Electrolytic production of magnesium

{
  "publication_number": "US4073703A",
  "country": "US",
  "kind": "A",
  "title": "Electrolytic production of magnesium",
  "abstract": "Magnesium is produced by decomposition of magnesium chloride contained in an electrolyte. The magnesium chloride containing electrolyte is provided in a refractory lined electrolytic cell having an anode and a cathode wherein magnesium is produced at the cathode and chlorine at the anode, the magnesium accumulating in a layer on the surface of the electrolyte. A shroud having a skirt portion therein formed from a nitride-based refractory projects into the electrolyte such that chlorine produced at the anode is removed from the cell without contacting the molten magnesium layer, the shroud being resistant to attack by molten magnesium, electrolyte and gases emanating therefrom.",
  "claims": [
    "1. An electrolytic cell having a refractory lining therein and an anode and a cathode for the production of magnesium by decomposition of molten magnesium chloride contained in an electrolyte, the magnesium produced at the cathode and chlorine at the anode, said magnesium accumulating in a layer at the surface of said molten magnesium chloride containing electrolyte, a shroud having a skirt portion thereon projecting into the electrolyte such that said chlorine produced at said anode is removed from said cell without contacting the molten magnesium layer, said shroud formed from a nitride-based refractory material selected from the group consisting of silicon oxynitride, silicon nitride bonded fused silica, silicon nitride and boron nitride resistant to said molten magnesium, magnesium chloride containing electrolyte and gases emanating therefrom.",
    "2. The cell according to claim 1 wherein at least a portion of the refractory lining extending above and below the molten magnesium layer is formed from a nitride-based refractory.",
    "3. The cell according to claim 2 wherein the nitride-based refractory employed is selected from the group consisting of silicon oxynitride, silicon nitride bonded fused silica, silicon nitride and boron nitride.",
    "4. The cell according to claim 2 wherein the nitride-based refractory is silicon oxynitride.",
    "5. An improved process for the production of metallic magnesium from magnesium chloride contained in an electrolyte comprising: (a) providing the electrolyte in an electrolytic, refractory lined cell having an anode and a cathode; (b) electrolytically decomposing said magnesium chloride to produce magnesium at the cathode and chlorine at the anode, the magnesium chloride accumulating in a layer on the surface of the electrolyte; and (c) utilizing a shroud having a skirt portion thereon formed from a nitride-based refractory and projecting into the electrolyte to remove chlorine produced at the anode without the chlorine contacting the molten magnesium layer, the nitride-based refractory selected from the group consisting of silicon oxynitride, silicon nitride bonded fused silica, silicon nitride and boron nitride resistant to attack by molten magnesium, electrolyte and gases emanating therefrom.",
    "6. The process according to claim 5 wherein at least a portion of the refractory lining extending above and below the molten magnesium layer is the nitride-based refractory.",
    "7. The process according to claim 6 wherein the nitride-based refractory is one selected from the group consisting of silicon oxynitride, silicon nitride bonded fused silica, silicon nitride and boron nitride.",
    "8. The process according the claim 6 wherein the nitride-based refractoy employed is silicon oxynitride.",
    "9. An electrolytic, refractory lined cell having an anode and a cathode for the production of magnesium by decomposition of magnesium chloride contained in an electrolyte, the magnesium produced at the cathode and chlorine at the anode, said magnesium accumulating in a layer on the surface of the electrolyte, a shroud surrounding the anode and having a skirt portion thereon projecting into the electrolyte such that the chlorine produced at the anode is removed from the cell without contacting the molten magnesium layer, said shroud and said refractory lining having at least a portion thereof extending above and below the magnesium layer and formed from silicon oxynitride, characterized by being substantially free of carbonaceous material and by being resistant to attack by said electrolyte molten magnesium and gases emanating therefrom."
  ],
  "description_excerpt": "This invention relates to the production of magnesium chloride. More particularly it relates to the production of magnesium chloride utilizing a refractory liner highly resistant to deterioration by reactants in the process.\n\nIt is known to produce magnesium chloride by the chlorination of magnesium oxide or an impure mixture of magnesium chloride and magnesium oxide by chlorinating the oxide in the presence of a reducing agent such as carbon or the like. For example, British patent specification No. 886,212 teaches the chlorination of a mixture of magnesium chloride and magnesium oxide by chlorinating a molten mixture of magnesium oxide and magnesium chloride while passing the materials through a carbonaceous material such as lump coal or coke or the like. However, such processes are normally carried out at elevated temperatures, for example the aforesaid British patent mentions the temperature of the chlorinator as 750° to 900° C. At this temperature, problems can arise with respect to the types of materials, particularly refractories, used in the apparatus from the standpoint of purity of the magnesium chloride and magnesium produced therefrom. Also, serious problems can arise if the refractories used are not resistant to attack by molten magnesium chloride in the chlorinator, for example, or gases emanating therefrom such as chlorine, phosgene, carbon tetrachloride and boron trichloride. For example, British patent specification No.",
  "cpc": [
    "C25C 3/04",
    "C25C 7/005"
  ],
  "ipc": [
    "C25C 3/04",
    "C25C 7/00"
  ],
  "assignees": [
    "Aluminum Company of America"
  ],
  "inventors": [
    "Donald L. Kinosz",
    "Warren E. Haupin"
  ],
  "filing_date": "1976-12-14",
  "publication_date": "1978-02-14",
  "grant_date": "1978-02-14",
  "priority_date": "1976-12-14",
  "application_number": "US-75050676-A",
  "family_id": "25018140",
  "cited_by_count": 26,
  "citations": [
    "US1597231A",
    "US2406935A",
    "US3021268A",
    "US3639101A"
  ]
}