Electrolytic production process for magnesium and its alloys

• US 5,593,566 A
• Filed: 06/09/1995
• Issued: 01/14/1997
• Est. Priority Date: 06/09/1995
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Sharma, Ram A.
• Primary Examiner(s): Bell, Bruce F.
• Assistant Examiner(s): Mee, Brendan
• Application Number:
  US08/488,698
• Time in Patent Office: 585 Days
• Field of Search: 205/404, 205/405, 205/408, 205/407, 205/409, 205/411, 205/349, 205/363, 205/373
• US Class Current: 205/363
• CPC Class Codes: C25C 3/04 of magnesium

Abstract

A process is disclosed for the electrolytic production of magnesium utilizing magnesium oxide and/or partially dehydrated magnesium chloride as a feedstock. An electrolyte containing magnesium chloride, potassium chloride and optionally sodium chloride is employed so that magnesium is produced. The magnesium is absorbed into a molten magnesium alloy cathode layer underlying the MgCl₂ -KCl electrolyte. In a bipolar embodiment, pure magnesium is electrolytically transported from the magnesium alloy through a second molten salt electrolyte to an overlying electrode where the magnesium collects as a pool on the second electrolyte.

Claims

1. A method of producing magnesium or magnesium alloys from a feedstock containing magnesium oxide comprising:

providing an electrolytic cell comprising (a) a molten salt electrolyte initially consisting essentially of one part by weight magnesium chloride and three to five parts by weight potassium chloride;

(b) a molten metal cathode comprising a magnesium alloy having a density greater than that of said electrolyte; and

(c) a nonconsumed anode immersed in said electrolyte,

heating the contents of the electrolytic cell to an operating temperature at which the electrolyte and cathode are molten,

applying a direct current potential between said anode and cathode to produce chlorine gas at said anode and to reduce magnesium cations in said electrolyte to produce magnesium metal at the interface of said electrolyte and said cathode, such magnesium being absorbed into said cathode layer, and

adding said feedstock to said electrolyte where it reacts with said chlorine gas as it is emitted to replenish magnesium cations in said electrolyte.

2. A method of producing magnesium from a feedstock containing magnesium oxide comprising:

providing an electrolytic cell comprising (a) a molten salt electrolyte initially consisting essentially of 5 to 25 percent by weight magnesium chloride, 60 to 75 percent by weight potassium chloride, and 0 to 20 percent sodium chloride;

(b) a molten metal cathode comprising a magnesium alloy having a density greater than that of said electrolyte; and

(c) an anode immersed in said electrolyte,

heating the contents of the electrolytic cell to a temperature in the range of 700°

C. to 850°

C.,

applying a direct current potential between said anode and cathode to produce chlorine gas at said anode and to reduce magnesium cations in said electrolyte to produce magnesium metal at the interface of said electrolyte and said cathode, such magnesium being absorbed into said cathode layer, and

adding said feedstock oxide to said electrolyte wherein it reacts with said chlorine gas as it is emitted to replenish magnesium cations in said electrolyte.

3. A method of producing magnesium from a feedstock containing magnesium oxide and/or partially dehydrated magnesium chloride comprising:

providing a first confined electrolytic cell comprising (a) a first molten salt electrolyte consisting essentially of, by weight, one part magnesium chloride and three to five parts potassium chloride;

(b) a molten magnesium alloy cathode having a density greater than that of said electrolyte and underlying said electrolyte; and

(c) an anode immersed in said electrolyte,

providing a second confined electrolytic cell comprising (a) a second molten salt electrolyte comprising magnesium cations and chloride anions, said second electrolyte overlying a portion of said molten alloy but separated from said first electrolyte and (b) a cathode immersed in the second electrolyte, said molten alloy serving as the cathode in said second cell, and

applying a direct current potential between said first cell anode and said second cell cathode to produce chlorine gas at said anode and magnesium at the interface of said first electrolyte and said molten metal alloy, said magnesium there being absorbed into said alloy, and magnesium further being electrolytically transported in said second cell from said molten alloy to the cathode in said second cell where magnesium is deposited and collected.

4. A method of producing magnesium from a feedstock containing magnesium oxide and/or partially dehydrated magnesium chloride comprising:

providing a first confined electrolytic cell comprising (a) a first molten salt electrolyte consisting essentially of, by weight, 5 to 25 percent magnesium chloride, 60 to 80 percent potassium chloride and 0 to 20 percent sodium chloride;

(b) a molten metal alloy cathode having a density greater than that of said electrolyte and underlying said electrolyte; and

(c) an anode immersed in said electrolyte,

providing a second confined electrolytic cell comprising (a) a second molten salt electrolyte comprising magnesium cations and chloride anions, said second electrolyte overlying a portion of said molten alloy but separated from said first electrolyte, (b) a cathode immersed at the upper surface of the second electrolyte, and (c) said molten alloy serving as the anode in said second cell, and

applying a direct current potential between said first cell anode and said second cell cathode to produce chlorine gas at said anode and magnesium at the interface of said first electrolyte and said molten metal alloy, said magnesium being absorbed into said alloy in said first cell, and magnesium being electrolytically transported from said molten alloy in said second cell to the cathode in said second cell where magnesium is deposited and collected.