Triborohydride salts as hydrogen storage materials and preparation thereof

• US 20050135996A1
• Filed: 12/19/2003
• Published: 06/23/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Millennium Cell Inc.
• Original Assignee: Millennium Cell Inc.
• Inventors: Ortega, Jeffrey V., Kelly, Michael T., Wu, Ying, Brady, Jason C., Snover, Jonathan L.
• Granted Patent: US 7,214,439 B2
• Time in Patent Office: Days
• US Class Current: 423/648.100
• CPC Class Codes: C01B 3/065 from a hydride
• CPC Class Codes: C01B 6/21 Preparation of borohydrides of alkali metals, alkaline earth metals, magnesium or beryllium; Addition complexes thereof, e.g. LiBH4.2N2H4, NaB2H7
• CPC Class Codes: F17C 11/005 for hydrogen
• CPC Class Codes: Y02E 60/32 Hydrogen storage
• CPC Class Codes: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

The present invention relates to the use of triborohydride salts as hydrogen storage materials. The present invention also relates to a system of using triborohydride salts to generate hydrogen gas for use in a fuel cell or other hydrogen-consuming device. A novel method of preparing triborohydride salts is also disclosed, wherein gaseous diborane is reacted with a carbonate suspended in a non-aqueous solvent in a suitable vessel with agitation. The process is typically carried out utilizing sodium carbonate to form sodium triborohydride. Other triborohydride salts can then be formed by cationic exchange. Hydrogen generating fuels according to the present invention include aqueous or hydroalcoholic solutions or slurries of a triborohydride salt, which may additionally contain a borohydride salt to provide operation over a broader temperature range.

Claims

1. A method of generating hydrogen gas comprising reacting a triborohydride salt represented by the formula MB₃H₈ with water in the presence of a hydrogen generating catalyst selected from the group consisting of acids and transition metals, wherein M is selected from the group consisting alkali metals, pseudo-alkali metals, alkaline earth metals, ammonium ions, phosphonium cations, and quaternary amines of the formula NR₄⁺, wherein each R is independently selected from hydrogen and a straight- or branched-chain C_1-4 alkyl group.

2. A method in accordance with claim 1, wherein M is selected from the group consisting of Na⁺, Li⁺, K⁺, Mg⁺⁺ and Ca⁺⁺.

3. A method in accordance with claim 2, wherein M is Na⁺.

4. A method in accordance with claim 1, wherein the catalyst is an acid selected from the group consisting of hydrochloric acid, sulfuric acid, and phosphoric acid.

5. A method in accordance with claim 1, wherein the catalyst comprises one or more transition metals selected from the metal families of nickel, cobalt and iron.

6. A method in accordance with claim 5, wherein the catalyst is ruthenium, cobalt or mixtures thereof.

7. A hydrogen generation system, comprising

(a) an aqueous fuel containing a triborohydride salt represented by the formula MB₃H₈, wherein M is selected from the group consisting alkali metals, pseudo-alkali metals, alkaline earth metals, ammonium ions, phosphonium cations, and quaternary amines of the formula NR₄⁺, wherein each R is independently selected from hydrogen and a straight- or branched-chain C_1-4 alkyl group;

and

(b) a hydrogen generating catalyst selected from the group consisting of acids and transition metals, and

(c) means to contact the aqueous fuel with the catalyst thereby generating hydrogen.

8. A hydrogen generation system in accordance with claim 7, wherein the hydrogen generating catalyst is an acid selected from the group consisting of hydrochloric acid, sulfuric acid, and phosphoric acid, and said acid and the aqueous fuel containing a triborohydride salt are stored in separate containers.

9. A hydrogen generation system in accordance with claim 7, wherein the hydrogen generating catalyst comprises a substrate having molecules of a transition metal bound thereto, entrapped within, and/or coated thereon and said means to contact comprises a containment system for said catalyst whereby the catalyst can be moved into and out of contact with the aqueous fuel.

10. A hydrogen generation system in accordance with claim 9, wherein said substrate is selected from the group consisting of plastics, polymers, textiles, metals, metal oxides, ceramics, and carbonaceous materials.

11. A hydrogen generation system in accordance with claim 7, additionally comprising a small buffer tank, wherein a constant level of hydrogen gas is maintained for immediate demand of hydrogen gas.

12. A hydrogen generation system in accordance with claim 7, additionally including a gas-liquid separator to separate hydrogen from the effluent stream.

13. A hydrogen generation system in accordance with claim 7, wherein at least a portion of the water in said aqueous fuel is obtained from the reaction product of a hydrogen-consuming device, said device being operably connected with said system.

14. A hydrogen generation system in accordance with claim 13, wherein the hydrogen-consuming device is selected from the group consisting of a fuel cell, a combustion engine, a gas turbine, and combinations thereof.

15. An aqueous fuel for a hydrogen generator comprising an aqueous or hydroalcoholic solution or slurry of a triborohydride salt represented by the formula MB₃H₈, wherein M is selected from the group consisting alkali metals, pseudo-alkali metals, alkaline earth metals, ammonium ions, phosphonium cations, and quaternary amines of the formula NR₄⁺, wherein each R is independently selected from hydrogen and a straight- or branched-chain C_1-4 alkyl group.

16. An aqueous fuel in accordance with claim 15, further comprising a borohydride salt and a hydroxide compound.

17. An aqueous fuel in accordance with claim 15, wherein said triborohydride salt is sodium borohydride, said borohydride salt is sodium borohydride, and said hydroxide compound is sodium hydroxide.

18. A process of making a triborohydride salt represented by the formula MB₃H₈, wherein M is selected from the group consisting alkali metals, pseudo-alkali metals, alkaline earth metals, ammonium ions, phosphonium cations, and quaternary amines of the formula NR₄⁺, wherein each R is independently selected from hydrogen and a straight- or branched-chain C_1-4 alkyl group, comprising reacting gaseous diborane with a M-containing base in suspension in a nonaqueous aprotic solvent or a nonaqueous polar solvent, said base being selected from those represented by the formula M₂O, MOH and M₂CO₃ to obtain MB₃H₈, MBO₂, CO₂ and H₂.

19. A process in accordance with claim 18, wherein the nonaqueous solvent is diglyme.

20. A process in accordance with claim 18, wherein said suspension is agitated during the reaction.

21. A process in accordance with claim 18, wherein M is Na⁺.