WO2010095761A2 - Catalyst for purification of exhaust gas and method of manufacturing the same - Google Patents

Catalyst for purification of exhaust gas and method of manufacturing the same Download PDF

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Publication number
WO2010095761A2
WO2010095761A2 PCT/JP2010/052909 JP2010052909W WO2010095761A2 WO 2010095761 A2 WO2010095761 A2 WO 2010095761A2 JP 2010052909 W JP2010052909 W JP 2010052909W WO 2010095761 A2 WO2010095761 A2 WO 2010095761A2
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Prior art keywords
metal
exhaust gas
catalyst
purification
support
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PCT/JP2010/052909
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French (fr)
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WO2010095761A3 (en
Inventor
Tsuyoshi Hamaguchi
Toshiyuki Tanaka
Masaoki Iwasaki
Chika Kato
Takeshi Nobukawa
Takashi Natsume
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Toyota Jidosha Kabushiki Kaisha
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Publication of WO2010095761A2 publication Critical patent/WO2010095761A2/en
Publication of WO2010095761A3 publication Critical patent/WO2010095761A3/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • 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
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
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Definitions

  • the present invention relates to a catalyst for purification of exhaust gas, a method of manufacturing the catalyst for purification of exhaust gas, and a method of purifying exhaust gas using the catalyst for purification of exhaust gas.
  • nitrogen oxide storage-reduction catalysts have been utilized to treat harmful nitrogen oxides contained in exhaust gas of automobiles and the like for purification.
  • nitrogen oxide storage-reduction catalysts which have been known include those obtained by supporting particles of a noble metal having a catalytic activity, such as Pt and Pd, and an alkali earth metal or an alkali metal, mainly such as barium, on a porous support such as a pellet or honeycomb formed body formed of a ceramic of alumina, zirconia or the like, or a metal honeycomb coated with a ceramic.
  • Patent Literature 1 Japanese Unexamined Patent Application Publication No. Hei 11-156193
  • Patent Literature 1 describes a catalyst for purification of exhaust gas comprising a support made of a metal oxide and metal particles supported on the support.
  • the metal particles includes particles of a first metal with an average particle diameter of 30 nm or less, and a layer made of one or more second metals other than the first metal, the layer being stacked on the particles of the first metal with a coverage of 45% or more.
  • Patent Literature 2 Japanese Unexamined Patent Application Publication No. 2004-267961
  • Patent Literature 3 each also describe a catalyst for purification of exhaust gas comprising a support made of a metal oxide, and metal particles supported on the support.
  • the metal particles are supported by use of a bimetallic colloid.
  • Patent Literatures 1 to 3 are not necessarily capable of sufficiently reducing nitrogen oxides stored in the catalysts, and thus are still unsatisfactory.
  • An object of the present invention is to provide: a catalyst for purification of exhaust gas capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same,- and a method of purifying exhaust gas using the same. [Solution to Problem]
  • the present inventors have earnestly studied in order to achieve the above object. As a result, the inventors have found that metal particles supported on a metal oxide can be classified into first metals which promote oxidation of nitrogen oxides and second metals which promote decomposition of nitrogen oxides . The inventors also have found that, when these metals are supported on a support made of a metal oxide, by disposing these metals as metal particles having a structure in which the first metal and the second metal are dissolved in each other to form a uniform solid solution, it is possible for the metal particles to exhibit a catalytic activity to sufficiently reduce nitrogen oxides. Such discovery has led the inventors to complete the present invention.
  • the catalyst for purification of exhaust gas of the present invention is a catalyst for purification of exhaust gas comprising: a support made of a metal oxide ; and metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less.
  • the first metal is Pt
  • the second metal is Pd
  • a method for manufacturing a catalyst for purification of exhaust gas is a method comprising: a step of supporting metal particles on a support made of a metal oxide, the metal particles being made of one metal of first metal and second metal, said first metal being at least one selected from the group consisting of Pt, Ag, Mn, Fe and
  • said second metal being at least one selected from the group consisting of Pd, Rh, Ir and Ru,- a step of heating the support with the metal particles supported thereon to 50 0 C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more, thereby dissolving hydrogen in the metal particles which remain in a solid state, a step of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support .
  • the manufacturing method of the present invention it is possible to obtain a catalyst for purification of exhaust gas whose average primary particle diameter of the metal particles made of the solid solution is 1.5 nm or less, and whose standard deviation in metal composition ratio of each primary particle of the metal particles made of the solid solution is 10% or less.
  • a method of purifying exhaust gas of the present invention is a method in which nitrogen oxides in exhaust gas are treated for purification by bringing the exhaust gas into contact with the catalyst for purification of exhaust gas in an oxygen-excess atmosphere .
  • a standard deviation in metal composition ratio of each primary particle of the metal particles be 10% or less .
  • Such a standard deviation is obtained as follows: 15 primary particles to be determined are sampled at random from primary particles of the metal • particles on the catalyst; the metal composition ratio of each of these primary particles is determined by TEM-EDX analysis; and then the standard deviation of the distribution of the obtained metal composition ratios is calculated.
  • the number of the measurement points (the number of primary particles determined) is set to 15, for the following reason. Specifically, no significant difference existed between a standard deviation in metal composition ratio obtained with 15 measurement points and a standard deviation in metal composition ratio obtained from calculation with the measurement points increased to more than 15 and with the observation area varied. Accordingly, sufficient reproducibility of standard deviation can be obtained, when the Standard deviation is obtained from 15 measurement points .
  • a measuring apparatus for the TEM-EDX analysis employed in the present invention a TEM-EDX apparatus which is a known transmission electron microscopy (TEM) equipped with a known energy-dispersive X-ray spectrometer (an EDX analyzer) can be used.
  • TEM transmission electron microscopy
  • an EDX analyzer an energy-dispersive X-ray spectrometer
  • an energy-dispersive X-ray fluorescence spectrum with a beam diameter from 1 to 2 nm and within the measurement point is obtained for a measurement -target metal particle on the catalyst for purification of exhaust gas.
  • the peak area attributable to the first metal element and the peak area attributable to the second metal element are found.
  • the ratio (peak area ratio (%) ) of the peak area of the first metal element to the sum of the peak area of the first metal element and the peak area of the second metal element is found.
  • peak area ratio is equal to the metal composition ratio of the primary particle of the measurement target metal particle.
  • peak herein refers to each peak in which a difference in intensity from the base line to the top of the peak in the spectrum is 1 cts or more. - For example, when the metal element is Pt, such a peak appears at a position which corresponds to an energy of 2.048 keV (Pt-Ma line), and when the metal element is Pd, such a peak appears at a poison of 2.838 keV (Pd-La line) .
  • the standard deviation of distribution of peak area ratios obtained as described above is found. Specifically, the TEM-EDX analysis is performed on 15 or more measurement points selected at random. Then, the peak area ratio at each of the measurement points is found. On the basis of the obtained peak area ratios, the standard deviation (%) of distribution of the peak area ratios can be found by calculation.
  • such a standard deviation of distribution of peak area ratios is 10% or less .
  • the first metal and the second metal are not dissolved in each other enough to form a sufficiently uniform solid solution, resulting in insufficient capability of reducing the stored nitrogen oxides.
  • the average primary particle diameter of the metal particles in the catalyst for purification of exhaust gas of the present invention needs to be 1.5 nm or less.
  • Such an average primary particle diameter can be found by a known CO chemisorption method.
  • the storage and the reduction of nitrogen oxides are not sufficiently promoted.
  • the first metal which promotes the oxidation of nitrogen oxides and the second metal which promotes the decomposition of nitrogen oxides are dissolved uniformly in each other in the metal particles made of small primary particles to form a solid solution. This allows the oxidation and the reduction of nitrogen oxides to proceed efficiently and reliably on the same metal particles.
  • the present inventors speculate that, as a result of this, a sufficiently high nitrogen oxides purification activity can be obtained.
  • the present invention it is possible to provide a catalyst for purification of exhaust gas capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same; and a method of purifying exhaust gas using the same.
  • Fig. 1 is a transmission electron microscopy (TEM) photograph showing a state of a certain region on a surface of a catalyst for purification of exhaust gas obtained in Example 1.
  • TEM transmission electron microscopy
  • Fig. 2 is a transmission electron microscopy (TEM) photograph showing a state of another certain region on a surface of the catalyst for purification of exhaust gas obtained in Example 1.
  • TEM transmission electron microscopy
  • Fig. 3 is a transmission electron microscopy (TEM) photograph showing a state of still another certain region on a surface of the catalyst for purification of exhaust gas obtained in Example 1.
  • TEM transmission electron microscopy
  • Fig. 4 is a transmission electron microscopy (TEM) photograph showing a state of a certain region on a surface of a catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • Fig. 5 is a transmission electron microscopy (TEM) photograph showing a state of another certain region on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • Fig. 6 is a transmission electron microscopy (TEM) photograph showing a state of still another certain region on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • TEM transmission electron microscopy
  • Fig. 7 is a graph showing energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on surfaces of metal particles of the catalyst for purification of exhaust gas obtained in Example 1.
  • Fig. 8 is a graph showing energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on surfaces of metal particles of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • Fig. 9 Fig. 9 is a graph showing conversion of nitrogen oxides to N 2 achieved with the catalysts for purification of exhaust gas obtained in Example 1 and Comparative Example 1 under a temperature condition of 300 0 C.
  • Fig. 10 is a graph showing conversion of nitrogen oxides to N 2 achieved with catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 2 under a temperature condition of 350 0 C.
  • Fig. 11 is a graph showing an average primary particle diameter of metal particles of catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 3. [Description of Embodiments]
  • the catalyst for purification of exhaust gas of the present invention comprises: a support made of a metal oxide ,- metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less.
  • the first metal used in the present invention is a metal which promotes the oxidation of nitrogen oxides, and is at least one selected from the group consisting of Pt, Ag, Mn, Fe and Au. Among those, from the viewpoint that the obtained catalyst tends to have a further improved performance of promoting the oxidation of nitrogen oxides, the first metal is more preferably Pt . Note that such first metals may be used alone or as a mixture of two or more .
  • the second metal used in the present invention is a metal which promotes the reduction of nitrogen oxides, and is at least one selected from the group consisting of Pd, Rh, Ir and Ru. Among these, from the viewpoint that the obtained catalyst tends to have a further improved performance of promoting the reduction of nitrogen oxides, the second metal is more preferably Pd. Note that such second metals may be used alone or as a mixture of two or more .
  • the first metal and the second metal need to be supported on the support as metal particles made of a solid solution of the first metal and the second metal .
  • the solid solution which is the structure of the metal particles , refers to a substance in which multiple elements
  • the composition ratio of the first metal and the second metal forming such a solid solution is not particularly limited, and it is preferable that the percentage of the number of atoms of the second metal to the total number of atoms of the first metal and the second metal be 10 to 90% by atom. If the concentration of the second metal is less than the lower limit, there is a tendency that the obtained catalyst does not sufficiently promote the reduction of nitrogen oxides. Meanwhile, if the concentration of the second metal exceeds the upper limit, there is a tendency that the obtained catalyst does not sufficiently promote the oxidation of nitrogen oxides.
  • the average primary particle diameter of the metal particles needs to be 1.5 nm or less, and is more preferably 0.3 to 1.3 nm. If an average primary particle diameter of the metal particles exceeds 1.5 nm, the obtained catalyst does not sufficiently promote the storage or the reduction of nitrogen oxides.
  • the standard deviation in metal composition ratio of each primary particle of the metal particles of the catalyst of the present invention needs to be 10% or less, and is more preferably 8% or less. If the standard deviation of the metal composition ratio exceeds 10%, the obtained catalyst does not sufficiently promote the oxidation or the reduction of nitrogen oxides.
  • the above -described metal particles are supported on the support made of the metal oxide .
  • the amount of the metal particles supported on the support is not particularly limited, and the amount of the metal particles is preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the support. If the amount of the metal particles supported is less than the lower limit, the catalytic activity achievable by the metal particles tends to be insufficient. Meanwhile, if the amount of the metal particles supported exceeds the upper limit, the cost for manufacturing the catalyst tends to be high and the grain growth of the metal particles is more likely to occur.
  • At least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba is preferably further supported on the support. From the viewpoints that such a third metal exhibits a sufficiently high nitrogen oxides storage performance when an oxide of the third metal is formed because of its high basicity, the third metal is preferably used. Among those, Ba is more preferably used. Note that such third metals may be used alone or as a mixture of two or more .
  • the amount of the third metal supported on the support is not particularly limited, and is preferably 0.05 mol/L or more, and more preferably 0.1 mol/L to 2.0 mol/L, relative to the volume of the support . If the amount of the third metal supported is less than the lower limit, the amount of nitrogen oxides stored by the obtained catalyst tends to be insufficient. Meanwhile, if the amount of the third metal supported exceeds the upper limit, the catalytic activity of the metal particles tends to be lowered.
  • the support made of a metal oxide employed in the present invention is not particularly limited, and preferably is made of alumina, zirconia, titania, or the like.
  • the shape of the support according to the present invention is not particularly limited, and a powder from is preferable because the specific surface area is improved, and because a higher catalytic activity can be obtained.
  • the particle size (secondary particle diameter) of the support is not particularly limited, and is preferably 1 to 100 ⁇ m. If the particle diameter of the support is less than the lower limit, there are tendencies that making the support fine is costly, and that the handling of the support becomes difficult. Meanwhile, if the particle diameter of the support exceeds the upper limit, it tends to be difficult to form stably a coat layer, of the catalyst for purification of exhaust gas of the present invention, on a substrate to be described later.
  • the specific surface area of such a support is preferably 20 m 2 /g or more, and further preferably 50 to 300 m 2 /g. If the specific surface area of the support is less than the lower limit , it tends to be difficult to support the metal particles having the oxidation and reduction performance in such an appropriate amount that a sufficient catalytic activity can be exhibited. Meanwhile, if the specific surface area of the support exceeds the upper limit, decrease in specific surface area due to thermal deterioration tends to be great. Note that such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm, by using the BET adsorption isotherm.
  • the method of manufacturing the catalyst for purification of exhaust of the present invention comprises:
  • the metal particles made of the first metal or the second metal be supported on the support, and a specific method for the first step is not particularly limited.
  • the support is immersed in a solution where the first metal or the second metal is dissolved in ionic state (for example, a solution of a dinitro diammine platinum complex or a solution of palladium nitrate) , and then the mixture is stirred to thereby causing the metal to selectively adsorb on the support .
  • a metal compound such as a salt (nitrate, acetate, carbonate, or the like) , a complex (a dinitro diammine complex or the like) , or a hydroxide, of the first metal or the second metal is suitably used.
  • a solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows the first metal or the second metal to be dissolved therein in ionic state.
  • the solvent is preferably water , because of its high affinity for the support .
  • the concentration of the metal in the solution is preferably 1% by mass or less, and more preferably 0.005 to 0.5% bymass. If the concentration exceeds 1% by mass, the first metal or the second metal is less likely to be supported on the support uniformly.
  • the treatment time in the first step is not particularly limited, and 0.5 to 3 hours is preferably employed in general .
  • the first metal or the second metal is uniformly supported on the support as metal particles with an average primary particle diameter being 1.5 nm or less (more preferably 0.3 to 1.3 nm) .
  • the support with the metal particles supported thereon is subjected to a drying treatment at 80 to 150 0 C for about 2 to 48 hours, if necessary, and then is subjected to the following second step.
  • the second step is the step of heating the support with the metal particles supported thereon to 50 0 C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more , thereby dissolving hydrogen in the metal particles which remain in a solid state .
  • the atmosphere needs to have a hydrogen concentration of 0.5% by volume or more, and more preferably has a hydrogen concentration of 1 to 6% by volume . If the hydrogen concentration is less than 0.5% by volume, the hydrogen cannot be sufficiently dissolved in the metal particles which are in solid state. Meanwhile, a hydrogen concentration exceeding 6% by volume tends to be dangerous, because the concentration exceeds the explosion limit concentration of hydrogen. Moreover, even with a hydrogen concentration exceeding 6% by volume, further improvement in effect tends to be unlikely to be obtained.
  • the treatment temperature in the second step needs to be 50 0 C or more, and is more preferably 100 0 C to 500 0 C. If the treatment temperature is less than 50 0 C, it is not possible to sufficiently dissolve hydrogen in the metal particles which are in a solid state. Meanwhile, if the treatment temperature exceeds 500 0 C, the metal particles tend to be sintered together, thereby increasing the average primary particle diameter of the metal particles.
  • the treatment time of the second step is not particularly limited, because the treatment time varies depending on the treatment temperature. In general, about 1 to 5 hours are suitably employed as the treatment time .
  • the balance gas used in the second step, other than hydrogen, is preferably an inert gas, and more preferably nitrogen or helium.
  • the amount of hydrogen dissolved through the second step in the metal particles which are in a solid state is not particularly limited. Such an amount of hydrogen as to enable a sufficient amount of metal to be reduced in the following third step is preferably uniformly dissolved in the metal particles which are in a solid state. Then, while being kept in an atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in a solid form and which have hydrogen dissolved therein is subjected to the third step.
  • the third step is the step of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support .
  • the method of keeping the support in an atmosphere having a hydrogen concentration of 0.5% by volume or more is not particularly limited, as long as the method allows the support to be prevented from exposure to a different atmosphere which has a hydrogen concentration exceeding 0.5% by volume.
  • the support is sealed in a container in which an atmosphere has a hydrogen concentration of 0.5% by volume or more, and transferred. Then, the support is immersed in the solution to be described below directly from the container.
  • a solution in which, of the first metal and the second metal, the metal (the other metal) which is not used in the first step is dissolved in ionic state for example, a solution of a dinitro diammine platinum complex or a solution of palladium nitrate
  • a metal compound such as a salt (a nitrate, an acetate, a carbonate, or the like) , a complex (a dinitro diammine complex or the like) , or a hydroxide, of the other metal is suitably used.
  • a solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows the other metal to be dissolved therein in ionic state.
  • the concentration of the other metal in the solution is preferably 1% by mass or less, and more preferably 0.005 to 0.5% by mass . If the concentration exceeds 1% by mass, the other metal is less likely to be deposited uniformly on the metal particles .
  • the treatment time in the third step is not particularly limited, and about 0.5 to 3 hours is suitably employed as the treatment time, in general .
  • the hydrogen dissolved through the second step in the metal particles which are in a solid state acts as a reductant in the solution, thereby reducing, on the metal particles, the other metal dissolved in ionic state, which results in deposition of the other metal on the metal particles.
  • the metal particles supported on the support are converted into a solid solution of the first metal and the second metal in the third step. Thereafter, the support supporting metal particles made of the solid solution is subjected to a drying treatment at 80 to 15O 0 C for 2 to 48 hours, if necessary. Moreover, if necessary, the resulting support is subjected to a heat treatment in an air atmosphere at 200 to 500 0 C for about 1 to 5 hours. Thereafter, the resulting material is used as a catalyst for purification of exhaust gas .
  • the catalyst for purification of exhaust gas of the present invention wherein the average primary particle diameter of the metal particles made of a solid solution of the first metal and the second metal is 1.5 nm or less , and the standard deviation in metal composition ratio of each primary particle of the metal particles made of the solid solution is 10% or less.
  • the first metal and the second metal are held, while being uniformly dissolved in each other to form a solid solution, the first metal and the second metal are sufficiently uniformly mixed with each other. Thereby, a sufficiently high reduction performance of nitrogen oxides is exhibited.
  • the manufacturing method of the present invention more preferably further comprises a step (a fourth step) of supporting at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba on the support supporting the metal particles made of the solid solution.
  • the specific method in the forth step is not particularly limited, as long as the method allows the third metal to be supported on the support supporting the metal particles made of the solid solution.
  • the support is immersed in a solution in which the third metal is dissolved in ionic state, and evaporation to dryness is performed.
  • a metal compound such as a salt (an acetate, a carbonate, a nitrate, or the like) , or a hydroxide, of the third metal is preferably used.
  • a solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows third metal be dissolved therein in ionic state.
  • the concentration of the metal in the solution is more preferably 0.001 to 2 mol/L .
  • the form of the catalyst for purification of exhaust gas of the present invention is not particularly limited, and the catalyst can be a monolithic catalyst with a honeycomb shape, a pelletized catalyst with a pellet shape, or the like.
  • the substrate used herein is also not particularly limited, and is selected as appropriate depending on the application or the like of the catalyst to be obtained.
  • a DPF substrate, a monolithic substrate, a pelletized substrate, a plate-shaped substrate, or the like is more suitably employed.
  • the material of such a substrate is not particularly limited, and suitably employed substrates are substrates made of ceramics such as cordierite, silicon carbide, and mullite, substrates made of metals such as stainless steel containing chromium and aluminum.
  • a method of manufacturing the catalyst using such a substrate is not particularly limited, and, for example, methods which can be employed are: a method in which a coat layer made of a powder of the support is formed by supporting the support on a monolithic substrate, then the metal particles are supported on the coat layer, and thereafter the third metal is supported on the coat layer; a method in which, using a support having the metal particles supported previously thereon, this support is supported on a monolithic substrate to form a coat layer, and thereafter the third metal is supported on the coat layer,- and other methods.
  • the method of purifying exhaust gas of the present invention is a method, wherein nitrogen oxides in exhaust gas are treated for purification by bringing the exhaust gas into contact with the above-described catalyst for purification of exhaust gas of the present invention in an oxygen-excess atmosphere .
  • oxygen-excess atmosphere in the present invention refers to an atmosphere containing oxidizing gases such as oxygen and nitrogen oxides in a stoichiometrically excessive amount over reducing gases such as H 2 , CO, and HC.
  • exhaust gas containing nitrogen oxides is brought into contact with the above-described catalyst for purification of exhaust gas of the present invention in such an oxygen-excess atmosphere .
  • the use of the catalyst for purification of exhaust gas of the present invention in the method of purifying exhaust gas of the present invention makes it possible to treat nitrogen oxides sufficiently for purification.
  • the method of purifying exhaust gas of the present invention can be employed as a method of purifying exhaust gas emitted from internal -combustion engines of automobiles or other emission sources, for example.
  • Example 1 First, 0.038g of Pd (NO 3 ) 2 was dissolved in 100 g of water to obtain an aqueous solution (Pd concentration: 0.0175% by mass) . To the aqueous solution, 10 g of an alumina powder (average secondary particle diameter: 8 ⁇ m, specific surface area: 200 m 2 /g) was added, and the mixture was stirred for one hour. Then, the resultant powder was taken out , and dried in an air atmosphere at 110 0 C for 24 hours. Thus, an alumina powder (Pd/Al 2 O 3 powder) on which palladium particles were supported was obtained (the first step) .
  • the Pd/Al 2 O 3 powder was placed in an atmosphere having a hydrogen concentration of 5% by volume (the balance gas was nitrogen) , and subjected to a hydrogenation treatment at 400 0 C for 3 hours .
  • an alumina powder (powder A) in which hydrogen was dissolved in the palladium particles which were in a solid state was obtained (the second step) .
  • the powder A was introduced into an aqueous solution (Pt concentration: 0.0425% by mass) obtained by dissolving 0.070 g of Pt (NO 2 ) 2 (NH 3 ) 2 in 100 g of water, directly from a container in which an atmosphere is kept to a hydrogen concentration of 5% by volume, without exposure to an air atmosphere.
  • the resultant powder was taken out, dried in an air atmosphere at 110 0 C for 24 hours, and further subjected to a heat treatment in an air atmosphere at 300 0 C for 3 hours.
  • an aluminum powder (powder B) supporting metal particles made of a solid solution of palladium and platinum was obtained (the third step) .
  • the powder B was immersed in an aqueous solution containing (CH 3 COO) 2 Ba, CH 3 COOK and CH 3 COOLi (Ba concentration: 0.1 mol/L, K concentration: 0.1 mol/L, Li concentration: 0.2 mol/L) . Thereafter, the resultant powder was taken out, and dried in an air atmosphere at 110 0 C for 24 hours, for evaporation to dryness. Moreover, the dried powder was subjected to a heat treatment in an air atmosphere at 300 0 C for 3 hours. Thus, a catalyst for purification of exhaust gas was obtained (the fourth step) .
  • the amount of metal particles which are made of the solid solution of palladium and platinum and supported in the obtained catalyst was 0.60 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum in the obtained catalyst was (Pd) 3% by atom: (Pt) 4% by atom.
  • the amounts of Ba, K and Li supported in the obtained catalyst were 0.1 mol/100 g, 0.1 mol/100 g, and 0.2 mol/100 g, respectively, relative to 100 parts by mass of the alumina powder.
  • the total amount of palladium and platinum supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
  • Example 2 A catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that, since the inside of a container in which the powder A was placed was purged with nitrogen gas after the hydrogenation treatment in the second step, the powder A was introduced into the aqueous solution in the third step after being exposed to a nitrogen atmosphere.
  • the amount of metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
  • TEM-EDX Analysis The catalysts for purification of exhaust gas obtained in Example 1 and Comparative Examples 1 and 2 were subjected to TEM-EDX analysis by the above-described method using an analyzer manufactured by JEOL Ltd. , under the trade name of "JEM-2010FEF.”
  • Figs. 1 to 3 show transmission electron microscopy (TEM) photographs of the catalyst for purification of exhaust gas obtained in Example 1
  • Figs. 4 to 6 show transmission electron microscopy (TEM) photographs of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • the symbols "x" marked with 001 to 015 shown in Figs . 1 to 6 represent measurement points for the EDX analysis.
  • FIG. 7 shows energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on a surface of the catalyst for purification of exhaust gas obtained in Example 1.
  • Fig. 8 shows energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
  • the catalyst for purification of exhaust gas (Example 1) of the present invention exhibited an excellent purification ratio of nitrogen oxides.
  • the purification ratio of nitrogen oxides was low.
  • the results showed that the catalyst for purification of exhaust gas of the present invention was capable of exhibiting a high purification performance of nitrogen oxides, since the obtained metal particles being a solid solution in which Pt and Pd were sufficiently uniformly dissolved were supported on the metal oxide support .
  • a catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the hydrogen concentration in the second step was 1% by volume.
  • Example 3 the amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Moreover, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1. (Example 3)
  • a catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the temperature for the hydrogenation treatment in the second step was 100 0 C.
  • the amount of metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom.
  • each of the amounts of Ba, K and Li supported in the obtained catalyst was the same as that obtained in Example 1. (Example 4)
  • a catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the temperature for the hydrogenation treatment in the second step was changed to 200 0 C.
  • the amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1. (Example 5)
  • a catalyst for purification of exhaust gas was obtained by the same method as in Example 1 , except that the temperature for the hydrogenation treatment in the second step was changed to 300 0 C.
  • the amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom.
  • each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
  • Purification ratio of nitrogen oxides was determined by employing the same method as in Nitrogen Oxides Treatment Test 1 described above, except that this test was performed by using the catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 2, at 350 0 C.
  • Fig. 10 shows the results. As apparent from the results shown in Fig. 10, each of the catalysts for purification of exhaust gas of the present invention (Examples 1 to 5) exhibited an excellent purification ratio of nitrogen oxides. In contrast, in the case (Comparative Example 2) where the catalyst for purification of exhaust gas according to the present invention was not used, the purification ratio of nitrogen oxides was low.
  • Example 2 a catalyst for purification of exhaust gas was obtained.
  • the total amount of palladium and platinum supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom.
  • each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
  • the average primary particle diameter of the metal particles supported in each of the catalysts for purification of exhaust gas of the present invention was 1.5 nm or less, which was sufficiently small.
  • the primary particle diameter of the metal particles was greater than 1.5 nm.
  • the results showed that, in each of the catalysts for purification of exhaust gas of the present invention, the average primary particle diameter of metal particles made of a solid solution of Pt and Pd was sufficiently small.
  • a catalyst for purification of exhaust gas in which a first metal and a second metal in a state of a uniform solid solution are supported on a metal oxide, capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same; and a method of purifying exhaust gas using the same .

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Abstract

A catalyst for purification of exhaust gas comprising: a support made of a metal oxide; and metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less.

Description

[DESCRIPTION] [Title of Invention]
CATALYST FOR PURIFICATION OF EXHAUST GAS AND METHOD OF MANUFACTURING THE SAME [Technical Field]
The present invention relates to a catalyst for purification of exhaust gas, a method of manufacturing the catalyst for purification of exhaust gas, and a method of purifying exhaust gas using the catalyst for purification of exhaust gas.
[Background Art]
Conventionally, nitrogen oxide storage-reduction catalysts have been utilized to treat harmful nitrogen oxides contained in exhaust gas of automobiles and the like for purification. Examples of such nitrogen oxide storage-reduction catalysts which have been known include those obtained by supporting particles of a noble metal having a catalytic activity, such as Pt and Pd, and an alkali earth metal or an alkali metal, mainly such as barium, on a porous support such as a pellet or honeycomb formed body formed of a ceramic of alumina, zirconia or the like, or a metal honeycomb coated with a ceramic.
However, such nitrogen oxide storage-reduction catalysts have a problem of insufficient reduction of nitrogen oxides stored in the catalysts.
To solve the above problem, for example, Japanese Unexamined Patent Application Publication No. Hei 11-156193 (Patent Literature 1) describes a catalyst for purification of exhaust gas comprising a support made of a metal oxide and metal particles supported on the support. In the catalyst, the metal particles includes particles of a first metal with an average particle diameter of 30 nm or less, and a layer made of one or more second metals other than the first metal, the layer being stacked on the particles of the first metal with a coverage of 45% or more. Japanese Unexamined Patent Application Publication No.
2002-1119 (Patent Literature 2) and Japanese Unexamined Patent Application Publication No. 2004-267961 (Patent Literature 3) each also describe a catalyst for purification of exhaust gas comprising a support made of a metal oxide, and metal particles supported on the support. In the catalyst, the metal particles are supported by use of a bimetallic colloid.
However, even the catalysts described in Patent Literatures 1 to 3 are not necessarily capable of sufficiently reducing nitrogen oxides stored in the catalysts, and thus are still unsatisfactory. [Citation List] [Patent Literature]
[PTL 1] Japanese Unexamined Patent Application Publication No. Hei 11-156193 [PTL 2] Japanese Unexamined Patent Application
Publication No. 2002-1119 [PTL 3] Japanese Unexamined Patent Application Publication No. 2004-267961 [Summary of Invention] [Technical Problem] The present invention has been made in consideration of the above-described problems of the conventional techniques. An object of the present invention is to provide: a catalyst for purification of exhaust gas capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same,- and a method of purifying exhaust gas using the same. [Solution to Problem]
The present inventors have earnestly studied in order to achieve the above object. As a result, the inventors have found that metal particles supported on a metal oxide can be classified into first metals which promote oxidation of nitrogen oxides and second metals which promote decomposition of nitrogen oxides . The inventors also have found that, when these metals are supported on a support made of a metal oxide, by disposing these metals as metal particles having a structure in which the first metal and the second metal are dissolved in each other to form a uniform solid solution, it is possible for the metal particles to exhibit a catalytic activity to sufficiently reduce nitrogen oxides. Such discovery has led the inventors to complete the present invention.
The catalyst for purification of exhaust gas of the present invention is a catalyst for purification of exhaust gas comprising: a support made of a metal oxide ; and metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less.
In the catalyst for purification of exhaust gas of the present invention, it is especially preferable that the first metal is Pt, and the second metal is Pd.
In the catalyst for purification of exhaust gas of the present invention, it is further preferable that at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba is further supported on the support. A method for manufacturing a catalyst for purification of exhaust gas is a method comprising: a step of supporting metal particles on a support made of a metal oxide, the metal particles being made of one metal of first metal and second metal, said first metal being at least one selected from the group consisting of Pt, Ag, Mn, Fe and
Au, said second metal being at least one selected from the group consisting of Pd, Rh, Ir and Ru,- a step of heating the support with the metal particles supported thereon to 500C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more, thereby dissolving hydrogen in the metal particles which remain in a solid state, a step of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support .
According to the manufacturing method of the present invention, it is possible to obtain a catalyst for purification of exhaust gas whose average primary particle diameter of the metal particles made of the solid solution is 1.5 nm or less, and whose standard deviation in metal composition ratio of each primary particle of the metal particles made of the solid solution is 10% or less. In the manufacturing method of the present invention, it is preferable to further comprise a step of supporting at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba on the support supporting the metal particles made of the solid solution.
A method of purifying exhaust gas of the present invention is a method in which nitrogen oxides in exhaust gas are treated for purification by bringing the exhaust gas into contact with the catalyst for purification of exhaust gas in an oxygen-excess atmosphere .
Note that, in the catalyst for purification of exhaust gas of the present invention, it is necessary that a standard deviation in metal composition ratio of each primary particle of the metal particles be 10% or less . Such a standard deviation is obtained as follows: 15 primary particles to be determined are sampled at random from primary particles of the metal • particles on the catalyst; the metal composition ratio of each of these primary particles is determined by TEM-EDX analysis; and then the standard deviation of the distribution of the obtained metal composition ratios is calculated.
Here, the number of the measurement points (the number of primary particles determined) is set to 15, for the following reason. Specifically, no significant difference existed between a standard deviation in metal composition ratio obtained with 15 measurement points and a standard deviation in metal composition ratio obtained from calculation with the measurement points increased to more than 15 and with the observation area varied. Accordingly, sufficient reproducibility of standard deviation can be obtained, when the Standard deviation is obtained from 15 measurement points . Meanwhile, as a measuring apparatus for the TEM-EDX analysis employed in the present invention, a TEM-EDX apparatus which is a known transmission electron microscopy (TEM) equipped with a known energy-dispersive X-ray spectrometer (an EDX analyzer) can be used.
In such a TEM-EDX analysis, first, by using a TEM-EDX apparatus, an energy-dispersive X-ray fluorescence spectrum with a beam diameter from 1 to 2 nm and within the measurement point is obtained for a measurement -target metal particle on the catalyst for purification of exhaust gas. From the energy-dispersive X-ray fluorescence spectrum, the peak area attributable to the first metal element and the peak area attributable to the second metal element are found. Then, the ratio (peak area ratio (%) ) of the peak area of the first metal element to the sum of the peak area of the first metal element and the peak area of the second metal element is found. Thus obtained peak area ratio is equal to the metal composition ratio of the primary particle of the measurement target metal particle. Note that, such a peak area ratio can be calculated on the basis of the following formula: [peak area ratio (%)]={ [peak area of first metal element] /( [peak area of first metal element] + [peak area of second metal element] )} χlOO . The term "peak" herein refers to each peak in which a difference in intensity from the base line to the top of the peak in the spectrum is 1 cts or more. - For example, when the metal element is Pt, such a peak appears at a position which corresponds to an energy of 2.048 keV (Pt-Ma line), and when the metal element is Pd, such a peak appears at a poison of 2.838 keV (Pd-La line) . Next, the standard deviation of distribution of peak area ratios obtained as described above is found. Specifically, the TEM-EDX analysis is performed on 15 or more measurement points selected at random. Then, the peak area ratio at each of the measurement points is found. On the basis of the obtained peak area ratios, the standard deviation (%) of distribution of the peak area ratios can be found by calculation.
In the catalyst for purification of exhaust gas of the present invention, such a standard deviation of distribution of peak area ratios (the standard deviation of metal composition ratio of each primary particle of the metal particles) is 10% or less . In a catalyst for purification of exhaust gas with such a standard deviation exceeding 10%, the first metal and the second metal are not dissolved in each other enough to form a sufficiently uniform solid solution, resulting in insufficient capability of reducing the stored nitrogen oxides.
Meanwhile, the average primary particle diameter of the metal particles in the catalyst for purification of exhaust gas of the present invention needs to be 1.5 nm or less. Such an average primary particle diameter can be found by a known CO chemisorption method. In a catalyst for purification of exhaust gas with such an average primary particle diameter of the metal particles exceeding 1.5 nm, the storage and the reduction of nitrogen oxides are not sufficiently promoted.
Note that , it is not exactly known why the catalyst for purification of exhaust gas of the present invention can achieve a sufficiently excellent reduction performance of nitrogen oxides. However, the present inventors speculate as follows.
Specifically, in the catalyst for purification of exhaust gas of the present invention, the first metal which promotes the oxidation of nitrogen oxides and the second metal which promotes the decomposition of nitrogen oxides are dissolved uniformly in each other in the metal particles made of small primary particles to form a solid solution. This allows the oxidation and the reduction of nitrogen oxides to proceed efficiently and reliably on the same metal particles. The present inventors speculate that, as a result of this, a sufficiently high nitrogen oxides purification activity can be obtained.
[Advantageous Effects of Invention]
According to the present invention, it is possible to provide a catalyst for purification of exhaust gas capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same; and a method of purifying exhaust gas using the same.
[Brief Description of Drawings] [Fig. 1] Fig. 1 is a transmission electron microscopy (TEM) photograph showing a state of a certain region on a surface of a catalyst for purification of exhaust gas obtained in Example 1.
[Fig. 2] Fig. 2 is a transmission electron microscopy (TEM) photograph showing a state of another certain region on a surface of the catalyst for purification of exhaust gas obtained in Example 1.
[Fig. 3] Fig. 3 is a transmission electron microscopy (TEM) photograph showing a state of still another certain region on a surface of the catalyst for purification of exhaust gas obtained in Example 1.
[Fig. 4] Fig. 4 is a transmission electron microscopy (TEM) photograph showing a state of a certain region on a surface of a catalyst for purification of exhaust gas obtained in Comparative Example 1. [Fig. 5] Fig. 5 is a transmission electron microscopy (TEM) photograph showing a state of another certain region on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
[Fig. 6] Fig. 6 is a transmission electron microscopy (TEM) photograph showing a state of still another certain region on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
[Fig. 7] Fig. 7 is a graph showing energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on surfaces of metal particles of the catalyst for purification of exhaust gas obtained in Example 1. [Fig. 8] Fig. 8 is a graph showing energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on surfaces of metal particles of the catalyst for purification of exhaust gas obtained in Comparative Example 1. [Fig. 9] Fig. 9 is a graph showing conversion of nitrogen oxides to N2 achieved with the catalysts for purification of exhaust gas obtained in Example 1 and Comparative Example 1 under a temperature condition of 3000C.
[Fig. 10] Fig. 10 is a graph showing conversion of nitrogen oxides to N2 achieved with catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 2 under a temperature condition of 3500C.
[Fig. 11] Fig. 11 is a graph showing an average primary particle diameter of metal particles of catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 3. [Description of Embodiments]
Hereinafter, the present invention will be described in detail on the basis of preferred embodiments thereof. First, a catalyst for purification of exhaust gas of the present invention will be described. The catalyst for purification of exhaust gas of the present invention comprises: a support made of a metal oxide ,- metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less.
The first metal used in the present invention is a metal which promotes the oxidation of nitrogen oxides, and is at least one selected from the group consisting of Pt, Ag, Mn, Fe and Au. Among those, from the viewpoint that the obtained catalyst tends to have a further improved performance of promoting the oxidation of nitrogen oxides, the first metal is more preferably Pt . Note that such first metals may be used alone or as a mixture of two or more . Meanwhile, the second metal used in the present invention is a metal which promotes the reduction of nitrogen oxides, and is at least one selected from the group consisting of Pd, Rh, Ir and Ru. Among these, from the viewpoint that the obtained catalyst tends to have a further improved performance of promoting the reduction of nitrogen oxides, the second metal is more preferably Pd. Note that such second metals may be used alone or as a mixture of two or more .
In the catalyst of the present invention, the first metal and the second metal need to be supported on the support as metal particles made of a solid solution of the first metal and the second metal . The solid solution, which is the structure of the metal particles , refers to a substance in which multiple elements
(the first metal and the second metal) are dissolved in each other to form a solid phase. The composition ratio of the first metal and the second metal forming such a solid solution is not particularly limited, and it is preferable that the percentage of the number of atoms of the second metal to the total number of atoms of the first metal and the second metal be 10 to 90% by atom. If the concentration of the second metal is less than the lower limit, there is a tendency that the obtained catalyst does not sufficiently promote the reduction of nitrogen oxides. Meanwhile, if the concentration of the second metal exceeds the upper limit, there is a tendency that the obtained catalyst does not sufficiently promote the oxidation of nitrogen oxides.
Moreover, in the catalyst of the present invention, the average primary particle diameter of the metal particles needs to be 1.5 nm or less, and is more preferably 0.3 to 1.3 nm. If an average primary particle diameter of the metal particles exceeds 1.5 nm, the obtained catalyst does not sufficiently promote the storage or the reduction of nitrogen oxides. Moreover, the standard deviation in metal composition ratio of each primary particle of the metal particles of the catalyst of the present invention needs to be 10% or less, and is more preferably 8% or less. If the standard deviation of the metal composition ratio exceeds 10%, the obtained catalyst does not sufficiently promote the oxidation or the reduction of nitrogen oxides. In the catalyst for purification of exhaust gas of the present invention, the above -described metal particles are supported on the support made of the metal oxide . In the catalyst for purification of exhaust gas of the present invention, the amount of the metal particles supported on the support is not particularly limited, and the amount of the metal particles is preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the support. If the amount of the metal particles supported is less than the lower limit, the catalytic activity achievable by the metal particles tends to be insufficient. Meanwhile, if the amount of the metal particles supported exceeds the upper limit, the cost for manufacturing the catalyst tends to be high and the grain growth of the metal particles is more likely to occur. In the catalyst for purification of exhaust gas of the present invention, at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba is preferably further supported on the support. From the viewpoints that such a third metal exhibits a sufficiently high nitrogen oxides storage performance when an oxide of the third metal is formed because of its high basicity, the third metal is preferably used. Among those, Ba is more preferably used. Note that such third metals may be used alone or as a mixture of two or more . In the catalyst for purification of exhaust gas of the present invention, the amount of the third metal supported on the support is not particularly limited, and is preferably 0.05 mol/L or more, and more preferably 0.1 mol/L to 2.0 mol/L, relative to the volume of the support . If the amount of the third metal supported is less than the lower limit, the amount of nitrogen oxides stored by the obtained catalyst tends to be insufficient. Meanwhile, if the amount of the third metal supported exceeds the upper limit, the catalytic activity of the metal particles tends to be lowered.
The support made of a metal oxide employed in the present invention is not particularly limited, and preferably is made of alumina, zirconia, titania, or the like. Moreover, the shape of the support according to the present invention is not particularly limited, and a powder from is preferable because the specific surface area is improved, and because a higher catalytic activity can be obtained. When such a support takes a powder form, the particle size (secondary particle diameter) of the support is not particularly limited, and is preferably 1 to 100 μm. If the particle diameter of the support is less than the lower limit, there are tendencies that making the support fine is costly, and that the handling of the support becomes difficult. Meanwhile, if the particle diameter of the support exceeds the upper limit, it tends to be difficult to form stably a coat layer, of the catalyst for purification of exhaust gas of the present invention, on a substrate to be described later.
The specific surface area of such a support is preferably 20 m2/g or more, and further preferably 50 to 300 m2/g. If the specific surface area of the support is less than the lower limit , it tends to be difficult to support the metal particles having the oxidation and reduction performance in such an appropriate amount that a sufficient catalytic activity can be exhibited. Meanwhile, if the specific surface area of the support exceeds the upper limit, decrease in specific surface area due to thermal deterioration tends to be great. Note that such a specific surface area can be calculated as a BET specific surface area from an adsorption isotherm, by using the BET adsorption isotherm.
Hereinabove, the catalyst for purification of exhaust gas of the present invention has been described. Next, a method of manufacturing the catalyst for purification of exhaust gas of the present invention will be described.
The method of manufacturing the catalyst for purification of exhaust of the present invention comprises:
(1) a step (first step) of supporting metal particles on a support made of a metal oxide, the metal particles being made of one metal of first metal and second metal, said first metal being at least one selected from the group consisting of Pt, Ag, Mn, Fe and Au, said second metal being at least one selected from the group consisting of Pd, Rh, Ir and Ru;
(2) a step (second step) of heating the support with the metal particles supported thereon to 5O0C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more, thereby dissolving hydrogen in the metal particles which remain in a solid state,
(3) a step (third step) of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support .
In the first step, it is only necessary that the metal particles made of the first metal or the second metal be supported on the support, and a specific method for the first step is not particularly limited. In an example of the method suitably used in the step, the support is immersed in a solution where the first metal or the second metal is dissolved in ionic state (for example, a solution of a dinitro diammine platinum complex or a solution of palladium nitrate) , and then the mixture is stirred to thereby causing the metal to selectively adsorb on the support . For the preparation of such a solution, a metal compound, such as a salt (nitrate, acetate, carbonate, or the like) , a complex (a dinitro diammine complex or the like) , or a hydroxide, of the first metal or the second metal is suitably used. A solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows the first metal or the second metal to be dissolved therein in ionic state. The solvent is preferably water , because of its high affinity for the support . Moreover, the concentration of the metal in the solution is preferably 1% by mass or less, and more preferably 0.005 to 0.5% bymass. If the concentration exceeds 1% by mass, the first metal or the second metal is less likely to be supported on the support uniformly. In addition, the treatment time in the first step is not particularly limited, and 0.5 to 3 hours is preferably employed in general .
As a result of such a first step, the first metal or the second metal is uniformly supported on the support as metal particles with an average primary particle diameter being 1.5 nm or less (more preferably 0.3 to 1.3 nm) . Then, the support with the metal particles supported thereon is subjected to a drying treatment at 80 to 1500C for about 2 to 48 hours, if necessary, and then is subjected to the following second step.
The second step is the step of heating the support with the metal particles supported thereon to 500C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more , thereby dissolving hydrogen in the metal particles which remain in a solid state . In the second step , the atmosphere needs to have a hydrogen concentration of 0.5% by volume or more, and more preferably has a hydrogen concentration of 1 to 6% by volume . If the hydrogen concentration is less than 0.5% by volume, the hydrogen cannot be sufficiently dissolved in the metal particles which are in solid state. Meanwhile, a hydrogen concentration exceeding 6% by volume tends to be dangerous, because the concentration exceeds the explosion limit concentration of hydrogen. Moreover, even with a hydrogen concentration exceeding 6% by volume, further improvement in effect tends to be unlikely to be obtained. Meanwhile, the treatment temperature in the second step needs to be 500C or more, and is more preferably 1000C to 5000C. If the treatment temperature is less than 500C, it is not possible to sufficiently dissolve hydrogen in the metal particles which are in a solid state. Meanwhile, if the treatment temperature exceeds 5000C, the metal particles tend to be sintered together, thereby increasing the average primary particle diameter of the metal particles. Moreover, the treatment time of the second step is not particularly limited, because the treatment time varies depending on the treatment temperature. In general, about 1 to 5 hours are suitably employed as the treatment time . The balance gas used in the second step, other than hydrogen, is preferably an inert gas, and more preferably nitrogen or helium.
The amount of hydrogen dissolved through the second step in the metal particles which are in a solid state is not particularly limited. Such an amount of hydrogen as to enable a sufficient amount of metal to be reduced in the following third step is preferably uniformly dissolved in the metal particles which are in a solid state. Then, while being kept in an atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in a solid form and which have hydrogen dissolved therein is subjected to the third step. The third step is the step of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support . The method of keeping the support in an atmosphere having a hydrogen concentration of 0.5% by volume or more is not particularly limited, as long as the method allows the support to be prevented from exposure to a different atmosphere which has a hydrogen concentration exceeding 0.5% by volume. In a method preferably employed as such a method, the support is sealed in a container in which an atmosphere has a hydrogen concentration of 0.5% by volume or more, and transferred. Then, the support is immersed in the solution to be described below directly from the container. In the third step, a solution in which, of the first metal and the second metal, the metal (the other metal) which is not used in the first step is dissolved in ionic state (for example, a solution of a dinitro diammine platinum complex or a solution of palladium nitrate) is used. For the preparation of such a solution, a metal compound, such as a salt (a nitrate, an acetate, a carbonate, or the like) , a complex (a dinitro diammine complex or the like) , or a hydroxide, of the other metal is suitably used. Meanwhile, a solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows the other metal to be dissolved therein in ionic state. In view of the high affinity for the support, water is preferable as the solvent. Moreover, the concentration of the other metal in the solution is preferably 1% by mass or less, and more preferably 0.005 to 0.5% by mass . If the concentration exceeds 1% by mass, the other metal is less likely to be deposited uniformly on the metal particles . Meanwhile, the treatment time in the third step is not particularly limited, and about 0.5 to 3 hours is suitably employed as the treatment time, in general .
The phenomena occurring in such a third step is not exactly known,- however, the present inventors speculate that the hydrogen dissolved through the second step in the metal particles which are in a solid state acts as a reductant in the solution, thereby reducing, on the metal particles, the other metal dissolved in ionic state, which results in deposition of the other metal on the metal particles. The metal particles supported on the support are converted into a solid solution of the first metal and the second metal in the third step. Thereafter, the support supporting metal particles made of the solid solution is subjected to a drying treatment at 80 to 15O0C for 2 to 48 hours, if necessary. Moreover, if necessary, the resulting support is subjected to a heat treatment in an air atmosphere at 200 to 5000C for about 1 to 5 hours. Thereafter, the resulting material is used as a catalyst for purification of exhaust gas .
According to the above-described manufacturing method of the present invention, it is possible to obtain the catalyst for purification of exhaust gas of the present invention, wherein the average primary particle diameter of the metal particles made of a solid solution of the first metal and the second metal is 1.5 nm or less , and the standard deviation in metal composition ratio of each primary particle of the metal particles made of the solid solution is 10% or less. In the catalyst for purification of exhaust gas of the present invention, in which the first metal and the second metal are held, while being uniformly dissolved in each other to form a solid solution, the first metal and the second metal are sufficiently uniformly mixed with each other. Thereby, a sufficiently high reduction performance of nitrogen oxides is exhibited. By bringing this catalyst into contact with nitrogen oxides, a sufficient amount of nitrogen oxides can be efficiently stored and reduced. In addition, the manufacturing method of the present invention more preferably further comprises a step (a fourth step) of supporting at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba on the support supporting the metal particles made of the solid solution.
The specific method in the forth step is not particularly limited, as long as the method allows the third metal to be supported on the support supporting the metal particles made of the solid solution. In an example of the method suitably used in the step, the support is immersed in a solution in which the third metal is dissolved in ionic state, and evaporation to dryness is performed. For the preparation of such a solution, a metal compound, such as a salt (an acetate, a carbonate, a nitrate, or the like) , or a hydroxide, of the third metal is preferably used. In addition, a solvent used for the preparation of the solution is not particularly limited, as long as the solvent allows third metal be dissolved therein in ionic state. In view of high affinity for the support, water is preferable as the solvent. Moreover, the concentration of the metal in the solution is more preferably 0.001 to 2 mol/L . Then, the support on which the third metal is supported in the fourth step is subjected to a heat treatment in an air atmosphere at 200 to 5000C for about 1 to 5 hours, if necessary. Then, the resultant substance is used as a catalyst for purification of exhaust gas .
Note that the form of the catalyst for purification of exhaust gas of the present invention is not particularly limited, and the catalyst can be a monolithic catalyst with a honeycomb shape, a pelletized catalyst with a pellet shape, or the like. The substrate used herein is also not particularly limited, and is selected as appropriate depending on the application or the like of the catalyst to be obtained. As the substrate, a DPF substrate, a monolithic substrate, a pelletized substrate, a plate-shaped substrate, or the like is more suitably employed. In addition, the material of such a substrate is not particularly limited, and suitably employed substrates are substrates made of ceramics such as cordierite, silicon carbide, and mullite, substrates made of metals such as stainless steel containing chromium and aluminum. Moreover, a method of manufacturing the catalyst using such a substrate is not particularly limited, and, for example, methods which can be employed are: a method in which a coat layer made of a powder of the support is formed by supporting the support on a monolithic substrate, then the metal particles are supported on the coat layer, and thereafter the third metal is supported on the coat layer; a method in which, using a support having the metal particles supported previously thereon, this support is supported on a monolithic substrate to form a coat layer, and thereafter the third metal is supported on the coat layer,- and other methods.
Hereinabove, the method of manufacturing a catalyst for purification of exhaust gas of the present invention has been described. Next, a method of purifying exhaust gas of the present invention will be described below.
The method of purifying exhaust gas of the present invention is a method, wherein nitrogen oxides in exhaust gas are treated for purification by bringing the exhaust gas into contact with the above-described catalyst for purification of exhaust gas of the present invention in an oxygen-excess atmosphere .
The term "oxygen-excess atmosphere" in the present invention refers to an atmosphere containing oxidizing gases such as oxygen and nitrogen oxides in a stoichiometrically excessive amount over reducing gases such as H2, CO, and HC. In the present invention, exhaust gas containing nitrogen oxides is brought into contact with the above-described catalyst for purification of exhaust gas of the present invention in such an oxygen-excess atmosphere . As described above , the use of the catalyst for purification of exhaust gas of the present invention in the method of purifying exhaust gas of the present invention makes it possible to treat nitrogen oxides sufficiently for purification. For this reason, the method of purifying exhaust gas of the present invention can be employed as a method of purifying exhaust gas emitted from internal -combustion engines of automobiles or other emission sources, for example. [Examples]
Hereinafter, the present invention will be described more specifically on the basis of Examples and Comparative Examples; however, the present invention is not limited to the following Examples .
(Example 1) First, 0.038g of Pd (NO3) 2 was dissolved in 100 g of water to obtain an aqueous solution (Pd concentration: 0.0175% by mass) . To the aqueous solution, 10 g of an alumina powder (average secondary particle diameter: 8 μm, specific surface area: 200 m2/g) was added, and the mixture was stirred for one hour. Then, the resultant powder was taken out , and dried in an air atmosphere at 1100C for 24 hours. Thus, an alumina powder (Pd/Al2O3 powder) on which palladium particles were supported was obtained (the first step) . Next, the Pd/Al2O3 powder was placed in an atmosphere having a hydrogen concentration of 5% by volume (the balance gas was nitrogen) , and subjected to a hydrogenation treatment at 4000C for 3 hours . Thus , an alumina powder (powder A) in which hydrogen was dissolved in the palladium particles which were in a solid state was obtained (the second step) .
Subsequently, the powder A was introduced into an aqueous solution (Pt concentration: 0.0425% by mass) obtained by dissolving 0.070 g of Pt (NO2) 2 (NH3) 2 in 100 g of water, directly from a container in which an atmosphere is kept to a hydrogen concentration of 5% by volume, without exposure to an air atmosphere. After one-hour stirring, the resultant powder was taken out, dried in an air atmosphere at 1100C for 24 hours, and further subjected to a heat treatment in an air atmosphere at 3000C for 3 hours. Thus, an aluminum powder (powder B) supporting metal particles made of a solid solution of palladium and platinum was obtained (the third step) . Moreover, the powder B was immersed in an aqueous solution containing (CH3COO)2Ba, CH3COOK and CH3COOLi (Ba concentration: 0.1 mol/L, K concentration: 0.1 mol/L, Li concentration: 0.2 mol/L) . Thereafter, the resultant powder was taken out, and dried in an air atmosphere at 1100C for 24 hours, for evaporation to dryness. Moreover, the dried powder was subjected to a heat treatment in an air atmosphere at 3000C for 3 hours. Thus, a catalyst for purification of exhaust gas was obtained (the fourth step) . Note that the amount of metal particles which are made of the solid solution of palladium and platinum and supported in the obtained catalyst was 0.60 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum in the obtained catalyst was (Pd) 3% by atom: (Pt) 4% by atom. The amounts of Ba, K and Li supported in the obtained catalyst were 0.1 mol/100 g, 0.1 mol/100 g, and 0.2 mol/100 g, respectively, relative to 100 parts by mass of the alumina powder.
(Comparative Example 1) First, 0.038 g of Pd(NO3) 2 and 0.068 g of Pt (NO2) 2 (NH3) 3 were dissolved in 100 g of water to obtain an aqueous solution
(Pd concentration: 0.0175% by mass, Pt concentration: 0.0425% by mass) . To the aqueous solution, 10 g of an alumina powder
(average secondary particle diameter: 8 μm, specific surface area: 200 m2/g) was added, and the mixture was stirred for one hour. Then, the resultant powder was taken out, and the dried in an air atmosphere at 1100C for 24 hours. Thus, an alumina powder on which palladium and platinum were supported by CO- impregnation was obtained. Next, the obtained powder was subjected to the fourth step, without being subjected to the second and third steps as in Example 1. Thus, a catalyst for purification of exhaust gas was obtained.
Note that, the total amount of palladium and platinum supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
(Comparative Example 2) A catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that, since the inside of a container in which the powder A was placed was purged with nitrogen gas after the hydrogenation treatment in the second step, the powder A was introduced into the aqueous solution in the third step after being exposed to a nitrogen atmosphere.
Note that the amount of metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
<Performance Test 1 of Catalysts for Purification of Exhaust Gas (Example 1 and Comparative Examples 1 and 2) >
[TEM-EDX Analysis] The catalysts for purification of exhaust gas obtained in Example 1 and Comparative Examples 1 and 2 were subjected to TEM-EDX analysis by the above-described method using an analyzer manufactured by JEOL Ltd. , under the trade name of "JEM-2010FEF." As a result of such measurement, Figs. 1 to 3 show transmission electron microscopy (TEM) photographs of the catalyst for purification of exhaust gas obtained in Example 1, and Figs. 4 to 6 show transmission electron microscopy (TEM) photographs of the catalyst for purification of exhaust gas obtained in Comparative Example 1. Note that, the symbols "x" marked with 001 to 015 shown in Figs . 1 to 6 represent measurement points for the EDX analysis. Fig. 7 shows energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on a surface of the catalyst for purification of exhaust gas obtained in Example 1. Fig. 8 shows energy-dispersive X-ray fluorescence spectra of measurement points 001 to 005 on a surface of the catalyst for purification of exhaust gas obtained in Comparative Example 1.
On the basis of the measurement results, the standard deviation in metal composition ratio (composition ratio of Pt to Pd) of each primary particle of the metal particles in each of the catalysts for purification of exhaust gas obtained in Example 1 and Comparative Examples 1 and 2 was determined by the above-described method. Table 1 shows the results. [Table 1]
Figure imgf000031_0001
As apparent from the results shown in Table 1, it was observed that the standard deviation of the distribution of the ratios of the peak area of the first metal (Pt) to the sum of the peak area of the first metal and the peak area of the second metal (Pd) ( [peak area of first metal] / [sum of peak area of first metal and peak area of second metal] ) determined by the TEM-EDX at the measurement points on the surfaces of metal particles supported in the catalyst for purification of exhaust gas of the present invention (Example 1) was 10% or less. From such a result, it was confirmed that , in the catalyst for purification of exhaust gas of the present invention, the metal particles being a solid solution in which Pt and Pd were sufficiently uniformly dissolved were supported on the metal oxide support. In contrast, it was observed that the standard deviations of the catalysts for purification of exhaust gas for comparison (Comparative Example 1 and Comparative Example 2) exceeded 10%, and Pt and Pd were not uniformly dissolved in each other enough to form a solid solution.
[Nitrogen Oxides Treatment Test 1]
In each container, 1.0 g of the catalyst for purification of exhaust gas obtained in Example 1 or Comparative Example 1 was placed. Under a temperature condition of 3000C, rich gas and lean gas having their respective compositions shown in Table 2 were alternately passed through the container, while a cycle of lean/rich = 40 seconds/5 seconds was repeated. Then, purification ratio of nitrogen oxides (conversion of nitrogen oxides to N2) in a steady state was determined. For each of the catalysts, the concentrations of nitrogen oxides contained in the gas before and after the contact with the catalyst were determined, and the purification ratio of nitrogen oxides was found on the basis of the values of the determined concentrations of nitrogen oxides. Fig. 9 shows the results. [Table 2]
Figure imgf000032_0001
As apparent from the results shown in Fig. 9, the catalyst for purification of exhaust gas (Example 1) of the present invention exhibited an excellent purification ratio of nitrogen oxides. In contrast, in the case (Comparative Example 1) where the catalyst for purification of exhaust gas according to the present invention was not used, the purification ratio of nitrogen oxides was low. The results showed that the catalyst for purification of exhaust gas of the present invention was capable of exhibiting a high purification performance of nitrogen oxides, since the obtained metal particles being a solid solution in which Pt and Pd were sufficiently uniformly dissolved were supported on the metal oxide support . (Example 2)
A catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the hydrogen concentration in the second step was 1% by volume.
Note that the amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Moreover, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1. (Example 3)
A catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the temperature for the hydrogenation treatment in the second step was 1000C. Note that the amount of metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Moreover, each of the amounts of Ba, K and Li supported in the obtained catalyst was the same as that obtained in Example 1. (Example 4)
A catalyst for purification of exhaust gas was obtained by the same method as in Example 1, except that the temperature for the hydrogenation treatment in the second step was changed to 2000C.
The amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1. (Example 5)
A catalyst for purification of exhaust gas was obtained by the same method as in Example 1 , except that the temperature for the hydrogenation treatment in the second step was changed to 3000C. Note that the amount of the metal particles which are made of a solid solution of palladium and platinum and supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
Performance Test 2 of Catalyst for Purification of Exhaust Gas (Examples 1 to 5 and Comparative Example 2)>
Purification ratio of nitrogen oxides (conversion of nitrogen oxides to N2) was determined by employing the same method as in Nitrogen Oxides Treatment Test 1 described above, except that this test was performed by using the catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 2, at 3500C. Fig. 10 shows the results. As apparent from the results shown in Fig. 10, each of the catalysts for purification of exhaust gas of the present invention (Examples 1 to 5) exhibited an excellent purification ratio of nitrogen oxides. In contrast, in the case (Comparative Example 2) where the catalyst for purification of exhaust gas according to the present invention was not used, the purification ratio of nitrogen oxides was low. The results showed that the catalysts for purification of exhaust gas of the present invention where capable of exhibiting a high purification performance of nitrogen oxides, since the obtained metal particles being a solid solution in which Pt and Pd were sufficiently uniformly dissolved were supported on the metal oxide support . (Comparative Example 3)
First, to a dispersion liquid (Pd concentration: 0.0175% by mass, Pt concentration: 0.0425% by mass) in which 0.06 g of Pt/Pd core -shell -PVP colloid particles (particle diameter: approximately 2 nm) were dispersed in 100 g of water, 10 g of an alumina powder (average secondary particle diameter: 8 μm, specific surface area: 200 m2/g) was added. Then, the resultant powder was taken out, and dried in an air atmosphere at 1100C for 5 hours, for evaporation to dryness . Thus , an alumina powder on which palladium and platinum were supported was obtained. Next, the obtained powder was subjected to the fourth step, without being subjected to the second step and the third step as in Example 1. Thus, a catalyst for purification of exhaust gas was obtained. Note that the total amount of palladium and platinum supported in the obtained catalyst was 0.6 parts by mass relative to 100 parts by mass of the alumina powder, and the composition ratio of palladium to platinum was (Pd) 3% by atom: (Pt) 4% by atom. Meanwhile, each of the amounts of Ba, K and Li supported in the obtained catalyst was similar to that obtained in Example 1.
<Average Primary Particle Diameter Measurement of Catalysts for purification of Exhaust gas (Examples 1 to 5 and Comparative Example 3) > An average primary particle diameter of the metal particles in each of the catalysts for purification of exhaust gas obtained in Examples 1 to 5 and Comparative Example 3 was determined by CO chemisorption. Fig. 11 shows the obtained results .
As apparent from the results shown in Fig. 11, the average primary particle diameter of the metal particles supported in each of the catalysts for purification of exhaust gas of the present invention (Examples 1 to 5) was 1.5 nm or less, which was sufficiently small. In contrast, it was found that, in the case (Comparative Example 3) where the catalyst for purification of exhaust gas according to the present invention was not used, the primary particle diameter of the metal particles was greater than 1.5 nm. The results showed that, in each of the catalysts for purification of exhaust gas of the present invention, the average primary particle diameter of metal particles made of a solid solution of Pt and Pd was sufficiently small. [Industrial Applicability]
As have been described above, according to the present invention, it is possible to provide : a catalyst for purification of exhaust gas, in which a first metal and a second metal in a state of a uniform solid solution are supported on a metal oxide, capable of sufficiently reducing nitrogen oxides contained in exhaust gas of automobiles and the like,- a method of manufacturing the same; and a method of purifying exhaust gas using the same .

Claims

[CLAIMS] [Claim 1]
A catalyst for purification of exhaust gas comprising: a support made of a metal oxide,- and metal particles supported on the support, wherein the metal particles are made of a solid solution of at least one first metal selected from the group consisting of Pt, Ag, Mn, Fe and Au with at least one second metal selected from the group consisting of Pd, Rh, Ir and Ru, an average primary particle diameter of the metal particles is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles is 10% or less. [Claim 2] The catalyst for purification of exhaust gas according to claim 1, wherein at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba is further supported on the support. [Claim 3] The catalyst for purification of exhaust gas according to claim 1, wherein the first metal is Pt, and the second metal is Pd. [Claim 4] A method of manufacturing a catalyst for purification of exhaust gas comprising: a step of supporting metal particles on a support made of a metal oxide, the metal particles being made of one metal of first metal and second metal, said first metal being at least one selected from the group consisting of Pt, Ag, Mn, Fe and Au, said second metal being at least one selected from the group consisting of Pd, Rh, Ir and Ru,- a step of heating the support with the metal particles supported thereon to 500C or higher in an atmosphere having a hydrogen concentration of 0.5% by volume or more, thereby dissolving hydrogen in the metal particles which remain in a solid state, a step of immersing the support in a solution, while keeping the support in the atmosphere having a hydrogen concentration of 0.5% by volume or more, the support supporting the metal particles which are in the solid state and which have hydrogen dissolved therein, the solution containing ions of the other metal of the first metal and the second metal, and thereby reducing the other metal by the hydrogen dissolved in the metal particles which are in the solid state, to thereby obtain a catalyst for purification of exhaust gas in which metal particles made of a solid solution of the first metal with the second metal are supported on the support . [Claim 5]
The method of manufacturing a catalyst for purification of exhaust gas according to claim 4 , wherein an average primary particle diameter of the metal particles made of the solid solution is 1.5 nm or less, and a standard deviation in metal composition ratio of each primary particle of the metal particles made of the solid solution is 10% or less. [Claim 6]
The method of manufacturing catalyst for purification of exhaust gas according to claim 4, further comprising: a step of supporting at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba on the support supporting the metal particles made of the solid solution. [Claim 7]
A method of purifying exhaust gas, wherein nitrogen oxides in exhaust gas are treated for purification by bringing the exhaust gas into contact with the catalyst for purification of exhaust gas according to claim 1 in an oxygen-excess atmosphere. [Claim 8]
The method of purifying exhaust gas according to claim 7, whrein at least one third metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba is further supported on the support . [Claim 9]
The method of purifying exhaust gas according to claim 7 , wherein the first metal is Pt, and the second metal is Pd.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013005345A1 (en) * 2011-07-07 2013-01-10 Toyota Jidosha Kabushiki Kaisha NOx PURIFICATION CATALYST AND METHOD OF PRODUCING THE SAME
CN103370153A (en) * 2011-03-04 2013-10-23 丰田自动车株式会社 Metal particles, catalyst for exhaust gas purification containing same, and production method therefor
US9114384B2 (en) 2011-08-23 2015-08-25 Toyota Jidosha Kabushiki Kaisha Exhaust gas purification catalyst and method for producing it

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5533782B2 (en) * 2011-05-19 2014-06-25 トヨタ自動車株式会社 Exhaust gas purification catalyst and method for producing the same
JP2013220377A (en) * 2012-04-16 2013-10-28 Cataler Corp Exhaust gas purification catalyst
JP6107683B2 (en) * 2014-01-27 2017-04-05 トヨタ自動車株式会社 Method for producing exhaust gas purification catalyst
CN105312050A (en) * 2014-06-02 2016-02-10 丰田自动车株式会社 Exhaust gas purification catalyst, method of producing the same, and exhaust gas purification method using the same
JP6508090B2 (en) * 2016-03-03 2019-05-08 トヨタ自動車株式会社 Exhaust gas purification catalyst

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11156193A (en) 1997-09-24 1999-06-15 Toyota Motor Corp Alloy catalyst and manufacture thereof
JP2002001119A (en) 2000-06-16 2002-01-08 Tanaka Kikinzoku Kogyo Kk Method for manufacturing catalyst for purification of exhaust gas and catalyst for purification of exhaust gas manufactured by that method
JP2004267961A (en) 2003-03-11 2004-09-30 Tanaka Kikinzoku Kogyo Kk Catalyst manufactured by utilizing polyphyletic metal colloid

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2546078B1 (en) * 1983-05-19 1987-05-07 Pro Catalyse PROCESS FOR THE MANUFACTURE OF CATALYSTS FOR THE TREATMENT OF EXHAUST GASES FROM INTERNAL COMBUSTION ENGINES
JPH07157806A (en) * 1993-12-02 1995-06-20 Tanaka Kikinzoku Kogyo Kk Production of multiple powder
US6534661B1 (en) * 2000-12-28 2003-03-18 Hydrocarbon Technologies, Inc. Integrated process and dual-function catalyst for olefin epoxidation
JP4199691B2 (en) * 2004-03-25 2008-12-17 田中貴金属工業株式会社 catalyst
US7507495B2 (en) * 2004-12-22 2009-03-24 Brookhaven Science Associates, Llc Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles
US7601668B2 (en) * 2006-09-29 2009-10-13 Headwaters Technology Innovation, Llc Methods for manufacturing bi-metallic catalysts having a controlled crystal face exposure
KR100917495B1 (en) * 2006-11-27 2009-09-16 나노스텔라 인코포레이티드 Engine exhaust catalysts containing palladium-gold
JP5116377B2 (en) * 2007-06-22 2013-01-09 旭化成株式会社 Exhaust NOx purification method
DE102008042243A1 (en) * 2008-09-22 2010-04-01 Robert Bosch Gmbh Catalytically active coating for use in catalytic converter for treating internal-combustion engine exhaust gases, comprises multiple different zones, where former zone is oxidation zone for nitrogenous compounds

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11156193A (en) 1997-09-24 1999-06-15 Toyota Motor Corp Alloy catalyst and manufacture thereof
JP2002001119A (en) 2000-06-16 2002-01-08 Tanaka Kikinzoku Kogyo Kk Method for manufacturing catalyst for purification of exhaust gas and catalyst for purification of exhaust gas manufactured by that method
JP2004267961A (en) 2003-03-11 2004-09-30 Tanaka Kikinzoku Kogyo Kk Catalyst manufactured by utilizing polyphyletic metal colloid

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103370153A (en) * 2011-03-04 2013-10-23 丰田自动车株式会社 Metal particles, catalyst for exhaust gas purification containing same, and production method therefor
EP2682206A1 (en) * 2011-03-04 2014-01-08 Toyota Jidosha Kabushiki Kaisha Metal particles, catalyst for exhaust gas purification containing same, and production method therefor
EP2682206A4 (en) * 2011-03-04 2014-09-17 Toyota Motor Co Ltd Metal particles, catalyst for exhaust gas purification containing same, and production method therefor
US9115621B2 (en) 2011-03-04 2015-08-25 Toyota Jidosha Kabushiki Kaisha Metal particles, exhaust gas purifying catalyst comprising metal particles, and methods for producing them
CN103370153B (en) * 2011-03-04 2016-01-13 丰田自动车株式会社 Metallic and containing the exhaust gas purification catalyst of this metallic and their manufacture method
WO2013005345A1 (en) * 2011-07-07 2013-01-10 Toyota Jidosha Kabushiki Kaisha NOx PURIFICATION CATALYST AND METHOD OF PRODUCING THE SAME
US9114384B2 (en) 2011-08-23 2015-08-25 Toyota Jidosha Kabushiki Kaisha Exhaust gas purification catalyst and method for producing it

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