JPH07256099A - Catalyst for treating organochlorine compound - Google Patents

Abstract

PURPOSE:To provide a catalyst capable of efficiently decomposing an organochlorine compd. in the presence of air and water and capable of keeping activity for a long period of time. CONSTITUTION:A boria-alumina compsn. wherein boria content is 5-15wt.% as B2O3 and a specific surface area calculated by a nitrogen gas adsorbing method is 50m<2>/g or more and a crystal structure due to X-ray diffraction is an aluminum borate structure is used as a carrier. A catalyst for treating an organochlorine compd. is mainly constituted of this carrier and a noble metal being an active metal or a noble metal and a transition metal and contains the active metal in an amt. of 0.1-5% by wt. of the catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for treating an organic chlorine compound, and more particularly to a catalyst used for catalytically cracking an organic chlorine compound.

[0002]

2. Description of the Related Art Organochlorine compounds such as trichlorethylene and tetrachloroethylene have been widely used in metal degreasing processes and dry cleaning processes. However, since the carcinogenic action of organochlorine compounds was discovered, soil pollution and groundwater pollution due to their discharge into the atmosphere, landfill disposal and dumping have become a problem. From the standpoint of environmental hygiene, laws and regulations have been implemented in various places. As described above, strict control is required for organic chlorine compounds and waste liquids containing them, and development of detoxification treatment techniques for these is strongly desired.

At present, these organochlorine compounds are
Although it is mainly adsorbed on activated carbon or zeolite and removed from the atmosphere or wastewater, no consideration has been given to a method for detoxifying the adsorbed organic chlorine compound.
A thermal decomposition method of desorbing these organic chlorine compounds from activated carbon and burning them at a high temperature of 800 ° C or higher, and a plasma decomposition method of irradiating them with ultraviolet rays to perform photolysis have been proposed. There's a problem. For example, in the thermal decomposition method and the plasma decomposition method, the equipment is large and the processing cost is high.

A catalytic cracking method in which decomposition and combustion are carried out in the presence of a catalyst is one of the methods with relatively few problems, and has recently attracted particular attention. For example, alumina, silica, zeolite, titania, a carrier obtained by combining inorganic oxides such as zirconia, copper, chromium,
A catalyst obtained by supporting iron, platinum, palladium or the like as an active metal is used. That is, these catalysts are contacted with an organic chlorine compound such as trichlorethylene in the presence of water vapor and oxygen or air at 400 to 500 ° C. (JP-A-55-30891, JP-A-3-30891).
12221, JP-A-3-47516).

Generally, in the catalytic reaction of gas using a catalyst,
It is required to carry out the reaction under the conditions of high SV (gas flow rate per unit time / catalyst volume) and fast LV (linear velocity). For this purpose, it is desirable that the catalyst used in the reaction has a large specific surface area. Further, when catalytically decomposing organic chlorine compounds, it is important that the catalyst is acid resistant, especially excellent in hydrogen chloride. From these points of view, looking at the above-mentioned catalyst, titania and zirconia, which are excellent in acid resistance, have a small specific surface area and cannot maintain their activity for a long period of time even if their initial activity is high.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above situation, and its object is to decompose an organic chlorine compound efficiently in the presence of air and water, and The purpose of the present invention is to provide a catalyst that can maintain activity for a long period of time.

[0007]

In order to achieve the above object, the present inventor has earnestly studied to obtain a catalyst composed of a carrier and an active metal component, which has acid resistance to hydrogen chloride and has a high specific surface area. As a result, the boria-alumina composite oxide having a crystal form of an aluminum borate structure has excellent acid resistance and a high specific surface area, and a noble metal and / or a noble metal conventionally proposed for the composite oxide carrier. The present invention has been completed by discovering that the obtained catalyst decomposes an organochlorine compound very efficiently when it is loaded with a transition metal.

That is, the catalyst of the present invention for solving the above-mentioned problems has a boria content of 5 to 15% by weight as B ₂ O ₃ and a specific surface area of 50 m ² obtained by a nitrogen gas adsorption method.
/ G or more and the carrier has a boria-alumina composition whose crystal structure by X-ray diffraction has an aluminum borate structure, and is mainly composed of this carrier and a noble metal as an active metal, or a noble metal and a transition metal. The amount of the active metal is equivalent to 0.1 to 5% by weight of the catalyst weight. The noble metal as an active metal used in the present invention is platinum, palladium, ruthenium, etc., and the transition metal is copper, chromium, cobalt, etc.

[0009]

The amount of B ₂ O ₃ in the boria-alumina composition used as the catalyst carrier is set to 5 to 15% by weight because the aluminum borate structure is not formed outside this range, and the nitrogen gas is not used. This is because the specific surface area measured by the BET method due to adsorption decreases. The reason why the specific surface area of the carrier determined by the nitrogen gas adsorption method is 50 m ² / g or more is that sufficient catalytic activity can be obtained only in this range.

In order to obtain a carrier having such a crystal structure and a specific surface area, for example, an alumina hydrate obtained by mixing an aqueous solution of aluminum sulfate and an aqueous solution of sodium aluminate, hydrolyzing, filtering and washing. Add a predetermined amount of boric acid aqueous solution to knead the moldable water to make a plasticized product,
After molding into the desired shape, dry it and leave it at 900-1
It is obtained by firing at 100 ° C. Alternatively or alternatively, the plasticized product is dried, crushed to a desired particle size, and then calcined at the same temperature.

The catalyst carrier of the present invention has excellent acid resistance to hydrogen chloride, as can be seen from the acid resistance test results described later. The reason for this is as follows. That is, both alumina and boron constituting the carrier are trivalent cations, and the coordination numbers are both tetracoordinate. As a result, boron is uniformly arranged in the skeleton of alumina, an aluminum borate phase is formed, and acid resistance is exhibited.

The catalyst of the present invention is manufactured by supporting a noble metal or a noble metal and a transition metal as an active metal on this catalyst carrier, then drying at a temperature of 80 to 110 ° C. and calcining at 400 to 600 ° C. In the catalyst of the present invention, the amount of the active metal supported is set to 0.1 to 5% by weight because sufficient activity cannot be obtained when the amount of the active metal supported is less than this range, and the amount of active metal is more than this range. This is because it is not possible to obtain a further increasing effect on the improvement, and it is not necessary to support above the above range in consideration of economical efficiency.

The catalyst for treating an organochlorine compound of the present invention produced as described above oxidizes and decomposes an organochlorine compound such as exhaust gas or waste liquid discharged from a metal degreasing process or a dry cleaning process to render it harmless. Is an effective catalyst for.

[0014]

EXAMPLES Examples and comparative examples of the present invention will be shown below. (Examples and Comparative Examples) (1) Production and Evaluation of Carrier Water 4 in a stainless steel reaction tank with an agitator having an internal volume of 100 liters.
Add 9.5 liters, heat to 70 ° C., hold at 70 ° C., and with stirring, 9540 g of aluminum sulfate aqueous solution (8% sulfuric acid band sold by Shimada Shoten Co., Ltd.) and sodium aluminate aqueous solution (Sumitomo Chemical Co., Ltd. stock) Company-made NA-17
0) 7080 g was put into a reaction tank to obtain an alumina hydrate slurry having a pH of 8.3. Next, this slurry was aged for 30 minutes, then filtered and washed to obtain an alumina hydrate cake. Next, 250 of this alumina hydrate cake
0 g (450 g as Al ₂ O ₃ ) of boric acid 1 of primary reagent
42 g (80 g as B ₂ O ₃ ) was added and kneaded by heating in a double-arm kneader with a heating jacket, and B ₂ O ₃ + Al ₂ O ₃
A kneaded product having a plasticity of 38% by weight was obtained.

Next, this kneaded product was molded into a cylindrical shape using an extrusion molding machine having a die with a diameter of 1.5 mm, and the obtained molded product was dried at 110 ° C. for 18 hours, and one of the dried products obtained was used. Parts at 900 ° C. (Example 1), 1000 ° C. (Example 2) and 1100 ° C. (Example 3) using an electric furnace for 5 parts each.
After time calcination, boria-alumina catalyst carriers a (Example 1), b (Example 2), and c (Example 3) containing 15% by weight of boron as B ₂ O ₃ were obtained.

Next, the amount of boric acid added to the alumina hydrate cake was 43 g (24 g as B ₂ O ₃ ) (Example 4).
And 89 g (50 g as B ₂ O ₃ ) (Example 5) except that the dried products were obtained in the same manner as above, and the dried products were fired at 1000 ° C. for 5 hours in an electric furnace to obtain boron. To obtain boria-alumina catalyst supports d (Example 4) and e (Example 5) containing 5% by weight and 10% by weight as B ₂ O ₃ , respectively.

Next, the amount of boric acid added was 9 g (B ₂ O ₃
5 g) (Comparative Example 1) and 204 g (115 g as B ₂ O ₃ ) (Comparative Example 2), but in the same manner as in Example 1 containing 1 wt% and 20 wt% of B ₂ O ₃ as a boria-alumina catalyst. Carriers f (Comparative Example 1) and g (Comparative Example 2) were obtained.

The specific surface areas of these carriers were measured by the nitrogen gas adsorption method, and the crystal morphology was examined by X-ray diffraction.

Next, using these carriers, an acid resistance test was conducted under the following conditions to investigate the change in specific surface area. The obtained results are also shown in Table 1.

(Acid resistance test condition) 400 ml of pure water was added to a 500 ml beaker, heated to 80 ° C., held, and crushed to 100 mesh or less carrier powder 60 with stirring.
g and 27 ml of hydrochloric acid having a concentration of 36% were added to form a slurry having a pH of 0.1, and the mixture was stirred for 10 hours. Then, cool, filter, and wash with pure water until chlorine is completely removed.
It is dried at 0 ° C for 15 hours and calcined at 500 ° C for 2 hours to obtain a carrier powder.

[0021]

As is clear from the results shown in Table 1, the catalyst carriers a, b, c, d and e satisfying the boria-alumina composition ratio and the crystal structure within the range of the present invention are sufficiently resistant to acid. I understand. Further, it is understood that the carriers f and g which do not satisfy the conditions of the present invention have poor acid resistance.

(2) Production of catalyst and its evaluation Next, using 100 g of each of the catalyst carriers a, b, c, d, e, f and g, a catalyst A (Example 6) was prepared in the following manner. , B (Example 7), C (Example 8), D (Example 9), E (Example 10), F (Comparative Example 3), and G (Comparative Example 4) were produced.

(Catalyst Preparation Method) A cis-dinitrodiamine platinum (II) salt (6 as Pt was added to 100 g of each of the above carriers).
0.7% by weight) was impregnated with a solution obtained by dissolving 1.7 g in 60 ml of water and dried at 110 ° C. for 15 hours, then 50
Bake at 0 ° C. for 2 hours.

Next, 1.2 g of cobalt nitrate hexahydrate and 1.2 g of cis-dinitrodiamine platinum (II) salt (60.7 wt% as Pt) were added to 100 g of carrier b in 60 ml of water.
Was impregnated with the resulting solution, dried at 110 ° C. for 15 hours, and then calcined at 500 ° C. for 2 hours to obtain a catalyst H (Example 11). Then, the specific surface area of each catalyst was measured, and the results are shown in Table 2.

Next, the resulting catalysts A to H were crushed to prepare particles having a particle size in the range of 500 to 840 microns,
The catalyst was packed in a fixed bed flow reactor of 10 ml, and the following sample gas was added at a reaction temperature of 500 ° C. to SV = 5,000 h.
-1 was passed through the catalyst layer to decompose trichlorethylene. The performance evaluation results of each catalyst 50 hours after the start of the reaction are also shown in Table 2.

The treated gas was analyzed by gas chromatography using a gas chromatograph manufactured by Shimadzu Corporation.

(Composition of sample gas) Trichlorethylene: 0.03 ml / min Water: 0.043 ml / min Air: 500 ml / min

[0029]

From the results shown in Table 2, it can be seen that the catalysts A to D and H have high treatment efficiency for trichlorethylene. This is because the carrier used for them satisfies the carrier conditions of the present invention in terms of composition ratio, specific surface area and crystal structure, and is also excellent in acid resistance of the carrier.

The catalysts F and G are within the range of the carrier conditions of the present invention with respect to the specific surface area of the carrier used, but the boria-
Alumina composition ratio and crystal structure are out of range,
It is considered that the treatment efficiency of trichlorethylene was low because the acid resistance of the catalyst carrier was poor.

The catalyst H is a catalyst supporting platinum and nickel as active metals, but it is clear that the treatment efficiency of trichlorethylene is high even when a noble metal and a transition metal are used in combination as active metals.

[0033]

The organochlorine compound can be efficiently treated by bringing the catalyst of the present invention into contact with the organochlorine compound in the presence of water vapor and air. The catalyst of the present invention has a long life and is practical. Therefore, the catalyst of the present invention can be used for detoxifying organic chlorine compounds such as exhaust gas and waste liquid discharged from a metal degreasing process, a dry cleaning process, etc., and is extremely effective in preventing environmental pollution.

Claims (3)

[Claims] 1. A boria content of 5 to 15 as B ₂ O _3.
The boria-alumina composition having a specific surface area of 50 m ² / g or more determined by a nitrogen gas adsorption method and having a crystal structure by X-ray diffraction of an aluminum borate structure is a carrier. And is mainly composed of this carrier and a noble metal as an active metal, or a noble metal and a transition metal, and the amount of the active metal supported is 0.1% by weight of the catalyst.
A catalyst for treating an organic chlorine compound, characterized in that the amount is equivalent to 5% by weight. 2. The catalyst for treating an organochlorine compound according to claim 1, wherein the noble metal as an active metal is at least one selected from the group consisting of platinum, palladium and ruthenium. 3. The catalyst for treating an organochlorine compound according to claim 1, wherein the transition metal as an active metal is at least one selected from the group consisting of copper, chromium and cobalt.