JPH038447A - Catalyst for decomposition of ozone - Google Patents

Abstract

PURPOSE:To obtain a catalyst for decomposition of ozone having high decomposition activity and hardly undergoing deterioration even under severe conditions by incorporating zeolite having a specified structure and a metal having a certain oxide formation enthalpy or the oxide of the metal. CONSTITUTION:Zeolite represented by a general formula Mx/n.[(AlO2)x.-(SiO2)y].mH2O (where M is an alkali or alkaline earth metal and n is the valence of the metal M) and a metal having <=100kcal oxide formation enthalpy- H<0>f per 1 gram atom of oxygen or the oxide of the metal such as Cr2O3 or Fe2O3 are used to obtain a catalyst for decomposition of ozone having high decomposition activity and hardly undergoing deterioration in the activity even under severe reaction conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ozone decomposition catalyst for decomposing and removing ozone contained in the atmosphere.

Conventional Techniques Traditionally, methods for removing harmful ozone contained in the atmosphere include adsorption methods using porous adsorbents such as activated carbon and zeolite, and catalytic oxidation decomposition methods using catalysts such as manganese dioxide. Are known.

However, none of the conventional methods described above are fully satisfactory. That is, according to the adsorption method, there is a limit to the adsorption capacity of the adsorbent, so it is necessary to regenerate it.
Therefore, not only is the operation cumbersome, but the processing cost is high. On the other hand, although methods using catalysts do not have the problems seen in the adsorption methods mentioned above, all conventionally known catalysts do not have sufficient decomposition performance and are difficult to treat gases with high ozone concentrations. Under harsh conditions, such as using high areal velocities in the process, the catalyst deteriorates rapidly and significantly.

The present invention was made to solve the problems in conventional ozone decomposition as described above, and has a higher decomposition activity than conventionally known catalysts, and The object of the present invention is to provide an ozone decomposition catalyst whose activity does not deteriorate even under severe reaction conditions.

According to the present invention, the general formula (I) Mxy,l. [(A10z) x.(SiOz) v)
・zeolite represented by m1lzO (where M is an alkali metal or alkaline earth gold (wherein M is the valence of the metal M)) and the enthalpy of formation of the oxide -ΔH°f is 100 Kcal/gram of oxygen Provided is an ozone decomposition catalyst characterized by containing a subatomic metal or metal oxide.

In the present invention, the catalyst refers to an active component having ozonolysis activity. Therefore, active ingredient and catalyst are synonymous. Such a catalyst can be made into a structure by supporting it on a suitable carrier, or by molding the active ingredient together with other molding components, but such a structure can be used as a catalyst structure. That's what it means.

In the present invention, the zeolite represented by the general formula (1) is natural zeolite such as borofluorite, faujasite, chabasite, soda fluorite, oxalite, mordenite, or zeolite-X, zeolite-Y, zeolite- Synthetic zeolites such as A and ZSM-5 can be exemplified. In particular, among these zeolites, A1□0. A zeolite with a high /5i02 ratio is preferably used, and type A zeolite is particularly preferably used.

As such zeolite, for example, Nihon Kagaku Kogyo ■
Zeolite KA-100P, which is a type A zeolite manufactured by
Commercially available synthetic zeolites such as NA-100P, GA-100P, X-type zeolites NX-100P and CX100P, and mordenite-type zeolite NM-100P can be suitably used.

The catalyst according to the invention, together with the zeolite, has an enthalpy of formation per gram atom of oxygen of the metal oxide - ΔH°
A metal or metal oxide whose f is 100 Kcal or less is contained.

Specific examples of such oxides include the following.

Metal oxide Cr2O in the range of 80-100 Kcal
3, ZnO metal oxide v203 in the range of 60 to 80 Kcal,
-03, Fe, 0. , MnO, , Mob340~60K
Metal oxide Nip in the cal range, Coz04,
RuO2 Metal oxides CuO1RhzOz, PdO1Ag20, Pt (h) having 40Kcal or less, among the above, in the present invention, in particular, CrzO=,
FezOz, MnO,, Co=On, Ru0z, Cub
, Rh, 0. , PdO1Ag20, Pt(h, etc.) are preferably used. These are used alone or as a mixture of two or more. For example, MnO, and Ag2O
A preferred example is the combination use with

The catalyst of the present invention is produced by repulping the zeolite represented by the general formula (1) in water to form a slurry of about 1°Og/1, and then adding the enthalpy of formation of the oxides -ΔH°f to the slurry. Add a predetermined amount of a metal salt, such as, but not limited to, nitrate or acetate, having an amount of less than 100 Kcal/gram atom of oxygen, and mix well with stirring. Next, ammonia water, alkali such as alkali metal or alkaline earth metal hydroxide is added to this mixture, and the mixture is neutralized to ρ117 to form precipitates of the above metals, which are filtered, washed with water, and dried. After that, by calcination, a zeolite as a catalyst according to the present invention containing the above metal or metal oxide can be obtained.

The above firing is carried out at 200-500°C, preferably at 300-400°C.
It is carried out at 00°C. When the calcination temperature is low, the water of crystallization from the metal precipitate is insufficiently removed, making it impossible to obtain the desired zeolite containing the metal or metal oxide. However, it is not preferable to perform the calcination at an excessively high temperature because there is a risk of structural destruction, especially in the A-type zeolite.

The amount of the metal or metal oxide in the catalyst thus obtained is preferably in the range of 5 to 30% by weight in terms of oxide. When the amount of metal or metal oxide in the catalyst is less than 5% by weight in terms of oxide, the resulting catalyst has low ozonolysis activity;
Even if it exceeds 0% by weight, there is no commensurate increase in activity.

Furthermore, according to the invention, general formula (II) M'-7,l
HbM" (X-(-/,ll-b+ ・[(A10
z) x・(Sing) v) -mHz.

(In the formula, the metal gate 1 is the enthalpy of oxide formation - ΔH°
Indicates a metal in which f is 100 Kcal/gram atom of oxygen or less, A2 indicates K or Na, and n indicates the valence of the metal M1, where O≦b<X. ) There is provided an ozone decomposition catalyst characterized by comprising a metal-substituted zeolite represented by:

In the general formula (II), metal M1 is a metal whose oxide formation enthalpy -ΔH°f is 100 Kcal/oxygen gram atom or less, and is a substitute metal for metal M2. Specific examples of such metal M1 are as described above.

-i, the ozone decomposition reaction converts the active site of the catalyst into metal M1
When doing so, it is said to proceed as follows.

03+M+-→ -M'-+0□ (1) 0:+
+ -M'--M'-+ 20z
(21) The above reaction fil is an M'-0 production reaction, and the larger the enthalpy of oxide formation of metal M1, the more likely it is to occur.
On the other hand, reaction (2) is an M'-0 dissociation reaction, and the smaller the enthalpy of oxide formation of metal M1, the more likely it is to occur; here, it is known that the rate-determining step is reaction (2). There is. Therefore, according to the present invention, a catalyst with high ozonolysis activity can be obtained by setting the oxide formation enthalpy -ΔH°f to 100 Kcal/oxygen gram atom or less.

The metal-substituted zeolite represented by the general formula (II) has the metal M2 in the zeolite as described above, that is,
It can be obtained by substituting part or all of K or Na with a metal. Specifically, the metal-substituted zeolite as a catalyst according to the present invention can be obtained by replacing the above zeolite in a solution containing metal M8 ions. at room temperature or under heating, if necessary, until a metal substitution amount of
It can be obtained by repeated immersion.

Zeolites that can be used here are as described above, and include, for example, borofluorite, faujasite,
Mention may be made of natural zeolites such as chabasite, sodalite, oxalite, mordenite, or synthetic zeolites such as zeolite-X1 zeolite-Y, zeolite-A, ZSM-5, etc. Among these zeolites, zeolites with a high AIto3/SiO□ ratio are preferably used, and type A zeolites are particularly preferably used.

As mentioned above, such zeolites include, for example, zeolites KA-100PSNA-100P and GA-100P, which are A-type zeolites manufactured by Nihon Kagaku Kogyo Side, and NX-100P and CX-100, which are X-type zeolites.
Commercially available synthetic zeolites such as NM-100P, which is a mordenite type zeolite, can be suitably used.

Since mordenite and ZSM-5 have high acid resistance, a solution containing a high concentration of substituting metal ions can be used in the production of metal-substituted zeolite, but the number of substitutable sites is about 2/3 that of A-type zeolite. On the other hand, A
Although , X- and Y-type zeolites have many sites that can be replaced, they have poor acid resistance, so they must be repeatedly immersed many times in a solution containing a low concentration of replacement metal ions to achieve the desired metal replacement. It is necessary to obtain quantity.

According to the present invention, the larger the amount of metal substitution in -1, the higher the ozone decomposition activity can be obtained, but usually A
When it is 20% or more for SX and Y type zeolites, and 30% or more for mordenite and ZSM-5 type zeolites,
A catalyst having sufficiently high ozonolysis activity can be obtained.

The catalyst according to the invention as an active component as described above is
Usually, it is supported on an inert carrier and put into practical use as a catalyst structure. For example, a honeycomb catalyst structure can be obtained by making a catalyst powder into a slurry, impregnating a porous honeycomb structure with the slurry, and drying the slurry. In addition, if necessary, a carrier made of inert ceramic powder, a molding aid to give shapeability to the active ingredient, a reinforcing material such as inorganic fiber to increase the mechanical strength of the resulting catalyst, and an organic binder are added. It is also possible to form a honeycomb or other structure by extrusion molding or the like.

In addition, the catalyst structure according to the present invention has a shape that is
It is not limited in any way, and for example, in addition to the honeycomb shape as described above, it can have various arbitrary shapes such as a pellet shape, a cylindrical shape, a plate shape, a pipe shape, and the like.

The catalyst structure according to the present invention may consist entirely of the above-mentioned active component, but especially when a reinforcing material or a carrier is used, the active component may be 50% by weight or more in the catalyst structure. Preferably, it is particularly preferably 75% by weight or more.

According to the present invention, a reaction gas, that is, a gas containing ozone, for example, air, is brought into contact with the catalyst structure described above,
Ozone can be decomposed and removed by carrying out a catalytic reaction. The reaction temperature is preferably in the range of 0 to 40°C, particularly preferably in the range of 10 to 30°C. When the reaction temperature is lower than 0°C, the reaction rate is slow (not practical).

However, in order to carry out the reaction at a temperature exceeding 40°C,
For this purpose, new thermal energy is required, and the ozone decomposition rate is not particularly improved, so from the viewpoint of the ozone decomposition rate and energy cost, there is no particular need to exceed 40°C.

Furthermore, according to the invention, the contact between the catalyst structure and the reactant gas is carried out at an area velocity of 5 to 50.
It is preferable to carry out the test within the range of . Here, the areal velocity is
It is the value obtained by dividing the reaction gas amount (m3/hr) by the gas contact area per unit volume of catalyst (m''/m3).

When the areal velocity is less than 5, it is undesirable because a very large amount of catalyst is required, and when it is more than 5°, ozone is not sufficiently decomposed and the decomposition rate is low.

In addition, conventionally known ozone decomposition catalysts are used for ozone decomposition in ozone concentration (ppm) at the inlet of the catalyst reactor.
) and the area velocity (hereinafter referred to as CA value), the catalyst will not substantially deteriorate when ozone decomposition is carried out under mild reaction conditions. Under these conditions, the catalyst deteriorates significantly. However, the catalyst according to the present invention does not deteriorate even when used for ozone decomposition under such severe conditions, so the CA value is 30.
It can be used under severe reaction conditions as described above.

As described above, the ozone decomposition catalyst according to the present invention has excellent ozone decomposition activity, and furthermore, there is little deterioration in performance even in the ozone decomposition reaction under severe conditions.

Implementation M The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

In addition, in the following examples, preparation of catalyst powder was described. Using this catalyst powder as a slurry, corrugate made of ceramic fibers was manufactured with a porosity of 81% and a pitch of 4.
．． After immersing 0 l of the honeycomb in the above slurry and drying it, the catalyst loading rate on the honeycomb was 95 to 10.
A catalyst structure was manufactured by supporting the catalyst at a concentration of 5%.

■, Catalyst A consisting of zeolite and metal or metal oxide, Preparation Example 1 of catalyst Mordenite (NM-100P manufactured by Nihon Kagaku Kogyo ■) represented by the compositional formula % formula % and with Y/X of 6.3 ) 200g was dispersed in water 21 to form a slurry. Add a predetermined amount of chromium nitrate aqueous solution to this slurry, stir and mix thoroughly, and then
% concentration of ammonia water until the pH reaches 7.0.
Neutralized.

Next, this slurry was filtered, washed with water, dried at 100°C for 8 hours, and then calcined at 400°C for 2 hours to obtain mordenite powder containing 5% by weight, 10% by weight, and 155% by weight of chromium in terms of oxide. was obtained as a catalyst.

Example 2 200 g of type A zeolite (NA-100P manufactured by Nippon Chemical Industry Co., Ltd.) represented by the compositional formula % formula % and having Y/X of 1.0 was dispersed in water 21 to form a slurry. After adding a predetermined amount of manganese acetate aqueous solution to this slurry and stirring thoroughly,
It was neutralized with aqueous ammonia at a concentration of % by weight until the pH reached 7.0.

Next, this slurry was filtered, washed with water, dried at 100°C for 8 hours, and then calcined at 300°C for 2 hours to catalyze A-type zeolite powder containing 5% by weight and 100% by weight of manganese in terms of oxides. obtained as.

Example 3 A type zeolite powder containing 10% by weight of cobalt in terms of oxide was catalyzed in the same manner as in Example 2, except that an aqueous cobalt acetate solution was used instead of an aqueous manganese acetate solution. obtained as.

Example 4 In the same manner as in Example 2, except that an iron nitrate aqueous solution was used instead of the manganese acetate aqueous solution, A-type zeolite powder containing 10% iron in terms of oxide was prepared. Obtained as a catalyst.

Example 5 A type zeolite powder containing 10% by weight of copper in terms of oxide was catalyzed in the same manner as in Example 2, except that a copper acetate aqueous solution was used instead of the manganese acetate aqueous solution. obtained as.

Example 6 In Example 2, a silver nitrate aqueous solution was used instead of the manganese acetate aqueous solution, and 10
Except that a sodium hydroxide aqueous solution with a concentration of 0 weight was used.
In the same manner as in Example 2, 10% by weight of silver was added in terms of oxide.
The A-type zeolite powder contained therein was obtained as a catalyst.

Example 7 In the same manner as in Example 2, except that a silver nitrate aqueous solution was used together with a manganese acetate aqueous solution, and a 100 weight concentration sodium hydroxide aqueous solution was used in place of ammonia water. A type A zeolite powder containing 3% by weight of silver and 7% by weight of manganese was obtained as a catalyst.

Comparative Example 1 70 g of a mixture of titanium tetrachloride and silica sol (TiOz/5iOz weight ratio 1/1) was added to 30 g of manganese dioxide with a specific surface area of 48 m/g, and while stirring and mixing, ammonia gas was blown into the mixture to neutralize it. A slurry-like precipitate was obtained.

After thoroughly washing this precipitate with water, it was calcined at a temperature of 500°C for 3 hours to give a specific surface area of 162r+? /g of three-way catalyst (Mn
Oz/Ti0z/5iOz (weight ratio 30/35/35
) was obtained.

B,' No. 1 The ozonolysis activity of the catalysts obtained in Examples 1 to 7 and Comparative Example 1 was measured. That is, as shown in FIG. 1, air was introduced into an ozone generator 1 to prepare air containing ozone at a predetermined concentration, and this was introduced into a catalytic reactor 2 to catalytically decompose ozone. . The ozone concentration in the air was measured at the inlet and outlet of the catalytic reactor using the ozone analyzer 3, and the ozone decomposition rate (%) was determined from these using the following formula.

The reaction was carried out at a temperature of 20°C, with each CA (1!!) being 1
The ozone concentration and areal velocity at the inlet of the catalytic reactor were variously varied so as to be 0.30 and 50, and the ozone decomposition rate at the initial stage, after 1 hour, and after 2 hours was determined. The results are shown in Table 1.

As is clear from these results, the catalysts obtained in Examples 1 to 7 have higher ozone decomposition activity than the catalyst obtained in Comparative Example 1, and are more durable under severe reaction conditions. It is excellent.

■ Catalyst Example 1 consisting of metal-substituted zeolite 500 g of mordenite (NM-100P manufactured by Nihon Kagaku Kogyo ■) represented by the compositional formula % formula % and having Y/X of 6.3 was 0.5
It was immersed in a chromium nitrate aqueous solution 51 with a mol/β concentration and heated at a temperature of 90 to 100°C in a three-necked flask with a reflux device.
After stirring for an hour, the solids were filtered off.

By repeating such operations, chromium-substituted mordenite represented by the composition formula 1 (%) and having substitution ratios of 0.21, 0.34 and 0.57, respectively, was obtained.

Example 2 500 g of A-type zeolite (NA-100P manufactured by Nihon Kagaku Kogyo ■), which is represented by the compositional formula % formula % and whose Y/X is 1.0, was added to a 5β aqueous solution of manganese acetate with a concentration of 0 and 1 mol/l. After stirring at room temperature for 5 hours, the solid content was filtered off.

Such operations were repeated to obtain manganese-substituted type A zeolites represented by the composition formula 1% (20) and substitution ratios of 0.23 and 0.49, respectively.

Example 3 In Example 2, instead of the manganese acetate aqueous solution, 06
Except for using a cobalt acetate aqueous solution with a concentration of 1 mol/l,
In the same manner as in Example 2, a cobalt-substituted type A zeolite represented by the compositional formula 1 % and having a substitution rate of 0.44 was obtained.

Example 4 In Example 2, instead of the manganese acetate aqueous solution, 0.
Except that an aqueous iron nitrate solution of 1 mol/l Rt degree was used.
In the same manner as in Example 2, an iron-substituted type A zeolite represented by the compositional formula 1% and having a substitution ratio of 0.35 was obtained.

Example 5 In Example 2, instead of the manganese acetate aqueous solution, 0.
1 mole/I! A copper-substituted type A zeolite represented by the compositional formula 1 (%) and having a substitution rate of 0.41 was obtained in the same manner as in Example 2, except that a copper acetate aqueous solution having a concentration of 0.41 was used.

Example 6 In Example 2, instead of the manganese acetate aqueous solution, 0.
A silver-substituted type A zeolite was obtained in the same manner as in Example 2, except that an aqueous silver nitrate solution having a concentration of 1 mol/l was used, and was represented by the compositional formula 1 (%) and had a substitution rate of 0.27.

Example 7 In Example 2, the composition formula % formula A manganese-silver substituted type A zeolite with a substitution rate of 0.38 was obtained.

Example 8 In Example 2, instead of the manganese acetate aqueous solution, 0.
1 mole/j! ? Palladium-substituted A, which is represented by the compositional formula 1 formula % and whose substitution rate is 0.19, was prepared in the same manner as in Example 2 except that an aqueous palladium chloride solution of M degree was used.
type zeolite was obtained.

The ozonolysis activities of the catalysts obtained in Examples 1 to 8 above were measured in the same manner as described above. The results are shown in Table 2.

As is clear from the above results, the catalysts obtained in Examples 1 to 8 all have high ozone decomposition activity and are also excellent in durability even under severe reaction conditions.

[Brief explanation of drawings]

FIG. 1 shows the configuration of an apparatus for measuring ozonolysis activity. 1... Ozone generator, 2... Catalyst reactor, 3...
Ozone analyzer.

Claims (2)

[Claims] (1) General formula (I) M_x_/_n・[(AlO_2)_X・(SiO_2
)_Y]・_MH_2O (In the formula, M represents an alkali metal or alkaline earth metal, and n is the valence of the metal M.) The enthalpy of formation of the oxide -ΔH°f is 100 Kcal/ A catalyst for ozone decomposition, characterized in that it contains a metal or metal oxide having an oxygen gram atom or less. (2) General formula (II) M^1_a_/_nH_bM^2_(_X_-_(_a
＿／＿n＿)＿−＿b・[(AlO_2)＿X・(Si
O_2)_Y]・_MH_2O (in the formula, metal M^1 is
Enthalpy of oxide formation - ΔH°f is 100 Kcal/
Denotes a metal that is less than a gram atom of oxygen, M^2 represents K or Na, and n represents the valence of the metal M^1, where 0≦b<X. ) A catalyst for ozone decomposition comprising a metal-substituted zeolite represented by: