Preparation and application of Pt-based molecular sieve catalyst

Abstract

The invention belongs to the field of environmental catalytic materials, and discloses preparation and application of a Pt-based molecular sieve catalyst. The preparation method of the Pt-based molecular sieve catalyst comprises the following steps: (1) obtaining a primary TS-1 molecular sieve; (2) calcining the preliminary TS-1 molecular sieve in an atmosphere containing H2 to obtain a defective molecular sieve BTS-1; and (3) dispersing the defect type molecular sieve BTS-1 into deionized water, then adding a precursor solution of Pt, reducing to obtain a mixture, and separating and drying the mixture to obtain the Pt-based molecular sieve catalyst Pt / BTS-1. The Pt / BTS-1 prepared by the method has excellent benzene adsorption capacity and oxidation activity, and catalytic oxidation of low-concentration benzene at room temperature can be realized without any external energy source.

Description

Technical Field

[0001] The present invention belongs to the field of environmental catalytic materials, and particularly relates to the preparation and application of a Pt-based molecular sieve catalyst. Background Art

[0002] As a typical indoor volatile organic compound (VOCs), benzene is listed as a Class I carcinogen by the World Health Organization, seriously threatening human health. The "Indoor Air Quality Standard" (GB / T 18883-2022) in China clearly stipulates that the indoor concentration limit of benzene is 0.03 mg / m 3 , and according to the latest data from the China National Environmental Monitoring Center, the benzene concentration exceeding rate in newly decorated residences is as high as 32.7%. Therefore, the purification of benzene in indoor air has become an urgent scientific problem to be solved. Currently, the indoor VOCs pollution purification technologies mainly include ventilation dilution, biological purification, photocatalytic oxidation, and physical adsorption, etc. Among them, the physical adsorption method has become the mainstream application technology due to its simple operation and low cost. However, in practical applications, this method still has deficiencies such as competitive adsorption, difficult regeneration, and temperature dependence. Therefore, it is necessary to develop a room-temperature benzene purification technology with characteristics such as low-carbon attributes (energy consumption < 0.1 kWh / m 3 ), no secondary pollution, and a wide application range.

[0003] In recent years, room-temperature catalytic oxidation technology has made remarkable progress in the treatment of small-molecule VOCs such as formaldehyde, because its reaction path is relatively simple and the activation energy is relatively low. For example, Professor He Hong of the Institute of Urban Environment, Chinese Academy of Sciences synthesized a Pt-Na / SiO2 catalyst by the impregnation method, which can completely remove formaldehyde at room temperature. Professor Zhang Pengyi of Tsinghua University synthesized a single-atom palladium-anchored manganese dioxide catalyst Pd / MnO2@C, which showed high efficiency in the removal of low-concentration hexanal under humid conditions. However, due to its stable aromatic ring structure and high C-H bond dissociation energy (about 460 kJ / mol), the catalytic oxidation of benzene series at room temperature still faces severe challenges. To solve the above problems, researchers have carried out many beneficial explorations: for example, the research group of Professor Huang Haibao of Sun Yat-sen University replaced oxygen with ozone to generate more active oxygen species, and used MnO 2 / ZSM-5 catalyst to achieve complete removal of 30 ppm benzene at 25°C. Although the above research provides effective solutions, the secondary risks that may be brought by ozone storage / decomposition limit the popularization and application of the technology. Moreover, generally speaking, the higher the concentration of benzene, the more conducive to the catalytic reaction, but the concentration of benzene in indoor air is not high. Therefore, it is of great significance to design a catalyst that can quickly capture and enrich benzene molecules at room temperature and spontaneously carry out oxidation reactions. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method and application of a Pt-based molecular sieve catalyst. By using the strategy of combining defective molecular sieve BTS-1 with noble metal Pt, the catalyst can effectively adsorb and enrich low-concentration benzene, and spontaneously complete the activation process of oxygen molecules, ultimately achieving the goal of degrading low-concentration benzene at room temperature.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] The present invention provides a preparation method of a Pt-based molecular sieve catalyst, comprising the following steps:

[0007] (1) Obtain preliminary TS-1 molecular sieve;

[0008] (2) Calcinate the preliminary TS-1 molecular sieve in an atmosphere containing H2 to obtain defective molecular sieve BTS-1;

[0009] (3) Disperse the defective molecular sieve BTS-1 into deionized water, then add a precursor solution of Pt, and obtain a mixture after reduction. Separate and dry the mixture to obtain a Pt-based molecular sieve catalyst Pt / BTS-1.

[0010] In some embodiments, in step (1), the preparation method of the preliminary TS-1 molecular sieve is: mix a silicon source, a titanium source, a template agent, an auxiliary agent and a solvent, and then carry out a hydrothermal reaction.

[0011] Preferably, the silicon source is tetraethyl orthosilicate, the titanium source is tetrabutyl titanate, the template agent is tetrapropylammonium hydroxide, the temperature of the hydrothermal reaction is 150-170 °C, and the time of the hydrothermal reaction is 36-48 h.

[0012] In some embodiments, in step (1), the titanium-silicon molar ratio of the preliminary TS-1 molecular sieve is 1:100-1:50.

[0013] In some embodiments, in step (2), the atmosphere containing H2 is at least one of a H2 / Ar mixed gas with 5% H2 by volume or a H2 / N2 mixed gas with 5% H2.

[0014] In some embodiments, in step (2), the calcination temperature is 400-600 °C, and the calcination time is 5-7 h.

[0015] In some embodiments, in step (3), the mass fraction of the Pt component in the Pt-based molecular sieve catalyst is 0.3 wt%-0.7 wt%.

[0016] In some embodiments, in step (3), the reduction method is reduction using a NaBH4 solution.

[0017] In some embodiments, in step (3), the separation method is to separate the mixture using a rotary evaporator.

[0018] The present invention also provides an application of the Pt-based molecular sieve catalyst prepared by the above-described preparation method in the catalytic oxidation of low-concentration benzene at room temperature.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] (1) Compared with the commonly used TiO2 support, the present invention uses TS-1 molecular sieve with a high specific surface area and rich pore structure as the support, which can effectively adsorb and enrich low-concentration benzene molecules, increase the local benzene concentration, enhance the adsorption rate and adsorption strength of the catalyst for benzene, and achieve the enrichment of 10 ppm low-concentration benzene.

[0021] (2) The present invention exfoliates O atoms in TS-1 through defect engineering, so that the treated TS-1 has abundant oxygen vacancies. The abundant oxygen vacancies not only facilitate the dispersion of Pt, but also can catalyze oxygen to form active oxygen species, and can regulate the interaction between Pt and the support, effectively overcoming the high energy barrier for the activation of reactant molecules in a low-temperature environment, and realizing the catalytic oxidation of benzene at room temperature.

[0022] (3) The catalyst obtained by the preparation method of the present invention can spontaneously carry out the catalytic reaction without an external energy source during the catalytic oxidation of benzene at room temperature, which is energy-saving and environmentally friendly; at the same time, it has good recyclability and regeneration performance, does not produce secondary pollution; the noble metal loading is low, the economic cost is controllable, and it has certain practical potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a benzene removal performance graph of the catalysts in Example 1 and Comparative Example 1;

[0024] Figure 2 It is a benzene removal cycle stability graph of the catalyst in Example 1;

[0025] Figure 3 It is an X-ray diffraction (XRD) graph of TS-1, BTS-1, Pt / TS-1 and Pt / BTS-1 in Example 1 and Comparative Example 2;

[0026] Figure 4 It is a transmission electron microscope (TEM) graph of the catalysts in Example 1 and Comparative Example 2. Among them, a and b are the TEM graph and particle size distribution graph of Pt / BTS-1, and c and d are the TEM graph and particle size distribution graph of Pt / TS-1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The embodiment of the present invention provides a preparation method of a Pt-based molecular sieve catalyst, including the following steps:

[0028] (1) Obtain the preliminary TS-1 molecular sieve;

[0029] In a preferred embodiment of the present invention, the method for obtaining the preliminary TS-1 molecular sieve comprises the following steps:

[0030] Step 1: Sequentially add tetraethyl orthosilicate, tetrabutyl titanate, tetrapropylammonium hydroxide, Tween 20 and a solvent. The preferred solvent is water and isopropanol;

[0031] Specifically, add Tween 20 to deionized water, stir, and then add tetrapropylammonium hydroxide (TPAOH) to the above clear solution. After stirring again, add tetraethyl orthosilicate (TEOS) and mix until the solution is clear. Then, add isopropanol (IPA) and tetrabutyl titanate (TBOT), heat to 80 °C and hold for 5 h to obtain a mixture.

[0032] It should be noted that control the addition amounts of the tetraethyl orthosilicate and tetrabutyl titanate so that the titanium-silicon molar ratio is controlled at 1:100 to 1:50. At this ratio, titanium atoms can be better dispersed in the silicon framework, forming isolated titanium active sites, maintaining the structural stability of the molecular sieve; higher crystallinity can be obtained, better maintaining its pore structure characteristics; reducing the usage amount of the titanium source and improving economy;

[0033] Step 2: After stirring and mixing the mixture obtained in Step 1, carry out hydrothermal reaction at 150 - 170 °C for 36 - 48 h, and wash three times with deionized water. Subsequently, place the product in an 80 °C oven and dry overnight to obtain the preliminary TS-1 molecular sieve.

[0034] It should be noted that a hydrothermal temperature of 150 - 170 °C can obtain a relatively complete and regular molecular sieve crystal structure. At this temperature range, titanium atoms can better enter the molecular sieve framework, thereby improving the uniform distribution of titanium. Too high a temperature may cause the crystal to grow too fast, resulting in uncontrollable defects or irregular structures, while too low a temperature will lead to too slow a crystallization rate; a hydrothermal duration of 36 - 48 h is convenient for better controlling the morphology and particle size of the molecular sieve crystal, ensuring that the crystallization reaction of the molecular sieve proceeds fully, and enabling the crystal to grow to a sufficient size and integrity. Too short a time may result in incomplete crystallization and poor crystal development; too long a time may cause the crystal to overgrow, resulting in too large crystal size.

[0035] (2) Calcinate the preliminary TS-1 molecular sieve in an atmosphere containing H2 to obtain the defective molecular sieve BTS-1;

[0036] In this embodiment, the preliminary TS-1 molecular sieve described in step (1) is placed in a tubular furnace and calcined for 5 to 7 hours in an atmosphere containing H2 to obtain the defective molecular sieve BTS-1. The atmosphere containing H2 is preferably at least one of a H2 / Ar mixture with a H2 volume fraction of 5% or a H2 / N2 mixture with a H2 volume fraction of 5%. The calcination temperature is preferably 400 to 600 °C. The specific calcination temperature can be 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable. The specific calcination duration can be 5 hours, 6 hours, 7 hours, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0037] It should be noted that when the calcination temperature during the preparation of BTS-1 is too low (less than 400 °C), it is not sufficient to burn off the template agent, and when the calcination temperature is too high (greater than 600 °C), it will affect the crystallization degree of the molecular sieve. Due to the presence of oxygen vacancies, BTS-1 is more likely to experience a collapse of the framework structure during calcination. In order to better maintain the pore structure of the molecular sieve, the calcination temperature range should be limited to a relatively small range, and the concentration of oxygen vacancies is appropriately regulated by the calcination duration.

[0038] (3) Disperse the defective molecular sieve BTS-1 in deionized water, then add a precursor solution of Pt, and obtain a mixture after reduction. Separate and dry the mixture to obtain the Pt-based molecular sieve catalyst Pt / BTS-1;

[0039] In this embodiment, the defective molecular sieve BTS-1 obtained in step (2) is dispersed in deionized water (0.5 - 1 g of defective molecular sieve BTS-1 is dispersed in 100 mL of deionized water), and then a precursor solution of Pt is added. The precursor of Pt is preferably at least one of H2PtCl6, PtCl6, Pt(NH3)4Cl2, and platinum acetylacetonate. More preferably, the precursor of Pt is H2PtCl6 because chloroplatinic acid has high chemical activity and can be rapidly converted into metallic platinum during the reduction process, making it easier to form highly dispersed platinum particles on the surface of the support. The addition amount of the precursor solution of Pt needs to make the mass fraction content of the Pt component in the Pt-based molecular sieve catalyst be 0.3 wt% - 0.7 wt%. The mass fraction content of the Pt component in the Pt-based molecular sieve catalyst can specifically be 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable. After uniformly stirring for 12 h, a NaBH4 solution is added and stirred uniformly for 1 - 5 h for reduction. Finally, the obtained mixture is placed in a rotary evaporator and rotary evaporated at 30 - 80 °C until the liquid is completely removed, and the product is collected and placed in an 80 °C oven for overnight drying. The mass-volume concentration of the NaBH4 solution can be 0.02 g / mL. Too high a concentration will severely etch the molecular sieve, and insufficient reduction will occur at a low concentration, and the reduction temperature needs to be increased.

[0040] It should be noted that in the embodiment of the present invention, the loading of Pt can also be achieved by hydrogen calcination reduction.

[0041] The present invention also provides an application of the Pt-based molecular sieve catalyst prepared by the above-mentioned preparation method in the catalytic oxidation of low-concentration benzene at room temperature.

[0042] It should be noted that "room temperature" in the present invention refers to a temperature ranging from about 10 °C to about 40 °C. In some embodiments, "room temperature" refers to a temperature ranging from about 20 °C to about 30 °C; in some other embodiments, "room temperature" refers to 20 °C, 22.5 °C, 25 °C, 27.5 °C, etc.

[0043] Low-concentration benzene in the present invention refers to benzene with a concentration of 8 - 12 ppm, preferably benzene with a concentration of 10 ppm.

[0044] The present invention has carried out a series of characterization tests on the prepared molecular sieve support and catalyst:

[0045] The structure of the prepared molecular sieve support and catalyst was characterized by X-ray diffraction (XRD), the dispersion of Pt in the catalyst was tested by transmission electron microscopy (TEM), and the specific surface area of the molecular sieve and its catalyst was tested by N2 adsorption-desorption measurement.

[0046] The evaluation method of the catalyst is as follows:

[0047] After grinding and screening, the catalyst with a particle size of 40 - 60 mesh and a mass of 0.05 g is loaded into a fixed-bed reactor. The reaction gas is 10 ppm benzene + 21% by volume of oxygen + nitrogen for balance. The reaction temperature is room temperature (30 °C), and the space velocity is 30,000 mL / (g×h).

[0048] The calculation method of benzene removal rate is: Benzene removal rate = (Benzene content at the reactor inlet - Benzene content at the reactor outlet) × 100% / Benzene content at the reactor inlet

[0049] The cyclic stability test of the catalyst: First, the catalyst is tested under the above-mentioned evaluation method. After the benzene removal rate of the catalyst significantly decreases, the reaction gas is switched to air conditions, calcined at 80 °C for 2 h, then the reaction gas is turned off. After the reactor is cooled to 30 °C, the reaction gas of 10 ppm benzene + 21% by volume of oxygen + nitrogen for balance with a space velocity of 30,000 mL / (g×h) is introduced and the reaction continues. Such tests are repeated.

[0050] In the present invention, unless otherwise specifically stated, the contents of all substances mentioned refer to their mass percentages.

[0051] The present invention will be further described in detail with specific embodiments. The following embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

[0052] Example 1:

[0053] This example provides a preparation method of a Pt-based molecular sieve catalyst, including the following steps:

[0054] 2.0 g of Tween 20 is added to 28.6 g of deionized water and stirred for 1 h. Subsequently, 22.0 g of tetrapropylammonium hydroxide (TPAOH) is added to the above clear solution. After stirring for another 1 h, 37.5 g of tetraethyl orthosilicate (TEOS) is added and mixed until the solution is clear. Then, 17.0 g of isopropanol (IPA) and tetrabutyl titanate (TBOT) are added. The mixture is heated to 80 °C and maintained for 5 h. The mixed solution is transferred to a 100 mL autoclave lined with polytetrafluoroethylene and reacted at 165 °C for 48 h. Then the white product is separated and washed three times with deionized water. Then the product is dried overnight at 80 °C to obtain a preliminary TS-1 molecular sieve. Subsequently, the preliminary TS-1 molecular sieve is calcined in a 5% H2 / Ar atmosphere at a heating rate of 5 °C / min at 550 °C for 6 h, and the obtained black product is named BTS-1.

[0055] Weigh 1 g of BTS-1 powder and place it in a conical flask. Add deionized water. After ultrasonic dispersion for 20 min, add the prepared H2PtCl6 solution to the mixture to ensure that the mass fraction of the Pt component in the catalyst is 0.5 wt%. Stir the mixture evenly for 12 h to obtain a mixed solution. Then, add 5 mL of a 0.02 g / mL NaBH4 solution dropwise to the mixed solution and stir evenly for 3 h to obtain a reduced solution. Transfer the reduced solution to a rotary evaporation flask and rotary evaporate at 60 °C until the liquid is completely removed. Collect the product and place it in an 80 °C oven for overnight drying to obtain the Pt / BTS-1 catalyst. After grinding it into powder, store it in a sealed container for later use.

[0056] Under the conditions of 30 °C and 30,000 mL / (g*h), complete purification of a continuous flow containing 10 ppm benzene was achieved for 702 min (see Figure 1 ); and as Figure 2 shown, after three cycles of regeneration, the stability of the catalyst remained above 90% of the initial value, and the performance did not decrease significantly.

[0057] Example 2:

[0058] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0059] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.3 wt%, and other conditions remained unchanged.

[0060] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration of complete purification of benzene was measured to be 378 min.

[0061] Example 3:

[0062] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0063] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.4 wt%, and other conditions remained unchanged.

[0064] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration of complete purification of benzene was measured to be 444 min.

[0065] Example 4:

[0066] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0067] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.6 wt%, and other conditions remained unchanged.

[0068] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration for complete purification of benzene was measured to be 667 min.

[0069] Example 5:

[0070] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0071] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.7 wt%, and other conditions remained unchanged.

[0072] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration for complete purification of benzene was measured to be 588 min.

[0073] Example 6:

[0074] This comparative example provides a preparation method of a Pt-based molecular sieve catalyst.

[0075] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.2 wt%, and other conditions remained unchanged.

[0076] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration for complete purification of benzene was measured to be 179 min.

[0077] Example 7:

[0078] This comparative example provides a preparation method of a Pt-based molecular sieve catalyst.

[0079] Compared with Example 1, the amount of H2PtCl6 added was such that the mass fraction of the Pt component in the catalyst was 0.8 wt%, and other conditions remained unchanged.

[0080] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration for complete purification of benzene was measured to be 324 min.

[0081] Example 8:

[0082] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0083] Compared with Example 1, the calcination temperature in a 5% H2 / Ar atmosphere was 500 °C, and other conditions remained unchanged.

[0084] The test conditions for benzene oxidation performance were the same as those in Example 1, and the stable duration for complete purification of benzene was measured to be 576 min.

[0085] Example 9:

[0086] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0087] Compared with Example 1, the calcination duration is 5 h under a 5% H2 / Ar atmosphere, and other conditions remain unchanged.

[0088] The test conditions for benzene oxidation performance are the same as those in Example 1, and the stable duration for complete purification of benzene is measured to be 660 min.

[0089] Example 10:

[0090] This example provides a preparation method of a Pt-based molecular sieve catalyst.

[0091] Compared with Example 1, the calcination duration is 7 h under a 5% H2 / Ar atmosphere, and other conditions remain unchanged.

[0092] The test conditions for benzene oxidation performance are the same as those in Example 1, and the stable duration for complete purification of benzene is measured to be 696 min.

[0093] Comparative Example 1:

[0094] This comparative example provides a preparation method of a Pt-based molecular sieve catalyst.

[0095] Compared with Example 1, the prepared BTS-1 is used as the catalyst without Pt loading, and other conditions are the same. The test conditions for benzene oxidation performance are the same as those in Example 1, and the stable duration for complete purification of benzene is measured to be 100 min.

[0096] Comparative Example 2:

[0097] This comparative example provides a preparation method of a Pt-based molecular sieve catalyst.

[0098] Compared with Example 1, the prepared preliminary TS-1 is calcined at 550 °C for 6 h in an air atmosphere at a heating rate of 5 °C / min, and the obtained TS-1 molecular sieve is used as the catalyst support to load Pt, and other conditions are the same.

[0099] The test conditions for benzene oxidation performance are the same as those in Example 1, and the stable duration for complete purification of benzene is measured to be 240 min.

[0100] Comparative Example 3:

[0101] This comparative example provides a preparation method of a Pt-based molecular sieve catalyst.

[0102] Compared with Example 1, the catalyst support used is nano-TiO2 with oxygen vacancies enriched on the surface, and its preparation method is as follows: Slowly add 1.48 mL of hydrochloric acid (HCl) to 2.56 mL of titanium tetraisopropoxide (TTIP), and stir well to mix thoroughly (Solution A). Dissolve 0.6 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in 9 g of ethanol (EtOH) until completely dissolved (Solution B). Add Solution B to Solution A. After stirring for 30 min, add 60 mL of ethylene glycol and hydrothermal react at 150 °C for 20 h. Wash the product with ethanol and dry it overnight at 80 °C. The dried product is calcined in a H2 atmosphere at 400 °C for 2 h. The Pt loading process is the same as that in Example 1.

[0103] The benzene oxidation performance test conditions are the same as those in Example 1, and the stable duration for complete benzene purification is measured to be 144 min.

[0104] Compare the BTS-1 prepared in Example 1 with the TS-1 molecular sieve prepared in Comparative Example 2, and the results are as Figure 3 shown. BTS-1 still maintains the configuration of the TS-1 molecular sieve, and no obvious diffraction peak of Pt substance appears in the XRD after loading Pt, indicating that the dispersion of Pt is better; through statistical analysis of the particle size of Pt captured by transmission electron microscopy (see Figure 4 ), it is found that the dispersion of Pt loaded on BTS-1 is better under the same conditions.

[0105] Perform N2 adsorption-desorption tests on the BTS-1 prepared in Example 1, the TS-1 molecular sieve prepared in Comparative Example 2, and the nano-TiO2 with oxygen vacancies enriched on the surface prepared in Comparative Example 3. The test results are as follows: The specific surface area of BTS-1 is 412.27 m 2 g -1 , the specific surface area of the prepared Pt / BTS-1 catalyst is 325.56 m 2 g -1 , the specific surface area of TS-1 is 420.98 m 2 g -1 , the specific surface area of the prepared Pt / TS-1 catalyst is 334.47 m 2 g -1 , the specific surface area of TiO2 is 141.47 m 2 g -1 , the specific surface area of the prepared Pt / TiO2 catalyst is 72.18 m 2 g -1, The above specific surface area test results indicate that the obtained BTS-1 and its catalyst still maintain a relatively high specific surface area, which is significantly higher than that of nano-TiO2 with surface-rich oxygen vacancies, facilitating the enrichment of low-concentration benzene. On the premise that the test conditions for benzene oxidation performance are the same, the duration of stable complete purification of benzene measured is also significantly longer.

[0106] By comparing Examples 1-5 with Examples 6-7, it is found that when the Pt loading is less than 0.3% or higher than 0.7%, the duration of stable complete purification of benzene is shorter. Therefore, the Pt loading range selected in this application is 0.3% - 0.7%.

[0107] In addition, surface-rich oxygen vacancy nano-TiO2 can also be obtained by directly calcining commercial nano-TiO2 at 400 °C. After loading Pt under the same conditions as in Example 1, the duration of stable complete purification of benzene measured is less than 144 min.

[0108] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A preparation method of a Pt-based molecular sieve catalyst, characterized in that, It includes the following steps: (1) Obtain a preliminary TS-1 molecular sieve; (2) Calcinate the preliminary TS-1 molecular sieve in an atmosphere containing H2 to obtain a defective molecular sieve BTS-1; (3) Disperse the defective molecular sieve BTS-1 into deionized water, then add a precursor solution of Pt, and after reduction, obtain a mixture. Separate and dry the mixture to obtain a Pt-based molecular sieve catalyst Pt / BTS-1.

2. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, characterized in that, In step (1), the preparation method of the preliminary TS-1 molecular sieve is: mix a silicon source, a titanium source, a template agent, an auxiliary agent and a solvent, and then carry out a hydrothermal reaction.

3. The preparation method of the Pt-based molecular sieve catalyst according to claim 2, wherein, The silicon source is tetraethyl orthosilicate, the titanium source is tetrabutyl titanate, the template agent is tetrapropylammonium hydroxide, the temperature of the hydrothermal reaction is 150-170°C, and the time of the hydrothermal reaction is 36-48 h.

4. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, wherein In step (1), the titanium-silicon molar ratio of the preliminary TS-1 molecular sieve is 1:100-1:

50.

5. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, characterized in that, In step (2), the atmosphere containing H2 is at least one of a H2 / Ar mixed gas with 5% volume percentage of H2 or a H2 / N2 mixed gas with 5% volume percentage of H2.

6. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, characterized in that, In step (2), the calcination temperature is 400-600°C, and the calcination time is 5-7 h.

7. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, wherein In step (3), the mass fraction of the Pt component in the Pt-based molecular sieve catalyst is 0.3 wt%-0.7 wt%.

8. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, wherein In step (3), the reduction method is to use a NaBH4 solution for reduction.

9. The preparation method of the Pt-based molecular sieve catalyst according to claim 1, characterized in that, In step (3), the separation method is to separate the mixture using a rotary evaporator.

10. Application of the Pt-based molecular sieve catalyst obtained by the preparation method according to any one of claims 1-9 in the oxidation of low-concentration benzene at room temperature.

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