PROCESS FOR PREPARING CHROMIC ANHYDRIDE

摘要

The invention relates to a process for preparing chromic anhydride by reacting concentrated sulphuric acid with sodium bichromate solution. After concentrating the sodium bichromate solution from a concentration of 650...720 g/l Cr2O3 to a concentration of 980...1,000 g/l Cr2O3 at a temperature of 150...160°C, the concentrated sulphuric acid is dosed in a stoichiometrically calculated amount, the dosing being followed by the completion of the reaction, afterwards the sodium bisulphate fusion phase is started at a temperature of 180...184°C followed by the chromic anhydride fusion phase at a temperature of 194...196°C and by the separation of the resulting chromic anhydride from the sodium bisulphate for 10 min, while maintaining the temperature at 198...202°C.