JP6483884B2 - Method for producing supported catalyst for malodor treatment - Google Patents

Description

  The present invention relates to a method for producing a supported catalyst for malodor treatment.

  Malodorous components emitted from factory exhaust gas can adversely affect the living environment and cause complaints. Examples of such bad odors include, for example, volatile organic compounds (hereinafter referred to as “VOC”) emitted from painting factories, printing factories, chemical manufacturing processes, leather factories, human waste processing factories, etc. There are ammonia compounds discharged from the sea, and spears discharged from paint factories and restaurants. Many of these compounds are harmful to the human body and the natural environment.

  Various methods such as a direct combustion method, a catalytic combustion method, a physicochemical adsorption method, a biological treatment method, and a plasma method have been proposed as treatment methods for these malodors. Widely adopted because it is easy to maintain.

  Currently, most catalysts used for malodor treatment such as VOC use noble metals such as platinum and palladium. Although noble metals show high catalytic activity, alternative materials have been sought because they are expensive. Around 1980, a metal oxide catalyst using a relatively inexpensive metal such as Co, Cu, or Ce was proposed as a noble metal alternative to an exhaust gas treatment catalyst for automobiles (Non-patent Document 1). However, there have been cases in which the decomposition efficiency of the metal oxide is greatly reduced due to the progress of sintering (aggregation) between metal oxides during the preparation of the catalyst and during the treatment operation. In addition, since the catalytic activity per unit surface area is lower than that of noble metals such as platinum, more catalyst volume is required to ensure the same performance, and the problem of increased pressure loss has occurred. The situation that did not reach has continued. Furthermore, the catalyst activity varied greatly depending on the use conditions such as the catalyst preparation method, the composition of the gas to be treated, the reaction temperature, etc., and was unstable compared to the catalyst using noble metal.

However, in recent years when environmental problems have attracted attention, attention has again been focused on inexpensive catalysts that can replace noble metals, and several patents have been filed, including metal oxide catalysts such as Cu, Co, and Ce. (Patent Documents 1 to 4). Patent Document 1 reports that a cerium oxide (CeO ₂ ) catalyst is effective in decomposing water vapor-containing VOCs. Patent Document 2 proposes that it is effective to use a composite oxide catalyst in which V (vanadium) is dispersed in a support containing Co and Ce-based oxides for VOC treatment containing chlorine. In addition, in the patent document 3, the present applicants aim to achieve high efficiency by using a Cu, Co, Ce complex oxide catalyst that is effective for VOC decomposition and converting light energy absorbed by the catalyst into thermal energy. Proposed new usage.

  In addition, catalysts currently used in industry, including catalysts for environmental purification or automobiles, have low pressure loss and can prevent clogging due to pulverization. The thing which carried | supported is used. For this reason, it is an important practical issue to develop a supported catalyst in which a catalyst is supported on a carrier processed into an optimum shape. However, even when exhaust gas treatment is performed using a catalyst in which a metal oxide catalyst is supported on these carriers in the same manner as a noble metal, its performance is significantly inferior to that of platinum catalysts. Further, the activity of the catalyst layer tends to fluctuate. This is also described as a major reason for impeding practical use in Non-Patent Document 1 described above. A large change in performance depending on manufacturing conditions is an obstacle to practical use. Therefore, for the purpose of mass-producing Co and Ce-based oxide catalysts practically and inexpensively, the present applicant has proposed a new catalyst loading method in which cerium oxide and cobalt oxide, or further copper oxide is added. Proposed in As a result, it has become possible to ensure performance at a low cost and equivalent to or better than that of a platinum catalyst. However, in subsequent long-term durability tests, it has become clear that catalyst delamination may occur and performance may gradually deteriorate. It was also confirmed that even with the same material, for example, a cordierite carrier, the adhesion of the catalyst may not always be good in the ball-shaped catalyst as compared with the honeycomb-shaped catalyst.

J.T.kummer, Prog, Energy Combust.Sci.6 (1980) 177-199

Japanese Patent No. 4602165 Japanese Patent No. 3626754 JP 2010-94671 A JP 2012-200688

  Although the present applicant succeeded in securing the VOC / smelly odor removal performance equal to or better than that of a commercially available platinum catalyst without using a precious metal by the method of supporting the Co and Ce-based oxide catalyst, In a test on an actual machine scale, there was a problem that the catalyst layer was peeled off and the performance was gradually deteriorated. The adhesion of the catalyst tends to be remarkably improved by sintering in a high-temperature atmosphere, but when fired in a high-temperature atmosphere, there is a concern that the specific surface area decreases and the catalyst compound collapses, and the activity is deactivated. In order to use it practically, it is essential to overcome these problems.

  Accordingly, an object of the present invention is to provide a supported catalyst that can further improve the performance and stability of the Co and Ce-based oxide supported catalyst and can effectively maintain the activity for a long time. Yes.

  The inventor paid attention to particles of cobalt oxide obtained by mechanical control to an average particle size of 0.8 to 2 μm. Then, the treated cobalt oxide particles are arranged on the surface of the carrier in a rough state, and a catalyst having a porous structure in which cobalt oxide and cerium oxide or further copper oxide are dispersed in the gap is provided. The inventors have found that the catalyst layer becomes a catalyst layer that retains the porous structure and hardly peels from the carrier. Furthermore, the dispersibility could be further improved by interposing the clay powder in the catalyst body having the above structure.

  The present invention has been completed based on such findings.

  That is, the present invention is characterized by the following.

  The method for producing a supported catalyst for malodor treatment according to the present invention includes the following steps.

  a) A catalyst immersion liquid is prepared by mixing cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm with a salt or compound capable of generating cobalt ions, a salt or compound capable of generating cerium ions, and water. A step, b) a step of immersing the obtained catalyst soaking solution in a carrier, and c) a step of firing the carrier after the immersion treatment.

  In this method for producing a malodor-treated supported catalyst, it is preferable to prepare cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm by calcining or drying a cobalt salt or compound in advance and then pulverizing it. .

  According to the method of the present invention, it is difficult for the catalyst obtained to peel off the catalyst layer from the carrier. Thereby, it can be used practically. The Co, Ce-based oxide-supported catalyst of the present invention is, for example, a fatty acid ester such as an aniline discharged in a coating drying process or an ethyl acetate used in a printing factory at a temperature lower by about 100 ° C. than a conventional platinum catalyst. Features such as complete disassembly. This makes it possible to expand applications to fields that were difficult to handle with existing platinum catalysts, contributing to the activation of the environmental catalyst and exhaust gas treatment equipment market, improvement of the working environment, improvement of the living environment, and the like.

Comparison of ultrasonic peelability test results by difference in average particle diameter of Co ₃ O ₄ powder (honeycomb type) (A: after improvement, B: before improvement). Long-term test results on actual machine scale [SV: 30000h ⁻¹ , operating temperature: 320 ° C. (however, changed to 280 ° C. when measuring removal rate), VOC: about 700 ppm ethyl acetate] (honeycomb type) (A: after improvement , B: Before improvement). Comparison of ultrasonic peelability test results based on differences in average particle size of Co ₃ O ₄ powder (ball type) (A: after improvement, B: before improvement). Long-term test results on an actual scale [SV: 22000 h ⁻¹ , operating temperature: 320 ° C. (however, changed to 280 ° C. when measuring the removal rate), VOC: ethyl acetate about 700 ppm] (ball type). The particle size distribution (average particle size of 1.09 μm) of the Co ₃ O ₄ powder after the grinding treatment of Example 1. 2 is a particle size distribution (average particle size 2.55 μm) of Co ₃ O ₄ powder before pulverization in Example 1. FIG.

  In the supported catalyst for malodor treatment of the present invention, catalyst particles having the above-described characteristics are supported on a support material. That is, the supported catalyst includes a support (support material) and catalyst particles supported on the support.

  In the catalyst particles, cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm are covered with cobalt oxide having cobalt ions as a precursor and cerium oxide having cerium ions as a precursor. Here, the average particle size means the particle size (d0.5) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction method. Moreover, “the periphery of the cobalt oxide particles is covered with cobalt oxide and cerium oxide” means that cobalt oxide and cerium oxide are formed on the surface of the cobalt oxide particles. Therefore, in the supported catalyst of the present invention, the catalyst particles include cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm, cobalt oxide having cobalt ion as a precursor, and cerium having cerium ion as a precursor. And the cobalt oxide and the cerium oxide are formed on the surface of the cobalt oxide particles. As will be described later, the catalyst particles may be covered with copper oxide having copper ions as precursors in addition to cobalt oxide and cerium oxide. That is, the catalyst particles further include a copper oxide having copper ions as a precursor, and the cobalt oxide, the cerium oxide, and the copper oxide are formed on the surface of the cobalt oxide particles. It may be. The supported catalyst may have a clay mineral mainly composed of a composite silicate in order to improve the dispersibility of the catalyst particles, or may have a structure in which the catalyst particles are dispersed.

  Cobalt oxide particles are a variety of cobalt compounds such as carbonates, nitrates, sulfates, chlorides and other inorganic acid salts, alcoholates, carboxylates, complex salts and other organic compounds and calcined products such as organic salts, and dried solids. It may be. Among these, a compound prepared by baking a compound having a carbonate as a precursor at a low temperature of 250 to 400 ° C. in air is preferable. Moreover, it is also preferable that the cobalt oxide particles have been pulverized within an average particle size range of 0.8 to 2.0 μm. The pulverization process may be a dry pulverization process or a wet pulverization process, and the processing method is not limited. For example, the pulverization may be performed using a dry jet mill, or the pulverization may be performed by a dry bead mill method, a wet rotating ball mill method, or the like.

  In the present invention, the average particle diameter of the cobalt oxide particles is in the range of 0.8 to 2.0 μm for the following reason.

  That is, when the average particle diameter is less than 0.8 μm, cobalt oxide particles are likely to aggregate with each other, causing a decrease in the specific surface area under heating and reducing the activity, which is not preferable. Moreover, when exceeding 2.0 micrometers, since an adhesion area with a support | carrier is small and it will become easy to peel, it is unpreferable. From this point of view, in order to obtain a supported catalyst having a good balance between durability and releasability, the average particle diameter of the cobalt oxide particles is as follows. The range of 0.8-2.0 micrometers is preferable.

  The cobalt ions and cerium ions in the present invention are formed as cobalt and cerium water-soluble as salts or compounds. For example, nitrate, sulfate and the like. Such cobalt ions and cerium ions may coexist with copper ions. In the supported catalyst produced by coexisting copper ions, the cobalt oxide particles are covered with copper oxide having a copper ion as a precursor in addition to cobalt oxide and cerium oxide. It is more preferable that the copper ions coexist in the cobalt ions and the cerium ions so that the weight ratio of the catalyst particles is 0.1 to 5 wt%. Thereby, a supported catalyst with better catalytic performance can be obtained.

  Examples of the clay mineral mainly composed of the composite silicate include at least one clay mineral powder of kaolin, bentonite clay, activated clay, and diatomaceous earth.

  And the support | carrier used in this invention may be various things including a conventionally well-known thing. For example, a preferable example is one in which any one of stainless steel, steel, copper alloy, aluminum alloy, and ceramic material is formed into a desired shape.

  As the support, a porous structure having pores with a diameter of 5 μm to 50 μm on the surface can be adopted, and the supported catalyst of the present invention can also have a structure in which catalyst particles are held on this support. By adopting the porous structure having pores as described above as a carrier, it is possible to more effectively suppress the separation of the catalyst particles. More preferably, a porous structure having pores with a diameter of 20 μm to 40 μm on the surface is employed as the carrier.

  The malodor treatment supported catalyst of the present invention constituted by the elements as described above may be various methods, but can be preferably produced by the following process.

  That is, first, cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm are mixed with a salt or compound capable of generating cobalt ions, a salt or compound capable of generating cerium ions, and water to prepare a catalyst immersion liquid. To do. If necessary, a catalyst soaking solution may be prepared by mixing a salt or compound capable of producing copper ions and clay minerals mainly composed of complex silicates such as kaolin and activated clay.

  Next, this is dipped in a carrier and baked after dehydration. By this firing, cobalt ions and cerium ions are each converted into oxides. When copper ions are contained in the catalyst immersion liquid, the copper ions are also converted into oxides by this firing.

  Unlike the conventional multi-stage dipping method, the above manufacturing process is dipping in one stage, and is simple and efficient. In addition, the adhesion strength of the catalyst to the carrier and the catalytic activity are further improved, and a supported catalyst for high-performance malodor treatment that is stabilized for a long time is realized.

  The structure of the catalyst in the supported state is confirmed as a characteristic different from the uniform particle adhesion in the conventional method even in the particle size distribution.

(A) cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm, with respect to the supported catalyst obtained by adding a clay mineral mainly composed of composite silicate in the supported catalyst of the present invention;
(B) cobalt oxide having cobalt ion as a precursor;
(C) a cerium oxide having a cerium ion as a precursor,
(D) The mass ratio of the clay mineral mainly composed of the composite silicate can be set in consideration of the main type of VOC to be treated for malodor, the treatment conditions, and the like.

  Generally, when the total amount of (a), (b), (c), and (d) is 100% by mass, the following ranges are considered.

(A): 20 to 50% by mass
(B): 6 to 12% by mass
(C): 39 to 66% by mass
(D): 2 to 5% by mass
Among these, the ratio for (a) and (b) is particularly preferably considered. As the reason, it is considered to maintain the dispersed state of the cobalt oxide particles.

  Further, the amount supported on the carrier can be appropriately determined in consideration of the type of VOC to be used for the catalyst and the processing conditions, but generally, the mass ratio is 10 to 30 wt. % Range is preferably considered.

  In addition, about the usage form of the supported catalyst of this invention, it may be various similarly to the conventional VOC malodor treatment.

Examples and comparative examples will be described below.
<Evaluation of catalyst peelability>
The mass after holding the sample at 110 ° C. for 24 hours is measured (referred to as M1). Further, the amount of catalyst (M2) carried on the sample is also obtained. Next, ultrasonic waves are applied to the sample for 30 seconds using an ultrasonic cleaner. Then, after hold | maintaining at 110 degreeC for 24 hours, after standing to cool in the desiccator containing a silica gel, the mass of a sample is measured (it is set as M3). The catalyst peeling rate h (%) is obtained from the equation h = (M1-M3) / M2 × 100. Moreover, the adhesion state of the catalyst at that time was observed.
<Evaluation of catalyst durability>
The flow rate of air heated to 320 ° C. with a gas heater was set so as to obtain a predetermined space velocity (SV), and the air was continuously fed in contact with the catalyst. When measuring the decomposition rate, the heater temperature is adjusted so that the temperature of the gas entering the reaction vessel is 280 ° C., and the gas before entering the reaction vessel and the gas passing through the reaction vessel are analyzed with a PID sensor. The gas concentration was determined (the gas concentration before entering the reaction tank is C1, and the gas concentration that has passed through the reaction tank is C2). The decomposition rate c (%) is obtained from the equation c = C2 / C1 × 100. Incidentally, SV Example 1 at this time, Comparative Example 2, 30000h ^-1, and an air-flow so that 22000H ^-1 in Example 2.
<Honeycomb carrier>
[Example 1]
The cobalt carbonate was fired in air at 300 ° C. for 5 hours to obtain cobalt oxide (Co ₃ O ₄ ), and then pulverized. Here, the average particle diameter of the cobalt oxide after the pulverization treatment was 1.09 μm (FIG. 5), and the average particle diameter of the cobalt oxide before the pulverization treatment (unground) was 2.55 μm (FIG. 6). ). 20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 39 g of cerium nitrate were added to 10 g of the pulverized cobalt oxide (average particle size 1.09 μm), and the mixture was mixed well to obtain Solution 1. After immersing the honeycomb-type ceramic carrier in a storage container for solution 1 for 1 minute, the ceramic carrier was fired in air at 300 ° C. for 1 hour to obtain a supported catalyst.
[Comparative Example 1]
20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 13 g of cerium nitrate were added to 10 g of the unpulverized cobalt oxide obtained in Example 1, and the mixture was stirred well to obtain the first liquid. After immersing the honeycomb-type ceramic carrier in the first liquid storage container prepared as described above for 1 minute, the ceramic carrier was taken out and fired in air at 250 ° C. for 1 hour. After that, the cooled honeycomb-type ceramic carrier is immersed in a storage container of the second liquid cerium nitrate solution (cerium nitrate hydrate 20 g + distilled water 20 ml) for 1 minute and then fired in air at 550 ° C. for 1 hour. Thus, a supported catalyst was produced.
[Performance evaluation]
With respect to the supported catalysts obtained in Example 1 and Comparative Example 1, the peelability and durability of the honeycomb type ceramic carrier supported catalyst were evaluated by the above method.

  FIG. 1 shows the evaluation of peelability.

  Evaluation result A is that of Example 1, and it is confirmed that no peeling occurs. On the other hand, in the case of the comparative example 1 of the evaluation result B, it can be seen that peeling has occurred.

Further, FIG. 2 shows the evaluation results of a long-term durability test of 30000 h ^{−1 on} an actual scale, operating temperature: 320 ° C. (however, changed to 280 ° C. when measuring the removal rate), VOC: about 700 ppm of ethyl acetate. Is.

  The evaluation result A is that of Example 1, and it is understood that the long-term durability is excellent. On the other hand, the evaluation result B is that of Comparative Example 1, and it is confirmed that deterioration with time progresses.

Further, a supported catalyst was produced in the same manner as in Example 1 using the cobalt oxide pulverized so as to have an average particle size of less than 0.8 in the pulverization treatment of the cobalt oxide of Example 1, and this supported catalyst. As a result of evaluating the catalyst releasability using the catalyst, the catalyst retention was reduced as compared with the result of Example 1.
<Ball type carrier>
[Example 2]
20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 39 g of cerium nitrate are added to 10 g of the pulverized cobalt oxide (average particle size 1.09 μm) obtained in Example 1, and mixed well. Solution 1 was obtained. A ball-type ceramic carrier was immersed in a storage container of Solution 1 for 1 minute, and then the ceramic carrier was fired in air at 300 ° C. for 1 hour to obtain a supported catalyst. Further, as the ceramic carrier at this time, a ball type carrier (a porous structure having pores with a diameter of 35 μm on the surface) produced using a ceramic raw material containing activated carbon as a pore forming agent and a pore forming agent are not used. The produced ball type carrier was used.
[Comparative Example 2]
Add 20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 13 g of cerium nitrate to 10 g of unground cobalt oxide (average particle size 2.25 μm) obtained in Example 1, and mix well. The first liquid was used. The ball-type ceramic carrier used in Example 2 was immersed in the first liquid storage container prepared as described above for 1 minute, and then the ceramic carrier was taken out and fired in air at 250 ° C. for 1 hour. Thereafter, the cooled ball-shaped ceramic carrier is immersed in a storage container of the second liquid cerium nitrate solution (cerium nitrate hydrate 20 g + distilled water 20 ml) for 1 minute, and then fired in air at 550 ° C. for 1 hour. Thus, a supported catalyst was produced.
[Example 3]
20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 39 g of cerium nitrate were added to 10 g of the cobalt oxide (average particle size 0.86 μm) after the grinding treatment obtained by the same grinding treatment as in Example 1. The solution 1 was mixed well by stirring. A ball-type ceramic carrier was immersed in a storage container of Solution 1 for 1 minute, and then the ceramic carrier was fired in air at 300 ° C. for 1 hour to obtain a supported catalyst. In addition, as the ceramic carrier at this time, a ball-type carrier (a porous structure having pores with a diameter of 35 μm on the surface) produced using a ceramic raw material containing activated carbon as a pore-forming agent was used.
[Example 4]
20 ml of distilled water, 1 g of activated clay powder, 10 g of cobalt nitrate, and 39 g of cerium nitrate were added to 10 g of the cobalt oxide (average particle size 1.99 μm) obtained by the same grinding treatment as in Example 1. The solution 1 was mixed well by stirring. A ball-type ceramic carrier was immersed in a storage container of Solution 1 for 1 minute, and then the ceramic carrier was fired in air at 300 ° C. for 1 hour to obtain a supported catalyst. In addition, as the ceramic carrier at this time, a ball-type carrier (a porous structure having pores with a diameter of 35 μm on the surface) produced using a ceramic raw material containing activated carbon as a pore-forming agent was used.
[Performance evaluation]
About the supported catalyst obtained in Example 2-4 and Comparative Example 2, the peelability and durability of the ball-type ceramic carrier-supported catalyst were evaluated by the above method and the ball-type ceramic carrier-supported catalyst by the above method.

  FIG. 3 shows the evaluation results for peelability. Table 1 also shows the results of the peel rate measurement using the supported catalyst obtained in Comparative Example 2 and Example 2-4.

  The evaluation result A in FIG. 3 is for a supported catalyst manufactured using a porous structure carrier having pores with a diameter of 35 μm on the surface in Example 2, and it is confirmed that no peeling occurs. On the other hand, the evaluation result B of FIG. 3 is that of the supported catalyst manufactured using the support prepared without using the pore forming agent in Comparative Example 2, and it can be seen that peeling occurs. In the peeling rate, the thing of Example 2 has fallen to about 1/50 compared with the case of the comparative example 2. FIG. As for the supported catalyst of Example 3-4, it was confirmed that the peel rate was lower than that of Comparative Example 2.

Further, FIG. 4 shows a long-term test on a real scale of a supported catalyst manufactured using a porous structure carrier having pores having a diameter of 35 μm on the surface in Example 2 [SV: 22000 h ^−1. , Operating temperature: 320 ° C. (however, changed to 280 ° C. when measuring the removal rate), VOC: about 700 ppm of ethyl acetate], and shows that the long-term durability is excellent. It was confirmed that the supported catalyst of Example 3-4 was also excellent in long-term durability.

From the above, catalyst particles are supported on the carrier, and the catalyst particles have cobalt oxide and cerium ions having cobalt ions as precursors around the cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm. It was confirmed that the supported catalyst covered with the cerium oxide as a precursor was difficult to peel off and was excellent in durability. From this, it was confirmed that the supported catalyst can further improve the performance and stability of the Co and Ce-based oxide supported catalyst, and can effectively maintain the activity for a long time.
[Example 5]
In Example 2, a copper ion was added to solution 1 so that the oxide particle weight ratio of the catalyst particles was 0.3 wt%, and coexisted in cobalt ions and cerium ions. Using this solution, the same as in Example 2 was used. A supported catalyst was produced by this method. As the carrier, a carrier prepared without using a pore-forming agent was used. In order to evaluate the catalytic performance of this supported catalyst and the supported catalyst of Example 2 produced using the same support, the decomposition rate of 1000 ppm of ethyl acetate was measured. The measurement conditions were such that SV was 22000 h ⁻¹ and the reaction tank filled with the catalyst was set to a predetermined temperature. Further, the gas before introduction of the catalyst tank and after passing through the catalyst tank was analyzed with a CO ₂ meter.

  The results are shown in Table 2.

  From this result, it was confirmed that the supported catalyst produced by adding copper ions had better catalytic performance.

Claims (2)

A method for producing a malodor-treated supported catalyst, comprising the following steps.
a) A catalyst immersion liquid is prepared by mixing cobalt oxide particles having an average particle diameter of 0.8 to 2.0 μm with a salt or compound capable of generating cobalt ions, a salt or compound capable of generating cerium ions, and water. Process,
b) a step of immersing the obtained catalyst immersion liquid in a carrier; and c) a step of firing the carrier after the immersion treatment. The malodor treatment according to claim 1, wherein cobalt oxide particles having an average particle size of 0.8 to 2.0 µm are prepared by calcining or drying and solidifying a cobalt salt or compound in advance. For producing a supported catalyst.