FI65092B - ELEKTROD FOER ELEKTROKEMISKA FOERFARANDEN - Google Patents

Description

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Patents · and Register Holders .... .......... .

. . (44) Date of issue of the publication. -

Patent- och register! Tyrelsan Ansekan iitlagd och utl.tkrifMn pubMcured 30.11. 83 (32) (33) (31) Requested stuolkeus Bag «rd prtorHst (71) (72) Vladimir Leonidovich Kubasov, Kirovogradskaya ulitsa, U, building 2, sq. Km. 135, Moscow, Leonid Ivanovich Jurkov, Tashkentskaya ulitsa 22, building 1, kv. 12l +, Moscow, Vladimir Borisovich Busse-Machukas, Izmailovsky Bulvar, 37, kv. 27, Moscow, Georgy Nikolaevich Kokhanov, ulitsa Melnikova, 23, kv. 29, Moscow, Florenty Iserovich Lvovich, 1 Nizhne-Mikhailovsky Proezd, 16, kv. The present invention relates to electrodes for electrochemical processes comprising an electrically conductive substrate coated with an active compound containing: Electrode for an electrochemical process comprising an electrically conductive substrate coated with an active compound containing metal and boron oxides.The electrodes can be used as an anode in the electrolysis of alkali metal chloride solutions to produce chlorine and sodium hydroxide using electrolysis equipment with a filter diaphragm.It is also suitable for electrolytic chlorate production, electroplating generating, electroorganic synthesis and wastewater treatment and similar effluents.

Until recently, graphite anodes have been widely used in various electrochemical processes. Obvious advantages of such anodes are the use of readily available electrode material and insensitivity to short circuits. However, graphite anodes have a high chlorine discharge potential and, in fact, a high electrolyzer voltage and are not long-lasting, a limit of 2,65092 that necessitates frequent opening of the electrolysers to allow anode series replacements to be performed. Besides, graphite anodes are large and heavy, a feature that increases the dimensions of electrolysis equipment and the effective surface area of electrolysis plants beyond reasonable limits.

Electrodes containing an electrically conductive substrate coated with an active mass are currently widely used. The electrically conductive substrate is suitably made of a metal such as titanium, tantalum, zirconium, niobium or an alloy of these metals passivated by anodic polarization. It can exist in substantially any form, such as a perforated or closed plate, a rod, a lattice, or a cermet.

An electrode assembly is known in the art in which the active mass contains oxides or oxide mixtures of platinum metals, e.g. ruthenium oxide (cf. GB Patent No. 1168558). The active surface is as thin as 3-10. Metal anodes are characterized by improved electrochemical properties, unchanged throughout long service life, smaller dimensions and lower weight, high active mass stability, and long anode series change intervals, e.g., several years, which is generally a clear advantage over prior art graphite anodes.

In the above-mentioned electrode for electrochemical processes, which contains an electrically conductive substrate made of a passivated material and coated with a layer of active mass containing a metal oxide or a mixture of metal oxides from a platinum group (platinum, iridium, ruthenium, rhodium, palladium, osmium); the active pulp may contain oxides of manganese, lead, cobalt, titanium, tantalum and zirconium or silica in an amount of less than 50% by weight of metal oxides or a mixture of metal oxides of platinum group origin (cf. GB patent No. 1168558) . In such an electrode, the wear of the active mass containing, for example, ruthenium oxide is 7.5 mg / 1000 amp-hours at a current density of 0.2 A / cm in chlorine diaphragm electrolysis under standard conditions, the loss of active mass being determined gravimetrically.

3,65092

An electrode is also known in the art in which an electrically conductive, passivated metal substrate is coated with a layer of active mass containing metal oxides from the platinum group and oxides of ferrous metals and manganese which do not have rectifying properties. The active mass contains less than 50% by weight of platinum metal oxide compared to the weight of the metal oxide or mixture of metal oxides which does not have rectifying properties (cf. "Electrochemistry", Vol. XII, No. 5,1976, SNTL Academy of Sciences, Moscow, pages 787 -789).

In such an electrode, the consumption of active mass is 2 4-5.7 mg / 1000 Ah at a current density of 0.2 A / cm in chlorine diaphragm electrolysis under standard conditions, the total number of ampere-hours during the test being 787-896 in the case where the active mass contains 31% by weight of ruthenium oxide and 69 % by weight of iron oxides.

In a known method of manufacturing an electrode, an active mass containing oxides of platinum metals, ferrous metals and manganese is deposited on an electrically conductive substrate made of a passivated material, and the steps include applying a solution of thermally decomposing compounds of said metals to said substrate and heat treating it. The solution of thermally decomposable metal compounds can be applied repeatedly (cf. "Electrochemistry", Vol. XII, No. 5, 1976, Academy of Sciences of the USSR, Moscow).

The active mass is applied to an electrically conductive substrate using a solution of platinum metals, ferrous metals and manganese thermally decomposable metal compounds, after which the substrate is thermally treated.

In another known method, the substrate is initially treated with a solution of a platinum group thermally decomposable metal compound, the subsequent steps being thermal treatment of the substrate, application of a solution of thermally decomposed compounds to the substrate and repeated thermal treatment of the substrate (cf. DE 2110043 and 2126840).

The object of the present invention is to reduce the consumption of platinum metals without deteriorating the electrochemical properties of the electrode and to extend its service life.

The present invention is based on the provision of an active mass of 4,65092 for an electrode, the composition of which makes it possible to reduce the consumption of platinum metals in the use of the electrode.

In the electrode for electrochemical processes according to the invention, comprising an electrically conductive substrate coated with a layer of active mass containing oxides of platinum metals, ferrous metals and manganese, the active mass according to the invention further contains 0.1 to 50% by weight of boron trioxide.

Briefly, the essence of the invention is as follows: providing an electrode for electrochemical methods with a substrate of electrically conductive material coated with an active mass consisting of the following components by weight of the active mass: at least one platinum metal oxide 5-45 at least one ferrous metal oxide; 19 - 94 5 manganese oxide 'boron oxide 0.1 - 50

In order to improve the durability of the electrode, it is preferable that the active mass contains ruthenium oxide and iron oxide or cobalt oxide or a mixture of manganese and cobalt oxide.

There is also provided a method of manufacturing an electrode for electrochemical methods, wherein a substrate of electrically conductive material is coated with an active mass by applying to the substrate a solution containing a boron thermally decomposable compound and at least one ferrous and possibly manganese thermally decomposable compound and at least one platinum metal thermally decomposable compound and said substrate at a temperature of 360-500 ° C. It is preferred that the amount of components contained in the solution, calculated as a percentage by weight of the amount of active mass, is as follows: at least one platinum metal oxide 5-45 at least one ferrous metal oxide, manganese oxide 19-94.5 boron oxide 0.1-50

It is expedient for said solution to contain either boron, iron and ruthenium or thermally decomposable compounds of boron, cobalt and ruthenium or boron, cobalt, manganese and ruthenium.

I; 5,65092

There is also provided a method of making an electrode for electrochemical methods, wherein an electrically conductive substrate is coated with an active mass by applying to said substrate a first solution of a platinum metal thermally decomposable compound and treating the substrate at 360-500 ° C, followed by applying a second solution containing a thermally decomposable boron compound and at least one ferrous metal thermally decomposable compound and optionally manganese thermally decomposable compound and at least one platinum metal thermally decomposable compound, and the substrate is thermally treated at a temperature of 360 to 500 ° C.

It is desirable that the amount of components contained in the solutions, calculated as a percentage by weight of the amount of active mass, is as follows: at least one platinum metal oxide 5-45 at least one ferrous metal oxide, manganese oxide 19 to 94.5 boron oxide 0.1 to 50

In order to improve the durability of the electrode, it is expedient for the first solution to contain a thermally decomposable ruthenium compound and the second solution for a thermally decomposable boron and cobalt compound or a boron, cobalt and manganese compound, and in addition at least one thermally decomposable platinum metal compound. ruthenium compound.

For electrochemical methods, there is provided an electrode consisting of a substrate of electrically conductive material and an active mass applied to the substrate, containing oxides of platinum metals, ferrous metals, manganese and further containing boron oxide in an amount of 0.1 to 50% by weight based on the amount of active mass.

The active pulp preferably contains ruthenium oxide and iron oxide or cobalt oxide or a mixture of manganese and cobalt oxides. In this proposed method of manufacturing an electrode for electrochemical processes, an active mass is deposited on an electrically conductive substrate by steps such as applying to the substrate a solution of platinum metals, ferrous metals and manganese thermally decomposable compounds and thermally treating the substrate at an elevated temperature. The process according to the invention is characterized in that 0.1 to 50% by weight of a thermally decomposable boron compound, based on the amount of active mass and expressed as boron trioxide, is added to the solution. To improve the stability of the electrode, said solution preferably contains thermally decomposable boron, iron and ruthenium or boron, cobalt and ruthenium or boron, cobalt, manganese and ruthenium compounds.

In another proposed method of making an electrode for electrochemical processes, an active mass is deposited on an electrically conductive substrate by applying a first solution of at least one platinum metal thermally decomposable compound, treating the substrate at an elevated temperature, then applying a second solution containing at least one ferrous metal and possibly manganese. a degradable compound, wherein the second solution may contain one or more platinum metal thermally degradable compounds, and treating the substrate at an elevated temperature. In this embodiment of the process according to the invention, 0.1 to 50% by weight of a thermally decomposable boron compound, based on the amount of active pulp and expressed as boron trioxide, is added to the second solution.

It is preferred that the first solution contains a thermally decomposable ruthenium compound and the second solution contains thermally decomposable boron and cobalt or boron, cobalt and manganese or boron, cobalt and ruthenium compounds.

The recommended concentrations of metal oxides guarantee a high electrochemical activity of the electrode, which no longer increases when the proportion of components exceeds 50% by weight. The incorporation of boron trioxide into the active mass greatly improves the stability of the electrode compared to electrodes whose active mass contains only oxides of platinum metals, ferrous metals and manganese.

It has been found that the stability of the active pulp increases with an amount of boron trioxide of 0.1 to 50% by weight. Increasing the boron trioxide content by more than 50% by weight severely impairs the electrochemical activity of the electrode.

7 65092

Electrodes made according to the method proposed herein have an active surface with a stability of 1.2 to 2 times the stability of prior art electrodes.

The electrocatalytic properties of the electrode of the present invention are substantially similar to those of known electrodes. Electrocatalytic activity has been evaluated by comparing the anode potential to a standard hydrogen electrode under chlorine diaphragm electrolysis conditions. At a current density of 0.2 A / cm at anodipolarization, the electrode potentials have been found to be 1.34-1.37 V compared to a standard hydrogen electrode (s.H.e.) with a solution containing 300 g / l NaCl at 90 ° C, except for combinations containing manganese oxide.

The electrode of the present invention can be manufactured as follows: a suitable electrically conductive material, such as a titanium substrate, is treated with a solution of a platinum metal compound mixed with a ferrous metal and manganese compound which also contains boric acid. The substrate is then thermally treated at a temperature of 360-500 ° C.

In electrode fabrication, the electrically conductive substrate can be treated with a solution of thermally decomposable compounds of platinum metals, the subsequent steps being thermal treatment of the substrate at 360-500 ° C, application of a solution of thermally decomposing compounds of boron and platinum metal, ferrous metal and manganese, and thermal treatment of the substrate.

In the manufacture of the electrode, the electrically conductive substrate can also be treated with a solution containing thermally decomposable metal compounds of platinum metals, the subsequent steps being thermal treatment of the substrate at 360-500 ° C, application of a second solution of boron and ferrous metal and manganese thermally decomposing compounds and thermal treatment of the substrate.

In the preparation of the electrode in another embodiment of the invention, the electrically conductive substrate can be treated with a solution containing thermally decomposable compounds of boron and platinum metals and ferrous metals and possibly manganese, the following steps being drying at 20-150 ° C and thermal treatment of the substrate 360-500 ° C: n temperature.

The application of the solution and the heat treatment operations can be performed repeatedly.

8 65092

Typical examples of the practice of the invention are set forth below.

Example 1

Consider an electrode containing an electrically conductive substrate, a titanium plate 30x40x2 mm in size, coated with a layer of active mass containing, by weight: boron trioxide 0.4: ruthenium oxide 31; and iron oxides 68.6.

The preparation procedure was as follows: the titanium plate was degreased with 5% NaOH solution at 60 ° C for 10 minutes and then pickled with 20% HCl solution at 100 ° C. To apply the active mass, a solution containing 7.8 ml of ferronitrate (1 molar solution), 1 g of a ruthenium chloride solution with a concentration of 19.2% by weight and 0.2 ml of boric acid solution (0.5 molar solution) was prepared. The solution was applied to the prepared titanium surface and allowed to dry for 40 minutes, gradually raising the temperature from 20 ° C to 150 ° C. Next, a waiting period of 20 minutes was maintained at 150 ° C and heat treatment was performed at 360 ° C for 20 minutes. The procedure was repeated 6 times. After all the layers were applied, the electrode was heated at 470 ° C for one hour. The total amount of active mass deposited on the electrode was 13.2 g / m 2.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-5 with a solution containing 300 g / l NaCl at 90 ° C at an anode current density of 0.2 A / cm 2. The anode potential compared to the standard hydrogen electrode was found to be 1.35 V (s.h.e.). The total number of ampere hours during the experiment was 2724.4. No losses of active mass were observed gravimetrically. The measurement accuracy of the anode weight was -0.05 mg.

Example 2

An electrode similar to Example 1 was prepared using the procedure described above. The solution was applied to the prepared titanium surface and allowed to dry at 120 ° C for 15 minutes. Next, a heat treatment was performed at 470 ° C for 10 minutes. The procedure was repeated eight times. The total amount of active mass deposited on the electrode was 17 g / m 2.

i <9 65092

The electrode was tested under chlorine diaphragm conditions at pH 4.5-5 with a solution containing 300 g / l NaCl at 90 ° C with an anode current density of 0.2 A / cm. The anode potential was found to be 1.35 V (s.h.e.). The total number of plotting hours during the experiment was 2486. The loss of active mass during the electrolysis procedure was 0.2 mg / 1000 A.h.

Example 3

An electrode similar to that described in Example 1 was prepared using the procedure described above, but omitting the preparative drying step.

The total amount of active mass deposited on the electrodes was 11 g / m 2.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-4 with a solution containing 280 g / NaCl at 90 ° C at an anode current density of 0.2 A / cm. The anode potential was found to be 1.36 V (s.h.e.). The total number of ampere hours during the experiment was 0.9 mg / 1000 A.h.

Example 4

An electrode similar to that described in Example 1 was prepared using the procedure described above, but omitting the preparative drying step. The active mass should contain as a percentage by weight: ruthenium oxide 31; iron oxides 67; and boron trioxide 2. The total amount of active mass deposited on the electrode was 15.3 g / m 2.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-4 with a solution containing 280 g / l NaCl at 90 ° C with an anode current density of 0.2 A / cm 2. The anode potential was found to be 1.35 V (s.h.e.). The total number of ampere hours during the experiment was 1605.6. Losses of active mass throughout the application procedure were 0.56 mg / 1000 A.h.

Example 5

An electrode similar to that described in Example 1 was prepared, but using an active coating containing, by weight: ruthenium oxide 31; iron oxide 59; and boron trioxide 10. The total amount of active mass deposited on the electrode was 10.5 g / m 2.

10 65092

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-5 with a solution containing 280 g / l NaCl at 90 ° C with an anode current density of 0.2 A / cm 2. The anode potential was found to be 1.37 V (s.h.e.). The total number of ampere hours during the experiment was 1751. No loss of active mass was observed.

Example 6

An electrode similar to that shown in Example 1 was prepared using the above procedure, but omitting the preparative drying step, the active mass containing as a percentage by weight: ruthenium oxide 31; iron oxides 19; and boron trioxide 50.

2

The total amount of active mass deposited on the electrode was 13 g / m. In the manufacture of the electrode, a heat treatment was performed at a temperature of 500 ° C.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-5 with a solution containing 300 g / l NaCl, o 2 at 90 ° C with an anode current density of 0.2 A / cm. The electrode potential was found to be 1.37 V (s.h.e.). The total number of ampere hours during the experiment was 900. The active pulp consumption during the electrolysis procedure was 1.2 mg / 1000 A.h.

Example 7

Consider an electrode comprising an electrically conductive substrate represented by a 30 x 40 x 2 mm titanium plate coated with a layer of active mass containing, by weight: ruthenium oxide 5; manganese oxide 84.3; cobalt oxide 10.3; and boron trioxide 0.4.

The manufacturing procedure was as follows. A titanium substrate was prepared using the procedure described in Example 1. Solutions containing magnesium nitrate (1-molar solution), cobalt nitrate (1-molar solution), boric acid solution (0.5 molar solution) and ruthenium chloride solution with a ruthenium concentration of 19.2% by weight were used to apply the active mass. %. A layer of ruthenium chloride solution was applied to the prepared titanium substrate and heat treated at 370 ° C for 10 minutes. The amount of deposited ruthenium metal was 1.3 g / m 2. Next, a mixed solution of cobalt nitrate, magnesium nitrate and boric acid prepared from the above solutions was applied, and heat treatment was performed at 380 ° C for 20 l.

11 for 65092 minutes. The procedure was repeated ten times. The total amount of active mass deposited on the electrode was 35 g / m 2.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 3-5 with a solution containing 280 g / l NaCl at 90 ° C with an anode current density of 0.1 A / cm 2. The anode potential compared to the standard hydrogen electrode was found to be 1.5 V (s.h.e.). The total number of ampere hours during the experiment was 1070. The active pulp consumption was 3 mg / 1000 A.h.

Example 8

Consider an electrode comprising an electrically conductive substrate represented by a 30 x 40 x 2 mm titanium plate coated with a layer of active mass containing, by weight: ruthenium oxide 5; cobalt oxide 94.9; and boron trioxide 0.1.

The manufacturing procedure was as follows. A titanium plate was prepared as described in Example 1. To apply the active pulp, a mixture of cobalt nitrate solution (1 molar solution), boric acid solution (0.5 molar solution) and ruthenium chloride solution with a ruthenium concentration of 19.2% by weight was prepared. A layer of ruthenium chloride solution was applied to the prepared titanium substrate and then heat treated at 370 ° C for 10 minutes. The amount of layered metallic ruthenium was 2 1.3 g / m of treated area. Next, a mixed solution of cobalt nitrate and boric acid prepared from the above solutions was applied and heat-treated at 450 ° C for 20 minutes. After all the layers were applied, the electrode was heated to 470 ° C for one hour. The total amount of active mass deposited on the electrode was 30 g / m 2.

The electrode was tested under chlorine diaphragm electrolysis conditions at pH 4-6 with a solution containing 280 g / l NaCl at 90 ° C with an anode current density of 0.2 A / cm 2. The anode potential was found to be 1.36 V (s.h.e.). The total number of ampere hours was 2050. The consumption of active pulp was 3 mg / 1000 A.h.

Example 9

Consider an electrode consisting of a 30 x 40 x 2 mm titanium plate coated with a layer of active mass containing, by weight: ruthenium oxide 12 6 5092 45; iron oxide 53; and boron trioxide 2. An electrode was prepared using the procedure described in Example 1. A layer of a ruthenium chloride solution having a ruthenium concentration of 19.2% by weight was applied to the prepared titanium substrate and then subjected to a heat treatment at 370 ° C for 10 minutes. The amount of layered metallic ruthenium was 1.3 g / m of treated surface. The total amount of pulp deposited on the titanium plate was 12.5 g / m 2.

The electrode was tested under diaphragm electrolysis conditions at pH 3-4 with a solution containing 300 g / l NaCl at 90 ° C at an anode current density of 0.2 A / cm. The anode potential was found to be 1.35 V (s.h.e.). The total number of ampere hours was 1900. The consumption of active pulp during the electrolysis process was 1 mg / 1000 A.h.

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Claims (3)

13 65092 An electrode for electrochemical methods, which electrode comprises a substrate of electrically conductive material coated with an active mass, characterized in that the composition of the active mass in percentages by weight is as follows: at least one platinum metal oxide 5-45 at least one ferrous metal oxide, manganese oxide 19-94, 5 boron oxides 0.1 - 50 A method of manufacturing an electrode for electrochemical methods according to claim 1, wherein a substrate of electrically conductive material is coated with an active mass by applying to said substrate a solution containing platinum metals, ferrous metals, manganese thermally decomposable compounds and heat treating the substrate at an elevated temperature. that 0.1 to 50% by weight of a thermally decomposable boron compound, based on the amount of active mass and expressed as boron oxide, is added to the solution. A method of manufacturing an electrode for electrochemical methods according to claim 1, wherein a substrate of electrically conductive material is coated with an active mass by applying to said substrate a first solution containing at least one platinum metal thermally decomposable compound and heat treating the substrate at an elevated temperature. contains at least one ferrous metal thermally decomposable compound and optionally a thermally decomposable manganese compound and which may contain one or more platinum metal thermally decomposable compounds, characterized in that 0.1 to 50% by weight of a thermally decomposable boron compound, based on the amount of active mass and expressed as boron oxide, is added to the second solution.