DD209854A5 - ELECTROLYSIS CELL - Google Patents

Abstract

An electrolytic cell having a septum separating an anode and cathode space and having an electrode assembly having a reticulated foam net structure arranged in physical contact with the septum. The power supply is connected to such an electrode assembly by intermetallic bonding. The electrolyte is circulated through a reticulated electrode by means of circulating means. The electrode assembly, in particular cathode assembly, can be produced in an electrolytic cell by making a foam cut to a suitable shape conductive and then galvanically coating it with a suitable metal coating. The foam carrier material can be removed by thermal treatment. The electrodes according to the invention require lower operating voltages than known electrodes and thus allow savings in electrical energy.

Description

'Berlin, 25.11.1983

62 576/17

Electrolysis cell Anwendungsgebi et the invention

The present invention relates to electrolytic cells, in particular to cells in which an alkaline product is produced at the cathode, such as, for example, chloralkali electrolysis cells. More particularly, the present invention relates to improved cathodes and cathode assemblies for use in such electrochemical cells and to methods for Preparation of these improved cathodes and cathode assemblies

Characteristic of the known technical solutions

Electrolysis cells for the production of products of various chemical reactions are widely used. "One field in which these cells have found a particularly wide application is the preparation of halogens and basic compounds from salts of halogen. In such cells, the halogen evolves in the general at the anode, while the basic compound is formed in the region of the cathode «

Significant efforts have recently been made to develop improved anode configurations that allow more efficient operation of the electrochemical cell. These efforts have led to the development of such improvements as the dimensionally stable anodes, a proprietary anode coating system, the improvements

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the anodes led to improved cost-effectiveness of the operation of chlor-alkali cells.

In the case of cells in which a septum, such as a diaphragm, "separates the cell to form anode and cathode spaces," considerable development efforts have been made to develop improved septa. It has been found, for example, that partition walls based on perfluorocarbon copolymers and having cation exchange groups, under certain operating conditions, provide the cell with an opportunity to improve the economics of operating such a cell. "

A continuing lack of efficiency in the operation of an electrochemical cell relates to power losses due to the distance, in most conventional cases, between the septum and the anodes and cathodes used in the cell. For the: presence of such a distance there are a variety of reasons. A common cause, for example, concerns the difficulty in releasing gas bubbles when an electrode is forced into a relatively soft diaphragm, such as a diaphragm-type diaphragm.

Distances between the anode and the cathode in an electrochemical cell cause the electric current to make its way through one or the cell electrolytes in which the resistance to the current passage is relieved.

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may be tively high _e Generally make it larger distances between the anode and the cathode required "that a higher voltage must be applied to the cell to carry out the desired electrochemical reaction" This increased tension contributes to the electricity consumption in the operation of the cell, the Cost of operating the cell increased «

There are already a number of proposals "which concern the reduction of the distance between the anode and the cathode in a cell and in this way also a reduction in the consumption of electrical energy during operation of the cell." A reduced distance between anode and cathode for Proposed cells which are separated by a hydraulically permeable diaphragm, as well as for cells which are divided by a hydraulically impermeable membrane

For example, in diaphragm cells, the distance between the anode and the cathode has been reduced until one or both electrodes touch the diaphragm. Many diaphragms are fabricated from materials that cause the diaphragm to swell in the cellular environment. Electrodes used in such cells often have a wire or mesh construction. "Swelling of a diaphragm in contact with such an electrode can result in a swelling of the diaphragm lead to partial blockage of openings in the electrode, resulting in a poor release of gas bubbles generated in the region of the electrode, as well as to a disabled flow of the

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Electrolytes from the anode compartment into the cathode compartment through the diaphragm "A counter-effect obtained may be an overvoltage at the electrode" which at least partially nullifies the energy gains achieved by reducing the distance between the anode and cathode.

In membrane cells, the membrane is generally a cation exchange material, usually very thin, on the order of a few hundredths of mm. In addition, such membranes often exhibit considerable dimensional stability, allowing for an array of electrodes adjacent to the membranes without any interference there is a significant risk that the openings in the electrode become plugged by an expansion of the membrane. However, if mesh electrodes or electrodes made of wire are placed adjacent to a membrane, allowing the electrodes to be only a few hundredths of a millimeter apart, For example, the lines of electrical flow between the individual elements of the electrodes often do not pass all of the membrane material separating the anode from the cathode. This causes the membrane to be used ineffectively, increasing the voltage drop that does not affect one optimal flow of the electrolyte through the membrane

In addition, when a mesh or mesh type electrode is brought into contact with a membrane, the gas bubbles also show a tendency to "lodge" in the openings of the grid.

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to stick to each other, and these gas bubbles often lead to an overvoltage at the electrode «

In a proposal for a closer arrangement of the anode to the cathode as described for example in US-PS 4,253,924, 4,253,922 and 4,250,013, a porous, optionally conductive material of a secondary electrode is used, in particular the cathode compartments The interface between the primary electrode and the porous secondary electrode material resulting from such action may contribute substantially to the electrode resistance between the two and at least partially obviate the advantages due to the large size of the cell Electrode surface potentially made available by the secondary electrode materials could be achieved «

Object of the invention

It is the object of the present invention to improve the efficiency of the operation of an electrolytic cell by new electrode structures compared to the known electrolysis cells, in particular to improve the economy of electrolysis cells with a small distance between the anode and the cathode (narrow-gap electrolysis cell).

Explanation of the essence of the invention It is the object of the present invention to provide a

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The economic electrolysis cell and an advantageous method for producing a new electrode structure

It has been found that a cell structure in which a primary foam electrode or reticulated electrode contacts a septum dividing the cell offers the possibility of improving the efficiency of the operation of the cell.

In accordance with the present invention, electrode assemblies are provided that can be used in electrochemical cells in which a septum divides the cell into anode and cathode compartments. A porous network, generally having the structure of an open cell foam, substantially fills the electrode compartment A terminal for the power supply is intermetallically bonded to the electrode such that voltage losses due to the current transfer between the electrode and the power supply are negligible. Means for circulating the electrolyte are provided for this purpose to introduce the electrolyte into the electrode and to remove it from the electrode. Such electrodes are advantageously used as anode.

The electrolytic cell having anode and cathode compartments separated by a septum is further characterized as comprising a cathode assembly comprising:

a) an open-pore net-like primary cathode, the

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At least partially fills the cathode compartment and has considerable physical contact with the septum,

b) a cathodic power supply "intermetallically bonded to the cathode" such that the electrical resistance between the power supply and the cathode is negligible in supplying the cathode with power, and

c) circulating means, which allow a circulation of the electrolyte into and out of the cathode compartment *

A narrow gap electrolytic cell in which the anode and cathode compartments in the cell are separated by a septum, and wherein at least one electrode of the cell has substantial physical contact with the septum, is characterized in that it comprises a narrow gap electrode assembly comprising:

a) at least one open-pore net-like primary electrode

-2 with pores of size in the range of 1.27. 10 mm up

-1 2.54 x 10 mm, which has substantial physical contact with the septum and substantially fills at least one of the electrode compartments of the electrolytic cell;

b) a power supply, which intermetallically connects the electrode with an electrical power source so that the electrical resistance between the power supply and the electrode is negligible ι and

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c) at least one electrolyte inlet for introducing the electrolyte into the electrode and at least one outlet for removing the catholyte from the electrode

These electrodes are also advantageously used as anode,

A narrow-gap electrolysis cell in which the anode and cathode compartments in the cell are separated by a septum and in which the cathode in the cell has substantial physical contact with the septum is further characterized in that it comprises a narrow-gap cathode cell. Comprising an assembly comprising

a) an open-pore reticulated primary cathode having pores of size in the range of 1.27. 10 "mm to 2.54 · 1Q ~ mm, which has a substantial physical contact with the septum and substantially fills the cathode compartment of the electrolysis cell;

b) a cathodic power supply interconnecting the cathode intermittently with a source of electrical current so that the electrical resistance between the power supply and the electrode is negligible; and

c) at least one catholyte inlet for introducing the catholyte into the cathode and at least one catholyte outlet for removing the catholyte from the cathode.

The method of manufacturing an electrode assembly

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for an electrolytic cell according to the invention with an anode and cathode compartments separated from one another by a septum and at least one inlet and outlet for the electrolyte into and out of the electrode compartments, characterized in that it comprises:

a) a substantially complete filling of at least one electrode space with an open-cell plastic foam, wherein the foam has a significant physical contact with the septum membrane;

b) arranging a power supply of an electrically conductive metal to each foam-filled electrode space «the power supply is at least partially immersed in the plastic foam;

c) treating the open cell plastic foam with an electroless plating solution until the foam has formed an electrically conductive topcoat of a desired thickness;

d) switching the foam as a cathode; and

e) passing a plating solution through the foam electrode until an electrodeposited coating of the desired thickness has formed on the foam.

Advantageously, the foam is thermally removed during plating.

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It is expedient if the foam has an open porosity.

-.2 -1

between 1.27 × 10 mm to 2.54 × 10 mm «

The metallization solutions on the foam cathode produce a coating of metallic nickel ·

A variant of the method of manufacturing an electrode assembly for an electrolytic cell having a septum separated anode and cathode spaces and at least one electrolyte inlet and outlet in each electrode space is characterized in that it comprises:

a) substantially complete filling of at least one electrode space with an open-pore conductive plastic foam, said foam has a significant physical contact with the septum membrane;

b) arranging a current supply of a conductive metal at each filled with foam electrode space, wherein the power supply is at least partially immersed in the plastic foam;

^C X switching of the foam as cathode; and

d) treatment of the foam electrode with a galvanizing solution until a galvanically produced coating of the desired thickness has formed on the foam

The foam belongs advantageously to the type with a

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electrically conductive substance impregnated foam.

For this purpose, the foam cathode is treated with a solution for electroless plating before it is switched as a cathode for depositing a desired metal coating on the foam cathode.

The plating solution advantageously contains a substantial content of nickel ions for galvanic nickel deposition on the foam cathode.

The septum is suitably a membrane which is hydraulically impervious to liquid movement between the electrode spaces, but which allows for easy passage of cations from one electrode space to the other.

It is advantageous if the membrane contains a substantial proportion of a perfluorocarbon copolymer with sulfonyl- or carbonyl-based cation-exchange groups.

The power supply is advantageously introduced into the foam by heating and immersing it in the foam. "

Another variant of the method for producing a cathode assembly for an electrochemical cell separated by a septum anode and cathode spaces and at least one inlet and at least

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an outlet for the catholyte is characterized in that:

a) selecting a porous reticulated foam material as the cathode material and fitting the foam into the cathode compartment of the electrolytic cell so that the foam substantially fills the cathode compartment and is in substantial physical contact with the septum;

b) rendering the foam conductive;

c) disposing a cathode current supply and making electrical contact with that supply with the foam cathode; and

d) galvanic deposition of a cathode metal on the foam cathode.

The reticular electrodes of the present invention, generally cathodes, can be rendered conductive by employing conventional techniques such as carbon impregnation or electroless plating. Electroplating or electrodeposition can be accomplished by conventional techniques. These techniques can be applied in situ in the electrolytic cell, or outside the cell.

An advantage of the method according to the invention for the production of electrode assemblies is that the various steps are carried out in alternating orders

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"For example, the foam can first be cut to the desired shape, or it can first be made conductive, or it can first be made conductive and electroplated before it is cut." Manufacturing route for a variety of end uses to choose ·

If one uses a porous foam electrode or reticulated electrode, which is in contact with the septum, the anode and the cathode are separated only by the distance required for the septum within the cell, resulting in a lowering of the required voltages for the current flow through Forced circulation or circulation of the electrolyte through the porous electrode assists in preventing bubble accumulation near the surfaces of the septum which is in contact with the electrode, and may further serve to establish concentration gradients within the electrode space, particularly in the cell space In the vicinity of the septum, to reduce both concentration gradients and blistering contribute to the formation of overvoltages, their reduction can lower the voltages required to operate an electrochemical cell in the electrode of the present invention en assemblies are used «

exemplary

The present invention will be explained in more detail below by means of an example with reference to the drawing.

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The sole drawing, FIG. 1, shows a cross section through an electrochemical cell with a cathode assembly according to a possible embodiment of the present invention.

Referring to the drawings, FIG. 1 shows an electrochemical cell 10, particularly a chloralkali cell, shown in cross-section. This cell comprises a housing 12, an anode assembly 14, a sheath 16, and a cathode assembly 18.

The housing 12 may be made of any suitable or conventional material that is chemically relatively inert to the electrochemical content of the cell. If, as in the preferred embodiment, the electrochemical cell is one for generating chlorine and basic products from one Brine of an alkali metal halide, the housing may be made of a plastic material, such as polypropylene. In general, the top of the cell is covered by a cell cover (not shown) during its operation. "

The cell is divided by the septum 16 into an anode space 22 and a cathode space 24. This septum may either be hydraulically porous, for example a diaphragm, or it may be hydraulically impermeable, for example a cation exchange membrane. If the septum is of the diaphragm type , the diaphragm may be a diaphragm made by a variety of well-known techniques which may become a hydraulically transmissive diaphragm.

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In general, such diaphragm diaphragms contain asbestos fibers when made for use in a chlor-alkali cell.

W _e nn the cell is divided by a membrane "separating the membrane, the electrode chambers 22 and 24 so that a free liquid movement is excluded between these electrode compartments. Such a membrane is required to allow electrical current flow between the electrode spaces, and such membranes are generally capable of passing a particular ion or charged particle form from one electrode space to the other. When the electrolyte filling of the electrochemical cell comprises aggressive compounds, it is desirable that the membrane be made of a compound which can withstand the aggressive attack of the electrolyte contained in the electrode spaces.

In the case of a chlor-alkali cell, which is the preferred electrolysis cell according to the invention, this membrane may be made of a suitable or conventional material, which is the aggressive materials in the electrolyte in each electrode space 22; 24 resists. A particularly preferred material is a perfluorinated copolymer having cation exchange groups. These perfluorocarbons are copolymers of at least two monomers wherein one monomer is selected from the group consisting of vinyl fluoride, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene-perfluoro (alkyl vinyl ether). Tetrafluoroethylene and mixtures thereof.

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The second monomer is often selected from a group of monomers "usually having a SO" _{2 "} F or sulfonyl fluoride side group. Examples of such second monomers can be generically represented by the formula CF" _{2 "} = CFR.SO" _{2 "} F in this general Formula R _{1 is} a bifunctional perfluorinated radical generally containing 1 to 8 carbon atoms, but may, if required, contain up to 25 carbon atoms. One constraint for the general formula is that at least one fluorine atom be present on the carbon atom to which the -SCLF Group, especially when the functional group is in the - (- SO ₂ NH) mQ form. In this latter form, Q may be hydrogen or an alkali or alkaline earth metal cation, and m is the valence of Q. The portion R * in the general formula may have any suitable or conventional form, but it has been found that the group R is bound to the vinyl radical of the comonomer, preferably via an ether bond. «

perfluorocarbons are generally commercially available, perfluorocarbon copolymers containing perfluoro (3,6 ~ dioxa-4 ~ methyl-7-octensulfonylfluorid) as comonomer, are particularly well established for chlorine cells. "If a sodium chloride brine to produce the chloroalkali It has been found advantageous to use membranes the majority of which is formed by a perfluorocarbon copolymer having functional groups derived from a sulfonyl fluoride, and which is a relatively thin layer

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of a perfluorocarbon copolymer with carbonyl fluoride-derived functional groups on a membrane surface «

The anode compartment 22 comprises an anode 26 and an anode current supply 28. The power supply 28 is connected to an electric power source, not shown. An electrolyte 30 generally fills the free space in the anode compartment. Generally, this electrolyte 30 or anolyte is a caustic an alkali metal halide salt prepared by well-known methods. The compositions of such bases are generally well known in the relevant industry.

The anode 26 is made of a suitable or conventional material which is suitably resistant to the anolyte and halogen compounds produced in the electrolytic cell. Typically, titanium comprising a layer of one or more metals or metal oxides, such as for example, ruthenium oxide, have «

The anode 26 may be located immediately adjacent the septum, or there may be a gap between the anode and the septum. In a similarly preferred alternative embodiment, a catalyst such as ruthenium oxide directly contacts the septum, a membrane, in contact a grid or rooftike power supply or electrode.

The cathode compartment 24 contains a cathode assembly 34 · The

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Cathode assembly 34 comprises a foam-like reticulated cathode 36, a cathode current supply 38, and an inlet 40 and an outlet 42 for the electrolyte. The cathode compartment is generally filled with an electrolyte 44 or catholyte containing a hydroxide of the alkali metal present in the halide salt which forms the liquor. This catholyte also fills the portion of the cathode compartment which is not occupied by the cathode 36.

The cathode is of open-pored reticular or reticulated nature. Although the pores may be any suitable or conventional size, pores between 0.0127 and 0.254 mm are preferred, with pores between about 0.0254 and 0.127 mm being particularly preferred. Under open-pore is to be understood that the cathode is substantially hydraulically permeable over its entire structure.

The cathode 36 comprises a backing formed from a resinous or plastic material such as urethanes, polyesters, olefin polymers such as polypropylene or polyethylene or other suitable or conventional materials. This carrier is used in the form of a foam and does not have to be a rigid foam.

The support is at least partially enveloped by one or more coatings of at least one conductive cathode material. These coatings can be applied to the support in any suitable or conventional manner, for example electrolytically by electroplating. For

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plating generally requires electrical conductivity of the resinous or plastic foam backing. The foam backing may generally be rendered conductive using any suitable or commonly known techniques, such as by electroless plating or by impregnation with a conductive substance such as carbon.

Application of the coating material renders the foam mesh conductive and thereby suitable as a cathode. Although a variety of cathode materials are known, for the best mode, i. In particular, nickel seems to act in such a way that it supports the electrochemical reaction at the cathode. The metal coating on the substrate need only be sufficiently thick and continuous so that the resistance to the flow of electrical current through the cathode to the point of decrease in electrical current is negligible.

The net-like cathode is disposed in the cathode space 24 so as to be in contact with the septum. However, since the foam network becomes relatively rigid upon application of the metal coating, it is often preferred to preform the foam and fit into the cathode space before the metal coating is applied.

The net-like cathode acts as a primary electrode within the cell. Oer electric power is this net-like primary cathode via the cathode current supply 38th

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fed. It is particularly preferred that "the electrical resistance" of each electrical connection of the net-like cathode with the power supply 38 can be assigned «is negligible. This low electrical resistance is preferably achieved by providing a connection of intermetallic nature.

One method that allows for the attachment of the cathode current supply to the net-like cathode is to insert the power supply 38 into the foam carrier material for the reticulated cathode 36 before applying the coating material. The insertion can be done so that the foam carrier is provided with the net-like structure with a slot into which the power supply is inserted, by heating the power supply to a temperature above the melting temperature of the foam and immersing the heated feed into the foam or by co-extruding or molding the foam with an embedded power supply. The intermetallic connection of the power supply to the net-like cathode can thereafter be effected by electrodepositing the coating metal for the support material, the power supply being used for the electrodeposition of the catalyst To supply coating metal.

The inlet 40 and outlet 42 are intended to allow circulation of the catholyte through the reticulated foam cathode. Since the net-like cathode is porous, the catholyte can relatively easily through

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the cathode can be printed or sucked by using any suitable or conventional circulating means such as a pump. One or more inputs and / or passages may be provided depending on the size of the cathode, the degree of circulation desired, and other factors.

In operation of the chloroalkali electrolytic cell of the preferred embodiment, metal ions, usually sodium ions, migrate from the anode space through the septum, at least in part as a result of the electrical current flowing through the cell. These sodium ions react at the cathode with hydroxyl radicals attached to the cathode However, as the electrochemical cell continues to operate, the concentration of these metal ions near the septum typically increases, resulting in a concentration gradient hindering the further migration of metal ions this resistance would normally require an increased cell voltage between the anode and the cathode in the cell, and consequently lead to an increase in energy consumption for the operation of the cell · The circulation, which in the sense of reducing this concentrate ion gradient resistance or overvoltage can help prevent increased power consumption in the operation of the cell.

Hydrogen can be formed at the decomposition of the water at the cathode

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these bubbles adhere to the cathode * they reduce very significantly the cathode surface _s is available for the electrochemical reaction available "resulting in an electrical resistance or a high-voltage" The circulation of the catholyte through the reticulate cathode can reduce the adhesion of bubbles and thereby to contribute "that an increased cell operating voltage is avoided, as would otherwise be required to compensate for this bubble overvoltage ·

The desired volume of catholyte circulating through the cathode may vary, with lower flow rates generally being preferred for energy savings. "Flow rates between about 1 l / min per cubic meter net-like cathode and 250 l / min are possible." Only such a flow rate is required sufficient to avoid the formation of a bubble and concentration overvoltage «

It is not necessary that the net-like cathode 36 completely fills the cathode space 24. "The cathode of the net-like or reticulated foam must fill only areas of the cathode space adjacent to the septum and be in substantial physical contact with the septum does not completely fill the cathode compartment, the remainder of the cathode compartment may be filled with a resistant material such as a foam capable of performing the task of pressing the meshed cathode against the septum

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net-like cathode, which does not completely fill the cathode compartment, can be pressed against the septum in any suitable or customary manner, for example, using an elastic grid.

In an alternative embodiment for the preferred embodiment, the cathode current feed is first embedded in the foam substrate of the net-like cathode. The foam substrate is placed in the cathode space of the cell. If the foam substrate has not been made electrically conductive in advance by impregnation with carbon or a similar method, a first metal coating is applied to the foam subtrate by electroless metallization techniques. Generally, this electroless metallization can be carried out within the electrolysis cells The most preferred forms of application are first performed "to make the foam substrate conductive for subsequent electrodeposition of the cathode metal."

The subsequent galvanic or electrochemical metal deposition on the cathode assembly to be generated with the net-like cathode is preferably carried out within the electrolysis cell. The plating bath is placed in the cathode compartment and the cathode current supply is connected to an electrical power source. As a result, metal ions contained in the plating bath are deposited on the substrate from the reticulated foam using well-known plating techniques.

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During operation of the electrochemical cell, the catholyte deposited on the foam carrier is cathodically protected from exposure to aggressive chemicals present in the catholyte. In a chloroalkali cell in which the septum is a cation-exchange membrane, metal ions such as sodium ions migrate from the anode space through the membrane and react with the hydroxyl radicals generated at the reticulated cathode to form a metal hydroxide solution containing the catholyte. By periodically removing and replacing some of the catholyte circulating through the reticulated cathode and replacing it with water, the concentration of metal hydroxide in the catholyte can be adjusted to the desired, well known, preferred limits for the operation of a membrane chlorine gas. alkaline cell to be controlled *

When the net-like cathode contacts a porous septum, such as a diaphragm, liquor containing ions of the metal flows through the diaphragm into the cathode space and merges with the catholyte which circulates through the cathode space. The removal of circulating catholyte compensates, in a well known manner, excess liquor volumes that have migrated through the septum and serves to control the concentration of metal hydroxide in the circulating catholyte.

Anodes may also be prepared for use in electrolytic cells, in a manner identical to the above-described generation of the foam or netlike cathode assemblies.

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or reticulated anodes can be used in electrochemical cells and in substantial physical contact with the septum that divides the cell into anode and cathode spaces. It is often advantageous when anodes prepared according to the present invention have an ocher coating or electrocatalytic coating applied after formation of the foam or mesh-like anode assembly.

The invention will be further explained by means of exemplary embodiments.

example 1

A reticulated nickel cathode was prepared by first attaching a Nbkel current distributor made of a nickel grid sheet starting material to a feed rail. The grid and feed rail were then heated above the melting point of polyurethane foam, such foam having already been given a shape to substantially fill the entire cathode compartment of an electrolytic cell. The hot feed rail with the grid was inserted into the foam where it was allowed to cool. During cooling, the foam melted by the heat of the feed rail and the grid and bonded to the grid. "The resulting cathode assembly was then metallized. Such metallated cathodes have proven to be effective cathodes for electrolysis cells, with the foam having between 4 and 18 pores per cm (between 10 and 45 pores per inch).

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For plating, the cathode assembly was immersed in a room temperature bath consisting of an aqueous solution of 10 g / L stannous chloride and 10 ml / 1 hydrochloric acid (20 ^° C.). After 5 minutes, the cathode assembly was carefully placed in Washed water from room temperature and then immersed in an aqueous solution of 0.5 g / l ^pdc l ₂ ^{and i0 ml} / l hydrochloric acid 5 min · After washing with water, the cathode assembly was 10 min · at 50 ⁰ C. immersed in a mixture containing one liter of an aqueous solution of 45 g / l nickel chloride hexahydrate, 50 g / l of ammonium chloride, 100 g / l of sodium nitrate, 0.5 1/1 of ammonium hydroxide and 27.3 ml of an aqueous solution of sodium hypophosphite of 450 g / l of · In this S _c hrittfolge the cathode assembly was plated electrolessly ·

Thereafter, the cathode assembly was immersed in an aqueous solution of 141 g / l nickel chloride hexahydrate, 291 g / l nickel sulfate hexahydrate and 45 g / l phosphoric acid, the solution using hydrochloric acid to a The cathode assembly was switched as a cathode to nickel anodes, which were about 3.8 cm from the surface of the foam-cathode assembly, and to a voltage of 2.25 V was nickel plated at 30 to 40 ^° C. for 3 hours. Nickel plating was continued until a topcoat having a thickness of 10 μm or more was formed on the foam.

Optionally, it is possible to ash after 11/2 hrs, nickel plating the polyurethane foam by the

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Keep the network in a flame or oven "until the foam has burnt out" After washing, nickel plating can then continue ·

Example 2

A reticulated nickel cathode was prepared as described in Example 1, except that after completion of electroless nickel plating, the cathode was immersed in an aqueous solution of 250 g / l nickel chloride hexahydrate and 50 g / l zinc chloride. This solution became 45 ^° C The pH was adjusted to about 4.5 by the addition of HCl. Nickel and nickel Zinik anodes were placed in close proximity to the surfaces of the cathode assembly and approximately at a voltage of 2.00V 1 h, connected as an anode with respect to the cathode · During the electrolytic or galvanic metallization, the solution was stirred.

Following the galvanic metallization was the

Cathode assembly immersed for 1 hr at 75 ^° C. in an aqueous solution of 200 g / l sodium hydroxide.

Example 3

The preparation steps of Example 1 were repeated except that the electrodeposition was carried out using an aqueous solution containing 265 g / l of cobalt chloride hexahydrate, 90 g / l of zinc chloride and 30 g / l of boric acid, having a temperature of 50 ^° C and

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a pH of 4 set by the addition of hydrochloric acid, zinc anodes placed at a distance of about 3.8 cm from the surface of the cathode assembly were used, at a voltage of 0.6 V, the cathode assembly in a period of 1 hour, to galvanize «

Example 4

As described in Example 1, a cathode assembly was prepared except that one of copper was used instead of the current distribution grid. By electroless copper plating, a copper coating was formed on the polyurethane foam by placing the cathode assembly for 5 min «Immersed in two baths successively at room temperature. The first bath contained 10 g / l stannous chloride and 10 ml / 1 hydrochloric acid (20 Be ⁰ ). The second bath contained 0.5 g / l palladium chloride and 10 ml / 1 hydrochloric acid (20 Be °). After each bath, it was washed with room temperature water. The cathode assembly was then immersed in a commercial electroless copper plating solution at room temperature for 20 minutes, prepared by mixing two commercial solutions in a 1: 1: 8 ratio with water, and then gently washed.

The cathode assembly was then immersed in a plating bath containing an aqueous solution of 40 g / l copper in the form of copper sulfate and 10 g / l sulfuric acid, having a pH of 1 maintained by the addition of sulfuric acid. and room temperature.

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The copper deposition was carried out by placing copper anodes 3,8 cm from the surface of the cathode assembly and switching the cathode assembly as a cathode opposite these copper anodes, followed by applying a voltage of 1 1/2 V for about 1 hour the polyurethane foam «can be ashed« as stated in example 1 if about half the plating time has elapsed *

Oa copper is extremely corroded as such in the cathode compartment of a chloralkali cell or is attacked, the copper-plated cathode assembly was then as described in Example 1, electrolytically nickel-plated »

Example 5

By attaching a power supply to a power distribution grid made of nickel as indicated in Example 1, a cathode assembly was fabricated. After heating, the power distribution grid and power supply were set as shown in Example 1 Pressed polyurethane foam, whereby a foam or mesh-like cathode assembly was obtained

The foam cathode assembly was then, as stated in Example 4, electroless copper and then also, as indicated in Example 4, still electroplated copper · Subsequently, on the foam-cathode assembly as described in Example 1, by galvanic means Nickel coating applied ·

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»Subsequently, as described in Example 2, a coating of nickel and zinc was produced by electroplating on the netlike cathode assembly.«

Example 6

A cathode assembly was fabricated as described in Example 1. Following the electroplated nickel coating, a palladium oxide "zirconia coating was applied to the cathode. This was accomplished by first forming a slurry of 1.5 grams of palladium chloride particles 2 g of zirconyl nitrate in 10 ml of water and 1 ml of acetic acid for 2 hours to stabilize the palladium chloride and reduce the size of all undissolved material particles. This slurry was then brushed onto the nickel plated net-like cathode assembly of Example 1, which had been ashed as indicated in Example 1. The brushed coating and cathode were heated at 125 ^° C. for 3 minutes and then at 500 ^° C. Cured in air to give the palladium chloride in palladium oxide and the zirconyl nitrate to zirconia. Next, 4 more coats of slurry were applied and cured. In an alternative manufacturing technique, up to half of the palladium chloride was replaced by cobalt and / or nickel when the cathode was manufactured »

Example 7

According to the steps of Example 1 including galvanic nickel plating, a foam or mesh

25 * 11 * 1983 '- 31 - 62 576/17

After cathodic nickel plating, the foam-cathode assembly was immersed in a plating bath containing 3.78 liters of water, 20 grams of sulfamic acid, and 20 grams of ruthenium sulfamate ruthenium a temperature between 80 and 100 C and a platinum coating was galvanically applied using platinum anodes, which were arranged about 3.8 cm from the surface of the foam-cathode assembly.

A cathode-connected foam-cathode assembly flowed between the platinum anodes and the foam-cathode assembly with a density of 0.15

2 A / cm at a voltage of 1.75 V,

Example 8

As described in Example 1, including galvanic nickel plating, a foam or net-like cathode assembly was prepared. Following galvanic nickel plating, the foam-cathode assembly was immersed in a stirred coating solution containing 5 ml of H ₃ Pt (SO ₃ J Containing ₂ OH in 150 ml of water and adjusted to pH 3 using IN-NaOH, and also containing about 15 ml of a 30% hydrogen peroxide solution. "The Schaurastoff cathode assembly was about 1 hr." The pH was then returned to 3 ° using a 1N-liquor, and the solution and the cathode assembly were stirred to stir the peroxide-containing solution

25 * 11 · 1983 - 32 - 62 576/17

heated to 80 ^° C. until the formation of bubbles by the peroxide ceased. After washing, the foam assembly was dried at 125 to 150 ^° C.,

Example _i 9

As described in Example 1, including galvanic nickel plating, "a foam cathode assembly was made." As described in Example 1, sintering or incineration was carried out. "Following electrolytic deposition of nickel, plasma spattering on the surfaces of the foam cathodes The assembly was then heat treated at 760 ^° C. for 8 hours in a nitrogen atmosphere so that mutual diffusion of nickel and aluminum occurred. When using such a cathode in a chlor-alkali cell, the aluminum would leach out of the interdigitated surface by the hot NaOH contained in the cell. This leaching creates a larger surface area on the foam-cathode assembly than it could be obtained without such diffusion and leaching

Beijtgiel_10

As indicated in Example 1, a foam or. net-like cathode assembly except that the electroplating was carried out so that the foam-cathode assembly in an aqueous solution of 240 g / l of iron (II) sulfate having a pH of 2.8 to 3.5 and one

25 * 11.1983 - 33 - 62 576/17

Temperature between 32 ⁰ C and 66 ⁰ C was immersed, Cathode * assembly was then compared to iron anodes, which had been placed about 3.8 cm from the surface of the cathode assembly connected "as cathodes * The generation of a galvanic coating was for a time period between

2 2

1 and 3 hrs. At between 0.04 A / cm and 0.11 A / cm. * During galvanic shaper formation, the ferrous sulfate bath was stirred to form a uniform topcoat on the foam cathode. To support the assembly

Example 11

As indicated in Example 4, a foam * or reticulated cathode assembly was prepared and then electroplated with an iron coating as described in Example 10,

Example 12

As described in Example 1, a foam or reticulated cathode assembly was fabricated, including intervening sintering or ashing during electrodeposition. The cathode assembly was then made using a mixture of 80 % nickel, 10 % molybdenum, and 10 % aluminum plasma sprayed · The molybdenum and aluminum were then leached out in hot sodium hydroxide by use in a chlor-alkali cell. "A cathode assembly having a substantially increased surface area was obtained.

25 * 11.1983 - 34 -, 62 576/17

Example 13

Example 1 was repeated except that a 1.25 cm thick polyurethane Schaurostoff was used as the starting material, which had been produced by laminating 4 layers of O ₄ , 32 cm thick foam »It obtained a structure that was not of the Example 1 could be distinguished «

Example 14

A cell was equipped with an anode as prepared in Example 1. The cathode of this first cell was a perforated plate of nickel. suitable for use in chlor-alkali electrolysis cells The cell was fed with an aqueous stream of sodium bicarbonate and sodium carbonate in a molar ratio of 1: 1

The second cell was identically equipped except that the cathode in the second cell was a porous foam or reticulated cathode prepared according to Example 1. This second cell was operated with the same starting materials as the first cell.

In both cases, the electrodes were in physical contact with the septum. The first cell worked

2 a voltage of 2.82 V at a current flow of 0.15 A / cm,

25.11 * 1983 - 35 - 62 576/17

2, while the second cell had a voltage of 2.63 V at 0.15 A / cm. At 0.31 A / cm, the voltage of the first cell was 3.33 V, while the voltage of the second cell was 3.05 V. " The current efficiency of both cells was equal within laboratory experimental accuracy. The second cell operated at a significantly lower voltage due to the presence of the nickel mesh or foam cathode assembly, resulting in lower energy consumption for commercial use The cell-like or foam-cathode assembly of the present invention provided an operating advantage of 200 mV at 0.15 A / cm and 280 mV at 0.31 A / cm ² ,

Example 15

Two electrolysis cells were operated in parallel with each other. One cell contained an anode made of a Titari mesh with rhombus-shaped openings of about 0.64-0.32 cm coated with an electrocatalytic topcoat for the production of chlorine, which is generally ruthenium oxide The cathode in this first cell was formed from a nickel mesh which had rhombic openings which also had a width of about 0.64 x 0.32 cm.

The cell contained a septum of NAFION 295 of

duPont, and both the anode and the cathode were in close contact with the septum on the room

the electrolysis cell containing the anode was with a

25 * 11 «1983 - 36 - 62 576/17

Sodium chloride solution (170 g / lj, fed «

The second cell of the parallel-operated pair was identically equipped except that the cathode used was a foam or net-like cathode assembly made according to Example 1. This cathode, like the anode of the second cell, had intimate contact with the septum.

This second cell was fed the same solution as the first cell. Both cells were operated at a current density of 0.31 A / cm of membrane surface, with 3.84 V being required for the electrolysis in the first cell, while for the second cell 3.18V were needed. "The current efficiency of both cells was equivalent. Using a reticulated foam electrode of the invention used in the second chlorine generating cell resulted in an operating voltage advantage of 660 mV at 0.31 A / cm "

Example 16

Two cells were operated parallel to each other. "One cell contained an anode made of a titanium mesh with an electrocatalytic topcoat attached to the mesh." The openings in the mesh were about 0.32 "0.32 cm." The cathode in this first The cell was made of a nickel mesh with the same opening dimensions. "The anode and cathode were in contact with a cation-exchange membrane that separated the two electrodes."

25.11 * 1983 .. - 37 - 62 576/17

which contained the anode, a sodium chloride solution containing 170 g / l of sodium chloride was added »

The second cell of this cell pair operated in parallel contained an identical anode and an identical septum, but was made of nickel using a foam or net-like cathode assembly made according to Example 1. This second cell was fed with an identical solution as the first cell.

While the first cell in a septum at the

measured current density of about 0.3 A / cm in the generation of chlorine had a voltage of 3.28 V, in the second cell an operating voltage of 3.13 V was achieved with an identical current density "The current efficiency of the cells were identical"

Example 17

In a cell, the anode was a porous reticulated foam anode prepared analogously to Example 1. "The first cell contained a cathode made from a perforated nickel plate." The foam or net-like anodes Assembly and the nickel plate were in close contact with a microporous polypropylene septum. "300 g / l sodium carbonate was added to this cell."

The second cell contained an identical anode and an identical septum, but a foam or mesh

25.11 · 1983 - 38 - 62 576/17

similar cathode assembly / was in contact with the septum, wherein the foam or mesh-like cathode was prepared according to Example 1 * This second

Cell was given an identical solution

the first cell operated at a current density of 0.15 A / cm at a voltage of 2.72 V, an operating voltage of 2.44 V was achieved in the second cell at an identical current density. "Within the experimental error width, the current efficiencies of the two cells were the same The cell using the net-like cathode provided an operating advantage of 280 mV over an identical cell operated without the net-like cathode.

Example 18

Two cells were operated in parallel. "The first cell contained a cathode made of a perforated nickel plate that had intimate contact with a porous ceramic alumina partition." The anode of this first cell was a sheet of titanium metal mesh with openings of a width 0.64 χ 0.32 cm and with a top coat useful when it is desired to release oxygen. "This first cell was fed with 300 g / L sodium carbonate."

The second cell was operated in equipment identical to the first cell, except that the anode of the second cell was a foam or reticulated anode prepared analogously to Example 1. This second cell

25.11.1983 - 39 - 62 576/17

was fed with the same solution as the first one.

While the first cell at a current density of

2 0.15 A / cm at an operating voltage of 3.4 V, the second cell in which the foam or mesh anode assembly was used operated at an identical current density at a voltage of 2.72 V. The current efficiency the two cells were identical within the experimental error width. The second cell, which used a foam or mesh-like anode assembly in contact with the septum, provided a 0.680 V operating advantage over an anode made of a perforated nickel plate that was also in contact with the septum.

Claims (15)

25 _# 11 · 1983 - 40 - 62 576/17 invention claim 1 electrolytic cell with an anode separated by a septum and cathode walls, characterized in that it comprises at least one electrode assembly comprising a) an open-pored net-like primary electrode which at least partially fills one of the electrode spaces and has a considerable physical contact with the septum * b) a power supply "which is intermetallically bonded to the electrode" that the electrical resistance between the power supply and the electrode in the supply of the electrode is negligible with power, and c) circulation means which allow a circulation of the electrolyte into and out of the electrode space « 2 »electrolytic cell according to item 1, characterized in that the electrode is an anode · 3 »An electrolytic cell having a septum-separated anode and cathode spaces, characterized by comprising a cathode assembly comprising: a) an open-pore net-like primary cathode, which at least partially fills the cathode space and a substantial phyeikaliscjnen contact with the septum ·. 'hasj '"''' ^: y- ^: \' ^: -r-- · / ¹ ; - - [; ', - ..,' - .. '\.,:":.'-;.:;'^{; :;} :: -v '['"'[ 25.11.1983 - 41 - 62 576/17 b) a cathodic power supply "which is intermetallically bonded to the cathode so that the electrical resistance between the power supply and the cathode when powering the cathode is negligible" and l c) circulating means, which is a circulation of the electrolyte into and out of the cathode compartment _" possible" 4, electrolytic cell, wherein the anode and cathode compartments in the cell are separated by a septum, and wherein at least one electrode of the cell has a substantial physical contact with the septum, characterized in that it comprises a narrow-gap electrode assembly, the comprising: a) at least one open-pore reticulated primary electrode with pores of a size in the range of 1.27 " -2 -1 10 mm to 2.54 "10 mm, which has considerable physical contact with the septum and substantially fills at least one of the electrode compartments of the electrolysis cell, b) a power supply that intermetallically connects the electrode to an electrical power source so that the electrical resistance between the power supply and the electrode is negligible, and c) at least one electrolyte inlet for the introduction of the electrolyte into the electrode and at least one 25.11.1983 - 42 - 62 576/17 Outlet for removing the catholyte from the electrode, 5 # electrolytic cell according to item 4, characterized in that »the electrode is an anode 6. electrolysis cell, wherein the anode and cathode spaces in the cell are separated by a septum and in which the cathode in the cell has a significant physical contact with the septum ι characterized in that it has a narrow-gap cathode assembly _f which includes: a) an open-pored reticulated primary cathode with polyvinyl ren a size in the range of 1.27 "10" mm to 2.54, 10 mm, which has a significant physical contact with the septum, and the cathode compartment of the electrolytic cell substantially fills, b) a cathodic power supply interconnecting said cathode intermetallically with a source of electrical current such that the electrical resistance between said power supply and said electrode is negligible, and c) at least one catholyte inlet for introducing the catholyte into the cathode and at least one catholyte outlet for removing the catholyte from the cathode, 7, a method for producing an electrode assembly for an electrolytic cell according to the items 1 to 6 with 25.11.1983 - 43 - 62 576/17 a septum of separate anode and cathode spaces and having at least one inlet and outlet for the electrolyte into and out of the electrode spaces, characterized in that it comprises: a) substantially complete filling of at least one electrode space with an open-cell plastic foam, wherein the foam has a considerable physical contact with the septum membrane af, b) arranging a power supply of an electrically conductive metal at each foam-filled electrode space, wherein the power supply is at least partially immersed in the plastic foam, c) treating the open-celled plastic foam with a solution for electroless metallization until an electrically conductive coating of a desired thickness has formed on the foam, d) switching the foam as a cathode, and e) passing a plating solution through the foam electrode until a galvanically deposited coating of the desired thickness has formed on the foam » 8, method according to item 7, characterized in that the foam is removed thermally during the galvanizing. 25.11.1983 - 44 - 62 576/17 9. The method according to item 7, characterized in that the foam has an open porosity between 1.27, IG * "mm to 2.54, ΙΟ"" ¹ mm, 10 »method according to item 7, characterized in that the metallizing solutions on the foam cathode produce a coating of metallic nickel. 11. A method for producing an electrode assembly for an electrolytic cell according to the items 1 to 6 with separated by a septum anode and cathode spaces and at least one electrolyte inlet and electrolyte outlet in each electrode space, characterized in that it comprises: a) substantially complete filling of at least one electrode space with an open-pored conductive plastic foam, said foam having a considerable physical contact with the septum membrane, b) arranging a current supply of a conductive metal at each foam-filled electrode space, wherein the power supply is at least partially immersed in the plastic foam, c) switching the foam as a cathode, and d) Treatment of the foam electrode with a plating solution until it settles on the foam 25.11.1983 - 45 - 62 576/17 formed galvanically coated coating of the desired thickness. 12. The method according to item 11, characterized in that the foam belongs to the type of a foam impregnated with an electrically conductive substance « 13. The method according to item 11, characterized in that the foam cathode is treated to deposit a desired metal coating on the foam cathode with a solution for electroless plating before being switched as a cathode. _# 14 The method of item 7 or 11, characterized in that the plating solution contains a substantial amount of nickel ions for the electrolytic deposition of nickel on the foam cathode. 15. The method according to item 7 or 11, characterized in that the septum is a membrane which is hydraulically impermeable to fluid movement between the electrode compartments but which permits easy passage of cations from one electrode compartment to the other. 16. The method according to item 15, characterized in that the membrane contains a substantial proportion of a perfluorocarbon copolymer with sulfonyl or carbonyl cation exchange groups. 25.11.1983 - 46 - 62 576/17 ί; 17. electrolytic cell according to a äer points 1, 2, 3, .4, 5 and 6, characterized in that the septum is a membrane which is hydraulically impermeable to fluid movement between the electrode spaces, but the free passage of cations allowed from one electrode space to the other. 18 * electrolysis cell according to item 17, characterized in that the membrane contains a substantial proportion of a sulfonyl or carbonyl-based copolymer of perfluorocarbon with cation exchange groups, 19. The method according to item 7 or 11, characterized in that the power supply is introduced into the foam by being heated and immersed in the foam. 20. A method for producing a cathode assembly for an electrochemical cell according to the items 1 to 6 with separated by a septum anode and cathode spaces and at least one inlet and at least one outlet for the catholyte, characterized in that it comprises: a) selecting a porous reticulated foam material as the cathode material and fitting the foam into the cathode compartment of the electrolytic cell such that the foam substantially fills the cathode compartment and is in substantial physical contact with the septum, 25.11.1983 - 47 - 62 576/17 b) rendering the foam conductive c) arranging a cathode current supply and establishing an electrical contact of this supply with the foam cathode, and d) electrodeposition of a Kathodenmotalls on the S _c haumstoff cathode. For this 1 page drawing