JPS59179112A - Manufacture of porous membrane body - Google Patents

Abstract

PURPOSE:To obtain a porous diaphragm having a small pore radius with a narrow distribution range and the excellent strength, heat resistance and gas separating performance by molding a mixture of metatitanic acid formed into sol, alumina sol and finely powdered silicic acid, drying and calcining. CONSTITUTION:The 5-30wt% finely powdered silicic acid having 5-50mum mean particle size and 20-50wt% alumina sol. are preferably added to 100wt% titanium oxide. In this case, the finely powdered silicic acid is added to the metatitanic acid sol. and the alumina sol., stirred and calcined. Meanwhile, the alumina sol. can also be added after the metatitanic acid added with the finely powdered silicic acid beforehand is formed into sol. The porous membrane body is obtained by removing the water content from the above-mentioned sol. mixture, molding, drying and calcining. The calcination temp. in this case is regulated to <=1,000 deg.C. In this way, the porous membrane body, provided with pores having 100-200Angstrom pore radius which is suitable for gas separation, can be obtained.

Description

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

A porous body obtained by sintering metal powder or ceramic powder or compression molding organic synthetic resin powder such as fluororesin as a base material with a micropore diameter, especially an average of several 10 to several 10 OA.
+7) When separating and concentrating gas using a porous diaphragm with ultra-fine pores, 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. It is not possible to make it extremely thin. Moreover, in such cases, it is difficult to mold into any desired shape. Therefore, 0 is a porous material with high gas permeability or wire mesh-like material with a thin porous material that has a large pore diameter so as not to interfere with gas diffusion, and a certain thickness to have sufficient strength. Measures are being taken to strengthen the membrane and create a multilayer structure.

For example, there are various methods to make 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. There is. However, if the porous material is highly flexible such as metal, circular tube forming can be performed at 5"r, but -
This is extremely difficult to do with inflexible materials such as ceramics. In addition, since porous metals are porous materials due to the presence of pores, their strength is lower than that of non-porous materials, and there is a limit to the radius of curvature that can be formed into a thin tube. This was extremely difficult.

One way to solve this problem is to hold the porous support tube and the pipe or core placed inside or outside of it in the same circular shape, and apply vibration to the porous support tube and the pipe or core. Blow out gas into the gap between the porous support tube and the pipe or core metal to uniformly fill the gap with powder,
A method of forming a tubular porous membrane is known in which powder filled in the void is bonded to a porous support tube by static pressure forming to form a compressed layer of powder on the porous support tube (Japanese Patent Laid-Open No. 50-774).
However, in reality, there are many disadvantages such as the ability to uniformly form the powder and the ability to produce very thin axillae.

The present inventors conducted the following research in order to overcome the above-mentioned problems regarding porous diaphragms used for gas separation, etc.

First, fine particles of silicic acid are uniformly dispersed in a mixture of titanium oxide and alumina sol, water is removed, and then a membrane is formed using an extrusion molding machine.

Dry and bake.

It is already known that fired titanium oxide products can be used as porous membranes, and the pore radius, specific surface area, crystal shape, mechanical strength, heat resistance, etc. that have an important influence on porous membranes depend on the manufacturing process. Various manufacturing methods have been proposed in the past because they differ depending on the method, presence or absence of additives, class B, lft, etc.

For example, according to a method in which titanium salts such as titanium tetrachloride or titanium sulfate are neutralized and hydrolyzed and then the generated titanium hydroxide is calcined to form titanium oxide, titanium hydroxide generated by water decomposition can be is likely to become orntetanic acid, and therefore, if this is fired, it is likely to become rutile-type titanium oxide. Rutile-type titanium oxide tends to have larger crystals than anatase-type titanium oxide, which will be described later (this is not a good idea if it is used as a membrane because the pores will be larger).

On the other hand, if titanate is thermally hydrolyzed, it becomes metatitanic acid, and if this is fired, it becomes anatase-type titanium oxide, although there are other factors involved. Anatase-type titanium oxide has a smaller crystal size than rutile-type titanium oxide, and when it is used as a membrane, the pore size becomes smaller, so it is preferable.The pore diameter of the porous body is the size of the constituent Mi crystals. Therefore, if anatase type titanium oxide is selected, a porous body with a small pore diameter can be obtained. However, in this method of forming titanium hydroxide or titanium oxide, drying and firing, the pore radius becomes several hundreds of amps or more, which is significantly thicker than that of the gas, because titanium oxide crystals grow during firing. (This makes it undesirable as a membrane for gas separation.

The present inventors solved this problem by increasing the thermal stability of anatase titanium oxide, which is the base material, by adding fine-particle silicic acid (to prevent crystal growth during firing), and by adding alumina sol. This can be solved by making molding easier and at the same time filling the gaps between the titanium oxide in the anatase-type titanium oxide molded body with alumina sol (which becomes alumina oxide when fired), which is even smaller than titanium oxide, to reduce the pore radius of the molded body. According to this method,
A porous body with a pore radius of about 100 to 200 A, which is suitable for gas separation, can be easily obtained.

In addition, with the method of adding silica to titanium hydroxide or titanium oxide and firing it, it is difficult to obtain a mixture with a uniform composition. In particular, when adding silica to titanium hydroxide, the titanium hydroxide becomes gel-like. Therefore, silica cannot be uniformly dispersed in titanium hydroxide, and the pore size is large.
The width of the pore distribution becomes wider. Therefore, silica needs to be added to the mixture of solized metatitanic acid and alumina sol.

The present invention was made in order to solve the various problems mentioned above, and the present invention has been made in order to solve the various problems mentioned above. The object of the present invention is to provide a method for manufacturing a porous diaphragm with excellent strength and heat resistance and high gas separation performance.

That is, the present invention relates to a method for producing a porous membrane body, which is characterized in that a mixture of sol-formed metatitanic acid, alumina sol, and fine-particle silicic acid is formed, dried, and fired.

The fine particle silicic acid used in the present invention is also known as white carbon, and one of its characteristics is that it has a very large specific surface area.

This fine particle silicic acid may be produced by either a wet method or a dry method (although in the present invention, ordinary commercially available products can be used).

In the present invention, the fine particle silicic acid has an average particle size of 5 to 50 fr.
Preferably, it is Lμ. Fish added with particulate silicic acid is
It is preferable to use 5 to 50 i [i%] of titanium oxide because it does not adversely affect the properties of the film.

The alumina sol used in the present invention may be obtained by any of the following methods: neutralizing or decomposing aluminum salts or aluminates, or hydrolyzing aluminum amalgams or aluminum alkoxides with water or steam. The addition lid of alumina sol is 20 to 5
A content of 0% by weight is preferable because it does not adversely affect the properties of the film.

In the method of the present invention, preferably the above-mentioned fine particles of silicic acid are added to the metatitanic acid sol and the alumina sol, and the mixture is stirred and then fired. However, if necessary, the fine particles of silicic acid are added to the metatitanic acid and then the metatitanic acid is added to the metatitanic acid sol. It is also possible to form a sol and add alumina sol. Since metatitanic acid is in the form of a gel, fine particles of silicic acid can be more uniformly dispersed in metatitanic acid by sol formation.

There are no particular restrictions on the method for solizing metatitanic acid, and for example, after washing metatitanic acid with water to remove most of the sulfuric acid groups, hydrochloric acid or nitric acid is added to partially or completely solify the metatitanic acid. Or
Especially when sulfuric acid roots are not removed by washing with water, add cyclized products of alkaline earth metals such as barium chloride, strontium chloride, and calcium chloride to metatitanic acid, or nitrates of alkaline earth metals such as barium nitrate, strontium nitrate, and calcium nitrate. While adding, the sulfate radical is fixed as a water-insoluble barium salt, and part or all of it is made into a sol.

The porous membrane body according to the present invention is obtained by removing water from the sol mixture, molding it by any conventionally known method such as extrusion molding, and then drying and baking. In this case, the firing temperature is 1000°C or less, preferably 900″C~
500” (j.

In this way, according to the present invention, a porous membrane body for gas separation can be obtained.

In the present invention, the firing atmosphere is not limited in any way, and may be any one of sudden air, combustion gas, inert gas, etc.1.
7-1° In the porous film body obtained by the present invention as described above, the crystal growth of titanium oxide is suppressed during firing of metatitanic acid due to the presence of fine particles of silicic acid, and it remains as an ungrown anatase type crystal. , the pore diameter of the resulting membrane is small.

In addition, alumina sol improves fluidity during molding and makes the pore size smaller than in the case of a mixture of metatitanic acid and silicic acid. In this way, a porous membrane body with excellent mechanical strength and heat resistance and excellent as a gas separation membrane can be obtained.

The present invention will be explained below with reference to Examples.

Example 1 Titanium sulfate obtained from the titanium oxide production process using the sulfuric acid method was thermally hydrolyzed to obtain metatitanic acid, 1 kg of this in terms of titanium oxide was taken out, and aluminum impropylate was hydrolyzed to this. 400 g of the obtained alumina sol was mixed in terms of alumina oxide. Next, commercially available particulate silicic acid (particle size 25 mμ) 200.9 was added, thoroughly stirred and mixed, water was removed, and an extrusion molding machine was used to form a mold with a diameter of 4 mm and a wall thickness of I Tr7! , a tube with a length of 50 cIn was molded.

For comparison, a tube was also molded using only metatitanic acid and alumina sol without adding fine particles of silicic acid.

After drying the two types of molded tubes at 100°C for 12 hours,
It was baked at a temperature of 00°C for 5 hours. After firing, the metatitanic acid and alumina sol had become titanium oxide and alumina oxide.

In order to use this fired product as a gas separation membrane, the pore size distribution was measured by mercury intrusion method, and at the same time a gas separation test was conducted.

Figure 1 shows the results of measuring pore radius and pore volume by mercury intrusion method. In FIG. 1, the horizontal axis is the pore radius and the vertical axis is the pore volume. Further, in the figure, ■ is the data for the comparative product titanium oxide + aluminum oxide, and ■ is the data for the invention product titanium oxide + aluminum oxide + silicic acid.

The product of the present invention with silicic acid added has an average pore radius of 150A and a sharp pore distribution, whereas the comparative product without silicic acid has an average pore radius of 660A and a broad pore size distribution. There is.

FIG. 2 shows the xi diffraction spectrum. 1 In Figure 2, the horizontal axis is the rotation angle 2θ, and the vertical axis is the intensity (arbitrary scale).
It is. In the figure, ■ is the X-ray diffraction data of the comparison product titanium oxide + altanium oxide, and ■ is the data of the invention product TECUN oxide + aluminum oxide + silicic acid. The data for titanium oxide + aluminum oxide + silicic acid of the product of the present invention is as follows:
Since the peak width is wide, it can be seen that the anatase type crystal, which is the crystal form of titanium oxide, remains ungrown. The data for the comparative product, titanium oxide + aluminum oxide, shows that the peak width is narrow, indicating that anatase crystals are growing well.

Next, for these porous membranes, the inlet side pressure s kg/cnI and the outlet side pressure 1 kg for a mixed gas of 50% hydrogen and 50% nitrogen using a gas separation test device.
/cIII, and conducted a gas separation test, and found that the gas composition of the gas after passing through the porous membrane was hydrogen 6, aluminum oxide, titanium oxide, and aluminum silicic acid of the present invention.
7% and nitrogen 55%, whereas in the case of only titanium oxide + aluminum oxide, hydrogen is 54% and nitrogen is 46%, and titanium oxide + aluminum oxide +
It was confirmed that hydrogen permeates through a porous silicic acid membrane.

Also, using the same gas separation test equipment, the inlet side pressure s kg / for a mixed gas of 50% hydrogen and 50% methane
crA, the outlet side pressure was set to 11G9/C11F, and a gas separation test was conducted.
In the case of a porous membrane of aluminum oxide + silicic acid, the gas composition after membrane permeation is 63% hydrogen and 67% methane, whereas in the case of the comparative porous membrane σ) of only titanium oxide + aluminum oxide. The gas composition after membrane permeation is 52% hydrogen.
, methane was 48%, and in this case as well, it was confirmed that the porous membrane of titanium oxide + aluminum oxide + silicic acid of the product of the present invention was permeating a large amount of hydrogen.

As is clear from this example, according to the porous membrane manufacturing method of the present invention, it is possible to obtain a porous membrane that is excellent in shape, strength, and gas separation performance.

Example 2 In Example 1, another commercially available fine particle silicic acid (particle size 20 mμ
A porous membrane was produced in the same manner as in Example 1 except that (2) was used.

For the porous membrane thus obtained, the inlet side pressure s kg/cIII was determined for a mixed gas of 50 g of hydrogen and 50 g of nitrogen using a scum separation test device.

When a gas separation test was carried out with the outlet pressure set at 1 kg/'cdK, the gas composition after permeation through the membrane was 7° hydrogen and 60° nitrogen, and selective permeation of hydrogen was observed.

Example 3 To a mixed solution of titanium tetrachloride (10,100 O in terms of titanium oxide) and sodium aluminate (200 g in terms of aluminum oxide), 100 g of commercially available fine silicic acid as in Example 1 was added, thoroughly stirred and mixed, and then neutralized. Hydrolysis was carried out.Then, an extruder was used to form a mold with a diameter of 4 man and a wall thickness of 1
A 60 cm long tube was formed, dried at 100" for 12 hours, and fired for 6 hours at soo'cvr.

For comparison, a sample having the same composition and thermally hydrolyzed was also molded and fired in the same manner.

In order to use this fired product as a membrane body for waste separation, the pore size distribution was measured by mercury intrusion method, and at the same time, a gas separation test was conducted.

Furthermore, according to the results of X-ray diffraction of the fired body, the crystal form of titanium oxide was rutile type when neutralized and hydrolyzed, and anatase type when thermally hydrolyzed.

Figure 3 shows the results of measuring pore radius and pore volume by mercury intrusion method. In FIG. 3, the horizontal axis is the pore radius and the vertical axis is the pore volume. In the figure, ■ and ■ indicate the pore distribution of the fired body obtained by neutralization hydrolysis and the fired body obtained by thermal hydrolysis, respectively. The pore diameter of the fired body that has become rutile-type titanium oxide is
It can be seen that the pore diameter is larger than that of the anatase-type titanium oxide fired body.

Next, for the porous membrane, using a gas separation test device, the inlet side pressure s kg/crll and the outlet side pressure 1 k, 9/cn for a mixed gas of 50% hydrogen and 50% nitrogen.
A gas separation test was conducted with the temperature set to 1.

The gas composition after passing through the porous membrane was 58% hydrogen and 42% nitrogen in the case of the fired body obtained by neutralization hydrolysis, but it was 58% hydrogen and 42% nitrogen in the case of the fired body obtained by thermal hydrolysis. hydrogen 70
%, and 50% nitrogen.

From this example, when the crystal form of titanium oxide becomes rutile type,
It was found that because the size of the crystal is larger than in the case of the anatase type, the pore radius becomes thicker (and the sludge separation performance becomes worse).

Example 4 Titanium sulfate obtained from the titanium oxide production process using the sulfuric acid method was thermally hydrolyzed to obtain metatitanic acid, 1 kg of this in terms of titanium oxide was taken out, and aluminum isopropylate was hydrolyzed to this to obtain metatitanic acid. 250g of alumina sol in terms of aluminum oxide was mixed. Next, Example 1
After adding 100 g of the same commercially available particulate silicic acid and thoroughly stirring and mixing, an extruder was used to mold a tube with a diameter of 4 mm, a wall thickness of 1 mm, and a length of socm.

For comparison, a tube without alumina sol was also molded.

The two-glaze tube thus formed was dried at 100°C for 12 hours and then fired at 850°C for 5 hours. In order to use this fired product as a gas separation membrane, the pore size distribution was measured by mercury intrusion method, and at the same time, a gas separation test was conducted.

Figure 4 shows the results of measuring pore radius and pore volume by mercury intrusion method. In FIG. 4, the horizontal axis is the pore radius and the vertical axis is the pore volume. Further, in the figure, ■ is data for titanium oxide + aluminum oxide + silicic acid of the product of the present invention, and ■ is data for titanium oxide + silicic acid of the comparative product. When the comparative product 0 alumina sol (aluminum oxide) was not used, the average pore radius was 260A, but by adding the alumina sol (aluminum oxide) of the present invention, the average pore radius was reduced to 15A, It can be seen that the pore distribution is sharp VC.

Next, using a gas separation test device for two types of VC porous membranes, for a mixed gas of 50% hydrogen and 50% nitrogen, the inlet side pressure is 6 g/crd, and the ti30 side pressure is 1 kg/
crd and conducted a gas separation test, the gas composition after passing through the porous membrane was 69% hydrogen and 61% nitrogen in the case of uninvented titanium oxide + aluminum oxide + silicic acid. In contrast, the comparative product titanium oxide + silicic acid contained 60% hydrogen and 40% nitrogen.

This example shows that alumina sol is effective for reducing the pore diameter of a porous body.

[Brief explanation of drawings]

FIG. 1, FIG. 3, and FIG. 4 are charts showing the pore size distribution and pore volume of porous membranes obtained in Examples of the present invention. FIG. 2 is a chart showing the difference in the X-ray N-fold pattern of anatase-type titanium oxide of a porous membrane with and without addition of silicic acid. Sub-agent 1) Clear agent Ryo Hagiwara - Figure ~ Pregnancy (6 mm) - Amount 1 m (15 pieces) Jinho glf' ψ

Claims (1)

[Claims] A method for producing a porous membrane body, which comprises forming a mixture of sol-formed metatitanic acid, alumina sol, and fine-particle silicic acid, drying, and firing.