A dual promoter Pd-Pt catalyst and a preparation method thereof
By loading Pd-Pt catalysts onto CeO2-La2O3-Al2O3 supports and combining the sol-gel method with the post-impregnation method, a uniformly distributed Pd-Pt catalyst was formed, which solved the problems of agglomeration and uneven distribution, improved catalytic activity and stability, reduced reaction temperature, and enhanced resistance to sulfur poisoning.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INFORMATION RES INST OF EMERGENCY MANAGEMENT DEPT
- Filing Date
- 2025-07-10
- Publication Date
- 2026-07-07
AI Technical Summary
Existing Pd-Pt catalysts are prone to agglomeration or uneven distribution during crushing and sieving, which leads to reduced activity and affects catalytic performance.
A three-dimensional cross-linked porous CeO2-La2O3-Al2O3 support was used to load Pd-Pt metal salts through a combination of sol-gel and post-impregnation methods, forming a uniformly distributed Pd-Pt catalyst. The promoters Ce and La improved the stability and sulfur poisoning resistance of the catalyst.
This study achieved high catalytic activity and stability of the Pd-Pt catalyst, reduced the reaction temperature of methane oxidation, improved catalytic efficiency, and enhanced resistance to sulfur poisoning.
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Figure CN120754845B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to a dual-promoter Pd-Pt catalyst and its preparation method. Background Technology
[0002] Methane is the world's largest emitter of non-carbon dioxide greenhouse gas. Methane emission reduction has become a key approach to achieving global warming control targets. Since the 21st century, anthropogenic methane emissions, particularly from the coal sector, have received significant attention. Ventilation gas (VAM), the largest source of methane emissions from coal mines, is difficult to utilize efficiently due to its characteristics of high flow rate, low concentration, wide fluctuation range, and numerous impurities. 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, lower emissions of carbon monoxide and nitrogen oxides, and higher combustion efficiency. In other words, catalytic oxidation of methane is 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 practical operating conditions, leading to a decrease in catalytic activity. To address this issue, researchers are currently conducting targeted studies from two main aspects.
[0004] On the one hand, by controlling the catalyst structure, the active component can be encapsulated in a support to construct 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, thus preventing poisoning, but also prevents the sintering of noble metals. Furthermore, by introducing a second metal or co-catalyst to form an alloy, or by enhancing the interactions between metals, more lattice oxygen can be released and migrated, thereby participating in the decomposition of carbon-hydrogen bonds, which ultimately promotes the enhancement of catalytic activity.
[0005] On the other hand, by regulating strong metal-support interactions (SMSI), unique structural and particle size changes in metal particles can be induced, anchoring active metals of specific particle sizes onto the support, thereby improving the stability and activity of the catalyst. Furthermore, the morphology and crystal structure of the catalyst support have a crucial impact on the dispersibility, stability, and overall catalytic performance of the active component. Therefore, regulating the structure and morphology of the support and the active component, as well as their strong interactions, is key to determining catalytic performance.
[0006] Existing catalysts undergo crushing and sieving during use. Loss of the catalyst's specific surface area directly affects the contact area and collision probability between the catalyst and reactant molecules. Under mechanical force, catalyst particles may break or agglomerate. This increases the surface area of some smaller catalyst particles, but also increases the contact area between particles, thus relatively reducing the overall specific surface area of the catalyst. During the crushing process, surface structures unfavorable to catalytic reactions, such as cracks or defects, may also form, potentially further reducing catalyst activity.
[0007] Therefore, it is necessary to select a suitable catalyst support to anchor 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, and molecular sieves.
[0008] In the conventional support used in existing Pd-Pt catalysts (such as powdered or granular supports), the active components (such as noble metal oxides) are prone to agglomeration or uneven distribution during the crushing and molding process, resulting in reduced exposure and thus weakened catalytic activity. Summary of the Invention
[0009] In view of this, the present invention provides a dual-catalyst Pd-Pt catalyst and its preparation method, in order to solve the problem that in the prior art, the active components (such as noble metal oxides) of Pd-Pt catalysts are prone to agglomeration or uneven distribution, resulting in reduced exposure and thus weakened catalytic activity.
[0010] To achieve the above-mentioned objective, a dual-catalyst Pd-Pt catalyst is provided, 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.
[0011] A method for preparing the dual-catalyst Pd-Pt catalyst according to the present invention includes the following steps:
[0012] S1. Disperse polyethylene oxide in an ethanol solution to obtain a polymer solution;
[0013] S2. Lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate are added to the polymer solution, stirred and dissolved, then propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain the precursor sol.
[0014] S3. The precursor sol is aged in a water bath at 40-45°C for 24-30 hours to obtain the carrier gel.
[0015] S4. Dry the carrier gel at 40-45℃ for 7-9 days, and calcine the dried carrier gel to obtain CeO2-La2O3-Al2O3 carrier.
[0016] S5. The CeO2-La2O3-Al2O3 support is placed in a Pd-Pt metal salt solution with a mass concentration of 1-2%, heated and stirred at 40-50℃ for 1-2 hours, dried at 110-120℃ for 2-4 hours, and then calcined in a muffle furnace to obtain the Pd-Pt / CeO2-La2O3-Al2O3 catalyst.
[0017] Preferably, the volume concentration of the ethanol solution in S1 is 48-52%.
[0018] Preferably, the mass ratio of the polyethylene oxide to the ethanol solution in S1 is 1:100-104.4.
[0019] 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.
[0020] Preferably, the calcination temperature in S4 is 800-850℃, and the calcination time is 2-3 hours.
[0021] Preferably, in step S5, the feeding ratio of CeO2-La2O3-Al2O3 support to Pd-Pt metal salt solution is 3g:20-25ml.
[0022] Preferably, the Pd-Pt metal salt solution in S5 is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2.
[0023] Preferably, the molar ratio of Pd ions to Pt ions in the Pd-Pt metal salt solution in S5 is 1~3:3~1.
[0024] Preferably, the roasting temperature in S5 is 550-600℃ and the time is 3-4h.
[0025] This invention incorporates two additives to enhance the activity and stability of the catalyst. These two additives work synergistically: Ce has excellent oxygen storage capacity, promoting oxygen adsorption and activation, while La stabilizes the structure of CeO2, preventing sintering. Simultaneously, CeO2 preferentially adsorbs SO2 to form sulfates, reducing sulfur poisoning of Pd and Pt active sites and improving resistance to sulfur poisoning. La reduces the irreversible adsorption of sulfur species.
[0026] Theoretically, a higher Pd-Pt loading results in better catalyst performance, but this significantly increases costs and reduces economic efficiency. Conversely, an excessively low loading may lead to insufficient active sites, preventing complete methane conversion and resulting in low catalytic efficiency. The optimal Pd-Pt loading range of this invention is 1–2%. Within this range, Pd-Pt exists as highly dispersed nanoparticles, maximizing the exposure of active sites. Simultaneously, it effectively matches the oxygen vacancies and anchoring sites provided by the promoter, preventing metal spillage or coverage of the promoter's active sites.
[0027] This invention proposes a three-dimensional cross-linked porous support design. This support maintains its mechanical strength without the need for additional binders, avoiding the reduction of active sites caused by binder blockage of pores. The porous structure (macropore-mesopore-micropore composite) ensures rapid diffusion of methane molecules to active sites (macropore channels) and provides abundant reaction interfaces (mesopore and micropore surfaces) through the synergistic effect of different pore sizes, thereby significantly improving catalytic efficiency. The preparation method combines the sol-gel method and the post-impregnation method, enabling more precise control of the formation of the hierarchical pore structure. The sol-gel method is mainly used to construct the Al2O3 framework network, and combined with the post-impregnation method to load PdO-PtO active components, it achieves uniform distribution of active components in the hierarchical pore structure while avoiding pore collapse caused by high-temperature calcination. The catalyst of this invention achieves T... 90 Only 328℃ is needed. This breakthrough is due to the effective protection of active sites by the porous structure (avoiding high-temperature sintering) and the enhanced activity at low temperatures.
[0028] Compared with the prior art, the beneficial effects of the present invention are that the three-dimensional cross-linked porous structure can provide better distribution space for the active component Pd-Pt, achieving uniform distribution, and at the same time provide a ladder distribution channel for methane molecules, which is more conducive to the catalytic reaction and improves catalytic efficiency.
[0029] The advantages of this invention involve the following principles:
[0030] This invention employs a one-step method to prepare a support with additives, which simplifies the process and shortens the preparation time, while also facilitating the construction of a three-dimensional cross-linked porous structure to improve the activity of the catalyst.
[0031] The three-dimensional cross-linked porous structure (or other characteristics) of the catalyst prepared by this invention improves the material's sulfur resistance. The complex pores facilitate sulfur expulsion, shorten sulfur residence time, and allow sulfur to more easily combine and react with solvent elements, rather than reacting with catalytic elements, thus enhancing the catalyst's sulfur resistance.
[0032] The catalyst of this invention incorporates two elemental promoters that complement each other. La stabilizes the structure of CeO2, preventing it from sintering. Simultaneously, CeO2 preferentially adsorbs SO2 to form sulfates, reducing the poisoning of Pd and Pt active sites by sulfur and improving its resistance to sulfur poisoning. Attached Figure Description
[0033] Figure 1 The image shows the XRD pattern of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1.
[0034] Figure 2 This is a bright-field TEM image of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1.
[0035] Figure 3 This is the energy dispersive spectral mapping (EDS) of aluminum (Al) in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1.
[0036] Figure 4 The energy spectrum distribution map of La element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 is shown.
[0037] Figure 5 The energy spectrum distribution map of Ce element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 is shown.
[0038] Figure 6 The energy spectrum distribution map of Pd element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 is shown.
[0039] Figure 7 The energy spectrum distribution map of Pt element in the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in Example 1 is shown.
[0040] Figure 8 The methane catalytic performance test diagram of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in this specific embodiment;
[0041] Figure 9 The sulfur resistance performance test diagram of the Pd-Pt / CeO2-La2O3-Al2O3 catalyst in this specific embodiment. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0043] The molecular weight of polyethylene oxide is 1,000,000.
[0044] Example 1
[0045] This embodiment provides a dual-catalyst 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.
[0046] A method for preparing the dual-catalyst Pd-Pt catalyst according to the present invention includes the following steps:
[0047] S1. Disperse polyethylene oxide in a 48% (v / v) ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:100.
[0048] S2. Lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate are added to the polymer solution and stirred until dissolved. Then, propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain a precursor sol. The mass ratio of polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, and propylene oxide is 1.0:0.3:0.5:53.5:38.9.
[0049] S3. The precursor sol was aged in a 40°C water bath for 30 hours to obtain the carrier gel.
[0050] S4. The carrier gel is dried at 40°C for 9 days, and the dried carrier gel is calcined at 800°C for 3 hours to obtain CeO2-La2O3-Al2O3 carrier.
[0051] S5. The CeO2-La2O3-Al2O3 support is added to a 1% Pd-Pt metal salt solution at a feeding ratio of 3g:20ml. The mixture is heated and stirred at 40℃ for 2h, dried at 110℃ for 4h, and then calcined in a muffle furnace at 550℃ for 4h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 1:3.
[0052] Example 2
[0053] This embodiment provides a dual-catalyst 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.
[0054] A method for preparing the dual-catalyst Pd-Pt catalyst according to the present invention includes the following steps:
[0055] S1. Disperse polyethylene oxide in a 50% ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:104.
[0056] S2. Lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate are added to the polymer solution and stirred until dissolved. Then, propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain a precursor sol. 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.
[0057] S3. The precursor sol was aged in a water bath at 43°C for 28 hours to obtain the carrier gel.
[0058] S4. The carrier gel is dried in a forced-air dryer at 43°C for 8 days, and the dried carrier gel is calcined at 830°C for 2.5 hours to obtain CeO2-La2O3-Al2O3 carrier.
[0059] S5. The CeO2-La2O3-Al2O3 support is added to a 1.5% Pd-Pt metal salt solution at a feeding ratio of 3g:23ml. The mixture is heated and stirred at 45℃ for 1.5h, dried at 115℃ for 3h, and then calcined in a muffle furnace at 580℃ for 3.5h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 1.5:2.
[0060] Example 3
[0061] This embodiment provides a dual-catalyst 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.
[0062] A method for preparing the dual-catalyst Pd-Pt catalyst according to the present invention includes the following steps:
[0063] S1. Disperse polyethylene oxide in a 52% ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:104.4.
[0064] S2. Lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate are added to the polymer solution and stirred until dissolved. Then, propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain a precursor sol. 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.
[0065] S3. The precursor sol was aged in a water bath at 45°C for 24 hours to obtain the carrier gel.
[0066] S4. The carrier gel is dried at 45°C for 7 days, and the dried carrier gel is calcined at 850°C for 2 hours to obtain CeO2-La2O3-Al2O3 carrier.
[0067] S5. The CeO2-La2O3-Al2O3 support is added to a 2% Pd-Pt metal salt solution at a feeding ratio of 3g:25ml. The mixture is heated and stirred at 50℃ for 1h, dried at 120℃ for 2h, and then calcined in a muffle furnace at 600℃ for 3h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 3:1.
[0068] Comparative Example 1
[0069] This comparative example provides a method for preparing a dual-auxiliary Pd-Pt catalyst using an impregnation method with supported additives, comprising the following steps:
[0070] S1. Disperse polyethylene oxide in a 48% (v / v) ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:100.
[0071] S2. Add aluminum chloride hexahydrate to the polymer solution, stir to dissolve, add propylene oxide, mix evenly and completely to obtain the precursor sol, the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:53.5:38.9;
[0072] S3. The precursor sol was aged in a 40°C water bath for 30 hours to obtain an Al2O3 carrier gel.
[0073] S4. The Al2O3 support gel was dried at 40℃ for 9 days, and then calcined at 800℃ for 3 hours to obtain the Al2O3 support. The water absorption rate of the Al2O3 support was tested. The test showed that 1g of Al2O3 support could absorb about 1ml of aqueous solution. An equal volume impregnation method was used (to ensure that lanthanum chloride and cerium nitrate hexahydrate could be completely adsorbed by the Al2O3 support). Lanthanum chloride and cerium nitrate hexahydrate were prepared into a mixed aqueous solution with a solute concentration of 1g:1ml. All Al2O3 support was placed in the 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 0.3:0.5:53.5. The mixture was impregnated at room temperature for 24 hours, dried at 120℃ for 2 hours, and then calcined in a muffle furnace at 800℃ for 3 hours to obtain the CeO2-La2O3 / Al2O3 support.
[0074] S5. The CeO2-La2O3 / Al2O3 support is added to a 1% Pd-Pt metal salt solution at a feeding ratio of 3g:20ml. The mixture is heated and stirred at 40℃ for 2h, dried at 110℃ for 4h, and then calcined in a muffle furnace at 550℃ for 4h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 1:3.
[0075] This comparative example is the same as Example 1, except that the additives in this comparative example are loaded using the impregnation method.
[0076] Comparative Example 2
[0077] This comparative example provides a method for preparing a dual-auxiliary Pd-Pt catalyst using an impregnation method with supported additives, comprising the following steps:
[0078] S1. Disperse polyethylene oxide in a 50% ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:104.
[0079] S2. Add aluminum chloride hexahydrate to the polymer solution, stir to dissolve, add propylene oxide, mix evenly and completely to obtain the precursor sol, the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:52.4:41;
[0080] S3. The precursor sol was aged in a water bath at 43°C for 28 hours to obtain the carrier gel.
[0081] S4. The carrier gel was dried at 43℃ for 8 days, and then calcined at 830℃ for 2.5h to obtain Al2O3 carrier. The water absorption rate of Al2O3 carrier was tested. The test showed that 1g of Al2O3 carrier could absorb about 1ml of aqueous solution. An equal volume impregnation method was used (to ensure that lanthanum chloride and cerium nitrate hexahydrate could be completely adsorbed by Al2O3 carrier). Lanthanum chloride and cerium nitrate hexahydrate were prepared into a mixed aqueous solution with a solute concentration of 1g:1ml. All Al2O3 carrier was placed in the 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 impregnated at room temperature for 24h, dried at 120℃ for 2h, and then calcined in a muffle furnace at 800℃ for 3h to obtain CeO2-La2O3 / Al2O3 carrier.
[0082] S5. The CeO2-La2O3 / Al2O3 support is added to a 1.5% Pd-Pt metal salt solution at a feeding ratio of 3g:23ml. The mixture is heated and stirred at 45℃ for 1.5h, dried at 115℃ for 3h, and then calcined in a muffle furnace at 580℃ for 3.5h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 1.5:2.
[0083] This comparative example is the same as Example 2, except that the additives in this comparative example are loaded using the impregnation method.
[0084] Comparative Example 3
[0085] This comparative example provides a method for preparing a dual-auxiliary Pd-Pt catalyst using an impregnation method with supported additives, comprising the following steps:
[0086] S1. Disperse polyethylene oxide in a 52% ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:104.4.
[0087] S2. Add aluminum chloride hexahydrate to the polymer solution, stir to dissolve, add propylene oxide, mix evenly and completely to obtain the precursor sol, the mass ratio of polyethylene oxide, aluminum chloride hexahydrate and propylene oxide is 1.0:50.2:40;
[0088] S3. The precursor sol was aged in a water bath at 45°C for 24 hours to obtain the carrier gel.
[0089] S4. The carrier gel was dried at 45℃ for 7 days, and then calcined at 850℃ for 2 hours to obtain Al2O3 carrier. The water absorption rate of Al2O3 carrier was tested. The test showed that 1g of Al2O3 carrier could absorb about 1ml of aqueous solution. An equal volume impregnation method was used (to ensure that lanthanum chloride and cerium nitrate hexahydrate could be completely adsorbed by Al2O3 carrier). Lanthanum chloride and cerium nitrate hexahydrate were prepared into a mixed aqueous solution with a solute concentration of 1g:1ml. All Al2O3 carriers were placed in the 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 impregnated at room temperature for 24 hours, dried at 120℃ for 2 hours, and then calcined in a muffle furnace at 800℃ for 3 hours to obtain CeO2-La2O3 / Al2O3 carrier.
[0090] S5. The CeO2-La2O3 / Al2O3 support is added to a 2% Pd-Pt metal salt solution at a feeding ratio of 3g:25ml. The mixture is heated and stirred at 50℃ for 1h, dried at 120℃ for 2h, and then calcined in a muffle furnace at 600℃ for 3h to obtain a Pd-Pt / CeO2-La2O3 / Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 3:1.
[0091] This comparative example is the same as Example 3, except that the additives in this comparative example are loaded using the impregnation method.
[0092] Comparative Example 4
[0093] This comparative example 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.
[0094] A method for preparing the dual-catalyst Pd-Pt catalyst according to the present invention includes the following steps:
[0095] S1. Disperse polyethylene oxide in a 48% (v / v) ethanol solution to obtain a polymer solution, wherein the mass ratio of polyethylene oxide to ethanol solution is 1:105.
[0096] S2. Lanthanum chloride, cerium nitrate hexahydrate, and aluminum chloride hexahydrate are added to the polymer solution and stirred until dissolved. Then, propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain a precursor sol. 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.
[0097] S3. The precursor sol was aged in a water bath at 48°C for 32 hours to obtain the carrier gel.
[0098] S4. The carrier gel is dried at 48°C for 11 days, and the dried carrier gel is calcined at 860°C for 4 hours to obtain CeO2-La2O3-Al2O3 carrier.
[0099] S5. The CeO2-La2O3-Al2O3 support is added to a 1% Pd-Pt metal salt solution at a feeding ratio of 3g:20ml. The mixture is heated and stirred at 40℃ for 2h, dried at 110℃ for 4h, and then calcined in a muffle furnace at 550℃ for 4h to obtain a Pd-Pt / CeO2-La2O3-Al2O3 catalyst. The Pd-Pt metal salt solution is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2, and the molar ratio of Pd ions to Pt ions in the mixture is 1:3.
[0100] This comparative example is the same as Example 1, except that the loading of the additives in this comparative example is too high.
[0101] The Pd-Pt / CeO2-La2O3-Al2O3 catalyst from Example 1 was subjected to XRD testing, and the test results are as follows: Figure 1 As can be seen, CeO2 (PDF#34-0394) exhibits distinct characteristic peaks at 28.5°, 33.0°, 47.4°, 56.3°, 76.6°, 79.0°, and 88.4°, while Al2O3 (PDF#04-0880) shows characteristic peaks at 37.4°, 42.8°, and 67.3°. La, Pd, and Pt, due to their lower loading levels and high dispersion, did not show any obvious characteristic peaks.
[0102] The Pd-Pt / CeO2-La2O3-Al2O3 catalyst from Example 1 was subjected to morphology and energy dispersive spectroscopy analysis using a JEOL JEM-F200 transmission electron microscope. Figure 2 These are the results of TEM bright-field image testing. Figure 3 This is an energy spectrum distribution mapping (EDS Mapping) of aluminum (Al). Figure 4 This is a map showing the energy spectrum distribution of the La element. Figure 5 This is a map showing the energy spectrum distribution of Ce. Figure 6 This is a map showing the energy spectrum distribution of Pd. Figure 7 This is the energy spectrum distribution map of Pt. It can be seen that the main constituent elements of the catalyst are evenly distributed.
[0103] The Pd-Pt / CeO2-La2O3 / Al2O3 catalysts from Examples 1-3 and Comparative Examples 1-4 were used to test the methane catalytic performance and sulfur resistance. The results of the methane catalytic performance tests are as follows: Figure 8 The results of the sulfur resistance test are as follows: Figure 9 The fixed-bed experimental setup wfcg-6088 was used.
[0104] from Figure 8 It can be seen that at 0.1% CH4 + air, 12000h -1 Under the reaction conditions described, the methane conversion rates of catalysts in Comparative Examples 1, 2, 3, and 4 were lower than those in Examples 1, 2, and 3, with catalyst 1 showing better performance. 90 The temperature is 328℃.
[0105] from Figure 9 It can be seen that at 0.1% CH4 + 25ppm SO2 + air, 12000h -1 Under the reaction conditions specified, the methane conversion rates of catalysts in Comparative Examples 1, 2, 3, and 4 were lower than those in the Example. The methane catalyst in the Example exhibited better performance under sulfur-containing conditions. 90 The temperature is 346℃.
[0106] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A dual-catalyst Pd-Pt catalyst, characterized in that, Its raw materials include polyethylene oxide, lanthanum chloride, cerium nitrate hexahydrate, aluminum chloride hexahydrate, propylene oxide, ethanol solution, and Pd-Pt metal salt, wherein the mass ratio of 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; The preparation method of the dual-promoter Pd-Pt catalyst includes the following steps: S1. Disperse polyethylene oxide in an ethanol solution to obtain a polymer solution; S2. Lanthanum chloride, cerium nitrate hexahydrate and aluminum chloride hexahydrate are added to the polymer solution, stirred and dissolved, then propylene oxide is added, and the mixture is mixed evenly and completely dissolved to obtain the precursor sol. S3. The precursor sol is aged in a water bath at 40-45°C for 24-30 hours to obtain the carrier gel. S4. The carrier gel is dried in a forced-air dryer at 40-45℃ for 7-9 days. The dried carrier gel is then calcined at 800-850℃ for 2-3 hours to obtain CeO2-La2O3-Al2O3 carrier. S5. The CeO2-La2O3-Al2O3 support is placed in a Pd-Pt metal salt solution with a mass concentration of 1-2%, heated and stirred at 40-50℃ for 1-2 hours, dried at 110-120℃ for 2-4 hours, and then calcined in a muffle furnace to obtain the Pd-Pt / CeO2-La2O3-Al2O3 catalyst.
2. The dual-auxiliary Pd-Pt catalyst according to claim 1, characterized in that, The volume concentration of the ethanol solution described in S1 is 48-52%.
3. The dual-auxiliary Pd-Pt catalyst according to claim 2, characterized in that, The mass ratio of the polyethylene oxide to the ethanol solution in S1 is 1:100-104.
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4. The dual-auxiliary Pd-Pt catalyst according to claim 1, characterized in that, In S5, the feeding ratio of CeO2-La2O3-Al2O3 support to Pd-Pt metal salt solution is 3g:20-25ml.
5. The dual-auxiliary Pd-Pt catalyst according to claim 1, characterized in that, The Pd-Pt metal salt solution mentioned in S5 is a mixture of Pd(NO3)2·2H2O and Pt(NH3)4(NO3)2.
6. The dual-auxiliary Pd-Pt catalyst according to claim 1, characterized in that, The molar ratio of Pd ions to Pt ions in the Pd-Pt metal salt solution described in S5 is 1~3:3~1.
7. The dual-auxiliary Pd-Pt catalyst according to claim 1, characterized in that, The roasting temperature described in S5 is 550-600℃, and the time is 3-4 hours.