JP4093789B2 - Method for initiating reaction in the production of 1,2-dichloroethane - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a novel reaction in a process for producing 1,2-dichloroethane in which metallic iron is present in a reaction system as a supply source of an iron-based catalyst, and ethylene and chlorine are reacted in the presence of the iron-based catalyst to be produced. Regarding the start method. Specifically, the present invention provides a reaction initiation method capable of achieving a high selectivity in a short time from the start of raw material supply.
[0002]
[Prior art]
As a method for producing 1,2-dichloroethane, a method of reacting chlorine and ethylene in the presence of an iron-based catalyst is performed. The above reaction is industrially carried out by filling the reaction system with metallic iron in the form of iron Raschig ring, scrap iron or the like to start the reaction and generating an iron catalyst in the reaction system. In this case, although the generation mechanism of the iron-based catalyst is not clear, it is generated by chlorination of the metallic iron due to the presence of hydrogen chloride or by-product water contained in the reaction system. It is considered a thing.
[0003]
On the other hand, metallic iron such as iron Raschig rings and scrap iron filled in the reaction system at the start of the reaction has a film formed of an oxide film or an oil film on the surface thereof. The concentration of the iron-based catalyst necessary for the reaction cannot be maintained due to the inhibition, and 1,2-dichloroethane cannot be produced with high selectivity.
[0004]
Therefore, at the start of the reaction, it was necessary to circulate the reaction solution for a long time until a sufficient iron-based catalyst concentration was obtained. By the way, after filling the metallic iron, the reaction has been started up so that the concentration of the iron catalyst is usually in a steady state over one day or more after starting the supply of the raw material.
[0005]
Therefore, the reaction liquid during that period is generally stored in a tank because of its low selectivity, and is discarded after iron removal treatment, or the tank is enlarged, and after the reaction has become steady, it is gradually supplied to the reaction tower. I had to deal with it. The amount of 1,2-dichloroethane, which is a raw material for vinyl chloride, is a large amount because it is a chemical product produced on a large scale, and a large amount of equipment for circulating the reaction solution was required. In addition, when starting using metallic iron with a film formed of an oxide film or oil film on the surface, since there are few iron catalysts present in the reaction liquid at the beginning of the reaction, -Increase in the amount of low-boiling by-product ethyl chloride due to the large amount of hydrogen chloride generated with the amount of trichloroethane produced, and promote the generation of iron chloride as a catalyst, while temporarily dissolving the filler metal locally. There is also concern about troubles due to the generation of insoluble iron.
[0006]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a process for producing 1,2-dichloroethane in which metallic iron is present in a reaction system as a supply source of an iron catalyst and ethylene and chlorine are reacted in the presence of the iron catalyst to be produced. A reaction that can reduce the generation of insoluble iron, etc. by achieving high selectivity in a short time from the start of raw material supply and stabilizing the concentration of iron, hydrogen chloride, etc. in the reaction system from the beginning of the reaction. It is to provide a starting method.
[0007]
[Means for Solving the Problems]
The inventors of the present invention have made extensive studies to achieve the above object. As a result, when starting the supply of raw materials to the reaction system, the metallic iron to be used is brought into contact with hydrochloric acid to renew the surface, or iron chloride capable of instantaneously supplying iron ions is added together with the metallic iron. By starting the reaction, it was found that a selectivity close to 100% could be achieved in a very short time after starting the supply of raw materials, and the problems in the previous period could be solved at once, and the present invention was completed. It was.
[0008]
That is, the present invention, the reaction system in the presence of metallic iron to a method for producing a by reacting ethylene and chlorine 1,2-dichloroethane in the presence of an iron-based catalyst for generating from the metallic iron, at the start of the reaction by supplying the iron chloride in the reaction system, both when allowed to rise iron ion concentration in the reaction system immediately after the start of the reaction, after the reaction rate was steady state is characterized by stopping the supply of the salt of iron In a method for producing 1,2-dichloroethane, and a method for producing 1,2-dichloroethane by allowing metallic iron to be present in a reaction system and reacting ethylene and chlorine in the presence of an iron-based catalyst produced from the metallic iron The production of 1,2-dichloroethane is characterized by increasing the iron ion concentration in the reaction system immediately after the start of the reaction by using the metallic iron after contacting with hydrochloric acid. It is a method.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as the iron metal present in the reaction system, a known iron source that has been conventionally used for 1,2-dichloroethane production is used without particular limitation. For example, the above-described iron Raschig rings and scrap iron are generally used. The shape of the metallic iron is not particularly limited, and generally a Raschig ring on a cylinder or the like can be used. Further, the surface area of the metallic iron, when the amount of produced per hour generally produced 1,2-dichloroethane was 1 kg, its use as the surface area for this product amount is 0.02～5M ² It is appropriate to determine the amount.
[0010]
Conventionally, the starting method of the reaction in the production of 1,2-dichloroethane using the above-mentioned metallic iron as a supply source of the iron-based catalyst is the circulation of 1,2-dichloroethane through the layer filled with the above-mentioned metallic iron while chlorine and This was done by supplying ethylene. According to such a method, it took 1 day or more to dissolve the metallic iron and to produce a sufficient amount of iron ions to be a catalyst for the reaction.
[0011]
On the other hand, after contacting the metallic iron of the present invention with hydrochloric acid, the method of use, or adding iron chloride to the circulating 1,2-dichloroethane in advance to start supplying chlorine and ethylene, the reaction is carried out. By starting, 1,2-dichloroethane can be produced with high selectivity immediately thereafter. Incidentally, according to the method of the present invention described above, although it depends on the amount of iron chloride added, a selectivity of almost 100% can usually be reached in several hours.
[0012]
After reaching a high reaction rate as described above, the supply of iron chloride is no longer necessary, and thereafter the supply of iron chloride is stopped, and the amount of iron-based catalyst required by the metal ions eluted from the metal iron Can be secured.
[0013]
In the present invention, the treatment of metallic iron with hydrochloric acid removes an oxide film or oil film such as Fe ₂ O ₃ , Fe ₃ O ₄ , and FeO that would inhibit the elution of iron from the surface of the metallic iron. The conditions to be obtained are adopted without particular limitation.
[0014]
In general, although there are influences of hydrochloric acid concentration, temperature, etc., it is generally preferable to contact for 2 hours or more. The hydrochloric acid concentration is preferably 0.1% by weight or more, particularly preferably 0.5 to 37.0% by weight.
[0015]
In addition, the method for treating metallic iron with hydrochloric acid is not particularly limited, and the method of filling the reactor with the metallic iron treated with hydrochloric acid in a separately prepared container or the like can also be applied to the metallic iron layer filled in the reactor. After treatment with flowing hydrochloric acid, the reaction may be started by removing hydrochloric acid.
[0016]
In the present invention, in the embodiment in which iron chloride is added, ferrous chloride (FeCl ₂ ) and ferric chloride (FeCl ₃ ) are used without particular limitation as the iron chloride, but ferric chloride (FeCl ₃ ) is used. ₃ ) is preferred.
[0017]
Further, the addition of iron chloride may be performed in a solid state, or may be performed in a liquid state after being dissolved in a solvent. A suitable solvent is 1,2-dichloroethane which does not require separation in the purification step.
[0018]
In the present invention, the iron ion concentration in the reaction system can be increased in a very short time by the above embodiment, but preferably the iron ion concentration is 15 ppmw or more, particularly 15 hours or less within 1 hour from the start of the reaction. It is preferable to be set to ˜200 ppmw, more preferably 20 to 100 ppmw.
[0019]
That is, when the iron ion concentration is less than 15 ppmw, the effect of the present invention is reduced, and the time from the start of the reaction to the target selectivity tends to increase. On the other hand, when the iron ion concentration exceeds 200 ppmw, the selectivity tends to decrease.
[0020]
For example, in the treatment with hydrochloric acid, the surface renewal rate is increased, and in the addition of iron chloride, the iron ion concentration in the reaction system is adjusted to be within the above range by adjusting the addition amount. In the present invention, the reaction can be started by supplying chlorine and ethylene while circulating 1,2-dichloroethane through the reaction system filled with metallic iron treated with hydrochloric acid through the layer filled with metallic iron. The reaction is started to start or the supply of chlorine and ethylene is started while circulating the 1,2-dichloroethane containing iron chloride to the layer filled with metallic iron. According to the present invention, immediately after the start of the reaction, the supply of chlorine and ethylene can be performed under almost steady conditions.
[0021]
In the present invention, the embodiment in which the metallic iron is used after being brought into contact with hydrochloric acid and the embodiment in which iron chloride is added together with the metallic iron may be carried out simultaneously, which is more effective.
[0022]
Furthermore, in the reaction, known conditions such as a supply ratio of chlorine and ethylene, a reaction temperature, a reaction pressure, and the like are employed without any particular limitation. For example, it is preferable to carry out the reaction at a supply ratio of chlorine and ethylene of approximately 1: 1. The reaction temperature is generally 30 to 70 ° C., and the pressure is normal pressure.
[0023]
As the reaction apparatus used in the present invention, a known reaction apparatus is basically used without any particular limitation. In the present invention, taking a mode of adding iron chloride as an example, a mode of a typical reactor that is suitably used is exemplified by the reactor shown in FIG.
[0024]
That is, the upper part has a packed bed filled with metallic iron 2, and the lower part has a liquid storage tank for storing 1,2-dichloroethane, and the ethylene introducing pipe 4 is provided in the liquid storage tank between the liquid storage tank and the packed bed. A reaction line 1 connected with a chlorine inlet pipe 3 to the gas phase part, a liquid drawn from a liquid storage tank below the reaction tower, and a circulation line for circulating the liquid above the packed bed by a circulation pump 5, produced from the circulation line The extraction pipe 7 for extracting 1,2-dichloroethane, the iron chloride introduction pipe 9 for supplying iron chloride to the circulation line, the gas extraction pipe 10 for extracting gas from the top of the reaction tower, and the gas extraction pipe A heat exchanger 11 for cooling the gas, a 1,2-dichloroethane recovery pipe 12 for returning the condensed liquid after cooling to the reaction tower, and an exhaust gas pipe 13 for taking out the uncondensed exhaust gas.
[0025]
In addition, 6 is a heat exchanger for cooling the liquid of a circulation line, 8 is an extraction valve for adjusting the extraction amount of extraction piping.
[0026]
The method for starting the reaction using the above apparatus can be performed as follows. First, the packed bed at the upper part of the reaction tower 1 is filled with metallic iron 2, and chlorine is supplied from a chlorine introduction pipe 3 provided at the lower part. 1,2-dichloroethane is stored in advance in the lower part of the reaction tower 1 and supplied from the ethylene introduction pipe 4 into this liquid. 1,2-dichloroethane is circulated by the circulation pump 5, and iron chloride is supplied from the iron chloride introduction pipe 9 in the middle of this circulation line.
After the reaction rate becomes steady, the supply of iron chloride from the iron chloride introduction pipe 9 is stopped.
[0027]
The reaction heat generated by the reaction between ethylene and chlorine is recovered by the heat exchanger 6 installed in the circulation line. Although not shown, a part of the circulating liquid in the circulation line may be returned to the middle part of the reaction tower.
[0028]
Further, an appropriate amount of 1,2-dichloroethane produced by the reaction is extracted from the extraction pipe 7 by operating the valve 8.
[0029]
The exhaust gas from the reaction tower 1 is cooled by the heat exchanger 11 from the exhaust gas pipe 10 at the top of the tower, 1,2-dichloroethane is recovered from the 1,2-dichloroethane recovery pipe 12, and uncondensed gas is discharged from the exhaust gas pipe 13. To do.
[0030]
【The invention's effect】
As understood from the above description, according to the present invention, metallic iron is present in the reaction system as a supply source of the iron-based catalyst, and ethylene and chlorine are reacted in the presence of the iron-based catalyst. When producing 2-dichloroethane, the metal iron is used after contacting with hydrochloric acid, or by adding iron chloride to the reaction system, the selectivity is almost 100% in a very short time from the start of raw material supply. The large-scale wastewater treatment equipment required at the start of the reaction and equipment such as a tank for wastewater storage can be significantly reduced, and the loss of ethylene and chlorine as raw materials can be reduced. Can also be effectively prevented.
[0031]
【Example】
EXAMPLES Hereinafter, examples will be shown to describe the present invention more specifically, but the present invention is not limited to these examples.
[0032]
Example 1
Production of 1,2-dichloroethane was started as follows using a reactor shown in FIG. 1 and having the following specifications.
[0033]
Reactor diameter: 38 mm
Catalytic iron: mixed with 1 / 4B iron Raschig ring filling amount 60mL, 1/4 magnetic Raschig ring 470mL, 1,2-dichloroethane retained in the reactor used: 900mL
Chlorine gas 50.5NL / hr and ethylene gas 50NL / hr are supplied to the reactor of the above specifications, 1,2-dichloroethane is circulated at 25L / hr, the reaction temperature is 50 ° C., the temperature of the heat exchanger at the top of the tower Was controlled at −10 ° C. Iron chloride was dissolved in 1,2-dichloroethane and fed at 6 mg / hr. The reaction rate and selectivity of this reaction at this time were calculated from the quantitative analysis of the produced 1,2-dichloroethane by gas chromatography.
[0034]
The iron concentration in 1,2-dichloroethane 1 hour after the start of the reaction was 17 ppmw, and the iron concentration in 1,2-dichloroethane after 5 hours was 19 ppmw. The reaction rate of 1,2-dichloroethane at that time was 99. The selectivity was 99.8%, 9%.
[0035]
Thereafter, the supply of iron chloride was stopped, but the reaction could be carried out in a steady state.
[0036]
From the start of the reaction, all 1,2-dichloroethane could be made into products.
[0037]
Comparative Example 1
The same procedure as in Example 1 was carried out except that no iron chloride was added.
[0038]
The iron concentration in 1,2-dichloroethane 1 hour after the start of the reaction was 6 ppmw, the iron concentration in 1,2-dichloroethane after 5 hours was 12 ppmw, and the reaction rate of 1,2-dichloroethane was 99.6%. The selectivity was 99.6%. 30 hours after the start of the reaction, the iron concentration in 1,2-dichloroethane was 25 ppmw, and the selectivity of 1,2-dichloroethane produced at that time was 99.9%.
During this time, 5.6 L of 1,2-dichloroethane produced could not be made into a product.
[0039]
Example 2
The same procedure as in Example 1 was carried out except that the input amount of iron chloride was 8 mg / h. The iron concentration in 1,2-dichloroethane 1 hour after the start of the reaction was 20 ppmw, the iron concentration in 1,2-dichloroethane after 4 hours was 25 ppmw, and the 1,2-dichloroethane selectivity at that time was 99.9%.
[0040]
Thereafter, the supply of iron chloride was stopped, but the reaction could be carried out in a steady state.
[0041]
Example 3
The same procedure as in Example 1 was performed except that the catalyst iron was immersed in 5 wt% hydrochloric acid for 2 hours.
[0042]
The iron concentration in 1,2-dichloroethane 1 hour after the start of the reaction was 25 ppmw, the iron concentration in 1,2-dichloroethane after 3 hours was 25 ppmw, and the selectivity for 1,2-dichloroethane at that time was 99.9%.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a typical embodiment of a reactor used in the method of the present invention.
1: Reaction tower 2: Metal iron packed bed 3: Chlorine introduction pipe 4: Ethylene introduction pipe 5: Circulation pump 6: Heat exchanger 7: Extraction pipe 8: Extraction valve 9: Iron chloride introduction pipe 10: Gas extraction pipe 11: Heat exchanger 12: 1,2-dichloroethane recovery piping 13: Exhaust gas piping

Claims (3)

In a method for producing 1,2-dichloroethane by causing metallic iron to be present in a reaction system and reacting ethylene and chlorine in the presence of an iron-based catalyst produced from the metallic iron, iron chloride is contained in the reaction system at the start of the reaction. by supplying both the allowed to rise iron ion concentration in the reaction system immediately after the start of the reaction, after the reaction rate was steady state, the 1,2-dichloroethane, characterized in that to stop the supply of the salt of iron Manufacturing method. The production method according to claim 1, wherein the supply of iron chloride at the start of the reaction is carried out as a solution dissolved in 1,2-dichloroethane. In a method for producing 1,2-dichloroethane by allowing metallic iron to be present in a reaction system and reacting ethylene and chlorine in the presence of an iron-based catalyst produced from the metallic iron, the metallic iron was brought into contact with hydrochloric acid. A method for producing 1,2-dichloroethane, which is used later to increase the iron ion concentration in the reaction system immediately after the start of the reaction.

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