Improved hydrocarbon trap for cold start hydrocarbon control from internal combustion engines

Abstract

The present invention provides a hydrocarbon trap catalyst for controlling hydrocarbon (HC) emissions from internal combustion engines. The catalyst comprises a molecular sieve containing potassium and silver, the molecular sieve having a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 9.0 to 90.0, in which case, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.1% to 4.0% by weight, and the amount of silver in the molecular sieve is in the range of 0.2% to 10.0% by weight. The present invention also provides a process for preparing the hydrocarbon trap catalyst. The present invention further provides a hydrocarbon trap catalyst article and its use as a cold-start hydrocarbon trap.

Description

[Technical Field]

[0001] The invention claimed in this application relates to a hydrocarbon trap catalyst.

[0002] Specifically, the invention claimed in this application relates to a hydrocarbon trap catalyst for controlling hydrocarbon (HC) emissions from an internal combustion engine.

[0003] More specifically, the invention claimed in this application relates to a hydrocarbon trap catalyst for controlling HC emissions from an internal combustion engine at low exhaust temperatures. [Background technology]

[0004] During the initial stages of engine operation or other periods when the engine is running at a low temperature, known as the "low-temperature operating period," the conversion of contaminants, particularly hydrocarbons, is known to be inefficient. Consequently, a very large proportion of total oxidizing pollutants, mainly hydrocarbons, are released into the atmosphere during the low-temperature operating period.

[0005] To improve this problem, in the art, there is a known method of using a hydrocarbon trapping material, such as a specific zeolite, together with the catalyst, which adsorbs hydrocarbons at low temperatures where the oxidation catalyst is relatively ineffective, and desorbs hydrocarbons only at higher temperatures where the conversion efficiency of the oxidation catalyst is higher than during the low-temperature operating period.

[0006] One drawback of known zeolite materials is that they tend to begin desorbing hydrocarbons and, consequently releasing hydrocarbons back into the catalyst, before the catalyst reaches a temperature high enough to achieve an acceptable conversion efficiency.

[0007] Furthermore, in most HC trapping materials, the HC release temperature is too low to oxidize the released HC with the PGM-containing catalyst. Therefore, a temperature gap exists between the HC release temperature and the catalyst's effective (or light-off) temperature. Catalyst aging further exacerbates this situation, potentially lowering the HC release temperature but raising the catalyst's light-off temperature. In applications such as gasoline vehicles, where the catalyst aging temperature can exceed 850°C, the temperature gap is at least 100°C. Overcoming this temperature gap is the biggest challenge in HC trapping material research.

[0008] Therefore, it is necessary to solve this problem by finding a catalyst that can bridge the temperature gap after hydrothermal aging at 850°C and effectively control cold-start HC emissions in gasoline vehicles.

[0009] Therefore, the object of the present invention is to provide a hydrocarbon (HC) trap composition that adsorbs hydrocarbons (HC) at low temperatures and efficiently desorbs the adsorbed hydrocarbons (HC) at high temperatures. [Brief explanation of the drawing]

[0010] To provide an understanding of embodiments of the present invention, the accompanying drawings are referenced, but these drawings are not necessarily drawn to scale, and the reference numerals refer to components of exemplary embodiments of the present invention. The drawings are for illustrative purposes only and should not be construed as limiting the present invention. The above and other features, their nature, and various advantages of the claimed invention will become more apparent when considered in conjunction with the accompanying drawings in the following detailed description. [Figure 1A] The effects of metal cations in beta-zeolite on the HC desorption profiles of fresh and aged samples are shown, respectively. [Figure 1B] The effects of metal cations in beta-zeolite on the HC desorption profiles of fresh and aged samples are shown, respectively. [Figure 1C] This shows a comparison of HC emission temperatures for fresh and aged samples. [Figure 2A] The effects of Ag, K, and Ag / K in the beta-zeolite on the HC desorption profiles of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2B] The effects of Ag, K, and Ag / K in the beta-zeolite on the HC desorption profiles of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2C] The effects of Ag, K, and Ag / K in beta-zeolite on the HC desorption profiles of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2D] The effects of Ag, K, and Ag / K in the beta zeolite on the HC emission temperature of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2E] The effects of Ag, K, and Ag / K in the beta zeolite on the HC emission temperature of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2F] The effects of Ag, K, and Ag / K in the beta zeolite on the HC emission temperature of a fresh catalyst, a catalyst aged at 750°C for 5 hours, and a catalyst aged at 850°C for 5 hours are shown, respectively. [Figure 2G] The effects of Ag, K, and Ag / K on the amount of HC released during storage and after aging at 750°C / 5 hours, respectively, are shown for a fresh catalyst, a catalyst aged at 750°C / 5 hours, and a catalyst aged at 850°C / 5 hours. [Figure 2H] The effects of Ag, K, and Ag / K on the amount of HC released during storage and after aging at 750°C / 5 hours, respectively, are shown for a fresh catalyst, a catalyst aged at 750°C / 5 hours, and a catalyst aged at 850°C / 5 hours. [Figure 2I]Shows the effects of Ag, K, and Ag / K on the amount of HC stored and released for fresh catalysts, catalysts aged at 750 °C / 5 h, and catalysts aged at 850 °C / 5 h, respectively. [Figure 3A] Shows the effect of zeolite composition (SAR) on the HC desorption profile of H-beta for fresh samples and aged samples, respectively. [Figure 3B] Shows the effect of zeolite composition (SAR) on the HC desorption profile of H-beta for fresh samples and aged samples, respectively. [Figure 3C] Shows the effect of zeolite composition (SAR) on the HC release temperature of H-beta. [Figure 3D] Shows the effect of zeolite composition (SAR) on the HC desorption profile of Ag / K modified beta for fresh samples and aged samples, respectively. [Figure 3E] Shows the effect of zeolite composition (SAR) on the HC desorption profile of Ag / K modified beta for fresh samples and aged samples, respectively. [Figure 3F] Shows the effect of zeolite composition (SAR) on the HC desorption (peak) temperature of Ag / K modified beta. [Figure 4A] Shows the effect of the binder in K / Ag / beta samples for fresh samples and aged samples, respectively. [Figure 4B] Shows the effect of the binder in K / Ag / beta samples for fresh samples and aged samples, respectively. [Figure 4C] Shows the HC desorption profiles in K / Ag, Mg / Ag, Ca / Ag, and Zn / Ag modified beta for fresh samples and aged samples, respectively. [Figure 4D] Shows the HC desorption profiles in K / Ag, Mg / Ag, Ca / Ag, and Zn / Ag modified beta for fresh samples and aged samples, respectively. [Figure 4E]Shows the effect of the binder on the HC emission peak temperature for K / Ag / beta, and the effect of divalent cations (Mg, Ca, Zn) in Ag / beta on the HC emission temperature. [Figure 5A] Shows the influence of the K and Ag loadings on the HC desorption profile of fresh samples. [Figure 5B] Shows the influence of the K and Ag loadings on the HC desorption profile of aged samples. [Figure 5C] Shows the influence of the K and Ag loadings on the HC emission temperature of fresh and aged samples. [Figure 6A] Shows the HC desorption profiles in Li / Ag, Na / Ag, and Cs / Ag modified beta for fresh samples. [Figure 6B] Shows the HC desorption profiles in Li / Ag, Na / Ag, and Cs / Ag modified beta for aged samples. [Figure 6C] Shows the effect of Li, Na, and Cs in Ag / beta on the HC emission temperature. [Figure 7A] Perspective view of a honeycomb-type substrate carrier that may include a catalyst according to an embodiment of the invention claimed in this application. [Figure 7B] An enlarged view of a plurality of gas flow paths shown in FIG. 7A, an enlarged view of FIG. 7A, and a partial cross-sectional view along a plane parallel to the end face of the substrate carrier in FIG. 7A. [Figure 8] A cut-away view of an enlarged cross-section of FIG. 7A, where the honeycomb-type substrate in FIG. 7A represents a wall-flow filter substrate monolith.

Mode for Carrying Out the Invention

[0011] The claimed invention is fully described below. The claimed invention can be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided to make the claimed invention detailed and complete and to fully convey the scope of the invention to those skilled in the art. No term in this specification should be construed as referring to any unclaimed element essential to the carrying out of the disclosed materials and methods.

[0012] All methods described herein may be carried out in any preferred order unless otherwise indicated herein or expressly rejected by the context. The use of any and all examples or illustrative terms provided herein (e.g., "etc.") is solely intended to better illustrate the materials and methods and does not impose any limitation on their scope unless otherwise claimed.

[0013] Definition: The terms “a,” “an,” “the,” and similar referents used in the context of describing the materials and methods discussed herein (in particular, in the context of the following claims) should be interpreted as encompassing both singular and plural forms unless otherwise indicated herein or explicitly rejected by the context.

[0014] The enumeration of value ranges in this specification is intended solely as an abbreviation for referring to each individual value within that range, unless otherwise indicated herein, and each individual value is incorporated herein as if it were individually enumerated.

[0015] Hydrocarbon trap A hydrocarbon trap (HC trap) is a storage material that adsorbs hydrocarbons while the exhaust gas is at a low temperature and the three-way catalyst is not yet activated (for example, during a cold start), and then desorbs and releases the hydrocarbons when the exhaust gas temperature rises and the three-way catalyst reaches its light-off temperature. Examples of HC trap materials include molecular sieves such as zeolites.

[0016] The term "three-way catalyst" or "TWC catalyst" refers to a catalyst that simultaneously carries out a) the reduction of nitrogen oxides to nitrogen and oxygen, b) the oxidation of carbon monoxide to carbon dioxide, and c) the oxidation of unburned hydrocarbons to carbon dioxide and water.

[0017] In the context of the present invention, the term “wash coat” is used interchangeably with “a catalyst or catalytic composition deposited on a substrate in the form of a slurry” which forms one or more layers on a portion of each substrate. As used herein, the term “wash coat” has its usual meaning in the art as a thin, adhesive coating of a catalyst material or other material applied to the material of a substrate. Generally, a wash coat is formed by preparing a slurry containing particles of a specific solid content (e.g., 15-60% by weight) in a liquid vehicle, which is then coated onto a substrate and dried to provide a wash coat layer on each substrate.

[0018] The term "NOx" refers to nitrogen oxide compounds such as NO and / or NO2.

[0019] As used herein, the term “flow” broadly refers to any combination of fluid gases that may contain solid or liquid particulate matter.

[0020] As used herein, the terms “upstream” and “downstream” refer to the relative direction of the flow of engine exhaust gases from the engine to the exhaust pipe, with the engine being in the upstream position and the tailpipe and any pollution reduction articles and catalysts being in the downstream position.

[0021] The term "tight coupling" refers to the position of one or more catalytic converters located in close proximity to the engine exhaust manifold.

[0022] The term "underbody" refers to the location of one or more catalytic converters that are positioned away from the tightly coupled catalytic converter. Typically, underbody catalytic converters are located under the vehicle body, between the tightly coupled catalytic converter and the muffler.

[0023] As used herein, “impregnated” or “impregnation” refers to the penetration of a catalytic material or metal / metal salt into the porous structure of a support material.

[0024] The term "co-impregnation" refers to a catalyst preparation method in which two soluble metal salts are mixed to obtain a mixture. The mixture is then impregnated into a support. According to the present invention, a soluble platinum group metal salt and a solubility-enhancing metal salt are mixed together to obtain a mixture. This mixture is then impregnated into a support.

[0025] Hydrocarbon trap catalyst: In one embodiment, the present invention provides a hydrocarbon trap catalyst comprising a molecular sieve, wherein the molecular sieve comprises a first metal and a second metal, the first metal being potassium and the second metal being silver, the molecular sieve having a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 9.0 to 90.0, and in either case, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.1% to 4.0% by weight, and the amount of silver in the molecular sieve is in the range of 0.2% to 10.0% by weight.

[0026] Molecular sieves: The term "molecular sieve" refers to a porous solid having pores with molecular dimensions ranging from 3 to 20 Å in diameter. Examples of molecular sieves include zeolites, carbon, glass, oxides, and phosphates. Some are crystalline, having uniform pore sizes as represented by their crystal structure, such as zeolites. Others are amorphous, such as carbon molecular sieves. Most molecular sieves currently on the market are zeolites.

[0027] Preferably, the molecular sieve is a zeolite. More preferably, the molecular sieve is a beta-zeolite.

[0028] Zeolites are defined as aluminosilicates having an open three-dimensional framework structure composed of TO4 tetrahedra (where T is Al or Si) sharing corners. The cations that balance the charge of the anionic framework are loosely associated with the skeletal oxygen, and the remaining pore volume is filled with water molecules. The non-skeletal cations are generally replaceable, and the water molecules are removable.

[0029] As used herein, the term “zeolite” refers to a specific type of molecular sieve having a composition containing aluminosilicates of Group IA and Group IIA elements such as hydrogen, sodium, potassium, magnesium, or calcium. Zeolites are crystalline materials with fairly uniform pores, ranging in diameter from about 3 to 10 angstroms, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. The silica-to-alumina molar ratio (SAR) of zeolites can vary over a wide range, but is generally greater than or equal to 2.

[0030] Beta-zeolite: Beta zeolite (with structural code BEA) has a complex structure consisting of intercrystals of two different structures, polymorph A and polymorph B. Both polymorphs contain a three-dimensional network structure with 12 ring pores. Each polymorph grows as a two-dimensional sheet, and the sheets within the beta zeolite are randomly alternating between the two polymorphs. The intercrystallization of the polymorphs has little effect on the pores in two dimensions, but in the defect direction, the pores meander rather than become blocked.

[0031] Beta-zeolites are widely used in various process industries for reducing pollutants and for controlling emissions in automobiles. Due to their large pore size, beta-zeolites are ideal for adsorbing hydrocarbon molecules of various sizes.

[0032] Beta-zeolites are typically protonated or H-type and are known to be the best zeolite structure for HC trapping. However, the HC release temperature of H-beta-zeolites is too low, around 200°C, which is far below the catalytic effective temperature for HC oxidation. After aging, there is little difference in HC release temperature among beta-zeolite materials regardless of the SiO2 / Al2O3 ratio.

[0033] Replacing transition metal cations (e.g., Cu, Ni, Co, or Pd) in beta-zeolite results in almost no difference in HC emission temperature.

[0034] BET surface area of ​​molecular sieves: "BET surface area" refers to the Brunauer, Emmett, and Teller methods used to determine surface area by N2 adsorption.

[0035] Preferably, the BET surface area of ​​the fresh molecular sieve is approximately 400 to 600 m². 2 It is / g.

[0036] Preferably, the BET surface area of ​​the molecular sieve after aging at 850°C for 5.0 hours is 300-500 m². 2 It is / g.

[0037] More preferably, the BET surface area of ​​the molecular sieve after aging at 850°C for 5.0 hours is 350-450 m². 2 It is / g.

[0038] Amount of metal: potassium Preferably, the amount of potassium is in the range of 0.1 to 4.0% by weight, based on the total weight of the hydrocarbon trap catalyst. More preferably, the amount of potassium is in the range of 0.4 to 2.0% by weight, based on the total weight of the hydrocarbon trap catalyst t. Even more preferably, the amount of potassium is in the range of 0.5 to 1.0% by weight, based on the total weight of the hydrocarbon trap catalyst.

[0039] silver Preferably, the amount of silver is in the range of 0.2 to 10% by weight, based on the total weight of the hydrocarbon trap catalyst. More preferably, the amount of silver is in the range of 1.0 to 5.0% by weight, based on the total weight of the hydrocarbon trap catalyst. Even more preferably, the amount of silver is in the range of 2.0 to 4.0% by weight, based on the total weight of the hydrocarbon trap catalyst.

[0040] Molar ratio: Preferably, the molar ratio of potassium to silver in the molecular sieve is in the range of 2:1 to 1:2. More preferably, the molar ratio of potassium to silver in the molecular sieve is in the range of 1.5:1 to 1:1.5. Preferably, the molar ratio of potassium to aluminum in the molecular sieve is in the range of 0.05 to 0.8. More preferably, the molar ratio of potassium to aluminum in the molecular sieve is in the range of 0.09 to 0.5.

[0041] Preferably, the molar ratio of silver to aluminum in the molecular sieve is in the range of 0.05 to 0.8. More preferably, the molar ratio of silver to aluminum in the molecular sieve is in the range of 0.09 to 0.5.

[0042] binder: The term "binder" refers to a substance intended to improve the cohesive forces between solid components in a slurry and to maintain the physical integrity of the wash coat after the slurry has been coated onto a substrate. While the primary role of the binder is inherently physical, it can have desirable or undesirable interactions with the active components in the slurry, thereby altering its performance in hydrocarbon adsorption and desorption.

[0043] Preferably, the catalyst comprises a binder selected from zirconia, alumina, silica, or any combination thereof. The binder may be in the form of an oxide, hydroxide, salt, or any combination thereof. More preferably, the binder is zirconia. Preferably, the zirconia source is zirconium acetate.

[0044] Preferably, the amount of binder is in the range of 1.0 to 20.0% by weight, based on the total weight of the molecular sieve. More preferably, the amount of binder is in the range of 2.5 to 7.5% by weight, based on the total weight of the molecular sieve.

[0045] Dopant: The term "dopant" refers to a metal cation chemically bonded to an interchangeable site in a zeolite. Depending on the properties of the metal, metal cations can have greater interactions with hydrocarbon molecules compared to protons. Furthermore, certain metal cations can stabilize the zeolite structure better against hydrothermal aging compared to protons. Mixed metal cations can have a synergistic effect, maintaining the hydrothermal stability of the zeolite and increasing the adsorption strength of hydrocarbons.

[0046] Preferably, the molecular sieve contains a dopant selected from lithium, sodium, cesium, calcium, magnesium, zinc, or any combination thereof. Preferably, the dopant is ion-exchanged and exists in elemental form. Preferably, the amount of dopant is in the range of 0.1 to 10% by weight based on the total weight of the molecular sieve. More preferably, the amount of dopant is in the range of 0.1 to 5.0% by weight based on the total weight of the molecular sieve. Even more preferably, the amount of dopant is in the range of 0.2 to 2.0% by weight based on the total weight of the molecular sieve.

[0047] In one embodiment, the molecular sieve contains silver and potassium impregnated into the molecular sieve.

[0048] In another embodiment, the molecular sieve contains liquid-phase ion-exchanged silver and potassium on the molecular sieve.

[0049] In yet another embodiment, the molecular sieve contains solid ion-exchanged silver and potassium on the molecular sieve.

[0050] In a preferred embodiment, the hydrocarbon trap catalyst comprises a molecular sieve comprising a first metal and a second metal, wherein the first metal is potassium and the second metal is silver, the molecular sieve having a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 20.0 to 64.0, in any case, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.4% to 2.0% by weight, the amount of silver in the molecular sieve is in the range of 1.0% to 5.0% by weight, and the molecular sieve is a zeolite.

[0051] In a more preferred embodiment, the hydrocarbon trap catalyst comprises a molecular sieve comprising a first metal and a second metal, wherein the first metal is potassium and the second metal is silver, the molecular sieve having a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 20.0 to 64.0, in either case, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.4% to 2.0% by weight, the amount of silver in the molecular sieve is in the range of 1.0% to 5.0% by weight, and the molecular sieve is beta-zeolite.

[0052] In one most preferred embodiment, the hydrocarbon trap catalyst comprises a molecular sieve and a binder, the molecular sieve comprising a first metal and a second metal, the first metal being potassium and the second metal being silver, the molecular sieve having a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 20.0 to 64.0, in any case, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.4% to 2.0% by weight, the amount of silver in the molecular sieve is in the range of 1.0% to 5.0% by weight, the molecular sieve is beta-zeolite, and the binder is zirconia.

[0053] Process for preparing hydrocarbon trap catalysts: The present invention also provides a process for preparing a hydrocarbon trap catalyst as defined above herein, the process comprising at least the following steps: Step a): Impregnate the molecular sieve with a silver salt solution to obtain a silver-containing molecular sieve material. Step b): The silver-containing molecular sieve material obtained in step (a) is calcined in air at a temperature in the range of 300 to 500°C for 1.0 to 2.0 hours to obtain calcined silver-containing molecular sieve material. Step c): A potassium salt solution is impregnated into the calcined silver-containing molecular sieve material to obtain a potassium-silver-containing molecular sieve material. Step d): The potassium-silver-containing molecular sieve material is calcined at a temperature in the range of 500-650°C for 1.0-2.0 hours to obtain a hydrocarbon trap catalyst.

[0054] Preferably, the molecular sieve is a zeolite. More preferably, the molecular sieve is a beta-zeolite.

[0055] Preferably, step (b) is carried out at a temperature of 350 to 450°C for 1.0 to 2.0 hours.

[0056] Preferably, step (d) is carried out at a temperature of 515 to 575°C for 1.5 to 2.0 hours.

[0057] Catalyst article: In another embodiment, the present invention provides a hydrocarbon trap catalyst article comprising a hydrocarbon trap catalyst as defined herein deposited on a first substrate, wherein the first substrate is a honeycomb substrate or a flow-through substrate. Preferably, the hydrocarbon trap catalyst article is a single-layer article, a two-layer catalyst article, or a zone-type catalyst article.

[0058] Preferably, the amount of the hydrocarbon trap catalyst supported in the wash coat is 1.0 to 4.0 g / in. 3 More preferably, the amount of the washcoat supporting the hydrocarbon trap catalyst is 2.0 to 3.0 g / in. 3 That is the case.

[0059] Preferably, the hydrocarbon trap catalyst article comprises a first layer deposited on at least a portion of a first substrate and a second layer deposited on at least a portion of the first layer, wherein the first layer comprises the hydrocarbon trap catalyst as defined herein, and the second layer comprises a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a carrier.

[0060] Preferably, the total platinum group metal (PGM) load is 1.0 to 200 g / ft. 3 More preferably, the total platinum group metal (PGM) load is 5.0 to 100 g / ft. 3 That is the case.

[0061] Carrier / Carrier material: In catalyst materials, catalyst compositions, or catalyst washcoats, "supporting body" refers to a material that accepts metals (e.g., PGMs), stabilizers, co-catalysts, binders, etc., by precipitation, association, dispersion, impregnation, or other suitable methods.

[0062] Throughout this application, the term “supported” has a general meaning in the field of heterogeneous catalysts. Generally, the term “supported” refers to catalytically active species or their respective precursors attached to a support material. The support material may be inert or may participate in the catalytic reaction. Commonly supported catalysts are prepared by impregnation or coprecipitation and optionally subsequent calcination.

[0063] Preferably, the support is selected from ceria-alumina composites, ceria-zirconia mixed oxides, alumina, and rare-earth metal oxide-doped ceria-zirconia solid solutions.

[0064] Ceria-alumina composite: Ceria-alumina composites are composites in which CeO2 is distributed on the surface and / or in the bulk of alumina as particles and / or nanoclusters. Each oxide may have its own distinct chemical and solid-physical state. Surface CeO2 modification of alumina can take the form of isolated parts (particles or clusters) or a layer of ceria that partially or completely covers the surface of the alumina.

[0065] Preferably, the amount of ceria-alumina composite present in the catalyst article is in the range of 5.0 to 80% by weight, based on the total weight of the second layer. More preferably, the amount of ceria-alumina composite present in the catalyst article is in the range of 10 to 60% by weight, based on the total weight of the second layer. More preferably, the amount of ceria-alumina composite present in the catalyst article is in the range of 15 to 40% by weight, based on the total weight of the second layer.

[0066] The amount of CeO2 (cerium oxide) in the ceria-alumina composite present in the second layer is preferably 1.0 to 60% by weight, based on the total weight of the ceria-alumina composite in the second layer. More preferably, the amount of CeO2 in the ceria-alumina composite present in the second layer is 5.0 to 50% by weight, based on the total weight of the ceria-alumina composite in the second layer. Even more preferably, the amount of CeO2 in the ceria-alumina composite present in the second layer is 5.0 to 30% by weight, based on the total weight of the ceria-alumina composite in the second layer. And even more preferably, the amount of CeO2 in the ceria-alumina composite present in the second layer is 8.0 to 20% by weight, based on the total weight of the ceria-alumina composite in the second layer.

[0067] The amount of Al2O3 (aluminum oxide) in the ceria-alumina composite present in the second layer is preferably 40 to 99% by weight, based on the total weight of the ceria-alumina composite in the second layer. More preferably, the amount of Al2O3 in the ceria-alumina composite present in the second layer is 50 to 95% by weight, based on the total weight of the ceria-alumina composite in the second layer. Even more preferably, the amount of Al2O3 in the ceria-alumina composite present in the second layer is 70 to 95% by weight, based on the total weight of the ceria-alumina composite in the second layer. And even more preferably, the amount of Al2O3 in the ceria-alumina composite present in the second layer is 80 to 92% by weight, based on the total weight of the ceria-alumina composite in the second layer.

[0068] Preferably, the average particle size of ceria in the ceria-alumina composite is less than 200 nm. More preferably, the particle size is in the range of 5.0 nm to 50 nm. The particle size is determined by transmission electron microscopy.

[0069] The ceria-alumina composite present in the second layer may contain dopants selected from zirconia, lantana, titania, hafnia, magnesia, calcia, strontian, barrier, or any combination thereof. The total amount of dopants in the ceria-alumina composite is preferably in the range of 0.001 to 15% by weight, based on the total weight of the ceria-alumina composite in the second layer.

[0070] Ceria-alumina composites can be prepared by methods known to those skilled in the art, such as coprecipitation or surface modification. In these methods, a suitable cerium-containing precursor is contacted with a suitable aluminum-containing precursor, and the resulting mixture is then converted into a ceria-alumina composite. Suitable cerium-containing precursors are, for example, water-soluble cerium salts and colloidal ceria suspensions. Ceria-alumina can also be prepared by atomic layer deposition, in which a ceria compound is selectively reacted with an alumina surface, and ceria is formed on the alumina surface after calcination. This deposition / calcination step may be repeated until a layer of the desired thickness is reached. Suitable aluminum-containing precursors are, for example, aluminum oxides such as gibbsite, boehmite-gamma alumina, delta alumina, or theta alumina, or combinations thereof. The mixture can then be converted into a ceria-alumina composite by a calcination step.

[0071] Ceria-zirconia mixed oxide (CZO): The term "complex metal oxide" refers to a mixed metal oxide containing an oxygen anion and at least two different metal cations. In ceria-zirconia mixed oxides, cerium cations and zirconium cations are distributed within the oxide lattice structure. The terms "complex oxide" and "mixed oxide" can be used interchangeably. Because the metal cations are distributed within the oxide lattice structure, these structures are also commonly referred to as solid solutions.

[0072] Preferably, the amount of ceria-zirconia mixed oxide present in the second layer is 20 to 80% by weight, based on the total weight of the second layer. More preferably, the amount of ceria-zirconia mixed oxide present in the second layer is in the range of 30 to 70% by weight, based on the total weight of the second layer. Most preferably, the amount of ceria-zirconia mixed oxide present in the second layer is in the range of 40 to 60% by weight, based on the total weight of the second layer. Preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 10 to 60% by weight, based on the total weight of the ceria-zirconia mixed oxide present in the second layer, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 40 to 90% by weight, based on the total weight of the ceria-zirconia mixed oxide present in the second layer.

[0073] More preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 20-50% by weight based on the total weight of the ceria-zirconia mixed oxide in the second layer, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 50-80% by weight based on the total weight of the ceria-zirconia mixed oxide in the second layer.

[0074] More preferably, the ceria (calculated as CeO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 30-50% by weight, based on the total weight of the ceria-zirconia mixed oxide in the second layer, and the zirconia (calculated as ZrO2) of the ceria-zirconia mixed oxide present in the second layer is present in an amount of 50-70% by weight, based on the total weight of the ceria-zirconia mixed oxide in the second layer.

[0075] Ceria-zirconia mixed oxides function as oxygen storage components. The term "oxygen storage component" (OSC) refers to an entity that has a polyvalent state and can react actively with reducing agents such as carbon monoxide (CO) and / or hydrogen under reducing conditions, and then react with oxidizing agents such as oxygen or nitrogen oxides under oxidizing conditions.

[0076] In preferred embodiments, the ceria-zirconia mixed oxide present in the second layer includes a dopant selected from lantana, titania, hafnia, magnesia, calcia, strontia, barrier, yttrium, hafnium, praseodymium, neodymium, or any combination thereof. The dopant metal may be incorporated into the crystalline structure of the composite metal oxide in cationic form, deposited on the surface of the composite metal oxide in oxide form, or present in a composite form having the composite metal oxide, so to speak, as a blend of mixtures of both the dopant and the composite metal oxide at a microscale in oxide form. Preferably, the dopant is present in an amount of 1.0 to 20% by weight, or more preferably 5.0 to 15% by weight, based on the total weight of the ceria-zirconia mixed oxide present in the second layer.

[0077] alumina: The alumina present in the second layer is preferably gamma alumina or activated alumina. It is typically more than 60 square meters / gram ("m² / g"), often up to about 200 m 2This indicates the BET surface area of ​​fresh material of 1 / g or more. Activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain a considerable amount of eta, kappa, and theta alumina phases. Preferably, the activated alumina is high bulk density gamma-alumina, low or medium bulk density large-pore gamma-alumina, low bulk density large-pore boehmite, or gamma-alumina.

[0078] Preferably, the amount of alumina present in the second layer is in the range of 1.0 to 40% by weight, based on the total weight of the second layer. More preferably, the amount of alumina present in the second layer is in the range of 5.0 to 30% by weight, based on the total weight of the second layer. Most preferably, the amount of alumina present in the second layer is in the range of 5.0 to 20% by weight, based on the total weight of the second layer.

[0079] The alumina present in the catalyst article is preferably doped with a dopant selected from barium, lantana, zirconia, neodymian, yttria, ceria, or titania, the amount of which is preferably 1.0 to 30% by weight, based on the total weight of the alumina and dopant present in the second layer. More preferably, the dopant-doped alumina is selected from lantana-alumina, titania-alumina, ceria-zirconia-alumina, zirconia-alumina, lantana-zirconia-alumina, barrier-alumina, barrier-lantana-alumina, barrier-lantana-neodymia-alumina, or any combination thereof.

[0080] Rare earth metal oxide-doped zirconia solid solution: Rare-earth metal oxide-doped zirconia solid solutions are defined as crystalline zirconia materials that incorporate one or more rare-earth metals into their bulk structure, forming a single crystalline phase when measured by an X-ray diffraction spectrometer.

[0081] Replacing a small portion of the cations in a host oxide lattice with external metal ions is called doping. In other words, in doping, the dopant element replaces the metal element in the parent structure without changing the type of crystal phase. However, the difference in size between the dopant element and the metal element in the parent structure may change the lattice parameters (crystallinity or surface area). For example, when La is incorporated into a monoclinic ZrO2 structure, the complex has the same structure as monoclinic ZrO2. However, because the ionic radius of La is small (relative to Zr), its lattice parameters (unit cell volume) are slightly smaller. The degree of contraction (or shift of the XRD 2-theta position) depends on the La dopant content.

[0082] The term "solid solution" refers to a homogeneous mixture of two different types of atoms in a solid state, which has a single-crystal structure.

[0083] Preferably, the rare earth metal is selected from lanthanum, praseodymium, neodymium, yttrium, or any combination thereof. More preferably, the rare earth metal is lanthanum.

[0084] Most preferably, the carrier is a lanthanum oxide-doped zirconia solid solution.

[0085] Preferably, the amount of rare earth metal in oxide form in the rare earth metal oxide-doped zirconia solid solution is in the range of 1.0 to 25% by weight, based on the total weight of the rare earth metal oxide-doped zirconia solid solution, and the amount of zirconia in the rare earth metal oxide-doped zirconia solid solution is in the range of 75 to 99% by weight, based on the total weight of the rare earth metal oxide-doped zirconia solid solution.

[0086] Preferably, the hydrocarbon trap catalyst article comprises a first zone and a second zone, the first zone comprising a hydrocarbon trap catalyst as defined herein, deposited on at least the inlet portion of a first substrate, and the second zone comprising a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a carrier, deposited on at least the outlet portion of the first substrate.

[0087] In the context of the present invention, the term “first zone” is used interchangeably with “inlet zone” or “forward zone,” and the term “second zone” is used interchangeably with “outlet zone” or “rear zone.” The terms “first zone” and “second zone” also describe the relative position of the catalyst article in the flow direction and the relative position of the catalyst article when it is placed within the exhaust gas treatment system, respectively. The first zone is located upstream, while the second zone is located downstream. The first zone covers at least a portion of the substrate from the inlet, while the second zone covers at least a portion of the substrate from the outlet. The inlet of the substrate is a first end (inlet end portion) that can receive the flow of engine exhaust gas from the engine, while the outlet of the substrate is a second end (outlet end portion) from which the treated exhaust gas flow exits.

[0088] The substrate is coated in a zone-type manner by catalyst layers, namely a first layer and a second layer. The first zone is coated with a first catalyst layer (i.e., a hydrocarbon trap catalyst), and the second zone is coated with a second catalyst layer (i.e., a ternary catalyst). The first catalyst layer covers 60-100% of the area of ​​the first zone, and the second catalyst layer covers 60-100% of the area of ​​the second zone.

[0089] The first zone occupies the inlet portion of the substrate, and the second zone occupies the outlet portion of the substrate.

[0090] The first and second zones together cover 50-100% of the length of the substrate. Preferably, the first and second zones together cover 90-100% of the length of the substrate, and more preferably, the first and second zones together cover the entire length of the substrate or the entire accessible surface area of ​​the substrate.

[0091] The term "accessible surface" refers to the surface of a substrate that can be covered by conventional coating techniques used in the field of catalyst preparation, such as impregnation techniques.

[0092] Preferably, the first zone covers 10-90% of the total length of the substrate from the inlet, and the second zone covers 10-90% of the total length of the substrate from the outlet, but the first and second zones together cover 20-100% of the length of the substrate. More preferably, the first zone covers 20-80% of the total length of the substrate from the inlet, and the second zone covers 20-80% of the total length of the substrate from the outlet, but the first and second zones together cover 40-100% of the length of the substrate. Even more preferably, the first zone covers 30-70% of the total length of the substrate from the inlet, and the second zone covers 30-70% of the total length of the substrate from the outlet, but the first and second zones together cover 60-100% of the length of the substrate. More preferably, the first zone covers 40-50% of the total length of the substrate from the entrance, and the second zone covers 40-50% of the total length of the substrate from the exit, but the first and second zones together cover 80-100% of the length of the substrate.

[0093] Zone 1: The first zone is coated with a first catalyst layer containing a hydrocarbon trap catalyst.

[0094] Preferably, the first catalyst layer covers 60-100% of the area of ​​the first zone. More preferably, the first catalyst layer covers 70-100% of the area of ​​the first zone. Most preferably, the first catalyst layer covers 80-100% of the area of ​​the first zone.

[0095] Zone 2: The second zone is coated with a second catalyst layer comprising a ternary catalyst containing at least one platinum group metal selected from platinum, palladium, or rhodium supported on a support. Preferably, the second catalyst layer covers 60-100% of the area of ​​the second zone. More preferably, the second catalyst layer covers 70-100% of the area of ​​the second zone. Most preferably, the second catalyst layer covers 80-100% of the area of ​​the second zone.

[0096] Base material: The substrate (first substrate or second substrate) of the catalyst article claimed in this application may be composed of any material typically used to prepare automotive catalysts. In a preferred embodiment, the substrate is a ceramic substrate, a metal substrate, a ceramic foam substrate, a polymer foam substrate, or a woven fiber substrate. In a more preferred embodiment, the substrate is a ceramic or metal monolithic honeycomb structure.

[0097] The substrate is provided with multiple wall surfaces to which the catalyst layer(s) or wash coat described herein is applied and bonded, thereby acting as a carrier for the catalyst material.

[0098] Preferred metal substrates 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 nickel, chromium, and / or aluminum, and the total amount of these metals may, advantageously, be at least 15 wt% of the alloy, for example, 1025 wt% of chromium, 3 to 8 wt% of aluminum, and up to 20 wt% of nickel. The alloy may also contain small or trace amounts of one or more metals such as manganese, copper, vanadium, and titanium. The surface of the metal substrate may be oxidized at a high temperature, for example, 1000°C or higher, to form an oxide layer on the surface of the substrate, thereby improving the corrosion resistance of the alloy and promoting adhesion of the wash coat layer to the metal surface.

[0099] Preferred ceramic materials used to construct the substrate include any suitable refractory material, such as cordierite, mullite, cordierite-alumina, silicon nitride, zircon mullite, scia pyroxene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alumina, and aluminosilicate.

[0100] Any suitable substrate may be used, such as a monolithic flow-through substrate having multiple fine parallel gas channels extending from the inlet to the outlet surface of the substrate so that the channels are open to the fluid flow. The channels, which are essentially straight paths from inlet to outlet, are defined by walls on which the catalyst material is coated as a wash coat so that the gas flowing through the channels comes into contact with the catalyst material. The channels in the monolithic substrate are thin-walled channels of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, or circular. Such structures contain about 60 to about 1200 or more gas inlet openings (i.e., "cells") (cpsi) per square inch of cross-section, more commonly about 300 to 900 cpsi. The wall thickness of the flow-through substrate can vary, but a typical range is 0.002 to 0.1 inches. Typical commercially available flow-through substrates are cordierite substrates with 400 cpsi and a wall thickness of 6 mil, or 600 cpsi and a wall thickness of 4 mil. However, it will be understood that the present invention is not limited to a particular type, material, or shape of substrate. In an alternative embodiment, the substrate may be a wall-flow substrate, where each passage is blocked by a non-porous plug at one end of the substrate body, and alternating passages are blocked at opposing end faces. This requires the gas to flow through the porous walls of the wall-flow substrate to reach the outlet. Such monolithic substrates can contain up to about 700 cpsi or more, e.g., about 100–400 cpsi, more typically about 200–300 cpsi. The cross-sectional shape of the cells can vary as described above. Wall-flow substrates typically have a wall thickness of 0.002–0.1 inches. Typical commercially available wall-flow substrates are constructed from porous cordierite, examples of which have a wall thickness of 200 cpsi and 10 mils or a wall thickness of 300 cpsi and 8 mils, and a wall porosity of 45–65%. Other ceramic materials such as aluminum titanate, silicon carbide, and silicon nitride are also used as wall-flow filter substrates. However, it will be understood that the present invention is not limited to a specific type, material, or shape of substrate.It should be noted that, when the substrate is a wall-flow substrate, the catalyst composition can penetrate into the pore structure of the porous wall in addition to being placed on the surface of the wall (i.e., partially or completely block the pore openings). In one embodiment, the substrate has a flow-through ceramic honeycomb structure, a wall-flow ceramic honeycomb structure, or a metal honeycomb structure.

[0101] Figures 7A and 7B show an exemplary substrate 2 in the form of a flow-through substrate coated with the washcoat composition / catalyst layer(s) described herein. Referring to Figure 7A, the exemplary substrate 2 has a cylindrical shape and has a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 which is identical to the end surface 6. The substrate 2 has a plurality of fine, parallel gas channels 10 formed therein. As can be seen from Figure 7B, the channels 10 are formed by walls 12 and extend through the substrate 2 from the upstream end surface 6 to the downstream end surface 8, and the channels 10 are not blocked so that a fluid, such as a gas flow, passing longitudinally through the substrate 2 can flow through the gas channels 10. As can be seen more clearly in Figure 7B, the walls 12 are dimensioned and constructed so that the gas channels 10 have a substantially regular polygonal shape. As shown in the figures, the washcoat composition / catalyst layer(s) can be applied in a plurality of separate layers if desired. In the illustrated embodiment, the wash coat comprises a separate first wash coat layer 14 adhered to the wall 12 of the base material member, and a second separate wash coat layer 16 coated on the first wash coat layer 14. In one embodiment, the present invention as claimed in this application can also be implemented with two or more wash coat layers (e.g., three or four layers), and is not limited to the illustrated two-layer embodiment.

[0102] Figure 8 shows an exemplary substrate 2 of a wall flow filter substrate coated with the washcoat composition described herein. As can be seen from Figure 8, the exemplary substrate 2 has a plurality of passages 52. The passages are tubularly enclosed by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. The alternating passages are blocked at the inlet end by an inlet plug 58 and at the outlet end by an outlet plug 60, forming a checkerboard pattern with opposing passages at the inlet 54 and outlet 56. The gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet plug 60, and diffuses through the channel wall 53 (which is porous) to the outlet side 66. The gas cannot return to the inlet side of the wall due to the inlet plug 58. The porous wall flow filter used in the present invention is catalytic in that the wall of the element has one or more catalytic materials on it or contains one or more catalytic materials within it. The catalyst material may be present only on the inlet side of the element wall, only on the outlet side, on both the inlet and outlet sides, or the wall itself may consist of all or part of the catalyst material. The present invention includes using one or more layers of catalyst material on the inlet and / or outlet walls of an element.

[0103] Preparation of catalyst articles: In another aspect of the present invention, a process for preparing the catalyst articles described herein is also provided.

[0104] Preferably, the process is This specification provides for the preparation of a first slurry containing the hydrocarbon trap catalyst defined above, The first slurry is deposited onto a first substrate, wherein the first substrate is a honeycomb substrate or a flow-through substrate. The first substrate is subjected to calcination at a temperature in the range of 400 to 700°C, Includes. Preferably, the process is This specification provides for the preparation of a first slurry containing the hydrocarbon trap catalyst defined above, The method involves preparing a second slurry containing a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium, supported on a support, The first slurry is deposited on at least a portion of the first substrate to obtain a first layer. The second layer is obtained by depositing the second slurry onto at least a portion of the first layer. The base material is subjected to calcination at a temperature in the range of 400 to 700°C, Includes.

[0105] Preferably, the process is This specification provides for the preparation of a first slurry containing a hydrocarbon trap catalyst as defined above, and a second slurry containing a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a support, The first slurry is deposited at the inlet end portion of the substrate to obtain a first zone, The second zone is obtained by depositing a second slurry at the outflow end of the substrate, The base material is subjected to calcination at a temperature in the range of 400 to 700°C, Includes.

[0106] The process for preparing the slurry includes techniques selected from incipient wetness impregnation, incipient wetness co-impregnation, and post-addition.

[0107] For the synthesis of heterogeneous materials, i.e., catalysts, an initial wet impregnation technique, also known as capillary impregnation or dry impregnation, is generally used.

[0108] Typically, a metal precursor is dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a catalyst carrier having a pore volume equal to the volume of the added solution. Capillary action draws the solution into the pores of the carrier. If the solution is added beyond the pore volume of the carrier, the solution transport changes from a capillary process to a much slower diffusion process. The catalyst is dried and calcined to remove volatile components in the solution and deposit the metal on the surface of the catalyst carrier. The concentration profile of the impregnated material depends on the mass transport conditions within the pores during impregnation and drying.

[0109] The carrier particles are typically dry enough to absorb substantially all of the solution and form a moist solid. Typical aqueous solutions of water-soluble compounds or complexes of the active metal are used, such as rhodium chloride, rhodium nitrate (e.g., Rh(NO)3 and its salts), rhodium acetate, or combinations thereof when rhodium is the active metal; palladium nitrate, tetraamine palladium nitrate, palladium acetate, or combinations thereof when palladium is the active metal; and platinum nitrate, platinum acetate, or combinations thereof when platinum is the active metal. After treating the carrier particles with the active metal solution, the particles are dried by heat treatment at a high temperature (e.g., 100-150°C) for a certain period of time (e.g., 1-3 hours), and then calcined to convert the active metal into a more catalytically active form. An exemplary calcination process involves heat treatment in air at a temperature of approximately 400-550°C for 10 minutes to 3 hours. The above process may be repeated as necessary to achieve the desired level of active metal impregnation.

[0110] Substrate coating: The catalyst compositions described above are typically prepared in the form of catalyst particles as described above. These catalyst particles are mixed with water to form a slurry for coating a catalyst substrate, such as a honeycomb substrate. In addition to the catalyst particles, the slurry may optionally contain a binder in the form of alumina, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide, an associative thickener, and / or a surfactant (including anionic, cationic, nonionic, or amphoteric surfactants). Other exemplary binders include boehmite, gamma-alumina, or delta / theta alumina, and silica sol. If present, the binder is typically used in an amount of about 1.0–5.0% by weight of the total washcoat load. Acidic or basic species are added to the slurry to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by adding ammonium hydroxide, aqueous nitric acid solution, or acetic acid. The typical pH range of the slurry is about 3.0–12. The slurry can be pulverized to reduce the particle size and promote particle mixing. Pulverization is achieved using a ball mill, continuous mill, or other similar equipment, and the solid content of the slurry may be, for example, about 20–60% by weight, more specifically about 20–40% by weight. In one embodiment, the pulverized slurry is characterized by a D90 particle size of about 10–40 micrometers, preferably 10–30 micrometers, and more preferably about 10–15 micrometers. D90 is determined using a dedicated particle size analyzer. The equipment used in this example measures the particle size in a small volume slurry using laser diffraction. Typically, D90 in micrometers means that 90% of the particles have a diameter less than that value.

[0111] The slurry is coated onto the catalyst substrate using any wash-coat technique known in the art. For example, the catalyst substrate is immersed in the slurry one or more times, or otherwise coated with the slurry. The coated substrate is then dried at a high temperature (e.g., 100-150°C) for a certain period of time (e.g., 10 minutes to 3 hours), and then calcined by heating at, for example, 400-700°C, typically for about 10 minutes to about 3 hours. After drying and calcining, the final wash-coat coating layer is considered to be essentially solvent-free.

[0112] After calcination, the amount of catalyst supported by the wash-coat technique described above can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the amount of catalyst supported can be changed by altering the slurry rheology. The coating / drying / calcination process for producing the wash-coat may be repeated as needed to build up the coating to the desired level of supported catalyst or thickness, meaning that more than one wash-coat may be applied.

[0113] The coated substrate may be aged by subjecting it to heat treatment. For example, aging is carried out at a temperature of about 850°C to about 1050°C, in the presence of steam, and under gasoline engine exhaust conditions for 50 to 300 hours. Thus, according to the present invention, an aged catalyst article is provided. An effective carrier material such as a ceria-alumina composite maintains a high percentage (e.g., about 50 to 100%) of its pore volume during aging (e.g., aging at about 850°C to about 1050°C in the presence of steam for about 50 to 300 hours).

[0114] Waste disposal system: In another aspect of the present invention, an exhaust gas treatment system, a) A hydrocarbon trap catalyst article as defined above in this specification, b) Optionally, a three-way catalyst article and An exhaust gas treatment system is also provided, which comprises

[0115] Preferably, the exhaust gas treatment system comprises i) an engine that generates an exhaust gas stream; ii) a hydrocarbon trap catalyst article as defined above herein; and iii) a three-way catalyst article, and is provided with The hydrocarbon trap catalyst article is disposed downstream of the engine, and the three-way catalyst article is disposed downstream in fluid communication with the hydrocarbon trap catalyst article.

[0116] Preferably, the three-way catalyst article contains at least one platinum group metal selected from platinum, palladium, or rhodium supported on a second substrate. Preferably, the three-way catalyst article is a single-layer catalyst article, or a two-layer catalyst article, or a zone-type catalyst article. Preferably, the total platinum group metal (PGM) loading is 1.0 to 200 g / ft 3 and more preferably, the total platinum group metal (PGM) loading is 5.0 to 100 g / ft 3

[0117] In another aspect of the present invention, a method for treating a gaseous exhaust stream containing hydrocarbons, carbon monoxide, and nitrogen oxides is provided, which comprises contacting the exhaust stream with a hydrocarbon trap catalyst article according to the present invention or an exhaust gas treatment system according to the present invention.

[0118] The present invention also provides a method for reducing the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in a gaseous exhaust stream, which comprises contacting the gaseous exhaust stream with a hydrocarbon trap catalyst article according to the present invention or an exhaust gas treatment system according to the present invention to reduce the levels of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas.

[0119] ​In another aspect of the present invention, the use of a hydrocarbon trap catalyst article as a cold start hydrocarbon trap is also provided. Preferably, the present invention provides the use of a hydrocarbon trap catalyst article as a cold start hydrocarbon trap in an internal combustion engine.

[0120] It has been found that the exchange of silver (Ag) into zeolites such as beta-zeolites can significantly affect the HC release temperature. Fresh Ag-beta zeolite exhibited a very high HC desorption temperature (approximately 390°C higher than fresh H-beta). However, after aging at 850°C, its HC peak temperature became comparable to that of aged H-beta zeolite.

[0121] Fresh K-beta zeolite can moderately raise the HC desorption temperature (by only about 50°C) compared to H-beta zeolite, but after aging at 850°C, the advantage decreased to less than 20°C.

[0122] Interestingly, materials obtained by supporting both Ag and K on zeolites such as beta-zeolite exhibited both high HC emission temperatures and excellent hydrothermal stability. Aged Ag / K / beta materials yielded HC emission peak temperatures more than 150°C higher than aged H-beta-zeolite reference materials.

[0123] When Ag and K are supported, the composition (SAR) of the beta-zeolite is important for HC capture / release performance. In a series of beta-zeolite materials with different SARs fabricated using a template-free method, Ag / K / beta materials with SARs of 9.0 to 64 have been found to exhibit superior performance compared to H-beta-zeolite reference materials that have an HC peak temperature at least 190°C higher after aging.

[0124] Furthermore, the addition of other alkali metals such as Na and Cs may also be effective in stabilizing Ag in zeolites. On the other hand, divalent metals such as Mg, Ca, and Zn have been found not to be effective in stabilizing Ag.

[0125] Furthermore, it has been found that the binder used in the preparation of Ag / K / beta compositions can make a difference in HC trapping performance. Zirconia-based binders are superior to alumina or silica-based binders, as well as to Ag / K / beta compositions without a binder.

[0126] The present invention will be further described by the following embodiments. Features of each embodiment can be combined with any of the other embodiments, where appropriate and practical.

[0127] Embodiment 1: The present invention relates to a hydrocarbon trap catalyst comprising a molecular sieve, wherein the molecular sieve comprises a first metal and a second metal, the first metal being potassium and the second metal being silver. The molecular sieve has a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 9.0 to 90.0. In either case, the hydrocarbon trap catalyst is provided, in which, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.1% to 4.0% by weight, and the amount of silver in the molecular sieve is in the range of 0.2% to 10.0% by weight.

[0128] Embodiment 2: The hydrocarbon trap catalyst according to Embodiment 1, wherein the molecular sieve contains ion-exchanged potassium and silver.

[0129] Embodiment 3: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 2, wherein the molecular sieve has a silica-to-alumina ratio (SAR) in the range of 20.0 to 64.0.

[0130] Embodiment 4: A hydrocarbon trap catalyst according to any one of embodiments 1 to 3, wherein the molecular sieve is a zeolite.

[0131] Embodiment 5: A hydrocarbon trap catalyst according to any one of embodiments 1 to 4, wherein the molecular sieve is a beta-zeolite.

[0132] Embodiment 6: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 5, wherein the molar ratio of potassium to silver in the molecular sieve is in the range of 1.5:1 to 1:1.5.

[0133] Embodiment 7: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 6, wherein the molar ratio of potassium to aluminum in the molecular sieve is in the range of 0.05 to 0.8.

[0134] Embodiment 8: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 7, wherein the molar ratio of silver to aluminum in the molecular sieve is in the range of 0.05 to 0.8.

[0135] Embodiment 9: A hydrocarbon trap catalyst according to any of Embodiments 1 to 8, wherein the catalyst further comprises a binder selected from zirconia, alumina, silica, or any combination thereof, the amount of the binder being in the range of 1.0 to 20.0% by weight based on the total weight of the molecular sieve.

[0136] Embodiment 10: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 9, wherein the molecular sieve further comprises a dopant selected from lithium, sodium, cesium, calcium, magnesium, zinc, or any combination thereof, the dopant being ion-exchanged and present in elemental form, and the amount of the dopant being in the range of 0.1 to 10% by weight based on the total weight of the molecular sieve.

[0137] Embodiment 11: A hydrocarbon trap catalyst according to any one of Embodiments 1 to 10, wherein the molecular sieve contains silver and potassium impregnated in the molecular sieve, or liquid-phase ion-exchanged silver and potassium on the molecular sieve, or solid-phase ion-exchanged silver and potassium on the molecular sieve.

[0138] Embodiment 12: The BET surface area of ​​the molecular sieve is 300-500 m² after aging at 850°C for 5.0 hours. 2 A hydrocarbon trap catalyst according to any one of embodiments 1 to 11, wherein the concentration is / g.

[0139] Embodiment 13: A process for preparing a hydrocarbon trap catalyst according to any one of Embodiments 1 to 12, comprising at least the following steps, namely: a. A step of impregnating a molecular sieve with a silver salt solution to obtain a silver-containing molecular sieve material, b. A process of obtaining a calcined silver-containing molecular sieve material by calcining a silver-containing molecular sieve material in air at a temperature in the range of 300 to 500°C for 1.0 to 2.0 hours, c. A step of impregnating a calcined silver-containing molecular sieve material with a potassium salt solution to obtain a potassium-silver-containing molecular sieve material, d. A step of obtaining a hydrocarbon trap catalyst by calcining a potassium-silver-containing molecular sieve material at a temperature in the range of 500-600°C for 1.0-2.0 hours, A process that includes this.

[0140] Embodiment 14: A hydrocarbon trap catalyst article comprising a hydrocarbon trap catalyst described in any of Embodiments 1 to 12 deposited on a first substrate, wherein the first substrate is a honeycomb substrate or a flow-through substrate.

[0141] Embodiment 15: A hydrocarbon trap catalyst article comprising a first layer deposited on at least a portion of a first substrate and a second layer deposited on at least a portion of the first layer, wherein the first layer comprises a hydrocarbon trap catalyst according to any of embodiments 1 to 12, and the second layer comprises a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a carrier.

[0142] Embodiment 16: A hydrocarbon trap catalyst article comprising a first zone and a second zone, wherein the first zone comprises a hydrocarbon trap catalyst according to any of embodiments 1 to 12 deposited on at least a portion of a first substrate, and the second zone comprises a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a carrier, deposited on at least a portion of the first substrate.

[0143] Embodiment 17: The present invention provides an exhaust gas treatment system comprising a hydrocarbon trap catalyst article described in any of embodiments 14 to 16, and optionally a three-way catalyst article.

[0144] Embodiment 18: An exhaust gas treatment system according to Embodiment 1, comprising an engine that generates an exhaust gas flow, a hydrocarbon trap catalyst article according to any one of Embodiments 14 to 16, and a three-way catalyst article, An exhaust gas treatment system in which a hydrocarbon trap catalyst is located downstream of the engine, and a three-way catalytic converter is located downstream in fluid communication with the hydrocarbon trap catalyst.

[0145] Embodiment 19: Use of a hydrocarbon trap catalyst article as a cold start hydrocarbon trap, according to any of embodiments 14 to 16.

[0146] The embodiments of the claimed invention are more adequately illustrated by the following embodiments, which are provided to illustrate specific embodiments of the invention and should not be construed as limiting them. [Examples]

[0147] Example 1: Preparation of different zeolites (with or without metal) Samples 1-6 Sample 1 is H-beta zeolite obtained by calcining commercially available NH4-beta zeolite in an oven at 550°C for 2 hours.

[0148] Samples 2-6 were prepared by ion exchange of NH4-beta zeolite (the precursor of sample 1) with metal cations in the liquid phase. Metal nitrates were used for samples 1, 5, and 6, and metal acetates were used for samples 3 and 4. Specifically, 20 g (dry basis) of the parent zeolite (NH4-beta) was weighed and set aside. The calculated amount of metal salt was dissolved in 800 mL of deionized water in a 2 L beaker to prepare a 0.1 M metal solution. The parent zeolite was added to the metal solution while constantly stirring. Since Ag is photosensitive, the beaker was completely covered with aluminum foil for Ag exchange. For all other exchanges, only the top of the beaker was covered with aluminum foil to minimize water evaporation. The slurry was heated using a hot plate until the solution temperature reached 70-80°C and maintained at this temperature for 24 hours. After the exchange, heating was stopped and the slurry was cooled to near room temperature. The slurry was filtered using a vacuum filter, and the filtered cake was washed with 1 L of deionized water while continuously stirring at room temperature for 2 hours, and then filtered again. The filtered cake was then dried at 110°C for 2 hours and baked in an oven at 500°C for 2 hours. The baked material was analyzed by XRF to obtain the SiO2 / Al2O3 molar ratio (SAR) and metal loading, which are shown in Table 1.

[0149] [Table 1]

[0150] Example 2: Zeolite containing potassium, silver, or both. Samples 7-12 Sample 7 was an H-beta zeolite with a SAR > 100, obtained from a commercial supplier. Sample 8 was Ag-beta obtained using the same procedure as for Sample 2. Specifically, 20 g (dry basis) of the parent zeolite (NH4-beta) was weighed and set aside. A 0.05 M metal solution was prepared by dissolving the calculated amount of metal salt in 800 mL of deionized water in a 2 L beaker. The parent zeolite (NH4-beta) was added to the metal solution with constant stirring. The beaker was completely covered with aluminum foil during the exchange. The slurry was heated using a hot plate until the solution temperature reached 70-80°C and maintained at this temperature for 24 hours. After the exchange, heating was stopped and the slurry was cooled to near room temperature. The slurry was filtered using a vacuum filter, and the filter cake was washed with 1 L of deionized water with constant stirring at room temperature for 2 hours, and then filtered again. Next, the filtered cake was dried at 110°C for 2 hours and baked in an oven at 500°C for 2 hours. XRF analysis of the baked material showed that the material contained 3.76% by weight of Ag. Sample 9 is Ag-beta obtained using the same procedure as Sample 2. Specifically, 20 g (dry basis) of parent zeolite (NH4-beta) was weighed and set aside. A calculated amount of metal salt was dissolved in 200 mL of deionized water in a 2 L beaker to prepare a 0.1 M metal solution. Parent zeolite (NH4-beta) was added to the metal solution while constantly stirring. During the exchange, the beaker was completely covered with aluminum foil. The slurry was heated using a hot plate until the solution temperature reached 70-80°C and maintained at this temperature for 24 hours. After the exchange, heating was stopped and the slurry was cooled to near room temperature. The slurry was filtered using a vacuum filter, and the filtered cake was washed with 1 L of deionized water while constantly stirring at room temperature for 2 hours, and then filtered again. The filtered cake was then dried at 110°C for 2 hours and baked in an oven at 500°C for 2 hours. XRF analysis of the baked material showed that the material contained 2.7 wt% Ag. Sample 10 was prepared by impregnating H-beta (Sample 1) with an Ag nitrate solution using the initial wetting technique. The impregnated sample was baked at 500°C for 1 hour. The baked sample was calculated to contain 3.7 wt% Ag.

[0151] Sample 11 was prepared by impregnating H-beta (Sample 1) with a potassium nitrate solution using an initial wetting technique. The impregnated sample was calcined at 500°C for 1 hour. The calcined sample was calculated to contain 1.1% by weight of potassium.

[0152] Sample 12 was prepared by impregnating 3.76Ag-beta (Sample 8) with a potassium nitrate solution using the initial wetting technique. The impregnated sample was calcined at 500°C for 1 hour. The calcined sample was calculated to contain 3.76% by weight of Ag and 1.1% by weight of K.

[0153] [Table 2]

[0154] Example 3: Zeolites with various SARs Samples 13-22 Sample 13 is an H-beta zeolite with a SAR of 21. The H-beta (SAR=21) was suspended in deionized water to prepare a slurry with approximately 30% by weight of solids. A zirconium acetate binder equivalent to 5% by weight of a zeolite support (as ZrO2) was added to the slurry while stirring, and then the slurry was pulverized for 5 minutes. The pulverized slurry was dried under stirring and then calcined in air at 550°C for 1 hour.

[0155] Sample 14 is an H-beta zeolite with a SAR of 64. The H-beta (SAR=64) was suspended in deionized water to prepare a slurry with approximately 30% by weight of solids. A zirconium acetate binder equivalent to 5% by weight of a zeolite support (as ZrO2) was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and then calcined in air at 550°C for 1 hour.

[0156] Sample 15 is an H-beta zeolite with a SAR of 100. The H-beta (SAR=100) was suspended in deionized water to prepare a slurry with approximately 30% by weight of solids. A zirconium acetate binder equivalent to 5% by weight of a zeolite support (as ZrO2) was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and then calcined in air at 550°C for 1 hour.

[0157] Sample 16 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0158] Sample 17 was prepared by sequentially impregnating H-beta zeolite with Ag and K using a SAR of 42. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0159] Sample 18 was prepared by sequentially impregnating H-beta zeolite with SAR=9 with Ag and K. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0160] Sample 19 was prepared by sequentially impregnating H-beta zeolite with SAR=16 with Ag and K. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0161] Sample 20 was prepared by sequentially impregnating H-beta zeolite with SAR=21 with Ag and K. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0162] Sample 21 was prepared by sequentially impregnating H-beta zeolite with SAR=64 with Ag and K. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0163] Sample 22 was prepared by sequentially impregnating H-beta zeolite with Ag and K using a SAR of 100. First, using the initial wetting technique, sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a K nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0164] [Table 3]

[0165] Example 4: Zeolite with Binder Samples 23-30 Sample 23 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, K nitrate solution was impregnated into the calcined Ag / beta zeolite and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. Zirconium acetate binder, equivalent to 5% by weight of zeolite support as ZrO2, was added to the slurry while stirring and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0166] Sample 24 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, K nitrate solution was impregnated into the calcined Ag / beta zeolite and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. An alumina-based binder (boehmite) equivalent to 5% by weight of Al2O3 as a zeolite support was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0167] Sample 25 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, K nitrate solution was impregnated into the calcined Ag / beta zeolite and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A colloidal silica binder equivalent to 5% by weight of SiO2 as a zeolite support was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0168] Sample 26 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, K nitrate solution was impregnated into the calcined Ag / beta zeolite and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 1.00% by weight of K. The calcined K / Ag / beta material was then suspended in deionized water to prepare a slurry with approximately 30% by weight of solids. The slurry was pulverized for 5 minutes. [No binder was added to this slurry.] The pulverized slurry was dried while stirring and calcined in air at 550°C for 1 hour.

[0169] Sample 27 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and Mg. First, using the initial wetting technique, Sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a Mg nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 0.32% by weight of Mg. Next, the calcined Mg / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0170] Sample 28 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and Ca. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, Ca nitrate solution was impregnated into the calcined Ag / beta, and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 0.54% by weight of Ca. Next, the calcined Ca / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. Zirconium acetate binder, equivalent to 5% by weight of a zeolite support as ZrO2, was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0171] Sample 29 was prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and Zn. First, using the initial wetting technique, Sample 1 was impregnated with an Ag nitrate solution and calcined in air at 400°C for 1 hour. Next, the calcined Ag / beta was impregnated with a Zn nitrate solution and then calcined in air at 550°C for 1 hour. The resulting material contained 2.76% by weight of Ag and 0.85% by weight of Zn. Next, the calcined Zn / Ag / beta material was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0172] Sample 30 is a K / Ag / Al2O3 reference material. It was prepared by sequentially impregnating a gamma-Al2O3 support with Ag and K. First, using the initial wetting technique, an Ag nitrate solution was impregnated into the Al2O3 support and calcined in air at 400°C for 1 hour. Next, a K nitrate solution was impregnated into the calcined Ag / Al2O3 and then calcined in air at 550°C for 1 hour. The resulting material contains 2.76% by weight of Ag and 1.00% by weight of K. Next, the calcined K / Ag / Al2O3 material was suspended in deionized water to form a slurry with a solid content of approximately 30% by weight. An alumina-based binder (boehmite) equivalent to 5% by weight of the Al2O3 support was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0173] [Table 4]

[0174] Example 5: HC trapping of K / Ag / zeolite as a function of K and Ag loading amounts Samples 31-37 Samples 31 to 37 were prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and K. First, using the initial wetting technique, Ag nitrate solution was impregnated into Sample 1 and calcined in air at 400°C for 1 hour. Next, K nitrate solution was impregnated into the calcined Ag / beta zeolite and then calcined in air at 550°C for 1 hour. The composition of the obtained materials is shown in Table 5. Each of the calcined K / Ag / beta materials was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. Zirconium acetate binder, equivalent to 5% by weight of zeolite support as ZrO2, was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0175] [Table 5]

[0176] Example 6: Ag / beta zeolite modified with Li, Na, or Cs Samples 38 to 40 were prepared by sequentially impregnating H-beta zeolite (Sample 1) with Ag and alkali metals (Li, Na, or Cs). First, using the initial wetting technique, a solution of Ag nitrate was impregnated into Sample 1, and it was calcined in air at 400°C for 1 hour. For the second impregnation, nitrate solutions of Li (Sample 38), Na (Sample 39), or Cs (Sample 40) were used as alkali metal precursors. After the second impregnation, all samples were calcined in air at 550°C for 1 hour. The composition of the obtained materials is shown in Table 6. Each of the calcined materials was suspended in deionized water to prepare a slurry with a solid content of approximately 30% by weight. A zirconium acetate binder equivalent to 5% by weight of a zeolite support as ZrO2 was added to the slurry while stirring, and then pulverized for 5 minutes. The pulverized slurry was dried under stirring and calcined in air at 550°C for 1 hour.

[0177] [Table 6]

[0178] Example 7: Test Sample molding and aging procedure: All samples were pulverized and sieved down to fragments of 250-500 pm, after which performance tests were conducted.

[0179] All samples were aged at 850°C for 5 hours with 10% steam using a lean / rich feed (4% O2 / N2 for 10 minutes / H2 / N2 for 10 minutes). Selected samples were also aged at 750°C for 5 hours under the same feed conditions.

[0180] HC trap test The HC trap was measured with a feed containing 200 ppm C1 toluene, 0.5% CO, 0.2% H2, 200 ppm NO, approximately 0.4% O2, 10% H2O, and the remainder N2 (actual O2 was adjusted to λ=1). When normalized for 3 mL of coated catalyst, the gas space-time velocity was 40,000 h -1The catalyst was initially set to 50°C and exposed to 10% H2O / air for 5 minutes. The entire feed was equilibrated in bypass mode for 15 minutes. The entire feed was then switched to the sample to be measured at 50°C and held at this temperature for 90 seconds. After the immersion period, the sample was heated to 550°C at a heating rate of 40°C / min, during which the feed was flowed through the sample. Hydrocarbon (HC) concentration was continuously monitored throughout the experiment using a flame ionization detector. HC concentrations below 200 ppm (inlet level) were considered HC adsorption, while those above 200 ppm were considered HC release or desorption. The HC concentration profile was plotted as a function of temperature to determine the HC release (desorption) temperature. The amount of adsorbed HC can be integrated with respect to time from time=0 to the point when the HC concentration reached 200 ppm. The amount of released HC is obtained by integrating the HC concentration above 200 ppm.

[0181] Insights: H-beta zeolite exhibited excessively low hydrocarbon desorption temperatures, particularly after hydrothermal aging. Similar performance was observed in all beta zeolites with different SARs. Several transition metals (Cu, Ni, Co, Pd, K, and Ag) were replaced with beta zeolites. The Cu, Ni, Co, and Pd-replaced beta samples did not show a significant difference in HC desorption temperature compared to H-beta zeolites. Fresh K-beta increased the HC desorption temperature (by approximately 50°C) compared to H-beta, but after aging at 850°C, the advantage decreased to less than 20°C. Fresh Ag-beta exhibited a very high HC desorption temperature (approximately 390°C higher than fresh H-beta). However, after aging at 850°C, its HC peak temperature became comparable to that of aged H-beta zeolite. The zeolite supported with Ag / K exhibited surprisingly high HC emission temperatures and excellent hydrothermal stability. • Fresh Ag / K / beta maintained the HC peak temperature of Ag / beta. Ag / K / beta aged at 850°C continued to exhibit a high HC peak temperature (approximately 180°C higher than aged H-beta). Therefore, Ag / K / beta retains almost the same performance as fresh Ag / K / beta and is far more thermally stable than all single cation / beta compounds. In the case of Ag / K / beta, the HC release characteristics are related to the zeolite composition. Among them, Ag / K / beta (SAR9), Ag / K / beta (SAR16), and Ag / K / beta (SAR64) showed the best overall performance. The binder used in sample preparation affects the properties of Ag / K / beta. Zr binders are superior not only to Al or Si binders, but also to Ag / K / beta samples without a binder. Other cations (Mg, Ca, Zn) used as substitutes for K in Ag / beta on an equimolar basis showed inferior performance compared to Ag / K / beta after aging. • Li or Na, used as an equimolar substitute for K in Ag / beta, showed inferior performance compared to Ag / K / beta after aging. • Cs, used as a substitute for K on an equimolar basis in Ag / K / beta, showed comparable performance to Ag / K / beta after aging.

Claims

1. A hydrocarbon trap catalyst comprising a molecular sieve, wherein the molecular sieve comprises a first metal and a second metal. The first metal is potassium, and the second metal is silver. The molecular sieve has a minimum pore size of at least 4.5 Å and a maximum pore size of less than 7.5 Å, and a silica-to-alumina ratio (SAR) in the range of 9.0 to 90.

0. In either case, the hydrocarbon trap catalyst wherein, based on the total weight of the hydrocarbon trap catalyst, the amount of potassium in the molecular sieve is in the range of 0.1% to 4.0% by weight, and the amount of silver in the molecular sieve is in the range of 0.2% to 10.0% by weight.

2. The hydrocarbon trap catalyst according to claim 1, wherein the molecular sieve comprises ion-exchanged potassium and silver.

3. The hydrocarbon trap catalyst according to any one of claims 1 to 2, wherein the molecular sieve has a silica-to-alumina ratio (SAR) in the range of 20 to 64.

4. The hydrocarbon trap catalyst according to any one of claims 1 to 3, wherein the molecular sieve is a zeolite.

5. The hydrocarbon trap catalyst according to any one of claims 1 to 4, wherein the molecular sieve is a beta-zeolite.

6. The hydrocarbon trap catalyst according to any one of claims 1 to 5, wherein the molar ratio of potassium to silver in the molecular sieve is in the range of 1.5:1 to 1:1.

5.

7. The hydrocarbon trap catalyst according to any one of claims 1 to 6, wherein the molar ratio of potassium to aluminum in the molecular sieve is in the range of 0.05 to 0.

8.

8. The hydrocarbon trap catalyst according to any one of claims 1 to 7, wherein the molar ratio of silver to aluminum in the molecular sieve is in the range of 0.05 to 0.

8.

9. The hydrocarbon trap catalyst according to any one of claims 1 to 8, wherein the catalyst comprises a binder selected from zirconia, alumina, silica, or any combination thereof, and the amount of the binder is in the range of 1.0 to 20.0% by weight based on the total weight of the molecular sieve.

10. The hydrocarbon trap catalyst according to any one of claims 1 to 9, wherein the molecular sieve comprises a dopant selected from lithium, sodium, cesium, calcium, magnesium, zinc, or any combination thereof, the dopant is ion-exchanged and exists in elemental form, and the amount of the dopant is in the range of 0.1 to 10.0% by weight based on the total weight of the molecular sieve.

11. The hydrocarbon trap catalyst according to any one of claims 1 to 10, wherein the molecular sieve contains silver and potassium impregnated in the molecular sieve, or liquid-phase ion-exchanged silver and potassium on the molecular sieve, or solid-phase ion-exchanged silver and potassium on the molecular sieve.

12. The BET surface area of ​​the molecular sieve is 300 to 500 m² after aging at 850°C for 5.0 hours. ２ A hydrocarbon trap catalyst according to any one of claims 1 to 11, wherein the amount is / g.

13. A process for preparing a hydrocarbon trap catalyst according to any one of claims 1 to 12, comprising at least the following steps, namely, a) A step of impregnating the molecular sieve with a silver salt solution to obtain a silver-containing molecular sieve material, b) A step of obtaining a calcined silver-containing molecular sieve material by calcining the silver-containing molecular sieve material in air at a temperature in the range of 300 to 500°C for 1.0 to 2.0 hours, c) A step of impregnating the calcined silver-containing molecular sieve material with a potassium salt solution to obtain a potassium-silver-containing molecular sieve material, d) A step of obtaining the hydrocarbon trap catalyst by calcining the potassium-silver-containing molecular sieve material at a temperature in the range of 500 to 600°C for 1.0 to 2.0 hours, A process that includes this.

14. A hydrocarbon trap catalyst article comprising a hydrocarbon trap catalyst according to any one of claims 1 to 12 deposited on a first substrate, wherein the first substrate is a honeycomb substrate or a flow-through substrate.

15. A hydrocarbon trap catalyst article comprising a first layer deposited on at least a portion of the first substrate and a second layer deposited on at least a portion of the first layer, wherein the first layer comprises the hydrocarbon trap catalyst according to any one of claims 1 to 12, and the second layer comprises a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium supported on a carrier.

16. A hydrocarbon trap catalyst article comprising a first zone and a second zone, wherein the first zone comprises the hydrocarbon trap catalyst according to any one of claims 1 to 12, deposited on at least a portion of the first substrate, and the second zone comprises a ternary catalyst comprising at least one platinum group metal selected from platinum, palladium, or rhodium, supported on a carrier, deposited on at least a portion of the first substrate.

17. a) A hydrocarbon trap catalyst article according to any one of claims 14 to 16, b) Optionally, a three-way catalyst article and An exhaust gas treatment system equipped with the following features.

18. The aforementioned system i. An engine that generates exhaust gas flow, ii. A hydrocarbon trap catalyst article according to any one of claims 14 to 16, iii. Three-way catalyst articles, Equipped with, The exhaust gas treatment system according to claim 17, wherein the hydrocarbon trap catalyst article is located downstream of the engine, and the three-way catalyst article is located downstream in fluid communication with the hydrocarbon trap catalyst article.

19. Use of the hydrocarbon trap catalyst article according to any one of claims 14 to 16 as a cold start hydrocarbon trap.

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