JPH04150943A - Composite catalyst for ozone decomposition and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite catalyst for ozone decomposition that can efficiently decompose and remove ozone, and a method for producing the same.

[Conventional technology]

The powerful oxidizing effect of ozone is used in various fields.

The main fields of use include disinfectants, deodorizers, pharmaceuticals, oxidizing agents in various manufacturing processes, and reactants in chemical analysis, and demand is increasing every year.

However, along with this, a new problem has arisen: collecting and removing ozone that is partially unreacted and released into the atmosphere.

Ozone is NIOSH (National In5
position for Occupational 5a
According to the definition of ``fety &Health'', it is classified as tumorigenic, mutagenic, teratogenic, and irritating to the skin and eyes, and its symptoms include headache, dizziness, fatigue, decreased blood pressure, difficulty breathing, and eye irritation. There are reports that it causes irritation to the mucous membranes of the respiratory system.

Therefore, it is necessary to remove ozone that leaks or is released from various ozone generating sources and renders it harmless.

Conventional ozone treatment techniques include activated carbon, chemical cleaning, and thermal decomposition. Activated carbon is used to treat low-concentration ozone, but since activated carbon is consumed by the oxidation reaction with ozone, it must be replenished, and when treating high-concentration ozone, the reaction heat is There is a risk that the activated carbon itself will ignite or burn, which may cause handling problems.

The chemical cleaning method is a method of cleaning waste ozone with an aqueous solution of a reducing substance, and there are problems in that the chemical solution is expensive and the cleaning waste liquid must be treated. The pyrolysis method is
In order to increase the decomposition efficiency, heating to 300° C. or higher is required, and if the amount of exhaust gas is large, the scale of the equipment will be large and the cost will increase.

Recently, in order to eliminate this type of drawback, research has been carried out on a decomposition method using a catalyst as a waste ozone treatment method. This method has no risk of ignition or explosion, does not require negative tests, and does not require wastewater treatment.
It is considered to be an advantageous method for decomposing and removing ozone at low cost. Many such ozone decomposition catalysts have been disclosed in which ozone active substances are supported on inorganic porous bodies. An example of using a composite oxide consisting of titanium, nitrogen, zirconia, etc. as the inorganic porous material (Japanese Patent Application Laid-Open No. 2-63552)
, an example using an aggregate of ceramic fibers (Japanese Patent Application Laid-Open No. 1-24
5850), and examples using alumina, silica, titania or alumina-silica carriers (JP-A-62-201
648), and A-type zeolite,
53) and crystalline heptaolide (JP-A-64-4220)
An example using . These methods focus on the solid acidity of the porous material or the size of the BET surface area. However, their ozone decomposition performance is still insufficient, and in order to put them into practical use, a catalyst with even higher ozone activity is required.

On the other hand, catalysts in which metals are supported on double-chain clay minerals have excellent adsorption ability for gases and liquids, and are conventionally used as catalysts for chemical reactions and purification adsorbents, and as ozone decomposition catalysts. is also considered promising. However, as shown in "Catalyst for Hydrogenation of Hydrocarbons" (Japanese Unexamined Patent Publication No. 53-34691), the structure of clay minerals is broken down with strong acids at low temperatures, and ions such as lanthanides and iron, which become catalyst metals, are supported. In this method, the amount of metal ions supported was small and it was not possible to impart sufficient catalytic activity.

Furthermore, when supporting a different catalytic metal to cause another catalytic reaction, it is difficult to support a different type of catalytic metal because the supported amount of the core metal is insufficient.

Furthermore, with this method, there was a risk that the crystal structure of the multi-chain clay mineral would be disrupted by the strong acid.

Furthermore, since strong acids are used, investment in manufacturing equipment and environmental purification is required, resulting in high manufacturing costs.

[Purpose of the invention]

A first object of the present invention is to provide a composite catalyst for ozone decomposition that efficiently decomposes ozone contained in the atmosphere.

The second purpose is to provide a composite catalyst for ozone decomposition that purifies the environment by highly efficiently decomposing waste ozone or by-product ozone after use for sterilization, deodorization, manufacturing, etc. be.

The third object is to provide a method for producing the composite catalyst for ozone decomposition shown in the first and second objects.

The fourth objective is to support the catalyst in a highly dispersed state while maintaining the structure of the double-chain clay mineral, which has excellent ozone adsorption properties, in the composite catalyst for ozone decomposition shown in the first and second objectives. An object of the present invention is to provide a method for producing a composite catalyst for ozone decomposition.

As a result of intensive research to achieve the above object, the present inventors have invented a composite catalyst using a double-chain clay mineral as a carrier, which will be disclosed below.

[Configuration of the first invention] The composite catalyst for ozone decomposition of the first invention comprises a double-chain structure type clay mineral having a structure in which at least a part of the highly distributed magnesium in the structure is replaced with a transition metal element; At least one transition metal oxide catalyst supported on the clay mineral is provided in parallel with the transition metal element.

As the double-chain structure type clay mineral of the first invention, sepiolite, palygorskite, and attapulgite can be used.

Its composition is sepiolite or Si, 2Mga 030 (
OH2)h -sH+ O, attapulgite and palygorskite are (Mg, l') 5(S 1Aj4
) B 020 (OH) 2 ·sH+o.

These are clay minerals whose main component is hydrated magnesium silicate and which has highly reactive hydroxyl groups on its surface. This clay mineral consists of fibers with a diameter of about 0.05 to 0.6 μm, and parallel to the fibers exists a rectangular cross-sectional area (channel) of about 1 to 0.6 nm.

The catalyst of the first invention has a structure in which magnesium in this clay mineral structure is replaced with a transition metal element.

Furthermore, since the catalyst of the first invention has a structure in which the transition metal substituted with magnesium is substituted with at least one transition metal oxide catalyst as the core, these catalysts also exist in a highly dispersed state and do not form the nucleus. The transition metal and the supported transition metal oxide are combined by contact or fusion.

[Effect of the first invention] The double-chain structure type clay mineral is an inorganic porous body,
It has a large ET specific surface area of 400 m/g.

In order to replace magnesium in the structure of this clay mineral with a transition metal element, the replaced transition metal catalyst blocks the diffusion paths of the ozone-containing medium between the fibers or in the channels and structures with excellent adsorption properties. can exist in a highly dispersed state without any

Therefore, effective pores for gas diffusion in the clay mineral are secured, and at the same time, the effective surface area of the transition metal element is increased, increasing the ability to decompose ozone into harmless oxygen. Furthermore, since a transition metal oxide catalyst is supported on the above catalyst to form a composite catalyst, the ability to decompose ozone is further increased.

This ability to decompose ozone into harmless oxygen is thought to occur through the following mechanism.

The ozone decomposition catalyst of the present invention has a large specific surface area, and has passages and spaces for sufficiently taking in the ozone-containing medium. When ozone introduced into the surface of the catalyst and such passages comes into contact with the transition metal element substituted with electron-rich magnesium and the transition metal oxide complexed with this, it is captured by these catalysts and becomes activated. , it is estimated that it will be in a state where it can be easily decomposed. This activated ozone is decomposed by the action of the composite catalyst and released as oxygen.

[Effects of the First Invention] The composite catalyst of the present invention can efficiently decompose and remove ozone contained in the atmosphere to the extent that it becomes almost harmless to the human body and other living organisms.

This has made it possible to purify the environment by removing waste ozone used for sterilization, deodorization, manufacturing, etc. or ozone generated as a by-product to levels below environmental standards.

[Structure of the second invention] The method for producing a composite catalyst for ozone decomposition according to the second invention heat-treats a double-chain structure type clay mineral at a temperature of 400'C or more and 800'C or less, thereby changing the structure of the clay mineral. It consists of a step of ion-exchanging magnesium ions in the structure with transition metal ions, and a step of supporting at least one type of transition metal oxide catalyst on the ion-exchanged double-chain structure type clay mineral.

The heat treatment temperature of the present invention is preferably 400°C to 800°C. A particularly preferred temperature is 600°C to 700°C. 40
If the temperature is below 0°C, the structure of the clay mineral cannot be sufficiently changed. At temperatures exceeding 800° C., the structure of the clay mineral changes to enstatite-type crystals, making it difficult to support metal elements and pores disappearing, which is not preferable.

When the pores disappear, it becomes impossible to secure gas adsorption sites and effective passages for gas diffusion.

By heat-treating the double-chain structure clay mineral, the bonding force within the clay mineral crystals is reduced, and at least one ion selected from transition elements is substituted for the magnesium ion in the clay mineral in the multi-chain structure clay mineral. In the process, amorphous clay minerals are first dispersed in water to create a suspension. The amount of water at this time is preferably 10 times the weight or more. If the amount is less than this, the clay mineral will be poorly suspended and it will be difficult to uniformly replace it with magnesium ions. The transition metal ion to replace the magnesium ion is suitably introduced in the form of a salt. In this step, these metal salts are added to the suspension and mixed.

Furthermore, in the step of highly dispersingly supporting at least one transition metal oxide having high catalytic activity toward ozone as a core of the transition metal supported in the above step, a double-chain structure substituted with the transition metal ion formed in the above step is used. At least one type of transition metal ion is added to a solution in which clay minerals are suspended to form an oxide and to be supported.

[Operation of the second invention] The double-chain structure type clay mineral changes from a crystal structure to an amorphous structure by heat. This structural change occurs from 400℃ to 800℃.
Occurs at ℃. First, the zeolite water and crystalline water present in the tunnels in the structure of the clay mineral escape. At the same time, the crystal structure changes, and the octahedral Mg of the MgO layer that makes up the crystal changes.
-0 binding strength decreases, and magnesium ions become easily eluted in water.

At this time, when transition metal ions are allowed to act in water, ions can be easily exchanged with magnesium ions whose binding strength has been reduced in the clay mineral. By replacing transition metal ions with high catalytic activity with magnesium ions and introducing them into the structure of the clay mineral, these transition metals are supported firmly and in a highly dispersed state.

On the other hand, a double-chain structure type clay mineral heat-treated at 400°C to 800°C has a BET specific surface area of 200 to 250 bo/g, but the specific surface area does not decrease due to ion substitution.

Further, the transition metal ions introduced into the structure of the clay mineral serve as a nucleus for supporting a new catalyst metal. this is,
Transition metal oxides with high catalytic activity towards ozone are
This is thought to be due to the fact that it is supported so as to be in contact with the previously introduced transition metal rather than the site with the surface hydroxyl group. For this reason, the supported catalyst metals become composited with each other.

[Effect of the second invention] According to the production method of the second invention, the ozone-containing transition metal which serves as a core for supporting at least one transition metal oxide catalyst and which itself has catalytic activity against ozone. It can be introduced into clay minerals in a highly dispersed state while maintaining the diffusion path or adsorption structure for the medium.

Furthermore, since at least one type of transition metal oxide is supported using the introduced transition metal as a core, these also maintain a highly dispersed state while ensuring a passage that facilitates the diffusion of the ozone-containing medium. It can be made to be composited with a previously supported transition metal and supported on clay minerals.

As described above, in the present invention, a transition metal catalyst and a transition metal oxide catalyst can be made into a composite catalyst and supported in a highly dispersed state on a double-chain clay mineral with adsorption properties, making it extremely useful as an ozone decomposition catalyst. It has high activity.

[Other inventions] As the transition metal element of the present invention, metal elements such as noble metals that are normally used as catalysts can be used, or metal elements such as cobalt, nickel, and manganese are particularly preferred for the purpose of the present invention. It is. As the transition metal oxide, titanium oxide or manganese oxide is particularly suitable.

As another invention of the second invention, a process of supporting titanium oxide and manganese oxide as at least one type of transition metal will be described. After adding and mixing ammonia water to a suspension of clay minerals dispersed in water to make this an alkaline solution, a sulfuric acid solution of titanyl sulfate (TiO3O4) was gradually added under stirring to bring the pH to around 7. titanium oxide is supported on the clay mineral. Thereafter, the mixture is washed with water, filtered, and dried in a conventional manner, and then calcined at 400 to 500°C to increase the binding strength between the clay mineral and titanium oxide, thereby obtaining the catalyst of the present invention and other inventions. When manganese oxide is further supported on this catalyst, an aqueous manganese nitrate solution is added to the obtained catalyst and mixed thoroughly. Thereafter, it is calcined at 450°C to obtain catalysts of the present invention and other inventions.

Titanium oxide and/or other inventions of the second invention
Alternatively, the preferable amount of treatment in the step of supporting manganese oxide is 70 to 100 parts by weight of 12% ammonia water and 20 to 100 parts by weight of 12% aqueous ammonia per 100 parts by weight of clay mineral.
parts by weight, and 10 to 30 parts by weight of manganese nitrate.

The amount of transition metal salt added is suitably 10 parts by weight to 70 parts by weight. When the amount is less than 10 parts by weight, the amount of metal supported decreases, and the ozone decomposition effect decreases significantly.

In addition, even if the amount added is more than 70 parts by weight, the amount of metal supported will not increase. Preferably, the amount is 30 to 60 parts by weight. Methods for adding metal salts include directly adding the salt itself, or adding a metal salt aqueous solution. Any commonly used addition method can be used.When extracting the metal-supported carrier of the present invention, commonly used methods such as washing with water, filtration, and drying may be used. I'll come.

The catalyst of the present invention exhibits great effects as an ozone decomposition catalyst as it is, but the ozone decomposition performance is further improved when subjected to reduction heat treatment at 400°C.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example 1) Seviolite powder from Turkey was used as the double-chain structure type clay mineral. This sepiolite powder was placed in an alumina crucible and heat treated in a nichrome furnace at a temperature range of 400°C to 800°C for 45 hours. 60 g of each heat-treated product was taken out into a mixer, and 600 g of ion-exchanged water was added thereto, and the mixture was operated for 10 minutes to fully disperse the heat-treated sepiolite in the ion-exchanged water. Thereafter, 10 to 70 parts by weight of cobalt chloride (CoCA2.6H20) was added to 100 parts by weight of the heat-treated sepiolite, and the mixer was operated again for 5 minutes to uniformly dissolve and mix the cobalt chloride. A mixed suspension consisting of a cobalt chloride solution and a heat-treated sepiolite product was stirred for 30 minutes using a disperser.
The heat-treated sepiolite was sufficiently reacted with cobalt ions. At the same time, suction filtration was repeated several times to thoroughly wash and remove chlorine ions, etc. Next, it was dried at 100° C. for 15 hours to prepare a cobalt-supported carrier.

The amount of cobalt in the cobalt supported catalyst prepared as described above was investigated by atomic absorption spectroscopy (Table 1).

Next, 500 parts by weight of ion-exchanged water was added to the cobalt-supported carrier prepared as described above and mixed for 10 minutes with a homomixer to fully disperse the cobalt-supported carrier, and then
74 parts by weight of aqueous ammonia was added and stirred for 5 minutes using a disper. A sulfuric acid solution containing 70 parts by weight of titanyl sulfate was gradually added to this suspension under stirring, the pH was adjusted to 6 to 9, a composite of the cobalt support and titanium oxide was formed, and the mixture was allowed to stand for 15 hours. did.

This composite was repeatedly washed by a suction filtration method using ion-exchanged water to sufficiently remove sulfate ions and the like. A cobalt/titanium oxide supported catalyst was prepared by drying at 120° C. and then firing at 550° C. for 4 hours.

In addition, in the preparation process of the cobalt/titanium oxide supported catalyst, the amount of 116% ammonia water added was 148 parts by weight,
A cobalt and titanium oxide supported catalyst was prepared using the same procedure and conditions, except that the amount of titanyl sulfate added was 25 parts by weight.

Next, the cobalt/titanium oxide supported catalyst produced as described above was placed in a mortar, an aqueous solution containing 20 parts by weight of manganese nitrate was added, and the mixture was thoroughly mixed in the mortar. Then 450℃
By firing for 3 hours to decompose and remove NO3 roots, etc., an ozone decomposition catalyst (No, A
-1 to A-9) were prepared.

An ozone decomposition test was conducted using the ozone decomposition catalyst prepared as described above. The ozone decomposition test was conducted by setting the test column shown in FIG. 1 in the test apparatus shown in FIG. 2.

In the figure, 1 is a glass pea, 2 is a composite catalyst for ozone decomposition of this example, 3 is a urethane foam, 4 is an ozone generator,
5 is a control column, 6 is a test column, 7 is an ozone monitor, 8 is a detection port for initial concentration measurement, and 9 is a detection port for high concentration measurement. Note that 10 indicates a switching cock.

The test column contained 0.5 g of a composite catalyst for ozone decomposition at 32
Filled in the form of ~70 mesh granules, air containing 35 ppm ozone was fed at a flow rate of 31'/min, and a space velocity of 236.
Pass through the test column under the condition of 000/h, and at the outlet of the test column, use a Kita type gas detection tube or Dayretsu 1003-AH.
Ozone concentration was measured using a model ozone monitor. From the ozone concentration measurement results at the inlet and outlet of the catalyst layer, the ozone decomposition rate (%) was determined using the following formula.

Ozone decomposition rate (%) = The results are shown in Table 1, No. A-1-A-9.

In addition, as a comparative example, 65 kg of sepiolite powder from Turkey was used.
Prepared by adding 70 parts by weight of titanyl sulfate and 20 parts by weight of manganese nitrate to 100 parts by weight of sepiolite to the carrier (No, R-1) which was heat treated at 0°C for 4.5 hours and used as it was. catalyst (NCLR-2)
The ozone decomposition rate was similarly determined and shown in Table 1. In addition, sepiolite powder from Turkey was heated to 200°C and 350°C, respectively.
, heat treated at 900℃ to convert cobalt chloride to sepiolite 1
After treating 00 parts by weight with 60 and 45 parts by weight to support cobalt, the catalyst was further treated with 70 parts by weight of titanyl sulfate and 20 parts by weight of manganese nitrate to support titanium oxide and manganese oxide (No. R-3). , R-4, R-7)
The ozone decomposition rate was determined.

Furthermore, Turkish sepiolite powder was heat-treated at 650°C, and 100 parts by weight of sepiolite was treated with 4 and 2 parts by weight of cobalt chloride to support cobalt, followed by 70 parts by weight of titanyl sulfate and 20 parts by weight of manganese nitrate. Parts by weight were treated to obtain catalysts (NαR-5, R-6) supporting titanium oxide and manganese oxide. The ozone decomposition rate was similarly determined and shown in Table 1.

Catalysts NαA-1 to A-9 in Table 1 all showed high ozone decomposition rates. In addition, if the heat treatment temperature shown in No. R-1 to R-7 is inappropriate, the amount of cobalt supported is too low, or the amount of cobalt supported is small, it is sufficient to support titanium oxide and manganese oxide. No ozone decomposition rate was shown.

(Example 2) After heat-treating Turkish sepiolite powder at 650°C for 45 hours, it was converted into nickel chloride (N i Cβ26 Hr○).
Composite catalyst for ozone decomposition (N(l
B-1) was prepared in the same manner as in Example 1, and the ozone decomposition rate was determined. The results are shown in Table 2.

Furthermore, the ozone decomposition rates of the catalyst prepared by excluding only the manganese nitrate treatment (NαB-2) and the catalyst prepared by excluding only the titanyl sulfate treatment (No. B-3) were determined.

In addition, as a comparative example, 90% of sepiolite powder from Turkey was used.
Heat treated at 0°C for 45 hours, treated with 70 parts by weight of nickel chloride per 100 parts by weight of sepiolite, and further treated with 70 parts by weight of titanyl sulfate and 20 parts by weight of manganese nitrate (NcR-8) was prepared and carried out. An ozone decomposition test was conducted in the same manner as in Example 1. The results are shown in Table 2.

Table 2 Samples Nos. B-1 to B-3 of this example all showed high ozone decomposition rates.

When sepiolite subjected to the inappropriate heat treatment shown in N+1R-8 was used, a sufficient ozone decomposition rate was not exhibited even when nickel, titanium oxide and manganese oxide were supported.

(Example 3) After heat-treating Turkish sepiolite powder at 650°C for 4.5 hours, manganese nitrate CMn(N O3)! 682
A composite catalyst for ozone decomposition (N
o, C) was prepared in the same manner as in Example 1, and the ozone decomposition rate was determined. The results are shown in Table 2.

In addition, as a comparative example, sepiolite powder from Turkey was used at 650%
After heat treatment at ℃ for 4.5 hours, manganese nitrate l:Mn
(NO3) 2 ・6H20) was treated with 4 parts by weight per 100 parts by weight of sepiolite, and then titanyl sulfate 7
A composite catalyst for ozone decomposition (NcR-9) treated with 0 parts by weight and 20 parts by weight of manganese nitrate was prepared in the same manner as in Example 1, and the ozone decomposition rate was determined. The results are shown in Table 2.

As can be seen from this table, catalysts No. and C into which manganese ions were introduced by ion exchange showed higher ozone decomposition rates than NcR-9 into which manganese ions were not introduced by ion exchange.

The present invention is not limited in any way by these Examples unless the gist of the present invention is exceeded.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the contents of a test column filled with the catalyst of this example, and Figure 2 is a diagram showing the test column packed with ozone.
It is a schematic diagram when installed in a detection system.

Claims (2)

[Claims] (1) A double-chain structure type clay mineral having a structure in which at least a part of the highly distributed magnesium in the structure is replaced with a transition metal element; A composite catalyst for ozone decomposition consisting of an oxide catalyst of one type of transition metal and (2) changing the structure of the clay mineral by heat-treating the double-chain structure type clay mineral at a temperature of 400°C or more and 800°C or less, and ion-exchanging the magnesium ions in the structure with transition metal ions; A method for producing a composite catalyst for ozone decomposition, comprising the steps of: supporting at least one transition metal oxide catalyst on the exchanged double-chain clay mineral.