JPH0429731A - Oxygen separation membrane - Google Patents

Abstract

PURPOSE:To obtain a membrane excellent in oxygen selectivity by forming a separating active layer consisting of a copolymer of vinyl imidazole and acrylic ester and picket fence porphyrin on porous glass. CONSTITUTION:A copolymer of vinyl imidazole such as 1-vinyl imidazole or a substituted compound thereof and acrylic acid ester is applied to plate-shaped or hollow yarn like porous glass and a picket fence porphyrin complex is subsequently applied to form a separating active layer. A coating order may be reverse or both of them may be simultaneously applied. Herein, the molar ratio of an imidazole group and the picket fence porphyrin complex is set to 1-30. When this ratio is below 1, oxygen absorbing and desorbing capacity is low and, when the ratio exceeds 30, the strength of a film is not obtained. By this method, a film showing high oxygen selectivity within the practically significant oxygen partial pressure range of supply gas of 16-76cmHg is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxygen separation membrane for separating, concentrating or diluting oxygen from the atmosphere. More specifically, the present invention relates to an oxygen separation membrane having, on porous glass, a separation active layer consisting of a copolymer of vinylimidazole or its substituted product and acrylic ester and picket fence porphyrin.

[Conventional technology]

Conventionally, polymer membranes have been used to separate, concentrate, or dilute oxygen from a mixed gas containing oxygen. However, since there is a limit to the ability of a polymer membrane alone to separate oxygen with good selectivity, attempts have been made to increase the selectivity of oxygen by introducing a metal complex that selectively coordinates oxygen into the membrane.

For oxygen separation membranes incorporating metal complexes, liquid membranes are manufactured by Bend Research Inc.
, ) researchers have developed a membrane with a selectivity α8 of approximately 30, expressed as the ratio of oxygen and nitrogen permeability coefficients, in JP-A-59-1270.
Publication No. 7 and Journal of Membrane Science (Journal of Membrane 5c)
ience) Vol. 31, pp. 15-89 (1987)
However, in reality, α8: decreases over time near room temperature.

From a practical standpoint, solid membranes are desirable as oxygen separation membranes, but oxygen separation membranes using solid membranes containing metal complexes have been proposed for a long time as an idea, but facilitated transport has not been experimentally confirmed. There are very few examples.

In particular, for practical purposes, it is necessary to concentrate oxygen from the atmosphere, and for this purpose 16
Facilitated transport is required at cmHg or higher, but it is no exaggeration to say that there are no such cases. In this field, Momode, Ueda et al. have reported that the so-called Co(II) bicket fence porphyrin, represented by the following formula [1] [Journal of the American Chemical Society]
8m herican Chemical 5ociety
) Volume 100, No. 9, Page 2761 (1978)]
An example of oxygen separation using a flat membrane in which 1-methyl imidazoe is dispersed in polybutyl methacrylate is described in Japanese Patent Application Laid-Open No. 6
Publication No. 2-17130 and ■ Macromolecules (
Macromolecules) Volume 20 No. 2 No. 41
Published on page 7 (1987).

However, in both examples, the concentration of bicket fence voluphyline in the membrane was low, and the practical oxygen supply pressure was 16c.
m) At a pressure of 1 g or more, the oxygen selectivity expressed by the permeation rate ratio of oxygen and nitrogen is low. Furthermore, in the case of a solid membrane containing a high concentration of picket fence porphyrin complex, the strength of the membrane decreases, so it is difficult to use the solid membrane alone as an oxygen separation membrane.

In an oxygen separation membrane, it is necessary to reduce the membrane thickness in order to improve the permeation rate, but if the membrane thickness is made thinner, the strength of the membrane further decreases, and it cannot be a practical membrane. In order to solve this problem, a porous membrane is used as a base membrane, and a solid membrane containing a high concentration of piquesotofen porphyrin complex is formed on the porous membrane to produce a composite membrane having an oxygen separation active layer. Is required.

As an example of using porous glass as a gas separation membrane, there is an example in JP-A-58115001 in which porous glass is directly used to separate hydrogen or helium. Examples of modifications with silane coupling agents and metal alkoxides having groups are shown in JP-A-64-90015, JP-A-1-3], JP-A-0713, and JP-A-1-310,714. It is used as a porous highly permeable gas separation membrane.

In other words, there is no known example of a composite separation active layer made of an organic polymer on a porous glass, and a separation active layer made of a solid membrane containing a complex with oxygen coordination ability on a porous glass. There are no oxygen separation membranes with composite layers.

[Problem to be solved by the invention]

In order to solve the problems of the prior art as described above, the present invention uses a porous membrane as a base film and forms a solid film containing a stable metal complex at a high concentration thereon. The purpose of the present invention is to manufacture an oxygen separation membrane that has excellent oxygen selectivity even at an oxygen supply pressure of 1 g or more (16 cm corresponding to the pressure).

[Means to solve the problem]

Therefore, the present inventors have intensively investigated a method of combining a solid membrane containing a picket fence porphyrin complex at a high concentration onto the surface of a porous membrane. However, many porous membranes made of organic materials cannot be used because their pore structures are modified by polar solvents that serve as solvents for porphyrin compounds. Furthermore, when using a porous membrane that is stable against polar solvents, such as a porous membrane made of polytetrafluoroethylene, it is difficult to form a composite membrane without pinholes, and a high α
No results were obtained indicating this.

Therefore, the present inventors investigated a wider variety of porous materials in order to find a porous base film that would enable a composite film with high α. Furthermore, they have discovered that a composite membrane exhibiting the desired high α8 ratio can be obtained by using a copolymer of vinylimidazole or its substituted product and acrylic ester as the matrix polymer of the solid membrane, and has completed the present invention. Ta.

That is, the present invention relates to an oxygen separation membrane characterized by having a separation active layer made of a copolymer of vinylimidazole or its substituted product and acrylic acid ester and pikentofensporphyrin on a porous glass.

The reason why porous glass is effective as a porous base film for solid membranes containing high carrier concentrations is not clear, but the pore structure and surface structure of porous glass are due to the combination of vinylimidazole or its substitutes and acrylic ester. This is presumed to be because it was suitable for holding a highly concentrated carrier-containing solid film consisting of a polymer and biket fence voluphyline without pinholes.

The present invention will be explained in more detail below.

The picket fence porphyrin used in the present invention represents a complex having a structure in which a plurality of sterically hindering groups stand on the same side with respect to the porphyrin ring plane, and an example thereof is represented by the following general formula (II). Examples include complexes such as

(Left below) [In the formula, M is a divalent transition metal selected from iron, cobalt, and manganese, preferably iron and cobalt, and particularly preferably cobalt.

A, 82. A3 and A are R1+ R21R, respectively
3 and R4 and a phenyl group, -CON
It represents HO-, and -CONH- is preferred. R1+R
1+R3 and R4 are a hydrocarbon group having 3 to 30 carbon atoms or a substituted product thereof. R,, R2+ R3 and R
The number of carbon atoms in 4 is preferably 4 to 21, particularly preferably 4 to 13.

The structure of the carbon atoms in the portions where R, R2, R, and R4 connect to A+, Az, A3, and A4 may be any of primary, secondary, and tertiary carbon, but a branched structure may be used. is preferred, and a tertiary carbon structure is particularly preferred.

Examples of substituents for R11R2+ R3 and R4 include alkoxy groups, acyloxy groups, alkoxycarbonyl groups having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, and halogen atoms such as chlorine and fluorine.

In the compound of general formula (II), A+, Az, A
The orientation direction of 3 and A4 is A,, Ih+ A3
A so-called αααα form in which A and A are all on the same side with respect to the porphyrin ring plane is preferred.

The compound of general formula (II) can be prepared by the same method as the compound of general formula [I] or by the method described in Chemistry Letters (Chemist).
ry Letters) 1983, page 1387, JP-A-62108893, JP-A-62-267233
Publication No. 61-47845, Special Publication No. 63-
Publication No. 5033, Tetrahedron Letters (Tetr
ahedron Letters) Volume 36 No. 3071
(1969), Journal of the American Chemical Society
e American Che+++1cal 5oc
It can be synthesized by applying the method described in Vol. 97, p. 226 (1975) and Vol. 94, p. 3986 (1972).

As a specific example of R1+ R2, R3 and R4, (C
Hz)+oOCL, (CLLeOCHa, C(
CL)z(CHz)+oOHC)I(CH3)z,
(CH3)ZCH2CH2CH3 and the like.

A specific example of the compound represented by the general formula [11] is a compound represented by the following general formula CIII).

(In the formula, M represents divalent cobalt or iron).

The polymer used in the present invention is a copolymer of vinylimidazole or its substituted product and acrylic ester, and preferably has an intrinsic viscosity of 0.1 to 10 d/g, and preferably 0.5 to 8 a/g. is more preferable, 0.8
to 5d1/g is particularly preferred. If the intrinsic viscosity is too low, the strength of the produced film will be low; if it is too high, the viscosity of the film-forming stock solution will be high, making it difficult to produce a thin film.

Specific examples of vinylimidazole or substituted products thereof used in the present invention include 1-vinylimidazole, 1
-vinyl-2-methylimidazole and 1-vinyl-
4-methylimidazole is mentioned. Further, the acrylic acid ester which is a copolymerizable monomer with these vinyl imidazoles is represented by the following general formula (IV).

CH2=CH (In the formula, R9 represents a hydrocarbon group having 1 to 8 carbon atoms or a fluorine atom-substituted product thereof, and these may contain an ether group.) Preferred specific examples of R9 include a methyl group and ethyl group. group, isopropyl group, n-butyl i, n-hexyCF.

group, -C8(CF3)! , -CF2CFOC
FZCF2CF3 is mentioned.

The content of vinylimidazole or its substituted product in the copolymer of vinylimidazole or its substituted product and acrylic ester is preferably 1 to 99 mol%, more preferably 5 to 99 mol%, and particularly preferably 10 to 99 mol%. . If the content of vinylimidazole or its substituted product in the copolymer is less than 1 mol %, the content of biket fence porphyrin capable of adsorbing and desorbing oxygen in the membrane will be low, and sufficient α02 will not be obtained.

Z The molar ratio of the imidazole group and the picenodophensporphyrin complex is usually 1 to 30, preferably 1 to 20.
, particularly preferably a range of 2 to 10 is used. If this ratio is less than 1, the amount of piquentophene porphyrin complex exhibiting oxygen adsorption/desorption ability will decrease, and if it exceeds 30, the concentration of piquentophene porphyrin in the solid film will become too low, which is not preferable. .

The content of pikenodofensporphyrin in the solid film composed of the polyvinylimidazole copolymer and the pichenodofensporphyrin complex used in the present invention is usually 0.05moE/kg-0.7mo f2.
/ kg, preferably 0.1 moE/kg
~0,5mol2. / Mausoleum, particularly preferably 0.2mof
A range of 2/kg to 0.5 moff/dazzle is used.

Specifically, for example, in the case of general 2 [1] picket fence porphyrin, it is usually 5% by weight to 70% by weight.
, preferably from 10% to 60% by weight, particularly preferably from 20% to 50% by weight.

If the concentration of the pikentofensvolphyrin complex in the solid membrane is too low, high oxygen selectivity cannot be expected, and if it is too high, the solid membrane becomes brittle and prone to defects such as cracks, so it is not preferred to be used in the present invention. The porous glass has a pore diameter R, which gives a maximum value v, 4 of the pore volume determined by the BET method, from 1 to
10100 nm, preferably in the range 1 to 50 nm, particularly preferably in the range 1 to 10 nm, and with a pore volume of %v1. The pore diameter of the pores I is 0.5R8 to 1.5R, preferably 0.8RM to 1.2RM,
Particularly preferred is a porous glass having pores in the range of 0.9 RM to 1.1 RH. If R, is too large than 1100n, or if the pore diameter at which the pore volume is 'Av,4 is larger than 1.5RM, pinholes are likely to be generated, making it impossible to obtain a high α02. On the other hand, if RsNχ is too smaller than lnm, or if the pore diameter at which the pore volume is % 8 is smaller than 0.5RM, the oxygen permeation rate decreases, making it impractical.

The shape of the porous glass may be either a flat plate or a hollow fiber, but the hollow fiber is preferable because the composite membrane has a high pressure resistance (and a compact oxygen separation membrane module with a high surface area is possible).

The oxygen separation membrane of the present invention can be prepared by first applying one of a copolymer of vinylimidazole or its substituted product and an acrylic ester, or bikket fence voluphyline, and then applying the other, or Alternatively, it can be manufactured by coating both simultaneously to form a separable active layer.

The composite membrane of the present invention prepared as described above can be stably used even when the pressure difference between the inside and outside of the composite membrane is around 76 cmHg, despite the high content of piquesotophensporphyrin, and is suitable for practical use. It has sufficient strength.

Further, the composite membrane of the present invention has an oxygen partial pressure of 15 cm in the supplied gas.
High oxygen selectivity is achieved even for oxygen separation at practically significant high oxygen partial pressures, such as oxygen partial pressures around Hg (oxygen partial pressure in the atmosphere) or around 76 cm Hg. show. Furthermore, as shown in the example of Bend Research, many complexes that exhibit oxygen adsorption/desorption ability rapidly lose their oxygen adsorption/desorption ability in an oxygen atmosphere; The sotofensporphyrin complex is extremely stable even in an oxygen atmosphere and maintains stable oxygen adsorption/desorption ability for a long period of time.

As described above, the composite membrane of the present invention enables a high-performance oxygen separation membrane with high oxygen separation ability, practical strength, and stability.

(Examples) Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples. Note that the following film forming operations were performed under dry nitrogen unless otherwise specified.

Synthesis Example 1 Meso-tetra(0-nitrophenyl)porphyrin (hereinafter referred to as "CPI'") was synthesized as follows.

Acetic acid 11 was refluxed, and 51.7 g (0,342 mo 1 ) of O-nitrobenzaldehyde was added thereto and dissolved. Next, 25 m of pyrrole (0.36 mol
) was added dropwise.

After reacting under reflux for 20 minutes, 1:1 CHCE was added and the mixture was allowed to cool.

This was cooled with water and then with ice to precipitate crystals.

The formed crystals were filtered off by suction filtration and washed with COCl2. The yield after vacuum drying is 10.2 g (0,01
28mol2, yield 15%).

Synthesis Example 2 Meso-tetra(0-aminophenyl)porphyrin (hereinafter referred to as "'CP2") was synthesized as follows.

4. Add CPI synthesized in Synthesis Example 1 to 210 mff of concentrated hydrochloric acid.
16g (5,23mo f2 > after dissolution, SnC12
18.1 g of z 2H20 was added and the temperature was rapidly raised to 65-75°C. After 25 minutes reaction at 65-75°C, 30%
Neutralized with 200 d of ammonia water. In this solution, CHCf
f:+ was added and extracted into the CHCj23 layer.

CHI! , the layer was concentrated by evaporation and washed with aqueous ammonia.
Washed twice with water. After dehydrating this with anhydrous NazsO4, CHCl
When 3 was slowly concentrated using an evaporator, crystals were formed. The crystals were separated by filtration and washed with methanol. Yield 2
．． 8 g (4.2 mmof!/g, yield 80%). The NMR spectra of the products are available in the literature [Journal of the American Chemical Society (J
Our own of the American Ch.
emical S.

vol. 100, No. 9, p. 2761 (1978
)].

Synthesis Example 3 CP2 synthesized in Synthesis Example 2 is a mixture of rotamers due to the rotation of the phenyl group (αααα-1αααβ-1 depending on which side of the porphyrin ring plane the amino group is located on).
A mixture of 4 types of ααβββ-2αβαβ).

Therefore, we isolated a so-called αααα form in which all the amino groups are on the same side with respect to the porphyrin ring plane.

23.18 g of Tributary CP was dissolved in CHi3 and charged into a silica gel column. First, it was developed in CHCE. CHCII until the color of the effluent becomes light red! After developing the column with CHC, ff:+/ether=1/1, the column was developed with CHC, ff:+/ether=1/1 until the coloring became very light. Thereafter, the αααα form was eluted using acetone/ether-1/1. ααα
The fraction containing the α-isomer was dried in an evaporator. Furthermore, this was dissolved in COCl23 and charged into a second silica gel column, and developed with benzene/ether 1/1 until the color of the effluent became very light. The pure αααα form was eluted with acetone/ether-1/1. The solvent was distilled off using an enovolator immersed in a water bath to obtain a solid. Yield 1.
22g (yield 38.2%). TLC showed a single spot.

Synthesis Example 4 αααα form CP2 obtained in Synthesis Example 3 was reacted with pivalic acid chloride to synthesize αααα form meso-tetra (O-bihalamidophenyl)porphyrin (hereinafter referred to as "CP3").

cxαaα body CP21.22g (1.8mmof!/
After dissolving g) in 1322 ml of CH (if the column effluent is used as it is, it will become an acetone-enanosin medium)
Add pyridine 0.7-, pivalic acid chloride 0.77-
was added dropwise, being careful not to raise the temperature too much. This mixed solution was stirred for 3 hours and then left overnight. The reaction solution was concentrated using an enovolator, washed with aqueous ammonia, and then
Washed twice with water. After drying over anhydrous NazSO4, it was concentrated on a rotary evaporator. This was applied to a silica gel column (C
C) ICP, 3/ether-4/1 was used as a developing solvent for purification. Yield 0.41g
(0.41 mmor, yield 23%).

The produced CP3 shows amide absorption at 1680 cm-', and the NMR measurement results are shown in the literature [Journal of the
American Chemical Society (Journal)
of the American Chemical
5ociety) Volume 100 No. 9 No. 2761 (19
1978)].

Synthesis Example 5 Co was introduced into CP3 obtained in Synthesis Example 4. The reaction was carried out with sufficient attention to temperature so that the picket did not rotate during the reaction. All operations were performed under N2.

0.41 g (0.41 mmoff) of CP3, 220.42 g (3.2 mmol) of anhydrous CoCI and 0.13 m (llmmoff) of 2,6-lutidine were dissolved in 32 d of THF and heated at 50"C under N2 for 54. The reaction was allowed to proceed for 5 hours.The progress of CO introduction was determined by the disappearance of the UV-visible spectrum of CP3 and the corresponding production of 2[1]
The generation of an absorption band (526,412 nm) based on the Co complex of CP3 (hereinafter referred to as "cpp'") shown in was tracked and monitored. After sufficiently drying the reaction product in an evaporator, Hensen was added and the alumina column (10 cmφ
x 25 cm, Hensen packing) and developed with benzene/ether solvent. Yield: 0.37g (yield: 85%)
).

The above operation was repeated to obtain the amount of cpp required for the example.

Example 1 8.5 g of 1-vinylimidazole, 27 g of n-butyl acrylate, and 0.1 g of 2,2'-azobis(isobutyronitrile) were placed in a glass ampoule, and after repeated freezing and degassing three times, the ampoule was was melt-sealed and polymerized at 80°C for 17 hours. After dissolving the produced polymer in acetone--
It was purified by reprecipitation by pouring it into xane.

The composition of the purified polymer (hereinafter referred to as "PT") was measured by NMR, and the molar ratio of 1-vinylimidazole to n-butyl acrylate was 228.

Further, when the viscosity of PI was measured in a toluene solution, the intrinsic viscosity was 1.2 dl/g.

Next, the diameter is 1 mm, the wall thickness is 140 am, and the BET
The pore diameter R9 that gives the maximum value V of the pore volume determined by the method is 4% m, and the pore diameter of the pore that gives the pore volume 1/2 ~ jM is 3.8% m (i.e. 0.95 RM ') and one end of a porous glass tube with pores at 4.2 nm (i.e. 1.05 RM) was glued and sealed with epoxy adhesive (Araldite™, manufactured by Chiha Geigy), and 5 g of PI was dissolved in 100 mf of chloroform. The porous glass tube was immersed in the solution, being careful not to let the solution enter the tube from the end that was not sealed with epoxy adhesive. After immersion for 3 minutes, the solvent was evaporated under a nitrogen atmosphere to obtain a porous glass tube holding PI (hereinafter referred to as "'PCI'").

Next, Co(II) picket fence porphyrin (obtained in Synthesis Example 5) represented by the general formula [■]
Place the porous glass tube holding the PI into a solution of 1 g of P") dissolved in 10 m of chloroform, being careful not to let the solution enter the tube from the end that is not sealed with epoxy adhesive. After immersion for 20 seconds, the solvent was evaporated under a nitrogen atmosphere to obtain a porous glass tube (hereinafter referred to as "PG2") holding PI and CPP.

The oxygen separation performance of PCI and PG2 was measured as follows. That is, to measure the gas permeation rate, after deaerating the inside and outside of the tubular membranes (PCI and PG2) to be measured, 76 cv Hg of oxygen or nitrogen, which is the gas whose permeation rate is to be measured, is added to the outside. The amount of gas permeating inside was measured using a pressure gauge.

As a result, the oxygen permeation rate Q of PCI. 2 is 1.2X10
-7 (cffl / crA -s -cmHg), the selectivity αg expressed as the ratio of oxygen and nitrogen permeation rates is 5,
Q of PG2. 2 is 1.1×10-” (cT1/ctos
-cmHg), αj3: was 16, and a significant improvement in αg: was observed in PG2 compared to PCI.

Furthermore, as a result of observing the cross section of PG2 with an optical microscope, it was revealed that the colored CPP layer was formed only on the surface of the porous glass and hardly entered into the pores.

Furthermore, the cross section of PG2 was analyzed by electron probe microanalysis (E
As a result of analysis using PMA), the concentration distribution of cpp in the thickness direction was almost constant (approximately 30% by weight) within the active layer. That is, it was found that CPP was introduced in a high concentration not only at the interface of PI but also in the entire region of the active layer, and that the entire active layer could contribute to oxygen transport.

Example 2 P of Example 1 except that the amount of Pl was changed from 5 g to 10 g.
The porous glass tube holding the PI was immersed in the same manner as in the fabrication of CI, taking care not to allow the solution to enter the tube from the end that was not sealed with epoxy adhesive. After immersion for 1 minute, the solvent was evaporated under a nitrogen atmosphere to obtain a porous glass (hereinafter referred to as "PG3") retaining PI and CPP.

When the oxygen separation performance of PG3 was measured in the same manner as in Example 1, QO2 was 7.7X10-' (crA
/ci-S-cmHg), a'4z was 11.

Example 3 When manufacturing a porous glass tube holding PI, the operation of immersing it in a chloroform solution and evaporating the solvent in a nitrogen atmosphere was performed three times (room temperature time: 3 minutes for the first time, 1 minute for the third time). ) in the same manner as in Example 2 except that P
Porous glass holding I and CPP (hereinafter referred to as “PG
4”) was obtained.

When the oxygen separation performance of PG4 was measured in the same manner as in Example 1, QO2 was 3.7×10-”<crA/
cM −s ・cmHg)′, α02 was 15.

Example 4 A separated active layer component was formed on the same porous glass tube as in Example 1 in the same manner as in the production of PG2 in Example 1 using the solution of CPP and PI in Example]. Furthermore, CPP and PI in Example 1 were mixed in advance (
A separated active layer component was formed on the same porous glass as in Example 1 in the same manner as in the production of PG2 in Example 1 using a CPP/pr=1/3 [moffi ratio]) solution. Place these two types of samples under pure oxygen,
When the change in the amount of oxygen-coordination active CPP0 was determined from the change in the amount of light absorption of 1 cpp at 412 nm in the ultraviolet and visible spectrum, the amount of decrease in oxygen-coordination active CPP over two weeks was found to be It was less than 1%. In other words, CPP is stable in the fabricated membrane due to its nature;
It has become clear that it is always oxygen-coordinating active and in a state where it can contribute to oxygen transport.

Patent applicant: Asahi Kasei Industries, Ltd. hand Continued Supplementary Positive calligraphy (spontaneous) Heisei 2 years July θ3

Claims (1)

[Claims] An oxygen separation membrane characterized in that it has a separation active layer on porous glass that is made of a copolymer of vinylimidazole or its substituted product and acrylic ester and picket fence porphyrin.