JPS6390533A - Separation of hydrogen - Google Patents

Abstract

PURPOSE:To accomplish separation of hydrogen in an advantageous manner from a gas by using a membrane made up of a material of asymmetrical structure consisting mainly of specific copolyamide-imide which is highly heat- resistant and capable of forming such as spinning at room temperature. CONSTITUTION:The objective separation of hydrogen from a gas can be accomplished by using a membrane made up of a material of asymmetrical structure consisting mainly of (A) a copolyimide of formula I (in this formula I, 10-30mol% of R being of formula II and the rest of R of formula III or IV) and/or (B) a copolyamide-imide constituted of (i) 90-70mol% recurring unit of formula V and (ii) 10-30mol% of recurring unit of formula VI. The copolymer A can be prepared by reaction of a mixture of 3,4,3',4'-benzophenone tetracarboxylic acid dianhydride, tolylene diisocyanate and methylenebisphenyl isocyanate; whereas, the copolymer B by reaction of a mixture of 4,4'- methylenebisphenol isocyanate, trimellitic anhydride and isophthalic acid.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is characterized in that -jl"l"l"-benzophenone tetracarboxylic dianhydride is reacted with a mixture of tolylene diin cyanate and himethylene bisphenyl isocyanate. The obtained aromatic Koboliimi)” and U / also 1d,
q, 4t'-methylenebisphenyl incyanate is reacted with a mixture of trimellitic anhydride and in7talic acid to produce a gas using an asymmetrically structured membrane whose main constituent is an aromatic copolyamideimide. The present invention relates to a method for separating hydrogen from hydrogen.

[Conventional technology and its problems]

Separating hydrogen from gas is an industrial Kt! ! So 89,
For example, separation of hydrogen and carbon monoxide in C1 chemistry, recovery of hydrogen in ammonia synthesis, etc. are widely practiced in connection with buttons.

A known example of a membrane that performs these separations is a composite membrane (Monnanto Prism Separator), which is made by coating the surface of polysulfone asymmetrically structured hollow fibers with silicone to a thickness of approximately 7μ. is 0
It is said that the temperature is ~70℃, but it cannot be said to be sufficient.

Also, asymmetrically structured hollow fibers made of biphenyltetracarboxylic acid-based aromatic polyimide (manufactured by Ube Industries, Ltd.) are known, but they use chlorine-based solvents such as parachlorophenol during spinning, and the temperature is higher than room temperature. However, it is not necessarily advantageous because it is difficult to handle.

[Means for solving problems]

In view of these circumstances, the inventors of the present invention have conducted intensive studies on a hydrogen separation method using a material that has high heat resistance and can be formed by spinning or the like at room temperature.
Aromatic copolyimide and/or 9,41'-methylenebisphenyl isocyanate obtained by reacting q'-bensibuenonetetracarboxylic dianhydride with a mixture of tolylene diisocyanate and methylenebisphenyl isocyanate By using an asymmetrically structured membrane whose main constituent material is an aromatic copolyamideimide which has high heat resistance and is soluble at room temperature, obtained by reacting trimellitic acid anhydride and isophthalic acid with a mixture of trimellitic acid anhydride and isophthalic acid. We have discovered that hydrogen can be advantageously separated from gas, and have arrived at the present invention.

That is, the gist of the present invention is a copolyimide having a structure represented by a repeating unit of the general formula (1), wherein 70% of the repeating unit is 90 to 70 molar units of the repeating units are polyimide, and/or 90 to 70 molar units of the repeating units have a structure represented by the formula (It), and Return unit lθ~3
The invention relates to a method for separating hydrogen, characterized in that hydrogen is separated from a gas using a membrane with an asymmetric structure, the main constituent material of which is copolyamideimide having a structure represented by the formula (1).

The present invention will be explained in detail below.

The aromatic copolyimide used in the present invention is a copolyimide characterized by the presence of repeating units of the general formula (1).
, where 90 to 70 moles of the repeating unit are R, and this copolyimide is, for example, UBPJ, 7or, ys.
, as stated in issue r, j, name f, 4I'
-benzophenonetetracarboxylic dianhydride in an appropriate molar ratio of da, q'-methylene bisphenyl isocyanate (F, y'-diphenylmethane diisocyanate) and tolylene diisocyanate (co, 4' -A, co, 6- isomers or mixtures thereof) in the presence of a polar solvent.

Further, the aromatic copolyamideimide used in the present invention has a structure in which 70 to 1 molar units of the repeating unit are represented by the formula (■), and 30 to 1 molar units of the repeating unit
Omolti is a copolyamideimide having a structure represented by formula (1).

This copolyamide-imide is covered by U.S. Patent No. 3, qco? , 49
It is easily manufactured by the method taught in No. 7. Such copolyamideimides can be prepared from about 70 mol. About 1 from O Molch vs. JO Molch
Mixture of trimellitic anhydride and inphthalic acid in proportion of 0 molti and #1 equivalent ioo molti proportion o + t <
It can be easily obtained from the reaction of r'-methylenebisphenyl isocyanate.

Polymerization of copolyimides or copolyamideimides and the solvents used to dissolve them are polar organic solvents such as dimethylformamide, dimethylacetamide,
Examples include N-methylpyrrolidone, dimethylsulfoxide, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, pyridine, etc., but are not particularly limited. Further, in the present invention, dimethylformamide and N-methylpyrrolidone are preferably used, and dimethylformamide is more preferably used as the copolyimide in the present invention, which may be used in combination.

For the copolyamideimide, preferably dimethylformamide, dimethylacetamide, N-methylpyrrolidone is used, more preferably dimethylformamide is used.

What is the amount of polar organic solvent used in the above polymerization?

It is preferred that there is at least sufficient initial dissolution of all reactants. The amount of solvent used is adjusted depending on the desired viscosity of the copolyimide or copolyamideimide, and the weight percent of sb, copolyimide, or copolyamideimide is not very important, but it is usually about 5% by weight.
to about 33% by weight is preferred.

The logarithmic viscosity (RI inh ) of the copolyimide or copolyamideimide used in the present invention is (7,161/1 or more,
y) Preferably 0.3 to da d1/I (N-Mef, Ax
in pyrrolidone, 0. j%, measured at 30°C).

The asymmetrically structured membrane using copolyimide and/or copolyamideimide refers to a membrane that has a non-uniform structure in the cross-sectional direction of the membrane, such as a dense and thin skin layer on the surface. Examples include those in which a porous sponge layer is present at the bottom, and these layers are integrally formed from the same material. The sponge layer may have finger-like pores formed therein.

In a membrane with such an asymmetric structure, the part having the separation function is the skin layer part. The porous layer does not have a separation function, but is thin and has insufficient mechanical strength to support the skin layer.

In a so-called homogeneous membrane that does not have an asymmetric structure, defects such as pinholes are more likely to occur as the membrane becomes thinner, so it is difficult to form a membrane with a practical level of permeation rate, and it cannot be said to be advantageous.

Various membrane shapes can be adopted, such as sheet, spiral, tubular, and hollow fiber shapes.Hollow fiber membranes can increase the effective membrane area per unit volume, and the outer periphery of the hollow fiber When pressurizing from the side, there are advantages such as high mechanical strength against high pressure despite the small thickness of the tube wall.

Methods for producing such a diaphragm include a method of casting a dope solution of the above-mentioned copolyimide and/or copolyamide-imide and a polar organic solvent as its polymerization solvent onto a flat plate such as a glass plate, and a roll method. This can be carried out by a known method such as a coating method, a spinning method, or a method of forming a hollow fiber, which is usually employed to increase the surface area.

It is also possible to further provide a support for BX by casting on a suitable porous (including porous hollow fiber) backing material. This porous support can be any inert porous material that does not block the passage of permeate gas through the membrane and is not attacked by the membrane material, solvent, or coagulation liquid. Preferred materials include metal mesh, porous ceramics, sintered glass, porous glass, sintered metal, paper, and porous non-dissolving plastics. For example, nonwoven fabrics such as rayon, asbestos,
Examples include porous polyimide. These materials do not participate in the separation and merely act as supports for the membrane. It is preferable that the thickness of the thin film of the dope liquid is usually /III or less.

Once a thin film is formed, it is immediately immersed in a coagulation solution.
In this case, while forming the thin film or after forming the thin film,
Part of the solvent in the thin film is evaporated by heating in the atmosphere at 730°C, preferably tio~10°C for 2~300 seconds, preferably 70~10 seconds, more preferably 10~10 seconds. It may be removed and then solidified, or hot air may be blown within the above range. This makes it possible to change the thickness of the surface dense layer in the structure of the asymmetric membrane, making it possible to easily control the separation performance of the resulting membrane.

The coagulating liquid can be appropriately selected from those having good compatibility with the dope liquid and having low solubility with the copolyimide or copolyamide-imide (poor solvent). For example, water, lower alcohols such as glopanol, ketones such as acetone, noethers such as ethylene glycol,
Examples include aromatics such as toluene and mixtures thereof, but water is preferably used from the viewpoint of economy and pollution.

The temperature of the coagulating liquid is preferably in the range of 0 to ioo°C, preferably θ to SO°C.

Any known method may be used to solidify the thin film in liquid form or in which a portion of the solvent has been evaporated. for example,
Examples include a method in which the thin film is immersed together with the substrate on which the thin film is formed in the coagulating solution, or a method in which only the hollow fiber thin film is immersed in the coagulating solution.

It is preferable that the coagulated wet film is air-dried or immersed in alcohols/hydrocarbons to maintain a low concentration of the solvent and coagulating liquid.

Next, in the case of a copolyimide film, the range is from jO to 00°C, preferably from 100 to 3SO°C, and in the case of a copolyamide-imide film, the temperature is from SO to 330°C, preferably from 100 to SOO°C.
The solvent and the impregnated coagulation liquid are removed by heating and drying within a range of May be increased. If heat drying is carried out too quickly, foaming may occur, which is not preferable.

The above-mentioned heating drying temperature, time, and coagulation film thickness of the coagulated wet film vary depending on the type of solvent, the amount of evaporated components in the coagulated wet fr4 film, etc., and may be determined as appropriate for each specific example.

Although it is possible to use the membrane without heating and drying as described above as a separation membrane, it is not recommended to perform the heating and drying as described above. The film strength, such as heat resistance, is significantly improved.

In the method of the present invention, the porosity and pore shape are determined by the concentration of copolyimide or copolyamideimide in the dope solution, the type of solvent, the combination of solvents, the addition of a swelling agent, the evaporation conditions, the type of coagulant, the coagulation conditions, etc. The thickness of the dense layer can be easily changed.

However, copolyimide or copolyamideimide dissolved in a polar organic solvent such as N,N-dimethylformamide, dimethylacetamide, or N-methylpyrrolidone at room temperature can be dissolved in a coagulating agent such as water without adding a swelling agent. Since a porous structure can be easily obtained, there is no need to add a swelling agent.

The thickness of the copolyimide and/or copolyamide-imide separator membrane is about 7~JOOμ, typically about 0μ~100μ.
An overall thickness of is preferred.

In the present invention, gas refers to any type of substance, including oxygen, nitrogen, helium, neon, argon, krypton,
Xenon, radon, fluorine, chlorine, bromine, carbon oxide, carbon dioxide, nitrogen oxide, nitrogen dioxide, ammonium 7, sulfur dioxide.

Examples include hydrogen sulfide, hydrogen chloride, paraffin hydrocarbons, olefin hydrocarbons, and mixtures thereof.

Paraffin hydrocarbons are also called saturated chain hydrocarbons, alkanes or methane hydrocarbons, and include methane with 7 carbon atoms, ethane with -, propane with 3, furin with q, pentane with j, and hexane with 6.

Preferred examples include No. 7 hebutane and No. 7 octane.

When the number of carbon atoms is 4IV, in addition to straight chain normal hydrocarbons, isomers with side chains are also included.

Olefinic hydrocarbons have one double bond and are also called unsaturated chain hydrocarbons, alkenes or ethylene hydrocarbons, and include ethylene with a carbon number of -, propylene with a carbon number of -3, propylene with a carbon number of -3, and q
Preferred examples include butylene of , amidino of j, and the like.

Hydrogen separation according to the present invention is carried out by a conventional method of separating hydrogen using a gas separation membrane using the above membrane.Examples The present invention will be described in more detail with reference to Examples below.

Manufacture Reference Example 1 Using the procedure described in Example q of U.S. Pat. No. 3,701,41jI, 3. J', II,? '-benzophenone tetracarboxylic anhydride and tolylene diisocyanate (gO molar ratio of about 5θ molar ratio, 6
- a mixture of about -0 molar of isomers) and 20 molar of 9.
A copolyimide was polymerized from a mixture containing q-diphenylmethane diisocyanate.

Polymerization solvent i; [+N'N dithylformamide The concentration of the resin used was 1/weight i-t.

This was applied to a concentrator to obtain a copolyimide solution with a copolyimide concentration of s t %.

This copolyimide has a logarithmic viscosity (η1nh
) (0.!% in dimethylformamide) 0.1.61/
It had l.

Production reference example I21! (1,
, 10 mol of trimellitic anhydride and I32. qo
It (o, tro mol) of in7talic acid was charged. The reactor was equipped with a thermometer, condenser, stirrer and nitrogen inlet.

In a dry bottle of jl / 000. Demiji (II,
II of 0 mo/l/)? '-Methylene/bisphenyl incyanate (hereinafter abbreviated as MDI) was weighed out, and then q3tml of N-methylpyrrolidone (hereinafter abbreviated as NMP) was weighed out to dissolve the MDI. This MDI solution was added to the reactor and then Jt, joul of NMP was added to weigh out the MDI and rinse the bottle.

The solution was stirred from j, y °C to /70' for 3 h qO min under a stirring speed of 1 m j rpm and a nitrogen atmosphere.
Heat to c and further 1 hour 3 J minutes 1tsq℃~/ri/'
It was heated to C. In this way, repeat the unit 4th place to
23 if IMF of a random copolyamideimide having a structure with a molar ratio of about 20 molar repeating units.
% solution was obtained.

The logarithmic viscosity (η
1nh) ('N-methylpyrrolidone, O, S) was 0.403 dl/i.

This solution was added to methanol to precipitate a polymer, which was then dried at /jO°C for 3 hours to obtain a copolyamide-imide powder. The obtained copolyamide-imide powder was dissolved in N,y-dimethylformamide to form a 17% by weight solution.

Example 1 The copolyimide solution obtained in Production Reference Example 1 was diluted with -dimethylformamide to prepare a 17% by weight copolyimide solution, and purified by filtration using a 7 μm Millipore filter. This dope solution was cast on a glass plate at room temperature,
Uniform thickness with a doctor knife / 41 nil, 1
A thin film of m11=Jμm) was formed, and the glass plate was immediately immersed in water at 10°C. After being left for 10 minutes, the peeled film was fixed on a metal rod and left in water at 0° C. for 30 minutes. After being left at room temperature for about 1 hour, it was heated and dried at -00 DEG C. for 10 minutes to remove the solvent, producing a copolyimide film with a thickness of about 1410 .mu.m.

When gas permeation performance was measured using this copolyimide membrane, the results shown in Table 7 were obtained.

A copolyamide-imide membrane was manufactured in the same manner as in Example except that the copolyamide-imide solution obtained in Example 1 was used, and the gas permeation performance was measured. The hydrogen permeation rate was j, ko×10 → d(sTP)/7・5ec-cIr
LHJi', what is the nitrogen permeation rate? , OX 10-Ku(
STP)/cIIl·sea-mH&, the ratio of the hydrogen permeation rate to the nitrogen permeation rate was j.

Example 3 A copolyimide solution was produced according to Production Reference Example.

The copolyimide solution was extruded at a constant flow rate from a hollow fiber manufacturing nozzle, and at the same time, a liquid mixture of water and dimethylformamide at a ratio of j O/J O (weight ratio) as a core liquid was extruded at a constant flow rate. The formed hollow fibers were introduced into a coagulation bath of water with an air gap of -m, immersed for 10 seconds, and then wound up at a constant speed of 1 minute. Thereafter, it was immersed in water for Kj minutes and air-dried. Furthermore, after this, both ends of the hollow fiber were fixed to metal rods, and heat treatment was performed at 320° C. for 30 minutes. Hydrogen using this hollow fiber! ! 1
101%, Elenda! A permeation test of a mixed gas consisting of m01 was conducted. High pressure side 3/di G, low pressure side open to atmospheric pressure. The temperature was measured on the Jj'C0 high-pressure side and the low-pressure side, and the respective gas compositions were measured using a gas chromatograph.

The results of the permeation test were as follows: hydrogen permeation rate co, lIX/(7-
Iall (8TP)/i-5ea-c! rIHy, ethylene permeation rate 3.2×/0'cj (BTP)
/aA·e e c ·cmHy, and the ratio of hydrogen permeation rate to ethylene permeation rate was 6.

〔Effect of the invention〕

According to the present invention, hydrogen can be advantageously separated from gas using a material that has high heat resistance and can be formed by spinning or the like at room temperature, and is therefore industrially useful.

Claims (2)

[Claims] (1) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...A copolyimide having a structure represented by repeating units of (I), in which 10 to 30 mol% of the above repeating units are R. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ It represents, and 90 to 70 mol% of the above repeating units are R.
There are chemical formulas, tables, etc.▼Copolyimide that represents ▼ and/or 90 to 70 mol% of the repeating units are formula (II) ▲There are numerical formulas, chemical formulas, tables, etc.▼…(II) and repeating units of 10 to 3
0 mol% is formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(III) Hydrogen is separated from gas using a membrane with an asymmetric structure whose main constituent material is copolyamideimide with the structure represented by A hydrogen separation method characterized by the following. (2) The separation method according to claim 1, wherein the main component of the gas other than hydrogen is a paraffinic hydrocarbon, an olefinic hydrocarbon, or a mixture thereof.