EP3060330A1 - Catalyst for the oxidation of co and hc at low temperatures - Google Patents

Catalyst for the oxidation of co and hc at low temperatures

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Publication number
EP3060330A1
EP3060330A1 EP14786682.6A EP14786682A EP3060330A1 EP 3060330 A1 EP3060330 A1 EP 3060330A1 EP 14786682 A EP14786682 A EP 14786682A EP 3060330 A1 EP3060330 A1 EP 3060330A1
Authority
EP
European Patent Office
Prior art keywords
platinum
catalyst
palladium
catalyst according
carbon monoxide
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Withdrawn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
EP14786682.6A
Other languages
German (de)
French (fr)
Inventor
Ruediger Hoyer
Fei WEN
Elena Mueller
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
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Filing date
Publication date
Application filed by Umicore AG and Co KG filed Critical Umicore AG and Co KG
Publication of EP3060330A1 publication Critical patent/EP3060330A1/en
Withdrawn legal-status Critical Current

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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • 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
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    • 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
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/08—Silica
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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    • 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
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
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    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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    • B01J37/0234—Impregnation and coating simultaneously
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    • B01J37/0248—Coatings comprising impregnated particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2255/1023—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/206—Rare earth metals
    • B01D2255/2065—Cerium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0205—Impregnation in several steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B01J37/0219—Coating the coating containing organic compounds
    • 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
    • B01J37/08—Heat treatment
    • 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

  • the present invention relates to a catalyst for the removal of carbon monoxide and hydrocarbon from the exhaust gas lean burned internal combustion engines, so for example, diesel engines, at very low temperatures, and a method for operating this
  • Oxidation Catalysts for Removing Noxious Gas Carbon monoxide (CO) and hydrocarbons (HC) from the exhaust of diesel and lean burn internal combustion engines are well known in the art and are based predominantly on platinum and alumina.
  • Examples of diesel oxidation catalysts can be found in the patent applications DE10308288 AI, DE19614540 AI, DE19753738 AI, DE3940758 AI, EP 0427970 A2 and DE4435073 AI. They use the oxygen present in the diesel exhaust gas in order to oxidize the noxious gases to carbon dioxide (CO2) and water vapor.
  • Hydrocarbons are described in WO2013 / 149881.
  • Diesel oxidation catalysts in addition to platinum and / or palladium ceria have significantly lower light-off temperatures, if they have certain peaks after CO adsorption in the Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy (DRIFTS).
  • DRIFTS Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy
  • DRIFTS Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy
  • the amount of platinum or platinum and palladium supported on the refractory carrier material is 0.5 to 10 wt .-%, preferably 1 to 5 wt .-%, each based on the component (i).
  • Component (i) platinum and palladium platinum and palladium.
  • the amount of palladium is selected to give a weight ratio Pt: Pd of 1: 1 to 20: 1.
  • component (i) on which the platinum or platinum and palladium are supported
  • all materials familiar to the person skilled in the art for this purpose come into consideration.
  • Such materials have a BET surface area of 30 to 250 m 2 / g, preferably from 100 to 200 m 2 / g (determined according to DIN 66132) and are in particular Alumina, silica, magnesia, titania, ceria, zeolite, and mixtures or mixed oxides thereof.
  • the assignment of the refractory support with platinum or palladium is carried out by known methods, for example by the "incipient-wetness” method using water-soluble platinum or palladium compounds.
  • ceria is
  • the BET value (determined according to DIN 66132) is fresh, that is not aged, cerium oxide, in particular at values of> 90 m 2 / g.
  • ceria is in the form of a dopant or mixed oxide with, for example, zirconium oxide, aluminum oxide, lanthanum oxide and / or praseodymium oxide.
  • the proportion of cerium oxide in the doped form or in the mixed oxide is in particular 80 to 99 wt.%.
  • the amount of cerium oxide in the catalyst according to the invention is the amount of cerium oxide.
  • the catalyst according to the invention shows the described DRIFTS peaks after reductive treatment at 250.degree.
  • this treatment is carried out by three 5 second long fuel pulses with a
  • Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy has been extensively described in the literature and known to those skilled in the art, see, for example, Catalysis Today 155 (2010) 164-171 and Catalysis Today 68 (2001) 263-381.
  • IR radiation is focused by means of a mirror on a powdery sample of the substance to be measured, whereby it by interaction with the sample to a superposition of reflection, diffraction, refraction,
  • the formation of formate species on the surface of the catalyst samples after reductive treatment at 250 ° C and adsorption of CO via DRIFTS was observed.
  • the catalyst according to the invention contains a NOx storage component, in particular an alkali or
  • Alkaline earth compound for example, barium oxide or strontium oxide is.
  • the NOx storage component is used in particular in amounts of 5 to 50 g / l, based on the volume of the support body. It is also usually supported on a high surface area refractory oxide than, for example, alumina, magnesium oxide and homogeneous magnesium / aluminum mixed oxide can be used.
  • the storage component may also be supported on ceria or a cerium mixed oxide.
  • the catalyst according to the invention can be obtained in a simple manner by mixing its constituents and applying it to a carrier body in the form of a washcoat.
  • catalysts show the claimed peaks with the claimed ratios of the peak heights, when at a constant amount of platinum, the ratio of the amount of cerium oxide to the amount of palladium is large.
  • Diesel engine exhaust can be used. Very particular preference is given to ceramic flow honeycomb bodies and ceramic wall flow filter substrates made of cordierite, aluminum titanate or silicon carbide.
  • the coating of the support body with the catalyst according to the invention is carried out in a known manner, in particular by the fact that a
  • washcoat which are the components of the
  • inventive catalyst or precursors thereof applied to the support body and then dried and calcined.
  • the application can be carried out by known methods, such as dipping, suction and / or pumping.
  • a washcoat for coating a support body with the catalyst according to the invention is preferably an aqueous one
  • Suspension in addition to optionally required auxiliaries with platinum and / or palladium-coated refractory carrier material (component (i)), cerium oxide (component (ii)), and optionally contains a NOx storage component.
  • the catalyst according to the invention can be operated in a known manner alone or as part of a catalyst system for removing carbon monoxide and hydrocarbon from the exhaust gas
  • the present invention thus also relates to a process for removing carbon monoxide and hydrocarbon from the exhaust gas of lean-burn internal combustion engines, which is characterized in that the exhaust gas is passed over a catalyst according to the invention.
  • the catalysts studied in the following examples consist of different components. These components were respectively made into an aqueous coating dispersion were coated with the flow-through honeycomb body of cordierite with a cell density of 62 cm "2 (number of flow channels of the honeycomb body per unit cross-sectional area) using a dipping process. The coated honeycombs were dried and then at 500 Calcined for a period of 2 hours in air The CO light-off behavior of the final catalysts thus obtained was after synthetic aging in a
  • the specimens were heated in the exhaust gas composition "conditioning 1" at a heating rate of 7.5 ° C per minute to 550 ° C and then again cooled to 80 ° C.
  • c (CO) is the concentration of CO at the catalyst inlet
  • condition 2 hereinafter also referred to as reductive treatment, consisting of a 200 second “lean” phase followed by a 5 second long "fat” phase exists.
  • the catalyst samples were first ground.
  • N2 was used as the inert gas, the total volume flow through the DRIFTS cell always being 6 L h -1 .
  • the milled catalyst sample in the DRIFTS cell was rinsed with 10% CO for 2 minutes at 25 ° C , then treated with 10% H2 for 10 minutes at 250 ° C., then the cell is metered for 6 minutes at 25 ° C. with 10% CO 2, and finally flushed again with N 2 for 6 minutes at 25 ° C.
  • the comparative catalyst VK1 thus prepared contained 100 g / cft of 3 platinum.
  • Example 2 (example catalyst K2)
  • a Pt-based oxidation catalyst To prepare a Pt-based oxidation catalyst, a high surface area commercial cerium oxide having a cerium oxide content of 100% by weight and lanthanum stabilized alumina having 3% by weight La 2 C> 3 based on the total weight of the mixed oxide previously described in US Pat. incipient wetness method with platinum from platinum-tetraamine acetate, was mixed with water to form a suspension, to which suspension was additionally injected palladium as Pd nitrate
  • Cordierite honeycomb body with a cell density of 62 cm "1 is coated with this suspension by means of a dipping process
  • Example 3 (example catalyst K3)
  • a catalyst was prepared which, instead of the cerium oxide with a cerium oxide content of 100% by weight, contained a commercially available doped cerium oxide with a cerium oxide content of 85% by weight. As stabilizers, the cerium oxide contained in each case 5% by weight of lanthanum oxide,
  • Praseodymium oxide and alumina Praseodymium oxide and alumina.
  • Example 2 In analogy to Example 2, another catalyst was prepared which contained another commercially available doped ceria having a cerium oxide content of 85 wt .-%, which was stabilized with 5 wt .-% lanthanum oxide, praseodymium oxide and silica.
  • Figure 1 shows the CO conversion of example catalyst Kl and
  • condition 1 Pretreatments in oxidizing atmosphere (conditioning 1, thin line) at temperatures up to 500 ° C and after pretreatment with 3 times reducing atmosphere (conditioning 2, thick line) for 5s at 250 ° C. While the CO conversion behavior of VK1 is relatively independent of the pretreatment, the CO conversion activity of
  • Example catalyst Kl significantly increased by pretreatment in a reducing atmosphere, ie. the temperature Tgo, at which the conversion reaches 90%, drops to 98 ° C.
  • DRIFTS measurements are the catalysts Kl and VK1 1 after adsorption of CO in the range of 3000 (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) - shown in 2600 cm "1, corresponding to the formation of formate species at the surface, while. If no peaks are formed in both catalysts after oxidative pretreatment (light curves), the spectra are clearly different after reductive pretreatment (dark curves), whereas in the case of comparative catalyst VK1 no formate species are formed (only one peak at 2906 cm -1 wavenumbers can be seen), the peaks at the wavenumbers 2879 cm “1 and 2847 cm “ 1 for example catalyst 1 show the presence of reactive centers.
  • Example catalysts K2 and K3, and the comparative catalyst VK2 shown Although all catalysts have a similar composition, there are clearly differences in the conversion after reductive pretreatment. Thus, the Tgo value for K2 and K3 is 85 ° C and 140 ° C, respectively, while the Tgo value for VK2 is 215 ° C.
  • the associated DRIFTS spectra after reductive pretreatment and CO adsorption are shown in FIG. (The curves of the fresh samples are also included here.) Must be removed then
  • VK2 ⁇ 0.005 ⁇ 0.005 ⁇ 0.005 - - 220

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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 Treatment By Means Of Catalyst (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The present invention relates to a catalyst for the removal of carbon monoxide and hydrocarbon from the exhaust gas of lean-operated internal combustion engines on a support, which bears platinum and/or palladium on one or more refractory supporting materials, and also contains cerium oxide and which, after reductive treatment at 250°C and after CO adsorption, is characterized by certain peaks in Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and also relates to use thereof for removing carbon monoxide and hydrocarbon from the exhaust gas of lean-operated internal combustion engines.

Description

Katalysator zur Oxidation von CO und HC bei niedrigen Temperaturen  Catalyst for the oxidation of CO and HC at low temperatures
Die vorliegende Erfindung betrifft einen Katalysator zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener Verbrennungsmotoren, also beispielsweise von Dieselmotoren, bei sehr niedrigen Temperaturen, sowie ein Verfahren zum Betreiben dieses The present invention relates to a catalyst for the removal of carbon monoxide and hydrocarbon from the exhaust gas lean burned internal combustion engines, so for example, diesel engines, at very low temperatures, and a method for operating this
Katalysators. Catalyst.
Oxidationskatalysatoren zur Entfernung der Schadgase Kohlenmonoxid (CO) und Kohlenwasserstoffe (HC) aus dem Abgas von Diesel- und mager betriebenen Verbrennungsmotoren sind aus dem Stand der Technik gut bekannt und basieren überwiegend auf Platin und Aluminiumoxid . Beispiele für Diesel-Oxidations-Katalysatoren können in den Patentanmeldungen DE10308288 AI, DE19614540 AI, DE19753738 AI, DE3940758 AI, EP 0427970 A2 und DE4435073 AI gefunden werden. Sie verwenden den im Dieselabgas in größerer Menge vorhandenen Sauerstoff, um die genannten Schadgase zu Kohlendioxid (CO2) und Wasserdampf zu oxidieren. Ceroxid enthaltende Katalysatoren zur Oxidation von Kohlenmonoxid und Oxidation Catalysts for Removing Noxious Gas Carbon monoxide (CO) and hydrocarbons (HC) from the exhaust of diesel and lean burn internal combustion engines are well known in the art and are based predominantly on platinum and alumina. Examples of diesel oxidation catalysts can be found in the patent applications DE10308288 AI, DE19614540 AI, DE19753738 AI, DE3940758 AI, EP 0427970 A2 and DE4435073 AI. They use the oxygen present in the diesel exhaust gas in order to oxidize the noxious gases to carbon dioxide (CO2) and water vapor. Cerium oxide-containing catalysts for the oxidation of carbon monoxide and
Kohlenwasserstoffen sind in der WO2013/149881 beschrieben. Hydrocarbons are described in WO2013 / 149881.
Im Zuge der C02-Optimierung werden Abgastemperaturen von zukünftigen Dieselmotoren zunehmend kälter, so dass die Umsetzung von HC und CO deutlich schwieriger wird . Im NEDC-Zyklus werden meist nur noch im außerstädtischen Fahrbetrieb Temperaturen von über 200°C erreicht und ein großer Teil der Konvertierung muss bei Temperaturen von < 150°C erfolgen, um die Emissionslimits einzuhalten. Dafür sind Katalysatoren mit einem CO-Light-off von T90 (Temperatur bei 90% Konvertierung) < 150°C erforderlich. Dies ist mit den derzeitigen Dieseloxidationskatalysatoren nach Alterung häufig nicht mehr möglich, so dass dringender Bedarf nach In the course of C0 2 optimization, exhaust gas temperatures of future diesel engines are becoming increasingly colder, making the conversion of HC and CO much more difficult. In the NEDC cycle, temperatures of over 200 ° C are usually reached only in non-urban driving conditions, and a large part of the conversion must take place at temperatures of <150 ° C in order to comply with the emission limits. This requires catalysts with a CO light-off of T90 (temperature at 90% conversion) <150 ° C. This is often no longer possible with the current diesel oxidation catalysts after aging, so that an urgent need for
Verbesserung besteht. Improvement exists.
Es wurde nun überraschenderweise gefunden, dass It has now surprisingly been found that
Dieseloxidationskatalysatoren, die neben Platin und/oder Palladium Ceroxid enthalten, deutlich niedrigere Light-off- Temperaturen aufweisen, wenn sie nach CO-Adsorption in der Diffuse Reflectance Infrared Fourier Transfrom Spectroscopy (DRIFTS) bestimmte Peaks aufweisen. Die vorliegende Erfindung betrifft somit einen Katalysator zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener Verbrennungsmotoren auf einem Tragkörper, der Diesel oxidation catalysts, in addition to platinum and / or palladium ceria have significantly lower light-off temperatures, if they have certain peaks after CO adsorption in the Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy (DRIFTS). The present invention thus relates to a catalyst for the removal of carbon monoxide and hydrocarbon from the exhaust gas lean burn internal combustion engines on a support body which
(i) Platin oder Platin und Palladium geträgert auf einem oder mehreren feuerfesten Trägermaterialien, sowie (i) platinum or platinum and palladium supported on one or more refractory substrates, as well
(ii) Ceroxid (ii) ceria
enthält, dadurch gekennzeichnet, dass er nach reduktiver Behandlung bei 250°C und nach CO-Adsorption in der Diffuse Reflectance Infrared Fourier Transfrom Spectroscopy (DRIFTS) Peaks bei 2906 cm_1 (± 5 cm"1), 2879 cm"1 (± 5 cm"1) und 2847 cm"1 (± 5 cm"1) Wellenzahlen aufweist und wobei das Verhältnis der Peakhöhen bei 2879 cm"1 und 2906 cm"1, sowie das Verhältnis der Peakhöhen bei 2847 cm"1 und 2906 cm"1 jeweils größer als 0,4 sind . contains, after reductive treatment at 250 ° C and CO adsorption in the Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy (DRIFTS) peaks at 2906 cm _1 (± 5 cm "1 ), 2879 cm " 1 (± 5 1 and 2847 cm -1 (± 5 cm -1 ) wavenumbers and wherein the ratio of peak heights at 2879 cm -1 and 2906 cm -1 , and the ratio of peak heights at 2847 cm -1 and 2906 cm -1 each greater than 0.4.
Üblicherweise beträgt die Menge an Platin oder Platin und Palladium, die auf dem feuerfesten Trägermaterial geträgert ist, 0,5 bis 10 Gew.-%, bevorzugt 1 bis 5 Gew.-%, jeweils bezogen auf die Komponente (i). Usually, the amount of platinum or platinum and palladium supported on the refractory carrier material is 0.5 to 10 wt .-%, preferably 1 to 5 wt .-%, each based on the component (i).
In einer Ausführungsform der vorliegenden Erfindung umfasst die In one embodiment of the present invention, the
Komponente (i) Platin und Palladium. In diesem Fall wird die Menge an Palladium beispielsweise so gewählt, dass ein Gewichtsverhältnis Pt: Pd von 1 : 1 bis 20 : 1 resultiert. Component (i) platinum and palladium. In this case, for example, the amount of palladium is selected to give a weight ratio Pt: Pd of 1: 1 to 20: 1.
Als feuerfeste Trägermaterialien der Komponente (i), auf denen das Platin oder das Platin und Palladium geträgert sind, kommen alle dem Fachmann für diesen Zweck geläufigen Materialien in Betracht. Solche Materialien weisen eine BET-Oberfläche von 30 bis 250 m2/g, bevorzugt von 100 bis 200 m2/g auf (bestimmt nach DIN 66132) und sind insbesondere Aluminiumoxid, Siliziumoxid, Magnesiumoxid, Titanoxid, Ceroxid, Zeolith, sowie Mischungen oder Mischoxide davon. As fireproof support materials of component (i), on which the platinum or platinum and palladium are supported, all materials familiar to the person skilled in the art for this purpose come into consideration. Such materials have a BET surface area of 30 to 250 m 2 / g, preferably from 100 to 200 m 2 / g (determined according to DIN 66132) and are in particular Alumina, silica, magnesia, titania, ceria, zeolite, and mixtures or mixed oxides thereof.
Bevorzugt sind Aluminiumoxid, Magnesium/Aluminium-Mischoxide und Aluminium/Silizium-Mischoxide. Sofern Aluminiumoxid verwendet wird, so ist es besonders bevorzugt stabilisiert, beispielsweise mit Lanthanoxid.  Preference is given to aluminum oxide, magnesium / aluminum mixed oxides and aluminum / silicon mixed oxides. If alumina is used, it is particularly preferably stabilized, for example with lanthanum oxide.
Die Belegung der feuerfesten Träger mit Platin bzw. Palladium erfolgt nach bekannten Verfahren, beispielsweise nach dem„incipient-wetness"- Verfahren unter Verwendung wasserlöslicher Platin- bzw. Palladiumverbindungen. The assignment of the refractory support with platinum or palladium is carried out by known methods, for example by the "incipient-wetness" method using water-soluble platinum or palladium compounds.
In einer Ausführungsform der vorliegenden Erfindung ist Ceroxid In one embodiment of the present invention, ceria is
undotiertes Ceroxid mit einem Ceroxid-Anteil von > 99 Gew.-%. Der BET- Wert (bestimmt nach DIN 66132) liegt bei frischem, also nicht gealterten Ceroxid insbesondere bei Werten von > 90m2/g - undoped ceria with a cerium oxide content of> 99 wt .-%. The BET value (determined according to DIN 66132) is fresh, that is not aged, cerium oxide, in particular at values of> 90 m 2 / g.
In einer weiteren Ausführungsform der vorliegenden Erfindung liegt Ceroxid in dotierer Form bzw. als Mischoxid mit beispielsweise Zirkoniumoxid, Aluminiumoxid, Lanthanoxid und/oder Praseodymoxid vor. Der Anteil an Ceroxid in der dotierten Form bzw. im Mischoxid beträgt insbesondere 80 bis 99 Gew.%. In a further embodiment of the present invention, ceria is in the form of a dopant or mixed oxide with, for example, zirconium oxide, aluminum oxide, lanthanum oxide and / or praseodymium oxide. The proportion of cerium oxide in the doped form or in the mixed oxide is in particular 80 to 99 wt.%.
Die Menge an Ceroxid im erfindungsgemäßen Katalysators liegt The amount of cerium oxide in the catalyst according to the invention is
insbesondere bei 50 bis 150 g/l, bezogen auf das Volumen des Tragkörpers. Der erfindungsgemäße Katalysator zeigt die beschriebenen DRIFTS Peaks nach reduktiver Behandlung bei 250°C. Bevorzugt wird diese Behandlung durchgeführt durch drei 5 Sekunden lange Kraftstoffpulse mit einem in particular at 50 to 150 g / l, based on the volume of the support body. The catalyst according to the invention shows the described DRIFTS peaks after reductive treatment at 250.degree. Preferably, this treatment is carried out by three 5 second long fuel pulses with a
Lambda von 0,95 bei 250°C. Sofern der erfindungsgemäße Katalysator einer oxidativen Atmosphäre, etwa bei Temperaturen von > 400°, ausgesetzt war, kann er durch eine reduktive Behandlung wieder aktiviert werden. Dies bedeutet, dass er die DRIFTS Peaks bei 2906 cm"1, 2879 cm"1 und 2847 cm"1 Wellenzahlen nach der reduktiven Behandlung wieder zeigt, wenn sie nach dem Einfluss der oxidativen Atmosphäre verschwunden waren. Lambda of 0.95 at 250 ° C. If the catalyst according to the invention was exposed to an oxidative atmosphere, for example at temperatures of> 400 °, it can be reactivated by a reductive treatment. This means that it shows the DRIFTS peaks at 2906 cm "1 , 2879 cm " 1 and 2847 cm "1 wavenumbers after the reductive treatment, when they disappeared after the influence of the oxidative atmosphere.
Die Diffuse Reflectance Infrared Fourier Transfrom Spectroscopy (DRIFTS) ist in der Literatur ausführlich beschrieben und dem Fachmann bekannt, siehe beispielsweise Catalysis Today 155 (2010) 164-171 und Catalysis Today 68 (2001) 263-381. Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy (DRIFTS) has been extensively described in the literature and known to those skilled in the art, see, for example, Catalysis Today 155 (2010) 164-171 and Catalysis Today 68 (2001) 263-381.
Dabei wird IR-Stahlung durch Spiegel auf eine pulverförmige Probe der zu messenden Substanz fokussiert, wodurch es durch Wechselwirkung mit der Probe zu einer Überlagerung von Reflexions-, Beugungs-, Brechungs-, In this case, IR radiation is focused by means of a mirror on a powdery sample of the substance to be measured, whereby it by interaction with the sample to a superposition of reflection, diffraction, refraction,
Transmissions- und Absorptionsvorgängen kommt. Ein Teil der gestreuten IR-Strahlung tritt aus der DRIFTS-Zelle aus und wird über weitere Spiegel zu einem Detektor weitergeleitet. Diese Methode erlaubt es, Proben als Pulver in der Zelle unter realitätsnahen Bedingungen zu untersuchen und Oberflächenkomplexe von adsorbierten Spezies zu detektieren. Transmission and absorption processes comes. Part of the scattered IR radiation exits the DRIFTS cell and is relayed via further mirrors to a detector. This method makes it possible to examine samples as powders in the cell under realistic conditions and to detect surface complexes of adsorbed species.
Gemäß vorliegender Erfindung wurde die Ausbildung von Formiat-Spezies an der Oberfläche der Katalysatorproben nach reduktiver Behandlung bei 250°C und Adsorption von CO über DRIFTS beobachtet. Dabei wurden drei Peaks bei den Wellenlängen 2906 cm"1, 2879 cm"1 und 2847 cm"1, wobei das Verhältnis der Peakhöhen bei 2879 cm"1 zu 2906 cm"1 sowie 2847 cm"1 zu 2906 cm"1 für den erfindungsgemäße Katalysator größer 0,4 ist. In accordance with the present invention, the formation of formate species on the surface of the catalyst samples after reductive treatment at 250 ° C and adsorption of CO via DRIFTS was observed. In this case, three peaks at the wavelengths 2906 cm "1 , 2879 cm " 1 and 2847 cm "1 , wherein the ratio of peak heights at 2879 cm " 1 to 2906 cm "1 and 2847 cm " 1 to 2906 cm "1 for the inventive Catalyst is greater than 0.4.
In einer Ausführungsform des erfindungsgemäßen Katalysators enthält er eine NOx-Speicherkomponente, die insbesondere eine Alkali- oder In one embodiment of the catalyst according to the invention, it contains a NOx storage component, in particular an alkali or
Erdalkaliverbindung, beispielsweise Bariumoxid oder Strontiumoxid, ist. Die NOx-Speicherkomponente wird insbesondere in Mengen von 5 bis 50 g/l, bezogen auf das Volumen des Tragkörpers eingesetzt. Sie ist darüber hinaus in der Regel auf einem hochoberflächigen feuerfesten Oxid geträgert, als das beispielsweise Aluminiumoxid, Magnesiumoxid und homogenes Magnesium/Aluminium-Mischoxid verwendet werden können.  Alkaline earth compound, for example, barium oxide or strontium oxide is. The NOx storage component is used in particular in amounts of 5 to 50 g / l, based on the volume of the support body. It is also usually supported on a high surface area refractory oxide than, for example, alumina, magnesium oxide and homogeneous magnesium / aluminum mixed oxide can be used.
Die Speicherkomponente kann außerdem auch auf Ceroxid oder einem Cer- Mischoxid geträgert sein. Der erfindungsgemäße Katalysator kann in einfacher Weise durch Mischen seiner Bestandteile und Aufbringen auf einen Tragkörper in Form eines Washcoats erhalten werden. The storage component may also be supported on ceria or a cerium mixed oxide. The catalyst according to the invention can be obtained in a simple manner by mixing its constituents and applying it to a carrier body in the form of a washcoat.
Der Fachmann kann nach anschließender reduktiver Behandlung bei 250°C und nach CO-Adsorption in routinemäßigen DRIFTS-Messungen feststellen, ob ein Katalysator die anspruchsgemäßen Peaks mit den  The person skilled in the art, after subsequent reductive treatment at 250 ° C. and after CO adsorption in routine DRIFTS measurements, can determine whether a catalyst satisfies the claimed peaks with the
anspruchsgemäßen Verhältnissen der Peakhöhen aufweist und damit erfindungsgemäß ist oder nicht. Es hat sich herausgestellt, dass die anspruchsgemäßen DRIFTS-Peaks auf die Ausbildung von Formiatspezies an der Katalysatoroberfläche zurückgehen und insbesondere vom verwendeten Ceroxid abhängen. has claimed ratios of the peak heights and thus according to the invention or not. It has been found that the claimed DRIFTS peaks are due to the formation of formate species on the catalyst surface and in particular depend on the ceria used.
In der Regel zeigen Katalysatoren die anspruchsgemäßen Peaks mit den anspruchsgemäßen Verhältnissen der Peakhöhen dann, wenn bei konstanter Platinmenge das Verhältnis der Menge an Ceroxid zur Menge an Palladium groß ist. In general, catalysts show the claimed peaks with the claimed ratios of the peak heights, when at a constant amount of platinum, the ratio of the amount of cerium oxide to the amount of palladium is large.
Als katalytisch inerte Tragkörper eignen sich grundsätzlich alle bekannten Tragkörper für Heterogenkatalysatoren. Bevorzugt sind monolithische und monolithähnliche Durchflusswabenkörper aus Keramik und Metall, sowie Partikelfiltersubstrate, wie sie üblicherweise zur Reinigung von In principle, all known support bodies for heterogeneous catalysts are suitable as catalytically inert support bodies. Preference is given to monolithic and monolithic flow-through honeycomb bodies made of ceramic and metal, as well as particle filter substrates, as is customary for the purification of
Dieselmotorenabgasen eingesetzt werden. Ganz besonders bevorzugt sind keramische Durchflusswabenkörper und keramische Wandflussfiltersubstrate aus Cordierit, Aluminiumtitanat oder Siliziumcarbid . Diesel engine exhaust can be used. Very particular preference is given to ceramic flow honeycomb bodies and ceramic wall flow filter substrates made of cordierite, aluminum titanate or silicon carbide.
Die Beschichtung des Tragkörpers mit dem erfindungsgemäßen Katalysator erfolgt in bekannter Weise, insbesondere dadurch, dass eine The coating of the support body with the catalyst according to the invention is carried out in a known manner, in particular by the fact that a
Beschichtungssuspension („Washcoat"), die die Bestandteile des Coating suspension ("washcoat"), which are the components of the
erfindungsgemäßen Katalysators oder Vorstufen davon enthält, auf den Tragkörper aufgebracht und anschließend getrocknet und kalziniert wird . Das Aufbringen kann nach bekannten Verfahren, wie Tauch-, Saug- und/oder Pumpverfahren erfolgen. Ein Washcoat zur Beschichtung eines Tragkörpers mit dem erfindungsgemäßen Katalysator ist bevorzugterweise eine wässrige inventive catalyst or precursors thereof, applied to the support body and then dried and calcined. The application can be carried out by known methods, such as dipping, suction and / or pumping. A washcoat for coating a support body with the catalyst according to the invention is preferably an aqueous one
Suspension, die neben gegebenenfalls erforderlichen Hilfsmitteln mit Platin und/oder Palladium belegtes feuerfestes Trägermaterial (Komponente (i)), Ceroxid (Komponete (ii)), sowie gegebenenfalls eine NOx- Speicherkomponete enthält. Suspension, in addition to optionally required auxiliaries with platinum and / or palladium-coated refractory carrier material (component (i)), cerium oxide (component (ii)), and optionally contains a NOx storage component.
Der erfindungsgemäße Katalysator kann in bekannter Weise allein oder als Bestandteil eines Katalysator-Systems zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener The catalyst according to the invention can be operated in a known manner alone or as part of a catalyst system for removing carbon monoxide and hydrocarbon from the exhaust gas
Verbrennungsmotoren verwendet werden. Internal combustion engines are used.
Die vorliegende Erfindung betrifft somit auch ein Verfahren zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener Verbrennungsmotoren, das dadurch gekennzeichnet ist, dass das Abgas über einen erfindungsgemäßen Katalysator geleitet wird.  The present invention thus also relates to a process for removing carbon monoxide and hydrocarbon from the exhaust gas of lean-burn internal combustion engines, which is characterized in that the exhaust gas is passed over a catalyst according to the invention.
Die in den folgenden Beispielen untersuchten Katalysatoren bestehen aus verschiedenen Komponenten. Diese Komponenten wurden jeweils zu einer wässerigen Beschichtungsdispersion verarbeitet, mit der Durchfluss- Wabenkörper aus Cordierit mit einer Zelldichte von 62 cm"2 (Anzahl der Strömungskanäle der Wabenkörper pro Querschnittsfläche) mit Hilfe eines Tauchverfahrens beschichtet wurden. Die beschichteten Wabenkörper wurden getrocknet und anschließend bei 500°C für eine Dauer von 2 Stunden an Luft kalziniert. Das CO-Light-off-Verhalten der derart erhaltenen fertigen Katalysatoren wurde nach synthetischer Alterung in einer The catalysts studied in the following examples consist of different components. These components were respectively made into an aqueous coating dispersion were coated with the flow-through honeycomb body of cordierite with a cell density of 62 cm "2 (number of flow channels of the honeycomb body per unit cross-sectional area) using a dipping process. The coated honeycombs were dried and then at 500 Calcined for a period of 2 hours in air The CO light-off behavior of the final catalysts thus obtained was after synthetic aging in a
Labormodellgasanlage untersucht. Zwecks Alterung wurden die Laboratory model gas system examined. For the purpose of aging, the
Katalysatoren bei einer Temperatur von 800°C für eine Dauer von 16 Stunden in einer hydrothermalen Atmosphäre, d.h. 10 vol% O2 und 10 vol% H2O in Stickstoff, gelagert. Testbedingungen : Catalysts at a temperature of 800 ° C for a period of 16 hours in a hydrothermal atmosphere, ie 10 vol% O2 and 10 vol% H2O in nitrogen, stored. Test conditions:
In einer Labor-Modellgasanlage wurde das CO-Light-Off-Verhalten der thermisch vorbehandelten („gealterten") Katalysatoren aus den  In a laboratory model gas system, the CO light-off behavior of the thermally pretreated ("aged") catalysts from the
nachstehenden Beispielen und Vergleichsbeispielen bestimmt. the following Examples and Comparative Examples.
Vor der Testung der Katalysatoren wurden dieser einer thermischen Before testing the catalysts, these were subjected to a thermal
Vorhandlung bei 800°C in 10vol% O2 und 10vol% H2O in N2 für 16h unterzogen. Lung forehand at 800 ° C in 10 vol% O2 10vol% H2O and subjected to N 2 for 16h.
Zur Testung der CO-Konvertierungsaktivität wurden die Prüflinge  To test the CO conversion activity, the samples were
nacheinander in den Reaktor der Modellgasanlage eingebaut und der folgenden Testprozedur unterzogen : successively installed in the reactor of the model gas system and subjected to the following test procedure:
1. Zur Darstellung typischer Diesel-Bedingungen, in denen der Katalysator nur mit magerem Abgas in Kontakt steht, wurden die Prüflinge in der Abgaszusammensetzung„Konditionierung 1" mit einer Heizrate von 7,5°C pro Minute auf 550°C aufgeheizt und dann wieder auf 80°C abgekühlt.  1. To illustrate typical diesel conditions in which the catalyst is only in contact with lean exhaust gas, the specimens were heated in the exhaust gas composition "conditioning 1" at a heating rate of 7.5 ° C per minute to 550 ° C and then again cooled to 80 ° C.
2. Danach wurden die Katalysatoren zur Bestimmung des CO-Light-Off- Verhaltens in der Abgaszusammensetzung für den Light-Off mit einer Heizrate von 7,5°C pro Minute auf 550°C aufgeheizt. Die CO-Konvertierung wurde dabei entsprechend der Formel 2. Thereafter, the catalysts were heated to 550 ° C at a heating rate of 7.5 ° C per minute to determine the CO light-off behavior in the exhaust gas composition for the light-off. The CO conversion was according to the formula
CO-Konvertierung [%] = 100% x (c(CO)ein - c(CO)aus) / c(CO)ein CO conversion [%] = 100% x (c (CO) on - c (CO) off ) / c (CO) on
berechnet. Hierin bezeichnen : calculated. Denote:
c(CO)ein die Konzentration von CO am Katalysatoreingang c (CO) is the concentration of CO at the catalyst inlet
c(CO)aus die Konzentration von CO am Katalysatorausgang c (CO) from the concentration of CO at the catalyst outlet
3. Zur Darstellung des CO-Light-Off-Verhaltens wurden die Prüflinge dreimal in Folge der„Konditionierung 2", im weiteren auch als reduktive Behandlung bezeichnet, unterzogen, die aus einer 200 Sekunden langen„mager"-Phase und einer anschließenden 5 Sekunden langen„fett"-Phase besteht.  3. To demonstrate the CO light-off behavior, the specimens were subjected three times in a row to "conditioning 2", hereinafter also referred to as reductive treatment, consisting of a 200 second "lean" phase followed by a 5 second long "fat" phase exists.
4. Nach Abkühlen auf 80°C wurde wieder die CO-Konvertierung  4. After cooling to 80 ° C, the CO conversion was again
entsprechend der oben beschriebenen Light-Off-Prozedur bestimmt. determined according to the light-off procedure described above.
Für die DRIFTS-Messungen wurden die Katalysatorproben zunächst aufgemahlen. Bei allen Messungen wurde N2 als Inertgas verwendet, wobei der gesamte Volumenstrom durch die DRIFTS-Zelle immer 6 L h"1 betrug . Zur reduktiven Vorbehandlung wurde die aufgemahlene Katalysatorprobe in der DRIFTS-Zelle erst 2 Minuten bei 25°C mit 10% CO gespült, dann 10 Minuten bei 250°C mit 10% H2 behandelt, anschließend die Zelle 6 Minuten bei 25°C mit 10% CO dosiert, und schließlich wieder 6 Minuten bei 25°C mit N2 gespült. Das Spektrum (Auflösung : 4 cm"1, Scan Time: 12 s, KBr alsFor the DRIFTS measurements, the catalyst samples were first ground. For all measurements, N2 was used as the inert gas, the total volume flow through the DRIFTS cell always being 6 L h -1 . For reductive pretreatment, the milled catalyst sample in the DRIFTS cell was rinsed with 10% CO for 2 minutes at 25 ° C , then treated with 10% H2 for 10 minutes at 250 ° C., then the cell is metered for 6 minutes at 25 ° C. with 10% CO 2, and finally flushed again with N 2 for 6 minutes at 25 ° C. The spectrum (resolution: 4 cm ) 1 , Scan Time: 12s, KBr as
Hintergrund) nach Schritt 4 wird als Ergebnis aufgezeichnet. Zur oxidativen Vorbehandlung wurde H2 durch O2 ersetzt. Reduktive Vorbehandlung : Background) after step 4 is recorded as a result. For oxidative pretreatment H2 was replaced by O2. Reductive pretreatment:
Oxidative Vorbehandlung : Oxidative pretreatment:
Beispiel 1 (Beispielkatalysator Kl) Example 1 (example catalyst Kl)
Zur Herstellung des Beispielkatalysators Kl wurde Lanthan-stabilisiertes Aluminiumoxid mit 3 Gew.-% La203 bezogen auf das Gesamtgewicht des Mischoxides, das zuvor im„incipient-wetness"-Verfahren mit Platin aus Platin-Tetraamin-Acetat belegt wurde, in Wasser zu einer Suspension gemischt. Dazu wurde Palladium als Pd-Nitrat injektiert und schließlich noch 150 g/l bezogen auf das Katalysatorvolumen eines hochoberflächigen Ceroxids mit einem Ceroxid-Gehalt von 100 Gew.-% gemischt. For the preparation of the example catalyst Kl lanthanum-stabilized alumina with 3 wt .-% La 2 03 based on the total weight of the mixed oxide, which was previously in the "incipient-wetness" method with platinum from platinum-tetraamine acetate, in water For this purpose, palladium was injected as Pd nitrate and finally 150 g / l based on the catalyst volume of a high surface area ceria with a cerium oxide content of 100 wt .-% mixed.
Anschließend wurde ein Durchflusswabenkörper aus Kordierit mit einer Zelldichte von 62 cm"1 mit Hilfe eines Tauchverfahrens mit dieser Subsequently, a flow honeycomb body made of cordierite having a cell density of 62 cm -1 by a dipping method with this
Suspension beschichtet. Der Wabenkörper wurde anschließend getrocknet und bei 500°C für die Dauer von 2 Stunden an Luft kalziniert. Der so erhaltene Katalysator Kl enthielt 100 g/ft3 Platin und 20 g/ft3 Palladium. Vergleichsbeispiel 1 (Vergleichskatalysator VK1) Suspension coated. The honeycomb body was then dried and calcined at 500 ° C for 2 hours in air. The catalyst Kl thus obtained contained 100 g / ft 3 of platinum and 20 g / ft 3 of palladium. Comparative Example 1 (Comparative Catalyst VK1)
Nach dem in Beispiel 1 beschriebenen Verfahren wurde das mit Pt belegte La-stabilisierte Alumina auf einen Wabenkörper aufgebracht. Der so hergestellte Vergleichskatalysator VK1 enthielt 100 g/cft3 Platin. Following the procedure described in Example 1, the Pt-stabilized La-stabilized alumina was applied to a honeycomb body. The comparative catalyst VK1 thus prepared contained 100 g / cft of 3 platinum.
Beispiel 2 (Beispielkatalysator K2) Example 2 (example catalyst K2)
Zur Herstellung eines Pt-basierten Oxidationskatalysators wurden ein hochoberflächiges handelsübliches Ceroxid mit einem Ceroxid-Gehalt von 100 Gew.-% und Lanthan-stabilisiertes Aluminiumoxid mit 3 Gew.-% La2C>3 bezogen auf das Gesamtgewicht des Mischoxides, das zuvor im„incipient- wetness"-Verfahren mit Platin aus Platin-Tetraamin-Acetat belegt, wurde mit Wasser zu einer Suspension gemischt. Zu dieser Suspension wurde zusätzlich Palladium als Pd-Nitrat injektiert. Anschließend wurde ein To prepare a Pt-based oxidation catalyst, a high surface area commercial cerium oxide having a cerium oxide content of 100% by weight and lanthanum stabilized alumina having 3% by weight La 2 C> 3 based on the total weight of the mixed oxide previously described in US Pat. incipient wetness method with platinum from platinum-tetraamine acetate, was mixed with water to form a suspension, to which suspension was additionally injected palladium as Pd nitrate
Durchflusswabenkörper aus Kordierit mit einer Zelldichte von 62 cm"1 mit Hilfe eines Tauchverfahrens mit dieser Suspension beschichtet. Der Cordierite honeycomb body with a cell density of 62 cm "1 is coated with this suspension by means of a dipping process
Wabenkörper wurde anschließend getrocknet und bei 500°C für die Dauer von 2 Stunden an Luft kalziniert. Der so erhaltene Katalysator K2 enthielt 50 g/ft3 Platin und 3 g/ft3 Palladium. Beispiel 3 (Beispielkatalysator K3) Honeycomb was then dried and calcined at 500 ° C for 2 hours in air. The catalyst K2 thus obtained contained 50 g / ft 3 of platinum and 3 g / ft 3 of palladium. Example 3 (example catalyst K3)
In Analogie zu Beispiel 2 wurde ein Katalysator hergestellt, der anstelle des Ceroxid mit einem Ceroxid-Gehalt von 100 Gew.-% ein handelsübliches dotiertes Ceroxid mit einem Ceroxidgehalt von 85 Gew: -% enthielt. Als Stabilisatoren enthielt das Ceroxid jeweils 5 Gew.-% Lanthanoxid,  In analogy to Example 2, a catalyst was prepared which, instead of the cerium oxide with a cerium oxide content of 100% by weight, contained a commercially available doped cerium oxide with a cerium oxide content of 85% by weight. As stabilizers, the cerium oxide contained in each case 5% by weight of lanthanum oxide,
Praseodymoxid und Aluminiumoxid. Praseodymium oxide and alumina.
Vergleichsbeispiel VK2 Comparative Example VK2
In Analogie zu Beispiel 2 wurde ein weiterer Katalysator hergestellt, der ein weiteres handelsübliches dotiertes Ceroxid mit einem Ceroxidgehalt von 85 Gew.-% enthielt, das mit jeweils 5 Gew.-% Lanthanoxid, Praseodymoxid und Siliciumoxid stabilisiert war. Figur 1 zeigt die CO-Konvertierung von Beispielkatalysator Kl und In analogy to Example 2, another catalyst was prepared which contained another commercially available doped ceria having a cerium oxide content of 85 wt .-%, which was stabilized with 5 wt .-% lanthanum oxide, praseodymium oxide and silica. Figure 1 shows the CO conversion of example catalyst Kl and
Vergleichskatalysator VK1 in Abhängigkeit von der Temperatur nach Comparative catalyst VK1 as a function of the temperature after
Vorbehandlungen in oxidierender Atmosphäre (Konditionierung 1; dünne Linie) bei Temperaturen bis 500°C und nach Vorbehandlung mit 3mal reduzierender Atmosphäre (Konditionierung 2; dicke Linie) für 5s bei 250°C. Während das CO-Konvertierungsverhalten von VK1 relativ unabhängig von der Vorbehandlung ist, wird die CO-Konvertierungsaktivtät von Pretreatments in oxidizing atmosphere (conditioning 1, thin line) at temperatures up to 500 ° C and after pretreatment with 3 times reducing atmosphere (conditioning 2, thick line) for 5s at 250 ° C. While the CO conversion behavior of VK1 is relatively independent of the pretreatment, the CO conversion activity of
Beispielkatalysator Kl durch Vorbehandlung in reduzierender Atmosphäre deutlich erhöht, d .h . die Temperatur Tgo, bei der die Konvertierung 90% erreicht, sinkt auf 98°C. Example catalyst Kl significantly increased by pretreatment in a reducing atmosphere, ie. the temperature Tgo, at which the conversion reaches 90%, drops to 98 ° C.
In Figur 2 sind DRIFTS-Messungen (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) der Katalysatoren Kl und VK1 1 nach Adsorption von CO im Bereich von 3000 - 2600 cm"1, die der Ausbildung von Formiat- Spezies an der Oberfläche entsprechen, gezeigt. Während sich bei beiden Katalysatoren nach oxidativer Vorbehandlung keine Peaks ausbilden (helle Kurven), unterscheiden sich die Spektren nach reduktiver Vorbehandlung (dunkle Kurven) deutlich. Während sich beim Vergleichskatalysator VK1 auch hier keine Formiatspezies ausbilden (es ist lediglich ein Peak bei 2906 cm"1 Wellenzahlen zu erkennen), zeigen die Peaks bei den Wellenzahlen 2879 cm"1 und 2847 cm"1 für Beispielkatalysator 1 das Vorhandensein reaktiver Zentren. 2 shows DRIFTS measurements are the catalysts Kl and VK1 1 after adsorption of CO in the range of 3000 (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) - shown in 2600 cm "1, corresponding to the formation of formate species at the surface, while. If no peaks are formed in both catalysts after oxidative pretreatment (light curves), the spectra are clearly different after reductive pretreatment (dark curves), whereas in the case of comparative catalyst VK1 no formate species are formed (only one peak at 2906 cm -1 wavenumbers can be seen), the peaks at the wavenumbers 2879 cm "1 and 2847 cm " 1 for example catalyst 1 show the presence of reactive centers.
In Figur 3 sind die CO-Konvertierungen der erfindungsgemäßen In Figure 3, the CO conversions of the invention
Beispielkatalysatoren K2 und K3, sowie des Vergleichskatalysators VK2 gezeigt. Obwohl alle Katalysatoren eine ähnliche Zusammensetzung haben, zeigen sich deutlich Unterschiede in der Konvertierung nach reduktiver Vorbehandlung . So liegt der Tgo-Wert für K2 und K3 bei 85°C bzw. 140°C während der Tgo-Wert für VK2 bei 215°C liegt. Die dazugehörigen DRIFTS- Spektren nach reduktiver Vorbehandlung und CO-Adsorption sind in Figur 4 gezeigt. (Es sind hier auch noch die Kurven der frischen Proben enthalten. Muss dann noch entfernt werden.) Während sich bei den Example catalysts K2 and K3, and the comparative catalyst VK2 shown. Although all catalysts have a similar composition, there are clearly differences in the conversion after reductive pretreatment. Thus, the Tgo value for K2 and K3 is 85 ° C and 140 ° C, respectively, while the Tgo value for VK2 is 215 ° C. The associated DRIFTS spectra after reductive pretreatment and CO adsorption are shown in FIG. (The curves of the fresh samples are also included here.) Must be removed then
erfindungsgemäßen Katalysatoren K2 und K3 deutlich Peaks im Bereich der Wellenzahlen 2906 cm"1 ,2879 cm"1 und 2847 cm"1 ausgebildet haben, sind diese im Vergleichskatalysator VK2 nicht zu erkennen. Für den erfindungsgemäßen Katalysator ist es daher maßgeblich, dass oben Inventive catalysts K2 and K3 have clearly peaks in the range of wavenumbers 2906 cm "1 , 2879 cm " 1 and 2847 cm "1 have formed these can not be recognized in the comparative catalyst VK2. It is therefore decisive for the catalyst according to the invention that above
genannte DRIFTS-Peak nach CO-Adsorption vorhanden sind. Die nachfolgende Tabelle fasst die Ergebnisse zusammen : mentioned DRIFTS peak after CO adsorption. The following table summarizes the results:
Ir itensität b ei Peakver nältnisse CO- KonvertierungIr tence peak connec tions CO conversion
2906 1 2879"1 2874"1 2879/2906 2847/2906 T90 [°C]2906 1 2879 "1 2874 " 1 2879/2906 2847/2906 T90 [° C]
Kl 0,0191 0,0194 0,0292 1,0 1,5 98Cl 0.0191 0.0194 0.0292 1.0 1.5 98
VK1 0,0078 < 0,005 < 0,005 - - 200VK1 0.0078 <0.005 <0.005 - - 200
K2 0,0247 0,0571 0,0415 2,3 1,7 90K2 0.0247 0.0571 0.0415 2.3 1.7 90
K3 0,0084 0,0125 0,0111 1,5 1,3 140K3 0.0084 0.0125 0.0111 1.5 1.3 140
VK2 < 0,005 < 0,005 < 0,005 - - 220 VK2 <0.005 <0.005 <0.005 - - 220

Claims

Patentansprüche claims
1. Katalysator zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener Verbrennungsmotoren auf einem 1. Catalyst for the removal of carbon monoxide and hydrocarbon from the exhaust lean burned internal combustion engines on a
Tragkörper, der  Supporting body, the
(i) Platin oder Platin und Palladium geträgert auf einem oder mehreren feuerfesten Trägermaterialien, sowie  (i) platinum or platinum and palladium supported on one or more refractory substrates, as well
(ii) Ceroxid  (ii) ceria
enthält, dadurch gekennzeichnet, dass er nach reduktiver Behandlung bei 250°C und nach CO-Adsorption in der Diffuse Reflectance Infrared Fourier Transfrom Spectroscopy (DRIFTS) Peaks bei 2906 cm_1 (± 5 cm"1), 2879 cm"1 (± 5 cm"1) und 2847 cm"1 (± 5 cm"1) Wellenzahlen aufweist und wobei das Verhältnis der Peakhöhen bei 2879 cm"1 und 2906 cm"1, sowie das Verhältnis der Peakhöhen bei 2847 cm"1 und 2906 cm"1 jeweils größer als 0,4 sind . contains, after reductive treatment at 250 ° C and CO adsorption in the Diffuse Reflectance Infrared Fourier Transmissive Spectroscopy (DRIFTS) peaks at 2906 cm _1 (± 5 cm "1 ), 2879 cm " 1 (± 5 1 and 2847 cm -1 (± 5 cm -1 ) wavenumbers and wherein the ratio of peak heights at 2879 cm -1 and 2906 cm -1 , and the ratio of peak heights at 2847 cm -1 and 2906 cm -1 each greater than 0.4.
2. Katalysator nach Anspruch 1, dadurch gekennzeichnet, dass die Menge an Platin oder Platin und Palladium 0,5 bis 10 Gew.-%, bezogen auf die Komponente (i) beträgt. 2. Catalyst according to claim 1, characterized in that the amount of platinum or platinum and palladium 0.5 to 10 wt .-%, based on the component (i).
3. Katalysator nach Anspruch 1 und/oder 2, dadurch gekennzeichnet, dass die Menge an Platin oder Platin und Palladium 1 bis 5 Gew.-%, bezogen auf die Komponente (i) beträgt. 3. Catalyst according to claim 1 and / or 2, characterized in that the amount of platinum or platinum and palladium 1 to 5 wt .-%, based on the component (i).
4. Katalysator nach einem oder mehreren der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass er Platin und Palladium enthält und das 4. Catalyst according to one or more of claims 1 to 3, characterized in that it contains platinum and palladium and the
Gewichtsverhältnis Pt: Pd 1 : 1 bis 20 : 1 ist. Weight ratio Pt: Pd 1: 1 to 20: 1.
5. Katalysator nach einem oder mehreren der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass als feuerfeste Trägermaterialien der Komponente (i) Aluminiumoxid, Siliziumoxid, Magnesiumoxid, Titanoxid, Ceroxid, Zeolith oder Mischungen oder Mischoxide davon eingesetzt werden. 5. Catalyst according to one or more of claims 1 to 4, characterized in that as refractory carrier materials of component (i) alumina, silica, magnesia, titania, ceria, zeolite or mixtures or mixed oxides thereof are used.
6. Katalysator nach einem oder mehreren der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass Ceroxid in Mengen von 50 bis 150g/l, bezogen auf das Volumen des Tragkörpers vorliegt. 6. Catalyst according to one or more of claims 1 to 5, characterized in that cerium oxide is present in amounts of 50 to 150 g / l, based on the volume of the supporting body.
7. Verfahren zur Entfernung von Kohlenmonoxid und Kohlenwasserstoff aus dem Abgas mager betriebener Verbrennungsmotoren, dadurch gekennzeichnet, dass das Abgas über einen Katalysator nach einem oder mehreren der Ansprüche 1 bis 6 geleitet wird . 7. A process for the removal of carbon monoxide and hydrocarbon from the exhaust lean burned internal combustion engines, characterized in that the exhaust gas is passed through a catalyst according to one or more of claims 1 to 6.
EP14786682.6A 2013-10-22 2014-10-22 Catalyst for the oxidation of co and hc at low temperatures Withdrawn EP3060330A1 (en)

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