CN1036767C - A hydrogen permeable membrane and its preparation method - Google Patents

Abstract

A high-strength selective hydrogen permeable membrane and its preparation method, which is to uniformly coat the solution of the pre-polymerized monomer of polybenzimidazole pyrrolidone on the wire mesh, and undergo polymerization and high temperature under the protection of nitrogen. Curing, that is, a selective high-strength hydrogen permeable membrane reinforced with a wire mesh is produced. This hydrogen permeable membrane has the same hydrogen selectivity as the homogeneous hydrogen permeable membrane without metal mesh reinforcement, but it has greatly improved in many aspects such as mechanical strength, hydrogen permeability rate, film forming conditions and the success rate of finished products. , so that the aromatic heterocyclic organic polymer compound hydrogen permeable membrane can expand the application in the field of membrane separation technology.

Description

A hydrogen permeable membrane and its preparation method

The invention relates to a high-strength selective hydrogen permeable membrane and a preparation method thereof, more precisely, the invention relates to a selective hydrogen permeable membrane reinforced with a wire mesh and a preparation method thereof, belonging to the field of membrane separation technology .

Polybenzimidazole pyrrole ketone (Polypyrrones) is a kind of stepped aromatic heterocyclic polymer compound obtained by polycondensation of aromatic tetraacid dianhydride and aromatic tetraamine in a polar solvent and treated at high temperature (Lu Fengcai et al., Aerospace Materials Technology, No. 2, pp. 15-18, 1984). The homogeneous membrane prepared by it is a hydrogen-rich membrane with good selective permeation to hydrogen (Lu Fengcai et al., Acta Polymer Sinica, No. 5, pp. 342-346. 1987), due to this homogeneous Good selectivity of thin film, CN91217597.4 utility model patent uses it as the pre-separation device of selective hydrogen detector. However, due to the existence of the following unfavorable factors, the preparation conditions of this homogeneous membrane are relatively harsh and difficult to produce in batches:

1. Since water can hydrolyze the pre-polymerized monomer and terminate the polycondensation reaction, it is required to strictly control the environmental humidity during the film forming process.

2. When forming a film, the pre-polymerized monomer needs to be evenly spread on a flat plate with a certain thickness, and the initial polymerization is carried out and the solvent is removed (the time is about 1.5 to 2 hours). During this process, it is easily disturbed by environmental conditions. . In addition, the uniformity of the finished film is not easy to control, and it is often thick at the periphery and thin at the middle, resulting in a very low yield of film formation.

3. The thinner the film is, the better the hydrogen permeability is. However, in order to ensure that the finished film has sufficient strength and the film cannot be too thin, this way of further improving the film permeability is limited.

In view of the above practical problems, the purpose of the present invention is to propose a film and a film forming method based on this new hydrogen-rich material, so that it can be better applied in practice.

In the present invention, the pre-polymerized monomer solution of polybenzimidazole pyrrolidone with a certain concentration is evenly coated on the wire mesh under certain conditions, and after preliminary polymerization and evaporation of the solvent, it is placed in an aging box. Under the protection of nitrogen, high-temperature polycondensation forms a hydrogen permeable membrane reinforced with wire mesh. Since this hydrogen permeable membrane is based on a high molecular polymer attached to a wire mesh, compared with a single homogeneous membrane, its mechanical strength is greatly increased. In addition, it can be coated multiple times during preparation, so the adjustment range of the thickness of the hydrogen permeable membrane is much wider than that of a single homogeneous membrane, and it can be coated with thick films or ultra-thin films. When the hydrogen permeable membrane is prepared, the time required for the initial polymerization process is only one-third or shorter (10 to 25 minutes) than that of the homogeneous membrane. When preparing the hydrogen permeable membrane of the present invention, it can be freed from the interference of ambient humidity to the greatest extent. The wire mesh used in the present invention has two effects, the one, as the skeleton of film, increases the strength of finished film, the 2nd, provides the mesh that makes the prepolymer of organic macromolecule evenly distributed, makes the thickness of finished film uniform, thus It avoids the disadvantage that the periphery is thick and the middle is thin which inevitably occurs when the homogeneous film is formed.

The preparation of the hydrogen permeable membrane of the present invention is shown in the accompanying drawings. In the accompanying drawings, 1 is an upper drum, 2 is a lower drum, 3 and 6 are fixed pinches, 4 is a pre-polymerized monomer solution, and 5 is a wire mesh. The preparation method steps are as follows:

1. According to the above method published by Lu Fengcai et al., synthesize aromatic heterocyclic polymer monomer resin.

2. Dilute the resin with N,N'-dimethylformamide (water content is less than 500ppm) to a solution with a concentration of 3-15% (weight), preferably 5-8% (weight), and seal it for subsequent use.

3. Cut the commercially available wire mesh (300-800 mesh), such as stainless steel, brass, nickel, etc., to a suitable length and width, soak it in acetone, and dry it to wait. use.

4. Install the above-mentioned wire mesh in the coating equipment shown in the attached drawing, and adjust the gap between the roller 1 and the two fixed rollers 3 and 6 until it is tight enough to move.

5. Add an appropriate amount of resin solution into the coating tank.

6. Pull the wire mesh back and forth several times at an even speed, so that the mesh holes are evenly coated with resin solution.

7. Use a hair dryer to dry the wire mesh coated with the resin solution.

8. Put the dried wire mesh in a sealed container, raise the temperature to 300°C under the protection of nitrogen, and then maintain a constant temperature for 2 to 3 hours, so that the aromatic heterocyclic polymer monomer resin coated on the surface of the wire mesh is fully Polymerization solidifies into a film.

9. The temperature is lowered to room temperature, and the selective hydrogen permeable membrane reinforced by the wire mesh of the present invention is obtained.

In the above preparation process, steps 2, 6, and 7 have a direct impact on the thickness and uniformity of the hydrogen permeable membrane. In order to ensure the uniformity of the coating, steps 6 and 7 should be repeated at least twice under normal circumstances. Low resin concentration, multiple coating, and drying processes are the key factors for making uniformly coated hydrogen permeable membranes. As can be seen from the following examples and the performance data of the oxygen-permeable membrane, the selective hydrogen-permeable membrane reinforced by the wire mesh of the present invention has the same selectivity and other properties as the homogeneous membrane, but the mechanical strength and hydrogen permeability There is a significant improvement.

Example 1

Pre-polymerization monomer concentration is 7.9% (weight), 325 order stainless steel wire mesh, is coated into film by above-mentioned preparation method, wherein 6, 7 two steps are repeated twice. Install the obtained hydrogen permeable membrane on the "hydrogen content detector" of CN91217597.4 utility model patent, replace the homogeneous membrane with the wire mesh reinforced hydrogen permeable membrane of the present invention, and the thermal conductivity detector (TCD) bridge current 112mA , temperature 80°C, nitrogen as carrier gas, flow rate 30ml/min, wire mesh reinforced membrane area 4.3cm ² , temperature 80°C, sample gas is hydrogen and nitrogen mixed gas prepared by Beijing Beifen Scientific Gas Company, hydrogen concentration is 20.9% (volume).

The quantitative response relation to hydrogen is: Y=0.456X

In the formula: Y is the response signal, mV;

X is the volume percent concentration of hydrogen.

When liquefied gas is used as a sample, the signal response is 0.82mV.

Under the same conditions, the quantitative response relationship of a homogeneous hydrogen permeable membrane with a thickness of 30μ to hydrogen is Y=0.167X

Example 2

Pre-polymerization monomer concentration is 10% (weight), 325 mesh stainless steel wire mesh, coating film-forming by the above-mentioned preparation method, wherein 6, 7 two steps are repeated three times. Measured on the same hydrogen content detector. Operating conditions are all identical with embodiment 1.

The quantitative response relation to hydrogen is: Y=0.133X

When using liquefied gas as a sample, the signal response is 0.04mV

Example 3

The concentration of pre-polymerization monomer is 5.4% (weight), 325 mesh stainless steel wire posts, coating film formation according to the above-mentioned preparation method, wherein 6, 7 two steps are repeated once. Its measuring condition is with embodiment 1.

The quantitative response relation to hydrogen is: Y=2.21X

When using liquefied gas as a sample, the signal response is 0.61mV

Example 4

Pre-polymerization monomer concentration is 5.4% (weight), 325 mesh stainless steel wire mesh, coating film-forming by the above-mentioned preparation method, wherein 6, 7 two steps are repeated three times. Its measuring condition is with embodiment 1.

The quantitative response relation to hydrogen is: Y=0.986X

Example 5

Pre-polymerized monomer concentration is 5.0% (weight), 400 order stainless steel wire mesh, is coated film-forming by above-mentioned preparation method, wherein 6,7 two steps are repeated six times, and its measuring condition is with embodiment 1.

The quantitative response relation to hydrogen is: Y=0.4X

When using liquefied gas as a sample, the signal response is 0.72mV

Example 6

Pre-polymerized monomer concentration is 5.0% (weight), 800 order stainless steel wire mesh, is coated film-forming by above-mentioned preparation method, wherein 6,7 two steps are repeated three times, and its measuring condition is with embodiment 1.

The quantitative response relation to hydrogen is: Y=0.797X

When using liquefied gas as a sample, the signal response is 0.91mV

In the examples listed above, the slope k in the quantitative response relationship to hydrogen Y=kX is related to the hydrogen permeability rate of the hydrogen permeable membrane, and the greater the hydrogen permeability rate, the greater the corresponding k value. The response value to petroleum liquefied gas reflects the selectivity of the hydrogen permeable membrane to hydrocarbon gases (generally C ₁ -C ₅ hydrocarbons). It can be seen that in the examples given, except for individual cases, the response value to liquefied petroleum gas is lower than that of gas with 1% hydrogen concentration. This shows that when this hydrogen permeable membrane is used to detect the hydrogen content in petroleum gas, the interference of hydrocarbon components is very small.

Claims (4)

1. a kind of preparation method taking polybenzimidazole pyrrole ketone aromatic heterocyclic high molecular compound as the selective hydrogen permeable membrane of matrix, it is characterized in that the pre-polymerized monomer solution is evenly coated on the wire mesh of fine mesh, Repeat at least twice, and form a selective hydrogen permeable membrane reinforced with wire mesh through polycondensation and final polymerization at high temperature and nitrogen, said pre-polymerization monomer solution has a solid content of 3-15% (weight) Aromatic tetraacid dianhydride and aromatic tetraamine are dissolved in a polar solvent, and said polar solvent is N, N'-dimethylformamide or N, N'-dimethylacetamide. 2. According to the said hydrogen permeable membrane preparation method of claim 1, it is characterized in that the solid content of said pre-polymerized monomer solution is 5-8% (weight). 3. The method for preparing a hydrogen permeable membrane according to claim 1, characterized in that said fine mesh wire mesh is a stainless steel mesh, and the mesh range is 200 to 1000. 4. A hydrogen permeable membrane based on a polybenzimidazole pyrrolidone aromatic heterocyclic polymer compound, characterized in that it is prepared by the method of claim 1.

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