Apparatus and process for the production of metals in stacked electrolytic cells

Abstract

A process and apparatus for reducing an alkali metal salt to an alkali metal through electrolysis in a series of electrolytic cells are disclosed. The process employs as a separator between anode and cathode compartments a material that is both an ionic conductor of the metal ion and an electrical insulator. Preferred metals are sodium, lithium and potassium.

1 . An apparatus for reducing an alkali metal salt to an alkali metal, comprising: 
 a plurality of serially connected electrolytic cells, each cell comprising an anode compartment, a cathode compartment, and an ionic conductor impermeable to water and water vapor separating the anode compartment from the cathode compartment; and    a voltage source for supplying a voltage across the cells.    
   
   
       2 . The apparatus of  claim 1 , wherein the cathode compartment contains a metal.  
   
   
       3 . The apparatus of  claim 2 , wherein the metal is sodium.  
   
   
       4 . The apparatus of  claim 2 , further comprising a heating means for heating the cathode compartment to a temperature sufficient to maintain at least a portion of the metal in a molten state.  
   
   
       5 . The apparatus of  claim 4 , wherein the cathode compartment is maintained at a temperature of above about 97.8° C.  
   
   
       6 . The apparatus of  claim 2 , wherein the cathode compartment contains an alkali metal.  
   
   
       7 . The apparatus of  claim 1 , wherein the anode compartment contains a liquid solution of a metal salt or a molten metal salt.  
   
   
       8 . The apparatus of  claim 7 , wherein the anode compartment contains a molten alkali metal salt.  
   
   
       9 . The apparatus of  claim 8 , wherein the anode compartment contains molten sodium hydroxide.  
   
   
       10 . The apparatus of  claim 1 , wherein the anode compartment contains an aqueous solution of a metal salt.  
   
   
       11 . The apparatus of  claim 10 , wherein the anode compartment contains an aqueous solution of a sodium salt.  
   
   
       12 . The apparatus of  claim 11 , wherein the anode compartment contains an aqueous solution of sodium hydroxide.  
   
   
       13 . The apparatus of  claim 1 , wherein the alkali metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       14 . The apparatus of  claim 13 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       15 . The apparatus of  claim 1 , wherein the alkali metal salt is a carbonate salt.  
   
   
       16 . The apparatus of  claim 1 , wherein the ionic conductor is a ceramic cation conductor.  
   
   
       17 . The apparatus of  claim 1 , wherein the ionic conductor comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       18 . The apparatus of  claim 1 , wherein the ionic conductor is a NaSICON membrane.  
   
   
       19 . The apparatus of  claim 1 , wherein the ionic conductor is a LiSICON membrane or a KSICON membrane.  
   
   
       20 . The apparatus of  claim 1 , wherein a heating means is provided in contact with at least one of the plurality of serially connected electrolytic cells.  
   
   
       21 . The apparatus of  claim 17 , wherein the heating means is a heat bath.  
   
   
       22 . The apparatus of  claim 17 , wherein the heating means includes heating coils.  
   
   
       23 . The apparatus of  claim 1 , further comprising a means for passing hydrogen gas into the anode compartment.  
   
   
       24 . The apparatus of  claim 1 , wherein the anode compartment further includes an inlet configured for supplying a hydrogen gas to the anode.  
   
   
       25 . The apparatus of  claim 1 , wherein a cathode of a first cell of the plurality of serially connected electrolytic cells is connected to a power supply, and the anode of a second cell of the plurality of serially connected electrolytic cells is connected to the power supply.  
   
   
       26 . An electrolytic cell for reducing metal salts to metals, comprising: 
 a stack of electrolytic cells wherein at least two of the electrolytic cells are electrically connected in series, and wherein each of the at least two of the electrolytic cells comprises:    an anode compartment containing a solution of an alkali metal salt;    a container at least partially immersed in the solution of the alkali metal salt; and    a cathode comprising at least an alkali metal, the cathode being provided within the container.    
   
   
       27 . The electrolytic cell of  claim 26 , wherein the container is a ceramic tube.  
   
   
       28 . The electrolytic cell of  claim 26 , wherein the container is formed of a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       29 . The electrolytic cell of  claim 26 , wherein the anode contains a solution of sodium hydroxide.  
   
   
       30 . The apparatus of  claim 26 , wherein the alkali metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       31 . The apparatus of  claim 30 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       32 . The apparatus of  claim 26 , wherein the alkali metal salt is a carbonate salt.  
   
   
       33 . The electrolytic cell of  claim 26 , further comprising a means for inputting an inert gas into the container.  
   
   
       34 . The electrolytic cell of  claim 33 , wherein the gas is nitrogen or argon.  
   
   
       35 . An electrolytic cell for reducing metal salts to metals, comprising: 
 a stack of electrolytic cells wherein at least two of the electrolytic cells are electrically connected in series, and wherein each of the at least two of the electrolytic cells comprises:    an anode compartment containing a molten metal salt;    a container at least partially immersed in the molten metal salt; and    a cathode comprising an alkali metal, the cathode being provided within the container.    
   
   
       36 . The electrolytic cell of  claim 35 , wherein the container is a ceramic tube.  
   
   
       37 . The electrolytic cell of  claim 35 , wherein the container is formed of a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       38 . The electrolytic cell of  claim 35 , wherein the anode contains molten sodium hydroxide.  
   
   
       39 . The apparatus of  claim 35 , wherein the metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       40 . The apparatus of  claim 39 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       41 . The apparatus of  claim 35 , wherein the metal salt is a carbonate salt.  
   
   
       42 . The electrolytic cell of  claim 35 , further comprising a means for inputting an inert gas to the container.  
   
   
       43 . An electrolysis system, comprising: 
 a plurality of electrolytic cells that are electrically connected in series, wherein at least one of the plurality of electrolytic cells comprises:    an anode compartment including an anolyte, the anolyte comprising a molten alkali metal salt or an aqueous solution of an alkali metal salt;    a cathode compartment including a catholyte, the catholyte comprising an alkali metal; and    an ionic conductor separating the anolyte from the catholyte.    
   
   
       44 . The electrolysis system of  claim 43 , wherein the alkali metal is sodium and further comprising heating means for maintaining the catholyte at a temperature of above about 95° C.  
   
   
       45 . The electrolysis system of  claim 44 , wherein the catholyte is maintained at a temperature of above about 97.8° C.  
   
   
       46 . The electrolysis system of  claim 43 , wherein the cathode compartment contains a seeded amount of an alkali metal.  
   
   
       47 . The electrolysis system of  claim 43 , wherein a heating means is provided in contact with at least one of the plurality of electrolytic cells.  
   
   
       48 . The electrolysis system of  claim 41 , wherein the heating means is a heat bath.  
   
   
       49 . The electrolysis system of  claim 47 , wherein the heating means includes heating coils.  
   
   
       50 . The electrolysis system of  claim 43 , further comprising an inlet configured to pass hydrogen gas into the anode compartment.  
   
   
       51 . A method for generating an alkali metal from an alkali metal salt, comprising: 
 providing a plurality of electrolytic cells, at least two of the plurality of electrolytic cells being electrically connected in series, wherein each of the at least two of the electrolytic cells comprises an anode compartment, a cathode compartment, and an ionic conductor separating the anode compartment from the cathode compartment; and    applying a voltage across the plurality of electrolytic cells.    
   
   
       52 . The method of  claim 51 , further comprising seeding the cathode compartment with an alkali metal.  
   
   
       53 . The method of  claim 51 , wherein the alkali metal is sodium.  
   
   
       54 . The method of  claim 51 , further comprising heating the cathode compartment to a temperature of above about 95° C. to maintain at least a portion of the sodium in a molten state.  
   
   
       55 . The method of  claim 54 , wherein the cathode compartment is heated to a temperature of above about 97.8° C.  
   
   
       56 . The method of  claim 51 , wherein the cathode compartment is maintained in an inert atmosphere.  
   
   
       57 . The method of  claim 51 , further comprising providing the anode compartment with a molten alkali metal salt.  
   
   
       58 . The method of  claim 57 , wherein the salt comprises molten sodium hydroxide.  
   
   
       59 . The method of  claim 51 , wherein the alkali metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       60 . The method of  claim 59 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       61 . The method of  claim 51 , wherein the alkali metal salt is a carbonate salt.  
   
   
       62 . The method of  claim 51 , further comprising providing the anode compartment with an aqueous solution of an alkali metal salt.  
   
   
       63 . The method of  claim 51 , wherein the ionic conductor is a ceramic cation conductor.  
   
   
       64 . The method of  claim 51 , wherein the ionic conductor comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       65 . The method of  claim 51 , wherein the ionic conductor is a NaSICON membrane.  
   
   
       66 . The method of  claim 51 , wherein the ionic conductor is a LiSICON membrane or KSICON membrane.  
   
   
       67 . The method of  claim 51 , further comprising providing a heating means in contact with at least one of the plurality of serially connected electrolytic cells.  
   
   
       68 . The method of  claim 67 , wherein the heating means is a heat bath.  
   
   
       69 . The method of  claim 57 , wherein the heating means includes heating coils.  
   
   
       70 . The method of  claim 51 , further comprising passing hydrogen gas into the anode compartment.  
   
   
       71 . The method of  claim 51 , wherein hydrogen is electro-oxidized at the anode.  
   
   
       72 . A method for reducing metal salts to metals, comprising: 
 providing a stack of electrolytic cells wherein at least two of the electrolytic cells are electrically connected in series, and wherein each of the at least two of the electrolytic cells comprises an anode containing a solution of an alkali metal salt, a container at least partially immersed in the solution of the alkali metal salt, and a cathode containing an alkali metal, the cathode being provided within the container; and    applying a voltage across the plurality of electrolytic cells.    
   
   
       73 . The method of  claim 72 , wherein the container is a ceramic tube.  
   
   
       74 . The method of  claim 73 , wherein the ceramic tube comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       75 . The method of  claim 72 , further comprising providing the anode with a solution of sodium hydroxide.  
   
   
       76 . The method of  claim 72 , wherein the alkali metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       77 . The method of  claim 76 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       78 . The method of  claim 72 , wherein the alkali metal salt is a carbonate salt.  
   
   
       79 . The method of  claim 72 , further comprising inputting an inert gas into the container.  
   
   
       80 . The method of  claim 79 , wherein the gas is nitrogen or argon.  
   
   
       81 . The method of  claim 72 , wherein hydrogen is electro-oxidized at the anode.  
   
   
       82 . A method of reducing metal salts to metals, comprising: 
 providing a stack of electrolytic cells wherein at least two of the electrolytic cells are electrically connected in series, and wherein each of the at least two of the electrolytic cells comprises an anode containing a molten metal salt, a container at least partially immersed in the molten metal salt, and a cathode containing an alkali metal, the cathode being provided within the container; and    applying a voltage across the plurality of electrolytic cells.    
   
   
       83 . The method of  claim 82 , wherein the container is a ceramic tube.  
   
   
       84 . The method of  claim 83 , wherein the ceramic tube comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β/β″-aluminum oxide, lithium-β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β/β″-aluminum oxide, sodium-β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β/β″-aluminum oxide and potassium-β″-aluminum oxide.  
   
   
       85 . The method of  claim 82 , further comprises immersing a metal wire at least partially into the molten metal salt.  
   
   
       86 . The method of  claim 82 , further comprising inputting an inert gas into the container.  
   
   
       87 . The method of  claim 86 , wherein the inert gas is nitrogen or argon.  
   
   
       88 . The method of  claim 82 , wherein the molten metal salt is molten sodium hydroxide.  
   
   
       89 . The method of  claim 82 , wherein the metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       90 . The method of  claim 89 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       91 . The method of  claim 82 , wherein the metal salt is a carbonate salt.  
   
   
       92 . The method of  claim 82 , wherein hydrogen is electro-oxidized at the anode.  
   
   
       93 . A method for generating an alkali metal from an alkali metal salt, comprising: 
 providing a series of at least two electrolytic cells, each electrolytic cell comprising an anode compartment, a cathode compartment, and an ionic conductor separating the anode compartment from the cathode compartment;    connecting the cathode compartment of one of the at least two electrolytic cells with the anode compartment of the other of the at least two electrolytic cells;    seeding the cathode compartment with an alkali metal;    providing an alkali metal salt in liquid form to the anode compartment; and    applying a voltage across the at least two electrolytic cells.    
   
   
       94 . The method of  claim 93 , further comprising providing hydrogen to the anode of at least one of the two electrolytic cells such that hydrogen is electro-oxidized at the anode.  
   
   
       95 . The method of  claim 93 , wherein the alkali metal is sodium.  
   
   
       96 . The method of  claim 93 , further comprising heating the cathode compartment of at least one of the cells to a temperature to allow at least a portion of the sodium to remain in a molten state.  
   
   
       97 . The method of  claim 96 , wherein the cathode compartment is a temperature of above about 95° C.  
   
   
       98 . The method of  claim 93 , wherein the alkali metal salt is a borate of formula zM 2 O.xB 2 O 3 .yH 2 O, wherein z is ½ to 5; x is 0.1 to 5; y is 0 to 10; and M is an alkali metal ion.  
   
   
       99 . The method of  claim 98 , wherein the alkali metal is selected from the group consisting of sodium, potassium, and lithium.  
   
   
       100 . The method of  claim 93 , wherein the alkali metal salt is a carbonate salt.  
   
   
       101 . The method of  claim 93 , wherein the ionic conductor is a ceramic cation conductor.  
   
   
       102 . The method of  claim 93 , further comprising providing a heating means in contact with at least one of the two electrolytic cells.  
   
   
       103 . The method of  claim 102 , wherein the heating means is a heat bath.  
   
   
       104 . The method of  claim 93 , wherein the alkali metal is sodium and the separator comprises a NaSICON membrane.  
   
   
       105 . A bipolar stack, comprising: 
 a plurality of electrolytic cells, each cell comprising an anode, an anode compartment, a cathode, a cathode compartment, and an ionic conductor separating the anode compartment from the cathode compartment;    wherein the anode of a first cell unit is in electrical contact with the cathode of a second cell unit; and    a voltage source for supplying a voltage across the cells.    
   
   
       106 . The bipolar stack of  claim 105 , wherein an ionic insulator separates the anode compartment of a first cell and the cathode compartment of a second cell.  
   
   
       107 . The bipolar stack of  claim 106 , wherein the anode of a first cell is a first face of the ionic insulator.  
   
   
       108 . The bipolar stack of  claim 107 , wherein the cathode of a second cell is a second face of the ionic insulator.  
   
   
       109 . The bipolar stack of  claim 108 , wherein the second face of the ionic insulator is in electrical communication with a liquid cathode of a second cell.  
   
   
       110 . The bipolar stack of  claim 105 , wherein the ionic insulator is comprised of a material selected from the group consisting of nickel, carbon, graphite, steel, platinum, and nickel alloys.