WO2011161834A1 - NOx PURGING CATALYST - Google Patents
NOx PURGING CATALYST Download PDFInfo
- Publication number
- WO2011161834A1 WO2011161834A1 PCT/JP2010/061289 JP2010061289W WO2011161834A1 WO 2011161834 A1 WO2011161834 A1 WO 2011161834A1 JP 2010061289 W JP2010061289 W JP 2010061289W WO 2011161834 A1 WO2011161834 A1 WO 2011161834A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- nox
- alumina
- amount
- group metal
- supported
- Prior art date
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/48—Silver or gold
- B01J23/50—Silver
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
- B01D53/9409—Nitrogen oxides
- B01D53/9413—Processes characterised by a specific catalyst
- B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/102—Platinum group metals
- B01D2255/1021—Platinum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/10—Noble metals or compounds thereof
- B01D2255/104—Silver
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2255/00—Catalysts
- B01D2255/20—Metals or compounds thereof
- B01D2255/209—Other metals
- B01D2255/2092—Aluminium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/40—Nitrogen compounds
- B01D2257/404—Nitrogen oxides other than dinitrogen oxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/01—Engine exhaust gases
- B01D2258/012—Diesel engines and lean burn gasoline engines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
Definitions
- the present invention relates to an exhaust gas purification catalyst, and more particularly to a NOx purification catalyst.
- an Ag / alumina-based NOx purification catalyst in which metal Ag is supported on an alumina carrier is known (Japanese Patent Laid-Open No. 9-290156).
- the Ag / alumina-based NOx purification catalyst is excellent in NOx adsorption performance at a relatively low temperature (for example, 200 ° C. or less) such as immediately after starting a diesel engine.
- Low-order NOx (eg, NO) contained in the exhaust gas containing excess oxygen during lean combustion is oxidized on Ag on the alumina surface to become high-order NOx (eg, NO 2 , NO 3 ), and the alumina surface layer portion It is adsorbed and held on the surface of solid solution Ag or alumina.
- NOx releasing catalyst of the above prior art has a low NOx releasing property even if the NOx releasing process is performed. In order to increase NOx release properties, excessive temperature rise is required, resulting in a problem that fuel consumption deteriorates. Further, NOx cannot be completely released, so that the adsorptive capacity is not recovered. There arises a problem that the purification rate is lowered.
- an object of the present invention is to provide an Ag / alumina-based NOx purification catalyst having improved release while ensuring excellent adsorption performance.
- the NOx purification catalyst of the present invention supports Ag and at least one of Pt group metals on an alumina support, and the amount of Pt group metal supported is the amount of Ag supported. It is characterized by 0.045 to 0.45 wt%.
- the supported amount of the Pt group metal is 0.30% or less of the supported amount of Ag.
- the Pt group metal is Pd.
- Ti may be further supported.
- the Pt group metal may be abbreviated as PGM (platinum group metals).
- FIG. 1 shows (A) an oxidation adsorption mechanism of NOx under lean combustion in an Ag / alumina-based NOx purification catalyst, (B) an adsorption form of NOx, and (C) a Pt group metal to which a Pt group metal is added according to the present invention.
- the reduction / desorption (release) mechanism of NOx under rich combustion in the -Ag / alumina-based NOx purification catalyst is schematically shown.
- FIG. 2 schematically shows an actual engine test system for the engine-catalyst used in the examples.
- FIG. 3 shows the correspondence between the time-dependent change pattern of the catalyst bed temperature used in the actual machine test in the example and the time-dependent change pattern of NOx adsorption / release.
- FIG. 1 shows (A) an oxidation adsorption mechanism of NOx under lean combustion in an Ag / alumina-based NOx purification catalyst, (B) an adsorption form of NOx, and (C) a P
- FIG. 4 shows the time-dependent change in the NOx emission amount corresponding to lean / rich exhaust gas switching for the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention and the Ag / alumina-based NOx purification catalyst not supporting the Pt group metal. Shown in comparison.
- FIG. 5 shows a Pt group metal-Ag / alumina-based NOx purification catalyst according to the present invention, a Pt group metal-Ti ⁇ Ag / alumina-based NOx purification catalyst as an application example, and an Ag / alumina-based NOx purification catalyst not supporting a Pt group metal. Shows the relationship between the peak catalyst bed temperature in rich combustion and the NOx desorption rate.
- FIG. 5 shows a Pt group metal-Ag / alumina-based NOx purification catalyst according to the present invention, a Pt group metal-Ti ⁇ Ag / alumina-based NOx purification catalyst as an application example, and an Ag /
- FIG. 6 shows a time-dependent change pattern of the gas temperature with catalyst used in the subsize test in the example.
- FIG. 7 shows the relationship between the supported amount of Pd, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate.
- FIG. 7A shows a wide range of Pd supported amount of 0 to 2 g / L, and FIG. The range of the supported amount of 0 to 0.1 g / L is shown enlarged.
- FIG. 8 shows the relationship between the loading amount of Rh, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate.
- FIG. 1A shows a NOx adsorption mechanism common to the present invention and the prior art.
- relatively low-order nitrogen oxides NOx for example, NO
- relatively high-order nitrogen oxides NOx for example, NO 2).
- NO 3 relatively high-order nitrogen oxides NOx
- FIG. 1B shows an adsorption form of NOx (NO 2 , NO 3 ).
- FIG. 1C shows a NOx reduction / desorption mechanism by the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention.
- PGM Pt group metal
- reducing material for example, CO, THC
- Example 1 The Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention was prepared according to the following procedure and conditions. ⁇ Alumina carrier coating> 1) Catalyst base material A cordierite base material of 13R square cell was used. 2) Slurry preparation A slurry was obtained by stirring with an attritor for 20 minutes at the following ratio. MI386 powder (made by Rhodia) 1600 g (100 parts) Binder A520 (Nissan Chemical) 710.4 g (44.4 parts) 3600g of water 3) Coating of slurry The obtained slurry was coated on the cordierite substrate. The coating amount was 200 g / L of alumina. 4) Firing treatment The moisture was completely removed by holding at 250 ° C.
- Impregnation support (Ag support amount: 0.2 mol / L)
- the calcined alumina carrier was immersed in the prepared aqueous silver nitrate solution for 30 minutes, and the aqueous silver nitrate solution equivalent to the amount of water absorption was absorbed and the Ag loading amount was 0.2 mol / L.
- Firing treatment Firing at 550 ° C. ⁇ 3r was performed in the air.
- H 2 reduction treatment Reduction treatment was performed by maintaining 500 ° C. ⁇ 3 hr in an atmosphere in which a 5% H 2 —N 2 mixed gas was circulated at a flow rate of 7 L / min.
- the Pt group metal-Ag / alumina NOx purification catalyst of the present invention in which Pd, Pt, and Rh were supported as Pt group metals on the Ag / alumina NOx purification catalyst not supporting the Pt group metal was obtained (sample). Name: AgPd0.1, AgPt0.1, AgRh0.1). For comparison, an Ag / alumina-based NOx purification catalyst that does not carry Pt group metal was also produced (sample name: Ag).
- a Pd—Ag / alumina-based NOx purification catalyst in which the alumina carrier contains 0.5 mol / L of titania was also prepared according to the following procedure and conditions (sample name: AgTiPd0.1).
- Example name: AgTiPd0.1 aqueous solution of titanium citrate complex
- Ti was supported on the Ag / alumina-based NOx purification catalyst so as to achieve the above-mentioned supported amount, and then Pd was supported in the same manner as described above. This was baked at 550 ° C. for 5 hours.
- FIG. 3 shows a temporal pattern of the catalyst bed temperature used in the test and a temporal pattern of NOx adsorption / release.
- FIG. 4 shows changes in the combustion pattern (lean ⁇ rich ⁇ lean) and NOx emission peak for the present example (Pt group metal-Ag / alumina-based NOx purification catalyst) and the conventional example (Ag / alumina-based NOx purification catalyst). Shows the relationship. As shown in the figure, release of NOx is recognized in any sample during rich combustion. The amount of release evaluated by the area under the release curve is improved by almost 10 times in the present invention compared to the conventional example. The NOx release performance is accurately evaluated by the ratio of the release amount to the adsorption amount.
- FIG. 5 and Table 1 show a comparison of NOx release rate (percentage of release amount with respect to adsorption amount).
- the inventive examples show a high release rate of 29.5 to 45.9 times that of the conventional example (Ag).
- the release rate is improved by 38.5 times compared to the conventional example (Ag).
- a sub-size (35 cc) sample was produced as an example of the present invention under the same procedure and conditions as described above.
- the supported amount of the Pt group metal was set to five levels of 0.01, 0.05, 0.1, 1.0, and 2.0 g / L with respect to the base material.
- the amount of Pd supported is in the range of 0.01 to 0.1 g / L with respect to the substrate. That is, the Pd loading (0.01 to 0.1 g / L) is 0.045 to 0.45 wt% with respect to the Ag loading (21.6 g / L). In order to secure a larger amount of adsorption and to further reduce the material cost of Pd, it is desirable that the amount of Pd supported is 0.30 wt% or less with respect to the amount of Ag supported.
- FIG. 8 and Table 3 show the measurement results when Rh is supported as a Pt group metal.
- an Ag / alumina-based NOx purification catalyst that has improved NOx release while ensuring excellent NOx adsorption performance.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Combustion & Propulsion (AREA)
- Biomedical Technology (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Provided is a NOx purging catalyst in which Ag and at least one Pt group metal are supported on an alumina carrier, and the amount of the Pt group metal supported is 0.045 to 0.45 wt% of the amount of the Ag supported. The Ag/alumina NOx purging catalyst has increased NOx releasability while excellent NOx adsorption capability is also guaranteed.
Description
本発明は、排ガス浄化用触媒に関し、詳しくはＮＯｘ浄化触媒に関する。
The present invention relates to an exhaust gas purification catalyst, and more particularly to a NOx purification catalyst.
排ガス浄化用触媒、特にＮＯｘ浄化用として、金属Ａｇをアルミナ担体に担持したＡｇ／アルミナ系ＮＯｘ浄化触媒が知られている（特開平９−２９０１５６号公報）。Ａｇ／アルミナ系ＮＯｘ浄化触媒は、ディーゼルエンジンの始動直後などの比較的低温（例えば２００℃以下）におけるＮＯｘ吸着性能が優れている。リーン燃焼時の過剰酸素を含む排ガス中に含まれる低次のＮＯｘ（例えばＮＯ）が、アルミナ表面のＡｇ上で酸化されて高次のＮＯｘ（例えばＮＯ２、ＮＯ３）となり、アルミナ表層部の固溶Ａｇまたはアルミナ表面に吸着して保持される。
吸着されたＮＯｘを放出させる要求があった際に、昇温によるＮＯｘ放出処理を行なう必要があるが、上記従来技術のＮＯｘ吸着触媒では該ＮＯｘ放出処理を行なってもＮＯｘ放出性が低い。ＮＯｘ放出性を高めるには過度な昇温が必要となり、それに起因して燃費が悪化するという問題が生じ、また、ＮＯｘが完全に放出できないために吸着能が回復されず、それに起因してＮＯｘ浄化率が低下するという問題が生ずる。 As an exhaust gas purification catalyst, particularly for NOx purification, an Ag / alumina-based NOx purification catalyst in which metal Ag is supported on an alumina carrier is known (Japanese Patent Laid-Open No. 9-290156). The Ag / alumina-based NOx purification catalyst is excellent in NOx adsorption performance at a relatively low temperature (for example, 200 ° C. or less) such as immediately after starting a diesel engine. Low-order NOx (eg, NO) contained in the exhaust gas containing excess oxygen during lean combustion is oxidized on Ag on the alumina surface to become high-order NOx (eg, NO 2 , NO 3 ), and the alumina surface layer portion It is adsorbed and held on the surface of solid solution Ag or alumina.
When there is a request to release the adsorbed NOx, it is necessary to perform a NOx releasing process by raising the temperature. However, the NOx releasing catalyst of the above prior art has a low NOx releasing property even if the NOx releasing process is performed. In order to increase NOx release properties, excessive temperature rise is required, resulting in a problem that fuel consumption deteriorates. Further, NOx cannot be completely released, so that the adsorptive capacity is not recovered. There arises a problem that the purification rate is lowered.
吸着されたＮＯｘを放出させる要求があった際に、昇温によるＮＯｘ放出処理を行なう必要があるが、上記従来技術のＮＯｘ吸着触媒では該ＮＯｘ放出処理を行なってもＮＯｘ放出性が低い。ＮＯｘ放出性を高めるには過度な昇温が必要となり、それに起因して燃費が悪化するという問題が生じ、また、ＮＯｘが完全に放出できないために吸着能が回復されず、それに起因してＮＯｘ浄化率が低下するという問題が生ずる。 As an exhaust gas purification catalyst, particularly for NOx purification, an Ag / alumina-based NOx purification catalyst in which metal Ag is supported on an alumina carrier is known (Japanese Patent Laid-Open No. 9-290156). The Ag / alumina-based NOx purification catalyst is excellent in NOx adsorption performance at a relatively low temperature (for example, 200 ° C. or less) such as immediately after starting a diesel engine. Low-order NOx (eg, NO) contained in the exhaust gas containing excess oxygen during lean combustion is oxidized on Ag on the alumina surface to become high-order NOx (eg, NO 2 , NO 3 ), and the alumina surface layer portion It is adsorbed and held on the surface of solid solution Ag or alumina.
When there is a request to release the adsorbed NOx, it is necessary to perform a NOx releasing process by raising the temperature. However, the NOx releasing catalyst of the above prior art has a low NOx releasing property even if the NOx releasing process is performed. In order to increase NOx release properties, excessive temperature rise is required, resulting in a problem that fuel consumption deteriorates. Further, NOx cannot be completely released, so that the adsorptive capacity is not recovered. There arises a problem that the purification rate is lowered.
本発明は、優れた吸着性能を確保しつつ放出性を高めたＡｇ／アルミナ系ＮＯｘ浄化触媒を提供することを目的とする。
上記の目的を達成するために、本発明のＮＯｘ浄化触媒は、アルミナ担体上に、Ａｇと、Ｐｔ族金属のうち少なくとも１種とを担持し、Ｐｔ族金属の担持量はＡｇの担持量の０．０４５~０．４５ｗｔ％であることを特徴とする。
望ましい形態においては、Ｐｔ族金属の担持量はＡｇの担持量の０．３０％以下である。
望ましい形態においては、Ｐｔ族金属はＰｄである。
応用形態において、更にＴｉを担持してもよい。
以下、Ｐｔ族金属をＰＧＭ（ｐｌａｔｉｎｕｍ ｇｒｏｕｐ ｍｅｔａｌｓ）と略称する場合がある。 An object of the present invention is to provide an Ag / alumina-based NOx purification catalyst having improved release while ensuring excellent adsorption performance.
In order to achieve the above object, the NOx purification catalyst of the present invention supports Ag and at least one of Pt group metals on an alumina support, and the amount of Pt group metal supported is the amount of Ag supported. It is characterized by 0.045 to 0.45 wt%.
In a desirable form, the supported amount of the Pt group metal is 0.30% or less of the supported amount of Ag.
In a preferred form, the Pt group metal is Pd.
In the application form, Ti may be further supported.
Hereinafter, the Pt group metal may be abbreviated as PGM (platinum group metals).
上記の目的を達成するために、本発明のＮＯｘ浄化触媒は、アルミナ担体上に、Ａｇと、Ｐｔ族金属のうち少なくとも１種とを担持し、Ｐｔ族金属の担持量はＡｇの担持量の０．０４５~０．４５ｗｔ％であることを特徴とする。
望ましい形態においては、Ｐｔ族金属の担持量はＡｇの担持量の０．３０％以下である。
望ましい形態においては、Ｐｔ族金属はＰｄである。
応用形態において、更にＴｉを担持してもよい。
以下、Ｐｔ族金属をＰＧＭ（ｐｌａｔｉｎｕｍ ｇｒｏｕｐ ｍｅｔａｌｓ）と略称する場合がある。 An object of the present invention is to provide an Ag / alumina-based NOx purification catalyst having improved release while ensuring excellent adsorption performance.
In order to achieve the above object, the NOx purification catalyst of the present invention supports Ag and at least one of Pt group metals on an alumina support, and the amount of Pt group metal supported is the amount of Ag supported. It is characterized by 0.045 to 0.45 wt%.
In a desirable form, the supported amount of the Pt group metal is 0.30% or less of the supported amount of Ag.
In a preferred form, the Pt group metal is Pd.
In the application form, Ti may be further supported.
Hereinafter, the Pt group metal may be abbreviated as PGM (platinum group metals).
図１は、（Ａ）Ａｇ／アルミナ系ＮＯｘ浄化触媒におけるリーン燃焼下でのＮＯｘの酸化吸着機構、（Ｂ）ＮＯｘの吸着形態、および（Ｃ）本発明によりＰｔ族金属を付加したＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒におけるリッチ燃焼下でのＮＯｘの還元脱離（放出）機構を模式的に示す。
図２は、実施例で用いたエンジン−触媒の実機試験系を模式的に示す。
図３は、実施例で実機試験に用いた触媒床温の経時変化パターンとＮＯｘの吸着／放出の経時変化パターンとの対応を示す。
図４は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒とＰｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒について、リーン／リッチの排ガス切り替えに対応したＮＯｘ放出量の経時変化を比較して示す。
図５は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒および応用例としてのＰｔ族金属−Ｔｉ・Ａｇ／アルミナ系ＮＯｘ浄化触媒とＰｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒について、リッチ燃焼でのピーク触媒床温とＮＯｘ脱離率との関係を示す。
図６は、実施例でサブサイズ試験に用いた触媒入りガス温度の経時変化パターンを示す。
図７は、Ｐｔ族金属であるＰｄの担持量とＮＯｘ吸着量およびＮＯｘ脱離率との関係を示し、（Ａ）はＰｄ担持量０~２ｇ／Ｌの広い範囲について、（Ｂ）はＰｄ担持量０~０．１ｇ／Ｌの範囲を拡大して示す。
図８は、Ｐｔ族金属であるＲｈの担持量とＮＯｘ吸着量およびＮＯｘ脱離率との関係を示す。 FIG. 1 shows (A) an oxidation adsorption mechanism of NOx under lean combustion in an Ag / alumina-based NOx purification catalyst, (B) an adsorption form of NOx, and (C) a Pt group metal to which a Pt group metal is added according to the present invention. The reduction / desorption (release) mechanism of NOx under rich combustion in the -Ag / alumina-based NOx purification catalyst is schematically shown.
FIG. 2 schematically shows an actual engine test system for the engine-catalyst used in the examples.
FIG. 3 shows the correspondence between the time-dependent change pattern of the catalyst bed temperature used in the actual machine test in the example and the time-dependent change pattern of NOx adsorption / release.
FIG. 4 shows the time-dependent change in the NOx emission amount corresponding to lean / rich exhaust gas switching for the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention and the Ag / alumina-based NOx purification catalyst not supporting the Pt group metal. Shown in comparison.
FIG. 5 shows a Pt group metal-Ag / alumina-based NOx purification catalyst according to the present invention, a Pt group metal-Ti · Ag / alumina-based NOx purification catalyst as an application example, and an Ag / alumina-based NOx purification catalyst not supporting a Pt group metal. Shows the relationship between the peak catalyst bed temperature in rich combustion and the NOx desorption rate.
FIG. 6 shows a time-dependent change pattern of the gas temperature with catalyst used in the subsize test in the example.
FIG. 7 shows the relationship between the supported amount of Pd, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate. FIG. 7A shows a wide range of Pd supported amount of 0 to 2 g / L, and FIG. The range of the supported amount of 0 to 0.1 g / L is shown enlarged.
FIG. 8 shows the relationship between the loading amount of Rh, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate.
図２は、実施例で用いたエンジン−触媒の実機試験系を模式的に示す。
図３は、実施例で実機試験に用いた触媒床温の経時変化パターンとＮＯｘの吸着／放出の経時変化パターンとの対応を示す。
図４は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒とＰｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒について、リーン／リッチの排ガス切り替えに対応したＮＯｘ放出量の経時変化を比較して示す。
図５は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒および応用例としてのＰｔ族金属−Ｔｉ・Ａｇ／アルミナ系ＮＯｘ浄化触媒とＰｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒について、リッチ燃焼でのピーク触媒床温とＮＯｘ脱離率との関係を示す。
図６は、実施例でサブサイズ試験に用いた触媒入りガス温度の経時変化パターンを示す。
図７は、Ｐｔ族金属であるＰｄの担持量とＮＯｘ吸着量およびＮＯｘ脱離率との関係を示し、（Ａ）はＰｄ担持量０~２ｇ／Ｌの広い範囲について、（Ｂ）はＰｄ担持量０~０．１ｇ／Ｌの範囲を拡大して示す。
図８は、Ｐｔ族金属であるＲｈの担持量とＮＯｘ吸着量およびＮＯｘ脱離率との関係を示す。 FIG. 1 shows (A) an oxidation adsorption mechanism of NOx under lean combustion in an Ag / alumina-based NOx purification catalyst, (B) an adsorption form of NOx, and (C) a Pt group metal to which a Pt group metal is added according to the present invention. The reduction / desorption (release) mechanism of NOx under rich combustion in the -Ag / alumina-based NOx purification catalyst is schematically shown.
FIG. 2 schematically shows an actual engine test system for the engine-catalyst used in the examples.
FIG. 3 shows the correspondence between the time-dependent change pattern of the catalyst bed temperature used in the actual machine test in the example and the time-dependent change pattern of NOx adsorption / release.
FIG. 4 shows the time-dependent change in the NOx emission amount corresponding to lean / rich exhaust gas switching for the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention and the Ag / alumina-based NOx purification catalyst not supporting the Pt group metal. Shown in comparison.
FIG. 5 shows a Pt group metal-Ag / alumina-based NOx purification catalyst according to the present invention, a Pt group metal-Ti · Ag / alumina-based NOx purification catalyst as an application example, and an Ag / alumina-based NOx purification catalyst not supporting a Pt group metal. Shows the relationship between the peak catalyst bed temperature in rich combustion and the NOx desorption rate.
FIG. 6 shows a time-dependent change pattern of the gas temperature with catalyst used in the subsize test in the example.
FIG. 7 shows the relationship between the supported amount of Pd, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate. FIG. 7A shows a wide range of Pd supported amount of 0 to 2 g / L, and FIG. The range of the supported amount of 0 to 0.1 g / L is shown enlarged.
FIG. 8 shows the relationship between the loading amount of Rh, which is a Pt group metal, the NOx adsorption amount, and the NOx desorption rate.
図１を参照して、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒におけるＮＯｘの吸着機構および脱離（放出）機構を説明する。
図１（Ａ）は、本発明と従来技術に共通のＮＯｘ吸着機構を示す。リーン燃焼下で排ガス中の相対的に低次の窒素酸化物ＮＯｘ（例えばＮＯ）が金属Ａｇ上で過剰酸素（Ｏ２）に酸化されて相対的に高次の窒素酸化物ＮＯｘ（例えばＮＯ２、ＮＯ３）となり、アルミナ担体に、またはアルミナ担体に固溶したＡｇに吸着される。
図１（Ｂ）は、ＮＯｘ（ＮＯ２、ＮＯ３）の吸着形態を示す。図中、Ｍはアルミナまたは固溶Ａｇを示す。ＮＯｘとＭとの吸着結合はＮＯｘのＮまたはＯがＭと結合して行なわれている。
図１（Ｃ）は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒によるＮＯｘの還元脱離機構を示す。リッチ燃焼下でＮＯｘ吸着結合中の酸素がＰｔ族金属（ＰＧＭ）上で多量の還元材（例えばＣＯ、ＴＨＣ）で還元されて消費し、酸素を介した吸着結合が破断される。すなわち、相対的に高次のＮＯｘ（ＮＯ２、ＮＯ３）が相対的に低次のＮＯｘ（ＮＯ、ＮＯ２）となって脱離する。これにより脱離性が飛躍的に向上する。Ｐｔ族金属を担持しないと上記の機構が作用しないので、ＮＯｘの脱離性すなわち放出性が低かった。 With reference to FIG. 1, the NOx adsorption mechanism and desorption (release) mechanism in the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention will be described.
FIG. 1A shows a NOx adsorption mechanism common to the present invention and the prior art. Under lean combustion, relatively low-order nitrogen oxides NOx (for example, NO) in the exhaust gas are oxidized on the metal Ag to excess oxygen (O 2 ), and relatively high-order nitrogen oxides NOx (for example, NO 2). , NO 3 ) and adsorbed on the alumina carrier or Ag dissolved in the alumina carrier.
FIG. 1B shows an adsorption form of NOx (NO 2 , NO 3 ). In the figure, M represents alumina or solid solution Ag. NOx and M are adsorbed and bonded by combining N or O of NOx with M.
FIG. 1C shows a NOx reduction / desorption mechanism by the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention. Under rich combustion, oxygen in the NOx adsorption bond is reduced on the Pt group metal (PGM) with a large amount of reducing material (for example, CO, THC) and consumed, and the adsorption bond via oxygen is broken. That is, relatively higher-order NOx (NO 2 , NO 3 ) is desorbed as relatively lower-order NOx (NO, NO 2 ). Thereby, the detachability is greatly improved. If the Pt group metal is not supported, the above mechanism does not work, so that NOx desorption, that is, release is low.
図１（Ａ）は、本発明と従来技術に共通のＮＯｘ吸着機構を示す。リーン燃焼下で排ガス中の相対的に低次の窒素酸化物ＮＯｘ（例えばＮＯ）が金属Ａｇ上で過剰酸素（Ｏ２）に酸化されて相対的に高次の窒素酸化物ＮＯｘ（例えばＮＯ２、ＮＯ３）となり、アルミナ担体に、またはアルミナ担体に固溶したＡｇに吸着される。
図１（Ｂ）は、ＮＯｘ（ＮＯ２、ＮＯ３）の吸着形態を示す。図中、Ｍはアルミナまたは固溶Ａｇを示す。ＮＯｘとＭとの吸着結合はＮＯｘのＮまたはＯがＭと結合して行なわれている。
図１（Ｃ）は、本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒によるＮＯｘの還元脱離機構を示す。リッチ燃焼下でＮＯｘ吸着結合中の酸素がＰｔ族金属（ＰＧＭ）上で多量の還元材（例えばＣＯ、ＴＨＣ）で還元されて消費し、酸素を介した吸着結合が破断される。すなわち、相対的に高次のＮＯｘ（ＮＯ２、ＮＯ３）が相対的に低次のＮＯｘ（ＮＯ、ＮＯ２）となって脱離する。これにより脱離性が飛躍的に向上する。Ｐｔ族金属を担持しないと上記の機構が作用しないので、ＮＯｘの脱離性すなわち放出性が低かった。 With reference to FIG. 1, the NOx adsorption mechanism and desorption (release) mechanism in the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention will be described.
FIG. 1A shows a NOx adsorption mechanism common to the present invention and the prior art. Under lean combustion, relatively low-order nitrogen oxides NOx (for example, NO) in the exhaust gas are oxidized on the metal Ag to excess oxygen (O 2 ), and relatively high-order nitrogen oxides NOx (for example, NO 2). , NO 3 ) and adsorbed on the alumina carrier or Ag dissolved in the alumina carrier.
FIG. 1B shows an adsorption form of NOx (NO 2 , NO 3 ). In the figure, M represents alumina or solid solution Ag. NOx and M are adsorbed and bonded by combining N or O of NOx with M.
FIG. 1C shows a NOx reduction / desorption mechanism by the Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention. Under rich combustion, oxygen in the NOx adsorption bond is reduced on the Pt group metal (PGM) with a large amount of reducing material (for example, CO, THC) and consumed, and the adsorption bond via oxygen is broken. That is, relatively higher-order NOx (NO 2 , NO 3 ) is desorbed as relatively lower-order NOx (NO, NO 2 ). Thereby, the detachability is greatly improved. If the Pt group metal is not supported, the above mechanism does not work, so that NOx desorption, that is, release is low.
実施例１
本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒を下記の手順および条件で作製した。
＜アルミナ担体のコーティング＞
１）触媒基材
１３Ｒ四角セルのコージェライト基材を用いた。
２）スラリー調製
下記割合でアトライタにて２０分攪拌してスラリーを得た。
ＭＩ３８６粉末（ローディア製） １６００ｇ（１００部）
バインダＡ５２０（日産化学製） ７１０．４ｇ（４４．４部）
水 ３６００ｇ
３）スラリーのコーティング
得られたスラリーを上記コージェライト基材にコーティングした。コート量はアルミナ２００ｇ／Ｌであった。
４）焼成処理
大気中にて２５０℃×３０ｍｉｎ保持して水分を完全に除去し、引き続き５００℃×１ｈｒの焼成を行なった。焼成後コート品の吸水量は３１８ｇ／１３Ｒであった。
＜Ａｇの担持＞
１）硝酸銀水溶液の調製（Ａｇ濃度：０．８２ｍｏｌ／Ｌ）
硝酸銀（和光純薬工業特級試薬）２３６．２ｇにイオン交換水を加えて溶解させ１７００ｃｃとし、Ａｇ濃度０．８２ｍｏｌ／Ｌの硝酸銀水溶液を調製した。
２）含浸担持（Ａｇ担持量：０．２ｍｏｌ／Ｌ）
調製した硝酸銀水溶液に、上記焼成したアルミナ担体を３０分浸漬し、吸水量分の硝酸銀水溶液を吸水担持させて、Ａｇ担持量０．２ｍｏｌ／Ｌとした。
３）乾燥
送風型乾燥機（家庭用寝具乾燥機）にて２０分乾燥を行った。
４）焼成処理
大気中にて５５０℃×３ｒの焼成を行なった。
５）Ｈ２還元処理
５％Ｈ２−Ｎ２混合ガスを流速７Ｌ／ｍｉｎで流通させた雰囲気中に５００℃×３ｈｒ保持して還元処理を行なった。
これにより、Ｐｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒を得た。
＜Ｐｔ族金属の担持＞
上記Ａｇ／アルミナ系ＮＯｘ浄化触媒に、Ｐｔ族金属としてＰｄ、ＰｔまたはＲｈを担持させた。すなわち、硝酸パラジウム水溶液（Ｐｄ担持用）、ジニトロジアミン白金硝酸水溶液（Ｐｔ担持用）、硝酸ロジウム水溶液（Ｒｈ担持用）を用いて、Ｐｄ、Ｐｔ、Ｒｈを含浸担持させた後、上記＜Ａｇの担持＞の処理３）~５）を行なった。基材に対する担持量はそれぞれ０．１ｇ／Ｌとした。Ａｇに対してはＰｔ族金属担持量０．４６ｗｔ％である。
すなわち、Ａｇ１ｍｏｌは１０８ｇであり、Ａｇ担持量＝０．２ｍｏｌ／Ｌ＝（１０８ｇ／ｍｏｌ×０．２ｍｏｌ）／Ｌ＝２１．６ｇ／Ｌである。したがって、Ｐｔ族金属の担持量０．１ｇ／Ｌは、Ａｇ担持量２１．６ｇ／Ｌに対して、０．１／２１．６×１００＝０．４６ｗｔ％となる。
以上により、Ｐｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒にＰｔ族金属としてＰｄ、Ｐｔ、Ｒｈをそれぞれ担持した本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒が得られた（サンプル名：ＡｇＰｄ０．１、ＡｇＰｔ０．１、ＡｇＲｈ０．１）。
なお、比較のために、Ｐｔ族金属の担持を行なわないＡｇ／アルミナ系ＮＯｘ浄化触媒も作製した（サンプル名：Ａｇ）。
また、本発明の応用例として、アルミナ担体がチタニアを０．５ｍｏｌ／Ｌ含むＰｄ−Ａｇ／アルミナ系ＮＯｘ浄化触媒も下記の手順および条件で作製した（サンプル名：ＡｇＴｉＰｄ０．１）。
＜チタニア入りサンプルの作製手順＞
チタンクエン酸錯体水溶液を用いて、上記の担持量となるようにＡｇ／アルミナ系ＮＯｘ浄化触媒にＴｉを担持させ、次に前記と同様にＰｄを担持させた。これを５５０℃で５時間焼成した。
上記の本発明例、従来例、応用例について、フルサイズ（１．０Ｌ）のサンプルについて、図２に示す実機排ガス系において、ＮＯｘの吸着および放出の試験を行なった。
＜エンジン−触媒系の諸元＞
エンジン：２．２Ｌディーゼルエンジン
酸化触媒：容量０．８Ｌ、使用Ｐｔ族金属１．８ｇ／Ｌ
図３に、試験に用いた触媒床温の経時パターンおよびＮＯｘの吸着／放出の経時パターンを示す。
図４に、本発例（Ｐｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒）および従来例（Ａｇ／アルミナ系ＮＯｘ浄化触媒）について、燃焼パターン（リーン→リッチ→リーン）の変化とＮＯｘの放出ピークとの関係を示す。図示したように、何れのサンプルもリッチ燃焼時にＮＯｘの放出が認められる。放出曲線下の面積で評価した放出量は、本発明例は従来例の１０倍近く向上している。ＮＯｘ放出性能は正確には、吸着量に対する放出量の比率で評価される。
図５および表１に、ＮＯｘの放出率（吸着量に対する放出量のパーセンテージ）を比較して示す。本発明例（ＡｇＰｄ０．１、ＡｇＰｔ０．１、ＡｇＲｈ０．１）は従来例（Ａｇ）に対して２９．５~４５．９倍の高い放出率を示している。
アルミナ担体がチタニアを０．５ｍｏｌ／Ｌ含む応用例（ＡｇＴｉＰｄ０．１）は、従来例（Ａｇ）に対して放出率が３８．５倍に向上している。
次に、前述と同様の手順および条件にて、本発明の実施例として、サブサイズ（３５ｃｃ）のサンプルを作製した。ただし、Ｐｔ族金属の担持量は、基材に対して０．０１、０．０５、０．１、１．０、２．０ｇ／Ｌの５水準とした。
下記組成のモデルガスを用いて、図６の入りガス温度変化パターンでＮＯｘの吸着／放出試験を行った。
＜モデルガス組成＞
《触媒パージ ５分》
ガス温度：６００℃、ＣＯ２：９％、Ｏ２：８％
《吸着 １０分》
ガス温度：１５０℃、ＮＯ：３００ｐｐｍ、ＣＯ２：９％、Ｏ２：８％、Ｈ２Ｏ：５％
《脱離 １５分》
ガス温度：２５０℃、ＣＯ：１％、ＣＯ２：９％、Ｏ２：０％、Ｈ２Ｏ：５％
ＳＶは共に２６０００／ｈであった。
図７および表２に、Ｐｔ族金属としてＰｄを担持した場合の測定結果を示す。基材に対するＰｄ担持量が、（Ａ）０~２．０ｇ／Ｌの試験範囲全体について、（Ｂ）０~０．１ｇ／Ｌの低担持量の範囲について、それぞれ示す。
図７および表２に示したように、ＮＯｘ放出率はＰｄ担持量０．０１ｇ／Ｌ以上であればほぼ１００％が得られる。一方、ＮＯｘ吸着量は、Ｐｄ担持量の増加に伴って減少し、Ｐｄ担持量０．１ｇ／Ｌで初期値（０．０１ｇ／Ｌでの値）の約１／２まで減少し、Ｐｄ担持量がそれ以上増加しても変化しない。しがたって、Ｐｄ担持量は基材に対して０．０１~０．１ｇ／Ｌの範囲とする。すなわち、Ｐｄ担持量（０．０１~０．１ｇ／Ｌ）はＡｇ担持量（２１．６ｇ／Ｌ）に対して０．０４５~０．４５ｗｔ％である。吸着量をより多く確保し、且つ、Ｐｄの材料コストをより低減するために、Ｐｄ担持量はＡｇ担持量に対して０．３０ｗｔ％以下であることが望ましい。
図８および表３は、Ｐｔ族金属としてＲｈを担持した場合の測定結果を示す。
Example 1
The Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention was prepared according to the following procedure and conditions.
<Alumina carrier coating>
1) Catalyst base material A cordierite base material of 13R square cell was used.
2) Slurry preparation A slurry was obtained by stirring with an attritor for 20 minutes at the following ratio.
MI386 powder (made by Rhodia) 1600 g (100 parts)
Binder A520 (Nissan Chemical) 710.4 g (44.4 parts)
3600g of water
3) Coating of slurry The obtained slurry was coated on the cordierite substrate. The coating amount was 200 g / L of alumina.
4) Firing treatment The moisture was completely removed by holding at 250 ° C. for 30 minutes in the atmosphere, and then firing was performed at 500 ° C. for 1 hour. The water absorption of the coated product after firing was 318 g / 13R.
<Supporting Ag>
1) Preparation of silver nitrate aqueous solution (Ag concentration: 0.82 mol / L)
Ion exchange water was added to 236.2 g of silver nitrate (Wako Pure Chemical Industries special grade reagent) and dissolved to make 1700 cc to prepare an aqueous silver nitrate solution with an Ag concentration of 0.82 mol / L.
2) Impregnation support (Ag support amount: 0.2 mol / L)
The calcined alumina carrier was immersed in the prepared aqueous silver nitrate solution for 30 minutes, and the aqueous silver nitrate solution equivalent to the amount of water absorption was absorbed and the Ag loading amount was 0.2 mol / L.
3) Drying It dried for 20 minutes with the ventilation type dryer (household bedding dryer).
4) Firing treatment Firing at 550 ° C. × 3r was performed in the air.
5) H 2 reduction treatment Reduction treatment was performed by maintaining 500 ° C. × 3 hr in an atmosphere in which a 5% H 2 —N 2 mixed gas was circulated at a flow rate of 7 L / min.
As a result, an Ag / alumina-based NOx purification catalyst not carrying a Pt group metal was obtained.
<Supporting of Pt group metal>
The above Ag / alumina-based NOx purification catalyst was loaded with Pd, Pt or Rh as a Pt group metal. That is, after impregnating and supporting Pd, Pt, and Rh using an aqueous palladium nitrate solution (for supporting Pd), an aqueous dinitrodiamine platinum nitrate solution (for supporting Pt), and an aqueous rhodium nitrate solution (for supporting Rh), the above <Ag The treatments 3) to 5) of loading> were performed. The amount supported on the substrate was 0.1 g / L, respectively. For Ag, the Pt group metal loading is 0.46 wt%.
That is, Ag1 mol is 108 g, and Ag loaded amount = 0.2 mol / L = (108 g / mol × 0.2 mol) /L=21.6 g / L. Therefore, the supported amount of Pt group metal of 0.1 g / L is 0.1 / 21.6 × 100 = 0.46 wt% with respect to the supported amount of Ag of 21.6 g / L.
As described above, the Pt group metal-Ag / alumina NOx purification catalyst of the present invention in which Pd, Pt, and Rh were supported as Pt group metals on the Ag / alumina NOx purification catalyst not supporting the Pt group metal was obtained (sample). Name: AgPd0.1, AgPt0.1, AgRh0.1).
For comparison, an Ag / alumina-based NOx purification catalyst that does not carry Pt group metal was also produced (sample name: Ag).
As an application example of the present invention, a Pd—Ag / alumina-based NOx purification catalyst in which the alumina carrier contains 0.5 mol / L of titania was also prepared according to the following procedure and conditions (sample name: AgTiPd0.1).
<Procedure for preparing a titania-containing sample>
Using an aqueous solution of titanium citrate complex, Ti was supported on the Ag / alumina-based NOx purification catalyst so as to achieve the above-mentioned supported amount, and then Pd was supported in the same manner as described above. This was baked at 550 ° C. for 5 hours.
Regarding the above-described invention examples, conventional examples, and application examples, NOx adsorption and release tests were conducted on full-size (1.0 L) samples in the actual exhaust gas system shown in FIG.
<Specifications of engine-catalyst system>
Engine: 2.2L diesel engine Oxidation catalyst: Capacity 0.8L, Pt group metal 1.8g / L
FIG. 3 shows a temporal pattern of the catalyst bed temperature used in the test and a temporal pattern of NOx adsorption / release.
FIG. 4 shows changes in the combustion pattern (lean → rich → lean) and NOx emission peak for the present example (Pt group metal-Ag / alumina-based NOx purification catalyst) and the conventional example (Ag / alumina-based NOx purification catalyst). Shows the relationship. As shown in the figure, release of NOx is recognized in any sample during rich combustion. The amount of release evaluated by the area under the release curve is improved by almost 10 times in the present invention compared to the conventional example. The NOx release performance is accurately evaluated by the ratio of the release amount to the adsorption amount.
FIG. 5 and Table 1 show a comparison of NOx release rate (percentage of release amount with respect to adsorption amount). The inventive examples (AgPd0.1, AgPt0.1, AgRh0.1) show a high release rate of 29.5 to 45.9 times that of the conventional example (Ag).
In the application example (AgTiPd0.1) in which the alumina carrier contains 0.5 mol / L of titania, the release rate is improved by 38.5 times compared to the conventional example (Ag).
Next, a sub-size (35 cc) sample was produced as an example of the present invention under the same procedure and conditions as described above. However, the supported amount of the Pt group metal was set to five levels of 0.01, 0.05, 0.1, 1.0, and 2.0 g / L with respect to the base material.
Using a model gas having the following composition, an NOx adsorption / release test was performed using the gas temperature change pattern shown in FIG.
<Model gas composition>
《Catalyst purge 5 minutes》
Gas temperature: 600 ° C., CO 2 : 9%, O 2 : 8%
<Adsorption 10 minutes>
Gas temperature: 150 ° C., NO: 300 ppm, CO 2 : 9%, O 2 : 8%, H 2 O: 5%
《Desorption 15 minutes》
Gas temperature: 250 ° C., CO: 1%, CO 2 : 9%, O 2 : 0%, H 2 O: 5%
Both SVs were 26000 / h.
FIG. 7 and Table 2 show the measurement results when Pd is supported as a Pt group metal. The Pd loading on the substrate is shown for (A) the entire test range of 0 to 2.0 g / L, and (B) the range of the low loading of 0 to 0.1 g / L.
As shown in FIG. 7 and Table 2, when the Pd loading is 0.01 g / L or more, the NOx release rate is almost 100%. On the other hand, the NOx adsorption amount decreases as the Pd carrying amount increases, and decreases to about 1/2 of the initial value (value at 0.01 g / L) at the Pd carrying amount of 0.1 g / L. It does not change as the amount increases further. Therefore, the amount of Pd supported is in the range of 0.01 to 0.1 g / L with respect to the substrate. That is, the Pd loading (0.01 to 0.1 g / L) is 0.045 to 0.45 wt% with respect to the Ag loading (21.6 g / L). In order to secure a larger amount of adsorption and to further reduce the material cost of Pd, it is desirable that the amount of Pd supported is 0.30 wt% or less with respect to the amount of Ag supported.
FIG. 8 and Table 3 show the measurement results when Rh is supported as a Pt group metal.
本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒を下記の手順および条件で作製した。
＜アルミナ担体のコーティング＞
１）触媒基材
１３Ｒ四角セルのコージェライト基材を用いた。
２）スラリー調製
下記割合でアトライタにて２０分攪拌してスラリーを得た。
ＭＩ３８６粉末（ローディア製） １６００ｇ（１００部）
バインダＡ５２０（日産化学製） ７１０．４ｇ（４４．４部）
水 ３６００ｇ
３）スラリーのコーティング
得られたスラリーを上記コージェライト基材にコーティングした。コート量はアルミナ２００ｇ／Ｌであった。
４）焼成処理
大気中にて２５０℃×３０ｍｉｎ保持して水分を完全に除去し、引き続き５００℃×１ｈｒの焼成を行なった。焼成後コート品の吸水量は３１８ｇ／１３Ｒであった。
＜Ａｇの担持＞
１）硝酸銀水溶液の調製（Ａｇ濃度：０．８２ｍｏｌ／Ｌ）
硝酸銀（和光純薬工業特級試薬）２３６．２ｇにイオン交換水を加えて溶解させ１７００ｃｃとし、Ａｇ濃度０．８２ｍｏｌ／Ｌの硝酸銀水溶液を調製した。
２）含浸担持（Ａｇ担持量：０．２ｍｏｌ／Ｌ）
調製した硝酸銀水溶液に、上記焼成したアルミナ担体を３０分浸漬し、吸水量分の硝酸銀水溶液を吸水担持させて、Ａｇ担持量０．２ｍｏｌ／Ｌとした。
３）乾燥
送風型乾燥機（家庭用寝具乾燥機）にて２０分乾燥を行った。
４）焼成処理
大気中にて５５０℃×３ｒの焼成を行なった。
５）Ｈ２還元処理
５％Ｈ２−Ｎ２混合ガスを流速７Ｌ／ｍｉｎで流通させた雰囲気中に５００℃×３ｈｒ保持して還元処理を行なった。
これにより、Ｐｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒を得た。
＜Ｐｔ族金属の担持＞
上記Ａｇ／アルミナ系ＮＯｘ浄化触媒に、Ｐｔ族金属としてＰｄ、ＰｔまたはＲｈを担持させた。すなわち、硝酸パラジウム水溶液（Ｐｄ担持用）、ジニトロジアミン白金硝酸水溶液（Ｐｔ担持用）、硝酸ロジウム水溶液（Ｒｈ担持用）を用いて、Ｐｄ、Ｐｔ、Ｒｈを含浸担持させた後、上記＜Ａｇの担持＞の処理３）~５）を行なった。基材に対する担持量はそれぞれ０．１ｇ／Ｌとした。Ａｇに対してはＰｔ族金属担持量０．４６ｗｔ％である。
すなわち、Ａｇ１ｍｏｌは１０８ｇであり、Ａｇ担持量＝０．２ｍｏｌ／Ｌ＝（１０８ｇ／ｍｏｌ×０．２ｍｏｌ）／Ｌ＝２１．６ｇ／Ｌである。したがって、Ｐｔ族金属の担持量０．１ｇ／Ｌは、Ａｇ担持量２１．６ｇ／Ｌに対して、０．１／２１．６×１００＝０．４６ｗｔ％となる。
以上により、Ｐｔ族金属を担持しないＡｇ／アルミナ系ＮＯｘ浄化触媒にＰｔ族金属としてＰｄ、Ｐｔ、Ｒｈをそれぞれ担持した本発明のＰｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒が得られた（サンプル名：ＡｇＰｄ０．１、ＡｇＰｔ０．１、ＡｇＲｈ０．１）。
なお、比較のために、Ｐｔ族金属の担持を行なわないＡｇ／アルミナ系ＮＯｘ浄化触媒も作製した（サンプル名：Ａｇ）。
また、本発明の応用例として、アルミナ担体がチタニアを０．５ｍｏｌ／Ｌ含むＰｄ−Ａｇ／アルミナ系ＮＯｘ浄化触媒も下記の手順および条件で作製した（サンプル名：ＡｇＴｉＰｄ０．１）。
＜チタニア入りサンプルの作製手順＞
チタンクエン酸錯体水溶液を用いて、上記の担持量となるようにＡｇ／アルミナ系ＮＯｘ浄化触媒にＴｉを担持させ、次に前記と同様にＰｄを担持させた。これを５５０℃で５時間焼成した。
上記の本発明例、従来例、応用例について、フルサイズ（１．０Ｌ）のサンプルについて、図２に示す実機排ガス系において、ＮＯｘの吸着および放出の試験を行なった。
＜エンジン−触媒系の諸元＞
エンジン：２．２Ｌディーゼルエンジン
酸化触媒：容量０．８Ｌ、使用Ｐｔ族金属１．８ｇ／Ｌ
図３に、試験に用いた触媒床温の経時パターンおよびＮＯｘの吸着／放出の経時パターンを示す。
図４に、本発例（Ｐｔ族金属−Ａｇ／アルミナ系ＮＯｘ浄化触媒）および従来例（Ａｇ／アルミナ系ＮＯｘ浄化触媒）について、燃焼パターン（リーン→リッチ→リーン）の変化とＮＯｘの放出ピークとの関係を示す。図示したように、何れのサンプルもリッチ燃焼時にＮＯｘの放出が認められる。放出曲線下の面積で評価した放出量は、本発明例は従来例の１０倍近く向上している。ＮＯｘ放出性能は正確には、吸着量に対する放出量の比率で評価される。
図５および表１に、ＮＯｘの放出率（吸着量に対する放出量のパーセンテージ）を比較して示す。本発明例（ＡｇＰｄ０．１、ＡｇＰｔ０．１、ＡｇＲｈ０．１）は従来例（Ａｇ）に対して２９．５~４５．９倍の高い放出率を示している。
次に、前述と同様の手順および条件にて、本発明の実施例として、サブサイズ（３５ｃｃ）のサンプルを作製した。ただし、Ｐｔ族金属の担持量は、基材に対して０．０１、０．０５、０．１、１．０、２．０ｇ／Ｌの５水準とした。
下記組成のモデルガスを用いて、図６の入りガス温度変化パターンでＮＯｘの吸着／放出試験を行った。
＜モデルガス組成＞
《触媒パージ ５分》
ガス温度：６００℃、ＣＯ２：９％、Ｏ２：８％
《吸着 １０分》
ガス温度：１５０℃、ＮＯ：３００ｐｐｍ、ＣＯ２：９％、Ｏ２：８％、Ｈ２Ｏ：５％
《脱離 １５分》
ガス温度：２５０℃、ＣＯ：１％、ＣＯ２：９％、Ｏ２：０％、Ｈ２Ｏ：５％
ＳＶは共に２６０００／ｈであった。
図７および表２に、Ｐｔ族金属としてＰｄを担持した場合の測定結果を示す。基材に対するＰｄ担持量が、（Ａ）０~２．０ｇ／Ｌの試験範囲全体について、（Ｂ）０~０．１ｇ／Ｌの低担持量の範囲について、それぞれ示す。
図８および表３は、Ｐｔ族金属としてＲｈを担持した場合の測定結果を示す。
The Pt group metal-Ag / alumina-based NOx purification catalyst of the present invention was prepared according to the following procedure and conditions.
<Alumina carrier coating>
1) Catalyst base material A cordierite base material of 13R square cell was used.
2) Slurry preparation A slurry was obtained by stirring with an attritor for 20 minutes at the following ratio.
MI386 powder (made by Rhodia) 1600 g (100 parts)
Binder A520 (Nissan Chemical) 710.4 g (44.4 parts)
3600g of water
3) Coating of slurry The obtained slurry was coated on the cordierite substrate. The coating amount was 200 g / L of alumina.
4) Firing treatment The moisture was completely removed by holding at 250 ° C. for 30 minutes in the atmosphere, and then firing was performed at 500 ° C. for 1 hour. The water absorption of the coated product after firing was 318 g / 13R.
<Supporting Ag>
1) Preparation of silver nitrate aqueous solution (Ag concentration: 0.82 mol / L)
Ion exchange water was added to 236.2 g of silver nitrate (Wako Pure Chemical Industries special grade reagent) and dissolved to make 1700 cc to prepare an aqueous silver nitrate solution with an Ag concentration of 0.82 mol / L.
2) Impregnation support (Ag support amount: 0.2 mol / L)
The calcined alumina carrier was immersed in the prepared aqueous silver nitrate solution for 30 minutes, and the aqueous silver nitrate solution equivalent to the amount of water absorption was absorbed and the Ag loading amount was 0.2 mol / L.
3) Drying It dried for 20 minutes with the ventilation type dryer (household bedding dryer).
4) Firing treatment Firing at 550 ° C. × 3r was performed in the air.
5) H 2 reduction treatment Reduction treatment was performed by maintaining 500 ° C. × 3 hr in an atmosphere in which a 5% H 2 —N 2 mixed gas was circulated at a flow rate of 7 L / min.
As a result, an Ag / alumina-based NOx purification catalyst not carrying a Pt group metal was obtained.
<Supporting of Pt group metal>
The above Ag / alumina-based NOx purification catalyst was loaded with Pd, Pt or Rh as a Pt group metal. That is, after impregnating and supporting Pd, Pt, and Rh using an aqueous palladium nitrate solution (for supporting Pd), an aqueous dinitrodiamine platinum nitrate solution (for supporting Pt), and an aqueous rhodium nitrate solution (for supporting Rh), the above <Ag The treatments 3) to 5) of loading> were performed. The amount supported on the substrate was 0.1 g / L, respectively. For Ag, the Pt group metal loading is 0.46 wt%.
That is, Ag1 mol is 108 g, and Ag loaded amount = 0.2 mol / L = (108 g / mol × 0.2 mol) /L=21.6 g / L. Therefore, the supported amount of Pt group metal of 0.1 g / L is 0.1 / 21.6 × 100 = 0.46 wt% with respect to the supported amount of Ag of 21.6 g / L.
As described above, the Pt group metal-Ag / alumina NOx purification catalyst of the present invention in which Pd, Pt, and Rh were supported as Pt group metals on the Ag / alumina NOx purification catalyst not supporting the Pt group metal was obtained (sample). Name: AgPd0.1, AgPt0.1, AgRh0.1).
For comparison, an Ag / alumina-based NOx purification catalyst that does not carry Pt group metal was also produced (sample name: Ag).
As an application example of the present invention, a Pd—Ag / alumina-based NOx purification catalyst in which the alumina carrier contains 0.5 mol / L of titania was also prepared according to the following procedure and conditions (sample name: AgTiPd0.1).
<Procedure for preparing a titania-containing sample>
Using an aqueous solution of titanium citrate complex, Ti was supported on the Ag / alumina-based NOx purification catalyst so as to achieve the above-mentioned supported amount, and then Pd was supported in the same manner as described above. This was baked at 550 ° C. for 5 hours.
Regarding the above-described invention examples, conventional examples, and application examples, NOx adsorption and release tests were conducted on full-size (1.0 L) samples in the actual exhaust gas system shown in FIG.
<Specifications of engine-catalyst system>
Engine: 2.2L diesel engine Oxidation catalyst: Capacity 0.8L, Pt group metal 1.8g / L
FIG. 3 shows a temporal pattern of the catalyst bed temperature used in the test and a temporal pattern of NOx adsorption / release.
FIG. 4 shows changes in the combustion pattern (lean → rich → lean) and NOx emission peak for the present example (Pt group metal-Ag / alumina-based NOx purification catalyst) and the conventional example (Ag / alumina-based NOx purification catalyst). Shows the relationship. As shown in the figure, release of NOx is recognized in any sample during rich combustion. The amount of release evaluated by the area under the release curve is improved by almost 10 times in the present invention compared to the conventional example. The NOx release performance is accurately evaluated by the ratio of the release amount to the adsorption amount.
FIG. 5 and Table 1 show a comparison of NOx release rate (percentage of release amount with respect to adsorption amount). The inventive examples (AgPd0.1, AgPt0.1, AgRh0.1) show a high release rate of 29.5 to 45.9 times that of the conventional example (Ag).
Next, a sub-size (35 cc) sample was produced as an example of the present invention under the same procedure and conditions as described above. However, the supported amount of the Pt group metal was set to five levels of 0.01, 0.05, 0.1, 1.0, and 2.0 g / L with respect to the base material.
Using a model gas having the following composition, an NOx adsorption / release test was performed using the gas temperature change pattern shown in FIG.
<Model gas composition>
《Catalyst purge 5 minutes》
Gas temperature: 600 ° C., CO 2 : 9%, O 2 : 8%
<Adsorption 10 minutes>
Gas temperature: 150 ° C., NO: 300 ppm, CO 2 : 9%, O 2 : 8%, H 2 O: 5%
《Desorption 15 minutes》
Gas temperature: 250 ° C., CO: 1%, CO 2 : 9%, O 2 : 0%, H 2 O: 5%
Both SVs were 26000 / h.
FIG. 7 and Table 2 show the measurement results when Pd is supported as a Pt group metal. The Pd loading on the substrate is shown for (A) the entire test range of 0 to 2.0 g / L, and (B) the range of the low loading of 0 to 0.1 g / L.
FIG. 8 and Table 3 show the measurement results when Rh is supported as a Pt group metal.
本発明によれば、優れたＮＯｘ吸着性能を確保しつつＮＯｘ放出性を高めたＡｇ／アルミナ系ＮＯｘ浄化触媒が提供される。
According to the present invention, there is provided an Ag / alumina-based NOx purification catalyst that has improved NOx release while ensuring excellent NOx adsorption performance.
Claims (4)
- アルミナ担体上に、Ａｇと、Ｐｔ族金属のうち少なくとも１種とを担持し、Ｐｔ族金属の担持量はＡｇの担持量の０．０４５~０．４５ｗｔ％であることを特徴とするＮＯｘ浄化触媒。 NOx purification characterized in that Ag and at least one of Pt group metals are supported on an alumina support, and the supported amount of Pt group metal is 0.045 to 0.45 wt% of the supported amount of Ag. catalyst.
- 請求項１において、Ｐｔ族金属の担持量がＡｇの担持量の０．３０ｗｔ％以下であることを特徴とするＮＯｘ浄化触媒。 2. The NOx purification catalyst according to claim 1, wherein the supported amount of the Pt group metal is 0.30 wt% or less of the supported amount of Ag.
- 請求項１または２において、Ｐｔ族金属がＰｄであることを特徴とするＮＯｘ浄化触媒。 3. The NOx purification catalyst according to claim 1, wherein the Pt group metal is Pd.
- 請求項１~３の１項において、アルミナ担体がチタニアを含むことを特徴とするＮＯｘ浄化触媒。 4. The NOx purification catalyst according to claim 1, wherein the alumina support contains titania.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2010/061289 WO2011161834A1 (en) | 2010-06-25 | 2010-06-25 | NOx PURGING CATALYST |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2010/061289 WO2011161834A1 (en) | 2010-06-25 | 2010-06-25 | NOx PURGING CATALYST |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2011161834A1 true WO2011161834A1 (en) | 2011-12-29 |
Family
ID=45371045
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/JP2010/061289 WO2011161834A1 (en) | 2010-06-25 | 2010-06-25 | NOx PURGING CATALYST |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO2011161834A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016191305A (en) * | 2015-03-30 | 2016-11-10 | 株式会社日本自動車部品総合研究所 | Nox elimination system control device and reducing agent addition system |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0372949A (en) * | 1989-08-10 | 1991-03-28 | Nippon Shokubai Kagaku Kogyo Co Ltd | Catalyst for purifying exhaust gas |
| JPH07163878A (en) * | 1992-12-25 | 1995-06-27 | Riken Corp | Nitrogen oxide removing catalyst and method |
| JPH0824583A (en) * | 1993-12-28 | 1996-01-30 | Riken Corp | Exhaust gas purifying material and method for purifying exhaust gas |
| JPH09248457A (en) * | 1996-03-18 | 1997-09-22 | Toyota Motor Corp | High heat-resistance catalyst |
| JPH09290156A (en) * | 1996-04-26 | 1997-11-11 | Sumitomo Metal Mining Co Ltd | Exhaust gas purifying catalyst and exhaust gas purifying method |
| JPH1066869A (en) * | 1997-05-30 | 1998-03-10 | Sakai Chem Ind Co Ltd | Nitrogen oxide decomposing catalyst |
| JPH1199319A (en) * | 1997-07-28 | 1999-04-13 | Petroleum Energy Center Found | Waste gas purifying method |
-
2010
- 2010-06-25 WO PCT/JP2010/061289 patent/WO2011161834A1/en active Application Filing
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0372949A (en) * | 1989-08-10 | 1991-03-28 | Nippon Shokubai Kagaku Kogyo Co Ltd | Catalyst for purifying exhaust gas |
| JPH07163878A (en) * | 1992-12-25 | 1995-06-27 | Riken Corp | Nitrogen oxide removing catalyst and method |
| JPH0824583A (en) * | 1993-12-28 | 1996-01-30 | Riken Corp | Exhaust gas purifying material and method for purifying exhaust gas |
| JPH09248457A (en) * | 1996-03-18 | 1997-09-22 | Toyota Motor Corp | High heat-resistance catalyst |
| JPH09290156A (en) * | 1996-04-26 | 1997-11-11 | Sumitomo Metal Mining Co Ltd | Exhaust gas purifying catalyst and exhaust gas purifying method |
| JPH1066869A (en) * | 1997-05-30 | 1998-03-10 | Sakai Chem Ind Co Ltd | Nitrogen oxide decomposing catalyst |
| JPH1199319A (en) * | 1997-07-28 | 1999-04-13 | Petroleum Energy Center Found | Waste gas purifying method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016191305A (en) * | 2015-03-30 | 2016-11-10 | 株式会社日本自動車部品総合研究所 | Nox elimination system control device and reducing agent addition system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4751916B2 (en) | Exhaust gas purification catalyst | |
| ES2458499T3 (en) | Method for preparing a NOx storage material | |
| CN102909020B (en) | Sulfur-resistant catalytic-combustion catalyst and preparation method thereof | |
| EP3064270B1 (en) | Carrier for exhaust gas purification catalyst, and exhaust gas purification catalyst | |
| WO2012161091A1 (en) | Exhaust gas purifying catalyst and carrier | |
| JP5865110B2 (en) | Methane oxidation catalyst and production method thereof | |
| JP2024501748A (en) | Three-way catalyst supporting noble metal in single atomic state, preparation method and use thereof | |
| WO2011161834A1 (en) | NOx PURGING CATALYST | |
| JP5503155B2 (en) | Carbon monoxide removal filter | |
| JP4779461B2 (en) | Catalyst carrier, method for producing the same, and exhaust gas purification catalyst | |
| JP7218402B2 (en) | Exhaust gas purification catalyst device | |
| JP2010125373A (en) | Silver catalyst for oxidation | |
| JP5544921B2 (en) | Exhaust gas purification catalyst | |
| JP2006233774A (en) | Exhaust emission control device and exhaust emission control method | |
| JP5488402B2 (en) | Exhaust gas purification catalyst | |
| JP5488371B2 (en) | Exhaust gas purification catalyst | |
| JP6066817B2 (en) | Exhaust purification catalyst and exhaust purification device | |
| WO2016002344A1 (en) | Catalyst carrier and exhaust gas purifying catalyst | |
| JP3185046B2 (en) | NOx adsorbent and method for producing the same | |
| JP2003135963A (en) | Catalyst for cleaning exhaust gas and manufacturing method therefor | |
| JP4760599B2 (en) | Aldehyde gas removal filter | |
| JP2015131283A (en) | Catalyst for exhaust gas purification | |
| JP2016135473A (en) | Carrier for exhaust gas purification catalyst and exhaust gas purification catalyst | |
| JP2023049914A (en) | Exhaust gas purification catalyst device | |
| JP2005296733A (en) | Catalyst manufacturing method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 10853694 Country of ref document: EP Kind code of ref document: A1 |
|
| NENP | Non-entry into the national phase |
Ref country code: DE |
|
| 122 | Ep: pct application non-entry in european phase |
Ref document number: 10853694 Country of ref document: EP Kind code of ref document: A1 |
|
| NENP | Non-entry into the national phase |
Ref country code: JP |