Solid state synthesis of metal borohydrides

Patent metadata

Field	Value
Publication number	US-11267702-B1
Application number	US-201816000683-A
Country	US
Kind code	B1
Filing date	Jun 5, 2018
Priority date	Jun 8, 2017
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

A method for obtaining solid-state metal borohydrides without toxic precursors and expensive solvents includes dry mixing of metal hydrides and metal polyhydro-closo-borate starting materials. High pressure and heating is also used in the method. These materials can be used for hydrogen storage, general reducing agents, organic synthesis, wastewater treatment, and paper pulp bleaching.

First claim

What is claimed is:

1. A process for making a metal borohydride, comprising the steps of:
mixing without solvent a metal polyhydro-closo-borate and a metal hydride under an inert atmosphere to form a mixture;
charging hydrogen gas to the mixture at a pressure of at least approximately 25 MPa, and heating the mixture at a temperature of approximately 350° C. to 540° C. to produce a metal borohydride product;
the metal in the metal polyhydro-closo-borate and the metal hydride is selected from the group consisting of Li, Na, K, Rb, and Cs.

2. The process of claim 1 , wherein the metal is Li.

3. The process of claim 1 , wherein the metal is Na.

4. The process of claim 1 , wherein the metal is K.

5. The process of claim 1 , wherein the metal is Rb.

6. The process of claim 1 , wherein the metal is Cs.

7. The process of claim 1 , wherein the metal polyhydro-closo-borate is M 2 B 10 H 10 or M 2 B 12 H 12 , wherein M is Li, Na, K, Rb, or Cs.

8. The process of claim 1 , wherein the metal borohydride product is free of contamination introduced from solvents or other chemicals.

9. The process of claim 1 , wherein the temperature is 490° C. to 540° C.

10. The process of claim 1 , wherein the pressure is 25 to 105 MPa.

11. The process of claim 1 , wherein the metal polyhydro-closo-borate and the metal hydride are mixed in stoichiometric amounts.

12. The process of claim 1 , wherein the metal hydride and the metal polyhydro-closo-borate in the mixing step are in a molar ratio of 5 to 24 metal hydride to 1 metal polyhydro-closo-borate.

13. The process of claim 1 , wherein the metal borohydride product is 97% or greater purity by weight without further purification steps.

14. The process of claim 1 , wherein the metal is one metal selected from the group consisting of Rb and Cs.

15. The process of claim 1 , further comprising mixing a catalyst or dopant in the mixing step.

16. The process of claim 1 , wherein the metal borohydride product has an isomorphic crystalline structure selected from the group consisting of: cubic, orthorhombic, tetragonal, hexagonal, trigonal, or monoclinic.

17. The process of claim 1 , wherein the mixing without solvent is performed in a ball mill.

18. The process of claim 1 , wherein the metal borohydride compound is produced at a yield of 80% by weight or higher.

19. The process of claim 10 , wherein the pressure is 70 to 105 MPa.

20. The process of claim 1 , wherein the charging and heating is performed until the mixture melts.

Assignees

• Nat Tech & Eng Solutions Sandia Llc

Inventors

• STAVILA Vitalie
• White James Lawrence

Classifications

• C01B6/21 Primary

  Preparation of borohydrides of alkali metals, alkaline earth metals, magnesium or beryllium; Addition complexes thereof, e.g. LiBH4.2N2H4, NaB2H7 · CPC title

• C01B35/026 Primary

  Higher boron hydrides, i.e. containing at least three boron atoms · CPC title

• C01P2004/38

  cube-like · CPC title