US3507769A - Simplified electrolytic cell - Google Patents

Description

April 21, 1970 D. H. GRANGAARD SIMPLIFIED ELECTROLYTIC CELL 2 Sheets-Sheet 1 Filed Jan. 30, 196'? 9(CATHODE) FIG. I

FIG. 2

April 21, 1970 I D. H. GRANGAARD SIMPLIFIED ELECTROLYTIC CELL 3 sheets sheet 2 Filed Jan. 30, 1967 HHHHHHU uunuuDnDuL TOUQDDDDDO HHU uouoununni Fnnuonunuu HHHHHHU oonuuuuuu unnnunnnuu unnnunuuuu HHHHHHU unuunnnnun nunuuuuuuu Tonunnuuni HHHHHHU uunnuunnuo P EEE E FIG. 3

FIG. 4

United States Patent 3,507,769 SIMPLIFIED ELECTROLYTIC CELL Donald H. Grangaard, Appleton, Wis., assignor to Kimberly-Clark Corporation, Neenah, Wis., a corporation of Delaware Filed Jan. 30, 1967, Ser. No. 612,514 Int. Cl. B01k 1/00; C01b 15/04; C22d 1/02 US. Cl. 204265 1 Claim ABSTRACT OF THE DISCLOSURE An electrolytic cell for peroxide production having an anode, a cathode, a separating semi-pervious diaphragm dividing the cell into an anode compartment and a cathode compartment, the diaphragm forming the sole flow path for electrolyte between inlet port means in the anode compartment and outlet port means in the cathode compartment. A process of electrolytic cell operation in the production of alkaline peroxide solutions by the electrochemical reduction of oxygen to perhydroxyl ions where the diaphragm of the cell serves as a control for the electrolyte flow.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to electrolytic cells of simplified constructional arrangement for the production of alkaline peroxide solutions having controlled and constant alkalinity.

The invention with relation to the prior art The construction of electrolytic cells for the production of peroxides tends to become relatively complicated in the provision of various inlets and outlets governing the flow of electrolyte (catholyte, anolyte), oxygen containing gases, and exhaust gases of the oxygen reduction reaction. I have found that a cell quite effective for the purpose may be formed of an open top type unit having otherwise only one inlet port and one outlet port for solution flow and a gas inlet port for oxygen or oxygen containing gases. In effect, I employ the diaphragm which divides the cell into the anode and cathode compartments as an element of the liquid or electrolyte flow control. Since such materially reduces the number of external connections necessary for cell operation, the cell isparticularly adapted as a unit of a battery of cells, the greater benefit being found as cell numbers and battery size increases.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood by reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is a diagrammatic representation of a cell adapted for the electrolytic reduction of oxygen to perhydroxyl ions;

FIG. 2 is an exploded view illustrating the relationship of the components of an operating cell in accordance with this invention;

FIG. 3 is a face view of an electrolytic cell end plate useful particularly in the anode compartment of the structure of FIG. 2; and

FIG. 4 is a view of another plate similar to that of FIG. 3 in purpose and employed as a cathode compartment plate in the arrangement of FIG. 2 of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the numeral 1 generally designates a cell casing of electrically non-conductive material and of generally rectangular configuration in longitudinal 3,507,769 Patented Apr. 21, 1970 and in tranverse section. The particular shape of the cel casing is, however, not critical. The casing has a bottom wall 2, partial top wall 3 and opposed side walls 4, 5. Bottom wall 2 'has an inlet port 6 adapted for the flow of electrolyte to anode compartment 7 containing therein an anode 8. Anode 8 is suitably of metal, resistant to alkaline electrolyte of about 2%5% alkali concentration and nickel metal serves the purpose well.

The anode 8 is oppositely disposed to a gas porous cathode 9 which is suitably of activated carbon and which has a surface such that it catalyzes the reduction of oxygen to perhydroxyl ions. Such is a known reaction and forms of itself no part of the present invention. Oxygen for the cathode 9 is fed as the pure gas or, more economically, as air, through inlet 10 to a manifold zone 11 which is sealed from the catholyte in any convenient manner at 12, 13. The exact method of preventing entry to the manifold zone 11 is of no significance to the practice of the invention though it is important that the zone be maintained substantially catholyte (or electrolyte) free for the purpose of eflicient cell operation. An exhaust port 14 provides for flow outwardly from cathode compartment 15 of the solution containing the perhydroxyl ion. The solution flow is so controlled that, although gases are vented at 16, 17, the solution itself is inhibited from overflowing through these passages. Electrical leads 18, 19 provide for the application of a voltage between the electrodes; such voltage, to serve the purpose of perhydroxyl ion formation, is suitably about 2 volts.

The anode compartment 7 and the cathode compartment 15 are separated by a semi-pervious diaphragm of conventional structure such as an asbestos sheet. This diaphragm, in the present instance, forms the only designed passage means for electrolyte between the inlet port 6 and the outlet 14. The liquid applied to the cell is limited to inhibit overflow through the open top. The diaphragm porosity is therefore a rather considerable factor in electrolyte flow control; the diaphragm must prevent the too rapid flow of electrolyte since such would inhibit the development of a significant peroxide concentration, the concentration being very generally inversely proportion-a1 to the flow rate. The diaphragm, however, must permit sutficient movement of ions to effect the reaction at the anode and cathode. In general, I have found that the porosity of a preferred diaphragm should be such as to permit, at a hydrostatic head of /2 to 2 inches, the flow of about 2 to 6 cc. of electrolyte per hour per square inch of diaphragm area.

FIGS. 2 to 4 illustrate an operative embodiment of a cell utilizing the principles set forth in connection with FIG. 1. As shown in FIGS. 2 and 3, the numeral 20 (FIG. 2) designates a planar plastic electrically nonconductive end plate of an electrolytic cell which is itself designated at 21. Plate 20 is both out out and planed off to provide a plurality of flat faced knobs 22 which project from surface 23 and provide channels 24 (FIG. 3) for the flow of liquid from an inlet 25 upwardly to a height of about that of a cell outlet designated at 26. The surface 23 is itself additionally partially cut out to provide channels 27 (FIG. 3) between ribs 28. The plate and ribs 28 extend well above the liquid outlet 26 and provide for venting of gases to the atmosphere.

In the assembled cell arrangement a separate spacer element 29 of resinous material, that is, plastic, having a central opening 30 is in abutment with surface 23 and bounds the knobs 22. The knobs extend through the opening 30 in the assembled condition of the cell and engage a wire screen anode 31. The anode is planar and is supported in a substantially planar position by a combination of knobs 22 and the separate element 29. Positioned against the screen anode and lying thereon is a diaphragm 32. The diaphragm may be of any of a number of materials known to the art but preferabl is basically a sheet of asbestos. Rightwardly (FIG. 2) of. the diaphragm is an additional support for the diaphragm in the form of a glass fiber mesh 33. This mesh in the assembled cell lies on plate 34 of plastic which, as its principal purpose, serves as the cathode chamber as well as to retain the porous cathode element 35.

The plate 34 to the depth indicated in FIG. 2 is completely cut out at 36 to provide a peripheral seat 37 for glass mesh support 38 in the form of a sheet. Support 38 receives the porous cathode 35, the mesh and the cathode being cemented, for example, on the seat 37. The plate 34 is also cut through (FIG. 4) to provide a plurality of slots 39 (FIG. 4) bonded laterally by vertically extending ribs 40. These slots in the operation of the cell fill with electrolyte flowing through the diaphragm 32 from the anode compartment area supplied at 25. The slots serve to communicate the electrolyte with the cathode 35. Plate 34 is cut out upwardly at 43 to provide wide channels bound by rib extensions 44, which are vertically above the outlet 26 in the assembled cell and provide for venting of gases from the cell.

In the structural arrangement shown an electrically conductive wire mesh screen 45 overlies the cathode 35 and plate 34 and an outlet gasket 46 seals between the end plate 47 and the cathode structure including the plate 34. The end plate 47 is itself out out to provide a manifold 48 which is coextensive with the cathode and communicates through a gas inlet port 49 with the exterior of the cell. The manifold in cell operation remains free of liquid as electrolyte does not pass the gas porous cathode.

The cell is retained in assembled condition by draw bolts 50 cooperating with nuts as at 51, one draw boltnut set being provided at each corner of the cell and two of which sets are shown in FIG. 3. In cell operation about 2 volts is applied between the electrolytic lead-in 52 attached to the anode and the lead-in 53 attached to the cathode screen 45. The electrolyte for the cathode, as already noted, is derived from the electrolyte solution provided through the inlet 25. Cell operation is so controlled that there is a flow of electrolyte-between the inlet 25 connecting directly with the anode compartment and outlet 26 connecting directly with the cathode compartment of the cell.

In the cell illustrations, as set out in the drawings, the cell proportions are somewhat exaggerated for purposes of clarity in the drawings. Accordingly, it may be noted, in a cell of the type under construction, the cathode compartment is such that the depth of the channels is usually between about to of an inch. The width of the channels, in turn, are about to inch. The anode compartment is of similar dimensions.

In specific application: in a cell designed as shown in FIG. 2, wherein the liquid channels in the anode compartment were of strictly vertical designinch deep and inch wide with a /s inch land area in between; and the liquid channels in the cathode compartment were likewise of strictly vertical design but inch deep x inch wide with at A inch land area in between; and wherein the total electrode area exposed to the channels was 28 sq. in.; 0.873 gram of peroxide per hour was obtained at electrolyte flow rate of 169 cc./hour. The applied voltage was 2 volts. The concentration of the peroxide solution was 5.168 g./liter. The power consumption was 1.743 k.w.h./lb. peroxide.

It is to be noted that, in addition to the simplified structural arrangement due to the elimination of ports, conduits and the like and their associated controls (valves, etc.), the present cell is also advantageous in that no alkali buildup in the cathode compartment can occur since only one electrolyte stream is passed through the cell. Thus, it follows that the alkalinity of the exit stream can be no greater than the inlet stream.

In the operation of the arrangement described, the electrolyte may suitably be sodium hydroxide, potassium hydroxide or other alkalies known to the art. In the specific embodiment mentioned the electrolyte was a 2% aqueous sodium hydroxide solution.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claim.

What is claimed is:

1. An electrolytic cell comprising a gas porous cathode, an anode, a semi-pervious diaphragm separating said anode and cathode and defining an anode compartment and a cathode compartment, an electrolyte inlet to said anode compartment, an electrolyte outlet from said cathode compartment, said diaphragm forming substantially the only passage means for electrolyte between said inlet and said outlet and said inlet serving as substantially the only source of catholyte for said cell, said diaphragm having a porosity such that it passes a flow of electrolyte of between about 2 to about 6 cc. per hour per square inch of diaphragm area under a hydrostatic head of between about /2 to 2 inches of water, a gas inlet and manifold communicating the exterior of the cell with the cathode for supplying oxygen to the cathode and an electrically non-conductive plate mounting said cathode and having a series of vertically extending ribs and channels projecting above the cathode for venting gases from the cell in the cathode area.

References Cited UNITED STATES PATENTS 2/1962 Le Blanc et a1. 204-283 XR 9/1967 Neipert et a1. 204266 U.S. c1. X.R. 204-266, 83

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