All-silica beta molecular sieve catalyst for ozone elimination and method for preparing and using same

Abstract

The present application relates to catalyst preparation technology, and aims to provide a full-silica Beta molecular sieve catalyst for ozone elimination and a preparation and application method thereof. The catalyst is a full-silica Beta molecular sieve with a three-dimensional twelve-membered ring BEA structure as a carrier, and Ag and Mn elements in a precursor solution are loaded on the molecular sieve by a two-step impregnation method to obtain the catalyst; wherein the mass percentage of Ag element in the catalyst is 1.0-10.0%, and the mass percentage of Mn element in the catalyst is 1.0-10.0%. The present application proposes to load Ag and Mn elements in a precursor solution on a molecular sieve by a two-step impregnation method, which belongs to a brand-new process in the preparation technology of multi-component active center catalysts; the catalytic performance of the catalyst is better than that of most catalysts reported at present, and the catalyst performs well in terms of moisture resistance, high air speed and low-temperature catalysis. The present application firstly uses a full-silica Beta molecular sieve with a BEA topological structure as a carrier for an ozone elimination catalyst, and provides a new idea for the research of catalysts.

Description

Technical Field

[0001] This invention relates to catalyst preparation technology, and in particular to an all-silica Beta molecular sieve catalyst for ozone removal and its preparation and application methods. Background Technology

[0002] Ozone is commonly used in wastewater treatment, air purification, drinking water bleaching, and sterilization of medical equipment. However, the use of ozone introduces new problems. For example, excessively high concentrations of ozone can damage users' eyes and respiratory tract, and in severe cases, cause chronic obstructive pulmonary disease. Furthermore, electronics factories, printers, lasers, ultraviolet equipment, and vehicle exhaust (photochemical smog secondary pollution) all produce large amounts of ozone, especially in large cities where ozone forms and accumulates, causing significant environmental harm. Currently, ozone has replaced PM2.5 as the primary air pollutant, making ozone pollution control a serious challenge.

[0003] Currently, the main ozone removal methods used in the industry include thermal decomposition, catalytic decomposition, activated carbon adsorption, and chemical absorption. Compared with other removal methods, catalytic decomposition has advantages such as low energy consumption, good safety, rapid reaction, high treatment efficiency, and less secondary pollution, and is therefore widely used in research and application.

[0004] The core of catalytic decomposition lies in the catalyst. However, most existing ozone removal catalyst technologies use Mn2O3 (such as CN109603817A, CN112473665A, CN110711579A) and activated carbon (such as CN201110031051.7) as supports. These mainstream catalysts mostly suffer from poor hydrophobicity, resulting in a short service life. Even the best-performing Mn2O3 support still cannot meet practical requirements in terms of water resistance.

[0005] Therefore, developing an ozone decomposition catalyst with high catalytic performance and good water resistance is particularly important for solving the problem of ozone pollution control. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects existing in the prior art and provide an all-silicon Beta molecular sieve catalyst for ozone removal and its preparation and application method.

[0007] To solve the above-mentioned technical problems, the solution adopted by the present invention is:

[0008] A fully silicate Beta molecular sieve catalyst for ozone removal is provided. The catalyst is obtained by loading Ag and Mn elements from a precursor solution onto the molecular sieve sequentially via a two-step impregnation method, using a fully silicate Beta molecular sieve with a three-dimensional twelve-membered ring BEA structure as a support. The mass percentage of Ag element in the catalyst is 1.0-10.0%, and the mass percentage of Mn element in the catalyst is 1.0-10.0%.

[0009] This invention further provides a method for preparing the all-silica Beta molecular sieve catalyst, which involves a two-step impregnation method to sequentially load Ag and Mn elements from the precursor solution onto a BEA-structured molecular sieve; specifically including:

[0010] (1) Powdered all-silica Beta molecular sieves are added to a precursor solution containing Ag elements, mixed evenly and impregnated; the impregnated mixture is ultrasonicated, stirred and rotary evaporated to obtain a solid, and then dried and calcined to obtain a powdered catalyst precursor;

[0011] (2) The catalyst precursor is added to a precursor solution containing Mn element, mixed evenly and impregnated; the impregnated mixture is ultrasonicated, stirred and rotary evaporated to obtain a solid, and then dried and calcined to obtain a powdered all-silicon Beta molecular sieve catalyst.

[0012] By changing the ratio of the amounts of the two precursor solutions to the all-silicon Beta molecular sieve, the mass ratio of Ag and Mn elements in the all-silicon Beta molecular sieve catalyst was adjusted.

[0013] As a preferred embodiment of the present invention, the all-silica Beta molecular sieve has a three-dimensional twelve-membered ring BEA structure, and its surface has mesopores with a specific surface area of ​​500-700 m². 2 .g -1 .

[0014] As a preferred embodiment of the present invention, the precursor solution containing Ag element refers to silver nitrate solution, and the precursor solution containing Mn element refers to manganese nitrate solution, and the concentration of both precursor solutions is 0.1 mol / L.

[0015] As a preferred embodiment of the present invention, the impregnation treatment is performed at room temperature for 10 to 12 hours.

[0016] As a preferred embodiment of the present invention, the ultrasonic treatment is performed at room temperature for 1 hour at a frequency of 45 Hz.

[0017] As a preferred embodiment of the present invention, the temperature during the rotary evaporation process is 80°C and the rotation speed is 70 rpm.

[0018] As a preferred embodiment of the present invention, the drying process is carried out at a temperature of 80°C for 2 hours.

[0019] As a preferred embodiment of the present invention, the heating rate during the calcination process is 5℃ / min, the calcination temperature is 450~550℃, and the calcination time is 4~6h; after calcination, it is naturally cooled to room temperature.

[0020] The present invention also provides a method for using the aforementioned all-silica Beta molecular sieve catalyst for catalytic ozone removal, comprising: loading the catalyst into a fixed-bed reactor, and then passing a reaction gas containing ozone and saturated water vapor through the catalyst bed in a continuous flow manner, thereby decomposing ozone into oxygen through a catalytic reaction; during the catalytic reaction, the reaction temperature is controlled at 30°C and the volume space-time velocity of the reaction gas is 840,000 h⁻¹. -1 The relative humidity during the reaction is 65-85%, and the reaction time is 6-120 hours.

[0021] Description of the invention principle:

[0022] 1. In existing technologies, using molecular sieves to support noble metal active components to prepare various catalysts is a common practice. However, molecular sieves are rarely used as supports in the preparation of catalysts for ozone removal; Mn2O3 or activated carbon are mostly used. This is because molecular sieves as supports often have surface defects, affecting mass transfer in the ozone catalytic reaction and leading to a decrease in catalytic activity. Using Mn2O3 or activated carbon avoids these problems. Therefore, researchers have generally followed a conventional approach, comparing the effects of various noble metal supports based on Mn2O3 or activated carbon. Research has also been limited to adjusting details such as the type of noble metal, reaction mode, and proportion of active components.

[0023] Therefore, based on the prevalent technical bias, when relevant technical personnel conduct research on ozone removal catalysts, even if there are publicly available records of using molecular sieves to deload metals, they will only consider molecular sieves with large specific surface areas, such as MCM-41, and relatively expensive metals such as Pt and Pd; while not considering relatively hydrophobic molecular sieve catalysts and relatively inexpensive metals such as Ag and Mn.

[0024] 2. Unlike existing technologies, this invention innovatively proposes to use all-silicon Beta molecular sieves and silver and manganese precursors, and through a series of processes such as mixing, impregnation, sonication, stirring, rotary evaporation, drying and calcination, to load the Ag and Mn elements in the precursor solution onto the molecular sieve in a two-step impregnation method to obtain an all-silicon Beta molecular sieve catalyst.

[0025] During this process, the ozone decomposition activity did not decrease due to the defects on the surface of the all-silicon Beta molecular sieve. On the contrary, the defects on its surface anchored the metals Ag and Mn better on the surface of the all-silicon molecular sieve. This means that what is usually considered a disadvantage in molecular sieve applications has become a technical advantage in this invention.

[0026] 3. This invention employs a two-step process to impregnate metallic Ag and Mn onto an all-silica Beta molecular sieve, resulting in better metal dispersion and superior performance compared to simultaneous impregnation of Ag and Mn. Initially, Ag exists as nanoclusters, mostly in a zero-valence state; while Mn appears as MnO2 or Mn2O3 (mostly MnO2). Therefore, when the catalyst is used for ozone catalysis, the surface of MnO2 is unstable upon initial contact with ozone and readily remodels. At this point, Ag enters the MnO2 interface to form AgMnO2, becoming a new active substance. This discovery is entirely new and has never been publicly reported in previous literature in the field of ozone decomposition technology.

[0027] Theoretical calculations revealed that AgMnO2 exhibits superior ozone catalytic decomposition activity compared to other commonly used Ag-based catalysts, which is one of the reasons why the catalyst of this invention can catalyze ozone elimination at low temperatures. Furthermore, the hydrophobicity of the all-silica Beta molecular sieve surface is superior to other molecular sieves, Mn2O3, and activated carbon, resulting in better moisture resistance at high space velocities and thus a longer service life.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention proposes a two-step impregnation method to load Ag and Mn elements from the precursor solution onto a molecular sieve sequentially, which is a novel process in the preparation technology of multi-component active center catalysts.

[0030] 2. The catalyst of the present invention has better catalytic performance than most catalysts reported to date, and performs better in terms of moisture resistance, high space velocity, and low temperature catalysis.

[0031] 3. This invention is the first to use all-silica Beta molecular sieves with BEA topology as a support for ozone elimination catalysts, providing a new approach for catalyst research. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the catalytic reaction process in this invention.

[0033] Figure 2 The images show the XRD patterns of the catalyst samples and the all-silicon Beta samples obtained in Examples 1-6.

[0034] Figure 3The images show the XRD patterns of the catalyst samples obtained in Examples 3, 7, 9, and 10.

[0035] Figure 4 The results of catalytic activity tests (ozone elimination curves) for the catalyst samples obtained in Examples 1-6 are shown.

[0036] Figure 5 The results of catalytic activity tests (ozone elimination curves) for the catalyst samples obtained in Examples 3, 7, 9, and 10 are shown.

[0037] Figure 6 The results of catalytic activity tests (ozone elimination curves) for the catalyst samples in Example 3 and Comparative Examples 1-6 are shown.

[0038] Figure 7 The results are the test results of the moisture resistance ozone elimination activity of the catalyst sample in Example 17.

[0039] Figure 8 The images show the long-term ozone elimination curves for the catalyst samples in Example 3 and Comparative Example 7.

[0040] Figure 9 This is a SEM image of the catalyst sample from Example 3.

[0041] Figure 10 The image shows the SEM image of the catalyst sample in Comparative Example 3.

[0042] Figure 11 This is an HRTEM image of the catalyst sample in Example 3.

[0043] Figure 12 The nitrogen adsorption diagrams are for the catalyst samples in Examples 1, 3, 6 and Comparative Examples 1, 2, 7.

[0044] Figure 13 This is a contact angle diagram of the catalyst sample in Example 3.

[0045] Figure 14 The image shows the contact angle of the catalyst sample in Comparative Example 7.

[0046] Figure 15 The HRTEM of AgMnO2 was obtained after 1 hour of reaction with the catalyst in column 3. Detailed Implementation Plan

[0047] The preferred embodiments of the present invention will be described in further detail below. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0048] Part One: Implementation Scheme, Evaluation System, and Embodiments of the Invention

[0049] 1. Implementation scheme of the present invention

[0050] This invention proposes a two-step impregnation method to sequentially load Ag and Mn elements from a precursor solution onto a BEA-structured molecular sieve; specifically, it includes:

[0051] (1) Powder with a specific surface area of ​​500-700 m² 2 .g -1 All-silica Beta molecular sieves were added to a precursor solution containing Ag elements, mixed evenly, and impregnated. The impregnated mixture was subjected to ultrasonication, stirring, and rotary evaporation to obtain a solid, which was then dried and calcined to obtain a powdered catalyst precursor.

[0052] The all-silica Beta molecular sieve has a three-dimensional twelve-membered ring BEA structure, and its surface has mesopores with a specific surface area of ​​500–700 m². 2 .g -1 The precursor solution containing Ag is a silver nitrate solution with a concentration of 0.1 mol / L.

[0053] The impregnation treatment was carried out at room temperature for 10–12 hours; the ultrasonic treatment was carried out at room temperature for 1 hour at a frequency of 45 Hz; the rotary evaporation treatment was carried out at a temperature of 80°C and a rotation speed of 70 rpm; the drying treatment was carried out at a temperature of 80°C for 2 hours; the calcination treatment was carried out at a heating rate of 5°C / min, a calcination temperature of 450–550°C, and a calcination time of 4–6 hours; after calcination, the mixture was allowed to cool naturally to room temperature.

[0054] (2) The catalyst precursor is added to a precursor solution containing Mn element, mixed evenly and impregnated; the impregnated mixture is ultrasonicated, stirred and rotary evaporated to obtain a solid, and then dried and calcined to obtain a powdered all-silicon Beta molecular sieve catalyst.

[0055] The precursor solution containing Mn element refers to a manganese nitrate solution with a concentration of 0.1 mol / L.

[0056] The operating conditions for impregnation, ultrasonication, stirring, rotary evaporation, drying, and calcination in this step are consistent with those in the previous step.

[0057] (3) By changing the ratio of the amount of the two precursor solutions to the all-silicon Beta molecular sieve, the mass ratio of Ag and Mn elements in the all-silicon Beta molecular sieve catalyst can be adjusted so that the mass percentage of Ag element in the final all-silicon Beta molecular sieve catalyst is 1.0 to 10.0%, and the mass percentage of Mn element in the catalyst is 1.0 to 10.0%.

[0058] This all-silicon Beta molecular sieve catalyst can be used for the catalytic elimination of ozone, and its specific application methods include:

[0059] The catalyst was loaded into a fixed-bed reactor, and then the reaction gas containing ozone and saturated water vapor was continuously flowed through the catalyst bed to decompose ozone into oxygen through a catalytic reaction. During this catalytic reaction, the reaction temperature was controlled at 30°C and the volume space-time velocity of the reaction gas was 840,000 h⁻¹. -1 The relative humidity during the reaction is 65-85%, and the reaction time is 6-120 hours.

[0060] 2. To verify the catalyst performance, the present invention constructs a catalyst evaluation system in the following manner:

[0061] like Figure 1 As shown, the evaluation system mainly consists of three parts: the gas path and control system, the catalytic reaction device system, and the online analysis and detection system. All gases used in the experiment (except water) are supplied by an air generator pump. After exiting the air generator pump, the air passes through a mass flow meter and enters the mixing tube, which then flows into the bubbler and ozone generator. Water is introduced into the mixed gas via bubbling, acting as a balance gas. Ozone is generated after air enters the ozone generator. In the catalytic reaction system, a quartz glass reaction tube with an inner diameter of 4 mm and an outer diameter of 6 mm is used. The catalytic reaction device system has two reaction tubes: one is a bypass reaction tube, and the other contains the catalyst. The two reaction tubes are switched using a three-way switch. The middle of the reaction tube contains catalyst with a mesh size of 40-60, and both ends are lined with quartz wool to support and evenly distribute the catalyst. The bypass reaction tube contains only quartz wool and no catalyst, serving as a control experiment for testing reaction space velocity and ozone concentration. The reaction tube is placed in a resistance furnace, ensuring that the catalyst center and thermocouple are both within the furnace's temperature control zone. The furnace's programmed temperature control is performed by a temperature controller. Online analysis and detection involve quantitatively measuring the ozone concentration using a Model 202 2B ozone detector derived from the catalytic reaction.

[0062] During catalytic activity testing, the controllable ranges for reaction atmosphere conditions and the proportions of each feed gas in the mixed gas are: relative humidity of water 0–85%, ozone concentration 0–40 ppm, and volume space velocity 600,000–840,000 h⁻¹. -1 .

[0063] The preparation and verification process of the all-silicon Beta molecular sieve catalyst of the present invention are illustrated in detail below through several embodiments.

[0064] 3. Specific details of Examples 1-16

[0065] Example 1

[0066] (1) Preparation of catalyst

[0067] Weigh 2 grams of material with a specific surface area of ​​500-700 m². 2 .g -1 11.30 g of a 0.1 mol / L silver nitrate solution was weighed from all-silicon Beta molecular sieve powder. The molecular sieve powder was added to the silver nitrate solution and impregnated at room temperature for 10 h, then sonicated at 45 Hz for 1 h, followed by stirring for another 1 h. The solid was obtained by rotary evaporation at 80 °C and 70 rpm, and then dried at 80 °C for 2 h. The solid was heated to 450 °C at a rate of 5 °C / min, calcined at that temperature for 4 h, and then naturally cooled to room temperature to obtain the all-silicon Beta molecular sieve catalyst precursor.

[0068] Weigh 1g of all-silica Beta molecular sieve catalyst precursor and 1.85g of 0.1mol / L manganese nitrate solution, and follow the same procedure as above, impregnating, sonicating, stirring, rotary evaporating, drying, and calcining to obtain the final 6%Ag-1%Mn / all-silica Beta molecular sieve catalyst.

[0069] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst. Its nitrogen adsorption results are as follows: Figure 12 As shown in the nitrogen adsorption diagram, a hysteresis loop is present, indicating that the catalyst has mesoporous structures.

[0070] (2) Performance verification of the catalyst

[0071] To verify the high catalytic activity of the 6% Ag-1% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0072] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 95% after 6 hours and over 93% after 12 hours. The ozone elimination curve over time is shown below. Figure 4 As shown.

[0073] Example 2

[0074] (1) Preparation of catalyst

[0075] Following the preparation method in Example 1, 3.70 g of a 0.1 mol / L manganese nitrate solution was weighed, and everything else was exactly the same as in Example 1, to prepare a 6% Ag-2% Mn / all-silica Beta molecular sieve catalyst.

[0076] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0077] (2) Performance verification of the catalyst

[0078] To verify the high catalytic activity of the 6% Ag-2% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0079] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 99% after 6 hours and over 98% after 12 hours. The ozone elimination curve over time is shown below. Figure 4 As shown.

[0080] Example 3

[0081] (1) Preparation of catalyst

[0082] Following the preparation method in Example 1, 7.40 g of a 0.1 mol / L manganese nitrate solution was weighed, and everything else was exactly the same as in Example 1, to prepare a 6% Ag-4% Mn / all-silicon Beta molecular sieve catalyst.

[0083] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 , 3 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst. Its nitrogen adsorption results are as follows: Figure 12 As shown, a hysteresis loop is present in its nitrogen adsorption diagram, indicating the presence of mesoporous material in the catalyst. Its SEM image is... Figure 9 No metal was observed, indicating that the metal is well dispersed on the Beta surface. Its contact angle is as follows: Figure 13 As shown, this indicates that it possesses a certain degree of hydrophobicity. Its HRTEM image is shown below. Figure 11 As shown, some of the silver elements on the catalyst are initially in the Ag0 state. After 1 hour of reaction, AgMnO2, a more active substance, appears on the catalyst surface. Its HRTEM is as follows. Figure 15 As shown.

[0084] (2) Performance verification of the catalyst

[0085] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0086] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the above test conditions, the ozone elimination rate was over 99% after 6 hours, over 99% after 12 hours, and over 85% after 120 hours. The ozone elimination curves over time are shown below. Figure 4-8 As shown. With other conditions remaining constant, the reaction time space velocity is changed to 600,000 h⁻¹. -1 720000h -1 It was found that under the test conditions of changing the reaction space velocity, the ozone elimination rate was above 99% for 6 hours and above 99% for 12 hours, which reflects the high catalytic activity of the all-silicon Beta molecular sieve catalyst.

[0087] Example 4

[0088] (1) Preparation of catalyst

[0089] Following the preparation method in Example 1, 11.10 g of manganese nitrate solution with a molar concentration of 0.1 mol / L was weighed, and everything else was exactly the same as in Example 1, to prepare a 6% Ag-6% Mn / all-silicon Beta molecular sieve catalyst.

[0090] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0091] (2) Performance verification of the catalyst

[0092] To verify the high catalytic activity of the 6% Ag-6% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0093] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 99% after 6 hours and over 98% after 12 hours. The ozone elimination curve over time is shown below. Figure 4 As shown.

[0094] Example 5

[0095] (1) Preparation of catalyst

[0096] Following the preparation method in Example 1, 14.80 g of a 0.1 mol / L manganese nitrate solution was weighed, and everything else was exactly the same as in Example 1, to prepare a 6% Ag-8% Mn / all-silicon Beta molecular sieve catalyst.

[0097] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0098] (2) Performance verification of the catalyst

[0099] To verify the high catalytic activity of the all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0100] In this embodiment, a 6% Ag-8% Mn / all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was above 98% after 6 hours and above 97% after 12 hours. The ozone elimination curve over time is shown below. Figure 4 As shown.

[0101] Example 6

[0102] (1) Preparation of catalyst

[0103] Following the preparation method in Example 1, 18.50 g of a 0.1 mol / L manganese nitrate solution was weighed, and everything else was exactly the same as in Example 1, to prepare a 6% Ag-10% Mn / all-silicon Beta molecular sieve catalyst.

[0104] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 2 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst. Its nitrogen adsorption results are as follows: Figure 12 As shown in the nitrogen adsorption diagram, a hysteresis loop is present, indicating that the catalyst has mesoporous structures.

[0105] (2) Performance verification of the catalyst

[0106] To verify the high catalytic activity of the 6% Ag-10% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0107] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 98% after 6 hours and over 96% after 12 hours. The ozone elimination curve over time is shown below. Figure 4 As shown.

[0108] Example 7

[0109] (1) Preparation of catalyst

[0110] Following the preparation method in Example 3, 18.83 g of silver nitrate solution with a molar concentration of 0.1 mol / L and 14.80 g of manganese nitrate solution with a molar concentration of 0.1 mol / L were weighed. Everything else was exactly the same as in Example 3, and a 10% Ag-8% Mn / all-silicon Beta molecular sieve catalyst was prepared.

[0111] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 3 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0112] (2) Performance verification of the catalyst

[0113] To verify the high catalytic activity of the 10% Ag-8% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0114] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 99% after 6 hours and over 99% after 12 hours. The ozone elimination curve over time is shown below. Figure 5 As shown.

[0115] Example 8

[0116] (1) Preparation of catalyst

[0117] Following the preparation method in Example 1, 1.88 g of silver nitrate solution with a molar concentration of 0.1 mol / L and 1.85 g of manganese nitrate solution with a molar concentration of 0.1 mol / L were weighed, and the rest was exactly the same as in Example 1, to prepare a 1% Ag-1% Mn / all-silicon Beta molecular sieve catalyst.

[0118] (2) Performance verification of the catalyst

[0119] To verify the catalytic activity of the 1% Ag-1% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0120] The all-silicon Beta molecular sieve catalyst prepared in this embodiment has an ozone elimination rate of over 15% under the test conditions.

[0121] Example 9

[0122] (1) Preparation of catalyst

[0123] Following the preparation method in Example 1, 3.77 g of silver nitrate solution with a molar concentration of 0.1 mol / L and 3.70 g of manganese nitrate solution with a molar concentration of 0.1 mol / L were weighed, and the rest was exactly the same as in Example 1, to prepare a 2% Ag-2% Mn / all-silicon Beta molecular sieve catalyst.

[0124] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 3 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0125] (2) Performance verification of the catalyst

[0126] To verify the catalytic activity of the 2% Ag-2% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0127] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 90% after 6 hours and over 85% after 12 hours. The ozone elimination curve over time is shown below. Figure 5 As shown.

[0128] Example 10

[0129] (1) Preparation of catalyst

[0130] Following the preparation method in Example 1, 7.53 g of silver nitrate solution with a molar concentration of 0.1 mol / L and 7.40 g of manganese nitrate solution with a molar concentration of 0.1 mol / L were weighed, and the rest was exactly the same as in Example 1, to prepare a 4% Ag-4% Mn / all-silicon Beta molecular sieve catalyst.

[0131] The X-ray diffraction curve of the all-silica Beta molecular sieve catalyst obtained in this embodiment is as follows: Figure 3 As shown, the positions of its diffraction peaks are all standard characteristic peaks of BEA topological molecular sieves, indicating that the metal is well dispersed on the catalyst.

[0132] (2) Performance verification of the catalyst

[0133] To verify the high catalytic activity of the 4% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0134] In this embodiment, an all-silica Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 98% after 6 hours and over 97% after 12 hours. The ozone elimination curve over time is shown below. Figure 5 As shown.

[0135] Example 11

[0136] (1) Preparation of catalyst

[0137] Following the preparation method in Example 3, except for changing the calcination temperature to 500°C, the other steps were exactly the same as in Example 3, and a 6%Ag-4%Mn / all-silicon Beta molecular sieve catalyst was prepared.

[0138] (2) Performance verification of the catalyst

[0139] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0140] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions of calcination temperature of 500℃, the ozone elimination rate was above 99% after 6 hours and above 99% after 12 hours.

[0141] Example 12

[0142] (1) Preparation of catalyst

[0143] Following the preparation method in Example 3, except for changing the calcination temperature to 550°C, the other steps were exactly the same as in Example 3, and a 6%Ag-4%Mn / all-silicon Beta molecular sieve catalyst was prepared.

[0144] (2) Performance verification of the catalyst

[0145] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0146] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions of calcination temperature of 550℃, the ozone elimination rate was above 99% after 6 hours and above 99% after 12 hours.

[0147] Example 13

[0148] (1) Preparation of catalyst

[0149] Following the preparation method in Example 3, except for changing the calcination time to 5 hours, the preparation was exactly the same as in Example 3, and a 6% Ag-4% Mn / all-silicon Beta molecular sieve catalyst was obtained.

[0150] (2) Performance verification of the catalyst

[0151] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0152] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions, when the calcination time was 5 hours, the ozone elimination rate was over 99% after 6 hours and over 99% after 12 hours.

[0153] Example 14

[0154] (1) Preparation of catalyst

[0155] Following the preparation method in Example 3, except for changing the calcination time to 6 hours, the preparation was exactly the same as in Example 3, and a 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst was obtained.

[0156] (2) Performance verification of the catalyst

[0157] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0158] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 99% after calcination for 6 hours and over 99% after 12 hours.

[0159] Example 15

[0160] (1) Preparation of catalyst

[0161] Following the preparation method in Example 1, except for changing the impregnation time to 11h, the other steps were exactly the same as in Example 1, and a 6%Ag-1%Mn / all-silica Beta molecular sieve catalyst was prepared.

[0162] (2) Performance verification of the catalyst

[0163] To verify the high catalytic activity of the 6% Ag-1% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0164] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 95% after calcination for 6 hours and over 93% after 12 hours.

[0165] Example 16

[0166] (1) Preparation of catalyst

[0167] Following the preparation method in Example 1, except for changing the impregnation time to 12h, the other steps were exactly the same as in Example 1, and a 6%Ag-1%Mn / all-silica Beta molecular sieve catalyst was prepared.

[0168] (2) Performance verification of the catalyst

[0169] To verify the high catalytic activity of the 6% Ag-1% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0170] In this embodiment, an all-silicon Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was over 95% after calcination for 6 hours and over 93% after 12 hours.

[0171] Example 17

[0172] (1) Preparation of catalyst

[0173] Following the preparation method in Example 3, a 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst was prepared.

[0174] (2) Performance verification of the catalyst

[0175] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to humidity conditions of 65%, 70%, 80%, and 85% RH and a space velocity of 840,000 h⁻¹. -1Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0176] Under otherwise unchanged conditions, it was verified that the ozone removal efficiency after 12 hours at RH=85% still reached over 96%, demonstrating the high catalytic activity of the all-silicon Beta molecular sieve catalyst. Its ozone removal curve changes with time and humidity as follows: Figure 7 As shown.

[0177] Example 18

[0178] (1) Preparation of catalyst

[0179] Following the preparation method in Example 3, a 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst was prepared.

[0180] (2) Performance verification of the catalyst

[0181] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at ozone concentrations of 10ppm, 20ppm, and 30ppm, and at a reaction temperature of 30℃.

[0182] Under otherwise unchanged conditions, it was found that the ozone elimination rate was above 99% after 6 hours and above 99% after 12 hours under different ozone concentrations, demonstrating the high catalytic activity of the all-silicon Beta molecular sieve catalyst.

[0183] Example 19

[0184] (1) Preparation of catalyst

[0185] Following the preparation method in Example 3, a 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst was prepared.

[0186] (2) Performance verification of the catalyst

[0187] To verify the high catalytic activity of the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 600,000 h⁻¹. -1 720000h -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0188] Under otherwise unchanged conditions, it was found that the ozone elimination rate was above 99% after 6 hours and above 99% after 12 hours under the test conditions of changing the reaction space velocity, which reflects the high catalytic activity of the all-silicon Beta molecular sieve catalyst.

[0189] Part Two: Catalyst Preparation and Performance Analysis (Comparative Example)

[0190] Comparative Example 1

[0191] (1) Preparation of catalyst

[0192] The all-silica Beta molecular sieve was replaced with an all-silica ZSM-5 molecular sieve; otherwise, it remained the same as in Example 3.

[0193] A 6% Ag-4% Mn / all-silica ZSM-5 molecular sieve catalyst was prepared.

[0194] The nitrogen adsorption results of the all-silicon ZSM-5 molecular sieve catalyst obtained in this comparative example are as follows: Figure 12 As shown in the figure, there is no hysteresis loop in its nitrogen adsorption diagram, indicating that the catalyst does not have mesoporous structure.

[0195] (2) Performance verification of the catalyst

[0196] To verify the catalytic activity of the 6% Ag-4% Mn / all-silica ZSM-5 molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0197] The all-silica ZSM-5 molecular sieve catalyst prepared in this comparative example showed an ozone elimination rate of over 97% after 6 hours and over 92% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0198] Comparative Example 2

[0199] (1) Preparation of catalyst

[0200] The all-silica Beta molecular sieve was replaced with Al2O3, and the rest was the same as in Example 3, to prepare a 6% Ag-4% Mn / Al2O3 catalyst.

[0201] The nitrogen adsorption results of the Al2O3 catalyst obtained in this comparative example are as follows: Figure 12 As shown in the figure, there is no hysteresis loop in its nitrogen adsorption diagram, indicating that the catalyst does not have mesoporous structure.

[0202] (2) Performance verification of the catalyst

[0203] To verify the catalytic activity of the 6% Ag-4% Mn / Al2O3 catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0204] The Al2O3 catalyst prepared in this comparative example exhibited an ozone elimination rate of over 90% after 6 hours and over 85% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0205] Comparative Example 3

[0206] (1) Preparation of catalyst

[0207] The all-silica Beta molecular sieve was replaced with α-Mn2O3, and manganese nitrate solution was no longer added. Everything else was the same as in Example 3, and a 6% Ag / α-Mn2O3 catalyst was prepared.

[0208] Its SEM image is Figure 10 No metal was observed, indicating that the metal was well dispersed on α-Mn2O3.

[0209] (2) Performance verification of the catalyst

[0210] To verify the catalytic activity of the 6% Ag / α-Mn2O3 catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0211] The α-Mn₂O₃ catalyst prepared in this comparative example exhibited an ozone elimination rate of over 79% after 6 hours and over 73% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0212] Comparative Example 4

[0213] (1) Preparation of catalyst

[0214] The all-silica Beta molecular sieve was replaced with MCM-41 molecular sieve, and the rest was the same as in Example 3, to prepare a 6% Ag-4% Mn / MCM-41 catalyst.

[0215] (2) Performance verification of the catalyst

[0216] To verify the catalytic activity of the 6% Ag-4% Mn / MCM-41 molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0217] The MCM-41 molecular sieve catalyst prepared in this comparative example showed an ozone elimination rate of over 77% after 6 hours and over 71% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0218] Comparative Example 5

[0219] (1) Preparation of catalyst

[0220] The all-silica Beta molecular sieve was replaced with a TiO2 molecular sieve, and the rest was the same as in Example 3, to prepare a 6% Ag-4% Mn / TiO2 catalyst.

[0221] (2) Performance verification of the catalyst

[0222] To verify the catalytic activity of the 6% Ag-4% Mn / TiO2 molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0223] The TiO2 catalyst prepared in this comparative example exhibited an ozone elimination rate of over 76% after 6 hours and over 63% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0224] Comparative Example 6

[0225] (1) Preparation of catalyst

[0226] The all-silica Beta molecular sieve was replaced with CeO2 molecular sieve, and the rest was the same as in Example 3, to prepare a 6% Ag-4% Mn / CeO2 catalyst.

[0227] (2) Performance verification of the catalyst

[0228] To verify the catalytic activity of the 6% Ag-4% Mn / CeO2 molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0229] The CeO2 catalyst prepared in this comparative example exhibited an ozone elimination rate of over 68% after 6 hours and over 65% after 12 hours under the test conditions. The ozone elimination curves over time are shown below. Figure 6 As shown.

[0230] Comparative Example 7

[0231] (1) Preparation of catalyst

[0232] Following the preparation method in Example 3, the all-silica Beta molecular sieve was replaced with an alumina-rich Beta molecular sieve (Si / Al = 4), while everything else remained exactly the same as in Example 3, to prepare a 6% Ag-4% Mn / alumina-rich Beta molecular sieve catalyst.

[0233] The nitrogen adsorption results in this embodiment are as follows: Figure 12 As shown in the nitrogen adsorption diagram, no hysteresis loop is present, indicating that the catalyst is not mesoporous. Its contact angle is as follows: Figure 14 As shown, its poor hydrophobicity is one of the reasons for the poor catalyst activity.

[0234] (2) Performance verification of the catalyst

[0235] To verify the catalytic activity of the alumina-rich Beta molecular sieve catalyst, it was subjected to an atmosphere with a humidity of RH = 65% and a space velocity of 840,000 h⁻¹. -1 Ozone elimination tests were conducted at a reaction temperature of 30℃.

[0236] In this embodiment, a 6% Ag-4% Mn / aluminum-rich Beta molecular sieve catalyst was prepared. Under the test conditions, the ozone elimination rate was above 61% after 6 hours, above 57% after 12 hours, and above 45% after 60 hours. The ozone elimination curve over time is shown below. Figure 8 As shown.

[0237] Based on the above experimental data, it can be seen that:

[0238] The all-silicon Beta catalyst provided by this invention performs well at 30°C, RH = 65-85%, and 840,000 h⁻¹. -1 The catalyst maintains high-efficiency and long-term ozone elimination activity under space velocity conditions (reaction time 6–120 h). Notably, the 6% Ag-4% Mn / all-silica Beta molecular sieve catalyst retains over 85% ozone elimination efficiency even under extreme conditions of 120 h. One important influencing factor is that, compared to the Mn₂O₃ and activated carbon supports used in existing technologies, the all-silica Beta molecular sieve used in this invention has mesoporous structure and stronger hydrophobicity; furthermore, the formation of AgMnO₂ with better ozone catalytic decomposition activity during the reaction is more beneficial to the ozone elimination reaction.

[0239] Therefore, compared with existing ozone elimination catalysts supported on activated carbon and Mn2O3, the catalyst of the present invention has significant advantages in terms of moisture resistance, high space velocity, and low temperature catalysis.

[0240] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an all-silica Beta molecular sieve catalyst for ozone removal, characterized in that, The catalyst is obtained by loading Ag and Mn elements from the precursor solution onto the molecular sieve using a two-step impregnation method. When the catalyst is used for ozone catalysis, the surface of MnO2 is unstable and easily reconstructed after contact with ozone. At this time, Ag enters the MnO2 interface to generate AgMnO2, which becomes a new active substance. The preparation method of this catalyst specifically includes the following steps: (1) Powdered all-silica Beta molecular sieve is added to a precursor solution containing Ag element, mixed evenly, and impregnated; the impregnated mixture is subjected to ultrasonication, stirring, and rotary evaporation to obtain a solid, which is then dried and calcined to obtain a powdered catalyst precursor; the all-silica Beta molecular sieve has a three-dimensional twelve-membered ring BEA structure, its surface has mesopores, and its specific surface area is 500~700 m². 2 .g -1 ; (2) The catalyst precursor is added to a precursor solution containing Mn element, mixed evenly and impregnated; the impregnated mixture is ultrasonicated, stirred and rotary evaporated to obtain a solid, and then dried and calcined to obtain a powdered all-silicon Beta molecular sieve catalyst. The precursor solution containing Ag is silver nitrate solution, and the precursor solution containing Mn is manganese nitrate solution. The mass percentage of Ag and Mn in the all-silicon Beta molecular sieve catalyst is adjusted by changing the ratio of the two precursor solutions to the all-silicon Beta molecular sieve. The mass percentage of Ag is 1.0-10.0%, and the mass percentage of Mn is 1.0-10.0%.

2. The method according to claim 1, characterized in that, The concentration of both precursor solutions was 0.1 mol / L.

3. The preparation method according to claim 1, characterized in that, The impregnation treatment is carried out at room temperature for 10 to 12 hours.

4. The preparation method according to claim 1, characterized in that, The ultrasonic treatment was performed at room temperature for 1 hour at a frequency of 45 Hz.

5. The preparation method according to claim 1, characterized in that, The temperature during the rotary evaporation process is 80°C and the rotation speed is 70 rpm.

6. The preparation method according to claim 1, characterized in that, The drying process is carried out at a temperature of 80°C for 2 hours.

7. The preparation method according to claim 1, characterized in that, The heating rate during the roasting process is 5℃ / min, the roasting temperature is 450~550℃, and the roasting time is 4~6h; after roasting, it is naturally cooled to room temperature.

8. A method for using the all-silica Beta molecular sieve catalyst prepared by the method of claim 1 to catalytically eliminate ozone, characterized in that, include: The catalyst was loaded into a fixed-bed reactor, and then the reaction gas containing ozone and saturated water vapor was continuously flowed through the catalyst bed to decompose ozone into oxygen through a catalytic reaction. When the catalyst was used for the ozone catalytic reaction, the surface of MnO2 was unstable after contact with ozone and was easily remodeled. At this time, Ag entered the MnO2 interface to form AgMnO2, which became a new active substance. In this catalytic reaction, the reaction temperature was controlled at 30°C and the volume space-time velocity of the reaction gas was 840,000 h⁻¹. -1 The relative humidity during the reaction is 65-85%, and the reaction time is 6-120 hours.

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