EP0356805B1 - Verfahren zur Herstellung von Alkalidichromaten und Chromsäure - Google Patents

Verfahren zur Herstellung von Alkalidichromaten und Chromsäure Download PDF

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Publication number
EP0356805B1
EP0356805B1 EP89115033A EP89115033A EP0356805B1 EP 0356805 B1 EP0356805 B1 EP 0356805B1 EP 89115033 A EP89115033 A EP 89115033A EP 89115033 A EP89115033 A EP 89115033A EP 0356805 B1 EP0356805 B1 EP 0356805B1
Authority
EP
European Patent Office
Prior art keywords
solution
chromic acid
dichromate
alkali
electrolysis
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
EP89115033A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0356805A2 (de
EP0356805A3 (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 EP0356805A2 publication Critical patent/EP0356805A2/de
Publication of EP0356805A3 publication Critical patent/EP0356805A3/de
Application granted granted Critical
Publication of EP0356805B1 publication Critical patent/EP0356805B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • C25B1/22—Inorganic acids

Definitions

  • the invention relates to processes for the production of alkali dichromates and chromic acid by electrolysis of monochromate and / or dichromate solutions in electrolytic cells whose anode and cathode spaces are separated by cation exchange membranes, an anolyte liquid containing dichromate and / or chromic acid and in the cathode space in the anode space an alkaline alkali ion-containing catholyte liquid is formed.
  • alkali monochromate solutions or suspensions are introduced into the anode compartment of the cell and converted into an alkali dichromate solution by selectively passing alkali ions through the membrane be transferred to the cathode compartment.
  • alkali dichromate or alkali monochromate solutions or a mixture of alkali dichromate and alkali monochromate solutions are introduced into the anode compartment and converted into solutions containing chromic acid.
  • sodium monochromate and / or sodium dichromate solutions are used for these processes.
  • the solutions formed in the anode compartments of the cells are concentrated, it being possible for crystallization of sodium dichromate to take place, for example, at 80 ° C. and that of chromic acid at 60-100 ° C.
  • the crystallized products are separated off, optionally washed and dried.
  • an alkaline alkali ion-containing catholyte liquid is obtained in the cathode compartment, which can consist, for example, of an aqueous sodium hydroxide solution or, as described in CA-A-739 447, of an aqueous solution containing sodium carbonate.
  • the object of the invention was to provide processes for the production of alkali dichromate and chromic acid by electrolysis which do not have the disadvantages described.
  • the invention thus relates to processes for the preparation of alkali dichromates and chromic acid by electrolysis of monochromate and / or dichromate solutions in electrolytic cells, the anode and cathode spaces of which are separated by cation exchange membranes, with anolyte liquid containing dichromate and / or chromic acid and alkaline alkali ions in the cathode space -containing catholyte liquids are formed, which is characterized in that the catholyte liquids are periodically replaced by a solution with a pH less than 6.
  • the method according to the invention is carried out while maintaining the electrolysis current.
  • the catholyte liquids are preferably periodically replaced by a solution with a pH less than 1. Suitable solutions are inorganic acids such as sulfuric acid, phosphoric acid, hydrochloric acid as well as organic acids with different concentrations.
  • the catholyte liquids are periodically replaced by a solution containing chromic acid. It is advantageous to use a solution containing chromic acid, the content of which is 10-900 g chromic acid per liter. This solution can of course also contain proportions of alkali dichromate.
  • the process according to the invention is preferably operated in such a way that the catholyte liquids are replaced by a solution with a pH of less than 6 after an electrolysis time of 1-100 days.
  • the timing of this measure depends on the content of polyvalent cations in the monochromate and / or dichromate solutions and on the anodic current density. If the cations are very low, the liquid can be exchanged even after a period of 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 DuPont 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 900 g / l Na2Cr2O7 ⁇ 2 H2O were introduced into the anode compartments with the levels of impurities listed in the individual examples.
  • the electrolysis temperature was 80 ° C in all cases.
  • the sodium dichromate solutions used in this experiment had the following levels of impurities:
  • the rate of introduction of the sodium dichromate solutions was chosen so that a molar ratio of sodium ions to chromium (VI) of 0.8 was established in the anolyte leaving the cell.
  • a white deposit had formed in the membrane, which essentially consisted of calcium hydroxide.
  • the cell voltage at this point was 4.04 V.
  • the anodes had to be replaced several times due to insufficient durability.
  • the procedure for dissolving and removing the storage was as follows: The cathodically formed 20% sodium hydroxide solution was first replaced by water in the cathode compartment of the cell and then by a solution containing CrO3- and Na2Cr2O7 ⁇ 2 H2O with a pH value of less than 1. This solution had the following composition: 30.3% Na2Cr2O7 ⁇ 2 H2O 30.3% CrO3 39.4% H2O.
  • the sodium dichromate solution used had the following levels of impurities:
  • the sodium dichromate solutions used in this example had the following contamination levels:
EP89115033A 1988-08-27 1989-08-15 Verfahren zur Herstellung von Alkalidichromaten und Chromsäure Expired - Lifetime EP0356805B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3829123A DE3829123A1 (de) 1988-08-27 1988-08-27 Verfahren zur herstellung von alkalidichromaten und chromsaeure
DE3829123 1988-08-27

Publications (3)

Publication Number Publication Date
EP0356805A2 EP0356805A2 (de) 1990-03-07
EP0356805A3 EP0356805A3 (en) 1990-04-18
EP0356805B1 true EP0356805B1 (de) 1992-05-20

Family

ID=6361723

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89115033A Expired - Lifetime EP0356805B1 (de) 1988-08-27 1989-08-15 Verfahren zur Herstellung von Alkalidichromaten und Chromsäure

Country Status (9)

Country Link
US (1) US5094729A (es)
EP (1) EP0356805B1 (es)
JP (1) JP2839155B2 (es)
AR (1) AR244811A1 (es)
BR (1) BR8904280A (es)
CA (1) CA1337807C (es)
DE (2) DE3829123A1 (es)
MX (1) MX170143B (es)
ZA (1) ZA896499B (es)

Families Citing this family (3)

* 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
RU2125120C1 (ru) * 1997-09-29 1999-01-20 Иткин Герман Евсеевич Способ проведения электролиза водного раствора соли
CN101892490A (zh) * 2010-06-24 2010-11-24 中国科学院青海盐湖研究所 一种离子膜电解法连续制备重铬酸钠的方法

Family Cites Families (6)

* 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
US1878918A (en) * 1926-06-02 1932-09-20 Electro Metallurg Co Manufacture of chromic acid
US2333578A (en) * 1939-06-16 1943-11-02 Internat Smelting & Refining C Electrolytic chromate production
US3305463A (en) * 1962-03-16 1967-02-21 Pittsburgh Plate Glass Co Electrolytic production of dichromates
JPS5839916B2 (ja) * 1975-12-29 1983-09-02 サイトウ カズオ ロウカクロムサンヨウエキノサイセイシヨリホウホウオヨビソウチ
US4290864A (en) * 1979-05-29 1981-09-22 Diamond Shamrock Corporation Chromic acid production process using a three-compartment cell

Also Published As

Publication number Publication date
EP0356805A2 (de) 1990-03-07
JPH02102128A (ja) 1990-04-13
CA1337807C (en) 1995-12-26
ZA896499B (en) 1990-05-30
BR8904280A (pt) 1990-04-17
MX170143B (es) 1993-08-09
DE3829123A1 (de) 1990-03-01
US5094729A (en) 1992-03-10
DE58901477D1 (de) 1992-06-25
AR244811A1 (es) 1993-11-30
EP0356805A3 (en) 1990-04-18
JP2839155B2 (ja) 1998-12-16

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