JPH0679122A - Porous structural body and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a porous structural body for use to separate a specified gas or liquid efficiently from a gas mixture or a liquid mixture. CONSTITUTION:A zeolite layer is formed on a porous support 1 made of a ceramic by mixing zeolite crystal 2 with finely granular ceramic or zeolite and sticking them with an adhesive. The finely granular ceramic or zeolite forms a filling layer 3 in the zeolite layer. To shut the gas ventilation, the surface part of the filling layer 3 is made to be a seal part 4 formed by filling gaps in the layer with the seal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous structure capable of separating a specific gas or liquid from a mixed gas or mixed liquid, and a method for producing the same.

[0002]

2. Description of the Related Art As to a porous structure for gas separation using zeolite, for example, as described in JP-A-63-221815, a zeolite synthesis raw material sol is coated on a porous support, A technique for precipitating zeolite crystals by hydrothermally treating this and then firing it, JP-A-59-213615
As described in JP-A-60-129119, a technique of depositing zeolite on the glass surface in an autoclave using a glass compound as a starting material, or as described in JP-A-60-129119, pores of a porous carrier. There is a technique of embedding zeolite powder in the inside. There is also known a technique in which zeolite raw materials are successively coated on a porous support, and these are sol-ized and then hydrothermally treated to deposit zeolite on the membrane surface.

[0003]

In all of the above-mentioned conventional techniques, a zeolite raw material is coated on a porous support, and then zeolite is deposited by hydrothermal treatment. However, since hydrothermal treatment is generally carried out by high-pressure steam or hot water, there is a drawback that the raw material sol on the porous support is flowed and the zeolite is not uniformly deposited. As a result, the produced gas separation membrane has many zeolite-free portions (defective portions).

Zeolite crystals have a large number of pores that contribute to gas separation, and the diameter of these pores is about several Å.
On the other hand, zeolite crystals are deposited as a crystal with a particle size of about several μm by the hydrothermal treatment, and this crystal has a structure that covers the film surface. However, a gap is formed between the crystals due to the defect. The size of this gap is several 10Å to several μm
Therefore, when used as a gas separation membrane, the gas passes through a wide gap portion rather than narrow pores.
Therefore, it is difficult to improve the gas separation performance.

Further, when zeolite is directly deposited on the porous support as described above, there is a problem that the bond between the porous support and the zeolite crystal is weak and the zeolite is easily peeled off.

[0006]

In order to solve the above-mentioned problems, the present invention comprises zeolite crystals for forming a zeolite layer on a ceramic porous support, finely divided ceramics or zeolite, and a binder. Use the mixture.
Therefore, the formed zeolite layer has a filling portion made of fine particle ceramic or zeolite between the zeolite crystals constituting the zeolite layer. Further, in the present invention, a sealing material is further used to block the ventilation of the filling portion except for the zeolite crystal portion exposed on the surface.

[0007]

[Function] The gap existing between the zeolite crystals in the zeolite layer is filled with fine-grained ceramics or zeolite, and a sealing material is used to block the ventilation of the filled portion, so that the mixture has only the zeolite crystal pores. And is efficiently separated.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is an enlarged partial sectional view showing an example of the porous structure of the present invention. In the figure, a zeolite crystal 2 and fine particle ceramics or zeolite are mixed on a porous support 1 made of ceramic and are bonded by a binder to form a zeolite layer. The ceramic or zeolite forms the packed bed 3. In addition, the surface portion of the filling layer 3 is a sealing portion 4 in which a gap is filled with a sealing material in order to block ventilation except for the zeolite crystal portion exposed on the surface.

The porous support 1 is for supporting the zeolite layer to increase its mechanical strength, and is made of one or more oxides or carbons selected from the group of alumina, silica, zirconia and titania. It is preferably formed.

When the filling layer 3 is formed of fine particle ceramics, it is preferable to use one or more substances selected from the group consisting of alumina, silica, zirconia, titania and carbon. The particulate ceramic or zeolite preferably has an average particle size of 10Å to 1000Å. These fine particles, together with the binder, play the role of binding zeolite crystals to each other and binding of the porous support 1 and the zeolite crystals 2. Since such fine particles have higher reactivity than crystals having a large diameter, they have a strong binding force. It also has the effect of making the gap between the zeolite crystals small and facilitating the formation of the seal portion 4.

The zeolite crystal 2 has an average particle size of 0.1 μm to 10 μm, and the diameter of the pores used for separating gas etc. is on the order of several Å.

The sealing material used in the sealing portion 4 is alumina, silica, zirconia, which is deposited from the gas phase or the liquid phase.
Titania and carbon or carbides such as SiC, Si
It is preferably formed from one or more materials selected from the group of nitrides such as 3N4.

An example of the method for producing the porous structure of the present invention is shown below. (1) Synthesis of Zeolite or the Like Using a metal oxide as a starting material, mixing at a predetermined ratio, and then hydrothermally treated to produce a zeolite crystal 2 and zeolite fine particles. When ceramic fine particles are used, they are produced by a precipitation method from a metal alkoxide, a hydrothermal synthesis method or a coprecipitation method. As these raw materials, commercially available products can be used. When the porous structure of the present invention is used as a filter for a specific molecule, it is preferable to use a zeolite crystal having a pore size slightly larger than this molecular size and a narrow pore size distribution width.

(2) Formation of Zeolite Layer The zeolite crystals 2 and the fine particles are dispersed in a dispersion medium such as water or ethanol, and a binder such as PVA (polyvinyl alcohol), ethyl cellulose or glass is added thereto. Stir well. Then, this mixture is coated on the porous support 1 by a method such as dipping, brushing, spraying, spin coating, and dried. Then this 2
By firing at 00 to 800 ° C., the adhesion between the porous support 1, the zeolite crystals 2 and the packing layer 3 is improved. The zeolite crystal layer thus formed is preferably as thin as possible because pressure loss can be reduced.

(3) Formation of Seal Portion 4 A raw material gas is sent to the porous structure obtained as described above from a vaporizer saturated with a metal alkoxide, and a ceramic is deposited in the packed bed 3 by a vapor phase synthesis method. ,
The seal portion 4 fills the gap of the filling layer 3. As the metal alkoxide, for example, ethyl orthosilicate can be used. In this case, silica is precipitated as a ceramic.

Examples of the use of the porous structure of the present invention formed as described above for separating a mixed gas are as follows: recovery of carbon dioxide gas from the atmosphere or from the exhaust gas of a combustion device, concentration of oxygen in the atmosphere, in air Separation of water vapor (dehumidification), etc. can be considered. Further, as an example used for separating the mixed liquid, a case where water is removed from the ethanol / water mixture that has reached the azeotropic point can be considered.

In the separation of gas etc. by the porous structure of the present invention, the raw material is brought into contact with one side of the porous structure and the other side is depressurized to allow only specific molecules to permeate, or
It is achieved by making only one side high pressure and the other side low pressure or atmospheric pressure to allow only specific molecules to permeate.

The method for separating only specific gas molecules will be specifically described above. In general, zeolite has a characteristic that it selectively adsorbs a molecule having a large polarity such as carbon dioxide because the cation in the crystal exerts an electrostatic attraction effect on the adsorbed gas molecule (polarity of carbon dioxide [quadrupole Moment: (Q / e) A ² ] is 0.65, whereas nitrogen is 0.27). An adsorbent such as zeolite has a property of adsorbing at low temperature and high pressure and desorbing at high temperature and low pressure. Utilizing these properties, one side of the porous structure is adsorbed with, for example, carbon dioxide at a relatively high pressure, atmospheric pressure or low temperature, and the other side is brought to atmospheric pressure, reduced pressure or high temperature, so that carbon dioxide is adsorbed It is desorbed, separated, and collected.

[0019]

As described above, according to the porous structure of the present invention, the mixed gas, the mixed liquid, or the like passes through only the pores of the zeolite crystal, and is efficiently separated.
Further, according to the production method of the present invention, the adhesiveness between the zeolite crystals and between the zeolite crystals and the porous support becomes good, so that a porous structure having high mechanical strength can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged partial sectional view showing an example of a porous structure of the present invention.

[Explanation of Codes] 1 ... Porous support, 2 ... Zeolite crystal, 3 ... Packed bed,
4 ... Seal part.

Claims (7)

[Claims] 1. In a porous structure in which a zeolite layer is formed on a ceramic porous support, fine particles of ceramic or zeolite are filled in the gaps between the zeolite crystals constituting the zeolite layer, and The porous structure is characterized in that the ventilation of the filled portion is blocked by a sealing material except for the zeolite crystal portion exposed on the surface. 2. The ceramic porous support according to claim 1, wherein the porous ceramic support is formed of one or more oxides or carbons selected from the group consisting of alumina, silica, zirconia, and titania. Porous structure. 3. The fine particle ceramic is formed of one or more kinds of substances selected from the group consisting of alumina, silica, zirconia, titania and carbon. Porous structure. 4. The zeolite crystals have an average particle size of 0.1 μm to 10 μm.
4. The porous structure according to any one of items 1 to 3. 5. The porous structure according to claim 1, wherein the particulate ceramic or zeolite has an average particle diameter of 10Å to 1000Å. 6. The sealing material is formed of one or more substances selected from the group consisting of alumina, silica, zirconia, titania and carbon or carbides, nitrides deposited from a gas phase or a liquid phase. The porous structure according to any one of claims 1 to 5, wherein 7. A method for producing a porous structure in which a zeolite layer is formed on a ceramic porous support, wherein a mixture containing zeolite crystals, finely divided ceramics or zeolite, and a binder is applied onto the support.・ Dry
Baking, and further, the part filled with the fine-grained ceramic or zeolite formed in the gap of the zeolite crystal by the above means is sealed with a sealing material except the part of the zeolite crystal exposed on the surface to block the ventilation. A method for producing a porous structure, comprising: