HK1115370A - Storage-stable fuel concentrate - Google Patents

Description

Storage stable fuel concentrates

Technical Field

The present invention relates to a storage stable concentrate for a fuel cell and a method of preventing or reducing decomposition of a fuel for a liquid fuel cell during storage thereof.

Background

Fuel cells are electrochemical power sources in which electrocatalytic oxidation of a fuel (e.g., molecular hydrogen or methanol) at the anode and electrocatalytic reduction of an oxidant (often molecular oxygen) at the cathode occur simultaneously. Conventional fuels such as hydrogen and methanol cause various storage and transportation problems, particularly for portable fuel cells (e.g., for portable electrical or electronic devices such as laptops, cell phones, etc.).

Fuels based on borohydrides (and other hydrides) are of particular interest for portable fuel cells due to their high specific energy capacity (see, e.g., j. of electrochem. soc.,150(3), A398-402, 2003). This type of fuel can be used directly as fuel or indirectly as a generator of hydrogen (which is oxidized at the anode), for example as a portable fuelProton Exchange Membrane (PEM) fuel cell components (see, e.g., US20010045364 a1, US 20030207160 a1, US 20030207157 a1, US 20030099876 a1, and U.S. patent nos.6,554,877B 2 and 6,562,497B 2). The disclosures of all of the above documents are expressly incorporated herein by reference in their entirety.

The main oxidation reaction of borohydride at the anode of a fuel cell can be represented as follows:

BH₄ ^-+8OH^-＝BO₂-+6H₂O+8e^-

however, there are also side reactions that lead to hydrogen evolution during electrocatalytic oxidation:

BH₄ ^-+4OH^-＝BO₂ ^-+2H₂O+2H₂+4e^-

moreover, during storage of borohydride fuels, spontaneous decomposition reactions typically occur:

BH₄ ^-+2H₂O＝BO₂ ^-+4H₂

the above decomposition reactions not only lead to an undesirable reduction in the specific energy capacity of the borohydride fuel, but also to problems of storage and transportation due to the production of hydrogen, which in particular can also lead to a dangerous increase in the pressure within the fuel cell.

One of the factors that has a strong influence on the decomposition rate of borohydride fuels and other metal hydride fuels is temperature. The rate of decomposition increases exponentially with increasing temperature. Also, the presence of catalytic impurities (salts of Ni, Fe, Co, Mg, Ca, etc.) can significantly affect (increase) the decomposition rate of the fuel.

Increasing the alkalinity of borohydride fuels and generally hydride-containing liquids for fuel cells is an inexpensive and effective way to increase their stability. However, increasing the alkalinity of a fuel to a level that provides the desired fuel stability for storage and transportation purposes often requires an impractical increase in the viscosity of the fuel (i.e., making pumping of the fuel difficult or even impossible), a decrease in the solubility of the reaction products in the fuel, and/or a decrease in the specific energy capacity of the fuel. In particular, for practical purposes, the optimum hydroxide concentration in the fuel is generally in the range of about 3 to about 6 mol/L. On the other hand, adherence to storage and transportation regulations requires fuel stability that can be achieved only at hydroxide ion concentrations of about 8mol/L or higher.

Disclosure of Invention

The present invention provides a storage stable liquid concentrate for use in a fuel cell. The concentrate comprises at least one metal hydride compound, a solvent comprising one or more polar solvent components, and at least one hydroxide ion providing compound. After the concentrate is stored at about 25 ℃ for 4 weeks, no more than about 2% of the at least one metal hydride compound will have decomposed.

In one aspect of the concentrate, the metal hydride compound is capable of undergoing anodic oxidation in a liquid fuel cell and/or decomposing to produce hydrogen under conditions that promote hydrolysis thereof. Preferably, the at least one metal hydride compound comprises a hydride, borohydride and/or alanate of an alkali metal and/or an alkaline earth metal. As a non-limiting example, the at least one metal hydride compound can comprise NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄Preferably NaBH₄、KBH₄、LiBH₄At least one of LiH, NaH and KH, e.g. NaBH₄And/or KBH₄。

In another aspect, the concentrate can have a hydroxide ion concentration of at least about 7.5mol/L, such as at least about 8mol/L, and/or the concentrate can contain at least one metal hydride compound at a concentration of at least about 3 mol/L.

In yet another aspect, the at least one hydroxide ion providing compound may comprise at least one alkali or alkaline earth metal hydroxide and/or aluminum hydroxide. As non-limiting examples, the at least one hydroxide ion providing compound can comprise LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH, preferably NaOH and/or KOH.

In yet another aspect, the solvent can comprise water, an aliphatic alcohol having up to about 6 carbon atoms and up to about 4 hydroxyl groups, C_2-4Alkylene glycol, di (C)_2-4Alkylene) glycol, C_2-4Alkylene glycol or di (C)_2-4Alkylene) glycol mono-C_1-4Alkyl ethers, C_2-4Alkylene glycol or di (C)_2-4Alkylene) glycol di-C_1-4Alkyl ethers, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms and/or C_1-3C of alkanoic acids_1-3An alkyl ether. As non-limiting examples, the solvent may comprise one or more of water, methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, and triglyme. The solvent may often comprise at least water.

In another aspect, the concentrate can include NaBH in a total concentration of at least about 4mol/L₄And KBH₄Water and NaOH and/or KOH.

In a further aspect, the concentrate can consist essentially of NaBH₄、KBH₄、LiBH₄、(CH₃)₃NHBH₃And/or NaCNBH₃A solvent comprising water, and NaOH and/or KOH, and may have a hydroxide ion concentration of at least about 8 mol/L.

In another aspect, the concentrate, when diluted to a hydroxide ion concentration of no greater than about 6 moles per liter, can contain a sufficient amount of metal hydride compounds useful as a liquid fuel and/or hydrogen generator for a fuel cell. As a non-limiting example, the concentrate can contain the metal hydride compound at a concentration of at least about 2 moles/L, such as at least about 3 moles/L, when diluted to a hydroxide ion concentration of about 6 moles/L.

In another aspect, the concentrate can be substantially free of any fuel additive that adversely affects the stability of the metal hydride compound. For example, it may be substantially free of plasticizers, detergents and antifreeze agents, and/or it may be substantially free of stabilizers for the metal hydride compound.

In another aspect, no more than about 5%, preferably no more than about 3%, and even more preferably no more than about 2% of the metal hydride compound will be decomposed after the concentrate is maintained at about 25 ℃ for 1 year.

The invention also provides a method of preparing a metal hydride containing liquid for use in a fuel cell from a storage stable concentrate. The method comprises combining a concentrate and a solvent in an amount of at least about 15% by volume of the concentrate. The concentrate comprises at least one metal hydride compound and a polar solvent and has a hydroxide ion concentration of at least about 7 moles/liter. The same is true. When the concentrate is held at about 25 ℃ for 4 weeks, no more than 2% of the metal hydride compound decomposes.

In one aspect of the process, the combination of concentrate and solvent preferably provides a hydroxide ion concentration of the resulting mixture of no more than about 6 moles/L.

In another aspect of the process, preferably no more than 0.5% of the metal hydride compound decomposes when the concentrate is held at about 25 ℃ for 4 weeks.

In another aspect, the hydroxide ion concentration in the concentrate can be at least about 7.5mol/L, such as at least about 8mol/L, and/or the concentration of the at least one metal hydride compound is at least about 3 mol/L.

In yet another aspect of the methodThe metal hydride compound may comprise NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄Preferably NaBH₄And/or KBH₄。

In yet another aspect, the concentrate can further comprise LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And/or NH₄OH。

In yet another aspect of the method, the solvent may comprise at least one of water, methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane (dioxin), tetrahydrofuran, diglyme, and triglyme.

In another aspect, the concentrate preferably comprises NaBH₄And/or KBH₄Water and NaOH and/or KOH.

In another aspect, dilution of the concentrate to a hydroxide ion concentration of about 6 moles/L will preferably result in a concentration of at least about 2 moles/L of the at least one metal hydride compound.

The invention also provides a method for providing a storage-stable packaged metal hydride containing liquid for use in a fuel cell. The liquid comprises at least one metal hydride compound and a polar solvent comprising a first portion and at least a second portion, and has a hydroxide ion concentration of no greater than about 7 moles per liter. The method comprises providing a container having a first compartment and at least one second compartment, partially or fully filling the first compartment with a concentrate and partially or fully filling the at least one second compartment with at least one second portion of the polar solvent, the concentrate differing from the liquid (at least) in that it contains only the first portion of the polar solvent and in that it has a hydroxide ion concentration of at least about 8 moles/liter.

In one aspect of the method, combining the contents of the first compartment with the contents of the at least one second compartment will preferably result in a hydroxide ion concentration of the combination of no more than about 6 moles/L.

In another aspect, preferably no more than about 1% of the at least one metal hydride compound will decompose when the concentrate is held at about 25 ℃ for 4 weeks.

In yet another aspect, the concentrate contains the at least one metal hydride compound in a concentration of at least about 3 mol/L.

In a further aspect of the method, the metal hydride compound can comprise NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄At least one of (1).

In another aspect, the concentrate can further comprise LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH.

In yet another aspect, the concentrate comprises NaBH₄And/or KBH₄Water and NaOH and/or KOH.

In yet another aspect, the concentrate preferably contains at least about 2 moles/L of the at least one metal hydride compound when diluted to a hydroxide ion concentration of about 6 moles/L.

In another aspect, the container may be designed such that the concentrate and at least a second component of the polar solvent are mixed within (i.e., at least some of) the container.

The present invention also provides a storage-stable packaged metal hydride containing liquid obtainable by the above method, including various aspects thereof.

The invention also provides a container filled with a metal hydride containing liquid. The container includes a first chamber and at least a second chamber. The first compartment contains a concentrate comprising at least one metal hydride compound and a polar solvent and having a hydroxide ion concentration of at least about 8 moles/liter. The at least one second compartment contains a solvent in an amount sufficient to result in a hydroxide ion concentration of no greater than about 7 moles per liter of solvent relative to the mixture of solvent in the at least one second compartment and concentrate in the first compartment.

In one aspect, the container may be sealed and the concentrate and at least a second component of the polar solvent mixed and then discharged from the container. The container is even accompanied by instructions to mix the concentrate and the at least one second component of the polar solvent before discharging it from the container.

In another aspect, the container may comprise an internal partition defining the first chamber and the at least one second chamber. By way of non-limiting example, the first chamber may be at least partially surrounded by the at least one second chamber, or the at least one second chamber may be at least partially surrounded by the first chamber.

In yet another aspect of the container, the amount of solvent in the at least one second compartment can be sufficient to result in a hydroxide ion concentration of no greater than about 6 moles/L relative to the mixture of solvent in the at least one second compartment and concentrate in the first compartment.

In yet another aspect, the concentrate can contain the at least one metal hydride compound in a concentration of at least about 3 mol/L.

In yet another aspect, the metal hydride compound can comprise NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄And/or the concentrate can further comprise LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH. As a non-limiting example, the concentrate can comprise NaBH₄And/or KBH₄Water and NaOH and/or KOH.

In another aspect of the container of the present invention, the concentrate, when diluted to provide a hydroxide ion concentration of about 6 moles/L, can contain the metal hydride compound at a concentration of at least about 2 moles/L, such as at least about 3 moles/L.

The present invention also provides a refilling device for a liquid fuel cell. The apparatus includes the container of the present invention, including its various aspects.

In one aspect, the apparatus is designed to be able to contain waste liquid from a liquid fuel cell.

The invention also provides a packaged combination for providing a metal hydride containing liquid for use in a fuel cell. The combination comprises a first container and at least one second container. The first container contains a concentrate comprising at least one metal hydride compound, a polar solvent, and at least one hydroxide ion providing compound and having a hydroxide ion concentration of at least about 8 moles/liter. The at least one second container contains a solvent in an amount sufficient to result in a hydroxide ion concentration of no greater than about 7 moles per liter of solvent relative to the mixture of solvent in the at least one second container and concentrate in the first container.

In one aspect, the combination can be accompanied by instructions to combine the concentrate in the first container with at least a portion of the solvent from the second container. In another aspect of the combination, the concentrate can comprise NaBH₄And/or KBH₄Water and NaOH and/or KOH.

In a further aspect of the combination, the solvent in the at least one second container may contain an additive for the fuel, preferably selected from plasticizers, detergents, stabilizers (e.g., aliphatic or aromatic amines) for the at least one metal hydride compound, and/or anti-freeze agents.

The present invention also provides a method of reducing decomposition of fuel for a liquid fuel cell during fuel storage. The method comprises maintaining the fuel, including its various aspects, in the form of the concentrate discussed above, and diluting the concentrate to produce the fuel only shortly before use of the fuel in the fuel cell.

The storage-stable liquid concentrate of the present invention comprises several components. In this regard, it is noted that recitation of these components herein and in the appended claims is not necessarily to be taken to mean that these components must be present in the concentrate as such. Rather, those skilled in the art will appreciate that these components may be the starting materials in preparing the concentrate and may react to form new species by reacting and/or interacting with other starting materials and/or components of the concentrate.

The metal hydride compound used in the concentrate of the invention is preferably a compound which can be oxidised as such at the anode of the fuel cell to provide electrons and/or which can (at least) be used as a generator of molecular hydrogen, for example by hydrolysis of the metal hydride compound, which in turn can be used as fuel for the fuel cell. It is to be understood that the term "metal hydride compound" as used in the present specification and appended claims is used broadly and includes, inter alia, compounds which are "simple" hydrides, such as NaH, KH, etc., as well as compounds which contain hydride complex ions, such as borohydrides, aluminum hydrides, etc. Non-limiting examples of metal hydride compounds useful in the present invention include hydrides, borohydrides (including cyanoborohydride) and aluminum hydrides of alkali metals such as Li, Na, K, Rb and Cs and alkaline earth metals such as Be, Mg, Ca, Sr and Ba and organic cations such as mono-, di-, tri-and tetraalkylammonium ions. Corresponding specific compounds include, but are not limited to, LiBH₄、NaBH₄、KBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄. For the purposes of the present invention, borohydrides, in particular NaBH₄And KBH₄Is preferred.

The solvent that forms another component of the concentrate of the present invention comprises one or more polar (protic and/or aprotic) solvent components. If the solvent is a pure solvent, i.e. only one solvent component is present, it must be polar. If the solvent is a solvent mixture, i.e., comprises one or more (e.g., two, three, four, or even more) separate solvents, at least one of the components of the mixture must be polar. Preferably, all or substantially all of the solvent component is polar. The solvents and solvent mixtures useful in the present invention are preferably liquid at room temperature and are preferably present in an amount sufficient to dissolve at least a portion (and preferably all) of the metal hydride compound and the hydroxide ion providing compound. Non-limiting examples of suitable solvents include water, mono-and poly-polyols (e.g., methanol, ethanol, propanol, isopropanol, butanol, and glycerol) and mono-and poly-alkylene glycols (e.g., ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol), aliphatic esters of mono-and poly-polycarboxylic acids (e.g., ethyl acetate, methyl acetate, ethyl formate, and diethyl oxalate), aliphatic ketones (e.g., acetone, methyl ethyl ketone, and diethyl ketone), and (cyclo) aliphatic ethers (such as tetrahydrofuran, dioxane, and partial or total alkyl esters of mono-and polyhydric alcohols with mono-and polyalkylene glycols). The preferred solvent component is water, so long as the metal hydride compound does not react with the protic solvent to any substantial extent. Other preferred solvent components include monohydric and polyhydric aliphatic and cycloaliphatic alcohols such as methanol and ethanol.

The hydroxide ion providing compound used in the concentrate of the present invention may be any compound capable of providing hydroxide ions in the concentrate, for example by dissociation, decomposition or by (in situ) reaction or interaction with any other compound that may be present in the concentrate. It will be appreciated that these compounds should not interfere to any significant extent with the operation of the fuel cell, particularly the electrochemical reactions that occur therein. Generally, hydroxide ionThe providing compound comprises at least one alkali or alkaline earth metal hydroxide and/or ammonium hydroxide. Non-limiting specific examples of suitable compounds are LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄And (5) OH. The corresponding oxides, carbonates and bicarbonates are non-limiting examples of further compounds which can be provided as hydroxide ion providing compounds. NaOH and/or KOH are often used. The amount of hydroxide ion providing compound is clearly dependent on the desired hydroxide ion concentration in the concentrate.

The concentrates of the present invention are storage stable, i.e., no more than about 2 mol%, more preferably no more than about 1%, e.g., no more than about 0.5%, no more than about 0.25%, or no more than about 0.1% of the metal hydride compound will have decomposed after the concentrate is stored for 4 weeks at about 25 ℃. Furthermore, preferably no more than about 5%, such as no more than about 3%, such as no more than about 2%, no more than about 1%, or even no more than about 0.5% of the metal hydride compound will have decomposed (on a molar basis) after storing the concentrate for 1 year at 25 ℃.

The hydroxide ion concentration of the concentrate to provide the desired stability depends, inter alia, on the particular metal hydride compound, the solvent and its amount, and the presence or absence of fuel additives and the like that may have an adverse effect on the stability of the metal hydride compound. Generally, the hydroxide ion concentration in the concentrate is generally greater than about 6mol/L, but is generally not greater than about 14mol/L, preferably not greater than about 12 mol/L. Typically, the hydroxide ion concentration in the concentrate is at least about 7mol/L, preferably at least about 7.5mol/L, even more preferably at least about 8mol/L, such as at least about 8.5mol/L, at least about 9mol/L, or even at least about 10 mol/L.

The desired concentration of the metal hydride compound in the concentrate of the present invention is somewhat related to the hydroxide ion concentration in the concentrate. In particular, because the concentrate is intended to be used in diluted form as a fuel/hydrogen generator for a fuel cell, the higher the hydroxide ion concentration in the concentrate and the lower the hydroxide ion concentration required in the diluted concentrate (i.e., the fuel/hydrogen generator), the higher the preferred concentration of metal hydride in the concentrate. In other words, after the concentrate is diluted to the desired hydroxide ion concentration, the resulting liquid should also contain a sufficient concentration of metal hydride compounds to serve as a fuel/hydrogen generator for a fuel cell. Although the concentration of the metal hydride compound that is useful depends, inter alia, on the fuel cell and its capacity, as well as on many other factors, the concentrate of the present invention will generally contain the metal hydride compound at a concentration that, upon dilution of the concentrate to a hydroxide ion concentration of about 6 moles/L, provides a concentration of the metal hydride compound of at least about 0.5 moles/L, preferably at least about 1 moles/L, or at least about 2 moles/L, such as at least about 3 moles/L, at least about 4 moles/L, or even at least about 5 moles/L. Typically, the (total) concentration of the metal hydride compound in the concentrate is often in the range of about 4mol/L to about 12 mol/L.

To further enhance the stability of the concentrates of the present invention, it is preferred that the concentrates be substantially free of any material that adversely affects the stability of the metal hydride compounds contained therein. For example, it may be desirable to have one or more of the additives, such as plasticizers, detergents and antifreeze, present in the fuel/hydrogen generator for the fuel cell. The concentrates of the present invention preferably contain no such additives or only very small amounts thereof (e.g., less than about 0.1 wt.% total, even more preferably less than about 0.01 wt.%). It is also preferred that the concentrate does not contain anything other than the metal hydride compound, the respective solvent or solvent component, and the hydroxide ion providing compound. If other materials are present, their total concentration is preferably no more than about 5% by weight, and preferably no more than 1% by weight. Unless otherwise indicated, the weight percentages given herein are based on the total weight of the concentrate. If it is desired that the final fuel/hydrogen generator contain any substances that are preferably not present in the concentrate (or at least not in the desired concentration), they may be added to the concentrate shortly before or during its dilution. For example, all or part of these desired substances may be added to the liquid (solvent) (i.e., diluent) used to dilute the concentrate. It is particularly advantageous to add one or more stabilizers for the metal hydride compound to the diluent because the diluted concentrate can no longer have a sufficiently high hydroxide ion concentration to satisfactorily stabilize the metal hydride compound over an extended period of time. Non-limiting examples of suitable stabilizers include aromatic and aliphatic amines. Non-limiting examples of other additives such as plasticizers, detergents and antifreeze include polyols such as glycerol and ethylene glycol (antifreeze). Of course, in many cases, the latter compounds may likewise be present as diluents (polar solvents) or as components thereof.

The diluent used in the concentrate of the present invention will generally comprise one or more solvent components present in the concentrate in the same or different proportions (preferably the same proportions) as in the concentrate. The diluent may also contain at least one different solvent component, or may consist entirely of one or more solvents not present in the concentrate. Of course, in the latter case, particular care must be taken that the solvent or solvents of the diluent are compatible with the solvent or solvent components of the concentrate, the hydroxide ion providing compound, and particularly the metal hydride compound. In particular, when the diluent is combined with the concentrate, the diluent should preferably not cause any significant precipitation. The diluent typically does not contain any metal hydride compounds. Also, it is typically free of hydroxide ion providing compounds, or if it does, it is also present at a concentration significantly lower than the hydroxide ion concentration in the concentrate. However, as already described above, the diluent may contain additives and other materials whose presence in the fuel is desirable but which may affect the (long term) stability of the metal hydride compound in the concentrate. The appropriate amount of diluent to combine with the concentrate depends on various factors, particularly the hydroxide ion concentration in the concentrate and the desired hydroxide ion concentration of the diluted concentrate (i.e., the fuel/hydrogen generator). Typically, the amount of diluent is at least about 15 vol%, often at least about 20 vol%, such as at least about 30 vol%, at least about 40 vol% or at least about 50 vol% of the concentrate.

Thus, for commercial purposes, there are various possible ways of providing a combination of concentrate and diluent. For example, the combination may be provided in a single container or in at least two separate containers, one containing the concentrate and the other containing the necessary amount of diluent to bring at least (and preferably exactly) the desired final concentration of the concentrate. In the latter case, the contents of the at least two containers may be combined, optionally by means of a mixing device, outside and/or inside the fuel cell.

If the concentrate and the diluent are provided in a single container, the container may have different designs. The container should be capable of substantially preventing direct liquid-liquid contact between the concentrate and the diluent. By way of non-limiting example, the container may comprise two compartments or chambers that share a partition, or the compartments or chambers may be completely separate from each other (i.e., without shared structural elements). The outlets of the chambers may be connected within the container and/or merge into a common outlet opening of the container. Alternatively, the container may be designed so that the contents of the compartments are substantially completely mixed while the concentrate and diluent remain inside the container. For example, the partition between the compartment containing the concentrate and the compartment containing the diluent may be removable and/or removable (preferably, while the container is still closed). Furthermore, a valve may be provided between the chambers. Alternatively, the barrier (e.g., septum) may tear (e.g., by bending or squeezing the container) or otherwise render it unsuitable for preventing direct contact between the concentrate and the diluent within the container (e.g., by piercing, using a zipper, e.g., Ziploc)Ridge-and-charmel of the kind, etc. ). Of course, once the concentrate is diluted (i.e., combined with a diluent), it should preferably be discharged from the container without undue delay, as the stability of the diluted concentrate, particularly the metal hydride compound contained therein, may no longer be suitable for long-term or medium-term storage.

Particularly preferred containers for concentrates (and diluents therefor) of the invention (e.g., refill cartridges for Fuel cells) are described in copending application (copending) filed on 16.1.2004 under the name of Refilling System for a Fuel Cell Method of Refilling a Fuel Cell (inventor: GennadiFinkellshtain, Mark Estrin, Moti Meron, Rami Hashimschoni and Erik Torgeman; application No. 10/758,080). The disclosure of this application is specifically incorporated herein by reference in its entirety.

Detailed Description

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

Example 1

22.4g KOH (Frutarom Ltd.) was dissolved in 80ml deionized water and cooled to room temperature. Stirring for 30min, adding 15.12g of NaBH₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 4M KOH and 4M NaBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 1.42 ml/min.

Example 2

Except that 44.8g KOH and 30.24g NaBH were used₄Resulting in a solution containing 8M KOH and 8M NaBH₄Example 1 was repeated except for the solution (c). The hydrogen evolution rate was determined to be 0.053 ml/min.

In parallel, 50ml of 8M KOH and 8M NaBH₄Mixed with 50ml of deionized water. The hydrogen evolution rate was determined in the same manner as in example 1. Thus, the KOH concentration was increased by two timesNaBH removal₄Is increased by a factor of about 25.

Example 3

18g KOH (from Ltd.) was dissolved in 65ml deionized water and cooled to room temperature. Stirring for 30min 19.5g of KBH₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 3.2M KOH and 3.6M KBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 0.23 ml/min.

Example 4

36g KOH (from Ltd.) was dissolved in 30ml deionized water and cooled to room temperature. Stirring for 30min to obtain 39g of KBH₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 6.4M KOH and 7.2M KBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 0.01 ml/min.

In parallel, 50ml of 6.4M KOH and 7.2M KBH₄Mixed with 50ml of deionized water. The hydrogen evolution rate was determined in the same manner as in example 3. Thus, a two-fold increase in KOH concentration causes KBH₄Is increased by a factor of about 23.

Example 5

14.11g of KOH and 6.72g of NaOH (from Ltd.) are dissolved in 60ml of deionized water and cooled to room temperature. 12.7g NaBH stirred for 30min₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 2.5M KOH, 1.7M NaOH and 3.4M NaBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 0.45 ml/min.

Example 6

28.22g of KOH and 13.44g of NaOH (from Ltd.) were dissolved in 30ml of deionized water and cooled to room temperature. 25.4g NaBH stirred for 30min₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 5M KOH, 3.4M NaOH and 6.8M NaBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 0.024 ml/min.

In parallel, 50ml of 5M KOH, 3.4M NaOH and 6.8M NaBH₄Mixed with 50ml of deionized water. The hydrogen evolution rate was determined as in example 5. Thus, a two-fold increase in KOH and NaOH concentrations causes NaBH₄Is increased by a factor of about 19.

Example 7

18.5g KOH (Frutarom Ltd.) was dissolved in 60ml deionized and cooled to room temperature. Stirring for 30min to obtain 15g of NaBH₄Dissolved in the resulting solution. Water was then added to a final volume of 100 ml. The solution contained 3.3M KOH and 4M NaBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 1.07 ml/min.

Example 8

18.5g KOH (from Ltd.) was dissolved in 60ml deionized water and cooled to room temperature. 15g of NaBH stirred for 30min₄Dissolved in the resulting solution. Then 10ml glycerol and water were added to a final volume of 100 ml. The solution contained 3.3M KOH and 4M NaBH₄. The solution (100ml) was placed in a flask and equilibrated at 70 ℃ for 10 minutes to reach a constant temperature. Thereafter, the evolution of hydrogen was measured by determining the amount of replacement water. The hydrogen evolution rate was determined to be 3.2 ml/min.

Thus, the addition of glycerol results inNaBH₄The thermal stability of (a) is reduced by about 3 times. However, glycerin lowers the freezing point of the mixture, so it is desirable to use it as a fuel additive and blend it into a diluent.

It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

Claims (69)

1. A storage-stable liquid concentrate for use in a fuel cell, wherein the concentrate comprises at least one metal hydride compound, a solvent comprising one or more polar solvent components, and at least one hydroxide ion providing compound, and wherein no more than about 2% of the at least one metal hydride compound has decomposed after storage of the concentrate for 4 weeks at about 25 ℃.

2. The concentrate of claim 1, wherein the at least one metal hydride compound is capable of at least one of undergoing anodic oxidation in a liquid fuel cell and undergoing decomposition to produce hydrogen gas under conditions that promote hydrolysis thereof.

3. The concentrate of claim 1, wherein the at least one metal hydride compound comprises at least one of alkali and alkaline earth metal hydrides, borohydrides, and aluminum hydrides.

4. The concentrate of claim 1, wherein the at least one metal hydride compound comprises NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄At least one of (1).

5. The concentrate of claim 1, wherein the at least one metal hydride compound comprises NaBH₄、KBH₄、LiBH₄At least one of LiH, NaH and KH.

6. The concentrate of claim 1, wherein the at least one metal hydride compound comprises NaBH₄And KBH₄At least one of (1).

7. The concentrate of claim 2, wherein the concentrate has a hydroxide ion concentration of at least about 7.5 mol/L.

8. The concentrate of claim 6, wherein the concentrate has a hydroxide ion concentration of at least about 8 mol/L.

9. The concentrate of claim 8, wherein the concentrate comprises the at least one metal hydride compound in a concentration of at least about 3 mol/L.

10. The concentrate of claim 4, wherein the at least one hydroxide ion providing compound comprises one or more of alkali and alkaline earth metal hydroxides and aluminum hydroxide.

11. The concentrate of claim 7, wherein the at least one hydroxide ion providing compound comprises LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH.

12. The concentrate of claim 1, wherein the at least one hydroxide ion providing compound comprises at least one of NaOH and KOH.

13. The concentrate of claim 11, wherein the solvent comprises water, an aliphatic alcohol having up to about 6 carbon atoms and up to about 4 hydroxyl groups, C_2-4Alkylene glycol, di (C)_2-4Alkylene) glycol, C_2-4Alkylene glycol or di (C)_2-4Alkylene) glycol mono-C_1-4Alkyl ethers, C_2-4Alkylene glycol or di (C)_2-4Alkylene) glycol di-C_1-4Alkyl ethers, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms and C_1-3C of alkanoic acids_1-3At least one alkyl ether.

14. The concentrate of claim 5, wherein the solvent comprises at least one of water, methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, and triglyme.

15. The concentrate of claim 6, wherein the solvent comprises water.

16. The concentrate of claim 1, wherein the concentrate comprises NaBH in a total concentration of at least about 4mol/L₄And KBH₄Water and at least one of NaOH and KOH.

17. The concentrate of claim 16, wherein the concentrate comprises hydroxide ions at a concentration of at least about 8 moles/L.

18. The concentrate of claim 1, wherein the concentrate consists essentially of NaBH₄、KBH₄、LiBH₄、(CH₃)₃NHBH₃And NaCNBH₃And at least one of NaOH and KOH, and has a hydroxide ion concentration of at least about 8 mol/L.

19. The concentrate of claim 18, wherein the concentrate, when diluted to a hydroxide ion concentration of not greater than about 6 moles per liter, contains a sufficient amount of the at least one metal hydride compound for use as at least one of a liquid fuel and a hydrogen generator for a fuel cell.

20. The concentrate of claim 13, wherein the concentrate, when diluted to a hydroxide ion concentration of about 6 moles/liter, comprises the at least one metal hydride compound at a concentration of at least about 2 moles/liter.

21. The concentrate of claim 6, wherein the concentrate, when diluted to a hydroxide ion concentration of about 6 moles/L, comprises the at least one metal hydride compound at a concentration of at least about 3 moles/L.

22. The concentrate of claim 20, wherein the concentrate is substantially free of any fuel additive that adversely affects the stability of the at least one metal hydride compound.

23. The concentrate of claim 21, wherein the concentrate is substantially free of plasticizers, detergents and antifreeze.

24. The concentrate of claim 1, wherein the concentrate is substantially free of stabilizers for the at least one metal hydride compound.

25. The concentrate of claim 24, wherein no more than about 5% of the at least one metal hydride compound has decomposed after the concentrate has been stored at about 25 ℃ for 1 year.

26. The concentrate of claim 19, wherein no more than about 3% of the at least one metal hydride compound has decomposed after the concentrate has been stored at about 25 ℃ for 1 year.

27. The concentrate of claim 22, wherein no more than about 2% of the at least one metal hydride compound has decomposed after the concentrate has been stored at about 25 ℃ for 1 year.

28. A process for preparing a metal hydride containing liquid for a fuel cell from a storage-stable concentrate, wherein the process comprises combining (a) a concentrate comprising at least one metal hydride compound and a polar solvent and having a hydroxide ion concentration of at least about 7 moles/liter with (b) a solvent in an amount of at least about 15 volume percent of the concentrate, wherein no more than 2 percent of the at least one metal hydride compound decomposes when the concentrate is held at about 25 ℃ for 4 weeks.

29. The method of claim 28, wherein combining (a) and (b) results in a hydroxide ion concentration of no greater than about 6 mol/L.

30. The method according to claim 29, wherein no more than 0.5% of the at least one metal hydride compound decomposes when the concentrate is stored at about 25 ℃ for 4 weeks.

31. The method of claim 29, wherein the concentrate comprises the at least one metal hydride compound at a concentration of at least about 3 mol/L.

32. The method of claim 30, wherein the hydroxide ion concentration in the concentrate is at least about 8 mol/L.

33. The method of claim 29, wherein the at least one metal hydride compound comprises NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄At least one of (1).

34. The method of claim 28, wherein the at least one metal hydride compound comprises NaBH₄And KBH₄At least one of (1).

35. The method of claim 28, wherein the concentrate further comprises LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH.

36. The method of claim 35, wherein the solvent comprises at least one of water, methanol, ethanol, ethylene glycol, diethylene glycol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, and triglyme.

37. The method of claim 32, wherein the concentrate comprises NaBH₄And KBH₄Water and at least one of NaOH and KOH.

38. The method of claim 36, wherein the concentrate, when diluted to a hydroxide ion concentration of about 6 moles/L, contains at least about 2 moles/L of the at least one metal hydride compound.

39. A method of providing a storage-stable packaged metal hydride containing liquid for use in a fuel cell, wherein the liquid comprises at least one metal hydride compound and a polar solvent comprising a first portion and at least a second portion, the liquid having a hydroxide ion concentration of not greater than about 7 moles/liter, and wherein the method comprises providing a container having a first compartment and at least a second compartment, partially or fully filling the first compartment with a concentrate and partially or fully filling the at least a second compartment with at least a second portion of the polar solvent, the concentrate differing from the liquid in that it comprises only the first portion of the polar solvent and in that it has a hydroxide ion concentration of at least about 8 moles/liter.

40. The method of claim 39, wherein combining the concentrate in the first compartment with the at least a second portion of the polar solvent in the at least a second compartment results in a hydroxide ion concentration of not greater than about 6 moles/L.

41. The method according to claim 40, wherein not greater than about 1% of the at least one metal hydride compound decomposes when the concentrate is stored at about 25 ℃ for 4 weeks.

42. The method according to claim 40 wherein the concentrate comprises the at least one metal hydride compound in a concentration of at least about 3 mol/L.

43. The method of claim 41, wherein the at least one metal hydride compound comprises NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄At least one of (1).

44. The method of claim 42, wherein the concentrate further comprises LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH.

45. The method of claim 40, wherein the concentrate comprises NaBH₄And KBH₄Water and at least one of NaOH and KOH.

46. The method of claim 41, wherein the concentrate comprises at least about 2 moles/L of the at least one metal hydride compound when diluted to a hydroxide ion concentration of about 6 moles/L.

47. A method according to claim 46, wherein the container is designed such that the concentrate and at least a second component of the polar solvent mix within the container.

48. A storage-stable packaged liquid-containing metal hydride obtainable by the process of claim 39.

49. A container filled with a metal hydride containing liquid, wherein the container comprises a first compartment containing a concentrate comprising at least one metal hydride compound and a polar solvent and having a hydroxide ion concentration of at least about 8 moles/liter and at least one second compartment containing a solvent in an amount sufficient to result in a hydroxide ion concentration of no greater than about 7 moles/liter relative to the combination of the solvent in the at least one second compartment and the concentrate in the first compartment.

50. The container of claim 49, wherein the container is sealed and the concentrate and at least a second component of the polar solvent are mixed and then discharged from the container.

51. The container of claim 50, wherein the container is associated with instructions to mix the concentrate and the at least a second component of the polar solvent prior to discharging them from the container.

52. The container of claim 49, wherein the container comprises an internal partition defining the first chamber and the at least one second chamber.

53. The container of claim 49, wherein the first chamber is at least partially surrounded by the at least one second chamber.

54. The container of claim 49, wherein the at least one second chamber is at least partially surrounded by the first chamber.

55. The container of claim 52, wherein the amount of solvent in the at least one second compartment is sufficient to result in a hydroxide ion concentration of no greater than about 6 moles/L relative to the mixture of solvent in the at least one second compartment and concentrate in the first compartment.

56. The container of claim 55, wherein the concentrate contains the at least one metal hydride compound at a concentration of at least about 3 mol/L.

57. The vessel of claim 49, wherein the at least one metal hydride compound comprises NaBH₄、KBH₄、LiBH₄、Be(BH₄)₂、Ca(BH₄)₂、Mg(BH₄)₂、(CH₃)₃NHBH₃、NaCNBH₃、LiH、NaH、KH、CaH₂、BeH₂、MgH₂、NaAlH₄、LiAlH₄And KAlH₄And the concentrate may further comprise LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH)₂、Mg(OH)₂、Ba(OH)₂And NH₄At least one of OH.

58. The container of claim 55, wherein the concentrate comprises NaBH₄And KBH₄Water and at least one of NaOH and KOH.

59. The container of claim 57, wherein the concentrate, when diluted to provide a hydroxide ion concentration of about 6 moles/L, will contain the at least one metal hydride compound at a concentration of at least about 2 moles/L.

60. The container of claim 58, wherein the concentrate, when diluted to provide a hydroxide ion concentration of about 6 moles/L, will contain the at least one metal hydride compound at a concentration of at least about 3 moles/L.

61. A refilling device for a liquid fuel cell, wherein the device comprises the container of claim 49.

62. The device of claim 61, designed to be able to contain waste liquid from a liquid fuel cell.

63. A packaged combination for providing a metal hydride containing liquid for use in a fuel cell, wherein the combination comprises a first container containing a concentrate comprising at least one metal hydride compound, a polar solvent and at least one hydroxide ion providing compound and having a hydroxide ion concentration of at least about 8 moles per liter, and at least a second container containing a solvent in an amount sufficient to result in a hydroxide ion concentration of no greater than about 7 moles per liter, relative to the mixture of solvent in the at least a second container and concentrate in the first container.

64. The packaged combination of claim 63, wherein the combination is accompanied by instructions to combine the concentrate in the first container with at least a portion of solvent from the second container.

65. The packaged combination of claim 64, wherein the concentrate comprises NaBH₄And KBH₄Water and at least one of NaOH and KOH.

66. The packaged combination of claim 63, wherein the solvent in the at least one second container comprises at least one additive for a fuel.

67. The packaged combination of claim 66, wherein the additive is selected from plasticizers, detergents, stabilizers for the at least one metal hydride compound, and antifreeze agents.

68. The packaged combination of claim 63, wherein the solvent in the at least one second container comprises at least one of an aliphatic and an aromatic amine stabilizer for the at least one metal hydride compound.

69. A method of reducing decomposition of a fuel for a liquid fuel cell during storage of the fuel, wherein the method comprises storing the fuel in a concentrate as claimed in claim 1 and diluting the concentrate to produce the fuel just prior to use of the fuel in the fuel cell.