A process for the production of chlorine dioxide

A process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, a mineral acid and methanol as a reducing agent in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50 DEG C to about 100 DEG C and at an acidity within the interval from about 2 to about 11 N and subjected to a subatmospheric pressure. Thereby water is evaporated and a mixture of chlorine dioxide, water vapour and gaseous by-products is withdrawn from an evaporation region in the reaction vessel. The alkali metal sulphate is precipitated in a crystallization region in the reaction vessel. The content of formic acid in the reaction vessel is increased by addition of formic acid to a content of formic acid exceeding about 0.3 M. The gaseous by-products are condensed to obtain formic acid and the content of formic acid in the reaction vessel is increased by recirculation of the condensate.