JPH08141367A - Catalytic cracking method for aliphatic halide - Google Patents

Abstract

PURPOSE: To make an aliphatic halide compound harmless for a long period by stopping supply of lower alcohol and/or ether and aliphatic halide after catalytic cracking for a desired time and continuing catalytic cracking of aliphatic halide after activation treatment of a carried catalyst. CONSTITUTION: Fixed bed multi-tubular type reaction pipes 41-43 are arranged in the body 4 of a reactor. Aliphatic halide is catalytically cracked in the presence of lower alcohol and/or ether using a catalyst which is introduced into the reaction pipes 41-43 and is prepared by carrying a co-catalyst selected from metallic halide of groups 1a and 1b on a principal catalyst selected from among metallic halides of groups IIb, 6a, 7a and 8. In this case, supply of lower alcohol and/or ether and aliphatic halides is stopped after catalytic cracking at a desired time and the carried catalyst is projected to activation treatment under the oxidization atmosphere. Thereafter, lower alcohol and/or ether and aliphatic halide are supplied and catalytic cracking of aliphatic halide is continued.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a decomposition method for detoxifying an aliphatic halide. More specifically, the present invention is industrially and economically harmless to use aliphatic halides such as chlorofluorocarbon, which is a problem in terms of pollution control, in the presence of alcohol and / or ether by using a specific high activity catalyst system. The present invention relates to a new method of converting and decomposing.

[0002]

2. Description of the Related Art Recently, aliphatic halides such as carbon tetrachloride and chlorofluorocarbon (hereinafter abbreviated as CFC) have been required to be rendered harmless in order to prevent environmental pollution on a global scale. In particular, the latter CFC is a harmful substance that destroys the ozone layer, and there is a strong demand for the development of a technology that can easily, efficiently and economically detoxify and decompose these aliphatic halides under mild conditions. Has been done.

Conventionally, as decomposition methods of aliphatic halides, (1) thermal decomposition / incineration method, (2) plasma discharge method, (3) catalytic decomposition method, (4) chemical reaction method, (5) supercritical water Solution methods have been proposed and tried. However, the above-mentioned various decomposition methods are not necessarily promising methods because there are many problems in the reaction operation and the material of the reaction apparatus because the decomposition conditions for practical use are severe.

Of the above decomposition methods, the catalytic decomposition method is
It is the most practical method in view of (i) decomposition at a relatively low temperature, (ii) downsizing of the decomposition device, and (iii) continuous processing.

Therefore, much research has been conducted on the catalytic decomposition method of aliphatic halides.
In this respect, the decomposition method of dichlorodifluoromethane as an aliphatic halide will be examined below. The following decomposition modes are considered: Decomposition reaction (1): CCl ₂ F ₂ = C + Cl ₂ + F ₂ Decomposition reaction (2): CCl ₂ F ₂ + O ₂ = CO ₂ + Cl ₂ +
F ₂ decomposition reaction (3): CCl ₂ F ₂ + 2H ₂ O = CO ₂ + 2H
Cl ₂ + 2HF decomposition reaction (4): CCl ₂ F ₂ + 2CH ₃ OH = CO ₂ +
2CH ₃ Cl + 2HF The reaction heat (ΔH) and free energy (ΔG) of the above decomposition reactions (1) to (4) are shown in Table 1 below.

[0006]

[Table 1]

As is clear from Table 1, the decomposition reaction of dichlorodifluoromethane alone is a large endothermic reaction, and therefore the reaction requires an extremely high temperature. On the other hand, since the decomposition reaction system in which oxygen, water (H ₂ O) or alcohol is added is an exothermic reaction, a decomposition method in which these compounds are added has been attempted. For example,
(i) The decomposition method of adding oxygen is PO ₄ as a catalyst.
/ ZrO ₂ (2nd Freon-related catalyst presentation, 1992.10.30) or BPO ₄ (Chemical Society of Japan, 645, 1991), (ii)
Further, as a decomposition method of adding water (H ₂ O), Fe ₂ O _{3 /} C (Chem, Lett., 190
1, 1989) and the like are known.
However, all of these reaction systems require a high temperature of about 500 ° C., and the sustainability of the catalytic activity is not sufficient, and there are many problems in practical use.

On the other hand, the present inventors have previously prepared 1,1,2,2-tetrachlorodifluoroethane in a metal halide (for example, ferric chloride) catalyst system supported on activated carbon in the presence of alcohol. Aliphatic halides such as 1,1,2-trichlorotrifluoroethane are 300
It has been found that it can be decomposed into CO and CO ₂ under mild conditions around ℃, chlorine can be recovered as alkyl chloride and fluorine can be recovered as hydrogen fluoride. In addition, this method has the advantage that these compounds can be easily recovered and the post-treatment for pollution-free can be carried out at an extremely low cost (C
hem. Lett. , 795, 1992; Japanese Patent Application No. 3-
348642).

However, the above-mentioned catalytic decomposition method of an aliphatic halide previously proposed by the present inventors is 300 ° C.
It has the advantage of being able to decompose aliphatic halides under mild decomposition conditions before and after, but like other catalytic decomposition methods, the catalytic activity decreases with the passage of reaction time, so it is an improvement for industrial commercialization. It leaves room for

Therefore, in order to improve the above-mentioned catalytic decomposition method proposed by the present inventor, the present inventor must: -make the catalyst a composite system of main / co-catalyst; , Which becomes an oxide with a lapse of reaction time and becomes low in activity, but when the catalyst system is designed with the idea of activating this with a co-catalyst and restoring it to a metal halide, the catalytic activity is highly durable. I found that I can do things. The present inventors have already proposed this point (Japanese Patent Application No. 5-141273).

[0011]

However, the catalytic decomposition method for aliphatic halides proposed by the present inventors (Japanese Patent Application No. 5-141273) is also evaluated from the viewpoint of maintaining long-term catalytic activity. There is still room for improvement. The present inventors diligently studied a method for maintaining the catalytic activity for a long period in the catalytic decomposition method of an aliphatic halide. As a result, in the main / co-catalyst (two-way catalyst) system previously proposed by the present inventor, when catalytic decomposition of an aliphatic halide is carried out for a long period of time, a co-catalyst,
For example, it is found that copper chloride (divalent) is changed to copper chloride (monovalent), and the ability to recover the main catalyst denatured during catalytic cracking is reduced, and in order to solve the above drawbacks, It has been found that it is extremely effective to periodically activate the catalyst system in an oxidizing atmosphere.

The present invention is based on the above-mentioned findings, and the intermittent and simple catalyst activation treatment according to the present invention renders an aliphatic halide harmless industrially and economically for a long period of time. A novel catalytic decomposition method is provided.

[0013]

SUMMARY OF THE INVENTION The present invention can be summarized as follows. The present invention uses a single-tube reaction tube or a multi-tube reaction tube heated by an external heating method and fills the inside of the reaction tube. Of a main catalyst selected from the group 2b, 6a, 7a, and 8 metal halides and a cocatalyst selected from the group 1a and 1b metal halides on a desired carrier In a catalytic decomposition method of an aliphatic halide in which an aliphatic halide is catalytically decomposed in the presence of a lower alcohol and / or ether under a catalyst,
(i) After the catalytic decomposition for a desired time, the supply of the lower alcohol and / or ether and the aliphatic halide to the reaction tube is stopped, (ii) the supported catalyst inside the reaction tube is activated under an oxidizing atmosphere, iii) Next, a lower alcohol and / or ether and an aliphatic halide are supplied to the reaction tube, and the catalytic decomposition of the aliphatic halide is continued, and a catalytic decomposition method of the aliphatic halide is characterized. . Hereinafter, the technical configuration of the present invention will be described in detail.

The aliphatic halide to be subjected to the catalytic decomposition method of the present invention is a halogenated aliphatic alkane or alkene, which is substituted with one or more halogens of chlorine, bromine or fluorine. It is a thing. In the present invention, mention may be made in particular of highly halogenated aliphatic alkanes or alkenes in which all hydrogens in the molecule are replaced by halogens. As the above-mentioned compound,
Carbon tetrachloride, perchloroethylene, hexachloroethane, trichlorofluoromethane, dichlorodifluoromethane, 1,1,2-trichlorotrifluoroethane,
Examples include 1,1,2,2-tetrachlorodifluoroethane, trifluorobromomethane, and the like. These can be used in the form of a single compound or a mixture thereof, and in practice, as the aliphatic halide, a perhaloalkane or alkene having 1 to 4 carbon atoms is advantageously used.

In the present invention, the lower alcohol is used from the following viewpoints. Generally, it is known that the dehalogenation reaction of halogenated hydrocarbons is caused by alcohols in the presence of alumina. For example, L. Andrussow et al.
It has been reported that reaction of 1,2,2-tetrachloroethane with methanol produces trichlorethylene and methyl chloride [Chem, Proc, Eng. , V
48, 41 (1967)]. In addition, Shinoda et al.
A series of studies have been reported on the co-pyrolysis of 1,2-trichloroethane and other chlorinated alkanes with methanol [Chem, Lett. , 877 (1973): Nikka, 316, 661, 1637 (1975)].

In the present invention, the lower alcohol is used from the above-mentioned viewpoint, that is, as a saucer for halogen. Examples of the lower alcohol include alcohols having up to about 6 carbon atoms, which are selected practically in consideration of utilization of by-products and the like, and alcohols having 1 to 4 carbon atoms are advantageously used. Examples of these alcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, 1-butanol, 2-butanol, and tertiary butyl alcohol. The lower alcohol used in the reaction does not necessarily have to be a single alcohol, and a mixture can be used.

Although the decomposition mechanism of the aliphatic halide of the present invention is not always clear, the decomposition proceeds by reacting one hydroxyl group of the lower alcohol with one of the halogens of the aliphatic halide, and the lower alcohol has a hydroxyl group moiety. Is converted to a lower monohaloalkyl substituted with halogen, and the carbon of the aliphatic halide is thought to be carbon dioxide or carbon monoxide. By the decomposition reaction,
It was also confirmed that hydrogen halide was produced and adsorbed on the carrier of the catalyst described later. Therefore, in order to decompose all the aliphatic halides at one time, it is necessary to use at least a molar amount of the lower alcohol corresponding to the number of halogens contained in the molecule with respect to 1 mol of the aliphatic halide. Conceivable. However, when it is not necessary to decompose all the aliphatic halides in a single reaction, it is sufficient to supply the lower alcohol in a slightly excess amount than the amount corresponding to the expected decomposition rate. There is no problem. Even in the experimental results, when the supply amount of lower alcohol is small, the formation of hydrogen halides such as intermediates and hydrogen chloride was observed, and the decomposition rate of aliphatic halides was improved, and from the viewpoint of recovering useful lower haloalkyl, It is preferred that the alcohol is in excess.

In the present invention, ether is used from the same viewpoint as the lower alcohol. That is, the ether also acts as a donor of the alkoxy anion on the catalyst, like the alcohol, and acts as a tray for the halogen. As this type of ether, those having up to about 12 carbon atoms are advantageously used, but those having 2 to 8 are economically valuable. In the present invention, the cyclic use of ether by-produced in the catalytic decomposition reaction between CFC and the alcohol is necessary for rationally operating the process of the present invention. From the above, it is extremely important to use ether alone or in combination with alcohol in the present invention. In the present invention, as the above-mentioned ether, methyl ether, ethyl ether, propyl ether, butyl ether or the like is used according to alcohol.

In the catalytic decomposition method of an aliphatic halide using the above-mentioned ether, generally, the increase of the alkyl group of the ether increases the electron density of the oxygen atom, and the nucleophilicity is improved as compared with alcohols to decompose. The rate tends to increase. However, when the alkyl group becomes large, the decomposition rate (reaction rate) tends to decrease due to its steric hindrance. This tendency is due to C ₂ H ₅ OC ₂ H ₅ and n-C ₃
Observed between ether H ₇ OC ₃ H ₇ and _{n-C 4 H 9 OC 4} H 9,.

Catalytic decomposition of the aliphatic halide of the present invention,
The catalyst system consists of a binary system consisting of a main catalyst and a cocatalyst. And
As the main catalyst, a halide of a 2b group, 6a group, 7a group, or 8 group metal is used. The main catalyst used in the present invention is composed of a 2b group, 6a group, 7a group or 8 group metal halide, and examples of the metal halide include Zn, Cr, Mn, Fe, Co and Ni. , Or a halide of Pd, or a mixture thereof, and the halogen includes chlorine and / or fluorine.

In the present invention, the above metal halide may be a compound containing plural kinds of halogens such as chromium trichloride and chromium trifluoride. Incidentally, when chlorofluorocarbon is treated with a chromium trichloride catalyst, a part of chlorine is replaced with fluorine during the treatment.
However, even in this case, the reaction activity does not decrease. In the present invention, it goes without saying that the above-mentioned main catalyst metal halide may be one kind or two or more kinds. As the seed catalyst of the present invention, ferric chloride and / or ferric fluoride is particularly excellent in terms of activity and sustainability.

Next, the co-catalyst system of the present invention will be described. The main idea of the main / co-catalyst system of the present invention is that the metal halide of the main catalyst becomes a low-activity oxide with the passage of reaction time, but it is restored to the halide by the co-catalyst. It is configured.

This point will be considered with respect to a catalyst system in which the main catalyst is ferric chloride or ferric fluoride. That is, in the catalytic decomposition method of an aliphatic halide, ferric chloride or ferric fluoride reacts with alcohol as the reaction time elapses, and as shown in the following reaction formulas (1) to (2), oxidation Produces ferric iron. The ferric oxide has a lower catalytic activity than the initial ferric chloride or ferric fluoride. (1) 2FeCl ₃ + 6CH ₃ OH = Fe ₂ O ₃ + 6CH
_{3 Cl + 3H 2 O (2} ) 2FeF 3 + 6CH 3 OH = Fe 2 O 3 + 6HF +
3CH ₃ OCH ₃

In the present invention, the use of, for example, cupric chloride as a co-catalyst makes it possible to maintain the activity of the catalyst system. This is because ferric oxide and cupric halide react with each other according to the following reaction formula (3) to produce a main catalyst (for example, ferric fluoride). That is, during the catalytic decomposition of the aliphatic halide, the main catalyst is partially converted into an oxide, which is restored by the cocatalyst. (3) Fe ₂ O ₃ + 3CuF ₂ = 2FeF ₃ + 3CuO

In the catalyst system of the present invention, the cocatalyst is changed to cupric oxide by the above reaction formula (3),
The cocatalyst is restored as follows. That is, cupric oxide reacts with hydrogen halide generated by catalytic decomposition of an aliphatic halide to form cupric halide (promoter) as shown in the following formulas (4) to (5). To do. (4) CuO + 2HF = CuF ₂ + H ₂ O (5) CuO + 2HCl = CuCl ₂ + H ₂ O

As a result of the above, a series of cyclic reactions are established between the above-mentioned reactions, and the sustainability of the catalytic activity of the catalyst system (main / cocatalyst system) is maintained.

As mentioned above, the promoter of the present invention plays an extremely important role. In the present invention, the cocatalyst described above is preferably a metal halide of group 1a or group 1b (copper group). This type of promoter is, for example, 1
In the case of Group a alkali metal halides, it forms a double salt with ferric chloride or ferric fluoride as the main catalyst, and is extremely effective in preventing volatilization of ferric halide as the main catalyst. (A COMPREHENSIVE TREATISE ONINORGANIC AND T
HEORETICAL CHEMISTRY, VoL.14,98, LONGMANS, 1961
Year). Further, the metal halide of Group 1b has a property of smoothly promoting an exchange reaction between halogen and oxygen, for example, a reversible reaction between cupric halide and cupric oxide. In the present invention, among these cocatalysts, cupric chloride is particularly preferable.

However, when the above-mentioned main / co-catalyst system (two-way catalyst system) is used to catalytically decompose an aliphatic halide for a long period of time, a decrease in catalytic activity is observed. This is
In addition to the elementary reactions of (1) to (5), the following reactions that reduce the catalytic activity are presumed to occur. (6) FeX ₃ → FeX ₂ (low activity species) (7) FeX ₃ → Fe ° (metal) The reaction formulas (6) to (7) are the catalytic decomposition system of an aliphatic halide under a reducing atmosphere. In, it is shown that the iron halide (trivalent) of the main catalyst is reduced to iron halide (divalent) or metallic iron, which reduces the catalytic activity with the passage of time.

Even if metallic iron is produced by the above-mentioned reaction, in the binary catalyst system of the present invention, metallic iron is converted into iron halide (according to the following formula) by a cocatalyst (CuX ₂ ), for example, copper chloride (divalent). It will be restored to trivalent) and the catalytic activity will be enhanced. (8) FeX ₂ + CuX ₂ = FeX ₃ + CuX (9) Fe + 3CuX ₂ = FeX ₃ + 3CuX

As shown in the above reaction formulas (8) to (9), the cocatalyst (CuX ₂ ) plays an important role in the recovery of the main catalyst (FeX ₃ ). It changes from valency to valency, weakening its effect on the recovery of the main catalyst. This reduces the catalytic activity in the long term. The major feature of the present invention is that the reaction formula
The point is to restore the change of the cocatalyst shown in (8) to (9) and to express the original function.

In the present invention, the functional recovery of the cocatalyst,
In other words, the activation treatment of the catalyst system is carried out in an oxidizing atmosphere as shown by the following equation. The following equation shows that the function of the co-catalyst is restored by air oxidation. (10) 2CuX + 1/2 · O ₂ + 2HX = 2CuX ₂ + H
₂ O As shown in the reaction formula (10), the activation treatment of the catalyst system of the present invention under an oxidizing atmosphere is carried out by hydrogen halide (HX)
The existence of is important. Hydrogen halide (HX) described above
In the method for catalytically decomposing an aliphatic halide of the present invention, is sufficiently supplied because it is adsorbed on the catalyst carrier described later as a by-product of the decomposition reaction. Needless to say, the activation treatment of the present invention promotes the presence of the hydrogen halide (HX), and the hydrogen halide (HX) has any meaning during the activation treatment. In the case where the hydrogen halide has disappeared, or when the existing amount is small, naturally hydrogen halide (HX) must be supplied.

The above-mentioned catalyst system activation treatment step of the present invention is inferred from the catalyst system (PdCl ₂ / CuCl ₂ / HCl) used in the Hoechst-Wacker method for producing acetaldehyde by reacting ethylene with oxygen. can do. By the activation treatment in the oxidizing atmosphere, the monovalent copper (CuX) is easily oxidized and divalent copper (CuX) is added.
It recovers to X ₂ ) and carries out the function as the original cocatalyst.

In the present invention, the activation treatment of the binary catalyst system in the oxidizing atmosphere may be carried out under desired conditions.
For example, depending on the type of carrier described later, air treatment (aeration) at room temperature or high temperature, or oxidation treatment using a desired oxidant may be performed. Needless to say, it is needless to say that when the carrier is activated carbon, air oxidation at high temperature should be avoided because the carrier itself burns.

Further, the activation treatment of the two-way catalyst system in the oxidizing atmosphere of the present invention may be carried out after the desired catalytic decomposition in which a decrease in catalytic activity is detected. Therefore,
A preferred catalyst activation treatment method may be adopted depending on the configuration of the reaction furnace and the reaction tube applied to the catalytic decomposition method of the aliphatic halogain compound. (i) For example, in the case of a single-tube type reaction tube, activation treatment is performed intermittently. Therefore, the catalytic decomposition of the aliphatic halide is a batch method.

(Ii) Further, in the case of the parallel multitubular system, the batch system described above may be adopted, or a part of the reaction tube,
That is, it is possible to employ a semi (semi) continuous semi system in which the desired number of reaction tubes is activated and catalytic cracking of the aliphatic halide is carried out in the remaining reaction tubes. In the present invention, the parallel multitubular reaction tubes are arranged in the heating zone in the reactor body, and when the aliphatic halide is catalytically decomposed in a semi- (semi) continuous manner, during the activation treatment of the two-way catalyst. Needless to say, the reaction tube to be activated may be removed from the reactor main body or may be performed without removing it. In the latter case, the supply of the aliphatic halide and the alcohol and / or ether to the reaction tube which is the target of the activation treatment is stopped, the supply of the oxidizing agent (such as air), and the aliphatic halide and the alcohol and / or The supply of ether may be restarted under a desired control mechanism.

It goes without saying that the catalyst system (main / cocatalyst system) used in the present invention can be used by supporting it on a desired carrier. As the carrier, activated carbon, alumina, activated alumina, silica gel or the like is used. The activated carbon as the carrier includes, for example, wood, sawdust, coconut husks and other plant materials, animal material such as beef meat and bones, lignite, peat, coal, petroleum, and pitches obtained by treating these. Activated carbon manufactured from the mineral materials described above can be used. As the shape of the activated carbon, since the decomposition reaction is carried out in a gas phase flow system, it is granular, for example, crushed and sieved, the one in which the particle size distribution range is adjusted, preformed at the time of production, or the powdered carbon is molded by adding a binder. Preferred are spherical and cylindrical granular activated carbon. The size of the particles is appropriately selected depending on whether the reaction mode is a fluidized bed system or a fixed bed system.

The catalyst system (main / co-catalyst system) of the present invention is loaded on a carrier by, for example, a so-called impregnation method in which activated carbon is thoroughly mixed and impregnated in an aqueous solution of a metal halide and then dried. can do. Further, the amount of the metal halide supported on the activated carbon is not particularly limited, but may be 0.
02-0.2 mol / 100g Activated carbon is preferable. In addition to the co-catalyst component, it is possible to add a third component to prevent volatilization of the catalyst component, adjustment of the melting point and the like in preparation of the catalyst.

The reaction temperature in the catalytic decomposition of the aliphatic halide is generally 100 ° C to 400 ° C, preferably 12 ° C.
It is 0 ° C to 350 ° C. If the reaction temperature is too low, the product, particularly water, may be condensed to dissolve the metal halide of the catalyst or corrode the reactor, which is not preferable.
The upper limit of the reaction temperature is determined by the difficulty of the reaction due to the difference in the type of aliphatic halide to be decomposed. In general,
If the amount of chlorine in the aliphatic halide is high, the reaction will occur at a relatively low temperature, but if the amount of fluorine increases, the reaction will become difficult.
It needs to be hot. In any case, the reaction temperature is 40
If the temperature exceeds 0 ° C, parts derived from lower alcohols and ethers will also be decomposed, and a reaction unsuitable for recovery of useful substances will occur. However, in actual use, the above problem can be sufficiently dealt with by experimentally confirming the target substance in advance. For example, when carbon tetrachloride is decomposed with ethanol, the reaction is almost complete at about 200 ° C, but 1,1,2-
In the case of trichlorotrifluoroethane and ethanol, 300 ° C or higher is required for efficient decomposition.
When a catalyst supporting ferric chloride is used, since ferric chloride sublimes at a relatively low temperature, a relatively low reaction temperature is adopted.

The decomposition reaction may be carried out in an ordinary gas phase flow type reaction apparatus. That is, as the reaction device, a fixed bed flow type reaction device, a fluidized bed type reaction device or the like can be applied.
The latter is preferable from the viewpoint of the uniformity of the reaction, but in that case, the abrasion resistance of the catalyst, the particle size distribution, etc. become problems, so it is necessary to give sufficient consideration to the preparation of the catalyst. There is no particular limitation on the reaction pressure, and it is sufficient if the pressure is such that the gas phase is maintained during the reaction. However, the reaction under pressure is preferable because the apparatus can be downsized. In the reaction, a diluent inert to the reaction can also be appropriately used.

According to the present invention, it is possible to decompose an aliphatic halide at extremely low temperatures, the carbon of the aliphatic halide being converted to carbon dioxide or carbon monoxide, while the halogen is converted to hydrogen halide. Not only is there an advantage that it can be recovered as an aliphatic monohalide by reacting with alcohols or ethers by selecting the reaction conditions. The present invention can also be used for treating carbon tetrachloride which is inevitably produced as a by-product when methylene chloride or chloroform is produced from methane or methanol as a raw material. In this case, since methanol is used for decomposing carbon tetrachloride and methanol is changed into methyl chloride, it is possible to produce methylene chloride or chloroform without substantially producing carbon tetrachloride as a by-product.

Next, an example of a reaction apparatus applied to the catalytic decomposition method of the aliphatic halide will be described with reference to the drawings. Needless to say, the present invention is not limited to the illustrated one. The reactor described below is a fixed bed type and multitubular type that can appropriately control the reaction, considering that the reaction elementary process of the decomposition of the aliphatic halide is a very large exothermic reaction. The configured reactor will be described. That is, the reactor described below has a multitubular structure for heating in the initial reaction and subsequent reaction processes under a multitubular configuration, or for cooling to prevent abnormal reaction under an exothermic reaction. It is capable of adequately exhibiting the characteristics and appropriately controlling the reaction, and capable of detoxifying and decomposing aliphatic halides efficiently and economically. Furthermore, the reaction device described below is an unreacted aliphatic halide reaction that is a problem in terms of pollution control, by appropriately controlling the reaction under a multi-tubular structure to completely catalytically decompose the aliphatic halide. Can be prevented from being discharged to the outside of the device.

1 and 2 are partial schematic views of the multi-tube catalytic cracking apparatus (A) of the present invention. That is, both FIG. 1 and FIG. 2 show a part of the multi-tube catalytic cracking apparatus (A) of the present invention, but as shown in FIG. 2 and FIG. 2 are combined to form an overall schematic diagram. Also,
1 and 2 also show a flow sheet for detoxifying and decomposing freon as an aliphatic halide in the presence of alcohol. In the figure, numbers in parentheses such as (300 ° C.) indicate the temperature of the reaction product gas and the like. Needless to say, these temperature conditions should be understood as an example. Hereinafter, each element constituting the multitubular catalytic cracking apparatus (A) of the present invention will be described with reference to the flow sheets of FIGS.

(1) shows a CFC feeder. this is,
It is a device for supplying the freon at a predetermined processing site, for example, a predetermined place where the collected freon is stored, for catalytic cracking by the present apparatus (A). In the figure, (p) indicates a pump, which pumps up CFC and supplies it to the next step.

(2) shows an alcohol supply device. This is a device in which a predetermined amount, for example, 3 to 4 times, of an amount of an alcohol such as methyl or ethyl alcohol, which promotes the catalytic decomposition of freon, is supplied to the freon flow rate.

(3) shows a mixing apparatus for freon and alcohol. This is an apparatus for mixing the CFC and alcohol supplied from the above (1) and (2). For example, chlorofluorocarbon and alcohol are heated to about 90 to 95 ° C. and mixed in a gas state, and the prepared mixed gas is used as a reactor body (4) for the next step.
Is a device for supplying to. It goes without saying that flashback prevention means may be delivered to the mixing device (3) for fire prevention. As the flashback prevention means, FIG. 1 shows one using silicone oil.

(4) shows a reactor (hereinafter, also referred to as a reactor main body) which is a central component of the multitubular catalytic cracking apparatus (A) of the present invention. As shown in the figure, the reactor body (4) has three fixed-bed multitubular reactors (41, 42, 4).
3) is provided. Needless to say, the desired number of reactors may be provided (4
1, 42, 43 ... 4n, n is an arbitrary integer). In the fixed-bed multitubular reaction tube of the present invention, each reaction tube has, as a fixed bed, a supported catalyst in which the above-described metal halide main catalyst and / or cocatalyst is supported on a carrier such as activated carbon. Is. In addition, the end of each reaction tube is the mixing device.
(3) is connected in a desired manner.

FIG. 3 is a sectional view of the reaction tube (41). The reaction tube (41) includes a cylindrical body (411), both side plates (412), and a baffle plate (41) having small holes of a desired diameter.
3), and the carrier catalyst (C) is filled between the baffle plates. In addition, the cylindrical body (411), both side plates (41
2) and the baffle plate (413) may be made of casters, ceramics or special metals. In the fixed-bed multitubular reaction tube of the present invention, each reaction tube (41, 42 ...
It goes without saying that 4n) may be detachably arranged in the reactor main body (4) so that operations such as activation and reweighting of the catalyst can be carried out smoothly.
Needless to say, it may be arranged so as to be rotatable with respect to the reactor body (4).

The reactor body (4) of the present invention is provided with heating means (4A) and cooling means (4B) as shown in the figure in order to appropriately control the catalytic decomposition reaction of the aliphatic halide. To be done. As the heating means (4A),
FIG. 1 shows a combustion hot stove (4A1), a burner (4A2),
And a fuel (kerosene) tank (4A3). Needless to say, in the present invention, the heating means (4A) is not limited to the one described above, and may be a desired heating means such as electric heat or a heat medium.

As the cooling means (4B), as shown in FIG.
Shows that the air circulation using a fan (F) is used. The fan (F) has two functions. That is, as is clear from FIG. 1, (i) heat is supplied to the mixing device (3), the reactor body (4) itself, and a heat exchanger (6) described later in cooperation with the heating means (4A). The first function of supplying each of the reactors (4)
1 to 43) has a second function of cooling each reactor (41 to 43) by air cooling when the temperature rises above a desired set temperature. Needless to say, in the present invention, the above two functions may be performed by independent means.

In the present invention, the cooling means (4B)
Needless to say, the cooling means is not limited to the one described above and may be a desired cooling means. In the present invention, as shown in FIG. 1, it is preferable to provide a temperature sensor (T) for detecting the internal temperature of the reactor (41) to control the catalytic decomposition temperature. That is, the detected temperature from the temperature sensor (T) is compared with a predetermined control temperature, and the burner (4) constituting the heating means (4A) is formed.
It is preferable to provide a control mechanism (not shown) for operating or stopping the fan (F) that constitutes A2) or the cooling means (4B) to appropriately control the catalytic decomposition reaction of the aliphatic halide. is there.

Reference numeral (5) shows a decomposition product neutralization processing apparatus.
This device constitutes a part of a post-treatment device after the catalytic decomposition of freon. Hydrofluoric acid (HF), hydrochloric acid (HCl), etc. are produced by the catalytic decomposition of freon, but the neutralization treatment device (5) neutralizes and removes this with an alkaline aqueous solution such as caustic soda (NaOH). This is to prevent harm to the process. As shown in the figure, the neutralization treatment device (5) has a cold water unit (51) and a condenser (52) as auxiliary devices. Of these gas components discharged from the neutralization treatment device (5), particularly water vapor (H ₂ O) is harmful to the treatment of the activated carbon adsorption device (7) described later. Therefore, this is to be removed. Also,
For supplying water to the neutralization treatment device (5), maintaining a neutralization agent caustic soda (NaOH) solution at a predetermined temperature and concentration, and performing the neutralization treatment under certain conditions. But also. In the figure, (pH) indicates a pH (pH) measuring device.

(6) shows a heat exchanger. After the catalytic decomposition of CFCs, the decomposition products (gas) that have passed through the neutralization treatment device (5) are mainly methyl chloride, methanol, CO,
The heat exchanger (6) which uses CO ₂ , H ₂ O or the like but uses waste heat is for drying these products. The drying step in the heat exchanger (6) is important for facilitating adsorption recovery of the product in the next step.

(7) shows an activated carbon adsorption device. Among the dry decomposition products introduced via the heat exchanger (6), mainly methyl chloride gas and methanol gas are absorbed and captured by the activated carbon absorption device (7) and recovered.
The exhaust gas discharged from the activated carbon adsorption device (7) is a gas component that is not absorbed by the activated carbon, and is mainly C
It consists of O ₂ and CO. These exhaust gases are used as fuel for burners, or after being subjected to treatments such as filtration, they are discharged into the atmosphere.

FIG. 4 shows a multi-tube catalytic cracking apparatus (A) for aliphatic halides according to the present invention designed to be mobile. Specifically, the multi-tube catalytic cracking device (A) of the present invention
Is mounted on a truck (4.5-ton vehicle) and systematized so as to satisfy the height limit. That is, (B) in the figure means a truck carrier flat plate, and the size thereof should be understood to be approximately (vertical (1750 mm) × horizontal (4300 mm)). The multi-tube catalytic cracking device (A) designed for the mobile type (on-board type) is
In view of the current situation where CFCs or aliphatic halides such as trichlorethylene and tetrachloroethylene as cleaning agents are stored in factories and the treatment thereof is difficult,
It is a very preferred form. That is, it is possible to periodically visit these desired sites and efficiently process them with the on-board multi-tube catalytic cracking apparatus (A).

[0055]

EXAMPLES The present invention will be described in detail below with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 (1) Preparation of catalyst 0.025 mol of ferric fluoride was dissolved in 200 ml of dilute hydrochloric acid, and the columnar activated carbon (Wako Pure) having an average length of 7 mm and a particle size of 4 mm and a critical area of 1280 m ² / g was used. After immersing 20 g of (Medicinal product) at room temperature, it was heated to evaporate water and loaded on activated carbon. Further, 0.025 mol of cupric chloride was dissolved in 200 ml of water, and then activated carbon carrying ferric fluoride was re-immersed thereinto and heated again to evaporate water to prepare a catalyst. (2) Aliphatic Halide Decomposition Experiment A solid reaction tube was formed by filling the central part of a stainless steel tube having a total length of 40 cm and an inner diameter of 25 mm with the total amount of the above-mentioned catalyst,
Heated to a temperature of ° C. Next, dichlorodifluoromethane (hereinafter abbreviated as CFC-12) and methanol were fed into the reaction tube at a constant rate of 10 mol / h using a microfider so that the ratio was 1 mol to 4 mol, and the decomposition experiment was conducted. I did. The reaction gas goes through the Liebig cooling pipe,
The condensed liquid was collected by introducing into a trap of an ice-cooled bath, and its composition was quantified by gas chromatography using a packing material porapak by an internal standard method. Gas components that did not condense were analyzed by gas chromatography using activated carbon as a packing material. The decomposition rate of CFC-12 was determined over time (Fig. 5).
reference). (3) Catalyst system activation treatment When the decomposition rate (conversion rate) dropped from 100% to 80% (26 hours after the initiation of the decomposition reaction), CFC-12 was used.
The supply of alcohol was stopped, and air was supplied for 3 hours to activate the catalyst. Then, the CFC-12 decomposition experiment was continued under the activated catalyst system. At this time, it was confirmed that the decomposition rate, which had dropped to 80% before the stop, returned to 100% again (see FIG. 5).

Example 2 An experiment of catalytic cracking of CFC-12 was conducted for a total of 2 cycles (58 hours), with the process of Example 1 as one cycle. As a result, as shown in FIG. 5, during the activation treatment of the catalyst system, a high activity was achieved, that is, a high conversion rate (100%) of CFC-12 was achieved. This shows the superiority of the catalytic decomposition method of the aliphatic halide of the present invention,
This shows that the aliphatic halide can be rendered harmless in the long term and economically. The CFC-12 is shown in FIG.
The relationship between the decomposition rate (conversion rate) at 270 ° C. and 300 ° C. and the reaction time is shown. These have a decomposition temperature of 3
Although the decomposition rate (conversion rate of CFC-12) was lower than that at 30 ° C, the same tendency was exhibited.

[0058]

INDUSTRIAL APPLICABILITY According to the present invention, an aliphatic halide such as chlorofluorocarbon, which has become a pollution control problem, can be treated in the presence of an alcohol and / or ether in a specific highly active and persistent catalyst system. Thus, it can be rendered harmless and decomposed for a long period of time under extremely mild temperature conditions as compared with the conventional one. In addition, the detoxification and catalytic decomposition method of the aliphatic halide of the present invention should be carried out by constructing a decomposition device suitable for large-scale and large-scale treatment of aliphatic halide as well as small-scale and small-scale treatment. Therefore, it is an extremely versatile catalytic decomposition method. Furthermore, by selecting the reaction conditions, it is possible to recover useful compounds such as aliphatic monohalides from aliphatic halides. Therefore, the catalytic decomposition method of the present invention for aliphatic halides such as chlorofluorocarbon, which has been urgently addressed due to the problem of ozone layer depletion, is extremely useful as a technique for preventing air pollution.

[Brief description of drawings]

FIG. 1 is a partial schematic view of a multi-tube catalytic cracking device of the present invention.

FIG. 2 is a partial schematic view of the multitubular catalytic cracking apparatus of the present invention, showing the whole apparatus in combination with FIG.

FIG. 3 is a cross-sectional view of a reaction tube attached to the reactor body of the present invention.

FIG. 4 is a plan view of a multi-tube catalytic cracking device of the present invention which is mounted on a vehicle.

FIG. 5 is a graph showing the relationship between the decomposition rate and the reaction time of an aliphatic halide (CFC-12) at a predetermined temperature.

[Explanation of symbols]

 A ……… Multi-tube catalytic cracking device 1 ……… Freon supply device 2 ……… Alcohol supply device 3 ……… Mixing device 4 ……… Reactor body 4A ……… Heating means 4B ……… Cooling means 5 ……… Decomposition product neutralization treatment device 6 ………… Heat exchanger 7 ………… Activated carbon adsorption device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C07C 19/00 9546-4H

Claims (10)

[Claims] 1. A single-tube reaction tube or a multi-tube reaction tube that is heated by an external heating system is used, and the 2b group, 6a group, 7a group, and 8 group filled inside the reaction tube are used. In the presence of a lower alcohol and / or an ether, a main catalyst selected from metal halides and a cocatalyst selected from metal halides of groups 1a and 1b are supported on a desired carrier. In the catalytic decomposition method of an aliphatic halide in which an aliphatic halide is catalytically decomposed, (i) after catalytic decomposition for a desired time, supply of lower alcohol and / or ether and aliphatic halide to the reaction tube is stopped, ii) activating the supported catalyst inside the reaction tube in an oxidizing atmosphere, and (iii) then supplying lower alcohol and / or ether and an aliphatic halide to the reaction tube to bring the aliphatic halide into contact. A catalytic decomposition method of an aliphatic halide, characterized by continuing catalytic decomposition. 2. The method for catalytic decomposition of an aliphatic halide according to claim 1, wherein the main catalyst is an iron (Fe) halide. 3. The method for catalytic decomposition of an aliphatic halide according to claim 2, wherein the iron (Fe) halide is ferric chloride and / or ferric fluoride. 4. The method for catalytic decomposition of an aliphatic halide according to claim 1, wherein the cocatalyst is cupric chloride. 5. The method of catalytic decomposition of an aliphatic halide according to claim 1, wherein the carrier is selected from activated carbon, alumina and silica. 6. The method of catalytic decomposition of an aliphatic halide according to claim 1, wherein the activation treatment in an oxidizing atmosphere is air oxidation. 7. The method for catalytically decomposing an aliphatic halide according to claim 1, wherein the reaction tube is a single tube type. 8. The catalytic decomposition method of an aliphatic halide according to claim 1, wherein the reaction tube is constituted by a parallel multitubular type. 9. In the catalytic cracking method for aliphatic halides using parallel multitubular reaction tubes, the reaction tubes are divided into small sections, and after the catalytic cracking for a desired time, the supported catalysts of each section are sequentially loaded. The method for catalytically decomposing an aliphatic halide according to claim 8, wherein the catalyst is activated. 10. The aliphatic halide according to claim 9, wherein another section of the reaction tube continuously catalytically decomposes the aliphatic halide during the activation treatment of the supported catalyst in the predetermined section of the reaction tube. Catalytic decomposition method