Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/75—Cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/745—Iron
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/80—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with zinc, cadmium or mercury
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/847—Vanadium, niobium or tantalum or polonium
  • B01J23/8472—Vanadium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/85—Chromium, molybdenum or tungsten
  • B01J23/88—Molybdenum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/90—Regeneration or reactivation
  • B01J23/94—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the iron group metals or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
  • B01J37/082—Decomposition and pyrolysis
  • B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
  • B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
  • B01J37/344—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of electromagnetic wave energy
  • B01J37/346—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of electromagnetic wave energy of microwave energy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J38/00—Regeneration or reactivation of catalysts, in general
  • B01J38/48—Liquid treating or treating in liquid phase, e.g. dissolved or suspended
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
  • C01B3/02—Production of hydrogen; Production of gaseous mixtures containing hydrogen
  • C01B3/06—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen with inorganic reducing agents
  • C01B3/065—Production of hydrogen; Production of gaseous mixtures containing hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen with inorganic reducing agents by reaction of inorganic compounds with hydrides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
  • C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
  • C08F4/60—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
  • C08F4/62—Refractory metals or compounds thereof
  • C08F4/68—Vanadium, niobium, tantalum or compounds thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
  • C08F4/72—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44
  • C08F4/74—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44 selected from refractory metals
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
  • C08F4/72—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44
  • C08F4/74—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44 selected from refractory metals
  • C08F4/76—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44 selected from refractory metals selected from titanium, zirconium, hafnium, vanadium, niobium or tantalum
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/584—Recycling of catalysts

Definitions

• the present invention relates to a metal oxide or mixed-metal oxide catalyst for hydrogen generation from metal borohydride.
• the invention also relates to a method of making, sintering, activating a metal oxide catalyst, regenerating a deactivated metal oxide catalyst, and the use of the catalyst for oxidative reaction on various chemical systems.
• Transition metal oxides have been employed as a catalyst in a variety of chemical processes, such as oxidation (U.S. Pat. No. 6,124,499), NOx treatment (U.S. Pat. No. 6,916,945), oxidation and ammoxidation of an alkane (U.S. Pat. No. 6,777,571 ), transesterification (U.S. Pat. No. 5,350,879) and oxidative coupling of methane (U.S. Pat. No 4,826,796). Nonetheless, metal oxides or mixed-metal oxides have not been investigated or used for the application of hydrogen generation from metal borohydride solution in our best knowledge.
• the catalytic activity of the metal oxides is closely associated with preparation conditions, electronic structures, degree of crystallization, oxidation states, surface area, and so on. Furthermore, the careful control of surface structures, compositions, phase or particle sizes of the metal oxides may play a critical role for diverse chemical catalyses.
• Hydrogen is one of fundamental gases, which is largely necessitated in synthetic chemical companies. In aspect of clean energy, hydrogen has been gained much attention for the applications of fuel cells, hydrogen combustion engines, turbines etc. Due to recent increasing demands of hydrogen gas, several different methods of hydrogen storage systems have been developed, which include compressed or liquefied hydrogen, H 2 adsorption on carbon nano-tube, activated carbon, or metals or mixed metal alloys. Compressed or liquefied H 2 is relatively easy to control the H 2 flow rate and pressure, but involves potential safety issues. The adsorption methods for H 2 storage also have many problems including low hydrogen density per unit volume, deterioration of the materials, and slow response time for H 2 generation, etc. Recently, hydrogen generation from aqueous borohydride solution using a catalyst has stirred many interests in scientific communities since it is not only stable in normal operation condition, but also releases hydrogen gas in safe and controllable way.
• the present invention provides a catalyst for hydrogen generation having high hydrogen generation efficiency and low manufacturing cost.
• the present invention also provides a method of manufacturing a catalyst for hydrogen generation having high hydrogen generation efficiency and low manufacturing cost.
• the present invention also provides another method of manufacturing a catalyst for hydrogen generation having high hydrogen generation efficiency and low manufacturing cost.
• the present invention also provides a method of regenerating a deactivated catalyst for hydrogen generation.
• a hydrogen generation catalyst comprising one or more metal oxides.
• a method of making the hydrogen generation catalyst from a metal source comprising oxidations of the metal in a temperature of about 200 to about 1200 degrees centigrade in the air or ozone.
• a method of making the metal oxide catalyst from a metal compound comprising decomposing the metal compound by heating.
• a method of regenerating deactivated metal oxide catalyst for hydrogen generation comprising: (a) sonicating the catalyst in solvent;
• FIG. 1 shows an X-ray diffraction pattern of an iron oxide catalyst according to an embodiment of the present invention.
• FIG. 2 shows a graph of hydrogen flow rate versus time for a Co 3 Fe 2 -oxide catalyst prepared from a glycine-nitrate process.
• FIG. 3 shows a graph of hydrogen flow rate versus time for a CoFe 4 -mixed oxide catalyst prepared from thermal oxidation in a microwave oven.
• FIG. 4 shows a graph of hydrogen flow rate versus time for a partially sintered Fe- oxide catalyst prepared from thermal oxidation in a microwave oven.
• FIG. 5 shows a graph of hydrogen flow rate versus time for a sintered Fe-oxide catalyst prepared from thermal oxidation in a microwave oven, and sintered at 1150 degree C.
• FIG. 6 shows a plot of maximum hydrogen flow rates versus a Co/Fe molar ratio for Co-Fe oxide catalysts prepared from a glycine-nitrate process.
• the present invention is directed to provide a cost-effective metal oxide catalyst for hydrogen generation having a high performance catalytic activity.
• the present invention also provides a method of making a supported and an unsupported catalyst based on metal oxides and a process of hydrogen generation.
• the present invention provides catalysts for hydrogen generation including one or more metal oxides.
• the metal oxide may include one or more transition metal oxides.
• the metal oxide catalyst for hydrogen generation comprises one or more transition metal oxide comprising oxides of metal elements selected from a group of Sc, T, V, Cr, Mn 1 Fe, Ni, Cu 1 Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and mixtures thereof, wherein transition metal oxide has mono, multiple oxidation states, or mixtures thereof.
• the transition metal oxides herein comprising oxides of metal elements selected from a group of Fe, Co, Ni, Cu, Ru, Rh, and mixtures thereof).
• the metal oxide catalyst comprises one or more transition metal oxides coupled with one or more non-transition metal oxides, wherein non-transition metal comprises Li, Na, Sr, K, Rb Cs, Fr, Mg, Ca, Sr, Ba, Ra, Al, Si, Fe, Ga, In, Sn, Pb or mixtures thereof.
• Some mixed-metal oxides show an inhibiting effect on hydrogen generation. Oxides of metal elements selected from Mo, Zn, V, W, and so on possessing an agtanotic effect on hydrogen generation are also useful for controlling hydrogen flow rates.
• the hydrogen generation catalyst herein refers to, but not particularly limited to, mixed-metal oxides comprising oxides of metal elements selected from Fe, Co, Cu, Ni, Ru, Rh, and a combination thereof.
• the oxidation states of those metals may be mono, multiple, or mixtures thereof.
• the ratio of Co to Fe may range from 0.001 to 1000. If the ratio of Co to Fe is less than 0.001 , hydrogen is hardly generated. If the ratio of Co to Fe is greater than 1000, the generation rate of hydrogen does not increase any more and since Co is expensive, it is not economical.
• mixed-metal oxide catalysts show not only higher catalytic activity due to a synergistic effect, but also much shorter activation time compared to single metal oxide catalysts.
• the metal or mixed-metal oxide may be coupled with ferromagnetic materials.
• the metal oxide catalyst can have a form of powder, chip, disk, rod, wire, mesh, bead, monolith with/without porosity, strip with/without porosity, or metal oxide particles supported on a substrate comprising metals, ceramics, polymers, glass, fibers, fabrics, textiles, wovens, nonwovens, alloys, zeolites, molecular sieves, ion exchange resins, graphite, metal oxide, metal carbide, metal boride, metal nitride, and mixtures thereof.
• the metal oxide may be supported by a carrier, or may be in the form of unsupported catalyst.
• the surface area of the metal oxide catalyst may range from 1 m 2 /g to 500 m 2 /g.
• the preparation of metal oxide may be carried out using a method of thermal or hydrothermal oxidation of metal or a decomposition process of a variety of metal compounds.
• An unsupported metal oxide catalyst is prepared by thermal oxidation of metal in an oxidative environment such as air or ozone.
• the temperature of thermal oxidation typically may be in the range of 200 ⁇ 1200 degree C, preferably 400 ⁇ 800 degree C. If the temperature of thermal oxidation is less than 200 degree C, oxidation does not occur sufficiently, thereby the metal oxide is not obtained sufficiently. If the temperature of thermal oxidation is greater than 1200 degree C, the catalyst becomes denser by melting and the activity of the catalyst is reduced.
• the color of oxidized metal may be an indication of degree of its surface oxidation.
• metal oxide The simplest way to make metal oxide is a microwave assisted thermal oxidation process in the air.
• the microwave heating process not only oxidizes metal powder, but also sinters the metal oxide particles within 0.5 - 20 minutes depending on the power (preferably 500 - 950 W) of the microwave.
• metals may be oxidized and sintered by open frame or electric discharge heating in the air or ozone. Structure analysis of those metal oxide samples are carried out by using a method of X-ray diffraction (XRD).
• FIG 1 shows an XRD pattern indicating the complete conversion of iron metal to iron oxide.
• the heating may be performed using, for example, a microwave oven, an electric high temperature furnace, an electric heating oven, a heat gun, a hot plate or combinations thereof, but is not limited thereto.
• the metal may be oxidized and sintered at the same time.
• metal oxide is to oxidize metal in an electric furnace at a temperature of 200 ⁇ 1200 degree C (preferably 400 ⁇ 800 degree C) in the air or ozone for 10 minutes to 12 hours (preferably 1 to 2 hours).
• Metal oxide also can be prepared by hydrothermal oxidation or steam oxidation. These processes may take more time to complete compared with the microwave heating process, and often require additional thermal treatments for the use of a catalyst for hydrogen generation.
• Another embodiment of the invention is to make metal oxide catalyst by thermal decomposition of metal compounds.
• Precursors of metal oxide catalysts may be, without limitation, metal fluoride, metal chloride, metal bromide, metal iodide, metal nitrate, metal carbonate, metal hydroxide, metal borate, metal acetate, metal oxalate, or an organometallic compound.
• a glycine-nitrate method may be employed for the preparation of metal oxide or mixed-metal oxide powder with high surface area. The size and porosity of the metal oxide particles can be controlled by adjusting the amount of glycine. Details of the glycine-nitrate method may be found in http://picturethis.pnl.gov/PictureT.nsf/AII/ 3QWS7T7opendocument.
• a supported metal oxide catalyst is prepared through a decomposition process of a metal compound that is bound to, entrapped within, and coated on a substrate comprising metals, ceramics, polymers, glass, fibers, fabrics, textiles, wovens, nonwovens, fibers, alloys, zeolites, molecular sieves, ion exchange resins, graphite, metal oxide, metal carbide, metal boride, metal nitride, and mixtures thereof.
• Another preparation method of a supported catalyst is the oxidation of coated metal on a substrate by heating in the air or ozone. Coating of metal film on a substrate can be achieved by an electroplating or electrodeless plating process, but is not limited to these processes.
• a process of hydrogen generation according to the present invention is initiated by contacting a metal oxide catalyst with a solution comprising metal borohydride, a base, and proton donor solvent.
• a base used herein plays a role to stabilize metal borohydride in a solution.
• a common base used in a metal borohydride solution may be lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium sulfide, sodium zincate, sodium gallate, sodium silicate, and mixtures thereof but is not limited thereto.
• Hydrogen generation from a metal borohydride solution results from solvorolysis of metal borohydride by proton donor solvent.
• any proton donor solvents can be used for the solvolysis of metal borohydride.
• the preferred solvent is water and any alcohol comprising without limitation, ethylene glycol, glycerol, methanol, ethanol, isopropanol, isobutanol, propanol, propanediol, butanol, and mixtures thereof.
• Another process of hydrogen generation starts by mixing a proton donor solvent with a solid system comprising a metal oxide catalyst and solid metal borohydride. Hydrogen generation of this process may be controlled by the amount of the added solvent to a solid mixture of the metal oxide catalyst and metal borohydride.
• the catalyst is activated, an instant increase of the amount of hydrogen gas is observed.
• heating is desirable.
• the preferred heating temperature is in the range of about 30 ⁇ 100 degree C (preferably 40 ⁇ 80 degree C).
• the activation process is not necessary unless the process of hydrogen generation needs immediate action.
• activation of metal oxide catalysts may be related with the amount of the catalysts, concentrations of metal borohydride and stabilizer, and particle sizes of the catalysts. Mixed-metal oxide catalysts often showed shorter activation time for hydrogen generation.
• the deactivated metal oxide catalyst can be re-activated through the following process: (1 ) sonicating the catalyst in solvent; (2) rinsing the catalysts with solvent several times; and (3) heating the catalyst at 200 ⁇ 1200 degree C (preferably 400 ⁇ 800 degree C).
• the solvent may be Dl water, but is not limited thereto.
• the heating may be performed using a high temperature furnace, electric heating oven, heat gun, hot plate, a microwave oven, an electric furnace or a combination thereof.
• the heating temperature is less than 200 degree C, the deactivated metal oxide is not properly regenerated. If the heating temperature is greater than 1200 degree C, the catalyst becomes denser by melting and the activity of the catalyst is reduced.
• Example 1 Preparation of a shaped CoFe 4 -oxide catalyst using a microwave assisted thermal oxidation process.
• Co-4Fe metal 1.7678 g of Co metal powder and 4.468 g g of Fe metal powder were mixed with a mechanical agitator for 10 minutes.
• Paste of Co-4Fe metal was prepared by mixing the Co-4Fe metal powder with deionized (Dl) water. The paste was spread out flat (approximately 2-3 mm thick) on a ceramic plate and chopped into 2 - 3 mm pieces. The shaped paste was dried and heated in a microwave oven with a power of 950 W for 10 minutes.
• Example 2 Preparation of an unsupported iron oxide catalyst using a microwave assisted thermal oxidation process.
• An iron oxide catalyst was prepared by thermal oxidation of 20 g of iron metal powder in a microwave oven for 10 minutes. The power of the microwave was set to
• Example 3 Preparation of mixed-metal oxide catalysts using a microwave assisted thermal oxidation process.
• mixed-metal oxide catalysts were prepared by thermal oxidation of mixed- metal powder in a microwave oven for 10 minutes.
• the other preparation conditions were the same as example 1.
• two kinds of metal powder mixture with a molar ratio of 50:50 were mixed by using a mechanical agitator before heating.
• TABLE 2 summaries a combination of coupled metal oxides with a molar ratio of 50:50.
• Example 4 Preparation of a shaped iron oxide catalyst using a microwave assisted thermal oxidation process. 30 g of iron metal powder was spread out flat on a ceramic plate and packed with a flat plastic plate. The packed flat iron metal powder was chopped into 2 - 3 mm pieces, and heated in a microwave oven with a power of 950 W for 10 minutes. The further sintering of the iron oxide catalyst was carried out by heating at 1150 degree C in an electric furnace for 2 hours. The sintered sample was crushed and grounded for the X- ray diffraction (XRD) analysis. FIG. 1 shows a XRD pattern of synthesized iron oxide sample in a microwave oven. The XRD phase shows no sign of the Fe metal phase implying complete oxidation.
• XRD X- ray diffraction
• Example 5 Preparation of an unsupported iron oxide catalyst in a high temperature furnace.
• Iron metal powder contained in an alumina crucible was placed in a high temperature furnace and heated at 800 degree C for 2 hours in air. The resulting sample was oxidized and sintered simultaneously.
• Cobalt-iron oxide catalysts with various molar ratios of cobalt and iron were synthesized using a glycine-nitrate process.
• an aqueous solution containing glycine and mixture of either cobalt nitrate/iron chloride or cobalt chloride/iron nitrate was prepared and heated until excess water had boiled away. Continuous heating of the remaining material resulted in self-ignition, which generated fine black powder.
• the molar ratios of glycine and metal salts in this invention were 1 : 1.
• Fig 6 shows a plot of maximum hydrogen flow rates of Co-Fe oxide catalysts having a molar ratio of Co: Fe from 0.25 to 9.
• Example 7 Preparation of a supported iron-cobalt oxide catalyst 2 M solution of cobalt and iron nitrates was prepared by dissolving equal molar cobalt and iron nitrates in de-ionized water. 2 ml of the resulting solution was introduced into a 100 ml beaker containing 3 g of molecular sieves (Yakuri Pure Chemicals Co. LTD, Osaka, Japan). The cobalt and iron ions impregnated molecular sieves were dried in an oven at 100 degree C for 1 hour, and consecutively heated on a hot plate with a maximum temperature setting for 1 hour.
• Hydrogen generation experiments were carried out to measure a flow rate of hydrogen.
• Several metal oxide and mixed-metal oxide samples were employed. The experiment was carried out by adding 20 ml of a sodium borohydride solution containing 16 wt. % NaBH 4 , 3.5 wt. % NaOH, and 80.5 wt. % of Dl water to a reaction vessel containing a certain amount (0.01 -0.3 g) of metal or mixed-metal oxide powder samples.
• FIGS. 2-6 shows a graph of the hydrogen flow rates of the various metal oxide catalysts.
• FIG.S 2-5 The plots of hydrogen flow rate vs. time of various metal oxide catalysts are shown in FIG.S 2-5.
• the hydrogen flow rate hit a peak of -50000 ml/min-g without temperature control (see FIG. 2).
• the CoFe 4 -oxide produced from a microwave assisted thermal oxidation process revealed the maximum hydrogen flow rate of 3065 ml/min-g (see FIG. 3), but its activation commenced immediately.
• the maximum hydrogen flow rates of Fe-oxide samples are 2193 and 2473 ml/min-g for partially sintered Fe-Oxide (microwave heating) and sintered Fe-Oxide (microwave heating + additional heating at 1150 degree C), respectively (see FIGS 4-5). Although it seemed that additional thermal treatments did not make big differences on the hydrogen flow rates, sintered catalysts are more favorable in terms of convenience of use and mechanical strength. In the system of the Co-Fe oxides prepared from a glycine-nitrate process, decreasing the amount of Fe contents elevated the maximum hydrogen flow rates, but it remained constant after the molar ratio of Co/Fe of 1.5 (see FIG. 6).
• the hydrogen flow rate may depend on concentration of sodium borohydride, the particle size and amount of the catalysts, compositions of hetero metals and so on. Maximum hydrogen flow rates of various mixed metal oxides are summarized in Table 1. Unlike a Co-Fe oxide system, Fe- or Co-oxide coupled with zinc oxide had no catalytic activity on hydrogen generation. Other metal oxides coupled with Co-oxides are relatively weak catalytic activities on hydrogen generation.
• Hydrogen can be manufactured efficiently and economically by using the metal oxide catalyst for hydrogen generation of the present invention.

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• 2006
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