ZA200300111B - Activation of a cathode. - Google Patents
Activation of a cathode. Download PDFInfo
- Publication number
- ZA200300111B ZA200300111B ZA200300111A ZA200300111A ZA200300111B ZA 200300111 B ZA200300111 B ZA 200300111B ZA 200300111 A ZA200300111 A ZA 200300111A ZA 200300111 A ZA200300111 A ZA 200300111A ZA 200300111 B ZA200300111 B ZA 200300111B
- Authority
- ZA
- South Africa
- Prior art keywords
- cathode
- electrocatalytic
- solution
- coating solution
- acid
- Prior art date
Links
- 230000004913 activation Effects 0.000 title claims abstract description 15
- 239000011248 coating agent Substances 0.000 claims abstract description 42
- 238000000576 coating method Methods 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 28
- 229910052751 metal Inorganic materials 0.000 claims abstract description 19
- 239000002184 metal Substances 0.000 claims abstract description 19
- 239000002904 solvent Substances 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 18
- 239000002253 acid Substances 0.000 claims abstract description 14
- 150000002739 metals Chemical class 0.000 claims abstract description 10
- 150000003839 salts Chemical class 0.000 claims abstract description 10
- 150000007513 acids Chemical class 0.000 claims abstract description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 6
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims abstract description 6
- 239000000460 chlorine Substances 0.000 claims abstract description 6
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 6
- 239000002244 precipitate Substances 0.000 claims abstract description 5
- 238000001035 drying Methods 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 51
- 229910052703 rhodium Inorganic materials 0.000 claims description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical group [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 9
- 239000008139 complexing agent Substances 0.000 claims description 7
- 229910052801 chlorine Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- -1 pB-aminopropionate Chemical compound 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 150000001298 alcohols Chemical class 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 229910052763 palladium Inorganic materials 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 2
- DHMQDGOQFOQNFH-UHFFFAOYSA-M Aminoacetate Chemical compound NCC([O-])=O DHMQDGOQFOQNFH-UHFFFAOYSA-M 0.000 claims description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 2
- AEMRFAOFKBGASW-UHFFFAOYSA-M Glycolate Chemical compound OCC([O-])=O AEMRFAOFKBGASW-UHFFFAOYSA-M 0.000 claims description 2
- OFOBLEOULBTSOW-UHFFFAOYSA-L Malonate Chemical compound [O-]C(=O)CC([O-])=O OFOBLEOULBTSOW-UHFFFAOYSA-L 0.000 claims description 2
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 claims description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 claims description 2
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims description 2
- 150000003863 ammonium salts Chemical class 0.000 claims description 2
- 239000003637 basic solution Substances 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- XPPKVPWEQAFLFU-UHFFFAOYSA-J diphosphate(4-) Chemical compound [O-]P([O-])(=O)OP([O-])([O-])=O XPPKVPWEQAFLFU-UHFFFAOYSA-J 0.000 claims description 2
- 235000011180 diphosphates Nutrition 0.000 claims description 2
- 235000011187 glycerol Nutrition 0.000 claims description 2
- 229910052737 gold Inorganic materials 0.000 claims description 2
- 239000010931 gold Substances 0.000 claims description 2
- 229910052741 iridium Inorganic materials 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229940049920 malate Drugs 0.000 claims description 2
- BJEPYKJPYRNKOW-UHFFFAOYSA-N malic acid Chemical compound OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 2
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical compound O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 claims description 2
- 229910052707 ruthenium Inorganic materials 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- KDYFGRWQOYBRFD-UHFFFAOYSA-L succinate(2-) Chemical compound [O-]C(=O)CCC([O-])=O KDYFGRWQOYBRFD-UHFFFAOYSA-L 0.000 claims description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-M Lactate Chemical compound CC(O)C([O-])=O JVTAAEKCZFNVCJ-UHFFFAOYSA-M 0.000 claims 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 abstract 1
- 229910001902 chlorine oxide Inorganic materials 0.000 abstract 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 16
- 239000010948 rhodium Substances 0.000 description 14
- 238000004140 cleaning Methods 0.000 description 12
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 10
- 239000003638 chemical reducing agent Substances 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000012487 rinsing solution Substances 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- AMQJEAYHLZJPGS-UHFFFAOYSA-N N-Pentanol Chemical compound CCCCCO AMQJEAYHLZJPGS-UHFFFAOYSA-N 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000010422 painting Methods 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 230000009849 deactivation Effects 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 150000007524 organic acids Chemical class 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000007420 reactivation Effects 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 2
- 239000003518 caustics Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 235000006408 oxalic acid Nutrition 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XMIIGOLPHOKFCH-UHFFFAOYSA-N 3-phenylpropionic acid Chemical compound OC(=O)CCC1=CC=CC=C1 XMIIGOLPHOKFCH-UHFFFAOYSA-N 0.000 description 1
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- 235000011054 acetic acid Nutrition 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- RJTANRZEWTUVMA-UHFFFAOYSA-N boron;n-methylmethanamine Chemical compound [B].CNC RJTANRZEWTUVMA-UHFFFAOYSA-N 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000005202 decontamination Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002815 nickel Chemical class 0.000 description 1
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 150000003283 rhodium Chemical class 0.000 description 1
- SONJTKJMTWTJCT-UHFFFAOYSA-K rhodium(iii) chloride Chemical class [Cl-].[Cl-].[Cl-].[Rh+3] SONJTKJMTWTJCT-UHFFFAOYSA-K 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000010944 silver (metal) Substances 0.000 description 1
- 229910001379 sodium hypophosphite Inorganic materials 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- QFJIELFEXWAVLU-UHFFFAOYSA-H tetrachloroplatinum(2+) dichloride Chemical compound Cl[Pt](Cl)(Cl)(Cl)(Cl)Cl QFJIELFEXWAVLU-UHFFFAOYSA-H 0.000 description 1
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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
-
- 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
- C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
- C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
Landscapes
- Chemical & Material Sciences (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Electrochemistry (AREA)
- Mechanical Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Cold Cathode And The Manufacture (AREA)
- Gas-Filled Discharge Tubes (AREA)
- Solid Thermionic Cathode (AREA)
- Chemically Coating (AREA)
- Secondary Cells (AREA)
Abstract
The present invention relates to a method for activation of a cathode comprising at least a cathode substrate wherein the cathode is cleaned by means of an acid,the cleaned cathode is coated with at least one electrocatalytic coating solution, drying the coated cathode until it is at least substantially dry, and thereafter contacting the cathode with a solvent redissolving precipitated electrocatalytic salts or acids formed on the cathode, originating from the electrocatalytic solution, to form dissolved electrocatalytic metal ions on the cathode surface, so that said electrocatalytic metal ions can precipitate as metals on the cathode. The invention also comprises a cathode obtainable by the method and the use of an activated cathode in an electrolytic cell for producing chlorine and alkali hydroxide.
Description
Activation of a cathode
The present invention relates to a method for activating a cathode suitable for activation on site at a production plant. The invention also relates to the use of the activated cathode in an electrolytic cell producing chlorine and alkali metal hydroxide.
Electrodes are commonly, when in operation, immersed in an electrolyte in an electrolytic cell where chemical products are produced by way of oxidation and reduction reactions of reactants present in the electrolyte. The reduction reactions take place at the cathode where reduction products are obtained. The oxidation reactions take place atthe anode where oxidation products are obtained.
Over time, the electrodes will become exhausted and deactivated due to various deactivation processes taking place while the electrolytic cells are in operation. in most electrolytic processes, the electric energy is the most expensive ‘raw material” in the 16 electrolytic reactions.
In the chlorine and alkali metal hydroxide production, it has been found that the cathodes are liable to progressive deactivation over time. The cathodes are subjected to deposition and precipitation of materials present in the electrolyte and to other deteriorating processes deactivating the cathode. The decrease in activity leads to a higher power consumption due to an increased overvoltage.
It is thus a big concern in electrolysis processes to provide active cathodes throughout the whole electrolysis cycle.
Earlier attempts to solve this problem have involved transportation of the deactivated cathodes to the electrode manufacturer for reactivation. However, the transportation of cathodes is a very expensive and time-consuming alternative to carry out. Another approach of providing active cathodes has involved replacement of the exhausted cathodes with new ones.
US 5 164 062 describes a method for preparing a new cathode comprising coating a cathode substrate of e.g. Ni with palladium and another electrocatalytic metal.
The pH of the coating solution may be adjusted by an organic acid, e.g. acetic acid, oxalic acid and formic acid, or inorganic acids to maintain the pH below 2.8. However, the activation by this method is not always satisfactorily increased. Furthermore, a portion of the active coating solution is wasted in the method described above, because some of the acidic electrocatalytic coating solution is rinsed away from the cathode substrate in order to avoid corrosion of the cathode. The rinsing solution that has taken up remaining electrocatalytic material must then be decontaminated from substrate ions, e.g. nickel or other contaminating ions, which also are present on the cathode before the electrocatalytic material can be reused as coating material in an electrocatalytic solution again. Such decontamination procedure may involve several cleaning steps before the electrocatalytic material has been satisfactorily cleaned.
The present invention intends to solve the above problems. 5 .
The present invention relates to a method of activating a cathode suitable for the production of e.g. chlorine and alkali metal hydroxide. The term “activate” or “activation” etc. as used herein encompass both activation of a new electrode, which is to be prepared, and activation of an electrode, which has already been in operation in an electrolytic cell and which may have lost at least some of its initial activity.
It has been surprisingly found that the activation of a cathode comprising at least a cathode substrate, which may have some remains of an electrocatalytic coating on the . substrate, can easily can be performed on site at the production site. The method comprises at least the following steps: e cleaning the cathode by means of an acid « coating the cleaned cathode with at least one electrocatalytic coating solution » drying the coated cathode until it is at least substantially dry, and thereafter contacting the cathode with a solvent redissolving precipitated electrocatalytic salts or acids formed on the cathode, originating from the electrocatalytic coating solution, to form dissolved electrocatalytic metal ions on the cathode surface, so that the electrocatalytic metal ions can precipitate as metals on the cathode.
The solvent must be able to redissolve any possible precipitated electrocatalytic salts or acids on the cathode originating from the electrocatalytic coating solution. The solvent may contain a small amount of electrocatalytic metals dissolved therein, which may originate from a rinsing solution containing remains of an electrocatalytic solution.
The contacting of the solvent with the cathode is suitably performed by spraying or in any other way putting solvent on the cathode in a suitable amount.
By the term “substantially dry” is meant a coated cathode which contains only a small quantity of solution on its surface such that the solution does not substantially flow away from the cathode. Suitably, such quantity ranges from about 0 to about 10 mi/im?, preferably from about 0 to about 5 ml/m? solution.
The cathode comprises a substrate of e.g. nickel, cobalt, copper, iron, steel, particularly stainless steel, or alloys or mixtures thereof, preferably nickel. The cathode may also comprise remains of an electrocatalytic coating deposited on the substrate, and/or contaminants from an electrolytical process.
Used cathodes are preferably disassembled from the cells before activation.
According to one embodiment, the cathode is welded to a pan. The used cathode pan structure, i.e. the cathode and the pan, is preferably disassembled and removed from the cell before activation. For simplicity, the term “cathode”, where otherwise not stated, will henceforth also signify the cathode pan structure.
The cathode is cleaned with a cleaning solution comprising at least one acid.
The pH of the cleaning solution is suitably adjusted by addition of an inorganic acid, e.g.
HCI, H,SO,, HNO;, or an organic acid, e.g. oxalic acid or other organic acids, or mixtures thereof, suitably to a pH from about —1 to about 6, preferably from about -1 to about 3.
The acid reacts with the cathode substrate and is also believed to react with precipitated substances on the substrate and the electrocatalytic coating. The cleaning time is not critical and may range from about a few minutes to about 30 minutes or more. The temperature during the cleaning is not critical and may be at e.g. room temperature, suitably the temperature ranges from about 0 to about 100 °C, preferably from about 0 to about 35 °C.
According to one preferred embodiment of the invention, also a reducing agent is comprised in the cleaning solution which is believed to prevent corrosion of the cathode and facilitate removal of deactivating precipitates on remaining electrocatalytic coating.
The reducing agent is also believed to stabilise activated areas of the cathode. The reducing agent may be present in the cleaning solution at a concentration of from about 0.5 to about 50 wit%, preferably from about 0.5 to about 10 wt%. The reducing agent is suitably selected from alcohols such as isopropyl alcohol or n-pentanol, HCI, H;PO,,
HsPOs, N.H;, NHOH, NH; NaS, NaBH, sodium hypophosphite (NaH.PO,), dimethylamine borane (CH;).NHBHj3, or mixtures thereof. Preferred reducing agents are selected from HCI, H;PO,, H;PO3;, NH, NH,OH, and NH;, and most preferably from HCI.
After the cleaning, the cathode is suitably rinsed and dried. The cathode is then contacted with at least one electrocatalytic coating solution, comprising an electrocatalytic metal and preferably a complexing agent.
According to one embodiment of the invention, several electrocatalytic coating solutions, e.g. two or more coating solutions, may be contacted with the cathode. The coating solutions are suitably contacted with the cathode one after the other, preferably when the previously applied coating solution has dried on the surface of the cathode.
The electrocatalytic coating solution or solutions are suitably applied by means of painting, rolling or any other plausible method suitable for on-site coating. The electrocatalytic coating solution suitably comprises one or several noble metals in the form of salts or acids or the like, selected from the platinum group, e.g. Ru, Rh, Os, Ir, Pd,
Pt, Au, Ag, or alloys or mixtures thereof. The noble metals can suitably be present in the coating solution at a concentration from about 25 to about 200, preferably from about 50 to about 150 g metalllitre coating solution. The electrocatalytic metals are suitably derived from salts or acids of e.g. platinum metals such as hexa chloro platinum acid, platinum metal alcoxi complexing materials, chlorides or the like. The coating time of the cathode is not critical and may be for about one hour or more. The temperature of the coating solution suitably is room temperature, but may range from about 0 to about 100 °C. The coating procedure is suitably carried out within the same temperature range, i.e. 0-100 °C, preferably between 0 and 35 °C. Also a complexing agent may be added to the coating solution preferably in a concentration of from about 100 to about 500, and most preferably from about 350 to about 450 g /litre coating solution. The optionally added complexing agent facilitates the oxidation and reduction reactions taking place when the coating solution is contacted with the substrate. The substrate metal of the cathode is spontaneously oxidised to its corresponding ionic form whereas the electrocatalytic metal or metals in the coating solution is reduced from its ionic form to its metallic form thereby forming an electrocatalytic coating on the substrate. It has been found that the complexing agent supports the reduction/oxidation reaction taking place so as to improve the precipitation reaction and the adherence of the electrocatalytic metal to the substrate.
Suitable complexing agents comprise hypophosphorous acid, sulphurous acid, nitrous acid, alcohols such as glycol, glycerine, acetate, propionate, succinate, hydroxyacetate, o-hydroxypropionate, aminoacetate, ethylenediamine, p-aminopropionate, malonate, pyrophosphate, malate, citrate, ammonium salts, EDTA, or mixtures thereof.
The coated cathode is then allowed to dry so it becomes at least substantially dried, suitably from about 0 to about 10 mi/m?, preferably from about 0 to about 5 mi/m?.
Preferably, the coated cathode is completely dried before it is contacted with the solvent.
The dried cathode is then contacted with a solvent suitably comprising a reducing agent.
It has been surprisingly found that the contacting of the solvent with the cathode results in a lower overpotential, often 10-30 mV lower or more, than a cathode not treated in this manner. The solvent may comprise water, suitably in combination with HCI, HsPO,,
HsPOs;, HO, NoHs NH,OH, NH; NaS, Na,SO;K,S0,;, alcohols such as isopropyl alcohol, n-pentanol, or mixtures thereof. The lower overpotential is considered to be principally due to a higher deposit level of electrocatalytic metals on the activated cathode. The concentration of a possible reducing agent in the solvent suitably ranges from about 10 to about 70 wit%, preferably from about 40 to about 50 wi%. The temperature during the contacting of the cathode with a solvent suitably ranges from about 8 to about 60 °C, preferably from about 15 to about 35 °C. The reaction time during which electrocatalytic metals can precipitate as metals on the cathode suitably is from about 1 to about 60 minutes or until the electrode is completely dried. Suitably, solvent can thereafter again be deposited on the cathode to repeat the precipitation procedure of electrocatalytic metals in case such remains exist on the cathode in the form of salts or acids. Suitably, an amount from about 10 to about 100 ml solvent/m? cathode area is contacted with the cathode, preferably from about 50 to about 100 ml solvent/m?.
The activated cathode is then preferably rinsed by a rinsing solution such as 5 water to avoid corrosion, preferably with a basic solution such as NaOH after that the solvent on the cathode has substantially dried. Preferably, the basic rinsing solution has a concentration of e.g. NaOH from about 0.0001 to about 50 wt%, and most preferably from about 0.0001 to about 20 wt%.
The activated cathodes are usually run in the electrolytic cells until their activity is found to be too low, i.e. at an uneconomically low level. This crucial extent of deactivation can be optimised by a person skilled in the art by estimating the electric energy consumed and the activation costs. When the reactivation is to be initiated, the used cathodes are preferably disassembled and removed from their cells. Suitably, the reactivation can be performed in connection with replacement of the membranes arranged in the electrolytic cell.
The present invention also relates to a cathode obtainable by the method as described above.
The invention further concerns the use of an activated cathode in an electrolytic cell for producing chlorine and alkali metal hydroxide.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the gist and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims. The following examples will further illustrate how the described invention may be performed without limiting the scope of it. :
Example 1: A cleaning solution was prepared from concentrated hydrochloric acid (37 wt%) to yield a final concentration of 20 wt% hydrochloric acid. The cathode to be activated was contacted with the cleaning solution by means of painting. 50 ml cleaning solution/m? geometric cathode area was applied. The solution was then allowed to react during 10 minutes at room temperature (25 °C). The cathode was thereafter rinsed thoroughly with deionised water. Meanwhile, a coating solution of RhCl; was prepared by dissolving the rhodium salt in a 20 wt% hydrochloric acid solution, resulting in a final rhodium concentration of 50 g Rh metalllitre coating solution. Also a coating solution of RuCl; was prepared by dissolving the Ru salt in another 20 wt% hydrochloric acid solution resulting in a concentration of 50 g Ru metal/litre coating solution. The rinsed cathode was allowed to dry in room temperature, whereafter the Rh coating solution was applied thereto in an amount of 50 mi/m? geometric cathode area by means of painting. The cathode was then allowed to dry for 1 hour. The Ru coating solution was then applied to the Rh coated cathode in an amount of 50 ml/m? geometric cathode area.
The cathode was then dried whereafter an aqueous solution of 50 wt% Hi;PO. was painted on the cathode. Thereafter, the cathode was allowed to dry whereupon it was rinsed with water. The cathode obtained showed satisfactory activation.
Example 2: Two deactivated nickel-based cathode samples P1 and P2 were cleaned by means of painting with a 20wt% hydrochloric acid solution for 5 minutes. The cathode samples were thereafter rinsed with water and thereafter dried. The two samples were both coated with a 40 ml RhCl; coating solution having a rhodium content of 150 gllitre /m®. The coated samples were then allowed to dry for 1 hour. Unreacted rhodium precipitated during the drying stage and formed rhodium chloride salt on the cathode substrate. The P1 sample was gently rinsed with a caustic solution having a pH of 10, whereupon unreacted precipitated rhodium metal salt (RhCl;) and nickel chloride were rinsed off the cathode sample. The remaining amount of rhodium on the P1 sample only amounted to a small portion of the initially precipitated rhodium content. This was judged from the rhodium colour the rinsing solution got since the metal was partially washed off.
The P2 cathode sample was gently sprayed with a 20 wit% hydrochloric acid after the
RhCl; solution had dried on the sample, whereupon precipitated RhCl; was redissolved.
Subsequent precipitation of metallic rhodium could then take place on the P2 sample.
The addition of hydrochloric acid to the P2 cathode was repeated once after that the P2 cathode had dried. 15 minutes after the second addition of hydrochloric acid, i.e. after that the cathode was substantially dry, the cathode was rinsed with caustic solution in the same manner as the P1 sample. No colour shift could be observed in the rinsing solution due to rinsed off rhodium. It was thus shown that a much higher amount of rhodium had adhered to the P2 sample than to the P1 sample as a result of adding the solvent to the coated and dried sample. Electrolytic trials performed involving use of the activated cathodes showed that the cell voltage was 230 mV lower for the P2 cathode than for the
P1 cathode when the used electrolytic cell was operated at a current density of 4.7 kA/m>.
Claims (11)
1. Method for activation of a cathode comprising at least a cathode substrate characterised inthat . o the cathode is cleaned by means of an acid « the cleaned cathode is coated with at least one electrocatalytic coating solution o drying the coated cathode until it is at least substantially dry, and thereafter contacting the cathode with a solvent 1adissolving precipitated electrocatalytic salts or acids formed on the cathode, originating from the electrocatalytic solution, to form dissolved electrocatalytic metal ions on the cathode surface, so that said electrocatalytic metal ions can precipitate as metals on the cathode.
2. A method according to claim 1, wherein the cathode substrate is selected from nickel, cobalt, copper, iron, steel, or alloys or mixtures thereof.
3. A method as claimed in any of the preceding claims, wherein the cathode substrate is nickel.
4. A method as claimed in any of the preceding claims, wherein the electrocatalytic coating solution comprises a complexing agent.
5. A method according to claim 4, wherein the complexing agent is selected from at least one of hypophosphorous acid, sulphurous acid, nitrous acid, alcohols, glycerine, acetate, propionate, succinate, hydroxyacetate, a-hydroxypropionate, aminoacetate, ethylenediamine, pB-aminopropionate, malonate, pyrophosphate, malate, citrate, ammonium salts, EDTA, or mixtures thereof.
6. A method as claimed in any of the preceding claims, wherein the solvent comprises water.
7. A method as claimed in any of the preceding claims, wherein the electrocatalytic coating solution contains salts or acids of Pt, Rh, Ru, Pd, Ir, Os, Ag, Au or alloys or mixtures thereof.
8. A method as claimed in any of the preceding claims, wherein the activation is performed on a used cathode.
9. A method as claimed in any of the preceding claims, wherein the activated cathode is rinsed with a basic solution.
10. A cathode obtainable by the method according to any of the preceding claims.
11. Use of an activated cathode according to any of the preceding claims in an electrolytic cell producing chlorine and alkali metal hydroxide.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP00850124 | 2000-07-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200300111B true ZA200300111B (en) | 2004-01-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA200300111A ZA200300111B (en) | 2000-07-06 | 2003-01-06 | Activation of a cathode. |
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| Country | Link |
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| EP (1) | EP1297200B1 (en) |
| JP (1) | JP3867913B2 (en) |
| KR (1) | KR100546928B1 (en) |
| CN (1) | CN1242099C (en) |
| AT (1) | ATE350513T1 (en) |
| AU (2) | AU6650201A (en) |
| BR (1) | BR0112203B1 (en) |
| CA (1) | CA2415020C (en) |
| DE (1) | DE60125763T2 (en) |
| WO (1) | WO2002002847A1 (en) |
| ZA (1) | ZA200300111B (en) |
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|---|---|---|---|---|
| JP4771467B2 (en) * | 2005-11-17 | 2011-09-14 | 東亞合成株式会社 | Method for producing high purity alkali metal hydroxide |
| EP1939182A1 (en) * | 2006-12-22 | 2008-07-02 | Speedel Experimenta AG | Process for the preparation of (R or S)-2-Alkyl-3-heterocyclyl-1-propanols |
| JPWO2010061766A1 (en) | 2008-11-25 | 2012-04-26 | 株式会社トクヤマ | Method for producing active cathode for electrolysis |
| US20190106797A1 (en) * | 2016-03-31 | 2019-04-11 | Siemens Aktiengesellschaft | In-Situ Anode Activation By A Cathode In An Alkaline Water Electrolytic Cell |
| JP6672211B2 (en) | 2017-03-21 | 2020-03-25 | 株式会社東芝 | Carbon dioxide electrolysis apparatus and carbon dioxide electrolysis method |
| CN113166953A (en) | 2018-11-30 | 2021-07-23 | 赛杜工程股份有限公司 | Removal of by-products (impurities) |
| WO2020109577A1 (en) | 2018-11-30 | 2020-06-04 | Sedo Engineering Sa | Leucodye (such as leucoindigo) as dispersing aid |
Family Cites Families (3)
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| GB2074190B (en) * | 1980-04-22 | 1984-03-14 | Johnson Matthey Co Ltd | Electrode |
| US5476688A (en) * | 1988-08-29 | 1995-12-19 | Ostolski; Marian J. | Process for the preparation of noble metal coated non-noble metal substrates, coated materials produced in accordance therewith and compositions utilizing the coated materials |
| US5035789A (en) * | 1990-05-29 | 1991-07-30 | The Dow Chemical Company | Electrocatalytic cathodes and methods of preparation |
-
2001
- 2001-06-25 JP JP2002507088A patent/JP3867913B2/en not_active Expired - Fee Related
- 2001-06-25 AT AT01944058T patent/ATE350513T1/en not_active IP Right Cessation
- 2001-06-25 EP EP01944058A patent/EP1297200B1/en not_active Expired - Lifetime
- 2001-06-25 CA CA002415020A patent/CA2415020C/en not_active Expired - Fee Related
- 2001-06-25 AU AU6650201A patent/AU6650201A/en active Pending
- 2001-06-25 KR KR1020027017509A patent/KR100546928B1/en not_active IP Right Cessation
- 2001-06-25 WO PCT/SE2001/001447 patent/WO2002002847A1/en active IP Right Grant
- 2001-06-25 CN CNB018123732A patent/CN1242099C/en not_active Expired - Fee Related
- 2001-06-25 BR BRPI0112203-7A patent/BR0112203B1/en not_active IP Right Cessation
- 2001-06-25 AU AU2001266502A patent/AU2001266502B2/en not_active Ceased
- 2001-06-25 DE DE60125763T patent/DE60125763T2/en not_active Expired - Lifetime
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- 2003-01-06 ZA ZA200300111A patent/ZA200300111B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO2002002847A1 (en) | 2002-01-10 |
| EP1297200A1 (en) | 2003-04-02 |
| KR20030013453A (en) | 2003-02-14 |
| CN1242099C (en) | 2006-02-15 |
| ATE350513T1 (en) | 2007-01-15 |
| KR100546928B1 (en) | 2006-01-26 |
| CA2415020C (en) | 2008-06-10 |
| BR0112203A (en) | 2003-05-13 |
| JP2004502035A (en) | 2004-01-22 |
| EP1297200B1 (en) | 2007-01-03 |
| BR0112203B1 (en) | 2012-05-15 |
| AU2001266502B2 (en) | 2004-05-20 |
| JP3867913B2 (en) | 2007-01-17 |
| DE60125763D1 (en) | 2007-02-15 |
| AU6650201A (en) | 2002-01-14 |
| CA2415020A1 (en) | 2002-01-10 |
| CN1440467A (en) | 2003-09-03 |
| DE60125763T2 (en) | 2007-10-18 |
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