GB956598A - Chlorine manufacture - Google Patents

Abstract

Chlorine is made by a four stage process, the first stage being the production of ammonium chloride from ammonia by known methods; the second stage being the reaction of the said ammonium chloride, a chloride of a metal in a lower valency state, and ammonia in an aqueous system with oxygen or air, whereby a chloride with the metal in a higher valency state is formed and is combined with ammonia in solution to give an ammine; the third stage involves the separation and drying of the ammine and heating it to drive off ammonia without decomposing the higher chloride, ammonia being returned to the first and second stages; and the fourth stage comprises heating the higher chloride to give chlorine, the lower chloride also formed being returned to the second stage. Metals whose chlorides may be used include copper, cobalt, and chromium. The second stage reaction is carried out at a temperature of 20 DEG to 70 DEG C., the initial concentrations of both ammonium chloride and metal chloride, e.g. cuprous chloride, ranging from 4 to 6 molar and that of ammonia from 12 to 18 molar. Using copper as the metal, the cupric chloride ammine formed may be decomposed into its components either at a temperature of 200 DEG to 250 DEG C. under atmospheric pressure or at a temperature of 180 DEG to 230 DEG C. under less than atmospheric pressure. Chlorine is then liberated from the cupric chloride by heating at a temperature above 450 DEG C. Ammonium chloride for the first stage may be obtained either by direct combination of ammonia and hydrogen chloride or as a product of the ammonia-soda process. It may be introduced to the second stage in solid form or as an aqueous solution, which may contain dissolved electrolytes e.g. sodium chloride provided that they do not interfere with the formation and separation of the ammine. Aeration with air or oxygen is effected at a gradually diminishing rate in order to prevent loss of ammonia. Carrier gas e.g. nitrogen may be used to recover ammonia liberated on heating ammine by rapidly passing the carrier gas through a fixed bed of solid ammine and silica wool at a preferred temperature of between 220 DEG and 230 DEG C. at atmospheric pressure.