COMPOSITION OF FUEL FOR CELLS OF FUEL CROSS REFERENCE TO RELATED REQUESTS The present application claims the priority under 35 U.S.C. § 119 (e) of the provisional application of E.U. No. 60 / 663,730, filed on March 22, 2005, the entire description of which is expressly incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fuel compositions containing hydride for liquid fuel cells, direct and indirect. 2. Exposure of Background Information Fuel cells are sources of electrochemical energy wherein the electrocatalytic oxidation of a fuel (e.g., methanol or molecular hydrogen) at an anode and the electrocatalytic reduction of an oxidant
(often molecular oxygen) at a cathode take place simultaneously. Conventional fuels such as hydrogen and methanol have various transport and storage problems, in particular, for portable fuel cells (e.g., for use with portable electronic and electrical devices such as laptops, cell phones, and the like).
The borohydride (and other hydride) based fuels are of particular interest for portable fuel cells, due to their very high specific energy capacity (see, eg, Electrochem J, Soc., 150, (3), A398- 402, 2003). These types of fuels can be used either directly as fuel or indirectly as a hydrogen generator (which is oxidized at the anode), eg, as part of a portable proton exchange membrane (PEM) fuel cell (see , eg, US 20010045364 Al, US 20030207160 Al, US 20030207157 Al, US 20030099876 Al, and US Patent Nos. 6,554,877 B2 and 6,562,497 B2). The descriptions of all the above documents are expressly incorporated by reference herein in their entireties. There are several factors that have to be taken into account when assessing the performance of a hydride-based fuel. One of these factors is fuel efficiency. Fuel efficiency can be determined, for example, by comparing the actual energy density (Wh / fuel volume unit) provided in a given fuel cell to the theoretical energy density. The absolute value of energy density is also one of the indicators of fuel efficiency. In this aspect, it will be
note that while a high concentration of (boron) hydride in the fuel can achieve a high desired energy density of the fuel, in some situations a high concentration of (boron) hydride in the liquid phase of the fuel can also be disadvantageous. For example, the corresponding fuel may be chemically too aggressive and as a result thereof, may damage one or more of the structural components of the fuel cell, in particular, the anode. Accordingly, a compromise must be found between fuel energy density and fuel compatibility with the fuel cell components and / or finding ways to avoid severe damage to the fuel cell components. despite a relatively high concentration of (boron) hydride in the fuel phase. Another factor that can affect the performance of a hydride-based fuel is its solubility. For example, the main oxidation reaction of a borohydride compound at the anode of a fuel cell can be represented as follows: BH4 ~ + 8 OH "= B02" + 6 H20 + 8 e. "In accordance with the above, during the use of a liquid fuel cell, such a raw material
how, e. g. , a borohydride compound becomes an anodic oxidation product such as, e. g. , a metaborate. The solubility of the raw material and that of the oxidation product in the liquid phase of the fuel, it can differ substantially. This difference in solubility can affect the efficiency of the fuel and in this way, the performance of the fuel cell. By way of non-limiting example, NaBH4 has relatively high solubility in an alkaline solution while its oxidation product, NaB02, is less soluble in this solution. If a relatively high concentration of NaBH occurs in the initial fuel, the fuel cell will have a high level of activity at the beginning of the discharge process, and the activity will be reduced gradually as more and more NaBH4 is present in oxidized form. In addition, the concentration of the oxidation product increases at the same rate as the concentration of BH4 ~ is reduced, and due to the high initial concentration of sodium borohydride, the less soluble sodium metaborate begins to precipitate at a relatively early stage of the process of download. The metaborate precipitate can block the anode, membranes and other components of the fuel cell and can thereby aggravate the reduction in fuel activity caused by
the reduction in the concentration of BH4 ~ in the liquid phase of the fuel. The situation with potassium borohydride is opposite to that with sodium borohydride. Potassium borohydride has relatively low solubility in caustic solution (in particular, at room temperature) while its oxidation product, potassium metaborate is significantly more soluble in the caustic solution than potassium borohydride. Due to the relatively low solubility of potassium borohydride in caustic solution, the initial BH4 ~ concentration in the liquid phase of the fuel may not be as high as in the case of sodium borohydride, making it more difficult to obtain a high current . On the other hand, the spent fuel (containing potassium metaborate) does not show any major problem due to the precipitation of the oxidation product. It would be advantageous to have available a fuel for a liquid fuel cell which allows a high concentration of desirable hydride in the liquid phase of the fuel and provides a high energy density and / or other advantages without causing problems such as, e. g. , premature precipitation of the anodic oxidation product of the hydride used from the liquid phase of the
fuel and / or damage to the components of the fuel cell. SUMMARY OF THE INVENTION The present invention provides a fuel composition containing hydride for a liquid fuel cell. The composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound. The solubility of the first hydride compound in the liquid phase is greater than the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase is less than the solubility of the product of anodic oxidation of the second hydride compound in the liquid phase. In one aspect of this composition, the first hydride compound and the hydride compound can be independently selected from hydrides, borohydrides (including polycarbohydrides and cyanoborohydrides) and aluminum hydrides of metals, preferably alkali and alkaline earth metals, Zn and Al, ammonium , and alkylamine-BH3 complexes, for example, of NaBH4, KBH4, L? BH4, NH4BH4, Be (BH4) 2, Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3, a polyhydrohydride such as, e. g. , a compound of the formula MB3H8, M2B? 0H? 0, MB? 0H? 3,
M2Bi2H? 2 or 2B20Hi8 where M = L ?, Na, K, NH4, Bex / 2, Ca? / 2, Mg? / 2, Zn1 / 2 or Al1 / 3, (CH3) 2NHBH3, NaCNBH3, LiH, NaH , KH, CaH2, BeH2, MgH2, NaAlH4, L? AlH4 and KA1H4. In another aspect, the first hydride compound and / or the second hydride compound may be selected from borohydrides, e.g., of alkali metal and alkaline earth borohydrides. For example, the first hydride compound and / or the second hydride compound may be selected from NaBH4 and KBH4. In another aspect of the composition, the molar ratio of the first hydride compound and the second hydride compound can be from about 95: 5 to about 5:95, eg, from about 90:10 to about 10:90, from about 80 : 20 to about 20:80, from about 75:25 to about 25:75, or from about 60:40 to about 40:60. In still another aspect, the composition may comprise hydride compounds in a total concentration of at least about 0.5 moles per liter of composition, for example, in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter , at least about 3 moles per liter, at least about 4 moles per liter, or at least
approximately 5 moles per liter of composition. Of course, if a compound were provided, the concentration of the hydride compounds can be as high as, for example, at least about 6 moles per liter, at least about 8 moles per liter, or at least about 10 moles per liter of the composition. In yet a further aspect, the liquid phase of the composition may comprise hydroxide ions. By way of non-limiting example, the hydroxide ions may be present in a concentration of at least about 0.01 moles per liter, for example, at least about 0.05 moles per liter, at least about 0.1 moles per liter, at least about 0.5 moles per liter. liter, at least about 1 mole per liter, at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter and / or in a concentration that is not greater than about 7 moles per liter of liquid phase. Especially, if a concentrate were provided, the ionic hydroxide concentration may still be higher, for example, up to about 14 moles per liter, for example, up to
approximately 12 moles per liter. In another aspect, the liquid phase can comprise at least one compound that provides hydroxide ions dissolved therein, said compound that provides hydroxide ions selected from hydroxides of alkali metals, alkaline earth metals, Zn and Al, and hydroxide of hydroxide. Ammonium, for example, of one or more of LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH) 2, Mg (OH) 2, Ba (OH) 2, Zn (OH) 2, A1 (0H) 3, and NH 4 OH. For example, the liquid phase may comprise dissolved in the same NaOH and / or KOH. In another aspect of the composition of the present invention, the liquid phase may comprise at least one solvent, for example, at least two solvents, which are selected from water and substances (preferably miscible in water and / or soluble in water), by example, of (cyclo) aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C2-4 alkylene glycols, di (C2.4 alkylene glycols), poly (C2-4 alkylenylene glycols), mono-C1 alkyl ethers ? 4 C2_4 alkylene glycols, di (C2_4 alkylene glycols) and poly (C2_4) polyglycols, C4-4 di-alkoyl ethers of C2-4 alkylenglycols, di (C2_4 alkylene glycols) and poly (C2_4 alkylene glycols), oxide block copolymers ethylene / oxide
propylene, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, propoxylated and ethoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms, aliphatic aldehydes having up to about 6 carbon atoms, esters of C alquilo alkyl- of C? _4 (aliphatic) alkanoic acids and primary, secondary and tertiary aliphatic amines having a total of up to about 10 carbon atoms. By way of non-limiting example, the liquid phase may comprise one or more of water, methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1,2,4-butanetriol, trimethylolpropane, pentaerythritol, sorbitol (or any other sugar alcohol ), glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, triglyme, monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine and tripropanolamine. In another aspect, the liquid phase may comprise water, either alone or in combination with one or more substances of (cyclo) aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C2_ aliphenyl glycols,
di (C2_4 alkylene glycols), poly (C2-4 alkylene glycols), C4_4 monoalkyl ethers of C2_4 alkylene glycols, di (C2_4 alkylene glycols) and poly (C2_) alkylene glycols, di_C1_4 alkyl ethers of C2_4 alkylene glycols, di (C2_4 alkylene glycols) and poly (C2-4 alkylene glycols), ethylene oxide / propylene oxide block copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, propoxylated and ethoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms, aliphatic aldehydes having up to about 6 carbon atoms, C este _ alkyl esters of C? _4 (aliphatic) alkanoic acids and primary, secondary and tertiary aliphatic amines which they have a total of up to about 10 carbon atoms. In another aspect, the composition of the present invention may comprise two hydride compounds. Still in a further aspect, it may comprise at least three hydride compounds. The present invention also provides a hydride-containing fuel composition for a liquid fuel cell, which composition comprises an alkaline liquid phase and at least a first hydride compound and a second hydride compound. The
The solubility of the first hydride compound in the liquid phase is greater than the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase is less than the solubility of the oxidation product. anodic of the second hydride compound in the liquid phase. The alkaline liquid phase has an ionic hydroxide concentration of at least about 0.5 moles per liter and comprises dissolved therein one or more LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH) 2, Mg (OH) 2, Ba (OH) 2, Zn (OH) 2, Al (OH) 3, and NH 4 OH. The first hydride compound and the second hydride compound are independently selected from NaBH4, KBH4, L? BH4, NH4BH4, Be (BH4) 2, Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3, polyhydrohydrides (CH3) 2NHBH3, NaCNBH3, LiH, NaH, KH, CaH2, BeH2, MgH2, NaAlH4, L? AlH4 and KA1H4. In one aspect of this composition, the first hydride compound and the second hydride compound can be independently selected from NaBH 4, KBH 4, L? BH 4, Be (BH 4) 2, NH 4 B 4, a poloborohydride, Ca (BH 4) 2, Mg (BH 4) ) 2, Zn (BH4) 2, Al (BH4) 3, (CH3) 2NHBH3 and NaCNBH3. For example, the first hydride compound and the second hydride compound may be NaBH4 and KBH4. In another aspect, the molar ratio of the first hydride compound and the second hydride compound
it can be from about 95: 5 to about 5:95, for example, from about 75:25 to about 25:75. In yet another aspect, the composition may comprise the hydride compounds in a total concentration of at least about 0.5 moles per liter of composition, for example, in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter. liter, or at least about 3 moles per liter of composition. In yet a further aspect of the composition, the ionic hydroxide concentration in the liquid phase may be at least about 1 mole per liter, for example, at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter and / or may not be greater than about 7 moles per liter. In another aspect of the composition, the liquid phase may comprise dissolved in the same NaOH and / or KOH. In another aspect, the liquid phase may comprise at least one, for example, at least two, solvents selected from water, alcohols
(cyclo) aliphatics having up to about 6 carbon atoms and up to about 6 hydroxy groups, C2_4 alkylene glycols, di (C2_4 alkylene glycols), poly (C2_4 alkylene glycols), C4_4 monoalkyl ethers of C2_4 alkylene glycols, di (C2_4 alkylene glycols) ) and poly (C 4 -alkylene glycols), di-C 4 alkyl ethers of C2_4 alkylene glycols, di (C2_4 alkylene glycols) and poly (C2_4 alkylene glycols), block copolymers of ethylene oxide / propylene oxide, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, propoxylated and ethoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms, aliphatic aldehydes having up to about 6 carbon atoms, C? _4 alkyl esters of C__4 (aliphatic) alkanoic acids and primary, secondary and tertiary aliphatic amines having a total of up to about amente 10 carbon atoms. For example, the liquid phase may comprise one or more of water, methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1,2,4-butanetriol, trimethylolpropane, pentaerythrol, sorbitol, glycerol, acetone, methyl ethyl ketone, diethyl ketone. , methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, triglyme, monoethanolamine, diethanolamine,
triethanolamine, monopropanolamine, dipropanolamine and tripropanolamine. In another aspect, the liquid phase may comprise water. For example, the liquid phase may comprise water and one or more of methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1,2,4-butanetriol, tpmethylolpropane, pentaepritol, sorbitol, glycerol, acetone, methyl ethyl ketone, diethyl ketone. , methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, triglyme, monoethanolamm, diethanolamm, tpetanolamm, monopropanolamine, dipropanolamine and tripropanolamine. The present invention also provides a mixture containing hydride for use in a fuel for a liquid fuel cell, which mixture comprises at least a first hydride compound and a second hydride compound, whose compounds are independently selected from hydrides, borohydrides
(including polybromohydrides and cyanoborohydrides) and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkylamines and wherein the molar ratio of the first hydride compound and the second hydride compound is from about 95: 5 to about 5: 95 In one aspect of the mixture, the molar ratio
of the hydride compounds can be from about 80:20 to about 20:80. In another aspect of the mixture, the first hydride compound and the second hydride compound can be independently selected from NaBH 4, KBH4, LiBH4, Be (BH4) 2, NH4BH4, a polycarbohydride, Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3, (CH3) 2NHBH3 and NaCNBH3. For example, the first hydride compound and / or the second hydride compound may be selected from borohydrides, for example, alkali metal and alkaline earth borohydrides. In particular, the first hydride compound and / or the second hydride compound may be NaBH 4 or KBH 4. The present invention also provides a hydride-containing fuel composition for a direct liquid fuel cell, which composition comprises the at least two different hydride compounds. The at least two different hydride compounds are selected such that the composition provides, under otherwise identical circumstances, a higher fuel efficiency than an otherwise identical fuel composition comprising only one of these different hydride compounds in a molar amount that is identical with a total molar amount of the at least two different
hydride compounds. In other words, there is a synergism. In one aspect of the composition, a first hydride compound of the at least two different hydride compounds may have the greater solubility in the liquid phase of a liquid fuel than a second hydride compound of the at least two different hydride compounds, and the anodic oxidation compound of the first hydride compound may have a lower solubility in the liquid phase of the liquid fuel than the anodic oxidation product of the second hydride compound. In another aspect, the first hydride compound and the second hydride compound can be independently selected from hydrides, borohydrides (including polycarbohydrides) and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkylamines, for example, of NaBH 4, KBH4, LiBH4, Be (BH4) 2, NH4BH4, polycarbohydrides Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3, (CH3) 2NHBH3 and NaCNBH3. For example, the first hydride compound and / or the second hydride compound can be selected from borohydrides, for example, from alkali metal and alkaline earth borohydrides. In particular, at least one of the first hydride compound and the second hydride compound
it can be NaBH4 or KBH4. In still another aspect, the molar ratio of the first hydride compound and the second hydride compound can be from about 95: 5 to about 5:95, for example, from about 90:10 to about 10:90, of about 80: 20 to about at about 20:80, from about 75:25 to about 25:75 to about 60:40 to about 40:60. The present invention also provides a method for increasing the fuel efficiency of a hydride compound containing liquid fuel composition for a direct, direct fuel cell, wherein the method comprises employing at least two different hydride compounds in the liquid fuel, the at least two different hydride compounds being selected such that a fuel comprising these different hydride compounds has a higher efficiency than that which is obtainable with a fuel comprising only one of these hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds. In one aspect of the method, a first hydride compound of the at least two different compounds of
hydride may have greater solubility in the liquid phase of the fuel composition than a second hydride compound of the at least two different hydride compounds, and an anodic oxidation product of the first hydride compound may have a lower solubility in the liquid of the fuel composition than an anodic oxidation product of the second hydride compound. In another aspect of the method, the first hydride compound and the second hydride compound can be independently selected from hydrides, borohydrides and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkyl amines, for example, of NaBH 4, KBH 4, LiBH4, Be (BH4) 2, NH4BH4, polycarbohydrides Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3,
(CH) 2NHBH3 and NaCNBH3. For example, the first hydride compound and / or the second hydride compound can be selected from borohydrides, for example, from alkali metal and alkaline earth borohydrides. In particular, the first hydride compound and / or the second hydride compound may be NaBH 4 or KBH 4. In still another aspect of the method of the invention, the molar ratio of the first hydride compound and the second hydride compound can be from about 95: 5 to about 5:95, for example,
from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 75:25 to about 25:75, or from about 60:40 to about 40:60. The present invention also provides a fuel composition containing hydride for a liquid fuel cell, which composition comprises an alkaline liquid phase and one or more hydride compounds. One or more hydride compounds dissolve in the liquid phase (eg, at about room temperature) in a total concentration of at least about 0.5 mole per liter of liquid phase and the solubility of the anodic oxidation products of one or more compounds of hydride in the liquid phase at about room temperature (eg, at about 25 ° C) is such that after anodic oxidation of about 80% of moles of one or more hydride compounds substantially none of the oxidation products are precipitated (at about room temperature). "Substantially not precipitated" as used herein and in the appended claims is meant to mean less than about 10%, preferably less than about 5%, for example, less than about 1% of the anodic oxidation product formed is presented
in undissolved form. In one aspect of the composition, substantially none of the oxidation products are precipitated after anodic oxidation of about 90 mol%, or even after anodic oxidation of about 95 mol% of one or more hydride compounds and / or one or more hydride compounds can be dissolved in the liquid phase in a total concentration of at least about 1 mole per liter, for example, in a total concentration of at least about 2 moles per liter, or at least about 3 moles per liter . In another aspect of the composition of the present invention, one or more hydride compounds can be independently selected from hydrides, borohydrides and aluminum hydrides of alkali and alkaline earth metals, Zn, Al, ammonium and dialkylamines, for example, of NaBH 4, KBH 4, LiBH4, Be (BH4) 2, NH4BH4, a polyhydrocarbon Ca (BH4) 2, Mg (BH4) 2, Zn (BH4) 2, A1 (BH4) 3, (CH3) 2NHBH3 and NaCNBH3. In particular, one or more hydride compounds may be selected from (poly) borohydrides, for example, from alkali metal and alkaline earth borohydrides. For example, at least one or more of the hydride compounds may be selected from NaBH 4 or KBH 4.
In still another aspect of the composition of the present invention, one or more of the hydride compounds may comprise at least a first hydride compound and a second hydride compound and the solubility of the first hydride compound in the liquefied phase may be greater that the solubility of the second hydride compound in the liquid phase and the solubility of the anodic oxidation product of the first hydride compound in the liquid phase may be less than the solubility of the anodic oxidation product of the second hydride compound in the liquid phase. In one aspect, the molar ratio of the first hydride compound and the second hydride compound can be from about 95: 5 to about 5:95, for example, from about 90:10 to about 10:90, from about 80:20 at about 20:80, from about 75:25 to about 25:75, or from about 60:40 to about 40:60. In yet a further aspect of the composition, the liquid phase may comprise hydroxide ions at a concentration of at least about 1 mole per liter, for example, at a concentration of at least about 1.5 moles per liter, at least about 2 moles per liter. liter and / or in a concentration of not more than about 7 moles
per liter. In yet another aspect, the liquid phase may comprise at least one compound that provides hydroxide ions dissolved therein, said compound which provides hydroxide ions being selected from alkali metal hydroxides, alkaline earth metals, Al and Zn and hydroxide ions. ammonium, such as, for example, LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH) 2, Mg (OH) 2, Ba (OH) 2, Zn (OH) 2, A1 (0H) 3, and NH 4 OH . In particular, the liquefied phase can comprise dissolved in the same NaOH and / or KOH. In yet a further aspect of the composition, the liquid phase may comprise at least one (eg, at least two) of water, (cyclo) aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C2- alkyl ene glycols. 4, di (C2_4 alkylene glycols), poly (C2_4) allylene glycols, C ?_4 mono-alkoyl ethers of C2_4 alkylenglycols, di (C2_4) and poly (C2_4) alkylenglycols, di_C alkyl_4 ethers of C2_ alkylenglycols -, di (C2_4 algylene glycols) and poly (C2_4 alkylene glycols), ethylene oxide / propylene oxide blog copolymers, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, propoxylated and ethoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms ,
aliphatic ketones having up to about 6 carbon atoms, aliphatic aldehydes having up to about 6 carbon atoms, C? -4 alquilo alkyl esters of C? _ _4 aliphatic (aliphatic) acids and primary, secondary and tertiary aliphatic amines having a total of up to about 10 carbon atoms, eg, at least one of water, methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1,2,4-butanediol, p-methylolpropane, pentaerythritol, sorbitol, glycerol, acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, tpglime, monoethanolamine , dietnolamma, trietanolamma, monopropanolamma, dipropanolamma and tripropanolamma. In another aspect, the liquid phase may comprise water, alone or in combination with one or more solvents selected from (cyclo) aliphatic alcohols having up to about 6 carbon atoms and up to about 6 hydroxy groups, C 2-4 alkylene glycols, di (alkylene glycols) C2-4), poly (C2_4 alkylene glycols), monoalkyl C_4 alkyl ethers of C2_4 alkylene glycols, di (C2_4 alkylene glycols) and poly (C2_4 alkylene glycols), di_C alkyl_4 ethers of C2_ alkylenglycols, di (C2_4 alkylene glycols) and poly (C2_) alkylene glycols, block copolymers of ethylene oxide / oxide
propylene, ethoxylated aliphatic polyols, propoxylated aliphatic polyols, propoxylated and ethoxylated aliphatic polyols, aliphatic ethers having up to about 6 carbon atoms, aliphatic ketones having up to about 6 carbon atoms, aliphatic aldehydes having up to about 6 carbon atoms, esters C 4 alkyl of C 4 -4 alkane acids (aliphatic) and primary, secondary and tertiary aliphatic amines having a total of up to about 10 carbon atoms. By way of non-limiting example, the liquid phase may comprise water and one or more (eg, two) of methanol, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, 1,2,4-butanediol, trimethylolpropane, pentaerythritol, sorbitol, glycerol , acetone, methyl ethyl ketone, diethyl ketone, methyl acetate, ethyl acetate, dioxane, tetrahydrofuran, diglyme, tpglime, monoethanolamine, diethanolamine, tpetanolamma, monopropanolamine, dipropanolamine and tripropanolamine, for example, water and at least one of methanol, ethanol , propanol, isopropanol and ethylene glycol. The present invention also provides a liguid fuel cell which comprises a fuel composition of the present invention, including various aspects thereof.
The present invention also provides a fuel cartridge for (re) filling a liquid fuel cell, which cartridge comprises a fuel composition of the present invention, including various aspects thereof. The present invention also provides a method for increasing the fuel efficiency of a liquid fuel composition containing hydride compound for a direct liquid fuel cell. This method comprises selecting one or more hydride compounds and one or more solvents such that one or more of the hydride compounds are soluble in one or more solvents in a concentration of at least about 0.5 moles per liter (at about room temperature). ) and that after anodic oxidation of about 80% moles of one or more hydride compounds substantially all of the anodic oxidation products formed are soluble in one or more solvents (at about room temperature). In one aspect of the method, one or more hydride compounds may comprise at least a first hydride compound and a second hydride compound and the solubility of the first hydride compound in one or more solvents may be greater than the solubility of the second hydride compound. hydride in one or more solvents and the
The solubility of the anodic oxidation product of the first hydride compound in one or more solvents may be less than the solubility of the anodic oxidation product of the second hydride compound in one or more solvents. The present invention also provides a method for increasing the fuel efficiency of a liquid fuel composition containing a hydride compound for a direct liquid fuel cell, which method comprises employing at least two different hydride compounds (eg, at least two different borohydride compounds) in the fuel composition. The at least two (eg, two, three or four) different hydride compounds are selected such that a fuel composition comprising these different hydride compounds, under otherwise identical conditions, has a higher efficiency than a composition of fuel of another identical form comprising only one of the at least two different hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds. In one aspect of the method, a first hydride compound of the at least two different hydride compounds may have the highest solubility in the phase
liquid of the liquid fuel composition that a second hydride compound of the at least two different hydride compounds and an anodic oxidation product of the first hydride compound may have a lower solubility in the liquid phase of the liquid fuel composition than a anodic oxidation product of the second hydride compound. In another aspect of the method, the at least two hydride compounds can be present in the liquid phase of the fuel composition in a total concentration of at least about 1 mole per liter, for example, at least about 2 moles per liter. The present invention also provides a method for improving the performance of a liquid fuel cell which comprises a liquid fuel composition containing a hydride compound. The method comprises employing at least two different hydride compounds (eg, two or more different borohydride compounds) in the liquid fuel composition, the at least two different hydride compounds being selected in such a way that under the otherwise identical conditions the Fuel composition comprising the at least two different hydride compounds is chemically less aggressive
towards at least one structural component of the fuel cell (eg, the anode), and shows at least the same efficiency as a liquid fuel composition which comprises only one of these two hydride compounds in a molar amount which is identical with a total molar amount of the at least two different hydride compounds. According to one aspect of the present invention, the performance of a fuel for a liquid fuel cell can be optimized by providing a relatively high initial concentration of dissolved boron (s) (s) compound (s) while at the same time it prevents the precipitation of substantial amounts of anodic oxidation products and / or while preventing any significant damage to the structural components of the fuel cell, in particular the anode, caused by being a chemically too aggressive fuel. In this aspect, the present invention employs various basic concepts which may be used individually or in combination. A first concept comprises the use of a mixture of two or more hydride compounds which differ in their solubilities in the liquid component of the fuel and also differ in the solubilities of their anodic oxidation products, with the compound of
more soluble hydride making the oxidation product less soluble. A second concept comprises the use of a mixture of the at least two different solvents that are selected in order to achieve the desirably high solubility of one or more hydride compounds and also the desirably high solubility of the product (s) of Anodic oxidation of these or more hydride compounds. In this case, if more than one hydride compound is used, the solubilities of the hydride compounds and the anodic reaction products may be similar or different, so long as the solvent mixture can dissolve both the hydride compounds and the products of the hydride. Anodic oxidation thereof to a desirable high degree. A third concept balances the concentrations of the various cations
(metallic) in the liquid phase of the fuel (which can be a suspension) in order to achieve a high concentration of (boron) desirable hydride in the liquid phase of the fuel while at the same time maintaining the chemical aggressiveness of the fuel at levels acceptable The use of the above concepts also facilitates the preparation of the pastes and / or fuel concentrates. Considering the corresponding products, reference is made to the application for
US patent co-pending No. 10 / 757,849, filed January 16, 2004 (Publication of U.S. Patent Application No. 2005/0155279 Al), the entire description of which is expressly incorporated by reference herein. Considering a method to produce corresponding products, reference is made to the provisional application of E.U. which has the title "Method and Production of Fuel Dispersion for a Fuel Cell" (Legal Registration No. P28866), filed therewith, the full description of which is expressly incorporated herein by reference. As stated above, the "efficiency" of a fuel can be assessed by using various parameters, for example, the initial current that is obtainable or the electrical output per unit volume, each determined in a fuel cell. The hydride compounds for use in the present invention are preferably compounds that can be oxidized as such at the anode of a fuel cell to provide electrons. It will be understood that the term "hydride compound" as used in the present specification and the appended claims is used in a broad sense and comprises, in
particular, compounds that are "simple" hydrides, such as, for example, NaH, KH, etc. as well as also compounds comprising a hydride complex ion such as, for example, borohydride, aluminum hydride and the like. Non-limiting examples of metal hydride compounds for use in the present invention include hydrides, borohydrides, including cyanoborohydrides and polycarbohydrides, and aluminum hydrides of alkali metals such as, for example, Li, Na, K, Rb and Cs, and alkaline earth metals such as, for example, Be, Mg, Ca, Sr and Ba, but also other metals such as Al and Zn, ammonium and BH3 complexes and mono-, di-, trialkylamines. Corresponding specific compounds include, but are not limited to, LiBH4, NaBH4, KBH4, NH4BH4, Be (BH4) 2, Ca (BH4) 2, Mg (BH4) 2,
(CH3) 3NHBH3, NaCNBH3, Li, NaH, KH, CaH2, BeH2, MgH2, NaAlH4,
LiAlH4 and KA1H4. The polyborhydrides can also be used. The non-limiting examples of polyhydrohydrides are those of the formulas MB3H_, M2B10H10, B10H13, M2B? _H? 2 and M2B20H? 8 where M = Li, Na, K, NH4, Be_ / 2, Ca? / 2, Mg1 2 , Zn? 2 or Al? / 3 (the fractions associated with Ca, Mg, Zn and Al take into account that these metals are bi- or trivalent). Additional examples of polyhydrohydride compounds that are suitable for use in the present invention are described in,
for example, the Patent Application Publication of E.U. 2005/0132640 Al, the full description thereof is incorporated for reference herein. Borohydrides and, in particular, NaBH 4 and KBH 4 are examples of preferred hydrides for the purposes of the present invention. The liquid phase of the compositions of the present invention preferably comprises one or more polar solvent components (protic and / or aprotic). If the solvent is a pure solvent, that is, there is only one solvent, the solvent is preferably polar. If the solvent is a solvent mixture, that is, it comprises one or more (e.g., two, three, four, or even more) individual solvents, at least one of the compounds in the mixture is preferably polar. For example, all or at least substantially all of the solvent components can be polar. The solvents and solvent mixtures for use in the present invention are preferably liquid (as) at room temperature and are preferably present in an amount that is sufficient to dissolve the hydride compound (s) and compound (s) that it provides. (n) hydroxide ions. Non-limiting examples of suitable solvent components include water, mono- and polyhydric alcohols (e.g., methanol, ethanol, propanol,
isopropanol, butanol, glycerol, 1,2,4-butanetriol, trimethylolpropane, and pentaerythritol) and mono- and polyalkylene glycols (such as, for example, ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol), aliphatic esters of mono- and polycarboxylic acids ( eg, ethyl acetate, methyl acetate, ethyl formate, and diethyl oxalate), aliphatic ketones (such as, for example, acetone, methyl ethyl ketone, and diethyl ketone), aliphatic aldehydes (such as acetaldehyde and propionaldehyde), and ethers (cyclo) ) aliphatics (such as tetrahydrofuran, dioxane and full or partial alkyl esters of mono- and polyhydric alcohols and mono- and polyalkylene glycols). A preferred solvent component is water. Examples of other preferred solvent components include aliphatic and cycloaliphatic and monohydric and polyhydric alcohols such as methanol and ethanol. If water is present, the concentration thereof will often be at least about 10% by volume, eg, at least about 30% by volume, at least about 50% by volume, or at least about 70% by volume, in based on the total volume of the combined solvents. The compounds that provide hydroxide ions for use in the compositions of the
present invention can be any of the compounds that are capable of providing hydroxide ions in the composition, for example, by dissociation, decomposition, or by reaction. { in si t u) or interaction with any other compound that may occur in the composition. Of course, these compounds should not interfere in any significant degree with the operation of the fuel cell and, in particular, the electro-chemical reactions that take place therein. Usually, the compound that provides hydroxide ions will include at least one alkali earth or alkali metal hydroxide and / or ammonium hydroxide. Non-limiting examples of suitable compounds are LiOH, NaOH, KOH, RbOH, CsOH, Ca (OH) 2, Mg (OH) 2, Ba (OH) 2, Zn (OH) 2, Al (OH) 3, and NH 4 OH . The corresponding oxides, carbonates and bicarbonates are non-limiting examples of additional compounds which can serve as compounds that provide hydroxide ions. Frequently, NaOH and / or KOH will be used. The amount of the compound (s) that provides (n) hydroxide ions is apparently dependent on the ionic concentration of hydroxide in the concentrate. If two different hydride compounds are used in the present invention, the molar ratio of these hydride compounds will usually be found in
the range of from about 99: 1 to about 1:99, particularly in the range of from about 95: 5 to about 5:95. Frequently the molar ratio will not be greater than about 90:10, for example, not greater than about 80:20, not greater than about 75:25, or no greater than about 60:40, and not less than about 10:90, for example, not less than about 20:80, not less than about 25:75, or not less than about 10:60. By way of non-limiting example, in the case of, for example, a caustic aqueous solution, a molar ratio of NaBH 4 and KBH 4 of about 25:75 can particularly achieve advantageous results. One skilled in the art will appreciate that when two different hydride compounds such as, for example, NaBH4 and KBH4 are used in a certain molar ratio, this molar ratio is not necessarily the molar ratio in which these two compounds are present in the molar ratio. the liquid phase of the fuel, even if both compounds are present in completely dissolved form. This is due to the fact that in the liquid phase these compounds will usually be present in dissociated form. For example, if at the same time a compound that provides hydroxide ions
such as NaOH is used, this compound will also present itself in dissociated form in the liquid phase, thereby increasing the concentration of sodium cations in relation to the potassium cations in the liquid phase and, consequently, increasing the concentration of NaBH 4. in relation to that of KBH4. Taken by the same, if NaBH4 is used as the only borohydride compound and KOH is used as the only compound that provides hydroxide ions, a corresponding solution could contain not only NaBH4, but also KBH4. In other words, if only one type of hydride compound is used (eg, only two or more borohydrides), the properties of a corresponding solution (fuel) are determined, inter alia, by the relative proportions of all cations (metallic). ) that occur in the solution, that is, not only the relative proportions in which these cations occur in the hydride compounds used. Preferably, a fuel composition of the present invention comprises one or more hydride compounds in a total concentration of at least about 0.5 moles per liter of composition (the composition including a liquid phase and an optionally present solid phase of undissolved material), by
example, in a total concentration of at least about 1 mole per liter, at least about 2 moles per liter, at least about 3 moles per liter, at least about 4 moles per liter, or at least about 5 moles per liter of liquid phase . The concentration may still be higher, especially in the case of fuel concentrates. Also, the liquid phase of a fuel composition of the present invention preferably comprises hydroxide ions in a concentration of at least about 0.01 moles per liter, for example, about 0.05 moles per liter, about 0.1 moles per liter, about 0.5 moles per liter. liter, at least about 1 mole per liter, at least about 1.5 moles per liter, at least about 2 moles per liter, at least about 3 moles per liter, or even at least about 6 moles per liter. On the other hand, the ionic hydroxide concentration is preferably not greater than about 8 moles per liter, for example, not greater than about 7 moles per liter. Especially in the case of fuel concentrates the ionic hydroxide concentration will often be greater than about 7 moles per liter, for example, up to about 14 moles per liter, or up to
approximately 12 moles per liter. One skilled in the art will recognize that the compositions of the present invention may optionally comprise various other components whose presence in the fuel may be desirable., at least while these other components do not significantly interfere with the intended use of the fuel composition. By way of non-limiting example, the compositions may comprise additives such as, for example, stabilizers. Preferred stabilizers include aromatic and aliphatic amines. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further described in the detailed description that follows, with reference to the indicated plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, wherein: Fig. 1 shows a curve discharge in a direct fuel borohydride-air fuel cell prepared according to Example 1; Fig. 2 shows a discharge curve in a direct borohydride-air fuel cell of the fuel prepared according to Example 2; Fig. 3 shows a discharge curve in a
direct fuel borohydride-air fuel cell prepared according to Example 3; and Fig. 4 shows a discharge curve in a direct borohydride-air fuel cell of the fuel prepared according to Example 4. DETAILED DESCRIPTION OF THE INVENTION The particulars shown herein are by way of example and for discussion purposes. illustrative of the embodiments of the present invention only and are presented in the cause of providing what is the most useful and easily understood description of the principles and conceptual aspects of the present invention. In this aspect, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description making apparent to those skilled in the art how various forms of the present invention may be included in the practice. Example 1 (comparative) A fuel of the following composition (in% by weight) is prepared: Water 58% KOH 23% KBH4 19%
The discharge curve of this fuel at a constant voltage of 0.6 V in a direct borohydride-air fuel cell (anode area = 17 cm2, volume of fuel 55 ce) is shown in Fig. 1. The discharge energy of the fuel is 13.8 h / 24h. Example 2 A fuel of the following composition (in% by weight) is prepared: Water 71% KOH 10% NaOH 7% NaBH4 7% KBH 5-_ The discharge curve of this fuel at a constant voltage of 0.6 V in a cell of direct borohydride-air fuel (anode area = 17 cm2; fuel volume 55 ce) is shown in Fig. 2. The fuel discharge energy is 16.2 Wh / 24h. Example 3 A fuel of the following composition (in% by weight) is prepared: Water 67% KOH 10% NaOH 7% NaBH4 9.5%
KBH4 6.5% The discharge curve of this fuel at a constant voltage of 0.6 V in a direct borohydride-air fuel cell (anode area = 17 cm2, fuel volume 55 ce) is shown in Fig. 3. The Fuel discharge energy is 18 Wh / 24h. Example 4 A fuel of the following composition (in% by weight) is prepared: Water 64.9% KOH 14.6% NaOH 3.5% KBH4 14% NaBH4 3% The discharge curve of this fuel at a constant voltage of 0.6 V in a cell of direct borohydride-air fuel (anode area = 17 cm2, fuel volume 55 ce) is shown in Fig. 4. Fuel discharge energy is 19.2 h / 24h. It is pointed out that the foregoing examples have been provided purely for the purpose of explanation and are in no way to be construed as limiting the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words that have been
used in the present are words of description and illustration, instead of words of limitation. The changes can be made, within the scope of the appended claims, as currently established and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference in particular to the medium, materials and embodiments, the present invention is not intended to be limited to the particulars described herein; in turn, the present invention extends to all structures, methods and uses, functionally equivalent, such as those within the scope of the appended claims.