JP2006320840A - Catalyst for cleaning exhaust gas and its manufacturing method - Google Patents
Catalyst for cleaning exhaust gas and its manufacturing method Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims description 84
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 238000004140 cleaning Methods 0.000 title description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 80
- 239000002245 particle Substances 0.000 claims abstract description 76
- 229910052751 metal Inorganic materials 0.000 claims abstract description 52
- 239000002184 metal Substances 0.000 claims abstract description 52
- 230000003197 catalytic effect Effects 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 8
- 230000002378 acidificating effect Effects 0.000 claims description 9
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 239000011164 primary particle Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 6
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- 150000004679 hydroxides Chemical class 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 35
- 239000010948 rhodium Substances 0.000 description 22
- 239000000843 powder Substances 0.000 description 16
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000000746 purification Methods 0.000 description 10
- 238000010304 firing Methods 0.000 description 9
- 238000005245 sintering Methods 0.000 description 9
- 238000002441 X-ray diffraction Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 230000032683 aging Effects 0.000 description 6
- 238000011068 loading method Methods 0.000 description 6
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
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- 230000002776 aggregation Effects 0.000 description 3
- 210000004027 cell Anatomy 0.000 description 3
- 210000002421 cell wall Anatomy 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
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- 239000003960 organic solvent Substances 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 238000005118 spray pyrolysis Methods 0.000 description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000003350 kerosene Substances 0.000 description 2
- YXEUGTSPQFTXTR-UHFFFAOYSA-K lanthanum(3+);trihydroxide Chemical compound [OH-].[OH-].[OH-].[La+3] YXEUGTSPQFTXTR-UHFFFAOYSA-K 0.000 description 2
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052703 rhodium Inorganic materials 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000012916 structural analysis Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000013210 evaluation model Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Abstract
Description
本発明は排気ガス浄化用触媒及びその製造方法に関する。 The present invention relates to an exhaust gas purification catalyst and a method for producing the same.
排気ガス浄化用触媒に関し、従来より触媒金属を担持する担体（サポート材）としてγ−アルミナを用いること、さらに、耐熱性を高めるためにＬａ等の希土類金属を添加した安定化アルミナを用いることは知られている。 Regarding exhaust gas purifying catalysts, using γ-alumina as a carrier (support material) for supporting a catalytic metal conventionally, and further using stabilized alumina to which a rare earth metal such as La is added in order to improve heat resistance, Are known.
また、Ｌａを添加した安定化アルミナ担体に関し、これを中空状に形成することにより、当該担体の粒径を大きくするとともに、その比表面積を増大させ、そのことによって耐熱性を高めるという提案も知られている（特許文献１，２参照）。これは、Ａｌ及びＬａが溶解した酸性溶液とケロシン、ガソリン等の可燃性有機溶媒とを混合してＷ／Ｏ型エマルションを形成し、これを噴霧燃焼させることによって中空状担体粒子を得るというものである。 In addition, regarding a stabilized alumina support to which La is added, there is also a proposal that, by forming this in a hollow shape, the particle size of the support is increased and the specific surface area is increased, thereby improving the heat resistance. (See Patent Documents 1 and 2). This is a mixture of an acidic solution in which Al and La are dissolved and a flammable organic solvent such as kerosene or gasoline to form a W / O emulsion, which is spray-combusted to obtain hollow carrier particles. It is.
上記特許文献１，２に記載の技術は、アルミナ担体の粒径を大きくすることによって、その粒成長或いは相変化（比表面積の低下）を抑制するというものであり、比表面積の増大によって触媒金属の高分散化が図れ、該触媒金属の熱によるシンタリングも抑制されると考えられる。但し、比表面積を増大させて触媒金属の高分散化を図る試みは、中空状アルミナ担体に限らず中実状アルミナ担体でも以前より行なわれている。
しかし、中空状アルミナ粒子であっても、或いは中実状アルミナ粒子であっても、これに触媒金属を担持させた場合、その触媒金属は当該粒子表面を比較的自由に移動することができるから、高温雰囲気におかれたときには、触媒金属が粒子表面を移動して凝集する、すなわち、シンタリングを生じ、触媒活性が低下していく。 However, even if hollow alumina particles or solid alumina particles are supported on a catalyst metal, the catalyst metal can move relatively freely on the particle surface. When placed in a high temperature atmosphere, the catalytic metal moves and aggregates on the particle surface, that is, sintering occurs, and the catalytic activity decreases.
そこで、本発明は、触媒金属が上記アルミナ粒子のような担体表面を移動してシンタリングを生ずることを抑制することができるようにして、排気ガスの熱による触媒活性の低下を少なくなることを課題とする。 Therefore, the present invention can suppress the catalyst metal from moving on the surface of the carrier such as the alumina particles and causing sintering, thereby reducing the decrease in catalytic activity due to the heat of the exhaust gas. Let it be an issue.
本発明はこのような課題に対して、担体粒子表面に細線状物を生成させることにより触媒金属のシンタリングを防止するようにした。 In the present invention, for such a problem, sintering of the catalytic metal is prevented by generating a fine wire on the surface of the carrier particles.
請求項１に係る発明は、触媒金属と該触媒金属を担持する粒子状担体とを含有する排気ガス浄化用触媒であって、
上記粒子状担体は、その粒子表面に当該担体の成分を含んでなる細線状物が生成していることを特徴とする。
The invention according to claim 1 is an exhaust gas purifying catalyst containing a catalyst metal and a particulate carrier supporting the catalyst metal,
The particulate carrier is characterized in that a fine wire containing the carrier component is formed on the particle surface.
従って、粒子状担体の表面に担持されている触媒金属は、該担体粒子表面を移動することが細線状物によって阻止され、すなわち、シンタリングが妨げられるため、排気ガスの熱による排気ガス浄化性能の低下が抑制される。また、上記細線状物に触媒金属が担持されている場合であっても、その触媒金属の移動に対して近傍の細線状物が同様に立体障害となるため、シンタリングが抑制される。 Therefore, the catalyst metal supported on the surface of the particulate carrier is prevented from moving on the surface of the carrier particle by the thin wire, that is, sintering is hindered. Is suppressed. Even when the catalyst metal is supported on the fine wire, the nearby fine wire is similarly sterically hindered by the movement of the catalyst metal, so that sintering is suppressed.
触媒金属としては、遷移金属、なかでもＰｔ、Ｒｈ、Ｐｄ等の貴金属が好ましい。 The catalyst metal is preferably a transition metal, especially a noble metal such as Pt, Rh, Pd.
請求項２に係る発明は、請求項１において、
上記粒子状担体は、平均粒子径１０ｎｍ以下のアルミナの一次粒子が凝集してなり、上記細線状物は、細線状アルミナよりなることを特徴とする。
The invention according to claim 2 is the invention according to claim 1,
The particulate carrier is formed by agglomeration of primary particles of alumina having an average particle diameter of 10 nm or less, and the fine wire is made of fine wire alumina.
従って、粒子状担体を構成するアルミナの一次粒子は平均粒子径１０ｎｍ以下であって微細であるから、当該担体の比表面積が大きなものになり、触媒金属の高分散担持に有利になる。 Therefore, the primary particles of alumina constituting the particulate support have an average particle diameter of 10 nm or less and are fine, so that the specific surface area of the support becomes large, which is advantageous for highly dispersed support of the catalyst metal.
ここに、上記粒子状担体を構成するアルミナ及び細線状アルミナは、普通のアルミナでもよいが、例えばＬａ等の希土類金属、ジルコニウム、珪素等を固溶させた安定化アルミナとすることが好ましい。このような安定化アルミナにすると、排気ガスの熱による当該アルミナの相変化が抑制されて当該担体の比表面積の低下が少なくなる。 Here, the alumina and the fine-line alumina constituting the particulate carrier may be ordinary alumina, but for example, stabilized alumina in which a rare earth metal such as La, zirconium, silicon, or the like is dissolved is preferable. When such stabilized alumina is used, the phase change of the alumina due to the heat of the exhaust gas is suppressed, and the decrease in the specific surface area of the carrier is reduced.
請求項３に係る発明は、請求項１又は請求項２において、
上記粒子状担体は中空状であることを特徴とする。
The invention according to claim 3 is the invention according to claim 1 or claim 2,
The particulate carrier is characterized by being hollow.
すなわち、一次粒子が凝集した中実状担体粒子の場合、その凝集によって生じた細孔内にも触媒金属が担持され、その触媒金属は排気ガスと接触し難くなるが、本発明に係る中空状担体粒子の場合、触媒金属が主として排気ガスと接触し易い中空状粒子の表面に担持されるから、触媒活性の向上に有利になる。また、担体粒子が中空状であることによって比表面積も大きくなり、触媒金属の高分散担持にも有利になる。 That is, in the case of solid carrier particles in which primary particles are aggregated, the catalyst metal is also supported in the pores generated by the aggregation, and the catalyst metal is difficult to come into contact with the exhaust gas, but the hollow carrier according to the present invention In the case of particles, the catalyst metal is mainly supported on the surface of hollow particles that easily come into contact with the exhaust gas, which is advantageous in improving the catalyst activity. Further, since the carrier particles are hollow, the specific surface area is increased, which is advantageous for highly dispersed support of the catalyst metal.
請求項４に係る発明は、上述の如き中空状担体粒子に触媒金属が担持されてなる排気ガス浄化用触媒の製造方法であって、
Ａｌが溶解した酸性水溶液を加熱炉内に噴霧することにより、表面に細線状のＡｌ水酸化物を有する中空状アルミナ粒子を生成し、
上記中空状アルミナ粒子に触媒金属が溶解した酸性水溶液を接触させた後、焼成することにより、該中空状アルミナ粒子の表面において上記細線状のＡｌ水酸化物から細線状アルミナを生成させるとともに、該中空状アルミナ粒子の表面に上記触媒金属を担持させることを特徴とする。
The invention according to claim 4 is a method for producing an exhaust gas purifying catalyst in which a catalytic metal is supported on the hollow carrier particles as described above,
By spraying an acidic aqueous solution in which Al is dissolved in a heating furnace, hollow alumina particles having fine Al hydroxides on the surface are generated,
The hollow alumina particles are brought into contact with an acidic aqueous solution in which a catalytic metal is dissolved, and then calcined to produce fine linear alumina from the fine linear Al hydroxide on the surface of the hollow alumina particles, and The catalyst metal is supported on the surface of the hollow alumina particles.
すなわち、この製造方法は、中空状アルミナ粒子の生成に噴霧熱分解法を採用したものであり、Ａｌが溶解した酸性水溶液の噴霧によって中空状アルミナ粒子が生成される際に、そのＡｌの一部が当該中空状粒子表面で水酸化物となって細線状に成長することになる。そうして、上記中空状アルミナ粒子に触媒金属が溶解した酸性水溶液を接触させた後の焼成により、上記細線状Ａｌ水酸化物は細線状アルミナに変化する一方、触媒金属は中空状アルミナ粒子表面に担持されて安定な状態になる。この場合、触媒金属は中空状アルミナ粒子本体の表面だけでなく、細線状アルミナの表面にも一部が担持されると考えられる。 That is, this production method employs a spray pyrolysis method for the production of hollow alumina particles. When hollow alumina particles are produced by spraying an acidic aqueous solution in which Al is dissolved, a part of the Al is produced. Will grow into a fine line as a hydroxide on the surface of the hollow particles. Then, by firing after the acidic aqueous solution in which the catalytic metal is dissolved in contact with the hollow alumina particles, the fine linear Al hydroxide is changed into fine linear alumina, while the catalytic metal is on the surface of the hollow alumina particles. To be in a stable state. In this case, it is considered that a part of the catalyst metal is supported not only on the surface of the hollow alumina particle body but also on the surface of the fine-line alumina.
従って、本発明に係る製造方法によれば、中空状アルミナ粒子の表面に細線状アルミナを有し且つ触媒金属が担持された排気ガス浄化用触媒を簡単に得ることができる。 Therefore, according to the production method of the present invention, it is possible to easily obtain an exhaust gas purifying catalyst having fine-line alumina on the surface of hollow alumina particles and carrying a catalytic metal.
ここに、上記Ａｌが溶解した酸性水溶液は、Ｌａ等の希土類金属、ジルコニウム、珪素等のアルミナに固溶して熱安定化作用を与える金属をも溶解したものとし、上記中空状アルミナ粒子及びその表面の細線状アルミナ各々を安定化アルミナとすることが好ましい。 Here, the acidic aqueous solution in which the Al is dissolved is a solution in which a rare earth metal such as La or a metal that dissolves in alumina such as zirconium or silicon is also dissolved, and the hollow alumina particles and its It is preferable that each thin fine-line alumina on the surface is stabilized alumina.
また、触媒金属としては、遷移金属、なかでもＰｔ、Ｒｈ、Ｐｄ等の貴金属が好ましい。 The catalyst metal is preferably a transition metal, especially a noble metal such as Pt, Rh, Pd.
以上のように、請求項１に係る発明によれば、触媒金属と該触媒金属を担持する粒子状担体とを含有する排気ガス浄化用触媒であって、上記粒子状担体の表面に当該担体の成分を含んでなる細線状物が生成しているから、細線状物が立体障害となって触媒金属のシンタリングが抑制され、排気ガスの熱による触媒活性の低下が少なくなる。 As described above, according to the first aspect of the present invention, there is provided an exhaust gas purifying catalyst comprising a catalyst metal and a particulate carrier supporting the catalyst metal, the surface of the particulate carrier comprising the carrier. Since the fine wire containing the component is generated, the fine wire becomes a steric hindrance and the sintering of the catalytic metal is suppressed, and the decrease in the catalytic activity due to the heat of the exhaust gas is reduced.
請求項２に係る発明によれば、上記粒子状担体は平均粒子径１０ｎｍ以下のアルミナの一次粒子が凝集してなり、上記細線状物は細線状アルミナよりなるから、当該触媒の耐熱性向上及び活性向上に有利になる。 According to the invention of claim 2, since the particulate carrier is formed by agglomerating primary particles of alumina having an average particle diameter of 10 nm or less, and the fine wire is made of fine wire alumina, the heat resistance of the catalyst is improved. It becomes advantageous for activity improvement.
請求項３に係る発明によれば、上記粒子状担体は中空状であるから、触媒活性の向上に有利になる。 According to the invention of claim 3, since the particulate carrier is hollow, it is advantageous for improving the catalytic activity.
請求項４に係る発明によれば、Ａｌが溶解した酸性水溶液を加熱炉内に噴霧することにより、表面に細線状のＡｌ水酸化物を有する中空状アルミナ粒子を生成し、該中空状アルミナ粒子に触媒金属が溶解した酸性水溶液を接触させた後、焼成することにより、該中空状アルミナ粒子の表面において上記細線状のＡｌ水酸化物から細線状アルミナを生成させるとともに、該中空状アルミナ粒子の表面に上記触媒金属を担持させるようにしたから、中空状アルミナ粒子の表面に細線状アルミナを有し且つ触媒金属が担持された排気ガス浄化用触媒を簡単に得ることができる。 According to the invention of claim 4, by spraying an acidic aqueous solution in which Al is dissolved into a heating furnace, hollow alumina particles having fine Al hydroxides on the surface are generated, and the hollow alumina particles After contacting the acidic aqueous solution in which the catalytic metal is dissolved in the catalyst, firing is performed to produce fine linear alumina from the fine linear Al hydroxide on the surface of the hollow alumina particles. Since the catalyst metal is supported on the surface, it is possible to easily obtain an exhaust gas purifying catalyst having fine-line alumina on the surface of the hollow alumina particles and supporting the catalyst metal.
以下、本発明の実施形態を図面に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
図１に示す本発明の実施形態に係る排気ガス浄化用触媒１は、自動車エンジンの排気ガス中のＨＣ（炭化水素）、ＣＯ（一酸化炭素）及びＮＯｘ（窒素酸化物）を浄化することに適したものである。この触媒１は、コージェライト等の無機多孔質によって形成されたハニカム状担体２のガス流路であるセル３の壁面に触媒層を形成したものである。すなわち、図２に示すように、ハニカム状担体の各セル３を隔てるセル壁５に触媒層６が形成されている。この触媒層６は、表面に細線状物が生成している担体粒子（サポート材）に触媒金属を担持させてなる触媒粉末をバインダと共に担体にウォッシュコートすることによって形成されている。 The exhaust gas purifying catalyst 1 according to the embodiment of the present invention shown in FIG. 1 purifies HC (hydrocarbon), CO (carbon monoxide) and NOx (nitrogen oxide) in the exhaust gas of an automobile engine. It is suitable. This catalyst 1 is obtained by forming a catalyst layer on the wall surface of a cell 3 which is a gas flow path of a honeycomb-shaped carrier 2 formed of an inorganic porous material such as cordierite. That is, as shown in FIG. 2, the catalyst layer 6 is formed on the cell wall 5 separating the cells 3 of the honeycomb-shaped carrier. The catalyst layer 6 is formed by wash-coating a carrier together with a binder with a catalyst powder in which a catalyst metal is supported on carrier particles (support material) on which fine wires are formed.
なお、上記触媒層６にはさらに他のサポート材に触媒金属を担持させてなる触媒粉末を含ませてもよく、或いは、セル壁５の表面に上記触媒層６と、該触媒層とは成分が異なる他の触媒層とを層状に形成してもよい。 The catalyst layer 6 may further contain a catalyst powder obtained by supporting a catalyst metal on another support material. Alternatively, the catalyst layer 6 on the surface of the cell wall 5 and the catalyst layer are composed of components. Other catalyst layers having different values may be formed in layers.
＜実施例＞
上記表面に細線状物が生成している担体粒子として、中空状アルミナ粒子を噴霧熱分解法によって製造した。すなわち、硝酸アルミニウム、硝酸ランタン及び硫酸マグネシウムの各所定量を水に溶解させることにより、上記担体粒子の原料溶液を調製した。次いで、上記原料溶液を、空気をキャリアガスとして噴霧することにより、液滴化させて加熱炉に供給した。加熱炉内の温度は７００℃±２５℃に設定した。加熱炉を出た粒子はバグフィルターによって捕集し、これを水洗後、乾燥させることにより、当該中空状アルミナ粒子を得た。
<Example>
Hollow alumina particles were produced by spray pyrolysis as carrier particles with fine wires formed on the surface. That is, a raw material solution of the carrier particles was prepared by dissolving predetermined amounts of aluminum nitrate, lanthanum nitrate and magnesium sulfate in water. Subsequently, the raw material solution was sprayed using air as a carrier gas to form droplets and supplied to the heating furnace. The temperature in the heating furnace was set to 700 ° C. ± 25 ° C. The particles exiting the heating furnace were collected by a bag filter, washed with water and dried to obtain the hollow alumina particles.
ここで、硝酸ランタンは、当該中空状アルミナにＬａを固溶させて安定化アルミナとするために添加したものであり、その添加量は５質量％である。また、硫酸マグネシウムは、中空状アルミナ粒子を製造する際の結晶子のシンタリングを抑制する、結晶子同士の接触点を減らしつつ中空構造に導く、という作用を有するものとして、各種添加化合物の中から選定されたものであり、その添加量、濃度等は適宜決定することができる。 Here, lanthanum nitrate is added to dissolve La in the hollow alumina to form stabilized alumina, and the amount added is 5% by mass. Magnesium sulfate has the effect of suppressing the sintering of crystallites when producing hollow alumina particles, and leading to a hollow structure while reducing the number of contact points between crystallites. The addition amount, concentration, and the like can be determined as appropriate.
次にＲｈ担持量が０．１２５質量％となるように上記中空状アルミナと０．８３質量％硝酸ロジウム溶液とを純水に投入し、蒸発乾固（乾燥）を行なった後、大気雰囲気で５００℃の温度に２時間保持する焼成を行なうことにより、上記触媒粉末、すなわち、Ｒｈ担持中空状アルミナ粉末を得た。 Next, the above hollow alumina and 0.83 mass% rhodium nitrate solution were put into pure water so that the Rh loading was 0.125 mass%, and after evaporating to dryness (drying), The catalyst powder, that is, the Rh-supported hollow alumina powder, was obtained by firing at a temperature of 500 ° C. for 2 hours.
図３はＲｈを担持する前の中空状アルミナ粒子のＴＥＭ（透過型電子顕微鏡）写真である。球形のものが中空状アルミナ粒子本体であり、これはＬａが固溶した安定化アルミナよりなる。この中空状アルミナ粒子本体は、１０ｎｍ以下の一次粒子（結晶子）が凝集して中空状になっている。中空状アルミナ粒子本体の表面に生成している毛状ないし細線状のものは、Ａｌを成分とする化合物であり、その殆どが水酸化アルミニウムよりなり、一部、水酸化ランタンを含んでいる。この点については後にＸＲＤデータに基いて説明する。 FIG. 3 is a TEM (transmission electron microscope) photograph of hollow alumina particles before carrying Rh. A spherical body is a hollow alumina particle body, which is made of stabilized alumina in which La is dissolved. The hollow alumina particle body is hollow by agglomerating primary particles (crystallites) of 10 nm or less. The hair-like or fine-line-like material generated on the surface of the hollow alumina particle main body is a compound containing Al as a component, most of which is made of aluminum hydroxide and partially contains lanthanum hydroxide. This point will be described later based on XRD data.
図４はＲｈを担持した中空状アルミナ粒子（触媒粉末）のＴＥＭ写真である。Ｒｈ担持のための上記蒸発乾固及び焼成を行なった後も、中空状アルミナ粒子の表面に毛状ないし細線状のものが残っていることがわかる。この細線状物はアルミナよりなる。この点も後にＸＲＤデータに基いて説明する。 FIG. 4 is a TEM photograph of hollow alumina particles (catalyst powder) supporting Rh. It can be seen that even after the above-described evaporation to dryness and firing for carrying Rh, hair or fine wire remains on the surface of the hollow alumina particles. This fine wire is made of alumina. This point will also be described later based on XRD data.
図５は上記Ｒｈを担持した中空状アルミナ粒子（触媒粉末）に大気雰囲気で７５０℃の温度に２４時間保持するエージング処理を行なった後のＴＥＭ写真である。エージング処理後も中空状アルミナ粒子の表面に細線状物が残っていることがわかる。 FIG. 5 is a TEM photograph after the aging treatment in which the hollow alumina particles (catalyst powder) supporting Rh are held at a temperature of 750 ° C. for 24 hours in an air atmosphere. It can be seen that fine wire remains on the surface of the hollow alumina particles even after the aging treatment.
＜比較例＞
担体粒子として、実施例の中空状アルミナ粉末に代えて、共沈法によって調製されている市販の５質量％Ｌａ安定化アルミナ粉末を採用し、実施例と同様に触媒金属源として０．８３質量％硝酸ロジウム溶液を用い、同様の蒸発乾固及び焼成を行なうことにより、触媒粉末を得た。
<Comparative example>
As a carrier particle, instead of the hollow alumina powder of the example, a commercially available 5 mass% La-stabilized alumina powder prepared by a coprecipitation method is employed, and 0.83 mass as a catalyst metal source as in the example. A catalyst powder was obtained by performing similar evaporation to dryness and calcination using a% rhodium nitrate solution.
＜ＸＲＤによる構造解析＞
上記実施例及び比較例に係るＲｈ担持前の担体粒子、並びにＲｈを担持させて焼成した後の触媒粉末についてＸＲＤ（Ｘ線回折）による構造解析を行なった。その結果を図６に示す。同図の「本発明」は上記実施例に係るものであり、「従来」は上記比較例に係るものである。
<Structural analysis by XRD>
Structural analysis by XRD (X-ray diffraction) was performed on the carrier particles before carrying Rh according to the above Examples and Comparative Examples, and the catalyst powder after carrying and calcining Rh. The result is shown in FIG. The “present invention” in the figure relates to the above embodiment, and the “conventional” relates to the above comparative example.
本発明（実施例）の場合、触媒金属担持前のデータをみると、γ−Ａｌ2Ｏ3のピークが現れているだけでなく、Ａｌ(ＯＨ)3のピークが強く現れている。これに対して、本発明の触媒金属担持焼成後のデータではこのＡｌ(ＯＨ)3のピークが実質的に消滅している一方、γ−Ａｌ2Ｏ3のピークが高くなっているとともに、新たな化合物のピークは現れていない。また、水酸化ランタンについても、本発明（実施例）の場合、触媒金属担持前のデータではＬａ(ＯＨ)3のピークが現れており、触媒金属担持焼成後のデータではこのＬａ(ＯＨ)3のピークが消滅している。 In the case of the present invention (Example), the data before supporting the catalyst metal shows not only a peak of γ-Al 2 O 3 but also a strong peak of Al (OH) 3 . On the other hand, in the data after the catalyst metal-supported firing of the present invention, the peak of Al (OH) 3 has substantially disappeared, while the peak of γ-Al 2 O 3 has increased, The peak of a simple compound does not appear. As for the lanthanum hydroxide, in the present invention (Example), the catalytic metal loading the data before and peaks appear for La (OH) 3, in the data after the catalytic metal supported firing the La (OH) 3 The peak of disappears.
このことから、先のＴＥＭ写真と併せて検討すると、本発明のＲｈ担持前の担体粒子は、その中空状の粒子本体がγーＡｌ2Ｏ3によって形成され、細線状のものがＡｌ(ＯＨ)3とＬａ(ＯＨ)3とによって形成されている、そして、Ｒｈを担持し焼成すると、細線状のＡｌ(ＯＨ)3がγ−Ａｌ2Ｏ3に変化している、即ち、Ｌａを固溶したγ−Ａｌ2Ｏ3（熱安定化アルミナ）に変化している、と判断することが妥当である。 From this, when examined together with the previous TEM photograph, the carrier particles before carrying Rh of the present invention have a hollow particle body formed of γ-Al 2 O 3 , and those with fine wires are Al (OH ) 3 and La (OH) 3 , and when Rh is supported and baked, the thin-line Al (OH) 3 is changed to γ-Al 2 O 3 , that is, La is solidified. It is reasonable to judge that it has changed to dissolved γ-Al 2 O 3 (heat-stabilized alumina).
Ｒｈ担持前の担体粒子に細線状Ａｌ(ＯＨ)3が生成している理由は、上記噴霧熱分解法において、加熱炉内の温度を結晶化度の高いアルミナが得られるような高い温度（例えば１０００℃）には設定していないこと、原料溶液には可燃性有機溶媒を加えていないこと、しかも原料溶液の噴霧から落下までの時間が短いことにあると考えられる。 The reason why fine linear Al (OH) 3 is formed on the carrier particles before Rh is supported is that the temperature in the heating furnace is set to a high temperature (for example, high crystallinity alumina) in the spray pyrolysis method (for example, 1000 ° C.), the combustible organic solvent is not added to the raw material solution, and the time from spraying to dropping of the raw material solution is considered to be short.
この点、特許文献１，２に記載された中空状担体粒子の製法の場合、ケロシン、ガソリン等の可燃性有機溶媒を用いてＷ／Ｏ型エマルションを形成し、これを噴霧燃焼させることから、噴霧燃焼時の火炎温度を６５０℃〜７５０℃に制御するとはいっても、噴霧によって形成される微粒子の熱容量を考慮すれば、その粒子は極短時間は当該制御温度を超えて高熱状態になり、このため、当該製法では、本発明の如きＡｌ水酸化物或いはアルミナの細線状結晶はできないものと考えられる（特許文献１の図２，図５参照）。 In this regard, in the case of the method for producing hollow carrier particles described in Patent Documents 1 and 2, a W / O type emulsion is formed using a combustible organic solvent such as kerosene and gasoline, and this is spray burned. Although the flame temperature during spray combustion is controlled to 650 ° C. to 750 ° C., considering the heat capacity of the fine particles formed by spraying, the particles will be in a high heat state exceeding the control temperature for a very short time, For this reason, it is considered that the production method cannot produce Al hydroxide or alumina fine wire crystals as in the present invention (see FIGS. 2 and 5 of Patent Document 1).
そうして、本発明の場合、Ｒｈの担持工程では、このような細線状物を表面に有する中空状アルミナ粒子に硝酸ロジウム溶液が接触することにより、Ｒｈイオンが中空状の粒子本体だけでなく、上記細線状物にも付着することになる。従って、その後の焼成により、Ｒｈは中空状アルミナ粒子本体及び細線状アルミナの両者に担持された状態になると考えられる。 Thus, in the case of the present invention, in the Rh loading step, the rhodium nitrate solution is brought into contact with the hollow alumina particles having such fine wires on the surface, so that the Rh ions are not only in the hollow particle main body. , It will also adhere to the fine wire. Therefore, it is considered that Rh is supported on both the hollow alumina particle main body and the fine-line alumina by subsequent firing.
なお、Ｒｈ担持後のＸＲＤデータに関し、Ｒｈのピークは確認できなかったが、これはＲｈ量が少なく、且つ高分散状態になっているためと考えられる。 In addition, regarding the XRD data after loading Rh, the peak of Rh could not be confirmed, but this is thought to be due to the small amount of Rh and the high dispersion state.
一方、比較例（図６の「従来」）のＸＲＤデータをみると、触媒金属担持前と触媒金属担持焼成後とで変化は殆ど認められない。なお、触媒金属担持前のデータにおいて、２θ＝２０゜位置の前後に結晶性の高くないＡｌ(ＯＨ)3と思われるピークが小さく現れているが、他の回折角位置にはＡｌ(ＯＨ)3のピークは現れておらず、また、２θ＝２０゜付近のピークも非常に小さいことから、本発明のような細線状物は存在しないと云うことができる。 On the other hand, in the XRD data of the comparative example ("conventional" in FIG. 6), there is almost no change between before the catalyst metal loading and after the catalyst metal loading firing. In the data before supporting the catalyst metal, a peak that is considered to be Al (OH) 3 that is not high in crystallinity appears before and after the 2θ = 20 ° position, but Al (OH) 3 appears at other diffraction angle positions. Since the peak of 3 does not appear and the peak around 2θ = 20 ° is very small, it can be said that there is no thin line like the present invention.
＜排気ガス浄化性能について＞
上記実施例及び比較例の触媒粉末について、各々をハニカム状担体に担持させて触媒層を形成してなる排気ガス浄化用触媒を調製した。この調製法は実施例も比較例も同じであり、ハニカム状担体１Ｌ当たりのＲｈ担持量が０．１３ｇ／Ｌとなるように触媒粉末を秤量し、該触媒粉末とジルコニアバインダとを純水に入れて攪拌することによりスラリーを調製した。このスラリーにハニカム状担体を浸漬して引き上げ、余分なスラリーをエアブローで除去し、１５０℃で乾燥させた後、大気雰囲気で５００℃の温度に２時間保持する焼成を行なうことによって実施例及び比較例各々の排気ガス浄化用触媒を得た。
<Exhaust gas purification performance>
About the catalyst powder of the said Example and comparative example, each was carry | supported on the honeycomb-shaped support | carrier, and the catalyst for exhaust gas purification | cleaning formed by forming a catalyst layer was prepared. This preparation method is the same in both examples and comparative examples. The catalyst powder is weighed so that the amount of Rh supported per liter of honeycomb-shaped carrier is 0.13 g / L, and the catalyst powder and the zirconia binder are put into pure water. A slurry was prepared by adding and stirring. Example and comparison by immersing and lifting the honeycomb-shaped carrier into this slurry, removing excess slurry by air blow, drying at 150 ° C., and firing at 500 ° C. for 2 hours in an air atmosphere Examples Exhaust gas purifying catalysts were obtained.
そうして、各排気ガス浄化用触媒を大気雰囲気で７５０℃の温度に２４時間保持するエージング処理を行なった後、モデルガス流通反応装置及び排気ガス分析装置を用いて排気ガス浄化性能を調べた。 Then, after performing an aging treatment in which each exhaust gas purification catalyst was maintained at a temperature of 750 ° C. for 24 hours in an air atmosphere, the exhaust gas purification performance was examined using a model gas flow reaction apparatus and an exhaust gas analyzer. .
すなわち、上記各触媒（上記エージング後のもの）をモデルガス流通反応装置に取り付け、空燃比リッチのモデルガス（温度６００℃）を２０分間流した後、評価用モデルガスにより、ＨＣ、ＣＯ及びＮＯｘの浄化に関するライトオフ温度Ｔ５０を測定した。Ｔ５０は、触媒に流入するモデルガス温度を１００℃から５００℃まで漸次上昇させていき、浄化率が５０％に達したときの触媒入口のガス温度である。評価用モデルガスは、Ａ／Ｆ＝１４．７±０．９とした。すなわち、Ａ／Ｆ＝１４．７のメインストリームガスを定常的に流しつつ、所定量の変動用ガスを１Ｈｚでパルス状に添加することにより、Ａ／Ｆを±０．９の振幅で強制的に振動させた。空間速度ＳＶは６００００ｈ-1、昇温速度は３０℃／分である。 That is, each catalyst (after aging) is attached to a model gas flow reactor, and after flowing an air-fuel ratio rich model gas (temperature 600 ° C.) for 20 minutes, HC, CO, and NOx are evaluated by the evaluation model gas. The light-off temperature T50 related to the purification of was measured. T50 is the gas temperature at the catalyst inlet when the model gas flowing into the catalyst is gradually raised from 100 ° C. to 500 ° C. and the purification rate reaches 50%. The model gas for evaluation was A / F = 14.7 ± 0.9. That is, the A / F is forced at an amplitude of ± 0.9 by adding a predetermined amount of fluctuation gas in a pulse form at 1 Hz while constantly flowing the main stream gas of A / F = 14.7. Vibrated. The space velocity SV is 60000 h −1 , and the heating rate is 30 ° C./min.
結果を図７に示す。実施例はＨＣ、ＣＯ及びＮＯｘのいずれに関しても比較例よりもライトオフ温度が低くなっており、特に、ＨＣ浄化に関するライトオフ温度が１０℃程度低くなっている。これは、実施例の場合、上記エージング処理に拘わらず、中空状アルミナ粒子表面の細線状アルミナが立体障害となってＲｈの移動、凝集が妨げられ、比較例に比べてＲｈのシンタリングが抑制されたためと考えられる。また、実施例の場合、担体粒子は平均粒子径１０ｎｍ以下のアルミナ一次粒子が凝集した中空状になっていて比表面積が比較例よりも大きいこと、また、Ｒｈが排気ガス（モデルガス）に接触し易い中空状担体粒子表面に担持されていることも、上記ライトオフ温度が低いことの一因になっていると考えられる。 The results are shown in FIG. In the example, the light-off temperature is lower than that of the comparative example for any of HC, CO, and NOx. In particular, the light-off temperature for HC purification is about 10 ° C. In the case of the examples, regardless of the above aging treatment, the fine linear alumina on the surface of the hollow alumina particles is sterically hindered to prevent the movement and aggregation of Rh, and the Rh sintering is suppressed compared to the comparative example. It is thought that it was because it was done. In the case of the examples, the carrier particles are in a hollow shape in which alumina primary particles having an average particle diameter of 10 nm or less are aggregated, the specific surface area is larger than that of the comparative example, and Rh is in contact with the exhaust gas (model gas). It is considered that the fact that it is supported on the surface of the hollow carrier particles, which is easy to do, also contributes to the low light-off temperature.
１ 排気ガス浄化用触媒
２ 担体
３ セル
５ セル壁
６ 触媒層
DESCRIPTION OF SYMBOLS 1 Exhaust gas purification catalyst 2 Carrier 3 Cell 5 Cell wall 6 Catalyst layer
Claims (4)
上記粒子状担体は、その粒子表面に当該担体の成分を含んでなる細線状物が生成していることを特徴とする排気ガス浄化用触媒。 An exhaust gas purifying catalyst comprising a catalytic metal and a particulate carrier supporting the catalytic metal,
An exhaust gas purifying catalyst, wherein the particulate carrier has a fine line-like material containing a component of the carrier generated on the particle surface.
上記粒子状担体は、平均粒子径１０ｎｍ以下のアルミナの一次粒子が凝集してなり、上記細線状物は、細線状アルミナよりなることを特徴とする排気ガス浄化用触媒。 In claim 1,
An exhaust gas purifying catalyst, wherein the particulate carrier is formed by agglomerating primary particles of alumina having an average particle diameter of 10 nm or less, and the fine wire is made of fine wire alumina.
上記粒子状担体は中空状であることを特徴とする排気ガス浄化用触媒。 In claim 1 or claim 2,
An exhaust gas purifying catalyst, wherein the particulate carrier is hollow.
上記中空状アルミナ粒子に触媒金属が溶解した酸性水溶液を接触させた後、焼成することにより、該中空状アルミナ粒子の表面において上記細線状のＡｌ水酸化物から細線状アルミナを生成させるとともに、該中空状アルミナ粒子の表面に上記触媒金属を担持させることを特徴とする排気ガス浄化用触媒の製造方法。 By spraying an acidic aqueous solution in which Al is dissolved in a heating furnace, hollow alumina particles having fine Al hydroxides on the surface are generated,
The hollow alumina particles are brought into contact with an acidic aqueous solution in which a catalytic metal is dissolved, and then calcined to produce fine linear alumina from the fine linear Al hydroxide on the surface of the hollow alumina particles, and A method for producing an exhaust gas purifying catalyst, wherein the catalyst metal is supported on the surface of hollow alumina particles.
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| JP2005146521A JP2006320840A (en) | 2005-05-19 | 2005-05-19 | Catalyst for cleaning exhaust gas and its manufacturing method |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5527830A (en) * | 1978-08-15 | 1980-02-28 | Chiyoda Chem Eng & Constr Co Ltd | Production of alumina carrier |
| JPS58156513A (en) * | 1982-03-08 | 1983-09-17 | Nippon Steel Corp | Carbon powder having thickly grown fine carbon cilia |
| JPH02290257A (en) * | 1989-02-17 | 1990-11-30 | Nippon Shokubai Kagaku Kogyo Co Ltd | Carrier for catalyst and its manufacture |
| JP2002233755A (en) * | 2001-02-08 | 2002-08-20 | Toyota Central Res & Dev Lab Inc | Catalyst for oxidizing saturated hydrocarbon |
| JP2003265964A (en) * | 2002-03-14 | 2003-09-24 | Ibiden Co Ltd | Catalyst-supporting filter useful for cleaning exhaust gas |
| JP2004074116A (en) * | 2002-08-22 | 2004-03-11 | Denso Corp | Catalyst body |
| JP2004141864A (en) * | 2002-10-01 | 2004-05-20 | Toyota Motor Corp | High thermal resistant catalyst carrier, catalyst for emission gas purification, and its production method |
| JP2004283739A (en) * | 2003-03-24 | 2004-10-14 | Toyota Central Res & Dev Lab Inc | Catalyst for cleaning exhaust gas |
-
2005
- 2005-05-19 JP JP2005146521A patent/JP2006320840A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5527830A (en) * | 1978-08-15 | 1980-02-28 | Chiyoda Chem Eng & Constr Co Ltd | Production of alumina carrier |
| JPS58156513A (en) * | 1982-03-08 | 1983-09-17 | Nippon Steel Corp | Carbon powder having thickly grown fine carbon cilia |
| JPH02290257A (en) * | 1989-02-17 | 1990-11-30 | Nippon Shokubai Kagaku Kogyo Co Ltd | Carrier for catalyst and its manufacture |
| JP2002233755A (en) * | 2001-02-08 | 2002-08-20 | Toyota Central Res & Dev Lab Inc | Catalyst for oxidizing saturated hydrocarbon |
| JP2003265964A (en) * | 2002-03-14 | 2003-09-24 | Ibiden Co Ltd | Catalyst-supporting filter useful for cleaning exhaust gas |
| JP2004074116A (en) * | 2002-08-22 | 2004-03-11 | Denso Corp | Catalyst body |
| JP2004141864A (en) * | 2002-10-01 | 2004-05-20 | Toyota Motor Corp | High thermal resistant catalyst carrier, catalyst for emission gas purification, and its production method |
| JP2004283739A (en) * | 2003-03-24 | 2004-10-14 | Toyota Central Res & Dev Lab Inc | Catalyst for cleaning exhaust gas |
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