JP2011005485A - Destabilized and catalyzed borohydride for reversible hydrogen storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming an improved hydrogen storage material which releases hydrogen at a lower temperature, and which is capable of producing hydride again even after the release of hydrogen.SOLUTION: The method of forming a hydrogen storage material includes the steps of: providing a first material of the formula M(BH), where M is an alkali metal or an alkaline earth metal, providing a second material selected from M among (AlH), a mixture of M(AlH)and MCl, a mixture of MCland Al, a mixture of MCland AlH, a mixture of MHand Al, Al, and AlH. The first and second materials are combined at an elevated temperature and at an elevated hydrogen pressure for a time period forming a third material having a lower hydrogen release temperature than the first material and a higher hydrogen gravimetric density than the second material.

Description

[Cross-reference with related applications]
This application is a continuation of US application Ser. No. 12 / 035,710, filed Feb. 22, 2008, and part of US application Ser. No. 11 / 130,750, filed May 17, 2005. Which is a continuation and claims the benefit of US Provisional Application No. 60 / 605,177, filed Aug. 27, 2004, which is hereby incorporated by reference.

[Statement of rights of inventions created from federal government-supported research and development]
This invention was made with government support under Contract No. DE-AC0996-SR18500 signed by the US Department of Energy. The government has certain rights in the invention.

  The present invention relates to a hydrogen storage material, and more particularly to a hydrogen storage material with improved thermodynamic properties.

  Current technology utilized for the storage of gaseous hydrogen is limited by small amounts of stored gas density, even at very high pressures, for example, in the range of 5,000-10,000 psi. The energy density per unit volume of gaseous hydrogen is smaller than the energy density of gasoline. The use of hydrogen as an alternative fuel is limited due to this lower energy density. Cryogenic storage of hydrogen at a temperature of about 20 K can improve volumetric energy density compared to gas storage, but is still less than the amount of energy obtained when compared to gasoline. In addition, the production of liquid hydrogen consumes large amounts of energy and requires special consideration due to cold storage to avoid hydrogen evaporation losses and other limitations of liquid hydrogen.

  Chemical storage of hydrogen in solids such as borohydride allows the release of hydrogen when heated or mixed with water. However, the use of borohydrides is limited due to the formation of solid by-products or the release of hydrogen at very high temperatures, usually above the melting point of borohydride. In addition, borohydrides generally cannot be rehydrided after releasing hydrogen.

  Therefore, there is a need in the art for improved hydrogen storage materials that can release hydrogen at lower temperatures and be hydride again after the release of hydrogen.

In one embodiment, providing a first material of formula M (BH ₄ ) _x , wherein M is an alkali metal or alkaline earth metal, M (AlH ₄ ) _x , A mixture of M (AlH ₄ ) _x and MCl _x, a mixture of MCl _x and Al, a mixture of MCl _x and AlH _3, a mixture of MH _x and Al or AlH _3, a second selected from Al and AlH ₃ Disclosed is a method of forming a hydrogen storage material comprising providing a material. The first and second materials are at a high temperature and high hydrogen pressure over a period of time to form a third material having a lower hydrogen release temperature than the first material and a higher hydrogen mass density than the second material. Can be combined.

  The fully feasible disclosure of the present invention, including its best mode for those skilled in the art, will be described in more detail in the remainder of this specification, including reference to the accompanying drawings.

2 is a graph showing the dehydrogenation characteristics of the catalyzed borohydride and control LiBH ₄ shown. 2 is a graph showing the rehydrogenation performance of borohydride catalyzed at 600 ° C. and 100 bar. Is a graph showing the hydrogen release characteristics of LiBH ₄ 75% -TiO ₂ 25% of the first and second cycles at the temperature indicated. 400 ° C., which is a graph showing a desorption data of LiBH ₄ 75% -TiO ₂ 25% at each temperature of 300 ° C. and 200 ° C.. LiBH is an X-ray diffraction spectrum having a unique crystal structure LiBH ₄ 75% compared to Sample -TiO ₂ 25% of _4. FIG. 6 is a graph comparing dehydrogenation of a destabilized LiBH ₄ material and a commercially available LiBH ₄ material. Comparison of Raman spectra between destabilized LiBH ₄ material and commercial LiBH ₄ material. First LiBH _{4-substituted} material is partially substituted is LiBH ₄ +0.2 moles of Mg, which is a graph showing the hydrogen release characteristics of the second and third cycles. FIG. 6 is a graph comparing dehydrogenation of destabilized LiBH ₄ and commercially available LiBH ₄ material. Figure ₃ is a graph showing desorption data for partially substituted LiBH4 material. 2 is a graph showing the rehydrogenation performance of a partially substituted borohydride material at 600 ° C. and a pressure of 70 bar. FIG. ₄ is a graph showing desorption data for LiBH ₄ partially substituted with the indicated catalyst. 2 is a graph showing the rehydrogenation performance of partially substituted borohydride and the catalyst shown. FIG. 6 is a graph showing desorption data for LiBH ₄ partially substituted with 0.2 moles of aluminum. FIG. 15 is a graph showing the rehydrogenation performance of partially substituted LiBH ₄ referred to in FIG. 14 at 600 ° C. and 100 bar hydrogen pressure. LiBH is a graph showing a desorption data related ₄ + 0.5LiAlH _4. 0.5LiAlH is a graph showing a partially substituted rehydrogenation performance LiBH ₄ in _4.

In one aspect of the present invention, the hydrogen storage material is from a first material, eg, a metal-containing borohydride, wherein the metal can be an alkali metal or an alkaline earth metal. Can be formed. The first material can have the formula M (BH ₄ ) _x , where M is an alkali metal or alkaline earth metal and 1 ≦ x ≦ 2.

The first material is a second material, eg, a metal alanate of formula M (AlH ₄ ) _x (where 1 ≦ x ≦ 2), a mixture of the metal alanate and metal chloride, a metal chloride and aluminum. It can be combined with a mixture, a mixture of metal chloride and alane (AlH ₃ ), a mixture of metal hydride of formula MH _x (where 1 ≦ x ≦ 2) and aluminum or alane, aluminum, and alane.

  The first and second materials have a higher hydrogen temperature and a higher hydrogen over a period to form a third material having a lower hydrogen release temperature than the first material and a higher hydrogen mass density than the second material. Can be combined with pressure.

  Various metal borohydrides can be used as the first material, such as lithium borohydride, sodium borohydride, potassium borohydride, or combinations of these materials. In addition, various alkaline earth metals can be included in the borohydride metal, which can be selected from magnesium, calcium, strontium, barium, aluminum, and two or more thereof.

  Various metal chlorides can be used in the second material described above. Such metal chlorides can include magnesium chloride, calcium chloride, strontium chloride, barium chloride, zirconium chloride, titanium chloride, and combinations thereof. Although chloride is described for its use in some embodiments, it should be understood that various metal halides including bromide and iodide can be used as well.

  Various metal hydrides are available in the second material described above. Such metal hydrides can include magnesium hydride, calcium hydride, titanium hydride, zirconium hydride, and combinations thereof.

As described above, various alanates can be used, the metal being selected from alkali metals or alkaline earth metals, lithium alanate having the formula LiAlH ₄ , sodium alanate having the formula NaAlH ₄ , and formula Mg (AlH ₄ ) _2. A magnesium alanate having

  In one aspect, the method of forming the hydrogen storage material can include ball milling the first and second materials prior to combining the first and second materials. In the ball milling process, the first and second materials can be introduced into a ball mill and ground to a particle size of about 50-100 nanometers.

  In one embodiment, a first material, a metal borohydride, such as lithium borohydride, and an alanate of the second material can be combined using a ball mixing or ball milling procedure. Following the ball milling procedure, the mixed materials can be processed at high temperatures at temperatures up to 300 ° C. under hydrogen pressures up to 5,500 psi for up to 24 hours. The third material formed from this method can have a lower hydrogen desorption temperature and a faster desorption rate compared to the initial metal borohydride material. In addition, the third material of this method can be reversibly hydrogenated after the release of the initial hydrogen composition. The third material formed by this method is a metal cation of lithium borohydride partially substituted with a metal cation of alanate, or boron borohydride partially substituted with aluminum, or borohydride It can contain substituted cations and boron.

  In another embodiment, the first material can be a metal borohydride, such as lithium borohydride, and the second material is an alanate and metal halide that can be mixed using a ball mixing procedure, For example, titanium chloride can be included. Following mixing, the first and second materials can be combined at a high temperature of up to 300 ° C. under a hydrogen pressure of up to 5,500 psi for up to 24 hours. The third material formed by the high temperature process can have a lower hydrogen desorption temperature and a faster desorption rate compared to the initial borohydride material. The formed third material can be reversibly hydrogenated when the initial hydrogen is removed from the composition. The third material is a metal cation of lithium borohydride partially substituted with a metal cation of alanate, or boron of borohydride partially substituted with aluminum, or partially substituted in borohydride Cations and boron.

  In another embodiment, the first material can be a metal borohydride, such as lithium borohydride, and the second material is a metal halide such as zirconium chloride or titanium chloride, magnesium chloride or calcium chloride. And aluminum or alane, which can be mixed using a ball mixing procedure. The first and second materials can be combined at elevated temperatures up to 300 ° C. under hydrogen pressure up to 5,500 psi for up to 24 hours. The third material formed by the high temperature process can have a lower hydrogen desorption temperature and a faster desorption rate compared to the initial borohydride material. In addition, the third material of this method can be reversibly hydrogenated after the release of the initial hydrogen composition. The third material is a metal cation of lithium borohydride partially substituted with a halide cation and / or boron borohydride partially substituted with aluminum, or partially in borohydride And cations substituted with boron and boron.

In another embodiment, the first material can be a metal borohydride, such as lithium borohydride, and the second material can be an alkaline earth hydride, such as magnesium hydride, hydrogenated Can be calcium, or transition metal hydrides, eg, hydrides such as zirconium hydride, titanium hydride, and aluminum or alane (AlH ₃ ), which are mixed using ball mixing and ball milling procedures. Can do. The first and second materials can be combined in a high temperature treatment at a temperature of up to 300 ° C. under a hydrogen pressure of up to 5,500 psi for up to 24 hours. As with the previously described embodiments, the third material of the method can have a lower hydrogen desorption temperature and a faster desorption rate compared to the first material and reversibly hydrogenate. be able to. The third material is a cation of a partially substituted borohydride and / or boron of a borohydride partially substituted with aluminum, or of a partially substituted cation and anion in borohydride. Can be both.

  In another embodiment, the first material can be a metal borohydride, such as lithium borohydride, and the second material can be allan and are mixed using a ball mixing procedure. be able to. The first and second materials can be combined in a high temperature treatment at a temperature of up to 300 ° C. under a hydrogen pressure of up to 5,500 psi for up to 24 hours. The third material of this method can have a lower hydrogen desorption temperature and a faster desorption rate compared to the first material. In addition, the third material can be reversibly hydrogenated. The third material can include a borohydride cation partially substituted with aluminum and / or a boron borohydride boron partially substituted with aluminum.

  In another embodiment, the first material can be a metal borohydride, such as lithium borohydride, and the second material can be aluminum, which is mixed using a ball mixing procedure. be able to. Following the ball mixing procedure, high temperature processing can be performed at temperatures up to 300 ° C. under hydrogen pressure up to 5,500 psi for up to 24 hours. The third material of this method can have a lower hydrogen desorption temperature and a faster desorption rate compared to the first material. The third material can also be reversibly hydrogenated. The third material can include a borohydride cation partially substituted with aluminum and / or a boron borohydride boron partially substituted with aluminum.

Following the ball milling process, about 0.250 g to about 0.500 g of the mixture sample is measured using a sievert volumetric measurement (TPD) from ambient temperature to 600 ° C. at a heating rate of 5 ° C./min. The device was evaluated. The desorption conditions included a back pressure of P ₀ = 5.4 mbar. The results of hydrogen desorption are listed in FIG. 1 as Samples 1-5 corresponding to Table 1 along with a suitable reference standard of commercially available LiBH ₄ (100%) (Sample 6).

  Following the desorption of hydrogen, the desorbed material was rehydrided at 600 ° C. and 100 bar of hydrogen for 45 minutes. As shown in FIG. 2, the percentage of hydrogen absorbed for the indicated material is reflected on the Y-axis.

As shown in FIG. 3, a sample of LiBH ₄ 75% -TiO ₂ 25% is a reversible hydrogen cycle characteristic as indicated by capacity in mass percent of material in the first and second dehydrogenation cycles. Indicates.

  As shown by the data described in the examples, the third material exhibits a reduced hydrogen release onset temperature from 400 ° C. to 200 ° C. In addition, the third material exhibited a reversible capacity of about 6 wt% to about 9 wt% hydrogen.

As described below, various metals, metal chlorides, metal hydrides, and other complex hydrides can be substituted for any proportion of Li or B atoms in LiBH ₄ to lower the dehydrogenation temperature. It has been demonstrated that it can be used as a second material in a method that yields. It has also been demonstrated that partial destabilization can lead to improvements in dehydrogenation and rehydrogenation kinetics. The method can include various steps, and can include the following steps.
(Step 1) A commercially available mixture of LiBH ₄ is a metal such as Mg, Ca, Sr, Ba and Al, a metal chloride such as MgCl ₂ , CaCl ₂ , SrCl ₂ and BaCl ₃ , MgH ₂ , CaH ₂ and AlH _3. Or other composite hydrides such as LiAlH ₄ , NaAlH ₄ and Mg (AlH ₄ ) ₂ , which are collectively ball milled to achieve a reduced particle size and materials Results in uniform mixing.
(Step 2) Following the initial ball milling and ball mixing, the resulting mixture is sintered in a given hydrogen atmosphere (100 bar) at temperatures up to 300 ° C., the hydrogen pressure being the decomposition pressure of LiBH _{4 at} the reaction temperature. To be higher.
(Step 3) The resulting sintered block of partially substituted material is crushed and ball milled to achieve a final average particle size of about 20 to about 100 nanometers or less. As demonstrated by the data described below, during the final ball milling process, catalysts such as TiCl ₃ and TiO ₂ can be added, providing additional improvements in reaction rates and hydrogen absorption and release characteristics. Enable.

[Example 1]
Using the above procedure, LiBH ₄ was mixed with 0.2 mole of magnesium, thereby obtaining partial substitution. As seen with respect to FIGS. 6-8, the destabilized material LiBH ₄ + 0.2Mg releases hydrogen at 60 ° C. compared to commercially pure LiBH ₄ that releases hydrogen at 325 ° C. As shown in FIG. 7 by spectrum 2, at room temperature, two Raman-active internal BH ₄ ⁻¹ vibrations v ₄ and v ′ ₄ appear at 1253 and 1287 cm ⁻¹ , respectively, and two harmonics at 2240 and 2274 cm ⁻¹ , respectively. 2v ₄ and 2v _'4 has appeared. However, the v ₄ , v ′ ₄ and 2v ₄ stretches disappear from the spectrum after adding destabilized LiBH ₄ + 0.2Mg. As spectrum 1 shows that the bond strength of BH is reduced by partial Li ⁺¹ substitution, the 2v ′ ₄ stretch is weakened and shifted to 2300 cm ⁻¹ . A weakened bond results in a lower dehydrogenation temperature. As further seen with respect to FIG. 8, the partially substituted LiBH ₄ material can undergo multiple rehydrogenation cycles.

[Example 2]
LiBH ₄ was combined with 0.3 MgCl ₂ and 0.2 mol of TiCl ₃ and subjected to the above process. As can be seen from the data described in FIG. 9, the partially substituted product is improved in terms of temperature and the proportion of hydrogen released at temperatures below 500 ° C. when compared to commercial LiBH _4. It has hydrogen desorption release characteristics.

As described in FIGS. 10 and 11, the data is written to show the repeated desorption and rehydrogenation performance of partially substituted LiBH ₄ , respectively.

[Example 3]
LiBH ₄ was mixed with 0.5 MgH ₂ and 0.007 TiCl ₃ and processed according to the above steps. The hydrogen desorption data at the indicated temperatures for the resulting product is set forth in FIG.

In FIG. 13, rehydrogenation data for partially substituted LiBH ₄ is described.

[Example 4]
80 wt% LiBH ₄ was combined with 0.2 mol Al and processed as described above. Data for hydrogen desorption and rehydrogenation are provided as described in FIGS. 14 and 15, respectively.

[Example 5]
LiBH ₄ was combined with 0.5LiAlH ₄ and subjected to the procedure described above. As seen with respect to FIGS. 16 and 17, the hydrogen desorption and rehydrogenation properties of partially substituted LiBH ₄ are provided, respectively.

As can be seen from the above example, a destabilizing agent can be used to partially replace the proportion of either Li atoms or B atoms (or both atoms) in LiBH ₄ , thereby replacing It is possible to achieve lower dehydrogenation temperatures than would otherwise be possible using untreated LiBH ₄ . In addition, as shown by the data described in the drawings, advantageous dehydrogenation and rehydrogenation kinetics can be achieved with an optional addition of a catalyst such as TiCl ₃ or TiO ₂ with a partial replacement procedure. Can be obtained.

  Although preferred embodiments of the present invention have been described using specific terms, apparatus, and methods, such description is for illustrative purposes only. The terms used are for explanation, not limitation. It should be understood that those skilled in the art can make changes and modifications without departing from the spirit or scope of the present invention as described in the claims. In addition, it should be understood that features of the various embodiments can be replaced 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 embodiments contained herein.

Claims (13)

Providing a first material of formula M (BH ₄ ) _x , wherein M is an alkali metal or alkaline earth metal and 1 ≦ x ≦ 2.
M (AlH ₄ ) _x (where 1 ≦ x ≦ 2), M (AlH ₄ ) _x (where 1 ≦ x ≦ 2) and MCl _x (where 1 ≦ x ≦ 4), MCl _x (where 1 ≦ x ≦ 4) and Al, MCl _x (where 1 ≦ x ≦ 4) and AlH ₃ , MH _x (where 1 ≦ x ≦ 2) and Al or AlH Providing a second material selected from a mixture of ₃ , Al, and AlH ₃ ;
A method of forming a hydrogen storage material comprising combining the first and second materials at a high temperature and high hydrogen pressure over a period of forming a third material having a lower hydrogen release temperature than the first material.   The method of claim 1, wherein the third material has a higher hydrogen mass density than the second material.   The method of claim 1, comprising ball milling the first and second materials prior to combining the first and second materials.   4. The method of claim 3, wherein the first and second materials are ground to a particle size of about 50-100 nanometers.   The method of claim 1, wherein the third material stores hydrogen reversibly.   The method of claim 1, wherein the third material is rehydrogenated, after which the third material reversibly releases at least about 6 wt% hydrogen.   The method of claim 1, wherein the first material is selected from the group consisting of lithium borohydride, sodium borohydride, potassium borohydride, or combinations thereof.   The method of claim 1, wherein the alkaline earth metal is selected from the group consisting of magnesium, calcium, strontium, barium, aluminum, and two or more thereof. The method of claim 1, wherein MCl _x is selected from the group consisting of MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₃ , ZrCl ₄ , TiCl ₃ , and combinations thereof. The method of claim 1, wherein MH _x is selected from the group consisting of MgH ₂ , CaH ₂ , TiH ₂ , ZrH ₂ , and combinations thereof. The method of claim 1, wherein M (AlH ₄ ) _x is selected from the group consisting of LiAlH ₄ , NaAlH ₄ , and Mg (AlH ₄ ) ₂ . Providing a first material of formula M (BH ₄ ) _x , wherein M is an alkali metal or alkaline earth metal and 1 ≦ x ≦ 2.
M (AlH ₄ ) _x (where 1 ≦ x ≦ 2), M (AlH ₄ ) _x (where 1 ≦ x ≦ 2) and MCl _x (where 1 ≦ x ≦ 4), MCl _x (where 1 ≦ x ≦ 4) and Al, MCl _x (where 1 ≦ x ≦ 4) and AlH ₃ , MH _x (where 1 ≦ x ≦ 2) and Al or AlH Providing a second material selected from a mixture of ₃ , Al, and AlH ₃ ;
A method of forming a hydrogen storage material comprising combining the first and second materials at high temperature and high hydrogen pressure over a period of forming a third material that stores hydrogen reversibly. Providing a first material of formula M (BH ₄ ) _x , wherein M is an alkali metal or alkaline earth metal and 1 ≦ x ≦ 2.
M (AlH ₄ ) _x (where 1 ≦ x ≦ 2), M (AlH ₄ ) _x (where 1 ≦ x ≦ 2) and MCl _x (where 1 ≦ x ≦ 4), MCl _x (where 1 ≦ x ≦ 4) and Al, MCl _x (where 1 ≦ x ≦ 4) and AlH ₃ , MH _x (where 1 ≦ x ≦ 2) and Al or AlH Providing a second material selected from a mixture of ₃ , Al, and AlH ₃ ;
High temperature and high hydrogen over a period of time when the first and second materials form a third material having a lower hydrogen release temperature than the first material and a higher hydrogen mass density than the second material. A method of forming a hydrogen storage material comprising the step of combining by pressure.

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