Methods and apparatus for synthesis of metal hydrides

Abstract

An electrochemical process and apparatus for preparing metal hydride compounds from metal salts under a hydrogen atmosphere are disclosed. The electrochemical process may be integrated with chemical reaction of a boron compound to produce borohydride compounds. A metal salt and a borate are charged to the cathode of an electrolytic cell wherein the borate reacts with the hydride, to produce the borohydride compound.

1 . A process for preparing a metal hydride compound, comprising: 
 providing an electrolytic cell containing anode and cathode compartments separated by a separator which is permeable to ions;    supplying at least one metal salt in molten form to the cathode compartment;    applying an electric potential to the cell; and    providing hydrogen to the cathode compartment.    
   
   
       2 . The process of  claim 1 , wherein the metal salt has the formula MX n , wherein M is an active metal cation selected from the group consisting of Li + , Na + , K + , Rb + , Cs + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 3+ , Ti 4+ , Zn 2+ , Al 3+ , Si 4+ , Y 3+ , Y + , Zr 2+ , Zr 3+ , Zr + , Hf 2+ , Hf 3+ , Hf 4+ , and lanthanides in the +3 oxidation state; X is an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides; and n is the valence of the active metal cation.  
   
   
       3 . The process of  claim 2 , wherein M is selected from the group consisting of Li + , Na + , K +  and Cs + ; and X is chloride or bromide.  
   
   
       4 . The process of  claim 1 , wherein the separator comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β″-aluminum oxide, lithium-β/β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β″-aluminum oxide, sodium-β/β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β″-aluminum oxide, and potassium-β/β″-aluminum oxide.  
   
   
       5 . The process of  claim 1 , wherein the separator is a NaSICON membrane.  
   
   
       6 . The process of  claim 1 , wherein the separator is a LiSICON membrane.  
   
   
       7 . The process of  claim 1 , wherein the separator comprises a material selected from the group consisting of porous glass, porous metals, porous ceramics, porous plastics, paper polymers, fluorinated polymers, ion-conducting polymers, and fluorinated ion-conducting polymers.  
   
   
       8 . The process of  claim 1 , wherein the electrical potential is from about 1 to about 10 volts.  
   
   
       9 . The process of  claim 7 , wherein the electrical potential is from about 1 to about 5 volts.  
   
   
       10 . The process of  claim 1 , further comprising passing hydrogen or a hydrogen containing gas to the cathode compartment through a gas inlet means.  
   
   
       11 . The process of  claim 1 , further comprising bubbling hydrogen gas through the cathode compartment to agitate the catholyte.  
   
   
       12 . The process of  claim 1 , further comprising providing hydrogen to the cathode compartment from hydrogen absorbed in a metal.  
   
   
       13 . The process of  claim 1 , further comprising providing hydrogen to the anode compartment and electrooxidizing hydrogen at the anode.  
   
   
       14 . A process for producing a metal hydride compound, comprising: 
 providing an electrolytic cell containing anode and cathode compartments separated by a separator which is permeable to ions;    supplying at least one metal salt to the cathode compartment, wherein the metal salt is at least partially dissolved in an ionic liquid;    applying an electric potential to the cell; and    providing hydrogen to the cathode compartment.    
   
   
       15 . The process of  claim 14 , wherein the metal salt has the formula MX n , wherein M is an active metal cation selected from the group consisting of Li + , Na + , K + , Rb + , Cs + , Be 2+  Mg 2+ , Ca 2+ , Sr 2+  Ba 2+ , Sc 3+ , Ti 3+ , Ti 4+ , Zn 2+ , Al 3+ , Si 4+ , Y 3+ , Y + , Zr 2+ , Zr 3+ , Zr 4+ , Hf 2+ , Hf 3+ , Hf 4+ , and lanthanides in the +3 oxidation state; X is an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides; and n is the valence of the active metal cation.  
   
   
       16 . The process of  claim 15 , wherein M is selected from the group consisting of Li + , Na + , K +  and Cs + ; and X is chloride or bromide.  
   
   
       17 . The process of  claim 14 , wherein the separator comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β″-aluminum oxide, lithium-β/β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β″-aluminum oxide, sodium-β/β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β″-aluminum oxide, and potassium-β/β″-aluminum oxide.  
   
   
       18 . The process of  claim 14 , wherein the separator is a NaSICON membrane.  
   
   
       19 . The process of  claim 14 , wherein the separator is a LiSICON membrane.  
   
   
       20 . The process of  claim 14 , wherein the separator comprises a material selected from the group consisting of porous glass, porous metals, porous ceramics, porous plastics, paper polymers, fluorinated polymers, ion-conducting polymers, and fluorinated ion-conducting polymers.  
   
   
       21 . The process of  claim 14 , wherein the electrical potential is from about 1 to about 10 volts.  
   
   
       22 . The process of  claim 21 , wherein the electrical potential is from about 1 to about 5 volts.  
   
   
       23 . The process of  claim 14 , further comprising passing hydrogen or a hydrogen containing gas to the cathode compartment through a gas inlet means.  
   
   
       24 . The process of  claim 14 , further comprising bubbling hydrogen the cathode compartment to agitate the catholyte.  
   
   
       25 . The process of  claim 14 , further comprising providing hydrogen to the cathode compartment from hydrogen absorbed in a metal.  
   
   
       26 . The process of  claim 14 , further comprising providing hydrogen to the anode compartment and electrooxidizing hydrogen at the anode.  
   
   
       27 . The process of  claim 14 , wherein the ionic liquid is a salt comprising a cation containing at least one carbon atom and having a melting point between about −100° C. to about 200° C.  
   
   
       28 . The process of  claim 14 , wherein the ionic liquid comprises a cation selected from the group consisting of mono-, di-, tri-, and tetra substituted ammonium; mono-, di-, tri-, and tetra substituted phosphonium, N-alkylpyridinium, 1,3-disubstituted pyridiniums, 1,4-disubstituted pyridiniums, 1,3-disubstituted imidazolium, 1,2,3-trisubstituted imidazolium, 1,1 disubstituted pyrrolidiums, trialkylsulfonium, and trialkyloxonium cations.  
   
   
       29 . The process of  claim 14 , wherein the ionic liquid comprises an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides.  
   
   
       30 . A process for producing a boron hydride compound, comprising: 
 providing an electrolytic cell containing anode and cathode compartments separated by a separator which is permeable to ions;    supplying at least one metal salt in molten form to the cathode compartment;    applying an electric potential to the cell;    providing hydrogen to the cathode compartment; and    providing a boron compound to the cathode compartment.    
   
   
       31 . The process of  claim 30 , wherein the metal salt has the formula MX n , wherein M is an active metal cation selected from the group consisting of Li + , Na + , K + , Rb + , Cs + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 3+ , Ti 4+ , Zn 2+ , Al 3+ , Si 4+  Y 3+ , Y + , Zr 2+ , Zr 3+  Zr 4+ , Hf 2+ , Hf 3+ , Hf 4+ , and lanthanides in the +3 oxidation state; X is an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides; and n is the valence of the active metal cation.  
   
   
       32 . The process of  claim 31 , wherein M is selected from the group consisting of Li + , Na + , K +  and Cs + ; and X is chloride or bromide.  
   
   
       33 . The process of  claim 30 , wherein the separator comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β″-aluminum oxide, lithium-β/β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β″-aluminum oxide, sodium-β/β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β″-aluminum oxide, and potassium-β/β″-aluminum oxide.  
   
   
       34 . The process of  claim 30 , wherein the separator comprises a material selected from the group consisting of NaSICON and LiSICON membranes.  
   
   
       35 . The process of  claim 30 , wherein the separator comprises a material selected from the group consisting of porous glass, porous metals, porous ceramics, and porous plastics.  
   
   
       36 . The process of  claim 30 , wherein the electrical potential is from about 1 to about 10 volts.  
   
   
       37 . The process of  claim 36 , wherein the electrical potential is from about 1 to about 5 volts.  
   
   
       38 . The process of  claim 30 , further comprising passing hydrogen or a hydrogen containing gas to the cathode compartment through a gas inlet means.  
   
   
       39 . The process of  claim 30 , further comprising bubbling hydrogen the cathode compartment to agitate the catholyte.  
   
   
       40 . The process of  claim 30 , further comprising providing hydrogen to the cathode compartment from hydrogen absorbed in a metal.  
   
   
       41 . The process of  claim 30 , wherein the boron compound is an oxidized boron compound.  
   
   
       42 . The process of  claim 41 , wherein the oxidized boron compound is sodium metaborate and the metal halide is lithium bromide.  
   
   
       43 . The process of  claim 30 , further comprising maintaining the cell at a temperature of about 70 to about 500° C.  
   
   
       44 . The process of  claim 30 , further comprising providing hydrogen to the anode compartment and electrooxidizing hydrogen at the anode.  
   
   
       45 . The process of  claim 30 , wherein the electric potential is removed before providing the boron compound.  
   
   
       46 . The process of  claim 30 , wherein the boron compound is provided before applying the electric potential.  
   
   
       47 . The process of  claim 30 , further comprising separating the boron hydride compound.  
   
   
       48 . The process of  claim 30 , wherein the boron compound is a boron halide.  
   
   
       49 . The process of  claim 30 , wherein the boron compound is an alkyl borate.  
   
   
       50 . The process of  claim 30 , wherein the boron compound is a borate.  
   
   
       51 . The process of  claim 30 , wherein the boron compound is selected from the group consisting of boric oxide and boric acid.  
   
   
       52 . The process of  claim 30 , wherein the boron compound is an alkali metal borate salt.  
   
   
       53 . A process for producing a boron hydride compound, comprising: 
 providing an electrolytic cell containing anode and cathode compartments separated by a separator which is permeable to ions;    supplying at least one metal salt to the cathode compartment, wherein the metal salt is at least partially dissolved in an ionic liquid;    applying an electric potential to the cell;    providing hydrogen to the cathode compartment; and    providing a boron compound to the cathode compartment.    
   
   
       54 . The process of  claim 53 , wherein the metal salt has the formula MX n , wherein M is an active metal cation selected from the group consisting of Li + , Na + , K + , Rb + , Cs + , Be 2+  Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Ti 3+ , Ti 4+ , Zn 2+ , Al 3+ , Si 4+ , Y 3+ , Y + , Zr 2+ , Zr 3+ , Zr 4+ , Hf 2+ , Hf 3+ , Hf 4+ , and lanthanides in the +3 oxidation state; X is an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides; and n is the valence of the active metal cation.  
   
   
       55 . The process of  claim 54 , wherein M is selected from the group consisting of Li + , Na + , K +  and Cs + ; and X is chloride or bromide.  
   
   
       56 . The process of  claim 53 , wherein the separator comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β″-aluminum oxide, lithium-β/β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β″-aluminum oxide, sodium-β/β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β″-aluminum oxide, and potassium-β/β″-aluminum oxide.  
   
   
       57 . The process of  claim 53 , wherein the separator comprises a material selected from the group consisting of NaSICON and LiSICON membranes.  
   
   
       58 . The process of  claim 53 , wherein the separator comprises a material selected from the group consisting of porous glass, porous metals, porous ceramics, porous plastics, paper polymers, fluorinated polymers, ion-conducting polymers, and fluorinated ion-conducting polymers.  
   
   
       59 . The process of  claim 53 , wherein the electrical potential is from about 1 to about 10 volts.  
   
   
       60 . The process of  claim 53 , wherein the electrical potential is from about 1 to about 5 volts.  
   
   
       61 . The process of  claim 53 , further comprising passing hydrogen or a hydrogen containing gas to the cathode compartment through a gas inlet means.  
   
   
       62 . The process of  claim 53 , further comprising bubbling hydrogen the cathode compartment to agitate the catholyte.  
   
   
       63 . The process of  claim 53 , further comprising providing hydrogen to the cathode compartment from hydrogen absorbed in a metal.  
   
   
       64 . The process of  claim 53 , wherein the ionic liquid is a salt comprising a cation containing at least one carbon atom and having a melting point between about −100° C. to about 200° C.  
   
   
       65 . The process of  claim 53 , wherein the ionic liquid comprises a cation selected from the group consisting of mono-, di-, tri-, and tetra substituted ammonium; mono-, di-, tri-, and tetra substituted phosphonium, N-alkylpyridinium, 1,3-disubstituted pyridiniums, 1,4-disubstituted pyridiniums, 1,3-disubstituted imidazolium, 1,2,3-trisubstituted imidazolium, 1,1 disubstituted pyrrolidiums, trialkylsulfonium, and trialkyloxonium cations.  
   
   
       66 . The process of  claim 53 , wherein the ionic liquid comprises an anion selected from the group consisting of halides, tosylate, sulfate, sulfonates, nitrate, phosphates, hexafluorophosphate, phosphates, phosphinates, dicyanamide, tetrafluoroborate, acetate, trifluoroacetate, borohydride, benzoate, tetrachloroaluminate, thiocyanate, thiosalicylate, methides, and imides.  
   
   
       67 . The process of  claim 53 , wherein the boron compound is a boron-oxygen compound.  
   
   
       68 . The process of  claim 53 , wherein the boron compound is an alkyl borate.  
   
   
       69 . The process of  claim 53 , wherein the boron compound is a borate.  
   
   
       70 . The process of  claim 53 , wherein the boron compound is selected from the group consisting of boric oxide and boric acid.  
   
   
       71 . The process of  claim 53 , wherein the boron compound is an alkali metal borate salt.  
   
   
       72 . The process of  claim 53 , wherein the boron compound is sodium metaborate and the metal halide is lithium bromide.  
   
   
       73 . The process of  claim 53 , further comprising maintaining the cell at a temperature of about 70 to about 500° C.  
   
   
       74 . The process of  claim 53 , further comprising providing hydrogen to the anode compartment and electrooxidizing hydrogen at the anode.  
   
   
       75 . The process of  claim 53 , wherein the electric potential is removed before providing the boron compound.  
   
   
       76 . The process of  claim 53 , wherein the boron compound is provided before applying the electric potential.  
   
   
       77 . The process of  claim 53 , further comprising separating the boron hydride compound.  
   
   
       78 . A process for producing borohydride anions comprising dissolving a metal hydride and a boron compound in at least one liquid salt.  
   
   
       79 . The process of  claim 78 , wherein the metal hydride is selected from the group consisting of alkali metal hydrides, alkaline earth metal hydrides, aluminum hydrides and zinc hydrides.  
   
   
       80 . The process of  claim 78 , wherein the metal hydride comprises a metal characterized in that the standard reduction potential for the reaction of the metal with oxygen is at least about 1.6 V.  
   
   
       81 . The process of  claim 78 , wherein the metal hydride is formed by the steps of: 
 supplying at least one active metal salt in molten form to a cathode compartment of an electrolytic cell containing anode and cathode compartments separated by a separator which is permeable to ions;    applying an electric potential to said cell to reduce the metal compound at the cathode; and    passing hydrogen or a hydrogen containing gas in the cathode compartment while the compound is reduced at the cathode.    
   
   
       82 . The process of  claim 78 , wherein the metal hydride is formed in situ.  
   
   
       83 . The process of  claim 78 , wherein the boron compound is an oxidized boron compound.  
   
   
       84 . The process of  claim 78 , wherein the liquid salt is a molten active metal salt.  
   
   
       85 . The process of  claim 78 , wherein the liquid salt is a mixture of molten active metal salts.  
   
   
       86 . The process of  claim 78 , wherein the liquid salt is an ionic liquid.  
   
   
       87 . The process of  claim 78 , wherein the liquid salt is a mixture of at least one molten active metal salt and at least one ionic liquid.  
   
   
       88 . An apparatus for reducing boron compounds to produce boron hydride compounds, comprising: 
 an anode compartment containing on anode;    a cathode compartment containing a cathode;    a separator between the anode and cathode compartments, wherein the separator is permeable to ions;    at least one inlet for charging metal salt and boron compounds to the cathode compartment; and    a means for supplying hydrogen to the cathode compartment.    
   
   
       89 . The apparatus of  claim 88 , wherein the apparatus is configured to maintain the cathode compartment at a temperature of about 70° C. to about 500° C.  
   
   
       90 . The apparatus of  claim 88 , wherein the separator comprises a material selected from the group consisting of lithium-β-aluminum oxide, lithium-β″-aluminum oxide, lithium-β/β″-aluminum oxide, sodium-β-aluminum oxide, sodium-β″-aluminum oxide, sodium-β/β″-aluminum oxide, potassium-β-aluminum oxide, potassium-β″-aluminum oxide, and potassium-β/β″-aluminum oxide.  
   
   
       91 . The apparatus of  claim 88 , wherein the separator is a NaSICON membrane.  
   
   
       92 . The apparatus of  claim 88 , wherein the separator is a LiSICON membrane.  
   
   
       93 . The apparatus of  claim 88 , wherein the separator comprises a material selected from the group consisting of porous glass, porous metals, porous ceramics, porous plastics, paper polymers, fluorinated polymers, ion-conducting polymers, and fluorinated ion-conducting polymers.  
   
   
       94 . The apparatus of  claim 88 , further comprising a means for bubbling hydrogen gas through the cathode compartment to agitate the catholyte.  
   
   
       95 . The apparatus of  claim 88 , wherein the cathode compartment contains hydrogen absorbed in a metal adapted to release hydrogen when heated.