Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
  • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/50—Processes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/061—Metal or alloy
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms

Definitions

• the invention relates to an electrode for gas evolution in electrolytic processes comprising a catalytic coating containing oxides of tin, ruthenium, titanium and one or more elements selected from the group consisting of niobium, tantalum and tungsten applied to a metallic substrate, and a method for its preparation.
• the diaphragm cell was the first technology developed for brine electrolysis, followed by the mercury process; it is only in the 1970s in which the chlor-alkali industry is revolutionized through the development of a new electrolysis process involving the use of ion-selective membranes.
• a partial improvement in terms of chlorine overvoltage and therefore of process voltage and total energy consumption can be obtained by adding to a formulation based on RuO2, mixed with SnO2, a certain amount of a second noble metal selected between iridium and platinum, for example as described in EP0153586; this, and other tin-containing formulations, however, present the problem of simultaneously lowering the overvoltage of the concurrent oxygen evolution reaction, so that the chlorine produced by the anodic reaction is contaminated with an excessive amount of oxygen.
• a further partial improvement in terms of performance can be obtained by applying on a metal substrate a formulation based on RuCh, TiCh and SnCh added with lrC>2, for example, as described in EP19731919.
• these catalytic coatings involve the presence of high quantities of noble metals.
• coatings of the prior art such as, for example, the formulation described in JPS6338592 based on tin oxides and noble metals, are generally prepared starting from tetravalent tin precursors, in particular tin tetrachloride (SnCI4), mixed with the corresponding precursors of the noble metal in aqueous solution.
• tetravalent tin precursors in particular tin tetrachloride (SnCI4)
• SnCI4 tin tetrachloride
• the extreme volatility of the precursors thus obtained makes them unfavorable for application in industrial processes.
• the present invention relates to the preparation of a catalytic coating for electrodes used, among other things, in alkali chloride brine electrolysis processes, such a coating is applied to a metal substrate, typically titanium, titanium alloy or other valve metal.
• the present invention consists in the application on a metal substrate of a formulation based on ruthenium, tin, titanium and one or more elements selected from the group consisting of niobium, tantalum and tungsten; a formulation thus obtained leads to reach excellent performances in terms of catalytic activity for the reaction of chlorine even with low quantities of noble metal.
• the invention in a first aspect, relates to an electrode for gas evolution in electrolytic processes comprising a metal substrate and a catalytic coating containing 10-20% tin, 25-45% ruthenium, 20-40% titanium, and 10-20% of one or more elements selected from the group consisting of niobium, tantalum, tungsten in the form of metals or their oxides in percentage by weight referred to the elements. It is evident that the person skilled in the art will select the molar percentages of the single elements in such a way that the total sum of the molar percentages of the components is 100.
• said one or more elements selected from the group consisting of niobium, tantalum, tungsten is tantalum.
• the titanium of the catalytic coating is present as an oxide in the rutile form.
• the inventors have observed that the presence of tantalum and/or its oxides, even in small amounts, allows the resulting titanium oxide to be organized in the rutile form, further allowing to obtain a homogeneous solid solution of rutile.
• electrodes of the prior art with coatings comprising ruthenium, tin and titanium often show, in the analysis of the crystalline structure, an anatase peak for the titanium oxide, which affects their performance in terms of duration. When this occurs, further heat treatment is required to allow a better organization of the oxide material.
• the metal substrate may be any metal suitable for use as an electrode support for electrochemical processes.
• a metal substrate for an anode to be used in chlor-alkali electrolysis processes can be chosen between titanium and titanium alloy.
• the catalytic coating has a specific ruthenium load comprised between 2.2 and 9 g/m 2 .
• the present invention relates to an electrode comprising a metal substrate and a catalytic coating wherein said catalytic coating is obtained by thermal decomposition of a solution of tin, ruthenium, titanium, and one or more selected elements in the group consisting of niobium, tantalum and tungsten.
• Said solution containing 10- 20% of tin, 25-45% of ruthenium, 20-40% of titanium, and 10-20% of one or more elements selected from the group consisting of niobium, tantalum, tungsten in percentage by weight referred to the elements.
• the present invention relates to an electrode comprising a metal substrate and a catalytic coating wherein said catalytic coating is obtained by thermal decomposition of a solution of tin, ruthenium, titanium, wherein said one or more elements chosen from the group consisting of niobium, tantalum and tungsten is tantalum.
• Said solution containing 10-20% of tin, 25-45% of ruthenium and 20-40% of titanium, and 10- 20% of tantalum in percentage by weight referred to the elements.
• the present invention relates to an electrode comprising a metal substrate and a catalytic coating wherein said catalytic coating is obtained by thermal decomposition of a solution of tin, ruthenium, titanium, wherein said one or more elements chosen from the group consisting of niobium, tantalum and tungsten is niobium.
• Said solution containing 10-20% of tin, 25-45% of ruthenium and 20-40% of titanium, and 10- 20% of niobium in percentage by weight referred to the elements.
• the present invention relates to a process for obtaining an electrode for the evolution of gaseous products in electrolytic cells, for example for the evolution of chlorine in alkaline brine electrolysis cells, comprising the following steps: a) application to a metal substrate of a solution comprising the precursors of ruthenium, tin, titanium and one or more elements selected from the group consisting of niobium, tantalum, tungsten, subsequent drying at 50-60°C and thermal decomposition at 450- 600°C for a time of 5 to 30 minutes; b) repetition of step a) until obtaining a catalytic coating with a specific ruthenium load comprised between 2.2 and 9 g/m 2 ; c) thermal treatment at 450-600°C for a time of 50 to 200 minutes.
• Ruthenium and titanium precursors and niobium, tantalum, or tungsten precursors are compounds selected from the group consisting of chlorides, nitrates, iodides, bromides, sulfates, butyls, or acetates of the metals and their mixtures thereof.
• the tin precursors are generally prepared according to the procedure described in WO 2005/014885.
• tin precursors as described in WO 2005/014885 not only allows to overcome the limitation of the prior art, providing an anodic catalytic coating with a well-controlled chemical composition, but also ensures a good distribution of the oxides of the elements of the catalytic coating, formed during the various thermal treatments, over the entire surface of the metal substrate.
• the method according to the invention does not exclude the application of additional coating compositions, such as a barrier coating composition applied directly to the metal substrate, prior to step a) and thus prior to the application of the catalytic coating, or a upper coating composition after stage b.
• additional coating compositions such as a barrier coating composition applied directly to the metal substrate, prior to step a) and thus prior to the application of the catalytic coating, or a upper coating composition after stage b.
• the invention relates to an electrolysis cell of alkaline chloride solutions and/or an electro-chlorination cell comprising an anodic compartment and a cathodic compartment wherein the anodic compartment is equipped with the electrode in one of the forms as described above, used as an anode for chlorine evolution.
• said anodic compartment and said cathodic compartment are separated by a diaphragm or an ion exchange membrane.
• the invention relates to an electrolyser for the production of chlorine and alkali starting from alkali chlorides solutions
• an electrolyser for the production of chlorine and alkali starting from alkali chlorides solutions
• a modular arrangement of electrolytic cells with the anodic and cathodic compartments separated by ion exchange membranes or by diaphragms, wherein the anodic compartment comprises an electrode in one of the forms as described above used as anode.
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the solution was applied to the titanium mesh by brushing. After each coat, drying was carried out at 50-60°C for about 10 minutes, followed by a heat treatment for 10 minutes at 500°C. The mesh was air cooled each time before the application of the next coat. The procedure was repeated until a total Ru load of 6 g/m 2 was reached.
• the electrode thus obtained was identified as sample #1 .
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the solution was applied to the titanium mesh by brushing. After each coat, drying was carried out at 50-60°C for about 10 minutes, followed by a heat treatment for 10 minutes at 500°C. The mesh was air cooled each time before the application of the next coat. The procedure was repeated until a total Ru load of 6 g/m 2 was reached.
• the electrode thus obtained was identified as sample #2.
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the solution was applied to the titanium mesh by brushing. After each coat, drying was carried out at 50-60°C for about 10 minutes, followed by a heat treatment for 10 minutes at 500°C. The mesh was air cooled each time before the application of the next coat.
• a final heat treatment was then carried out at 500°C for 100 minutes.
• the electrode thus obtained was identified as sample #3.
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the electrode thus obtained was identified as sample #1 C.
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the solution was applied to the titanium mesh by brushing. After each coat, drying was carried out at 50-60°C for about 10 minutes, followed by a heat treatment for 10 minutes at 500°C. The piece was air cooled each time before the next coat was applied.
• the electrode thus obtained was identified as sample #2C.
• a titanium mesh of 10 cm x 10 cm was washed three times in deionized water at 60°C, changing the liquid each time. Washing was followed by a 2-hour thermal treatment at 350°C. The mesh was then subjected to a treatment in a 20% HCI solution, boiling for 30 minutes.
• the samples from the examples were characterized as anodes for evolution of chlorine in a laboratory cell fed with sulfuric acid at a concentration of 150 g/l, at a temperature of 65°C.
• Table 1 shows the lifetime performances (expressed in hours online - HOL) measured at a current density of 4 kA/m 2 .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)

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• 2022
  • 2022-07-08 IT IT102022000014359A patent/IT202200014359A1/it unknown
• 2023
  • 2023-07-06 WO PCT/EP2023/068785 patent/WO2024008895A2/en not_active Ceased
  • 2023-07-06 EP EP23735802.3A patent/EP4522785A2/de active Pending
  • 2023-07-06 US US18/868,246 patent/US20250327200A1/en active Pending

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