JPH0852353A - Catalyst for decomposing volatile organochlorine compound - Google Patents

Abstract

PURPOSE:To provide a catalyst capable of efficiently decomposing a volatile organochlorine compd. in the coexistence of steam and oxygen and keeping activity over a long period of time by supporting a cocatalyst component and a main catalytically active metal component on the surface layer of a carrier. CONSTITUTION:A catalyst is obtained by supporting at least one of a component selected from the group consisting of platinum, palladium and ruthenium on the surface layer of a carrier based on titania as a main catalytically active metal component and further supporting a boron oxide thereon as a cocatalyst component and the supporting amt. of the main catalytically active metal component is 0.1-2wt.% of the catalyst in terms of metal and that of the cocatalyst component is 1-3wt.% of the catalyst as diboron trioxide.

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. Then, the catalytic cracking method is to decompose by 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 organic chlorine compound is desired 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-mentioned problems, the present inventors have prepared a carrier using titania having excellent resistance to hydrogen chloride, and prepared various carriers with various main catalytically active metal components on this carrier. 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 a main catalytically active metal component and boric acid is used as a cocatalyst component, the obtained catalyst decomposes a volatile organochlorine compound very efficiently, and has reached the present invention.

That is, in the catalyst of the present invention for solving the above problems, a main catalytically active metal component and a cocatalyst component are supported on the surface layer of a carrier containing titania as a main component, and the main catalytically active metal component is platinum or palladium. , Ruthenium, and at least one selected from the group consisting of ruthenium, and the co-catalyst component is boron oxide. And, the supported amount of the main catalytically active metal component is equivalent to 0.1 to 2% by weight in terms of metal relative to the catalyst,
The amount of the cocatalyst component supported is 1 to 3% by weight as diboron trioxide with respect to the catalyst.

[0013]

It is already known that a catalyst having a high decomposition activity can be obtained by using a carrier containing titania as a main component and a catalytically active metal component such as platinum, palladium or rhodium in the structure of the catalyst according to the present invention. However, this range is not new.

What the present invention can provide is as follows:
By using boron oxide as a co-catalyst component in addition to these catalytically active metal components, and by selectively supporting the catalytically active metal component and the co-catalyst component on the surface layer of a carrier containing titania as a main component. is there. 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, hydrolyze the titanium salt,
Obtain titania hydrate. Next, the hydrate and a molding aid are mixed, kneaded sufficiently to be plasticized, molded, dried and fired. Titanium salts that can be used here are titanium sulfate, titanium trichloride, titanium tetrachloride, titanium isoprocoxide, 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 calcination temperature is low, sufficient carrier strength cannot be obtained, and if it is too high, the crystal structure undergoes thermal transition from anatase type to rutile type, and the specific surface area of the resulting titania carrier decreases.

On the carrier thus obtained, metals such as platinum, palladium and ruthenium are loaded as a main catalytically active metal component, and boric acid and the like are loaded as a cocatalyst component.
The catalyst of the present invention is manufactured by drying at 0 ° C. and calcining at a temperature of 400 to 600 ° C. At this time, the amount of the main catalytically active metal component supported is set to an amount equivalent to 0.1 to 2% by weight based on the amount of the catalyst in terms of metal, 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.

When the amount of the cocatalyst component supported is equivalent to 1 to 3% by weight based on the amount of the catalyst in terms of oxide, it is impossible to maintain stable decomposition activity for a long time when the amount supported is outside this range. Because.

The catalyst of the present invention is used under conditions of high SV and high LV. Therefore, it is not expected that the volatile organic chlorine compound diffuses inside the catalyst carrier and reacts therewith. In the catalyst of the present invention, it is in consideration of this point that the main catalytically active metal component and the co-catalyst component are selectively supported on the carrier surface layer. In order to support the main catalytically active metal component and the co-catalyst component on the carrier surface layer, after the alkali treatment of the titania carrier with sodium hydroxide solution, aqueous ammonia, etc.,
It can be obtained by impregnating a mixed solution of a main catalytically active component and a cocatalyst component.

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 molecule of the volatile organochlorine compound. It decomposes molecules. The catalyst of the present invention can decompose volatile organochlorine compounds extremely efficiently because the addition of boron oxide as a co-catalyst component shows a synergistic effect between the main catalytically active metal component and the co-catalyst component. It seems that the number will increase significantly.

[0021]

【Example】

(Examples 1 and 2) (1) Preparation of carrier 45 liters of water was placed in a reaction vessel made of stainless steel with an agitator and having an internal volume of 100 liters, heated to 70 ° C, and kept at this temperature. Next, 190 g of 14% concentration aqueous ammonia was added to adjust the pH of the solution to 9.5. Next, ₂₀ kg of an aqueous solution containing 2400 g of titanium sulfate as TiO ₂ and 18.2 kg of 14% -concentrated ammonia water were added to
The entire amount was dropped at the same time in 15 minutes while adjusting the H to be 9.0 to 9.5. After the dropping was completed, stirring was continued for another 30 minutes to obtain a titania hydrate slurry having a concentration of 2.85% by weight as TiO ₂ . The obtained slurry was filtered to obtain a titania hydrate cake, which was heated with hot water at a temperature of 50 ° C.
Pour into 0 liters, stir to redisperse and then filter. This repulp washing operation was repeated three times in total to obtain a titania hydrate cake from which the ammonia content was removed.

Then, in the hydrate cake obtained, 9.
0 kg (1260 g as TiO 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
5%.

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 by nitrogen gas adsorption was 108 m ² / g.

(2) Preparation of catalyst 200 g of the carrier was impregnated with 65 ml of 14% ammonia water, and the surface was dried. Then, a solution obtained by dissolving 2.13 g of chloroplatinic acid in 10 ml of water and a solution obtained by dissolving 3.59 g of boric acid in 35 ml of warm water were mixed to obtain an impregnating liquid. The entire amount of the impregnating solution was impregnated with the entire amount of the ammonia-treated carrier, the impregnated product was dried at 110 ° C for 15 hours, and then at 500 ° C for 2 hours.
It was calcined for a time to obtain catalyst A (Example 1).

Next, the amount of chloroplatinic acid at the time of preparing the impregnating liquid was 2.1.
Catalyst B (Example 2) was obtained in the same manner as in the above method except that the amount of boric acid was 8 g and the amount of boric acid was 11.0 g. Table 1 shows the amounts of platinum and boric acid supported on the obtained catalysts A and B.

The supported states of platinum and boric acid on the catalysts A and B were measured with an EPMA-2300 type X-ray microanalyzer manufactured by Shimadzu Corporation. The measurement result of the catalyst A is shown in FIG. 1, and the catalyst B was also in the same loaded state.

(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) Chloroplatinic acid was 2.12 g, and boric acid was added. Catalyst C as in Example 1 except that 1.79 g was used.
(Comparative example 1) was obtained.

Also, catalyst D was prepared in the same manner as in Example 1 except that 2.22 g of chloroplatinic acid and 18.73 g of boric acid were used.
(Comparative example 2) was obtained. 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) 0.85 g of chloroplatinic acid
Then, a catalyst E (Example 3) was obtained in the same manner as in Example 1 except that boric acid was changed to 3.58 g.

A catalyst F (Example 4) was obtained in the same manner as in Example 1 except that 4.34 g of chloroplatinic acid and 7.3 g of boric acid were used. 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) A catalyst G was obtained in the same manner as in Example 1 except that chloroplatinic acid was 2.13 g and boric acid was 3.59 g, and no alkali treatment was performed.

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 4 200 g of the carrier obtained in Example 1
Was impregnated with a solution of 4.25 g of chloroplatinic acid dissolved in 70 ml of water without alkali treatment with ammonia water, dried at 110 ° C. for 15 hours, and then calcined at 500 ° C. for 2 hours to obtain a catalyst H. . Table 1 shows the loading amounts and loading states of platinum and boron oxide of the obtained catalyst H.

[0037] From the results shown in Table 1, it can be seen that the catalysts A, B, E and F are catalysts within the scope of the present invention and can decompose trichlorethylene efficiently for a long time to render it harmless.

The catalysts C and D had a supported amount of boron oxide as a co-catalyst component outside the range of the present invention and had high initial activity, but when used for a long time, the catalyst deteriorated and the trichloroethylene decomposition efficiency decreased. To do. The supported amount of boron oxide that is a promoter component is 1 to 3% by weight in terms of diboron trioxide.
This is because the effect of increasing the number of active sites due to the synergistic effect of the main catalytically active metal component and the cocatalyst component is exerted within the range, and the effect is decreased when the amount of boron oxide supported is further increased.

The catalyst G is a catalyst in which the main catalytically active metal component and the cocatalyst component are within the scope of the present invention, but platinum and boric acid are evenly supported inside the catalyst. Then, it is understood that the catalyst deteriorates and the trichlorethylene decomposition efficiency decreases.

The catalyst H is a catalyst in which boron oxide, which is a co-catalyst component, is not supported, and platinum is evenly supported inside the catalyst. Although the initial activity is high, the catalyst deteriorates when used for a long time and decomposes trichloroethylene. It can be seen that the efficiency decreases.

By thus supporting platinum as the main catalytically active metal component and boron oxide as the cocatalyst component on the surface layer of the carrier, the amount of the catalyst component supported can be reduced and the catalyst life is long. Therefore, it is clear that the decomposition treatment of trichlorethylene can be performed efficiently.

[0042]

In the catalyst of the present invention, boron oxide added as a cocatalyst component has a synergistic effect with the main catalytically active metal component.
Then, the main catalytically active metal component and the co-catalyst component are concentratedly carried on the carrier surface layer. 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, etc., and is extremely effective in preventing environmental pollution.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B01J 23/46 301 A (72) Inventor Toru Hayakawa Ichikawa, Chiba Chugoku 3-18-5 Residence Central Research Laboratory, Tomo Metal Mining Co., Ltd.

Claims (2)

[Claims] 1. A main catalyst-active metal component and a co-catalyst component are carried on the surface layer of a carrier containing titania as a main component, and the main catalyst-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, which is a seed and whose promoter component is boron oxide. 2. A supported amount of the main catalytically active metal component is 0.1 to 2% by weight in terms of metal with respect to the catalyst, and a supported amount of the cocatalyst component is 1 in terms of diboron trioxide based on the catalyst. The catalyst according to claim 1, which is equivalent to about 3% by weight.