JPH0838896A - Catalyst for decomposing volatile organochlorine compound - Google Patents

Abstract

PURPOSE:To provide a catalyst capable of efficiently decomposing a volatile organochlorine compd. in coexistence of steam and oxygen and keeping activity over a long period of time. CONSTITUTION:A catalyst is constituted by supporting at least one kind of a component selected from a group consisting of platinum, palladium and ruthenium on a carrier based on zirconia as a main catalytically active metal component and supporting boron oxide thereon as a promotor component. The supporting amt. of the main catalytically active metal component is 0.1-5% by wt. of the catalyst in terms of metal and that of the promotor component is 2-5% by wt. of the catalyst as diboron trioxide. In this catalyst, bron oxide added as the promotor catalyst shows synergistic effect with respect to the main catalytically active metal component. As a result, a volatile organochlorine compd. can be efficiently treated for a long time and this catalyst is practical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst used for catalytically cracking volatile organic chlorine compounds.

[0002]

Freon is a volatile organic halogen compound,
There are various compounds including organic chlorine compounds such as trichlorethylene and tetrachloroethylene. Some of these volatile organic halogen compounds are widely used not only for industrial use but also for general household use because of their chemical stability and ease of handling.

For example, chlorofluorocarbon is used as a propellant, a refrigerant, etc. in a cooler, a refrigerator, etc. because it is easily liquefied and vaporized. Further, for example, trichloroethylene, tetrachloroethylene and the like are widely used in a degreasing process at the time of plating a metal, a dry cleaning and the like.

However, it has been pointed out that CFC causes the destruction of the ozone layer, and its use has been regarded as a problem from the viewpoint of protecting the global environment. The use of specific CFCs is now prohibited, and some kind of detoxification treatment is required when CFCs are released into the atmosphere. In addition, it has been found that trichlorethylene and tetrachloroethylene have a carcinogenic effect. For this reason, discharge into the atmosphere, soil contamination due to landfill disposal or illegal dumping, and groundwater contamination have become problems.

From the standpoint of environmental hygiene, legal regulations have been implemented in various places regarding the use and disposal of these compounds. Along with this, development of a detoxifying treatment technique for volatile organic chlorine compounds is strongly desired.

[0006] Conventionally, CFCs in exhaust gas or drainage,
Trichloroethylene, tetrachloroethylene, etc. are adsorbed and removed by activated carbon, zeolite, etc. However, a method for detoxifying these adsorbed compounds has not been established.

Recently proposed decomposition methods for volatile organochlorine compounds include thermal decomposition method, photodecomposition method and catalytic decomposition method. The thermal decomposition method is to burn a volatile organic chlorine compound at high temperature and high pressure, and the photolysis method is to irradiate ultraviolet rays with the volatile organic chlorine compound as it is or in the presence of ozone. The catalytic cracking method is to decompose and burn using a catalyst.

The thermal decomposition method has problems that the apparatus used is large-scale and the processing cost is high. The photolysis method is effective when the volatile organic chlorine compound is contained in the treated gas at a low concentration, but is not suitable when it is contained at a high concentration. On the other hand, the catalytic decomposition method is a simple method, is effective even for a gas containing a volatile organic chlorine compound at a high concentration, and has recently attracted particular attention. In this catalytic cracking method, alumina, silica, zeolite, titania,
A catalyst in which an inorganic oxide such as zirconia is used alone or in combination to prepare a carrier and a metal such as copper, chromium, iron, platinum or palladium is supported as a catalytically active metal component on the obtained carrier is used. This catalyst is contacted with a volatile organic chlorine compound at 400 to 500 ° C. in the presence of water vapor and oxygen (Japanese Patent Laid-Open No. 50-2669, Japanese Patent Laid-Open No. 3-12221).
JP-A-3-47516). It should be noted that these disclosed proposals do not disclose the use of the promoter component.

Generally, in the catalytic reaction of gas using a catalyst,
High SV (gas flow rate per unit time / catalyst volume), high L
A reaction under conditions such as V (linear velocity) is required. For this purpose, it is desired that the catalyst used in the reaction has a high solid acidity and a large number of active sites. In particular, a catalyst that catalytically decomposes a volatile halogenated organic compound is required to have excellent hydrogen chloride resistance. Considering acid resistance among the above conventional catalysts, it is preferable to configure the catalyst with a carrier using zirconia or titania. Certainly, the initial activity of a catalyst in which a metal such as platinum or palladium is carried as a catalytically active metal component on these carriers is high. However, the one which maintains the activity for a long time has not been found yet.

[0010]

The present invention has been made in consideration of the above situation, and its object is to decompose a volatile organic chlorine compound efficiently in the presence of water vapor and oxygen, and for a long period of time. The purpose is to provide a catalyst that maintains the activity.

[0011]

In order to solve the above problems, the inventors of the present invention prepared a carrier using zirconia having excellent hydrogen chloride resistance, and prepared various carriers with various main catalytically active metal components. The catalyst component was loaded and the catalyst activity was measured.
As a result, they have found that when a noble metal is used as the main catalytically active metal component and boric acid is used as the cocatalyst component, the resulting catalyst decomposes volatile halogenated organic compounds very efficiently, and reached the present invention.

That is, the catalyst of the present invention which solves the above-mentioned problems carries at least one selected from the group consisting of platinum, palladium and ruthenium as a main catalytically active metal component on a carrier containing zirconia as a main component, It is a catalyst supporting boron oxide as a promoter component. And, the supported amount of the main catalytically active metal component is 0.1 to 100 in terms of metal with respect to the catalyst.
The amount corresponding to 5% by weight and the amount of the cocatalyst component supported are 2 to 5% by weight as diboron trioxide with respect to the catalyst.

[0013]

In the structure of the catalyst according to the present invention, a catalyst mainly composed of zirconia is loaded with 0.1 to 5% by weight of a metal such as platinum, palladium or rhodium as a catalytically active metal component, so that the decomposition activity is high. It is already known that a catalyst can be obtained, and this range is not new.

What the present invention can provide is as follows:
Both the main catalytically active metal component and the boron oxide as the co-catalyst component are supported on a carrier containing zirconia as a main component. Thus, for the first time, a catalyst for decomposing a volatile organic chlorine compound having both high activity and long life is obtained.

The carrier used in the present invention is obtained as follows. First, the zirconium salt is hydrolyzed to obtain a zirconia hydrate. Next, the hydrate and a molding aid are mixed, kneaded sufficiently to be plasticized, molded, dried and fired. Zirconium salts that can be used here are zirconium nitrate, zirconium acetate, zirconium chloride, etc., which are hydrolyzed using a solution of aqueous ammonia, sodium hydroxide, ammonium carbonate or the like. The molding aid used may be a conventional one used for producing a catalyst carrier, and is not particularly limited, but it is convenient if it is an organic molding aid that does not leave any residue after firing.

The shape of the molded body may be a cylindrical shape, a spherical shape, or a honeycomb shape generally used as a catalyst carrier, and a shape suitable for the catalytic reaction may be selected. Therefore, it is also possible to use a catalyst in which a catalytically active metal component and a co-catalyst component are supported on a powdery carrier by adhering it to a refractory substrate. Also, the molded body is fired to obtain a carrier, and the firing temperature at this time is 50
The temperature is preferably 0 to 600 ° C. This is because if the baking temperature is low, sufficient carrier strength cannot be obtained, and if it is too high, the specific surface area of the obtained carrier decreases.

The carrier thus obtained was loaded with a metal such as platinum, palladium, ruthenium, etc. as the main catalytically active metal component and boric acid as the co-catalyst component, and then dried to give 400
The catalyst of the present invention is manufactured by calcining at a temperature of ~ 600 ° C.
At this time, the amount of the main catalytically active metal component supported is set to 0.1 to 5% by weight based on the catalyst amount in terms of metal, because when the supported amount is less than this range, sufficient catalytic activity cannot be obtained. Because. Further, even if it exceeds this range, the further effect on the activity improvement cannot be obtained, and the economical efficiency is only impaired.

The amount of the cocatalyst component supported on the catalyst is equivalent to 2 to 5% by weight based on the amount of the catalyst. If the supported amount is outside this range, stable decomposition activity cannot be maintained for a long time. Because.

In the catalytic reaction of the present invention, water molecules are adsorbed at the acidic points of the solid acid in the catalyst to exhibit Bronsted acid type activity, and the chlorine atom is extracted from the volatile organic chlorine compound molecule to remove the compound. It decomposes molecules. The catalyst of the present invention can decompose volatile organochlorine compounds very efficiently because the main catalytically active metal component and the cocatalyst component show a synergistic effect by adding boric acid as a cocatalyst component, and the number of active sites is It seems that it will increase significantly.

[0020]

EXAMPLES Next, examples of the present invention will be described.

(Examples 1 and 2) (1) Preparation of carrier 36 liters of water was placed in a stainless steel reactor having an internal volume of 100 liters equipped with a stirrer, heated to 70 ° C., and kept at this temperature. Next, 150 ml of 14% concentration aqueous ammonia was added to adjust the pH of the solution to 9.5. Then Zr
18 liters of an aqueous solution containing 2349 g of zirconium nitrate as O ₂ and 19.1 liters of 14% -concentrated aqueous ammonia were adjusted so that the pH of the reaction solution was 9.0 to 9.5, and the total amount was changed in 15 minutes. It was dripped at the same time. After the dropping was completed, stirring was continued for another 30 minutes to obtain ZrO ₂ of 3.2.
A zirconia hydrate slurry with a concentration of wt% was obtained. The resulting slurry was filtered to obtain a zirconia hydrate cake, which was poured into 80 liters of warm water at a temperature of 50 ° C., stirred and redispersed, and then filtered. This repulp washing operation was repeated three times in total to obtain a zirconia hydrate cake from which the ammonia content was removed.

Then, in the hydrate cake obtained, 9.
0 kg (1395 g as ZrO ₂ ) and 45 g Avicel (trade name, manufactured by Asahi Kasei Co., Ltd.) as an organic molding aid
15 g of Metroose (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and kneaded in a kneader with a heating jacket until it was sufficiently plasticized. The loss on ignition of the kneaded material at 500 ° C is 5
It was 3%.

Next, the kneaded material obtained was granulated into beads having a diameter of about 2.0 mm by a rounding machine, dried at a temperature of 100 ° C. for 15 hours, and then calcined at 500 ° C. for 2 hours. In this way, a catalyst carrier was obtained. The specific surface area of this carrier as determined by the BET method using nitrogen gas adsorption was 115 m ² / g.

(2) Preparation of catalyst A solution obtained by dissolving 4.34 g of chloroplatinic acid in 10 ml of water and a solution obtained by dissolving 7.3 g of boric acid in 50 ml of warm water were mixed to obtain an impregnating solution. Got 200 g of the carrier was impregnated with the entire amount of the impregnating liquid to obtain 110
The catalyst was dried at 15 ° C. for 15 hours and then calcined at 500 ° C. for 2 hours to obtain catalyst A (Example 1).

Next, the amount of chloroplatinic acid at the time of preparing the impregnating solution was set to 4.4.
Catalyst B (Example 2) was obtained in substantially the same manner as above except that the amount was 7 g and the amount of boric acid was 18.83 g.
Table 1 shows the amounts of platinum and boric acid supported on the obtained catalysts A and B.
It was shown to.

(3) Evaluation of catalytic activity A catalyst bed was formed by filling each of the obtained catalysts A and B in a fixed bed flow type reactor having a catalyst filling amount of 50 ml. Then, a sample gas having the following composition was passed through the catalyst layer at SV = 5000 hr ⁻¹ while keeping the reaction temperature at 500 ° C. 50 hours and 300 after passing the sample gas
After a period of time, the amount of trichlorethylene in the exhaust gas was analyzed using a gas chromatograph manufactured by Shimadzu Corporation,
The decomposition rate of trichlorethylene was determined. The obtained results are also shown in Table 1.

(Sample Gas Composition) Trichlorethylene: 0.23 ml / min Water: 0.33 ml / min Air: 3704.2 ml / min (Comparative Examples 1 and 2) 4.29 g of chloroplatinic acid was added to 10 ml of water. The solution obtained by dissolving was mixed with a solution obtained by dissolving 3.61 g of boric acid in 50 ml of warm water to obtain an impregnating solution. The total amount of this impregnating liquid is the carrier 200 obtained in Example 1.
g, and the impregnated product was dried at 110 ° C. for 15 hours and then calcined at 500 ° C. for 2 hours to obtain catalyst C (Comparative Example 1).

A catalyst D (Comparative Example 2) was obtained in the same manner with 4.57 g of chloroplatinic acid and 26.93 g of boric acid. Table 1 shows the amounts of platinum and boric acid supported on the obtained catalysts C and D.

Then, the activity of these catalysts was evaluated in the same manner as in Example 1. The obtained results are also shown in Table 1.

(Examples 3 and 4) A solution obtained by dissolving 2.16 g of chloroplatinic acid in 10 ml of water and 7.
A solution obtained by dissolving 26 g in 50 ml of warm water was mixed to obtain an impregnating solution. 200 g of the carrier obtained in Example 1 was impregnated with the entire amount of this impregnating solution, and the impregnated product was dried at 110 ° C. for 15 hours and then calcined at 500 ° C. for 2 hours to obtain catalyst E (Example 3).

Also, catalyst F (Example 4) was obtained in the same manner by using chloroplatinic acid as 8.76 g and boric acid as 7.37 g. Table 1 shows the amounts of platinum and boric acid supported on the obtained catalysts E and F.

Then, the activity of these catalysts was evaluated in the same manner as in Example 1. The obtained results are also shown in Table 1.

(Comparative Example 3) 4.25 g of chloroplatinic acid was added to 6 parts of water.
It was dissolved in 5 ml to obtain an impregnating liquid. 200 g of the carrier obtained in Example 1 was impregnated with the entire amount of this impregnating solution, and the impregnated product was dried at 110 ° C. for 15 hours and then calcined at 500 ° C. for 2 hours to obtain catalyst G (Comparative Example 3).

Then, the activity of these catalysts was evaluated in the same manner as in Example 1. The obtained results are also shown in Table 1.

[0035] From the results in Table 1, catalysts A and B, which are catalysts within the scope of the present invention,
It is understood that E and F can decompose trichlorethylene efficiently for a long time.

The catalysts D and E have a supported amount of boric acid as a cocatalyst component outside the range of the present invention and have high initial activity, but when used for a long time, the catalyst deteriorates and the trichlorethylene decomposition efficiency decreases. When the amount of boric acid which is a promoter component is in the range of 2 to 5% by weight in terms of oxide, it exerts the effect of increasing the number of active sites by the synergistic effect of the main catalyst metal component and the promoter component. This is because the effect decreases on the contrary as the number increases.

The catalyst G is a catalyst that does not support boric acid as a co-catalyst component and has a high initial activity, but it is understood that the catalyst deteriorates and the trichlorethylene decomposition efficiency decreases when used for a long time.

(Effect) In the catalyst of the present invention, boric acid added as a cocatalyst component has a synergistic effect with the main catalyst metal component.
As a result, the volatile organic chlorine compound can be efficiently treated for a long time, which is practical.

Therefore, the catalyst of the present invention can be used for detoxifying volatile organic chlorine compounds such as exhaust gas discharged from a metal degreasing process and dry cleaning, waste liquid, and the like, and is extremely effective in preventing environmental pollution.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/86 ZAB B01J 23/44 ZAB 23/46 301 B01D 53/36 ZAB G (72) Inventor Hayakawa Toshi Ichikawa, Chiba Chugoku 3-18-5 Sumitomo Metal Mining Co., Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. A support containing zirconia as a main component, a main catalytically active metal component and a cocatalyst component, wherein the main catalytically active metal component is at least one selected from the group consisting of platinum, palladium and ruthenium. A catalyst for decomposing volatile organic chlorine compounds, in which the cocatalyst component is boron oxide. 2. The amount of the main catalytically active metal component supported on the catalyst is equivalent to 0.1 to 5% by weight in terms of metal, and the amount of the cocatalyst component supported is 2 on the catalyst in terms of diboron trioxide. The catalyst according to claim 1, which is equivalent to about 5% by weight.