Low-temperature plasma catalysts, their preparation methods and applications

Abstract

This invention relates to the field of low-temperature plasma catalysts, and discloses a low-temperature plasma catalyst, its preparation method, and its applications. The low-temperature plasma catalyst includes a support and an active component supported on the support; the active component contains manganese oxide, and the support is spherical θ-Al₂O₃. This low-temperature plasma catalyst has a rich porous structure, significantly increasing the specific surface area of ​​the catalyst, further improving the catalytic degradation efficiency for VOCs and intermediate organic small molecules, while simultaneously avoiding the generation of byproducts and secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma catalysts, specifically to a low-temperature plasma catalyst, its preparation method, and its application. Background Technology

[0002] Low-temperature plasma technology is widely used to treat volatile organic compounds (VOCs) in petrochemical, painting, aquaculture, and municipal wastewater treatment industries due to its advantages such as simple process, quick start-up and shutdown, and low operating costs. The main reaction principle of this technology is that by applying a high voltage to the positive and negative electrodes, the outer electrons in the gas molecules, under the influence of the electric field formed in the gas gap between the electrodes, can undergo inelastic collisions with both VOC molecules and background gas molecules (such as nitrogen, oxygen, and water vapor), generating active groups such as N radicals, O radicals, and OH radicals, which continue to react with VOC molecules, ultimately mineralizing the VOCs into CO2 and H2O. However, using low-temperature plasma alone to degrade VOCs will produce many toxic intermediate organic small molecules, as well as reaction byproducts such as NOx and O3, causing secondary pollution.

[0003] Studies have shown that combining catalysts with low-temperature plasma technology can effectively suppress the formation of intermediate organic small molecules and reaction byproducts (such as NOx and O3), thereby improving the energy efficiency of VOCs degradation. Based on the placement of the catalyst, plasma-coupled catalysis technology is divided into two types: plasma-embedded catalysis and plasma-post-catalysis. Plasma-embedded catalysis effectively suppresses the formation of intermediate organic small molecules by increasing the local electric field strength and prolonging the reaction time between VOCs molecules and active particles, thus improving the mineralization efficiency of VOCs. However, its decomposition efficiency for byproducts NOx and O3 is lower than that of plasma-post-catalysis. To achieve optimal comprehensive control of organic intermediate products and reaction byproducts, most plasma industrial waste gas treatment devices adopt a post-catalysis coupling method. However, plasma-post-catalysis technology has low mineralization efficiency for intermediate organic small molecules and still cannot completely avoid the emission of byproducts, making it difficult to improve the degradation effect of VOCs. Furthermore, current low-temperature plasma catalysts, in plasma post-catalytic coupling methods, cannot simultaneously address both the catalytic degradation of VOCs, intermediate organic small molecules, and the control of byproduct NOx and O3 emissions. They cannot improve the catalytic degradation efficiency of VOCs while avoiding byproduct emissions, and the catalytic degradation efficiency of VOCs urgently needs to be improved. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low degradation efficiency and easy secondary pollution of VOCs in the process of plasma and catalyst synergistic treatment of VOCs in the existing technology, and to provide a low-temperature plasma catalyst, its preparation method and application. The low-temperature plasma catalyst has a rich pore structure, which greatly increases the specific surface area of ​​the catalyst, further improves the catalytic degradation efficiency of VOCs and intermediate organic small molecules, and can also avoid the generation of by-products and secondary pollution.

[0005] To achieve the above objectives, the present invention provides a low-temperature plasma catalyst, the low-temperature plasma catalyst comprising a support and an active component supported on the support;

[0006] The active component contains manganese oxide, and the support is spherical θ-Al2O3.

[0007] Preferably, the active component further contains a second active component, which is selected from one or more oxides of Ti, Ce, Co and Cu.

[0008] Preferably, the manganese oxide comprises α-MnO2 and one or more of MnO, Mn3O4 and Mn2O3.

[0009] Preferably, based on the total weight of the low-temperature plasma catalyst, the content of the spherical θ-Al2O3 is 60-90 wt%, and the content of the manganese oxide is 10-40 wt%.

[0010] Preferably, based on the total weight of the low-temperature plasma catalyst, the content of the spherical θ-Al2O3 is 40-90 wt%, the content of the manganese oxide is 5-40 wt%, and the content of the second active component is 2.5-20 wt%.

[0011] The second aspect of the present invention provides a method for preparing a low-temperature plasma catalyst, the method comprising: mixing manganese salt, spherical θ-Al2O3, optional second active component precursor with water, spray granulating the resulting mixture, and then calcining it.

[0012] Preferably, the second active component precursor solution is selected from one or more of Ti salt, Ce salt, Co salt and Cu salt.

[0013] Preferably, the particle size of the spherical θ-Al2O3 is 80-600 nm;

[0014] Preferably, the specific surface area of ​​the spherical θ-Al2O3 is 5-50 m². 2 / g;

[0015] Preferably, the surface charge of the spherical θ-Al2O3 is ≥35mV.

[0016] Preferably, the molar ratio of manganese salt, the second active component precursor, and spherical θ-Al2O3 is 0.2-32:1:1.6-61;

[0017] The molar amounts of manganese salt and the second active component precursor are expressed as metal elements.

[0018] Preferably, the conditions for spray granulation include: an inlet temperature of 200-250°C and an outlet temperature of 100-130°C;

[0019] Preferably, the feed rate of the spray granulation is 10-30 mL / min.

[0020] Preferably, the calcination conditions include: a temperature of 500-1000℃ and a time of 4-12h.

[0021] A third aspect of the present invention provides a low-temperature plasma catalyst obtained by the above preparation method.

[0022] The fourth aspect of the present invention provides an application of the aforementioned low-temperature plasma catalyst in the low-temperature plasma degradation of acetone and / or pentane.

[0023] Preferably, the concentration of acetone is 50-2000 ppm;

[0024] Preferably, the concentration of pentane is 50-2000 ppm.

[0025] The low-temperature plasma catalyst of this invention features a rich pore structure with various types of pores, facilitating the passage of large amounts of gas and increasing the contact area with reactants. Furthermore, the low-temperature plasma catalyst utilizes spherical θ-Al₂O₃ as the catalyst support. The stability and large specific surface area of ​​this support allow for uniform loading of the active components, thereby enhancing the catalyst's superior catalytic activity. In addition, the synergistic interaction between the active component manganese oxide and the spherical θ-Al₂O₃ support effectively improves the decomposition efficiency of ozone and NOx on the catalyst's surface, while lowering the thermodynamic energy barrier required for hydroxyl radical generation. This significantly increases the amount of hydroxyl radicals generated and reduces their self-decomposition rate, improving their utilization efficiency. Consequently, it enhances the degradation rate of VOCs and the decomposition rate of byproducts, greatly reducing ozone and NOx emissions and preventing secondary pollution while degrading VOCs.

[0026] Furthermore, in the method described in this invention, the preparation process of the low-temperature plasma catalyst is further simplified by using spray granulation molding, and the prepared catalyst has a rich pore structure, which facilitates the loading of more active components and has great application prospects. Attached Figure Description

[0027] Figure 1 This is a SEM image of spherical θ-Al2O3 in the raw material;

[0028] Figure 2 The image shows a SEM image of the low-temperature plasma catalyst prepared in Example 1.

[0029] Figure 3 This is the XRD pattern of spherical θ-Al2O3 in the raw material;

[0030] Figure 4 These are the XRD patterns of the low-temperature plasma catalysts prepared in Examples 1-3 and Example 9. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] In this invention, the low-temperature plasma catalyst includes a support and an active component loaded on the support; the active component contains manganese oxide, and the support is spherical θ-Al2O3. The low-temperature plasma catalyst of this invention is coupled with plasma technology via post-plasma coupling catalysis, meaning the low-temperature plasma catalyst is placed outside the plasma electric field region. The low-temperature plasma catalyst of this invention can effectively improve the decomposition efficiency of ozone, while lowering the thermodynamic energy barrier required for hydroxyl radical generation, increasing the amount of hydroxyl radicals generated by ozone decomposition, and reducing the rate of self-decomposition of hydroxyl radicals, thereby improving the utilization efficiency of hydroxyl radicals and thus increasing the degradation rate of pollutants and the decomposition rate of byproducts. Hydroxyl radicals are strong oxidizing species. The low-temperature plasma catalyst of this invention catalyzes the decomposition of ozone and further utilizes the hydroxyl radicals obtained from ozone decomposition to degrade intermediate products generated in the plasma region, thereby achieving efficient VOCs degradation while avoiding secondary pollution, and simultaneously reducing ozone and NOx emissions during plasma VOCs degradation.

[0034] In this invention, spherical θ-Al2O3 is selected as a support for loading active components. The spherical θ-Al2O3 has a Zeta potential ≥35mV in aqueous solution, and has advantages such as high dispersibility and high specific surface area. This can make the distribution of the loaded active components more uniform, and can also make the low-temperature plasma catalyst have better stability.

[0035] In this invention, the manganese oxide can be a type of manganese oxide commonly used in the art, such as one or more of MnO, Mn2O3, and MnO2. By combining the supported spherical θ-Al2O3 with the manganese oxide, the low-temperature plasma catalyst can possess both high activity and high selectivity while exhibiting excellent stability.

[0036] In a preferred embodiment, to enhance the catalytic activity of the low-temperature plasma catalyst and improve its removal efficiency of ozone and NOx from the byproducts, the manganese oxide comprises α-MnO2 and optionally one or more of MnO, Mn3O4, and Mn2O3. Understandably, α-MnO2 is a necessary component of the manganese oxide, which may also contain one or more of MnO, Mn3O4, and Mn2O3. For example, the composition of the manganese oxide can be α-MnO2, α-MnO2 and MnO, or α-MnO2, MnO, and Mn3O4. In this invention, the α-MnO2 contained in the manganese oxide possesses excellent activity, primarily functioning to decompose ozone. By further defining the crystal form and composition of the manganese oxide in the active component, the catalytic performance of the low-temperature plasma catalyst can be further improved, thereby further achieving the degradation of VOCs and the control of byproducts.

[0037] In a preferred embodiment, in order to accelerate the generation rate of hydroxyl radicals during the catalytic reaction, the active component further contains a second active component, which is selected from one or more oxides of Ti, Ce, Co and Cu, preferably one or more oxides of Co, Cu and Ce, and more preferably oxides of Ce and / or Co.

[0038] In this invention, through the synergistic cooperation between the support θ-Al2O3, the active component manganese oxide, and the second active component, the low-temperature plasma catalyst can rapidly further treat the byproducts ozone and NOx generated by plasma degradation, and can also improve the degradation rate of VOCs. While realizing the degradation of VOCs by plasma technology, it can also avoid the emission of byproducts, giving full play to the advantages of low-temperature plasma technology and catalytic technology, and realizing the green treatment of VOCs.

[0039] In a preferred embodiment, the content of the components in the low-temperature plasma catalyst is limited. Based on the total weight of the low-temperature plasma post-coupling catalyst, the content of spherical θ-Al₂O₃ is 60-90 wt%, preferably 70-80 wt%; and the content of manganese oxide is 10-40 wt%, preferably 10-30 wt%. Specifically, the content of spherical θ-Al₂O₃ can be 60 wt%, 65 wt%, 68 wt%, 70 wt%, 75 wt%, or 80 wt%; and the content of manganese oxide can be 10 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, 28 wt%, or 30 wt%.

[0040] In this invention, when the active components of the low-temperature plasma catalyst also contain a second active component, based on the total weight of the low-temperature plasma post-coupling catalyst, the content of the spherical θ-Al₂O₃ is 40-90 wt%, preferably 60-80 wt%; the content of the manganese oxide is 5-40 wt%, preferably 10-30 wt%; and the content of the second active component is 2.5-20 wt%, preferably 5-18 wt%. By limiting the content of each component in the low-temperature plasma catalyst, the low-temperature plasma post-coupling catalyst can exhibit superior activity. Specifically, the content of the spherical θ-Al2O3 can be 40wt%, 50wt%, 60wt%, 65wt%, 68wt%, 70wt%, 75wt%, 80wt%, or 90wt%; the content of the manganese oxide can be 10wt%, 15wt%, 18wt%, 20wt%, 25wt%, 28wt%, 30wt%, or 40wt%; and the content of the second active component can be 2.5wt%, 5wt%, 10wt%, 15wt%, or 20wt%.

[0041] According to some embodiments of the present invention, the catalyst comprises a support and an active component supported on the support; the active component contains manganese oxide, and the support is spherical θ-Al₂O₃. The manganese oxide comprises α-MnO₂ and optionally one or more of MnO, Mn₃O₄, and Mn₂O₃. Based on the total weight of the low-temperature plasma post-coupling catalyst, the content of the spherical θ-Al₂O₃ is 60-90 wt%, and the content of the manganese oxide is 10-40 wt%.

[0042] According to other embodiments of the present invention, the catalyst comprises a support and an active component supported on the support; the active component contains manganese oxide, and the support is spherical θ-Al₂O₃. The active component further contains a second active component, the second active component being selected from one or more oxides of Ti, Ce, Co, and Cu. The manganese oxide comprises α-MnO₂ and optionally one or more of MnO, Mn₃O₄, and Mn₂O₃. Based on the total weight of the low-temperature plasma catalyst, the content of the spherical θ-Al₂O₃ is 40-90 wt%, the content of the manganese oxide is 5-40 wt%, and the content of the second active component is 2.5-20 wt%.

[0043] The present invention also provides a method for preparing a low-temperature plasma catalyst, the method comprising: mixing manganese salt, spherical θ-Al2O3, optional second active component precursor with water, spray granulating the resulting mixture, and then calcining it.

[0044] In a specific embodiment, in order to further improve the solubility of manganese salt and optional second active component precursor in water, and to improve the dispersion of the spherical θ-Al2O3 in water, ultrasonic methods can be used to dissolve and disperse them.

[0045] In a specific embodiment, the spherical θ-Al2O3 can be obtained commercially or prepared according to conventional methods in the art, such as the method of patent CN 102515233B.

[0046] In a preferred embodiment, in order to further enrich the pore structure and pore volume of the prepared low-temperature plasma catalyst, the particle size of the spherical θ-Al2O3 is limited to 50-800 nm, preferably 80-600 nm.

[0047] In a preferred embodiment, the specific surface area of ​​the spherical θ-Al2O3 is 5-50 m². 2 / g, preferably 10-40m 2 / g.

[0048] In this invention, the surface charge of the spherical θ-Al2O3 is positive. Preferably, the surface charge of the spherical θ-Al2O3 is ≥30mV, for example, 32-43mV. In the prior art, the surface charge of common spherical Al2O3 is usually negative, which easily leads to agglomeration and sedimentation in aqueous solution. In the method of this invention, by selecting spherical θ-Al2O3 with a positive surface charge as the catalyst support, the specific surface area and pore volume of the prepared low-temperature plasma post-coupling catalyst are increased, and the dispersibility of the prepared low-temperature plasma post-coupling catalyst in aqueous solution is further increased. This can prevent agglomeration and sedimentation for a long time, which is beneficial to the uniformity of the active component loading, provides more sites for the active component to be loaded, prevents the agglomeration of the active component from reducing the catalytic activity, and further improves the catalytic activity of the prepared low-temperature plasma catalyst.

[0049] In this invention, the manganese salt is a water-soluble manganese salt, such as MnCl2 and / or Mn(NO3)2.

[0050] In this invention, the second active component precursor is selected from soluble metal salts other than manganese salts, preferably one or more of Ti salts, Ce salts, Co salts, and Cu salts. The Ti salts, Ce salts, Co salts, and Cu salts are all soluble metal salts.

[0051] In this invention, when the prepared low-temperature plasma catalyst does not contain a second active component, the molar ratio of manganese salt to spherical θ-Al2O3 is 1:8-1.3, wherein the molar amount of manganese salt is calculated as manganese element.

[0052] In a preferred embodiment, when the prepared low-temperature plasma catalyst contains a second active component, the molar ratio of manganese salt, the precursor of the second active component, and spherical θ-Al2O3 is 0.2-32:1:1.6-61, preferably 0.5-10:1:3-15; wherein the molar amounts of manganese salt and the precursor of the second active component are calculated as metal elements.

[0053] In a specific embodiment, to ensure that the prepared low-temperature plasma catalyst has a more uniform particle size and more regular morphology, the obtained mixture can be sieved to remove the agglomerated precipitates before spray granulation. Then, the sieved material is mechanically stirred, and the resulting dispersion is spray granulated. Preferably, the mechanical stirring speed is 200-500 rpm, and the stirring time is 4-8 hours.

[0054] In this invention, the low-temperature plasma catalyst is prepared by spray granulation. Compared with the commonly used solvothermal methods in the prior art, the spray granulation method used in this invention does not require high temperature and high pressure, and the prepared low-temperature plasma catalyst has a more uniform particle size, regular morphology, and abundant pore structure, which greatly increases the specific surface area of ​​the obtained isothermal plasma catalyst. The constructed porous channels facilitate gas flow, thereby improving catalytic efficiency. Furthermore, spray granulation can complete the particle configuration and drying in a very short time, forming a spherical composite oxide catalyst precursor, which greatly shortens the preparation time.

[0055] In a preferred embodiment, the low-temperature plasma catalyst prepared is made to have a relatively regular spherical structure by controlling the inlet and outlet temperatures during the spray granulation process. Preferably, the spray granulation conditions include: an inlet temperature of 200-250°C, more preferably 200-230°C, and even more preferably 210-220°C; and an outlet temperature of 100-130°C, more preferably 100-115°C, and even more preferably 112-114°C.

[0056] In a preferred embodiment, the feed rate for spray granulation is 10-30 mL / min, preferably 10-20 mL / min. The feed rate for spray granulation refers to the rate at which the dispersion is introduced into the spray granulation apparatus.

[0057] In a specific embodiment, the cyclone volume of the spray granulation is 90-100%, preferably 95-100%.

[0058] In this invention, the instrument used for spray granulation in the method is not limited; for example, it can be a spray granulator commonly used in the art.

[0059] In a specific embodiment, the product obtained by spray granulation needs to be dried before calcination. Specifically, the drying temperature can be 100-120℃, preferably 110-115℃; the drying time can be 4-12 hours, preferably 6-10 hours.

[0060] In this invention, the product obtained by spray granulation is dried and then calcined. After calcination, the low-temperature plasma catalyst can be prepared.

[0061] In a preferred embodiment, the calcination conditions include: a temperature of 500-1000℃, preferably 600-800℃; and a time of 4-12h, preferably 6-10h.

[0062] In a preferred embodiment, the heating rate of the roasting process is further defined as 1-5°C / min. Specifically, the heating rate of the roasting process refers to the rate at which the ambient temperature is raised from room temperature to the roasting temperature during the roasting process.

[0063] The present invention further provides a low-temperature plasma catalyst obtained by the above preparation method.

[0064] In this invention, the low-temperature plasma catalyst obtained by the above preparation method includes a support and an active component loaded on the support; the active component contains manganese oxide, and the support is spherical θ-Al2O3. By selecting spherical θ-Al2O3 as the catalyst support, its large specific surface area and other advantages result in a more uniform distribution of the active component on the support. Furthermore, through the synergistic effect between the spherical θ-Al2O3 and the manganese oxide, the energy required for the generation of hydroxyl radicals is further reduced, and ozone is decomposed into reactive hydroxyl radicals more quickly. This achieves the simultaneous degradation of VOCs using plasma while minimizing the emission of ozone and NOx byproducts, truly realizing the harmless treatment of VOCs through plasma-catalyst coupling.

[0065] The present invention also provides an application of the aforementioned low-temperature plasma catalyst in the low-temperature plasma degradation of acetone and / or pentane.

[0066] In this invention, the low-temperature plasma catalyst, after being coupled with plasma technology, can efficiently degrade acetone and / or pentane in VOCs, exhibiting high selectivity for acetone and pentane. More importantly, by coupling the low-temperature plasma catalyst with low-temperature plasma technology, the tail gas after treating acetone and / or pentane can be treated secondary at the downstream end of the low-temperature plasma reactor, significantly improving the degradation rate of acetone and pentane and the total hydrocarbon mineralization rate. Simultaneously, the byproducts O3 and NOx in the tail gas can also be degraded concurrently, resulting in an O3 concentration of less than 1 ppm and a NOx concentration of less than 5 ppm in the final tail gas emission. This achieves effective dual control of intermediate organic small molecules and reaction byproducts generated in the plasma discharge zone, realizing the harmless treatment of acetone and pentane.

[0067] In a preferred embodiment, the concentration of acetone is 50-2000 ppm.

[0068] In a preferred embodiment, the concentration of pentane is 50-2000 ppm.

[0069] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. The embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, but the scope of protection of the present invention is not limited to the following embodiments.

[0070] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0071] The spherical θ-Al2O3 used in the following examples and comparative examples was prepared according to the method of patent CN 102515233B.

[0072] Example 1

[0073] (1) Spherical θ-Al2O3 (particle size 100-200nm, Zeta potential ≥30mV), manganese nitrate, cerium nitrate and cobalt nitrate (n θ-Al2O3 :n Mn :n Ce :n Co =10:3:1:1) mixed with water, sonicated for 30 minutes to mix evenly, the resulting mixture was passed through a 500-mesh sieve, and the sieve material was mechanically stirred at 200 rpm for 4 hours to obtain a dispersion.

[0074] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 220℃, the outlet temperature to 110℃, the cyclone volume to 95%, and the feed rate to 10mL / min. Then, the product obtained by spray granulation is placed in an oven and dried at 115℃ for 8 hours. Then, the dried material is heated to 600℃ at a rate of 5℃ / min and calcined for 6 hours to obtain a low-temperature plasma catalyst.

[0075] XRF testing revealed that the low-temperature plasma catalyst contained 66.5 wt% spherical θ-Al2O3, 17 wt% manganese oxide, 11.3 wt% cerium oxide, and 5.2 wt% cobalt oxide.

[0076] Example 2

[0077] (1) Spherical θ-Al2O3 (particle size 100-500 nm, Zeta potential ≥30 mV), manganese nitrate, cerium nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Ce :n Co =12:4:1:2) and water, sonicate for 30 minutes to mix evenly, pass the resulting mixture through a 500-mesh sieve, take the sieve material and mechanically stir at 150 rpm for 4 hours to obtain a dispersion;

[0078] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 220℃, the outlet temperature to 110℃, the cyclone volume to 95%, and the feed rate to 10mL / min. Then, the product obtained by spray granulation is placed in an oven and dried at 110℃ for 8 hours. Then, the dried material is heated to 600℃ at a rate of 5℃ / min and calcined for 6 hours to obtain a low-temperature plasma catalyst.

[0079] XRF testing revealed that the low-temperature plasma catalyst contained 64.3 wt% spherical θ-Al2O3, 18.3 wt% manganese oxide, 9 wt% cerium oxide, and 8.4 wt% cobalt oxide.

[0080] Example 3

[0081] (1) Spherical θ-Al2O3 (particle size 200-500 nm, Zeta potential ≥35 mV), manganese nitrate, cerium nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Ce :n Co=10:2:1:1) mixed with water, sonicated for 30 minutes to mix evenly, the resulting mixture was passed through a 500-mesh sieve, and the sieve-passing material was mechanically stirred at 200 rpm for 6 hours to obtain a dispersion.

[0082] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 215℃, the outlet temperature to 115℃, the cyclone volume to 98%, and the feed rate to 10ml / min. Then, the product obtained by spray granulation is placed in an oven and dried at 120℃ for 6h. Then, the dried material is heated to 650℃ at a rate of 10℃ / min and calcined for 4h to obtain a low-temperature plasma catalyst.

[0083] XRF testing revealed that the low-temperature plasma catalyst contained 70.5 wt% spherical θ-Al2O3, 12 wt% manganese oxide, 11.9 wt% cerium oxide, and 5.6 wt% cobalt oxide.

[0084] Example 4

[0085] (1) Spherical θ-Al2O3 (particle size 200-500 nm, Zeta potential ≥35 mV), manganese nitrate, copper nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Cu :n Co =10:4:2:1) mixed with water, sonicated for 30 minutes to mix evenly, the resulting mixture was passed through a 500-mesh sieve, and the sieve material was mechanically stirred at 300 rpm for 6 hours to obtain a dispersion.

[0086] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 215℃, the outlet temperature to 115℃, the cyclone volume to 95%, and the feed rate to 15ml / min. Then, the product obtained by spray granulation is placed in an oven and dried at 110℃ for 4h. Then, the dried material is heated to 600℃ at a rate of 2℃ / min and calcined for 5h to obtain a low-temperature plasma post-coupling catalyst.

[0087] XRF testing revealed that the low-temperature plasma catalyst contained 66.8 wt% spherical θ-Al2O3, 22.8 wt% manganese oxide, 5.2 wt% copper oxide, and 5.2 wt% cobalt oxide.

[0088] Example 5

[0089] (1) Spherical θ-Al2O3 (particle size 100-600nm, Zeta potential ≥35mV), manganese nitrate, copper nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Cu :n Co =13:6:1:1) and water, sonicate for 30 minutes to mix evenly, pass the resulting mixture through a 500-mesh sieve, take the sieve material and mechanically stir at 300 rpm for 5 hours to obtain a dispersion;

[0090] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 220℃, the outlet temperature to 110℃, the cyclone volume to 98%, and the feed rate to 10ml / min. Then, the product obtained by spray granulation is placed in an oven and dried at 110℃ for 4h. Then, the dried material is heated to 600℃ at a rate of 2℃ / min and calcined for 5h to obtain a low-temperature plasma catalyst.

[0091] XRF testing revealed that the low-temperature plasma catalyst contained 66 wt% spherical θ-Al2O3, 26 wt% manganese oxide, 4 wt% copper oxide, and 4 wt% cobalt oxide.

[0092] Example 6

[0093] (1) Spherical θ-Al2O3 (particle size 100-800 nm, Zeta potential ≥35 mV), manganese nitrate (n θ-Al2O3 :n Mn =10:3) and water, sonicate for 30 minutes to mix evenly, pass the resulting mixture through a 500-mesh sieve, take the sieve material and mechanically stir at 300 rpm for 5 hours to obtain a dispersion;

[0094] (2) Using a centrifugal nozzle, the dispersion obtained in step (1) is spray-dried in a spray granulator. The inlet temperature is set to 220℃, the outlet temperature to 110℃, the cyclone volume to 98%, and the feed rate to 10ml / min. Then, the product obtained by spray granulation is placed in an oven and dried at 110℃ for 4h. Then, the dried material is heated to 600℃ at a rate of 2℃ / min and calcined for 5h to obtain a low-temperature plasma catalyst.

[0095] XRF testing revealed that the low-temperature plasma catalyst contained 79.6 wt% spherical θ-Al2O3 and 20.4 wt% manganese oxides.

[0096] Example 7

[0097] The method of Example 1 was implemented, except that in step (2), the inlet temperature of spray granulation was 170°C, and a low-temperature plasma catalyst was prepared.

[0098] XRF testing revealed that the low-temperature plasma catalyst contained 66.5 wt% spherical θ-Al2O3, 17 wt% manganese oxide, 11.3 wt% cerium oxide, and 5.2 wt% cobalt oxide.

[0099] Example 8

[0100] The method of Example 1 was implemented, except that the particle size of the selected spherical θ-Al2O3 was 1-10 μm and the Zeta potential was -15 mV.

[0101] XRF testing revealed that the prepared low-temperature plasma catalyst contained 66.5 wt% spherical θ-Al2O3, 17 wt% manganese oxide, 11.3 wt% cerium oxide, and 5.2 wt% cobalt oxide.

[0102] Example 9

[0103] The method of Example 1 was implemented, except that the calcination temperature in step (2) was 400°C;

[0104] XRF testing revealed that the low-temperature plasma catalyst contained 70.5 wt% spherical θ-Al2O3, 12 wt% manganese oxide, 11.9 wt% cerium oxide, and 5.6 wt% cobalt oxide.

[0105] Example 10

[0106] The method of Example 1 was carried out, except that cerium nitrate was replaced with an equal amount of ferric nitrate for preparation.

[0107] XRF testing revealed that the low-temperature plasma catalyst contained 66.9 wt% spherical θ-Al2O3, 26.3 wt% manganese oxide, 2.7 wt% iron oxide, and 4.1 wt% cobalt oxide.

[0108] Example 11

[0109] The method was carried out according to Example 1, except that the molar ratio of θ-Al2O3, manganese nitrate, cerium nitrate and cobalt nitrate was 10:10:10:3;

[0110] XRF testing revealed that the low-temperature plasma catalyst contained 26.5 wt% spherical θ-Al2O3, 22.6 wt% manganese oxide, 44.7 wt% cerium oxide, and 6.2 wt% cobalt oxide.

[0111] Example 12

[0112] The method of Example 1 was implemented, except that the calcination temperature in step (2) was 1100°C.

[0113] XRF testing revealed that the low-temperature plasma catalyst contained 59.4 wt% spherical θ-Al2O3, 23 wt% manganese oxide, 9.1 wt% cerium oxide, and 8.5 wt% cobalt oxide.

[0114] Comparative Example 1

[0115] The method of Example 1 was carried out, except that the spherical θ-Al2O3 was replaced with an equal weight of γ-Al2O3 for preparation.

[0116] XRF testing revealed that the low-temperature plasma catalyst contained 66.5 wt% spherical γ-Al2O3, 17 wt% manganese oxide, 11.3 wt% cerium oxide, and 5.2 wt% cobalt oxide.

[0117] Comparative Example 2

[0118] The method of Example 1 was carried out, except that manganese nitrate was not added during the preparation.

[0119] XRF testing revealed that the low-temperature plasma catalyst contained 80.2 wt% spherical θ-Al2O3, 13.5 wt% cerium oxide, and 6.3 wt% cobalt oxide.

[0120] Test case

[0121] Test Example 1

[0122] The surface morphology of θ-Al2O3 in the raw material was tested using SEM, such as... Figure 1 As shown, the carrier is spherical with a regular morphology and a particle size of approximately 50-800 nm.

[0123] The surface morphology of the low-temperature plasma catalyst prepared in Example 1 was tested using SEM, as shown below. Figure 2 As shown, the low-temperature plasma catalyst is spherical, and the surface of the support θ-Al2O3 is loaded with active components and a second active component, with a regular structure.

[0124] Test Example 2

[0125] XRD was used to determine the crystal form of spherical θ-Al2O3 in the raw material, and the results are as follows: Figure 3 As shown. By Figure 3 It is known that the alumina used as the carrier in this invention is θ-Al2O3;

[0126] The low-temperature plasma catalysts prepared in Examples 1-3 and 9 were tested by XRD, and the results are as follows: Figure 4 As shown. By Figure 4 It is known that in the low-temperature plasma catalysts prepared in Examples 1-3 of the present invention, the active component manganese oxide contains α-MnO2, and the crystal form of the support alumina is θ-Al2O3. In the low-temperature plasma catalyst prepared in Example 9, the active component does not contain α-MnO2 or the content of α-MnO2 is too low due to the calcination temperature being too low, thereby affecting the effect of the low-temperature plasma catalyst on the degradation of by-products.

[0127] Test Example 3

[0128] The degradation rate of pentane was tested on the low-temperature plasma catalysts prepared in Examples 1-12 and Comparative Examples 1-2, and the concentrations of O3 and NOx in the tail gas were also tested.

[0129] Test method: A simulated gas (pentane concentration of 300 ppm) was passed into a plasma device for treatment. The pentane content in the treated pollutants was determined using an Agilent 8890B gas chromatograph, equipped with a dual-flame ionization detector, according to the formula: (M 模拟气体中戊烷的浓度 -M 降解后气体中戊烷的浓度 )÷M 模拟气体中戊烷的浓度 The degradation rate of pentane was calculated by multiplying the value by 100%, and the results are shown in Table 1.

[0130] The concentration of NOx in the exhaust gas was analyzed online using a gas analyzer (model Antaris IGS), and the results are shown in Table 1.

[0131] The changes in O3 concentration in the treated exhaust gas were detected using a 106-M ozone analyzer from 2B Corporation of the United States. The results are shown in Table 1.

[0132] Table 1

[0133] Example number Degradation rate of pentane <![CDATA[Concentration of O3 in the exhaust gas / ppm]]> NOx concentration in exhaust gas / ppm Example 1 98.5％ 0.01 1.1 Example 2 98.3％ 0.01 0.9 Example 3 98.4％ 0.06 2.3 Example 4 98.3％ 0.10 3.7 Example 5 98.1％ 0.03 1.5 Example 6 92％ 1.51 35.6 Example 7 81％ 97 68.5 Example 8 77％ 49 79.5 Example 9 75％ 41 77.6 Example 10 89％ 0.85 15.6 Example 11 90％ 0.57 7.8 Example 12 69％ 36.5 50.2 Comparative Example 1 74％ 53 115.2 Comparative Example 2 45％ 560 350.4

[0134] As can be seen from the results in Table 1, the low-temperature plasma post-coupling catalyst of the present invention, after being coupled with plasma technology, can significantly improve the degradation rate and mineralization rate of pentane without increasing the discharge power. The degradation rate of pentane can reach about 98.5%, while greatly reducing the emission of by-products such as O3 and NOx, thus achieving the harmless treatment of VOCs.

[0135] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A low-temperature plasma catalyst, characterized in that, The catalyst includes a support and an active component supported on the support; the active component contains manganese oxide, and the support is spherical θ-Al2O3. The preparation method of the low-temperature plasma catalyst includes: mixing manganese salt, spherical θ-Al2O3 with water, spray granulating the resulting mixture, and then calcining it; The spherical θ-Al2O3 has a particle size of 50-800 nm, a surface Zeta potential of ≥30 mV, and an inlet temperature of 200-250 °C for spray granulation.

2. The low-temperature plasma catalyst according to claim 1, characterized in that, The active component further contains a second active component, which is selected from one or more oxides of Ti, Ce, Co and Cu. The preparation method of the low-temperature plasma catalyst includes: mixing manganese salt, spherical θ-Al2O3, a second active component precursor and water, spray granulating the resulting mixture, and then calcining it.

3. The low-temperature plasma catalyst according to claim 1, characterized in that, The manganese oxide comprises α-MnO2 and one or more of MnO, Mn3O4 and Mn2O3.

4. The low-temperature plasma catalyst according to claim 1 or 3, characterized in that, The total weight of the low-temperature plasma catalyst is 100wt%, the content of the spherical θ-Al2O3 is 60-90wt%, and the content of the manganese oxide is 10-40wt%.

5. The low-temperature plasma catalyst according to claim 2, characterized in that, With a total weight of 100wt% for the low-temperature plasma catalyst, the content of the spherical θ-Al2O3 is 40-90wt%, the content of the manganese oxide is 5-40wt%, and the content of the second active component is 2.5-20wt%.

6. The low-temperature plasma catalyst according to claim 2, characterized in that, The second active component precursor is selected from one or more of Ti salts, Ce salts, Co salts and Cu salts.

7. The low-temperature plasma catalyst according to claim 1, characterized in that, The specific surface area of ​​the spherical θ-Al2O3 is 5-50 m². 2 / g.

8. The low-temperature plasma catalyst according to claim 2 or 6, characterized in that, The molar ratio of manganese salt, the precursor of the second active component, and spherical θ-Al2O3 is 0.2-32:1:1.6-61; The molar amounts of manganese salt and the second active component precursor are expressed as metal elements.

9. The low-temperature plasma catalyst according to claim 1, characterized in that, The outlet temperature of the spray granulation is 100-130℃.

10. The low-temperature plasma catalyst according to claim 1 or 9, characterized in that, The feed rate for spray granulation is 10-30 mL / min.

11. The low-temperature plasma catalyst according to claim 1, characterized in that, The roasting conditions include a temperature of 500-1000℃ and a time of 4-12 hours.

12. The use of the low-temperature plasma catalyst according to any one of claims 1-11 in the low-temperature plasma degradation of acetone and / or pentane.

13. The application according to claim 12, characterized in that, The concentration of acetone is 50-2000 ppm.

14. The application according to claim 12, characterized in that, The concentration of pentane is 50-2000 ppm.

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