JPS61212309A - Gas separation process - Google Patents

Abstract

PURPOSE:To obtain a material for separating gaseous mixture having superior heat resistance by coating a soln. contg. alkoxysilane and a boron compd. on the surface of a porous ceramic, calcining and treating with acid to elute the boron oxide. CONSTITUTION:A sintered body consisting primarily of alumina, iron oxide, TiO2, etc. having <=5mum mean pore size is used as supporting body. A porous glass film is formed on the surface of said supporting body. Alkoxysilane is used for the silica source of the glass and a boron compd. such as boric acid, borax, etc. is used for the component for forming fine pores. These materials are dissolved in water or alcohol, and the soln. is coated on the supporting body. Silica glass is formed after drying and calcination and phase separation of boron oxide is caused simultaneously. The boron oxide is eluted with HCl or H2SO4 and fine pores are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas separation method, and more specifically, the present invention relates to a gas separation method. This invention relates to a method for efficiently separating a mixed gas into its components using a fractionation material with excellent properties.

Conventional technology: In recent years, the development of separation technology using porous membranes has been remarkable, such as reverse osmosis, ultrafiltration, electrophoresis, etc., to separate solutes and solvents in solutions, and to separate each solute. technology,
Alternatively, a technique for separating a mixed gas into each component using the porous membrane has been put into practical use.

Conventionally, the fractionation materials used in such separation techniques include inorganic fractionation materials made of porous ceramics and organic fractionation materials made of organic polymer compounds such as cellulose acetate, polyacrylonitrile, polybenzimidazole, and polyamide. Are known.

However, with inorganic fractionation materials, it is difficult to form thin films with micropores on the order of angstroms, so their applications are inevitably limited, and organic fractionation materials cannot withstand high temperatures. Moreover, it is easy to cause compaction, and in addition, the membrane must be thick in order to withstand high pressure, which has disadvantages such as a lack of permeation flux.

In addition, there is a fractionating material developed by the present inventors that has a structure in which a semipermeable organic polymer compound layer is laminated on the surface of porous ceramics (Japanese Patent Application No. 58-81562), but this material uses an organic material. Due to the nature of the material, it has drawbacks in heat resistance and durability, which inevitably limits its uses.

Problems to be Solved by the Invention The purpose of the present invention is to overcome the drawbacks of conventional fractionation materials and to provide a fractionation material with excellent heat resistance and durability that exhibits stable performance under any usage conditions. An object of the present invention is to provide a method for efficiently separating a mixed gas into each component using a hammer.

Means for Solving the Problems As a result of intensive research, the present inventors used an alkoxysilane as a silica source and a boron compound as a micropore-forming component, and applied a solution containing these to the surface of porous ceramics. The fractionation material obtained by coating it on the glass, baking it to form a complete glass film, and treating it with acid to elute the boron oxide present in it,
It is composed only of inorganic materials, has uniform and fine communicating pores, and has excellent heat resistance and durability.We discovered that the above purpose could be achieved by using this material, and based on this knowledge, we created this book. The invention was completed.

That is, in the present invention, when a mixed gas gold containing two or more components with different molecular weights is separated into the respective components by a differential pressure permeation method using a fractionation material, the fractionation material has an average pore diameter of 0, To provide a gas separation method characterized in that the surface of porous ceramics of 5 μm or less is coated with a solution containing an alkoxysilane and a boron compound, heated and fired, and then treated with an acid.

In the method of the present invention, the porous ceramic used as the support for the fractionation material can be arbitrarily selected from those used as supports for ordinary ceramic-based fractionation materials. Examples of such materials include alumina,
Examples include all sintered bodies whose main components are iron oxide, titanium oxide, magnesium oxide, silica, etc. Usually, this support has an average pore diameter of 5 μm or less, and the pore diameter may be realized in a single structure or in a multilayer structure. Then, on the surface, oxide particles with an average particle diameter of about 065 μm, for example, alumina particles of about 30 μm, are added to the surface.
It is used as a plate or tube with a thickness of ~1 own.

On the other hand, the bath liquid used to form a porous glass film on the surface of this ceramic support contains alkoxysilane as a silica source for producing glass by firing, and a mixture of alkoxysilane, which forms micropores in the produced glass layer. A solution containing all the boron compounds added as components for display is used.

The alkoxylan used in the present invention is a compound represented by the general formula 8 (in the formula, R and I are an alkyl group, and n is an integer of 1 to 4), and this is a compound represented by the general formula Any of alkoxysilane, dialkoxysilane, and monoalkoxysilane may be used. Examples of such compounds include tetramethoxysilane, monomethyltriethoxysilane, tetraethoxysilane, monoethyltriethoxysilane, and the like.

Further, as the boron compound, soluble compounds such as boric acid, metaboric acid, and borax are used.

These alkoxysilanes and boron compounds are dissolved in a suitable solvent and used as a solution, and the solvent in this case is usually water, alcohol, or a mixture thereof. The concentration of alkoxysilane in this solution is 10
~40% by weight, the concentration of boron compounds is 0.3-5% by weight
It is desirable to choose within the range. In addition, in order to obtain an appropriate distribution of micropores in the porous glass layer to be produced, the weight ratio of the boron compound to the alkoxysilane should be adjusted to 510, respectively.
It is preferable that the ratio is in the range of 50:1 to 4:1 in terms of 2 and B2O3.

In addition, a small amount of a mineral acid such as hydrochloric acid or an organic acid such as acetic acid may be added to this solution in order to promote the dissolution of each component and the reaction between each component.

The amount of these added is selected within the range of 0.1 to 1.0% by weight based on the total amount of the solution.

Any method such as dipping, coating, or spraying can be used to coat the porous ceramic surface of the support with this solution, but it is possible to form a uniform film on the surface and control the film thickness. It is preferable to use dipping because it is easy to use.

The fractionation material used in the method of the present invention can be obtained by coating the surface of a porous ceramic with a predetermined solution in this manner, followed by drying, baking, and then acid treatment. The firing treatment is usually performed by heating at a temperature of 450 to 700°C for 30 minutes to 5 hours. Through this treatment, the alkoxysilane is decomposed to produce silica glass, and at the same time, a phase separation phenomenon of boron oxide occurs.

On the other hand, acid treatment is performed by bringing the thus produced glass film into contact with a mineral acid such as hydrochloric acid or sulfuric acid. Through this treatment, phase-separated boron oxide is eluted and micropores are formed. This acid treatment may be carried out at room temperature, but in order to shorten the total treatment time, it is advantageous to carry out the acid treatment at a temperature of 70° C. or higher.

After the acid treatment in this manner, the material is washed with water and dried to obtain a fractionation material having micropores with a pore diameter of 20 to 150 A.

In addition, the thickness of the porous glass membrane can be adjusted by repeating the cycle of coating with a predetermined solution, drying, and firing.
It can be increased appropriately.

For example, FIG. 1 of the accompanying drawings shows tetraethoxysilane 28
．． 7 parts by weight of ethanol, 43.2 parts by weight of water, 27.2 parts by weight of water, 0.3 parts by weight of hydrochloric acid, and 0.6 parts by weight of boric acid to form a glass layer and the number of coatings and film. This is a graph showing the relationship between thickness (μm), and as is clear from the graph, the film thickness increases regularly as the number of coatings increases.

The fractionation material obtained by such a method can be further heat-treated at a temperature of 900 to 1200°C to reduce the pore size of the glass membrane.

In the method of the present invention, a mixed gas gold containing two or more components having different molecular weights is separated into each component using the fractionation metal produced in this way. This gas separation is
This can be carried out in the same manner as gas separation, which is normally carried out using a porous membrane. −j In other words, a pressure difference is created between the mixed gas side (non-permeated side) and the permeated side by sandwiching the fractionating material, and the mixed gas is separated into molecules by the porous glass layer provided on the fractionating material. separate into each component.

At this time, as a method of generating a pressure difference, the pressure on the mixed gas side may be increased, the permeate side may be depressurized, or both may be performed simultaneously. Moreover, either a batch method or a continuous method can be employed.

Effects of the Invention The fractionation material used in the method of the present invention uses alkoxysilane as a silica source and boron compound gold as a micropore-forming component, and after coating the surface of porous ceramics with a solution containing these, it is fired to form glass. It is obtained by forming a film and treating it with acid to elute the boron oxide present therein. It is made of only inorganic materials, and has uniform and fine communicating pores. It has excellent durability.

The method of the present invention uses the fractionation material to separate a mixed gas containing two or more components with different molecular weights into their respective components. For example, the mixed gas has a volume ratio of methane and carbon dioxide. When using 1=1, the separation coefficient is approximately 1.5 gold at room temperature and a differential pressure of 0.5 Kg/cdi, and the fractionation material used is highly heat resistant and durable. This is an excellent method, as it allows gas separation to be performed even under severe conditions.

Example Next, the present invention will be explained in more detail with reference to examples.

For the gas separation experiment, a Kongo apparatus as shown in Figure 2 was used.

In Fig. 2, 1 is a component gas cylinder for preparing a mixed gas, 2 is a pressure regulator, 3 is a flow meter for measuring the total flow rate of component gases, 4 is a pressure gauge, 5 is a mixed gas cylinder, and 6 is a gas cylinder. A cell for performing separation, 7 a holder for gas sampling, 8 an oil seal, 9 a mercury manometer, 10 and 12 a trap, 11 a rotary vacuum pump, 13 a near compressor, and 14 a system for moving droplets. It is a graduated capillary tube that can measure permeation flux.

Further, a cross-sectional view of the gas separation cell 6 is shown in FIG. 3(A), and a cross-sectional view of the fractionating material is shown in FIG. 3(B). In the figure, reference numeral 21 is a fractionating material for separating gas, 22 is a sealing material made of epoxy resin, and 23 is a gas impermeable material in which the surface of clay is covered with a glass film.

24 and 25 indicate the mixed gas inflow side and the permeate gas side, respectively.

Note that all experiments were conducted at room temperature.

EXAMPLE Preparation of fractionation material A coating solution having the composition shown in Table 1 was prepared using tetraethoxydisilane, ethanol, water, hydrochloric acid, and boron oxide or boric acid. Then, the average pore diameter is 0.5
Porous alumina sintered tube gold of μm size was immersed in the above solution, then gradually pulled up, dried at room temperature for about 2 minutes, and heated and fired at 500°C for 1 hour using an electric furnace to form a glass film. I let it happen. These soaking, drying, and firing operations i
After repeating this process 10 times to make the total film thickness of the glass film 50 μm or more, the glass film was immersed in 5% hydrochloric acid maintained at about 70° C. for 1 hour to elute the phase-separated boron oxide and washed with water.

In this way, a fractionation material made of porous ceramics laminated with porous glass layers having micropores with a pore diameter of 60 to 10 A was obtained.

Next, this fractionation material was placed in an electric furnace and heated at 1000°C for 30
By reheating for a minute, a fractionated material having micropores with a pore diameter of 30 to 50^ was obtained. The physical properties of the fractionation material are shown in Table 1 along with the composition of the coating solution.

Gas Separation A gas separation experiment was conducted using an apparatus in which the fractionation material obtained as described above was set as shown in FIG. 3, and this gas separation cell was arranged as shown in FIG.

First, the mixed gas cylinder 5 is evacuated using the rotary vacuum pump 11, and then methane gas and carbon dioxide gas are injected into the mixed gas cylinder from the component gas cylinder 1 so that the CH42CO□ ratio is 1:1 (capacity ratio ) was prepared. Next, this mixed gas flowed into the gold gas separation cell 6, and a gas separation experiment was performed by creating a pressure difference between the mixed gas side and the permeated gas side. Permeation flux was measured by capillary tube 14, and gas composition was analyzed by certified gas chromatography.

Also, regarding pure methane gas and carbon dioxide gas,
Using the above device, the permeation flux and permeation coefficient were determined.

Table 2 shows the relationship between the differential pressure, permeation flux, and permeation coefficient for pure methane gas and carbon dioxide gas when using the 71L3 fractionation material.

Also, & 3 minute painting supplies? The relationship between the differential pressure and permeation flux for pure methane gas and carbon dioxide gas when using
This is shown graphically in the figure. In the figure, A is methane gas and B is carbon dioxide.

Tables 2 and 3 show the relationship between the differential pressure and separation performance of each fractionating material when a mixed gas with a methane/carbon dioxide volume ratio of 1=1 is used.

In addition, the relationship between the differential pressure and the separation coefficient, the relationship between the differential pressure and the permeability coefficient, and the relationship between the differential pressure and the total flux in each fractionation material when using a mixed gas with a methane-di-carbon dioxide volume ratio of 1:l. The relationships are shown graphically in FIGS. 5, 6, and 7, respectively. In each figure, C is the case where the 3-part fraction material is used, D is the case where the 2-part fraction material is used, and E is the case where the 1-part fraction material is used. In FIG. 6, the solid line is for carbon dioxide, and the broken line is for methane.

From these results, the separation coefficient decreases as the differential pressure increases in any fractionation material, and in the A3 fractionation material, the separation coefficient reaches its maximum of about 1.5 when the differential pressure is 0.5 Kg/-. 'I see what you mean.

A fractionating material was prepared in the same manner as in the example, except that no boron compound was used in the coating solution in the preparation of the fractionating material in the comparative example example series.

Using this fractionation material, a gas separation experiment was conducted in the same manner as in the example, but this material did not transmit any gas at all.

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of the relationship between the number of coatings and the thickness of a porous glass film in the fractionating material according to the present invention. Figures 2, 3 (A) and 3 (B) are an explanatory view of the apparatus used in the gas separation experiment, a cross-sectional view of the gas separation cell and the fractionation material, and the reference numeral 5 in the figure shows the mixed gas. 6 is a gas separation cell, and 21 is a fractionation material. Furthermore, FIG. 4 is a graph showing an example of the relationship between differential pressure and permeation flux in pure methane gas and carbon dioxide gas when using the fractionation material according to the present invention, and FIGS. and Figure 7 show the relationship between differential pressure and separation coefficient, and the relationship between differential pressure and permeability coefficient, respectively, when the fractionation material according to the present invention is used to separate a mixed gas with a methane/carbon dioxide volume ratio of 1 to 1. It is a graph which shows an example of the relationship and the relationship between differential pressure and total flux. Figure 3 (AJ
(B) Fig. 4 ∆P CKg/crn') Fig. 5 Yuka expression (Kg/cm2) Fig. 6 Work force breath ∆P [Kglc〆]

Claims (1)

[Claims] 1 When a mixed gas containing two or more components with different molecular weights is separated into each component by differential pressure permeation method using a fractionation material, the fractionation material has an average pore diameter of 0.5μ.
1. A gas separation method characterized in that the surface of a porous ceramic having a diameter of 1.5 m or less is coated with a solution containing an alkoxysilane and a boron compound, heated and fired, and then treated with an acid.