taken out from the dryer was air-cooled and then used as a sample.

The amount of cobalt complex on the membrane surface was 1.88n+g/-.

When the gas permeation performance of this membrane was measured, it was found to be 1.2 x 10cj/cd-cm)Ig for nitrogen gas.
s.

4.7×10-/cIa-CIII for oxygen gas
IIg-3, and the separation coefficient was 3.92.

Claims (1)

[Claims] A gas separation membrane characterized in that a Schiff base metal complex is supported on a porous polymer support membrane.