Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B6/00—Hydrides of metals including fully or partially hydrided metals, alloys or intermetallic compounds ; Compounds containing at least one metal-hydrogen bond, e.g. (GeH3)2S, SiH GeH; Monoborane or diborane; Addition complexes thereof
  • C01B6/06—Hydrides of aluminium, gallium, indium, thallium, germanium, tin, lead, arsenic, antimony, bismuth or polonium; Monoborane; Diborane; Addition complexes thereof
  • C01B6/10—Monoborane; Diborane; Addition complexes thereof
  • C01B6/13—Addition complexes of monoborane or diborane, e.g. with phosphine, arsine or hydrazine
  • C01B6/15—Metal borohydrides; Addition complexes thereof
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B6/00—Hydrides of metals including fully or partially hydrided metals, alloys or intermetallic compounds ; Compounds containing at least one metal-hydrogen bond, e.g. (GeH3)2S, SiH GeH; Monoborane or diborane; Addition complexes thereof
  • C01B6/06—Hydrides of aluminium, gallium, indium, thallium, germanium, tin, lead, arsenic, antimony, bismuth or polonium; Monoborane; Diborane; Addition complexes thereof
  • C01B6/10—Monoborane; Diborane; Addition complexes thereof
  • C01B6/13—Addition complexes of monoborane or diborane, e.g. with phosphine, arsine or hydrazine
  • C01B6/15—Metal borohydrides; Addition complexes thereof
  • C01B6/19—Preparation from other compounds of boron
  • C01B6/23—Preparation of borohydrides of other metals, e.g. aluminium borohydride; Addition complexes thereof, e.g. Li[Al(BH4)3H]

Definitions

• This invention relates to solution synthesis of mixed metal borohydrides. These compounds can be used to store and release hydrogen for many different applications, including fuel cells.
• PEM fuel cells proton exchange membrane (PEM) fuel cells; their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special polymer electrolyte membrane.
• the fuel in a PEM fuel cell is typically hydrogen; in order to utilize hydrogen for a consumer electronic device fuel cell, it needs to be delivered or supplied as part of a solid material that can store it.
• a hydrogen storage cartridge In order to be competitive with lithium ion battery technology, a hydrogen storage cartridge must achieve volumetric energy densities on the order of 1200 Wh/L.
• the amount of fuel required in the hydrogen storage cartridge such that 1200 Wh/L are provided depends on the fuel material density and gravimetric hydrogen density.Because hydrogen has poor energy content per volume (0.01 kJ/L at standard temperature and pressure (STP) and 8.4 MJ/L for liquid hydrogen vs. 32 MJ/L for petroleum), physical transport and storage as a gas or liquid is impractical. Additionally, the compression process to achieve the pressures necessary to reach a high density is energy-intensive and doesn't solve the hazard issue. Also, the densities of compressed H 2 are still below those required to reach practical fuel storage goals.
• Physical means to store hydrogen include complex hydrides such as metal alanates, amides, and borohydrides.
• Complex hydrides are salts consisting of a metal cation and an anion containing hydride such as tetrahydroborate [BH 4 ] ⁇ and tetrahydroaluminate [AIFU]-.
• the hydrogen in complex hydrides can be released hydrolytically, which is essentially an irreversible process, and by heating or reduction of vessel pressure, which are reversible processes if a pressure increase or temperature decrease also leads to readsorption of hydrogen.
• thermodynamic tuning is the investigation of alkali and alkaline earth metal mixed cation alanates and borohydrides (Graetz, J. Chem. Soc. Rev. 2009, 38, 73-82.). These types of compounds could include new compositions (inorganic ate complexes), reactive hydride composites (i.e., react during heating in the solid state and release hydrogen at temperatures below that of the constituent borohydrides), or react on heating as a simple mixture of constituent borohydrides (in other words, not be useful for the production of hydrogen gas).
• Mixed metal borohydride materials have been studied by many research groups in the past five to ten years.
• the synthetic methods used to prepare these materials can be divided into three groups: solution synthesis, solid-state mechanochemical synthesis such as ball-milling, and high temperature/pressure synthesis (Hagemann, H.; Cerny, R. Dalton Trans. 2010, 39, 6006-6012.).
• solution synthesis solid-state mechanochemical synthesis
• high temperature/pressure synthesis Hagemann, H.; Cerny, R. Dalton Trans. 2010, 39, 6006-6012.
• the most prevalent method currently being used for the synthesis of the reported mixed metal borohydride ate complexes is ball-milling.
• mechanochemical synthesis particularly for the synthesis of highly reactive materials, is the difficulty preparing pure, halogen-free samples of the expected products. Purification after mechanochemical synthesis is labor-intensive and can be difficult.
• High temperature/pressure synthesis is neither convenient nor scalable in a practical sense, since material impurities can have a profound impact on dehydrogenation temperature and material stability.
• the objectives of the present invention include providing new mixed metal borohydride complexes that are suitable for solid hydrogen storage at practical operating conditions.
• the complexes are preferably stable under ambient conditions, including ambient air and temperature conditions.
• the objectives include complexes that can release hydrogen within a temperature range of 100°C to 400°C and more preferably within a range of 100°C to 250°C.
• the objectives also include having a hydrogen storage material that has shelf stability.
• the objectives also include creating complexes with lower reaction temperatures and/or greater hydrogen storage capacities than any of the parent compounds.
• the hydrogen generating apparatus can include a housing; a pellet strip including a flexible carrier and a plurality of pellets disposed on the carrier, each pellet including a mixed metal borohydride that will release hydrogen gas when heated; an ignition system comprising a heater; and a feed system configured to feed the pellet strip to sequentially position one or more pellets in proximity to the heater such that the heater is capable of heating the proximal pellet to release hydrogen gas.
• a pellet strip including a flexible carrier and a plurality of pellets disposed on the carrier, each pellet including a mixed metal borohydride that will release hydrogen gas when heated
• an ignition system comprising a heater
• a feed system configured to feed the pellet strip to sequentially position one or more pellets in proximity to the heater such that the heater is capable of heating the proximal pellet to release hydrogen gas.
• Embodiments can include one or more of the following features:
• the hydrogen generator includes a plurality of pellet strips; the plurality of pellet strips can be disposed on a single reel, or at least one pellet strip can be disposed on each of a plurality of reels;
• the pellet strip is in a folded configuration, preferably in a Z-fold pattern
• the hydrogen generator includes a plurality of pellet strips
• the carrier is in the form of a strip with surfaces on opposite sides thereof; the pellets can be disposed on one of the surfaces of the carrier, or the pellets can be disposed on both surfaces of the carrier; the pellets can be disposed in a linear array along the carrier; the pellets can be disposed in a plurality of linear arrays along the carrier;
• the pellet strip is disposed in a storage compartment within the housing;
• the hydrogen generator comprises a plurality of storage compartments within the housing, each configured to contain at least one pellet strip; each compartment can have a feed system configured to feed the at least one pellet strip therein;
• the storage compartment is defined by a moveable wall; the moveable wall can be
• the moveable wall can separate the storage compartment from a waste compartment within the housing; a portion of the feed system can be moveable together with the moveable wall;
• the feed system includes a sprocket that cooperates with the pellets disposed on the
• the sprocket can be an indexing sprocket
• the feed system can include a ratchet configured to allow the carrier to be advanced in only one direction
• the feed system can include a bellows that engages an escapement to rotate the sprocket
• the ignition system includes more than one heater; • the pellet strip is contained in a user-replaceable container;
• each pellet includes at least one mixed metal borohydride
• the pellet includes an ignition material.
• the hydrogen generator includes a sealable housing having an openable member and a hydrogen outlet; a plurality of fuel units removably disposed within the housing, each fuel unit including a casing containing a stack of pellets, and each pellet containing at least one mixed metal borohydride capable of producing hydrogen gas when heated; and a heating system for selectively heating one or more pellets to produce hydrogen gas.
• the heating system includes a plurality of heating elements disposed on an inside surface of the housing, each heating element in contact with a portion of the fuel unit casing that is in contact with one or more of the pellets contained therein. Heat selectively produced by one of the heating elements can be conducted through the corresponding portion of the fuel unit casing to heat one or more of the pellets.
• Embodiments can include one or more of the following features:
• the heating system can further include a plurality of heat concentrators, each heat concentrator in contact with and configured to conduct heat to, a portion of a pellet; the heat concentrators can be disposed on external surfaces of the pellets; the heat concentrators can be at least partially disposed within the pellets; a single heat concentrator can be in contact with a single pellet; a single heat concentrator can be in contact with more than one pellet; more than one heat concentrator can be in contact with a single pellet;
• the fuel unit includes thermal insulation between adjacent pellets
• each fuel unit casing includes a metal such as aluminum or stainless steel;
• each fuel unit includes a hydrogen exit
• the hydrogen generator can include one or more hydrogen flow paths from the hydrogen exits to the hydrogen outlet; one or more filters can be disposed within a portion of the one or more hydrogen flow paths;
• the housing includes thermal insulation
• the hydrogen generator includes at least a portion of a control system for controlling the selective heating of the pellets; the control system can be configured to monitor at least one of temperature and pressure and selectively heat one or more pellets based at least in part on at least one of the temperature and pressure.
• a hydrogen generator including a cartridge, a compartment configured to removably contain the cartridge, and an ignition system.
• the cartridge includes a sealed casing with a side wall, a base wall, and a lid; a plurality of pellets, each comprising at least one mixed metal borohydride capable of producing hydrogen gas when heated; a heat concentrator in direct contact with the casing and capable of conducting heat from the casing to the at least one reactant; a hydrogen outlet valve in the casing; and a hydrogen flow path from each fuel pellet to the hydrogen outlet valve.
• the compartment includes a housing with a side wall and a lid; a hydrogen outlet through the housing; a cavity within the housing within which the cartridge can be disposed; and a plurality of heating elements disposed on an inside surface of the housing, such that each heating element is in contact with an outer surface of the cartridge casing and aligned with a heat concentrator when the cartridge is disposed within the cavity.
• the ignition system includes the heat concentrators, the heating elements, and circuitry for conducting an electric current to the heating elements, such that the electrical current can be applied selectively to one or more heating elements for generating heat to selectively heat one or more pellets to initiate a reaction to produce hydrogen gas.
• Embodiments can include one or more of the following features:
• the cartridge has a cylindrical shape
• the cartridge has a prismatic shape
• the cartridge and the compartment cooperate such that the cartridge can be inserted into the compartment only such that the heating elements and the heat concentrators are properly aligned;
• pellets are arranged in multiple layers, each layer having a single pellet;
• pellets are arranged in multiple layers, each layer containing more than one pellet;
• each heat concentrator has a cartridge casing contact portion that extends beyond the pellet
• each heat concentrator comprise aluminum
• each heat concentrator comprises a layer of pyrolictic carbon in contact with the pellet
• the heat concentrators are in pressure contact with the inside surface of the casing; • a thermally insulating material is disposed between at least portions of adjacent pellets; a layer of the insulating material can separate layers of the pellets; pellet surfaces can be coated with a layer of the insulating material;
• the portion of the cartridge casing that makes contact with the heating element comprises stainless steel or aluminum
• the housing comprises a material with low electrical and thermal conductivity
• the heating elements are disposed on an inside surface of at least one of the side wall, the lid and the door of the housing;
• the heating elements make pressure contact with the outer surface of the cartridge casing when the cartridge is disposed within the compartment;
• the cartridge can include means for maintaining contact between the heat concentrators and the solid compositions and/or maintaining alignment between the heat concentrators and the heating elements as the heat generator is being used;
• the hydrogen flow path comprises a channel extending through all layers of pellets; the hydrogen flow path can include a central channel; the hydrogen flow path can comprise more than one channel;
• the cartridge comprises a foil seal over the hydrogen outlet valve prior to insertion of the cartridge into the compartment; the foil seal can be broken upon insertion of the cartridge into the compartment;
• the pellets further comprise an ignition material, preferably at least one material selected from the group of iron powder plus KC10 4 , TiH 2 plus CIO4, Mn0 2 plus L1AIH4, Ni plus Al, Zr plus PbCr0 4 , Fe 2 0 3 plus Al, and LiAlH 4 plus NH 4 C1.
• an ignition material preferably at least one material selected from the group of iron powder plus KC10 4 , TiH 2 plus CIO4, Mn0 2 plus L1AIH4, Ni plus Al, Zr plus PbCr0 4 , Fe 2 0 3 plus Al, and LiAlH 4 plus NH 4 C1.
• a hydrogen generator including a cartridge including a sealed casing and a plurality of pellets stacked within the casing, each pellet containing at least one mixed metal borohydride capable of producing hydrogen gas when heated; a compartment including a housing, a hydrogen outlet through the housing, and a cavity within the housing within which the cartridge can be removably disposed; and an induction heating system.
• the induction heating system includes a plurality of secondary coils within the cartridge casing, with each secondary coil in contact with one or more of the pellets.
• the induction heating system also includes at least one primary coil within the compartment housing.
• the induction heating system is configured to receive an electric current from a power source, provide an electromagnetic field from a flow of the current in the at least one primaiy coil, induce an electric current in the at least one secondary coil, and provide heat from a flow of the induced electric current; thereby heating the pellets.
• the cartridge has a cylindrical shape
• the cartridge has a prismatic shape
• pellets are arranged in multiple layers, each layer having a single pellet;
• each pellet is in contact with a secondary coil; each pellet can be in contact with a separate secondary coil; more than one pellet can be in contact with the same secondary coil;
• the at least one secondary coil is disposed at least partially within a pellet
• the induction heating system includes a moveable primary coil
• the induction heating system includes a plurality of primary coils; the primary coils can be adjacent to, on or at least partially recessed in an inner surface of the compartment housing;
• the cartridge can include means for maintaining contact between the solid compoistions and the secondary coils;
• the cartridge can include means for maintaining alignment between the secondary coils and the primary coils as the heat generator is being used;
• the hydrogen flow path comprises a channel extending through and/or around the pellets;
• the hydrogen flow path can include a central channel;
• the hydrogen flow path can comprise more than one channel;
• the cartridge comprises a foil seal over the hydrogen outlet valve prior to insertion of the cartridge into the compartment; the foil seal can be broken upon insertion of the cartridge into the compartment;
• the pellets further comprise an ignition material, preferably at least one material selected from the group of iron powder plus KCIO4, TiH 2 plus KCIO4, Mn0 2 plus L1AIH4, Ni plus Al, Zr plus PbCr0 4 , Fe 2 0 3 plus Al, and L1AIH4 plus NH 4 C1.
• an ignition material preferably at least one material selected from the group of iron powder plus KCIO4, TiH 2 plus KCIO4, Mn0 2 plus L1AIH4, Ni plus Al, Zr plus PbCr0 4 , Fe 2 0 3 plus Al, and L1AIH4 plus NH 4 C1.
• a fuel cell system including a fuel cell with an anode, a cathode, and an electrolyte that that is used with any of the hydrogen generators as described herein. Hydrogen gas from a hydrogen generator is supplied to the anode of the fuel cell.
• Embodiments can include one or more of the following features:
• the fuel cell system further includes a control system configured to control an ignition system and a feed system based on at least one of a pressure within the fuel cell system, an electrical characteristic of the fuel cell system, or an electrical characteristic of an electronic device in electrical communication with the fuel cell system;
• the control system can include at least one of a microprocessor, a micro controller; digital circuitry, analog circuitry, hybrid digital and analog circuitry; a switching device; a capacitor, and sensing instrumentation.
• the fuel cells are "stacked,” or placed in series or parallel circuits, to increase the voltage and current output to meet an application's power generation requirements.
• the fuel cell system includes a control system for controlling the selective heating of the pellets; a portion of the control system can be disposed within the hydrogen generator; a portion of the control system can be disposed outside the hydrogen generator.
• the ignition system is configured to monitor at least one of temperature and pressure and selectively heat one or more pellets to provide hydrogen as needed by the fuel cell stack.
• a method of producing a mixed metal borohydride includes preparing a first precursor solution consisting essentially of a homometallic borohydride compound and a solvent, the homometallic borohydride being lithium borohydride; preparing a second precursor solution consisting essentially of a borohydride compound containing one or more metal cations selected from the group of metals consisting of sodium, magnesium, calcium and titanium; combining the first and second precursor solutions to create a mixture; forming the mixed metal borohydride in the mixture; and removing the solvent from the mixture containing the mixed metal borohydride to produce a solid mixed metal borohydride.
• Embodiments of the invention can include one or a combination of the following:
• a third precursor solution consisting essentially of a third borohydride
• the compound different from the borohydride compound in the second precursor solution and containing one or more metal cations selected from the group of metals consisting of sodium, magnesium, calcium and titanium, and wherein the third precursor solution is combined with the first and second precursor solutions to create the mixture;
• the second precursor solution consists essentially of one or more of sodium borohydride, magnesium borohydride, calcium borohydride and titanium borohydride;
• the second precursor solution consists essentially of calcium borohydride
• the second precursor solution consists essentially of titanium borohydride;
• the solid mixed metal borohydride can be Li 3 Ti(BH 4 ) 2 ;
• the second precursor solution consists essentially of sodium borohydride and titanium borohydride;
• the solid mixed metal borohydride can contain less than 5 atomic weight percent of titanium;
• the second precursor solution consists essentially of sodium borohydride, calcium
• the solid mixed metal borohydride can contain less than 5 atomic weight percent of titanium
• the second precursor solution consists essentially of magnesium borohydride
• the solid mixed metal borohydride can be Li 2 Mg(BH 4 ) 2
• the solid mixed metal borohydride can be Li 3 Mg(BH 4 ) 5 ;
• the solid mixed metal borohydride is coated; the solid mixed metal borohydride can be coated with an inert material.
• FIG. shows an illustration of the particle size optimization and encapsulation of the mixed metal borohydrides.
• mixtureed metal borohydrides means a borohydride compound that contains two or more different metals
• nanoparticle refers to particle or a structure in the nanometer (nm) range, typically from about 0.1 nm to about 1000 nm in diameter;
• THF tetrahydrofuran
• GC/MS means gas chromatography/mass spectrometry.
• the borohydrides of the alkaline earth and light transition metals Mg(BH 4 ) 2 , A1(BH4) 3 , Mn(BH 4 ) 2 , Zn(BH 4 ) 2 , Zr(BH 4 ) 4 , Ti(BH 4 ) 3 , and Sc(BH 4 ) 3 are for the most part known compounds and their solution synthesis has been described. Briefly, these compounds are prepared as follows according to literature reports.
• a toluene solution of aluminum borohydride (A1(BH 4 ) 3 ) was prepared in 78% yield by reaction of purified A1C1 3 with lithium borohydride, followed by distillation of the filtrate.
• Titanium Borohydride (Mirviss, S.B.; Dougherty, H.W.; Looney, R.W. US3,310,547 March 21 , 1967.): A THF solution of titanium borohydride (Ti(BH ) 3 ) was prepared by reaction of titanium tetraisopropoxide with diborane in THF. The titanium was reduced from the +4 to +3 valence state during the reaction. When complexed with two and three molecules of THF the titanium compounds are blue and reddish-violet crystalline solids, respectively.
• a THF solution of zinc tetrahydroborate (Zn(BH 4 ) 2 ) was prepared by reaction of two equivalents of sodium borohydride with ZnCl 2 in THF in quantitative yield. The supernatant liquid was free of chloride according to a silver nitrate test. The solution could be stored under N 2 and used as required.
• Table 1 shows the gravimetric hydrogen density of the homometallic borohydride compounds on the left and some mixed metal borohydride compounds on the right.
• the precursor compounds and the mixed metal borohydride compounds in Table 1 can be described by the generic formulas, such as shown in Tables 2A and 2B.
• the binary (i.e., two metals) complex hydride compositions are derived by the combination of parent compounds from the different groups.
• the mixed metal borohydride compounds can have more than two metals.
• Table 2A shows groups of homometallic borohydride precursor compounds.
• Groups A and B can be prepared using solution methods or purchased if commercially available. By combining a compound from Group A with one from Group B in the appropriate stoichiometry and removal of solvent, a wide variety of mixed metal borohydride ate complexes or reactive borohydride complexes can be synthesized, as seen in the list in the block on the right of Table 3, where the Na and cations in parentheses are alternatives to Li. Although illustrated using a 1 : 1 mole ratio of a compound from Group A with Group B, other mole ratios can be used. The materials can be converted to nanoparticles, or directly prepared as a monodispersion of nanoparticles in the target size range of 5-50 nm. It is believed that particle size can effect the dehydrogenation temperature.
• coating protocols can be used to create a stabilizing shell of inert material.
• the goal of the stabilization is both chemical, to reduce the flammability of the materials and prevent degradation, and mechanical, to reinforce the material so that any structural changes during dehydrogenation (and potentially, rehydrogenation cycles) are accommodated without loss of reactivity.
• the shell layer very thin compared to the size of the core, the impact on gravimetric and volumetric hydrogen density is minimized.
• having a hydrogen storage compound that can release hydrogen with a 100° to 400°C range is preferred. Even more preferential is a range of 100° to 250°C.
• the following compounds are ones that should release hydrogen within the preferred reange. As the gravimetric capacity increases, a higher desoption temperature is allowable given the benefit of hydrogen storage and release capacity.
• Li 3 Mg(BH 4 )5 and some characterization was carried out.
• the Mg(BH 4 ) 2 was prepared using literature methods and blended with a commercial solution of LiBH 4 in ether at low temperature.
• Li 2 Mg(BH 4 ) 2 began to evolve H 2 at 130°C and delivered 10.5 wt% H 2 after heating to 375°C.
• the Li 3 Mg(BH 4 ) 5 sample began to lose H 2 at 166°C and delivered 7.8wt% H 2 after heating to about 370°C.
• the additional weight loss in the TGA is probably residual solvent, as the GC/MS analysis of the headspace only showed trace amounts of solvents and did not show the presence of diborane/pentaborane.
• Li 3 Ti(BH 4 ) 6 by blending a commercial solution of LiBH in ether with Ti(BH 4 ) 3 »THF prepared using literature methods (Franz, .; Fusstetter, H.; Noth, H. Z anorg. Allg. Chemie 1976, 427(2), 97-1 13.). Upon thermolysis the tarry aubergine colored material began to release H 2 at 159°C and delivered 7.3wt% H 2 after heating to 292°C.
• the particle size can be optimized and coating protocols can be used to create a stabilizing shell of inert material, as illustrated in the FIG.
• coating protocols can be used to create a stabilizing shell of inert material, as illustrated in the FIG.
• thin polyelectrolyte or polymer-inorganic hybrid coatings can be added using layer-by-layer self-assembly techniques, such as described by Dobbins et al. ⁇ Material Matters 2007, 2(2) 19) and others (Broderick et al., Chem. Mater. 2012, 24(10), 1786; Borodina et al., ACS Applied Mater. Interfaces 2009, 1 (15) 996) for encapsulation of metal hydrides.
• uncharged polymers can be deposited on metal borohydrides using an interfacial polymer precipitation protocol that is induced by solvent evaporation (Borodina et al., J. Materials Chemistry 2010, 20(8), 1452).
• the mixed metal borohydrides can be formed into nanoparticles that can be encapsulated.
• the goal of the stabilization is both chemical, to reduce potential flammability of the materials and prevent degradation, and mechanical, to reinforce the material so that any structural changes during dehydrogenation are accommodated and volume expansion is minimized.
• the shell layer very thin compared to the size of the core, the impact on gravimetric and volumetric hydrogen density is minimized.
• Mg(BH 4 ) 2 was prepared from dibutylmagnesium and borane-methyl sulfide complex as described in the literature (Zanella, P.; et al. Inorg. Chem. 2007, 46, 9039-9041 ).
• a 0.5 M solution of Mg(BH 4 ) 2 was prepared by dissolving 0.498 g of Mg(BH 4 ) 2 (9.22 mmol) in 10 mL of anhydrous diethyl ether with stirring under Ar at room temperature.
• a commercial 0.5 M LiBH 4 in diethyl ether was added to the Mg(BH 4 ) 2 solution using a canula.
• Li 3 Mg(BH ) 5 complexed with residual solvent was obtained after drying on a vacuum line overnight at room temperature.
• the Li 3 Mg(BH ) 5 sample began to lose H 2 at 166°C and delivered 7.8 wt% H 2 (measured) after heating to about 370°C.
• Mg(BH 4 ) 2 is prepared from dibutylmagnesium and borane-methyl sulfide complex as described in the literature (Zanella, P.; el al. Inorg. Chem. 2007, 46, 9039-9041 ).
• a 0.5 M solution of Mg(BH 4 ) 2 is prepared by dissolving 0.27 g (5.00 mmol) of Mg(BH 4 ) 2 in 10 mL of anhydrous diethyl ether with stirring under Ar at room temperature.
• a commercial 0.5 M LiBH 4 in diethyl ether (20 mL, 10.00 mmol) is combined with a solution of NaBH prepared by dissolving 0.19 g ofNaBH in 10 mL of anhydrous 1 ,2-dimethoxy ethane.
• the Mg(BH 4 ) 2 solution is added to the LiBLL aBLL solution using a syringe.
• the resulting mixture is stirred overnight at room temperature.
• the solvent is removed in vacuo and the resulting product (Li 2 NaMg(BH 4 ) 5 ) is dried on a high vacuum line overnight.
• This material contains
• A1(BH 4 ) 3 (1.42 g, 19.889 mmol) is prepared as described by Zhao, J-C, et al. (J Phys. Chem. C. 2009, 113, 2) and dissolved in anhydrous diethyl ether as described by Bird and Wallbridge (J. Chem. Soc. 1965, 3923).
• a commercial 0.5 M L1BH4 in diethyl ether (53 mL, 26.52 mmol) is added to the A1(BH 4 ) 3 solution by syringe at -78°C.
• the resulting mixture is allowed to warm slowly to room temperature and stirred for three hours under Ar.
• the solvent is removed in vacuo and the resulting product (Li 4 Al 3 (BH 4 )i3) is dried on a high vacuum line overnight.
• This material contains approximately 17.2 wt% 3 ⁇ 4 (theoretical).
• Titanium borohydride (Ti(BH4)3) was prepared as the THF complex by reacting titanium (IV) isopropoxide (Aldrich, 2.22 mL, 0.008 mol) with borane-tetrahydrofuran (Aldrich, 1 M solution in THF, 33 mL, 0.033 mol) in 10 mL of anhydrous THF at 0°C with stirring for two hours under argon atmosphere (Mirviss, S.B.; Dougherty, H.W.; Looney, R.W.
• Titanium borohydride (Ti(BH 4 ) 3 ) is prepared as the THF complex by reacting titanium (IV) isopropoxide (Aldrich, 2.22 mL, 7.5 mmol) with borane-tetrahydrofuran (Aldrich, 1 M solution in THF, 33 mL, 0.033 mol) in 10 mL of anhydrous THF at 0°C with stirring for two hours under Argon atmosphere (Mirviss, S.B.; Dougherty, H.W.; Looney, R.W.
• A1(BH 4 ) 3 (1.31 g, 18.271 mmol) is prepared as described by Zhao, J-C, et al. (J Phys. Chem. C. 2009, 113, 2) and dissolved in 40 mL of anhydrous diethyl ether as described by Bird and Wallbridge (J. Chem. Soc. 1965, 3923).
• a commercial solution of 1.0 M LiAlFL in diethyl ether (18.3 mL, 18.27 mmol) is added to the A1(B L)3 solution by syringe at -78°C. The resulting mixture is allowed to warm slowly to room temperature and stirred for three hours under argon. The solvent is removed in vacuo and the resulting product (LiAl(AlH 4 )(BH 4 )3) is dried on a high vacuum line overnight. This material contains approximately 14.6 wt% H 2 (theoretical).
• A1(BH 4 ) 3 (0.97 g, 13.579 mmol) is prepared as described by Zhao, J-C, et al. (J. Phys. Chem. C. 2009, 113, 2) and dissolved in 27 mL of anhydrous diethyl ether as described by Bird and Wallbridge (J. Chem. Soc. 1965, 3923).
• Mg(BH 4 ) 2 is prepared from
• a 0.5 M solution of Mg(BH 4 ) 2 is prepared by dissolving 0.733 g (13.579 mmol) of Mg(BH ) 2 in 13.6 mL of anhydrous diethyl ether with stirring under Ar at room temperature.
• the A1(BH 4 ) 3 and Mg(BH 4 )2 solutions are combined at -78°C with stirring under argon by canula transfer of the Mg(BH ) 2 solution into the A1(BH 4 ) 3 solution.
• Mg(BH ) 2 was prepared from dibutylmagnesium and borane-methyl sulfide complex as described in the literature (Zanella, P.; et al. Inorg. Chem. 2007, 46, 9039-9041 ).
• a 0.5 M solution of Mg(BH 4 ) 2 was prepared by dissolving 0.498 g of Mg(BH ) 2 (9.22 mmol) in 10 mLs of anhydrous diethyl ether with stirring under Ar at room temperature.
• a commercial 0.5 M LiBH in diethyl ether 36.86 mL, 18.43 mmol
• Arrays of the synthesized borohydrides were transferred to an ultra-high vacuum (UHV) chamber and degassed at approximately 3 x 10 "9 Torr) for approximately 10 hours. While in the UHV chamber, each of the synthesized borohydrides was tested using Temperature Programmed Desorption, heating each of the microhotplates sequentially, while monitoring the temperature and measuring the hydrogen partial pressure using a mass spectrometer.
• UHV ultra-high vacuum
• the compounds produced included the lithium based mixed metal borohydrides identified in Table 5. These mixed metal borohydrides did not react upon exposure to air and would release hydrogen gas within the 100°C to 260°C temperature range. As a comparison, the metal borohydride precursors used are shown in the lower portion of Table 5. Approximate onset and peak temperatures and gravimetric hydrogen capacities are shown. In general, the onset and peak temperatures for the mixed metal borohydrides in Table 5 were lower than those for the precursor compounds, and in most cases the gravimetric capacities were greater than the combined gravimetric capacities of the precursor compounds.
• the hydrogen generator is a hydrogen gas generating apparatus that produces hydrogen gas that is consumed by the fuel cell to produce electricity for an electronic device.
• the hydrogen generator includes a housing, a mixed metal borohydride as the reactant that will release hydrogen gas when heated, an ignition system including a heater to heat the reactant, and optionally a feed system.
• the reactant is contained in a solid composition that can be segregated into individual quantites of the composition. Quantities of the composition are referred to herein as pellets.
• pellet means a mass of a solid composition that includes a reactant whose reaction is initiated by heating.
• the optional feed system is configured so individual pellets or groups of pellets are sequentially positioned in proximity to the heater, which can heat the pellets to initiate their thermal decomposition and evolve hydrogen gas.
• the ignition system can include a plurality of heaters for heating a plurality of stationary pellets.
• the pellets can be of any suitable size and shape. They can be sized and shaped to fit into the housing in a volume-efficient manner. For example, the pellets can be in the shape of round, oval or prismatic (e.g., trapezoidal, rectangular or square) pills, tablets, wafers, cakes or volumes of powder or granules.
• the pellet size and composition can be chosen to provide a desired quantity of hydrogen from each pellet, based on the size of the fuel cell stack and the power requirements of the electronic device, for example.
• the pellets can be formed in various ways. For example, they can be fed, poured, deposited (e.g., by coating, printing or otherwise applying), or formed (e.g., by molding or shaping) and secured (e.g., by adhering, fastening or the like) onto one or both surfaces of a carrier (e.g., in the form of a strip, ribbon, belt, sheet, string or the like).
• a carrier e.g., in the form of a strip, ribbon, belt, sheet, string or the like.
• strip is intended to include any such carrier configuration.
• the pellets contain at least one mixed metal borohydride reactant that releases hydrogen as the reactant decomposes by heating or otherwise. More than one reactant can be included.
• the pellets can also contain one or more additives.
• additives include binders (e.g., acrylates and styrene block copolymers), stabilizing compounds (e.g., solid bases), reaction accelerators (e.g., solid acids), catalysts as described above, ignition materials as described below, thermally conductive materials (e.g., metals, graphites and combinations and composites thereof), and so on.
• a pellet carrier strip should be sufficiently flexible to be fed by the feed system.
• the carrier including the pellets i.e., the pellet strip
• the carrier including the pellets can be loaded into the housing in a rolled, folded or other configuration.
• a pellet strip is wound on a reel. More than one pellet strip can be disposed on a single reel, or one or more pellet strips can be disposed on separate reels.
• a pellet strip is folded in a Z-fold pattern (i.e., with alternating folds in opposite directions to create a stack of multiple layers of the pellet strip).
• the pellet strip can be disposed in a storage compartment within the housing, or the pellet strip can be disposed in a separate container that can be loaded into or attached to the housing.
• the hydrogen generator can be configured to contain one or more pellet strips, such as with at least one pellet strip in each of a plurality of compartments or containers, each of which can have a separate feed system.
• Pellets can be disposed on the carrier and the pellet strip can be disposed is such a manner as to facilitate feeding and provide a high density of pellets within the hydrogen generator.
• the pellets can be disposed in one or more linear arrays along the carrier, or the pellet strip can be arranged so that pellets on one section of the carrier are nested between pellets on another section of the carrier.
• the carrier can be a material that is not a good conductor of heat.
• the carrier can be made from a material that does not react substantially during the thermal decomposition of the hydrogen containing reactant. This has the advantage of not generating any reaction products that might interfere with the functioning of the hydrogen generator or that would have to be removed from the hydrogen gas before being used by the fuel cell stack.
• the carrier can be made from a material that does react during the thermal decomposition of the hydrogen containing reactant, e.g., by burning. This can eliminate the need to collect and store the carrier after the pellets have been consumed. Examples of materials that can be suitable as carrier materials include polyimides such as KAPTON® from E.I. duPont de Nemours; polypropylene such as
• a feed system feeds the pellet strip to sequentially position pellets, either individually or in groups, in proximity to the heater(s).
• feed systems can be used, such as augers, sprockets, ratchet wheels, and rotating belts.
• the feed system includes a sprocket.
• teeth on the sprocket can engage or create perforations or indentations along the carrier to feed the pellet strip as the sprocket rotates (e.g., in a manner similar to that of a movie projector feeding film).
• the pellets and spaces between them function like the links of a chain that is driven by a sprocket.
• the feed system can include an indexing mechanism for indexing the pellet strip in increments.
• An example of an indexing mechanism is a ratchet, which will only allow movement of the drive mechanism in one direction.
• a ratchet may be mounted on a sprocket, for example.
• the ignition system heater heats one or more pellets positioned in proximity to the heater, resulting in a thermal decomposition reaction of the hydrogen containing reactant in the pellet(s).
• the ignition system can include more than one heater. Multiple heaters can be advantageous when a single heater does not produce sufficient heat, when more than one pellet is to be ignited at one time, when there are more than one stationary pellet, and when the hydrogen generator uses more than one pellet strip for example.
• Various types of heaters can be used. Examples include resistive heaters, infrared heaters, laser heaters, microwave heaters, semiconductor bridges, and so on.
• heating elements can be incorporated into the pellets or into the carrier. Electrical leads from the ignition system can make contact with heating element contacts so current to heat the heating elements is provided when the pellets are positioned in the desired location.
• One or more pellets are positioned in close enough proximity to the heater(s) for the heater(s) to heat the pellet(s) sufficiently that the hydrogen-containing reactant releases hydrogen gas.
• These "proximal" pellets may be spaced apart from the heater(s), or they may make contact with the heater(s).
• the heater can heat the hydrogen containing reactant directly, or it can heat an ignition material (a material that will react exothermally, producing the heat necessary for the thermal decomposition reaction of the hydrogen containing reactant). If the heater initiates reaction of the hydrogen containing reactant directly, the heater may provide heat only long enough to start the reaction, if the reaction is self-sustaining, or it may continue to provide heat for the entire reaction time. If an ignition material is used, the ignition material can be disposed within or in contact with a pellet, the ignition material can be a separate layer of the pellet (i.e., separate from a layer containing the hydrogen containing reactant), or the ignition material can be mixed with the hydrogen containing reactant.
• an ignition material a material that will react exothermally, producing the heat necessary for the thermal decomposition reaction of the hydrogen containing reactant. If the heater initiates reaction of the hydrogen containing reactant directly, the heater may provide heat only long enough to start the reaction, if the reaction is self-sustaining, or it may continue to provide heat for the entire reaction time.
• Examples of ignition materials include thermite (Fe 2 03 plus Al), iron powder plus KC10 4 , TiH 2 plus KCIO4, Mn0 2 plus L1AIH4, Ni plus Al, Zr plus PbCr0 4 , and L1AIH4 plus NH4CI.
• the hydrogen generator can include a waste zone for accumulating decomposing pellets, spent pellets and any residue (e.g., carrier material, ashes or other reaction or combustion byproducts) from the pellet strip.
• the waste zone can be separated from the pellet strip storage compartment by a wall.
• the wall can be a moving wall that defines a portion of the storage compartment. The wall can move as the pellet strip is consumed, thereby reducing the size of the storage compartment and increasing the size of the waste area.
• the hydrogen generator includes more than one storage compartment, it can include a waste zone for the pellet strip in each compartment, or a single waste zone can be associated with more than one storage compartment.
• a portion of the feed system e.g., a feed sprocket
• Operation of the optional feed system, the ignition system or both can be controlled in various ways.
• a control system can be used.
• the control system can determine the need for hydrogen by monitoring the pressure within the fuel cell system, one or more electrical characteristics of the fuel cell stack, or one or more electrical characteristics of the electronic device, for example.
• the controller may communicate with the device or the fuel cell stack to determine when more hydrogen is needed.
• the control system can be completely or partially disposed in the hydrogen generator, the fuel cell stack, the electronic device being powered by the fuel cell stack, or any combination thereof.
• the control system can include a microprocessor or micro controller; digital, analog and/or hybrid circuitry; solid state and/or electromechanical switching devices; capacitors, sensing instrumentation, and so on.
• the housing of the hydrogen generator is made of a material that will withstand the heat and internal pressure that are produced to maintain desired dimensions and an adequate hydrogen seal.
• materials that may be suitable include metals such as aluminum and steel and polymeric materials such as polyphenylene sulfide and acrylonitrile butadiene styrene.
• the hydrogen generator can include various filters and/or purification units to remove undesired reaction byproducts and other contaminants from the hydrogen gas.
• the hydrogen gas can follow a pathway within the hydrogen generator after being released from the mixed metal borohydride fuel source.
• the fillers and/or purification units can be contained within this pathway or external to the hydrogen generator.
• the hydrogen generator can also include various fittings, valves, and electrical connections for providing hydrogen to and interfacing with the fuel cell and/or an electrical appliance being provided with power by the fuel cell system.
• the hydrogen generator can include various safety features such as a pressure relief vent to release excessive pressure and a mechanism to stop the feeding of pellets to the ignition system if the internal temperature exceeds an established limit.

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• 2013
  • 2013-08-12 WO PCT/US2013/054478 patent/WO2014031373A1/fr not_active Ceased

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