JPH0473419B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing dichloroethane by reacting ethylene and chlorine in a liquid reaction medium mainly composed of dichloroethane. This method has been improved to suppress the side reaction of producing 2-trichloroethane and to industrially advantageously produce dichloroethane. (Prior Art and Problems) Ethane dichloride is industrially important as a raw material for vinyl chloride, and is mass-produced by reacting ethylene and chlorine in a liquid phase. There are two methods for carrying out this reaction industrially: a low-temperature method in which the reaction is carried out at 40°C to 60°C, and a high-temperature method in which the reaction is carried out at a temperature above the boiling point of ethane dichloride at normal pressure. Among these methods, the high temperature method can effectively utilize a large amount of reaction heat of about 50 Kcal/mol generated by this reaction, and if the reaction heat is removed by the latent heat of vaporization of the reaction medium, special cooling means are not required. It has many advantages, such as not requiring the use of ferric chloride and the ease of separating the catalysts normally used in this reaction, such as ferric chloride.
No. 2929852 and others show how to implement it. One drawback of the high-temperature method, which has these advantages, is that the amount of side reaction products such as 1,1,2-trichloroethane increases compared to the low-temperature method, making it difficult to obtain the desired selectivity and yield of dichlorethane. This means that the rate will decrease. Conventionally, methods proposed to suppress the side reaction of producing 1,1,2-trichloroethane in high-temperature processes include, for example, JP-A-48-57906, which involves high-temperature reaction with a large excess of ethylene and conversion of the excess ethylene. In addition to the two-step reaction method that combines low-temperature reactions, there is also a method of adding additives to chemically suppress side reactions. 58−50203
In this issue, a method using benzenes is shown. (Means for Solving the Problems) The present inventors have made extensive studies aimed at chemically suppressing the side reaction of producing 1,1,2-trichloroethane in the liquid phase reaction between ethylene and chlorine. The present invention was completed by discovering that a side reaction suppressing effect can be obtained when a specified amount or more of a chlorinated aliphatic unsaturated hydrocarbon shown below is present in a liquid reaction medium. That is, the present invention provides a method for producing dichloride ethane by reacting ethylene and chlorine in a liquid reaction medium containing dichloride ethane as a main component.

This is a method for producing ethane dichloride, characterized in that at least 0.003 wt% (30 ppm) of a chlorinated aliphatic unsaturated hydrocarbon represented by the formula is present in a liquid reaction medium. The details will be explained below. The present invention normally uses a metal chloride such as ferric chloride as a catalyst and uses the general formula

Ethylene and chlorine are reacted in a dichloroethane solution in the presence of a chlorinated aliphatic unsaturated hydrocarbon represented by the formula. Examples of chlorinated aliphatic unsaturated hydrocarbons include tetrachlorethylene as the substance where n=1 in the above general formula, or hexachlor 1 as the substance where n=2,
3-Butadiene etc. can be used, and the amount in the reaction medium is 0.001 wt% or more, preferably 0.005 wt%.
It is present in a range of 0.1wt%. At 0.001wt% or less, the effect of the present invention is not achieved, and at 0.05wt% or more, the effect remains the same even if the concentration increases.
Practically speaking, it is preferable to use up to about 0.1 wt%. Tetrachlorethylene or hexachlor
The concentration of 1,3-butadiene can be measured using gas chromatography, etc., so if necessary, analyze the concentration in the reaction medium, and if it is insufficient, add it externally to find the desired concentration. can be kept. In the case where these additive substances are discharged from the system together with the produced dichloride ethane, they can be added continuously. or,
When a small amount of these chlorinated aliphatic unsaturated hydrocarbons is produced as a reaction product, this product can be concentrated to reach a desired concentration to achieve the objective. Furthermore, both concentration and addition can also be used together. The reaction temperature can range from 40℃ to 180℃, but if the reaction is carried out under the boiling conditions of ethane dichloride, the reaction heat can be removed by vaporizing the reaction medium and the reaction heat can be used effectively. It is usually preferable to select a temperature in the range of 90°C to 160°C, because it is possible and because if the reaction temperature is too high, by-products will increase and the reactor pressure will increase. The amounts of ethylene and chlorine supplied are usually approximately equal stoichiometrically, but an excess of ethylene or a small excess of chlorine may be used, and in the case of a high temperature reaction, it is preferred that ethylene:chlorine = 1.001 to 1.20.
The chlorine to be supplied can normally be obtained by electrolysis of common salt, and can contain impurities such as oxygen. The amount of oxygen contained in chlorine can usually be about 0.1 to 5.0 mol%. The reactor can be of a tank type, tower type, circulation type, etc., and iron can also be used as the material, but it is preferable to use a stainless steel type reactor since iron is particularly susceptible to corrosion at high temperatures. Ethane dichloride produced by the reaction is taken out from the reactor and, if necessary, purified by being introduced into a step to remove ferric chloride and a distillation step. If a method is used in which the produced ethane dichloride is extracted as vapor, the step of separating and removing ferric chloride can be omitted. By connecting a distillation column to the upper part of the reactor and distilling the dichloroethane generated by the reaction heat, purified dichloride ethane can be obtained. In order to concentrate the desired chloride in the reaction medium, for example, a gas-liquid contact tower is installed in the upper part of the reactor, and the liquid reaction is carried out by bringing the reaction medium vapor generated by the reaction heat into contact with its condensate. A method can be used in which a chlorinated aliphatic hydrocarbon having the effect of suppressing side reactions is concentrated and maintained in the medium. As the gas-liquid contact tower, a normal multi-stage tower, packed tower, etc. can be used. When a gas-liquid contact tower is not used, side reaction inhibiting substances are discharged together with the reaction medium, but in large quantities. In addition, when dichloroethane is purified by distillation in a gas-liquid contact tower connected to the top of the reactor, side reaction inhibiting substances are also discharged as a liquid containing concentrated high-boiling impurities is extracted from near the bottom of the tower. So I don't like it. The present inventors have discovered that among the side reaction inhibiting substances used in the present invention, hexachloro-1,3-butadiene is produced in minute amounts in the reactor. Therefore, if a method of connecting a gas-liquid contact tower to the upper part of the reactor and concentrating hexachloro-1,3-butadiene in the reaction liquid according to a preferred embodiment of the present invention is used, it is possible to specifically eliminate side reaction inhibiting substances. Even without addition, the concentration of hexachloro-1,3-butadiene in the reaction solution can be maintained at a preferable level. When purifying ethane dichloride produced by the reaction, it is usually first fed to a distillation column that removes low-boiling point impurities, and then fed to a distillation column that removes high-boiling point impurities to obtain highly pure dichloride. Ethane can be obtained. In order to effectively utilize the reaction heat, a method can be used in which latent heat during condensation and liquefaction of the reaction medium vapor is recovered using a heat exchanger or the like. (Effects of the Invention) As described above, according to the present invention, an effective amount of a chlorinated aliphatic unsaturated hydrocarbon such as hexachloro-1,3-butadiene or tetrachlorethylene is present as a side reaction inhibitor. 1,1,2 by reacting ethylene and chlorine in a liquid reaction medium mainly composed of ethane dichloride.
- The amount of side reaction products such as trichloroethane can be significantly suppressed, making it possible to produce dichloroethane in high yield even in high-temperature reactions. The effect is that it enables industrial implementation of high-temperature reactions that have many advantages in terms of purification and the like. (Example) Examples and comparative examples will be given and explained in detail below. Example 1 Ethane dichloride solution was charged into a stainless steel reactor A with a tower diameter of 20 cm as shown in the attached drawing (Figure 1) to a liquid level height of 6 m, and anhydrous ferric chloride was added until the dissolved concentration was approximately 500 wtppm. I made it so that Add hexachlor-1,3-butadiene to increase the dissolved concentration.
It was set to 200wtppm. Ethylene (1) and chlorine (2) were each supplied from near the bottom of the reactor at a flow rate of 40 Nm ³ /hr. Chlorine contained approximately 1.5 mol% oxygen. When the pressure at the top of the reactor was maintained at about 29 Kg/cm ² G, the reaction temperature was about 135° C., and the reactor could be operated with the reaction medium boiling. Ethane dichloride vapor vaporized by the reaction heat is extracted from the top of the reactor tower, condensed and liquefied in heat exchanger B, guided to receiver C, and refluxed to maintain the reactor liquid level (3). The remainder was taken out as product (4). Approximately 50 hours after the start of the reaction, a sufficiently steady state was achieved, and the product, ethane dichloride, was collected and analyzed by gas chromatography, and it was found to be the following side reaction product. 1,1,2-trichloroethane 0.36wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.04 〃 Others 0.06 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.61% based on ethylene. It was hot. Comparative Example 1 The same procedure as in Example 1 was carried out except that hexachloro-1,3-butadiene was not added at all.
Approximately 50 hours after the start of the reaction, the liquid in the reactor was collected and analyzed by gas chromatography, and no hexachloro-1,3-butadiene was detected. The product ethane dichloride at this time was collected and analyzed by gas chromatography, and it was found to be the following side reaction product. 1,1,2-trichloroethane 0.96wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.01 〃 Others 0.10 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.11% based on ethylene. It was hot. Example 2 Hexachloro-1,3-butadiene was not added at all, but tetrachlorethylene was added so that the dissolved concentration was 300 wtppm. The reactor top pressure was about 2.7 Kg/cm ² G, and the reaction temperature was about 130°C. The rest was the same as in Example 1. Approximately 50 hours after the start of the reaction, the product ethane dichloride was analyzed and found to be the following side reaction product. 1,1,2-trichloroethane 0.25wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.02 〃 Others 0.03 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.74% based on ethylene. It was hot. Comparative Example 2 The same procedure as in Example 2 was carried out except that no tetrachlorethylene was added. About 50 hours after the start of the reaction, the dichloroethane product was analyzed and the following side reaction products were found. 1,1,2-trichloroethane 0.87wt% Ethylene chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.09 〃 Others 0.11 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.16% based on ethylene. It was hot. Example 3 Hexachloro-1,3-butadiene was added to make the dissolved concentration 60 wtppm, the reactor top pressure was 1.8 Kg/cm ² G, the temperature was 120°C, and the rest was carried out in the same manner as in Example 1. Ivy. About 50 hours after the start of the reaction, the product ethane dichloride was analyzed and the side reaction products were as follows. 1,1,2-trichloroethane 0.19wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.02 〃 Others 0.03 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.79% based on ethylene. It was hot. Comparative Example 3 The same procedure as in Example 3 was carried out except that hexachloro-1,3-butadiene was not added at all. About 50 hours after the start of the reaction, the dichloroethane product was analyzed and the side reaction products were as follows. 1,1,2-trichloroethane 0.68wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.08 〃 Other 0.10 〃 At this time, the reaction selectivity to dichloroethane was approximately 99.31% based on ethylene. It was hot. Example 4 Ethane dichloride solution was placed in a stainless steel reactor having a circulation shell as shown in the attached Figure 2, and anhydrous ferric chloride was added to the reactor to give a dissolved concentration of 60 wtppm. Ethylene and chlorine are each introduced from near the bottom of the reactor.
The reaction was carried out by supplying 50Nm ³ /hr. Chlorine contains approx.
It contained 1.0 mol% oxygen. The reaction temperature is 135
The reaction medium vapor generated by the heat of reaction was introduced into a gas-liquid contact column connected to the top of the reactor, and the top vapor was brought into continuous countercurrent contact with the condensed reflux liquid. Non-condensable components in the condenser at the top of the gas-liquid contact column were discharged as exhaust gas. Ethane dichloride produced by the reaction was continuously extracted from the middle of the gas-liquid contact tower. The reaction solution was not withdrawn. After starting the reaction and operating it continuously for 10 days, the impurity composition in the reactor and in the produced dichloroethane became constant, and when the reaction solution was sampled and analyzed by gas chromatography, the dissolved concentration was approximately
250 wtppm of hexachloro-1,3-butadiene was detected. By-products in the liquid extracted as dichloroethane produced at this time were 1,1,2-trichloroethane 0.39wt% ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane 0.05 〃 Hexachlor-1, 3-Butadiene 0.0002 Others 0.05 At this time, the reaction selectivity to dichloroethane was about 99.60% based on ethylene. Comparative Example 4 The reaction was carried out in the same manner as in Example 4, except that the reaction solution was continuously withdrawn in order to purify the produced dichloride ethane by distillation to obtain highly pure dichloride ethane. The amount of reaction liquid withdrawn was about 20 kg/hr, which was about 10% of the amount of dichloroethane produced. The amount of dichloroethane obtained by distillation purification was approximately 200 kg/hr. still,
Since dissolved ferric chloride was carried out by withdrawing the reaction solution, anhydrous ferric chloride corresponding to the dissolved ferric chloride was added to maintain a constant concentration. After the reaction was started in this manner, the reactor was operated continuously for 10 days, and the concentration of byproducts concentrated in the liquid taken out from the reactor was analyzed, and the results were as follows. 1,1,2-trichloroethane 8.29wt% Ethyl chloride 0.005 〃 1,1,2,2-tetrachloroethane 2.31 〃 Hexachloro-1,3-butadiene 0.002 〃 Others 1.56 〃 Ethane dichloride obtained by distillation purification The impurity concentration inside was as follows. 1,1,2-trichloroethane 0.01wt% Ethyl chloride 0.02 〃 1,1,2,2-tetrachloroethane
0.001 〃 Hexachloro-1,3-butadiene Not detected Others 0.04wt% Therefore, when calculating the reaction selectivity to ethane dichloride based on the total amount of by-products, it is approximately
It is 99.10%.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams for explaining the apparatus used in the examples. A...reactor, B...condenser, C...tank,
D... Gas-liquid contact tower, 1-14... Conduit.

Claims (1)

[Scope of Claims] 1. In producing dichloroethane by reacting ethylene and chlorine in a liquid reaction medium containing dichloride ethane as a main component, an aliphatic unsaturated hydrocarbon represented by the general formula [formula] A method for producing ethane dichloride, characterized in that a chloride is present in a liquid reaction medium at least 0.003 wt% (30 ppm). 2. As a chlorinated product of unsaturated aliphatic hydrocarbons, tetrachlorethylene or hexachlor-1,
The method according to claim 1, using 3-butadiene or a mixture thereof. 3. The method according to claim 1 or 2, wherein the chlorinated aliphatic unsaturated hydrocarbon is added externally into the liquid reaction medium. 4. By concentrating the chlorinated aliphatic hydrocarbons in the reaction by-products into the liquid reaction medium.
The method according to claim 1 or 3, which achieves a content of 0.003 wt% or more. 5. The method according to claim 4, wherein the concentration is carried out using a gas-liquid contact tower connected to the upper part of the reactor.