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WO2008002323A2 - Production de grains d'oxyde métallique contenant du cérium - Google Patents

Production de grains d'oxyde métallique contenant du cérium Download PDF

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Publication number
WO2008002323A2
WO2008002323A2 PCT/US2006/048143 US2006048143W WO2008002323A2 WO 2008002323 A2 WO2008002323 A2 WO 2008002323A2 US 2006048143 W US2006048143 W US 2006048143W WO 2008002323 A2 WO2008002323 A2 WO 2008002323A2
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cerium
metal oxide
oxide particles
less
reactor
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WO2008002323A3 (fr
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David Wallace Sandford
Thomas Nelson Blanton
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Eastman Kodak Co
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Eastman Kodak Co
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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • C01F17/241—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion containing two or more rare earth metals, e.g. NdPrO3 or LaNdPrO3
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/60—Compounds characterised by their crystallite size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/50—Agglomerated particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • 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
    • C01P2006/12—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
    • C01P2006/40—Electric properties

Definitions

  • the present invention relates to the production of stable dispersions of nanometer size cerium containing metal oxide particles with uniform size and morphology produced by aqueous precipitation methods.
  • aqueous or organic co-precipitation spray co-precipitation, chemical vapor deposition (Bai, Wei; Choy, K. L.; Stelzer, N. H. J.; Schoonman, J. Solid State Ionics (1999), 116(3,4), 225-228), plasmas (laser, microwave, radio frequency, electric arc; see for example US 6,669,823 Sarkas et al.) and hydrothermal (aqueous solutions at around 80° C) techniques.
  • the precipitation techniques often involve the subsequent step of calcination, i.e. heating the material to very high temperatures, usually 500-900° C.
  • Another viable synthetic route is the polyol-mediated preparation of nanoscale oxides in which a suitable metal precursor (acetate, halogenide, or alcoholate) is dissolved in high boiling point (246° C) diethylene glycol, DEG, and rapidly heated to between 180 and 240° C until a precipitate forms.
  • a suitable metal precursor acetate, halogenide, or alcoholate
  • DEG high boiling point diethylene glycol
  • the DEG acts as a chelating agent to stabilize the resultant particles and restrain their growth (Feldmann, C, Adv. Fund. Mater. (2003) 13 101-107).
  • Cerium dioxide (CeO 2 , i.e. ceria) based metal oxide particulate materials demonstrate a broad spectrum of applications such as: catalysts for hydrocarbon fuel combustion, three-way catalysts for automotive exhaust gas treatment (catalytic converters), anode materials for solid oxide fuel cells, oxygen storage capacitors, fast ion conductors and ultra-violet radiation blockers.
  • ceria is widely used as a polishing agent for glass, quartz or silicon materials, which are used to make optical elements such as lenses, or hard disk data drives. Given the range of uses for ceria it is not surprising that there are a number of different methods used for its preparation.
  • Cerium is a unique rare earth element for which the dioxide is the normal stable oxide phase; contrary to the other lanthanide rare earths for which Ln 2 O 3 is the normal stoichiometry (the other exceptions being Pr 6 On and Tb 4 O 7 ).
  • Ceria exhibits the cubic CaF 2 fluorite structure consisting of a network of Ce ions in a face centered cubic array leading to interior octahedral and tetrahedral holes, the latter of which are occupied by oxyanions.
  • OSF oxygen storage function
  • Equation 1 2 CeO 2 ⁇ > Ce 2 O 3 + Vi O 2
  • the OSF enables ceria to act as an oxidation/reduction (redox) buffer, which is especially important in its catalytic applications.
  • redox oxidation/reduction
  • small particles are critical for optimal performance and to avoid settling.
  • particle size metrics this corresponds to producing both a small primary crystallite size and a small grain size, along with a narrow grain size distribution, as described below.
  • crystallite size By primary crystallite size one refers to that size which is commonly determined by X-Ray Powder Diffraction (XRPD). A wider XRPD line width implies a smaller primary crystallite size. Quantitatively, the crystallite size (t) is calculated from the measured X-ray peak half width (B(radians)), the wavelength of the X-ray ( ⁇ ), and the diffraction angle ( ⁇ ) using the Scherrer equation
  • a crystallite itself is typically composed of many unit cells, which is the most irreducible representation of the crystal structure.
  • the primary crystallite size should not be confused with the final grain size.
  • the final grain size is determined by how many of the crystallites agglomerate. Typically the grain size measurement is determined from dynamic light scattering experiments (provided by Honeywell Microtrac UPA- Ultrafine Particle Analyzer, or Zetasizer Nano ZS from Malvern Instruments). This also affords the size frequency distribution of the grains, the more uniform distributions being preferred. It is important to make the distinction that having a small primary crystallite size does not guarantee a small final grain size - this must be measured separately from the XRPD spectrum. However, a large primary crystallite size will preclude a small final grain size. Thus to fully characterize a particulate dispersion one would need a knowledge of final grain size (UPA or Zetasizer), size-frequency distribution (UPA or Zetasizer) and primary crystallite size (XRPD).
  • the basic precipitation process involves adding a cerium (+3) salt and a base such as ammonium hydroxide together under turbulent mixing conditions in a reactor in the presence of an oxidant, and converting the cerium (III) into a CeO 2 precipitate.
  • a cerium (+3) salt and a base such as ammonium hydroxide
  • a base such as ammonium hydroxide
  • the nitrate ion of a cerous nitrate salt may perform the required oxidation function, although at higher temperatures than are typically required in the presence of added peroxide.
  • the resultant solution can then be washed (e.g. ultrafiltration) to remove unwanted salts and materials from the ceria dispersion.
  • US 5,389,352 discloses the precipitation of CeO 2 from an aqueous solution comprised of a water soluble trivalent cerium salt and an oxidizing agent wherein the solution is aged for a time not less than 4 hours, where no subsequent calcination or milling steps are required to produce materials for polishing applications.
  • Redox reactions that result in the evolution of colorless gases (hydrogen and/or oxygen) are disclosed as part of the reaction mechanism.
  • Examples employ reaction of cerous nitrate and ammonia either at elevated temperatures (above 100° C) and in a closed reaction container, or at room temperature and with the addition of hydrogen peroxide.
  • High yields of crystalline CeO 2 are reported to be produced in elevated temperature examples, while no yield data is reported for the example at room temperature.
  • An average crystallite size of 7 nm is indicated in the room temperature hydrogen peroxide example, but no final agglomerated grain size nor grain size distribution are reported.
  • US 5,938,837 also discloses the precipitation OfCeO 2 from an aqueous solution based on reaction of cerous nitrate and ammonia.
  • a pH range of between 5 and 10 (preferably between 7 and 9) along with a carefully timed temperature ramp up to 70-100° C within 10 minutes of initial mixing of reactants are employed, in combination with a maturation time for the reaction of between 0.2 to 20 hours, in order to achieve a direct aqueous precipitated cerium oxide with a desired single crystal grain size aim in the range 10 to 80 nm.
  • US 2003/0215378 discloses another aqueous precipitation process for formation of cerium dioxide particles, with or without lanthanide metal (Zr, Y, Nb, Sm) dopants.
  • a double jet addition (cerium nitrate vs. ammonium hydroxide in the range 0.1 to 1.5 mol/1) at a rate of 0.5 to 10 ml/min to a reactor with good impeller stirring (100-5000 rpm) followed by heating, affords single crystal particles which are claimed to be uniform in size and shape and smaller than 10 nm in size.
  • the cerium nitrate salt may be added to a reactor already containing ammonia to produce what are claimed to be 3 nm size particles.
  • Gaseous oxygen may be passed through the reactant solution.
  • Particle size measurements were obtained from TEM samples prepared by ultrasonically dispersing the powders in ethanol, and confirmed to represent single crystal particle sizes by X-ray diffraction patterns, rather than aggregated precipitated grain size prior to ultrasonic dispersion. No data is given with respect to actual grain size in solution prior to ultrasonic dispersion.
  • WO 00/48939 (Pickering) describes a precipitation process in which an oxidant is added to a solution of a metal capable of existing in two cationic oxidation states under conditions such that mixing of the solution and oxidant is substantially complete before precipitation of an oxide of the metal in its higher oxidation state occurs.
  • a cerium nitrate solution maybe combined first with hydrogen peroxide and then with ammonium hydroxide, e.g., to undergo a homogeneous precipitation to produce a precipitate of the formula Ce(OH) 4 . yOOHy. This washed and dried precipitate can suhsequently be hydrothermally treated in the temperature range 100 to 300° C to produce the metal oxide as a weakly agglomerated nanocrystalline powder.
  • WO 03/040270 discloses mixed metal cerium oxide (Ce 1 -XM x O 2 ) used as a fuel additive, which has been doped with divalent or trivalent metals or metalloids that are transition metals or else a metal from group ILA, IIIB, VB or VIB of the Periodic Table (e.g. Rh, Cu, Ag, Au, Pd, Pt, Fe, Mn, Cr, Co, V). Rare earth oxide combinations of these cerium oxides are also claimed.
  • the fuel additive composition is in a polar or non-polar organic solvent (aliphatic or aromatic hydrocarbon or aliphatic alcohol) and contains the above oxide coated with an organic acid (oleic acid), anhydride (dodecylsuccinic anhydride), or ester or a Lewis base additive.
  • Other additives to the fuel composition can comprise: detergents, dehazers, anti-foamants, ignition improvers, anti-rust agents, deodorants, anti-oxidants, metal deactivators or lubricity agents.
  • the present invention is directed towards an aqueous precipitation process for the preparation of metal oxide particles, comprising adding a cerium +3 nitrate salt solution and a base together under turbulent mixing conditions in a precipitation reactor, where cerium +3 ions are oxidized to cerium +4 and precipitated metal oxide particles are directly obtained without need for a calcination step, wherein the improvement comprises adding acetic acid to the precipitation reactor in an amount of from 1 to 40 molar percent, relative to the molar amount of cerium, and obtaining stable, substantially non-agglomerated nanometer size dispersed metal oxide particles.
  • the present invention provides a facile and rapid method of production of stable dispersions of nanometer grain size cerium containing metal oxide particles with uniform morphology and size produced by aqueous precipitation methods well adapted to large-scale commercial production.
  • the directly obtained precipitated nano-sized grains are stabilized against aggregation by an acetic acid additive, resulting in a minimally agglomerated and stable dispersion in aqueous media, avoiding the additional and potentially complicating steps of calcination (which may lead to agglomeration), milling or grinding.
  • a cerium +3 nitrate salt solution and a base are added together under turbulent mixing conditions in a precipitation reactor, where cerium +3 ions are oxidized to cerium +4 and precipitated metal oxide particles are directly obtained. Temperature and pH are maintained in the reactor so as to enable precipitated metal oxide particles to be directly obtained without need for a subsequent calcination step.
  • the cerium +3 nitrate salt solution and base are added together in the reactor and maintained at a temperature below the boiling point of water at ambient pressure to obtain the metal oxide particles.
  • a specific preferred process employs the hexahydrate of cerous nitrate, with the pH of the reaction immediately following the complete addition of reactants being between 5 and 10.
  • any known base may be used in reactions with cerous nitrate to form precipitated cerium dioxide particles, but aqueous ammonia may be preferred over the use of hydroxides of alkali metals or alkaline earth metals if it is desired to avoid contamination of the final cerium dioxide with impurities such as the corresponding alkali metals or alkaline earth metals.
  • cerium hydroxynitrate Ce(OH) 2 (N ⁇ 3 ) ⁇ 2 ⁇ or (NH 4 ) 2 Ce(NO 3 ) 5 -4HsO may be initially formed (depending upon whether cerous nitrate or ammonia is in excess).
  • an additional oxidation step is required to obtain tetra-valent cerium and the resulting cerium dioxide particles. This oxidation step can be carried out by the nitrate anion accompanying the precursor cerium salt as specifically proposed below:
  • oxidizing agents e.g., hydrogen peroxide or gaseous oxygen
  • additional oxidizing agents may also be added if desired to further facilitate the oxidation of the cerium +3 ions, and such added oxidizing agents may enable direct precipitation of metal oxide at lower temperatures (e.g., ambient room temperature).
  • reaction temperatures and maturation or aging times may be optimized to allow the oxidation reactions to go to completion.
  • the resulting precipitated particle dispersion may be subsequently subjected to the steps of filtration and drying. While previous cerium containing metal oxide particle precipitation processes have described obtaining nano-sized metal oxide primary crystallites, such previous processes typically also resulted in substantial aggregation of the precipitated primary crystallites such that the actual precipitated grain sizes were larger than may be desired for some applications.
  • acetic acid is added in an amount of from 1 to 40, more preferably 2 to 25 molar percent, relative to the molar amount of cerium, although other concentrations may also be preferred depending upon optimized precipitation reaction conditions.
  • the acetic acid may be added to the reactor before, during or after addition of the cerium nitrate salt solution and/or base to the precipitation reactor. In preferred embodiments, the acetic acid is present during the precipitation reaction.
  • the use of acetic acid additive in the precipitation process of the present invention enables stable, substantially non-agglomerated nanometer size dispersed precipitated metal oxide particles to be obtained that have an average crystallite size of less than 20 nm (more preferably less than 15 nm) and an average aggregated grain size of less than 40 nm (more preferably less than 30 nm, and even more preferably less than 25 nm).
  • Crystallite size refers to that size which is commonly determined by X-Ray Powder Diffraction (XRPD), while aggregated grain size refers to grain size measurement derived from dynamic light scattering analysis of the precipitated particles.
  • Ultra- fine cerium containing metal oxide particles produced in accordance with the invention are also relatively uniform in both shape and size, that is to say the size frequency distribution is narrow, hi preferred embodiments of the invention, nanometer size dispersed precipitated metal oxide particles may be obtained with the desired very fine average grain sizes note above, as well with the substantial absence of significantly larger grains (e.g., with 99% of the particles having a size of less than 100 nm).
  • the area weighted size frequency distribution of the grains may have less than a 25% coefficient of variation.
  • the resulting ultra-fine cerium containing metal oxide particles may be conveniently re- dispersed in an organic solvent for use as a fuel additive similarly as described in WO 03/040270 and US 2003/0154646 referenced above.
  • Turbulent mixing conditions may be obtained in the precipitation reactor by means of conventional stirrers and impellers such as disclosed, e.g., in Zhou et al. US 2003/0215378 referenced above.
  • the reactants are preferably contacted in a highly agitated zone of a precipitation reactor.
  • Preferred mixing apparatus which may be used in accordance with such embodiment includes rotary agitators of the type which have been previously disclosed for use in the photographic silver halide emulsion art for precipitating silver halide particles by reaction of simultaneously introduced silver and halide salt solution feed streams.
  • Such rotary agitators may include, e.g., turbines, marine propellers, discs, and other mixing impellers known in the art (see, e.g., U.S. 3,415,650; U.S.6,513,965, U.S. 6,422,736; U.S. 5,690,428, U.S. 5,334,359, U.S. 4,289,733; U.S. 5,096,690; U.S. 4,666,669, EP 1156875, WO-Ol 60511).
  • rotary agitators While the specific configurations of the rotary agitators which may be employed in preferred embodiments of the invention may vary significantly, they preferably will each employ at least one impeller having a surface and a diameter, which impeller is effective in creating a highly agitated zone in the vicinity of the agitator.
  • the term "highly agitated zone” describes a zone in the close proximity of the agitator within which a significant fraction of the power provided for mixing is dissipated by the material flow. Typically it is contained within a distance of one impeller diameter from a rotary impeller surface.
  • a reactant feed stream into a precipitation reactor in close proximity to a rotary mixer, such that the feed stream is introduced into a relatively highly agitated zone created by the action of the rotary agitator provides for accomplishing meso-, micro-, and macro-mixing of the feed stream components to practically useful degrees.
  • the rotary agitator preferably employed may be selected to optimize meso-, micro-, and macro-mixing to varying practically useful degrees.
  • Mixing apparatus that may be employed in one particular embodiment of the invention includes mixing devices of the type disclosed in Research Disclosure, Vol. 382, February 1996, Item 38213.
  • means are provided for introducing feed streams from a remote source by conduits that terminate close to an adjacent inlet zone of the mixing device (less than one impeller diameter from the surface of the mixer impeller).
  • the mixing device is vertically disposed in a reaction vessel, and attached to the end of a shaft driven at high speed hy a suitable means, such as a motor.
  • the lower end of the rotating mixing device is spaced up from the bottom of the reaction vessel, but beneath the surface of the fluid contained within the vessel. Baffles, sufficient in number to inhibit horizontal rotation of the contents of the vessel, may be located around the mixing device.
  • Such mixing devices are also schematically depicted in US Pat. Nos. 5,549,879 and 6,048,683.
  • Mixing apparatus that may be employed in another embodiment of the invention includes mixers that facilitate separate control of feed stream dispersion (micromixing and mesomixing) and bulk circulation in the precipitation reactor (macromixing), such as descried in US Pat. No. 6,422,736.
  • Such apparatus comprises a vertically oriented draft tube, a bottom impeller positioned in the draft tube, and a top impeller positioned in the draft tube above the first impeller and spaced therefrom a distance sufficient for independent operation.
  • the bottom impeller is preferably a flat blade turbine (FBT) and is used to efficiently disperse the feed streams, which are added at the bottom of the draft tube.
  • FBT flat blade turbine
  • the top impeller is preferably a pitched blade turbine (PBT) and is used to circulate the bulk fluid through the draft tube in an upward direction providing a narrow circulation time distribution through the reaction zone.
  • PBT pitched blade turbine
  • the two impellers are placed at a distance such that independent operation is obtained. This independent operation and the simplicity of its geometry are features that make this mixer well suited in the scale-up of precipitation processes.
  • Such apparatus provides intense micromixing, that is, it provides very high power dissipation in the region of feed stream introduction.
  • the invention is described primarily with respect to precipitation of cerium dioxide particles, however, it is also applicable to the precipitation of doped ceria wherein some fraction of the eerie ions is replaced by other metal ions.
  • Possible dopants include, e.g., first row transition metals such as chromium, manganese, iron and cobalt, and lanthanide metals such as lanthanum, neodymium, samarium and gadolinium.
  • the fraction of eerie ions replaced by the dopant can be as high as 50% but is typically no more than 25%.
  • the presence of the dopant can usually be confirmed by a shift in the X-ray diffraction peaks for ceria indicating the substitution of an ion of different size than the eerie ion. For cases in which the dopant is of similar size as the eerie ion, other approaches need to be used to confirm the presence of the dopant.
  • the dopant is of lesser charge than the eerie ion but this appears to be accommodated by altering the oxygen content of the ceria.
  • substitution of a 3+ ion for the eerie ion (4+) results in a product with the following formulation (wherein M is the 3+ dopant):
  • a six-liter stainless steel sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • a planar mixing device previously described (Research Disclosure 38213, February 1996 ppl 11-114 "Mixer for Improved Control Over Reaction Environment") operating at 3000 rpm was used to ensure the homogeneity of the reactor contents.
  • To this reactor 4OmL of a 28-30% solution OfNH 4 OH was added. The resultant pH was 10.1.
  • a peristaltic pump was used to deliver a solution containing 15Og of Ce(N ⁇ 3 ) 3 -6H 2 ⁇ (0.34 moles) diluted to 25OmL with distilled water at a rate of 400mL/min. The measured pH was 6.3 and the solution was grayish/brown.
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and 3.7 grams (0.044 moles) of potassium formate were added (additive approximately 12.5 molar % relative to moles of cerium to be added).
  • a peristaltic pump was used to deliver a solution containing 150g of CeQMOsV ⁇ H ⁇ O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution and the solution turned white.
  • the final pH was 2.88.
  • the final product was washed to a conductivity of ⁇ 3mS.
  • the mean grain size from UPA after washing was 64nm with a grain size frequency distribution ranging from 36nm to 204nm (UPA data; 1% of grains are less than 36nm, 99% of grains
  • Example 3 Comparative, sodium butyrate stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and 4.8 grams (0.044 moles) of sodium butyrate were added.
  • a peristaltic pump was used to deliver a solution containing 150g of Ce(NO 3 )S-OH 2 O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution and a whitish precipitate was formed.
  • the final product was foamy and malodorous, and particle size was accordingly not measured.
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and amounts of malonic acid ranging from lower to higher than 0.044 moles were added.
  • a peristaltic pump was used to deliver a solution containing 150g of Ce(NC>3) 3 -6H 2 ⁇ diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution.
  • the final pH was 3.42 and the reaction product was tan in color.
  • the final product was washed to a conductivity of ⁇ 3mS.
  • the mean grain size from UPA after washing was about 80nm with a grain size frequency distribution ranging from 43nm to 289nm (1% of grains are less than 43nm, 99% of grains less than 289nm).
  • the reaction products were purple in color indicative of incomplete reaction.
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and amounts of malic acid ranging from lower to higher than 0.044 moles were added.
  • a peristaltic pump was used to deliver a solution containing 15Og of Ce(NOa) 3 -OHaO diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution.
  • the final pH was 4.1 and the reaction product was purple in color, indicative of incomplete reaction.
  • the final product was washed to a conductivity of ⁇ 3mS.
  • the mean grain size from UPA after washing was about 75nm with a grain size frequency distribution ranging from 43 nm to 486nm (1% of grains are less than 43 nm, 99% of grains less than 486nm). At higher levels of malic acid, the reaction products were again purple in color.
  • Example 6 Comparative, EDTA stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and amounts of ethylenediaminetetraacetic acid (EDTA) ranging from lower to higher than 0.044 moles were added.
  • EDTA ethylenediaminetetraacetic acid
  • a peristaltic pump was used to deliver a solution containing 150g of Ce(NOs)S-OH 2 O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution.
  • the final pH was about 4.5 and the reaction product was purple in color, indicative of incomplete reaction.
  • the final product was washed to a conductivity of ⁇ 3mS.
  • the mean grain size from UPA after washing was about 200nm with a grain size frequency distribution ranging from 36nm to 1635nm (1% of grains are less than 36nm, 99% of grains less than 1635nm).
  • the reaction products were again purple in color.
  • Example 7 Comparative, citric acid stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and amounts of citric acid (a tricarboxylic acid, HO 2 CCH 2 C(OH)(CO 2 H)CH 2 CO 2 H) ranging from lower to higher than 0.044 moles were added.
  • a peristaltic pump was used to deliver a solution containing 15Og of Ce(NO 3 ) 3 -6H 2 O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the reaction was held at 80° C for 90min during which time there was gas evolution.
  • the final pH was about 5 and the reaction product was tan in color.
  • the mean grain size from UPA after washing was about greater than lOOOnm, with a grain size frequency distribution ranging from 102nm to 6500nm (1% of grains are less than 102nm, 99% of grains less than 6500nm).
  • the reaction yield appeared to be low and XRD measurements showed the product to be somewhat amorphous.
  • Example 8 Comparative, lauric acid stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and lauric acid were added.
  • a peristaltic pump was used to deliver a solution containing 15Og of Ce(NO 3 ) 3 -6H 2 O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • a very thick gray product with a final pH of 6.4 was formed. Failure of the pH to decrease below 6.4 indicates the reaction failed to proceed very far toward completion. The final product was so viscous no attempt was made to measure grain size.
  • Example 9 Inventive, acetic acid stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 80° C.
  • the reactor contents were mixed as described in Example 1.
  • 42.5mL of a 28-30% solution OfNH 4 OH and 2.5mL (0.044 moles) of glacial acetic acid were added (acetic acid approximately 12.5 molar % relative to moles of cerium to be added).
  • the resultant pH was 9.1.
  • a peristaltic pump was used to deliver a solution containing 15Og of Ce(NOs) 3 -OHaO diluted to 25OmL with distilled water at a rate of 400mL/min.
  • the measured pH was 6.2 and the solution was grayish/brown.
  • the reaction was held at 80° C for 90min during which time there was gas evolution and the solution turned white.
  • the final pH was 3.0.
  • the final product was washed to a conductivity of ⁇ 3mS and a portion was dried at ambient temperature. Powder X-ray diffraction confirmed the product was single-phase cerium dioxide.
  • the mean crystallite size was 1 lnm (XRPD data) and the mean grain size after washing was 14nm with a grain size frequency distribution ranging from 9nm to 36nm (UPA data; 1% of grains are less than 9nm, 99% of grains less than 36nm).
  • B.E.T. surface area was determined to be 102 m 2 /g. High resolution TEM analysis was consistent with the presence of very small crystallites.
  • Example 10 Inventive, same as Example 9 but the cerium nitrate is in the kettle and the base is pumped
  • Example 9 The procedure from Example 9 was repeated except the NH 4 OH solution was pumped into a kettle that contained the Ce(NOs)S-OH 2 O solution.
  • the mean crystallite size was 14nm and the mean grain size was 25nm with a grain size frequency distribution ranging from 15nm to 61nm (1% of grains are less than 15nm, 99% of grains less than 6 lnm).
  • Example 11 Inventive, same as Example 9 but the cerium nitrate and the base are added by double jet addition
  • Example 9 The procedure from Example 9 was repeated except the NH 4 OH solution and the Ce(N ⁇ 3) 3 -6H 2 ⁇ solution were added by double jet addition.
  • the mean crystallite size was 14nm and the mean grain size was 25nm with a grain size frequency distribution ranging from 15nm to 61nm (1 % of grains are less than 15nm, 99% of grains less than 61nm).
  • Example 12 Inventive, Same as Example 9 with less (2/5x) acetic acid stabilizer The procedure from Example 9 was repeated but with ImL (0.017 moles) of glacial acetic acid.
  • the mean crystallite size was lOntn and the mean grain size was 16nm with a grain size frequency distribution ranging from 1 lnm to 36nm (1% of grains are less than 1 lnm, 99% of grains less than 36nm).
  • Example 13 Comparative, Same as Example 9 with more (4x) acetic acid stabilizer
  • Example 14 Inventive, Same as Example 9 with acetic acid stabilizer added after the 90 s hold
  • Example 9 The procedure from Example 9 was repeated but with the glacial acetic acid added after the 90min hold, just prior to the washing step.
  • the mean crystallite size was 12nm and the mean grain size was 35nm with a grain size frequency distribution ranging from 15nm to 243nm (1% of grains are less than 15nm, 99% of grains less than 243 nm).
  • Example 15 Inventive, Same as Example 9 with 2OmL NH 4 OH The procedure from Example 9 was repeated but with 2OmL of a
  • Example 9 28-30% solution OfNH 4 OH.
  • the final pH was 2.85 and the product yield was significantly less than in Example 9.
  • the mean crystallite size was 9nm and the mean grain size was 13nm with a grain size frequency distribution ranging from 9nm to 26nm (1% of grains are less than 9nm, 99% of grains less than 26nm).
  • Example 16 Inventive, Same as Example 9 with 62.5mL NH4OH
  • Example 9 The procedure from Example 9 was repeated but with 62.5mL of a 28-30% solution OfNH 4 OH.
  • the mean crystallite size was 12nm and the mean grain size was 18nm with a grain size frequency distribution ranging from 13nm to 43nm (1 % of grains are less than 13nm, 99% of grains less than 43 nm).
  • Example 17 Inventive, Same as Example 9 but with prop mixing
  • Example 9 The procedure from Example 9 was repeated but with pitched blade turbine mixing.
  • the mean crystallite size was 1 lnm and the mean grain size was 16nm with a grain size frequency distribution ranging from 1 lnm to 5 lnm (1% of grains are less than 1 lnm, 99% of grains less than 5 lnm).
  • Examples 9-12 and 14-17 employing acetic acid in accordance with the invention demonstrated a grain size reduction in comparison to Examples 1-8 employing no or other additives, as well as Example 13 employing acetic acid at approximately 50 molar% relative to cerium.
  • Examples 9-12 and 15-17, wherein acetic acid was present during the precipitation reaction demonstrated particularly advantageous results (average aggregated grain sizes of less than 30 nm, with 99% of the particles having a size of less than 100 nm).
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 40° C.
  • the reactor contents were mixed as described in Example 1.
  • 75.OmL of a 28-30% solution OfNH 4 OH was added to this reactor.
  • a peristaltic pump was used to deliver a solution containing 127.5g of Ce(NO 3 )3-6H 2 O diluted to 25OmL with distilled water at a rate of 400mL/min.
  • a peristaltic pump was used to deliver a solution containing 22.5g of La(NO 3 ) 3 -6H 2 O diluted to 10OmL with distilled water at a rate of 400mL/min.
  • the solution was tan in color.
  • the temperature was raised to 80° C and held for 90min during which time there was gas evolution and the solution turned white.
  • the final product was washed to a conductivity of ⁇ 3mS and a portion was dried at ambient temperature. Powder X-ray diffraction peaks were shifted to lower two-theta values compared to undoped CeO 2 , consistent with the substitution of the larger La 3+ ion for the Ce 4+ ion.
  • the mean grain size (UPA) was 130nm with a grain size frequency distribution ranging from 5 lnm to 289nm (1 % of grains are less than 5 lnm, 99% of grains less than 289nm).
  • Example 19 Inventive, La doped ceria with acetic acid stabilizer
  • a six-liter sponge kettle was charged with 2L of distilled water and the temperature controlled at 40° C.
  • the reactor contents were mixed as described in Example 1.
  • 75.OmL of a 28-30% solution OfNH 4 OH and 2.5mL of glacial acetic acid were added.
  • the resultant pH was 10.1.
  • a peristaltic pump was used to deliver a solution containing 127.5g of Ce(NO 3 ) 3 -6H 2 ⁇ diluted to 25OmL with distilled water at a rate of 400mL/min.
  • a peristaltic pump was used to deliver a solution containing 22.5g of La(NO 3 ) 3 -6H 2 O diluted to 10OmL with distilled water at a rate of 400mL/min.
  • the measured pH was 8.3 and the solution was tan. The temperature was raised to 80° C and held for 90min during which time there was gas evolution and the solution turned white. The final pH was 5.4. The final product was washed to a conductivity of ⁇ 3mS and a portion was dried at ambient temperature. Powder X-ray diffraction peaks were shifted to lower two-theta values compared to undoped CeO 2 , consistent with the substitution of the larger La 3+ ion for the Ce 4+ ion.
  • the mean crystallite size was lOnm and the mean grain size (UPA) was 22nm with a grain size frequency distribution ranging from 15nm to 43nm (1% of grains are less than 15ran, 99% of grains less than 43nm).

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Abstract

L'invention concerne un procédé de précipitation en milieu aqueux destiné à la préparation de particules d'oxyde métallique, ledit procédé comprenant l'introduction d'une solution de sel de nitrate de cérium 3+ et d'une base, sous agitation turbulente, dans un réacteur de précipitation, les ions cérium 3+ étant oxydés en cérium 4+ et les particules d'oxyde métallique précipitées étant obtenues directement, sans nécessiter d'étape de calcination. Selon l'invention, l'amélioration comprend l'ajout d'acide acétique à la précipitation en une quantité de 1 à 40 pourcent molaire, par rapport à la quantité molaire de cérium, et l'obtention de particules d'oxyde métallique dispersées, pratiquement pas agglomérées, de taille nanométrique.
PCT/US2006/048143 2005-12-23 2006-12-18 Production de grains d'oxyde métallique contenant du cérium Ceased WO2008002323A2 (fr)

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US8679344B2 (en) 2008-12-17 2014-03-25 Cerion Technology, Inc. Process for solvent shifting a nanoparticle dispersion
US8883865B2 (en) 2006-09-05 2014-11-11 Cerion Technology, Inc. Cerium-containing nanoparticles
WO2015058037A1 (fr) * 2013-10-17 2015-04-23 Cerion, Llc Nanoparticules de cérium stabilisées à l'acide malique
US9221032B2 (en) 2006-09-05 2015-12-29 Cerion, Llc Process for making cerium dioxide nanoparticles
US9446070B2 (en) 2012-06-13 2016-09-20 Cerion, Llc Nanoceria with citric acid additive
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CN115448354A (zh) * 2022-09-16 2022-12-09 包头稀土研究院 二氧化铈颗粒及其制备方法
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US5308548A (en) * 1985-06-20 1994-05-03 Rhone-Poulenc Specialities Chimiques Preparing a dispersible, sol-forming cerium (IV) composition
FR2608583B1 (fr) * 1986-12-19 1990-12-07 Rhone Poulenc Chimie Oxyde cerique a nouvelles caracteristiques morphologiques et son procede d'obtention
US6133194A (en) * 1997-04-21 2000-10-17 Rhodia Rare Earths Inc. Cerium oxides, zirconium oxides, Ce/Zr mixed oxides and Ce/Zr solid solutions having improved thermal stability and oxygen storage capacity
US7025943B2 (en) * 2002-05-15 2006-04-11 The Curators Of The University Of Missouri Method for preparation of nanometer cerium-based oxide particles

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US9308265B2 (en) 2012-04-17 2016-04-12 Cerion Llc Nanoparticles of cerium and amino acids
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