JP2002306973A - Detoxification catalyst for halogen-containing organic compound and method for detoxifying halogen-containing organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a catalyst with which a halogen-containing organic compound can be sufficiently, efficiently and surely detoxified at low temperature and to provide a method for detoxifying the halogen-containing organic compound by using the above catalyst. SOLUTION: The detoxification catalyst for the halogen-containing compound consists of an oxide and a noble metal carried by the oxide. The oxide consists of at least one kind selected from the group of cerium oxide, iron oxide, manganese oxide, oxides of cerium and zirconium and oxides of cerium, zirconium and aluminum, and oxygen defects are introduced by reduction treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a catalyst for detoxifying halogen-containing organic compounds and a method for detoxifying halogen-containing organic compounds.

[0002]

2. Description of the Related Art In the field of refrigeration and air conditioning equipment, chlorofluorocarbon (CFC)
The replacement of refrigerants from hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) is being promoted. However, HFCs have a high global warming potential and are not necessarily small in environmental impact.

[0003] Industrial waste and municipal waste are usually
Kerosene or the like as a dissolution aid for abrasive powder containing water oil or as a combustion aid is added and treated in an incinerator, etc., but the exhaust gas discharged from the incinerator is toxic in addition to SOx, NOx, etc. May be contained.

[0004] Therefore, studies are being made on techniques for detoxifying halogen-containing organic compounds that are recovered from waste or generated during the treatment of waste, and various methods have been proposed. For example, JP-A-8-215566
In the publication, chlorofluorocarbon is added in the presence of a TiO ₂ -WO ₃ catalyst.
A method of decomposing by heating to 00 ° C. is disclosed. Japanese Patent Application Laid-Open No. 9-150055 discloses a method of decomposing CFCs using a plasma arc. In addition, Proceedings of the 8th Waste Management Research Conference, p558
(1997), Proceedings of the 9th Annual Conference of the Society of Waste Management Research, p751 (1998), describes a technique for decomposing orthochlorotoluene and orthochlorophenol using a noble metal catalyst.

[0005]

However, the above-mentioned conventional catalysts do not always have a sufficient activity, and are still insufficient to effectively and surely detoxify halogen-containing organic compounds. Was not. Also,
TiO ₂ -WO ₃ or a catalyst of a noble metal or the like, or even in the case of using any of the plasma arc, the cost increases because a very large external energy such as heating and plasma generation is required.

The present invention has been made in view of the above-mentioned problems of the prior art, and a catalyst capable of efficiently and reliably detoxifying a halogen-containing organic compound at a sufficiently low temperature, and a catalyst using the same. An object of the present invention is to provide a method for detoxifying a halogen-containing organic compound.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that the use of a catalyst in which a noble metal is supported on a specific oxide into which oxygen vacancies have been introduced is used. The inventors have found that the problem is solved, and have accomplished the present invention.

That is, the catalyst for detoxifying a halogen-containing organic compound of the present invention is selected from the group consisting of cerium oxide, iron oxide, manganese oxide, oxides of cerium and zirconium, and oxides of cerium, zirconium and aluminum. And at least one oxide having oxygen vacancies introduced by a reduction treatment, and a noble metal supported on the oxide.

Further, the method for detoxifying a halogen-containing organic compound according to the present invention comprises the step of:
It is characterized in that it is brought into contact with an object to be treated containing a halogen-containing organic compound.

In the catalyst for detoxifying a halogen-containing organic compound according to the present invention, the oxide itself is activated by introducing an oxygen vacancy into the above-mentioned specific oxide, and the activated metal oxide and the noble metal react with each other. Since the catalytic activity is sufficiently enhanced by the synergistic effect, it is possible to efficiently and reliably detoxify the halogen-containing organic compound even when the processing temperature is low.

In the present invention, the reason why the halogen-containing organic compound can be efficiently and reliably rendered harmless even at a low treatment temperature is not clear, but the catalyst for detoxifying the halogen-containing organic compound of the present invention is not clear. The present inventors presume that it exhibits a high catalytic activity against the breaking of the bond between a carbon atom and a halogen atom.

In the catalyst for detoxifying a halogen-containing organic compound according to the present invention, the noble metal is at least one selected from the group consisting of platinum, palladium, rhodium and iridium.
It is preferably a seed, more preferably platinum. When these noble metals are used, higher catalytic activity tends to be obtained.

In the method for detoxifying a halogen-containing organic compound according to the present invention, the catalyst for detoxifying the halogen-containing organic compound may be brought into contact with the object at a temperature of 0 to 1;
Preferably it is 00 ° C. If the temperature is lower than 0 ° C., the catalytic activity tends to be insufficient. On the other hand, if the temperature exceeds 100 ° C., oxygen vacancies in the metal oxide tend to be hardly retained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

The catalyst for detoxifying a halogen-containing organic compound according to the present invention is at least one selected from the group consisting of cerium oxide, iron oxide, manganese oxide, oxides of cerium and zirconium, and oxides of cerium, zirconium and aluminum. It is characterized by comprising an oxide having oxygen vacancies introduced by a reduction treatment and a noble metal supported on the metal oxide, and efficiently converting the halogen-containing organic compound at a sufficiently low temperature. In addition, it can be surely rendered harmless.

The halogen-containing organic compound according to the present invention refers to an organic compound containing a halogen element such as fluorine, chlorine, bromine and iodine. , Orthochlorophenol, orthobromophenol, chlorobenzene, bromobenzene and the like. The catalyst for detoxifying halogen-containing organic compounds of the present invention tends to exhibit higher catalytic activity in detoxifying orthochlorophenol, orthobromophenol, chlorobenzene, and bromobenzene among the above-mentioned halogen-containing organic compounds.

As described above, the oxide used in the present invention is at least one selected from the group consisting of cerium oxide, iron oxide, manganese oxide, oxide of cerium and zirconium, and oxide of cerium, zirconium and aluminum. It is composed of one type and has oxygen defects introduced therein. Here, the oxide in which oxygen vacancies are introduced means that the content of oxygen atoms is smaller than a value obtained based on the valence of atoms such as cerium, iron, manganese, zirconium, and aluminum which constitute the oxide. Oxide. For example, cerium oxide into which oxygen vacancies have been introduced means that the content of oxygen atoms is less than twice the mole of cerium atoms, that is, CeO _x (where x represents a number less than 2). Means something. The composition of the oxide into which oxygen vacancies have been introduced can be determined by, for example, X-ray diffraction measurement.

The introduction of oxygen vacancies into the oxide can be carried out, for example, by carrying a reduction treatment after supporting the noble metal on the oxide. Also, before supporting the noble metal,
Oxygen defects may be introduced by reducing the oxide in advance. The method of the reduction treatment is not particularly limited, but is preferably 100 to 800 ° C. (more preferably 200 to 6 ° C.) in a reducing gas atmosphere.
By performing the reduction treatment at (00 ° C.) for 0.2 to 10 hours, oxygen vacancies can be efficiently and reliably introduced into the oxide. If the temperature of the reduction treatment is lower than 100 ° C., the reduction reaction does not easily proceed, and the introduction of oxygen vacancies into the oxide tends to be insufficient. On the other hand,
If the reduction treatment temperature exceeds 800 ° C., the specific surface area of the oxide tends to decrease, and the catalytic activity tends to be insufficient.

Specific examples of the reducing gas used in the above-mentioned reduction treatment include hydrogen, carbon monoxide, methane, formaldehyde, etc., but are not limited to these as long as they can reduce the above-mentioned catalyst. It is not something to be done. The concentration of these reducing gases in the reducing atmosphere is
It is preferably 0.1 to 100% by volume, and 1 to 10%.
More preferably, it is 0% by volume.

Further, in addition to the above-mentioned method, an oxygen vacancy can be introduced into the oxide by using a reducing reagent such as hydrazine or sodium borohydride.

CeO _x (where, x is a number from less than 2) the composition of the cerium oxide used [0021] As the oxide of the present invention when expressed in, x is preferably less than 2 1.5 or more, More preferably, it is 1.5 or more and 1.8 or less. When x is within the above range, higher catalytic activity tends to be obtained. In particular, when the cerium oxide is in the form of particles, it is preferable that x be 1.5 or more and 1.8 or less in the surface layer (a layer from the surface to a depth of 100 nm).

Further, Fe ₂ (wherein, x is a number from less than 3) O _x The composition of the iron oxide used as an oxide according to the present invention when expressed in, x is to be less than 2 or more 3 preferable. When x is within the above range, higher catalytic activity tends to be obtained.

Further, when the composition of manganese oxide used as the oxide according to the present invention is represented by MnO _x (where x represents a number less than 2), x may be 1.5 or more and less than 2. preferable. When x is within the above range, higher catalytic activity tends to be obtained.

When the oxide according to the present invention contains two or more elements as a metal element or a rare earth element, the oxide is a mixture or solid solution of oxides of the respective elements, or two or more elements. Any of the composite oxides may be used. For example, the oxide of cerium and zirconium may be a mixture or a solid solution of cerium oxide and zirconium oxide, or a composite oxide of cerium and zirconium. Among these oxides, it is preferable to use a solid solution or a composite oxide of two or more kinds of oxides because introduction of oxygen vacancies becomes easy. A solid solution or a composite oxide of two or more oxides can be suitably obtained by using a predetermined raw material compound to obtain a precipitate by, for example, a coprecipitation method, and firing the precipitate.

When an oxide of cerium and zirconium is used, the molar ratio of cerium atoms to zirconium atoms in the oxide is preferably from 100: 1 to 1: 100, more preferably from 20: 1 to 1: 100. 20 and more preferably 10: 1 to 1: 1. When the molar ratio between the cerium atom and the zirconium atom is within the above range, the oxygen vacancy tends to be more stably held.

When an oxide of cerium, zirconium and aluminum is used, the molar ratio of cerium atoms to zirconium atoms in the oxide is preferably 100:
1-1: 100, more preferably 20: 1 to 1:20,
More preferably, it is 10: 1 to 1: 1 and the molar ratio of cerium atoms to aluminum atoms is preferably 100: 1.
１ ： 1: 100. When the molar ratio of each atom is within the above range, oxygen deficiency tends to be more stably maintained.

In the present invention, the above oxides may be used alone, and in addition to the above oxides, oxides of rare earth elements such as yttrium, lanthanum, neodymium, braseodymium, cobalt, chromium, An oxide of a transition metal such as nickel or copper may be further blended.

Specific examples of the noble metal supported on the above oxide include platinum, palladium, rhodium, iridium, gold, ruthenium and the like. These may be used alone or in combination of two or more. These may be used in combination. Among these noble metals, it is preferable to use platinum, palladium, rhodium, and iridium (more preferably, platinum) because higher catalytic activity can be obtained. The average particle size of these noble metals is preferably 10 nm or less, more preferably 1 nm or less. When the average particle size of the noble metal exceeds the above upper limit, the catalytic activity tends to be insufficient.

The method of supporting these noble metals on the above oxide is not particularly limited, but specific examples include an impregnation method, an evaporation to dryness method, and a supercritical fluid method.

The amount of the noble metal supported on the oxide is appropriately selected depending on the combination of the oxide and the noble metal. When cerium oxide is used as the oxide, the amount of the noble metal supported is 150 g of cerium oxide. Preferably 0.1 to
20 g, more preferably 0.5 to 5 g, and the noble metal in the case of using iron oxide, manganese oxide, an oxide of cerium and zirconium, or an oxide of cerium, zirconium and aluminum as the oxide. The loading amount is preferably 0.1 to 20 g with respect to 150 g of the oxide.
And more preferably 0.5 to 5 g. When any oxide is used, the catalytic activity tends to be insufficient if the amount of the noble metal supported is less than the lower limit, and the noble metal supported even if the amount of the noble metal exceeds the upper limit. The effect of improving the catalytic activity corresponding to the amount cannot be obtained, and in addition, the cost tends to be increased by using a large amount of expensive noble metal.

As described above, oxygen vacancies can be introduced into the oxide by carrying out a reduction treatment after loading the noble metal on the oxide. However, the BET of the catalyst after the introduction of the oxygen deficiency can be achieved. The specific surface area is preferably 50 m ² / g or more when reduced at 500 ° C.
When the reduction treatment is performed at 0 ° C., it is preferably 15 m ² / g or more.

The catalyst for detoxifying a halogen-containing organic compound of the present invention includes titanium oxide, alumina, silica, zeolite, sepiolite, and titanium oxide which are conventionally known as catalyst carriers.
It may be supported on zirconia, activated carbon, or the like, or used as a mixture. In addition, the catalyst for detoxifying the halogen-containing organic compound of the present invention can be used after being supported on or mixed with the above-mentioned carrier, then formed into pellets, or held on a honeycomb or foam base.

Next, the method for detoxifying a halogen-containing organic compound of the present invention will be described.

The method for detoxifying a halogen-containing organic compound of the present invention is characterized in that the catalyst for detoxifying a halogen-containing organic compound of the present invention is brought into contact with an object to be treated containing a halogen-containing organic compound. is there. Here, the material to be treated may consist only of a halogen-containing organic compound, and may be exhaust gas or combustion ash (dust) discharged from an incinerator during incineration of industrial waste or municipal waste. May contain other components such as In particular, when detoxifying the halogen-containing organic compound contained in the exhaust gas or combustion ash, it is possible to sufficiently detoxify without separating the halogen-containing organic compound from the exhaust gas or combustion ash. The method is particularly useful.

The amount of the catalyst for detoxifying the halogen-containing organic compound of the present invention in the method of the present invention is appropriately selected depending on the amount of the halogen-containing organic compound contained in the article to be treated and the like.

In the method of the present invention, the temperature at which the catalyst for detoxifying the halogen-containing organic compound of the present invention is brought into contact with the object to be treated is preferably from 0 to 100 ° C, more preferably from 10 to 70 ° C. Is more preferable. If the temperature is lower than 0 ° C., the catalytic activity tends to be insufficient. On the other hand, if the temperature exceeds 100 ° C., oxygen vacancies in the metal oxide tend to be hardly retained.

Furthermore, in the above method of the present invention, the contact time between the catalyst for detoxifying the halogen-containing organic compound of the present invention and the object to be treated is not particularly limited.

[0038]

EXAMPLES Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 First, 434.2 g of cerium (III) nitrate and 53.5 g of zirconium oxynitrate were added to 1500 g of water to prepare an aqueous solution containing 5: 1 (molar ratio) of cerium atoms and zirconium atoms. did. Ammonia water was added dropwise while stirring this aqueous solution to form a precipitate, and then an aqueous solution containing hydrogen peroxide corresponding to half the number of moles of cerium atoms contained in the aqueous solution, An aqueous solution containing alkylbenzenesulfonic acid corresponding to 10% by weight (theoretical value) was dropped, and the mixed solution was stirred to form a slurry. The slurry was dried to remove the coexisting ammonium nitrate to obtain a cerium oxide-zirconium oxide solid solution.

Next, 150 g of the obtained cerium oxide-zirconium oxide solid solution was impregnated with a nitric acid aqueous solution of dinitrodiammine platinum aqueous solution (platinum content: 2 g), and heated with stirring to evaporate the aqueous solution to dryness. . The residue is calcined in air at 500 ° C. for 3 hours, and cerium oxide-zirconium oxide supported on platinum (hereinafter referred to as Pt / CZ).
I got

Further, the obtained Pt / CZ was placed in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen concentration: 10% by volume) for 50 hours.
A reduction treatment was performed at 0 ° C. for 3 hours to obtain a powdery catalyst.

Comparative Example 1 In a test described below, activated carbon was used as a catalyst.

Comparative Example 2 A catalyst was prepared as in Example 1 except that the hydrogen reduction treatment was not performed, and used in a test described later.

(Decomposition Test of o-Bromophenol) Using each of the catalysts of Example 1 and Comparative Examples 1 and 2, a decomposition test of o-bromophenol was performed in the following procedure.

First, 0.5 g of the catalyst and 0.023 g (20 μl) of o-bromophenol were mixed and kept at room temperature for a predetermined time. Thereafter, 35 mg of the mixture was taken out, introduced into a sample chamber of a differential thermal balance-gas chromatography mass spectrometry simultaneous measurement device (TG-MS measurement device, manufactured by Rigaku Corporation), and the differential heating section was heated to 800 ° C. The amount of o-bromophenol contained in the sometimes released gas was measured by gas chromatography mass spectrometry. In performing the above test, the peak area of the mass number 129 in the mass spectrum was used as an index of the amount of o-bromophenol.

FIG. 1 shows the correlation between the retention time of the mixture at room temperature and the residual concentration of o-bromophenol when the catalysts of Example 1 and Comparative Examples 1 and 2 were used. The residual concentration of o-bromophenol shown in FIG.
It is a value obtained by normalizing the amount of o-bromophenol (the amount of o-bromophenol when the retention time is 0 hour) as 1 when it is introduced into the sample chamber immediately after mixing with bromophenol and measured. That is, the residual concentration at each holding time represents a value obtained by dividing the amount of o-bromophenol obtained in each measurement by the amount of o-bromophenol at the holding time of 0 hour.

As is apparent from the results shown in FIG. 1, when the catalyst of Example 1 was used, the amount of o-bromophenol could be sufficiently reduced at room temperature.

[0048]

As described above, according to the catalyst for detoxifying a halogen-containing organic compound of the present invention and the method for detoxifying a halogen-containing organic compound using the same, the halogen-containing organic compound can be efficiently treated at a sufficiently low treatment temperature. It is possible to detoxify well and reliably. Therefore, the catalyst and detoxification method of the present invention are very useful for detoxifying halogen-containing organic compounds contained in exhaust gas and combustion ash when treating industrial waste and municipal waste in an incinerator. It is.

[Brief description of the drawings]

FIG. 1 is a graph showing the correlation between the retention time of a mixture at room temperature and the residual concentration of o-bromophenol when using the catalysts of Example 1 and Comparative Examples 1 and 2.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C07C 39/28 B01J 23/56 301A B01D 53/36 G (72) Inventor Kenichiro Suzuki Okucho, Nagakute-cho, Aichi-gun, Aichi Prefecture 41, Yokomichi No. 1, Toyota Central Research Laboratory Co., Ltd. (72) Inventor J. Sasaki 41, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Yokomichi No. 41 Inside Toyota Central Research Laboratory Co., Ltd. 41, Toyoda Central Research Institute Co., Ltd. (72) Inventor Hiroaki Hayashi Hiroaki Hayashi 41st, Toyoda Central Research Institute Co., Ltd. Person Masataka Sugiura 41 No. 41, Chukku Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central R & D Laboratories, Inc. (reference) 2E191 BA15 BC01 BD13 4D048 AA11 BA05Y BA08X BA18X BA28Y BA30X BA31Y BA32Y BA33Y BA34Y BA36Y BA42X DA03 DA06 DA13 4G069 AA03 AA08 BB06A BB20B BC16A BC3 2A BC33A BC43A BC43B BC51A BC51B BC62A BC66A BC69A BC71A BC72A BC74A BC75A BC75B CA01 CA02 CA19 DA05 EA01Y FA01 FA02 FB09 FB14 FB30 FB44 4H006 AA05 AC13 FC50 FE13 FE73

Claims (5)

[Claims] Cerium oxide, iron oxide, manganese oxide,
An oxide of at least one selected from the group consisting of an oxide of cerium and zirconium, and an oxide of cerium, zirconium and aluminum, wherein an oxide in which an oxygen vacancy has been introduced by a reduction treatment, A catalyst for detoxifying a halogen-containing organic compound, comprising a noble metal. 2. The method of claim 1, wherein the noble metal is at least one selected from the group consisting of platinum, palladium, rhodium and iridium.
The catalyst for detoxifying a halogen-containing organic compound according to claim 1, wherein the catalyst is a seed. 3. The catalyst for detoxifying a halogen-containing organic compound according to claim 1, wherein the noble metal is platinum. 4. A halogen-containing organic compound, comprising: contacting the halogen-containing organic compound detoxification catalyst according to claim 1 with an object to be treated containing the halogen-containing organic compound. A method for detoxifying organic compounds. 5. The halogen-containing organic compound according to claim 4, wherein the temperature at which the catalyst for detoxifying the halogen-containing organic compound is brought into contact with the halogen-containing organic compound is 0 to 100 ° C. Detoxification method.