Recovery of Chlorine from Anhydrous Hydrogen Chloride

Abstract

Chlorine and hydrogen chloride are classified as potentially hazardous and toxic chemicals. Large-scale industrial processes worldwide use chlorine as primary raw material from which hydrogen chloride is obtained as a major byproduct. Hydrogen chloride is sold as aqueous HCl or used as a raw material for the production of chlorinated products, but the quantity of HCl produced by chlorine processes is much more than what the market can absorb, resulting in a toxic waste disposal problem. Recovery of material chlorine from this hydrogen chloride is very important and is of utmost industrial interest as it would cut down on the production of chlorine at the same time solve the waste disposal problem. It is theoretically possible to convert hydrogen chloride to chlorine for the recycling and reuse of chlorine. In this paper we have developed a process for recovery of chlorine from anhydrous hydrogen chloride obtained as a byproduct during low temperature vapor phase hydrolysis of titanium chloride to get TiO2. It is a two-stage process where chlorination is carried out in a fixed bed reactor using copper oxide catalyst at a temperature in the range of 423-523 K followed by oxidation of copper chloride catalyst in a second fixed bed reactor operating at 573-653 K. This process operates under conditions in which the catalyst does not volatilize and in which the activity of the catalyst remains stable. Operation at relatively moderate temperature prevents corrosion and minimizes the extrinsic energy input required. The chlorine recovery process makes the new generation chloride process for synthesis of TiO2 economical.