EP1102629A1 - Systeme ameliore d'adsorbeur catalyse pour traiter des gaz d'echappement de moteur a combustion interne et son procede de fabrication - Google Patents

Systeme ameliore d'adsorbeur catalyse pour traiter des gaz d'echappement de moteur a combustion interne et son procede de fabrication

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Publication number
EP1102629A1
EP1102629A1 EP98934425A EP98934425A EP1102629A1 EP 1102629 A1 EP1102629 A1 EP 1102629A1 EP 98934425 A EP98934425 A EP 98934425A EP 98934425 A EP98934425 A EP 98934425A EP 1102629 A1 EP1102629 A1 EP 1102629A1
Authority
EP
European Patent Office
Prior art keywords
adsorber
washcoat
catalyzed
zeolite
impregnated
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.)
Withdrawn
Application number
EP98934425A
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German (de)
English (en)
Other versions
EP1102629A4 (fr
Inventor
Ronald G. Silver
Danan Dou
Stephen R. Dunne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Umicore Autocat USA Inc
Original Assignee
Umicore Autocat USA Inc
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Filing date
Publication date
Application filed by Umicore Autocat USA Inc filed Critical Umicore Autocat USA Inc
Publication of EP1102629A1 publication Critical patent/EP1102629A1/fr
Publication of EP1102629A4 publication Critical patent/EP1102629A4/fr
Withdrawn legal-status Critical Current

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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
    • 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
    • B01J37/0248—Coatings comprising impregnated particles
    • 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
    • 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
    • B01J29/064—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing iron group metals, noble metals or copper
    • B01J29/068—Noble metals
    • 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
    • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
    • B01J29/10—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing iron group metals, noble metals or copper
    • B01J29/12—Noble metals
    • B01J29/126—Y-type faujasite
    • 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
    • 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

  • This invention relates to catalyzed adsorbers for treating motor vehicle exhaust gas comprising a substrate having dispersed thereon a zeolite and an inorganic oxide washcoat, said washcoat having been impregnated with a catalytically effective amount of noble metals prior to being mixed or layered with said zeolite and optionally with a promoter.
  • This invention further relates to a method of making such catalyzed adsorbers.
  • Catalytic converters containing various catalysts have been employed for years by automobile manufacturers to meet the ever-more-stringent regulations on emissions of hydrocarbons, carbon monoxide and nitrogen oxides from internal combustion engines.
  • the continuing evolution and tightening of these regulations has made necessary the development of systems that control emission of hydrocarbons during the period immediately after start of a cold engine and before the catalytic converter normally supplied by automobile manufacturers has been sufficiently warmed by engine exhaust gas to be effective in converting hydrocarbons (often referred to as "cold start conditions").
  • An attractive approach has been the incorporation in the exhaust system of an adsorbent capable of adsorbing hydrocarbons at the low exhaust gas temperatures associated with cold start (0 to 250°C) and further capable of releasing those hydrocarbons when normal exhaust system operating temperatures are achieved.
  • Such an adsorber would normally be combined with a conventional three- way catalyst (i.e., a catalyst capable of oxidizing hydrocarbons and carbon monoxide while reducing nitrogen oxides, often referred to as a "TWC") or some other non-adsorber-containing catalyst.
  • TWC's of various types have been employed by themselves in the reduction of automobile emissions and have been effective in meeting the standards of the past.
  • Ever- tightening regulations have, however, made necessary a more effective system for controlling emissions of unburnt hydrocarbons from internal combustion engines during cold start.
  • the present invention provides such an improved system.
  • Various researchers have taught catalyst formulations and methods for preparation that resemble superficially the catalyzed adsorbers and method for their preparation taught here. For example, U.S.
  • Patent N 2 4,151,121 (Gladrow) teaches a catalyst for promoting the combustion of CO in the regenerators of fluid catalytic crackers to avoid afterburning.
  • the catalyst of that patent comprises a Group VIII element supported on an inorganic oxide and admixed with a zeolite, but also requires the presence of rhenium, chromium, manganese, or some combination thereof.
  • U.S. Patent N a 5,273,945 also teaches catalysts for fluid catalytic cracking having metal supported on inorganic oxide binder or zeolite, but is indifferent to the nature of the metal employed and as to whether the metal is supported on the inorganic oxide or the zeolite.
  • U.S. Patent N 2 3.833,499 (Egan et al. ) teaches a catalyst for hydrocracking of hydrocarbons that employs palladium impregnated on an inorganic oxide prior to addition to a zeolite, but requires that the zeolite already be impregnated with palladium.
  • U.S. Patent N 2 5,278,113 (Ono et al.) teaches a catalyst for deodorization in room heating comprising a platinum group metal dispersed on alumina prior to being mixed with a zeolite.
  • the catalyst of that invention is intended to effect the adsorption of odors from the environment in which it is deployed, periodically being heated to release and oxidatively decompose the odor components and thereby regenerating the catalyst.
  • U.S. Patent N a 5,354,720 (Leyrer et al.) teaches a catalyst for reducing the quantity of nitrogen oxides in lean exhaust gas that comprises a first layer of aluminum or cerium oxide impregnated with a mixture of platinum and iridium and a second layer of zeolite impregnated with copper and/or iron.
  • the present invention is concerned with reducing the amount of hydrocarbons contained in an exhaust gas stream containing a lower oxygen concentration than those taught by the Leyrer patent.
  • U.S. Patent N 2 5,510,086 (Hemingway, et al.) teaches the use of three catalyst zones for the reduction of automobile exhaust emissions, the first of which is a conventional TWC, followed in the direction of the exhaust flow by a hydrocarbon adsorber/catalyst, which is in turn followed by another TWC.
  • the hydrocarbon adsorber/catalyst is claimed to have a coating comprising an adhered washcoat including a zeolite and palladium.
  • '086 teaches that the noble metal is to be applied to the zeolite, thereby yielding a catalytic adsorber inferior in performance to that of the instant application.
  • European Patent Application N 2 94309790.7 (Abe, et al) teaches the use of one honeycomb monolith substrate which is coated in one region of the substrate with adsorbent for hydrocarbon, and in a completely different and distinct region of the substrate is coated with a catalyst layer active for three-way catalytic activity.
  • the catalyst and adsorber in this example are not combined in any manner.
  • European Patent Application N 2 95110617.8 (Hertl, et al) teaches a three brick system like Hemingway ' s, with the middle adsorber brick containing a hole in the -loneycoitfb ⁇ floIitft ⁇ bstrate to allow exhaust gas to bypass the adsorber.
  • the invention further requires some sort of means to divert exhaust flow into or away from the adsorber brick.
  • This invention provides for a catalyzed adsorber that is effective and durable in treating exhaust gas from internal combustion engines, and in particular, for adsorbing hydrocarbons contained in engine exhaust gas during cold start, releasing these hydrocarbons when the engine exhaust gas has heated the adsorber to normal operating temperature and catalyzing the conversion of these hydrocarbons to carbon dioxide and water, all over one catalytic embodiment and without requiring the diversion of exhaust gas at any time during operation of the engine. Furthermore, the catalyzed adsorber of this application retains its function after exposure to severe aging by engine exhaust gas simulating 160,000 km (100,000 miles) of use in the underfloor position.
  • the catalyzed adsorber of this invention comprises a substrate upon which has been dispersed a coating comprising an inorganic oxide that has been impregnated with a noble metal, and optionally a promoter, and an appropriate zeolite.
  • this invention teaches a method of combining the zeolite, noble metal, inorganic oxide and optional promoter to provide optimal conversion of hydrocarbon trapped on the adsorber.
  • This invention also includes a method of making such a catalyzed adsorber.
  • FIG. 1 compares the amount of weighted cumulative non-methane hydrocarbon (NMHC) emissions per mile vs. time from two catalyzed adsorbers of the present invention (aged 50 h.) to those from a conventional catalyst, a conventional catalyzed adsorber and a conventional non- catalyzed adsorber (all aged 50 h.).
  • FIG. 2 shows the rate of NHMC emissions over time during the first 200 seconds of the EPA
  • FIG. 3 shows the conversion of HC and CO vs. temperature for 2.54-cm (1-inch) diameter cores taken from Pt and Pd catalyzed adsorbers of the present invention.
  • FIG. 4 shows the conversion of HC and NO x vs. temperature for 2.54-cm ( 1 -inch) diameter cores taken from Rh and Pd catalyzed adsorbers of the present invention.
  • FIG. 5 shows the impact of noble metal loading on the coking rates of fresh zeolite cores.
  • FIG. 6 shows the amount of weighted cumulative non-methane hydrocarbon (NMHC) emissions per mile vs. time from three catalyzed adsorbers of the present invention (aged 65 h.) DETAILED DESCRIPTION OF THE INVENTION
  • the catalyzed adsorber of the present invention comprises a substrate which has been coated with a suitable zeolite and an inorganic oxide washcoat, the washcoat having been impregnated with a catalytically effective amount of a noble metal, and optionally admixed with a promoter, prior to being mixed with the zeolite.
  • the noble metal and washcoat can optionally be layered on top of or underneath the zeolite layer and optional promoter, or multiple layers of zeolite and washcoat can be applied to the substrate in any combination.
  • An important element of the present invention is the impregnation of washcoat with the noble metal prior to mixing or layering with zeolite. This prevents the noble metal or its chemical precursors from interacting with the zeolite, which would negatively impact the performance of the catalyzed adsorber after aging.
  • the catalyzed adsorber (“A-brick”) of the present invention may be used alone or in conjunction with a pre-adsorber catalyst (“P-brick”) and/or a post-adsorber TWC (“C-brick”) to reduce hydrocarbon emissions during cold start conditions of a vehicle. It is preferred that the catalyzed adsorber be placed in a location where the heat emitted by the engine will not damage the zeolite and where the temperature window is suitable for the A-brick to work well, such as in the underfloor position.
  • the catalyzed adsorber of the present invention should be placed downstream of the P-brick; if used as part of a pre-adsorber catalyst/ adsorber of the present invention/ post-adsorber catalyst ("PAC") system, the catalyzed adsorber should be placed downstream of the P-brick and upstream of the C-brick.
  • the P-brick and C-brick may be any noble metal catalyst formulation which may be used as a TWC, such as, but not limited to, Pd-only, Rh-only, Pd/Rh, Pt/Rh, or Pt/Pd/Rh.
  • the P-brick preferably will be designed to provide rapid light-off and conversion of hydrocarbons.
  • the catalyzed adsorber should be sized so that the HC mass emissions during cold start conditions (i.e., before the P-brick lights off) are no more than 80 % of the desired emission or standard. If used as part of a PAC system, the catalyzed adsorber should be sized so that its volume is between about one quarter of to about twice the volume of the C-brick. The size of the C-brick is determined by methods known to those skilled in the art.
  • the substrate should be inert in the sense that it does not react with the coating or with the exhaust gas to which it is exposed during engine operation.
  • the substrate may be any of the shapes employed by those skilled in the art such as extrudates, spheres, beads, tablets, ceramic foams, and the like, but monoliths, either metallic or ceramic, are preferred. If a monolith is employed as the substrate, it should be sized and shaped so that it fits within whatever vessel is employed as a container and leaves no gaps between the vessel interior wall and the outside surface of the monolith which might result in blow-by of the exhaust gas past the monolith (i.e., bypassing of the catalyzed adsorber).
  • Ceramic monoliths if employed, should be provided with a mat-mount between the exterior surface of the monolith and the vessel wall, as is customary in the industry, to cushion vibration during engine operation and to prevent blow-by of the engine exhaust gas past the catalyst.
  • Metallic monoliths should be attached to the vessel wall, as is customary.
  • Monolith coating loads will depend on the engine and vehicle characteristics along with the zeolite adsorption capacity and noble metal activity, but should be coated with between about 0.061 gram of zeolite plus washcoat and about 0.366 grams of zeolite plus washcoat per cm 3 (between 1 and 6 gram/in 3 ) of substrate, preferably between 0.183 and 0.305 grams of zeolite plus washcoat per cm 3 (between 3 and 5 gram/in 3 ) of substrate.
  • zeolites may be advantageously used in the catalyzed adsorbers of the present invention.
  • choice of zeolite is dictated by the characteristics of the exhaust gas for which treatment is intended.
  • the zeolite by itself must be capable of retaining adsorption capacity for hydrocarbons when exposed to the same operating conditions as a conventional TWC located in an underfloor position for 160,000 km (100,000 miles).
  • the zeolite chosen must have the following characteristics: a) It must be capable of adsorbing hydrocarbon preferentially over water in the range of operating temperatures which it will encounter in its application; that is, from near ambient temperature to normal operating temperature, and when exposed to exhaust gas compositions, which generally include about 10 vol.% steam. b) It should have a high heat of adsorption for all the hydrocarbon molecules contained in the exhaust gas to be treated. The heat of adsorption should be at least about 4.5 kcal per gram-mol. of hydrocarbon adsorbed at 150°C, and preferably should be at least about 9.5 kcal per gram-mol. of hydrocarbon adsorbed at 150°C.
  • the zeolite chosen should be capable of experiencing little damage to its hydrocarbon storage and release properties from exposure to steam at temperatures up to about 850°C and should not be subject to crystal collapse at temperatures below 980°C.
  • the inorganic oxide binder chosen for the desired application suitable for application on a monolithic substrate, yielding a tough, adherent coating not subject to dusting, flaking, or spalling.
  • the preferred zeolite to be used in the manufacture of a catalyzed adsorber of the present invention is a faujisite having a Si/Al ratio between about 3.0 and about 10 and a Na content less than about 0.1 wt.%.
  • the low sodium content is achieved by ion exchanging the zeolite with ammonium cation or other metal cations by means well known in the art.
  • An example of the preferred zeolite is LZ-210 manufactured by UOP, Inc. which is described in U.S. Patent No. 4,711,770, incorporated herein by reference.
  • the inorganic oxide washcoat serves two functions simultaneously. First, the washcoat serves as a noble metal support. Second, when mixed with zeolite before application to a substrate, the washcoat improves the adhesion of the mixture as a whole.
  • the catalyzed adsorber must contain at least one inorganic oxide washcoat in addition to a noble metal and a zeolite.
  • Washcoats appropriate for combining or layering with the useful zeolites herein include inorganic oxides such as alumina, silica, alumina-silicates, titania, magnesia, zirconia, beryllia, and mixtures thereof, with alumina, titania, and zirconia being preferred. Small amounts, up to about 30 wt. % of a rare earth oxide, such as ceria, lanthana, zirconia, or mixtures thereof may be added to the washcoat to act as a promoter for the noble metal employed. In addition, a small amount of a stabilizer, such as barium oxide or barium sulfate may be added.
  • the washcoat may consist of a stabilized ceria, such as ceria-zirconia, entirely or in part.
  • the relative proportions of zeolite and inorganic oxide washcoat in the coating to be applied to the substrate may vary widely with the zeolite content ranging from about 40 to about 80 wt. %, preferably in the range of about 70 to about 80 wt. % for catalyzed adsorbers made by mixing the zeolite and washcoat together before application to the substrate and preferably in the range of about 40 to about 60 wt. % for catalyzed adsorbers made by layering the zeolite and the washcoat.
  • the noble metals of choice for this invention are palladium, platinum, rhodium, and mixtures and alloys of rhodium with either palladium or platinum, but any Group VIII metal, or mixture thereof, may be used.
  • the preferred noble metal is palladium due to its relatively low lightoff temperature (i.e., the catalyzed adsorber temperature that results in conversion of 50 % of the hydrocarbons contained in the exhaust gas) and relatively low cost.
  • the loading should be between about 1,765 and about 8,830 grams of Pd per m 3 (between about 50 and about
  • the loading is typically, but not limited to, between about 350 and about 2,470 grams of Pt per m 3 (between about 10 and about 70 grams of Pt per ft. 3 ) of monolithic substrate, and preferably between about 1,410 and about 2,470 grams of Pt per m 3 (between about 40 and about
  • the loading is typically, but not limited to, between about 175 and about 1,060 grams of Rh per m 3 (between about 5 and about 30 grams of Rh per ft. 3 ) of monolithic substrate, and preferably between about 530 and about 1,060 grams of Rh per m 3 (between about 15 and about 30 grams of Rh per ft. 3 ) of monolithic substrate.
  • catalyzed adsorbers As illustrated by FIG. 1 , the manner in which catalyzed adsorbers are made has a large impact on fresh and particularly aged performance.
  • An important consideration in preparing a catalyzed adsorber of the present invention is the requirement that impregnation or dispersion of the noble metal be predominately on the inorganic oxide washcoat material in the final catalyzed adsorber formulation. The most convenient method for accomplishing this is through the application of a suitable noble metal reagent directly to the washcoat in the absence of zeolite. Other methods that result in the noble metal being dispersed predominately on the washcoat and not on the zeolite are known and may be employed as a matter of choice.
  • Separating the noble metal from the zeolite helps eliminate interactions between highly acidic and reactive noble metal solutions and the zeolite material. This separation thus improves the durability of the zeolite as well as preserving noble metal dispersion, and it limits potential poisoning of active noble metal sites by the debris or mobile components from the zeolite during high temperature aging. This action also improves the durability of the noble metal thereby improving aged light-off and steady state conversion of hydrocarbons, carbon monoxide, and nitrogen oxides in the engine exhaust with which the catalyzed adsorber is contacted. Having the noble metal in close proximity to the zeolite, on the other hand, is important to prevent coking of the zeolite and to enhance combustion of hydrocarbon as it desorbs from the zeolite.
  • the preferred method of preparation calls for a wet impregnation of noble metal reagent on an inorganic oxide washcoat, sufficient to provide the desired loading of noble metal on the final catalyzed adsorber part.
  • Any noble metal reagent known to those skilled in the art may be employed. For instance, but not by way of limitation, a 7-8 wt. % aqueous solution of palladium nitrate is impregnated on the washcoat of a catalyzed adsorber employing Pd as the noble metal. A similar solution of platinum nitrate would be preferred for deposition of Pt.
  • the impregnated washcoat is dried for at least 24 hours to allow precious metal to fully chemisorb on the inorganic oxide washcoat and then calcined at a temperature equal to or less than 250° C for 2 hours.
  • the calcined, impregnated washcoat is then slurried in water and the pH is adjusted to between about 3.1 and about 3.9 by the addition of an organic acid, preferably acetic acid, and the mixture is milled for about
  • the coated substrate is dried and then calcined at a temperature of between about 400°C and about 550°C for 2 to 4 hours.
  • Another method of preparation calls for a wet impregnation of noble metal reagent on an inorganic oxide washcoat, sufficient to provide the desired loading of noble metal on the final catalyzed adsorber part. Any noble metal reagent known to those skilled in the art may be employed. As in the method above, a 7-8 wt% aqueous solution of palladium nitrate is impregnated on the washcoat of a catalyzed adsorber employing Pd as the noble metal, and a similar solution of platinum nitrate would be preferred for deposition of Pt.
  • the impregnated washcoat is dried for at least 24 hours and then calcined at a temperature equal to or less than 250° C for 2 hours.
  • the calcined, impregnated washcoat is then slurried in water and its pH is adjusted to between about 3.1 and about 3.9 by the addition of an organic acid, preferably acetic acid, and the suspension is milled for about one hour to provide good coatability.
  • An aqueous suspension of zeolite is prepared separately and then milled briefly, not more than 10 minutes, as required for good coating.
  • the zeolite suspension or the impregnated washcoat suspension is then applied to the substrate by any of the methods known to those skilled in the art, including immersion of the substrate in the suspension or spraying of the suspension onto the substrate.
  • the coated substrate is dried and then calcined at a temperature between 400°C and 550°C for 2 to 4 hours.
  • the process is repeated with the suspension which was not coated in the first coating step.
  • the layered and coated substrate is dried and then calcined at a temperature of between about 400°C and about 550°C for 2 to 4 hours. The process may be repeated again as many times as desired if a multi-layered washcoat is required.
  • EXAMPLE 1 This example describes the preparation of a catalyzed adsorber of the present invention.
  • An aqueous Pd nitrate solution was uniformly impregnated onto alumina powder in an amount such that the resulting impregnated powder contained 132.2 grams of Pd per kg of alumina.
  • the powder was dried for 24 hours in room temperature air, and then calcined for 2 hours at 250°C.
  • An aqueous suspension of the impregnated powder was then prepared and the pH was measured. If needed, sufficient acetic acid to lower the pH to about 3.5 was then added and then the suspension was milled to obtain a particle size between 7 and 15 microns.
  • EXAMPLE 2 This example describes the preparation of a catalyzed adsorber of the prior art.
  • An aqueous suspension of alumina powder was prepared and sufficient Pd nitrate was added to yield an aqueous suspension of alumina powder having 165.4 grams of Pd per kg of alumina.
  • the pH of the suspension was lowered to about 3.5 with acetic acid and then was milled to obtain a particle size between 7 and 15 microns.
  • a sufficient quantity of a milled suspension of UOP CSX-455 zeolite was added to the washcoat suspension to form a slurry in which the ratio of zeolite to washcoat was about 3:1.
  • the mixture was then stirred and coated onto monolith substrates as in Example 1.
  • PAC systems were made in the same manner as Example 1 , except the adsorber brick was made by the method of this example.
  • EXAMPLE 3 This example describes an alternative preparation of a catalyzed adsorber of the present invention.
  • An aqueous Pd nitrate solution was uniformly impregnated onto a mixture of alumina powder and Zr-rich mixed oxide ZrO 2 /CeO 2 powder such that the weight ratio of the mixed oxide and the alumina was 1.0, and such that the resulting impregnated powder contained 132.2 grams of Pd per kg of alumina/mixed oxide powder.
  • the powder was dried for 24 hours in room temperature air, and then calcined for 2 hours at 250°C.
  • An aqueous suspension of the impregnated powder was then prepared and the pH was measured.
  • the pH of the suspension was lowered to about 3.5 with acetic acid and then was milled to obtain a particle size between 7 and 15 microns.
  • a sufficient quantity of a milled suspension of UOP CSX-455 zeolite was added to the suspension of impregnated powder to form a slurry in which the ratio of zeolite to alumina was about 3:1.
  • the mixture was then stirred for 3 hours, following which it was coated onto ceramic monoliths, then the coated monoliths were dried and then calcined at a temperature of about 550°C for 2 hours.
  • One finished catalyzed adsorber was installed in a converter between a 7,060 g Pd per m 3 (200 g Pd per ft. 3 ) of substrate P-brick and a 5,300 g Pd/Rh in a 15/1 ratio per m 3 (150 g Pd/Rh per ft. 3 ) of substrate C- brick to form a PAC system suitable for performance evaluation.
  • This example describes an alternate preparation of a catalyzed adsorber of the present invention.
  • aqueous Pd nitrate solution was uniformly impregnated onto a mixture of alumina powder and stabilized Zr powder (83.6 wt. % ZrO 2 . 14.5 wt. % CeO, and 1.9 wt.% L ) such that the weight ratio of the stabilized Zr to the alumina was 2.0, and such that the resulting impregnated powder contained 132.2 grams of Pd per kg of alumina/mixed oxide powder.
  • the powder was dried for 24 hours in room temperature air, and then calcined for 2 hours at 250°C. An aqueous suspension of the impregnated powder was then prepared and the pH was measured.
  • Example 1 The pH of the suspension was lowered to about 3.5 with acetic acid and then was milled to obtain a particle size between 7 and 15 microns. The mixture was then stirred for three hours, following which it was coated onto the ceramic monoliths which were previously coated with zeolite. The coated monoliths were dried and then calcined at a temperature of about 550°C for 2 hours.
  • One finished catalyzed adsorber made by the method of this example was installed in a converter in a PAC configuration as in Example 1.
  • EXAMPLE 5 This example describes the preparation of a non-catalyzed adsorber sample.
  • EXAMPLE 6 This example describes an alternate preparation of a catalyzed adsorber of the present invention.
  • aqueous Pt nitrate solution was uniformly impregnated onto alumina powder in an amount such that the resulting impregnated powder contained 46.3 grams of Pt per kg of alumina.
  • the powder was dried for 24 hours in room temperature air, and then calcined for 2 hours at 250°C.
  • An aqueous suspension of the impregnated powder was then prepared and the pH was measured. The pH of the suspension was lowered to about 3.5 with acetic acid and then was milled to obtain a particle size between 7 and 15 microns.
  • aqueous Rh nitrate solution was uniformly impregnated onto a mixture of alumina powder and stabilized Zr powder such that the weight ratio of the stabilized Zr powder and the alumina was
  • the resulting impregnated powder contained 19.8 grams of Rh per kg of alumina/mixed oxide powder.
  • the powder was dried for 24 hours in room temperature air, and then calcined for 2 hours at 250°C.
  • An aqueous suspension of the impregnated powder was then prepared and the pH was measured.
  • the pH of the suspension was lowered to about 3.5 with acetic acid and then was milled to obtain a particle size between 7 and 15 microns.
  • a sufficient quantity of a milled suspension of UOP CSX-455 zeolite was added to the suspension of impregnated powder to form a slurry in which the ratio of zeolite to alumina was about 3 to 1.
  • the mixture was then stirred for three hours, following which it was coated onto ceramic monoliths.
  • the coated monoliths were dried and then calcined at a temperature of about 550 °C for 2 hours.
  • EXAMPLE 8 This example describes an alternate preparation of a catalyzed adsorber of the present invention.
  • An important element of the present invention is the impregnation of washcoat with the noble metal prior to mixing or layering with zeolite. This prevents the noble metal or its chemical precursors from interacting with the zeolite, which will negatively impact the light-off of the catalyzed adsorber after aging.
  • Catalyzed HC Adsorbers made using the methods of Examples 1 and 2 were aged in an oven for 2 hours at 800°C and then an additional 2 hours at 900°C in 10% water and nitrogen. The aged HC adsorbers were placed in converters, which were then installed one at a time on a 1995 Oldsmobile with a 3.8L engine, and the vehicle's emissions with each converter were evaluated using the EPA's Federal Test Procedure for Determination of Vehicle Emissions. Table 1 shows a comparison of the light-off performance on the vehicle of Examples 1 and 2. A shorter time to light-off or a lower light-off temperature will result in lower emissions.
  • Light-off Temperature is the temperature at which 50% of the incoming HC has been converted.
  • Catalyzed HC Adsorbers made using the methods of Examples 1, 2, 5, and 8 were combined with Pd-only front bricks and conventional TWC rear bricks in PAC systems, and then installed in
  • Example 1 was installed in an additional converter. This sample served to illustrate what could be converted in the absence of HC adsorption. All of the converters were aged using a high temperature aging cycle on an engine dynamometer to simulate 100,000 miles of use on a vehicle. (The accelerated aging constituted 50 hours on an engine dynamometer exposing the adsorber to bed temperatures up to 910°C.) The aged converters were installed one at a time on a 1995 Oldsmobile with a 3.8 L engine, and the vehicle's emissions with each converter were evaluated using the EPA's Federal Test Procedure for Determination of Vehicle Emissions.
  • test results are shown in Figure 1 as weighted accumulated HC emissions per mile over time, and indicate that the systems which used HC Adsorbers of the present invention were able to meet the California Low Emission Vehicle Standard for passenger cars of 0.04688 grams per km (0.075 grams per mile).
  • Results also indicate that the use of Pd precursor in Example 8 provides equivalent performance to Pd nitrate at a lower loading.
  • Figure 2 shows the rate of HC emission in grams HC per second provided by each converter over the first 100 seconds of the emission test.
  • This figure clearly shows the benefit of an adsorber during the first 40 seconds of vehicle operation, since the emissions from the adsorber containing converter systems during this time are significantly less than those from the non-adsorber system.
  • the HC emissions from the converters which contain adsorbers of the present invention are less than those which contain adsorbers which are of the prior art (Examples 2 and 5) during this same 40 second time period.
  • Table 2 shows the results for HC, CO and NO x tailpipe emissions for the PAC converters tested above. It shows that CO and NO x conversions over the three brick catalyzed adsorber systems of the present invention are equivalent to conventional three-way catalysts.
  • Catalyzed HC Adsorbers were made using the methods of Examples 1 , 6 and 7, and then a one inch diameter core was cut from each finished monolith part.
  • the cores were aged in a quartz tube furnace for 2 hours at 800°C and 2 hours at 900°C in an atmosphere of nitrogen and 10% water. After aging, the cores were tested in a laboratory reactor using a synthetic gas mixture which was representative of an automobile running at a stoichiometric air/fuel ratio.
  • the inlet temperature to the cores was ramped from 25°C to 350°C at 10°C/minute as the synthetic gas mixture was passed over the cores, and the exhaust from each core was analyzed. The percent conversion of HC and CO vs.
  • Catalyzed HC Adsorbers were made using the methods of Examples 1 and 5, then a one inch diameter core was cut from each finished monolith part. A conventional Pd catalyst was made separately and a core was also cut from it. The cores were tested in a laboratory reactor using a synthetic gas mixture which was representative of an automobile running at a rich air/fuel ratio. As the synthetic gas was passed over each core, the temperature was cycled between 50 and 250 °C at 7°C/minute in such a manner as to promote coking on the zeolite.
  • Figure 5 is a plot of the grams of HC adsorbed during each cycle of the test versus the cycle number.
  • Catalyzed HC Adsorbers made using the methods of Examples 1, 3, and 4 were combined with Pd/Rh front bricks in Pre-adsorber catalyst /Adsorber of the present invention (PA) systems, and then installed in 2.7 L converters. All of the converters were aged using a European severe temperature aging cycle on an engine dynamometer to simulate 160,000 km (100,000 miles) of use
  • PA Pre-adsorber catalyst /Adsorber of the present invention

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Abstract

L'invention concerne des adsorbeurs catalysés servant à traiter des gaz d'échappement de véhicules à moteur, qui comportent un substrat présentant une zéolithe et une couche d'imprégnation d'oxyde inorganique dispersées sur celui-ci. Ladite couche d'imprégnation est imprégnée à l'aide d'une quantité de métal noble efficace d'un point de vue catalytique, avant d'être mélangée à ladite zéolithe et éventuellement à un promoteur. Un procédé de fabrication de ces adsorbeurs catalysés comporte les étapes consistant à traiter un oxyde inorganique à l'aide d'un réactif à base de métal noble, mélanger le produit à la zéolithe, enrober un substrat, sécher et calciner celui-ci.
EP98934425A 1998-07-10 1998-07-10 Systeme ameliore d'adsorbeur catalyse pour traiter des gaz d'echappement de moteur a combustion interne et son procede de fabrication Withdrawn EP1102629A4 (fr)

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PCT/US1998/014370 WO2000059630A1 (fr) 1998-07-10 1998-07-10 Systeme ameliore d'adsorbeur catalyse pour traiter des gaz d'echappement de moteur a combustion interne et son procede de fabrication

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JP3859940B2 (ja) * 1999-08-06 2006-12-20 日産自動車株式会社 排気ガス浄化用触媒及びその製造方法
JP4642978B2 (ja) 2000-08-08 2011-03-02 株式会社キャタラー 排ガス浄化用触媒
EP2322267B1 (fr) * 2002-02-01 2017-08-23 Cataler Corporation Catalyseur pour purifier des gaz d'échappement
US8329607B2 (en) 2009-01-16 2012-12-11 Basf Corporation Layered diesel oxidation catalyst composites
JP5938819B2 (ja) 2011-10-06 2016-06-22 ジョンソン、マッセイ、パブリック、リミテッド、カンパニーＪｏｈｎｓｏｎ Ｍａｔｔｈｅｙ Ｐｕｂｌｉｃ Ｌｉｍｉｔｅｄ Ｃｏｍｐａｎｙ 排気ガス処理用酸化触媒
GB2497598A (en) * 2011-12-12 2013-06-19 Johnson Matthey Plc Catalysed substrate monolith and its use in an exhaust system for a lean burn ic engine
GB2497597A (en) 2011-12-12 2013-06-19 Johnson Matthey Plc A Catalysed Substrate Monolith with Two Wash-Coats
GB201200783D0 (en) 2011-12-12 2012-02-29 Johnson Matthey Plc Substrate monolith comprising SCR catalyst
GB201200784D0 (en) 2011-12-12 2012-02-29 Johnson Matthey Plc Exhaust system for a lean-burn internal combustion engine including SCR catalyst
GB201200781D0 (en) 2011-12-12 2012-02-29 Johnson Matthey Plc Exhaust system for a lean-burn ic engine comprising a pgm component and a scr catalyst
CN113244931B (zh) * 2020-02-11 2022-05-03 中国石油化工股份有限公司 催化剂以及含不饱和烃气体的催化氧化脱氧方法
CN115888755B (zh) * 2022-11-04 2024-09-20 中国空气动力研究与发展中心超高速空气动力研究所 用于rp-3航空煤油催化裂化和抗磨的催化剂涂层的制备及应用
CN117700107B (zh) * 2024-02-02 2024-04-12 淄博双特化工设备有限公司 一种耐酸耐碱性能优异的高品质瓷釉及其制备方法

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