JPH06254399A - Decomposition reaction catalyst and method for removing organic halogen compound with the same - Google Patents

Abstract

PURPOSE:To provide a catalyst for oxidative decomposition having stable catalytic function which does not deteriorate over a long term and to provide a method for removing an org. halogen compd. in gas by oxidative decomposition with the catalyst in the presence of air and water. CONSTITUTION:A zirconia carrier contg. 0.5-5wt.% phosphoric acid is prepd. and 0.1-5wt.% platinum is carried on the carrier to obtain the objective catalyst for oxidative decomposition. Gas contg. an org. halogen compd. is brought into a catalytic reaction with the catalyst in the presence of air and water to remove the org. halogen compd. by oxidative decomposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decomposition reaction catalyst and a method for decomposing and removing an organic halogen compound containing chlorine, fluorine and the like using the catalyst.

[0002]

Fluorocarbons, organic halogen compounds such as trichloroethylene, etc. are widely used for these purposes because they have excellent chemical properties as solvents, cooling agents, foaming agents and the like.

However, since these substances are generally highly volatile, and particularly, CFCs are highly stable, when they are released into the atmosphere as exhaust gas, the ozone layer is destroyed and the global warming is promoted. As a causative agent, the development of emission prevention technology is desired, and since organic chlorine compound-based substances such as trichlorethylene are carcinogenic substances, elution contamination into groundwater is a problem. Development of detoxification treatment technology for waste liquid is desired.

It is considered that the most economical method for detoxifying the organic halogen compounds such as CFCs or trichlorethylene is to decompose these compounds into harmless substances. Although thermal decomposition method, plasma decomposition method, reagent decomposition method, etc. have been proposed as a decomposition method for CFCs and organic chlorine compounds, they have not yet reached a practical level from an economical point of view. However,
Recently, attention has been focused on a technique for detoxifying these compounds under a drastic condition by carrying out a catalytic decomposition reaction using a CFC and an organic chlorine compound as a catalyst.

In Japanese Patent Laid-Open No. 3-47516, a granular titania-zirconia catalyst or a granular silica-zirconia carrier on which 5% by weight of copper ions are supported is used at a temperature of 500.degree. CFC% by volume
A method of decomposing 113 or trichlorethylene to hydrogen halide is disclosed.

Further, Japanese Patent Laid-Open No. 3-106419 discloses that
0.5% by weight platinum and 1 cobalt oxide on titania carrier
Using a catalyst supporting 0% by weight, air containing 0.3% by volume of freon-113 and 1% by volume of steam is reacted at a temperature of 400 ° C. to decompose freon-113 into hydrogen halide. A method is disclosed.

Further, US Pat. No. 4,935,212 discloses a method of decomposing a fluorocarbon and an organochlorine compound by contacting with a gas containing water vapor using a sulfated titania or a titania catalyst supported on copper.

[0008]

As described above, when an organic halogen compound such as freon or trichlorethylene is treated with a catalyst at a temperature of about 400 to 500 ° C. in the presence of water vapor, oxygen, etc., freon is oxidatively decomposed. Hydrogen chloride, hydrogen fluoride, carbon dioxide gas, etc. are produced, and an organic chlorine compound produces hydrogen chloride, carbon dioxide gas, etc. However, in the method proposed hitherto, the catalyst is apt to react with a halogen compound decomposed and produced to form a fluoride or a chloride, and particularly when treating a gas containing 5% by volume or more of an organic halogen compound, Since the tendency becomes remarkable, the catalyst activity becomes unstable and there is a problem that the catalyst function is deteriorated or the catalyst life is shortened.

The present invention solves the above-mentioned problems in removing a gas containing an organic halogen compound such as Freon or trichlorethylene by oxidative decomposition treatment with a catalyst in the presence of air and water, and has a stable catalytic function for a long time. An object of the present invention is to provide a decomposition reaction catalyst that does not deteriorate the catalytic function and a method for removing an organic halogen compound using the decomposition reaction catalyst.

[0010]

[Means for Solving the Problems] In order to achieve the above object, the present inventors use a catalyst comprising a combination of a chemically stable carrier and an active substance to remove an organic halogen compound by oxidative decomposition. As a result of earnest studies, it was found that when a catalyst in which an appropriate amount of platinum and / or platinum oxide is supported on a zirconia carrier containing phosphoric acid is used, the catalytic decomposition function of a halogen compound is exhibited very effectively. That is, the present invention has been completed.

That is, in the present invention, at least one kind of platinum or platinum oxide is contained in a zirconia carrier containing 0.5 to 5% by weight of phosphoric acid in an amount of 0.1 to 5% by weight (in the case of platinum oxide, a platinum equivalent amount). A method for removing an organohalogen compound, which is a decomposition reaction catalyst characterized in that it is supported, and a gas containing an organohalogen compound is brought into contact with the catalyst in the presence of air and water.

[0012]

The operation and details of the present invention will be described below.

As described above, the present invention provides a decomposition reaction catalyst in which platinum and / or platinum oxide is supported on a zirconia carrier containing phosphoric acid and decomposition of an organohalogen compound in the presence of air and water using the catalyst. The zirconia carrier containing phosphoric acid used in the present invention is a zirconia hydrate produced by hydrolysis of a zirconyl salt, which is washed and dried to obtain a powder, and then this powder is used. It is obtained by immersing the body in a phosphoric acid solution (H ₃ PO ₄ ) and then firing the powder at a temperature of, for example, 550 ° C. The concentration of phosphoric acid (PO ₄ ) in the zirconia carrier is adjusted to 0.5 to 5% by weight in the above dipping step. This is because if the phosphoric acid concentration is less than 0.5% by weight, the catalytic activity will be low, and if it exceeds 5% by weight, the catalytic activity will be low. As the zirconyl salt, zirconyl nitrate, zirconyl carbonate, zirconyl acetate, zirconyl oxalate, zirconyl chloride or the like can be used, and among these zirconyl nitrate is most preferable. As a hydrolyzing agent,
It can be selected from basic compounds such as aqueous ammonia and sodium hydroxide.

The shape of the phosphoric acid-containing zirconia carrier in the present invention is not particularly limited, but it is desirable to mold it into a monolith such as a honeycomb in order to reduce pressure loss during use. Further, in order to improve heat resistance and acid resistance, a monolithic substrate may be coated with a powder carrier. In order to support platinum or platinum oxide on a phosphoric acid-containing zirconia carrier whose specific surface area has been increased by firing, a method of dipping the carrier in a platinum-containing liquid or a platinum-containing liquid in an amount corresponding to the liquid absorption amount of the carrier is used as the carrier. The method of impregnation is adopted. As the platinum salt compound for supporting platinum, chloride, nitrate, acetate, amine complex salt, organic acid salt and the like can be used.

The phosphoric acid-containing zirconia carrier impregnated with the platinum-containing solution is dried at a temperature of about 100 ° C. and then 500
Calcination is performed at a temperature of around ℃ to decompose the platinum salt into a catalyst. The amount of platinum or platinum oxide supported is 0.1 to 5% by weight, more preferably 0.3 to 3% by weight, as platinum metal, and the catalyst supported in this range provides excellent contact for halide decomposition reaction. Indicates a function. If the supported amount of platinum is less than 0.1% by weight, the activity of the catalyst will be low, and if it is more than 5% by weight, the catalytic activity will be low, and it is not economically preferable.

There is no particular limitation on the type of apparatus used for decomposing fluorocarbons and halogen compounds such as organic chlorine compounds using the catalyst of the present invention, but the catalyst is used as a fixed bed,
It is desirable to use a flow-type catalytic reactor in which the halogen compound to be decomposed is introduced and flowed into the catalyst layer together with air containing water vapor. In order to carry out the catalytic reaction with this apparatus, it is necessary to select reaction conditions in which the organic halogen compound is almost completely decomposed and no harmful by-products are produced. Preferred reaction conditions include a reaction temperature of 300 to 6
00 ° C., the concentration of the organohalogen compound is 10% by volume or less, and the space velocity of the organohalogen compound supplied is 100.
It is suitable to select in the range of ⁰ to 10000H ^-1 .

In the above catalytic reaction, air is a suitable source of oxygen to be used from an economical point of view. Including an appropriate amount of water vapor in the air is effective in preventing deterioration of catalyst performance, and the amount of air and water vapor introduced is sufficient for the reaction products to become hydrogen chloride, hydrogen fluoride, carbon dioxide gas. It is desirable to use a stoichiometric amount or more. Hydrogen chloride, hydrogen fluoride, etc. present in the treated gas after the reaction can be recovered and removed by absorption with an alkaline aqueous solution, and thereafter, the treated gas can be released into the atmosphere as an exhaust gas.

Organohalogen compounds harmful by the above method are harmless hydrochloric acid (HCl), hydrogen fluoride (HF),
It is decomposed and removed into carbon dioxide (CO ₂ ). Phosphoric acid contained in the zirconia carrier has the effect of reducing the erosion of the carrier by hydrochloric acid or hydrogen fluoride generated during the decomposition reaction, stabilizing the catalyst function and improving the catalyst life. Further, platinum supported on the zirconia carrier has an effect of promoting the decomposition reaction of the organic halogen compound, and also has an effect of promoting the oxidation reaction of harmful carbon monoxide generated during the decomposition reaction to carbon dioxide. .

[0019]

EXAMPLES Next, the present invention will be described in more detail with reference to the following examples. In a beaker of Example 1 2 l, 80 g of zirconyl nitrate and _{(ZrO (NO 3) 3 ·} 2H 2 O) was dissolved in distilled water,
A 500 cc 0.6 molar aqueous zirconyl nitrate solution was prepared. On the other hand, 29% ammonia water was diluted to 1 liter with distilled water to prepare 4.25 mol of diluted ammonia water, and
While stirring in the zirconyl nitrate aqueous solution kept at ℃ 2
The slurry was added at an addition rate of 0 cc / min to bring the final pH to 10 to obtain a slurry in which a precipitate of zirconium hydroxide was generated.

After leaving this slurry for 3 hours, it was transferred to a Buchner funnel and filtered under reduced pressure, and the precipitate was washed 5 times with 1 liter of distilled water to remove nitrate ions and ammonium ions.
The resulting precipitate was resuspended in 1 liter of distilled water and
The mixture was kept at 5 ° C. for half a day, filtered under reduced pressure with a Buchner funnel, and the precipitate was washed again with 1 liter of distilled water. The precipitate was dried in a drier at a temperature of 110 ° C. for 36 hours.

Next, 40 g of this precipitate was placed in a vacuum desiccator and 60 cc of a 0.2 molar phosphoric acid solution (H ₃ PO ₄ ) was added.
It was immersed in 20 ° C. for 7 hours. After the immersion, the precipitate was transferred to an electric muffle furnace, heated from room temperature to 550 ° C. at a temperature rising rate of 4 ° C./min, and kept at 550 ° C. for 5 hours for firing to obtain a zirconia carrier. The phosphoric acid content of the carrier was 3% by weight, and the surface area by the BET method was 74 m ² / g.

Next, 1 g of chloroplatinic acid (H ₂ PtCl ₆
6H ₂ O) was dissolved in 50 cc of 0.6 mol hydrochloric acid, and this was poured into 37 g of a carrier to impregnate platinum. Even more so that the carrier is uniformly impregnated with the platinum solution 0.6
After adding 100 cc of molar hydrochloric acid, the mixture was kept at room temperature for 7 hours in a vacuum desiccator, and then the carrier A was transferred to a dryer and dried at 110 ° C. for 16 hours.
5 g of the dried product thus obtained was put into a quartz tube having an inner diameter of 20 mmφ, and calcined at a temperature of 525 ° C. for 16 hours under an air flow of 125 cc / min to obtain a platinum zirconia catalyst (catalyst 1). The platinum content of the catalyst 1 is 0.9
% By weight, the content of chlorine was 1.0% by weight, and the specific surface area according to the BET method was 74 m ² / g. In addition, as a result of analysis by X-ray diffraction of the catalyst, monoclinic zirconia (Zr
The presence of O ₂ ) was confirmed.

Next, using this catalyst 1, Freon-11
A catalyst performance evaluation test for oxidative decomposition of No. 3 was conducted. In the evaluation test, a quartz reaction tube having an inner diameter of 20 mmφ was used, the catalyst 1 was filled in the quartz reaction tube, and chlorofluorocarbon-113 was circulated together with steam and air under normal pressure for oxidative decomposition treatment. The reaction conditions were as shown in Table 1.
The molecular ratio of water / flon-113 is kept at 5 or more,
The flow rates of water and Freon-113 were adjusted so that excessive steam was kept on the catalyst.

[0024]

[Table 1] Catalyst amount: 7.4 g Freon-113 liquid flow rate: 0.032 cc /
min Water flow rate: 0.043cc /
min Air gas flow rate: 500 cc / mi
n Space velocity: 5,000 h ⁻¹ Reaction temperature: 500 ° C. Reaction time (500 ° C.): 50 hours The decomposition rate of CFC-113 is CFC-113 before and after the treatment.
The concentration was quantitatively analyzed with a gas chromatograph and calculated from this. The results are shown in Table 3 together with the results of other examples and comparative examples. In addition, FIG. 1 shows the change in catalyst activity due to the transition of reaction time. In addition, in FIG. 1, the transition of the reaction time of the catalyst in Conventional Example 1 described later together with the catalyst 1 in Example 1 is shown on the horizontal axis, and the decomposition rate is shown on the vertical axis. As shown in Table 3 and FIG. 1, when the Freon-113 was oxidatively decomposed using the catalyst 1, the decomposition performance after treatment time of 60 hours was 99.6%.
It is found that the catalyst activity is high and that deterioration of the catalytic activity is hardly recognized after 280 hours. The decomposition performance of CFC-113 is desired to be 97% or more.

The BET specific surface area of the treated catalyst A was 17 m ² / g, and monoclinic zirconia was confirmed by X-ray diffraction. Moreover, when the fluorine content and the chlorine content were quantified by chemical analysis, they were each 0.1
It was 2% by weight and 0.15% by weight, and it was confirmed that the catalyst was hardly fluorinated. Examples 2 to 5 The content of phosphoric acid was 0.5% by weight (Example 2),
1.0 wt% (Example 3), 2.0 wt% (Example 4)
Example 1 except that and 5.0% by weight (Example 5)
Catalysts 2 to 5 were obtained by the same procedure as above. The decomposition performance of these catalysts for Freon-113 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performances of the catalysts obtained in Examples 2 to 5 are 97.5%, respectively.
(Catalyst 2), 98.7% (Catalyst 3), 99.4% (Catalyst 4) and 99.0% (Catalyst 5) were confirmed to have a high decomposition performance. Examples 6 to 9 The loading amount of platinum was 0.1% by weight (Example 6),
0.5 wt% (Example 7), 3.0 wt% (Example 8)
Example 1 except that and 5.0% by weight (Example 9)
Catalysts 6 to 9 were obtained by the same procedure. The decomposition performance of these catalysts for Freon-113 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performances of the catalysts obtained in Examples 6 to 9 are 97.9% respectively.
(Catalyst 6), 99.2% (Catalyst 7), 98.9% (Catalyst 8) and 97.6% (Catalyst 9) were confirmed to show high decomposition performance. Conventional Example 1 A catalyst 10 was obtained by the same procedure as in Example 1 except that phosphoric acid was not added to zirconia. Freon-11 of this catalyst 10
The decomposition performance for No. 3 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performance of the catalyst 10 obtained from the conventional zirconia support containing no phosphoric acid is 96.1%, which is higher than that of the catalysts of the present invention (catalysts 1 to 9). Poor performance. In addition, FIG. 1 shows the change in the catalytic activity of the catalyst 10 depending on the elapsed time of the decomposition reaction of Freon-113. As can be seen from FIG. 1, the decomposition performance of the conventional catalyst deteriorates remarkably over time. Comparative Example 1 A catalyst 11 was obtained by the same procedure as in Example 1 except that the content of phosphoric acid was changed to 10% by weight. Freon-1 of this catalyst 11
The decomposition performance for No. 13 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performance of the catalyst 11 containing phosphoric acid in a range outside the scope of the present invention is:
96.7%, which is inferior in performance to the catalyst of the present invention. Comparative Example 2 A catalyst 12 was obtained by the same procedure as in Example 1 except that platinum was not supported. The decomposition performance of this catalyst 12 with respect to Freon-113 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performance of the catalyst 12 containing no platinum is 92.9%, which is significantly inferior to the catalyst of the present invention. Comparative Example 3 A catalyst 13 was obtained in the same procedure as in Example 1 except that the platinum content was 10% by weight. Freon-1 of this catalyst 13
The decomposition performance for No. 13 was evaluated in the same manner as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, the decomposition performance of the catalyst 13 loaded with platinum outside the scope of the present invention is 9
It is 4.1%, which is significantly inferior in performance to the catalyst of the present invention. Examples 10 and 11 Using the catalyst 1 obtained in Example 1, a performance evaluation test of a decomposition reaction with respect to 1.3 mol of trichlorethylene was conducted. The test was performed by the same procedure as in Example 1 except that the contact conditions were as shown in Table 2. The results are also shown in Table 3.

As can be seen from Table 3, the decomposition performance of the catalyst of the present invention for trichlorethylene is 40 ° C.
When the temperature is 0 ° C. (Example 10), it is 99.7.
%, And when the reaction temperature was 500 ° C. (Example 11), high decomposition performance was exhibited in all cases, 99.9%.

[0033]

[Table 2] Catalyst amount: 7.4 g Trichlorethylene liquid flow rate: 0.03 cc / m
in Water flow rate: 0.043cc /
min Air gas flow rate: 500 cc / mi
n space velocity: 5,000 h ⁻¹ reaction temperature: 400 ° C., 500
℃ reaction time: 60 hours

[0034]

[Table 3] Example catalyst Phosphoric acid-containing platinum-containing Decomposition * Contact temperature Decomposition performance No. Number Number (%) Amount (%) Substance (° C) (%) Example 1 1 3.0 0.9 C 500 99.6 〃 2 2 0.4 0.9 C 500 97.5 〃 3 3 1.0 0.9 C 500 98.7 〃 4 4 2.0 0.9 C 500 99.4 〃 5 5 5.0 0.9 C 500 99.0 〃 6 6 3.0 0.1 C 500 97.9 〃 7 7 3.0 0.5 C 500 99.2 〃 8 8 3.0 3.0 C 500 98.9 〃 9 9 3.0 5.0 C 500 97.6 Conventional Example 1 10 0.0 0.9 C 500 96.1 Comparative Example 1 11 10.0 0.9 C 500 96.7 Comparative Example 2 12 3.0 0.0 C 500 92.9 Comparative Example 3 13 3.0 10.0 C 500 94.1 Example 10 1 3.0 0.9 T 400 99.7 〃 11 1 3.0 0.9 T 500 99.9 Note: *… C is CFC-113… T is trichlorethylene

[0035]

According to the method of the present invention, when oxidative decomposition of an organic halogen compound is carried out in the presence of water vapor and air, a phosphoric acid-containing zirconia carrying platinum used as a catalyst is formed by a decomposition reaction. It is extremely stable against hydrogen and hydrogen fluoride, and can withstand long-term use without lowering its catalytic function compared to when using conventional catalysts, even when the concentration of organic halogen compounds is high. Therefore, the organic halogen compound can be efficiently removed, which is extremely effective in preventing environmental pollution.

[Brief description of drawings]

FIG. 1 Freon-1 using the present invention and a conventional catalyst.
It is the drawing which compared the time change of the decomposition performance of No. 13.

[Explanation of symbols]

 □ Curve with the catalyst of the present invention △ Curve with the conventional catalyst

Claims (2)

[Claims] 1. A zirconia carrier containing 0.5 to 5% by weight of phosphoric acid and 0.1 to 5% by weight (in the case of platinum oxide, platinum equivalent) of at least one of platinum and platinum oxide. Decomposition reaction catalyst. 2. A zirconia carrier containing 0.5 to 5% by weight of phosphoric acid in a gas containing an organic halogen compound in the presence of air and water, and 0.1 to 5 of at least one of platinum and platinum oxide. A method for removing an organohalogen compound, which comprises bringing the catalyst into contact with a catalyst supported by weight% (in terms of platinum in the case of platinum oxide).