STEPHENSON NEVILLE CHARLES (AU)
| US3449078A | 1969-06-10 | |||
| US5019263A | 1991-05-28 | |||
| US4699892A | 1987-10-13 | |||
| US6726893B2 | 2004-04-27 |
| Claims 1. A system in which single, isolated metal ions with low oxidation states are dispersed through an Al/SiO4 ceramic framework in order that the chemical looping cycles can be carried out without surface kinetic problems and at atomic levels. 2. A system according to claim 1 in which the ceramic frameworks can be useα as filters to separate hydrogen from water via chemical reaction and the framework can be regenerated by the reverse passage of carbon-based reductants or by electrolytic means using renewable energy sources. 3. A catalytic material having a framework supporting catalytic ions as isolated atomic species. 4. A catalytic membrane having a framework supporting catalytic ions as isolated atomic species. 5. A method for forming a catalytic membrane having a framework supporting catalytic ions as isolated atomic species, the method including the steps of providing a metal cation containing molecular species, using an ion exchange reaction to replace at least some of the metal cations with a catalytic metal ion having a lower oxidation state to produce a catalytic metal ion-containing molecular species in which the catalytic metal ions occur as isolated atomic species. 6. An apparatus for producing hydrogen via catalytic separation, the system including a catalytic membrane including a framework supporting catalytic ions as isolated atomic species, an input stream of H2O to a first side of the catalytic membrane, and forced removal of a product stream from a second opposite side of the membrane. 7. A method for producing hydrogen via catalytic separation, the method including the steps of providing a catalytic membrane including a framework supporting catalytic ions as isolated atomic species, introducing an input stream of H2O to a first side of the catalytic membrane, reacting the H2O with the catalytic ions in the membrane and removal of a product stream from a second opposite side of the membrane. |
METHOD OF USE Field of the Invention.
The present invention relates to catalytic materials particularly catalytic materials engineered at a microscopic level to contain catalytic ions in a stable molecular framework.
Background Art.
In many chemical reactions, the surface area/weight ratio of the reactants is particularly important. This is particularly relevant to the Fe/steam reaction where the surface area per particle of iron is inversely proportional to the radius of the particle. Thus, the smaller the iron particles, the greater the surface to weight ratio. Typically, the surface area to weight ratio is 3/rp where r is the particle radius and p is the density of the reactant.
Adanez et al (2004) addressed this problem by mixing metal oxide powders with an inert substrate to act as a porous support and provide a higher surface area for reaction with, for example, steam. Particle sizes of <10 "5 m were claimed.
The porosity and density of the sintered particles were dependent on the sintering temperatures.
Other methods for increasing the surface area to weight ratios include the impregnation of support particles by concentrated metal nitrate solutions followed by calcinations to form the metal oxides (Zafar et al., 2005).
The alternative oxidation and reduction of macroscopic, and even microscopic particles of metal oxide results in the formation of an insulating layer of product around the reactant. For example, in the oxidation of wustite (FeO) to haematite (Fe 2 O 3 ) by steam, a layer of Fe 2 O 3 is formed around the wustite this reducing the ability of the remaining wustite to be further oxidized. The reaction rate drops off exponentially and limits of 5% oxidation have been recommended as being efficient before reduction processes are implemented. This of course, means that 95% of the reactant is not utilized in any one chemical reaction loop. The problem of surface area and impeded access to these surfaces would likely be overcome if the reactant(s) are separated at atomic levels, that is, at 10 "10 m. It is therefore desirous to produce a useable material in which the reactant/catalyst are separated at an atomic level. It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.
Summary of the Invention. The present invention is directed to a catalytic material, method of manufacture and method of use, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.
With the foregoing in view, the present invention in one form, resides broadly in a catalytic material having a framework supporting catalytic ions as isolated atomic species.
In an alternative form, the invention resides in a catalytic membrane having a framework supporting catalytic ions as isolated atomic species.
The framework will typically be formed from a silicate, preferably a tectosilicate and more preferably from an alkali feldspar (K 5 Na)AlSi 3 O 8 ) or alumo- silicate containing saturated metal ions. Phyllosilicates may also find use according to the present invention as a raw material.
The framework will preferably be provided as a molecular framework of atoms in a framework structure. It is preferred that the framework will be provided as a crystalline solid material preferably an ionic molecular crystalline solid. The preferred frameworks are three dimensional networks but layered or sheet molecular systems may be used.
The feldspars are the most common minerals in the Earth's crust. They consist of three end-members, namely KAlSi 3 Og - Orthoclase (or), NaAlSi 3 Os - Albite (ab), and CaAl 2 Si 2 O 8 -Anorthite (an).
KAlSi 3 O 8 and NaAlSi 3 O 8 form a complete solid solution series, known as the alkali feldspars and NaAlSi 3 O 8 and CaAl 2 Si 2 O 8 form a complete solid solution series known as the plagioclase feldspars.
The feldspars have a framework structure, consisting of SiO 4 tetrahedra sharing all of the corner oxygens. However, in the alkali feldspars 1/4 of the Si + ions are replaced by Al +3 and in the plagioclase feldspars 1/4 to 1/2 of the Si +4 ions are replaced by AI +3 . This allows for the cations K + , Na + , and Ca +2 to be substituted into void spaces to maintain charge balance. Tectosilicates that may find application according to the present invention include:
• Coombsite (Potassium Manganese Iron Magnesium Aluminum Silicate
Hydroxide) • The Feldspar Group o Albite (Sodium Aluminum Silicate) o Andesine (Sodium Calcium Aluminum Silicate) o Anorthite (Calcium Aluminum Silicate) o Bytownite (Calcium Sodium Aluminum Silicate) o Labradorite (Sodium Calcium Aluminum Silicate) o Microcline (Potassium Aluminum Silicate) o Oligoclase (Sodium Calcium Silicate) o Orthoclase (Potassium Aluminum Silicate) o Sanidine (Potassium Aluminum Silicate) r • The Feldspathoid Group: o Cancrinite (Sodium Calcium Aluminum Silicate Carbonate) o Danalite (Iron Beryllium Silicate Sulfide) o Davyne (Sodium Potassium Calcium Aluminum Silicate Sulfate
Chloride) o Helvite (Manganese Beryllium Silicate Sulfide) o Hydroxycancrinite (Hydrated Sodium Aluminum Silicate Hydroxide) o Leucite (Potassium Aluminum Silicate) o Nepheline (Sodium Potassium Aluminum Silicate) o The Sodahte Group. ■ Hauyne (Sodium Calcium Aluminum Silicate Sulfate)
• Lazurite (Sodium Calcium Aluminum Silicate Sulfate Sulfide Chloride)
• Nosean (Sodium Aluminum Silicate Sulfate)
• Sodalite (Sodium Aluminum Silicate Chloride) ■ Tugtupite (Sodium Aluminum Beryllium Silicate Chloride) o Vishnevite (Hydrated Sodium Calcium Potassium Aluminum Silicate Sulfate Carbonate Chloride) • Leifite (Hydrated Sodium Beryllium Aluminum Silicate Hydroxide Fluoride)
• Marialite (Sodium Aluminum Silicate Chloride)
• Meionite (Calcium Aluminum Silicate Carbonate Sulfate)
• Pitaglianoite (Hydrated Potassium Sodium Aluminum Silicate Sulfate) • Sarcolite (Sodium Calcium Aluminum Silicate Fluoride)
• Scapolite (Calcium Sodium Aluminum Silicate Chloride Carbonate Sulfate)
• Silhydrite (Hydrated Silicate Dioxide)
• Ussingite (Sodium Aluminum Silicate Hydroxide)
• The Zeolite Group: o The Analcime Family:
■ Analcime (Hydrated Sodium Aluminum Silicate)
■ Pollucite (Hydrated Cesium Sodium Aluminum Silicate)
■ Wairakite (Hydrated Calcium Sodium Aluminum Silicate) o Bellbergite (Hydrated Potassium Barium Strontium Sodium Aluminum Silicate) o Bikitaite (Hydrated Lithium Aluminum Silicate) o Boggsite (Hydrated calcium Sodium Aluminum Silicate) o Brewsterite (Hydrated Strontium Barium Sodium Calcium Aluminum Silicate) o The Chabazite Family:
■ Chabazite (Hydrated Calcium Aluminum Silicate)
* Willhendersonite (Hydrated Potassium Calcium Aluminum
Silicate) o Cowlesite (Hydrated Calcium Aluminum Silicate) o Dachiardite (Hydrated calcium Sodium Potassium Aluminum Silicate) o Edingtonite (Hydrated Barium Calcium Aluminum Silicate) o Epistilbite (Hydrated Calcium Aluminum Silicate) o Erionite (Hydrated Sodium Potassium Calcium Aluminum Silicate) o Faujasite (Hydrated Sodium Calcium Magnesium Aluminum Silicate) o Ferrierite (Hydrated Sodium Potassium Magnesium Calcium
Aluminum Silicate) o The Gismondine Family: ■ Amicite (Hydrated Potassium Sodium Aluminum Silicate)
■ Garronite (Hydrated Calcium Aluminum Silicate)
■ Gismondine (Hydrated Barium Calcium Aluminum Silicate)
' Gobbinsite (Hydrated Sodium Potassium Calcium Aluminum Silicate) o Gmelinite (Hydrated Sodium Calcium Aluminum Silicate) o Gonnardite (Hydrated Sodium Calcium Aluminum Silicate) o Goosecreekite (Hydrated Calcium Aluminum Silicate) o The Harmotome Family: ■ Harmotome (Hydrated Barium Potassium Aluminum Silicate)
* Phillipsite (Hydrated Potassium Sodium Calcium Aluminum Silicate)
■ Wellsite (Hydrated Barium Calcium Potassium Aluminum Silicate) o The Heulandite Family:
* Clinoptilolite (Hydrated Sodium Potassium Calcium Aluminum Silicate)
* Heulandite (Hydrated Sodium Calcium Aluminum Silicate) o Laumontite (Hydrated Calcium Aluminum Silicate) o Levyne (Hydrated Calcium Sodium Potassium Aluminum Silicate) o Mazzite (Hydrated Potassium Sodium Magnesium Calcium Aluminum
Silicate) o Merlinoite (Hydrated Potassium Sodium Calcium Barium Aluminum
Silicate) o Montesommaite (Hydrated Potassium Sodium Aluminum Silicate) o Mordenite (Hydrated Sodium Potassium Calcium Aluminum Silicate) o The Natrolite Family:
■ Mesolite (Hydrated Sodium Calcium Aluminum Silicate)
■ Natrolite (Hydrated Sodium Aluminum Silicate) ■ Scolecite (Hydrated Calcium Aluminum Silicate) o Offretite (Hydrated Calcium Potassium Magnesium Aluminum Silicate) o Paranatrolite (Hydrated Sodium Aluminum Silicate) o Paulingite (Hydrated Potassium Calcium Sodium Barium Aluminum
Silicate) o Perlialite (Hydrated Potassium Sodium Calcium Strontium Aluminum Silicate) o The Stilbite Family:
• Barrerite (Hydrated Sodium Potassium Calcium Aluminum
Silicate)
■ Stilbite (Hydrated Sodium Calcium Aluminum Silicate) ■ Stellerite (Hydrated Calcium Aluminum Silicate) o Thomsonite (Hydrated Sodium Calcium Aluminum Silicate) o Tschernichite (Hydrated Calcium Aluminum Silicate) o Yugawaralite (Hydrated Calcium Aluminum Silicate)
Materials from the Feldspar, Feldspathoid and Zeolite groups are particularly preferred. .
More open silicate structures such as montmorillonite (a phyllosilicate) may also be effective with ferrous ions located between the charged MgZSiO 4 sheets. Chemically, montmorillonite is hydrated sodium calcium aluminium magnesium silicate hydroxide (Na,Ca)o 33 (Al 5 Mg) 2 (Si 4 Oi O )(OH) 2 -WH 2 O. Potassium, iron, and other cations are common substitutes, the exact ratio and type of cations varies with source and therefore preference in use in the present invention.
In an alternative form, the invention resides in a method for forming a catalytic membrane having a framework supporting catalytic ions as isolated atomic species, the method including the steps of providing a metal cation containing molecular species, using an ion exchange reaction to replace at least some of the metal cations with an iron ion to produce a iron ion-containing molecular species in which the iron ions occur as isolated atomic species.
In this embodiment, the catalytic metal ions in this case the iron ions in the product species possesses the catalytic metal ions unencumbered by close packed metal oxide neighbouring ions. This allows the catalytic metal ions to be more reactive than in other forms. Preferably, ionic substitution is used to form the catalytic material from the raw material, satisfying the valence imbalance.
A particular example of this method is forming a catalytic material of the formula Fe 4 Al 6 Si 6 O 24 Cl 2 from the mineral sodalite (Na 8 Al 6 Si 6 O 24 Cl 2 ) using ion exchange methods. Mineral sodalite contains a tetrahedral framework of aluminium
(Al) and silicon (Si) atoms to form a structure containing large voids or cages approximately 5 angstroms across. Using ion exchange methods, the sodium ions which are positioned in these cages, are replaced with ferrous ions which are smaller
(0.83 Angstroms Fe 2+ vs 0.95 Angstroms Na + atomic radii) and more polar. The molecular formula then becomes Fe 4 Al 6 Si 6 O 24 Cl 2 and the w/w percentage of the ferrous ions is 22.12%, considerably greater than the 5% reacted at macroscopic levels in the oxidation of wustite (FeO) to haematite (Fe 2 O 3 ) discussed above. This is due to the occurrence of the ferrous ions in the Fe 4 Al 6 Si 6 O 24 Cl 2 material as isolated atomic species, unencumbered by close packed oxide neighbours as in the crystalline forms Of Fe 2 O 3 and Fe 3 O 4 .
In an alternative form, the invention resides in an apparatus for producing hydrogen via catalytic separation, the system including a catalytic membrane including a framework supporting catalytic ions as isolated atomic species, an input stream of H 2 O to a first side of the catalytic membrane, and forced removal of a product stream from a second opposite side of the membrane.
In an alternative form, the invention resides in a method for producing hydrogen via catalytic separation, the method including the steps of providing a catalytic membrane including a framework supporting catalytic ions as isolated atomic species, introducing an input stream of H 2 O to a first side of the catalytic membrane, reacting the H 2 O with the catalytic ions in the membrane and removal of a product stream from a second opposite side of the membrane.
The present invention is directed toward providing single, isolated metal ions with a low oxidation state dispersed through a silicate material in order that reactive cycles of oxidation and reduction can be carried out utilising the metal ions as a catalyst material at an atomic level to obviate surface kinetic issues.
The catalytic material may be regenerated using carbon based reductants such as biogas or methane or alternatively by electrolytic means, preferably utilising renewable energy sources. The present invention utilises the principles that apply to standard deslatination processes, which involve reverse osmosis, to a chemical looping system which separates hydrogen from water rather than salt. The desalination process involves pure water travelling transversely through a sulphone membrane from a pressurised saline stream. This step is illustrated in Figure 1.
The saturated membrane can be cleaned or recharged, by reversing the water flow in order to concentrate the salt back into the original saline stream. This step is illustrated in Figure 2.
Preferably, the system of the present invention replaces the sulphone membrane used in the desalination process with a ferrous iron charged zeolite or a suitable alumina silicate framework containing interstitial ions from elements such as copper, manganese, cobalt, chromium or any other element having multiple ionic states. Steaming preferably superheated steam replaces the saline stream and is reduced to hydrogen and oxide of ions, the latter remaining in the large voids containing the oxidised ferric lines or other oxidised metal ions. The hydrogen and unreactive steam pass through the catalytic membrane and are gathered and then separated via condensation methods as one example of a viable separation technique.
After a suitable time interval, the the catalytic membrane can be cleaned or recharged by passing a ,reductant, typically methane or other carbon-based reductive gas through the catalytic membrane in order to reduce the oxidation state of the metal ion and produce carbon dioxide and water from the resident oxide or ions.
In a further aspect of the invention, the metal ion may be electrolytically reduced in situ liberate oxygen as an anode material during the regeneration step, thus providing a carbon free pathway for the production of hydrogen from water.
Preferably, the dehydrogenation and regeneration reactions will take place at elevated temperature and/or pressure in order to increase the reaction rate.
Preferably, the catalytic material will be provided in a tubular configuration in order that the reactants can be passed through the tube and the products withdrawn laterally through the tube. The catalytic material can therefore be provided as the tubular reactor.
The catalytic material may be provided in a cartridge, and preferably a tubular cartridge. The provision of a cartridge reactor results in an ability to remove and replace the cartridge when spent in order that regeneration of the catalytic material take place elsewhere. Similarly, the regeneration of the catalytic material may take place in situ.
Typically, a pair of reactors will be provided, each of the pair alternatively used for dehydrogenation, whilst the other is in the regeneration condition and can be reactors can be swapped.
Typically, the water provided for the dehydrogenation step will be provided as steam and as such, superheated steam may be used in order to provide at least the portion of the activation energy for the reaction to occur. In addition, there may be forced removal of the products from the reactor in order to drive the reaction towards the products.
Where the catalytic material is provided in the preferred tubular form, a partially closed or restricted outlet may be provided for the steam in order to force the steam laterally into contact with the catalytic material. By provision in this manner, the steam will typically be provided at at least a slightly elevated pressure. Normally, a plurality of catalytic material tubes will be provided in a reaction vessel and the entire reaction vessel will operate under elevated temperature and pressure.
Brief Description of the Drawings.
Various embodiments of the invention will be described with reference to the following drawings, in which:
Figure 1 is a schematic illustration of the mass transfer operation during desalination of seawater using a sulphone membrane tube.
Figure 2 a schematic illustration of the mass transfer operation during v regeneration of seawater using a sulphone membrane tube. Figure 3 a schematic illustration of the mass transfer operation during dehydrogenation of water using a silicon/aluminium framework catalytic tube.
Figure 4 a schematic illustration of the mass transfer operation during regeneration of a silicon/aluminium framework catalytic tube using methane.
Figure 5 is an atomic diagram of a tectosilicate material. Figure 6 is a schematic diagram of electrolytic regeneration of a metal ion by reduction in situ to liberate oxygen at the anode.
Detailed Description of the Preferred Embodiment. According to a preferred embodiment of the present invention, a system for producing a product gas via catalytic separation, utilising a particular catalytic material is provided.
The present invention utilises the principles that apply to standard deslatination processes, which involve reverse osmosis, to a chemical looping system which separates hydrogen from water rather than salt. The desalination process involves pure water travelling transversely through a sulphone membrane from a pressurised saline stream. This step is illustrated in Figure 1.
The preferred embodiment of the present invention is directed toward providing single, isolated metal ions with a low oxidation state dispersed through a silicate material in order that reactive cycles of oxidation and reduction can be carried out utilising the metal ions as a catalyst material at an atomic level to obviate surface kinetic issues.
The catalytic material is regenerated using carbon-based reductants such as biogas or methane or alternatively by electrolytic means, preferably utilising renewable energy sources.
The saturated membrane can be cleaned or recharged, by reversing the water flow in order to concentrate the salt back into the original saline stream. This step is illustrated in Figure 2.
The catalytic membrane of the preferred embodiment has an Al/SiO 4 ceramic framework supporting single isolated metal ions with lower oxidation states.
In this embodiment, the catalytic metal ions in the product species possesses the catalytic metal ions unencumbered by close packed catalytic metal oxide neighbouring ions. This allows the catalytic metal ions to be more reactive than in other forms. Ionic substitution is used to form the catalytic material from the raw material, satisfying the valence imbalance.
A particular example of this method is forming a catalytic material of the formula Fe 4 Al 6 Si 6 O 24 Cl 2 from the mineral sodalite (Na 8 Al 6 Si 6 O 24 Cl 2 ) using ion exchange methods. Mineral sodalite contains a tetrahedral framework of aluminium (Al) and silicon (Si) atoms to form a structure containing large voids or cages approximately 5 angstroms across (illustrated generally in Figure 5).
Using ion exchange methods, the sodium ions which are positioned in cages, are replaced with ferrous ions which are smaller (0.83 Angstroms Fe 2+ vs 0.95 Angstroms Na + atomic radii) and more polar. The molecular formula then becomes Fe 4 Al 6 Si 6 O 24 Cl 2 and the w/w percentage of the ferrous ions is 22.12%, considerably greater than the 5% reacted at macroscopic levels in the oxidation of wustite (FeO) to haematite (Fe 2 O 3 ) discussed above. This is due to the occurrence of the ferrous ions in the Fe 4 Al 6 Si 6 O 24 Cl 2 material as isolated atomic species, unencumbered by close packed oxide neighbours as in the crystalline forms of Fe 2 O 3 and Fe 3 O 4 .
The chemical looping reaction system of the catalytic dehydrogenation of water to form hydrogen gas and regeneration of the catalytic material illustrated in figures 3 and 4 then includes the alternate oxidation of the Fe ion by steam and the reduction of the oxide of Fe using methane as an example.
The catalytic dehydrogenation of water to form hydrogen gas illustrated in Figure 4 involves the entry of one polar steam molecule into a 5 A cage in order to oxidised the resident ferrous ion to a ferric ion, with an oxide on remaining in the cage and nonpolar hydrogen released into the molecular framework. The regeneration step includes entry of a methane molecule into the cage to reduce the ferric ion to a ferrous ion, with the omission of carbon dioxide and water into the molecular framework. This reduction in situ leaves or recreates the original ferrous iron in the framework.
As illustrated in figure 6, the metal ion may be electrolytically reduced in situ to liberate oxygen as an anode material during the regeneration step, thus providing a carbon free pathway for the production of hydrogen from water.
In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations. In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.
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