MXPA00011824A - Filter press electrolyzer - Google Patents

Abstract

A monopolar or bipolar filter press electrolyzer containing a bipolar electrode assembly consisting of a metal anode (20) and metal cathode (32) electrically connected to respective current collectors (22) which can be electrically connected by welding either directly or through an intermediate metal layer different than said metal anode or cathode, or by adhesive (42) bonding utilizing an electrically conductive adhesive. The cell frames (36, 38) are formed of laminated thermoplastic or thermosetting polymer sheets. Bipolar electrode assemblies include at least a pair of thermoplastic or thermosetting polymer sheet. Bipolar electrode assemblies can include at least a pair of thermoplastic or thermosetting cell frame units which are assembled with either a single gasket or a polymer adhesive.

Description

PRESS FILTER ELECTROLYZER TECHNICAL FIELD This invention relates to a novel multipurpose electrolytic cell.

PREVIOUS TECHNIQUE Bipolar filter press electrolysers are known. They have a bipolar wall or support plate that separates the cathodic compartment from the anodic compartment of the adjacent cell units in a series array of the unit cells. On one side of the cell wall or support plate is the structure of the cathode and on the other side the structure of the anode. When multiple bipolar cell structures are connected in series to form the electrolyser, an anode end plate and a cathode end plate are used at each end of the. series to apply appropriate pressure in order to hold the units of the series together. In electrochemical processes in which the anolyte and the catholyte and the respective products of electrolysis must be kept separate, a permeable diaphragm or a semi-permeable membrane or a permselective membrane is placed between the anode of a bipolar element and the cathode of an adjacent bipolar element. The electrical continuity between the anode of a unit in the series of bipolar elements and the cathode of an adjacent cell unit in the series is provided through the bipolar wall or support plate. The bipolar wall or support plate is, according to the above, cathodically polarized and in contact with the catholyte on one side and anodically polarized and in contact with the anolyte on the other side of the support plate. Consequently, the two surfaces of the bipolar wall or support plate can exhibit quite different corrosion resistance properties as a result of the use of different electrolytes and electrolysis products in contact therewith. In the bipolar electrolysers of the prior art, the support plate is considered to have three functions. First, the support plate separates the catholyte from a bipolar cell of the anolyte of the adjacent bipolar cell of the electrolyser. Second, the support plate serves as a conductive member that connects the cathode of a bipolar electrolytic cell unit to the anode of an adjacent cell of the bipolar electrolyser. Third, the support plate acts as a structural member because both anodes and cathodes extend substantially perpendicular to the support plate. Bipolar cells in which titanium or other metals are used as anodes in processes in which hydrogen is released from the cathodic surface are subject to the disadvantage that during electrolysis, the nascent hydrogen, which is formed on the cathodic surface of the metal, permeates through the cathode of the metal and attacks the titanium or other valve metal, on the side of the anode of the bipolar electrode. Titanium hydride is formed, which can be the cause of blistering, caustic cracking, peeling, misalignment, and stress cracking of the anode. Hydrogen continues to permeate through the titanium hydride in this manner which results in additional formation of titanium hydride and further deterioration of the anode. The deterioration of the titanium anodes significantly decreases the useful life of the bipolar electrodes, contaminates the products produced by the bipolar cells and increases the cost of operation of the cell. Although other materials may be used in place of iron or steel for the cathode portion of 1 electrode, most metals that are useful are also permeable to hydrogen to a certain degree. The press filter electrolysers have assembled cell units that use a molded thermoplastic polymer filter press structure. It is known that such filter press electrolysers use a molded plastic injection structure that includes a chamber for the electrolyte therebetween., as shown in E.U. 5,421,977 and the references cited therein. In E.U. 5,082,543, for Gnann et al. A press filter electrolysis cell is described for the production of peroxy and perhalogenated compounds including peroxydis sulphites and peroxydisulphuric acid. The platinum-coated valve metal substrates are described as anodes, the platinum layer being applied to the substrates by pressure by isostatic heating or diffusion welding of a platinum sheet on the valve metal substrate. Preferably, the platinum sheet has a thickness of about 20 to about 100 microns. The cathode used in the electrolytic cell is a perforated cathode, permeable to liquids and gases, of stainless steel which is also identified as tool steel number 1.4539. The electrolysis cell separators are described as exchange membranes such as Nafion® 423. These are fastened between the structures of the cell and the structures are sealed by packing a copolymer of fluoride-hexafluoropropyl vinylidene. In the press filter electrolysis cell described in E.U. 5,082,543 for Gnann et al. , hollow anodes and cathodes are described in which the hollow bodies of the cathode are permeable to liquids and gases and the hollow bodies of the anode have, above and below a layer of platinum, openings for the introduction and extraction of the anolyte. The effective surface of the anode is formed by the platinum layer of a composite anode comprising a valve metal substrate and a layer of platinum present therein which is obtainable by pressure by isostatic heating of a platinum sheet on a substrate. of valve metal. The cells of this reference are described as being useful for the production of peroxy compounds, specifically, peroxydiphostes. By providing circulation of cooling water at the anode, the electrolysis operation is described as being able to proceed with current densities of up to 15kA / m2 by reducing the ohmic losses of voltage caused by heating the anodic surface. Gnann et al. , in the patent 543 describe an electrolysis cell having a hollow body of anode and a hollow body of cathode through which the cooling water circulates in order to dissipate the heat formed, particularly, in the anodic production of peroxodisulfates and salts thereof. Because such a cell design in which hollow electrodes are used is fraught with danger of leakage of cooling water to the electrolyte of the cell and, according to the foregoing, requires an effective, reliable seal in order to avoid such leaks, with the possibility of precipitation of one or more electrolysis products within the cell, such a cell design has been intentionally avoided in favor of the use of external heat exchangers in the process of the invention.

DESCRIPTION OF THE INVENTION According to the invention, a bipolar electrolytic filter press cell is described. The electrolytic cell is, generally, useful for any electrochemical process. For example, the cell is useful for the production of crude oil or its salts using an overvoltage anode comprising a valve metal substrate having a discontinuous coating of a metal from the group of platinum. In this process, a stainless steel cathode is preferred which has substantially higher concentrations of nickel, chromium, and molybdenum compared to 316 stainless steel. The novel electrolytic filter cell preferably has laminated sheets that form the cell structures plastics, generally, of a thermoplastic or thermosetting polymer, preferably of polyvinyl chloride and, generally, laminated with a polymeric adhesive, preferably laminated with an elastomer modified vinyl ester polymer or an elastomer modified copolymer styrene adhesive. The individual cell units of the filter press electrolyzer are assembled to form the filter press electrolyser using a polymeric adhesive or a simple packing between the individual cell units. Where the electrolytic cell is used in a bipolar electrode configuration, the anode and the cathode or the double support plates of the anode and cathode which - if also known as current collectors, are electrically connected when welding, or, preferably, by using an electrically conductive polymer, preferably, a vinyl ester polymer containing a substantial proportion of graphite or metal particles to make the mixture electrically conductive. The filter press electrolysis cell can be operated using a cell separator either a permselect membrane or a porous diaphragm, preferably microporous, between the anodic and cathodic compartments of the cell.

BRIEF DESCRIPTION OF THE DRAWINGS The electrolysis cell of the present invention and the advantages derived therefrom will become apparent in consideration of the following specification in conjunction with reference to the accompanying drawings, in which: FIGURE 1 is a diagrammatic view, in perspective, exploded, of a preferred cell unit of the bipolar electrolyzer of the invention which is simplified by eliminating the cathode and anode bipolar cover structures, the bipolar electrolyte structures of cathode and anode and the structures of the packaging. FIGURE 2 is a diagrammatic, cross-sectional, partial view through section 2-2 of Figure 1. FIGURE 3 is a diagrammatic, transverse, partial view, similar to Figure 2 but with the addition of structures of partial cell.

DESCRIPTION OF THE PREFERRED MODALITIES Referring to the drawings, a partial, perspective, diagrammatic view of a single unit mode of a multiple filter press electrolyser is shown in an explosive view in Figure 1. The cell unit comprises the anode 20, the separating terminals of the anode 24, the support plate or anode current collector 22, the adhesive layer 26, the support plate or current collector of the cathode 28, the separator terminals of the cathode 30, cathode of expanded metal 32, and cell or membrane separator 34. It will be understood that when the cell unit is assembled in a multiple filter press electrolyser, each of the electrodes of the electrodes of the adjacent cell unit is separated by the membrane 34 The anode and cathode separator terminals allow the adjustment of the gap between the anode or cathode of the adjacent cell units and the membrane 34. The stress portions are not shown. They include the bipolar electrode and allow the internal flow of electrolyte. The anode and cathode structures which are formed from a laminate of polymer sheets, generally, laminated with a polymeric adhesive allow the secure assembly of each unit in multiple units by providing opposing cell structure unit surfaces that can be joined as shown in Figure 3, using a polymeric adhesive. Alternatively, a single packing of uniform thickness can be used between the cell units in conjunction with a cell structure sealing face having a depressed area for joining multiple cell units in order to form the multiple bipolar electrolyzer of the invention. In Figure 2, a simplified diagrammatic partial view of a single unit of a bipolar electrolyzer embodiment of the invention in which the anode 20 is shown in contact is shown in cross section through section 2-2 of Figure 1. with the anode separator terminal 24 which in turn is in electrical contact with the support plate or anode current collector 22. The cathode 32 is in electrical contact with the current collector or cathode support plate 28 by means of the cathode separator terminal 30. The electrical contact of the anode separator terminal 24 with the anode 20 and the anode current collector or support plate 22 or the cathode separator terminal 30 with the cathode 32 can be carried out by any convenient means such as spot welding. The adhesive layer 26 is used to join the current collector of the anode 22 to the current collector of the cathode 28. The adhesive layer 26 is preferably formed of a vinyl ester polymer which is modified by elastomer in order to provide greater flexibility and ductility of the vinyl ester polymer. The electrical conductivity can be provided in the adhesive layer by using a sufficient amount of either or both graphite powder and metal particles as components of the adhesive layer of the vinyl ester polymer 26. The use of a polymeric adhesive to join the collector of anode current 22 and cathode current collector 28 prevents the possibility of hydride formation and subsequent failure during the use of the preferred valve metal anode. The use of a conductive adhesive at the junction of the anode and cathode current collectors, metals being selected to resist the corrosive effects of either the anode or cathode electrolytes and the electrolysis products. In Figure 3, the partial diagrammatic and simplified view shown in Figure 2 is shown in cross-section through section 2-2 of Figure 1 with the addition of a partial view of the electrolyte external flow structures of the unit. of cell 38 and internal flow structures 36. Structures 36 and 38 define the internal electrolyte flow channels 40. Adhesive 42 is preferably used to join the coupling surfaces of structures 36 and 38.

MODES FOR CARRYING OUT THE INVENTION In the preferred bipolar electrolyser of the invention shown in Figures 1, 2 and 3, the cells and components thereof are electrically connected to the bipolar electrode requiring only one current distribution bar of the cathode, not shown, for the final assembly of the cell anode. The current flows from each cathode through the compartments of the cells to the anode. The circulation medium of the anolyte and the catholyte is preferably internal. The filter press electrolyser components of the invention can be easily standardized and adapted by making either a monopolar cell or a bipolar cell each having a number of identical cell units, providing savings in production. The cathodes and anodes of the electrolysers of the present invention may comprise various anodes and cathodes of the prior art such as foraminous anodes and cathodes which are generally known in the art. The anode and cathode active surface may be a non-coated substrate, for example, for processes other than the persulfate process described herein, anodes of the prior art such as nickel anodes may also be used. Alternatively, the active surface of the anodes may comprise a valve metal coated substrate having an electrocatalytic coating applied thereto. The electrocatalytic coating can be a precious metal and / or oxides thereof, a transition metal oxide, or mixtures of any of these materials. Any foraminous metal cathode such as a foraminated metal mesh, a perforated or non-perforated plate, or metal grid can be used. The electrical connection of the bipolar electrode can be formed by welding. For example, the anode, cathode and the anode and cathode current collectors of the bipolar cell of the invention can be electrically connected, respectively, to the anode and cathode separator terminals, for example, by spot welding. When a welding procedure is used to form the bipolar electrode and to join the separating terminals to the electrodes and current collectors, such welding can also take the form of resistance welding, flame welding to inert tungsten gas, welding by electronic beam, diffusion welding and laser welding. The gap between the electrodes and the cell membrane can be adjusted by extending or decreasing the dimension of the spacer terminals located between the electrodes and the current collectors. The cell membrane and the electrode gap can be easily maintained during the operation of the cell by providing a series of non-conducting filaments on the face of the electrodes. Typically, the electrodes are wound with a polymer chain such as a TEFLON® chain. Other useful and representative polymers for use are the chains or filaments of polyvinyl chloride, styrene polymer of butadiene of acrylonitrile, copolymer of styrene and polypropylene. One skilled in the art will understand that when the bipolar cell of the invention is used in any electrolytic process, both the anode and cathode current collectors and the anodes and cathodes will be selected in order to be resistant to electrolyte and electrolysis products with which they are in contact. Similarly, the anode separator terminals and the cathode separator terminals will be selected so as to be of a material which is resistant to the electrolyte and electrolysis products with which they are in contact during the operation of the cell. It will be understood that although the spacer terminals are shown in the bar-like drawings, other shapes such as oval, circular, rectangular can be used. In addition, the reference to suitable metals for use as anodes, cathodes, separating terminals and current collectors means that it includes the alloys and intermetallic mixtures of the metals referred to. In the formation of the structures of each of the cell units of the monopolar or bipolar electrode, preferably bipolar, each structure cell unit is preferably formed using laminated sheets of thermoplastic or thermostable polymers. Cell structures can also be formed by molding thermoplastic polymers. The laminated sheets are bonded - using any suitable polymeric adhesive. Representative useful polymeric adhesives include epoxy and phenolic polymers and silicone, polyurethane, and fluorine rubbers. Such structures must have the chemical resistance required to operate in contact with the electrolytes that will be used. For example, the monopolar or bipolar electrode cell structure units may be selected to have an electrolyte corrosion resistance suitable for "" using polymeric materials such as polyester, phenolic or epoxy polymers, KYNAR®, CPVC, TEFLON®, styrene copolymers such as polymers of styrene of acrylonitrile butadiene (ABS), polypropylene, copolymers of styrene and polyvinyl chloride (PVC). Suitable cell separators can be porous, preferably microporous membranes or diaphragms, and permselective membranes. Such cell separators for use between the anodes and cathodes of the preferred bipolar electrolyzer of the invention can be any of the various types that are commercially available. For example, the cell membranes may be formed from an in fl uorouted copolymer having pendant cation exchange functional groups. Such fluorocarbons are copolymers of at least two monomers in which a monomer is selected from the group consisting of vinyl fluoride, hexafluoropropylene, vinylidene fluoride, t-fluoroethylene, chlorotrifluoroethylene, perfluoro (alkyl ether 1-vinyl). , tetrafluoroethylene and mixtures thereof. In the formation of such copolymers, a second monomer may be selected from a group of monomers containing S0 F or a sulfonyl fluorine pending group. Such perfluorocarbons can be obtained commercially from the duPont company and sold under the trademark NAFION®. The cell membrane can be a porous, microporous or semi-permeable membrane such as those known in the art. Examples of porous membranes are those made of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), glass fiber, polyvinyl chloride (PVC) and styrene-acrylonitrile polymers. The cell design of the invention can accommodate any permselective membrane of the prior art or porous diaphragm cell separator of any suitable material of the prior art having the appropriate thickness. When a simple packing seal is formed between the cell separator and the cell units, the cell separator is assembled into a structure unit by placing the peripheral area of the separator in an annular depressed area or recess of the structure. This area is machined to a depth of approximately 13 thousandths of a centimeter less than the thickness of the cell separator. The simple packing that separates the structure units in the filter press electrolyser of the invention is then placed on top of the cell separator so that it overlaps the cover structure and covers the same peripheral area of the separator. When pressure is applied, that is, when the cell is bolted together, the cell separator is firmly sealed between the cover structure and the packing thereby forming a leak-proof seal between the structures. Alternatively, the cell structure units are assembled by joining with a polymeric adhesive. Where laminated or molded thermoplastic polymer structures are used, the cell structure units can also be assembled by solvent bonding, for example, the styrene copolymer or polyvinyl chloride units can be joined using ketone solvents such as acetone and methyl ethyl ketone to make the surface of the adhesive self-adhesive. structure material of styrene copolymer or polyvinyl chloride lo. The advantages of this simple packing sealing method are as follows: (1) machining the recess of the separator or depressed area in the roof structure to a depth slightly less than the thickness of the cell separator ensures that there is a fixing pressure of proper bolts on the separator with minimum packing compression. (2) Only one gasket is used, thus allowing the cell separator to remain exposed to one side of the electrolyte, in order to remain flexible and resistant to tearing. The prior art cell designs use two packages, one on each side of the separator leaving the sealed area of the separator dry. (3) In addition to eliminating a second package, this approach eliminates a persistent source of separator failure in many filter press cell designs that use two packages. With the two packing method of the prior art, the separator remains impermeable on both sides and therefore tends to dry under the packages. This sometimes causes the separator to crack and therefore fail, either under the gaskets or at the liquid edge of the gasket. This problem is particularly serious when the O-rings are used against the membrane. (4) The use of a simple package also allows a choice of packing location, ie on either the anode side or the cathode side of the cell unit so that the gasket can be used to seal against the less corrosive of the two electrolytes. In some situations, one of the electrolytes is very corrosive and would require very expensive gaskets, such as Teflon gaskets, although the other electrolyte is relatively benign and would allow the use of cheaper and more conventional gaskets than those formed of elastomers, for example, Neoprene or polymers of ethylene propylene diene monomer. This is the situation in the electrolytic manufacture of peroxydisulfuric acid and salts thereof where the anolyte is strongly oxidizing and very corrosive while the catholyte is only mildly corrosive. Any suitable elastomeric material of any suitable variable or uniform thickness can be used to package between the structures of the cell units, although cable packages such as those sold under the trade name of Gore-Tex and o-rings can also be used. Preferred packing materials are ethylene propylene diene monomer polymers, fluoroelastomers such as VITON®, and polychloroprenes such as Neoprene. The gaskets can be used as tapes that cover only the required sealing areas or full-face gaskets that cover the entire face of the structure except for the window area and the holes in the top. Full face gaskets are preferred because with tape gaskets it is difficult to control the amount of packing compression. Without good control over compression, it is difficult to control the gap between the anode and the membrane. In situations where narrow interstices are used, too much packing compression could close the gap upward by completely pushing the anode towards the membrane. This is particularly likely with thicker packages. This problem in one embodiment of the cell of the invention is solved by using a packing of variable thickness such that the thickest part exceeds the thickness of the thin part by an amount equal to amount of compression desired used to seal the faces of the structure seal. The opposing structures are tightened until the faces of the structure meet the thin part of the package. The preferred full face gaskets are cut to cover the entire face of the structure surface except for the area of the window forming the electrolyte compartment and the holes of the upper part for the electrolyte flow. In this way the total sealing area is maximized. Nevertheless, control over the amount of compression may be a problem in the prior art. In addition, because full-face gaskets cover such a large area, the high bolt-clamping forces in the prior art cells are sometimes required to compress the gasket enough to obtain a good seal. In the cell design of the invention, these problems can be overcome in another embodiment of the cell of the invention when machining a depressed area of the structure material of the seal face of the structure in such a way that critical sealing areas they are at least one or multiple ridges raised. It is preferred to machine a quantity of structure material equal to the desired compression of the package. For example, if the packaging is 0.318 centimeters thick and the desired compression is 30% the amount of material made by machine would be 0.318 * 0.3 = 0.097 centimeters. This allows the maximum pressure to be applied to the critical sealing areas with minimum bolt clamping forces. The cold flow in a thermoplastic cell structure seal face under the packing is much less than a problem with the inventive cell design because the compression required to seal adjacent cell units results in no more than a slight rounding of the flange or flanges of the seal face of structure which would not affect the ability to make a seal and would not cause the overall distortion of the seal face of the structure. The preferred packing thickness is 0.318 centimeters. Thicker gaskets compress too much making it difficult to control the membrane anode gap and they are very expensive too. Thinner packages are not prone to overcoming the effects of imperfections in the seal face of the structure and also require more precise machining of the seal face of the structure. Although it is known that the sealing of the plastic structures of each cell unit with other cell units of a filter press electrolyser can be carried out by means of o-rings or flat gaskets between the individual cell units, it has been found to be advantageous to assemble molded or laminated thermoplastic or thermoplastic polymer cell structure units using an adhesive such as the preferred vinyl ester polymer described above in which the adhesive strength of conventional vinyl esters has been improved by reacting an elastomer on the structure main of this vinyl. Improved bond strength can be obtained by mechanical or chemical abrasion or chemical etching of the cell structure surfaces to be bonded. Sandblasting or chemical etching with organic solvent has proven effective in preparing the plastic cell structure surface for bonding. It has been found that this vinyl ester resin is superior to the use of an epoxy resin adhesive. Alternative adhesive compositions for laminating the plastic sheets to form the cell structure units comprise the following compositions: epoxy, polyester, phenolic, silicone, polyurethane, and fluorine rubber polymers. For use in the process described above, the anode is generally formed of a valve metal substrate such as titanium, tantalum, niobium or zirconium, preferably titanium, coated with a catalytic coating suitable for the desired electrolysis reactions. This catalytic coating is preferably a platinum group metal, preferably, a platinum sheet that is applied in order to coat only a portion of the valve metal substrate to result in a discontinuously coated anode. The metal coating of the platinum group can be applied as various coating sheets, for example, strips, ordered points, random spots or any other shape. The coverage percentage can range from about 1 to about 99% although a coverage of about 20% is preferred for the production of fumaric acid peroxidisul and salts thereof. The individual parts of the preferred discontinuous catalytic anode coating are, more preferably, as small and numerous as possible in such a way that the distance between them is minimized. The distance between the coating forms is up to twice the distance between the coated anode and the membrane separator, also known as the anode and the membrane gap. The metal of the preferred platinum group, platinum, is preferably applied as strips which are cold rolled onto the valve metal substrate in order to produce a durable anode material which is capable of operating under the necessary elevated overvoltage conditions. for the production of peroxydisulfuric acid and salts thereof. The use of titanium as a preferred anode substrate in the presence of sulfuric acid, which has a reducing effect on titanium, is made possible by the application of an anodic cell potential which oxidizes the anode environment. The discontinuously coated anode is also described in the co-pending application of the assignee of the applicants, Serial No. 09 / 044,364, filed on March 19, 1998. A novel electrode which can be used as an anode or cathode in the electrolytic cell of The invention is a mesh or flat sheet of foraminated metal of a stainless steel having higher concentrations of nickel, chromium, and molybdenum than 316 stainless steel which has been used as a cathode in the electrolytic cells for the production of peroxydisulfuric acids. and you come out of them. Specifically, the stainless steel electrode comprises in parts by weight about 20 to about 30 parts of nickel, about 15 to about 25 parts of chromium, and about 5 to about 7 parts of molybdenum. A typical composition is determined in percent by weight of stainless steels which are suitable as cathodes in the electrolytic cell of the invention in Table I compared to stainless steel 316. TABLE I Stainless Steel Components, Weight percent The electrolytic cells of the invention can have electrodes arranged in either monopolar or bipolar configuration. Preferably, the electrolytic cells have a bipolar electrode configuration because, given the relatively high cost of the electrode materials, the use of thin flat sheets of electrode material allows economical use of such high cost electrode materials. In addition, with a bipolar electrode configuration, the multiple electrical connections and the multiple seals required in the monopolar electrode that are conducted through a cell wall are avoided. In addition, because the electrolytic cells for the production of peroxydisulfate and salts thereof require a relatively high current density at the anode of the cell, even a slightly higher resistivity of electrode material can lead to severe generation of heat in the cell. It is a monopolar connection. In contrast, a bipolar electrode in such a cell avoids such current distribution problems, which are a result of the resistivity of the electrode. Although the bipolar electrode configuration is less desirable from a current leakage point of view compared to a monopolar electrode configuration, the use of small inter-cellular electrolyte flow channels must be balanced in order to reduce current leakage and the use of larger channels of electrolyte flow to aid in the distribution of electrolyte and for the extraction of heat. In the preferred electrolytic cell bipolar electrode configuration having a valve metal anode substrate coated with a discontinuous coating of a metal of the platinum group, preferably platinum, the valve metal anode substrate is subjected to the exposure of the hydrogen produced in the cathode of the cell. Hydrogen can migrate as atomic hydrogen through the bipolar cathode through the valve metal anode substrate. The bipolar cell configurations of the prior art have undergone the formation of a metal hydride at the single junction of the support plate or current collector of an anode and valve metal cathode of a bipolar electrode. Although the hydride formed in this way is a conductive material, the hydride's resistance is greater than the resistance of the anode and cathode electrodes but, more importantly, because the hydride has a lower density than that of a pure metal from which they are formed the anode substrate and the cathode, the formed mechanical resistances may be large enough to cause bipolar connection failures. It is understood that the formation of hydride in the electrical connection between the anode and the cathode of the bipolar electrode is a consideration only when the anode and cathode are of different metals. Where the anode and cathode are of the same metal, the same piece of material is used for both the anode and the cathode; the anode is welded on one side of the current collector and the cathode welded on the other side, both in separating terminals made with the same materials as the anode and the cathode. In such a bipolar electrode, the penetration of hydrogen into the current collector does not occur. When the anode and cathode current collectors are made of different metals, the electrical connection can be made by joining the current collectors with an electrically conductive polymer mixture or by direct welding techniques. Spot welding is the preferred welding technique. Not all anode materials are sensitive to hydride formation. However, if the anode metal is subjected to hydride formation, as is the case with an anode comprising a valve metal, measures must be taken to avoid rupture of the welded connection by the formation of hydride. As an alternative for direct welding in order to make the bipolar electrical connection or join the bipolar electrode using a conductive polymer mixture, an intermediate metal layer can be used between the anode and cathode or the anode and cathode current collectors which allows to weld both the anode and cathode current collectors to the intermediate metal layer. Examples of such metal materials are vanadium, copper, silver and gold. In addition to the formation of the bipolar electrode by the aforementioned means that prevent the formation of hydride and consequently avoid the subsequent rupture of the bipolar electrode, it has been discovered that the use of separating terminals separating the anode and the cathode from, respectively the collectors of - 3? The anode and cathode current greatly decreases the probability of the migration of atomic hydrogen through the bipolar cathode to the anode current collector. It has been discovered that the spacer terminals that separate the electrodes from the current collectors by at least about 0.476 centimeters are effective in decreasing the susceptibility of the anode substrate for hydride formation. In addition, filling in the spaces surrounding the spacer terminals that separate the cathode from the cathode current collector with a non-conductive material such as a layer of polyvinyl chloride sheet material, provides additional resistance to the formation of hydride in the cathode. electrical connection of the bipolar electrode. Other useful non-conductive materials are polyesters, styrene copolymers, fluoropolymers, polychloroprene, and ethylene propylene diene monomer polymers. In order for the atomic hydrogen to reach the anode, the hydrogen would have to travel through the layer of non-conductive material located between the cathode-separating terminals to the cathode substrate or hydrogen would have to be released from the substrate around the base of the cathode. the separating terminals. In the first case, it would take hydrogen a very long time to travel through a metal of such thickness. In the second case, the evolution of hydrogen by electrolysis will tend to take place preferably in the areas of the cathode assembly closest to the anode. These areas are the cathode and not the cathode current collector because the current would have to move at least another 0.476 centimeters of electrolyte to reach the current collector. Another means to reduce the likelihood of hydride formation has been found in the use of electrocatalytic precious metal coatings only in selected portions of the cathode assembly, consequently decreasing the electrode potential to 0.5 volts above the potential required to release hydrogen from the cathodes coated with non-precious metals. Additional improvements arise where the electrode and current collectors are composed of different metals. In this case, the cathodes can be coated with an electrocatalytic precious metal coating and the current collectors left uncoated so that it is more favorable to release hydrogen from the cathode than from the current collector. In the preferred embodiment of the electrolytic filter press cell of the invention, the possibility of hydride formation and the probability of failure of the anode and cathode junction, or the anode and cathode current collectors is avoided by the use of a electrically conductive adhesive for electrically connecting the anode and cathode or support plates or double current collectors. The preferred conductive vinyl ester polymer adhesive used for bonding resists hydrogen migration so as to avoid failures of the bipolar electrode as a result of hydride formation. Alternatively, in another preferred embodiment, the formation of hydride can be prevented by placing an intermediate metal barrier layer not susceptible to hydrogen penetration between the bipolar anode and cathode or the anode and cathode current collectors. The barrier layer must be made of a metal which is weldable for both the anode and cathode electrodes or for both the anode and cathode current collectors. The bipolar anode and cathode assemblies can be welded directly where both are from the same metal or from different metals which are weldable. Alternatively, in another preferred embodiment, the formation of hydride can be prevented by the use of a sheet of non-conductive material between the current collector or cathode support plate and the cathode. The preferred polymer material used to laminate the sheets forming the laminated cell structures is an elastomer modified vinyl ester polymer which is superior to polyesters used as adhesives in most conventional polyester applications. Other representative useful adhesive compositions can be prepared by compressing the following polymer compositions: epoxy, polyester, phenolic, silicone, polyurethane, and fluorine rubber polymers. The preferred vinyl ester polymer lamination adhesive for forming the cell structures or selected polymer as component of the component adhesive used to join the anode and the cathode of the bipolar electrode cell becomes more flexible and ductile by reacting an elastomer on the main structure of the vinyl polymer of the resin. This provides increased adhesive strength, superior abrasion resistance and mechanical strengths with double or triple the tester performance properties of standard vinyl ester polymers. As with the more conventional vinyl ester polymers, the elastomer modified vinyl ester polymer can be reacted with peroxides such as methyl ethyl ketone peroxide and benzoyl peroxide to cure the resin so that it becomes resistant to a highly acid electrolyte. In order to provide the necessary conductivity, the vinyl ester polymer can be mixed with metal particles or graphite powder in the proportion of about 20 to about 60 weight percent of the total composition. Preferably, about 30 to about 50 weight percent of a graphite powder having a particle size of about 10 microns is mixed with about 70 to about 50 weight percent of the vinyl ester polymer to form the electrically conductive adhesive composition. preferably used to join the anode and cathode current collectors of the bipolar electrode. The anode and the cathode are preferably electrically connected to their respective current collectors by means of separating terminals which are soldered in points to their respective current collectors which, in turn, preferably join to make the bipolar electrical connection with an electrically conductive adhesive, as described above. The separator terminals allow the adjustment of the anode and cathode gap between the cell separator by selecting the length of the separator terminal. Generally, the respective anode and cathode current collectors can be omitted and the anode and cathode joined directly. Although this invention has been described with reference to some specific embodiments, those skilled in the art will recognize that many variations are possible without being insulated from the scope and spirit of the invention, and it will be understood that it is intended to cover all changes and modifications of the invention described. in the present for purposes of illustration which do not constitute deviations from the spirit and scope of the invention. Where not indicated differently, the parts and percentages are by weight and the temperature is in degrees centigrade.

Claims (31)

1. CLAIMS Having described the invention as an antecedent, the content of the following claims is claimed as property: 1. In a bipolar filter press electrolyzer comprising a bipolar electrode comprising a cathode and cathode current collector, an anode and a current collector Anode, a cell separator and cell structures, the improvement characterized in that said structures comprise a laminate of thermoplastic or thermoplastic polymer sheets with an adhesive between the adjacent sheets or thermoplastic or self-adhering polymer sheets upon self-adhesive return at least a surface of the adjacent sheets using a solvent for said thermoplastic polymer. The filter press electrolyser according to claim 1, characterized in that said laminate comprises multiple layers of said polymeric sheets and a polymeric adhesive selected from the group consisting of a polymer of vinyl ester, an epoxy polymer, a phenolic polymer, a silicone polymer, a polyurethane polymer, and a fluorine rubber polymer. The filter press electrolyser according to claim 2, characterized in that said laminate comprises thermostable polymer sheets selected from polymers of the group consisting of vinyl esters, epoxy and phenolic polymers. 4. The filter press electrolyser according to claim 2, characterized in that said laminate comprises polymer sheets selected from polymers of the group consisting of polymers of styrene of acrylonitrile butadiene, polypropylene, copolymers of styrene and polyvinyl chloride. The filter press electrolyser according to claim 4, characterized in that said cell structures are laminated with a polymeric vinyl ester adhesive. The filter press electrolyser according to claim 4, characterized in that said laminate comprises sheets of styrene copolymer or polyvinyl chloride and a polymeric vinyl ester adhesive therebetween. The filter press electrolyser according to claim 1 comprising multiple cell units, characterized in that each cell unit comprises a cell structure defining with an adjacent cell structure compartments of anolyte or catholyte, wherein said units of adjacent cells they seal against electrolyte leaks using at least one simple package. The filter press electrolyser according to claim 7, characterized in that said single package is a tape or full-face package having variable thickness and wherein a sealing surface of at least one cell unit of a pair of said cell units comprises at least one depressed area sufficient to receive a portion of said single package. The filter press electrolyser according to claim 7, characterized in that said simple packing is a tape or full-face pack having uniform thickness and wherein a sealing surface of at least one cell unit of a pair of said units of the cell comprises at least one depressed area sufficient to receive a portion of said single package. The filter press electrolyser according to claim 9, characterized in that said packing is an elastomeric material selected from the group consisting of ethylene propylene diene monomer polymers and vinylidene fluorine and hexafluoropropylene copolymers. The filter press electrolyser according to claim 7, characterized in that said cell unit comprises a laminated thermoplastic polymeric sheet cell structure or a laminated thermosetting polymeric sheet cell structure, said anolyte and catholyte compartments are separated by a cell separator and a peripheral portion of said cell separator is placed in an annular depressed area of a sealing surface of said cell structure. 12. The filter press electrolyser according to claim 11, characterized in that the depth of said annular depressed area is approximately 13 thousandths of a centimeter less than the thickness of said cell separator. 13. The filter press electrolyser according to claim 12, characterized in that said cell separator is a permselective membrane or a microporous polyvinylchloride cell membrane. The filter press electrolyser according to claim 1, comprising multiple cell units, characterized in that each cell unit comprises a laminated thermoplastic polymer cell structure defining with an adjacent cell structure an anolyte or catholyte compartment, wherein the adjacent cell units are bonded with an adhesive polymer or are joined by the application of a solvent for said thermoplastic polymer cell structure to a sealing area surface prior to bonding. 15. The filter press electrolyser according to claim 14, characterized in that said polymeric adhesive is selected from the group consisting of a polymer of vinyl ester, an epoxy polymer, a polymer-phenolic, a silicone polymer, a polyurethane polymer. , and a fluorine rubber polymer. 16. The filter press electrolyser according to claim 15, characterized in that said polymeric adhesive comprises a vinyl ester polymer. 17. The filter press electrolyser according to claim 15, characterized in that said structures of said cell units are self-adhesive by means of the partial solution in a solvent for said structures. 18. The bipolar filter press electrolyzer according to claim 1, characterized in that said bipolar electrode comprises a flat anode and a flat current collector, a flat cathode and a flat cathode current collector, wherein the bipolar electrode is electrically connected between said cathode or said anode and cathode current collectors by means comprising joining with an electrically conductive polymer mixture, welding or welding through an intermediate layer of a metal other than that of the anode and said cathode. The filter press electrolyser according to claim 18, characterized in that said electrically conductive polymer mixture comprises a polymeric adhesive selected from the group consisting of a polymer of vinyl ester, epoxy, phenolic, silicone, polyurethane, and fluorine rubber. The filter press electrolyser according to claim 19, characterized in that said electrically conductive polymer mixture comprises a polymer of styrene vinyl ester or copolymer and a filler material comprising a graphite powder or a metal powder. 21. The filter press electrolyser according to claim 18, characterized in that said bipolar electrode is electrically connected by resistance welding, flame welding to inert tungsten gas, electron beam welding, diffusion welding and laser welding. 22. The filter press electrolyser according to claim 18, characterized in that said bipolar electrode is electrically connected by welding through an intermediate layer of a metal selected from the group consisting of vanadium, copper, silver and gold. 23. The bipolar filter press electrolyzer according to the rei indication 18, characterized in that said intermediate layer is vanadium. 24. The filter press electrolyser according to claim 18, characterized in that said anode is catalytically coated and comprises a discontinuous coating of a metal of the platinum group on a valve metal substrate and said cathode comprises a stainless steel. 25. The bipolar filter press electrolyzer according to claim 24, characterized in that said valve metal substrate is selected from the group consisting of titanium., niobium, and zirconium, and said platinum group metal is platinum, and said stainless steel comprises about 20 to 30 weight percent nickel, about 15 to about 25 weight percent chromium, and about 5 to about 7 weight percent. percent in molybdenum. 26. The filter press electrolyser according to claim 1 comprising multiple cell structure units comprising a cell separator, an anode, and a cathode wherein characterized in that the contact of said cell separator with said anode and cathode is prevented when welding filaments or multiple chains of a non-conductive material around said anode and cathode. 27. The filter press electrolyser according to claim 26, characterized in that said filaments of non-conductive material are selected from the group consisting of polyesters, styrene copolymers, fluoropolymers, polychloroprene and polymers of ethylene propylene diene monomer. 28. The bipolar filter press electrolyzer according to claim 1 comprising a flat valve anode coated or uncoated catalytically, a flat cathode and a flat cathode current collector, characterized in that said cathode and said cathode current collectors they are separated by electrically conductive separator terminals and where a layer of non-conductive material is placed in an area surrounding said separating terminals between said cathode and said cathode current collector. 29. The bipolar filter press electrolyzer according to claim 28, characterized in that said non-conductive layer is selected from the group consisting of polyesters, styrene copolymers, fluoropolymers, polychloroprene and polymers of ethylene propylene diene monomer. The bipolar filter press electrolyzer according to claim 29, characterized in that said catalytically coated anode comprises a discontinuous coating of a metal of the platinum group on a valve metal substrate and said cathode comprises a stainless steel comprising approximately 20 to approximately 30 weight percent nickel, about 15 to about 25 weight percent chromium, and about 5 to about 7 weight percent molybdenum. 31. The bipolar filter press electrolyzer according to claim 30, characterized in that said valve metal substrate is selected from the group consisting of titanium, niobium, and zirconium and said platinum group metal is platinum.