JPH0393634A - Preparation of porous sintered product having open pores - Google Patents

Abstract

PURPOSE:To prepare a porous sintered product capable of being precisely controlled the sizes and shapes of opened pores thereof and useful as a catalyst carrier, etc., by sintering a mixture of a glass basic material powder and a carbonaceous material in a reducible atmosphere and subsequently burning the carbonaceous material in an oxidizable atmosphere. CONSTITUTION:Solid glass powder, a glass raw material for a sol-gel method, ceramic powder, etc., is mixed with a carbonaceous material, advantageously carbon such as graphite or a porous carbon such as charcoal or active carbon. When the solid glass powder is used, the carbonaceous material is usually mixed in a mixing ratio of 1-2500 pts.wt. per 50 pts.wt. of the basic material. The mixture is sintered under a reducible condition to prepare a sintered mixture wherein the carbonaceous material exists in the state mixed in the basic material. Although the carbonaceous material in the reduced sintered product can be sufficiently burnt in an oxidizable atmosphere, the reduced sintered product is held in the oxidizable atmosphere at a temperature not melting and changing the mixture to provide the porous sintered product.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a porous sintered body having open pores, and more specifically, to a method for manufacturing a porous sintered body having open pores, and more specifically, to a method for manufacturing a porous sintered body having open pores, and more specifically, a method for manufacturing a porous sintered body having open pores, and more specifically, a method for manufacturing a porous sintered body having open pores. The present invention relates to a method for manufacturing a porous sintered body.

[Conventional technology]

Conventionally, as a method for producing a porous sintered body having open pores, for example, methods (1) and (2) below are known.

(1) A method of using glass with a particle size that matches the pore diameter of the porous sintered body to be obtained, and firing at a temperature that allows the glass particles to bond with each other and not collapse the pores between the particles.

[2] A mixture of a glass or ceramic base material and a substance that is solid at the firing temperature and is soluble in water, preferably salts, is sintered in the air or in an oxidizing atmosphere, and then sintered. A method of producing a porous body by dissolving the fusible substance with water after completion of solidification.

[Problem to be solved by the invention]

However, with method +1) above, the appropriate firing temperature range is narrow, and the firing temperature varies greatly depending on the properties of the base material. It is not possible to manufacture products with high porosity. There are drawbacks such as less freedom in the shape of the pores.

In addition, in the method (2) above, since pores are obtained after burning, a separate elution treatment with a solution is required, which has the drawback of complicating the equipment and process and increasing costs.

Furthermore, since there is a possibility that the soluble substance may react with the base material, there is a drawback that the range of selection of the base material is narrowed and the firing temperature is also restricted.

An object of the present invention is to eliminate such conventional drawbacks and provide a method for manufacturing a porous sintered body in which the size and shape of open pores can be precisely controlled over a wide range.

[Means to solve the problem]

In order to solve the above problems, in the present invention, a raw material mixture consisting of at least one base material selected from the group consisting of a solid glass powder and a glass raw material for sol-gel method and a carbonaceous material is prepared under reducing conditions. sintering to produce a sintered mixture;
The method is characterized in that the sintered mixture is then heated in an oxidizing atmosphere to burn the carbonaceous material while maintaining the shape of the sintered mixture. In the present invention, first, a base material and a carbonaceous material are thoroughly mixed to produce a raw material mixture. Here, the base material is solid glass powder, sol,
Glass raw materials for the gel method are used, and these may be used alone or in a mixture of multiple types.

Most glass powders can be used as solid glass powders. The glass raw material for the sol-gel method refers to a sol or gel that becomes glassy by drying or heating, such as tetraethoxysilane Si (QC z H s ).
4, aluminum isopropoxide ^1 (QC 3
H? ) It is a sol or gel obtained by adding water to a solution of a metal alkoxide such as 3 and an acid dissolved in alcohol and stirring. The sol or gel obtained from this metal alkoxide is
It becomes glassy by heating at a temperature of 400 to 1000°C to remove moisture and pores.

Furthermore, in the present invention, ceramic powders other than those mentioned above can also be selected as the base material. The ceramic powder is not particularly limited, and metal oxide ceramics, metal non-oxide ceramics, etc. are used.

As the carbonaceous material, substances that can be carbonized at high temperatures are advantageously used, such as carbon such as graphite, porous carbon such as charcoal, activated carbon, organic substances such as cellulose and crystalline cellulose, and preferably carbon and porous carbon. It is. The combined ratio of the base material and the carbonaceous material varies depending on the type of base material and carbonaceous material used, and it depends on the size and shape of the pores in the porous sintered body obtained by the present invention and the proportion of the total volume of the sintered body. It controls the volume ratio of pores (porosity), but usually when solid glass powder is used as the base material, 1 to 2500 parts of carbonaceous material per 50 parts by weight of the base material.
For example, in the case of manufacturing a porous sintered body used as a bacterial carrier, 5 parts by weight of carbonaceous material per 100 parts by weight of the base material.
~200 parts by weight. Further, when the base material is a glass raw material for sol-gel method, the weight ratio of the weight after removing water to the carbonaceous material is in the range of 100 to 1 and 1 to 100. Note that even when ceramic powder is used as the base material, the amount of carbonaceous material is 5 to 200 parts by weight per 100 parts by weight of the base material.

The particle size of the base material is controlled by the pore size of the resulting porous sintered body, but is usually 3 times or less, preferably 1/3 or less, of the carbonaceous material.

On the other hand, the particle size of the carbonaceous material is usually 1 μ to 10 n+s, which is the same as the pore size of the resulting porous sintered body, and is usually selected according to the pore size.

The shape of this carbonaceous material may be powder, spherical, cylindrical, triangular pyramid, spherical with many protrusions on the surface, etc. A wetting agent such as water may be added to the raw material mixture, and auxiliary materials such as carboxymethyl cellulose, starch paste, etc. may be added to prevent the raw material mixture from deforming during shaping. Various thickening agents can also be added to increase the viscosity of the product. Further, the raw material mixture is appropriately shaped into a desired shape, and methods such as pressing, centrifugation, casting, extrusion, etc. are employed for shaping.

In the present invention, the obtained raw material mixture is appropriately shaped and then heated and sintered under reducing conditions or heated and sintered under pressure, so that the carbonaceous material is sintered while remaining unchanged. A sintered mixture mixed in a base material is produced.

Here, the term "reducing conditions" refers to a state in which the base material can be sintered without burning the carbonaceous material, such as a non-oxidizing gas atmosphere such as nitrogen or carbon dioxide, or a non-oxidizing gas atmosphere such as helium or neon. A state where the above mixture is covered with a reducing substance such as carbon or an organic substance under an inert gas atmosphere, or a state where the above mixture is covered with a reducing substance such as carbon under an atmosphere of a non-oxidizing gas or an inert gas. is included. The sintering temperature varies greatly depending on the base material used. For example, when soda lime glass is used alone as the base material, the temperature is 500 to 800℃.
When a ceramic material is used, it is preferable to use the temperature that is passed through the ceramic material.

Due to this sintering, the carbonaceous material is mixed into the base material without being burned away. Next, in the present invention, the obtained sintered mixture is heated in an oxidizing atmosphere while maintaining the shape of the sintered mixture, thereby oxidizing and burning the carbonaceous material to form open pores. In other words, the carbonaceous material is maintained at a temperature that is sufficient to combust the carbonaceous material in an oxidizing atmosphere but does not cause the sintered mixture to melt and deform. Oxidizing atmosphere means an atmosphere of air, oxygen or oxygen-enriched air. In addition, this temperature is normally preferably 400°C or higher. A porous sintered body with open pores is obtained by combustion of the carbonaceous material.

The obtained sintered body is used as a product as it is or after cleaning, and has uses such as supporting catalysts in chemical reactions or attaching bacterial cells.

Examples of the present invention will be described below. [Example] Examples 1 to 3 After stirring and mixing soda-lime glass and activated carbon in a dry state at the mixing ratio shown in Table 1 below, CMC was added as an auxiliary material.
(carboxymethylcellulose) and distilled water as a wetting agent and knead to obtain a diameter of 1 to 1.5+eo+,
It has a cylindrical shape with a length of 2 to 5 now. This precept was buried in activated carbon with a particle size of less than 250 μm, sealed, and then incinerated at 650°C for 2 hours. The obtained firing mixture was taken out from the activated carbon and held at 550° C. for 12 hours in the atmosphere to produce a porous sintered body.

Table 1 Among these sintered bodies, the physical properties of Example 3 were measured and the following results were obtained. True specific gravity: 2.5 Apparent specific gravity: 0.675 Porosity: 73% Pore diameter: 100% when measured using the water suppression method
The porosity below μ1 was 33%. Therefore, the diameter is 100
The porosity of pores with a diameter of μ1 or more is estimated to be 40%.

Example 4 Using the sintered body obtained in Example 3, a bacterial adhesion test was conducted by a mesotemperature digestion method.

That is, the sintered body was placed in an anaerobic digestion tank maintained at 37°C with a vSS concentration of 6 g/l and a volume load of 3 gTOc/1 day, and after the following number of days had elapsed, it was taken out, washed, and the amount of bacteria attached ( weight increase) was measured.

The results are shown below.

After 10 days: 35.9 mg/g After 20 days: 37.8 mg/g After 35 days: 40.9 mg/g After 50 days: 44.6 mg/g The raw water concentration was 500 mg TOC/1 in an anaerobic digestion tank using the immobilized bacteria attached using the above method. (glucose, peptone-based artificial sewage) was supplied, and digestion was performed.
The IRT for phase digestion (acidic t&) was found to be 2 to 3 hours. These results showed that the HRT was about 1/2 to 173 compared to the suspended bacteria complete mixing type digester, indicating excellent characteristics. [Effects of the Invention] As described above, according to the present invention, since the raw material mixture is sintered under reducing conditions, the carbonaceous material can be mixed into the base material without being damaged by combustion. In general, carbonaceous materials have low reactivity under reducing conditions and at high temperatures, so it is possible to avoid reaction between the base material and the carbonaceous material even if the sintering temperature of the base material is quite high. Furthermore, since the substances that may be mixed into the base material can be limited to carbonaceous materials, the properties of the base material after sintering are hardly changed. Even if thickeners or auxiliary materials are mixed into the raw material mixture, they will carbonize during firing, so they will have little effect on the properties of the base material.

Furthermore, in the present invention, after the carbonaceous material is mixed into the base material under a reducing atmosphere, the carbonaceous material is burned under an oxidizing atmosphere while maintaining the shape of the sintered mixture.
Changes in shape due to shrinkage of the sintered mixture due to the shape of open pores can be avoided as much as possible. Moreover, the shape and size of pores are basically controlled by the type and amount of carbonaceous material added, but carbonaceous materials have good workability and are available in many types, so there is a high degree of freedom in selection. Pore shape and size can be controlled over a wide range and precisely. Further, unlike conventional methods, post-processing such as elution of soluble substances is not required after sintering, so manufacturing costs can be easily reduced.

Furthermore, the obtained porous sintered body has an outer diameter of 11 to several 10 mm, an inner diameter of 0.5 to several 10 mm, and a thickness of 0.5 to several 10 mm.
If it is ring-shaped, when used as a catalyst carrier,
It becomes easy to control column packing and bulk density, and it is possible to ensure sufficient strength and uniformity within the column. Agent for Okamoto Special Glass Co., Ltd. and Kōei Shoji Co., Ltd., sub-agents of the Director of the Agency of Industrial Science and Technology

Claims (1)

[Claims] A raw material mixture consisting of at least one base material selected from the group consisting of solid glass powder and glass raw materials for sol-gel method and a carbonaceous material is sintered under reducing conditions to produce a sintered mixture. , and then heating the sintered mixture in an oxidizing atmosphere to burn the carbonaceous material while maintaining the shape of the sintered mixture.