JPH10137589A - Catalyst for decomposition of fluorocarbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decompose and remove fluorocarbons by incorporating palladium and an oxide of one element selected from palladium, titanium, silicon, zirconium, aluminum, niobium and tungsten and/or a multiple oxide of these to prepare a catalyst for decomposition of fluorocarbon. SOLUTION: A catalyst to decompose fluorocarbons is prepared by incorporating palladium and oxide of one element selected from titanium, silicon, zirconium, aluminum, niobium and tungsten and/or a multiple oxide of these. As for the multiple oxide, a multiple oxide containing tungsten is preferably used. The proportion of the palladium to oxides is 0.01 to 5wt.%, preferably 0.05 to 3wt.%. To decompose a fluorocarbon gas, the fluorocarbon gas is decomposed in the presence of at least one kind selected from hydrocarbons, alcohols and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst for decomposing CFCs and a method for decomposing CFCs. More specifically, the present invention relates to a chlorofluorocarbon decomposition catalyst containing palladium and a specific oxide and a chlorofluorocarbon decomposition method.

[0002]

Freon decomposes ozone in the atmosphere to cause depletion of the ozone layer, and has become a global problem, and measures for it are needed. However, since CFC gas is very stable, it is difficult to decompose it. Therefore, various countermeasures have been disclosed. For example, there are a combustion method, a plasma decomposition method, an adsorption method and the like, all of which have technical and cost problems and are not necessarily effective methods.

Further, a method of decomposing with a catalyst in which platinum is supported on ZrO ₂ (JP-A-5-317645, 6-254)
399, 6-335419) and other methods for decomposing CFCs using a catalyst such as titania are disclosed (JP-A-4-313344, JP-A-8-10).
572). A method for decomposing chlorofluorocarbons using a Ti-W type catalyst (Japanese Patent Application Laid-Open No. 8-229354), and a method for supplying hydrogen when using a Ti-W type chlorofluorocarbon decomposition catalyst to promote the decomposition (Japanese Patent Application Laid-Open No. 8-215566) However, the chlorofluorocarbon decomposition catalyst in this method is a catalyst such as Ti or a Ti-W type catalyst. When these catalysts are used, carbon monoxide is generated during the decomposition of chlorofluorocarbon. Has been pointed out as a new problem (Japanese Patent Laid-Open No. 8-23841).
8) Further, the present inventors decompose the chlorofluorocarbon with a chlorofluorocarbon decomposition catalyst, and then further reduce the carbon monoxide with a oxidized carbon monoxide catalyst for the purpose of removing carbon monoxide which is generated simultaneously when the fluorocarbon is decomposed. There is also proposed a method of treating CFCs (Japanese Patent Application Laid-Open No. H8-238418). However, these methods are not simple methods because they require a plurality of disassembling steps, and the system becomes large. Therefore, conventionally, development of a catalyst and a treatment method capable of treating CFCs by a simple method has been expected.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using palladium and a specific oxide, decomposed the chlorofluorocarbon with almost no generation of carbon monoxide. The inventors have found a catalyst that can be formed, and have also found a method of using the catalyst at the same time, thereby completing the invention. The present invention is specified as a fluorocarbon decomposition catalyst and a fluorocarbon gas decomposition method as described below.

(1) Decomposition of chlorofluorocarbons containing palladium and an oxide and / or composite oxide of at least one element selected from the group consisting of titanium, silicon, zirconium, aluminum, niobium and tungsten. catalyst.

(2) The CFC decomposition catalyst according to the above (1), wherein the composite oxide is a composite oxide containing tungsten.

(3) The CFC decomposition catalyst according to the above (1), wherein platinum is further added to the catalyst.

(4) A method for decomposing CFCs, comprising decomposing CFCs using the catalyst described in any one of 1 to 3 above.

(5) In the method for decomposing freon gas,
5. The CFC gas decomposing method according to the above item 4, wherein the CFC gas is decomposed in the presence of at least one selected from the group consisting of hydrocarbons, alcohols and water.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The palladium according to the present invention may exist not only as a metal but also as a metal oxide. Raw materials for palladium may be water-soluble salts such as palladium chloride and palladium nitrate, as well as water-insoluble salts, and metals such as palladium black.

An oxide of at least one element selected from the group consisting of titanium, silicon, zirconium, aluminum, niobium and tungsten according to the present invention and / or
Alternatively, the composite oxide (hereinafter sometimes referred to as “oxide A”) may be a mixture of single oxides, a composite oxide, composite oxides, or a mixture thereof. Further, among the oxides A, preferably, a composite oxide containing tungsten, for example, TiO ₂ —WO ₃ or ZrO ₂
-W0 is _{3, Al 2 O 3 -WO 3} , Nb 2 O 3 -WO 3,
Even more preferably _{TiO 2 -WO 3, ZrO 2 -W0} 3.

The raw material of the oxide A may be any of water-soluble and insoluble compounds, for example, sulfates, nitrates, chlorides, and organometallic compounds. Any of these may be used.

The oxide can be used directly as a component of the catalyst. In the case of a water-soluble salt or the like, a precipitate is generated by adjusting the pH, and the oxide or composite oxide is formed by drying and calcining. Can also. For example,
A method for preparing an oxide of tungsten by adding ammonia to an aqueous solution of a water-soluble tungsten salt, and precipitating, drying and calcining the same. There is a method of preparing a composite oxide by drying and firing.

Examples of the method of coexisting palladium and oxide A include a method of physically mixing oxide A and palladium, a method of impregnating oxide A with an aqueous solution containing palladium, and a method of mixing oxide precursor. And a method of mixing and coprecipitating and drying and baking, and a method of mixing a gel of the precursor of oxide A with an aqueous solution of palladium or palladium metal, followed by drying and baking.

The amount of palladium and oxide A is preferably 0.01 to 5% by weight of palladium,
It is 0.05% by weight to 3% by weight. If the content is less than 0.01% by weight, the decomposition of chlorofluorocarbon is not sufficient, and carbon monoxide may be generated in some cases. If the content is more than 5% by weight, the cost increases and the effect corresponding thereto cannot be obtained.

In the present invention, platinum can be further added, and platinum is contained in an atomic ratio of 0.1 to 2 with respect to palladium 1.
Can be contained at a ratio of, preferably, 0.2 to
1.0. Raw materials for platinum include chlorides, nitrates,
Ammine complex salts.

The catalyst according to the present invention further comprises P, S, C
Components such as e and Ni can also be added.

The shape of the catalyst according to the present invention may be spherical, cylindrical, cylindrical, pellet, honeycomb, or the like.

The chlorofluorocarbon to be used in the present invention may be any chlorofluorocarbon, which is generally referred to as chlorofluorocarbon. For example, in addition to CFCs such as CFCs 11, 12, 113, 114 and 115, HCFC, HFCs are also included. The Freon gas is not particularly limited as long as it contains the above-mentioned Freon, and other than Freon, a gas such as carbon monoxide, a hydrocarbon, an aromatic hydrocarbon, a sulfur-containing compound, or a nitrogen-containing compound is simultaneously used. May be included. The concentration of Freon in the target gas is 6% by volume or less, preferably 4% by volume or less.

The temperature of the chlorofluorocarbon gas during the treatment is 100 ° C.
The temperature is 600 ° C, preferably 150 ° C to 500 ° C. If the temperature is lower than 100 ° C., the decomposition efficiency of chlorofluorocarbon is not sufficient, and if it exceeds 600 ° C., there is no effect corresponding to an increase in the gas temperature.

The space velocity (SV) for the catalyst is 50
0 to 50,000 hr to ¹ , preferably 1,000 to 50,000 hr.
It is a 20000hr ~ ^1. If it is 500 hr ~ less than ¹ is not economical increases the amount of catalyst, 50000h
In the case of more than r ~ ¹ is because the decomposition efficiency of CFCs is not sufficient.

In the treatment, the decomposition of the chlorofluorocarbon gas may be carried out in the presence of at least one selected from the group consisting of hydrocarbons, alcohols and water in the chlorofluorocarbon gas (hereinafter sometimes referred to as "addition gas"). preferable. More preferably, it is water. In particular, when water is added, it is effective to promote the generation of hydrogen halide such as HF and HCl during the decomposition of chlorofluorocarbon. When adding hydrocarbons or alcohols, the amount of heat generated is large, so it is necessary to limit the amount of addition compared to water. The use of hydrocarbons and the like in combination with water can limit heat generation.

The added amount of the added gas and the like is 5
0 vol% or less, more preferably 30 vol% or less.

Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to the following embodiments.

[0025]

By using the catalyst of the present invention, CFCs can be decomposed with high efficiency. Further, by using palladium and oxide A together, the decomposition of chlorofluorocarbon and the generation of carbon monoxide can be simultaneously suppressed for the first time. This point can be sufficiently understood from Examples and Comparative Examples because palladium is particularly effective even in the case of noble metals, and that it is also effective as compared with conventionally disclosed oxides. Since the method of the present invention does not require the use of a catalyst for treating carbon monoxide, the apparatus itself can be made compact. Further, the use of the additional component allows the fluorocarbons to be more efficiently decomposed and removed.

[0026]

【Example】

(Example 1) 10.0 kg of an aqueous solution of ammonium metatungstate (solution containing 50% as WO ₃ ), 10.0 kg of aqueous ammonia (25%), and 61.7 kg of water
Is mixed with an aqueous solution of titanyl sulfate in sulfuric acid (TiO ₂
310g as 70 g / 1 liter as H ₂ SO ₄ /
Liter) was gradually added dropwise to obtain a gel-like substance, which was filtered, washed, dried at 150 ° C. for 10 hours, and calcined at 600 ° C. for 3 hours.
7.5: 2.5 (weight ratio) as TiO ₂ : WO ₃ , BE
A titanium-tungsten composite oxide having a T surface area of 80 m ² / g was obtained. Starch and water were added to 10 kg of this powder as molding aids, mixed and kneaded with a kneader, and then extruded with an extruder to form an outer shape of 80 mm square, 3.2 mm opening, and 0.5 wall thickness.
The honeycomb was formed into a honeycomb having a thickness of 450 mm and a length of 450 mm, dried at 80 ° C., and fired at 600 ° C. for 5 hours.

This molded product is treated with an aqueous solution of palladium nitrate (P
20 g / liter as d), dried at 150 ° C., and calcined at 500 ° C. for 2 hours in air. Palladium supported 0.5% by weight of Pd.

(Example 2) In Example 1, chloroplatinic acid aqueous solution (20 g as Pt) was used instead of palladium nitrate.
/ L) and an aqueous solution of palladium nitrate (20 g / l as Pd) were obtained in the same manner as in Example 1. Platinum is 0.5% by weight as Pt,
Palladium was supported at 0.5% by weight as Pd.

(Evaluation conditions) SV: 3000 hr- ¹ ; gas amount: 11.6 normal liter / min; gas composition: CFC
113 1.0% H ₂ O 10%, the remainder being air. The catalyst is 450mm long, 6 cell square (232cc)
It is. The evaluation results are shown in Table 1.

Comparative Example 1 A catalyst was obtained in the same manner as in Example 1, except that an aqueous solution of chloroauric acid (7 g / liter as Au) was used instead of palladium nitrate. 0.2% by weight of gold was carried as Au. The evaluation conditions were the same as in Examples 1 and 2.

Example 3 The catalyst of Example 1 was evaluated under the following evaluation conditions. SV = 3000hr ~ ¹ ,
Gas amount 11.6 normal liter / min, gas composition CFC
113 is 1000 ppm, water is 5%, and the rest is air.

Comparative Example 2 The procedure of Example 1 was repeated, except that an aqueous solution containing ammonium monovanamate monoethanolamine (170 g / L as V ₂ O ₅ ) was used instead of palladium nitrate. To obtain a catalyst. V ₂ O ₅ was loaded at 3% by weight. Evaluation conditions are the same as those of the third embodiment.

Example 4 The catalyst obtained from Example 1 was evaluated under the following conditions. SV = 5000 hr ~ ¹ , gas amount 6.96 normal liter / min, gas composition CFC11 is 1000 ppm, water is 5%, and the rest is air.

Comparative Example 3 In Example 1, copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O) was used instead of palladium nitrate.
A catalyst was obtained in the same manner as in Example 1, except that an aqueous solution (160 g / liter as CuO) was supported. Copper is CuO
5% by weight. The evaluation conditions were the same as in Example 4.
Is the same as

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Atsushi Okamura 992, Nishioki, Okihama-shi, Aboshi-ku, Himeji-shi, Hyogo

Claims (5)

[Claims] 1. A CFC decomposition catalyst containing palladium and an oxide and / or composite oxide of at least one element selected from the group consisting of titanium, silicon, zirconium, aluminum, niobium and tungsten. . 2. The CFC decomposition catalyst according to claim 1, wherein the composite oxide is a composite oxide containing tungsten. 3. The CFC decomposition catalyst according to claim 1, wherein platinum is further added to the catalyst. 4. A method for decomposing freon gas, comprising decomposing freon gas using the catalyst according to claim 1. 5. The CFC gas decomposing method according to claim 4, wherein the CFC gas is decomposed in the presence of at least one selected from the group consisting of hydrocarbons, alcohols and water.