A synergistic removal of NO x Three-way catalysts for toluene, their preparation methods and applications

Abstract

This invention discloses a synergistic method for removing NO x This paper describes a three-way catalyst for toluene, its preparation method, and its application, belonging to the field of industrial waste gas treatment technology. The catalyst is prepared by hydrothermal synthesis of Ce, Ti, and Mn-based metal-organic frameworks (MOFs), which are then used as sacrificial templates and calcined in air to obtain Ce1Ti. x A Mn₂O / MOFs ternary catalyst, wherein 1 ≤ x ≤ 5. This invention also discloses a method for preparing this catalyst, including steps such as solution preparation, stirring, hydrothermal reaction, vacuum drying, and high-temperature calcination. This catalyst can achieve NO reduction at 240-300℃. x It can be used in synergistic removal with toluene, with removal efficiencies of over 80%. It has the advantages of simple preparation process, low raw material cost, high catalytic activity, good stability and no secondary pollution. It is suitable for the simultaneous purification of nitrogen oxides and volatile organic compounds in industrial stationary source flue gas.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste gas treatment technology, specifically relating to a method for synergistic removal of NO. x Three-way catalysts for toluene, their preparation methods, and applications. Background Technology

[0002] Nitrogen oxides (NOx) emitted from industrial stationary sources x NOx and volatile organic compounds (VOCs) are key precursors to acid rain, photochemical smog, haze, and PM2.5 pollution, posing a serious threat to the ecological environment and human health. With increasingly stringent environmental standards, achieving NOx emission reduction in a single reactor is becoming increasingly challenging. x Synergistic catalytic technology for simultaneous low-temperature purification of VOCs has become a research hotspot and core technology direction in the field of air pollution control. Selective catalytic reduction (NO3) SCR) is currently NO x Catalytic oxidation is the most effective means of eliminating VOCs, which is the mainstream technology for treatment. However, the reaction mechanisms of the two are significantly different. On the same catalyst surface, problems such as competition for active sites, mutual interference of intermediate products, and insufficient activity at low temperatures can easily occur, making it difficult to achieve efficient and synergistic removal.

[0003] Existing synergistic catalysis systems mostly employ single / bimetallic oxide catalysts, using elements such as Fe and W to modulate acidity and redox properties. However, such doping can only modify the original active sites and cannot construct physically separated, functionally specific dual-active modules, leading to NO... x Reduction and VOCs oxidation mutually inhibit each other, making it difficult to maintain high purification efficiency over a wide temperature range. Metal-organic frameworks (MOFs), due to their large specific surface area, tunable pore size, and easily modifiable structure, have become ideal precursors for catalytic material design. Calcining metal oxide catalysts using MOFs as sacrificial templates can preserve the framework pore structure and multi-metal synergistic sites, providing a new approach to solving the problem of competition for synergistic catalytic sites. However, existing Ce... Mn-based MOFs-derived catalysts still suffer from defects such as mismatched Ti doping ratios, uneven distribution of active sites, insufficient low-temperature synergistic activity, and complex preparation processes, making it difficult to meet the requirements of low-temperature, high-efficiency, and stable synergistic purification of industrial flue gas.

[0004] Therefore, it is necessary to develop a method that is simple to prepare, low in cost, has controllable active site structure, and can efficiently and synergistically remove NO at low temperatures. x The three-way catalyst for toluene and toluene solves the technical bottlenecks of existing catalysts, such as low synergistic efficiency, poor stability, mutual inhibition of reactions, and complex preparation. It has important engineering value and theoretical significance for the purification of composite waste gas from industrial stationary sources. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art, such as low synergistic catalytic efficiency, competition for active sites, high preparation cost, complex process, and poor low-temperature stability. Therefore, this invention provides a Ce1Ti... x The Mn2O / MOFs ternary catalyst, through the synergistic effect of Ce, Ti, and Mn trimetallic elements and MOFs template-derived structures, constructs physically separated SCR active sites and VOCs oxidation sites, significantly improving NO2O2 activity. x Low-temperature synergistic removal efficiency with toluene.

[0006] The present invention also provides a method for preparing the above-mentioned three-way catalyst, which is simple, mild, and uses readily available raw materials, making it suitable for industrial production.

[0007] This invention also provides the application of the above-mentioned three-way catalyst in the synergistic removal of NOx and toluene from industrial flue gas, which has relaxed operating conditions, no secondary pollution, and high purification efficiency.

[0008] The first aspect of the present invention provides a synergistic removal of NO x A method for preparing a three-way catalyst for toluene includes the following steps: S1: Mix 2-aminoterephthalic acid, N,N dimethylformamide and methanol in a solvent to obtain solution A. Mix Mn(NO3)3·4H2O, Ce(NO3)3·6H2O and Ti(OCH2CH2CH2CH3)4 and add them to solution A to obtain solution B. S2: Mix the solution B at room temperature; S3: Perform a hydrothermal reaction on the mixed solution obtained in step S2; S4: The product from calcination step S3 is obtained to achieve the synergistic removal of NO. x A three-way catalyst for toluene.

[0009] This invention relates to the synergistic removal of NO x The preparation method of the three-way catalyst for toluene has at least the following beneficial effects: No expensive equipment or complex process control is required; the reaction conditions are mild and reproducible; the raw materials are all commercially available conventional reagents, resulting in low cost; and multi-metal oxide composite materials can be prepared by adjusting the metal ratio, making it easy to scale up production.

[0010] According to some embodiments of the present invention, in step S1, the solvent includes at least one of DMF, DMAC and DMSO.

[0011] According to some embodiments of the present invention, in step S1, the molar ratio of Ce(NO3)3·6H2O:Ti(OCH2CH2CH2CH3)4:Mn(NO3)3·4H2O is 1:(1-5):2.

[0012] According to some embodiments of the present invention, in step S2, the mixing is carried out in a magnetic stirrer at a stirring speed of 300-500 r / min for a stirring time of 90-120 min.

[0013] According to some embodiments of the present invention, in step S2, the mixing is carried out in a magnetic stirrer, and the stirring speed is any value among 300 r / min, 320 r / min, 340 r / min, 360 r / min, 380 r / min, 400 r / min, 420 r / min, 440 r / min, 460 r / min, 480 r / min, and 500 r / min, such as 400 r / min, or any range formed by both, such as 350 r / min to 450 r / min; the stirring time is any value among 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, and 120 min, such as 100 min, or any range formed by both, such as 95 min to 110 min.

[0014] According to some embodiments of the present invention, the temperature of the hydrothermal reaction is 100℃-120℃.

[0015] According to some embodiments of the present invention, the temperature of the hydrothermal reaction is any value among 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃, and 120℃, such as 110℃, or any range formed by both, such as 105℃ to 115℃.

[0016] According to some embodiments of the present invention, the hydrothermal reaction time is 22-24 hours.

[0017] According to some embodiments of the present invention, the hydrothermal reaction time is any value among 22h, 22.5h, 23h, 23.5h, and 24h, such as 23h, or a range formed by any two, such as 22.5h to 23.5h.

[0018] According to some embodiments of the present invention, the calcination temperature is 100℃-120℃.

[0019] According to some embodiments of the present invention, the calcination temperature is any value among 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, and 120℃, such as 110℃, or a range formed by any two, such as 105℃ to 115℃.

[0020] According to some embodiments of the present invention, step S3 further includes vacuum drying of the product after the hydrothermal reaction.

[0021] According to some embodiments of the present invention, the temperature of the vacuum drying is 100°C. 120℃.

[0022] According to some embodiments of the present invention, the vacuum drying temperature is any value among 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, and 120℃, such as 110℃, or any range formed by both, such as 105℃ to 115℃.

[0023] According to some embodiments of the present invention, the vacuum drying time is 12 hours. 14h.

[0024] According to some embodiments of the present invention, the vacuum drying time is any value among 12h, 12.5h, 13h, 13.5h, and 14h, such as 13h, or a range of any two, such as 12.5h to 13.5h.

[0025] A second aspect of the present invention provides a synergistic removal of NO x The three-way catalyst for toluene is prepared by the preparation method of the first aspect of the present invention.

[0026] The catalyst of this invention is centered on three metals: Ce, Ti, and Mn, with 2 Aminoterephthalic acid was used as an organic ligand to synthesize MOF precursors via hydrothermal synthesis, followed by calcination to obtain Ce1Ti. x Mn2O / MOFs, 1≤x≤5.

[0027] The catalyst of this invention uses MOFs as a sacrificial template, retaining a high specific surface area and ordered pores, thus achieving a highly dispersed active site; independent NO is constructed through Ti doping. x A dual-function module for reduction and toluene oxidation alleviates reaction competition; at 240 NO at 300℃ x Both the toluene removal efficiency and the toluene removal efficiency are greater than 80%, and the stability is excellent.

[0028] The catalyst of this invention has a controllable ratio of Ce, Ti, and Mn metal elements. The gradient control of x = 1 to 5 can be achieved by adjusting the amount of tetrabutyl titanate fed, which can be adapted to the flue gas purification requirements of different working conditions.

[0029] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0030] The third aspect of the present invention provides for the synergistic removal of NO by the first aspect of the present invention. x Three-way catalysts for the synergistic removal of NO from industrial flue gas with toluene x Applications in toluene.

[0031] The application of this invention has at least the following beneficial effects: it can achieve simultaneous purification of two pollutants in a single reactor, simplifying the process; it has high activity at low temperatures and low operating energy consumption; the catalytic process does not produce secondary pollutants, making it environmentally friendly; the catalyst has a long service life and strong anti-interference ability, making it suitable for complex industrial flue gas conditions.

[0032] According to some embodiments of the present invention, the catalyst is reacted at a temperature of 90°C. 300℃, gas space velocity 60000 mL / (g) It can operate stably under h) conditions and can withstand interference from 5% O2 and a certain concentration of water vapor. Attached Figure Description

[0033] Figure 1 It is Ce1Ti x XRD pattern of Mn2O / MOFs ternary catalyst.

[0034] Figure 2 It is Ce1Ti x Performance test diagram of Mn2O / MOFs ternary catalyst. Detailed Implementation

[0035] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0036] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0037] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0038] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0039] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0040] Example 1 A synergistic NO removal method was prepared x The preparation method of the three-way catalyst Ce1Ti1Mn2O / MOFs for toluene is as follows: (1) Weigh 3.62291g of H2BDC-NH2 (2-aminoterephthalic acid) into a beaker using an analytical balance, add 170mL of LDMF (N,N-dimethylformamide) and 30mL of methanol mixed solvent, and stir continuously on a magnetic stirrer until completely dissolved to obtain solution A. The stirring speed is 300r / min and the stirring time is 20min. (2) Using a pipette, take 1.81 mL of Ti(OCH2CH2CH2CH3)4 (tetrabutyl titanate), and weigh 2.295 g of Ce(NO3)3·6H2O (cerium nitrate hexahydrate) and 2.654 g of Mn(NO3)3·4H2O (manganese nitrate tetrahydrate) using an analytical balance. Mix them and add them to solution A. Stir continuously on a magnetic stirrer until completely dissolved to obtain solution B. The stirring speed is 450 r / min and the stirring time is 120 min. (3) Transfer the mixture B into a polytetrafluoroethylene sealed reactor and heat it at 120°C for 24 hours. After the reaction is completed, cool it to room temperature naturally, wash it three times with DMF and methanol respectively and filter it. Dry the filtered product under vacuum at 120°C for 12 hours. (4) The dried material was calcined in a muffle furnace at 450°C for 3 hours with a heating rate of 5°C per minute to obtain the final catalyst Ce1Ti1Mn2O.

[0041] Example 2 A synergistic NO removal method was prepared x The preparation method of the three-way catalyst Ce1Ti2Mn2O / MOFs for toluene is as follows: (1) Weigh 3.62291g of H2BDC-NH2 (2-aminoterephthalic acid) into a beaker using an analytical balance, add 170mL of LDMF (N,N-dimethylformamide) and 30mL of methanol mixed solvent, and stir continuously on a magnetic stirrer until completely dissolved to obtain solution A. The stirring speed is 300r / min and the stirring time is 20min. (2) Using a pipette, take 2.89 mL of Ti(OCH2CH2CH2CH3)4 (tetrabutyl titanate), and weigh 1.836 g of Ce(NO3)3·6H2O (cerium nitrate hexahydrate) and 2.123 g of Mn(NO3)3·4H2O (manganese nitrate tetrahydrate) using an analytical balance. Mix them and add them to solution A. Stir continuously on a magnetic stirrer until completely dissolved to obtain solution B. The stirring speed is 450 r / min and the stirring time is 120 min. (3) Transfer the mixture B into a polytetrafluoroethylene sealed reactor and heat it at 120°C for 24 hours. After the reaction is completed, cool it to room temperature naturally, wash it three times with DMF and methanol respectively and filter it. Dry the filtered product under vacuum at 120°C for 12 hours. (4) The dried material was calcined in a muffle furnace at 450°C for 3 hours with a heating rate of 5°C per minute to obtain the final catalyst Ce1Ti2Mn2O.

[0042] Example 3 A synergistic NO removal method was prepared x The preparation method of the three-way catalyst Ce1Ti5Mn2O / MOFs for toluene is as follows: (1) Weigh 3.62291g of H2BDC-NH2 (2-aminoterephthalic acid) into a beaker using an analytical balance, add 170mL of LDMF (N,N-dimethylformamide) and 30mL of methanol mixed solvent, and stir continuously on a magnetic stirrer until completely dissolved to obtain solution A. The stirring speed is 300r / min and the stirring time is 20min. (2) Using a pipette, take 4.51 mL of Ti(OCH2CH2CH2CH3)4 (tetrabutyl titanate), and weigh 1.147 g of Ce(NO3)3·6H2O (cerium nitrate hexahydrate) and 5.286 g of Mn(NO3)3·4H2O (manganese nitrate tetrahydrate) using an analytical balance. Mix them and add them to solution A. Stir continuously on a magnetic stirrer until completely dissolved to obtain solution B. The stirring speed is 450 r / min and the stirring time is 120 min. (3) Transfer the mixture B into a polytetrafluoroethylene sealed reactor and heat it at 120°C for 24 hours. After the reaction is completed, cool it to room temperature naturally, wash it three times with DMF and methanol respectively and filter it. Dry the filtered product under vacuum at 120°C for 12 hours. (4) The dried material was calcined in a muffle furnace at 450°C for 3 hours with a heating rate of 5°C per minute to obtain the final catalyst Ce1Ti5Mn2O.

[0043] The XRD test results of Examples 1 to 3 are as follows: Figure 1 As shown. From Figure 1 It can be seen that Ce appears in all catalyst samples. Mn Characteristic diffraction peaks of Ti composite oxides, no MOF precursor, no individual CeO2 or MnO x The diffraction peaks of TiO2 are well-defined and of moderate intensity, indicating good crystallinity and a complete crystal structure. With variations in the Ti doping ratio x (1-5), the diffraction peak positions remain largely unchanged, while the peak intensities show slight differences, indicating a stable crystal phase structure. This suggests that after calcination at 450℃, the MOF precursor completely decomposes and successfully transforms into a trimetallic composite oxide. Furthermore, this indicates that Ti is not simply physically mixed, but successfully doped into the oxide lattice, forming a uniform Ce₂. Ti Mn ternary solid solution. The catalyst prepared by this invention maintains a pure phase, high crystallinity, and structural stability regardless of different Ti doping concentrations, indicating that the catalyst phase is controllable and reproducible, thus facilitating efficient and synergistic removal of NO. x Toluene and toluene provide a stable crystalline phase basis.

[0044] In this invention, the catalyst activity test was conducted in a fixed-bed reactor equipped with a quartz tube with an inner diameter of 8 mm at a reaction temperature of 90℃-300℃, with a total simulated flue gas flow rate of 100 ppm toluene (411.3 mg / m³). 3 ), 500ppmNO (669.5mg / m³) 3 The reaction mixture consisted of 500 ppm NH3, 5% O2, and a balance gas N2, with a gas flow rate of 100 mL / min and a gas hourly space velocity (GHSV) of 60,000 mL / (g·h). Activity test results are as follows: Figure 2 As shown. From Figure 2 It can be seen that: NO x Regarding the removal behavior, as the reaction temperature increases, NO... x The removal efficiency continued to increase, showing a clear trend of activation at low temperatures and stability at high temperatures. Efficiency rapidly increased in the 90–240℃ range, stabilizing and reaching its peak after 240℃. All three catalysts with different Ti doping concentrations exhibited excellent low-temperature activity, with efficiencies exceeding 85% at 240℃.

[0045] Regarding toluene removal behavior, the toluene removal efficiency increases significantly with increasing temperature, reaching over 80% after 240℃, and approaching complete conversion at 270–300℃. The catalyst's oxidation activity for toluene is related to NO. x The reducing activities are highly matched, with no obvious competitive inhibition.

[0046] Regarding the effect of Ti doping content, the Ce1Ti1Mn2O catalyst exhibits the best overall catalytic performance, while NO... x Both the toluene removal efficiency and the efficiency of the catalyst were the highest among the three groups. As the Ti ratio increased from 1 to 5, the catalytic efficiency decreased slightly, but remained at a high level. All three catalysts could achieve NO removal at 240–300℃. x It can be effectively removed from toluene.

[0047] The catalyst activity test results above show that the Ce1Ti prepared in this invention... x Mn2O / MOFs catalysts exhibit excellent synergistic catalytic performance, enabling simultaneous and efficient removal of NO within the same temperature window. x And toluene. This catalyst exhibits good low-temperature activity, achieving NO at temperatures above 240℃. x Both the toluene removal efficiency and the efficiency of the catalyst are greater than 80%, meeting the requirements for low-temperature synergistic purification in industry. The amount of Ti doping has a regulatory effect on the catalytic performance, and the optimal ratio of Ce:Ti:Mn = 1:1:2 is the highest catalytic activity.

[0048] The catalyst maintains high stability and high activity over a wide temperature range of 240~300℃, and there is no significant mutual inhibition between the two types of reactions, proving that a bifunctional synergistic active site has been successfully constructed.

[0049] Overall results show that this catalyst can reduce NO in industrial flue gas. x Its efficient, simultaneous, and stable purification of toluene has extremely high practical value.

[0050] In summary, the Ce1Ti provided by this invention x Mn2O / MOFs ternary catalysts have advantages such as simple preparation, low cost, and strong catalytic activity; this strategy provides a solid theoretical basis and feasible technical path for solving the challenges of complex industrial flue gas purification.

[0051] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for synergistic removal of NO x A method for preparing a three-way catalyst for toluene, characterized in that, Includes the following steps: S1: Mix 2-aminoterephthalic acid, N,N dimethylformamide and methanol in a solvent to obtain solution A. Mix Mn(NO3)3·4H2O, Ce(NO3)3·6H2O and Ti(OCH2CH2CH2CH3)4 and add them to solution A to obtain solution B. S2: Mix the solution B at room temperature; S3: Perform a hydrothermal reaction on the mixed solution obtained in step S2; S4: The product from calcination step S3 is obtained to achieve the synergistic removal of NO. x A three-way catalyst for toluene.

2. The preparation method according to claim 1, characterized in that, In step S1, the solvent includes at least one of DMF, DMAC, and DMSO.

3. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of Ce(NO3)3·6H2O:Ti(OCH2CH2CH2CH3)4:Mn(NO3)3·4H2O is 1:(1-5):

2.

4. The preparation method according to claim 1, characterized in that, In step S2, the mixing is carried out in a magnetic stirrer at a speed of 300-500 r / min for a duration of 90-120 min.

5. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction is 100℃-120℃.

6. The preparation method according to claim 1, characterized in that, The hydrothermal reaction takes 22-24 hours.

7. The preparation method according to claim 1, characterized in that, The calcination temperature is 100℃-120℃.

8. The preparation method according to claim 1, characterized in that, Step S3 also includes vacuum drying of the product after the hydrothermal reaction.

9. A method for synergistic removal of NO x A three-way catalyst for toluene, characterized in that, It is prepared by any one of claims 1 to 8.

10. The synergistic NO removal method as described in claim 9 x Three-way catalysts for the synergistic removal of NO from industrial flue gas with toluene x Applications in toluene.

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