EP0004880B1 - Elektroden für elektrolytische Verfahren, insbesondere zur Herstellung von Perchloraten - Google Patents

Elektroden für elektrolytische Verfahren, insbesondere zur Herstellung von Perchloraten Download PDF

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Publication number
EP0004880B1
EP0004880B1 EP79100917A EP79100917A EP0004880B1 EP 0004880 B1 EP0004880 B1 EP 0004880B1 EP 79100917 A EP79100917 A EP 79100917A EP 79100917 A EP79100917 A EP 79100917A EP 0004880 B1 EP0004880 B1 EP 0004880B1
Authority
EP
European Patent Office
Prior art keywords
weight
platinum
tin
coating
platinum group
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP79100917A
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English (en)
French (fr)
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EP0004880A1 (de
Inventor
Vittorio De Nora
Antonio Nidola
Placido Maria Spaziante
Guisseppe Bianchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dst SA Te Carouge Zwitserland
De Nora SpA
Original Assignee
Diamond Shamrock Technologies SA
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Filing date
Publication date
Application filed by Diamond Shamrock Technologies SA filed Critical Diamond Shamrock Technologies SA
Publication of EP0004880A1 publication Critical patent/EP0004880A1/de
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    • 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

Definitions

  • the invention relates to electrodes for use in electrolytic processes, of the type comprising an electrically-conductive and corrosion-resistant substrate having an electrocatalytically-active surface coating, and to electrolytic processes using such electrodes, especially (but not exclusively) as anodes for the production of chlorates, perchlorates and other persalts and percompounds including organic peroxyacids.
  • Patent Specification 3,882,002 proposed an anode for chlorine production having a valve metal substrate coated with an intermediate layer of tin dioxide which was covered with an outer layer of a platinum group metal or oxide thereof. Neither of these proposals was directed to improving electrolytic performance in the production of percompounds.
  • An object of the invention therefore is to provide an improved electrode suitable for use as an anode for the production of perchlorates and other persalts, but which may also be used in other applications, such as chlorate production.
  • an electrode comprises an electrically-conductive corrosion-resistant substrate having an electrocatalytic coating and is characterised in that the coating consists of a mixture of at least one platinum group metal and tin dioxide dispersed in one another throughout the coating in the ratio of 8.5:1 to 3:2 by weight of the platinum group metal(s) to the tin (as metal) of the tin dioxide and, optionally, as dopant of the tin dioxide in a total quantity of up to about 30% by weight of the tin, at least one additional metal or oxide of zinc, cadmium, arsenic, antimony, bismuth, selenium and tellurium.
  • the coating may contain one or more oxides of antimony and/or bismuth in an amount of at most 1 part by weight of Sb/Bi to 4 parts by weight of Sn.
  • the preferred amount corresponds to a ratio expressed as parts by weight of Sb/Bi:Sn (as metal) of at most about 1:4 to about 1:10 or even as low as 1:100.
  • the platinum group metals are ruthenium, rhodium, palladium, osmium, oridium and platinum. Platinum is the preferred platinum group metal in the coating, when a single metal is present, especially in anodes for perchlorate production. However, it is understood that alloys such as platinum-iridium and platinum- rhodium are also useful for other applications. An alloy of platinum-palladium containing up to 20% palladium by weight of the alloy has given very satisfactory results for perchlorate production.
  • the substrate may consist of any of the valve metals, namely titanium, zirconium, hafnium, vanadium, niobium and tantalum, or alloys thereof, porous sintered titanium being preferred.
  • valve metals namely titanium, zirconium, hafnium, vanadium, niobium and tantalum, or alloys thereof, porous sintered titanium being preferred.
  • other electrically-conductive and corrosion-resistant substrates may be used, such as expanded graphite.
  • platinum group metal(s) and tin dioxide with possible additional dopants may be co-deposited chemically from solutions of appropriate salts which are painted, sprayed or otherwise applied on the substrate and then subjected to heat treatment, this process being repeated until a sufficiently thick layer has been built up.
  • thin layers of different components can be built up in such a way that the components are effectively mixed and dispersed in one another throughout the coating, possibly with diffusion between the layers, in contrast to the known prior art coatings such as that of U.S. Patent Specification 3,882,002, in which the tin dioxide was applied as a separate intermediate layer covered by a platinum group metal.
  • alternate layers it is possible to deposit thin layers of platinum galvanically, which is advantageous, because galvanically-deposited platinum has a lower oxygen evolution potential than chemi-deposited platinum.
  • the platinum-group metal or alloy/tin dioxide layer may be applied directly to the substrate, or to an intermediate layer, e.g. of co-deposited tin and antimony oxides or tin and bismuth oxides, or to intermediate layers consisting of one or more platinum group metals or their oxides, mixtures or mixed crystals of platinum group metals and valve metal oxides, intermetallics of platinum group metals and non-platinum group metals.
  • an intermediate layer e.g. of co-deposited tin and antimony oxides or tin and bismuth oxides
  • intermediate layers consisting of one or more platinum group metals or their oxides, mixtures or mixed crystals of platinum group metals and valve metal oxides, intermetallics of platinum group metals and non-platinum group metals.
  • the coating comprises 40 to 85 parts by weight of platinum, 0 to 20 parts by weight of palladium and 15 to 40 parts by weight (as Sn metal) of tin dioxide on a titanium, tantalum or titanium- tantalum alloy substrate.
  • This embodiment of an electrode of the invention when used as anode for perchlorate or persulphate production, has been found to have selective properties favouring the persalt production while hindering oxygen evolution.
  • the platinum metal acts as a catalyst for persalt production.
  • the tin dioxide acts as an oxygen evolution inhibitor by blocking peroxide decomposition, which can be regarded as the intermediate step of the unwanted oxygen evolution reaction.
  • the palladium acts as a diluent for the relatively more expensive platinum, without adversely affecting the oxygen inhibition effect of the tin dioxide.
  • Another aspect of the invention is a process for the production of chlorates, perchlorates and other percompounds, e.g. persulphates, which is characterised by using as anode an electrode according to the invention, as defined above.
  • Titanium coupons measuring 10 ⁇ 10 ⁇ 1 mm were sandblasted and etched in 20% hydrochloric acid and were thoroughly washed in water.
  • the coupons were then coated with an aqueous solution of chlorides of platinum and tin in different weight ratios, dried at 95° to 100°C and then heated at 450°C for 15 minutes in an oven with forced air ventilation. The procedure was repeated five times and the coupons were given a final heat treatment at 450°C for 60 minutes.
  • the coatings so produced contained Sn0 2 and platinum metal dispersed in one another.
  • the coated coupons were tested as anodes for the production of sodium perchlorate by the electrolysis of a solution consisting of 100 g/I NaClO 3 , 400 g/i NaC10 4 and 5 g/I Na 2 Cr0 4 at 30°C using a stainless steel cathode and a current density of 2 KA/m 2 .
  • Sodium chlorate was supplied and sodium perchlorate removed to maintain the concentrations in the electrolyte at a steady state.
  • the faraday efficiency of the oxygen evolution reaction i.e. the unwanted side reaction in perchlorate production
  • Titanium coupons were coated as in Example I, but using various coating solutions containing platinum, palladium and tin chlorides, to produce mixed Pt-Pd-Sn0 2 coatings having compositions as follows:
  • Example I and II were tested at different current densities, and it was found that the oxygen evolution faraday efficiency decreased with increasing current density up to about 2 KAlm 2 , then remained stable above 2 KAlm 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)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Claims (5)

1. Elektrode zur Verwendung in elektrolytischen Prozessen, die ein elektrisch leitfähiges, korrosionsbeständiges Substrat mit einer elektrokatalytischen Beschichtung aufweist, dadurch gekennzeichnet, daß die Beschichtung aus einer Mischung von mindestens einem Platinmetall und Zinndioxid, die über die gesamte Beschichtung im Gewichtsverhältnis von Platinmetall(en) zu Zinn des Zinndioxids von 8,5:1 bis 3:2 ineinander dispergiert sind, und gegebenenfalls einer Gesamtmenge von bis zu etwa 30 Gew.% bezogen auf das Zinn mindestens eines zusätzlichen Metalls oder Oxids von Zink, Cadmium, Arsen, Antimon, Wismut, Selen und Tellur besteht.
2. Elektrode nach Anspruch 1, dadurch gekennzeichnet, daß das Platinmetall Platin ist.
3. Elektrode nach Anspruch 1, dadurch gekennzeichnet, daß die Beschichtung 40 bis 85 Gewichtsteile Platin, 0 bis 20 Gewichtsteile Palladium und 15 bis 40 Gewichtsteile Zinn enthält.
4. Elektrode nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß die Beschichtung eine oder mehrere Oxide von Antimon und/oder Wismut in einer Menge von höchstens 1 Gewichtsteil Sb/Bi zu 4 Gewichtsteilen Sn enthält.
5. Verfahren zur Herstellung von Chloraten, Perchloraten und anderen Perverbindungen durch Elektrolyse, dadurch gekennzeichnet, daß als Anode eine Elektrode gemäß eines der vorangegangenen Ansprüche verwendet wird.
EP79100917A 1978-03-28 1979-03-27 Elektroden für elektrolytische Verfahren, insbesondere zur Herstellung von Perchloraten Expired EP0004880B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1205278 1978-03-28
GB1205278 1978-03-28

Publications (2)

Publication Number Publication Date
EP0004880A1 EP0004880A1 (de) 1979-10-31
EP0004880B1 true EP0004880B1 (de) 1983-07-06

Family

ID=9997561

Family Applications (2)

Application Number Title Priority Date Filing Date
EP79100917A Expired EP0004880B1 (de) 1978-03-28 1979-03-27 Elektroden für elektrolytische Verfahren, insbesondere zur Herstellung von Perchloraten
EP79900338A Withdrawn EP0018970A1 (de) 1978-03-28 1979-11-05 Elektroden für elektrolyseverfahren, insbesondere perchlorat-herstellung

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP79900338A Withdrawn EP0018970A1 (de) 1978-03-28 1979-11-05 Elektroden für elektrolyseverfahren, insbesondere perchlorat-herstellung

Country Status (5)

Country Link
EP (2) EP0004880B1 (de)
CA (1) CA1129809A (de)
DE (1) DE2965811D1 (de)
FI (1) FI66919C (de)
WO (1) WO1979000843A1 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5544514A (en) * 1978-09-22 1980-03-28 Permelec Electrode Ltd Electrode for electrolysis and production thereof

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3616445A (en) * 1967-12-14 1971-10-26 Electronor Corp Titanium or tantalum base electrodes with applied titanium or tantalum oxide face activated with noble metals or noble metal oxides

Also Published As

Publication number Publication date
DE2965811D1 (en) 1983-08-11
EP0004880A1 (de) 1979-10-31
WO1979000843A1 (fr) 1979-11-01
FI66919C (fi) 1984-12-10
FI791004A7 (fi) 1979-09-29
EP0018970A1 (de) 1980-11-26
CA1129809A (en) 1982-08-17
FI66919B (fi) 1984-08-31

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