JPH0128007B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for producing 1,2-dichloroethane by subjecting ethylene and chlorine to a high temperature reaction in a liquid phase in a reaction medium containing 1,2-dichloroethane as a main component. The present invention relates to an industrially advantageous method for producing 1,2-dichloroethane by suppressing the side reaction of producing 2-trichloroethane. 65-160°C in the presence of a metal chloride catalyst in a reaction medium based on 1,2-dichloroethane.
A high temperature method for producing 1,2-dichloroethane through a liquid phase reaction of ethylene and chlorine at a temperature of ，
2-dichloroethane can be taken out as a vapor, and in that case, the reaction zone can be effectively cooled by the latent heat of vaporization of 1,2-dichloroethane, so there is an advantage that special reaction zone cooling means can be omitted. It will be done. Not only that, but also the evaporated 1,2
-If dichloroethane is directly supplied as vapor to a rectification column for purifying 1,2-dichloroethane, the heat source for rectifying the product can be saved, which is a win-win situation. In recent years, such high-temperature methods have attracted attention due to energy-saving issues. However, although such high-temperature methods have the above-mentioned characteristics, the reaction temperature is 60°C or higher, especially when the boiling point of 1,2-dichloroethane as the reaction medium ( When the temperature reaches 83℃ or higher, 1,
1,2-trichloroethane production side reaction increases,
There was a fundamental drawback that the selectivity of the target 1,2-dichloroethane decreased and the yield decreased. Conventionally, methods for improving the drawbacks of such high temperature methods have also been proposed. For example, UK patent
1186742 uses oxygen as a side reaction inhibitor,
A method is shown in which a small amount of oxygen is added to the reaction mixture to suppress the formation of 1,1,2-trichloroethane. However, although this method has the effect of suppressing side reaction products, when the produced 1,2-dichloroethane is distilled from the top of the column and obtained by condensation and liquefaction, the uncondensed gas separated from the condensate is It contains unreacted ethylene and oxygen, and this ethylene and oxygen may form an explosive mixture, and treatment is required to prevent this. In addition, U.S. Patent No. 3911036 adopts a two-step reaction method,
In the first stage, about 17% conversion is carried out at a high temperature, and then in the second stage, the remaining conversion is carried out at a low temperature to suppress the formation of side reaction products. However, such a two-stage reaction method has a fatal drawback that the process is complicated. The present inventor conducted various studies on the liquid phase reaction between ethylene and chlorine, particularly on suppressing the side reaction of producing 1,1,2-trichloroethane in the high-temperature liquid phase reaction. It has been discovered that this objective can be achieved by allowing benzene and/or a chlorinated product of benzene to exist in a specified amount or more as a side reaction inhibitor (Japanese Patent Application No. 81,486/1986). Further, as a result of various studies on the side reaction inhibitor, the present inventor learned that a specific aromatic compound has an effect similar to that of benzene, and thus arrived at the present invention. That is, the present invention involves a liquid phase reaction of ethylene and chlorine at a reaction temperature of 65 to 160°C in a reaction medium containing 1,2-dichloroethane as a main component in the presence of a metal chloride catalyst to produce 1,2-dichloroethane. - In the method for producing dichloroethane, the general formula (In the formula, R ₁ is an alkyl group having 1 to 5 carbon atoms, R ₂
and R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. ) 1,2- characterized in that at least one aromatic compound selected from the group consisting of alkylbenzene hydrocarbons and chlorinated products thereof is present in the liquid phase in an amount of 0.001% by weight or more based on the liquid phase. The present invention provides a method for producing dichloroethane. The present invention generally comprises a reactor containing effective amounts of a metal chloride catalyst and the above-mentioned side reaction inhibitor,
It is carried out by continuously introducing ethylene and chlorine into a 2-dichloroethane reaction medium and carrying out a continuous reaction at a temperature of 65 to 160°C. In the present invention, the reaction medium present in at least the upper liquid level layer of the reaction medium (i.e., the produced 1,2-dichloroethane) is boiled by the heat of reaction between ethylene and chlorine, but the reaction medium in the raw material introduction region is boiled. The medium may be boiling or may be maintained below the boiling temperature under the conditions. The latter is more preferable than the former because it can prevent the raw material inlet from being blocked due to adhesion of the metal chloride catalyst. The reaction medium in the introduction area can be easily cooled by slightly cooling the bottom of the reactor, or by withdrawing the reaction medium from near the liquid surface and circulating it in a loop at the bottom of the reactor. I can do it. In the present invention, the amounts of ethylene and chlorine blown into the reactor are normally determined by the superficial gas velocity of the reactor.
100~10000m/Hr, preferably 500~5000m/Hr
Hr range. The molar ratio of ethylene and chlorine is usually 0.9 to 1.3, preferably 1.00.
~1.10. Generally, it is desirable to carry out the reaction with an excess of ethylene; in this case, the conversion rate of chlorine is
It will be close to 100%. However, the reaction can also be carried out with excess chlorine, in which case the ethylene conversion rate will be close to 100%. The pressure inside the reactor in the present invention is usually in the range of reduced pressure to 20 kg/cm ² G, preferably normal pressure to 5 kg/cm ² G. In addition, the reaction temperature is the temperature at which the upper liquid level layer of the reaction medium boils under the pressure inside the reactor, and the temperature is usually 65-160℃, preferably 70-160℃.
It is in the range of 150℃. When the reaction temperature is below 65℃,
The amount of 1,1,2-trichloroethane produced is extremely small, so there is no need to add a side reaction inhibitor, and at temperatures above 160°C, the amount of 1,1,2-trichloroethane produced increases significantly, causing side reactions. This is not economical because the amount of inhibitor added increases. In the high temperature method in which the reaction is carried out at a temperature of 65 to 160°C and the upper liquid level layer of the reaction medium is boiled as in the present invention, the reaction zone can be effectively cooled by the latent heat of vaporization of the reaction medium, and the reaction zone The advantage is that no special cooling means are required to cool the . In this high temperature method, if the reaction product 1,2-dichloroethane is supplied to the 1,2-dichloroethane rectification column with all or part of the top steam of the reactor kept as vapor, the reaction heat produced can be used for rectification. It can be used as a heat source, making it extremely advantageous industrially. As the metal chloride catalyst present in the reaction medium in the present invention, metal chloride catalysts generally known in this reaction can be used. For example, ferric chloride, aluminum chloride, antimony chloride, copper chloride, etc. can be used. A preferred metal chloride catalyst is ferric chloride. The amount of metal chloride catalyst used is usually 10 to 10% as the catalyst concentration in the liquid phase of the reaction zone.
6000ppm (weight), preferably 30-2000ppm (weight)
It is. If the main body of the reactor or other container is made of mild steel, ferric chloride will naturally elute and the above catalyst concentration can be easily obtained, so there is no need to specially supply a metal chloride as a catalyst. Too high a catalyst concentration is undesirable because it causes troubles such as clogging of the apparatus due to precipitation of metal chlorides. In the present invention, the general formula (In the formula, R ₁ is an alkyl group having 1 to 5 carbon atoms, R ₂
Alternatively, R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. ) At least one aromatic compound selected from the group consisting of alkylbenzene hydrocarbons and their chlorinated products is present, and this point is the most distinctive feature of the present invention. It is something. The presence of an effective amount of such a side reaction inhibitor makes the production of 1,1,2-trichloroethane extremely effective despite the use of high temperature reaction conditions where the reaction medium, 1,2-dichloroethane, boils. This results in excellent effects that enable industrial implementation of the high temperature method with the advantages described above. Specific compounds represented by the above general formula used in the present invention include, for example, toluene, xylene, ethylbenzene, ethyltoluene, mesitylene, n-butylbenzene, alkylbenzene hydrocarbons such as cumene, and benzyl chloride. Chlorinated products of the above-mentioned alkylbenzene hydrocarbons can be mentioned. These aromatic compounds may be used alone or as a mixture thereof. For example, when toluene is used as a side reaction inhibitor and is supplied into the reactor, the toluene quickly converts to toluene monochloride in the reactor, and then sequentially to toluene dichloride, toluene trichloride, and toluene tetrachloride. and converted to toluene pentachloride. Therefore, when toluene is fed into the reactor little by little and reacted, the various chlorinated products of toluene described above are present in significantly larger amounts than toluene in the liquid phase of the reaction zone. Therefore, each of these chlorinated compounds also exhibits side reaction suppressing effects in the same way as toluene. Therefore, the side reaction inhibitor supplied to the reactor is not limited to toluene alone, and may be one or more of these various chlorinated toluenes. The aromatic compounds used industrially are preferably inexpensive, and toluene is most advantageously used. The amount of the aromatic compound present in the present invention is 0.001% by weight or more based on the liquid phase of the reaction zone,
Preferably 0.01 to 20% by weight, more preferably
It is 0.01 to 5% by weight. If the amount of side reaction inhibitor is insufficient, 1,1,2-trichloroethane will be produced in large quantities, and at the same time, the amount of by-produced hydrogen chloride will also increase, resulting in a decrease in the conversion rate of 1,2-dichloroethane. . If a sufficient amount of side reaction inhibitor is present, the amount of 1,1,2-trichloroethane produced can be easily reduced to 1.5% by weight or less based on the 1,2-dichloroethane produced, and 1,2-dichloroethane However, if the amount of the side reaction inhibitor is less than 0.001% by weight, the amount of 1,1,2-trichloroethane produced will be as high as 3% by weight. In this case, the selectivity of 1,2-dichloroethane decreases to about 97% or less. The side reaction inhibitor may be supplied to the reaction zone either as a highly concentrated compound itself or as a diluted compound with a solvent such as 1,2-dichloroethane. When using the side reaction inhibitor diluted with 1,2-dichloroethane, as 1,2-dichloroethane,
It is preferable to use 1,2-dichloroethane, which does not contain impurities that would inhibit the reaction between ethylene and chlorine. When using 1,2-dichloroethane, which contains a large amount of impurities that inhibit the above reaction, and using a large amount of this to dilute the side reaction inhibitor, and using the side reaction inhibitor at a low concentration, the reaction between ethylene and chlorine The reaction is inhibited, the conversion rate of ethylene to 1,2-dichloroethane decreases, and the yield deteriorates. Note that the side reaction in the reaction to produce 1,2-dichloroethane from ethylene and chlorine is mainly the 1,1,2-trichloroethane producing reaction, so if the 1,1,2-trichloroethane producing reaction can be suppressed, 1 , 2-dichloroethane is inevitably improved. FIG. 1 schematically shows a 1,2-dichloroethane manufacturing apparatus used in Examples of the present invention to be described later. A in the figure is a reactor, which is equipped with a chlorine gas introduction pipe 1, an ethylene introduction pipe 2, and a side reaction inhibitor supply pipe 3. B is a condenser;
The steam flowing out from the top of the reactor A can be cooled and condensed through the pipe 4, and the condensed liquid is passed through the pipe 5.
It can be returned to the reactor A via the pipe 6, or taken out to the outside via the pipe 6. 7 is a pipe for discharging non-condensable gas from the condenser B. C
is a receiver, and the bottom liquid of the reactor A overflowing through a pipe 8 is stored in this receiver C, and can be further taken out to the outside via a pipe 9. To describe the mode of producing 1,2-dichloroethane using the apparatus shown in FIG. metal chloride catalyst is present. As mentioned above, if reactor A etc. are made of mild steel, 1,2
- Ferric chloride naturally elutes during the dichloroethane production reaction, so there is no need to specifically supply it as a metal chloride. Chlorine gas and ethylene are blown into the reaction medium of this reactor A at predetermined flow rates from the chlorine gas introduction pipe 1 and the ethylene introduction pipe 2, respectively. Further, a side reaction inhibitor (for example, toluene) is supplied from the side reaction inhibitor supply pipe 3 at a predetermined flow rate. Then, ethylene and chlorine react to produce 1,
While 2-dichloroethane is produced, the heat of reaction causes the reaction medium and the reaction product to become 1,2-
Dichloroethane boils and releases its vapor. According to one embodiment, the overhead vapor (mainly 1,2-dichloroethane) of reactor A is cooled and condensed in condenser B via line 4, and a portion of the condensate is transferred via line 5 to reactor A. The residue is taken out through tube 6 as crude 1,2-dichloroethane. In this case, the gas that is not condensed in the condenser B is taken out from the pipe 7 as exhaust gas. According to another embodiment, in order to effectively utilize the reaction heat of reactor A for distillation purification of the product 1,2-dichloroethane, the top vapor of reactor A is not condensed at all in the condenser. Alternatively, the condensation in the condenser is reduced to the minimum amount required for reflux for liquid level adjustment in reactor A, etc., and all or most of the vapor remains as vapor for distillation and purification of 1,2-dichloroethane. column (this embodiment is most preferred in industrial practice). Furthermore, according to another embodiment, the top vapor is completely condensed except for non-condensable gases, and the condensate is refluxed in its entirety to reactor A via line 5. In this case, the reaction product 1,2-dichloroethane is removed as an overflow from the bottom of reactor A via line 8, receiver C and line 9. Since the composition of the bottom overflow liquid of reactor A taken out by this embodiment is almost the same as the liquid composition of the reaction zone of reactor A, the liquid phase composition (for example, side reaction inhibitor content) in the reaction zone is examined. It is convenient for Accordingly, some of the examples described herein were performed in this manner.
Note that reactor A can be provided with a separate cooling means (not shown), so that, for example, reactor A
It is possible to adjust the temperature of the lower part. In an embodiment in which substantially all of the top vapor of reactor A is refluxed in condenser B and the reaction product 1,2-dichloroethane is taken out as an overflow liquid at the bottom of reactor A, a small amount of 1,1, 2-trichloroethane and the like are taken out together with the 1,2-dichloroethane that is taken out, and do not accumulate in the reaction zone. However, when the reaction product 1,2-dichloroethane is taken out from the pipe 6 as a condensate from condenser B, or when the top vapor of reactor A is taken out as a vapor to the rectification column, etc. Since a small amount of 1,1,2-trichloroethane (bp 113°C), which is produced as a by-product, gradually accumulates in the reaction medium, even in these cases, the reaction medium should be kept in liquid form from reactor A to the extent that the accumulation is prevented. It is necessary to take out small amounts intermittently or continuously. In such a case, it is necessary to additionally add the aromatic compound as a side reaction inhibitor to the liquid phase of the reaction zone intermittently or continuously to maintain the amount of the side reaction inhibitor at a predetermined level. . The following is a more detailed explanation of Examples and Comparative Examples. Example 1 In a mild steel reactor A shown in the attached drawings with a diameter of 250 mm and a height of 10 m, a 1,2-
Charge dichloroethane, and add 20Nm ³ /Hr of chlorine gas and ethylene through inlet pipes 1 and 2, respectively.
85 g/m of toluene was injected continuously from the supply pipe 3 as a side reaction inhibitor using a metering pump.
Continuous reactions were carried out by continuously supplying Hr at the same rate. Ferric chloride was eluted from the reactor wall and contained 50 to 200 ppm (by weight) in the reaction medium. During the continuous reaction, the pressure in reactor A was maintained at 1.3 Kg/cm ² G near the ethylene gas blowing part, and the temperature in the reactor was kept at 100 to 110°C at the temperature of the liquid phase. Therefore, although the reaction medium in the reaction zone, 1,2-dichloroethane, was boiling, its vapor was transferred to tube 4.
It reaches condenser B, where it is cooled and condensed, and the entire amount of the condensate (60°C) is refluxed to the top of reactor A through pipe 5, and the uncondensed gas in condenser B is
It was taken out from pipe 7 as exhaust gas at 30-40°C.
The liquid phase in the reaction zone of reactor A was boiling due to the heat of reaction as described above, but the amount of liquid increased by the 1,2-dichloroethane production reaction was discharged from the bottom of reactor A as an overflow liquid. It was taken out to receiver C through tube 8, and further taken out from receiver C through tube 9. The composition of the overflowing reaction liquid taken out from receiver C is as shown in the table below, and this composition coincided with the liquid phase composition of the boiling reaction zone, which was separately taken out by sampling directly from the reaction zone. In addition, the selectivity of each product in this reaction is added to the table below, and the selectivity is calculated based on ethylene, taking into account uncondensed gas (the same applies hereinafter).

[Table] Thus, the selectivity of 1,2-dichloroethane in this continuous reaction was 99.18%. Comparative Example 1 A continuous reaction was carried out in the same manner as in Example 1 except that no toluene was supplied. As a result, an overflow liquid having the following composition was taken out, and the selectivity of 1,2-dichloroethane in this continuous reaction was 96.93%.

[Table] Example 2 A continuous reaction was carried out under the same conditions as in Example 1 except that xylene was supplied at 85 g/Hr instead of toluene. As a result, reactor A
The following reaction solution was taken out as an overflow from the bottom of the reactor. The selectivity of 1,2-dichloroethane in this reaction was 99.03%.

[Table] Example 3 Using 2,4-dichlorotoluene instead of toluene
Continuous reaction was carried out under the same conditions as in Example 1 except that 85 g/Hr was supplied. As a result, the following reaction liquid was taken out as an overflow liquid from the bottom of reactor A. The selectivity of 1,2-dichloroethane in this reaction was 99.09%.

[Table] According to the present invention, despite the high temperature reaction, it is possible to suppress the formation of side reactants, and it is possible to produce 1,2-dichloroethane in high yield, which is extremely industrially possible. It's advantageous.

[Brief explanation of drawings]

The attached drawings are 1 and 2 used in each example.
1 is a schematic diagram showing a dichloroethane manufacturing apparatus. Each symbol in the drawings indicates the following. A: Reactor, B: Condenser, C: Receiver, 1: Chlorine gas introduction pipe, 2: Ethylene introduction pipe, 3: Reaction inhibitor supply pipe, 4, 5, 6, 7, 8, 9: Piping.

Claims (1)

[Scope of Claims] 1. A liquid phase reaction of ethylene and chlorine at a reaction temperature of 65 to 160°C in a reaction medium containing 1,2-dichloroethane as a main component in the presence of a metal chloride catalyst. In the method for producing 2-dichloroethane, the general formula (In the formula, R ₁ is an alkyl group having 1 to 5 carbon atoms, R ₂
and R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. ) 1,2- characterized in that at least one aromatic compound selected from the group consisting of alkylbenzene hydrocarbons and chlorinated products thereof is present in the liquid phase in an amount of 0.001% by weight or more based on the liquid phase. Method for producing dichloroethane. 2. The method according to claim 1, wherein the aromatic compound is toluene, xylene, or a chlorinated product thereof. 3 The aromatic compound is 0.01 to 20wt relative to the liquid phase.
% of the method according to claim 1 or 2. 4. The method according to any one of claims 1 to 3, wherein the metal chloride catalyst is ferric chloride, and ferric chloride is present in the reaction medium in an amount of 10 to 6000 ppm. 5. The reaction medium is brought to a boil by the heat of reaction and 1,2-dichloroethane is removed from the reaction zone in gaseous form and then condensed to obtain 1,2-dichloroethane. Any one of the methods. 6 The reaction medium is brought to a boil by the heat of reaction, and 1,2-dichloroethane is removed from the reaction zone in gaseous form and then condensed to obtain 1,2-dichloroethane, while high boiling impurities are present in the reaction medium. To prevent accumulation, a portion of the reaction medium is removed in liquid form from the reaction zone intermittently or continuously;
6. The method according to claim 5, wherein the side reaction inhibitor is additionally added intermittently or continuously to the reaction medium, and the amount of the side reaction inhibitor is maintained at a predetermined amount.