WO2013048294A1 - Exhaust gas after treatment system comprising multiple catalytic objects - Google Patents

Exhaust gas after treatment system comprising multiple catalytic objects Download PDF

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Publication number
WO2013048294A1
WO2013048294A1 PCT/SE2011/000169 SE2011000169W WO2013048294A1 WO 2013048294 A1 WO2013048294 A1 WO 2013048294A1 SE 2011000169 W SE2011000169 W SE 2011000169W WO 2013048294 A1 WO2013048294 A1 WO 2013048294A1
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Prior art keywords
catalytic
exhaust gas
treatment system
catalytic object
group
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PCT/SE2011/000169
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French (fr)
Inventor
Sara ERKFELDT
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Volvo Technology Corporation
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Priority to PCT/SE2011/000169 priority Critical patent/WO2013048294A1/en
Publication of WO2013048294A1 publication Critical patent/WO2013048294A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/08—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of gallium, indium or thallium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • 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
    • B01J23/54—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
    • B01J23/62—Platinum group metals with gallium, indium, thallium, germanium, tin or lead
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/19—Catalysts containing parts with different compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • 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
    • B01J35/61—Surface area
    • B01J35/615—100-500 m2/g
    • 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
    • B01J35/63—Pore volume
    • B01J35/633—Pore volume less than 0.5 ml/g
    • 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
    • B01J35/63—Pore volume
    • B01J35/635—0.5-1.0 ml/g
    • 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
    • B01J35/64—Pore diameter
    • B01J35/647—2-50 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/208—Hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/21—Organic compounds not provided for in groups B01D2251/206 or B01D2251/208
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/903—Multi-zoned catalysts
    • B01D2255/9032—Two zones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • 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

Definitions

  • the invention relates to an exhaust gas after treatment system and a method for treating an exhaust gas in an exhaust gas after treatment system as well as a vehicle with an exhaust gas after treatment system.
  • a diesel engine has an efficiency of up to about 52% and is thus the best converter of fossil energy.
  • NO x emission concentration i.e. the emission of nitrogen oxides NO and NO2
  • Said high engine efficiency is however only possible at an elevated combustion temperature at which high NO x levels are inevitable.
  • a suppression of NO x formation by internal means has the tendency to cause an increase in particulates, known as the ⁇ -particulates trade off.
  • an excess of oxygen in the exhaust gas from a diesel engine prevents the use of stoichiometric 3-way-catalyst technology for reduction of NO x as is used in gasoline engine cars from the late eighties.
  • urea-water solution is needed and has to be fuelled and carried on-board in addition to the vehicle fuel.
  • urea may crystallize at lower temperatures, like -10°C, and thus the risk of plugging of the injector or similar devices is enhanced.
  • SCR by ammonia or urea is the SCR by hydrocarbons from the fuel.
  • Diesel engines are being developed to run on new fuels such as methanol and DME.
  • a large additional tank for the reducing agent as in the case with SCR by ammonia or urea is avoided.
  • NO x conversion is generally lower than for SCR by ammonia or urea especially at lower temperatures and a large amount of hydrocarbon is needed.
  • the catalysts used for SCR with diesel such as Ag/AI 2 O 3 (US 5534237 A) and Cu-ZSM-5 (US 4297328 A) have generally low activity with other fuels such as methanol and DME.
  • AI2O3 promoted with indium a higher activity at lower temperature compared with pure AI 2 O 3 is achieved.
  • the active temperature range is very narrow.
  • an exhaust gas after treatment system comprising a catalytic converter arrangement, wherein the catalytic converter arrangement is arranged in an exhaust gas path, wherein the catalytic converter arrangement comprises a first catalytic object including as a catalytic acting material at least an oxidized boron compound and at least a second catalytic object including at least a catalytic acting material.
  • An advantage with the present invention is that a NO x conversion over the combination of the oxidized boron compound and the catalytic acting material is increased, especially at low temperatures and over a wide temperature range, compared to the catalytic reaction without the presence of the combination of the first and second catalytic objects or in the presence of each catalytic acting material alone.
  • the active temperature range of the combination of the catalytic acting materials according to the invention is closer to the exhaust gas
  • the catalytic converter arrangement can have more than the two catalytic objects, like a further NO x reducing catalyst, a soot removing component such as a catalyst or particulate filter or any component and/or catalyst which is feasible for a person skilled in the art.
  • the catalytic objects or catalysts may be arranged in any arbitrary order. In an expedient arrangement the NO x reducing catalysts are arranged downstream of the soot catalyst.
  • a catalytic acting material is intended to mean a material, which has a catalytic activity, especially referring to a conversion of nitrogen species, like NO or NO2. It could be any material feasible for a person skilled in the art, like an elemental metal or a metal compound, e.g. a metal oxide, or any combination thereof.
  • An oxidized boron compound is intended to mean any compound feasible for a person skilled in the art which comprises boron and oxygen, like Na2B 4 Orx10H2O, H3BO3, B 2 O, B2O3.
  • the first catalytic object comprises boron preferably in a range between 0.01 and 5 percent by weight, advantageously between 0.025 and 3 percent by weight and especially advantageously between 0.05 and 1 percent by weight.
  • the stated amounts refer to the total weight of the first catalytic object.
  • the rest of the percentages of the first catalytic object may be built from the material of a carrier and is preferably AI 2 O 3 .
  • the first catalytic object is mostly AI 2 O 3 .
  • the first catalytic object comprises at least an AI 2 O3-compound.
  • a compound with a basic NO x - reduction ability can be provided, especially at high temperatures or above 350°C, respectively.
  • a favourably usability of the first catalytic object could be facilitated when the at least oxidized boron compound is arranged on at least a carrier.
  • a carrier is intended to mean any structure, which is feasible for a person skilled in the art that may act as a support for the oxidized boron compound.
  • a material of the carrier could chemically and/or energetically interact with the oxidized boron compound or be independent of the latter.
  • the carrier or the material of the carrier, respectively may have a catalytic activity for itself, like an activity for a soot reduction, an oxidation catalyst or a NO x reduction.
  • the material of the carrier is for example ⁇ -, ⁇ -, ⁇ -, ⁇ -, ⁇ -, ⁇ -, ⁇ -, ⁇ - or ⁇ - ⁇ 2 0 3 and preferably ⁇ - or ⁇ - ⁇ 2 0 3 .
  • the carrier containing the oxidized boron may be put on a substrate of monolithic structure. This structure could be any structure feasible for a person in the art and may be of a metallic material or a ceramic material such as cordierite.
  • AI2O3 itself could be extruded to a monolithic structure.
  • the at least oxidized boron compound is B 2 O 3 , thus providing a compound with a high NO x conversion over a wide temperature range.
  • the B2O3 is advantageously arranged on a carrier out of an AI 2 03-compound.
  • Al 2 0 3 is a commonly used carrier with its own catalytic activity and with good durability in high temperature applications.
  • the above mentioned scaling of the amounts of boron refers to an amount of B 2 03 in the first catalytic object which have the following scaling: preferably 0.032 and 16 percent by weight, advantageously between 0.08 and 10 percent by weight and especially advantageously between 0.16 and 3.33 percent by weight.
  • the catalytic acting material of the at least second catalytic object is at least one selected out of the group consisting of the 10 th , 1 1 th or 13 th group of the periodic system of the chemical elements.
  • the naming refers to the currently valid lUPAC nomenclature.
  • Group 10 is the nickel group or numeral VIIIA (lUPAC) or VIIIB (CAS) of the obsolete nomenclature, respectively.
  • Group 1 1 belongs to the Copper group (numeral IB (lUPAC and CAS) and group 13 represents the boron group or numerals 1MB (lUPAC) or IMA (CAS), respectively.
  • the catalytic acting material could also be a member out of the platinum group, like ruthenium, rhodium, palladium, osmium, iridium and platinum.
  • a well known and established catalytic concept could be used.
  • at least one element selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd may be utilized.
  • a wide range of different catalytic acting materials can be used which results advantageously in a reduction of costs.
  • the catalytic acting material of the at least second catalytic object is arranged on at least a carrier, hence, providing a favourable usability of the catalytic acting material of the at least second catalytic object.
  • the carrier of the oxidized boron compound of the first catalytic object could also apply to this carrier.
  • the second catalytic acting material is arranged on a carrier out of an AI 2 03-compound and thus, having its own catalytic activity.
  • the at least second catalytic object comprises at least one compound selected out of the group consisting of Ag2O/Al2O 3 , Ga20 3 /AI 2 O3 or In 2 0 3 /Al203.
  • the at least second catalytic object comprises and/or is at least ⁇ 2 ⁇ 3/ ⁇ 2 ⁇ 3, wherein an especially effective catalyst can be provided.
  • the catalytic converter arrangement can be designed most efficient, when an amount of catalytic acting material in the first and/or second catalytic object is between 0.01 and 15 percent by weight and/or an amount of oxidized catalytic acting material in the first and/or second catalytic object is between 0.05 and 15 percent by weight.
  • the catalytic acting material in the second catalytic object is preferably Ga, In and/or B and the amount for gallium is preferably 0.61 to 6 percent by weight, for indium preferably 0.1 to 10 percent by weight and for boron preferably 0.05 to 0.9 percent by weight.
  • the percentages of the elemental element belong to the following percentages of the element oxide: For gallium 0.82 to 8.2 percent by weight, for indium 0.12 - 12 percent by weight and for boron 0.16 - 3.0 percent by weight.
  • the stated amounts refer to the total weight of the second catalytic object.
  • the rest of the percentages of the second catalytic object may be built from the material of the carrier and is preferably Al 2 0 3 .
  • the lion's share of the second catalytic object is Al 2 0 3 .
  • the catalytic converter arrangement is arranged in the exhaust gas path downstream of a combustion engine, which is an internal combustion engine.
  • the combustion engine may be a compression ignition internal combustion engine and/or preferably a diesel engine.
  • the temperatures of the working condition of the combination of the oxidized boron compound of the first catalytic object and the catalytic acting material of the second catalytic object and the exhaust gas can be effortlessly combined and adjusted to each other.
  • the inventive embodiments can easily compensate a lower combustion temperature of a diesel engine in comparison with a petrol or gasoline engine.
  • the exhaust gas after treatment system comprises a source for a reducing agent for NO x reduction.
  • the source for the reducing agent may be a tank with a dosing interface, which comprises an injector, a nozzle, a vaporizer, an atomizer and/or any other interface which is feasible for a person skilled in the art.
  • the source for the reducing agent for NO x reduction is coupled to the exhaust gas path. It may be arranged downstream of the combustion engine and upstream of the catalytic converter arrangement and particularly, upstream of the NO x reducing catalysts.
  • the reducing agent for NO x reduction may comprise at least a hydrocarbon.
  • the reducing agent is a hydrocarbon. Due to this, a wide plurality of substances is possible and available.
  • the reducing agent comprises at least one oxygenated hydrocarbon or is an oxygenated hydrocarbon.
  • the reducing agent can be a fuel, especially a diesel fuel. The process can be understood as a selective catalytic reduction
  • the reducing agent for NO x reduction is at least an oxygenated hydrocarbon selected out of the group consisting of ethers, esters, alcohols, ketons and particularly the reducing agent is methanol or preferably, dimethly ether (DME).
  • DME dimethly ether
  • a material with known characteristics can be used.
  • diesel fuels could be efficiently used in selective catalytic reduction as reducing agents for NO x reduction, particularly at lower temperatures.
  • Still another advantage of the present invention lies in a reduction of an amount of reducing agent which had to be carried on board the vehicle compared to the selective catalytic reduction with ammonia or urea.
  • the first catalytic object and the at least second catalytic object can be arranged in any arbitrary order feasible for a person skilled in the art, like in vertical layers or in series axially.
  • the first catalytic object and the at least second catalytic object are arranged in series along the exhaust gas path. Due to this, the catalytic acting materials of the first catalytic object and the at least second catalytic object may conduct their activity independently from each other. Hence, they may deploy their activity unhindered.
  • the at least second catalytic object is arranged downstream of the first catalytic object with regard to the exhaust gas path. By arranging the at least second catalytic object (e.g.
  • the first catalytic object e.g. B2O3/AI2O3
  • the at least second catalytic object is more active at lower temperatures, but less active at higher temperatures.
  • the first catalytic object would only oxidise the reducing agent and not convert NO x and the reducing agent would not reach the at least second catalytic object, and thus the activity at higher temperature would be lost.
  • the wider temperature window is obtained.
  • a good catalytic activity could be achieved, when the first and/or the second catalytic object has a porous structure.
  • a large surface area of the catalytic object(s) is provided.
  • the large surface area is typically around 100 m 2 /g - 200 m 2 /g.
  • the first and/or the second catalytic object may have an average pore diameter which is, by way of example, at least or larger than 2 nm.
  • a pore volume is about 0.5 cm 3 /g. It is to be understood that the pore volume may vary depending on the pore structure.
  • the Al 2 0 3 -structure of the carrier has such a pore diameter or pore volume that the Al 2 03-structures are large enough to accommodate the reacting molecules (reactants), like the reducing agent and nitrogen oxides.
  • a method for treating an exhaust gas in an exhaust gas after treatment system comprises the steps: providing a first catalytic object and providing a second catalytic object, which comprises at least a catalytic acting material, wherein the first catalytic object comprises at least an oxidized boron compound.
  • Another advantage of the present invention is that an alternative selective catalytic reduction process to the SCR process using ammonia or urea can be used. This results in a less failure-sensitive process due to alternative substances to ammonia or urea.
  • first catalytic object is one selected out of the group consisting of oxidized boron compounds
  • at least second catalytic object is one selected out of the group consisting of the 10 th , 1 1 th or 13 th group of the periodic system of the chemical elements, in particular one selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd, so that a catalytic activity of a catalytic converter arrangement is enhanced compared to the catalytic activity of said catalytic converter
  • the combination of the first catalytic object and of the at least second catalytic object may cause the enhancement of the catalytic activity of the catalytic converter arrangement at least at a temperature of the exhaust gas in the temperature range of substantially 200°C to 500°C.
  • the temperature may be reduced by substantially 100°C to substantially 200°C.
  • a wide plurality of fuels could be employed.
  • a vehicle is provided, particularly a truck, with at least one exhaust gas after treatment system. Consequently, the inventive exhaust gas after treatment system can be deployed in a field where highly sophisticated solutions are requested.
  • a method for manufacturing at least an exhaust gas after treatment system is provided.
  • the exhaust gas after treatment system may be manufactured by means of an incipient wetness impregnation or a sol-gel method. Due to this, the first and/or second catalytic object or the B2O3, Ga 2 0 3 , ln 2 0 3 , respectively, are arranged on a surface and/or in pores of the carrier or the AI2O3, respectively. They are not a part of a crystal structure of the carrier.
  • Fig. 1 a vehicle with a combustion engine and an example embodiment of an exhaust gas after treatment system according to the invention
  • Fig. 2 the combustion engine and the exhaust gas after treatment system from Fig. 1 in a detailed illustration
  • Fig. 3 a catalyst from the exhaust gas after treatment system from Fig. 1 in a detailed illustration
  • Fig. 4 an exemplary diagram depicting the results of three different
  • FIG. 1 depicts schematically a vehicle 36, embodied as a truck, with a
  • the exhaust gas after treatment system 10 comprises a catalytic converter arrangement 12 which is arranged in an exhaust gas path 14 or an exhaust pipe, respectively, downstream of the combustion engine 28, which is embodied as a diesel engine 30.
  • the catalytic converter arrangement 12 comprises a component for reducing soot content, such as a catalyst for soot reduction or a particulate filter (not shown) and a catalyst 38 for NO x reduction which comprises a first catalytic object 16 and a second catalytic object 20.
  • the exhaust gas after treatment system 10 comprises a source 32, embodied as a tank, which is coupled to the exhaust gas path 14.
  • the source 32 has a dosing interface 40 in the form of an injector.
  • the dosing interface 40 is arranged downstream of the combustion engine 28 and upstream of the catalytic converter arrangement 12. Further, the dosing interface 40 feeds or injects a reducing agent 34 for NO x reduction into an exhaust gas 42 streaming from the combustion engine 28 along the exhaust gas path 14 to the catalytic converter arrangement 12.
  • the reducing agent 34 for NO x reduction is by way of an example a hydrocarbon or an oxygenated hydrocarbon which is a component of fuel.
  • the reducing agent 34 is dimethyl ether (DME). Since DME can be function as a fuel 44 for a diesel engine, the reducing agent 34 for NO x reduction is the fuel 44 on board the vehicle 36.
  • DME dimethyl ether
  • the first catalytic object 16 and the second catalytic object 20 are arranged in series along the exhaust gas path 14, in particular, the second catalytic object 20 is arranged downstream of the first catalytic object 16 with regard to the exhaust gas path 14.
  • the first catalytic object 16 comprises a carrier 24 out of an Al2O3-compound, specifically Y-AI2O3.
  • B2O3 containing AI2O3 material can be put on a substrate 46 of monolithic structure, which could be of a metallic material or a ceramic material such as cordierite.
  • the Al 2 0 3 itself could be extruded to a monolithic structure.
  • the first catalytic object 16 includes as a catalytic acting material an oxidized boron compound 18, namely B2O3.
  • the oxidized boron compound 18 or the B2O3, respectively, is arranged on the carrier 24.
  • the amount of catalytic acting material or boron in the first catalytic object 16 is between 0.05 and 0.9 percent by weight, preferably about 0.06 percent by weight. This corresponds to an amount of the oxidized boron compound 18 or B2O3, respectively, in the first catalytic object 16 of between 0.16 and 3.0 percent by weight.
  • the rest of the first catalytic object 16 consists of AI 2 O 3 .
  • the second catalytic object 20 comprises a carrier 26 out of an AI 2 O 3 -compound, namely ⁇ - ⁇ 2 ⁇ 3 .
  • the AI2O3 material may be put on a substrate 46 of monolithic structure, which could be of a metallic material or a ceramic material such as cordierite (only shown in detail in Figure 3 for the first catalytic object 16).
  • the AI 2 O 3 itself could be extruded to a monolithic structure.
  • the second catalytic object 20 includes a catalytic acting material 22, which is arranged on the carrier 26.
  • the catalytic acting material 22 of the second catalytic object 20 is preferably indium or gallium, thus it is a member of the 13 th group of the periodic system of the chemical elements.
  • the indium and/or gallium prevails in the second catalytic object 20 as an oxidized compound, specifically it is Ga2O3 and/or ln 2 O 3 .
  • the second catalytic object 20 is composed out of Ga 2 O3/Al2O3 and/or ln 2 O3/Al2O 3 .
  • the amount of the catalytic acting material 22 in the second catalytic object 20 is for gallium between 0.61 and 6.0 percent by weight and for indium between 0.1 and 10 percent by weight.
  • the corresponding amounts of the oxidized catalytic acting material 22 in the second catalytic object 20 is for Ga2O 3 between 0.82 and 8.2 percent by weight and for ln2O 3 between 0.12 to 12 percent by weight.
  • the remaining amount of the second catalytic object 20 consists of AI 2 O 3 .
  • the first and the second catalytic objects 16, 20 have a porous structure which provides a large surface area, which may be, by way of example, about 200 m 2 /g. Moreover, the first and the second catalytic objects 16, 20 may have for example an estimated average pore diameter D of about 8 nm and an estimated pore volume V of about 0.5 cm 3 /g (only exemplary shown for the first catalytic object 16). Of course, the numbers given here may differ in other embodiments. As could be seen in the enlarged section of Figure 3, the pores are arranged irregularly over the first catalytic object 16. Further the pore diameters D and the pore volumes V of the AI2O3 are embodied with inhomogeneous pore diameter or volume over the first catalytic object 16.
  • the first catalytic object 16 and the second catalytic object 20 of the exhaust gas after treatment system 10 were prepared by incipient wetness impregnation.
  • the Al 2 0 3 carrier 24, 26 out of a commercial available ⁇ -alumina were impregnated with a suitable compound and particularly with ln(N03)3 or Ga(NO 3 )3 or B(OH) 3 in aqueous solution.
  • the combination of the first catalytic object 16 and the second catalytic object 20 is arranged to cause an enhancement of a catalytic activity of the catalytic converter arrangement 12 compared to the catalytic activity of a catalytic converter arrangement without the presence of the combination of the first catalytic object 16 and of the second catalytic object 20 at least in a given temperature range.
  • the combination enhances the catalytic activity or efficiency of the catalytic converter arrangement 12 at a temperature of the exhaust gas 42 in a temperature range of substantially 250°C to 550°C.
  • the catalytic converter arrangement 12 is even able to operate at a temperature lower than substantially 280°C. Therefore, the reducing agent 34, or the hydrocarbons in the fuel 44, respectively, fed into the exhaust gas 42 can perform a selective catalytic reduction (SCR) for the reduction of the amount of NO x in the exhaust gas 42. Consequently, the provided combination of the first and second catalytic objects 16, 20 increases the conversion of NO x , especially at low temperatures of the exhaust gas 42 so that the active temperature range of the catalytic converter arrangement 12 or the catalyst 38 corresponds better to the exhaust gas temperature.
  • SCR selective catalytic reduction
  • Figure 4 shows in a diagram the results of three different experimental setups of an exhaust gas after treatment system with three different catalysts, namely, an Al 2 0 3 catalyst (graph C1), an ln 2 O3/AI 2 03 catalyst (graph C2) and a B2O3/AI2O3 catalyst (graph C3).
  • the y-axis refers to NO x conversion and on the x-axis the temperature in °C is plotted.
  • Graph C1 represents the setup with the AI2O3
  • Graph C2 shows the results of the setup with the ⁇ 2 ⁇ 3/ ⁇ 2 0 3 catalyst.
  • Graph C3 shows the results of the setup with the B2O3/AI2O3 catalyst.
  • the range of high NO x conversion is with a range between 300°C and 350°C less wide than the range of the Al 2 0 3 catalyst (graph C1 ).
  • the B2O3/AI2O3 catalyst (graph C3) the NO x conversion is nearly constant over a wide temperature range between approximately 350°C and 550°C and even higher compared to the NO x conversion of the AI 2 O 3 catalyst (graph C1).
  • the properties of the ln 2 0 3 /AI 2 O3 catalyst and that of the B2O3/AI2O3 catalyst can advantageously be improved.
  • the conversion of NO x can be shifting towards lower temperature values of approximately 280°C or even below 250°C according to the properties of the ln 2 0 3 /AI 2 0 3 catalyst.
  • it enables an effective NO x conversion over a wider temperature range between 350°C and 550°C according to the properties of the B2O3/AI2O3 catalyst.
  • the combination of the oxidized boron 18 and the catalytic acting material 22 causes an enhancement of a catalytic activity of the catalytic converter arrangement 12 compared to a catalytic activity of a catalytic converter arrangement without the combination of the oxidized boron 18 and the catalytic acting material 22 or with the oxidized boron 18 and the catalytic acting material 22 alone at least in a given temperature range.
  • the invention can provide an improved exhaust gas after treatment resulting in a less failure-sensitive system.

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Abstract

The invention relates to an exhaust gas after treatment system (10) comprising a catalytic converter arrangement (12), wherein the catalytic converter arrangement (12) is arranged in an exhaust gas path (14), wherein the catalytic converter arrangement (12) comprises; a first catalytic object (16) including as a catalytic acting material at least an oxidized boron compound (18) and at least a second catalytic object (20) including at least a catalytic acting material (22).

Description

D E S C R I P T I O N
Exhaust gas after treatment system comprising multiple catalytic objects
TECHNICAL FIELD
The invention relates to an exhaust gas after treatment system and a method for treating an exhaust gas in an exhaust gas after treatment system as well as a vehicle with an exhaust gas after treatment system.
BACKGROUND OF THE INVENTION
Present regulatory conditions in the automotive market have led to an increasing demand to improve fuel economy and reduce emissions in present vehicles.
These regulatory conditions must be balanced with the demands of a consumer for high performance and quick response for a vehicle.
A diesel engine has an efficiency of up to about 52% and is thus the best converter of fossil energy. NOx emission concentration, i.e. the emission of nitrogen oxides NO and NO2, is dependent upon local oxygen atom concentration and the local temperature in the combustion process in the engine. Said high engine efficiency is however only possible at an elevated combustion temperature at which high NOx levels are inevitable.
Moreover, a suppression of NOx formation by internal means (such as a specific air/fuel ratio) has the tendency to cause an increase in particulates, known as the ΝΟχ-particulates trade off. Furthermore, an excess of oxygen in the exhaust gas from a diesel engine prevents the use of stoichiometric 3-way-catalyst technology for reduction of NOx as is used in gasoline engine cars from the late eighties.
Both carbon particulates and NOx are typical emissions in the exhaust gas of diesel engines. Requirements for reducing such emissions increase and trigger various approaches in the art to reduce emissions. In EP 1 054 722 B1 an exhaust after treatment system is disclosed which combines a particulate filter collecting soot and nitrogen-oxides reduction catalysts in the exhaust tract. For removing soot, NO2 is generated by oxidation of NO in an oxidation catalyst. Soot which is collected in a particulate filter is oxidized by NO2. Residual amounts of NO and NO2 in the exhaust gas are reduced to nitrogen gas in a Selective-Catalytic- Reduction (SCR) catalyst by injecting a 32% urea-water solution into the SCR catalyst. However, a large amount of this urea-water solution is needed and has to be fuelled and carried on-board in addition to the vehicle fuel. Moreover, urea may crystallize at lower temperatures, like -10°C, and thus the risk of plugging of the injector or similar devices is enhanced.
An alternative system to SCR by ammonia or urea is the SCR by hydrocarbons from the fuel. In the future not only diesel will be used, but there is a growing divergence of engine fuels. Diesel engines are being developed to run on new fuels such as methanol and DME. When the vehicle fuel is used as reducing agent a large additional tank for the reducing agent as in the case with SCR by ammonia or urea is avoided. However, the NOx conversion is generally lower than for SCR by ammonia or urea especially at lower temperatures and a large amount of hydrocarbon is needed. Moreover, the catalysts used for SCR with diesel such as Ag/AI2O3 (US 5534237 A) and Cu-ZSM-5 (US 4297328 A) have generally low activity with other fuels such as methanol and DME. When using AI2O3 promoted with indium a higher activity at lower temperature compared with pure AI2O3 is achieved. However, the active temperature range is very narrow. In
US 2010/0055013 A1 a system with AI2O3 in series with ln/AI2O3 is shown, wherein it gives a high NOx conversion over a wider temperature range than either AI2O3 or ln/AI2O3 alone.
Therefore, it is desirable to employ an exhaust gas after treatment system which gives a high NOx conversion over a wider temperature range, operates with smaller amounts of deployed materials and is less failure-sensitive. SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved exhaust after treatment system. It is another object of the invention to provide an adequate improved method for treating an exhaust gas in an improved exhaust gas after treatment system. Another object is to provide a vehicle with an improved exhaust gas after treatment system. Yet another object is to provide a method for preparing an improved exhaust gas after treatment system. The objects are achieved by the features of the independent claims. The other claims, the drawing and the description disclose advantageous embodiments of the invention.
In a first aspect of the present invention it is provided an exhaust gas after treatment system comprising a catalytic converter arrangement, wherein the catalytic converter arrangement is arranged in an exhaust gas path, wherein the catalytic converter arrangement comprises a first catalytic object including as a catalytic acting material at least an oxidized boron compound and at least a second catalytic object including at least a catalytic acting material.
An advantage with the present invention is that a NOx conversion over the combination of the oxidized boron compound and the catalytic acting material is increased, especially at low temperatures and over a wide temperature range, compared to the catalytic reaction without the presence of the combination of the first and second catalytic objects or in the presence of each catalytic acting material alone. The active temperature range of the combination of the catalytic acting materials according to the invention is closer to the exhaust gas
temperature than otherwise. Another advantage with the present invention is that an alternative selective catalytic reduction process to the procedure with ammonia or urea can be maintained. This results in a reduction of an amount of a reducing agent which had to be carried on board the vehicle as well as in a less failure- sensitive process due to alternative substances to urea and/or ammonia. Further, an unwanted emission of ammonia in case of unfavourable process conditions is avoided. The catalytic converter arrangement can have more than the two catalytic objects, like a further NOx reducing catalyst, a soot removing component such as a catalyst or particulate filter or any component and/or catalyst which is feasible for a person skilled in the art. Furthermore, the catalytic objects or catalysts may be arranged in any arbitrary order. In an expedient arrangement the NOx reducing catalysts are arranged downstream of the soot catalyst.
A catalytic acting material is intended to mean a material, which has a catalytic activity, especially referring to a conversion of nitrogen species, like NO or NO2. It could be any material feasible for a person skilled in the art, like an elemental metal or a metal compound, e.g. a metal oxide, or any combination thereof. An oxidized boron compound is intended to mean any compound feasible for a person skilled in the art which comprises boron and oxygen, like Na2B4Orx10H2O, H3BO3, B2O, B2O3. The first catalytic object comprises boron preferably in a range between 0.01 and 5 percent by weight, advantageously between 0.025 and 3 percent by weight and especially advantageously between 0.05 and 1 percent by weight. The stated amounts refer to the total weight of the first catalytic object. The rest of the percentages of the first catalytic object may be built from the material of a carrier and is preferably AI2O3. Thus, the first catalytic object is mostly AI2O3.
According to a favourable embodiment of the invention, the first catalytic object comprises at least an AI2O3-compound. Thus, a compound with a basic NOx- reduction ability can be provided, especially at high temperatures or above 350°C, respectively.
A favourably usability of the first catalytic object could be facilitated when the at least oxidized boron compound is arranged on at least a carrier. A carrier is intended to mean any structure, which is feasible for a person skilled in the art that may act as a support for the oxidized boron compound. A material of the carrier could chemically and/or energetically interact with the oxidized boron compound or be independent of the latter. Moreover, the carrier or the material of the carrier, respectively, may have a catalytic activity for itself, like an activity for a soot reduction, an oxidation catalyst or a NOx reduction. The material of the carrier is for example γ-, α-, δ-, θ-, κ-, χ-, η- or ρ-ΑΙ203 and preferably γ- or α-ΑΙ203. The carrier containing the oxidized boron may be put on a substrate of monolithic structure. This structure could be any structure feasible for a person in the art and may be of a metallic material or a ceramic material such as cordierite.
Alternatively, the AI2O3 itself could be extruded to a monolithic structure.
Preferably, the at least oxidized boron compound is B2O3, thus providing a compound with a high NOx conversion over a wide temperature range. The B2O3 is advantageously arranged on a carrier out of an AI203-compound. Al203 is a commonly used carrier with its own catalytic activity and with good durability in high temperature applications. The above mentioned scaling of the amounts of boron refers to an amount of B203 in the first catalytic object which have the following scaling: preferably 0.032 and 16 percent by weight, advantageously between 0.08 and 10 percent by weight and especially advantageously between 0.16 and 3.33 percent by weight.
In yet another example embodiment of the present invention the catalytic acting material of the at least second catalytic object is at least one selected out of the group consisting of the 10th, 1 1th or 13th group of the periodic system of the chemical elements. The naming refers to the currently valid lUPAC nomenclature. Group 10 is the nickel group or numeral VIIIA (lUPAC) or VIIIB (CAS) of the obsolete nomenclature, respectively. Group 1 1 belongs to the Copper group (numeral IB (lUPAC and CAS) and group 13 represents the boron group or numerals 1MB (lUPAC) or IMA (CAS), respectively. Additionally, the catalytic acting material could also be a member out of the platinum group, like ruthenium, rhodium, palladium, osmium, iridium and platinum. Thus, a well known and established catalytic concept could be used. Preferably, at least one element selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd may be utilized. As could be seen a wide range of different catalytic acting materials can be used which results advantageously in a reduction of costs.
According to another favourable embodiment of the invention the catalytic acting material of the at least second catalytic object is arranged on at least a carrier, hence, providing a favourable usability of the catalytic acting material of the at least second catalytic object. The remarks stated above concerning the carrier of the oxidized boron compound of the first catalytic object could also apply to this carrier. Preferably, the second catalytic acting material is arranged on a carrier out of an AI203-compound and thus, having its own catalytic activity. In a preferred embodiment the at least second catalytic object comprises at least one compound selected out of the group consisting of Ag2O/Al2O3, Ga203/AI2O3 or In203/Al203. Due to this inventive embodiment the enhancement of the catalytic activity and efficiency of the catalytic converter arrangement can be easily obtained. Advantageously, the at least second catalytic object comprises and/or is at least Ιη2θ3/ΑΙ2θ3, wherein an especially effective catalyst can be provided.
The catalytic converter arrangement can be designed most efficient, when an amount of catalytic acting material in the first and/or second catalytic object is between 0.01 and 15 percent by weight and/or an amount of oxidized catalytic acting material in the first and/or second catalytic object is between 0.05 and 15 percent by weight. The catalytic acting material in the second catalytic object is preferably Ga, In and/or B and the amount for gallium is preferably 0.61 to 6 percent by weight, for indium preferably 0.1 to 10 percent by weight and for boron preferably 0.05 to 0.9 percent by weight. The percentages of the elemental element belong to the following percentages of the element oxide: For gallium 0.82 to 8.2 percent by weight, for indium 0.12 - 12 percent by weight and for boron 0.16 - 3.0 percent by weight. The stated amounts refer to the total weight of the second catalytic object. The rest of the percentages of the second catalytic object may be built from the material of the carrier and is preferably Al203. Thus, preferably the lion's share of the second catalytic object is Al203.
According to another example embodiment the catalytic converter arrangement is arranged in the exhaust gas path downstream of a combustion engine, which is an internal combustion engine. The combustion engine may be a compression ignition internal combustion engine and/or preferably a diesel engine. Hence, the temperatures of the working condition of the combination of the oxidized boron compound of the first catalytic object and the catalytic acting material of the second catalytic object and the exhaust gas can be effortlessly combined and adjusted to each other. Thus, the inventive embodiments can easily compensate a lower combustion temperature of a diesel engine in comparison with a petrol or gasoline engine.
According to another example embodiment the exhaust gas after treatment system comprises a source for a reducing agent for NOx reduction. The source for the reducing agent may be a tank with a dosing interface, which comprises an injector, a nozzle, a vaporizer, an atomizer and/or any other interface which is feasible for a person skilled in the art. Advantageously, the source for the reducing agent for NOx reduction is coupled to the exhaust gas path. It may be arranged downstream of the combustion engine and upstream of the catalytic converter arrangement and particularly, upstream of the NOx reducing catalysts.
Alternatively, it is also possible to apply the reducing agent in one or more cylinders of the combustion engine e. g. via post-injection. In another embodiment of the present invention the reducing agent for NOx reduction may comprise at least a hydrocarbon. Preferably, the reducing agent is a hydrocarbon. Due to this, a wide plurality of substances is possible and available. Preferably, the reducing agent comprises at least one oxygenated hydrocarbon or is an oxygenated hydrocarbon. The reducing agent can be a fuel, especially a diesel fuel. The process can be understood as a selective catalytic reduction
(SCR) with hydrocarbons in the fuel. Advantageously, the reducing agent for NOx reduction is at least an oxygenated hydrocarbon selected out of the group consisting of ethers, esters, alcohols, ketons and particularly the reducing agent is methanol or preferably, dimethly ether (DME). By means of such a substance a material with known characteristics can be used. According to the inventive combination of the oxidized boron and the catalytic acting material alternative diesel fuels could be efficiently used in selective catalytic reduction as reducing agents for NOx reduction, particularly at lower temperatures. Still another advantage of the present invention lies in a reduction of an amount of reducing agent which had to be carried on board the vehicle compared to the selective catalytic reduction with ammonia or urea.
The first catalytic object and the at least second catalytic object can be arranged in any arbitrary order feasible for a person skilled in the art, like in vertical layers or in series axially. Advantageously, the first catalytic object and the at least second catalytic object are arranged in series along the exhaust gas path. Due to this, the catalytic acting materials of the first catalytic object and the at least second catalytic object may conduct their activity independently from each other. Hence, they may deploy their activity unhindered. In particular, the at least second catalytic object is arranged downstream of the first catalytic object with regard to the exhaust gas path. By arranging the at least second catalytic object (e.g.
In203/Al203) after the first catalytic object (e.g. B2O3/AI2O3) a high activity over a wide temperature range is obtained. The at least second catalytic object is more active at lower temperatures, but less active at higher temperatures. Thus, by an arrangement in an opposite order it would be good at low temperatures, but at higher temperatures the first catalytic object would only oxidise the reducing agent and not convert NOx and the reducing agent would not reach the at least second catalytic object, and thus the activity at higher temperature would be lost. In conclusion, it is only in the preferred arrangement that the wider temperature window is obtained.
A good catalytic activity could be achieved, when the first and/or the second catalytic object has a porous structure. By means of the porous structure a large surface area of the catalytic object(s) is provided. The large surface area is typically around 100 m2/g - 200 m2/g. Experimentally it has turned out that these values provide an efficient catalytic activity. Moreover, the first and/or the second catalytic object may have an average pore diameter which is, by way of example, at least or larger than 2 nm. For instance, a pore volume is about 0.5 cm3/g. It is to be understood that the pore volume may vary depending on the pore structure. Especially, the Al203-structure of the carrier has such a pore diameter or pore volume that the Al203-structures are large enough to accommodate the reacting molecules (reactants), like the reducing agent and nitrogen oxides. In a further aspect of the present invention a method for treating an exhaust gas in an exhaust gas after treatment system is provided, wherein the method comprises the steps: providing a first catalytic object and providing a second catalytic object, which comprises at least a catalytic acting material, wherein the first catalytic object comprises at least an oxidized boron compound. Thus, a conversion over the catalytic acting materials is advantageously
increased, especially at low temperatures, so that the active temperature range of the catalytic acting materials corresponds better to the exhaust gas temperature. Another advantage of the present invention is that an alternative selective catalytic reduction process to the SCR process using ammonia or urea can be used. This results in a less failure-sensitive process due to alternative substances to ammonia or urea. It is further proposed that a selection of a combination of the first catalytic object and the at least second catalytic object is provided, wherein the first catalytic object is one selected out of the group consisting of oxidized boron compounds, wherein the at least second catalytic object is one selected out of the group consisting of the 10th, 1 1th or 13th group of the periodic system of the chemical elements, in particular one selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd, so that a catalytic activity of a catalytic converter arrangement is enhanced compared to the catalytic activity of said catalytic converter
arrangement without the presence of the combination of the first catalytic object and of the at least second catalytic object at least in a given temperature range.
Advantageously, the combination of the first catalytic object and of the at least second catalytic object may cause the enhancement of the catalytic activity of the catalytic converter arrangement at least at a temperature of the exhaust gas in the temperature range of substantially 200°C to 500°C. Compared to the case without the presence of the combination of the first catalytic object and of the at least second catalytic object or with only one of the catalytic objects present, the temperature may be reduced by substantially 100°C to substantially 200°C. As a result, a wide plurality of fuels could be employed. In a third aspect of the invention a vehicle is provided, particularly a truck, with at least one exhaust gas after treatment system. Consequently, the inventive exhaust gas after treatment system can be deployed in a field where highly sophisticated solutions are requested. In a forth aspect of the invention a method for manufacturing at least an exhaust gas after treatment system is provided. The exhaust gas after treatment system may be manufactured by means of an incipient wetness impregnation or a sol-gel method. Due to this, the first and/or second catalytic object or the B2O3, Ga203, ln203, respectively, are arranged on a surface and/or in pores of the carrier or the AI2O3, respectively. They are not a part of a crystal structure of the carrier.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiment, but not restricted to the embodiment, wherein is shown
schematically:
Fig. 1 a vehicle with a combustion engine and an example embodiment of an exhaust gas after treatment system according to the invention; Fig. 2 the combustion engine and the exhaust gas after treatment system from Fig. 1 in a detailed illustration;
Fig. 3 a catalyst from the exhaust gas after treatment system from Fig. 1 in a detailed illustration and
Fig. 4 an exemplary diagram depicting the results of three different
experimental setups.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention. Figure 1 depicts schematically a vehicle 36, embodied as a truck, with a
combustion engine 28 and an exhaust gas after treatment system 10 downstream of the combustion engine 28. An example embodiment of the exhaust gas after treatment system 10 is illustrated in detail in Figure 2.
The exhaust gas after treatment system 10 comprises a catalytic converter arrangement 12 which is arranged in an exhaust gas path 14 or an exhaust pipe, respectively, downstream of the combustion engine 28, which is embodied as a diesel engine 30. The catalytic converter arrangement 12 comprises a component for reducing soot content, such as a catalyst for soot reduction or a particulate filter (not shown) and a catalyst 38 for NOx reduction which comprises a first catalytic object 16 and a second catalytic object 20.
Further, the exhaust gas after treatment system 10 comprises a source 32, embodied as a tank, which is coupled to the exhaust gas path 14. The source 32 has a dosing interface 40 in the form of an injector. The dosing interface 40 is arranged downstream of the combustion engine 28 and upstream of the catalytic converter arrangement 12. Further, the dosing interface 40 feeds or injects a reducing agent 34 for NOx reduction into an exhaust gas 42 streaming from the combustion engine 28 along the exhaust gas path 14 to the catalytic converter arrangement 12. The reducing agent 34 for NOx reduction is by way of an example a hydrocarbon or an oxygenated hydrocarbon which is a component of fuel.
Preferably, the reducing agent 34 is dimethyl ether (DME). Since DME can be function as a fuel 44 for a diesel engine, the reducing agent 34 for NOx reduction is the fuel 44 on board the vehicle 36.
In Figure 3 the catalyst 38 of the catalytic converter arrangement 12 is shown in detail. The first catalytic object 16 and the second catalytic object 20 are arranged in series along the exhaust gas path 14, in particular, the second catalytic object 20 is arranged downstream of the first catalytic object 16 with regard to the exhaust gas path 14. The first catalytic object 16 comprises a carrier 24 out of an Al2O3-compound, specifically Y-AI2O3. B2O3 containing AI2O3 material can be put on a substrate 46 of monolithic structure, which could be of a metallic material or a ceramic material such as cordierite. Alternatively, the Al203 itself could be extruded to a monolithic structure. Moreover, the first catalytic object 16 includes as a catalytic acting material an oxidized boron compound 18, namely B2O3.The oxidized boron compound 18 or the B2O3, respectively, is arranged on the carrier 24. The amount of catalytic acting material or boron in the first catalytic object 16 is between 0.05 and 0.9 percent by weight, preferably about 0.06 percent by weight. This corresponds to an amount of the oxidized boron compound 18 or B2O3, respectively, in the first catalytic object 16 of between 0.16 and 3.0 percent by weight. The rest of the first catalytic object 16 consists of AI2O3. The second catalytic object 20 comprises a carrier 26 out of an AI2O3-compound, namely γ-ΑΙ2Ο3. The AI2O3 material may be put on a substrate 46 of monolithic structure, which could be of a metallic material or a ceramic material such as cordierite (only shown in detail in Figure 3 for the first catalytic object 16).
Alternatively, the AI2O3 itself could be extruded to a monolithic structure.
Furthermore, the second catalytic object 20 includes a catalytic acting material 22, which is arranged on the carrier 26. The catalytic acting material 22 of the second catalytic object 20 is preferably indium or gallium, thus it is a member of the 13th group of the periodic system of the chemical elements. The indium and/or gallium prevails in the second catalytic object 20 as an oxidized compound, specifically it is Ga2O3 and/or ln2O3. Thus, the second catalytic object 20 is composed out of Ga2O3/Al2O3 and/or ln2O3/Al2O3. The amount of the catalytic acting material 22 in the second catalytic object 20 is for gallium between 0.61 and 6.0 percent by weight and for indium between 0.1 and 10 percent by weight. The corresponding amounts of the oxidized catalytic acting material 22 in the second catalytic object 20 is for Ga2O3 between 0.82 and 8.2 percent by weight and for ln2O3 between 0.12 to 12 percent by weight. The remaining amount of the second catalytic object 20 consists of AI2O3.
The first and the second catalytic objects 16, 20 have a porous structure which provides a large surface area, which may be, by way of example, about 200 m2/g. Moreover, the first and the second catalytic objects 16, 20 may have for example an estimated average pore diameter D of about 8 nm and an estimated pore volume V of about 0.5 cm3/g (only exemplary shown for the first catalytic object 16). Of course, the numbers given here may differ in other embodiments. As could be seen in the enlarged section of Figure 3, the pores are arranged irregularly over the first catalytic object 16. Further the pore diameters D and the pore volumes V of the AI2O3 are embodied with inhomogeneous pore diameter or volume over the first catalytic object 16.
The first catalytic object 16 and the second catalytic object 20 of the exhaust gas after treatment system 10 were prepared by incipient wetness impregnation.
Therefore, the Al203 carrier 24, 26 out of a commercial available γ-alumina were impregnated with a suitable compound and particularly with ln(N03)3 or Ga(NO3)3 or B(OH)3 in aqueous solution. In a following step the resulting powders of
Ιη203/Αΐ2θ3 or Ga203/AI203 or B203/AI203 were calcined in air at a temperature of 550°C. This results in an arrangement of the B203, ln203 or Ga203 on a surface and inside the pores of the carrier 24, 26 or Al203, respectively (see enlarged section of Figure 3).
The combination of the first catalytic object 16 and the second catalytic object 20 is arranged to cause an enhancement of a catalytic activity of the catalytic converter arrangement 12 compared to the catalytic activity of a catalytic converter arrangement without the presence of the combination of the first catalytic object 16 and of the second catalytic object 20 at least in a given temperature range.
Further, the combination enhances the catalytic activity or efficiency of the catalytic converter arrangement 12 at a temperature of the exhaust gas 42 in a temperature range of substantially 250°C to 550°C. Thus, the catalytic converter arrangement 12 is even able to operate at a temperature lower than substantially 280°C. Therefore, the reducing agent 34, or the hydrocarbons in the fuel 44, respectively, fed into the exhaust gas 42 can perform a selective catalytic reduction (SCR) for the reduction of the amount of NOx in the exhaust gas 42. Consequently, the provided combination of the first and second catalytic objects 16, 20 increases the conversion of NOx, especially at low temperatures of the exhaust gas 42 so that the active temperature range of the catalytic converter arrangement 12 or the catalyst 38 corresponds better to the exhaust gas temperature. Figure 4 shows in a diagram the results of three different experimental setups of an exhaust gas after treatment system with three different catalysts, namely, an Al203 catalyst (graph C1), an ln2O3/AI203 catalyst (graph C2) and a B2O3/AI2O3 catalyst (graph C3). The y-axis refers to NOx conversion and on the x-axis the temperature in °C is plotted. Graph C1 represents the setup with the AI2O3
catalyst. Graph C2 shows the results of the setup with the Ιη2θ3/ΑΙ203 catalyst. Graph C3 shows the results of the setup with the B2O3/AI2O3 catalyst.
As can be seen in the diagram of Figure 4 for the setup with the Al203 catalyst (graph C1) the conversion of NOx is almost zero at temperatures below
approximately 350°C, but has a nearly constant NOx conversion over a wide temperature range between approximately 350°C and 550°C. In case of the ln203/AI203 catalyst (graph C2) the temperature threshold for an effective conversion of NOx can be shifted towards lower temperature values of
approximately 280°C. However, the range of high NOx conversion is with a range between 300°C and 350°C less wide than the range of the Al203 catalyst (graph C1 ). With the B2O3/AI2O3 catalyst (graph C3) the NOx conversion is nearly constant over a wide temperature range between approximately 350°C and 550°C and even higher compared to the NOx conversion of the AI2O3 catalyst (graph C1).
By using a catalytic converter arrangement 12 according to the invention the properties of the ln203/AI2O3 catalyst and that of the B2O3/AI2O3 catalyst can advantageously be improved. Thus, in such a catalytic converter arrangement 12 the conversion of NOx can be shifting towards lower temperature values of approximately 280°C or even below 250°C according to the properties of the ln203/AI203 catalyst. Moreover, it enables an effective NOx conversion over a wider temperature range between 350°C and 550°C according to the properties of the B2O3/AI2O3 catalyst. Thus, due to the combination of the ln203/AI203 catalyst and the B203/AI203 catalyst an effective NOx conversion could be provided over a wide temperature range between approximately 250°C and 550°C. Such a NOx conversion is even higher that that of the AI2O3 catalyst alone. Further, by using the combination of the In203/Al203 catalyst (graph C2) and the B2O3/AI2O3 catalyst (graph C3) instead of a combination of the AI2O3 catalyst (graph C1) and the ln203/AI203 catalyst (graph C2) a potential drop in the NOx conversion in the temperature range between about 350°C and 400°C of the latter combination, could advantageously be avoided or at least reduced. Hence, the combination of the oxidized boron 18 and the catalytic acting material 22 causes an enhancement of a catalytic activity of the catalytic converter arrangement 12 compared to a catalytic activity of a catalytic converter arrangement without the combination of the oxidized boron 18 and the catalytic acting material 22 or with the oxidized boron 18 and the catalytic acting material 22 alone at least in a given temperature range. The invention can provide an improved exhaust gas after treatment resulting in a less failure-sensitive system.

Claims

C L A I M S
1. An exhaust gas after treatment system (10) comprising a catalytic converter arrangement (12), wherein the catalytic converter arrangement (12) is arranged in an exhaust gas path (14), wherein the catalytic converter arrangement (12) comprises:
- a first catalytic object (16) including as a catalytic acting material at least an oxidized boron compound (18) and
- at least a second catalytic object (20) including at least a catalytic acting material (22).
2. The exhaust gas after treatment system according to claim 1 , wherein the first catalytic object (16) comprises at least an A^Oa-compound.
3. The exhaust gas after treatment system according to claims 1 or 2, wherein the at least oxidized boron compound (18) is arranged on at least a carrier (24), in particular, the at least oxidized boron compound (18) is B2O3 arranged on a carrier (24) out of an AI2O3-compound
4. The exhaust gas after treatment system according to any one of the
preceding claims, wherein the catalytic acting material (22) of the at least second catalytic object (20) is at least one selected out of the group consisting of the 10th, 11th or 13th group of the periodic system of the chemical elements, in particular at least one selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd.
5. The exhaust gas after treatment system according to any one of the
preceding claims, wherein the catalytic acting material (22) of the at least second catalytic object (20) is arranged on at least a carrier (26), in particular, a carrier (26) out of an A^Oa-compound.
6. The exhaust gas after treatment system according to any one of the preceding claims, wherein the at least second catalytic object (20) comprises at least one compound selected out of the group consisting of Ag20/Al203, Ga2O3/AI203 or Ιη2θ3/ΑΙ2θ3.
7. The exhaust gas after treatment system according to any one of the
preceding claims, wherein an amount of catalytic acting material (18, 22) in the first and/or second catalytic object (16, 20) is between 0.01 and 5 percent by weight and/or an amount of oxidized catalytic acting material (18, 22) in the first and/or second catalytic object (16, 20) is between 0.05 and 15 percent by weight.
8. The exhaust gas after treatment system according to any one of the
preceding claims, wherein the catalytic converter arrangement (12) is arranged in the exhaust gas path (14) downstream of a combustion engine (28), which is an internal combustion engine (30).
9. The exhaust gas after treatment system according to any one of the
preceding claims, wherein a source (32) for a reducing agent (34) for NOx reduction is coupled to the exhaust gas path (14), wherein the reducing agent (34) comprises at least an oxygenated hydrocarbon, in particular at least an oxygenated hydrocarbon selected out of the group consisting of ethers, esters, alcohols, ketons and particularly, the reducing agent (34) is methanol or dimethyl ether.
10. The exhaust gas after treatment system according to any one of the
preceding claims, wherein the first catalytic object (16) and the at least second catalytic object (20) are arranged in series along the exhaust gas path (14), in particular the at least second catalytic object (20) is arranged downstream of the first catalytic object (16) with regard to the exhaust gas path (14).
1. The exhaust gas after treatment system according to any one of the preceding claims, wherein the first and/or the second catalytic object (16, 20) has a porous structure.
A method for treating an exhaust gas (22) in an exhaust gas after treatment system (10), comprising the steps:
- providing a first catalytic object (16),
- providing a second catalytic object (20) comprises at least a catalytic acting material (22),
- wherein the first catalytic object (16) comprises at least an oxidized boron compound (18).
The method according to claim 12, wherein a selection of a combination of the first catalytic object (16) and the at least second catalytic object (20) is provided, wherein the first catalytic object (16) is one selected out of the group consisting of oxidized boron compounds (18), wherein the at least second catalytic object (20) is one selected out of the group consisting of the 10th, 11th or 13th group of the periodic system of the chemical elements, in particular one selected out of the group consisting of B, Al, In, Ga, Ag, Au, Pt or Pd, so that a catalytic activity of a catalytic converter arrangement (12) is enhanced compared to the catalytic activity of said catalytic converter arrangement (12) without the presence of the combination of the first catalytic object (16) and of the at least second catalytic object (20) at least in a given temperature range.
A vehicle (36) with at least an exhaust gas after treatment system (10) according to any one of the preceding claims 1 to 11.
Method for preparing at least an exhaust gas after treatment system (10) according to any one of the claims 1 to 11.
PCT/SE2011/000169 2011-09-30 2011-09-30 Exhaust gas after treatment system comprising multiple catalytic objects WO2013048294A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016038192A1 (en) 2014-09-12 2016-03-17 Basf Se Method for preparing 2'-o-fucosyllactose
WO2017153452A1 (en) 2016-03-09 2017-09-14 Basf Se Method for preparing 2'-o-fucosyllactose

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Publication number Priority date Publication date Assignee Title
WO2016038192A1 (en) 2014-09-12 2016-03-17 Basf Se Method for preparing 2'-o-fucosyllactose
US11098075B2 (en) 2014-09-12 2021-08-24 Basf Se Method for preparing 2′-O-fucosyllactose
WO2017153452A1 (en) 2016-03-09 2017-09-14 Basf Se Method for preparing 2'-o-fucosyllactose

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