EP2451995A1 - Bipolar electrodes with high energy efficiency, and use thereof for synthesising sodium chlorate - Google Patents

Bipolar electrodes with high energy efficiency, and use thereof for synthesising sodium chlorate

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Publication number
EP2451995A1
EP2451995A1 EP10796605A EP10796605A EP2451995A1 EP 2451995 A1 EP2451995 A1 EP 2451995A1 EP 10796605 A EP10796605 A EP 10796605A EP 10796605 A EP10796605 A EP 10796605A EP 2451995 A1 EP2451995 A1 EP 2451995A1
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EP
European Patent Office
Prior art keywords
coating
bipolar
electrode
electrodes
bipolar electrode
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.)
Withdrawn
Application number
EP10796605A
Other languages
German (de)
French (fr)
Other versions
EP2451995A4 (en
Inventor
Robert Schulz
Sylvio Savoie
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.)
Hydro Quebec
Meeir Technologie Inc
Original Assignee
Hydro Quebec
Meeir Technologie Inc
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Publication date
Application filed by Hydro Quebec, Meeir Technologie Inc filed Critical Hydro Quebec
Publication of EP2451995A1 publication Critical patent/EP2451995A1/en
Publication of EP2451995A4 publication Critical patent/EP2451995A4/en
Withdrawn legal-status Critical Current

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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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • C25B1/265—Chlorates
    • 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

Definitions

  • the present invention relates to novel bipolar electrodes having a cathodic coating on one part of the electrode and an anodic coating on another part of this same electrode. It also relates to the use of these new electrodes for the synthesis of sodium chlorate.
  • Figures 1a and 1b are schematic views of single pole electrodes; Figures 2a and 2b are schematic views of bipolar electrodes;
  • Figure 3 is an illustration of an adhesion test of an aluminide coating
  • Figure 4 is an illustration of an adhesion test of an iron aluminide coating on titanium
  • Figure 5 is a diagram illustrating the mounting of the sleeves, traction used for adhesion tests
  • Figure 6 is an illustration of a corrosion test in a chlorate solution of a DSA electrode and a coating of the type Fe3_ x AI-
  • Figure 7 is a schematic view of a bipolar electrode according to the invention
  • Figures 8a, 8b and 8c are schematic views of bipolar modules according to the invention
  • Figures 9a, 9b and 9c are photographs of bipolar electrodes manufactured so that a portion of these electrodes is coated with a DSA-type coating and another, a Fe-type coating. ⁇ Ali + x M y T z .
  • Sodium chlorate (NaCIO 3 ) is commonly used as a bleaching agent in the pulp and paper industry. It is produced by electrolysis of the sodium salt (NaCl) according to the chemical reaction:
  • Electrolysis cells in which a high DC current flows usually comprise dimensionally stable anodes (DSA) and uncoated steel or titanium cathodes.
  • DSA anodes are well known in the art of electrolysis cells, see for example: WO 4101852, WO 4094698, US 6071570, US 4528084, US 5989396, US 6572758, US 4233340, US 5419824, US 5593556 and US 5672394.
  • These DSA anodes typically comprise a titanium substrate to which a coating of ruthenium oxide is applied with possibly other oxides or compounds such as iridium oxide.
  • the energy losses on the anode side are low. This is reflected by a low anodic surge of a few tens of millivolts. However, this is not the case on the cathodic side.
  • the cathode overvoltage on the surface of a steel plate is about 900 mV while on the surface of a titanium plate, it is about 1200 mV.
  • the energy losses on the cathode side thus represent the main source of energy losses in the process. It is for this reason that in recent years In recent years, the inventors of the present invention have attempted to find efficient cathode coatings for lowering the surge voltage at these electrodes.
  • WO / 2008/138148 which also originates from the inventors of the present invention, gives an example of such cathode coatings. It describes alloys of the type Fe3_ x Ali + x MyT z that is applied to the surface of an electrode to make a coated cathode very energy efficient.
  • the cathodes and the anodes are assembled in electrolysis cells in different configurations. There are two types of assembly. Monopolar cells and bipolar cells.
  • Figure 1 shows schematic views of single pole electrodes. In such configurations, each electrode plays only one role, that of anode or cathode. Therefore, there is no ambiguity on the type of coating to be applied if one wishes to improve the energy efficiency of such cells.
  • a titanium substrate will be chosen and a ruthenium oxide coating will be applied to form a DSA and at the cathode a steel plate may be chosen and a Fe3_ x Ali + x MyT coating applied to it. z to make it a cathode with high energy performance.
  • Figure 2 shows schematic views of bipolar electrodes.
  • an electrode or electrode module plays both the anode and the cathode roles.
  • the negative side of the bipolar electrode is cathodic while the positive side is anodic.
  • the electrodes in the left part of the bipolar module (negative sign) are cathodic while the electrodes on the right side (positive sign) are anodic.
  • a bipolar electrode module such as that shown at the bottom of Figure 2 presents an additional problem.
  • the electrodes on the anode side (right side of the module) are usually DSA on titanium substrates while the electrodes on the cathode side (left side of the module) are steel plates. But it is very difficult to weld titanium to steel. Such a module thus has a difficulty of assembly.
  • the present invention aims to solve these problems associated with bipolar electrodes.
  • the invention therefore has for first object a bipolar electrode with high energy efficiency, said electrode having a portion provided with a cathodic coating and another part which is distinct from the first and is provided with an anodic coating.
  • the anodic coating is of the DSA type
  • the cathodic coating is of an alloy of formula:
  • M represents one or more catalytic species selected from Ru, Ir, Pd 1 Pt, Rh, Os, Re, Ag and Ni;
  • T represents one or more of Mo, Co, Cr, V, Cu, Zn, Nb, W, Zr, Y; Mn, Cb, Si, B, C, O, N, P, F, S, Cl and Na;
  • x is a number greater than -1 and less than or equal to +1;
  • y is a number greater than 0 and less than or equal to +1;
  • z is a number between 0 and +1.
  • the substrate on which the coatings are applied may be a steel substrate or a titanium substrate.
  • the invention also relates to a bipolar electrode module containing a plurality of electrodes such as those described above.
  • the invention also relates to the use of the bipolar electrode or the bipolar module according to the invention for the electrosynthesis of sodium chlorate.
  • Figure 3 shows a adhesion test of a Fe ⁇ AI coating on a 1020 steel substrate according to ASTM C633. The fracture occurred at a stress of 11922 psi which is close to the breakage limit of the glue used to mount the tensile bushings (see diagram in Figure 5). The adhesion of an iron aluminide coating to a steel substrate is therefore excellent.
  • Figure 4 shows a similar adhesion test of a coating of the same type on a titanium substrate. The rupture occurred at a stress of 10604 psi, almost as high as previously measured. Therefore, the adhesion of the coating is as good on a titanium substrate as on a steel substrate.
  • a steel substrate preferably a stainless steel of ferritic type and not containing Ni.
  • a method such as the "cold spray" before applying on the same side and on the Ti layer, the type of coating DSA.
  • the type of coating DSA On the other side, it will apply as before but this time on the steel a Fe type coating 3 .
  • x Ali + x M y T z The only remaining potential problem of such electrode configurations is that of the galvanic corrosion caused by the fact that there is on one side of the electrode, a ruthenium oxide DSA type and on the other, an alloy AI-type Fe3_ x
  • Figure 6 shows "current-voltage" curves in a chlorate solution at 22 ° C measured against an Ag / AgCl reference electrode by scanning the potential at 5 mV / sec for a DSA electrode and a coating such as
  • Figure 7 shows schematic views of bipolar electrodes according to the invention.
  • first electrode one side has an anode coating while the other side has a cathode coating.
  • second bipolar electrode one end of the electrode is coated on both sides with a cathode coating while the other end is coated with anodic coating.
  • Figure 8 shows schematic views of bipolar modules consisting of a bipolar electrode assembly shown in Figure 7.
  • Figures 9a and 9b show photographs of bipolar electrodes as schematically represented in Figure 7
  • Figure 9c shows the appearance of a bipolar electrode according to the invention after immersion of 69 hours in 22 ° chlorate solution C. There is a beginning of pitting corrosion of the cathode part but the structural integrity of the coating is still excellent.

Abstract

The invention relates to novel bipolar electrodes with a cathodic coating on one portion of the electrode and an anodic coating on another portion of the same electrode. The anodic coating is preferably a DSA coating and the cathodic coating is an alloy such as Fe3-xAl-1+xMyTz. The invention also relates to the use of said novel electrodes for synthesising sodium chlorate.

Description

ELECTRODES BIPOLAIRES À HAUTE EFFICACITÉ ÉNERGÉTIQUE ET USAGE DE CELLES-CI POUR LA SYNTHÈSE DU CHLORATE DE SODIUM  ENERGY EFFICIENT BIPOLAR ELECTRODES AND USE THEREOF FOR THE SYNTHESIS OF SODIUM CHLORATE
DOMAINE DE L'INVENTION FIELD OF THE INVENTION
La présente invention a pour objet de nouvelles électrodes bipolaires ayant un revêtement cathodique sur une partie de l'électrode et un revêtement anodique sur une autre partie de cette même électrode. Elle a également pour objet l'usage de ces nouvelles électrodes pour la synthèse du chlorate de sodium. The present invention relates to novel bipolar electrodes having a cathodic coating on one part of the electrode and an anodic coating on another part of this same electrode. It also relates to the use of these new electrodes for the synthesis of sodium chlorate.
BRÈVE DESCRIPTION DES DESSINS BRIEF DESCRIPTION OF THE DRAWINGS
Dans les dessins annexés : les Figures 1a et 1b sont des vues schématiques d'électrodes mono-polaires; les Figures 2a et 2b sont des vues schématiques d'électrodes bipolaires; In the accompanying drawings: Figures 1a and 1b are schematic views of single pole electrodes; Figures 2a and 2b are schematic views of bipolar electrodes;
la Figure 3 est une illustration d'un test d'adhésion d'un revêtement d'aluminure  Figure 3 is an illustration of an adhesion test of an aluminide coating
de fer sur de l'acier 1020;  iron on 1020 steel;
- la Figure 4 est une illustration d'un test d'adhésion d'un revêtement d'aluminure de fer sur du titane; Figure 4 is an illustration of an adhesion test of an iron aluminide coating on titanium;
la Figure 5 est un schéma illustrant le montage des douilles, de traction utilisées pour les tests d'adhésion;  Figure 5 is a diagram illustrating the mounting of the sleeves, traction used for adhesion tests;
la Figure 6 est une illustration d'un test de corrosion dans une solution chlorate d'une électrode DSA et d'un revêtement du type Fe3_xAI-|+xMyTz sur un substrat de titane; Figure 6 is an illustration of a corrosion test in a chlorate solution of a DSA electrode and a coating of the type Fe3_ x AI- | + x MyT z on a titanium substrate;
la Figure 7 est une vue schématique d'une électrode bipolaire selon l'invention; les Figures 8a, 8b et 8c sont des vues schématiques de modules bipolaires selon l'invention; et les Figures 9a, 9b et 9c, sont des photographies d'électrodes bipolaires fabriquées de façon à ce qu'une partie de ces électrodes soit recouverte d'un revêtement de type DSA et une autre, un revêtement de type Fe^. χAli+xMyTz. Figure 7 is a schematic view of a bipolar electrode according to the invention; Figures 8a, 8b and 8c are schematic views of bipolar modules according to the invention; and Figures 9a, 9b and 9c are photographs of bipolar electrodes manufactured so that a portion of these electrodes is coated with a DSA-type coating and another, a Fe-type coating. χAli + x M y T z .
ARRIÈRE PLAN TECHNOLOGIQUE BACKGROUND TECHNOLOGY
Le chlorate de sodium (NaCIO3) est couramment utilisé comme agent de blanchiment dans l'industrie des pâtes et papier. Il est produit par électrolyse du sel de sodium (NaCI) suivant la réaction chimique : Sodium chlorate (NaCIO 3 ) is commonly used as a bleaching agent in the pulp and paper industry. It is produced by electrolysis of the sodium salt (NaCl) according to the chemical reaction:
NaCI + 3 H2O → NaCIO3 + 3H2 NaCl + 3H 2 O → NaCl 3 + 3H 2
Le procédé est très énergivore et requiert entre 5000 et 5500 kWh d'électricité par tonne de chlorate de sodium. Les cellules d'électrolyse dans lesquelles circule un fort courant continu comprennent habituellement des anodes dimensionnellement stables (DSA) et des cathodes d'acier ou de titane non-revêtues. Les anodes DSA sont bien connues dans l'art des cellules d'électrolyse, voir par exemples : WO 4101852, WO 4094698, US 6071570, US 4528084, US 5989396, US 6572758, US 4233340, US 5419824, US 5593556 and US 5672394. Ces anodes DSA comprennent typiquement un substrat de titane sur lequel on applique un revêtement d'oxyde de ruthénium avec possiblement, d'autres oxydes ou composés tel que l'oxyde d'iridium. Grâce à ce revêtement catalytique, les pertes d'énergie du coté anodique sont faibles. Cela se reflète par une basse surtension anodique de quelques dizaines de millivolts. Il n'en est cependant pas de même du coté cathodique. La surtension cathodique à la surface d'une plaque d'acier est d'environ 900 mV alors qu'à la surface d'une plaque de titane, elle est d'environ 1200 mV. Les pertes d'énergie du coté cathodique représentent ainsi la principale source de pertes d'énergie dans le procédé. C'est pour cette raison qu'au cours des dernières années, les inventeurs de la présente invention ont tenté de trouver des revêtements de cathode performants permettant d'abaisser la surtension à ces électrodes. WO/2008/138148 qui origine également des inventeurs de la présente invention, donne un exemple de tels revêtements de cathode. Elle décrit des alliages du type Fe3_xAli+xMyTz qu'on applique sur la surface d'une électrode pour en faire une cathode revêtue très performante du point de vue énergétique. The process is very energy intensive and requires between 5000 and 5500 kWh of electricity per tonne of sodium chlorate. Electrolysis cells in which a high DC current flows usually comprise dimensionally stable anodes (DSA) and uncoated steel or titanium cathodes. DSA anodes are well known in the art of electrolysis cells, see for example: WO 4101852, WO 4094698, US 6071570, US 4528084, US 5989396, US 6572758, US 4233340, US 5419824, US 5593556 and US 5672394. These DSA anodes typically comprise a titanium substrate to which a coating of ruthenium oxide is applied with possibly other oxides or compounds such as iridium oxide. Thanks to this catalytic coating, the energy losses on the anode side are low. This is reflected by a low anodic surge of a few tens of millivolts. However, this is not the case on the cathodic side. The cathode overvoltage on the surface of a steel plate is about 900 mV while on the surface of a titanium plate, it is about 1200 mV. The energy losses on the cathode side thus represent the main source of energy losses in the process. It is for this reason that in recent years In recent years, the inventors of the present invention have attempted to find efficient cathode coatings for lowering the surge voltage at these electrodes. WO / 2008/138148 which also originates from the inventors of the present invention, gives an example of such cathode coatings. It describes alloys of the type Fe3_ x Ali + x MyT z that is applied to the surface of an electrode to make a coated cathode very energy efficient.
Les cathodes et les anodes sont assemblées dans des cellules d'électrolyse suivant différentes configurations. On distingue deux types d'assemblage. Les cellules mono-polaires et les cellules bipolaires. La Figure 1 présente des vues schématiques d'électrodes mono-polaires. Dans de telles configurations, chaque électrode ne joue qu'un seul rôle, celui d'anode ou de cathode. Par conséquent, il n'existe aucune ambiguïté sur le type de revêtement à appliquer si on souhaite améliorer l'efficacité énergétique de telles cellules. À l'anode on choisira un substrat de titane et on appliquera un revêtement d'oxyde de ruthénium pour en faire une DSA et à la cathode on pourra choisir une plaque d'acier et y appliquer un revêtement de type Fe3_xAli+xMyTz pour en faire une cathode à haute performance énergétique. La Figure 2 présente des vues schématiques d'électrodes bipolaires. Dans une configuration bipolaire, une électrode ou un module d'électrodes joue à la fois le rôle d'anode et celui de cathode. Dans le schéma du haut de la Figure 2a, la face négative de l'électrode bipolaire est cathodique alors que la face positive est anodique. Dans le schéma du bas de la Figure 2b, les électrodes dans la partie gauche du module bipolaire (signe négatif) sont cathodiques alors que les électrodes du coté droit (signe positif) sont anodiques. Ces électrodes sont assemblées et soudées ensemble pour en faire un module bipolaire d'électrodes. Puisqu'une électrode bipolaire telle que celle montrée à la Figure 2a, joue à la fois le rôle d'anode et de cathode, quel type d'électrode choisira-t-on pour améliorer globalement l'efficacité du procédé ? Va-t-on opter pour une électrode DSA sur substrat de titane qui a été développée pour optimiser la réaction anodique ou une plaque d'acier avec revêtement catalytique pour favoriser la réaction cathodique. En plus de cette difficulté, un module bipolaire d'électrodes tel que celui montré au bas de la Figure 2 présente une problématique additionnelle. Les électrodes du coté anodique (coté droit du module) sont habituellement des DSA sur des substrats de titane alors que les électrodes du coté cathodique (coté gauche du module) sont des plaques d'acier. Or il est très difficile de souder du titane à de l'acier. Un tel module présente donc une difficulté d'assemblage. The cathodes and the anodes are assembled in electrolysis cells in different configurations. There are two types of assembly. Monopolar cells and bipolar cells. Figure 1 shows schematic views of single pole electrodes. In such configurations, each electrode plays only one role, that of anode or cathode. Therefore, there is no ambiguity on the type of coating to be applied if one wishes to improve the energy efficiency of such cells. At the anode, a titanium substrate will be chosen and a ruthenium oxide coating will be applied to form a DSA and at the cathode a steel plate may be chosen and a Fe3_ x Ali + x MyT coating applied to it. z to make it a cathode with high energy performance. Figure 2 shows schematic views of bipolar electrodes. In a bipolar configuration, an electrode or electrode module plays both the anode and the cathode roles. In the diagram at the top of Figure 2a, the negative side of the bipolar electrode is cathodic while the positive side is anodic. In the diagram at the bottom of Figure 2b, the electrodes in the left part of the bipolar module (negative sign) are cathodic while the electrodes on the right side (positive sign) are anodic. These electrodes are assembled and welded together to make a bipolar electrode module. Since a bipolar electrode such as that shown in Figure 2a, plays both the role of anode and cathode, what type of electrode will be chosen to improve overall the efficiency of the process? Will one opt for a DSA electrode on titanium substrate that has been developed to optimize the anodic reaction or a steel plate with catalytic coating to promote the cathodic reaction. In addition to this difficulty, a bipolar electrode module such as that shown at the bottom of Figure 2 presents an additional problem. The electrodes on the anode side (right side of the module) are usually DSA on titanium substrates while the electrodes on the cathode side (left side of the module) are steel plates. But it is very difficult to weld titanium to steel. Such a module thus has a difficulty of assembly.
Enfin lorsqu'on a des métaux différents tels que l'acier et le titane en contact direct dans une solution hautement corrosive comme celle du chlorate de sodium, on a une problématique supplémentaire de corrosion galvanique. Lorsqu'il y a arrêt de production et coupure de courant à l'usine, un courant causé par la corrosion galvanique circule en sens inverse dans les modules bipolaires d'électrodes et cet effet engendre une détérioration sévère des électrodes les moins nobles. Finally, when different metals such as steel and titanium are in direct contact in a highly corrosive solution such as sodium chlorate, there is an additional problem of galvanic corrosion. When production is interrupted and the power fails at the plant, a current caused by galvanic corrosion flows in the opposite direction in the bipolar electrode modules and this effect causes severe deterioration of the less noble electrodes.
La présente invention vise à résoudre ces problématiques associées aux électrodes bipolaires. The present invention aims to solve these problems associated with bipolar electrodes.
SOMMAIRE DE L'INVENTION SUMMARY OF THE INVENTION
Alors qu'ils effectuaient leur recherche sur les revêtements cathodiques à haute performance énergétique du type Fe3_xAI-|+xMyTz qui ont fait l'objet de l'inventionWhile conducting their research on high performance cathode coatings of the type Fe3_ x AI- | + x MyT z which were the subject of the invention
WO/2008/138148, les inventeurs de la présente invention ont constaté à leur grande surprise que les revêtements de ce type adhéraient tout aussi bien sur des substrats d'acier que sur des substrats de titane. L'invention a donc pour premier objet une électrode bipolaire à haute efficacité énergétique, ladite électrode possédant une partie pourvue d'un revêtement cathodique et une autre partie qui est distincte de la première et est pourvue d'un revêtement anodique. WO / 2008/138148, the inventors of the present invention have found to their great surprise that coatings of this type adhere just as well to steel substrates as to titanium substrates. The invention therefore has for first object a bipolar electrode with high energy efficiency, said electrode having a portion provided with a cathodic coating and another part which is distinct from the first and is provided with an anodic coating.
De préférence : le revêtement anodique est de type DSA; Preferably: the anodic coating is of the DSA type;
le revêtement cathodique est d'un alliage de formule :  the cathodic coating is of an alloy of formula:
Fe3-xAH+xMyτz F e3-x A H + x M y τ z
dans laquelle : in which :
M représente une ou plusieurs espèces catalytiques choisies parmi Ru, Ir, Pd1 Pt, Rh, Os, Re, Ag et Ni; M represents one or more catalytic species selected from Ru, Ir, Pd 1 Pt, Rh, Os, Re, Ag and Ni;
T représente un ou plusieurs éléments parmi Mo, Co, Cr, V, Cu, Zn, Nb, W, Zr, Y; Mn, Cb, Si, B, C, O, N, P, F, S , Cl et Na;  T represents one or more of Mo, Co, Cr, V, Cu, Zn, Nb, W, Zr, Y; Mn, Cb, Si, B, C, O, N, P, F, S, Cl and Na;
x est un nombre supérieur à -1 et inférieur ou égal à +1 ; x is a number greater than -1 and less than or equal to +1;
y est un nombre supérieur à O et inférieur ou égal +1 ; et y is a number greater than 0 and less than or equal to +1; and
z est un nombre compris entre O et +1. z is a number between 0 and +1.
Le substrat sur lequel sont appliqués les revêtements peut être un substrat d'acier ou un substrat de titane. The substrate on which the coatings are applied may be a steel substrate or a titanium substrate.
L'invention a aussi pour objet un module bipolaire d'électrodes contenant plusieurs électrodes telles que celles ci-dessus décrites. The invention also relates to a bipolar electrode module containing a plurality of electrodes such as those described above.
L'invention a également pour objet l'usage de l'électrode bipolaire ou du module bipolaire selon l'invention pour l'électrosynthèse du chlorate de sodium. EXEMPLES The invention also relates to the use of the bipolar electrode or the bipolar module according to the invention for the electrosynthesis of sodium chlorate. EXAMPLES
La Figure 3 montre un test d'adhésion d'un revêtement du type FeβAI sur un substrat d'acier 1020 selon la norme ASTM C633. La rupture a eu lieu à une contrainte de 11922 psi qui est tout près de la limite à la rupture de la colle servant au montage des douilles de traction (voir le schéma de la Figure 5). L'adhésion d'un revêtement d'aluminure de fer sur un substrat d'acier est donc excellente. La Figure 4 montre un test d'adhésion similaire d'un revêtement du même type sur un substrat de titane. La rupture a eu lieu à une contrainte de 10604 psi soit une valeur presque aussi élevée que celle mesurée précédemment. Par conséquent, l'adhésion du revêtement est aussi bonne sur un substrat de titane que sur un substrat d'acier. Figure 3 shows a adhesion test of a FeβAI coating on a 1020 steel substrate according to ASTM C633. The fracture occurred at a stress of 11922 psi which is close to the breakage limit of the glue used to mount the tensile bushings (see diagram in Figure 5). The adhesion of an iron aluminide coating to a steel substrate is therefore excellent. Figure 4 shows a similar adhesion test of a coating of the same type on a titanium substrate. The rupture occurred at a stress of 10604 psi, almost as high as previously measured. Therefore, the adhesion of the coating is as good on a titanium substrate as on a steel substrate.
Puisque le titane sert habituellement de substrat aux revêtements de type DSA1 cette découverte ouvre la possibilité d'appliquer sur un coté du substrat de titane un revêtement DSA pour la réaction anodique et sur l'autre, un revêtement de type Fe3_xAli+xMyTz pour la réaction cathodique. En d'autre mot, cette découverte conduit directement à l'optimisation énergétique des électrodes de type bipolaire. Since titanium usually serves as a substrate for DSA-type coatings 1, this discovery opens the possibility of applying a DSA coating on one side of the titanium substrate for the anodic reaction and, on the other, a coating of the Fe3_ x Ali + x type. MyT z for the cathodic reaction. In other words, this discovery leads directly to the energy optimization of bipolar electrodes.
On peut cependant utiliser également un substrat d'acier, de préférence un acier inoxydable de type ferritique et ne contenant pas de Ni. Dans ce cas, on appliquera préférentiellement une couche de Ti sur un coté par une méthode telle le « cold spray » avant d'appliquer sur ce même coté et sur la couche de Ti, le revêtement de type DSA. De l'autre coté, on appliquera comme précédemment mais cette fois- ci sur l'acier un revêtement de type Fe3.xAli+xMyTz. Le seul problème potentiel restant de telles configurations d'électrode est celui de la corrosion galvanique causé par le fait qu'il y a d'un coté de l'électrode, un oxyde de ruthénium de type DSA et de l'autre, un alliage de type Fe3_xAI-|+xMyTz. Or il a été découvert qu'il était possible d'ajuster la composition chimique des alliages du type Fe3-χAli+χMyTz par un choix judicieux des éléments M et T et des compositions x, y et z de façon à équilibrer les potentiels avec la DSA et à canceller la corrosion galvanique du couple constituant l'électrode bipolaire. However, it is also possible to use a steel substrate, preferably a stainless steel of ferritic type and not containing Ni. In this case, one will preferentially apply a layer of Ti on one side by a method such as the "cold spray" before applying on the same side and on the Ti layer, the type of coating DSA. On the other side, it will apply as before but this time on the steel a Fe type coating 3 . x Ali + x M y T z . The only remaining potential problem of such electrode configurations is that of the galvanic corrosion caused by the fact that there is on one side of the electrode, a ruthenium oxide DSA type and on the other, an alloy AI-type Fe3_ x | x + z MyT. Now it has been discovered that it was possible to adjust the chemical composition of the F e 3-χAli + χMyT z type alloys by a judicious choice of the M and T elements and the x, y and z compositions in order to balance the potential with the DSA and cancel the galvanic corrosion of the couple constituting the bipolar electrode.
La Figure 6 montre des courbes « courant-tension » dans une solution chlorate à 22°C mesurées par rapport à une électrode de référence Ag/AgCI en balayant le potentiel à 5 mV/sec pour une électrode DSA et un revêtement de typeFigure 6 shows "current-voltage" curves in a chlorate solution at 22 ° C measured against an Ag / AgCl reference electrode by scanning the potential at 5 mV / sec for a DSA electrode and a coating such as
Fe3-χAI-|+xMyTz sur un substrat de titane. On constate que le revêtement cathodique est tout aussi résistant à la corrosion que la DSA. Le seuil de corrosion est de 1.2V environ. Le couple galvanique entre ces matériaux dissimilaires est ainsi réduit par un choix approprié de la composition chimique du revêtement à base d'aluminure de fer. Fe 3-χAI- | + x MyT z on a titanium substrate. It is found that the cathodic coating is just as resistant to corrosion as the DSA. The corrosion threshold is about 1.2V. The galvanic torque between these dissimilar materials is thus reduced by a suitable choice of the chemical composition of the iron aluminide coating.
Sans être restrictif, la Figure 7 montre des vues schématiques d'électrodes bipolaires selon l'invention. Pour la première électrode, une face possède un revêtement anodique alors que l'autre face possède un revêtement cathodique. Dans la deuxième électrode bipolaire, un bout de l'électrode est revêtu des deux cotés par un revêtement cathodique alors que l'autre bout est revêtu par un revêtement anodique. Without being restrictive, Figure 7 shows schematic views of bipolar electrodes according to the invention. For the first electrode, one side has an anode coating while the other side has a cathode coating. In the second bipolar electrode, one end of the electrode is coated on both sides with a cathode coating while the other end is coated with anodic coating.
Sans être restrictif, la Figure 8 montre des vues schématiques de modules bipolaires constitués d'un assemblage d'électrodes bipolaires représentées à la Figure 7. Les Figures 9a et 9b montrent des photographies d'électrodes bipolaires telles que représentées schématiquement à la Figure 7 et la Figure 9c montre l'apparence d'une électrode bipolaire selon l'invention après une immersion de 69 heures dans une solution chlorate à 22°C. On observe un début de corrosion par piqûre de la partie cathodique mais l'intégrité structurale du revêtement est encore excellente. Without being restrictive, Figure 8 shows schematic views of bipolar modules consisting of a bipolar electrode assembly shown in Figure 7. Figures 9a and 9b show photographs of bipolar electrodes as schematically represented in Figure 7 and Figure 9c shows the appearance of a bipolar electrode according to the invention after immersion of 69 hours in 22 ° chlorate solution C. There is a beginning of pitting corrosion of the cathode part but the structural integrity of the coating is still excellent.

Claims

REVENDICATIONS
1. Une électrode bipolaire à haute efficacité énergétique, ladite électrode possédant une partie pourvue d'un revêtement cathodique et une autre partie qui est distincte de la première et est pourvue d'un revêtement anodique. 1. A high energy efficient bipolar electrode, said electrode having a portion provided with a cathodic coating and another portion which is distinct from the first and is provided with an anode coating.
2. Une électrode bipolaire selon la revendication 1 , caractérisée en ce que le revêtement anodique est de type DSA2. A bipolar electrode according to claim 1, characterized in that the anode coating is of the DSA type.
3. Une électrode bipolaire selon la revendication 1 ou 2, caractérisée en ce que le revêtement cathodique est d'un alliage de formule : 3. A bipolar electrode according to claim 1 or 2, characterized in that the cathodic coating is of an alloy of formula:
Fe3-χAI1 +xMyTz Fe3-χAl 1 + x M y T z
dans laquelle : in which :
M représente une ou plusieurs espèces catalytiques choisies parmi Ru, Ir, Pd, Pt, Rh, Os, Re, Ag et Ni;  M represents one or more catalytic species selected from Ru, Ir, Pd, Pt, Rh, Os, Re, Ag and Ni;
T représente un ou plusieurs éléments parmi Mo, Co, Cr, V, Cu, Zn, Nb, W, Zr, Y, Mn, Cb, Si, B, C, O, N, P, F, S1 Cl et Na; T represents one or more elements among Mo, Co, Cr, V, Cu, Zn, Nb, W, Zr, Y, Mn, Cb, Si, B, C, O, N, P, F, S 1 Cl and Na ;
x est un nombre supérieur à -1 et inférieur ou égal à +1; x is a number greater than -1 and less than or equal to +1;
y est un nombre supérieur à O et inférieur ou égal à +1 ; et y is a number greater than 0 and less than or equal to +1; and
z est un nombre compris entre O et +1. z is a number between 0 and +1.
4. Une électrode bipolaire selon la revendication 1 , 2 ou 3, caractérisée en ce que les revêtements sont appliqués sur un substrat d'acier ou de titane. 4. A bipolar electrode according to claim 1, 2 or 3, characterized in that the coatings are applied to a substrate of steel or titanium.
5. Un module bipolaire d'électrodes caractérisé en ce qu'il contient plusieurs électrodes selon l'une quelconque des revendications 1 à 4. 5. A bipolar electrode module characterized in that it contains a plurality of electrodes according to any one of claims 1 to 4.
6. Usage d'une électrode bipolaire selon l'une quelconque des revendications 1 à 4, pour l'électrosynthèse du chlorate de sodium. 6. Use of a bipolar electrode according to any one of claims 1 to 4, for the electrosynthesis of sodium chlorate.
7. Usage d'un module bipolaire d'électrodes selon la revendication 5, pour l'électrosynthèse du chlorate de sodium. 7. Use of a bipolar electrode module according to claim 5 for the electrosynthesis of sodium chlorate.
EP10796605.3A 2009-07-08 2010-04-08 Bipolar electrodes with high energy efficiency, and use thereof for synthesising sodium chlorate Withdrawn EP2451995A4 (en)

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CA2671211A CA2671211A1 (en) 2009-07-08 2009-07-08 Highly energy efficient bipolar electrodes and use thereof for the synthesis of sodium chlorate
PCT/CA2010/000531 WO2011003173A1 (en) 2009-07-08 2010-04-08 Bipolar electrodes with high energy efficiency, and use thereof for synthesising sodium chlorate

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US9278241B2 (en) * 2013-04-01 2016-03-08 Jeffry L. VanElverdinghe Trampoline with elongate spring mount and bed with integral spring cover
US9050482B1 (en) * 2013-04-01 2015-06-09 Jeffry L. VanElverdinghe Trampoline with elongate spring mount and bed with integral spring cover
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