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WO1998015500A1 - Compositions et procedes pour preparer des oxydes metalliques poreux - Google Patents

Compositions et procedes pour preparer des oxydes metalliques poreux Download PDF

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WO1998015500A1
WO1998015500A1 PCT/IB1996/001163 IB9601163W WO9815500A1 WO 1998015500 A1 WO1998015500 A1 WO 1998015500A1 IB 9601163 W IB9601163 W IB 9601163W WO 9815500 A1 WO9815500 A1 WO 9815500A1
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metal oxide
surfactant
molecular sieve
metal
lanthanide
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PCT/IB1996/001163
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English (en)
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Jackie Y. Ying
David M. Antonelli
Tao Sun
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Massachusetts Institute Of Technology
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Priority to CA002268090A priority Critical patent/CA2268090A1/fr
Priority to AU72262/96A priority patent/AU7226296A/en
Priority to PCT/IB1996/001163 priority patent/WO1998015500A1/fr
Publication of WO1998015500A1 publication Critical patent/WO1998015500A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • C01B37/02—Crystalline silica-polymorphs, e.g. silicalites dealuminated aluminosilicate zeolites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/14—Methods for preparing oxides or hydroxides in general
    • C01B13/32—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
    • C—CHEMISTRY; METALLURGY
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C01F17/218—Yttrium oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C01F17/224—Oxides or hydroxides of lanthanides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C01F17/224—Oxides or hydroxides of lanthanides
    • C01F17/235—Cerium oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G33/00—Compounds of niobium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C—CHEMISTRY; METALLURGY
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C01P2006/17—Pore diameter distribution

Definitions

  • Porous inorganic solids have found great utility as catalysts and separation media for industrial applications.
  • the openness of the microstructure allows molecules access to the surface area of the materials that enhance their catalytic and sorption activity.
  • the porous materials in use today can be sorted into several categories based on their microstructure, molecular sieves being one of these.
  • Molecular sieves are structurally defined materials with a pore size distribution that is typically very narrow because of the crystalline nature of the material's microstructure. Examples of molecular sieves are zeolites and mesoporous materials. Zeolites are generally aluminosilicate materials with pore sizes in the microporous range which is between two to twenty Angstroms.
  • Zeolites have been demonstrated to exhibit catalytic properties. Zeolites are porous crystalline aluminosilicates which have a definite crystalline structure within which a large number of smaller cavities may be interconnected by a number of still smaller channels or pores. Relatively little advance has been achieved in fine chemical synthesis with zeolite-based catalysis due, at least in part, to the limitations of redox activity in currently available molecular sieves (B. Notari, Stud. Surf. Sci. Catal. 37 (1988) 413; P. Roftia, Stud. Surf. Sci. Catal. 55 (1990) 43; N. Herron, et al . J. Am. Chem. Soc. 109 (1987) 2837; R.F.
  • metal cations need to be introduced into the zeolitic matrices. This can be achieved only in very limited concentration in the form of dopants without affecting the crystallinity of the zeolitic structure. More commonly, metal cations are introduced into the zeolitic cage structure by cation exchange or metal salt impregnation. The metal cations introduced into zeolites have been found capable of catalyzing some redox reactions.
  • the turnover frequency (TOF) of the catalyst is, however, very restricted by the number of catalytically active sites that can be introduced, which is in turn limited by the Si/Al ratio in the zeolite framework structure.
  • the catalytic activity of the zeolite materials can be severely reduced due to aggregation of metal cations caused by hydration of the metal cations and/or dealumination of the zeolite framework in the presence of water vapor at temperatures of 500-800°C.
  • Mesoporous materials generally have larger pore sizes.
  • Mesoporous materials have a pore size from about 10 to 500 Angstroms.
  • Examples of conventional mesoporous solids include silicas and modified layered materials, but these are amorphous or 2-dimensional crystalline structures, with pores that are irregularly spaced and broadly distributed in size. Pore size has been controlled by intercalation of layered clays with a surfactant species, but the final products have typically retained the layered nature of the precursor material.
  • Porous transition metal oxides have been the subject of increasing interest as materials which can be utilized in partial oxidation, complete combustion, NO x decomposition, hydrodesulfurization, photocatalytic decomposition of organic compounds and solid acid catalysis. Most attempts, however, to prepare mesoporous materials suitable for such purposes have typically led to lamellar phases where surfactant and metal oxide phases are layered.
  • transition metal-containing hexagonally packed mesoporous material has only a small percentage of titanium dioxide incorporated into a silica structure. (Tanev et al . Nature 368 : 221 (1994)).
  • the method used to form the hexagonal mesoporous materials utilized a primary, rather than a quaternary ammonium ion surfactant as the templating reagent.
  • the titanium-doped silicate-based hexagonal mesoporous materials were found to be more active in the catalytic oxidation of arenes than the conventional microporous titanium silicate zeolites.
  • a need exists for a thermally stable mesoporous transition metal material and a method for forming mesoporous transition metal materials which overcome or minimize the above mentioned problems.
  • a need also exits for a crystalline microporous metal oxide having a dimensionally consistent pore structure and a method for forming crystalline microporous metal oxide materials which overcome or minimize the above mentioned problems.
  • the present invention relates to a composition and a method for producing stable hexagonally-packed metal oxide mesostructure (TMSl) wherein the metal oxide is selected from transition metal oxides and lanthanide metal oxides.
  • TMSl stable hexagonally-packed metal oxide mesostructure
  • a stable hexagonally-packed mesoporous metal oxide is prepared by combining a transition metal oxide precursor or lanthanide metal oxide precursor, a surfactant having an appropriate head group under conditions suitable for causing the formation of a complex between the head group of the surfactant and the metal oxide precursor, an aqueous solvent and a chelating agent (such as a 2,4- diketone) added in an amount to decrease, without arresting, the rate of hydrolysis.
  • the complex is then maintained under conditions suitable for controlled micelle formation and hydrolysis of the metal oxide precursor.
  • the hydrolysed complex is aged for a period of time at a temperature suitable for causing the formation of a hexagonally packed metal oxide mesostructure.
  • the surfactant, or organic portion of the surfactant is removed from the metal oxide mesostructure, resulting in the stable mesoporous material.
  • the metal oxide is selected from transition metal oxides and lanthanide metal oxides .
  • the present invention also relates to molecular sieves comprising a crystalline microporous or mesoporous metal oxide having a dimensionally consistent pore structure.
  • the metal of the metal oxide can be either silicon oxide, aluminum oxide, transition metal oxides, lanthanide metal oxides, or combinations thereof. These metal oxides can have either, for example, a hexagonal or a cubic arrangement. Further, the dimensionally consistent pore structure can be rod-shaped.
  • the invention is related to method for synthesizing a crystalline porous metal oxide having a dimensionally consistent pore structure by combining a metal oxide precursor and a small organic moiety, having at least one head group, under conditions which are suitable for causing the formation of a complex between the head group of the small organic moiety and the metal oxide precursor.
  • the complex is hydrolyzed and the reaction mixture is aged for a period of time and at a temperature suitable for causing the formation of the crystalline porous metal oxide having a dimensionally consistent pore structure.
  • the small organic moiety can be removed from the crystalline porous metal oxide by washing or by calcination, resulting in the crystalline porous metal oxide having a dimensionally consistent pore structure.
  • the invention is related to a method of synthesizing a crystalline mesoporous metal oxide having a dimensionally consistent pore structure by combining a metal oxide precursor with water for a sufficient period of time to form a gel.
  • the gel is combined with a surfactant, having at least one head group, under conditions suitable for physical interaction between the head group of the surfactant and the gel.
  • the combination of the gel and surfactant is aged for a period of time at a temperature suitable for causing the formation of the crystalline mesoporous metal oxide having a dimensionally consistent pore structure.
  • the present invention relates to the synthesis of a crystalline porous metal oxide having a dimensionally consistent pore structure by combining a metal oxide precursor with water for a sufficient period of time to form a gel.
  • the gel is combined with a small organic moiety having at least one head group, under conditions suitable for physical interaction between the head group of the small organic moiety and the gel.
  • the combination of the gel and the small organic moiety is aged for a period of time at a temperature suitable for causing the formation of the crystalline porous metal oxide having a dimensionally consistent pore structure.
  • hexagonally packed transition metal oxide or lanthanide metal oxide mesostructures prepared by the present method are stable, i.e. they substantially retain the hexagonal mesostructure upon removal of the surfactant, thereby presenting a hexagonally packed mesoporous structure with well-defined pore diameter and morphology.
  • This invention also has the advantage of enabling the formation of a wide variety of stable crystalline porous metal oxides having a dimensionally consistent pore structure.
  • crystalline porous metal oxides prepared by the present method are stable, retaining a dimensionally consistent pore structure and morphology.
  • Figure 1 is XRD (powder X-ray diffraction) data of Ti- TMS1 obtained using a phosphate surfactant with a chain length of 14 carbons atoms.
  • Figure 2 illustrates the XRD (powder X-ray diffraction) patterns of Nb-TMSl synthesized with tetradecylamine. The d-spacing for the (100) reflection appears at 31 A, the secondary (110) , (200) , and (210) reflections appear between 4° and 7° 20, however the (110) and (200) peaks are not well resolved.
  • Pattern (a) represents the result of surfactant removal by calcination.
  • Figures 4A, 4B and 4C represent the micellar array of (C 12 H 25 NH 2 )Nb(OEt) 5 , alkoxide and Nb-TMSl respectively.
  • ISA/EP Figure 8 is an XRD of as-prepared M-TMS5 (M is metal) .
  • V-TMS5 synthesized by mixing VOS0 4 and propylphosphonic acid (C 3 H 5 OP0 2 H) and aging at 96°C for 2 days, (See Example 19)
  • Nb-TMS5 synthesized with niobium ethoxide and a hexylamine as a templating agent at 180°C for 4 days (See Example 13)
  • Ti-TMS5 synthesized with titanium ethoxide and a hexylamine templating agent at 96 °C for 4 days See Example 12
  • Ta-TMS5 synthesized with tantalum ethoxide and hexylamine templating agent at 180°C for 7 days See Example 12) .
  • Figure 9(a) shows N 2 adsorption and desorption isotherms of microporous Nb-TMS5.
  • the sample was synthesized with a niobium ethoxide : hexylamine molar ratio of 1:0.75 (by the method of Example 13), aged at 180°C for 4 days and subjected to template removal by acidic isopropanol-water wash (with the pH adjusted to 1.5 using nitric acid) ,
  • (b) Pore size distribution of microporous Nb- TMS5 obtained by applying Horvath-Kawazoe method to a cylindrical pore model.
  • Figure 10(a) shows No adsorption and desorption isotherms of microporous Si-TMS5.
  • the sample was synthesized with a silicon ethoxide : hexylamine molar ratio of 5:1 (by the method of Example 17), aged at room temperature for 48 hours and subjected to template removal by calcination at 500°C for 2 hours, (b) Pore size distribution of microporous Si-TMS5 derived by applying Horvath-Kawazoe method to a cylindrical pore model.
  • Figure 12 shows XRD patterns of as-prepared Ta-TMS5 synthesized with a tantalum ethoxide : hexylamine molar ratio of (a) 1:1, (b) 0.75:1 and (c) 0.5:1. The samples were aged at 180°C for 7 days (see synthesis of Example 12).
  • Figure 13 shows XRD patterns of as-prepared microporous silica synthesized with a Si : adamantanamine molar ratio of (a) 5 (Si-TMS5) and (b) 2.5 (Si-TMS7). Both samples were aged at room temperature for 48 hours (see synthesis of Example 17) .
  • Figure 14 shows XRD patterns of as-prepared Si-TMS5 synthesized with a Si : hexylamine ratio of (a) 5:1 and (b) 1:1. Both samples were aged at room temperature for 48 hours (see synthesis of Example 17).
  • Figure 15 shows XRD patterns of as-prepared niobium oxide samples derived from hydrolysis of Nb(OC 2 H 5 ) 5 without amine templating agent (a) and with subsequent hexylamine addition (b)-(f).
  • the samples were analyzed after subjecting each to different aging conditions (a) and (b) at 25°C for 24 hours, (c) 96°C for 24 hours, (d) 180°C for 24 hours, (e) 180°C for 48 hours and (f) 180°C for 96 hours.
  • the samples in (b)-(f) were prepared with a Nb:hexylamine molar ratio of 1:0.75 (see synthesis of Example 13) .
  • Figure 16 shows Raman spectra of niobium oxide samples derived from hydrolysis of Nb(OC 2 H 5 ) 5 without amine templating agent (a) and with subsequent hexylamine addition (b)-(f).
  • the samples were analyzed after subjecting each to different aging conditions: (a) and (b) at 25°C for 24 hours, (c) 96°C for 24 hours, (d) 180°C for 24 hours, (e) 180°C for 48 hours and (f) 180°C for 72 hours.
  • the samples in (b)-(f) were prepared with a Nbrhexylamine molar ratio of 1:0.75 (see synthesis of Example 13) .
  • Figure 17 shows PA-FTIR spectra of niobium oxide samples derived from hydrolysis of Nb(OC-,H 5 ) 5 without amine templating agent (a) and with subsequent hexylamine addition (b)-(f).
  • the samples were analyzed after subjecting each to different aging conditions (a) and (b) at 25°C for 24 hours, (c) 96°C for 24 hours, (d) 180°C for 24 hours, (e) 180°C for 48 hours and (f) 180°C for 72 hours.
  • the samples in (b)-(f) were prepared with a Nb:hexylamine molar ratio of 1:0.75 (see synthesis of Example 13) .
  • Figure 18 shows TGAs of as-prepared Nb-TMS5 samples derived from hydrolysis of Nb(OC 2 H 5 ) 5 with subsequent hexylamine addition.
  • the samples were analyzed after subjecting each to different aging conditions: (a) 25°C for 24 hours, (b) 96°C for 24 hours and (c) 180°C for 24 hours.
  • the samples were prepared with a Nb: hexylamine molar ratio of 1:0.75 (see synthesis of Example 13).
  • Figure 19 shows XRD patterns of as-prepared Ta-TMS5 derived from hydrolysis of tantalum ethoxide in the presence of hexylamine (see synthesis of Example 12). The samples were analyzed after subjecting each to different aging conditions: (a) 25°C for 48 hours, (b) 96°C for 48 hours and (c) 180°C for 4 days.
  • Figure 20 shows PA-FTIR spectra of as-prepared Ta-TMS5 derived from hydrolysis of tantalum ethoxide in the presence of hexylamine (see synthesis of Example 12). The samples were analyzed after subjecting each to different aging conditions: (a) 25°C for 48 hours, (b) 96°C for 48 hours and (c) 180°C for 4 days.
  • Figure 21 shows XRD patterns of as-prepared niobium oxide nanocomposites from aging at (a) 96°C for 4 days and (b) 180°C for 4 days. Both samples were synthesized with a niobium ethoxide: adamantanamine ratio of 1:0.75 (see synthesis of Example 16) .
  • Figure 22 shows XRD patterns of as-prepared Si-TMS5 synthesized with (a) Si(OC 2 H 5 ) 4 , (b) Si ( i-OC 3 H 7 ) 4 , and (c) Si(OC 4 H 9 ) 4 .
  • the samples were prepared with a Si : hexylamine ratio of 5:1 and aged at room temperature for 48 hours (see synthesis of Example 18) .
  • Figure 23 shows XRD patterns of as-prepared Ta-TMS5 synthesized with amylamine, (b) hexylamine and (c) heptylamine as templating agents.
  • Figure 25 shows XRD patterns of as-prepared Nb-TMS6 synthesized with (a) 1, 7-diaminoheptane, (b) 1,8- diaminooctane, (c) 1, 10-diaminodecane and (d) 1,12- diaminododecane as templating agents .
  • the samples were prepared with a niobium ethoxide :diamine ratio of 1:0.5 and aged at 150°C for 4 days (see synthesis of Example 15) .
  • Figure 27 shows XRD patterns of as-prepared Ta-TMS5 synthesized at a sol pH of (a) 3, (b) 5, (c) 7, (d) 11 and (e) 13.
  • the samples were prepared with a tantalum ethoxide: hexylamine ratio of 1:0.75 and aged at 180°C for 4 days (see synthesis of Example 12) .
  • hexagonally packed transition metal oxide molecular sieves can be synthesized by a ligand-to-metal surfactant interaction in which the propagating metal fragment is incorporated into the surfactant head group.
  • a metal oxide precursor is chemically linked to one or more heteroatoms in the head group of a surfactant molecule.
  • the resulting organometallic species is then subsequently hydrolyzed and subjected to conditions which result in micelle formation, thereby resulting in the hexagonally-packed mesostructure.
  • These hexagonally-packed mesostructures are stable enough so that the structure is substantially maintained after the surfactant is removed under conditions which break the chemical interaction between the metal and the head group heteroatom of the surfactant such that the surfactant is removed from the structure.
  • crystalline porous metal oxides having dimensionally stable pore structures can be synthesized by a ligand-to-metal interaction in which the propagating metal fragment is incorporated into the head group of a small organic moiety.
  • a metal oxide precursor is chemically linked to one or more heteroatoms in the head group of the small organic moiety.
  • the resulting organometallic species is then subsequently hydrolyzed and subjected to conditions which result in the tightly-packed rod-shaped porous metal oxide.
  • These crystalline porous metal oxides which have dimensionally consistent pore structures are stable enouqh so that the structure is substantially maintained after the small organic moiety is removed under conditions which break the chemical interaction between the metal and the head group heteroato of the small organic moiety such that the small organic moiety is removed from the structure.
  • crystalline porous metal oxides having dimensionally consistent pore structures can be synthesized by combining a metal oxide precursor with water for a sufficient period of time to form a gel.
  • the gel a partially hydrolyzed metal oxide precursor, is combined with a compound, such as a surfactant, having at least one head group, under conditions suitable for physical interaction between a head group of the surfactant and the gel.
  • the combination of the gel and the compound is aged for a period of time at a temperature suitable for causing the formation of the crystalline porous metal oxide having a dimensionally consistent pore structure.
  • the compound, or surfactant, or organic portion of thereof, can be removed from the porous metal oxide, resulting in a stable crystalline porous metal oxide having a dimensionally consistent pore structure.
  • the compound can also include small organic moieties, such as, described below.
  • One embodiment of the present invention is a composition comprising a hexagonally-packed mesoporous metal oxide, wherein the metal oxide is selected from transition metals and lanthanide metals, in which a heteroatom on the head group of a surfactant is coordinated or complexed with the metal.
  • a "mesoporous structure” is a structure with a regular array of channels having a substantially uniform diameter or "pore" size ranging from about 10 A to about 500 A, preferably from about 20 A to about 200 A, more preferably from about 20 A to about 50 A.
  • the arrangement of the crystalline microporous metal oxide can be either hexagonal, as defined above, or cubic.
  • a "hexagonally packed” structure is a structure with a regular hexagonal array of channels having a substantially uniform diameter or "pore” size.
  • a “cubic” mesoporous structure is a structure with a regular cubic packing of pores which can be an intersecting array of channels having a substantially uniform diameter or "pore” size.
  • the crystalline microporous metal oxide can be rod-shaped. "Rod-shaped,” as used herein, means that the channel formed by the crystalline packing of the microporous structure is a hollow tube.
  • Yet another embodiment of the invention is a composition comprising a crystalline porous transition metal oxide or lanthanide metal oxide having a dimensionally consistent pore structure.
  • the metal oxide can be niobium, titanium, zirconium, cerium, tantalum or yttrium.
  • the pore structure can be either microporous or mesoporous and can be a regular hexagonal array or cubic array of channels having a substantially uniform diameter or "pore" size.
  • a "transition metal”, as used herein, is an element designated in the Periodic Table as belonging to Group IIIB (e.g. scandium and yttrium), Group IVB (e.g. titanium, zirconium and hafnium), Group VB (e.g. vanadium, niobium and tantalum), Group VIB (e.g. chromium, molybdenum and tungsten), Group VIIB (e.g. manganese, technetium and rhenium), Group VIIIB (iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium and platinum), Group IB (e.g.
  • Group IIIB e.g. scandium and yttrium
  • Group IVB e.g. titanium, zirconium and hafnium
  • Group VB e.g. vanadium, niobium and tantalum
  • Group VIB e.g. chromium, molyb
  • a "lanthanide metal” is a metal belonging to the lanthanide series in the Periodic Table (e.g. lanthanide, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium) .
  • Preferred metals include titanium, niobium, cerium, yttrium, zirconium and tantalum.
  • a “transition metal oxide”, as used herein, is a transition metal bonded to one or more oxygen atoms.
  • a “lanthanide metal oxide”, as used herein, is a lanthanide metal bonded to one or more oxygen atoms.
  • stable porous metal oxides such as microporous or mesoporous structures, wherein the metal can be selected from transition metals and lanthanide metals.
  • a “stable porous metal oxide” is one in which the porous metal oxide structure is substantially maintained following removal of the compound, such as a surfactant or small organic moiety, or tail group of the compound (hereinafter collectively referred to as removal of the surfactant) .
  • the porous metal oxide structure is maintained with a narrow range of pore diameter following removal of the surfactant or tail group of the surfactant.
  • the stable porous metal oxide the present invention would have an accessible surface area of 50-1200 m/g.
  • a stable porous metal oxide structure is also indicated by the substantial preservation of the porous structure as evidenced by the lack of substantial pore collapse by powder X-ray diffraction patterns (XRD) of metal oxide after removal of the surfactant compared with prior to removal.
  • the stable porous metal oxides of the present invention would correspond to a narrow pore size distribution with at least 50 m 2 /g of B.E.T. (Brunauer-Em ett-Teller) surface area.
  • “stable” refers to thermal stability.
  • thermally stable means that the porosity and B.E.T. surface area of the surfactant-free porous structures remain substantially unchanged at temperatures above about 50° C and below about 900° C, preferably below about 600°C and more preferably below about 900°C.
  • the loss of accessible surface area of the porous structure upon thermal treatment is less than 20%, more preferably less than 5%.
  • the inorganic oxides are oxides of Y, V, Ti, Zr, Ir, Os, Rh, Pt, Pd, Au , Fe, Re, Ru , Cu, Co, Hg, Tl, Ni, and/or Cr .
  • Suitable metal salts include alkali metal salts, alkaline earth metal salts and transition metal salts.
  • Preferred salts include alkali metal halides, such as KC1 and NaCl.
  • Such porous metal oxides can be prepared by "doping" as is generally known in the art, for example, or including a corresponding inorganic precursor in the processes described herein. Suitable concentrations of the inorganic oxide are from about .1 mole % to about 50 mole %, preferably from about 1 to about 10 mol %.
  • the preparation of hexagonally-packed mesoporous metal oxides involves first complexing a heteroatom with the metal of a metal oxide precursor before allowing substantial micelle formation and/or hydrolysis to occur.
  • previous methods of preparing a hexagonally-packed mesoporous transition metal oxide involve pre-formation of a miceller template around which the metal oxide assembles, drawn by electrostatic forces (Huo et al . , Chem . Mater . 6:1176 (1994)).
  • hexagonally-packed transition metal oxide mesostructures prepared by this method have not been stable, i.e. the mesostructure is not maintained after removal of the surfactant.
  • One embodiment of the present invention is a method of preparing a hexagonally-packed mesoporous metal oxide wherein the metal oxide is selected from transition metals and lanthanide metals.
  • a transition metal oxide precursor or lanthanide metal oxide precursor and a surfactant are combined under conditions which cause the formation of a complex between a heteroatom in the head group of the surfactant and the metal of the metal oxide precursor in the substantial absence of water.
  • the reactants can be contacted in the presence of a suitable organic solvent, such as in an alcoholic solvent (Example 2) or can be carried out neat (Example 4).
  • the complex thus formed is subjected to conditions suitable for micelle formation and hydrolysis of the metal oxide precursor.
  • This reaction product is then allowed to age for a period of time and at a temperature suitable for causing the formation of a hexagonally-packed metal oxide mesostructure.
  • the metal oxide precursor can be contacted with the surfactant in the presence of water.
  • the surfactant and precursor prior to precursor addition, are contacted in a quantity of water such that the surfactant concentration is above the critical micelle concentration, i.e. the concentration of surfactant below which micelles do not form.
  • the "critical micelle concentration" i.e., the concentration at which micelles form
  • a chelating agent such as a 2,4-diketone (e.g.
  • acetylacetone to the metal oxide precursor (preferably prior to contacting the precursor with surfactant and/or water) in order to prevent premature hydrolysis of the metal oxide precursor. It is preferable to use acetylacetone when using metal oxide precursors of yttrium, titanium and zirconium. Typically, about 0.1 to about 10 equivalents of acetylacetone to metal oxide precursor, preferably about one equivalent, are added to the reaction mixture.
  • a lanthanide metal oxide precursor is a compound comprising a lanthanide metal which as a result of a chemical reaction (such as hydrolysis and polycondensation) forms a lanthanide metal oxide.
  • a chemical reaction such as hydrolysis and polycondensation
  • Examples include lanthanide metal alkoxides, lanthanide metal salts, lanthanide metal hydroxides, or colloidal dispersions of lanthanide metal oxides or lanthanide metal hydroxides.
  • Lanthanide metal alkoxides are preferred.
  • a suitable surfactant is a straight chain hydrocarbon having a head group, wherein the head group is defined above.
  • the straight chain hydrocarbon can have from about 8 to 24 carbon atoms, preferably from about 12 to 18 carbon atoms.
  • the size of the micelles is determined, in part, by the size or length of the surfactants used.
  • the length of the hydrocarbon tail of the surfactant can be used to vary the pore size of the hexagonally packed mesostructure.
  • Swelling agents can be added to the hydrophilic regions of the micelles to further increase the pore diameters. Examples of swelling agents include cyclohexane, mesitylene, xylene, toluene and ethanol.
  • the swelling agent is hydrophobic and resides within the tail group regions of the inverse micelle upon addition to the surfactant solution.
  • Pore sizes made according to this process can range from about 20 A to about 200 A, and preferably 20 A to about 40 A.
  • the preparation of crystalline porous metal oxides having dimensionally consistent pore structure involves either: 1) complexing a heteroatom of a head group of a small organic moiety with the metal of a metal oxide precursor before allowing substantial micelle formation and/or hydrolysis to occur, or 2) combining a metal oxide precursor with water for a sufficient period of time to from a gel and thereafter combining the gel with a small organic moiety, having at least one head group, under conditions suitable for a physical interaction to take place between the head group of the small organic moiety and the gel.
  • Under conditions suitable for physical interaction between a head group of a surfactant or a small organic moiety and a gel (formed by hydrolysis of a metal oxide precursor) refers to an interaction between one or more atoms within the head group of the surfactant or small organic moiety and the metal oxide. Electrostatic interactions, van der Waals interactions or hydrogen bonding are encompassed by the physical interaction between the metal oxide of the gel and the head group, thereby forming a supermolecular template. The strength of the physical interaction is less than that of typical covalent bonding.
  • One embodiment of the present invention is a method of preparing a crystalline porous metal oxide having a dimensionally consistent pore structure.
  • a metal oxide precursor and a small organic moiety are combined under conditions which cause the formation of a complex between a heteroatom in the head group of the surfactant and the metal of the metal oxide precursor in the substantial absence of water.
  • the reactants can be contacted in the presence of a suitable organic solvent, such as in an alcoholic solvent (Example 16) or can be carried out neat (Example 12).
  • the complex thus formed is subjected to conditions suitable for micelle formation and hydrolysis of the metal oxide precursor.
  • Another embodiment of the present invention is a method of preparing of a crystalline porous metal oxide having a dimensionally consistent pore structure by combining a metal oxide precursor with water for a sufficient period of time to form a gel.
  • the gel is combined with a small organic moiety, having at least one head group, under conditions suitable for physical interaction between the head group of the small organic moiety and the gel.
  • the combination of the gel and the small organic moiety is aged for a period of time at a temperature suitable for causing the formation of the crystalline porous metal oxide having a dimensionally consistent pore structure.
  • Still another embodiment of the present invention is a method of preparing a crystalline mesoporous metal oxide having a dimensionally consistent pore structure by combining a metal oxide precursor with water for a sufficient period of time to form a gel.
  • the gel is combined with a surfactant, having at least one head group, under conditions suitable for physical interaction between the head group of the surfactant and the gel.
  • the combination of the gel and surfactant is aged for a period of time at a temperature suitable for causing the formation of the crystalline mesoporous metal oxide having a dimensionally consistent pore structure.
  • Yet another embodiment of the present invention is a method of preparing a crystalline porous metal oxide having a dimensionally consistent pore structure by combining a solution of a metal oxide precursor in a non-polar organic solvent with an aqueous alcohol solution of a compound, such as a surfactant or small organic moiety, with stirring to create an oil-in-water emulsion.
  • the emulsion is aged for a period of time at a temperature suitable for causing the formation of the crystalline mesoporous metal oxide having a dimensionally consistent pore structure.
  • Suitable non-polar organic solvents include cyclohexane, hexane, benzene, mesitylene, etc.
  • a metal salt is added to the mixture being aged in an amount sufficient to accelerate the formation of crystalline porous or mesoporous metal oxide having dimensionally consistent pore structures.
  • Suitable metal salts include Group IA metal salts (alkali metal salts) , Group IIA metal salts, transition metal salts and lanthanide metal salts. Alkali halides (e.g., potassium chloride) are preferred. Typically, about 0.1-20.0 equivalents of metal salt are sufficient to cause an increase in the crystallization rate; about 0.5-2.0 equivalents is preferred.
  • a neutral amine component can be further substituted.
  • the amine can be mono or disubstituted with alkyl groups, such as methyl, ethyl, propyl etc.
  • alkyl groups such as methyl, ethyl, propyl etc.
  • a particularly preferred amine is 2- aminoadamantane.
  • the small organic moiety can include at least two head groups, located at ends of a hydrocarbon chain.
  • 1 , 7-diaminoheptane, 1 , 8-diaminooctane, 1, 10-diaminodecane, 1 , 12-diaminododecane, etc. are suitable as templating agents for organizing the supermolecular structure.
  • These small organic moieties, which have head groups located at the respective ends of a hydrocarbon chain, are believed to fold so that both amine head groups interact with the inorganic oxide precursor.
  • the metal oxide precursor can also have an effect on pore size of the pore size of the porous composition.
  • the length and steric bulk of the hydrocarbon portion of the precursor can be used to vary the pore size of the porous metal oxides having dimensionally consistent pore structures.
  • suitable metal oxide precursors include alkoxides such as ethoxide, iso-propoxide , butyloxide and pentyl oxide. Additional examples of suitable functional groups attached as metal oxide precursors include esters, amides, alkyla ines, etc. Pore sizes made according to these processes, can range from about 2 A to about 200 A, preferably 20 A to about 40 A, most preferably 2 to 20 A.
  • the materials of the present invention are characterized by the regularity of its large open pores in arrangement and size (pore size distribution within a single phase of, for example, ⁇ 25%, usually ⁇ 15% or less of the average pore size of that phase) .
  • the term "hexagonal” is intended to encompass materials that exhibit a hexagonal symmetry including significant observable deviations, for example ⁇ 25% random deviation from the repeat distance between adjacent channels.
  • the term "cubic” is intended to encompass materials that exhibit a cubic symmetry including significant observable deviations, for example ⁇ 25% random deviation from the repeat distance between adjacent channels.
  • rod-shaped is intended to encompass materials that exhibit a rod-shape symmetry, i.e. hollow tubes wherein the tube or rod portion is composed of the metal oxide.
  • Suitable head groups include phosphate, carboxylate, sulfate, amino and acetylacetonate.
  • the stability of hexagonally-packed mesostructure formation can be dependent on the optimization of the head group of the surfactant and the precursor. That is, the surfactant head group is selected to form an optimal complex with the precursor (e.g., a strong ligand interaction).
  • the precursor e.g., a strong ligand interaction
  • titanium, cerium and zirconium containing metal oxide precursors e.g. titanium isopropoxide, cerium isoproxide and zirconium n-propoxide
  • niobium and tantalum mesostructures were prepared with niobium and tantalum oxide precursors (e.g., niobium ethoxide and tantalum ethoxide) and neutral amine surfactants.
  • Sulfate surfactants formed strong ligand interactions with yttrium oxide precursors, such as yttrium isopropoxide.
  • the optimal surfactant head groups for each metal can be determined by routine experimentation in which the method of preparing hexagonally packed metal oxide mesostructures is carried out in the presence of various surfactants having different head groups. Such an optimization is described in Example 7.
  • Surfactant/metal oxide precursor ratios can vary from about 1:1 to about 1:9 and is preferably about 1:1, e.g., for the titanium oxide precursor (Example 6) .
  • Conditions suitable for micelle formation and hydrolysis of the metal oxide precursor refer to adding sufficient water to the surfactant/metal oxide complex such that the concentration of surfactant is above the critical micelle concentration.
  • Micelle formation is preferably carried out with cooling to temperatures of about -78 °C to about 0°C, following which water is added and the mixture is allowed to warm to room temperature to promote hydrolysis. Temperatures as high as about 50° C can be used.
  • the period of time suitable for causing the formation of hexagonally packed metal oxide mesostructures, and crystalline porous and mesoporous metal oxides having dimensionally consistent pore structures varies according to the metal oxide precursor and temperature selected. In general, aging lasts from about 1 minute to about 14 days, preferably from about one hour to about fourteen days, and more preferably about 3-7 days. Suitable temperatures for aging can range between about 15°C to about 200°C. Optimal time periods can be determined from the XRD pattern through comparison of intensities and resolution of the peaks corresponding to the hexagonal or cubic structure. Time periods are chosen to maximize the distinctness of these peaks.
  • an XRD pattern for hexagonally packed titanium oxide mesostructure made with 0.5-1 mol equivalents of potassium dodecyl phosphate isolated after one day aging at room temperature had a diffraction pattern in which the (100) peak was broad and the smaller peaks were not clearly distinguished.
  • the low-intensity (110), (200) , and (210) peaks became more intense and distinct when the sample was aged for longer periods.
  • materials aged at room temperature generally had broad humps at around 2 2 ⁇ in the XRD.
  • the aging temperature is increased to over 100° C, decomposition of the mesostructure occurs with the premature removal of surfactants in the case of Zr, Ce, and Ti oxides with phosphate surfactants.
  • aging temperatures below about 180" C can be used without porous metal oxide structural decomposition.
  • suitable aging temperatures include ambient conditions.
  • aging temperatures of about 80 °C can be used without porous metal oxide structural decomposition.
  • Optimal aging temperatures can be readily determined by one skilled in the art by carrying out the aging process at various temperatures and then examining the XRD peaks of the hexagonal pattern for sharpness, as described above.
  • Optimal aging temperatures and aging times for hexagonally-packed niobium oxide, yttrium oxide, zirconium oxide, titanium oxide and tantalum oxide mesostructures are given in the Examples.
  • the pH and ionic strength of the solution in which the hydrolysis, micelle formation and aging occur can vary over a wide range.
  • the rate of hydrolysis, the rate of aging or polycondensation and the quality of the hexagonally-packed mesostructures, as determined by the intensity and resolution of the hexagonal XRD pattern is affected by these parameters and can vary according to the metal oxide precursor.
  • the pH used in the aging process can range from about 1-14, but is preferably between about 3-8. In the specific case of titanium oxide precursors, the preferred pH ranges between about 4-6.
  • Preferred pHs for hexagonally-packed niobium oxide, yttrium oxide, zirconium oxide, and tantalum oxide mesostructures are given below in the Examples.
  • One of ordinary skill in the art can determine optimal pHs and ionic strengths for other metal oxide precursors using the methods described herein, for example.
  • the invention relates to the formation of a strong ligand interaction or complex between the surfactant head group and the metal oxide precursor prior to the substantial formation of micelles, hydrolysis and polycondensation of the metal oxide.
  • This favors the ligand assisted templating of hexagonal mesostructure formation instead of layered or amorphous phase formation.
  • the chemical or ligand bond can be subsequently broken by suitable treatment to allow surfactant removal without significant disturbance of the mesostructure.
  • the surfactant is removed by chemical means. Typically, this is carried out by washing the hexagonally-packed mesostructure with a solution which is capable of breaking the coordination between the metal and the head group of the surfactant without substantially disturbing the hexagonal metal oxide mesostructure.
  • a chemical means of removing the surfactant from the hexagonally-packed mesostructures is by washing with a suitable solvent under acidic or basic conditions.
  • the titanium oxide mesostructure of Example 1 can be washed with an alcohol solvent, such as ethanol, in the presence of a strong base, such as potassium hydroxide.
  • the resulting B.E.T. surface area from a sample prepared from C, 4 H 29 phosphate was 420 m 2 /g.
  • hexagonally-packed niobium oxide mesostructures prepared as described herein are washed with a strong acid, such as nitric acid, in a suitable solvent, such as ethanol.
  • a strong acid such as nitric acid
  • a suitable solvent such as ethanol.
  • Evidence that the material had retained the hexagonal mesostructure was provided by the resulting B.E.T. surface area, which was 434m/g.
  • the N 2 adsorption-desorption isotherms of Nb-TMSl ( Figure 3a) presented no hysteresis, indicating the cylindrical nature of the pores.
  • the pore size distribution of this material (Figure 3b) involved one narrow peak at 27 A.
  • the surfactant can be removed by calcination. This process is carried out by heating the sample at a sufficient temperature and for a sufficient period of time to combust the surfactant. Suitable temperatures are up to about 600 °C, preferably at about 200°C to about 500°C. Sufficient time periods vary from about 1 hour to about 24 hours, and are preferably from about 6 hours to about 10 hours. Hexagonally-packed titanium oxide mesoporous structures were substantially preserved in calcination at 550° C under air or oxygen. Some structural collapse occurred as illustrated by some broadening of the XRD pattern of the calcined sample as compared to the as synthesized sample which still retains the surfactants.
  • the invention relates to the formation of a strong ligand interaction or complex between the surfactant head group and the metal oxide precursor prior to the substantial formation of micelles, hydrolysis and polycondensation of the metal oxide.
  • This favors the ligand assisted templating of crystalline porous and mesoporous metal oxide formation instead of layered or amorphous phase formation.
  • the chemical or ligand bond can be subsequently broken by suitable treatment to allow surfactant removal without significant disturbance of the crystalline porous or mesoporous metal oxide.
  • the invention relates to the formation of a physical interaction between a metal oxide gel (partially hydrolyzed metal oxide precursor) and surfactant or small organic moiety head groups.
  • a metal oxide gel partially hydrolyzed metal oxide precursor
  • surfactant or small organic moiety head groups This favors the super olecular assisted templating of crystalline porous, microporous and mesoporous metal oxide formation instead of layered or amorphous phase formation.
  • the association can be subsequently broken by suitable treatment to allow surfactant or small organic moiety removal without significant disturbance of the crystalline porous, microporous or mesoporous metal oxide.
  • the surfactant is removed by chemical means.
  • this is carried out by washing the crystalline porous or mesoporous metal oxide with a solution which is capable of breaking the coordination between the metal and the head group of the surfactant without substantially disturbing the crystalline porous or mesoporous metal oxide structure.
  • a chemical means of removing the surfactant from the crystalline porous or mesoporous metal oxide structures is by washing with a suitable solvent under acidic or basic conditions.
  • microporous niobium oxide of Example 12 can be washed with an alcoholic solvent, such as isopropanol, at a pH of 0.5-3.0 adjusted by addition of nitric acid.
  • hexagonally-packed niobium oxide mesostructures prepared as described herein are washed with a strong acid, such as nitric acid, in a suitable solvent, such as ethanol.
  • a strong acid such as nitric acid
  • a suitable solvent such as ethanol
  • the surfactant or small organic moiety can be removed by calcination.
  • This process is carried out by heating the sample at a sufficient temperature and for a sufficient period of time to combust the surfactant or small organic moiety. Suitable temperatures are up to about 900°C, preferably at about 200°C to about 500°C. Sufficient time periods vary from about 1 hour to about 24 hours, and are preferably from about 6 hours to about 10 hours. Porous, microporous and mesoporous structures were substantially preserved in calcination at 550 C under air or oxygen. Some structural collapse occurred as illustrated by some broadening of the XRD pattern of the calcined sample as compared to the as synthesized sample which still retains the surfactants.
  • a hexagonally-packed niobium oxide mesostructure was prepared by the method of the present invention.
  • a solution of niobium ethoxide (Nb(0Et) 5 ) (5.0 g) in isopropanol (10 ml) was treated with tetradecyl amine (3.4 g, 1 equivalent) , resulting in a octahedral niobium amino ethoxy complex (Mehrotra et al . , Inorg. Chim . Acta 16 : 231 (1976) ) .
  • this solution was further treated with water (20 ml) , a rapid polymerization reaction ensued giving a white gelatinous precipitate.
  • Nb-TMSl white powder
  • XRD hexagonal X-ray powder diffraction pattern
  • Nb-TMSl, C The mechanism of forming Nb-TMSl, C, (shown in Figure 4C) is depicted below:
  • the invention represents a novel approach to the synthesis of mesoporous materials in that the surfactant, C 12 H 25 NH 2 ⁇ is chemically bonded to the metal atom in the precursor, Nb(OEt) 5 , as organometallic precursor, (C 12 H 25 NH 2 ) Nb (OEt) 5 , and possibly throughout the entire aging process.
  • This mechanism contrasts to that proposed for the synthesis of MCM-41, where a ligand interaction between the tetra- alkylammonium surfactant head group and the Si center is neither present nor possible.
  • the surfactant phase templates the assembly of the inorganic phase via either preformed micelles (Chen et al . , Microporous Ma ter. 2 : 21 (1993)) or electrostatic charge matching between the silicate oligomers and the individual surfactant head groups (Huo et al . Nature 368 : 311 (1994); Monnier et al . Science 261 : 1299 (1993); Huo et al . Chem . Mater. 6 : 1116 (1994)).
  • Nb-TMSl, C ( Figure 4C)
  • the surfactant (C 12 H 25 NH 2)
  • the surfactant (C 12 H 25 NH 2)
  • the Nb-N bond present in the organometallic precursor, (C 12 H 25 NH 2 ) Nb (OEt) 5 is believed to remain intact during at least the initial phase of the synthesis. If the ammonium form of the surfactant was dominant, Nb-TMSl, C ( Figure 4C) , could be formed starting from the alkyl ammonium salt.
  • reaction scheme, I represents the two possible synthesis pathways for Nb-TMSl, C ( Figure 4C) , under a ligand assisted templating mechanism.
  • pathway A the organometallic precursor, (C 12 H 25 NH 2 )Nb (OEt) 5 self-assembles in ethanol prior to hydrolysis and this micellar array, A ( Figure 4A) , holds the Nb-containing head groups in place during subsequent hydrolysis to Nb-TMSl, C ( Figure 4C) .
  • alcohol can disrupt micelle formation, this phenomenon is largely dependent on concentration of the surfactant and the dielectric constant of the medium.
  • the self-assembly occurs during hydrolysis and polycondensation of the alkoxide B, ( Figure 4B) to Nb-TMSl, C ( Figure 4C) .
  • the self-assembly of polymers containing hydrophobic and hydrophilic regions during chain growth has been noted before.
  • the niobium head group is initially hydrophobic, the hydrolytic replacement of ethoxide groups with hydroxide and oxide linkages may have given rise to progressively more hydrophilic head group assembly in forming the final mesoporous structure depicted.
  • Ti- TMSl - Example 1 A hexagonally-packed titanium oxide mesostructure (Ti- TMSl - Example 1) was prepared with titanium acetylacetonate tris-isopropoxide as a precursor and tetradecyl phosphate surfactant (10 wt.%) at pH 3-6 after
  • the B.E.T. surface area of calcined Ti-TMSl was obtained using N 2 adsorption and found to be 150 m 2 /g.
  • the surfactant was removed by treatment with KOH in ethanol/water at pH 9, the surface area was 420 m 2 /g. This indicated that the mesostructure was preserved to a greater
  • Novel syntheses illustrate that the addition of small organic templating agents to a sol-gel alkoxide precursor solution can lead to the formation of porous metal oxides with a well-defined crystal structure for a broad range of chemical compositions. Only amorphous metal oxides with a broad pore size distribution are obtained if no organic templating agent has been introduced during the hydrolysis and polycondensation of the alkoxides.
  • V-TMS5, Nb-TMS5, Ti-TMS5 and TaTMS5 were successfully prepared with a hexagonally-packed pore structure, analogous to that obtained to MCM-41 (C.T. Kresge, et al .
  • the d-spacings of the TMS5 materials are much smaller than those noted for mesoporous MCM-41 or TMSl, reflecting the microporous nature of the former.
  • the X-ray diffraction patterns of V-TMS5 and Nb-TMS5 have distinct higher order diffraction peaks.
  • Ti-TMS5 and Ta-TMS5 on the other hand, have fairly weak higher order diffractions beyond the (100) diffraction. This may be due to a lack of long-range packing of individual oxide tubes or a preferred crystal orientation along the (hOO) direction.
  • -37- The porous nature of the materials was analyzed by N adsorption and desorption.
  • Nb-TMS5 and Si-TMS5 samples were subjected to template removal by an acidic organic wash and by 500°C calcination, respectively.
  • the materials obtained were degassed at 150°C before characterization.
  • the adsorption-desorption isotherms of Figures 9(a) and 10(a) illustrate the microporous nature of these oxide samples.
  • the pore size distributions of Nb-TMS5 and Si-TMS5 were obtained by applying the Horvath-Kawazoe method to a cylindrical pore model.
  • Nb-TMS5 Figure 9(b) and SiTMS5 Figure 10(b)
  • the templating amines captured in the pore structure of Nb-TMS5 were held strongly by the niobium oxides, and could only be removed at 80 °C by treating the nanocomposite powder (an arrangement of blocks of organic and inorganic material in nanometer scale) in an acidic 4:1 mixture of isopropanol and deionized water.
  • Nitric acid was found to be most effective for protonating and dissociating amine templating agents from the niobium oxide network.
  • Isopropanol was used to facilitate the removal of the templating agent during the treatment by enhancing the solubility of the protonated amines in the liquid form.
  • FIG. 11 shows a TEM micrograph of Nb-TMS5 synthesized by a procedure described in Example 13. Nb(OC 2 H 5 ) 5 was first hydrolyzed in water to produce a loosely bound niobium oxide gel to which hexylamine templating agents were added. The resulting nanocomposite was hydrothermally aged at 180°C for 30 days and dried at - 38 - room conditions. The microstructure of the Nb-TMS5 material obtained appeared to feature well-aligned planes with detailed texture in the form of discrete bright spots, representing the presence of well packed micropores (see Figure 11) .
  • the materials described herein can be utilized as catalysts in partial oxidation reactions, combustion, NO ⁇ decomposition, hydrodesulfurization, photocatalytic decomposition of organic compounds, absorbants and/or solid acid catalysis, by methods generally known in the art.
  • the material of the invention can also be incorporated into a matrix, such as a matrix derived from alumina, silica, silica-alumina, titania, zirconia, clay or combination thereof. Such a matrix can improve the crush strength of the catalyst.
  • the matrix material is added to the hexagonally-packed metal oxide mesostructure in colloidal form and then extruded as a bead or pellet.
  • the content of the mesostructure within the matrix generally ranges from about 1 to about 90 weight percent and more particularly from about 2 to about 80 weight percent.
  • Tetradecyl phosphate (5.20 g, 17.6 mmol) was dissolved in 25 ml of water with KOH (0.49 g, 17.6 mmol) and the pH adjusted to 5.0 with 12.5 M HCI.
  • - 3 9 - titanium isopropoxide (5.0 g, 17.6 mmol) was treated with acetylacetone (0.9 mL, 17.6 mmol).
  • the solution immediately turned yellow and heat was liberated.
  • This solution was cooled and then added to the surfactant solution with vigorous stirring. The resultant thick yellow meringue was then aged at ambient temperature for two hours and then at 80° C for five days.
  • TEM's of Ti-TMSl showed the hexagonal array of stacked tubes of approximately 27 A in pore diameter.
  • the inner walls of this material are approximately 5 A thick, corresponding to what is expected on the basis of the XRD data .
  • Example 2 Ti-TMSl Preparation by the Non-aqueous Route Titanium isopropoxide (5.0 g, 17.6 mmol) and tetradecyl phosphate (5.20 g, 17.6 mmol) were mixed with evolution of heat. After 1 h of stirring at room temperature, ethanol (10 ml) was added and the resulting -40- solution was cooled to -78° C. Dilute hydrochloric acid (pH 5, 20 ml) was added dropwise to this suspension. The solution was warmed gradually to room temperature and left at ambient temperature for two hours. After addition of 1.0 g KCl, the solution was heated to 80° C for five days. The product was similar to that obtained in Example 1.
  • the solid was then dried at 120 C for 1 day and calcined in oxygen at 500 C for 5 h to give stable Nb-TMSl with a B.E.T. surface area of 61m 2 /g.
  • the experiment was again repeated, except surfactant was removed from the product by refluxing the solid in a mixture of 3:1 EtOH:H 2 0 ratio and nitric acid at pH below 1 for 24 h.
  • the Nb-TMSl obtained after washing with water, ethanol and acetone had a surface area in excess of 434 m 2 /g.
  • pattern a is an XRD (powder X-ray diffraction) pattern of Nb-TMSl synthesized with tetradecylamine. This data was recorded on a Siemens D-5000 diffracto eter using CuK ⁇ radiation and a scintillation detector at 2.2 kW. The d-spacing for the (100) reflection appears at 31 A, which is slightly smaller than the approximate value of 35 A observed for as-synthesized MCM-41 made with tetradecyl trimethylammonium bromide, possibly reflecting the greater degree of extension of the trimethylammonium head group over the amine head group for the same surfactant chain length.
  • Fig. 3a is the N adsorption-desorption isotherms for Nb-TMSl synthesized with tetradecylamine and washed three times with ethanol/HN0 3 at 40 C. This data was obtained on a Micromeritics ASAP 2000 Sorption Analyzer using standard procedures. The isotherms display the sharp incline at values of P/Po in the 0.3 to 0.5 range which is typical of the mesoporous materials produced with similar surfactant chain length. The absence of hysteresis also supports the cylindrical nature of the mesopores.
  • the pH was varied in integer steps from 2-6, the acetylacetone-to-Ti ratio was varied from 0-3 in one integer steps, and the surfactant-to-Ti ratio was studied at levels of 1:9, 1:6, 1:4, 1:3, 1:2, and 1:1. In all cases, one parameter was changed while the other two were held constant.
  • the aging temperature and time were held constant at 80° C and five days, respectively.
  • the weight percent of surfactant used was 7-10 % depending on the pH. This slight variation was necessary because the surfactant is less soluble at lower pH and higher ionic strength. In the appropriate weight percent and pH ranges, liquid crystal micelle formation for phosphates of chain length greater than 10 carbon atoms is favored (Cooper J . Am . Oil .
  • Figure 5 shows the XRD patterns obtained for samples synthesized with Ti-to- surfactant ratios of 1:1, 3:1 and 9:1, respectively.
  • the route was not applicable to the amine and acetylacetone surfactants because of the very low pK b of the deprotonated form.
  • the second approach involved first mixing the protic form of the anionic or neutral surfactant in ethanol with the Ti alkoxide acetylacetonate precursor (note: although acetoacetonate was not added normally in the non-aqueous approach, it was added in this example for comparison) followed by hydrolysis with water of a preadjusted pH from -78° to room temperature and subsequent aging. This approach was not used for tetradecyl ammonium bromide since it does not have a conjugate acid. Metal alkoxides react quickly with a wide -46- variety of donor ligands. Below is a depiction demonstrating that the head group is chemically bonded to the Ti-alkoxide fragment.
  • the acetylacetonate-functionalized surfactant (3-tetradecyl-2 , 5-pentanedione) worked the best in the series studied using the low temperature route, giving materials with broadened hexagonal patterns at room temperature. Further heating led to leaching away of the insoluble surfactant as a separate phase on top of the water layer. Since neither the carboxylate nor acetylacetonate surfactants are soluble in water to any degree, the equilibrium between the aqueous form and the unsolvated form of the surfactant lies heavily in favor of the latter, drawing the surfactant out of the system into a separate phase on the surface of the supernatant. In -47 - accordance with the low solubility of the surfactant and LeChatlier's principle, the organic is leached out of the biphasic liquid crystal micelles.
  • the preferred synthesis conditions for Ti-TMSl involve either: a) the prior addition of tetradecyl phosphate to titanium acetylacetonate tris-isopropoxide, followed by hydrolysis from -78 C to 80 C at pH 4-6 at a 1:1 surfactant-to-Ti ratio in the presence of 1 equivalent of KCl, or b) the addition of titanium acetylacetonate tris-isopropoxide to a 10 weight % solution of the mono- -48 - potassium salt of the surfactant at pH 4-6 followed by aging at 80° C for several days.
  • Nb(0Et) 5 (4.5 g, 0.0141 mol) was warmed to 60°C with octadecylamine (4.22 g, 0.0157 mol) and vanadium oxide isopropoxide (0.380 g, 0.0016 mol) for ten minutes.
  • the resulting yellow oil was cooled to ambient temperature and then water (25 ml) was added with stirring, causing the immediate precipitation of an off-white mass. This mixture was left at ambient temperature overnight and then aged at 80°C for 1 day and 150°C for five days.
  • Example 11 Swelling Agents Nb(0Et) 5 (5.0 g, 0.0157 mol) was warmed to 60°C with octadecylamine (4.22 g, 0.0157 mol) and mesitylene (3.0 g, 0.0250 mol) for ten minutes. The resulting solution was then cooled to ambient temperature and water (25 ml) was added with stirring. At this point a white solid mass separated from the solution. The mixture was left overnight at ambient temperature and then aged with addition of 1.0 g KCl for 1 day at 80°C followed by five days at 150°C. The resulting solid was collected by filtration and washed with two fifty ml portions each of water, acetone, and ether.
  • the material thus synthesized has a (100) peak at a d-spacing of 55 A as recorded by XRD.
  • the surfactant was removed as described in previous examples. Without the addition of mesitylene swelling agent, the d-spacing of the product would have been 38 A.
  • the term "hydrothermally,” as used herein, means the material was heated in a sealed vessel in an aqueous environment, whereby pressure develops in the sealed vessel.)
  • the aged product was recovered by filtration, washed with water, ethanol and acetone, and then dried at ambient conditions.
  • the organic templating agent could be removed by stirring 0.5 grams of the nanocomposite for 24 hours at 80°C in 500 mL of a 4:1 isopropanol-water mixture, with a pH of 0.5-1.5 adjusted by nitric acid addition.
  • the resulting material was then washed with water and ethanol before drying.
  • the microporous niobium oxide thus obtained was designated Nb-TMS5 and had a pore size of 7.4 A.
  • microporous oxide systems can be prepared following a similar procedure. Selection of organic templating agent, molar ratio of alkoxide to templating agent, sol pH, aging conditions, and the surfactant removal procedure may need to be adjusted to optimize the crystallinity of the final products.
  • the aging temperature could be varied from ambient to 180 °C and the aging period needed for crystallizing stable mesostructures can range from 2 hours to months.
  • Ta-TMS5 microporous tantalum oxide
  • 2 grams of tantalum ethoxide, Ta(OC 2 H 5 ) 5 was mixed directly with 0.37 grams of hexylamine at ambient conditions to prepare an organic-inorganic nanocomposite.
  • Beside hexylamine, alkyl amines of carbon atom chain lengths of about three to twenty, can also be used in the supermolecular templating approach described in Examples 12 and 13. This provides a flexible basis for tailoring the pore size in a range of between about 3 A to about 50 A.
  • 2 grams of niobium ethoxide was mixed with 27 grams of deionized water at ambient conditions for 2 hours to prepare a loosely bound niobium oxide gel to which was added 0.34 g of butylamine.
  • the gel solution which was -52 - generated was stirred at room temperature for 2 hours prior to subjecting the material to hydrothermal treatment at 180°C for 4 days.
  • 0.42 grams of amyla ine, 0.48 grams of hexylamine or 0.54 gram of heptyla ine was used in place of 0.34 grams of butylamine to prepare Nb-TMS5.
  • diamines can be used in the supermolecular templating approach described in Examples 12 and 13.
  • a diamine give rise to a smaller pore size than a mono-a ine. This is most likely due to the folding of the molecule such that both amine heads interact with the inorganic oxide precursor.
  • Alkyl diamines of a carbon atom chain length of between about three and 20 carbon atoms can be used in the synthesis of mesoporous oxides to enable flexible tailoring of the pore size in a range of about 3 A to about 30 A.
  • niobium ethoxide 8 grams was added to produce a self- assembled organic-inorganic nanocomposite solution. 56 grams of deionized water was subsequently introduced to the solution with stirring to hydrolyze the niobium ethoxide. Immediate precipitation was observed on hydrolysis of the alkoxide precursor and the suspension was subjected to aging under hydrothermal conditions at 180 °C for 4 days. The solid sample was recovered by filtering the suspension and washed with ethanol and water to remove any physically adsorbed organic templating agents on the external surface of the particles.
  • Microporous silica can also be prepared by the supermolecular templating approach. 4 grams of Si(OCH 5 ) 4 was mixed with 0.97 grams of hexylamine at ambient conditions, followed by addition of 42 mL of deionized water, producing an aqueous suspension. After aging at ambient conditions with stirring for 1 to 2 days, the precipitate was collected by filtration. It was then subjected to washing with water and dried overnight at 120°C. Besides alkyl amines, adamantanamine (Aldrich Chemical Co.) could also be used in this approach as a templating agent. The templating molecules were removed by calcination in air at 500°C for 2 hours.
  • the pore size of the metal oxides synthesized by the supermolecular templating approach can be varied not only by changing the size of the templating agent, but also by using different metal oxide precursors. Silicon ethoxide, isopropoxide and butoxide were used as metal precursors for the synthesis of microporous silicon oxides (as described in Example 17) . The X-ray diffraction d-spacing of the -54- silica-amine nanocomposite derived was found to increase with the chain length of the alkoxy group as shown in Figure 22.
  • Example 19 Phosphate acids having carbon atom chain lengths between three and twenty carbon atoms can be used in place of alkyl amines in the templating synthesis of porous oxides of a wide range of pore sizes. This can be applied to various different metal oxide systems. For example, in preparing a nanocomposite of vanadium oxide and organic molecules, 0.5 grams of VOS0 4 was dissolved in 10 mL of deionized water and then mixed with 0.29 grams of C 3 H 7 OP0 2 H at ambient conditions for 2 hours. The resulting gel was subjected to aging at 96°C for 2 days. The powdery precipitates were then recovered by filtration, washed with water and ethanol and air dried.
  • Swelling agents such as mesitylene and cyclohexane, could be used in conjunction with the organic templating molecules to expand the pore size of the oxide materials derived.
  • Si(OC 2 H 5 ) 4 1 gram of Si(OC 2 H 5 ) 4 , 0.1 gram of hexylamine, 11 g of deionized water and 0.12 grams of mesitylene were mixed by stirring the mixture at ambient conditions for 2 days. The resulting suspension was aged at ambient conditions with stirring for 48 hours and the precipitate was collected by filtration. This synthesis provides a method for obtaining mesoporous materials with pore sizes as large as 200 A.
  • Example 21 To 0.54 grams of N-methylhexylamine was added 2 grams of niobium ethoxide at room temperature followed by 27 -55- grams of deionized water with immediate formation of gel. The gel was aged at room temperature for 2 hours before being hydrothermally treated at 180 °C for 4 days. Similarly, 0.61 grams of N, N-dimethylhexylamine was used in place of N-methylhexylamine to prepare Nb-TMS5.
  • Powder X-ray diffraction (XRD) patterns of the products were recorded on a Siemens D5000 diffractometer using CuK ⁇ radiation at 2.2kW and a scintillation detector. The samples were scanned from 1.5° to 20° ( 2 ⁇ ) in steps of 0.04°. Narrow incident and diffracted beam slits were used to protect the detector from the high energy of the incident X-ray beam and to obtain a better resolution on low angle peaks.
  • the surface area and pore size distribution of the mesoporous metal oxides were characterized by a nitrogen adsorption-desorption analysis on a Micromeritics ASAP 2010 unit. Prior to analysis, all samples were degassed at 150°C under vacuum. To better characterize the mesoporous structure of the materials, only 0.5 mL doses of nitrogen gas were introduced in the low pressure range at 2-hour -56- intervals. The long interval was used to ensure that the equilibration surface coverage was reached.
  • the weight percentage of the organic templating agents in the mesoporous metal oxides was analyzed by thermogravimetric analysis (TGA) using a Perkin Elmer TGA7. Each sample was purged with nitrogen for 1 hour at 25°C prior to analysis. Weight loss measurements between 25 and 500°C were performed at a programmed heating rate of 5°C/min under nitrogen. Raman spectra of some of the liquid and solid samples were collected with a Bio-Rad Fourier-transform Raman spectrometer. The excitation source was a Nd-YAG laser operated at 1064 nm with an input power of 60 mW. The signal was detected with a liquid nitrogen-cooled Ge detector.
  • Photoacoustic Fourier-transform infrared (PA-FTIR) spectra of the liquid and solid samples were obtained with a MTEC Model 200 photoacousticcell on a Bio-Rad FTS-60A spectrometer. The spectra were collected using 2.5 kHz rapid scans at 4cm "1 resolution.
  • Ta-TMS5 in Figure 12 there was negligible change in the d- spacing and no change in crystalline phase when the Ta-to- hexylamine molar ratio was decreased from 1 to 0.5. A similar phenomenon was observed in the synthesis of microporous Nb-TMS5.
  • a hexagonally- packed TMS5 phase (Figure 13(a)) was obtained when the molar ratio of Si to adamantanamine was greater than 2.5. As the ratio was decreased to 2.5 and lower, a new highly crystalline TMS7 phase was obtained ( Figure 13(b)). In contrast, using straight chain amine templating agents, the TMS5 phase was always obtained as the Si-to-amine ratio was varied between 1 and 5 ( Figure 14) . It was noted that the optimal Si: amine ratio for Si-TMS5 formation was between 1 and 5, a value much larger than the optimal metal: amine ratio of 0.75 to 1.25 for Ta-TMS5, Nb-TMS5, Ti-TMS5 formation.
  • silicon alkoxide precursors are present in polymer form (e.g. tetramer or pentamers) in the partially hydrolyzed gel. Some of these polymers could be directly incorporated into the wall of the inorganic oxide framework while others remained solubilized in the aqueous medium.
  • the aging temperature represents a critical processing parameter that governs the crystalline phase formation of an organic-inorganic nanocomposite. Temperature can also affect the kinetics of the gel condensation and the oxide crystallization processes.
  • Figures 15(b) -(f) illustrate the XRD patterns of niobium oxide-hexylamine nanocomposites derived using different aging temperatures.
  • a product prepared by direct hydrolysis of niobium ethoxide in the - 58 - absence of an amine templating agent is shown in Figure 15(a).
  • the material derived without a templating agent was amorphous, with no distinct XRD peaks in the 2 ⁇ range of 1.5° to 15°.
  • hexylamine was introduced to the amorphous niobium oxide gel as described in Example 13, a broad, low-intensity (100) diffraction peak was developed upon aging at 25°C for 24 hours.
  • Thermogravimetric analysis was used to characterize the amount of templating agent captured in the Nb-TMS5 samples obtained from aging at different temperature (see Figure 18).
  • the weight loss below 120° C was assumed to be associated with the burnout of amine templating agents.
  • the molar ratio of niobium to hexylamine was calculated to have decreased from 4 to 2.4.
  • the molar ratio of organic templating agent in the as- prepared microporous materials was confirmed to be 2.25 by elemental analysis for the Nb-TMS5 sample aged at 180°C. This suggests that each amine molecule was primarily associated with a metal ethoxide dimer in the self-assembly of the hexagonally-packed nanocomposite structure.
  • Si-TMS5 At aging temperatures higher than 25°C or 96°C, the well-defined pore structure of the respective Si-TMS5 and Ti-TMS5 collapsed, as indicated by the disappearance of distinct hexagonally XRD diffraction peaks. Since Si-TMS5 could retain its well-defined icroporosity even after calcination at 500°C, the structural damage from the high aging temperature could not be attributed to Si-TMS5's lack of thermal stability. The damage may be due to the dissolution of inorganic species and the restructuring of the oxide framework without coordination with the supermolecular templating agents at high aging temperatures .
  • Organic templating agents have three major effects on the formation of porous structure form inorganic precursors: (i) the hydrocarbon chain length of the templating agents can be varied to tune the pore size of the oxide materials, (ii) the concentration of the templating agent in the synthesis solution can be adjusted -62 - to derive a variety of liquid crystalline phases, and (iii) the hydrophilic head group of the organic molecule can be changed to match the chemical affinity of the inorganic precursors. For hexagonally-packed mesoporous MCM-41 and TMSl materials, it has been found that the pore size can be increased by using surfactants with longer hydrocarbon chain lengths. This flexibility does not typically exist in zeolite synthesis.
  • the pore diameter of ZSM-5 cannot be expanded by using a slightly larger templating agent.
  • the pore size dependence of mesoporous oxides on the surfactant chain length can be understood as a simple steric effect: the metal oxide network has to provide enough space to accommodate the micellar structure assembled from the organic templating agents.
  • the steric effect of templating agents was also observed in the synthesis of microporous metal oxides, although the organic molecules were too small to be considered as surfactants.
  • the hydrocarbon chain length of the amine templating agents increased from a carbon atom chain length of 5 carbon atoms to 7 carbons atoms
  • the d-spacing of the microporous tantalum oxides increased from 25.9 A to 28.7 A while the hexagonally- packed crystal structure remained unchanged (Example 14 and Figure 23) .
  • the crystallinity of Ta-TMS5 was also improved when larger amines were used.
  • ⁇ can also be used to construct microporous oxides.
  • diamines can be used in the supermolecular templating approach described in Examples 12 and 13. The success of such a synthesis was made possible because the hydrophilic affinity of the large surfactant molecules could be tailored by introducing more than one head group to the hydrocarbon chain. When a second hydrophilic group was introduced at the tail of the surfactant molecule, the middle of the hydrocarbon chain became the new tail of the molecule. This folding of the molecule occurred so that both amine heads could interact with the inorganic oxide precursor. Consequently, a diamine gave rise to a smaller pore size than a mono-amine of the same hydrocarbon chain length.
  • a microporous TMS- 6 structure was generated instead of a mesoporous structure (Example 15 and Figure 25) .
  • Alkyl diamines having a carbon atom chain length of between about three and twenty carbon atoms can be used in the synthesis of porous oxides to enable flexible tailoring of the pore size in the range of 3 A and 30 A.
  • materials with a smaller d-spacing and a lower crystallinity were derived for both Nb-TMS6 and Ta-TMS6.
  • the lower crystallinity associated with diamines of shorter carbon atom chain lengths may be due to the reduced hydrophobicity of the hydrocarbon tails.
  • Substituted amines were also investigated to examine the effect of charge density of the template head groups on the formation of the porous inorganic framework. Unlike the mesoporous materials, synthesis in which both mono- or di-methyl substituted amine surfactants led to amorphous niobium oxides, methyl-substituted short-chain amines did - 64 - lead to formation of hexagonally-packed microporous metal oxides.
  • Figure 26 shows that when methyl- substituted hexyla ines were employed as templating agents, the microporous Nb-TMS5 phase was still produced in the hydrolysis of niobium ethoxides. However, the crystallinity of the microporous niobium oxides decreased with methyl substitution in the amine head group. This may be attributed to a weakening of the interaction between the niobium and the nitrogen of the amine molecule due to the steric hindrance of the methyl group. It may also be caused by a variation in the basicity and charge density of the different amine head groups. The varying steric effect and charge density imposed by the differently substituted amines may have also given rise to the peak shifts obtained in the XRD patterns of Nb-TMS5.
  • the crystal structure of the microporous materials was found to be dependent on the interaction between the inorganic precursor and the head groups of the organic templating agents. Combining straight chain phosphonic acid templating agents with metal ethoxides and aging in an aqueous medium led to the formation of amorphous materials for niobium oxide, but promoted a hexagonal TMS5 phase formation for vanadium oxide. When a linear amine was used as a templating agent, the hexagonal TMS5 could be readily obtained for niobium oxide, but only a lamellar phase was derived for vanadium oxide regardless of the metal: amine ratio or theamine chain length used.
  • Control of pH in the reaction medium is critical for several reasons: pH can alter the surface charge and solubility of the inorganic species, the chemical nature and charge density of the templating agents, and the alkoxide hydrolysis and condensation rates.
  • the effect of pH on the synthesis of microporous metal oxides was -65- investigated.
  • the pH of the reaction medium had to be within a range of 5-11, or an amorphous tantalum oxide would be generated instead (Example 22 and Figure 27).
  • the lack of crystallinity in a tantalum oxide synthesized from a sol pH of less than 5 could be attributed to the protonation of amines, producing positively charged R-NH 3 + species that may not have interacted as strongly with the Ta precursor.

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Abstract

L'invention concerne une composition et un procédé permettant de produire des oxydes métalliques mésoporeux à empilement hexagonal, dans lesquels l'oxyde métallique est choisi parmi les métaux de transition et les lanthanides. La composition comprend des mésostructures d'oxydes métalliques à empilement hexagonal, qui résistent à l'écrasement des pores après élimination du tensioactif et qui sont thermiquement stables. La composition peut comprendre un tensioactif formant un complexe avec le métal. L'invention décrit également des procédés permettant de produire lesdits oxydes métalliques mésoporeux à empilement hexagonal. Elle concerne aussi des compositions et des procédés permettant de produire des oxydes métalliques poreux. Les compositions contiennent des oxydes métalliques microporeux et mésoporeux, qui résistent à l'écrasement des pores après élimination du tensioactif et qui sont thermiquement stables. L'invention décrit aussi des procédés permettant de produire des oxydes métalliques microporeux.
PCT/IB1996/001163 1996-10-10 1996-10-10 Compositions et procedes pour preparer des oxydes metalliques poreux WO1998015500A1 (fr)

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US6511642B1 (en) 1999-01-12 2003-01-28 Kabushiki Kaisha Toyota Chuo Kenkyusho Porous material, catalyst, method of producing the porous material and method for purifying exhaust gas
US6926875B2 (en) 1999-01-12 2005-08-09 Kabushiki Kaisha Toyota Chuo Kenkyusho Porous material process of producing the porous material, catalyst for purifying exhaust gas comprising the porous material, method of purifying exhaust gas
EP1020223A3 (fr) * 1999-01-12 2001-09-12 Kabushiki Kaisha Toyota Chuo Kenkyusho Matériau poreux, son procédé de préparation, catalyseur de traitement de gaz comprenant ledit matériau et procédé d'épuration de gaz
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FR2803223A1 (fr) * 1999-12-30 2001-07-06 Rhodia Chimie Sa Procede de preparation d'un materiau mesostructure a partir de particules de dimensions nanometriques
WO2001049606A1 (fr) * 1999-12-30 2001-07-12 Rhodia Chimie Procede de preparation d'un materiau mesostructure a partir de particules de dimensions nanometriques
JP2003519074A (ja) * 1999-12-30 2003-06-17 ロディア・シミ ナノメートル寸法の粒子からのメソ構造物質の製造法
WO2003068678A3 (fr) * 2002-02-15 2004-03-25 Rhodia Chimie Sa Compose mesoporeux comprenant une phase minérale d'alumine et des particules d'oxyde de cérium, de titane ou de zirconium, et éventuellement un élément en solution solide dans ces particules, procédés de préparation et ses utilisations
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