GB473342A - Improvements in the manufacture of hydrogen peroxide - Google Patents

Abstract

<PICT:0473342/III/1> In obtaining hydrogen peroxide by a cyclic process in which solutions comprising ammonium sulphate and sulphuric acid are electrolyzed and the resulting solution is distilled to liberate hydrogen peroxide, all or part of the residual solution from the hydrogen peroxide distillation is subjected to a separate, rapid, thin layer distillation in the presence of water or steam at a high temperature in order to evaporate ammonia and sulphuric acid which are condensed and cooled for return to the electrolysis step. Residual lye from the hydrogen peroxide distillation containing ammonium sulphate and sulphuric acid flows from a tank 1 down a quartz tube 3 which is externally heated by combustion gases to 300--400 DEG C. The vapours pass through a pipe 8 to a washing tower 9 which is irrigated by a circulation of washing liquid passing through a cooler 11, pump 12 and spray 13. The circulating liquid has the same composition as the distillate coming from the pipe 8. The undistilled residue passes through an outlet 6 to a receptacle 7 and may consist of 10 per cent of the original liquid. It contains all the catalytic impurities of the original liquid. If the residue consists of 30 per cent it may be returned continuously to the tank 1 until it has been sufficiently concentrated when it can be neutralized to precipitate catalytic impurities and evaporated. This step is preferable if non-volatile compounds such as sodium or calcium sulphates are employed during the electrolysis. The residue may be treated with water and allowed to stand in order to hydrolyze the pyrosulphates it contains prior to the neutralization step. It is preferable to maintain, by the addition of water, a water concentration of not lower than 30 per cent in the liquor proceeding to the tube 3. Alternatively, the distillation may be effected by flowing the liquors down a quartz filled tower up which passes steam, superheated to 500 DEG C., the vapours being treated as before; or the residue from the distillation set forth in the Figure, can be subjected to a steam distillation, a common condensing plant being employed. The distillation may be conducted at atmospheric or diminished pressure.