WO2009034479A2

WO2009034479A2 - Hydrogen production by contacting a composition with water under an ultrasonic action

Info

Publication number: WO2009034479A2
Application number: PCT/IB2008/003423
Authority: WO
Inventors: Alex Sergienko; Yakov Yasman
Original assignee: Hydpo Ltd.
Priority date: 2007-07-19
Filing date: 2008-07-18
Publication date: 2009-03-19
Also published as: WO2009034479A3

Abstract

A method of hydrogen production can include providing a composition, that contains at least one hydrogen displacing element and has a passivating layer; contacting the composition with water; exposing the composition in contact with the water to an ultrasonic action in a presence of a soniσation enhancer, so that the exposing activates the composition by reducing the passivating layer and therein the activated composition reacts with the water to generate a hydrogen gas; and collecting the generated hydrogen gas. The composition can comprise aluminum.

Description

HYDROGEN PRODUCTION

RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisional application no. 60/929,947 filed July 19, 2007, and U.S. provisional application no. 61/006,929 filed February 6, 2008, which are both incorporated herein by reference in their entirety.

FIELD

[0002] The present invention relates in general to methods, apparatuses and kits for hydrogen production and, more specifically, to methods, apparatuses and kits for hydrogen production utilizing compositions having passivating layers.

BACKGROUND

[0003] Hydrogen is the simplest chemical element and the most plentiful gas in the universe. Transportation and energy companies recognize that hydrogen has the potential to fuel the world as a sustainable energy resource. Hydrogen is now the focus of intense research interest to develop fuel cells for clean transportation and distributed power generation.

[0004] Unfortunately, elemental molecular hydrogen, H₂, is relatively rare on Earth as hydrogen usually combines with other elements, such as oxygen and carbon, to form chemical compounds, such as hydrocarbons and water. Still, hydrogen can be produced from a wide variety of resources, which include coal, oil, natural gas, biomass and water using a variety of process technologies. [0005] Some of the specific technologies for producing hydrogen include: water electrolysis and reforming of fossil fuels. Electrolysis uses electrical current to split water into hydrogen at the cathode (+) and oxygen at the anode (-). Electrolysis requires large amounts of energy and is presently considered to be significantly more expensive commercially than reforming.

[0006] Reforming involves extraction of molecular hydrogen from fossil fuels, such as natural gas. Reforming processes may be complex and usually result in residues, such as carbon dioxide. An additional disadvantage of reforming technology is that only a limited amount of fossil fuel is available on Earth. Also to be economically feasible, hydrogen production via reforming has to be done in large plants, which creates a necessity for hydrogen storage and transportation. Safe, reliable and low cost options for hydrogen storage and delivery currently are not commercially available.

[0007] Other methods of hydrogen production include thermo-chemical water splitting using chemicals and heat in multiple steps; photoelectrochemical water splitting using semiconductor material exposed to the sunlight; biophotolysis of water using microorganisms, such as microalgae and cyanobacteria; and microbial hydrogen production by breaking down a biomass feedstock. Each of these alternative methods of hydrogen production has at least one the following disadvantages: high energy consumption, high cost, long start-up times, low yield and low throughput.

[0008] Various methods and systems related to hydrogen production are disclosed in the following patent documents:

[0009] US 3,942,51 1 ; US 3,957,483; US 3,966,895; US 3,970,745; US 3,975,913; US 3,985,865; US 4,064,226; US 4,072,514; US 4,223,661 ; US 4,269,818; US 4,340,850; US 4,356,163, US 4,358,291; US 4,598,552; US 4,643,166; US 4,670,018; US 4,730,601 ; US 4,745,204; US 4,752,463; US 4,769,044; US 5,143,047; US 5,514,353; US 5,728,464; US 5,817,157; US 5,833,934; US 5,867,978; US 6,440,385; US 6,506,360; US 6,582,676; US 7,141,216; US 20060249393; US 20070048563; US 20080063597 and US 20080056986.

SUMMARY

[0010] According to one embodiment, a method of hydrogen production comprises (A) providing a composition that contains at least one hydrogen displacing element and has a passivating layer; contacting the composition with water; exposing the composition in contact with the water to an ultrasonic action in a presence of a sonication enhancer, wherein the exposing activates the composition by reducing the passivating layer and therein the activated composition reacts with the water to generate a hydrogen gas; and collecting the generated hydrogen gas. [0011] According to another embodiment, a hydrogen production method comprising providing a flow comprising water and a composition, that contains at least one hydrogen displacing element and has a passivating layer; exposing said flow to an ultrasonic action, wherein the exposing activates the composition by reducing the passivating layer and therein the activated composition reacts with the water to generate a hydrogen gas; and collecting the hydrogen gas. [0012] According to yet another embodiment, a hydrogen production apparatus comprising at least one ultrasonic source and a vessel having an inlet and an outlet fludically connected to the inlet through an inner space of the vessel, wherein the inlet of the vessel is configured to introduce a flow comprising water and a composition, that contains at least one hydrogen displacing element and has a passivating layer, into the inner space of the vessel and wherein the at least one ultrasonic source is configured to produce an ultrasonic action that activates the composition passing through the inner volume of the vessel by reducing the passivating layer of the composition, so that the activated metal composition reacts with the water and thereby generates hydrogen gas.

DRAWINGS

[0013] FIG. 1 is a flow diagram schematically illustrating a cyclic hydrogen production process.

[0014] FIG. 2 is a flow diagram schematically illustrating a hydrogen production process with extraction of non-hydrogen products of the process.

[0015] FIG. 3 schematically illustrates a reactor for hydrogen production from water.

[0016] FIG. 4 is a graph representing time dependence of ultrasonic hydrogen production: 1) from aluminum powder; 2) from aluminum powder in a presence of

CO₂ flow provided in the reactor; and 3) from aluminum powder in a presence of

CO₂ flow and solid Al₂O₃ provided in the reactor. [0017] FIG. 5 schematically illustrates one embodiment of an apparatus for ultrasonic hydrogen generation.

[0018] FIG. 6 schematically illustrates and presents photographs of an embodiment flow-through ultrasonic reactor for hydrogen production.

[0019] FIG. 7 presents a photograph of an embodiment flow-through ultrasonic apparatus for hydrogen production.

[0020] FIG. 8 is a photograph of a hydrogen production apparatus that includes an activation reactor, a hydrogen production reactor and a circulator/pump.

[0021] FIG. 9 is a photograph of a flow through vessel with clamp on sonotrodes.

[0022] FIG. 10 schematically illustrates an apparatus that is capable to produce hydrogen on kg/h scale.

[0023] FIG. 11 is a photograph of a stainless steel tube, which may be used as an activation reactor in one of embodiments of hydrogen production apparatus.

[0024] FIG. 12 is a photograph of a tubular activation reactor with two clamp-on sonotrodes.

DETAILED DESCRIPTION

Related application

[0025] The present application incorporates herein by reference in its entirety U.S. provisional patent application no. 61/000,751 "Hydrogenation method and apparatus" filed October 29, 2007 by Alex Sergienko and Yakov Yasman.

Disclosure

[0026] Unless otherwise specified, "a" or "an" refers to one or more. [0027] The inventors developed methods and apparatuses that allow safe hydrogen production at low cost. The methods of the present invention do not require the large amounts of energy used in water electrolysis. In some embodiments, the hydrogen production can be performed without utilizing external energy. The methods and apparatuses of the present invention can be adapted for hydrogen production at a particular location based on particular materials and/or particular sources of energy available at such location. Thus, the methods and apparatuses of the present invention may not require additional infrastructure for hydrogen storage and/or delivery. The hydrogen generation methods of the present invention can produce one or more non- hydrogen products that can be easily recycled into one or more starting materials of hydrogen production. Alternatively, the one or more non-hydrogen products can be also used as a final commercial product.

[0028] The hydrogen production can be based on a reaction between a composition that comprises at least one hydrogen displacing element, i.e. a element that can displace hydrogen when the composition is brought in contact with water. [0029] In some embodiments, the composition can be a metal composition comprising at least one hydrogen displacing metal in an elemental form, which can be a metal with a higher reactivity than hydrogen in the metal reactivity series. In such a case, the hydrogen producing reaction between water and the at least one metal may begin, with or without an additional reagent, such as an acid or a hydroxide, once the metal per se is exposed to water. Examples of hydrogen displacing metals include Mg, Al, Mn, Zn and Cr. For aluminum containing metal compositions the hydrogen producing reaction can be as follows: [0030] 2 Al + 6 H₂O -> 2 Al(OH)₃ + 3 H₂

[0031] Yet in some embodiments, the composition can be a composition comprising a hydrogen displacing non-metallic element in an elemental form. One example of non-metallic hydrogen displacing element can be elemental Si. For silicon containing compositions, the hydrogen production reaction can be as follows: [0032] Si + 4 H₂O -> Si(OH)₄ + 2 H₂.-> SiO₂ + 2 H₂O + 2 H₂ [0033] A hydrogen producing reaction between Si and water may require an excess of OH^" ions in water. The reaction may require raising a temperature of the mixture comprising water and the silicon containing composition to a temperature that can initiate the reaction. Such reaction initiating temperature can be 50-100 ⁰C or 60-95 °C or 70-95 °C or 80-90 ⁰C and any integer between these ranges. Additional OH^" ions can be provided, for example, by a base, such as alkali metal hydroxide, e.g. KOH or NaOH. In some embodiments, the base can be added to a mixture comprising water and the silicon containing composition. Yet in some other embodiments, one can form initially a dry mixture comprising the silicon containing composition and a dry base and then add water to such a mixture. The elevated temperature required for initiating the hydrogen production reaction between silicon and water can be achieved using a number of ways. In some embodiments, the elevated temperature may be achieved by heating a mixture comprising water and a silicon containing composition using an external heating source, such as a resistive heater. In some other embodiments, the elevated temperature may be achieved without using an external heating source. For example, in some cases, the elevated temperature may be achieved due to heat produced during an exothermic reaction. Such an exothermic reaction may be a dissolution of a dry base, such as KOH or NaOH, in water. Such reaction can produce both for the case, when a dry base is added to a mixture comprising a silicon containing composition and water, and for the case, when water is added to a dry mixture comprising a silicon containing composition and a dry base. The exothermic reaction providing heat to reach the elevated temperature for initiating the hydrogen producing reaction between water and silicon can be also an exothermic hydrogen producing reaction between water and another composition that comprises a hydrogen displacing element, such as a hydrogen producing reaction between water and aluminum. The other metal composition can be added to water before the silicon containing composition, at the same time as the silicon containing composition or after the silicon containing composition.

[0034] The composition can be a composition that contains at least one oxidizable hydrogen-displacing element, i.e., a hydrogen displacing element that under normal conditions has a natural protective layer comprising the element's oxide and/or hydroxide. In many embodiments, the composition can be such that it does not react with water when the passivating layer is present on it under normal conditions. [0035] Examples of oxidizable elements include, but not limited to, aluminum having a protective layer comprising Al₂O₃ and/or aluminum hydroxide; titanium having a protective layer comprising TiO₂; iron having a protective layer comprising Fe₂O₃; copper having a protective layer comprising CuO; nickel having a protective layer comprising NiO; magnesium having a protective layer comprising MgO; silicon having a protective layer comprising SiO₂; and zinc having a protective layer comprising ZnO. The composition can include more than one oxidizable element. [0036] In many embodiments, the composition does not contain gallium. In general, the hydrogen production methods of this application do not utilize gallium in the hydrogen producing reactions.

[0037] The composition can be in a variety of forms, which include, but not limited to, bars, particles, spheres, pellets, beads, granules and the like. [0038] In some embodiments, the composition can be in a form of particles with an average particle size ranging from 1 micron to 10 mm, or from 3 microns to 10 microns, or from 10 microns to 100 microns, or from 1 mm to 5 mm or any integer between these ranges.

[0039] In some embodiments, the composition can be a scrap composition. In some embodiments, the composition may be a scrap aluminum composition or scrap aluminum alloy composition. Examples of such scrap compositions include, but, are not limited to, old mixed aluminum, including scrap aluminum under Institute of Scrap Recycling, Inc. (ISRI) code TABOR and chopped mixed aluminum; utensil scrap aluminum including scrap aluminum under ISRI code TAINT; scrap aluminum turnings, borings or grindings including mixed scrap aluminum turnings and borings under ISRI code TELIC, segregated aluminum borings and turnings under ISRI code TEENS and aluminum grindings under ISRI code THIGH; scrap aluminum extrusions including scrap aluminum extrusions under ISRI codes TATA, TOTO and TUTU; scrap low copper aluminum including mixed low copper aluminum clippings and solids under ISRI code TABOO; aluminum lithographic sheets including those under ISRI code TABLET and TABLOID; aluminum castings including mixed aluminum castings under ISRI code TENSE, aluminum airplane castings under ISRI code TWIST and aluminum auto castings under ISRI code TRUMP; painted aluminum including clean painted aluminum under ISRI code TALE and insulated painted aluminum; coated aluminum including coated aluminum under ISRI code TALENT; used beverage can (UBC) scrap including post-consumer aluminum UBC scrap under ISRI code TALC, shredded aluminum UBC scrap under ISRI code TALCRED, densified aluminum UBC scrap under ISRI code TALDACK, baled UBC under ISRI code TALDON, briqueted UBC under ISRI code TALDORK; new aluminum can stock including that under ISRI code TAKE; remelt aluminum ingot and sows including sweated aluminum under ISRI code THROB; mixed irony aluminum including low grade irony aluminum with a minimum content of aluminum of 50%; aluminum auto transmissions and aluminum auto radiators including aluminum copper radiators under ISRI code TALK and all aluminum radiators under ISRI code TALLY; insulated aluminum wire scrap including that under ISRI code TWANG; supported aluminum cables; bare aluminum wire and cable including new pure aluminum wire and cable under ISRI code TALON, new mixed aluminum wire and cable under ISRI code TANN, old pure aluminum wire and cable under ISRI code TASTE and old mixed aluminum wire and cable under ISRI code TASSEL; aluminum auto and truck wheels including those under ISRI code TROMA; aluminum nodules including those under ISRI code tall; aluminum foil including new aluminum foil under ISRI code TERSE, post consumer aluminum foil under ISRI code TESLA, new coated aluminum foil under ISRI code TETRA, old coated aluminum foil under ISRI code TESTY and paperbacked aluminum foil; aluminum drosses, spatters, spillings, skimmings and sweepings including those under ISRI code THIRL; aluminum pistons including clean aluminum pistons under ISRI code TARRY A, clean aluminum pistons with struts under ISRI code TARRY B and irony aluminum pistons under ISRI code TARRY C; aircraft sheet aluminum including that under ISRI code TEPID; aluminum alloy clippings and solids including segregated aluminum alloy clippings and solids under ISRI code TOOTH and mixed aluminum alloy clippings and solids under ISRI code TOUGH; aluminum castings, forgings and extrusions including those under ISRI code TREAD; fragmentized aluminum scrap such as fragmentized aluminum scrap from automobile shredders, including floated fragmentized aluminum scrap under ISRI code TWITCH, fragmentized aluminum scrap under ISRI code TWEAK and burnt fragmentized aluminum scrap under ISRI code TWIRE. All the ISRI codes mentioned above are those effective on November 19, 2007.

[0040] In some embodiments, the composition may comprise or consist essentially of silicon. In some embodiments, the composition can be a metallurgical grade i

silicon, chemical grade silicon or silicon metal powder. The content of silicon in the silicon metal composition may be at least 90% or at least 95 % or at least 96% or at least 97% or at least 98 % or at least 99 %. In some embodiments, the silicon composition can be a scrap silicon composition. Examples of scrap silicon compositions include polysilicon scrap, scrap polysilicon chips, scrap polysilicon rods , scrap granular polysilicon, scrap silicon powder, scrap silicon ingots, reclaim silicon wafers, broken silicon wafers, pseudo square wafers, half-moon wafers, silicon slugs (disks), broken disks, pot scrap, scrap solar cells and broken solar cells. [0041] A particular choice of the scrap composition may depend on a number of factors including economic factors, such as a current market price. [0042] In many embodiments, it may be preferable to use compositions with an extended surface area in order to maximize the contact between water and the hydrogen displacing element. Thus, in some embodiments, the composition may be ground or milled in order to increase its surface area. Yet in some embodiments, the composition can have an extended surface area without preliminary grinding or milling. For example, the composition may be a scrap composition in a form of grindings, turnings or boarings. Such scrap compositions, especially when they have an average particle size of less than 5 mm, or less than 2 mm, or less than 1 mm, may present a problem when being remelted into a bulk aluminum in a recycling process because they burn out at the recycling temperatures. However, for purposes of hydrogen production, such scrap compositions may be one of the preferred systems because they have an extended surface area which may allow for carrying out the hydrogen production more effectively.

[0043] In some embodiments, the composition can be a naturally occurring composition readily available at a particular location selected for hydrogen production. Alternatively, the composition can be a composition that is produced from a naturally occurring material that is abundant at a particular location selected for hydrogen production.

[0044] In some embodiments, the composition can be an alloy comprising one or more hydrogen-displacing metals. DISPLACING METHOD

[0045] According to one embodiment, a composition that comprises a hydrogen displacing element and a passivating layer, can be initially exposed to an oxide stripper. The exposure to the oxide stripper can activate the composition for hydrogen production by reducing the passivating layer of the composition. After activation by the oxide stripper, the composition can be exposed to an aqueous solution that does not contain the oxide stripper, so that water in the aqueous solution can react with the activated composition thereby producing hydrogen gas and one or more non-hydrogen products. The produced hydrogen gas can then be collected. [0046] The oxide stripper can be any compound that is capable of reducing or inhibiting the protective layer of the composition, so that one or more hydrogen displacing elements contained in the composition can react with water of the aqueous solution to produce hydrogen gas. Based on the composition, the oxide striper may be a salt, a hydroxide or an acid. In some embodiments, the oxide stripper can be dissolved in water or other appropriate solvent when applied to the composition. A particular oxide stripper can depend on particular one or more hydrogen displacing elements contained in the composition. For example, when the composition comprises aluminum, the oxide stripper can be an acid or a hydroxide of a metal, that is more electropositive that aluminum.

[0047] In some embodiments, the composition can consist essentially of aluminum, which can be an oxidized aluminum per se or an aluminum composition that may contain besides an oxidized aluminum one or more inactive ingredients, which can not react with water to produce hydrogen.

[0048] An oxide stripper for an aluminum-containing composition can comprise an alkali hydroxide, such as potassium hydroxide or sodium hydroxide. For example, in some embodiments, the oxide stripper for the aluminum containing composition can be an aqueous solution of the alkali hydroxide.

[0049] In some other embodiments, the oxide stripper for the aluminum containing composition can be a compound that forms an acid when exposed to water. Examples of such compounds include, but are not limited to, aluminum sulfonate A1₂(SO₄)₃, which can form a sulfuric acid when exposed to water, and carbon dioxide, which can form a carbonic acid when exposed to water.

[0050] Preferably, the aqueous solution that does not contain the oxide stripper consists essentially of water, which means that the aqueous solution contains no other ingredients that are capable of reacting with the activated composition. In some embodiments, the aqueous solution can be water per se.

[0051] The composition can be provided in a reactor and the oxide stripper can be introduced into the reactor to activate the composition. The aqueous solution that does not contain the oxide stripper can be introduced in the reactor after the composition is activated to remove the oxide stripper from the reactor. If the composition becomes passivated during the reaction with water, a fresh amount of the oxide stripper may be introduced in the reactor to reactivate the composition and then removed by introducing of a fresh amount of the aqueous solution that does not contain the oxide stripper.

[0052] The method may allow for producing one or more non-hydrogen products of the reaction of the composition with water, that are substantially free of products of the reaction of the composition with the oxide stripper when the presence of such products is not desirable.

[0053] For example, when hydrogen is produced using prior art methods by reacting aluminum with an alkali hydroxide, such as sodium hydroxide or potassium hydroxide, non-hydrogen products of such hydrogen production can include alkali metal aluminates, such as NaAlO₂ or KAlO₂, which may be difficult to transfer back into aluminum in an energy efficient manner.

[0054] In the present method, aluminum or aluminum containing composition may be stripped of its passivating layer with an alkali hydroxide, which can be subsequently removed from the reactor by introducing the aqueous solution, that does not contain the alkali hydroxide. As a result, the one or more non-hydrogen products of the hydrogen production in the present invention are substantially free of alkali metal compounds, such as alkali aluminates. For example, the non-hydrogen products of the hydrogen production from the oxidized aluminum per se can consist essentially of aluminum hydroxide and/or alumina. DISPLACING APPARATUS

[0055] In some embodiments, the method of hydrogen production can be practiced in a displacing apparatus 300 illustrated in Figure 3. The apparatus 300 includes a reactor 301. The reactor 301 is connected via a valve 302 and an inlet 307 to a water source 303 and via a valve 304 and an inlet 308 to an oxide stripper source 305, which can be a vessel containing an oxide stripper such as a solution of an alkali hydroxide. The reactor 301 contains a composition 306.

[0056] To activate the composition 306 for hydrogen production, the oxide stripper from the oxide stripper source 305 is introduced in the reactor 301 through the inlet 308 by opening the valve 304. Upon the activation of the composition 306, water from the water source 303 is introduced in the reactor 301 via the inlet 307 by opening the valve 302. The valve 304 is closed when the composition 306 is activated. Water introduced into the reactor 301 pushes the oxide stripper out of the reactor 301 through drain plugs 311. Hydrogen gas can be collected from the reactor 301 through a hydrogen outlet 309 and a valve 310. Heat generated in the reactor 301 during the hydrogen generation can be transferred using a heat exchanger (not shown in Figure 3), such as a heat pipe, in thermal contact with the reactor 301. The generated heat can be used, for example, for drying one or more non-hydrogen products of the production and/or for recycling the one or more non-hydrogen products. The heat exchanger can be used for controlling a temperature in the reactor 301.

NON-HYDROGEN PRODUCTS AS A FINAL PRODUCT

[0057] In some embodiments, the one or more non-hydrogen products of hydrogen generation that are free or substantially free of products of reaction of the composition and the oxide stripper can be dried and used as a final commercial product or an intermediate for manufacturing a final commercial product. [0058] For example, when the hydrogen is produced from an oxidized aluminum per se or an aluminum containing composition, the one or more non-hydrogen products can be aluminum hydroxide and/or alumina substantially free of products of reaction of aluminum and the oxide stripper. In some cases, aluminum hydroxide can be used as a final commercial product. In some cases, aluminum hydroxide can be transformed into alumina, which can be used as a final commercial product. Alumina as a commercial product can be in a form of alpha alumina, gamma alumina or a combination thereof. For example, alumina can be used as a fire retardants-smoke suppressant; as a component of a healthcare product, such as a toothpaste; as an abrasive or polishing material in a polishing or cutting product, such as sandpaper. Alumina dispersed in a solvent, such as water, organic or polymeric solvent can be also used as a filling material in paints, inks and related products. Aluminum oxide can be also used in preparation of coating suspensions in compact fluorescent lamps. In addition, Al₂O₃ can be used in fluoride water filters. Alumina can be also used as an orthopedic biomaterial.

[0059] When the hydrogen is produced from an oxidized silicon, the one or more non-hydrogen products can include silicon oxide, which can be used as a final commercial product.

[0060] Figure 2 presents a flow diagram of the process of hydrogen production, where one or more non-hydrogen products are used as a final product. As illustrated in Figure 2, water 204 and an active material 205, i.e. a composition, that contains at least one hydrogen displacing element and has a passivating layer, are reacted in a reactor 201 to produce hydrogen gas 203 and one or more non-hydrogen products 202. Heat can be applied to the one or more non-hydrogen products 202 in order, for example, to dry them.

RECYCLING ON NON-HYDROGEN PRODUCTS

[0061] In some embodiments, the one or more non-hydrogen products of hydrogen production can be recycled back into one or more elements that constituted the initial composition used for hydrogen production.

[0062] Figure 1 presents a flow diagram of the process of hydrogen production, where one or more non-hydrogen products of hydrogen production is recycled back in one or more elements that constituted the initial composition. As illustrated in Figure 1, water 104 and an active material 105, i.e. a composition, that contains at least one hydrogen displacing element and has a passivating layer, are reacted in a reactor 101 to produce hydrogen gas 103 and one or more non-hydrogen products 102, which can be recycled into an active material, which can be used for further hydrogen production. Products of the recycling can include CO and H₂, a mixture of which can form together a synthesis gas 106, which can be used in a fuel cell 107 for producing heat and/or electric power.

[0063] Recycling of the one or more non-hydrogen compounds back into one or more elements of the initial composition will be illustrated below using an example of recycling of aluminum hydroxide and alumina back into a metallic aluminum. [0064] When the initial composition is an aluminum containing composition, such as an oxidized aluminum per se, the non-hydrogen products can include aluminum hydroxide and/or alumina, which can be recycled back into a metallic aluminum. Such recycled aluminum can be used for a further hydrogen production. [0065] Aluminum hydroxide can be, for example, transformed into gamma-alumina by being exposed to a temperature of above around 250⁰C and below 700 ⁰C according to the following reaction: [0066] 2Al(OH)₃ + Q = Al₂O₃ (gamma).

[0067] The heat required for the above reaction can be transferred, for example, from the hydrogen producing reaction between aluminum and water. [0068] Gamma-alumina can be then recycled in a metallic aluminum via a variety of ways. In some embodiments, gamma-alumina can be reacted with a carbon- containing compound, which can be, for example, carbon per se or a hydrocarbon, such as methane. Recycling of gamma-alumina can result in non-aluminum products, which may include CO and H₂, which can form together synthesis gas. For example, when the carbon-containing compound is carbon, aluminum can be recycled from gamma-alumina according to the following reaction: [0069] Al₂O₃ (gamma) + 3C = 2 Al + 3CO.

[0070] The carbon monoxide can further react with water as follows: [0071] CO + H₂O = H₂ + CO₂.

[0072] Carbon used in such recycling process can be a low quality carbon, such as a recycled carbon produced by burning an industrial waste. [0073] When the carbon-containing compound is methane, aluminum can be recycled according to the following reaction:

[0074] Al₂O₃ (gamma) + CH₄ = 2 Al + CO₂ + 2H₂.

[0075] Aluminum oxidation products can be also recycled into a metallic aluminum using sodium carbonate as detailed below in the present disclosure.

HYDROGEN PRODUCTION UTILIZING MULTIPLE COMPOSITIONS

[0076] In some embodiments, the hydrogen production can involve more than one composition. For example, a first composition, that comprises a first hydrogen displacing element and has a passivating layer, can be provided initially in a reactor. The first composition can be activated by being exposed to its oxide stripper, which can be then removed by introducing in the reactor an aqueous solution that does not contain the oxide stripper for the first composition. A reaction of water in the aqueous solution and the activated composition can generate hydrogen. If the reaction is exothermic, i.e. if the reaction generates heat, such heat can be utilized for activating a second composition, that contains a second hydrogen displacing element and has its own passivating oxide, by reducing or inhibiting the passivating layer using an oxide stripper for the second composition. In some cases, the second composition can be present in the reactor initially together with the first composition. In some cases, the second composition can be introduced in the reactor during the reaction between the first composition and water of the aqueous solution. The oxide stripper for the second composition can be the same or different from the oxide stripper for the first composition. In some cases, the oxide stripper for the second composition can be introduced into the reactor when the second composition is already present there. Yet in some cases, the oxide stripper for the second composition can be introduced into the reactor prior or at the same time as the second composition is introduced in the reactor. In some embodiments, after the second composition is activated by its oxide stripper, the oxide stripper for the second composition may be removed from the reactor by introducing in the reactor an aqueous solution that does not contain the oxide stripper for the second composition. Yet in other embodiments, the oxide stripper for the second composition may stay in the reactor. For example, when the second composition is a silicon containing composition, the oxide stripper for the second composition may be an alkali hydroxide, which can also act as a catalyst of the hydrogen producing reaction between silicon and water.

[0077] In some embodiments, the first composition used for generating hydrogen can comprise aluminum and the second composition can comprise silicon.

SILICON DIOXIDE RECYCLING

[0078] Silicon dioxide can be recycled by a variety of ways. In some embodiments, silicon dioxide can be recycled into silicon by exposing silicon dioxide to a heat according to the following reaction:

[0079] SiO₂ + Q → Si + O₂.

[0080] In some embodiments, silicon dioxide can be recycled into silicon by reacting silicon dioxide with a carbon containing compound, such as carbon per se or a hydrocarbon, such as methane. For example, when the carbon-containing compound is carbon per se, the recycling can follow the following reaction:

[0081] SiO₂ + 2C = Si + 2CO.

[0082] The reaction between the silicon dioxide and carbon can also lead to silicon carbide, which can be also used as a commercial product:

[0083] SiO₂ + 3C = SiC + 2CO.

ULTRASONIC TREATMENT

[0084] The present inventors also developed methods and apparatuses for hydrogen production based on the removal of a passivating layer of a composition that contains at least one hydrogen displacing element using ultrasonic treatment. In some embodiments, the composition can be a metal composition comprising at least one hydrogen displacing metal, such as Al. Yet in some other embodiments, the composition can be a composition comprising at least one hydrogen displacing non- metallic element, such Si or Ge. The removal of the passivating layer activates the composition for the hydrogen producing reaction with water. [0085] Thus, according to one embodiment, a method of hydrogen production involves exposing a composition that contains at least one hydrogen displacing element and has a natural passivating layer, which composition is in contact with water, to an ultrasonic treatment. The ultrasonic treatment can activate the composition for hydrogen production by reducing the passivating layer, so that the activated composition reacts with water to produce hydrogen gas. [0086] A physical phenomenon underlying the ultrasonic activation of the composition is cavitation. Briefly, a liquid exposed to ultrasonic waves of a sufficiently high intensity undergoes compression (high pressure) and rarification/expansion (low pressure) cycles with a frequency of the ultrasonic waves. During the rarification cycle, the ultrasonic waves can create small gas bubbles or voids in the liquid. The bubbles can grow in size as they absorb the energy of the ultrasonic wave. When the bubbles attain a volume such that they can no longer absorb the energy, they collapse during the high pressure cycle. The collapse of such bubbles, also known as cavitation bubbles, results in a shock wave, which produces micro-turbulences and micro-jets in the liquid. When such a collapse occurs near a surface of the composition having a passivating layer in the liquid, the micro-jets and micro-turbulences can remove particles of the passivating layer, which usually comprises oxides or hydroxides of one or more elements of the composition, from the surface, thereby exposing the one or more hydrogen displacing elements of the composition directly to the liquid.

[0087] Although the ultrasonic treatment may be either continuous or pulsed, the pulsed ultrasonic treatment may be preferred. The pulsed ultrasonic treatment refers to a sequence of active ultrasonic impulses, during which an ultrasonic source radiates an ultrasonic wave, and inactive pauses, each of which separates consequent individual impulses. During the pauses, the ultrasonic source does not radiate an ultrasonic wave.

[0088] The pulsed ultrasonic treatment can allow for applying a higher ultrasonic wave intensity to the composition than a continuous ultrasonic action. The pulsed ultrasonic treatment can also prevent overheating of an ultrasonic wave generator. [0089] The pulsed ultrasonic treatment also allows for a more efficient energy consumption by the ultrasonic source.

[0090] The pulsed ultrasonic treatment may also allow for controlling a temperature in a reactor containing the composition and water by manipulating one or more parameters of the treatment, such as a duration of an individual pause between subsequent impulses of the treatment; a duration of an individual impulse, as well as the impulse's intensity and frequency. Durations of individual pulses and pauses can vary. For example, a duration of individual pulse can range from about 1 ms to 20 s or from about 1 ms to about 10 s from about 1 ms to about 2 s, or from about 10 ms to about 1 s, or from about 50 to about 500 ms or any integer between these ranges. Same time ranges also apply to a duration of an individual pause. [0091] Ultrasonic frequencies used for the treatment can vary. For example, in some embodiments, the ultrasonic frequency can be from about 15 kHz to about 2 MHz or from about 20 kHz to about 1 MHz or from about 15 kHz to 500 kHz or from about 20 kHz to about 500 kHz or any integer between those ranges. [0092] The ultrasonic treatment can be generated using an ultrasonic source or transducer, which is in a sonic communication with the composition and water in the reactor. The sonic communication means that ultrasonic waves generated by the ultrasonic source can reach the composition and water in the reactor. In some embodiments, the ultrasonic source can be outside of the reactor but in sonic communication with the composition and water. In some other embodiments, the ultrasonic source can be in a physical contact with the water in the reactor. For example, the ultrasonic source can be completely or partially immersed in the water. In some embodiments, the ultrasonic source is in physical contact with the water and may have a roughened surface on at least part of the total surface area of the source in contact with the water. The roughened surface of the ultrasonic source can facilitate generation of cavitational bubbles in the water and thereby increase an efficiency of ultrasonic removal/inhibition of the passivating layer from the composition. [0093] In some embodiments, the roughened surface of the ultrasonic source can be made of a ceramic material. The ceramic material can comprise, for example, at least one oxide compound, such as silicon oxide, aluminum oxide, zirconium oxide or magnesium oxide. Such an oxide compound can shift a chemical equilibrium in a reaction between a hydrogen radical (atomic hydrogen), which is produced in one of intermediate reactions between the ultrasonically activated composition and water, and hydrogen peroxide, which is present in water, towards initial reagents. In other words, due to the presence of the oxide compound in the ultrasonic source, a hydrogen radical will less likely react with hydrogen peroxide and more likely react with another hydrogen radical to produce molecular hydrogen. Thus, the oxide compound in the ceramic material of the ultrasonic source can increase an efficiency of ultrasonic hydrogen production.

[0094] The ceramic material can further comprise at least one catalytically active metal, which can be, for example, a metal of the platinum group, such as Ru, Rh, Pd,

Os, Ir, Pt, Co or Ni. Such a metal can shift an equilibrium in a reaction between hydrogen radicals towards a final product, which is molecular hydrogen. Thus, the metal of the platinum group can also increase the efficiency of ultrasonic hydrogen production.

[0095] For example, in some embodiments, the ultrasonic source can be a commercially ceramic sonotrode, which can be optionally modified by doping with at least one catalytically active metal

[0096] Doping of ceramic materials with catalytically active metals, such as the metals of the platinum groups, is disclosed, for example, in US patent application publication 20040067175.

[0097] In some embodiments, the ultrasonic activation of a composition, that contains at least one hydrogen displacing element and has a passivating layer for hydrogen production can be facilitated by a sonication enhancer. Such a sonication enhancer can be a gaseous sonication enhancer, a solid sonication enhancer or a combination thereof. In general, a type of gas that may be used as the gaseous sonication enhancer is not particularly limited.

[0098] Introduction of the gaseous sonication enhancer into a reactor containing water and the composition can produce bubbles in the water and thereby enhance cavitation. In some embodiments, the gaseous enhancer can be such that it can react with water to become an oxide stripper for the composition. One example of such gaseous enhancer is carbon dioxide, CO₂, which can produce by reacting with water a carbonic acid H₂CO₃, which can act as oxide stripper for certain hydrogen displacing elements, such as aluminum.

[0099] A solid sonication enhancer can comprise a plurality of solid particles. Such solid particles can form a suspension in the aqueous solution or water during the ultrasonic treatment. The solid particles oscillating in the suspension with a frequency of the ultrasonic wave can facilitate the activation of the composition by mechanically scratching or milling its passivating layer. In some embodiments, the solid particles can be ceramic particles comprising, for example, Al₂O₃, SiC or another hard material. Preferably, an average size of solid particles used as a solid sonication enhancer is sufficiently smaller that an average size of particles or pieces of the composition. For example, an average size of solid particles for enhancing ultrasonic activation of the composition in a form of a fine powder can be smaller than an average size of solid particles for enhancing ultrasonic activation of the composition in a form of chips. In some embodiments, the average size of particles used as a solid sonication enhancer can be at 1.5 or at least 2 or at least 5 or at least 10 times smaller than the average size of particles or pieces of the composition. [0100] The size of particles that can be used as solid sonication enhancers can vary. In some embodiments, such particles can have an average size of no more than 5 mm or no more than 2 mm or no more than 1 mm or no more than 0.5 mm or no more than 0.2 mm or more than 0.1 mm or no more than 0.05 mm or no more than 0.02 mm or no more than 0.01 mm or no more than 0.005 mm.

[0101] For ultrasonic activation, a molar ratio between hydrogen-displacing element(s) in the composition and water can be stoichiometric or non stoichiometric. In some embodiments, it may be preferred to use the molar ratio between the hydrogen-displacing elements(s) in the composition and water that is no more than 2 times less than the stoichiometric ratio, or no more than 1.5 times less than the stoichiometric ratio, or no more than 1.2 time less than the stoichiometric ratio, or no less than the stoichiometric ratio or no more than 0.8 time less than the stoichiometric ratio. For example, when the composition is an aluminum composition, a stoichiometric molar ratio between aluminum and water in hydrogen producing reaction is 1 :3. For effective ultrasonic activation of the aluminum composition, it may be preferred to provide aluminum and water in a molar ratio (A1:H₂O) of no less than 1 :6, or no less than 1 :4.5, or no less 1 :3.6, or no less than 1 :3, or no less than 1 :2.4. or no less than 1 :1.8.

[0102] In some embodiments, it may be useful to preheat the mixture comprising of water and the composition prior to ultrasonic activation to an elevated temperature, which can be from 50 to 120 C or from 50 to 100 C or from 60 to 80 C. [0103] In some embodiments, the composition and water may be exposed to the ultrasonic treatment in a presence of an oxide stripper.

[0104] When the composition is a silicon containing composition, the composition and water may be exposed to the ultrasonic treatment in a presence of an excess of OH^* ions in water , which means that a concentration of OH^" is higher than can be normally found in water. The excess of OH^" ions may be achieved by adding to water an alkali hydroxide, such as KOH or NaOH, prior or during the ultrasonic treatment. [0105] Non-hydrogen products of ultrasonic hydrogen production can be such that they do not contain by-products of chemical oxide strippers, such as, for example, alkali aluminates. Accordingly, the non-hydrogen products of the hydrogen production can be recycled in an energy efficient manner using, for example, when the composition comprises aluminum, the recycling techniques detailed above or an alkali carbonate based technique discussed in details below. The non-hydrogen products of ultrasonic hydrogen production can be also used as a final commercial product after drying.

ULTRASONIC APPARATUS

[0106] Figure 5 illustrates an embodiment of an apparatus 700 that can be used for ultrasonic hydrogen production. The apparatus 700 includes a vessel or container 701 and an ultrasonic source 702.

[0107] The vessel or container 701 preferably has an inner volume that can contain an aqueous solution or water per se and a composition, that contains at least one hydrogen displacing element and has a passivating layer. The composition illustrated in Figure 5 can be in a form of a plurality of particles 706. The vessel or container 701 can be formed of a conventional material, such as stainless steel, zinc -plated steel or zinc. The material of the vessel or container 701 may be selected to be such that it does not react with water when the ultrasonic action is applied. The ultrasonic source

702 is configured to be in a sonic communication with the aqueous solution in the inner volume of the vessel or container 701. Although the ultrasonic source 702 as shown in Figure 5 is in a direct physical contact with the aqueous solution, in some embodiments, an ultrasonic source can be in a sonic communication, but not in a direct physical contact, with the aqueous solution and the composition.

[0108] The ultrasonic source 702 includes at least a portion configured to produce an ultrasonic action. The portion can include a transducer 712, which can be, for example, a horn type transducer, and a connected tip 708, which is also know as a sonotrode. The transducer is an electro-mechanical component that converts electrical oscillations at ultrasonic frequencies generated by a generator 703 into mechanical vibrations, which are transmitted by the sonotrode 708 into materials to be sonified, i.e. the materials contained in the vessel or container 701. At least a portion or the entire sonotrode 708 can be configured so as to be immersed or dipped in the aqueous solution. At least a portion of the transducer 712 can be also configured to be immersed or dipped into the aqueous solution as well.

[0109] The ultrasonic transducer 712 can be a horn type transducer, such as the one available commercially, for example, from Hielscher Ultrasonics GmbH, Germany. [0110] The ultrasonic sonotrode 708 can be a glass or ceramic sonotrode available commercially from, for example, Hielscher Ultrasonics GmbH, Germany. In some embodiments, a surface of the glass or ceramic sonotrode can be modified by doping with at least one metal of the platinum group, such as Ru, Rh, Pd, Os, Ir, Pt, Co or Ni. [0111] Dimensions of each of the transducer 712 and the sonotrode 708 can be adjusted with the dimensions of the vessel or container 701 in order to provide an efficient sonication of the materials contained in the vessel or container 701 as known to those of ordinary skill in the art.

[0112] The transducer 712 is connected to the generator 703. The generator 703 can control a frequency and/or intensity of the ultrasonic signal and can also control whether the ultrasonic signal is generated in continuous or pulsed manner. When the ultrasonic signal is a pulsed ultrasonic signal, the generator 703 can also regulate a duration of individual pulses and pauses. The generator can be configured to provide an intensity of the ultrasonic signal efficient to activate the composition contained in the vessel or container 701.

[0113] The ultrasonic generator 703 can be an ultrasonic generator commercially available, for example, from Hielscher Ultrasonics GmbH, Germany, or from Sonics & Materials, Inc., Newtown, Connecticut.

[0114] Power output of the transducer, the sonotrode and/or the generator can be adjusted according to the dimensions of the vessel or container 701 as known to those of ordinary skill in the art.

[0115] For example, for larger scale applications, the transducer, the sonotrode and the generator can be such that they can produce an ultrasonic signal with power of at least 50 W or at least 100 W or at least 250 W or of at least 500 W or at least 1 kW or at least 2 kW or at least 5 kW or at least 10 kW or at least 15 kW or at least 20 kW. [0116] In general, for a larger volume of the may require a larger power of the ultrasonic signal.

[0117] The vessel or container 701 can be surrounded by a conventional heat exchange system 709. The heat exchange system can be a fluid circulating heat exchange system, such as a water circulating heat exchange system. The circulating heat exchange system can include a thermostat 704 that controls the flow and/or the temperature of the fluid to regulate the temperature in the vessel or container 701. [0118] The apparatus 700 can include a cover 710 for the vessel or container 701. The cover 710 has an inlet 705 for feeding the composition 706 into the vessel or container 701 and an outlet 711 for collecting the generated hydrogen gas. The inlet 705 also can be used for introducing a gaseous sonication enhancer, such as CO₂, in the vessel or container 701.

[0119] Figure 5 also shows bubbles 707, which can be created in the aqueous solution contained in the vessel or container 701, when ultrasonic oscillations are generated by the ultrasonic source 702. Collapse of the bubbles 707 near a surface of particles 706 of the composition, can reduce the passivating layer of the composition, thereby activating the composition for reacting with water of the aqueous solution to produce hydrogen gas, which can be collected through the outlet 711.

ULTRASONIC FLOW THROUGH METHOD AND APPARATUS

[0120] The present inventors also developed a flow-through ultrasonic method and apparatus for producing hydrogen.

[0121] The flow-though hydrogen producing method involves providing a flowing mixture that comprises water and a composition that comprises at least one hydrogen displacing element and has a natural passivating layer, and exposing the mixture to an ultrasonic action, which can activate the composition by reducing its passivating layer so that the activated composition can react with water and produce the hydrogen gas, which can be collected.

[0122] The flowing mixture refers to a non-static mixture that moves with a nonzero flow rate.

[0123] In some embodiments, the flowing mixture can further comprise at least one oxide stripper, such as those discussed in a greater detail above. [0124] In some embodiments, the flowing mixture may further include at least one sonication enhancer, which may be a gaseous sonication enhancer, such as CO₂, a solid sonication enhancer or a combination thereof.

[0125] Preferably, the composition is a metal composition comprising at least one hydrogen displacing metal.

[0126] The composition may be in any form that is capable of moving in a flow. For example, the composition may in a form of particles including grindings, turnings or boarings. A size of the particles may vary. In some embodiments, the particles of the composition may have an average size of less than about 20 mm or less than about 10 mm or less than about 5 mm or less than about 2 mm or less than about 1 mm. [0127] In some embodiments, the composition may comprise aluminum. In many embodiments, the composition may consist essentially of aluminum. In such a case, the reaction between the composition and water may be written as: [0128] 2Al + 6H₂O -> 2Al(OH)₃ + 3H₂ [0129] The composition for hydrogen production may be a scrap composition. [0130] Prior to or during exposing the composition to the ultrasonic action, the size of particles in the composition may be reduced to a desired size by, for example, grinding or milling the composition. Such desired size can be, for example, less than 5 mm or less than 2 mm or less than 1 mm or less than 0.5 mm. [0131] Prior to or during exposing the mixture to the ultrasonic action, the mixture may be premixed to create a more homogenous mixture. Such premixing or homogenizing may be accomplished using a variety of methods, including mechanical techniques, such as grinding or milling. In certain embodiments, the mixture may be premixed or homogenized ultrasonically. An ultrasonic generator that is used for such ultrasonic premixing or homogenizing may the same or different than an ultrasonic generator used to produce the ultrasonic action that can activate the composition.

[0132] The ultrasonic action that can activate the composition in the flowing mixture may have a frequency ranging from 15 kHz to 2 MHz or from 15 kHz to 1 MHz or from 15 kHz to 500 kHz or from 15 kHz to 200 kHz or from 15 kHz to 100 kHz or from 15 kHz to 50 kHz or from 15 kHz to 30 kHz or from 15 kHz to 25 kHz. [0133] A source of the ultrasonic action, such as an ultrasonic converter or an ultrasonic sonotrode, may or may be not in a direct physical contact with the flow. The above disclosure related to the ultrasonic treatment is in general applicable to the flow through method and apparatus as well.

[0134] In some embodiments, non-hydrogen products of the reaction between the composition and water may be collected.

[0135] The produced hydrogen may be separated from other gaseous components, such as water vapors, CO₂ and/or air components, using, for example, a hydrogen membrane or filter, such as those commercially available SAES Pure Gas; Quest Air Technologies Inc., Texaco Ovonic Hydrogen Systems; or FuelCellStore, San Diego. [0136] FIG. 6 illustrates a flow through ultrasonic hydrogen production apparatus

600. The apparatus 600 includes an ultrasonic source 602 and a flow through vessel

601, which is configured to process a flow of a mixture comprising water and a composition having a passivating layer. The vessel 601 has an inner space 615 defined by the vessel's wall(s), an inlet 606 and an outlet 607. The ultrasonic source 602 is configured to produce an ultrasonic action that can activate the composition processing through the inner space 615 of the vessel 601 by reducing the passivating layer of the composition, so that the activated composition can react with water. [0137] The ultrasonic source 602 can include a ultrasonic generator 604, which can be powered by an electric power source 605. The ultrasonic generator 604 is configured to generate electric oscillations at least one ultrasonic frequency. The ultrasonic source 602 can further include an electro-mechanical component, which is known as a transducer, that is configured to convert the electric oscillations produced by the generator 604 into ultrasonic mechanical vibrations. Such an electromechanical component may expose the mixture in the inner space 615 of the vessel 601 directly or indirectly to the ultrasonic mechanical vibrations. For the indirect exposure to the ultrasonic mechanical vibrations, the ultrasonic source 602 may include an ultrasonic transmitter or a sonotrode that can transmit the ultrasonic mechanical vibrations from the transducer to the mixture flowing through the inner space 615 of the vessel 601.

[0138] An element of the ultrasonic source, such as a transducer or a sonotrode, that exposes the mixture flowing through the inner volume of the vessel 601 to the ultrasonic mechanical vibrations, may or may be not in a direct physical contact with the mixture.

[0139] The ultrasonic source may include multiple sonotrodes, each configured to transmit ultrasonic mechanical vibrations into the mixture. For example, the ultrasonic source in Figure 6 includes a sonotrode 603 and a sonotrode 617, that is located downstream from the sonotrode 603. Multiple sonotrodes may be connected to the same transducer or different transducers. In Figure 6, sonotrodes 603 and 617 are connected to the same transducer 616, which in turn connected to the generator 604.

[0140] The ultrasonic generator of the ultrasonic source 602 can control a frequency and/or intensity of the ultrasonic vibrations. The ultrasonic generator may also control whether the ultrasonic vibrations are generated in a continuous or pulsed manner. When the ultrasonic vibrations are generated in a pulsed manner, the generator can regulate a duration of individual pulses and pauses. When the ultrasonic source includes multiple sonotrodes, the ultrasonic generator may be configured to provide the same or different pulse sequences to the sonotrodes. The pulse sequences provided on separate sonotrodes may be correlated. For example, for the apparatus in Figure 6, respective pulses sequences provided on the sonotrodes 603 and 617 may be such that a pause on the sonotrode 603 may correspond to a pulse on the sonotrode 617 and vice versa.

[0141] The ultrasonic generator can be configured to produce ultrasonic vibrations having an intensity sufficient to activate the composition. Such intensity may vary depending on a number of parameters including a size of the vessel 601 and a mass of the composition. In some embodiments, the ultrasonic generator may be such that it can deliver ultrasonic power up to 20 kW or up to 15kW or up to 10 kW or up to 5 kW or up to 3 kW or up to 2 kW W or up to 1 kW W or up to 600 W or up to 300 W or up to 200 W or up to 100 W. Appropriate ultrasonic generators are commercially available from a number of companies including Hielscher Ultrasonics GmbH, Germany and MPI Ultrasonics, Switzerland.

[0142] The ultrasonic source 602 may be configured to produce ultrasonic vibrations at at least one frequency ranging from 15 kHz to 2 MHz or from 15 kHz to 1 MHz or from 15 kHz to 500 kHz or from 15 kHz to 200 kHz or from 15 kHz to 100 kHz or from 15 kHz to 50 kHz or from 15 kHz to 30 kHz or from 15 kHz to 25 kHz. [0143] The flow-through vessel may have a number of shapes. In many embodiments, the flow-through vessel may be a pipe or tube. In such a case, one can use one or more clamp-on sonotrodes, which may be clamped on the pipe or tube. For example, Figure 9 presents a photograph of a flow-through vessel made as a stainless steel pipe, which has two clamp on sonotrodes clamped on it. Clamp-on sonotrodes are commercially available from MPI Ultrasonics, Switzerland. [0144] Preferably, walls of the flow-through vessel, that define its inner volume, are such that they are able to withhold a pressure of the flow of the mixture passing through the vessel. In certain embodiments, the walls of the vessel may be configured to withhold a pressure of at least 1 atm or at least 2 atm or at least 3 atm or at least 5 atm. Preferably, the walls of the follow-through material are made of the materials that does not react with water when exposed to ultrasonic vibrations that can activate the composition of the flow passing through the inner volume of the vessel. One non- limiting example of appropriate material for the walls of the vessel may be stainless steel.

[0145] The hydrogen produced in the reaction between the composition and water may be collected in the apparatus 600 using a number of ways. In some embodiments, the produced hydrogen may be collected through the outlet 607. Yet in some embodiments, the vessel 601 may have a hydrogen outlet 608 configured to collect the produce hydrogen. Because the hydrogen is a light gas, the hydrogen outlet 608 is preferably located on the upper side of the vessel 601. The outlet 608 may include a valve or a vent configured to open when a gaseous pressure in the vessel reaches a certain value. The outlet 608 may include a filter or condenser configured to separate the produced hydrogen from other gaseous components, which may be present in the inner volume of the vessel, such CO₂ or water vapor. The filter may allow increasing a purity of hydrogen gas to a desired value, such as 99.9% or 99.99% or 99.999%. In certain embodiments, the filter may be a hydrogen membrane. The outlet 608 may include a hydrogen sensor or detector configured to determine a purity of produced hydrogen gas. The hydrogen sensor or detector can be, for example, a sensor or detector commercially available from Neodym Tech, Inc., Canada.

[0146] One or more non-hydrogen products of the reaction between the composition and water may be collected in a collector 611, which may be fluidically connected to the outlet 607 of the vessel 601. For example, when the composition consists essentially of aluminum, the non-hydrogen products of the reaction between the composition and water include may consist essentially of aluminum hydroxide and/or aluminum oxide. Such non-hydrogen products can be recycled using, for example, one of the recycling processes disclosed in the present application or used in a final commercial product.

[0147] In some embodiments, the flow through vessel 601 may have a gaseous inlet 609, which can be used for introducing one or more gaseous compounds into the inner volume of the vessel 601 from a gas source, such as a compressed gas tank. Such a gaseous compound may act as a gaseous sonication enhancer as explained above. A preferable gaseous compound to be introduced in the inner volume of the vessel may be CO₂, which may act as both a sonication enhancer and an oxide stripper. In some embodiments, the flow through vessel may also comprise an inlet that be used for introducing one or more oxide strippers into the inner space of the flow through vessel. Such oxide strippers can facilitate the activation of the composition. [0148] In many embodiments, the ultrasonic flow through apparatus 600 may further comprise a mixer 613, which is configured to mix or homogenize the mixture comprising water and the composition prior to its entry to the inner space of vessel through the inlet 606. Such a homogenization of the mixture may facilitate the reaction of water and the composition under the ultrasonic action in the vessel. [0149] A particular type of the mixer 613 is not limiting. In some embodiments, for example, the mixer 613 may be a mechanical mixer. Yet in some embodiments, the mixer 613 may be an ultrasonic mixer. For example, Figure 6 shows a ultrasonic sonotrode 614 configured to homogenize the mixture by transmitting the ultrasonic mechanical vibrations in the mixture. In such a case, the ultrasonic sonotrode 614 may be in a functional relationship with the ultrasonic generator 604 or an ultrasonic generator that is different from the generator 604.

[0150] An outlet of the mixer 613 is fluidically connected to the inlet 606 through, for example, a pipe or a hose. The fluidic connection between the mixer 613 and the vessel 606 may include one or valves and/or one or more pumps, which may be used to control the flow of the mixture.

[0151] The mixer 613 may have one or more inlets for introducing the composition and water. In some embodiments, the composition and water may introduced into the mixer as part of the same mixture through the same inlet. Yet in some embodiments, water and the composition may introduced into the mixer through separate inlets. Such a case is illustrated in Figure 6, which shows a water source 61 1 fluidically connected to the mixer 613 through one inlet, and a source 612 of the composition, which is configured to provide the composition in another inlet of the mixer 613. [0152] The apparatus 600 may further include a control system, which may comprise a computer. Such a control system may be configured to control the reaction between the composition and water by, for example, monitoring hydrogen production at the hydrogen outlet and by varying parameters of the ultrasonic action, such as ultrasonic intensity, and parameters of the flowing mixture, such as a flow rate.

[0153] The apparatus 600 may function as a single hydrogen production unit or serve as a building block of a larger hydrogen production facility. Such hydrogen production facility may include a plurality of single hydrogen production units, each comprising an ultrasonic source, such as the source 602, a flow-through vessel, such as the vessel 601 and optionally a mixer, such as the mixer 613. [0154] The apparatus 600 may also include a mill or a grinder configured reduce a size of particles in the composition to a desired size. In some embodiments, such a mill or a grinder may be a part of the mixer 613. Yet in some embodiments, the mill or grinder may be functionally connected with a pump and thus be separate from the mixer 613.

[0155] Figure 7 is a photograph demonstrating a flow though ultrasonic hydrogen production apparatus, similar to the apparatus 600. The following elements of the apparatus are shown in Figure 7 a pump; a mixer, such as the mixer 613; a flow- through vessel with an associated sonotrode; a hydrogen detector and a ultrasonic generator connected to the sonotrode.

HYDROGEN PRODUCTION ON SMALL AND MEDIUM SCALE

[0156] The present inventors also developed hydrogen production method and apparatus, which may allow production of hydrogen gas on small and medium scales. In particular, the method and apparatus may allow for production of at least 10 g/h, or at least 20 g/h, or at least 30 g/h, or at least 50 g/h, or at least 100 g/h, or at least 200 g/h, or at least 300 g/h, or at least 500 g/h, or at least 1 kg/h, or at least 2 kg/h, or at least 3 kg/h, or at least 4 kg/h, or at least 5 kg/h, or at least 6 kg/h, or at least 7 kg/h, or at least 8 kg/h, or least 9 kg/h, or at least 10 kg/h, of hydrogen gas, or at least 15 kg/h of hydrogen gas, or more.

[0157] The method and apparatus can utilize at least two types of reactors, which have different purposes. In particular, a reactor of a first type ("activating reactor") serves primarily for activating a composition, that contains at least one hydrogen displacing element and has a passivating layer, for a reaction with water by reducing the passivating layer; while a reactor of a second type ("hydrogen production reactor") serves primarily for conducting a hydrogen producing reaction between water and the activated composition transferred from the first reactor. Such an arrangement can make hydrogen production more efficient by utilizing multiple hydrogen production reactors with a single activating reactor. [0158] According to one embodiment, the method involves providing into a first reactor a first portion of a mixture comprising water and a composition that contains at least one hydrogen displacing element and has a passivating layer; activating the composition in the first reactor for a reaction with water by reducing the passivating layer of the composition; transferring the first portion of the mixture, which now comprises the activated composition, into a second reactor and collecting from the second reactor a hydrogen gas produced in the reaction between water and the activated hydrogen composition.

[0159] In some embodiments, the mixture can be formed prior to entering the first reactor. Yet in some embodiments, the mixture can be formed directly in the first reactor, i.e. the composition and water can be provided separately. [0160] The activation of the composition in the first reactor can be performed via a number of methods. In many embodiments, the activation of the composition by exposing the composition to ultrasonic vibrations. The exposure to ultrasonic vibrations may be performed as detailed in the above sections of this disclosure. [0161] In some embodiments, the ultrasonic action may be enhanced by exposing the composition to one or more sonication enhancers, which can be a gaseous sonication enhancer, a solid sonication enhancer or a combination thereof. The sonication enhancers that can be used in the present method can be the same as those discussed above.

[0162] In some embodiments, the mixture may be non-static during the activation in the first reactor, i.e. when the mixture comprising water and the composition has a non-zero flow rate. Yet in some other embodiments, the mixture may be static during the activation in the first reactor, i.e. when the mixture comprising water and the composition has a zero flow rate. Performing the ultrasonic activation on the static composition may allow one to increase an efficiency of the activation as a particular portion of the composition may be exposed to the ultrasonic vibrations for a prolonged period of time. In some embodiments, the static mixture may be exposed to the ultrasonic vibrations for at least 5 sec or at least 10 sec or at least 20 sec or at least 0.5 min or at least 1 min or at least 2 min or at least 5 min or from 5 sec to 10 min or from 10 sec to 10 min or from 10 sec to 5 min or from 0.5 min to 3 min or from 20 sec to 5 min or from 1 min to 2 min.

[0163] In some embodiments, the method may involve grinding or milling the composition the composition. Such grinding or milling can be performed outside or inside the first reactor. The grinding or milling may reduce an effective size of particles of the composition. The grinding or milling may also expose on the composition one or more fresh surfaces, which are not yet covered by the passivating layer, and thus contribute to the activation of the composition for the reaction with water.

[0164] In some embodiments, the method may involve monitoring hydrogen production in the second reactor, which may be done using a hydrogen detector. Once a rate of hydrogen production in the second reactor is reduced below a certain threshold due to formation of a fresh passivating layer on the composition, the composition may be transferred to an activation reactor for reactivation. The fresh passivating layer may be the same or different in a chemical composition as the initial passivating layer. For example, for aluminum, the initial passivating layer can be an aluminum oxide layer, while the passivating layer form during the reaction with water can be an aluminum hydroxide layer.

[0165] In some embodiments, the composition may be transferred back to the first reactor for reactivation. Yet in some embodiments, the composition may be transferred for reactivation to an activation reactor, which is different from the first reactor.

[0166] As the activation, the reactivation may be performed on a static or a non- static mixture comprising the partially reacted composition and water. [0167] In many embodiments, the freshly formed passivating layer may be removed under milder conditions than the initial passivating layer. For example, for ultrasonic reactivation of the static mixture comprising the partially reacted composition, the reactivation time may be less than the initial activation time for the same otherwise parameters of the ultrasonic vibrations in the activation and reactivation steps. For example, if the initial composition was ultrasonically activated for 2 minutes, the partially reacted composition may be ultrasonically reactivated for 1 minute.

APPARATUS FOR SMALL/MEDIUM SCALE HYDROGEN PRODUCTION

[0168] Figure 10 schematically illustrates an apparatus 1000 that can allow a production of hydrogen gas on a small/medium scale. The apparatus 1000 includes an activating reactor 1012, which has an inner volume with an inlet 1017 and an outlet 1018. The inlet 1017 serves for introduction of water and a composition, that contains at least one hydrogen displacing element and has a passivating layer, into the inner volume of the reactor 1012 and the outlet 1018 serves for removing from the inner volume of the reactor 1012 the composition activated in the reactor 1012. The reactor 1012 can be a tube or a pipe, see e.g. FIG. 11 and 12. A wall or walls of the reactor 1012 that define its inner volume, can be made from a number of materials, as long as this material does not react with water during the activation of the composition and is able to withheld pressures under which the apparatus 1000 operates. Such pressures can be at least 1 atm or at least 2 atm or at least 3 atm. One non-limiting example of the appropriate material is a stainless steel.

[0169] The reactor 1012 can have one or more ultrasonic sources configured to expose the composition in the inner volume of the reactor 1012 to ultrasonic vibrations. The ultrasonic source can be similar to ultrasonic sources discussed above in this disclosure. The ultrasonic source can include an element, such as a transducer or a sonotrode that exposes the mixture of water and the composition in the inner volume of the reactor 1012 to mechanical ultrasonic vibrations. Such an element may or may not be in a direct physical contact with the mixture comprising water and the composition in the inner volume of the reactor 1012.

[0170] The reactor 1012 may have multiple sonotrodes, each configured to transmit ultrasonic mechanical vibrations to the mixture in the reactor's inner volume. Multiple sonotrodes may be powered by the same or different ultrasonic generators. [0171] In some embodiments, the reactor 1012 can be a hollow tube with two clamp-on sonotrodes 1019, such as those available commercially from MPI

Ultrasonics, Switzerland clamped over its outer surface.

[0172] The composition activated in the reactor 1012 is transferred to a hydrogen production reactor 1015, where the activated composition can react with water to produce hydrogen gas. To transfer the activated composition, the outlet of the reactor

1012 may be connected to an inlet 1020 of the reactor 1015 through a fluidic connection such as a pipe or hose. The fluidic connection between the reactors 1012 and 1012 may include one or more valves, such as a valve 1022.

[0173] The reactor 1015 can be a vessel or a chamber that has an inner space defined by its wall(s). The material of the wall(s) of the reactor can be such that it does not interfere with the hydrogen producing reaction. One non limiting example of an appropriate material can be stainless steel.

[0174] The inner space of the hydrogen production reactor 1015 can have a volume no less than a volume of the inner space of the activating reactor 1012 so that the hydrogen production reactor is capable to accommodate the composition activated in the activating reactor.

[0175] The activating reactor 1012 may be connected to multiple hydrogen production reactors. For example, as shown in Figure 10, the activating reactor is connected to five hydrogen production reactors 1015A-1015E.

[0176] The hydrogen production reactor 1015 can be a vessel having an inner space with an inlet configured for introduction of the mixture comprising the activated composition and water. The hydrogen production reactor 1015 can have a hydrogen outlet configured to release hydrogen gas produced in the reaction between the activated composition and water from the inner space of the reactor 1015. Because hydrogen is lighter that air, the hydrogen outlet is preferably located in the upper portion of the reactor 1015, which is above the part of the reactor filled with the mixture comprising the composition and water.

[0177] The hydrogen outlet may include a filter or a condenser configured to separate the produced hydrogen from other gaseous components, which may be present in the inner space of the reactor 1015. The filter may allow to increase a purity of hydrogen gas to a desired value, such as 99.9% or 99.99% or 99.999%. In some embodiments, the filter may comprise a hydrogen membrane, such as those commercially available from SAES Pure Gas.

[0178] In addition to the hydrogen outlet, the hydrogen production reactor may also include a non-hydrogen outlet, through which one or more non-hydrogen products of the reaction and/or non-reacted composition may removed from the reactor 1015. [0179] The apparatus 1000 may also include one or more hydrogen detectors, which may used to monitor hydrogen production in one or more hydrogen production reactors, such as reactors 1015A-1015E. A single hydrogen detector may used to monitor in one or more hydrogen production reactors. For illustrative purposes only, Figure 10 shows a hydrogen detector 1023 used to monitor in hydrogen production reactors 1015A-1015E. The hydrogen detector may be positioned inside the hydrogen production reactor, at the hydrogen outlet of the hydrogen production reactor or on a hydrogen transport line 1025.

[0180] During the hydrogen forming reaction between the composition and water, a new passivating layer may form on the composition, which may reduce the rate of the reaction and eventually stop it. The newly passivating formed layer may be chemically the same or different than the initial passivating layer on the composition. For example, in case of aluminum, the initial passivating layer comprises predominantly aluminum oxide, while the passivating layer formed during the reaction with water comprises predominantly aluminum hydroxide. [0181] When hydrogen production stops or reduces below a certain level due to the formation of the new passivating layer on the composition, the unreacted composition may be reactivated. In some embodiments, the reactivation of the unreacted composition may performed in the same activating reactor, where the initial activation was performed. Yet in some embodiments, the reactivation may be performed in an activating reactor that is different from the activating reactor, where the initial activation was carried out. For example, the apparatus 1000 in Figure 10 can include a reactivating reactor 1014. The reactor 1014 can be similar to the reactor 1012. An inlet of the reactor 1014 can be connected to the non-hydrogen non outlet of the reactor 1015 through a fluidic connection, such as a pipe and a hose. Similarly to the reactor 1012, the reactor 1014 may be connected to one or more hydrogen production reactors, labeled as 1026 in Figure 10.

[0182] An activating reactor, such as reactors 1012 or 1014, and associated with it one or more hydrogen production reactors, such as reactors 1015 for the reactor 1012 or the reactors 1026 for the reactor 1014, form a single hydrogen production stage. The apparatus may include multiple hydrogen production stages, which may be connected in parallel and/or in series. For example, in Figure 10, the hydrogen production stage that comprises the activating reactor 1012 and associated hydrogen production reactors 1015, is in parallel with a hydrogen production stage that comprises an activating reactor 1013 and associated with it hydrogen production reactors 1016. At the same time, the hydrogen production stage that comprises the activating reactor 1012 and associated hydrogen production reactors 1015 is in series with the hydrogen production stage that comprises the reactivating reactor 1014 and associated hydrogen production reactors 1026.

[0183] Multiple hydrogen production stages in parallel may increase an amount of the composition that the apparatus can process at the same time and thereby increase an amount of hydrogen gas the apparatus produces per unit of time. [0184] Multiple hydrogen production stages in series may allow one to utilize the composition for hydrogen production more efficiently because a greater percentage of the composition can participate in the hydrogen producing reaction with water. The method and apparatus of the present inventions may allow at least 50 % or at least 60 % or at least 70 % or at least 80 % or at least 90 % or 95 % or at least 99 % or at least 99.5 % or at least 99.9 % of the composition by mass to react with water in the hydrogen -producing reaction.

[0185] The hydrogen production stages, each comprising an activating reactor and one or more hydrogen production reactors, can provide a flexibility for the use of the hydrogen production apparatus 1000. A number of hydrogen production stages in parallel may be adjusted in the apparatus based on the desired or required hydrogen producing capability (mass of hydrogen gas produced per hour), while a number of hydrogen production stages in series may be varied based on the initial formulation of the composition. A greater number of stages in series may be required for a composition with a larger average size of particles, than to the otherwise identical composition but with a smaller size of particle.

[0186] The hydrogen production apparatus may also include a mixing reactor which can be configured to mix or homogenize the mixture comprising water and the composition prior to its entry in an activator reactor. For example, Figure 10 shows a mixing reactor 1027, which is configured to mix and or homogenize the mixture comprising water and the composition, before the mixture's entry to the activating reactor 1012 and/or the activating reactor 1013. The mixing reactor can have a inner space with one or inlets configured for introducing water and the composition and an outlet for removing the mixture from the inner space of the mixing reactor. For example, the mixing reactor 1027 has an inner space 1004 defined by its body 1003; an inlet 1028 for introducing the composition into the inner space of the mixing reactor, an inlet 1029 for introducing water in the inner space of the mixing reactor and an outlet 1011 for removing the mixture from the reactor. The inlet 1029 is connected to a water supply line 1002; the inlet 1028 is connected to a composition supply line 1001; while the outlet 1011 is connected through a fluidic connection 1030 to the inlet of the activating reactor 1012. The mixing reactor can include a mixer, i.e. a device configured to perform mixing or homogenizing of water and the composition. A particular type of the mixer is not limiting. In some embodiment, the mixer may be a mechanical mixer, such a mixer 1005 in Figure 10. Yet in some other embodiments, the mixer may be an ultrasonic mixer. The mixing reactor 1027 can also optionally include a drain outlet 1007 configured to drain water from the inner space 1004 of the reactor; a reagent inlet 1006, which can be used to introduce one or more reagents into the mixture; an overflow outlet 1034 connected to an overflow line 1010 and a vent overflow outlet connected to a vent overflow line 1009. [0187] For transferring the mixture in its different states between various reactors, the hydrogen production apparatus may include one or more pressurizing devices, such as pumps. For example, as shown in Figure 10, a fluidic connection 1030 between the mixing reactor 1027 and the activating reactor 1012 includes a pump 1031, which may be used for transferring the mixture in an unactivated state from the mixing reactor 1027 into the activating reactor 1012 and also for transferring the mixture in the activated state from the activating reactor 1012 into one or more of the hydrogen production reactors 1015. Similarly, a fluidic connection 1033 between the hydrogen production reactors 1015 and/or the reactivating reactor 1014 may include a pump 1032 which may be for transferring the mixture in a partially reacted state from one or more hydrogen production reactors 1015 into the reactivating reactor 1014 and/or for transferring the mixture in a reactivated state from the reactivating reactor 1014 into one or more hydrogen production reactors 1026. [0188] Transferring the mixture in its different state from one reactor to another may be performed by regulating a state of one or more valves of the apparatus 1000. For example, for transferring the mixture in the unactivated state from the mixing reactor 1027 into the activating reactor 1012, valves 1034, 1035 and 1036 can be open while inlet valves 1022 (1022A-1022E) of the hydrogen production reactors 1015 can be closed. For transferring the mixture in the activated state from the activating reactor 1012 into one of the hydrogen production reactors 1015 (e.g. reactor 1015A), the valves 1035, 1036 and the inlet valves 1022A of the reactor 1015A can be open, while the valve 1034, the inlet 1022B-1022E of the reactors 1015B-1015E as well as the outlet valve 1037 A of the reactor 1015 A can be closed. [0189] Volumes of the activation reactors, such as reactors 1012 and 1014, and hydrogen production reactors, such as reactors 1015, 1016 and 1026, may vary depending on desired hydrogen production scale. For example, if the volume of each hydrogen production reactor and each activation reactor is about 2 L, the apparatus may be capable of producing as much as 6 kg/h of hydrogen. [0190] The hydrogen production apparatus may include a control system, which may comprise a computer. The control system may be configured to perform a number of tasks, such as regulating transfer of the mixture from one reactor to another thought the valve system; monitoring hydrogen production in the hydrogen production reactors; controlling one or more parameters in one of the reactors, e.g. controlling one or more ultrasonic action parameters in the activating reactor, such as a duration of action; a pulse sequence, an intensity of action and a frequency of the action, or controlling one or more parameters in the hydrogen production reactor, such temperature or pressure. The control system may coordinate operation of the reactors of the apparatus. For example, when the control system receives a reading from the hydrogen detector 1023 that hydrogen production in the hydrogen production reactor 1015 stopped or reduced below a certain threshold level, the system may change a configuration of the valves for transferring the mixture from the hydrogen production reactor 1015 into the reactivation reactor 1014.

[0191] Non-hydrogen products of the hydrogen producing reaction may be collected from the hydrogen production reactors of the last stage of the apparatus 1000, such hydrogen production reactors 1026, in a collection vessel 1040, which may be connected to the hydrogen production reactors of the last stage through a line 1041. [0192] Hydrogen produced in the apparatus 1000 may be delivered directly to a hydrogen consuming machine or apparatus or alternatively produced hydrogen may be stored for a future use. The produced hydrogen may be stored using a number of methods including a) pressurizing hydrogen for storing in gas cylinders; b) storing hydrogen in metal hydride forming materials and c) methods disclosed in U.S. provisional patent application no. 61/000,751.

[0193] Figure 8 presents a photograph of a hydrogen producing apparatus, which includes the following elements: an activation reactor, which includes a tube with two clamp on sonotrodes, a hydrogen production reactor and a circulator/pump, which can be used for transferring a hydrogen producing composition activated in the activation reactor in the hydrogen production reactor. Rubber hoses are used for fluidic connections between the activation reactor, the hydrogen production reactor and the circulator/pump. The circulator/pump in Figure 13 is Lauda® Ecoline Refrigerating Circulator RE-206, commercially available from Brinkmann Instruments.

HYDROGEN PRODUCTION COMPOSITIONS WITH AN ARTIFICIAL ANTI- OXIDATION LAYER

[0194] The present inventors have also developed an activated composition that comprises an oxidizable hydrogen-displacing element, preferably an oxidizable hydrogen displacing metal, such as Al, and has an artificial, i.e. a non-natural, protective layer that can prevent a formation of a natural passivating layer of the activated composition. In other words, the hydrogen production composition has its natural passivating layer fully or partially removed and replaced by the artificial protective layer.

[0195] Preferably, the artificial layer may be such that it can be easily removed for the hydrogen-producing reaction of the activated composition with water, i.e. removed under the conditions that are milder than those required for removal of the natural passivating layer of the composition.

[0196] In some embodiments, the artificial layer on the composition may be a water soluble layer. Examples of water soluble protective layers include layers comprising polyvinyl alcohol or polyacrylic acid. In some embodiments, water soluble protective layers can pH-dependent protective layers, i.e. protective layers that can dissolve in water at a certain pH range.

[0197] In some embodiments, the artificial layer on the composition may be a thermally activatable protective layer, i.e. a protective layer that can be removed by being exposed to an elevated temperature. The elevated temperature that can be used for activation may range from 35 C to 150 C or from 50 C to 150 C or from 50 C to 100 C or from 50 C to 80 C or from 60 C to 80 C or from 60 C to 100 C or from 70 C to 90 C or from 70 C to 120 C. Examples of thermally activatable protective layers are thermosetting resins disclosed in US patent no. 6,576,718. [0198] The activated compositions with an artificial protective layer may be provided in a form of a kit for hydrogen production.

[0199] The activated composition with an artificial protective layer may be used for hydrogen production, when it is brought in contact with water and has its artificial protective layer removed. When the artificial protective layer is water soluble, removal of the layer can occur upon the contact of the composition with water. In some embodiments, the removal of the water soluble artificial protective layer may be facilitated by increasing the temperature of water to, for example, 40 C or to 50 C or 60 C or 70 C or 80 C or 90 C or 95 C. When the artificial protective layer is a pH dependent water soluble layer, the removal of the protective layer can occur when pH of the mixture comprising water and the activated composition is adjusted to a value at which the protective layer dissolves in water. When the artificial protective layer is a thermally activatable protective layer, the removal of the protective layer can occur when the composition is heated to a temperature that activates the removal. [0200] An activated composition with an artificial protective layer may be prepared from a composition having a natural passivating layer by partially or fully removing the passivating layer, thereby activating the composition, and disposing an artificial protective layer on the activated composition.

[0201] Activation of the composition having a natural passivating layer can be performed a number of ways including exposing to an ultrasonic action a mixture comprising water and the composition and/or adding to the mixture an oxide stripper, such as the one discussed above in this disclosure.

[0202] When an oxide stripper, such as aluminum sulfate, is used for activating the composition, the artificial protective layer may comprise the oxide stripper together with a protective material, such as a water soluble protective material or a thermally activated protective material.

[0203] The disposition of the artificial protective layer may be done by adding to the mixture a material, that can form the artificial protective layer, or its precursor before, during or after the activation of the composition. In some embodiments, one or more non-aqueous solvents can be added to the mixture in order to dissolve the artificial protective layer forming material or its precursor. For example, for the formation of polyvinyl alcohol layer or polyacrylic acid layer, the non-aqueous solvent may be an organic solvent, which can be, for instance, an ether, such as an alkyl ether, or an alkyl alcohol, such as ethanol or methanol. After the artificial layer is formed on the activated composition, the composition may be dried by, for example, centrifugating the mixture.

HYDROGEN PRODUCTION FROM Cu/Al COMPOSITIONS

[0204] The present invention also provides a method of hydrogen production from a metal composition, preferably an alloy, that contains copper and aluminum. The metal composition has a passivating layer, which can be reduced or inhibited by exposing the metal composition to an aqueous solution that contains a copper oxide stripper. Such an exposure activates the metal composition, so that the aluminum can react with water of the aqueous solution to generate a hydrogen gas, which can be subsequently collected.

[0205] The copper oxide stripper can be a copper oxide stripping salt, such as sodium chloride or potassium chloride. In some embodiments, for example, the aqueous solution can comprise seawater. The seawater as the aqueous solution can be preferred for hydrogen production in places located in a close proximity to natural seawater sources, such as oceans, seas and lakes.

[0206] A weight percentage of aluminum in the metal composition can vary. For example, the metal composition can contain at least 20 weight % of Al; or at least 40 weight % of Al or at least 50 weight % of Aluminum or at least 80 weight % of

Aluminum.

[0207] In some embodiments, the metal composition can further contain one or more additional metals, such as Mn, Mg, Si, Ti, Fe or Zn.

[0208] In some embodiments, the metal composition can be an alloy comprising aluminum and copper. For example, in some embodiments, the metal composition can be an alloy containing 2.0-5.2 weight % Cu, 0.2-1.0 weight % Mn; 0.2-2.7 weight

% Mg and 91.1-97.5 weight % Al. In some embodiments, the metal composition can be an alloy containing contain 3.0-25 weight % Si or 4.0-22.0 weight % or 4.0-13.0 weight % Si.

USE OF PRODUCED HYDROGEN

[0209] Produced hydrogen may be delivered directly to a hydrogen consuming machine or apparatus or alternatively produced hydrogen may be stored for a future use. The produced hydrogen may be stored using a number of methods including a) pressurizing hydrogen for storing in gas cylinders; b) storing hydrogen in metal hydride forming materials and c) methods disclosed in U.S. provisional patent application no. 61/000,751.

ALUMINUM RECOVERY USING ALKALI CARBONATE

[0210] The present invention also provides a method of transforming an aluminum oxidation product into metallic aluminum. Such a method can be used, for example, for transforming alpha-alumina and/or aluminum hydroxide produced during hydrogen production. The method involves reacting aluminum halide, such as aluminum chloride, produced from the aluminum oxidation product, such as gamma alumina or aluminum hydroxide, with an alkali metal produced by reacting a carbonate of the alkali metal and carbon. The reaction of the aluminum halide and the alkali metal produces the halide of the alkali metal and metallic aluminum. [0211] When the aluminum oxidation product is gamma-alumina, aluminum halide can be produced, for example, by reacting gamma-alumina with alkali earth metal halide, such as calcium chloride.

[0212] When the aluminum oxidation product is aluminum hydroxide, aluminum halide can be produced, for example, by reacting the aluminum hydroxide with a hydrohalogenic acid, such as a hydrochloric acid.

[0213] The following reactions can illustrate the method of transformation gamma- alumina into a metallic aluminum:

[0214] 1) reaction of carbon and alkali carbonate exemplified by sodium carbonate produces an alkali metal (sodium in the present case) and carbon dioxide: [0215] 2Na₂CO₃ + C = 4Na + 3CO₂;

[0216] 2) reaction of alpha-alumina and alkali earth halide exemplified calcium chloride produces aluminum halide (AlCl₃ in this case) and alkali earth metal oxide: [0217] Al₂O₃ + 3CaCl₂ = AlCl₃ + 3 CaO

[0218] 3) the alkali metal (Na) produced in reaction (1) reacts with aluminum halide produced in (2) to produce metallic aluminum and alkali halide (NaCl in the present case):

[0219] AlCl₃ + 3Na = Al + 3 NaCl.

[0220] The method of transformation of aluminum hydroxide into a metallic aluminum can be illustrated by the following reactions:

[0221] 1) reaction of carbon and alkali carbonate exemplified by sodium carbonate produces an alkali metal (sodium in the present case) and carbon dioxide: [0222] 2Na₂CO₃ + C = 4Na + 3CO₂;

[0223] 2) reaction of aluminum hydroxide and a hydrohalogenic acid, such as hydrochloric acid in the present case, produces an aluminum halide and water: [0224] Al(OH)₃ + 3 HCl = AlCl₃ + 3 H₂O;

[0225] 3) the alkali metal (Na) produced in reaction (1) reacts with the aluminum halide produced in (2) to produce a metallic aluminum and an alkali halide (NaCl in the present case):

[0226] AlCl₃ + 3Na = Al + 3 NaCl.

[0227] The present invention, thus generally described, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.

ULTRASONIC TREATMENT

[0228] Ultrasonic experiments of Examples 4, 7-9 were performed in an apparatus as described in Figure 5. Walls of a reactive vessel (reactor) of the apparatus were made of stainless steel. The inner diameter of the reactive vessel was 25 mm. 13 mm diameter ceramic sonotrode from Hielscher was used. The ultrasonic generator used was Sonics & Materials Model 2020 generator. To fasten the sonotrode in the reactor standard O-rings were used. The reactor had double walls for circulating a cooling liquid, which was looped through a standard thermostat. The thermostat maintained a temperature in the reactor within ± 1 ⁰C.

[0229] CO₂ in Examples 8 and 9 was supplied to the reactor from a gas cylinder through a flowmeter. The CO₂ flow varied from 1 to 100 mL /min.

EXAMPLE 1

[0230] 300 g of aluminum powder (particles of pure Al with oxide layer) with an average particle size of 5 μm were reacted with 500 g of water and lOOg of 5 weight % NaOH solution in a reactor. The temperature of the reactor was maintained at 50 ⁰C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 20 g.

EXAMPLE 2

[0231] 300 g of aluminum powder with an average particle size of 5 μm were reacted with 500 g of water and lOOg of 5 weight % NaOH solution in a reactor. The temperature of the reactor was maintained at 85 °C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 27 g.

EXAMPLE 3

[0232] 30Og of 5 weight % NaOH solution were used to activate 100 g of aluminum powder with an average particle size of 5 μm in a reactor. NaOH solution was subsequently replaced in the reactor with 50O g of water. The temperature of the reactor was maintained at 50 °C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 18 g.

EXAMPLE 4

[0233] 300 g of aluminum powder with an average particle size of 5 μm in a reactor with 500 g of water were exposed to an ultrasonic treatment (20 kHz, 75 W) to reduce the passivating oxide layer on the aluminum. The ultrasonic treatment was generated by a ceramic sonotrode immersed in the reactor. The ceramic sonotrode was made of Al₂O₃ ceramic with incorporated Pd. The temperature of the reactor was maintained at 50 ⁰C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 28 g.

EXAMPLE 5

[0234] 300 g of Duralumin alloy (Cu: 5 weight %; Mn: 1 weight %; Mg: 2.7 weight %; Al: 91.3 weight %) chips were reacted with in a reactor with 500g of water and lOOg of 5 weight % NaOH solution. The temperature of the reactor was maintained at 50 ⁰C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 14 g.

EXAMPLE 6

[0235] 300 g of Duralumin alloy (Cu: 5 weight %; Mn: 1 weight %; Mg: 2.7 weight %; Al: 91.3 weight %) chips were reacted with in a reactor with 500g of seawater (maximum salt content 3.5 %). The temperature of the reactor was maintained at 95 °C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 9 g.

EXAMPLE 7

[0236] 300 g of Duralumin alloy (Cu: 5 weight %; Mn: 1 weight %; Mg: 2.7 weight %; Al: 91.3 weight %) chips were reacted with in a reactor with 500g of seawater (maximum salt content 3.5 %) and exposed to an ultrasonic treatment (20 kHz, pulsed power output 75 W). The ultrasonic waves were generated through a ceramic (Al₂O₃ with Pd) sonotrode immersed in the reactor. The temperature of the reactor was maintained at 95 ⁰C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 16 g.

EXAMPLE 8

[0237] 300 g of aluminum powder with an average particle size of 5 μm in a reactor with 500 g of water were exposed to an ultrasonic treatment (20 kHz, 75 W) to reduce the passivating oxide layer on the aluminum. A continuous flow of CO₂ was introduced in the reactor. The CO₂ flow was maintained at a level providing pH equal to 4 in the water. The water pH was measured using a pH meter. The ultrasonic treatment was generated by a ceramic (Al₂O₃ with Pd) sonotrode immersed in the reactor. The temperature of the reactor was maintained at 50 °C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 35 g.

EXAMPLE 9

[0238] 300 g of aluminum powder with an average particle size of 5 μm in a reactor with 500 g of water were exposed to an ultrasonic treatment (20 kHz, 75 W) to reduce the passivating oxide layer on the aluminum. The reactor also contained Al₂O₃ particles with an average particle size 1-3 microns. A weight ratio of Al to Al₂O₃ particles in the reactor was 10:1. A continuous flow of CO₂ was introduced in the reactor. The CO₂ flow was maintained at a level providing pH equal to 4 in the water. The water pH was measured using a pH meter. The ultrasonic treatment was generated by a ceramic (Al₂O₃) sonotrode immersed in the reactor. The temperature of the reactor was maintained at 50 °C at atmospheric pressure. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 38 g. [0239] Figure 4 compares molecular hydrogen yield as a function of time for experiments detailed in 1) Example 4, 2) Example 7 and 3) Example 8. Comparison of hydrogen yield for experimental arrangement of Example 4, i.e. ultrasonic treatment of aluminum powder in water without exposure to CO₂ flow and without Al₂O₃ particles in the reactor, and Example 7, i.e. ultrasonic treatment of aluminum powder in water exposed to CO₂ flow, but still without Al₂O₃ particles in the reactor, indicates that an introduction of CO₂ flow in the reactor increases hydrogen production. Comparison of hydrogen yield for experimental arrangement of Example 7, i.e. ultrasonic treatment of aluminum powder in water exposed to CO₂ flow, but without Al₂O₃ particles in the reactor, and Example 8, i.e. ultrasonic treatment of aluminum powder in water exposed to CO₂ flow with Al₂O₃ particles present in the reactor, indicates that an introduction of Al₂O₃ particles in the reactor increases hydrogen production.

EXAMPLE 10

[0240] 300 g of aluminum scrap (turnings) containing Cu: 5 weight %; Mn: 1%; Mg: 2,7%, Al: 91,3%- as determined by Thermo Scientific NITON XL3p XRF x-ray fluorescence analyzer with an average particle size of 5-10 mm was reacted with 50Og of sea water (maximum salt content 3,5%) and lOOg of 5 weight % NaOH solution in a reactor. No external heat was provided to the reactor. The temperature in the reactor was maintained at 8OC at atmospheric pressure by adding water in portions. The total mass of hydrogen gas H2 released from the reactor after 1 hour was 3Og H2.

EXAMPLE I l

[0241] 30Og of silicon powder (SIGMA-ALDRICH Laborchemikalien GMBH, MW = 28,09 g/mol, CAS: 7440-21-3, purity min. 97%) with an average particle size of 3 μm was reacted in a reactor with 50Og of water and lOOg of 10 weight % NaOH solution. The temperature in the reactor was maintained at 9OC at atmospheric pressure by adding water in portions. Initially 1O g of dry NaOH were mixed with 300 g of silicon powder and then 100 g of water were added to initiate the hydrogen producing reaction. Additional 500 g of water were added later in small portions to maintain the temperature at 90 C. No external heat was provided to the reactor. The total mass of hydrogen gas H2 released from the reactor after 1 hour was 35g.

EXAMPLE 12

[0242] 300g of silicon powder (SIGMA- ALDRICH Laborchemikalien GMBH, MW =28,09g/mol, CAS No.: 7440-21-3, purity min 97%) with an average particle size of 3 μm was reacted with 50Og of sea water and lOOg of 10 weight % KOH solution in a reactor. The temperature in the reactor was maintained at 85C at atmospheric pressure by adding water in portions. Initially 1O g of dry KOH were mixed with 300 g of silicon powder and then 100 g of water were added to initiate the hydrogen producing reaction. Additional 500 g of water were added later in small portions to maintain the temperature at 85 C. No external heat was provided to the reactor. The total mass of hydrogen gas released from the reactor after 1 hour was 32g.

EXAMPLE 13

[0243] 300 g of aluminum powder with an average particle size of 5 μm in a reactor with 500 g of water was exposed to an ultrasonic treatment (20 kHz, 75 W) to reduce a passivating oxide layer on the aluminum. An ultrasonic source was configured to produce a pulsed (durations of individual pulse and pause were 10s and 2s, respectively) ultrasonic action to activate the aluminum powder . A continuous flow of CO₂ was introduced in the reactor. The CO₂ flow was maintained at a level providing pH = 4 in the reactor. The pH level was measured using a pH meter. The ultrasonic treatment was generated by a ceramic (Al₂O₃ with Pd) sonotrode immersed in the reactor. The temperature of the reactor was maintained at 70 ⁰C at atmospheric pressure. No external heat was provided to the reactor. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 32 g. EXAMPLE 14

[0244] 300 g of aluminum powder with an average particle size of 5 μm in a reactor with 500 g of water were exposed to an ultrasonic treatment (20 kHz, 75 W) to reduce a passivating oxide layer on the aluminum. A ultrasonic source being configured to produce a pulsed (duration of individual pulse was range 5s and pause 2s) ultrasonic action that activates the aluminum powder. A continuous flow of CO₂ was introduced in the reactor. The CO₂ flow was maintained at a level providing pH equal to 4 in the water. The pH level was measured using a pH meter. The ultrasonic treatment was generated by a ceramic (Al₂O₃ with Pd) sonotrode immersed in the reactor. The temperature of the reactor was maintained at 70 ⁰C at atmospheric pressure. No external heat was provided to the reactor. The total mass of hydrogen gas (H₂) released from the reactor after 1 hour was 25 g.

***

[0245] Although the foregoing refers to particular preferred embodiments, it will be understood that the present invention is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the present invention.

[0246] All of the publications, patent applications and patents cited in this specification are incorporated herein by reference in their entirety.

ADDITIONAL EMBODIMENTS

1. A method of hydrogen production comprising

(A) providing in a reactor a first metal composition having a passivating layer;

(B) exposing in the reactor the first metal composition to an effective amount of an oxide stripper for the first metal composition, wherein the exposing activates the first metal composition by reducing the passivating layer on the first metal composition;

(C) introducing in the reactor a first aqueous solution, that does not contain the oxide stripper for the first metal composition, and thereby contacting the first aqueous solution with the activated first metal composition, wherein the introducing removes the oxide stripper for the first metal composition from the reactor and wherein the contacting results in generating a hydrogen gas and

(D) collecting the generated hydrogen gas.

2. The method of embodiment 1, wherein the first metal composition is a recycled metal composition.

3. The method of embodiment 1, wherein the steps of (B) and (C) are performed more than once.

4. The method of embodiment 1, wherein the introducing comprises dispersing the first aqueous solution so that the dispersed aqueous solution contacts the activated first metal composition.

5. The method of embodiment 1, wherein one or more non-hydrogen products of the generating the hydrogen gas are substantially free of a by-product of the oxide stripper for the first metal composition.

6. The method of embodiment 1, wherein the first metal composition comprises aluminum.

7. The method of embodiment 6, wherein the first metal composition consists essentially of aluminum.

8. The method of embodiment 6, wherein the contacting does not comprise exposing the reactor to an external heat.

9. The method of embodiment 6, wherein the oxide stripper comprises A1₂(SO₄)₃. 10. The method of embodiment 6, wherein the oxide stripper for the first metal composition comprises a alkali hydroxide.

11. The method of embodiment 10, wherein the oxide stripper for the first metal composition is a solution of the alkali hydroxide.

12. The method of embodiment 11, wherein a molar ratio of (i) the aluminum in the first metal composition, (ii) the alkali hydroxide in the solution of the alkali hydroxide and (iii) water in the solution of the alkali hydroxide is around 1 :2:4.

13. The method of embodiment 6, further comprising collecting one or more non- hydrogen products of the contacting the first aqueous solution with the activated first metal composition.

14. The method of embodiment 13, wherein the one or more non-hydrogen products of the contacting the first aqueous solution with the activated first metal composition are substantially free of a sodium aluminate or potassium aluminate.

15. The method of embodiment 13, wherein the one or more non-hydrogen products of the contacting the first aqueous solution with the activated first metal composition comprise alumina hydroxide, gamma-alumina or a combination thereof.

16. The method of embodiment 15, further comprising recycling the one or more non-hydrogen products of the contacting the first aqueous solution with the activated first metal composition.

17. The method of embodiment 16, wherein at least one product of said recycling is aluminum.

18. The method of embodiment 16, wherein the recycling comprises reacting the one or more non-hydrogen products of the contacting the first aqueous solution with the activated first metal composition with a carbon-containing compound.

19. The method of embodiment 18, wherein the carbon-containing compound is carbon.

20. The method of embodiment 19, wherein the carbon is a recycled carbon.

21. The method of embodiment 18, wherein the carbon-containing compound is methane.

22. The method of embodiment 18, wherein products of the recycling comprise CO and hydrogen. 23. The method of embodiment 16, wherein said recycling utilizes a heat produced by the contacting the first aqueous solution with the activated first metal composition.

24. The method of embodiment 1, wherein the first aqueous solution consists essentially of water.

25. The method of embodiment 1, further comprising introducing in the reactor a second metal composition having a passivating layer and an oxide stripper for the second metal composition and thereby exposing the second metal composition to the oxide stripper for the second metal composition, wherein the exposing the second metal composition to the oxide stripper for the second metal composition in a presence of a heat generated by the contacting the first metal composition and the first aqueous solution activates the second metal composition by reducing the passivating layer on the second metal composition.

26. The method of embodiment 25, wherein the reducing the passivating layer on the second metal composition does not comprise exposing the reactor to an external heat.

27. The method of embodiment 25, further comprising introducing in the reactor a second aqueous solution, that does not contain the oxide stripper for the second metal composition, and thereby contacting the second aqueous solution with the activated second metal composition, wherein the introducing the second aqueous solution removes the oxide stripper for the second metal composition from the reactor and wherein the contacting the second aqueous solution with the activated second metal composition results in generating a hydrogen gas and collecting the generated hydrogen gas.

28. The method of embodiment 18, wherein the first metal composition comprises aluminum and the second composition comprises silicon.

29. The method of embodiment 28, wherein the oxide stripper for the first metal composition comprises an alkali hydroxide.

30. The method of embodiment 28, further comprising collecting one or more non-hydrogen products of the contacting the second aqueous solution with the activated second metal composition. 31. The method of embodiment 30, further comprising recycling the one or more non-hydrogen products of the contacting the second aqueous solution with the activated second metal composition.

32. The method of embodiment 31, wherein at least one product of said recycling is silicon.

33. The method of embodiment 31, wherein the recycling comprises reacting the one or more non-hydrogen products of the contacting the second aqueous solution with the activated second metal composition with a carbon-containing compound.

34. The method of embodiment 33, wherein the carbon-containing compound is carbon.

35. The method of embodiment 34, wherein the carbon is a recycled carbon.

36. The method of embodiment 33, wherein the carbon-containing compound is methane.

37. The method of embodiment 33, wherein products of the recycling comprise CO and hydrogen.

38. The method of embodiment 27, wherein the second aqueous solution consists essentially of water.

39. A method of hydrogen production comprising

(A) providing in a reactor a metal composition having a passivating layer;

(B) contacting in the reactor the metal composition with water;

(C) exposing in the reactor the metal composition in contact with the water to a pulsed ultrasonic action, wherein the exposing activates the metal composition by reducing the passivating layer and therein the activated metal composition reacts with the water generating a hydrogen gas; and

(D) collecting the generated hydrogen.

40. The method of embodiment 39, wherein the metal composition comprises aluminum.

41. The method of embodiment 40, wherein the metal composition consists essentially of aluminum.

42. The method of embodiment 39, further comprising controlling a temperature in the reactor by manipulating the pulsed ultrasonic action. 43. The method of embodiment 42, wherein the manipulating the pulsed ultrasonic action comprises controlling a duration of an individual pause of the pulsed ultrasonic action; a duration, an intensity and/or a frequency of an individual impulse of the pulsed ultrasonic action or a combination thereof.

44. The method of embodiment 39, wherein the pulsed ultrasonic action is produced by a ceramic ultrasonic source in a physical contact with the water.

45. The method of embodiment 44, wherein the ceramic ultrasonic source comprises at least one of aluminum oxide, zirconium oxide or magnesium oxide.

46. The method of embodiment 45, wherein the ceramic ultrasonic source further comprises at least one metal selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, Ni and Co.

47. The method of embodiment 39, wherein the exposing is performed in a presence of one or more sonication enhancers.

48. The method of embodiment 47, wherein the one or more sonication enhancers comprise a gaseous sonication enhancer, a solid sonication enhancer or a combination thereof.

49. The method of embodiment 48, wherein the gaseous sonication enhancer comprises CO₂.

50. The method of embodiment 49, wherein the solid sonication enhancer comprises solid particles.

51. The method of embodiment 50, wherein the solid particles comprise Al₂O₃, SiC or a combination thereof.

52. The method of embodiment 39, further comprising recycling one or more non- hydrogen products of the generating hydrogen gas.

53. A method of hydrogen production comprising

(A) providing a metal composition having a passivating layer;

(B) contacting the metal composition with water;

(C) exposing the metal composition in contact with the water to an ultrasonic action in a presence of a sonication enhancer, wherein the exposing activates the metal composition by reducing the passivating layer and therein the activated metal composition reacts with the water to generate a hydrogen gas; and (D) collecting the generated hydrogen.

54. The method of embodiment 53, wherein the sonication enhancer comprises a gaseous sonication enhancer, a solid sonication enhancer or a combination thereof.

55. The method of embodiment 54, wherein the gaseous sonication enhancer comprises CO₂.

56. The method of embodiment 54, wherein the solid sonication enhancer comprises solid particles.

57. The method of embodiment 56, wherein the solid particles comprise SiC, Al₂O₃ or a combination thereof.

58. A method of hydrogen production comprising

(A) providing a metal composition having a passivating layer;

(B) contacting the metal composition with water;

(C) exposing the metal composition in contact with the water to an ultrasonic action produced by a ceramic ultrasonic source in a physical contact with the water, wherein the exposing activates the metal composition by reducing the passivating layer and therein the activated metal composition reacts with the water to generate a hydrogen gas; and

(D) collecting the generated hydrogen.

59. The method of embodiment 58, wherein the ceramic ultrasonic source comprises at least one of aluminum oxide, zirconium oxide or magnesium oxide.

60. The method of embodiment 59, wherein the ceramic ultrasonic source further comprises at least one metal selected from the group consisting of Pd, Ru, Rh, Os, Ir, Pt, Ni and Co.

61. An apparatus for hydrogen generation, comprising a vessel having an inner volume configured to contain an aqueous solution and a metal composition having a passivating layer; and an ultrasonic source in a sonic communication with the inner volume of the vessel, the ultrasonic source being configured to produce a pulsed ultrasonic action that activates the metal composition contained in the inner volume of the vessel by reducing the passivating layer of the metal composition, so that the activated metal composition reacts with water of the aqueous solution contained in the inner volume of the vessel to generate hydrogen gas.

62. The apparatus of embodiment 61, wherein the ultrasonic source is configured to be in direct physical contact with the aqueous solution contained in the inner volume vessel, when the pulsed ultrasonic action is generated.

63. An apparatus for hydrogen generation, comprising a vessel having an inner volume configured to contain an aqueous solution and a metal composition having a passivating layer, the vessel has an inlet for introducing a gaseous sonication enhancer in the inner volume of the vessel and an outlet for removing hydrogen gas from the inner volume of the vessel and an ultrasonic source in a sonic communication with the inner volume of the vessel, the ultrasonic source being configured to produce an ultrasonic action that activates the metal composition contained in the inner volume of the vessel in the presence of the gaseous sonication enhancer by reducing the passivating layer of the metal composition, so that the activated metal composition reacts with water of the aqueous solution to generate hydrogen gas.

64. An apparatus for hydrogen generation, comprising a vessel having an inner volume configured to contain an aqueous solution and a metal composition having a passivating layer and an ultrasonic source, with a ceramic portion, configured to produce an ultrasonic action when the ceramic portion is in a direct physical contact with the aqueous solution contained in the inner volume of the vessel, wherein the ultrasonic action produced by the ultrasonic source activates the metal composition contained in the inner volume of the vessel by reducing the passivating layer of the metal composition, so that the activated metal composition reacts with water of the aqueous solution to generate hydrogen gas.

65. The apparatus of embodiment 64, wherein the ceramic portion of the ultrasonic source comprises at least one of aluminum oxide, zirconium oxide and magnesium oxide. 66. The apparatus of embodiment 65, wherein the ceramic portion of the ultrasonic source further comprises at least one metal selected from Rh, Ir, Pt, Pd, Ni, Co, Ru and Os.

67. A method of hydrogen production comprising

(A) providing a metal composition comprising aluminum and copper, wherein the metal composition has a passivating layer and wherein a content of the aluminum in the metal composition is no less than 20%;

(B) contacting the metal composition with an aqueous solution comprising a copper oxide stripper, wherein the contacting activates the metal composition and wherein the activated metal composition reacts with water of the aqueous solution to generate a hydrogen gas; and

(C) collecting the generated hydrogen gas.

68. The method of embodiment 67, wherein the metal composition is a metal alloy.

69. The method of embodiment 67, wherein the metal composition is a recycled metal composition.

70. The method of embodiment 67, wherein the content of the aluminum in the metal composition is no less than 50%.

71. The method of embodiment 67, wherein the content of the aluminum in the metal composition is no less than 80%.

72. The method of embodiment 67, wherein the metal composition further comprises Mn, Mg, Si, Zn, Ti, Fe or combinations thereof.

73. The method of embodiment 67, wherein the metal composition comprises 2.2- 5.2% Cu, 0.2-1% Mn, 0.2-2.7% Mg, and 91.1-97.5% Al.

74. The method of embodiment 67, wherein the metal composition comprises 4- 22% Si.

75. The method of embodiment 67, wherein the copper oxide stripper comprises a copper oxide stripping salt.

76. The method of embodiment 67, wherein the copper oxide stripper comprises NaCl, KCl or a combination thereof. 77. The method of embodiment 67, wherein the aqueous solution consists essentially of seawater.

78. The method of embodiment 77, wherein the aqueous solution is seawater.

79. The method of embodiment 67, wherein the contacting comprises exposing the metal composition and the aqueous solution to an ultrasonic action to facilitate the activation of the metal composition.

80. A method of transforming an aluminum oxidation product into aluminum comprising

(A) reacting a carbonate of an alkali metal with carbon to produce the alkali metal and carbon dioxide;

(B) producing aluminum halide from the aluminum oxidation product;

(C) reacting the produced aluminum halide and the produced alkali metal to produce aluminum and a halide of the alkali metal.

81. The method of embodiment 80, wherein the alkali metal is sodium.

82. The method of embodiment 80, wherein the aluminum halide is aluminum chloride.

83. The method of embodiment 80, wherein the aluminum oxidation product is gamma-alumina and wherein the producing aluminum chloride comprises reacting the gamma alumina and a chloride of an alkali-earth metal.

84. The method of embodiment 83, wherein the alkali-earth metal is calcium.

85. The method of embodiment 80, wherein the aluminum oxidation product is aluminum hydroxide and wherein the producing aluminum halide comprises reacting the aluminum hydroxide with a hydrohalogenic acid.

86. A kit for hydrogen production comprising an effective amount of a metal composition having a passivating layer and an effective amount of an oxide stripper for the metal composition.

87. The kit of embodiment 86, wherein the metal composition comprises aluminum.

88. The kit of embodiment 86, wherein the metal composition consists essentially of aluminum. 89. The kit of embodiment 86, wherein the oxide stripper for the metal composition is an alkali hydroxide.

90. The kit of embodiment 89, wherein a molar ratio of the aluminum and the alkali hydroxide is about 1 :2.

91. A method of making a paint comprising collecting non-hydrogen products of a reaction between aluminum and water; transferring said non-hydrogen products into aluminum oxide; and dispersing said aluminum oxide in a solvent to produce a paint.

92. An apparatus for hydrogen generation, comprising a vessel having an inner volume configured to contain an aqueous solution and a metal composition having a passivating layer, an ultrasonic source in a sonic communication with the inner volume of the vessel, the ultrasonic source being configured to produce an ultrasonic action that activates the metal composition contained in the inner volume of the vessel by reducing the passivating layer of the metal composition, so that the activated metal composition reacts with water of the aqueous solution contained in the inner volume of the volume to generate hydrogen gas and a heat exchange system configured to regulate a temperature in the inner volume of the vessel.

93. A hydrogen production apparatus comprising at least one ultrasonic source and a flow-through vessel having an inlet and an outlet fludically connected to the inlet through an inner volume of the vessel, wherein the inlet of the vessel is configured to introduce a flow comprising water and a metal composition into the inner volume of the vessel and wherein the at least one ultrasonic source is configured to produce an ultrasonic action that activates the metal composition passing through the inner volume of the vessel by reducing the passivating layer of the metal composition, so that the activated metal composition reacts with the water and thereby generates hydrogen gas. 94. The apparatus of embodiment 93, wherein said at least one ultrasonic source comprises at least two sonotrodes, each in a sonic contact with the flow in the inner volume of the vessel.

95. The apparatus of embodiment 93, wherein the at least one ultrasonic source is configured to produce the ultrasonic action at a frequency ranging from about 15 kHz to about 2 MHz.

96. The apparatus of embodiment 93, wherein the at least one ultrasonic source is configured to produce the ultrasonic action at a frequency ranging from about 15 kHz to about 30 kHz.

97. The apparatus of embodiment 93, wherein the at least one ultrasonic source is configured to produce a pulsed ultrasonic action.

98. The apparatus of embodiment 93, wherein the at least one ultrasonic source is in a direct physical contact with said flow.

99. The apparatus of embodiment 93, wherein the at least one ultrasonic source comprises a cooler configured to cool down the source during the ultrasonic action.

100. The apparatus of embodiment 93, wherein the vessel comprises a pipe or a tube.

101. The apparatus of embodiment 100, wherein the at least one ultrasonic source comprises a clamp-on ultrasonic converter clamped on said pipe.

102. The apparatus of embodiment 93, wherein the vessel comprises a hydrogen outlet configured to collect produced hydrogen.

103. The apparatus of embodiment 102, wherein the hydrogen outlet comprises a gas valve.

104. The apparatus of embodiment 102, wherein the hydrogen outlet comprises a hydrogen membrane.

105. The apparatus of embodiment 93, wherein the vessel comprises a gas inlet configured to introduce at least one gaseous compound in the inner volume of the vessel.

106. The apparatus of embodiment 93, wherein the outlet of the vessel is fluidically connected to a collector configured to collect at least one non-hydrogen product of the reaction between the water and the metal composition. 107. The apparatus of embodiment 93, further comprising at least one pump configured to introduce the flow into the inlet of the vessel.

108. The apparatus of embodiment 93, further comprising a mixer configured to mix the water and the metal composition in the flow.

109. The apparatus of embodiment 93, further comprising a control system configured to control the reaction between the water and the metal composition in the vessel.

110. The apparatus of embodiment 109, wherein the control system comprises a computer.

111. The apparatus of embodiment 93, further comprising a mill configured to reduce a particle size in the metal composition.

112. A hydrogen production method comprising providing a flow comprising water and a metal composition having a passivating layer; exposing said flow to an ultrasonic action, wherein the exposing activates the metal composition by reducing the passivating layer and therein the activated metal composition reacts with the water to generate a hydrogen gas; and collecting the hydrogen gas.

113. The method of embodiment 112, wherein the flow further comprises at least one oxide stripper.

113. The method of embodiment 112, wherein the flow further comprises at least one sonication enhancer.

114. The method of embodiment 112, wherein the metal composition comprises particles having an average size less than 5 mm.

115. The method of embodiment 112, wherein the metal composition comprises particles having an average size less than 2 mm.

116. The method of embodiment 112, wherein the metal composition comprises aluminum.

117. The method of embodiment 1 12, wherein the metal composition consists essentially of aluminum. 118. The method of embodiment 112, wherein the metal composition is a scrap metal composition.

119. The method of embodiment 112, wherein the providing comprises mixing the water and the metal composition.

120. The method of embodiment 112, wherein the providing comprises reducing a particle size of the metal composition.

121. The method of embodiment 112, wherein said ultrasonic action is a pulsed ultrasonic action.

122. The method of embodiment 112, wherein the ultrasonic action has a frequency ranging from about 15 kHz to about 2 MHz.

123. The method of embodiment 112, wherein the ultrasonic action has a frequency ranging from about 15 kHz to about 30 KHz.

124. The method of embodiment 112, wherein a source of the ultrasonic action is in direct physical contact with the flow.

125. The method of embodiment 112, wherein a source of the ultrasonic action is not in direct physical contact with the flow.

126. The method of embodiment 1 12, further comprising collecting at least one non-hydrogen product of the reaction between the metal composition and the water.

127. The method of embodiment 126, further comprising recycling the at least one non-hydrogen product.

128. The method of embodiment 112, wherein the collecting the hydrogen gas comprises purifying the hydrogen gas.

129. A hydrogen production method comprising providing a first portion of a mixture comprising water and a metal composition having a passivating layer into a first reactor; activating the metal composition in the first reactor for a reaction with water by reducing the passivating layer of the metal composition; transferring the first portion of the mixture to a second reactor; and collecting from the second reactor a hydrogen gas formed in the reaction between water and the activated metal composition. 130. The method of embodiment 129, wherein the metal composition comprises aluminum.

131. The method of embodiment 129, wherein the metal composition consists essentially of aluminum.

132. The method of embodiment 129, wherein the metal composition comprises silicon.

133. The method of embodiment 129, wherein the metal composition is a scrap metal composition.

134. The method of embodiment 129, further comprising mixing the metal composition and water to form the mixture.

135. The method of embodiment 129, further comprising milling the metal composition.

136. The method of embodiment 135, wherein said milling is performed in the first reactor.

137. The method of embodiment 129, wherein said activating comprises exposing the first portion of the mixture to an ultrasonic action.

138. The method of embodiment 137, wherein further comprising providing in the first reactor at least one sonication enhancer.

139. The method of embodiment 138, wherein the at least one sonication enhancer comprises a gaseous sonication enhancer.

140. The method of embodiment 129, further comprising adjusting pH of the provided mixture.

141. The method of embodiment 129, further comprises monitoring hydrogen production in the second reactor.

142. The method of embodiment 129, further comprising transferring an unreacted portion of the metal composition into a third reactor and reactivating the unreacted portion of the metal composition for the reaction with water.

143. The method of embodiment 142, further comprising transferring the reactivated portion of the metal composition into a fourth reactor and collecting from the fourth reactor a hydrogen gas produced in a reaction between water and the reactivated portion of the metal composition. 144. The method of embodiment 129, further comprising collecting at least one non-hydrogen product of the reaction between water and the metal composition.

148. An apparatus comprising a first reactor having an inner volume with an inlet and an outlet, the first reactor comprises at least one ultrasonic source configured to produce an ultrasonic action activating a metal composition in the inner volume of the first reactor for a reaction with water by reducing a passivating layer of the metal composition; at least one second reactor having an inner volume with an inlet, a hydrogen outlet and a non-hydrogen outlet, the inlet of the second reactor is fluidically connected to the outlet of the first reactor; and a pressurizing device configured to transfer the activated metal composition from the inner volume of the first reactor to the inner volume of the second reactor, wherein the hydrogen outlet of the second reactor is configured to collect hydrogen gas produced in a reaction between the activated metal composition and the water.

149. The apparatus of embodiment 148, comprising more than one second reactor.

150. The apparatus of embodiment 148, further comprising a hydrogen detector configured to detect hydrogen gas at the hydrogen outlet of the second detector.

151. The apparatus of embodiment 148, further comprising a third reactor having an inner volume with an inlet and an outlet, wherein the non-hydrogen outlet of the second reactor is fluidically connected to the inlet of the third reactor and wherein the third reactor comprises at least one ultrasonic source configured to produce an ultrasonic action reactivating the metal composition in the inner volume of the first reactor for a reaction with water.

153. The apparatus of embodiment 151, further comprising at least one fourth reactor having an inner volume with an inlet, a hydrogen outlet and a non-hydrogen outlet, the inlet of the second reactor is fluidically connected to the outlet of the first reactor; and a second pressurizing device configured to transfer the activated metal composition from the inner volume of the third reactor to the inner volume of the fourth reactor. 154. The apparatus of embodiment 148, further comprising a collecting vessel configured to collect one or more non-hydrogen products of the reaction between the metal composition and water.

155. The apparatus of embodiment 148, further comprising a control system in a functional relationship with the pressurizing device, the outlet of the first reactor and the inlet of the second reactor.

156. The apparatus of embodiment 148, further comprising a mixing reactor configured to mix the metal composition and water.

157. The apparatus of embodiment 156, wherein the mixing reactor is fiuidically connected to the inlet of the first reactor.

158. A kit for hydrogen production comprising an activated metal composition comprising a hydrogen-displacing metal and having an artificial protective layer.

159. The kit of embodiment 158, wherein the metal composition comprises aluminum.

160. The kit of embodiment 158, wherein the metal composition consisting essentially of aluminum.

161. The kit of embodiment 158, comprising particles of the metal composition, wherein the particles have the artificial protective layer.

162. The kit of embodiment 158, wherein the protective layer is a water soluble protective layer.

163. The kit of embodiment 158, wherein the protective layer is thermally activatable.

164. A method of making a hydrogen production kit comprising providing a metal composition having a natural passivating layer; activating the metal composition by removing the natural passivating layer and disposing an artificial protective layer on the activated metal composition.

165. The method of embodiment 164, wherein the providing comprises providing particles of the metal composition.

166. The method of embodiment 164, wherein the metal composition comprises aluminum. 167. The method of embodiment 164, wherein the metal composition consists essentially of aluminum.

168. The method of embodiment 164, wherein the activating is performed ultrasonically.

169. The method of embodiment 164, wherein the artificial protective layer is a water soluble layer.

170. The method of embodiment 164, wherein the activatable protective layer is thermally activatable.

171. A method of producing hydrogen comprising contacting an activated metal composition having an artificial protective layer with water; removing the protective layer and thereby initiating a reaction between the activated metal composition and water; and collecting hydrogen gas produced the reaction of the activated metal composition and water.

172. The method of embodiment 171, wherein the metal composition comprises aluminum.

173. The method of embodiment 171, wherein the metal composition consists essentially of aluminum.

174. The method of embodiment 171, wherein said protective layer is a water soluble layer and said removing occurs upon said contacting.

175. The method of embodiment 171, wherein said protecting layer is a thermally activatable layer and said removing comprises heating the metal composition in contact with water.

176. A method of hydrogen production comprising forming a dry mixture comprising a dry base and a composition comprising silicon; adding to the mixture an amount of water to form a solution of the base in water, wherein the amount of water is effective to increase a temperature of the solution to an initiation temperature of a hydrogen producing reaction between the silicon in the composition and water; and collecting hydrogen gas formed in the hydrogen producing reaction. 177. The method of embodiment 176, wherein the composition contains at least 95 % of silicon by weight.

178. The method of embodiment 176, wherein the dry base comprises at least one ofNaOH or KOH.

179. The method of embodiment 176, wherein the composition is a powder comprising silicon.

180. A hydrogen production kit comprising

A) a composition comprising elemental silicon;

B) a dry base;

C) water, wherein the water and the dry base are provided in amounts effective to heat a solution formed by dissolving the dry base in the water to an initiating temperature for a hydrogen producing reaction between silicon and water.

181. The kit of embodiment 180, comprising a mixture comprising the composition and the dry base.

182. The kit of embodiment 180, wherein the dry base comprises at least one of NaOH or KOH.

183. The kit of embodiment 180, comprising the composition contains at least 95% silicon by weight.

Claims

WHAT IS CLAIMED IS:

1. A method of hydrogen production comprising

(A) providing a composition that comprises at least one hydrogen displacing element and has a passivating layer;

(B) contacting the composition with water;

(C) exposing the composition in contact with the water to an ultrasonic action in a presence of a sonication enhancer, wherein the exposing activates the composition by reducing the passivating layer and therein the activated composition reacts with the water to generate a hydrogen gas; and

(D) collecting the generated hydrogen gas.

2. The method of claim 1, wherein the composition comprises aluminum.

3. The method of claim 2, wherein the composition consists essentially of aluminum.

4. The method of claim 2, wherein aluminum and water are provided in a molar ratio that is no less than a stoichiometric molar ratio for a reaction between water and aluminum.

5. The method of claim 4, wherein aluminum and water are provided in a molar ration of no less than 1 :2.4.

6. The method of claim 1, wherein the sonication enhancer comprises a gaseous sonication enhancer, a solid sonication enhancer or a combination thereof.

7. The method of claim 6, wherein the sonication enhancer comprises a gaseous sonication enhancer.

8. The method of claim 7, wherein the gaseous sonication enhancer comprises CO₂.

9. The method of claim 6, wherein the solid sonication enhancer comprises solid particles.

10. The method of claim 9, wherein the solid particles comprise SiC, Al₂O₃ or a combination thereof.

11. The method of claim 1 , wherein the ultrasonic action is a pulsed ultrasonic action.

12. The method of claim 1 1, manipulating one or more parameters of the pulsed ultrasonic action selected from a duration of an individual pause of the pulsed ultrasonic action, a duration of an individual impulse of the pulsed ultrasonic action, a frequency of the pulsed ultrasonic action, and an intensity of the pulsed ultrasonic action.

13. The method of claim 1, wherein the ultrasonic action is produced by a ceramic ultrasonic source in a physical contact with the water.

14. The method of claim 13, wherein the ceramic ultrasonic source comprises at least one of silicon oxide, zirconium oxide or magnesium oxide.

15. The method of claim 14, wherein the ceramic source further comprises at least one metal selected from Ru, Rh, Pd, Os, Ir, Pt, Ni or Co.

16. The method of claim 1, wherein the composition comprises silicon and wherein the method further comprises adding an alkali metal hydroxide to the water prior to the exposing the composition to the ultrasonic action.

17. A hydrogen production method comprising providing a flow comprising water and a composition, that contains at least one hydrogen displacing element and has a passivating layer; exposing said flow to an ultrasonic action, wherein the exposing activates the composition by reducing the passivating layer and therein the activated composition reacts with the water to generate a hydrogen gas; and collecting the hydrogen gas.

18. The method of claim 17, wherein the flow further comprises at least one oxide stripper.

19. The method of claim 17, wherein the flow further comprises at least one sonication enhancer.

20. The method of claim 17, wherein the composition comprises particles having an average size less than 1 mm.

21. The method of claim 17, wherein the composition comprises aluminum.

22. The method of claim 17, wherein the composition consists essentially of aluminum.

23. The method of claim 17, wherein the composition is a scrap metal composition.

24. The method of claim 17, wherein the providing comprises mixing the water and the composition.

25. The method of claim 17, wherein the providing comprises reducing a particle size of the composition.

26. The method of claim 17, wherein said ultrasonic action is a pulsed ultrasonic action.

27. The method of claim 17, wherein a source of the ultrasonic action is in direct physical contact with the flow.

28. The method of claim 17, wherein a source of the ultrasonic action is not in direct physical contact with the flow.

29. The method of claim 17, wherein the collecting the hydrogen gas comprises purifying the hydrogen gas.

30. A hydrogen production apparatus comprising at least one ultrasonic source and a vessel having an inlet and an outlet fludically connected to the inlet through an inner space of the vessel, wherein the inlet of the vessel is configured to introduce a flow comprising water and a composition, that contains at least one hydrogen displacing element and has a passivating layer, into the inner space of the vessel and wherein the at least one ultrasonic source is configured to produce an ultrasonic action that activates the composition passing through the inner volume of the vessel by reducing the passivating layer of the composition, so that the activated metal composition reacts with the water and thereby generates hydrogen gas.

31. The apparatus of claim 30, wherein said at least one ultrasonic source comprises at least two sonotrodes, each in a sonic contact with the flow in the inner volume of the vessel.

32. The apparatus of claim 30, wherein the at least one ultrasonic source is configured to produce the ultrasonic action at a frequency ranging from about 15 kHz to about 30 kHz.

33. The apparatus of claim 30, wherein the at least one ultrasonic source is configured to produce a pulsed ultrasonic action.

34. The apparatus of claim 30, wherein the at least one ultrasonic source is in a direct physical contact with said flow.

35. The apparatus of claim 30, wherein the vessel comprises a pipe or a tube.

36. The apparatus of claim 35, wherein the at least one ultrasonic source comprises a clamp-on ultrasonic converter clamped on said pipe.

37. The apparatus of claim 30, wherein the vessel comprises a hydrogen outlet configured to collect produced hydrogen.

38. The apparatus of claim 37, wherein the hydrogen outlet comprises at least one of a hydrogen membrane or a hydrogen detector.

39. The apparatus of claim 30, wherein the vessel comprises a gas inlet configured to introduce at least one gaseous compound in the inner volume of the vessel.

40. The apparatus of claim 30, wherein the outlet of the vessel is fluidically connected to a collector configured to collect at least one non-hydrogen product of the reaction between the water and the composition.

41. The apparatus of claim 30, further comprising at least one pump configured to introduce the flow into the inlet of the vessel.

42. The apparatus of claim 30, further comprising a mixer configured to mix the water and the metal composition in the flow.

43. The apparatus of claim 30, further comprising a control system configured to control the reaction between the water and the metal composition in the vessel.

4. The apparatus of claim 43, wherein the control system comprises a computer.