US20120285148A1 - Catalyst device - Google Patents

Catalyst device Download PDF

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US20120285148A1
US20120285148A1 US13/468,305 US201213468305A US2012285148A1 US 20120285148 A1 US20120285148 A1 US 20120285148A1 US 201213468305 A US201213468305 A US 201213468305A US 2012285148 A1 US2012285148 A1 US 2012285148A1
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Prior art keywords
catalyst
base material
layer
oxidation catalyst
porosity
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Takanori Murasaki
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Toyota Industries Corp
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Toyota Industries Corp
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Assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI reassignment KABUSHIKI KAISHA TOYOTA JIDOSHOKKI ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MURASAKI, TAKANORI
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9463—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick
    • B01D53/9468—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick in different layers
    • 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
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • 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
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
    • B01J29/46—Iron group metals or copper
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/19—Catalysts containing parts with different compositions
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0246—Coatings comprising a zeolite
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/103—Oxidation catalysts for HC and CO only
    • 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
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—Urea
    • 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
    • B01D2255/102—Platinum group metals
    • B01D2255/1023—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B01D2255/504—ZSM 5 zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/80—Type of catalytic reaction
    • B01D2255/808—Hydrolytic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/915—Catalyst supported on particulate filters
    • B01D2255/9155—Wall flow filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/92—Dimensions
    • B01D2255/9205—Porosity
    • 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
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
    • F01N2510/0684—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having more than one coating layer, e.g. multi-layered coatings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to a catalyst device, and more particularly, to a catalyst device that is used in an exhaust gas purification apparatus that utilizes a urea selective catalytic reduction (SCR) system.
  • SCR selective catalytic reduction
  • a urea SCR system comprises: an oxidation catalyst for oxidizing nitrogen monoxide (NO) into nitrogen dioxide (NO 2 ); an SCR catalyst, disposed downstream of the oxidation catalyst, for reducing NOx to nitrogen and water through a chemical reaction between NOx and ammonia generated out of the aqueous urea solution; a urea addition system for adding the aqueous urea solution to the SCR catalyst; and an oxidation catalyst, disposed downstream of the SCR catalyst, for oxidizing residual ammonia that is not consumed in the chemical reaction in the SCR catalyst.
  • a diesel particulate filter (DPF) for removing particulate matter (PM) can be provided between the SCR catalyst and the oxidation catalyst that oxidizes NO.
  • the present invention provides a catalyst device that purifies an exhaust gas discharged by an internal combustion engine, comprising: a porous base material that supports, in the interior thereof, an SCR catalyst that reduces NOx in the exhaust gas; a trapping layer that traps PM in the exhaust gas and is coated on a surface of the base material on the internal combustion engine side; and an oxidation catalyst layer that contains an oxidation catalyst and is coated on a surface of the base material on a side opposite to the internal combustion engine side.
  • FIG. 1 is a schematic diagram of the configuration of an exhaust gas purification apparatus provided with a catalyst device according to an embodiment of the present invention.
  • FIG. 2 is a cross-sectional diagram of a substrate in the catalyst device according to the embodiment.
  • FIG. 1 illustrates a schematic diagram of the configuration of an exhaust gas purification apparatus provided with catalyst device according to an embodiment of the present invention.
  • An exhaust pipe 2 through which exhaust gas discharged from a diesel engine 1 flows is provided with an oxidation catalyst device 3 and a catalyst device 4 that purifies the exhaust gas.
  • An injection nozzle 7 that injects an aqueous urea solution, as a reductant, is provided between the oxidation catalyst device 3 and the catalyst device 4 .
  • the injection nozzle 7 communicates, via piping 8 , with an aqueous urea solution tank 9 that stores an aqueous urea solution.
  • the piping 8 is provided with an aqueous urea solution addition system 6 for supplying aqueous urea solution from inside the aqueous urea solution tank 9 to the injection nozzle 7 .
  • the aqueous urea solution addition system 6 is electrically connected to an ECU 5 which is a control device.
  • the catalyst device 4 has a wall flow-type substrate 14 .
  • the substrate 14 includes a porous base material 11 .
  • the material used in the base material 11 may be a ceramic material ordinarily used as a filter substrate, for instance cordierite, alumina, silicon carbide or the like.
  • An SCR catalyst for reduction of NOx is supported in the pores in the interior of the base material 11 .
  • a surface 11 a of the base material 11 on the diesel engine 1 side is coated with a trapping layer 12 that traps PM in the exhaust gas.
  • the same material as in the base material 11 can be used as the material of the trapping layer 12 .
  • a surface 11 b of the base material 11 on the side opposite to the diesel engine 1 side is coated with an oxidation catalyst layer 13 that is formed of an oxidation catalyst.
  • a thickness X 1 of the base material 11 is greater than both a thickness X 2 of the trapping layer 12 and a thickness X 3 of the oxidation catalyst layer 13 .
  • the thickness X 1 of the base material 11 ranges from 200 ⁇ m to 400 ⁇ m.
  • the thickness X 2 of the trapping layer 12 ranges preferably from 10 ⁇ m to less than 200 ⁇ m, and the thickness X 3 of the oxidation catalyst layer 13 ranges preferably from 0.1 ⁇ m to less than 200 ⁇ m.
  • the porosity of the base material 11 is greater than the porosity of the trapping layer 12 , and the porosity of the oxidation catalyst layer 13 is equal to or greater than the porosity of the base material 11 .
  • the porosity of the base material 11 and of the oxidation catalyst layer 13 range from 55% to 70%, and the porosity of the trapping layer 12 ranges preferably from 20% to less than 55%.
  • the average pore size of the base material 11 is greater than the average pore size of the trapping layer 12 , and the average pore size of the oxidation catalyst layer 13 is equal to or greater than the average pore size of the base material 11 .
  • the average pore size of the base material 11 and the oxidation catalyst layer 13 ranges from 15 ⁇ m to 100 ⁇ m, and the average pore size of the trapping layer 12 ranges preferably from 6 ⁇ m to less than 15 ⁇ m.
  • exhaust gas discharged by the diesel engine 1 flows through the exhaust pipe 2 .
  • the exhaust gas flows into the oxidation catalyst device 3 , whereupon NO in the exhaust gas is oxidized into NO 2 .
  • the exhaust gas flows into the catalyst device 4 .
  • the ECU 5 operates the aqueous urea solution addition system 6 at an appropriate timing, to supply aqueous urea solution in the aqueous urea solution tank 9 to the injection nozzle 7 via the piping 8 , and cause the aqueous urea solution to be added into the catalyst device 4 from the injection nozzle 7 .
  • the PM in the exhaust gas that flows into the catalyst device 4 is captured by the trapping layer 12 as the exhaust gas passes through the trapping layer 12 .
  • the exhaust gas diffuses into the pores of the base material 11 .
  • the aqueous urea solution added into the catalyst device 4 is hydrolyzed on account of the heat of the exhaust gas, to yield ammonia and carbon dioxide.
  • the SCR catalyst supported in the pores in the base material 11 the generated ammonia reacts with NOx in the exhaust gas that has diffused into the pores, and NOx is reduced thereby to nitrogen and water. Residual ammonia that has not been consumed in the base material 11 is oxidized at the oxidation catalyst in the oxidation catalyst layer 13 , and the purified exhaust gas is discharged to the atmosphere.
  • the amount of PM captured in the trapping layer 12 increases as time goes by.
  • the trapping layer 12 can be regenerated in accordance with known methods, for instance through addition of fuel to the exhaust gas.
  • hydrocarbons and carbon monoxide are oxidized by the oxidation catalyst in the oxidation catalyst layer 13 .
  • the SCR catalyst is supported in the interior of the porous base material 11 , and hence the coating amount need not be reduced to thereby reduce the pressure loss.
  • the trapping layer 12 is coated onto the surface 11 a of the base material 11 on the diesel engine 1 side. Therefore, it is not necessary to reduce the pressure loss by using a high-porosity base material.
  • a DPF, an SCR catalyst and an oxidation catalyst can be integrated together while fulfilling a combined DPF function and SCR catalyst function.
  • the trapping layer 12 may be coated with, for instance, alumina, titania, a zeolite, silica or the like, as the hydrolysis catalyst for hydrolysis of urea.
  • urea can be hydrolyzed on account of the heat of the exhaust gas
  • the hydrolysis catalyst allows urea to be hydrolyzed reliably also when the temperature of the exhaust gas is low, for instance immediately after startup of the diesel engine 1 .
  • a second SCR catalyst different from the SCR catalyst that is supported in the interior of the base material 11 may be incorporated in the oxidation catalyst layer 13 .
  • NOx can be reduced in the oxidation catalyst layer 13 as well, and the NOx purification power can be thus enhanced.
  • Table 1 sets forth the features of Examples 1 to 3, which correspond to catalyst devices according to the present invention, and the features of catalyst devices according to Comparative examples 1 to 9 (Comparative example 1 is a conventional urea SCR system wherein a DPF, an SCR catalyst and an oxidation catalyst are separate members).
  • Examples 1 to 3 have a three-layer structure explained in the embodiment, comprising a trapping layer coated with Al 2 O 3 as a hydrolysis catalyst, a porous base material in which Fe-ZSM5 as an SCR catalyst is supported in internal pores, and an oxidation catalyst layer that contains Fe-ZSM5 as a second SCR catalyst and PtPd/Al 2 O 3 as an oxidation catalyst.
  • Table 1 gives the porosity, average pore size (APS) and thickness for each layer, as well as the coating amount of SCR catalyst in the base material.
  • Comparative example 1 is a conventional urea SCR system having a DPF, an SCR catalyst and an oxidation catalyst as separate members.
  • Comparative examples 2 to 4 have a one-layer structure in which Fe-ZSM5, as an SCR catalyst, is supported in pores of a porous base material.
  • Comparative examples 5 to 9 have a two-layer structure comprising a trapping layer coated with Al 2 O 3 , as a hydrolysis catalyst, and a porous base material in which Fe-ZSM5, as an SCR catalyst, is supported in internal pores.
  • Table 1 gives the porosity, average pore size and thickness for each layer, as well as the coating amount of SCR catalyst in the base material.
  • Table 2 sets forth evaluation results obtained upon evaluation of the performance of the catalyst devices of Examples 1 to 3 and Comparative examples 2 to 9, using these catalyst devices installed as the catalyst device 4 of the exhaust gas purification apparatus illustrated in FIG. 1 , and using a conventional urea SCR system as Comparative example 1.
  • the evaluation results were graded qualitatively into a three-grade ranking in which a double circle denotes excellent results, a single circle denotes good results, and a cross mark denotes problematic results.
  • Examples 1 to 3 and Comparative examples 2 to 9 utilize integrated catalyst devices, and hence exhibit superior compactness vis-à-vis Comparative example 1, which is a conventional urea SCR system in which a DPF, an SCR catalyst and an oxidation catalyst are separate members.
  • PM trapping ability, pressure loss derived from PM deposition and NOx purification rate are related to compatibility between the DPF function and SCR catalyst function.
  • Comparative examples 2 to 4 there is no trapping layer, and PM is trapped in the base material.
  • the coating amount of SCR catalyst decreases and the NOx purification rate becomes poorer.
  • the pressure loss derived from PM deposition becomes worse when the coating amount of SCR catalyst is increased with respect to that of Comparative example 2, as in Comparative example 3.
  • the PM trapping ability becomes worse when adjusting the porosity and average pore size in Comparative example 3 in order to improve the pressure drop, as in Comparative example 4.
  • the pressure loss derived from PM deposition is yet worse.
  • the pressure loss derived from PM deposition is improved by reducing the coating amount of SCR catalyst, but the NOx purification rate drops in doing so.
  • the thickness of the trapping layer is set to 300 ⁇ m and the thickness of the base material is set to 70 ⁇ m. The results of Comparative examples 8 and 9 indicate that it is difficult to achieve, on the basis of such a thickness relationship, both the coating amount of SCR catalyst (NOx purification rate) and pressure loss derived from PM deposition as are required.
  • Comparative examples 2 to 9 which lack an oxidation catalyst layer that is formed of an oxidation catalyst that oxidizes ammonia, hydrocarbons and carbon monoxide, yielded problematic results in terms of ammonia slip properties, and slip-through properties of hydrocarbons and carbon monoxide during PM regeneration.
  • Examples 1 to 3 which are specific embodiments of the catalyst device according to the present invention, display a satisfactory DPF function, SCR catalyst function and oxidation catalyst function, while integrating those functions with each other. That is, high PM trapping (low pressure loss) and high coating amount of an SCR catalyst (high NOx purification rate) can be realized. It also becomes possible to achieve further size reduction through coating of the oxidation catalyst layer.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Combustion & Propulsion (AREA)
  • Health & Medical Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Toxicology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
US13/468,305 2011-05-13 2012-05-10 Catalyst device Abandoned US20120285148A1 (en)

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JP2011-108165 2011-05-13
JP2011108165A JP2012237282A (ja) 2011-05-13 2011-05-13 触媒装置

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* Cited by examiner, † Cited by third party
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CN109891064A (zh) * 2016-10-26 2019-06-14 斗山英维高株式会社 废气后处理系统

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