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EP0356806B1 - Procédé de production d'acide chromique - Google Patents

Procédé de production d'acide chromique Download PDF

Info

Publication number
EP0356806B1
EP0356806B1 EP89115034A EP89115034A EP0356806B1 EP 0356806 B1 EP0356806 B1 EP 0356806B1 EP 89115034 A EP89115034 A EP 89115034A EP 89115034 A EP89115034 A EP 89115034A EP 0356806 B1 EP0356806 B1 EP 0356806B1
Authority
EP
European Patent Office
Prior art keywords
chromic acid
electrolysis
dichromate
solution
membrane
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89115034A
Other languages
German (de)
English (en)
Other versions
EP0356806A2 (fr
EP0356806A3 (en
Inventor
Helmut Dr. Klotz
Hans Dieter Pinter
Rainer Dr. Weber
Hans-Dieter Dr. Block
Norbert Dr. Lönhoff
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.)
Bayer AG
Original Assignee
Bayer AG
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 Bayer AG filed Critical Bayer AG
Publication of EP0356806A2 publication Critical patent/EP0356806A2/fr
Publication of EP0356806A3 publication Critical patent/EP0356806A3/de
Application granted granted Critical
Publication of EP0356806B1 publication Critical patent/EP0356806B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • C25B1/22—Inorganic acids

Definitions

  • the invention relates to a process for the production of chromic acid by electrolysis of dichromate and / or monochromate solutions in electrolysis cells, the anode and cathode spaces of which are separated by cation exchange membranes.
  • the electrolytic production of chromic acid takes place in an electrolytic cell, the electrode spaces of which are separated by a cation exchange membrane.
  • a solution of alkali dichromate - usually sodium dichromate -, alkali monochromate or a mixture of alkali dichromate with alkali monochromate is introduced into the anode compartment and converted into a solution containing chromic acid by selectively transferring alkali ions through the membrane into the cathode compartment.
  • alkali dichromate usually sodium dichromate -, alkali monochromate or a mixture of alkali dichromate with alkali monochromate
  • the electrolysis is operated so that constant ratios of chromic acid to alkali ions are established in continuous operation.
  • the solutions formed in the anode compartment of the cell are concentrated, it being possible for the crystallization to take place, for example, at 60 to 100.degree.
  • the crystallized chromic acid is separated off, washed and dried.
  • the object of the invention was to provide a process for the production of chromic acid by electrolysis which does not have the disadvantages described.
  • the invention relates to a process for the production of chromic acid by electrolysis of dichromate and / or monochromate solutions in electrolysis cells, the anode and cathode spaces of which are separated by a cation exchange membrane, which is characterized in that the chromic acid content of the solution in the anode space increases periodically compared to a continuous operating state becomes.
  • This increase is preferably carried out by lowering the throughput of the dichromate and / or monochromate solution through the anode compartment of the cell.
  • the process according to the invention is preferably operated so that the periodic increase in the chromic acid concentration is carried out after an electrolysis time of 1 to 100 days.
  • the choice of the time of this measure depends on the content of polyvalent cations in the dichromate and / or monochromate solution. If these cations are very low, the measure can also be carried out after more than 100 days.
  • the electrolytic cells used in the examples consisted of anode compartments made of pure titanium and cathode compartments made of stainless steel. Cation exchange membranes from Du Pont with the designation Nafion® 324 were used as membranes.
  • the cathodes were made of stainless steel and the anodes were made of expanded titanium with an electrocatalytically active layer of tantalum oxide and iridium oxide. Such anodes are described, for example, in US Pat. No. 3,878,083.
  • the distance between the electrodes and the membrane was 1.5 mm in all cases.
  • Sodium dichromate solutions with a content of 800 g / l Na2Cr2O7 ⁇ 2 H2O and with the levels of impurities listed in the individual examples were introduced into the anode compartments.
  • the electrolysis temperature was 80 ° C. in all cases and the current density was 3 kA / m2 of the projected area of the anode and cathode facing the membrane, this area being 11.4 cm ⁇ 6.7 cm.
  • these solutions were converted into solutions containing chromic acid, the rate of introduction of the sodium dichromate solutions being chosen such that molar ratios of sodium ions to chromium (VI) of 0.8 and 0.4 were established in the anolytes.
  • the electrolysis cells were operated in such a way that molar ratios of sodium ions to chromium (VI) of 0.8 and in each case 3 days of 0.4 were obtained in the anolyte.
  • the membrane had and was like the membrane of Example 1 interspersed with white inclusions.
  • the life of the membrane was considerably extended under the selected conditions with high calcium contents in the electrolyte.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Claims (4)

1. Procédé de préparation d'acide chromique par électrolyse de solutions de dichromate et/ou de monochromate dans des cellules d'électrolyse dont les compartiments anodique et cathodique sont séparés par des membranes échangeuses de cations, caractérisé en ce que la teneur en acide chromique de la solution dans le compartiment anodique est augmentée périodiquement par rapport à un régime continu.
2. Procédé selon la revendication 1, caractérisé en ce que l'augmentation périodique de la teneur en acide chromique est effectuée par abaissement du débit de la solution de dichromate et/ou de monochromate à travers le compartiment anodique.
3. Procédé selon la revendication 1, caractérisé en ce que l'augmentation périodique de la teneur en acide chromique est réalisée par élévation de l'intensité du courant et/ou par addition externe d'acide chromique ou d'une solution d'acide chromique.
4. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que l'augmentation périodique est effectuée après un temps d'électrolyse de 1 à 100 jours.
EP89115034A 1988-08-27 1989-08-15 Procédé de production d'acide chromique Expired - Lifetime EP0356806B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3829125 1988-08-27
DE3829125A DE3829125A1 (de) 1988-08-27 1988-08-27 Verfahren zur herstellung von chromsaeure

Publications (3)

Publication Number Publication Date
EP0356806A2 EP0356806A2 (fr) 1990-03-07
EP0356806A3 EP0356806A3 (en) 1990-04-18
EP0356806B1 true EP0356806B1 (fr) 1992-06-24

Family

ID=6361724

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89115034A Expired - Lifetime EP0356806B1 (fr) 1988-08-27 1989-08-15 Procédé de production d'acide chromique

Country Status (10)

Country Link
US (1) US5071522A (fr)
EP (1) EP0356806B1 (fr)
JP (1) JP2839154B2 (fr)
AR (1) AR244351A1 (fr)
BR (1) BR8904279A (fr)
CA (1) CA1337808C (fr)
DE (2) DE3829125A1 (fr)
ES (1) ES2032636T3 (fr)
MX (1) MX171486B (fr)
TR (1) TR24639A (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6063252A (en) * 1997-08-08 2000-05-16 Raymond; John L. Method and apparatus for enriching the chromium in a chromium plating bath

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA739447A (en) * 1966-07-26 W. Carlin William Electrolytic production of chromic acid
US2099658A (en) * 1933-11-09 1937-11-16 Gilbert Preparation of chromic acid and sparingly soluble chromates
US2213249A (en) * 1934-07-23 1940-09-03 Armstrong Cork Co Insulation board and method of making the same
US3305463A (en) * 1962-03-16 1967-02-21 Pittsburgh Plate Glass Co Electrolytic production of dichromates
GB1399402A (en) * 1972-02-10 1975-07-02 Marley Homes Ltd Reinforced woodwool slab
DE2854228C2 (de) * 1978-12-15 1983-11-24 Ytong AG, 8000 München Mehrschichtenplatte aus Gasbeton sowie Verfahren zu ihrer Herstellung
FR2455984A1 (fr) * 1979-05-10 1980-12-05 Dvihally Sandor Procede de fabrication de panneaux de particules
CA1141640A (fr) * 1979-06-08 1983-02-22 Thomas A. Pilgrim Elements de construction
WO1983001410A1 (fr) * 1981-10-26 1983-04-28 Teare, John, W. Procede et dispositif de production de panneaux en beton
DE3313641C2 (de) * 1983-04-15 1986-06-12 M.A.N.- Roland Druckmaschinen AG, 6050 Offenbach Vorrichtung zum Auftragen einer Schicht aus einer flüssigen feinkeramischen Masse auf einen Träger
GB2236876A (en) * 1989-10-12 1991-04-17 Bpb Industries Plc Control of the manufacture of plaster board
DE9313351U1 (de) * 1993-09-04 1993-11-04 Wedi, Helmut, 48282 Emsdetten Plattenförmiges Bauteil
DE59307325D1 (de) * 1992-10-29 1997-10-16 Helmut Wedi Verfahren zur Herstellung von Winkelhalbzeug aus Verbundplatten

Also Published As

Publication number Publication date
DE58901743D1 (de) 1992-07-30
MX171486B (es) 1993-10-29
EP0356806A2 (fr) 1990-03-07
TR24639A (tr) 1991-12-25
AR244351A1 (es) 1993-10-29
ES2032636T3 (es) 1993-02-16
BR8904279A (pt) 1990-04-17
JP2839154B2 (ja) 1998-12-16
DE3829125A1 (de) 1990-03-01
JPH02102127A (ja) 1990-04-13
EP0356806A3 (en) 1990-04-18
US5071522A (en) 1991-12-10
CA1337808C (fr) 1995-12-26

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