CS240987B2 - Production method of 1,2-dichloroethane - Google Patents

Abstract

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 iron(III) chloride and a nitrogen base or a salt of this base, at a temperature below the boiling point of the 1,2-dichloroethane and removal of the 1,2-dichloroethane from the chlorination mixture, which is characterised in that a) the chlorination mixture is fed to a distillation column, the 1,2-dichloroethane is distilled off from the mixture until the catalyst precipitates from the liquid bottom product, the precipitated catalyst is removed from the bottom product and the latter is used again for reaction of ethylene with chlorine or in that b) the chlorination mixture is passed over an adsorbent, the catalyst contained in the mixture is adsorbed on the adsorbent, 1,2-dichloroethane is removed from the resulting filtrate by distillation and the catalyst is recovered from the adsorbent or in that c) the process is carried out according to a), but the catalyst-containing bottom product is discarded in the case of low contents of catalyst.

Description

(54) A method for producing 1,2-dichloroethane

Process for preparing 1,2-dichloroethane by reacting ethylene with chlorine in a solvent in the presence of a mixed catalyst consisting of anhydrous ferric chloride and a nitrogenous base or a salt thereof, and optionally in the presence of an inhibitor to prevent the formation of by-products at a boiling point of 1,2-dichloroethane about 20 to 100 ° C and at atmospheric or elevated pressure and separating 1,2-dichloroethane from the chlorination mixture, characterized in that the concentration of ferric chloride in the reaction mixture is 0.001 to 0.5% by weight based on the amount of solvent, and a nitrogen base or a salt of this base is added to the reaction mixture in an amount equivalent to the ferric chloride concentration, the chlorination mixture being fed to the distillation column, distilling off the mixture

1,2-dichloroethane until the catalyst is separated from the liquid product at the bottom of the column.

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

The production of 1 _t- 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, as catalyst to accelerate the addition of chlorine. to VI. of the Periodic Table of the Elements, in particular anhydrous ferric chloride, optionally in the presence of oxygen, since ferric chloride is readily accessible and affordable. 1,1,2-Trichloroethane is a major by-product of this reaction by substituting dichloroethane.

The addition of chlorine to ethylene is carried out on a technical scale both at reaction temperatures of about 90 ° C, whereby the reaction product is distilled off from the reaction mixture using the released reaction heat, and at lower temperatures of 30 to 60 ° C as described in the Ullmann Encyclopadie. 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 removed, for example, in DE-OS 19 05 517 by pumping the reaction medium through a heat exchanger.

The crude dichloroethane produced at the lower temperatures containing the catalyst was generally removed from the reaction vessel and washed to remove the catalyst and hydrogen chloride contained in the crude product with water or aqueous alkali solutions, then the dichloroethane was separated from the aqueous layer and worked up in a known manner by distillation.

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 act advantageously 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.

The nitrogenous base may be ammonia, a primary, secondary or tertiary alkylamine, aralkylamine, arylamine or an alicyclic amine or polyamine. The nitrogenous base salt is preferably a salt with a halogen such as ammonium chloride.

The mixed catalyst described in DE-OS 31 48 450 is particularly suitable for carrying out the chlorination of ethylene at elevated temperature, whereby the heat of reaction of the ethylene chlorination can be utilized by removing the 1,2-dichloroethane produced from the reaction mixture in the form of vapors. The catalyst remains in the reaction mixture, the slight losses of catalyst being compensated from time to time.

In contrast, chlorination processes are carried out below the boiling range

1,2-dichloroethane, the catalyst elutes, for example with water, from the crude dichloroethane formed, whereby the catalyst is dissolved in the wash water, so that the resulting catalyst loss must be compensated by the addition of fresh catalyst.

Since in the process of DE-OS 31 48 450 the catalyst components used in the form of anhydrous ferric chloride and nitrogen base react in the chlorination mixture to a catalyst which is highly effective even in small quantities, it has proved advantageous to obtain this catalyst in a treatment of the chlorination mixture in dependence on its concentration in the chlorination mixture. of the mixture to be reused for the reaction of ethylene with chlorine.

A suitable process for treating the chlorination mixture containing the above catalyst has now been found in the process of the present invention.

Accordingly, the present invention provides a process for the preparation of 1,2-dicCloortCan by reacting ethylene with chlorine in a solvent in the presence of a mixed catalyst consisting of anhydrous ferric chloride and a nitrogen base or a salt thereof and optionally in the presence of an inhibitor to prevent by-products formation below 1. 2-dicCloortChnu from about 20 to 100 ° C, and ^p and s ^ ^^ axis CTAM increase or t ^l and ^k u ^ sepa Vani ^_1/2 - ICC ^{h d h} orrt AAU zc ^ orační composition which comprises, The concentration of ferric chloride in the reaction mixture is 0.001 to 0.5% by weight, in particular 0.002 to 0.01% by weight, based on the amount of the solvent, and a nitrogen base or a salt of this base is added to the reaction mixture in an amount equivalent to the concentration ferric chloride, while the cooling mixture is fed to a distillation column, 1,2'-hicClore is distilled off from the mixture to remove the catalyst from the bottom column liquid product, the bottom column liquid product is separated and the catalyst is reused to react ethylene with chlorine or the bottom column liquid catalyst product is discarded at a catalyst content of not more than 0.001% by weight , based on the liquid fractions in the bottom product.

As in the case of the corresponding known processes for the preparation of 1,2-dichloroethane, 1,2-dichloroethane itself is also used as solvent.

An alternative embodiment of the process according to the invention is to dispense with the isolation of the catalyst and to discard the product remaining at the bottom of the column containing the catalyst. This embodiment is economically advantageous if the bottom product contains a catalyst in an amount of not more than about 0.001% by weight, based on the liquid portions of the bottom product, which would cause difficulties in separating the catalyst.

The catalyst used in the process of the present invention can be described as technically advanced since its use suppresses or completely eliminates the formation of by-products, with the exception of a small amount of 1,1,2-tricorphancan and the corresponding small amount of hydrogen chloride.

In addition, the reaction solution remains bright even if the reaction time is longer, if the nitrogenous base to be added to the chlorination mixture is, for example, ammonia. Alternatively, during the reaction, the darkened reaction mixture again brightens again after a short time, depending on the ammonia addition.

Finally, it has been found that the conversion according to the invention is almost quantitative in a high yield per unit of space and time. This result has been achieved. Even at catalyst concentrations of less than 0.003% by weight, based on ferric chloride.

The technical instructions for the treatment of the chlorinating mixture presented in accordance with the present invention were not obvious, since it had to be preceded by the fact that the chlorinating mixture to be treated does not contain already used catalyst components in the form of ferric chloride and nitrogenous base; a product of ferric chloride and a nitrogenous base which, in terms of its catalytic activity, significantly exceeds the catalytic activity of ferric chloride. Therefore, it has been shown to be useful in recovering this catalyst, as opposed to the prior art.

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

The following example invention. . it does not limit the scope in any way. and

Example

To REA ^to a torus-shaped ^cylinder is ^h o ^{f H} contained amounts, and ^{even 25} m ³ p e ^of the ^{dl 20000 lit Gd} Ru ^{l, 2-di-} chloroethane and the reactor charge were added. 170 mg of ferric chloride per kg of 1,2-dichloroethane In addition, about 600 liters of ammonia are added to this solution.

When the pressure in the reactor head, about 0.13 M ^at aa ^p te rt ^{pl of CZK} rea n ⁱ as ^{well as} mixtures ^{and 4} 0 ° C do.reaktoru introduced per hour 1008 kg of ethylene and 2540 kg of chlorine gas, which additionally contains □

about 4% by volume of inert gases as well as 8 m air. In addition, about 80 liters of ammonia and 170 mg of ferric chloride are added to the chlorination mixture every hour.

About 3,525 kg / h of crude dichloroethane are removed from the reactor and fed to the bottom of the distillation column. The raw product fed has the following composition:

C2H4 (ethylene) 0.0069% by weight

C 1 H 8 Cl / ethyl chloride / 0.0081% by weight 1 H -dilhlereanane 99.8% by weight

1,1,2-trichloroethane 0.15% by weight

The column is operated at a slight vacuum (about 0.07 MPa absolute pressure) at the top of the column. 95% of the desired reaction product is distilled off from the reaction mixture, the purified 1,2-dicilhretea having the following composition:

C2H5Cl

1,2- dichlorhletian

1.1.2- tllcelhlerian

0.01% by weight

99.98% by weight

0.01% by weight

After cooling, the residue at the bottom of the column is passed through a filter and filtered. The filtrate is fed to a vacuum column for further processing. The separated catalyst is removed from the filter with the exclusion of moisture and fed to a dissolution tank containing 1,2-dichloroethane.

In the further course of the chlorination process, the amount of catalysts required for the reaction from the recovered portion is added, while the feed of ferric chloride and ammonia could be shut off.

Claims (1)

SUBJECT OF THE INVENTION A method for producing 1,2-dichlhrethanu reacting ethylene with chlorine in a solvent in the presence of a mixed catalyst consisting of anhydrous ferric chloride and a nitrogen base or a salt of a base and optionally in the presence of an inhibitor to prevent production of by p ^ at ^ dijktů Ptot ^{after about} l ^ep dt ^ou t reflux for ^1, 2-d ⁱ c ^{h e} ORER anu ^b ru from ^H and from ²⁰ to WO DEG C. and ^at mos ^{t f} Erick pressure or elevated pressure and separating the 1,2-dichlorereaau · from the chlorination mixture, which comprises wherein the concentration of ferric chloride in the reaction mixture is 0.001 to 0.5% by weight, in particular 0.002 to 0.01%. by weight based on the amount of solvent and to the reaction mixture is added a nitrogen base or a salt of this base in an amount equivalent to the ferric chloride concentration, the chlorination mixture being fed to the distillation column, 1,2-dichloroethane is distilled off of the catalyst of. at the bottom of the column product, the separated catalyst product is separated from the column bottom product. the catalyst is reused to react ethylene with chlorine or liquid. the bottom product containing the catalyst is ejected at a catalyst content of not more than 0.001% by weight, based on the liquid fractions of the bottom product.