Catalytic active material as well as preparation method and application thereof

Abstract

The invention relates to a catalytic active material as well as a preparation method and application thereof, and belongs to the technical field of three-way catalysis. The catalytic active material comprises an active material body and a molecular sieve, the molecular sieve is provided with a plurality of pore channels, the active material body is packaged in the pore channels, and the active material body comprises a first precious metal and a second precious metal; wherein the first precious metal or the second precious metal is independently packaged in part of the pore channels; by packaging multiple metals on the molecular sieve, when the molecular sieve is used as a three-way catalyst, multiple precious metals on a single coating component are integrated, and back pressure rise is avoided. And at least part of the noble metal is independently encapsulated in the pore channels of the molecular sieve, and spatial isolation of the molecular sieve structure is utilized to avoid agglomeration of noble metal oxide nanoparticles due to movement at high temperature and catalyst deactivation caused by easy formation of PdRh, PtRh and other noble metal alloys due to Ostwaldski curing of the noble metal in a reducing atmosphere.

Description

Technical Field

[0001] The present application relates to the field of three-way catalysis technology, and in particular to a catalytically active material and a preparation method and application thereof. Background Art

[0002] The three-way catalytic converter is the most important off-board purification device in the automobile exhaust system. It can convert harmful gases such as CO (carbon monoxide), HC (hydrocarbons) and NOx (nitrogen oxides) emitted from automobile exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction. In theory, the three-way catalyst for automobiles has an infinite service life, but in actual use, the three-way catalyst often faces problems such as active metal sintering and active metal poisoning, which cause the three-way catalyst to become deactivated and need to be cleaned or replaced.

[0003] Traditional three-way catalyst preparation methods mostly use a simple impregnation method to load precious metals such as platinum (Pt), rhodium (Rh), palladium (Pd) on the surface of an alumina carrier or a mixed carrier of alumina and oxygen storage materials, using only the surface of the oxygen storage material and the alumina carrier itself as the site for precious metal loading. However, CO and HC in automobile exhaust have strong reducibility, which can easily cause the reduction of precious metals during use. After being reduced, the precious metals will sinter or alloy due to the high temperature environment, which will reduce the service life and catalytic stability of the three-way catalyst and ultimately affect the emission performance of the vehicle. Some people have proposed encapsulating precious metals in molecular sieves to eliminate the deactivation caused by reduction sintering, but usually only one metal is encapsulated on one molecular sieve. Faced with the need for catalytic coatings that require multiple metals, the only way is to increase the type of loaded precious metals added to the coating, resulting in an increase in the thickness of the coating, which will cause the back pressure of the three-way catalytic converter to increase and affect the power economy. Summary of the invention

[0004] The present application provides a catalytically active material and a preparation method and application thereof, which can encapsulate multiple metals on a molecular sieve to achieve a collection of multiple precious metals on a single coating component.

[0005] In a first aspect, the present application provides a catalytically active material, which includes an active material body and a molecular sieve, wherein the molecular sieve has a plurality of pores, the active material body is encapsulated in the pores, and the active material body includes a first precious metal and a second precious metal; wherein the first precious metal or the second precious metal is individually encapsulated in part of the pores.

[0006] As an optional embodiment, the first precious metal and the second precious metal both include one of platinum, rhodium and palladium, and the first precious metal and the second precious metal are different.

[0007] As an optional embodiment, the molecular sieve includes at least one of S-1 molecular sieve, Y-type molecular sieve and ZSM-5 molecular sieve.

[0008] As an optional implementation manner, the mass of the active material body is 0.05% to 20% of the total mass of the molecular sieve.

[0009] In a second aspect, the present application provides a method for preparing the catalytically active material provided in the first aspect, the method comprising:

[0010] Mixing the precursor of the first noble metal and a silane coupling agent to prepare a first gel;

[0011] Mixing the first gel and a molecular sieve raw material to obtain a second gel;

[0012] Obtaining a seed molecular sieve encapsulated with the second noble metal;

[0013] mixing the second gel and the seed molecular sieve to obtain a mixture;

[0014] performing a hydrothermal reaction on the mixture to obtain a hydrothermal reaction product;

[0015] The hydrothermal reaction product is calcined to obtain a catalytically active material.

[0016] As an optional implementation, the diameter of the pores of the seed molecular sieve is smaller than the diameter of the silane coupling agent.

[0017] As an optional embodiment, the silane coupling agent includes at least one of the carbon chain silane coupling agent-chloromethyl triethoxysilane, chloropropyl triethoxysilane, aminopropyl triethoxysilane, γ-(β-aminoethyl)aminopropyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, γ-mercaptopropyl triethoxysilane and γ-mercaptopropyl trimethoxysilane; and / or

[0018] The precursor of the first noble metal includes at least one of a nitrate, a chloride, an acetate and an alkoxide of the noble metal; and / or

[0019] The molecular sieve raw materials include silicon source, aluminum source, inorganic base and template agent.

[0020] As an optional embodiment, when the molecular sieve raw material contains a silicon source, an aluminum source and a template, the silicon source includes at least one of tetraethyl orthosilicate, silica gel and silicon dioxide; and / or

[0021] The aluminum source includes at least one of sodium metaaluminate, aluminum chloride, aluminum isopropoxide and aluminum sulfate; and / or.

[0022] The template agent includes at least one of tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride and N-octadecyl-N′-hexyl-tetramethyl-1,6-hexanediammonium.

[0023] In a third aspect, the present application provides a three-way catalyst, the three-way catalyst comprising a ceramic carrier and a three-way catalyst coating material, the three-way catalyst coating material comprising the catalytically active material provided in the first aspect.

[0024] As an optional embodiment, the ceramic carrier comprises cordierite; and / or

[0025] The three-way catalyst coating material also includes an oxygen storage material; and / or

[0026] The oxygen storage material comprises a cerium-zirconium composite material; and / or

[0027] The three-way catalyst coating material also includes a supported molecular sieve; and / or

[0028] The supported molecular sieve includes at least one of an S-1 molecular sieve, a Y-type molecular sieve and a ZSM-5 molecular sieve.

[0029] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0030] The catalytically active material provided in the embodiment of the present application, by encapsulating multiple precious metals on a molecular sieve, realizes the collection of multiple precious metals on a single coating component when used as a three-way catalyst, thereby avoiding the increase of back pressure. In addition, at least part of a precious metal is individually encapsulated in the pores of the molecular sieve, and the spatial isolation of the molecular sieve structure is utilized to avoid the movement and agglomeration of precious metal oxide nanoparticles at high temperatures and the Oswalds ripening of precious metals in a reducing atmosphere to easily form precious metal alloys such as PdRh and PtRh, thereby causing catalyst deactivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A flowchart of the method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0035] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] An embodiment of the present application provides a catalytically active material, which includes an active material body and a molecular sieve, wherein the molecular sieve has a plurality of pores, the active material body is encapsulated in the pores, and the active material body includes a first precious metal and a second precious metal; wherein the first precious metal or the second precious metal is individually encapsulated in a portion of the pores.

[0037] The catalytically active material is used as a three-way catalyst by encapsulating multiple precious metals on a molecular sieve, so that multiple precious metals are assembled on a single coating component to avoid increasing back pressure. At least part of a precious metal is encapsulated separately in the pores of the molecular sieve, and the spatial isolation of the molecular sieve structure is used to avoid the movement and agglomeration of precious metal oxide nanoparticles at high temperatures and the Oswalds ripening of precious metals in a reducing atmosphere to easily form precious metal alloys such as PdRh and PtRh, which causes catalyst deactivation.

[0038] Preferably, the first noble metal and the second noble metal are encapsulated in different channels. The first noble metal and the second noble metal are not in the same channel with other active materials, which can better prevent the noble metal oxide nanoparticles from moving and agglomerating at high temperatures and the noble metal from undergoing Oswalds ripening in a reducing atmosphere to easily form noble metal alloys such as PdRh and PtRh, causing catalyst deactivation.

[0039] In some embodiments, the first precious metal and the second precious metal both include one of platinum, rhodium, and palladium, and the first precious metal and the second precious metal are different.

[0040] In some embodiments, the molecular sieve includes at least one of an S-1 molecular sieve, a Y-type molecular sieve, and a ZSM-5 molecular sieve.

[0041] In some embodiments, the active material bulk accounts for 0.05% to 20% of the molecular sieve mass.

[0042] Exemplarily, the active material body can account for 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5% or 20% of the mass of the molecular sieve, etc., and it can also be any value in the range of 0.05% to 20%.

[0043] Based on a general inventive concept, an embodiment of the present application also provides a method for preparing a catalytically active material.

[0044] The method is used for preparing the above-mentioned catalytically active material. The specific content of the catalytically active material can be referred to the above-mentioned embodiment. Since the method adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here one by one.

[0045] Figure 1 A flow chart of the method provided in the embodiment of the present application is as follows: Figure 1 As shown, in some embodiments, the method includes:

[0046] S1. mixing the first noble metal precursor and the silane coupling agent to prepare a first gel;

[0047] Specifically, a large volume of silane coupling agent is added dropwise to the first noble metal precursor solution, and stirring is continued until a clear solution is formed. A small amount of ethyl orthosilicate is added and stirred continuously to form a stable gel, namely the first gel.

[0048] In some embodiments, the bulky silane coupling agent includes at least one of silane coupling agents containing only one non-hydrolyzable carbon chain - chloromethyltriethoxysilane, chloropropyltriethoxysilane, aminopropyltriethoxysilane, γ-(β-aminoethyl)aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane and γ-mercaptopropyltrimethoxysilane.

[0049] In some embodiments, the first noble metal precursor includes at least one of nitrate, chloride, acetate and alkoxide of the noble metal. For example, the noble metal precursor is one of nitrate, chloride, acetate and alkoxide of Pd, Rh and Pd.

[0050] S2. The first gel and the molecular sieve raw material are mixed to obtain a second gel;

[0051] Specifically, molecular sieve raw materials and water are added to the first gel according to the ratio of the target synthesized molecular sieve, and stirred continuously to form a stable gel, namely the second gel.

[0052] In some embodiments, the molecular sieve raw material includes a silicon source, an aluminum source, an inorganic base and a template. Further, the silicon source includes at least one of tetraethyl orthosilicate, silica gel and silicon dioxide; the aluminum source includes at least one of sodium metaaluminate, aluminum chloride, aluminum isopropoxide and aluminum sulfate; the template includes at least one of tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride and N-octadecyl-N'-hexyl-tetramethyl-1,6-hexanediammonium. The addition ratio of the molecular sieve raw material is determined according to the target synthetic molecular sieve. For example, when the target synthetic molecular sieve is a Y-type molecular sieve, the addition ratio of the molecular sieve raw material can be 7.8SiO2 / 1Al2O3 / 2.2Na2O / 174H2O. When the target synthetic molecular sieve is S-1 molecular sieve, the addition ratio of the molecular sieve raw material can be 4-10SiO2 / 1 template agent. When the target synthetic molecular sieve is ZSM-5 molecular sieve, the addition ratio of the molecular sieve raw material can be 50NaOH / Al2O3 / 300SiO2 / 20 template agent / 2300H2O.

[0053] S3. Obtaining a seed molecular sieve encapsulated with the second precious metal;

[0054] In some embodiments, the pore diameter of the seed molecular sieve is smaller than the diameter of the silane coupling agent.

[0055] S4. mixing the second gel and the seed molecular sieve to obtain a mixture;

[0056] Specifically, in this embodiment, a molecular sieve encapsulating one noble metal (i.e., the second noble metal) (M1@molecular sieve) or a molecular sieve encapsulating two noble metals (including the second noble metal) (M1 / M2@molecular sieve) is added to the second gel and stirred continuously to mix evenly to form a stable mixture.

[0057] S5. performing a hydrothermal reaction on the mixture to obtain a hydrothermal reaction product;

[0058] S6. calcining the hydrothermal reaction product to obtain a catalytically active material.

[0059] Specifically, in this embodiment, the mixture is transferred to a reactor, a hydrothermal reaction is carried out at the crystallization temperature of the corresponding molecular sieve, and after cooling, the powder is filtered and collected and washed to neutrality and then dried, and then the powder is transferred to a muffle furnace to heat and calcine. The calcination temperature can be 550°C, and the calcination time can be 24h. The block after calcination and cooling is taken out, the block is crushed using a ball mill and sieved with a sieve to obtain a powder of the target particle size, that is, a catalytically active material. For example, a sieve of 800 mesh can be used for sieving to obtain a powder with a particle diameter of less than 18 microns.

[0060] The method can synthesize a molecular sieve encapsulated with another noble metal oxide or single substance nanoparticle (i.e., the first noble metal) on the original component by using a large volume organic ligand to protect the noble metal ions and to synthesize in situ on the encapsulated noble metal molecular sieve based on the seed molecular sieve encapsulated with at least one noble metal (i.e., the second noble metal). A plurality of noble metals can be assembled on a single coating component, and the spatial isolation of the molecular sieve structure between the noble metals avoids the noble metal oxide nanoparticles from moving and agglomerating at high temperatures and the noble metals from undergoing Oswalds ripening in a reducing atmosphere, which easily forms noble metal alloys such as PdRh and PtRh, causing catalyst deactivation. At the same time, the method encapsulates two or more noble metals in the same molecular sieve and then mixes them with an oxygen storage material to form a uniform three-way catalyst coating, which can avoid increasing the coating component to increase the number of noble metals, resulting in an increase in the coating thickness, which causes an increase in the back pressure of the three-way catalyst and thus affects the power economy.

[0061] Based on a general inventive concept, an embodiment of the present application further provides a three-way catalyst, the three-way catalyst comprising a ceramic carrier and a three-way catalyst coating material, the three-way catalyst coating material comprising the catalytically active material provided above.

[0062] The three-way catalyst is realized based on the above-mentioned catalytically active material. The specific content of the catalytically active material can be referred to the above-mentioned embodiment. Since the three-way catalyst adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0063] In some embodiments, the ceramic support includes cordierite.

[0064] In some embodiments, the three-way catalyst coating material further comprises an oxygen storage material. Further, the oxygen storage material comprises a cerium-zirconium composite material.

[0065] In some embodiments, the three-way catalyst coating material also includes a supporting molecular sieve. Further, the supporting molecular sieve includes at least one of S-1 molecular sieve, Y-type molecular sieve and ZSM-5 molecular sieve. By introducing molecular sieves into the coating material, pollutants such as HC, NOx, and CO can be enriched to a certain extent, the concentration of pollutants contacting the catalytic active center can be increased, and the catalytic efficiency can be improved.

[0066] In some embodiments, a palladium-rhodium coating, a platinum coating and a palladium-platinum coating are attached to the ceramic carrier at one time, wherein the active material in the catalytically active material of the palladium-rhodium coating includes palladium and rhodium, the active material in the catalytically active material of the platinum coating includes platinum, and the active material in the catalytically active material of the palladium-platinum coating includes palladium and platinum. The front-stage catalyst includes a palladium-rhodium coating and a platinum coating, wherein the palladium-rhodium coating is located in the front half of the front stage, and the platinum coating is located in the rear half of the front stage; the rear-stage catalyst only includes a palladium-platinum coating.

[0067] The preparation process of the three-way catalyst can be:

[0068] S1: Provide ceramic carrier, support carrier material, oxygen storage material (cerium-zirconium oxygen storage material), and catalytic active material;

[0069] S2: According to the mass percentage of 10-30wt% of catalytic active material, 30%-50% of cerium-zirconium oxygen storage material, 20-60wt% of supporting molecular sieve material, 3-7wt% of binder and 1-5wt% of protective agent polyvinyl pyrrolidone (PVP), the materials are weighed, deionized water is added, and the mixture is placed in a horizontal grinder and continuously ground to a coatable viscosity to obtain a catalytic coating slurry.

[0070] S3: applying the catalytic coating slurry onto a ceramic carrier, drying it, and then calcining it at 550° C. for 3 h to obtain a three-way catalyst.

[0071] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0072] Example 1

[0073] A three-way catalyst, the preparation process of which is as follows:

[0074] Add silica powder into a ball mill and add a 1.5% by mass aqueous solution of tetrapropylammonium hydroxide (1.0 Min H2O cosolvent: 10% methanol) and continue stirring for 1 h to form a stable milky white gel.

[0075] A precursor of precious metal Pd with a mass percentage of 5% of silica powder was added to the milky white gel, and then the mixture was stirred for 1 hour to form a uniform gel.

[0076] The gel was transferred to a reactor and heated to 180°C under sealed conditions and kept warm for 3 days. After cooling, the block in the reactor was taken out and transferred to a muffle furnace and heated to 550°C and calcined for 24 hours.

[0077] The cooled block was taken out and crushed using a ball mill and sieved using an 800-mesh sieve to obtain a powder with a particle diameter of less than 18 μm and named Pd@S-1.

[0078] A silane coupling agent was added dropwise to the precursor solution of Rh or Pt, and stirring was continued until a clear solution was formed. After adding tetraethyl orthosilicate to form a stable gel, an aqueous solution of tetrapropylammonium hydroxide (1.0 M in H2O cosolvent: 10% methanol) with a mass fraction of 0.2 wt% of tetraethyl orthosilicate and Pd@S-1 with an equal molar number as Rh or Pt were added and stirring was continued for 2 h to form a stable mixture.

[0079] The mixture was transferred to a reactor for hydrothermal reaction at 180°C. After cooling, the powder was filtered out and transferred to a muffle furnace and heated to 550°C for calcination for 24 hours.

[0080] The cooled block was taken out and crushed with a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Rh / Pd@S-1 or Pt / Pd@S-1.

[0081] According to the mass percentage of Pd@S-1 30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, the materials were weighed, deionized water was added, and the materials were put into a horizontal grinder and continuously ground until the coating viscosity was reached to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry were prepared respectively.

[0082] The front stage catalyst includes palladium-rhodium coating, platinum coating and palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes the palladium-platinum coating of the three-way catalyst coating structure for coating. After drying, it is calcined at 550°C for 5 hours to obtain a three-way catalyst with long life and high stability.

[0083] Example 2

[0084] A three-way catalyst, the preparation process of which is as follows:

[0085] A small amount of tetraethyl orthosilicate was added to the precursor solution of precious metal Pd and stirred continuously at 25°C for 2 hours to form a clear solution.

[0086] Sodium aluminate was added to the clear solution and stirred for 2 hours, then sodium hydroxide was added and stirred for 2 hours, and finally 50 wt % of silica gel was added and stirred for 8 hours to form a stable gel.

[0087] The gel was transferred to a reactor and heated to 100°C for 4 days. After cooling, the powder was collected by filtration, washed and dried, and then calcined at 550°C in air for 12 hours.

[0088] The cooled powder was taken out and the block was crushed using a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Pd@NaY.

[0089] Silane coupling agent is added dropwise to the precursor solution of Rh or Pt, and stirring is continued until a clear solution is formed. After adding tetraethyl orthosilicate to form a stable gel, a small amount of tetraethyl orthosilicate is added and stirring is continued for 2 hours to form a stable gel.

[0090] Sodium aluminate was added to the clear solution and stirred for 2 hours, then sodium hydroxide was added and stirred for 2 hours, and finally 50 wt% silica gel was added and stirred for 8 hours to form a stable gel. Then Pd@NaY with the same molar number as Rh or Pt was added to the gel and stirred for 2 hours to form a stable mixture.

[0091] The mixture was transferred to a reactor and heated to 100°C for 4 days. After cooling, the powder was collected by filtration, washed and dried, and then calcined at 550°C in air for 12 hours.

[0092] The cooled powder was taken out and the block was crushed using a ball mill and sieved with a 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Rh / Pd@NaY or Pt / Pd@NaY.

[0093] According to the mass percentage of Pd@NaY30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, the materials were weighed, deionized water was added, and the materials were put into a horizontal grinder and continuously ground until the coating viscosity was reached to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry were respectively obtained.

[0094] The front stage catalyst includes palladium-rhodium coating, platinum coating and palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes the palladium-platinum coating of the three-way catalyst coating structure for coating. After drying, it is calcined at 550°C for 5 hours to obtain a three-way catalyst with long life and high stability.

[0095] Example 3

[0096] A three-way catalyst, the preparation process of which is as follows:

[0097] The precursor of precious metal Pd and tetraethyl orthosilicate were added to deionized water and stirred at 25°C for 2 hours.

[0098] Tetrapropylammonium hydroxide, aluminum hydroxide and sodium hydroxide were added to the above solution and stirred for 1 hour, and then 50 wt % of silica gel was added and the mixture was stirred for 4 hours.

[0099] The mixture was transferred to a reactor, heated to 90°C for 3 days, cooled, filtered, collected, washed, dried, and then calcined in air at 550°C for 12 h.

[0100] The cooled powder was taken out and the blocks were crushed using a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Pd@ZSM-5.

[0101] Silane coupling agent is added dropwise to the precursor solution of Rh or Pt, and stirring is continued until a clear solution is formed. After adding tetraethyl orthosilicate to form a stable gel, a small amount of tetraethyl orthosilicate is added and stirring is continued for 2 hours to form a stable gel.

[0102] Then, tetrapropylammonium hydroxide, aluminum hydroxide, and sodium hydroxide were added to the above solution and stirred for 1 hour, and then 50 wt% silica gel was added and the mixture was stirred for 4 hours to form a stable gel. Then, Pd@ZSM-5 with the same molar number as Rh or Pt was added to the gel and stirred for 2 hours to form a stable mixture.

[0103] The mixture was transferred to a reactor, heated to 90°C for 3 days, cooled, filtered, collected, washed, dried, and then calcined in air at 550°C for 12 h.

[0104] The cooled powder was taken out and the blocks were crushed using a ball mill and sieved with an 800-mesh sieve to obtain powder with a particle diameter less than 18 μm and named Rh / Pd@ZSM-5 or Pt / Pd@ZSM-5.

[0105] According to the mass percentage of Pd@ZSM-5 30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, the materials were weighed, deionized water was added, and the materials were put into a horizontal grinder and continuously ground until the coating viscosity was reached to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry were prepared respectively.

[0106] The front stage catalyst includes palladium-rhodium coating, platinum coating and palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes the palladium-platinum coating of the three-way catalyst coating structure for coating. After drying, it is calcined at 550°C for 5 hours to obtain a three-way catalyst with long life and high stability.

[0107] Comparative Example 1

[0108] A three-way catalyst, the preparation process of which is as follows:

[0109] One or two noble metal precursors were added to deionized water and stirred continuously until completely dissolved, then S-1 molecular sieve was added and stirred continuously at room temperature for 24 hours, then the powder was collected by filtration and washed and dried, and then calcined at 550°C in air for 12 hours.

[0110] The cooled block is taken out, crushed using a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 microns and named Rh+Pd / S-1 or Pt+Pd / S-1 or Pd / S-1 or Pt / S-1.

[0111] According to the mass percentage of Pd / S-1 30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, weigh the materials, add deionized water, put them into a horizontal grinder and grind them continuously until the coating viscosity is obtained to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry are respectively obtained.

[0112] The front stage catalyst includes a palladium-rhodium coating, a platinum coating and a palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes a palladium-platinum coating, and the three-way catalyst coating structure is coated. After drying, it is calcined at 550°C for 5 hours to obtain the three-way catalyst of Comparative Example 1.

[0113] Comparative Example 2

[0114] A three-way catalyst, the preparation process of which is as follows:

[0115] One or two noble metal precursors were added to deionized water and stirred continuously until completely dissolved, then NaY molecular sieves were added and stirred continuously at room temperature for 24 hours, and then the powder was collected by filtration and washed and dried, and then calcined at 550° C. in air for 12 hours.

[0116] The cooled block is taken out, crushed with a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Rh+Pd / NaY or Pt+Pd / NaY or Pd / NaY or Pt / NaY.

[0117] According to the mass percentage of Pd / NaY 30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, the materials were weighed, deionized water was added, and the materials were put into a horizontal grinder and continuously ground until the coating viscosity was reached to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry were respectively obtained.

[0118] The front stage catalyst includes a palladium-rhodium coating, a platinum coating and a palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes a palladium-platinum coating, and the three-way catalyst coating structure is coated. After drying, it is calcined at 550°C for 5h to obtain the three-way catalyst of Comparative Example 2.

[0119] Comparative Example 3

[0120] A three-way catalyst, the preparation process of which is as follows:

[0121] One or two noble metal precursors are added to deionized water and stirred continuously until completely dissolved, then ZSM-5 molecular sieve is added and stirred continuously at room temperature for 24 hours, then the powder is collected by filtration and washed and dried, and then calcined at 550° C. in air for 12 hours.

[0122] The cooled block is taken out, crushed with a ball mill and sieved with an 800-mesh sieve to obtain a powder with a particle diameter less than 18 μm and named Rh+Pd / ZSM-5 or Pt+Pd / ZSM-5 or Pd / ZSM-5 or Pt / ZSM-5.

[0123] According to the mass percentage of Pd / ZSM-5 30wt%, cerium zirconium oxygen storage material 50%, support carrier material 20wt%, binder 3wt%, protective agent polyvinyl pyrrolidone (PVP) 4wt%, the materials were weighed, deionized water was added, and the materials were put into a horizontal grinder and continuously ground until the coating viscosity was reached to obtain palladium coating slurry. According to the same mass percentage and process requirements, palladium-rhodium coating slurry, platinum coating slurry and palladium-platinum coating slurry were respectively obtained.

[0124] The front stage catalyst includes a palladium-rhodium coating, a platinum coating and a palladium coating, wherein the palladium-rhodium coating is located in the front half of the front stage, the platinum coating is located in the rear half of the front stage, and the palladium coating is placed on the surface of the rhodium coating and the platinum coating; the rear stage catalyst only includes a palladium-platinum coating, and the three-way catalyst coating structure is coated. After drying, it is calcined at 550°C for 5h to obtain the three-way catalyst of Comparative Example 3.

[0125] Generally, the life and stability of the three-way catalyst are characterized by the change in tail gas conversion efficiency before and after aging. The three-way catalysts provided in each embodiment and comparative example are tested for life and stability. The results are shown in the following table:

[0126] Exhaust gas conversion efficiency before aging Exhaust gas conversion efficiency after aging Example 1 98.4％ 94.2％ Example 2 99％ 95％ Example 3 99.3％ 94.7％ Comparative Example 1 97％ 84％ Comparative Example 2 98.5％ 86.3％ Comparative Example 3 98％ 85.8％

[0127] It can be seen from the above table that the three-way catalyst prepared by the method provided in the examples of the present application has a longer service life and higher stability.

[0128] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0129] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b and c can be single or multiple.

[0130] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A catalytically active material, characterized in that The catalytically active material comprises an active material body and a molecular sieve, wherein the molecular sieve has a plurality of pores, the active material body is encapsulated in the pores, and the active material body comprises a first noble metal and a second noble metal; Wherein, the first precious metal or the second precious metal is individually encapsulated in part of the channels.

2. The catalytically active material according to claim 1, characterized in that The first noble metal and the second noble metal both include one of platinum, rhodium and palladium, and the first noble metal and the second noble metal are different.

3. The catalytically active material according to claim 1, characterized in that The molecular sieve includes at least one of S-1 molecular sieve, Y-type molecular sieve and ZSM-5 molecular sieve.

4. The catalytically active material according to any one of claims 1 to 3, characterized in that The mass of the active material body is 0.05% to 20% of the total mass of the molecular sieve.

5. A method for preparing a catalytically active material according to any one of claims 1 to 4, characterized in that: The method comprises: Mixing the precursor of the first noble metal and a silane coupling agent to prepare a first gel; Mixing the first gel and a molecular sieve raw material to obtain a second gel; Obtaining a seed molecular sieve encapsulated with the second noble metal; mixing the second gel and the seed molecular sieve to obtain a mixture; performing a hydrothermal reaction on the mixture to obtain a hydrothermal reaction product; The hydrothermal reaction product is calcined to obtain a catalytically active material.

6. The method for preparing a catalytically active material according to claim 5, characterized in that: The diameter of the pores of the seed molecular sieve is smaller than the diameter of the silane coupling agent.

7. The method for preparing a catalytically active material according to claim 5 or 6, characterized in that: The silane coupling agent includes at least one of the carbon chain silane coupling agents: chloromethyl triethoxysilane, chloropropyl triethoxysilane, aminopropyl triethoxysilane, γ-(β-aminoethyl)aminopropyl triethoxysilane, γ-methacryloxypropyl trimethoxysilane, γ-mercaptopropyl triethoxysilane and γ-mercaptopropyl trimethoxysilane; and / or The precursor of the first noble metal comprises at least one of nitrate, chloride, acetate and alkoxide of the noble metal; and / or The molecular sieve raw materials include a silicon source, an aluminum source, an inorganic base and a template agent.

8. The method for preparing a catalytically active material according to claim 7, characterized in that: In the case where the molecular sieve raw material contains a silicon source, an aluminum source and a template, the silicon source comprises at least one of tetraethyl orthosilicate, silica gel and silicon dioxide; and / or The aluminum source comprises at least one of sodium metaaluminate, aluminum chloride, aluminum isopropoxide and aluminum sulfate; and / or The template agent includes at least one of tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride and N-octadecyl-N'-hexyl-tetramethyl-1,6-hexanediammonium.

9. A three-way catalyst, characterized in that: The three-way catalyst comprises a ceramic carrier and a three-way catalyst coating material, and the three-way catalyst coating material comprises the catalytically active material according to any one of claims 1 to 4.

10. The three-way catalyst according to claim 9, characterized in that: The ceramic support comprises cordierite; and / or The three-way catalyst coating material further includes an oxygen storage material; and / or The oxygen storage material comprises a cerium-zirconium composite material; and / or The three-way catalyst coating material also includes a supported molecular sieve; and / or The supported molecular sieve includes at least one of an S-1 molecular sieve, a Y-type molecular sieve and a ZSM-5 molecular sieve.

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