Method for reversibly storing hydrogen on the basis of...

Details Method for reversibly storing hydrogen on the basis of... Method for reversibly storing hydrogen on the basis of...

2002-09-12

2004-11-09

Spitzer, Robert H. (Department: 1724)

Gas separation: processes

Solid sorption

Inorganic gas or liquid particle sorbed

C252S182350, C423S644000, C423S648100

Reexamination Certificate

active

06814782

ABSTRACT:

The present invention relates to a method for reversibly storing hydrogen using alkali metals or their hydrides and aluminum metal as hydrogen storage materials and doping with transition metal catalysts.
According to the patent application PCT/WO 97/03919 of the Studiengesellschaft Kohle mbH (SGK), a method for reversibly storing hydrogen is known using the alkali metal alanates of general formula M
1
p(1−x)
M
2
px
AlH
3+p
(1) as storage materials, where M
1
=Na, K; M
2
=Li, K; 0≦x≦~0.8; 1≦p≦3. To improve the hydrogenation/dehydrogenation kinetics, the alkali metal alanates are doped with transition metal compounds in catalytic amounts. In particular, the alanates NaAlH
4
, Na
3
AlH
6
and Na
2
LiAlH
6
are employed.
The drawbacks of the previous SGK method are that the preparation and purification of commercial sodium alanate, the preparation of Na
3
AlH
6
or Na
2
LiAlH
6
and the subsequent doping in organic solvents are relatively complicated on a preparative level and in most cases require the use of solvents which are highly volatile and highly inflammable (ether, pentane) or tend to form peroxides (ether, THF).
Surprisingly, it has now been found that instead of using the transition-metal doped alkali metal alanates as hydrogen storage materials, the starting materials used for their preparation in the form of alkali metal hydrides or alkali metals (especially NaH and Na), Al powder and doping agents can be employed. The alanates formed in one hydrogenation step from such starting materials are immediately functioning as H
2
storage materials and have improved storage properties as compared to PCT/WO 97/03919.
Methods for the preparation of alkali metal alanates from alkali metal hydrides (or alkali metals), aluminum and hydrogen are known. A survey of the methods for the preparation of NaAlH
4
, Na
3
AlH
6
and Na
2
LiAlH
6
can be found in J. Alloys & Compounds, 298 (2000) 125-134. Thus, according to the German Patent Specification 1 136 987 (1962), Na and Li alanates can be prepared by reacting the corresponding alkali metal hydrides (or alkali metals) and aluminum in ethers, amines and aliphatic or aromatic hydrocarbons, optionally in the presence of catalytic amounts of organoaluminum compounds, with hydrogen under pressure. The U.S. Pat. No. 3,138,433 (1964) describes, inter alia, a method for the preparation of NaAlH
4
from NaH, Al and hydrogen under pressure in THF using Ti, Zr, Hf and Th tetrahalides as catalysts; however, in the only patent example contained therein, a maximum of 21.8% is stated as the yield of NaAlH
4
. The direct synthesis of Na
3
AlH
6
can be successfully performed with 98% yield according to Inorg. Chem. 5 (1966) 1615 by reacting Na and activated Al powder in diglyme in the presence of Et
3
Al with hydrogen under pressure (350 bar). The synthesis of NaAlH4 from the elements Na, Al and H
2
is also possible in the absence of organic solvents according to Dokl. Akad. Nauk SSSR 215 (1974) 1369, Engl. 256, by performing the process in the molten state (≧175 bar, <280° C.). The alkali metal alanates prepared according to the methods mentioned were not considered for purposes of hydrogen storage.
In contrast, the preparation of the storage material according to the present invention is very simple, completely dispensing with organic solvents. The aluminum powder used according to the present method is cheaper and more easily handled than sodium alanate, which was previously employed. It was particularly surprising that the hydrogenation of aluminum in the presence of alkali metals or metal hydrides can be successfully performed at temperatures which are considerably below the melting points of the metal/metal hydride educts involved and the metal alanate products, i.e., in a solid state (in contrast to the above referenced direct synthesis according to Dymova et al., Dokl. Akad. Nauk SSSR 215 (1974) 1369, Engl. 256 “Direct Synthesis of Alkali Metal Aluminium Hydrides in the Melt”).
According to the present invention, for example, aluminum powder is mixed with powdered sodium hydride and admixed with catalytic amounts of titanium tetrabutylate. The composition thus obtained can be used directly as a reversible hydrogen storage material, When Al and NaH are employed at a molar ratio 1:1, NaAlH
4
is obtained in the hydrogenation, whereas a molar ratio of 1:3 yields Na
3
AlH
6
after hydrogenation.
Another particular advantage of the present method for reversibly storing hydrogen is that the desorption and absorption kinetics could be significantly improved by facilitating the previously known method according to PCT/WO 97/03919.


REFERENCES:
patent: 3210150 (1965-10-01), Powers, Jr.
patent: 3222122 (1965-12-01), Johnson et al.
patent: 3290123 (1966-12-01), Del Giudice et al.
patent: 3298800 (1967-01-01), Wade
patent: 3734863 (1973-05-01), Beckert et al.
patent: 3755555 (1973-08-01), Dymova et al.
patent: 3931395 (1976-01-01), Beckert et al.
patent: 3959454 (1976-05-01), Rogler et al.
patent: 4790985 (1988-12-01), Nelson
patent: 4832934 (1989-05-01), Bogdanovic et al.
patent: 6106801 (2000-08-01), Bogdanovic et al.
patent: 6251349 (2001-06-01), Zaluska et al.
patent: 6342198 (2002-01-01), Zaluska et al.
patent: 6471935 (2002-10-01), Jensen et al.
patent: WO 97/03919 (1997-02-01), None
patent: WO 00/07930 (2000-02-01), None
L. Zaluski et al., “Hydrogenation properties of complex alkali metal hydrides fabricated by mechano-chemical synthesis”, J. of Alloys and Compounds 290 (1999) 71-78.*
A. Zaluska et al., “Sodium alanates for reversible hydrogen storage”, J. of Alloys and Compounds 298 (2000) 125-134.*
E. C. Ashby et al., “Direct Synthesis of Complex Metal Hydrides”, Inorganic Chemistry vol. 2, No. 3, Jun. 1963 499-504.

Affiliated with

Also associated with

Rating

Method for reversibly storing hydrogen on the basis of... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method for reversibly storing hydrogen on the basis of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reversibly storing hydrogen on the basis of... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3360404