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1. WO1988003966 - ELEMENT DE PRODUCTION DE PEROXYDE D'HYDROGENE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

Claims :
1. An electrolytic cell characterized by an electrolyte inlet, an electrolyte outlet, a porous cathode permeable to a gas, the cathode having a first surface contacting the electrolyte and a second surface forming an exterior surface of the cell in contact with an oxygen-containing gas, an anode, means to divert oxygen gas away from the anode, separating means between the cathode and the anode, and means to urge the electrolyte from the electrolyte inlet to the electrolyte outlet, the separating means defining an anode compartment and a cathode compartment in the cell, the separating means being substantially permeable to an ion in the electrolyte, the cell being disposed with the cathode and anode in a generally vertical, horizontal or inclined attitude, the anode compartment being provided with means to urge electrolyte to flow across the surface of the anode, and the cathode compartment being provided with means to urge the electrolyte from the electrolyte inlet across the first surface of the cathode.
2. The cell of claim 1 characterized in that porous cathode is self-draining and the separating means is permeable to an ion of the electrolyte and is sufficiently permeable to the electrolyte to controllably urge the electrolyte from the electrolyte inlet through the separating means into the self-draining cathode at a rate substantially equal to the drainage rate of the cathode into the electrolyte outlet and in a quantity sufficient to fill only a portion of the cathode, the means in the anode compartment which urge the electrolyte to flow across the surface of the anode divert the oxygen gas in the anode compartment away from the separating means and out of the electrolytic cell.
3. The cell of claim 2 characterized in that the anode and cathode are disposed in a generally horizontal attitude with a difference of static head between the electrolyte inlet and the electrolyte outlet urging the electrolyte from the electrolyte inlet to the electrolyte outlet and the separating means has a wicking action sufficient to urge the electrolyte across the surface of the anode and cathode and controllably urge electrolyte into the cathode and is also sufficiently gas permeable to urge the oxygen gas out of the anode compartment.
4. The cell of claim 1 characterized in that the cathode and anode are disposed in a generally horizontal attitude with the cathode superior to the anode and the separating means being substantially permeable to an ion in the electrolyte and to oxygen gas to urge oxygen gas out of the anode compartment into the cathode compartment, but being substantially impermeable to the electrolyte.
5. The cell of claim 4 characterized in that the separating means is a microporous film punctured with openings to permit the flow of oxygen gas from the anode compartment into the cathode compartment.
6. The cell of claims 4 or 5 characterized in that the anode compartment is provided with a first porous means to distribute oxygen gas generated at the anode to the separating means and to urge the electrolyte to flow across the surface of the anode and the cathode compartment is provided with a second porous means to urge the electrolyte from the electrolyte inlet across the surface of the cathode.
7. The process of manufacturing hydrogen peroxide by introducing an aqueous alkaline electrolyte into the electrolyte inlet of the cells of claims 1 to 6 and reducing oxygen at the cathode to hydrogen peroxide and withdrawing hydrogen peroxide from the cell.
8. An article of manufacture useful to construct the electrolytic cell of claim 6 suitable for the manufacture of hydrogen peroxide by the reduction of oxygen at a cathode, the article of manufacture characterized by layers in sequence; a first nonconductive porous means inert to an alkaline liquid, separating means, a second nonconductive porous means inert to an alkaline liquid containing hydrogen peroxide, and a porous cathode, said separating means being substantially permeable both to ions and to gases but being substantially impermeable to liquids, said first and second porous means being permeable to fluids, fastening means holding each of said layers in contact with a surface of the adjacent layer.
9. A method for fabricating a gas diffusion cathode for an electrolytic cell of claims 4 to 6 having a first cathode surface contacting electrolyte in the cell and a second cathode surface forming an upper surface of the cell characterized by perforating the cathode with a plurality of perforations, each perforation having sufficient open area that the force of gravity on the electrolyte is greater than the capillary forces on the electrolyte and sufficient to prevent a localized nonuniform flow of electrolyte in the cell.
10. The method of claim 9 characterized in that the cathode is prepared by
a. impregnating a graphite fabric with sufficient polytetrafluoroethylene resin to provide 40% to
70% by weight of the resin on the graphite
fabric, coating the impregnated graphite fabric with an aqueous slurry of about equal parts of carbon black and polytetrafluoroethylene and sintering the coated impregnated fabric, the carbon black being applied in an amount sufficient to provide about 5 to 15 parts by weight of carbon black per 100 aarts of graphite fabric originally employed, and applying a sufficient quantity of a second coating of a slurry of quan tity of a suspension of about 9 parts of carbon black to one part of a polytetrafluoroethylene resin by weight as a slurry in about 105 parts by weight water and about 15 parts by weight of a nonionic surfactant to provide about 5% to 15% carbon by weight of the graphite fabric after sintering, and sintering the fabric in air at about 360°C to 370ºC.

AMENDED CLAIMS
[received by the International Bureau on 5 April 1988 (05.04.88)
original claims 1 - 10 replaced by new claims 1 - 12 ( 4 pages)]
1. An electrolytic cell for reducing oxygen to hydrogen peroxide at a cathode in the presence of an aqueous alkaline electrolyte characterized by a cell having an electrolyte inlet, a porous, self-draining cathode with a first surface contacting electrolyte and a second surface forming an exterior surface of the cell, an electrolyte outlet disposed to receive electrolyte draining from the cathode, an anode, separating means between the cathode and the anode defining an anode compartment containing the electrolyte inlet and a cathode compartment, the separating means being substantially permeable to the electrolyte, the second surface of the cathode contacting an oxygen-containing gas, said cell having means to controllably urge the electrolyte from the electrolyte inlet through the separating means and into the self-draining cathode at a rate about equal to the drainage rate of the electrolyte from the cathode and in a quantity sufficient to fill only a portion of the pores of the cathode and having means to divert oxygen gas away from the separating means and means to exhaust a gas in the anode compartment out of the electrolytic cell.
2. The electrolytic cell of claim 1 characterized in that the cathode is substantially vertical and the cell contains means to divert oxygen gas in the anode compartment electrolyte away from the separating means comprises louvres in the anode.
3. The cell of claim 1 characterized in that the cathode and anode are disposed in a generally horizontal attitude with the cathode superior to the anode and the separating means being substantially permeable to the electrolyte and to oxygen gas to urge oxygen gas out of the anode compartment into the cathode compartment.
4. The electrolytic cell of claims 1, 2, or 3 wherein the cathode comprises carbon black bonded to graphite chips by polytetrafluoroethylene.
5. An electrolytic cell for reducing oxygen to hydrogen peroxide at a cathode in the presence of an aqueous, alkaline electrolyte characterized by a cell having an electrolyte inlet, an electrolyte outlet, a porous cathode impermeable to the electrolyte but permeable to a gas, the cathode having a first surface contacting the electrolyte and a second surface forming an exterior surface of the cell in contact with an oxygen-containing gas, an anode, separating means between the cathode and the anode defining an anode compartment and a cathode compartment in the cell, and means to urge the electrolyte from the electrolyte inlet to the electrolyte outlet, the separating means being substantially permeable both to an ion in the electrolyte and to bubbles of oxygen gas generated at the anode, but being substantially impermeable to the flow of the electrolyte from the cathode compartment to the anode compartment, the cathode and anode of said cell disposed in a generally horizontal attitude with the cathode superior to the anode, the anode compartment being provided with means to distribute bubbles of oxygen gas generated at the anode to the separating means and to urge electrolyte to flow across the surface of the anode, and the cathode compartment being provided with means to urge the electrolyte from the electrolyte inlet across the first surface of the cathode.
6. The cell of claim 5 characterized in that the separating means is a microporous film punctured with openings to permit the flow of oxygen gas from the anode compartment into the cathode compartment.
7. The cell of claim 5 characterized in that the separating means is an ion conductive membrane punctured with openings to permit the flow of oxygen gas from the anode compartment into the cathode compartment.
8. The cell of claims 5, 6 or 7 characterized in that the first and second porous means are
selected from the group consisting of a felt of inert fibers, a woven fabric of inert fibers, a knit fabric of inert fibers and an inert material having interconnected pores.
9. The electrolytic cell of claims 1, 3, 5, 6, 7 or 8 characterized in that the cathode is inclined at an angle of from 5° to 25°, the electrolyte inlet being above the electrolyte outlet to provide a static head, and the porous separating means and cathode providing means to divert oxygen gas out of the electrolytic cell.
10. An article of manufacture useful to construct the electrolytic cell of claims 5, 6, 7, 8 or 9 suitable for the manufacture of hydrogen peroxide by the reduction of oxygen at a cathode, the article of manufacture characterized by layers in sequence; a first nonconductive porous means inert to an alkaline liquid, separating means, a second nonconductive porous means inert to an alkaline liquid containing hydrogen peroxide, and a porous cathode, said separating means being substantially permeable both to ions and to gases but being substantially impermeable to liquids, said first and second porous means being permeable to fluids, fastening means holding each of said layers in contact with a surface of the adjacent layer.
11. A method for fabricating a gas diffusion cathode for an electrolytic cell of claims 5, 6, 7, 8 or 9 having a first cathode surface contacting
electrolyte in the cell and a second cathode surface forming an upper surface of the cell characterized by perforating the cathode with a plurality of
perforations, each perforation having sufficient open area that the force of gravity on the electrolyte is greater than the capillary forces on the electrolyte and sufficient to prevent a localized nonuniform flow of electrolyte in the cell.
12. The method of claim 11 characterized in that the cathode is prepared by
a. impregnating a graphite fabric with sufficient polytetrafluoroethylene resin to provide 40% to 70% by weight of the resin on
the graphite fabric, coating the impregnated graphite fabric with an aqueous slurry of
about equal parts of carbon black and polytetrafluoroethylene and sintering the coated impregnated fabric, the carbon black being
applied in an amount sufficient to provide
about 5 to 15 parts by weight of carbon
black per 100 parts of graphite fabric originally employed, and applying a sufficient quantity of a second coating of a slurry of quantity of a suspension of about 9 parts of carbon black to one part of a polytetrafluoroethylene resin by weight as a slurry
in about 105 parts by weight water and about 15 parts by weight of a nonionic surfactant to provide about 5% to 15% carbon by weight of the graphite fabric after sintering, and sintering the fabric in air at about 360°C
to 370°C.