Patent EA-003368-B1 (EA)
Title: Method for preparing an aqueous hydrogen peroxide solution directly from hydrogen and oxygen and implementing device
Inventor: DEVIC MICHEL
IPC: B01J23/44
Filed: 1999-01-29
Abstract: 1. Process for the preparation of an aqueous hydrogen peroxide solution directly from hydrogen and oxygen, which comprising providing a stirred reactor containing an aqueous reaction medium, wherein the aqueous reaction medium comprises a catalyst in a dispersed state and has a lower part and an upper part; adding a mineral acid to the aqueous medium so that the aqueous medium becomes acidic; injecting hydrogen and oxygen, in the form of small bubbles, into the lower part of the aqueous reaction medium a hydrogen molar flow rate and an oxygen molar flow rate, wherein the ratio of the hydrogen molar flow rate to the oxygen molar flow rate is greater than 0.0416; and introducing oxygen into a continuous gas phase in the stirred reactor and/or into the upper part of the aqueous reaction medium in an amount such that the molar ratio of hydrogen to oxygen in the continuous gas phase is less than 0.0416. 2. Process according to claim 1, wherein the injections of hydrogen and of oxygen in the form of small bubbles into the lower part of the aqueous reaction medium are situated at the bottom of the stirred reactor. 3. Process according to claim 1, or 2 wherein the injections of hydrogen and oxygen into the lower part of the aqueous reaction medium are contiguous. 4. Process according to any one of claims 1 to 3, wherein the reaction medium comprises stabilizers for hydrogen peroxide. 5. Process according to claim 1-4, wherein the reaction medium comprises halides. 6. Process according to claim 5, wherein the halide is the bromide. 7. Process according to claim 6, wherein the bromide is used in combination with bromine in the free state. 8. Process according to claim 1-7, wherein the catalyst comprises palladium. 9. Process according to claim 8, wherein the catalyst comprises platinum. 10. Process according to claim 8 or 9, wherein the catalyst is supported. 11. Process according to claim 10, wherein the support is chosen from silica, alumina and silica-aluminas. 12. Process according to claim 1-11, wherein the oxygen, which is introduced into the continuous gas phase and/or into the upper part of the aqueous reaction medium, comprises hydrogen. 13. Process according to claim 1, wherein the oxygen, which is injected into the lower part of the aqueous reaction medium, comprises hydrogen. 14. Device for the preparation of an aqueous hydrogen peroxide solution directly from hydrogen and oxygen, comprising a stirred reactor fed continuously or periodically with working solution, characterized in that the reactor is equipped: with one or more inlet (s) for gaseous hydrogen, in the form of small bubbles, into the lower part of the aqueous reaction medium; with one or more inlet(s) for gaseous oxygen, optionally containing hydrogen, in the form of small bubbles, into the lower part of the aqueous reaction medium; with a pressure regulator which makes it possible to keep the pressure prevailing inside the reactor constant by discharging excess unconsumed gaseous reactants; and with one or more inlet(s) for gaseous oxygen, optionally containing hydrogen, into the continuous gas phase and/or into the upper part of the aqueous reaction medium, which is/are controlled by an analyzer of the gas flow exiting from the reactor so that the molar ratio of hydrogen to oxygen in the continuous gas phase is less than 0.0416. 15. Device according to claim 14, characterized in that the reactor is equipped with an outlet for the extraction of the aqueous hydrogen peroxide solution. 16. Device according to claim 14 or 15, characterized in that the gas flow exiting from the reactor is reinjected into the circuit feeding the lower part of the aqueous reaction medium with oxygen. 17. Device according to claim 14 or 15, characterized in that the gas flow exiting from the reactor, is reinjected, after optional adjustment by addition of oxygen and optionally by removal of hydrogen, into the circuit feeding with oxygen the continuous gas phase and/or the upper part of the aqueous reaction medium. 18. Device according to any one of claims 14 to 17, characterized in that at least one inlet for hydrogen and at least one inlet for oxygen, in the form of small bubbles, are situated at the bottom of the stirred reactor. 19. Device according to one of claims 14 to 18, characterized in that the inlets for oxygen and for hydrogen in the lower part of the aqueous reaction medium are adjacent. 20. Device according to any one of claims 14 to 19, characterized in that the stirring of the reactor is provided by one or more independent impellers or turbines. 21. Device according to claim 20, characterized in that the turbines are floppy turbines. 22. Device according to claim 20, characterized in that the turbines are self-suction turbines. 23. Device according to any one of claims 14 to 22, characterized in that the stirred reactor is equipped with a heat exchanger. 24. Device according to claim 23, characterized in that the exchanger is a vertical tubular bundle or wound spirals or a bundle of vertical plates positioned radially. 25. Device according to any one of claims 14 to 24, characterized in that all the small bubbles in the aqueous reaction medium rise solely under the influence of gravity to the interface between the aqueous medium and the continuous gas phase when stirring is halted.