JPH0516892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a ceramic membrane used for separating condensable components.

(Prior art) Porous material having ultra-fine pores with an average pore diameter of several tens to several hundreds of angstroms, made by sintering metal powder or ceramic powder, or compression molding organic synthetic resin powder such as fluororesin. It has been difficult to mold the diaphragm into an arbitrary shape for use in separation.
Therefore, in many cases, the above-mentioned thin porous membrane with micropores is reinforced with a porous material or wire mesh-like material with a certain thickness and high gas permeability in order to have sufficient strength, resulting in a multilayer structure. Measures are being taken to

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. Gluing is being done. 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. In addition, since porous metals are porous bodies even if they are metals, their strength is lower than that of non-porous bodies due to the presence of pores, and there is a limit to the radius of curvature that can be formed into a circular shape. It was extremely difficult to mold it into a shape.

Therefore, as a method to solve these 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. while giving
Gas is ejected into the cavity between the porous support tube and the pipe or core metal to uniformly fill the cavity with powder, and the powder filled in the cavity is applied to the porous support tube under static pressure. A method of forming a tubular porous membrane is known in which a porous membrane is compressed by molding to form a compressed layer of powder on a porous support tube (see Japanese Patent Application Laid-Open No. 77410/1983). In practice, there are many difficulties, such as creating very thin films.

(Problems to be Solved by the Invention) The present invention was made in view of the current situation, and allows the size and shape to be freely selected, and the pore diameter is approximately 10 Å, which is extremely large. The present invention provides a method for manufacturing a ceramic porous diaphragm having a small pore diameter.

(Means for Solving the Problems) The present invention involves impregnating an alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate into the pores of a porous ceramic material, and then impregnating the material with an aqueous solution of sodium silicate. The present invention relates to a method for manufacturing a ceramic membrane for separating condensed components, which is characterized by steam treatment in steam.

More specifically, the present invention involves impregnating the pores of a ceramic porous body with an alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate, and then impregnating it with a 0.01 to 0.5 mol/aqueous sodium silicate solution. Furthermore, the present invention relates to a method for producing a ceramic membrane for separating condensed components, which comprises steam treatment for 0.5 to 5 hours in steam at 95 to 100°C.

In the method of the present invention, first, an aluminum alcoholate or an aluminum chelate compound is applied to a porous base material of any shape having relatively large pores (usually 1000 Å or more in pore diameter) such as foamed silica, sintered alumina, and mullite. After being impregnated with alumina sol (AlOOH) obtained by hydrolyzing , it is impregnated with an aqueous solution of sodium silicate and kept in high-temperature steam. Next, it is immersed in normal water to wash and remove alkaline components.

The pores are filled by the above operation. A single operation may cause cracks due to drying shrinkage, and the pores cannot be completely filled with the sol, so repeating the process several times will complete the process.

Examples of aluminum alcoholates used in the present invention include aluminum isopropoxide and aluminum-2-butyrate, and examples of aluminum chelates include aluminum tris (ethylacetoacetate) and ethylacetoacetate aluminum diisopropylate.

According to the method of the present invention, it is possible to produce a ceramic membrane having pores with a pore diameter of 10 Å or less.

By using the ceramic membrane obtained by the method of the present invention, it is possible to separate condensable components in a gas. For example, in order to separate moisture (water vapor) from the air, one side of a ceramic membrane is filled with air containing water vapor, and the other side of the membrane is vacuumed.
Moisture in the air condenses in the pores and comes out on the vacuum side, reducing the amount of water vapor in the air. Possible uses for such a membrane include use in a dehumidifying device in a closed system.

(Effects of the Invention) The ceramic membrane obtained by the method of the present invention has good separation performance for condensable components, although the performance varies slightly depending on the gas temperature and the content of condensable components. The method for producing the membrane is also easy, and the present invention is industrially useful.

Examples of the present invention are shown below.

Example 1 After mixing kaolin and graphite at a weight ratio of 2:1, water was added to form a mixture with a diameter of 12 mm and a thickness of 1.2 mm.
mm, and a length of 12 cm, a clay tube with one side plugged was molded. After drying this indoors, the temperature was raised to 1250°C at a rate of 200°C/h and held at 1250°C for 10 hours to obtain a fired clay body. The firing atmosphere was air. As a result, the pore diameter was 0.8 μm.
(8000Å), pore volume 0.2cc/g, shape 10mm in diameter
A porous sintered body measuring 1 mm in thickness, 1 mm in length, and 10 cm in length was obtained.

5 g of aluminum isopropoxide was added to 100 g of water maintained at 80 to 90° C., and the aluminum isopropoxide was hydrolyzed. To this, 0.6 ml of concentrated nitric acid was added, and the mixture was kept at 80 to 90°C for 24 hours to peptize and obtain an alumina sol. The porous sintered body obtained above was immersed in this alumina sol for 5 minutes, then immersed in a 0.1 mol/aqueous sodium silicate solution for 1 minute, and kept in steam at 100°C for 1 hour. After repeating this operation four times, it was immersed in hot water at 90°C for 1 minute to wash and remove the alkali.

The pore distribution of the finally obtained microporous ceramic material was determined by water vapor adsorption, and the results are shown in FIG.
In FIG. 1, the horizontal axis is the relative humidity, and the vertical axis is the dimensionless water vapor adsorption amount. Note that this measurement was performed at 32°C, and the values of 94 Å, 24 Å, and 10 Å in the figure are pore diameters determined from the Kelvin equation regarding capillary condensation. From this figure, it is clear that the ceramic membrane prepared by the method of the present invention has pores of 10 Å or less. That is, the Kelvin equation gives the pore radius (condensation radius) when the components begin to condense, and is expressed by the following equation.

r=2Vσ/RTln (P/P ₀ ) where r: Condensation radius σ: Surface tension of liquid V: Molecular volume of liquid P ₀ : Saturated vapor pressure P: Pressure that causes capillary condensation The relative humidity at a certain temperature is the pressure Expressed as P/P ₀ , the pore radius can be obtained by calculating by entering these values into the Kelvin equation. 1st
In the figure, 10Å, 24Å, and 94Å shown with arrows are
These are the condensation radii for the relative humidity of 13%, 50%, and 80%, respectively, and since condensation adsorption is clearly observed at 10 Å, it can be seen that a pore diameter of 10 Å was formed in the present invention.

Regarding this ceramic membrane, a condensable component separation performance evaluation test was conducted using a water vapor separation test apparatus shown in FIGS. 2A and 2B. In FIG. 2A, 1 and 2 are corrugated pipes for gas heating, 3 and 4 are condensable component gas addition parts, and in the case of this test, water (steam) was used as the condensable component. 5 is a condensable component separation section, 6 and 7 are condensable component condensation sections, and 8 is a vacuum pump. FIG. 2B is an enlarged view of the membrane portion of the condensable component separation section 5. FIG. In the figure, 9 is alumina having fine pores filled in pores 11, and 10 is a base material.

The test was conducted by impregnating nitrogen gas with water vapor using the gas heating coil 1 and the condensable component adding section 3, and then evacuating the nitrogen gas using the vacuum pump 8 through the ceramic membrane 5. Here, the ceramic film 5
The water vapor that has passed through the condensable component condensing section 6
Or it is condensed with liquid nitrogen filled in 7.
The water permeation rate was then measured by weighing the condensed water.

Figure 3 shows the results of measuring the water permeation rate. In FIG. 3, the horizontal axis is relative humidity (%), the vertical axis is permeation rate (mol/m ² h), and the measurement temperature was 76.2°C. In FIG. 3, curve 1 is the water vapor permeation rate, and curve 2 is the nitrogen permeation rate. As is clear from FIG. 3, at relative humidity of 20% or more, the water vapor permeation rate is greater than the nitrogen permeation rate. Furthermore, as the relative humidity increases, the water vapor permeation rate increases and the nitrogen permeation rate decreases.

Example 2 An alumina porous sintered body with a pore diameter of 1500 Å and a pore volume of 0.18 cc/g was impregnated with alumina sol three times in the same manner as in Example 1, and then impregnated with a 0.2 mol/sodium silicate aqueous solution. The operation of immersing the sample for a minute and holding it in steam at 100°C for 1 hour was repeated four times. The water vapor equilibrium adsorption curve (32°C) of the obtained ceramic membrane is shown in Figure 4. In Figure 4,
The horizontal axis is the relative humidity (%), and the vertical axis is the dimensionless water vapor adsorption amount. Value of pore diameter according to Kelvin formula10
Å, 24 Å are shown in the figure. As a result of water vapor equilibrium adsorption curve measurement, the pore diameter of the ceramic porous material obtained was
It became clear that the diameter was smaller than 10 Å.

Next, the resulting ceramic membrane was subjected to a condensable component (water vapor) separation performance test in the same manner as in Example 1. The test results are shown in Figure 5. In FIG. 5, the horizontal axis is relative humidity (%), and the vertical axis is permeation rate (mol/m ² ·h). In Figure 5, ○ is
Water vapor at 76.8℃, △ is air at 76.8℃, ● is 58.0℃
water vapor, △ is the air permeation rate data at 58.0℃. In this case as well, it has become clear that at relative humidity levels of 20% or higher, more water vapor permeates than air. Furthermore, as the humidity increases, the air permeation rate decreases, but the water vapor permeation rate increases. Furthermore, when comparing the amount of water vapor permeation due to humidity, it was found that the amount of water vapor permeation at 76.8°C was greater than the amount of water vapor permeation at 58.0°C, indicating that the higher the humidity, the greater the amount of water vapor permeation.

[Brief explanation of the drawing]

Figures 1 and 4 are diagrams showing water vapor equilibrium adsorption curves of ceramic membranes prototyped according to the method of the present invention, and Figure 2A is a diagram showing condensability curves for evaluating the ceramic membrane obtained by the method of the present invention. FIG. 2B, a schematic diagram of the component separation test apparatus, is a partially enlarged view of FIG. 2A. 3 and 5 are diagrams showing the results of a gas permeation test using a prototype ceramic membrane.

Claims (1)

[Claims] 1. A condensed component characterized by impregnating the pores of a ceramic porous body with an alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate, then impregnating it with an aqueous sodium silicate solution, and further steaming it in high-temperature steam. A method for producing a ceramic membrane for separation.