Manganese-potassium hidden ore-based core-shell catalyst for synergistically removing NOx and VOCs at medium and low temperatures as well as preparation method and application of manganese-potassium hidden ore-based core-shell catalyst

Abstract

The invention discloses a manganese-potassium hidden ore-based core-shell catalyst for synergistically removing NOx and VOCs at medium and low temperatures as well as a preparation method and application of the manganese-potassium hidden ore-based core-shell catalyst. According to the catalyst, manganese potassium hidden ore loaded copper oxide (Cu-OMS-2) is taken as a core, TiO2 is taken as a shell, a Cu-OMS-2-coated TiO2 core-shell composite structure is formed, the TiO2 accounts for 20%-35%, the doping amount of CuO is 5%-20%, and the balance is manganese potassium hidden ore (OMS-2). Active sites are separated by utilizing space confinement coupling interface electron confinement under the condition of 175-300 DEG C, efficient synergistic removal of NOx and VOCs is realized, the efficiency is greater than 90%, mutual inhibition between two reactions is remarkably relieved, generation of secondary pollutants is reduced, and the catalyst has excellent stability. The catalyst is suitable for medium and low temperature industrial flue gas purification, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental catalysis technology, and in particular to a manganese-potassium cryptomelane-based core-shell catalyst for synergistically removing NO x and VOCs at medium and low temperatures, a preparation method and application thereof. BACKGROUND

[0002] Nitrogen oxides (NO x ) emissions account for a significant proportion of total industrial emissions. In the steel production process, the main pollutants generated in the coking process include NO x and volatile organic compounds (VOCs). Achieving synergistic and efficient removal of NO x and VOCs has become a key technical problem that needs to be solved in the industry. NO x and VOCs not only directly harm human health, but also undergo photochemical reactions under light conditions to generate ozone and secondary fine particulate matter (PM 2.5 ), exacerbating haze and ozone pollution and causing respiratory and cardiovascular diseases. Toluene and other VOC components are toxic and carcinogenic, posing a serious threat to the environment and public safety.

[0003] Currently, ammonia selective catalytic reduction (NH3-SCR) is the most widely used deNOx technology in industry, and the mainstream commercial catalyst is V2O5-WO3 / MoO3 / TiO2 catalyst. However, this type of catalyst has poor catalytic reduction activity for NO at low temperatures (180-320℃), and does not show obvious removal effect for VOCs. The traditional vanadium-based catalyst is difficult to meet the current requirements for synergistic control of multiple pollutants due to the characteristics of low flue gas temperature, complex composition, and large fluctuations in pollutant concentration of coke oven flue gas.

[0004] Manganese-based catalysts, especially manganese dioxide (MnO2), have shown good potential in the field of low-temperature NH3-SCR and VOCs catalytic oxidation due to their multi-valence (Mn 2+ / Mn 3+ / Mn 4+ ) characteristics and excellent low-temperature redox ability. Among them, natural manganese potassium cryptomelane (OMS-2) has a unique 2×2 tunnel structure, which is beneficial to the adsorption and activation of NH3 molecules and exhibits excellent low-temperature deNOx performance. However, natural OMS-2 still has problems such as low specific surface area and insufficient exposure of active sites, which limits its catalytic performance and stability under real complex flue gas conditions. In addition, manganese-based catalysts often have problems such as low nitrogen selectivity and high generation of N2O byproducts in the SCR reaction, which can easily cause secondary pollution.

[0005] To improve the catalytic performance of natural OMS-2, researchers have explored various modification methods. Acid treatment (such as washing with glacial acetic acid) enhances the redox capacity of the catalyst by creating abundant defect structures and increasing the specific surface area on the catalyst surface, thereby increasing lattice oxygen activity and reducing the contact restriction between reactants and active sites. On the other hand, introducing copper species to form a Cu-O-Mn interface structure creates a highly efficient electron transport channel. Redox cycles enhance lattice oxygen mobility, accelerate oxygen vacancy generation, and improve low-temperature SCR activity. However, while single-doping modification (such as Cu modification) improves performance to some extent, it fails to fundamentally solve the problem of competitive adsorption and reaction inhibition between NH3 and VOCs (such as toluene) molecules at the same active sites, making it difficult to achieve truly efficient synergistic removal.

[0006] In summary, the development of a method for efficient and synergistic NO removal at medium and low temperatures is crucial. x Catalysts that can neutralize VOCs and possess high N2 selectivity and low secondary pollution characteristics have become an urgent need in the field of flue gas purification. Overcoming competition for active sites and interference with reaction pathways through material structure design is crucial for achieving NO reduction. x The key lies in the synergistic degradation with VOCs. Summary of the Invention

[0007] To address the limitations of existing manganese-based catalysts in the synergistic removal of NO x To address the technical problems encountered in the removal of NO from VOCs, such as insufficient low-temperature activity, low N2 selectivity, easy generation of secondary N2O pollution, and competitive adsorption of NH3 and VOCs molecules at active sites leading to mutual inhibition of the reaction, this invention provides a medium-to-low temperature synergistic removal method for NO. x A manganese-potassium cryptomineral-based core-shell catalyst for NO and VOCs, its preparation method, and its application. This catalyst can achieve NO reduction in a low-temperature range of 175–300℃. x It can efficiently reduce VOCs while efficiently oxidizing them, and has good structural stability and nitrogen selectivity.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A medium-low temperature synergistic NO removal method x The manganese potassium cryptomineral-based core-shell catalyst for VOCs is a Cu-OMS-2@TiO2 core-shell structure with CuO-modified manganese potassium cryptomineral Cu-OMS-2 as the core and ordered mesoporous TiO2 as the shell. The ordered mesoporous TiO2 shell layer is confined and coated on the surface of the Cu-OMS-2 core layer by a general kinetic control coating method.

[0010] Further, the composition of the manganese cryptomelane-based core-shell catalyst is, based on the total mass of the catalyst, as follows:

[0011] TiO2: 20%~35% (more preferably 25%~30%), CuO: 5%~20% (more preferably 10%~15%), and the balance being manganese cryptomelane OMS-2.

[0012] Further, the ordered mesoporous TiO2 shell layer provides spatial confinement, interface electronic confinement and lattice confinement effects for the Cu-OMS-2 core layer, and the manganese cryptomelane-based core-shell catalyst has a rich pore structure, with a specific surface area, total pore volume and average pore diameter of 100-150 m 2 / g, 0.2-0.3 cm 3 / g, 5-20 nm.

[0013] The preparation method of the manganese cryptomelane-based core-shell catalyst described above comprises the following steps:

[0014] S1, water washing and acid washing pretreatment of natural manganese cryptomelane to obtain an OMS-2 material after acid washing, denoted as HAc-OMS-2;

[0015] S2, using a deposition precipitation method to load CuO on the HAc-OMS-2 obtained in step S1 to obtain a Cu-OMS-2 core layer material;

[0016] S3, using a general kinetic control coating method, using tetrabutyl titanate as a titanium source to coat a TiO2 shell on the Cu-OMS-2 core layer material obtained in step S2 to obtain a precursor;

[0017] S4, calcining the precursor obtained in step S3 to obtain a manganese cryptomelane-based core-shell catalyst Cu-OMS-2@TiO2.

[0018] Further, in step S1, the acid used for acid washing is an ice acetic acid solution with a concentration of 0.75~1.25 mol / L, the treatment temperature is 60±1℃, and the treatment time is 2~4h.

[0019] Further, in step S2, the copper source is copper nitrate trihydrate, the precipitating agent is a Na2CO3 solution with a concentration of 0.3~0.6 mol / L, the pH value of the reaction system is adjusted to 9~10, and the aging time is 40~80 min.

[0020] Further, in step S3, the general kinetic control coating method is to add tetrabutyl titanate to a mixed system containing Cu-OMS-2, anhydrous ethanol and ammonia water at a rate of 0.15~0.5 mL / min under constant temperature conditions of 45±1℃, and the reaction is carried out for 12~36 hours, wherein the volume of ammonia water accounts for 0.2%~0.4% of the mixed system.

[0021] Further, in step S4, the calcination treatment is performed at a rate of 1-5 ℃ / min to 350-450 ℃ under an air atmosphere, and the temperature is maintained for 3-6 h.

[0022] The preparation principle of the above general kinetic control coating method is: in the construction process of the core-shell nanoparticle, the improved Stöber method is used to precisely control the dropping rate of the titanium source solution under constant temperature and magnetic stirring environment, the growth process of the mesoporous TiO2 shell is controlled through this means, and the controllable construction of the TiO2 shell in the core-shell structure is realized. The method can control the growth rate and thickness of the shell layer by adjusting the ratio of ammonia water to anhydrous ethanol (0.2-0.4 vol %) to control the hydrolysis and condensation rate, effectively control the order and integrity of the mesoporous structure, and provide a reliable process path for the structure regulation of the core-shell nanoparticle.

[0023] The application of the above manganese potassium cryptomelane-based core-shell catalyst is used for the removal of nitrogen oxides NO x and volatile organic compounds VOCs in low-temperature flue gas.

[0024] Further, the atmosphere conditions of the flue gas are: the concentration of NO is 400-600 ppm, the concentration of NH3 is 400-600 ppm, the concentration of VOCs is 50-200 ppm, the volume fraction of O2 is 8-12%, the reaction temperature is 175-300 ℃, and the gas space velocity is 20000-60000 h -1 .

[0025] The ordered mesoporous TiO2 confined CuO / manganese potassium cryptomelane core-shell catalyst Cu-OMS-2@TiO2 of the application can be used for the catalytic purification of NO and VOCs in low-temperature flue gas of stationary sources or mobile sources. The catalyst obtains a unique triple confinement effect (spatial confinement, interface confinement, and lattice confinement) and optimized surface chemical properties through a precise preparation process design (including deionized water washing, ice acetic acid washing modification, CuO doping by deposition precipitation method, and TiO2 confined coating by general kinetic control coating method). During the calcination process, the dispersion of CuO species is promoted due to the confined coating of TiO2, and the agglomeration of CuO species is effectively inhibited, so as to maintain the activity. Due to the special core-shell structure and the confinement effect, more active oxygen and acidic sites are brought, the redox performance is improved, the synergistic catalytic reaction of multiple pollutants is facilitated, and the catalyst has wide application prospect and economic value in the field of flue gas purification.

[0026] Compared with the prior art, the advantages and effects of the application are:

[0027] (1) The catalyst preparation process of this invention is simple, and can be completed by a series of simple and controllable treatment steps such as water washing, acid modification, loading and calcination. It does not require complex equipment or template agents, thus avoiding purity and pollution problems caused by template agent residues. The process is easy to scale up and standardize. The selected raw materials are inexpensive, readily available and environmentally friendly, and have the advantages of being both green and low-cost. Moreover, they do not contain toxic substances such as vanadium, which is more in line with the concept of green chemistry.

[0028] (2) By optimizing process parameters, the present invention can achieve a high yield in the laboratory, and the process is stable and easy to scale up, with good potential for industrial mass production, overcoming the problem that most core-shell catalysts have low yields due to complex preparation.

[0029] (3) The catalyst of this invention has a unique “heterogeneous dual-effect” synergistic mechanism: NO and NH3 can diffuse through the TiO2 shell pores to the core Mn site to undergo SCR reaction and realize the denitrification process; while VOCs (such as toluene) are spatially confined and are mainly catalytically oxidized at the Cu site of the shell and core-shell interface. This mechanism realizes the spatial separation of reaction sites, effectively avoids competitive adsorption, and significantly improves the synergistic removal efficiency.

[0030] (4) The catalyst of this invention has excellent NO content. x Reduction and VOCs oxidation performance. NO removal efficiency is above 70% within 100–350℃, and can reach over 90% within 125–300℃; the ignition temperature of toluene is as low as 175℃, with a conversion rate exceeding 90%. Simultaneous and efficient removal of NO and VOCs (efficiency > 90%) can be achieved within the 175–300℃ range, suitable for multi-pollutant control in medium- and low-temperature flue gas. Attached Figure Description

[0031] Figure 1 The NO2-based products prepared for the synergistic removal of NO2 from medium- and low-temperature flue gas in Examples 1 and 1 and 2 are as follows. x NO removal rate test graph of catalysts containing VOCs under the conditions of Example 2;

[0032] Figure 2 The NO2-based products prepared for the synergistic removal of NO2 from medium- and low-temperature flue gas in Examples 1 and 1 and 2 are as follows. x The toluene conversion test graph of the catalyst containing VOCs under the conditions of Example 2;

[0033] Figure 3 The NO2-based products prepared for the synergistic removal of NO2 from medium- and low-temperature flue gas in Examples 1 and 1 and 2 are as follows. x Nitrogen selectivity curve for catalysts containing VOCs under the conditions of Example 2;

[0034] Figure 4 The NO2-based products prepared for the synergistic removal of NO2 from medium- and low-temperature flue gas in Examples 1 and 1 and 2 are as follows.x Carbon dioxide selectivity plot of catalysts with VOCs under the conditions of Example 2;

[0035] Figure 5 Scanning electron microscope image of OMS-2 catalyst prepared for Comparative Example 1 to Example 3;

[0036] Figure 6 Scanning electron microscope image of Cu-OMS-2@TiO2 core-shell catalyst prepared for Example 1 to Example 3;

[0037] Figure 7 Adsorption-desorption curve of Cu-OMS-2@TiO2 core-shell catalyst prepared for Example 1 to Example 3;

[0038] Figure 8 Pore size distribution plot of Cu-OMS-2@TiO2 core-shell catalyst prepared for Example 1 to Example 3;

[0039] Figure 9 XRD test plot of Cu-OMS-2@TiO2 core-shell catalyst prepared for Example 1 to Example 4. DETAILED DESCRIPTION

[0040] The application will be further described below in conjunction with the accompanying drawings and specific embodiments, but the application is not limited thereto.

[0041] Example 1

[0042] The preparation method of the core-shell catalyst Cu-OMS-2@TiO2 is as follows:

[0043] (1) 6 g of natural cryptomelane was weighed and placed in a 250 mL beaker, and 100 mL of deionized water was added; it was magnetically stirred at room temperature (25 °C) for 30 min, then it was left to stand for 30 min, and the supernatant was discarded; the stirring- standing-discarding operation was repeated twice, and then the sample was filtered under suction; the solid sample was washed with deionized water during the filtration process; after the filtration was completed, the filter paper with the sample attached was transferred to a clean beaker, and the beaker was placed in a blast drying oven and dried at 60 °C for 12 h; the dried sample was ground to 60-100 mesh to obtain the deionized water washed natural cryptomelane sample, which was denoted as OMS-2.

[0044] (2) 1 mol / L glacial acetic acid solution was prepared, 90 mL of deionized water was taken and poured into a volumetric flask; 5.75 mL of glacial acetic acid solution was taken with a pipette and transferred to the above volumetric flask; deionized water was continuously added to the volumetric flask, and the volume was adjusted to 100 mL scale line, and after shaking, 1 mol / L glacial acetic acid solution was obtained.

[0045] (3) glacial acetic acid modification treatment: 2 g of 60-100 mesh OMS-2 prepared in step (1) was added into a 250 mL beaker, and then 100 mL of 1 mol / L glacial acetic acid solution prepared in step (2) was poured into the beaker; the beaker was placed in a 60°C water bath, and magnetic stirring was performed for 3 h; after stirring, the sample was allowed to stand for 30 min, and then filtration was performed; during the filtration, the solid sample was washed with deionized water until the filtrate was neutral; after the filtration, the filter paper with the sample was transferred to a clean beaker, and dried in a blast drying oven at 60°C for 12 h; the dried sample was ground to 60-100 mesh, and was recorded as HAc-OMS-2.

[0046] (4) Preparation of 50 mL of 0.5 mol / L Na2CO3 solution: 2.65 g of Na2CO3 solid was weighed into a 100 mL beaker, 30 mL of deionized water was added, and the Na2CO3 was completely dissolved by ultrasonic treatment at 25°C for 3 min; the solution was transferred to a 50 mL volumetric flask, and the beaker was washed with deionized water for 2-3 times, and the washing liquid was also transferred to the volumetric flask; deionized water was added to the volumetric flask to the calibration line, and the bottle stopper was inverted and shaken to obtain 50 mL of 0.5 mol / L Na2CO3 solution, which was ready for use.

[0047] (5) 0.911 g of copper nitrate trihydrate was weighed into a 250 mL beaker, 90 mL of deionized water was added, and the solution was completely dissolved by ultrasonic treatment at 25°C for 3 min. 1.1 g of 60-100 mesh HAc-OMS-2 prepared in step (3) was added to the solution, and the solution was continuously ultrasonically treated at 25°C for 5 min; then the beaker was transferred to a water bath, and magnetic stirring was performed at 25°C. 10±1 mL of 0.5 mol / L Na2CO3 solution prepared in step (4) was slowly added dropwise into the beaker, and the pH of the system was adjusted to 9-10 by a pH meter; after the addition was completed, stirring was continued for 20 min, and the total process time was 30 min; then the beaker was placed at room temperature (25°C) for 1 h for aging; after the aging was completed, the solid sample was collected by filtration, and the sample was washed with deionized water to remove impurities during the filtration; after the filtration was completed, the filter paper with the sample was transferred to a clean beaker, and dried in a blast drying oven at 60°C for 12 h; the dried sample was ground to 60-100 mesh, and was recorded as Cu-OMS-2.

[0048] (6) Preparation of solution A: 0.411 g of 60-100 mesh Cu-OMS-2 prepared in step (5) was weighed into a 250 mL beaker containing 100 mL of anhydrous ethanol and 0.3 mL of 25-28% ammonia water solution, and the mixture was ultrasonically treated at 25°C for 15 min to obtain a mixed system, which was recorded as solution A.

[0049] (7) Titanium source loading: The beaker containing solution A was transferred to a 45 °C water bath for magnetic stirring; 0.75 mL of tetrabutyl titanate solution was slowly injected into solution A within 5 min; the 45 °C water bath was continuously maintained for magnetic stirring for 24 h, and then centrifugal treatment was performed under the conditions of 8000 rpm for 8 min; the solid sample after centrifugation was collected and placed in a blast drying oven for drying at 60 °C for 12 h; the dried sample was denoted as Cu-OMS-2@TiO2.

[0050] (8) The Cu-OMS-2@TiO2 prepared in step (7) was transferred to a crucible and calcined in a muffle furnace under an air atmosphere at a temperature increasing rate of 2 °C / min to 400 °C and maintained for 4 h; after annealing cooling for 400 min, the sample was taken out, and the powder sample was sieved, and the sample with a mesh size of 60-100 was selected as the core-shell catalyst Cu-OMS-2@TiO2, denoted as 15Cu-OMS-2@30TiO2, wherein 15 represents that CuO accounts for 15% of the total mass of the catalyst, and 30 represents that TiO2 accounts for 30% of the total mass of the catalyst.

[0051] Comparative Example 1

[0052] The specific preparation steps of the OMS-2 catalyst of Comparative Example 1 are as follows:

[0053] 2 g of natural cryptomelane ore without ion exchange water washing was weighed and transferred to a crucible and calcined in a muffle furnace under an air atmosphere at a temperature increasing rate of 2 °C / min to 400 °C and maintained for 4 h; after annealing cooling for 400 min, the sample was taken out, and the powder sample was sieved, and the sample with a mesh size of 60-100 was selected as the OMS-2 catalyst.

[0054] Comparative Example 2

[0055] The specific preparation steps of the non-core-shell catalyst Cu-OMS-2 / TiO2 of Comparative Example 2 are as follows:

[0056] 1.4 g of the Cu-OMS-2 sample prepared in step (5) of Example 1 and 0.6 g of nano-TiO2 powder (anatase, hydrophilic, 99.8%) were added to a 100 mL beaker containing 50 mL of deionized water, and ultrasonic dispersion was performed at 25 °C for 10 min; then the beaker was transferred to a magnetic stirring water bath, and stirring was first performed at room temperature for 1 h, and then the water bath temperature was increased to 80 °C, and stirring was continuously performed until the deionized water was completely evaporated; after evaporation, the beaker was transferred to a 60 °C oven for drying for 12 h; after drying, the sample was transferred to a crucible and calcined in a muffle furnace under an air atmosphere at a temperature increasing rate of 2 °C / min to 400 °C and maintained for 4 h; after annealing cooling for 400 min, the sample was taken out, and the powder sample was sieved, and the sample with a mesh size of 60-100 was selected as the non-core-shell catalyst Cu-OMS-2 / TiO2.

[0057] Activity tests of the catalysts described in Example 1, Comparative Example 1, and Comparative Example 2 for synergistic removal of NO and toluene

[0058] 2.12 mL of catalyst was loaded into a quartz tube fixed-bed reactor with an inner diameter of 6 mm. The total gas flow rate was 400 mL / min and the volume hourly space velocity was 40,000 h⁻¹. -1 The reaction test temperature range was 100~350℃, and the simulated atmosphere composition was: 500ppm NO, 500ppm NH3, 50ppm toluene, 10 vol% O2, and the remainder N2. The performance of the catalyst in catalytically reducing NO and simultaneously catalytically oxidizing toluene under flue gas conditions with coexisting NO and toluene was tested. The test results are as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the results indicate that the 15Cu-OMS-2@30TiO2 core-shell catalyst prepared in Example 1 exhibits excellent performance in the synergistic degradation of NO and toluene under medium and low temperature conditions, and there is a significant mutual promoting effect between the selective catalytic reduction reaction of NH3 and the oxidation reaction of toluene.

[0059] SEM and BET tests of the catalyst of this invention

[0060] This invention utilizes a Thermo Fisher Scientific Apreo 2S field emission scanning electron microscope to observe the morphology and surface structure of the catalyst. N2 physical adsorption-desorption experiments were performed using a 3Flex America Micromeritics instrument to characterize the specific surface area and pore size distribution of the catalyst. After pretreatment of a 0.1 g sample, N2 was used as the adsorbent at 77 K. Appropriate specific surface area, total pore volume, and average pore size were obtained according to the Brunauer-Joyner-Halenda (BET) and Density Functional Theory (DFT) methods.

[0061] Taking the test results of the samples obtained in Example 1 and Comparative Example 1 as examples, the test results are as follows: Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown in the figure, the results indicate that the OMS-2 prepared in Comparative Example 1 exhibits a typical nanorod structure with a rough surface and a specific surface area of ​​30.42 m². 2 / g, pore volume is 0.22cm³ 3 / g, with an average pore size of 29.09 nm, the 15Cu-OMS-2@30TiO2 prepared in Example 1 maintained the nucleus morphology of OMS-2, with no obvious CuO species agglomeration. The outer layer was covered by a uniform, dense, and porous TiO2 shell, with a specific surface area of ​​104.40 m² / g. 2 / g, pore volume is 0.22cm³ 3 It has an average pore size of 8.43 nm and a rich micro-mesoporous structure and a large specific surface area.

[0062] XRD testing of the catalyst of this invention

[0063] The phase structure of the catalyst in this invention was analyzed and characterized using a Bruker-D8 ADVANCE X-ray diffractometer (Germany). The test conditions were: Cu target Kα rays (λ=1.5406Å), scanning 2θ range of 10°~80°, and scanning speed of 5° / min. The test results are as follows: Figure 9 As shown, OMS-2 (crypto-type α-MnO2) exhibits characteristic diffraction peaks at 2θ values ​​of approximately 12.8°, 18.1°, 28.8°, 37.5°, 49.9°, 56.9°, 60.3°, and 69.7°, corresponding to the (110), (200), (310), (211), (411), (600), (521), and (541) crystal planes, respectively, which are similar to those of the standard tetragonal KMn8O. 16 The structure (JCPDS No. 29-1020) is highly consistent. The anatase TiO2 phase exhibits significant peaks at 25.3°, 37.8°, 48.0°, 53.9°, 55.1°, 62.7°, and 75.0°, which are indexed to the (101), (004), (200), (105), (204), and (215) crystal planes, respectively, consistent with the anatase TiO2 reference standard (JCPDS No. 21-1272). The diffraction peaks of the 15Cu-OMS-2@30TiO2 catalyst mainly correspond to the α-MnO2 and anatase TiO2 phases, with a small contribution from CuMn2O4. This indicates that Cu was successfully incorporated into the OMS-2 framework, and that TiO2 was uniformly dispersed without significant phase separation. The (211) diffraction peak of 15Cu-OMS-2@30TiO2 shows a significant low-angle shift relative to OMS-2. This shift indicates an increase in the interlayer spacing within the (211) plane, confirming lattice expansion due to Cu incorporation. This is attributed to the larger ionic radius of Cu ions relative to Mn, leading to distortion of the OMS-2 tunnel structure. This lattice distortion achieves a lattice confinement effect, which, through the Cu-O-Mn interface modulation, promotes the generation of oxygen vacancies and electron transfer, thereby enhancing the redox performance and stability of the catalyst.

Claims

1. A low-medium temperature co-removal of NO x and VOCs manganese cryptomelane-based core-shell catalyst characterized by, The manganese cryptomelane-based core-shell catalyst is a Cu-OMS-2@TiO2 core-shell structure with CuO-modified manganese cryptomelane as the core and ordered mesoporous TiO2 as the shell, and the ordered mesoporous TiO2 shell is limitedly coated on the surface of the Cu-OMS-2 core layer by a general kinetic control coating method.

2. The medium-low temperature co-removal of NO x Manganese-potassium cryptomelane-based core-shell catalyst for the simultaneous removal of NO The composition of the manganese cryptomelane-based core-shell catalyst is, based on the total mass of the catalyst being 100%: TiO2: 20% to 35%, CuO: 5% to 20%, and the balance being manganese cryptomelane OMS-2.

3. The medium-low temperature co-removal of NO x Manganese potassium cryptomelane-based core-shell catalyst for the simultaneous removal of NO and VOCs, characterized in that, The ordered mesoporous TiO2 shell layer provides space confinement, interface electron confinement and lattice confinement effects for the Cu-OMS-2 core layer. The surface area, total pore volume and average pore diameter of the manganese potassium cryptomelane-based core-shell catalyst are 100-150 m 2 / g, 0.2-0.3 cm 3 / g, 5-20 nm.

4. Process for the preparation of a manganese-potassium cryptate core-shell catalyst according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, water washing and acid washing pretreatment of natural manganese cryptomelane to obtain an acid-washed OMS-2 material, denoted as HAc-OMS-2; S2, deposition precipitation method is used to load CuO on the HAc-OMS-2 obtained in step S1 to obtain a Cu-OMS-2 core layer material; S3, general kinetic control coating method is used to coat TiO2 shell on the Cu-OMS-2 core layer material obtained in step S2 using tetrabutyl titanate as the titanium source to obtain a precursor; S4, calcination treatment of the precursor obtained in step S3 to obtain the manganese cryptomelane-based core-shell catalyst Cu-OMS-2@TiO2.

5. The process for the preparation of a Manganese-Potassium Cryptate core-shell catalyst according to claim 4, characterized in that, In step S1, the acid used for acid washing is an ice acetic acid solution with a concentration of 0.75 to 1.25 mol / L, the treatment temperature is 60±1℃, and the treatment time is 2 to 4 hours.

6. The process for the preparation of a Manganese-Potassium Cryptate core-shell catalyst according to claim 4, characterized in that, In step S2, the copper source is copper nitrate trihydrate, the precipitating agent is a Na2CO3 solution with a concentration of 0.3 to 0.6 mol / L, the pH value of the reaction system is adjusted to 9 to 10, and the aging time is 40 to 80 minutes.

7. The process for the preparation of a Manganese-Potassium Cryptate core-shell catalyst according to claim 4, characterized in that, In step S3, the general kinetic control coating method is to add tetrabutyl titanate to a mixed system containing Cu-OMS-2, anhydrous ethanol and ammonia water at a rate of 0.15 to 0.5 mL / min under constant temperature conditions of 45±1℃, and the reaction is carried out for 12 to 36 hours, wherein the volume of ammonia water accounts for 0.2% to 0.4% of the mixed system.

8. The process for the preparation of a Manganese-Potassium Cryptate core-shell catalyst according to claim 4, characterized in that, In step S4, the calcination treatment conditions are as follows: under air atmosphere, the temperature is raised to 350 to 450℃ at a rate of 1 to 5℃ / min, and the temperature is kept for 3 to 6 hours.

9. Use of the manganese cryptate-based core-shell catalyst according to any one of claims 1 to 3 or of the manganese cryptate-based core-shell catalyst obtained by the preparation process according to any one of claims 4 to 8, characterized in that, The manganese potassium cryptate core-shell catalyst is used for low-temperature synergistic removal of nitrogen oxides NO x and volatile organic compounds VOCs.

10. Use according to claim 9, characterized in that, The atmosphere conditions of the flue gas are: NO concentration 400-600 ppm, NH3 concentration 400-600 ppm, VOCs concentration 50-200 ppm, O2 volume fraction 8-12%, reaction temperature 175-300 ℃, and gas space velocity 20000-60000 h -1 .

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