GB673769A - The production of chlorine dioxide - Google Patents

Abstract

<PICT:0673769/III/1> Chlorine dioxide is produced by reacting a gaseous mixture containing diluent gas and nitrogen dioxide, say at least 2 per cent, and an aqueous solution of a chlorate, e.g. of an alkali or alkaline earth metal such as sodium, lithium, calcium, or magnesium, containing at least 2 gram ions per litre of chlorate ion advancing through the reaction zone as a thin film, and withdrawing spent liquor and the chlorine dioxide-diluent mixture from the zone. The nitrogen dioxide may be mixed with the diluent gas, e.g. air, nitrogen, carbon dioxide, or oxygen, constituting, say not more than 80 per cent of the mixture and may include water vapour, or alternatively the nitrogen dioxide-diluent mixture may be produced by passing air through an electric arc. The ratio of nitrogen dioxide molecules to chlorate ions in the reaction zone should not be greater than 2:1. Concentrated chlorate solution is passed at controlled rate from tube 18 into tower 10, which is filled with granules or pellets 15, having a large surface area per unit volume of reactor, say at least 11 sq.cm., per c.c., resting on perforated partition 11. Dilute nitrogen dioxide enters at 24 and flows cocurrent with the chlorate solution, which forms a thin film over the exposed filling. Dilute chlorine dioxide and spent solution are withdrawn at 25, 13, respectively. Suitable fillings are pumice, silica gel, or alumina with at least 30 per cent porosity. Specifications 595,528 and 666,677 are referred to.