FI74997C - ELEKTROD FOER ELEKTROLYS AV ELEKTROLYTLOESNINGAR. - Google Patents

Description

1 74997

Electrode for electrolyzing electrolyte solutions

The present invention relates to electrochemistry, more particularly to the electrolysis of electrolyte solutions and in particular to an electrode for the electrolysis of electrolyte solutions.

The present invention is useful as an anode in the electrolysis of alkali metal chloride solutions in the production of chlorine and alkali in filter membrane or ion exchange membrane electrolysis equipment and in mercury cathode electrolysis equipment and electrolytic processes in the preparation of chlorates, hypochlorites, wastewater

Before the early 1970s, graphite electrodes were mainly used as anodes in electrochemical methods. Graphite anodes have numerous advantages, namely the use of a cheap and readily available electrode material, the anodes are not sensitive to short circuits. At the same time, however, the graphite anodes are less catalytically active, requiring a high voltage in the electrolysis unit, and their wear is also high, so that the electrolysis units often have to be dismantled to change the ano group. In addition, the total dimensions and weight of the graphite anodes are large, which results in an undesirable increase in the size of the electrolysis apparatus as well as an increase in the floor area of the electrolysis plant.

In current electrochemical methods, the use of metal oxide anodes has greatly increased as the anodes form an electrically conductive support substrate to which an active coating of metal oxide has been applied. The electrically conductive support is made of a metal that is passivated by anodic polarization, for example, titanium, tantalum, zirconium, niobium 35, or a mixture of these metals. The electrically conductive support or base can be made in the desired shape, for example torn into a flat plate, for example, with or without holes in the form of a rod, screen, grating or metal-ceramic body.

An electrode for electrochemical methods is previously known, the electrode having an electrically conductive substrate, for example a titanium, on which an active coating of a mixture of titanium, iridium and ruthenium oxides has been applied. The content of titanium oxides in this coating is considerable, up to more than 75 mol%. For example, the composition of the electrode coating known from En-10 is as follows, in mole percent: IrC> 2 to 3.91, RuO 2 to 7.43, and TiC> 2 to 88.66 (Samples B and D in U.S. Patent 3,948,751, Table 2). ); IrCl 2 - 7.25, RuO 2 - 13.8 and TiO 2 - 78.95 (Sample C of U.S. Patent 3,948,751, Table 2).

As can be seen from the above proportions, the coating components are used in the above electrode in the following ratio (mol%): TiO 2: (IrC> 2 + RuO 2) = (3.8-7.8): 1 and IrO 2: RuO 2 = 0, 5: 1 (cf. U.S. Patent 3,948,751, C, 204-290F, 1976).

20 The anode potential of a previously known electrode is unstable in electrolysis, its current efficiency is poor, and the duration of the electrode is insufficient in use.

In this case, when examining samples "B", "C" and "D" in saturated NaCl solution at a current density of 1 A / cm and at a temperature of 65 ° C, the anode potential of sample "B" ranged from 1.53 to 1.62 V after 2000 hours of electrolysis. the anode potential of sample "C" ranged from 1.35 to 1.38 V during 2300 hours (approximately 96 days) of electrolysis and from sample 1.44 to 30 to 1.50 V during 816 hours (approximately 34 days). during the day) during electrolysis.

Metal oxide anodes with an active coating containing 30 mole percent ruthenium oxide and 70 mole percent titanium dioxide-35 oxide, formerly known as DSA anodes (dimensionally stable anodes), are commercially available and are commercially available in the Soviet Union at 11,374,997. The OPTA electrodes are protected by USSR Inventor's Certificate No. 369,923.

The wear rate of the active mass of this electrode in stationary chlorine electrolysis at a current density of 0.2 to 0.4-0.4 A / cm according to the radiochemical method, as determined by 2, is 2.6 x 10 g / cm .h.

The resistance of the active coating of the electrode can be determined by a method using variable polarity and amalgamation, which is widely used as a research method to determine the quality of the active coating, examining the resistance to amalgamation, adhesion to a conductive substrate, resistance to cathodic polarization and resistance to cathodic polarization.

The measurement results of the wear of the active coating mass of the OPTA electrode obtained by the method using variable polarity and amalgamation are shown in the following table.

Number of test cycles 20_1-3 4-6 7-9 10-12 13-15 16-18

Consumption of active mass for each successive 3 cycles, 25 mg / cm2 0.595 0.610 0.140 0.180 0.190 0.170

Compared to the graphite electrode, the OPTA electrode under the conditions of electrolysis of alkali metal chlorides makes it possible to reduce the overvoltage of chlorine evolution, to lower the voltage in the electrolyser and to save about 200 kW.h. per tonne of sodium hydroxide (based on 100% product) and improves the purity of electrolysis products, extends the life of the anodes from 7-8 months to 5-7 years and reduces the cost of re-installing the electrode 35. However, the OPTA electrode has the following disadvantages: the relatively high wear rate of precious metals 4 74997 / which is observed especially in the large-scale use of these electrodes; insufficient duration of the coating under conditions where both oxygen and chlorine are formed together; as the oxygen content in the anode gas increases, ta-5 "clogging" of the electrode occurs with a still high residual concentration of ruthenium in the active coating of the electrode. These factors impair the operational reliability of this electrode, especially under conditions of electrolysis with an ion exchange membrane.

It is an object of the present invention to provide an electrode suitable for the electrolysis of electrolyte solutions, the composition of the active coating being such as to ensure improved durability of the electrode under conditions of both oxygen and chlorine evolution and a stable value of the anode potential during prolonged electrolysis.

This object is achieved in that the electrode consists of a passivating metal support provided with a coating of a mixture of titanium, iridium and ruthenium oxides in which the titanium oxide content is greater than 50 mole percent and according to the present invention the coating contains the above-mentioned constituents. the total amount of iridium and ruthenium oxides is 1: 1 to 3: 1 and the molar ratio of iridium oxide to ruthenium oxide is 0.75: 1 to 3: 1.

When applied to the electrolysis of electrolyte solutions, the stability of the electrode of the present invention, as determined by the loss of active mass by a method using variable polarity and amalgamation under difficult conditions (electrolyte - 200 g / l NaOH) exceeds 1.5-2 times that of U.S. Patent No. 3,948. 751 (samples 2 and 3) and twice the OPTA electrode according to USSR Biscuit Certificate No. 369,923. The electrode I according to the present invention! The stability of the catalytic properties of the 74 747 compared to the OPTA electrode is particularly evident in the case where the oxygen concentration in the chlorine has increased until the development of pure oxygen.

The stability of the electrode of the present invention compared to the OPTA electrode can be estimated to be 1.5 to 2 times higher.

According to the present invention, it is preferable that the electrode coating contains the above-mentioned ingredients so that the molar ratio of titanium oxide to total oxides of iridium and ruthenium is 1.75: 1 to 3: 1 and the molar ratio of iridium oxide to ruthenium oxide is 0.75: 1 to 1.75: 1.

According to one embodiment of the present invention, the electrode coating contains the above-mentioned ingredients such that the molar ratio of titanium oxide to total iridium oxide and ruthenium oxide is 1.25: 1 to 2.5: 1 and the molar ratio of iridium oxide to ruthenium oxide is 1.25: 1 to 2.5: 1. 1.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the electrode for the electrolysis of electrolyte solutions, as well as from specific illustrative examples.

The electrode for the electrolysis of electrolyte solutions is made of a metal which is passivated by anodic polarization, for example titanium, tantalum, zirconium, niobium or a mixture thereof, and which acts as a base or support for the electrode.

The electrode support base can be of any shape, for example a flat plate, with or without holes, a rod, a screen, a grating or a metal-ceramic body.

The electrode support base is provided with a coating of a mixture of titanium, iridium and ruthenium oxides.

According to the present invention, these oxides are present such that the molar ratio of titanium oxide to total iridium oxide 6 74997 and ruthenium oxide is 1: 1 to 3: 1 and the molar ratio of iridium oxide to ruthenium oxide is 0.75: 1 to 3: 1, respectively. These conditions make it possible to improve the stability of the electrode with this coating approximately twice under conditions in which both oxygen and chlorine are formed together and to achieve a stable value of the anode dipotential in a long-term electrolysis process.

Therefore, it has been very surprising to find that it is possible to significantly improve the durability and stability of the electrode during its use by partially replacing ruthenium oxide with iridium oxide in the ratio according to the present invention compared to the known coating.

The high corrosion resistance of metal oxide coatings containing oxides of titanium and platinum group metals is related to the known formation of substitution solutions by them. The presence of the free phase of individual oxides of platinum group metals causes higher losses of noble metal. The addition of iridium oxide to the active mass of the electrode - its coating - results in an increase in its corrosion resistance under conditions where oxygen and chlorine are formed together, as iridium does not tend to form volatile oxygen compounds. The effect of the addition of iridium oxide 25 has been found to be significant when ruthenium oxide is used in the coating at the same time, as only in this particular case do the conditions for solid solutions form in the coating range throughout the invention achieve a substantial increase in coating electrolytic activity and improved catalytic activity. The ratio of iridium oxide to ruthenium oxide must be 0.75: 1-3: 1, because in this range, as we have found, the catalytic activity is maximal and at the same time a high resistance of the electrode coating is guaranteed.

It should be noted that the increase in corrosion resistance is particularly

II

74997 is evident under the conditions under which oxygen is evolved upon electrolysis of aqueous solutions of alkali metal hydroxides, with ruthenium oxide alone being relatively unstable.

If the molar ratio of titanium oxide to total iridium oxide and ruthenium oxide is less than 1: 1, the losses of precious metals during electrolysis apparently increase due to the formation of the free phase of the individual oxides of iridium and ruthenium. As the ratio of the total amount of titanium oxide to iridium oxide to ruthenium oxide increases to more than 3: 1, the catalytic activity of the coating apparently decreases due to a change in the conductivity nature as the titanium oxide becomes enriched in the coating because titanium oxide is an n-type semiconductor.

If the molar ratio of iridium oxide to ruthenium oxide is less than 0.75: 1 to 1: 1, the durability of the coating decreases, especially with respect to the oxygen evolved, while above a ratio of 3: 1 the adhesion properties of the coating deteriorate.

The electrode of the present invention can be manufactured by a conventional method.

For example, the titanium substrate of the electrode is pre-degreased, etched, rinsed in deionized water, and dried, after which the active coating is applied to the pretreated titanium substrate by various known methods. For example, a coating solution is prepared containing thermally decomposable metal compounds of the active coating components - iridium, ruthenium and titanium compounds. After applying the solution to the electrode substrate, the electrode is dried and then calcined at an elevated temperature. Thereby, thermal decomposition of the compounds takes place and a mixture of the corresponding metal oxides is formed. The coating is made multi-layered. Each layer is applied according to the above procedure. The number of layers is determined by the desired proportion of active coating to be applied to the unit area.

8 74997

Another known method that can be used to apply the active coating to the electrode substrate comprises electron beam treatment of the oxide mixture, the mixture being pre-applied uniformly to the surface of the electrically conductive substrate by precipitation. According to this procedure, a finely ground, powdered mixture of titanium, iridium, and ruthenium is applied by precipitation in alcohol or acetone on a titanium substrate placed on the bottom of a vessel. The electrode is then dried in a folder of precipitated powder and calcined. The semi-finished product thus prepared is then placed in a vacuum chamber where it is subjected to electron spraying.

The composition of the coating thus prepared can be analyzed, for example, by analytical chemistry methods, for example, by peeling the coating from the substrate, melting a portion of the coating layer to separate it from the substrate, melting the coating with alkali or alkali metal oxides, dissolving the sample and then performing chemical analysis.

Example 1

An electrode is prepared with an active coating having the following composition in mole percent: TiCl 2 -70.8, Ι1Ι2 “12.5, RuC> 2-16.7 and the ratio TiCl 2: (IrCl 2 + 25 RuO 2) = 2.44: 1 and IrCl 2: RuCl 2 = 0.75: 1.

The electrode is manufactured as follows. The titanium plate (size 20 x 30 x 2 mm) is degreased in a solution containing 5 g / l NaOH, 30 g / l Na3PO4 and 40 g / l Na2CO3 at 80 ° C for 10 minutes, washed and etched for 15 minutes in hydrochloric acid solution (25% by mass) at 100 ° C, then rinsed in deionized water and dried at 40 ° C.

For application of the active coating, a coating solution is prepared from the following starting solutions: an aqueous solution of ruthenium hydroxide (RuOHCl 2) at a concentration of 150 g / l; an aqueous solution of titanium tetrachloride (TiCl 2) with a concentration of 220 g / l (calculated as TiCl 4); an aqueous solution of iridium trichloride (IrCl 2) at a concentration of 199.6 g / l.

The coating solution for applying the active coating is prepared by mixing together the above-mentioned solutions of ruthenium hydroxide and titanium tetrachloride and adding a solution of iridium trichloride (IrCl-) to the mixed RuOHCl 2 / TiCl 4 solution.

J 3 The coating solution contains 5.35 cm of RuOHCl 2 solution,

3 3 J

5.35 cm TiCl 2 solution and 4.0 cm IrCl 2 solution. The active coating is made multilayer. Each layer is applied according to the following procedure: the application rate of the coating solution 2 for the 1st layer is 25-30 ml / m 2. In this way 4-6 coats are applied. The total consumption of precious metals 2 is 7-9 g / m of work surface. After application of each layer, the electrode is first dried at 150 ° C, then calcined at 350 ° C for 20 minutes while treating the first 2-3 layers, subsequent layers are calcined at 450-500 ° C for 20-40 minutes.

The electrode was tested to determine its anodic potential and durability.

Anodic potential measurements were performed under chlorine electrolysis conditions: sodium chloride solution concentration - 280 g / l, temperature 90 ° C, pH 3.0 - 3.5, current density 1000; in 2000; 4000; 6000 and 10,000 A / m2 and chlorate-25 under electrolysis conditions: 400 g / l NaClO-j, 100 g / l NaCl, pH value 7, current density 1000-3000 A / m2, temperature 80 ° C.

The durability of the electrodes was studied using several methods: a method using variable polarity and amalgamation; by electrolysis in NaOH solution.

30 The method using variable polarity and amalgamation is based on the following: the test sample is subjected to alternating anodic and cathodic polarization for 40 minutes at a current density of 1 A / cm2 at 60 ° C in a 300 g / l solution of sodium chloride. The Elekt-35 Rodi is then immersed in sodium amalgam for 30 seconds at a sodium content of 0.2% by mass. After this treatment, the electrode is rinsed in distilled water, dried and the weight loss is determined.

The wear resistance of the electrodes in the electrolysis of NaOH solutions is examined under the following conditions: NaOH solution concentration 200 g / l, temperature 90 ° C, current density 2 A / cm 2, 5 the weight loss of the sample and the time taken to "clog" the anode are determined.

The electrode thus manufactured and tested corresponds exactly to the electrode of the present invention.

The test results (sample A) are shown in the table below.

Example 2

The electrode is prepared as described in Example 1 above except that the composition of its active coating is as follows in molar percent: TiC> 2 -70.0, 15 IrO 2 "15.0" RuO 2 ~ 15.0 3a ratio TiO 2: (IrO 2 + RuO 2 = 2, 33: 1 and IrC> 2; RuO 2 = 1: 1.

For the application of the active coating, a coating solution is prepared by mixing together the solutions mentioned in Example 1? ruthenium hydroxide solution and titanium-20 tetrachloride solution and then adding a solution of iridium trichloride (IrCl 2) to the stirred RuOHCl 4 / TiCl 2 solution.

The coating solution contains 4.8 cm 2 of RuOHCl 2 solution,

3 3 J

5.2 cm TiCl4 solution and 4.8 cm IrCl4 solution.

The test results are shown in Table 25 later (Sample B).

Example 3

The electrode is prepared according to Example 1 above except that the composition of the active coating is as follows, in molar percentages: TiO 2 to 70.0, IrO 2 to 20.0, 30 RuC> 2 “3-0.0 and the ratio TiO 2: (IrC> 2 + RuO 2) - 2.33: 1 and IrO 2: RuC> 2 = 2: 1.

The coating solution for applying the active coating is prepared by mixing together the solutions of ruthenium hydroxide and titanium tetrachloride according to Example 1, followed by adding a solution of iridium trichloride (IrCl 2) to the stirred RuOHCl 3 / TiCl 4 solution.

Il 11 74997 3 The coating solution contains 3.2 cm of RuOHCl .. solution,

3 3 J

5.3 cm TiCl3 solution and 6.4 cm IrCl3 solution.

The composition of the electrode thus prepared corresponds to the composition of the electrode of the present invention. The test results are shown in the table later (sample C).

Example 4

The electrode is prepared as described in Example 1 except that the composition of the active coating is as follows, in molar percentages: TiCl 2 to 75.0, IrCl 2 to 18.7, RuCl 2 to 10 6.3 and the ratio TiO 2: 2 + RuO 2) = 3: 1 and IrCl 2 = RuCl 2 = 3: 1.

For application of the active coating, a coating solution is prepared by mixing together the ruthenium hydrochloride and titanium tetrachloride solutions mentioned in Example 1 and adding a solution of iridium trichloride (IrCl ..) to the mixed RuOHCl 3 / TiCl 4 solution.

J 3 The coating solution contains 2,0 cm of RuOHCl,

3 -3 J

5.7 cm TiCl 2 solution and 6.0 cm IrCl 2 solution.

The electrode prepared in this example (sample D) corresponds in composition to the electrode of the present invention.

Example 5

The electrode is prepared as described in Example 1 except that the composition of the active coating in molar percentages is as follows: TiO 2 - 50.0, IrO 2 - 30.0, RuO 2 - 20.0 and the ratio TiO 2: (lrO 2 + RuC> 2) = 1: 1 and IrO 2: RuCl 2 = 1.5: 1.

For application of the active coating, a coating solution is prepared by mixing together the ruthenium hydroxide and titanium tetrachloride solutions mentioned in Example 1 and adding a solution of iridium trichloride (IrCl 2) to the mixed RuOHCl 3 / TiCl 4 solution.

J 3 The coating solution contains 6,4 cm of RuOHCl solution,

3 3 J

3.8 cm TiCl 3 solution and 9.6 cm IrCl 3 solution.

The electrode produced corresponds to the electrode of the present invention. The test results of the electrode thus prepared (sample E) 35 are shown in the table later.

12 74997

Example 6

An electrode consisting of an electrically conductive titanium substrate measuring 20 x 30 x 2 mm and having an active coating having the following composition in molar percentages is as follows: TiO 2 to 63.5, IrO 2 to 2 3.3, RuO 2 to 13 , 2 and the ratio TiC> 2: (IrO 2 + RuC> 2) = 1.75: 1 and IrC> 2: RuC> 2 = 1.75: 1. The electrode is prepared as follows.

The titanium plate is degreased in a solution containing 5 g / l NaOH, 30 g / l Na 2 PO 4, 40 g / l Na 2 O 2 at 80 ° C for 10 minutes, after rinsing it is etched in 25% HCl solution. At 100 ° C for 15 minutes and then washed in deionized water and dried at 40 ° C.

15 For the application of the active coating, the oxides of titanium, iridium and ruthenium are ground and sieved through a sieve with apertures of 30 micrometers. The screened powder is mixed with alcohol or acetone.

Depending on the surface area of the titanium substrate, the weighed amount of the oxide mixtures 2 is 1.5 to 2 mg / cm. The powder is evenly deposited on the titanium substrate by allowing it to settle on the substrate at the bottom of the vessel. The electrode with the precipitated powder is dried and then calcined in air at 450-600 ° C for 10-20 minutes. The semi-blank thus prepared is placed in a vacuum chamber where it is subjected to electron beam treatment at a scanning frequency of 20 Hz and a treatment current of 80 microamperes. The electrode thus prepared corresponds to the electrode of the present invention. The test results are shown in the table later.

30 Example 7

The electrode is prepared as described in Example 1 except that the composition of its active coating is as follows in molar percentages: TiO 2 to 55.6, IrCl 2 to 24.7, RuCl 2 to 19.7 and the ratio TiO 2: (IrCl 2 + RuO 2) = 1, 25: 1 and IrO 2:35 RuO 2 = 25 '1.

For application of the active coating, a coating solution is prepared by mixing together the ruthenium hydroxide and titanium tetrachloride compounds of Example 1.

It 13 74997 solutions and adding a solution of iridium trichloride (IrCl 2) to the stirred RuOHCl / TiCl 2 solution.

J 3 The coating solution contains 6.3 cm of RuOHCl solution, 3 3 3 of 4.2 cm of TiCl4 solution and 7.9 cm of IrCl-j solution.

The electrode obtained (sample G) corresponds in composition to the composition of the present invention.

The test results are shown in the table later.

Example 8

The electrode is prepared as described in Example 1 above, except that the composition of the active coating is as follows in molar percentages: TiO 2 to 66.7, IrO 2 to 23.8, RuO 2 to 9.52 and the ratio TiO 2: (IrO 2 + RuO 2> = 2: 1 and IrC> 2: RuO 2 = 2.5: 1.

For application of the active coating, a coating solution is prepared by mixing together the solutions of ruthenium hydroxide and titanium tetrachloride shown in Example 1 and adding a solution of iridium trichloride (IrCl 3) to the stirred RuOHCl 3 / TiCl 4 solution. The coating solution 3 J 3 contains 3.0 cm RuOHCl solution, 5.1 cm TiCl 3 solution and 3 J 4 7.6 cm IrCl 3 solution.

The composition of the electrode thus prepared corresponds to the composition of the electrode of the present invention. The test results are shown in the table later (sample H). Example 9 An electrode is prepared in the same manner as the electrode shown in Example 1 except that the composition of the active coating in molar percentages is as follows: TiO 2 to 45.0, IrO 2 to 22.0, RuO 2 to 33 and the ratio TiO 2: (IrO 2 + RuO 2 = 0, 82: 1 and IrO 2: RuO 2 = 0.67: 1.

To apply the active coating, a solution is prepared by mixing together the ruthenium hydroxide and titanium tetrachloride solutions mentioned in Example 1 and adding a solution of iridium trichloride (IrCl 3) to the resulting mixed RuOHCl 3 / TiCl 4 solution.

J 3 35 The coating solution contains 10,5 cm of RuOHCl solution,

3 3 J

3.4 cm TiCl 3 solution and 7.0 cm IrCl 3 solution.

14 74997

The obtained electrode (Sample J) shows an electrode whose active coating contains oxides of titanium, ruthenium and iridium, the content of titanium oxide in the mixture being less than 50 mol%.

5 The test results for this sample are shown in Table 5 below.

Example 10

The electrode prepared according to Example 2, the active coating of which contains in molar percent: TiO 2 - 70.0, 10 IrO 2 "" * 5.0, RuO 2 - 15.0, was tested under the electrolysis conditions of the effluent, the effluent containing 27.5 mg / l of phenols at pH 2. at 4 and a current density of 2.8 A / dm. Wastewater treatment from phenols was 95% with a power consumption of 32 kWh / m \ 15 Example 11

The electrode of Example 2, the active coating of which contains in molar percentages: TiO 2 to 70.0, IrC> 2 to 15.0, RuC> 2 to 15.0, is used in the galvanic glazing process of objects. The electrolyte contains 30 g / l KAu (CN) 2, 20 citric acid 100 g / l, KOH 40 g / l and 100 mg / l cobalt sulphate.

The method uses a pH of 3.5 to 30 ° C, a temperature of 2 and a current density of 10 mA / cm. The current efficiency when galvanizing a copper cathode is 90%.

25 Example 12

Several electrodes are fabricated and tested for comparison purposes.

An electrode is prepared consisting of a conductive titanium plate substrate measuring 20 x 30 x 2 mm 30 and coated with an active coating having the following composition in molar percentages: TiO 2 to 67.0, RuO 2 to 33.0 and a ratio of TiO 9: RuO, = 2: 1.

Δ 3 The coating solution contains 10.6 cm RuOHCl

3 J

and 5.2 cm of TiCl 2 solution. The application of the coating solution was performed as described in Example 1 above.

The composition of the electrode thus prepared (Sample 1) corresponds to the composition of the known OPTA electrode according to USSR Inventor's Certificate No. 369,923.

il is 74997 The test results of this electrode are shown in the following table (Sample 1).

The electrode is prepared in the same manner as the electrode shown in Example 1, except that its active coating contains the following components in molar percentages: T1O2 to 88.66, IrO2 to 3.91, RuO4 to 7.4 3 and the ratio TiO2: (IrC> 2 + RuO 2) = 7.8: 1 and IrO 2: RuO 2 = 0.528: 1.

For application of the active coating, a coating solution is prepared by mixing together the solutions of ruthenium hydroxide and titanium tetrachloride shown in Example 10 and adding a solution of iridium trichloride (IrCl 2) to the resulting stirred RuOHCl 3 / TiCl 4 solution.

The coating solution contains 2.4 cm 2 of RuOHCl 2 solution,

3 3 J

6.7 cm TiCl 2 solution and 1.25 cm IrCl 2 solution.

The obtained electrode (Sample 2) corresponds in composition to a known electrode according to U.S. Patent No. 3,948,751.

The test results (sample 2) are shown in the table.

An electrode is prepared as in Example 1 except that the composition of its active coating in mole percent is as follows: TiO 2 - 78.95, IrO 2 - 7.25, RuO 2 - 13.8 and the ratio TiO 2: (IrCl 2 + RuO 2 = 3 , 75: 1 and IrO 2: RuCl 2 = 0.525: 1.

For application of the active coating, a coating solution is prepared by mixing together the RuOHCl-1 and TiCl 4 solutions mentioned in Example 25 and adding a solution of iridium trichloride (IrCl-J) to the resulting mixed RuOHCl 3 / TiCl 4 solution.

J 3 The coating solution contains 4.4 cm of RuOHCl solution, 3 3 · * 6 cm of TiCl 2 solution and 2.3 cm of IrCl 2 solution.

The resulting electrode (Sample 3) is similar in composition to the active coating of the electrode of U.S. Patent No. 3,948,751.

The test results for sample 3 are shown in the following table.

Table 16 74997

No. Properties __________________________1_____2______3______A____B__ 1 2 3456 7

Ratio of oxides in active mass mol% 1 TiO 2 67 88.66 78.95 70; 8 70; 0 2 IrO 2 - 3.91 7.25 12.5 15.0 3 RuO 2 33 7.43 13.8 16.7 15.0 4 TiO 2} (IrO 2 RuO 2) 2: 1 7.8: 1 3- 75: 1 2.44: 1 2.33: 15 IrO 2: RuO 2 - 0.528: 1 0.525: 1 0.75: 1 1: 1

Anode potential under chloroelectrolysis conditions at V (ΤΪΗΕ) current density, A / nr 6 I; 000 1.3 1.45 I; 32 1.30 1.30 7 2,000 1.33 1.50 1.34 1.32 1.31 8 4,000 1.35 1.55 1.36 1.35 1.33 9 6,000 1.37 1.60 '1.38 1.36 1.34 10 10,000 1.40 1.62 1.39 1.37 1/36

Anode potential under chlorate electrolysis conditions, v (NHE) current at density, A / itr 11 1,000 1.40 1 * 37

12 2,000 1.43 I; 4I

15 3,000 1.49 1.44 11 17 74997

Table (continued) 'No: t Properties

1 2 3 AB

"I --------------- --------- 2 3 4 ------- ------ ----- 5 5 ----- T

Electrode resistance to germination of disappearing polarity and amalgamation method, mg / cnr 14 0.2 0.4 0.3 0.15 0.7

Electrode resistance when electrolysing a solution containing 200 g / l NaCH, loss of active mass (mg) during electrolysis, hours

15 5 0.4 0.3 0.6 0.3 0? I

16 10 0.9 0.6 0.8 0.4 0; 2 17 15 1.2 0.9 1.2 0.6 0.3 18 20 1.7 1.4 1.5 0.8 0, 7 19 25 2.1 1.8 2.0 0.9 1.1 20 30 2.4 2.5 1.7 2.5 21 3.7 ij9 3.0 22 45 2.8 3.6 25 50 4.0 5.0 24 55 4.6 5.5 25 60 4.8 5.5 26 70 5.8 Operating time for anode rupture, hours 27 23 30 40 60 70

Initial amount of active mass, mg 28 5.6 5.5 5.8 5.4 5.8 18

Table (cont'd) 74997

Ho Samples

C D E F G H I

1 8 9 10 11 12 15 14 1 70.0 75.0 50; 0 65.5 55.6 66.7 45 2 20.0 18.7 50.0 25.3 24.7 25.8 22 5 10.0 6.5 20.0 15.2 19.7 9.5 33 4 2.33: 1 3: 1 1: 1 1.75: 1 1.25: 1 2: 1 0.82: 1 5 2: 1 3: 1 1.5 * 1 1.75: 1 1.25: 1 2.5: 1 0.67: 1 6 1.30 1.51 1.32 1.50 1.50 1.50 1.31 7 1.31 1.32 1.33 1.31 1.31 1.31 1.32 8 1.33 1.34 1.35 1.33 1.32 1.33 1.34 9 1.34 1, 35 1.36 1.34 1.33 1.34 1.36 10 1.35 1, .36 1.37 1.36 1.35 1.35 1.37 ΪΪ 1 ^ 36 12 1.40 13 1, 43 14 0.05 0.08 0jl7 0.5 15 0.2 0.1 0.3 0? 4 0; 2 0.1 0.3 16 0.3 0.2 0.5 0.7 0.3 0.4 0.5 17 0.5 0.4 0.9 0.9 0.4 0.5 0.7 18 0.6 0.5 1.7 1.7 1.5 0.6 0.7 0.9 19 0.8 0.9 2.5 2.1 0.7 0.8 1.1 20 1.8 1.2 3.1 2.7 1.1 1.3 1.7 21 2.7 2, 5 3.8 3.3 2.5 2.0 2.9 22 3.6 2.9 4.5 4.7 3.3 3.0 23 4.2 3.3 5.2 4.2.5.5 4 , 7 and 19

Table (cont'd) 74997

Ho Samples

C D S F G H I

18 9 10 11 12 13 14 24 5.0 3.6 5.0 5.1 25 5.3 4.3 5.1 5.2 26 5.4 5.4 5.1 5.5 5.4 27 70 70 50 45 70 70 40 28 5.5 5.2 5.6 5? 7 5.6 5.7 5.8

Claims (3)

An electrode for the electrolysis of electrolyte solutions, comprising a passivated metal support having a coating of a mixture of titanium, iridium and ruthenium oxides having a titanium oxide content of more than 50 mol%, characterized in that said coating contains the above-mentioned constituents of titanium oxide. the total amount of oxides of iridium 10 and ruthenium is 1: 1 to 3: 1 and the molar ratio of iridium oxide to ruthenium oxide is 0.75: 1 to 3: 1. Electrode for electrolysis of electrolyte solutions according to Claim 1, characterized in that the molar ratio of titanium oxide to total oxides of iridium and ruthenium is from 1.75: 1 to 3: 1 and the molar ratio of iridium oxide to ruthenium oxide is from 0.75: 1 to 1.75: 1. 2 ° 74997 Electrode for electrolysis of electrolyte solutions according to Claim 1, characterized in that the molar ratio of titanium oxide to total iridium oxide and ruthenium oxide is 1.25: 1 to 2.5: 1 and the molar ratio of iridium oxide to ruthenium oxide is 1.25: 1 to 2.5: 1. 1. II