Anti-aging high-activity CO oxidation catalyst and preparation method thereof

Abstract

The invention discloses an anti-aging high-activity CO oxidation catalyst and a preparation method thereof, and relates to the technical field of catalysts. According to the technical scheme, the catalyst comprises the following components in percentage by mass: 0.1-2% of an iridium ruthenium alloy active component, 80-90% of a tantalum-doped zirconium oxide carrier and 10-20% of a compound additive, the composite additive is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is (1-3): 1. The CO conversion rate and the sulfur poisoning resistance of the catalyst are remarkably improved by optimizing the active components, the carrier and the auxiliary agent system and combining an innovative preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to an anti-aging highly active CO oxidation catalyst and a preparation method thereof. Background Art

[0002] As a key link in iron and steel production, the flue gas generated during the iron and steel sintering process contains a large amount of harmful gases such as carbon monoxide (CO) and sulfur dioxide (SO2). These gases not only cause serious environmental pollution but also pose a threat to human health. To effectively purify these harmful gases, traditional CO oxidation catalysts with noble metals such as platinum (Pt) and palladium (Pd) as the core are mostly used.

[0003] However, the traditional Pt / Pd noble metal catalyst system has many problems in practical applications. First, noble metals such as Pt and Pd are expensive, resulting in high catalyst costs and increasing the production costs of iron and steel enterprises. Second, these catalysts are relatively sensitive to sulfur poisoning and are prone to deactivation in a sulfur-containing environment, reducing the catalytic efficiency and service life. Moreover, insufficient high-temperature stability is also a major drawback. In a high-temperature sintering environment, the catalyst is prone to structural changes or sintering, further affecting the catalytic performance.

[0004] In addition to the above problems, the carrier and promoter systems of conventional catalysts also have limitations in the regulation ability of oxygen vacancies. Oxygen vacancies are an important part of the surface active sites of the catalyst and play a crucial role in the adsorption and activation of CO. Due to the limited regulation ability of the carrier and promoter systems on oxygen vacancies, the catalytic activity of the catalyst is insufficient, making it difficult to meet the requirements of efficient purification.

[0005] In view of the above problems, it is of great practical significance and scientific research value to develop an efficient, stable and sulfur-poisoning-resistant CO oxidation catalyst. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art and provide an anti-aging highly active CO oxidation catalyst and a preparation method thereof. By optimizing the active components, carrier and promoter systems and combining an innovative preparation process, the CO conversion rate and sulfur-poisoning resistance of the catalyst are significantly improved.

[0007] The technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides an anti-aging highly active CO oxidation catalyst, which comprises the following components in mass percentage: 0.1-2% of an iridium-ruthenium alloy active component, 80-90% of a tantalum-doped zirconia carrier, and 10-20% of a composite promoter; the composite promoter is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 satisfies (1-3):1.

[0009] Preferably, in the iridium-ruthenium alloy active component, the mass ratio of iridium to ruthenium is 1:(1 - 5).

[0010] Preferably, in the tantalum-doped zirconia support, the molar ratio of zirconium to tantalum is (9 - 19):1.

[0011] On the other hand, the present invention provides a method for preparing the above anti-aging highly active CO oxidation catalyst, comprising the following steps:

[0012] S1 Support preparation: Prepare the tantalum-doped zirconia support by sol-gel combustion synthesis method;

[0013] S2 Support pretreatment: Calcinate the tantalum-doped zirconia support by gradient calcination method. First, raise the temperature to 400 - 450°C at a rate of 5 - 10°C / min, hold for 1 - 2 h, then raise the temperature to 550 - 600°C at a rate of 3 - 5°C / min, and hold for 2 - 3 h;

[0014] S3 Composite promoter impregnation: Use ammonium tartrate as a complexing agent to load MoO3 on the tantalum-doped zirconia support by first impregnation, and then use ultrasonic-assisted microwave drying method for the second impregnation to load Nb2O5 on the tantalum-doped zirconia support;

[0015] S4 Active component loading: Load the iridium-ruthenium alloy active component on the tantalum-doped zirconia support impregnated with the composite promoter by supercritical CO2 fluid deposition method to obtain the anti-aging highly active CO oxidation catalyst.

[0016] Preferably, in step S1, the preparation of the tantalum-doped zirconia support by sol-gel combustion synthesis method comprises the following steps:

[0017] (1) Dissolve metal salts: Dissolve zirconyl nitrate and tantalum pentachloride (TaCl5) in deionized water, stir until transparent; add a combustion agent and continue stirring; adjust the pH of the solution to 3 - 4 to promote the complexation reaction and form a homogeneous sol;

[0018] (2) Gelation and drying: Place the solution in a water bath at 80 - 90°C and continuously stir and evaporate until it becomes a viscous gel; transfer it to an oven for drying to obtain a porous dry gel precursor;

[0019] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity, place the powder in a refractory crucible, and raise the temperature to 250 - 300°C at a rate of 5 - 10°C / min in a muffle furnace to trigger the self-propagating combustion reaction;

[0020] (4) High-temperature calcination: Continue to raise the temperature to 600 - 800°C and hold for 2 - 4 h to completely decompose the organic matter and obtain the tantalum-doped zirconia crystal;

[0021] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain a tantalum-doped zirconia support.

[0022] Preferably, in step (1), the combustion agent is glycine and citric acid with a mass ratio of 1:(2 - 3); the molar ratio of zirconium oxynitrate to tantalum pentachloride is (9 - 19):1; the molar ratio of the combustion agent to the total molar amount of Zr 4+ and Ta 5+ is (1.5 - 2):1.

[0023] Preferably, in step (2), the drying temperature is 100 - 110 °C and the drying time is 10 - 12 h.

[0024] Preferably, in step S3, the first impregnation for loading MoO3 includes the following steps:

[0025] (1) Solution preparation: Prepare a precursor solution of ammonium molybdate ((NH4)6Mo7O 24 ·4H2O) with a concentration of 0.1 - 0.5 mol / L using deionized water, add ammonium tartrate ((NH4)2C4H4O6) according to the molar ratio of ammonium tartrate to Mo of (1 - 2):1, stir until completely dissolved, and adjust the pH of the solution to 3 - 5 to inhibit the rapid hydrolysis of MoO3;

[0026] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0027] (3) Static aging: Let it stand at room temperature for 6 - 12 h in a closed environment to promote the uniform adsorption of Mo complexes;

[0028] (4) Drying and calcination: Dry at 60 - 80 °C for 12 h to slowly remove moisture, then calcine in a muffle furnace at 400 - 500 °C for 4 - 5 h with a heating rate of 2 - 3 °C / min to form the MoO3 crystal phase;

[0029] The secondary impregnation for loading Nb2O5 includes the following steps:

[0030] 1) Solution preparation: Prepare a precursor solution of ammonium niobium oxalate (NH4NbO(C2O4)2·nH2O) with a concentration of 0.05 - 0.2 mol / L using an oxalic acid solution;

[0031] 2) Ultrasound-assisted impregnation: Immerse the tantalum-doped zirconia support loaded with the MoO3 precursor into the ammonium niobium oxalate precursor solution and place it in an ultrasonic bath at 40 - 50 kHz for impregnation for 30 - 60 min;

[0032] 3) Microwave-enhanced drying: Use the microwave pulse mode for drying, turn on for 30 - 40 s and turn off for 15 - 20 s, with a power of 300 - 600 W until completely dry;

[0033] 4) Decomposition and crystallization: Pre-sinter at 200-250℃ for 2-3h to decompose organic matter, then heat to 450-550℃ and calcine for 3-4h to form Nb2O5.

[0034] Preferably, in step S4, the supercritical CO2 fluid deposition method comprises the following steps:

[0035] (1) Preparation of iridium-ruthenium alloy precursor solution: prepare iridium acetylacetonate (Ir(acac)3) and ruthenium acetylacetonate (Ru(acac)3) solutions with methanol, with the methanol ratio being 5-10 vol.%, and dissolve with ultrasound until the solution is clear and free of precipitation; filter through a 0.22-0.25 μm organic filter membrane to remove undissolved impurities;

[0036] (2) Preactivation: In a H2 / N2 (5 vol.% H2) atmosphere, the tantalum-doped zirconia carrier loaded with the composite additive is treated at 250-350°C for 1-22 h to enhance the activity of the surface hydroxyl groups;

[0037] (3) Supercritical setting: Place the carrier in a reactor at 40-60°C, 10-15 MPa, and a CO2 flow rate of 0.5-2 L / min, introduce pure CO2 to a supercritical state, and maintain for 30 min to exclude air;

[0038] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reactor through a high-pressure pump to ensure that CO2 and the precursor are fully mixed;

[0039] (5) Dynamic impregnation: Under stirring conditions, maintain supercritical conditions for 2-4 hours to allow the precursor to be uniformly adsorbed into the pores of the support;

[0040] (6) Decompression deposition: release the pressure (rate ≤ 0.5 MPa / min), CO2 gradually vaporizes, and the precursor is directionally deposited on the support surface;

[0041] (7) Hydrogen reduction: A H2 / Ar mixed gas (H2 accounts for 5-10 vol.%) is introduced into a tubular furnace, and the temperature is raised to 300-400°C at 2°C / min and kept at this temperature for 2-3 h to reduce Ir 3+ 、Ru 3+ Reduce to metallic state; further heat to 450-550℃ and keep warm for 1-2h to promote alloying.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention significantly improves the CO conversion rate and sulfur poisoning resistance of the catalyst by optimizing the active components, carrier and additive system and combining an innovative preparation process, and is particularly suitable for sintering flue gas environments with high humidity and high sulfur.

[0044] 2. The present invention selects an Ir-Ru alloy to replace the conventional Pt / Pd as the active component. By utilizing the high stability of Ir and the electronic synergy effect of Ru, the Ir-Ru alloy may form a bimetallic interface structure. The exposed Ir-Ru atom pairs on the surface can provide unique bifunctional active sites. Through the geometric-electronic dual synergy effect, a dynamic balance between the CO adsorption strength and the oxygen activation ability is achieved, while taking into account high activity, stability, and anti-poisoning properties. In addition, the Ir-Ru alloy inhibits SO2 adsorption through electronic regulation, promotes the dynamic desorption of sulfur oxides through interface synergy, and the high stability of Ir prevents the deep penetration of sulfates, making its anti-SO2 poisoning performance significantly superior to that of traditional Pt / Pd catalysts. At the same time, the present invention develops a tantalum-doped zirconia support, which induces the generation of stable oxygen defect sites through Ta 5+ to enhance the ability of the catalyst to activate oxygen, promote the oxidation of SO2 to SO3 that is easily desorbed, rather than forming stable sulfates, reducing the poisoning of active sites by sulfur species. At the same time, the stable existence of oxygen defects can inhibit the dissociative adsorption of water molecules on the support surface, reduce the generation of hydroxyl groups, avoid the phase change of the support under hydrothermal conditions, and maintain the integrity of the support structure, thereby reducing the poisoning of the catalyst by water. In addition, the present invention also constructs a Mo-Nb system, in which MoO3 provides acidic sites and Nb2O5 enhances electron transfer. Through the dual synergy of acidic site activation and electron transfer, the all-round optimization of the CO oxidation reaction kinetics is achieved, while endowing the catalyst with excellent anti-poisoning properties, thermal stability, and wide temperature range adaptability.

[0045] 3. The present invention innovatively combines supercritical deposition and gradient calcination technologies to achieve the highly dispersed loading of active components, thereby enabling the active components to form more interface contact points with the support, forming more "metal-oxide interface" active sites, enhancing the interface coordination of the CO oxidation reaction, and improving the reaction activity of the catalyst. Detailed implementation manners

[0046] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention.

[0047] Example 1

[0048] The anti-aging and highly active CO oxidation catalyst of this example comprises the following components by mass percentage: 1% of iridium-ruthenium alloy active component (the mass ratio of iridium to ruthenium is 1:1), 85% of tantalum-doped zirconia support (the molar ratio of zirconium to tantalum is 9:1), and 14% of composite auxiliary agent. Among them, the composite auxiliary agent is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is 1:1.

[0049] The preparation method of the anti-aging and highly active CO oxidation catalyst of this example comprises the following steps:

[0050] Preparation of S1 support: Prepare tantalum-doped zirconia support by sol-gel combustion synthesis method, including the following steps:

[0051] (1) Dissolve metal salts: Dissolve zirconyl nitrate and TaCl5 with a molar ratio of 9:1 in deionized water and stir until transparent; add glycine and citric acid as combustion agents with a mass ratio of 1:2 to the above solution and continue to stir for 30 min; adjust the pH of the solution to 3 with dilute nitric acid to promote complexation reaction and form a homogeneous sol; the molar ratio of the combustion agent to the total molar number of Zr 4+ and Ta 5+ is 1.5:1;

[0052] (2) Gelation and drying: Place the solution in a 90 °C water bath and continuously stir and evaporate until it becomes a viscous gel; transfer it to an oven and dry it at 100 °C for 12 h to obtain a porous dry gel precursor;

[0053] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity, place the powder in a refractory crucible, and heat it to 250 °C at a rate of 5 °C / min in a muffle furnace to trigger self-propagating combustion reaction;

[0054] (4) High-temperature calcination: Continue to heat up to 600 °C and keep it for 4 h to completely decompose the organic matter and obtain tantalum-doped zirconia crystals;

[0055] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain tantalum-doped zirconia support.

[0056] S2 support pretreatment: Calcinate the tantalum-doped zirconia support by gradient calcination method. First, heat it to 400 °C at a rate of 5 °C / min and keep it for 1 h, then heat it to 600 °C at a rate of 3 °C / min and keep it for 2 h.

[0057] S3 Composite additive impregnation, and the first impregnation and loading of MoO3 includes the following steps:

[0058] (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.1 mol / L using deionized water, add ammonium tartrate according to the molar ratio of ammonium tartrate to Mo of 1:1, stir until completely dissolved, and adjust the pH of the solution to 4 with dilute nitric acid to inhibit the rapid hydrolysis of MoO3;

[0059] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0060] (3) Static aging: Stand still at room temperature for 12 h in a closed environment to promote the uniform adsorption of Mo complexes;

[0061] (4) Drying and calcination: Dry at 60 °C for 12 h to slowly remove moisture, then calcine in a muffle furnace at 500 °C for 4 h with a heating rate of 3 °C / min to form the MoO3 crystal phase;

[0062] The secondary impregnation for loading Nb2O5 includes the following steps:

[0063] 1) Solution preparation: Prepare an ammonium niobium oxalate precursor solution with a concentration of 0.05 mol / L using an oxalic acid solution;

[0064] 2) Ultrasonic-assisted impregnation: Immerse the tantalum-doped zirconia support loaded with the MoO3 precursor into the ammonium niobium oxalate precursor solution and place it in a 40 kHz ultrasonic bath for impregnation for 60 min;

[0065] 3) Microwave-enhanced drying: Perform drying using a microwave pulse mode, 30 s on and 15 s off, with a power of 300 W until completely dry;

[0066] 4) Decomposition and crystallization: First pre-calcine at 200 °C for 3 h to decompose organic substances, then raise the temperature to 550 °C and calcine for 3 h to form Nb2O5.

[0067] S4 Loading of active components: Load the iridium-ruthenium alloy active component on the tantalum-doped zirconia support impregnated with the composite promoter using the supercritical CO2 fluid deposition method to obtain the anti-aging highly active CO oxidation catalyst, which specifically includes the following steps:

[0068] (1) Preparation of iridium-ruthenium alloy precursor solution: Prepare a solution of iridium acetylacetonate and ruthenium acetylacetonate using methanol, with methanol accounting for 5 vol.%, and ultrasonically assist in dissolving (40 kHz, 30 min) until the solution is clear and free of precipitation; Filter through a 0.22 μm organic filter membrane to remove undissolved impurities;

[0069] (2) Pre-activation: In an H2 / N2 (5 vol.% H2) atmosphere, treat the tantalum-doped zirconia support loaded with the composite promoter at 250 °C for 2 h to enhance the surface hydroxyl activity;

[0070] (3) Supercritical setting: Under the conditions of 40 °C, 15 MPa, and a CO2 flow rate of 0.5 L / min, place the support in a reaction kettle, introduce pure CO2 to the supercritical state, and maintain for 30 min to remove air;

[0071] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reaction kettle through a high-pressure pump to ensure sufficient mixing of CO2 and the precursor;

[0072] (5) Dynamic impregnation: Turn on magnetic stirring (500 rpm), maintain the supercritical conditions for 4 h, and make the precursor uniformly adsorbed on the pores of the support;

[0073] (6) Decompression deposition: release the pressure (rate 0.2 MPa / min), CO2 gradually vaporizes, and the precursor is directionally deposited on the support surface;

[0074] (7) Hydrogen reduction: A H2 / Ar mixed gas (H2 accounts for 5 vol.%) was introduced into a tubular furnace, and the temperature was raised to 300°C at 2°C / min and kept at this temperature for 3 h. 3+ 、Ru 3+ Reduce to a metallic state; further heat to 550°C and keep warm for 1 hour to promote alloying;

[0075] (8) In-situ alloying verification

[0076] XRD analysis: detect whether the characteristic peaks of Ir-Ru alloy appear (such as face-centered cubic phase, 2θ≈40.5°, 47.2°).

[0077] TEM-EDS scan: confirm the overlap between Ir and Ru element distribution (correlation coefficient>0.9 is required).

[0078] The aging-resistant high-activity CO oxidation catalyst prepared in this example was used for a small test to simulate the composition of steel sintering flue gas. The initial activity test conditions were 4000ppm CO+15%O2, and the air velocity was 100000h -1 The anti-poisoning aging test conditions were 4000ppm CO+15%O2+2000ppm SO2+1000ppm NO+50ppm NH3+15%H2O, and the CO conversion rate was 98.2% under the initial activity test conditions at 270°C. After aging for 24 hours under the above anti-poisoning aging test conditions, the CO conversion rate was 93.6%.

[0079] Example 2

[0080] The anti-aging high-activity CO oxidation catalyst of this embodiment includes the following components in mass percentage: 0.5% of iridium-ruthenium alloy active component (the mass ratio of iridium to ruthenium is 1:3), 88% of tantalum-doped zirconium oxide carrier (the molar ratio of zirconium to tantalum is 15:1), and 11.5% of composite additive. The composite additive is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is 2:1.

[0081] The method for preparing the anti-aging high-activity CO oxidation catalyst of this embodiment comprises the following steps:

[0082] S1 carrier preparation: The tantalum-doped zirconium oxide carrier is prepared by a sol-gel combustion synthesis method, comprising the following steps:

[0083] (1) Dissolve metal salts: Dissolve zirconium oxynitrate and TaCl5 with a molar ratio of 15:1 in deionized water and stir until transparent; add glycine and citric acid, which are combustion agents with a mass ratio of 1:3, to the above solution and continue stirring for 30 min; adjust the pH of the solution to 4 with dilute nitric acid to promote the complexation reaction and form a homogeneous sol; the molar ratio of the combustion agents to the total molar amount of Zr 4+ 、Ta 5+ is 2:1;

[0084] (2) Gelation and drying: Place the solution in a 90 °C water bath and continuously stir and evaporate until it becomes a viscous gel; transfer it to an oven and dry it at 110 °C for 12 h to obtain a porous dry gel precursor;

[0085] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity, place the powder in a refractory crucible, and heat it in a muffle furnace to 300 °C at a rate of 5 °C / min to trigger the self-propagating combustion reaction;

[0086] (4) High-temperature calcination: Continue to heat up to 700 °C and hold for 3 h to completely decompose the organic matter and obtain tantalum-doped zirconia crystals;

[0087] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain a tantalum-doped zirconia support.

[0088] S2 support pretreatment: Calcinate the tantalum-doped zirconia support by the gradient calcination method. First, heat it to 450 °C at a rate of 8 °C / min and hold for 2 h, then heat it to 600 °C at a rate of 5 °C / min and hold for 3 h.

[0089] S3 Composite additive impregnation, where the first impregnation and loading of MoO3 include the following steps:

[0090] (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.3 mol / L using deionized water, add ammonium tartrate according to the molar ratio of ammonium tartrate to Mo of 2:1, stir until completely dissolved, and adjust the pH of the solution to 5 with dilute nitric acid to inhibit the rapid hydrolysis of MoO3;

[0091] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0092] (3) Static aging: Let it stand at room temperature for 10 h in a closed environment to promote the uniform adsorption of Mo complexes;

[0093] (4) Drying and calcination: Dry it at 70 °C for 12 h to slowly remove the moisture, and then calcine it in a muffle furnace at 450 °C for 5 h with a heating rate of 3 °C / min to form the MoO3 crystal phase;

[0094] The second impregnation and loading of Nb2O5 includes the following steps:

[0095] 1) Solution preparation: prepare an ammonium niobium oxalate precursor solution with a concentration of 0.1 mol / L using an oxalic acid solution;

[0096] 2) Ultrasonic assisted impregnation: The tantalum-doped zirconia support loaded with MoO3 precursor was immersed in the niobium oxalate precursor solution and placed in a 50kHz ultrasonic bath for 60 minutes;

[0097] 3) Microwave enhanced drying: Drying is carried out in microwave pulse mode, 40s on, 20s off, power of 500W, until completely dry;

[0098] 4) Decomposition and crystallization: Pre-sinter at 250℃ for 2h to decompose organic matter, then heat to 550℃ and calcine for 3h to form Nb2O5.

[0099] S4 Active component loading: The iridium-ruthenium alloy active component is loaded on the tantalum-doped zirconia carrier impregnated with the composite additive by supercritical CO2 fluid deposition method to obtain an anti-aging high-activity CO oxidation catalyst, which specifically includes the following steps:

[0100] (1) Preparation of iridium-ruthenium alloy precursor solution: prepare iridium acetylacetonate and ruthenium acetylacetonate solutions with methanol, with the methanol ratio being 8 vol.%, and dissolve with ultrasound assistance (40 kHz, 30 min) until the solution is clear and free of precipitation; filter through a 0.25 μm organic filter membrane to remove undissolved impurities;

[0101] (2) Preactivation: The tantalum-doped zirconia support loaded with the composite additive was treated at 300°C for 10 h in a H2 / N2 (5 vol.% H2) atmosphere to enhance the activity of the surface hydroxyl groups;

[0102] (3) Supercritical setting: Place the carrier in a reactor at 60°C, 13 MPa, and a CO2 flow rate of 2 L / min, introduce pure CO2 to a supercritical state, and maintain for 30 min to exclude air;

[0103] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reactor through a high-pressure pump to ensure that CO2 and the precursor are fully mixed;

[0104] (5) Dynamic impregnation: Turn on magnetic stirring (600 rpm) and maintain supercritical conditions for 3 h to allow the precursor to be uniformly adsorbed into the pores of the support;

[0105] (6) Decompression deposition: release the pressure (rate 0.3 MPa / min), CO2 gradually vaporizes, and the precursor is directionally deposited on the support surface;

[0106] (7) Hydrogen reduction: Pass a H2 / Ar mixed gas (H2 accounts for 8 vol.%) into a tubular furnace, heat it to 400 °C at a rate of 2 °C / min, and hold the temperature for 2 h to reduce Ir 3+ and Ru 3+ to the metallic state; further heat it to 550 °C and hold the temperature for 2 h to promote alloying;

[0107] (8) In-situ alloying verification

[0108] XRD analysis: Detect whether the characteristic peaks of the Ir-Ru alloy appear (such as the face-centered cubic phase, 2θ≈40.5°, 47.2°).

[0109] TEM-EDS surface scanning: Confirm the overlap degree of the distribution of Ir and Ru elements (the required correlation coefficient > 0.9).

[0110] The anti-aging highly active CO oxidation catalyst prepared in this example was used for small-scale testing of the composition of simulated iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 97.8% under the initial activity test conditions at 270 °C, and the CO conversion rate after aging was 92.6%.

[0111] Example 3

[0112] The anti-aging highly active CO oxidation catalyst of this example includes the following components by mass percentage: 1.5% of the iridium-ruthenium alloy active component (the mass ratio of iridium to ruthenium is 1:5), 82% of the tantalum-doped zirconia support (the molar ratio of zirconium to tantalum is 19:1), and 16.5% of the composite promoter. Among them, the composite promoter is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is 3:1.

[0113] The preparation method of the anti-aging highly active CO oxidation catalyst of this example includes the following steps:

[0114] S1 Support preparation: Prepare the tantalum-doped zirconia support by the sol-gel combustion synthesis method, including the following steps:

[0115] (1) Dissolve metal salts: Dissolve zirconyl nitrate and TaCl5 with a molar ratio of 19:1 in deionized water and stir until transparent; add glycine and citric acid with a mass ratio of 1:2 to the above solution and continue stirring for 30 min; adjust the pH of the solution to 3 with dilute nitric acid to promote the complexation reaction and form a homogeneous sol; the molar ratio of the combustion agent to the total molar number of Zr 4+ and Ta 5+ is 1.8:1;

[0116] (2) Gelation and drying: Place the solution in a 90 °C water bath and continuously stir to evaporate it until it becomes a viscous gel; transfer it to an oven and dry it at 110 °C for 12 h to obtain a porous dry gel precursor;

[0117] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity. Place the powder in a refractory crucible and heat it in a muffle furnace to 300 °C at a rate of 5 °C / min to trigger the self-propagating combustion reaction;

[0118] (4) High-temperature calcination: Continue to heat up to 800 °C and hold for 2 h to completely decompose the organic matter and obtain tantalum-doped zirconia crystals;

[0119] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain a tantalum-doped zirconia support.

[0120] S2 Support pretreatment: Calcinate the tantalum-doped zirconia support using the gradient calcination method. First, heat it to 400 °C at a rate of 10 °C / min and hold for 2 h, then heat it to 600 °C at a rate of 5 °C / min and hold for 3 h.

[0121] S3 Composite additive impregnation. The first impregnation and loading of MoO3 includes the following steps:

[0122] (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.5 mol / L using deionized water. Add ammonium tartrate according to a molar ratio of ammonium tartrate to Mo of 2:1 and stir until completely dissolved. Adjust the pH of the solution to 5 with dilute nitric acid to inhibit the rapid hydrolysis of MoO3;

[0123] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0124] (3) Static aging: Let it stand at room temperature for 12 h in a sealed environment to promote the uniform adsorption of Mo complexes;

[0125] (4) Drying and calcination: Dry at 80 °C for 12 h to slowly remove moisture, and then calcine at 500 °C for 5 h in a muffle furnace with a heating rate of 3 °C / min to form the MoO3 crystal phase;

[0126] The second impregnation and loading of Nb2O5 includes the following steps:

[0127] 1) Solution preparation: Prepare an ammonium niobium oxalate precursor solution with a concentration of 0.2 mol / L using an oxalic acid solution;

[0128] 2) Ultrasound-assisted impregnation: Immerse the tantalum-doped zirconia support loaded with the MoO3 precursor into the ammonium niobium oxalate precursor solution and place it in a 50 kHz ultrasonic bath for impregnation for 60 min;

[0129] 3) Microwave-assisted drying: Drying is carried out in a microwave pulse mode, with 40 s on and 15 s off, at a power of 600 W until completely dry;

[0130] 4) Decomposition and crystallization: First, pre-calcine at 250 °C for 3 h to decompose organic substances, then raise the temperature to 550 °C and calcine for 4 h to form Nb2O5.

[0131] S4 Active component loading: The iridium-ruthenium alloy active component is loaded onto the tantalum-doped zirconia support impregnated with the composite promoter by the supercritical CO2 fluid deposition method to obtain the anti-aging high-activity CO oxidation catalyst, which specifically includes the following steps:

[0132] (1) Preparation of iridium-ruthenium alloy precursor solution: Prepare a solution of iridium acetylacetonate and ruthenium acetylacetonate with methanol, with methanol accounting for 10 vol.%, and ultrasonically assist in dissolution (40 kHz, 30 min) until the solution is clear and free of precipitation; filter through a 0.25 μm organic filter membrane to remove undissolved impurities;

[0133] (2) Pre-activation: In an H2 / N2 (5 vol.% H2) atmosphere, treat the tantalum-doped zirconia support loaded with the composite promoter at 350 °C for 22 h to enhance the surface hydroxyl activity;

[0134] (3) Supercritical setting: Place the support in a reaction kettle under the conditions of 60 °C, 12 MPa, and a CO2 flow rate of 2 L / min, introduce pure CO2 to the supercritical state, and maintain for 30 min to remove air;

[0135] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reaction kettle through a high-pressure pump to ensure sufficient mixing of CO2 and the precursor;

[0136] (5) Dynamic impregnation: Turn on magnetic stirring (800 rpm), maintain the supercritical conditions for 4 h, and allow the precursor to be uniformly adsorbed in the pores of the support;

[0137] (6) Depressurization deposition: Release the pressure (rate 0.5 MPa / min), CO2 gradually gasifies, and the precursor is directionally deposited on the surface of the support;

[0138] (7) Hydrogen reduction: Pass an H2 / Ar mixed gas (H2 accounting for 10 vol.%) into a tubular furnace, heat up to 400 °C at a rate of 2 °C / min, and hold for 3 h to reduce Ir 3+ 、Ru 3+ to the metallic state; further heat up to 550 °C and hold for 2 h to promote alloying;

[0139] (8) In-situ alloying verification

[0140] XRD analysis: Detect whether the characteristic peaks of the Ir-Ru alloy appear (such as the face-centered cubic phase, 2θ≈40.5°, 47.2°).

[0141] TEM-EDS surface scanning: Confirm the overlap degree of the distributions of Ir and Ru elements (the required correlation coefficient > 0.9).

[0142] The anti-aging highly active CO oxidation catalyst prepared in this example was used for small-scale detection of the components of simulated iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 98.5% under the initial activity test conditions at 280°C, and the CO conversion rate after aging was 95.6%.

[0143] Example 4

[0144] The anti-aging highly active CO oxidation catalyst of this example includes the following components in mass percentage: 0.8% of the iridium-ruthenium alloy active component (the mass ratio of iridium to ruthenium is 1:3), 87% of the tantalum-doped zirconia support (the molar ratio of zirconium to tantalum is 16:1), and 12.2% of the composite promoter. Among them, the composite promoter is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is 2:1.

[0145] The preparation method of the anti-aging highly active CO oxidation catalyst of this example includes the following steps:

[0146] S1 Support preparation: Prepare the tantalum-doped zirconia support by the sol-gel combustion synthesis method, including the following steps:

[0147] (1) Dissolve metal salts: Dissolve zirconyl nitrate and TaCl5 with a molar ratio of 16:1 in deionized water and stir until transparent; add glycine and citric acid with a mass ratio of 1:2 to the above solution and continue stirring for 30 min; adjust the pH of the solution to 4 with dilute nitric acid to promote the complexation reaction and form a homogeneous sol; the molar ratio of the combustion agent to the total molar number of Zr 4+ , Ta 5+ is 2:1;

[0148] (2) Gelation and drying: Place the solution in an 80°C water bath and continuously stir and evaporate until it becomes a viscous gel; transfer it to an oven and dry it at 105°C for 11 h to obtain a porous dry gel precursor;

[0149] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity, place the powder in a refractory crucible, and heat it in a muffle furnace from room temperature to 300°C at a rate of 10°C / min to trigger the self-propagating combustion reaction;

[0150] (4) High-temperature calcination: Continue to heat up to 700°C and hold for 3 h to completely decompose the organic matter and obtain tantalum-doped zirconia crystals;

[0151] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain a tantalum-doped zirconia support.

[0152] S2 Support pretreatment: The tantalum-doped zirconia support is calcined by the gradient calcination method. First, it is heated to 450 °C at a rate of 10 °C / min and held for 1 h, then heated to 550 °C at a rate of 3 °C / min and held for 3 h.

[0153] S3 Composite promoter impregnation, where the first impregnation and loading of MoO3 includes the following steps:

[0154] (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.5 mol / L using deionized water. Add ammonium tartrate according to a molar ratio of ammonium tartrate to Mo of 2:1 and stir until completely dissolved. Adjust the pH of the solution to 3 with dilute nitric acid to inhibit the rapid hydrolysis of MoO3;

[0155] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0156] (3) Static aging: Static aging at room temperature for 6 h in a closed environment to promote the uniform adsorption of Mo complexes;

[0157] (4) Drying and calcination: Dry at 80 °C for 12 h to slowly remove moisture, and then calcine in a muffle furnace at 400 °C for 4.5 h with a heating rate of 2 °C / min to form the MoO3 crystal phase;

[0158] The second impregnation and loading of Nb2O5 includes the following steps:

[0159] 1) Solution preparation: Prepare an ammonium niobium oxalate precursor solution with a concentration of 0.05 mol / L using an oxalic acid solution;

[0160] 2) Ultrasound-assisted impregnation: Immerse the tantalum-doped zirconia support loaded with the MoO3 precursor into the ammonium niobium oxalate precursor solution and place it in an ultrasonic bath at 45 kHz for impregnation for 30 min;

[0161] 3) Microwave-enhanced drying: Use the microwave pulse mode for drying, 30 s on, 20 s off, with a power of 600 W until completely dry;

[0162] 4) Decomposition and crystallization: First, pre-calcine at 250 °C for 3 h to decompose organic substances, and then raise the temperature to 450 °C for calcination for 4 h to form Nb2O5.

[0163] S4 Active component loading: Use the supercritical CO2 fluid deposition method to load the iridium-ruthenium alloy active component on the tantalum-doped zirconia support impregnated with the composite promoter, that is, obtain an anti-aging and highly active CO oxidation catalyst, which specifically includes the following steps:

[0164] (1) Preparation of iridium-ruthenium alloy precursor solution: Prepare a solution of iridium acetylacetonate and ruthenium acetylacetonate with methanol, where the proportion of methanol is 10 vol.%, and ultrasonically assist in dissolution (40 kHz, 30 min) until the solution is clear and free of precipitation; filter through a 0.25 μm organic filter membrane to remove undissolved impurities;

[0165] (2) Pre-activation: In an atmosphere of H2 / N2 (5 vol.% H2), treat the tantalum-doped zirconia support loaded with the composite promoter at 350 °C for 20 h to enhance the activity of surface hydroxyl groups;

[0166] (3) Supercritical setting: Place the support in a reaction kettle under the conditions of 50 °C, 10 MPa, and a CO2 flow rate of 2 L / min, introduce pure CO2 to the supercritical state, and maintain for 30 min to remove air;

[0167] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reaction kettle through a high-pressure pump to ensure sufficient mixing of CO2 and the precursor;

[0168] (5) Dynamic impregnation: Turn on magnetic stirring (800 rpm), maintain the supercritical conditions for 2 h, and make the precursor uniformly adsorbed in the pores of the support;

[0169] (6) Depressurization deposition: Release the pressure (rate 0.4 MPa / min), CO2 gradually vaporizes, and the precursor is directionally deposited on the surface of the support;

[0170] (7) Hydrogen reduction: Pass a H2 / Ar mixed gas (H2 proportion 10 vol.%) into a tubular furnace, heat up to 350 °C at a rate of 2 °C / min, and keep the temperature for 3 h to reduce Ir 3+ , Ru 3+ to the metallic state; further heat up to 450 °C and keep the temperature for 2 h to promote alloying;

[0171] (8) In-situ alloying verification

[0172] XRD analysis: Detect whether the characteristic peaks of the Ir-Ru alloy appear (such as the face-centered cubic phase, 2θ≈40.5°, 47.2°).

[0173] TEM-EDS surface scan: Confirm the overlap degree of the distribution of Ir and Ru elements (the required correlation coefficient > 0.9).

[0174] The anti-aging high-activity CO oxidation catalyst prepared in this example was used for small-scale testing of the simulated steel sintering flue gas composition. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 98% under the initial activity test conditions at 280 °C, and the CO conversion rate after aging was 94.8%.

[0175] Example 5

[0176] The anti-aging highly active CO oxidation catalyst of this embodiment comprises components in the following mass percentages: 1.2% of an iridium-ruthenium alloy active component (the mass ratio of iridium to ruthenium is 1:3), 84% of a tantalum-doped zirconia support (the molar ratio of zirconium to tantalum is 9:1), and 14.8% of a composite promoter. Among them, the composite promoter is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is 2:1.

[0177] The preparation method of the anti-aging highly active CO oxidation catalyst of this embodiment comprises the following steps:

[0178] S1 Support preparation: Prepare the tantalum-doped zirconia support by the sol-gel combustion synthesis method, which comprises the following steps:

[0179] (1) Dissolve metal salts: Dissolve zirconyl nitrate and TaCl5 with a molar ratio of 9:1 in deionized water and stir until transparent; add glycine and citric acid with a mass ratio of 1:2 to the above solution and continue stirring for 30 min; adjust the pH of the solution to 3 with dilute nitric acid to promote the complexation reaction and form a homogeneous sol; the molar ratio of the combustion agent to the total molar number of Zr 4+ 、Ta 5+ is 1.5:1;

[0180] (2) Gelation and drying: Place the solution in an 85°C water bath and continuously stir and evaporate until it becomes a viscous gel; transfer it to an oven and dry it at 110°C for 10 h to obtain a porous dry gel precursor;

[0181] (3) Combustion synthesis: Grind the porous dry gel precursor into powder to ensure uniformity, place the powder in a refractory crucible, and heat it in a muffle furnace to 300°C at a rate of 5°C / min to trigger the self-propagating combustion reaction;

[0182] (4) High-temperature calcination: Continue to heat up to 800°C and hold for 3 h to completely decompose the organic matter and obtain tantalum-doped zirconia crystals;

[0183] (5) Cooling and grinding: Naturally cool to room temperature and grind again to obtain the tantalum-doped zirconia support.

[0184] S2 Support pretreatment: Calcinate the tantalum-doped zirconia support by the gradient calcination method. First, heat it to 400°C at a rate of 5°C / min and hold for 1 h, then heat it to 550°C at a rate of 4°C / min and hold for 2 h.

[0185] S3 Composite promoter impregnation, where the first impregnation and loading of MoO3 comprises the following steps:

[0186] (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.5 mol / L using deionized water. Add ammonium tartrate according to a molar ratio of ammonium tartrate to Mo of 2:1, stir until completely dissolved, and adjust the pH of the solution to 5 with dilute nitric acid to inhibit the rapid hydrolysis of MoO3;

[0187] (2) Equal-volume impregnation: Dropwise add the precursor solution to the tantalum-doped zirconia support until the pore volume is saturated;

[0188] (3) Static aging: Let it stand at room temperature for 6 h in a closed environment to promote the uniform adsorption of Mo complexes;

[0189] (4) Drying and calcination: Dry at 80 °C for 12 h to slowly remove moisture, and then calcine in a muffle furnace at 400 °C for 4 h with a heating rate of 2 °C / min to form the MoO3 crystal phase;

[0190] The secondary impregnation for loading Nb2O5 includes the following steps:

[0191] 1) Solution preparation: Prepare an ammonium niobium oxalate precursor solution with a concentration of 0.2 mol / L using an oxalic acid solution;

[0192] 2) Ultrasound-assisted impregnation: Immerse the tantalum-doped zirconia support loaded with the MoO3 precursor into the ammonium niobium oxalate precursor solution and place it in a 50 kHz ultrasonic bath for impregnation for 50 min;

[0193] 3) Microwave-enhanced drying: Dry using a microwave pulse mode, turn on for 40 s and stop for 20 s, with a power of 500 W until completely dry;

[0194] 4) Decomposition and crystallization: First pre-calcine at 220 °C for 3 h to decompose organic substances, and then raise the temperature to 500 °C for calcination for 4 h to form Nb2O5.

[0195] S4 Active component loading: Load the iridium-ruthenium alloy active component on the tantalum-doped zirconia support impregnated with the composite promoter by supercritical CO2 fluid deposition method to obtain the anti-aging and highly active CO oxidation catalyst, which specifically includes the following steps:

[0196] (1) Preparation of iridium-ruthenium alloy precursor solution: Prepare a solution of iridium acetylacetonate and ruthenium acetylacetonate using methanol, with methanol accounting for 10 vol.%, and ultrasonically assist in dissolving (40 kHz, 30 min) until the solution is clear and free of precipitation; Filter through a 0.24 μm organic filter membrane to remove undissolved impurities;

[0197] (2) Pre-activation: In an H2 / N2 (5 vol.% H2) atmosphere, treat the tantalum-doped zirconia support loaded with the composite promoter at 350 °C for 1 h to enhance the surface hydroxyl activity;

[0198] (3) Supercritical setting: Place the carrier in a reactor at 60°C, 10 MPa, and a CO2 flow rate of 1 L / min, introduce pure CO2 to a supercritical state, and maintain for 30 min to exclude air;

[0199] (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reactor through a high-pressure pump to ensure that CO2 and the precursor are fully mixed;

[0200] (5) Dynamic impregnation: Turn on magnetic stirring (800 rpm) and maintain supercritical conditions for 4 h to allow the precursor to be uniformly adsorbed into the pores of the support;

[0201] (6) Decompression deposition: release the pressure (rate 0.5 MPa / min), CO2 gradually vaporizes, and the precursor is directionally deposited on the support surface;

[0202] (7) Hydrogen reduction: A H2 / Ar mixed gas (H2 accounts for 10 vol.%) was introduced into a tubular furnace, and the temperature was raised to 400°C at 2°C / min and kept at this temperature for 3 h. 3+ 、Ru 3+ Reduce to a metallic state; further heat to 500°C and keep warm for 2h to promote alloying;

[0203] (8) In-situ alloying verification

[0204] XRD analysis: detect whether the characteristic peaks of Ir-Ru alloy appear (such as face-centered cubic phase, 2θ≈40.5°, 47.2°).

[0205] TEM-EDS scan: confirm the overlap between Ir and Ru element distribution (correlation coefficient>0.9 is required).

[0206] The aging-resistant and highly active CO oxidation catalyst prepared in this example was used for a small test to simulate the composition of steel sintering flue gas. Under the same test conditions as in Example 1, its CO conversion rate was measured to be 98.3% under the initial activity test conditions of 280°C, and the CO conversion rate after aging was 94.3%.

[0207] Comparative Example 1

[0208] The difference from Example 1 is that in the composite additive, the mass ratio of MoO3 to Nb2O5 is 5:1.

[0209] The CO oxidation catalyst prepared in Comparative Example 1 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 83.8% under the initial activity test conditions at 270 °C, and the CO conversion rate after aging was 70.6%. This is because the excessive addition of Mo leads to too many and too strong acidic sites, resulting in excessive adsorption of CO, enrichment of NH3, and an increase in side reactions, ultimately reducing the catalytic efficiency and anti-poisoning ability.

[0210] Comparative Example 2

[0211] The difference from Example 1 is that in the composite promoter, the mass ratio of MoO3 to Nb2O5 is 0.8:1.

[0212] The CO oxidation catalyst prepared in Comparative Example 2 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 76.9% under the initial activity test conditions at 270 °C, and the CO conversion rate after aging was 65.7%. This is because the Mo content is too low, resulting in too few and too weak acidic sites on the catalyst, and the adsorption capacity for CO becomes weak, so the activity of the catalyst decreases.

[0213] Comparative Example 3

[0214] The difference from Example 1 is that the active component uses a pure iridium active component.

[0215] The CO oxidation catalyst prepared in Comparative Example 3 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 82.5% under the initial activity test conditions at 270 °C, and the CO conversion rate after aging was 71.7%.

[0216] Comparative Example 4

[0217] The difference from Example 1 is that the active component uses a pure ruthenium active component.

[0218] The CO oxidation catalyst prepared in Comparative Example 4 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, the CO conversion rate was measured to be 75.8% under the initial activity test conditions at 270 °C, and the CO conversion rate after aging was 62.3%.

[0219] Compared with Example 1, the catalyst performance of Comparative Examples 3-4 decreased because the core of the electronic synergy between Ir and Ru lies in optimizing the electronic state of the active sites through charge transfer, energy band regulation, and interface coupling, weakening CO adsorption, avoiding blocking of active sites; promoting O2 activation, providing sufficient active oxygen species; reducing the reaction energy barrier, accelerating the conversion of CO→CO2; enhancing stability, and resisting poisons and sintering. Therefore, the lack of Ru in Comparative Example 3 and the lack of Ir in Comparative Example 4 weakened the electronic synergy between active species, so both the activity and anti-poisoning ability of the catalyst were weakened.

[0220] Comparative Example 5

[0221] The difference from Example 1 is that a Pt / Pd active component (the mass ratio of Pt to Pd is 1:3) is used instead of the iridium-ruthenium alloy active component.

[0222] The CO oxidation catalyst prepared in Comparative Example 5 was used for small-scale testing of the simulated iron and steel sintering flue gas composition. Under the same test conditions as Example 1, the CO conversion rate was measured to be 82.7% under the initial activity test conditions at 270°C, and the CO conversion rate after aging was 69.6%. This is because Ir / Ru oxides can reduce the reaction energy barrier through the lattice oxygen participation mechanism, while Pt / Pd relies on the traditional adsorbate mechanism, resulting in a high reaction energy barrier and thus low reaction activity; and the surface of Ir / Ru is more inert: Pt / Pd is easily poisoned by small molecules such as NO\SO2, and the surface active sites are occupied, while Ir / Ru has a weaker binding energy for adsorbates and stronger anti-poisoning ability.

[0223] Comparative Example 6

[0224] The difference from Example 1 is that a Ce-doped zirconia support is used.

[0225] The CO oxidation catalyst prepared in Comparative Example 6 was used for small-scale testing of the simulated iron and steel sintering flue gas composition. Under the same test conditions as Example 1, the CO conversion rate was measured to be 73.2% under the initial activity test conditions at 270°C, and the CO conversion rate after aging was 63.6%.

[0226] The present invention develops a tantalum-doped zirconia support, which induces the generation of stable oxygen defect sites through Ta 5+ thereby enhancing the ability of the catalyst to activate oxygen, promoting the oxidation of SO2 to SO3 that is easily desorbed, rather than forming stable sulfates, and reducing the poisoning of active sites by sulfur species. The oxygen storage and release ability of CeO2 depends on the Ce 3+ / Ce 4+ cycle, the surface is enriched with active oxygen, and it is easy to combine with SO3 to form stable Ce2(SO4)3, resulting in catalyst poisoning.

[0227] Comparative Example 7

[0228] The difference from Example 1 is that MoO3 is not added to the composite promoter.

[0229] The CO oxidation catalyst prepared in Comparative Example 7 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, its CO conversion rate under the initial activity test conditions at 270 °C was measured to be 75.9%, and the CO conversion rate after aging was 60.9%. This is because without adding MoO3, the acidic sites of the catalyst decrease, and its ability to adsorb and activate CO weakens, resulting in a decrease in the activity and anti-poisoning ability of the catalyst.

[0230] Comparative Example 8

[0231] The difference from Example 1 is that Nb2O5 is not added to the composite promoter.

[0232] The CO oxidation catalyst prepared in Comparative Example 8 was used for small-scale detection simulating the composition of iron and steel sintering flue gas. Under the same test conditions as in Example 1, its CO conversion rate under the initial activity test conditions at 270 °C was measured to be 80.5%, and the CO conversion rate after aging was 68.7%. This is because the synergistic effect of electrons weakens, resulting in a decrease in the activity and anti-poisoning ability of the catalyst.

Claims

1. A highly active CO oxidation catalyst with high aging resistance, characterized in that: The invention comprises the following components in percentage by mass: 0.1-2% of an iridium-ruthenium alloy active component, 80-90% of a tantalum-doped zirconia carrier, and 10-20% of a composite auxiliary agent; the composite auxiliary agent is a composite oxide of MoO3 and Nb2O5, and the mass ratio of MoO3 to Nb2O5 is (1-3):

1.

2. The aging-resistant high-activity CO oxidation catalyst according to claim 1, characterized in that: In the iridium-ruthenium alloy active component, the mass ratio of iridium to ruthenium is 1:(1-5).

3. The aging-resistant high-activity CO oxidation catalyst according to claim 1, characterized in that: In the tantalum-doped zirconia carrier, the molar ratio of zirconium to tantalum is (9-19):

1.

4. The method for preparing an anti-aging high-activity CO oxidation catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1 carrier preparation: Tantalum-doped zirconia carrier was prepared by sol-gel combustion synthesis method; S2 carrier pretreatment: The tantalum-doped zirconia carrier was calcined by a gradient calcination method, firstly raised to 400-450°C at a rate of 5-10°C / min, kept warm for 1-2h, then raised to 550-600°C at a rate of 3-5°C / min, kept warm for 2-3h; S3 composite additive impregnation: using ammonium tartrate as a complexing agent, MoO3 was loaded on the tantalum-doped zirconia support by the first impregnation, followed by a second impregnation using an ultrasonic-assisted microwave drying method to load Nb2O5 on the tantalum-doped zirconia support; S4 Active component loading: The iridium-ruthenium alloy active component is loaded on a tantalum-doped zirconia carrier impregnated with a composite additive by supercritical CO2 fluid deposition method to obtain an anti-aging and highly active CO oxidation catalyst.

5. The method for preparing an anti-aging high-activity CO oxidation catalyst according to claim 4, characterized in that: In step S1, preparing the tantalum-doped zirconium oxide carrier by the sol-gel combustion synthesis method comprises the following steps: (1) Dissolving metal salts: dissolving zirconium oxynitrate and tantalum pentachloride in deionized water and stirring until transparent; adding combustion agent and continuing stirring; adjusting the pH of the solution to 3-4; (2) Gelation and drying: placing the solution in a water bath at 80-90°C, stirring continuously and evaporating until it becomes a viscous gel; transferring to an oven for drying to obtain a porous xerogel precursor; (3) Combustion synthesis: The porous xerogel precursor is ground into powder, and the powder is placed in a muffle furnace and heated to 250-300 °C at 5-10 °C / min to trigger a self-propagating combustion reaction; (4) High temperature calcination: Continue to raise the temperature to 600-800°C and keep it at this temperature for 2-4 hours to completely decompose the organic matter and obtain tantalum-doped zirconium oxide crystals; (5) Cooling and grinding: Cool naturally to room temperature and grind again to obtain a tantalum-doped zirconia carrier.

6. The method for preparing an anti-aging high-activity CO oxidation catalyst according to claim 5, characterized in that: In step (1), the combustion agent is glycine and citric acid in a mass ratio of 1:(2-3); the combustion agent and Zr 4+ 、 5+ The molar ratio of the total moles is (1.5-2):

1.

7. The method for preparing an anti-aging high-activity CO oxidation catalyst according to claim 5, characterized in that: In step (2), the drying temperature is 100-110° C. and the drying time is 10-12 h.

8. The method for preparing an anti-aging high-activity CO oxidation catalyst according to claim 4, characterized in that: In step S3, the first impregnation loading of MoO3 includes the following steps: (1) Solution preparation: Prepare an ammonium molybdate precursor solution with a concentration of 0.1-0.5 mol / L with deionized water, add ammonium tartrate at a molar ratio of ammonium tartrate to Mo of (1-2):1, stir until completely dissolved, and adjust the solution pH to 3-5; (2) Equal volume impregnation: the precursor solution is added dropwise to the tantalum-doped zirconia support until the pore volume is saturated; (3) Static aging: Static aging at room temperature in a closed environment for 6-12 hours; (4) Drying and calcination: Dry at 60-80°C for 12 h, then calcined in a muffle furnace at 400-500°C for 4-5 h at a heating rate of 2-3°C / min to form a MoO3 crystalline phase; The secondary impregnation loading of Nb2O5 includes the following steps: 1) Solution preparation: prepare an ammonium niobium oxalate precursor solution with a concentration of 0.05-0.2 mol / L using an oxalic acid solution; 2) Ultrasonic assisted impregnation: The tantalum-doped zirconia support loaded with MoO3 precursor is immersed in the niobium oxalate precursor solution and placed in a 40-50kHz ultrasonic bath for 30-60 minutes; 3) Microwave enhanced drying: Use microwave pulse mode for drying, 30-40s on, 15-20s off, power 300-600W, until completely dry; 4) Decomposition and crystallization: Pre-sinter at 200-250℃ for 2-3h, then heat to 450-550℃ and calcine for 3-4h.

9. The method for preparing an anti-aging high-activity CO oxidation catalyst according to claim 4, characterized in that: In step S4, the supercritical CO2 fluid deposition method includes the following steps: (1) Preparation of iridium-ruthenium alloy precursor solution: prepare iridium acetylacetonate and ruthenium acetylacetonate solutions with methanol, with the methanol accounting for 5-10 vol.%; (2) Preactivation: treating the tantalum-doped zirconia carrier loaded with the composite additive at 250-350° C. for 1-22 h in a H2 / N2 atmosphere; (3) Supercritical setting: Place the carrier in a reactor at 40-60°C, 10-15 MPa, and a CO2 flow rate of 0.5-2 L / min, introduce pure CO2 to a supercritical state, and maintain for 30 min to exclude air; (4) Precursor injection: Inject the iridium-ruthenium alloy precursor solution into the reactor to ensure that CO2 and the precursor are fully mixed; (5) Dynamic impregnation: Under stirring conditions, maintain supercritical conditions for 2-4 hours to allow the precursor to be uniformly adsorbed into the pores of the support; (6) Decompression deposition: The pressure is released, CO2 gradually vaporizes, and the precursor is deposited directionally on the support surface; (7) Hydrogen reduction: Introduce H2 / Ar mixed gas into a tubular furnace, raise the temperature to 300-400℃ at 2℃ / min, and keep it at this temperature for 2-3h to reduce Ir 3+ 、Ru 3+ Reduce to metallic state; further heat to 450-550℃ and keep warm for 1-2h to promote alloying.