A catalyst for exhaust gas aftertreatment of a methanol engine, and a preparation method and application thereof

Abstract

This invention provides a methanol engine exhaust aftertreatment catalyst, its preparation method, and its application. The methanol engine exhaust aftertreatment catalyst includes a sheet-like catalyst support and a first catalyst coating and a second catalyst coating sequentially stacked and loaded on at least one surface of the sheet-like catalyst support. The active component in the first catalyst coating includes a composite metal oxide framework and a noble metal loaded on the composite metal oxide framework. The active component in the second catalyst coating includes a metal oxide solid solution material, which includes a metal oxide and a metal element. The second catalyst coating of this invention can effectively intercept toxic sulfur and phosphorus substances in the exhaust components, preventing them from reaching the first catalyst coating located below, thereby protecting the noble metal active component in the first catalyst coating from sulfur and phosphorus poisoning.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, and relates to a methanol engine exhaust aftertreatment catalyst, its preparation method and application. Background Technology

[0002] Methanol, as a clean energy source, boasts excellent fuel characteristics, wide applicability, clean emissions, and low pollution, and is widely available. Developing methanol engines and their aftertreatment systems is of great significance. However, methanol engines produce a certain amount of exhaust gas during combustion, including nitrogen oxides (NOx). x Pollutants such as [list of pollutants] require effective post-treatment catalysts for purification.

[0003] CN118950030A discloses a methanol fuel vehicle exhaust purification catalyst, comprising a pre-stage catalyst and a post-stage catalyst. The raw materials for the pre-stage catalyst are pre-stage rare earth main material, pre-stage active material, and pre-stage auxiliary material. The raw materials for the post-stage catalyst are post-stage rare earth main material, post-stage active material, and post-stage auxiliary material. The pre-stage rare earth main material consists of high-cerium rare earth, medium-cerium medium-zirconium rare earth, pre-stage metal oxide, pre-stage precious metal, and cobalt black material. The post-stage rare earth main material consists of high-zirconium rare earth, medium-cerium medium-zirconium rare earth, post-stage metal oxide, and post-stage precious metal. The cerium content of the high-cerium rare earth is 50wt%~60wt%. The cerium content of the medium-cerium medium-zirconium rare earth is 30wt%~40wt%, and the zirconium content is 40wt%~50wt%. The zirconium content of the high-zirconium rare earth is 60wt%~70wt%.

[0004] CN111939898A discloses a methanol fuel vehicle exhaust purification catalyst and its preparation method. The catalyst includes a sheet-like catalyst support and a catalyst coating. The catalyst coating includes a first coating and a second coating. The first coating uses ZrO2-Al2O3 as the first support material and Pd and / or Pt as the first active component. ZrO2-Al2O3 is prepared by a co-precipitation method. The second coating uses CeO2-Al2O3 as the second support material and Rh as the second active component. CeO2-Al2O3 is prepared by a sol-gel method. The catalyst coating is applied to the sheet-like catalyst support in a layered manner to obtain the methanol fuel vehicle exhaust purification catalyst.

[0005] The catalysts prepared by the above schemes have poor resistance to poisoning and require a high amount of precious metals, resulting in poor practicality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a methanol engine exhaust aftertreatment catalyst, its preparation method, and its application. The second catalyst coating of the present invention can effectively intercept toxic sulfur and phosphorus substances in the exhaust components, preventing them from reaching the first catalyst coating located below, thereby protecting the precious metal active components in the first catalyst coating from sulfur and phosphorus poisoning.

[0007] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a methanol engine exhaust aftertreatment catalyst, the methanol engine exhaust aftertreatment catalyst comprising a sheet-like catalyst support and a first catalyst coating and a second catalyst coating sequentially stacked and loaded on at least one surface of the sheet-like catalyst support. The active components in the first catalyst coating include a composite metal oxide framework and a noble metal supported on the composite metal oxide framework; The active component in the second catalyst coating includes a metal oxide solid solution material, which includes metal oxides and elemental metals.

[0008] In the methanol engine exhaust aftertreatment catalyst of this invention, a second catalyst coating composed of a metal oxide solid solution is formed on a first catalyst coating containing precious metals. The solid solution material in the second coating contains metal oxides and elemental metals, with the elemental metals dispersed within the solid solution material. As an active component, it can enhance the catalyst's conversion capacity and significantly reduce the overall amount of precious metals used in the catalyst. Simultaneously, the second catalyst coating can effectively prevent the diffusion of harmful sulfur and phosphorus substances into the first catalyst coating, thereby protecting the precious metal active components of the first catalyst coating from poisoning and significantly improving the catalyst's resistance to sulfur and phosphorus poisoning.

[0009] In the first catalyst coating of the present invention, the noble metal is loaded onto the composite metal oxide framework, which can significantly improve the catalytic activity and selectivity of the noble metal element. The noble metal loaded on the composite metal oxide framework includes elemental noble metal and / or noble metal oxide.

[0010] Preferably, the precious metal includes a first precious metal and a second precious metal.

[0011] Preferably, the first noble metal includes platinum and / or palladium.

[0012] Preferably, the second noble metal includes rhodium.

[0013] In the methanol engine exhaust aftertreatment catalyst of the present invention, a combination of precious metal active ingredients of Pt / Rh type, Pd / Rh type or Pt / Pd / Rh type can be selected according to different vehicle types and exhaust treatment requirements to maximize cost-effectiveness.

[0014] Preferably, based on the mass of the solid material in the first catalyst coating being 100%, the mass fraction of the first precious metal is 0.5-0.9%, for example: 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] Preferably, based on the mass of the solid material in the first catalyst coating being 100%, the mass fraction of the second precious metal is 0.01~0.2%, for example: 0.01%, 0.05%, 0.1%, 0.15% or 0.2%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0016] Preferably, the composite metal oxide framework includes any two or at least three combinations of alumina, transition metal oxides, alkali metal oxides, alkaline earth metal oxides, or rare earth metal oxides. Typical but non-limiting combinations include combinations of transition metal oxides and alkali metal oxides, combinations of alkali metal oxides and alkaline earth metal oxides, or combinations of transition metal oxides, alkali metal oxides and rare earth metal oxides, etc.

[0017] Preferably, the transition metal oxide includes any one or a combination of at least two of manganese oxide, copper oxide, or iron oxide.

[0018] Preferably, the alkali metal oxide includes any one or a combination of at least two of sodium oxide, potassium oxide, or lithium oxide. Typical but non-limiting combinations include combinations of sodium oxide and potassium oxide, combinations of potassium oxide and lithium oxide, or combinations of sodium oxide and lithium oxide.

[0019] Preferably, the alkaline earth metal oxide includes any one or a combination of at least two of magnesium oxide, barium oxide, calcium oxide, or strontium oxide. Typical but non-limiting combinations include combinations of magnesium oxide and barium oxide, combinations of barium oxide and calcium oxide, or combinations of calcium oxide and strontium oxide.

[0020] Preferably, the rare earth metal oxide includes any one or a combination of at least two of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, or samarium oxide. Typical but non-limiting combinations include combinations of lanthanum oxide and cerium oxide, cerium oxide and praseodymium oxide, or praseodymium oxide and neodymium oxide, etc.

[0021] Preferably, the first catalyst coating further includes a first binder.

[0022] Preferably, the first binder comprises any one or a combination of at least two of silica sol, alumina sol, cellulose, or polyvinyl alcohol. Typical but non-limiting combinations include combinations of silica sol and alumina sol, combinations of cellulose and polyvinyl alcohol, or combinations of alumina sol and cellulose.

[0023] Preferably, based on the mass of the solid material in the first catalyst coating being 100%, the mass fraction of the first binder is 3% to 10%, for example: 3%, 5%, 6%, 8% or 10%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] Preferably, the median particle size D50 of the solid material in the first catalyst coating is 5μm to 20μm, for example: 5μm, 8μm, 10μm, 15μm or 20μm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the metal oxide solid solution material includes a composite metal oxide solid solution material.

[0026] Preferably, the metal oxide in the composite metal oxide solid solution material includes ZrO2 and / or ZnO.

[0027] Preferably, the elemental metal in the composite metal oxide solid solution material includes elemental zinc.

[0028] Preferably, the second catalyst coating further includes a second binder.

[0029] Preferably, the second binder comprises any one or a combination of at least two of silica sol, alumina sol, cellulose, or polyvinyl alcohol. Typical but non-limiting combinations include combinations of silica sol and alumina sol, combinations of cellulose and polyvinyl alcohol, or combinations of alumina sol and cellulose.

[0030] Preferably, based on the mass of the solid material in the second catalyst coating being 100%, the mass fraction of the second binder is 3% to 10%, for example: 3%, 5%, 6%, 8% or 10%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] Preferably, the median particle size D50 of the solid material in the second catalyst coating is 3μm to 10μm, for example: 3μm, 5μm, 6μm, 8μm or 10μm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the sheet-like catalyst support comprises any one or a combination of at least two of alumina, silica, or porous ceramic materials. Typical but non-limiting combinations include combinations of alumina and silica, silica and porous ceramic materials, or alumina and porous ceramic materials.

[0033] Preferably, the mass ratio of the active component in the first catalyst coating to the active component in the second catalyst coating is (0.5~2):1, for example: 0.5:1, 0.8:1, 1:1, 1.5:1 or 2:1, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the thickness of the sheet-like catalyst support is 50~500μm; Preferably, the thickness of the first catalyst coating is 20~100μm; Preferably, the thickness of the second catalyst coating is 20~100μm.

[0035] In a second aspect, the present invention provides a method for preparing a methanol engine exhaust aftertreatment catalyst as described in the first aspect, the preparation method comprising the following steps: (1) A composite metal oxide framework precursor is prepared by co-precipitation method, and the composite metal oxide framework precursor is subjected to a first sintering treatment to obtain a composite metal oxide framework. A noble metal salt solution is loaded on the surface of the composite metal oxide framework and subjected to a second sintering treatment to obtain a first catalyst. (2) The second catalyst precursor was prepared by sol-gel method, and the second catalyst precursor was calcined to obtain a solid solution material; (3) The first catalyst and the solid solution material are respectively made into a first slurry and a second slurry. The first slurry is coated on the surface of the sheet catalyst carrier and heat-treated to form a first catalyst coating. The second slurry is coated on the surface of the first catalyst coating and reduced to form a second catalyst coating, thus obtaining a methanol engine exhaust gas aftertreatment catalyst.

[0036] The preparation method described in this invention does not limit the order of operation of steps (1) and (2). Step (1) can be performed first, or step (2) can be performed first.

[0037] This invention prepares a composite metal oxide framework via co-precipitation to support noble metals, forming the first catalyst coating. Simultaneously, a second catalyst precursor is prepared via a sol-gel method and reduced to obtain highly dispersed elemental metals on the metal oxide, which are then used as the active component in the second catalyst coating. By using highly dispersed elemental metals as the active component, the amount of noble metals such as platinum, palladium, and rhodium can be significantly reduced. The methanol engine exhaust aftertreatment catalyst prepared by the method of this invention exhibits high conversion rate and high selectivity, achieving low ignition temperature, high conversion efficiency, and low cost with relatively low noble metal usage, effectively purifying both conventional and unconventional pollutants in methanol fuel vehicle exhaust.

[0038] Preferably, the precipitant used in the co-precipitation method in step (1) includes ammonia.

[0039] Preferably, step (1) the first sintering process includes one-step sintering and two-step sintering.

[0040] Preferably, the sintering temperature in the first step is 500℃~600℃, for example: 500℃, 520℃, 550℃, 580℃ or 600℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the sintering time in the first step is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the temperature of the two-step sintering is 800℃~1000℃, for example: 800℃, 850℃, 900℃, 950℃ or 1000℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the two-step sintering time is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the second sintering temperature in step (1) is 450℃~600℃, for example: 450℃, 480℃, 500℃, 550℃ or 600℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] Preferably, the second sintering time in step (1) is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0046] Preferably, the roasting process in step (2) includes one-step roasting and two-step roasting.

[0047] Preferably, the temperature of the first-step roasting is 500℃~600℃, for example: 500℃, 520℃, 550℃, 580℃ or 600℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the roasting time for the first step is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the temperature of the two-step roasting is 800℃~1000℃, for example: 800℃, 850℃, 900℃, 950℃ or 1000℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the two-step roasting time is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0051] Preferably, in step (3), the solid content of the first slurry is 20% to 35%, for example: 20%, 25%, 28%, 30% or 35%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0052] Preferably, the solid content of the second slurry in step (3) is 15% to 38%, for example: 15%, 20%, 25%, 30% or 38%, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] Preferably, in step (3), the coating amount of the first slurry is 150g / L to 250g / L, for example: 150g / L, 180g / L, 200g / L, 220g / L or 250g / L, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0054] Preferably, in step (3), the coating amount of the second slurry is 200g / L to 300g / L, for example: 200g / L, 220g / L, 250g / L, 280g / L or 300g / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] The coating amount mentioned in this invention is the weight to be coated calculated based on the volume of the carrier. For example, if the carrier is 1L and the coating amount is 200g / L to 300g / L, then the coating amount is 200g to 300g.

[0056] Preferably, the heat treatment temperature in step (3) is 500℃~600℃, for example: 500℃, 520℃, 550℃, 580℃ or 600℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0057] Preferably, the heat treatment time in step (3) is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0058] Preferably, the temperature of the reduction treatment in step (3) is 200℃~600℃, for example: 200℃, 300℃, 400℃, 500℃ or 600℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0059] Preferably, the reduction process in step (3) takes 0.5h to 5h, for example: 0.5h, 1h, 2h, 4h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Thirdly, the present invention provides an application of the methanol engine exhaust aftertreatment catalyst as described in the first aspect, wherein the methanol engine exhaust aftertreatment catalyst is used for the purification of exhaust gas from methanol fuel vehicles.

[0060] Compared with the prior art, the present invention has the following beneficial effects: (1) The methanol engine exhaust gas aftertreatment catalyst of the present invention can efficiently remove NO in methanol engine exhaust gas. x Pollutants such as methanol, hydrocarbons, and CO are effectively converted into harmless substances, meeting stringent environmental regulations.

[0061] (2) The methanol engine exhaust aftertreatment catalyst has good stability and can maintain catalytic activity for a long time under harsh environments such as high temperature and high pressure.

[0062] (3) The methanol engine exhaust aftertreatment catalyst of the present invention has excellent resistance to sulfur and phosphorus poisoning and can effectively resist the poisoning effects of sulfur and phosphorus during its service life. The methanol engine exhaust aftertreatment catalyst has a long service life, which reduces the replacement frequency and cost.

[0063] (4) The methanol engine exhaust gas aftertreatment catalyst of the present invention has the characteristics of high dispersion of precious metals, which reduces the amount of precious metals used and the cost. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the structure of the methanol engine exhaust aftertreatment catalyst provided in an embodiment of the present invention.

[0065] Figure 2 This is a catalytic effect curve of the methanol engine exhaust aftertreatment catalyst described in Example 1 of the present invention after hydrothermal aging and sulfur and phosphorus poisoning. Detailed Implementation

[0066] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0067] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0068] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0069] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0070] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined according to its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order in which they are written or in any order that does not conflict with the technology.

[0071] Example 1 This embodiment provides a methanol engine exhaust aftertreatment catalyst, the structural schematic diagram of which is shown below. Figure 1 As shown, the methanol engine exhaust aftertreatment catalyst includes a cordierite honeycomb ceramic carrier with a thickness of 101.6 μm and a first catalyst coating with a thickness of 50 μm and a second catalyst coating with a thickness of 50 μm, which are sequentially stacked on one side surface of the cordierite honeycomb ceramic carrier. The first catalyst coating comprises 0.4% by mass of platinum, 0.4% by mass of palladium, 0.1% by mass of rhodium, and 5% by mass of polyvinyl alcohol binder, with the remainder being a CeO2-Al2O3-MgO composite metal oxide framework. Platinum, palladium, and rhodium are supported on the CeO2-Al2O3-MgO composite metal oxide framework, and the median particle size D50 of the solid material of the first catalyst coating is 10 μm. The second catalyst coating comprises a ZrO2-ZnO (molar ratio of 1:4) solid solution, elemental zinc dispersed in the ZrO2-ZnO solid solution, and a polyvinyl alcohol binder with a mass fraction of 5%. The median particle size D50 of the solid material of the second catalyst coating is 5 μm.

[0072] The mass ratio of the active component in the first catalyst coating to the active component in the second catalyst coating is 1:1, wherein the active component is all solid materials except the binder.

[0073] The methanol engine exhaust aftertreatment catalyst is prepared by the following method: (1) After mixing cerium nitrate, boehmite and magnesium nitrate evenly, add an appropriate amount of ammonia water, precipitate and filter to obtain a composite metal oxide framework precursor. Sinter at 550℃ for 3h and then at 900℃ for 3h to obtain CeO2-Al2O3-MgO (molar ratio of 4:5:1) composite metal oxide framework. Impregnate a mixed solution of palladium nitrate and platinum nitrate onto the CeO2-Al2O3-MgO composite metal oxide framework, dry at 100℃ for 4h and then calcine at 500℃ for 3h. Impregnate with rhodium nitrate solution, dry at 100℃ for 4h and then calcine at 500℃ for 3h to obtain the first catalyst. (2) Zn(NO3)2 and Zr(NO3)4 are mixed and dissolved in deionized water to prepare a metal nitrate mixed solution, wherein the molar ratio of Zr to Zn in the metal nitrate mixed solution is 1:4. CTAB and PEG2000 are mixed and dissolved in deionized water to prepare a template agent mixed solution, and the solution is completely dissolved and mixed. The ratio of the total molar number of CTAB and PEG2000 to the total molar number of metal ions in the template agent mixed solution is 1:10, and the molar ratio of CTAB to PEG2000 is 2:1. The metal nitrate mixed solution is poured into the template agent mixed solution and magnetically stirred for 25 min. At a reaction temperature of 70°C, the metal nitrate and template agent mixed solution and a 0.8 mol / L Na2CO3 solution are added dropwise into the reaction vessel in a parallel flow manner. After titration, the above reaction temperature is maintained, and magnetic stirring is continued for 0.8 h before stirring is stopped. The solution is then aged for 4 h at the above reaction temperature. After aging, the product is cooled, centrifuged to obtain a solid precipitate, washed with deionized water, dried, and then placed in a tube furnace at 500°C for calcination to obtain ZnO-ZrO2 solid solution material. (3) The first catalyst and the solid solution material are mixed with polyvinyl alcohol binder and water respectively to prepare a first slurry with a solid content of 25% and a second slurry with a solid content of 35%. The first slurry is coated on the surface of the cordierite honeycomb ceramic carrier and heat-treated at 500°C for 2 hours to form a first catalyst coating. The second slurry is coated on the surface of the first catalyst coating and reduced at 500°C for 4 hours to form a second catalyst coating, thus obtaining a methanol engine exhaust aftertreatment catalyst.

[0074] Example 2 This embodiment provides a methanol engine exhaust aftertreatment catalyst, the structural schematic diagram of which is shown below. Figure 1 As shown, the methanol engine exhaust aftertreatment catalyst includes a cordierite honeycomb ceramic carrier with a thickness of 101.6 μm and a first catalyst coating with a thickness of 40 μm and a second catalyst coating with a thickness of 60 μm, which are sequentially stacked on one side surface of the cordierite honeycomb ceramic carrier. The first catalyst coating comprises 0.3% by mass of platinum, 0.5% by mass of palladium, 0.2% by mass of rhodium, 3% by mass of polyvinyl alcohol binder, and the remainder is a CeO2-Al2O3-MgO composite metal oxide framework. Platinum, palladium and rhodium are supported on the CeO2-Al2O3-MgO composite metal oxide framework. The median particle size D50 of the solid material of the first catalyst coating is 10 μm. The second catalyst coating comprises a ZrO2-ZnO (molar ratio of 1:4) solid solution, elemental zinc dispersed in the ZrO2-ZnO solid solution, and a silica sol binder with a mass fraction of 3%. The median particle size D50 of the solid material of the second catalyst coating is 5 μm.

[0075] The mass ratio of the active component in the first catalyst coating to the active component in the second catalyst coating is 0.5:1, wherein the active component refers to all solid materials except the binder.

[0076] The methanol engine exhaust aftertreatment catalyst is prepared by the following method: (1) After mixing cerium nitrate, boehmite and magnesium nitrate evenly, add an appropriate amount of ammonia water, precipitate and filter to obtain a composite metal oxide framework precursor. Sinter at 500℃ for 5h and then at 800℃ for 3h to obtain CeO2-Al2O3-MgO (molar ratio of 2:2:1) composite metal oxide framework. Impregnate a mixed solution of palladium nitrate and platinum nitrate onto the CeO2-Al2O3-MgO composite metal oxide framework, dry at 100℃ for 4h and then calcine at 550℃ for 3h. Impregnate with rhodium nitrate solution, dry at 100℃ for 4h and then calcine at 600℃ for 3h to obtain the first catalyst. (2) Zn(NO3)2 and Zr(NO3)4 are mixed and dissolved in deionized water to prepare a metal nitrate mixed solution, wherein the molar ratio of Zr to Zn in the metal nitrate mixed solution is 1:4. CTAB and PEG2000 are mixed and dissolved in deionized water to prepare a template agent mixed solution, and the solution is completely dissolved and mixed. The ratio of the total molar number of CTAB and PEG2000 to the total molar number of metal ions in the template agent mixed solution is 1:10, and the molar ratio of CTAB to PEG2000 is 2:1. The metal nitrate mixed solution is poured into the template agent mixed solution and magnetically stirred for 25 min. At a reaction temperature of 70°C, the metal nitrate and template agent mixed solution and a 0.8 mol / L Na2CO3 solution are added dropwise into the reaction vessel in a parallel flow manner. After titration, the above reaction temperature is maintained, and magnetic stirring is continued for 0.8 h before stirring is stopped. The solution is then aged for 4 h at the above reaction temperature. After aging, the product is cooled, centrifuged to obtain a solid precipitate, washed with deionized water, dried, and then placed in a tube furnace at 500°C for calcination to obtain ZnO-ZrO2 solid solution material. (3) The first catalyst and the solid solution material are mixed with polyvinyl alcohol binder and water respectively to prepare a first slurry with a solid content of 20% and a second slurry with a solid content of 15%. The first slurry is coated on the surface of the cordierite honeycomb ceramic carrier and heat-treated at 500°C for 4 hours to form a first catalyst coating. The second slurry is coated on the surface of the first catalyst coating and reduced at 300°C for 4 hours to form a second catalyst coating, thus obtaining a methanol engine exhaust aftertreatment catalyst.

[0077] Example 3 This embodiment provides a methanol engine exhaust aftertreatment catalyst, the structural schematic diagram of which is shown below. Figure 1 As shown, the methanol engine exhaust aftertreatment catalyst includes a cordierite honeycomb ceramic carrier with a thickness of 101.6 μm and a first catalyst coating with a thickness of 100 μm and a second catalyst coating with a thickness of 50 μm, which are sequentially stacked on one side surface of the cordierite honeycomb ceramic carrier. The first catalyst coating comprises 0.5% by mass of platinum, 0.4% by mass of palladium, 0.01% by mass of rhodium, 3% by mass of polyvinyl alcohol binder, and the remainder is a CeO2-Fe2O3-MgO composite metal oxide framework. Platinum, palladium and rhodium are supported on the CeO2-Fe2O3-MgO composite metal oxide framework. The median particle size D50 of the solid material of the first catalyst coating is 20 μm. The second catalyst coating comprises a ZrO2-ZnO (molar ratio of 1:4) solid solution, elemental zinc dispersed in the ZrO2-ZnO solid solution, and a silica sol binder with a mass fraction of 3%. The median particle size D50 of the solid material of the second catalyst coating is 3 μm.

[0078] The mass ratio of the active component in the first catalyst coating to the active component in the second catalyst coating is 2:1, wherein the active component refers to all solid materials except the binder.

[0079] The methanol engine exhaust aftertreatment catalyst is prepared by the following method: (1) After mixing cerium nitrate, ferric nitrate and magnesium nitrate evenly, add an appropriate amount of ammonia water, precipitate and filter to obtain a composite metal oxide framework precursor, sinter at 600℃ for 2h and then at 1000℃ for 2h to obtain CeO2-Fe2O3-MgO composite metal oxide framework, impregnate a mixed solution of palladium nitrate and platinum nitrate onto CeO2-Fe2O3-MgO composite metal oxide framework, dry at 100℃ for 4h and then calcine at 450℃ for 5h, then impregnate with rhodium nitrate solution, dry at 100℃ for 4h and then calcine at 600℃ for 3h to obtain the first catalyst; (2) Zn(NO3)2 and Zr(NO3)4 are mixed and dissolved in deionized water to prepare a metal nitrate mixed solution, wherein the molar ratio of Zr to Zn in the metal nitrate mixed solution is 1:4. CTAB and PEG2000 are mixed and dissolved in deionized water to prepare a template agent mixed solution, and the solution is completely dissolved and mixed. The ratio of the total molar number of CTAB and PEG2000 to the total molar number of metal ions in the template agent mixed solution is 1:10, and the molar ratio of CTAB to PEG2000 is 2:1. The metal nitrate mixed solution is poured into the template agent mixed solution and magnetically stirred for 25 min. At a reaction temperature of 70°C, the metal nitrate and template agent mixed solution and a 0.8 mol / L Na2CO3 solution are added dropwise into the reaction vessel in a parallel flow manner. After titration, the above reaction temperature is maintained, and magnetic stirring is continued for 0.8 h before stirring is stopped. The solution is then aged for 4 h at the above reaction temperature. After aging, the product is cooled, centrifuged to obtain a solid precipitate, washed with deionized water, dried, and then placed in a tube furnace at 500°C for calcination to obtain ZnO-ZrO2 solid solution material. (3) The first catalyst and the solid solution material are mixed with polyvinyl alcohol binder and water respectively to prepare a first slurry with a solid content of 35% and a second slurry with a solid content of 38%. The first slurry is coated on the surface of cordierite honeycomb ceramic carrier and heat-treated at 500°C for 2 hours to form a first catalyst coating. The second slurry is coated on the surface of the first catalyst coating and reduced at 500°C for 1 hour to form a second catalyst coating, thus obtaining a methanol engine exhaust aftertreatment catalyst.

[0080] Example 4 The only difference between this embodiment and Example 1 is that the first catalyst coating does not contain rhodium; all other conditions and parameters are exactly the same as in Example 1.

[0081] Example 5 The only difference between this embodiment and Embodiment 1 is that the thickness of the second catalyst coating is 30 μm; all other conditions and parameters are exactly the same as in Embodiment 1.

[0082] Example 6 The only difference between this embodiment and Embodiment 1 is that the thickness of the second catalyst coating is 80 μm; all other conditions and parameters are exactly the same as in Embodiment 1.

[0083] Comparative Example 1 The only difference between this comparative example and Example 1 is that the second catalyst coating is not provided; all other conditions and parameters are exactly the same as in Example 1.

[0084] Comparative Example 2 The only difference between this comparative example and Example 1 is that no reduction treatment is performed, that is, the second catalyst coating does not contain any elemental metal. All other conditions and parameters are exactly the same as in Example 1.

[0085] The catalyst performance was evaluated using a fixed-bed reactor. The reaction gases were 4000 ppm CO, 3000 ppm methanol (MEOH), 2500 ppm NO, 2 vol.% O2, 10 vol.% CO2, 10 vol.% H2O, with N2 as the equilibrium gas and a space velocity of 800,000 h⁻¹. -1 The reaction pressure was 0.1 MPa. The change in methanol concentration before and after the reaction was measured using Fourier transform infrared spectroscopy, and the conversion rate was calculated. Based on the performance test data... Figure 2 The catalyst catalytic effect curve shown is as follows: Figure 2 As shown, the purification efficiency of the fresh catalyst for methanol at 200℃ can reach or exceed 99%; after hydrothermal aging with 10% H2O at 750℃ for 50 hours, the purification efficiency of the catalyst for methanol at 200℃ can still reach or exceed 98%; after poisoning with 100ppm phosphorus and sulfur for 30 hours, the purification efficiency of the catalyst for methanol at 200℃ can still reach or exceed 96%. It can be seen that the catalyst obtained by this technical solution can achieve low-temperature sulfur resistance and high-temperature hydrothermal resistance. The test results of other examples and comparative examples are summarized in Table 1. Table 1 As shown in Table 1, and based on Examples 1-3, the methanol engine exhaust aftertreatment catalyst of the present invention achieves a methanol conversion rate of over 99.7% at 200℃, over 98.1% after hydrothermal aging, and over 95.3% after sulfur and phosphorus poisoning, demonstrating excellent stability. When the platinum-palladium ratio is 1:1 and the thickness of the first and second catalyst coatings is 50 μm, the resulting catalyst exhibits the highest methanol catalytic performance, along with the highest resistance to sulfur and phosphorus poisoning and hydrothermal aging.

[0086] A comparison of Examples 1 and 4 shows that the methanol engine exhaust aftertreatment catalyst of the present invention, by combining with a variety of precious metals, can improve the catalyst’s catalytic performance for methanol.

[0087] A comparison of Examples 1 and 5-6 shows that the thickness of the second catalyst coating in the methanol engine exhaust aftertreatment catalyst of the present invention affects its performance. Controlling the thickness of the second catalyst coating to 50 μm results in a methanol engine exhaust aftertreatment catalyst with better performance. If the thickness of the second catalyst coating is too large, it is not conducive to sufficient contact between the exhaust gas and the catalyst, thereby reducing the catalytic performance. If the thickness of the second catalyst coating is too small, the catalyst is prone to sulfur and phosphorus poisoning.

[0088] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, in the methanol engine exhaust aftertreatment catalyst of the present invention, a second catalyst coating composed of a metal oxide solid solution material is provided on a first catalyst coating containing precious metals. The solid solution material in the second coating contains metal oxides and elemental metals, with the elemental metals dispersed in the solid solution material as an active component. This enhances the catalyst's conversion capacity and resistance to hydrothermal aging, while significantly reducing the overall amount of precious metals used in the catalyst. Simultaneously, the second catalyst coating effectively prevents the diffusion of harmful sulfur and phosphorus substances to the first catalyst coating, thereby protecting the precious metal active components of the first catalyst coating from poisoning and significantly improving the catalyst's resistance to sulfur and phosphorus poisoning.

[0089] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A catalyst for aftertreatment of methanol engine exhaust gas, characterized in that, The methanol engine exhaust aftertreatment catalyst includes a sheet-like catalyst support and a first catalyst coating and a second catalyst coating sequentially stacked and loaded on at least one side surface of the sheet-like catalyst support. The active components in the first catalyst coating include a composite metal oxide framework and a noble metal supported on the composite metal oxide framework; The active component in the second catalyst coating includes a metal oxide solid solution material, which includes metal oxides and elemental metals.

2. The methanol engine exhaust aftertreatment catalyst as described in claim 1, characterized in that, The precious metals include a first precious metal and a second precious metal; Preferably, the first noble metal includes platinum and / or palladium; Preferably, the second noble metal includes rhodium; Preferably, based on the mass of the solid material in the first catalyst coating being 100%, the mass fraction of the first precious metal is 0.5% to 0.9%. Preferably, based on the mass of the solid material in the first catalyst coating being 100%, the mass fraction of the second precious metal is 0.01~0.2%; Preferably, the composite metal oxide framework comprises any two or at least three of alumina, transition metal oxides, alkali metal oxides, alkaline earth metal oxides, or rare earth metal oxides. Preferably, the transition metal oxide includes any one or a combination of at least two of manganese oxide, copper oxide, or iron oxide; Preferably, the alkali metal oxide includes any one or a combination of at least two of sodium oxide, potassium oxide, or lithium oxide; Preferably, the alkaline earth metal oxide includes any one or a combination of at least two of magnesium oxide, barium oxide, calcium oxide, or strontium oxide; Preferably, the rare earth metal oxide includes any one or a combination of at least two of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, or samarium oxide; Preferably, the first catalyst coating further includes a first binder; Preferably, the first binder comprises any one or a combination of at least two of silica sol, alumina sol, cellulose, or polyvinyl alcohol; Preferably, based on the mass of solid material in the first catalyst coating being 100%, the mass fraction of the first binder is 3% to 10%; Preferably, the median particle size D50 of the solid material in the first catalyst coating is 5 μm to 20 μm.

3. The methanol engine exhaust aftertreatment catalyst as described in claim 1 or 2, characterized in that, The metal oxide solid solution material includes a composite metal oxide solid solution material; Preferably, the metal oxide in the composite metal oxide solid solution material includes ZrO2 and / or ZnO; Preferably, the metallic element in the composite metal oxide solid solution material includes elemental zinc; Preferably, the second catalyst coating further includes a second binder; Preferably, the second binder comprises any one or a combination of at least two of silica sol, alumina sol, cellulose, or polyvinyl alcohol; Preferably, based on the mass of solid material in the second catalyst coating being 100%, the mass fraction of the second binder is 3% to 10%; Preferably, the median particle size D50 of the solid material in the second catalyst coating is 3 μm to 10 μm.

4. The methanol engine exhaust aftertreatment catalyst according to any one of claims 1-3, characterized in that, The sheet-like catalyst support includes any one or a combination of at least two of alumina, silica, or porous ceramic materials. Preferably, the mass ratio of the active component in the first catalyst coating to the active component in the second catalyst coating is (0.5~2):

1.

5. The methanol engine exhaust aftertreatment catalyst according to any one of claims 1-4, characterized in that, The thickness of the sheet-like catalyst support is 50~500μm; Preferably, the thickness of the first catalyst coating is 20~100μm; Preferably, the thickness of the second catalyst coating is 20~100μm.

6. A method for preparing a methanol engine exhaust aftertreatment catalyst as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) A composite metal oxide framework precursor is prepared by co-precipitation method, and the composite metal oxide framework precursor is subjected to a first sintering treatment to obtain a composite metal oxide framework. A noble metal salt solution is loaded on the surface of the composite metal oxide framework and subjected to a second sintering treatment to obtain a first catalyst. (2) The second catalyst precursor was prepared by sol-gel method, and the second catalyst precursor was calcined to obtain a solid solution material; (3) The first catalyst and the solid solution material are respectively made into a first slurry and a second slurry. The first slurry is coated on the surface of the sheet catalyst carrier and heat-treated to form a first catalyst coating. The second slurry is coated on the surface of the first catalyst coating and reduced to form a second catalyst coating, thus obtaining a methanol engine exhaust gas aftertreatment catalyst.

7. The preparation method according to claim 6, characterized in that, The precipitant used in the co-precipitation method described in step (1) includes ammonia. Preferably, step (1) the first sintering process includes one-step sintering and two-step sintering; Preferably, the temperature of the one-step sintering is 500℃~600℃; Preferably, the sintering time in the first step is 2 hours to 5 hours; Preferably, the temperature of the two-step sintering is 800℃~1000℃; Preferably, the two-step sintering time is 2h~5h; Preferably, the sintering temperature in step (1) is 450℃~600℃; Preferably, the second sintering time in step (1) is 2h~5h.

8. The preparation method according to claim 6 or 7, characterized in that, The roasting process in step (2) includes one-step roasting and two-step roasting; Preferably, the temperature of the first-step calcination is 500℃~600℃; Preferably, the roasting time for the first step is 2 hours to 5 hours; Preferably, the temperature of the two-step calcination is 800℃~1000℃; Preferably, the two-step roasting time is 2h to 5h.

9. The preparation method according to any one of claims 6-8, characterized in that, Step (3) The solid content of the first slurry is 20%~35%; Preferably, in step (3), the solid content of the second slurry is 15%~38%; Preferably, in step (3), the coating amount of the first slurry is 150g / L to 250g / L; Preferably, in step (3), the coating amount of the second slurry is 200g / L~300g / L; Preferably, the heat treatment temperature in step (3) is 500℃~600℃; Preferably, the heat treatment time in step (3) is 2h~5h; Preferably, the temperature of the reduction treatment in step (3) is 200℃~600℃; Preferably, the reduction process in step (3) takes 0.5h to 5h.

10. The application of a methanol engine exhaust aftertreatment catalyst as described in any one of claims 1-5, characterized in that, The methanol engine exhaust aftertreatment catalyst is used for the purification of methanol fuel vehicle exhaust.

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