JPH06335619A - Method for removing organic halide - Google Patents

Abstract

PURPOSE:To provide a method for removing an organic halide by which stable catalytic function and prevention of the deterioration of catalytic function can be maintained for a long time at the time of removing the organic halide such as fluorocarbon or trichloroethylene by oxidative decomposition of an organic halide-containing gas in the presence of air and water with a catalyst. CONSTITUTION:The organic halide is removed by bringing the organic halide- wcontaining gas into contact with the catalyst, made by making platinum or platinum oxide carried on a zirconia as a carrier obtained by reacting zirconyl nitrate with an ammonia aq. solution, in the presence of air and water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing an organic halide containing chlorine, fluorine or the like by catalytic oxidative decomposition.

[0002]

2. Description of the Related Art Organic halides such as chlorofluorocarbon and trichlorethylene 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, and when they are released into the atmosphere as exhaust gas, they destroy the ozone layer and promote global warming. The development of technology to prevent its release as a causative substance of destruction is desired, and since organic chlorine compound-based substances such as trichlorethylene are carcinogenic substances, elution pollution into groundwater is a problem. Further, development of a detoxification treatment technology for waste liquid is desired.

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

Japanese Patent Laid-Open No. 3-47516 discloses a CFC.
Are detailed for several catalysts for decomposition, eg _{SiO 2 -TiO 2, TiO 2 -ZrO} 2, Al 2 O 3
Strongly acidic catalyst such as -B ₂ O ₃ and zeolite have been tried extensively for the decomposition of organic chlorine compounds ppm orders as alone or supported catalyst supported on the metal. In this case, mainly cobalt, copper and palladium are used as carrier metals.

In US Pat. No. 4,935,212, a sulphided TiO ₂ or Cu / TiO ₂ catalyst was used for the decomposition of CFCs and chlorinated hydrocarbons in the presence of water with N ₂ or air as carrier gas. ing.

Japanese Unexamined Patent Publication No. 3-42015 discloses 500
Pt, Rh, P as a carrier of ZrO ₂ —TiO ₂ for decomposing CFC113 of 500 ppm in air at ℃
Metallic ranges of d, Mn, Cu, Fe have been tried.

Japanese Unexamined Patent Publication (Kokai) No. 3-106419 describes in detail a two-step method for catalytic decomposition of an organic chlorine compound. That is, in this method, in the first stage, the organochlorine compound in the gas stream is adsorbed on the activated carbon bed, and then the activated carbon bed is heated for desorption of the organochlorine compound, and then transferred to the second stage. To do. In the second stage, zeolite, alumina or zirconia and Cu, Ag, V,
Cr, Mo, W, Mn, Fe, Co, Ni, Pt, P
It is disclosed that catalytic decomposition of an organochlorine compound is carried out by a catalyst supported on a carrier selected from active metals such as d, Rh, La, Ce or Nb. In this second step, air is used as a carrier gas. , O ₂ , O ₃ or steam is described.

[0009]

As described above, the use of organic chlorine compounds such as CFCs or trichlorethylene in an amount of 40
When treated with a catalyst in the presence of water vapor, oxygen, etc. at a temperature near 0 to 500 ° C., Freon is oxidatively decomposed to produce hydrogen chloride, hydrogen fluoride, carbon dioxide gas, etc., and an organic chlorine compound is hydrogen chloride, Generates carbon dioxide gas. However, in the conventionally proposed catalyst, in a high temperature atmosphere of 400 to 500 ° C. in the presence of water vapor, the catalyst is likely to react with a halogen compound decomposed and produced to form a fluoride or a chloride, and particularly 5% by volume or more. When treating a gas containing a high concentration of freon or an organic chlorine compound, the tendency becomes remarkable, so that the catalytic activity becomes unstable and the catalytic function is deteriorated or the catalyst life is shortened. .

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

[0011]

[Means for Solving the Problems] To achieve the above object, the present inventor uses a catalyst composed of a combination of a chemically stable and highly active carrier and an active substance to oxidize and decompose an organic halide. As a result of extensive research on removal, zirconia obtained by hydrolyzing zirconyl nitrate in an aqueous ammonia solution was used as a carrier, and when using a catalyst having platinum or platinum oxide supported thereon, it was extremely It is possible to effectively carry out catalytic decomposition reaction of organic halides such as Freon, and it is stable against decomposition products such as hydrogen fluoride and hydrochloric acid, and also deteriorates catalytic function even after long-term use. The present invention has been completed by finding that there is no such problem.

That is, in the present invention, zirconia obtained by reacting zirconyl nitrate with an aqueous ammonia solution in the presence of an organic halide-containing gas in the presence of air and water is used as a carrier, on which platinum or platinum oxide is added. It is a method for removing an organic halide, which comprises bringing the catalyst into contact with a catalyst which is supported by about 5% by weight (platinum equivalent amount in the case of platinum oxide). In the present invention, since zirconia obtained by reacting zirconyl nitrate in an aqueous ammonia solution is hydrous zirconia, it is desirable to use it by calcining and dehydrating, and the calcining temperature at this time is preferably 700 to 950 ° C.

[0013]

As described above, the method for removing an organic halide according to the present invention is carried out by oxidative decomposition of the organic halide.
It is characterized in that the reaction is carried out using a catalyst in which platinum is supported on a zirconia carrier obtained by hydrolyzing zirconyl nitrate in an aqueous ammonia solution.
This is a zirconia carrier obtained by drying and calcining hydrous zirconia produced by hydrolyzing zirconyl nitrate, which is mainly composed of monoclinic system, the monoclinic system zirconia has a large surface area, This is because not only it has an excellent ability to support an active metal catalyst such as platinum, but also has a very high activity for decomposing an organochlorine compound as compared with zirconia having another crystal system.

The shape of the zirconia carrier is not particularly limited, but in order to reduce the pressure loss during use, a monolithic shaped carrier such as a honeycomb or a heat resistant and acid resistant monolithic substrate coated with a powder carrier is used. An acid-resistant monolithic carrier can also be used.

In order to support platinum, which is an active metal, on a zirconia carrier in order to obtain the catalyst of the present invention, the carrier is immersed in a platinum-containing solution, or a platinum-containing solution corresponding to the liquid absorption of the carrier is impregnated. Method etc. are 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 catalyst precursor supporting the platinum-containing solution is 1
The catalyst can be obtained by drying at a temperature of around 00 ° C and then firing at a temperature of around 500 ° C to decompose the platinum salt. The amount of platinum supported is 0.1 to 0.1 as platinum metal.
It is necessary to set the content to 5% by weight, and in particular, the catalyst supporting platinum in the range of 0.5 to 2% by weight exhibits an excellent contact function for the decomposition reaction of the halide.

There is no particular limitation on the type of apparatus used for decomposing halogenated compounds such as fluorocarbons or organochlorine compounds using the catalyst of the present invention, but in general, the catalyst should be used as a fixed bed for decomposition. A flow-type catalytic reaction device is used in which the halide is introduced and flowed into the catalyst layer together with air containing water vapor. The catalytic reaction conditions must be selected under the condition that the fluorocarbon or the organic chlorine compound is almost completely decomposed and no harmful by-products are generated. A preferable reaction temperature is 300 to 600 ° C. under 1 to 3 atm, and it is particularly advantageous to set the temperature to a high temperature side to accelerate the reaction, the concentration of the organic chlorine compound is 10% by volume or less, and the space velocity is 10
000h- ¹ or less is suitable. Oxygen is required for oxidative decomposition, and air is a suitable source of the oxygen 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 and hydrogen fluoride in the treatment gas can be collected and removed by absorption with an alkaline aqueous solution, and then the treatment gas can be released into the atmosphere as exhaust gas.

Table 1 shows typical contact conditions when the CFC-113 is decomposed using the platinum-zirconia catalyst of the present invention.

[0018]

[Table 1] ──────────────────────────────── Contact reaction temperature: 400-600 ℃ Contact reaction pressure (atmospheric pressure) : 1.0 to 3.0 atm space velocity: 1000~10000hr ^-1 freon -113 fluid flow rate: 0.02~4.0hr ^-1 water vapor flow rate: 0.04~6.0hr ^-1 carrier gas: air ─ ───────────────────────────────

[0019]

EXAMPLES Next, the present invention will be described in more detail with reference to the following examples. Example 1 2-liter beaker, and dissolved in distilled water nitrate of 134g zirconyl _{(ZrO (NO 3) 3 ·} 2H 2 O) 1
A 000 cc 0.5 molar aqueous zirconyl nitrate solution was prepared. On the other hand, 29% ammonia water was diluted with 1 liter of distilled water to prepare 4.25 mol of diluted ammonia water (pH 11). First, 500 cc of the ammonia water was poured into a 5 liter beaker, kept at 20 ° C., and the above aqueous solution of zirconyl nitrate was added thereto at a rate of 20 cc / min while stirring with a burette to adjust the pH to 10
At the same time, the remaining 500 cc of ammonia water was simultaneously added using another burette at an addition rate of 20 cc / min without changing the pH to obtain a slurry in which a precipitate of zirconium hydroxide was formed.

After leaving this slurry for about 3 hours, the supernatant ammonia water was removed and filtered to obtain a precipitate, which was washed 3 times with 1 liter of distilled water to remove nitrate ions and ammonium ions. The obtained precipitate was resuspended in 1 liter of distilled water, kept at 25 ° C. for about 15 hours, the residual ammonia was dissolved in distilled water and then filtered, and the obtained precipitate was dissolved in 2 liter of distilled water. Washed with water. After repeating this operation three times, the resulting precipitate was dried in a drier for 11
Dry for 36 hours at a temperature of 0 ° C., transfer to an electric muffle furnace, raise the temperature from room temperature to 750 ° C. at a temperature rising rate of 4 ° C./min, hold at the same temperature for 5 hours, and calcine to room temperature. After cooling, the zirconia carrier of the present invention was obtained. The surface area of the carrier according to the liquid N ₂ adsorption BET method was 31 m ² / g. As a result of X-ray diffraction, the zirconia crystals were found to be 9
9% was monoclinic.

Next, 1 g of chloroplatinic acid (H ₂ Pt)
C ₁₆ ) was dissolved in 50 cc of 0.6 mol hydrochloric acid to prepare a platinum impregnating solution. On the other hand, the zirconia carrier prepared above was calcined at 550 ° C. for 2 hours to remove water that was tightly bound, cooled in a vacuum desiccator, and poured into 37 g of the zirconia carrier with a sufficient excess amount of a platinum impregnating solution. After impregnating platinum, 100 cc of 0.6 mol hydrochloric acid was further added, and the obtained impregnated zirconia carrier was kept in a vacuum desiccator for 7 hours to complete impregnation, and then in a drying oven.
After drying at 10 ° C. for 15 hours, the platinum zirconia catalyst of the present invention was obtained. The BET surface area of this platinum-impregnated catalyst was the same as that of the support, and the chemical analysis showed that the platinum content was 0.9% by weight and the chlorine content was 1.2% by weight.

7.4 g of the obtained platinum zirconia catalyst was placed in a quartz reaction tube having an inner diameter of 20 mmφ, and 100 to 200 cc was obtained.
Firing was performed at a temperature of 500 to 550 ° C. for 15 hours under an air flow of / min, and then cooled to 300 ° C. under a flow of 500 cc / min.

Next, using this catalyst, Freon-113
A catalyst performance evaluation test for oxidative decomposition of was conducted. In the evaluation test, a quartz reaction tube having an inner diameter of 20 mm was used, a catalyst was filled in the quartz reaction tube, and Freon-113 was circulated together with water vapor under normal pressure to perform oxidative decomposition treatment.
Flow rate of water is 0.043cc / min, CFC-1
The flow rate of 13 is 0.032 cc / min, and this flow rate is set so that a molar ratio of H ₂ O: Freon-113 is sufficient to obtain sufficient amount of water for the CFC molecules to react with the catalyst surface. This is the flow velocity selected in order to achieve a value of 5 or more.

Then, the temperature was raised to 500 ° C. which is a catalytic reaction temperature, and a decomposition test of CFC-113 was carried out for 60 hours.
FIG. 1 shows the change in the decomposition rate with the elapsed time of the test, and Table 2 shows the decomposition rate after 60 hours.

The decomposition rate of CFC-113 was calculated from the concentration of CFC-113 before and after the treatment, which was quantified by a gas chromatograph.

As can be seen from the results shown in FIG. 1 and Table 2, the decomposition rate of CFC-113 by the catalyst of the present invention is as high as 99.5% at the initial stage of the reaction,
Even after 60 hours, the decomposition rate is 98.1%
It maintains a high level, that is, there is almost no change over time. Moreover, when the chlorine content and the fluorine content of the catalyst after the treatment were chemically analyzed, they were low values of 0.15% by weight and 0.18% by weight, respectively, and the catalysts were almost all catalytically decomposed with CFCs. It did not react with the hydrochloric acid or hydrogen fluoride produced by. Example 2 A platinum zirconia catalyst was prepared in the same procedure as in Example 1 except that the firing temperature of the zirconia carrier was 900 ° C. The BET surface area of this catalyst was 15 m ² / g, and X-ray diffraction showed that the crystals were 100% monoclinic. The results of a catalyst performance evaluation test conducted on this catalyst by the same procedure as in Example 1 are shown in FIG. 1 and Table 2.

As can be seen from the results shown in FIG. 1 and Table 2,
The CFC-113 decomposition rate of the catalyst of the present invention was as high as 97.9%, and it was 96.3% even after 60 hours, indicating that the decomposition rate was hardly reduced. The BET surface area of the treated catalyst was measured and found to be 15 m ² / g.
There was no change from the ET surface area. The chlorine content and the fluorine content of the treated catalyst were 0.07 and 0.21% by weight, respectively, and almost no reaction with the decomposed hydrochloric acid and hydrogen fluoride occurred like the catalyst of Example 1. It was Examples 3 to 6 Each of the platinum contents of the catalysts impregnated with platinum was 0.1.
% By weight (Example 3), 0.5% by weight (Example 4), 2.
A platinum zirconia catalyst was prepared in the same procedure as in Example 1 except that the impregnation was performed by changing the amounts to 0% by weight and 5.0% by weight. A catalyst performance test was conducted on these catalysts by the same procedure as in Example 1, and CFC-113 after 60 hours had passed.
The decomposition rate was measured. The results are shown in Table 2.

As can be seen from the results in Table 2, all the catalysts of the present invention were 90% after the treatment time of 60 hours.
The above decomposition rates are exhibited and it can withstand long-term use. Comparative Example 1 A platinum zirconia catalyst was prepared in the same procedure as in Example 1 except that the firing temperature of the zirconia carrier was 550 ° C. The liquid N ₂ adsorption BET surface area of this catalyst was 59 m ² / g. According to X-ray diffraction, 77% of the crystals were monoclinic and the remaining 23% were tetragonal. As a result of chemical analysis, the platinum content is 0.9% by weight and the chlorine content is 1.1.
% By weight. The results of a catalyst performance evaluation test conducted on this catalyst by the same procedure as in Example 1 are shown in FIG. 1 and Table 2.

As can be seen from the results shown in FIG. 1 and Table 2,
The CFC-113 decomposition rate of the catalyst of the present invention is initially 99.4.
%, Which is not so different from the case of Example 1, but becomes 94.5% after 60 hours, and the catalytic activity deteriorates sharply. When the BET surface area of the treated catalyst was measured, it was 15 m ² / g, which was about ¼ of the initial BET surface area. The chlorine content and fluorine content of the catalyst after the treatment were 0.52% by weight and 0.21% by weight, respectively, which were higher than those of the catalyst of Example 1, and the hydrochloric acid and fluorine decomposed by the catalytic treatment were The value suggested that a reaction with hydrogen fluoride had occurred. The decomposition rate after the lapse of 60 hours was 94.5, which was higher than the decomposition rate of the catalyst of the present invention in Example 6 of 93.3%, and although the decomposition rate seemed to be good, the deterioration of the decomposition rate was rapid. Not only is it unstable in use as a catalyst, but it cannot withstand use for a long time.

The difference in the catalytic function as described above is that the calcination temperature of the zirconia support in the catalyst production process of the comparative example is significantly lower than the calcination temperature range of 750 to 900 ° C. defined in the present invention. It is presumed that this is because a large amount of a tetragonal crystal phase unstable to a halogen compound is contained in the crystal phase in. Comparative Example 2 A platinum zirconia catalyst was prepared in the same procedure as in Example 1 except that the firing temperature of the zirconia carrier was set to 1150 ° C.
The liquid N ₂ adsorption BET surface area of this catalyst was 5 m ² / g. According to X-ray diffraction, 100% of the crystal phase was monoclinic. A catalyst performance evaluation test was conducted on this catalyst by the same procedure as in Example 1, and the decomposition rate of Freon-113 after 60 hours was measured. The results are shown in Table 2.

As can be seen from the results in Table 2, the CFC-113 decomposition rate of the catalyst of the present invention was 2 after 60 hours.
It was 0.2%, indicating that the catalytic activity was almost lost. The BET surface area did not change after 60 hours. The reason why the catalytic function in this case is remarkably low is presumed to be that all of the crystal phases of the catalyst obtained when the zirconia support is carried out at a high temperature of 1150 ° C. are a tetragonal system having a low decomposition function for Freon-113. To be done. Comparative Example 3 Example 1 was carried out until the zirconia carrier was calcined at 750 ° C.
After performing the same procedure as above, a catalyst performance evaluation test was performed by the same procedure as in Example 1 using only the zirconia support without subjecting it to platinum impregnation treatment. The decomposition rate was measured. The results are shown in Table 2.

As can be seen from the results shown in Table 2, the decomposition efficiency after 60 hours was 81.3% for the catalyst impregnated with platinum, that is, the catalyst containing no platinum, and the decomposition efficiency was extremely low. Comparative Example 4 A platinum zirconia catalyst was prepared in the same procedure as in Example 1 except that the amount of platinum supported on the zirconia carrier by the platinum impregnation treatment was 10.0% by weight. A catalyst performance test was conducted on this catalyst by the same procedure as in Example 1, and 60
The decomposition rate of Freon-113 after the elapse of time was measured.
The results are shown in Table 2.

As can be seen from the results shown in Table 2, it is within the range of 0.1 to 5% by weight, which is the amount of platinum supported in the present invention, within the range of 1.
A catalyst containing 0.0% by weight of platinum was CFC-113.
The decomposition rate is 87.1%, which is low. Comparative Example 5 A platinum zirconia catalyst was prepared in substantially the same procedure as in Example 1 except that zirconyl chloride was used instead of zirconyl nitrate to obtain a zirconia carrier. A catalyst performance evaluation test was conducted on this catalyst by the same procedure as in Example 1,
The decomposition rate of Freon-113 after 60 hours was measured. The results are shown in Table 2.

As can be seen from the results in Table 2, the catalyst obtained by using zirconyl chloride as the zirconia carrier was Freon-1.
The decomposition rate of 13 is 88.6%, which is lower than that of zirconyl nitrate of the present invention.

[0035]

[Table 2] ──────────────────────────────────── Example catalyst composition / history CFC decomposition rate No. (%) ──────────────────────────────────── Example 1 1.0 wt% Pt / ZrO ₂ (ZrO ₂ calcination temperature 750 ° C.) 98.1 Example 2 1.0 wt% Pt / ZrO ₂ (ZrO ₂ calcination temperature 900 ° C.) 96.2 Example 3 0.1 wt% Pt / ZrO ₂ (ZrO ₂ Firing temperature 750 ° C.) 91.8 Example 4 0.5 wt% Pt / ZrO ₂ (same as above) 97.5 Example 5 2.0 wt% Pt / ZrO ₂ (same as above) 96.0 Example 6 5.0 wt% Pt / ZrO ₂ (same as above) 93.3 ─────────────────────────────────── Comparative Example 1 1.0 wt% Pt / ZrO ₂ (ZrO ₂ firing temperature 550 ° C.) 94.5 Comparative Example 2 1.0 wt% Pt / ZrO ₂ (ZrO ₂ firing temperature 1100 20.2 Comparative Example 3 ZrO ₂ only (ZrO ₂ firing temperature 750 ° C.) 81.3 Comparative Example 4 10.0 wt% Pt / ZrO ₂ (ZrO ₂ firing temperature 750 ° C.) 87.7 Comparative Example 5 1. 0 wt% Pt / ZrO ₂ (ZrO ₂ is obtained from chloride) 88.6 ─────────────────────────────── ─────

[0036]

According to the method of the present invention, hydrogen chloride produced by the decomposition reaction of platinum and zirconia used as catalysts when oxidative decomposition of an organic halide such as freon in the presence of steam and air is carried out. It is extremely stable against hydrogen fluoride and can be used for a long period of time without lowering its catalytic function over a long period of time compared to when a conventional catalyst is used, even if the concentration of organic halogen compounds is high. Since it can withstand, it can efficiently remove organic halides and is extremely friendly in terms of environmental pollution prevention measures.

[Brief description of drawings]

FIG. 1 is a drawing showing the time course of the catalytic activity of various catalysts against the oxidative decomposition of Freon-113.

[Explanation of symbols]

 □ Curve according to Example 1 △ Curve according to Example 2 ○ Curve according to Comparative Example 1

Claims (3)

[Claims] 1. A zirconia obtained by reacting a gas containing an organic halide with an aqueous ammonia solution in the presence of air and water to cause zirconia nitrate to precipitate, and using this as a carrier, platinum or platinum oxide. A method for removing an organic halide, which comprises contacting the catalyst with supported catalyst. 2. The method for removing an organic halide according to claim 1, wherein the zirconia carrier is obtained by firing zirconia deposited in an aqueous ammonia solution in a temperature range of 700 to 950 ° C. 3. The method for removing an organic halide according to claim 1, wherein the amount of platinum or platinum oxide supported (in the case of platinum oxide, the platinum equivalent amount) is 0.1 to 5% by weight.