Iron modified three-way catalyst and method for its production and use

Abstract

The present application relates to a kind of iron modified three-way catalyst and its preparation method and use, the iron modified three-way catalyst includes carrier, first noble metal, iron-doped cerium-zirconium solid solution and second noble metal;The first noble metal is supported on carrier;The iron-doped cerium-zirconium solid solution covers the surface of carrier and first noble metal, and the second noble metal is dispersed on the surface of iron-doped cerium-zirconium solid solution;The first noble metal includes Pd and Pt;The second noble metal includes Rh.The Fe doped in the cerium-zirconium solid solution of the present application can regulate carrier defect structure and noble metal dispersion state, can significantly improve the low-temperature activity and high-temperature hydrothermal stability of catalyst under the condition of not increasing noble metal consumption, effectively reduce catalyst production cost, and has important application value for promoting the development of methanol alternative fuel in transportation field.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an iron-modified three-way catalyst, its preparation method, and its uses. Background Technology

[0002] In recent years, methanol has been widely promoted as a clean alternative fuel, and the methanol vehicle industry is experiencing rapid growth. However, with the continuous increase in the number of methanol vehicles, the problem of exhaust pollution has become increasingly prominent. During the cold start phase, methanol vehicles emit large amounts of unburned methanol and formaldehyde, which are highly toxic and directly endanger environmental safety and human health. Under long-term high-speed operation, the catalyst must withstand temperatures above 800°C and high-concentration water vapor impacts, which can easily lead to problems such as carrier sintering, precious metal agglomeration, and loss of active sites, resulting in a sharp decline in catalytic performance.

[0003] Therefore, the poor low-temperature activity and easy deactivation at high temperatures have become key technological bottlenecks restricting the large-scale promotion of methanol vehicles. Currently, researchers often increase the amount of precious metals used to ensure catalytic efficiency, but this will significantly increase the cost of catalysts and increase the burden on vehicle manufacturers.

[0004] Therefore, there is an urgent need to develop a three-way catalyst that combines excellent low-temperature activity and high-temperature stability while controlling the amount of precious metals used. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide an iron-modified three-way catalyst, its preparation method, and its applications. The iron-modified three-way catalyst of the present invention, through Fe doping to regulate the defect structure of the support and the dispersion state of the precious metal, can significantly improve the low-temperature activity and high-temperature hydrothermal stability of the catalyst without increasing the amount of precious metal, effectively solving existing technical problems, reducing catalyst production costs, and having important application value for promoting the development of methanol alternative fuels in the transportation sector.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an iron-modified three-way catalyst, the iron-modified three-way catalyst comprising a support, a first noble metal, an iron-doped cerium-zirconium solid solution, and a second noble metal; the first noble metal is supported on the support; the iron-doped cerium-zirconium solid solution covers the surface of the support and the first noble metal, and the second noble metal is dispersed on the surface of the iron-doped cerium-zirconium solid solution; the first noble metal comprises Pd and Pt; the second noble metal comprises Rh.

[0008] This invention employs an iron-doped CeZr solid solution. The presence of Fe in the crystal lattice causes distortion in the CeZr solid solution, generating more oxygen vacancy defects. These oxygen vacancies serve as storage and release sites for active oxygen, significantly enhancing the oxygen migration ability of the catalyst. Simultaneously, after Fe doping, due to Fe… 3+ / Fe 2+ Redox Cycles and Ce 4+ / Ce 3+ The formation of synergistic electronic coupling significantly promotes oxygen vacancy generation and lattice oxygen migration, thereby increasing the active oxygen concentration and oxygen storage / release capacity on the catalyst surface. Simultaneously, Fe species enhance the interaction between noble metals and the support, improve the dispersion state of Pd, Pt, and Rh, and regulate their electronic structure, thus promoting low-temperature oxygen activation and reactant conversion.

[0009] Fe interacts electronically with noble metals, optimizing the valence state distribution and dispersion of the noble metals, making the active centers of the noble metals more efficient and stable. Furthermore, Fe doping enhances the metal-support interaction, and the interaction between CO and NO... x The redox reaction with CH3OH is smoother. Without increasing the amount of precious metals, doping with the non-precious metal Fe significantly improves the low-temperature activity and overall catalytic efficiency of the catalyst.

[0010] When doped with other metals, such as Co or Ni, Co or Ni is more likely to form independent oxide phases, with weaker oxygen migration synergy and limited ability to regulate the electronic structure of noble metals. Therefore, the effect of improving low-temperature activity is not as significant as that of Fe.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0012] In some embodiments, the general chemical formula of the undoped cerium-zirconium solid solution is Ce. x Zr y O2, where 0.2≤x≤0.8, x+y=1. x can be, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, but is not limited to the listed values. Other unlisted values ​​within the range also apply.

[0013] In some embodiments, the carrier comprises aluminum oxide.

[0014] In some embodiments, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of Pd is 0.1 wt.% to 1 wt.%, for example, it can be 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, or 1 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In some embodiments, with a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of Pt is 0.1 wt.% to 1 wt.%, for example, it can be 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, or 1 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In some embodiments, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of the second noble metal is 0.1 wt.% to 1 wt.%, for example, it can be 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, or 1 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] In some embodiments, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of the iron-doped cerium-zirconium solid solution is 40 wt.%-60 wt.%, for example, it can be 40 wt.%, 42 wt.%, 45 wt.%, 48 wt.%, 50 wt.%, 52 wt.%, 55 wt.%, 58 wt.%, or 60 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In some embodiments, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the iron doping amount is 2 wt.% to 6 wt.%, for example, it can be 2 wt.%, 2.2 wt.%, 2.5 wt.%, 2.8 wt.%, 3 wt.%, 3.2 wt.%, 3.5 wt.%, 3.8 wt.%, 4 wt.%, 4.2 wt.%, 4.5 wt.%, 4.8 wt.%, 5.0 wt.%, 5.5 wt.%, or 6 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] This invention further controls the iron doping amount to 2wt.%-6wt.%, as the iron doping amount affects the oxygen vacancy concentration and the stability of the solid solution structure; when the appropriate doping amount (2wt.%) is reached, Fe... 3+ Entering the CeZr lattice, it induces lattice distortion and charge compensation effects, promoting Ce 4+ →Ce 3+ The conversion and generation of oxygen vacancies enhance oxygen storage and release capacity and oxygen migration performance, while optimizing the electronic state and dispersion of noble metals, synergistically improving the low-temperature three-way catalytic activity. If the iron doping amount is too large, Fe species segregate to form the Fe2O3 phase, which destroys the solid solution structure, blocks pores, and covers active sites, leading to deterioration of catalytic performance; if the iron doping amount is too small, the solid solution formation is insufficient, oxygen vacancies are insufficient, and the improvement in oxygen storage and release capacity is limited.

[0020] In some embodiments, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the iron doping amount is 2 wt.%-3 wt.%, for example, it can be 2 wt.%, 2.1 wt.%, 2.2 wt.%, 2.3 wt.%, 2.4 wt.%, 2.5 wt.%, 2.6 wt.%, 2.7 wt.%, 2.8 wt.%, 2.9 wt.%, or 3 wt.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In a second aspect, the present invention provides a method for preparing an iron-modified three-way catalyst as described in the first aspect, the method comprising the following steps:

[0022] A first intermediate is obtained by mixing a carrier and a first noble metal salt solution, followed by a first impregnation treatment and a first calcination.

[0023] The first intermediate, cerium salt solution, zirconium salt solution and alkaline solution are mixed to obtain a mixed solution, which is then subjected to a co-precipitation reaction and a second calcination to obtain the second intermediate;

[0024] The second intermediate, the second noble metal salt solution, and the iron salt solution are mixed, and then subjected to a second impregnation treatment and a third calcination to obtain the third intermediate;

[0025] The third intermediate was heat-treated to obtain the iron-modified three-way catalyst.

[0026] This invention significantly improves catalyst performance compared to untreated catalysts by heat-treating the third intermediate. Heat treatment promotes structural homogenization of the CeZr solid solution, induces enrichment of surface reactive oxygen species, optimizes the distribution of noble metal valence states, and moderately enhances metal-support interactions, thereby significantly improving low-temperature catalytic activity. Without heat treatment, the solid solution exhibits poor homogeneity, insufficient reactive oxygen species, and unoptimized noble metal states, failing to achieve the aforementioned synergistic improvement effect.

[0027] Unlike the traditional view that hydrothermal aging only leads to catalyst deactivation, this invention reveals for the first time the "activation" effect of moderate hydrothermal aging on three-way catalysts for methanol vehicles and its microscopic mechanism, providing a new strategy for reverse optimization of catalyst performance. Furthermore, this technology differs from existing hydrothermal aging research (mainly focused on gasoline vehicle catalysts or used only as a durability testing method), possessing a clear application orientation towards methanol vehicles, optimal processing condition parameters, and synergistic Fe doping modification technical characteristics, significantly improving the low-temperature activity and high-temperature stability of the catalyst in methanol exhaust purification.

[0028] In some embodiments, the first noble metal salt solution includes a palladium salt solution and a platinum salt solution.

[0029] In some embodiments, the second noble metal salt solution includes a rhodium salt solution.

[0030] In some embodiments, the total concentration of metal ions in the first noble metal salt solution is 2.5 mmol / L to 11.5 mmol / L, for example, it can be 2.5 mmol / L, 3.0 mmol / L, 3.5 mmol / L, 4.0 mmol / L, 4.5 mmol / L, 5.0 mmol / L, 5.5 mmol / L, 6.0 mmol / L, 7.0 mmol / L, 8.0 mmol / L, 9.0 mmol / L, 10.0 mmol / L, 11.0 mmol / L, or 11.5 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] In some embodiments, the total concentration of cerium-zirconium ions in the mixed solution is 0.15 mol / L to 0.85 mol / L, for example, it can be 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, or 0.85 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In some embodiments, the total concentration of metal ions in the second noble metal salt solution is 1 mmol / L to 6 mmol / L, for example, it can be 1 mmol / L, 1.5 mmol / L, 2 mmol / L, 2.5 mmol / L, 3 mmol / L, 3.5 mmol / L, 4 mmol / L, 4.5 mmol / L, 5 mmol / L, 5.5 mmol / L or 6 mmol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] In some embodiments, the concentration of the iron salt solution is 0.005 mol / L to 0.250 mol / L, for example, it can be 0.005 mol / L, 0.010 mol / L, 0.020 mol / L, 0.050 mol / L, 0.080 mol / L, 0.100 mol / L, 0.150 mol / L, 0.180 mol / L, 0.200 mol / L, 0.220 mol / L or 0.250 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] In some embodiments, the alkaline solution includes an aqueous ammonia solution and an ammonium carbonate solution.

[0035] In some embodiments, the molar concentration of the ammonia solution is 2 mol / L to 5 mol / L, for example, it can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] In some embodiments, the molar concentration of the ammonium carbonate solution is 0.2 mol / L to 1 mol / L, for example, it can be 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] In some embodiments, the temperature of the first calcination is 450°C-950°C, for example, it can be 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0038] In some embodiments, the first calcination time is 1h-24h, for example, it can be 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] In some embodiments, the second calcination temperature is 450°C-950°C, for example, it can be 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0040] In some embodiments, the second calcination time is 1h-24h, for example, it can be 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] In some embodiments, the temperature of the third calcination is 450℃-950℃, for example, it can be 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃ or 950℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] In some embodiments, the third calcination time is 1h-24h, for example, it can be 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] In some embodiments, the heat treatment is carried out under conditions where the water vapor content is 5 vol.% to 20 vol.%, for example, it can be 5 vol.%, 10 vol.%, 12 vol.%, 15 vol.%, 18 vol.%, or 20 vol.%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In some embodiments, the heat treatment temperature is 700°C-900°C, for example, it can be 700°C, 750°C, 800°C, 850°C or 900°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0045] This invention further controls the heat treatment temperature to 700℃-900℃. The heat treatment temperature affects the structural uniformity of CeZr solid solution, the dispersion and valence distribution of noble metals, the concentration of surface active oxygen species, and the intensity of metal-carrier interaction. If the heat treatment temperature is too high, the solid solution phases separate, noble metals sinter, and the surface active oxygen content decreases. If the heat treatment temperature is too low, the CeZr solid solution is not uniform and the active oxygen content is insufficient.

[0046] In some embodiments, the heat treatment time is 5h-20h, for example, it can be 5h, 8h, 10h, 12h, 14h, 15h, 18h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] In some embodiments, the palladium salt solution includes any one or a combination of at least two of palladium nitrate solution, palladium sulfate solution, palladium chloride solution, or palladium acetate solution. Typical but non-limiting combinations include combinations of palladium nitrate and palladium sulfate, palladium sulfate and palladium chloride, palladium chloride and palladium acetate, palladium nitrate and palladium chloride, palladium sulfate, palladium chloride and palladium acetate, or palladium nitrate, palladium sulfate, palladium chloride and palladium acetate, preferably palladium nitrate.

[0048] In some embodiments, the platinum salt solution includes any one or a combination of at least two of platinum nitrate solution, platinum sulfate solution, platinum chloride solution, or platinum acetate solution. Typical but non-limiting combinations include combinations of platinum nitrate and platinum sulfate, platinum sulfate and platinum chloride, platinum chloride and platinum acetate, platinum nitrate and platinum chloride, platinum sulfate, platinum chloride and platinum acetate, or platinum nitrate, platinum sulfate, platinum chloride and platinum acetate, preferably platinum nitrate.

[0049] In some embodiments, the cerium salt solution includes any one or a combination of at least two of cerium nitrate solution, cerium sulfate solution, cerium chloride solution, or cerium acetate solution. Typical but non-limiting combinations include combinations of cerium nitrate solution and cerium sulfate solution, combinations of cerium sulfate solution and cerium chloride solution, combinations of cerium chloride solution and cerium acetate solution, combinations of cerium nitrate solution and cerium chloride solution, combinations of cerium sulfate solution, cerium chloride solution, and cerium acetate solution, or combinations of cerium nitrate solution, cerium sulfate solution, cerium chloride solution, and cerium acetate solution, preferably cerium nitrate solution.

[0050] In some embodiments, the zirconium salt solution comprises any one or a combination of at least two of zirconium nitrate solution, zirconium oxynitrate solution, zirconium sulfate solution, zirconium chloride solution, or zirconium acetate solution. Typical but non-limiting combinations include combinations of zirconium nitrate solution and zirconium oxynitrate solution, combinations of zirconium oxynitrate solution and zirconium sulfate solution, combinations of zirconium nitrate solution and zirconium sulfate solution, combinations of zirconium chloride solution and zirconium acetate solution, and combinations of zirconium oxynitrate solution, zirconium sulfate solution, zirconium chloride solution, and zirconium acetate solution, preferably zirconium oxynitrate solution.

[0051] In some embodiments, the rhodium salt solution includes any one or a combination of at least two of rhodium nitrate solution, rhodium sulfate solution, rhodium chloride solution, or rhodium acetate solution. Typical but non-limiting combinations include combinations of rhodium nitrate and rhodium sulfate, rhodium sulfate and rhodium chloride, rhodium chloride and rhodium acetate, rhodium nitrate and rhodium chloride, rhodium sulfate, rhodium chloride and rhodium acetate, or rhodium nitrate, rhodium sulfate, rhodium chloride and rhodium acetate, preferably rhodium nitrate.

[0052] In some embodiments, the iron salt solution comprises any one or a combination of at least two of ferric nitrate, ferric sulfate, or ferric chloride. Typical but non-limiting combinations include combinations of ferric nitrate and ferric sulfate, combinations of cerium sulfate and cerium chloride, combinations of ferric nitrate and ferric chloride, and combinations of ferric nitrate, ferric sulfate, and ferric chloride, preferably ferric nitrate.

[0053] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0054] (1) Mix the carrier and the first precious metal salt solution, perform the first impregnation treatment on a rotary evaporator, dry at 100℃-130℃ for 12h-24h, and then calcine at 500℃-600℃ for 1h-5h to obtain the first intermediate.

[0055] (2) Mix the first intermediate, cerium salt solution and zirconium salt solution to obtain a mixed solution. Add alkali solution to the mixed solution to adjust the pH of the reaction system to 8-11. Stir the reaction at 300rpm-500rpm for 0.5h-1h, let it stand for 2h-24h to carry out co-precipitation reaction. Wash the obtained precipitate with deionized water until neutral, dry it at 100℃-130℃ for 12h-24h, and then calcine it at 500℃-600℃ for 1h-24h to obtain the second intermediate.

[0056] (3) Mix the second intermediate, the second noble metal salt solution and the iron salt solution, perform a second impregnation treatment on a rotary evaporator, dry at 100℃-130℃ for 12h-24h, and then calcine at 500℃-600℃ for 1h-5h to obtain the third intermediate;

[0057] (4) Under the condition that the water vapor content is 5 vol.%-20 vol.%, the third intermediate is heat-treated at 700℃-900℃ for 10h-15h to obtain the iron-modified three-way catalyst.

[0058] Thirdly, the present invention provides the use of the iron-modified three-way catalyst as described in the first aspect, wherein the iron-modified three-way catalyst is used for the treatment of methanol vehicle exhaust to degrade carbon monoxide, nitrogen oxides and methanol.

[0059] The Fe doping in the cerium-zirconium solid solution of this invention can regulate the defect structure of the support and the dispersion state of the noble metal. It can significantly improve the low-temperature activity and high-temperature hydrothermal stability of the catalyst without increasing the amount of noble metal, effectively reduce the production cost of the catalyst, and has important application value for promoting the development of methanol alternative fuel in the transportation field.

[0060] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0061] Compared with the prior art, the present invention has at least the following beneficial effects:

[0062] (1) This invention employs an iron-doped CeZr solid solution. The entry of Fe into the crystal lattice causes distortion in the CeZr solid solution, generating more oxygen vacancy defects. These oxygen vacancies serve as storage and release sites for active oxygen, significantly enhancing the oxygen migration ability of the catalyst. Simultaneously, Fe interacts electronically with noble metals, optimizing the valence state distribution and dispersion of the noble metals, making the active centers of the noble metals more efficient and stable. Furthermore, Fe doping enhances the metal-support interaction, promoting the release of CO and NO. x The redox reaction with CH3OH is smoother. Without increasing the amount of precious metals, doping with the non-precious metal Fe significantly improves the low-temperature activity and overall catalytic efficiency of the catalyst.

[0063] (2) By heat-treating the third intermediate, the performance of the catalyst is significantly improved compared to that without heat treatment. Heat treatment can promote the structural homogenization of CeZr solid solution, induce the enrichment of surface active oxygen, optimize the distribution of noble metal valence states, and moderately enhance metal-support interactions, thereby significantly improving the low-temperature catalytic activity. Without heat treatment, the solid solution has poor homogenization, insufficient active oxygen, and the state of noble metals is not optimized, so the above-mentioned synergistic improvement effect cannot be achieved.

[0064] (3) The Fe doping in the cerium-zirconium solid solution of the present invention can regulate the defect structure of the support and the dispersion state of the noble metal. It can significantly improve the low-temperature activity and high-temperature hydrothermal stability of the catalyst without increasing the amount of noble metal, effectively reduce the production cost of the catalyst, and has important application value for promoting the development of methanol alternative fuel in the transportation field. Attached Figure Description

[0065] Figure 1 This is a graph showing the conversion rate of CO by the iron-modified three-way catalysts obtained in Examples 1-3 and Comparative Example 6, and the three-way catalyst obtained in Comparative Example 1.

[0066] Figure 2 This is a graph showing the conversion rate of NO by the iron-modified three-way catalysts obtained in Examples 1-3 and Comparative Example 6, and the three-way catalyst obtained in Comparative Example 1.

[0067] Figure 3 This is a graph showing the conversion rate of CH3OH by the iron-modified three-way catalysts obtained in Examples 1-3 and Comparative Example 6, and the three-way catalyst obtained in Comparative Example 1. Detailed Implementation

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0073] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0074] Example 1

[0075] This embodiment provides an iron-modified three-way catalyst. With a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the catalyst comprises an alumina support, 0.5 wt.% Pd, 0.2 wt.% Pt, 50 wt.% cerium-zirconium solid solution (with 2 wt.% iron doping), and 0.3 wt.% a second noble metal Rh. The first noble metal is supported on the support; the cerium-zirconium solid solution covers the surfaces of the support and the first noble metal; and the second noble metal is dispersed on the surface of the cerium-zirconium solid solution.

[0076] The preparation method of the iron-modified three-way catalyst provided in this embodiment includes the following steps:

[0077] (1) Mix Al2O3 support, Pd(NO3)2 solution and Pt(NO3)2 solution, perform first impregnation treatment on rotary evaporator, dry at 110℃ for 15h, and then calcine at 550℃ for 3h to obtain the first intermediate;

[0078] (2) Mix the first intermediate, Ce(NO3)2·6H2O solution and ZrO(NO3)2 solution to obtain a mixed solution. Add alkaline solution (ammonia solution with a molar concentration of 2.0 mol / L and ammonium carbonate solution with a molar concentration of 0.2 mol / L) to the mixed solution to adjust the pH of the reaction system to 9.5. Stir the reaction at 300 rpm for 0.5 h, let it stand for 4 h to carry out co-precipitation reaction. Wash the obtained precipitate with deionized water until neutral, dry it at 110 °C for 15 h, and then calcine it at 550 °C for 3 h to obtain the second intermediate.

[0079] (3) Mix the second intermediate, Rh(NO3)3 solution and ferric nitrate solution, perform a second impregnation treatment on a rotary evaporator, dry at 110°C for 15 h, and then calcine at 550°C for 3 h to obtain the third intermediate;

[0080] (4) The third intermediate was heat-treated at 800°C for 10 h under the condition that the water vapor content was 10 vol.% to obtain the iron-modified three-way catalyst.

[0081] Example 2

[0082] This embodiment provides an iron-modified three-way catalyst. Based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the iron-modified three-way catalyst includes an alumina support, 1 wt.% Pd, 0.8 wt.% Pt, 40 wt.% cerium-zirconium solid solution (with 3 wt.% iron doping), and 0.3 wt.% Rh, a second noble metal.

[0083] The first noble metal is loaded on a carrier; the cerium-zirconium solid solution covers the surface of the carrier and the first noble metal, and the second noble metal is dispersed on the surface of the cerium-zirconium solid solution.

[0084] The preparation method of the iron-modified three-way catalyst provided in this embodiment includes the following steps:

[0085] (1) Mix Al2O3 support, platinum sulfate solution and palladium sulfate solution, perform the first impregnation treatment on a rotary evaporator, dry at 100°C for 24 h, and then calcine at 800°C for 2 h to obtain the first intermediate;

[0086] (2) Mix the first intermediate, cerium sulfate solution and zirconium sulfate solution to obtain a mixed solution. Add alkaline solution (ammonia solution with a molar concentration of 1.0 mol / L and ammonium carbonate solution with a molar concentration of 0.2 mol / L) to the mixed solution to adjust the pH of the reaction system to 8. Stir the reaction at 400 rpm for 1 h and let it stand for 10 h to carry out a co-precipitation reaction. Wash the obtained precipitate with deionized water until neutral, dry it at 100 °C for 24 h, and then calcine it at 800 °C for 2 h to obtain the second intermediate.

[0087] (3) Mix the second intermediate, rhodium sulfate solution and ferric sulfate solution, perform a second impregnation treatment on a rotary evaporator, dry at 100°C for 24 hours, and then calcine at 800°C for 2 hours to obtain the third intermediate;

[0088] (4) Under the condition that the water vapor content is 20 vol.%, the third intermediate is heat-treated at 700 °C for 5 h to obtain the iron-modified three-way catalyst.

[0089] Example 3

[0090] This embodiment provides an iron-modified three-way catalyst. Based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the iron-modified three-way catalyst includes an alumina support, 0.1 wt.% Pd, 0.2 wt.% Pt, 60 wt.% cerium-zirconium solid solution (with iron doping at 6 wt.%), and 0.5 wt.% Rh, a second noble metal.

[0091] The first noble metal is loaded on a carrier; the cerium-zirconium solid solution covers the surface of the carrier and the first noble metal, and the second noble metal is dispersed on the surface of the cerium-zirconium solid solution.

[0092] The preparation method of the iron-modified three-way catalyst provided in this embodiment includes the following steps:

[0093] (1) Mix Al2O3 support, platinum chloride solution and palladium chloride solution, perform first impregnation treatment on rotary evaporator, dry at 130°C for 12h, and then calcine at 500°C for 5h to obtain the first intermediate;

[0094] (2) Mix the first intermediate, cerium acetate solution and zirconium acetate solution to obtain a mixture. Add alkaline solution (ammonia solution with a molar concentration of 4.0 mol / L and ammonium carbonate solution with a molar concentration of 0.5 mol / L) to the mixture to adjust the pH of the reaction system to 10. Stir the reaction at 300 rpm for 0.5 h-1 h and let it stand for 15 h to carry out co-precipitation reaction. Wash the obtained precipitate with deionized water until neutral, dry it at 130 °C for 12 h, and then calcine it at 500 °C for 8 h to obtain the second intermediate.

[0095] (3) Mix the second intermediate, rhodium chloride solution and ferric chloride solution, perform a second impregnation treatment on a rotary evaporator, dry at 130°C for 12 hours, and then calcine at 500°C for 5 hours to obtain the third intermediate;

[0096] (4) Under the condition that the water vapor content is 5 vol.%, the third intermediate is heat-treated at 900 °C for 11 h to obtain the iron-modified three-way catalyst.

[0097] Example 4

[0098] This embodiment provides an iron-modified three-way catalyst, which differs from Example 1 only in that the iron doping amount is 1 wt.%, and the amount of iron salt solution added in step (3) of the preparation method is adapted, while the other steps remain unchanged.

[0099] Example 5

[0100] This embodiment provides an iron-modified three-way catalyst, which differs from Example 1 only in that the iron doping amount is 7 wt.%, and the amount of iron salt solution added in step (3) of the preparation method is adapted, while the other steps remain unchanged.

[0101] Example 6

[0102] This embodiment provides an iron-modified three-way catalyst. The only difference from Example 1 is that when preparing the iron-modified three-way catalyst, the temperature of the heat treatment in step (4) is changed from 800℃ to 600℃, while the other steps remain unchanged.

[0103] Example 7

[0104] This embodiment provides an iron-modified three-way catalyst. The only difference from Example 1 is that when preparing the iron-modified three-way catalyst, the temperature of the heat treatment in step (4) is changed from 800℃ to 1000℃, while the other steps remain unchanged.

[0105] Comparative Example 1

[0106] This comparative example provides a three-way catalyst, which differs from Example 1 only in that iron salt was not added in step (3) when preparing the three-way catalyst.

[0107] Comparative Example 2

[0108] This comparative example provides a cobalt-modified three-way catalyst. The only difference from Example 1 is that, in preparing the cobalt-modified three-way catalyst, step (3) replaces the iron salt with an equimolar amount of cobalt nitrate.

[0109] Comparative Example 3

[0110] This comparative example provides a nickel-modified three-way catalyst. The only difference from Example 1 is that, in preparing this nickel-modified three-way catalyst, step (3) replaces the iron salt with an equimolar amount of nickel nitrate.

[0111] Comparative Example 4

[0112] This comparative example provides a sodium-modified three-way catalyst. The only difference from Example 2 is that, in preparing this sodium-modified three-way catalyst, step (3) replaces the iron salt with an equimolar amount of sodium nitrate.

[0113] Comparative Example 5

[0114] This comparative example provides a potassium-modified three-way catalyst. The only difference from Example 2 is that, in preparing this potassium-modified three-way catalyst, step (3) replaces the iron salt with an equimolar amount of potassium nitrate.

[0115] Comparative Example 6

[0116] This comparative example provides an iron-modified three-way catalyst, which differs from Example 1 only in that the heat treatment in step (4) was not performed when preparing the iron-modified three-way catalyst.

[0117] Comparative Example 7

[0118] This comparative example provides a three-way catalyst, which differs from Comparative Example 1 only in that the heat treatment in step (4) was not performed during the preparation of the three-way catalyst.

[0119] test:

[0120] The three-way catalysts prepared in the examples and comparative examples were tested: The activity evaluation of the catalysts in this invention was carried out in a fixed-bed quartz tube reactor with an inner diameter of 5 mm. The mass of the catalyst used in the test was 54 mg, and the particle size of the catalyst used in the test was 40-60 mesh. The inner diameter of the quartz tube used in the experiment was 5 mm, and the height was 430 mm. Quartz wool was placed at the bottom of the catalyst to prevent catalyst loss.

[0121] The introduced gas composition was 0.03% CH3OH, 0.43% CO, 0.03% NO, 0.21% O2, 10% H2O, with N2 as the equilibrium gas. Water vapor was generated by flowing N2 gas through a water bath bubbler. The total flow rate was 300 mL / min. The mass hourly space velocity (MSV) during the activity test was 50,000 mL / (g∙h), and the theoretical air-fuel ratio λ = 0.9986. The flow rate of the reaction gas was controlled by a mass control flow meter. The reactants during the reaction were CH3OH, NO, NO2, CO, CO2, N2O, NH3, and NO. x The concentration was continuously monitored using an Antaris IGS gas analyzer (ThermoFisher). The reaction temperature was controlled by a tube furnace.

[0122] In all experiments, the formulas for calculating the exhaust gas conversion are as follows. The conversion rates of CH3OH, CO, and NO are defined as follows:

[0123] CH3OH conversion(%)={1-[CH3OH] out / [CH3OH] in}×100%;

[0124] CO conversion (%) = {1 - [CO]} out / [CO] in}×100%;

[0125] NO conversion(%) = {1 - [NO]} out / [NO] in}×100%;

[0126] Among them, [CH3OH] in and [CH3OH] out These represent the methanol concentrations at import and export levels, respectively, and [CO]. in and [CO] out These are the concentrations of imported CO and exported CO, [NO]. in and [NO] out These represent the import and export nitric oxide concentrations, respectively. The test results are shown in Table 1 below.

[0127] The comparison graph of the CO conversion rates of the iron-modified three-way catalysts of Examples 1-3 and the three-way catalyst obtained in Comparative Example 6 is shown in the figure. Figure 1 As shown in the figure, the CO conversion curves of the heat-treated catalysts in Examples 1-3 are all significantly shifted to the left compared to the untreated control catalyst 6. Example 1 (heat-treated at 800℃) shows the largest leftward shift and the lowest ignition temperature. This indicates that heat treatment can significantly improve the low-temperature CO oxidation activity of the catalyst, and the heat treatment temperature has a significant impact on the performance improvement. Heat treatment temperatures that are too low (700℃) or too high (900℃) are not as effective as the optimal temperature (800℃).

[0128] The comparison graph of the conversion rate of NO by the iron-modified three-way catalysts of Examples 1-3 and the three-way catalyst obtained in Comparative Example 6 is shown in the figure. Figure 2 As shown in the figure, the NO conversion curves of the heat-treated catalysts in Examples 1-3 all shift significantly towards lower temperatures compared to the untreated control catalyst 6. Example 1 exhibits the lowest NO ignition temperature and the best low-temperature reduction performance. This indicates that heat treatment effectively enhances the NO reduction capacity of the catalyst. This is attributed to the fact that heat treatment promotes the homogenization of the CeZr solid solution structure, enrichment of surface active oxygen, and optimization of the noble metal valence state, thereby improving the adsorption and reduction efficiency of NO.

[0129] The comparison graph of the conversion rates of CH3OH by the iron-modified three-way catalysts of Examples 1-3 and the three-way catalyst obtained in Comparative Example 6 is shown in the figure. Figure 3 As shown in the figure, the CH3OH conversion curves of the heat-treated catalysts in Examples 1-3 are significantly shifted to the left compared to the untreated control catalyst 6, indicating a significant improvement in low-temperature ignition performance. This demonstrates that heat treatment effectively promotes the deep oxidation conversion of methanol, attributed to the increased concentration of surface active oxygen species and oxygen migration capacity, which accelerates the rapid consumption and complete oxidation of oxygen-containing intermediates such as methoxy groups and formates. Example 1 (heat treatment at 800℃) showed the best results, further confirming the crucial role of the optimal heat treatment temperature in catalytic performance.

[0130] Table 1

[0131]

[0132] The test results show that:

[0133] (1) As can be seen from Examples 1-3, by using an iron-doped CeZr solid solution, Fe can promote the generation of oxygen vacancy defects, significantly enhancing the oxygen migration ability of the catalyst. At the same time, Fe optimizes the valence distribution and dispersion state of the noble metal, making the active center of the noble metal more efficient and stable. Fe doping also enhances the metal-support interaction, and CO and NO... xThe redox reaction with CH3OH is smoother. This invention, without increasing the amount of precious metals, significantly improves the low-temperature activity and overall catalytic efficiency of the catalyst by doping with the non-precious metal Fe, which has important application value for promoting the development of methanol as an alternative fuel in the transportation sector.

[0134] (2) By comparing Example 1 with Examples 4-5, it can be seen that by further controlling the iron doping amount to 2wt.%-6wt.%, the iron doping amount affects the catalyst lattice defect concentration, oxygen vacancy quantity, noble metal electronic state, and metal-support interaction strength. If the iron doping amount is too large, the Fe species exceed the solid solution limit of the CeZr lattice and cannot continue to enter the lattice. Instead, they segregate on the catalyst surface in the form of independent oxides such as Fe2O3. These surface Fe oxide species do not have catalytic activity and will block the pores, cover the noble metal active sites, and destroy the structural integrity of the CeZr solid solution. This leads to a decrease in the effective oxygen vacancy concentration instead of an increase, and the oxygen storage and release capacity and oxygen migration capacity are both inhibited. The metal-support interaction is unbalanced, and the catalytic performance deteriorates. If the iron doping amount is too small, the Fe 3+ The insufficient number of CeZr atoms entering the CeZr lattice results in incomplete solid solution formation and a limited induced oxygen vacancy concentration. 4+ →Ce 3+ The conversion rate is limited, the oxygen storage and release capacity and oxygen migration capacity of the catalyst are not sufficiently improved, and the electronic state regulation effect of precious metals is not obvious, resulting in limited improvement in catalytic activity at low temperatures.

[0135] (3) By comparing Example 1 with Examples 6-7, it can be seen that the present invention further controls the heat treatment temperature to 700℃-900℃ to optimize the structural uniformity of CeZr solid solution, the dispersion and valence distribution of noble metals, the concentration of surface active oxygen species, and the intensity of metal-support interaction. If the heat treatment temperature is too high, the CeZr solid solution will undergo phase separation, precipitating independent CeO2 and ZrO2 phases, destroying oxygen migration channels; the noble metal particles will be severely sintered, and the dispersion will decrease sharply; the effective oxygen vacancy concentration will decrease, and the proportion of surface active oxygen will decrease significantly; the metal-support interaction will be severely weakened, and the reduction temperature of noble metal oxides will shift towards higher temperatures, resulting in a significant decrease in catalytic activity. If the heat treatment temperature is too low, the CeZr solid solution will not be formed sufficiently, the distribution of Ce and Zr elements will be uneven, and independent CeO2 crystal phases will still exist; the interaction between noble metals and support will be too strong or mismatched, inhibiting the reducibility of noble metal oxides; the generation of surface active oxygen species will be limited, and the oxygen migration ability will be insufficient, resulting in the catalyst's low-temperature redox performance not being fully utilized.

[0136] (4) As can be seen from Example 1 and Comparative Examples 1-5, the present invention modifies CeZr solid solution by specifically doping with iron, and can utilize Fe3+ A suitable ionic radius (approximately 0.65 Å) enters the CeZr lattice, inducing local lattice distortion and charge compensation effects, thus promoting Ce... 4+ →Ce 3+ Conversion and oxygen vacancy generation enhance oxygen storage and release capacity and oxygen migration performance; simultaneously, Fe 3+ / Fe 4+ With Ce 4+ / Ce 3+ The two redox pairs produce a synergistic effect, optimizing the electronic state and dispersion of the noble metal, thereby significantly improving the low-temperature activity of the catalyst. However, when other metals (such as Co, Ni, Na, and K) are doped, their ionic radii, valence states, and redox properties differ fundamentally from those of Fe: although Co and Ni are transition metals, they are difficult to form a stable ternary solid solution structure similar to Fe; Na and K are alkali metals, do not have variable valence states, cannot provide additional redox electron pairs, and their larger ionic radii will disrupt the lattice stability of CeZr, failing to achieve the unique "lattice distortion-oxygen vacancy-redox synergistic" technical effect of Fe doping. Therefore, the improvement in low-temperature activity is limited or even inhibited.

[0137] (5) As can be seen from Example 1 and Comparative Example 6, the performance of the catalyst of the present invention is significantly improved by heat treatment of the third intermediate compared with that without heat treatment. Heat treatment can promote the structural reforming and homogenization of CeZr solid solution, so that Ce and Zr elements achieve atomic-level uniform distribution; and induce surface active oxygen species (O β A significant increase in ); optimization of the price distribution of precious metals (Pd with Pd 2+ Mainly, maintain a moderate Rh level. 0 / Rh 3+ (Proportion); adjust the metal-support interaction strength; without heat treatment of the third intermediate, the CeZr solid solution is not fully formed, the element distribution is uneven, the interaction between the noble metal and the support is not optimized, and the surface active oxygen concentration is low. It cannot achieve the technical effect of "structural rearrangement-active site activation-surface oxygen enrichment". The low-temperature activity and overall catalytic efficiency of the catalyst are significantly lower than those of the heat-treated optimized sample.

[0138] (6) By comparing Comparative Example 1 with Comparative Example 7, and Example 1 with Comparative Example 7, it can be seen that the present invention can achieve the technical effect of synergistic improvement of low-temperature activity and high-temperature stability of catalyst through the synergistic effect of Fe doping and heat treatment. Specifically, Fe doping introduces oxygen vacancy defects and redox electron pairs (Fe0.05, Fe0.05, into the catalyst in advance. 3+ / Fe 4+This provides a structural basis for subsequent heat treatment; appropriate heat treatment further promotes the structural homogenization of the CeZr solid solution, enrichment of surface active oxygen, and reconstruction of noble metal valence states. However, without Fe doping and heat treatment (Comparative Example 7), the catalyst lacks both chemical pre-positioning of defect sites and thermal driving force for structural remodeling, resulting in poor uniformity of the CeZr solid solution, poor dispersion of noble metals, and low concentration of surface active oxygen, failing to achieve synergistic enhancement. When only heat treatment is performed without Fe doping (Comparative Example 6), although structural uniformity can be partially optimized, the lack of Fe-induced oxygen vacancies and redox electron pairs results in suboptimal activity. When only Fe doping is performed without heat treatment (Comparative Example 1), although Fe can enter the lattice to generate oxygen vacancies, the solid solution structural uniformity is insufficient, the noble metal valence states and dispersion are not optimized to the best, and surface active oxygen is not sufficiently enriched, resulting in significantly lower catalytic performance than in Example 1 with the synergistic effect of Fe doping and heat treatment. Therefore, the synergy between Fe doping and heat treatment is the core technical feature of this invention; both are indispensable and together achieve a leapfrog improvement in catalyst performance.

[0139] In summary, this invention, by employing an iron-doped CeZr solid solution, allows Fe to promote the generation of oxygen vacancy defects, significantly enhancing the oxygen migration ability of the catalyst. Simultaneously, Fe optimizes the valence state distribution and dispersion of the noble metal, making the active centers of the noble metal more efficient and stable. Fe doping also enhances the metal-support interaction, reducing CO and NO emissions. x The redox reaction with CH3OH is smoother. Without increasing the amount of precious metals, doping with the non-precious metal Fe significantly improves the low-temperature activity and overall catalytic efficiency of the catalyst, which has important application value in promoting the development of methanol as an alternative fuel in the transportation sector.

[0140] 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. An iron-modified three-way catalyst, characterized in that, The iron-modified three-way catalyst comprises a support, a first noble metal, an iron-doped cerium-zirconium solid solution, and a second noble metal. The first noble metal is loaded on a carrier; the iron-doped cerium-zirconium solid solution covers the surface of the carrier and the first noble metal, and the second noble metal is dispersed on the surface of the iron-doped cerium-zirconium solid solution. The first precious metal includes Pd and Pt; the second precious metal includes Rh.

2. The iron-modified three-way catalyst according to claim 1, characterized in that, The carrier includes aluminum oxide; And / or, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of Pd is 0.1 wt.%-1 wt.%; And / or, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of Pt is 0.1 wt.%-1 wt.%; And / or, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of the second noble metal is 0.1 wt.%-1 wt.%; And / or, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the mass fraction of the iron-doped cerium-zirconium solid solution is 40 wt.%-60 wt.%; And / or, based on a total mass fraction of 100 wt.% for the iron-modified three-way catalyst, the iron doping amount is 2 wt.%-6 wt.%.

3. The iron-modified three-way catalyst according to claim 2, characterized in that, Based on a total mass fraction of 100 wt.% for iron-modified three-way catalyst, the iron doping amount is 2 wt.%-3 wt.%.

4. A method for preparing an iron-modified three-way catalyst as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: A first intermediate is obtained by mixing a carrier and a first noble metal salt solution, followed by a first impregnation treatment and a first calcination. The first intermediate, cerium salt solution, zirconium salt solution and alkaline solution are mixed to obtain a mixed solution, which is then subjected to a co-precipitation reaction and a second calcination to obtain the second intermediate; The second intermediate, the second noble metal salt solution, and the iron salt solution are mixed, and then subjected to a second impregnation treatment and a third calcination to obtain the third intermediate; The third intermediate was heat-treated to obtain the iron-modified three-way catalyst.

5. The preparation method according to claim 4, characterized in that, The first noble metal salt solution includes a palladium salt solution and a platinum salt solution; And / or, the second noble metal salt solution includes a rhodium salt solution.

6. The preparation method according to claim 4 or 5, characterized in that, The total concentration of metal ions in the first noble metal salt solution is 2.5 mmol / L-11.5 mmol / L; And / or, the total concentration of cerium-zirconium ions in the mixed solution is 0.15 mol / L to 0.85 mol / L; And / or, the total concentration of metal ions in the second noble metal salt solution is 1 mmol / L-6 mmol / L; And / or, the concentration of the iron salt solution is 0.005 mol / L to 0.250 mol / L; And / or, the alkaline solution includes an aqueous ammonia solution and an ammonium carbonate solution.

7. The preparation method according to any one of claims 4-6, characterized in that, The first calcination temperature is 450℃-950℃; And / or, the second calcination temperature is 450℃-950℃; And / or, the temperature of the third calcination is 450℃-950℃; And / or, the third calcination time is 1h-24h.

8. The preparation method according to any one of claims 4-7, characterized in that, The heat treatment was carried out under conditions where the water vapor content was 5 vol.%-20 vol.%. And / or, the temperature of the heat treatment is 700℃-900℃; And / or, the heat treatment time is 5h-20h.

9. The preparation method according to any one of claims 4-8, characterized in that, The preparation method includes the following steps: (1) Mix the carrier and the first precious metal salt solution, perform the first impregnation treatment on a rotary evaporator, dry at 100℃-130℃ for 12h-24h, and then calcine at 500℃-600℃ for 1h-5h to obtain the first intermediate. (2) Mix the first intermediate, cerium salt solution and zirconium salt solution to obtain a mixed solution. Add alkali solution to the mixed solution to adjust the pH of the reaction system to 8-11. Stir the reaction at 300rpm-500rpm for 0.5h-1h, let it stand for 2h-24h to carry out co-precipitation reaction. Wash the obtained precipitate with deionized water until neutral, dry it at 100℃-130℃ for 12h-24h, and then calcine it at 500℃-600℃ for 1h-24h to obtain the second intermediate. (3) Mix the second intermediate, the second noble metal salt solution and the iron salt solution, perform a second impregnation treatment on a rotary evaporator, dry at 100℃-130℃ for 12h-24h, and then calcine at 500℃-600℃ for 1h-5h to obtain the third intermediate; (4) Under the condition that the water vapor content is 5 vol.%-20 vol.%, the third intermediate is heat-treated at 700℃-900℃ for 5h-20h to obtain the iron-modified three-way catalyst.

10. The use of an iron-modified three-way catalyst as described in any one of claims 1-3, characterized in that, The iron-modified three-way catalyst is used for treating methanol vehicle exhaust to degrade carbon monoxide, nitrogen oxides, and methanol.

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