A platinum group metal-v element doped hexagonal phase molybdenum / tungsten oxide-based sulfur-resistant selenium-resistant CO oxidation composite catalyst and a preparation method and application thereof

Abstract

The application discloses a platinum group metal-V group element doped hexagonal phase molybdenum / tungsten oxide-based sulfur-resistant selenium-resistant CO oxidation composite catalyst and a preparation method and application thereof, and belongs to the technical field of flue gas catalytic materials. The composite catalyst comprises a CO oxidation catalytic component and a poisoning-resistant functional component, and comprises or does not comprise a barium-based molecular sieve selenium-trapping carrier; the CO oxidation catalytic component is composed of TiO2 and a platinum group metal oxide active component; the poisoning-resistant functional component is a V group element doped hexagonal phase MO3, denoted as R-HMO3, R is at least one of V, Nb and Ta, H represents a hexagonal crystal phase, and M is at least one of Mo and W; and the barium-based molecular sieve selenium-trapping carrier is composed of a molecular sieve and a barium-based selenium-trapping component loaded on the surface and / or the channel of the molecular sieve. The catalyst has the characteristics of low noble metal consumption, clear functional partition, good poisoning-resistant stability and the like, and is suitable for CO catalytic oxidation of flue gas containing SO2, H2O and SeO2.

Description

Technical Field

[0001] This invention relates to the field of flue gas catalytic materials technology, and more specifically, to a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based anti-sulfur and anti-selenium CO oxidation composite catalyst, its preparation method and application. Background Technology

[0002] Flue gases emitted from industrial processes such as iron and steel sintering, coking, metallurgy, coal combustion, and waste incineration are typically characterized by low temperatures, complex compositions, and significant fluctuations in operating conditions. These flue gases may simultaneously contain CO, O2, SO2, H2O, dust, SeO2, and other oxygen-containing selenium species. Direct emission of CO without effective oxidation not only causes environmental pollution but also hinders the comprehensive utilization of combustible components and waste heat resources in the flue gas. Therefore, achieving low-temperature stable catalytic oxidation of CO under sulfur-, water-, and selenium-containing conditions is a crucial problem that needs to be solved in the field of complex industrial flue gas purification.

[0003] Platinum group metal (Pt, Pd, Ru, etc.) based catalysts exhibit good low-temperature CO oxidation activity, and TiO2 support can provide dispersion and interfacial anchoring sites for the active components of platinum group metal oxides. However, in actual flue gas treatment, SO2 can adsorb on the catalyst surface and form sulfite or sulfate species, covering active sites and hindering the migration of interfacial oxygen species; H2O can compete with CO, O2, and sulfur-containing species for adsorption; although selenium-containing species such as SeO2 are present in low concentrations, they may gradually deposit on noble metal active sites, support surfaces, or metal-support interfaces during long-term operation, altering the electronic state of noble metal active centers and weakening CO adsorption and activation capabilities. When SO2, H2O, and selenium-containing species coexist, they may also produce a superimposed poisoning effect, making it difficult to simultaneously achieve initial catalyst activity and long-term stability.

[0004] Existing technologies typically improve the performance of platinum group metal-based catalysts by increasing the loading of noble metals, introducing solid acid promoters, or employing impregnation, co-impregnation, and physical mixing. However, increasing the loading of noble metals increases material costs; and in materials obtained through ordinary impregnation or physical mixing, the contact mode and spatial distribution of functional components are difficult to control, easily leading to problems such as mutual shielding between CO oxidation active regions and anti-poisoning regions, insufficient interfacial bonding, or low utilization of functional components. Solid acid promoters can participate in redox reactions and surface acidity regulation, but when selenium-containing species interact directly with solid acid components, they consume or alter the original functional sites. Therefore, existing methods cannot simultaneously meet the comprehensive requirements of low-temperature CO oxidation, sulfur resistance, water resistance, and selenium resistance in catalysts, necessitating the development of a novel sulfur- and selenium-resistant CO oxidation composite catalyst. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based anti-sulfur and anti-selenium CO oxidation composite catalyst, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A platinum group metal-V element doped hexagonal molybdenum / tungsten oxide-based sulfur- and selenium-resistant CO oxidation composite catalyst, wherein the composite catalyst includes a CO oxidation catalytic component and an anti-poisoning functional component, and may or may not include a barium-based molecular sieve selenium-capturing support.

[0008] The CO oxidation catalytic component is composed of TiO2 and platinum group metal oxide active components; the anti-poisoning functional component is hexagonal MO3 doped with group V elements, denoted as R-HMO3, where R is at least one of V, Nb, and Ta, H represents hexagonal crystal phase, and M is at least one of Mo and W; the barium-based molecular sieve selenium-capturing support is composed of a molecular sieve and a barium-based selenium-capturing component loaded on the surface and / or pores of the molecular sieve.

[0009] Furthermore, the CO oxidation catalytic component is mixed with R-HMO3 to form an integrated co-doped catalyst, and the platinum group metal oxide active component is distributed on R-HMO3 and TiO2; or the CO oxidation catalytic component and R-HMO3 form a core-shell interface composite catalyst, and TiO2 coats or partially coats the outer surface of R-HMO3 to form a shell, and the platinum group metal oxide active component is loaded on the surface of the shell and / or the interface region between the shell and R-HMO3.

[0010] Furthermore, when a barium-based molecular sieve selenium-capturing support is introduced, the composite catalyst is formed by mixing one of an integrated co-doped structure catalyst or a core-shell interface composite structure catalyst with the barium-based molecular sieve selenium-capturing support, or the composite catalyst is formed by stacking one of an integrated co-doped structure catalyst or a core-shell interface composite structure catalyst with the barium-based molecular sieve selenium-capturing support, with the two layers separated by high-temperature resistant cotton.

[0011] Furthermore, the platinum group metal is at least one of Pt, Pd, and Ru, and the barium-based selenium-capturing component is barium carbonate.

[0012] A method for preparing a platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation includes a one-step hydrothermal co-doping method or a stepwise core-shell coating method, and an optional enhanced selenium-resistant composite step or an optional stacking step, wherein the enhanced selenium-resistant composite step or the stacking step is performed only when a barium-based molecular sieve selenium-capturing support is introduced.

[0013] Furthermore, the one-step hydrothermal co-doping preparation steps are as follows: M precursor, R precursor, Ti precursor and platinum group metal precursor are dissolved in deionized water, the pH value is adjusted to acidic and then a hydrothermal reaction is carried out. After the reaction, solid-liquid separation, washing, drying and calcination are performed to obtain an integrated co-doped catalyst.

[0014] Furthermore, the stepwise core-shell coating method preparation steps are as follows:

[0015] (1) Dissolve M precursor and R precursor in deionized water, adjust the pH value to acidic and carry out hydrothermal reaction. After the reaction, perform solid-liquid separation, washing, drying and calcination to obtain R-HMO3.

[0016] (2) R-HMO3 was dispersed in a dispersion medium, Ti precursor was added and the pH value was adjusted to alkaline. The mixture was stirred to deposit the Ti precursor on the surface of R-HMO3. After solid-liquid separation, the mixture was dried and calcined to obtain R-HMO3@TiO2 core-shell support.

[0017] (3) After mixing the platinum group metal precursor, the slow-release precipitant and the R-HMO3@TiO2 core-shell support, the mixture was aged. The product was then washed, dried and calcined to obtain a core-shell interface composite catalyst.

[0018] Furthermore, the molecular sieve is immersed in a barium precursor solution, and a carbonate precursor is added to react, so that the barium-based selenium-capturing component is deposited on the surface and / or in the pores of the molecular sieve. After the reaction, solid-liquid separation, drying, and calcination are performed to obtain a barium-based molecular sieve selenium-capturing carrier.

[0019] Furthermore, the enhanced selenium-resistant composite step involves mixing one of the integrated co-doped structure catalyst and the core-shell interface composite structure catalyst with a barium-based molecular sieve selenium-trapping support to obtain a composite catalyst.

[0020] Application of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for sulfur and selenium-resistant CO oxidation, wherein the composite catalyst is used for the catalytic oxidation treatment of CO in sulfur- and selenium-containing industrial flue gas.

[0021] In summary, the present invention has the following beneficial effects:

[0022] (1) Forming a composite structure that differs from ordinary impregnated or physically mixed catalysts, thereby enhancing the spatial synergistic effect between CO oxidation components and anti-poisoning functional components:

[0023] This invention does not simply involve ordinary impregnation of noble metals, Ti precursors, R precursors, and M precursors, or random mixing of their corresponding oxides. Instead, it sets up two schemes: an integrated co-doped structure of noble metals, TiO2, and R-HMO3, and a core-shell interface composite structure. In the integrated co-doped structure, platinum group metal oxide active components, TiO2, and R-HMO3 are mixed and distributed within the same composite particle. In the core-shell interface composite structure, R-HMO3 serves as the core or functional host, TiO2 forms a semi-encapsulated or fully encapsulated shell, and platinum group metal oxides are loaded on the surface of the TiO2 shell and / or the interface region between the TiO2 shell and R-HMO3. This establishes a contact interface between the two types of functional components, thereby improving the problems of uncontrollable component distribution, insufficient interface bonding, and mutual shielding of functional regions in ordinary impregnation or random mixing structures. It also reduces the direct shielding of CO oxidation active regions by anti-poisoning components and improves the interface stability under conditions of coexistence of SO2, H2O, and oxygen-containing selenium species.

[0024] (2) Improve the utilization efficiency of precious metal active components while taking into account material costs:

[0025] This invention uses platinum group metal oxides and TiO2 as CO oxidation catalytic components. Through integrated co-doped structure or core-shell interface composite structure design, the active components of platinum group metal oxides and the anti-poisoning functional components of TiO2 and R-HMO3 are made to form stable contact, which improves the dispersion and interface utilization efficiency of the active components of platinum group metal oxides. This allows the CO oxidation active region and the anti-poisoning functional region to cooperate with each other, thereby controlling the amount of precious metal precursors while taking into account CO catalytic oxidation performance and material cost.

[0026] (3) Provide optional independent barium-based molecular sieve second selenium-capturing support or unit to flexibly balance selenium-capturing capacity and initial activity:

[0027] This invention can further selectively introduce barium-based molecular sieves without platinum group metal oxide active components as a second selenium-capturing carrier or unit (only introduced as an enhancement component to supplement selenium-capturing capacity when the selenium-capturing capacity of the R-HMO3 anti-poisoning functional host is insufficient to meet the long-term operation requirements of specific selenium-containing conditions). The specific surface area and pore structure of the molecular sieve are used to disperse the barium-based selenium-capturing components and to allow selenium-containing species to preferentially contact the barium-based selenium-capturing region. At the same time, Mo and W in R-HMO3 can promote the decomposition and volatilization of selenium-containing species above 350°C, forming a complementary selenium removal pathway of "high-temperature volatilization assistance + low-temperature chemical capture" with barium-based selenium capture, further reducing the stable deposition of selenium-containing species on the catalyst surface and further improving the long-term adaptability of the composite catalyst to selenium-containing industrial flue gas.

[0028] (4) Functional zoning to achieve anti-poisoning zone, optional selenium capture zone and CO oxidation zone:

[0029] This invention utilizes R-HMO3 as the primary component for anti-poisoning regulation, platinum group metal oxides and TiO2 for CO catalytic oxidation, and optional barium-based molecular sieves for enhanced selenium capture. This forms functional regions that complement each other and can be flexibly configured as needed. By functional partitioning, the direct coverage of precious metal active sites by sulfur- and selenium-containing species is reduced, and the mutual consumption of functional sites caused by a single component simultaneously undertaking CO oxidation, anti-sulfurization, and selenium capture functions is avoided, thereby improving the utilization efficiency of each functional component.

[0030] (5) The material system has strong adjustability and a wide range of applications:

[0031] In this invention, M is at least one of Mo and W, R can be at least one of V, Nb, and Ta, and the precious metal is at least one of Pt, Pd, and Ru. The catalyst can be flexibly selected and combined according to different flue gas conditions and cost requirements to carry out customized catalyst design. It is especially suitable for complex industrial flue gas purification processes that need to take into account both low-temperature CO oxidation and adaptability to sulfur-containing, water-containing, and selenium-containing conditions.

[0032] (6) Applicable to CO catalytic oxidation treatment in complex low-temperature industrial flue gas:

[0033] The composite catalyst of this invention combines the CO oxidation catalytic function of platinum group metal oxides and TiO2, the anti-poisoning function of R-HMO3, and the optional barium-based molecular sieve to enhance selenium capture function. It is suitable for the catalytic oxidation treatment of CO in industrial flue gas (such as iron and steel sintering flue gas, coking flue gas, metallurgical flue gas, coal-fired flue gas, and waste incineration flue gas) containing CO, O2, SO2, H2O, and SeO2 and / or other oxygen-containing selenium species at 150-300℃. Attached Figure Description

[0034] Figure 1 This is a transmission electron microscope (TEM) image of V-HMoO3 prepared in Example 1;

[0035] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the catalyst obtained in Comparative Example 2. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0037] The platinum group metal-V element doped hexagonal molybdenum / tungsten oxide-based anti-sulfur and anti-selenium CO oxidation composite catalyst of the present invention includes a CO oxidation catalytic component and an anti-poisoning functional component, including or excluding a barium-based molecular sieve selenium-capturing support.

[0038] The anti-poisoning functional component is a hexagonal MO3 doped with group V elements, denoted as R-HMO3, where R is at least one of V, Nb, and Ta, H represents the hexagonal crystal phase, and M is at least one of Mo and W. R-HMO3 has a hexagonal MO3 crystal structure, a one-dimensional channel structure (pore size 0.25-0.60 nm), and a rod-like or short rod-like morphology (the length of the rod-like or short rod-like particles is 0.1-10 μm, and the diameter is 20-500 nm). The functions of R-HMO3 include: promoting the decomposition and desorption of SO2-derived sulfur species by regulating surface acidity and redox properties at the interface, and inhibiting the accumulation and deposition of sulfate on active sites; at temperatures above 350℃, M can promote the decomposition and volatilization of SeO2 and other oxygen-containing selenium species, and help reduce the stable adsorption and poisoning of selenium-containing species on the catalyst surface.

[0039] The CO oxidation catalytic component consists of TiO2 and platinum group metal oxide active components, where the platinum group metal is at least one of Pt, Pd, and Ru. The CO oxidation catalytic component is mixed with R-HMO3 to form an integrated co-doped catalyst structure, with the platinum group metal oxide active components distributed on both R-HMO3 and TiO2, and more concentrated on TiO2; or the CO oxidation catalytic component forms a core-shell interface composite catalyst structure with R-HMO3, where TiO2 coats or partially coats the outer surface of R-HMO3 to form a shell, and the platinum group metal oxide active components are supported on the shell surface and / or at the interface between the shell and R-HMO3.

[0040] The barium-based molecular sieve selenium-capturing support (as an optional second selenium-capturing support or pre-selenium-capturing unit) consists of a molecular sieve and a barium-based selenium-capturing component (preferably barium carbonate) supported on the surface and / or channels of the molecular sieve. The barium-based molecular sieve selenium-capturing support does not support platinum group metal oxide active components. The barium-based molecular sieve selenium-capturing support is introduced only when the selenium-capturing capacity of R-HMO3 is insufficient to meet the requirements of long-term operation, to supplement the selenium-capturing capacity. The composite catalyst is formed by mixing one of an integrated co-doped catalyst or a core-shell interface composite catalyst with the barium-based molecular sieve selenium-capturing support, or by stacking one of an integrated co-doped catalyst or a core-shell interface composite catalyst with the barium-based molecular sieve selenium-capturing support, with the two layers separated by high-temperature resistant cotton (i.e., one of the barium-based molecular sieve selenium-capturing support and the integrated co-doped catalyst is sequentially stacked with high-temperature resistant cotton and the barium-based molecular sieve selenium-capturing support).

[0041] The preparation method of the platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based anti-sulfur and anti-selenium CO oxidation composite catalyst of the present invention includes a one-step hydrothermal co-doping method or a stepwise core-shell coating method, and an optional enhanced anti-selenium composite step or an optional stacking step, wherein the enhanced anti-selenium composite step or the stacking step is performed only when a barium-based molecular sieve selenium-capturing support is introduced.

[0042] The one-step hydrothermal co-doping preparation method includes the following steps:

[0043] a1. Dissolve the M precursor, R precursor, Ti precursor, and platinum group metal precursor in deionized water and adjust the pH to acidic (pH = 0.5-2.0) to obtain a noble metal-Ti-RM mixed precursor solution; the ratio of the amounts of M precursor, R precursor, Ti precursor, and platinum group metal precursor is 1 mol:(0.35-1.05) mol:(0.37-0.81) mol:(0.05-0.12) mol;

[0044] a2. Place the noble metal-Ti-RM mixed precursor solution in a hydrothermal reactor and carry out a hydrothermal reaction at 160-180℃ for 14-24 hours.

[0045] a3. After the reaction, the system is subjected to solid-liquid separation. The solid product is washed, dried at 80-120℃, and then calcined (calcined at 300-400℃ for 1-5 hours, or at 500-600℃ for 2-6 hours) to obtain an integrated co-doped catalyst.

[0046] The step-by-step core-shell coating method includes the following steps:

[0047] b1. Dissolve the M precursor and R precursor in deionized water, adjust the pH to acidic (pH=0.5-2.0), and carry out a hydrothermal reaction at 160-180℃ for 14-24h. After the reaction, perform solid-liquid separation. The solid product is washed, dried at 80-120℃, and then calcined (calcined at 300-400℃ for 1-5h, calcined at 500-600℃ for 2-6h) to obtain R-HMO3.

[0048] b2. Disperse R-HMO3 in a dispersion medium (preferably ethanol), add Ti precursor and adjust the pH to alkaline (pH=8-9), stir at room temperature for 6-12 h to allow Ti precursor to deposit on the surface of R-HMO3, separate the solid product from the liquid and dry the product (80-120℃), and then calcine at 450-550℃ for 2-6 h to obtain R-HMO3@TiO2 core-shell support;

[0049] b3. The platinum group metal precursor, the slow-release precipitant, and the R-HMO3@TiO2 core-shell support are mixed, ultrasonically treated (10-60 min), and aged at 60-90℃ for 1-4 h. The product is washed, dried at 80-120℃, and calcined at 500-600℃ for 2-6 h to obtain the core-shell interface composite catalyst. The molar ratio of M precursor, R precursor, Ti precursor, platinum group metal precursor, and slow-release precipitant is 1:(0.35-1.05):(0.37-0.81):(0.05-0.12):(1.00-2.40).

[0050] The preparation method of barium-based molecular sieve selenium-capturing support is as follows: the molecular sieve is immersed in a barium precursor solution, and a carbonate precursor is added to deposit the barium-based selenium-capturing component on the surface and / or pores of the molecular sieve. After solid-liquid separation, the solid is dried at 80-120℃ for 6-12h, and then calcined at 350-450℃ for 2-5h to obtain the barium-based molecular sieve selenium-capturing support; the molar ratio of barium precursor to carbonate precursor is 1:(1-3).

[0051] An optional enhanced selenium-resistant composite step is to mix one of the integrated co-doped structure catalyst and the core-shell interface composite structure catalyst with a barium-based molecular sieve selenium-capturing support at a mass ratio of (1-5):1 to obtain a composite catalyst.

[0052] The stacking process is as follows: one of the integrated co-doped structure catalyst and the core-shell interface composite structure catalyst is stacked with a barium-based molecular sieve selenium-capturing support, with the two layers separated by high-temperature resistant cotton, to form a composite catalyst.

[0053] When performing CO catalytic oxidation, if the composite catalyst does not introduce a barium-based molecular sieve selenium-capturing support or introduces a barium-based molecular sieve selenium-capturing support through an enhanced anti-selenium composite step, the sulfur- and selenium-containing industrial flue gas is brought into contact with the composite catalyst and treated at 150-300℃. If the composite catalyst introduces a barium-based molecular sieve selenium-capturing support in a stacked configuration, the sulfur- and selenium-containing industrial flue gas first flows through the upstream barium-based molecular sieve selenium-capturing support, then flows through the downstream integrated co-doped catalyst or core-shell interface composite catalyst, and CO catalytic oxidation is performed at 150-300℃.

[0054] In the preparation of the above composite catalyst, the M precursor is at least one of ammonium heptamolybdate tetrahydrate, ammonium molybdate, ammonium paramolybdate, sodium molybdate, sodium tungstate, ammonium metatungstate, and ammonium paratungstate; the R precursor is at least one of ammonium metavanadate, vanadium oxalate, vanadium oxychloride, vanadium oxysulfate, niobium oxalate, niobium chloride, niobium pentoxide, tantalum ethoxide, and tantalum chloride; the Ti precursor is at least one of tetrabutyl titanate, isopropyl titanate, titanium sulfate, titanium oxysulfate, and titanium tetrachloride; the platinum group metal precursor is at least one of chloroplatinic acid, potassium chloroplatinate, platinum nitrate, platinum acetylacetonate, palladium nitrate, palladium acetate, palladium chloride, palladium acetylacetonate, ruthenium trichloride, ruthenium acetate, and ruthenium acetylacetonate. The slow-release precipitant is at least one of urea, hexamethylenetetramine, and ammonium bicarbonate. The molecular sieve is at least one of SBA-15 molecular sieve, MCM-41 molecular sieve, 13X molecular sieve, Y-type molecular sieve, β-molecular sieve, ZSM-5 molecular sieve, and chalcogenide molecular sieve. The barium precursor is at least one of barium nitrate, barium acetate, barium chloride, and barium hydroxide, and the solvent for the barium precursor solution is deionized water; the carbonate precursor is at least one of ammonium carbonate, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate.

[0055] The composite catalyst of this invention features low precious metal content, tunable composite structure, clear functional partitioning, and high interface utilization efficiency. Platinum group metal oxides and TiO2 provide CO low-temperature oxidation activity, while hexagonal MO3 doped with group V elements plays a role in anti-poisoning regulation. V and Mo / W synergistically promote the decomposition and removal of sulfur species, while Mo and W promote the decomposition and volatilization of selenium-containing species above 350℃. Optional barium-based molecular sieves form independent selenium-capturing regions (introduced only when needed), which can reduce the coverage and poisoning of precious metal active sites by sulfur- and selenium-containing species. This is beneficial to improving the low-temperature CO oxidation stability of the catalyst under conditions of coexistence of SO2, H2O, and oxygen-containing selenium species, making it suitable for the catalytic oxidation treatment of CO in complex industrial flue gas from steel sintering, coking, metallurgy, coal combustion, and waste incineration.

[0056] The composite catalyst of this invention can be used for the catalytic oxidation treatment of CO in sulfur- and selenium-containing industrial flue gas. The sulfur- and selenium-containing industrial flue gas contains CO, O2, SO2, H2O, and SeO2 and / or oxygen-containing selenium species, and the catalytic oxidation reaction temperature for CO is 150-300℃. Furthermore, the sulfur- and selenium-containing industrial flue gas includes sintering flue gas from iron and steel production, coking flue gas, metallurgical flue gas, coal-fired flue gas, waste incineration flue gas, or other low-temperature industrial flue gas containing CO, SO2, and SeO2.

[0057] The preferred embodiments are as follows:

[0058] Example 1

[0059] This embodiment employs a stepwise core-shell coating method to prepare a V-HMoO3@Pd / TiO2 core-shell interface composite catalyst, and further enhances its selenium resistance through composite enhancement to obtain a platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst resistant to sulfur and selenium CO oxidation. The specific steps are as follows:

[0060] S1. Weigh 2.4717 g of ammonium heptamolybdate tetrahydrate and 0.1638 g of ammonium metavanadate, dissolve them in 80 mL of deionized water, stir until evenly dispersed, and adjust the pH of the solution to 1.0 with dilute nitric acid. Transfer the obtained precursor solution to a polytetrafluoroethylene-lined hydrothermal reactor and react it hydrothermally at 180 °C for 18 h. After the reaction is complete, allow it to cool naturally, centrifuge to separate the solid product, wash it with deionized water, dry it at 105 °C, and then calcine it at 350 °C for 3 h in air atmosphere, followed by calcination at 550 °C for 4 h to obtain V-HMoO3 (TEM image see [link]). Figure 1 ).

[0061] S2. The obtained V-HMoO3 was dispersed in 50 mL of ethanol, 0.4193 g of tetrabutyl titanate was added, the pH was adjusted to 8.5 with ammonia, and the mixture was stirred at room temperature for 12 h. The solid product was separated by centrifugation and dried at 105 °C, and then calcined at 500 °C for 4 h in air atmosphere to obtain V-HMoO3@TiO2 core-shell support.

[0062] S3. Weigh 0.6667 g of palladium nitrate solution and add it to 30 mL of deionized water, wherein the mass of Pd elemental in the palladium nitrate solution is 0.1 g; then add 1.1287 g of urea as a slow-release precipitant. Subsequently, add the obtained V-HMoO@TiO2 core-shell support, sonicate for 30 min, and then age at 80 °C for 2 h. The resulting product is washed, dried at 105 °C, and calcined at 550 °C for 4 h to obtain the V-HMoO3@Pd / TiO2 core-shell interface composite catalyst.

[0063] S4. Weigh 1.0 g of SBA-15 molecular sieve (purchased from Shanghai Yuanye Biotechnology Co., Ltd., catalog number S28269), add it to 20 mL of deionized water, and sonicate for 20 min. Weigh 0.3310 g of barium nitrate, dissolve it in 10 mL of deionized water, and slowly add it to the above SBA-15 dispersion, stirring at room temperature for 2 h. Then weigh 0.1200 g of ammonium bicarbonate, dissolve it in 10 mL of deionized water, and slowly add it dropwise to the above mixture, continuing to stir for 2 h. After solid-liquid separation, the system is dried at 100 °C for 10 h, and then calcined at 400 °C for 3 h to obtain BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support.

[0064] S5. Weigh 5.0g of the obtained V-HMoO3@Pd / TiO2 core-shell interface composite catalyst and 1.0g of the obtained BaCO3 / SBA-15 barium-based molecular sieve selenium-capturing support, and mechanically mix them evenly to obtain the final composite catalyst.

[0065] Example 2

[0066] This embodiment employs a one-step hydrothermal co-doping method to prepare a Pd-Ti-V-HMoO3 integrated co-doped catalyst, and then enhances its selenium resistance through composite preparation to obtain a platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst resistant to sulfur and selenium CO oxidation. The specific steps are as follows:

[0067] S1. Weigh 2.4717g ammonium heptamolybdate tetrahydrate, 0.1638g ammonium metavanadate, 0.4193g tetrabutyl titanate, and 0.6667g palladium nitrate solution, and dissolve them in 80mL of deionized water. The palladium nitrate solution contains 0.1g of elemental Pd. Adjust the pH of the mixed precursor solution to 1.0 with dilute nitric acid. Transfer the resulting precursor solution to a polytetrafluoroethylene-lined hydrothermal reactor and react it hydrothermally at 180℃ for 18h. After the reaction, allow it to cool naturally, centrifuge to separate the solid product, wash it with deionized water, dry it at 105℃, and then calcine it at 350℃ for 3h in air atmosphere, followed by calcine at 550℃ for 4h to obtain a Pd-Ti-V-HMoO3 integrated co-doped catalyst.

[0068] S2. Prepare BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support according to step S4 of Example 1.

[0069] S3. Weigh 5.0g of the Pd-Ti-V-HMoO3 integrated co-doped catalyst obtained in step S1 and 1.0g of the BaCO3 / SBA-15 barium-based molecular sieve selenium-capturing support obtained in step S2, and mechanically mix them evenly to obtain the final composite catalyst.

[0070] Example 3 (using a layered filling method)

[0071] S1. Prepare V-HMoO3@Pd / TiO2 core-shell interface composite catalyst according to steps S1 to S3 of Example 1.

[0072] S2. Prepare BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support according to step S4 of Example 1.

[0073] S3, Layered Packing: Weigh 1.0g of the BaCO3 / SBA-15 barium-based molecular sieve selenium-capturing support obtained in step S2 as the upstream selenium-capturing layer, and weigh 5.0g of the V-HMoO3@Pd / TiO2 core-shell interface composite catalyst obtained in step S1 as the downstream selenium-capturing and CO oxidation catalyst layer. The layers are packed in a fixed-bed reactor, with the two layers physically separated by 0.5cm thick aluminum silicate fiber cotton. This allows the sulfur- and selenium-containing industrial flue gas to first flow through the BaCO3 / SBA-15 barium-based molecular sieve selenium-capturing support, and then through the core-shell interface composite catalyst.

[0074] Comparative Example 1

[0075] The V-HMoO3@Pd / TiO2 core-shell interface composite catalyst was prepared according to steps S1 to S3 of Example 1, i.e., steps S4 and S5 of Example 1 were omitted.

[0076] Comparative Example 2

[0077] The Pd-Ti-V-HMoO3 integrated co-doped catalyst was prepared according to step S1 of Example 2 (XRD pattern shown). Figure 2 (i.e., steps S2 and S3 of Example 2 are omitted).

[0078] Comparative Example 3

[0079] V-HMoO3 (prepared according to step S1 of Example 1), Pd / TiO2 catalyst (prepared according to step S3 of Example 1, except that the V-HMoO@TiO2 core-shell support was replaced with TiO2, which was purchased from Merck Life Sciences, catalog number 232033), and BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support (prepared according to step S4 of Example 1) were prepared separately. Then, the three were mechanically mixed evenly (4.5 g of V-HMoO3, 0.5 g of Pd / TiO2 catalyst, and 1.0 g of BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support) to obtain the final catalyst.

[0080] Comparative Example 4

[0081] Pd / TiO2 catalyst (method as in Comparative Example 3) and BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support (prepared according to step S4 of Example 1) were prepared separately. Then, the two were mechanically mixed evenly (5g of Pd / TiO2 catalyst and 1g of BaCO3 / SBA-15 barium-based molecular sieve selenium-trapping support) to obtain the final catalyst.

[0082] Comparative Example 5

[0083] The catalyst was prepared according to Example 1, except that ammonium metavanadate was not added in step S1.

[0084] Comparative Example 6

[0085] The catalyst was prepared according to Example 1, except that ammonium heptamolybdate tetrahydrate was not added in step S1.

[0086] Comparative Example 7

[0087] The catalyst was prepared according to Example 1, except that step S3 was omitted, and 5g of the V-HMoO3@TiO2 core-shell support obtained in step S2 and 1.0g of BaCO3 / SBA-15 barium-based molecular sieve selenium-capturing support were mechanically mixed evenly.

[0088] The specific surface area, average pore size, grain size, and cell volume of the final catalysts obtained in the above embodiments and comparative examples are shown in Table 1.

[0089] The testing method was as follows: Texture properties were determined by N2 physisorption using an Anton Pal Autosorb IQ analyzer (USA). Before analyzing the BET surface area and BJH pore size distribution, the sample was degassed at 220°C for 1 hour. The specific surface area and average pore size of the catalyst were then measured. Powder X-ray diffraction patterns were recorded using Cu Kα radiation (λ=0.15418nm, 40kV, 40mA) on an X-ray diffractometer. The patterns were then processed using MDI Jade 6 software, and the grain size was calculated using the Scherrer formula. The unit cell volume was calculated based on the XRD results.

[0090] Table 1

[0091]

[0092] Application examples

[0093] The performance of the final catalysts obtained in the above embodiments and comparative examples was tested, and the results are shown in Table 2.

[0094] The experimental conditions for testing the catalytic oxidation performance of CO in sulfur-free and selenium-free simulated flue gas are as follows: the initial concentrations of each gas are controlled by mass flow meter as follows: CO 4000ppm, O2 5vol%, H2O 10vol%, N2 as balance gas; the total gas flow rate is 700mL / min, the catalyst dosage is 0.6mL, and the initial activity test temperature range for CO catalytic oxidation is 100-550℃.

[0095] The experimental conditions for sulfur resistance stability testing are as follows: the test temperature is 225℃, the initial concentrations of each gas are CO 4000ppm, O2 5vol%, H2O 10vol%, SO2 400ppm, and N2 is the equilibrium gas; the total gas flow rate is 700mL / min, and the catalyst dosage is 0.6mL.

[0096] The experimental conditions for selenium resistance stability testing were as follows: the test temperature was 225℃, the initial concentrations of each gas were CO 4000ppm, O2 5vol%, H2O 10vol%, SeO2 15ppm, N2 was the equilibrium gas, the total gas flow rate was 700mL / min, and the catalyst dosage was 0.6mL. SO2 and SeO2 were introduced as follows: solid SeO2 was placed in an independent isothermal generating unit and heated to 300℃ to sublimate and generate gaseous SeO2. N2 was used as the carrier gas to carry the volatilized gaseous SeO2, which was then mixed with CO, O2, H2O, and the equilibrium gas through a heated delivery pipeline and continuously introduced into the fixed-bed reactor. By adjusting the temperature of the SeO2 isothermal generating unit, the carrier gas flow rate, and the dilution gas flow rate, the concentration of SeO2 entering the fixed-bed reactor was stably maintained at 15ppm.

[0097] The sulfur and selenium resistance stability test conditions were as follows: the test temperature was 225℃, the initial concentrations of each gas were CO 4000ppm, O2 5vol%, H2O 10vol%, SO2 400ppm, SeO2 15ppm, N2 as the balance gas, the total gas flow rate was 700mL / min, and the catalyst dosage was 0.6mL. The introduction methods of SO2 and SeO2 were consistent with those in the selenium resistance stability test.

[0098] The formula for calculating the catalytic oxidation efficiency of CO is η(CO)=(C1-C2) / C1×100%, where C1 and C2 are the inlet and outlet concentrations of CO, respectively, which are obtained by measuring the flue gas analyzer.

[0099] Table 2

[0100]

[0101] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation, characterized in that, The composite catalyst includes a CO oxidation catalytic component and an anti-poisoning functional component, and may or may not include a barium-based molecular sieve selenium-capturing support. The CO oxidation catalytic component is composed of TiO2 and platinum group metal oxide active components; the anti-poisoning functional component is hexagonal MO3 doped with group V elements, denoted as R-HMO3, where R is at least one of V, Nb, and Ta, H represents hexagonal crystal phase, and M is at least one of Mo and W; the barium-based molecular sieve selenium-capturing support is composed of a molecular sieve and a barium-based selenium-capturing component loaded on the surface and / or pores of the molecular sieve.

2. The platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation as described in claim 1, characterized in that, The CO oxidation catalytic component is mixed with R-HMO3 to form an integrated co-doped catalyst, and the platinum group metal oxide active component is distributed on R-HMO3 and TiO2; or the CO oxidation catalytic component and R-HMO3 form a core-shell interface composite catalyst, and TiO2 coats or partially coats the outer surface of R-HMO3 to form a shell, and the platinum group metal oxide active component is loaded on the surface of the shell and / or the interface region between the shell and R-HMO3.

3. The platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 2, characterized in that, When a barium-based molecular sieve selenium-capturing support is introduced, the composite catalyst is formed by mixing one of an integrated co-doped structure catalyst or a core-shell interface composite structure catalyst with the barium-based molecular sieve selenium-capturing support, or the composite catalyst is formed by stacking one of an integrated co-doped structure catalyst or a core-shell interface composite structure catalyst with the barium-based molecular sieve selenium-capturing support, with the two layers separated by high-temperature resistant cotton.

4. The platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 1, characterized in that, The platinum group metal is at least one of Pt, Pd, and Ru, and the barium-based selenium-capturing component is barium carbonate.

5. A method for preparing a platinum group metal-group V element-doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to any one of claims 1-4, characterized in that, It includes a one-step hydrothermal co-doping method or a stepwise core-shell coating method for preparation, as well as an optional enhanced selenium-resistant composite step or an optional stacking step, wherein the enhanced selenium-resistant composite step or the stacking step is performed only when a barium-based molecular sieve selenium-capturing support is introduced.

6. The preparation method of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 5, characterized in that, The one-step hydrothermal co-doping method involves dissolving M precursor, R precursor, Ti precursor and platinum group metal precursor in deionized water, adjusting the pH to acidic, and then carrying out a hydrothermal reaction. After the reaction, solid-liquid separation, washing, drying and calcination are performed to obtain an integrated co-doped catalyst.

7. The preparation method of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 5, characterized in that, The step-by-step core-shell coating method preparation steps are as follows: (1) Dissolve M precursor and R precursor in deionized water, adjust the pH value to acidic and carry out hydrothermal reaction. After the reaction, perform solid-liquid separation, washing, drying and calcination to obtain R-HMO3. (2) R-HMO3 was dispersed in a dispersion medium, Ti precursor was added and the pH value was adjusted to alkaline. The mixture was stirred to deposit the Ti precursor on the surface of R-HMO3. After solid-liquid separation, the mixture was dried and calcined to obtain R-HMO3@TiO2 core-shell support. (3) After mixing the platinum group metal precursor, the slow-release precipitant and the R-HMO3@TiO2 core-shell support, the mixture was aged. The product was then washed, dried and calcined to obtain a core-shell interface composite catalyst.

8. The preparation method of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 5, characterized in that, Molecular sieves are immersed in a barium precursor solution, and carbonate precursors are added to react, causing the barium-based selenium-capturing component to deposit on the surface and / or in the pores of the molecular sieve. After the reaction, solid-liquid separation, drying, and calcination are performed to obtain a barium-based molecular sieve selenium-capturing carrier.

9. The preparation method of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for resisting sulfur and selenium CO oxidation according to claim 5, characterized in that, The enhanced selenium-resistant composite step is as follows: one of the integrated co-doped structure catalyst and the core-shell interface composite structure catalyst is mixed with a barium-based molecular sieve selenium-capturing support to obtain a composite catalyst.

10. The application of a platinum group metal-group V element doped hexagonal molybdenum / tungsten oxide-based composite catalyst for sulfur and selenium oxidation resistance according to any one of claims 1-4, characterized in that, The composite catalyst is used for the catalytic oxidation treatment of CO in sulfur- and selenium-containing industrial flue gas.

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