JPS6297643A - Ozone decomposing catalyst - Google Patents

Abstract

PURPOSE:To enhance ozone decomposition capacity, by forming the titled catalyst from a specific amount of a catalytic component (A) constituted of oxide consisting of Ti and Si and oxide consisting of Ti and Zr and a catalytic component (B) of Mn, Fe, Co, Ni and Pt, etc. CONSTITUTION:A TiO2-SiO2 powder and a molding aid are mixed and kneaded while a proper amount of water is added to both of them and the kneaded mixture is molded into a pellet or honeycomb shape by an extrusion molding machine. The molded substance is dried at 50-120 deg.C and subsequently baked at 300-800 deg.C for 1-10hr to obtain a catalyst. Further, when the catalyst is obtained by adding a metal selected from Mn, Fe, Ni, Co, Ag, Pt, Pd and Rh is added to TiO2-ZrO2, said catalyst can be prepared by a method wherein an aqueous solution of the salt of the aforementioned metal is infiltrated in a TiO2-ZrO2 molded body to support said salt and the impregnated molded body is dried and baked. A separate method wherein the aforementioned aqueous solution of the metal salt is added to the TiO2-ZrO2 powder along with the molding aid and the resulting mixture is kneaded and mixed, can be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ozone decomposition catalyst, and particularly to a catalyst for catalytically decomposing ozone contained in gas.

<Prior art and its problems> Ozone has strong oxidizing ability and becomes harmless oxygen when decomposed, so it is widely used in various fields for purposes such as deodorization, sterilization, bleaching, and reducing COD in wastewater. There is. However, some of the ozone used in the treatment is released into the atmosphere unreacted, which may cause secondary pollution such as photochemical smog.

Also, the aircraft has become a reality! When flying on an IPJ, air containing ozone is introduced into the cabin, which poses the risk of adversely affecting passengers and crew.

Furthermore, recently, the generation of ozone from devices that incorporate various high-voltage generators, such as dry copying machines, has become a problem, and since these devices are mainly placed indoors, the amount of ozone generated has increased. Even a small amount can contaminate the room.

The odor of ozone can be detected at a concentration of 1ppl or less;
Concentrations above 91 cause irritation to the respiratory system and are harmful to the human body, so it is necessary to remove ozone emitted from various sources and render it harmless.

Conventionally used waste ozone treatment techniques include an activated carbon method, a chemical cleaning method, and a thermal decomposition method. The activated carbon method is used to treat low-concentration ozone, but as ozone decomposition progresses, the activated carbon is consumed and needs to be replenished, and when treating high-concentration ozone, the activated carbon is depleted by the heat of reaction. It poses a problem in handling as there is a risk of it catching fire or burning.

In the chemical cleaning method, waste ozone is cleaned with an aqueous solution of a reducing substance, so the treatment cost is high and problems arise in wastewater treatment.

The thermal decomposition method requires heating to 300° C. or higher in order to increase the decomposition efficiency, and has drawbacks such as high heating costs and high processing costs in order to treat a large amount of exhaust gas.

On the other hand, in recent years, research has been conducted on the catalytic decomposition method as a waste ozone treatment method.This method is advantageous because it has no risk of ignition or explosion, does not require wastewater treatment, and can decompose and remove ozone at a low cost. has been done.

As ozone decomposition catalysts, catalysts using oxides such as nickel, manganese, and cobalt have excellent decomposition efficiency.
Although disclosed in Japanese Patent Application Laid-Open No. 60-97049, a catalyst that exhibits high activity in a lower temperature range is required as a practical catalyst.

<Objective of the Invention> An object of the present invention is to provide an inexpensive ozone decomposition catalyst with excellent low-temperature activity for catalytically decomposing ozone contained in gas into oxygen.

<Means for Solving the Problems> As a result of intensive research in accordance with the above objectives, the present inventors have developed a binary oxide consisting of titanium and silicon as a catalyst for catalytically decomposing and removing ozone in ozone-containing gas. Binary oxide consisting of titanium and zirconium, or titanium,
A ternary oxide consisting of silicon and zirconium contains 50
It has been found that it exhibits excellent ozone decomposition performance at low temperatures below ℃.

Furthermore, manganese (Mn), iron (Fe), cobalt (Co), nickel (N i ), silver (Ag), platinum (Pt), palladium (Pd) are added to the above binary oxide or ternary oxide. ) and rhodium (Rh), and rhodium (Rh), it was discovered that a catalyst prepared by adding at least one element selected from the group consisting of rhodium (Rh) or a compound thereof exhibits high ozone decomposition activity even in an extremely low temperature region of around 20°C, and the present invention was achieved. It has been completed.

That is, the present invention can be specified as follows.

A binary oxide consisting of titanium and silicon, a binary oxide consisting of titanium and zirconium, and/or a ternary oxide consisting of titanium, silicon, and zirconium as a catalyst for catalytically decomposing and removing ozone in ozone-containing gas. Manganese (Mn), iron (Fe
), cobalt (Go), nickel (N i >, silver (
Aa), a catalyst comprising at least one element selected from the group consisting of platinum (Pt), palladium (Pd) and rhodium (Rh) as a catalytic component, wherein the composition of the catalyst is such that component A is an oxide. 40 to 100% by weight as oxides, and 0 to 60% by weight as oxides for manganese (Mn), iron (Fe), cobalt (Co), nickel (N + ), and silver (80). %, platinum (Pt), palladium (Pd), and rhodium (Rh) are in the range of 0 to 10% by weight as metal elements.

<Function> The catalyst according to the present invention is characterized by a binary composite oxide consisting of titanium and silicon (hereinafter referred to as TiO2-8io2) and a binary composite oxide consisting of titanium and zirconium (hereinafter referred to as TiO2-ZrO2). ), titanium, silicon, and zirconium (hereinafter referred to as TiO2-3i02-Zro2) is used as a catalyst component.

In general, binary composite oxides consisting of titanium and silicon are known as solid acids, as is well known, for example, by Kozo Tabe (Catalysts, Vol. 17, No. 3, p. 72 (1975)), and each of the constituents is It exhibits remarkable acidity that is not found in individual oxides, and also has a high surface area.

In other words, TiO2-8iO2 is not simply a mixture of titanium oxide and silicon oxide, but it can be recognized that titanium and silicon form a so-called binary oxide, resulting in its unique physical properties. . Furthermore, binary composite oxides consisting of titanium and zirconium and ternary composite oxides consisting of titanium, zirconium and silicon are also specified as composite oxides having properties similar to TiO2-8iO2.

Furthermore, as a result of analysis by X-ray diffraction, the above composite oxide
Amorphous or almost amorphous @IIIJ! It has 14 buildings.

Although the mechanism by which the catalyst of the present invention exhibits excellent ozonolysis activity, particularly at low temperatures, is not certain, it is believed that the various properties of the composite oxide described above have a favorable influence on ozonolysis activity. Furthermore, by adding elements such as manganese, iron, nickel, cobalt, silver, platinum, palladium, rhodium, etc. or their compounds to the above composite oxide, it acts even more effectively and plays a role in increasing ozone decomposition activity. It is thought that there are.

T i 02- which is the catalyst A component forming the present invention
8 ioz, Ti02-ZrO2 and Ti02-8
The surface area of 1o2-ZrO2 is 30rd/Q
It is preferable that it is above.

The composition of the catalyst A component is Ti0z of 20~20 in terms of oxide.
95 mol%, SiO2 or ZrO2 or SiO2
The sum of ZrO+ and ZrO+ is 5 to 80 mol% (both TiO2+
ZrO2 + 5iO2 = 100 mol %) gives preferable results.

The composition of the catalyst according to the present invention is that component A is 40 to 100% by weight as an oxide, and component B is manganese (Mn).
, silver (Aq), iron (Fe), cobalt (Co) and nickel (N i > 0 to 60% by weight percentage as oxides, platinum (Pt), palladium (Pd')
And rhodium (Rh) is preferably in the range of 0 to 10% by weight.

If the B component is outside the above range, the ozonolytic activity will be insufficient, and in the case of platinum, palladium, and rhodium, the raw material cost will be high and sufficient effects cannot be exhibited.

To prepare TiO2-8iO2 used in the present invention, first, a titanium source can be selected from inorganic titanium compounds such as titanium chlorides and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate. The silicon source can be selected from inorganic silicon compounds such as colloidal silica, water glass, silicon tetrachloride, and organic silicon compounds such as tetraethyl silicate. And among these raw materials,
Although there may be some impurities and contaminants at low temperature, the T obtained
There is no problem as long as it does not significantly affect the physical properties of iO2-8iO2.

A preferred method for preparing TiO2-8iO2 includes the following method.

(2) A method in which titanium chloride is mixed with silica sol, ammonia is added to form a precipitate, the precipitate is washed, dried, and then calcined at 300 to 650°C.

■ Add sodium silicate aqueous solution to titanium tetrachloride and react to form a precipitate, which is washed and dried for 300 min.
A method of firing at ~650°C.

■ Add ethyl silicate [(C2HsO)4si] to a water-alcohol solution of titanium tetrachloride to cause a hydrolysis reaction to form a precipitate, which is washed and dried to a
A method of firing at ℃.

(2) A method in which ammonia is added to a water-alcohol solution of titanium oxide chloride (TiOCl2) and ethyl silicate to form a precipitate, which is washed, dried, and then calcined at 300 to 650°C.

Among the preferred methods on the station, method (2) is particularly preferred, and this method is specifically carried out as follows. That is, the titanium source and silicon source compounds are replaced by TiO
The molar ratio of 2 and SiO2 is set to a predetermined amount, and the concentration of titanium and silicon in terms of oxides is 1 to 100 g/l in an acidic aqueous solution state or sol state.
Keep at ℃. Aqueous ammonia was added dropwise as a neutralizing agent into the mixture while stirring, and a coprecipitated compound consisting of titanium and silicon was formed at 82 to 1oC for 10 minutes to 3 hours. After being separated from the furnace and thoroughly washed, the mixture was heated to 80 to 140°C. TiO
+-3iO2 can be obtained.

In addition, when T 1o2-ZrO2-8io2 is
iO2-8iO2 is prepared by the same method,
The zirconium source can be selected from inorganic zirconium compounds such as zirconium chloride and zirconium sulfate, and organic zirconium compounds such as zirconium oxalate.

That is, by treating a zirconium compound together with a titanium compound in the same manner as in the above method, T i 02-ZrO
2-8i 02 is easily prepared. And the amount of zirconium present is TiO2+Zr0z
It is preferably within a range of up to 30% by weight in terms of ZrO2 with respect to the total ω of +S io2. Ti02-Zr
The method for preparing O2 can be carried out in the same manner.

TiO2-8iO2, Ti02 prepared by the above method
Using -ZrO2 and TiO2-8iO2-2r02, a finished catalyst is obtained by the method shown below. - For example, adding TiO2-8iO2 powder together with molding aids;
Mix and knead while adding an appropriate amount of water, and mold into pellets or honeycomb shapes using an extruder.

After drying the molded product at 50 to 120°C, drying at 300 to 8°C, preferably 350 to 600'C, for 1 to 10 hours, and Ti
O2-8iO2 contains manganese, iron, nickel, cobalt,
When catalyzing by adding silver, platinum, palladium, or rhodium, the catalyst can be obtained by impregnating and supporting a TiO2-8iO2 molded body with an aqueous solution of the metal salt, followed by drying and firing.

On the other hand, as an alternative method, an aqueous solution of the above metal salt may be added to the TiO2-8iO2 powder together with a molding aid, and the mixture may be kneaded and molded.

It is also possible to further use a striking body.

Examples of carriers include alumina, silica, silica alumina, bentonite, diatomaceous earth, silicon carbide,
titania, zirconia, magnesia, copillite,
Mullite, pumice, activated carbon, inorganic fibers, etc. can be used; for example, granular silicon carbide with TiO2-8
It can be prepared by forming a slurry of iO2 and other catalyst components and supporting the slurry by an impregnation method. Of course, the catalyst preparation method is not limited to these methods.

The catalyst shape is not limited to the above-mentioned pellet shape and honeycomb shape, but also cylindrical shape, cylindrical shape, plate shape, ribbon shape, corrugated plate shape, etc.
A vibrator shape, a donut shape, a lattice shape, and other integrally molded shapes are appropriately selected.

Next, starting materials for the catalyst component used together with the VXA component in the catalyst of the present invention include oxides, hydroxides, a-acid salts, a-l salts, etc., especially ammonium salts, oxalate salts, etc. It is appropriately selected from nitrates, sulfates, halides, etc.

The ozone concentration treated by the catalyst of the present invention is contained in the gas at about 0.01 to 100,000 DI11, but is not necessarily limited to this range.

The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 A composite oxide consisting of titanium and silicon was prepared by the method described below. A sulfuric acid aqueous solution of titanyl sulfate having the following composition was used as a titanium source.

Ti08Oa (Ti02 conversion>250g/j
! Total H28041100Q/j Separately water 401 and ammonia water (NH3, 25%) 28j
! and Snowtex-NC8-30 (8
2.4 kg of silica sol manufactured by Sankagaku Co., Ltd. (containing approximately 30% by weight as SiO2) was added. Into the obtained solution, a titanium-containing aqueous sulfuric acid solution diluted by adding 15.3 J of the above titanyl sulfate aqueous sulfuric acid solution to 301 ml of water was added dropwise to the body under stirring.
A coprecipitated gel was produced.

Further, it was left as it was for 15 hours. The thus obtained TiO2-8iO2 gel was filtered and washed with water at 200°C.
It was dried for 10 hours.

Then, it was fired at 550° C. for 6 hours in an air atmosphere. The composition of the obtained powder was TiO2:5iO2-4:1 (molar ratio), and the BET surface area was 1851 d/q. The powder thus obtained was hereinafter referred to as TS-1 and was used to prepare an ozone decomposition catalyst by the method described below.

Above TS-1 powder 1. Add 20g of microcrystalline cellulose (manufactured by Asahi Kasei Corporation, trade name: Avicel) to ON9 along with a suitable amount of water, mix and knead well with a kneader, and then use an extrusion molding machine to form 3.0 m in diameter and 3° in length. The pellets were molded into 0-sized pellets, dried at 100°C for 10 hours, and then calcined at 500°C for 6 hours in an air atmosphere to obtain a catalyst consisting of 7i02-8i02.

Example 2 TiO2-ZrO2 was prepared by the method described below.

Zirconium oxychloride [Zr0C+2
・8H20] 1.93Kg is dissolved and mixed well while adding 8 pieces of an aqueous sulfuric acid solution of titanyl sulfate having the same composition as used in Example 1. While maintaining the temperature at about 30°C and stirring well, ammonia water was gradually added dropwise to the mixture, l)
The mixture was added until the H value reached 7, and then left as it was for 15 hours.

The TiO2-ZrO2 gel thus obtained was filtered, washed with water, and then dried at 200°C for 10 hours. It was then fired at 550'C for 6 hours in an air atmosphere. The composition of the obtained powder is T
The iO2:ZrO2 gel: 1 (molar ratio), and the SET surface area was 14o711/g. The powder obtained here is hereinafter referred to as TZ-1.

T i according to the method described in Example 1 using TZ-1
A catalyst consisting of 02-Z ro2 was prepared.

Example 3 TiO2-3i02-Z according to the method of Examples 1 and 2
Seven preparations of r02 were made. Composition of the obtained powder ttTi02
:5i02:Zr02=80:16:4 (molar ratio),
BET surface area 4. There was t180Td/Qr. The powder obtained here is hereinafter referred to as TSZ-1.

Using TSZ-1, T was prepared according to the method described in Example 1.
A catalyst consisting of iO2-81o2-ZrO2 was prepared as C1.

Examples 4 to 6 A catalyst consisting of TiO2-8iO2 was used as I in accordance with Example 1 except that the molar ratio of T i 02 /S i 02 was changed.
Made by I.

The composition and BET surface area of the obtained catalyst are shown in Table 1.

Comparative Example 1 Using the method of Example 1 without using silica sol
Powder No. 02 was prepared according to Example 1.

The SET surface area of the obtained T i 02 powder is 60rd
/a.

Using this powder, a catalyst consisting only of T t o2 was prepared in the same manner as in Example 1.

Comparative Example 2 According to Example 1, a powder containing only SiO2 without titanium was prepared. The surface area of the obtained powder is 250 TIt/g
Met. Using this powder, s was prepared in the same manner as in Example 1.
A catalyst consisting only of i02 was prepared.

Comparative Example 3 The powders of T i 02 and 5102 obtained by the methods of Comparative Example 1 and Comparative Example 2 were mixed with TiO2/5iO2=4 (molar ratio).
Mix well. SE of mixed powder
The T surface area was 90TIt/Q.

A catalyst consisting of the above mixed powder was prepared according to Example 1.

Example 7 The ozone decomposition rate was determined for each of the catalysts obtained in Examples 1 to 6 and Comparative Examples 1 to 3 using the following method.

A Pyrex reaction tube with an inner diameter of 20 mm has a diameter of 3.0 mm and a length of 3.0 mm. Filled with 10.5 cc of Otrys pellet-shaped catalyst and 0.21 Nm of air containing 1 oppm of ozone.
:/Hr flow rate (space velocity 20.000 Hr-1) was introduced into the catalyst layer, and the ozone decomposition rate at a reaction temperature of 20 to 100°C was determined.

The ozone decomposition rate was determined using the following formula.

Example 8 The same TS-1 powder 1 as used in Example 1. Manganese nitrate Mn (NO3)2-68200, 366 in OKg
After adding an aqueous solution containing Kg and thoroughly mixing and kneading with a kneader while adding an appropriate amount of water, it was formed into a pellet shape in the same manner as in Example 1, dried and fired, and the weight ratio as an oxide was determined. A catalyst having a composition of TS-1:Mn02=90:10 was obtained. Ozone decomposition performance was measured according to the method described in Example 7, and the results are shown in Table 3.

Examples 9 to 12 Using the same TS-1 powder as used in Example 1, catalysts were prepared according to the preparation method of Example 8 by changing the catalyst components added to the catalyst A component.

Nitrates of iron, cobalt, nickel, and silver were used as catalyst sources.

Ozone decomposition performance was measured according to the method described in Example 7, and the catalyst components and the results obtained are shown in Table 3.

Example 13 Catalyst consisting of TiO2-8iO2 obtained in Example 1 (
3al φ Then, it was fired in an electric furnace at 400° C. for 3 hours in an air atmosphere.

The composition of the obtained catalyst was TS-1:Pt=99:1, O
(Ratio).

Ozone decomposition performance was measured according to the method described in Example 7, and the results are shown in Table 3.

Examples 14-15 A catalyst was prepared in the same manner as in Example 13 except that palladium (Pd) and rhodium (Rh) chlorides were used instead of platinum (Pt).

Ozone decomposition performance was measured according to the method described in Example 7, and the catalyst components and the results obtained are shown in Table 3.

As shown in Table-2 and Table-3, the catalyst of the present invention has 5
It can be seen that this is an excellent catalyst that can efficiently decompose ozone at low temperatures below 0°C, especially at temperatures near room temperature.

Table-I TiO2-3iO2 catalyst table-3 Ozone decomposition rate (%)

Claims (1)

[Claims] (1) A binary oxide consisting of titanium and silicon, a binary oxide consisting of titanium and zirconium, and/or a ternary oxide consisting of titanium, silicon, and zirconium as a catalyst for catalytically decomposing and removing ozone in an ozone-containing gas. The base oxide is used as the catalyst A component, manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), silver (
A catalyst comprising at least one element selected from the group consisting of platinum (Pt), palladium (Pd), and rhodium (Rh) as the catalyst component B, wherein the composition of the catalyst is such that the component A is an oxide. 40 to 100% by weight, component B is manganese (Mn), iron (Fe), cobalt (Co),
Nickel (Ni) and silver (Ag) are from 0 to 60% by weight as oxides, and platinum (Pt), palladium (Pd), and rhodium (Rh) are from 0 to 10% by weight as metal elements. An ozone decomposition catalyst characterized by: