Apparatus for electrolysis of molten oxides

Abstract

The invention provides improved electrodes for electrolytic cells operating with molten salt electrolytes. Nonconsumable iridium-based anodes of the invention facilitate the release of gaseous oxygen from oxide-containing melts, for example in the electro-chemical production of liquid or gaseous reactive metals from oxides. Cathode substrates of the invention are constructed of a tungsten-based alloy and enable deposition of an overlying liquid-metal cathode. Incorporation of the anode and cathode substrate of the invention into molten-oxide cells establishes a novel method for electrolytic extraction of titanium and other reactive metals.

1 . An apparatus for extracting liquid titanium metal from titanium dioxide by electrolysis, the apparatus comprising:
 a. a cathode substrate of a tungsten-based material, the liquid titanium metal forming a deposit over the cathode substrate;   b. an anode of iridium-based material upon which gaseous oxygen evolves;   c. a molten electrolyte containing the titanium dioxide, the electrolyte being in contact with the anode over a contact interface, the contact interface being a substantially continuous iridium surface, the titanium dioxide being dissolved in the molten electrolyte.   
   
   
       2 . The apparatus of  claim 1  wherein the tungsten-based material contains rhenium. 
   
   
       3 . The apparatus of  claim 1  wherein the tungsten-based material is W-25Re. 
   
   
       4 . The apparatus of  claim 1  wherein the molten electrolyte comprises a molten oxide solvent. 
   
   
       5 . The apparatus of  claim 4  wherein the molten oxide solvent comprises at least one member of the group comprising beryllium oxide, magnesium oxide, calcium oxide, aluminum oxide, and lithium oxide. 
   
   
       6 . The apparatus of  claim 1  wherein the iridium-based material contains at least 80% iridium. 
   
   
       7 . The apparatus of  claim 1  wherein the apparatus has an exterior, the anode being constructed with channels for conveying the oxygen from the substantially continuous iridium surface to the exterior. 
   
   
       8 . The apparatus of  claim 1  wherein the iridium-based material is substantially pure iridium. 
   
   
       9 . An apparatus for extracting a reactive metal from an oxide feedstock by the action of electric current, the apparatus comprising:
 a. a cathode substrate of a tungsten-based material, the reactive metal forming a deposit over the cathode substrate;   b. a molten electrolyte in which the feedstock is dissolved.   
   
   
       10 . The apparatus of  claim 9  wherein the reactive metal is titanium. 
   
   
       11 . The apparatus of  claim 10  wherein the deposit is liquid titanium. 
   
   
       12 . The apparatus of  claim 9  wherein the reactive metal is a member of the group comprising beryllium, aluminum, silicon, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, germanium, yttrium, zirconium, hafnium, indium, tin, barium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, actinium, thorium, protactinium and uranium. 
   
   
       13 . The apparatus of  claim 9  wherein the tungsten-based material contains rhenium. 
   
   
       14 . The apparatus of  claim 9  wherein the tungsten-based material is W-25Re. 
   
   
       15 . An apparatus for producing oxygen by the action of electric current, the apparatus comprising:
 a. a molten electrolyte containing a source of the oxygen;   b. an anode of an iridium-based material contacting the electrolyte over a contact interface, the contact interface being a substantially continuous iridium surface, the oxygen evolving on the anode.   
   
   
       16 . The apparatus of  claim 15  wherein the electrolyte contains an oxide source of a reactive metal, the apparatus further comprising a cathode substrate, a liquid deposit of the reactive metal deposit forming over the cathode substrate by the action of the electric current. 
   
   
       17 . The apparatus of  claim 16  wherein the reactive metal is aluminum. 
   
   
       18 . The apparatus of  claim 16  wherein the reactive metal is titanium. 
   
   
       19 . The apparatus of  claim 16  wherein the reactive metal is a member of the group comprising beryllium, aluminum, silicon, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, germanium, yttrium, zirconium, hafnium, indium, tin, barium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, actinium, thorium, protactinium and uranium. 
   
   
       20 . An apparatus for extracting a reactive metal from an oxide feedstock by the action of electric current, the apparatus comprising:
 a. a molten electrolyte in which the oxide feedstock is dissolved;   b. a cathode contacting the electrolyte;   c. an anode of an iridium-based material contacting the electrolyte over a contact interface, the contact interface being a substantially continuous iridium surface, the oxygen evolving on the anode.   
   
   
       21 . The apparatus of  claim 20  wherein the reactive metal is extracted as a vapor. 
   
   
       22 . The apparatus of  claim 20  wherein the reactive metal is extracted as a liquid. 
   
   
       23 . An apparatus for extracting liquid aluminum from an aluminum oxide feedstock by electrolysis, the apparatus comprising:
 a. a molten electrolyte in which the feedstock is dissolved;   b. an anode of iridium-based material contacting the electroyte over a contact interface, the contact interface being a substantially continuous iridium surface.   
   
   
       24 . The apparatus of  claim 1  wherein the titanium dioxide is derived from anatase. 
   
   
       25 . The apparatus of  claim 1  wherein the titanium dioxide is derived from rutile 
   
   
       26 . The apparatus of  claim 21  wherein the reactive metal is a member of the group comprising lithium, sodium, magnesium, potassium, calcium, rubidium, strontium and cesium. 
   
   
       27 . The apparatus of  claim 22  wherein the reactive metal is a member of the group comprising beryllium, aluminum, titanium silicon, scandium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, germanium, yttrium, zirconium, hafnium, indium, tin, barium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, actinium, thorium, protactinium and uranium.