Quenching preparation process of high-performance MnO2-based catalyst

Abstract

The invention discloses a quenching preparation process of a high-performance MnO-based catalyst, relates to a preparation method of a MnO2-based catalyst, and provides a unique quenching technology for preparing the high-performance MnO2-based catalyst. The technology can be applied to construction of oxygen deficiency in MnO2 so as to promote catalytic oxidation decomposition of volatile organic compounds (VOCs). According to the technical scheme, the preparation method comprises the following steps: (1) firstly, preparing MnO2 or heteroatom modified MnO2; (2) carrying out high-temperature calcination on MnO2 or heteroatom modified MnO prepared in the step (1) to a certain temperature; and (3) dipping the calcined MnO2 or heteroatom modified MnO2 in a coolant, and rapidly cooling to a certain temperature. The finally prepared MnO2 catalyst is rich in defects, can realize complete oxygenolysis of volatile organic compounds at a low temperature, and shows excellent stability, cycling stability and water resistance.

Description

Technical Field

[0001] The present invention relates to a preparation method of an MnO2-based catalyst, and particularly to a quenching method for preparing a high-performance MnO2-based catalyst. Background Art

[0002] The technology for efficient purification and removal of volatile organic compounds has important theoretical and practical significance for improving air quality and ensuring human health. Catalytic oxidation technology has the advantages of high efficiency and low operating temperature, and is one of the most promising methods for VOCs removal at present. The focus of catalytic oxidation revolves around the design and preparation of catalysts that are efficient at low temperatures, stable at high temperatures, and economically feasible.

[0003] MnO2-based catalysts are widely used in the catalytic degradation of VOCs due to their economic price, adjustable crystal phase, and excellent oxygen storage capacity. In the design and preparation of MnO2-based catalysts, constructing oxygen defects is an effective approach. The large number of oxygen defects can not only improve the reaction activity of lattice oxygen molecules in the catalyst, but also promote the adsorption and activation of gaseous oxygen species, thereby enhancing the catalytic purification of volatile organic compounds. Developing new defect construction strategies is of great significance for enriching the design and preparation methods of MnO2-based catalysts. Summary of the Invention

[0004] The purpose of the present invention is to provide a quenching method for preparing a high-performance MnO2-based catalyst. The present invention develops a unique quenching technique to prepare a high-performance MnO2-based catalyst, thereby realizing the low-temperature oxidative decomposition of VOCs; the high-performance MnO2-based catalyst prepared by the present invention has significant low-temperature catalytic activity, water resistance, durability, and cycle stability for the prepared catalyst rich in defects.

[0005] The present invention adopts the following technical solutions: A quenching method for preparing a high-performance MnO2-based catalyst, the method comprising the following steps: 1) Prepare a manganese-containing solution, then transfer the solution to a high-pressure reaction kettle for reaction. After the reaction is completed, perform suction filtration, washing, and drying to obtain an MnO2 precursor; 2) Place the obtained MnO2 precursor in a muffle furnace for high-temperature calcination; 3) After taking out the MnO2 after high-temperature calcination from the muffle furnace, directly immerse it in a cooling medium to rapidly cool it to below 100 °C to obtain an MnO2 catalyst rich in oxygen defects; 4) The MnO2 catalyst rich in oxygen defects is used for the preparation of manganese dioxide-based catalysts of three crystal phases: α-MnO2, β-MnO2, and γ-MnO2.

[0006] The described quenching method for preparing a high-performance MnO2-based catalyst, where the temperature is higher than 300 °C when calcining the MnO2 precursor.

[0007] The described quenching method for preparing a high-performance MnO2-based catalyst, where the cooling medium is an ice-water mixture or liquid nitrogen coolant.

[0008] The described quenching method for preparing a high-performance MnO2-based catalyst, where the preparation of the manganese dioxide-based catalyst with three crystal phases of α-MnO2, β-MnO2, and γ-MnO2 includes the preparation of metal-ion-doped α-MnO2, β-MnO2, and γ-MnO2 catalysts.

[0009] The described quenching method for preparing a high-performance MnO2-based catalyst, where the doped metals include Ce, Co, Cu, Ni, Ag, and Fe.

[0010] The described quenching method for preparing a high-performance MnO2-based catalyst, where the α-MnO2, β-MnO2, and γ-MnO2 catalysts rich in defect sites and the metal-ion-doped α-MnO2, β-MnO2, and γ-MnO2 catalysts can be widely applied to the catalytic oxidation and removal of VOCs.

[0011] The significant advantages of the present invention are as follows: 1. The quenching technique can efficiently create defects in the MnO2 (or metal-doped MnO2) structure. The presence of defects can significantly enhance the reactivity of lattice oxygen and simultaneously promote the adsorption and activation of gaseous oxygen molecules. Therefore, the high-defect MnO2 (or metal-doped MnO2) catalyst prepared by the present invention exhibits advantages such as good low-temperature activity, strong water resistance, strong recyclability, and strong stability in the catalytic oxidation purification reaction of volatile organic waste gases.

[0012] 2. The MnO2 (or metal-doped MnO2) catalyst prepared by the present invention is rich in structural defects and oxygen defects, which can significantly enhance the reactivity of lattice oxygen and simultaneously promote the adsorption and activation of gaseous oxygen molecules. The high-defect MnO2 (or metal-doped MnO2) catalyst prepared by the present invention exhibits advantages such as good low-temperature activity, strong water resistance, strong recyclability, and strong stability in the catalytic oxidation purification reaction of volatile organic waste gases. Description of the Drawings

[0013] Figure 1 is the VOCs decomposition rate of α-MnO2-500 and α / β / γ-CuMnO2-500 and α / β / γ-CuMnO2-500-Q with different phases (using toluene as the probe molecule); Figure 2It is the activity diagram of α-CuMnO2-500-Q, α-CuMnO2-400, α-CuMnO2-400-Q, α-CuMnO2-300, α-CuMnO2-300-Q, and α-CuMnO2-500 catalysts; Figure 3 It is the SEM diagram of α-CuMnO2-500-Q; Figure 4 It is the SEM diagram of α-CuMnO2-500; Figure 5 It is the Raman diagram of α-CuMnO2-500-Q and α-CuMnO2-500; Figure 6 It is the EPR diagram of α-CuMnO2-500-Q and α-CuMnO2-500. Detailed implementation method

[0014] The embodiments of the present invention are described in detail below. The following described examples are illustrative only and are used to explain the present invention, but not to limit the present invention.

[0015] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared according to the conventional methods well-known to those skilled in the art.

[0016] A quenching method for preparing a high-performance MnO2-based catalyst includes the following steps: (1) Dissolve the manganese source (or the salt solution of the manganese source and the doped metal) in water, and continuously stir for 30 min to form a uniform solution; (2) Transfer the above uniform solution to a high-pressure reaction kettle, react at a specific temperature for a certain time, and after the reaction is completed, perform suction filtration, washing, and drying; (3) Calcinate the dried precipitate in a muffle furnace to obtain MnO2 (or metal-doped MnO2).

[0017] (4) Immediately take out the obtained MnO2 (or metal-doped MnO2) from the furnace and immerse it in a coolant, and a MnO2 (or metal-doped MnO2) catalyst rich in defects can be prepared without going through a conventional cooling process.

[0018] The manganese source described in step (1) is potassium permanganate and a salt solution of manganese.

[0019] The salt solution of the doped metal described in step (1) can be nitrate, chloride, acetate, or sulfate.

[0020] The molar ratio of the doped metal to MnO2 described in step (1) is between 0.01 and 0.2.

[0021] The reaction temperature of the mixed solution described in step (1) is between 100 - 200 °C.

[0022] The calcination temperature range described in step (3) is 300 - 800 °C, and the calcination time range is 1 - 10 h.

[0023] The MnO2 (or metal-doped MnO2) catalyst prepared in step (4) is applied to the field of catalytic oxidation and decomposition of volatile organic compounds.

[0024] The catalyst prepared in the present invention is prepared in Cu-doped α-MnO2 through a unique quenching strategy. The specific operation details of the synthesis catalyst are shown in the following examples. Example 1

[0025] 1) Dissolve 1.50 g of potassium permanganate (KMnO4) and 0.28 g of manganese sulfate monohydrate (MnSO4·H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reaction kettle, heat it at 160 °C for 12 h, and after the reaction is completed, perform suction filtration, washing, and drying; 3) Place the dried precipitate in a muffle furnace and heat it at a heating rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h to obtain α-MnO2-500. Example 2

[0026] 1) Dissolve 1.50 g of potassium permanganate (KMnO4), 0.28 g of manganese sulfate monohydrate (MnSO4·H2O) and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reaction kettle, heat it at 160 °C for 12 h, and after the reaction is completed, perform suction filtration, washing, and drying; 3) Place the dried precipitate in a muffle furnace and heat it at a heating rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h to obtain α-CuMnO2-500; 4) Immediately take out the obtained α-CuMnO2-500 from the furnace and immerse it in ice water without going through the conventional cooling process, that is, the prepared one is the copper-doped α-MnO2 catalyst with rich defects (α-CuMnO2-500-Q). Example 3

[0027] 1) Dissolve 0.28 g of potassium permanganate (KMnO4), 0.45 g of manganese sulfate monohydrate (MnSO4·H2O), and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reactor, heat it at 160 °C for 12 h, and perform suction filtration, washing, and drying after the reaction; 3) Calcinate the dried precipitate in a muffle furnace, program the temperature to rise at a rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h. The sample is named β-CuMnO2-500. Example 4

[0028] 1) Dissolve 0.28 g of potassium permanganate (KMnO4), 0.45 g of manganese sulfate monohydrate (MnSO4·H2O), and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reactor, heat it at 160 °C for 12 h, and perform suction filtration, washing, and drying after the reaction; 3) Calcinate the dried precipitate in a muffle furnace, program the temperature to rise at a rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h. The sample is named β-CuMnO2-500; 4) Immediately take out the obtained β-CuMnO2-500 from the furnace and immerse it in ice water without going through the conventional cooling process. The prepared catalyst is a copper-doped β-MnO2 catalyst with rich defects (β-CuMnO2-500-Q). Example 5

[0029] 1) Dissolve 3.38 g of manganese sulfate monohydrate (MnSO4·H2O), 4.56 g of ammonium persulfate ((NH4)2S2O8), and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reactor and heat it at 90 °C for 24 h. Perform suction filtration, washing, and drying after the reaction; 3) Calcinate the dried precipitate in a muffle furnace, program the temperature to rise at a rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h. The sample is named γ-CuMnO2-500. Example 6

[0030] 1) Dissolve 3.38 g of manganese sulfate monohydrate (MnSO4·H2O), 4.56 g of ammonium persulfate ((NH4)2S2O8), and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reactor and heat at 90 °C for 24 h. After the reaction is completed, perform suction filtration, washing, and drying; 3) Place the dried precipitate in a muffle furnace and calcine it with a heating rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h. The sample is named γ-CuMnO2-500; 4) Immediately take out the obtained γ-CuMnO2-500 from the furnace and immerse it in ice water without going through the conventional cooling process. The prepared catalyst is the copper-doped γ-MnO2 catalyst with rich defects (γ-CuMnO2-500-Q).

[0031] Comparative Example 1 1) Dissolve 1.50 g of potassium permanganate (KMnO4), 0.28 g of manganese sulfate monohydrate (MnSO4·H2O), and 0.27 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 80 mL of deionized water, and stir for 30 min with a magnetic stirrer to form a homogeneous solution; 2) Transfer the above homogeneous solution to a high-pressure reactor and heat at 160 °C for 12 h. After the reaction is completed, perform suction filtration, washing, and drying; 3) Place the dried precipitate in a muffle furnace and calcine it with a heating rate of 1 °C / min to 500 °C, and keep it at a constant temperature for 2 h to obtain α-CuMnO2-500.

[0032] Test Example 1 The catalysts α-MnO2-500, α-CuMnO2-500, α-CuMnO2-500-Q, α-CuMnO2-400, α-CuMnO2-400-Q, α-CuMnO2-300, α-CuMnO2-300-Q, β-CuMnO2-500, β-CuMnO2-500-Q, γ-CuMnO2-500, and γ-CuMnO2-500-Q were used for the catalytic oxidative combustion of volatile organic compounds (using toluene as a probe molecule) to evaluate the performance of the catalysts. At the beginning of the experiment, 100 mg of the catalyst sample was accurately loaded into a quartz tube, and quartz wool was safely filled at the end of the catalyst to ensure the stability of the reaction process. During the experiment, the reaction gas composition was toluene with a concentration of 500 ppm, an oxygen-nitrogen volume ratio of 20%, a flow rate of 100 mL / min, and a gas hourly space velocity (WHSV) of 60,000 mL / (g·h). We used an online gas chromatograph (FULI 9790 II) and a flame ionization detector (FID) to analyze the concentration of the exhaust gas. To eliminate the influence of toluene adsorption on the catalyst, a stable reaction was carried out at low temperature, and data were recorded for calculation.

[0033] Figure 1 It clearly shows that the quenching treatment effectively improves the catalytic activity of catalysts with different phases; Figure 2 Among the catalytic activities of Cu-doped α-MnO2 catalysts calcined at different temperatures, the T of α-CuMnO2-500-Q 90 is 80 °C lower than that of α-CuMnO2-500. Without a doubt, α-CuMnO2-500-Q exhibits the highest catalytic performance.

[0034] Test Example 2 SEM tests were carried out on the α-CuMnO2-500-Q and α-CuMnO2-500 catalyst samples of Example 2 and Comparative Example 1 using a scanning electron microscope. Figure 3 、 Figure 4 The SEM images in show that α-CuMnO2-500-Q and α-CuMnO2-500 exhibit a flower-like morphology constructed by countless nanorods, and the quenching treatment does not change the structure of α-CuMnO2-500-Q.

[0035] Test Example 3 The structural characteristics of α-CuMnO2-500-Q and α-CuMnO2-500 of Example 2 and Comparative Example 1 were further studied by Raman spectroscopy. Figure 5Among them, compared with α-CuMnO2-500, the Raman peaks of α-CuMnO2 - 500-Q showed significant red shifts. As a direct signal of lattice defects, the shifted Raman peaks demonstrated an increase in oxygen vacancies in α-CuMnO2 -500-Q.

[0036] Test Example 4 As Figure 6 To more intuitively reveal the role of quenching treatment in generating oxygen vacancies, EPR tests were performed on the α-CuMnO2 -500-Q and α-CuMnO2 -500 catalysts of Example 2 and Comparative Example 1. The symmetric signal at g = 2.002 can be attributed to oxygen vacancies. Obviously, α-CuMnO2 -500-Q showed a stronger signal, indicating a higher content of oxygen defects.

[0037] The above embodiments are only preferred embodiments of the present invention and are not limitations on the implementation manners. The protection scope of the present invention should be subject to the scope defined by the claims. Other different forms of changes or modifications can be made on the basis of the above description. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A quenching method for preparing a high-performance MnO2-based catalyst, characterized in that, The method includes the following steps: 1) Prepare a manganese-containing solution, then transfer the solution to a high-pressure reactor for reaction. After the reaction, perform suction filtration, washing, and drying to obtain a MnO2 precursor; 2) Place the obtained MnO2 precursor in a muffle furnace for high-temperature calcination; 3) After taking out the MnO2 after high-temperature calcination from the muffle furnace, directly immerse it in a cooling medium to rapidly cool it to below 100 °C to obtain a MnO2 catalyst rich in oxygen defects; 4) The MnO2 catalyst rich in oxygen defects is used for the preparation of manganese dioxide-based catalysts of three crystal phases of α-MnO2, β-MnO2, and γ-MnO2.

2. The quenching method for preparing a high-performance MnO2-based catalyst according to claim 1, characterized in that, When calcining the MnO2 precursor, the temperature is higher than 300 °C.

3. The quenching method for preparing a high-performance MnO2-based catalyst according to claim 1, characterized in that, The cooling medium is an ice-water mixture or liquid nitrogen coolant.

4. The quenching method preparation process of a high-performance MnO2-based catalyst according to claim 1, characterized in that, The manganese dioxide-based catalysts of the three crystal phases of α-MnO2, β-MnO2, and γ-MnO2 include the preparation of α-MnO2, β-MnO2, and γ-MnO2 catalysts doped with metal ions.

5. The quenching method for preparing a high-performance MnO2-based catalyst according to claim 1, characterized in that, The doped metals include Ce, Co, Cu, Ni, Ag, and Fe.

6. The quenching method for preparing a high-performance MnO2-based catalyst according to claim 1, characterized in that, The α-MnO2, β-MnO2, and γ-MnO2 catalysts rich in defect sites and the α-MnO2, β-MnO2, and γ-MnO2 catalysts doped with metal ions can be widely used in the catalytic oxidation and removal of VOCs.

Images