EP0130250B1

EP0130250B1 - Electrolysis using two electrolytically conducting phases

Info

Publication number: EP0130250B1
Application number: EP83303854A
Authority: EP
Inventors: Frank Stanley Holland
Original assignee: Manchem Ltd
Current assignee: Manchem Ltd
Priority date: 1983-07-01
Filing date: 1983-07-01
Publication date: 1990-09-26
Anticipated expiration: 2003-07-01
Also published as: EP0130250A1; ATE56992T1; DE3381913D1

Abstract

A method of electrolysis is provided wherein an electric current is passed between two electrodes (23, 21) and through an at least two-phase electrolyte system having as a first phase an aqueous electrolyte solution (25) and as a second phase an aqueous-immiscible electrolytically conductive liquid (24) other than a halogenotin complex, at least one electrode (21) being located solely in said second phase and said first and second phases being in direct liquid-liquid interfacial contact with each other.

Description

This invention relates to a novel method of electrolysis, particularly, for the deposition and/or recovery of metals in their elemental state and other redox reactions.
The electrolysis method provided by this invention can be used for, among other uses, electrodeposition of a metal in the form of dendrites, and for electro-plating a metal onto a substrate. It can also be used for electrolytically effecting chemical redox reactions, e.g. the oxidation or reduction of chemical species.
The method of this invention particularly uses an electrolyte system having at least two phases, one of which is aqueous while another is aqueous-immiscible, and wherein the inter-facial current passage is ionic rather than electronic.
Certain other two-phase electrolysis systems are already known. For instance, the mercury cell commonly used for the electrolysis of sodium chloride solutions to produce chlorine and sodium amalgam, and eventually sodium hydroxide, utilizes two phases, i.e. the aqueous sodium chloride and the metallic mercury. In this case, however, the mercury phase conducts electronically, i.e. by the movement of electrons as in any conducting metal. In reality the mercury phase behaves as a liquid cathode. Also in the sodium- hydroxide-chlorine industry, electrolyses using two aqueous phases separated by an ion exchange membrane have been used. Here the sodium chloride solution forms the anolyte, evolving chlorine at the anode therein; the electrolyte on the other side of the membrane is aqueous sodium hydroxide in which there is a cathode evolving hydrogen. Thus, these are both aqueous phases, and but for the ion exchange membrane, the same would be miscible with each other.
US-A-3361653 describes a two-phase electrolysis system which involves the electrolysis of an aqueous electrolyte in interfacial contact with a material of low electrical conductivity and substantial insolubility. One electrode is in contact with only the aqueous electrolyte, whereas the other extends through the interface and contacts both phases. JP-A-77/31313 describes a further two-phase electrolysis system in which one electrolyte which has low conductivity and is capable of wetting electrodes is separated by a cation exchange membrane from a second electrolyte which has high conductivity and is not capable of wetting electrodes.
Such systems are severely limited in regard to the types of electrochemical processes which can be conducted therein.
A further common and well known problem, typically in organic electrochemistry is in dealing with the oxidation or reduction of water insoluble species. Dueto the typically dielectric character of, for instance, organic liquids, electrolysis techniques are generally unsatisfactory. Usually the approach to overcome, to some extent, this difficulty is to use a water-miscible co-solvent, e.g. ethanol or acetone, to co-solve the water-insoluble species in the aqueous phase. Another technique is to use a solubilizing compound such as an aromatic sulphonic acid which co-solves the insoluble species and which can also act as the electrolyte. Both these techniques are intended to produce a single water-miscible phase for the electrolysis, and the same are also limited in their applications. See, for example, Organic Electrochemistry, by M. M. Baizer Ed., published by Dekker, New York, 1973.
We have nowfound a method making it possible to conduct electrolyses using two immiscible phases, one aqueous, the other non-aqueous, but with both being electrolytically conducting. That is, the current passes therebetween by ion movement rather than mere electron movement.
Thus the present invention provides a method of electrolysis which comprises passing an electric current between two electrodes through a two-phase electrolyte system having as a first phase an aqueous electrolyte solution with one of the electrodes immersed solely therein and as a second phase an aqueous-immiscible electrolytically conductive liquid which contains a halogenometal complex other than a halogenotin complex with another electrode immersed solely therein, there being a liquid-liquid interface between said first phase and said second phase. The second non-aqueous phase generally contains or is substantially composed of a liquid (at the temperatures employed) containing or composed of a halogenometal complex other than a halogenotin complex. The halogenometal complex is substantially water-insoluble, or at least preferentially substantially soluble in an organic solvent used to form the water-immiscible phase.
The aqueous phase will ordinarily have a solution of a highly ionic salt, acid or alkali, and can commonly have a high conductivity or low resistivity, e.g. from 5 to 10 ohm-cms, by contrast the non-aqueous water immiscible phase used herein will normally have a much high resistivity e.g. of the order of 100 ohm-cms. Electrolysis using the non-aqueous phase alone would therefore normally require very high voltages; whereas, using the method of the present invention, much lower cell voltages can be used. Thus, one advantage of this invention is that otherwise poorly conducting systems can now be operated at pragmatic, economically acceptable cell voltages.
Our invention can also be used very readily for electrolytic redox reactions with water immiscible species because the aqueous-immiscible electrolyte phase is usually a very good solvent for other (organic) water immiscible species including various non-polar organic species, for example olefins such as ethylene.
The accompanying drawings illustratetwo basic electrode cell arrangements which may be used in the practice of this invention, and two presently preferred practical embodiments thereof:

Figure I schematically illustrates a two-phase electrode cell using three electrodes, and three electrolytes, as described hereinafter;
Figure II schematically illustrates a two-electrode two-phase system, as described hereinafter;

Figures III-VI illustrate a two cell embodiment.
Considering Figure II first, a suitable cell container (either rectangular, cylindrical, or of any other desired shape) 20 may be formed of a suitable corrosion-resistant and electrolytically stable material such a polyproplylene. Suspended near the bottom of the cell 20 is an electrode 21 connected to an insulated current feeder line 22, which as shown would be connected to the cathode terminal of a direct current power source. In use, the cathode 21 will be completely and solely immersed within the aqueous-immiscible phase 24. The aqueous electrolyte, an anolyte as shown, 25 is here depicted as above the catholyte 24, being of lower specific gravity, with a liquid-liquid interface 26 therebetween. Suspended in the aqueous anolyte phase is an anode 23, connected by its feeder 27 to the anode direct current power supply. It will be understood that current passes between the two electrodes, and across the liquid-liquid interface 26. In the practice of this invention, such passage of electricity is ionically conducted.
The electrode used in the aqueous electrolyte phase can be either the cathode or the anode, and the electrode in the non-aqueous phase will be conversely an anode or a cathode, depending on the electrolytic process desired.
When the phases are of different specific gravities, one can float on the other with merely the liquid-liquid interface between them, as shown in Figure II. Alternatively, the two immiscible phases (anolyte and catholyte) may be separated by an ion-exchange membrane or a porous separator, e.g., a ceramic or a filter cloth, and then be located side by side. In another practical embodiment described below, the anolyte is the aqueous phase floating on the heavier aqueous immiscible catholyte.
One electrode may be a corrodible metal anode immersed in the aqueous anolyte, while the other electrode is an inert cathode immersed in the non-aqueous catholyte. If in this arrangement the corrodible anode is, e.g., tin, that electrode corrodes away during the electrolysis and dendrites of tin are deposited on the cathode. The invention thus provides, as one feature, a method of forming dendritic tin from a massive block of tin. Such dendritic tin is a valuable starting material for the preparation of organotin halides by direct reaction of tin with an organic halide.
As described in EP-A-84932 (which forms part of the state of the art by virtue of Art 54(3) EPC) when tin is the anode, the catholyte comprises a halogenotin complex such as a complex of formula Cat⁺SnX3 , where Cat+ is a group derived from a positively charged species such as the R_zQ⁺ (defined below), and X is chlorine, bromine or iodine, or other mineral acid anion species.
An example of R_zQ⁺ is tetrabutylammonium. In general R is an organic hydrocarbyl group (or similarly inert group including hydrocarbyl groups carrying inert substituents) which will form this 'onium ion; and Q represents N, P. As or Sb, in which case z is 4, or Q may be S or Se, in which case z is 3. Compounds of the formula R_zQX may be used as catalysts or as reagents in the production of, e.g., organotin halides, and when so used, there is formed as a by-product a tin-containing halostannite complex, for instance of the formula R_zQ⁺SnX₃ ^-, e.g., tetrabutylammonium bromostannite. The by-product formed in the direct reaction of tin with an organic halide in the presence of a compound of formula Cat⁺X- is specifically suitable as a catholyte in a process for the electrolysis of tin according to EP-A-84932.
Alternatively, when in accordance with the invention another metal is employed as the corrodible anode, then a complex of that metal would be formed with the Cat⁺X- species.
Thus, instead of using tin as the anode, there may alternatively be used, for instance, an aluminum anode, with an aqueous solution of aluminum trichloride and sodium chloride as anolyte, the catholyte now suitably being of the formula Cat⁺AICI₄- .
Such other metals which may be used generally include those having a standard electrode potential (versus a normal hydrogen electrode from about plus 1.5 volts down to about minus 1.66 volts, including such metals as silver, gold, platinum, palladium, copper, lead, nickel, cobalt, indium, cadmium, iron, gallium, chromium, zinc, manganese, titanium, and aluminium.
These other metals may be used with a suitably chosen Cat⁺X- species.
In another embodiment of the invention there is used a non-corrodible anode, such as of nickel, graphite or stainless steel, immersed solely in the aqueous electrolyte and an inert cathode immersed solely in the non-aqueous catholyte.
Whatever R_zQ⁺ species is selected, and whatever anion is selected, there must be Compliance with the basic requirements of immiscibility and solubility of the metal complex therewith.
Fundamentally, it will be appreciated that this invention thus uses as one feature a water-immiscible liquid phase, which may in fact be a solution, and which contains a substantial concentration of a halogenometal complex other than a haloganotin complex (which is nonetheless substantially water-insoluble), while such phase is nonetheless relatively nonconductive by at least an order of magnitude with respect to the aqueous phase.
The aqueous phase electrolyte, by contrast, is desirably a highly conductive system and this is easily established, as is already known in the art, by the introduction of a suitable inorganic salt, for instance. Alternatively, or in addition, to the salt, there may be used an alkali or an acid aqueous phase as such electrolyte. The particular choice of the anolyte system and of the catholyte system being determined and selected according to the particular electorlytic process desired to be conducted, in accordance with the foregoing principles.
Instead of a single corrodible anode such as, for instance, tin, aluminum or lead which is transferred electrolytically and deposited on the cathode, there may be used a two-anode system as illustrated in Figure I.
In this system, the electrolysis cell 10 again has an electrode 11 connected to a suitably insulated feeder 12 to a power source (the negative power source being shown, but it could also be the positive source if desired), and this cathode (as shown) is fully immersed within the aqueous-immiscible catholyte phase 13. Above he catholyte phase 13 is the aqueous anolyte phase 14 with an interface 14a between the two phases. Also extending into the anolyte phase 14 is a chamber of compartment 15 having at least one wall member portion which is formed of an ion exchange membrane, which membrane will permit the passage of ions, while not permitting the mixing of the separate anolyte 16 with the anolyte 14. Extending into the chamber 15 is, suitably, a non-corrodible anode 17, again connected to a DC current power supply. Extending into the anolyte 14, hereinafter referred to in this embodiment as the "intermediate" anolyte, is a corrodible electrode 18, connected by its feeder 19 to the power supply. As shown, electrodes 17 and 18 are both anodes.
In such a system, the chamber 15 may contain as its anolyte 16 an aqueous sodium hydroxide solution, while the intermediate anolyte 14 may conveniently be an aqueous solution of a metal salt, e.g., a metal chloride such as sodium chloride. The catholyte 13 is a non-tin metal complex with Cat+X- -immiscible with the aqueous phase anolyte 14. Various metals may be used as the salt used in the anolyte 14 including variously, without limitation, cobalt, nickel, titanium, manganese, vanadium, etc.
The techniques permitted by the electrolysis cell of Figure I include the method of recovering elemental metal from a dissolved salt thereof, which salt may in turn have been obtained as a waste product from an independent chemical process. The metal thus recovered may be used for the production of various metal compounds, including metal organic compounds. Such dissolved salt may be present in either the aqueous-immiscible phase or the aqueous phase, or both, with the metal being reduced to the elemental state at the cathode.
In particular, since the electrolytic process of this invention valuably produces dendritic metal species, which are highly reactive, the invention provides a means for forming valuable metal carboxylates (e.g., used as paint driers, for instance) directly from the dendritic metal formed and the desired carboxylic acid, the same being heated together with air or oxygen (outside the electrolysis cell) causing the dendritic metal to dissolve at good reaction speed with high yield by direct reaction with the carboxylic acid.
In the three electrode embodiment of Figure I, if an alkali is used as tpe anolyte 16, oxygen will be evolved at the anode 17, as is necessary to balance the overall electrolytic reaction equation.
The two-phase electrolysis system of this invention can also be used for electrolyses involving organic species only. Thus, as an example, there may be used in the embodiment of Figure I or Figure II an inert anode 18 or 23, respectively, such as platinum, suspended in an aqueous sulphuric acid solution, as anolyte 14 or 25, respectively, which is in turn in interfacial contact with a water immiscible phase containing, e.g. acrylonitrile or adiponitrile. Electrolyses thereof leads to oxygen evolution at the anode and hydrodimerisation of acrylonitrile to make aniponitrile at the cathode.
Other organic species may be similarly reduced electrolytically by the process of this invention such as benzaldehyde to benzyl alcohol, benzil to benzylidene, salicaldehyde to the corresponding alcohol; nitrophenol to hydroxyaniline; or allyl bromide to propyl bromide. As with acrylonitrile, other reductive dimerization or polymerization, reactions using organic entities may also be performed electrolytically whenever the organic species suitable for such an electrolytic reduction is soluble in the aqueous-immiscible catholyte phase.
The electrolytic method of this invention can also be used for electro-plating an alloy onto a cathodic substrate. For example, two or more metals may be used as anode-either as separate metal anodes (i.e., two anodes such as anode 23), or as a single alloy anode - with an aqueous solution of chlorides of these metals used as anolyte and a water-insoluble complex chloride of a metal other than tin, e.g. in the form Bu₄N⁺MCI_m- (where Bu is butyl, M is the metal other than tin, and m is a number equal to the valency of the metal plus one), as catholyte. When two different corrodible anodes are employed the relative amounts of the metals deposited can be varied by the amounts of current independently supplied to said respective anodes.
The following example uses a catholyte containing a halogenotin complex and illustrates a process according to EP-A-84932. The method of the present invention requires the use of a catholyte containing a halogenometal complex other than a halogenotin complex.

Example

The apparatus used in this example was the cell schematically shown in the accompanying drawing of Figure I.
This cell comprises a polypropylene tank 10, 40 cmx40x25 cm, containing a stainless steel cathode 11, 35 cmx25 cmxO.3 cm connected to an insulated feeder 12. The bottom of the cell was loaded with tetrabutylammonium bromostannite (B_U4N'SnBr3-, prepared synthetically from Bu₄NBr and HSnBr₃ solutions), (11 kg) as catholyte 13.
Above this, 16 liters of 20% NaBr solution in water was placed as the intermediate electrolyte 14. Dipping into the intermediate electrolyte was an ion-exchange membrane-covered box (Naf- ion^TM, duPont membrane) 15 containing NaOH solution 16 and a nickel anode 17. Also dipping into the intermediate electrolyte was tin anode 18 held on a feeder 19.
The anodes 17 and 18 were connected to the positive terminal of a variable power supply and the cathode feeder 12 to the negative terminal. A current ranging from 40 amp at the beginning to 100 amp at the end was passed through the cell over a period of 17 hours. During this time the temperature in the cell rose to 75-85°, the cell voltage at the start was 19 volts and this declined to 5 volts at the end. During this time 596 amp-hrs were passed through the tin anode 18 resulting in a loss of 1500 g of tin. 540 amp-hrs were passed through the nickel anode 17.
The combined anode currents-1136 amp-hrs-passed through the cathode 11 caused the deposition of fine dendritic tin particles (2513 g). 1320 g of this tin product were derived from the tin anode 18 and 1193 g came from the catholyte 13. Thus, the final catholyte phase comprised dendritic tin (2513 g), tetrabutylammonium bromide (3238 g), and unreacted tetrabutylammonium bromostannite (5040 g).
In this example, the catholyte was prepared as a special catholyte, but there could be used instead the halogenotin by-product complex which is formed in the production of organotin halides by the direct reaction of tin with an organic halide in the presence of reagent amounts of a compound of formula Cat⁺X-, e.g. of formula R₇Q'X-, as defined above. That overall reaction may be represented according to the stoichiometric equation
At the end of the reaction the organotin halide product is recovered by extraction in a hydrocarbon solvent, leaving a hydrocarbon-insoluble, water-insoluble yellow-khaki by-product which contains or consists of the R₌Q⁺SnX₃-. This is the halogenotin by-product complex which may be used as catholyte in this embodiment of EP-A-84932.
A suitable practical cell for this electrolysis invention is illustrated in Figure III. This cell has a polypropylene body 41 with a cross section of approximately 30 cmx30 cm and an overall height of approximately 45 cm. The cell has a polypropylene bottom valve 42 and is mounted on feet (not shown) so that the bottom inverted pyramidal part extends through a hole in a supporting platform. The cell is heated by external electrical heating tapes 43 and is insulated and clad 44. The cell has two further taps, 45 and 46, in its higher portion.
Internally the cell has two cathode plates 47 connected to cathode feeder lines 56. Above the cathodes there are two tin anodes 48 (one shown) mounted in mild steel feeders 58 which in turn are supported on insulated bushes on an anode support frame 49 which is screwed to the platform.
Alongside the tin anodes is a third anode 50 made of nickel. This nickel anode is supported on mild steel feeders 57 and held from the anode support frame. The nickel anode 50 is separated from the rest of the cell inside a compartment made up from outer clamping members 51, an inner member 52 and two ion exchange membranes 53. Parts 51 and 52 are U-shaped in section and are clamped together with bolts sandwiching the membranes 53 so that a five-sided compartment with an open top is formed.
The cell has two polypropylene scrapers 54, with blades, 54a which can be pushed across the top of the cathodes 47 to scrape and dislodge metal formed on the cathodes and allow this metal to fall into the bottom part of the cell (i.e., below the cathodes). The cell has an agitator on a shaft 55 connected to the motor (not shown). This agitator is used to stir the bottom phase containing such metal particles.
In operation the tin anode feeders 58 and the right-hand cathode feeder 56 are connected to one rectifier (not shown) and the nickel anode feeder 57 and the left-hand cathode feeder 56 are connected to another rectifier. The tin anodes can be adjusted up and down on their feeders 58.
The cell has been operated in accordance with EP-A-84932 by loading it with 25.9 kg of mixed halogenotin complex by-product from the manufacture of tributyltin bromide as shown in respect to Table II of EP-A-84932, and 16 liters of 10% wt/volume sodium bromide solution. This resulted in a two-phase system with the halogenotin complex below the aqueous solution and with the interface therebetween about 1 cm above the cathode plates 47. Aqueous sodium hydroxide (25%, 2 1.) was poured into the anode compartment formed by 51, 52 and 53. The cell contents were heated to 75-95° and current passed from both rectifiers. A total of 1103 amp-hrs was passed through the nickel anode and 1163 amp-hrs through the tin anodes. Currents ranging from 5 to 150 amps (aqueous-nonaqueous interfacial current densities of 5.5 mA/cm² to 167 mA/cm² respectively) were passed during this electrolysis and the relative currents passed through the tin anodes and the nickel anode were adjusted to give approximately the same number of coulombs through each anode system. The starting cell voltage was about 20 volts and this declined during the electrolysis to about 8-10 volts.
The electrolysis products were 17.7 liters of 30% wt/volume sodium bromide solution and 24 kg of a mixture of Bu₄N⁺Br^--dendritic tin- halogenotin by-product. The tin anodes had lost a total of 2.57 kg of tin.
In addition to the cell illustrated in Figure III, for larger production purposes the cell construction illustrated in Figures IV, V and VI is presently preferred.
Figure IV illustrates in cross section a 2000 ampere cell which would be equipped with conventional rectifiers and controls, etc. (not shown). In general, the construction of this cell is analogous to that of Figure III. However, the polypropylene body 60 is in this instance supported by a mild steel casing 61 which sits in turn on load cells 62 (only one shown) which are held on a supporting platform. In common with the Figure III apparatus, steel supporting structures 63 hold two tin, or other corrodible metal anodes 64 (one shown) and the drive motor 65. This agitator drive may be a variable DC motor coupled at 66 to the shaft 67 which drives the lower agitator blades 68 and scraper blades 69. The upper part of the scraper blades also serve as an agitator for the phase. The scraper blades 69 serve a dual purpose of creating upward flow movement of the halogenometal complexes to replace electrolyzed material at the liquid-liquid interface, while also dislodging deposited metal from the cathode surface.
The conical bottom of the cell is fitted with a push-up-type valve 70 at the bottom of the cone to permit removal of metal dendrites and/or electrolyte from the cell. The push-up valve is useful in the event unstirred dendritic metal settles to form a crust, as this can then be broken open to allow drainage of the lower phase.
each metal anode 64 may weigh, for instance, 100 to 200 kg at start-up, and are held on a threaded steel rod 71 supported on an insulated bushing structure 72, respectively connected to feeder cables 79. By this means the vertical position of the anodes can be adjusted up and down.
The non-corrodible anode compartment is shown as 73 and is simply a polypropylene box with an open top, and a bottom closed by an ion exchange membrane having suitable supports and seals. This anode chamber may be supported from the mild steel casing 61 by suitable steel work 74, and the chamber is fitted with a non-corrodible anode (not shown) connected to feeder cable 75.
The cathode plates 74 are here two semicircles of stainless steel supported on suitable polypropylene lugs within the cell and connected to the cathode cables 78 (see Figure VII). Suitable plate heater 80 may be hung underneath the cathode plates. A cooling coil 76 is also arranged within the cell, and the water-immiscible catholyte phase interface with the aqueous anolyte solution may be approximately 1 cm above the level of the cathode plates although this level can vary according to most efficient operation of a given device. During full operation at, e.g., 2,000 amps and approximately 10 volts, the cooling coil 76 should be capable of removing approximately 20 kW.
Figure VI is partly broken away to show the space or gap 77 between the cathode plates to permit dendritic metal particles to fall through to the lower conical section of the cell, as the same are dislodged by the scraper blades. This gap may be approximately 2 cm wide, and additionally a spacing of approximately 0.5 cm clearance is maintained between the circumference of the cathode plates and the polypropylene cell body.
When used in the process of EP-A-84932 the capacity of this cell can be designed to receive, for instance, some 450 kg of the halogenotin complex by-product (as described above), approximately 500 liters of 10% sodium bromide solution and approximately 100 liters of 25% sodium hydroxide solution for the nickel anode compartment 73, all to be heated with constant agitation to about 70-80°.
At a current load of approximately 1,500 Fara- days and about 20 hours running time at 2,000 amps dendritic tin production is a little under 90 kg with current production of about Bu₄NBr of 120 Kg and NaBr of about 77 kg, with NaOH usage of about 30 kg. The loss of tin from the tin anodes is a little more than 44 kg, the balance of the dendritic tin coming from decomposition of the halogenotin complex.
It will be understood that the foregoing example is merely illustrative of the practice according to EP-A-84932. While tin is there employed as the corrodible metal anode, and is obtained as the dendritic cathode deposit, in accordance with the invention any of the other metals mentioned hereinabove may be used in lieu of tin. Similarly, other Cat+ species may be used, and other halogens (e.g., chlorine or iodine) may be used instead of bromine. The mineral acid anion represented generally by X- will of course be selected to avoid complications from the formation of insoluble metal salt species. Additionally, a Cat+ species may be formed from alkali or alkaline earth metal complex with poly- oxygen or organic compounds such as diglyme, polyoxyalkylene glycol, glycol ether or crown ether.
In any given embodiment practiced according to this invention, the precise conditions to be employed for optimum results will be dictated by the various parameters which are adopted for the overall equipment in process. Thus, the geometry of the cell itself, and of the various electrodes, including the surface area of the electrolyte interface, will in part determine the performance and preferred operating conditions. Consequently, the current density applied for optimum results will vary substantially from system to system, and precise guidelines cannot therefore be laid down in advance. However, each of these conditions can be readily determined once the foregoing principles are revealed, as they are in accordance with this invention, and a person skilled in the art may easily adapt the procedures outlined above to whatever electrolytic reaction he desires to perform within the scope of the foregoing disclosure.
For instance, as will be appreciated, the temperature of the system is not itself critical to achieving operability, so long as the respective electrolytes are in the liquid state and below any adverse decomposition temperature. The interrelationship of temperature, applied current, concentrations and reaction velocity will of course be optimized in any given system for best results, and may otherwise vary broadly.

Claims

1. A method of electrolysis, which comprises passing an electric current between two electrodes and through a two-phase electrolyte system having as a first phase an aqueous electrolyte solution with one of the electrodes immersed solely therein and as a second phase an aqueous-immiscible electrolytically conductive liquid which contains a halogenometal complex other than a halogenotin complex with another electrode immersed solely therein, there being a liquid-liquid interface between said first phase and said second phase.

2. A method according to claim 1, wherein a first electrode is a corrodible metal anode immersed solely in said first phase as anolyte, and a second electrode is an inert cathode immersed solely in said second phase as catholyte.

3. A method according to claim 2, wherein said corrodible anode is made of tin and elemental tin is deposited on said cathode in dendritic form.

4. A method according to claim 2 wherein said corrodible metal anode is formed of a metal having a standard electrode potential from plus 1.5 volts down to minus 1.66 volts.

5. A method according to claim 2 wherein said corrodible metal anode is formed of a metal of the group of silver, gold, platinum, palladium, copper, lead, tin, nickel, cobalt, indium, cadmium, iron, gallium, chromium, zinc, manganese, titanium, and aluminum.

6. A method according to claim 1, wherein a first electrode is a non-corrodible anode immersed solely in said first phase as anolyte and a second electrode is an inert cathode immersed solely in said second phase as catholyte.

7. A method according to claim 6, wherein said anode is nickel, graphite or stainless steel.

8. A method according to claim 1 wherein an organic compound is contained in said second phase and undergoes electrolytic reduction upon passing electric current.