FR2487861A1 - Electrochemical cell electrode - has porous graphite base contg. electro:catalytic metal or cpd. and inert insol. organic cpd. - Google Patents

Abstract

Electrode comprises (a) a porous graphite base, contg in (part of) its pores, (b) an electrocatalytic metal (cpd) electrically contacting the graphite and (c) an electrochemically inert organic cpd insol in the electrolyte and having a dropping point and/or point of transition to the gas state above the electrode temp during electrolysis. It is made by introducing the metal (cpd), then the organic cpd into the graphite base. The metal (cpd)has an overtension of the basic electrode reaction below, or at least equal to, the overtension of the reaction on graphite and a rate of breaking not faster than graphite under electrolysis conditions. The organic cpd is pref from carbochain or heterochain polymers; natural or synthetic resins; bitumens; pitches; polymerisation prods of oils and stand oils. Electrodes are useful in electrolytic prodn of C12, chlorates and hypochlorites. They exhibit lower wear rates at commercial current densities than previous graphite electrodes, extending life by several times, and are cheaper and less subject to shorting than metal oxide base electrodes.

Description

 The present invention relates to electrochemical processes and particularly relates to an electrode for said processes.

 At present, particularly in the electrochemical production of chlorine with a solid or liquid cathode, as well as in the production of chlorates, hypochlorite and other products, graphite anodes are used, the drawbacks of which are short. service life and the formation of a large quantity of sludge during electrolysis.

 During the last decade, electrodes having a metal base on which a thin coating has been deposited which is substantially endowed with electrocatalytic properties have been used more and more.

 In particular, electrodes comprising a current feed substrate made of titanium, niobium, tantalum and zirconium, on which is deposited a coating resistant to electrolyte and electrolysis products, consisting of a mixture of a or several oxides of film-forming metals: aluminum, tantalum, titanium, zirconium, niobium, bismuth and tungsten, with one or more metals: palladium, platinum, rhodium, iridium, ruthenium, osmium, gold, silver, iron, nickel, chromium, lead, copper, manganese, the oxides of these metals, nitrides, carbides, sulphides, as well as mixtures of these substances (USSR Inventor's Certificate No. 369,923).

These electrodes have significant advantages over graphite electrodes. The main advantages of these oxide-metal electrodes over graphite electrodes are
1) a much longer life of electrodes
2) stable dimensions of the electrodes, excluding the growth of voltage over time when used in solid-cathode electrolysis processes, as well as the need to adjust their position in order to keep the voltage across the electrolysers constant cathode of mercury;
3) the absence of sludge fouling the diaphragm.

 However, despite the advantages indicated, the large-scale application of metal oxide anodes is hampered, above all, by their high price in comparison with graphite.

 A notable disadvantage of metal oxide anodes is their high sensitivity to short circuits, limiting their application on a large scale in mercury cathode electrolyzers.

 For these reasons, work continues on a marked improvement in the use characteristics of graphite electrodes.

 Graphite electrodes impregnated with various electrochemically inert organic substances, for example oil polymerization products (Canadian Patent No. 602,053), a polyester resin (Czechoslovak Patent No. 95463), allylic resins (Japanese patent) are known. 13/7 / D 131 Nos. 48-15149), products of polymerization of tallic drying agent (USSR Authors Certificate No. 167832).

 Practically when graphite electrodes impregnated with electrochemically inert organic substances are used as anodes in chlorine electrolyzers, the anode resistance increases compared to that of unpregnated graphite anodes by 1.5 times. maximum.

 A disadvantage of these anodes is the limitation of permissible current densities in service (for example, they must not exceed 1.5 kA / m 2 in the production of chlorine with a solid cathode, and 8 to 9 kA / m 2 in the production chlorine with a cathode of mercury). Higher current densities can cause accelerated destruction of the anode due to exceeding the critical swelling potential. The cause of the limitation of the current density is the higher potential of the anode after its impregnation with an inert organic substance. For an impregnated electrode with total pore closure, which is the most advantageous from the point of view of lowering-internal wear, the permissible current density is much lower than that used in modern electrolysers.

 Graphite-based electrodes are also known in which the porous base or core has, on its surface or in its pores, metals or metal compounds endowed with electrocatalytic properties.

In particular, an electrode comprising an electroconductive graphite base is contacted with a coating consisting of a mixture of one or more oxides of aluminum, titanium, tental, zirconium, bismuth and tungsten film-forming metals, with one or more metals: palladium, platinum, rhodium, iridium, ruthenium, osmium, gold, silver, iron, nickel, chromium, lead, copper, manganese, oxides of these metals, nitrides, carbides, sulphides, as well as mixtures of these substances (USSR Invention Certificate No. 369,923).

 In addition, electroconductive base electrodes, including graphite bases, coated with oxides of platinum group metals with the addition of base or common metal oxides, in particular tin (application filed in FRG No. 2) are known. 710 802), ss-manganese hydroxide (application filed in FRG

 No. 2,636,447), cobalt oxides of general composition Co304 (USSR 492,301).

 These electrodes are much cheaper than those based on metal and their wear during the initial period of use (generally of the order of a month) is much lower than the wear of a graphite anode impregnated with electrochemically inert substance. However, subsequently, because of the degradation of the contact "electrocatalytic graphite compound", the electrochemical process begins to unfold almost entirely on the graphite, and the anode is subjected to wear of the same degree as that of a untreated graphite anode.

It is because of this drawback that graphite anodes comprising electrocatalytic compounds have not found practical applications.

 The object of the invention is therefore to create a graphite electrode designed for a long service life and able to operate at current densities in use in industry.

 The solution consists of an electrode consisting of a porous base or core of graphite in the pores of which there are metals or metal compounds having electrocalytic properties and being in electrical contact with the graphite electrode which, according to the invention. invention, comprises, in at least a portion of the pores of said graphite base, an electrochemically inert organic substance which is insoluble in the electrolyte and has a higher dropping point and / or gaseous temperature than the temperature of the electrode during the electrolysis. It is obvious that the substances solid at the said temperature of the electrode satisfy these requirements.

 As an electrochemically inert organic substance, the electrode comprises substances selected from the group of carbon chain polymers, heterogeneous chain polymers, natural and synthetic resins, bitumens, pitches, drying oil polymerization products and non-drying agents, as well as mixtures of these substances.

 In the group of carbon chain polymers, the inert organic substance chosen for the electrode may be, in particular, polystyrene, polyethylene, polymethyl methacrylate, polyvinyl chloride.

 In the group of heterogeneous chain polymers, the inert substance selected for the electrode may be the polyesteracrylate.

 In the group of natural and synthetic resins, the inert substance chosen for the electrode may be rosin, phenolformaldehyde resins, furans and polyesters.

In the group of bitumens, the inert substance chosen for the electrode may be the oxidized bitumen of oil.
In the pit group, the substance chosen may be coal pitch.

 In the group of drying and drying oil polymerization products, the inert substance selected for the electrode may be a copolymerization product of tall oil and linseed oil or a drying tallicylic acid polymerization product.

 The above enumeration does not exhaust all possible concrete substances that can be used as an inert impregnating substance.

 The electrode can comprise both only one of the indicated substances and mixtures of these substances.

 As metals or metal compounds having electrocatalytic properties, the electrode may comprise substantially any metals, oxides of. simple and mixed metals, as well as mixtures of oxides and metals) mixtures of various oxides with each other and mixtures of oxides with other metal compounds, having a fundamental reaction overvoltage at the lower electrode or less than the overvoltage of this reaction on graphite and whose destruction does not intervene faster than the destruction of it under the conditions of electrolysis.

Said electrocatalytic substances chosen for the electrode may be metals such as platinum, palladium, iridium, ruthenium, mixtures, alloys and oxides of these metals
as well as the oxides of gold, silver, iron, cobalt, nickel, chromium, copper, lead, manganese, taken separately or in mixtures, as well as in mixtures with oxides of film-forming metals , for example titanium, tantalum, zirconium, aluminum, bismuth, tungsten, niobium, and with compounds of tin, vanadium, molybdenum, silicon, carbon, phosphorus, boron and sulfur.

 Mixtures of oxides of cobalt and platinum group metals and lanthanides, mixtures of ruthenium oxide with carbides of boron, silicon, titanium, hafnium, vanadium, tantalum, chromium and molybdenum.

 The high strength of the electrode according to the invention is due to the fact that the electrochemically inert organic substance not only ensures the protection of the surface of the internal pores of the electrode against the electrochemical and chemical destruction, but also the robustness and the reliability of the contact of the electrocatalytic substance with the graphite.

 At the same time, the presence in the pores and on the graphite surface of an electrocatalytic substance having a fundamental fundamental reaction overvoltage at a lower electrode than that of graphite, as well as the inert organic substance indicated above. high, significantly reduces the true surface of the electrode in contact with the electrolyte.

In this way, it is possible to use an electrode comprising an amount of inert organic substance greater than the known electrode, without exceeding the critical swelling potential.

 Another object of the invention is a method of manufacturing a porous core or graphite core electrode, comprising introducing, into at least a portion of the pores of the graphite base, at least one metal and / or or a metal compound having electrocatalytic properties, wherein, according to the invention, after the introduction of the metal and / or the metal compound having electrocatalytic properties into the graphite base, at least one part of the pores of said graphite base an electrochemically inert organic substance, insoluble in the electrolyte, this substance having a drop point and / or a temperature of transition to the gaseous state higher than the temperature of the electrode during l electrolysis, or this organic substance is obtained directly in the pores of the graphite base.

 The introduction of said organic substance can be carried out by any known method but the preferable method is impregnation, because it is the simplest and most convenient.

 For this purpose solutions of organic substance are used, with which the graphite base is impregnated, then the solvent is removed, or the graphite base is impregnated with said organic substance in melt, then cooled to the point of drop of this substance.

 The organic substance having indicated properties can be obtained directly from the pores of the graphite base, by impregnation of this base with a liquid monomer, for example with styrene, or with a liquid oligomer, followed by polymerization or polycondensation.

To impregnate the graphite base, the following substances can be used in the molten state: solutions of polystyrene, polyvinyl chloride, polymethylmethacrylate, polyethylene, or oxidized bitumen of petroleum, coal tar pitch of the rosin h and other appropriate substances
As graphite graphite is used
porous in which is cut a base (a block) of desired dimensions. This base is placed under vacuum and impregnated first with the solutions of the metal compounds indicated above X, then dried and carried out a heat treatment, then impregnated with said organic substance in solution or in fusion.

 Metals or metal compounds having electrocatalytic properties can be introduced into the pores of the graphite base, for example, by impregnating this base with solutions of the metal compounds, followed by drying and heat treatment. by depositing the metals or their compounds from a gaseous phase, by impregnation with the molten metals, or by other known methods.

 Depending on the conditions of the electrolysis, the properties of the electrocatalytic substance and the quality of the graphite, the electrode can be made either with virtually total pore closure by the inert substance (impregnation with the melt subsrance; impregnation with the liquid monomer , followed by its bulk polymerization in the pores of the electrode), or with partial filling of the pores (impregnation with solutions of solvent volatiis).

 The use of the electrode according to the invention provides the following technical advantages.

 In electrochemical manufacturing, its use in place of ordinary graphite anodes makes it possible to increase the service life of the anodes by several times and to reduce the electrical energy consumption without re-equipping the electrolyzers with metal anodes, as well as remove the use of expensive and quota-based metals as a base, including the use of titanium.

 The electrode according to the invention resists shorts substantially like an ordinary graphite electrode, which is a big advantage compared to metal electrodes, whose active coating dissolves and whose metal base is destroyed during short circuits. . This makes it possible to use electrolyzers without a short-circuit protection system and to reduce the requirements with regard to the purity of the electrolyte and mercury, compared to electrolyzers equipped with metal-based anodes.

These advantages of the electrode are not obtained if the order of introduction of the electrocatalytic substance and the electrochemically inert organic substance into the pores of the graphite base is not respected.

 The order of the operations indicated above is necessary for carrying out the process that is the subject of the invention, because if the order of the operations is reversed, that is to say if the electrochemically inert organic substance is introduced first and that it fills the entire volume of open pores of the graphite base, the execution of the second operation- introduction of the electrocatalytic substance becomes impossible.If the graphite base is impregnated with organic substance that partially, during the subsequent introduction of the electrocatalytic substance it will be difficult to obtain the electrical contact between it and the graphite base and nothing will protect this contact against the action of the electrolyte and electrolysis products; in this case the destruction rate of the electrode does not differ substantially from the destruction rate of the untreated graphite base, which is confirmed by one of the examples given below.

What has just been said shows that the order of operations in the process according to the invention is a feature which is characteristic of it.
For a better understanding of the invention, several concrete but non-limiting examples of obtaining the electrode that is its object are described below, as well as, for comparison, examples of obtaining the known electrode.

 Example 1

 A graphite electrode according to the invention, of dimensions 50 × 50 × 100 mm, had a graphite base with a porosity of 20. The electrode was manufactured by the following method. A block (base) of dimensions 50 × 50 × 100 mm was cut from a graphite plate for electrodes.

The graphite block was vacuum-packed and then impregnated with an aqueous solution of Co (NO 3) 2 at a concentration of 125 g / l, after which it was dried by gradually raising the temperature to 1400 C. then calcined for 10 minutes at 3000C.

After calcination, the graphite block was evacuated and then impregnated with polystyrene solution in styrene at a concentration of 90 g / l, at an effective or relative pressure of 10 atm, dried for 3 hours by increasing its temperature gradually from 80 to 1600 ° C., after which the impregnation with the polystyrene solution and drying was repeated once more.

The electrode thus manufactured contained 0.5% Co304 and 1% polystyrene (polystyrene is a substance that is solid up to 900 ° C). The electrode was tested as anode in a laboratory electrolyzer. For the electrolysis of a solution of
Nacl at a concentration of 280 to 300 g / l, at a temperature of 80 to 850 ° C. and at a pH of 2.5 to 3 × 1, the intensity of the current passing through the anode was 125 A (current density 5 kA / m2). The temperature of the electrode, in this example and in the following examples, did not exceed that of the electrolyte by more than 50 ° C.
The reduction in the weight of the electrode (wear) was 15.3 g for the first ten test days of 34.4 g for the second ten days and 38.9 g for the third ten days. days, which corresponded respectively to a relative speed of wear of 0.0005 g / Ah, 0.00115 g / Ah and 0.001295 g / Ah

 For comparison, known graphite electrodes containing Co3O4 or impregnated with polystyrene were tested, as well as a graphite electrode which had not undergone any special treatment.

 A graphite electrode of the same dimensions as those indicated above, based on the same graphite and containing 0.5% Cl304 in its pores, was tested under the conditions described above. The introduction of Co304 was carried out as described above.

The reduction in the weight of the electrode was 18.7 g for the first ten days of testing, 53.5 g for the second ten days and 74.6 g for the third ten days.

 A graphite electrode of the same dimensions based on the same graphite and containing in its pores 1.5% polystyrene was tested under the conditions described above. The polystyrene was introduced as described above. The level of 1.5% polystyrene was chosen because this value ensures a maximum wear reduction for the considered kind of graphite in the test conditions with impregnation only with polystyrene. The reduction in the weight of the electrode was 31.3 g for the first ten days of testing, 49.2 g for the second ten days and 54.8 g for the third ten days.

 A graphite electrode of the same dimensions, made with the same graphite and having undergone no special treatment (that is to say identical to the base of the electrodes described above) was tested under the conditions described above. The decrease in the weight of the electrode was 55s2 g for the first 10 days of testing, 75.0 g for the second ten days and 82.1 g for the third decade.

 Example 2

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 2050 '. C.sub.3 O.sub.4 was introduced into the graphite block as described in Example 1, and then the block was impregnated with styrene; the impregnation was carried out in the same way as the impregnation with the solution of Co (NO 3) 2 in Example 1. After impregnation with styrene, the block was gradually heated for the polymerization of styrene, by raising the temperature of 100 to 1400C in 35 hours. The electrode thus manufactured contained 0.5% of Co304 and 9% of polystyrene (polystyrene and Co3O4 occupied practically the entire volume of the open pores of graphite). The electrode was tested in the conditions described in Example 1 The decrease in the weight of the electrode was 17.2 g for the first 10 days of testing, 21.4 g for the second ten days and 21.6 g for the third ten days.

 For comparison, an electrode made by a known method was tested. The electrode had the same dimensions as those mentioned above, a base of the same graphite, and contained 9% of polystyrene in its layers. The conditions of the test were the same as in Example 1. The introduction of styrene and its polymerization were carried out as described above in Example 2. After the first 10 days of testing, the electrode was completely destroyed.

 Example 3

A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. Co304 was introduced into the graphite block as described in Example 1, and the block was then evacuated and impregnated with molten petroleum oxidized bitumen (BOP), heated to a temperature of 50.degree. from 220 to 2300C, effective or relative pressure of 10 atm; the drop point of the BOP was 1350 ° C. (here and further on, the drop point is determined by the Ukheloh method of the Encyclopedia of Polymers "Moscow, Editions" Sovetskaja entsiklopedia "1974, tl, pp. 934). made in this way contained 0.5% Co304 and 9% BOP (the
BOP and Co304 occupied practically the entire volume of open pores of graphite). The electrode was tested under the conditions described in Example 1.

The decrease in the weight of the electrode was 19.3 g for the first 10 days of testing, 21.6 g for the second ten days and 21.7 g for the third ten days.

 For comparison, an electrode made by a known method was tested. The graphite electrode had the same dimensions as those indicated above, a base of the same graphite, and contained in its pares 9% of BOP. The conditions of the test were the same as in Example 1. The introduction of the BOP was carried out as described above in Example 3. After the first 10 days of testing, the electrode was completely destroyed. .

 EXAMPLE 4

A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. The graphite block was impregnated with an aqueous solution of RuCl 3 and
TiCl3 at a concentration of 65 g / l, calculated as RuO2, and 79.5 g / l, calculated as TiO5, and then dried.

The impregnation and drying were carried out as was the impregnation with the Co (NO 3) 2 solution in Example 1. After drying, the graphite block was evacuated and then impregnated under effective or relative pressure of 20 atm with a mixture of the following composition (parts by weight): unsaturated polyester resin of the maleate type, modified rosin
(50), styrene (47), isopropylbenzene hydroperoxide
(3). To cure the resin, the block was gradually heated to 1000 ° C, and the block was held at that temperature for 5 hours.

 The electrode thus manufactured contained 1.5% ruthenium oxide-titanium mixture and 10% polyester resin (substance that is solid at the electrode temperature during electrolysis). The resin and the oxides occupied practically the whole volume of the open chips of the graphite. The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode was 18.3 g for the first 10 days of testing, 23.2 g for the second ten days and 25.4 g for the third ten days.

 Example 5

 A graphite electrode according to the invention of the same dimensions as in Example 1 had a graphite base with a porosity of 20. The block was impregnated with an aqueous solution of H 2 PtCl 6 with a metal concentration of 55 g / l. The impregnation was carried out in the same way as the impregnation with the aqueous solution of Co (NO 3) 2 in Example 1. The impregnated block was dried for 2 hours at 1000 ° C., then it was taken in a Argon atmosphere at 5500C for 1 hour.

After introduction of the platinum, the graphite block was evacuated, then, at a temperature of 1300C and at an effective or relative pressure of 10 atm, it was impregnated with rosin having a drop point of 700C
The electrode thus manufactured contained 0.5% platinum and 9% rosin. The electrode was tested as anode in a cathodic protection system in water containing 35 mg / l Caret 40 mg / l SO4, with anodic current density of 250 A / m2 at a temperature of 16. at 21 ° C. The relative wear rate of the electrode was 0.048 g / Aoh.

 In the conditions described above in this example, a graphite electrode of the same dimensions as those indicated above, but having undergone no special treatment, was tested. The relative wear rate of this electrode was 0.128 g / A.h.

 Example 6

 A graphite electrode according to the invention, of dimensions 40 × 40 × 12 mm, had a graphite base with a porosity of 27%. This electrode was manufactured by the following method.

A block of 40x40x12 mm was cut from a graphite plate for electrodes. We introduced
Co304 as in Example 1, but with a concentration of the Co (NO3) 2 solution of 500 g / l. After a first calcination of the block, the impregnation and calcination operations were repeated once again.

 After the second calcination, the graphite block was evacuated and then impregnated with a drying tall oil solution in CCl 2 containing 15% by volume of tall drying agent and a drying agent with a pyrolusite content of 0.45. % and a litharge rate of 0.9% based on the weight of tall oil. Then the block was dried under vacuum for 3 hours at normal temperature, for 3 hours with gradual rise in temperature from the normal value to 900C, and then to a constant weight at 900C and without vacuum. The electrode thus produced contained 8% of Co304 and 3% of the tallow drying polymerization product (decomposes forming gaseous products above 260 ° C.). The electrode was tested under the conditions of the production of chlorate. sodium, in an electrolyte titrating 1D g / l of NaCl, 450 g / l of NaClO3 and 2 g / l of Na2CrO4 at a pH of 6.6 to 7.6, at the temperature of 400C and at a current intensity of 5 , 1 A. The decrease in the weight of the electrode was 0.9 g for the first 10 days of testing, 1.2 g for the second ten days and 1.3 g for the third decade of days.

 For the comparison, there have been tried, under the same conditions, known electrodes, as well as a graphite electrode which has not undergone any special treatment and a graphite electrode manufactured without respecting the indicated order of the operations.

 A graphite electrode of the same dimensions as those indicated above, with a base of the same graphite and containing 8% Co304 in its beds, was tested under the conditions described above. The introduction of Co304 was carried out as described above in Example 6. The decrease in the weight of the electrode was 1.5 g for the first 10 days of testing, 2.7 g for the second ten days and 4.6 g for the third ten days.

 A graphite electrode of the same dimensions as those indicated above, with a base of the same graphite and containing in its parts 3% of product of polymerization of tall drying siccatif was tested under the conditions described above. The impregnation with the drying tall oil solution and the heat treatment were carried out as described above. The decrease in the weight of the electrode was 1.1 g for the first 10 days of testing, 1.9 g for the second ten days and 2.4 g for the third ten days.

 A graphite electrode of the same dimensions as those indicated above, with a base of the same graphite and having not undergone any special treatment, was tested under the conditions described above.

The reduction in the weight of the electrode was 2.4 g for the first 10 days of testing, 2.8 g for the second ten days and 4.6 g for the third ten days.

 In a graphite base of the same dimensions as those indicated above, made with the same graphite, was introduced a drying polyol polymerization product, as described above in Example 6, then introduced Co304 as described above. in example 6.

 The electrode thus manufactured was tested under the conditions described above. The reduction in the weight of the electrode was 2.2 g for the first 10 days of the test, 2.75 g for the second ten days, and 4.6 g for the third ten days.

 Example 7

 A graphite electrode according to the invention of the same dimensions as in Example 6, had a graphite base with a porosity of 27%. Co3O4 was introduced into the graphite block as described in Example 6, and then the graphite block was evacuated and impregnated with a mixture of the following composition (parts by volume): 5), flaxseed oil (4,5), CCl4 (85), to which a 0.5% pyrolusite lead-manganese dryer was added and 1.0% by weight tall oil. The block was then dried in the same manner as after impregnating with the tallow solution in Example 6. The resulting electrode contained 8% Co 3 O 4 and 3% copolymerization product of tall oil and linseed oil. (decomposes with formation of gaseous products above 2600C).

 The electrode was tested under the conditions described in Example 6. The decrease in the weight of the electrode was 0.7 g for the first 10 days of testing, 1.3 g for the second decade of days and 1.5 g for the third ten days.

 Example 8.

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. The graphite block was impregnated with an aqueous solution containing 17.5 g / l RuCl 3 and 30 g / l Fe (OH) 3 prepared by precipitation from FeCl 3 solution with ammonia.

The impregnation was carried out in the same way as with the Co (NO3) 2 solution in Example 1, then the graphite block was dried at 100C for 1 hour, after which the temperature was uniformly raised. up to 450 C in 1 hour and the block was maintained at 450 C during the hour.

 The block thus treated was impregnated with phthalic anhydride-based oligomer-esteracrylate, triethylene glycol and methacrylic acid, containing 2% benzoyl peroxide. The impregnation was carried out in the same way as with styrene in Example 2.

To form the polyesteracrylate, the block was maintained at 800C for 3 hours and at 1000C for 3 hours.

The electrode made by this process contained 0.3% ruthenium and iron oxide mixture and 10.5% polyesteracrylate (substance that is solid at the electrode temperature during electrodyse).

The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode in 10 days of testing was 20.2 g
Example 9.

A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20. The graphite block was impregnated first with an aqueous solution of Mn (NO 3) 2 concentration of 52 g / l, then, after drying at 1000C for 1 hour and calcination at 1900C for 10 minutes, with an aqueous solution of Co (N03) 2 at a concentration of 65 g / l, after which it was dried and calcined block Impregnation with aqueous solutions, as well as drying and calcination after impregnation with the solute of
Co (N03) 2, were carried out as described in Example 1.

 The thus-treated block was vacuum-packed and then plummeted in a phenol-formaldehyde resin in the form of a resin, heated to 80 ° C., after which an affective or relative pressure of argon was created over the molten resin. 10 atm and impregnation at the indicated pressure and temperature for two hours. The graphite block was then extracted from the resin, the surface of the resin was rinsed off and heat-treated to harden the resin, raising the temperature from 80 to 1300C at a rate of 80.degree. 30C / h.

 The electrode thus made contained 0.5% MnO 2 + Co 3 O 4 in the ratio of 1: 1 to 7% phenol-formaldehyde resin (substance which is solid at the electrode temperature during electrolysis).

 The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode was 18.5 g for the first 10 days of ssai, 20.2 g for the second ten days and 20.6 g for the third ten days.

 Example 10

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. The graphite block was impregnated with a RuCl3 solution at a concentration of 35 g / l and then subjected to a heat treatment.

Impregnation and heat treatment were carried out as for the mixture of ruthenium and iron oxides in Example 8. Then the graphite block was immersed in a boiling solution of polyethylene in CCl 4, at a concentration of 110 g / l, and boiled with a reflux condenser for 4 hours, after which the impregnation with this polyethylene solution was carried out under an effective or relative dilution of 10atm at 750C for four hours. After impregnation on The graphite block was dried at 700 ° C. for 1 hour at 100 ° C. for 1 hour and 2000 ° C. for 1 hour.

The electrode thus manufactured contained 0.2% of
RuO 2 and 1% polyethylene (substance that is solid at electrode temperature during electrolysis).

 The electrode was tested as an anode in a laboratory electrolyzer to produce sodium hypochlorite. The electrolyte contained 90 g / l NaCl and 10 g / l NaClO; the electrolysis was carried out at 25 ° C., with a current density of 2 kA / m 2. The reduction in the weight of the electrode in 10 days of testing amounted to 63 g.

 For the comparison, an electrode of the same dimensions, made of the same graphite but having undergone no special treatment, was tested under the same conditions. The reduction of the weight of the electrode in 10 days of testing amounted to 150 g.

 Example 11

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. The Ru02 graphite block was introduced, as in Example 10, and the block was evacuated and impregnated with a mixture of mono and difurfurylidene acetone in the ratio of 3: 2, containing 5% para-toluene sulfonyl chloride.

 The block impregnated with the normal temperature was heated at 800 ° C. in 1 hour, then from 80 ° C. to 1500 ° C. at a rate of 10 ° C./h, and was kept at 1500 ° C. for 3 hours.

 The electrode thus manufactured contained 0.2% RuO 2 and 8.5% furanic resin (substance which is solid at electrode temperature during electrolysis).

 The electrode was tested under the conditions described in Example 5. The relative wear rate of this electrode was 0.056 g / A.h.

 Example 12.

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. Platinum was introduced into the graphite block in the same manner as in Example 5. Then the block was impregnated with a 2% solution of polyvinyl chloride in cyclohexanone (the impregnation was carried out in the same way as with the polystyrene solution in Example 1) and dried at 90 ° C. for 3 hours. The impregnation and drying were repeated each time increasing the drying time by 1 hour until a weight increase of 2% (based on the weight of the base) was obtained.

 The electrode thus manufactured contained 0.5% platinum and 2% polyvinyl chloride (the polyvinyl chloride decomposes forming gaseous products at a temperature above 900C). The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode was 16.7 g for the first 10 days of testing, 31.3 g for the second decade of days and 33.2 g for the third ten days.

Example 13
A graphite electrode according to the invention of the same dimensions as in Example 6, had a graphite base with a porosity of 20%. The graphite block was evacuated and impregnated with 20 g / l aqueous Na 2 SiO 3 solution, dried at 100 OC for 1 hour and at 150 OC for 1 hour. boiled for 2 hours in water, then dried at 1500C for 1 hour, then Ru02 was introduced into the graphite block as described in Example 10.

 Then the graphite block was evacuated and impregnated under an effective or relative pressure of 20 atm with a solution of methyl polymethacrylate in cyclohexanone, at a concentration of 20 g / l, and then the block was dried. at 150 ° C. for 2 hours and at 170 ° C. for 1 hour. Impregnation was detected with the polymethyl methacrylate solution and drying until an increase in weight of 1.2% was obtained.

The electrode thus manufactured contained 0.1% of
SiO 2, 0.2% RuO 2 and 1.2% polymethyl methacrylate.

 The electrode was tested under the conditions described in Example 6. The decrease in the weight of the electrode was 1, Og for the first 10 days of testing, 1.5 g for the second ten days and 1.7 g for the third ten days.

 Example 14.

A graphite electrode according to the invention of the same dimensions as in Example 1, had a graphite base with a porosity of 20%. The graphite block was impregnated in an aqueous solution at 41.5 g / l of
Co (NO 3) 2 and 97.2 g / l of Al (NO 3) 3; the impregnation was carried out in the same way as with the solution of Co (NO 3) 2 in Example 1. The impregnated block was heated gradually to 1200 ° C., held at 1200 ° C. for 1 hour, then heated gradually to 4500C and maintained at that temperature for 2 hours. Then 0.2% RuO 2 was introduced into the base as described in Example 10. The thus treated block was vacuum-treated and then impregnated with coal tar pitch (950C drop point). ) heated to 2200C under an effective or relative 10 atm.

 The electrode thus manufactured contained 0.5% of aluminum oxide and cobalt mixture, 0.2% RuO 2 and 11.5% coal tar pitch.

 The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode in 10 days of testing was raised to 22.5 g.

 Example 15

 A graphite electrode according to the invention of the same dimensions as in Example 6, had a graphite base with a porosity of 27. 2.4% of a mixture of ruthenium oxides was introduced into the graphite base. and titanium by impregnation with an aqueous solution of RuCl3 and TiCl3, followed by drying and calcination as described in Example 4. Then 1% of a paraffin wax mixture was introduced into the base. drop of 550C and polyethylene in the ratio of 1: 1 by impregnation with a solution of 55 g / l of polyethylene and 55 g / l of paraffin in CCL; the impregnation and drying were carried out as for the polyethylene in Example 10.

The electrode thus manufactured contained 2.4% of ruthenium oxide and titanium mixture and 1% of paraffin and polyethylene mixture (this mixture is solid at electrode temperature during electrolysis)
The electrode was tested under the conditions described in Example 10. The decrease in the weight of the electrode in 10 days of testing amounted to 54.2 g.

 Example 16

 A graphite electrode according to the invention of the same dimensions as in Example 1, had a porosity graphite base of 20%. Co304 was introduced into the graphite block as described in Example 1, and then the block was impregnated with a solution of polystyrene (80 g / l) and polymethyl methacrylate (10 g / l) in stabilized styrene. hydroquinone; the impregnation and drying after impregnation were carried out in the same way as with the polystyrene solution in styrene in Example 1. The impregnation and drying were carried out twice.

The electrode thus manufactured contained 0.5% of
Co304 and 1.5% blend of polystyrene and polymethyl methacrylate (solid) is solid at the electrode temperature during electrolysis.

 The electrode was tested under the conditions described in Example 1. The decrease in the weight of the electrode was 16.6 g for the first 10 days of testing, 34.7 g for the second decade of days and 37.3 g for the third ten days.

 To better highlight the substance of the invention, the results of the tests of electrodes in the electrolysis of NaCl at a concentration of 280 to 300 g / l at 80-850C (conditions of production of chlorine and caustic soda ) and under the conditions of production of sodium chlorate are respectively grouped in Tables 1 and 2.

 The examples given show that the electrode which is the subject of the invention has significant advantages compared with known pH electrode, the effect of lowering the wear rate of the electrode according to the invention. not being equal to the sum of the partial effects.Thus for the known electrodes of Example 1, the average wear speed during the period between the 20th and the 30th day after the start of the test (period during which the wear rate is close to a stationary value) was respectively -90.9% and 66.7% of the average wear speed of the untreated graphite electrode during this same period of time. It could be expected that the association of an electrocatalytic substance with an electrochemically inert organic substance in the pores of the electrode would result in a 60.6% increase in wear rate. the untilled electrode; in fact, it only went up to 47.4%, that is to say, it turned out to be 1.3 times lower, which is an unexpected effect, but an even greater fact. Unexpectedly, the stationary wear rate of the electrode decreases several times when the known impregnating substances are combined in such quantities that, taken separately each, they give either a very small favorable effect or even an acceleration of wear. .

Thus, the introduction of 0.5% Co304 (Example 1) decreases the wear rate by 1.1 times; the introduction of 9% of polystyrene (example 2) or 9% of BOP (example 3) gives an increase of the wear fast to a catastrophic value; however, it has been found that the stationary wear rate of an electrode containing 0.5% of Cog04 and 9% of polystyrene (Example 2) or 0.5% of Co304 and 9% of BOP (Example 3) was 3,5 times lower than that of an untreated electrode.

 Of course, the invention is not limited to the embodiments described which have been given by way of example. In particular, it comprises all the means constituting technical equivalents of the means described, and their combinations if they are executed according to its spirit and implemented in the context of protection as claimed. Table 1.

Results of tests of graphite-based electrodes with a porosity of 20% under the conditions of electrolysis of NaCl solutions at a concentration of 280 to 300 g / l at 80 ° -85 ° C.

N <SEP> of <SEP> Addition <SEP> substance <SEP> organic <SEP> inert <SEP> Wear <SEP> of <SEP> electrode <SEP> (g) <SEP> during <SEP> la
<tb> examples <SEP> electro- <SEP> test <SEP> period <SEP> in <SEP> days
<tb> catalytic <SEP> 0-10 <SEP> 10-20 <SEP> 20-30
<tb> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6
<tb> 1 * <SEP> - <SEP> - <SEP> 55.2 <SEP> 75.0 <SEP> 82.1
<tb> 1 * <SEP> 0.5% <SEP> Co3O4 <SEP> - <SEP> 18.7 <SEP> 53.5 <SE> 74.6
<tb> 1 * <SEP> - <SEP> 1.5% <SEP> of <SEP> polystyrene <SEP> 31.3 <SEP> 49.2 <SE> 54.8
<tb> 1 <SEP> 0.5% <SEP> Co3O4 <SEP> 1.5% <SEP> of <SEP> polystyrene <SEP> 15.3 <SEP> 34.4 <SEP> 38.9
<tb> 2 * <SEP> - <SEP> 9% <SEP> of <SEP> polystyrene <SEP> Destruction <SEP> total <SEP> - <SEP> 2 <SEP> 0.5% <SEP> Co3O4 <MS> 9% <SEP> of <SEP> polystyrene <SEP> 17.2 <SEP> 21.4 <SEP> 21.6
<tb> 3 * <SEP> - <SEP> 9% <SEP> of <SEP> oxidized <SEP> bitumen <SEP> of <SEP> Destruction <SEP> total <SEP> - <SEP> oil
<tb> 3 <SEP> 0.5% <SEP> Co3O4 <SEP> 9% <SEP> of <SEP> oxidized bitumen <SEP><SEP> of <SEP> 19.3 <SEP> 21.6 <SEP > 21.7
<tb> oil
<tb> 4 <SEP> 1.3% <SEP> TiO2 + RuO2 <SEP> 10% <SEP> of <SEP> resin <SEP> polyester <SEP> 18.3 <SEP> 23.2 <SEP> 25 4
<tb> Table 1 (continued)

1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6
<tb> 8 <SEP> 0.3% <SEP> Fe3O4 + RuO2 <SEP> 10.5% <SEP> of <SEP> polyesteracrylate <SEP> 20.2 <SEP> - <SEP> 9 <SEP> 0 , 5% <SEP> MnO2 + Co3O4 <SEP> 7% <SEP> of <SEP> resin <SEP> phenol-for- <SEP> 18.5 <SEP> 20.2 <SEP> 20.6
<tb> maldehyde
<tb> 12 <SEP> 0.5% <SEP> Pt <SEP> 2% <SEP> of <SEP> chloride <SEP> of <SEP> poly- <SEP> 16.7 <SEP> 31.3 <SEP> 33.2
<tb> vinyl
<tb> 14 <SEP> 0.5% <SEP> (Al2O3 +
<tb> Co3O4 + <SEP> 0.2% <SEP> RuO2) <SEP> 11.5% <SEP> of <SEP> pitch <SEP> of <SEP> coal <SEP> 22.5 <SEP> - <SEP> 16 <SEP> 0.5% <SEP> Co3O4 <SEP> 1.5% <SEP> of <SEP><SEP> mixture of <SEP> polystyrene <SEP> and <SEP> of <SEP> polymethacrylate <SEP> of <SEP> methyl <SEP> 16.6 <SEP> 34.7 <SEP> 37.3
<tb> * known electrodes Test results for graphite-based electrodes with a porosity of 27% under the conditions of sodium chlorate production
Table 2

N <SEP> of <SEP> Addition <SEP> ee <SEP> Substance <SEP> organic <SEP> inert <SEP> Wear <SEP> of <SEP> electrode <SEP> (g) <SEP> during
<tb> examples <SEP> trocatalytic <SEP> the <SEP> test <SEP> period, <SEP> in <SEP> days
<tb> 0-10 <SEP> 10-20 <SEP> 20-30
<tb> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6
<tb> 6 * <SEP> - <SEP> 2,4 <SEP> 2,8 <SEP> 4,6
<tb> 6 * <SEP> 8% <SEP> Co3O4 <SEP> - <SEP> 1.5 <SEP> 2.7 <SEP> 4,6
<tb> 6 * <SEP> - <SEP> 3% <SEP> of <SEP> Product <SEP> of <SEP> Polymerization
<tb> of <SEP> tallöl <SEP> siccative <SEP> 1,1 <SEP> 1,9 <SEP> 2,4
<tb> 6 <SEP> 8% <SEP> Co3O4 <SEP> 3% <SEP> of <SEP> Product <SEP> of <SEP> Polymerization
<tb> of <SEP> tallöl <SEP> siccative <SEP> 0.9 <SEP> 1.2 <SEP> 1,3
<tb> 7 <SEP> 8% <SEP> Co3O4 <SEP> 3% <SEP> of <SEP> product <SEP> of <SEP> copolymerization <SEP> of <SEP> tallöl <SEP> and <SEP> d 'oil
<tb><SEP> lin <SEP> 0.7 <SEP> 1.3 <SEP> 1.5
<tb> 13 <SEP> 0.1% <SEP> SiO2 <SEP> 1.2% <SEP> of <SEP> polymethacrylate <SEP> from
<tb> 0.2% <SEP> RuO2 <SEP> methyl <SEP> 1.0 <SEP> 1.5 <SEP> 1.7
<tb> * known electrodes.

Claims (2)

 Electrode for electrochemical processes, of the type consisting of a porous graphite base or core, at least part of which contains pores containing metals or metal compounds having electrocatalytic properties and in electrical contact with graphite, characterized in that it contains, in at least a portion of the pores of the graphite base, an organic substance, electrochemically inert, insoluble in the electrolyte and having a higher point of drop and / or a temperature of gaseous state as the temperature of the electrode during electrolysis.  Electrode electrode for electrochemical process according to claim 1, characterized in that said electrolyte-insoluble and electrochemically inert organic substance is selected from the group of carbon chain polymers, heterogeneous chain polymers, natural and synthetic resins, bitumens, pitches, drying and drying oil polymerization products, and mixtures of these substances.  3. Electrode for electrochemical process according to claims 1 and 2, characterized in that said organic substance insoluble in SiKtrflyte and electrochemically inert is polystyrene  4. Electrode for electrochemical processes according to one of claims 1 and 2 characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is polyethylene.  5. Electrode for electrochemical processes according to one of claims 1 and 2 characterized in that the organic substance insoluble in the electrolyte and electrochemically inert is polymethyl methacrylate.  6. Electrode for electrochemical processes according to one of claims 1 and 2 characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is polyvinyl chloride.  7. electrode for electrochemical processes according to one of claims 1 and 2 characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is the polyesteracrylate.  8. electrode for electrochemical processes according to claims 1 and 2 characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is rosin.  9. Electrode for electrochemical processes according to one of claims 1 and 2 characterized in that said electrolyte-insoluble and electrochemically inert organic substance is a phenol-formaldehyde resin.  10.Electrode for electrochemical processes according to one of claims 1 and 2 characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a uranic resin.  11.Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a polyester resin.  12.Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is an oxidized bitumen of petroleum.  13.Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said electrolyte-insoluble and electrochemically inert organic substance is a copolymerization product tallöl and linseed oil.  14.Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a product of polymerization of tallöl desiccative.  15.Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a coal tar pitch.  16. Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a mixture of polyethylene and paraffin  17. Electrode for electrochemical processes according to one of claims 1 and 2, characterized in that said organic substance insoluble in the electrolyte and electrochemically inert is a mixture of polystyrene and polymethyl methacrylate.  18.Process for manufacturing the electrochemical process electrode comprising a porous graphite base or core according to one of claims 1 to 17, of the type comprising introducing into at least a portion of the pores of said graphite base, of at least one metal and / or a metal compound endowed with electrocatalytic properties, characterized in that after the introduction of the metal and / or the metal compound endowed with electrocatalytic properties into at least a part of the pores of the base of graphite, is introduced into this part of the pores of said graphite base an electrochemically inert organic substance insoluble in the elechdlyte and whose drop point and / or the temperature of gaseous state are higher than the temperature of the electrode during electrolysis, or one obtains said organic substance directly in the pores of the graphite base.  19. A method for manufacturing an electrode for electrochemical processes, according to claim 18, characterized in that the electrochemically inert organic substance insoluble in the electrolyte is introduced by impregnation with a solution of said substance or with said substance. in fusion, then the electrode is subjected to an athermic treatment,  20o Process for manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that to obtain in the pores of the graphite base the electrochemically inert organic substance, insoluble in the electrolyte and having a drop point and / or a gaseous temperature higher than the electrode temperature during the electrolysis, the graphite base is impregnated with a liquid monomer or a monomer solution in a organic solvent, then the polymerization or the polycondensation is carried out  21. A method for manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that to obtain in the pores of the graphite base the electrochemically inert organic substance, which is insoluble in water. electrolyte and having a drop point and / or a gaseous temperature higher than the electrode temperature during the electrolysis, the graphite base is impregnated with a liquid oligomer or an oligomer solution in an organic solvent, then said polymerization or said polycondensation is carried out.  22. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19 characterized in that the impregnation is performed with a polystyrene solution in styrene and the electrode is dried.  23. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 20, characterized in that the impregnation is performed with styrene, then the styrene is subjected to thermal polymerization.  24. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is performed with an oxidized bitumen of molten oil, and the electrode is cooled to a temperature below the drop point of the petroleum bitumen.  Method for manufacturing an electrochemical process electrode according to one of Claims 18 and 21, characterized in that the impregnaton is carried out with an unsaturated polyester resin containing a polymerization catalyst such as isopropylbenzene hydroperoxide, then the electrode is heat treated to accelerate the polymerization.  26. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is carried out with a molten rosin and the electrode is then cooled down to a temperature below the drop point of rosin.  27. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 21, characterized in that the impregnation is carried out with a solution of drying tall oil in CCl4 containing a drying agent, then the The electrode is dried and subjected to a heat treatment for the polymerization of tallic drying agent.  28. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 20 characterized in that the impregnation is carried out with a solution of tall oil and linseed oil in Cul4, containing a drying agent, then the electrode is dried and subjected to a heat treatment for the copolymerization of tallbl and linseed oil.  29. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 21, characterized in that the impregnation is performed with an oligo-esteracrylate containing a polymerization catalyst held peroxide benzoyl, then the electrode undergoes a treatment  to accelerate the polymerization of the oligoesteracrylate.  30. A method for manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 21, characterized in that the impregnation is carried out with a phenol-formaldehyde resin of the Resol type, and then the electrode undergoes a heat treatment for the polycondensation of the resin with resin formation.  31. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19 characterized in that the impregnation is performed with a polyethylene solution in CCl4 and the electrode is dried.  32. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 20, characterized in that the impregnation is carried out with a mixture of monofurfurylidene-acetone and difurfurylidene-acetone, containing 5 % of para-toluenesulphonyl chloride, then the electrode undergoes heat treatment for the polycondensation of monofurfurylidene-acetone and difurfurylideneacetone with formation of furan resin.  33. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is carried out with a solution of polyvinyl chloride in cyclohexanone, and then the electrode is dried.  34. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is performed with a solution of polymethyl methacrylate in cyclohexanone, and then the electrode is dried.  35.Process for manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is performed with a molten coal pitch, then the electrode is cooled to at a temperature below the drop point of the pitch.  36. A method of manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is carried out with polyethylene and paraffin solution in CCl4 then electrode is dried.  37. A method for manufacturing an electrode for electrochemical processes, subject of one of claims 18 and 19, characterized in that the impregnation is performed with a solution of polystyrene and polymethyl methacrylate in styrene and then the electrode is dried.