Synthesis of tetramethylammonium hydroxide

Abstract

In order to prepare tetramethylammonium hydroxide by electrolysis of a tetramethylammonium salt in a cell with a cation-exchange membrane, the operation is carried out continuously under stationary conditions obtained, on the one hand, by the introduction, into the anode electrolysis loop, of a tetramethylammonium salt solution which is more concentrated than that present in the cell and by an input of water into the cathode loop and, on the other hand, by the withdrawal of a portion of each of the solutions circulating in the anode and cathode loops.

1 . Process for the preparation of tetramethylammonium hydroxide by electrolysis of a tetramethylammonium salt in a cell with a cation-exchange membrane, characterized in that the operation is carried out continuously under stationary conditions (concentrations of the solutions in the cell for a fixed current density) obtained, on the one hand, by the introduction, into the anode electrolysis loop, of a tetramethylammonium salt solution which is more concentrated than that present in the cell and by an input of water into the cathode loop and, on the other hand, by the withdrawal of a portion of each of the solutions circulating in the anode and cathode loops.  
     
     
         2 . Process according to    claim 1   , in which the tetramethylammonium salt is the chloride, the hydrogencarbonate or the hydrogensulphate.  
     
     
         3 . Process according to    claim 1    or    2   , in which the operation is carried out with a cathode for the evolution of hydrogen.  
     
     
         4 . Process according to    claim 3   , in which the cathode is made of stainless steel or of nickel.  
     
     
         5 . Process according to    claim 1    or    2   , in which the operation is carried out with a cathode for the reduction of oxygen.  
     
     
         6 . Process according to    claim 5   , in which the cathode is based on platinized or silvered carbon.  
     
     
         7 . Process according to one of    claims 1    to    6   , in which the anode is based on platinum or on a ruthenium, iridium or platinum oxide.  
     
     
         8 . Process according to one of    claims 1    to    7   , in which the current density is between 1 and 5 kA/m 2 , preferably between 3 and 4 kA/m 2 .  
     
     
         9 . Process according to one of    claims 1    to    8   , in which the operation is carried out at a temperature of between room temperature and 80° C., preferably between 40 and 60° C.  
     
     
         10 . Process according to one of    claims 1    to    9   , in which the concentration of TMAH in the cathode loop is between 5 and 40% by weight, preferably between 10 and 25%.  
     
     
         11 . Process according to one of    claims 1    to    10   , in which the concentration of tetramethylammonium salt in the anode loop is between 15 and 40% by weight, preferably between 20 and 35%.  
     
     
         12 . Process according to one of    claims 1    to    11   , in which the cation-exchange membrane is composed of at least two layers of polymers with perfluorosulphonated and/or perfluorocarboxylated chains.  
     
     
         13 . Process according to one of    claims 1    to    12   , in which the cathode loop and the storage of the tetramethylammonium hydroxide produced are rendered inert with hydrogen, nitrogen, argon or a mixture of these gases.