JP6729012B2 - Method for manufacturing hollow fiber carbon membrane - Google Patents

Description

The present invention relates to a method for manufacturing a carbon film and the like.

From the viewpoint of environmental problems and energy saving in recent years, the membrane separation method has been attracting attention in the separation of a specific component from a mixture of various gases, the dehydration/purification process of an organic solvent, and the like. As a separation membrane to be used, a polymer membrane such as a polyimide membrane or a polysulfone membrane has been proposed, but such a polymer membrane has problems in heat resistance and solvent resistance. It is also known to use a zeolite membrane, which has better heat resistance than a polymer membrane, as a separation membrane, but the zeolite membrane has a problem of poor acid resistance.

Therefore, in recent years, a carbon membrane has been developed as a separation membrane having excellent heat resistance, solvent resistance, and acid resistance. The carbon film is roughly classified into two types: a support-type carbon film formed on the surface of a support (porous substrate) and a self-supporting carbon film that does not use a support. Typical free-standing carbon membranes include a flat membrane type and a hollow fiber type. Among them, a hollow fiber type (hereinafter, referred to as "hollow fiber carbon membrane") can be used because the membrane area per unit volume can be increased. Is considered to be preferred.

Regarding a self-standing hollow fiber carbon membrane excellent in gas separation performance, for example, in Patent Document 1, PPO hollow fiber carbon obtained by carbonizing a precursor polymer membrane containing polyphenylene oxide (PPO) after infusibilizing treatment Membranes are disclosed.

Further, for example, in Patent Document 2, a film-forming stock solution containing sulfonated polyphenylene oxide (SPPO) is extruded into an aqueous coagulation bath from an outer tube of a hollow fiber spinning nozzle having a double tube ring structure to prepare a precursor polymer film, There is disclosed a SPPO hollow fiber carbon membrane obtained by carbonizing this precursor polymer membrane after infusibilizing treatment.

JP, 2006-231095, A JP, 2009-34614, A JP-A-3-65227

G. Chowdhury, B. Kruczek, T. Matsuura, Polyphenylene Oxide and Modified Polyphenylene Oxide Membranes Gas, Vapor and Liquid Separation, 2001, Springer

However, the PPO hollow fiber carbon membrane disclosed in Patent Document 1 is economical because PPO is a relatively inexpensive polymer, but has a problem that the separation performance as a membrane is low.

Further, in the SPPO hollow fiber carbon membrane disclosed in Patent Document 2, SPPO having a high sulfonation degree (for example, the sulfonation degree of 45% described as an example in Patent Document 2) has high polymer hydrophilicity. In addition, as a result of containing a large amount of water in the spinning process, the strength of the film becomes weak. In addition, the hollow fiber membranes tend to adhere to each other in the drying process, which makes the handling in the mass production process difficult.

Further, Patent Document 2 discloses a method for producing an SPPO polymer (for example, Example 1 and Example 7 of Patent Document 2), in which PPO is subjected to a sulfonation reaction with chlorosulfuric acid to prepare SPPO. However, SPPO has poor solubility in chloroform, which is a solvent for PPO, and thus the reaction proceeds while precipitating, resulting in poor reproducibility and making it difficult to prepare a stable polymer. Furthermore, since chloroform and chlorosulfuric acid, which are deleterious substances, are used, they are not industrially safe in terms of environment and safety.

The present invention has been made to solve the above problems, and an object thereof is to provide a highly reproducible production method of a hollow fiber carbon membrane having high permeation/separation performance.

The inventors of the present invention have earnestly studied in order to solve the above problems, and finally have completed the present invention. That is, the present invention is as follows.
1. A method for producing a hollow fiber carbon membrane, the step of dissolving polyphenylene oxide in an aprotic solvent, and the step of discharging the dissolved polyphenylene oxide from a spinning nozzle at a temperature above a temperature-induced phase separation point to form a hollow fiber And a step of coagulating the hollow-fiber-shaped polyphenylene oxide with water or a mixed solution of water and an organic solvent, the coagulated hollow-fiber-shaped polyphenylene oxide, without performing solvent replacement treatment, from a state containing water. A step of drying to obtain a hollow fiber carbon membrane precursor, and a step of adding a sulfur-containing compound to polyphenylene oxide in at least one step of each of the above steps, and further, the sulfur-containing compound is added. A method for producing a hollow fiber carbon membrane, comprising the step of carbonizing the hollow fiber carbon membrane precursor.
2. 2. The hollow fiber carbon membrane precursor to which the sulfur-containing compound has been added, wherein the addition rate of elemental sulfur is 0.5% or more based on the mass of the hollow fiber carbon membrane precursor. Membrane manufacturing method.
3. 3. The method for producing a hollow fiber carbon membrane according to 1 or 2, wherein the sulfur-containing compound has a boiling point or a decomposition temperature of 100° C. or higher and 300° C. or lower.
4. 4. The method for producing a hollow fiber carbon membrane according to any one of 1 to 3 above, wherein the sulfur-containing compound has a sulfo group.
5. A hollow carbon membrane produced by the method for producing a hollow fiber carbon membrane according to any one of 1 to 4 above.
6. A separation membrane module formed using the hollow fiber carbon membrane as described in 5 above.

According to the method for producing a hollow fiber carbon membrane of the present invention, a hollow fiber carbon membrane having excellent gas separation performance and flexibility can be produced with high reproducibility. Further, the hollow fiber carbon membrane of the present invention is excellent in gas separation performance and flexibility, hard to break, easy to modularize, and excellent in practicality.

It is a figure which shows the structure of the evaluation apparatus of a separation performance.

Hereinafter, modes for carrying out the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and it is understood that appropriate design changes, improvements and the like can be added based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be.

The method for producing a hollow fiber carbon membrane of the present invention comprises (1) a step of dissolving polyphenylene oxide (PPO) in an aprotic solvent (dissolution step), and (2) a temperature of the dissolved PPO at a temperature above a temperature-induced phase separation point. A step of discharging from a spinning nozzle to form a hollow fiber (a discharging step), (3) a step of solidifying hollow fiber PPO with water or a mixed solution of water and an organic solvent (a solidifying step), and (4) solidification The hollow fiber-shaped PPO is washed with water without performing a solvent replacement treatment, and is dried from a state containing water to obtain a hollow fiber carbon membrane precursor (drying step), and (5)(1) to (4) ) Step of adding a sulfur-containing compound to PPO in at least one step (compound applying step), and (6) carbonizing the hollow fiber carbon membrane precursor to which the sulfur-containing compound has been added (carbonization) Processing step).

The hollow fiber carbon membrane of the present invention is produced by the method for producing a hollow fiber carbon membrane described above. A module using the hollow fiber carbon membrane of the present invention is also included in the scope of the present invention.

[1] Dissolution step In the method for producing a hollow fiber carbon membrane of the present invention, first, PPO is dissolved in an aprotic solvent. For example, as summarized in Non-Patent Document 1, the solvent of PPO has a large environmental load such as benzene, toluene, and chloroform, and many of them are harmful to the human body. On the other hand, for example, Patent Document 3 discloses that PPO is dissolved in an aprotic solvent having a relatively small environmental load at a temperature of about 100° C. or higher.

Examples of the aprotic solvent used in the method for producing a hollow fiber carbon membrane of the present invention include N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide. Among them, the solubility of PPO is particularly preferable. Since it is excellent, it is preferable to use N-methyl-2-pyrrolidone as the aprotic solvent.

When N-methyl-2-pyrrolidone is used as the aprotic solvent, N-methyl-2-pyrrolidone can uniformly dissolve PPO at a temperature of about 100° C. or higher. Further, a desired poor solvent (for example, methanol, ethanol, acetone, tetrahydrofuran, methyl ethyl ketone, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, etc.) is added to N-methyl-2-pyrrolidone within a range in which the solubility of the polymer is secured. Thus, the pore size and pore size distribution of the membrane can be changed.

[2] Discharging Step In the subsequent discharging step, the solution (PPO spinning stock solution) obtained by dissolving PPO in the aprotic solvent as described above is discharged from the spinning nozzle to form a hollow fiber. The spinning method in the method for producing a hollow fiber carbon membrane of the present invention is not particularly limited, and a conventionally known spinning method can be applied. However, it is preferable to apply the dry-wet spinning method from the viewpoint of precisely controlling the structure of the PPO hollow fiber membrane and the viewpoint of ease of production.

In the method for producing a hollow fiber carbon membrane of the present invention, the PPO spinning dope is discharged at a temperature equal to or higher than the temperature-induced phase separation point. Here, the "temperature-induced phase separation point" refers to a temperature at which solidification does not occur due to temperature-induced phase separation, and for example, the temperature-induced phase separation point of a PPO spinning stock solution in which PPO is dissolved in N-methyl-2-pyrrolidone. Is approximately 80° C. (50 to 120° C.), although it varies depending on the concentration of the spinning dope and the solvent composition. Therefore, in the discharging step, spinning is performed together with the internal liquid from the double cylindrical tube nozzle while maintaining a uniform liquid state at a temperature of 80° C. or higher, preferably 100° C. or higher. It is needless to say that the temperature in the discharging step is set to 200° C. or lower from the viewpoint that the temperature is not higher than the boiling point of the solvent and that the viscosity of the spinning dope is not too low and the spinning stability is impaired. More preferably, the temperature is 180° C. or lower.

The hollow fiber PPO spinning stock solution discharged together with the internal solution as described above is solidified by the nonsolvent-induced phase separation from the internal solution. The inner liquid is preferably discharged to the inside of the PPO spinning stock solution discharged in the form of hollow fibers and capable of solidifying the PPO spinning stock solution by nonsolvent-induced phase separation. As such an internal solution, a solvent having a boiling point higher than that of water is preferably used when the spinning dope is discharged at 100° C. or higher as described above. Examples of such an internal solution include glycerin, ethylene glycol, diethylene glycol and the like. Above all, it is preferable to use ethylene glycol as the inner liquid because it facilitates the subsequent washing with water.

[3] Coagulation step In the subsequent coagulation step, the spinning dope discharged in the above-mentioned discharge step is immersed in a coagulation bath filled with a poor solvent. From the viewpoint of controlling the membrane structure such as increasing the polymer concentration on the surface of the hollow fiber material to make the surface denser, the PPO spinning stock solution formed in the hollow fiber shape after the discharging step partially contains the solvent. After the drying treatment, it is preferable to use the coagulation process. In the coagulation step, the hollow fiber-shaped PPO spinning dope is coagulated into a hollow fiber material by nonsolvent-induced phase separation.

Examples of the poor solvent used in the coagulation step include water or a mixed solution of water and an organic solvent, because the PPO polymer in the spinning dope can be rapidly coagulated and is easy to use. .. When the organic solvent is mixed, examples of the organic solvent include methanol, ethanol, glycerin, ethylene glycol, diethylene glycol, acetone, tetrahydrofuran, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and the like. -Methyl-2-pyrrolidone is preferred.

The temperature of the poor solvent when the PPO spinning dope is immersed is not particularly limited, but is preferably in the range of 0 to 50°C, more preferably 0 to 20°C. This is because when the temperature of the poor solvent is lower than 0° C., the liquid in the coagulation bath freezes, or the viscosity becomes too low, so that the spinning stability tends to deteriorate. On the other hand, if the temperature of the poor solvent exceeds 50° C., the viscosity of the coagulation bath becomes too low, the membrane structure becomes unstable, and the spinning stability tends to deteriorate. Further, the time for immersing the PPO discharge stock solution in the poor solvent is not particularly limited, but it is 0.1 to 100 seconds from the viewpoint that coagulation is sufficiently advanced to maintain the hollow fiber shape and the process is not unnecessarily lengthened. Is preferably in the range of 1, and more preferably in the range of 1 to 50 seconds.

[4] Drying Step After the above-mentioned coagulation step, the coagulated hollow fiber PPO (hollow fiber material) is dried from the state containing water without performing the solvent replacement treatment to obtain a hollow fiber carbon membrane precursor. .. In addition, it is preferable that the hollow fiber-shaped material that has been phase-separated in the coagulation step is sufficiently washed with water to remove the remaining solvent and then subjected to the drying step.

The "solvent replacement treatment" not performed in the drying step in the present invention is, for example, a hollow fiber material containing water, a solvent such as alcohol having a surface tension smaller than that of water, and gradually increasing the solvent concentration to a solvent miscible with water. However, this is a method of finally completely replacing the solvent. In addition, the hollow fiber-like substance substituted with alcohol may be substituted with a solvent having a smaller surface tension such as cyclohexane or n-hexane. It is said that the hollow fiber material dried from the state of containing the solvent having a low surface tension is likely to maintain the initial pore structure. As a method similar to the solvent replacement, the same effect can be obtained when the poor solvent of the coagulation bath in the discharging step is previously made to have a small surface tension, such as alcohol.

However, in the method for producing a hollow fiber carbon membrane of the present invention, such solvent substitution treatment is unnecessary. According to the knowledge of the present inventors, even if such a solvent replacement treatment is performed, the hollow fiber-like material formed from the PPO discharge stock solution has a porous structure in a flame resistance treatment step and a carbonization treatment step described later. This is because, when melted and observed with a scanning electron microscope (SEM), at first glance it becomes a so-called homogeneous film structure that is dense and uniform. The PPO hollow fiber carbon membrane produced by carrying out the solvent substitution treatment becomes brittle and has low flexibility, despite having such a homogeneous membrane structure. Therefore, in the method for producing a hollow fiber carbon membrane of the present invention, it is possible to prevent problems by not performing such solvent substitution treatment.

[4] Compound Applying Step The compound applying step of adding the sulfur-containing compound may be performed at any step before the carbonization treatment step described later. The application may be performed in a plurality of steps as necessary. The method of application is not particularly limited, but the sulfur-containing compound may be added to the aprotic solvent in the case of [1] dissolution step. [2] If it is a discharging step, it may be added to the internal liquid. [3] If it is the coagulation step, it may be added to the poor solvent used in the coagulation step. [4] In the drying step, when the solidified hollow fiber material is washed with water to remove the remaining solvent, it may be added to the water, or after drying, it may be added to the dried hollow fiber material. Good. Among them, [4] it is preferably applied in the drying step, and particularly preferably applied to the dried hollow fiber material after drying.

The amount of the sulfur-containing compound added is preferably 0.5% or more with respect to the mass of the hollow fiber carbon membrane precursor. The effect is small when the amount of elemental sulfur is small. The upper limit of the amount added is not particularly limited and may be appropriately adjusted depending on the physical properties of the hollow fiber carbon membrane precursor and the carbonization treatment conditions. The amount is preferably such that the separation performance of the hollow fiber carbon membrane can be improved and the flexibility of the hollow fiber carbon membrane can be maintained, that is, the amount can be carbonized to maintain the hollow fiber state.

The sulfur-containing compound added in the method for producing a hollow fiber carbon membrane of the present invention preferably has a boiling point or decomposition temperature of 100° C. or higher and 300° C. or lower, more preferably 150° C. or higher and 300° C. or lower, and further preferably It is 200° C. or higher and 300° C. or lower. When the temperature is lower than 100° C., the residual ratio of the sulfur-containing compound to PPO in the melting step and the discharging step decreases, which is not preferable. Further, when the temperature is higher than 300° C., it is difficult to obtain the effect of volatilization or thermal decomposition of the sulfur-containing compound in the carbonization reaction in the carbonization treatment step or the thermal crosslinking reaction in the flameproofing treatment as the pretreatment of the carbonization treatment. Therefore, it is not preferable.

As the sulfur-containing compound, those having a sulfo group are preferable. By having a sulfo group, sulfur-containing compounds are decomposed during the carbonization process and oxidizable substances such as sulfur dioxide and sulfur trioxide are generated, and the carbonization reaction in the carbonization process and the pretreatment of the carbonization process are performed. This is because the thermal crosslinking reaction in the flameproofing treatment is likely to proceed.

As the sulfur-containing compound, a low molecular weight compound that is easy to handle and has a high sulfonic acid content is preferable. Examples thereof include sulfuric acid, sulfamic acid (amido sulfuric acid), ammonium sulfate, ammonium hydrogen sulfate, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-phenolsulfonic acid, sulfamic acid, and naphthalenesulfonic acid. To be The sulfur-containing compounds may be used alone or in combination of two or more. Moreover, when adding in multiple steps, you may use the same kind or different kinds.

[5] Carbonization treatment step Finally, the hollow fiber carbon membrane precursor obtained in the drying step is carbonized. Preferably, a flameproofing treatment is performed as a pretreatment of the carbonization treatment. In the flameproofing treatment, the hollow fiber carbon membrane precursor is heated in an air atmosphere at 200 to 350°C, more preferably 250 to 300°C for about 5 minutes to 3 hours. By performing such a flameproofing treatment, the thermal crosslinking reaction of the polymer is promoted, the membrane structure after carbonization becomes strong, and it is advantageous for improving the separation performance.

As described above, the hollow fiber carbon membrane precursor preferably subjected to the flameproofing treatment is carbonized by a known method to obtain a hollow fiber carbon membrane. For the carbonization treatment, for example, the hollow fiber carbon membrane precursor is housed in a high-temperature furnace and heat-treated under reduced pressure or in an inert gas atmosphere replaced with helium, argon gas, nitrogen gas, etc. without reducing the pressure. Done by. Alternatively, a method of carrying out the carbonization treatment in a continuous carbonization furnace which performs high temperature treatment under an inert gas atmosphere while continuously conveying the hollow fiber carbon membrane precursor may be adopted.

The heating conditions in the carbonization treatment are optimally selected depending on the kind of the polymer constituting the precursor and the like, but are preferably under reduced pressure or in an inert gas atmosphere at 400 to 1000° C. for 10 minutes to 4 minutes. It's time. More preferably, it is at 500 to 850° C. for 30 minutes to 2 hours. When the temperature is lower than 500°C, sufficient carbonization does not occur, and thus the obtained hollow fiber carbon membrane is flexible, but sufficient gas separability cannot be obtained, and chemical resistance and heat resistance are poor. This is not desirable. On the other hand, if the carbonization treatment is performed at a temperature higher than 1000° C., the carbonized film becomes brittle, which is not preferable.

<Hollow fiber carbon membrane and separation membrane module>
The hollow fiber carbon membrane produced by the above-described method for producing a hollow fiber carbon membrane of the present invention, and a separation membrane module using the hollow fiber carbon membrane are also included in the scope of the present invention. Then, the separation membrane module of the present invention using the hollow fiber carbon membrane of the present invention manufactured by the above-described method of manufacturing the hollow fiber carbon membrane of the present invention will be described.

The separation membrane module itself is publicly known, and the separation membrane module of the present invention can also be realized by combining conventionally known appropriate materials and structures except that the hollow fiber carbon membrane of the present invention is used. For example, as a separation membrane module having a typical structure, there is a separation membrane module in which a plurality of hollow fiber carbon membranes of the present invention cut into a predetermined length are bundled, and both ends thereof are solidified with an adhesive. To be This separation membrane module has a structure in which one end of a hollow fiber carbon membrane in a bundled state is open, and the hollow fiber carbon membrane is hardened with an adhesive, and a cap having an opening is attached. On the other hand, the other end of the bundled hollow fiber carbon membrane is closed, and is solidified with an adhesive, and a cap having no opening is attached. Note that this is merely an example, and the hollow fiber carbon membranes in a bundled state may have a structure in which one end is open and the other end is closed.

As a method for producing the separation membrane module of the present invention, a known method can be appropriately adopted and is not particularly limited. For example, a plurality of hollow fiber carbon membranes of the present invention is produced, and each is bundled in a state of being cut into a predetermined length, and one end of the bundled plurality of hollow fiber carbon membranes is bonded with an adhesive, Glue the other end with an adhesive. Then, one end of the bundled hollow fiber carbon membrane is cut together with the adhesive to open it. Then, the above-mentioned separation membrane module can be manufactured by attaching the above-mentioned caps to the respective end portions.

The hollow fiber carbon membrane of the present invention and the separation membrane module using the same are particularly useful as a carbon membrane for gas separation. It can be particularly suitably used in the fields of hydrogen production, carbon dioxide separation and recovery, exhaust gas separation and recovery, natural gas separation, gas dehumidification, production of oxygen from air, and the like.

The hollow fiber carbon membrane of the present invention is suitably used for separating water from a volatile organic compound containing water. Further, it is also suitably used for separating the volatile organic compound from the air containing the volatile organic compound.

The details of the examples of the present invention are shown below, but the present invention is not limited thereto.

<Example 1>
36.25 g of N-methyl-2-pyrrolidone was added to 13.75 g of polyphenylene oxide (PPO) (Poly(2,6-dimethyl-1,4-phenylene oxide product number 181781, manufactured by Aldrich Co.) and kneaded. After preparing a uniform suspension, a uniform spinning dope was obtained by heating while kneading at a temperature in the range of 100 to 150° C. The same spinning dope was kept at 150° C. The spinning stock solution extruder was heated and kept at 130° C., and the spinning stock solution was quantitatively extruded from the slit portion of the double cylindrical tube nozzle.Ethylene glycol was quantitatively measured as an internal solution from the inner hole of the double cylindrical tube nozzle. The surface of the spinning dope was dried with an air gap of 50 mm while inducing phase separation in the inner layer of the spinning dope extruded in a hollow shape, and then N-methyl-2 kept at 10°C. -Complete phase separation proceeded in a coagulation bath filled with a 30% aqueous solution of pyrrolidone.The solidified hollow fiber membrane was thoroughly washed with water and then dried in an oven at 80°C while containing water. did.

The obtained hollow fiber material was cut into a length of 50 cm and immersed in a 5 wt% sulfamic acid aqueous solution for 15 hours as a sulfur-containing compound. After removing the excess aqueous solution, air drying was performed to obtain a sulfur-containing compound-added PPO hollow fiber membrane (hollow fiber carbon membrane precursor). From the weight change of the hollow fiber membrane before and after the attachment, the attachment amount was 4.0% by mass.

The obtained sulfur-containing compound-added PPO hollow fiber membrane was heated in a muffle furnace at a rate of 10°C/min in an air atmosphere to reach 285°C, and then heated at the same temperature for 90 minutes, and thereafter. I let it cool.

The hollow fiber membrane that has been subjected to air oxidation treatment is heated in a high-temperature firing furnace in a nitrogen atmosphere at a rate of 10° C./min, and after reaching 800° C., is heated at the same temperature for 1 hour and then released. After cooling, a sulfur-containing compound-added PPO hollow fiber carbon membrane was obtained.

<Example 2>
A PPO hollow fiber carbon membrane provided with a sulfur-containing compound was obtained in the same manner as in Example 1 except that the concentration of the sulfamic acid aqueous solution was changed to 10% by mass as the addition of the sulfur-containing compound. From the weight change of the hollow fiber membrane before and after the attachment, the attachment amount was 9.4 mass %.

<Example 3>
A PPO hollow fiber carbon membrane to which a sulfur-containing compound was added was obtained in the same manner as in Example 1 except that the sulfur-containing compound was changed to a 5% by mass aqueous p-toluenesulfonic acid solution. From the weight change of the hollow fiber membrane before and after the attachment, the attachment amount was 4.5% by mass.

<Example 4>
A PPO hollow fiber carbon membrane provided with a sulfur-containing compound was obtained in the same manner as in Example 1 except that the addition of the sulfur-containing compound was changed to a 5 mass% ammonium sulfate aqueous solution. From the weight change of the hollow fiber membrane before and after the attachment, the attachment amount was 3.6% by mass.

<Example 5>
A PPO hollow fiber carbon membrane provided with a sulfur-containing compound was obtained in the same manner as in Example 1 except that the addition of the sulfur-containing compound was changed to a 5% by mass aqueous solution of ammonium hydrogen sulfate. From the weight change of the hollow fiber membrane before and after the attachment, the attachment amount was 3.6% by mass.

<Comparative Example 1>
A PPO hollow fiber carbon membrane was obtained in the same manner as in Example 1 except that the sulfur-containing compound was not added.

<Reference example 1>
A PPO hollow fiber carbon membrane provided with a sulfur-containing compound was obtained in the same manner as in Example 1 except that the sulfur-containing compound was changed to a 2% by mass aqueous sulfamic acid solution. From the weight change of the hollow fiber membrane before and after attachment, the attachment amount was 1.0% by mass.

<Comparative example 2>
Polyphenylene oxide (PPO) (Poly(2,6-dimethyl-1,4-phenylene oxide product number 181781, Aldrich)) was dissolved in chloroform, and a mixed solution of chlorosulfuric acid and chloroform was added dropwise at room temperature. Then, the sulfonation reaction was allowed to proceed for a predetermined period of time, then reprecipitated, and the reaction product washed with water was dried to obtain a sulfonated polyphenylene oxide (SPPO) having a sulfonation degree of DS=25%.

To a mixed solvent of methanol and dimethylacetamide in a mass ratio of 50/50, SPPO with DS=25% was added so as to have a polymer concentration of 30 mass %, and dissolved to obtain a spinning stock solution. This is extruded from the outer tube of the hollow fiber spinning nozzle of the double cylindrical tube nozzle into the coagulation bath phase, and the aqueous solution of ammonium nitrate of 5 mass% is simultaneously extruded from the inner tube of the hollow fiber spinning nozzle to perform spinning, and the hollow fiber material is ionized. Unnecessary mixed solvent and ammonium ammonium nitrate were removed by washing with exchanged water, and this was dried to obtain a hollow fiber polymer membrane.

The SPPO hollow fiber membrane was air-oxidized by the same method as in Example 1 to obtain an SPPO air-oxidized hollow fiber membrane. Thereafter, the SPPO air oxidation treatment hollow fiber membrane was subjected to carbonization treatment in the same manner as in Example 1 to obtain an SPPO hollow fiber carbon membrane.

The samples (sulfur-containing material-added PPO hollow fiber carbon membrane, PPO hollow fiber carbon membrane, SPPO hollow fiber carbon membrane) obtained in Examples 1 to 5, Reference Example 1 and Comparative Examples 1 and 2 are described below. Evaluation was performed by the evaluation method.

(Evaluation of gas separation performance of hollow fiber carbon membrane)
The method for measuring the gas separation performance of the hollow fiber carbon membrane using the test gas (He, CO ₂ , N ₂ ) is shown below. The test gas was supplied at a constant pressure to the inner surface of the hollow fiber module mounted on the hollow fiber gas permeability measuring device, and the flow rate of the gas to be permeated was measured by a flow meter. At this time, the gas separation performance was evaluated by the gas permeation rate Q obtained by the following formula. Further, the ideal separation coefficient α of gas was obtained from the Q ratio.
Q={gas permeation flow rate (cm ³ ·STP)}÷{membrane area (cm ² )×time (sec)×pressure difference (
cmHg)}

(Evaluation of water-ethyl acetate separation performance)
With the evaluation device 100 shown in FIG. 1, the water separation performance and the permeation performance of the hollow fiber carbon membranes obtained in Examples, Reference Examples and Comparative Examples were evaluated by the pervaporation separation method.
Feed liquid composition: ethyl acetate/water=97/3 wt %, feed liquid temperature: 70° C., permeation side pressure 100 Pa. The hollow part of the hollow fiber carbon membrane 1 is evacuated by the vacuum pump 14, and every 1 hour after the evaluation is started, the following formula 1 is calculated from the mass of the permeated liquid trapped by the cooling trap 7 cooled by the liquid nitrogen 8. The permeation flux (kg·m ⁻² ·h ⁻¹ ) was determined by. The permeation flow rate after 7 hours when the separation performance of the hollow fiber carbon membrane 1 was stable is shown in the table.

Permeation flux (kg·m ⁻² ·h ⁻¹ )=(mass of permeate (kg))÷{area of hollow fiber carbon membrane (m ² )×time (h)} (Equation 1)
Further, the permeated liquid trapped by the cooling trap 7 was analyzed by an FID (Flame Ionizer Detector) gas chromatograph, the ethyl acetate concentration in the permeated liquid was determined, and the separation coefficient SF was calculated by the following formula 2.
Separation factor SF (water/ethyl acetate)={water concentration of permeate (mass %)/ethyl acetate concentration of permeate (mass %)}÷{water concentration of feed liquid (mass %)/ethyl acetate concentration of feed liquid (Mass %)} (Formula 2)

(Evaluation of reproducibility of hollow fiber carbon membrane)
The methods described in Examples and Comparative Examples were each repeated 10 times to evaluate the reproducibility of the water-ethyl acetate separation performance. The average value μ and the standard deviation σ were calculated with the population of all values of the permeation flow velocity after 10 hours for 7 times.

Table 1 shows the amount of the sulfur-containing compound added to the hollow fiber carbon membrane precursor and the gas permeation characteristics of the hollow fiber carbon membrane, and Table 2 shows the results of the reproducibility evaluation of the water-ethyl acetate separation performance.

In Table 1, the molar mass (A) of the sulfur-containing compound, the atomic weight of elemental sulfur in the sulfur-containing compound (B), and the addition rate (C) of the sulfur-containing compound to the hollow fiber carbon membrane precursor are described. Therefore, the addition ratio (B/A×C) of elemental sulfur to the mass of the hollow fiber carbon membrane precursor can be calculated from this value. As can be seen from the results of the gas separability of the carbon membrane using the hollow fiber carbon membrane precursor having such an addition rate of the sulfur element, the addition rate of the sulfur element to the mass of the hollow fiber carbon membrane precursor (B/A× When C) is 0.5% or more, the separation coefficient α between He and CO ₂ shows a high value.

Further, as can be seen from Table 2, both high permeation flow rate and separation coefficient were achieved with water-ethyl acetate. It was confirmed that the standard deviation of the permeation flow rate was also small and the reproducibility was good, and the effect of applying the sulfur-containing compound of the present invention was clarified. On the other hand, the SPPO carbon membrane of Comparative Example 2 shows a high separation coefficient α between He and CO ₂ , but as shown in Table 2, it was confirmed that the reproducibility of the water-ethyl acetate permeation flow rate was very poor. Was done. This is because, as described above, it is due to instability in the synthesis of SPPO.

The embodiments and examples described above are examples in all respects and are not restrictive. The technical scope of the present invention is defined by the claims, and includes the meaning equivalent to the description of the claims and all modifications within the scope.

INDUSTRIAL APPLICABILITY According to the present invention, a hollow fiber carbon membrane having stable performance can be produced, which can greatly contribute to the industrial world.

1 hollow fiber carbon membrane, 2 supply liquid, 3 container, 4 constant temperature bath, 5 stirrer, 6 stirrer, 7 cooling trap, 8 liquid nitrogen, 9 thermometer, 10 stainless pipe, 11 heat retaining tape, 12 stop valve, 13 vacuum Degree meter, 14 vacuum pump

Claims (3)

A method for producing a hollow fiber carbon membrane, comprising:
A step of dissolving polyphenylene oxide in an aprotic solvent,
A step of discharging the dissolved polyphenylene oxide from a spinning nozzle at a temperature of a temperature-induced phase separation point or higher to form a hollow fiber;
A step of coagulating the hollow fiber-shaped polyphenylene oxide with water or a mixed solution of water and an organic solvent;
The solidified hollow fiber polyphenylene oxide, without performing a solvent replacement treatment, to obtain a hollow fiber carbon membrane precursor by drying from a state containing water,
At least one step of each of the above steps, the step of adding a sulfur-containing compound to polyphenylene oxide,
Furthermore, a hollow fiber carbon membrane precursor said sulfur-containing compound is applied see step including treating carbonization,
The method for producing a hollow fiber carbon membrane, wherein the sulfur-containing compound has a sulfo group . The hollow fiber carbon membrane precursor to which the sulfur-containing compound has been added, wherein the addition rate of elemental sulfur is 0.5% or more based on the mass of the hollow fiber carbon membrane precursor. Carbon film manufacturing method. The method for producing a hollow fiber carbon membrane according to claim 1 or 2, wherein the boiling point or the decomposition temperature of the sulfur-containing compound is 100°C or higher and 300°C or lower.