GB956569A - Process for the manufacture of chlorine dioxide - Google Patents

Abstract

Chlorine dioxide is prepared by reducing an alkali metal or alkaline earth metal chlorate with hydrogen chloride in aqueous solution, in the presence of manganese and/or silver ions as catalyst. The reaction may be effected at 0-100 DEG C., preferably at 20-70 DEG C. The manganese and/or silver ions may be added in the form of manganese chloride or dioxide, or of silver nitrate, oxide or chloride. Concentrations of 0.5-1.5 gm. of Mn2+ ions per litre of reaction solution and 0.05-0.3 gms. of Ag + ions per litre of reaction solution may be used. At lower temperatures, manganese ions are preferably used only in conjunction with silver ions. The chlorate solution may be a calcium chlorate solution obtained by chlorinating lime, a chloride-free calcium chlorate solution to which NaCl or CaCl2 is preferably added, or a sodium or potassium chlorate solution. The hydrogen chloride required may be introduced into the solution in the form of aqueous hydrochloric acid or gaseous HCl, or it may be produced in situ, e.g. by adding a NaCl solution to a solution of the chlorate in a non-reducing acid such as H2SO4, in the presence of the manganese and/or silver ions.