JPS6038972B2 - Ozone decomposition catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ozone decomposition catalyst, particularly for use in exhaust ozone treatment.

Ozone, which has strong oxidizing ability, is widely used for purposes such as decolorization, deodorization, sterilization, and COD removal, but in the process of its use, unreacted ozone is emitted into the atmosphere, causing secondary pollution. Therefore, it is necessary to treat the exhausted ozone. This exhaust ozone treatment method is desired to have high ozone decomposition efficiency, safety, maintainability, compact size, and excellent economic efficiency. Technologies currently employed in the field of exhaust ozone treatment include activated carbon method, pyrolysis method,
There are chemical cleaning methods, etc., and the activated carbon method is used to treat low concentrations of exhausted ozone, while thermal decomposition is used to treat high concentrations of 8E ozone of several hundred ppm or more from the standpoint of safety, maintainability, and ozone decomposition efficiency. laws are often adopted.

However, the thermal decomposition method requires a residence time of 2 seconds or more at a temperature of 30,000 or more in order to obtain a high ozone decomposition efficiency of 99% or more, and is therefore unfavorable in terms of economy and compactness.

In order to eliminate the drawbacks of this thermal decomposition method, the use of ozone decomposition catalysts has recently been considered, and it has been reported that, for example, manganese dioxide (Mn02) has excellent ozone decomposition properties as a catalyst ( Japanese Unexamined Patent Publication No. 55-73
No. 323, JP-A-60-80293). Transition metal oxides are known as excellent catalytic materials, and because they are relatively inexpensive, they are widely known as components of industrial catalysts. In particular, Mn oxide, which has the second Clark number (percentage of elements constituting other shells) of transition metals after iron, is one of the cheapest transition metal oxides and has no resource constraints. It is widely used as a catalyst component because it is hardly affected. However, as a result of further studies by the present inventors on the ozone decomposition performance of Mn02 catalysts, it was found that the ozone decomposition performance of these catalysts was insufficient when used at low temperatures.
It was also found that it has the disadvantage of gradually decreasing. Therefore, an object of the present invention is to provide an ozone decomposition catalyst that has superior ozone decomposition performance and durability even at low temperatures, particularly at low temperatures of about 50 qo.

As a result of repeated research on the performance deterioration of Mn02 catalysts, especially at low temperatures, the present inventor found that Mn02 contains 1 to 20 atomic % of Co oxide (Coox) and 0.1 to 20% by weight, preferably 0.5 to 20% by weight. It has been found that if 1% by weight of silver (Ag) is added, a catalyst having excellent ozone decomposition performance and durability at a low temperature of about 50 qo can be obtained.

Therefore, according to the present invention, 1 to 20% Coox and 0.1 to 20% by weight expressed in atomic % of Co in Mn02,
An ozonolysis catalyst is provided, preferably with addition of 0.5 to 1% by weight of Ag.

As used herein, the term "atomic % of Co" means
It means the percentage (%) of Co atoms expressed by the following formula.

Number of Co atoms Co atoms % = to.

In the present invention, "cobalt oxide" refers to Coo, Co204, Co
304 etc. are collectively called. When the catalyst of the present invention was analyzed by X-ray diffraction, it was found that Co304 was present as a main component in many cases. However, since it has been confirmed that other substances are also active phases, in the present invention they are expressed as ``Coox'' to include all of them. Co
oX is generally 1 to 2 o atom%, preferably 5 to 15
Co is added in an amount of atomic percent. Ag is generally added in a weight ratio of 0.1 to 20%, preferably 0.5 to 10%, based on the weight of all components. Regarding the amount of Ag added, if it is less than 0.1% by weight, the effect will not be sufficient;
The above decision was made in consideration of the fact that the effect is reduced if the content exceeds 2% by weight, and the economic disadvantage of using a large amount of expensive Ag. The catalyst of the invention may be in the form of a finely divided powder or of any size and shape, such as pellets, jaws, or other granules.

Preferably, it is bound with an inert binder and can take the form of crushed granules. As such a binder, for example, silica sol is used. The catalyst according to the present invention can be produced by a method such as a kneading method, an impregnation method, a coprecipitation method, or a combination thereof.

For example, the catalyst of the present invention uses Mn02 obtained by thermally decomposing manganese carbonate in an oxygen stream, and Coox obtained by calcining a precipitate produced by adding a sodium hydroxide aqueous solution to a cobalt nitrate aqueous solution in an air stream. This is mixed with silica sol, and then fired in an air stream to form a Mn02-Coox mixture.The granules obtained by crushing this are added to an aqueous silver nitrate solution for impregnation treatment, and then fired in an air stream. It can be manufactured by The catalyst of the present invention is a conventional Mn
Compared to the 02 catalyst, it has excellent ozone decomposition performance and durability, especially at low temperatures, and its adoption has made the exhaust ozone treatment equipment more compact and improved economic efficiency by lowering the operating temperature. It makes it possible to do so.

Although it is not clear why the catalyst of the present invention has such excellent performance at low temperatures, it is important to note that Ag and Mn02-
It is thought that this is because Coox effectively shares the functions and exerts a synergistic effect. Although the catalyst of the present invention has been described above as being used to treat high-concentration ozone, it can also be applied to treat low-concentration ozone generated from various devices such as copying machines. .

Examples are now presented to further illustrate the invention.

Manganese carbonate (Mn02) was prepared at 350 oo in an oxygen stream.
Mn02 obtained by time thermal decomposition and cobalt nitrate (Co
(N03)2・Navy20) Sodium hydroxide (N
C obtained by washing the precipitate generated by adding aOH) aqueous solution with pure water and then calcining it at 250°C for 3 hours in an air stream.
oox, and the amount of Coox added to Mn02 is Co
expressed in atomic percent of 0:1; 5:10:15 and 20%
mixed so that

Next, 2% by weight of silica sol was added to this, thoroughly kneaded, and then calcined at 250qC in an air flow for 3 hours to reduce Mn0.
A 2-Coox mixture was obtained. Furthermore, by crushing this
After adjusting the particle size to 0 to 12 mesh, it was added to a silver nitrate aqueous solution with a predetermined concentration and soaked at room temperature for 5 hours, and the excess silver nitrate aqueous solution was filtered through a sieve to remove it.
After drying for 6 hours at 25,000 in air flow, 0.1; 0.5:3:6:15 and 20 wt% Ag
Various Ag-Mn02-CooX catalysts containing the following were obtained. Catalyst Ozone Decomposition Performance Testing Apparatus FIG. 1 is a schematic diagram of the ozone decomposition performance testing apparatus.

First, air that has passed through the compressor and dehumidifier is supplied to the ozonizer A. This air is converted by ozonizer A into air containing ozone at a predetermined concentration. After passing through a needle valve B and a flow meter F, this ozone-containing air is led to a gas scrubber G, which simulates a water treatment device, and is humidified. The humidified ozone-containing air is supplied through a three-way cock C.
, and then supplied to an ozone decomposition device M consisting of an electric furnace E equipped with an ozone decomposition catalyst D. This ozone decomposition apparatus M has a temperature detector (not shown) for detecting the temperature of the catalyst layer of the ozone decomposition catalyst D. After passing through the ozone decomposition device M, the ozone-containing air is passed through the three-way cock C2.
, dehumidifier day and flowmeter F2 and then discarded. In order to measure the ozone concentration in the air before entering the ozone decomposition device M and the ozone concentration in the air after passing through the decomposition device M,
Ozone concentration measuring devices K and K2 are connected to the three-way cocks C and C2, respectively. By switching the flow path of the ozone-containing air to the ozone concentration measuring devices K and K2, the respective ozone concentrations can be determined. Ozone decomposition performance of catalyst and its durability test {1)
Test 1 Using the apparatus shown in FIG.
The ozone decomposition performance of the catalyst and the Mn02-CooX catalyst without the addition of Ag was tested.

The results are shown in FIG. The test conditions were as follows. Catalyst loading amount: 1.5 cc, catalyst layer temperature: 50 cm, ozone-containing air (exhaust ozone) flow rate: 1.0 so/min, space velocity OHSV: 40,000 hr-1, catalyst layer inlet ozone concentration: 2, 000pPm.

The characteristic lines A, C, C, and C in FIG. 2 are as follows, respectively.

A: Initial performance (ozone decomposition efficiency) of 3 wt% Ag-Mn02-Coox catalyst: 3 wt% Ag-Mn02-Co
Performance after using ox catalyst for 15 feeding hours: Mn02-Co
Initial performance of ox catalyst 2: Performance of Mn02-Coox catalyst after 15 field hours [
2) Similarly to Test 2, using the apparatus shown in FIG. 1, 0.1; 0.5:3; 6:15 and 2 weight% Ag-Mn02-10% COO The ozone decomposition performance of the catalyst was tested.

The results are shown in FIG. The test conditions were as follows. Catalyst loading amount: 1.5 cc, catalyst layer temperature: 50°C, ozone-containing air (pseudo ozone) flow rate: 1.0 z/min, space velocity GHSV: 40,00 plates r-1, catalyst layer inlet ozone concentration: 2 ,00 cost pm.

Characteristic lines A and A in FIG. 3 are respectively Ag-Mn
The initial performance (ozone decomposition performance) and the performance after 15 hours of use of the 02-10% Coox catalyst are shown.

'3} Test 3 Similarly, using the apparatus shown in FIG. 1, the durability of the Mn02-10% CooX catalyst and the 3wt% Ag-M 2-10% Coox catalyst at low temperatures (5000) was tested. did.

The results are shown in FIG. The test conditions were as follows. Catalyst loading amount: 1.5 cc, catalyst layer temperature: 50 qo, ozone-containing air (exhaust ozone) flow rate: 1.0 evening/min, space velocity GHSV: 40,000 hr-1, catalyst layer inlet ozone concentration: 2,00 p.m.

Characteristic lines A and A in FIG. 4 are Mn02-
10% Coox catalyst and 3wt% Ag-Mn02-10
%Coox catalyst versus test time.

In addition, in FIGS. 2 to 5, the ozone decomposition efficiency was determined by the following formula.

Ozone decomposition efficiency (%) : (・-Mizomen layer Eimeji 苧三≧Rokuken)X・〇.

As can be seen from Figures 2 to 4, Mn02
The Ag-Mn02-Coox catalyst of the present invention, in which 1 to 2 o atom % of Coox and about 0.1 to 20 wt.%, preferably 0.5 to 1 wt.
It has dramatically improved ozone decomposition performance and durability at low temperatures compared to OOX catalysts.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an ozone decomposition performance testing device. FIG. 2 is a graph showing the composition and ozone decomposition performance of a 3% by weight Ag-Mn02-COOx catalyst and a Mn02-Coox catalyst. Figure 3 shows Ag-Mn02-10%Co
It is a graph showing the amount of A9 added to the ox catalyst and the ozone decomposition performance. Figure 4 shows Mn02-10%Coox catalyst and 3
It is a graph showing the durability of o0x catalyst in weight %Ag-Mn02-1. Tayu zu 2 zu tayu zu 9

Claims (1)

[Scope of Claims] 1 An ozone decomposition catalyst formed by adding 1 to 20% Co oxide expressed as Co atomic % and 0.1 to 20 weight % Ag to MnO_2. 2. The ozone decomposition catalyst according to claim 1, characterized in that the amount of Ag is 0.5 to 10% by weight.