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    • 专利摘要:
    PERFECTED DIESEL OXIDATION CATALYST. The present invention relates to a catalyst for the purification of exhaust gases from diesel engines, in particular to an oxidation catalyst, which is suitable, in particular, for the purification of exhaust gases from heavy-duty vehicles, when other flue gas purification aggregates, for example, a particulate filter and / or nitrogen oxide reduction catalyst are connected on its outlet side. The catalyst contains two catalytically active coatings, different in composition, of which only one is in direct contact with the exhaust exhaust gases. The coating (1) that is in direct contact with the exhaust exhaust gases is rich in platinum, and contains, on the side, more noble metal (platinum and palladium) than the coating (2) that is not in direct contact with the exhaust exhaust gases. The coating (2) that is not in direct contact with the exhaust exhaust gases provides a "het-up performance" of the catalyst.
    公开号:BR112012011292B1
    申请号:R112012011292-9
    申请日:2009-11-12
    公开日:2020-12-08
    发明作者:Frank-Walter Schuetze；Gerald Jeske；Christoph Hengst；Stéphanie Frantz
    申请人:Umicore Ag & Co.Kg；
    IPC主号:
    专利说明:

    description
    [001] The present invention relates to a catalyst for the purification of exhaust gases from diesel engines, in particular, to an oxidation catalyst, which is suitable, among other things, particularly well, for the purification of gases exhaust systems of heavy-duty vehicles, when other exhaust gas purifying aggregates, such as a particulate filter and / or a nitrogen oxide reduction catalyst, are connected on its outlet side.
    [002] The crude exhaust gases from diesel engines contain, alongside carbon monoxide CO, HC hydrocarbons and NOx nitrogen oxides, a relatively high oxygen content of up to 15% by volume. In addition, particulate emissions are contained, which are predominantly made up of soot residues and eventually organic agglomerates, and which come from partially incomplete fuel combustion in the cylinder. Polluting gases of carbon monoxide and hydrocarbons can easily become harmless through oxidation in an appropriate oxidation catalyst. For the removal of particulate emissions, diesel particulate filter aggregates are suitable with and without catalytically active coating. The reduction of nitrogen oxide to nitrogen ("denitrification" of the exhaust gases), due to the high oxygen content is difficult. A known process is the selective catalytic reduction (Selective Catalytic Reduction SCR) of nitrogen oxides in an appropriate catalyst, SCR for short. This process is currently preferred for the denitrification of exhaust gases from diesel engines. The reduction of nitrogen oxides contained in the exhaust gases occurs in the SCR process, with the aid of a reduction medium measured in the exhaust gas line from an external source. As a reducing medium, preferably ammonia or an ammonia-releasing alloy such as urea or ammonia carbamates is used. The ammonia produced in situ from the precursor alloy eventually reacts in the SCR catalyst with the nitrogen oxides from the exhaust gases in a nitrogen and water proportioning reaction.
    [003] Observation of the legal exhaust gas values valid in the future in Europe, North America and Japan requires, in principle, a combination of different exhaust gas purification aggregates. Exhaust gas purification systems have already been suggested and for a multitude of vehicle types (passenger vehicles, trucks) are currently being tested or in series preparation.
    [004] Thus, EP-B-1 054 722 describes a system for the treatment of NO and diesel exhaust gases containing particles, in which a particle filter is connected before an oxidation catalyst. On the exhaust side, a source of reduction medium and a dosing device for the reduction medium are provided in relation to the particulate filter, as well as an SCR catalyst. US patent 6,928,806 likewise describes a system for removing nitrogen oxides and particles from the exhaust gas of diesel engines. In it, in principle, an oxidation catalyst is subsequently connected to an SCR catalyst with dosage of the reduction medium connected before. A diesel particulate filter is located on the exhaust side for the SCR catalyst.
    [005] In combination systems of this type, the oxidation catalyst connected before is presented with special requirements. Through the conversions that take place in the oxidation catalyst, the exhaust gases must be prepared in such a way that, in the aggregates that are subsequently connected, the most optimized result of purification of the exhaust gases can be obtained. In this case, for example, the fact that the SCR catalyst shows the best nitrogen oxide conversion rates should be considered, if there is an optimized NO / NO2 ratio at the entrance of the SCR catalyst. This optimized NO / NO2 ratio for all currently known SCR catalysts is approximately 1. If the NOx contained in the exhaust gases consists only of NO and NO2 then the optimized NO2 / NOx ratio is between 0.3 and 0.7, preferably between 0.4 and 0.6 and particularly preferably at 0.5. Whether this relationship is obtained in a system according to US patent 6,928,806, depends on the temperature of the exhaust gases and, therefore, on the operating state of the engine, and on the oxidation catalyst activity. In a system according to the patent EP-B-1 054 722, the shape and the soot load of the diesel particle filter connected afterwards to the oxidation catalyst is added as another influence quantity, since during the oxidation of soot with NO2, next to CO and CO2 NO appears predominantly.
    [006] Another essential requirement for an oxidation catalyst in a combination system results from the requirement that a diesel particulate filter connected afterwards needs to be regenerated sporadically. In most systems, particles are deposited on the filter over the duration of operation, which cannot be burned to the same extent by oxygen or NO2 in situ, that is, during operation, as they are introduced into the filter. In this way, the back pressure of the exhaust gases increases through the filter. When a predefined limit value is reached, a so-called regeneration of the particulate filter is released, ie the particle filter is heated to a higher temperature level in order to exceed the soot ignition temperature, which may be lowered catalytically, and burn the soot separated in the filter with oxygen to form CO2. In this case, several strategies are valid, such as how the particle filter at the beginning of the regeneration phase can be heated. The established strategies include fuel injection into the cylinder's combustion chamber during the discharge piston stroke or as a secondary injection into the exhaust gas system. The injected fuel is burned catalytically through the oxidation catalyst, the reaction heat to be released in this case, is supplied to the exhaust gases, and is used to heat the particulate filter afterwards to a temperature above the ignition temperature soot.
    [007] In a combined system with particles and SCR catalyst, in addition to the usual requirements such as long term thermal stability, good resistance to poisoning in relation to sulfur-containing alloys (in particular SOx) and a conversion of CO and the highest possible HC with the lowest possible ignition temperature (Light-Off temperature), therefore, two additional requirements are presented: 1. The NO oxidation rate needs to be adjusted as best as possible to the SCR catalyst connected afterwards, ie , the NO2 / NOx ratio produced by the oxidation catalyst should be around or above 0.5. 2. The oxidation catalyst needs to be well suited as a "heating catalyst" for a particle filter disposed later, that is, it must be able to convert very large volumes of unburnt hydrocarbons in an oxidizing manner in a short time, without, in this case, , the oxidation reaction does not succumb. In this case, the conversion of unburned hydrocarbons needs to be as complete as possible, since the irruption of unburned hydrocarbons through the oxidation catalyst at the latest in the SCR catalyst, which is arranged on the discharge side, can take intoxications. In addition, an irruption of unburned hydrocarbons at the end of the exhaust gas system can lead to non-compliance with legal limit values. In this case, the combustion of fuel through the oxidation catalyst already needs to "ignite" with the lowest possible exhaust gas temperatures (180 to 250 ° C). In short, the oxidation catalyst, therefore, should show HC conversion rates with very low exhaust gas temperatures, and the HC conversion from the "ignition temperature" range (Light-Off temperature) ) should suddenly increase as much as possible to the maximum values. In addition, the catalyst must be stable to aging, so that, due to the reaction heat released during the combustion of exothermic hydrocarbons, it is not affected too much in its activity. These power requirements are referred to below as "heat-up-performance".
    [008] For the use of the catalyst in combination systems for the purification of exhaust gases from diesel engines, moreover, the fact that, for example, heavy utility vehicles such as city buses, waste removal fleets must be considered , construction and agricultural machines are often used, in principle, in a different movement operation, such as diesel passenger vehicles. This results in another flue gas profile with considerably lower flue gas temperatures, and other flue gas compositions. Thus, compared to exhaust gases from diesel passenger cars, the nitrogen oxide content in the raw exhaust gases is markedly lower, but the share of particulate emissions, however, possibly increases considerably. The capacity capacity of the pre-stocked oxidation catalyst needs to be adapted to such an exhaust gas profile.
    [009] Traditional oxidation catalysts do not live up to the requirements described, in particular, in the case of the use of the catalyst in combination systems for the purification of the exhaust gases of heavy utility vehicles.
    [0010] Thus, for example, the applicant's EP-B-0 800 856 describes a diesel oxidation catalyst, consisting of one or more zeolites, which are available in the form of Na + or H +, as well as, in addition to one or more metal oxides, selected from aluminum silicate (silicon dioxide / aluminum oxide = 0.005 to 1 weight ratio), aluminum oxide and titanium oxide and at least one metal from the platinum group. The catalyst, in which the metals of the platinum group are separated only for the additional metal oxides, is in a position to oxidize, in particular, long-chain paraffins, which are hardly oxidizable, in the exhaust gases at temperatures below 200 ° C . However, the reaction at low temperatures is very slow, and insufficiently incomplete, such that, in the case of using the catalyst as a heating catalyst for the active regeneration of a later connected filter, it leads to outbursts of unburned hydrocarbons. For use in combination systems with an SCR catalyst, this catalyst is not suitable either, due to its insufficient NO oxidation activity.
    [0011] Applicant's EP-B-1 370 357 describes a catalytically active coating lyser on an inert ceramic or metal hive body. The coating comprises at least one of the metals in the group of platinum, platinum, palladium, rhodium and iridium, on a thin part oxide support material, with small porosity on the basis of silicon dioxide. The support material contains aggregates of primary particles, in essence, spherical in shape, with an average particle diameter between 7 and 60 nm. The catalyst is characterized by an improved thermal resistance to aging, and a reduced tendency towards poisoning by components of the sulfur-containing exhaust gases (in particular, SOx). However, for use in combination systems with an SCR catalyst, this catalyst also shows neither sufficient NO oxidation activity nor sufficient "heat-up performance".
    [0012] Like the catalysts described above, most diesel oxidation catalysts contain only a homogeneously composed functional coating. Catalysts with two functional coatings composed in different ways, such as those known, for example, as three-way catalysts, for the purification of exhaust gases from Otto engines, in the case of diesel oxidation catalysts are rare. US patent 2008/00450405 describes such a diesel oxidation catalyst. In it, on a support substrate, a bottom layer ("bottom washcoat layer") or a zone on the discharge side ("downstream washcoat layer") is applied, which contains a high surface support material, in essence, free from silicon dioxide with platinum and / or palladium. This bottom layer or zone on the affluence side does not contain any HC stock components (for example, zeolite). On the bottom layer or before the zone on the discharge side, a top layer ("top washcoat layer") or a zone on the upstream side ("upstream washcoat layer") is applied, which likewise contains a support material high-surface, and platinum and / or palladium and complementing this an HC stock material. Characteristic for the catalyst is that the weight ratio of Pt: Pd in the upper layer (or in the zone on the side of the inflow) is greater than the weight ratio of Pt: Pd in the bottom layer (or in the zone on the side of the discharge) . The top layer (zone on the inflow side) of the catalyst with respect to sulfur tolerance and paraffin oxidation is optimized, the bottom layer (zone on the discharge side) in terms of hydrothermal stability. Undoubtedly, with respect to the sulfur tolerance of the optimized and therefore acidic coating layer, this catalyst does not show any sufficient NO oxidation activity.
    [0013] The task of the invention in question is to prepare an oxidation catalyst, which is suitable for use in a combination system with particulate filter and SCR catalyst with reduction medium injection, for the purification of exhaust gases from diesel engines, in particular, for the purification of exhaust gases from heavy commercial vehicles, which in this case, fulfill the requirements described above better than the oxidation catalysts known in the state of the art.
    [0014] This task is solved by a catalyst for the purification of exhaust gases from diesel engines consisting of a support body and two catalytically active coatings, different in composition, of which only one is in direct contact with the gases exhaust exhaust. The two coatings contain the metals of the platinum group, platinum (Pt) and palladium (Pd) as catalytically active components, and the coating that is in direct contact with the exhaust exhaust gases is richer in Pt than Pd. The catalyst is characterized by the fact that the coating that is in direct contact with the exhaust exhaust gases contains more metal in the platinum group than the coating that is not in direct contact with the exhaust exhaust gases.
    [0015] The coatings on the catalyst according to the invention are assigned various functions. Thus, the coating that is in direct contact with the exhaust exhaust gases is characterized by an excellent oxidation activity in relation to the HC and CO components and, above all, in relation to NO. By combining an increased total noble metal content of the layer with a high weight ratio of Pt: Pd, the oxidation force of the coating that is in direct contact with the exhaust gases is markedly greater than that of oxidation strength of the coating that is not in direct contact with the exhaust exhaust gases, as a whole, poorer in noble metal. This causes that, during the "regulation operation phases" independent of an active regeneration of a particle filter connected afterwards, next to an almost complete conversion of CO and HC, the catalyst according to the invention shows excellent formation rates of NO2. With a view to the components: particle filter and SCR catalyst for purification of the exhaust gases, later connected in a combining system, this has two advantages: due to the high NO2 part in the exhaust gases, the part of the particles separated over the filter, which can be oxidized and thereby burned in situ, that is, during the regulation operation, without additional heating measures. As a result, the formation of a "filter cake" formed of soot particles is delayed in the filter and, as a result, the back pressure of the exhaust gases increases through the filter. The filter rarely needs to be regenerated. In addition, through the excellent NO2 formation rates through the catalyst according to the invention during the regulation operation, it is ensured that the NO2 / NO2 ratio at the inlet of the SCR catalyst subsequently connected is in the range of 0.3 up to 0.7. In this way, excellent NOx conversion rates are also possible with low temperatures (180 to 250 ° C) through the SCR catalyst.
    [0016] Preferably, the coating that is in direct contact with the exhaust exhaust gases contains from 1.2 to two times more metals of the platinum group than the coating that is not in direct contact with the exhaust exhaust gases . In the preferred embodiments of the catalyst according to the invention, from 55 to 80% by weight of the noble metal contained, in all, in the catalyst are available in the coating which is in direct contact with the exhaust exhaust gases, particularly preferably , from 55 to 70% by weight and, ideally from 57 to 60% by weight. In addition, it preferably presents a weight ratio of Pt: Pd, which is greater than or equal to 6: 1. Most preferably, the weight ratio of Pt: Pd is between 6: 1 and 20: 1, more particularly preferably between 6: 1 and 10: 1, and ideally at 7: 1. The strength oxidation of the coating that is in direct contact with the exhaust exhaust gases is then very well adjusted to the required NO2 conversion rates, in this case, without having to spend altogether too high noble metal volumes, in particular, volumes of the most expensive noble metal platinum.
    [0017] The second coating, which is not in direct contact with the exhaust exhaust gases, contains altogether less noble metal and is characterized by a markedly smaller Pt: Pd weight ratio, that is, by a part of significantly higher palladium in the ratio. Preferably, this coating, which is not in direct contact with the exhaust exhaust gases, has a weight ratio of Pt: Pd from 1: 4 to 2: 1, particularly preferably from 1: 2 to 1: 1 It takes on the function of the so-called "heat-up" during the active regeneration of a particle filter connected afterwards, and is characterized by a very good "heat-up performance" (as described above).
    [0018] To support the conversion of HC in general, and "heat-up performance" in particular, particularly preferred embodiments of the catalyst according to the invention, in the coating, which is not in direct contact with gases exhaust exhaust, in addition, contained one or more zeolite alloys, which are selected from the group of beta-zeolites, zeolites X, zeolites Y, mordenites and zeolites of ZSM-5. These zeolites show an accumulated effect in relation to the hydrocarbons that appear in the diesel exhaust gases. The mixture of the accumulated HC zeolite in the coating, which is not in direct contact with the exhaust exhaust gases has the advantage that hydrocarbons, which, for example, during the cold start phase, or due to their volume during a heat-up phase were deposited in the zeolites for filter regeneration, and at a later time under appropriate operating conditions they are released again from the HC reservoir by compulsory current, the noble metal-rich coating, which is in direct contact with the exhaust exhaust gases, they need to pass. This ensures that these hydrocarbons can be converted as completely as possible into CO2 and water, as the coating that is in direct contact with the exhaust exhaust gases, as explained above, is the coating with the oxidation force. bigger. In this way, in corresponding embodiments of the catalyst according to the invention, better conversion capacities of HC are obtained throughout the entire cycle of movement than in catalysts according to the state of the art, in which there are no alloys of accumulated HC zeolites, or in which these alloys are arranged in a coating that is in direct contact with the exhaust exhaust gases.
    [0019] Through the combination of the two layers, according to the knowledge of the inventors, for the first time, it is successful to provide an oxidation catalyst, which can fulfill all the requirements in a combination system presented to the oxidation catalyst with metal content noble total commercially sustainable. In this case, the two technical effects that act in different operating states of the NO oxidation catalyst, on the one hand, and "heat-up performance", on the other hand, according to the inventors' knowledge, only then fully flaunted , if the spatial arrangement of the coatings is maintained, that is, if the coating that is richest in noble metal and platinum, which has the greatest oxidation force, is the one that is in direct contact with the exhaust exhaust gases.
    [0020] In the preferred embodiments of the catalyst according to the invention, platinum and / or palladium are applied in two layers on one or more support oxides with a high melting point, of high surface, which are chosen from the group of aluminum oxides, aluminum oxides with zirconium oxide and / or titanium oxide, or mixed silicon and aluminum oxides. For the manufacture of an appropriate coating suspension, the selected support oxides are suspended in water. Platinum and palladium are added to the suspension under stirring in the form of appropriate temporary alloys, soluble in water, for example, palladium nitrate, or hexahydroplatinic acid, and eventually, by setting the pH value and / or by adding auxiliary reagent are attached to the support material. Corresponding temporary alloys and auxiliary reagents are familiar to the specialist. The suspensions obtained in this way are then ground and after one of the known coating processes are applied to an inert support body. After each coating step, the coated part is dried in the hot air stream and, eventually, calcined. As a support body for catalytically active coatings, passive hive bodies, preferably ceramic or for the manufacture of the catalyst according to the invention.
    [0021] In this case, there are several possibilities for the arrangement of the coverings on the support body.
    [0022] Figure 1 shows the preferred forms of execution. As shown in figure 1 b) it is preferred that the coating (2) that is electrically active, which is not in direct contact with the exhaust exhaust gases, is applied directly over the passive hive body, being that it extends through the entire length of the component, and is covered by the coating (1) that is in direct contact with the exhaust exhaust gases, along the entire length of the component on the exhaust gas side. In this way, a so-called 2-layer catalyst or "layer catalyst" appears, in which the coating with a palladium-rich heat-up function and possibly containing zeolites exists as a lower layer, and is completely covered by the richest coating in platinum with higher oxidation strength than the top layer.
    [0023] In addition, in the catalyst according to the invention, the catalytically active coating (2), which is not in direct contact with the exhaust exhaust gases, can be applied over the passing hive body in such a way whereas, it extends on the affluence side only through 5 to 50% of the length of the component, and thereby forms a zone on the affluence side. The lining (1) that is in direct contact with the exhaust exhaust gases then extends across the length of the remaining component, and thereby forms a zone on the outlet side adjacent to it. Figure 1 c) shows such an execution as "catalyst per zone". The advantage of a catalyst per zone is that the lengths of the zones can be easily adjusted to the power profile required by the combination system, in which the catalyst must be used. If a particulate filter is first connected to the catalyst according to the invention, then an SCR catalyst, so that, as a result of the soot combustion with NO2 that occurs during the regulation operation, relations must be prepared beforehand larger NO2 / NO2 (0.6 to 0.9), then the zone on the outlet side can cover 70 to 95% of the length L of the passive hive body. If - for example, due to the special motion profile of a utility vehicle, in which very high particle volumes are produced at previously cold exhaust gas temperatures - active regeneration of a later connected particle filter is often necessary , in such a way that, the length of the heatup coating zone on the inflow side can, without problems, be 40 to 50% of the length of the passing hive body.
    [0024] Regardless of the question, whether the catalyst according to the invention is performed as a "layer catalyst" or as a "zone catalyst", it is particularly advantageous if the (bottom) layer or the zone on the inflow side applied directly to the passing hive body, furthermore, it contains one or more zeolite alloys, which are selected from the group of beta zeolites, X zeolites, Y zenolites of mordenites and ZSM-5 zeolites, and that show an accumulated effect in relation to hydrocarbons that occur in diesel exhaust gases. It has already been explained above that, this mixture of zeolite produces an improvement in the conversion of HC in general, and of "heat-up-performance" in particular.
    [0025] The catalyst according to the invention is suitable for use in devices, for the purification of exhaust gases from diesel engines. Particularly preferably, such a device, moreover, contains a diesel particulate filter and / or a catalyst for the selective catalytic reduction of nitrogen oxides, the catalyst according to the invention itself being connected before diesel particulate filter and / or catalyst for selective catalytic reduction of nitrogen oxides.
    [0026] The invention will be explained in more detail, below, with the help of some figures and examples. They are shown:
    [0027] Figure 1: several forms of execution of the catalyst according to the invention; the arrows indicate the direction of the exhaust gas stream to be purified. 1a) General design: hive body (3) of length L containing catalytically active coatings (1) and (2); 1b) Execution as a "layer catalyst", represented as a cut-out of the passage hive body (3) that shows exactly one current channel; the catalytically active coating (2) that is not in direct contact with the exhaust exhaust gases is applied directly over the passage hive body (3) and is covered by the coating (1) that is in direct contact with the exhaust gases discharge exhaust along the entire length of the passing hive body (3); 1c) Execution as a "catalyst per zone", represented as a cut-out of the passage hive body (3), which shows exactly one current channel; the catalytically active coating (2) that is not in direct contact with the exhaust exhaust gases is carried out as a zone of affluence and covers 5 to 50% of the length of the passage hive body; the lining (1) which is in direct contact with the exhaust exhaust gases forms a zone on the discharge side, and covers the rest of the length of the hive body.
    [0028] Figure 2: NO2 yield of catalyst K1 according to the invention, as a function of temperature before the catalyst compared to a one-layer catalyst according to the state of the art VK1.
    [0029] Figure 3: outbreaks of HC ("HC escape") through a K1 catalyst according to the invention compared to a catalyst according to the state of the art VK1, at operating points with catalyst HC load visibly increased.
    [0030] Figure 4: NO2 yield through the VK3 coating that is in direct contact with the exhaust exhaust gases, compared to the NO2 yield through the VK2 coating that is not in direct contact with the exhaust exhaust gases from the catalyst K1 according to the invention, as a function of the temperature before the catalyst.
    [0031] Figure 5: HC flares ("HC exhaust") through the VK3 coating that is in direct contact with the exhaust exhaust gases, compared to HC flares through the VK2 coating that is not in direct contact with exhaust exhaust gases from catalyst K1 according to the invention, at operating points with visibly increased HC load of the catalyst.
    [0032] Figure 6: NO2 yield of catalyst K2 according to the invention, which does not contain any zeolite alloy in the coating that is not in direct contact with the exhaust exhaust gases, compared to the NO2 yield of the catalyst K3 according to the invention, with the addition of zeolite in the coating that is not in direct contact with the exhaust exhaust gases, as a function of the temperature before the catalyst.
    [0033] Figure 7: outbreaks of HC ("HC escape") through catalyst K2 according to the invention, which do not contain any zeolite alloy in the coating that is not in direct contact with the exhaust exhaust gases, compared to the escape of HC through the catalyst K3, with the addition of zeolite in the coating that is not in direct contact with the exhaust exhaust gases.
    [0034] Figure 8: NO2 yield of a VK5 comparison catalyst with a spatial arrangement of the function layers according to the invention and zeolite alloy in the coating that is not in direct contact with the exhaust exhaust gases, in comparison with the NO2 yield of the comparison catalyst VK4 of the same composition with inverted spatial arrangement of the layers, as a function of the temperature before the catalyst.
    [0035] Catalysts were manufactured according to the invention, and some comparison catalysts. For this, according to a traditional immersion process, ceramic honeycomb bodies with a diameter of 266.7 mm and a length of 152.4 mm were coated, which presented 62 cells per cm2 with a cell wall thickness of 0 , 1651 mm, with coating suspensions of the composition mentioned below. After applying the coating suspension, the hive bodies were dried in heating blowers, and were heat treated at 500 ° C.
    [0036] The catalytic activity of the finished catalysts was examined on an engine test bench, which was equipped with a Common - Rail MAN D2066 diesel engine, with a cubic capacity of 10.5 L (Euro IV). In addition to temperature measurement points before the catalyst, the test bench had possibilities for detailed analysis of the exhaust gases before and after the catalyst.
    [0037] Before the test, the catalysts were first subjected to artificial aging. For this, they were stored for 16 hours at a temperature of 750 ° C in an oven with a hydrothermal atmosphere (10% by volume of H2O and 10% by volume O2 in the air).
    [0038] For the examination of the NO oxidation capacity of the catalysts, a so-called "Light-Off-Test" was performed. In this case, the catalyst is heated in the exhaust gases to be purified, under defined conditions:

    [0039] Meanwhile, the concentrations of NO and NO2 in the exhaust gases were recorded before and after the catalyst with the aid of chemiluminescence detectors (CLD; AVL) with a frequency of 1 Hz. From these data, the NO2 yield can then be determined as a function of the temperature from:


    [0040] For the examination of "heat-up-performance", the following points of operation were adjusted, one after another:

    [0041] With the aid of flame ionisation detectors (FID, AVL), the residual hydrocarbon part erupted through the oxidation catalyst in Vppm was recorded with a measurement frequency of 1 Hz. Comparison Example 1:
    [0042] A traditional diesel oxidation catalyst was manufactured, with only one active layer. For the manufacture of an appropriate coating suspension, a mixed oxide of silicon and aluminum, containing up to 20% by weight of SiO2, was impregnated, filling the pores with platinum nitrate solution and dried palladium nitrate solution. After the thermal fixation of the noble metal, the powder obtained in this way was suspended in water and, as previously described, after grinding it was applied over a ceramic honeycomb body. After drying and calcination, in relation to the volume of the hive body, the VK1 ready catalyst contained: 100 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.681 g / L of platinum ex solution of 0.272 g / L palladium nitrate ex nitrate solution Example 1
    [0043] A catalyst was manufactured according to the invention, whose total noble metal content and ratio of platinum to palladium corresponded to the traditional diesel oxidation catalyst of comparison example 1.
    [0044] For this, the ceramic hive body was firstly provided with a first coating which, in relation to the volume of the finished catalyst, presented the following composition: 40 g / L of mixed aluminum and silicon oxide with up to 20% in weight of SiO2 0.204 g / L platinum ex nitrate solution 0.204 g / L palladium ex nitrate solution 15 g / L beta zeolite commercially available
    [0045] After finishing the catalyst, this coating represented the coating, which was not in direct contact with the exhaust gases discharged.
    [0046] After drying and calcining the first layer, a second layer was then applied over it, which, in relation to the volume of the finished catalyst, had the following composition: 40 g / L of mixed aluminum and silicon oxide with up to 20 % by weight of SiO2 0.477 g / L platinum ex nitrate solution 0.068 g / L palladium ex nitrate solution
    [0047] After finishing the catalyst, this coating represented the coating that was in direct contact with the exhaust gases discharged.
    [0048] The compositions for the ready K1 catalyst result after drying and calcination.
    [0049] Figure 2 shows the NO2 yield of the catalyst K1 according to the invention as a function of the temperature before the catalyst, in comparison with the layer catalyst according to the state of the art VK1. The NO2 yield obtained with the catalyst according to the invention is up to 20% higher in a comparable temperature range.
    [0050] Figure 3 shows the HC leak to be observed after the catalyst at the operating points mentioned above of the "heat-up test" for the K1 catalyst according to the invention, and for the catalyst according to the state of the VK1 technique. The catalyst according to the invention shows considerably smaller outbreaks of HC at six of eight operating points tested than the catalyst according to the state of the art VK1.
    [0051] Using the two comparison catalysts VK2 and VK3, the functionalities of both coatings contained in the catalyst according to the invention were examined independently of each other. Comparison Catalyst 2
    [0052] A ceramic honeycomb body was provided with a coating that, in relation to the volume of the ready VK2 catalyst, presented the following composition: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.204 g / L platinum ex nitrate solution 0.204 g / L palladium ex nitrate solution 15 g / L beta zeolite commercially available
    [0053] This coating corresponded to the lower coating of catalyst K1 of example 1, which is not in direct contact with exhaust exhaust gases. Comparison catalyst 3
    [0054] A ceramic honeycomb body was provided with a coating that, in relation to the volume of the ready VK3 catalyst, presented the following composition: 40 g / L mixture of aluminum oxide and silicon with up to 20% by weight of SiO2 0.477 g / L platinum ex 0.068 g nitrate solution / L palladium ex nitrate solution
    [0055] This coating corresponded to the top coating of catalyst K1 of example 1, which is directly in contact with the exhaust exhaust gases.
    [0056] Figure 4 shows the NO2 yield through the VK2 and VK3 catalysts. It is evident that VK3, which corresponds to the coating that is in direct contact with the exhaust gases discharged into the K1 catalyst according to the invention, provides a significantly higher NO2 yield than VK2, which corresponds to the coating that is not directly in contact with exhaust exhaust gases.
    [0057] Figure 5 shows the escape of HC through VK2 and VK3 that can be compared for the two layers. More interesting is the comparison with the HC of the K1 catalyst according to the invention in figure 2: combining the two coatings, which, as shown in figure 3, examined individually, do not show any good "heat-up-performance" "in relation to the catalyst according to the invention, then, in the case of the spatial arrangement of the two layers according to the invention, the escape of HC is drastically reduced through the existing catalyst. At operation points 6, 7 and 8, where there are high HC loads, the HC exhaust is reduced from 3000 - 3500 Vppm, which is characteristic for individual layers, to less than 1000 Vppm at operation points 6 and 8, and for less than 1500 Vppm at operating point 7. This effect, as such, is not expected due to the individual power of the respective function coatings. The cause for this is a synergy effect in conjunction between the palladium-rich coating, which is not in direct contact with the exhaust exhaust gases, and the second coating which is in direct contact with the exhaust exhaust gases. By compulsory current, the exhaust exhaust gases are conducted through the coating with the greatest oxidation force. With this, the residual hydrocarbons, which could not be converted by the "heat-up coating" or which were prematurely desorbed, are converted in an oxidizing manner. This leads to a considerable reduction in the exhaust of HC through the catalyst according to the invention and, with this, to an excellent "heat-up-performance".
    [0058] By means of the two catalysts k2 and K3 according to the invention, the influence of the addition of zeolite in the coating that is not in direct contact with the exhaust exhaust gases is illustrated. Example 2
    [0059] According to the procedure described in example 1, a K2 catalyst according to the invention was manufactured with two overlapping layers of the following composition: 1st layer = lower layer = coating that is not in direct contact with the exhaust gases of discharge: 92 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.302 g / L of platinum ex nitrate solution 0.302 g / L palladium ex nitrate solution 2nd Layer = top layer = coating that is in direct contact with exhaust exhaust gases: 45 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.706 g / L of platinum ex nitrate solution 0.101 g / L palladium ex nitrate solution Example 3
    [0060] According to the procedure described in example 1, a K2 catalyst according to the invention was manufactured with two overlapping layers of the following composition: 1st layer = lower layer = coating that is not in direct contact with the exhaust gases of discharge: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.303 g / L of platinum ex nitrate solution 0.303 g / L of palladium ex nitrate solution 15 g / L of beta zeolite commercially at sale 2nd Layer = top layer = coating that is in direct contact with exhaust exhaust gases: 45 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.706 g / L of platinum ex nitrate solution 0.101 g / L palladium ex nitrate solution
    [0061] Figure 6 shows that the addition of zeolite in the coating that is not in direct contact with the exhaust exhaust gases, has no significant influence on the NO2 yield of the catalyst.
    [0062] Figure 7 shows that, however, an addition of zeolite has considerably reducing consequences on the escape of HC through the catalyst and, with this, has very positive consequences on the "heat-up-performance" of the catalyst.
    [0063] In addition, it was examined what the basic influence the spatial arrangement of the function layers has on the capacity of the catalyst. For this, two other comparison catalysts were manufactured: Comparison Example 4
    [0064] According to the procedure described in example 1, a two-layer comparison catalyst VK4 of the se-guintecomposition was manufactured, referring to the volume of the ready catalyst: 1st layer = lower layer = coating that is not in direct contact with gases exhaust exhaust: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.681 g / L of platinum ex nitrate solution 0.068 g / L palladium ex nitrate solution 2nd Layer = top layer = coating that is in direct contact with exhaust exhaust gases: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.204 g / L of platinum ex solution of nitrate 15 g / L of zeolite beta commercially for sale Comparison Example 5
    [0065] According to the procedure described in example 1, a two-layer comparison catalyst VK5 of the following composition was manufactured, referring to the volume of the ready catalyst: 1st layer = bottom layer = coating that is not directly in contact with gases exhaust exhaust: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.204 g / L of platinum ex solution of nitrate 15 g / L of beta zeolite commercially on sale 2nd Layer = top layer = coating that is in direct contact with exhaust exhaust gases: 40 g / L of mixed aluminum oxide and silicon with up to 20% by weight of SiO2 0.681 g / L of platinum ex nitrate solution 0.068 g / L of palladium ex nitrate solution
    [0066] Figure 8 shows the NO2 yield through the catalysts VK4 and VK5. It can be clearly seen that the arrangement of the zeolite-free coating and which has a greater oxidation force, as a coating that is not in direct contact with the exhaust exhaust gases, clearly acts as a disadvantage on the oxidation capacity of NO of the catalyst.
    权利要求:
    Claims (8)
    [0001]
    1. Catalyst for the purification of exhaust gases from diesel engines, consisting of a support body (3) and two catalytically active coatings, different in composition, of which only one (1) is in direct contact with the exhaust gases discharge exhaust, the two coatings being applied to a passage honeycomb body (3) made of ceramic or metal as a support body (3) and containing the metals in the group platinum, platinum (Pt) and palladium (Pd) as catalytically active components, and the coating (1) that is in direct contact with the exhaust exhaust gases contains more Pt than Pd, characterized by the fact that the coating (1) that is in direct contact with exhaust exhaust gases contain more metal in the platinum group in total than the coating (2) that is not in direct contact with the exhaust exhaust gases and the catalytically active coating (2) that is not in direct contact with the exhaust exhaust gases mortar is applied directly over the passage hive body (3), and it extends through the entire length of the component, and is covered by the coating (1) that is in direct contact with the exhaust exhaust gases, through the entire length of the component on the exhaust gas side.
    [0002]
    2. Catalyst according to claim 1, characterized by the fact that the coating (1) which is in direct contact with the exhaust exhaust gases contains from 1.2 to twice more metals of the platinum group than the coating (2 ) that is not in direct contact with the exhaust exhaust gases.
    [0003]
    3. Catalyst according to claim 2, characterized by the fact that the coating (1) that is in direct contact with the exhaust exhaust gases has a Pt: Pd weight ratio that is greater than or equal to 6: 1.
    [0004]
    4. Catalyst according to claim 2 or 3, characterized by the fact that the coating (2) that is not in direct contact with the exhaust exhaust gases has a weight ratio of Pt: Pd of 1: 4 up to 2: 1.
    [0005]
    5. Catalyst according to any one of the preceding claims, characterized by the fact that platinum and / or palladium are applied in both layers on one or more support oxides with a high melting point, with a high surface, which are chosen from the group aluminum oxides, aluminum oxides with zirconium oxide and / or titanium oxide, or mixed silicon and aluminum oxides.
    [0006]
    6. Catalyst according to claim 1, characterized by the fact that the layer (2) applied directly on the passing hive body (3), furthermore, contains one or more zeolite alloys, which are chosen from the group of beta zeolites, X zeolites, Y zeolites, mordenites and 5 ZSM zeolites, which show an accumulated effect in relation to hydrocarbons that occur in diesel exhaust gases.
    [0007]
    7. Device for the purification of exhaust gases from diesel engines, characterized by the fact that it has a catalyst as defined in any one of claims 1 to 6.
    [0008]
    8. Device according to claim 7, characterized by the fact that the catalyst as defined in any of claims 1 to 6, is connected in series to a diesel particulate filter and / or to a catalyst for selective catalytic reduction of nitrogen oxides.
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    同族专利:
    公开号 | 公开日
    WO2011057649A8|2012-05-24|
    PL2498898T3|2016-12-30|
    US9011783B2|2015-04-21|
    CN102574055A|2012-07-11|
    BR112012011292A2|2016-04-12|
    CN102574055B|2015-11-25|
    US20120213674A1|2012-08-23|
    RU2559502C2|2015-08-10|
    WO2011057649A1|2011-05-19|
    EP2498898B1|2016-07-13|
    EP2498898A1|2012-09-19|
    JP2013510702A|2013-03-28|
    RU2012123950A|2014-02-20|
    JP5683598B2|2015-03-11|
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    法律状态:
    2018-04-17| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2020-03-24| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-08-18| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2020-12-08| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 10 (DEZ) ANOS CONTADOS A PARTIR DE 08/12/2020, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    PCT/EP2009/008047|WO2011057649A1|2009-11-12|2009-11-12|Improved diesel oxidation catalytic converter|
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