Method for producing 1,2-dichloroethane

Abstract

A process for the preparation of 1,2-dichloroethane that is very pure with respect to chloral or/and chloral hydrate and carbon dioxide is described herein. The process comprises oxychlorination of ethylene, using hydrogen chloride and an oxygen-containing gas, and alkali treatment of the 1,2-dichloroethane produced. In the process, the carbon dioxide present in the 1,2-dichloroethane-containing organic phase is, in accordance with the invention, substantially separated out from the 1,2-dichloroethane-containing organic phase before the alkali treatment.

1 . Process for the preparation of 1,2-dichloroethane, wherein oxychlorination of ethylene, using hydrogen chloride and an oxygen-containing gas, and alkali treatment of the dichloroethane are carried out, characterised in that carbon dioxide is separated out before alkali treatment of the 1,2-dichloroethane.  
     
     
         2 . Process according to  claim 1 , characterised in that the carbon dioxide is separated out by relieving the 1,2-dichloroethane-containing reaction mixture of pressure.  
     
     
         3 . Process according to  claim 1  or  2 , characterised in that the carbon dioxide is separated out from the 1,2-dichloroethane-containing reaction mixture in a column ( 2 A) by introducing an inert gas.  
     
     
         4 . Process according to one of the preceding claims, characterised in that the inert gas is nitrogen.  
     
     
         5 . Process according to one of the preceding claims, characterised in that the carbon dioxide is separated out from the 1,2-dichloroethane-containing reaction mixture by indirect introduction of heat.  
     
     
         6 . Process according to one of the preceding claims, characterised in that separating out of the carbon dioxide is additionally or alternatively carried out by means of a heat exchanger.  
     
     
         7 . Process according to one of the preceding claims, characterised in that the reaction mixture, after separating out of the carbon dioxide, has a carbon dioxide content of less than 0.3% (w/w), preferably less than 0.1% (w/w) and especially less than 0.06% (w/w).  
     
     
         8 . Process according to one of the preceding claims, characterised in that the 1,2-dichloroethane-containing product from oxychlorination is quenched, cooled and/or liquefied before separating out of the carbon dioxide.  
     
     
         9 . Process according to  claim 8 , characterised in that quenching is carried out by means of introduction into a sump region of a washing zone, which sump region is in the form of a bubble column and contains a washing liquid.  
     
     
         10 . Process according to one of claims  8  or  9 , characterised in that quenching is carried out by means of bringing into contact with an aqueous solution, especially water.  
     
     
         11 . Process according to one of the preceding claims, characterised in that the 1,2-dichloroethane-containing reaction mixture is treated with an aqueous alkali solution after separating out of the carbon dioxide.  
     
     
         12 . Process according to  claim 11 , characterised in that the 1,2-dichloroethane-containing reaction mixture or the 1,2-dichloroethane is separated from the aqueous alkali solution after treatment with the aqueous alkali solution and, before the treatment, the aqueous alkali solution preferably has a pH greater than 8.5.  
     
     
         13 . Process according to  claim 12 , characterised in that the aqueous alkali solution is recycled.  
     
     
         14 . Process according to  claim 13 , characterised in that the aqueous alkali solution is recycled to the quench.  
     
     
         15 . Process according to one of the preceding claims, characterised in that, after separation of the aqueous alkali phase from the organic phase, a pH in the range of from 10.5 to 13 is set.  
     
     
         16 . Process according to one of the preceding claims, characterised in that the 1,2-dichloroethane-containing reaction mixture has a chloral or/and chloral hydrate content of less than 0.02% (w/w), preferably less than 0.005% (w/w) and especially less than 0.002% (w/w).  
     
     
         17 . 1,2-Dichloroethane obtainable using a process according to one of  claims 1  to  16 .