KR100535299B1 - ceramics honey comb having high specific surface area and method for manufacturing the ceramics honey comb - Google Patents

Abstract

PURPOSE: The present invention provides a method and a composition for preparing a ceramic honeycomb of a specific surface area raw material in the manufacture of a large-size honeycomb that further improves the existing characteristics of the ceramic honeycomb having a large surface area by using a raw material having a large surface area. There is a purpose.

Composition: The method for producing ceramic honeycomb of the high specific surface raw material includes a raw material mixing step of mixing an inorganic additive, an organic binder, a plasticizer and a lubricant together with a solvent in a ceramic raw material having a specific surface area of 50 (m 2 / ㏄) or more; and the raw material mixing A molding step of forming a honeycomb structure by extruding the mixture mixed in the step; and a first drying step of sealing the honeycomb structure formed in the forming step and rapidly drying the high frequency drying furnace; and sealing the first dried honeycomb structure. A second drying step of storing in a state and drying in a constant temperature and humidity drying furnace; And a heat treatment step of heat-treating the honeycomb structure dried in the second drying step at 500 to 700 ° C., and the composition of the ceramic honeycomb of the high specific surface area raw material used in the manufacturing method has a specific surface area of 50. A ceramic raw material of not less than m 2 / mm 2; Organic additives such as powdered methyl cellulose as a binder, liquid triethylene glycol as a plasticizer, and liquid wax as a lubricant; It is composed of glass fiber to reinforce strength, sepiolite to reinforce dough properties, bentonite of clay and inorganic binder, and inorganic additive of silica and alumina to sol.

Effect: The present invention is by adding organic and inorganic additives appropriately to the ceramic material of high specific surface area, in combination with high-frequency drying and constant temperature and humidity drying during the drying process, and proceeding the heat treatment process within the range of 500 ℃ to 700 ℃ relatively low temperature Large size ceramic honeycomb can be manufactured.

Description

Ceramic honey comb having high specific surface area and method for manufacturing the ceramics honey comb}

The present invention relates to a method and a composition for producing a ceramic honeycomb of a high specific surface area raw material that can be applied to the application of a new catalyst carrier by producing a ceramic honeycomb structure having a high specific surface area in a large size.

Since ceramic honeycomb is a kind of porous material, it is structurally increased in strength and morphologically increased in specific surface area to increase activity, improve breathability, lower pressure loss, and increase thermal insulation. In addition, the ceramic honeycomb is formed into cells of various shapes such as triangular, octagonal, hexagonal, circular, and corrugated, depending on the purpose of use, and its functional characteristics vary according to the shape, size, and wall thickness of the cell.

Ceramic honeycomb types include columnar, square, block, plate and ellipsoidal cylinders. For automobile exhaust gas, columnar and elliptic cylinders are used for deodorizing catalysts. Many types are used.

When manufacturing honeycomb, materials with low thermal expansion are applied to the raw materials for automobile exhaust gas purification or rotary heat exchanger, which have a high temperature change at high temperatures. Heat-resistant materials such as mullite are used for molten metal filters, It is applied to high temperatures, such as fireproof gloves. Materials having a high specific surface area can be applied to catalyst carriers and dehumidifiers, gas adsorbents, and gas separation membranes by utilizing the structural advantages of the particles, and are already used in environmental catalyst carriers.

In general, the application field of the ceramic honeycomb is a catalyst carrier for exhaust gas purification of automobiles, but has recently spread to other fields due to the strengthening of atmospheric environmental regulations. Representative examples are SCR catalyst, a key component of Selective Catalytic Reduction (SCR), which harmlessly converts nitrogen oxides generated during combustion of power plants, incinerators, and marine engines. Adsorption rotor to remove the volatile and various volatile organic solvents (VOC) removal catalyst.

In order to be used as a catalyst carrier, the ceramic honeycomb must have catalytic activity, selectivity and mechanical strength, have a large specific surface area, and have good pore structure. The ceramic honeycomb made of cordierite-based raw materials used as a catalyst carrier for automobile exhaust gas purification has advantages of being resistant to thermal shock and relatively high in mechanical strength, since it is mounted on a high temperature mobile source, but has a specific surface area of 1㎡. Since it has a low value of / cc or less, it is used as a catalyst carrier by wash coating with a raw material having a high specific surface area, such as gamma alumina, which increases the specific surface area when used as a catalyst carrier.

The honeycomb structure is most preferable to have a high specific surface area and maintain a moderate strength at the use temperature in order to be widely applied in the industry, but it is difficult to satisfy both because the honeycomb structure has properties opposite to the strength and the high specific surface area. Therefore, in order to use the catalyst carrier in a stationary source except when mechanical strength is required, such as a mobile source, it is necessary to have a larger specific surface area value even if the mechanical strength is slightly decreased.

 There are various problems to be solved when manufacturing honeycomb with a material having a large specific surface area. Key among them are the choice of raw materials, the effects of additives on the conditions of the dough, the identification of the drying conditions, and the optimum conditions for the heat treatment conditions. In addition, the honeycomb thus prepared should have appropriate physical properties.

The manufacturing process of the ceramic honeycomb is to crush and combine the raw materials, mix additives such as plasticizers, and then make a honeycomb structure through various molding operations, and then dry and fire it into a solid monolith.

Pressure molding does not significantly matter the plasticity of the raw material powder, but extrusion molding requires various molding aids such as binders, lubricants, plasticizers, peptizers, etc., in order to make the raw material suitable for molding (or kneading). Molding aids are mostly organic compounds such as methyl cellulose (MC), poly vinyl acrylic (PVA), carboxymethyl cellulose (CMC), and polyethylene glycol (PEG). Mainly used.

The molded article extruded using the molding aid is subjected to a drying process to remove some of the additives added during the drying by drying, thereby maintaining strength in a state capable of baking. These semi-finished products are processed and cut to fit the application and heat-treated at high temperatures to give a finished product.

In the extrusion of raw materials having a high specific surface area, in order to facilitate the extrusion of the raw materials, a large amount of solvents and additives are added to the raw materials, and how to control defects generated during drying and heat treatment is a major management factor in manufacturing. Considering the flow characteristics of the raw material inside the molding machine, how the raw material passes through the mold and the design of the mold related to the flow flow are important management factors.

However, until now, the molding additive, drying, and heat treatment management, which are extrusion conditions when extruding into a raw material having a high specific surface area, have not been known.

Ceramic honeycomb structure is applied to various fields by taking full advantage of its shape and functional characteristics, and is mainly used in the field of environmental pollution removal, and in the future, various functional materials will be used to reinforce its functional aspects.

In view of the above-described trend, the present invention uses a raw material having a large surface area to manufacture a honeycomb of a large size that further improves existing characteristics of a ceramic honeycomb having a large surface area, thereby further expanding the application field of the ceramic honeycomb. It is an object of the present invention to provide a method for producing a ceramic honeycomb of a high specific surface area raw material and a composition thereof.

A method for producing a ceramic honeycomb of a high specific surface area raw material of the present invention that achieves this object is a raw material mixing step of mixing an inorganic additive, an organic binder, a plasticizer, and a lubricant together with a solvent to a ceramic raw material having a specific surface area of 50 (m 2 / ㏄) or more. A molding step of forming a honeycomb structure by extruding the mixture mixed in the raw material mixing step; and a first drying step of sealing the honeycomb structure formed in the forming step and rapidly drying the mixture in a high frequency drying furnace; and the first drying A second drying step of keeping the honeycomb structured in a sealed state and then drying in a constant temperature and humidity drying furnace; And a heat treatment step of heat-treating the honeycomb structure dried in the second drying step at 500 to 700 ° C .;

Characterized in that it comprises a.

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This heat treatment step, the first step of raising the temperature to 0.5 ℃ / min to 110 ℃ to completely remove the residual moisture from the honeycomb structure after the drying process;

A second step of maintaining at 110 ° C. for 60 minutes;

A third step of raising the temperature to 420 ° C. at which the organic material is completely removed at a rate of 1 ° C./min;

A fourth step of maintaining at 420 ° C. for 60 minutes;

A fifth step of raising the temperature to 1 ° C./min to a final temperature of 500 ° C. to 700 ° C .;

A sixth step of holding at a final temperature for 120 minutes; And

It consists of a seventh step of cooling at a rate of 2 ℃ / min to room temperature.

Moreover, the composition of the ceramic honeycomb of the high specific surface area raw material which concerns on this invention,

Ceramic raw materials having a value of a specific surface area of 50 m 2 / ㎡ or more;

Organic additives such as powdered methyl cellulose as a binder, liquid triethylene glycol as a plasticizer, and liquid wax as a lubricant;

It contains glass fiber to reinforce strength, sepiolite to reinforce dough properties, bentonite of inorganic binder clay and inorganic additives of silica and alumina of sol.

The zeolite raw material has an average particle size of 2 to 4 (μm), loss on ignition of 21 ± 2 (wt%), PH (1% suspension) of 11.0 ± 0.5, and a specific surface area of 300-500 (m2 / cc). The crystalline phase is composed of synthetic zeolite or natural zeolite of type A or X type or Y type.

The zeolite has a combination ratio of at least -70 w% zeolite, bentonite-1-5 w%, and sepiolite-10-20 w%, and as additives, glass fiber-5-15 parts by weight, silica sol-10-30 parts by weight, and methyl cellulose- 0.5-5 parts by weight, polyethylene glycol-0.5-3 parts by weight, wax-0.5-13, and water-40-50 parts by weight. The zeolite strength of this zeolite is a penitrometer of 0.7-1.0 inch.

In addition, the titania raw material has an average particle size of 20 to 30 nm, a loss of ignition less than 2 (wt%), a pH (1% suspension) of 3.5 to 4.5, and a specific surface area of 50 to 65 (m 2 / cc). ), And the crystalline phase is composed of titania, which is anatase or rutile, or a mixture of anatase and rutile.

This titania has a combination ratio of titania-100 wt%, and as an additive, glass fiber-10-20 parts by weight, methylcellulose -0.5-5 parts by weight, polyethylene glycol -0.5-3 parts by weight, wax -0.5-3 parts by weight, water It consists of -50-60 parts by weight. The dough strength of this titania is 1-1.25 inch with penitometer.

In addition, the amorphous silica raw material has an average particle size of 68.9 (µm), loss of ignition (at 1000 ° C) of 12 (wt%), PH (1% suspension) of 6.5 to 7.5, and a specific surface area of 280-350 (m2). / cc), and the crystalline phase is composed of amorphous silica or precipitated silica.

This silica has a combination ratio of silica: 80-95 wt%, bentonite: 5-20 wt%, glass fiber: 10-30 parts by weight, alumina sol: 20-30 parts by weight, methyl cellulose: 0.5-5 weight And polyethylene glycol: 0.5-3 parts by weight, wax: 0.5-3 parts by weight, and water: 80-120 parts by weight. The kneading strength of this silica is 0.7-1.2 inches in penitometer.

Glass fiber has an average particle size of short 13 (µm) and long axis of 100-300 (µm), and its composition (wt%) is ignition loss -0.1, SiO ₂ -52.0, Al ₂ O ₃ -14.2, MgO-6.0, Fe ₂ O ₃ -0.75, TiO ₂ -0.75, CaO-25.0, Na ₂ O & K ₂ O-1.0.

Sepiolite has an average particle size of 150-250 (μm) in long axis, and its composition (wt%) consists of ignition loss 26.43, SiO ₂ -39.9, MgO-15.98, CaO-17.78, and Na ₂ O & K ₂ O-1.0.

Bentonite has a specific gravity of 2.43, and its composition (wt%) is ignition loss-6.19, SiO ₂ -69.21, Al ₂ O ₃ -16.74, MgO-2.25, Fe ₂ O ₃ -2.60, TiO ₂ -0.08, CaO-1.50 , Na ₂ O & K ₂ O-1.42, MnO-0.01.

Colloidal silica has a specific gravity of 1.2 to 1.22 and a solid content of 30%.

Colloidal alumina has a specific gravity of 1.09 to 1.22 and a solid content of 10%.

Advantages and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments based on the drawings and experimental data.

First, in this embodiment, a screw type is used to manufacture a small honeycomb structure (50 × 50 × 50 mm), and a piston type extrusion machine is used to manufacture a large honeycomb structure (150 × 150 × 300 mm).

The high specific surface honeycomb structure is a catalyst carrier for purifying nitrogen oxide (NO _x ) gases generated during the combustion of fossil fuels used in thermal power plants, as well as adsorption rotors used to remove various gases generated in semiconductor manufacturing processes. Various materials are applied as environmental materials.

 This embodiment illustrates the manufacture of a honeycomb shape of a large size (150 × 150 × 100 mm or more) using various high specific surface area raw materials as starting materials. In order to implement this, a complex relationship is expected depending on the content of the high specific surface area and the manufacturing size of the honeycomb. Therefore, the honeycomb of the small size (50 × 50 × 50mm) is first manufactured and the basic properties thereof are evaluated. X 150 x 100 mm or more) will be discussed.

Here, the starting raw materials used are zeolites, titania, and silicas having a specific surface area value of 50 m 2 / ㏄ or more. The basic specifications of these raw materials are shown in Table 1.

Basic specification of high specific surface area raw materials  Average particle size (㎛) Combustion loss (wt%) PH (1% suspension) Specific surface area (㎡ / cc) Crystal phase Zeolite 2-4 21 ± 2 11.0 ± 0.5 390 Na-XZeolite Titania 20-30nm <2 3.5-4.5 55 Anatase / Rutil Silica 68.9 * 13 (1000 ℃) 6.5-7.5 288 Amorphous silica

Here, * indicates the size of the secondary particles in an aggregated state because the size of the primary particles is in nanometers.

However, extrusion molding with only these starting materials lacks plasticity and requires the introduction of suitable organic binders, plasticizers and lubricants. Therefore, as shown in Table 2, organic additives such as methylcellulose, triethylene glycol, and wax, which are generally used in the molding process, are used. Organic additives used to make high specific surface area honeycomb Kinds additive shape Binder Methylcellulose powder Plasticizer Triethylene glycol Liquid slush Wax Liquid In addition, after the molding process, the honeycomb structure should have a suitable handling strength in the drying and heat treatment process, but should not cause cracks, various inorganic additives are used. Sepiolite, a mineral that exists in the form of glass fibers and fibers, is used to prevent cracking due to shrinkage during the drying process of extrusion specimens with a high specific surface area. Sols and clays on phosphorus colloids are used.

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Since the inorganic additives need to be different for each raw material used, two kinds of alumina and silica are applied in case of sol, and bentonite and ordinary clay are applied in appropriate combination in case of clay. The properties of these inorganic additives are as described in Table 3. Properties of Inorganic Additives Fiberglass Sepiolite Bentonite Sol Silica Alumina Average particle size shorten 13 μm Long axis 120 μm 150-250㎛ importance 2.54 2.43 1.2-1.22 1.09-1.14 Solid content 30% 10% Composition (wt%) Ignition loss 0.1 26.42 6.19 SiO ₂ 52.0 39.90 69.21 Al ₂ O ₃ 14.4 16.54 MgO 6.0 15.98 2.25 Fe ₂ O ₃ 0.75 2.60 TiO ₂ 0.75 0.08 CaO 25.0 16.7 1.50 Na ₂ O & K ₂ O 1.0 1.42 MnO 0.01 role Strength reinforcement Weapon bind Weapon bind Weapon bind On the other hand, after investigating the influence of the appropriate amount of the solvent and the effects of the organic and inorganic additives through a small alumina-induced operation, it is possible to obtain a combination ratio capable of extrusion molding.

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Based on this combination ratio, 5Kg of each raw material is combined and dry mixed for 3 minutes by a high-speed shear mixer, and then water is further mixed with a wet mixer by adding water as a solvent.

After mixing the raw materials mixed so that the water is uniformly distributed in a plastic container and aged for 24 hours, a 50 x 50 x 100 mm small honeycomb-shaped specimen of 20 cells and 50 cells is prepared by a screw type extrusion machine. And 150 × 150 × 300mm large size specimens are produced by a piston type extrusion molding machine.

Various drying methods are used to confirm the drying conditions of the specimen thus prepared. That is, the conditions without cracks were investigated by drying in an electric oven at 110 ° C. for 24 hours, in a microwave drying furnace for 10 minutes, and hot air at 70 ° C. for 72 hours. In addition, in order to dry the honeycomb of the large size which is the final target, it is further rapidly dried by high frequency dryer and finally dried by constant temperature and humidity drying.

Thermal expansion meters are used to investigate the appropriate heat treatment temperature at which the specimen may have a maximum specific surface area while maintaining adequate strength. This meter allows you to examine the temperature range where the specimen changes abruptly during the heat treatment period. Measure the specimen for 5 × 5 × L25mm (± 0.05mm) and measure it to the temperature range of 20 ℃ ~ 700 ℃.

For small specimens, use an electric furnace at intervals of 100 ° C in the range of 500 ° C to 700 ° C, which is a step before shrinkage occurs sharply, after confirming the expansion curve. Heat treatment using.

In order to investigate the specific surface area value of the specimens prepared for each raw material, it is measured by the BET method by pretreatment at 200 ° C. for 1 hour using a specific surface area meter.

In order to investigate the mechanical strength of the honeycomb shape, the compressive strength (S) value in the direction of the main axis of the honeycomb shape is measured using a universal testing machine, and the value is obtained by the following equation.

(Kgf / ㎠)

Where P is the pressure and A is the area of the honeycomb.

When using a high specific surface honeycomb as a dehumidifying and adsorbent, the porosity and absorption rate of the honeycomb may be important factors. Apparent porosity and water absorption are measured as follows with reference to Korean Industrial Standards (KS L 3114).

In the measurement method, the specimen is weighed after complete drying at 110 ° C. for 24 hours (W1), the specimen is kept in distilled water for 24 hours, and then suspended in water to measure the weight (W2). After that, take out the catched specimen and shake it out by hand vigorously three times to remove excess moisture on the surface of honeycomb, wipe it off with a squeezed wet compress, and measure the weight (W3) by the following equation.

Apparent porosity (%) =

% Absorption =

In order to observe the crystal phase and microstructure generated after the heat treatment of the prepared specimens, the X-ray peak is irradiated in the 2θ range of 10 ~ 90 ° using an X-ray diffractometer. The microstructure is coated with gold (Au) on the specimen and observed with a scanning electron microscope.

Through the manufacturing method as described above it can be seen that.

First, find out the amount of solvent added to each raw material.

In order to examine the solvent addition amount conditions that can be extruded for each raw material, the experimented addition amount of solvent (water) using pure high surface area raw materials and general honeycomb organic additives is shown in Table 4.

Appropriate solvent addition amount and organic additive amount for each raw material Raw material specific surface area (㎡ / cc) Zeolite Silica Titania Cordierite 390 288 55 <1 Methylcellulose 0.5-5 parts by weight Triethylene glycol 0.5-5 parts by weight Wax 0.5-5 parts by weight Solvent Amount (%) 90-100 150-170 50-60 20-30

The biggest feature is that it requires a large amount of solvent (water) addition as expected. In the manufacture of honeycomb, the most common raw material, cordierite, is added about 20-30% of solvent, whereas zeolite, silica, and titania are 90-100, 150-170, and 50-60 (%), respectively. It requires a large amount of solvent. The reason is that the surface area of zeolite, silica and titania to be surrounded by solvent is larger than the surface area of cordierite.

Table 4 shows a phenomenon that the amount of solvent added increases as the raw material having a large specific surface area. In particular, silica requires about 170 parts by weight of a solvent of the powder despite its smaller surface area than zeolite. This is because finely divided amorphous silica is used as a raw material of silica. The amorphous silica is composed of primary particles in nanometer units, and primary particles are aggregated to form final particles. In addition to filling the voids between the primary particles as well as surrounding the secondary particles aggregated with the primary particles, the most solvent is added to form the dough.

However, even if such a large amount of solvent is added, the high surface area raw material is somewhat lacking in plasticity and lubricity to proceed with extrusion. In this case, the frictional force with the inner wall of the cylinder increases during extrusion demolding, resulting in a product breakage in the longitudinal direction or lack of beam formation. Therefore, in order to prevent such a shape, a general plasticizer and a lubricant, triethylene glycol and wax are used. In this case, since the amount of solvent addition does not change much, 0.5-5 parts by weight is added to each raw material to improve dough properties. The characteristics of the dough are appropriate conditions when the penetration depth is in the range of 0.7 to 1.3 inches when pressurized using a penitometer to measure the strength after kneading. However, since the amount of the solvent may also vary due to the addition of the inorganic raw material, the influence of the inorganic additive for each raw material should be examined and the appropriate amount of solvent should be selected.

Investigate the selection of inorganic additives and their added amounts.

Each raw material used in the present embodiment, when manufactured in a honeycomb shape, has to have a large specific surface area and maintain mechanical strength and have an appropriate porosity, so that an appropriate inorganic sintering aid and reinforcing agent are required to satisfy this. do.

First of all, titania has the smallest surface area and the particle size of the raw material is very finely divided into nanometers, so preliminary experiments show the possibility of low temperature sintering with organic additives alone. Only by introducing glass fibers in order to prevent cracking during drying and heat treatment can a sufficiently honeycomb shape be produced. Therefore, the addition amount of the solvent is also 50-60 parts by weight, which does not change significantly compared to the preliminary test results, where the phentomometer strength value is also 1-1.25 to obtain a suitable dough strength. In addition, since titania on pure anatase is known to exhibit photocatalytic properties, it is preferable to manufacture as high a titania quality honeycomb as possible as possible for use in photocatalysts, so that the amount of glass fibers added is at most 20 parts by weight.

However, as shown in Table 4, silica is composed of pure amorphous silica, and the particle size is also coarse, and it is judged to be insufficient with only an organic plasticizer. Therefore, it is preferable to add the same silica base raw material as the starting raw material component capable of introducing inorganic additives. In addition, bentonite is used because it has excellent viscosity and contains Na and can help to promote sintering at low temperature. However, bentonite generally swells more than about 5 times its volume when it absorbs moisture, and if it is exposed to moisture after manufacturing honeycomb shapes, it may cause breakage due to rapid expansion, and its amount should be 5% or less. In this case, the colloidal alumina sol and the glass fiber are introduced to prevent cracks during drying and heat treatment, and the amount of each added does not exceed 30 parts by weight, so that the silica content is as high as possible. The reason for using alumina sol as a sintering aid of silica can be seen in the following evaluation of physical properties, but the final heat treatment temperature of silica is 700 ° C due to low temperature sintering reaction with silica when the temperature is higher than other raw materials used. This is because it shows higher strength.

Thus, when the inorganic additive is introduced, the appropriate dough strength can be obtained at 80-120 parts by weight, which is considerably reduced compared with the use of the organic additive alone, because the plasticity of the dough is increased by introducing the viscous and plastic inorganic additive. .

On the other hand, zeolite, which is the raw material with the largest specific surface area, requires a large amount of solvent in terms of pure zeolite. Can be. Since zeolite, like silica, lacks plasticity and sintering itself occurs at 800 ° C. or higher, selection of an appropriate inorganic binder and reinforcing agent is important. In the present invention, in addition to the addition of sepiolite as an inorganic additive of zeolite, a colloidal sol is used as a sintering accelerator, but a silica sol is used in this embodiment. The reason is that silica sol is easy to manufacture with a colloid with a relatively high solid content, and the sol has a high solid content, which can be more helpful in promoting sintering, and since zeolite is mainly composed of silica base, it is effective in promoting sintering. This is because the price is also lower than that of alumina sol, which is advantageous in commercial production. In addition, the use of glass fibers used in amorphous silica can solve the problem of cracking after honeycomb production.

Sepiolite, which is applied only to zeolite, is a fibrous α-sepiolite and forms a fibrous shape with a length of about 150 to 250 μm, and its component is composed of hydro silicate, which reduces the amount of solvent addition and plasticity. It also increases and acts as a strength enhancer because of its fibrous structural properties. In the case of zeolite as well, the content of additives is not higher than 20% for sepiolite and not more than 15 parts by weight of glass fiber to manufacture zeolite honeycomb with the highest content of 70% or more.

Appropriate molding combination ratio for each raw material obtained through the experiment is shown in Table 5.

Molding combination ratio and dough strength for each raw material Titania Zeolite Silica Raw material name Combination Raw material name Combination Raw material name Combination Titania 100% Zeolite 70-75% Amorphous silica 80-95% Bentonite 1-5% Bentonite 5-20% Sepiolite 10-20% Fiberglass 10-20 parts by weight Fiberglass 5-15 parts by weight Fiberglass 10-30 parts by weight Methylcellulose 0.5-5 parts by weight Silica sol 10-30 parts by weight Alumina sol 20-30 parts by weight Polyethylene glycol 0.5-5 parts by weight Methylcellulose 0.5-5 parts by weight Methylcellulose 0.5-5 parts by weight Wax 0.5-5 parts by weight Polyethylene glycol 0.5-5 parts by weight Polyethylene glycol 0.5-5 parts by weight Wax 0.5-5 parts by weight Wax 0.5-5 parts by weight water 50-60 parts by weight water 40-50 parts by weight water 80-120 parts by weight Phenitometer Strength Values (Inches) 1-1.25 Phenitometer Strength Values (Inches) 0.7-1 Phenitometer Strength Values (Inches) 0.7-1.2

After the raw materials were mixed dry and wet by a high-speed shear mixer at a combination ratio as shown in Table 5, and aged at room temperature for 24 hours, a honeycomb of 50 × 50 × 50 mm was used by a small screw type extruder, and a large size (150 X 150 x 300 mm) The honeycomb is extruded, and the extrusion speed is 0.3 m / min. The mold used at this time is formed of 20 cells and 50 cells.

For uniform drying of the extruded specimens, moisture is removed by hot air drying, high frequency drying, and constant temperature and humidity drying. Especially, the honeycomb of large size finds the optimum condition by combining high frequency drying and constant temperature and humidity drying. . The reason is that the manufacturing of a large size honeycomb requires a continuous process, and since the cell wall thickness is thin due to the characteristics of honeycomb, it is necessary to uniformly and rapidly dry to reduce defects such as cracks. Because there is.

According to the method of use, constant temperature and humidity drying is an excellent drying method that can reduce cracks due to relatively small stress generation by controlled water evaporation rate, but at least 10 days are required for complete drying due to the slow drying rate, Due to the very careful management of humidity, it is difficult to apply in mass production, and also requires a large loading space, which is high in installation cost and economically unsuitable for mass production conditions.

Hot air drying has a problem in that it is difficult to make the rate of evaporation of the water inside and outside the honeycomb constant, so that severe cracks are frequently generated during the drying process, thereby lowering the yield of the product.

The high-frequency drying method is not only to obtain uniform drying conditions but also very fast drying rate is suitable for products such as honeycomb shape, and is widely used in manufacturing general cordierite honeycomb. This embodiment is also applied for drying large honeycomb (150 × 150mm). The frequency and the distance between the electrode plate and the specimen are fixed at a constant and the continuous drying condition is observed according to the belt movement speed. When repeated drying at / min, it can be seen that a large difference occurs depending on the honeycomb size. In small specimens (50 × 50 × 50mm), no problems occur during high-frequency drying, and cracks do not occur up to the size of 140 × 150 × 50mm even in large specimens, and there is no difference between honeycomb cells. However, if the size of the specimen exceeds 150 × 150 × 300 mm, cracking occurs in the parallel direction of the honeycomb cell during the drying process, which is more severe in zeolites and silicas having a large specific surface area. This is because the high specific surface area raw material is added with a lot of water during extrusion, so that more stress is generated during the evaporation of water by rapid drying. This phenomenon is more severe as the size of the specimen increases, and the drying occurs in part during the evaporation of water, and thus burning occurs at the edge of the honeycomb preferentially. In order to solve this problem, the large sized specimen is controlled so that the escape of moisture from the high frequency drier proceeds slowly, and the specimen is immediately transferred to a constant temperature drier at 70 ° C. and maintained for 24 hours to obtain a large product without defects. . The dried specimen thus absorbs moisture rapidly when exposed to the air because it has a large specific surface area.

In order to heat-treat the molded product at an appropriate temperature, the shrinkage curve of each raw material is examined and then heat-treated with reference to it. The result is as shown in FIG.

In other words, Titania has a slight shrinkage due to the combustion of organic additives from around 200 ° C, and shows a large shrinkage due to sintering and phase transition (Anatase-rutile) from around 200 ° C. It is preferable that the temperature is 500 ° C., which is a temperature at which the change is less severe than 550 ° C.

The heat treatment process according to this consists of seven steps. That is, the first step is to increase the temperature to 0.5 ℃ / min up to 110 ℃ to completely remove the residual moisture. Step 2 is maintained at 110 ° C. for 60 minutes. The third step is to increase the temperature to 110 ° C to 420 ° C to completely remove the organic matter at 1 ° C / min. Step 4 is maintained at 420 ° C. for 60 minutes. In step 5, the temperature is increased to 1 ° C./min from 420 ° C. to 500 ° C., the final temperature. Step 6 is maintained at the final temperature of 500 ° C. for 120 minutes. Step 7 cools at 500 ° C. to room temperature at 2 ° C./min to avoid rapid heating and cooling as much as possible.

On the other hand, the zeolite with the largest specific surface area shows rapid shrinkage over three stages. The first stage shrinkage is a shrinkage occurring below 150 ° C due to evaporation of moisture absorbed due to exposure to the atmosphere, even if the specimen is completely dried. The second step is the shrinkage at 350 ° C. to 400 ° C., which is the temperature at which shrinkage is caused by the combustion of organic materials added during molding and the removal of crystal water of zeolite. It can be seen that the shrinkage occurs rapidly from 550 ° C., which is expected to be the temperature at which the sintering starts to progress at the particle interface by the role.

Therefore, zeolite is also preferably heat-treated at the same 500 ° C as titania, and heat treatment conditions are performed in the same manner as titania, but at 0.5 ° C / min to 350 ° C, which is only up to the temperature at which crystal water is removed.

Since silica continues to undergo large shrinkage, it is very difficult to determine an appropriate heat treatment temperature. Near 400 ° C, it is also due to the shrinkage due to the combustion of the added organic matter and at the same time the inorganic additive used as the sintering aid reacts at the particle interface, thereby eliminating the voids between the secondary particles that are aggregated. After 500 ℃, the shrinkage of sintering of the primary particles in nanometers occurs, but the specific surface area and strength values after heat treatment at 100 ℃ intervals from 500 ℃ to 900 to confirm the accuracy This temperature is determined to meet the temperature of 700 ℃ and the heat treatment conditions for each section is performed in the same manner as zeolite. The photograph of the product manufactured by heat treatment is as shown in FIGS. 2 and 4.

2 is an actual photograph of a small (50 × 50 × 100 mm, 20 cell, 50 cell) honeycomb prepared from each raw material.

3 is an actual photograph of a large honeycomb prepared from each raw material. The left side (not shown in Figure 3, below) is a zeolite honeycomb (150 × 150 × 300mm, 50 cells), the center is a titania honeycomb (150 × 150 × 300mm, 20 cells, 150 × 150 × 100mm, 50 cells), and The right side shows silica material honeycomb (150x150x300mm, 20 cells, 150x150x100mm, 50 cells), respectively.

Looking at the physical properties of each raw material of the ceramic honeycomb prepared as follows.

Titania used in this example has a specific surface area value of 56 m 2 / g of the initial powder. As shown in FIG. 4, titania shows no significant change up to 500 ° C. and then the specific surface area value decreases very rapidly up to 700 ° C. This rapid decrease in specific surface area coincides with the trend in the previous shrinkage curve due to densification by sintering between particles.

As shown in Table 1 and Figure 4, since titania is a microparticle having a particle size of 20 to 30 nanometers, the surface energy is high, about 550, which is much lower than the phase transition temperature of rutile to 915 ° C in anatase in general titania. A sharp decrease in specific surface area due to phase transition is observed in the vicinity of ℃ to 600 ℃. Therefore, in this embodiment, the heat treatment at 500 ° C. where the specific surface area value is similar to the initial state of the raw material is preferable, and as a result, the strength value is about 32 Kgf / cm 2, exceeding the desired target value.

In addition, Titania honeycomb products are intended to be applied as a photocatalyst after development. For this purpose, since the titania crystal phase is preferably left as an anatase phase after the final heat treatment, the crystal phase after the heat treatment is confirmed. X-ray diffraction analysis of the specimen after heat treatment at intervals of 100 ° C. to 500˜900 ° C. are shown in FIG. 5. According to these results, titania has anatase as the main crystalline phase and some rutile crystals exist at 500 ℃, but the crystal phase is changed mostly from anatase to rutile at around 600 ℃. To change. The optimum heat treatment condition is therefore 500 ° C. in which case the specific surface area and strength values are achieved in the final target.

On the other hand, as shown in Figure 6, the apparent porosity and water absorption rate according to the heat treatment temperature is showing a similar aspect, the porosity of about 47% as a result of 500 ℃ heat treatment, after that since 600 ℃ shows that the porosity is greatly reduced This also indicates that the heat treatment at 500 ° C. is a temperature at which the target value set in the present embodiment is obtained.

Zeolite is Na-X type and has a specific surface area of 400 m 2 / g, which has the largest value among the raw materials of this embodiment. Since honeycomb using zeolite can be used as a dehumidifying agent and a catalyst carrier, the specific surface area, porosity, water absorption rate and compressive strength values for the use for this purpose are examined.

First, the Na-X type zeolite is maintained at a considerably high state with a specific surface area value of 270 m 2 / g at 500 ° C. heat treatment, but since then, the degree of change has been increased. As described above, the specific surface area decreases because sintering at the particle interface by the sintering aid proceeds to densification between the particles. However, the reason for maintaining a large specific surface area is because of the unique three-dimensional characteristics of the zeolite structure. This is because the network structure still exists. It can be seen from the X-ray diffraction results that the crystal structure is changed to some cristobalite at 900 ℃ temperature, as shown in FIG. As a result, as shown in FIG. 8, it can be seen that the strength value is rapidly increased while accompanied by a large decrease in the specific surface area.

The compressive strength value of the zeolite according to the heat treatment temperature of the zeolite was slightly increased from 500 ° C. to 700 ° C., but the value rapidly increased from 700 ° C. At this temperature, the specific surface area value is almost reduced to about half, and the porosity is considerably lowered, which indicates that the Na-x type zeolite starts sintering. As a result of examining the pattern, it can be seen that a crystal peak is generated at 700 ° C. Therefore, it is more appropriate to heat-treat at 500 ° C., which is a temperature at which shrinkage does not largely occur when manufacturing honeycomb.

9 shows the apparent porosity and the water absorption according to the heat treatment temperature of the zeolite. That is, at 500 ° C., both porosity and water absorption show a large value of about 60%. At 600 ° C., the water absorption remains similar but the porosity shows a large decrease. This is because the sintering at the grain boundary due to the sintering aid has been progressed, but there are still pupils in the molecular sieve existing inside each particle. In general, the porosity and the absorption rate are determined by the same pore structure, but in the case of zeolite, the difference is due to the crystal structure in the specific particle. Therefore, considering the above specific surface area and strength data, 600 ° C. heat treatment is preferable, but the heat treatment is finally performed at 500 ° C. in view of the rapid decrease in porosity at this temperature.

On the other hand, as a high specific surface area silica, a precipitated silica called amorphous white carbon is used, and its development is used as a lightweight catalyst carrier. This requires high specific surface area and mechanical strength, and pore characteristics are important.

As shown in FIG. 10, amorphous silica has a specific particle formation structure. That is, the particle size of the elementary particle (a) is composed of 10 ~ 40nm, these elementary particles (a) are secondary to the secondary (b) to achieve a size of about 100 ~ 400nm, the final The particles of are made of the size of about 1 ~ 2mm as these secondary particles are agglomerated again.

Fig. 11 shows the relationship between specific surface area and strength according to the heat treatment temperature of silica. Although the specific surface area of the initial raw material was about 300 m 2 / g, the specific surface area value was the highest among the three raw materials used even after the heat treatment to 600 ℃. As mentioned above, it is due to the unique particle structure of silica. That is, the sintering aid reacts and liquid phase sintering occurs at the interface of the final particles. However, the surface area is not greatly reduced because the amount of pores existing between the secondary particles and the primary particles is very small in view of the overall surface area. However, from 700 ° C, the specific surface area is rapidly decreased, which is caused by the change of amorphous silica into the mullite crystal phase due to the addition of alumina sol. As shown in FIG. Does not represent. This is because the solid content of the alumina sol is only 10%, so that sufficient crystallization does not proceed. Therefore, this is due to the liquid phase sintering by the sintering aid at the interface between the secondary particles. On the other hand, the intensity | strength value shows the value lower than the target 20Kgf / cm <2> below 700 degreeC, and shows the value which reaches | attains the target value only even at 700 degreeC. Only from the above results, it is desirable to treat the heat treatment temperature above 700 ° C. However, as shown in FIG. 13, in view of the relationship between porosity and water absorption, it is preferable to form a honeycomb structure at a final heat treatment temperature of 700 ° C. since the porosity is rapidly lowered at 700 ° C. or higher.

14 and 16 are actual photographs of microstructures observed by an electron microscope of a honeycomb structure of titania, zeolite, and silica (in order from the left on the drawing) after heat treatment at 500 ° C and 700 ° C.

Titania and zeolite both showed that the glass fiber was properly dispersed to help prevent cracking, and the sintering process was performed at 700 ° C. rather than at 500 ° C., indicating the compactness. This is consistent with the rapid change at 700 ° C. based on the porosity and strength data shown above.

However, in the case of silica, the structure is very sparse at 500 ° C., but the structure is very dense at 700 ° C., which is consistent with other physical properties.

As described above, the present invention evaluates the physical properties through basic preliminary experiments using various raw materials having a high specific surface area, and can be used to manufacture honeycomb of a large size (150 × 150 × 300mm) by practical application.

In particular, when using a high specific surface area of the raw material, suitable organic and inorganic additives can be used to find the optimum condition of the solvent addition amount, thereby reducing the solvent addition amount by up to half. In addition, it is possible to manufacture a large content of honeycomb (150 × 150 × 300mm) without defects by using an appropriate additive for each raw material. In high specific surface area honeycomb drying, large-sized drying among various drying methods requires high frequency drying and constant temperature and humidity drying to be free from defects. The optimum heat treatment condition for each raw material is preferably 500 ° C to 700 ° C, which is relatively low temperature.

Therefore, the present invention can form a large honeycomb structure having the following physical properties.

Target property Titania Zeolite Silica Specific surface area (㎡ / g) 50 or more 55 170 129 Compressive strength (Kg / ㎠) 20 or more 32 24 23 Porosity (%) 46 and above 47 55 60

1 is a shrinkage ratio of each raw material by temperature.

Figure 3 is a real picture of a small honeycomb prepared from each raw material.

3 is a real picture of a large honeycomb prepared from each raw material.

4 is a graph showing the relationship between the specific surface area and the strength according to the heat treatment temperature of titania.

5 is a graph showing X-ray diffraction peaks according to heat treatment temperatures of titania.

6 is a graph showing the relationship between porosity and water absorption at each heat treatment temperature of titania.

7 is a graph showing X-ray diffraction peaks according to heat treatment temperatures of zeolites.

8 is a graph showing the relationship between the specific surface area and the strength according to the heat treatment temperature of the zeolite.

FIG. 9 is a graph showing the relationship between porosity and water absorption at each heat treatment temperature of zeolite. FIG.

10 is a particle diagram of amorphous silica.

11 is a graph showing the relationship between the specific surface area and the strength according to the heat treatment temperature of silica.

12 is a graph showing X-ray diffraction pits according to heat treatment temperatures of silica.

FIG. 13 is a graph showing the relationship between porosity and water absorption at different heat treatment temperatures of silica; FIG.

14 is a structure photograph of a specimen heat-treated at 500 ℃.

15 is a structure photograph of a specimen heat-treated at 700 ℃.

Claims (9)

A raw material mixing step of mixing an inorganic additive, an organic binder, a plasticizer and a lubricant together with a solvent to a ceramic raw material having a specific surface area of 50 (㎡ / ㏄) or more; and A molding step of forming a honeycomb structure having a large size of 150 × 150 × 100 mm or more by extruding the mixture mixed in the raw material mixing step; and A first drying step of sealing the honeycomb structure formed in the molding step and drying in a high frequency drying furnace; and A second drying step of storing the first dried honeycomb structure in a sealed state and then drying in a constant temperature and humidity drying furnace; And A heat treatment step of heat-treating the honeycomb structure dried in the second drying step at 500 to 700 ° C .; Ceramic honeycomb manufacturing method of a high specific surface area comprising a. delete The method of claim 1, wherein the ceramic raw material is any one of zeolite or titania or silica, the inorganic additive is at least one selected from glass fiber or sepiolite or bentonite or silica sol or alumina sol, the organic binder is methyl cellulose And the plasticizer is triethylene glycol, and the lubricant is a wax. The method of claim 3, wherein the ceramic raw material is a zeolite, natural zeolite or the crystal phase is any one of the type A, X type, Y type, the combination ratio of zeolite-70-75wt%, bentonite-1-5wt%, Sepiolite-10 -20 wt%, glass fiber-5-15 parts by weight, silica sol-10-30 parts by weight, methylcellulose -0.5-5 parts by weight, polyethylene glycol -0.5-5 parts by weight, wax -0.5-5 parts by weight Part, water 40-50 parts by weight of a ceramic honeycomb manufacturing method of a high specific surface area raw material. The method of claim 3, wherein The ceramic raw material is any one of anatase or rutile, or a mixed crystal phase of anatase and rutile as titania, and a combination ratio of titania-100 wt%, glass fiber-10-20 parts by weight and methylcellulose-0.5-5 weight as an additive. Part, polyethylene glycol-0.5-5 parts by weight, wax-0.5-5 parts by weight, water-50-60 parts by weight, The heat treatment step, the first step of increasing the temperature to 0.5 (℃ / min) to 110 (℃) to completely remove the residual moisture of the honeycomb structure dried in the drying step; A second step of maintaining at 110 ° C. for 60 minutes; A third step of raising the temperature from 110 (° C.) to 420 ° C. at which organic matter is completely removed at a rate of 1 (° C./min); A fourth step of maintaining at 60 minutes at 420 ° C .; A fifth step of raising the temperature from 420 (° C.) to 1 (° C./min) from the final temperature to 500 (° C.); A sixth step of maintaining the final temperature at 500 ° C. for 120 minutes; And A seventh step of cooling at a rate of 2 (° C./minute) from 500 ° C. to room temperature; Ceramic honeycomb manufacturing method of a high specific surface area, characterized in that consisting of. 4. The ceramic raw material according to claim 3, wherein the ceramic raw material is any one of amorphous silica or precipitated silica (white carbon) as silica, and the combination ratio is silica-80-95 wt%, bentonite-5-20 wt%, and glass fiber as an additive. -10-30 parts by weight, alumina sol-20-30 parts by weight, methylcellulose-0.5-5 parts by weight, polyethylene glycol-0.5-5 parts by weight, wax-0.5-5 parts by weight, water-80-120 parts by weight Ceramic honeycomb manufacturing method of a high specific surface area, characterized in that. 7. The ceramic honeycomb manufacturing according to any one of claims 3 to 6, wherein the glass fiber has a shorter average particle size of 10-20 (µm) and a long axis of 100-300 (µm). Way. The method of manufacturing ceramic honeycomb of a specific surface area raw material according to any one of claims 3 to 6, wherein the sepiolite is fibrous having an average particle size of 150-250 (μm). delete