CN101733026A - Method for preparing polyoxyethylene-introduced cross-linked modified polyimide gas separation membrane - Google Patents

Abstract

The present invention relates to polymer separation membrane technology, specifically the preparation method of the polyimide gas separation membrane that polyoxyethylene introduces cross-linking modification, 1) the carrying out of cross-linking reaction: take polyimide and cross-linking agent Polyether amine is dissolved in the solvent respectively, and the polymer and the crosslinking agent are completely dissolved; after mixing the two solutions, stir for 5-30 hours to react; 2) Preparation of homogeneous membrane: after the solution is completely mixed and reacted, pour the solution on Dry the film on a polyethylene board at 25-60°C, put the homogeneous film in water for 1-5 days to remove the unreacted cross-linking agent, and then put the film in a vacuum oven at 50-120°C for 5 ～24h; the obtained film thickness is between 50～150 μm. In the present invention, the polyimide is fully cross-linked and modified with the special cross-linking agent polyetheramine, and a homogeneous membrane with excellent _CO2 gas separation performance is obtained.

Description

Preparation method of polyimide gas separation membrane introduced with cross-linking modification by polyoxyethylene

technical field

The invention relates to polymer separation membrane technology, in particular to polyimide materials and polyether amine cross-linked modified membrane materials and a preparation method for a homogeneous membrane. The prepared homogeneous membrane is cross-linked by polyoxyethylene The modified polyimide gas separation membrane contains ether oxygen functional groups and has a cross-linked structure.

Background technique

The separation and removal of _CO2 is a separation process with great potential and industrial prospects. Hydrogen is one of the main energy sources in the future; at present, the main source of hydrogen is still through the reforming of alkanes and the reaction of hydration gas, and CO ₂ impurity gas is produced in the process. In order to obtain pure hydrogen source, the removal of CO ₂ is very important. Natural gas is one of the main energy and chemical raw materials in the world today, and natural gas products often contain a large amount of CO ₂ impurities, which not only affects the quality of natural gas combustion but also corrodes the pipelines and equipment for transporting natural gas (CO ₂ is acid gas). CO ₂ is also a major greenhouse gas. Removing CO ₂ from the flue gas (mainly containing nitrogen and carbon dioxide) has a great effect on reducing the greenhouse effect.

The current commercial membrane separation material is mainly polyimide because of its excellent mechanical and thermal stability and gas separation performance. Polyimide gas separation membrane has a strong screening ability, mainly relying on the diffusion selectivity to separate the gas; so people often improve the gas separation performance of the polymer by changing the structure to improve the screening ability of the polymer, because the gas The diffusion coefficient is much more sensitive to the polymer structure than the solubility coefficient. However, many raw materials such as raw natural gas contain CO ₂ with high partial pressure and high content, and the plasticizing phenomenon caused by it can greatly reduce the sieving ability of the polymer, so only by increasing the sieving capacity of the polymer Sometimes it is difficult to improve the separation performance of gas, especially when the gas contains a large amount of acid gases such as _CO2 . Based on Freeman's two observations beyond the "Robeson's upper limit", we employ increased dissolution selectivity to improve the gas performance of the membrane.

Contents of the invention

The purpose of the present invention is to provide a preparation method of polyimide gas separation membrane introduced by cross-linking modification of polyoxyethylene. The present invention utilizes polyether amine containing a large amount of ether oxygen groups and terminal amine groups at both ends as a cross-linking agent to cross-link and modify polyimide materials, and the obtained gas performance is much better than that of general polyimide membrane materials .

To achieve the above object, the technical solution adopted in the present invention is:

Use polyether diamine and polyimide materials containing a large number of ether oxygen groups to cross-link at a certain ratio to obtain a homogeneous film.

Specifically, its steps of preparation method of the present invention are as follows:

(1) Carrying out the crosslinking reaction: take the polyimide and the crosslinking agent polyetheramine and dissolve them in the solvent respectively, and wait until the polymer and the crosslinking agent are completely dissolved; after mixing the two solutions, stir for 5 to 30 hours to react;

(2) Preparation of homogeneous film: After the solution is completely mixed and reacted, pour the solution on a polyethylene plate, dry it at room temperature to form a film, and put the obtained homogeneous film in water for 1 to 5 days to remove unreacted crosslinking agent, and then put the film in a vacuum oven at 50-120 ° C for 5-24 hours; the obtained film thickness is between 50-150 μm;

(3) Preservation of the film: the film is stored in a desiccator at room temperature.

The cross-linking agent polyether amine substance used in step (1) is two-terminal amino group ethylene glycol, two-terminal amino group propylene glycol, two-terminal amino group polyethylene glycol, two-terminal amino group polypropylene glycol or two-terminal amino group Polyethylene glycol copolymerized polypropylene glycol, the molecular weight range is 100-10000; The polyimide material used in the step (1) is Matrimid-218, Uteml-1000 and the polyimide (wherein n is 6FDA , ODPA, BPDA, BTDA; m is mPDA, ODA, TMPDA, 2,6-DAT, MDA); the molar ratio of the amine group in the crosslinking agent to the imide group in the polyimide is 0:1～1 : 1.

In the step (1), the solvent is a polar solvent THF (tetrahydrofuran), DMAc (N, N-dimethylacetamide), DMF (N, N-dimethylformamide), NMP (N-methyl-2- pyrrolidone) or DMSO (dimethyl sulfoxide), the dosage is: 1-50g/1g total mass polyimide and crosslinking agent diamine.

The present invention has the following advantages:

1. The introduced ether oxygen group cross-linking agent makes the polymer membrane cross-linked to obtain a gas separation membrane with large flux and good separation performance.

2. The present invention uses the special cross-linking agent polyether amine (containing a large amount of ether oxygen groups, both ends of which are amine groups) to carry out comprehensive cross-linking modification on polyimide, and obtains a polyimide with excellent _CO2 gas separation performance Homogenous film. The membrane material has greatly improved CO ₂ permeability and CO ₂ /H ₂ and CO ₂ /N ₂ separation performance.

Detailed ways

Example 1

Take 1g of Matrimid and 1.185g of two-terminal amino polyethylene glycol molecular weight (2000) and add them to about 5g of THF respectively. After the two solutions are completely dissolved, mix and stir for 24 hours. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 100°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~100 μm.

Test gas separation performance:

P _CO2 = 59.2 Barrer

(1Barrer＝10 ^-10 cm ³ (STP)cm/(cm ² scmHg))

α _CO2/CH4 = 17.6 α _CO2/N2 = 52.2 α _CO2/H2 = 5.9

Example 2

Take 1g of Matrimid and 3.63g of two-terminal amino polyethylene glycol molecular weight (2000) and add them to about 10g of THF respectively. After the two solutions are completely dissolved, mix and stir for 24 hours. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 100°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~100 μm.

Test gas separation performance:

P _CO2 = 115.2 Barrer

α _CO2/CH4 = 16.9 α _CO2/N2 = 52.5 α _CO2/H2 = 7.3

Example 3

Take 1g of Matrimid and 1.089g of two-terminal amino polyethylene glycol (molecular weight: 600) and add them to about 10g of THF respectively. After the two solutions are completely dissolved, mix and stir for 24 hours. The solution is cast on a flat plate and dried at 25°C. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 100°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~100 μm.

Test gas separation performance:

P _CO2 = 1.47 Barrer

α _CO2/CH4 = 23.18 α _CO2/N2 = 34.82 α _CO2/H2 = 0.65

Example 4

Take 1g of Ultem and 3.63g of two-terminal amino polyethylene glycol (molecular weight: 2000) and add them to about 10g of DMAc respectively. After the two solutions are completely dissolved, mix and stir for 24h. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 120°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~100 μm.

Test gas separation performance:

P _CO2 = 83.27 Barrer

α _CO2/CH4 = 15.02 α _CO2/N2 = 51.97 α _CO2/H2 = 6.46

Example 5

Take 1g of 6FDA-MPDA and 4.06g of two-terminal amino polyethylene glycol (molecular weight: 2000) and add them to about 10g of DMAc respectively. After the two solutions are completely dissolved, mix and stir for 24h. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 120°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~100 μm.

Test gas separation performance:

P _CO2 = 61.61 Barrer

α _CO2/CH4 = 8.94 α _CO2/N2 = 23.86 α _CO2/H2 = 2.58

Example 6

Take 1g of 6FDA-MPDA and 4.06g of two-terminal amino-based polypropylene glycol (molecular weight: 2000) and add them to about 10g of NMP respectively. After the two solutions are completely dissolved, mix and stir for 24 hours. The solution is cast on a flat plate and dried at 60°C. The film was placed in water for 2 days to remove unreacted cross-linking agent, and then baked in a vacuum oven at 120°C for 24 hours. The membrane was stored in a desiccator at room temperature, and the thickness of the obtained membrane was ~50 μm.

Test gas separation performance:

P _CO2 = 26.98 Barrer

α _CO2/CH4 = 21.08 α _CO2/N2 = 47.58 α _CO2/H2 = 3.48

comparative example

Table 1 is a comparison between the polyimide cross-linked modified homogeneous membrane in Examples 1-6 of the present invention and the Matrimid homogeneous membrane reported in the literature (Journal of Membrane Science, 2003, 225, 77-90). The addition of the cross-linking agent containing ether oxygen in the present invention leads to different changes in the polymer structure, so that the overall separation performance of the polymer separation membrane is better than that of a simple Matrimid membrane, and the air permeability and selectivity have been improved.

Table 1 Matrimid cross-linked modified membrane of the present invention and Matrimid membrane performance comparison

Comparing Example 2 with the literature values, it can be seen that the cross-linked modified Matrimid has a large flux and a high separation coefficient. It is proved that the cross-linking of polyether diamine can greatly improve the gas permeation and separation performance of the original polyimide.

Comparing Example 1 and Example 2, it can be seen that the polyether diamine crosslinking agent with different contents still has a certain effect on Matrimid, and improves the gas permeation and separation performance of Matrimid to a certain extent. It can be seen that the effect of cross-linking modification is not good when the content of polyether diamine is small.

Comparing Example 2 with Example 3, it can be seen that low molecular weight polyether diamine can also have a certain modification effect on the original Matrimid, but the flux is reduced. It is proved that the polyether diamine with molecular weight within a certain range can play a certain effect on the crosslinking of Matrimid modification.

Comparing Examples 4 and 5 with Example 2, it can be seen that for different aromatic polyimides, polyether diamines can be modified and cross-linked to obtain a good modification effect, which greatly improves the gas permeation and separation performance of raw materials. And because of the different polyimides used, different solvents and drying temperatures were used. It can be seen that different solvents and drying temperatures will not affect polyetherdiamine within a certain range.

Comparing Embodiment 5 and Embodiment 6, it can be seen that different types of polyether diamines also have a good modification effect on the original polyimide, greatly improving the gas permeation and separation performance of the polyimide. Therefore, the polyether diamines we use include polyethylene glycol and polypropylene glycol diamines.

Claims (4)

1. the preparation method of polyoxyethylene-introduced cross-linked modified polyimide gas separating film is characterized in that:

(1) the carrying out of cross-linking reaction: get polyimides and the crosslinking agent polyetheramine is dissolved in respectively in the solvent, treat that polymer and crosslinking agent dissolve fully; After two kinds of solution mixing, stir 5～30h reaction;

(2) preparation of homogeneous membrane: after the complete hybrid reaction of solution, solution is poured on the polyethylene board 25～60 ℃ of following drying and forming-films, the homogeneous membrane that obtains, put into water and removed wherein unreacted crosslinking agent in 1～5 day, then film is put into 50～120 ℃ of bakings of vacuum drying oven, 5～24h; The film thickness that obtains is between 50～150 μ m.

2. according to the described preparation method of claim 1, it is characterized in that: used crosslinking agent polyether monoamine material is two end amido ethylene glycol, two end amido propane diols, two end amido polyethylene glycol, two end amido polypropylene glycols or two end amido polyethylene glycol copolymerization polypropylene glycols in the step (1), and molecular weight ranges is 100-10000;

Used polyimide material is Matrimid-218, Uteml-1000 or the polyimides be made up of n-m in the step (1), and wherein n is 6FDA, ODPA, BPDA or BTDA; M is mPDA, ODA, TMPDA, 2,6-DAT or MDA.

3. according to the described preparation method of claim 1, it is characterized in that: in the step (1) in the crosslinking agent in amido and the polyimides molar ratio of imide group be 0: 1～1: 1.

4. according to the described preparation method of claim 1, it is characterized in that: solvent is polar solvent oxolane, N in the step (1), N-dimethylacetylamide, N, dinethylformamide, N-N-methyl-2-2-pyrrolidone N-or dimethyl sulfoxide (DMSO), its consumption is: 1～50g/lg gross mass polyimides and crosslinking agent diamines.