WO2015121248A1 - Procédé de traitement de gaz d'échappement diesel utilisant des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium produites par pyrolyse - Google Patents

Procédé de traitement de gaz d'échappement diesel utilisant des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium produites par pyrolyse Download PDF

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WO2015121248A1
WO2015121248A1 PCT/EP2015/052749 EP2015052749W WO2015121248A1 WO 2015121248 A1 WO2015121248 A1 WO 2015121248A1 EP 2015052749 W EP2015052749 W EP 2015052749W WO 2015121248 A1 WO2015121248 A1 WO 2015121248A1
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ceria
oxide particles
zirconia
mixed oxide
oxides
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PCT/EP2015/052749
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Stefan Hannemann
Olga Gerlach
Gerd Grubert
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Basf Se
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/349—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of flames, plasmas or lasers
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G25/00—Compounds of zirconium
    • C01G25/02—Oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
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    • B01D2255/102—Platinum group metals
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
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    • B01D—SEPARATION
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    • B01D2255/908—O2-storage component incorporated in the catalyst
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
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    • B01D2255/9202—Linear dimensions
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/502—Carbon monoxide
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/612—Surface area less than 10 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
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    • B01J35/61—Surface area
    • B01J35/613—10-100 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
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    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C—CHEMISTRY; METALLURGY
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    • C01P2006/12—Surface area

Definitions

  • the present invention relates to a process for the production of mixed oxide particles comprising ceria and zirconia as well as to mixed oxide particles obtainable from the inventive process and in particular from flame spray pyrolysis. Furthermore, the present invention relates to the use of mixed oxide particles obtainable according to the inventive process.
  • cerium and zirconium containing mixed oxides have found use therein, in particular as OSC component in automotive catalysts.
  • processes for their production a variety of processes have been employed such as solid state synthesis (e.g. ceramic method and mechanical grinding), liquid to solid synthesis (e.g. precursor method), various precipitation methods, hydrothermal and solvothermal synthesis, sol-gel methods, emulsion and microemulsion methods, impregnation methods, as well as gas to solid synthesis (e.g. chemical vapor deposition).
  • Ceria is the key component in three-way catalyst technologies, due to its oxygen storage properties.
  • ceria loaded with Pd is beneficial due to its activity towards a water as- sisted low-temperature CO oxidation activity.
  • Ceria has a capacity to create good chemical and physical contacts with Pd on the surface due to an electron transfer from ceria to the highly dispersed palladium. It is also known, that ceria-Pd bonding is stable at intermediate temperatures.
  • US 8,080,495 B2 relates to a diesel oxidation catalyst comprising a particulate support and catalyst nanoparticles on the support, wherein the support particles may comprise at least one of alumina, ceria, zirconia, and magnesia, as well as to a process for producing a catalyst composition comprising providing a precursor medium of a liquid containing particles of a refractory oxide support and precursors of Pt and Pd, forming an aerosol of said precursor medium and heating the resulting droplets to remove the liquid and chemically convert the one or more precursors to catalyst nanoparticles. According to the process, heating may be conducted at a temperature of from about 300 to 3,000°C.
  • ceria when using a flame spray pyrolysis technology for obtaining ceria-zirconia mixed oxide particles, ceria may be substituted by zirconia in a large range without observing any reduction in the oxidation activity of the diesel oxidation catalyst, in particular relative to the oxidation of carbon monoxide to carbon dioxide.
  • the present invention relates to a process for the treatment of diesel exhaust gas comprising
  • diesel oxidation catalyst comprises ceria-zirconia mixed oxide particles
  • the average particle size d50 of the ceria-zirconia mixed oxide particles is comprised in the range of from 5 nm to 40 ⁇ .
  • step (a) no particular restrictions apply such that any conceivable exhaust gas stream resulting from the combustion of diesel fuel may be employed, and in particular any conceivable exhaust gas stream as obtained either from a stationary source, or from a mobile source such as automotive diesel exhaust gas.
  • the diesel exhaust gas stream is provided in step (a) as directly obtained from the combustion of the diesel fuel.
  • the diesel exhaust gas stream provided in step (a) may have been subject to one or more pretreatment steps such as in particular one or more steps of removing particulate matter from the diesel exhaust gas and/or one or more steps of treating the diesel exhaust gas for removal of hydrocarbons, NOx, and/or carbon monoxide.
  • the exhaust gas stream provided in step (a) contains carbon monoxide, wherein preferably carbon monoxide is contained in an amount ranging from 10 to 5000 ppmv, and preferably from 50 to 3000 ppmv, more preferably from 100 to 2500 ppmv, more preferably from 500 to 2200 ppmv, more preferably from 1000 to 2000 ppmv, more preferably from 1200 to 1800 ppmv, more preferably from 1400 to 1600 ppmv.
  • the exhaust gas stream provided in step (a) contains hydrocarbons.
  • hydrocarbons may comprise hydrocarbons contained in diesel fuel which have accordingly not reacted during the combustion process leading to the diesel exhaust gas stream, and/or hydrocarbons resulting from the partial combustion of the diesel fuel and/or hydrocarbons resulting from the chemical transformation of hydrocarbons contained in diesel fuel during the aforementioned combustion process.
  • amounts in which said hydrocarbons may be contained in the diesel exhaust gas stream provided in step (a) no particular restrictions apply such that these may be contained therein in any suitable amount such as for example in an amount ranging from 5 to 4000 ppmv.
  • the diesel exhaust gas stream provided in step (a) contains hydrocarbons in an amount ranging from 10 to 3000 ppmv, more preferably from 30 to 2000 ppmv, more preferably from 50 to 1000 ppmv, more preferably from 80 to 500 ppmv, more preferably from 100 to 200 ppmv.
  • step (a) again said exhaust gas stream may be provided at any suitable temperature ' , wherein preferably the diesel exhaust gas stream provided in step (a) has a temperature preferably comprised in the range of from 100 to 600 °C, and more preferably of from 150 to 500 °C, more preferably of from 200 to 450 °C, and more preferably of from 250 to 400 °C.
  • step (b) of the inventive process the diesel exhaust gas stream provided in step (a) is contacted with a diesel oxidation catalyst.
  • the diesel exhaust stream and the diesel oxidation catalyst may chemically interact, wherein a suitable temperature and pressure al- lows for the chemical conversion of at least a portion of the components contained in the diesel exhaust gas stream when contacting the surface and/or bulk of the diesel oxidation catalyst.
  • the temperature at which the contacting of the diesel exhaust gas stream in step (b) with the diesel oxidation catalyst takes place is not particularly restricted, provided that at east a portion of the components in the diesel exhaust gas stream may be converted by chemical reaction as a result of said contacting, wherein preferably said temperature ranges from 100 to 600 °C.
  • the contacting of the diesel exhaust gas stream provided in step (a) with the diesel oxidation catalyst in step (b) is conducted at a temperature ranging from 150 to 500 °C, more preferably of from 200 to 450 °C, and more preferably of from 250 to 400 °C.
  • a diesel oxidation catalyst is employed which comprises ceria-zirconia mixed oxide particles having an average particle size d50 comprised in the range of 5 nm to 40 ⁇ .
  • the method which is used for providing ceria-zirconia mixed oxide particles having an average particle size d50 comprised in the inventive range there is no particular restriction as to the method which is used for providing ceria-zirconia mixed oxide particles having an average particle size d50 comprised in the inventive range.
  • any suitable method may be employed for their production.
  • the ceria-zirconia mixed oxide particles may be initially produced at a larger particle size d50 and then subsequently subject to a procedure such as a milling procedure for attaining the inventive average particle sizes d50.
  • the ceria-zirconia mixed oxide particles employed in step (b) display the average particle size d50 as synthesized, i.e. without necessitating a reduction of the particle size such as by a milling procedure or the like.
  • the ceria-zirconia mixed oxide particles are obtainable and/or obtained, and preferably are obtained from a method allowing for the direct synthesis of the ceria- zirconia mixed oxide particles having an average particle size d50 comprised in the range of from 5 nm to 40 ⁇ .
  • no particular restriction applies relative to the synthesis method which may be chosen for achieving the in- ventive average particle sizes d50 directly upon synthesis thereof. Accordingly, any suitable synthetic procedure may be employed to this effect, wherein it is preferred according to the present invention that the ceria-zirconia mixed oxide particles are obtainable and/or obtained and preferably obtained from flame spray pyrolysis to this effect.
  • the ceria-zirconia mixed oxide particles employed in step (b) of the inventive process display an average particle size d50 comprised in the range of from 5nm to 40 ⁇ .
  • the average particle size d50 of the ceria-zirconia mixed oxide particles is comprised in the range of from 10 nm to 20 ⁇ , more preferably of from 15 nm to 10 ⁇ , more preferably of from 20 nm to 5 ⁇ , more preferably of from 25 nm to 2 ⁇ , more preferably of from 30 nm to 1 ⁇ , more preferably of from 35 to 500 nm, more preferably of from 40 to 200 nm, more preferably of from 45 to 150 nm, and more preferably of from 50 to 100 nm.
  • the average particle size d50 of the ceria-zirconia mixed oxide particles is comprised in the range of from 5 to 800 nm, preferably from 10 to 500 nm, more preferably from 30 to 300 nm, more preferably from 50 to 250 nm, more preferably from 70 to 200 nm, more preferably from 80 to 170 nm, more preferably from 90 to 150 nm, more preferably from 100 to 130 nm.
  • the average particle size d50 of the ceria-zirconia mixed oxide particles is comprised in the range of from 0.01 to 20 ⁇ , preferably of from 0.05 to 10 ⁇ , more preferably of from 0.1 to 8 ⁇ , more preferably of from 0.3 to 5 ⁇ , more preferably of from 0.5 to 3 ⁇ , more preferably of from 0.8 to 2.5 ⁇ , more preferably of from 1 to 2 ⁇ .
  • said mixed oxide particles are not restricted to ceria and zirconia but may further contain any suitable components such as in particular one or more platinum group metals and/or one or more oxides of one or more rare earth elements other than cerium and/or yttria.
  • the ceria-zirconia mixed oxide particles further comprise one or more platinum group metals, and preferably one or more platinum group metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd.
  • platinum group metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd.
  • the ceria-zirconia mixed oxide particles may comprise the one or more platinum group metals in an amount ranging from 0.01 to 15 wt.-% based on the total weight of ceria, zirconia, and optional one or more oxides of one or more rare earth elements other than Cerium, and/or optional yttria, respectively calculat- ed as their oxides.
  • the ceria- zirconia mixed oxide particles comprise the one or more platinum group metals in an amount ranging from from 0.05 to 10 wt.-%, and more preferably from 0.1 to 7 wt.-%, more preferably from 0.5 to 5 wt.-%, more preferably from 1 to 3 wt.-%, and even more preferably from 1.5 to 2.5 wt.-%.
  • the ceria-zirconia mixed oxide particles may further comprise one or more oxides of one or more rare earth elements other than cerium, and/or may further contain yttria.
  • the one or more oxides of one or more rare earth oxides other than cerium and/or yttria any one or a combination of two or more of the aforementioned oxides may principally be contained in the ceria-zirconia mixed oxide particles wherein it is preferred according to the present invention that the one or more rare earth oxides other than ceria is selected from the group consisting of lanthana, praseodymia, neodymia, and mixtures of two or three thereof, wherein preferably the one or more rare earth oxides other than ceria comprises lanthana, and wherein more preferably the one or more rare earth oxides other than ceria is lanthana.
  • the designation of the rare earth oxides does not refer to a particular type thereof, in particular relative to the oxidation state of the rare earth metal, such that in principle any one or more rare earth oxides may be designated.
  • the term “ceria” principally refers to the compounds CeC>2, Ce2C>3, and any mixtures of the aforementioned compounds. According to a preferred meaning of the present invention, however, the term “ceria” designates the compound CeC>2. Same applies accordingly relative to the term “praseodymia” such that in general said term designates any one of the compounds Pr 2 C>3, Pr 6 On, PrC>2, and any mixtures of two or more thereof. According to a preferred meaning of the present invention, the term “praseo- dymia" designates the compound Pr2C>3.
  • the content of the rare earth ox- ides other than ceria and/or of yttria in the mixed oxide calculated as their respective oxides may be comprised in the range of from 0.5 to 25 wt.-% based on the total weight of ceria, zirconia, and the one or more oxides of the one or more rare earth elements other than Cerium, and/or yttria.
  • the content of the rare earth oxides other than ceria and/or of yttria in the mixed oxide is comprised in the range of 1 to 20 wt.-%, and more preferably of from 3 to 15 wt.-%, more preferably of from 5 to 12 wt.-%, more preferably of from 6 to 10 wt.-%, more preferably of from 7 to 9 wt.-%, and more preferably of from 7.5 to 8.5 wt.-%.
  • the ceria-zirconia mixed oxide particles do not comprise lanthanum. According to the present invention it is further alternatively preferred that the ceria-zirconia mixed oxide particles do not comprise praseodymium. According to the present invention it is yet further preferred that the ceria-zirconia mixed oxide particles do not comprise neodymium.
  • the ceria-zirconia mixed oxide particles do not comprise any one of lanthanum, praseodymium, or neodymium. According to the present invention it is yet further preferred that the ceria- zirconia mixed oxide particles do not comprise any one of lanthanum, praseodymium, neodymium, or yttrium, wherein more preferably the ceria-zirconia mixed oxide particles do not comprise any rare earth elements other than cerium and furthermore do not comprise yttrium.
  • one or more elements are not comprised in the ceria-zirconia mixed oxide particles when the content of said one or more elements therein based on the total weight of ceria and zirconia is 1 wt.-% or less, and preferably 0.5 wt.-% or less, more preferably 0.1 wt.-% or less, more preferably 0.05 wt.-% or less, more preferably 0.01 wt.-% or less, more preferably 0.005 wt.-% or less, more preferably 0.001 wt.-% or less, more preferably 0.0005 wt- % or less, and more preferably 0.0001 wt.-% or less.
  • ceria may be contained therein for example in an amount ranging from 1 to 95 wt.-% based on the total weight of the one or more rare earth oxides, zirconia, and optional yttria con- tained in the mixed oxide particles, wherein preferably the content of ceria in the mixed oxide particles is comprised in the range of from 5 to 90 wt.-%, more preferably from 10 to 80 wt.-%, more preferably from 20 to 70 wt.-%, more preferably from 30 to 60 wt.-%, more preferably from 40 to 55 wt.-%, and even more preferably from 45 to 50 wt.-%.
  • the content of ZrC>2 in the mixed oxide particles which is not particularly limited and may by way of example range from 1 to 95 wt.-% based on the total weight of the one or more rare earth oxides, zirconia, and optional yttria contained in the mixed oxide particles.
  • the content of the content of ZrC>2 in the mixed oxide particles is comprised in the range of from 5 to 90 wt.-%, more preferably from 10 to 80 wt.-%, more preferably from 20 to 70 wt.-%, more preferably from 30 to 60 wt.-%, more prefera- bly from 40 to 55 wt.-%, and even more preferably from 45 to 50 wt.-%.
  • the BET surface area of the mixed oxide particles may be comprised in the range of anywhere from 5 to 300 m 2 /g, wherein preferably the BET surface area is comprised in the range of from 20 to 280 m 2 /g, preferably of from 50 to 250 m 2 /g, preferably of from 80 to 220 m 2 /g, more preferably of from 100 to 200 m 2 /g, more preferably of from 120 to 180 m 2 /g, more preferably of from 140 to 160 m 2 /g, and even more preferably of from 145 to 150 m 2 /g.
  • the BET surface area as defined in the present invention, it is noted that this refers in particular to a BET surface area determined according to DIN 66135.
  • the average size of the crystallites in the mixed oxide particles i.e. of the primary crystals of the ceria-zirconia mixed oxide is comprised in the range of 0.5 to 50 nm.
  • the average size of the crystallites in the ceria-zirconia mixed oxide particles is comprised in the range of from 1 to 25 nm, and more preferably of from 4 to 20 nm, more preferably of from 6 to 17 nm, more preferably of from 8 to 15 nm, more preferably of from 10 to 14 nm, and even more preferably of from 12 to 13 nm, wherein preferably the average particle size is obtained using the Scherrer formula.
  • the mixed oxide particles display an average particle size comprised in the range of from 1 1 to 12.5 nm.
  • K is the shape factor
  • lambda ( ⁇ ) is the X-ray wave length
  • beta ( ⁇ ) is the line broadening at half the maximum intensity (FWHM) in radians
  • theta ( ⁇ ) is the Bragg angle.
  • tao ( ⁇ ) this stands for the mean size of the ordered (crystalline) domains, which may be smaller or equal to the grain size.
  • the dimensionless shape factor has a typical value of about 0.9, and may be adapted to the actual shape of the crystallite if necessary.
  • the ceria- zirconia mixed oxide particles are obtainable and/or obtained and preferably obtained from flame spray pyrolysis.
  • the specific type of flame spray pyrolysis which may be employed to this effect such that in principle any suitable flame spray pyrolysis procedure may be employed.
  • the flame spray pyrolysis from which the ceria-zirconia mixed oxide particles are obtainable and/or obtained comprises
  • (1 ) providing a mixture comprising a solvent, one or more precursor compounds of ce- ria, and one or more precursor compounds of zirconia, and optionally one or more precursor compounds of one or more rare earth oxides other than ceria and/or optionally one or more precursor compounds of yttria;
  • step (3) pyrolyzing the aerosol of step (2) to obtain ceria-zirconia mixed oxide particles.
  • step (1 ) of the preferred process for obtaining the ceria-zirconia mixed oxide particles there is no particular restriction as to the means which are employed for forming a mixture provided that a homogenous mixture may be provided.
  • a homogenous mixture may be provided.
  • means of homogenizing the mixture are employed for achieving a high dispersion of said one or more precursor compounds therein.
  • the homogenous mixture may be provided by appropriate means of agitation such as by stirring, shaking, rotating, and sonication, wherein preferably the mixture is provided by appropriate stirring of the one or more precursors in the solution for providing a high dispersion thereof.
  • the one or more precursor compounds provided in step (1 ) are respectively soluble in the solvent which is provided such that a homogenous mixture is provided by dissolution of all components in the solvent.
  • the aerosol may be formed by any appropriate means for dispersing the mixture provided in step (1 ) in a gaseous medium such as by spraying the mixture provided in step (1 ) into said medium.
  • the mixture provided in step (1 ) is sprayed into a gas stream for obtaining a stream of said aerosol which may then be conducted into a pyrolysing zone for achieving step (3) of the preferred process.
  • step (3) may be achieved with the aid of any suitable heat source of which the temperature is sufficient for pyrolysing at least a portion of the aerosol provided in step (2).
  • the preferred process for the production of mixed oxide particles is preferably conducted in a continuous mode, wherein the aerosol according to particular and preferred embodiments of the present invention is provided as a gas stream which is allowed to pass a pyrolysing zone for obtaining mixed oxide particles from at least a portion of said aerosol in the gas stream exiting the pyrolysing zone.
  • the weight hourly space velocity of the aerosol gas stream which is conducted to the pyroylsing zone there is no particular restriction as to the extent of the pyrolysing zone provided that the weight hourly space velocity is chosen such depending on the extent of the pyrolysing zone at least a portion of the aerosol may be pyrolysed in step (3) for obtaining mixed oxide particles.
  • the gas in which the aerosol is formed in step (2) of the preferred process for obtaining the ceria-zirconia mixed oxide particles there is again no particular restriction regarding its composition such that it may contain one type of gas or several different types of gases.
  • the gas employed for providing the aerosol in step (2) may consist of one or more inert gases, wherein according to the present invention said one or more inert gases do not re- act under the conditions of pyrolysis in step (3) of the preferred process.
  • at least a portion of the gas employed for forming an aerosol in step (2) is a gas which reacts with at least a portion of the mixture provided in step (1 ), wherein it is further preferred that said gas has an oxidizing effect on the mixture provided in step (1 ), in particular during pyrolysis of the mixture in step (3).
  • the portion of the gas contained in the aerosol provided in step (2) which has an oxidizing effect on the mixture provided in step (1 ) reacts with at least a portion of the mixture during pyrolysis in step (3), wherein said reaction is exothermic for providing at least a portion of the heat source required in step (3) for the pyrolysis of the mixture provided in step (1 ).
  • the oxidizing gas comprised in the aerosol in step (2) comprises oxygen, wherein more preferably the oxidizing gas contained in the aerosol of step (2) is oxygen.
  • zirconia designates zirconia, hafnia, and mixtures thereof.
  • step (1 ) As concerns the concentration of the one or more precursor compounds of ceria and zirconia and the optional one or more precursor compounds of one or more rare earth oxides other than ceria and/or of the one or more precursor compounds of yttria comprised in the mixture provided in step (1 ), no particular restriction applies provided that an aerosol may be formed in step (2) which may then be pyrolyzed in step (3) to obtain ceria-zirconia mixed oxide particles.
  • the molality of the mixture provided in step (1 ) relative to the one or more precursor compounds of ceria and zirconia and to one or more precursor compounds of one or more rare earth oxides other than ceria and/or one or more precursor compounds of yttria optionally further comprised in the mixture provided in step (1 ) may range anywhere from 0.05 to 5 mol/kg based on the total weight of the mixture provided in step (1 ), wherein preferably the mo- lality of the mixture provided in step (1 ) ranges from 0.1 to 3 mol/kg, more preferably from 0.2 to 2 mol/kg, more preferably from 0.3 to 1 mol/kg, more preferably from 0.35 to 0.7 mol/kg, and even more preferably from 0.4 to 0.5 mol/kg.
  • step (1 ) of the preferred process there is no particular restriction as to the amounts of the solvent, nor with respect to the amount of the one or more precursor compounds of ceria, zirconia, or of the optional one or more rare earth oxides other than ceria and/or of optional yttria, provided that depending on the specific parameters and conditions which are employed in the steps of providing the mixture in step (1 ), of forming the aerosol from said mixture in step (2), and of pyrolysing the aerosol in step (3), at least a portion of the ceria-zirconia mixed oxide particles are formed in step (3).
  • the optional one or more rare earth oxides other than ceria provided in step (1 ) of the preferred process there is no particular restriction according to the present invention neither with respect to the type nor with respect to the number of the optional one or more precursor compounds of one or more rare earth oxides other than ceria which may be provided.
  • said optional one or more rare earth oxides other than ceria comprise one or more of lanthana, praseodymia, and neodymia, including mixtures of two or three thereof, wherein it is further preferred that the optional one or more rare earth oxides other than ceria comprise lanthana and/or neodymia.
  • the optional one or more rare earth oxides other than ceria provided in step (1 ) of the inventive process include lanthana, wherein even more preferably the optional rare earth oxide other than ceria is lanthana.
  • the one or more rare earth oxides other than ceria is selected from the group consisting of lanthana, praseodymia, neodymia, and mixtures of two or three thereof, wherein the one or more rare earth oxides preferably comprises lanthana and/or neodymia, preferably lanthana, wherein even more preferably the rare earth oxide other than ceria is lanthana.
  • the solvent provided in step (1 ) of the preferred process for obtaining the ceria- zirconia mixed oxide particles there is again no particular restriction neither with respect to the composition nor with respect to the amount of said solvent.
  • the solvent provided in step (1 ) may comprise one or more compounds such as those selected from the group consisting of aliphatic and aromatic hydrocarbons, alcohols, heterocyclic compounds, carboxylic acids, nitriles, water, and mixtures of two or more thereof.
  • the solvent provided in step (1 ) of the preferred process comprises one or more selected from the group consisting of aromatic hydrocarbons, N-containing heterocycles, tetrahy- drofurane, (C5-Cio)hydrocarbons, (Ci-C5)alcohols, (Ci-C8)carboxylic acids, (Ci-C5)nitriles, water, and combinations of two or more thereof, more preferably from the group consisting of (C6-C12) aromatic hydrocarbons, pyrrolidine, pyrrole, piperidine, pyridine, azepane, azepine, tetrahydro- furane, (C5-C7)hydrocarbons, (Ci-C3)alcohols, (C2-C8)carboxylic acids, (CrC3)nitriles, water, and combinations of two or more thereof, more preferably from the group consisting of Cs aromatic hydrocarbons, pyrrolidine, pyrrole, piperidine, pyr
  • the solvent provided in step (1 ) it is not necessary that the solvent provided in step (1 ) be in the liquid state at room temperature.
  • room temperature refers to a temperature of 25°C.
  • the solvent provided in step (1 ) is not in a liquid state but rather in a solid or semi-solid state at room temperature and the mixture provided in step (1 ) is employed in the inventive process at a temperature greater than room temperature for forming an aerosol in step (2).
  • the solvent provided in step (1 ) therefore comprises one or more compounds having a melting point above room temperature, wherein said one or more compounds may accordingly be selected from the group consisting of higher molecular weight aliphatic and aromatic hydrocarbons, alcohols, heterocyclic compounds, carboxylic acids, nitriles, water, and mixtures of two or more thereof, wherein said compounds have melting points above room temperature, respectively.
  • said one or more higher molecular weight compounds having melting points above room temperature may be comprised in the solvent provided in step (1 ) together with one or more compounds having a melting point at and/or below room temperature.
  • the solvent provided in step (1 ) sub- stantially consists of one or more compounds having a melting point above room temperature, wherein preferably said one or more compounds are selected from the group consisting of aliphatic and aromatic hydrocarbons, alcohols, heterocyclic compounds, carboxylic acids, nitriles, water, and mixtures of two or more thereof, and more preferably from the group consisting of aliphatic hydrocarbons, alcohols, carboxylic acids, nitriles, and mixtures of two or more thereof.
  • the solvent provided in step (1 ) comprises xylene and/or acetonitrile, preferably xylene.
  • the solvent provided in step (1 ) comprises a mixture of acetic acid and water.
  • the aromatic hydrocarbons may be selected from the group consisting of branched and/or unbranched (C6-Ci2)hydrocarbons, preferably of (C7-Cn)hydrocarbons, more preferably of (C8-Cio)hydrocarbons, more preferably of (Cs-C ⁇ hydrocarbons, and even more preferably of branched and/or unbranched Cs-hydrocarbons, wherein even more preferably the solvent com- prises one or more aromatic hydrocarbons selected from the group consisting of toluene, ethylbenzene, xylene, mesitylene, durene, and mixtures of two or more thereof, more preferably from the group consisting of toluene, ethylbenzene,
  • nitriles preferably comprised in the solvent in the mixture of step (1 ) of the preferred process for the flame spray pyrolysis
  • no particular restriction applies neither with respect to the particular type or types of nitriles which may be contained therein, nor with respect to the amounts in which these are used in the solvent.
  • the preferred nitriles may comprise one or more nitriles selected from the group consisting of branched and/or unbranched (Ci-Ce)nitriles, wherein preferably the nitriles comprise one or more nitriles selected from the group consisting of branched and/or unbranched (Ci-C6)nitriles, more preferably from branched and/or unbranched (C1-C5) nitriles, more preferably from the group consisting of pen- tanenitrile, pivalonitrile, butyronitrile, propionitrile, acetonitrile, and mixtures of two or more thereof, wherein more preferably the one or more nitriles comprise propionitrile and/or acetonitrile, preferably acetonitrile.
  • aliphatic hydrocarbons preferably comprised in the solvent provided in step (1 ) of the preferred process.
  • these may in principle be any one or more branched or unbranched aliphatic hydrocarbons or any conceivable mixture of branched and/or unbranched hydrocarbons, wherein the aliphatic hydrocarbons are preferably unbranched.
  • the aliphatic hydrocarbons comprise one or more hydrocarbons selected from the group consisting of branched and/or unbranched (C4-Ci2)hydrocarbons, preferably of (C5-Cio)hydrocarbons, more preferably of (C6-C8)hydrocarbons, more preferably of (C6-C7)hydrocarbons, and even more preferably of branched and/or unbranched, preferably unbranched C6-hydrocarbons, wherein even more preferably the solvent comprises one or more aliphatic hydrocarbons selected from the group consisting of pentane, hexane, heptane, octane, and mixtures of two or more thereof, wherein even more preferably the aliphatic hydrocarbons comprise pentane and/or hexane, preferably hexane.
  • the one or more carboxylic acids may be selected from the group consisting of branched and/or unbranched (Ci-Cs) carboxylic acids, preferably from the group consisting of branched and/or unbranched (C1-C6) carboxylic acids, more preferably from the group consisting of branched and/or unbranched (C1-C5) carboxylic acids, more preferably from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and mixtures of two or more thereof, more preferably from the group consisting of acetic acid, propionic acid, butyric acid, 2-ethylhxanoic acid and mixtures of two or more there- of, wherein more preferably the carb
  • the one or more precursor compounds of ceria comprised in the mixture provided in step (1 ) of the preferred process for obtaining the ceria-zirconia mixed oxide particles there is no particular restriction neither with respect to the particular type or number of precursor compounds which may be employed nor with respect to the amount in which they may be provided in the mixture provided that depending on the further components provided in the mixture and the specific means of executing steps (1 ), (2), and (3) of the inventive process affords mixed oxide particles in step (3).
  • any one or more of said precursor compounds may be provided in any suitable form provided that their interaction with the solvent and/or with the further components of the mixture in step (1 ) as well as the specific methods for forming an aerosol employed in step (2) and the pyrolysis of the aerosol in step (3) allows for the formation of mixed oxide particles in step (3).
  • the one or more precursor com- pounds of ceria and/or of the optional rare earth oxides other than ceria and/or of optional yttria may be any suitable compound of the rare earth metals or yttrium, wherein it is preferred that one or more salts of the rare earth metals and/or of yttrium be provided in step (1 ) of the inventive process.
  • any conceivable salts may again be employed, wherein it is preferred that the one or more salts may completely dissolve in the solvent provided in step (1 ), wherein the type of salt chosen may accordingly depend on the type and amount of salts chosen for the other precursor compounds provided in step (1 ) and in particular on the type of solvent and the amount thereof provided in the mixture.
  • the one or more precursor compounds of ceria and/or of the optional rare earth oxides other than ceria and/or of optional yttria comprise one or more salts selected from the group consisting of carboxylates, nitrates, carbonates, alcoholates, and chelating ligand containing complexes, wherein the carboxylates are preferably selected from branched and/or unbranched (C 4 - Ci2)carboxylates, more preferably from (C5-Cn)carboxylates, more preferably from (C6- Cio)carboxylates, more preferably from (C7-Cg)carboxylates, more preferably from branched and/or unbranched Cs-carboxylates, more preferably from branched Cs-carboxylate, wherein more preferably the one or more precursor compounds comprise a 2-ethylhexanoate salt, and wherein even more preferably the one or more precursor compounds of c
  • the one or more precursor compounds comprise one or more salts
  • said salts do not lower the solubility of the one or more further precursor compounds as a result of the specific type of salt which is used.
  • the salts which are preferably used as the one or more precursor compounds do not have a negative impact on the apparatus which is used and in particular does not generate reactive side products which may damage said apparatus, e.g., by corrosion thereof.
  • the mixture provided in step (1 ) does not contain any halides and in particular does not contain any fluorides, chlorides, and/or bromides and even more preferably does not contain any fluorides and/or chlorides.
  • the mixture provided in step (1 ) does not contain any halides when no substantial amount of a hal- ide-containing salt is present in the mixture provided in step (1 ), wherein the term "substantial” as employed for example in the terms “substantially not", or “not any substantial amount of” within the meaning of the present invention respectively refer to there practically being not any amount of said component in the mixture provided in step (1 ) and/or in the aerosol formed in step (2) of the inventive process, wherein preferably 0.1 wt.-% or less of said one or more components is contained therein based on the total weight of the mixture and/or of the liquids and/or solids contained in the aerosol, preferably an amount of 0.05 wt.-% or less, more preferably of 0.001 wt.-% or less, more preferably of 0.0005 wt.-% or less, and even more preferably of 0.0001 wt.-% or less.
  • one or more chelating ligand-containing complexes are comprised as the one or more precursor compounds of ceria and/or of the optional rare earth oxides other than ceria and/or of optional yttria in the mixture provided in step (1 )
  • the type or number of chelating ligand-containing complexes which may be comprised in said mixture.
  • the type of the one or more chelat- ing ligands such that said ligands may for example be selected from the group consisting of bi-, tri-, tetra-, penta-, and hexadentate ligands.
  • the chelating ligand-containing complexes comprise one or more chelating ligands selected from the group consisting of oxalate, ethylenediamine, 2,2'-bipyridine, 1 ,10- phenanthroline, acetylacetonate, 2,2,2-crypt, diethylenetriamine, dimethylglyoximate, EDTA, ethylenediaminetriacetate, glycinate, triethylenetetramine, tris(2-aminoethyl)amine, and combinations of two or more thereof, more preferably from the group consisting of oxalate, ethylene- diamine, acetylacetonate, diethylenetriamine, dimethylglyoximate, EDTA, ethylenediaminetriacetate, glycinate, triethylenetetramine, tris(2-aminoethyl)amine, and combinations of two or more thereof, more preferably from the group consisting of oxalate, ethylene- diamine, acetylaceton
  • any conceivable precursor compound or compounds of zirconium may be employed, wherein again one or more salts are preferably employed as the one or more precursor com- pounds for the same reasons as given above with respect to the further one or more precursor compounds contained in the mixture according to step (1 ) of the preferred process.
  • the one or more salts of zirconium preferably comprised in the mixture of step (1 ) preferably comprise one or more salts selected from the group consisting of carboxylates, nitrates, carbonates, alcoholates, and chelating ligand containing complexes, preferably diketone ligand containing complexes, and more preferably acetylacetonate complexes, wherein the alcoholates are preferably selected from branched and/or unbranched (C2-C5) alcoholates, more preferably from (C3-C4) alcoholates, and more preferably from branched and/or unbranched, preferably unbranched C3-alcoholat.es, wherein more preferably the one or more precursor compounds comprise zirconium(IV)-n-propoxide, and wherein even more preferably the one or more precursor compounds of zirconia is zirconium(IV)-n-propoxide.
  • the alcoholates are preferably selected from branched and/or unbranched (C2-C5) alcohol
  • zirconium salts which may be employed in the inventive process which do not form a complex with the counter-ion, it is preferred according to the present invention that said zirconium salts contain the zirconyl cation, wherein according to particularly preferred embodiments the one or more precursor compounds of zirconia comprise one or more zirconyl salts, preferably one or more ziconyl halides, more preferably zirconyl bromide and/or zirconyl halide, and more preferably zirconyl chloride.
  • step (1 ) of the preferred process there is also no particular restriction which would apply relative to any further compounds which may be contained therein, provided that mixed oxide particles according to any of the particular or preferred embodiments of the present invention may be formed in step (3).
  • any suitable auxiliary agent may further be comprised in the mixture of step (1 ) and/or any further compound or compounds may be provided therein for incorporation into the mixed oxide particles formed in step (3) of the in- ventive process.
  • one or more transition metal- containing compounds be provided in step (1 ) as precursor compounds for the incorporation of said one or more transition metals into the mixed oxide particles generated in step (3) of the preferred process.
  • one or more platinum group metals are included in the mixture of step (1 ) for incorporation thereof in the metal oxide particles resulting from the inventive process.
  • the one or more platinum group metals are preferably selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd.
  • the one or more platinum group metal containing compounds comprise one or more salts, wherein the one or more salts are preferably selected from the group consisting of carboxylates, nitrates, and chelating ligand containing complexes, wherein the one or more salts are preferably nitrates and/or chelating ligand containing complexes, wherein even more preferably the one or more salts comprise one or more chelating ligand containing com- plexes.
  • the chelating ligand containing complexes comprise one or more chelating ligands selected from the group consisting of bi-, tri-, tetra-, penta-, and hexadentate ligands, more preferably from the group consisting of oxalate, ethylenediamine, 2,2'-bipyridine, 1 ,10- phenanthroline, acetylacetonate, 2,2,2-crypt, diethylenetriamine, dimethylglyoximate, EDTA, ethylenediaminetriacetate, glycinate, triethylenetetramine, tris(2-aminoethyl)amine, and combinations of two or more thereof, more preferably from the group consisting of oxalate, ethylene- diamine, acetylacetonate, diethylenetriamine, dimethylglyoximate, ED
  • the temperature at which the pyrolysis is performed may be comprised in the range of anywhere from 800 to 2,200°C, wherein preferably the temperature in step (3) is comprised in the range of from 900 to 1 ,800°C, more preferably of from 950 to 1 ,500°C, and more preferably of from 1 ,000 to 1 ,300°C.
  • pyrolysis in step (3) is performed at a temperature comprised in the range of from 1 ,050 to 1 ,150°C.
  • the components are at least in part contained in the mixed oxide particles as a mixed oxide and in particular as a solid solution.
  • the crystalline phases formed in the mixed oxide particles are accordingly crystalline phases formed by the mixed oxides and in particular by the ceria-zirconia mixed oxides.
  • the present invention includes the following embodiments, wherein these include the specific combinations of embodiments as indicated by the respective interdependencies defined therein:
  • a process for the treatment of diesel exhaust gas comprising
  • the diesel oxidation catalyst comprises ceria-zirconia mixed oxide particles, wherein the average particle size d50 of the ceria-zirconia mixed oxide particles, prefera- bly of the ceria-zirconia mixed oxide particles as synthesized, is comprised in the range of from 5 nm to 40 ⁇ , preferably of from 10 nm to 20 ⁇ , more preferably of from 15 nm to 10 ⁇ , more preferably of from 20 nm to 5 ⁇ , more preferably of from 25 nm to 2 ⁇ , more preferably of from 30 nm to 1 ⁇ , more preferably of from 35 to 500 nm, more preferably of from 40 to 200 nm, more preferably of from 45 to 150 nm, and more preferably of from 50 to 100 nm.
  • the ceria-zirconia mixed-oxide particles further comprise one or more platinum group metals, preferably one or more platinum group metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd.
  • platinum group metals preferably one or more platinum group metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd.
  • the ceria-zirconia mixed-oxide particles comprise the one or more platinum group metals in an amount ranging from 0.01 to 15 wt.-% based on the total weight of ceria, zirconia, and optional one or more oxides of one or more rare earth elements other than Ce, and/or optional yttria, respectively calculated as their oxides, preferably from 0.05 to 10 wt.-%, more preferably from 0.1 to 7 wt.-%, more preferably from 0.5 to 5 wt.-%, more preferably from 1 to 3 wt.-%, and even more preferably from 1.5 to 2.5 wt.-%.
  • the ceria-zirconia mixed-oxide particles further comprise one or more oxides of one or more rare earth elements other than Ce, and/or yttria, wherein the one or more rare earth oxides other than ceria is preferably selected from the group consisting of lanthana, praseodymia, neodymia, and mixtures of two or three thereof, wherein preferably the one or more rare earth oxides other than ceria comprises lanthana, and wherein more preferably the one or more rare earth oxides other than ceria is lanthana.
  • the content of the rare earth oxides other than ceria, and/or of yttria in the mixed oxide calculated as their respective oxides is comprised in the range of from 0.5 to 25 wt.-% based on the total weight of ceria, zirconia, and the one or more oxides of the one or more rare earth elements other than Ce, and/or yttria, respectively calculated as their oxides, preferably of from 1 to 20 wt.-%, more preferably of from 3 to 15 wt.-%, more preferably of from 5 to 12 wt.-%, more preferably of from 6 to 10 wt.-%, more preferably of from 7 to 9 wt.-%, and more preferably of from 7.5 to 8.5 wt- %.
  • any of embodiments 1 to 7, wherein the content of ZrC>2 in the mixed oxide particles is comprised in the range of from 1 to 95 wt.-% based on the total weight of the one or more rare earth oxides, zirconia, and optional yttria contained in the mixed oxide particles, preferably from 5 to 90 wt.-%, more preferably from 10 to 80 wt.-%, more preferably from 20 to 70 wt.-%, more preferably from 30 to 60 wt.-%, more preferably from 40 to 55 wt.-%, and even more preferably from 45 to 50 wt.-%.
  • the BET surface area of the mixed oxide particles is comprised in the range of from 5 to 300 m 2 /g, preferably of from 20 to 280 m 2 /g, more preferably of from 50 to 250 m 2 /g, more preferably of from 80 to 220 m 2 /g, more preferably of from 100 to 200 m 2 /g, more preferably of from 120 to 180 m 2 /g, more preferably of from 140 to 160 m 2 /g, and even more preferably of from 145 to 150 m 2 /g.
  • the average size of the crystallites in the mixed oxide particles is comprised in the range of from 0.5 to 50 nm, preferably of from 1 to 25 nm, more preferably of from 4 to 20 nm, more preferably of from 6 to 17 nm, more preferably of from 8 to 15 nm, more preferably of from 10 to 14 nm, and even more preferably of from 12 to 13 nm, wherein preferably the average particle size is obtained using the Scherrer formula.
  • (1 ) providing a mixture comprising a solvent, one or more precursor compounds of ceria, and one or more precursor compounds of zirconia, and optionally one or more precursor compounds of one or more rare earth oxides other than ceria and/or optionally one or more precursor compounds of yttria;
  • step (3) pyrolyzing the aerosol of step (2) to obtain ceria-zirconia mixed oxide particles.
  • molality of the mixture provided in step (1 ) relative to the one or more precursor compounds of ceria and zirconia and to one or more precursor compounds of one or more rare earth oxides other than ceria and/or one or more precursor compounds of yttria optionally further comprised in the mixture provided in step (1 ) ranges from 0.05 to 5 mol/kg based on the total weight of the mixture provided in step (1 ), preferably from 0.1 to 3 mol/kg, more preferably from 0.2 to 2 mol/kg, more preferably from 0.3 to 1 mol/kg, more preferably from 0.35 to 0.7 mol/kg, and even more preferably from 0.4 to 0.5 mol/kg.
  • the solvent comprises one or more selected from the group consisting of aliphatic and aromatic hydrocarbons, alcohols, heterocyclic compounds, carboxylic acids, nitriles, water, and mixtures of two or more thereof, preferably from the group consisting of aromatic hydrocarbons, N-containing heterocycles, tetrahydrofurane, (C5-Cio)hydrocarbons, (Ci-C5)alcohols, (Ci-C8)carboxylic acids, (Ci- C5)nitriles, water, and combinations of two or more thereof, more preferably from the group consisting of (C6-C12) aromatic hydrocarbons, pyrrolidine, pyrrole, piperidine, pyridine, azepane, azepine, tetrahydrofurane, (C5-C7)hydrocarbons, (Ci-C3)alcohols, (C2- C8)carboxylic acids, (Ci-C3)nitriles,
  • the aromatic hydrocarbons comprise one or more aromatic hydrocarbons selected from the group consisting of branched and/or un- branched (C6-Ci2)hydrocarbons, preferably of (C7-Cn)hydrocarbons, more preferably of (C8-Cio)hydrocarbons, more preferably of (Ce-C ⁇ hydrocarbons, and even more preferably of branched and/or unbranched Cs-hydrocarbons, wherein even more preferably the solvent comprises one or more aromatic hydrocarbons selected from the group consisting of toluene, ethylbenzene, xylene, mesitylene, durene, and mixtures of two or more thereof, more preferably from the group consisting of toluene, ethylbenzene, xylene, and mixtures of two or more thereof, wherein even more preferably the solvent comprises toluene and/or xylene, preferably xylene.
  • the aliphatic hydrocarbons comprise one or more hydrocarbons selected from the group consisting of branched and/or unbranched (C4-Ci2)hydrocarbons, preferably of (C5-Cio)hydrocarbons, more preferably of (C6- C8)hydrocarbons, more preferably of (C6-C7)hydrocarbons, and even more preferably of branched and/or unbranched, preferably unbranched C6-hydrocarbons, wherein even more preferably the solvent comprises one or more aliphatic hydrocarbons selected from the group consisting of pentane, hexane, heptane, octane, and mixtures of two or more thereof, wherein even more preferably the aliphatic hydrocarbons comprise pentane and/or hexane, preferably hexane.
  • carboxylic acids comprise one or more carboxylic acids selected from the group consisting of branched and/or un- branched (Ci-Cs) carboxylic acids, preferably from the group consisting of branched and/or unbranched (Ci-Ce) carboxylic acids, more preferably from the group consisting of branched and/or unbranched (C1-C5) carboxylic acids, more preferably from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and mixtures of two or more thereof, more preferably from the group consisting of acetic acid, propionic acid, bu- tyric acid, 2-ethylhxanoic acid and mixtures of two or more thereof, wherein more preferably the carboxylic acid comprises acetic acid and/or propionic acid, preferably acetic acid.
  • nitriles comprise one or more nitriles selected from the group consisting of branched and/or unbranched (Ci-Cejnitriles, preferably from branched and/or unbranched (Ci-C6)nitriles, more preferably from branched and/or unbranched (C1-C5) nitriles, more preferably from the group consisting of pentanenitrile, pivalonitrile, butyronitrile, propionitrile, acetonitrile, and mixtures of two or more thereof, wherein more preferably the one or more nitriles comprise propionitrile and/or acetonitrile, preferably acetonitrile.
  • the one or more precursor compounds of ceria and/or of the optional rare earth oxides other than ceria and/or of optional yttria comprise one or more salts, preferably one or more salts selected from the group consisting of carboxylates, nitrates, carbonates, alcoholates, and chelating ligand containing complexes, wherein the carboxylates are preferably selected from branched and/or unbranched (C4-Ci2)carboxylates, more preferably from (C5-Cn)carboxylates, more preferably from (C6-Cio)carboxylates, more preferably from (C7-Cg)carboxylates, more preferably from branched and/or unbranched Cs-carboxylates, more preferably from branched Cs-carboxylate, wherein more preferably the one or more precursor compounds comprise a 2-ethylhexanoate salt, and wherein even more
  • the one or more precursor compounds of zirconia comprise one or more salts, preferably one or more salts selected from the group consisting of carboxylates, nitrates, carbonates, alcoholates, and chelating lig- and containing complexes, preferably diketone ligand containing complexes, and more preferably acetylacetonate complexes, wherein the alcoholates are preferably selected from branched and/or unbranched (C2-C5) alcoholates, more preferably from (C3-C4) alcoholates, and more preferably from branched and/or unbranched, preferably unbranched C3-alcoholat.es, wherein more preferably the one or more precursor compounds comprise zirconium(IV)-n-propoxide, and wherein even more preferably the one or more precursor compounds of zirconia is zirconium(IV)-n-propoxide.
  • the alcoholates are preferably selected from branched and/or unbranched (C2-C5) alcoholates, more preferably
  • step (1 ) further comprises one or more platinum group metal containing compounds, wherein the one or more platinum group metals are selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, and mixtures of two or more thereof, more preferably from the group consisting of Rh, Pd, Pt, and mixtures of two or more thereof, wherein more preferably the platinum group metal is Pd and/or Pt, preferably Pd. 21.
  • the one or more platinum group metal containing compounds comprise one or more salts, wherein the one or more salts are preferably selected from the group consisting of carboxylates, nitrates, and chelating ligand containing complexes, wherein the one or more salts are preferably nitrates and/or chelating ligand containing complexes, wherein even more preferably the one or more salts comprise one or more chelating ligand containing complexes.
  • the chelating ligand containing complexes comprise one or more chelating ligands selected from the group consisting of bi-, tri-, tetra-, penta-, and hexadentate ligands, more preferably from the group consisting of oxalate, ethylenediamine, 2,2'-bipyridine, 1 ,10-phenanthroline, acetylacetonate, 2,2,2- crypt, diethylenetriamine, dimethylglyoximate, EDTA, ethylenediaminetriacetate, glycinate, triethylenetetramine, tris(2-aminoethyl)amine, and combinations of two or more thereof, more preferably from the group consisting of oxalate, ethylenediamine, acetylacetonate, diethylenetriamine, dimethylglyoximate, EDTA, ethylenediaminetriacetate, glycinate, triethylenet
  • step (3) The process of any of embodiments 1 1 to 22, wherein pyrolysis in step (3) is performed in an atmosphere containing oxygen, preferably in air or in an oxygen atmosphere.
  • step (3) The process of any of embodiments 1 1 to 23, wherein pyrolysis in step (3) is performed at a temperature comprised in the range of from 800 to 2,200°C, preferably of from 900 to 1 ,800°C, preferably of from 950 to 1 ,500°C, more preferably of from 1 ,000 to 1 ,300°C, and even more preferably of from 1 ,050 to 1 ,150°C. 25.
  • the exhaust gas stream provided in (a) contains carbon monoxide, preferably in an amount ranging from 10 to 5000 ppmv, preferably from 50 to 3000 ppmv, more preferably from 100 to 2500 ppmv, more preferably from 500 to 2200 ppmv, more preferably from 1000 to 2000 ppmv, more preferably from 1200 to 1800 ppmv, more preferably from 1400 to 1600 ppmv. 27.
  • Figure 1 shows the set-up of the particle generator used for flame spray pyrolysis in Example 6.
  • Figure 2 displays the burner configuration (top and side view) in an apparatus which may be employed for flame spray pyrolysis.
  • Figure 3 displays the particle size distribution obtained for Example 7.
  • the particle in ⁇ is plotted along the ordinate, wherein the symbols “ ⁇ ” and “ ⁇ ” represent the relative amounts of particles for a given particle size as obtained in separate measurements of the same sample.
  • the cumulative distribution in % is plotted along the abscissa, wherein the symbols "a” and “o” represent the cumulative distribution for the aforementioned separate measurements of the sample.
  • Figure 4 displays the results of catalytic testing in the oxidation of carbon monoxide as obtained for the aged samples of Examples 1 - 6 and Comparative Examples 1 - 7, respectively.
  • the T 5 o,co temperature indicating the conversion of 50% of carbon monoxide over the respective catalyst is plotted along the ordinate, whereas the concentration of ceria in wt.-% based on the total weight of ceria, zirconia, optional lanthana, and optional yttria is plotted along the abscissa.
  • the symbols “ ⁇ ” indicate the results obtained for Examples 1 - 5, and Comparative Examples 1 and 2, respectively, the symbol “ A " the result obtained for Example 6, and the symbols “ ⁇ ” the results for Comparative Examples 3 - 7, respectively.
  • an aerosol booster was used as flame spray pyrolysis apparatus.
  • an oxygen gas feed was employed for the combustion, wherein natural gas was used for the flame.
  • the apparatus contained a water cooling unit for the cooling of the resulting particles from flame pyrolysis, which were then collected on a filter.
  • the nozzle used for the spraying of the precursor feed to form an aerosol had a diameter of 0.8 mm.
  • Example 6 For the synthesis of the mixed oxide particles in Example 6, a particle generator was employed of which the set-up is displayed in Figure 1 . In this set up, air was used for the combustion in Example 6 and ethylene was employed for the flame. The apparatus was insulated in the zone following the combustion, such that a large high temperature zone was utilized compared to the aerosol booster set-up. The resulting particles were collected on a filter. The nozzle used for the spraying of the precursor feed to form the aerosol has a diameter of 0.3 mm.
  • a flame spray pyrolysis apparatus as depicted in Figure 2 was employed. More specifically, the nozzles for the flame spray pyrolysis are located in the upper portion of a burning chamber. As indicated in Figure 2 (top view), the main nozzle for the vaporization of the precursor is located in the middle of the nozzle arrangement. Two lines are connected to said main nozzle wherein the first line is connected to a piston pump for pumping the precursor solution into the chamber. The second line provides air wherein the oxygen content thereof may be varied by the injection of oxygen or nitrogen therein. Both lines converge in the main nozzle.
  • Further nozzles are arranged around said main nozzle, wherein in the first half of said nozzles a gas mixture of air/oxygen/nitrogen is introduced and in the second half ethylene, respectively.
  • the further nozzles provide auxiliary flames for providing a constant temperature and a uniform combustion in the burning chamber.
  • a quench portion is provided for rapid cooling of the particles generated in the upper portion of the burning chamber. Determination of the Particle Size Distribution
  • Example 7 The particle size distribution of the mixed-oxide particles obtained in Example 7 was measured using a CPS Disc Centrifuge using propanol/water mixtures of varying concentration as the density gradient. For preparing the sample for measurement, 0.5 g of the sample were dis- persed in 100 ml propanol using an ultrasound sonotrode for 10 min. 0.1 - 0.2 ml of the resulting dispersion was then syringed into the CPS-centrifuge which was filled with the density gradient beforehand. Flame Spray Pyrolysis
  • Precursor solutions for Examples 1 -7 and Comparative Examples 1 and 2 were prepared as indicated in Table 1 by admixture of the respective precursor components with the solvent.
  • the resulting solvent containing cerium, zirconium, and palladium (furthermore lanthanum in Examples 6 and 7), were conveyed by a reciprocating piston pump (DESAGA - KP 2000, 0- 2000 ml/h) through the nozzle (0.3 mm in diameter for the particle generator, 0.8 mm for the aerosol booster).
  • Air particle generator
  • O2 aerosol booster
  • thermocouples three thermocouples in the particle generator, two in the aerosol booster. Below the flame, nitrogen was injected into the lower section of the reactors for subsequently quenching the particle-containing gas. One filter war used at a time to obtain the powder. The average yields were estimated to be 80%. The remaining 20% could be obtained from the combustion chamber, tubes and filters.
  • methane flow (reac1 ,000 1 ,000 300 300 300 —(3) —(3) 1 ,000 1 ,000 tor) [l/h]
  • Comparative Example 7 was prepared by co- precipitation of ceria with lanthana and yttria for demonstrating the effect of the latter on the per- formance of ceria in the comparative testing experiments discussed below. Comparative Example 7 contained a total of 10 wt.-% of lanthana and yttria in addition to ceria.
  • the BET surface area of the particles and the average diameter of the primary particles (crystallites) as determined by XRD as determined for the fresh samples is indicated in Table 2. Furthermore, the particle size distribution of the sample obtained for Example 7 was determined and is displayed in Figure 3, wherein furthermore the average d 10, d50, and d90 values are displayed in Table 2.
  • the catalytic activity of the samples from Examples 1 - 6 and Comparative Examples 1 - 7 was measured between 120°C and 300°C using a standard DOC test protocol without liquid hydrocarbons.
  • the T5o,co-values for the respective samples were determined, i.e. the temperature at which 50% conversion of CO in the feed gas is achieved after having passed the respective catalyst in the reactor.
  • the catalyst samples obtained from flame spray pyrolysis display constantly low Tso.co-values after aging, irrespective of their zirconia content.
  • the addition of zirconia to ceria in the samples from the comparative examples obtained according to a co- precipitation method leads to an increase in the Tso.co-values depending on the amount of ceria which has been substituted with zirconia.
  • Comparative Example 7 containing lanthana and yttria instead of zirconia already at low concentrations thereof the Tso.co-value increases considerably.
  • a highly improved process for the treatment of diesel exhaust gas is obtained according to the present invention when using ceria-zirconia mixed oxides obtained according to flame spray pyrolysis, in particular in view of the lower amount of mixed oxide which may be employed in a diesel oxidation catalyst for achieving the same results as when using ceria-zirconia mixed oxides obtained from co-precipitation.

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Abstract

La présente invention concerne un procédé pour le traitement de gaz d'échappement diesel comprenant (a) la fourniture d'un flux de gaz d'échappement diesel; (b) la mise en contact du flux de gaz d'échappement diesel fourni en (a) avec un catalyseur d'oxydation diesel; dans lequel le catalyseur d'oxydation diesel comprend des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium, dans lequel la taille moyenne de particule d50 des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium, de préférence des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium comme synthétisé, est comprise dans la plage allant de 5 nm à 40 µm.
PCT/EP2015/052749 2014-02-11 2015-02-10 Procédé de traitement de gaz d'échappement diesel utilisant des particules d'oxyde mixte d'oxyde de cérium et d'oxyde de zirconium produites par pyrolyse WO2015121248A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220325645A1 (en) * 2018-11-08 2022-10-13 Umicore Ag & Co. Kg High-filtration efficiency wall-flow filter
EP4096832A4 (fr) * 2020-01-30 2024-02-21 Pyrochem Catalyst Company Système de pyrolyse par pulvérisation et procédé de fabrication de compositions d'oxydes métalliques mixtes

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US20090325792A1 (en) * 2008-06-27 2009-12-31 Cabot Corporation Process for producing exhaust treatment catalyst powders, and their use
JP2010156206A (ja) * 2008-12-26 2010-07-15 Sumitomo Osaka Cement Co Ltd 排ガス浄化フィルタ
US20100183490A1 (en) * 2009-01-16 2010-07-22 BASF Catalystic LLC Diesel oxidation catalyst and use thereof in diesel and advanced combustion diesel engine systems
WO2012088373A2 (fr) * 2010-12-22 2012-06-28 Pacific Industrial Development Corporation Matériaux de support de catalyseur ayant la capacité de stocker de l'oxygène (osc) et leur procédé de fabrication
WO2013042080A1 (fr) * 2011-09-23 2013-03-28 Basf Se Catalyseur d'oxydation diesel à structure en couches, contenant une composition d'oxyde de cérium comme matériau de support de palladium pour conversion de gaz hc et co améliorée
US20130084222A1 (en) * 2011-09-23 2013-04-04 Basf Corporation Diesel Oxidation Catalyst with Layered Structure Containing Ceria Composition as Palladium Support Material for Enhanced HC and CO Gas Conversion

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090325792A1 (en) * 2008-06-27 2009-12-31 Cabot Corporation Process for producing exhaust treatment catalyst powders, and their use
JP2010156206A (ja) * 2008-12-26 2010-07-15 Sumitomo Osaka Cement Co Ltd 排ガス浄化フィルタ
US20100183490A1 (en) * 2009-01-16 2010-07-22 BASF Catalystic LLC Diesel oxidation catalyst and use thereof in diesel and advanced combustion diesel engine systems
WO2012088373A2 (fr) * 2010-12-22 2012-06-28 Pacific Industrial Development Corporation Matériaux de support de catalyseur ayant la capacité de stocker de l'oxygène (osc) et leur procédé de fabrication
WO2013042080A1 (fr) * 2011-09-23 2013-03-28 Basf Se Catalyseur d'oxydation diesel à structure en couches, contenant une composition d'oxyde de cérium comme matériau de support de palladium pour conversion de gaz hc et co améliorée
US20130084222A1 (en) * 2011-09-23 2013-04-04 Basf Corporation Diesel Oxidation Catalyst with Layered Structure Containing Ceria Composition as Palladium Support Material for Enhanced HC and CO Gas Conversion

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220325645A1 (en) * 2018-11-08 2022-10-13 Umicore Ag & Co. Kg High-filtration efficiency wall-flow filter
US11808189B2 (en) * 2018-11-08 2023-11-07 Umicore Ag & Co. Kg High-filtration efficiency wall-flow filter
EP4096832A4 (fr) * 2020-01-30 2024-02-21 Pyrochem Catalyst Company Système de pyrolyse par pulvérisation et procédé de fabrication de compositions d'oxydes métalliques mixtes

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