JP3031508B2 - Reduction method of polychlorinated alkanes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing chlorine and carbon atoms.
Or only chlorine, hydrogen, and carbon.
Polychlorinated alkanes (hereinafter simply referred to as polychlorinated alkanes)
Hereinafter), for example, the global environment protection and carbon tetrachloride that is a restricted from the standpoint of the raw material, to a method of converting the hydrogen-containing chlorocarbons such as useful chloroform as a raw material of various fluorine compounds.

[0002]

2. Description of the Related Art Conventionally, carbon tetrachloride has been mainly used as a raw material for various fluorocarbons. However, the production of carbon tetrachloride as a raw material as well as these fluorocarbons is to be regulated. There is a widespread worldwide demand for a technology for decomposing and removing or converting it to a useful one.

[0003] On the other hand, hydrogen-containing chlorocarbons such as chloroform obtained by replacing chlorine atoms in carbon tetrachloride with hydrogen atoms are useful as raw materials for various chemical products. Therefore, there is a need for technology development for efficiently introducing hydrogen into polychlorinated alkanes such as carbon tetrachloride and converting the same to hydrogen-containing chlorocarbons.

Various methods are known for introducing hydrogen into carbon tetrachloride. The method of performing electrolytic reduction in the presence of a protic solvent has disadvantages such as a low reaction rate, and is difficult to employ industrially. The method of reducing with a base metal such as zinc has a high reaction rate, but has a problem in treating by-product metal chloride. On the other hand, the method of reducing hydrogen using a reducing catalyst such as JP-A-3-33939 has a high reaction rate,
In addition, by-product hydrogen chloride can be recovered and used, which is advantageous for industrial development. However, in the method of performing hydrogen reduction in the gas phase using a general-purpose reduction catalyst such as nickel or platinum, the catalyst is deactivated very rapidly, and a polymer having a high boiling point and a carbon number of 5 or more, particularly at high temperatures. However, there is a problem that the yield of the target product is not always high, such as by-products.

[0005]

SUMMARY OF THE INVENTION First, the present inventors have reduced the hydrogen content of polychlorocarbons in the liquid phase in the presence of a reduction catalyst, thereby eliminating short-term deterioration of the catalyst and containing the catalyst in high yield. It has been found that hydrogen chlorocarbons can be obtained. In such a liquid phase hydrogen reduction method, a liquid phase suspension bed system using a powdery catalyst such as a noble metal catalyst supporting activated carbon powder is advantageous in securing the reaction yield. However, in order to perform a continuous reaction, it is necessary to circulate a powdery catalyst,
Therefore, there are various problems to be overcome in industrialization, such as equipment investment and reduction of catalyst cost, such as the necessity of installing a catalyst separation system.

In the gas-phase hydrogen reduction of polychlorocarbons, heavy substances tend to be deposited on the catalyst due to strong interaction between the catalyst and the polychlorocarbons, and the catalytic activity is reduced in a very short time. In addition, it is difficult to obtain the target hydrogen-containing chlorocarbons in high yield. On the other hand, conducting the reaction in the liquid phase means that the adsorption of polychlorocarbons having a large adsorption energy can be controlled by the use of a reaction solvent and the like. It has an advantage that it can be easily dissolved and removed, and thus the decrease in active sites can be suppressed. In particular, in the suspension bed method, the catalyst and the reactants are easily stirred, and good reaction characteristics are easily achieved. For small-scale industrialization, a batch suspension bed system can be used.

However, in the suspension bed method, there is a loss due to abrasion of the catalyst due to agitation, and a system for separating and recycling the catalyst is necessary in order to continue the necessary reaction when the scale is increased. is there. Further, the catalyst used in the suspension bed method usually uses an extremely fine carrier of about several tens to 100 μm, and there are many problems associated with separation and recycling of the catalyst. For example, filter clogging measures,
There are many issues to be overcome, such as measures to reduce catalyst loss during recycling.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies on the optimization of a liquid-phase hydrogen reduction continuous reaction system, and have found that at least one element selected from Group 8, Group 9, and Group 10 elements can be obtained. The present inventors have found that polychlorocarbons can be converted to hydrogen-containing chlorocarbons with hydrogen at a very efficient and low cost by using a reduction catalyst as a main component in a fixed bed system, and the present invention has been completed. It is.

Thus, the present invention provides a method for reducing polychlorinated alkanes, which comprises reducing polychlorinated alkanes with hydrogen in the liquid phase in the presence of a fixed-bed reduction catalyst.

According to the present invention, at least one element selected from Group 8 element, Group 9 element and Group 10 element, in particular, a platinum group element such as ruthenium, rhodium, palladium, platinum and the like, which is excellent in acid resistance and highly active, is used as a main component. Hydrogen reduction of polychlorocarbons in the liquid phase by using a reduction catalyst containing as a fixed bed with hydrogen can eliminate short-term deterioration of the catalyst and efficiently produce hydrogen-containing chlorocarbons in high yield. .

In the present invention, it is important to use the reduction catalyst in a fixed bed system. The fixed bed system can be operated with a reaction system having a relatively simple structure, and can efficiently distribute polychlorinated alkanes such as raw material carbon tetrachloride and disperse hydrogen. In addition, by optimizing the reaction apparatus, reaction conditions and catalyst, hydrogen-containing chlorocarbons such as chloroform, methylene chloride, and methyl chloride can be obtained with a high yield equivalent to or higher than that of the suspension bed method. is there. This is because, when hydrogen reduction is performed in the liquid phase, if the diffusion of hydrogen in the liquid is rate-limiting, the reduction in hydrogen concentration on the catalyst surface may lead to a reduction in reaction rate and a decrease in selectivity. By determining the reaction conditions while paying attention to the above, good reaction results can be obtained. In particular, in a dropping bed system in which a raw material is supplied in a downflow manner, the liquid phase diffusion distance of hydrogen is short and a decrease in the hydrogen concentration on the catalyst surface is easily suppressed, which is advantageous in improving the reaction rate and the catalyst durability. .

Hereinafter, the present invention will be described in detail with examples.

In the present invention, examples of polychlorinated alkanes include, for example, carbon tetrachloride, chloroform, methylene chloride, hexachloroethane, and dichloropropane. Specifically, chloroform, chloride, and the like are obtained by reduction of carbon tetrachloride. Methylene, methyl chloride, methylene chloride and methyl chloride by reduction of chloroform, further, methyl chloride by reduction of methylene chloride, tetrachloroethylene and the like by reduction of hexachloroethane,
Propylene and the like can be obtained by reduction of dichloropropane. Further, polychlorinated alkanes having 4 or more carbon atoms may be used.

In the present invention, groups 8, 9 and 10
A reduction catalyst containing at least one element selected from group elements as a main component can be used. In particular, in the reaction of the present invention, since hydrogen chloride is generated as a by-product, it is preferable to contain a platinum group element having a high reduction activity such as ruthenium, rhodium, palladium, and platinum in order to obtain durability of the catalyst. . These main component elements may be used alone or in combination of two or more.

The reduction catalyst of the present invention contains, as an essential component, the main elements of Groups 8 to 10, but may further contain other elements other than these essential components as long as the catalytic performance is not impaired. . For example, as an additive component, copper, silver,
Group 11 elements such as gold may be exemplified. One or more of these additional component elements can be used. When additional components are used in combination, the amount of addition is 0.1.
The content is preferably from 01 to 50% by weight, preferably from 0.1 to 50% by weight, particularly preferably from 1 to 50% by weight.

For use in a fixed bed, these catalysts are preferably supported on a carrier. As the carrier, those commonly used, such as activated carbon, alumina, zirconia, and silica, can be used. The carrier must have such strength that it does not become powdered by the flow of the liquid. The shape of the carrier is preferably in the form of pellets that are not easily affected by abrasion loss because the catalyst is easily vibrated, especially when the liquid is circulated in the upflow.However, in the case of the dropping bed method, crushed charcoal can be used, There is no particular limitation. An appropriate size is about 0.5 mm to 20 mm. Further, the loading amount is 0.01 to 2
0% by weight, preferably about 0.1 to 5% by weight, is suitable in terms of catalyst loading efficiency, reaction activity, dispersion of catalyst components, catalyst production cost, and the like.

The method for preparing the catalyst is not particularly limited. Conventional methods such as an impregnation method, a coprecipitation method and a kneading method can be applied.
The method for supporting the catalyst component and the like can also be appropriately selected from the range usually employed. For example, a method in which a simple salt or a complex salt of the above element is used and supported by an impregnation method, an ion exchange method, or the like can be applied.

Further, when using the catalyst, it is not always necessary to carry out a reduction treatment of the catalyst, but it is desirable to carry out a hydrogen reduction in advance to obtain stable characteristics.
As a method for reducing the supported catalyst component, a method of reducing in a liquid phase with hydrogen, hydrazine, formaldehyde, sodium borohydride, a borane dimethylamine complex salt, and a method of reducing in a gas phase with hydrogen can be applied.

The use of a reaction solvent is effective for controlling the product ratio and stabilizing the reaction activity, and can be carried out as appropriate. For example, alcohols such as methanol and ethanol, amines such as triethylamine, carboxylic acids such as acetic acid, and ketones such as acetone can be used as a reaction solvent.

The temperature of the reduction reaction can be appropriately selected from a wide range of about 0 ° C. to 300 ° C., but in a preferable liquid phase reaction, it is particularly preferable to select about 50 ° C. to 250 ° C.

The supply molar ratio of hydrogen to polychlorinated alkanes is not particularly limited. Increasing the amount of hydrogen increases the reaction rate,
Although it is advantageous in terms of the life of the catalyst, etc., the rate of formation of more dechlorinated / hydrogenated products increases. Although 50 mol or more of hydrogen can be used per 1 mol of the polychlorinated alkanes, it is usually preferable to supply about 1 to 20 mol of hydrogen to 1 mol of the polychlorinated alkanes. Excess hydrogen can be recycled to increase the utilization of hydrogen.

The reaction pressure is suitably normal pressure or higher.
Increasing the pressure increases the reaction rate. Usually several kg /
pressure up to cm ² G~10kg / cm ² of about G can be employed. If the reaction pressure is too high, difficulties such as an increase in the cost of the apparatus will be recognized even if the reaction rate increases.

[0023]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

Example 1 4 liters of a 3 mm-diameter platinum catalyst supported on molded charcoal (supporting amount: 2% by weight, manufactured by NE Chemcat Co.)
mm cylindrical reactor. After filling the catalyst layer with carbon tetrachloride, nitrogen was sealed. After the temperature was raised to 80 ° C., the supply of hydrogen was started. The reaction was continued by continuously supplying 3 moles of hydrogen to 1 mole of carbon tetrachloride in an upflow manner. The gaseous components such as chloroform generated were continuously taken out by a gas-liquid separator, and the unreacted liquid components such as carbon tetrachloride were returned to the reactor and recycled. The pressure is 5kg / cm
Was ² G. For the product, gas phase component, liquid phase component,
All were analyzed using gas chromatography. 100 hours after the start of the reaction, the reaction rate of carbon tetrachloride in one pass was 91%, and chloroform (selectivity:
90%) and perchlorethylene (selectivity: 5%).

Example 2 An experiment was carried out in the same manner as in Example 1 except that a palladium catalyst supported on molded charcoal having a diameter of 5 mm (loading amount: 2% by weight, manufactured by NE Chemcat) was used as a catalyst. Analysis was carried out. 100 hours after the start of the reaction, the conversion of carbon tetrachloride in one pass was 92%, and chloroform (selectivity: 85%) and perchlorethylene (selectivity: 10).
%), Methane (selectivity: 5%) and the like were confirmed.

Example 3 As a catalyst, a platinum-supported platinum catalyst having a diameter of 1 mm (amount supported: 2)
1 liter (weight%, manufactured by NE Chemcat) was charged into a cylindrical reactor having an inner diameter of 30 mm. After filling with nitrogen, the temperature was raised to 80 ° C. After the catalyst was sufficiently reduced with hydrogen, hydrogen and carbon tetrachloride were supplied in a down flow at a molar ratio of 5: 1. The product was analyzed using gas chromatography for both the gas phase component and the liquid phase component. 100 hours after the start of the reaction, the conversion of carbon tetrachloride was 94%, and formation of chloroform (selectivity: 90%), perchloroethylene (selectivity: 5%), and the like was confirmed.

Example 4 As a catalyst, a platinum catalyst supported on molded charcoal having a diameter of 1 mm (amount supported: 2)
1 liter (weight%, manufactured by NE Chemcat) was charged into a cylindrical reactor having an inner diameter of 30 mm. After filling with nitrogen, the temperature was raised to 90 ° C. After the catalyst was sufficiently reduced with hydrogen, hydrogen, hexachloroethane and chloroform were supplied in a down flow at a molar ratio of 5: 1: 1. Regarding the product, both the gas phase component and the liquid phase component were analyzed using gas chromatography. 100 hours after the start of the reaction, the conversion of hexachloroethane was 81%, and formation of perchlorethylene (selectivity: 95%), pentachloroethane (selectivity: 1%) and the like was confirmed.

Example 5 As a catalyst, 1 liter of a formed palladium catalyst supported on charcoal having a diameter of 1 mm (loading amount: 2% by weight, manufactured by NE Chemcat) was charged into a cylindrical reactor having an inner diameter of 30 mm. After filling with nitrogen, the temperature was raised to 95 ° C. After the catalyst was sufficiently reduced with hydrogen, hydrogen and dichloropropane were supplied in a down flow at a molar ratio of 2: 1. The pressure was 10 kg / cm ² G. Regarding the product, both the gas phase component and the liquid phase component were analyzed using gas chromatography. 100 hours after the start of the reaction, the conversion of dichloropropane was 81%, and production of propylene (selectivity: 80%), propane (selectivity: 20%) and the like was confirmed.

[0029]

As shown in the examples, the present invention reduces hydrogenated chlorocarbons in a high yield by reducing polychlorinated alkanes with hydrogen in the liquid phase in the presence of a fixed bed catalyst. This has the effect of being able to be manufactured with. Further, the method of the present invention has an effect that even if the reaction rate of the raw material polychlorinated alkanes is increased, the target hydrogen-containing chlorocarbons can be obtained with a high selectivity. Furthermore, in the present invention, since a side reaction that generates impurities that impair the catalytic activity can be effectively suppressed, it is extremely advantageous from the viewpoint of catalyst life. Furthermore, the method of the present invention is extremely advantageous as a continuous process, and particularly suitable as an industrial-scale continuous process.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B01J 23/46 311 B01J 23/46 311X C07C 11/06 C07C 11/06 (72) Inventor Yu Yoshitake Hazawa, Kanagawa-ku, Kanagawa-ku, Kanagawa Prefecture 1150, Asahi Glass Co., Ltd., Central Research Laboratory (72) Inventor Shin Tachimatsu 1150, Hazawacho, Kanagawa-ku, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd., Central Research Laboratory (56) JP-A-3-133939 (JP, A) Table 4 JP-A-4-504728 (JP, A) US Patent 3,579,596 (US, A)

Claims (4)

(57) [Claims] (1) chlorine atom in a liquid phase in the presence of a fixed bed reduction catalyst ;
And carbon and only or chlorine and hydrogen and carbon
A method for reducing polychlorinated alkanes, which comprises reducing hydrogenated polychlorinated alkanes consisting only of : 2. A group reduction catalyst 8, Group 9 and at least one method of reducing claim 1, wherein the element is a catalyst mainly composed of selected from Group 10 elements. 3. The method according to claim 1, wherein the main component element in the reduction catalyst is ruthenium,
Rhodium, at least one method of reducing claim 1 or 2, wherein the platinum group element selected from palladium and platinum. 4. A method of reducing claim 1, wherein the reduction temperature is 0 ° C. to 300 ° C..