US 4,672,142 AGranted

Process for making 1,2-dichloroethane

AssigneeHoechst Aktiengesellschaft

InventorsJoachim Hundeck, Harald Scholz, Hans Hennen, Bernhard Kuxdorf, Herbert Pusche

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Abstract

The disclosure relates to a process for making 1,2-dichloroethane by reacting ethylene and chlorine in a reaction zone having a liquid medium containing chlorinated C.sub.2 -hydrocarbons circulated therein. To this end, the disclosure provides: (a) for approximately equimolar proportions of ethylene and chlorine to be introduced into the circulated liquid medium; for the whole to be reacted in a reaction zone at a temperature of about 75.degree. up to 200.degree. C. under a pressure of about 1 up to 15 bars, the mean sojourn time of the reaction mixture in the mixing zone and reaction zone being equal to about 1 to 15 hours; (b) for a portion of liquid reaction mixture to be removed from the reaction zone and subdivided into two streams, for one of these streams to be passed through a heat exchanger for the abstraction of calorific energy and reduction of its initial temperature, and for it to be recycled to the mixing and reaction zone; for the second stream to be introduced into an expansion vessel and for proportions corresponding to the quantity of reaction product formed in the reaction zone to be evaporated therein; for resulting vaporous matter to be introduced into a fractionating column, unevaporated liquid matter of the second stream being recycled into the liquid medium circulated in the mixing and reaction zone; and (c) for 1,2-dichloroethane to be distillatively separated from the vaporous matter introduced into the fractionating column with the use of a portion of the heat energy transferred inside the heat exchanger and for the 1,2-dichloroethane to be removed overhead.

In the process for making 1,2-dichloroethane by reacting ethylene and chlorine in a reaction zone having a liquid medium containing chlorinated C.sub.2 -hydrocarbons circulated therein at a temperature lower than the evaporation temperature of said medium under the pressure prevailing inside the reaction zone, in the presence of a conventional chlorination-inducing catalyst so as to obtain crude 1,2-dichloroethane, removing the crude dichloroethane from the reaction zone and purifying it in a separate downstream fractionating zone, the improvement which comprises:

(a) introducing approximately equimolar proportions of ethylene and chlorine into the circulated liquid medium;
intensively mixing the whole in a mixing zone and then reacting the mixture in a reaction zone at a temperature of about 75.degree. up to 200.degree. C. under a pressure of about 1 up to 15 bars, the mean sojourn time of the reaction mixture in the mixing zone and reaction zone being equal to about 1 to 15 hours;
(b) removing a portion of the liquid reaction mixture from the reaction zone and subdividing said portion into two partial streams, passing one of these partial streams through a heat exchanger for extraction of chlorific energy and reduction of its initial temperature and recycling it to the mixing and reaction zone;
introducing the second partial stream into an expansion vessel and evaporating therein a proportion corresponding to the quantity of reaction product formed in the reaction zone;
introducing resulting vaporous mater into a fractionating column and recycling unevaportated liquid matter of the second partial stream into the liquid medium circulated in the mixing and reaction zone;
and
(c) separating distillatively 1,2-dichloroethane from the vaporous matter introduced into the fractionating column with the use of a portion of the heat energy transferred inside the heat exchanger and removing the 1,2-dichloroethane overhead, higher chlorinated products being obtained in the column's base portion from which they are removed and worked up separately.

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Abstract

Claims10