JPH0260602B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel activated carbon honeycomb molded body for ozone decomposition, and more particularly to an activated carbon honeycomb molded body for ozone decomposition used as a filter for decomposing ozone emitted from aircraft, copying machines, etc. This article provides a historical explanation of the usage structure of activated carbon up until now. Activated carbon has long been widely used as an adsorbent for deodorization or decolorization, as a catalyst for ozone decomposition, or as a carrier for various catalysts. However, most of them are in the form of powder or pellets, and there are only a few molded bodies of a certain shape. In one of the latter activated carbon molded bodies, a mixture of activated carbon raw material powder such as charcoal or coal and a caking agent such as tar or pitch is pressure molded, dried at about 100℃, and then heated to 600℃ or less. Some products are carbonized at high temperatures and then activated by passing steam through them in an activation furnace. However, since this product uses pitch and tar, which are difficult to handle and can themselves become activated carbon through activation treatment, as a binder, it is difficult to apply various molding methods other than pressure molding, and furthermore, it is difficult to apply molding methods other than pressure molding. Since the treatment is carried out, it is difficult to fully activate the inside of the product if it has a complicated shape that makes it difficult for water vapor to pass through. Therefore, the reality is that this type of activated carbon molded body has no choice but to have a plate-like shape or a very simple shape similar to this, and it is difficult to obtain a variety of shapes suitable for various uses. In addition, as a different type of activated carbon molded body from the one mentioned above, there is one in which activated activated carbon powder is bound with an organic binder. However, this type of molded product cannot exhibit sufficient activity because the binder covers the surface of the activated carbon particles, and furthermore, the binder deteriorates due to heating, changes over time, etc., resulting in a decrease in strength. It has drawbacks and is of little practical use. Another type of activated carbon molded body is one in which activated carbon powder is coated on the surface of a ceramic base with a rubber-based or other organic binder. This molded product has higher activity and only a slight decrease in strength than the one bound with the organic binder described above, but since the base surface is coated with activated carbon powder, the amount of activated carbon powder retained is small, and However, they have the disadvantage of losing their activity after relatively short use. In addition, products similar to the above-mentioned activated carbon molded products, such as those made by layering activated carbon fiber paper in a cardboard shape, have been developed for applications such as filters, but since they are made of paper, they do not change shape due to moisture. The disadvantage is that the strength is not comparable to the above-mentioned activated carbon molded product, and the pot life is not long because the activated carbon fiber content is not large. In light of the above problems, an activated carbon molded body was proposed in which activated carbon powder particles were bonded and supported in an inorganic support such as mountain skin, bentonite, clay minerals other than bentonite, and silicates, and then fired. It seems that no product that can guarantee sufficient practicality has yet appeared on the market. On the other hand, in the field of application of activated carbon molded bodies, more compactness and high performance functionality are required in the structure of the molded body, and when taking a honeycomb molded body as an example, the number of cells in the effective contact unit area is large. In addition, it is desirable that each cell wall is extremely thin (0.10 to 0.25 mm) and has appropriate mechanical strength.For example, the number of cells is 300 cells/1 square inch or more, preferably 400 cells/1 square inch, or Something that exceeds that requirement has been proposed as something that can meet the above requirements. By the way, based on general extrusion technology, it is 300
It is a thin structure with a maximum size of 1 square inch. However, it has been extremely difficult to extrude and mold such a multi-cell structure (thin-walled cell structure) using only the above-mentioned inorganic carrier. The reason for this is that the binding force of the carrier and the lubricity of the molding material are insufficient, and the cells collapse or deform to such an extent that their shape cannot be maintained after extrusion. Even if organic binders such as starch, funori, and polyether resin are used to prevent this, the required properties are still not satisfied due to insufficient binding strength and/or lack of slipperiness. This is assumed to be the cause of its appearance. The present invention has succeeded in commercializing a honeycomb molded body with a fine and thin-walled cell structure by adopting a specific organic binder and manufacturing conditions described below, and also when this honeycomb molded body is applied to ozone decomposition. The optimal range of cell space ratio (opening ratio) was established from the viewpoint of contact area with ozone gas, ventilation resistance, and mechanical viewpoint. Another noteworthy point in the present invention is that the activated carbon particles supported in the carrier have their adsorption surfaces exposed by actively making the carrier porous, and lose their catalytic adsorption ability. In addition, Kibushi clay, which is advantageous among clay minerals in terms of pore-forming properties, cost, and market availability, was selected as the carrier. According to the honeycomb molded body of the present invention, a thin-walled cell structure with a cell count of 450 (cells)/1 square inch can be obtained. Hereinafter, the present invention will be described in detail with reference to the drawings showing preferred embodiments. Fig. 1 is a perspective view showing an embodiment of the activated carbon honeycomb molded body of the present invention together with a partially enlarged view thereof; The figure is an explanatory view schematically showing the internal structure of the activated carbon honeycomb molded body of the present invention. The present invention comprises activated carbon powder 2 and a fired Kibushi clay carrier 1 that supports the activated carbon powder 2 in a porous body. The honeycomb molded body has a large number of fine pores 3 formed to allow contact between the adsorption surface of the bonded activated carbon 2 and ozone, and the honeycomb molded body has approximately the number of cells per unit area of effective contact with ozone.
This invention relates to an activated carbon honeycomb molded body for ozone decomposition, which has a multi-cell structure of 450 cells per square inch and has a cell space factor of 60 to 70%. Such a honeycomb molded body is made of activated carbon powder 2
and sinterable Kibushi clay powder, and an organic binder that serves as a binding force and lubricating agent and for forming pores by pyrolysis gas, that is, polyvinyl alcohol and methyl cellulose, either alone or in combination, may be added to the above mixed powder. Knead this kneaded material,
To obtain a honeycomb-shaped molded body as shown in Figure 1, it is extruded from a honeycomb die, cut into rounds of a predetermined thickness, dried, and then fired in a non-oxidizing atmosphere (fired at approximately 1100°C, which is above the decomposition temperature of the organic binder). This is obtained by forming a fired Kibushi clay carrier 1 containing activated carbon powder particles 2 in a porous body, and the fired Kibushi clay carrier 1 of this honeycomb molded body is The above-mentioned Kibushi clay powders are fired together and irregularly connected in a three-dimensional direction, so that the activated carbon powder particles 2 are intermingled in the body, and the activated carbon powder particles 2 are mixed and supported while maintaining the porous structure described below. That is, in such an activated carbon honeycomb molded body A, the fired Kibushi clay carrier 1 that supports the activated carbon powder particles 2 has a high strength and has little thermal deterioration or change over time, and the water content is lower than that in Example 1, which will be described later. As can be seen from the measurement results, it is extremely porous due to the large number of pores 3 created by the thermally decomposed volatile gases of polyvinyl alcohol and methyl cellulose, which are thermally decomposable organic binders, and does not block the effective contact surface of the activated carbon particles 2. Therefore, ozone can penetrate well into the inside and come into sufficient contact with the activated carbon powder particles 2, thereby exhibiting satisfactory activity. Polyvinyl alcohol or methyl cellulose, singly or in combination, as an organic binder increases the binding strength of the clay, improves the lubricity during extrusion, ensures a fine, thin-walled honeycomb structure, and prevents thermal decomposition before reaching the firing temperature. This exposes the adsorption surface of the activated carbon powder particles 2. In the case of the activated carbon honeycomb molded body A of the present invention having the internal structure as described above, the fired Kibushi clay carrier 1
It is preferable that the proportion of Kibushi clay to obtain the desired value is 5 to 90% by weight (including an appropriate amount of the organic binder described below), and the proportion of activated carbon powder 2 to be 95 to 10% by weight. If the proportion of Kibushi clay is less than 5% by weight and the activated carbon powder 2 exceeds 95% by weight, the Kibushi clay will be in a state close to an irregular three-dimensional network full of defects,
Since it becomes difficult to sufficiently bond and support the activated carbon powder particles 2,
The mechanical strength of the molded body A is significantly reduced and there is a risk of it collapsing even with a small external force.On the other hand, if the Kibushi clay exceeds 90% by weight and the activated carbon powder 2 accounts for less than 10% by weight, the activated carbon Since the powder particles 2 are buried in the structure of the Kibushi clay carrier 1, the contact of ozone with the activated carbon powder particles 2 is reduced, making it difficult to exhibit sufficient activity, that is, adsorption properties, and the activated carbon This is because the amount of powder particles 2 held is small, causing disadvantages such as a considerably shortened pot life. As described above, the activated carbon honeycomb molded body for ozone decomposition of the present invention has a large content of activated carbon powder, as high as 90% by weight, and most of it works effectively, so it can withstand long-term use. can. In addition, when comparing and weighing the strength, activity, and pot life of the activated carbon honeycomb molded body, it is more desirable that the Kibushi clay be in the range of 20 to 70% by weight and the activated carbon powder 2 be in the range of 80 to 30% by weight. Within this range, the molded product will have sufficiently satisfactory strength, activity, and pot life. However, if Kibushi clay is added at the above-mentioned upper limit of 90% by weight, the binding force (cohesive force) of activated carbon powder particles due to Kibushi clay is still insufficient to extrude a fine and thin-walled cell structure, for example, the number of cells decreases. In a honeycomb structure where the effective contact unit area of the honeycomb extrusion is 450 cells/1 square inch, each cell has a thin wall (0.10 to 0.25 mm).
Therefore, sufficient shape retention cannot be guaranteed in the extruded state. For this reason, an additional binder is required to supplement the binding force, but in addition to providing binding force, this binder improves the slipperiness of the extruded material and prevents material from pooling inside and outside the die during extrusion. If this is not prevented, the thin-walled cell structure cannot be extruded smoothly, and at the same time, if it is not thermally decomposed and gasified at the firing temperature of Kibushi clay, the effective adsorption surface of the activated carbon powder particles 2 must be closed with a solid coating. Therefore, it must be thermally decomposed before firing (making it impossible to breathe). It has been discovered that polyvinyl alcohol and methyl cellulose, alone or in combination, are optimal as binders that meet these conditions. The blending amount of these organic binders is an appropriate amount, for example, 5 to 20% by weight. Also, the thermal decomposition temperature of PVA is
250 to 600°, and that of methylcellulose is 200 to 500°. As the activated carbon powder 2, any of various commercially available activated carbon powders can be used, but among them, those with a relatively high purity with a surface area of 800 m ² /g or more obtained by the steam activation method have good activity. It is desirable to use selectively. In addition, Kibushi clay is most suitable as the inorganic powder for forming the fired support 1, taking into consideration its pore-forming property, market availability, price, and the fact that the support 1 is not required to have much hardness. From the viewpoints of kneading, handling, moldability, pore-forming properties, etc., the compacted clay powder and the activated carbon powder have a particle size of 100 to 300.
Preferably, the particles have a mesh-like particle size. The ozone-decomposing activated carbon honeycomb molded body of the present invention as described above can be easily manufactured by a method similar to the ceramic manufacturing method as described above, and therefore can be used in ozone exhaust gas decomposition filters for copying machines and aircraft. provide The present inventor further learned that in order to make a honeycomb molded body having such a thin-walled cell structure suitable for ozone decomposition, a cell space ratio (opening ratio) of 60 to 70% is a necessary condition ( Reason below). A honeycomb-shaped molded body with such a cell space factor has good contact with ozone, low ventilation resistance, and high mechanical strength, and satisfies various requirements for ozone decomposition. This is because they are preparing for In other words, if it is less than 60%, the contact with ozone and ventilation resistance will be poor;
%, the structural mechanical strength is insufficient. Therefore, in a honeycomb structure of 450 cells per square inch, such a cell space factor is a limiting requirement. Next, the activated carbon molded article of the present invention will be described in more detail with reference to Examples. (Example) In order to clarify the effects in the following examples, the three-point bending strength and water supply rate of a plate-shaped molded body were measured by the water absorption method. That is, 100-mesh-passed palm activated carbon powder, Kibushi clay, and a mixture of PVA and methyl cellulose were kneaded in the proportions shown in Table 1 below to produce five types of raw material compositions (a), (b), and (c).
(d) and (e) were prepared, each composition was pressure-molded into a plate shape of 5 mm x 10 mm x 30 mm using a hydraulic press (50 tons), and then dried. Next, these plate-shaped molded products were heated with _H2 .
It was fired at 1100° C. for 2 hours in a non-oxidizing atmosphere furnace containing N ₂ to obtain five types of activated carbon plate-shaped molded bodies. For the five types of molded bodies thus obtained, three-point bending strength (span 20 mm) and water supply rate were determined by the water absorption method. The results are shown in FIGS. 3 and 4. Looking at this Figure 3, the bending strength of the molded body increases at an accelerating rate as the proportion of Kibushi clay that binds and supports activated carbon powder particles 2 increases, but when Kibushi clay is 5% by weight, it is 1 Kg/cm ² , which may be a little insufficient in strength. Therefore, in order to provide a bending strength of several kg/cm ² or more that can withstand practical use, it is found that it is desirable to use Kibushi clay in an amount of 20% by weight or more. Furthermore, if you look at Figure 4, the water absorption of the molded body decreases as the amount of Kibushi clay increases, but even if the amount of Kibushi clay is 90% by weight, it will still absorb 20% of the water.
The water absorption rate shown above shows how highly porous this molded body is.

[Table] (Example 1) Raw material compositions (B) (C) (D) (E) (
(However, an appropriate amount of water was added to improve moldability) were extruded through a honeycomb die, dried, and fired at 1100°C for 3 hours in a non-oxidizing atmosphere furnace to form square cells per square inch. The number of pieces is 450,
Four types of activated carbon honeycomb molded bodies having dimensions of 25 mm in diameter and 22 mm in length were obtained. Of the molded bodies thus obtained, three types, B, C, and D, were subjected to an adsorption test under the following conditions. (Conditions) Two molded bodies B, C, and D are stacked, and an air-styrene mixed gas containing styrene monomer of 5000 ppm or more is passed through them at a flow rate of 1.26/min to increase the adsorbed weight over time. Determine. The results are shown in FIG. Furthermore, for molded bodies B and E, a similar adsorption test was conducted by changing the flow rate of the air-styrene mixed gas to 2/min. The results are shown in FIG.
For comparison, a similar adsorption test was also conducted on a conventional product of the same shape and size in which activated carbon powder was coated on the surface of a cordierite honeycomb structure, and the results are also shown in FIG. Looking at Figure 5, it can be seen that the smaller the proportion of Kibushi clay is, the larger the increase in adsorption weight is, and the better the adsorption ability is. There is not much difference from molded body 2,
Therefore, it can be seen that even a molded body containing 70% by weight of Kibushi clay can exhibit sufficient performance. Moreover, if you look at Figure 6, the molded body RO containing 30% by weight of Kibushi clay exhibits 4 to 5 times the adsorption capacity compared to that applied to a conventional honeycomb structure, and the adsorption capacity of the molded body containing 30% by weight of Kibushi clay is 4 to 5 times higher than that applied to a conventional honeycomb structure. The molded body E shows almost the same adsorption capacity as the conventional product, which shows how highly active and high-performance the honeycomb molded body of the present invention is. (Example 2) Honeycomb molded body obtained in Example 1 (activated carbon powder)
Air containing 1 ppm of n-butyl methacrylate was passed through 70% by weight of Kibushi clay and 30% by weight of Kibushi clay at a flow rate of 0.5 m/sec, and the n-
The pot life was investigated by measuring the butyl methacrylate concentration C over time. The results are shown in the 7th section.
As shown in the figure. For comparison, we also investigated the pot life under the same conditions for a conventional honeycomb molded body in which activated carbon powder was coated on the surface of a cordierite carrier, and a conventional filter in which activated carbon fiber paper was layered in a cardboard shape. The results are also shown in FIG. Looking at Figure 7, the C/Co value is 0.5, that is, the n-butyl methacrylate concentration C at the outlet is half of the n-butyl methacrylate concentration Co (1 ppm) at the inlet of the activated carbon honeycomb molded body. It takes about 400 hours for the honeycomb molded body of the present invention, about 25 hours for the conventional honeycomb molded body, and about 240 hours for the conventional activated carbon fiber paper laminated filter. It can be seen how long the pot life of the activated carbon honeycomb molded body is. Next, the ozone decomposition performance of the product of the present invention is shown in FIG. 8 in comparison with a conventional product. "Cavro" indicates a product according to an embodiment of the present invention, "N" indicates a known activated carbon fiber cloth, and "Kavro" indicates a known granular activated carbon, respectively. As is clear from the figure, with the product of the present invention, the emitted ozone concentration hardly changes over time, that is, the ozone decomposition performance is almost constant, whereas with the conventional product,
Both of the results show that the emitted ozone concentration increases with the passage of time, that is, the ozone decomposition ability decreases, and in addition to this tendency, it can be seen that the potential value of the emitted ozone concentration is also much higher. FIG. 9 shows how the number of cells in a honeycomb molded body varies with the ozone concentration before and after the honeycomb molded body. Straight line B shows a product with 450 cells in Example (B), and straight line Wa shows a product with exactly the same configuration as Example (B) but with 300 cells. From the figure,
The ozone concentration before the honeycomb molded body (filter inlet concentration) and the ozone concentration after the same (filter outlet concentration) maintain a linear proportional relationship in relation to the number of cells.In other words, if the inlet concentration is known, the outlet concentration can also be determined. It was found that the ozone removal rate was found to be proportional, and that the ozone removal rate was constant.
It has been found that the ozone decomposition ability is superior to that of the conventional extrusion technology. As can be understood from the above description, the activated carbon honeycomb molded body for ozone decomposition of the present invention has a thin-walled (thin-walled) cell count of 450/1 square inch, which has not been realized with the prior art. ) It is a honeycomb molded body with a cellular structure, and has high resolution with a wide range of contact with ozone.It is structured so that activated carbon powder particles are bonded and supported by a fired Kibushi clay carrier. , it has a large amount of activated carbon powder, which makes it possible to greatly increase the pot life (service life), and it also has a large number of pores formed by the decomposition gas of the organic binder, making it porous. Activated carbon powder has good contact with ozone and exhibits excellent activity. Furthermore, by setting the cell space factor of the honeycomb to 60 to 70%, the honeycomb molded body has excellent contact efficiency with gas, low ventilation resistance, and sufficient mechanical strength. effective.

[Brief explanation of drawings]

FIG. 1 is a tilted view showing an embodiment of the activated carbon honeycomb molded body for ozone decomposition of the present invention together with a partially enlarged view, FIG. 2 is an explanatory diagram schematically showing the internal structure of the honeycomb molded body, and FIG. 3 and Fig. 4 are graphs showing the bending strength and water absorption rate of the molded body of an experimental example of the present invention, Fig. 5 is a graph showing the adsorption performance of the activated carbon honeycomb molded body for ozone decomposition of the present invention, and Fig. 6 is a graph showing the same honeycomb molded body. Figure 7 is a comparison graph of the pot life of the same honeycomb molded body and a conventional product, and Figure 8 is a comparison graph of the ozone decomposition performance of the honeycomb molded body of the present invention with a conventional product. The graph shown in FIG. 9 is a graph showing the relationship between the number of cells and ozone decomposition performance. Explanation of symbols, 1...Calcined Kibushi clay carrier, 2...
...Activated carbon powder, A...Activated carbon honeycomb molded body for ozone decomposition of the present invention, a...Cell.

Claims (1)

[Claims] 1 Consists of activated carbon powder and a fired Kibushi clay carrier that supports the activated carbon powder in a porous body. The honeycomb molded body has a small number of cells of approximately 450 cells/1 square inch in the unit area of effective contact with ozone, allowing contact between the adsorption surface of the activated carbon and the adsorption surface of the activated carbon that is bonded and supported in large numbers. An activated carbon honeycomb molded body for ozone decomposition that has a cell structure and a cell space factor of 60 to 70%.