JP2006212527A - Catalyst, catalyst carrier, and manufacturing method of catalyst carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which is capable of exhibiting a higher gas purification function than the catalyst of conventional technology while utilizing molding sand, and to provide a catalyst carrier which can form the catalyst carrier utilizing molding sand and which enhances gas diffusibility and to provide its manufacturing method. <P>SOLUTION: The catalyst carrier is prepared by having an alumina layer formed on the surface of a porous material which is formed by the molding sand and the gas diffusibility can be enhanced at the inside due to pores of the porous material. The manufacturing method of the catalyst carrier comprises granulating the kneaded material by adding water to the molding sand to obtain the granular, then forming the porous material by calcining its granular and further forming the alumina layer on the surface of the porous material. The catalyst which is illustrated separately is to carry the catalyst material on the catalyst carrier and has the high gas purification function (removability). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catalyst carrier for carrying a catalyst substance such as platinum, a method for producing the catalyst carrier for producing the catalyst carrier, and a gas purification catalyst comprising the catalyst substance carried on the catalyst carrier. About.

Conventionally, as a gas purification catalyst used for purifying a gas, a catalyst in which a catalyst material such as platinum is supported on a granular catalyst carrier made of alumina is known (see, for example, Patent Document 1). In recent years, from the viewpoint of environmental conservation and effective use of resources, various by-products that have been disposed of in the past have been recycled and reused. In the foundry industry as well, waste sand generated during the casting process is being used. Various techniques for diverting casting sand such as (waste casting sand or casting waste sand) to other uses have been proposed (for example, see Patent Document 2).
Japanese Patent Publication No.59-26335 Japanese Patent Laid-Open No. 11-128968

  However, in the catalyst according to the above-mentioned prior art, although the surface area of the granular catalyst carrier made of alumina is large, the pores of the catalyst carrier are too fine, so the gas diffusibility inside the catalyst is poor, and the gas purification function is sufficient. There was a possibility that it could not be demonstrated. In the foundry industry, problems such as a shortage of disposal sites and rising disposal costs are becoming increasingly serious, and it is strongly desired to expand the application range of foundry sand and other foundry sand.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a catalyst capable of exhibiting a higher gas purification function than a catalyst according to the prior art while utilizing foundry sand. It is in. Another object of the present invention is to form a catalyst carrier (a porous body as a base thereof) using foundry sand, and to improve the gas diffusivity inside the catalyst carrier and to produce the catalyst carrier. It is to provide a method.

  As a result of intensive studies focusing on diverting foundry sand and other foundry sands to the gas purification catalyst field, the inventor has obtained a porous body formed from the foundry sand as a raw material as the base of the catalyst carrier. And the catalyst is formed by supporting a catalyst substance on a catalyst support formed by forming an alumina layer on the surface of the porous body, thereby making the catalyst more than the catalyst according to the prior art. The present inventors have found that an excellent gas purification function can be sufficiently exhibited, and have completed the present invention.

  That is, the gist of the catalyst carrier of the invention described in claim 1 is that an alumina layer is further formed on the surface of a porous body formed from foundry sand.

  According to the catalyst carrier of the first aspect of the present invention, since the alumina layer is formed on the surface of the porous body, the catalyst carrier has a large number of pores in the porous body. Thus, the alumina layer on the surface of the porous body can sufficiently serve as a catalyst support layer for supporting the catalyst substance. In the catalyst carrier according to the first aspect of the present invention, since the porous body serving as the base is formed from foundry sand, the use of foundry sand can be achieved.

  The gist of the invention according to claim 2 is that, in the catalyst carrier according to claim 1, the foundry sand is waste sand discharged from a foundry.

  According to the catalyst carrier of the invention described in claim 2, in addition to the effects of the invention described in claim 1, since the waste sand discharged from the foundry is used as foundry sand, it is disposed as waste. It becomes possible to effectively use the waste sand that was needed. By effectively using the waste sand as waste in this way, waste disposal costs related to the waste sand are not necessary, and the waste sand can be efficiently used as the base of the catalyst carrier, so that the cost can be reduced.

  According to a third aspect of the present invention, there is provided a method for producing a catalyst carrier comprising the steps of granulating a kneaded product obtained by adding water to a foundry sand and kneading the granulated product, and then firing the granulated product to obtain a porous body. The gist is to form a catalyst carrier by forming an alumina layer on the surface of the porous body.

  The invention according to claim 3 is a method for producing a catalyst carrier suitable for producing the catalyst carrier according to claim 1 or claim 2. According to the third aspect of the present invention, after the kneaded material obtained by adding water to the foundry sand and kneading is granulated to obtain a granulated product, the granulated product is fired to form a porous body. Further, by further forming an alumina layer on the surface of the porous body, a catalyst carrier having the effects described in claim 1 and claim 2 can be suitably obtained. Further, since the porous body serving as the base of the catalyst carrier is a fired body (sintered body) formed by firing (sintering) the granulated product, the mechanical strength of the catalyst carrier is sufficiently exhibited.

  According to a fourth aspect of the present invention, there is provided a method for producing a catalyst carrier comprising a kneading step of kneading 90-60% by mass of foundry sand and 10-40% by mass of water to obtain a kneaded product, and granulating the kneaded product. A granulation step for obtaining a granulated product, a first firing step for obtaining a porous body by firing the granulated product at a heating temperature of 600 to 1100 ° C., and the porous body in an alumina-containing solution. An immersing step for immersing, a drying step for drying the immersed porous body, and an alumina layer on the surface of the porous body by firing the dried porous body at a heating temperature of 300 to 600 ° C. The gist is to provide a second firing step to be formed.

  The invention according to claim 4 is a method for producing a catalyst carrier suitable for producing the catalyst carrier according to claim 1 or claim 2. According to the invention described in claim 4, the kneading step, the granulation step, the first firing step, the dipping step, the drying step, and the second firing step according to claim 4 are sequentially performed. Thus, a catalyst carrier having the effects described in claims 1 and 2 can be suitably obtained. Further, in the first firing step, the porous body serving as the base of the catalyst carrier is a fired body (sintered body) formed by firing (sintering) the granulated product, so that the mechanical strength of the catalyst carrier is It is fully demonstrated.

  The gist of the catalyst of the invention described in claim 5 is that the catalyst material is supported on the catalyst carrier described in claim 1 or claim 2.

  According to the fifth aspect of the present invention, the catalyst has an excellent gas purification function by supporting the catalytic material according to the first and second aspects (particularly the alumina layer) as a catalyst. It becomes possible to fully demonstrate. That is, the catalyst according to the present invention can exhibit a higher gas purification function than the catalyst according to the prior art.

  According to the first and second aspects of the invention, it is possible to form a catalyst carrier (a porous body as a base thereof) using foundry sand, and to improve gas diffusibility inside the catalyst carrier. Can be raised. Further, according to the invention described in claim 2, since waste sand which is waste can be used effectively, cost can be reduced. According to the third and fourth aspects of the invention, it is possible to form a catalyst carrier (a porous body that is the base) using casting sand and to increase gas diffusibility inside. A catalyst support capable of being obtained can be suitably obtained. Moreover, according to the invention of Claim 3 and Claim 4, the catalyst support | carrier (especially porous body) can fully exhibit the mechanical strength. According to the fifth aspect of the present invention, a gas purification function higher than that of the catalyst according to the prior art can be exhibited while using foundry sand (high gas diffusibility inside the catalyst can be exhibited).

  As the catalyst carrier according to the present invention, it is necessary to use a catalyst in which an alumina layer (wash coat) is further formed on the surface of a porous body formed from casting sand as a raw material. Here, as the catalyst carrier according to the present invention, for example, after casting sand and water are kneaded to obtain a kneaded product, the kneaded product is granulated into pellets to obtain a granulated product, and the granulated product. The pellet can be used by firing the product to form a pellet-like porous body and further forming an alumina layer on the surface of the porous body. Thus, after kneading foundry sand and water to form a kneaded product, the kneaded product is granulated into pellets, and the granulated product is fired to form a pellet-like porous material. The method of forming a body and further forming an alumina layer on the surface of the porous body is an example of a method for producing a catalyst carrier.

  The shape of the catalyst carrier is appropriately set in order to correspond to various uses, and is not particularly limited. However, it is preferable to use a pellet shape for gas purification. The particle size of the catalyst carrier is also appropriately set in order to cope with various uses, and is not particularly limited, but it is considered that a size of 0.1 to 30 mm is desirable. The particle size of the catalyst carrier is more preferably 0.3 to 25 mm and 0.5 to 20 mm, and further preferably 1 to 15 mm, 1.5 to 10 mm, 2 to 8 mm, and 3 to 5 mm. .

  As the foundry sand, sand (new sand) used for making a cast can be used as it is, or used foundry sand (waste sand) discharged from a foundry and treated as waste can be used. In this case, it is preferable to use waste sand (waste cast sand or cast waste sand) as the foundry sand. By using the waste sand, it is possible to effectively use the waste sand and to reduce the manufacturing cost of the catalyst carrier and the catalyst. Examples of the waste sand include dust collection dust collected by a dust collector in a foundry, fine sand generated when a used casting sand mold is opened, and the like.

  As components of the dust collection dust, 50 to 85% by mass of silica (silicon dioxide), 5 to 30% by mass of alumina (aluminum oxide), 2 to 20% by mass of iron oxide, 2 to 10% by mass of carbon, 0 Examples include 0.5 to 5% by mass of magnesia (magnesium oxide), 0.3 to 5% by mass or less of calcia (calcium oxide), and 5.2% by mass or less. Examples of other components include manganese oxide, sodium oxide, potassium oxide, sulfur, phosphorus, titanium oxide, chromium, zinc, nickel, copper, molybdenum, lead, cadmium, arsenic, and chlorine. Moreover, 1-250 micrometers can be illustrated as a particle size of dust collection dust. The particle size of the dust collection dust is more preferably 3 to 200 μm, still more preferably 7 to 150 μm, and still more preferably 10 to 110 μm.

  In forming the porous body from the granulated product, the granulated product is slightly baked when the granulated product is baked (during sintering). It is preferable to set in advance so that the particle size of the product becomes slightly larger. A granulated product having a predetermined particle size is fired (sintered) to form a pellet-shaped porous body (fired body or sintered body). This porous body has a pore diameter of 0.01 to 10 μm, with 1 μm being the most frequent pore diameter. In addition, the porous body is an inorganic porous body formed from a material derived from foundry sand, and the porous body loses organic substances such as carbon in the granulated product when the granulated product is fired. Innumerable pores are formed as disappearance traces of organic matter. In addition, this porous body has irregularities when viewed microscopically and has sufficient mechanical strength. Due to the unevenness of the porous body, the alumina layer can be easily held on the surface of the porous body. Further, by forming the alumina layer on the surface (unevenness) of the porous body, the surface area of the catalyst carrier based on the porous body is dramatically increased. Thus, dramatically increasing the surface area of the catalyst carrier can greatly contribute to the improvement of the gas purification function of the catalyst carrier.

  As alumina forming the alumina layer (wash coat), γ-alumina, δ-alumina, η-alumina, χ-alumina, θ-alumina, κ-alumina, ρ-alumina, α-alumina, amorphous alumina ( Amorphous alumina) or the like can be used. Moreover, as alumina, one of these may be used alone, or two or more may be used in combination. When the alumina layer is formed on the surface of the porous body, the alumina layer may be formed on the entire surface of the porous body, or the alumina layer may be formed only on a part of the surface of the porous body. Then, an alumina layer may be formed on a portion excluding a part of the surface of the porous body. Furthermore, the alumina layer may be a single layer composed of one layer or a multilayer composed of two or more layers. The alumina layer plays a role as a catalyst support layer that can contribute to support the catalyst material. In particular, it is preferable to use γ-alumina as the alumina forming the alumina layer. γ-alumina has a pore diameter (pores) of 0.015 μm or less centered on 0.01 μm.

  The catalyst according to the present invention can be obtained by supporting the catalyst material on the catalyst carrier (particularly the alumina layer) described above. In particular, it is preferable to apply the gas purification catalyst according to the present invention as a pellet-shaped catalyst (pellet catalyst). Since the catalyst is simply a catalyst substance supported on the catalyst carrier, it can be said that the catalyst particle size is almost the same as the catalyst carrier particle size. As the catalytic substance (catalytically active substance), noble metals such as platinum, palladium, rhodium, ruthenium, iridium, gold and silver, and base metals such as manganese and iron can be used, but are not limited thereto. . When a catalyst material is supported on the catalyst carrier, one type of catalyst material may be used alone, or two or more types of catalyst materials may be used in combination. In addition, since platinum and palladium tend to be highly active against various gases, it is preferable to use platinum or palladium as a catalyst substance.

  Gases for purification include acetaldehyde, hydrogen, carbon monoxide, methanol, ethylene, cyclohexane, toluene, methyl ethyl ketone, methyl disulfide, xylene, ammonia, trimethylamine, ethanol, triethylamine, acetic acid, formaldehyde, benzene, styrene, methyl isobutyl Examples include ketones, acrolein, butyl alcohol, acetic acid, butyric acid, ethyl acetate, phenol, methyl mercaptan, ethyl mercaptan, and hydrogen sulfide. In particular, it is preferable to apply the gas purification catalyst according to the present invention to acetaldehyde.

  As a method for producing the above-mentioned catalyst carrier, a kneading step of kneading 90-60% by mass of foundry sand and 10-40% by mass of water to obtain a kneaded product, granulating the kneaded product, and granulating A granulating step for obtaining a product, a first firing step for obtaining a porous body by firing the granulated product at a heating temperature of 600 to 1100 ° C., and an immersion step for immersing the porous body in an alumina-containing solution A drying step of drying the immersed porous body, and a second step of forming an alumina layer on the surface of the porous body by firing the dried porous body at a heating temperature of 300 to 600 ° C. A method comprising a firing step can be exemplified. However, the method for producing the catalyst carrier according to the present invention is not particularly limited to the exemplified production method.

  In the kneading step of the catalyst carrier production method, it is preferable to knead 85 to 65% by weight of foundry sand and 15 to 35% by weight of water, and 83 to 70% by weight of foundry sand and 17 to 30% by weight of water. It is more preferable to knead. In the granulation step, the kneaded product is preferably granulated as a pellet-shaped granulated product. Furthermore, the first calcination step of the method for producing a catalyst carrier is performed after the granulated product is heated at, for example, 400 to 500 ° C. for 8 hours to burn the organic matter in the granulated product (after the organic matter burning step). preferable. In the first firing step of the catalyst carrier production method, the granulated product is preferably calcined at a heating temperature of 700 to 1000 ° C. and 700 to 950 ° C., and the granulated product is heated at 750 to 900 ° C. and 750 to 850 ° C. Baking at a temperature is more preferable. Examples of the heating time for the first firing step include 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours.

  As the alumina-containing solution corresponding to the coating solution for coating the porous body with the alumina layer in the dipping step of the catalyst carrier production method, a solution obtained by adding alumina particles to a colloidal solution of silica sol can be used. However, it is not particularly limited to this alumina-containing solution. Moreover, in the drying step of the method for producing a catalyst carrier, the porous body can be dried by heating the porous body immersed in the alumina-containing solution at a temperature of 100 to 150 ° C. In the second firing step of the catalyst carrier production method, it is preferable to fire the dried porous body at a heating temperature of 350 to 550 ° C. and 400 to 550 ° C., and the dried porous body is 425 to 525 ° C., 450 to Baking at a heating temperature of 525 ° C. is more preferable. Examples of the heating time for the second baking step include 12 hours, 24 hours, 48 hours, and the like.

  The method for producing a catalyst according to the present invention is exemplified by a production method further comprising a catalyst carrying step for carrying a catalyst substance on the catalyst carrier after the production step for producing the catalyst carrier using the above-described catalyst carrier production method. be able to. The catalyst carrier (especially the alumina layer) is supported on the catalyst carrier (especially the alumina layer) by spraying a solution containing the catalyst substance on the catalyst carrier (especially the alumina layer) and then firing, thereby supporting the catalyst substance on the alumina layer of the catalyst carrier. Although the carrying | support method to be made can be illustrated, it is not limited to this carrying method in particular.

  Below, the Example 1 and Example 2 which further embodied this invention, and the comparative example which concerns on a prior art are demonstrated.

  First, 20% by mass of water is added to 80% by mass of dust collection dust as waste sand discharged from a foundry, and these dust collection dust and water are kneaded using a kneader to collect the dust collection dust and water. A kneaded material in which and were mixed was obtained. Here, the components of the dust collection dust are 68.3 mass% silica, 13.4 mass% alumina, 3.92 mass% iron oxide, 5.22 mass% carbon, 1.96 mass% magnesia, 1.2 calcia. The mass was 6.0% by mass.

  And the obtained kneaded material was thrown into the granulation container provided with the stirring blade, and this stirring blade was rotated with the motor, and the several granulated material which has a particle size of about 3-5 mm was granulated. These granulated products are heated at 400 to 500 ° C. for 8 hours to burn the organic matter in the granulated products, and then fired at 800 ° C. for 3 hours to form a pellet-like inorganic porous body having a particle size of 3 to 5 mm. Formed. This inorganic porous body had a pore size of 0.01 to 10 μm with 1 μm being the most frequent pore size, an apparent porosity of about 30%, and a crushing strength of about 123 N.

  Next, 33% by mass of γ-alumina particles (particle size: 10 to 15 μm) was added to a 67% by mass silica sol colloidal solution to prepare a coating solution. After injecting 3 kg of the prepared coating liquid into the container, 1 kg of the inorganic porous body was immersed in the coating liquid in a state where the coating liquid was stirred with a stirrer for 0.5 hour. Thereafter, the inorganic porous body was taken out from the coating solution and heated at 110 ° C. for 24 hours to dry the inorganic porous body.

  After the inorganic porous body is dried, the inorganic porous body is further baked at 500 ° C. for 2 hours to form a γ-alumina layer on the entire surface of the inorganic porous body. As a result, a catalyst carrier having a particle diameter of 3 to 5 mm was obtained in a state where the entire surface having γ was coated with γ-alumina particles (coated state). In addition, since the γ-alumina layer on the inorganic porous body has pores of 0.015 μm or less centering on 0.01 μm, the pores of the γ-alumina layer and the pores of the inorganic porous body are Communication is established.

  After spraying a hexaammineplatinum (IV) chloride aqueous solution to the γ-alumina layer of the obtained catalyst carrier, the catalyst carrier is calcined at 500 ° C. for 2 hours, and platinum and a catalyst material are added to the γ-alumina layer of the catalyst carrier. The oxide was supported. Thus, platinum etc. were carry | supported by the (gamma) -alumina layer of a catalyst support | carrier, and the pellet-shaped catalyst (pellet catalyst) with a particle size of 3-5 mm was obtained. The amount of platinum (Pt) supported per liter of the pellet catalyst was 2 g.

Next, the gas purification function (acetaldehyde removal function) of the obtained pellet catalyst (Example 1) was evaluated. As an evaluation method, a predetermined amount of the pellet catalyst (Example 1) is arranged in the catalytic reaction apparatus (catalytic oxidation apparatus), and acetaldehyde is continuously flowed into the catalytic reaction apparatus from the upstream side of the pellet catalyst inlet. An experimental method was used to measure the acetaldehyde removal rate (acetaldehyde concentration downstream of the pellet catalyst outlet) of the pellet catalyst (Example 1) 10 minutes after flowing in. In this case, the SV value was set to 5000 (h ⁻¹ ), and the catalyst inlet temperature (pellet catalyst inlet temperature) was changed by three points (210 ° C., 310 ° C., 410 ° C.) and evaluated. The evaluation results are shown in FIG. As shown in FIG. 1, in the pellet catalyst of Example 1, the acetaldehyde removal rate at a catalyst inlet temperature of 210 ° C. is 80%, and the acetaldehyde removal rate at a catalyst inlet temperature of 310 ° C. is 90%. The removal rate of acetaldehyde at a catalyst inlet temperature of 410 ° C. was 95%.

When acetaldehyde is removed (purification or oxidative decomposition) by the pellet catalyst, acetaldehyde undergoes a chemical reaction as described in the following chemical reaction formulas (1) and (2). That is, when the chemical reaction described in the chemical reaction formula (1) occurs, acetic acid (CH ₃ COOH) is generated as an intermediate, and the generated acetic acid (CH ₃ COOH) is further described in the chemical reaction formula (2). Try to do a chemical reaction. In the experiment for evaluating the gas purification function (acetaldehyde removal function) of the above-described pellet catalyst (Example 1), the acetaldehyde removal rate of the pellet catalyst (Example 1) (acetaldehyde concentration downstream from the pellet catalyst outlet) At the same time, the acetic acid concentration (acetic acid production concentration) downstream from the pellet catalyst outlet was also measured according to the catalyst inlet temperature (pellet catalyst inlet temperature). The measurement results are shown in FIG. As shown in FIG. 2, in the pellet catalyst of Example 1, the acetic acid concentration at a catalyst inlet temperature of 210 ° C. is 2.8 ppm, and the acetic acid concentration at a catalyst inlet temperature of 310 ° C. is 3.9 ppm. The acetic acid concentration at an inlet temperature of 410 ° C. was 4.0 ppm.

  Here, the description of the same parts as those in the first embodiment will be omitted, and differences from the first embodiment will be mainly described. In the pellet catalyst of Example 2, after forming a γ-alumina layer on the entire surface of the inorganic porous material in the same manner as in Example 1, a γ-alumina layer is formed by applying the same coating treatment. As a result, a catalyst carrier was obtained. That is, in the catalyst carrier of Example 2, two γ-alumina layers are formed on the inorganic porous body (or the γ-alumina layer is formed thicker than the catalyst carrier of Example 1), This is different from the catalyst carrier of Example 1 in which one γ-alumina layer is formed on an inorganic porous body (or formed into a thin layer). And the catalyst support process similar to Example 1 was performed with respect to the (gamma) -alumina layer of the obtained catalyst support, and the pellet-shaped catalyst (pellet catalyst) with a particle size of 3-5 mm was obtained. The amount of platinum (Pt) supported per liter of the pellet catalyst was 2 g.

Next, also in Example 2, while evaluating the gas purification function (acetaldehyde removal function) of the pellet catalyst (Example 2) under the same conditions as in Example 1, acetic acid at the downstream side of the pellet catalyst outlet was also evaluated. The concentration (acetic acid production concentration) was also measured according to the catalyst inlet temperature (inlet temperature of the pellet catalyst). The evaluation results and measurement results are shown in FIGS. As shown in FIG. 1, in the pellet catalyst of Example 2, the removal rates of acetaldehyde at the catalyst inlet temperatures of 210 ° C., 310 ° C., and 410 ° C. were all 100%. Further, as shown in FIG. 2, in the pellet catalyst of Example 2, the acetic acid concentration at the catalyst inlet temperature 210 ° C. is 0.5 ppm, and the acetic acid concentration at the catalyst inlet temperature 310 ° C. is 0.6 ppm. The acetic acid concentration at a catalyst inlet temperature of 410 ° C. was 0.5 ppm.
(Comparative example)

  Here, the description of the same parts as in the first embodiment will be omitted, and differences from the first embodiment will be mainly described. In the comparative example, 1 kg of a catalyst carrier having a particle diameter of 3 to 5 mm and made of γ-alumina was prepared. The prepared catalyst carrier (γ-alumina carrier) was subjected to the same catalyst loading step as in Example 1 to obtain a pellet-shaped catalyst (pellet catalyst) having a particle diameter of 3 to 5 mm. In addition, this pellet catalyst (comparative example) is one in which platinum or the like is supported on a γ-alumina carrier. The amount of platinum (Pt) supported per liter of the pellet catalyst was 2 g.

For the comparative example, the gas purification function (acetaldehyde removal function) of the pellet catalyst (comparative example) was evaluated under the same conditions as in Example 1, and the acetic acid concentration (acetic acid production concentration) downstream from the pellet catalyst outlet. ) Was also measured according to the catalyst inlet temperature (inlet temperature of the pellet catalyst). The evaluation results and measurement results are shown in FIGS. As shown in FIG. 1, in the pellet catalyst of the comparative example, the removal rate of acetaldehyde at a catalyst inlet temperature of 210 ° C. is 63%, and the removal rate of acetaldehyde at a catalyst inlet temperature of 310 ° C. is 78%, The acetaldehyde removal rate at a catalyst inlet temperature of 410 ° C. was 84%. Further, as shown in FIG. 2, in the pellet catalyst of the comparative example, the acetic acid concentration at the catalyst inlet temperature 210 ° C. is 6.1 ppm, and the acetic acid concentration at the catalyst inlet temperature 310 ° C. is 8.2 ppm. The acetic acid concentration at the catalyst inlet temperature of 410 ° C. was 9.8 ppm.
(Comparison between Examples and Comparative Examples)

  From the evaluation results of FIG. 1, when the example and the comparative example are compared, the catalyst of the example 1 and the example 2 is superior in the acetaldehyde removal function (purification function) than the catalyst of the comparative example. It could be confirmed. Further, from the measurement results of FIG. 2 and the chemical reaction formulas (1) and (2), when the examples and the comparative examples are compared, the catalysts (oxidation catalysts) of the examples 1 and 2 are the comparative examples. The rate of oxidative decomposition (reaction rate) of acetaldehyde was faster than that of the catalyst (oxidation catalyst), and the concentration of acetic acid remaining as an intermediate was also low. Therefore, it was confirmed that the oxidation resolution (removal function or purification function) of acetaldehyde was high. . Furthermore, from comparison between Example 1 and Example 2, Example 2 (or γ-alumina layer having a thickness greater than that of Example 1 in which one layer of γ-alumina layer was formed on the inorganic porous body was formed. It was found that the one formed in the layer) was superior in the acetaldehyde removal function (purification function).

The reason why the catalyst of the example is superior in the gas purification function of acetaldehyde than the catalyst of the comparative example is that, in the comparative example, the pores of the γ-alumina carrier (catalyst carrier) are too small. While the inside of the γ-alumina support cannot be effectively used for gas purification, in the examples, not only the γ-alumina layer but also the pores (inorganic porous body) due to the relatively large pores of the inorganic porous body. Or the inside of the catalyst carrier) is presumed to be effective for gas purification (in the catalyst of the comparative example, since the γ-alumina carrier has only fine pores, the gas diffusibility inside the catalyst is low). Although it is worse, in the catalyst of the example, the base of the catalyst carrier is a porous body having relatively large pores, so the gas diffusivity inside the catalyst is clearly improved over the catalyst of the comparative example. Thought to be That).
(Appendix)

  In addition, technical ideas that are not described in each claim of the claims and that are grasped from the best mode for carrying out the invention will be described below together with the effects thereof.

(A) The method for producing a catalyst carrier according to claim 4, wherein the first firing step is performed after the organic matter combustion step in which the organic matter in the granulated material is burned.

  According to said (a), in addition to the effect of the invention of Claim 4, by performing a 1st baking process after an organic substance combustion process, the porous body from which organic substances, such as carbon, lose | disappeared completely is more reliable. Can get to.

(B) After adding water to the foundry sand and kneading, the kneaded product is granulated to obtain a granulated product, and the granulated product is fired to form a porous body. A catalyst carrier comprising an alumina layer further formed on the surface.

  According to the above (b), since the alumina layer is formed on the surface of the porous body, the gas diffusibility inside the catalyst carrier is increased due to the numerous pores of the porous body. In addition, the alumina layer on the surface of the porous body can sufficiently serve as a catalyst support layer for supporting the catalyst substance. Further, since the porous body serving as the base of the catalyst carrier is a fired body (sintered body) formed by firing (sintering) the granulated product, the catalyst carrier can sufficiently exhibit its mechanical strength. Furthermore, in the catalyst carrier of (b) above, the kneaded product is formed using foundry sand and water, so that the foundry sand can be used.

(C) After adding water to the foundry sand and kneading, the kneaded product is granulated to obtain a granulated product, and the granulated product is fired to form a porous body. A catalyst carrier comprising an alumina layer formed on the surface and an alumina layer further formed on the alumina layer.

  According to the above (c), since the two alumina layers are formed on the surface of the porous body, gas diffusion inside the catalyst carrier due to the numerous pores of the porous body Therefore, the alumina layer can sufficiently exhibit the role as a catalyst support layer for supporting the catalyst substance. In addition, according to the above (c), compared with a catalyst carrier (corresponding to the above (b)) in which one alumina layer is formed on the surface of the porous body, there is one extra alumina layer. Since the surface area of the catalyst carrier increases accordingly, the gas purification function of the catalyst carrier can be enhanced. Furthermore, since the porous body serving as the base of the catalyst carrier is a fired body (sintered body) formed by firing (sintering) the granulated product, the catalyst carrier can sufficiently exhibit its mechanical strength. In addition, in the catalyst carrier described in (c) above, since the kneaded material is formed using foundry sand and water, the foundry sand can be used.

(D) a kneading step of kneading 90-60% by mass of foundry sand and 10-40% by mass of water to obtain a kneaded product;
A granulation step of granulating the kneaded product to obtain a granulated product;
A first firing step of obtaining a porous body by firing the granulated material at a heating temperature of 600 to 1100 ° C;
A first immersing step of immersing the porous body in an alumina-containing solution;
A first drying step of drying the immersed porous body;
A second firing step of forming an alumina layer on the surface of the porous body by firing the dried porous body at a heating temperature of 300 to 600 ° C .;
A second immersion step of immersing a porous body having an alumina layer formed on the surface after the second firing step in an alumina-containing solution;
A second drying step of drying the porous body having an alumina layer formed on the surface after the second immersion step;
The 3rd baking which forms an alumina layer further on the alumina layer of this porous body surface by baking the porous body by which the alumina layer was formed on the surface after the 2nd drying process at the heating temperature of 300-600 degreeC And a process for producing a catalyst carrier.

  The above (d) is a method for producing a catalyst carrier suitable for producing the catalyst carrier described in (c) above. According to (d) above, the kneading step, granulation step, first firing step, first immersion step, first drying step, second firing step, and second immersion according to (d) above. By carrying out the step, the second drying step, and the third firing step in order, a catalyst carrier that exhibits the effects described in (c) above can be suitably obtained.

(E) a kneading step of kneading 90-60% by weight of foundry sand and 10-40% by weight of water to obtain a kneaded product;
A granulation step of granulating the kneaded product to obtain a granulated product;
A first firing step of obtaining a porous body by firing the granulated material at a heating temperature of 600 to 1100 ° C;
An immersion step of immersing the porous body in an alumina-containing solution;
A drying step of drying the immersed porous body;
A second calcining step of calcining the dried porous body at a heating temperature of 300 to 600 ° C. to form an alumina layer on the surface of the porous body to obtain a catalyst carrier;
And a catalyst supporting step of supporting a catalyst substance on the alumina layer of the catalyst carrier.

  The above (e) is a method for producing a catalyst suitable for producing the catalyst according to claim 5. According to the above (e), the kneading step, the granulation step, the first firing step, the dipping step, the drying step, the second firing step, and the catalyst supporting step according to the above (e) are sequentially performed. By doing so, the catalyst which has the effect of the said Claim 5 can be obtained suitably.

It is a graph which shows the gas purification performance of the catalyst of an Example and a comparative example. It is a graph which shows the acetic acid density | concentration downstream from the catalyst exit of an Example and a comparative example.

Claims (5)

  A catalyst carrier, wherein an alumina layer is further formed on the surface of a porous body formed from casting sand as a raw material.   The catalyst carrier according to claim 1, wherein the foundry sand is waste sand discharged from a foundry.   After granulating a kneaded product obtained by adding water to the foundry sand and kneading it into a granulated product, the granulated product is fired to form a porous body, and an alumina layer is further formed on the surface of the porous body. A method for producing a catalyst carrier, comprising forming a catalyst carrier by forming the catalyst carrier. A kneading step of kneading 90-60% by weight of foundry sand and 10-40% by weight of water to obtain a kneaded product;
A granulation step of granulating the kneaded product to obtain a granulated product;
A first firing step of obtaining a porous body by firing the granulated material at a heating temperature of 600 to 1100 ° C;
An immersion step of immersing the porous body in an alumina-containing solution;
A drying step of drying the immersed porous body;
And a second calcining step of calcining the dried porous body at a heating temperature of 300 to 600 ° C. to form an alumina layer on the surface of the porous body.   A catalyst comprising the catalyst carrier according to claim 1 or 2 supported on a catalyst material.

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