WO2011116055A2

WO2011116055A2 - High surface area catalysts

Info

Publication number: WO2011116055A2
Application number: PCT/US2011/028612
Authority: WO
Inventors: Leonid V. Budaragin; Michael M. Pozvonkov; Mark A. Deininger; Chaitanya Narula
Original assignee: C3 International, Llc; Ut-Battelle, Llc
Priority date: 2010-03-17
Filing date: 2011-03-16
Publication date: 2011-09-22
Also published as: WO2011116055A3

Abstract

The invention relates to methods for forming at least one metal oxide to make a catalytic material, and to the resulting catalytic materials. The method involves applying at least one metal compound to a substrate, which can be zeolyte, non-porous particles, ceramic paper, or monolithic structure, among others. Then, the at least one metal compound is converted to at least one metal oxide. Optionally, further catalytic material such as catalytic metals are formed on or added to the metal oxide. Small amounts of metal oxides provide for substantial catalytic activity, in some embodiments.

Description

HIGH SURFACE AREA CATALYSTS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001 ] The present application claims benefit of priority under PCT Article 8 and 35 U.S.C. § 1 19(e) of U.S. Provisional Application No. 61/314,610, filed on March 17, 2010, entitled, "HIGH SURFACE AREA CATALYSTS." That provisional application is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] The Government has rights in this invention pursuant to Work for Others Agreement No. NFE-08-01900.

FIELD OF THE INVENTION

[0003] This invention relates to high surface area catalysts, and methods for making and using them.

BACKGROUND

[0004] Many industrial and chemical processes rely on the use of certain heterogeneous catalysts. Those catalysts facilitate useful reactions by speeding up the reaction rate, lowering reaction temperature, or even causing reactions to occur that otherwise would be practically impossible. In the course of many catalyzed chemical reactions, the catalyst is not consumed, and so can be reused indefinitely, at least theoretically speaking. Thus, a very small amount of catalyst can potentially facilitate quite a lot of chemistry. A problem in the catalyst art involves bulk catalytic material. Heterogeneous catalysis occurs at the surface of the catalyst.

Accordingly, catalytic material forming the bulk of the catalyst beneath the surface does not participate in the chemistry and is therefore wasted. Similarly, catalytic material that is buried in a supporting material, or is otherwise not exposed to the reactants, also is wasted. Thus, improved methods for forming catalytic materials with a maximum surface exposure are desired.

[0005] Alumina and silica are known catalysts, and are also useful as supports for other catalytic materials such as platinum. In high surface area substrates known as zeolytes, alumina and silica provide cationic surface sites at which catalysis can occur. Adding a catalytic material such as platinum enhances and expands the catalytic activity of the zeolyte. However, many zeolytes begin to destabilize around 550-600 °C due to dealumination, capping their useful temperature range. To address that instability, U.S. Patent No. 5,968,463 proposes, for example, to provide zeolyte catalyst with a rare earth metal under specific conditions to stabilize the zeolyte. The present invention provides additional methods for stabilizing zeolytes. The present invention also provides alternatives to aluminum.

[0006] Ceramic papers also provide catalysts and catalytic support surfaces. U.S. Patent Application Publication No. US 2007/0015002 A1 , of U.S. Patent Application No. 1 1/181 ,314, discloses methods to coat ceramic papers with catalytic material, among other disclosures. For example, ceramic papers coated with ceria doped with platinum were able to burn off carbon fouling, while uncoated ceramic papers were not. U.S. Patent Application No. 1 1/181 ,314 is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

[0007] Various embodiments of the present invention are described herein.

These embodiments are merely illustrations of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0008] Some embodiments provide a catalytic material having a substrate comprising:

at least one metal oxide, wherein the at least one metal oxide is made according to the process of:

applying at least one metal compound to the substrate; and

converting at least some of the at least one metal compound to form the at least one metal oxide on the substrate.

[0009] In some embodiments, the substrate is a catalytic material. In other embodiments, the at least one metal oxide is a catalytic material. In still other embodiments, a further catalytic material is formed on or added to the substrate, the at least one metal oxide, or both.

[0010] The at least one metal oxide can be formed on the substrate by (1 ) placing at least one metal compound on the substrate and (2) converting at least some of the at least one metal compound into at least one metal oxide. Metal compounds useful in the present invention contain at least one metal atom and at least one oxygen atom. Non-limiting examples of useful metal compounds include metal carboxylates, metal alkoxides, and metal β-diketonates. Converting the metal compound can be accomplished by a wide variety of methods, such as, for example, heating the environment around the metal compound, heating the substrate under the metal compound, heating the metal compound itself, or a combination of those three. In other embodiments, converting the metal compound can be accomplished by catalysis.

[001 1 ] Some embodiments of the present invention provide a method for making a high surface area catalytic material comprising: applying at least one metal compound to a substrate; and exposing the substrate with the applied at least one metal compound to an environment that will convert at least some of the compound to at least one metal oxide. In certain embodiments, the at least one metal oxide can be removed from the substrate to provide catalytic material separate from the substrate. In other embodiments, the at least one metal oxide remains on the substrate.

[0012] Other embodiments provide a method for making a catalytic material, comprising: applying at least one metal compound to a substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to make the catalytic material. In certain embodiments, the at least one metal oxide can be removed from the substrate to provide catalytic material separate from the substrate. In other embodiments, the at least one metal oxide remains on the substrate.

[0013] Further embodiments provide a method for making a metal oxide catalytic material, comprising: applying at least one metal compound to a substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to make the metal oxide catalytic material. In certain embodiments, the at least one metal oxide can be removed from the substrate to provide catalytic material separate from the substrate. In other embodiments, the at least one metal oxide remains on the substrate.

[0014] Still other embodiments relate to a method for regenerating a catalytic material having a substrate, comprising: applying at least one metal compound to the substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to regenerate the catalytic material.

[0015] In some embodiments, the invention relates to a method for making a catalytic material having a substrate, comprising: applying a metal compound composition to the substrate, wherein the metal compound composition comprises at least one metal salt of at least one carboxylic acid; and exposing the substrate with the applied metal compound composition to an environment that will convert at least some of the salt to at least one metal oxide.

[0016] In some embodiments, the invention relates to a method for making a catalytic material having a substrate, comprising: applying a metal compound composition to the substrate, wherein the metal compound composition comprises at least one metal alkoxide; and exposing the substrate with the applied metal compound composition to an environment that will convert at least some of the metal alkoxide to at least one metal oxide.

[0017] In some embodiments, the invention relates to a method for making a catalytic material having a substrate, comprising: applying a metal compound composition to the substrate, wherein the metal compound composition comprises at least one metal β-diketonate; and exposing the substrate with the applied metal compound composition to an environment that will convert at least some of the metal β-diketonate to at least one metal oxide.

[0018] In further embodiments, the invention relates to a method for forming at least one metal oxide on a high surface area substrate, comprising: applying at least one metal compound to the substrate, and converting at least some of the at least one metal compound to at least one metal oxide. A material having a high surface area indicates a surface that is not flat on the micrometer or nanometer scale. For example, a zeolyte has a high surface area, due to its micro- and nanoscale pores. Embodiments of the present invention can be high surface area or non-high surface area, as illustrated herein.

[0019] In some embodiments, the at least one metal compound is present in a metal compound composition. In still other embodiments, a metal compound composition comprises at least one rare earth metal compound, and at least one transition metal compound.

[0020] In some embodiments of methods of forming at least one metal oxide on a high surface area substrate, the at least one metal oxide comprises a metal oxide coating or metal oxide film. In other embodiments, contiguous or noncontiguous domains of metal oxide are formed. A metal oxide coating, film, or domain, in some embodiments, is crystalline, nanocrystalline, amorphous, thin film, or diffuse, or a combination of any of the foregoing. For example, a metal oxide domain in some embodiments of the present invention may comprise a film that contains both nanocrystalline and amorphous regions. In some embodiments, a metal oxide domain at least partially diffuses or penetrates into the substrate thereby precluding the need for any intermediate bonding layers.

[0021 ] In other embodiments, the invention relates to a catalytic material containing two or more rare earth metal oxides and at least one transition metal oxide. Further embodiments of the invention relate to a catalytic material containing ceria, a second rare earth metal oxide, and a transition metal oxide. Some embodiments relate to a high surface area substrate containing yttria, zirconia, and a second rare earth metal oxide. In some cases, the second rare earth metal oxide can include platinum or other known catalytic elements. Still further embodiments of the invention relate to a catalytic material containing alumina, silica, ceria, or a combination thereof, and at least one metal.

[0022] Some embodiments of the present invention allow for cost savings by reducing the bulk amount of the catalyst. And, it also allows a wider variety of catalysts to be applied either as mixtures or in disparate domains to achieve tightly targeted results.

[0023] Additional embodiments provide a low cost means to form a useful catalytic material comprising alumina, silica, zirconia or ceria, the material having a nanocrystalline microstructure.

[0024] Some embodiments provide a metal oxide domain comprising only one metal oxide. Other embodiments provide a metal oxide domain comprising only two metal oxides. Still other embodiments provide a metal oxide domain comprising only three metal oxides. In yet other embodiments, the metal oxide domain comprises four or more metal oxides.

[0025] Additional embodiments of the invention provide a means to form a metal oxide catalytic material either at the point of manufacture or after the material has been used. For example, a catalyst may be regenerated in some embodiments of the present invention.

[0026] Further embodiments provide a method of stabilizing alumina in an alumina-containing catalytic material, comprising:

applying at least one metal compound on the catalytic material, and

converting the at least one metal compound to at least one metal oxide to stabilize the alumina. In some embodiments, stabilized alumina is indicated by increased catalytic activity at a given temperature, relative to the catalytic material without stabilization. In other embodiments, stabilized alumina is indicated by increased operating temperature by the alumina-containing catalytic material. In certain embodiments, "on" the catalytic material includes "in" the pores of a zeolyte, for example.

[0027] Still further embodiments provide a method for making a catalytic material, comprising:

applying at least one metal compound to a substrate; and

converting the at least one metal compound to form at least one metal oxide to make the at least one catalytic material, wherein the at least one metal oxide provides at least one cationic site having catalytic activity. In additional embodiments, at least one metal is formed or is added to the at least one metal oxide. In yet other embodiments, the at least one metal is located at the at least one cationic site having catalytic activity. The at least one metal oxide is alumina in some embodiments. In other embodiments, the at least one metal oxide does not comprise alumina. The at least one metal oxide exhibits thermal stability and catalytic activity at higher temperatures compared to alumina, in certain embodiments.

[0028] Other embodiments of the invention provide a method of forming a metal oxide that is well-adhered to high surface area catalytic materials.

[0029] Additional embodiments of the invention provide a means to

economically form a metal oxide catalytic material. Still other embodiments relate to those metal oxide catalytic materials.

[0030] Some of the catalytic materials according to the present invention are not possible with conventional technology. Others of those catalytic materials are more economical than conventional catalytic materials, such as platinum or palladium. Still other have greater catalytic activity, last longer, catalyze longer between regeneration cycles, or can face more regeneration cycles than

conventional catalysts, or a combination thereof. Still others of the inventive catalytic materials show synergistic effects when combined with conventional catalytic metals, such as platinum, palladium, rhodium, nickel, cerium, gold, silver, zinc, lead, rhenium, ruthenium, and combinations of two or more thereof.

[0031 ] Other embodiments of the invention provide a method of forming multiple domains of at least one metal oxide catalytic material. In still other embodiments, the process of applying and converting can be repeated, forming at least one metal oxide in more than one domain.

[0032] In some embodiments of methods of the present invention, at least one metal oxide is formed in an inert environment, including an environment wherein no or substantially no oxygen is present. In other embodiments, at least one metal oxide is formed in an aerobic environment.

DETAILED DESCRIPTION

[0033] As used herein, the term "rare earth metal" includes those metals in the lanthanide series of the Periodic Table, including lanthanum. The term "transition metal" includes metals in Groups 3-12 of the Periodic Table (but excludes rare earth metals). The term "metal oxide" particularly as used in conjunction with the above terms includes any oxide that can form or be prepared from the metal, irrespective of whether it is naturally occurring or not. The "metal" atoms of the metal oxides of the present invention are not necessarily limited to those elements that readily form metallic phases in the pure form. "Metal compounds" include substances such as molecules comprising at least one metal atom and at least one oxygen atom. Metal compounds can be converted into metal oxides by exposure to a suitable

environment for a suitable amount of time.

[0034] As used herein, the term "phase deposition" includes any depositing process onto a substrate that is subsequently followed by the exposure of the substrate and/or the deposited material to an environment that causes a phase change in either the deposited material, one or more components of the material, or of the substrate itself. A phase change may be a physical phase change, such as for example, a change from fluid to solid, or from one crystal phase to another, or from amorphous to crystalline or vice versa.

[0035] Catalytic materials include, without limitation, those used in industry to facilitate chemical reaction. Catalysts used in petroleum cracking, combustion engine exhaust treatment, sulfuric acid production, and the like represent a few examples. Some embodiments provide catalytic material for catalytic systems useful in the petroleum refining industry, such as, for example, fluidized beds, continuous flow, catalytic reformers, and the like. The catalytic material, in some embodiments, can comprise metal, metal oxide, ceramic, cermet, polymer, or combinations thereof. The catalytic material can be in any suitable form, such as, for example, aerosol, sol, gel, zeolyte, non-porous substrate, pellet, paper, and bulk material.

[0036] The term alkyl, as used herein, refers to a saturated straight, branched, or cyclic hydrocarbon, or a combination thereof, including Ci to C₂₄, methyl, ethyl, n- propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, cyclopentyl, isopentyl, neopentyl, n-hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl.

[0037] The term alkoxy, as used herein, refers to a saturated straight, branched, or cyclic hydrocarbon, or a combination thereof, including Ci to C₂₄, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, cyclopentyl, isopentyl, neopentyl, n-hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl, in which the hydrocarbon contains a single-bonded oxygen atom that can bond to or is bonded to another atom or molecule.

[0038] The terms alkenyl and alkynyl, as used herein, refer to Ci to C₂₄ straight, branched, or cyclic hydrocarbon with at least one double or triple bond, respectively.

[0039] The term aryl or aromatic, as used herein, refers to monocyclic or bicyclic hydrocarbon ring molecule having conjugated double bonds about the ring. In some embodiments, the ring molecule has 5- to 12-members, but is not limited thereto. The ring may be unsubstituted or substituted having one or more alike or different independently-chosen substituents, wherein the substituents are chosen from alkyl, alkenyl, alkynyl, alkoxy, hydroxyl, and amino radicals, and halogen atoms. Aryl includes, for example, unsubstituted or substituted phenyl and unsubstituted or substituted naphthyl.

[0040] The term heteroaryl as used herein refers to a monocyclic or bicyclic aromatic hydrocarbon ring molecule having at least one heteroatom chosen from 0, N, P, and S as a member of the ring, and the ring is unsubstituted or substituted with one or more alike or different substituents independently chosen from alkyl, alkenyl, alkynyl, hydroxyl, alkoxy, amino, alkylamino, dialkylamino, thiol, alkylthio, =0, =NH, =PH, =S, and halogen atoms. In some embodiments, the ring molecule has 5- to 12- members, but is not limited thereto.

[0041 ] The term hydrocarbon refers to molecules that contain carbon and hydrogen. [0042] "Alike or different," when describing three or more substituents for example, indicates combinations in which (a) all substituents are alike, (b) all substituents are different, and (c) some substituents are alike but different from other substituents.

[0043] Suitable metal compounds that form metal oxides include substances such as molecules containing at least one metal atom and at least one oxygen atom. In some embodiments, metal compounds that form metal oxides include metal carboxylates, metal alkoxides, and metal β-diketonates.

A. METAL CARBOXYLATES

[0044] The metal salts of carboxylic acids useful in the present invention can be made from any suitable carboxylic acids according to methods known in the art. For example, U.S. Patent No. 5,952,769 to Budaragin discloses suitable carboxylic acids and methods of making metal salts of carboxylic acids, among other places, at columns 5-6. The disclosure of U.S. Patent No. 5,952,769 is incorporated herein by reference. In some embodiments, the metal carboxylate can be chosen from metal salts of 2-hexanoic acid. Moreover, suitable metal carboxylates can be purchased from chemical supply companies. For example, cerium(lll) 2-ethylhexanoate, magnesium(ll) stearate, manganese(ll) cyclohexanebutyrate, and zinc(ll)

methacrylate are available from Sigma-Aldrich of St. Louis, MO. See Aldrich Catalogue, 2005-2006. Additional metal carboxylates are available from, for example, Alfa-Aesar of Ward Hill, MA.

[0045] The metal carboxylate composition, in some embodiments of the present invention, comprises one or more metal salts of one or more carboxylic acids ("metal carboxylate"). Metal carboxylates suitable for use in the present invention include at least one metal atom and at least one carboxylate radical -OC(0)R bonded to the at least one metal atom. As stated above, metal carboxylates can be produced by a variety of methods known to one skilled in the art. Non-limiting examples of methods for producing the metal carboxylate are shown in the following reaction schemes: nRCOOH + Me → (RCOO)_nMeⁿ⁺ + 0.5nH₂ (for alkaline earth metals, alkali metals, and thallium).

nRCOOH + Meⁿ⁺(OH)_n → (RCOO)_nMeⁿ⁺ + nH₂0 (for practically all metals having a solid hydroxide).

nRCOOH + Meⁿ⁺(C0₃)o.5n → (RCOO)_nMeⁿ⁺ + 0.5nH₂O + 0.5nCO₂ (for alkaline earth metals, alkali metals, and thallium). nRCOOH + Meⁿ⁺(X)n/m → (RCOO)_nMeⁿ⁺ + n/mH_mX (liquid extraction, usable for practically all metals having solid salts).

In the foregoing reaction schemes, X is an anion having a negative charge m, such as, e.g., halide anion, sulfate anion, carbonate anion, phosphate anion, among others; n is a positive integer; and Me represents a metal atom.

[0046] R in the foregoing reaction schemes can be chosen from a wide variety of radicals. Suitable carboxylic acids for use in making metal carboxylates include, for example:

Monocarboxylic acids:

[0047] Monocarboxylic acids where R is hydrogen or unbranched hydrocarbon radical, such as, for example, HCOOH - formic, CH₃COOH - acetic, CH₃CH₂COOH

- propionic, CH₃CH₂CH₂COOH (C₄H₈0₂)- butyric, C₅H₁₀O₂ - valeric, C₆Hi₂0₂ - caproic, C₇Hi₄ - enanthic; further: caprylic, pelargonic, undecanoic, dodecanoic, tridecylic, myristic, pentadecylic, palmitic, margaric, stearic, and nonadecylic acids;

[0048] Monocarboxylic acids where R is a branched hydrocarbon radical, such as, for example, (CH₃)₂CHCOOH - isobutyric, (CH₃) ₂CHCH₂COOH - 3-methylbutanoic, (CH₃)₃CCOOH - trimethylacetic, including VERSATIC 10 (trade name) which is a mixture of synthetic, saturated carboxylic acid isomers, derived from a highly- branched Cio structure;

[0049] Monocarboxylic acids in which R is a branched or unbranched hydrocarbon radical containing one or more double bonds, such as, for example, CH₂=CHCOOH

- acrylic, CH₃CH=CHCOOH - crotonic, CH₃(CH₂)₇CH=CH(CH₂)₇COOH - oleic, CH₃CH=CHCH=CHCOOH - hexa-2,4-dienoic,

(CH₃)₂C=CHCH₂CH₂C(CH₃)=CHCOOH - 3,7-dimethylocta-2,6-dienoic,

CH₃(CH₂)₄CH=CHCH₂CH=CH(CH₂)₇COOH - linoleic, further: angelic, tiglic, and elaidic acids;

[0050] Monocarboxylic acids in which R is a branched or unbranched hydrocarbon radical containing one or more triple bonds, such as, for example, CH≡CCOOH - propiolic, CH₃C≡CCOOH - tetrolic, CH₃(CH₂)₄C≡CCOOH - oct-2-ynoic, and stearolic acids;

[0051 ] Monocarboxylic acids in which R is a branched or unbranched hydrocarbon radical containing one or more double bonds and one or more triple bonds; [0052] Monocarboxylic acids in which R is a branched or unbranched hydrocarbon radical containing one or more double bonds and one or more triple bonds and one or more aryl groups;

[0053] Monohydroxymonocarboxylic acids in which R is a branched or unbranched hydrocarbon radical that contains one hydroxyl substituent, such as, for example, HOCH₂COOH - glycolic, CH3CHOHCOOH - lactic, C₆H₅CHOHCOOH - amygdalic, and 2-hydroxybutyric acids;

[0054] Dihydroxymonocarboxylic acids in which R is a branched or unbranched hydrocarbon radical that contains two hydroxyl substituents, such as, for example, (HO)₂CHCOOH - 2,2-dihydroxyacetic acid;

[0055] Dioxycarboxylic acids, in which R is a branched or unbranched hydrocarbon radical that contains two oxygen atoms each bonded to two adjacent carbon atoms, such as, for example, C₆H₃(OH)₂COOH - dihydroxy benzoic, C₆H₂(CH₃)(OH)₂COOH - orsellinic; further: caffeic, and piperic acids;

[0056] Aldehyde-carboxylic acids in which R is a branched or unbranched hydrocarbon radical that contains one aldehyde group, such as, for example, CHOCOOH - glyoxalic acid;

[0057] Keto-carboxylic acids in which R is a branched or unbranched hydrocarbon radical that contains one ketone group, such as, for example, CH₃COCOOH - pyruvic, CH₃COCH₂COOH - acetoacetic, and CH₃COCH₂CH₂COOH - levulinic acids;

[0058] Monoaromatic carboxylic acids, in which R is a branched or unbranched hydrocarbon radical that contains one aryl substituent, such as, for example, C₆H₅COOH - benzoic, C₆H₅CH₂COOH - phenylacetic, C₆H₅CH(CH₃)COOH - 2-phenylpropanoic, C₆H₅CH=CHCOOH - 3-phenylacrylic, and C₆H₅C≡CCOOH - 3- phenyl-propiolic acids;

Multicarboxylic acids:

[0059] Saturated dicarboxylic acids, in which R is a branched or unbranched saturated hydrocarbon radical that contains one carboxylic acid group, such as, for example, HOOC-COOH - oxalic, HOOC-CH₂-COOH - malonic,

HOOC-(CH₂)₂-COOH - succinic, HOOC-(CH₂)₃-COOH - glutaric,

HOOC-(CH₂)₄-COOH - adipic; further: pimelic, suberic, azelaic, and sebacic acids;

[0060] Unsaturated dicarboxylic acids, in which R is a branched or unbranched hydrocarbon radical that contains one carboxylic acid group and at least one carbon- carbon multiple bond, such as, for example, HOOC-CH=CH-COOH - fumaric;

further: maleic, citraconic, mesaconic, and itaconic acids;

[0061 ] Polybasic aromatic carboxylic acids, in which R is a branched or unbranched hydrocarbon radical that contains at least one aryl group and at least one carboxylic acid group, such as, for example, C₆H₄(COOH)₂ - phthalic (isophthalic, terephthalic), and C6H₃(COOH)₃ - benzyl-tri-carboxylic acids;

[0062] Polybasic saturated carboxylic acids, in which R is a branched or unbranched hydrocarbon radical that contains at least one carboxylic acid group, such as, for example, ethylene diamine Ν,Ν'-diacetic acid, and ethylene diamine tetraacetic acid (EDTA);

Polybasic oxyacids:

[0063] Polybasic oxyacids, in which R is a branched or unbranched hydrocarbon radical containing at least one hydroxyl substituent and at least one carboxylic acid group, such as, for example, HOOC-CHOH-COOH - tartronic,

HOOC-CHOH-CH₂-COOH - malic, HOOC-C(OH)=CH-COOH - oxaloacetic, HOOC- CHOH-CHOH-COOH - tartaric, and

HOOC-CH₂-C(OH) COOH-CH2COOH - citric acids.

[0064] In some embodiments, the monocarboxylic acid comprises one or more carboxylic acids having the formula I below:

R°-C(R")(R')-COOH (I)

wherein:

R° is selected from H or Ci to C₂₄ alkyl groups; and

R' and R" are each independently selected from H and Ci to C₂₄ alkyl groups;

wherein the alkyl groups of R°, R', and R" are optionally and independently substituted with one or more substituents, which are alike or different, chosen from hydroxy, alkoxy, amino, and aryl radicals, and halogen atoms.

[0065] Some suitable alpha branched carboxylic acids typically have an average molecular weight in the range 130 to 420. In some embodiments, the carboxylic acids have an average molecular weight in the range 220 to 270. The carboxylic acid may also be a mixture of tertiary and quaternary carboxylic acids of formula I. VIK acids can be used as well. See U.S. Patent No. 5,952,769, at col. 6, II. 12-51.

[0066] Either a single carboxylic acid or a mixture of carboxylic acids can be used to form the metal carboxylate composition. In some embodiments, a mixture of carboxylic acids is used. In still other embodiments, the mixture contains 2- ethylhexanoic acid where R° is H, R" is C₂H₅ and R' is C H₉ in formula (I) above. In some embodiments, this acid is the lowest boiling acid constituent in the mixture. When a mixture of metal carboxylates is used, the mixture has a broader evaporation temperature range, making it more likely that the evaporation temperature of the mixture will overlap the metal carboxylate decomposition temperature, allowing the formation of a solid metal oxide. Moreover, the possibility of using a mixture of carboxylates avoids the need and expense of purifying an individual carboxylic acid.

B. METAL ALKOXIDES

[0067] Metal alkoxides suitable for use in the present invention include at least one metal atom and at least one alkoxide radical -OR² bonded to the at least one metal atom. Such metal alkoxides include those of formula II:

M(OR²)_z (II)

in which M is a metal atom of valence z+;

z is a positive integer, such as, for example, 1 , 2, 3, 4, 5, 6, 7, and 8;

R² can be alike or different and are independently chosen from unsubstituted and substituted alkyl, unsubstituted and substituted alkenyl, unsubstituted and substituted alkynyl, unsubstituted and substituted heteroaryl, and

unsubstituted and substituted aryl radicals,

wherein substituted alkyl, alkenyl, alkynyl, heteroaryl, and aryl radicals are substituted with one or more alike or different substituents independently chosen from halogen, hydroxy, alkoxy, amino, heteroaryl, and aryl radicals. In some embodiments, z is chosen from 2, 3, and 4.

[0068] Metal alkoxides are available from Alfa-Aesar and Gelest, Inc., of Morrisville, PA. Lanthanoid alkoxides such as those of Ce, Nd, Eu, Dy, and Er are sold by Kojundo Chemical Co., Saitama, Japan, as well as alkoxides of Al, Zr, and Hf, among others. See, e.g.,

http://www.kojundo.co.jp/English/Guide/material/lanthagen.html.

[0069] Examples of metal alkoxides useful in embodiments of the present invention include methoxides, ethoxides, propoxides, isopropoxides, and butoxides and isomers thereof. The alkoxide substituents on a give metal atom are the same or different. Thus, for example, metal dimethoxide diethoxide, metal methoxide diisopropoxide t-butoxide, and similar metal alkoxides can be used. Suitable alkoxide substituents also may be chosen from: 1 . Aliphatic series alcohols from methyl to dodecyl including branched and isostructured.

2. Aromatic series alcohols: benzyl alcohol - C₆H₅CH₂OH; phenyl-ethyl alcohol - C₈HioO; phenyl- propyl alcohol - CgHi₂0, and so on.

[0070] Metal alkoxides useful in the present invention can be made according to many methods known in the art. One method includes converting the metal halide to the metal alkoxide in the presence of the alcohol and its corresponding base. For example:

MX_Z + zHOR² → M(OR²)z + zHX

in which M, R², and z are as defined above for formula II, and X is a halide anion.

C. METAL β-DIKETONATES

[0071 ] Metal β-diketonates suitable for use in the present invention contain at least one metal atom and at least one β-diketone of formula III as a ligand:

in which

R³, R⁴, R⁵, and R⁶ are alike or different, and are independently chosen from hydrogen, unsubstituted and substituted alkyl, unsubstituted and substituted alkoxy, unsubstituted and substituted alkenyl, unsubstituted and substituted alkynyl, unsubstituted and substituted heteroaryl, unsubstituted and substituted aryl, carboxylic acid groups, ester groups having unsubstituted and substituted alkyl, and combinations thereof,

wherein substituted alkyl, alkoxy, alkenyl, alkynyl, heteroaryl, and aryl radicals are substituted with one or more alike or different substituents independently chosen from halogen atoms, hydroxy, alkoxy, amino, heteroaryl, and aryl radicals.

[0072] It is understood that the β-diketone of formula I II may assume different isomeric and electronic configurations before and while chelated to the metal atom. For example, the free β-diketone may exhibit enolate isomerism. Also, the β- diketone may not retain strict carbon-oxygen double bonds when the molecule is bound to the metal atom.

[0073] Examples of β-diketones useful in embodiments of the present invention include acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, 2,2,6,6- tetramethyl-3,5-heptanedione, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5- octanedione, ethyl acetoacetate, 2-methoxyethyl acetoacetate,

benzoyltrifluoroacetone, pivaloyltrifluoroacetone, benzoyl-pyruvic acid, and methyl- 2,4-dioxo-4-phenylbutanoate.

[0074] Other ligands are possible on the metal β-diketonates useful in the present invention, such as, for example, alkoxides such as -OR² as defined above, and dienyl radicals such as, for example, 1 ,5-cyclooctadiene and norbornadiene.

[0075] Metal β-diketonates useful in the present invention can be made according to any method known in the art. β-diketones are well known as chelating agents for metals, facilitating synthesis of the diketonate from readily available metal salts.

[0076] Metal β-diketonates are available from Alfa-Aesar and Gelest, Inc. Also, Strem Chemicals, Inc. of Newburyport, MA, sells a wide variety of metal β- diketonates on the internet at

http://www.strem.com/code/template.ghc?direct=cvdindex.

[0077] In some embodiments of the present invention, a metal compound comprises a transition metal atom. In other embodiments, a metal compound comprises a rare earth metal atom. In further embodiments, the metal compound composition comprises a plurality of metal compounds. In some embodiments, a plurality of metal compounds comprises at least one rare earth metal compound and at least one transition metal compound, while in other embodiments, a plurality of metal compounds comprises other than at least one rare earth metal compound and at least one transition metal compound. Metal carboxylates, metal alkoxides, and metal β-diketonates can be chosen for some embodiments of the present invention.

[0078] In further embodiments, a metal compound mixture comprises one metal compound as its major component and one or more additional metal compounds which may function as stabilizing additives. Stabilizing additives, in some embodiments, comprise trivalent metal compounds. Trivalent metal compounds include, but are not limited to, chromium, iron, manganese, and nickel compounds. A metal compound composition, in some embodiments, comprises both cerium and chromium compounds. [0079] In some embodiments, the metal compound that is the major component of the metal compound composition contains an amount of metal that ranges from about 65 to about 97% by weight or from about 80 to about 87% by weight of the total weight of metal in the composition. In other embodiments, the amount of metal forming the major component of the metal compound composition ranges from about 90 to about 97% by weight of the total metal present in the composition. In still other embodiments, the amount of metal forming the major component of the metal compound composition ranges from about 97 to about 100% by weight of the total metal present in the composition.

[0080] The metal compounds that may function as stabilizing additives, in some embodiments, may be present in amounts such that the total amount of the metal in metal compounds which are the stabilizing additives is at least 3% by weight, relative to the total weight of the metal in the metal compound composition. This can be achieved in some embodiments by using a single stabilizing additive, or multiple stabilizing additives, provided that the total weight of the metal in the stabilizing additives is greater than 3%. In other embodiments, the amount of the stabilizing metal is less than 3 % relative to the total weight of metal in the metal compound composition. In yet other embodiments, the total weight of the metal in the stabilizing additives ranges from about 3% to about 35% by weight. In still other embodiments, the total weight for the metal in the stabilizing additives ranges from about 3 to about 30% by weight, relative to the total weight of the metal in the metal compound composition. In other embodiments, the total weight range for the metal in the stabilizing additives ranges from about 3 to about 10% by weight. In some embodiments, the total weight range for the metal in the stabilizing additives is from about 7 to about 8% by weight, relative to the total weight of the metal in the metal compound composition. Still other embodiments provide the stabilizing metal in an amount greater than about 35 % by weight relative to the total weight of the metal in the metal compound composition.

[0081 ] The amount of metal in the metal compound composition, according to some embodiments, ranges from about 20 to about 150 grams of metal per kilogram of metal compound composition. In other embodiments, the amount of metal in the metal compound composition ranges from about 30 to about 50 grams of metal per kilogram of metal compound composition. In further embodiments, the metal compound composition can contain from about 30 to about 40 grams of metal per kg of composition. Amounts of metal less than 20 grams of metal per kilogram of metal compound composition or greater than about 150 grams of metal per kilogram of metal compound composition also can be used.

[0082] The metal compound may be present in any suitable composition. Finely divided powder, nanoparticles, solution, suspension, multi-phase composition, gel, vapor, aerosol, and paste, among others, are possible.

[0083] The metal compound composition may also include nanoparticles in the size range of less than 100 nm in average size and being composed of a variety of elements or combination thereof, for example, Al₂0₃, Ce0₂, Ce₂0₃, Ti0₂, Zr0₂ and others. In some cases, the nanoparticles can be dispersed, agglomerated, or a mixture of dispersed and agglomerated nanoparticles. Nanoparticles may have a charge applied to them, negative or positive, to aid dispersion. Moreover, dispersion agents, such as known acids or surface modifying agents, may be used.

[0084] The applying of the metal compound composition may be

accomplished by various processes, including dipping, spraying, flushing, vapor deposition, printing, lithography, rolling, spin coating, brushing, swabbing or any other means that allows the metal compound composition to contact the substrate to be treated. In this regard, the metal compound composition may be liquid, and may also comprise a solvent. The optional solvent may be any hydrocarbon and mixtures thereof. In some embodiments, the solvent can be chosen from carboxylic acids; toluene; xylene; benzene; alkanes, such as for example, propane, butane, isobutene, hexane, heptane, octane, and decane; alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; mineral spirits; β- diketones, such as acetylacetone; ketones such as acetone; high-paraffin, aromatic hydrocarbons; and combinations of two or more of the foregoing. Some

embodiments employ solvents that contain no water or water in trace amounts or greater, while other embodiments employ water as the solvent. In some

embodiments, the metal compound composition further comprises at least one carboxylic acid. Some embodiments employ no solvent in the metal compound composition. Other embodiments employ no carboxylic acid in the metal compound composition.

[0085] The metal compound composition can applied in some embodiments in which the composition has a temperature less than about 250 °C. That composition also can be applied to the substrate in further embodiments at a temperature less than about 50 °C. In other embodiments, the liquid metal compound composition is applied to the substrate at room temperature. In still other embodiments, that composition is applied at a temperature greater than about 250 °C.

[0086] Following application, the at least one metal compound is at least partially converted to at least one metal oxide. In some embodiments the at least one metal compound is fully converted to at least one metal oxide.

[0087] Suitable environments for converting the at least one metal compound into at least one metal oxide include vacuum, partial vacuum, atmospheric pressure, high pressure equal to several atmospheres, high pressure equal to several hundred atmospheres, inert gases, and reactive gases such as gases comprising oxygen, including pure oxygen, air, dry air, and mixtures of oxygen in various ratios with one or more other gases such as nitrogen, carbon dioxide, helium, neon, and argon, as well as hydrogen, mixtures of hydrogen in various ratios with one or more other gases such as nitrogen, carbon dioxide, helium, neon, and argon, also other gases such as, for example, nitrogen, NH₃, hydrocarbons, H₂S, PH₃, each alone or in combination with various gases, and still other gases which may or may not be inert in the converting environment. In some embodiments, a suitable environment for converting the at least one metal compound into at least one metal oxide is free or substantially free of oxygen.

[0088] The environment may be heated relative to ambient conditions by suitable methods, in some embodiments. In other embodiments, the environment may comprise reactive species that cause or catalyze the conversion of the metal compound to the metal oxide, such as, for example, acid-catalyzed hydrolysis of metal alkoxides. In still other embodiments, the metal compound is caused to convert to the metal oxide by the use of induction heating, lasers, microwave emission, or plasma, as explained below.

[0089] The conversion environment may be accomplished in a number of ways. For example, a conventional oven may be used to bring the wetted substrate up to a temperature exceeding approximately 250°C for a given period of time. In some embodiments, the environment of the wetted substrate is heated to a temperature exceeding about 400°C but less than about 450°C or less than about 500°C for a chosen period of time. In other embodiments, the environment of the substrate is heated to a temperature ranging from about 400°C to about 650°C. In further embodiments, the environment is heated to a temperature ranging from about 400°C to about 550°C. In still further embodiments, the environment is heated to a temperature ranging from about 550 °C to about 650 °C, from about 650 °C to about 800 °C, or from about 800 °C to about 1000 °C. In one embodiment, the

environment is heated to a temperature of up to about 425°C or 450°C. Depending on the amount of substrate, the time period may be extended such that sufficient conversion of a desired amount of the metal compound to metal oxides has been accomplished.

[0090] In some applications, the oxidation of the substrate being treated or other material is not desired. In these cases, an inert atmosphere may be provided in the conversion environment to prevent such oxidation. In the case of heating the substrate in a conventional oven, a nitrogen or argon atmosphere can be used, among other inert gases, to prevent or reduce the oxidation of the substrate or other material prior to or during the conversion process.

[0091 ] The conversion environment may also be created using induction heating through means familiar to those skilled in the art of induction heating.

Alternatively, the conversion environment may be provided using a laser applied to the substrate for sufficient time to allow at least some of the metal compounds to convert to metal oxides. In other applications, the conversion environment may be created using an infra-red light source which can reach sufficient temperatures to convert at least some of the metal compounds to metal oxides. Some embodiments may employ a microwave emission device to cause at least some of the metal compound to convert. Still other embodiments employ a plasma to provide the environment for converting the metal compound into metal oxide. In the case of induction heating, microwave heating, lasers, plasmas, and other heating methods that can produce the necessary heat levels in a short time, for example, within seconds, 1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, or one hour. Accordingly, in some embodiments, the conversion environment can be created without the use of an inert gaseous environment, thus enabling conversion to be done in open air, outside of a closed system due to the reduced time for undesirable compounds to develop on the material's surface in the presence of ambient air.

[0092] The gas above the metal compound on the substrate can be heated, in some embodiments, to convert the metal compound to the metal oxide. Heating can be accomplished by introducing high temperature gases, for example. This high temperature gas can be produced by a conventional oven, induction heating coils, heat exchangers, industrial process furnaces, exothermic reactions, microwave emission, or other suitable heating method. Still other embodiments provide a fluidized bed of particles, such as high surface area particles, on which at least one metal oxide is to be formed. A gas is passed through the particles to fluidize them. Vapor of one or more metal compounds is introduced into the gas, and condenses onto the particles. Then, the fluidizing gas is heated sufficiently to convert at least some of the metal compounds to metal oxide, in some embodiments.

[0093] In some embodiments a feed of an inert gas may be provided to create a non-oxidizing atmosphere for the conversion process.

[0094] In other embodiments of the present invention, similar or differing metal oxides can be formed on the substrate to make the catalytic material.

Representative metal oxide compositions that have been found to be suitable in embodiments of the present invention include, but are not limited to:

Zr0₂ for example, at 0-90 wt%

Ce0₂ for example, at 0-90 wt%

Ce0₂-Zr0₂ where Ce0₂ is about 10-90 wt%

Y2O3 Yttria-stabilized Zirconia where Y is about 1 -50% mol%

Ti0₂ for example, at 0-90 wt%

Fe₂0₃ for example, at 0-90 wt%

NiO for example, at 0-90 wt%

AI₂0₃ for example, at 0-90 wt%

Si0₂

Y₂0₃

Cr₂0₃

Mo₂0₃

Hf0₂

La₂0₃

Pr₂0₃

Nd₂0₃

Sm₂0₃

Eu₂0₃

Gd₂0₃

Tb₂0₃

Dy₂0₃ Er₂0₃

Tm₂0₃

Yb₂0₃

Lu₂0₃

Mixtures of these compositions are also suitable for use in the invention.

[0095] Oxides of the following elements also can be used in embodiments of the present invention: Lithium, Beryllium, Sodium, Magnesium, Aluminum, Silicon, Potassium, Calcium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Gallium, Germanium, Arsenic, Bromine, Rubidium, Strontium, Yttrium, Zirconium, Niobium, Molybdenum, Technetium, Ruthenium, Rhodium, Palladium, Antimony, Tellurium, Silver, Cadmium, Indium, Tin, Cesium, Barium, Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Hafnium, Tantalum, Tungsten, Rhenium, Osmium, Iridium, Platinum, Gold, Mercury, Thallium, Lead, Bismuth, Radium, Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, and Lawrencium. Oxides containing more than one of the foregoing elements, and oxides containing elements in addition to the foregoing elements, also can be used in embodiments of the present invention. For example, SrTi0₃ and MgAI₂0₄ are included. Those materials are likely to form at least in small amounts when appropriate metal compounds are used, depending on the conditions of the conversion process. In some

embodiments, the molar ratio of metal compounds deposited on the surface corresponds to the molar ratio of metal oxides after conversion.

[0096] The invention relates, in some embodiments, to diffused domains of metal oxide. As used herein, "diffused" means that metal oxide molecules, nanoparticles, nanocrystals, larger domains, or more than one of the foregoing, have penetrated the substrate. The diffusion of metal oxides can range in concentration from rare interstitial inclusions in the substrate, up to the formation of materials that contain significant amounts of metal oxide. A thin film is understood to indicate a layer, no matter how thin, composed substantially of metal oxide. In some embodiments, a thin film has very little or no substrate material present, while in other embodiments, a thin film comprises atoms, molecules, nanoparticles, or larger domains of substrate ingredients. In some embodiments, it may be possible to distinguish between diffused portions and thin films. In other embodiments, a gradient may exist in which it becomes difficult to observe a boundary between the diffused domain and the thin film. Furthermore, some embodiments may exhibit only one of a diffused domain and a thin film. Still other embodiments include thin films in which one or more species have migrated from the substrate into the thin film.

Additional embodiments provide contiguous domains of metal oxide on a substrate, while other embodiments provide non-contiguous domains, for example, for catalytic applications. The terms "metal oxide" and "surface comprises at least one metal oxide" include all of those possibilities, including diffused coatings, thin films, stacked thin films, contiguous and non-contiguous domains, and combinations thereof. The term "metal oxide coating" includes, for example, diffused coatings, thin films, stacked thin films, and combinations thereof.

[0097] As explained herein, the diffused domains of some embodiments of the invention provides increased performance, in part, because it penetrates the surface of the substrate to a depth providing a firm anchor to the material without the need for intermediate bonding layers. In some embodiments, the diffused domain penetrates the substrate to a depth of less than about 100 Angstroms. In other embodiments, the diffused metal oxide penetrates from about 100 Angstroms to about 200 Angstroms, from about 200 Angstroms to about 400 Angstroms, from about 400 Angstroms to about 600 Angstroms, and greater than about 600

Angstroms, and in some embodiments from about 200 to about 600 Angstroms. This diffused metal oxide allows much thinner domains [in some embodiments around 0.1 to 1 microns in thickness (or about 0.5 microns when approximately 6 layers are used)] to be applied. This, in turn, allows for less metal oxide to be used, reducing significantly the cost of materials attaching to the substrate. Thus, some embodiments of the present invention provide a domain no thicker than about 5 nm. Other embodiments provide a domain no thicker than about 10 nm. Still other embodiments provide a domain no thicker than about 20 nm. Still other

embodiments provide a domain no thicker than about 100 nm. Other embodiments provide a domain having a thickness less than about 25 microns. Still other embodiments provide a domain having a thickness less than about 20 microns. Still other embodiments provide a domain having a thickness less than about 10 microns. Yet other embodiments provide a domain having a thickness less than about 5 microns. Some embodiments provide a domain having a thickness less than about 2.5 microns. Even other embodiments provide a domain having a thickness less than about 1 micron.

[0098] In some embodiments of the invention, the metal oxide can contain other species, such as, for example, species that have migrated from the substrate into the metal oxide. In other embodiments, those other species can come from the atmosphere in which the at least one metal compound is converted. For example, the conversion can be performed in an environment in which other species are provided via known vapor deposition methods. Still other embodiments provide other species present in or derived from the at least one metal compound or the composition comprising the compound. Suitable other species include metal atoms, metal compounds including those metal atoms, such as oxides, carbides, nitrides, sulfides, phosphides, and mixtures thereof, and the like. The inclusion of other species can be accomplished by controlling the conditions during conversion, such as the use of a chosen atmosphere during the heat conversion process, for example, a partial vacuum or atmosphere containing O2, N₂, NH₃, one or more hydrocarbons, H₂S, alkylthiols, PH₃, or a combination thereof.

[0099] Some embodiments of the present invention provide metal oxides that are substantially free of other species. For example, small amounts of carbides may form along side oxides when, for example, metal carboxylates are converted, if no special measures are taken to eliminate the carbon from the carboxylate ligands. Thus, converting metal compounds in the presence of oxygen gas, air, or oxygen mixed with other gases reduces or eliminates carbide formation in some

embodiments of the present invention. Also, rapid heating of the conversion environment, such as, for example, by induction heating, microwave heating, lasers, plasmas, and other heating methods that can produce the necessary heat levels in a short time, reduces or eliminates formation of other species, in other embodiments. At least one rapid heating technique is used in combination with an oxygen- containing atmosphere in still other embodiments.

[00100] Additional embodiments employ various heating steps to reduce or eliminate the formation of other species. For example, carbide formation can be lessened during metal oxide formation in some embodiments by applying a metal compound precursor composition containing a metal carboxylate to a surface, subjecting the surface to a low-temperature bake at about 250 °C under a vacuum, introducing air and maintaining the temperature, and then increasing the temperature to about 420 °C under vacuum or inert atmosphere to convert the metal carboxylate into the metal oxide. Without wanting to be bound by theory, it is believed that the low-temperature bake drives off most or all of the carboxylate ligand, resulting in an oxide substantially free of metal carbide.

[00101 ] Still other embodiments employ more than one application to achieve at least one metal oxide substantially without other species. For example, in some embodiments, a base of at least one metal oxide is formed from at least one metal carboxylate under an inert atmosphere. Such a base may contain metal carbides due to the initial presence of the carboxylate ligands. Moreover, such a base may exhibit good adhesion and strength, for example, when the surface comprises a carbon steel alloy. Then, one or more subsequent metal compounds are repeatedly applied and converted in an oxygen-containing atmosphere, for example, and the subsequent layers of metal oxide form substantially without metal carbides. In some embodiments, six or more layers are formed on the base.

[00102] In addition, the effect of any mismatches in physical, chemical, or crystallographic properties (particularly with regard to differences in thermal expansion coefficients) may be minimized by the use of much thinner coating materials and the resulting films. Furthermore, the smaller crystallite structure of the film (3-6 nanometers, in some embodiments) increases Hall-Petch strength in the film's structure significantly.

[00103] The nanocrystalline grains resulting from some embodiments of the methods of the present invention have an average size, or diameter, of less than about 50 nm. In some embodiments, nanocrystalline grains of metal oxide have an average size ranging from about 1 nm to about 40 nm or from about 5 nm to about 30 nm. In another embodiment, nanocrystalline grains have an average size ranging from about 10 nm to about 25 nm. In further embodiments, nanocrystalline grains have an average size of less than about 10 nm, or less than about 5 nm.

[00104] In other embodiments, the invention relates to metal oxide domains (whether diffused, thin film, contiguous, non-contiguous, or a combination thereof) and catalytic materials comprising such domains, in which the domains contain two or more rare earth metal oxides and at least one transition metal oxide. Further embodiments of the invention relate to metal oxide domains (and catalytic materials comprising them), containing ceria, a second rare earth metal oxide, and a transition metal oxide. Some embodiments relate to metal oxide domains (and catalytic materials comprising them), containing yttria, zirconia, and a second rare earth metal oxide. In some cases, the second rare earth metal oxide can include platinum or other known catalytic elements. Still other embodiments relate to metal oxide domains (and catalytic materials comprising them), containing alumina, silica, and combinations thereof. Additional embodiments relate to metal oxide domains (and catalytic materials comprising them), containing alumina, silica, titania, and combinations thereof.

[00105] In some embodiments, the metal compound applied to the substrate comprises a cerium compound, and the metal oxide comprises cerium oxide (or ceria). In other embodiments, the metal compound applied to the substrate comprises a zirconium compound, and the metal oxide comprises zirconia. In yet other embodiments, a solution comprising both a cerium compound and a zirconium compound is applied, and the resulting metal oxide comprises ceria and zirconia. In some cases, the zirconia formed by the process of the invention comprises crystal grains having an average size of about 3-9 nm, and the ceria formed by the process of the invention comprises crystal grains having an average size of about 9-18 nm. The nanostructured zirconia can be stabilized in some embodiments with yttria or other stabilizing species alone or in combination. In still other embodiments, the metal oxide comprises zirconia, yttria, or alumina, each alone or in combination with one or both of the others.

[00106] As explained herein, additional metal oxides, which can be the same or different, can be added. In some embodiments, the at least one metal oxide serves as a bond base for at least one additional material. Such additional materials need not be formed according to the present invention. Some embodiments provide a metal oxide bond base that allows an additional material that would not adhere to the substrate as well in the absence of the bond base.

[00107] The process of the invention may permit the use of metal oxides on a wide variety of materials, including application of AI2O3, Si0₂, CeC>2 and Zr0₂ to ceramics and/or solid metals previously not thought possible of being treated with these materials. Some embodiments of the present invention provide a relatively low temperature process that does not damage or distort many substrates, does not produce toxic or corrosive water materials, and can be done on site, or "in the field" without the procurement of expensive capital equipment. [00108] In some embodiments of the present invention, a substrate which will form at least a portion of a catalytic material is placed within a vacuum chamber, and the chamber is evacuated. Optionally, the substrate can be heated or cooled, for example, with gas introduced into the chamber or by heat transfer fluid flowing through the substrate mounting structure. If a gas is introduced, care should be taken that it will not alter the substrate in an unintended manner, such as by oxidation of a hot iron-containing surface by an oxygen-containing gas. Introduced gas optionally can be evacuated once the substrate achieves the desired

temperature. Vapor of one or more metal compounds, such as silicon(IV) 2- hexanoate, enters the vacuum chamber and deposits on the substrate. A specific volume of a fluid composition containing the metal compound can provide a specific amount of compound to the surface of the substrate within the vacuum chamber, depending on the size of the chamber and other factors. Optionally, a chosen gas is vented into the chamber and fills the vacuum chamber to a chosen pressure, in one example, equal to one atmosphere. The chamber is heated to a temperature sufficient to convert at least some of the compounds into oxides, for example, 450 ^°C, for a discrete amount of time sufficient for the conversion process, for example, thirty minutes. In this example, silica domains form on the substrate. Optionally, the process can be repeated as many times as desired, forming contiguous domains, a uniform coating, or even a thicker coating of silica on the substrate. In some embodiments, the component can be cooled relative to ambient temperature, such as, for example, to liquid nitrogen temperature, to aid the deposition process. In other embodiments, a reducing atmosphere may be used to convert at least a portion of the metal oxides to metal.

[00109] In other embodiments, the substrate can comprise one or more polymers, such as polyvinyl chloride. The polymer substrate can be kept at lower temperatures sufficient to prevent the degradation of the substrate during the heating process, for example, at liquid nitrogen temperatures while the metal compound converts to the oxide due to any technique that heats the metal compound but not the substrate to a significant degree. Examples of such heating techniques include flash lamps, lasers, and microwave heating. In addition, materials that would become degraded by exposure to high temperatures can be kept at lower temperatures using the same techniques. For example, glasses, low-melting-temperature metals, polycarbonates, and similar substrates can be kept cooler while the at least one metal compound is converted to at least one metal oxide.

[001 10] As used herein in reference to process gases used to carry out the process of the invention, the term "high temperature" means a temperature sufficiently high to convert the metal compound to metal oxide, generally in the range of about 200 °C to about 1000 °C, such as, for example, about 200 °C to about 400 °C, or about 400 °C to about 500 °C, about 500 °C to about 650 °C, about 650 °C to about 800 °C, or about 800 °C to about 1000 °C.

[001 1 1 ] In some embodiments of the invention, an oxidizing material may be formed on a substrate by applying a liquid metal compound composition to the substrate using a dipping process, spraying, vapor deposition, swabbing, brushing, or other known means of applying a liquid to substrate. This liquid metal compound composition comprises at least one rare earth metal salt of a carboxylic acid and at least one transition metal salt of a carboxylic acid, in a solvent, in some

embodiments. The substrate, once wetted with the composition is then exposed to a heated environment that will convert at least some of the metal compounds to metal oxides, thereby forming an oxidizing material on the substrate.

[001 12] The process may be used to create a nanocrystalline structure that comprises an oxygen containing molecule for chosen applications. Alternately, the resulting nanocrystalline structure may comprise a metal containing compound, a metal, a ceramic, or a cermet.

[001 13] In some applications, where it is desirable to reduce a metal oxide to a pure metal, the treated substrate may be exposed to a reducing agent, such as hydrogen or other known reducing agent using known means for oxide reduction. For example, 7 % hydrogen in argon heated to 350 °C can be used to form platinum in certain embodiments. Other metals that may be desired, such as for catalytic purposes, for example, include but are not limited to platinum, palladium, rhodium, nickel, cerium, gold, silver, zinc, lead, rhenium, ruthenium, and combinations of two or more thereof.

[001 14] Other embodiments provide for the introduction of metal catalysts. This can be accomplished in any suitable manner, in addition to the reduction process explained above. For example, metal nanoparticles can be dispersed in the metal compound composition. Or, metal nanoparticles can be applied to the substrate wetted with at least one metal compound, and then the compound is converted to at least one metal oxide, thereby binding the metal nanoparticles at the surface of the metal oxide. That method improves on conventional technology that buries catalytic metals in the interior of the metal oxide. In some embodiments, alumina, ceria, silica, titania, or a combination thereof comprises one or more catalytic metal sites on the surface of the metal oxide. In further embodiments, the at least one metal oxide slows or stops the growth of catalytic metal grains during high temperature catalysis, by immobilizing the catalytic metal domains.

[001 15] Further embodiments provide high surface area films and monoliths. In some of those embodiments, a particulate substrate is wetted with at least one metal compound, and the compound is converted to the at least one metal oxide. In one variation, the substrate is held in such density so that the metal oxide binds the particles together, forming a high surface area film or monolith of the metal oxide- containing particles. In another variation, the compound is converted so that the particles do not substantially agglomerate. Then, a polymer material is mixed in with the particles containing metal oxide, and the polymer is sintered away, causing the particles to fuse together, thereby forming a high surface area film or monolith of the metal oxide-containing particles.

[001 16] As previously stated, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms. It will be appreciated that many modifications and other variations that will be appreciated by those skilled in the art are within the intended scope of this invention as claimed below without departing from the teachings, spirit, and intended scope of the invention. Furthermore, the foregoing description of various embodiments does not necessarily imply exclusion. For example, "some" embodiments may include all or part of "other" and "further" embodiments within the scope of this invention.

Claims

WE CLAIM:

1 . A method for making a catalytic material, comprising: applying at least one metal compound to a substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to make the catalytic material.

2. The method of claim 1 , further comprising removing the catalytic material from the substrate.

3. The method of claim 1 , wherein the substrate is a high surface area substrate.

4. The method of claim 1 , wherein the at least one metal compound is present in a metal compound composition, which comprises at least one nanoparticle.

5. The method of claim 4, wherein the at least one nanoparticle is chosen from Al₂0₃, Ce0₂, Ce₂0₃, Ti0₂, Zr0₂, and combinations of two or more thereof.

6. The method of claim 1 , wherein the converting comprises

heating the at least one metal compound to about 250 °C under a vacuum;

introducing air and maintaining the temperature; and

increasing the temperature to about 420 °C under vacuum or inert atmosphere.

7. The method of claim 1 , wherein the substrate comprises one or more polymers, glasses, low-melting-temperature metals, polycarbonates, or a combination thereof.

8. A method of stabilizing alumina in an alumina-containing catalytic material, comprising:

applying at least one metal compound on the catalytic material, and

converting the at least one metal compound to at least one metal oxide to stabilize the alumina.

9. The method of claim 8, wherein the at least one metal oxide exhibits thermal stability at a higher temperature compared to alumina.

10. The method of claim 8, wherein the at least one metal oxide exhibits catalytic activity at a higher temperature compared to alumina.

1 1. A method of regenerating a catalytic material having a substrate, comprising: applying at least one metal compound to the substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to regenerate the catalytic material.

12. A catalytic material comprising at least one metal oxide, wherein the at least one metal oxide is made by a process comprising:

applying at least one metal compound to a substrate; and converting at least some of the compound to at least one metal oxide on the substrate, to make the catalytic material.

13. A catalytic material comprising at least one metal oxide wherein the at least one metal oxide is substantially free of metal carbide.

14. The catalytic material of claim 13, wherein the catalytic material is present on a substrate, and wherein a portion of the at least one metal oxide is diffused into the substrate.

15. The catalytic material of claim 13, further comprising one or more metals chosen from platinum, palladium, rhodium, nickel, cerium, gold, silver, zinc, lead, rhenium, ruthenium, and combinations of two or more thereof.