DE102009002182A1 - Filter useful for removing particulate component, preferably carbon black particle of exhaust gas, comprises a substrate that forms several gas channels and a washcoat coating comprising catalytic composition on inner surface of substrate - Google Patents

Abstract

The invention relates to a filter for removing particulate components from internal combustion engine exhaust gases, in particular a diesel particulate filter. The filter comprises a substrate forming a plurality of gas channels and a washcoat coating disposed on an interior surface of the substrate comprising a catalytic composition that oxidizes unburned or partially burned hydrocarbons and soot particles in the presence of oxygen without reacting nitrogen oxides catalyzes, wherein the catalytic composition (A) comprises at least one catalytic Tägeroxid and (B) at least one doping of a catalytically active, metallic and / or oxidic metal present. According to the invention, both the at least one catalytic carrier oxide and the at least one catalytically active metal are present individually or as a structure with one another in the form of nanoscale particles and / or a nanoscale porous structure. The catalytic composition can be prepared by an impregnation process, a sol-gel process or pulsed laser deposition (PLD). The filter according to the invention is characterized by a low activation temperature, which allows continuous regeneration in vehicle operation without additional heating measures.

Description

The The invention relates to a catalytic filter for removing particulate matter Components from combustion exhaust gases, in particular a diesel particulate filter for removal of soot-containing particles from engine combustion. The invention further provides various methods for Preparation of a catalytic composition for a Washcoat coating of such a filter.

The use of diesel particulate filters (DPF) in the exhaust passage of diesel vehicles for the separation of soot particles from diesel engine exhaust gases is known. In order to restore their storage capacity and counteract the increase in exhaust back pressure with increasing filter loading, DPF must be regenerated intermittently or continuously by combustion (oxidation) of the soot. For this purpose, the thermal regeneration, in which the soot is burned with the formation of carbon dioxide and water vapor, enforced as the most environmentally friendly method. The (uncatalyzed) combustion temperature of carbon black in the presence of oxygen is about 600 ° C. Since such exhaust gas temperatures are not reached frequently enough in the operation of a diesel vehicle, currently active regeneration measures are necessary. Thus, a post-injection of fuel is usually carried out during the power stroke of the engine, so that unburned hydrocarbons are exothermally burned on a DPF upstream oxidation catalyst and thus the exhaust gas temperature is increased. However, this approach leads to a fuel cut, additional technical effort and an oil dilution. In addition, the increased exhaust gas back pressure between two regenerations through the loaded filter also leads to an increased consumption of fuel. An alternative is continuously regenerating particulate filters, so-called CRT (Continuous Regeneration Trap), which cause a catalytic soot oxidation in the presence of nitrogen oxides NO _x , in particular of NO ₂ , as an oxidizing agent. For this purpose, the particulate filter has a catalytic loading with platinum, which oxidizes nitrogen monoxide NO contained in the exhaust gas to nitrogen dioxide NO ₂ , the latter in turn, in its capacity as a strong oxidizing agent, causes the combustion of soot. Since this method is thus dependent on the presence of high levels of nitrogen oxides in the diesel engine exhaust, its use for future automotive applications is limited, however, since in modern diesel engines, the necessary ratio of nitrogen oxides to soot will no longer be sufficient.

Thus, there are efforts to develop diesel particulate filters with catalytic coatings that cause oxidative soot combustion in the presence of oxygen, especially at relatively low nitrogen oxide levels in the exhaust gas. It is based on coating materials comprising a catalytic base material, which is typically cerium oxide (CeO ₂ ) or, more recently, zirconium oxide (ZrO ₂ ). These oxidic support materials, which themselves already have a catalytic activity, may optionally have dopants with further catalytic materials, in particular platinum group metals (PGM), transition metals, lanthanides, alkali metals and / or alkaline earth metals and their oxides. However, PGMs are expensive and their occurrence is limited. In addition, they have a relatively low activity and specificity. Alkali metals have the disadvantageous property of high mobility and leaching in the presence of water vapor; Both lead to a deactivation of the catalyst. In addition, the catalysts currently being developed for DPF do not yet have sufficient activity and long-term stability under thermal loads.

In high throughput syntheses, hundreds of binary, ternary, quaternary, and quaternary metal oxide catalysts free of alkali and noble metals were prepared by the sol-gel process by coprecipitation and then calcined at 400 ° C and their working temperature the oxidative combustion of synthetic carbon black under laboratory conditions. In this case, cobalt-based and in particular lanthanum and / or cerium-doped binary and ternary oxides have proven particularly suitable for reducing the combustion temperature. As particularly promising candidates were about Pb ₁₀ La ₅ Co ₈₅ O _x (which, however, due to the toxic lead content is to be regarded as problematic for automotive application) and Ce ₅₀ Co ₁₅ Mo ₃₅ O _x identified, which according to thermogravimetric measurements 50% of the artificial Oxidize soot at temperatures of 433 or 451 ° C. ( NE Olong et al. "HT-search for alkaline and noble-metal-free mixed oxide catalysts for soot oxidation" Catalysis Today 137 (2008), 110-118 ). Although the use of catalytic diesel particulate filters is discussed, all experiments were conducted under laboratory conditions only.

In a similar approach, the catalytic base oxides CoO _x , CeO _x and MnO _{x were} doped with 50 different metals and their combinations to also produce binary oxides using the sol-gel process. The most promising candidates among the tested for temperature reduction of soot combustion were the binary oxides Cu ₃ Cs ₂₀ Co ₇₇ , Cu ₁₀ Cs ₂₀ Co ₇₀ and Ag ₁₀ Cs ₂₀ Co ₇₀ ( NE Olong et al. "A combinatorial approach to the discovery of low temperature soot oxidation catalysts" Applied Catalysis B: Environmental 74 (2007), 19-25 ). The disadvantageous properties of the alkali metal catalysts have already been mentioned above.

The currently proven catalytic diesel particulate filter have the Disadvantage of the need for a high exhaust gas temperature to the catalytic assisted thermal regeneration in normal operation often can not be achieved. Although it is possible with the above, the required combustion temperature in the laboratory model tested DPF significantly lower from about 600 ° C (without catalyst), however, further degradation is desirable.

Of the present invention is based on the object, in particular to provide for diesel engines suitable filter, the in the presence of oxygen in combustion engine exhaust gases and especially at relatively low levels of nitrogen oxide of the Exhaust gas oxidation of unburned or partially burned Hydrocarbons and soot particles already at relative catalyzes low exhaust gas temperatures. It should also at least for preparing a catalytic composition for such a diesel particulate filter suitable method shown become.

These Tasks are with the features of the independent claims solved. Further preferred embodiments of the invention arise from the rest, in the dependent claims mentioned features.

In its first aspect, the invention relates to a filter for removing particulate constituents from combustion exhaust gases, in particular from engine combustion. The filter comprises a substrate, which forms a plurality of gas channels of any design, which can be traversed by an exhaust gas flow. Usually, these gas channels are interrupted by porous gas-permeable barrier walls, which retain the exhaust particles. On an inner surface of the substrate, ie in particular on the walls of the gas channels and / or the barrier walls, a washcoat (or simply: washcoat) is applied comprising a catalytic composition, which in the presence of oxygen but - unlike the Initially discussed CRT concepts - without reactive participation of nitrogen oxides NO _x (in particular NO and N ₂ O) catalyzes an oxidation of unburned or partially burned hydrocarbons and soot particles. The catalytic composition comprises, as a first component, at least one catalytic carrier oxide and, as a second component, a doping of at least one catalytically active metal, which is present in metallic, oxidic or mixed forms. According to the invention, the at least one catalytic carrier oxide as well as the at least one catalytically active metal (also referred to as doping metal) in each case present individually or as a structure in the form of nanoscale particles and / or a nanoscale porous structure.

there is in the context of the present invention by the term "carrier oxide" in Differentiation to the possibly also oxide present Doping metal that component with the predominant Understood mole fraction within the catalytic composition. In particular, the metal of the carrier oxide (ie without Oxygen) at least 50 mol% based on the sum of all Metals of the catalytic composition. In general amounts the mole fraction of the carrier oxide metal is much more, in particular at least 60 mol%, preferably at least 75 mol% based on the total amount of metal. Furthermore, it is present under the term "nanoscale porous structure" a Secondary structure understood in the single nanoscale Particles of the respective material (primary structure) in conglomerates but without completely merging with each other. Thus, for example, the substantially spherical Particles to more or less ordered two- or three-dimensional Grid structures are joined together. This means, that the mean particle diameter of the secondary structure constituent particles the nanoscale dimension of the porous Structure determined.

By doing in the catalytic composition of the washcoat according to the present invention not only the catalytically active metal in a nanoscale dimension, but also the catalytic carrier oxide, will have a very high specific surface of the whole obtained catalytic material, which makes it surprising succeeds, necessary for the soot combustion Temperature significantly lower than the prior art. In particular, it is by the invention Construction succeeded, the combustion of soot already at temperatures of about 400 ° C or even below it. Here, combustion temperature is understood to mean the temperature burned at the 50% of the existing particulate mass are.

Depending on the chosen production method of the catalytic composition, different structural arrangements of the catalytically active metal and the catalytic carrier oxide relative to each other can be realized. In particular, the present in this embodiment, preferably particulate ka talytically active metal on the surface of the catalytic carrier oxide, which may be present here particulate or in the form of a nanoscale porous structure, be arranged. This structure can be obtained, for example, with the impregnation method described below or the laser deposition. In an alternative embodiment, the nanoscale catalytically active metal may be wholly or partially enclosed by the carrier oxide. This structure can be represented by the sol-gel method shown below. Also, mixed structures between the two mentioned embodiments are conceivable.

In a preferred embodiment, the filter according to the invention is a diesel particulate filter (DPF) for removing diesel engine particulate constituents of the exhaust gas, in particular of soot particles. The low combustion temperatures of the DPF make it possible to ensure quasi-continuous regeneration of the filter even at typical temperatures of diesel engine exhaust gases. Since practically no high filter loading with soot during vehicle operation occurs, the DPF can be dimensioned comparatively small, whereby material and weight (and thereby fuel) can be saved. Since the DPF according to the invention catalyzes the oxidation of soot particles without the involvement of NO or other nitrogen oxides, no nitrogen oxides in the exhaust gas are necessary for its regeneration. Thus, the regeneration of the DPF can also take place in the absence of NO _x or at relatively low NO _x levels of modern diesel engines.

in the Within the scope of the present invention, the term "nanoscale" is used in principle understood a dimension that does not exceed 250 nm. In this context, it is preferably provided that the nanoscale Particles and / or the nanoscale porous structure of the catalytic Trägeroxids a mean particle diameter or a average structure dimension in the range of 1 to 200 nm, in particular of 2 to 100 nm. Preferably, here are average particle diameter or maintained average structural dimensions of 5 to 50 nm. Regarding The catalytic metal doping tends to be even lower Dimensions of advantage. In particular, the catalytic metal is located with a mean particle diameter or a mean structure dimension in the range from 1 to 50 nm, in particular from 1 to 20 nm. In a particularly preferred embodiment are particle diameter or structure dimensions in the range of 2 to 10 nm implemented. As with increasing minimization of particle and structure sizes an increasing proportion of the atoms are on the exposed surface The composition stands with smaller structures relatively more active material available for catalysis. This effect explains the lowering of the necessary combustion temperature the filter according to the invention as well as his high activity.

From a material point of view, the at least one catalytic carrier oxide in an advantageous embodiment of the invention is selected from the group consisting of CeO ₂ , ZrO ₂ , TiO ₂ , Fe ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO and V ₂ O _{5 are} selected, of which CeO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , Co ₃ O ₄ and ZrO _{2 are} particularly preferred. In principle, all of these oxides, taken by itself, have a good catalytic activity with respect to the oxidation of unburned hydrocarbons and of carbon black, with the temperature reduction of the catalytic working range, which is aimed at within the scope of the present invention, not yet being achieved by these materials alone. For this reason, the catalytic composition contains the doping of the catalytically active metal, which in particular from the group consisting of Ag, Ca, Ce, Co, Cr, Cu, Cs, Fe, In, Ir, La, Mg, Mn, Mo, Nb , Ni, Pd, Pr, Pt, Re, Rh, Sm, Sr, Ti, V, W, Zn and Zr, as well as their mixtures and alloys with each other. The catalytically active metals may be present in the form of their oxides or elementally (ie in the oxidation state zero). Likewise, binary, ternary, quaternary or even quintary metal oxides may be realized and / or alloys of two or more of said elements in metallic form. Due to the limited availability of the platinum group metals (PGM) and the associated high costs is provided in a preferred embodiment that the at least one catalytically active metal is selected from the aforementioned group, but excluding the platinum group metals Pd, Pt and Rh proved that many of the transition metals mentioned have a higher specificity than the PGM with respect to the catalyzed soot oxidation. The partial or preferably complete substitution of PGM by metals of higher specific catalytic activity allows a further reduction of the filter dimension and thus further weight and resource savings. Additionally or alternatively, the selection of catalytic metal doping may also be made excluding the alkali and alkaline earth metals Ca, Cs, Mg and Sr which, due to their high mobility and ease of leaching from the catalyst in the presence of water vapor, may lead to premature loss of activity of the DPF ,

It is difficult to give general information on preferred combinations of catalytic carrier oxide and catalytic metal doping, since one and the same carrier oxide works well with one doping and is less active with another; latter doping, however, on a different carrier oxide may have an unusual high activity. As an advantageous combination with regard to low combustion temperatures, for example, the carrier oxide Fe ₂ O ₃ with dopings of Cr (or Cr ₂ O ₃ ) and optionally further dopings has been found, in particular with Cu (or CuO) and / or Co (or CO ₃ O ₄ ). Particularly preferred catalytic compositions have, for example, the (theoretical) empirical formula Fe ₉₄ Cr ₃ Cu ₃ O _x and Fe ₉₄ Cr ₃ Co ₃ O _x , the oxygen content x resulting from the oxidation states of the metals. Furthermore, a doping of the carrier oxide Co ₃ O ₄ with Cr ₂ O ₃ and optionally further doping and vice versa of the carrier oxide Cr ₂ O ₃ with Co ₃ O ₄ and optionally further doping has been found to be particularly active, in which case the theoretical composition Co _{0, 75} Cr _0.25 O _{x is} particularly preferred. Further advantageous specific compositions of the invention may be taken from the embodiments.

Based on the total amount of substance in the catalytic composition metals present (i.e., the sum of carrier oxide (s) and doping / ene-derived metals, without oxygen) has that at least a catalytically active metal preferably a mole fraction of 0.01-50 mol%, especially from 0.1 to 10 mol%, preferably from 0.1 to 3 mol%. Besides, it has to be advantageous proven when the single catalytically active metal at most 5 mol%, in particular at most 3 mol% based on the sum of the metals of the catalytic composition is present is (in the case of Ir) at most 1 mol%, especially at most 0.5 mol%).

The catalytic composition of Trägeroxid / en and catalytic / n doping / s is part of a known washcoat. It is understood that the washcoat coating in addition to the catalytic composition of the invention may usually contain other components. In particular, conventional washcoats comprise, as is known, surface-enlarging, in particular ceramic, materials, for example Al ₂ O ₃ or the like. Such materials themselves have no catalytic activity, but serve only the surface enlargement and the immobilization of the actual catalytic materials. In addition, the washcoat may contain binders, additives and other components.

A particularly preferred embodiment of the invention provides the washcoat coating further comprises a sintering inhibiting component contains. While in the prior art to this Purpose added to the platinum as the actual catalyst palladium are in the context of the present invention, PGM-free formulations preferred, in particular combinations of different transition metal components.

For the substrate of the filter conventional structures are suitable, for example metallic structures, but preferably ceramic bodies, in particular of silicon carbide (SiC), cordierite, mullite, aluminum titanate (AlTiO _x ) and others.

The catalytic composition according to the invention, for producing a washcoat for a filter, comprising (A) at least one in the form of nanoscale particles and / or a nanoscale Size structure of catalytic carrier oxide and (B) at least one doping of a nanoscale particle and / or a nanoscale porous structure present, catalytic active metal, can be prepared by different methods which are further objects of the present invention represent.

According to a first preferred variant, the preparation of the catalytic composition is carried out with the impregnation method. For this purpose, the catalytic carrier oxide, which is already present in the form of nanoscale particles and / or a nanoscale porous structure, is brought into contact with a solution of a salt of the at least one catalytic metal, with an impregnation of the (undissolved) carrier oxide with the metal salt. If the catalytic carrier oxide is to be multiply doped with different catalytic metals, the solution may contain a mixture of the various metal salts or the carrier oxide may be brought into contact successively with the individual solutions of the respective metal salts. After impregnation, the impregnated carrier oxide thus obtained is dried, the solvent used being removed, and a calcination to form the at least one catalytically active, metallic and / or oxidic metal in its nanoscale form. The calcination is preferably carried out at temperatures in the range of 200-600 ° C, in particular from 300-500 ° C. If the catalytically active metal is predominantly oxidic, the calcination can take place in the presence of oxygen. If, however, the elemental metal is preferred, the calcination is preferably carried out in a reductive atmosphere, for example in the presence of hydrogen H ₂ . In particular, the active elements Ca, Cr, Cs, Fe, In, La, Mg, Mn, Mo, Re, Sr, V and W can be deposited in a simple manner with the impregnation method in the desired nanoscale structure. Product of impregnation tion method is a powder containing nanoscale particles and / or a nanoscale porous structure of the at least one catalytic carrier oxide and on the surface of which immobilized nanoscale particles of at least one catalytic metal.

Corresponding a second method, the preparation of the invention catalytic composition by so-called laser deposition. In this case, a target, which is the at least one catalytically active Contains metal in its metallic and / or oxidic form, with an energy-rich, in particular pulsed laser radiation bombarded so that nanoscale particles of the metal in a submerged Negative pressure chamber to be ablated (laser ablation). The particles are then applied to the at least one catalytic carrier oxide deposited, already in the form of nanoscale particles and / or a nanoscale porous structure is present. Should one Multiple doping of the carrier oxides, the target can a mixture or alloy of the two or more catalytically active Contain metals. Alternatively, separate targets can be used be removed simultaneously by parallel laser bombardment and in this way a co-deposition of the metal particles on the carrier oxide respectively. In a further modification is also conceivable, different Targets of different metals successively laser ablation and thus successively multiply doping the carrier oxides. Advantage of the method of laser deposition is that by choice the laser energy and / or by choosing the negative pressure in the chamber both the mean particle diameter of the metal and the Porosity of the deposited particle clusters themselves can be set in a wide bandwidth.

In both of the aforementioned methods, the impregnation method as well as the (pulsed) laser deposition process, are already nanoscale, in particular nanoparticulate carrier oxides used. These are partly commercially available or can be made with pyrogenic processes.

In a third alternative embodiment, the production takes place the catalytic composition of the invention in the sol-gel process. This will be a sol of a suitable precursor the at least one catalytic carrier oxide and a suitable precursor of the at least one catalytic metal produced. Suitable precursors are, for example, alcoholates the respective metals (for example, ethylates, propylates or Butylates), carboxylates (e.g., acetates), nitrates, and others. The solvents are mainly water and alcoholic Solvent or mixtures thereof in question. In the production of the Sols undergo hydrolysis of the precursor compounds Cleavage of corresponding groups, for example alcohol molecules and their substitution by OH groups on the precursor compound. Subsequent spontaneous condensation reactions of the resulting hydroxides form oligomers, from which finally Form particles and particle aggregates (secondary particles), resulting in an increase in viscosity and eventually leads to gelation. That way, the sol gets into Gel transferred. Subsequently, the thus obtained gel to obtain a powder. The Drying can be done for example by spray drying. Finally, the powder is calcined, as already in Connection with the impregnation described has been. The sol-gel process is preferred for the active elements Fe, Co, Cr, Cu, Ce, Ti and Zr used. As with the sol-gel method both nanoscale components of the catalytic composition can be generated in parallel in a joint process in situ the structure of the product is slightly different from those of the aforementioned methods differ. The product here is a powder, the nanoscale particles and / or a nanoscale porous structure of at least contains a catalytic carrier oxide and the nanoscale catalytic doping metal, partly on the surface of the Trägeroxidstrukturen immobilized is present and can be partially enclosed by this.

Each of the catalytic compositions prepared by one of said processes is a powder which is incorporated into a typically aqueous washcoat solution which may contain other ingredients such as a ceramic surface enlarging material such as Al ₂ O ₃ . The coating of the filter substrate with the washcoat solution is carried out in a known manner, for example by dipping the substrate in the solution and subsequent drying, optionally followed by a high-temperature process. Alternatively, the filter substrate can also initially be coated only with the washcoat and then provided with the catalytic composition according to the invention, for example by impregnation.

Due to the high specific catalytic activity of the catalytic coating of the diesel particulate filter according to the invention, in particular in a partial or complete substitution of the platinum group metals by said materials, advantageously the dimensions of the DPF can be reduced, thereby saving not only resources, but also weight and thus fuel can be. In addition, due to the high activity and starting at low temperatures operating temperature window, a virtually continuous regeneration of the filter during vehicle operation on be maintained. In this way, an increase in the filter load of soot between two regeneration intervals according to the prior art is avoided, whereby a temporary increase in the exhaust backpressure and the associated fuel consumption is counteracted.

The Invention will be described below in embodiments the accompanying drawings explained. Show it:

1 Activation temperatures of various dual-doped CeO ₂ and Fe ₂ O ₃ -based catalytic compositions;

2 Activation temperatures of various catalytic compositions according to the invention;

3 Construction of an apparatus for excimer laser deposition; and

4 TEM and SEM images of deposited on a carrier oxide Pd particles and derived particle diameter.

• (A) zumindest ein katalytisches Trägeroxid, das in Form nanoskaliger Partikel und/oder einer nanoskaligen porösen Struktur vorliegt, sowie
• (B) zumindest eine Dotierung eines katalytisch aktiven, metallisch und/oder oxidisch vorliegenden Metalls, das in Form nanoskaliger Partikel und/oder einer nanoskaligen porösen Struktur vorliegt.

The catalytic composition according to the invention for use in a washcoat coating for a filter designed in particular as a diesel particle filter

• (A) at least one catalytic carrier oxide, which is in the form of nanoscale particles and / or a nanoscale porous structure, as well as
• (B) at least one doping of a catalytically active, metallic and / or oxidic metal present in the form of nanoscale particles and / or a nanoscale porous structure.

Hereinafter, the preparation of such catalytic compositions will be explained by various methods in embodiments. It was the in NE Olong et al. "HT-search for alkaline and noble-metal-free mixed oxide catalysts for soot oxidation" Catalysis Today 137 (2008), 110-118 as in NE Olong et al. "Applied combinatorial approach to the discovery of low temperature soot oxidation catalysts" Applied Catalysis B: Environmental 74 (2007), 19-25 described strategy for screening for suitable compositions and their successive optimization applied. For this purpose, starting from relatively simple systems, in which each composition contains only a single carrier oxide and only two doping metals (or doping metal oxides), in each optimization stage (generation) the candidates most active with respect to their working temperature are selected and their composition is further doped and / or further Carrier oxides and / or further optimized by varying the atomic proportions of the individual components (so-called composition spread).

Example 1: Preparation of catalytic Compositions in the sol-gel process

in the Within the scope of the present invention, the sol-gel process was used for Preparation of the catalytic according to the invention Composition used in two variants, the ethylene glycol route or the propionic acid route.

Example 1.1: Sol-gel process (ethylene glycol route)

In the molar ratio 20: 40: 4: 1 of EG: H ₂ O: HNO ₃ : metal, the samples were pipetted together. According to the illustrated reaction scheme, this leads to oxidation and polycondensation of the ethylene glycol (EG) by the nitric acid and subsequently to a complexation of the metal cations M ^{n +} . In the reaction scheme, the abbreviation designates both metal cations of the metal / metals (= carrier metal) determined as carrier oxide and metal cations of the metal / metals (= dopant metal) determined as dopants. Both support metal and dopant metal (s) were used in the form of suitable salts.

The Samples were oven dried according to the following temperature program and calcined. First, the samples were starting with Room temperature to 80 ° C with a heating rate of 0.1 ° C / min heated. The temperature of 80 ° C was for Held for 12 hours, before at 0.1 ° C / min to 105 ° C was heated up. The temperature of 105 ° C was for Held constant for 60 hours and then at 0.2 ° C to a Temperature of 400 ° C increases, which subsequently was held for 5 hours. After that, it was brought to room temperature cooled at a rate of -1 ° C / min.

Example 1.2 Sol-gel Method (Propionic Acid Route)

M

= Trägermetalle (1–2) + Dotiermetalle (2) (jeweils in Form eines geeigneten Salzes)

KB

= Komplexbildner (4-Hydroxy-4-methyl-2-pentanon)

S

= Lösungsmittel (Methanol)

PS

= Propionsäure

A molar ratio of M: KB: S: PS of 1: 3: 29: 0.02 was used

M

= Carrier metals (1-2) + doping metals (2) (each in the form of a suitable salt)

KB

= Complexing agent (4-hydroxy-4-methyl-2-pentanone)

S

= Solvent (methanol)

PS

= Propionic acid

After pipetting together the solutions in glass vessels, these were placed open at 40 ° C in a drying oven and left there for about 5-8 days, until gelation occurred. Thereafter, further drying and calcination in a programmable furnace followed the following temperature programs summarized in Table 1. After drying according to program no. 1, the obtained xerogels were finely ground and then treated according to temperature program no. Table 1: No. T1 [° C] Heating rate1 [° C / min] T2 [° C] Duration1 [min] Heating rate2 [° C / min] T3 [° C] Duration2 [min] Heating rate3 [° C / min] T4 [° C] 1 20 0.2 65 300 0.2 250 300 1 20 2 20 0.2 400 300 3.0 20 - - -

Thermoanalytical measurements:

The samples prepared by the sol-gel method were further thermoanalytically analyzed at the University of the Saarland (Mettler Toledo TGA / DSC1, large furnace). The following gas mixture was selected as the exhaust gas model: 8% O ₂ , 250 ppm NO, 350 ppm CO, 50 ppm HC in N ₂ .

In the first approach, the carrier oxides CeO ₂ , ZrO ₂ and Fe ₂ O _{3 were} doped twice, the dopants used being Co, Cu, La, W, Cr, Ir, Mn, Nb, Re, In, Mo, V and Fe. The doping metals were used in each case 3 mol% (exception Ir: 0.5 mol%). For the cerium and zirconium carrier oxides, the propionic acid route (Example 1.2) and for the iron oxide the ethylene glycol route (Example 1.1) were chosen. The results of the thermoanalytical investigations of these ternary oxides of the first generation are summarized in Table 2. In each case, the element specified in the first position refers to the metal of the carrier oxide and the two following elements to the doping metals. The indications T20, T50 and T75 indicate those temperatures at which 20%, 50% and 75%, respectively, of the model black is burned (determined by mass loss of carbon black above 150 ° C). The activities of the best 14 compositions of this generation are in 1 shown. Table 2: Ternary catalytic compositions prepared by the sol-gel method materials T20 T50 T75 materials T20 T50 T75 Ce, Co, Cu 448 495 520 Ce, W, Nb 495 541 566 Ce, Co, Cr 487 548 579 Ce, W, Cr 465 521 548 Ce, Co, Ir 486 542 568 Ce, W, In 511 555 580 Ce, Co, Re 485 520 536 Ce, W, Fe 449 503 530 Ce, Co, In 482 538 566 Ce, W, Mo 462 514 539 Ce, Co, Fe 578 620 641 Ce, Cr, Ir 471 524 552 Ce, Co, Mo 495 553 581 Ce, Cr, Mn 481 536 561 Ce, Cu, Cr 472 502 517 Ce, Cr, Zn 485 542 572 Ce, Cu, Ir 470 509 525 Ce, Cr, Nb 477 515 533 Ce, Cu, Mn 506 540 553 Ce, Cr, In 474 527 554 Ce, Cu, Fe 444 502 532 Ce, Cr, Fe 470 522 550 Ce, Cu, Mo 476 534 565 Ce, Cr, Mo 478 529 556 Ce, La, Mn 448 504 533 Ce, Zn, Mo 487 535 561 Ce, La, Zn 466 521 548 Ce, Fe, Mo 453 503 528 Ce, La, Nb 471 515 538 Zr, Co, Cr 570 610 631 Ce, La, Re 456 509 536 Zr, Co, Fe 600 644 667 Ce, La, In 525 569 593 Zr, La, Mo 597 642 665 Ce, La, Fe, 451 502 527 Zr, W, Mo 591 624 624 Ce, La, Mo 475 525 551 Zr, Cr, Ir 574 612 630

The most active candidates of the first generation were varied by adding a further carrier oxide (in the same molar ranges as the first) and other doping metals. The results of the thermoanalytical investigations of these ternary, quaternary and quintary second generation oxides are summarized in Table 3. In each case, the two elements mentioned first refer to the metals of the carrier oxides (in the case of the ternary only the first element) and all the following elements to the doping metals. The ternary oxides Fe ₉₄ Cu ₃ Cr ₃ O _x and Fe ₉₄ Co ₃ Cr ₃ O _x (the indices given in the empirical formulas correspond to the theoretical compositions according to the approach, whereby the non-specific oxygen content x results from the (unknown) oxidation states of the metals ) of the second generation samples tested had the lowest activation temperature of T50 = 465 ° C and 467 ° C, respectively. Table 3: 2nd generation catalytic compositions prepared by the sol-gel method material T20 T50 T75 material T20 T50 T75 Fe, Cu, Cr 421 465 497 Fe, Ce, Cu, Ir 465 518 545 Fe, Co, Cr 419 467 502 Fe, Ce, Cr, V 467 518 542 Fe, Ce, Cu, Re 442 479 501 Fe, Ce, Zr, Cu, Mn 469 519 543 Fe, Ce, Re, Ir 444 481 498 Fe, Ce, Cu, Mo 470 520 546 Fe, Zr, Cr, V 431 482 514 Fe, Ce, Cu, Cr 474 522 547 Fe, La, Re 462 485 498 Fe, Zr, La, Ir 459 522 552 Fe, Cu, Ir 435 485 518 Fe, Ce, Zr, Cu, Ir 472 522 547 Fe, Zr, Co, Cr 440 488 515 Fe, Cr, Ir 462 523 552 Fe, Zr, Cu, Re 467 498 510 Fe, Ce, Zr, Mo, Mn 477 523 547 Fe, Ce, Cu, Zn 449 498 524 Fe, Co, Cu 466 524 551 Fe, Ce, Co, Cu 447 499 524 Fe, Co, Ir 469 524 552 Fe, Ce, Co, Cr 448 501 528 Fe, Ce, Zn, Ir 472 524 549 Fe, Ce, Mn, Ir 450 505 531 Fe, Ce, Mn, V 468 527 555 Fe, Ce, Co, Mo 448 505 534 Fe, Ce, In, Ir 470 527 558 Fe, Ce, Zr, Cr, Ir 459 506 528 Fe, Zr, Zn, Ir 468 528 557 Fe, Ce, Cr, Mn 457 506 532 Fe, Cu, Zn 473 529 556 Fe, Ce, Cr, Ir 459 507 531 Fe, Ce, Re, Mo 478 530 559 Fe, Ce, Mn, In 453 508 535 Fe, Co, Mn 468 531 561 Fe, Ce, Co, In 450 508 537 Fe, Co, Mo 477 532 560 Fe, Ce, Mn, Zn 458 509 537 Fe, Co, In 476 533 562 Fe, Ce, Co, Zn 457 510 538 Fe, Ce, Co, V 474 534 563 Fe, Ce, Cr, Mo 465 511 534 Fe, Ce, Cu, V 474 536 566 Fe, Ce, Zr, Co, Cr 465 512 536 Fe, Ce, Co, V 471 538 569 Fe, Ce, Zr, Cu, Ir 471 515 536 Fe, Ce, Co, Ir 480 538 568 Fe, Ce, Zr, Co, Cu 463 515 541 Fe, Cu, Mo 484 539 566 Fe, Ce, La, Zn 463 515 542 Fe, Ce, V, Ir 481 539 566 Fe, Ce, Zr, Co, Mo 465 515 540 Fe, Ce, Mo, V 477 540 570 Fe, Zr, Cr, In 469 517 540 Fe, Ce, Zr, Cr, V 491 546 573 Fe, Zr, Cr, La 467 517 544 Fe, Ce, Zr, Co, V 485 548 577 Fe, Ce, Zr, Co, Ir 463 517 543 Fe, Zr, La, In 508 559 586

Characterization:

The two most active samples Fe ₉₄ Cu ₃ Cr ₃ O _x and Fe ₉₄ Co ₃ Cr ₃ O _x were characterized by XRF (X-ray fluorescence analysis), XPS and nitrogen adsorption measurements. From the RFA spectra (standardless analysis, fundamental parameter model) the following actual compositions were obtained for these ternary oxides: Fe ₉₄ Cr ₃ Cu ₃ O _x : Fe 94.60 mol%; Cr 2.33 mol%; Cu 4.63 mol% Fe ₉₄ Cr ₃ Co ₃ O _x : Fe 93.04 mol%; Cr 2.12 mol%; Cu 3.28 mol%

From the nitrogen adsorption measurements, pore structure data were obtained, which are summarized in Table 4. Table 4: Fe ₉₄ Cr ₃ Cu ₃ O _x Fe ₉₄ Cr ₃ CoO _x Cr _0.2 Co _0.8 isothermal Pore volume (p / p ° = 0.95) [cm ³ / g] 0.2826 0.2771 0.2526 Surface BET Monolayers volume [cm ³ / g] 29936 26465 8.4442 Monolayers amount [mmol / g] 1.3356 1.1807 0.3767 BET surface area [m ² / g] 130.3 115.19 36754 mesopores Mean pore radius [nm] 4.3817 4.8218 7.3939 Maximum pore radius [nm] 3.2687 3.5095 5.9937 Cumulative pore volume [cm ³ / g] 0.2666 0.3177 0.4873 Cumulative pore area [m ² / g] 136.68 142.65 146.63 micropores Mean pore radius [nm] 0.4744 0.4876 13945 Maximum pore radius [nm] 12:57 0.6114 1.2633 Cumulative pore volume [cm ³ / g] 0067 0.0581 0.0189 Cumulative pore area [m ² / g] 138.3 104.84 38729

Starting from Fe ₉₄ Cr ₃ Co ₃ O _x and Fe ₉₄ Cr ₃ Cu ₃ O _x , a quaternary composition spread was set up with Fe, Cr, Co and Cu, in which the molar compositions were varied. The results are shown in Table 5. Table 5 also shows the results of a composition spread of the binary CrCo oxide, which was determined in a parallel screening. The most active area of the quaternary composition spread was in the range of relatively high chromium and high cobalt concentrations. Particularly active compositions in the range Fe _a Cr _b Co _c Cu _d O _x with a = 0.1-0; b = 1 - 0; c = 1 - 0; d = 0.1-0 and a + b + c + d = 1. It can be seen that the activation temperature T50 of the catalytic compositions developed in the third generation was lowered significantly compared to the previous generation and many of the mixed oxides burn even at temperatures around 400 ° C. or even lower 50% of the carbon black used. This will be special 2 clearly where the activities of the best 10 compositions of this generation are shown (compared to the two best of the first generation). These compositions are preferably used in DPF. Table 5: 2nd generation catalytic compositions prepared by the sol-gel method composition T20 T50 T75 composition T20 T50 T75 Cr0,25Co0,75 331 372 400 Cr0,4Co0,6 367 407 435 Fe0,05Cr0,15Co0,8 332 372 401 Fe0,1Cr0,4Co0,5 369 409 435 Fe0,05Cr0,2Co0,75 333 373 402 Fe0,1Cr0,4Cu0,1Co0,4 378 418 444 Cr0,15Co0,85 333 375 406 Fe0,1Cr0,3Cu0,1Co0,5 376 418 445 Cr0,35Co0,65 338 378 402 Fe0,15Cr0,05Co0,8 359 419 466 Cr0,65Co0,35 340 380 403 Fe0,2Cr0,7Co0,1 388 428 453 Fe0,05Cr0,6Co0,3Cu0,05 340 381 404 Fe0,2Cr0,55Co0,25 385 428 450 Cr0,75Co0,25 344 382 403 Fe0,15Cr0,35Co0,4Cu0,1 382 429 457 Fe0,05Cr0,15Co0,75Cu0,05 341 383 414 Fe0,1Cr0,3Co0,5Cu0,1 390 439 467 Cr0,8Co0,2 344 384 409 Fe0,05Cr0,8Co0,1Cu0,05 414 458 480 Cr0,5Co0,4Cu0,1 344 385 408 Fe0,1Cr0,7Co0,1Cu0,1 415 458 480 Fe0,1Cr0,6Co0,3 343 385 408 Fe0,05Co0,9Cu0,05 440 506 533 Fe0,05Cr0,35Co0,55Cu0,05 346 386 409 Fe0,1Cu0,2Co0,7 440 509 539 Cr0,55Co0,45 344 386 409 Fe0,1Cu0,1Co0,8 442 511 541 Fe0,05Cr0,35Co0,5Cu0,1 348 388 412 Fe0,4Co0,6 436 514 548 Cr0,75Co0,2Cu0,05 347 388 414 Fe0,5, Co0,5 444 516 549 Fe0,05Cr0,4Co0,5Cu0,05 348 389 412 Fe0,1Co0,9 449 519 549 Fe0,05Cr0,4Co0,45Cu0,1 349 389 412 Fe0,5Cu0,1Co0,4 450 520 552 Cr0,15Co0,8Cu0,05 344 389 420 Fe0,3Co0,7 449 520 553 Cr0,2Co0,75Cu0,05 346 393 425 Fe0,3Cu0,2Co0,5 452 523 555 Cr0,2Co0,8 362 400 430 Fe0,4Cu0,2Co0,4 452 524 555 Cr0,5Co0,5 365 405 432 Fe0,3Cu0,3Co0,4 459 525 555 Cr0,35Co0,55Cu0,1 358 405 437 Fe0,4Cu0,1Co0,5 457 528 559 Fe0,1Cr0,7Co0,1 370 406 428 Fe0,3Cu0,1Co0,6 461 529 561 Fe0,1Cr0,3Co0,6 367 407 435 Fe0,9Cu0,1 486 548 576

Example 2: Preparation of catalytic Compositions in the impregnation process

It were highly porous catalytic carrier oxides with very large specific surfaces with doping metals impregnated. These were suspensions of solid carrier oxides in a surplus of solutions of suitable Salts produced the different doping metals. To one better penetration of the catalytically active metals into the carrier pores to achieve a vacuum was applied. Subsequently, the Samples dried for 5 h, giving a homogeneous distribution the doping metals has been reached. The dried suspensions were then calcined in three steps: heating to 400 ° C at 1 ° C / min, hold at 400 ° C for 2 h and cooled to room temperature at 3 ° C / min.

For the preparation of the first-generation catalytic compositions, various carrier oxides having one alkali metal or one alkaline earth metal and two redox-active transition metals according to Table 6 were doped in succession. Table 6: Carrier oxides (91 mol%) (Degussa-Evonik) TiO ₂ , CeO ₂ (AdNano Ceria), ZrO ₂ (P25 Titania) doping metals: Alkali and alkaline earth metals (3 mol%) K, Ca, Ba, Rb, Cs, Sr 2 transition metals (3 mol% each) Fe, Cu, Ni, Cr, W, Ta, Nb, Mo, Mn, Re, V, Co

Based on activity measurements with ecIRT, the best candidates of the first generation were selected and further doping metals (Na, Mg, In, Zn, Cd, B, Ga, Ge, Sn, Sb, Bi, Se, Te, La, Rh, Pt, Pd , Ir, Ag, Au) to obtain second-generation catalytic compositions (88 mole% carrier oxide, 3 mole% each of dopant metals). The thermogravimetric results of selected compositions are shown in Table 7. (For notation: for example CeO ₂ Sr ₍₃₎ W ₍₃₎ Cr ₍₃₎ Pt ₍₃₎ corresponds to Ce ₈₈ K ₃ Fe ₃ Cr ₃ Pt ₃ O _x = formal composition). Table 7: catalyst material T20 T50 T80 ZrO ₂ Cs ₃ Fe ₃ Mo ₃ 404 445 428 TiO ₂ Ca ₃ V ₃ Re ₃ 419 454 479 CeO ₂ Sr ₃ W ₃ Cr ₃ Pt ₃ 425 460 485 CeO ₂ Ba ₃ V ₃ Cr ₃ Pt ₃ 433 471 496

Example 3: Preparation of catalytic Compositions by means of pulsed laser deposition (PLD)

3 shows schematically the structure of the apparatus which was used for pulsed laser deposition. In a vacuum chamber, in the presence of a buffer gas (eg He in the pressure range between 10 and 100 mbar), a rotating monometallic or alloyed metal body (target) was irradiated with an intense pulsed laser (λ = 248 nm). Hereby, the metal is atomized and generates a directional plasma flag, which is directed to the located below the target on a rotating plate oxide support material. CeO ₂ (see Table 8), ZrO ₂ , TiO ₂ , Fe ₂ O ₃ and SiO _{2 were} used as support materials. As in 4 , left side exemplified by transmission electron microscopy (TEM) showed, using a Pd target at a He-buffer gas pressure of 10 mbar Pd-doped metal particles having a size distribution of 5.3 to 6.3 nm and a average particle diameter of 5.8 nm are deposited. Furthermore, it was shown by scanning tunneling microscopy (STM) ( 4 , right side) that by varying the buffer gas pressure, the particle size distribution of the dopant metal particles deposited on the carrier material from the plasma lane can be adjusted in a targeted manner in the range from 6.5 to 11 nm. As doping metal target materials, Pt, Pd, Rh, Pt / Rh, Pt / Pd, Fe, Cu, Mo, Nb, V, W, Cr were used. As a buffer gas He, H ₂ , and O _{2 was} used. Table 8: Thermogravimetric results for soot burn-off of selected PLD-produced CeO ₂ -supported catalyst formulations. support material T20 [° C] T50 [° C] T75 [° C] Doping material, [% by weight] CeO ₂ 429 492 521 Pt [1,0] CeO ₂ 445 503 529 Pt [0,1] CeO ₂ 450 526 555 Cu [0.5] CeO ₂ 467 536 566 Nb [0.5] CeO ₂ 459 534 564 Cu [0.25], Fe [0.25] CeO ₂ 474 547 577 W [0.5] CeO ₂ 485 552 581 V [0.5] CeO ₂ 495 560 592 Mo [0.5] CeO ₂ 477 543 573 Fe [0.5]

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• NE Olong et al. "HT-search for alkaline and noble-metal-free mixed oxide catalysts for soot oxidation" Catalysis Today 137 (2008), 110-118 [0004]
• NE Olong et al. "A combinatorial approach to the discovery of low temperature soot oxidation catalysts" Applied Catalysis B: Environmental 74 (2007), 19-25 [0005]
• NE Olong et al. "HT-search for alkaline and noble-metal-free mixed oxide catalysts for soot oxidation" Catalysis Today 137 (2008), 110-118 [0034]
• NE Olong et al. "A combinatorial approach to the discovery of low temperature soot oxidation catalysts" Applied Catalysis B: Environmental 74 (2007), 19-25 [0034]

Claims (13)

A filter for removing particulate matter from combustion exhaust gases, comprising a substrate forming a plurality of gas passages, and a washcoat coating disposed on an inner surface of the substrate comprising a catalytic composition capable of oxidizing unburned oxygen in the presence of oxygen without reacting nitrogen oxides partially catalyzed hydrocarbons and soot particles, wherein the catalytic composition comprises at least one catalytic carrier oxide and at least one doping of a catalytically active, metallic and / or oxidic metal, characterized in that the at least one catalytic carrier oxide and the at least one catalytically active metal individually or is present as a structure in the form of nanoscale particles and / or a nanoscale porous structure. Filter according to claim 1, characterized in that the at least one catalytically active metal on a surface the catalytic carrier oxide is arranged and / or of this is included in whole or in part. Filter according to one of the preceding claims, characterized in that the nanoscale particles and / or the nanoscale porous structure of the catalytic carrier oxide a mean particle diameter and / or a mean structural dimension in the range from 1 to 200 nm, in particular from 2 to 100 nm, preferably 5 to 50 nm. Filter according to one of the preceding claims, characterized in that the nanoscale particles and / or the nanoscale porous structure of the catalytic metal a mean particle diameter and / or average structural dimensions in the range of 1 to 50 nm, especially 1 to 20 nm, preferably 2 to 10 nm. Filter according to one of the preceding claims, characterized in that the at least one catalytic carrier oxide from the group consisting of CeO ₂ , ZrO ₂ , TiO ₂ , Fe ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO and V ₂ O _{5 is} selected, in particular from the group consisting of CeO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , Co ₃ O ₄ and ZrO ₂ . Filter according to one of the preceding claims, characterized in that the at least one catalytically active Metal is selected from the group consisting of Ag, Ca, Ce, Co, Cr, Cu, Cs, Fe, In, Ir, La, Mg, Mn, Mo, Nb, Ni, Pd, Pr, Pt, Re, Rh, Sm, Sr, Ti, V, W, Zn and Zr, and mixtures thereof and alloys with each other. Filter according to claim 6, characterized in that the at least one catalytically active metal selected is from the named group excluding the platinum group metals Pd, Pt and Rh and / or excluding the alkali and / or alkaline earth metals Ca, Cs, Mg and Sr. Filter according to one of the preceding claims, characterized in that the catalytic composition is 0.01 to 50 mol%, especially 0.1 to 10 mol%, preferably 0.1 to 3 mol%, which comprises at least one catalytically active metal. Filter according to one of the preceding claims, characterized in that the washcoat coating in addition to the catalytic composition as further components a surface enlarging, in particular contains ceramic material. Filter according to one of the preceding claims, characterized in that the washcoat coating further comprises a Contains sinterungshemmende component. Filter according to one of the preceding claims, characterized in that the substrate is a ceramic body, in particular of silicon carbide, cordierite, mullite and aluminum titanate, is. Filter according to one of the preceding claims, characterized in that the filter is a diesel particulate filter for the removal of particulate matter from diesel engine Exhaust gases, in particular for the removal of soot particles. Process for the preparation of a catalytic composition for a filter according to one of claims 1 to 12, wherein the catalytic composition (A) comprises at least one catalytic carrier oxide present in the form of nanoscale particles and / or a nanoscale porous structure and (B) at least one Doping of a present in the form of nanoscale particles and / or a nanoscale porous structure, catalytically active, metallic and / or oxidic metal present, with one of the methods: - impregnation of at least one present in the form of nanoscale particles and / or a nanoscale porous structure catalytic Trägeroxids with a solution of a salt of the at least one catalytic metal, drying of the thus obtained impregnated carrier oxide and calcination to form the catalytically active, metallic and / or oxidic metal present in nanoscale form; Preparing a sol of a precursor of the at least one catalytic carrier oxide and a precursor of the at least one catalytic metal, converting the sol into a gel, drying and calcining the gel to form the catalytic composition; and ablation of nanoscale particles by laser bombardment of a target containing the at least one metallically and / or oxidically present catalytically active metal and deposition of the metal particles onto the at least one catalytic carrier oxide present in the form of the nanoscale particles and / or the nanoscale porous structure.