JP3358350B2 - Method for producing porous ceramic hollow fiber laminated with multilayer thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hollow fiber of a multilayer ceramic laminated porous ceramic. More particularly, the present invention relates to a method for producing a porous ceramic hollow fiber which is effectively used as a gas separation membrane, a separation membrane for a membrane reactor or the like by laminating a multilayer thin film on an outer wall surface.

[0002]

2. Description of the Related Art When a gas is separated using a porous membrane, for example, when separating H ₂ and CO, and H ₂ and N ₂ , the porous membrane is formed so that the pores are controlled by Knudsen diffusion. It is necessary to use one whose pore diameter has been adjusted to about several tens of mm or less.

[0003] As a specific gas separation membrane, about
An inorganic porous Vycor glass having a pore size of 40 ° has been conventionally known. Since this Vycor glass is a high silicate, it has the characteristic of being excellent in heat resistance and corrosion resistance, but its thickness is about 0.5 m in terms of strength.
Since it is difficult to reduce the diameter to less than m, there is a disadvantage that the gas permeation rate per unit area is small.

Therefore, in order to produce a separation membrane having a high gas permeation rate, it is desirable to adjust the pore diameter of the porous membrane so as to be fine pores by controlling Knudsen diffusion and to reduce the film thickness. The so-called multi-layer structure in which a gas separation layer with a small thickness is coated on a porous support with a relatively large pore diameter of about 1 mm and reinforced because the film thickness cannot be extremely thin due to its mechanical strength Has been adopted.

[0005] The thin-film laminated porous structure used here is usually used in the form of a hollow tube in terms of handling or strength, and its production is generally carried out by powder metallurgy or sintering. First, a porous hollow tube having a thickness of about 1 mm is manufactured, and a thin film having micropores is laminated thereon by various methods.

As a method of laminating such a thin film, a thickness of 1 μm
There are vacuum deposition method and sputtering method for forming an extremely thin film to the extent that these methods are not practical because of the difficulty in controlling the uniform pore size and the limitation of the apparatus volume, and therefore, it is usually not practical. A method of attaching powder to a thickness of several tens of μm is used.

[0007] Such a method of forming a fine powder layer includes a dry method and a wet method. However, the dry method has poor fluidity of powder particles and is extremely difficult to form a layer having a uniform thickness. The wet method is the mainstream.

In the wet method, a porous hollow tube is rotated, a fine powder slurry is supplied to the inside of the hollow tube, and the powder is adhered by centrifugal force. Electrophoresis using the surface potential of the slurry is carried out. There are an electrophoresis method of attaching a slurry to a porous hollow tube, and a commonly used coating method. In these methods, water or an organic solvent such as alcohol or acetone is added to a fine powder and used as a slurry. Therefore, it has a feature that it has good fluidity and a layer having a uniform thickness can be easily formed.

As described above, a uniform thin film can be formed by the wet method, but the pore diameter that can be easily formed is several tens of mm or more.
When an ultrafine powder of about 100 ° or less is used, there is a disadvantage that cracks are easily generated when the liquid is evaporated and dried after the formation of the slurry adhesion layer. There is also a method of adding a binder to the slurry to prevent the occurrence of cracks,
It is difficult to remove the binder later to obtain micropores.

[0010] One of the methods for obtaining micropores is as follows.
There is also a method of producing a porous substance by filling fine particles in a coarse porous substrate by an immersion method, but this method has a disadvantage that the fine particles are filled in the entire coarse porous substrate.

Therefore, the present inventor has previously found that it is difficult to control such various drawbacks found in the prior art, namely, to control the uniform pore size, to make the pore size smaller, to make the film thinner, and to reduce the occurrence of cracks and peel strength. In order to overcome any problems such as low temperature, a method has been proposed in which a silica sol is flowed into and contacted with a porous alumina hollow fiber, and then dried and fired to produce a thin-film laminated porous alumina hollow fiber (Japanese Patent Laid-Open No. Hei 5 (1994)). -132822).

Although the thin-film laminated porous alumina hollow fiber produced by the proposed method achieves the intended purpose, for example, the H ₂ / N ₂ separation coefficient has a lower H ₂ permeation rate. Further improvement in performance as a gas separation membrane was required.

The present inventor has also conducted a forced filtration of the boehmite sol in the porous alumina hollow fiber, and dried and fired the γ.
-After forming an alumina thin film on the inner wall surface of a hollow fiber, a silica sol is introduced from one end side of the hollow fiber, brought into contact, dried and fired to produce a multilayer thin film laminated porous alumina hollow fiber (Japanese Patent Laid-Open Publication No. 5-57162). However, the lamination of the multilayer thin film on the inner wall surface side of the porous alumina hollow fiber,
Not only is it not easy in terms of operation, but the H ₂ / N ₂ separation coefficient is about 3, and further improvement in gas separation performance was required.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-layer thin film laminated porous ceramic hollow fiber in which a γ-alumina thin film and a silica thin film are sequentially laminated on a porous ceramic hollow fiber, thereby further improving the gas separation performance. It is to provide a manufacturing method of the product.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
The porous ceramic hollow fiber is immersed in the boehmite sol, dried and fired, then immersed in silica sol with both ends sealed, dried and fired to obtain a multilayer thin film laminated porous ceramic hollow fiber. Achieved by manufacturing.

As the porous ceramic hollow fiber, Al ₂ O ₃ hollow fiber is generally used, but other than this, Y ₂ O ₃ , SiO _2
2 , hollow fibers such as Si ₃ N ₄ and ZrO ₂ can be used, and these have an average pore diameter of about 0.1 to 10 μm, preferably about 0.1 to 2 μm.

These porous ceramic hollow fibers are immersed in a boehmite sol, dried and fired, so that a γ-alumina thin film is mainly laminated on the outer wall surface of the hollow fiber. The boehmite sol used here is, for example, after hydrolyzing aluminum isopropoxide in distilled water of about 100 times the molar amount by heating to 75 ° C or more, hydrochloric acid of about 0.07 to 0.20 times the molar amount of aluminum, etc. And pulverized at 95 ° C. Also,
Commercially available ones are also used.

The immersion in the boehmite sol and the withdrawal therefrom are carried out using a low-speed motor at an immersion speed of about 6 to 600 mm / min, preferably about 20 to 360 mm / min and about 6 to 600 mm / min.
Min, preferably about 20 to 360 mm / min, followed by drying at room temperature for about 12 hours, followed by firing at about 400 to 800 ° C. for about 1 to 10 hours. At this time, drying can also be performed at the firing temperature. Such a series of operations is generally repeated a plurality of times, preferably about two to three times.

The porous hollow fiber thus laminated with the γ-alumina thin film is immersed in silica sol, dried and fired with both ends sealed. Sealing of both ends of the hollow fiber is generally performed using a commercially available adhesive such as an epoxy resin, but as described in JP-A-5-221752, immersed in silica sol and dried at 200 ° C. After that, an impregnation sealing method such as baking at 400 ° C. may be adopted.

The silica sol is prepared by hydrolyzing a tetraalkoxysilane such as tetraethoxysilane in an aqueous alcohol solution using an inorganic acid such as hydrochloric acid, and sealing both ends thereof to a γ-alumina thin film laminated porous material. The porous ceramics hollow fiber is immersed at about 2 mm /
Immersion speed of at least one minute, preferably immersion at a stretch, and after pulling up at a pulling rate of about 0.1 to 2 mm / min, preferably about 0.4 to 1.8 mm / min, for example, constant temperature constant of 40 ° C. and 90% RH Under wet conditions, drying is performed for about 10 minutes to 10 hours, preferably for about 1 to 3 hours. Next, if necessary, further drying is performed at about 150 to 250 ° C. for about 10 minutes to 5 hours, followed by baking at about 400 to 600 ° C. for about 1 to 5 hours.
At this time, drying can also be performed at the firing temperature. Such a series of operations is generally performed a plurality of times.

By gradually applying the boehmite sol and the silica sol to the porous ceramic hollow fiber, about 0.1 to 5
A γ-alumina thin film is laminated with a thickness of μm,
A porous ceramic hollow fiber is obtained in which a fine porous silica layer is laminated on the alumina thin film and in the thin film layer in a multilayer thickness of about 0.1 to 3 μm.

[0022]

According to the method of the present invention, since the γ-alumina thin film and the silica layer are formed on the outer wall surface of the porous ceramic hollow fiber, the production thereof is easy, and the obtained multilayer thin film laminated porous film is easy to manufacture. When the porous ceramic hollow fiber is used as a gas separation membrane, the separation accuracy is remarkably improved while maintaining a high permeation speed.

[0023]

Next, the present invention will be described with reference to examples.

Example 1 A porous ceramic hollow fiber was placed in a boehmite sol prepared by diluting Nissan Chemical's Al sol 200 with an equal weight of distilled water.
(Average pore diameter 0.15μm, porosity 40%, inner diameter 1.7mm, outer diameter 2.2m
m, 300 mm in length) was immersed at a speed of 60 mm / min using a low-speed motor and pulled up at a speed of 24 mm / min. Then 1 at room temperature
Drying for 2 hours and baking at 600 ° C. for 2 hours were performed. Such a series of operations is performed once more, twice in total, and γ
-An alumina thin film laminated porous ceramic hollow fiber was obtained.
When the fractionation performance of this laminated hollow fiber was evaluated using a PEG mixed aqueous solution, the result was that the molecular weight cut off was 1,000.

25 g of tetraethoxysilane, 37.
6 g, 0.3 g of 36% hydrochloric acid and 23.5 g of distilled water are stirred at room temperature for 2 hours, and the above-mentioned laminated hollow fiber sealed at both ends with an epoxy resin is prepared in a silica sol prepared by hydrolysis using a low-speed motor. It was immersed at a speed of 2.0 mm / min and pulled up at a speed of 1.6 mm / min. Thereafter, drying was performed for 2 hours under a constant temperature and humidity condition of 40 ° C. and 90% RH, and firing was performed at 500 ° C. for 5 hours.
Such a series of operations was performed once, twice or three times for the sample A, B or C, respectively, and the following measurement was performed each time.

That is, with respect to each of the obtained samples (silica-γ-alumina multilayer thin film laminated porous ceramic hollow fibers), the gas permeation rates of H ₂ and N ₂ (unit: mol / m ² · s · Pa)
Was measured at 250 ° C. and the H ₂ / N ₂ transmission rate ratio was calculated therefrom. The results obtained are shown in Table 1 below. Table 1 Silica sol H ₂ gas N ₂ gas H ₂ / N ₂ Number of times of lamination of silica layer Permeation speed Permeation speed Permeability ratio Thickness (μm) One time Sample A 6.30 × 10 ^-7 3.47 × 10 ^-8 15.25 0.5 Ｂ B 1.21 × 10 ^-6 3.47 × 10 ^-7 7.24 0.8 〃 C 1.26 × 10 ^-6 1.93 × 10 ^-7 6.53 0.8 Sample A 4.84 × 10 ^-7 3.03 × 10 ^-8 15.98 1.2 Ｂ B 9.82 × 10 ^-7 7.33 × 10 ^-8 13.40 1.1 〃 C 4.49 × 10 ^-7 4.07 × 10 ^-8 11.03 1.2 3 samples A 5.76 × 10 ^-7 1.74 × 10 ^-8 33.19 1.6 Ｂ B 4.57 × 10 ^-7 3.00 × 10 ^-8 15.20 1.8 〃 C 6.93 × 10 ^-7 6.68 × 10 ^-8 10.37 1.5

Example 2 A porous ceramic hollow fiber was placed in a boehmite sol prepared by diluting Nissan Chemical's Al sol 500 with an equal weight of distilled water.
(Average pore diameter 0.15μm, porosity 40%, inner diameter 1.7mm, outer diameter 2.2m
m, 300 mm in length) was immersed at a speed of 60 mm / min using a low-speed motor and pulled up at a speed of 60 mm / min. Then 1 at room temperature
Drying for 2 hours and baking at 600 ° C. for 2 hours were performed. Such a series of operations is performed once more, twice in total, and γ
-An alumina thin film laminated porous ceramic hollow fiber was obtained.
When the fractionation performance of this laminated hollow fiber was evaluated using a PEG mixed aqueous solution, the result was that the fractional molecular weight was 6000.

25 g of tetraethoxysilane, 37.
6 g, 0.3 g of 36% hydrochloric acid and 23.5 g of distilled water are stirred at room temperature for 2 hours, and the above-mentioned laminated hollow fiber sealed at both ends with an epoxy resin is prepared in a silica sol prepared by hydrolysis using a low-speed motor. It was immersed at a speed of 2.0 mm / min and pulled up at a speed of 1.6 mm / min. Thereafter, drying was performed for 2 hours under a constant temperature and humidity condition of 40 ° C. and 90% RH, and firing was performed at 500 ° C. for 5 hours.
Such a series of operations was performed four or five times for the sample D or E, respectively, and the following measurement was performed each time.

That is, for each of the obtained samples (silica-γ-alumina multilayer thin film laminated porous ceramic hollow fiber), the gas permeation rate of H ₂ and N ₂ (unit: mol / m ² · s · Pa)
Was measured at 250 ° C. and the H ₂ / N ₂ transmission rate ratio was calculated therefrom. The results obtained are shown in Table 2 below. Table 2 Silica sol H ₂ gas N ₂ gas H ₂ / N ₂ silica layer lamination number Permeation speed Permeation speed Permeation speed specific film thickness (μm) 4 times Sample D 8.23 × 10 ^-7 1.84 × 10 ^-8 44.69 1.9 〃 E 8.01 × 10 ^-7 1.21 × 10 ^-8 66.04 2.1 5 times Sample D 1.19 × 10 ^-7 3.33 × 10 ^-9 35.79 2.9 Ｅ E 6.41 × 10 ^-7 5.53 × 10 ^-9 115.88 2.5

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 67/00-71/82 510 B01D 53/22

Claims (2)

(57) [Claims] 1. A porous ceramic hollow fiber is immersed in a boehmite sol, dried and fired, then immersed in a silica sol with both ends sealed, dried and fired. A method for producing a porous ceramic hollow fiber laminated with a multilayer thin film. 2. A gas separation membrane comprising a multilayer thin film laminated porous ceramic hollow fiber produced by the method of claim 1.