Catalyst for reducing co emission at sintering end and preparation method thereof

Abstract

The application discloses a catalyst for reducing CO at the end of sintering and a preparation method thereof. The preparation method comprises the steps of raw material selection, mixing, calcining of the carrier, grinding, impregnation and calcination. Through specific selection of raw materials, W and V are doped into TiO2 to form a carrier in a molar ratio of 3:7, and Pd is loaded through specific equal-volume impregnation, so that a Pd / TiW3V7O x catalyst is obtained, which has high efficient catalytic oxidation of CO at a relatively low temperature and high resistance to sulfur poisoning. The catalyst can be used for catalytic oxidation of CO in the existing sintering process under the flue gas environment, thereby efficiently reducing the content of CO in the sintering flue gas, and the service life of the catalyst is obviously improved due to the resistance to sulfur.

Description

Technical Field

[0001] This invention relates to the fields of emission reduction and catalyst technology in sintering processes, and particularly to a catalyst for reducing CO emissions at the end of sintering and its preparation method. Background Technology

[0002] The steelmaking industry is a major source of CO emissions from my country's air pollution, with the sintering process for producing sintered ore being the largest contributor to CO emissions in steel production. During the high-temperature sintering of sintered ore, incomplete combustion of solid fuels and the high-temperature reduction reaction of iron ore generate large amounts of carbon monoxide. Currently, CO emission concentrations in sintering flue gas are subject to mandatory control, with current emission standards requiring CO concentrations not to exceed 300 mg / m³. 3 In some key control areas, the requirement is to further reduce the concentration to 100 mg / m³. 3 Therefore, developing efficient CO emission reduction technologies for sintering flue gas has become an urgent need for pollution control in the steel industry.

[0003] The most widely used CO end-of-pipe treatment technology in sintering is catalytic oxidation. This means that after the sintering flue gas is treated by the front-end desulfurization and denitrification unit, it enters the catalytic oxidation reactor, where CO is oxidized to CO2 under the action of a catalyst. This process has the advantages of mild reaction conditions, high CO removal efficiency and no secondary pollution, and can reduce CO emissions in sintering flue gas to more than 70%.

[0004] Chinese invention patent publication CN121755215A discloses a CO removal catalyst and its preparation method, which achieves the catalytic oxidation of CO by loading active components such as CuO and NiO on a porous support. However, it is not suitable for the chemical environment of sintering flue gas.

[0005] Many existing industrial CO oxidation catalysts are supported noble metal catalysts, among which Pd-supported TiO2-based catalysts are widely used. TiO2 supports offer excellent thermal stability, some resistance to poisoning, and low preparation costs. Pd (palladium), as the noble metal active component, possesses excellent CO adsorption and activation capabilities, achieving high CO conversion rates in the medium-to-high temperature range. Therefore, it is widely used in CO emission reduction processes for sintering flue gas. However, with the iteration of pollutant control technologies at the front end of the sintering process, this traditional catalyst system has gradually revealed some shortcomings. Firstly, its low-temperature catalytic activity is insufficient and cannot adapt to low flue gas temperature conditions. Current mainstream sintering flue gas desulfurization and denitrification processes mostly employ wet desulfurization and low-temperature denitrification. After treatment by the desulfurization and denitrification units, the temperature of the flue gas drops to around 150-180℃, while the activity temperature window of traditional Pd / TiO2 catalysts is mainly above 220℃. Therefore, in the low-temperature range, the CO adsorption activation energy barrier is high, and the oxygen dissociation efficiency is low, resulting in this type of traditional catalyst being unable to achieve efficient CO oxidation over a wide temperature range. Secondly, this type of catalyst is prone to sulfur poisoning, which shortens its lifespan. Although most sulfur oxides are removed after the sintering flue gas is treated by a wet desulfurization unit, a certain volume fraction of SO2 remains in the flue gas. Existing traditional catalysts will suffer severe sulfur poisoning when operating in sulfur-containing flue gas for a long time. This is mainly because SO2 in the flue gas will undergo catalytic oxidation on the Pd active sites and TiO2 support surface to generate SO3. SO3 will further combine with the metal cations in the support and the active component Pd to generate stable sulfates (such as PdSO4, Ti(SO4)2, etc.). Sulfates will cover the Pd active sites, block the adsorption and activation pathways of CO and O2, reduce the effective number of active sites, and accumulate in the support pores, causing pore blockage. It will also destroy the electronic interaction between Pd and the support, causing Pd particles to agglomerate and grow, ultimately resulting in a significant decrease in the catalyst's CO oxidation activity.

[0006] Chinese invention patent publication CN121847136A discloses a titanium-modified composite catalyst, its preparation method and its uses. By loading Pd and Pt onto titanium oxide and setting a modified CeO2 composite support, it achieves a highly efficient CO purification effect, but it does not solve the problem of sulfur poisoning.

[0007] Therefore, there is an urgent need to develop a catalyst that can achieve CO catalytic oxidation over a wide temperature range and will not or will not cause sulfur poisoning. Summary of the Invention

[0008] The purpose of this invention is to provide a catalyst for reducing CO emissions at the end of sintering and its preparation method by solving the above-mentioned technical problems.

[0009] The present invention adopts the following technical solution: A method for preparing a catalyst for reducing CO emissions at the end of sintering includes the following steps; S1, Raw material selection: Anatase TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are selected.

[0010] S2, Mixing: Mix 19-20 parts by weight of TiO2 powder, 1.01-1.04 parts by weight of (NH4)2WO4 powder and 0.98-1.01 parts by weight of NH4VO3 powder selected in S1, and heat to 58-63°C. Stir evenly at this temperature, and then continue to heat to 75-85°C for continuous drying to obtain a dry mixture.

[0011] S3, calcined support: The dried mixture of S2 is placed in a calcination furnace and heated to 390~410℃. It is calcined at this temperature and then removed to obtain a TiO2 composite oxide support doped with W and V.

[0012] S4, Grinding: Grind the composite oxide carrier obtained in S3 and sieve it to 40~60 mesh to obtain a refined composite oxide carrier.

[0013] S5, Impregnation: The obtained composite oxide support is impregnated with an aqueous solution of palladium nitrate dihydrate with a concentration of 18.00~18.20 wt.% Pd in ​​equal volume, and the ratio is based on the amount of Pd loading to form 0.09~0.11 wt%.

[0014] S6, Calcination: After S5 impregnation, the material is placed in an oven at 95~105℃ and dried for 11~13 hours. Then it is placed in a calcination furnace and heated to 395~405℃. The catalyst product is obtained by calcination at this temperature.

[0015] Preferably, the mixing in step S2 is as follows: 13-14 parts by weight of TiO2 powder, 0.1-0.12 parts by weight of (NH4)2WO4 powder, and 0.09-0.1 parts by weight of NH4VO3 powder are mixed and heated to 58-63°C, and stirred at this temperature (stirring time is further preferably 5.5-6.5 h). Then, the temperature is further increased to 75-85°C for continuous drying (drying time is further preferably 11-13 h). The resulting mixture is then subjected to a pressure of 9-11 MPa and a holding time of 0.9-1.1 min. The core block is obtained by pressing under the following conditions; simultaneously, the remaining TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are mixed and heated to 58~63℃, and stirred at this temperature (stirring time is further preferably 5.5~6.5h), and then the temperature is further increased to 75~85℃ for continuous drying (drying time is further preferably 11~13h). The resulting mixture is then coated on the outside of the core block and pressed in a pressing tank under the conditions of 14~16MPa pressure and 1.5~2.5min to obtain a dry mixture of complete blank.

[0016] Preferably, in step S5, the composite oxide support is impregnated with an aqueous solution of palladium nitrate dihydrate with a concentration of 18.00~18.20 wt.% Pd for 12~25 hours in an equal volume.

[0017] Preferably, in step S6, after the impregnation in S5 is completed, the material is placed in an oven at 95~105℃ and dried for 11~13h. Then, it is placed in a calcining furnace and heated to 395~405℃ at a heating rate of 1.5~2.5℃ / min. After calcining at this temperature for 3.6~4.2h, the catalyst product is obtained.

[0018] Preferably, the calcination support in step S3 is specifically as follows: the dried mixture of the complete blank from S2 is placed in a calcination furnace and heated to 390-410°C at a rate of 4-6°C / min, and calcined at this temperature for 3.8-4.5 hours. Then, the temperature is further increased to 540-560°C and held at this temperature for 1.5-2.5 hours. After removal, a TiO2 composite oxide support doped with W and V is obtained.

[0019] Preferably, in step S5, the equal-volume impregnation specifically includes: first, spraying an aqueous solution of palladium nitrate dihydrate onto the mixed powder obtained in S4 using an atomization method, then sealing and letting it stand for 0.9~1.2h, then mechanically stirring at a speed of 80~150rpm (more preferably for a duration of 10~20min); then ultrasonically stirring at a speed of 100~200rpm (ultrasonic stirring time more preferably 10~20min); finally reducing the stirring speed and ultrasonically stirring at a speed of 60~90rpm (ultrasonic stirring time more preferably 6~15min); and letting it stand after stirring (standing time more preferably 11~25h).

[0020] Preferably, in step S2, 13-14 parts by weight of TiO2 powder, 0.1-0.12 parts by weight of (NH4)2WO4 powder and 0.09-0.1 parts by weight of NH4VO3 powder are mixed first, and then the mixed powder is placed in a ball mill and ball-milled at a speed of 290-310 rpm for 25-35 minutes before being taken out.

[0021] The remaining TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are mixed simultaneously. Then, the mixed powder is placed in a ball mill and ball-milled for 25 to 35 minutes at a speed of 290 to 310 rpm before being taken out.

[0022] Preferably, in step S2, the molar ratio of Ti:W:V in the dried mixture is 200:3:7.

[0023] Preferably, in steps S3 and S6, the calcining furnace is a muffle furnace.

[0024] Preferably, in step S5, the solid-liquid ratio of the mixed powder to the aqueous palladium nitrate dihydrate is (0.8~1.1) kg: (4.5~5.5) ml.

[0025] Preferably, step S4' is included after step S4 and before step S5: S4', In-situ hydroxyl activation: The composite oxide support obtained in S4 is spread flat on a plasma reaction disk with a thickness of 2-3 mm. The plasma reaction disk is placed in the reaction chamber of a plasma cleaner, and a vacuum is drawn to 10-20 Pa. Then, a mixed gas of Ar and O2 with a volume ratio of 3.5-4.5:1 is introduced. The amount of mixed gas introduced is such that the pressure in the reaction chamber is kept stable at 30-40 Pa. The pulse plasma parameters are set as follows: power 95-105 W, pulse duty cycle 10% (i.e., 1 second on and 9 seconds off), and total processing time 58-65 s. Then, the processed powder is taken out and stirred for 25-35 s to obtain the composite oxide support after in-situ hydroxyl activation.

[0026] A catalyst for reducing CO emissions at the end of sintering, wherein the catalyst is prepared by the above-described preparation method, and the average particle size of the catalyst is 0.5~1.3µm, and more than 80% of the particles are less than 1.8µm.

[0027] Preferably, the catalyst has a pore size of 6-10 nm and a specific surface area of ​​93-108 m². 2 / g, pore volume 0.23~0.29 cm³ 3 / g.

[0028] The beneficial effects of this invention are: 1. This invention constructs a composite support with electronic regulation and stability by doping a TiO2 support with W and V in a specific molar ratio. After loading Pd, a multi-active-site synergistic catalytic system is formed. 6+ With V 5+ Both act as strong electron acceptors and can synergistically regulate the surface electron density of the TiO2 support, thereby promoting the formation of highly active Pd. δ+ The valence state is adjusted, thereby lowering the energy barrier for CO adsorption activation and O2 dissociation, allowing the CO catalytic oxidation reaction to proceed efficiently at relatively low temperatures. Verification through examples shows that the catalyst of this invention can maintain a CO conversion rate of over 90% over a wide temperature range of 160–250°C, completely covering the actual flue gas temperature range of 150–250°C after desulfurization and denitrification of sintering flue gas. This solves the problem that traditional Pd / TiO2 catalysts only exhibit high activity above 250°C, and is compatible with the operating conditions of existing sintering flue gas end-of-pipe treatment devices. Simultaneously, the specific molar amounts of W and V doping modification in this invention fundamentally alter the acidity / basicity and adsorption characteristics of the catalyst surface, significantly improving the catalyst's resistance to sulfur poisoning. The core mechanism of sulfur poisoning in traditional catalysts is the oxidation of SO2 to SO3 at active sites, which then further combines with the active components and support to form stable sulfates, covering the active sites and destroying the catalyst structure. This invention preferentially adsorbs and disperses SO2 through W and V doping, avoiding direct contact between SO2 and the active sites of Pd. Simultaneously, it inhibits the formation and accumulation of sulfate near the active sites, and SO2 does not block the adsorption and activation pathways of CO and O2. Sulfur poisoning is virtually absent, and calculations suggest that its theoretical lifespan can be more than three times that of traditional catalysts.

[0029] 2. This invention provides a segmented optimization of the traditional equal-volume impregnation method. In the initial stirring stage, a specific stirring time is applied after spraying the Pd precursor solution to prevent localized accumulation of the solution, ensuring uniform initial dispersion of the active component on the carrier surface. This avoids subsequent aggregation problems caused by excessively high local Pd concentrations. Then, ultrasonic stirring is used in the middle stage to assist dispersion; the cavitation effect of ultrasound further promotes the efficient entry of the Pd precursor into the carrier pores. Finally, the stirring rate is reduced in the final stage to prevent high-speed stirring from causing the active component to detach from the carrier surface. After stirring, the mixture is allowed to stand, allowing the Pd precursor to fully diffuse into the carrier interior, preventing excessive adhesion of the active component to the outer surface of the carrier and effectively increasing the number of active sites.

[0030] 3. In the W and V doping process, this invention, by adjusting the calcination steps, fully utilizes existing raw materials and calcination equipment. Through adjustments to the calcination steps and parameters, a radial gradient distribution of W and V is achieved. First, ammonium tungstate and ammonium metavanadate are completely decomposed at approximately 400℃ for about 4 hours. Then, a further heating to approximately 550℃ is applied to achieve short-range gradient diffusion of WO3 and V2O5. This temperature does not damage the original TiO2 crystal structure or induce TiO2 particle agglomeration, thus preserving the complete carrier pore structure and specific surface area. Compared to traditional uniform W or V doping, the gradient method set in this invention enables the enrichment of W and V on the surface with relatively less spatial distribution inside. The surface-enriched W and V can provide more anchoring points for Pd, avoiding carrier pore blockage and crystal structure damage caused by excessive bulk doping. Furthermore, this invention adds a room-temperature atomization pre-adsorption step during the Pd impregnation process, allowing the Pd precursor to spread uniformly on the carrier surface through atomization. Combined with the aforementioned gradient distribution of W and V, it can be preferentially anchored by the high W and V sites on the surface, spontaneously forming W-Pd and V-Pd spatially confined structures, with hexavalent W... 6+ A stable W-Pd electron bridge is formed between Pd and V, and the pentavalent V 5+ A stable V-Pd electron bridge is formed between Pd and Pd, increasing the strength of electron-electron interactions and making it more favorable for Pd. δ+ The stable presence of active sites further enhances the adsorption and activation capacity for CO. The above improvements do not require new equipment; they can be achieved simply by adjusting the steps and parameters, making the modification relatively simple and suitable for industrial production.

[0031] 4. This invention adds an Ar / O2 low-temperature pulsed plasma pretreatment step before impregnation, which can significantly increase the surface hydroxyl density of the WV-TiO2 support in a very short time. More surface hydroxyl groups can provide more anchoring sites for the Pd precursor, avoiding the aggregation and nucleation of the Pd precursor, thereby further improving the dispersion of Pd. At the same time, the plasma pretreatment introduces a large number of oxygen vacancies on the support surface. The oxygen vacancies formed can not only promote the adsorption and dissociation of O2, but also promote the Pd... 2+ The ions are reduced to highly reactive zero-valent Pd, ultimately forming Pd. δ+ and Pd 0 The dual active centers adsorb CO and activate oxygen, respectively, further reducing the activation energy for CO oxidation. Additionally, plasma treatment improves the wettability of the support surface. For the low Pd loading system (e.g., 0.1 wt.%) of this invention, trace amounts of Pd precursor solution can spread more evenly on the support surface, further enhancing the uniformity of Pd distribution and avoiding the problem of uneven Pd distribution leading to activity fluctuations under low loading. Attached Figure Description

[0032] All accompanying drawings of this invention are schematic diagrams and are used for illustration only, and do not limit the scope of protection.

[0033] Figure 1 The above are schematic diagrams of the catalyst powders obtained in Example 1 and Comparative Examples 1-5 of the present invention.

[0034] Figure 2 This is a schematic diagram showing the CO conversion rate of the catalysts obtained in Example 1 and Comparative Examples 1-5 of the present invention as a function of temperature.

[0035] Figure 3 This is a schematic diagram showing the CO conversion rate of the catalysts obtained in Example 1 and Comparative Examples 1-5 of the present invention as a function of temperature in the presence of sulfur-containing gas.

[0036] Figure 4 This is a schematic diagram showing the CO conversion rate of the catalysts obtained in Example 1 and Comparative Examples 1-5 of the present invention as a function of time at 220°C in the presence of sulfur-containing gas.

[0037] Figure 5 The XRD patterns of the catalysts obtained in Example 1 and Comparative Examples 1-5 of the present invention are shown.

[0038] Figure 6 This is a schematic diagram comparing the SEM microstructure of the catalysts obtained in Example 1 and Comparative Examples 1-5 of the present invention.

[0039] in Figure 6In the image, (a) shows the SEM microstructure of Pd / TiO2 in Comparative Example 1, and (b) shows the SEM microstructure of Pd / TiWO2 in Comparative Example 2. x SEM microstructure of Pd / TiW7V3O (c) is Comparative Example 3. x The SEM microstructure of Pd / TiW5V5O is shown in (d), which is the Pd / TiW5V5O of ​​Comparative Example 4. x The SEM microstructure of (e) is that of Pd / TiW3V7O in Example 1. x The SEM microstructure of Pd / TiVO2 is shown in (f), which is the microstructure of Pd / TiVO2 in Comparative Example 5. x The SEM microstructure. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0041] This embodiment is used to illustrate the Pd-TiW3V7O of the present invention. X A method for preparing a catalyst includes the following steps: S1, Raw material selection: Anatase TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are selected.

[0042] S2, Mixing: First, mix 13.5 parts by weight of TiO2 powder, 0.1 parts by weight of (NH4)2WO4 powder, and 0.1 parts by weight of NH4VO3 powder. Place the resulting powder into a ball mill and ball mill at 300 rpm for 30 minutes. Then remove the powder and heat it to 60°C. Stir the mixture at this temperature for 6 hours, then continue to heat it to 80°C and dry it for 12 hours. Finally, dry the resulting mixture under a pressure of 10 MPa and a holding time of 1 minute. The mixture was pressed to obtain core blocks. The remaining TiO2 powder, (NH4)2WO4 powder, and NH4VO3 powder (totaling 19.5 parts by weight of TiO2 powder, 1.03 parts by weight of (NH4)2WO4 powder, and 1 part by weight of NH4VO3 powder) were mixed. The resulting powder was then placed in a ball mill and ball-milled at 300 rpm for 31 minutes. The mixture was then removed, heated to 60°C, stirred at this temperature for 6 hours, and then further heated to 80°C and dried for 12 hours. The resulting dried mixture had a molar ratio of Ti:W:V of 200:3:7.

[0043] The resulting mixture is then coated onto the outside of the core block and pressed in a pressing groove at a pressure of 15 MPa for a holding time of 2 min to obtain a dry mixture of complete blanks.

[0044] S3, calcined support: The dried mixture of the complete S2 blank is placed in a muffle furnace and heated to 400°C at a rate of 5°C / min. It is calcined at this temperature for 4 hours, and then the temperature is further increased to 550°C and held at this temperature for 2 hours. After removal, the TiO2 composite oxide support doped with W and V is obtained.

[0045] S4, Grinding: Grind the composite oxide carrier obtained in S3 and sieve it to 40~60 mesh to obtain a refined composite oxide carrier; S5, Impregnation: The obtained composite oxide support is impregnated with an aqueous solution of palladium nitrate dihydrate with a concentration of 18.09 wt.% Pd at a solid-liquid ratio of 1 kg: 5 ml, with a Pd loading of 0.1 wt%. The equal-volume impregnation specifically includes: first, spraying the aqueous solution of palladium nitrate dihydrate onto the mixed powder obtained in S4 using an atomization method, then sealing and letting it stand for 1 hour, then mechanically stirring at 120 rpm for 15 minutes; then ultrasonically stirring at 160 rpm for 16 minutes; finally, reducing the stirring speed and ultrasonically stirring at 68 rpm for 10 minutes; and finally letting it stand for 24 hours after stirring.

[0046] S6, Calcination: After S5 impregnation, the material is dried in an oven at 95~105℃ for 11~13 hours, then placed in a muffle furnace and heated to 395~405℃ at a heating rate of 1.5~2.5℃ / min. Calcination at this temperature is carried out for 3.6~4.2 hours to obtain the catalyst product. Its pore size and specific surface area were measured, and the specific surface area was found to be 105.1 m². 2 / g, pore volume is 0.259cm³ 3 / g, with an average pore size of 8.5nm. Example 2

[0047] This embodiment illustrates an example of adding an in-situ hydroxyl activation step to Example 1. Based on Example 1, step S4' is further included after step S4 and before S5: S4', In-situ hydroxyl activation: The composite oxide support obtained in S4 is spread on a plasma reaction plate with a thickness of 2.5 mm. The plasma reaction plate is placed in the reaction chamber of a plasma cleaner, and the vacuum is evacuated to 15 Pa. Then, a mixed gas of Ar and O2 with a volume ratio of 4:1 is introduced. The amount of mixed gas introduced is such that the pressure in the reaction chamber is kept stable at 35 Pa. The pulse plasma parameters are set as follows: power 100 W, pulse duty cycle 10% (i.e., 1 s on and 9 s off), and total processing time 60 s. Then, the processed powder is taken out and stirred for 30 s to obtain the composite oxide support after in-situ hydroxyl activation.

[0048] Other settings are the same as in Example 1. Comparative Example 1

[0049] This comparative example illustrates a comparative experiment of Pd-loaded TiO2 support without W and V doping. The steps include: preparing a catalyst with a Pd loading of 0.1 wt% using an equal-volume impregnation method with TiO2. Specifically, the prepared support was ground and sieved to an average mesh size of 50 mesh; subsequently, the support was impregnated with an aqueous solution of palladium nitrate dihydrate (Pd(NO3)2·2H2O) as a precursor. After impregnation, the sample was dried in an oven at 100℃ for 12 h, and then calcined in a muffle furnace at a rate of 2℃ / min to 400℃ for 4 h. The resulting Pd / TiO2 catalyst was obtained. Comparative Example 2

[0050] This comparative example illustrates a comparative experiment of Pd loaded on a TiO2 support doped only with W. The preparation process is basically the same as in Example 1, except that the V doping process was not included, i.e., ammonium metavanadate was not added. All other proportions are the remaining proportions without vanadium doping, resulting in Pd / TiWO2. x catalyst. Comparative Example 3

[0051] This comparative example illustrates a comparative experiment for preparing a product with a W / V doping ratio of 7 moles and a V / V ratio of 3 moles. The preparation process is basically the same as in Example 1, except that step S2 is as follows: 12.5 parts by weight of TiO2 powder, 0.1 parts by weight of (NH4)2WO4 powder, and 0.1 parts by weight of NH4VO3 powder are mixed. The resulting powder is then placed in a ball mill and ball-milled at 300 rpm for 30 minutes. After milling, the powder is removed and heated to 60°C, stirred at this temperature for 6 hours, and then further heated to 80°C and dried for 12 hours. The resulting mixture was pressed into core blocks under a pressure of 10 MPa and a holding time of 1 min. The remaining TiO2 powder, (NH4)2WO4 powder, and NH4VO3 powder (totaling 15.9 parts by weight of TiO2 powder, 0.85 parts by weight of (NH4)2WO4 powder, and 0.82 parts by weight of NH4VO3 powder) were mixed. The resulting powder was then ball-milled at 300 rpm for 31 min, removed, heated to 60°C, stirred at this temperature for 6 h, and then further heated to 80°C for continuous drying for 12 h. The molar ratio of Ti:W:V in the resulting dried mixture was approximately 200:7:3.

[0052] The other steps are the same as in Example 1, and Pd / TiW7V3O is finally obtained. x catalyst. Comparative Example 4

[0053] This comparative example illustrates a comparative experiment for preparing a product with a W and V doping ratio of 5 moles of W and 5 moles of V. The preparation process is basically the same as in Example 1, except that step S2 is as follows: 13.5 parts by weight of TiO2 powder, 0.17 parts by weight of (NH4)2WO4 powder, and 0.07 parts by weight of NH4VO3 powder are mixed. The resulting powder is then placed in a ball mill and ball-milled at 300 rpm for 30 minutes. After milling, the powder is removed and heated to 60°C, stirred at this temperature for 6 hours, and then further heated to 80°C and dried for 12 hours. The obtained mixture was pressed into a core block under a pressure of 10 MPa and a holding time of 1 min. The remaining TiO2 powder, (NH4)2WO4 powder, and NH4VO3 powder (totaling 19.5 parts by weight of TiO2 powder, 1.73 parts by weight of (NH4)2WO4 powder, and 0.714 parts by weight of NH4VO3 powder) were mixed. The resulting powder was placed in a ball mill and ball-milled at 300 rpm for 31 min. After milling, the mixture was removed, heated to 60°C, stirred at this temperature for 6 h, and then further heated to 80°C and dried for 12 h. The molar ratio of Ti:W:V in the resulting dried mixture was approximately 200:5:5. Other steps were the same as in Example 1, finally yielding Pd / TiW5V5O x catalyst. Comparative Example 5

[0054] This comparative example illustrates a comparative experiment of Pd loaded on a TiO2 support doped only with V. The preparation process is basically the same as in Example 1, except that the W doping process was not included, i.e., ammonium tungstate was not added. All other proportions are the remaining proportions of the undoped tungsten, resulting in Pd / TiVO2. x catalyst.

[0055] Verification measurements were performed by comparative experiments on all catalysts in Example 1 and Comparative Examples 1-5, and the results were as follows: Figures 1 to 6 The comparative test results are shown. (As shown) Figure 1 As shown, the powders obtained in Example 1 and each comparative example are fine and uniform.

[0056] Validation of CO catalytic conversion at low temperatures: To evaluate the performance of the modified catalyst, CO catalytic oxidation experiments were first conducted under SO2-free atmosphere conditions. The test gas composition was 1 vol.% CO, 4 vol.% CO2, 16 vol.% O2, with the remainder being N2, and the space velocity was 60000 ml·g. -1 ·h -1 The catalyst dosage is 0.2g, such as Figure 2The figure shows the CO conversion performance of six catalysts as a function of temperature (the vertical axis represents CO conversion rate, i.e., CO catalytic oxidation rate). The CO conversion rate of all catalysts increases with increasing reaction temperature, and catalysts modified with different elements exhibit different performance trends. It can be seen that the Pd / TiWO3 catalyst in Comparative Example 2... x The ignition temperature of the catalyst was significantly increased, and the overall conversion curve shifted downward, indicating that the introduction of W had an inhibitory effect on the CO oxidation reaction; while the Pd / TiVO4 catalyst in Comparative Example 5... x The catalyst exhibited significantly enhanced low-temperature activity, with its conversion curve shifting upwards overall. 90 The temperature at which the conversion rate reaches 90% is significantly reduced, indicating that the introduction of V helps to improve the redox capacity of the catalyst. (Through...) Figure 2 It can be seen that the CO conversion performance of the catalyst gradually improves with the increase of V content, among which Pd / TiW3V7O x and Pd / TiVO x The optimal performance is achieved, reaching a conversion rate of 90% at relatively low temperatures and close to 100% at around 160°C. This demonstrates the superior performance of the Pd / TiW3V7O structure developed in this invention. x The catalyst can achieve 100% conversion at a relatively low temperature (around 160°C).

[0057] Comparative verification of sulfur resistance (the ability to resist sulfur poisoning): Due to the complexity of sintering flue gas and sulfur poisoning of the catalyst, SO2 in the flue gas reduces the catalytic performance and lifespan of the catalyst in practical CO oxidation applications. Therefore, to evaluate the catalyst's sulfur resistance, 0.2 g of the catalyst was tested in a balanced mixture containing 1 vol.% CO, 4 vol.% CO2, 16 vol.% O2, 100 ppm SO2, and the balance N2 (simulating sulfur-containing sintering flue gas). The results are as follows: Figure 3 and Figure 4 The results are shown. Figure 3 This is a schematic diagram showing the catalytic oxidation rate of CO at different temperatures. Figure 3 It can be seen that, due to the addition of sulfur-containing gas, the catalytic performance of all catalysts is relatively... Figure 2 All showed a decrease, while the temperatures at which CO conversion exceeded 90% all increased, particularly for Pd / TiO2 in Comparative Example 1 and Pd / TiWO2 in Comparative Example 2. x Comparative Example 3: Pd / TiW7V3O x Comparative Example 4: Pd / TiW5V5O x Comparative Example 5: Pd / TiVO x And Pd / TiW3V7O of Example 1 x T 90The values ​​increased by 40℃, 30℃, 22℃, 8℃, 15℃, and 2℃, respectively. It can be seen that the Pd / TiW3V7O of Example 1 of this invention... x The change in activity was relatively minimal, and the conversion rate remained stable at over 98% after 200℃, indicating that the Pd / TiW3V7O of Example 1 of this invention exhibited the best performance. x It exhibits higher resistance to SO2 poisoning. (Comparative Example 2: Pd / TiWO3) x Although the performance decreased under sulfur-containing atmosphere, the overall performance at 200℃ was higher than that of Pd / TiO2 in Comparative Example 1. This was mainly due to the doping of W, which increased the acidity of the catalyst and thus suppressed the adsorption of sulfur dioxide.

[0058] To evaluate the stability of the catalyst under prolonged SO2 exposure, a temperature of 220°C was fixed, and results were obtained by extending the exposure time at this temperature. Figure 4 The results shown Figure 4 This is a schematic diagram showing the CO oxidation activity of Example 1 and various comparative examples at different durations under a temperature condition of 220°C. Figure 4 It can be seen that the catalytic activity of all catalysts decreases to some extent as the reaction proceeds. When SO2 is introduced as the reactant gas, the CO conversion rate of Pd / TiO2 in Comparative Example 1 drops sharply to about 80%, and after 10 hours of reaction, it drops to about 70%. Other comparative examples also show varying degrees of decrease. However, within the 10-hour test time range, the Pd / TiW3V7O2 of Example 1 of this invention... x The CO conversion rate eventually stabilized at around 90%, demonstrating the best catalytic activity and sulfur resistance.

[0059] Comparative verification using XRD detection: XRD analysis was performed on all catalyst samples obtained in Example 1 and Comparative Examples 1-5, and the results were as follows: Figure 5 The results are shown. (Through) Figure 5 It can be seen that no Pd or PdO compounds were observed in any of the catalysts obtained in Example 1 and Comparative Examples 1-5. x The X-ray diffraction peaks of the species indicate that it is either Pd or PdO. xThe species were highly dispersed on the Pd / TiO2-based catalyst, without any aggregation in any one place. All catalysts exhibited typical TiO2 anatase phase at 2θ = 25.28, 36.95, 37.8, 38.6, 48, 53.9, 55.1, 62.1, and 66.7°, with sharp and strong diffraction peaks. This indicates that the anatase titanium dioxide selected in this invention is suitable for the gaseous environment of sintering flue gas and can effectively catalyze the oxidation of CO. No diffraction peaks for V2O5 and WO3 were present in any of the catalysts, indicating that V2O5 and WO3 were highly dispersed, meaning that the method steps of this invention can achieve such high dispersion. However, the intensity of these diffraction peaks was significantly weakened, and their width was larger than that of the Pd / TiO2 diffraction peaks. This is related to the reduction in TiO2 grain size, indicating that the introduction of V and W doping will reduce TiO2 crystallinity. Simultaneously, after doping with V₂O₅ and WO₃, the main peak of TiO₂ on the catalyst (2θ = 25.28°) gradually shifts to lower angles. This is because V₂O₅ and WO₃ are doped. 5+ and W 6+ With Ti 4+ The charge coordination mismatch generates oxygen vacancies, leading to lattice expansion. This corresponds to the improved CO catalytic oxidation and sulfur resistance effects achieved by doping with W and V in this invention. This demonstrates that the anatase titanium dioxide selected in this invention is suitable for the operating environment of the catalyst, and that doping with specific amounts of W and V can generate oxygen vacancies, thereby enhancing its CO acceptance capacity.

[0060] Comparative verification of SEM microstructure: To further investigate the microstructure characteristics of the catalyst, its morphology was characterized using SEM, and the results are as follows: Figure 6 As shown. (Through) Figure 6 It can be seen that all catalysts are composed of nanoparticles of different sizes, exhibiting a certain degree of aggregation. In contrast, the pure W-doped sample (Pd / TiWO3) in Comparative Example 2... x ), and its particle size is significantly increased (e.g. Figure 6 (b) shows that the introduction of W promotes particle migration and aggregation. In contrast, the pure V-doped sample (Pd / TiVO) in Comparative Example 5... x The effect on particle size is relatively small (e.g.) Figure 6 In example (f), the overall morphology is quite similar to that of Pd / TiO2 in Comparative Example 1, with only a slight decrease in dispersibility. As can be seen from Example 1 of the present invention, which is a W and V co-doped sample, Pd / TiW3V7O xThe particle distribution is relatively uniform, with an average particle size similar to that of Pd / TiO2 in Comparative Example 1, and no obvious particle growth or severe agglomeration is observed. This indicates that, under the ratio specified in this invention, the synergistic effect of V and W helps to suppress excessive particle growth, thereby maintaining the structural stability of the catalyst to a certain extent. Figure 6 As can be seen from (e) in the above, the average particle size in the microstructure of the CO emission reduction catalyst at the end of the sintering process is about 0.5~1.3µm, and more than 80% of the particles are smaller than 1.8µm.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst for reducing CO emissions at the end of sintering, characterized in that, Includes the following steps: S1, Raw material selection: Anatase TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are selected; S2, Mixing: Mix 19-20 parts by weight of TiO2 powder, 1.01-1.04 parts by weight of (NH4)2WO4 powder and 0.98-1.01 parts by weight of NH4VO3 powder selected in S1, and heat to 58-63°C. Stir evenly at this temperature, and then continue to heat to 75-85°C to continue drying to obtain a dry mixture. S3, calcined support: The dried mixture of S2 is placed in a calcination furnace and heated to 390~410℃. It is calcined at this temperature and then removed to obtain a TiO2 composite oxide support doped with W and V. S4, Grinding: Grind the composite oxide carrier obtained in S3 and sieve it to 40~60 mesh to obtain a refined composite oxide carrier; S5, Impregnation: The obtained composite oxide support is impregnated with an aqueous solution of palladium nitrate dihydrate with a concentration of 18.00~18.20 wt.% Pd in ​​equal volume, and the ratio is based on the amount of Pd loading to form 0.09~0.11 wt%. S6, Calcination: After S5 impregnation, the material is dried in an oven at 95~105℃, and then placed in a calcination furnace and heated to 395~405℃. After calcination at this temperature, the catalyst product is obtained.

2. The method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1, characterized in that, The mixing in step S2 is as follows: First, 13-14 parts by weight of TiO2 powder, 0.1-0.12 parts by weight of (NH4)2WO4 powder and 0.09-0.1 parts by weight of NH4VO3 powder are mixed and heated to 58-63°C. The mixture is stirred at this temperature and then heated to 75-85°C for continuous drying. The resulting mixture is then pressed to obtain a core block under a pressure of 9-11 MPa and a holding time of 0.9-1.1 min. Simultaneously, the remaining TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are mixed and heated to 58-63°C. The mixture is stirred at this temperature and then heated to 75-85°C for continuous drying. The resulting mixture is then coated on the outside of the core block and pressed in a pressing tank under a pressure of 14-16 MPa and a holding time of 1.5-2.5 min to obtain a dry mixture of a complete blank. The calcination support in step S3 is specifically as follows: the dried mixture of the complete blank from S2 is placed in a calcination furnace and heated to 390-410°C at a rate of 4-6°C / min. It is then calcined at this temperature for 3.8-4.5 hours, and then the temperature is further increased to 540-560°C. It is then held at this temperature for 1.5-2.5 hours. After removal, a TiO2 composite oxide support doped with W and V is obtained.

3. The method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1, characterized in that, In step S5, the equal volume impregnation specifically includes: first, spraying an aqueous solution of palladium nitrate dihydrate onto the mixed powder obtained in S4 using an atomization method, then sealing and letting it stand for 0.9~1.2h, then mechanically stirring at a speed of 80~150rpm; then ultrasonically stirring at a speed of 100~200rpm; finally reducing the stirring speed and ultrasonically stirring at a speed of 60~90rpm; and letting it stand after stirring is completed.

4. A method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1 or 2, characterized in that, In step S2, 13-14 parts by weight of TiO2 powder, 0.1-0.12 parts by weight of (NH4)2WO4 powder and 0.09-0.1 parts by weight of NH4VO3 powder are mixed. Then, the mixed powder is placed in a ball mill and ball-milled at a speed of 290-310 rpm for 25-35 minutes and then taken out. The remaining TiO2 powder, (NH4)2WO4 powder and NH4VO3 powder are mixed simultaneously. Then, the mixed powder is placed in a ball mill and ball-milled for 25 to 35 minutes at a speed of 290 to 310 rpm before being taken out.

5. A method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1 or 2, characterized in that, In step S2, the molar ratio of Ti:W:V in the dried mixture is 200:3:

7.

6. A method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1 or 2, characterized in that, In steps S3 and S6, the calcining furnace is a muffle furnace.

7. A method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1, 2, or 3, characterized in that, In step S5, the solid-liquid ratio of the composite oxide support to the aqueous palladium nitrate dihydrate is (0.8~1.1) kg: (4.5~5.5) ml.

8. A method for preparing a catalyst for CO emission reduction at the end of sintering according to claim 1 or 3, characterized in that, Step S4' is included after step S4 and before step S5: S4', In-situ hydroxyl activation: The composite oxide support obtained in S4 is spread evenly on a plasma reaction disk with a thickness of 2-3 mm. The plasma reaction disk is placed in the reaction chamber of a plasma cleaner, and the vacuum is evacuated to 10-20 Pa. Then, a mixed gas of Ar and O2 with a volume ratio of 3.5-4.5:1 is introduced. The amount of mixed gas introduced is enough to maintain the pressure in the reaction chamber at 30-40 Pa. The pulse plasma parameters are set as follows: power 95-105 W, pulse duty cycle 10%, and total processing time 58-65 s. Then, the processed powder is taken out and stirred for 25-35 s to obtain the composite oxide support after in-situ hydroxyl activation.

9. A catalyst for reducing CO emissions at the end of sintering, characterized in that, The catalyst for reducing CO emissions at the end of sintering is prepared by the preparation method described in any one of claims 1 to 8. In the microstructure of the catalyst for reducing CO emissions at the end of sintering, the average particle size is 0.5 to 1.3 µm, and more than 80% of the particles are smaller than 1.8 µm.

10. A catalyst for reducing CO emissions at the end of sintering according to claim 9, characterized in that, The catalyst has an average pore size of 6-10 nm and a specific surface area of ​​93-108 m². 2 / g, pore volume 0.23~0.29cm³ 3 / g.

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