EP1954855A2 - System zur elektrolytischen herstellung von natriumchlorat - Google Patents

System zur elektrolytischen herstellung von natriumchlorat

Info

Publication number
EP1954855A2
EP1954855A2 EP06819847A EP06819847A EP1954855A2 EP 1954855 A2 EP1954855 A2 EP 1954855A2 EP 06819847 A EP06819847 A EP 06819847A EP 06819847 A EP06819847 A EP 06819847A EP 1954855 A2 EP1954855 A2 EP 1954855A2
Authority
EP
European Patent Office
Prior art keywords
cathodes
chlorate
anodes
coating
sodium chlorate
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Withdrawn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
EP06819847A
Other languages
English (en)
French (fr)
Inventor
Nedeljko Krstajic
Vladimir Jovic
Gian Nicola Martelli
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.)
Industrie de Nora SpA
Original Assignee
Industrie de Nora SpA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Industrie de Nora SpA filed Critical Industrie de Nora SpA
Publication of EP1954855A2 publication Critical patent/EP1954855A2/de
Withdrawn legal-status Critical Current

Links

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 a process for the industrial electrolytic production of sodium chlorate, characterised by a high yield and a high electrical efficiency.
  • the production of chlorates ranks among the most important processes of industrial electrochemistry, since sodium chlorate is the raw matter for the production of sodium perchlorate and chlorite and more importantly of chlorine dioxide, employed for water treatment and for bleaching in the paper industry, as a replacement for chlorine.
  • Sodium chlorate is commonly produced in electrolytic cells of the undivided type starting from a sodium chloride brine at controlled pH, with anodic production of hypochlorite and hypochlorous acid, which quickly disproportionate at the process temperatures (60-90 0 C) generating chlorate, while hydrogen evolution takes place at the cathode side.
  • the electrolytic cells for chlorate production can be of the monopolar or of the bipolar type: in the most common case, they consist however of a multiplicity of cathodes and a multiplicity of anodes disposed in a comb-like structure and mutually intercalated.
  • the anodes generally consist of a titanium substrate activated with suitable catalytic coatings for chlorine evolution, comprising noble metals such as platinum, ruthenium, palladium, iridium or oxides thereof, as such or in admixture with other stabilising oxides for instance as disclosed in US 3,632,498;
  • the cathodes are generally made of a ferrous material, such as for example low carbon steels, and are normally not activated.
  • Some catalytic coatings for hydrogen evolution suitable for ferrous cathodic substrates are in fact known in the art, for instance comprising molybdenum and/or tungsten alloys with iron, cobalt or nickel, as disclosed in GB 992,350 and GB 1 ,004,380, in the attempt of improving the process voltage and thus decreasing the rather high energy costs; the voltage gain obtained with these types of activation is nevertheless considered too small for justifying the adoption thereof in industrial manufacturing processes.
  • the electrolyte initially consisting of a sodium chloride brine is either progressively enriched in chlorate until reaching the required concentration in a batch cycle, or it is at least partially withdrawn at the cell outlet and subjected to a chlorate separation process, while a restoration of sodium chloride concentration is simultaneously carried out in the cell.
  • the control of pH is an essential factor to keep the efficiency high, due to the competition between the chlorate generation reaction and the anodic oxygen evolution, and even more between the cathodic hydrogen evolution and the undesirable hypochlorite reduction; the optimum pH interval to maximise the efficiency ranges between 6 and 7, and even more preferably between 6.3 and 6.6.
  • the invention consists of a system for sodium chlorate production comprising electrolytic cells fed with a buffered sodium chloride brine, wherein the buffering agent comprises phosphate ions at a concentration not lower than 1 g/l.
  • phosphate ion concentration it is hereby intended the sum of the concentrations of all the ionic species derived from phosphoric acid according to their mutual equilibrium in aqueous solutions, for instance comprising HbPO 4 " , HPO 4 2" , PO 4 3" anions and optionally the oligomers derived therefrom.
  • the sodium chloride brine of the system of the invention contains chromate and/or dichromate ions at a concentration not higher than 0.1 g/l; in an even more preferred embodiment, the sodium chloride brine is free of chromium in any form.
  • the electrolytic cells of the system of the invention are equipped with cathodes consisting of a ferrous matrix, for instance carbon steel, activated with a coating consisting of a molybdenum or tungsten alloy with a metal selected between iron, cobalt and nickel.
  • cathodes consisting of a ferrous matrix, for instance carbon steel
  • a coating consisting of a molybdenum or tungsten alloy with a metal selected between iron, cobalt and nickel.
  • the catalytic effect of coatings such as Fe-Mo alloy can be for instance attributable in part to the higher ionic adsorption and to the formation of inhibiting films of higher efficacy, most likely due to their reduced thickness. Such an effect is already sensible with the chromium oxide polymer films generated under the effect of chromate or dichromate adsorption, but it is much more evident in presence of films containing phosphoric species.
  • the cathodic catalytic coating as herein described are preferably applied galvanically, with a thickness preferably comprised between 10 and 50 micrometres.
  • a series of cathodes for electrolytic cell was prepared starting from 0.5 mm thick carbon steel perforated sheets; the sheets were degreased in a saturated solution of caustic soda in ethanol for 5 minutes, then etched in 25% by weight HCI for 2 minutes. The samples were then rinsed with distilled water, dried, weighed and immersed in a bath for Fe-Mo alloy electrodeposition.
  • the bath was prepared by dissolution of 9 g/l FeCI 3 , 40 g/l Na 2 MoO 4 , 75 g/l NaHCO 3 and 45 g/l Na 2 P 2 O 7 in distilled water, and the deposition was carried out at a constant current density of 100 mA/cm 2 at a temperature of 60 0 C, making use of a platinum fine mesh as the counterelectrode, under stirring.
  • the deposition was protracted until obtaining a 20 micrometre thick alloy comprised of 47% by weight molybdenum and 53% by weight iron, as detected by a subsequent EDS test (X-ray energy dispersion spectroscopy).
  • the cells of example 1 one comprising Fe-Mo alloy-coated steel cathodes and the other with non activated cathodes, were employed in a discontinuous sodium chlorate manufacturing process.
  • the feed brine had an initial composition of 300 g/l NaCI added with 3 g/l of Na 2 Cr 2 O 7 , as known in the art.
  • the initial feed pH was 6.41.
  • Each of the two cells was operated at a current density of 2.5 kA/m 2 at a temperature of 61 0 C, and the test was protracted for 8 hours, until obtaining a chlorate concentration of about 0.8 mol/l.
  • the cell with the activated cathodes worked at a very stable voltage, comprised between 3.01 and 3.02 V, with a 98% efficiency; the cell with the non activated cathodes worked at a voltage comprised between 3.14 and 3.17 V with 97% efficiency.
  • the hypochlorite concentration was quickly stabilised at a value of 0.06 mol/l.
  • the test of example 2 was repeated with a feed brine having a starting composition of 300 g/l NaCI added with 3 g/l of sodium acid phosphates (as the sum of Na 2 HPO 4 and NaH 2 PO 4 ) and 0.1 g/l Na 2 Cr 2 O 7 , in accordance with the invention.
  • the initial feed pH was 6.40.
  • Each of the two cells, equipped with new cathodes, was operated at a current density of 2.5 kA/m 2 at a temperature comprised between 60 and 61 0 C, and the test was protracted for 8 hours, until obtaining a chlorate concentration of about 0.8 mol/l.
  • the cell with the activated cathodes worked at a voltage comprised between 2.86 and 2.87 V, with a 97% efficiency; the cell with the non activated cathodes worked at a voltage comprised between 3.08 and 3.12 V with 91 % efficiency.
  • the hypochlorite concentration was quickly stabilised at a value of 0.06 mol/l for the cell with activated cathodes, and of 0.07 mol/l for the cell with non activated cathodes.
  • the test of example 2 was repeated with a feed brine having a starting composition of 300 g/l NaCI added with 3 g/l of sodium acid phosphates (as the sum of Na2HPO4 and NaH 2 PO 4 ) and free of chromium, in accordance with the invention.
  • the initial feed pH was 6.41.
  • ach of the two cells, equipped with new cathodes, was operated at a current density of 2.5 kA/m 2 at a temperature of 61 0 C, and the test was protracted for 8 hours, until obtaining a chlorate concentration of about 0.8 mol/l.
  • the cell with the activated cathodes worked at a voltage comprised between 2.50 and 2.53 V, with a 94% efficiency; the cell with the non activated cathodes worked at a voltage comprised between 3.16 and 3.17 V with 72% efficiency.
  • the hypochlorite concentration was quickly stabilised at a value of 0.065 mol/l for the cell with activated cathodes, and of 0.076 mol/l for the cell with non activated cathodes.
  • Example 2 shows, as known by those skilled in the art, that the activation of cathodes consisting of a ferrous substrate by means of a molybdenum and iron alloy in combination with a brine of the prior art improves the electrochemical performances and the process efficiency; the extent of such improvement is nevertheless rather modest.
  • Example 3 shows that the brine in accordance with the invention, with a significant phosphate content, allows reducing the addition of chromium to minimum levels, maintaining in any case the process efficiency at acceptable levels also making use of non activated cathodes. Moreover, the energy saving obtainable through the use of non activated cathodes is more than interesting, and the efficiency in this case is substantially preserved.
  • Example 4 shows that the brine totally free of chromium according to a preferred embodiment of the invention, coupled to the use of activated cathodes, allows such a high energy saving that the small efficiency loss of the process can be considered negligible, also in view of the lower cost for the treatment of exhausts permitted by the absence of chromium.
  • the total elimination of chromium does not allow the use of non activated cathodes any more, because the process efficiency is lowered to non acceptable levels.

Landscapes

  • 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)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
EP06819847A 2005-11-30 2006-11-29 System zur elektrolytischen herstellung von natriumchlorat Withdrawn EP1954855A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT002298A ITMI20052298A1 (it) 2005-11-30 2005-11-30 Sistema per la produzione elettrolitica di clorato sodico
PCT/EP2006/069079 WO2007063081A2 (en) 2005-11-30 2006-11-29 System for the electrolytic production of sodium chlorate

Publications (1)

Publication Number Publication Date
EP1954855A2 true EP1954855A2 (de) 2008-08-13

Family

ID=38001688

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06819847A Withdrawn EP1954855A2 (de) 2005-11-30 2006-11-29 System zur elektrolytischen herstellung von natriumchlorat

Country Status (9)

Country Link
US (1) US20080230381A1 (de)
EP (1) EP1954855A2 (de)
CN (1) CN101321897A (de)
AR (1) AR058261A1 (de)
BR (1) BRPI0619215A2 (de)
CA (1) CA2631817A1 (de)
IT (1) ITMI20052298A1 (de)
NO (1) NO20082616L (de)
WO (1) WO2007063081A2 (de)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010130546A1 (en) * 2009-05-15 2010-11-18 Akzo Nobel Chemicals International B.V. Activation of cathode
EP2681159A2 (de) 2011-03-04 2014-01-08 Tennant Company Reinigungslösungserzeuger
CA2750881A1 (fr) * 2011-08-23 2013-02-23 Hydro-Quebec Methode pour reduire l`impact negatif des impuretes sur les electrodes servant a l`electrosynthese du chlorate de sodium
CA2870097A1 (en) * 2012-04-23 2013-10-31 Chemetics Inc. Surface modified stainless steel cathode for electrolyser
US9556526B2 (en) 2012-06-29 2017-01-31 Tennant Company Generator and method for forming hypochlorous acid
WO2020070172A1 (en) 2018-10-02 2020-04-09 Nouryon Chemicals International B.V. Selective cathode for use in electrolytic chlorate process
CN113718274B (zh) * 2020-09-28 2023-06-20 上海赛一水处理科技股份有限公司 一种固体剂型的电解质及其制备方法和用途
IT202200025551A1 (it) 2022-12-14 2024-06-14 Soc Chimica Bussi S P A Procedimento per la produzione di clorati

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5084149A (en) * 1989-12-26 1992-01-28 Olin Corporation Electrolytic process for producing chlorine dioxide

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887444A (en) * 1957-03-25 1959-05-19 George H Graves Process of and means for chlorinating swimming pools or the like
US3350294A (en) * 1962-11-21 1967-10-31 Ici Australia Ltd Electrodes
GB1195871A (en) * 1967-02-10 1970-06-24 Chemnor Ag Improvements in or relating to the Manufacture of Electrodes.
FR2244708B1 (de) * 1973-09-25 1977-08-12 Ugine Kuhlmann
FR2446869A1 (fr) * 1979-01-16 1980-08-14 Ugine Kuhlmann Amelioration du rendement faraday dans la preparation electrolytique du chlorate de sodium
US4194953A (en) * 1979-02-16 1980-03-25 Erco Industries Limited Process for producing chlorate and chlorate cell construction
US4354915A (en) * 1979-12-17 1982-10-19 Hooker Chemicals & Plastics Corp. Low overvoltage hydrogen cathodes
US4461692A (en) * 1982-05-26 1984-07-24 Ppg Industries, Inc. Electrolytic cell
NO168145C (no) * 1989-08-21 1992-01-15 Forsvarets Forsknings Celle
US5294307A (en) * 1992-07-31 1994-03-15 Huron Tech Corp Integrated process for the production of alkali and alkaline earth metal chlorates and chlorine dioxide
US7329388B2 (en) * 1999-11-08 2008-02-12 Princeton Biochemicals, Inc. Electrophoresis apparatus having staggered passage configuration

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5084149A (en) * 1989-12-26 1992-01-28 Olin Corporation Electrolytic process for producing chlorine dioxide

Also Published As

Publication number Publication date
BRPI0619215A2 (pt) 2011-09-20
ITMI20052298A1 (it) 2007-06-01
WO2007063081A2 (en) 2007-06-07
WO2007063081A3 (en) 2007-11-08
AR058261A1 (es) 2008-01-30
US20080230381A1 (en) 2008-09-25
CN101321897A (zh) 2008-12-10
CA2631817A1 (en) 2007-06-07
NO20082616L (no) 2008-06-12

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