KR100450211B1 - Method for manufacturing silicon-containing carbon molecular sieve membrane for gas separation - Google Patents

Abstract

The present invention relates to a method for producing a silicon-containing carbon molecular sieve separation membrane for gas separation, and to a component and a composition of a polymer serving as a precursor thereof, and more particularly, to prepare a polymer precursor membrane containing silicon; A composition determination step of copolymerizing an oligomer of an amine group in a sock end containing a monomer and a siloxane group used in the synthesis of a conventional polyimide, and heating the polymer precursor membrane to 400 ° C. at a temperature increase rate of 5-10 ° C./min, and then 3 After heating up to 550-600 ° C. at a temperature increase rate of −5 ° C./min, undergoing an isothermal process for 1-2 hours in the same temperature range, and raising the temperature of 1-5 ° C./min. It relates to a composition and manufacturing method of a gas-molecular separation membrane for carbon separation membrane comprising the step of raising the temperature to 800 ℃ and 1000 ℃ at a rate, respectively, and carbonization through an isothermal process at 1-2 hours. The separator can very efficiently separate gases such as helium, hydrogen, oxygen, nitrogen, methane or carbon dioxide.

Description

Method for manufacturing silicon-containing carbon molecular sieve membrane for gas separation

The present invention relates to a polymer precursor composition and a method for producing a carbon-molecular separator containing silicon, and more particularly, it is possible to efficiently separate gases such as helium, hydrogen, nitrogen, oxygen, methane or carbon dioxide with high permeability. The present invention relates to a polymer precursor composition and method for producing a silicon-containing carbon molecular separator.

Generally, polymers that have been widely used as materials for gas separation membranes are polymers, and polymers that are frequently used as materials for gas separation membranes include polysulfone, polycarbonate, cellulose, and polyimide. These polymer membranes are polymers having a relatively high gas separation performance, and are mainly manufactured in the form of an asymmetric structure having a thin selection layer on the porous support. However, these polymer membranes have a disadvantage that the separation performance of the membrane is significantly reduced by consolidation and plasticization of the membrane after prolonged exposure in a high pressure or high temperature process or a process including a hydrocarbon, an aromatic, and a polar solvent. In general, polymer membranes currently known have a disadvantage that high selectivity is low and low selectivity, and low selectivity does not exceed an upper limit of correlation.

In contrast, inorganic membranes such as zeolites and carbon molecular sieve membranes, which have excellent thermal stability and chemical resistance, have received much attention and attention in gas separation. Among these, the carbon molecular film can be obtained by pyrolysis of the polymer precursor under vacuum or inert gas flow, and the carbon molecular film shows a very high permeation selectivity compared to the conventional polymer film.

The control of the carbonization process through pyrolysis of these polymer precursors increased the stability of the polymer membrane and produced a carbon molecule membrane by pyrolyzing organic precursors for the first time in 1983 by Koresh and Soffer as a promising method of producing high permeation efficiency. 4,685,940). Polymers that have been used as precursors of such carbon films include polyfurfuryl alcohol, polyvinylidene chloride, phenol formaldehyde, and polyimide.

Carbon molecular membranes prepared using these organic precursors can be used for the separation of various gas mixtures. Gas mixtures, which have been the main researches on the separation performance of carbon membranes, are oxygen / nitrogen, helium / nitrogen, hydrogen / nitrogen, hydrogen Carbon monoxide, carbon dioxide / nitrogen, methane / ethane, ethylene / ethane and propylene / propane.

Looking at the existing research on the carbon film produced using the organic precursor described above, first, polyacrylonitrile, which was used as a material of carbon fiber, is used a lot. However, membranes made by carbonization show very low gas permeability, which greatly reduces commercial value. Also, in Journal of Membrane Science 109 (1996) 267-270, a carbonized membrane was prepared by W. Shusen et al in China as a precursor of formaldehyde resin, and the oxygen permeability was 2300 10 ^-10 × cm 3 (STP) cm / cm 2. sec.cmHg (Barrer) and oxygen / nitrogen selectivity was 10.65, which was very good. However, the mechanical properties of the material is very low, the practicality is very poor. In U.S. Patent No. 4,685,940, a membrane carbonized by cellulose was reported by Koresh et al. Of the United States, with an oxygen / nitrogen selectivity of 7.1 and an oxygen permeability of 0.71 × 10 ⁻⁶ cm 3 (STP) / cm ² .sec.cm Hg (GPU). Showed.

In this case, the production time through the pyrolysis of the carbon film is very long, and thus, in order to shorten the time, increasing the temperature increase rate causes the weight reduction rate of the film to be knocked out, resulting in a decrease in mechanical strength. In addition, in the Journal of Physical Chemistry B 101 (1997) 3988-3994, the results of gas separation performance on carbon membranes prepared under vacuum and inert gas streams were reported by Suda et al in Japan using a commercial polyimide Kapton film. Although it has high selectivity with selectivity of 36, oxygen permeability is 0.96 Barrer and shows very low permeability, which makes it difficult to put to practical use. In US Pat. No. 5,288,304, a polyimide hollow fiber membrane prepared as in the case of a hollow fiber asymmetric membrane for gas separation is coated with a resin containing fluorine to prevent cracks and to reduce the long-term performance degradation of the carbon film against moisture. However, this film has a disadvantage that the material is expensive and it is difficult to maintain high mechanical strength by carbonizing hollow fiber.

Thus, the present inventors have diligently studied to find a carbon molecular film that has a significantly improved permeability without significantly decreasing selectivity. As a result, the siloxane oligomer forms a copolymer with polyimide, that is, has two different regions and has a microphase separation structure. Carbonized polymer film, such as polyimide siloxane, was prepared by pyrolysis to produce silicon-containing carbon molecular film, and silicon or initial polymer precursor was formed by interfering the gap between silicon and regular densely packed carbon crystals in the carbon molecule. According to the siloxane content, it has been found that the present invention can be selectively applied in gas separation such as oxygen / nitrogen, helium / nitrogen, hydrogen / nitrogen, carbon dioxide / nitrogen, and carbon dioxide / methane.

Accordingly, it is an object of the present invention to provide a composition and method for preparing a silicon-containing carbon molecular sieve membrane having excellent selectivity and high permeability.

The method of the present invention for achieving the above object comprises the steps of preparing a polymer precursor film containing silicon; The composition determination step of copolymerizing the monomer used in the synthesis of the polyimide and the siloxane group copolymerizes the oligomer of the amine group, the polymer precursor film is heated to 400 ℃ at a temperature increase rate of 5-10 ℃ / min, 3 After heating up to 550-600 ° C. at a temperature increase rate of −5 ° C./min, undergoing an isothermal process for 1-2 hours in the same temperature range, and raising the temperature of 1-5 ° C./min. Including the step of raising the temperature to 800 ℃ and 1000 ℃ at a rate of carbonization through an isothermal process of 1-2 hours at the same temperature.

Hereinafter, the method of the present invention will be described in more detail.

In the present invention, a polyimide containing a siloxane group was prepared in various compositions to prepare a silicon-containing carbon molecular separation membrane. The polyimide is used by condensing anhydride, diamine, and a siloxane oligomer containing an amine group in a sock end. Anhydrides include pyromellitic anhydride, benzophenone anhydride, 2,2-bis (3,4-dicarbophenyl) propane anhydride, 3,3 ', 4,4'-bisphenyl tetracarboxylic anhydride, Bis (3,4-dicarboxylphenyl) ether anhydride, bis (3,4-dicarboxyphenyl) thioether anhydride, 2,3,6,7-naphthalene tetracarboxylic anhydride and bis (3,4-di One or more selected from the group consisting of carboxyphenyl) sulfone anhydride was used. Diamines include m- or p-phenylenediamine, 2,4- or 2,6-diaminotoluene, 4,4'-diamino phenylether, 4,4'-diaminobenzophenone, 4,4'- One or more selected from the group consisting of diamino phenylsulfide, 4,4'-diamino phenyl methane, 3,3'-dimethylbenzidine, and 4,4'-isopropyl-idene diamine were used. As the siloxane oligomer containing an amine group in the sock end, the polymer may be synthesized by selecting one or more from the dimethylsiloxane group in which the sock end is diamine having a number average molecular weight of 900 to 1600.

In addition, polar solvents such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and the like are used to synthesize the polymer. Using a nonpolar solvent as a cosolvent, the volume ratio of 1: 1, 1: 2, 1: 3, etc. was used according to the amount of siloxane oligomer used in the synthesis.The ratio of these solvents is limited to the above three ratios. It doesn't happen.

Pyrolysis is carried out in a tubular pyrolysis electric furnace equipped with a temperature program capable of controlling a temperature of up to 1500 degrees in order to carbonize polyimide siloxanes of various compositions serving as precursors of the carbon molecular separation membrane of the present invention. The pyrolysis is preferably performed under an inert gas stream such as helium, nitrogen, or argon of 10 cc / min or more, but is not limited to the gas.

In addition, the pyrolysis can be produced even in a vacuum of 0.1 atm or less. If the thermal decomposition is carried out in the presence of oxidizing agents such as oxygen, carbon dioxide, and water rather than inert or vacuum, the polymer precursors are almost decomposed and cannot maintain the desired mechanical strength.

On the other hand, in order to know the desirable temperature increase rate and final processing temperature for the carbonization process, a thermogravimetry equipped with a mass spectrometer can be used to analyze the type of gas generated in the weight loss curve and the part where the weight loss occurs in real time. This was used to determine the elevated temperature condition and final treatment temperature of the present invention. In addition, the weight loss at each final treatment temperature was divided by the initial weight to compare the thermogravimetric reduction curves. In addition, the conversion rate for the carbonization reaction of the polymer precursor prepared above can be measured using FT-IR and Elemental Analyzer (EA). In the case of FT-IR, the height of the peak of 1360, 1600 cm ^-1 In the case of EA, it can be confirmed by comparing the relative element content for C, H, O, N, Si. The prepared membrane was confirmed gas separation performance by measuring the gas permeability for helium, nitrogen, oxygen and carbon dioxide, but is not limited to the type of these gases.

Comparative Examples 1 to 3

4,4'-diamino phenyl ether powder (1 mol) is placed in a flask and dissolved by stirring in dimethylacetamide (DMAC) under a nitrogen atmosphere. After slowly injecting pyromellitic anhydride powder (1 mol) into the completely dissolved solution, a solution having a yellow transparent viscosity was prepared after 12 hours. After casting the above solution on a teflon plate, heat curing for 2 hours at 100 ° C, 1 hour at 200 ° C and 1 hour at 300 ° C in a drying oven, and then in a vacuum oven at 60 ° C to completely remove the residual solvent. After vacuum drying for 24 hours, a pale yellow transparent polyimide film of 30-125 μm was prepared. A polyimide film having a thickness of 30 μm and having a thickness of 4 cm × 4 cm was placed between holders made of flat alumina, and the temperature was increased at 600 ° C. and 800 ° C., respectively, at a temperature of 1-10 ° C./min under Ar air flow in a tubular pyrolysis furnace. Thermal decomposition was carried out to 1000 ℃ to prepare a carbon molecular sieve film. The inner diameter of the alumina tube used during pyrolysis was 12 cm, and the film and the film holder were placed at the center of the electric furnace to which heat was applied, and were manufactured in the temperature range where they were fixed. The permeability of helium, oxygen, nitrogen, and carbon dioxide was measured for the prepared carbon molecular film, and the selectivity was calculated and shown in Table 1 below. Gas permeability was measured using a reduced pressure method, and the pressure difference between the top and bottom of the permeation cell was adjusted from 200 tor to as much as 760 tor. The calculation of permeability was calculated from the slope with respect to the increase in the bottom pressure over time in the defined bottom volume. The selectivity is also expressed as permeability / nitrogen permeability of the select gas.

TABLE 1

Permeability (Barrer), 1 Barrer = 10 ^-10 × cm3 (STP) cm / cm2.sec.cmHg

Comparative Examples 4 to 6

Polyimide film having a thickness of 30 μm containing 0.2 mol of dimethylsiloxane oligomer in a polyimide siloxane film prepared as in Examples 1 to 9 was cut to a size of 4 cm × 4 cm, and then sandwiched between holders made of flat alumina and tubular pyrolysis. In the electric furnace, a carbon molecular film was prepared by thermally decomposing the film under a single air temperature condition of 1 ° C./min, 5 ° C./min, and 10 ° C./min, respectively, to a final temperature of 800 ° C. without any temperature raising program under an Ar stream. The inner diameter of the alumina tube used during pyrolysis was 12 cm, and the film and the film holder were placed at the center of the electric furnace to which heat was applied, and thus they were manufactured in the correct temperature range. The permeability of helium, oxygen, nitrogen, and carbon dioxide was measured for the prepared carbon molecular film, and the selectivity was calculated and shown in Table 2. Gas permeability was measured in the same manner as in Comparative Examples 1 to 3.

TABLE 2

Permeability (Barrer), 1 Sarrer = 10 ^-10 × cm3 (STP) cm / cm2.sec.cmHg

Examples 1-9

Dimethylsiloxane having a number-average molecular weight of 900 having an amine group at the end of the sock end is dissolved in ODMS (0.2-2 mol) in a flask and stirred in tetrahydrofuran (THF) under a nitrogen atmosphere. Pyromelic anhydride powder (10 mol) is slowly injected and then stirred at room temperature. After 1 hour, 4,4'-diamino phenyl ether (9.8-8 mol) solution completely dissolved in N-methylpyrrolidone (NMP) was slowly added dropwise to the solution for a predetermined time, and then reacted with stirring for 12 hours. After casting the above solution on a teflon plate, heat curing for 2 hours at 100 ° C, 1 hour at 200 ° C and 1 hour at 300 ° C in a drying oven, and then in a vacuum oven at 60 ° C to completely remove the residual solvent. After vacuum drying for 24 hours, a light yellow transparent polyimide siloxane film having a thickness of 30-125 μm was prepared. A 4 cm × 4 cm polyimide film having a thickness of 30 μm prepared above was placed between holders made of flat alumina. In the tubular pyrolysis furnace, after raising the temperature to 400 ° C at a relatively fast temperature increase rate of 10 ° C / min in the initial stage under Ar flow, between 3 ° C and 400 ° C between 400 ° C and 600 ° C, which is a dominant section in which decomposition gases such as carbon dioxide, carbon monoxide and methane are released. Maintain a heating rate of / min. After the isothermal stage at 600 ℃ for 90 minutes, and then pyrolyzes to 800 ℃ and 1000 ℃ at a temperature rising rate of 3 ℃ / min, respectively, after each isothermal step of more than 1 hour in each stage, and then slowly lowered the temperature The carbon-molecular film contained therein was prepared. The permeability of helium, oxygen, nitrogen, and carbon dioxide was measured for the silicon-containing carbon-molecular film, and the selectivity was calculated and shown in Table 3. The measurement of gas permeability and the calculation of selectivity to nitrogen are the same as those measured in Comparative Examples 1 to 3.

TABLE 3

Permeability (Barrer), 1 Barrer = 10 ^-10 × cm3 (STP) cm / cm2.sec.cmHg

As shown in Table 3, Examples 1 to 9 measure the permeability of helium, oxygen, nitrogen and carbon dioxide at three final pyrolysis temperatures by changing the content of siloxane in the polyimide siloxane polymer composition. Comparing Examples 1 to 9 with Comparative Examples 1-3, for example, as the content (mole number) of the siloxane increases in the polyimide siloxane matrix as a precursor, the oxygen / nitrogen selectivity is about 10-23. In comparison with Comparative Example 1-3, the transmittance to oxygen was increased to 180 Barrer. Also, the composition of polyimide siloxane was the same as that of Comparative Example 4-6, which was prepared without a single temperature increase rate and isothermal step without a special temperature increase program. Comparing the case of Example 2 prepared using the temperature raising program described above, both the transmittance and the selectivity were significantly improved.

Examples 10-12

The polyimide film having a thickness of 30 μm containing 1.0 mol of dimethylsiloxane oligomer, which is the polymer precursor prepared in Example 1, was cut to a size of 4 cm × 4 cm, and then placed between the holders made of flat alumina, and subjected to tubular pyrolysis. After raising the temperature to 400 ° C at a relatively rapid temperature increase rate of 10 ° C / min in the initial stage under vacuum in an electric furnace, the temperature of 3 ° C / min is between 400 ° C and 600 ° C, which is the dominant section in which decomposition gases such as carbon dioxide, carbon monoxide and methane are released. Maintain the rate of temperature increase. After the isothermal stage at 600 ℃ for 90 minutes, and then pyrolyzes to 800 ℃ and 1000 ℃ at a temperature rising rate of 3 ℃ / min, respectively, after each isothermal step of more than 1 hour in each stage, and then slowly lowered the temperature A carbon molecular film containing was prepared.

The permeability of helium, oxygen, nitrogen, and carbon dioxide was measured for the prepared carbon molecular film, and the selectivity was calculated and shown in Table 4 below. Gas permeability was measured in the same manner as in Comparative Examples 1 to 3.

TABLE 4

Permeability (Barrer), 1 Barrer = 10 ^-10 × cm3 (STP) cm / cm2.sec.cmHg

As can be seen from Table 4, the permeability and selectivity of the same pyrolysis temperature rise conditions under vacuum of not more than 0.1 atm but not under an inert gas stream such as Ar are similar to or slightly higher than those under Ar stream. have.

As described above, the present invention is a carbon molecular film prepared by pyrolysis in a vacuum or inert atmosphere using polyimide, which is generally made only of aromatic diamine and aromatic anhydride, as a precursor. Although the permeability is increased as shown in Table 1 it can be seen that the permeability is greatly reduced to 0.96 Barrer. However, silicon-containing carbon molecular film prepared by pyrolysis in a vacuum or inert atmosphere using polyimide containing siloxane as a precursor generally increases the amount of siloxane in the polyimide siloxane matrix as a precursor. The gas permeability was significantly improved, and at the same time, the gas selectivity was maintained at 10 or more for oxygen / nitrogen.

Claims (6)

Preparing a polyimide siloxane, which is a polymer precursor of a silicon-containing carbon molecule separator; Heating the polyimide siloxane polymer film to 400 ° C. at a temperature rising rate of 5-10 ° C./min; The polymer membrane is heated up to 400 ℃, again, the temperature is raised to 550-600 ℃ at a temperature increase rate of 1-3 ℃ / min and subjected to an isothermal process of 1-2 hours in the same temperature range; And It characterized in that it comprises the step of carbonizing the stabilized separation membrane undergoing the isothermal process to 800 ℃ and 1000 ℃ at a temperature increase rate of 1-5 ℃ / min through an isothermal process of 1-2 hours at the same temperature Method for producing a silicon-containing carbon molecular sieve separation membrane. delete The silicon-containing carbon powder according to claim 1, wherein the solvent used for the polymerization of polyimide siloxane, which is a polymer precursor of the silicon-containing carbon molecular sieve separation membrane, is a mixed solvent of N-methylpyrrolidone (NMP) and tetrahydrofuran (THF). Method for producing a self separation membrane. The method of producing a silicon-containing carbon molecular sieve membrane according to claim 1, wherein the siloxane content of the polyimide siloxane, which is a polymer precursor of the silicon-containing carbon molecular sieve membrane, is within a range of 10 mol% of all monomers. The method of claim 1, wherein the carbonization step is performed under a vacuum of 0.1 atm or less or in an inert gas atmosphere of 10 cc / min or more. delete