DD215527A5 - PROCESS FOR THE PREPARATION OF 1,2-DICHLORETHANE - Google Patents

Abstract

The invention relates to a process for the preparation of 1,2-dichloroethane by reaction of ethylene with chlorine in a solvent in the presence of a catalyst mixture consisting of anhydrous ferric chloride and a nitrogen base or a salt of this base at a temperature below the boiling point of 1,2-dichloroethane and separating the 1,2-dichloroethane from the chlorination mixture, which is characterized in that a) the chlorination mixture in a distillation column promotes, from the mixture, the 1,2-dichloroethane to the precipitation of the catalyst from the liquid Distilled off from the bottoms product, the precipitated catalyst and the latter again used to react ethylene with chlorine or that b) the chlorination over an adsorbent passes, adsorbs the catalyst contained in the mixture to the adsorbent, from the resulting filtrate 1,2- Separating dichloroethane by distillation and the catalyst is recovered from the adsorbent or that c) is moved according to a), but discards the catalyst-containing bottom product at low catalyst contents.

Description

Berlin, 10, 4. 84 AP C 07 C / 258 474 6 63 258 11

Process for the preparation of ! 2-Oichloroethane Field of application of the invention

The invention relates to a process for the preparation of 1,2-dichloroethane.

Characteristic of the known technical solutions

The preparation of 1,2-dichloroethane by reaction of ethylene with chlorine in 1,2-oichloroethane as solvent and reaction medium is known. To accelerate the chlorine addition is used as a catalyst in addition to the chlorides of the elements of IV, to VI. Group of the Periodic Table, especially anhydrous iron-lII-chloride, optionally in the presence of oxygen; because ferric chloride is easily accessible and inexpensive. The main by-product of this reaction is 1,1,2-trichloroethane by substitution of dichloroethane.

The addition of chlorine to ethylene is in the art both at reaction temperatures of 90 ⁰ C, wherein the reaction product is distilled off by utilizing the released heat of reaction from the reaction mixture, as well as at lower * temperatures of 30 to 60 ⁰ C, as in Ullmanns Encyklöpädie the technical chemistry, Bd * 9, 4th edition 1975, page 427, carried out carried out «The heat of reaction can not be used in the latter case for the rectification of Rohdichlorethans, but must. As stated for example in DE-OS 1 905 517 ^ be discharged by pumping the reaction medium via heat exchangers.

; ; ' The crude, catalysätorhaltige dichloroethane prepared at lower temperatures has been generally withdrawn from the reaction vessel and washed to remove the''catalyst and the hydrogen chloride contained in the crude product with water or aqueous Alkalilö $ ments, the dichloroethane separated from the aqueous layer and then in he is known way distilled by distillation.

The use of FeCl * as a catalyst in the addition of ν chlorination of ethylene has certain disadvantages. Thus, in the presence of water, FeCl 3 is corrosive to the metallic materials of reactors, columns or heat exchangers as far as they come into contact with the catalyst. Normally used for chlorination is the technically pure chlorine

Traces of moisture, also always produces chlorinated water ' from unwanted side reactions.

According to the process of DE-OS 31 48 450, the corrosion caused by FeCl 3 'as a catalyst in the production of 1,2-dichloroethane in non-corrosion-resistant reactors can be considerably reduced by adding certain additives to the FeCl 2 catalyst. Darüberhinäus has been found that these additives are also advantageously "'effect,..' .. '''''·.' .... '.''On the side product formation which is decreased by'':'.'"·.-.,"'

The subject matter of DE-OS 31 48 450 is a catalyst mixture consisting of anhydrous iron (III) chloride and a further mixture component for the preparation of 1, 1-dichloroethane by reaction of ethylene with chlorine in a solvent under normal or excess pressure, which is characterized in that the further mixture component is one with respect to the iron III *

63 258 11

, '' V '. '' .. ::. ^: '-' 3 -. - ... , ''. ^: .- Λ:

amount of chloride about equivalent amount of a nitrogen base or a salt of this base is «

The nitrogen base may be NH, a primary, secondary or tertiary alkyl, aralkyl, aryl or aiicyclic amine or a polyamine. The salt of the nitrogen base is preferably a halogen salt, for example

The Katalysatbrgemisch described in DE-OS 3148 450 is particularly suitable for carrying out the chlorination of ethylene at elevated temperature, the heat of reaction of the ethylene chlorination can be used such that the produced portion of! ^ - »Dichlorethane is driven off vapor from the reaction mixture , The catalyst remains in the reaction mixture, so that at most slight catalyst losses must be compensated from time to time.

In contrast, in chlorination processes, which are operated below the boiling range of 1,2-dichloroethane, the catalyst is washed out of the crude dichloroethane formed, for example, with water, the catalyst is dissolved in the wash water, so that the case occurring catalyst loss by addition of fresh Catalyst must be balanced «

The catalyst-forming components in the form of anhydrous FeCl 2 and a nitrogen base used in the process of DE-OS 3,148,450 react in the chlorination mixture

63 258 11

a highly effective even in small amounts catalyst. Object of the invention

It is the object of the invention to recover this highly effective catalyst in the work-up of the chlorination mixture as a function of its concentration in the chlorination mixture in order to be able to use it again for the reaction of ethylene with chlorine.

Explanation of the essence of the invention

The invention has for its object to find a process for the recovery of the catalyst from the chlorination mixture.

Suitable ways of working up the above catalyst-containing chlorination mixture are

mediated by the erfIndungsgemäße method.

The invention thus provides a process for the preparation of 1,2-dichloroethane by reaction of ethylene with chlorine in a solvent in the presence of a catalyst mixture consisting of anhydrous ferric chloride and a nitrogen base or a salt of this base and optionally one Inhibitors to prevent by-product formation at a temperature below the boiling point of the 1,2-dichloroethane of about 20 - 10O ⁰ C and normal or positive pressure and separating the 1,2-dichloroethane from the chlorination mixture, which is characterized in that

a) the chlorination mixture in a distillation column promotes, distilled from the mixture, the 1,2-dichloroethane until the precipitation of the catalyst from the liquid bottom product, distilled from the bottom product, the precipitated catalyst and the latter again used to react ethylene with chlorine or that - / ·; , · '.' ... '·. , \ '''·

b) the chlorination mixture passes through an adsorbent adsorbs the catalyst contained in the mixture on the adsorbent, separated from the resulting FiI-1,2-dichloroethane by distillation and the catalyst from the adsorbent by elution with a solvent recovered or that

c) proceeds in accordance with a), but the catalyst-containing: bottoms product is obtained in the case of low catalyst contents.

In the practice of the invention, it was found that the concentration of FeCl, in the reaction mixture on

0.001 to about 0.5% by weight, in particular 0.002 to 0.01% by weight, based on the amount of the solvent, to be metered, while the amount of nitrogen base or its salt should be equivalent to the FeCl-z amount.

As the solvent has as in the corresponding known processes for the preparation of 1,2-dichloroethane, in the present case, the. 1,2-dichloroethane itself be- • ^; -. 'lasts. ';... "''';.''-.''''·^;' · "

According to a preferred embodiment of the invention, relating to the treatment of the chlorination mixture with an adsorbent, the use of activated carbon, basic ion exchangers or SiOp or aluminum oxide has proven to be expedient. For the elution of the catalyst from the adsorbent, the use of 1,2-dichloroethane or other volatile chlorinated hydrocarbons or hydrochloric acid is recommended.

The alternative embodiment of the process according to the invention, consisting in eliminating the isolation of the catalyst and discarding the catalyst-containing bottom product, is then economically advantageous if the bottom product has a catalyst content of at most about 0.001% by weight, based on the liquid fractions of the bottom product, and therefore the separation of the catalyst would cause difficulties.

The catalyst used in the process of the invention is technically advanced because it suppresses or largely eliminates byproduct formation except for small amounts of 1,1,2-trichloroethane and a correspondingly small amount of hydrogen chloride. In addition, even if the reaction time is longer, the reaction solution remains light when the nitrogen base added to the chlorination batch is, for example, ammonia. A possibly dark colored reaction mixture in the course of the reaction lightens to the extent

/ ... ' : '.,;;.:;.'..:";:..' 63 ü5a η;; ' , '.: ..-.;;,>:; /. ·

"·" · '.- ⁶ -'-.' Ν- ". - · ^; -:."'"" ... ".

the ammonia addition after a short time again. Finally, it should be noted that in the process of the invention the conversion is nearly quantitative with high space / time yield. This result is also in Katalysatorkorizentrationen of less than 0.003 wt _t -% ,; based on FeCl ₃ , achieved ·

The issued according to the invention technical teaching for the work-up of the chlorination mixture was not obvious4 since her knowledge had to go out that the specified for workup Ghlorierungsgemisch no longer contains the catalyst components used in the form of FeCl and the nitrogen base, but that the catalytically active substance Reaction product of FeCl and the nitrogen base, which far exceeds that of FeCl 2 in terms of its catalytic activity. "In this respect, it proved to be useful to recover this catalyst, in contrast to FeCl ₃ in the conventional processes."

The process of the invention can be carried out, for example, in the loop reactor described in DE-OS 2 427 045 or else in any other suitable reactor,

Working Example

The invention is explained in more detail below with reference to some examples.

63 258 11

; ^: · ^; ·:. , ; · /.: ^ .-- 6a .- '· -; V- "./ " ^; .-; ;. ' V ^; ' Example 1 ; , ''.'.-.^; - / ' v :; ; ^: - ··. '' - '' ^: ';''"''.:': / '[".

A cylindrical reactor whose volume was about 25 m, was charged with 20,000 liters of 1,2-oichloroethane and the reactor charge with 170 mg of iron-HI chloride per kg of 1,2-dichloroethane added addition, this solution about 600 1 attached ammonia at a pressure at the top of the reactor of approximately "1.3 bar and a temperature of the reaction mixture of about 40 ° C was added into the reactor every hour l _# 008 kg of ethylene and 2.540 kg of chlorine gas

..- / · -; - -. ; .,. : _{,, η} :.

additionally contained about 4 Vo of 1% inert gases and introduced 8 m of air. In addition, the chlorination mixture was admixed with about 80 l of ammonia and 170 mg of FeCl 2 per hour

About 3.542 kg / h of crude dichloroethane were withdrawn from the reactor and fed to the bottom of a distillation column. The crude product fed had the following composition: ;

C ₂ H ₄ 0.0069 Gev%

C ₂ H ₅ Cl 0.0081% by weight

1,2-EDC 99.8% by weight

1,1,2, etc. ' 0.15% by weight

(EDC = dichloroethane, ETC = trichloroethane)

The column was operated at a moderate reduced pressure (about 0.7 bar absolute) at the top of the column. From the reaction mixture, 95 % of the desired reaction product was distilled off, the purified 1,2-dichloroethane having the following composition:

C ₂ H ₅ Cl 0.01% by weight

1,2-EDC 99.98% by weight .1, 1, 2-ETC 0> 01

The bottom of the column was passed through a filter after cooling and filtered. The filtrate was fed to a further workup of a vacuum column. The separated catalyst was removed from the filter under the exclusion of atmospheric moisture and fed to a dissolving tank, which was charged with 1,2-dichloroethane. In the further course of the chlorination process, the amount of catalyst required for the reaction was added from the portion recovered, while the iron (III) chloride and ammonia feed could be shut off.

'Example 2'. .. '''.-. , - ^: -,, .- '. ··'. , . ''..'. ^: ϊ ·. ^, -. V.;.; -.

From the crude product obtained according to Example 1, about 1.2 kg per hour were passed through a column containing a bed of 335 g activated carbon over a length of 850 mm. In the course of the absorber, no iron could be detected in the course of 6 days. From the obtained filtrate, the 1 _f 2-dichloroethane was separated by distillation. The activated carbon was regenerated with dilute hydrochloric acid. ,

'.' Example 3 ·. '''. -. "''' - / -. < :. · ··;''-'.

A reaction mixture prepared according to the method of Example 1, containing 0.275% by weight of FeCl 2, and an equivalent amount of ammonia for separating off the catalyst was passed through an absorption column charged with fine-particle SiO 2. After V! , A quantity of catalyst which, 3.85 g FeGl-x / ^ pO ^ jgj; _Ä SiO 2 corresponded, by the adsorbent the latter was saturated. By eluting the adsorbent with hot 1,2-dichloroethane, 2.3 g of FeCl 2/100 g of SiO 2 could be recovered. The concentrated catalyst solution was returned to the chlorination reactor and thus maintained the necessary catalyst concentration in the reactor without further addition of FeCl 2 and NH 2.

Claims (7)

63 258 ii Invention claim: 1. A process for the preparation of 1,2-dichloroethane by reaction of ethylene with chlorine in a solvent in the presence of a catalyst mixture consisting of anhydrous ferric chloride / and a nitrogen base or a salt of this base and optionally an inhibitor to prevent by-product formation at a temperature below the boiling point of the 1,2-dichloroethane of about 20-100 C and normal or positive pressure and separating the 1 _# 2-dichloroethane from the chlorination mixture, characterized in that a) the chlorination mixture into a distillation column promotes distilled off from the mixture, the 1,2-dichloroethane to the precipitation of the catalyst from the liquid bottom product, separated from the bottom product, the precipitated catalyst and the latter used again for the reaction of ethylene with chlorine or that b) the chlorination passes through an adsorbent adsorbs the catalyst contained in the mixture on the adsorbent, separated from the resulting filtrate 1,2-dichloroethane by distillation and the catalyst from the adsorbent by elution with a solvent recovered or that c) according to a) procedure, but at low catalysis :. : ';. -.- "V- '"''' V --'--. , ^: 'V' ^{63 258 1} V ^v '..- -V ¹ ^ -V.' / 'Y ... ν' .. VV, - ^ /.·. .: - 10 - "' ^: \ ^; ' .. ·. ';:'.' the catalyst-containing bottoms product discards, V / '.' .. '''':. .- '. · ... /''"''''/"'"ϊ / 2. Method naqh item 1, characterized in that concentration of the ferrous chloride in the reaction mixture from 0.001 to about 0.5 wt.% -., In particular 0.002 to 0.01 wt .-%, based on the amount of the solvent, is. 3. The method according to item 1 or 2, characterized in that in the reaction mixture of the iron-III chloride concentration equivalent amount of nitrogen base or * of the salt of this base is introduced. 4. Process according to point 1 to Z » characterized in that the solvent is 1,2-oichloroethane» 5 # Process according to items 1 to 4 »characterized in that the adsorbent is activated carbon or a basic ion exchanger or SiO or aluminum oxide. 6. The method according to item 1 to 5, characterized in that eluting the catalyst from the adsorbent with, 1,2-dichloroethane or other volatile chlorinated hydrocarbons or hydrochloric acid. 7. The method according to item 1 to 6, characterized in that one rejects the catalyst-containing liquid bottom product at a catalyst content of at most about 0.001 wt -% catalyst, based on the liquid portions of the bottom product.