JPS59145007A - Preparation of porous diaphragm for gas separation - Google Patents

Abstract

PURPOSE:To obtain a diaphragm excellent in strength and gas separability, by molding, drying and baking a mixture of a silica sol or alumina sol fine particle with a specific particle size and a fine particle comprising a material good in moldability. CONSTITUTION:This porous diaphragm is obtained by such a method that an extremely fine silica or alumina sol with a particle size of 30-500Angstrom are well kneaded with a particle good in moldability and having a particle size of 1,000- 10,000Angstrom comprising titania, zirconia, clay or silicon carbide in a water contained state and the kneaded mixture is molded into a porous diaphragm which is, in turn, dried and baked. The obtained diaphragm generates no crack in a drying stage, can be formed into a large molded body and has a fine pore size capable of performing gas separation in good efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a porous diaphragm used for gas separation and the like.

Porous material with micro pores, especially ultra-fine pores with an average size of several tens to several hundreds of times When separating and concentrating gases using a diaphragm, for example, by the gas diffusion method, it is necessary to make the porous diaphragm as thin as possible in order to perform it efficiently, but from the viewpoint of strength, it is not recommended to make it extremely thin. Can not. or,
In such cases, it is difficult to mold into any desired shape. Therefore, it is necessary to use a porous material with high gas permeability that has a large pore diameter and a certain thickness to have sufficient strength so as not to impede gas diffusion, or to use a porous material with high gas permeability that has fine pores such as a wire mesh. Measures have been taken to strengthen the porous diaphragm to create a multilayer structure.

For example, there are various methods for making a multilayered porous membrane into a tubular shape, but in general, a sheet-like multilayered porous diaphragm is formed into a circular tube shape, and the ends are butt welded or overlapped and bonded. ing. However, if the porous material is highly flexible, such as metal, it is possible to form a circular tube, but if the porous material is inflexible, such as ceramic, it is extremely difficult. Also, since porous metals are porous materials, their strength is lower than that of non-porous tetrahedral materials due to the presence of pores.)
However, there was a limit to the radius of curvature that could be formed into a circular tube, and it was extremely difficult to form it into a thin tube.

Therefore, as a method to solve such difficulties, the porous support tube and the pipe or core metal placed inside or outside of it are held in the same circular shape, and the porous support tube and the pipe or core metal are vibrated. The powder is uniformly filled in the gap by blowing gas into the gap between the porous support tube and the top of the pipe or core metal while giving a A method for forming a tubular porous membrane is known, in which the porous membrane is tightly crimped to form a crimped layer of powder on a porous support tube (Japanese Unexamined Patent Publication No.
However, there are many difficulties in practice, such as uniformly filling the powder and producing a very thin film.

The present inventors conducted intensive research to overcome the above-mentioned problems regarding porous diaphragms used for gas separation, and as a result, they developed the present invention.

In the production of porous diaphragms, the present invention uses very small particles such as silica sol or alumina sol with a particle size of 30 to 500, and moldability such as titanium, clay, and silicon carpite. After kneading well and relatively small particles with a particle size of 1,000 to 10,000 in a water-containing state, they are molded into the desired porous diaphragm shape by compression molding or extrusion molding, and then dried. The present invention relates to a method for manufacturing a porous diaphragm for gas separation, which is characterized by performing firing.

In order to efficiently perform gas separation using a porous diaphragm, it is desirable that the pore diameter of the porous diaphragm is 30 to 500X, preferably 100 to 200X. Furthermore, the pore diameter of the porous body obtained by molding, drying, and firing the fine particles is approximately on the order of the size of the fine particles forming the porous body.

Therefore, in order to produce a porous diaphragm with good gas separation performance, it is necessary to use silica sol or alumina sol, which has a particle size of 3.
Molding particles of 0 to 5ooX.

It can be dried and fired. However, such a molded product of fine particles undergoes a large shrinkage during the drying stage, and therefore cracks occur, making it difficult to obtain a large molded product.

On the other hand, particles such as titania, zirconia, and clay have a particle size of 1,
Molding particles of 000 to 1o, oooK.

When drying and firing, shrinkage during the drying stage of the molded product is not a big problem, but the size of the pores that are generated is several orders of magnitude larger.
If it is 00A or more, gas separation using this molded body (porous diaphragm) is inefficient because the pore diameter is too large, and sufficient gas separation performance cannot be obtained.

In the present invention, as described above, particles of silica sol or alumina sol with a particle size of 30 to 500X are sufficiently mixed with particles of titania, zirconia, clay, silicon carbide, etc. with a particle size of 1,000 to 10,000 and good moldability. After that, it is molded into a porous diaphragm of any shape by compression molding or extrusion molding, and then dried and fired, resulting in a porous diaphragm with good moldability and gas separation performance. .

Particles having a particle size of 30 to 500X used in the present invention.

It is desirable that the size of each particle is as uniform as possible for particles with particle diameters of 1,000 to 1o and oooK. Particles with a particle size of 3o~soo4 and a particle size of 1,000~1
The mixing ratio of 0.00oX particles is 20 by weight:
A ratio of 80 to 80:200 is preferable, and the properties of the two types of particles to be mixed are determined within the above range, taking into consideration moldability, gas separation performance, etc.

The present invention will be explained in detail by way of examples below.

Example 1 After thoroughly mixing dry titania with an average particle size of 1,500 and alumina sol with a particle size of 2OOX in a weight ratio of 1:1, a small amount of water was added to make it soft enough to extrude. Then, it was molded into an extruder with a thickness of 1fi and a width of 2.
0m! After extrusion molding into a plate shape of n, air drying for 1 day, put in an electric furnace, heated to 900 ° C at a temperature increase rate of ta o ° C / h, and held at 900 ° C for 2 hours, A porous diaphragm was obtained by cooling in a furnace.

In addition, as a porous diaphragm for comparison, an average particle size of 1.5
A porous diaphragm was obtained as above using only 0OA of titania.

The υ pore size distribution of the two types of porous membranes thus obtained was determined by mercury intrusion method. The results are shown in FIG. In Figure 1, the horizontal axis shows the pore radius (e), and the vertical axis shows the cumulative pore volume (ac/,), where 1 is a comparison porous diaphragm made only of titania, and 2 is a mixture of titania and alumina sol. A porous diaphragm according to the present invention.

In addition, the comparison porous diaphragm made only of titania has an average pore radius of 51 s Og and a pore volume of 0.15 rx-/y, whereas the porous diaphragm of the present invention made of a mixture of titania and alumina sol has an average pore radius of 51 s Og and a pore volume of 0.15 rx-/y. The average pore radius was 14oX, and the pore volume was 0.275 cr/y.

For these two types of porous diaphragms, using a gas separation test device, a mixed gas of 50 parts hydrogen and 50 parts nitrogen was tested at an inlet pressure of 5 kg/am2. Outlet side pressure 1/c
When a gas separation test was conducted with the setting set to rn2, a comparison porous membrane made only of titania had 53% hydrogen and 47% nitrogen.
The porous diaphragm of the present invention made of a mixture of titania and alumina sol had an exit gas composition of 71% hydrogen.
It was revealed that the gas separation performance of the porous diaphragm according to the present invention was excellent when the outlet gas composition was 29q6 and 29q6 nitrogen.

Example 2 Kaolin (clay) with an average particle size of 2.50OA and particle size 2
After thoroughly mixing dry 00x alumina sol in a weight ratio of 1:2, add a small amount of water to make it soft enough to extrude, and then use an extrusion molding machine to form a plate with a thickness of 1 mm and a width of 20 mm. After extrusion molding into
The mixture was heated to 00°C, held at 900°C for 2 hours, and then cooled in a furnace to obtain a porous diaphragm.

In addition, as a porous diaphragm for comparison, an average particle size of 2,
A porous diaphragm was obtained in the same manner as above using only 5ooX kaolin.

The pore size distribution of the two types of porous diaphragms thus obtained was determined by mercury intrusion method. The results are shown in FIG. In Fig. 2, the horizontal axis shows the pore radius (X), and the vertical axis shows the cumulative pore volume (Cc/, A porous diaphragm according to the invention of a mixture of.

In addition, a comparative porous diaphragm made only of kaolin had an average pore radius of 73° and a pore volume of 11 cc/.

In comparison, the porous diaphragm of the present invention made of a mixture of kaolin and alumina sol had an average pore diameter of 140.chi. and a pore volume of 0.28 CI-/y.

For these two types of porous diaphragms, a gas separation test device was used to test a mixed gas of 50 cm of hydrogen and 50 cm of nitrogen at an inlet side pressure of 5 K17 cm2. Outlet side pressure 1Kq/
cm2 and conducted a gas separation test, a comparative porous membrane made only of kaolin had 51% hydrogen and 49% nitrogen.
compared to 73% hydrogen in the porous membrane of the present invention made of a mixture of kaolin and alumina sol.

It became clear that the gas separation performance of the porous diaphragm according to the present invention was excellent when the outlet gas composition was 27% nitrogen.

Example 3 Average particle size 3. After thoroughly mixing oooX zirconia and dry silica sol with a particle size of 3oX in a weight ratio of 1=1, add a small amount of water to make it soft enough to extrude, and then put it in an extruder to a thickness of 1 It was extruded into a plate shape with a width of 20 mm, air-dried for 1 day, then placed in an electric furnace and heated to 1,200°C at a temperature increase rate of 100°C/h. After holding for a period of time, the mixture was cooled in a furnace to obtain a porous diaphragm.

For comparison, a porous diaphragm with an average particle diameter of 3. oo
A porous diaphragm was obtained in the same manner as above using only OK zirconia.

The pore size distribution of the two types of porous diaphragms thus obtained was determined by mercury intrusion method. The results are shown in FIG. In Fig. 3, the horizontal axis shows the pore radius (A)-, the vertical axis shows the cumulative pore volume (cc/,), 5 is a comparison porous diaphragm made of only zirconia, and 6 is a porous diaphragm made of zirconia and silica sol. A porous diaphragm according to the present invention is a mixture of the following.

In addition, the comparative porous diaphragm made only of zirconia had an average pore radius of 74°K and a pore volume of Q, 15 ct/liter, whereas the porous diaphragm of the present invention made of a mixture of zirconia and silica sol had an average pore radius of 74°K and a pore volume of 15 ct/liter. The radius was 2 oom and the pore volume was 0.21 oC/y.

In addition, in the porous diaphragm according to the present invention made of a mixture of zirconia and silica sol, the pore radius distribution is in two locations, 5aX and aaaX.

For these two types of porous diaphragms, using a gas separation test device, a mixed gas of 50% hydrogen and 50% methane was tested with an inlet pressure of 3 kg/cm2 and an outlet pressure of 1/9 kg/cm2.
When a gas separation test was carried out with the zirconia sol set at It was revealed that the porous diaphragm had an outlet gas composition of 65% hydrogen and 35% methane, and that the porous diaphragm according to the present invention had an excellent gas separation performance.

Example 4 Average particle size 2. After thoroughly mixing oooX silicon carbide and dry alumina sol with a particle size of 1:1 in a weight ratio of 1:1, add a small amount of water to make it soft enough to extrude, and then put it into an extruder to give it a thickness. 1m
, extruded into a plate shape with a width of 20+ m, air-dried for 1 day, then placed in an electric furnace and heated to 1,500°C at a temperature increase rate of 100°C/h, and held at 1,500°C for 2 hours. After that, the mixture was cooled in a furnace to obtain a porous diaphragm.

In addition, as a porous diaphragm for comparison, the average particle size was 2,000.
A porous diaphragm was obtained in the same manner as above using only 0A silicon carbide.

The pore size distribution of the two types of porous diaphragms thus obtained was determined by mercury intrusion method. The results are shown in FIG. In Fig. 4, the horizontal axis shows the pore radius (X) and the vertical axis shows the cumulative pore volume (H), 7 is a comparative porous diaphragm made of silicon carbide alone, and 8 is a comparative porous diaphragm made of silicon carbide and alumina sol. A porous diaphragm according to the invention of a mixture of.

In addition, with a comparative porous diaphragm made only of silicon carbide,
Average pore radius is 430χ, pore volume is 0.20ω/1
In contrast, the porous diaphragm of the present invention made of a mixture of silicon carbide and alumina sol had an average pore radius of 1soX and a pore volume of 0.25 cc/p.

In addition, in the porous diaphragm according to the present invention made of a mixture of silicon carbide and alumina sol, the distribution of pore radius is 60λ and 2.
There are two locations at 50x.

28I like this! Regarding the porous diaphragm, using a gas separation test device, a mixed gas of 50% hydrogen and 50% carbon oxide was tested at an inlet pressure of 3 kg on the Z side. Outlet side pressure 1
When a gas separation test was carried out using a gas separation test of 5 kg/cm2, it was found that a comparative porous membrane made only of silicon carbide had hydrogen of 5.
Part 4, -72% hydrogen and 28% carbon oxide in the porous diaphragm according to the invention of a mixture of silicon cannibite and alumina sol, compared to rarely with an exit gas composition of 464 -carbon oxides.
It became clear that the gas separation performance of the porous diaphragm according to the present invention was excellent with respect to the outlet gas composition.

[Brief explanation of the drawing]

FIGS. 1 to 4 are diagrams showing the pore size distribution of a porous diaphragm experimentally produced using the method of the present invention. Sub-agent 1) Meiji agent Ryo Hagiwara - Figure 1 Figure 2 Pore diameter (in) Pore radius (in) Pore radius value)

Claims (1)

[Claims] A porous diaphragm for gas separation characterized in that fine particles of silica sol or alumina sol with a particle size of 30 to 500A and fine particles with good moldability of a particle size of 1,000 to 10,000χ are mixed, then molded, dried, and fired. Production method.