# US 7,608,233 B1 · Direct synthesis of calcium borohydride

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- Number: US 7,608,233 B1
- Document ID: US7608233B1
- Status: Granted
- Kind: B1
- Application number: 11/807,012
- Filed: 2007-05-24
- Granted: 2009-10-27
- Earliest claimed: 2007-02-12
- Assignees: Sandia Corporation
- Inventors: Ewa Carin Ellinor Rönnebro; Eric H. Majzoub
- Web page: https://patentgrep.com/patent/US7608233B1

## CPC

- C01B 6/21: Preparation of borohydrides of alkali metals, alkaline earth metals, magnesium or beryllium; Addition complexes thereof, e.g. LiBH4.2N2H4, NaB2H7
- C01B 3/0026: Metals or metal hydrides
- C01B 3/065: by reaction of inorganic compounds with hydrides
- Y02E 60/32: Hydrogen storage
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A method is disclosed for directly preparing an alkaline earth metal borohydride, i.e. Ca(BH4)2, from the alkaline earth metal hydride and the alkaline earth metal boride. The borohydride thus prepared is doped with a small portion of a metal chloride catalyst compound, such as RuCl3, TiCl3, or a mixture of TiCl3 and palladium metal. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen at about 70 MPa while heating the mixture to about 400° C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

## Claims

### Claim 1

A method of producing a complex borohydride compound capable of reversible hydrogenation, comprising:
mechanically mixing an alkaline earth metal hydride with an alkaline earth metal boride powder and a powder of metal chloride catalyst compound in order to provide a compound mixture, wherein the metal chloride catalyst comprises about 4 to about 8 weight percent of the combined weight of the alkaline earth metal hydride and the alkaline earth metal boride; and
hydrogenating the compounded mixture at an elevated temperature and pressure to provide an alkaline earth metal borohydride compound.

### Claim 2 (depends on 1)

The method according to claim 1, further comprising the step of compacting the compounded powder mixture prior to the step of hydrogenating the compounded powder mixture.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the molar ratio of the alkaline earth metal hydride and an alkaline earth metal boride is at least 2:1.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the alkaline earth metal hydride is selected from the group of hydrides consisting essentially of CaH2.

### Claim 5 (depends on 3)

The method according to claim 3, wherein the alkaline earth metal boride is selected from the group of borides consisting essentially of CaB6.

### Claim 6 (depends on 3)

The method according to claim 3, wherein said metal chloride catalyst compound is selected from the group of compounds consisting essentially of TiCl3, a mixture of palladium and TiCl3, and RuCl3.

### Claim 7 (depends on 1)

The method according to claim 1, wherein said step of mechanically mixing comprises a process selected from the group consisting of ball milling, plate or impact grinding, and blending, stirring, or agitating with or without a mechanical aid.

### Claim 8 (depends on 7)

The method according to claim 7, wherein said step of mechanically mixing comprises ball milling the alkaline earth metal hydride, the alkaline earth metal boride, and the metal chloride catalyst for about 30 minutes.

### Claim 9 (depends on 8)

The method according to claim 8, wherein said step of mechanically mixing is carried out in an atmosphere consisting essentially of high purity argon gas.

### Claim 10 (depends on 8)

The method according to claim 8, wherein said step of mechanically mixing is carried out at about room temperature.

### Claim 11 (depends on 1)

The method according to claim 1, wherein said step of hydrogenation is performed at a temperature of above about 400° C., and wherein said hydrogen pressure is maintained at about a pressure of 70 MPa.

### Claim 12 (depends on 1)

The method according to claim 1, wherein the hydrogen pressure is maintained for at least about 2 hours.