Electrolytic production of magnesium

Abstract

Magnesium metal is produced by electrolysis of magnesium chloride employing a high surface area anode, for example, a porous anode to which hydrogen gas is fed. Hydrogen chloride is formed from the chloride ions at the anode, rather than chlorine gas; the process also has the advantage of operating at a lower voltage with a lower energy requirement than the conventional process in which chlorine gas is generated at the anode.

1 . In a process for the electrolytic production of magnesium from magnesium chloride dissolved in a molten salt electrolyte in an electrolytic cell having an anode and a cathode, and in which magnesium is generated at the cathode, the improvement wherein hydrogen gas is fed to the anode and hydrogen chloride is formed in situ at the anode.  
     
     
         2 . A process according to  claim 1 , wherein the anode is a high surface area anode.  
     
     
         3 . A process according to  claim 1 , wherein the anode is a porous anode and the hydrogen gas permeates the pores of the anode.  
     
     
         4 . A process according to  claim 1 , wherein said anode is a porous anode and the molten electrolyte permeates the pores of the porous anode.  
     
     
         5 . A process according to  claim 1 , wherein the anode is of graphite, silicon carbide or silicon nitride.  
     
     
         6 . A process, according to  claim 1 , for the electrolytic production of magnesium comprising: 
 i) electrolysing magnesium chloride in a molten salt electrolyte in an electrolysis cell having a cathode and an anode, with formation of magnesium metal at said cathode,    ii) feeding hydrogen gas to said anode and reacting chloride ions at said anode with the hydrogen gas to form hydrogen chloride,    iii) recovering the magnesium metal from said cell, and    iv) recovering the hydrogen chloride from said cell.    
     
     
         7 . A process according to  claim 6 , wherein said cell is operated at a cell voltage lower than the cell voltage of a corresponding cell having a carbon anode, without hydrogen gas, in which chlorine gas is developed at the anode.  
     
     
         8 . A process according to  claim 6 , wherein said anode is a high surface area anode.  
     
     
         9 . A process according to  claim 6 , wherein said anode is a porous anode and the hydrogen gas permeates from the pores of the anode into the cell.  
     
     
         10 . A process according to  claim 6 , wherein said anode is a porous anode and the molten electrolyte permeates the pores of the porous anode.  
     
     
         11 . A process according to  claim 6 , wherein said anode is of graphite, silicon carbide or silicon nitride  
     
     
         12 . An electrolytic cell for production of magnesium metal from magnesium chloride comprising: 
 a) a cell for housing magnesium chloride in a molten salt electrolyte, said cell having a cathode and an anode,    b) means for feeding hydrogen gas to said anode for production of hydrogen chloride at said anode,    c) means for recovery from said cell of magnesium metal produced at said cathode, and    d) means for recovery from said cell of hydrogen chloride developed at said anode.    
     
     
         13 . A cell according to  claim 12 , further including a conduit for delivery of hydrogen gas to said anode.  
     
     
         14 . A cell according to  claim 12 , wherein said anode is a high surface area anode.  
     
     
         15 . A cell according to  claim 12 , wherein said anode is a porous anode.  
     
     
         16 . A cell according to  claim 12 , wherein said anode is of graphite, silicon carbide or silicon nitride  
     
     
         17 . A cell according to  claim 15 , wherein said means for feeding hydrogen to said anode, feeds the hydrogen gas such that the hydrogen gas permeates from the pores of the porous anode into the cell.