GB577054A - Improvements in processes for producing chlorine dioxide - Google Patents

Abstract

577,054. Chlorine dioxide. MOOCH DOMSJO AKTIEBOLAG. May 5, 1944, No. 8532. Convention date, June 2, 1943. [Class 1 (ii)] Chlorine dioxide is produced by reacting a gaseous reducing agent with a metal chlorate in an aqueous solution previously acidified by a strong acid (except halogenic acids) so that the acidity of the solution is at least 2-normal. Sufficient strong acid, e.g., 14.5 N sulphuric acid, is added to an aqueous solution of a metal chlorate, at least a 3-molar solution, so that the concentration of free acid is equivalent to at least a 2N but preferably 7 to 8 N solution. Sulphur dioxide, not in excess of 10 per cent. but preferably 5 per cent. by volume, is mixed with an inert gas such as nitrogen or air, and an even flow of the final divided mixture introduced at room temperature, into the acid chlorate solution which is subjected to vigorous stirring. Chlorine dioxide, almost free from chlorine, is evolved during the greater part of the process. The process may be carried out at 10-40‹C., but preferably from 20-25‹C. The residual acid solution may be re-used by evaporating, adding fresh acid if desired. separating the acid sodium sulphate which crystallises on cooling, and adjusting the concentration to the desired value, or the used acid solution may be utilised for acidifying the chlorate solution with or without addition of fresh acid. An example is given. U.S.A. Specification 2,089,913 is referred to.