JP2002522209A - Novel hydrogen storage material and production method by dry homogenization - Google Patents

Abstract

  (57) [Summary] Dry homogenized metal hydrides, especially aluminum hydride compounds, are provided as materials for reversible hydrogen storage. The reversible hydrogen storage material comprises a dry homogenized material having transition metal catalyst sites on a metal aluminum hydride or a mixture of metal aluminum hydrides. Also provided is a method for producing such a reversible hydrogen storage material by dry doping, which comprises powdering a metal aluminum hydride together with a transition metal catalyst by dry homogenizing the metal hydride by mechanical mixing such as grinding or ball milling. Including the step of forming In another aspect of the invention, a method is provided for powering a vehicle device with the reversible hydrogen storage material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates generally to the field of reversible hydrogen storage. More particularly, the present invention relates to dry homogenized metal hydrides, especially aluminum hydride compounds, as a material for reversible hydrogen storage, and a method for producing the same. BACKGROUND OF THE INVENTION For decades, hydrogen has been targeted as the ideal fuel of the future because of its abundance and environmental friendliness. A major difficulty in using hydrogen as a fuel is the problem of on-board hydrogen storage. High pressure and low temperature hydrogen storage systems are not practical in vehicle applications due to safety concerns and volume constraints. This has facilitated a wide range of attempts to develop solid hydrogen storage systems for automotive applications. Metal hydrides, activated carbon, and carbon nanotubes have been studied as hydrogen carriers. For example, although LaNiH ₅ were studied, but failed to fully satisfied with the expensiveness due. Unfortunately, despite decades of extensive efforts, especially in the field of metal hydrides, a combination of high gravimetric hydrogen density, sufficient hydrogen dissociation energy, and the low cost required for commercial vehicle applications No material having the following has been found.

[0002] It is known that the dehydrogenation of NaAlH ₄ is thermodynamically favorable at moderate temperatures.
It is believed that dehydrogenation occurs in multiple processes, including reactions as shown in Equations 1 and 2 below. 3NaAlH ₄ → Na ₃ AlH ₆ + 2Al + 3H ₂ (1) Na ₃ AlH ₆ → 3NaH + Al + 3 / 2H ₂ (2) This process is characterized by very slow kinetics and reversibility only under severe conditions. Thus, despite having 5.6% by mass of thermodynamically available hydrogen at moderate temperatures, NaAlH ₄ was not generally considered as a potential hydrogen storage material. This idea is due to Bogudanobikku (Bogdanovic) and Gerhard bit Cardi (Schwickardi), that titanium doping of NaAlH ₄ is to improve the kinetics of hydrogen desorption, and provide a reversible dehydrogenation process in a moderate condition It has changed with recent discoveries. Bogdanovic has 2 mol% titanium tetra-n-
Butoxide, when titanium wet doped with Ti (OBu ⁿ⁾ evaporation of ether a suspension of NaAlH ₄ containing ₄ found that initiation of initial dehydrogenation decreases about 50 ° C.. However, this prior art approach is subject to many limitations. For example, temperatures are still quite high, and their kinetics are not enough to produce materials suitable for real vehicle applications.

[0003] Therefore, there is a need for further development of the kinetics of the dehydrogenation process in order to produce materials suitable for real vehicle applications. It is a concern that a further development in the kinetics of reversible dehydrogenation of a metal hydride such as NaAlH ₄ or the like is studied whether achievable. Further, as the above discussion indicates, there is a need for safe, abundant, low cost, and effective materials and methods for storing and releasing hydrogen.

SUMMARY OF THE INVENTION [0004] The present invention provides novel reversible hydrogen storage materials that are easily prepared from inexpensive and abundant starting materials, and methods of making the materials. More specifically, the present invention is a novel dry doping method, comprising the steps of mechanically mixing a metal aluminum hydride powder with a transition metal catalyst, such as grinding or ball milling, to form a metal hydride. A method comprising dry homogenizing is provided. The metal aluminum hydride is of the general formula: X ₁ AlH ₄ , where X ₁ is an alkali metal; X ₂ (AlH ₄ ) ₂ , where X ₂ is an alkaline earth metal X ₃ (AlH ₄ ) ₄ , wherein X ₃ is Ti, Zr or Hf; X ₄ AlH ₆ , wherein X ₄ is an alkali metal; X ₅ (AlH ₆ ) ₂ , wherein X ₅ is X ₆ (AlH ₆ ) ₄ , wherein X ₆ is Ti, Zr or Hf; or any combination of the above hydrides.

[0005] In another aspect of the invention, a material for storing and releasing hydrogen comprises a dry homogenized material having transition metal catalyst sites on a metal aluminum hydride or a mixture of metal aluminum hydrides. Is provided. The inventors have found that the method for homogenizing a metal aluminum hydride with a transition metal catalyst of the present invention lowers the dehydrogenation temperature by as much as 75 ° C. and significantly increases the recyclable hydrogen capacity. These findings represent a significant advance in the application of this class of hydrides to hydrogen storage. In particular, these discoveries enable the development of practical hydrogen storage materials and methods for vehicle powering, a previously unrecognized success. These and other objects and advantages of the invention will be apparent from reading the specification and claims with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION An important advantage of the present invention is that it provides a novel reversible hydrogen storage material that is readily prepared from inexpensive and abundant starting materials and a method of making the material. More specifically, the present invention is a novel dry doping method, comprising the steps of mechanically mixing a metal aluminum hydride powder with a transition metal catalyst, such as grinding or ball milling, to form a metal hydride. A method comprising dry homogenizing is provided. The metal aluminum hydride is of the general formula: X ₁ AlH ₄ , where X ₁ is an alkali metal; X ₂ (AlH ₄ ) ₂ , where X ₂ is an alkaline earth metal X ₃ (AlH ₄ ) ₄ , wherein X ₃ is Ti, Zr or Hf; X ₄ AlH ₆ , wherein X ₄ is an alkali metal; X ₅ (AlH ₆ ) ₂ , wherein X ₅ is X ₆ (AlH ₆ ) ₄ , wherein X ₆ is Ti, Zr or Hf; or any combination of the above hydrides.

In another aspect of the invention, a material for storage and release comprising a dry homogenized material having transition metal catalyst sites on a metal aluminum hydride or a mixture of metal aluminum hydrides. Provided. In another aspect of the invention, the hydrogen storage material is used to power a vehicle device, and the novel method further comprises dehydrogenating the dry homogenized hydrogen storage material to release hydrogen; and Powering the vehicle device with the released hydrogen.

The materials and methods of the present invention are quite different from the prior art (particularly Bogdanovic dope materials), exhibit significantly improved and unexpected catalytic effects. The present inventors have found that the method for homogenizing a metal aluminum hydride with a transition metal catalyst of the present invention lowers the dehydrogenation temperature by as much as 75 ° C. and remarkably increases the recyclable hydrogen capacity. These findings represent a significant advance in the application of this class of hydrides to hydrogen storage. In particular, these discoveries enable the development of practical hydrogen storage materials and methods for vehicle powering, a previously unrecognized success.

As mentioned in the background of the invention, certain metal aluminum hydrides, especially NaAl
H ₄ dehydrogenation is thermodynamically favorable at moderate temperatures. It is known to occur in a multi-step process involving the reactions shown in equations 1 and 2. While this material has a relatively high rate of hydrogen, the process exhibits very slow kinetics and is reversible only under harsh conditions. Examples of severe conditions are about 270 ° C and about 1.77 × 10 ⁷ P
a (175 atm) hydrogen pressure.

In sharp contrast to the prior art, the dehydrogenation kinetics of NaAlH ₄ of the present invention is:
The kinetics far improved previously achieved by titanium doping of the host hydride was improved. In one exemplary embodiment, under an argon atmosphere, about 2 mol% of titanium catalyst, in particular Ti homogenization (OBu ⁿ⁾ ₄ involves NaAlH _4, to produce a novel material containing only traces of carbon. Measurements of thermal programmed desorption (TPD) show that dehydrogenation of this material occurs at about 30 ° C. lower than previously seen for NaAlH ₄ doped with titanium by wet chemical methods. This reduction in dehydrogenation temperature is a significant advance in enabling the material to be used as a hydrogen storage material to power vehicles with hydrogen. This new titanium-containing material is 170
It can be completely rehydrogenated at 150 ° C under a hydrogen pressure of 1.52 x 10 ⁷ Pa (150 atm). In further contrast to the "wet dope" NaAlH ₄ material, dehydrogenation kinetics observed in this new material is not reduced during the several dehydrogenation / hydrogenation cycles.

More particularly, the present invention provides doping of aluminum hydride with a transition metal catalyst by dry homogenization. Suitable aluminum hydrides that can be practiced in the present method typically have the formula: X ₁ AlH ₄ , where X ₁ is an alkali metal; X ₂ (
AlH ₄ ) ₂ , wherein X ₂ is an alkaline earth metal; X ₃ (AlH ₄ ) ₄ , wherein X ₃ is Ti
, Zr or Hf; X ₄ AlH ₆ , wherein X ₄ is an alkali metal; X ₅ (Al
H ₆ ) ₂ , wherein X ₅ is an alkaline earth metal; X ₆ (AlH ₆ ) ₄ , wherein X ₆ is Ti, Z
r or Hf; or any combination of the above hydrides. Examples of such suitable aluminum hydrides include, but are not limited to: sodium aluminum hydride (NaAlH ₃ ), sodium aluminum hydride (N
a ₃ AlH ₆ ), aluminum magnesium hydride (Mg (AlH ₄ ) ₂ ), aluminum titanium hydride (Ti (AlH ₄ ) ₄ ), aluminum zirconium hydride (Zr (Al
H ₄ ) ₄ ). The transition metal catalyst used in the present invention includes titanium, zirconium, vanadium, iron, cobalt or nickel. Suitable catalyst precursor complexes of transition metal and lanthanide metal include, but are not limited to, Ti (OBu) ₄ , Zr (OPr) ₄ , VO (OPri) ₃ , Fe (acac) ₂ , Co (
acac) ₂ , Ni (1,5-cyclooctadiene) ₂ , La (acac) ₃ , and mixtures thereof, wherein acac is acetylacetonate and Pri is isopropyl. In one preferred embodiment, the hydrogen storage material of the present invention is comprised of NaAlH ₄ doped with Ti (OBu ⁿ ) ₄ by dry homogenization. In another preferred embodiment, the hydrogen storage material of the present invention is composed of NaAlH ₄ doped with Zr (OPr) ₄ catalyst by dry homogenization.

According to the present invention, dry homogenization is performed and aluminum hydride is doped with a transition metal catalyst. Homogenization is, for example, manual grinding with a mortar and pestle, preferably for about 15 minutes;
Occasional mixing in a mixer-grinder mill, preferably by a mechanical method such as a time in the range of about 5 to 10 minutes; or by boring, preferably a time in the range of about 5 to 20 minutes. The homogenization process is considered "dry" as it occurs in the absence of solvent or any aqueous medium. Preferably, this homogenization process is performed under an inert atmosphere such as argon or the like.

[0013] The amount of the transition metal catalyst used in the dry homogenization of the present invention is not particularly limited, and is usually selected as an amount effective to impart desired catalytic activity. For example, when a titanium catalyst is used, at least 0.2 mol% of a titanium precursor is used for hydride doping to obtain a catalytic effect. The maximum catalytic effect is observed at about 2.0 mol% of the titanium precursor, and does not improve when doped with about 2.0 mol% or more of the titanium precursor. Exemplary preferred ranges for doping hydrides with titanium catalysts are:
About 0.5 to about 1 mol% of Ti catalyst based on aluminum hydride. An exemplary preferred range when doping the hydride with a zirconium catalyst is from about 0.5 to about 1 mole% Zr catalyst, based on aluminum hydride.

In an exemplary embodiment, NaAlH ₄ is doped with Ti (OBu ⁿ ) ₄ under an inert atmosphere according to the method of the present invention to produce an inventive material for hydrogen storage and release.
The novel titanium-containing (dry dope) material, the amount of Ti (OBu ⁿ⁾ ₄ fresh recrystallization NaAlH _4, was prepared by adding under an argon atmosphere. The initial colorless mixture was homogenized using a mortar and pestle until they became magenta. This color change suggests that at least some of the Ti4 + was reduced to Ti3 +. The resulting paste was visually significantly different from the brown powder obtained by the Bogdanovic procedure for the production of titanium-containing (wet-doped) materials. By elemental analysis,
It was found that only traces of carbon were present in the dry homogenized material of the present invention. Apparently, β-hydrogenation from the alkoxy ligand dissociates the organic group as butanal from the titanium center and precipitates titanium hydride species on the NaAlH ₄ host material. The presence of non-metallic titanium on the surface of the new material was confirmed by surface X-ray studies. Thus, dry homogenization method, create a titanium catalytic sites on fresh milled crystals of NaAlH _4. Due to the important advantages, these dry homogenized materials repeatedly store and release hydrogen at the resulting temperatures and moderate pressures. In one exemplary embodiment, the dry homogenization method of the present invention releases about 4-4.5% by weight of hydrogen with a fast release of hydrogen occurring at a temperature in the range of about 80C to 120C.

[0015] In another exemplary embodiment, the inventors investigated the dehydrogenation / rehydrogenation behavior of NaAlH ₄ loaded with a zirconium catalyst by the dry homogenization doping method of the present invention. Zirconium has been found to improve the dehydrogenation kinetics of NaAlH _4, but the catalytic activity was found to be different from that of titanium. further,
The inventors have found that the different catalytic effects of titanium and zirconium are achieved correspondingly. TPD measurements were performed on the following samples: dry dope material of the present invention ("Sample 1"); wet dope material of the prior art ("Sample 2"); and undoped Na of the prior art.
AlH ₄ ( "sample 3"). Excellent agreement was found between samples prepared at different time points. The data obtained for sample 2 was consistent with Bogdanovic's findings. TPD
The measurement was performed on samples of three kinds of materials. The plot of mass% desorbed hydrogen as a function of temperature shown in FIG. 1 is based on the collected TPD data. The catalytic effect of titanium is evident for both samples 1 and 2, but due to significant advantages,
It can be seen that the dehydrogenation temperature is about 30 ° C. lower than that of sample 2.

The differences observed in the dehydrogenation behavior of Samples 1 and 2 are believed to be solely due to changes in the titanium loading levels of the two materials. To prove this possibility, 1.0, 2.0, and 4.0 mol% of Ti (OBu ⁿ⁾ ₄ Sample 1 was prepared using the independently about 2 T
PD measurements were made and are shown in curves 11, 12 and 13, respectively. As shown in FIG. 2, changing the amount of Ti (OBu ⁿ ) ₄ used in the preparation had little effect on the dehydrogenation temperature. However, increasing the titanium content of the material has the weight effect of reducing the H / M mass% (ie the mass of hydrogen derived per mass unit of metal aluminum hydride). These results indicate that only a portion of the titanium introduced into the material is catalytically active. In addition, Sample 1 was clearly higher than Sample 2
Has a significant amount of catalytically active titanium. Obviously, the dry doping method is more effective than the wet doping method for generating active titanium sites. While the activity of the wet doping method is limited to the hydride surface, the dry doping method is believed to introduce active titanium sites into most of the material.

Since reversibility is an important requirement for most hydrogen storage applications, the behavior of the sample during repeated cycles was investigated. The test material of the present invention is 200 ° C., 1.1 × 10 ⁷ Pa (1600 psi)
Under hydrogen pressure. Only about 40% of the hydrogen of the original material is replaced at a moderate hydrogen pressure. Then, TPD measurement was performed on the rehydrogenated sample.
FIG. 3 shows the percentage of hydrogen desorbed from the sample as a function of temperature, with 100% desorbed hydrogen in the first cycle. The incorporation is clearly less than seen in the original sample, indicating that only some hydrogenation can be obtained under these conditions. The second dehydrogenation cycle of Sample 1 was
It occurs at about the same temperature as observed in the first run. This means that the dehydrogenation behavior of sample 2 (prior art), where dehydrogenation occurs at a fairly high temperature, was reduced in the second cycle by sample 1
In contrast to approaching it.

The inventors have found that the improvement of the dehydration kinetics of NaAlH ₄ by introducing titanium into the material is quite susceptible to doping methods. The novel dry doping method of the present invention is much more effective at generating catalytically active titanium sites than the previously reported wet doping method. It is also important that, unlike wet dope materials, the kinetic enhancement of dry dope materials does not decrease during several dehydrogenation / rehydrogenation cycles. This result indicates that the catalytic effect of the titanium doped material is due to the fact that only a partial amount of titanium is introduced into the host hydride.

In another exemplary embodiment of the present invention, zirconium-doped NaAlH ₄ was prepared by homogenizing a fresh recrystallized hydride with Zr (OPr) ₄ under an argon atmosphere. The release of hydrogen from this zirconium-doped hydride sample was examined by thermal programmed desorption (TPD). A plot of the weight percent of desorbed hydrogen as a function of temperature is shown in FIG. The discontinuity of the desorption curve is given by Equations 1 and 2
This reflects the difference in the activation energies of the dehydrogenation reactions as seen in Figure 1. In contrast to the titanium-doped material, catalyst effect, NaAlH ₄ of Na ₃ AlH ₆ and Al (Equation 1
) Is much more pronounced for the dehydrogenation of Na ₃ AlH ₆ to NaH and Al (formula 2). Given that titanium and zirconium are closely related chemically, it is surprising that their initial catalytic effect is exerted on the different reactions of the dehydrogenation process. Dehydrogenation is also catalyzed by zirconium doping. Titanium-doped Na
As observed for AlH ₄ , the refill of dehydrogenated material was 170 ° C., 1.52 × 1
It can be achieved at a hydrogen pressure of 0 ⁷ Pa (150atm).

An important aspect of a hydrogen storage material is its ability to perform after repeated dehydrogenation / rehydrogenation cycles. Particularly advantageously, after a preliminary cycle of dehydrogenation / rehydrogenation, the TPD spectrum of the zirconium-containing material showed excellent reproducibility. As shown in FIG. 4, the temperature required for dehydrogenation is consistently 20 ° C. lower than the first cycle. Similar behavior was observed in corresponding tests on materials doped with 2 mol% titanium according to the homogenization method of the present invention. As further shown in FIG. 5, the temperature required for the dehydrogenation reaction is as low as about 20 ° C. after the preliminary dehydrogenation / rehydrogenation cycle. The onset of rapid dehydrogenation at 100 ° C. in titanium-doped materials is significant, suggesting their usefulness as hydrogen carriers for onboard fuel cells.

The hydrogen capacity of these materials drops to 4.5% by mass in the second cycle, but is stable by the third cycle. We describe a similar stabilization of the hydrogen storage capacity in the titanium-doped NaAlH ₄ were prepared by homogenization methods of the present invention before. Chain advances in the development of a metal catalyst NaAlH ₄ is indicated by a comparison of TPD spectra third dehydrogenation cycles for various doping materials. As shown in FIG. 6, the hydride doped with titanium by the Bogdanovic method has a recyclable hydrogen capacity of 3.2% by weight. Titanium doping by the homogenization method of the present invention significantly improves the kinetics of the first dehydrogenation reaction and increases the recyclable hydrogen capacity to 4.0% by mass. The zirconium-doped material improves the kinetics of the second dehydrogenation reaction and further increases the recyclable hydrogen capacity to 4.5% by weight. But,
The kinetics of the first dehydrogenation reaction of the Zr-doped material is inferior to that of the titanium-doped material of the present invention.

To determine the suitability of the catalytic activity of the zirconium and titanium of the present invention, 1 mol%
A sample of NaAlH ₄ homogenized with both Zr (OPr) ₄ and Ti (OBu ⁿ ) ₄ was prepared. The sample was then stabilized with three dehydrogenation / rehydrogenation cycles. Still referring to FIG. 6, it can be seen that the TPD spectrum of the titanium / zirconium doped material effectively overlaps the first segment of the curve for the titanium doped material and the second segment of the curve for the zirconium doped material. in this way,
Titanium and zirconium act in concert, to optimize the dehydrogenation / re-hydrogenation behavior of NaAlH _4. The inventors have found that the dehydrogenation kinetics of NaAlH ₄ is significantly enhanced by zirconium doping. Zirconium is Na ₃ Al of NaAlH ₄
Although inferior to titanium as a catalyst for dehydrogenation to H ₆ and Al, it is an excellent catalyst for dehydrogenation of Na ₃ AlH ₆ to NaH and Al. Materials containing both combinations of titanium and zirconium catalysts will benefit from both catalytic effects. NaAlH ₄ doped with titanium and / or zirconium is stabilized with more than 4% by weight of recyclable hydrogen after the first dehydrogenation / rehydrogenation cycle. Finally,
The onset of rapid dehydrogenation of titanium-containing materials below 100 ° C. suggests their utility as hydrogen carriers for onboard fuel cells.

Experiments The following experiments are provided for illustrative purposes only and do not limit the invention in any way. General experiments All reactions and manipulations were performed in a glove box under argon or by the standard Schlenk method with oxygen and water free solvents. Sodium aluminum hydride, NaAlH ₄ were purchased from Aldrich Chemical Inc., and recrystallized from THF / pentane prior to use. Ti (OBu ⁿ ) ₄ is available from Strem Chemical Inc.
Purchased from and used. "Wet" titanium-doped NaAlH _4, as previously described by Bogudanobikku, 2 moles of Ti NaAlH ₄ comprising (OBu ⁿ⁾ ₄
Was prepared from the ether suspension by evaporation. Elemental analysis, Oneida
Performed by Research Service Inc., Whisboro, NY.

[0024] In the titanium-doped material glovebox, NaAlH ₄ (0.54g, 10mol) and Ti (OBu ⁿ⁾ ₄ (0.2
6 g, 0.76 mol). The mixture was homogenized in a mortar and pestle for 15 minutes until a magenta paste formed. Elemental analysis of the produced material showed that its composition was C, 0
.25%; H, 7.01%. In this procedure, 0.13 mL (0.38 mol) and 0.5
Samples were also prepared using 2 mL (1.52 mol) Ti (OBu ⁿ ) ₄ . A gas-solid interaction between hydrogen and the sodium aluminum hydride system was characterized using a thermal volumetric analyzer (TVA) based on a modified Sievert-type instrument. TVA has two stainless steel Parr reactors (Model 452HC-T316)
, One being used to hold the sample and the other being used as a gas reservoir, between which a very small, precisely measured volume of hydrogen can be transferred. The sample container includes an aluminum insert with two narrow cylindrical holes. A K-type thermocouple was placed inside each of the holes. The sample holes were designed to ensure intimate contact between the aluminum insert and the sample. This, coupled with the high thermal conductivity of the aluminum insert, helps to minimize temperature fluctuations in the sample caused by heat of reaction or rapid pressure changes. For the entire sample container, a sample temperature of -77 to 400 ° C. (196
６７673 K) can be heated and cooled using a PID programmable controller unit that controls and programs. The entire sample container was placed in a container surrounded by a mixture of dry ice and acetone to reach -77 ° C (196K).

The hydrogen pressure in the container was measured using a high-precision pressure transducer. Utilizing various sizes of aluminum inserts to adjust the dead volume on the sample and to maintain the total pressure and pressure changes within the range and accuracy of our instruments depending on the changing sample size and hydrogen filling. I made it. The volume of the sample container and gas reservoir and the flow of gas between them were calibrated with hydrogen and argon. The gas system was constructed using a high-purity regulator, a sealed VCR that could be operated multi-sidedly under reduced pressure or high pressure, a diaphragm shut-off valve, and a micro-valve to control the flow of gas between the reactors. . Gas lines and vessels were tested for steady-state standards for inboard or outboard gas leaks. System temperatures and pressures were recorded using a data acquisition system with software developed for this task.

The hydrogen desorption rates of each of the three samples were measured using a thermal programmed desorption (TPD) method. About 0.5 g of the sample was weighed and filled in a high-pressure reactor under an argon atmosphere. The sample was then heated from room temperature to 280 ° C. at a rate of 2 ° C. per minute while maintaining low hydrogen over the pressure in the sealed reactor. The rate of hydrogen desorption was measured as a function of temperature. TPD measurements were repeated on selected samples to ensure sample and measurement reproducibility.

Reagents All reactions and manipulations were performed in a glove box under argon. NaAl
H ₄ and zirconium tetra -n- propoxide, Zr (OPr) ₄ (70 wt% propanol solution) were purchased from Aldrich Chemical Inc.. NaAlH ₄ was recrystallized from THF / pentane by a standard Schlenk method with a solvent free of oxygen and water. Ti (OBu ⁿ ) ₄ was purchased from Strem Chemical Inc. and used.

Zirconium and titanium doped material In a glove box, NaAlH ₄ (0.54 g, 10 mmol) was mixed with 94 μL of a 70% by weight solution of Zr (OPr) _{4 in} propanol. A homogenized sample was prepared by first mixing by hand with a mortar and pestle for 15 minutes and then mechanically mixing with a Wig-L-Bug electric grinder / mixer for 15 minutes. The titanium-doped sample is Ti (OBu ⁿ ) ₄ (
(70 μL, 0.2 mmol). The titanium / zirconium-doped hydride was homogenized with 0.047 mL of a 70% by weight solution of Zr (OPr) ₄ and Ti (OBu ⁿ ) ₄ (35 μL, 0.10 mmol).

Thermal Program Desorption (TPD) Measurement Using a modified volumetric Sievert-type instrument, a thermal volumetric analyzer (TVA) is used to characterize the gas-solid interaction between hydrogen and the sodium aluminum hydride system. Was. T
The VA system includes a high pressure reactor with a PID programmable temperature controller unit. The hydrogen pressure in the vessel was measured using a high precision pressure transducer. Utilizing various sizes of aluminum inserts to adjust the dead volume on the sample and to maintain the total pressure and pressure changes within the range and accuracy of our instruments depending on the changing sample size and hydrogen filling. I made it. The volume of the sample container and gas reservoir and the flow of gas between them were calibrated with hydrogen and argon. The gas system was configured using a high-purity regulator, a sealed VCR capable of multi-sided operation under reduced pressure or high pressure, a diaphragm type shut-off valve, and a micro-valve for controlling gas flow between the reactors. Gas lines and vessels were tested for steady state standards for gas leaks. System temperatures and pressures were recorded using a precision 16-bit National Instrument Data Acquisition System with software developed for this task.

The hydrogen desorption behavior of the sample was observed using thermal programmed desorption (TPD) spectroscopy as a function of temperature. A sample (about 0.5 g) was charged into a high pressure reactor under an argon atmosphere and the sample was heated from room temperature to 280 ° C. at a rate of 2 ° C. per minute from room temperature while maintaining low hydrogen over the pressure in the sealed reactor. For selected samples, TPD measurements were repeated to ensure sample and measurement reproducibility.

In summary, the above description and drawings illustrate the development of new and advanced materials useful as reversible hydrogen storage materials and methods of making the same. As a significant advantage, the dehydrogenation and rehydrogenation of such materials occurs under conditions that make them usable as hydrogen storage materials in automotive applications. Other features and advantages of the present invention will be apparent to one skilled in the art who studies the present disclosure. The foregoing description of specific embodiments and examples of the present invention has been presented for purposes of illustration and description only, and the present invention has been illustrated by, but is not limited to, the specific above examples. Should not be understood. They do not exhaust or limit the invention to the precise form disclosed,
And many modifications, embodiments, and variations are possible in view of the above teachings.
It is intended that the scope of the invention cover the general scope as disclosed herein and by the appended claims and their equivalents.

[Brief description of the drawings]

FIG. 1: Thermal desorption of hydrogen (2 ° C.) from prior art undoped and wet titanium doped NaAlH ₄ and the material of one embodiment of the present invention when dry homogenized titanium doped NaAlH _4. / Min).

[2] 1, 2 and 4 (0.5x, x, and 2x) moles of a transition metal catalyst Ti (OBu ⁿ⁾ of hydrogen from a sample of the dry titanium-doped NaAlH ₄ of the present invention prepared in _four thermal program de Release (2 ° C./min).

FIG. 3. Prior art undoped and wet titanium doped NaAlH ₄ and one embodiment of the present invention, dry homogenized titanium doped NaA after one cycle of dehydrogenation / rehydrogenation.
₄ shows a comparison of thermal programmed desorption (2 ° C./min) of hydrogen from lH ₄ .

FIG. 4 shows the effect of a dehydrogenation / rehydrogenation cycle on thermally programmed desorption (2 ° C. min ⁻¹ ) from zirconium-doped NaAlH ₄ with a material of another embodiment of the present invention.

FIG. 5 shows the effect of a dehydrogenation / rehydrogenation cycle on thermal programmed desorption (2 ° C. min ⁻¹ ) from titanium-doped NaAlH ₄ using the homogenization method of the present invention.

FIG. 6 shows the thermal programmed desorption (2 ° C. min ⁻¹ ) of NaAlH ₄ of the invention from various doped samples after three cycles of dehydrogenation / rehydrogenation.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZA, ZWF terms (reference) 4G040 AA42 4G066 AA11B AB23D CA38 DA04 FA02 FA37 4G140 AA42 4K017 AA04 BB09 BB10 BB11 DA09 EA02

Claims (20)

[Claims] 1. A method for producing a hydrogen storage material, comprising: supplying an aluminum hydride compound; supplying a transition metal compound as a catalyst; and providing the hydrogen in a dry environment. A step of homogenizing the aluminum halide compound together with the transition metal catalyst metal to produce a dry homogenized hydrogen storage material. 2. The method of claim 1, wherein said homogenizing step is performed in an inert atmosphere. 3. The method of claim 1, wherein said homogenizing step is performed for a time ranging from about 5 to 20 minutes. 4. The method of claim 1, wherein the mole percent ratio of said aluminum hydride compound to said transition metal catalyst is in the range of about 0.2 to 2.0. Wherein said aluminum hydride is represented by the general formula: X ₁ AlH _4, wherein X ₁
Is an alkali metal; X ₂ (AlH ₄ ) ₂ , wherein X ₂ is an alkaline earth metal; X ₃ (AlH ₄ ) ₄ , wherein X ₃ is Ti, Zr or Hf; X ₄ AlH _6, wherein X ₄ is an alkali metal; X ₅ (AlH _{6) 2,} wherein X ₅ is an alkaline earth metal; X ₆ (A
1H ₆ ) ₄ , wherein X ₆ is Ti, Zr or Hf; or any combination of the above;
The method of claim 1, wherein the method comprises: 6. The transition metal catalyst is titanium, zirconium, vanadium,
The method according to claim 1, comprising an iron, cobalt or nickel catalyst, and mixtures thereof. Wherein said transition metal catalyst is _{^{less: Ti (OBu n) 4,}} Zr (OPr) 4, VO (OPri) 3, Fe (acac) 2, Co (acac) 2, Ni (1,5- _2. The method of claim 1, wherein the method is selected from the group consisting of: cyclooctadiene) ₂ , La (acac) ₃ , and mixtures thereof, wherein acac is acetylacetonate and Pri is isopropyl. 8. The method of claim 1 wherein said aluminum hydride is NaAlH ₄ and said transition metal catalyst is Ti (OBu ⁿ ) ₄ . 9. The method of claim 1 wherein said aluminum hydride is NaAlH ₄ and said transition metal catalyst is Zr (OPr) ₄ . 10. A method of reversible storage of hydrogen, comprising subjecting aluminum hydride to a dehydrogenation / rehydrogenation process and doping said sodium aluminum hydride with zirconium or a mixture of zirconium and titanium.
A method for reversible storage of hydrogen that enhances the process. 11. The method according to claim 10, wherein the doping is performed by homogenizing the aluminum hydride with the zirconium or a mixture of zirconium and titanium in a dry environment. 12. A hydrogen storage and release material comprising a dry homogenized material having a dry homogenized doped transition metal catalyst site on an aluminum hydride compound. 13. The material of claim 12, wherein said transition metal catalyst site has a composition comprising titanium, zirconium, vanadium, iron, cobalt or nickel and mixtures thereof. 14. The material of claim 12, wherein said dry homogenized material is titanium doped NaAlH ₄ . 15. The dry homogenizing material is zirconium-doped NaAlH _4.
The material according to claim 12, which is: 16. The dry homogenizing material is titanium and zirconium doped N.
The material of claim 12 AAlH _4. 17. The material of claim 12, wherein said dry homogenized material exhibits dehydrogenation at a temperature in the range of about 80-120 ° C. 18. The material of claim 12, wherein said dry homogenized material exhibits a recyclable hydrogen capacity of about 4.0% by weight or greater. 19. The method of claim 1, wherein the hydrogen storage material is used to power a vehicle device. 20. The method of claim 1, further comprising: dehydrogenating the dry homogenized hydrogen storage material to release hydrogen; and powering the vehicle equipment with the released hydrogen. 2. The method of claim 1, comprising providing