Electrochemical methods for production of alkali metal hydroxides without the co-production of chlorine

A method for producing an alkali metal hydroxide without the simultaneous production of chlorine, which comprises the steps of:

• a) providing an electrochemical cell comprising a hydrogen consuming anode in an anolyte compartment, a high performance cathode in a catholyte compartment and a cell divider positioned therebetween;
• b) introducing an electrolyte solution into said anolyte compartment, said solution comprising a salt selected from the group consisting of an alkali metal carbonate, alkali metal bicarbonate, and mixtures thereof;
• c) introducing an aqueous solution into said catholyte compartment, said aqueous solution comprising alkali metal cartions from said anolyte compartment;
• d) impressing a voltage across said anode and cathode to produce alkali metal hydroxide and hydrogen at the cathode;
• e) feeding a source of hydrogen to said hydrogen consuming anode while maintaining the electrolyte solution in said anolyte compartment at a pH >7 to produce carbon dioxide and water, and
• f) maintaining a sufficient concentration of said alkali metal salt in solution in said anolyte compartment and at a sufficiently high temperature while facilitating the discharge of carbon dioxide at said anode to provide a cell voltage of <2.0 V at a current density of at least 100 mA/cm.sup.2 and a alkali metal hydroxide current efficiency in the range of about 90 to about 95 percent.

A method for producing an alkali metal hydroxide without the simultaneous production of chlorine, which comprises the steps of:

• a) providing an electrochemical cell comprising a hydrogen consuming anode and a gas consuming cathode;
• b) introducing an electrolyte solution into said electro-chemical cell, said solution comprising a salt selected from the group consisting of an alkali metal carbonate, alkali metal bicarbonate, and mixtures thereof;
• c) feeding a source of gas to said gas consuming cathode selected from the group consisting of air, oxygen and mixtures thereof;
• d) impressing a voltage across said anode and cathode to produce alkali metal hydroxide at the cathode, and
• e) feeding a source of hydrogen to said hydrogen consuming anode while maintaining said electrolyte solution in said electro-chemical cell at a pH >7 to produce carbon dioxide and water at said anode.