DD206775A5 - PROCESS FOR THE PREPARATION OF 1,2-DICHLORETHANE - Google Patents

Abstract

THE INVENTION RELATES TO A METHOD FOR PRODUCING 1,2 - DICHLOROETHANE BY REACTION OF ETHYLENE AND CHLORINE IN A REACTION ZONE WHICH AN OUTSTANDING END liquid MEDI UM CONTAINING CHLORINATED HYDROCARBONS WITH TWO CARBON ATOMS AND ONE FOR CHLORUEBERTRAGUNG USUAL CATALYST CONTAINS, AT A TEMPERATURE OF ET WA 75-200 DEG CELSIUS, A PRESSURE OF ABOUT 1 TO 15 BAR AND A MIDDLE DWELLING TIME OF THE MIXTURE IN THE MIX AND REACTION ZONE OF ABOUT 1-15 HOURS, CHARACTERIZED BY THE MANUFACTURE OF 1,2-DICHLORETHANE IN A DOUBLE LOOP REACTOR.

Description

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Process for the preparation of 1,2-dichloroethane

Field of application of the invention

The invention relates to a process for the preparation of 1,2-dichloroethane by reaction of ethylene and chlorine in liquid! 1,2-dichloroethane in the presence of a customary catalyst, wherein the heat of reaction formed in the reaction used useful and the undesirable formation of higher chlorinated products, such as tri-, tetra- and pentachloroethane, largely avoided in the reactor and the accumulation of such products in the reaction zone is prevented·

Characteristic of the known technical solutions

Chlorination of olefins by chlorine is known to be an exothermic reaction. In the case of chlorination of ethylene with chlorine, the heat of reaction is 2,200 kJ per kilogram of 1,2-dichloroethane. Thus, producing one ton of 1,2-dichloroethane will produce enough heat to produce about one ton of steam. In the known processes for the preparation of dichloroethane, the heat of reaction was either removed by cooling the reactor or it was partly for immediate evaporation and abortion of the dichloroethane formed in the reaction from the reaction mixture or the reactor and in some cases also for the exclusive rectification of after used in another procedure, more or less completely used 1,2-dichloroethane.

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A combined removal of the heat of reaction in the chlorination of ethylene with chlorine is also practiced, for example, in the process described in DE-PS 15 43 108. Here, the provided for carrying out the reaction iron reactor is provided with a cooling device which is acted upon with cooling water to dissipate heat generated during the reaction and to comply with the predetermined reaction temperature of 50 - 70 ⁰ C can. The compliance with the below the boiling point of 1,2-dichloroethane reaction temperature is controlled during the reaction, so that the formed 1,2-dichloroethane in the vapor state is continuously removed from the reaction space. Although no accumulation of higher chlorinated products in the reactor takes place in this procedure, while 3 »3 % trichloroethane are formed and the heat of reaction can not be used because the condensed 1,2-dichloroethane still has to be freed from the mentioned by-product.

A in principle with the method of DE-PS 15 43 108 matching method is disclosed in DE-OS 29 35 884, wherein the characteristic features of the latter method are that the reactor charge during the reaction via a communicating with the reactor ring line is recirculated and the withdrawing at the top of the reactor vapor products are separated in a rectification column to yield 1,2-dichloroethane. Higher boiling by-products are thereby disadvantageously returned from the bottom of the rectification column in the reactor, whereby in this case a separate workup of discontinuously withdrawn amounts of reaction bottoms is required and the heat of reaction can be used only partially.

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Finally, "there is a further procedure for the production of ethylene chloride according to DE-OS 24 27 045 is that

a) ethylene and chlorine in a reaction zone under elevated pressure, which contains a circulating liquid medium containing two carbon atoms chlorinated hydrocarbons or mixtures of these chlorinated hydrocarbons, at a temperature below the evaporation temperature of the medium at the pressure prevailing in the reaction zone initiates, whereby crude liquid ethylene dichloride is formed;

b) passing the crude liquid ethylene di-chloride with the circulating medium to a lower pressure zone, maintaining the pressure and temperature of said zone at values at which the impure ethylene dichloride evaporates through the heat of reaction liberated by the reaction of chlorine and ethylene, and

c) the vaporous impure ethylenedi chloride is introduced into a recirculation zone and rectified by means of the heat of reaction liberated in the reaction of chlorine and ethylene, the purified ethylene dichloride being withdrawn from the rectification zone, while the bottom product of the rectification column is withdrawn into the zone of lower pressure returned and combined with the circulating medium

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The recycling of the bottom product into the reactor is disadvantageous in that the circulating liquid medium is enriched with higher-boiling chlorination products, which must be removed from the latter. According to Example 4

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DE-OS 24 27 045, the proportion of 1,1,2-trichloroethane in the circulating medium is about 60%. This means that the known chlorination reaction proceeds with the formation of considerable amounts of undesired by-products.

Object of the invention

The aim of the invention is to provide an improved process for the preparation of 1,2-dichloroethane.

Explanation of the essence of the invention

The invention is based on the object to improve the known procedures to the extent that the formation of by-products largely avoided and the heat of reaction incurred in the reaction is optimally used · This task is already largely by the method of the German patent ... ...... (patent application P 31 37 513.8) solved. The subject of this patent is a process for producing 1,2-dichloroethane by reacting ethylene and chlorine in a reaction zone containing a circulating liquid medium containing two carbon atoms chlorinated hydrocarbons at a temperature below the evaporation temperature of the medium the pressure prevailing in the reaction zone and in the presence of a conventional catalyst for the transfer of chlorine and optionally an inhibitor to reduce by-product formation to give crude 1,2-dichloroethane which is withdrawn from the reaction zone and purified in a subsequent separate fractionating column characterized is that one

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a) initiates approximately equimolar amounts of ethylene and chlorine in the circulating liquid medium and after intensive mixing in a mixing zone, the mixture in a reaction zone at a temperature of about 75 - 200 ⁰ G and a pressure of about 1-15 tar reacts, wherein the average residence time of the reaction mixture in the mixing and Reaktxonszone is about 1-15 hours;

b) withdrawing a portion of the liquid reaction mixture from the reaction zone and dividing the latter into two substreams, wherein a substream for passing heat energy passes through a heat exchanger and then returns to the mixing and reaction zone at reduced temperature while the second substream is fed to a flash vessel; in which an adequate amount of the reaction product formed in the reaction zone and optionally a proportion prepared by another procedure and fed to the reaction zone 1,2-dichloroethane evaporated from the second substream, wherein the vapors are introduced into a Fraktionierkolonne, while the non-evaporated, liquid fraction the second substream returns to the mixing and reaction zone of the circulating liquid medium, and

c) from the vapors introduced into the fractionation, the 1,2-dichloroethane by distillation using a portion of the transferred thermal energy in the heat exchanger and the latter is withdrawn overhead the column, wherein the bottom of the column higher chlorinated products incurred, which are deducted and worked up separately

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The invention is now a preferred embodiment of the method according to patent (Patent Application P 31 37 513.8) by practicing the method is practiced in a double-loop reactor.

The inventively improved process for the preparation of 1,2-dichloroethane by reacting ethylene and chlorine in a reaction zone, which comprises a circulating liquid medium containing chlorinated hydrocarbons having two carbon atoms and a conventional catalyst for the chlorine transfer and optionally an inhibitor for reducing by-product formation contains, where one

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a) initiates approximately equimolar amounts of ethylene and Ghlor in the circulating liquid medium, mixes and the mixture in a reaction zone at a temperature of about 75 - 200 ⁰ C, a pressure of about 1-15 bar and a mean Yerweilzeit of the mixture in the The reaction mixture is allowed to react for about 1-15 hours

b) withdrawing a portion of the liquid reaction mixture from the reaction zone and dividing the latter into two substreams, wherein a substream for passing heat energy passes through a heat exchanger and then returns to the mixing and reaction zone at reduced temperature while the second substream is fed to a flash vessel; in which an adequate amount of the reaction product formed in the reaction zone from the second partial stream is evaporated, the vapors are introduced into a fractionating and the 1,2-dichloroethane is separated by distillation, while the non-evaporated, liquid portion of the second partial stream in the mixing and reaction zone of the circulating liquid medium is characterized in that one carries out the preparation of the 1,2-dichloroethane in a double-loop reactor, such

A) via a line ethylene and via a line CHorgas in the rise part of a loop below a mixing zone located in the ascent part and finely distributed in the circulating in the loop liquid medium, after which the reaction components in the adjoining the mixing zone reaction zone or the Yerweilzone implements: that one

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B) withdrawing from the loop two partial streams of the reaction mixture, of which a partial stream for delivering heat energy Woex passes through a supply line and then returns via a line to the descent part of the loop, while the second partial stream is connected to an integrally connected to the loop second Loop and a relaxation zone located in the Sehlaufenkreislauf flows in which an adequate amount of the reaction product formed in the reaction zone from the second partial stream is evaporated, the vapors are fed via a discharge line Kcaktionierkolonne, while the non-evaporated FlüsäLge portion of the second partial stream via the descent part the second loop returns to the mixing zone or reaction zone of the loop

Another feature of the process of the invention is that inert gases or low boiling hydrocarbons such as ethyl chloride contained in the reaction mixture are withdrawn from the residence zone via a conduit or from the descent portion of the loop via a conduit.

In particular, the following is to be noted for the method of the invention:

The reactants ethylene and chlorine may be diluted by inert gases. Chlorine can be introduced into the oil zone in liquid form or as gas, but it is expedient to introduce liquid chlorine into the reactor before it enters the reactor by means of a part of the reaction enthalpy

Heat exchanger to evaporate. The catalyst recommended is the use of iron (III) chloride and as an inhibitor to avoid by-product formation, preferably oxygen

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The circulation of the liquid medium in the reactor is effected according to the thermosiphon or mammoth pump principle. The circulation rate of the liquid medium should not be less than 0.1 m / sec in the mixing zone. The circulation for product evaporation in the expansion zone also takes place according to the thermosiphon principle. The heat exchanger can be integrated in the product circuits or fed separately by pump.

The method of the invention will be explained in more detail below in conjunction with the drawing.

A double loop reactor with loop loops I and II is first charged with liquid 1,2-dichloroethane and the latter is introduced by introducing ethylene via line 1 and chlorine gas via line 2 according to the mammoth pump principle in circulation. After the reaction of the ethylene with the chlorine gas, which begins in the charged with packing mixing zone 3 and is completed in the reaction zone 4 and in the residence zone 5, there is an additional buoyancy in the ascent part of the loop I, due to the released heat of reaction. The temperature in Schläüfenkreislauf I is slightly lower than the boiling point of 1,2-dichloroethane at the pressure prevailing in the reactor. Possibly present in the loop I inert gases are withdrawn via lines 11 and 12 and cooled in a, not shown in the drawing cooler for the condensation of entrained 1,2-dichloroethane vapors. The non-condensed gases are blown off and worked up in a known manner. By regulating the inert gas flow in terms of the amount blown off, the desired pressure can be set in the loop I.

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In order to obtain the produced in the loop circuit I 1,2-dichloroethane two partial streams are branched off from the I ³ IUssigkeitsstrom, wherein a partial flow for delivery of '// heat energy via the feed line 8 to heat exchanger 10 passes and then through the line 9 in the descent part of the Loop I returns while the second substream flows in loop II integrally connected to loop II and a flash zone II flash zone 6 in which an adequate amount of the reaction product formed in the reaction zone 4 evaporates from the second split stream, passing the vapors through the flue 7 are fed to the fractionation column, not shown in the drawing, while the non-evaporated, liquid portion of the second partial stream via the descent part of the loop II in the mixing zone 3 or «reaction zone 4 of the loop I returns · In the reaction mixture contained inert gases or lightly -sied End hydrocarbons, such as ethyl chloride, are withdrawn from the residence zone 5 via line 11 or from the descent section of loop I via line 12.

The method of the invention is characterized by the same advantages as are inherent in the method of the patent .. · .... (Patent Application P 31 37 513-8). They result from the continuous removal of a portion of the liquid reactor contents and its division into two partial streams, of which a partial flow enables the continuous recovery of the heat of reaction, while the partial evaporation of the second partial stream and the exclusive 'working up of the vapor fraction in the fractionation results in that only catalyst-free crude dichloroethane enters the Fraktionierkolonne. With the above-mentioned vapors, however, the higher-chlorinated by-products are also fed to the fractionating column,

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whereby an accumulation of by-products in loop loop I is avoided. The latter causes namely in the known method an enrichment of higher chlorinated by-products and forces for the separation of the by-products from the reactor. This catalyst losses must be supplemented, whereby the efficiency of these methods is impaired. By the Verfahrerrsablauf invention also the average residence time of all substances involved in the reaction under the given reaction conditions in the reactor is so far reduced that undesirable side reactions leading to -Nebenproduktbildung be largely avoided.

Furthermore, the process of the invention also makes it possible to use starting materials contaminated with inert gases which, as is known, present difficulties in purifying the dichloroethane in the fractionating column. According to the invention, these inert gases are already withdrawn from the loop I via the inert gas lines 11 and 12, so that they can not interfere with the further work-up process of the reaction mixture.

Finally, the method of the invention also proves to be superior to the method of the patent

(Patent Application P 31 37 513.8) as advantageous by the use of a double loop reactor, in which the continuous circulation of the reaction mixture in the Schlau fen I and II takes place according to the thermosiphon or Mammutpumpenprinzip, the use of special pumps for promoting the reaction mixture from or in the reactor is unnecessary, which is also associated with energy savings.

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embodiment

The invention will be explained in more detail below by way of example.

example

In a reactor according to the drawing, which holds about 15 1, were about 15 kg of 1,2-dichloroethane with 0.1 % iron (III) chloride as a catalyst. 110 l / h of ethylene and, via line 2, about 110 l / h of chlorine and 10 l / h of air were introduced via line 1. The temperature in the reactor was about 115 ⁰ C, the pressure above the dwell 5 about bar and the pressure difference between dwell zone 5 and flash zone 6 about 0.5 bar.

From the reactor exhaust gas which left the resting zone 5 via line ,, condensable components were deposited in a cold trap at -30 ⁰ C. Via line 7, 480.1 g / h of dichloroethane were removed in vapor form from the flash vessel 6 and condensed.

To dissipate the heat of reaction, approximately 200 l / h of reactor liquid were circulated via lines 8 and 9. In the heat exchanger 10, the heat was used for distillation at a bottom temperature of the corresponding column of 80 - 85 ⁰ C used.

After running for 48 hours, the analysis of the 1,2-dichloroethane removed gave the following values:

C ₂ H ₅ Cl 0.0024% by weight

1,1-BDC <0.002 wt%

1,2-EDC 99.86% by weight

1,1,2-ETC 0.13 wt%

Claims (2)

invention claim An improved process for the preparation of 1,2-dichloroethane by reacting ethylene and chlorine in a reaction zone comprising a circulating liquid medium containing two carbon atoms of chlorinated hydrocarbons and a catalyst customary for chlorine transfer and optionally an inhibitor for reducing heel product formation contains, where one a) initiates approximately equimolar amounts of ethylene and chlorine in da3 circulating liquid medium, and mixes the mixture in a reaction zone at a temperature of about 75 - 200 ⁰ C, a pressure of about 1-15 bar and an average residence time of the mixture in the Mixing and reaction zone of about 1-15 hours to the reaction, wherein b) withdrawing a portion of the liquid reaction mixture from the reaction zone and dividing the latter into two substreams, wherein a substream for passing heat energy passes through a heat exchanger and then returns to the mixing and annealing zone at reduced temperature while the second substream is fed to a flash vessel; in which an adequate amount of the reaction product formed in the reaction zone evaporates from the second substream, the vapors being converted into a pretreatment AP G 07 G / 245 051/6 61 604 11 column are introduced and the 1,2-dichloroethane is separated by distillation, while the non-evaporated, liquid portion of the second substream in the mixing and reaction zone of the circulating liquid medium returns, characterized in that the preparation of 1,2-Dichloräthans in a Double loop reactor performs such that one A) introduces via the line (1) ethylene and via the line (2) chlorine gas into the ascent part of the loop (I) below the mixing zone (3) located in the ascent section and finely distributed in the liquid medium circulating in the loop (I), after which the Reaktionskoniponent en in the mixing zone (3) adjoining the reaction zone (4) or the Terweilzone (5) is reacted; that he B) from the loop (I) subtracts two partial streams of the reaction mixture, of which 'a partial flow for discharging .. heat energy through the supply line (8) passes through the heat exchanger (10) and then via the line (9) in the descent part of the loop ( I), while the second partial stream flows in through the loop (II) integrally connected to the loop (I) and into a relaxation zone (6) in the loop circuit (II). which vaporizes an adequate amount of the reaction product formed in the reaction zone (4) from the second part-stream, the vapors being fed to the fractionating column via the withdrawal line (7), while the non-evaporated, liquid part of the second part-stream supplies the descending part of the loop (II ) in the AP C 07 G / 245 051/6 61 604 11 9/5051 5 -1 - Mixing zone (3) or reaction zone (4) of the loop (I) returns. 2. The method according to item 1, characterized in that in the reaction mixture contained inert gases or low-boiling hydrocarbons, such as methyl chloride, from the residence zone (5) via the line (11) or from the descent part of the loop (I) via the line (12 ) subtracts. Hlei »to 1 ropes drawings