ZIDAN RAGAIY (US)
| WO2007112203A2 | 2007-10-04 |
| DE1141623B | 1962-12-27 |
THAT WHICH IS CLAIMED:
1. An electrochemical process of producing AIH 3 comprising: supplying an anode; supplying a cathode; placing said anode and said cathode in an electrolytic solution comprising THF and NaAIH 4 , LiAIH 4 , KHAI 4 or any similar ionic solution; and, passing a current through the electrochemical cell thereby forming AIH 3 .
2. The process according to claim 1 wherein said anode is an aluminum or palladium anode.
3. The process according to claim 1 wherein said cathode is a platinum or palladium hydride cathode.
4. The process according to claim 1 comprising the additional step of removing AIH 3 from a surface of said anode.
5. The electrochemical process of producing AIH 3 comprising: supplying an anode selected from the materials of palladium, titanium, zirconium, aluminum, magnesium, calcium, or hydride forming metals; supplying a cathode selected from [the materials of] platinum or a metallic hydride; placing said anode and said cathode in an electrolytic solution containing NaAIH 4 , said NaAIH 4 formed from direct hydrogenation of aluminum, said aluminum being recovered from dehydrided AIH 3 ; and, passing a current through the electrochemical cell thereby forming AIH 3 .
6. An electrochemical process of producing an alane comprising: supplying an anode selected from the materials of palladium, titanium, zirconium, aluminum, magnesium, calcium, and combinations thereof; supplying a cathode selected from the materials of platinum, a metallic hydride, and combinations thereof; placing said anode and said cathode in an electrolytic solution containing an electrolyte selected from the group consisting of NaAIH 4 , LiAIH 4 , KAIH 4 , triethylenediamines, aluminum etherates, borohydrides, and combinations thereof; and, passing a current through the electrochemical cell thereby forming at least one of a metal hydride or metal hydride adduct.
7. The process according to claim 6 wherein said electrolyte is formed from a dehydrided metal hydride, said metal hydride being formed from the process according to claim 6.
8. The process according to claim 1 wherein when said cathode is platinum, atomization of hydrogen occurs at said cathode.
9. The process according to claim 6 wherein when said cathode is platinum, atomization of hydrogen occurs at said cathode. |
ELECTROCHEMICAL PROCESS AND PRODUCTION OF NOVEL
COMPLEX HYDRIDES
RELATED APPLICATIONS
This application claims the benefit of U.S. Application Serial No. 11/891 ,125 filed on August 9, 2007, and which is incorporated herein by reference.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY
SPONSORED RESEARCH AND DEVELOPMENT This invention was made with Government support under Contract No. DE-AC09-08SR22470 awarded by the United States Department of Energy. The Government has certain rights in the invention.
FIELD OF THE INVENTION
This invention is directed towards use of electrochemical cells to generate aluminum hydride (AIH 3 ) and other high hydrogen capacity complex hydrides. The ability to produce the AIH 3 in an electrolytic cell allows the possibility of creating a reversible alane product in a cost effective manner which avoids the formation of unused or unwanted byproducts. Other hydrides such as Mg(AIH 4 ) 2 and Ca(AIH 4 J 2 can be formed by varying the electrodes and/or the electrolyte present within the electrolytic cell. For instance, the same principle can be used to form Borohydhde Complexes such as AI(BH 4 J 3 . The invention is further directed to an alane formation using an electrolytic cell which uses polar, non-volatile solvents that allow the use of more efficient higher temperatures for the electrolytic process.
The invention is further directed to an electrolytic process of forming metal hydrides using polar solvents which can be carried out under elevated pressures to facilitate favorable reactions.
BACKGROUND OF THE INVENTION
AIH 3 has great potential as a source of hydrogen for fuel cells and other technologies. AIH 3 is made out of aluminum, which is relatively inexpensive, and has a high weight percent hydrogen when hydrided. Heretofore, the ability to regenerate the aluminum metal back into aluminum hydride has proven too expensive for large scale commercial use.
For instance, AIH 3 can be formed using high pressure conditions such as 10 5 bars hydrogen pressure at room temperatures. While such conditions can be achieved in laboratory and small scale demonstration conditions, the high pressures, competing reactions, and overall energy budget have prevented high pressure alane formation from being widely considered for production of alanes for a hydrogen fuel cell.
Additional conditions for alane formation require plasma conditions or the use of non-economical chemical reactions. Under all these conditions, there are competing reactions that can lead to unstable phases of alane formation and hence generation of an end product that is unsuitable for large scale commercial production of alanes which is needed for fuel cells in the automotive industry.
Accordingly, there remains room for improvement and variation within the art.
SUMMARY OF THE INVENTION
It is one aspect of at least one of the present embodiments to provide for an electrochemical cell using an organic solvent that allows the formation of AIH 3 and other high hydrogen capacity complex hydrides in a cost effective manner.
It is a further aspect of at least one of the present embodiments of the invention to provide for an electrochemical cell in which NaAIH 4 , in combination with a polar solvent such as THF which allows for the direct formation of AIH 3 .
It is another aspect of at least one of the present embodiments to provide for an electrochemical cell for the production of AIH 3 using NaAIH 4 dissolved in a polar solvent and using one of at least an elevated pressure or
an elevated temperature in order to increase the efficiency of the AIH 3 production.
It is a further aspect of at least one of the present embodiments to provide for the production of AIH 3 which can be used as a source of hydrogen for use in a vehicle. The resulting aluminum metal can be mixed with NaH and hydrided using titanium catalyst. The NaH can subsequently combine with the aluminum metal in a direct hydrogenation to yield NaAIH 4 . The NaAIH 4 is used in an electrochemical cell to produce AIH 3 . The resulting cyclic production of AIH 3 is a closed process in which no byproducts are generated. The same process can apply to other iconic complex hydrides such as LiAIH 4 and KaIH 4 .
It is another aspect of at least one embodiment of the present invention to provide for a reversible alane formation in which AIH 3 can be used as a source of hydrogen in which the resulting aluminum metal can be hydrogenated in the presence of NaH to provide NaAIH 4 . Using an electrolytic cell, the NaAIH 4 may be used to regenerate the AIH 3 . The sodium and hydrogen ions produced in the electrochemical cell may be reused in the direct hydrogenation of aluminum metal to regenerate the NaAIH 4 . KAIH 4 or LiAIH 4 dissolved in polar solvent such as THF may also be used as a suitable non-aqueous electrolyte since LiAIH 4 and KAIH 4 may be regenerated in a manner similar to NaAIH 4
It is yet another aspect of at least one of the present embodiments to provide for a cost effective, reusable process that permits the use of AIH 3 as a hydrogen source with the aluminum metal being recharged into a NaAIH 4 . It is yet another aspect of at least one of the present embodiments to use an electrolytic cell having an electrolyte selected from the group consisting of NaAIH 4 , KAIH 4 , triethylenediamine (and other similar amines), aluminum etherates, borohydride adducts, and combinations thereof to generate an organo-metallic hydride by passing current through the electrochemical cell.
It is yet another aspect of at least one of present embodiments to provide a process of using an electrolytic cell to form adducts of hydrogen storage materials using an electrolytic cell.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
A fully enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings. Figure 1 is a schematic diagram describing the process of a reversible alane formation.
Figure 2 is a " schematic diagram of an electrolytic apparatus which may be used with a non-aqueous electrolyte to form AIH 3 .
Figure 3 is an X-ray showing diffraction analysis graph of AIH 3 produced by an electrochemical cell.
Figure 4 is an X-ray diffraction analysis graph of AIH 3 -TEDA produced by an electrolytic cell.
DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions.
In describing the various figures herein, the same reference numbers are used throughout to describe the same material, apparatus, or process pathway. To avoid redundancy, detailed descriptions of much of the apparatus once described in relation to a figure is not repeated in the descriptions of subsequent figures, although such apparatus or process is labeled with the same reference numbers.
In accordance with the present invention, it has been found that a complex hydride such as NaAIH 4 , LiAIH 4 , or KAIH 4 may be dissolved in the polar solvent THF within an electrolytic cell. The use of an organic solvent prevents the oxidation of the product and allows for the dissolving of the product which would interfere with the desired reaction. The reaction product may be recovered later. Using a cathode of platinum and an anode of aluminum results in the electrolytic formation of AIH 3 . While the AIH 3 will tend to accumulate on the anode, it has been found that mixing ether with the THF solvent will dissolve the AIH 3 from the anode and allow the reaction to continue. The aluminum hydride can be crystallized and separated later by evaporating the solvent under vacuum. Alternatively, it is envisioned that a mechanical scraper, ultrasonic vibration, or similar processes can be used to periodically or continuously remove the deposited AIH 3 from the anode.
The electrolytic conditions can be varied to bring about a more efficient production of AIH 3 . For instance, operating the electrolytic process under high pressure will facilitate the reaction speed. Likewise, using the electrolytic process at high temperatures will also favor a more rapid and efficient reaction rate of AIH 3 production. Since the electrolytic conditions are using non-volatile polar solvents, loss of solvents to high temperature is not a limitation. In addition, the cathode forms NaH along with the evolution of hydrogen gas.
Example 1 An electrolytic cell was used to produce AIH 3 on a palladium anode and an aluminum cathode and an electrolyte of NaAIH 4 dissolved in THF. The reaction occurred at ambient pressure at room temperature using 5 v and 4 mA over a 2 hour period producing 10 mg of
AIH 3 . The formation of AIH 3 was detected on the anode. The formation of AIH 3 was confirmed using X-ray diffraction.
Example 2 A high pressure electrochemical cell was utilized to generate AIH 3 . The non-aqueous electrolyte NaAIH 4 , dissolved in THF, was used in conjunction with a palladium anode and a platinum cathode and an electrolyte of NaAIH 4 dissolved in THF. The electrochemical cell was operated under an elevated hydrogen pressure of 500 psi H 2 and at a temperature of 60° C using a voltage of 10 volts over a 2 hour period. 3 mg of AIH 3 was produced. The formation of AIH 3 was detected on the palladium anode and was subsequently confirmed by X-ray analysis.
Example 3 As seen in reference to Figure 3, an adduct was made using an electrochemical cell to generate AIH 3 -triethylenediamine (AIH 3 - TEDA). The electrolyte was made using NaAIH 4 and THF which was mixed with TEDA dissolved in THF, the combination being used as the electrolyte with a platinum electrode as the cathode and an aluminum electrode as the anode. Using ambient pressure and room temperature and operating conditions of 1.5 v and 30 mA over an 8 hour time period, 10 gm of AIH 3 - TEDA were precipitated out of solution. The x-ray diffraction pattern set forth in Figure 4 shows the recovered product produced by the electrochemical process in comparison to a standard obtained through conventional methodologies. The additional peaks of the competitive standard represent aluminum and LiAIH 6 which are not present in the electrochemically produced AIH 3 -TEDA.
The AIH 3 -TEDA made by conventional methodologies is known to be a desirable hydrogen storage material in that the material can store 2.7 times its weight at 88° C as reported by J. Gretz et al in the J. Phys. Chem. 2000, Vol. 111, page 19148.
As seen in reference to Figures 1 and 3 and Examples 1 and 2, the ability to use an electrochemical cell having dissolved NaAIH 4 as an electrolyte and subsequently form AIH 3 allows for the desirable production of a reliable source of AIH 3 as part of a cyclic process loop. The AIH 3 product can
be used to generate hydrogen gas for automotive or other commercial purposes. The resulting aluminum metal (spent aluminum) can be combined with NaH and hydrogen in the presence of a titanium catalyst to regenerate NaAIH 4 as is known in the art and as set forth and described in the following publications.
B. Bogdanovic and M. Schwickardi. J. Alloys Comp. 253-254 (1997);
CM. Jensen, R. Zidan, N. Mariels, A. Hee and C. Hagen. Int. J. Hydrogen Energy 24 (1999), p. 461 ;
R.A. Zidan, S. Takara, A.G. Hee and CM. Jensen. J. Alloys Comp. 285 (1999), p. 119;
CM. Jensen, R.A. Zidan, US Patent 6,471 ,935 (2002); and
B. Bogdanovic, R.A. Brand, A. Marjanovic, M. Schwickardi and J. Tόlle. J. Alloys Comp. 302 (2000), p. 36, all of which are incorporated herein by reference for all purposes. As seen in reference to Figure 1, the entire process loop results in no unused byproducts, but provides for a closed system. The aluminum metal may be again converted into AIH 3 . Since no byproducts are produced, there is little waste associated with the process.
The ability to generate AIH 3 has been demonstrated using a non- aqueous solvent under both ambient conditions and elevated pressure and temperature conditions. While aluminum or palladium anodes and platinum or palladium hydride cathodes were utilized in the experiments, it is believed that other material choices for anodes and cathodes may be used.
For instance, suitable anodes provided by palladium, titanium, zirconium, and other hydride forming metals are suitable for forming AIH 3 , borohydrides, and other alanates and complex hydrides. Likewise, suitable cathodes include materials such as platinum or a metallic hydride such as palladium hydride or titanium hydride. Where platinum is used as the cathode, it is noted that hydrogen gas is evolved from the surface of the cathode.
In addition, it is believed that without undue experimentation, one having ordinary skill in the art can evaluate various process conditions for the
electrolytic cell so as to optimize the production of AIH 3 using various combinations of voltage, operating temperature, and operating pressure. It is also understood that the ability to regenerate aluminum into aluminum hydride holds enormous possibilities as a fuel source of hydrogen for transportation needs. Accordingly, it is recognized that within an overall energy budget, the most desirable operating conditions for generating AIH 3 in the electrolytic system described above may be under conditions that may not achieve the highest yield, but does achieve a commercial product in the most cost effective manner.
It is envisioned that the AIH 3 can be provided to the automotive industry for use as a hydrogen source at various supply stations. The spent aluminum metal may be collected and subsequently treated at a commercial facility to regenerate the aluminum metal into an AIH 3 using the polar, non-aqueous electrochemical cell. Depending upon the processing facility, the electrolytic cell may be operated under high pressure and/or high temperature conditions so as to generate a more favorable reaction rate.
The methodology reported herein is not limited to the specific electrolyte and specific electrodes. For instance, a variety of aluminum etherates such as AI-TEA, LiBH 4 -TEDA and other borohydride adducts may be employed. The electrochemical methodology described herein is a new method of making organo-metallic hydrides such as AIH 3 -TEDA or AI(BH 4 J 3 - TEDA or other MH-Amine combinations where M is a metal that can have application in hydrogen storage for the automotive industry and portable energy systems such as batteries and fuel cells. The methodology lends itself to economical charging and re-charging systems as part of a renewable fuel cell.
Heretofore, electrolytic processes involving the formation of alanes arid other complex hydrides involve the use of salt containing electrolytic solutions, which are detrimental to the desired pathway described herein. In comparison, the present chemical formation process has a very high yield in that there are no competing side reactions that result in undesired end products.
Although preferred embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged, both in whole, or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.
Next Patent: DIRECT EPOXIDATION PROCESS USING A MIXED CATALYST SYSTEM