Chemistry: electrical and wave energy – Processes and products
Patent
1980-09-23
1982-06-15
Andrews, R. L.
Chemistry: electrical and wave energy
Processes and products
C25B 306
Patent
active
043349676
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the preparation of chlorine-containing organic compounds and, more particularly, to methods for preparing 1,2-dichloroethane.
STATE OF THE ART
Known in the art is a chemical method for preparing 1,2-dichloroethane by chlorination of ethylene. The process is carried out in a medium of anhydrous 1,2-dichloroethane saturated with ferric chloride at the temperature of 50.degree. C. The yield of 1,2-dichloroethane is approaching 100% as calculated for the reacted chlorine (cf. Japanese Patent No. 48-7083, Cl. C 07 c).
This method necessitates a preliminary production of chlorine, a subsequent purification thereof, compression and a thorough drying. Traces of moisture impair the process parameters by inactivating ferric chloride which is an inhibitor of the substitutive chlorination.
Also known in the art is a method for preparing 1,2-dichloroethane by way of electrolysis of a 4.4-20% aqueous solution of hydrochloric acid having a temperature within the range of from 20.degree. to 70.degree. C. with the simultaneous supply of ethylene into the anodic space. By the term anodic space, which is generally accepted, the space is meant surrounding the anode and occupying not more than 1-2% of the anode height. Ethylene is supplied at such a rate that the amount of hydrochloric acid fed into the solution is 10 times higher than its stoichiometric amount. The electrolysis is carried out in an electrolyzer of the membrane type at an anodic current density of from 0.07 to 0.35 A/cm.sup.2. The current yield of 1,2-dichloroethane (which is equivalent to the yield calculated for the reacted chlorine in the chemical method) is 20 to 44%. The rest of the current is consumed mainly for the formation of epichlorohydrin. The yield of 1,2-dichloroethane as calculated for the passed ethylene does not exceed 10% (cf. I. A. Kalinin, V. V. Stender "Electrolytic Oxidation and Chlorination of Ethylene", Journal of Applied Chemistry, vol. 19, No. 10-11, 1946, p. 1045).
This prior art method has a low yield of 1,2-dichloroethane and insufficient purity thereof. The low anodic current density as employed in the process results in a reduced efficiency of the electrolyzer operation. On the other hand, increasing the anodic current density results in the appearance of chlorine in the gases effluent from the electrolyzer which is intolerable due to the formation of an explosive mixture. Carrying-out the process in a membrane-type electrolyzer causes additional losses of electric power due to the voltage drop on the membrane and complicates the process technology and equipment.
DISCLOSURE OF THE INVENTION
The present invention is directed to the provision, in the process of preparing 1,2-dichloroethane by electrolysis of an aqueous solution of hydrochloric acid, of such conditions of the electrolytic process which would make it possible to produce 1,2-dichloroethane with a a high yield (both current yield and yield as calculated for the passed ethylene) and a high purity, as well as to make use of higher anodic current density values and simplify the technology and equipment of the electrolysis.
This object is accomplished by a method of preparing 1,2-dichloroethane by electrolysis of a 12-36% aqueous solution of hydrochloric acid at a temperature within the range of from 45.degree. to 70.degree. C. with a simultaneous admission of ethylene into the anodic space, wherein, in accordance with the present invention, prior to electrolysis, an additive is introduced into the aqueous solution of hydrochloric acid; this additive comprises a metal belonging to the group of iron or a compound of a metal of this group, or an alloy containing at least one metal of the iron group or any combinations of the above-mentioned substances; the additive is introduced in such an amount that the concentration of ions of the metal of the group of iron in the aqueous solution of hydrochloric acid be at least equal to 0.006 g-ion per liter of said solution.
It is generally accepted that the metals of the g
REFERENCES:
patent: 4162948 (1979-07-01), Yagii et al.
Paprotskaya Valentina A.
Ponomarenko Evegina A.
Sokolov Jury M.
Tedoradze Gurami A.
Tomilov Andrei P.
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