JP4324856B2 - Exhaust gas purification catalyst carrier and catalyst - Google Patents
Exhaust gas purification catalyst carrier and catalyst Download PDFInfo
- Publication number
- JP4324856B2 JP4324856B2 JP2003382973A JP2003382973A JP4324856B2 JP 4324856 B2 JP4324856 B2 JP 4324856B2 JP 2003382973 A JP2003382973 A JP 2003382973A JP 2003382973 A JP2003382973 A JP 2003382973A JP 4324856 B2 JP4324856 B2 JP 4324856B2
- Authority
- JP
- Japan
- Prior art keywords
- catalyst
- oxide
- exhaust gas
- tio
- zro
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000003054 catalyst Substances 0.000 title claims description 72
- 238000000746 purification Methods 0.000 title claims description 14
- 239000011148 porous material Substances 0.000 claims description 53
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 30
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 30
- 239000002245 particle Substances 0.000 claims description 28
- 239000011232 storage material Substances 0.000 claims description 22
- 239000011163 secondary particle Substances 0.000 claims description 21
- 239000006104 solid solution Substances 0.000 claims description 17
- 229910000510 noble metal Inorganic materials 0.000 claims description 16
- 229910052719 titanium Inorganic materials 0.000 claims description 15
- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- 239000002131 composite material Substances 0.000 claims description 14
- 229910052726 zirconium Inorganic materials 0.000 claims description 14
- 239000010419 fine particle Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 239000002244 precipitate Substances 0.000 description 32
- 239000007789 gas Substances 0.000 description 25
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 22
- 239000000243 solution Substances 0.000 description 22
- 239000011593 sulfur Substances 0.000 description 22
- 229910052717 sulfur Inorganic materials 0.000 description 22
- 239000000843 powder Substances 0.000 description 19
- 231100000572 poisoning Toxicity 0.000 description 18
- 230000000607 poisoning effect Effects 0.000 description 18
- 239000010936 titanium Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 12
- 238000000034 method Methods 0.000 description 12
- 238000003860 storage Methods 0.000 description 12
- 229910052761 rare earth metal Inorganic materials 0.000 description 11
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- 230000007423 decrease Effects 0.000 description 8
- 238000010304 firing Methods 0.000 description 8
- 239000012266 salt solution Substances 0.000 description 7
- 150000003839 salts Chemical class 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 5
- 150000001342 alkaline earth metals Chemical class 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- 150000001340 alkali metals Chemical class 0.000 description 4
- 239000012670 alkaline solution Substances 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- 238000000975 co-precipitation Methods 0.000 description 4
- 238000003795 desorption Methods 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000032683 aging Effects 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 238000001354 calcination Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000010948 rhodium Substances 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000001099 ammonium carbonate Substances 0.000 description 2
- 235000012501 ammonium carbonate Nutrition 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- SCVFZCLFOSHCOH-UHFFFAOYSA-M potassium acetate Chemical compound [K+].CC([O-])=O SCVFZCLFOSHCOH-UHFFFAOYSA-M 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 230000007704 transition Effects 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
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000010718 Oxidation Activity Effects 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- -1 carbonate Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000002431 foraging effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 235000011056 potassium acetate Nutrition 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000001226 reprecipitation Methods 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 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 1
- 230000005070 ripening Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
Images
Landscapes
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
本発明は、自動車などの排気系に用いられる排ガス浄化触媒用の担体と、その担体を用いたNOx 吸蔵還元型の触媒に関する。 The present invention relates to a carrier for an exhaust gas purification catalyst used in an exhaust system of an automobile or the like, and a NO x storage reduction type catalyst using the carrier .
近年、希薄燃焼ガソリンエンジンからの排ガスを浄化する触媒として、NOx 吸蔵還元型触媒が実用化されている。このNOx 吸蔵還元型触媒は、アルカリ金属、アルカリ土類金属などのNOx 吸蔵材と貴金属をアルミナ( Al2O3)などの多孔質担体に担持したものである。このNOx 吸蔵還元型触媒では、空燃比を燃料リーン側からパルス状に燃料ストイキ〜リッチ側となるように制御することにより、リーン側ではNOx がNOx 吸蔵材に吸蔵される。そして吸蔵されたNOx はストイキ〜リッチ側で放出され、貴金属の触媒作用によりHCやCOなどの還元性成分と反応して浄化される。したがって、リーン側においてもNOx の排出が抑制されるので、全体として高いNOx 浄化能が発現する。 In recent years, NO x storage reduction type catalysts have been put into practical use as catalysts for purifying exhaust gas from lean burn gasoline engines. This NO x storage-reduction catalyst is a catalyst in which a NO x storage material such as an alkali metal or an alkaline earth metal and a noble metal are supported on a porous carrier such as alumina (Al 2 O 3 ). This NO x storage-and-reduction type catalyst, by controlling the air-fuel ratio so that the fuel stoichiometric-rich side from the fuel-lean side in a pulsed manner, NO x is occluded in the NO x storage material in the lean side. The occluded NO x is released on the stoichiometric to rich side, and is purified by reacting with reducing components such as HC and CO by the catalytic action of noble metals. Therefore, since NO x emission is suppressed even on the lean side, a high NO x purification ability is exhibited as a whole.
ところが排ガス中には、燃料中に含まれる硫黄(S)が燃焼して生成したSO2 が含まれ、それが酸素過剰雰囲気中で貴金属により酸化されてSO3 となる。そしてこれが排ガス中に含まれる水蒸気により容易に硫酸となり、これらがNOx 吸蔵材と反応して亜硫酸塩や硫酸塩が生成し、これによりNOx 吸蔵材が被毒劣化することが明らかとなった。この現象はNOx 吸蔵材の硫黄被毒と称されている。また、 Al2O3などの多孔質担体はSOx を吸着しやすいという性質があることから、上記硫黄被毒が促進されるという問題があった。そして、このようにNOx 吸蔵材が亜硫塩や硫酸塩となると、もはやNOx を吸蔵することができなくなり、その結果上記触媒では、耐久後のNOx 浄化能が低下するという不具合があった。 However, the exhaust gas contains SO 2 produced by combustion of sulfur (S) contained in the fuel, which is oxidized by a noble metal in an oxygen-excess atmosphere to become SO 3 . And it became clear that this was easily converted into sulfuric acid by the water vapor contained in the exhaust gas, and these reacted with the NO x storage material to produce sulfite and sulfate, which poisoned and deteriorated the NO x storage material. . This phenomenon is called sulfur poisoning of NO x storage material. In addition, a porous carrier such as Al 2 O 3 has a property that it easily adsorbs SO x , so that there is a problem that the sulfur poisoning is promoted. And when the NO x storage material becomes a sulfite or sulfate as described above, it is no longer possible to store NO x , and as a result, the above catalyst has a problem that the NO x purification ability after durability is lowered. .
そこで特開平08−099034号公報には、TiO2-Al2O3、ZrO2-Al2O3及びSiO2-Al2O3から選ばれる少なくとも1種の複合担体を用いることが提案されている。また特開平09−000926号公報には、 TiO2-Al2O3-ZrO2複合酸化物を担体とする排ガス浄化用触媒が開示されている。TiO2などは Al2O3に比べて酸性度が大きいため、SOx との親和性が低くなる結果、NOx 吸蔵材の硫黄被毒を抑制することが可能となる。またTiO2及びZrO2を Al2O3と複合酸化物とすることにより、硫黄被毒が抑制されるとともに、耐熱性が向上する。 Therefore, Japanese Patent Laid-Open No. 08-099034 proposes to use at least one composite carrier selected from TiO 2 —Al 2 O 3 , ZrO 2 —Al 2 O 3 and SiO 2 —Al 2 O 3. Yes. Japanese Patent Application Laid-Open No. 09-000926 discloses an exhaust gas purification catalyst using a TiO 2 —Al 2 O 3 —ZrO 2 composite oxide as a carrier. Since TiO 2 and the like have a higher acidity than Al 2 O 3 , the affinity with SO x is lowered, and as a result, sulfur poisoning of the NO x storage material can be suppressed. Further, by using TiO 2 and ZrO 2 as a composite oxide with Al 2 O 3 , sulfur poisoning is suppressed and heat resistance is improved.
例えばZrO2−TiO2固溶体は、硫黄被毒に対する耐性が大きいため Al2O3と複合化させることで耐硫黄被毒性に優れ、かつ高比表面積を有する触媒担体とすることができる。しかしながら、 Al2O3粉末とZrO2−TiO2固溶体粉末とを単に混合した担体では、 Al2O3の二次粒子とZrO2−TiO2の二次粒子とが混合された状態であり、両粒子の接触界面が少なく硫黄被毒を十分に抑制することができない。したがって二次粒子を粉砕して微細にすることが望ましいが、種類の異なる二次粒子を同時に粉砕しても一様に粉砕することは困難であり、平均粒子径を制御することは困難である。 For example, ZrO 2 —TiO 2 solid solution has a high resistance to sulfur poisoning, and can be combined with Al 2 O 3 to provide a catalyst carrier having excellent sulfur poisoning resistance and a high specific surface area. However, in a carrier in which Al 2 O 3 powder and ZrO 2 —TiO 2 solid solution powder are simply mixed, secondary particles of Al 2 O 3 and secondary particles of ZrO 2 —TiO 2 are mixed, There are few contact interfaces of both particles, and sulfur poisoning cannot be suppressed sufficiently. Therefore, it is desirable to pulverize the secondary particles, but it is difficult to uniformly pulverize different types of secondary particles at the same time, and it is difficult to control the average particle size. .
そこで特開2002−282688号公報には、Al2O3-ZrO2-TiO2系複合酸化物よりなり、メソ細孔領域の細孔を有するとともに、テトラゴナル型ジルコニアを含み、かつZrO2及びTiO2の少なくとも一部がZrO2−TiO2固溶体となっている触媒担体が提案されている。この触媒担体によれば、予め 550℃以上で焼成されているため、触媒として使用時の比表面積の低下が抑制される。また高温での焼成によって触媒担体中の不純物が除去され、その結果、担持された貴金属及びNOx 吸蔵材の本来の特性が発現される。そして触媒として高温で使用した場合でも、貴金属及びNOx 吸蔵材のシンタリングが抑制されるとともに、耐硫黄被毒性が向上する。しかもこの触媒担体は、高温耐久後でも 120m2/g以上の比表面積を有しているので、高い触媒活性が得られる。 Therefore, JP-A-2002-282688 discloses an Al 2 O 3 —ZrO 2 —TiO 2 based composite oxide, has pores in a mesopore region, contains tetragonal zirconia, and contains ZrO 2 and TiO 2. at least a part of 2 is proposed a catalyst carrier has a ZrO 2 -TiO 2 solid solution. According to this catalyst carrier, since it is calcined at 550 ° C. or higher in advance, a decrease in specific surface area when used as a catalyst is suppressed. Further, the impurities in the catalyst carrier are removed by calcination at a high temperature, and as a result, the original characteristics of the supported noble metal and NO x storage material are expressed. Even when the catalyst is used at a high temperature, sintering of the noble metal and the NO x storage material is suppressed and sulfur poisoning resistance is improved. In addition, since this catalyst carrier has a specific surface area of 120 m 2 / g or more even after high temperature durability, high catalytic activity can be obtained.
また特開2002−253968号公報には、孔径 0.1〜20μmの細孔の細孔容積が孔径50μm以下の細孔の細孔容積の50%以上を占め、かつ孔径 0.5〜10μmの細孔の細孔容積が孔径50μm以下の細孔の細孔容積の20%以上を占めるコート層をもつ排ガス浄化用触媒が開示されている。 Japanese Patent Laid-Open No. 2002-253968 discloses that the pore volume of pores having a pore diameter of 0.1 to 20 μm accounts for 50% or more of the pore volume of pores having a pore diameter of 50 μm or less, and fine pores having a pore diameter of 0.5 to 10 μm. An exhaust gas purifying catalyst having a coat layer that occupies 20% or more of the pore volume of pores having a pore diameter of 50 μm or less is disclosed.
孔径 0.1〜20μmの比較的大きな細孔を含むことで、孔径が0.01μmの細孔が大部分を占める従来のコート層に比べて細孔径が10〜2000倍となり、細孔中をガスが拡散する速度も10〜2000倍となる。したがって短時間のリッチスパイクでも、排ガスがコート層の内部まで到達可能となり、コート層内部のNOx 吸蔵材に吸蔵されているNOx を還元浄化することが可能となる。 By including relatively large pores with a pore size of 0.1 to 20 μm, the pore size is 10 to 2000 times that of conventional coating layers, where the majority of pores have a pore size of 0.01 μm, and gas diffuses in the pores. Speed is also 10 to 2000 times. Therefore, even in a short time of the rich spike, the exhaust gas is reachable to the inside of the coat layer, the a NO x occluded in the the NO x storage material of the inner coat layer can be reduced and purified.
なお特開2002−253968号公報には、コート層の細孔分布を上記のようにするために、コート層を形成するスラリー中に界面活性剤を添加し、気泡を混入させたスラリーをウォッシュコートする方法を開示している。またカーボン粉末などの可燃性粉末を混入させてコート層を形成し、焼成時に可燃性粉末を焼失することで細孔を形成する方法も知られている。
孔径が1〜20μmの範囲のマクロ細孔を有する触媒担体を用いることで、ガス拡散性が向上し、その触媒のNOx 浄化性能が向上する。しかしながら従来は、コート層の細孔をそのように制御することが知られているだけであり、担体自体の細孔をそのように制御することは知られていない。 Pore size by using a catalyst support having a macropore range of 1 to 20 [mu] m, improved gas diffusivity, improved the NO x purification performance of the catalyst. Conventionally, however, it is only known to control the pores of the coating layer as such, and it is not known to control the pores of the support itself.
例えば特開2002−282688号公報に記載の触媒担体は、メソ細孔領域の細孔を有することが記載されているが、メソ細孔とは、一般には細孔直径が1〜 100nmの細孔をいうものであり、マクロ細孔に関する記載はない。 For example, the catalyst carrier described in JP-A-2002-282688 is described as having pores in the mesopore region, but the mesopore is generally a pore having a pore diameter of 1 to 100 nm. There is no description about macropores.
本発明はこのような事情に鑑みてなされたものであり、担体自体の細孔を最適化し、高いNOx 浄化性能と耐硫黄被毒性とが両立したNOx 吸蔵還元型触媒とすることを課題とする。 The present invention has been made in view of these circumstances, problems that optimizes the pores of the support itself, and NO x storage-and-reduction type catalyst and high the NO x purification performance and resistance to sulfur poisoning has both And
上記課題を解決する本発明の排ガス浄化触媒用担体の特徴は、Al、Zr及びTiから選ばれる複数種の酸化物粒子からなる二次粒子の集合体である凝集粒子よりなり、粒径が20μm以下の二次粒子中に Al 2 O 3 、ZrO 2 及びTiO 2 からなる複合酸化物又は固溶体が50nm以下の微粒子として分散し、凝集粒子は孔径が1〜20μmのマクロ細孔を有することにある。 The feature of the carrier for exhaust gas purification catalyst of the present invention that solves the above problems is composed of aggregated particles that are aggregates of secondary particles composed of a plurality of types of oxide particles selected from Al, Zr, and Ti, and has a particle size of 20 μm. In the following secondary particles, a composite oxide or solid solution composed of Al 2 O 3 , ZrO 2 and TiO 2 is dispersed as fine particles of 50 nm or less, and the aggregated particles have macropores having a pore diameter of 1 to 20 μm. .
二次粒子は、アルミナ系酸化物と他の酸化物との混合体からなることが好ましく、他の酸化物は少なくとも一部が固溶したZrO2−TiO2複合酸化物を含むことが望ましい。 The secondary particles are preferably composed of a mixture of an alumina-based oxide and another oxide, and the other oxide preferably contains a ZrO 2 —TiO 2 composite oxide in which at least a part thereof is in solid solution.
また平均粒子径を20〜80μmとした場合に、全細孔容積に対するマクロ細孔の細孔容積が30%以上を占めることが好ましく、中心細孔径が5〜15μmの範囲にあることが望ましい。 When the average particle size is 20 to 80 μm, the pore volume of the macropores relative to the total pore volume preferably occupies 30% or more, and the center pore diameter is preferably in the range of 5 to 15 μm.
本発明の触媒の特徴は、本発明の担体に貴金属及びNOx 吸蔵材を担持してなることにある。 A feature of the catalyst of the present invention is that the support of the present invention carries a noble metal and a NO x storage material.
本発明の担体によれば、孔径が1〜20μmの細孔であるマクロ細孔を有しているので、ガス拡散性に優れている。したがって本発明の触媒によれば、短時間のリッチスパイクでも排ガスが触媒の内部まで到達可能となり、内部の貴金属及びNOx 吸蔵材まで有効利用することができる。さらに、細孔容積が大きいため単位容積あたりに流通する排ガス量が低下し、穏やかな反応場を提供することができる。これらの作用により、本発明の触媒は高いNOx 吸蔵能が発現される。 According to the carrier of the present invention, since it has macropores which are pores having a pore diameter of 1 to 20 μm, it has excellent gas diffusibility. Therefore, according to the catalyst of the present invention, the exhaust gas can reach the inside of the catalyst even with a short rich spike, and the internal precious metal and the NO x storage material can be effectively used. Furthermore, since the pore volume is large, the amount of exhaust gas flowing per unit volume is reduced, and a gentle reaction field can be provided. By these actions, the catalyst of the present invention exhibits a high NO x storage capacity.
さらに本発明の担体によれば、複数種の酸化物粒子がナノレベルで混合されてなる二次粒子の集合体であるので、酸化物としてTiO2、ZrO2−TiO2などを含むことで高い耐硫黄被毒性が発現され、本発明の触媒は耐久性に優れている。 Furthermore, according to the carrier of the present invention, since it is an aggregate of secondary particles in which a plurality of types of oxide particles are mixed at the nano level, it is high by including TiO 2 , ZrO 2 —TiO 2, etc. as oxides. Sulfur resistance is exhibited and the catalyst of the present invention is excellent in durability.
本発明の担体は、Al、Zr及びTiから選ばれる複数種の酸化物粒子からなる二次粒子の集合体である凝集粒子よりなり、粒径が20μm以下の二次粒子中に Al 2 O 3 、ZrO 2 及びTiO 2 からなる複合酸化物又は固溶体が50nm以下の微粒子として分散し、凝集粒子は孔径が1〜20μmのマクロ細孔を有している。アルミナ系酸化物と他の酸化物との混合体からなることが好ましく、さらに少なくとも一部が固溶したZrO2−TiO2複合酸化物を含むことが望ましい。 The carrier of the present invention comprises aggregated particles that are aggregates of secondary particles composed of a plurality of types of oxide particles selected from Al, Zr, and Ti, and Al 2 O 3 in secondary particles having a particle size of 20 μm or less. The composite oxide or solid solution composed of ZrO 2 and Ti 2 O 2 is dispersed as fine particles of 50 nm or less, and the agglomerated particles have macropores having a pore diameter of 1 to 20 μm. It is preferably composed of a mixture of an alumina-based oxide and another oxide, and further desirably contains a ZrO 2 —TiO 2 composite oxide in which at least a part thereof is in solid solution.
そして粒径が20μm以下の二次粒子中に Al2O3、ZrO2及びTiO2からなる複合酸化物又は固溶体が50nm以下の微粒子として分散していることで、 Al2O3、ZrO2及びTiO2が高分散状態であっても、既に凝集した状態であるので更なる凝集が抑制され、耐熱性が向上するとともに耐硫黄被毒性が一層向上する。 Then, in the secondary particles having a particle size of 20 μm or less, a composite oxide or solid solution composed of Al 2 O 3 , ZrO 2 and TiO 2 is dispersed as fine particles of 50 nm or less, so that Al 2 O 3 , ZrO 2 and Even if TiO 2 is in a highly dispersed state, since it is already in an aggregated state, further aggregation is suppressed, heat resistance is improved, and sulfur poisoning resistance is further improved.
またこの担体では、二次粒子は表面と内部とで金属元素の分布が異なっていることが望ましい。例えば表面に Al2O3が多い構成とすれば、担持される貴金属を安定化することができる。また表面にZrO2−TiO2固溶体が多い構成とすれば、SOx が付着しにくくなり耐硫黄被毒性が格段に向上する。 In this carrier, it is desirable that the secondary particles have different metal element distributions on the surface and inside. For example, if the surface has a large amount of Al 2 O 3 , the supported noble metal can be stabilized. In addition, if the surface has a large amount of ZrO 2 —TiO 2 solid solution, SO x hardly adheres and sulfur poisoning resistance is significantly improved.
この担体においては、凝集粒子はさらに希土類元素酸化物及びアルカリ土類金属酸化物の少なくとも一種を含み、希土類元素酸化物及びアルカリ土類金属酸化物の少なくとも一種の70mol%以上が Al2O3中に固溶していることが望ましい。これにより Al2O3の耐熱性が向上するとともに、希土類元素酸化物及びアルカリ土類金属酸化物の少なくとも一種の固溶によるZrO2−TiO2固溶体の耐硫黄被毒性の低下が抑制される。希土類元素酸化物及びアルカリ土類金属酸化物の少なくとも一種の90mol%以上が Al2O3中に固溶していることがさらに望ましい。この希土類元素酸化物及びアルカリ土類金属酸化物の少なくとも一種は、 Al2O3に対して70〜95mol%の範囲で固溶していることが望ましい。希土類元素酸化物としては、La,Sc,Nd,Sm,Prなどの酸化物が例示され、アルカリ土類金属酸化物としてはBe,Mg,Ca,Sr,Baなどの酸化物が例示される。中でも La2O3が最も好ましい。 In this carrier, the agglomerated particles further contain at least one kind of rare earth element oxide and alkaline earth metal oxide, and 70 mol% or more of at least one kind of rare earth element oxide and alkaline earth metal oxide is contained in Al 2 O 3 . It is desirable to be dissolved in. This improves the heat resistance of Al 2 O 3 and suppresses the reduction of the sulfur poisoning resistance of the ZrO 2 —TiO 2 solid solution due to the solid solution of at least one rare earth element oxide and alkaline earth metal oxide. It is further desirable that 90 mol% or more of at least one kind of rare earth element oxide and alkaline earth metal oxide is dissolved in Al 2 O 3 . It is desirable that at least one of the rare earth element oxide and the alkaline earth metal oxide is dissolved in a range of 70 to 95 mol% with respect to Al 2 O 3 . Examples of rare earth element oxides include oxides such as La, Sc, Nd, Sm, and Pr, and examples of alkaline earth metal oxides include oxides such as Be, Mg, Ca, Sr, and Ba. Of these, La 2 O 3 is most preferred.
そして La2O3の70mol%以上が Al2O3中に固溶し、かつ二次粒子の表面にZrO2−TiO2固溶体が多い構成とした担体から調製された触媒は、高い耐硫黄被毒性を有するとともに耐熱性が格段に向上するため、SOx を含む雰囲気下における高温耐久後にもきわめて高い活性が発現される。 A catalyst prepared from a support in which 70 mol% or more of La 2 O 3 is dissolved in Al 2 O 3 and the surface of the secondary particles is rich in ZrO 2 —TiO 2 solid solution has a high sulfur resistance. Since it has toxicity and heat resistance is remarkably improved, extremely high activity is exhibited even after high temperature durability in an atmosphere containing SO x .
上記担体において、それぞれの酸化物の構成比は、モル比で Al2O3:ZrO2:TiO2=19〜82:8〜66:3〜49の範囲とすることが好ましい。 Al2O3の比率がこの範囲より少ないと活性が低下し、この範囲より多くなると耐硫黄被毒性が低下するようになる。またZrO2の比率がこの範囲より少ないとNOx 吸蔵材と担体の固相反応が起こりやすくなり、この範囲より多いと担体の比表面積低下を引き起こす原因となる。さらにTiO2の比率がこの範囲より少ないと耐硫黄被毒性が低下し、この範囲より多くなると担体の比表面積が低下する。 In the above support, the constituent ratio of each oxide is preferably in the range of Al 2 O 3 : ZrO 2 : TiO 2 = 19 to 82: 8 to 66: 3 to 49 in terms of molar ratio. If the Al 2 O 3 ratio is less than this range, the activity decreases, and if it exceeds this range, the sulfur poisoning resistance decreases. If the ratio of ZrO 2 is less than this range, a solid phase reaction between the NO x storage material and the carrier tends to occur, and if it exceeds this range, the specific surface area of the carrier is reduced. Further, when the ratio of TiO 2 is less than this range, the sulfur poisoning resistance decreases, and when it exceeds the range, the specific surface area of the support decreases.
孔径が1〜20μmのマクロ細孔は、担体の粉砕程度を制御することで容易に形成することができる。本発明の担体は、複数の酸化物粒子がナノレベルで混合されてなる二次粒子からなるので、一様に粉砕することができ粉砕程度の制御が容易である。 Macropores having a pore diameter of 1 to 20 μm can be easily formed by controlling the degree of pulverization of the carrier. Since the carrier of the present invention is composed of secondary particles in which a plurality of oxide particles are mixed at the nano level, it can be uniformly pulverized and the degree of pulverization can be easily controlled.
本発明の担体は、二次粒子の平均粒子径を20〜80μmとした場合に、全細孔容積に対するマクロ細孔の細孔容積が30%以上を占めることが望ましい。また中心細孔径が5〜15μmの範囲にあることが望ましい。このようにすることで、ガス拡散性が特に向上し、耐硫黄被毒性を維持しつつ高いNOx 浄化性能をもつ触媒とすることができる。 In the carrier of the present invention, it is desirable that the pore volume of macropores accounts for 30% or more with respect to the total pore volume when the average particle diameter of secondary particles is 20 to 80 μm. Moreover, it is desirable that the center pore diameter is in the range of 5 to 15 μm. By doing so, the gas diffusibility is particularly improved, and a catalyst having high NO x purification performance can be obtained while maintaining sulfur poisoning resistance.
本発明の担体を製造するには、例えばAl、Zr及びTiの塩の溶液をそれぞれ用意し、それぞれの塩の溶液とアルカリ溶液とを混合してそれぞれ沈殿を形成し、それぞれの沈殿を混合した沈殿物を 550℃以上で焼成する。あるいは、Al、Zr及びTiの塩の溶液をそれぞれ用意し、塩の全量を中和可能なアルカリ溶液と混合することで塩の溶液から沈殿物を逐次生成し、この沈殿物を 550℃以上で焼成する。 In order to produce the carrier of the present invention, for example, a salt solution of Al, Zr, and Ti is prepared, respectively, a solution of each salt and an alkali solution are mixed to form a precipitate, and each precipitate is mixed. Bake the precipitate at 550 ° C or higher. Alternatively, a salt solution of Al, Zr, and Ti is prepared, and a precipitate is sequentially generated from the salt solution by mixing the total amount of the salt with a neutralizable alkali solution. Bake.
沈殿物の焼成温度は 550℃以上であることが必要であるが、 650℃以上がさらに望ましく、 650〜900℃であることが特に望ましい。焼成温度が 550℃未満であると、触媒として耐久試験を行った場合に貴金属などのシンタリングが生じやすく、耐硫黄被毒性も低下する。また焼成温度が 900℃を超えると、 Al2O3の結晶化並びに相転移による比表面積の低下などが生じるため好ましくない。 The calcination temperature of the precipitate needs to be 550 ° C or higher, more preferably 650 ° C or higher, and particularly preferably 650 to 900 ° C. When the calcination temperature is less than 550 ° C., when a durability test is performed as a catalyst, sintering of noble metals and the like is likely to occur, and sulfur poisoning resistance is also reduced. Further, if the firing temperature exceeds 900 ° C., the specific surface area will decrease due to crystallization of Al 2 O 3 and phase transition, which is not preferable.
また上記方法において、Al、Zr及びTiの塩の溶液をアルカリ溶液に逐次添加して沈殿を生成してもよい。この方法を逐次共沈法と称する。実際には、複数種の塩が溶解した混合溶液から沈殿させる場合でも、溶解度あるいはイオン化傾向などの差から沈殿は逐次生成している。しかしこれでは制御が困難であるので、逐次共沈法を用いることが好ましい。この逐次共沈法によれば、先ず先に添加された溶液から塩が中和され金属水酸化物として析出する。そして後から添加された塩溶液が中和されると、新しい金属水酸化物は先に生成している析出物を核としてその表面に優先的に析出し、沈殿する。あるいは析出物を介在物としてその粒界に析出し、沈殿する。 In the above method, a precipitate may be generated by sequentially adding a salt solution of Al, Zr and Ti to an alkaline solution. This method is called a sequential coprecipitation method. Actually, even when precipitation is performed from a mixed solution in which a plurality of types of salts are dissolved, precipitates are sequentially generated due to differences in solubility or ionization tendency. However, since this is difficult to control, it is preferable to use the sequential coprecipitation method. According to this sequential coprecipitation method, the salt is first neutralized from the previously added solution and precipitated as a metal hydroxide. Then, when the salt solution added later is neutralized, the new metal hydroxide is preferentially deposited on the surface with the precipitates that have been generated as nuclei, and is precipitated. Alternatively, the precipitate is deposited as an inclusion at the grain boundary and precipitated.
望ましくは、Al、Zr及びTiを含む溶液からAl、Zr及びTiを含む第1沈殿を生成し、次いでAlを含む溶液からAlを含む第2沈殿を生成する。あるいは逆にAlを含む溶液からAlを含む第1沈殿を生成し、次いでAl、Zr及びTiを含む溶液からAl、Zr及びTiを含む第2沈殿を生成する。又はAl、Zr及びTiを含む溶液からAl、Zr及びTiを含む第1沈殿を生成し、次いで希土類元素及びアルカリ土類金属酸化物の少なくとも一種及びAlを含む溶液から希土類元素及びアルカリ土類金属酸化物の少なくとも一種及びAlを含む第2沈殿を生成する。あるいはその逆に、希土類元素及びアルカリ土類金属酸化物の少なくとも一種及びAlを含む溶液から希土類元素及びアルカリ土類金属酸化物の少なくとも一種及びAlを含む第1沈殿を生成し、次いでAl、Zr及びTiを含む溶液からAl、Zr及びTiを含む第2沈殿を生成する。 Desirably, a first precipitate containing Al, Zr and Ti is generated from a solution containing Al, Zr and Ti, and then a second precipitate containing Al is generated from the solution containing Al. Or conversely, a first precipitate containing Al is produced from a solution containing Al, and then a second precipitate containing Al, Zr and Ti is produced from a solution containing Al, Zr and Ti. Alternatively, a first precipitate containing Al, Zr and Ti is produced from a solution containing Al, Zr and Ti, and then a rare earth element and an alkaline earth metal are produced from the solution containing at least one kind of rare earth element and alkaline earth metal oxide and Al. A second precipitate containing at least one oxide and Al is generated. Alternatively, conversely, a first precipitate containing at least one rare earth element and alkaline earth metal oxide and Al is generated from a solution containing at least one rare earth element and alkaline earth metal oxide and Al, and then Al, Zr. And a second precipitate containing Al, Zr and Ti is produced from the solution containing Ti and Ti.
第1沈殿と第2沈殿を同一容器内で生成させるには、先ず単一又は複数種の第1金属元素を含む溶液とその酸量を中和する量のアルカリ溶液とを接触させて第1沈殿を生成し、その後さらに複数種又は単一の第2金属元素を含む溶液とその酸量を中和する量のアルカリ溶液を添加して第2沈殿を生成すればよい。なお第3あるいは第4の沈殿をさらに混合してもよいし、第2沈殿生成後に第3あるいは第4の沈殿を生成してもよい。 In order to generate the first precipitate and the second precipitate in the same container, first, a solution containing a single or plural kinds of first metal elements is contacted with an alkaline solution in an amount that neutralizes the acid amount. A second precipitate may be generated by adding a solution containing a plurality of types or a single second metal element and an alkali solution in an amount that neutralizes the acid amount after that. The third or fourth precipitate may be further mixed, or the third or fourth precipitate may be generated after the second precipitate is generated.
この沈殿物を焼成して得られる複合酸化物では、一次粒子が凝集して生成する二次粒子において、中心部分と表面部分とで金属元素の分布が異なることとなり、用いる塩の種類を適切に選択することで、表面と内部とで金属元素の分布が異なる担体を製造することができる。 In the composite oxide obtained by firing this precipitate, the distribution of metal elements in the central part and the surface part will be different in the secondary particles produced by agglomeration of the primary particles. By selecting, a carrier having a different distribution of metal elements on the surface and inside can be produced.
塩としては必要とされる水又はアルコールへの溶解度を有するものであれば特に制限がないが、硝酸塩が特に好ましく用いられる。アルカリ溶液としては、アンモニア、炭酸アンモニウム、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウムなどを溶解した水溶液、アルコール溶液が使用できる。焼成時に揮散するアンモニア、炭酸アンモニウムが特に好ましい。なお、アルカリ溶液のpHは、9以上であることがより好ましい。 The salt is not particularly limited as long as it has the required solubility in water or alcohol, but nitrate is particularly preferably used. As the alkaline solution, an aqueous solution or alcohol solution in which ammonia, ammonium carbonate, sodium hydroxide, potassium hydroxide, sodium carbonate or the like is dissolved can be used. Particularly preferred are ammonia and ammonium carbonate which volatilize during firing. The pH of the alkaline solution is more preferably 9 or higher.
沈殿の析出方法には、様々な調節方法があり、アンモニア水などを瞬時に添加し強撹拌する方法や、過酸化水素などを加えることで酸化物前駆体の沈殿し始めるpHを調節した後、アンモニア水などで沈殿を析出させる方法などがある。またアンモニア水などで中和させる際にかかる時間を十分に長くし、好ましくは10分以上で中和させる方法や、pHをモニターしながら段階的に中和する又は所定のpHに保つような緩衝溶液を添加する方法などがある。 There are various adjustment methods for precipitation, such as adding ammonia water instantly and stirring vigorously, or adjusting the pH at which the oxide precursor starts to precipitate by adding hydrogen peroxide, etc. There is a method of depositing a precipitate with ammonia water or the like. In addition, the time required for neutralization with aqueous ammonia or the like is sufficiently long, preferably a method of neutralization in 10 minutes or more, or a buffer that neutralizes stepwise while monitoring the pH or maintains a predetermined pH. There is a method of adding a solution.
また塩の溶液を添加するには、塩の溶液を一度に添加するのが好ましい。これにより沈殿粒子の粒径をより微細とすることができ、50nm以下の微粒子が凝集した20μm以下の二次粒子からなる複合酸化物を容易に製造することができる。そして逐次添加するには、2段階以上の複数段階で行うことができ、段階の上限は特に規制されない。 In order to add a salt solution, it is preferable to add the salt solution all at once. As a result, the particle size of the precipitated particles can be made finer, and a composite oxide composed of secondary particles of 20 μm or less in which fine particles of 50 nm or less are aggregated can be easily produced. Further, the sequential addition can be carried out in two or more stages, and the upper limit of the stage is not particularly restricted.
そして、水又は水を含む溶液を分散媒とした懸濁状態または系内に水が十分に存在する状態で混合物を加温する熟成工程を行うことがさらに望ましい。これにより、メカニズムは不明であるが、細孔が制御された担体が得られる。 It is further desirable to perform an aging step in which the mixture is heated in a suspended state using water or a solution containing water as a dispersion medium or in a state where water is sufficiently present in the system. Thereby, although the mechanism is unknown, a carrier with controlled pores can be obtained.
系内に水分が充分に存在している状態で沈殿を熟成するには、沈殿を含む溶液ごと加熱して溶媒を蒸発させ、そのまま焼成することで行うことができる。あるいは濾別された沈殿物を水蒸気の存在下で焼成してもよい。この場合は、飽和水蒸気雰囲気で焼成することが好ましい。 In order to mature the precipitate in a state where moisture is sufficiently present in the system, the solution containing the precipitate can be heated to evaporate the solvent, and then baked as it is. Alternatively, the precipitate separated by filtration may be calcined in the presence of water vapor. In this case, it is preferable to bake in a saturated steam atmosphere.
上記した熟成工程を行った場合には、加温の熱によって溶解・再析出が促進されるとともに粒子の成長が生じる。この場合は、塩の全てを中和できる当量以上の塩基で中和することが望ましい。これにより酸化物前駆体がより均一に熟成され、細孔が効果的に形成されるとともに、ZrO2−TiO2固溶体の固溶がさらに促進される。 When the above-described ripening step is performed, dissolution / reprecipitation is promoted by heating heat and particle growth occurs. In this case, it is desirable to neutralize with an equivalent base or more that can neutralize all of the salt. Thereby, the oxide precursor is aged more uniformly, the pores are effectively formed, and the solid solution of the ZrO 2 —TiO 2 solid solution is further promoted.
この熟成工程は、室温以上、好ましくは 100〜 200℃で、さらに好ましくは 100〜 150℃で行うことが望ましい。 100℃未満の加温では熟成の促進効果が小さく、熟成に要する時間が長大となる。また 200℃より高い温度では、10気圧以上に耐えうる合成装置が必要となり、設備コストが高くなるため触媒担体には適さない。 This aging step is desirably performed at room temperature or higher, preferably 100 to 200 ° C, more preferably 100 to 150 ° C. When heating at less than 100 ° C., the effect of promoting aging is small, and the time required for aging becomes long. At temperatures higher than 200 ° C., a synthesizer that can withstand 10 atm or more is required, which increases equipment costs and is not suitable for a catalyst carrier.
得られた沈殿は、 550℃以上で焼成される。上記したように、焼成温度が 550℃未満であると、触媒として耐久試験を行った場合に貴金属などのシンタリングが生じやすく、耐硫黄被毒性も低下する。また焼成温度が 900℃を超えると、 Al2O3の結晶化並びに相転移による比表面積低下が生じるため好ましくない。 The resulting precipitate is calcined at 550 ° C or higher. As described above, when the firing temperature is less than 550 ° C., when a durability test is performed as a catalyst, sintering of noble metals and the like is likely to occur, and sulfur poisoning resistance is also reduced. On the other hand, if the firing temperature exceeds 900 ° C., the specific surface area decreases due to crystallization of Al 2 O 3 and phase transition.
そして本発明の担体に、貴金属及びNOx 吸蔵材を担持することで本発明の触媒が得られる。本発明の触媒は、ガソリンエンジン、ディーゼルエンジンあるいはガスエンジン( GHP)などからの排ガスの浄化に利用できる。 The catalyst of the present invention is obtained by supporting the noble metal and the NO x storage material on the support of the present invention. The catalyst of the present invention can be used for purification of exhaust gas from a gasoline engine, a diesel engine, a gas engine (GHP) or the like.
貴金属としては、Pt,Rh,Pd,Ir,Ruなどが利用できるが、NOの酸化活性が高いPtが特に好ましい。この貴金属の担持量は、触媒1リットル当たり 0.1〜20gとすることができる。貴金属の担持量がこの範囲より少ないとNOx 浄化活性が低く、この範囲より多く担持しても活性が飽和するとともにコストが上昇する。 Pt, Rh, Pd, Ir, Ru, etc. can be used as the noble metal, but Pt having a high NO oxidation activity is particularly preferable. The amount of the noble metal supported can be 0.1 to 20 g per liter of the catalyst. If the amount of noble metal supported is less than this range, the NO x purification activity is low, and if it is supported in excess of this range, the activity is saturated and the cost increases.
NOx 吸蔵材は、アルカリ金属、アルカリ土類金属及び希土類元素から選ばれる少なくとも1種であり、塩基度が高いアルカリ金属及びアルカリ土類金属の少なくとも一方を用いることが望ましい。アルカリ金属は高温域におけるNOx 吸蔵能が高く、アルカリ土類金属は低温域におけるNOx 吸蔵能が高いので、両者を併用することが好ましく中でもK及びBaを併用するとよい。このNOx 吸蔵材は、炭酸塩などの塩あるいは酸化物、水酸化物などの状態で担持される。 The NO x storage material is at least one selected from alkali metals, alkaline earth metals and rare earth elements, and it is desirable to use at least one of alkali metals and alkaline earth metals having a high basicity. Alkali metals have a high NO x storage capacity in the high temperature range, and alkaline earth metals have a high NO x storage capacity in the low temperature range. Therefore, it is preferable to use both in combination. This NO x storage material is supported in the state of a salt such as carbonate, an oxide, or a hydroxide.
NOx 吸蔵材の担持量は、触媒1リットル当たり 0.1〜 1.2モル担持されていることが望ましい。なおNOx 吸蔵材の担持量が多すぎると、貴金属がNOx 吸蔵材で覆われる現象が生じ、NOx 浄化活性が低下するようになる。 The loading amount of the NO x storage material is desirably 0.1 to 1.2 moles per liter of catalyst. When the amount of the NO x storage material supported is too large, a phenomenon that the noble metal is covered with the NO x storage material occurs, and the NO x purification activity decreases.
以下、実施例及び比較例により本発明を具体的に説明する。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
(実施例)
硝酸アルミニウムと、オキシ硝酸ジルコニル及び四塩化チタンを水中で撹拌混合し、混合水溶液を調製した。これにアンモニア水を添加して中和し、共沈法により沈殿物を得た。この沈殿物を溶液とともに2気圧下 120℃で2時間保持する熟成を行った。その後、沈殿物を 400℃で5時間仮焼した後 800℃で5時間焼成し、乾式粉砕器にてメジアン径D50≒40μmに粉砕して触媒担体粉末を調製した。各酸化物の組成は、重量比で Al2O3:ZrO2:TiO2=50:35:15である。
(Example)
Aluminum nitrate, zirconyl oxynitrate and titanium tetrachloride were stirred and mixed in water to prepare a mixed aqueous solution. Ammonia water was added thereto for neutralization, and a precipitate was obtained by a coprecipitation method. The precipitate was aged with the solution at 2 ° C. and 120 ° C. for 2 hours. Thereafter, the precipitate was calcined at 400 ° C. for 5 hours, then calcined at 800 ° C. for 5 hours, and pulverized to a median diameter D50≈40 μm by a dry pulverizer to prepare a catalyst carrier powder. The composition of each oxide is Al 2 O 3 : ZrO 2 : TiO 2 = 50: 35: 15 by weight ratio.
この触媒担体粉末は、 Al2O3-ZrO2-TiO2複合酸化物よりなり、ZrO2及びTiO2の少なくとも一部がZrO2−TiO2固溶体となっていた。また BET比表面積は 120m2/gであった。 This catalyst carrier powder was made of Al 2 O 3 —ZrO 2 —TiO 2 composite oxide, and at least part of ZrO 2 and TiO 2 was a ZrO 2 —TiO 2 solid solution. The BET specific surface area was 120 m 2 / g.
この触媒担体粉末に、ジニトロジアンミン白金水溶液を用いてPtを担持し、次いで硝酸ロジウム水溶液を用いてRhを担持した。触媒担体粉末 120gに対して、Ptは2g、Rhは 0.1g担持された。貴金属担持後の焼成条件は、大気中、 250℃で1時間とした。さらに酢酸バリウム水溶液を用いてBaを担持し、酢酸カリウム水溶液を用いてKを担持した。触媒担体粉末 120gに対して、Baは 0.2モル、Kは 0.1モル担持された。NOx 吸蔵材担持後の焼成条件は、大気中、 500℃で3時間とした。 On this catalyst support powder, Pt was supported using a dinitrodiammine platinum aqueous solution, and then Rh was supported using a rhodium nitrate aqueous solution. 2 g of Pt and 0.1 g of Rh were supported on 120 g of the catalyst carrier powder. Firing conditions after loading the noble metal were 1 hour at 250 ° C. in the air. Further, Ba was supported using an aqueous barium acetate solution, and K was supported using an aqueous potassium acetate solution. 0.2 mol of Ba and 0.1 mol of K were supported on 120 g of catalyst support powder. Firing conditions after loading the NO x storage material were set at 500 ° C. for 3 hours in the air.
(比較例)
γ-Al2O3粉末 100gと、重量比ZrO2/TiO2が70/30のZrO2−TiO2固溶体粉末 100gと、を物理混合し、比較例の触媒担体粉末とした。そしてこの触媒担体粉末を用いたこと以外は実施例と同様にして、触媒を調製した。
(Comparative example)
100 g of γ-Al 2 O 3 powder and 100 g of ZrO 2 —TiO 2 solid solution powder having a weight ratio ZrO 2 / TiO 2 of 70/30 were physically mixed to obtain a catalyst support powder of a comparative example. A catalyst was prepared in the same manner as in Example except that this catalyst carrier powder was used.
<試験例1:細孔分布>
実施例及び比較例で調製された触媒担体粉末の粒度分布を図1に、平均粒子径を表1に示す。また水銀ポロシメータで測定された触媒粉末の細孔分布を図2に、孔径が1〜20μmの細孔よりなるマクロ細孔の細孔容積が全細孔容積に対する割合を表2に示す。
<Test Example 1: Pore distribution>
FIG. 1 shows the particle size distribution of the catalyst carrier powders prepared in Examples and Comparative Examples, and Table 1 shows the average particle size. FIG. 2 shows the pore distribution of the catalyst powder measured with a mercury porosimeter, and Table 2 shows the ratio of the pore volume of macropores composed of pores having a pore diameter of 1 to 20 μm to the total pore volume.
図1及び表1より、実施例の触媒担体粉末は比較例に比べて粒子径が大きいことがわかる。また図2及び表2より、比較例の触媒では、触媒粉末の細孔は大部分が1μm以下の範囲に分布し、1〜20μmのマクロ細孔を20.3%しか有さないのに対し、実施例の触媒では、触媒粉末は1〜20μmのマクロ細孔を30%以上有していることがわかる。 From FIG. 1 and Table 1, it can be seen that the catalyst carrier powder of the example has a larger particle size than the comparative example. 2 and Table 2, in the catalyst of the comparative example, the pores of the catalyst powder are mostly distributed in the range of 1 μm or less, and the macropores of 1 to 20 μm have only 20.3%. In the example catalyst, it can be seen that the catalyst powder has 30% or more of macropores of 1 to 20 μm.
すなわち実施例の触媒では、10μm付近に二次粒子どうしの隙間に由来すると考えられるマクロ細孔のピークが存在するが、比較例の触媒にはほとんど存在しない。 That is, in the catalyst of the example, there is a macropore peak considered to be derived from the gap between the secondary particles in the vicinity of 10 μm, but the catalyst of the comparative example hardly exists.
<試験例2:硫黄脱離特性> <Test Example 2: Sulfur desorption characteristics>
実施例及び比較例の触媒を評価装置にそれぞれ配置し、表3に示す付着時モデルガスを 600℃で30分間流通させてSO2 を付着させた。その後表3に示す昇温時モデルガスを用いて、触媒入りガス温度を 100℃から 800℃まで15℃/分の速度で昇温し、触媒から脱離するSOx 量を測定した。結果を図3に示し、 600℃までのSOx 脱離量を表4に示す。 The catalysts of Examples and Comparative Examples were respectively placed in the evaluation apparatus, and the model gas during deposition shown in Table 3 was allowed to flow at 600 ° C. for 30 minutes to deposit SO 2 . Thereafter, the temperature of the gas containing the catalyst was increased from 100 ° C. to 800 ° C. at a rate of 15 ° C./min using the model gas during temperature increase shown in Table 3, and the amount of SO x desorbed from the catalyst was measured. The results are shown in FIG. 3, and the SO x desorption amount up to 600 ° C. is shown in Table 4.
図3及び表4より、実施例の触媒は、比較例の触媒に比べて低温からSOx が脱離し、低温から高温までSOx が平均的に脱離していることがわかる。また表3より、 600℃までのSOx 脱離量は、実施例の触媒は比較例の触媒に対して 2.1倍であった。 3 and Table 4, it can be seen that in the catalyst of the example, SO x is desorbed from a low temperature and SO x is desorbed on average from the low temperature to the high temperature as compared with the catalyst of the comparative example. Also, from Table 3, the SO x desorption amount up to 600 ° C. was 2.1 times that of the catalyst of the example compared to the catalyst of the comparative example.
<試験例3:NOx 吸蔵量> <Test Example 3: NO x storage amount>
実施例及び比較例の触媒を評価装置にそれぞれ配置し、表5に示すリーンガスとリッチガスを30秒毎に切り替えながら、 600℃で 140分間流通させSOx を付着させた。その後、表6に示すモデルガスを流通させながら、 250〜 600℃の各温度におけるNOx 吸蔵量を測定した。測定は、リーンガスを流通後に3秒間リッチガスを流通させ、次にリーンガスに切り替えた際のNOx 吸蔵量(リッチスパイクNOx 吸蔵量)を測定した。結果を図4及び表7に示す。 The catalysts of Examples and Comparative Examples were respectively placed in an evaluation apparatus, and SO x was deposited by flowing at 600 ° C. for 140 minutes while switching between lean gas and rich gas shown in Table 5 every 30 seconds. Thereafter, the NO x storage amount at each temperature of 250 to 600 ° C. was measured while circulating the model gas shown in Table 6. Measured was circulated for 3 seconds rich gas after flowing through the lean gas, then the NO x storage amount at the time of switching to a lean gas (the rich spike the NO x storage amount) was measured. The results are shown in FIG.
図4及び表7より、実施例の触媒は比較例に比べて特に高温域におけるNOx 吸蔵量が多いことがわかり、実施例の触媒ではNOx 吸蔵材の硫黄被毒が抑制されていることが明らかである。これは、実施例の触媒担体粉末では1〜20μmのマクロ細孔を多く有していることに起因していると考えられる。 From FIG. 4 and Table 7, the catalyst of Example was found to be often the NO x storage amount in the particular high temperature range as compared with the comparative example, the sulfur poisoning of the NO x storage material in the catalyst of Example is suppressed Is clear. This is considered to be due to the fact that the catalyst support powder of the example has many macropores of 1 to 20 μm.
Claims (6)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2003382973A JP4324856B2 (en) | 2003-11-12 | 2003-11-12 | Exhaust gas purification catalyst carrier and catalyst |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2003382973A JP4324856B2 (en) | 2003-11-12 | 2003-11-12 | Exhaust gas purification catalyst carrier and catalyst |
Publications (2)
Publication Number | Publication Date |
---|---|
JP2005144274A JP2005144274A (en) | 2005-06-09 |
JP4324856B2 true JP4324856B2 (en) | 2009-09-02 |
Family
ID=34691877
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2003382973A Expired - Fee Related JP4324856B2 (en) | 2003-11-12 | 2003-11-12 | Exhaust gas purification catalyst carrier and catalyst |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP4324856B2 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2009028575A (en) * | 2007-07-24 | 2009-02-12 | Toyota Motor Corp | Catalyst for cleaning exhaust gas |
JP7450359B2 (en) * | 2019-10-01 | 2024-03-15 | 株式会社キャタラー | Exhaust gas purification catalyst |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS51104488A (en) * | 1975-03-13 | 1976-09-16 | Toyota Motor Co Ltd | Shokubaitantai oyobi shokubai |
JPS5339281A (en) * | 1976-09-22 | 1978-04-11 | Toyoda Chuo Kenkyusho Kk | Manufacture of carriers |
JP4098835B2 (en) * | 1993-12-07 | 2008-06-11 | トヨタ自動車株式会社 | Exhaust gas purification catalyst |
JP3436427B2 (en) * | 1994-10-21 | 2003-08-11 | 株式会社豊田中央研究所 | Exhaust gas purification catalyst and exhaust gas purification method |
JP3446915B2 (en) * | 1995-06-22 | 2003-09-16 | 株式会社豊田中央研究所 | Exhaust gas purification catalyst |
JP2000001365A (en) * | 1998-04-16 | 2000-01-07 | Denso Corp | Honeycomb structure and its production |
JP3388255B2 (en) * | 1998-06-03 | 2003-03-17 | トヨタ自動車株式会社 | Exhaust gas purification catalyst and method for producing the same |
JP3643948B2 (en) * | 1999-03-15 | 2005-04-27 | 株式会社豊田中央研究所 | Titania-zirconia powder and method for producing the same |
JP3766568B2 (en) * | 1999-07-30 | 2006-04-12 | 株式会社豊田中央研究所 | Exhaust gas purification catalyst and exhaust gas purification method |
JP2001347167A (en) * | 2000-06-09 | 2001-12-18 | Toyota Central Res & Dev Lab Inc | Exhaust gas cleaning catalyst |
JP3997783B2 (en) * | 2001-01-16 | 2007-10-24 | 株式会社豊田中央研究所 | Method for producing catalyst carrier |
JP2002253968A (en) * | 2001-03-02 | 2002-09-10 | Toyota Central Res & Dev Lab Inc | Catalyst for purifying exhaust gas |
JP2003020227A (en) * | 2001-07-02 | 2003-01-24 | Toyota Central Res & Dev Lab Inc | Fine mixed oxide powder, production method thereor and catalyst |
-
2003
- 2003-11-12 JP JP2003382973A patent/JP4324856B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JP2005144274A (en) | 2005-06-09 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP4006976B2 (en) | Composite oxide powder, method for producing the same and catalyst | |
JP3858625B2 (en) | Composite oxide and its production method, exhaust gas purification catalyst and its production method | |
JP4032652B2 (en) | Composite oxide powder and method for producing the same | |
JP3826358B2 (en) | Exhaust gas purification catalyst | |
JP2003126694A (en) | Catalyst for cleaning exhaust gas | |
JPH11314035A (en) | Catalyst carrier and catalyst, manufacture thereof | |
JP3997783B2 (en) | Method for producing catalyst carrier | |
JP2004074138A (en) | Catalyst for exhaust gas purification, and exhaust gas purification method | |
JP2005000829A (en) | Catalyst for purifying exhaust gas and production method therefor | |
JP5168527B2 (en) | Oxide powder and production method thereof | |
JP4171977B2 (en) | Catalyst carrier, production method thereof, catalyst, and exhaust gas purification method | |
EP0963781A2 (en) | Catalyst for purifying exhaust gas and process for producing the same | |
JP2001347167A (en) | Exhaust gas cleaning catalyst | |
JP2004016838A (en) | Catalyst for purifying exhaust gas, method for producing the catalyst, and method for using catalyst | |
JP4697503B2 (en) | Composite oxide powder, method for producing the same and catalyst | |
JP3766568B2 (en) | Exhaust gas purification catalyst and exhaust gas purification method | |
JP4324856B2 (en) | Exhaust gas purification catalyst carrier and catalyst | |
JP2001009279A (en) | Catalyst for purification of exhaust gas, its production and method for purifying exhaust gas | |
JP5019019B2 (en) | Exhaust gas purification catalyst carrier, exhaust gas purification catalyst and exhaust gas purification method using the same | |
JP3362532B2 (en) | Exhaust gas purification catalyst and method for producing the same | |
JP2003305363A (en) | Catalyst carrier and catalyst for exhaust gas treatment | |
JP2000246107A (en) | Catalyst for cleaning exhaust gas, its production and method for cleaning exhaust gas | |
JP4737149B2 (en) | Catalyst carrier and catalyst | |
JP2004167354A (en) | Carrier for catalyst, no oxidation catalyst, and no oxidation method | |
JP2008279319A (en) | Catalyst for cleaning exhaust gas and method for producing acidic oxide-deposited alumina to be used therefor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20060622 |
|
A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20090304 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20090310 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20090415 |
|
TRDD | Decision of grant or rejection written | ||
A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20090514 |
|
A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20090527 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120619 Year of fee payment: 3 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120619 Year of fee payment: 3 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120619 Year of fee payment: 3 |
|
S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313532 |
|
R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130619 Year of fee payment: 4 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130619 Year of fee payment: 4 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140619 Year of fee payment: 5 |
|
LAPS | Cancellation because of no payment of annual fees |