JP2014505166A - Electrode for electrolytic cell - Google Patents

Abstract

The present invention relates to an electrode for generating a gaseous product in an electrolytic cell, the electrode comprising a metal support coated with at least two catalyst compositions, the outermost catalyst composition being chemically or physically Deposited by chemical vapor deposition and having a composition comprising a noble metal selected from the group of platinum group metals or oxides thereof.
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Description

  The present invention relates to an electrode suitable for operation as an anode in an electrolytic cell, for example as an anode for chlorine generation in a chlor-alkali electrolytic cell.

  The use of metal electrodes with catalyst coatings in electrolysis applications is known in the art. Electrodes consisting of a metal support with a coating based on precious metals or their oxides are used, for example, as cathodes for generating hydrogen in water or alkaline chloride electrolysis processes, It is used as an anode for generating oxygen in the electrometallurgical process and for generating chlorine in the electrolysis of alkali chlorides. This type of electrode can be produced by a thermal process, i.e. suitable pyrolysis of a solution containing the metal precursor to be deposited, galvanic deposition from a suitable electrolytic bath, or spraying or plasma spraying. Alternatively, it can be produced by direct metallization by chemical (or physical) vapor deposition.

For example, the electrolysis of sodium chloride brine aimed at producing chlorine and caustic soda has been activated with a surface layer of ruthenium dioxide (RuO ₂ ) to reduce the overvoltage of the reaction of generating chlorine at the anode. This can often be done with an anode consisting of a support of titanium or other valve metal. For this type of electrolysis, catalyst formulations based on a mixture of ruthenium, iridium and titanium oxides are also known, all of which can reduce the overvoltage of the reaction that generates chlorine at the anode. it can.

  This type of electrode is generally manufactured by a thermal process.

  The catalyst formulation can be deposited on the support by vapor deposition, which has the advantage that the deposition parameters of the coating can be controlled very accurately. However, these are basically characterized by being a batch type process, and in order to be able to process a single piece, the support is loaded into a suitable deposition chamber. There is a need to place this chamber in a slow pressure drop process that lasts for several hours. In addition to the significant duration of the process (usually several hours depending on the amount of precious metal required), applying a large amount of catalyst coating results in a coating with a very short life.

  Various aspects of the invention are set out in the accompanying claims.

In a first aspect, the present invention relates to an electrode for generating a gaseous product in an electrolytic cell, the electrode comprising a valve metal coated with at least one first catalyst composition and an outer catalyst composition. The at least one first catalyst composition comprises a noble metal selected from the group consisting of a valve metal oxide or a tin oxide and a white metal (PM), or an oxide thereof alone or in combination. Wherein the at least one first catalyst composition is obtained by pyrolysis of a precursor and the outer catalyst composition is an oxide of a noble metal selected from the group of white metals, or a single or mixture thereof wherein the said outer catalyst composition is deposited by chemical or physical vapor deposition method, the amount of noble metal in the first catalyst composition more than 5 g / m ² for the surface, and the outer The amount of the noble metal in the catalyst composition is in the range of 0.1 to 3.0 g / ^{m 2} for the surface.

  Surprisingly, the inventors have unforeseen features for both lifetime and potential reduction by depositing one final catalyst layer with specific properties via a chemical or physical gas phase. It has been found that an electrode having the same is obtained.

  In one embodiment, the first catalyst composition of the electrode according to the present invention contains titanium, iridium, ruthenium in the form of a metal or oxide.

  In one embodiment, the outer catalyst composition comprises ruthenium and / or iridium in the form of a metal or oxide.

In one embodiment, the amount of specific noble metal used in the first catalyst composition is in the range of 6-8 g / m ^{2 and} the amount of specific metal used in the outer catalyst composition is 1.5-2. The range is 5 g / m ² .

  In another aspect, the present invention relates to a method of manufacturing an electrode, the method comprising depositing an outer catalyst composition by chemical or physical vapor deposition, preferably in a group of white metals. By reactive sputtering of a noble metal selected from

  In a further aspect, the present invention relates to reactivating a used electrode, which comprises chemistry of an outer catalyst composition comprising an oxide of a noble metal selected from the group of white metals, or a single or mixture thereof. Depositing by physical or physical vapor deposition.

  In a further aspect, the present invention relates to an alkaline chloride solution electrolyzer, for example a sodium chloride brine electrolyzer intended to produce chlorine and caustic soda, which produces an anodic generation of chlorine (anode) on the electrode described above. Generation).

  The following examples are presented to demonstrate certain embodiments of the invention, and the feasibility of the invention is well demonstrated within the numerical values recited in the claims. One skilled in the art should understand that the compositions and techniques disclosed in the examples are indicative of the compositions and techniques found by the inventors to be sufficiently functional to practice the present invention. However, one of ordinary skill in the art, in light of the disclosure herein, may make many modifications in the specific embodiments disclosed without departing from the scope of the present invention. It should be understood that similar or similar results can be obtained.

Comparative Example 1
Corundum was sprayed on a sample of titanium mesh having a size of 10 cm × 10 cm, and the remaining portion was washed by jetting compressed air. The sample was then degreased with acetone in an ultrasonic bath for about 10 minutes. After drying, the sample was immersed in an aqueous solution containing 250 g / l NaOH and 50 g / l KNO ₃ at about 100 ° C. for 1 hour. After this alkali treatment, the sample was rinsed three times at 60 ° C. in deionized water, with the water being changed every time. The final rinse was done by adding a small amount of HCl (about 1 ml per liter of solution). After drying with air, the formation of a brown color due to the growth of the TiO _x thin film was observed. Then, RuCl ₃ · _3H 2 _O in a mixture of acidified water and 2-propanol in _{HCl, H 2 IrCl 6 · 6H} 2 O, comprises TiCl _3, 36% for metals Ru, 20% Ir, 44% Ti 100 ml of an aqueous alcohol solution having a molar composition of

  The solution is applied to the titanium mesh sample by brushing as 5 coatings, each coating is applied, followed by drying at 100-110 ° C. for about 10 minutes, and then at 450 ° C. for 15 minutes. The heat treatment was performed. Each time the sample was cooled in air before applying subsequent coatings.

At the end of all procedures, a total noble metal content of 9 g / m ² expressed as the sum of Ru and Ir for the metal was obtained.

  The electrode thus obtained was designated as sample number 1.

Comparative Example 2
Corundum was sprayed on a sample of titanium mesh having a size of 10 cm × 10 cm, and the remaining portion was washed by jetting compressed air. The sample was then degreased with acetone in an ultrasonic bath for about 10 minutes. After drying, the sample was immersed in an aqueous solution containing 250 g / l NaOH and 50 g / l KNO ₃ at about 100 ° C. for 1 hour. After this alkali treatment, the sample was rinsed three times at 60 ° C. in deionized water, with the water being changed every time. The final rinse was done by adding a small amount of HCl (about 1 ml per liter of solution). After drying with air, the formation of a brown color due to the growth of the TiO _x thin film was observed.

  The mesh sample was then placed in a vacuum chamber of a reactive sputtering apparatus.

When a mixture of oxygen with 20% argon was supplied and the dynamic vacuum reached about ^50-4 mbar, the sputtering target was polarized with the following outputs: ruthenium 35W, iridium 24W, titanium 250W. The gap between the target and the electrode substrate was about 10 centimeters.

Over the entire duration of 220 minutes, the deposition process was carried out alternately under the same conditions on both sides of the titanium mesh. In the electrode thus obtained, a catalyst coating of about 1 micron was formed and the total precious metal content, expressed as the sum of Ru and Ir for the metal, was about 9 g / m ² .

  The electrode thus obtained was designated as sample number 2.

Example 1
Corundum was sprayed on a sample of titanium mesh having a size of 10 cm × 10 cm, and the remaining portion was washed by jetting compressed air. The sample was then degreased with acetone in an ultrasonic bath for about 10 minutes. After drying, the sample was immersed in an aqueous solution containing 250 g / l NaOH and 50 g / l KNO ₃ at about 100 ° C. for 1 hour. After this alkali treatment, the sample was rinsed three times at 60 ° C. in deionized water, with the water being changed every time. The final rinse was done by adding a small amount of HCl (about 1 ml per liter of solution). After drying with air, the formation of a brown color due to the growth of the TiO _x thin film was observed.

Then, acidified water and 2- RuCl ₃ · _3H 2 _O in a mixture of _{propanol, H 2 IrCl 6 · 6H 2} O, the aqueous alcohol solution containing the TiCl ₃ was 100ml prepared with HCl. This solution has a molar composition of 36% Ru, 20% Ir, 44% Ti for the metal.

  The solution is applied to the titanium mesh sample by brushing as 5 coatings, each coating is applied, followed by drying at 100-110 ° C. for about 10 minutes, and then at 450 ° C. for 15 minutes. The heat treatment was performed. Each time the sample was cooled in air before applying subsequent coatings.

At the end of all procedures, a total noble metal content of 7 g / m ² expressed as the sum of Ru and Ir for the metal was obtained.

  The semi-finished electrode was then placed in a vacuum chamber of a reactive sputtering apparatus.

When a mixture of oxygen with 20% argon was supplied and the dynamic vacuum reached about ^100-4 mbar, the sputtering target was polarized with the following outputs: ruthenium 30W, iridium 35W. The gap between the target and the electrode substrate was about 10 centimeters. The remaining polarization of about 150V was further applied to the substrate in order to impart optimal properties to the resulting coating.

Over the total duration of 40 minutes, the deposition process was carried out alternately under the same conditions on both sides of the electrode. The electrode thus obtained has an outer catalyst coating of about 0.1 μm thickness and the total precious metal content is about 9 g / m ² expressed as the sum of Ru and Ir for the metal. there were.

  The electrode thus obtained was designated as sample number 3.

The sample of the above example was characterized as an anode for generating chlorine while strictly controlling the pH to 3 in a laboratory electrolytic cell containing 200 g / l sodium chloride brine. . The chlorine overvoltage measured at a current density of 4 kA / m ² and the volume percent of oxygen in the chlorine produced are reported in Table 1.

  Similarly, a durability test was performed on the samples of the above examples. This endurance test is a simulation in an independent electrolyzer under industrial electrolysis conditions for electrolyte concentration and temperature, but in order to promote experimental reactivity, the current density Was increased appropriately to a value 2-3 times higher than the standard value.

  The amount of noble metal decreased per unit current is reported in Table 2.

  The above description is not intended to limit the present invention, and the present invention can be used in accordance with various embodiments without departing from the scope thereof, and the scope of the present invention is unambiguously defined by the appended claims. To be confirmed.

  Throughout the specification and claims of this application, the term “comprising” is not intended to exclude the presence of other elements or additions.

  Literature considerations, statutes, materials, devices, articles, and the like are included herein for the purpose of merely providing a background for the present invention. Some of these matters, or all of them, form part of the prior art basis, or they are in the field relevant to the present invention before the priority date of each claim of this application. It has not been suggested or expressed that it was a general consensus.

Claims (9)

An electrode for generating a gaseous product in an electrochemical cell, the electrode comprising a valve metal support coated with at least one first catalyst composition and an outer catalyst composition, said electrode The at least one first catalyst composition includes a mixture of a valve metal or tin or an oxide thereof and a noble metal selected from a platinum group metal or an oxide thereof alone or in combination, and the at least one first catalyst composition. And the outer catalyst composition is deposited by chemical or physical vapor deposition, and the amount of noble metal in the at least one first catalyst composition is 5 g. The electrode, greater than / m ² and the amount of noble metal in the outer catalyst composition is in the range of 0.1 to 3.0 g / m ² .   The electrode of claim 1, wherein the at least one first catalyst composition comprises titanium, iridium and ruthenium.   The electrode according to claim 1, wherein the outer catalyst composition comprises ruthenium and / or iridium. The amount of the specific noble metal used in the at least one first catalyst composition is 6 to 8 g / m ² , and the amount of the specific noble metal used in the outer catalyst composition is 1.5 to 2.5 g / m ^2. The electrode according to claim 1, which is m ² .   5. A method for manufacturing an electrode according to any one of claims 1 to 4, comprising depositing the outer catalyst composition by chemical or physical vapor deposition.   5. The electrode according to claim 1, comprising depositing the outer catalyst composition as a mixture of oxides by reactive sputtering of a noble metal selected from the group of white metals. Method.   A method for reactivating a spent electrode comprising a metal support and a spent catalyst coating, wherein the outer catalyst composition is formed by reactive sputtering of iridium and ruthenium on the spent catalyst coating. Depositing as a mixture of oxides.   Spent according to claim 7, comprising depositing an outer catalyst composition comprising a noble metal selected from the group of white metals or an oxide thereof alone or in a mixture by chemical or physical vapor deposition. Method for reactivating the electrode.   An electrolyzer having a cathode compartment comprising a cathode and an anode compartment comprising an anode separated by a diaphragm or diaphragm, wherein the anode compartment is supplied with alkaline chloride brine, the anode of the anode compartment comprising: 4. The electrolytic cell, which is the electrode according to any one of 4 above.