EP0008470B1 - Verfahren zur Elektrolyse wässriger Alkalihalogenid-Lösungen - Google Patents

Verfahren zur Elektrolyse wässriger Alkalihalogenid-Lösungen Download PDF

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Publication number
EP0008470B1
EP0008470B1 EP79200382A EP79200382A EP0008470B1 EP 0008470 B1 EP0008470 B1 EP 0008470B1 EP 79200382 A EP79200382 A EP 79200382A EP 79200382 A EP79200382 A EP 79200382A EP 0008470 B1 EP0008470 B1 EP 0008470B1
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EP
European Patent Office
Prior art keywords
adjusted
solution
value
alkali metal
membrane
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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
Application number
EP79200382A
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German (de)
English (en)
French (fr)
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EP0008470A1 (de
Inventor
Karl Dipl.-Ing. Lohrberg
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GEA Group AG
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Metallgesellschaft AG
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Application filed by Metallgesellschaft AG filed Critical Metallgesellschaft AG
Priority to AT79200382T priority Critical patent/ATE978T1/de
Publication of EP0008470A1 publication Critical patent/EP0008470A1/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
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • 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
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells

Definitions

  • the invention relates to a method for the electrical analysis of aqueous alkali halide solutions in membrane cells at pH values above 1.0 in the anode compartment, the alkali halide solution being passed through the anode compartment and zones for concentration with alkali halide and for pH adjustment.
  • amalgam has the advantage of permitting the production of highly concentrated alkali lye of high purity, but due to the use of mercury requires high costs for environmental protection.
  • diaphragm process does not require such expenditure, but only enables the production of alkali lye of considerably lower concentration, which also has considerable alkali halide contents.
  • the anode and cathode spaces of the electrolysis cell are separated by an ion exchange membrane, through which essentially only the alkali ions can pass. These are electrically neutralized at the cathode and form alkali water and hydrogen in the cathode compartment with water. Halogen ions cannot pass through the membrane and are therefore only released in the anode compartment in the form of halogen gas.
  • the OH ions formed in the cathode space migrate through the membrane into the anode space.
  • the OH ions form with halogen gas - depending on the pH of the anolyte chlorine-oxygen acids or their salts, especially hypochlorite and chlorate, which can only be destroyed by adding acid.
  • the pH of the anolyte is in the range from about 1 to 5, preferably 3.0 to 4.0 (DE-A-2 409 193) or at about 2 ( DE-A-2 631 523).
  • the anolyte is adjusted to a pH in the range from 0 to 3 and preferably from 1 to 2.5 by means of hydrochloric acid.
  • the alkali metal halide solution enriched with alkali metal halide is adjusted to a pH of 0.2 to 4.5 and preferably 1.5 to 4.
  • the temperature of the anolyte is kept in the range of 85 to 100 ° C.
  • the object of the invention is to provide a process which is simple to carry out, avoids the disadvantages of the known processes and leads to advantageous results with regard to both halogen yield and alkali yield.
  • the object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that only a partial stream of the enriched alkali metal halide solution is adjusted to a pH below 1.0.
  • a partial flow of 15% should only be set to a pH of 0.67.
  • a part Stream of 10% should be brought to a pH of 0.6 if, after combining with the main stream, a final pH of 1.7 is desired.
  • the pH is preferably set below 1 at a temperature above 70 ° C., in particular in the range from 80 to 90 ° C., since this promotes decomposition.
  • the pH of the electrolyte to be fed to the anode chamber is set to a value in the range from 1 to 2.5.
  • a partial stream is in turn branched off from this stream for the purpose of virtually complete destruction of the halogen oxygen acids or their salts, so that ultimately a steady state is established in which as much halogen oxygen acids are destroyed by the partial stream treatment as are formed in the anode compartment.
  • the pH is adjusted to 0.6 and the pH of the anolyte after recombining is 1.1, a content of chlorine-oxygen acid or its salts of 20 g / l (calculated as sodium chlorate ) maintained.
  • a further advantageous embodiment of the invention consists in not degassing the electrolyte emerging from the anode space of the membrane cell before strengthening with alkali metal halide, but instead to adjust it to a pH of about 7 to 10 by adding alkali metal hydroxide solution.
  • the dissolved halogen gas which is present in small amounts, is converted into halogen oxygen acids or their salts, which are largely eliminated anyway by the acidification that occurs after the saturation and removal of the impurities.
  • the membrane cell itself has the known constructive elements.
  • Polyfluorohydrocarbons with cation-exchanging groups such as, for example, sulfonic acid (SO, H), carboxylic acid (COOH) and phosphonic acid (PO 3 H 2 ) groups, are suitable as membrane material.
  • Individual fluorine atoms can also be replaced by other halogen atoms, in particular chlorine atoms.
  • suitable membrane materials cf. also D. Bergner 1. c., page 441, right column ff.
  • the anodes to be used in carrying out the method according to the invention can consist of graphite.
  • titanium, niobium or tantalum electrodes coated with noble metal or noble metal oxide or so-called dimensionally stable anodes, in which the electrocatalytic effect of mixed oxides of noble metals and film-forming metals, in particular titanium, originate, are particularly advantageous.
  • the method according to the invention in its preferred embodiment with partial flow separation gives the possibility of changing the pH of the anolyte during operation of the membrane cell by appropriately dimensioning its quantity and its pH.
  • signs of aging in the membrane can be compensated for by lowering the pH of the anolyte.
  • Different membrane cells can also be supplied with anolyte of different pH values by differently dimensioning the partial and main streams.
  • Chlorine gas is discharged via line 20.
  • the electrolyte depleted in sodium chloride reaches the treatment room 4 via lines 2 and 3, is mixed there with sodium hydroxide solution supplied via line 5 and adjusted to a pH of 7 to 10.
  • sodium hydroxide solution supplied via line 5 and adjusted to a pH of 7 to 10.
  • dissolved chlorine gas is converted into hypochlorite, from which, depending on pH, temperature and time, some or all of the sodium chlorate is formed.
  • the solution then passes into the saturator 6 and is brought to a concentration of about 310 g / l with sodium chloride introduced over 7.
  • the impurities in particular the calcium and magnesium ions, are precipitated by adding sodium hydroxide solution above 9 to a pH of approximately 11.
  • the treatment in the filter device 10 and discharge of the precipitated impurities via line 11 reaches the Lö - solution in line 12 and is introduced into a partial stream 13 and a principal stream 14 split.
  • the main stream 14 flows in the direction of the anode compartments 1
  • the partial stream 13 in the device 15 is brought to a pH below 1.0, preferably below 0.8, by adding concentrated hydrochloric acid via line 16.
  • Chlorine oxygen acids or their salts are largely destroyed with the formation of chlorine.
  • the chlorine gas is combined with the chlorine gas originating from the anode spaces 1 of the membrane cells using a line 21
  • the solution then flows off via line 17 and - mixed with the solution of the main stream 14 - is fed via line 18 or 19 to the anode compartments 1.
  • variable mixing ratios and thus different pH values can be set in the solutions flowing through lines 18 and 19, respectively.
  • the membranes were used for the electrolysis.
  • the membranes consisted of ethylenediamine-modified Nafion® (a product from DuPont).
  • the applied cell voltage was 3.8 volts.
  • the anode compartments 1 of the membrane cells were charged with a brine which contained 310 g / l NaCl and had a pH of 1.7 and a temperature of 85 ° C.
  • the residence time of the anolyte in the anode compartments 1 was measured in such a way that the decrease in NaCl was 25 g / l. During this time, approx. 2 g / l chlorine oxygen acids (calculated as NaClO 3 ) were formed.
  • the electrolyte solution emerging from the anode compartments 1 was adjusted to pH 8 in the treatment compartment 4 with sodium hydroxide solution, then strengthened again in the saturator 6 to a NaCl concentration of 310 g / l and brought to pH 11 in the device 8 with additional sodium hydroxide solution, the contamination was felled.
  • the electrolyte was adjusted to pH 1.7 in the initial phase of the process and returned to the anode compartments.
  • the concentration of chlorine-oxygen acid had increased to 22 g / l (calculated as NaClO 3 )
  • a 10% partial stream of the pure sols emerging from the filter device 10 was passed via line 13 into the device 15 and there to pH 0 by adding hydrochloric acid , 6 set. As a result of this measure, the content of chlorine-oxygen acid in the partial stream was reduced to 2 g / l.
  • the chlorine gas formed was passed via line 21 to line 20.

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  • 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)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Electroluminescent Light Sources (AREA)
  • Developing Agents For Electrophotography (AREA)
EP79200382A 1978-08-26 1979-08-20 Verfahren zur Elektrolyse wässriger Alkalihalogenid-Lösungen Expired EP0008470B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT79200382T ATE978T1 (de) 1978-08-26 1979-08-20 Verfahren zur elektrolyse waessriger alkalihalogenid-loesungen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19782837313 DE2837313A1 (de) 1978-08-26 1978-08-26 Verfahren zur elektrolyse waessriger alkalihalogenid-loesungen
DE2837313 1978-08-26

Publications (2)

Publication Number Publication Date
EP0008470A1 EP0008470A1 (de) 1980-03-05
EP0008470B1 true EP0008470B1 (de) 1982-05-05

Family

ID=6047970

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79200382A Expired EP0008470B1 (de) 1978-08-26 1979-08-20 Verfahren zur Elektrolyse wässriger Alkalihalogenid-Lösungen

Country Status (12)

Country Link
US (1) US4247375A (es)
EP (1) EP0008470B1 (es)
JP (1) JPS5531199A (es)
AT (1) ATE978T1 (es)
BR (1) BR7905453A (es)
CA (1) CA1158196A (es)
DE (2) DE2837313A1 (es)
ES (1) ES483640A1 (es)
FI (1) FI63260C (es)
MX (1) MX152740A (es)
NO (1) NO151973C (es)
ZA (1) ZA793571B (es)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4381230A (en) * 1981-06-22 1983-04-26 The Dow Chemical Company Operation and regeneration of permselective ion-exchange membranes in brine electrolysis cells
US4391680A (en) * 1981-12-03 1983-07-05 Allied Corporation Preparing alkali metal hydroxide by water splitting and hydrolysis
DE3216418A1 (de) * 1982-05-03 1983-11-03 Bayer Ag, 5090 Leverkusen Verfahren zur elektrolytischen herstellung von chlor und natronlauge aus sulfathaltigem salz
US4481088A (en) * 1982-07-06 1984-11-06 Olin Corporation Removal of chlorate from electrolyte cell brine
JPS6068997A (ja) * 1983-09-27 1985-04-19 Fuji Photo Film Co Ltd 平版印刷版用アルミニウム支持体の製造方法
JP3115440B2 (ja) * 1992-12-10 2000-12-04 ペルメレック電極株式会社 塩化アルカリ水溶液の電解方法

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL136394C (es) * 1965-11-29 1900-01-01
US3438879A (en) * 1967-07-31 1969-04-15 Hooker Chemical Corp Protection of permselective diaphragm during electrolysis
US3616328A (en) * 1968-09-23 1971-10-26 Hooker Chemical Corp Catholyte recirculation in diaphragm chlor-alkali cells
DE1803638A1 (de) * 1968-10-17 1970-05-27 Bayer Ag Verfahren zur Herstellung von Chlor und Natronlauge
BE795460A (fr) * 1972-02-16 1973-08-16 Diamond Shamrock Corp Perfectionnements relatifs a des cuves electrolytiques
US4040919A (en) * 1974-10-29 1977-08-09 Hooker Chemicals & Plastics Corporation Voltage reduction of membrane cell for the electrolysis of brine
JPS5318498A (en) * 1976-08-03 1978-02-20 Nippon Soda Co Ltd Preventing method for accumulation of alkali chlorates in salt water in ion exchange membrane method electrolysis of alkali chlorides

Also Published As

Publication number Publication date
BR7905453A (pt) 1980-05-20
FI792470A (fi) 1980-02-27
CA1158196A (en) 1983-12-06
NO792723L (no) 1980-02-27
MX152740A (es) 1985-11-01
ES483640A1 (es) 1980-04-16
EP0008470A1 (de) 1980-03-05
NO151973B (no) 1985-04-01
JPS5531199A (en) 1980-03-05
FI63260C (fi) 1983-05-10
JPS636635B2 (es) 1988-02-10
FI63260B (fi) 1983-01-31
DE2837313A1 (de) 1980-03-13
ZA793571B (en) 1980-07-30
DE2962706D1 (en) 1982-06-24
NO151973C (no) 1985-07-31
US4247375A (en) 1981-01-27
ATE978T1 (de) 1982-05-15

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