JPH07112530B2 - Method for producing ceramic membrane for separating condensed components - Google Patents

Description

The present invention relates to a method for modifying a ceramic membrane used for separating condensable components.

[Conventional technology]

So far, a method for producing a ceramic porous membrane for separating condensed components has been proposed, in which the size and shape can be freely selected and the pore diameter is also very small, about 10Å. No. 60-30546). This method involves impregnating the alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate into the pores of the ceramic porous body, immersing it in an aqueous sodium silicate solution, and further steaming in high temperature steam to separate condensed components. This is a method of producing a ceramic membrane, and the membrane produced by this method is highly hydrophilic because it is made of an alumina-based material and has a property of selectively permeating water.

[Problems to be solved by the invention]

Therefore, the above-mentioned ceramic porous membrane for separating condensed components (hereinafter, abbreviated as ceramic porous membrane) has extremely good performance as a selective permeation membrane for water, but is not suitable for permeation of other substances such as an organic solvent. It was not always suitable.

[Object of the Invention]

The present invention intends to provide a method for improving the ceramic porous membrane to provide a method for producing a ceramic membrane for separating a condensed component in which the permeability of an organic solvent is increased.

[Means for solving problems]

The inventors of the present invention have conducted extensive studies on a method of suppressing the selective permeability of water in a ceramic porous membrane and imparting the selective permeability of an organic solvent to the porous membrane, and as a result, the Japanese Patent Application No. 60-30546.
It was confirmed that the above object can be achieved by further treating the ceramic film for separating condensed components obtained by the production method proposed in the above-mentioned publication with alkoxyalkylsilane, and the present invention has been completed.

That is, the present invention, after impregnating alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate in the pores of the ceramic porous body, immersed in an aqueous solution of sodium silicate, treated in high temperature steam, A method for producing a ceramic film for separating condensed components, characterized by dipping in an alkoxyalkylsilane.

[Action]

That is, by treating the previously proposed ceramic porous membrane with an alkoxyalkylsilane, the hydroxyl groups present on the surface of the porous membrane and the alkoxysilane are condensed, and an alkyl group is introduced through a siloxane bond. The alkyl group increases the affinity between the ceramic porous membrane and the organic solvent, so that the selective permeability of water in the porous membrane is suppressed and the selective permeability of the organic solvent is imparted to the porous membrane. Result.

The alkoxyalkylsilane referred to here is The compound represented by the following chemical formula (wherein R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups such as methyl group and ethyl group).

The treatment of the ceramic porous membrane with the alkoxyalkylsilane is carried out by adding 0.1% of the porous membrane to a solution of the alkoxyalkylsilane or the alkoxyalkylsilane at room temperature to 100 ° C.
Dip for ~ 24 hours to complete.

In addition, even if an alkoxyalkylsilane is added to water to change the alkoxy group into a silanol group, and then the ceramic porous membrane is immersed in this aqueous solution, the alkyl group is similarly introduced to the surface of the porous membrane through a siloxane bond. However, since this treatment method may produce a water-insoluble siloxane oligomer as a by-product, it is not recommended so much.

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

[Example 1] 5 g of aluminum isopropoxide was added to 100 g of water kept at 80 to 90 ° C to hydrolyze aluminum isopropoxide. To this, add 0.6 ml of concentrated nitric acid,
It was kept at 0 ° C. for 24 hours and peptized to obtain an alumina sol.

This alumina sol has a pore diameter of 1500Å and a pore volume of 0.18cc
A cylindrical alumina porous sintered body having a diameter of 10 mm, a thickness of 1 mm, and a length of 150 mm, sealed at one end, was dipped for 5 minutes, and then dipped in a 0.1 mol / sodium silicate aqueous solution for 1 minute. It was left in steam at 100 ° C for 1 hour. After repeating this operation 4 times, the alkali was washed away by immersing in hot water at 90 ° C. for 1 minute to obtain a ceramic porous membrane.

The relationship between the relative humidity and the amount of water vapor adsorbed at 32 ° C. was investigated for this ceramic porous membrane.
%, 50%, 80% the dimensionless water vapor adsorption amount is 0.
It was 3, 0.7, 1.0. The pore radius (condensing radius) when a certain component starts to condense is the Kelvin formula Given in. Here, r is the radius of condensation, V is the molecular volume of the liquid, σ is the surface tension of the liquid, R is the gas constant, T is the absolute temperature, Po is the saturated vapor pressure, and P is the pressure that causes capillary condensation.
Since the relative humidity is expressed by 100P / Po, the aggregate diameters for the relative humidity of 13%, 50%, and 80% are calculated from the Kelvin equation to be 10Å, 30Å, and 92Å, respectively. It is clear that it has pores of.

The ceramic porous membrane described above (hereinafter referred to as the precursor porous membrane) was treated and modified as follows according to the method of the present invention.

First, the precursor porous membrane was dried under reduced pressure of 2 mmHg at 60 to 70 ° C for 4 hours, and then dried with 600 ml of 100 ml of dehydrated benzene.
It was immersed in a solution containing methoxytrimethylsilane.

After maintaining the temperature of the above solution at 55 ° C. and stirring the liquid phase for 24 hours, the treated precursor porous membrane was taken out and dried at room temperature under reduced pressure of 2 mmHg for 4 hours, and then subjected to the method of the present invention. A modified ceramic porous membrane (hereinafter abbreviated as modified ceramic porous membrane) was obtained.

Example 2 The precursor porous film shown in Example 1 was treated in exactly the same manner as in Example 2 except that trimethoxy (methyl) silane was used in place of methoxytrimethylsilane to obtain a modified ceramic porous film.

Next, with respect to the precursor porous membrane shown in Example 1 and the modified ceramic membrane shown in Examples 1 and 2, the open end of the cylindrical membrane was connected to a vacuum pump, and the other closed end was connected. 25 ° C
The permeation rate of perchlorethylene and water when the inner diameter of the cylindrical membrane was reduced to 2 mmHg was measured by immersing it in perchlorethylene and water. The measurement results are shown in Table 1.

According to the results shown in Table 1, the precursor porous membrane shown in Example 1 has a higher water permeation rate than perchlorethylene, but the modified ceramic porous membrane and Example described in Example 1 In the modified ceramic porous membrane described in 2, the permeation of water is suppressed, and the permeation rate of perchlorethylene is high. Therefore, the method of the present invention is used to suppress water permeation of a porous ceramic membrane and perchlorate. It is clear that it is effective in increasing the permeability of ethylene.

[Effects of the Invention] As described above, the ceramic porous membrane obtained by the method of the present invention has the property of suppressing the permeability of water and increasing the permeability of organic solvents, The ceramic porous membrane modified by 1. is extremely useful for separating various organic solvents including the recovery of perchlorethylene as a dry cleaner detergent.

Claims (1)

[Claims] 1. Pores of a ceramic porous body are impregnated with an alumina sol obtained by hydrolyzing an aluminum alcoholate or an aluminum chelate, then immersed in an aqueous solution of sodium silicate, treated in high temperature steam, and further 1. A method for producing a ceramic membrane for separating condensed components, which comprises dipping in an alkoxyalkylsilane.