Dual-aid Pd-Pt catalyst and preparation method thereof

Abstract

The invention provides a dual-assistant Pd-Pt catalyst and a preparation method thereof, and belongs to the technical field of catalysts. The raw materials of the catalyst comprise polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, Pd-Pt metal salt and the like, and the preparation method of the catalyst comprises the following steps: dispersing polyethylene oxide in an ethanol solution to obtain a high-molecular polymer solution; the preparation method comprises the following steps: adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate into a high-molecular polymer solution, dissolving, adding epoxypropane, and dissolving to obtain precursor sol; carrying out aging, drying and calcining on the mixture to obtain a CeO2-La2O3-Al2O3 carrier; the carrier is put into a Pd-Pt metal salt solution to be soaked, and after drying and roasting, the Pd-Pt / CeO2-La2O3-Al2O3 catalyst is obtained. The catalyst is high in catalytic activity and high in sulfur resistance in the catalytic process.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and particularly relates to a double-auxiliary Pd-Pt catalyst and a preparation method thereof. Background Art

[0002] Methane is the largest non-CO2 greenhouse gas emitted globally. Reducing methane emissions has become a key approach to achieving temperature control targets. Since the 21st century, anthropogenic methane emissions from the energy sector, particularly the coal sector, have attracted considerable attention. As the largest source of methane emissions from coal mines, ventilation air methane (VAM) is difficult to efficiently utilize due to its high flow rate, low concentration, wide fluctuation range, and numerous impurity components. Currently, thermal oxidation and catalytic oxidation technologies are commonly used to reduce VAM emissions from coal mines. Compared to thermal oxidation, catalytic oxidation of methane offers advantages such as lower reaction temperatures, reduced carbon monoxide and nitrogen oxide emissions, and higher combustion efficiency. This makes catalytic oxidation of methane a more effective method for controlling methane emissions.

[0003] In recent years, palladium-based catalysts have been widely used in the catalytic oxidation of methane due to their excellent low-temperature activity. However, palladium species are prone to sintering at high temperatures and are poisoned by water vapor or sulfur dioxide under actual operating conditions, resulting in a decrease in catalytic activity. To address this issue, researchers are currently conducting targeted research in two areas.

[0004] On the one hand, by manipulating the catalyst structure, the active component can be encapsulated in a support to create a core-shell catalyst. The protective effect of the shell not only prevents water vapor or sulfur dioxide from entering and reacting with the active component, leading to poisoning, but also prevents sintering of the precious metal. Furthermore, by introducing a second metal or co-catalyst to form an alloy, or by enhancing interactions between metals, the release and migration of more lattice oxygen can be promoted, thereby participating in the decomposition of carbon-hydrogen bonds, ultimately promoting enhanced catalytic activity.

[0005] On the other hand, by manipulating the strong metal-support interaction (SMSI), unique structural and size changes in the metal particles are triggered, anchoring the active metal of a specific particle size to the support, thereby improving the stability and activity of the catalyst. Furthermore, the morphology and crystal structure of the catalyst support have a crucial influence on the dispersion and stability of the catalytically active components, as well as the overall catalytic performance of the catalyst. Therefore, regulating the structure, morphology, and strong interaction between the support and the active components is key to determining catalytic performance.

[0006] Catalysts in the prior art are crushed and screened during use. If the specific surface area of ​​the catalyst is lost, it will directly affect the contact area and collision probability between the catalyst and the reaction molecules. Under the action of mechanical force, the catalyst particles may be broken or agglomerated. This will cause the surface area of ​​some small-sized catalysts to increase, but it will also increase the contact area between the catalyst particles, thereby reducing the specific surface area of ​​the catalyst as a whole. During the crushing process, some surface structures that are not conducive to the catalytic reaction, such as cracks or defects, may also be formed. These structures may further reduce the activity of the catalyst.

[0007] Therefore, it is necessary to select a suitable catalyst support to anchor the palladium or platinum species and provide a favorable reaction environment for the catalytic oxidation of methane. Commonly used methane catalyst supports include Al2O3, SiO2, Co3O4, molecular sieves, etc.

[0008] During the crushing and molding process of traditional catalyst carriers (such as powdered or granular carriers) used in Pd-Pt catalysts in the prior art, active components (such as precious metal oxides) are prone to agglomeration or uneven distribution, resulting in reduced exposure and thus weakening the catalytic activity. Summary of the Invention

[0009] In view of this, the present invention provides a dual-additive Pd-Pt catalyst and a preparation method thereof to solve the problem in the prior art that the active components of the Pd-Pt catalyst (such as precious metal oxides) are prone to agglomeration or uneven distribution, resulting in reduced exposure and thus weakening the catalytic activity.

[0010] To achieve the above-mentioned purpose of the invention, a dual-additive Pd-Pt catalyst is provided, whose raw materials include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, ethanol solution and Pd-Pt metal salt.

[0011] A method for preparing the dual-adjuvant Pd-Pt catalyst of the present invention comprises the following steps: S1, dispersing polyethylene oxide in an ethanol solution to obtain a high molecular polymer solution; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate to the polymer solution, stirring to dissolve, adding propylene oxide, mixing evenly and completely dissolving to obtain a precursor sol; S3, aging the precursor sol in a water bath at 40-45° C. for 24-30 hours to obtain a carrier gel; S4, drying the carrier gel at 40-45° C. for 7-9 days, and calcining the dried carrier gel to obtain a CeO2-La2O3-Al2O3 carrier; S5, put the CeO2-La2O3-Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1-2%, heat and stir at 40-50℃ for 1-2h, dry at 110-120℃ for 2-4h, and then calcine in a muffle furnace to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst.

[0012] Preferably, the volume concentration of the ethanol solution in S1 is 48-52%.

[0013] Preferably, the mass ratio of the polyethylene oxide to the ethanol solution in S1 is 1:100-104.4.

[0014] Preferably, the mass ratio of the polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, and propylene oxide is 1.0:0.3-1.9:0.5-3.4:50.2-53.5:38.9-41.

[0015] Preferably, the calcining temperature in S4 is 800-850℃, and the calcining time is 2-3h.

[0016] Preferably, the feeding ratio in the process of putting the CeO2-La2O3-Al2O3 carrier into the Pd-Pt metal salt solution in S5 is 3g:20-25ml.

[0017] Preferably, the Pd-Pt metal salt solution in S5 is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2.

[0018] Preferably, the molar ratio of Pd ions to Pt ions in the Pd-Pt metal salt solution in S5 is 1~3:3~1.

[0019] Preferably, the calcining temperature in S5 is 550-600℃, and the time is 3-4h.

[0020] The two additives are added to improve the activity and stability of the catalyst, and the two additives complement each other. Ce has excellent oxygen storage capacity, promotes the adsorption and activation of oxygen, La stabilizes the structure of CeO2 and prevents sintering. At the same time, CeO2 can preferentially adsorb SO2 to form sulfates, reduce the poisoning of sulfur to the active sites of Pd and Pt, and improve the sulfur poisoning resistance. La reduces the irreversible adsorption of sulfur species.

[0021] Theoretically, a higher Pd-Pt loading improves the catalyst's effectiveness, but this also significantly increases costs and reduces economic efficiency. A loading that is too low can also result in insufficient active sites, insufficient methane conversion, and low catalytic efficiency. The optimal Pd-Pt loading range of the present invention is 1-2%. Within this range, Pd-Pt can exist as highly dispersed nanoparticles, maximizing exposure to active sites while also effectively matching the oxygen vacancies and anchoring sites provided by the additive, preventing metal overflow or coverage of the additive's active sites.

[0022] The present invention proposes a three-dimensional cross-linked porous carrier design. This carrier can maintain mechanical strength without the need for additional binders, avoiding the reduction of active sites caused by the clogging of the pores by binders. The porous structure (macropore-mesopore-micropore composite) ensures the rapid diffusion of methane molecules to the active sites (macropore channels) through the synergistic effect of different pore sizes, and provides a rich reaction interface (mesopore and micropore surfaces), thereby significantly improving the catalytic efficiency. The preparation method combines the sol-gel method with the post-impregnation method, which can more accurately control the formation of the hierarchical pore structure. The sol-gel method is mainly used to construct the skeleton network of Al2O3, combined with the post-impregnation method to load the PdO-PtO active components, to achieve a uniform distribution of the active components in the hierarchical pore structure, while avoiding the collapse of the pores caused by high-temperature calcination. The catalyst of the present invention reaches T 90 Only 328°C is required. This breakthrough is due to the effective protection of active sites by the porous structure (avoiding high-temperature sintering) and the enhancement of low-temperature activity.

[0023] Compared with the prior art, the beneficial effect of the present invention is that the three-dimensional cross-linked porous structure can provide better distribution space for the active components Pd-Pt to achieve uniform distribution, while providing a stepped distribution channel for methane molecules, which is more conducive to the catalytic reaction and improves the catalytic efficiency.

[0024] The advantages of the present invention involve the following principles: The present invention adopts a one-step method to prepare the carrier with auxiliary agents, which, on the one hand, simplifies the process and shortens the preparation time, and on the other hand, is conducive to constructing a three-dimensional cross-linked porous special structure and improving the activity of the catalyst.

[0025] The catalyst prepared by this invention exhibits a three-dimensional, cross-linked, porous structure (or other properties) that enhances the material's sulfur resistance. The complex pores facilitate sulfur expulsion, shortening its residence time. Sulfur more readily reacts with solvent elements, preventing it from reacting with catalytic elements, thereby enhancing the catalyst's sulfur resistance.

[0026] The catalyst of the present invention contains two elemental additives, which complement each other. La stabilizes the structure of CeO2 and prevents it from sintering. CeO2 also preferentially adsorbs SO2 to form sulfate, reducing sulfur poisoning on the active sites of Pd and Pt and improving resistance to sulfur poisoning. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the XRD test pattern of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 2 This is a TEM bright field image test image of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 3 This is the energy spectrum distribution mapping (EDS Mapping) of aluminum element (Al) of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 4 This is the energy spectrum distribution map of the La element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 5 This is the energy spectrum distribution map of the Ce element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 6 This is the energy spectrum distribution map of the Pd element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 7 This is the energy spectrum distribution map of the Pt element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1; Figure 8 A graph showing the methane catalytic performance test of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in this embodiment; Figure 9 Figure 2 is a test chart of the sulfur resistance performance of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in this specific embodiment. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The molecular weight of polyethylene oxide is 1,000,000.

[0030] Example 1 The embodiment provides a double-assistant Pd-Pt catalyst, raw materials of which include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, an ethanol solution and a Pd-Pt metal salt.

[0031] A preparation method of the double-assistant Pd-Pt catalyst is provided, and the method comprises the following steps: S1, dispersing polyethylene oxide in an ethanol solution with a volume concentration of 48% to obtain a high-molecular polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:100; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate into the high-molecular polymer solution, stirring and dissolving, then adding propylene oxide, uniformly mixing and completely dissolving to obtain a precursor sol, wherein the mass ratio of the polyethylene oxide, the lanthanum chloride, the cerium nitrate hexahydrate, the aluminum chloride hexahydrate and the propylene oxide is 1.0:0.3:0.5:53.5:38.9; S3, aging the precursor sol in a 40 DEG C water bath for 30h to obtain a carrier gel; S4, drying the carrier gel in a blast dryer at 40 DEG C for 9 days, calcining the dried carrier gel at 800 DEG C for 3h to obtain a CeO2-La2O3-Al2O3 carrier; S5, putting the CeO2-La2O3-Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1% according to a feeding ratio of 3g:20ml, heating and stirring at 40 DEG C for 2h, drying at 110 DEG C for 4h, then placing in a muffle furnace and calcining at 550 DEG C for 4h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst, wherein the Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2.2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 1:3.

[0032] Embodiment 2 The embodiment provides a double-assistant Pd-Pt catalyst, raw materials of which include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, an ethanol solution and a Pd-Pt metal salt.

[0033] A preparation method of the double-assistant Pd-Pt catalyst is provided, and the method comprises the following steps: S1, dispersing polyethylene oxide in an ethanol solution with a volume concentration of 48% to obtain a high-molecular polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:100; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate to the polymer solution, stirring and dissolving, adding propylene oxide, mixing and dissolving completely to obtain a precursor sol, wherein the mass ratio of polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate and propylene oxide is 1.0:0.8:1.5:52.4:41; S3, aging the precursor sol in a water bath at 43° C. for 28 h to obtain a carrier gel; S4, drying the carrier gel at 43° C. for 8 days, and calcining the dried carrier gel at 830° C. for 2.5 hours to obtain a CeO2-La2O3-Al2O3 carrier; S5. Place the CeO2-La2O3-Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1.5% in a feed ratio of 3g:23ml, heat and stir at 45°C for 1.5h, dry at 115°C for 3h, and then place in a muffle furnace and calcine at 580°C for 3.5h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 1.5:2.

[0034] Example 3 This embodiment provides a dual-promoter Pd-Pt catalyst, the raw materials of which include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, ethanol solution and Pd-Pt metal salt.

[0035] A method for preparing the dual-adjuvant Pd-Pt catalyst of the present invention comprises the following steps: S1. Dispersing polyethylene oxide in a 52% volume concentration ethanol solution to obtain a polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:104.4; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate to the polymer solution, stirring and dissolving, adding propylene oxide, mixing and dissolving completely to obtain a precursor sol, wherein the mass ratio of polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate and propylene oxide is 1.0:1.9:3.4:50.2:40; S3, aging the precursor sol in a water bath at 45° C. for 24 h to obtain a carrier gel; S4, drying the carrier gel at 45° C. for 7 days, and calcining the dried carrier gel at 850° C. for 2 hours to obtain a CeO2-La2O3-Al2O3 carrier; S5, the CeO2-La2O3-Al2O3 carrier is put into a 2% Pd-Pt metal salt solution according to the ratio of 3g:25ml, heated and stirred at 50°C for 1h, dried at 120°C for 2h, and then placed in a muffle furnace and calcined at 600°C for 3h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 3:1.

[0036] Comparative Example 1 The present comparative example provides a preparation method for preparing a double-adjuvant Pd-Pt catalyst by loading adjuvants using an impregnation method, comprising the following steps: S1, polyethylene oxide is dispersed in an ethanol solution with a volume concentration of 48% to obtain a high polymer solution, and the mass ratio of polyethylene oxide to ethanol solution is 1:100; S2, aluminum chloride hexahydrate is added to the high polymer solution, stirred and dissolved, then propylene oxide is added, mixed uniformly and completely dissolved to obtain a precursor sol, and the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:53.5:38.9; S3, the precursor sol is aged in a 40°C water bath for 30h to obtain an Al2O3 carrier gel; S4, the Al2O3 carrier gel is dried at 40°C for 9 days, and the dried carrier gel is calcined at 800°C for 3h to obtain an Al2O3 carrier. The water absorption rate of the Al2O3 carrier is tested, and the test shows that 1g of Al2O3 carrier can absorb about 1ml of aqueous solution. An equal volume impregnation method is used (to ensure that lanthanum chloride and cerium nitrate hexahydrate can be completely absorbed by the Al2O3 carrier), and lanthanum chloride and cerium nitrate hexahydrate are prepared into a mixed aqueous solution with a solute concentration. The ratio of Al2O3 carrier to mixed aqueous solution is 1g:1ml. All the Al2O3 carriers are placed in the lanthanum chloride and cerium nitrate hexahydrate mixed aqueous solution, wherein the mass ratio of lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate in S3 is 0.3:0.5:53.5. The impregnation is carried out at room temperature for 24h, dried at 120°C for 2h, and then calcined at 800°C in a muffle furnace for 3h to obtain a CeO2-La2O3 / Al2O3 carrier. S5. Place the CeO2-La2O3 / Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1% in a feed ratio of 3g:20ml, heat and stir at 40°C for 2h, dry at 110°C for 4h, and then place in a muffle furnace and calcine at 550°C for 4h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 1:3.

[0037] This comparative example is the same as Example 1, except that in this comparative example, the auxiliary agent is loaded by an impregnation method.

[0038] Comparative Example 2 This comparative example provides a preparation method for a dual-additive Pd-Pt catalyst using an impregnation method to load an additive, comprising the following steps: S1, dispersing polyethylene oxide in a 50% volume concentration ethanol solution to obtain a polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:104; S2. Add aluminum chloride hexahydrate to the polymer solution, stir and dissolve, then add propylene oxide, mix well and completely dissolve to obtain a precursor sol, wherein the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:52.4:41; S3, aging the precursor sol in a water bath at 43° C. for 28 h to obtain a carrier gel; S4, the carrier gel was dried at 43 ° C for 8 days, and the dried carrier gel was calcined at 830 ° C for 2.5 h to obtain an Al2O3 carrier. The water absorption rate of the Al2O3 carrier was tested. The test showed that 1g of the Al2O3 carrier could absorb about 1ml of the aqueous solution. The equal volume impregnation method was adopted (to ensure that lanthanum chloride and cerium nitrate hexahydrate could be completely adsorbed by the Al2O3 carrier). Lanthanum chloride and cerium nitrate hexahydrate were prepared into a mixed aqueous solution with a solute concentration of 1g:1ml. All the Al2O3 carriers were placed in a mixed aqueous solution of lanthanum chloride and cerium nitrate hexahydrate, wherein the mass ratio of lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate in S3 was 0.8:1.5:52.4. The mixture was immersed at room temperature for 24h, dried at 120 ° C for 2h, and then calcined in a muffle furnace at 800 ° C for 3h to obtain a CeO2-La2O3 / Al2O3 carrier. S5. Place the CeO2-La2O3 / Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1.5% in a feed ratio of 3g:23ml, heat and stir at 45°C for 1.5h, dry at 115°C for 3h, and then place in a muffle furnace and calcine at 580°C for 3.5h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 1.5:2.

[0039] This comparative example is the same as Example 2, except that in this comparative example, the auxiliary agent is loaded by an impregnation method.

[0040] Comparative Example 3 This comparative example provides a preparation method for a dual-additive Pd-Pt catalyst using an impregnation method to load an additive, comprising the following steps: S1. Dispersing polyethylene oxide in a 52% volume concentration ethanol solution to obtain a polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:104.4; S2, adding aluminum chloride hexahydrate to the polymer solution, stirring and dissolving, adding propylene oxide, mixing evenly and completely dissolving to obtain a precursor sol, wherein the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:50.2:40; S3, aging the precursor sol in a water bath at 45° C. for 24 h to obtain a carrier gel; S4, the carrier gel was dried at 45 ° C for 7 days, and the dried carrier gel was calcined at 850 ° C for 2 hours to obtain an Al2O3 carrier, and the water absorption rate of the Al2O3 carrier was tested. The test showed that 1g of the Al2O3 carrier could absorb about 1ml of the aqueous solution. The equal volume impregnation method was adopted (to ensure that lanthanum chloride and cerium nitrate hexahydrate could be completely adsorbed by the Al2O3 carrier), and lanthanum chloride and cerium nitrate hexahydrate were prepared into a mixed aqueous solution with a solute concentration of 1g:1ml. All the Al2O3 carriers were placed in a mixed aqueous solution of lanthanum chloride and cerium nitrate hexahydrate, wherein the mass ratio of lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate in S3 was 1.9:3.4:50.2. The mixture was immersed at room temperature for 24 hours, dried at 120 ° C for 2 hours, and then calcined in a muffle furnace at 800 ° C for 3 hours to obtain a CeO2-La2O3 / Al2O3 carrier; S5. Place the CeO2-La2O3 / Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 2% in a feed ratio of 3g:25ml, heat and stir at 50°C for 1h, dry at 120°C for 2h, and then place in a muffle furnace and calcine at 600°C for 3h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 3:1.

[0041] This comparative example is the same as Example 3, except that in this comparative example, the auxiliary agent is loaded by an impregnation method.

[0042] Comparative Example 4 This comparative example provides a dual-additive Pd-Pt catalyst, the raw materials of which include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, ethanol solution and Pd-Pt metal salt.

[0043] A method for preparing the dual-adjuvant Pd-Pt catalyst of the present invention comprises the following steps: S1. Dispersing polyethylene oxide in a 48% volume concentration ethanol solution to obtain a polymer solution, wherein the mass ratio of the polyethylene oxide to the ethanol solution is 1:105; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate to the polymer solution, stirring and dissolving, adding propylene oxide, mixing and dissolving completely to obtain a precursor sol, wherein the mass ratio of polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate and propylene oxide is 1.0:3.0:5.3:48.1:42; S3, aging the precursor sol in a water bath at 48° C. for 32 h to obtain a carrier gel; S4, drying the carrier gel at 48° C. for 11 days, and calcining the dried carrier gel at 860° C. for 4 hours to obtain a CeO2-La2O3-Al2O3 carrier; S5. Place the CeO2-La2O3-Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1% in a feed ratio of 3g:20ml, heat and stir at 40°C for 2h, dry at 110°C for 4h, and then place in a muffle furnace and calcine at 550°C for 4h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixed solution is 1:3.

[0044] This comparative example is the same as Example 1, except that in this comparative example, the loading amount of the auxiliary agent is too much.

[0045] Take the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 and perform XRD test. The test results are as follows: Figure 1 It can be seen that the characteristic peaks of CeO2 (PDF#34-0394) are obvious, appearing at 28.5°, 33.0°, 47.4°, 56.3°, 76.6°, 79.0°, and 88.4°, while the characteristic peaks of Al2O3 (PDF#04-0880) appear at 37.4°, 42.8°, and 67.3°. Due to the low loading and high dispersion of La, Pd, and Pt, no obvious characteristic peaks were detected.

[0046] The Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 was tested for morphology and energy spectrum using a transmission electron microscope JEOL JEM-F200. Figure 2 This is the TEM bright field image test result. Figure 3 This is the energy spectrum distribution mapping (EDS Mapping) of aluminum element (Al). Figure 4 is the energy spectrum distribution map of La element, Figure 5 is the energy spectrum distribution map of Ce element, Figure 6 is the energy spectrum distribution map of Pd element, Figure 7 This is the energy spectrum distribution map of the Pt element. It can be seen that the main components of the catalyst are evenly distributed.

[0047] The Pd-Pt / CeO2-La2O3 / Al2O3 catalysts in Examples 1-3 and Comparative Examples 1-4 were tested for methane catalytic performance and sulfur resistance. The results of the methane catalytic performance test are shown in Figure 2. Figure 8 ; Anti-sulfur performance test results are as follows Figure 9 , using the fixed bed experimental device wfcg-6088.

[0048] from Figure 8 It can be seen that in 0.1% CH4 + air, 12000h -1 Under the reaction conditions, the methane conversion rates of the catalysts in Comparative Examples 1, 2, 3 and 4 are lower than those in Examples 1, 2 and 3, among which the catalyst in Example 1 has better performance. 90 It is 328℃.

[0049] from Figure 9 It can be seen that in 0.1% CH4+25ppmSO2+air, ​​12000h -1 Under the reaction conditions, the methane conversion rates of the catalysts of Comparative Examples 1, 2, 3, and 4 are lower than those of the embodiment, among which the methane catalyst performance of the embodiment under sulfur-containing conditions is better, T 90 It is 346℃.

[0050] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A dual-promoter Pd-Pt catalyst, characterized in that: The raw materials include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, ethanol solution and Pd-Pt metal salt.

2. A method for preparing the dual-adjuvant Pd-Pt catalyst according to claim 1, characterized in that: The following steps are involved: S1, dispersing polyethylene oxide in an ethanol solution to obtain a high molecular polymer solution; S2, adding lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate to the polymer solution, stirring to dissolve, adding propylene oxide, mixing evenly and completely dissolving to obtain a precursor sol; S3, aging the precursor sol in a water bath at 40-45° C. for 24-30 hours to obtain a carrier gel; S4, drying the carrier gel at 40-45° C. for 7-9 days, and calcining the dried carrier gel to obtain a CeO2-La2O3-Al2O3 carrier; S5. Place the CeO2-La2O3-Al2O3 carrier into a Pd-Pt metal salt solution with a mass concentration of 1-2%, heat and stir at 40-50°C for 1-2h, dry at 110-120°C for 2-4h, and then calcine in a muffle furnace to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst.

3. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, wherein: The volume concentration of the ethanol solution in S1 is 48-52%.

4. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 3, wherein: The mass ratio of the polyethylene oxide to the ethanol solution in S1 is 1:100-104.

4.

5. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, wherein: The mass ratio of the polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate and propylene oxide is 1.0:0.3-1.9:0.5-3.4:50.2-53.5:38.9-41.

6. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, characterized in that: The calcination temperature in S4 is 800-850° C., and the calcination time is 2-3 hours.

7. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, characterized in that: In S5, the feeding ratio of the CeO2-La2O3-Al2O3 carrier into the Pd-Pt metal salt solution is 3g:20-25ml.

8. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, wherein: The Pd-Pt metal salt solution in S5 is a mixed solution of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2.

9. The method for preparing a dual-adjuvant Pd-Pt catalyst according to claim 2, wherein: The molar ratio of Pd ions to Pt ions in the Pd-Pt metal salt solution in S5 is 1-3:3-1.

10. The method for preparing a dual-additive Pd-Pt catalyst according to claim 2, characterized in that: The calcination temperature in S5 is 550-600° C. and the calcination time is 3-4 hours.

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