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
  • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
  • C25B1/36—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in mercury cathode cells
• • 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
  • C25B1/36—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in mercury cathode cells
  • C25B1/42—Decomposition of amalgams
  • C25B1/44—Decomposition of amalgams with the aid of catalysts

Definitions

• ABSTRACT 12Claims, No Drawings PROCESS FOR THE ELECTROLYSIS OF ALKALI v CHLORIDE SOLUTION This is a continuation, of application Ser. No. 130,472, filed Apr. l, 1971 and now abandoned which in turn was a continuation-in-part of application Ser.
• This invention relates to a process for the electrolysis of solutions of alkaline chlorides. More particularly, this invention has for its object a process for reducing the anodic overvoltage during the electrolysis of solutions of alkaline chlorides in cells having a mercury cathode and in diaphragm cells and for reducing the decomposition of the amalgam during the electrolysis of said solutions in cells having a mercury cathode.
• explosive mixtures may form.
• one object of this invention is that of reducing the anodic overvoltage during the electrolysis of solutions of alkaline chlorides in electrolytic cells having a mercury cathode and in diaphragm cells.
• Still another object of this invention is that of reducing the decomposition of the amalgam in electrolytic cells having a mercury cathode.
• a further object is that of attaining all the objects specified before also in the electrolysis operations when carried out under high temperatures, that is, at temperatures between 70 and 90C.
• the process of this invention according to which the anodic overvoltage (in cells having a mercury cathode and in diaphragm cells) and the decomposition of the amalgam (in cells having a mercury cathode) during the electrolysis of solutions of alkaline chlorides are reduced by adding to the electrolyte from 2 to 200 ppm of at least one compound selected from a group consisting of alcohol ethers or phenol ethers with polyoxyethylenes and of esters of carboxylic acids with polyoxyethylenes.
• the alcohols used are generally aliphatic or aromatic alcohols of which the alkyl radical contains from 2 to carbon atoms.
• the aliphatic chain linked to the alcoholic group may be linear or variously branched.
• the alcohols may contain one or more additional functional groups, and more particularly: OH, Cl, Br, F, SO H, SO Me wherein Me is an alkali metal, COOR wherein Ris an alkyl radical containing from one to four carbon atoms, and
• R and R are hydrogen or alkyl radicals containing from 1 to 12 carbon atoms.
• the alcohols contain from 8 to 20 carbon atoms.
• Particularly suitable are the aliphatic alcohols containing from 12 to 18 carbon atoms.
• Suitable alcohols are, for instance, lauryl alcohol, oleyl alcohol, stearyl alcohol and phenylethyl alcohol.
• the ethers derived from the condensation of such alcohols with ethylene oxide contain, in general, from 2 to l5O molecules of ethylene oxide for each molecule of alcohol. Preferably they contain from 10 to molecules of ethylene oxide for each alcohol molecule.
• the degree of ethoxylation that gives the best results depends in part on the nature of the R-radical. Amongst the alcohol ethers with polyoxyethylenes which have yielded the best results may be listed the monolaurylethers of polyethylenglycols containing from 10 to 30 ethoxy groups and the monooleylethers of polyethylenglycols containing from 60 to 120 ethoxy groups.
• ethers of phenols with polyoxyethylenes suited for the purposes of this invention may be represented by the general formula:
• R is an alkyl or aralkyl radical having from 1 to 20 carbon atoms and n is between 2 and 40, inclusive.
• the alkyl radical R (or the alkyl part of the radical) may be linear or variously branched.
• the radical may contain one or more additional functional groups, in particular those already specified for the alcohol condensates with ethylene oxide.
• the R radical contains from 8 to 20 carbon atoms. Particularly suitable are the compounds in which R contains from 8 to 13 carbon atoms. If R is an alkyl radical, it may for instance be an octyl, nonyl, dodecyl or tridecyl group.'lf it is an aralkyl radical it may, for instance, be a cumyl or methylcumyl group. The radical may be in an ortho-, paraor metaposition with respect to the polyethoxy chain.
• n is between 5 and 25, inclusive.
• esters of carboxylic acids with polyoxyethylenes suitable for the purposes of thisinvention are compounds having a degree of ethoxylation between 200 and 6000, derived from aliphatic or aromatic acids containing from 6 to 20 carbonatoms.
• the aliphatic radical of these acids may be linear or variously branched.
• the acids may contain one or more additional functional groups, and in particular those already specified previously.
• Preferably the acids are aliphatic acids containing from 12 to 18 carbon atoms.
• a few specific examples of acids suitable for the purpose are lauric, oleic, stearic and palmitic acids.
• mixtures of compounds such as for instance a mixture of compounds having a differentdegree of ethoxylation derived from the same hydroxy compound or a mixture of compounds derived from different hydroxy compounds.
• the quantities of additive may be varied within wide limits. Excellent results are obtained by using quantities between 5 and 20 p.p.m. by weight. The results are, however, just as good when greater quantities are used, for instance, from 20 to 200 ppm, although it is not necessary to make use of these higher quantities. Good results are also obtained with lower quantities, for instance with from 2 to 5 p.p.m.
• the additives may be used with excellent results at any temperature between room temperature and C.
• the process of this invention may be applied with excellent results to all types of mercury cathode cells, that is, both to the horizontal cathode types and to the vertical cathode types and to all types of diaphragm cells as well as to all the types of anodes, that is both to the graphite anodes and to the metal anodes, for instance titanium anodes.
• the additives have proved to be equally efficacious throughout the range of current densities that are used in the electrolytic cells, that is in the range from about 20 to about amp/dm when working with graphite anodes and from about 20 to about 200 amp/dm when working with metal anodes.
• the current density is not a critical feature of the process of the invention but depends solely upon the characteristics of the cells employed.
• the additive which at room temperature may be solid or liquid, may be added as such to the brine before the introduction thereof into the cell or as solution in water or in the brine.
• the solutions used for the purposes of the present invention have in general a concentration between 0.1 to 10 percent by weight.
• EXAMPLE 1 The tests were carried out in small experimental cells having Plexiglass walls, into which were placed in a horizontal position one or two graphite anodes at an adjustable distance from the level of the mercury that flowed on the bottom of the cell.
• the anodic surface amounts to about 2.0 dm
• the concentration in NaCl of the brine fed into the cell amounts to 310 gr/lt (grams per liter): its pH is between 3 and 4. Its NaCl concentration at the outletequals 260-270 gr/lt. Its content in impurities is the following:
• Turbidity (expressed as SiO,) 10 ppm (parts per million) CaO 0.0l-0.04 gr/lt MgO 0.005 gr/lt Fe 0.00l grllt Other metal cations 0.0l ppm Sulphate anions, expressed as S0, 2-5 grllt A current density of 70 amp/dm was applied. The temperature of the brine at the outlet of the cell was 76C.
• PCP-7 mono(para-alpha-cumylphenyl) ether of heptaethyleneglycol
• PCP-7 mono-para-alpha-cumylphenyl
• Tests nos. 1, 2 and 4 were carried out with anodes having been in operation for several months; in the case at the outlet of the ether of heptaeobserved a better distribution and uniformity in the development of gaseous bubbles on the anodes and inside th sqluti t.-. .1
• test no. 2 the cell was very dirty.
• Test no. 3 was carried out with new anodes.
• the cells that operated with additive were maini. the ethers of alcohols with polyoxyethylenes tained in a condition of greater cleanliness.
• R a. are derived from alcohols selected between all- EXAMPLE 3 phatic and aromatic ones and having from 8 to 20 carbon atoms, and
• b. contain from 2 to 150 molecules of ethylene oxide for each molecule of alcohol, ii. the ethers of phenols with polyoxyethylenes having the following formula:
• the whole anodic surface amounted to about 54.0 dm o-orr,-orr, norr
• the operational characteristics were: distance between anodes and cathode: about 3 mm;
• R is a radical selected between alkyl and aralkyl 85C; and has from 1 to carbon atoms, and current density: 125 (test 1) and 150 (test ,2) b.
• n is between 2 and 40, inclusive,
• amp/dm iii. the esters of carboxylic acids with polyoxyethy-
• the brine used was identical with that used in Examlenes ple 1, its concentration in NaCl at the outlet of the cell which being 290 gr/lt. a. are derived from acids selected between ali-
• the experiments were carried out with nonylphenphatic and aromatic ones and having from 6 to ylethers of -ethyleneglycol (NF-30), the mixture 20 carbon atoms, and containing about 90 percent of para-isomers and 10 b. contain from 200 to 6000 ethylene oxide molepercent of ortho-isomers. 30 cules for each molecule of acid.
• the voltage of the cell hols with polyoxyethylenes contain from 10 to 120 and the concentration in hydrogen of the electrolysis molecules of ethylene oxide for each molecule of alcogas were measured, the electrolysis gas containing hol.
• b ht f 10 d 11.

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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)

Priority Applications (5)

Applications Claiming Priority (3)

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Family Applications (1)

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Cited By (2)

Citations (1)

• 1969
  • 1969-01-31 NL NL6901571A patent/NL6901571A/xx unknown
  • 1969-02-04 FR FR6902404A patent/FR2001394A1/fr not_active Withdrawn
  • 1969-02-04 DE DE19691905278 patent/DE1905278A1/de active Pending
  • 1969-02-06 BE BE728017D patent/BE728017A/xx unknown
• 1973
  • 1973-08-02 US US00385042A patent/US3849266A/en not_active Expired - Lifetime

Patent Citations (1)

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