oxidation catalyst composite, method for treating an exhaust gas stream, and system for treating an

专利摘要:
ZONED CATALYST FOR DIESEL APPLICATIONS. An oxidation catalyst compound, methods and systems for treating exhaust emissions from a diesel engine are described. More particularly, an oxidation catalyst compound, including a zoned diesel oxidation catalyst, with a first washcoat zone that has a Pt / Pd ratio that is less than 3: 1 and a PGM load at least twice that of than that of a second washcoat zone.
公开号:BR112015022281B1
申请号:R112015022281-1
申请日:2014-03-13
公开日:2021-02-09
发明作者:Shahjahan M. Kazi；Fabien A. Rioult；Stanley A. Roth；Kenneth E. Voss
申请人:Basf Corporation；
IPC主号:

专利说明:

TECHNICAL FIELD
[0001] The present invention relates to oxidation catalysts that have zoned designs. More specifically, modalities are directed to zonated catalyst composites comprising Pt and Pd in refractory metal oxide supports and their use to reduce the emission of carbon monoxide and hydrocarbons in diesel engine systems. BACKGROUND OF THE INVENTION
[0002] The operation of poor combustion engines, for example, diesel engines and gasoline engines with poor combustion, provides the user with excellent fuel economy and has low emissions of gas hydrocarbons and carbon monoxide due to their operation of them at high air / fuel ratios in poor fuel conditions. In addition, diesel engines offer significant advantages over gasoline (spark ignition) engines in terms of fuel economy, durability and their ability to generate high torque at low speed.
[0003] From the point of view of emissions, however, diesel engines present more serious problems than their spark ignition counterparts. Because the exhaust gas of the diesel engine is a heterogeneous mixture, emission problems are related to particulate material (PM), nitrogen oxides (NOx), unburned hydrocarbons (HC) and carbon monoxide (CO).
[0004] NOx is a term used to describe several chemical species of nitrogen oxides, including nitrogen monoxide (NO), and nitrogen dioxide (NO2), among others. NO is a concern because it is believed that it goes through a process known as photochemical smog formation, through a series of reactions in the presence of sunlight and hydrocarbons, being a major contributor to acid rain. NO2, on the other hand, has a high potential as an oxidizer and is highly irritating to the lung.
[0005] Effective NOx reduction in poor combustion engines is difficult to achieve because high NOx conversion rates typically require conditions that are rich in reducers. The conversion of the NOx component from exhaust streams into harmless components generally requires specialized NOx reduction strategies for operation in poor fuel conditions.
[0006] Such a strategy for reducing NOx in the exhaust current of poor combustion engines uses NOx storage reduction (NSR) catalysts, also known as "lean NOx trap (LNT)." Lean NOx trap technology can involve the catalytic oxidation of NO to NO2 by catalytic metal components effective for such oxidation, such as precious metals. However, in the "lean NOx trap" technology, the formation of NO2 is followed by the formation of a nitrate when NO2 is adsorbed on the surface of the catalyst. NO2 is therefore "trapped", that is, stored on the catalyst surface in the form of nitrate and subsequently decomposed by periodic operation of the system under fuel-rich combustion conditions that effect a reduction of NO x (nitrate) released in N2.
[0007] Oxidation catalysts comprising a precious metal dispersed in a refractory metal oxide support are known for use in the treatment of exhaust gases from diesel engines in order to convert both gaseous pollutants from hydrocarbons and carbon monoxide through catalyzing the oxidation of these pollutants to carbon dioxide and water. Such catalysts have generally been contained in units called diesel oxidation catalysts (COD), or more simply catalytic converters, which are placed in the exhaust flow path of a diesel engine to treat exhaust gases prior to exhaust into the atmosphere. . Typically, diesel oxidation catalysts are formed on ceramic or metal substrate carriers (such as a flow-through monolith carrier) on which one or more catalyst coating compositions are deposited. In addition to the conversion of gaseous HC and CO, and the soluble organic fraction (SOF) of the particulate material, oxidation catalysts that contain metals of the platinum group (which are typically dispersed on a refractory oxide support) promote the oxidation of nitric oxide (NO ) in NO2.
[0008] The catalysts used for the treatment of exhaust gases from internal combustion engines are less effective during periods of relatively low temperature operation, such as the initial period of engine operation by cold start, since the exhaust gases from the engine they are not at a high enough temperature for the efficient catalytic conversion of harmful components in the exhaust gases.
[0009] Oxidation catalysts comprising a platinum group metal (PGM) dispersed on a refractory metal oxide support are known for their use in the treatment of exhaust gas emissions from diesel engines. Platinum (Pt) is an effective metal for the oxidation of CO and HC in a COD after high temperature aging in poor conditions and in the presence of fuel sulfur. On the other hand, palladium-rich diesel oxidation catalysts (Pd) typically demonstrate higher ignition temperatures for CO and HC oxidation, especially when used to treat exhaust gases containing high levels of sulfur (from fuels with high sulfur content) or when used with HC storage materials. "Ignition" temperature for a specific component is the temperature at which 50% of that component reacts. Cds containing Pd can poison Pt activity to convert HCs and / or oxidize NOx and can also make the catalyst more susceptible to sulfur poisoning. These characteristics typically prevent the use of Pd-rich oxidation catalysts in poor combustion operations, especially for diesel applications for light vehicles where engine temperatures remain below 250 ° C for most driving conditions.
[0010] Oxidation catalysts with high levels of platinum content cause high conversion rates to diesel exhaust gases in the oxidation of NO to form NO2. Oxidation catalysts that have a large amount of palladium can provide almost complete conversion of high amounts of unburned hydrocarbons in the exhaust gases of diesel engines, even at low temperatures. However, aged catalysts with high levels of platinum content have a tendency to dissipate in the case of high levels of hydrocarbon content, while palladium does not have a sufficient level of NO oxidation activity. Thus, there is a conflict between the NO conversion performance and the colder temperature performance. For cost reasons, this conflict cannot be resolved by adding two of the noble metals palladium and platinum to the oxidation catalyst. In addition, platinum and palladium can interact negatively when combined, so that the additive effect is effectively lost. Thus, a diesel oxidation catalyst is needed to resolve such a conflict. Conversion NO to NO2 can impact the downstream SCR (selective catalytic reduction, SCR) reaction, especially the "fast" SCR reaction, as described below.
[0011] As emission regulations have become more stringent, there is a continuing need to develop diesel oxidation catalyst systems that provide improved performance, for example, lower ignition temperature for the fuel used in active filter regeneration of diesel particles downstream. There is also a need to use COD components, for example Pd, as effectively as possible. ABSTRACT
[0012] A first modality refers to an oxidation catalyst composite for reducing exhaust gas emissions from a diesel engine comprising: a substrate having a length, an inlet end and an outlet end, a catalyst material in the carrier, the catalyst material including a first coating zone and a second coating zone; the first coating zone comprising a first coating layer including platinum group metals (PGM) platinum Pt and palladium Pd and a first refractory metal oxide support, the first coating zone adjacent the substrate inlet end; and the second coating zone comprising a second coating layer including platinum and PGM palladium and platinum components and a second refractory metal oxide support, the second coating layer adjacent the outlet end of the substrate; wherein the first coating zone has a shorter length than the second coating zone, where the oxidation catalyst does not include a high load of PGM on the inlet face of the catalyst and the first coating zone has a load of PGM at least at least twice as large as that of the second coating zone, and the first coating zone has a Pt / Pd ratio of less than 3: 1.
[0013] In a second embodiment, the oxidation catalyst composite of the first embodiment is modified, in which the second coating zone has a Pt: Pd ratio greater than 3: 1.
[0014] In a third mode, modes 1 or 2 are modified, in which the Pt: Pd ratio in the second coating zone is greater than 5: 1.
[0015] In a fourth mode, modes 1 to 3 are modified, in which the Pt: Pd ratio in the second coating zone is greater than 8: 1.
[0016] In a fifth modality, modalities 1 to 4 are modified, in which the refractory metal oxide support comprises alumina with a large pore.
[0017] In a sixth modality, the fifth modality is modified, in which the alumina is stabilized by doping.
[0018] In a seventh modality, the first to sixth modality is modified, in which the coating load is the same in the first coating zone and the second coating zone.
[0019] In an eighth mode, modes 1 to 6 are modified, in which the coating load is different in the first coating zone and in the second coating zone.
[0020] In a ninth modality, the eighth modality is modified, in which the first coating zone comprises a Pt / Pd component in an amount in the range of about 40 g / ft3 to 60 g / ft3 (1.41 kg / m3 2.12 kg / m3).
[0021] In a tenth modality, modes 8 or 9 are modified, in which the second coating zone comprises a Pd / Pd component in an amount in the range of about 15 g / ft3 to 25 g / ft3 (0.53 kg / m3 to 0.88 kg / m3).
[0022] In an eleventh modality, any of the modalities 1 to 9 are modified, in which the first coating zone further comprises an alkaline earth metal in an amount in the range of about 60 g / ft3 to 70 g / foot3 (2.12 kg / m3 to 2.47 kg / m3).
[0023] In a twelfth modality, modes 1 to 11 are modified, in which the ratio between the length of the second coating zone and the length of the first coating zone is 1.5: 1 or greater.
[0024] Another aspect of the invention concerns a method. In a thirteenth embodiment, a method for treating a diesel engine exhaust gas stream comprising passing the exhaust gas stream through an inlet end towards an outlet end of a catalyzed soot filter, the exhaust gas first passing through a first coating zone on the catalyzed soot filter comprising a first coating layer including Pt platinum and Pd palladium component and a first refractory metal oxide support and then passing the exhaust gas stream through of a second coating zone on the catalyzed soot filter comprising a second coating layer including platinum and palladium components and a second refractory metal oxide support, wherein the first coating zone is less than the second coating zone. coating, where the first coating zone has a PGM load at least twice that of the than that of the second coating zone, and the first coating zone having a Pt / Pd ratio less than 3: 1.
[0025] In a fourteenth modality, modality 13 is modified, in which the second coating zone has a Pt: Pd ratio greater than 3: 1.
[0026] In a fifteenth modality, modes 12 to 14 are modified, in which the Pt: Pd ratio in the second coating zone is greater than 5: 1.
[0027] In a sixteenth modality, modes 12 to 15 are modified, in which the Pt: Pd ratio in the second coating zone is greater than 8: 1.
[0028] IN a seventeenth modality, the modalities 12 to 16 can be modified, in which the coating load is the same in the first coating zone and in the second coating zone.
[0029] In an eighteenth modality, the modalities 12 to 16 can be modified, in which the coating load is different in the first coating zone and in the second coating zone.
[0030] In a nineteenth modality, modalities 12 to 18 can be modified, in which the oxidation catalyst composite is effective for reducing carbon monoxide and hydrocarbons, and for oxidizing NO to NO2 from the gas stream of exhaustion.
[0031] A twentieth modality refers to a system for treating a poor combustion engine exhaust gas stream including hydrocarbons, carbon monoxide and other exhaust components, the emission treatment system comprising: an exhaust conduit in fluid communication with the poor combustion engine through a collector; the oxidation catalyst composite of any of embodiments 1 to 19 in which the substrate is a continuous flow substrate or a wall flow substrate; and a catalyzed soot filter and an SCR catalyst located downstream of the oxidation catalyst composite.
[0032] In a twenty-first modality, modality 20 is modified so that the SCR catalyst is loaded into the catalyzed soot filter. BRIEF DESCRIPTION OF THE FIGURES
[0033] FIG. 1 is a perspective view of a "honeycomb" type refractory carrier member that can comprise oxidation catalyst composites according to one or more embodiments; FIG. 2 is an enlarged view in partial cross-section with respect to FIG. 1, showing an enlarged view of one of the gas flow passages shown in FIG. 1; FIGS. 3A and 3B show a cross-sectional view of the oxidation catalyst composite according to various embodiments; and FIG. 4 is a schematic diagram of a system for treating engine emissions according to one or more modalities. DETAILED DESCRIPTION
[0034] Before describing the various examples of modalities of the invention, it should be understood that these modalities are merely illustrative of the principles and applications of the present invention. It is, therefore, to be understood that numerous modifications can be made to the illustrative modalities and that other arrangements can be designed without departing from the spirit and scope of the present invention as disclosed.
[0035] Modalities are directed towards the use of catalyst zoning strategies that can improve the performance of Pt / Pd catalysts in applications of poor combustion engines. While the catalyst can be used in any poor combustion engine, including diesel engines, engines with direct gasoline injection with poor combustion, and compressed natural gas engines, specific modalities, the catalysts should be used in applications for heavy duty engines. diesel. Heavy duty diesel engines include engines in gross vehicle weight rating (GVWR) above £ 8,500. As one skilled in the art will understand, there are several subgroups of heavy duty vehicles, such as diesel continuous working engines, medium-continuous diesel working engines and heavy duty diesel engines (more than 33,000 GVWR, including city buses). The present invention may also have applicability for diesel engines that are not for roads, which includes engines that are used off-road (off-road), as in farms and in the construction industry. Heavy duty diesel engines can also include the following categories of non-road engines: locomotives; marine engines; engines used in engines for underground mining equipment, stationary and miniature engines.
[0036] Although platinum has good ignition characteristics for CO and HC and has been preferred as a precious metal for catalyst compositions to reduce diesel engine exhaust, palladium has become interesting due to its relatively lower cost.
[0037] Zone coating of a catalyst coating is a technique used to improve the performance of the catalyst in transient engine operation. Zone coating is generally achieved by segregating the precious metal composition and / or the amount of precious metal, at specific locations (or zones) along a substrate (for example, a monolithic honeycomb-shaped catalyst carrier). Zone coating allows the placement of metal oxide coating materials and other coating additives in specific locations that improve the performance of the supported precious metals. Typically, a greater amount of precious metal (particularly Pt) is located at the front (inlet) of the conveyor to achieve faster ignition for the fuel. Palladium can be located at the rear (outlet) portion of the conveyor since the conveyor outlet is generally hotter due to the ignition of the catalyst, and Pd has better resistance to thermal sintering than Pt.
[0038] According to one or more embodiments of the invention, it has been determined that a zoning configuration in which there is a high load of PGM in an upstream zone that is less in length than a downstream zone that has a greater amount platinum than palladium in the rear provides excellent fuel ignition. Modalities of the present invention use a catalyst zoning strategy that can improve the performance of Pt / Pd formulations in diesel applications by locating a higher percentage of Pd in front of or in the first coating zone of the carrier with a corresponding higher percentage Pt in the rear or in the second coating area of the conveyor. This zoning strategy can be particularly useful for burning fuel.
[0039] Another aspect of the invention relates to a diesel oxidation catalyst that uses a high porosity support. As used in this document, "high porosity support" refers to a refractory metal oxide support, which has an average pore radius of at least 100 Angstroms, for example, an average in the range of 100 Angstroms to 150 Angstroms. In a specific embodiment, a high porosity support of refractory metal oxide has an average pore radius of 120 Angstroms. As shown below, oxidation catalysts made with high porosity supports demonstrate better fuel burning properties and improved NO2 production, compared to less porous supports.
[0040] As used in this document, the term "first" is used to indicate the location of the diesel oxidation catalyst in the direction of the exhaust current flow. Equivalent terms would be "principal" or "upstream" or "forward" or "entry".
[0041] As used in this document, the term "second" is used to indicate the location of the diesel oxidation catalyst in the direction of the exhaust current flow. Equivalent terms would be "downstream" or "rear" or "outgoing".
[0042] The first coating zone and the second coating zone can be present in the form of two separate components forming two separate and distinct zones. Alternatively, the first coating zone can be on the upstream side of the substrate, while the second coating zone can be located on the downstream section of the same substrate.
[0043] The catalyst zoning design provides thermally durable NO2 generation in conjunction with efficient heating performance, and ignition activity for low temperature fuel. Significantly, the zonated catalyst provides both functions at the same time, minimizing the use of PGM and its impact associated with the cost of the catalyst. A first coating zone with a higher load with a low Pt / Pd ratio followed by a second coating zone with a lower load with a higher Pt / Pd ratio provides a catalyst with balanced performance.
[0044] The zoning strategy of the present invention goes against conventional science, providing an oxidation catalyst in which most of the platinum in the hottest part of the carrier (i.e., the rear coating zone or the second coating zone) it may be more prone to sintering. The zone placement of palladium and platinum provides a diesel oxidation catalyst with surprisingly good fuel ignition, even after aging. Such a diesel oxidation catalyst is particularly useful for heavy duty diesel applications such as trucks, buses and heavy equipment (tractors, excavators, etc.).
[0045] In one or more embodiments, the oxidation catalyst composite comprises a substrate that has a length, an inlet end and an outlet end, a catalyst material on the carrier. The catalyst material includes a first coating zone and a second coating zone. The first coating zone may comprise a first coating layer, including Pt platinum and palladium Pd components and a first metal oxide support, the first coating zone adjacent the substrate inlet end. The second coating zone comprises a second coating layer including Pt platinum and Pd palladium components, and a second refractory metal oxide support, the second coating layer adjacent to the outlet end of the substrate. The first coating zone has a length that is less than the second coating zone. The catalyst material of the oxidation catalyst does not include a high PGM load on the inlet face of the catalyst, and the first coating zone has a PGM load that is at least twice that of the second coating zone. The first coating zone has a Pt / Pd ratio of less than 3: 1. In other words, the Pt / Pd charge is relatively high in the first (front) coating zone, and the Pt / Pd load in the second (rear) coating zone is relatively low.
[0046] In one or more embodiments, the oxidation catalyst composite does not include a high load of PGM on the inlet face of the catalyst.
[0047] In one or more modalities, more than 50% of the total PGM load is applied to the front (inlet) or the first coating zone of the substrate. In one or more embodiments, the first coating zone has a PGM charge of at least twice that of the second coating zone. The ratio of the loading of the first coating zone to the loading of the second coating zone can be greater than 2: 1 and up to 15: 1 (including 2: 1, 3: 1.4: 1, 5: 1, 10: 1 and 15: 1).
[0048] The first and second coating zones can consist of platinum and palladium containing catalytically active coating over a flow of ceramic or metal through the honeycomb shaped body. In one or more embodiments, the substrate is a continuous flow substrate composed of ceramic materials including, but not limited to, silicon carbide, cordierite, aluminum titanate and mullite. In one or more embodiments, continuous flow metal substrates can be used as a substrate. Continuous flow ceramic substrates such as a honeycomb-shaped body can be used as a substrate. Ceramic honeycomb bodies that have cell densities of 15 to 150 cells per square centimeter, or 60 to 100 cells per square centimeter can be used.
[0049] The ratio of platinum to palladium in the first coating zone can have a wide range of variation. As a result of the variation in the Pt / Pd ratio in the first coating zone, it is possible to provide an exhaust system with optimized costs for diesel engines. In one or more embodiments, the first coating zone has a Pt: Pd ratio that is less than 3: 1. In one or more embodiments, the first coating zone has a Pt: Pd ratio of 2: 1 or 1 or 1: 2 or even only with palladium (0: 1). In a specific embodiment, the first coating zone has a Pt: Pd ratio of 1: 2. In one or more embodiments, the first coating zone may comprise only Pd. The load for the first coating zone can be 30 to 110 g / ft3 (1.05 kg / m3 to 3.88 kg / m3), more specifically 30 to 80 g / ft3 (1.05 kg / m3 to 2 , 83 kg / m3), or more specifically from 40 to 60 g / ft3 (1.41 kg / m3 to 2.12 kg / m3) of PGM.
[0050] The ratio of platinum to palladium in the second coating zone can have a wide range of variation. In one or more embodiments, the second coating zone has a Pt: Pd ratio that is greater than 3: 1. In one or more embodiments, the second coating zone has a Pt: Pd ratio of 5: 1 or 8: 1 or 10: 1. In a specific embodiment, the second coating zone has a Pt: Pd ratio that is greater than 8: 1. In a very specific embodiment, the second coating zone has a Pt: Pd ratio that is 10: 1. In one or more embodiments, the second coating zone may comprise only Pt (Pt: Pd ratio of 1: 0).
[0051] Reference to a catalyst or catalytic composite article means a catalyst article including a substrate, for example, a honeycomb-shaped substrate with one or more layers of coating containing a catalyst component, for example, a PGM component that is effective to catalyze the burning of fuel.
[0052] As used in this document, the terms "refractory metal oxide support" and "support" refer to the underlying high surface area material on which chemical compounds or additional elements are made. The support particles have pores larger than 20 A and a wide distribution of pores. As defined in this document, such metal oxide supports do not include molecular sieves, specifically zeolites. In particular embodiments, high surface area refractory metal oxide supports can be used, for example, alumina support materials, also referred to as "gamma alumina" or "activated alumina", which typically have an excess BEI surface area 60 square meters per gram ("m2 / g"), often up to about 200 m2 / g or more. Such activated alumina is generally a mixture of the alumina gamma and delta phases, but it can also contain substantial amounts of eta, kappa and theta alumina phases. Refractory metal oxides other than activated alumina can be used as a support for at least some of the catalytic components in a given catalyst. For example, bulk ceria, zirconia, alpha alumina and other materials are known for such use. Although many of these materials suffer from the disadvantage of having a considerably smaller BEI surface area than activated alumina, this disadvantage tends to be offset by a longer durability of the resulting catalyst. "BET surface area" has its usual meaning when referring to the method of Brunauer, Emmett, Teller to determine the surface area by N2 adsorption. Pore diameter and pore volume can also be determined using adsorption or desorption experiments with N2 type BET.
[0053] In one or more embodiments, the refractory metal oxide support is a large pore alumina or silica-alumina. The support has pores larger than 90 A. Large pore alumina is highly porous, having a narrow pore distribution.
[0054] As used in this document, molecular sieves, such as zeolites, refer to materials that can particularly support groups of precious metal catalysts, the materials having a substantially uniform pore distribution, with the average pore size not being greater than 20 A. Reference to a "non-zeolite support" in a catalyst layer refers to a material that is not a molecular sieve or zeolite and that receives precious metals, stabilizers, promoters, binders and the like through association, dispersion, impregnation or other appropriate methods. Examples of such supports include, but are not limited to, high-surface refractory metal oxides. One or more embodiments of the present invention include a refractory metal oxide support with a high area surface comprising an activated compound selected from the group consisting of alumina, zirconia, silica, titania, silica-alumina, zirconia-alumina, titania-alumina, lanthanum -alumina, lantana-zirconia-alumina, baria-alumina, baria-lantana-alumina, baria-lantana- neodymia-alumina, zirconia-silica, titania-silica and zirconia-titania.
[0055] The reference to "impregnated" means that a solution containing precious metal is placed in the pores of a material such as a zeolite or a non-zeolite support. In detailed modalities, impregnation of precious metals is achieved by incipient moisture, where a volume of the solution containing diluted precious metal is approximately equal to the volume of pores of the support bodies. Incipient moisture impregnation generally leads to a substantially uniform distribution of the precursor solution throughout the material's pore system. Other methods of adding precious metals are also known in the art and can be used.
[0056] In one or more embodiments, the diesel oxidation catalyst is applied to one or more oxide support materials selected from aluminum oxide, aluminum oxide stabilized by lanthanum oxide, aluminosilicate, silicon dioxide, dioxide of titanium, cerium oxide, mixed cerium-zirconium oxides, rare earth metal sesquioxide, zeolite and their mixtures. In one or more embodiments, aluminum oxide, aluminum oxide stabilized by lanthanum oxide, aluminosilicate, titanium dioxide and zeolites are used as support materials for refractory metal oxide. In one embodiment, the first coating zone and the second coating zone are applied to the aluminum oxide and / or aluminosilicate support materials. The diesel oxidation catalyst plus the refractory metal oxide support or coating is then applied to a continuous flow substrate.
[0057] Details of the components of a gas treatment article and the system according to the modalities of the invention are provided below. The Substrate
[0058] As used in this document, the term "substrate" "refers to the monolithic material on which the carrier is placed, typically in the form of a coating containing a plurality of supports having the catalyst species in it. According to one or more embodiments, the substrate can be any of the materials normally used to prepare DOC catalysts and which preferably comprise a metallic or ceramic honeycomb structure Any suitable substrate can be employed, such as a monolithic substrate of the type having a plurality parallel thin passages of gas flow that extend through an inlet face or an outlet face of the substrate, so that the passages are open for the flow of fluid through them. The passages, which are essentially straight paths from the their fluid inlet to the fluid outlet, are defined by walls on which the catalyst material is coated as a "coating" so that the gases s that flow through the passages come into contact with the catalyst material. A coating is formed by preparing a paste containing a specified content of solids (for example, 30-50% by weight) of supports in a liquid vehicle, which is then coated on a substrate and dried to provide a coating layer.
[0059] The flow passages of the monolithic substrate are thin-walled channels, which can have any suitable shape and cross-sectional size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular etc. Such structures can contain from about 60 to about 600 or more gas inlet openings (i.e., "cells") per square inch of cross section.
[0060] The ceramic substrate can be made of any suitable refractory material, for example, cordierite, cordierite-α alumina, silicon nitride, silicon carbide, zircon mullite, spodumene, magnesia alumina, zircon silicate, silimanite , magnesium silicate, zircon, petalite, α-alumina, aluminosilicate and the like.
[0061] The substrates useful for layered oxidation catalyst composites according to one or more modalities may also be of a metallic nature and may be composed of one or more metals or metallic alloys. Metal substrates can be used in various forms, such as pellets, corrugated sheet or monolithic form. Metal supports include heat-resistant metals and metal alloys, such as titanium and stainless steel, as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium and / or aluminum, and the total amount of these metals may advantageously comprise at least 15% by weight of the alloy, for example, 10-25% by weight of chromium, 3- 8% by weight of aluminum and up to 20% by weight of nickel. The alloys can also contain small amounts or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium and the like. The metal surface or substrates can be oxidized at high temperatures, for example, 1000 ° C and higher, to improve the corrosion resistance of the alloy by forming an oxide layer on the surface of the substrate. Such oxidations induced by high temperature can improve the adhesion of the refractory metal oxide support and metallic components of catalytic promotion to the substrate. Preparation of Catalyst Composites
[0062] Catalyst composites according to one or more modalities can be formed in a single layer or in multiple layers. In some circumstances, it may be suitable to prepare a paste of catalytic material and use this paste to form multiple layers on the substrate. Catalyst composites can be prepared by known processes, for example, incipient moisture. A representative process is defined below. As used in this document, the term "coating" has its common meaning as a thin, adherent coating of a catalytic material or other material applied to a substrate material, such as a honeycomb-shaped carrier member, which is sufficiently porous to allow the flow of gas being treated to pass through.
[0063] The catalyst composite can be prepared in layers on a monolithic substrate. For a first layer of a specific coating, the finely divided particles of a high surface area refractory metal oxide, such as gamma alumina, are dissolved in an appropriate vehicle, such as water. The substrate can then be dipped one or more times in such a paste or the paste can be coated on the substrate so that the desired charge of the metal oxide will be deposited on the substrate. To incorporate components such as precious metals (for example, palladium, platinum, rhodium and / or their combinations) and stabilizers and / or promoters, such components can be incorporated into the paste before coating the substrate, as a mixture of soluble or dispersible compounds or complexes. in water. Then, the coated substrate is calcined by heating, for example, at 400-600 ° C for about 10 minutes to about 4 hours. When palladium is needed, the palladium component is used in the form of a compound or complex to achieve dispersion of the component in the refractory metal oxide support, for example, activated alumina. As used in this document, the "palladium component" refers to any compound, complex or similar that, after calcination or use, decomposes or else converts to a catalytically active form, usually metal or metal oxide. Water-soluble compounds or water-dispersible compounds or metal component complexes may be used, provided that the liquid medium used to impregnate or deposit the refractory metal component on the particles of the metal oxide support does not react adversely with the metal or its compounds or complexes or other components that may be present in the catalyst composition and is capable of being removed from the metal component by volatilization or decomposition after heating and / or applying a vacuum. In some cases, the completion of the removal of the liquid may not occur until the catalyst is put into use and subjected to the high temperatures encountered during operation. Generally, aqueous solutions of soluble compounds or complexes of precious metals are used. Non-limiting examples of suitable compounds include palladium nitrate, palladium nitrate, tetraamine, platinum chloride and platinum nitrate. During the calcination step, or at least during the initial use phase of the compound, such compounds are converted into a catalytically active form of the metal or a compound thereof.
[0064] A suitable method of preparing any layer of the layered catalyst composite of the invention is to prepare a mixture of a solution of a desired precious metal compound (for example, a palladium compound and at least one support, such as a finely divided high surface area refractory metal oxide support, such as gamma alumina, which is sufficiently dry to absorb substantially all of the solution to form a wet solid, which is later combined with water to form a coating paste In one or more embodiments, the slurry is acidic, for example, having a pH of about 2 to less than about 7. The pH of the slurry can be reduced by adding an appropriate amount of an inorganic acid or an acid organic to the paste. Combinations of both can be used when compatibility of acidic materials and raw materials is considered. Inorganic acids include, but are not limited to, nitric acid. Organic s include, but are not limited to, acetic, propionic, oxalic, malonic, succinic, adipic, glutamic, maleic, fumaric, phthalic, tartaric, citric and the like. Thereafter, if desired, compounds and / or water-soluble or dispersible stabilizers, for example, barium acetate, and a promoter, for example, lanthanum nitrate, can be added to the slurry.
[0065] A suitable method of preparing any layer of the layered catalyst compound is to prepare a mixture of a solution of a desired precious metal compound (for example, a palladium compound) and at least one support, as a support. of finely divided high surface area refractory metal oxide, such as gamma alumina, which is sufficiently dry to absorb substantially all of the solution to form a wet solid, which is later combined with water to form a coating paste. In one or more embodiments, the paste is acidic, having, for example, a pH of about 2 to less than about 7.
[0066] In one or more embodiments, the paste is sprayed to result in substantially all solids having a particle size of less than 18 microns. Spraying can be carried out on a spherical end mill or other similar equipment, and the solids content of the paste can be, for example, about 20-60% by weight or 30-40% by weight.
[0067] Additional layers, that is, second and third layers, can be prepared and deposited on the first layer, in the same way as described for the deposition of the first layer on the substrate.
[0068] Palladium has become of greater interest for use in CODs due to its relatively lower cost. However, cost is not the only factor to consider when designing an oxidative catalyst composition. Regardless of the cost, if a particular catalyst is susceptible to intoxication or degradation in a particular engine exhaust environment, that particular material will not be used in a catalyst composition. Palladium can have performance advantages over platinum in diesel engines, especially heavy duty diesel engines. For example, platinum is susceptible to inhibition (ie, intoxication) by CO in high concentrations, and platinum has a poor performance for the oxidation of methane. Palladium, on the other hand, is not self-inhibiting by CO and is known to be more effective than platinum for oxidizing methane. Since increases in CO and methane emissions are expected from some diesel engines, the use of palladium can have a significant benefit.
[0069] The catalyst composite according to one or more embodiments can be more easily appreciated by reference to FIGS. 1 and 2. FIGS. 1 and 2 show a refractory substrate member 2, according to one or more embodiments. With reference to FIG. 1, the refractory substrate member 2 is a cylindrical shape with a cylindrical outer surface 4, an upstream end face 6 and a downstream end face 8, which is identical to the end face 6. Substrate member 2 has a plurality of thin, parallel gas flow passages 10 formed within it. As seen in FIG. 2, flow passages 10 are formed by walls 12 and extend through substrate 2 from the upstream end face 6 to the downstream end face 8, the passages 10 being unobstructed so as to allow the flow of a fluid , for example, a gas stream, longitudinally through the substrate 2 through the gas flow passages 10 thereof. As is most easily seen in FIG. 2, the walls 12 are dimensioned and configured so that the gas flow passages 10 have a substantially regular polygonal shape, substantially square in the illustrated embodiment, but with rounded corners in accordance with US Patent No. 4,335,023. The first coating layer 14 undergoes adhesion to or is coated on the walls 12 of the substrate member. As shown in FIG. 2, a second coating layer 16 is coated over the first coating layer 14. In one or more embodiments, a subcoat (not shown) can be applied to the substrate below the first coating layer 14.
[0070] As shown in FIG. 2, the substrate member 2 includes voids provided by the gas flow passages 10, and the cross-sectional area of these passages 10 and the thickness of the walls 12 that define the passages can vary from one type of substrate member to another. Likewise, the weight of the coating applied to such substrates will vary from case to case. Therefore, to describe the amount of coating or catalytic metal component or other component of the composition, it is convenient to use units of component weight per unit volume of the catalytic substrate. Therefore, the units of grams per cubic inch ("g / in3") and grams per cubic foot ("g / foot3") are used in this document to mean the weight of one component per volume of the substrate member, including the volume of spaces voids of the substrate member.
[0071] In another embodiment, the coating layers can be coated by zone so that the first coating zone is at the upstream end, and the second coating zone is at the downstream end of the substrate. For example, a first coating zone or an upstream coating zone can be coated over a portion of the region upstream of the substrate, and a second coating zone or a downstream coating zone can be coated over a portion of the region a downstream of the substrate. In embodiments, the length of the first coating zone is less than the length of the second coating zone.
[0072] The catalyst composite embodiments including the first coating zone and the second coating zone can be more easily understood by reference to FIGS. 3A and 3B. FIG. 3A shows a modality of a zoned oxidation catalyst composite 20 for reducing exhaust gas emissions from a diesel engine. A substrate 22, for example, a honeycomb-shaped monolith with a length 23 and an inlet end or upstream 28 and outlet end or downstream 29 contains two separate coated coating zones. The first coating zone 24 is located adjacent to the upstream or inlet end 28 of the substrate 22 and comprises a first coating layer including Pt and Pd components and a first refractory metal oxide support. The second coating zone 27 is located adjacent to the outlet end or downstream 29 and includes Pt and Pd components and a second refractory metal oxide support. The first coating zone 24 on the upstream or inlet end 28 has a length 25 that is less than the length 26 of the second coating zone 27 on the downstream or outlet end 29 of the substrate 22. The oxidation catalyst composite 20 does not include a high load of platinum group metals (PGM) on the inlet face 28 of the catalyst. The first coating zone 24 has a PGM charge that is at least twice that of the second coating zone 27, and the first coating zone 24 has a Pt: Pd ratio that is less than 3: 1.
[0073] In one or more embodiments, the second coating zone 27 has a Pt: Pd ratio that is greater than 3: 1. In a specific embodiment, the Pt: Pd ratio in the second coating zone 27 is greater than 5: 1. In a more specific embodiment, the Pt: Pd ratio in the second coating zone 27 is greater than 1: 1. In one or more embodiments, the second coating zone 27 may comprise only Pt.
[0074] The first coating zone 24 extends from the inlet end 28 of the substrate 22 and has a length 25 that extends over the range of about 5% and about 49% of the length 23 of the substrate 22. The second coating zone 27 extends from the outlet end 29 of the substrate 22 and has a length 26 that is greater than the length 25 of the first coating zone 24. The length 29 of the second coating zone 27 extends for about from 51% to about 95% of the length 23 of the substrate 22. In one or more embodiments, the length 25 of the first coating zone 24 is 25% of the length 23 of the substrate 22, and the length 29 of the second coating zone 27 it is about 75% of the substrate length 23. In one embodiment, the first zone is in the range of 20% to 40% of the substrate length, and more specifically, 25% to 35% of the substrate. According to one or more modalities, the first coating zone promotes efficient burning of diesel fuel to create an exothermic reaction to regenerate a downstream particle filter, and the second coating promotes the oxidation of NO to NO2, which can promote the reaction Fast SCR in a downstream SCR catalyst.
[0075] According to one or more modalities, as shown in FIG. 3B, a subcoat layer 30 can be applied to the substrate 22 before the first coating zone 24 or the second coating zone 27, whichever is applied first. In a specific embodiment, the subcoat 30 does not contain any precious metal components intentionally added to the subcoat composition. For example, the inner layer may comprise a refractory oxide support. Through diffusion or migration, however, some Pd or Pt from the first coating zone 24 or the second coating zone 27 may be present in the subcoat 30. The compositions of the first coating zone 24 and the second coating zone 26 may be as described above with reference to FIG. 3A.
[0076] In one or more embodiments, the coating load is the same in the first coating zone and in the second coating zone. In other embodiments, the coating load is different in the first coating zone from the second coating zone. In one or more embodiments, the first coating zone has a PGM charge of at least twice that of the second coating zone. Suitable loads for the components in the first and second coating layers are as follows.
[0077] In one or more embodiments, the first coating zone may further comprise an alkaline earth metal selected from Ba, Be, Mg, Ca, Sr and Ra. In a specific embodiment, the first coating zone also comprises Ba. Alkaline earth can be present in an amount of about 20 g / ft3 to about 120 g / ft3 (0.70 kg / m3 to 4.24 kg / m3) (including 20, 30, 40, 50, 60, 70 , 80, 90, 100, 110 and 120 g / ft3, which correspond respectively to 0.70, 1.05, 1.41, 1.76, 2.12, 2.47, 2.83, 3.18, 3.53, 3.88 and 4.24 kg / m3).
[0078] The oxidation catalyst composite can be used in an integrated emission treatment system that comprises one or more additional components for the treatment of diesel exhaust gas emissions. For example, the emission treatment system may comprise a soot filter component and / or a selective catalytic reduction (SCR) catalytic article.
[0079] In addition to treating exhaust gas emissions through the use of the oxidation catalyst composite according to one or more modalities, a soot filter can be used to remove particulate material. The soot filter may be located upstream or downstream of the oxidation catalyst composite, but generally the soot filter will be located downstream of the oxidation catalyst composite. In one or more embodiments, the soot filter is a catalyzed soot filter (CSF). The CSF may comprise a substrate coated with a coating layer containing one or more catalysts for burning the retained soot and / or oxidizing exhaust gas stream emissions. In general, the soot-burning catalyst can be any known soot combustion catalyst. For example, CSF can be coated with one or more refractory oxides from the high surface area (for example, aluminum oxide or cerium-zirconia oxide) for the combustion of unburned hydrocarbons and, to some degree, particulate material. The soot-burning catalyst may be an oxidation catalyst comprising one or more catalysts (platinum, palladium and / or rhodium catalysts) of precious metals (PM).
[0080] In one or more modalities, the system comprises an exhaust conduit in fluid communication with a diesel engine by means of an exhaust manifold, the oxidation catalyst composite according to one or more modalities in which the substrate is a substrate continuous flow or a flow wall substrate, and a catalyzed soot filter and an SCR catalyst located downstream of the oxidation catalyst composite.
[0081] In general, any known filter substrate can be used, including, for example, a honeycomb-shaped wall flow filter, rolled or packaged fiber filter, open cell foam, sintered metal filter, etc. ., wall flow filters being preferred. Wall flow substrates useful for supporting CSF compositions have a plurality of thin, substantially parallel gas flow passages that extend along the substrate's longitudinal axis. Typically, each passage is blocked at one end of the substrate body, with alternative passages blocked at opposite end faces. Such monolithic carriers can contain up to about 700 or more flow passages (or "cells") per square inch of the cross section, although much less can be used. For example, the carrier can be about 7 to 600, more generally about 100 to 400 cells per square inch (cells per square inch, "cpsi"). The cells can have cross sections that are rectangular, square, circular, oval, triangular, hexagonal, or with other polygonal shapes. Flow wall substrates typically have a wall thickness between 0.002 and 0.1 inches. Preferred wall flow substrates have a wall thickness between 0.002 and 0.015 inches.
[0082] Typical wall flow filter substrates are composed of ceramic materials, such as, such as cordierite, a-alumina, silicon carbide, silicon nitride, zirconium dioxide, mullite, spodumene, silica alumina-magnesia or silicate zirconium or a porous, refractory metal. Wall flow substrates can also be formed from materials composed of ceramic fiber. Preferred wall flow substrates are formed from silicon carbide and cordierite. Such materials are able to withstand the environment, especially at high temperatures, found in the treatment of exhaust currents.
[0083] The exhaust gas treatment system may also comprise a selective catalytic reduction (SCR) component. The SCR component can be located upstream or downstream of the COD and / or the soot filter. Preferably, the SCR component is located downstream of a soot filter component. An SCR catalyst component suitable for use in the emission treatment system is able to effectively catalyze the reduction of the NO x component at temperatures below 600 ° C, so that adequate levels of NOx can be treated even under low load conditions, which are typically associated with lower exhaust temperatures. Preferably, the catalyst article is capable of converting at least 50% of the NOx component to N2, depending on the amount of reducing agent added to the system. Another desirable attribute for the composition is that it has the ability to catalyze the reaction of O2 with any excess of NH3 to N2 and H2O, so that NH3 is not emitted to the atmosphere. The useful SCR catalyst compositions used in the emission treatment system should also have thermal resistance at temperatures above 650 ° C. Such high temperatures can be found during regeneration of the upstream catalyzed soot filter.
Suitable SCR catalyst compositions are described, for example, in U.S. Patent Nos. 4,961,917 (the '917 patent) and 5,516,497, which are both incorporated herein by reference in their entirety. The compositions disclosed in the '917 patent include one or both of an iron and a copper promoter present in a zeolite in an amount of about 0.1 to 30 percent by weight, preferably about 1 to 5 percent by weight of the total weight of the promoter plus zeolite. In addition to their ability to catalyze the reduction of NOx with NH3 to N2, the disclosed compositions can also promote the oxidation of excess NH3 with O2, especially for those compositions that have higher concentrations of promoter. Other specific SCR compositions that can be used according to one or more modalities of the invention include 8-ring small pore molecular sieve, for example, those having the type of structure selected from the group consisting of AEI, AFT, AFX , CHA, EAB, ERI, KFI, LEV, SAS, SAT and SAV. In a specific embodiment, the 8-ring small pore molecular sieve has the CHA structure and is a zeolite. CHA zeolite may contain copper. Examples of CHA zeolites have a silica to alumina ratio (silica to alumina ratio, SAR) above about 15, and the copper content above about 0.2% by weight. In a more specific embodiment, the molar ratio of silica to alumina is from about 15 to about 256, and the copper content from about 0.2% by weight to about 5% by weight. Other compositions useful for SCR include non-zeolitic molecular sieves that have the CHA crystal structure. For example, silicoaluminophosphates such as SAPO-34, SAPO-44 and SAPO-18 can be used according to one or more modalities. Other useful SCR catalysts can include a mixed oxide, including one or more of V2O5, WO3 and TiO2.
[0085] For an SCR reaction, there are three reaction conditions that can be considered according to the NO2 / NO ratio: (1) Standard: 4 NH3 + 4 NO + O2 -> 4 N2 + 6 H2O (2) " Fast ": 4 NH3 + 2 NO + 2 NO2 -> 4 N2 + 6 H2O (3)" Slow ": (4) NH3 + 3 NO2 -> 3.5 N2 + 6 H2O.
[0086] According to modalities of the invention, the PGM on the diesel oxidation catalyst can contribute to promote the rapid reaction of SCR, and adaptation of the PGM charge and ratio can be used to achieve this goal. According to an embodiment of the invention, the oxidation catalyst provides an optimized NO2 / NOx ratio in the exhaust gases to promote the SCR reaction, in particular, what is known as the "rapid" SCR reaction.
[0087] The system may also include a NOx storage and release catalytic article (NO storage and release, NSR). In certain embodiments, either an SCR or NSR catalytic article is included in the system.
[0088] In one or more modalities, the emission treatment system comprises one or more additional components for the treatment of emission of diesel gases. An example of an emission treatment system can be more easily appreciated with reference to FIG. 4, which depicts a schematic representation of an emission treatment system 40 according to one or more modalities. With reference to FIG. 4, an exhaust gas stream containing gaseous pollutants (eg, unburned hydrocarbons, carbon monoxide, and NOx) and particulate matter is transported via conduit line 44 from an engine 42 to a diesel oxidation catalyst (COD) 46, which is coated with the oxidation catalyst composite according to various modalities. In COD 46, gaseous and non-volatile unburned hydrocarbons (for example, the soluble organic fraction or SOF, acronym for soluble organic fraction) and carbon monoxide are ignited to form carbon dioxide and water. In addition, the NOx ratio of the NOx component can be oxidized to NO2 in COD 46. The exhaust stream is then transported through conduit line 48 to a catalyzed soot filter (CSF) 50 , which retains particulate material present in the exhaust gas stream. CSF 50 is optionally catalyzed by passive regeneration. After the removal of particulate material by means of CSF 50, the exhaust gas stream is transported through conduit line 52 for a selective catalytic reduction (SCR) downstream of component 54 for treatment and / or conversion of NOx. noticed that COD 46 can be placed in a position with short coupling.
[0089] One or more modalities are directed to methods for treating a diesel engine exhaust gas stream, comprising carbon monoxide, hydrocarbons and NOx. The exhaust gas stream is passed through an inlet end and an end outlet of a catalyzed soot filter, the exhaust gas passing first through a first coating zone over the catalyzed soot filter comprising a first coating layer, including Pt and Pd components and a first metal oxide support refractory, then passing the stream of exhaust gases through a second coating zone over the catalyzed soot filter comprising a second coating layer, including platinum and palladium components and a second refractory metal oxide support. The first coating zone has a length that is less than the second coating zone. In one or more embodiments, the first coating zone has a PGM charge of at least twice that of the second coating zone. The first coating zone has a Pt / Pd ratio of less than 3: 1.
[0090] In other modalities, the subsequent diesel exhaust gas stream in contact with the CSF is directed to a selective catalytic reduction component located downstream of the CSF.
[0091] The invention is now described with reference to the following examples. Before describing several exemplary embodiments of the invention, it should be understood that the invention is not limited to the details of construction or process steps set out in the following description. The invention is capable of other modalities and can be practiced or carried out in various ways. EXAMPLES Comparative Example 1: Sample A (Uniform Coating)
[0092] A Pt / Pd coating composition was prepared with a uniform mixture of Pt and Pd on a support of a 50/50 mixture of a pseudoboemite alumina and a support of alumina stabilized with 4% lanthanum oxide by coating a aqueous paste containing PT- and Pd on a monolith substrate in cordierite honeycomb. The total load of precious metal was 40 g / ft3, and the Pt / Pd ratio was 10: 1. The aqueous paste containing Pt- and Pd was prepared as follows:
[0093] An inner layer was applied to a cordierite honeycomb substrate 300 cpsi of core 1 "DX 3" L by applying a coating of a ground pseudoboemite alumina up to a particle size 90% less than 10 μM for a charge 1 g / in3
[0094] An upper layer was prepared as follows. A support material comprising a 50/50 mixture of a pseudoboemite alumina and an alumina stabilized with 4% lanthanum oxide with D90 particles in the range of 10-12 microns was impregnated with a water-soluble Pt salt using moisture techniques incipient. Subsequently, the same support material comprising was impregnated with a water-soluble Pd salt using incipient moisture techniques. The resulting powders impregnated with Pd and Pt were placed in deionized water with zirconium acetate (5% of the total solids of the paste by weight of ZrO2), and the pH of the resulting aqueous suspension was reduced to pH by the addition of an organic acid. After the particle size reduction to 90% less than 10 μM per grind, the paste was coated on the cordierite substrate that contains the inner layer. The coated monolith was dried and then calcined in the range of 400-550 ° C for 2-4 hours. The total coating load of the top layer is approximately 2.1 g / in3 for a PGM load of 40 g / ft3 (1.41 kg / m3). Comparative Example 2: Sample B (Zonated Catalyst with a Pt / Pd ratio of 10: 1 in the first zone)
[0095] Coatings were made in a similar manner to that of Comparative Example 1, and an inner layer was applied to the honeycomb substrate. An entry zone (front) coating was applied to a PGM load of 40 g / ft3 (1.41 kg / m3), and an exit zone (rear) with a PGM load of 20 g / ft3 (0 , 70 kg / m3). Each zone had a Pt / Pd ratio of 10: 1. Each zone is approximately the same length. Example 3: Sample C
[0096] A Pt / Pd coating composition was prepared in the same way as in Comparative Example 2 above, with the precious metal charge in the entry zone being 40 g / ft3 (1.41 kg / m3) and the ratio Pt / Pd being 2: 1; the rear zone had a PGM load of 20 g / ft3 (0.70 kg / m3) and the Pt / Pd ratio was 10: 1. Example 4: Catalyst D sample
[0097] The coatings were made and applied in a similar manner to Example 3, except that the support particles were a pure alumina support with a large pore volume (average pore radius at 120 Angstrom) ground to a size of 18-20 micron D90 particle. Example 5: Catalyst E sample
[0098] A catalytic article was prepared similarly to Example 4, except that the entry zone had a Pt / Pd ratio of 1: 1. The loads were the same as in the entry and exit zone and the ratio in the Pt / Pd exit zone was 10: 1 Example 6: Catalyst F Zoned
[0099] The zoned catalyst described in this example was prepared following the same procedure as described for Example 5, except that the entry zone was only Pd (Pt: Pd = 0: 1). Example 7: Catalyst G Zoned
The zonated catalyst described in this example was prepared following the same procedure as described for Example 5, except that the exit coating zone comprises Pt / Pd in a 3: 1 ratio and the support was a silica-alumina ( 5% silica) with large pore volume. Example 8: Catalyst H Zoned
[00101] The zonated catalyst described in this example was prepared following the same procedure as described for Example 7, except that the exit coating zone comprises Pt / Pd in a 5: 1 ratio. Example 9: Catalyst I Zoned
The zonated catalyst described in this example was prepared following the same procedure as described for Example 7, except that the exit coating zone comprises Pt / Pd in a 10: 1 ratio. Example 10: Catalyst J Zoned
[00103] The zoned catalyst described in this example was prepared following the same procedure as described for Example 7, except that the inlet coating zone was only Pt (Pt: Pd = 1: 0). Example 11: Catalyst K Zoned
[00104] Example 11 comprises a full size honeycomb substrate of 300 cpsi 10.5 "D X 6" L similar to that of Comparative Example 2 above, with the entry and exit zones having an equal length. The total PGM load was 10: 1, and the entry zone had a PGM of 60 g / ft3 (2.12 kg / m3) and the exit zone had a rear PGM load of 20 g / ft3 (0 , 70 kg / m3). Example 12: Catalyst L Zoned
[00105] Example 12 was prepared in a similar manner to Example 11, except that the support particles were a support of pure alumina with a large pore volume (average pore radius at 120 Angstrom) ground to a particle size D90 18-20 microns. The total load of PGM was 40 g / ft3 (1.41 kg / m3). The entry zone was 33% of the total length of the substrate, and the exit zone was 67% of the total length. The PGM load input zone was 57.5 g / ft3 (2.03 kg / m3) with a Pt / Pd ratio of 1: 2 and the PGM load output zone was 20 g / ft3 (0.70 kg / m3) with a Pt / Pd ratio of 10: 1. Example 13: M zonated catalyst
[00106] Example 13 was similar to Example 12, except that the support particles were ~ 5% silica-alumina with a D50 particle size of 6 microns. Example 14: Catalyst N Zoned
[00107] Example 14 was similar to Example 13, except that there was no inner layer Sample Testing Examples 1-10 Fuel Ignition
[00108] Examples 1-10 were tested on samples of the 1 ”D X 3” L core in a 300 CPSI / 5mil honeycomb substrate core sample. Samples from Examples 1-10 were tested in a laboratory reactor under simulated heavy diesel conditions. Each sample was aged at 700 ° C for 5 hours in air and 10% steam. The spatial speed was 100,000 / h. The gas composition was 8% O2, with N2 equilibrium. The simulated exhaust gas was kept in a range from 300 ° C, then 275 ° C and 250 ° C to test the ignition of the fuel. Diesel fuel was injected into the gas stream to simulate an active regeneration cycle, and the injection rate increased as the temperature of the inlet gas was reduced. The target temperature of the DOC outlet gas was 600 ° C. Examples 1-10 Oxidation of NO
[00109] Core samples selected from Examples 1-10 were also tested for NO oxidation under the following conditions. The gas composition was 500 ppm CO, total HC 400 ppm, 10% O2, 300 ppm NO, 5% CO2 and 5% H2O at a spatial speed of 50,000 / h. Examples 11-14 Engine Testing
[00110] The coated catalyst compositions prepared in Examples 11-14 were tested as follows. First, the coated monoliths were mounted in the exhaust gas stream of a test diesel engine and then subjected to aging after injection at high temperature. This was achieved by maintaining the temperature at the inlet (front) face of the catalyst at 400 ° C and then periodically injecting fuel into the exhaust gas stream in front of the catalyst. The injected fuel passed to the catalyst and was burned, thus increasing the temperature measured at the outlet (rear) side of the catalyst. The temperature on the outlet (rear) side of the catalyst was controlled by controlling the amount of fuel injected into the exhaust stream. Using this method, the temperature at the rear of the catalyst was 650 ° C for 50 hours. The fuel burning ability was tested at various temperatures and spatial speeds to determine the lowest temperate in which the catalyst is active for sustained fuel burning. During the executions, the NOx emission of the DOC was measured.
[00111] After aging, the coated monoliths were evaluated for combustion of diesel fuel and NO oxidation performance in a test engine. The monoliths were individually mounted on the exhaust gas stream of a diesel engine that had a typical engine expelling NOx and soot emissions.
[00112] Test results for the coated monoliths prepared in Examples 1-14 are provided in Table 1 below. Table 1

[00113] Examples 3-6 show the benefit of catalysts prepared according to embodiments of the invention. The higher outlet temperature shows a more active catalyst for burning fuel. Example 4 shows the advantage of using an alumina support with a large pore volume.
[00114] Examples 7-10 NO oxidation data are shown in Table 2. Table 2

[00115] Table 2 shows that NO2 / NOx can be adapted according to a specific application or engine strategy.
[00116] Other experiments were conducted to optimize the load of PGM in the entrance / front coating zone. As the total load of PGM was increased (30, 40, 50, 65 g / ft3, corresponding to 1.05, 1.41, 1.76 and 2.30 kg / m3 respectively) in the frontal zone in samples based on Example 6 above, it was demonstrated that increasing the PGM load resulted in a higher outlet temperature.
[00117] Table 3 shows the data for Examples 11 and 12. Table 3

[00118] Example 12 showed a fuel ignition compared to Example 11, in which there was no ignition at 240 ° C and was unstable at 250 ° C.
[00119] Example 13 was tested, and the results are shown in Table 4. Table 4

[00120] Example 13 was a test to determine the lowest inlet temperature at which the DOC outlet temperature can reach 550 ° C in sustained fuel combustion.
[00121] Example 14 was tested and the data are shown in Table 5. Table 5

[00122] Table 5 shows that the activity decreased slightly for fuel ignition compared to Example 13.
[00123] The reference throughout this specification to "a modality", "certain modalities", "one or more modalities" or "the modality" means that a particular resource, structure, material, or characteristic described in connection with the modality is included in at least one embodiment of the invention. Thus, the appearance of phrases such as "in one or more embodiments", "in certain embodiments", "in an embodiment" or "in an embodiment" in various parts throughout this specification are not necessarily referring to the same embodiment of the invention. In addition, specific resources, structures, materials or characteristics can be combined in any suitable way in one or more modalities.
[00124] Although the invention of this document has been described with reference to specific modalities, it should be understood that these modalities are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention includes modifications and variations that are within the scope of the appended claims and their equivalents.

权利要求:
Claims (14)
[0001]
1. OXIDATION CATALYST COMPOSITE to reduce exhaust gas emissions from a diesel engine, characterized by comprising: a substrate that has a length, an inlet and an outlet end, a catalytic material in the substrate, the catalytic material including a first coating zone and a second coating zone; the first coating zone comprising a first coating layer which includes components from the group of platinum metals (PGM), platinum Pt and palladium Pd, and a first support of refractory metal oxide, the first coating zone adjacent to the inlet end of the substrate; and the second coating zone comprising a second coating layer including components of PGM, Pt platinum and palladium Pd, and a second refractory metal oxide support, the second coating layer adjacent to the outlet end of the substrate; wherein the first coating zone has a length that is less than the second coating zone, where the oxidation catalyst does not include a high PGM load on the inlet face of the catalyst and the first coating zone has a load of PGM which is at least twice that of the second coating zone, and the first coating zone has a Pt / Pd ratio less than 3: 1, the second coating zone has a Pt / Pd ratio greater than 3: 1 .
[0002]
2. COMPOSITE according to claim 1, characterized in that the Pt: Pd ratio in the second coating zone is greater than 5: 1.
[0003]
COMPOSITE according to claim 1, characterized in that the Pt: Pd ratio in the second coating zone is greater than 8: 1.
[0004]
COMPOSITE according to claim 1, characterized in that the refractory metal oxide support comprises an alumina with a pore size greater than 90 A.
[0005]
5. COMPOSITE according to claim 4, characterized in that the alumina is stabilized by doping.
[0006]
6. COMPOSITE according to claim 1, characterized in that the coating load is the same in the first coating zone and in the second coating zone.
[0007]
7. COMPOSITE according to claim 1, characterized in that the coating load is different in the first coating zone and in the second coating zone.
[0008]
8. COMPOSITE according to claim 1, characterized in that the first coating zone comprises a Pt / Pd component in an amount in the range of 40 g / ft3 to 60 g / ft3 (1.41 kg / m3 to 2.12 kg / m3).
[0009]
9. COMPOSITE according to claim 1, characterized in that the second coating zone comprises a Pd / Pd component in an amount in the range of 15 g / ft3 to 25 g / ft3 (0.53 kg / m3 to 0.88 kg / m3).
[0010]
10. COMPOSITE according to claim 8, characterized in that the first coating zone further comprises an alkaline earth metal in an amount in the range of 60 g / ft3 to 70 g / ft3 (2.12 kg / m3 to 2.47 kg / m3).
[0011]
11. COMPOSITE according to claim 1, characterized in that the length of the second coating zone and the length of the first coating zone is 1.5: 1 or greater.
[0012]
12. METHOD FOR TREATING A CHAIN OF EXHAUST GAS IN DIESEL ENGINES, characterized by comprising the passage of the exhaust gas stream through an inlet end towards an outlet end of a catalyzed soot filter, the exhaust gas. exhaust by first passing through a first coating zone on the catalyzed soot filter comprising a first coating layer including Pt platinum and Pd palladium components and a first refractory metal oxide support, and then passing the exhaust gas stream through a second coating zone on the catalyzed soot filter comprising a second coating layer including platinum and palladium components and a second refractory metal oxide support, wherein the first coating zone has a shorter length than the second coating zone , in which the first coating zone has a PGM load at least twice that of second coating zone, and the first coating zone having a Pt / Pd ratio less than 3: 1.
[0013]
13. SYSTEM FOR TREATING AN EXHAUST GAS CHAIN of a poor combustion engine including hydrocarbons, carbon monoxide and other exhaust components, the emission treatment system characterized by comprising: an exhaust conduit in fluid communication with the engine poor combustion by means of an exhaust manifold; the oxidation catalyst composite, as defined in any one of claims 1 to 11, wherein the substrate is a continuous flow substrate or a wall flow substrate; and a catalyzed soot filter and an SCR catalyst located downstream of the oxidation catalyst composite.
[0014]
14. SYSTEM, according to claim 13, characterized in that the SCR catalyst is loaded into the catalyzed soot filter.

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同族专利:

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公开号 | 公开日

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US9333490B2|2016-05-10|

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MX2015011410A|2016-04-20|

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JP6727119B2|2020-07-22|

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CA2898327A1|2014-09-25|

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CN105188930B|2018-04-03|

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WO2014151677A1|2014-09-25|

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KR102251564B1|2021-05-13|

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JP2020104112A|2020-07-09|

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CN105188930A|2015-12-23|

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EP2969205A1|2016-01-20|

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KR20150131029A|2015-11-24|

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JP2016513584A|2016-05-16|

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US20140271429A1|2014-09-18|

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BR112015022281A2|2017-07-18|

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RU2015143688A|2017-04-18|

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法律状态:
2018-11-13| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-10-08| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-08-18| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|

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2020-12-01| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-02-09| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 13/03/2014, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US201361784561P| true| 2013-03-14|2013-03-14|

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US61/784,561|2013-03-14|

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PCT/US2014/026230|WO2014151677A1|2013-03-14|2014-03-13|Zoned catalyst for diesel applications|

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