EP0391192B1 - Verfahren zur Herstellung von Alkalidichromaten und Chromsäuren durch Elektrolyse - Google Patents

Verfahren zur Herstellung von Alkalidichromaten und Chromsäuren durch Elektrolyse Download PDF

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Publication number
EP0391192B1
EP0391192B1 EP90105661A EP90105661A EP0391192B1 EP 0391192 B1 EP0391192 B1 EP 0391192B1 EP 90105661 A EP90105661 A EP 90105661A EP 90105661 A EP90105661 A EP 90105661A EP 0391192 B1 EP0391192 B1 EP 0391192B1
Authority
EP
European Patent Office
Prior art keywords
alkali metal
dichromate
sodium
monochromate
chromic acid
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
EP90105661A
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German (de)
English (en)
French (fr)
Other versions
EP0391192A3 (de
EP0391192A2 (de
Inventor
Helmut Dr. Klotz
Rainer Dr. Weber
Norbert Dr. Lönhoff
Hans-Dieter Dr. Block
Hans Dieter Pinter
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Bayer AG
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Bayer AG
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Publication date
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Publication of EP0391192A3 publication Critical patent/EP0391192A3/de
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    • 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
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • 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
    • 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
    • C25B1/28—Per-compounds

Definitions

  • the invention relates to a process for the simultaneous production of alkali dichromates and chromic acid.
  • chromic acid electrolytically from an alkali dichromate solution.
  • the chromic acid is produced in a 3-chamber cell.
  • the alkali dichromate solution introduced into the middle cell is separated from the anode compartment via a diaphragm membrane and from the cathode compartment via a cation exchange membrane, an anolyte solution containing chromic acid and NaOH being formed as the catholyte.
  • membranes based on perfluorinated polymers with exchanger groups are preferably used as cation exchange membranes.
  • These membranes can have both a single-layer and a two-layer structure, the two-layer membranes generally more effectively suppressing the diffusion of hydroxide ions through the membrane, which leads to a higher current efficiency of the electrolysis.
  • this improved current yield is mostly associated with a higher cell voltage than is achieved when using single-layer membranes.
  • Such cation exchange membranes are described, for example, in "H Simmrock, E. Griesenbeck, J. Jörissen and R. Rodermund, Chemie-Ing. Techn. 53 (1981), No. 1, pp. 10 to 25” and are described, for example, under the name Nafion® (Manufacturer: EI DuPont De Nemours & Co., Wilmington, Del./USA) commercially available.
  • single-layer membranes have the advantage that, compared to double-layer membranes, they are less sensitive to multivalent cations, in particular calcium and strontium ions in the alkali metal chromate and / or alkali metal dichromate solutions, which lead to deterioration - and consequently - deterioration the functionality of the membrane.
  • the object of the invention was to provide a process for the simultaneous production of alkali dichromates and chromic acid which does not have the disadvantages described.
  • the invention thus relates to a process for the simultaneous production of alkali dichromate and chromic acid according to claim 1.
  • the aqueous solution which is produced in the cathode compartment consists of an alkali monochromate-containing solution which may also contain alkali dichromate components, preferably of a sodium monochromate-containing solution which may also contain sodium dichromate components.
  • alkali monochromate-containing solution which may also contain alkali dichromate components, preferably of a sodium monochromate-containing solution which may also contain sodium dichromate components.
  • Such solutions are obtained by supplying an alkali dichromate solution or alkali monochromate-containing alkali dichromate solution to the cathode compartment of the cells becomes. It is advantageous to supply an alkali chromate-containing solution to the cathode compartment, in which 70 to 95% of the chromate ions are in the form of dichromations and 5 to 30% are in the form of monochromations.
  • Such solutions are obtained, for example, in the production of sodium dichromate solution from sodium monochromate solution by acidification with carbon dioxide under pressure.
  • an aqueous solution containing sodium monochromate which can also contain sodium dichromate, with a pH of 6 to 7.5 is produced in the cathode compartment.
  • FIG. 1 The method according to the invention is explained in more detail with reference to FIG. 1.
  • the variant of the method according to the invention described in FIG. 1 represents a particularly advantageous embodiment.
  • Chrome ore is broken down by alkaline oxidative digestion with soda and atmospheric oxygen at 1000 to 1100 ° C in the presence of a lean agent in a rotary kiln (1).
  • the resulting brick clinker is then leached with water or dilute chromate solution and adjusted to a pH between 7 and 9.5 with a solution containing sodium dichromate (2).
  • Soluble alkali compounds of iron, aluminum and silicon are converted into insoluble and easily filterable hydroxides or oxyhydrates, which are separated off together with the insoluble constituents of the kiln clinker (3).
  • the resulting sodium monochromate solution with a content of 300 to 500 g / l of Na2CrO4 can then, as described in EP-A-47 799, be freed from dissolved vanadate by adding calcium oxide at pH values of 10 to 13 (4).
  • the sodium monochromate solution is then concentrated to a content of 750 to 1000 g / l of Na2CrO4 by single or multi-stage evaporation (5).
  • the sodium monochromate solution can, if appropriate, be evaporated from the main amount before the evaporation (5) by adding or in situ generation of sodium carbonate by precipitation as carbonates on alkaline earth metal ions and other polyvalent cations.
  • the precipitation is preferably carried out at temperatures from 50 to 100 ° C., at pH values between 8 and 12 and with an approximately 2 to 10-fold molar excess of carbonate, based on the amount of alkaline earth metal ions.
  • a pH value below 6.5 is set by single-stage or multi-stage supply of carbon dioxide up to a final pressure of 4 to 15 bar at a final temperature of not more than 50 ° C. and in this way a 70 to with precipitation of sodium hydrogen carbonate 95% conversion of sodium monochromate to sodium dichromate achieved (6).
  • the sodium bicarbonate is separated from the resulting suspension under continuing carbon dioxide pressure or, after the pressure has been let down, the sodium bicarbonate is rapidly separated off before it reacts with the sodium dichromate.
  • the resulting sodium monochromate / sodium dichromate solution, separated from the sodium bicarbonate, is now separated into two streams after removal of a partial stream for the pH adjustment of the leached kiln clinker divided.
  • Material stream I is used for the electrolytic production of chromic acid and material stream II is used for the production of sodium dichromate solutions and crystals.
  • stream I is divided into two sub-streams and fed to the anode and cathode compartments of two-chamber electrolysis cells with single-layer membranes as partitions (7).
  • Suitable single-layer membranes are, for example, Nafion® 117, Nafion® 417, Nafion® 423 and Nafion® 430, the active exchange groups of which are sulfonic acid.
  • the single-layer membranes can also have coatings which reduce the gas bubble adhesion or promote the wetting of the membrane with electrolytes.
  • Such membranes are described, for example, in “FY Masuda, J. Appl. Electrochem. 16 (1986), p. 317 ff".
  • Membranes with reduced gas bubble adhesion can also be obtained by physical treatment, such as mechanical roughening or Corana treatment. Corresponding methods are described in US-A-4 610 762 and EP-A-72 485.
  • the electrolysis is preferably carried out in several stages: a substream of stream I is introduced into the anode chamber of the first stage and then, after a partial conversion of the monochromations into dichromations and optionally chromic acid or after a partial conversion of the dichromations into chromic acid Stages are supplied, which bring about a further partial conversion into chromic acid until in the last stage a degree of conversion of the dichromate into chromic acid of 55 to 70% corresponding to a molar ratio of sodium ions to chromic acid of 0.45: 0.55 to 0.30: 0 , 70 is reached.
  • the number of stages can be chosen as desired, a 6 to 15-stage electrolysis being preferred.
  • the other partial flow of stream I if necessary after admixing a partial flow of the sodium chromate solution before evaporation to 750 to 1000 g / l, is fed to all the cathode spaces of the electrolytic cells at such a rate that a pH of 6 in the solution leaving the cells up to 7.5.
  • This solution containing sodium dichromate and sodium monochromate is optionally fed in after concentration of the carbon dioxide acidification (6), the monochromations formed in the cathode compartments being converted back into dichromations. It is also possible to return the solution of the cathode spaces to another point in the process, such as, for example, in the pH adjustment (2) or before the alkali cleaning (4).
  • the chromic acid formed during the electrolysis and a solution containing sodium dichromate is brought to a water content of approx. 12 to 22% by weight of water at temperatures between 55 and 110 ° C by evaporation, the majority of the chromic acid crystallizing out (8).
  • the resulting suspension is then in by centrifugation at 50 to 110 ° C. a solid consisting essentially of crystalline chromic acid and separated into a liquid phase, hereinafter called mother liquor (9).
  • the mother liquor obtained is, optionally after dilution with water, in an anode compartment of the electrolysis at a suitable location, i.e. to a level of dichromate conversion degree that is as similar as possible.
  • part of the mother liquor is removed and used in the residual acidification of stream II or, if stream II has not been removed, in the sodium dichromate process at a point before the sodium chromate solution cleaning, e.g. returned to the pH setting (2).
  • the crystalline chromic acid is freed from adhering mother liquor by washing once or several times with 10 to 50% by weight, based on the weight of the solid, of saturated or almost saturated chromic acid solution and by centrifuging each time after washing.
  • the washed pure chromic acid crystals can now be used directly or after drying.
  • the solution of stream II is fed to the residual acidification (10).
  • this residual acidification is carried out with mother liquor from the chromic acid filtration (9). However, it can also be carried out partly or entirely by electrolysis and / or by adding sulfuric acid.
  • the solution obtained after the residual acidification (10) is then concentrated to about 60 to 70% by weight Na2Cr2O7 ⁇ 2 H2O to produce sodium dichromate solution.
  • the solution is concentrated to about 1650 g / l Na2Cr2O7 ⁇ 2 H2O (11) and then cooled to 30 to 40 ° C (12), sodium dichromate precipitating in the form of Na2Cr2O7 ⁇ 2 H2O crystals.
  • the crystals are then centrifugally separated from the mother liquor and dried at temperatures of approx. 70 to 85 ° C.
  • 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 names Nafion® 324 and Nafion® 430 were used as membranes, Nafion® 324 being a two-layer membrane and Nafion® 430 being a single-layer membrane.
  • the cathodes were made of stainless steel and the anodes were made of titanium with the electrocatalytically active coatings mentioned in the individual examples.
  • the distance between the electrodes and the membrane was 1.5 mm in all cases.
  • Sodium dichromate solutions containing 800 g / l Na2Cr2O7 ⁇ 2 H2O were introduced into the anode compartments. The rate of introduction was chosen so that a molar ratio of sodium ions to chromium (VI) of 0.6 was established in the anolytes leaving the cells.
  • the electrolysis temperature was 80 ° C in all cases and the current density was 3 kA / m 2 projected front area of the anodes and cathodes, which area was 11.4 cm x 6.7 cm.
  • the single-layer Nafion® 430 membrane was used to separate the anode and cathode compartments.
  • the anode was a titanium anode with an iridium oxide-containing electrocatalytically active layer, as described, for example, in US Pat. No. 3,878,083.
  • titanium anodes with a platinum layer produced by melt electroplating were used, as are described in "G. Dick, Galvanotechnik 79 (1988), No. 12, pp. 4066-4071".

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  • 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)
EP90105661A 1989-04-06 1990-03-24 Verfahren zur Herstellung von Alkalidichromaten und Chromsäuren durch Elektrolyse Expired - Lifetime EP0391192B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3911065A DE3911065A1 (de) 1989-04-06 1989-04-06 Verfahren zur herstellung von alkalidichromaten und chromsaeuren durch elektrolyse
DE3911065 1989-04-06

Publications (3)

Publication Number Publication Date
EP0391192A2 EP0391192A2 (de) 1990-10-10
EP0391192A3 EP0391192A3 (de) 1991-12-11
EP0391192B1 true EP0391192B1 (de) 1995-06-21

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EP90105661A Expired - Lifetime EP0391192B1 (de) 1989-04-06 1990-03-24 Verfahren zur Herstellung von Alkalidichromaten und Chromsäuren durch Elektrolyse

Country Status (15)

Country Link
US (1) US5127999A (ja)
EP (1) EP0391192B1 (ja)
JP (1) JP2904860B2 (ja)
KR (1) KR960016417B1 (ja)
AR (1) AR246559A1 (ja)
BR (1) BR9001593A (ja)
CA (1) CA2013782A1 (ja)
DD (1) DD298004A5 (ja)
DE (2) DE3911065A1 (ja)
ES (1) ES2075083T3 (ja)
PL (1) PL163448B1 (ja)
RO (1) RO108989B1 (ja)
RU (1) RU1806221C (ja)
TR (1) TR26262A (ja)
ZA (1) ZA902626B (ja)

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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
AUPP521298A0 (en) * 1998-08-12 1998-09-03 Life Therapeutics Limited Purification of fibrinogen
AUPP790898A0 (en) 1998-12-23 1999-01-28 Life Therapeutics Limited Renal dialysis
US20050224355A1 (en) * 1999-12-23 2005-10-13 Brendon Conlan Removal of biological contaminants
AUPP790698A0 (en) * 1998-12-23 1999-01-28 Life Therapeutics Limited Separation of microorganisms
US7077942B1 (en) * 1999-12-23 2006-07-18 Gradipore Limited Removal of biological contaminants
AUPQ691400A0 (en) * 2000-04-14 2000-05-11 Life Therapeutics Limited Separation of micromolecules
WO2001078877A1 (en) 2000-04-18 2001-10-25 Gradipore Limited Electrophoresis separation and treatment of samples
AUPQ697300A0 (en) * 2000-04-18 2000-05-11 Life Therapeutics Limited Separation apparatus
US6923896B2 (en) * 2000-09-22 2005-08-02 The Texas A&M University System Electrophoresis apparatus and method
US20030019753A1 (en) * 2000-10-05 2003-01-30 David Ogle Multi-port separation apparatus and method
AUPR222300A0 (en) * 2000-12-21 2001-01-25 Life Therapeutics Limited Electrophoresis device and method
CN107587156B (zh) * 2017-09-07 2019-06-14 中国科学院青海盐湖研究所 利用铬铁制备铬酸酐的方法
KR20220007142A (ko) 2019-05-10 2022-01-18 마테리온 코포레이션 고강도를 갖는 구리-베릴륨 합금

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Publication number Priority date Publication date Assignee Title
US3305463A (en) * 1962-03-16 1967-02-21 Pittsburgh Plate Glass Co Electrolytic production of dichromates
US4290864A (en) * 1979-05-29 1981-09-22 Diamond Shamrock Corporation Chromic acid production process using a three-compartment cell
US4273628A (en) * 1979-05-29 1981-06-16 Diamond Shamrock Corp. Production of chromic acid using two-compartment and three-compartment cells

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Publication number Publication date
PL163448B1 (pl) 1994-03-31
RO108989B1 (ro) 1994-10-31
DE59009265D1 (de) 1995-07-27
JP2904860B2 (ja) 1999-06-14
EP0391192A3 (de) 1991-12-11
DE3911065A1 (de) 1990-10-11
KR960016417B1 (ko) 1996-12-11
BR9001593A (pt) 1991-05-07
ES2075083T3 (es) 1995-10-01
US5127999A (en) 1992-07-07
CA2013782A1 (en) 1990-10-06
DD298004A5 (de) 1992-01-30
AR246559A1 (es) 1994-08-31
KR900016501A (ko) 1990-11-13
TR26262A (tr) 1995-02-15
RU1806221C (ru) 1993-03-30
JPH02285084A (ja) 1990-11-22
ZA902626B (en) 1991-01-30
EP0391192A2 (de) 1990-10-10

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