EP0004191B1 - Chloralkali electrolytic cell and method for operating same - Google Patents

Chloralkali electrolytic cell and method for operating same Download PDF

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EP0004191B1
EP0004191B1 EP79300369A EP79300369A EP0004191B1 EP 0004191 B1 EP0004191 B1 EP 0004191B1 EP 79300369 A EP79300369 A EP 79300369A EP 79300369 A EP79300369 A EP 79300369A EP 0004191 B1 EP0004191 B1 EP 0004191B1
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Prior art keywords
oxygen
compartment
cathode
anode
gas
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French (fr)
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EP0004191A3 (en
EP0004191A2 (en
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Ronald Lowry Labarre
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Eltech Systems Corp
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Eltech Systems Corp
Diamond Shamrock Corp
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells

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  • the present invention relates generally to the operation of an oxygen electrode in an electrolytic cell, particularly for the production of chlorine and caustic (sodium hydroxide) in such a manner as to reduce significantly the voltages necessary for the operation of such electrolytic cells and to increase substantially the power efficiencies available from such electrolytic cells utilizing oxygen electrodes.
  • the present disclosure relates to improved methods of operation of chlor-alkali electrolytic cells having oxygen electrodes, which include utilizing a positive air to liquid pressure drop on the air feed side of the oxygen electrode to improve performance, control of the total flow of the gas feed stream to improve the mass transfer on the air feed side of the oxygen electrode at the reaction sites, humidification of the gas feed to the oxygen electrode to reduce drying out and delamination of the oxygen electrode, so that it functions at a higher current density over a longer lifetime, and the elimination of certain gases such as carbon dioxide, so as to increase the lifetime of the oxygen electrode by elimination of salts which might be formed upon the porous structure of the oxygen electrode during use.
  • These methods of operation may be utilized singularly or preferably in combination to produce higher power efficiencies at lower voltages so as to produce a more energy- efficient oxygen electrode in an electrolytic cell especially suitable for the production of chlorine and caustic (sodium hydroxide).
  • Chlorine and caustic are essential large-volume commodities which are basic chemicals required by all industrial societies. They are produced almost entirely electrolytically from aqueous solutions of alkali metal halides, more particularly sodium chloride, with a major portion of such production coming from diaphragm type electrolytic cells.
  • brine sodium chloride solution
  • the flow rate is always maintained in excess of the conversion rate, so that the resulting catholyte solution has unused or unreacted sodium chloride present.
  • the hydrogen ions are discharged from the solution at the cathode in the form of hydrogen gas.
  • the catholyte solution containing caustic soda (sodium hydroxide), unreacted sodium chloride and other impurities, must then be concentrated and purified to obtain a marketable sodium hydroxide commodity and sodium chloride which is to be reused in electrolytic cells for further production of sodium hydroxide and chlorine.
  • the evolution of the hydrogen gas utilizes a higher voltage so as to reduce the power efficiency possible from such an electrolytic cell, this creating an energy inefficient means of producing sodium hydroxide and chlorine gas.
  • Patent Number 3, 926,769 discloses an apparatus and process for the production of chlorine gas and an alakali metal hydroxide in a diaphragm cell, where the diaphragm is a cation exchange material and an oxidising gas of controlled moisture content is supplied so as to contact a foraminous cathode in the cathode compartment during operation of the cell.
  • the electrolytic cell has become more efficient, in that the power efficiency is greatly enhanced by the use of these dimensionally stable anodes.
  • the hydraulically-impermeable membrane has added a great deal to the use of electrolytic cells in terms of selective migration of various ions across the membrane, so as to exclude contaminants from the resultant product and thereby eliminate some of the costly purification and concentration steps from the later processing stages.
  • the great advances of the past have tended to improve the efficiency of the anodic side and the membrane or separator portion of electrolytic cells.
  • the cathodic side of the electrolytic cell in an effort to improve the power efficiency of cathodes utilized in electrolytic cells and thus make significant energy savings in the production of chlorine and caustic.
  • the electrolytic reaction at the cathode may be represented as:
  • the oxygen electrode presents one possibility of elimination of this reaction, since it consumes electro-chemically-activated oxygen, which combines with water and the electrons available at the cathode in accordance with the following equation
  • this reaction is more energy efficient, due to the absence of any production of hydrogen at the cathode and the reduction in potential as shown above.
  • This reaction is brought about by feeding an oxygen-rich fluid such as air or oxygen to the oxygen side of an oxygen electrode, where the oxygen finds ready access to the electrolytic surface and is thus consumed in accordance with the above equation.
  • an oxygen-rich fluid such as air or oxygen
  • this requires a slightly different structure for the electrolytic cell itself, so as to provide an oxygen compartment on the cathodic side of the cathode, so that the oxygen-rich fluid may be fed thereto.
  • the oxygen electrode itself is well known in the art, since the many NASA projects set up to promote space travel during the 1960s also provided funds for the development of a fuel cell utilizing an oxygen electrode and a hydrogen anode so that the feeding of hydrogen and oxygen gas would produce an electrical current for utilization in a space craft. While this major governent-financed research effort produced many fuel cell components, including an oxygen electrode, the circumstances and the environment in which the oxygen electrode functioned were quite different from those experienced in a chlor-alkali cell. While much of the technology developed in the NASA projects is of value in the chlor-alkali industry with regard to development of an oxygen electrode, much further development is necessary to adapt the oxygen electrode to the chlor-alkali cell environment.
  • a method for operating a chlor-alkali electrolytic cell having an anode compartment, a cathode compartment divided from the anode compartment by a separator and an oxygen compartment divided from the cathode compartment by an oxygen electrode comprises feeding an alkali metal halide solution to the interior of the anode compartment, feeding an aqueous alkaline solution to the interior of the cathode compartment, feeding a gas containing molecular oxygen to the interior of the oxygen compartment, applying an electrical potential between the cathode and the anode, removing halogen gas from the anode compartment, removing alkali metal hydroxide from the cathode compartment and removing an oxygen-depleted gas from the oxygen compartment, characterized in that the gas containing molecular oxygen is depleted of carbon dioxide and humidified and it is fed to the oxygen compartment at a positive gauge pressure in the range from 0.25 to 500 grams per square centimetre (0.1 to 200 inches of H 2 0) and so as to provide a
  • a chlor-alkali electrolytic cell for the production of chlorine and alkali metal hydroxide, comprising an anode compartment for containing an anolyte comprising an alkali metal chloride, a cathode compartment for containing a catholyte comprising an alkali metal hydroxide, a separator dividing the cathode compartment from the anode compartment, an oxygen compartment for receiving an oxygen-containing gas, means for controlling the moisture content of the oxygen-containing gas, means for controlling the total flow-rate of the oxygen-containing gas within the oxygen compartment, an oxygen electrode dividing the cathode compartment from the oxygen compartment, means for removing chlorine from the anode compartment, means for removing alkali metal hydroxide from the cathode compartment, means for supplying alkali metal chloride to the anode compartment and means for supplying electrolyzing electrical energy to the anode and the cathode, characterized in that the cell includes means for controlling the pressure of the oxygen-containing
  • the total flow rate is in the range from 1.5 to 21 times and, most preferably, in the range from 1.5 to 5 times the theoretical stoichiometric amount of oxygen.
  • the oxygen-containing gas is preferably supplied at a positive gauge pressure in the range from 0.25 to 250 grams per square centimetre (most preferably, from 100 to 200 grams per square centimetre). These ranges are respectively equivalent to, firstly, the range from 2 to 100 inches of H 2 0 and, secondly, from 40 to 80 inches of H 2 0.
  • a monopolar divided electrolytic cell is indicated at 12, which is suitable for use according to the present invention. It is recognized that various other designs of electrolytic cells can operate according to the method of the present invention but, for purposes of illustration, the present schematic view amply allows the details of the invention to be appreciated.
  • the electrolytic cell 12, as shown in Figure 1, would generally have some environmental supporting structure or foundation to maintain it in correct alignment with other like cells, so as to build a bank of electrolytic cells for production purposes. The details of this environmental structure have not been shown, to facilitate illustration of the present invention.
  • the cell itself could be manufactured from various metallic or plastics materials, provided these materials resist the caustic surroundings of the chlorine cell environment and the temperature conditions which arise during the operation of basic chlor-alkali cells, which are well known in the art.
  • Such materials generally include (but are not limited to) metallic materials, such as steel, nickel, titanium and other valve metals, and plastics materials, such as polyvinyl chloride, polyethylene, polypropylene, "Fiberglas” (Regd. Trademark) and others too numerous to mention.
  • the valve metals include aluminium, molybdenum, niobium, titanium, tungsten, zirconium and alloys thereof.
  • the electrolytic cell 12 has an anode 14, a separator 16 and a cathode 18, so that three individual compartments are formed within the electrolytic cell, namely an anode compartment 20, a cathode compartment 22 and an oxygen compartment 24.
  • the anode 14 generally is constructed of a metallic substance, although graphitic carbon could be used, as in the old electrodes now largely discarded by industry.
  • Anodes for use in the chlor-alkali cell 12 generally are of active materials resistant to the anolyte, such as a valve metal.
  • a preferred valve metal based upon cost, availability and electrical and chemical properties is titanium.
  • Titanium substrates used in the manufacture of electrodes may take a number of forms for example, solid metal sheet, expanded metal mesh, with a large percentage of open area, and porous titanium with a density of 30% to 70% of that of pure titanium, which can be produced by cold compacting titanium powder.
  • Porous titanium is usually the preferred material, because of its long life characteristics and its relative structural integrity. If desired, porous titanium can be reinforced with titanium mesh, e.g. for large electrodes.
  • these substrate materials carry a surface coating to protect the material against passivation and give a so-called dimensionally-stable anode.
  • Most of these coatings contain a noble metal, a noble metal oxide (either alone or in combination with a valve metal oxide) or other electro- catalytically-active corrosion-resistant materials.
  • Dimensionally stable anodes are well-known and are widely used in the industry.
  • One type of coating is a Beer-type coating, described in U.S. Patent Specfications 3,236,756, 3,623,498, 3,711,385, 3,751,296 and 3,933,616.
  • Another type of coating contains tin, titanium and ruthenium oxides, as described in U.S. Patent Specifications 3,776,834 and 3,855,092.
  • surface coatings are one containing tin, antimony and titanium and ruthernium oxides, described in U.S. Patent Specification 3,875,043, and another containing tantalum and iridium oxides, described in U.S. Patent Specification 3,878,083.
  • other coatings are available, as those skilled in the art will know, for use in chlor-alkali cells as well as in other applications in which electrodes are required for electrolytic reactions.
  • a number of materials may be used for the separator 16 shown in the drawing.
  • One type of material predicates the use of a substantially hydraulically-impermeable structure, namely a cation exchange membrane, as it is known in the art.
  • One type of hydraulically-impermeable cation exchange membrane which can be used in the apparatus of the present invention is a thin film of fluorinated copolymer having pendant sulphonic acid groups.
  • the fluorinated copolymer is derived from monomers of the formulae: in which the pendant -S0 2 F groups are converted to -S0 3 H groups, and wherein R represents the group R' being fluorine or a fluoralkyl group having 1 to 10 carbon atoms, Y being fluorine or a trifluoromethyl group and m being 1, 2 or 3; n is 0 or 1; X is fluorine, chlorine or a trifluoromethyl group and X' is X or , wherein a is zero or an integer from 1 to 5.
  • the copolymer there should be sufficient repeating units according to formula (3) above to provide an -S0 3 H equivalent weight of about 800 to 1600.
  • Materials having a water absorption of about 25 percent or greater are preferred, since higher cell voltages at any given current density are required for materials having less water absorption.
  • Materials having a film thickness (unlaminated) of about 0.20 mm (8 mils) or more require higher cell voltages, resulting in lower power efficiencies.
  • the substrate film material typically is laminated with and impregnated into a hydraulically-permeable electrically non-conductive inert reinforcing member, such as a woven or non-woven fabric made of fibres of asbestos, glass, .Teflon (Regd. Trademark) or the like.
  • a hydraulically-permeable electrically non-conductive inert reinforcing member such as a woven or non-woven fabric made of fibres of asbestos, glass, .Teflon (Regd. Trademark) or the like.
  • Hydraulically-impermeable cation exchange substrate materials comprising fluorinated copolymers having pendant sulphonic groups as aforedescribed, are available from E. I. duPont deNemours and Co. under the trademark Nafion.
  • Polymeric materials according to formulae (3) and (4) can also be made, wherein other types of ion exchange groups are present, instead of sulphonic acid exchange groups.
  • One particular type of structure is a carboxyl group ending in either an acid, an ester or a salt to form an ion exchange group similar in behaviour to the sulphonic acid.
  • the group COOR 2 instead of S0 2 F, the group COOR 2 is in its place, wherein R 2 may be a hydrogen or alkali metal ion or an organic group.
  • R 2 may be a hydrogen or alkali metal ion or an organic group.
  • Trademark may have any ion exchange group or any functional group capable of being converted into an ion exchange group or into which an ion exchange group can easily be introduced, including oxy acids, salts or esters of carbon, nitrogen, silicon, phosphorus, sulphur, chlorine, arsenic, selenium and tellurium.
  • a second type of substrate material has a backbone chain of copolymers of tetrafluoroethylene and hexafluoropropylene and, grafted on to this backbone, a 50/50 mixture of styrene and alpha-methyl styrene. These grafts may then be sulphonated or carbonated to obtain the desired ion exchange characteristic.
  • This type of substrate while having different pendant groups has a fluorinated backbone chain, so that the chemical resistivities are reasonably high.
  • substrate film material comprises polymeric substances having pendant carboxylic or sulphonic acid groups wherein the polymeric backbone is derived from polyvinyl aromatic and monovinyl aromatic components in an inorganic solvent, under conditions which prevent solvent evaporation and result in a generally copolymeric substance, although a 100 percent polyvinyl aromatic compound may be prepared which is satisfactory.
  • the polyvinyl aromatic component may be chosen from divinyl benzenes, divinyl toluenes, divinyl naphthalenes, divinyl diphenyls, divinyl-phenyl vinyl ethers, substituted alkyl derivatives thereof such as dimethyldivinyl-benzenes and similar polymerizable aromatic compounds which are polyfunctional with respect to vinyl groups.
  • the monovinyl aromatic component is generally the impurities present in commercial grades of polyvinyl aromatic compounds, including styrene, isomeric vinyl toluenes, vinyl naphthalenes, vinyl ethyl benzenes, vinyl chlorobenzenes, vinyl xylenes and alpha-substituted alkyl derivatives thereof, such as alpha-methyl-vinyl-benzene.
  • polyvinyl aromatic compounds including styrene, isomeric vinyl toluenes, vinyl naphthalenes, vinyl ethyl benzenes, vinyl chlorobenzenes, vinyl xylenes and alpha-substituted alkyl derivatives thereof, such as alpha-methyl-vinyl-benzene.
  • monovinyl aromatic compounds it may be desirable to add monovinyl aromatic compounds so that the polyvinyl aromatic compounds constitute 30 to 80 mole percent of the polymerizable material.
  • Solvents for dissolving the polymerizable material prior to polymerization are suitable if they are inert to the polymerization (in that they do not react chemically with the monomers or the polymer), have a boiling point greater than 60°C and are miscible with the sulphonation medium.
  • Polymerization is effected by any of the well-known expedients, for instance, heat, pressure and catalytic accelerators, and is continued until an insoluble, infusible gel is formed substantially throughout the volume of solution.
  • the resulting gel structures are then sulphonated in a solvated condition and to such an extent that not more than 4 equivalents of sulphonic acid groups are formed for each mole of polyvinyl aromatic compound in the polymer and not less than one equivalent of sulphonic acid groups are formed for each 10 moles of polyvinyl and monovinyl aromatic compounds in the polymer.
  • Nafion (Regd. Trademark) material these materials may require reinforcing with similar materials.
  • Substrate film materials of this type are further described in U.S. Patent Specifications 2,731,408, 2,731,411 and 3,887,499. These materials are available from lonics, Inc. under the trademark Ionics CR6.
  • these substrate materials have been sought, one of the most effective of which is the surface chemical treatment of the substrate itself.
  • these treatments consist of reacting the pendant groups with substances which will yield less polar bonding and thereby absorb fewer water molecules by hydrogen bonding. This has a tendency to narrow the pore openings through which the cations travel, so that less water of hydration is transmitted with the cations through the membrane.
  • An example of this is to react ethylene-diamine with the pendant groups so as to tie two of the pendant groups together by the two nitrogen atoms in the ethylene-diamine.
  • the surface treatment will be done to a depth of approximately 0.05 mm (2 mils) on one side of the film, by controlling the time of reaction. This results in good electrical conductivity and cation transmission with less hydroxide ion and associated water reverse migration.
  • the separator 16 may also be a porous diaphragm made of any material compatible with the cell liquor environment, the relevant bubble pressure and electrical conductivity characteristics.
  • a material is asbestos, which can be used either in paper sheet form or as vacuum- deposited fibres.
  • a further modification can be effected by adding polymeric substances, generally fluorinated, to the slurry from which the diaphragm is deposited.
  • polymeric materials themselves can be made porous to such an extent that they show the operational characteristics of a diaphragm.
  • the cathode 18 in order to be utilized according to the methods of the present invention, necessarily is an oxygen cathode.
  • An oxygen electrode or oxygen cathode may be defined as an electrode which is supplied with a molecular-oxygen-containing fluid in order to lower the voltage below that necessary for the evolution of hydrogen.
  • the basic support for an oxygen cathode generally includes a current collector, constructed for instance of a base metal, although carbon black may also be used.
  • base metal is used herein to refer to inexpensive metals which are commercially available for common construction purposes.
  • Base metals are characterized by low cost, ready availability and adequate resistance to chemical corrosion when utilized as a cathode in electrolytic cells.
  • Base metals include, for instance, iron, nickel, lead and tin.
  • Base metals also include alloys such as mild steels, stainless steel, bronze, monel and cast iron.
  • the base metal preferably is chemically-resistant to the catholyte and has a high electrical conductivity.
  • the material is generally slightly porous, such as a mesh, when used in the construction of an oxygen cathode.
  • a preferred metal, based upon cost, resistance to the catholyte and voltages available, is nickel.
  • Other current collectors include tantalum, titanium, silver, gold and plated base metals.
  • this basic support material carries a coating of a porous material, either compacted in such a fashion as to adhere to the nickel or other support or held together with some kind of binding substance so as to produce a porous substrate material.
  • a preferred porous material based upon cost is carbon.
  • Anchored within the porous portion of the oxygen cathode is a catalyst to promote the reaction wherein molecular oxygen combines with water molecules to produce hydroxide groups.
  • the cathode 18 is preferably constructed according to U.S. Patent Specfication 3,423,247.
  • the anode 14, the separator 16 and the oxygen cathode 18 divide the electrolytic cell 12 into three compartments, namely the anode compartment 20, the cathode compartment 22 and the oxygen compartment 24.
  • an alkali metal halide solution is fed to the andoe compartment 20, by way of an alkali metal halide solution inlet 26.
  • the alkali metal halide solution is preferably one which evolves chlorine gas in use, such as sodium chloride or potassium chloride.
  • the cathode compartment 22 is supplied with an aqueous solution by way of an aqueous solution inlet 28.
  • the aqueous solution must contain sufficient water molecules to be broken down to form the hydroxide groups necessary for the reaction.
  • the oxygen compartment 24 is supplied through an oxygen inlet 30 with a fluid containing a sufficient amount of molecular oxygen to permit operation of the cell as desired.
  • a gas most preferably air, which has had any carbon dioxide removed and has been humidified or pure molecular oxygen which has been humidified, is used as the fluid.
  • Reaction products such as chlorine gas are removed from the anode compartment 20 through a halogen outlet 32, while aqueous NaOH or KOH is removed from the cathode compartment 22 through an alkali metal hydroxide outlet 34 and an oxygen-depleted fluid, either in the form of residual pure oxygen or air, is preferably removed via a depleted fluid outlet 36.
  • a pressure differential is applied across the porous cathode 18, so that the pressure in the oxygen compartment 24 is higher than that in the cathode compartment 22.
  • the increased pressure which may be a zero gauge pressure in order to bubble through but, due to the electrolyte head, may be a negative absolute pressure, assists in mass transfer of the oxidizing gas such as oxygen into the cathode 18 thereby preventing oxygen depletion in the reaction zone within the cathode 18 and leading to a longer lifetime for the cathode. It should be remembered that this pressure differential is based upon the partial pressure of the oxygen present, if less than 100% oxygen is used.
  • the mass transfer of oxygen into the reaction sites within the cathode 18 is also enhanced. This is particularly important when less than 100% pure O2 is used.
  • Molecular oxygen is consumed by the reaction taking place at the catalytic sites within the porous material of the oxygen cathode 18. As oxygen is consumed, additional quantities must become available continuously and must, therefore, be fed continuously into the oxygen compartment 24.
  • the preferred total flow rate is between 1.5 and 10 times the theoretical stoichiometric amount of oxygen necessary for the reaction, a flow rate of about 2.5 times being the best.
  • Pure oxygen gas may be supplied to the oxygen compartment 24.
  • air may also be used, since it contains approximately 23% free molecular oxygen by weight.
  • carbon dioxide must be removed before the air is delivered to the oxygen compartment 24. It has been found that carbon dioxide promotes the formation of certain carbonate deposits upon the cathode, which sharply reduce its lifetime and power efficiencies while increasing the voltage. By eliminating the major portion of carbon dioxide from the air, this problem is also largely eliminated.
  • the evaporative driving force which causes mass transfer of the water from the cathode compartment 22 into the cathode structure 18 causes crystallization of the electrolyte and the solids formed reduce seriously the lifetime of a given cathode 18, because they obstruct the pores.
  • Humidification of the feed gas to the oxygen compartment 24 drastically reduces this by eliminating the evaporative driving force involved in transferring the liquid electrolyte from the cathode compartment 22.
  • the gas stream dew point is advantageously adjusted to balance these two deleterious effects, so as to maintain the dew point a few degrees below the cathode skin temperature and keep the relative humidity within a range so as to eliminate the evaporative driving force involved. It should be noted that higher operation temperatures lower the voltage of the cell, but may shorten the life of the cathode 18. A temperature in the range of 60° to 85°C. is considered optimum.
  • An oxygen cathode according to U.S. Patent No. 3,423,247 was installed in an electrolytic cell so that the carbon side faced the oxygen compartment and the nickel side faced the cathode compartment, in which an electrolyte was placed.
  • a stream of carbon-dioxide-free air was passed into the oxygen compartment of the cell at a flow rate of approximately 790 cubic centimetres per minute, which is approximately 21 times the theoretical stoichiometric amount needed when the cell is operated at a current density of 0.15 amperes per square centimetre (1 ampere per square inch).
  • the pressure in the oxygen compartment was adjusted to approximately 110 grams per square centimetre (44 inches of water) above atmospheric pressure, by restricting the flow from the outlet 36. The pressure was maintained at that level during the test.
  • Electrolyte consisting of approximately 400 grams per litre of NaOH was then added to the cathode compartment 22 and agitated continuously by magnetic stirring apparatus.
  • the cathode was then conditioned by operating the cell at 60°C. and a current density of approximately 0.05 amperes per square centimetre (1/3 ampere per square inch) for about one day. After conditioning was completed, the current density was increased to approximately 0.15 amperes per square centimetre (1 ampere per square inch).
  • the air flow, pressure, temperature and current density were held constant during the remainder of the test. It should be noted that these tests were used with sodium hydroxide electrolyte only and the cell was not used as a chlor-alkali cell per se. However, the results from these tests correlate closely with those obtained by using chlor-alkali cells, since the type of anode or the spacing of the anode to the cathode are not critical factors, although the anode must be stable in sodium hydroxide solution.
  • the cathodes were conditioned at the reduced current density because it was thought that the catalytic platinum layer becomes partially oxidized, during the period when the cathodes are stored before use.
  • the conditioning process restores the catalytic layer to high activity without causing deterioration in the quality of the cathode. Slow break-in for less noble catalysts may be harmful, however.
  • the electrical connection was made on the nickel side of the cathode because it is easier to make a good electrical contact on nickel than on carbon.
  • the cathode reference voltage measured versus a mercury/mercuric oxide reference electrode cell, changed from -0.31 on day 1 to -1.03 on day 98, when the test was considered completed. The lifetime of this cathode under these test conditions was 2350 hours.
  • a cathode test was done as described in Example 1, except that the air flow rate was reduced from 790 to 220 cubic centimetres per minute (approximately 6 times the theoretical stoichiometric amount necessary for reaction).
  • the reference voltage changed from -0.43 on day 1 to -2.27 on day 52.
  • the cathode lifetime was 1240 hours in this test, as compared to 2350 when increased air flow was used in Example 1. This shows that, when the total flow increases, the potentials are lower and the life-times are extended.
  • a cathode test was done as described in Example 1, except that an oxygen flow rate of 150 cubic centimetres per minute was used instead of an air flow rate of 790 cubic centimetres per minute. This oxygen flowrate was about 19 times the theoretical stoichiometric flow required at 0.15 ampere per square centimere (1 ampere per square inch) current density for operation of a cell. For this test, the electrical connection was made on the carbon side of the cathode.
  • the cathode was conditioned by running the cell at a current density of 0.05 amperes per square centimetre (1/3 ampere per square inch) for about 24t hours, then increasing it to 0.1 ampere per square centimetre (2/3 ampere per square inch) for about 24 hours and finally increasing it to about 0.15 ampere per square centimetre (1 ampere per square inch), at which level it was held for the remainder of the test.
  • the reference voltage changed from -0.38 on day 2 to -0.42 on day 293.
  • the test was discontinued on day 293 because delamination of the cathode occurred.
  • the cathode lifetime was about 7030 hours. This again shows that when the total flow is increased, in terms of stoichiometric amounts of available oxygen, the life is extended at lower potentials.
  • An oxygen cathode test was done according to Example 1, with an operating temperature of approximately 85°C at a current density of approximately 0.3 amperes per square centimetre (2 amperes per square inch), using an NaOH solution of 300 grams per litre. Furthermore, the membrane utilized in the subject test was a standard National (Regd. Trademark) film. This experimental cell was operated using various types of cathodes. Comparative cell voltages for the different cathodes were obtained as follows:
  • each of these cathodes when compared to a standard hydrogen-evolving steel-mesh cathode shows superior performance utilizing the methods of the present invention.
  • An oxygen cathode test was done according to Example 1, using air which had not been scrubbed free from carbon dioxide. The cathode was broken in on oxygen and then switched to air. Failure occurred less than 48 hours after switching to air. This performance was typical of cathodes supplied with air which contained carbon dioxide, thus showing the necessity of removing carbon dioxide for the lifetime of an oxygen cathode.
  • the basic conditions were the same as those according to Examples 1-3 and the table below shows the cell voltages and reference voltage, along with remarks.
  • Oxygen cathode tests were done according to Example 1 wherein the total air flow rate was varied according to Figure 2 of the drawings and the pressure was also varied. As shown in Figure 2, the cathode potential decreased with increasing flowrates and also decreased with increasing pressures. In each case, the air supplied was free from carbon dioxide and was humidified.
  • cathode tests given in the Examples above were ended in each case when the reference voltage reached -1.00 or when delamination of the various layers of the cathode occurred.
  • the air (or oxygen) flow was recorded on cathode life cell test data sheets as the height (in millimetres) of the steel ball on the Matheson 601 flow meter (except for Example 3, where a Matheson 602 flow meter was used). These readings were then converted into cubic centimetres per minute by referring to the appropriate calibration curves.
  • the Examples give the results of cathode tests where pressure differentials were approximately 100 grams per square centimetre (40 inches of water). The term "pressure differential" means the net pressure exerted between the two sides of the cathode.
  • the difference between the pressure and the oxidizing gas compartment (100 grams per square centimetre above atmospheric pressure) and the average hydrostatic pressure exerted by the electrolyte on the other side of the cathode (10 grams per square metre) is approximately 100 grams per square centimetre.
  • the hydrostatic pressure is calculated by multiplying the density of the electrolyte (1.33) by the average height above the cathode, which was 7.5 cm (3 inches). According to an estimate, the useful range of pressure differential is probably from 0.25 to 500 grams per square centimetre (0.1 to 200 inches of water column). It is expected that those cathodes utilizing atmospheric pressure or where the gas compartment pressure is not allowed to exceed atmospheric pressure would have a lifetime less than the 1240 hours of Example 2, for instance.

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EP79300369A 1978-03-13 1979-03-09 Chloralkali electrolytic cell and method for operating same Expired EP0004191B1 (en)

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US88575478A 1978-03-13 1978-03-13
US885754 1978-03-13

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EP0004191A2 EP0004191A2 (en) 1979-09-19
EP0004191A3 EP0004191A3 (en) 1979-10-31
EP0004191B1 true EP0004191B1 (en) 1982-05-05

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EP79300369A Expired EP0004191B1 (en) 1978-03-13 1979-03-09 Chloralkali electrolytic cell and method for operating same

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EP (1) EP0004191B1 (pt)
JP (1) JPS54132498A (pt)
AU (1) AU529294B2 (pt)
BR (1) BR7901504A (pt)
CA (1) CA1155792A (pt)
DD (1) DD142456A5 (pt)
DE (1) DE2962670D1 (pt)
ES (1) ES478598A1 (pt)
IL (1) IL56855A (pt)
IN (1) IN152982B (pt)
MX (1) MX154417A (pt)
NO (1) NO153224C (pt)
PL (1) PL116783B2 (pt)
SU (1) SU860711A1 (pt)
YU (1) YU58579A (pt)
ZA (1) ZA791153B (pt)

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DE3420483A1 (de) * 1984-06-01 1985-12-05 Hoechst Ag, 6230 Frankfurt Bipolarer elektrolyseapparat mit gasdiffusionskathode
US4566957A (en) * 1984-12-10 1986-01-28 United Technologies Corporation Use of gas depolarized anodes for the electrochemical production of adiponitrile
US6627662B2 (en) 1995-10-10 2003-09-30 William John Louis, Austin And Repatriation Medical Centre 3-amino-propoxyphenyl derivatives (I)
PL409557A1 (pl) 2014-09-22 2016-03-29 Ori-Med Spółka Z Ograniczoną Odpowiedzialnością Krzesło ortopedyczne zwłaszcza do rehabilitacji skolioz
DE102015014515A1 (de) 2015-11-11 2017-05-11 Dräger Safety AG & Co. KGaA Elektrolytleiter, Verfahren zur Herstellung eines Elektrolytleiters sowie ein elektrochemischer Gassensor und ein Gasmessgerät mit einem solchen

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Publication number Priority date Publication date Assignee Title
US2681887A (en) * 1950-02-03 1954-06-22 Diamond Alkali Co Electrolytic cell
GB832196A (en) * 1955-01-21 1960-04-06 Jean Billiter Electrolytic processes
US3775272A (en) * 1972-02-25 1973-11-27 Olin Corp Mercury diaphragm chlor-alkali cell and process for decomposing alkali metal halides
US3923628A (en) * 1973-05-18 1975-12-02 Dow Chemical Co Diaphragm cell chlorine production
US3926769A (en) * 1973-05-18 1975-12-16 Dow Chemical Co Diaphragm cell chlorine production
JPS52124496A (en) * 1976-04-14 1977-10-19 Japan Storage Battery Co Ltd Method of electrolyzing alkali metal chloride and apparatus therefor

Also Published As

Publication number Publication date
SU860711A1 (ru) 1981-08-30
IL56855A0 (en) 1979-05-31
DD142456A5 (de) 1980-06-25
MX154417A (es) 1987-08-14
PL116783B2 (en) 1981-06-30
PL214074A1 (pt) 1980-03-24
EP0004191A3 (en) 1979-10-31
JPS54132498A (en) 1979-10-15
ZA791153B (en) 1980-03-26
IN152982B (pt) 1984-05-19
NO153224B (no) 1985-10-28
BR7901504A (pt) 1979-10-09
YU58579A (en) 1983-01-21
IL56855A (en) 1982-07-30
NO153224C (no) 1986-02-05
EP0004191A2 (en) 1979-09-19
DE2962670D1 (en) 1982-06-24
AU529294B2 (en) 1983-06-02
NO790819L (no) 1979-09-14
AU4504779A (en) 1979-09-20
CA1155792A (en) 1983-10-25
ES478598A1 (es) 1980-06-16

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