Confined monatomic pt on mesoporous molecular sieve and WO x Nanocluster catalysts, methods of making and using same

Abstract

The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO x The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO x The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO x The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO x The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO x The application discloses a kind of mesoporous molecular sieve confined single atom Pt and WO

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and more particularly to a mesoporous molecular sieve confining single-atom Pt and WO3. x Nanocluster catalysts, their preparation methods, and applications. Background Technology

[0002] Volatile organic compounds (VOCs) are toxic and carcinogenic, and long-term exposure can cause serious harm to human health and the ecological environment. Controlling their emissions has become a key task in the environmental protection field. Catalytic combustion is one of the most effective methods for treating VOCs in the air, offering advantages such as low energy consumption, no secondary pollution, and high purification efficiency. The performance of the catalyst is the core factor determining the effectiveness of catalytic combustion.

[0003] Pt-based catalysts, due to their excellent redox properties, are widely used in the catalytic combustion of benzene. Ordered mesoporous molecular sieve SBA-15, with its ordered hexagonal mesoporous structure, large specific surface area and pore volume, and good thermal stability, is an ideal support for loading Pt, effectively dispersing active components and improving catalyst activity and stability. However, traditional SBA-15 supported catalysts are mostly prepared using wet methods such as impregnation and precipitation, which are cumbersome, require large amounts of solvent, and are prone to environmental pollution. Furthermore, during preparation, Pt species tend to agglomerate into large particles, resulting in insufficient exposure of active sites and poor low-temperature catalytic activity, making it difficult to meet the requirements of low-temperature, high-efficiency benzene treatment in practical industrial applications.

[0004] Single-atom catalysts have attracted widespread attention in the field of catalysis due to their high atom utilization, unique electronic structure, and excellent catalytic activity. Supporting single-atom Pt on SBA-15 can significantly improve the low-temperature activity of benzene catalytic combustion. However, single-atom catalysts suffer from drawbacks such as low loading, poor thermal stability, and easy migration and aggregation, leading to rapid deactivation during long-term reactions, which limits their practical application.

[0005] Therefore, there is a need to provide a new mesoporous molecular sieve for confining single-atom Pt and WO3. x Nanocluster catalysts. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a mesoporous molecular sieve for confining single-atom Pt and WO3. x Nanocluster catalysts and their preparation methods. This mesoporous molecular sieve confines single-atom Pt and WO3. x Nanocluster catalysts utilize the synergistic effect of dual active sites to enhance the low-temperature activity and stability of catalysts.

[0007] A further technical problem to be solved by the present invention is to provide a mesoporous molecular sieve for confining single-atom Pt and WO. xApplications of nanocluster catalysts.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A mesoporous molecular sieve confines single-atom Pt and WO x A nanocluster catalyst, comprising a support and an active component supported on the support;

[0010] The support is an ordered mesoporous molecular sieve; the active components are single-atom Pt and WO. x Composite coexistence systems composed of nanoclusters;

[0011] Wherein, the loading amount of the single-atom Pt is 0.05~0.5 wt%, and the WO x The loading of nanoclusters was 4–20 wt%;

[0012] The single-atom Pt and WO x The nanoclusters are all confined and loaded inside the mesoporous channels of the ordered mesoporous molecular sieve, and the ordered mesoporous structure of the ordered mesoporous molecular sieve remains intact and undamaged after loading.

[0013] The ordered mesoporous molecular sieve is an SBA-15 support, and the ordered mesoporous structure of the SBA-15 support is an ordered hexagonal mesoporous structure; the pore size of the SBA-15 support is 6~10 nm.

[0014] Wherein, the WO x The size of the nanoclusters is 2~5 nm.

[0015] The loading of the single-atom Pt is 0.08~0.38 wt%, and the WO x The loading of nanoclusters was 8-16 wt%, and the WO x The nanoclusters have a particle size of 2.5–4.0 nm. At this ratio, single-atom Pt and WO... x The synergistic effect of nanoclusters is optimal, achieving the best balance between low-temperature activity and stability.

[0016] Preferably, the specific surface area of ​​the SBA-15 carrier is 500~800 m². 2 / g, pore volume 0.8~1.5 cm³ 3 / g. A large specific surface area and pore volume provide sufficient active sites while ensuring the unobstructed flow of mesoporous channels, which is conducive to the diffusion of reactants and products and improves catalytic efficiency.

[0017] The above-mentioned mesoporous molecular sieve confines single-atom Pt and WO xThe preparation method of the nanocluster catalyst, which adopts a solvent-free mechanical ball milling method, includes the following steps:

[0018] (1) Raw material mixing: The ordered mesoporous molecular sieve, platinum source precursor, tungsten source precursor and ball milling media are mixed evenly to obtain a mixture; wherein, the mass ratio of ordered mesoporous molecular sieve to platinum source precursor is 1:(0.001~0.02), and the mass ratio of ordered mesoporous molecular sieve to tungsten source precursor is 1:(0.01~0.3);

[0019] (2) Room temperature ball milling: The mixture obtained in step (1) is placed in a ball mill and ball milled at 400-600 rpm for 3-6 h at room temperature to obtain a uniform composite ball milling product; through the mechanochemical action of ball milling, the platinum source and tungsten source precursors can be induced to dissociate, and the dissociated Pt and W species are uniformly dispersed and anchored in the mesoporous channels of SBA-15 to achieve single-atom Pt and WO x Simultaneous formation of nanoclusters;

[0020] (3) High-temperature calcination: The uniform composite ball-milled product obtained in step (2) is placed in an air atmosphere and heated to a calcination temperature of 450-550 ℃ at a heating rate of 2-5 ℃ / min. The temperature is held for 1-3 h and then naturally cooled to room temperature to obtain mesoporous molecular sieve confined single-atom Pt and WO. x Nanocluster catalyst. The calcination process removes impurities from the precursor and simultaneously oxidizes W species to form WO. x Nanoclusters enhance the interaction between single-atom Pt and the SBA-15 support, thereby improving the thermal stability of the catalyst.

[0021] In step (1), the platinum source precursor is one or more of chloroplatinic acid and platinum acetylacetonate, preferably chloroplatinic acid; the tungsten source precursor is one or more of ammonium metatungstate and sodium tungstate, preferably ammonium metatungstate, which has a suitable decomposition temperature and can form high-purity WO3 after decomposition. x The species are easily dispersed; the milling media are agate balls, which have high hardness and good wear resistance, which can avoid the introduction of impurities during the milling process and ensure the uniform transmission of mechanical force.

[0022] In step (2), the ball milling speed is 450~550 rpm and the ball milling time is 3.5~5 h. Under these conditions, the platinum source and tungsten source precursors can be fully dissociated and dispersed, avoiding uneven dispersion due to excessively low speed and damage to the SBA-15 mesoporous structure due to excessively high speed.

[0023] The heating rate in step (3) is 3~4 ℃ / min, the calcination temperature is 480~520 ℃, and the holding time is 1.5~2.5 h. These conditions can prevent the active components from agglomerating due to excessive heating, while ensuring that impurities are fully removed and improving the crystallinity and stability of the catalyst.

[0024] The above-mentioned mesoporous molecular sieve confines single-atom Pt and WO x Application of nanocluster catalysts in the low-temperature catalytic combustion purification reaction of benzene-based VOCs.

[0025] Among them, benzene VOCs are benzene; the conditions for the low-temperature catalytic combustion purification reaction of benzene are: reaction temperature 200~350℃, benzene inlet concentration 500~3000 ppm, reaction space velocity 10,000~80,000 mL / (gh), and reaction atmosphere is air.

[0026] The mesoporous molecular sieve confines single-atom Pt and WO x The temperature T at which the conversion rate of benzene reaches 90% in the low-temperature catalytic combustion purification reaction of nanocluster catalysts. 90 The catalytic conversion rate of benzene can still be maintained above 89% after continuous operation at a constant temperature of 230 ℃ for 300 h.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The mesoporous molecular sieve of the present invention confines single-atom Pt and WO x In nanocluster catalysts, single-atom Pt and WO x Nanoclusters form a dual-active-site synergistic system: Single-atom Pt possesses extremely high atomic utilization and low-temperature catalytic activity, which can reduce the ignition temperature of benzene catalytic combustion; WO x Nanoclusters possess excellent thermal stability and oxygen storage capacity, which can inhibit the migration and aggregation of single-atom Pt and enhance the catalyst's resistance to poisoning. The synergistic effect of these two factors significantly improves the low-temperature activity and long-term stability of the catalyst, overcoming the shortcomings of catalysts with single active components.

[0029] (2) The mesoporous molecular sieve of the present invention confines single-atom Pt and WO x In nanocluster catalysts, the mesoporous channels (6~10 nm) of SBA-15 are conducive to single-atom Pt and WO. x Nanoclusters provide excellent confinement, enabling precise control of WO3. x The size of the nanoclusters (2~5 nm) prevents them from agglomerating and growing, while providing unobstructed diffusion channels for the reactants benzene and the products carbon dioxide and water, thereby further improving catalytic efficiency.

[0030] (3) The present invention uses a solvent-free ball milling method to prepare SBA-15 confined single-atom Pt and WO in one step. x Nanocluster catalysts offer advantages such as simple processing, solvent-free production, low cost, and easy industrial scale-up. The mechanochemical action of ball milling can induce complete dissociation of platinum and tungsten source precursors, achieving single-atom Pt and WO3 reactions. x The simultaneous confined loading of nanoclusters within the mesoporous channels of SBA-15 avoids problems such as uneven dispersion of active components and pore blockage in traditional wet preparation methods, while preserving the ordered mesoporous structure of SBA-15.

[0031] (4) The mesoporous molecular sieve of the present invention confines single-atom Pt and WO x Nanocluster catalysts are used for the low-temperature catalytic combustion reaction of benzene, T 90 ≤230 ℃, compared to the traditional SBA-15 load WO x The catalyst exhibits significantly improved low-temperature activity when the temperature is reduced by 50 °C. After continuous reaction at 230 °C for 300 h, the conversion rate remains above 95%, demonstrating excellent stability. It also exhibits good resistance to water and sulfur, meeting the industrial demand for low-temperature and efficient treatment of VOCs such as benzene. Attached Figure Description

[0032] Figure 1 Mesoporous molecular sieves containing single atoms of Pt and WO prepared in Example 3 of this invention x TEM images of nanocluster catalysts; among which Figure 1 Image (a) is a low magnification image at 50 nm. Figure 1 (b) in the image is a high-magnification 20 nm image;

[0033] Figure 2 PtWO prepared for Comparative Example 1 x TEM image of the SBA-15 supported catalyst;

[0034] Figure 3 The catalytic combustion activity curves of the catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention for benzene are shown.

[0035] Figure 4 The catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention are shown as long-term stability curves at 230 °C.

[0036] Figure 5 The catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention exhibit water and sulfur resistance stability curves at 230 °C. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In the various embodiments and comparative examples of this invention, the support used is an ordered mesoporous SBA-15 molecular sieve with an initial specific surface area of ​​650 m². 2 / g, pore volume 1.2 cm³ 3 / g. Chloroplatinic acid and ammonium metatungstate were uniformly selected as platinum and tungsten source precursors, respectively, and agate balls were used as the solvent-free ball milling medium. The catalyst microstructure, active component distribution, and pore structure properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption tests, respectively. The benzene catalytic combustion performance was tested using a fixed-bed reactor, with gas chromatography used to detect the benzene content in the tail gas and calculate the benzene conversion rate. The standardized test conditions were: benzene inlet concentration 2,000 ppm, reaction space velocity 30,000 mL / g / h, air reaction atmosphere, and programmed temperature rise rate 2 ℃ / min.

[0039] Example 1:

[0040] This embodiment provides a mesoporous molecular sieve for confining single-atom Pt and WO. x The specific steps for preparing nanocluster catalysts are as follows:

[0041] (1) Raw material mixing: Accurately weigh 1 g SBA-15 molecular sieve, 0.01 g chloroplatinic acid, and 0.15 g ammonium metatungstate, and place them together in a ball mill jar. Manually shake and mix for 10 min to obtain a homogeneous mixture; the target single-atom Pt loading in this embodiment is 0.33 wt%, WO x The target loading of nanoclusters is 12.32 wt%.

[0042] (2) Ball milling treatment: The ball milling jar was fixed in a planetary ball mill, and the ball milling speed was set to 500 rpm at room temperature. The ball milling was continued for 4 hours to obtain a uniform gray powder ball milling product.

[0043] (3) Calcination treatment: The ball-milled product was placed in a muffle furnace and heated to 500 ℃ at a heating rate of 3 ℃ / min in an air atmosphere. After constant temperature calcination for 2 h, it was naturally cooled to room temperature to obtain a mesoporous molecular sieve confined single-atom Pt and WOx nanocluster catalyst.

[0044] Catalyst characterization results: TEM results show that the catalyst prepared in Example 1 completely retains the ordered hexagonal mesoporous structure of SBA-15, with a pore size of 8 nm and no pore blockage; WO3 with a size of 3 nm... x Nanoclusters are uniformly dispersed within mesoporous channels.

[0045] Inductively coupled plasma (ICP) testing showed that the actual single-atom Pt loading was 0.31 wt%, and WO3 was... x The actual loading of nanoclusters was 11.93 wt%, which is basically consistent with the theoretical target loading.

[0046] Nitrogen adsorption-desorption tests showed that the catalyst had a specific surface area of ​​580 m². 2 / g, pore volume 1.0 cm³ 3 / g, the carrier's mesoporous structure remains intact and undamaged.

[0047] Catalytic performance test results: Under standard test conditions, the reaction temperature T corresponding to a 90% benzene conversion rate for this catalyst is... 90 =218 ℃. Long-term stability test: After continuous operation at a constant temperature of 230 ℃ for 300 h, the benzene conversion rate remained above 95% throughout, with no obvious deactivation.

[0048] Water resistance test: When 10 ppm SO2 and 10 vol% water vapor are introduced into the reaction atmosphere and the reaction is run continuously for 120 h, the benzene conversion rate remains stable at over 93%, demonstrating good resistance to water and sulfur poisoning.

[0049] Example 2:

[0050] This embodiment provides a mesoporous molecular sieve for confining single-atom Pt and WO. x The specific steps for preparing nanocluster catalysts are as follows:

[0051] (1) Raw material mixing: Accurately weigh 1 g SBA-15 molecular sieve, 0.01 g chloroplatinic acid, and 0.1 g ammonium metatungstate, and manually shake and mix for 10 min to obtain a homogeneous mixture; the target single-atom Pt loading in this embodiment is 0.34 wt%, WO x The target loading of nanoclusters is 8.75 wt%.

[0052] (2) Ball milling treatment: Under room temperature conditions, the ball milling speed was set to 450 rpm and the ball milling was continued for 5 h to obtain a gray powder product.

[0053] (3) Calcination treatment: The temperature was raised to 480 ℃ at a heating rate of 3 ℃ / min under air atmosphere, and calcined at a constant temperature for 2.5 h. The mixture was then naturally cooled to room temperature to obtain the target composite catalyst.

[0054] Catalyst characterization results: The actual single-atom Pt loading was 0.32 wt%, WO3... x The actual loading of nanoclusters was 8.32 wt%, WO3 x The average particle size of the nanoclusters is 2.5 nm, the mesopore size of the catalyst is 7.8 nm, and the specific surface area is 600 m². 2 / g, pore volume 1.05 cm³ 3 / g, the active components are evenly dispersed and the pore structure is well intact.

[0055] Catalytic performance test results: Under standard test conditions, catalyst T 90 Under constant temperature conditions of 220 ℃ and 230 ℃, the benzene conversion rate remained above 93% for 300 h, demonstrating excellent long-term catalytic stability.

[0056] Example 3:

[0057] In this embodiment, the platinum source precursor is replaced with platinum acetylacetone.

[0058] A mesoporous molecular sieve confines single-atom Pt and WO x The specific steps for preparing nanocluster catalysts are as follows:

[0059] (1) Raw material mixing: Accurately weigh 1 g SBA-15 molecular sieve, 0.0076 g platinum acetylacetonate, and 0.2 g ammonium metatungstate, and manually shake and mix for 10 min until uniform; the target single-atom Pt loading in this embodiment is 0.32 wt%, WO x The target loading of nanoclusters is 15.78 wt%.

[0060] (2) Ball milling treatment: Under room temperature conditions, the ball milling speed is 550 rpm and the ball milling is continued for 3.5 h to obtain a uniform gray powder product.

[0061] (3) Calcination treatment: The temperature was raised to 520 ℃ at a heating rate of 4 ℃ / min in air atmosphere, and calcined at a constant temperature for 1.5 h. The mixture was then naturally cooled to room temperature to obtain the target composite catalyst.

[0062] Figure 1 This is a TEM image of the mesoporous molecular sieve-confined single-atom Pt and WOx nanocluster catalyst prepared in Example 3 of the present invention, wherein... Figure 1 Image (a) is a low magnification image at 50 nm. Figure 1 Image (b) is a high-magnification image at 20 nm. From... Figure 1 It can be seen that the pore structure obtained in Example 3 remains intact under high loading conditions. The characterization results of the catalyst prepared in Example 3 are as follows: the actual single-atom Pt loading is 0.3 wt%, WO₂... xThe actual loading of nanoclusters was 15.2 wt%, WO3 x The average particle size of the nanoclusters is 4.0 nm; the mesopore size of the catalyst is 8.2 nm, and the specific surface area is 560 m². 2 / g, pore volume 0.95 cm³ 3 / g.

[0063] Catalytic performance test results: Under standard test conditions, the catalyst exhibits excellent low-temperature activity. 90 =207 ℃; continuous operation at 230 ℃ for 300 h, the benzene conversion rate remained stable at over 98%, and the synergistic catalytic effect was significant.

[0064] Example 4 (Low Load):

[0065] This embodiment prepares low-load mesoporous molecular sieves containing confined single-atom Pt and WO. x The specific steps for nanocluster catalysts are as follows:

[0066] (1) Raw material mixing: Take 1 g SBA-15, 0.0025 g chloroplatinic acid and 0.05 g ammonium metatungstate and mix them by hand for 10 min to mix evenly; the target single-atom Pt loading is 0.09 wt%, WO x The nanocluster loading was 4.49 wt%.

[0067] (2) Ball milling treatment: ball milling at room temperature and 400 rpm for 6 h to obtain a uniform powder product.

[0068] (3) Calcination treatment: The temperature was increased to 450 ℃ at 2 ℃ / min in air atmosphere, and calcined at a constant temperature for 3 h. The catalyst was then naturally cooled to room temperature to obtain the target catalyst.

[0069] Catalyst characterization results: Actual single-atom Pt loading 0.08 wt%, WO x Actual load: 4.41 wt%, WO x The average particle size of the nanoclusters is 2.0 nm; the catalyst has a mesopore size of 6.6 nm and a specific surface area of ​​625 m². 2 / g, pore volume 1.12 cm 3 / g, with no pore blockage and no aggregation of active components.

[0070] Catalytic performance test results: Under standard test conditions, T 90 =225 ℃; 230 ℃ for 300 h of continuous operation, the benzene conversion rate remained above 89%. The results of Example 4 show that it still has stable catalytic performance under low load.

[0071] Example 5 (High Load):

[0072] This embodiment prepares high-load mesoporous molecular sieves to confine single-atom Pt and WO. x The specific steps for nanocluster catalysts are as follows:

[0073] (1) Raw material mixing: Take 1 g SBA-15, 0.0125 g chloroplatinic acid and 0.18 g ammonium metatungstate and mix them by hand for 10 min to mix evenly; the target single-atom Pt loading is 0.4 wt%, WO x The nanocluster loading was 14.42 wt%.

[0074] (2) Ball milling treatment: ball milling at room temperature and 600 rpm for 3 h to obtain uniform gray powder.

[0075] (3) Calcination treatment: The temperature was increased to 550 ℃ at 5 ℃ / min in air atmosphere, and calcined at a constant temperature for 1 h. The catalyst was then naturally cooled to room temperature to obtain the target catalyst.

[0076] Catalyst characterization results: Actual single-atom Pt loading was 0.39 wt%, WO3... x Actual load: 14.11 wt%, WO x The average particle size of the nanoclusters is 5.0 nm; the catalyst has a mesopore size of 7.4 nm, a specific surface area of ​​515 m² / g, and a pore volume of 0.83 cm³. 3 / g, the mesoporous structure remains intact under high load, and the active components are evenly dispersed.

[0077] Catalytic performance test results: Under standard test conditions, T 90 =214 ℃; 230 ℃ for 300 h of continuous operation, the benzene conversion rate remained stable at over 95%, with no agglomeration or deactivation issues. The results of Example 5 show that it has good adaptability to high load.

[0078] Example 6 (Medium-temperature optimized calcination process):

[0079] This embodiment optimizes the calcination temperature and holding time to verify the influence of process parameters. The specific steps are as follows:

[0080] (1) Raw material mixing: Take 1 g SBA-15, 0.01 g chloroplatinic acid and 0.12 g ammonium metatungstate and mix them by hand shaking for 10 min to mix evenly; the target Pt loading is 0.34 wt%, WO x Loading capacity: 10.11 wt%.

[0081] (2) Ball milling treatment: ball milling at room temperature and 500 rpm for 4 h to obtain ball milled powder product.

[0082] (3) Calcination treatment: The temperature was increased to 490 ℃ at 3 ℃ / min under air atmosphere, and calcined at a constant temperature for 2 h. The catalyst was then naturally cooled to room temperature to obtain the target catalyst.

[0083] Catalyst characterization results: Actual single-atom Pt loading was 0.31 wt%, WO3 x Actual load 9.98 wt%, WO x The nanoclusters have a particle size of 3.2 nm; the catalyst has a mesopore size of 8.0 nm and a specific surface area of ​​590 m². 2 / g, pore volume 1.02 cm³ 3 / g, with excellent structure and dispersibility.

[0084] Catalytic performance test results: Under standard test conditions, T 90 =222 ℃; 230 ℃ continuous operation for 300 h, benzene conversion rate maintained above 94%, process stability is good.

[0085] Example 7 (High-speed short-time ball milling process):

[0086] This embodiment optimizes the ball milling speed and duration to enhance the mechanical force dispersion effect. The specific steps are as follows:

[0087] (1) Raw material mixing: Take 1 g SBA-15, 0.011 g chloroplatinic acid and 0.17 g ammonium metatungstate and mix them by hand shaking for 10 min to mix evenly; the target Pt loading is 0.36 wt%, WO x Loading capacity: 13.74 wt%.

[0088] (2) Ball milling treatment: ball milling at room temperature and 580 rpm for 3.5 h to achieve full dissociation and dispersion of precursors by using strong mechanical force.

[0089] (3) Calcination treatment: The temperature was increased to 510 °C at 4 °C / min under air atmosphere, and calcined at a constant temperature for 1.8 h. The catalyst was then naturally cooled to room temperature to obtain the target catalyst.

[0090] Catalyst characterization results: Actual single-atom Pt loading was 0.34 wt%, WO3... x Actual load 13.25 wt%, WO x The nanoclusters have a particle size of 3.8 nm; the catalyst has a mesopore size of 8.1 nm and a specific surface area of ​​570 m². 2 / g, pore volume 0.98 cm³ 3 / g, further improving the dispersion of active components.

[0091] Catalytic performance test results: Under standard test conditions, T 90 =209 ℃; continuous operation at 230 ℃ for 300 h can achieve a benzene conversion rate of over 95%, further optimizing catalytic activity.

[0092] Example 8 (Low-speed, long-duration ball milling process):

[0093] This embodiment uses a low-speed, long-term ball milling process to verify the process's universality. The specific steps are as follows:

[0094] (1) Raw material mixing: Take 1 g SBA-15, 0.01 g chloroplatinic acid and 0.16 g ammonium metatungstate and mix them by hand shaking for 10 min to mix evenly; the target Pt loading is 0.33 wt%, WO x Loading capacity: 13.04 wt%.

[0095] (2) Ball milling treatment: ball milling at room temperature and 420 rpm for 5.5 h to slowly achieve uniform loading of the precursor.

[0096] (3) Calcination treatment: The temperature was increased to 500 ℃ at 3 ℃ / min in air atmosphere, and calcined at a constant temperature for 2 h. The catalyst was then naturally cooled to room temperature to obtain the target catalyst.

[0097] Catalyst characterization results: Actual single-atom Pt loading was 0.31 wt%, WO3 x Actual load: 12.96 wt%, WO x The nanoclusters have a particle size of 3.3 nm; the catalyst has a mesopore size of 7.9 nm and a specific surface area of ​​585 m². 2 / g, pore volume 1.01 cm 3 / g, with good dispersion uniformity.

[0098] Catalytic performance test results: Under standard test conditions, T 90 =232 ℃; continuous operation at 230 ℃ for 300 h, the benzene conversion rate remained above 89%, proving that the preparation process of this invention has a wide tolerance range and strong reproducibility.

[0099] Example 9 (Verification under high-load industrial conditions):

[0100] This embodiment uses the optimal formulation of Example 3 to prepare the catalyst. The industrial suitability is verified by variable operating condition test. The catalyst preparation parameters are exactly the same as those in Example 1. The catalytic test is conducted under high-load industrial conditions: benzene inlet concentration 3,000 ppm, space velocity 80,000 mL / g / h, and other conditions remain unchanged.

[0101] Catalytic performance test results: Under high load conditions, catalyst T 90 At 240℃ and 230℃ for continuous operation at a constant temperature for 300 hours, the benzene conversion rate remained stable at over 81%. These results demonstrate that the catalyst of this invention exhibits excellent adaptability and resistance to load shocks in high-concentration, high-space-velocity industrial VOCs waste gases.

[0102] Comparative Example 1 (Preparation of PtWO by conventional impregnation method) x / SBA-15 catalyst):

[0103] This comparative example uses the traditional liquid phase impregnation method to prepare PtWO3. x The specific steps for using the SBA-15 supported catalyst are as follows:

[0104] (1) Take 1 g of SBA-15 molecular sieve, add 5 mL of deionized water solution containing 0.01 g of chloroplatinic acid and 0.15 g of ammonium metatungstate, stir thoroughly and then statically impregnate at room temperature for 12 h;

[0105] (2) The impregnation mixture was placed in an 80 ℃ water bath to evaporate to dryness, and then transferred to an oven to be dried at a constant temperature of 110 ℃ for 12 h;

[0106] (3) The dried product was placed in a muffle furnace and calcined at 500 °C for 2 h in air atmosphere, and then naturally cooled to room temperature to obtain Pt-WO. x / SBA-15 catalyst, theoretical Pt loading 0.33 wt%, WO x Theoretical loading capacity: 12.32 wt%.

[0107] Figure 2 TEM image of the catalyst prepared in Comparative Example 1. From Figure 2 It can be seen that in catalysts prepared by the traditional impregnation method, WO3... x The particle size is 8-12 nm, with severe particle agglomeration and extremely uneven dispersion; some SBA-15 mesoporous channels are blocked; the catalyst specific surface area is only 450 m². 2 / g, pore volume 0.7 cm 3 / g, the carrier pore structure is severely damaged.

[0108] Catalytic performance test results: Under standard test conditions, catalyst T 90 At temperatures above 260 °C, the low-temperature catalytic activity is significantly worse than that of the mesoporous molecular sieve-confined single-atom Pt and WOx nanocluster catalyst prepared by the ball milling method of this invention. The catalyst prepared in Comparative Example 1, after continuous reaction at 230 °C under conditions containing water and sulfur for 30 h, showed a decrease in benzene conversion to 10%, indicating poor stability. This suggests that single-atom Pt is prone to agglomeration and deactivation, and lacks WOx. x Synergistic stabilizing effect of nanoclusters.

[0109] Comparative Example 2 (Pt@SBA-15 catalyst, WO3-free) x (Synergistic effect of nanoclusters)

[0110] This proportional cancellation WO x The nanocluster component was used to prepare a single-atom Pt supported catalyst to verify the synergistic effect of the two active components. The specific steps are as follows:

[0111] (1) Take 1 g of SBA-15 molecular sieve and 0.01 g of chloroplatinic acid, mix them evenly, and ball mill at 500 rpm at room temperature for 4 h;

[0112] (2) The single-atom Pt@SBA-15 catalyst was prepared by calcination at 500 °C for 2 h in air atmosphere, with an actual single-atom Pt loading of 0.33 wt%.

[0113] Catalytic performance test results: Under standard test conditions, the catalyst exhibits better low-temperature activity, T 10 =142 ℃, T 50 =194℃, T 90 The reaction temperature was >260℃; however, at 230℃, under conditions containing water and sulfur, the benzene conversion rate decreased to 30% after 80 hours of continuous reaction, indicating poor stability. The experimental results of Comparative Example 2 show that WO3 was lacking. x The bidirectional synergistic effect of nanoclusters means that single-atom Pt site catalysts are easily deactivated under water- and sulfur-containing conditions, and their performance is far inferior to the dual-active-site composite catalyst of this invention.

[0114] Comparative Example 3 (WO) x (@SBA-15 catalyst, without single-atom Pt synergy):

[0115] In this comparative example, the active component Pt was removed, and only nanoclusters WO were prepared. x The supported catalyst was used to verify the synergistic effect of the two active components. The specific steps are as follows:

[0116] (1) Take 1 g of SBA-15 molecular sieve and mix it with 0.15 g of ammonium metatungstate. Then, ball mill it at 500 rpm at room temperature for 4 h.

[0117] (2) WO3 was obtained by calcination at 500 °C for 2 h in air atmosphere. x / SBA-15 catalyst, actual WOx loading 12.37wt%.

[0118] Catalytic performance test results of Comparative Example 3: Under standard test conditions, the catalyst showed better low-temperature activity, T 10 =182℃, T 90 >260 ℃. The experimental results of Comparative Example 3 indicate the absence of single-atom Pt and WO. x The bidirectional synergistic effect of nanoclusters, with only a single nanocluster WO x Active site catalysts are easily deactivated and their performance is far inferior to the dual-active-site composite catalyst of this invention.

[0119] Benzene catalytic combustion activity test: reaction conditions were the same as in Example 1, T 10 =200 ℃, T 90At temperatures above 260 ℃, the activity is extremely poor; however, at 230 ℃, under conditions containing water and sulfur, the benzene conversion rate decreases to 10% after 20 hours of continuous reaction, indicating poor stability.

[0120] Experimental Example 1: Catalytic Performance Test;

[0121] The performance testing method is as follows: 400 mg of noble metal catalyst was loaded into a fixed-bed microreactor. The evaluation parameters included a gas flow rate of 200 mL / min, an initial concentration of benzene gas of 2,000 ppm, and a balance gas of 80% N2 + 20% O2. The concentration of the tail gas after the reaction was detected using a Fuli GC-9790 gas chromatograph. The performance evaluation space velocity was 30,000 mL / g / h.

[0122] In this embodiment, the benzene conversion rate = ((initial benzene concentration in the inlet gas - benzene concentration in the exhaust gas) / (initial benzene concentration in the inlet gas)) × 100%.

[0123] Figure 3 The images show the catalytic combustion activity curves of the catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention for benzene. Figure 3 It can be seen that the catalysts prepared in Examples 1-9 of the present invention have significantly better activity than those in Comparative Examples 1-3, and the benzene conversion rate of the catalysts is greater than 99% at 230°C.

[0124] Test Example 2: Thermal Stability Test;

[0125] The method for thermal stability testing was as follows: 400 mg of catalyst was loaded into a fixed-bed microreactor. Evaluation parameters included a gas flow rate of 200 mL / min, an initial benzene gas concentration of 2,000 ppm, and a balance gas composition of 80% N₂ + 20% O₂. The concentration of the tail gas after the reaction was detected using a Fuli GC-9790 gas chromatograph. The stability test space velocity was 30,000 mL / g / h, the test temperature was 230 ℃, and the test time was 0–300 h.

[0126] Figure 4 The figures show the long-term stability curves of the catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention at 230 °C. Compared with Comparative Examples 1-3, the catalysts prepared in Examples 1-9 of this invention exhibit excellent thermal stability at 230 °C, and no deactivation was observed during long-term testing.

[0127] Test Example 3: Water and Sulfur Resistance Test;

[0128] Water resistance test method: 400 mg of catalyst was loaded into a fixed-bed microreactor. Evaluation parameters included a gas flow rate of 200 mL / min, an initial benzene gas concentration of 2,000 ppm, and a balance gas of 80% N2 + 20% O2. The concentration of benzene in the reaction tail gas was detected using a Fuli GC-9790 gas chromatograph. The water and sulfur resistance stability test space velocity was 30,000 mL / g / h, the water vapor content was 5 vol.%, the SO2 concentration was 10 ppm, the test temperatures were 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃, and 240 ℃, and the test time was 0–300 h.

[0129] Figure 5 The figures show the water and sulfur resistance stability curves of the catalysts prepared in Examples 1-9 and Comparative Examples 1-3 of this invention at 230 °C. Figure 5 As shown, compared with Comparative Examples 1-3, the catalysts prepared in Examples 1-9 have excellent resistance to water and sulfur poisoning at 230 °C, and no deactivation was observed during long-term testing.

[0130] As can be seen from the above examples and comparative examples, the mesoporous molecular sieve prepared by the present invention confines single atoms of Pt and WO. x Nanocluster catalysts were synthesized by ball milling to produce single-atom Pt and WO3. x The simultaneous confined loading of nanoclusters and the synergistic effect of dual active sites significantly improve the low-temperature activity and stability of the catalyst, and its T 50 Compared with the traditional impregnation method, Pt / WO x The / SBA-15 catalyst exhibits a 30-60 °C reduction in temperature, demonstrating significantly superior long-term stability compared to single-atom Pt / SBA-15 catalysts. Furthermore, the preparation method of this invention is solvent-free, simple, low-cost, and easily scaled up for industrial applications, making it widely applicable for the low-temperature, high-efficiency treatment of VOCs such as benzene.

[0131] This invention employs a solvent-free ball milling method to prepare mesoporous molecular sieves containing confined single-atom Pt and WO3 in a one-step process. x Nanocluster catalysts offer advantages such as simple processing, solvent-free production, low cost, and easy industrial scale-up. Through ball milling and mechanochemical processes, the tungsten precursor can be fully dissociated, achieving single-atom Pt and WO3 reactions. x The simultaneous confined loading of nanoclusters within the mesoporous channels of SBA-15 avoids problems such as uneven dispersion of active components and channel blockage in traditional wet preparation methods, while preserving the ordered mesoporous structure of SBA-15. In the catalyst of this invention, single-atom Pt and WO... x Nanoclusters form a dual-active-site synergistic system: on the one hand, single-atom Pt has extremely high atomic utilization and low-temperature catalytic activity, which can reduce the ignition temperature of benzene catalytic combustion; on the other hand, WO... xNanoclusters possess excellent thermal stability and oxygen storage capacity, which can inhibit the migration and aggregation of single-atom Pt, while simultaneously enhancing the catalyst's resistance to poisoning. The synergistic effect of these two factors significantly improves the catalyst's low-temperature activity and long-term stability, overcoming the shortcomings of single-active-component catalysts. Furthermore, the mesoporous channels (6~10 nm) of SBA-15 facilitate the interaction of single-atom Pt and WO3. x Nanoclusters provide excellent confinement, enabling precise control of WO3. x The nanoclusters are 2-5 nm in size, preventing their aggregation and growth, while providing unobstructed diffusion channels for the reactants benzene and the products carbon dioxide and water, further improving catalytic efficiency. This invention's catalyst is used for the low-temperature catalytic combustion reaction of benzene, T... 90 ≤240 ℃; after continuous reaction at 230 ℃ for 300 h, the conversion rate still remains above 95%, exhibiting excellent stability. It also has good resistance to water and sulfur, meeting the industrial demand for low-temperature and efficient treatment of VOCs such as benzene.

[0132] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A mesoporous molecular sieve for confining single-atom Pt and WO3 x Nanocluster catalysts, characterized in that, Includes a carrier and an active component loaded on the carrier; The support is an ordered mesoporous molecular sieve; the active components are single-atom Pt and WO. x Composite coexistence systems composed of nanoclusters; Wherein, the loading amount of the single-atom Pt is 0.05~0.5 wt%, and the WO x The loading of nanoclusters was 4–20 wt%; The single-atom Pt and WO x The nanoclusters are all confined and loaded inside the mesoporous channels of the ordered mesoporous molecular sieve, and the ordered mesoporous structure of the ordered mesoporous molecular sieve remains intact and undamaged after loading.

2. The mesoporous molecular sieve confining single-atom Pt and WO3 according to claim 1 x Nanocluster catalysts, characterized in that, The ordered mesoporous molecular sieve is an SBA-15 support, and the ordered mesoporous structure of the SBA-15 support is an ordered hexagonal mesoporous structure; the pore size of the SBA-15 support is 6~10 nm.

3. The mesoporous molecular sieve according to claim 2 that confines single-atom Pt and WO x Nanocluster catalysts, characterized in that, The WO x The size of the nanoclusters is 2~5 nm.

4. The mesoporous molecular sieve according to claim 3 that confines single-atom Pt and WO x Nanocluster catalysts, characterized in that, The loading of the single-atom Pt is 0.08~0.38 wt%, and the WO x The loading of nanoclusters was 8-16 wt%, and the WO x The particle size of the nanoclusters is 2.5~4.0 nm.

5. The mesoporous molecular sieve according to claim 2 that confines single-atom Pt and WO x Nanocluster catalysts, characterized in that, The specific surface area of ​​the SBA-15 carrier is 500~800 m². 2 / g, pore volume 0.8~1.5 cm³ 3 / g.

6. The mesoporous molecular sieve according to any one of claims 1 to 5 that confines single-atom Pt and WO x A method for preparing nanocluster catalysts, characterized in that, The preparation method employs a solvent-free mechanical ball milling method, which includes the following steps: (1) Raw material mixing: The ordered mesoporous molecular sieve, platinum source precursor, tungsten source precursor and ball milling media are mixed evenly to obtain a mixture; wherein, the mass ratio of ordered mesoporous molecular sieve to platinum source precursor is 1:(0.001~0.02), and the mass ratio of ordered mesoporous molecular sieve to tungsten source precursor is 1:(0.01~0.3); (2) Room temperature ball milling: The mixture obtained in step (1) is placed in a ball mill and ball milled at a speed of 400~600 rpm for 3~6 h at room temperature to obtain a uniform composite ball milling product; (3) High-temperature calcination: The uniform composite ball-milled product obtained in step (2) is placed in an air atmosphere and heated to a calcination temperature of 450-550 ℃ at a heating rate of 2-5 ℃ / min. The temperature is held for 1-3 h and then naturally cooled to room temperature to obtain mesoporous molecular sieve confined single-atom Pt and WO. x Nanocluster catalysts.

7. The mesoporous molecular sieve confining single-atom Pt and WO according to claim 6 x A method for preparing nanocluster catalysts, characterized in that, The platinum source precursor is one or more of chloroplatinic acid and platinum acetylacetonate, and the tungsten source precursor is at least one of ammonium metatungstate and sodium tungstate; the milling media is agate balls.

8. The mesoporous molecular sieve confining single-atom Pt and WO according to claim 6 x A method for preparing nanocluster catalysts, characterized in that, In step (2), the ball milling speed is 450~550 rpm and the ball milling time is 3.5~5 h; The heating rate in step (3) is 3~4 ℃ / min, the calcination temperature is 480~520 ℃, and the holding time is 1.5~2.5 h.

9. The mesoporous molecular sieve according to any one of claims 1 to 5 that confines single-atom Pt and WO x Application of nanocluster catalysts in the low-temperature catalytic combustion purification reaction of benzene-based VOCs.

10. The application according to claim 9, characterized in that, Benzene-related VOCs are benzene; The conditions for the low-temperature catalytic combustion purification reaction of benzene are: reaction temperature 200~350 ℃, benzene inlet gas concentration 500~3000 ppm, reaction space velocity 10,000~80,000 mL / (gh), and reaction atmosphere is air. The mesoporous molecular sieve confines single-atom Pt and WO x The temperature T at which the conversion rate of benzene reaches 90% in the low-temperature catalytic combustion purification reaction of nanocluster catalysts. 90 The catalytic conversion rate of benzene can still be maintained above 89% after continuous operation at a constant temperature of 230 ℃ for 300 h.

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