Hydrogen peroxide electrolytic production

The electrolytic processes for commercial production of hydrogen peroxide are based on (/) the oxidation of sulfuric acid or sulfates to peroxydisulfuric acid [13445-49-3] (peroxydisulfates) with the formation of hydrogen and (2) the double hydrolysis of the peroxydisulfuric acid (peroxydisulfates) to Caro s acid and then hydrogen peroxide. To avoid electrolysis of water, smooth platinum electrodes are used because of the high oxygen overvoltage. The overall reaction is... 

Because the electrolyte contains excess alkaH which could cause spontaneous decomposition of the hydrogen peroxide, the H2O2 in the product... 

Inorganic Methods. Before the development of electrolytic processes, hydrogen peroxide was manufactured solely from metal peroxides. Eady methods based on barium peroxide, obtained by air-roasting barium oxide, used dilute sulfuric or phosphoric acid to form hydrogen peroxide in 3—8% concentration and the corresponding insoluble barium salt. Mote recent patents propose acidification with carbon dioxide and calcination of the by-product barium carbonate to the oxide for recycle. 

Carbon is widely used in the catalytic processes of the chemical industry due to its unique characteristics, such as chemical inertness, high surface area and porosity, good mechanical properties and low cost. It is used for the production of chlorine and aluminum, in metal refining (gold, silver, and grain refinement of Mg-Al alloys) as well as for the electrolytic production of hydrogen peroxide and photoelectrochemical water splitting. 

Applications. At one time the main route for the production of hydrogen peroxide was the electrolytic reduction of 02 in acidic media ... 

Feeding device. 2 — Electrolytic cells, 3 — Catholyte receiver, i — Container for electrolyte which passed through the cathode spaces of the electrolyzer, 5 — anolyte receiver, 6 — Feeding device for ammonium persulphate solution (anolyte) to distillation equipment. 1, 7a— Distillation equipment, S, 9 — Separators, 10 — Container for returned electrolyte, 11 — Droplets separator, 12. 13, 14 — Stoneware fractionating columns, IS — Aluminium tube condenser, 19, 17, IS — Receivers for individual fractions of hydrogen peroxide, 19 — Receiver for manufactured product, 20 — Reservoir for recycled electrolyte, 21 — Tank for purification of the electrolyte. 

PBE can be used for the destruction of organic compounds, regeneration ofhexavalent chromium, production of hydrogen peroxide, but their major application is in metal removal from dilute solutions. In this situation, the choice of small-sized particles is tempting for the increase of process efficiency nevertheless, a compromise must be considered since very fine particles also decrease the bed permeability causing problems to the electrolyte flow. 

Sodium percarbonate, Na2C206.—The percarbonate is said4 to be formed by the electrolytic oxidation of the normal carbonate, but it has not been isolated by this method. A substance of the formula 2Na2COs,3H2Oa is obtained by the interaction of 3 molecules of hydrogen peroxide in aqueous solution and 2 molecules of sodium carbonate, the product being subsequently dried in vacuo Other percarbon-ates have been described,8 but their existence is still a subject of debate. 

The same authors also demonstrated the feasibility of synthesizing ozone and hydrogen peroxide simultaneously using pure water and oxygen as the reactants [71]. Commercially available yS lead dioxide and graphite powders were used as the anode and cathode, respectively. While the lead dioxide was deposited directly onto a solid polymer electrolyte (Nafion 117), the graphite powder was deposited onto a carbon fiber paper and pressed against the membrane. At an applied potential of 4.5 V, with a current density of 2 A/cm, a 4.5% current efficiency was obtained for ozone evolution while the current efficiency for peroxide production was 0.8%. 

Synthesis of pure hydrogen peroxide using solid polymer electrolytes (SPE) could eliminate the need to separate the product from liquid electrolytes (basic or acidic). Designs of the (SPE) fuel cell type of reactor could be investigated for such a process. Tatapudi and Fenton [71, 80] demonstrated the basic feasibility of this process (with or without concurrent anodic ozone evolution). However, new cathode materials and... 

---