CS247189B2 - Method of 1,2-dichloroethane production - Google Patents

Abstract

Die Erfindung betrifft ein Verfahren zur Herstellung von 1,2-Dichlorethan durch Umsetzung von Ethylen mit Chlor in einem Lösemittel bei Temperaturen unterhalb des Siedepunktes des 1,2-Dichlorethans von 20 - 100°C und Drücken von 1 - 15 bar in Gegenwart eines Katalysatorgemisches bestehend aus wasserfreiem Eisen-III-chlorid und einer Stickstoffbase oder einem Salz dieser Base sowie gegebenenfalls eines Inhibitors zur Verminderung der Bildung von Nebenprodukten und Abtrennen des 1,2-Dichlorethans aus dem Chlorierungsgemisch durch Destillation, welches dadurch gekennzeichnet ist, daß man das Chlorierungsgemisch in eine Destillationskolonne fördert, das 1,2-Dichlorethan höchstens bis zur beginnenden Ausscheidung des Katalysators abdestilliert und einen Teil des verbleibenden flüssigen Sumpfprodukts zur erneuten Umsetzung von Ethylen mit Chlor in die Reaktionszone zurückführt.

Description

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

The preparation of 1,2-dichloroethane by reaction of ethylene with chlorine in 1,2-dichloroethane as solvent and reaction medium is known. In addition to the chlorides of elements IV, catalysts are used as catalysts to accelerate the addition of chlorine. to VI. The groups of the periodic system of the elements, in particular anhydrous ferric chloride, optionally in the presence of oxygen to prevent the formation of by-products, since ferric chloride is readily available and also cost effective. 1,1,2-Trichloroethane is a major by-product of this reaction by substituting dichloroethane.

The addition of chlorine to ethylene in an industrial scale is carried out both at the reaction temperatures ^to ol 90 ° C ataos ^ rick-pressure pn ^ MZ REAT for ^d u ^k t, i.e. ^{1, 2-di} chloro ^e tha ⁿ ( Tv ^83.7 ° ^{C) and} about ^dd est ^à lováv from the reaction mixture ^{as well} as ^{characterized} by three uvozovaného reaction ^fo ^ he te ^{p Ia to} the IP n ^{s Iz} months ^h te ^{pl rt H} c ^{30 d 60} C, j and ^k to ^p of the ^PI suje UHmannc Enc ^y ^ ^l to about ^PA die der technischen Chemie, Vol. 9, 4th edition 1975, p. 427.

In the latter case, the heat of reaction cannot be utilized to rectify the crude dichloroethane, but must be dissipated, for example, in De-AS 19 05 517, by pumping the reaction medium through a heat exchanger.

Crude dichloroethane produced at lower temperatures containing the catalyst has so far generally been removed from the reaction vessel and washed to remove the catalyst and hydrogen chloride contained in the crude product with water and / or aqueous alkali solutions, then the dichloroethane is separated from the aqueous layer and worked up in a known manner.

The use of ferric chloride as a catalyst in the addition chlorination of ethylene is associated with certain disadvantages. Thus, ferric chloride is corrosive in the presence of water to metallic materials of reactors, columns or heat exchangers when these materials come into contact with the catalyst.

Chlorine of the technical grade, usually used for chlorination, always contains traces of moisture and, in addition, undesirable side reactions always result in hydrogen chloride.

According to the process described in DE-OS 31 48 450, the corrosion caused by ferric chloride as a catalyst in the production of 1,2-dichloroethane in reactors from corrosion-resistant materials can be considerably reduced if ferric chloride is used as catalyst with certain additives. In addition, it has been found that these additives also have an advantageous effect on the formation of by-products, which is reduced by this measure.

The subject of DE-OS 31 48 450 is a mixed catalyst consisting of ferric chloride and other components of the mixture for the production of 1,2-dichloroethane by reaction of ethylene with chlorine in a solvent at atmospheric or elevated pressure, characterized in that the other component of the mixture is a nitrogenous base or a salt thereof in an amount about equivalent to the amount of ferric chloride.

Since the catalyst constituents used in the form of anhydrous ferric chloride and nitrogenous bases react in the chlorination mixture to a catalyst which is highly effective even in small amounts in DE-OS 31 48 450, it has proven advantageous to obtain this catalyst in a treating the chlorination mixture as a function of its concentration in the chlorination mixture so that it can be reused for the reaction of ethylene with chlorine.

A suitable process for the treatment of the chlorination mixture containing the aforementioned catalyst allows the process disclosed in German patent application P 32 47 988. ·

P 32 47 988 discloses, inter alia, a process for producing 1,2-dichloroethane by reacting ethylene with chlorine in a solvent, preferably 1,2-dichloroethane alone, in the presence of a mixed catalyst consisting of anhydrous ferric chloride and a nitrogen base or salt thereof. a base and optionally in the presence of an inhibitor to prevent the formation of by CH ^{width d} ro ^p gr ^{Herein, t pl} e ot ^{e p d} te ^pl of boiling Otto ^{l, 2-di} ch ^l orethanu of about ^{d. 20-1} 0 ⁰ C and ^BC and atmospheric or elevated pressure and separating the 1,2-dichloroethane from the chlorination mixture, which comprises the chlorinating mixture is fed to a distillation column is distilled off from a mixture of 1,2-dichloroethane until removing the catalyst from the liquid product remaining at the bottom of the column, the separated catalyst being used to react ethylene with chlorine.

from the liquid product remaining at the bottom of the column and again according to German patent application P 32 47 988 arising from the concentration of the chlorination reaction mixture

It has now been found that in the process, the crystallizer of the catalytically active components of ethylene at the bottom of the distillation column and after the subsequent return of the crude catalyst consisting of ferric chloride and, for example, ammonia as the nitrogen base, each decreases.

the degree of returning

On the other hand, it has been surprisingly found that the liquid fraction at the bottom of the return to the reaction zone simultaneously has full catalytic activity for column chlorination at ethylene.

The present invention is a process for making 1,2-dichloroethane by reacting ethylene with chlorine in 1,2-dichloroethane as solvent at temperatures below the boiling point of ^1,2-h dichloret ^anu, i.e. p ^s te ^pl rt ^and CH ^{20-1 0 O} ° C, at! .acíc ^{h 0, 1-1,} 5 ^{MP pres} omnos and ^those of a mixed catalyst consisting of anhydrous ferric chloride and a nitrogen base or a base salt thereof, wherein the concentration of ferric chloride in the reaction mixture is from 0.001 to 0.5 % by weight, based on the amount of solvent and optionally inhibitor to prevent by-products formation, and by separating 1,2-dichloroethane from the chlorination mixture by distillation, by feeding the chlorination mixture to the distillation column, does not distil at most and 50 to 80 tu

The 1,2-dichloroethane is separated from the remaining liquid production reaction zone.

at the bottom of the column it is returned to react the ethylene with chlorine to

In addition, the process according to the invention can be arbitrarily and preferably

and)

(b)

c) the concentration of ferric chloride in the reaction mixture, which is in particular 0.002 to 0.3% by weight, based on the amount further characterized in that it is used for the reaction, makes solvents, the nitrogenous base or a salt of this base in equivalent to the ferric chloride concentration , the amount that the reaction zone comprises steel filler bodies.

The filler bodies of steel, which are optionally within the chlorination reaction conditions to form a small amount of ferric chloride. On the reactor, on the other hand, some catalyst losses can also be compensated for by direct feeding of ferric chloride to the chlorination reactor.

In each case, approximately equivalent amounts of ammonia are simultaneously introduced. Instead of ammonia, a primary, secondary alkylamine, arylalkylamine, arylamine or alicyclic amine or polyamine may also serve as the nitrogenous base.

nitrogenous bases. or tertiary

The salts of these bases can advantageously be used. Optimum concentrations of ferric chloride for the process additionally return a portion of the product from the bottom of the post-reaction zone.

halides such as ammonium chloride. the reaction is now achieved by introducing a distillation column into the chlorination reactor

The amount of new ferric chloride produced by the chlorination in the presence of the steel packing bodies is eliminated in the residue at the bottom of the column, along with the higher-boiling by-products of the chlorination reaction, and discarded.

Further, after complete emptying, the reactor can be restarted with the aid of the catalyst concentrate at the bottom of the distillation column, without the need to add fresh ferric chloride.

The process according to the invention can be carried out, for example, in a loop-shaped reactor as described in DE-OS 24 27 045.

Example

Cylinder ^for rea ^{tor h} is a ^{Z b} diarrhea ^{or tup 25} m ^3, a ^pl n ^s tru ^{20,000 if 1,} 2-d ⁱ ch ^l orethanu. The reactor contains a Raschig ring of steel at the bottom. The reaction liquid contained a mixed catalyst of ferric chloride and an equivalent amount of ammonia, the ferric chloride content being determined to be 137 mg / kg.

^When t ^{l 0.13 Mp} battery and mauve REA ^for the torus and ⁱⁿ this ^pl ^ ot ^of REAT a mixture ^{of 40} ° C to REA ^kt oru hourly introduced 2,326 kg of ethylene and 5884 kg of chlorine gas, which additionally contains about 3.5% by volume of inert gases, as well as 20 m of air as an inhibitor to prevent by-products and 40 liters of ammonia.

The reaction mixture is fed to a distillation column in which 8 173 kg / h of 1,2-dichloroethane with a purity of 99.9% can be separated every hour. 70% of the contents from the bottom of the column are returned to the reaction zone, the remaining 30% is treated in a known manner and the proportion of catalyst contained therein is fed to the combustion plant together with the high-boiling by-products.

The 96-hour balance shows no 99.6% yield of 1,2-dichloroethane based on the ethylene used.

Claims (4)

A process for the preparation of 1,2-dichloroethane by reacting ethylene with chlorine in 1,2-dichloroethane as a solvent at temperatures below the boiling point of 1,2-dichloroethane, i.e. at temperatures of 20 to 20 ° C.^{100 ALIGN!} ° C, m.p.^lac^andC^h 0,¹ to I,⁵ M^pand in the presence of pH. mixtures^éhabout katatyz ^ oru ses^thevaj^andC^andho z^bezvodé ferric chloride and a nitrogenous base or a salt thereof, wherein the concentration of ferric chloride in the reaction mixture is 0.001 to 0.5% by weight, based on the amount of solvent and optionally an inhibitor, to prevent by-products formation and separation of 1,2-dichloroethane from by distilling the chlorination mixture, characterized in that the chlorination mixture is fed to the distillation column, the 1,2-dichloroethane is distilled off at most up to the onset of catalyst deposition, and 50 to 80% of the residual liquid product at the bottom of the column is returned to ethylene reaction zone. 2. The process according to claim 1, wherein the concentration of ferric chloride in the reaction mixture is from 0.002 to 0.3% by weight, based on the amount of solvent. 3. A process according to claim 1 or 2, characterized in that nitrogenous base or a salt of said base is added in an amount equivalent to the ferric chloride concentration. Method according to one of Claims 1 to 3, characterized in that the reaction zone comprises steel filler bodies. '