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Production of alkali metal carbonates in a cell having a carboxyl membrane

  • US 4,147,599 A
  • Filed: 07/19/1977
  • Issued: 04/03/1979
  • Est. Priority Date: 07/19/1977
  • Status: Expired due to Term
First Claim
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1. In a method for producing an alkali metal carbonate wherein:

  • A. an alkali metal chloride is electrolyzed in an electrolytic cell having an anode and cathode in anolyte and catholyte compartments separated by a permselective cation-exchange membrane that is impervious to hydraulic flow and is spaced apart from the cathode;

    B. carbon dioxide is injected into the catholyte compartment to give catholyte solids wherein substantially all of the alkali metal hydroxide formed therein is converted to alkali metal carbonate; and

    C. catholyte containing the alkali metal carbonate is removed from the catholyte compartment;

    the improvement which comprises;

    D. utilizing a membrane which;

    1. consists essentially of a film having a thickness not exceeding 8 mils of a copolymer having recurring structural units of the formula;

    ##STR6## and
    
    
    space="preserve" listing-type="equation">(II) --CXX'"'"'--CF.sub.2 -- wherein R represents the group
    
    
    space="preserve" listing-type="equation">--OCF.sub.2 --CFY--.sub.m O--CF.sub.2 --(G).sub.e -- in which Y is fluorine or trifluoromethyl, G is --CF2 -- or ##STR7## m is 1, 2 or 3, e is 0 or 1, and a is an integer from 1 to 10;

    n is 0 or 1;

    A is H, Na, or K;

    X is fluorine, chlorine, or trifluoromethyl;

    X'"'"' is X or CF3 --CF2 --z wherein z is 0 or an integer from 1 to 5;

    the units of formula (I) being present in an amount to provide a copolymer having in the acid form an --CO2 H equivalent weight of about 800 to 1400; and

    2.

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