A catalyst for removing CO and NMHC, its preparation method and application

Abstract

This invention relates to a catalyst for removing CO and NMHC, its preparation method, and its application, belonging to the field of flue gas purification technology. The catalyst comprises a porous TiO2 support, on which MnO2, CeO2, CuFe2O4, and La2O3 are loaded in a mass ratio of (15~25):(8~12):(10~18):(3~5). The catalyst achieves dual activity for CO oxidation and NMHC catalytic oxidation through transition metals and rare earth metals; and employs a gradient pore structure and surface modification technology to effectively suppress sulfate deposition on the catalyst surface.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification technology, specifically relating to a catalyst for removing CO and NMHC, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In addition to desulfurization and denitrification, the pollutant reduction process for coking flue gas also requires the removal of non-methane total hydrocarbons (NMHC). If the CO contained in coking flue gas is directly discharged into the atmosphere, it will also cause environmental pollution.

[0004] Existing technologies include dedicated catalysts for treating CO and NMHC separately, but these require separate reactors, preventing integrated treatment. Furthermore, the optimal activity of CO catalysts typically exceeds 300°C, which is incompatible with the temperature of coke oven flue gas, leading to reduced catalytic efficiency. Meanwhile, NMHC catalysts are prone to oxidation side reactions in sulfur-containing flue gas, generating sulfate particles that clog catalyst pores, causing sulfation poisoning and a rapid decline in NMHC conversion. Existing catalysts that synergistically catalyze the oxidation of CO and NH3 are not suitable for treating NMHC. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a catalyst for removing CO and NMHC, its preparation method, and its application. The catalyst integrates both CO oxidation and NMHC oxidation functions onto a single catalyst, and optimizes its active components and support structure, enabling it to operate efficiently within the actual temperature range of coke oven flue gas. Furthermore, it can be reasonably matched with existing denitrification systems, saving significant energy consumption.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, a catalyst for removing CO and NMHC includes a porous TiO2 support on which MnO2, CeO2, CuFe2O4 and La2O3 are loaded in a mass ratio of (15~25):(8~12):(10~18):(3~5).

[0007] Secondly, the preparation method of the above-mentioned catalyst for removing CO and NMHC includes the following steps: The porous TiO2 support was immersed in a mixed solution prepared with manganese and cerium sources and then dried to obtain the first impregnated material; The first impregnated material was placed in a sol prepared from a copper source and an iron source, and the second impregnated material was obtained by the sol-gel method. Then, after calcining in air at 550℃ for 4-6 hours, a 3-5 nm thick layer of La2O3 is deposited on the surface of the calcined product to obtain the catalyst to be reduced. The catalyst to be reduced is placed in a reducing atmosphere and treated at 300~350℃ for 4~6 hours to obtain the catalyst for removing CO and NMHC.

[0008] Thirdly, the aforementioned catalysts for removing CO and NMHC are applied in the treatment of coking flue gas.

[0009] The beneficial effects of this invention are as follows: 1. This invention proposes a catalyst for removing CO and NMHC. By using a predetermined ratio of transition metals and rare earth metals, it achieves dual activity in both CO oxidation and NMHC catalytic oxidation. As a single-stage bifunctional catalyst, it integrates the two purification processes, which originally required multiple independent units, into a single reactor, significantly simplifying the process flow. The use of a gradient pore structure and surface modification technology effectively inhibits sulfate deposition on the catalyst surface, significantly extending the catalyst lifetime.

[0010] 2. This invention uses processes such as impregnation-reduction and sol-gel methods to uniformly disperse active components with different functions on a carrier, avoiding the performance degradation problem caused by the separation of active components in traditional processes.

[0011] 3. The catalyst provided by this invention can achieve a CO and NMHC removal efficiency of over 90% within the typical temperature range of coke oven flue gas (180-250℃), without the need for additional heating equipment. Furthermore, during the removal of CO and NMHC, these two substances are catalytically oxidized to CO2 and H2O, respectively. The heat released in this process can raise the flue gas temperature by more than 50℃, thereby naturally meeting the temperature requirements of the subsequent denitrification process. There is no need to configure an additional hot air furnace, achieving the dual benefits of energy saving and environmental protection. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 The figures show the temperature-dependent catalytic oxidation CO activity curves of the catalysts in Examples 1 to 6 of the specific implementation methods.

[0014] Figure 2 The figures show the temperature-dependent activity curves of the catalysts used in Examples 1 to 6 of the specific implementation methods for catalytic oxidation of NMHC.

[0015] Figure 3 The curves showing the sulfation rate of the catalysts in Examples 1 to 6 of the specific implementation method as a function of temperature in an atmosphere containing SO2 are shown.

[0016] Figure 4 The figures show the temperature-dependent catalytic oxidation activity curves of the catalysts in Examples 2, 1 to 4, and the comparative examples in the specific implementation embodiments.

[0017] Figure 5 The specific implementation plan shows the activity curves of the catalysts in Example 2, Comparative Examples 1 to 4, and the comparative examples for catalytic oxidation of NMHC as a function of temperature.

[0018] Figure 6 The curves showing the sulfation rate of the catalysts in Example 2, Comparative Examples 1 to 4 in the specific implementation method as a function of temperature in an atmosphere containing SO2 are shown. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] One or more embodiments of the present invention provide a catalyst for removing CO and NMHC, comprising a porous TiO2 support, wherein the porous TiO2 support is loaded with MnO2, CeO2, CuFe2O4 and La2O3 in a mass ratio of (15~25):(8~12):(10~18):(3~5).

[0022] Among the above components, the porous TiO2 support provides structural support, MnO2 serves as the active center for CO oxidation, and CeO2 stores and releases oxygen; CuFe2O4 serves as the active site for NMHC cleavage, and La2O3 has the function of resisting sulfur poisoning protection, which can simultaneously achieve the removal of CO and NMHC.

[0023] Optionally, the La2O3 is a La2O3 protective film with a thickness of 3~5nm coating on the surface of the catalyst, thereby maximizing sulfur resistance and thermal stabilization of the core active sites.

[0024] Optionally, the mass ratio of the porous TiO2 support, MnO2, CeO2, CuFe2O4 and La2O3 is (40~64):(15~25):(8~12):(10~18):(3~5).

[0025] Optionally, the porous TiO2 support is loaded with MnO2, CeO2, CuFe2O4, La2O3 and Al2O3 in a mass ratio of (15~25):(8~12):(10~18):(3~5):1, wherein the Al2O3 serves as an inert isolation layer located inside the La2O3 protective film; the Al2O3 acts as a physical barrier, preventing the migration and agglomeration of active components at high temperatures (anti-sintering), and mitigating the mutual diffusion between the La2O3 layer and the internal active components.

[0026] Optionally, the mass ratio of the porous TiO2 support, MnO2, CeO2, CuFe2O4, La2O3, and Al2O3 is (40~64):(15~25):(8~12):(10~18):(3~5):1 Optionally, the porous TiO2 support has a gradient pore structure with a bimodal or multimodal pore size distribution. Specific features include: in terms of pore size distribution, the support simultaneously possesses mesopores (mainly 5-15 nm) and macropores (30-100 nm); in terms of porosity, the total porosity is not less than 65%; of which macropore porosity accounts for 20%-35% of the total porosity; in terms of pore structure morphology, the macropores are interconnected to form the main transport channels, and their pore walls are composed of a mesoporous network with a high specific surface area; the above structure forms a synergistic system of "rapid mass transfer through macropores - efficient reaction through mesopores".

[0027] One or more embodiments of the present invention provide a method for preparing the above-mentioned catalyst for removing CO and NMHC, comprising the following steps: S1. The TiO2 support is immersed in a mixed solution prepared from manganese and cerium sources and then dried to obtain the first impregnated material; S2. Place the first impregnated material in a sol prepared from a copper source and an iron source, and obtain the second impregnated material by the sol-gel method; S3. After calcining the second impregnated material at 500-550℃ for 4-6 hours, a 3-5 nm thick La2O3 layer is deposited on the surface of the calcined product to obtain the catalyst to be reduced. S4. Place the catalyst to be reduced in a reducing atmosphere and treat it at 300~350℃ for 4~6 hours to obtain the catalyst for removing CO and NMHC.

[0028] In the above process, active components with different functions are uniformly dispersed on the carrier through impregnation-reduction method, sol-gel method and other processes; and a La2O3 layer is prepared by deposition method. This surface protective film can effectively prevent sulfur poisoning of active sites; finally, a catalyst with catalytic activity is obtained by reduction.

[0029] Optionally, in S1, the porous TiO2 support is pretreated, including: calcining at 500~550℃ for 2~3h; forming anatase crystals; providing high specific surface area and optimal surface activity, while maintaining sufficient crystal structure stability.

[0030] Optionally, in S1, the manganese source includes one or more of manganese nitrate, manganese acetate, and manganese chloride; the cerium source includes one or more of cerium nitrate, cerium acetate, and cerium chloride; a mixed solution can be formed to prepare active sites by impregnation-reduction method.

[0031] Optionally, in S1, the total solute concentration of the mixed solution is 0.5~1.5 mol / L, and the mass-volume ratio of the porous TiO2 support to the mixed solution is 1g:(2~5)mL.

[0032] Optionally, in S2, the copper source includes one or more of copper nitrate, copper acetate, and copper chloride; the iron source includes one or more of ferric nitrate, ferric acetate, and ferric chloride; CuFe2O4 is generated in situ using the sol-gel method. CuFe2O4 is a copper ferrite and belongs to spinel-type composite metal oxides.

[0033] Optionally, in S2, the sol-gel method includes: using anhydrous ethanol as a solvent, acetylacetone as a chelating agent to control the hydrolysis rate, and concentrated nitric acid as a catalyst; dissolving the copper source and iron source in anhydrous ethanol, stirring and mixing with acetylacetone and concentrated nitric acid to obtain a stable and uniform reddish-brown Cu-Fe sol; then immersing the first impregnated material in the sol, stirring and aging at 50~70℃ for 2~4 hours, and then drying at 80~100℃ to obtain the second impregnated material.

[0034] Optionally, in S3, the second impregnated material is calcined in air at 300~350℃ for 2~3 hours, and then calcined in air at 550℃ for 4~6 hours; the second impregnated material is subjected to gradient calcination, with the temperature of 300~350℃ used to slowly remove organic matter and the temperature of 500~550℃ used for crystallization.

[0035] The calcination in S3 was carried out in an air atmosphere, where manganese / cerium nitrates decomposed, forming highly dispersed MnO2 / Mn2O3 and CeO2 particles on the TiO2 surface, thus initially constructing a "MnO2 / Ce ... xThe synergistic unit of "catalytic oxidation - CeO2 oxygen storage"; the copper-iron hydroxide / hydroxy oxide precursor of S2 sol-gel undergoes decomposition and solid-phase reaction at high temperature to generate spinel-type copper ferrite in situ, forming a stable NMHC cleavage active center.

[0036] Optionally, in S3, a 2-3 nm thick Al2O3 layer is first deposited on the surface of the calcined product as an inert isolation layer, and then a La2O3 layer is deposited on the surface of the inert isolation layer; the inner Al2O3 layer acts as a physical barrier, which can prevent the migration and agglomeration of active components at high temperatures (anti-sintering) and alleviate the mutual diffusion between the La2O3 layer and the internal active components.

[0037] Optionally, in S3, the deposition method includes the ALD deposition method; using a deposition method for surface modification is superior to the impregnation method, and can obtain a nanoscale deposition layer with high density and high uniformity.

[0038] Optionally, in S4, the catalyst to be reduced is subjected to a reduction treatment, wherein the reduction atmosphere includes a mixed atmosphere of N2 and H2 with a volume ratio of (9~4):1; during the reduction process, some metal oxides are moderately reduced, forming more oxygen vacancies and active sites.

[0039] Thirdly, the aforementioned catalysts for removing CO and NMHC are applied in the treatment of coking flue gas.

[0040] In the process of treating coking flue gas, MnO serves as the active center for CO oxidation, and CuFe2O4 serves as the active site for NMHC cleavage. CeO acts as an oxygen storage and release agent, La2O3 provides protection against sulfur poisoning, and TiO2 provides a stable support with a high specific surface area, ensuring that the active components are highly dispersed and do not agglomerate. CO and small-molecule NMHC (such as benzene and toluene) in the flue gas diffuse rapidly into the interior of the catalyst through macroporous channels, reaching the huge reaction interface composed of mesopores. CeO2 contains Ce 4+ / Ce 3+ Reversible redox pairs, their lattice oxygen (O 2- It exhibits high mobility, maintaining a constant high concentration of active oxygen species on the catalyst surface; the active oxygen species provided by CeO2 (or gaseous oxygen activated at the MnO2-CeO2 interface) rapidly interact with the active sites adsorbed on the MnO2 surface (such as MnO2, Ce ... 3+ / Mn 4+ CO reaction at sites; Cu in CuFe2O4 + / Cu 2+ and Fe 2+ / Fe 3+Redox pairs can efficiently activate CH bonds, "cracking" large NMHC molecules into smaller, more easily oxidized intermediate fragments (such as aldehydes and carboxylates). The intermediate products generated by cracking diffuse into the adjacent MnO2-CeO2 active region and are further oxidized to CO2 and H2O. At the same time, the catalytic cycle of CuFe2O4 also requires oxygen and benefits from the oxygen supply of CeO2. La2O3 is strongly basic and has a very strong thermodynamic affinity for acidic gas SO2. When SO2 diffuses to the catalyst surface, it preferentially reacts with the outermost La2O3 to generate La2(SO4)3, which is thermodynamically very stable.

[0041] When Al2O3 is added as an inert isolation layer, the inert isolation layer plays an anti-sintering role and can also act as a physical barrier to prevent the migration and agglomeration of active components at high temperatures (anti-sintering) and alleviate the mutual diffusion between the La2O3 layer and the internal active components.

[0042] Optionally, the coking flue gas is treated with the catalyst for removing CO and NMHC at 180~250℃, and then the treated flue gas is subjected to SCR denitrification. During the removal of CO and NMHC, the two are oxidized to CO2 and H2O. The heat released in this process can raise the flue gas temperature by more than 50℃, raising the temperature of the treated coking flue gas to the medium-high temperature range for denitrification. No additional hot air furnace is required, achieving the dual benefits of energy saving and environmental protection.

[0043] The present invention will be further described below with reference to specific embodiments.

[0044] Example 1 A catalyst for removing CO and NMHC, the preparation method of which includes: S1. Take a porous TiO2 support with a gradient pore structure and calcine it at 500℃ for 2 hours to form anatase crystals, completing the pretreatment. Dissolve 15g of Mn(NO3)2·4H2O (15 parts by mass as MnO2) and 12g of Ce(NO3)3·6H2O (8 parts by mass as CeO2) in 100mL of deionized water to prepare a mixed solution with a total solute concentration of approximately 0.6 mol / L. Immerse 50g of the pretreated porous TiO2 support in the mixed solution for 12 hours and then dry it to obtain the first impregnated material.

[0045] S2. Dissolve 10g Cu(NO3)2·3H2O and 30g Fe(NO3)3·9H2O (10 parts by mass, calculated as CuFe2O4) together in 200mL anhydrous ethanol. Stir magnetically in a 40℃ water bath until completely dissolved, forming a clear solution A. In another container, add 10mL acetylacetone and 5mL concentrated nitric acid to 50mL deionized water and mix thoroughly to form solution B. Slowly add solution B dropwise to solution A with vigorous stirring. After the addition is complete, continue stirring at 40℃ for 2 hours to obtain a stable and homogeneous reddish-brown Cu-Fe sol. Immerse the first impregnation obtained in S1 into this sol, stir slowly in a 60℃ water bath for 3 hours, allow to stand for aging for 12 hours, and then dry at 80℃ for 12 hours to obtain the second impregnation.

[0046] S3. The second impregnated material is calcined in air at 500°C for 5 hours to obtain the calcined product. A 3 nm thick La2O3 layer (3 parts by mass of La2O3) is deposited on the surface of the calcined product using ALD technology to obtain the catalyst to be reduced.

[0047] S4. The catalyst to be reduced is placed in a reducing atmosphere consisting of N2 and H2 in a volume ratio of 9:1 and reduced at 300°C for 4 hours to obtain a catalyst for removing CO and NMHC.

[0048] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, and La2O3 in the catalyst prepared in this embodiment was 15:8:10:3, with the remainder being a porous TiO2 support.

[0049] Example 2 A catalyst for removing CO and NMHC, the preparation method of which includes: The difference from Example 1 lies in the different proportions of active ingredients.

[0050] S1 contains 20g Mn(NO3)2·4H2O (20 parts by mass as MnO2) and 15g Ce(NO3)3·6H2O (10 parts by mass as CeO2). S2 contains 14g Cu(NO3)2·3H2O (calculated as 14 parts by mass as CuFe2O4) and 42g Fe(NO3)3·9H2O; In S3, the La2O3 deposition thickness is maintained at 3 nm (4 parts by mass based on La2O3). The remaining steps are the same as in Example 1.

[0051] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, and La2O3 in the catalyst prepared in this embodiment was 20:10:14:4.

[0052] Example 3 A catalyst for removing CO and NMHC, the preparation method of which includes: The difference from Example 1 lies in the different proportions of active ingredients.

[0053] S1 contains 25g Mn(NO3)2·4H2O (25 parts by mass as MnO2) and 18g Ce(NO3)3·6H2O (12 parts by mass as CeO2). S2 contains 18g Cu(NO3)2·3H2O (calculated as 18 parts by mass of CuFe2O4) and 54g Fe(NO3)3·9H2O; In S3, the La2O3 deposition thickness was adjusted to 5 nm (5 parts by mass of La2O3). The remaining steps were the same as in Example 1.

[0054] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, and La2O3 in the catalyst prepared in this embodiment was 25:12:18:5.

[0055] Example 4 The difference from Example 1 is that an Al2O3 inert isolation layer is added in step S3.

[0056] Specifically, the second impregnated material was subjected to gradient calcination in air (calcination at 300°C for 2 hours, followed by calcination at 500°C for 5 hours) to obtain the calcined product. Using ALD technology, a 2 nm thick Al2O3 layer (1 part by mass of Al2O3) was first deposited on the surface of the calcined product, and then a 3 nm thick La2O3 layer was deposited on top of it. The remaining steps were the same as in Example 1.

[0057] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, La2O3, and Al2O3 in the catalyst prepared in this embodiment was 15:8:10:3:1.

[0058] Example 5 The difference from Example 2 is that an Al2O3 inert isolation layer is added in step S3. The specific operation is the same as in Example 4.

[0059] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, La2O3, and Al2O3 in the catalyst prepared in this embodiment was 20:10:14:4:1.

[0060] Example 6 The difference from Example 3 is that an Al2O3 inert isolation layer is added in step S3. The specific operation is the same as in Example 4.

[0061] Testing revealed that the mass ratio of MnO2, CeO2, CuFe2O4, La2O3, and Al2O3 in the catalyst prepared in this embodiment was 25:12:18:5:1.

[0062] Comparative Example 1 The difference from Example 2 is that no manganese source is added in S1. Specifically, in S1, only 15g of Ce(NO3)3·6H2O is used to prepare the mixed solution (without Mn(NO3)2), and the remaining steps are the same as in Example 2. The resulting catalyst does not contain MnO2.

[0063] Comparative Example 2 The difference from Example 2 is that no cerium source is added in S1. Specifically, in S1, only 20g of Mn(NO3)2·4H2O is used to prepare a mixed solution (without Ce(NO3)3), and the remaining steps are the same as in Example 2. The resulting catalyst does not contain CeO2.

[0064] Comparative Example 3 The difference from Example 2 is that no copper or iron source is added in S2. Specifically, the addition of Cu(NO3)2·3H2O and Fe(NO3)3·9H2O is omitted in S2. The first impregnated material is directly immersed in anhydrous ethanol (containing acetylacetone and concentrated nitric acid) without copper or iron salts for sol-gel treatment. The remaining steps are the same as in Example 2. The resulting catalyst does not contain CuFe2O4.

[0065] Comparative Example 4 The difference from Example 2 is that no La2O3 layer is deposited in S3. Specifically, the second impregnated material is calcined and directly used as the catalyst to be reduced in step S4, and the remaining steps are the same as in Example 2. The resulting catalyst does not contain La2O3.

[0066] The above-mentioned catalysts for removing CO and NMHC are used in the treatment of coking flue gas.

[0067] The process includes the following steps: Simulating coke oven flue gas conditions, including: CO concentration of 8000 mg / m³, NMHC concentration of 500 mg / m³, SO2 concentration of 200 mg / m³, flue gas temperature of 220℃, and space velocity of 20000 h⁻¹. - ¹; Using the catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 4 for removing CO and NMHC, simulated coke oven flue gas was treated under the same conditions, and the conversion rates of each pollutant were shown in Table 1.

[0068] Table 1

[0069] In this process, flue gas at 220°C passes through a catalyst, and the catalyst is heated. When the catalyst in Example 6 reaches 170°C or above, it exhibits good catalytic activity. The CO and NMHC in the flue gas treated by the catalyst are significantly reduced, with CO conversion rate ≥98%, NMHC conversion rate ≥94%, and sulfation rate 0.6% / 100h.

[0070] The sulfation rate was determined through accelerated sulfur aging experiments in the laboratory and validated using various characterization data, resulting in a comprehensive evaluation index. Correspondingly, data for comparative catalysts were obtained. Table 1 shows that the catalyst of this invention achieves the activation temperature (T0) of CO and NMHC. 50 The temperature is significantly reduced from the typical ≥250℃ in the market to 170-200℃ (170℃ in Example 6); within the optimal operating window (e.g., 250℃), the CO conversion rate is ≥98% and the NMHC conversion rate is ≥95%, achieving near-complete removal of pollutants and meeting the most stringent ultra-low emission standards. This invention's catalyst achieves highly efficient simultaneous removal of CO and NMHC in the same reactor under the same operating conditions, overturning the traditional "series" multi-bed process, simplifying the system, and reducing investment and operating costs.

[0071] After treatment with the catalyst of Example 6, the flue gas temperature rises to 280~285℃, which is within the temperature range of medium-high temperature denitrification. Therefore, the equipment prepared based on the catalyst of Example 6 can be installed upstream of the NH3-SCR denitrification device in the existing denitrification system. The heated flue gas can be directly denitrified at medium and high temperatures without the need for an additional hot air furnace.

[0072] Depend on Figure 1 It can be seen that the CO conversion rate of Examples 1-6 increases rapidly with increasing temperature, reaching 68%-90% at 180℃, 88%-97% at 200℃, and 96%-99.5% at 250℃.

[0073] Example 6 showed the best performance, with a conversion rate of 76% at 160°C and 90% at 180°C, and the lowest activation temperature.

[0074] Depend on Figure 2 As can be seen, the NMHC conversion rate of Examples 1-6 steadily increased with increasing temperature, reaching 78%-92% at 200℃ and 88%-97% at 250℃.

[0075] Example 6 showed the best performance, with NMHC conversion rates of 78% at 180°C, 92% at 200°C, and 97% at 250°C.

[0076] Depend on Figure 3It can be seen that the sulfation rate of all samples increases with increasing temperature, which is consistent with the rule that high temperature promotes the conversion of SO2 to SO3 and the deposition of sulfate.

[0077] The sulfation rates of Examples 1-3 (without Al2O3) were at a moderate level, approximately 7.5-12.5% / 100h at 250°C.

[0078] The sulfation rate of Examples 4-6 (containing an Al2O3 inert isolation layer) was significantly reduced, reaching only 1.2-2.0% / 100h at 250℃, and the sulfur poisoning resistance was greatly improved. It remained at a low level (≤2.0% / 100h) within the working window of 180-250℃.

[0079] Depend on Figure 4 It can be seen that the CO conversion rate of Comparative Example 1 (without MnO2) was significantly lower than that of other samples at all temperatures, reaching only 45% at 250℃, proving that MnO2 is the core active site for CO oxidation.

[0080] Depend on Figure 5 It can be seen that the NMHC conversion rate of Comparative Example 2 (without CeO2) and Comparative Example 3 (without CuFe2O4) decreased significantly, with Comparative Example 3 at only 35% at 200℃, proving that the oxygen storage function of CeO2 and the cracking activity of CuFe2O4 are both indispensable for NMHC removal.

[0081] Depend on Figure 6 It is evident that the sulfation rate of Comparative Example 4 (without La2O3) was significantly higher than that of other samples at all temperatures, reaching as high as 28.0% / 100h at 250℃, demonstrating that the La2O3 protective film is key to resisting sulfur poisoning.

[0082] This invention innovates the traditional "series" purification process into a "single-stage synergistic" model, providing an economically feasible technical path for ultra-low emissions in the coking industry. It not only offers advantages in investment and operating costs but also enhances the inherent safety of the system from the design stage, solving several pain points in traditional processes, specifically including: 1) Reduced operating costs: Due to the low operating temperature, no additional heating is required, resulting in a significant reduction in energy consumption; at the same time, the simplified process reduces the number of equipment and maintenance work, thereby reducing long-term operating costs.

[0083] 2) Enhance the value of heat recovery: Low-temperature flue gas has less expansion, resulting in lower equipment costs. Furthermore, when the purified flue gas enters the waste heat boiler to recover heat, it will not cause blockage of the furnace tubes, thereby improving the boiler's thermal efficiency and steam output.

[0084] 3) Enhanced inherent safety: The integrated design eliminates the risks of flue gas reheating, catalyst blockage and poisoning caused by independent equipment layout in traditional processes, ensuring long-term stable operation.

[0085] 4) This invention fundamentally solves the problems of insufficient activity and easy poisoning of traditional catalysts when treating complex coking flue gas through innovative catalyst materials and structural design.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A catalyst for removing CO and NMHC, characterized in that, It includes a porous TiO2 support on which MnO2, CeO2, CuFe2O4 and La2O3 are loaded in a mass ratio of (15~25):(8~12):(10~18):(3~5).

2. The catalyst for removing CO and NMHC as described in claim 1, characterized in that, The mass ratio of the porous TiO2 support, MnO2, CeO2, CuFe2O4 and La2O3 is (40~64):(15~25):(8~12):(10~18):(3~5); Alternatively, the La2O3 may be a La2O3 layer coating the surface of the catalyst.

3. The catalyst for removing CO and NMHC as described in claim 1, characterized in that, The porous TiO2 support is loaded with MnO2, CeO2, CuFe2O4, La2O3 and Al2O3 in a mass ratio of (15~25):(8~12):(10~18):(3~5):1, and the Al2O3 is located inside the La2O3 protective film as an inert isolation layer. Alternatively, the mass ratio of the porous TiO2 support, MnO2, CeO2, CuFe2O4, La2O3 and Al2O3 is (40~64):(15~25):(8~12):(10~18):(3~5):

1.

4. The catalyst for removing CO and NMHC as described in claim 1, characterized in that, The porous TiO2 support has a gradient pore structure.

5. A method for preparing a catalyst for removing CO and NMHC as described in any one of claims 1-4, characterized in that, Includes the following steps: The TiO2 support was immersed in a mixed solution prepared with manganese and cerium sources and then dried to obtain the first impregnated material; The first impregnated material was placed in a sol prepared from a copper source and an iron source, and the second impregnated material was obtained by the sol-gel method. After calcining the second impregnated material at 500-550℃ for 4-6 hours, a 3-5 nm thick La2O3 layer is deposited on the surface of the calcined product to obtain the catalyst to be reduced. The catalyst to be reduced is placed in a reducing atmosphere and treated at 300~350℃ for 4~6 hours to obtain the catalyst for removing CO and NMHC.

6. The method for preparing the catalyst for removing CO and NMHC as described in claim 5, characterized in that, The porous TiO2 support is pretreated, including calcination at 500~550℃ for 2~3 hours; Alternatively, the manganese source may include one or more of manganese nitrate, manganese acetate, and manganese chloride; the cerium source may include one or more of cerium nitrate, cerium acetate, and cerium chloride. Alternatively, the total solute concentration of the mixed solution is 0.5~1.5 mol / L, and the mass-volume ratio of the porous TiO2 support to the mixed solution is 1g:(2~5)mL.

7. The method for preparing the catalyst for removing CO and NMHC as described in claim 5, characterized in that, The copper source includes one or more of copper nitrate, copper acetate, and copper chloride; the iron source includes one or more of ferric nitrate, ferric acetate, and ferric chloride. Alternatively, the sol-gel method includes: using anhydrous ethanol as a solvent, acetylacetone as a chelating agent to control the hydrolysis rate, and concentrated nitric acid as a catalyst; dissolving the copper and iron sources in anhydrous ethanol, stirring and mixing with acetylacetone and concentrated nitric acid to obtain a stable and uniform reddish-brown Cu-Fe sol; then immersing the first impregnated material in the sol, stirring and aging at 50~70℃ for 2~4 hours, and then drying at 80~100℃ to obtain the second impregnated material.

8. The method for preparing the catalyst for removing CO and NMHC as described in claim 5, characterized in that, The second impregnated material was calcined in air at 300-350°C for 2-3 hours, and then calcined in air at 550°C for 4-6 hours. Alternatively, a 2-3 nm thick Al2O3 layer can be deposited on the surface of the calcined product as an inert isolation layer, and then a La2O3 layer can be deposited on the surface of the inert isolation layer. Alternatively, the deposition method includes the ALD deposition method; Alternatively, the catalyst to be reduced may be subjected to a reduction treatment, wherein the reduction atmosphere comprises a mixed atmosphere of N2 and H2 in a volume ratio of (9~4):

1.

9. The application of a catalyst for removing CO and NMHC as described in any one of claims 1-4 in the treatment of coking flue gas.

10. The application of the catalyst for removing CO and NMHC as described in claim 9 in the treatment of coking flue gas, characterized in that, The coking flue gas was treated with the catalyst for removing CO and NMHC at 180~250℃, and then the treated flue gas was subjected to SCR denitrification.

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