Process of preparing alkali peroxide solutions

A process of preparing an aqueous alkaline solution containing alkali hydroxide and hydrogen peroxide and having an alkali hydroxide/H.sub.2 O.sub.2 molar ratio of 0.5 to 2.5, said process comprising the steps of:

• a) providing an electrochemical cell divided into an anode chamber containing an anode and an anolyte, a cathode chamber containing a porous oxygen diffusion cathode and a catholyte, and an intermediate chamber between the cathode chamber and the anode chamber containing an intermediate solution, said electrochemical cell having an anion exchange membrane separating the anode chamber from the intermediate chamber and a cation exchange membrane separating the cathode chamber from the intermediate chamber, and providing a decomposition tank outside the electrochemical cell for receiving an aqueous starting solution containing at least one alkali salt selected from the group consisting of alkali sulfates, alkali hydrogen sulfates, alkali sulfites, alkali hydrogen sulfites, alkali carbonates and alkali hydrogen carbonates;
• b) feeding said aqueous starting solution to the decomposition tank, feeding an alkali hydrogen sulfate-containing feed solution from the decomposition tank into the intermediate solution in the intermediate chamber, feeding an oxygen-containing gas to the porous oxygen diffusion cathode and feeding an alkali hydroxide-containing solution into the catholyte in the cathode chamber;
• c) passing an electric current between the anode and the cathode to form said hydrogen peroxide and said alkali hydroxide in the catholyte by cathodic reduction and to form sulfuric acid in the anolyte;
• and
• d) withdrawing a portion of the anolyte from the anode chamber, feeding said portion of the anolyte back into the anolyte in the anode chamber, withdrawing another portion of the anolyte from the anode chamber as a by-product solution containing the sulfuric acid, withdrawing a portion of the intermediate solution in the intermediate chamber and feeding said portion of the intermediate solution into the decomposition tank and withdrawing a portion of the catholyte from the cathode chamber to form the aqueous alkaline solution containing the alkali hydroxide and the hydrogen peroxide.

A process of preparing an aqueous alkaline solution containing alkali hydroxide and hydrogen peroxide and having an alkali hydroxide/H.sub.2 O.sub.2 molar ratio of 0.5 to 2.5, said process comprising the steps of:

• a) providing an electrochemical cell having an anode chamber containing an anode and an anolyte, a cathode chamber containing a porous oxygen diffusion cathode and a catholyte, an intermediate chamber between the anode chamber and the cathode chamber, said intermediate chamber containing an intermediate solution, and a cation exchange membrane separating the anode chamber from the intermediate chamber and another cation exchange membrane separating the cathode chamber from the intermediate chamber, and providing a decomposition tank outside the electrochemical cell for receiving an aqueous starting solution containing at least one alkali salt selected from the group consisting of alkali sulfates, alkali hydrogen sulfates, alkali sulfites, alkali hydrogen sulfites, alkali carbonates and alkali hydrogen carbonates;
• b) feeding said aqueous starting solution to the decomposition tank, feeding an alkali hydrogen sulfate-containing feed solution from the decomposition tank into the anolyte in the anode chamber, feeding an oxygen-containing gas to the porous oxygen diffusion cathode and feeding an alkali hydroxide-containing electrolyte into the catholyte in the cathode chamber;
• c) passing an electric current between the anode and the cathode to form the hydrogen peroxide and the alkali hydroxide in the catholyte by cathodic reduction and to form sulfuric acid in the anolyte;
• and
• d) withdrawing a portion of the anolyte from the anode chamber as a sulfuric-acid containing solution, feeding said portion of the sulfuric acid-containing solution into the decomposition tank together with the aqueous starting solution and feeding a portion of the catholyte containing the alkali hydroxide and the hydrogen peroxide into the intermediate chamber and withdrawing a portion of the intermediate solution in the intermediate chamber as the aqueous alkaline solution containing the alkali hydroxide and the hydrogen peroxide.