EP2300156A1 - Oxidation catalyst for commercial vehicles comprising a diesel motor - Google Patents

Oxidation catalyst for commercial vehicles comprising a diesel motor

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Publication number
EP2300156A1
EP2300156A1 EP09765551A EP09765551A EP2300156A1 EP 2300156 A1 EP2300156 A1 EP 2300156A1 EP 09765551 A EP09765551 A EP 09765551A EP 09765551 A EP09765551 A EP 09765551A EP 2300156 A1 EP2300156 A1 EP 2300156A1
Authority
EP
European Patent Office
Prior art keywords
aluminum
platinum
catalyst
mixed oxide
oxidation catalyst
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Withdrawn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
EP09765551A
Other languages
German (de)
French (fr)
Inventor
Stéphanie FRANTZ
Frank-Walter Schuetze
Anke Woerz
Gerald Jeske
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 AG and Co KG
Original Assignee
Umicore AG and Co KG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Umicore AG and Co KG filed Critical Umicore AG and Co KG
Priority to EP09765551A priority Critical patent/EP2300156A1/en
Publication of EP2300156A1 publication Critical patent/EP2300156A1/en
Withdrawn legal-status Critical Current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
    • 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
    • B01J23/42—Platinum
    • 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
    • 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
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/12—Silica and 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • 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
    • B01D2251/2062—Ammonia
    • 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
    • B01D2255/20—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
    • B01D2255/00—Catalysts
    • B01D2255/30—Silica
    • 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
    • B01D2255/9207—Specific surface
    • 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
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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

  • Oxidation catalytic converter for commercial vehicles with diesel engine
  • the present invention relates to the exhaust gas purification of commercial vehicles with diesel engine, especially an especially suitable for this application field oxidation catalyst.
  • Diesel oxidation catalysts especially Pt / alumina based oxidation catalysts, are well known in the art. They are used to oxidise the harmful gases carbon monoxide CO and hydrocarbons HC contained in the exhaust gas of diesel engines with the help of the oxygen contained in the diesel exhaust in large quantities to the innocuous compounds carbon dioxide CO 2 and water vapor.
  • the exhaust gas from diesel engines contains nitrogen oxides NO x and particles resulting from the incomplete combustion of diesel fuel and lubricating oil in the cylinder at too low temperatures and consisting predominantly of soot residues and possibly organic agglomerates.
  • oxidation catalyst and particulate filter according to EP-BO 341 832 in principle, if an open particulate filter substrate is used.
  • the particle filter regeneration is then carried out in situ by reacting the deposited in the filter fabric soot particles with NO 2 , which is generated over the upstream oxidation catalyst.
  • oxidation catalysts containing platinum supported on alumina are used.
  • EP-A1 147 801 describes the suitability of an aluminum oxide stabilized with about 5% by weight of silica as support material for platinum in an NO 2 -producing oxidation catalyst.
  • Oxidation catalysts according to the prior art which contain homogeneously distributed platinum on one or more carrier oxides, for example aluminum oxide, aluminum-silicon mixed oxide, cerium oxide or zeolite, have good oxidation capacities for HC, CO and NO and are not infrequently characterized by outstanding properties thermal aging stabilities. However, they are susceptible to poisoning by sulfur oxides, so that in their long-term use, a thermal desulfation is inevitable. Therefore, they can not be used in commercial vehicles with the exhaust profile described with satisfactory results. It is an object of the present invention to provide an oxidation catalytic converter for diesel engine-driven commercial vehicles with a particle filter, which is distinguished by high NO oxidation rates even at low exhaust gas temperatures, good long-term stability and excellent poisoning resistance to sulfur compounds.
  • carrier oxides for example aluminum oxide, aluminum-silicon mixed oxide, cerium oxide or zeolite
  • the inventors have now surprisingly found that the defined distribution of the total amount of platinum used in the catalyst on the carrier oxide materials active alumina and aluminum-silicon mixed oxide leads to an advantageous resolution of the conflict between the NO oxidation performance and the poisoning vulnerability to sulfur oxides.
  • active alumina denotes the following finely divided materials: active alumina, fumed alumina, ⁇ -alumina, ⁇ -alumina, ⁇ -alumina, and in particular ⁇ -alumina, diaspore and boehmite
  • active alumina includes however, no rare earth or other oxides doped or stabilized aluminas, and no homogeneous mixed oxides or solid solutions of alumina with other oxides
  • aluminum-silicon mixed oxide is the following finely divided
  • Carrier oxides summarized: aluminosilicates (tectosilicates), wherein tetravalent silicon atoms in a SiO 2 network structure by trivalent aluminum atoms be replaced except zeolites; Neso, soro, cyclo, ino and phyllosilicates containing tetrahedral [SiO 4 ] units as basic building units with aluminum ions as countercations; Aluminum silicates in the sense of silicon dioxide-doped or stabilized aluminum oxide, which may contain octahedral [AlO 6 ] units in addition to tetrahedral [SiO 4 ] units and optionally [AlO 4 ] units as basic building blocks; homogeneous mixed oxides and solid solutions of alumina and silica; Mixtures of the abovementioned compounds.
  • aluminosilicates tectosilicates
  • the object underlying the invention can be achieved by an oxidation catalyst containing a support body and a catalytically active coating of platinum, active alumina and aluminum-silicon mixed oxide, which is characterized in that alumina and aluminum-silicon mixed oxide means Catalytically activated platinum, wherein 55 to 95 wt .-% of the present in the catalyst amount of platinum on the active alumina, and the remaining amount of platinum on the aluminum-silicon mixed oxide is supported.
  • aluminum oxide and aluminum-silicon mixed oxide are present in a ratio of 1: 1.5 to 1: 4 with respect to one another.
  • aluminum oxide and aluminum-silicon mixed oxide are present in the catalyst according to the invention in a ratio of more than 1: 1, 5 to 1: 4 to one another.
  • the type of platinum distribution over the two oxidic support materials predominantly influences the NO oxidation characteristic, while the ratio of alumina to aluminum-silicon mixed oxide predominantly influences the poisoning resistance to sulfur compounds. This can be used to optimally adapt the composition of the oxidation catalyst to the respective target application within the range-relevant range limits.
  • the ratio of alumina to aluminum-silicon mixed oxide is preferably in the range 1: 2 to 1: 4.
  • proportions of aluminum oxide to aluminum-silicon mixed oxide of more than 1: 1.5 up to 1: 2.5 are to support the NO oxidation characteristic and more preferably ratios of more than 1: 1.5 to 1: 2.
  • the local concentration of platinum on alumina is at least twice as high as the local concentration of platinum on the aluminum-silicon mixed oxide.
  • the platinum concentration on alumina based on the total weight of platinum and alumina applied thereto, is two to six times higher than the concentration of aluminum-silicon mixed oxide platinum on the alumina-silicon composite oxide, based on the total weight of itself and the aluminum-silicon mixed oxide.
  • Influence on the poisoning resistance of the oxidation catalyst according to the invention also has the content of silicon dioxide SiO 2 in the aluminum-silicon mixed oxide.
  • high surface area aluminum-silicon mixed oxides are used which contain 5 to 40 wt .-% SiO 2 based on the total weight of the aluminum-silicon mixed oxide and have a specific surface area of more than 60 m 2 / g (BET).
  • BET specific surface area of more than 60 m 2 / g
  • oxidation catalyst In addition to aluminum oxide and aluminum-silicon mixed oxide, no additional oxidic support materials are necessary in the catalyst according to the invention in order to achieve the properties fulfilling the object. In particular, additional basic oxides are not desirable in the catalyst according to the invention, since these significantly reduce the poisoning resistance to sulfur.
  • Preferred versions Structures of the oxidation catalyst are free of rare earth oxides, in particular free of cerium oxide, lanthanum oxide, praseodymium oxide and neodymium oxide.
  • preferred embodiments of the catalyst contain no zeolite compounds and zeolite-like materials with a lower channel width of more than 4 ⁇ ngström ( ⁇ ), since such materials incorporate hydrocarbons and thus especially at temperatures below 200 ° C by redox reactions between these embedded hydrocarbons and NO or NO 2 can undesirably reduce the NO 2 formation rates.
  • the platinum content of the oxidation catalyst according to the invention is preferably between 0.07 and 7 grams per liter [g / L], based on the volume of the catalyst support body.
  • the platinum content is between 0.15 and 1.5 g / L, more preferably between 0.17 and 0.7 g / L, based on the volume of the catalyst support body.
  • Other noble metals, in particular palladium and rhodium may possibly have an adverse effect on the NO oxidation behavior and / or the poisoning resistance of the catalyst. Iridium, ruthenium and gold can also adversely affect the performance characteristics of the catalyst.
  • the additional use of palladium and / or rhodium in particular would cause undesirable additional costs.
  • the catalyst according to the invention therefore contains, in addition to platinum, no further noble metal, in particular not palladium and rhodium, in its preferred embodiments. It preferably also contains no noble metal selected from the group consisting of iridium, ruthenium and gold.
  • Platinum can be introduced into the catalyst by customary methods described in the prior art by impregnation, by sorption, by precipitation and by means of incipient wetness methods known from the literature.
  • the coating suspension prepared in this manner in which platinum is prefixed to alumina and aluminum-silicon mixed oxide in the quantitative proportions according to the invention is ground and is ground in a defined manner by sorption and / or precipitation onto the carrier oxides in conventional dipping, suction and pumping on a ceramic or metallic honeycomb body or, if advantageous, applied to a metallic or ceramic filter body.
  • the resulting coated substrate is calcined to complete the catalyst of the invention and optionally thermally reduced in atmosphere containing Formiergas.
  • the resulting catalyst is suitable for the treatment of diesel exhaust gases, wherein the treatment of the exhaust gas takes place by passing the exhaust gas over the oxidation catalyst according to the invention.
  • the catalyst according to the invention is suitable for the treatment of diesel exhaust gases when the temperature of the exhaust gas at the inlet of the oxidation catalyst is always below 500 ° C, as is not untypical for commercial vehicles such as city buses, waste disposal vehicles and construction and working machines.
  • the catalyst according to the invention is arranged in an exhaust gas purification system for vehicles with diesel engine upstream of a particle filter, wherein the particulate filter is preferably selected from the group of metallic and ceramic fürflußfiltersubstrate, Sintermetallf ⁇ lter emotions, the ceramic and metallic knit and fabric structures.
  • the catalyst according to the invention may be arranged in an exhaust gas purification system for vehicles with a diesel engine upstream of an SCR catalytic converter.
  • SCR selective catalytic reduction
  • a reducing agent metered from an external source into the exhaust gas line or an ammonia-releasing compound such as urea or ammonium carbamate
  • the ammonia generated in situ from the precursor compound reacts with the nitrogen oxides from the exhaust gas in the SCR catalyst in a comproportionation reaction to nitrogen and water
  • the denitrification rates over the SCR catalyst are At exhaust gas temperatures below 250 ° C., as expected in the underfloor area of commercial vehicle applications, it is always particularly good when an NO 2 / NO x ratio of 0.3 to 0.7, above an oxidation catalytic converter arranged upstream of the SCR catalytic converter, Favor gt is set from 0.4 to 0.6.
  • Figure 1 Conversion of NO to NO 2 on a catalyst according to the invention Kl and on a catalyst according to the prior art VKL after a synthetic aging in SO 2 -containing exhaust gas
  • FIG. 2 Conversion of NO to NO 2 on a catalyst according to the invention in the freshly prepared state (Kl ”) and after a synthetic aging in SO 2 -containing exhaust gas (Kl)
  • FIG. 3 Conversion of NO to NO 2 on a catalyst according to the invention Kl 'and on a catalyst according to the prior art VKl' after a synthetic aging in a hydrothermal atmosphere
  • a catalyst according to the invention with an aluminum oxide: aluminum-silicon mixed oxide ratio of 1: 2 was prepared.
  • the alumina was first suspended in water. Then, half of the amount of platinum to be introduced into the catalyst was added to the suspension by injecting a conventional water-soluble platinum precursor compound. After addition of the aluminum-silicon mixed oxide (specific surface: -212 m7g (BET), 10 wt% SiO 2 ) to the suspension, the remaining amount of platinum was injected.
  • the coating suspension was applied in a dipping method according to the prior art to a cordierite honeycomb body with 62 cells per cm 2 and a wall thickness of 0.17 mm. The coated honeycomb body was dried and calcined for 4 hours at 350 ° C.
  • the finished catalyst thus prepared contained 0.883 g / L of platinum based on the volume of the honeycomb body. He was taken for research on catalytic activity and aging resistance three cylindrical cores with a diameter of 25.4 mm and a length of 76.2 mm, which are hereinafter referred to as Kl, Kl 'and Kl ".
  • a commercially available diesel oxidation catalyst with the same platinum content (0.883 g / L platinum, based on the volume of the honeycomb body) was used, in which the total amount of total supported on an aluminum-silicon mixed oxide with a SiC " 2 content of 5 wt
  • This commercial diesel oxidation catalyst was also present as a coated cordierite honeycomb with 62 cells per cm 2 and a wall thickness of 0.17 mm.
  • a second catalyst according to the invention was prepared, which differed from the catalyst of Example 1 only in that it contained only 0.706 g / L of platinum, based on the volume of the honeycomb body.
  • this catalyst was taken from a cylindrical core with a diameter of 25.4 mm and a length of 76.2 mm, which is hereinafter referred to as K2. Comparative Example 2:
  • this comparative catalyst was taken from a cylindrical core with a diameter of 25.4 mm and a length of 76.2 mm, which is hereinafter referred to as VK2.
  • the cores Kl, VK1, K2 and VK2 were heated for 48 hours at 35O 0 C in an atmosphere of 10 vol .-% CO 2 , 10 vol .-% O 2 , 10 vol .-% H 2 O, 85 Vppm SO 2 and 270 Vppm NO were treated in nitrogen (flowed through, 15,000 h -1 ), thereby simulating a typical loss of activity in SO 2 -containing combustion exhaust gas.
  • the cores Kl 'and VKl' were treated for 16 hours at 700 ° C in an atmosphere containing 10 vol.% H 2 O and 10 vol.% O 2 in nitrogen. As a result, the loss of activity of a catalyst is adjusted over a long-term use in a hydrothermal exhaust gas.
  • Figure 1 shows the NO conversion to NO 2 of the catalyst of the invention Kl from Example 1 and the comparative catalyst according to the prior art VKL from Comparative Example 1 after synthetic aging in a SO 2 -containing exhaust gas. Between 200 and 400 ° C., the catalyst according to the invention shows markedly better NO oxidation rates than the catalyst according to the prior art.
  • Example 2 To verify the long-term stability of the inventive catalyst from Example 1, the NO oxidation activity of Kl 'and the comparative catalyst according to the prior art VKl' from Comparative Example 1 was also investigated after synthetic aging under hydrothermal conditions.
  • FIG. 3 shows the result. It is clear that the catalyst according to the invention also shows an improved long-term stability of NO oxidation activity in the temperature range between 200 and 400 ° C.
  • Figure 4 shows how large the influence of the ratio of carrier oxides on the effective resolution of the conflict between NO oxidation ability and SO 2 - poisoning resistance.
  • the NO oxidation activity after synthetic aging in SO 2 -containing waste gas of a catalyst according to the invention K 2 from Example 2 with a ratio of aluminum oxide: aluminum-silicon mixed oxide of 1: 2 of the comparative catalyst VK 2 from Comparative Example 2 with a quantitative ratio of alumina: aluminum Silicon mixed oxide of 2.5: 1 compared. It can be clearly seen that an excess of alumina leads to dramatic losses of NO oxidation ability after loading of the comparative catalyst with alumina excess, while the catalyst according to the invention, the load under SO 2 -containing atmosphere with respect to its NO oxidation ability is almost unscathed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Environmental & Geological Engineering (AREA)
  • Biomedical Technology (AREA)
  • Combustion & Propulsion (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

The invention relates to an oxidation catalyst for cleaning the exhaust gases of commercial vehicles comprising a diesel motor, said catalyst containing a support body and a catalytically active coating consisting of platinum, active aluminium oxide and aluminium-silicon mixed oxide. Both oxidic support materials, aluminium oxide and aluminium-silicon mixed oxide, are catalytically activated using platinum, whereby the majority of the platinum is present on the aluminium oxide. The oxidation catalyst is characterised by excellent NO oxidation rates and a high resistance to poisoning in relation to sulphur compounds.

Description

Oxidationskatalysator für Nutzfahrzeuge mit Dieselmotor Oxidation catalytic converter for commercial vehicles with diesel engine
Beschreibungdescription
Die vorliegende Erfindung betrifft die Abgasreinigung von Nutzfahrzeugen mit Dieselmotor, speziell einen für dieses Applikationsfeld besonders gut geeigneten Oxidations- katalysator.The present invention relates to the exhaust gas purification of commercial vehicles with diesel engine, especially an especially suitable for this application field oxidation catalyst.
Dieseloxidationskatalysatoren, insbesondere Pt/Alumina-basierte Oxidationskatalysato- ren, sind im Stand der Technik gut bekannt. Sie werden verwendet, um die im Abgas von Dieselmotoren enthaltenen Schadgase Kohlenmonoxid CO und Kohlenwasserstoffe HC mit Hilfe des im Dieselabgas in größerer Menge enthaltenen Sauerstoffs zu den unschädlichen Verbindungen Kohlendioxid CO2 und Wasserdampf zu oxidieren. Neben Kohlenmonoxid CO und den Kohlenwasserstoffen HC enthält das Abgas von Dieselmotoren Stickoxide NOx und Partikel, die aus der unvollständigen Verbrennung von Dieselkraftstoff und Schmieröl im Zylinder bei zu niedrigen Temperaturen resultieren und überwiegend aus Rußrückständen und gegebenenfalls organischen Agglomeraten bestehen.Diesel oxidation catalysts, especially Pt / alumina based oxidation catalysts, are well known in the art. They are used to oxidise the harmful gases carbon monoxide CO and hydrocarbons HC contained in the exhaust gas of diesel engines with the help of the oxygen contained in the diesel exhaust in large quantities to the innocuous compounds carbon dioxide CO 2 and water vapor. In addition to carbon monoxide CO and the hydrocarbons HC, the exhaust gas from diesel engines contains nitrogen oxides NO x and particles resulting from the incomplete combustion of diesel fuel and lubricating oil in the cylinder at too low temperatures and consisting predominantly of soot residues and possibly organic agglomerates.
Nutzfahrzeuge wie beispielsweise Stadtbusse, Abfallentsorgungsflotten, Bau- oder Landmaschinen werden oft in einem grundsätzlich anderen Fahrbetrieb genutzt als Diesel-Pkw. Daraus resultiert ein anderes Abgasprofil mit erheblich niedrigeren Abgastemperaturen und anderen Abgaszusammensetzungen. So ist im Vergleich zu Diesel-Pkw-Abgasen der Stickoxid-Gehalt deutlich geringer, der Anteil an Partikelemissionen aber unter Umständen merklich erhöht. Wie auch das Abgas von Diesel-Pkw enthält das Abgas der Nutzfahrzeuge ferner Spuren von Schwefeloxiden SOx, die aus der Verbrennung schwefelhaltiger Organyle im Dieselkraftstoff herrühren. Schwefeloxide wirken als Katalysatorgift, da sie an den aktiven Platinzentren chemisorbiert werden und diese somit für die gewünschten katalytischen Umsetzungen blockieren. Im Diesel-Pkw werden solche Vergiftungen von Zeit zu Zeit durch Anfetrung und Erhöhung der Abgastemperaturen auf mehr als 400°C und daraus resultierende thermische Desorption entfernt. In einem ähnlichen Verfahren wird im Diesel-Pkw auch gelegentlich eine aktive Regeneration des Partikelfilters vorgenom- men, bei dem im Filter abgelagerte Rußpartikel mit dem im Abgas enthaltenen Sauerstoff katalytisch verbrannt werden. Dies gilt, obgleich dieses Verfahren auch für andere Ausfuhrungsformen verwendet wird, insbesondere dann, wenn das Partikelfϊlter ein Wandflußpartikelfilter ist.Commercial vehicles such as city buses, waste disposal fleets, construction or agricultural machinery are often used in a fundamentally different driving operation than diesel cars. This results in a different exhaust profile with significantly lower exhaust gas temperatures and other exhaust gas compositions. Thus, the nitrogen oxide content is significantly lower compared to diesel car exhaust gases, but the proportion of particulate emissions may be significantly increased. Like exhaust from diesel cars, commercial vehicle exhaust also contains traces of sulfur oxides SO x resulting from the combustion of sulfur-containing organyls in diesel fuel. Sulfur oxides act as a catalyst poison because they are chemisorbed at the active platinum centers and thus block them for the desired catalytic reactions. In the diesel car, such poisonings are removed from time to time by adding and increasing the exhaust gas temperatures to more than 400 ° C and resulting thermal desorption. In a similar process, occasional active regeneration of the particulate filter is also carried out in the diesel passenger car. men, in which deposited in the filter soot particles are catalytically burned with the oxygen contained in the exhaust gas. This is true, although this method is also used for other embodiments, especially if the Partikelfϊlter is a Wandflußpartikelfilter.
Bei vielen Nutzfahrzeuganwendungen verbieten sich aktive thermische Desulfati- sierungen und aktive Partikelfilterregenerationen aufgrund der zu geringen Abgastemperaturen. Sie lassen sich aufgrund des für Nutzfahrzeuge typischen Fahrprofils meist nicht ohne zusätzliche Heizmaßnahmen applizieren, was zu einer nicht akzeptablen Erhöhung des Kraftstoffverbrauchs führt. Abgasreinigungsanlagen für Nutzfahrzeuge müssen daher mit schwefelvergiftungsresistenten Abgasreinigungsaggregaten ausgerüstet sein, die effektiv CO-, HC- und Partikelemissionen entfernen, ohne daß aktive Partikelfilterregenerationen oder spezielle Desulfatisierungsmaßnahmen zum Erhalt der Funktionalitäten nötig sind.In many commercial vehicle applications, active thermal desulphation and active particulate filter regeneration are prohibited due to low exhaust gas temperatures. Due to the typical driving profile for commercial vehicles, they can not usually be applied without additional heating measures, which leads to an unacceptable increase in fuel consumption. Exhaust gas purification systems for commercial vehicles must therefore be equipped with sulfur poisoning-resistant exhaust gas purification units which effectively remove CO, HC and particulate emissions without requiring active particulate filter regeneration or special desulfating measures to maintain functionality.
Hierfür bietet sich eine Kombination aus Oxidationskatalysator und Partikelfilter gemäß der EP-B-O 341 832 grundsätzlich an, sofern ein offenes Partikelfiltersubstrat verwendet wird. Die Partikelfilterregeneration erfolgt dann in situ durch Umsetzung der im Filtergewebe abgeschiedenen Rußpartikel mit NO2, das über dem vorgeschalteten Oxidationskatalysator erzeugt wird. Dabei werden typischerweise Oxidationskatalysatoren verwendet, die Platin getragen auf Aluminiumoxid enthalten. In der EP-A-I 147 801 wird außerdem die Eignung eines mit etwa 5 Gew.-% Siliziumdioxid stabilisierten Aluminiumoxids als Trägermaterial für Platin in einem NO2-erzeugenden Oxidationskatalysator beschrieben.For this purpose, a combination of oxidation catalyst and particulate filter according to EP-BO 341 832 in principle, if an open particulate filter substrate is used. The particle filter regeneration is then carried out in situ by reacting the deposited in the filter fabric soot particles with NO 2 , which is generated over the upstream oxidation catalyst. Typically, oxidation catalysts containing platinum supported on alumina are used. In addition, EP-A1 147 801 describes the suitability of an aluminum oxide stabilized with about 5% by weight of silica as support material for platinum in an NO 2 -producing oxidation catalyst.
Oxidationskatalysatoren nach dem Stand der Technik, die homogen verteiltes Platin auf einem oder mehreren Trägeroxiden, beispielsweise Aluminiumoxid, Aluminium-Sili- zium-Mischoxid, Ceroxid oder Zeolith enthalten, weisen gute Oxidationsleistungen für HC, CO und NO auf und zeichnen sich nicht selten durch hervorragende thermische Alterungsstabilitäten aus. Allerdings sind sie gegenüber der Vergiftung durch Schwefeloxide anfällig, sodaß bei ihrem Langzeiteinsatz eine thermische Desulfatisierung unumgänglich ist. Daher können sie in Nutzfahrzeugen mit dem beschriebenen Abgas- profil nicht mit zufriedenstellendem Ergebnis eingesetzt werden. Es ist Aufgabe der vorliegenden Erfindung, einen Oxidationskatalysator für mit Dieselmotor betriebene Nutzfahrzeuge mit Partikelfilter zur Verfügung zu stellen, der sich durch hohe NO-Oxidationsraten auch bei niedrigen Abgastemperaturen, durch gute Langzeitstabilität und durch eine exzellente Vergiftungsresistenz gegenüber Schwefel- Verbindungen auszeichnet.Oxidation catalysts according to the prior art which contain homogeneously distributed platinum on one or more carrier oxides, for example aluminum oxide, aluminum-silicon mixed oxide, cerium oxide or zeolite, have good oxidation capacities for HC, CO and NO and are not infrequently characterized by outstanding properties thermal aging stabilities. However, they are susceptible to poisoning by sulfur oxides, so that in their long-term use, a thermal desulfation is inevitable. Therefore, they can not be used in commercial vehicles with the exhaust profile described with satisfactory results. It is an object of the present invention to provide an oxidation catalytic converter for diesel engine-driven commercial vehicles with a particle filter, which is distinguished by high NO oxidation rates even at low exhaust gas temperatures, good long-term stability and excellent poisoning resistance to sulfur compounds.
Zwischen der Fähigkeit, NO zu NO2 zu oxidieren und der Vergiftungsresistenz gegenüber Schwefeloxiden besteht ein Zielkonflikt, dessen Ursache im aciden Charakter von Stickoxiden (NOx) und Schwefeloxiden (SOx) liegt. Katalysatoren, die gute NO- Konvertierungsraten zeigen, enthalten meist leicht basische Trägeroxide, auf denen auch Schwefeloxide gut chemisorbieren. Demzufolge zeigt beispielsweise Platin geträgert allein auf Aluminiumoxid und/oder Selten-Erd-stabilisiertem Aluminiumoxid eine hohe Affinität zu SOx und dementsprechend eine hohe Vergiftungsanfälligkeit. Katalysatoren, in denen Platin auf einem leicht sauren Trägeroxid, beispielsweise auf Siliziumdioxid oder Aluminium-Silizium-Mischoxid homogen verteilt ist, zeigt unter Langzeitalterungsbedingungen dagegen meist gute SOx- Vergiftungsresistenz bei jedoch nur mäßigen NO-Konvertierungsraten.There is a conflict of objectives between the ability to oxidise NO to NO 2 and the poisoning resistance to sulfur oxides, the cause of which lies in the acidic nature of nitrogen oxides (NO x ) and sulfur oxides (SO x ). Catalysts which show good NO conversion rates usually contain slightly basic carrier oxides, on which sulfur oxides also chemisorbed well. Accordingly, for example, platinum supported alone on alumina and / or rare earth stabilized alumina shows a high affinity for SO x and, accordingly, a high susceptibility to poisoning. Catalysts in which platinum is homogeneously distributed on a slightly acidic carrier oxide, for example on silicon dioxide or aluminum-silicon mixed oxide, on the other hand shows mostly good SO x poisoning resistance under long-term aging conditions but only moderate NO conversion rates.
Die Erfinder haben nun überraschend festgestellt, daß die definierte Verteilung der im Katalysator verwendeten Platingesamtmenge auf die Trägeroxidmaterialien aktives Aluminiumoxid und Aluminium- Silizium-Mischoxid zu einer vorteilhaften Auflösung des Zielkonfliktes zwischen der NO-Oxidationsleistung und der Vergiftungsanfälligkeit durch Schwefeloxide führt.The inventors have now surprisingly found that the defined distribution of the total amount of platinum used in the catalyst on the carrier oxide materials active alumina and aluminum-silicon mixed oxide leads to an advantageous resolution of the conflict between the NO oxidation performance and the poisoning vulnerability to sulfur oxides.
Dabei werden mit dem Begriff „aktives Aluminiumoxid" die folgenden feinteiligen Materialien bezeichnet: aktive Tonerde, pyrogenes Aluminiumoxid, α-Aluminiumoxid, δ-Aluminiumoxid, Θ-Aluminiumoxid, und insbesondere γ-Aluminiumoxid, Diaspor und Böhmit. Der Begriff „aktives Aluminiumoxid" umfasst jedoch keine mit Seltenen Erden oder anderen Oxiden dotierten oder stabilisierten Aluminiumoxide, sowie keine homogenen Mischoxide oder festen Lösungen von Aluminiumoxid mit anderen OxidenThe term "active alumina" denotes the following finely divided materials: active alumina, fumed alumina, α-alumina, δ-alumina, Θ-alumina, and in particular γ-alumina, diaspore and boehmite The term "active alumina" includes however, no rare earth or other oxides doped or stabilized aluminas, and no homogeneous mixed oxides or solid solutions of alumina with other oxides
Unter dem Begriff „Aluminium-Silizium-Mischoxid" werden die folgenden feinteiligenThe term "aluminum-silicon mixed oxide" is the following finely divided
Trägeroxide zusammengefasst: Aluminosilikate (Tectosilikate), worin vierwertige Siliziumatone in einer SiO2-Raumnetzstruktur durch dreiwertige Aluminiumatome ersetzt werden ausgenommen Zeolithe; Neso-, Soro-, Cyclo-, Ino- und Phyllosilikate, die tetraedrische [SiO4] -Einheiten als Grundbaueinheiten enthalten, mit Aluminiumionen als Gegenkationen; Aluminiumsilikate im Sinne von mit Siliziumdioxid dotiertem oder stabilisiertem Aluminiumoxid, welche oktaedrische [AlO6] -Einheiten neben tetra- edrischen [SiO4] -Einheiten sowie gegebenenfalls [AlO4] -Einheiten als Grundbaueinheiten enthalten können; homogene Mischoxide und feste Lösungen von Aluminiumoxid und Siliziumdioxid; Mischungen der vorstehend genannten Verbindungen.Carrier oxides summarized: aluminosilicates (tectosilicates), wherein tetravalent silicon atoms in a SiO 2 network structure by trivalent aluminum atoms be replaced except zeolites; Neso, soro, cyclo, ino and phyllosilicates containing tetrahedral [SiO 4 ] units as basic building units with aluminum ions as countercations; Aluminum silicates in the sense of silicon dioxide-doped or stabilized aluminum oxide, which may contain octahedral [AlO 6 ] units in addition to tetrahedral [SiO 4 ] units and optionally [AlO 4 ] units as basic building blocks; homogeneous mixed oxides and solid solutions of alumina and silica; Mixtures of the abovementioned compounds.
Mit Hilfe dieser Erkenntnis kann die der Erfindung zugrunde liegende Aufgabe gelöst werden durch einen Oxidationskatalysator enthaltend einen Tragkörper und eine katalytisch aktive Beschichtung aus Platin, aktivem Aluminiumoxid und Aluminium- Silizium-Mischoxid, der dadurch gekennzeichnet ist, daß Aluminiumoxid und Aluminium-Silizium-Mischoxid mittels Platin katalytisch aktiviert sind, wobei 55 bis 95 Gew.-% der im Katalysator vorhandenen Platinmenge auf dem aktiven Aluminiumoxid vorliegen, und die verbleibende Platinmenge auf dem Aluminium- Silizium-Mischoxid geträgert ist. Im erfindungsgemäßen Katalysator liegen Aluminiumoxid und Aluminium-Silizium-Mischoxid in einem Mengenverhältnis von 1:1,5 bis 1 :4 zueinander vor.With the help of this finding, the object underlying the invention can be achieved by an oxidation catalyst containing a support body and a catalytically active coating of platinum, active alumina and aluminum-silicon mixed oxide, which is characterized in that alumina and aluminum-silicon mixed oxide means Catalytically activated platinum, wherein 55 to 95 wt .-% of the present in the catalyst amount of platinum on the active alumina, and the remaining amount of platinum on the aluminum-silicon mixed oxide is supported. In the catalyst according to the invention, aluminum oxide and aluminum-silicon mixed oxide are present in a ratio of 1: 1.5 to 1: 4 with respect to one another.
Bevorzugt liegen Aluminiumoxid und Aluminium-Silizium-Mischoxid im erfindungsgemäßen Katalysator in einem Mengenverhältnis von mehr als 1 :1 ,5 bis zu 1 :4 zuein- ander vor. Dabei beeinflußt nach Erkenntnissen der Erfinder die Art der Platinverteilung über die beiden oxidischen Trägermaterialien überwiegend die NO-Oxidations- charakteristik, während das Mengenverhältnis von Aluminiumoxid zu Aluminium- Silizium-Mischoxid überwiegend Einfluß auf die Vergiftungsresistenz gegenüber Schwefelverbindungen hat. Dies kann genutzt werden, um die Zusammensetzung des Oxidationskatalysators innerhalb der erfϊndungswesentlichen Bereichsgrenzen optimal auf die jeweilige Zielapplikation anzupassen. So liegen in einem erfindungsgemäßen Oxidationskatalysator für eine Applikation, in der beispielsweise im Hinblick auf einen passiv zu regenerierenden Dieselpartikelfilter möglichst viel NO2 zur Verfügung gestellt werden muß, bevorzugt 60 bis 80 Gew.-% der im Katalysator vorhandenen Platinmenge auf dem aktiven Aluminiumoxid vor, besonders bevorzugt 70 bis 75 Gew.-%. Weist das zu reinigende Abgas darüber hinaus hohe SOx-Gehalte auf, sodaß eine besonders hohe Vergiftungsresistenz gefordert ist, so liegt das Verhältnis von Aluminiumoxid zu Aluminium-Silizium-Mischoxid bevorzugt im Bereich 1:2 bis zu 1 :4. Werden - beispielsweise bei gewährleistetem Einsatz guter Kraftstoffqualitäten - geringere SOx- Gehalte im Abgas erwartet, so sind zur Unterstützung der NO-Oxidationscharakteristik Mengenverhältnisse von Aluminiumoxid zu Aluminium-Silizium-Mischoxid von mehr als 1:1,5 bis zu 1:2,5 bevorzugt und Mengenverhältnisse von mehr als 1:1,5 bis zu 1 :2 besonders bevorzugt.Preferably, aluminum oxide and aluminum-silicon mixed oxide are present in the catalyst according to the invention in a ratio of more than 1: 1, 5 to 1: 4 to one another. According to findings of the inventors, the type of platinum distribution over the two oxidic support materials predominantly influences the NO oxidation characteristic, while the ratio of alumina to aluminum-silicon mixed oxide predominantly influences the poisoning resistance to sulfur compounds. This can be used to optimally adapt the composition of the oxidation catalyst to the respective target application within the range-relevant range limits. Thus, in an oxidation catalyst according to the invention for an application in which, for example, with respect to a passively regenerated diesel particulate filter as much NO 2 must be provided, preferably 60 to 80 wt .-% present in the catalyst amount of platinum on the active alumina, particularly preferably from 70 to 75% by weight. In addition, the exhaust gas to be cleaned on high SO x content, so that a particularly high Poisoning resistance is required, the ratio of alumina to aluminum-silicon mixed oxide is preferably in the range 1: 2 to 1: 4. If, for example, with guaranteed use of good fuel qualities, lower SO x contents are expected in the exhaust gas, then proportions of aluminum oxide to aluminum-silicon mixed oxide of more than 1: 1.5 up to 1: 2.5 are to support the NO oxidation characteristic and more preferably ratios of more than 1: 1.5 to 1: 2.
In den bevorzugten Ausführungsformen des erfindungsgemäßen Katalysators ist die lokale Konzentration von Platin auf Aluminiumoxid mindestens zweimal so hoch, wie die lokale Konzentration von Platin auf dem Aluminium-Silizium-Mischoxid. Vorzugsweise ist die Platinkonzentration auf Aluminiumoxid, bezogen auf das Gesamtgewicht aus darauf aufgebrachtem Platin und Aluminiumoxid, zwei- bis sechsmal so hoch wie die Konzentration des auf Aluminium-Silizium-Mischoxid aufgebrachten Platins auf dem Aluminium-Silizium-Mischoxid, bezogen auf das Gesamtgewicht seinerselbst und dem Aluminium-Silizium-Mischoxid.In the preferred embodiments of the catalyst of the invention, the local concentration of platinum on alumina is at least twice as high as the local concentration of platinum on the aluminum-silicon mixed oxide. Preferably, the platinum concentration on alumina, based on the total weight of platinum and alumina applied thereto, is two to six times higher than the concentration of aluminum-silicon mixed oxide platinum on the alumina-silicon composite oxide, based on the total weight of itself and the aluminum-silicon mixed oxide.
Einfluß auf die Vergiftungsresistenz des erfindungsgemäßen Oxidationskatalysators hat auch der Gehalt an Siliziumdioxid SiO2 im Aluminium-Silizium-Mischoxid. Vorzugsweise werden hochoberflächige Aluminium-Silizium-Mischoxide eingesetzt, die 5 bis 40 Gew.-% SiO2 bezogen auf das Gesamtgewicht des Aluminium-Silizium-Mischoxids enthalten und eine spezifische Oberfläche von mehr als 60 m2/g (BET) aufweisen. Bevorzugt sind Aluminium-Silizium-Mischoxide mit 5 bis 25 Gew.-% SiO2, bezogen auf das Gesamtgewicht des Aluminium-Silizium-Mischoxids. In Ausgestaltungen des Katalysators, in denen besonderes Augenmerk auf die NO-Bildungscharakteristik gelegt wird, kommen ganz besonders bevorzugt Aluminium-Silizium-Mischoxide mit 5 bis 10 Gew.-% SiO2, bezogen auf das Gesamtgewicht des Aluminium-Silizium-Mischoxids und einer spezifischen Oberfläche von 150 bis 220 m2/g zum Einsatz.Influence on the poisoning resistance of the oxidation catalyst according to the invention also has the content of silicon dioxide SiO 2 in the aluminum-silicon mixed oxide. Preferably, high surface area aluminum-silicon mixed oxides are used which contain 5 to 40 wt .-% SiO 2 based on the total weight of the aluminum-silicon mixed oxide and have a specific surface area of more than 60 m 2 / g (BET). Preference is given to aluminum-silicon mixed oxides containing from 5 to 25% by weight of SiO 2 , based on the total weight of the aluminum-silicon mixed oxide. In embodiments of the catalyst, in which particular attention is paid to the NO formation characteristic, very particular preference is given to using aluminum-silicon mixed oxides containing 5 to 10% by weight SiO 2 , based on the total weight of the aluminum-silicon mixed oxide and a specific one Surface of 150 to 220 m 2 / g used.
Im erfindungsgemäßen Katalysator sind neben Aluminiumoxid und Aluminium- Silizium-Mischoxid zur Erzielung der die Aufgabe erfüllenden Eigenschaften keine zusätzlichen oxidischen Trägermaterialien notwendig. Insbesondere sind im erfindungs- gemäßen Katalysator zusätzliche basische Oxide nicht wünschenswert, da diese die Vergiftungsresistenz gegenüber Schwefel deutlich herabsetzen. Bevorzugte Ausge- staltungen des Oxidationskatalysators sind frei von Seltenerdoxiden, insbesondere frei von Ceroxid, Lanthanoxid, Praseodymoxid und Neodymoxid. Darüber hinaus enthalten bevorzugte Ausgestaltungen des Katalysators keine Zeolithverbindungen und keine zeolithähnlichen Materialien mit einer unteren Kanalweite von mehr als 4 Ängström (Ä), da solche Materialien Kohlenwasserstoffe einlagern und somit insbesondere bei Temperaturen unterhalb von 200°C durch Redoxreaktionen zwischen diesen eingelagerten Kohlenwasserstoffen und NO bzw. NO2 die Nθ2-Bildungsraten unerwünscht vermindern können.In addition to aluminum oxide and aluminum-silicon mixed oxide, no additional oxidic support materials are necessary in the catalyst according to the invention in order to achieve the properties fulfilling the object. In particular, additional basic oxides are not desirable in the catalyst according to the invention, since these significantly reduce the poisoning resistance to sulfur. Preferred versions Structures of the oxidation catalyst are free of rare earth oxides, in particular free of cerium oxide, lanthanum oxide, praseodymium oxide and neodymium oxide. In addition, preferred embodiments of the catalyst contain no zeolite compounds and zeolite-like materials with a lower channel width of more than 4 Ängström (Ä), since such materials incorporate hydrocarbons and thus especially at temperatures below 200 ° C by redox reactions between these embedded hydrocarbons and NO or NO 2 can undesirably reduce the NO 2 formation rates.
Der Platingehalt des erfindungsgemäßen Oxidationskatalysators liegt vorzugsweise zwischen 0,07 und 7 Gramm pro Liter [g/L], bezogen auf das Volumen des Katalysatortragkörpers. Bevorzugt liegt der Platingehalt zwischen 0,15 und 1,5 g/L, besonders bevorzugt zwischen 0,17 und 0,7 g/L, bezogen auf das Volumen des Katalysatortragkörpers. Andere Edelmetalle, insbesondere Palladium und Rhodium, können sich gegebenenfalls nachteilig auf das NO-Oxidationsverhalten und/oder die Vergiftungs- resistenz des Katalysators auswirken. Auch Iridium, Ruthenium und Gold können die Leistungseigenschaften des Katalysator unvorteilhaft beeinflussen. Zudem würde insbesondere der zusätzliche Einsatz von Palladium und/oder Rhodium unerwünschte Mehrkosten verursachen. Der erfindungsgemäße Katalysator enthält daher in seinen bevorzugten Ausführungsformen neben Platin kein weiteres Edelmetall, insbesondere nicht Palladium und Rhodium. Er enthält bevorzugt auch kein Edelmetall ausgewählt aus der Gruppe bestehend aus Iridium, Ruthenium und Gold.The platinum content of the oxidation catalyst according to the invention is preferably between 0.07 and 7 grams per liter [g / L], based on the volume of the catalyst support body. Preferably, the platinum content is between 0.15 and 1.5 g / L, more preferably between 0.17 and 0.7 g / L, based on the volume of the catalyst support body. Other noble metals, in particular palladium and rhodium, may possibly have an adverse effect on the NO oxidation behavior and / or the poisoning resistance of the catalyst. Iridium, ruthenium and gold can also adversely affect the performance characteristics of the catalyst. In addition, the additional use of palladium and / or rhodium in particular would cause undesirable additional costs. The catalyst according to the invention therefore contains, in addition to platinum, no further noble metal, in particular not palladium and rhodium, in its preferred embodiments. It preferably also contains no noble metal selected from the group consisting of iridium, ruthenium and gold.
Platin kann nach den üblichen, im Stand der Technik beschriebenen Verfahren durch Imprägnierung, durch Sorption, durch Auffällung und mit literaturbekannten „incipient- wetness"-Methoden in den Katalysator eingebracht werden. Bevorzugt wird Platin in Form einer geeigneten wasserlöslichen Vorläuferverbindung in eine Aluminiumoxid und/oder Aluminium-Slizium-Mischoxid enthaltende Beschichtungssuspension eingebracht und in definierter Weise durch Sorption und/oder Auffällung auf den Trägeroxiden fixiert. Die so vorbereitete Beschichtungssuspension, in der Platin in den erfindungsgemäßen Mengenverhältnissen auf Aluminiumoxid und Aluminium-Silizium- Mischoxid vorfixiert vorliegt, wird vermählen und in herkömmlichen Tauch-, Saug- und Pumpverfahren auf einen keramischen oder metallischen Wabenkörper oder, wenn vorteilhaft, auf einen metallischen oder keramischen Filterkörper aufgebracht. Das so erhaltene beschichtete Substrat wird zur Fertigstellung des erfindungsgemäßen Katalysators kalziniert und gegebenenfalls in Formiergas haltiger Atmosphäre thermisch reduziert.Platinum can be introduced into the catalyst by customary methods described in the prior art by impregnation, by sorption, by precipitation and by means of incipient wetness methods known from the literature. The coating suspension prepared in this manner in which platinum is prefixed to alumina and aluminum-silicon mixed oxide in the quantitative proportions according to the invention is ground and is ground in a defined manner by sorption and / or precipitation onto the carrier oxides in conventional dipping, suction and pumping on a ceramic or metallic honeycomb body or, if advantageous, applied to a metallic or ceramic filter body. The resulting coated substrate is calcined to complete the catalyst of the invention and optionally thermally reduced in atmosphere containing Formiergas.
Der resultierende Katalysator eignet sich zur Behandlung von Dieselabgasen, wobei die Behandlung des Abgases durch Überleiten des Abgases über den erfindungsgemäßen Oxidationskatalysator erfolgt. Insbesondere eignet sich der erfindungsgemäße Katalysator zur Behandlung von Dieselabgasen, wenn die Temperatur des Abgases am Eintritt des Oxidationskatalysators stets unterhalb von 500°C liegt, wie es für Nutzfahrzeuge wie Stadtbusse, Abfallentsorgungsfahrzeuge und Bau- und Arbeitsmaschinen nicht untypisch ist.The resulting catalyst is suitable for the treatment of diesel exhaust gases, wherein the treatment of the exhaust gas takes place by passing the exhaust gas over the oxidation catalyst according to the invention. In particular, the catalyst according to the invention is suitable for the treatment of diesel exhaust gases when the temperature of the exhaust gas at the inlet of the oxidation catalyst is always below 500 ° C, as is not untypical for commercial vehicles such as city buses, waste disposal vehicles and construction and working machines.
Hierzu wird der erfindungsgemäße Katalysator in einer Abgasreinigungsanlage für Fahrzeuge mit Dieselmotor anströmseitig zu einem Partikelfilter angeordnet, wobei das Partikelfilter vorzugsweise ausgewählt ist aus der Gruppe der metallischen und keramischen Durchflußfiltersubstrate, der Sintermetallfϊlterkörper, der keramischen und metallischen Gestrick- und Gewebestrukturen.For this purpose, the catalyst according to the invention is arranged in an exhaust gas purification system for vehicles with diesel engine upstream of a particle filter, wherein the particulate filter is preferably selected from the group of metallic and ceramic Durchflußfiltersubstrate, Sintermetallfϊlterkörper, the ceramic and metallic knit and fabric structures.
Alternativ kann der erfindungsgemäße Katalysator in einer Abgasreinigungsanlage für Fahrzeuge mit Dieselmotor anströmseitig zu einem SCR-Katalysator angeordnet sein. Mit Hilfe dieses SCR-Katalysators erfolgt im Bedarfsfalle die Reduktion der Stickoxide zu Stickstoff („Entstickung" des Abgases) durch selektive katalytische Reduktion (Selective Catalytic Reduktion SCR) unter Zuhilfenahme eines aus einer externen Quelle in den Abgasstrang eindosierten Reduktionsmittels. Als Reduktionsmittel wird bevorzugt Ammoniak oder eine Ammoniak freisetzende Verbindung wie beispielsweise Harnstoff oder Ammoniumcarbamat eingesetzt. Das gegebenenfalls aus der Vorläufer- Verbindung in situ erzeugte Ammoniak reagiert am SCR-Katalysator mit den Stickoxiden aus dem Abgas in einer Komproportionierungsreaktion zu Stickstoff und Wasser. Die Entstickungsraten über dem SCR-Katalysator sind bei Abgastemperaturen unterhalb von 250°C, wie sie im Unterbodenbereich von Nutzfahrzeuganwendungen zu erwarten sind, immer dann besonders gut, wenn über einem anströmseitig zum SCR- Katalysator angeordneten Oxidationskatalysator ein NO2/NOX- Verhältnis von 0,3 bis 0,7, bevorzugt von 0,4 bis 0,6 eingestellt wird. Durch Anpassung des Platingehalts, der Platinverteilung über Aluminiumoxid und Aluminim-Silizium-Mischoxid und dem Mengenverhältnis Aluminiumoxid : Aluminium-Silizium-Mischoxid im Rahmen der in dieser Schrift angegebenen Grenzen kann der erfindungsgemäße Oxidationskatalysator auch für diese Anwendung hervorragend angepaßt werden.Alternatively, the catalyst according to the invention may be arranged in an exhaust gas purification system for vehicles with a diesel engine upstream of an SCR catalytic converter. With the aid of this SCR catalyst, the reduction of the nitrogen oxides to nitrogen ("denitrification" of the exhaust gas) takes place by selective catalytic reduction (SCR) with the aid of a reducing agent metered from an external source into the exhaust gas line or an ammonia-releasing compound such as urea or ammonium carbamate The ammonia generated in situ from the precursor compound reacts with the nitrogen oxides from the exhaust gas in the SCR catalyst in a comproportionation reaction to nitrogen and water The denitrification rates over the SCR catalyst are At exhaust gas temperatures below 250 ° C., as expected in the underfloor area of commercial vehicle applications, it is always particularly good when an NO 2 / NO x ratio of 0.3 to 0.7, above an oxidation catalytic converter arranged upstream of the SCR catalytic converter, Favor gt is set from 0.4 to 0.6. By adjusting the platinum content, the Platinum distribution over alumina and aluminum-silicon mixed oxide and the ratio of alumina: aluminum-silicon mixed oxide within the limits specified in this document, the oxidation catalyst according to the invention can also be excellently adapted for this application.
Die Erfindung wird nachfolgend anhand einiger Beispiele und der folgenden Figuren weitergehend beschrieben:The invention will be further described below with reference to some examples and the following figures:
Figur 1: Konvertierung von NO zu NO2 an einem erfindungsgemäßen Katalysator Kl und an einem Katalysator nach dem Stand der Technik VKl nach einer synthetischen Alterung in SO2-haltigem AbgasFigure 1: Conversion of NO to NO 2 on a catalyst according to the invention Kl and on a catalyst according to the prior art VKL after a synthetic aging in SO 2 -containing exhaust gas
Figur 2: Konvertierung von NO zu NO2 an einem erfindungsgemäßen Katalysator im frisch hergestelltem Zustand (Kl") und nach einer synthetischen Alterung in SO2-haltigem Abgas (Kl)FIG. 2: Conversion of NO to NO 2 on a catalyst according to the invention in the freshly prepared state (Kl ") and after a synthetic aging in SO 2 -containing exhaust gas (Kl)
Figur 3; Konvertierung von NO zu NO2 an einem erfindungsgemäßen Katalysator Kl ' und an einem Katalysator nach dem Stand der Technik VKl ' nach einer synthetischen Alterung in hydrothermaler AtmosphäreFIG. 3; Conversion of NO to NO 2 on a catalyst according to the invention Kl 'and on a catalyst according to the prior art VKl' after a synthetic aging in a hydrothermal atmosphere
Figur 4; Konvertierung von NO zu NO2 an einem erfindungsgemäßen Katalysator K2 mit einem Aluminium : Aluminium-Silizium-Mischoxid-Mengenverhältnis von 1 : 2 und an einem Vergleichskatalysator VK2 mit einem Aluminium : Aluminium-Silizium-Mischoxid-Mengenverhältnis von 2,5 : 1, jeweils nach einer synthetischen Alterung in SO2-haltigem AbgasFigure 4; Conversion of NO to NO 2 on a catalyst K2 according to the invention with an aluminum: aluminum-silicon mixed oxide ratio of 1: 2 and on a comparative catalyst VK2 with an aluminum: aluminum-silicon mixed oxide ratio of 2.5: 1, respectively after a synthetic aging in SO 2 -containing exhaust gas
Beispiel 1:Example 1:
Es wurde ein erfindungsgemäßer Katalysators mit einem Mengenverhältnis Aluminiumoxid : Aluminium-Silizium-Mischoxid von 1 : 2 hergestellt. Dazu wurde zunächst das Aluminiumoxid in Wasser suspendiert. Dann wurde die Hälfte der in den Katalysator einzubringenden Platinmenge durch Injektion einer herkömmlichen, wasserlöslichen Platinvorläuferverbindung zur Suspension hinzugefügt. Nach Zugabe des Aluminium- Silizium-Mischoxids (spezifische Oberfläche: -212 m7g (BET); 10 Gew.-% SiO2) zur Suspension wurde die restliche Platinmenge injektiert. Die Beschichtungssuspension wurde in einem Tauchverfahren nach dem Stand der Technik auf einen Cordierit- Wabenkörper mit 62 Zellen pro cm2 und einer Wandstärke von 0,17 mm aufgebracht. Der beschichtete Wabenkörper wurde getrocknet und für 4 Stunden bei 350°C kalziniert.A catalyst according to the invention with an aluminum oxide: aluminum-silicon mixed oxide ratio of 1: 2 was prepared. For this purpose, the alumina was first suspended in water. Then, half of the amount of platinum to be introduced into the catalyst was added to the suspension by injecting a conventional water-soluble platinum precursor compound. After addition of the aluminum-silicon mixed oxide (specific surface: -212 m7g (BET), 10 wt% SiO 2 ) to the suspension, the remaining amount of platinum was injected. The coating suspension was applied in a dipping method according to the prior art to a cordierite honeycomb body with 62 cells per cm 2 and a wall thickness of 0.17 mm. The coated honeycomb body was dried and calcined for 4 hours at 350 ° C.
Der so hergestellte, fertige Katalysator enthielt 0,883 g/L Platin, bezogen auf das Volumen des Wabenkörpers. Ihm wurden für Untersuchungen zur katalytischen Aktivität und Alterungsbeständigkeit drei zylindrische Bohrkerne mit einem Durchmesser von 25,4 mm und einer Länge von 76,2 mm entnommen, die im folgenden unter den Bezeichnungen Kl, Kl ' und Kl" geführt werden.The finished catalyst thus prepared contained 0.883 g / L of platinum based on the volume of the honeycomb body. He was taken for research on catalytic activity and aging resistance three cylindrical cores with a diameter of 25.4 mm and a length of 76.2 mm, which are hereinafter referred to as Kl, Kl 'and Kl ".
Vergleichsbeispiel 1:Comparative Example 1
Für Vergleichsuntersuchungen wurde ein kommerziell erhältlicher Dieseloxidations- katalysator mit demselben Platingehalt (0,883 g/L Platin, bezogen auf das Volumen des Wabenkörpers) eingesetzt, in welchem die Platingesamtmenge geträgert auf einem Aluminium-Silizium-Mischoxid mit einem SiC"2-Anteil von 5 Gew.-% vorliegt, und welcher desweiteren Zeolithverbindungen enthält. Auch dieser kommerzielle Dieseloxidationskatalysator lag als beschichteter Cordierit- Wabenkörper mit 62 Zellen pro cm2 und einer Wandstärke von 0,17 mm vor.For comparative investigations, a commercially available diesel oxidation catalyst with the same platinum content (0.883 g / L platinum, based on the volume of the honeycomb body) was used, in which the total amount of total supported on an aluminum-silicon mixed oxide with a SiC " 2 content of 5 wt This commercial diesel oxidation catalyst was also present as a coated cordierite honeycomb with 62 cells per cm 2 and a wall thickness of 0.17 mm.
Diesem Vergleichskatalysator wurden für Vergleichsuntersuchungen zur katalytischen Aktivität und Alterungsbeständigkeit zwei zylindrische Bohrkerne mit einem Durchmesser von 25,4 mm und einer Länge von 76,2 mm entnommen, die im folgenden unter den Bezeichnungen VKl und VKl ' geführt werden.For comparison experiments on catalytic activity and aging resistance, two cylindrical drill cores having a diameter of 25.4 mm and a length of 76.2 mm were taken from this comparative catalyst, which are subsequently referred to under the designations VK1 and VK1.
Beispiel 2:Example 2:
Es wurde ein zweiter erfindungsgemäßer Katalysator hergestellt, der sich von dem Katalysator aus Beispiel 1 nur dadurch unterschied, daß er nur 0,706 g/L Platin, bezogen auf das Volumen des Wabenkörpers, enthielt.A second catalyst according to the invention was prepared, which differed from the catalyst of Example 1 only in that it contained only 0.706 g / L of platinum, based on the volume of the honeycomb body.
Auch diesem Katalysator wurde ein zylindrischer Bohrkern mit einem Durchmesser von 25,4 mm und einer Länge von 76,2 mm entnommen, der im folgenden unter der Bezeichnung K2 geführt wird. Vergleichsbeispiel 2:Also, this catalyst was taken from a cylindrical core with a diameter of 25.4 mm and a length of 76.2 mm, which is hereinafter referred to as K2. Comparative Example 2:
Entsprechend der in den Beispiel 1 und 2 beschriebenen Vorgehensweise wurde ein weiterer Vergleichskatalysator hergestellt. Dieser enthielt 0,706 g/L Platin und wies ein nicht erfindungsgemäßes Mengenverhältnis Aluminiumoxid : Aluminium- S ilizium- Mischoxid von 2,5:1 auf.According to the procedure described in Examples 1 and 2, a further comparative catalyst was prepared. This contained 0.706 g / L of platinum and had a non-inventive ratio of aluminum oxide: aluminum-silicon mixed oxide of 2.5: 1.
Auch diesem Vergleichskatalysator wurde ein zylindrischer Bohrkern mit einem Durchmesser von 25,4 mm und einer Länge von 76,2 mm entnommen, der im folgenden unter der Bezeichnung VK2 geführt wird.Also, this comparative catalyst was taken from a cylindrical core with a diameter of 25.4 mm and a length of 76.2 mm, which is hereinafter referred to as VK2.
Alterungen;Aging;
Vor der Untersuchung der NO-Oxidationseigenschaften der Bohrkerne wurden diese - mit Ausnahme des Bohrkerns Kl", der in frisch hergestelltem Zustand vermessen wurde - unter speziellen Bedingungen thermisch vorbehandelt und somit einer gezielten Alterung unter synthetischen Bedingugen unterzogen.Prior to investigating the NO oxidation properties of the cores, they were thermally pretreated under special conditions with the exception of the Kl "core, which was measured freshly prepared, and thus subjected to targeted aging under synthetic conditions.
Die Bohrkerne Kl, VKl, K2 und VK2 wurden für 48 Stunden bei 35O0C in einer Atmo- Sphäre aus 10 Vol.-% CO2, 10 Vol.-% O2, 10 Vol.-% H2O, 85 Vppm SO2 und 270 Vppm NO in Stickstoff (durchströmt; 15.000 h"1) behandelt. Dadurch wurde ein üblicher Aktivitätsverlust in SO2-haltigem Verbrennungsabgas nachgestellt.The cores Kl, VK1, K2 and VK2 were heated for 48 hours at 35O 0 C in an atmosphere of 10 vol .-% CO 2 , 10 vol .-% O 2 , 10 vol .-% H 2 O, 85 Vppm SO 2 and 270 Vppm NO were treated in nitrogen (flowed through, 15,000 h -1 ), thereby simulating a typical loss of activity in SO 2 -containing combustion exhaust gas.
Die Bohrkerne Kl' und VKl' wurden für die Dauer von 16 Stunden bei 700°C in einer Atmosphäre enthaltend 10 Vol.-% H2O und 10 Vol.-% O2 in Stickstoff behandelt. Dadurch wird der Aktivitätsverlust eines Katalysators über einen Langzeiteinsatz in einem hydrothermalen Abgas nachgestellt.The cores Kl 'and VKl' were treated for 16 hours at 700 ° C in an atmosphere containing 10 vol.% H 2 O and 10 vol.% O 2 in nitrogen. As a result, the loss of activity of a catalyst is adjusted over a long-term use in a hydrothermal exhaust gas.
Überprüfung der NO-Oxidationsfähigkeit in verschiedenen Alterungszuständen:Verification of NO oxidation ability in different aging states:
Alle Bohrkerne wurden in einer Labor-Modellgasanlage auf ihre katalytische Aktivität in der NO-Oxidationsreaktion hin untersucht, wobei die folgenden Testbedingungen eingestellt wurden: All drill cores were tested in a laboratory model gas facility for their catalytic activity in the NO oxidation reaction, with the following test conditions being set:
Figur 1 zeigt die NO-Konvertierung zu NO2 des erfindungsgemäßen Katalysators Kl aus Beispiel 1 und des Vergleichskatalysators nach dem Stand der Technik VKl aus Vergleichsbeispiel 1 nach synthetischer Alterung in einem SO2-haltigen Abgas. Zwischen 200 und 4000C zeigt der erfindungsgemäße Katalysator deutlich bessere NO- Oxidationsraten als der Katalysator nach dem Stand der Technik.Figure 1 shows the NO conversion to NO 2 of the catalyst of the invention Kl from Example 1 and the comparative catalyst according to the prior art VKL from Comparative Example 1 after synthetic aging in a SO 2 -containing exhaust gas. Between 200 and 400 ° C., the catalyst according to the invention shows markedly better NO oxidation rates than the catalyst according to the prior art.
Figur 2 zeigt einen Vergleich der NO-Konvertierungsraten des erfindungsgemäßen Katalysators aus Beispiel 1 in frisch hergestelltem Zustand (Kl ") und nach synthetischer Alterung in einem SO2-haltigen Abgas (Kl). Daraus wird deutlich, daß die Belastung mit SO2-haltigem Abgas praktisch keine nachteiligen Auswirkungen auf die NO-Oxidationsaktivität des erfindungsgemäßen Katalysator hat.2 shows a comparison of the NO conversion rates of the inventive catalyst from Example 1 in the freshly prepared state (Kl ") and after synthetic aging in an exhaust gas containing SO 2 (Kl) Exposure to SO 2 -containing exhaust gas has practically no adverse effects on the NO oxidation activity of the catalyst according to the invention.
Zur Überprüfung der Langzeitstabilität des erfindungsgemäßen Katalysators aus Beispiel 1 wurde die NO-Oxidationsaktivität von Kl ' und dem Vergleichskatalysator nach dem Stand der Technik VKl' aus Vergleichsbeispiel 1 auch nach synthetischer Alterung unter hydrothermalen Bedingungen untersucht. Figur 3 zeigt das Ergebnis. Daraus wird deutlich, daß der erfindungsgemäße Katalysator auch eine verbesserte Langzeitstabilität der NO-Oxidationsaktivität im Temperaturbereich zwischen 200 und 400°C zeigt.To verify the long-term stability of the inventive catalyst from Example 1, the NO oxidation activity of Kl 'and the comparative catalyst according to the prior art VKl' from Comparative Example 1 was also investigated after synthetic aging under hydrothermal conditions. FIG. 3 shows the result. It is clear that the catalyst according to the invention also shows an improved long-term stability of NO oxidation activity in the temperature range between 200 and 400 ° C.
Figur 4 zeigt, wie groß der Einfluß des Mengenverhältnisses der Trägeroxide auf die wirksame Auflösung des Zielkonfliktes zwischen NO-Oxidationsfähigkeit und SO2- Vergiftungsresistenz ist. Es wurde die NO-Oxidationsaktivität nach synthetischer Alterung in SO2-haltigem Abgas eines erfindungsgemäßen Katalysators K2 aus Beispiel 2 mit einem Mengenverhältnis Aluminiumoxid : Aluminium-Silizium-Mischoxid von 1 : 2 der des Vergleichskatalysators VK2 aus Vergleichsbeispiel 2 mit einem Mengenverhältnis Aluminiumoxid : Aluminium-Silizium-Mischoxid von 2,5 : 1 gegenübergestellt. Es ist deutlich zu erkennen, daß ein Überschuß an Aluminiumoxid zu dramatischen Einbußen der NO-Oxidationsfähigkeit nach Belastung des Vergleichskatalysators mit Aluminiumoxid-Überschuß führt, während der erfindungsgemäße Katalysator die Belastung unter SO2-haltiger Atmosphäre bezüglich seiner NO- Oxidationsfähigkeit nahezu unbeschadet übersteht. Figure 4 shows how large the influence of the ratio of carrier oxides on the effective resolution of the conflict between NO oxidation ability and SO 2 - poisoning resistance. The NO oxidation activity after synthetic aging in SO 2 -containing waste gas of a catalyst according to the invention K 2 from Example 2 with a ratio of aluminum oxide: aluminum-silicon mixed oxide of 1: 2 of the comparative catalyst VK 2 from Comparative Example 2 with a quantitative ratio of alumina: aluminum Silicon mixed oxide of 2.5: 1 compared. It can be clearly seen that an excess of alumina leads to dramatic losses of NO oxidation ability after loading of the comparative catalyst with alumina excess, while the catalyst according to the invention, the load under SO 2 -containing atmosphere with respect to its NO oxidation ability is almost unscathed.

Claims

Patentansprüche claims
1. Oxidationskatalysator enthaltend einen Tragkörper und eine katalytisch aktive Beschichtung aus Platin, aktivem Aluminiumoxid und Aluminium-Silizium- Mischoxid, dadurc h ge kennzei c hnet, daß Aluminiumoxid und Aluminium-Silizium-Mischoxid mittels Platin katalytisch aktiviert sind, wobei 55 bis 95 Gew.-% der im Katalysator vorhandenen Platinmenge auf dem aktiven Aluminiumoxid vorliegen, und die verbleibende Platinmenge auf dem Aluminium-Silizium-Mischoxid geträgert ist, wobei Aluminiumoxid und Aluminium- Silizium-Mischoxid in einem Mengenverhältnis von 1 :1,5 bis 1:4 zueinander vorliegen.1. oxidation catalyst containing a support body and a catalytically active coating of platinum, active alumina and aluminum-silicon mixed oxide, d h ac kennzei c hnet that alumina and aluminum-silicon mixed oxide are catalytically activated by platinum, wherein 55 to 95 wt. -% of the amount of platinum present in the catalyst on the active alumina, and the remaining amount of platinum supported on the aluminum-silicon mixed oxide, wherein alumina and aluminum-silicon mixed oxide in a ratio of 1: 1.5 to 1: 4 to each other ,
2. Oxidationskatalysator nach Anspruch 1, dadurch gekennze i chnet , daß das Aluminium-Silizium-Mischoxid 5 bis 40 Gew.-% SiO2, bezogen auf das Gesamtgewicht des Aluminium-Silizium-Mischoxids enthält.2. An oxidation catalyst according to claim 1, characterized gekennze i seframe that the aluminum-silicon mixed oxide contains 5 to 40 wt .-% SiO 2, based on the total weight of the aluminum-silicon mixed oxide.
3. Oxidationskatalysator nach Anspruch 2, dadurch gekennze i chnet , daß das Aluminium-Silizium-Mischoxid eine spezifische Oberfläche von mehr als 60 m2/g (BET) aufweist.3. Oxidation catalyst according to claim 2, characterized izech that the aluminum-silicon mixed oxide has a specific surface area of more than 60 m 2 / g (BET).
4. Oxidationskatalysator nach einem der Ansprüche 1 bis 3, dadurc h gekennze i chnet , daß der Platingehalt des Katalysators zwischen 0,07 und 7 Gramm pro Liter beträgt, bezogen auf das Volumen des Katalysatortragkörpers.4. Oxidation catalyst according to one of claims 1 to 3, dadurc h gekennze i chnet that the platinum content of the catalyst is between 0.07 and 7 grams per liter, based on the volume of the catalyst support body.
5. Oxidationskatalysator nach Anspruch 4, dadurch ge ke nnz e ic hnet , daß der Katalysator neben Platin kein weiteres Edelmetall enthält, insbesondere frei ist von Palladium und Rhodium.5. oxidation catalyst according to claim 4, characterized ge ke nnz e ic hnet that the catalyst in addition to platinum contains no further noble metal, in particular is free of palladium and rhodium.
6. Oxidationskatalysator nach Anspruch 4, d adurch ge kennzei c hnet , daß der Katalysator kein Edelmetall ausgewählt aus der Gruppe bestehend aus Iridium, Ruthenium und Gold enthält.6. oxidation catalyst according to claim 4, d adurch ge kennzei c hnet, that the catalyst does not contain a noble metal selected from the group consisting of iridium, ruthenium and gold.
7. Oxidationskatalysator nach einem der Ansprüche 4 bis 6, d ad urch g ekennze i chnet , daß der Katalysator frei ist von Seltenerdoxiden, insbesondere frei von Ceroxid,7. Oxidation catalyst according to one of claims 4 to 6, characterized in that the catalyst is free of rare earth oxides, in particular free of cerium oxide,
Lanthanoxid, Praseodymoxid und NeodymoxidLanthanum oxide, praseodymium oxide and neodymium oxide
8. Oxidationskatalysator nach einem der Ansprüche 4 bis 7, dadurch gekennze i chnet, daß der Katalysator frei ist von Zeolithverbindungen und zeolithähnlichen Materialien mit einer unteren Kanalweite von mehr als 4 Ängström.8. Oxidation catalyst according to one of claims 4 to 7, characterized i chnet, that the catalyst is free of zeolite compounds and zeolite-like materials having a lower channel width of more than 4 Ängström.
9. Abgasreinigungsanlage für Fahrzeuge mit Dieselmotoren, worin ein Oxidationskatalysator enthaltend einen Tragkörper und eine katalytisch aktive Beschichtung aus Platin, aktivem Aluminiumoxid und Aluminium-Silizium- Mischoxid anströmseitig zu einem Partikelfilter angeordnet ist, dadurch g ekennzei chnet , daß im Oxidationskatalysator Aluminiumoxid und Aluminium-Silizium- Mischoxid mittels Platin katalytisch aktiviert sind, wobei 55 bis 95 Gew.-% der im Katalysator vorhandenen Platinmenge auf dem aktiven Aluminiumoxid vorliegen, und die verbleibende Platinmenge auf dem Aluminium-Silizium- Mischoxid geträgert ist, wobei Aluminiumoxid und Aluminium-Silizium-9. exhaust gas purification system for vehicles with diesel engines, wherein an oxidation catalyst comprising a support body and a catalytically active coating of platinum, active alumina and aluminum-silicon mixed oxide is arranged upstream of a particle filter, characterized g ekennzei chnet that in the oxidation catalyst alumina and aluminum-silicon - Mixed oxide are catalytically activated by means of platinum, wherein 55 to 95 wt .-% of the present in the catalyst amount of platinum on the active alumina, and the remaining amount of platinum on the aluminum-silicon composite oxide is supported, with alumina and aluminum-silicon
Mischoxid in einem Mengenverhältnis von 1 : 1,5 bis 1 :4 zueinander vorliegen.Mixed oxide in a ratio of 1: 1.5 to 1: 4 to each other.
10. Abgasreinigungsanlage nach Anspruch 9, dadurch gekennzei chnet , daß das Partikelfilter ausgewählt ist aus der Gruppe der metallischen und keramischen Durchflußfiltersubstrate, der Sintermetallfilterkörper, der keramischen oder metallischen Schaumstrukturen und der keramischen und metallischen Gestrick- und Gewebestrukturen.10. The exhaust gas purification system according to claim 9, characterized gekennzei chnet, that the particulate filter is selected from the group of metallic and ceramic Durchflußfiltersubstrate, the sintered metal filter body, the ceramic or metallic foam structures and the ceramic and metallic knit and fabric structures.
11. Abgasreinigungsanlage für Fahrzeuge mit Dieselmotoren, worin ein Oxidationskatalysator enthaltend einen Tragkörper und eine katalytisch aktive Beschichtung aus Platin, aktivem Aluminiumoxid und Aluminium-Silizium- Mischoxid anströmseitig zu einem SCR-Katalysator angeordnet ist, d adurch ge ke nnzei chnet , daß im Oxidationskatalysator Aluminiumoxid und Aluminium-Silizium- Mischoxid mittels Platin katalytisch aktiviert sind, wobei 55 bis 95 Gew.-% der im Katalysator vorhandenen Platinmenge auf dem aktiven Aluminiumoxid vorliegen, und die verbleibende Platinmenge auf dem Aluminium-Silizium- Mischoxid geträgert ist, wobei Aluminiumoxid und Aluminium- Silizium- Mischoxid in einem Mengenverhältnis von 1 :1,5 bis 1:4 zueinander vorliegen.11. An exhaust gas purification system for vehicles with diesel engines, wherein an oxidation catalyst comprising a support body and a catalytically active Coating of platinum, active alumina and aluminum-silicon mixed oxide is arranged upstream of an SCR catalyst, d the zeke nnzei chnet that in the oxidation catalyst alumina and aluminum-silicon mixed oxide are catalytically activated by platinum, wherein 55 to 95 wt. -% of the amount of platinum present in the catalyst on the active alumina, and the remaining amount of platinum supported on the aluminum-silicon mixed oxide, wherein aluminum oxide and aluminum-silicon mixed oxide in a ratio of 1: 1.5 to 1: 4 to each other ,
12. Verfahren zur Behandlung von Dieselabgasen, dadurch geke nnze i c hnet , daß das Abgas über einen Oxidationskatalysators nach einem der Ansprüche 1 bis 8 geleitet wird.12. A method for treating diesel exhaust gases, characterized in that the exhaust gas is passed over an oxidation catalyst according to one of claims 1 to 8 GE.
13. Verfahren zur Behandlung von Dieselabgasen nach Anspruch 12, dadurch g ekennze i chnet , daß die Temperatur des Abgases am Eintritt des Oxidationskatalysators stets unterhalb von 500°C liegt. 13. A method for the treatment of diesel exhaust gases according to claim 12, characterized ekennze i chnet that the temperature of the exhaust gas at the entrance of the oxidation catalyst is always below 500 ° C.
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CN102065997B (en) 2014-02-05
WO2009152971A1 (en) 2009-12-23
US20110229392A1 (en) 2011-09-22
JP5404778B2 (en) 2014-02-05
BRPI0914166A2 (en) 2015-10-20
US8445403B2 (en) 2013-05-21
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KR101571660B1 (en) 2015-11-25
KR20110030618A (en) 2011-03-23

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