Method for degrading n-pentane by using Mn-CeO2 doped oxide catalyst in cooperation with low-temperature plasma

Abstract

The present application belongs to the technical field of catalyst and low-temperature plasma purification of n-pentane-containing waste gas, and discloses a method for degrading n-pentane by using Mn-CeO2 doped oxides as catalysts in cooperation with low-temperature plasma. x The present application can realize 100% conversion of n-pentane under the conditions of temperature ≥ 30℃ and plasma energy density 10-150 J / L, and can release active sites by using non-noble metal doping, plasma-catalyzed oxidation reaction, nano engineering and interface reaction to realize low-temperature gasification of carbonates on the surface of the catalyst. The selectivity can reach up to 97%, and the generation of ozone by-products in the reaction process is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst-assisted low-temperature plasma purification of n-pentane-containing waste gas, and specifically relates to a method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma. Background Art

[0002] VOCs are mainly divided into alkanes, alkenes, alkynes, benzene series, alcohols, aldehydes, ethers, ketones, acids, esters, halogenated hydrocarbons and others, among which alkanes have the greatest impact on air pollution. 12 As a typical alkane VOCs, its emission control has become a research hotspot in the field of environmental science due to its wide application in industrial production, such as paints, solvents and petrochemical fuels.

[0003] Traditional VOCs purification methods, such as activated carbon adsorption, thermal catalytic combustion, and biodegradation, can reduce VOCs emissions to a certain extent, but they often have problems such as high energy consumption, low treatment efficiency, or secondary pollution. Therefore, the development of new and efficient VOCs purification technologies is particularly important. In recent years, plasma catalysis technology has attracted widespread attention due to its unique advantages. Due to the advantages of plasma-catalytic systems such as high degradation efficiency and good selectivity, many research works have focused on using plasma-catalytic systems to degrade various VOCs. The generation method of NTP and the type of catalyst in the plasma-catalytic system are key factors affecting its catalytic oxidation degradation rate, byproducts, and energy efficiency. Due to the shortage of precious metal resources and high cost, the development of efficient non-metallic catalysts has become necessary.

[0004] Patent No. CN115704097A relates to an M1M2 diatomic catalyst, its preparation method, and application. The core active site of this catalyst consists of two metal atoms, M1 and M2, separated by a distance L. M1 and M2 can be the same metal or different metals, both selected from Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Ru, Rh, Pd, Ir, Pt, Ag, and Au. The catalyst support can be a carbonaceous support or a metal oxide, prepared by high-temperature pyrolysis in an inert gas environment.

[0005] Patent number CN2019110111392A "A three-dimensional ordered macroporous oxygen-deficient cerium dioxide catalyst, its preparation method and application" uses a polymethyl methacrylate (PMMA) colloidal crystal template method to prepare a cerium dioxide catalyst. The prepared catalyst shows excellent activity and stability in the photothermal catalytic purification of typical atmospheric pollutants such as styrene, n-hexane and cyclohexane.

[0006] Patent No. CN114206781A describes a nickel composite hydroxide and its use as a precursor for a positive electrode active material in a non-aqueous electrolyte secondary battery. The composite hydroxide contains nickel (Ni), cobalt (Co), and at least one additional metal element selected from manganese (Mn), aluminum (Al), iron (Fe), and titanium (Ti). The method for preparing the nickel composite hydroxide includes mixing an aqueous solution containing a nickel salt, a cobalt salt, and a salt of the selected additional metal element with an aqueous solution containing an ammonium ion source and a pH adjuster, and performing a coprecipitation reaction in a reaction vessel to produce a crude nickel composite hydroxide.

[0007] Despite these significant advances in plasma-catalyzed degradation of VOCs, challenges remain. Although low-temperature plasma technology is highly efficient and applicable in treating volatile organic compounds, it also has some disadvantages. First, the technology has relatively high energy consumption, especially when treating VOCs with large space velocities and low concentrations, the energy consumption problem is more significant and the economic benefits are low. Second, in some cases, plasma-catalyzed degradation of VOCs will produce secondary pollution, such as ozone and harmful byproducts that are not completely converted into CO2. These byproducts will not only aggravate damage to the environment, but also endanger people's health. Finally, some plasma-catalyzed degradation of VOCs has high requirements for reaction environment conditions, requiring high reaction temperature, a certain pressure and some other environmental factors. Therefore, although plasma technology has broad prospects, it still needs to be improved and optimized in many aspects.

[0008] Therefore, this patent develops a catalyst that is simple to prepare, has mature and reliable technology, and has less environmental pollution, and a method for purifying n-pentane-containing waste gas at room temperature with efficient plasma, low energy consumption, less secondary pollution, high CO2 selectivity, and synergistic plasma. Summary of the Invention

[0009] The present invention relates to a method for degrading n-pentane using a Mn-CeO2 doped oxide catalyst in conjunction with low-temperature plasma. The Mn-CeO2 doped oxide is used as a catalyst. The catalyst can achieve C5H2O2 degradation under conditions of a relatively low temperature (30°C) and a plasma energy density (ED) of 10 to 150 J / L. 12 (i.e. 100% conversion of n-pentane), CO x The selectivity is as high as 97%, and the generation of ozone can be greatly reduced.

[0010] Specifically, the Mn-CeO2 doped oxide catalyst of the present invention is characterized in that the atomic ratio of manganese Mn to cerium Ce in the catalyst is in the range of 0.25 to 4, more specifically, the ratio is in the range of 0.75 to 4. Preferably, the ratio is in the range of 1-2. This specific atomic ratio helps to improve the activity of the catalyst in synergistic plasma degradation of n-pentane and COx Selective.

[0011] Furthermore, the Mn-CeO2-doped oxide catalyst has a unique structure, appearing as a sphere or hollow crushed sphere. These shells can be open or closed, with outer diameters ranging from 10 nanometers to 5 microns. A novel burr structure has been observed on the shells. This burr structure on the spherical shells increases the catalyst's specific surface area and surface defects, a key factor in the efficient purification of n-pentane using low-temperature plasma.

[0012] The above-mentioned Mn-CeO2 doped oxide catalyst is prepared by aerosol high temperature decomposition method. The Mn-CeO2 doped oxide catalyst prepared by this method can achieve high conversion rate in cooperation with low temperature plasma under room temperature conditions, and has high efficiency, low energy consumption, less secondary pollution, and high CO x The catalyst of the present invention has the advantages of selectivity and room temperature purification. By precisely controlling the ratio of manganese and cerium and the nanostructure of the catalyst, it exhibits excellent performance in the synergistic low-temperature plasma catalytic degradation of n-pentane.

[0013] The preparation method of the Mn-CeO2 doped oxide catalyst comprises the following steps:

[0014] S1: Atomizing an aqueous solution containing a manganese compound and a cerium compound. The mist is carried into an insulated pipe by an inert gas, and the water vaporizes to form an aerosol containing small solid particles of manganese nitrate and cerium nitrate.

[0015] S2: the aerosol is introduced into a high-temperature decomposition tube along with the inert gas to decompose into manganese and cerium oxide, wherein the manganese is doped into the cerium oxide lattice to form a partially or fully doped Mn-CeO2 doped oxide solid product;

[0016] S3: The Mn-CeO2 doped oxide solid product enters the water absorption bottle along with the inert gas, is absorbed by water, and is then separated by high-speed centrifugation to obtain the Mn-CeO2 doped oxide catalyst after drying.

[0017] Furthermore, the temperature of the heat-insulating pipe is 60-70°C, and the temperature of the high-temperature decomposition tube is 500-800°C.

[0018] Furthermore, the temperature of the insulation pipe is 70°C, and the temperature of the high-temperature decomposition tube is 600°C.

[0019] Furthermore, the drying temperature is 80° C. and the drying time is 12 hours.

[0020] The method for degrading n-pentane using a Mn-CeO2 doped oxide catalyst in conjunction with a low-temperature plasma of the present invention uses Mn-CeO2 doped oxide as a catalyst and performs catalytic oxidation degradation of n-pentane at a plasma energy density of 10-150 J / L and a temperature of ≥30°C.

[0021] Furthermore, the n-pentane concentration is 30-330 mg / m 3 ; The gas volume space velocity is 5000-50000mL / (gh).

[0022] Furthermore, applications of the n-pentane degradation process include purification of n-pentane-containing gas and degradation of n-pentane produced in petrochemical enterprises and refineries.

[0023] The beneficial effects of the present invention are:

[0024] The present invention adopts non-precious metal doping, high temperature, nano-engineering and interface to realize the catalyst-cooperated low-temperature plasma through the low-temperature gasification of carbonate on the catalyst surface, releasing active sites, achieving 100% conversion of n-pentane at a temperature of ≥30°C and an energy density of 10 to 150 J / L, CO x The selectivity is as high as 97%, which significantly reduces the generation of ozone by-products while reducing the generation of by-products of n-pentane degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A method for preparing a Mn-CeO2 doped oxide catalyst provided by the present invention;

[0026] Figure 2 The catalyst preparation device provided in Examples 1-10;

[0027] Figure 3 An electron micrograph of the Mn-CeO2 doped oxide catalyst provided in Example 6 when the ratio of manganese (Mn) to cerium (Ce) is 1.5;

[0028] Figure 4 A transmission electron microscope image of the Mn-CeO2 doped oxide catalyst provided in Example 6 when the ratio of manganese (Mn) to cerium (Ce) is 1.5;

[0029] Figure 5 XRD spectrum of the Mn-CeO2 doped oxide catalyst provided in Example 6 when the ratio of manganese Mn to cerium Ce is 1.5;

[0030] Figure 6 A graph showing the relationship between n-pentane conversion and energy density (ED) of Mn-CeO2-doped oxide catalysts with different manganese Mn / cerium Ce atomic ratios provided in Examples 1-10;

[0031] Figure 7A graph showing the relationship between n-pentane conversion and atomic ratio of Mn-CeO2-doped oxide catalysts with different manganese Mn / cerium Ce atomic ratios provided in Examples 1-10 at 30° C. and an energy density of 150 J / L;

[0032] Figure 8 A diagram showing ozone generation by a Mn-CeO2-doped oxide catalyst with a manganese / cerium ratio of 1.5 provided in Example 6 using a collaborative low-temperature plasma technique and a simple plasma at 30°C and an energy density of 100 J / L;

[0033] Figure 9 This is a diagram of the degradation of n-pentane by the Mn-CeO2 doped oxide catalyst provided in Example 6 when the manganese Mn / cerium Ce=1.5 under the synergistic low-temperature plasma technology and the simple plasma at different energy densities at 30°C.

[0034] These drawings together constitute the technical solution of the present invention, which not only demonstrates the preparation process of the Mn-CeO2 doped oxide catalyst, but also provides an in-depth analysis of its structure and performance, providing a scientific basis for achieving efficient catalysis. DETAILED DESCRIPTION

[0035] In order to make the purpose, features and advantages of the present invention clearer and easier to understand, the following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be emphasized that these descriptions do not constitute a limitation on the scope of the present invention.

[0036] The present invention adopts non-precious metal doping, high temperature, nano-engineering and interface to realize the catalyst-cooperated low-temperature plasma through the low-temperature gasification of carbonate on the catalyst surface, releasing active sites, and achieving 100% conversion of n-pentane at 30°C and energy density of 10-150J / L, CO x The selectivity is as high as 97%, and the generation of ozone during the reaction is greatly reduced.

[0037] The present invention provides a device for preparing a Mn-CeO2-doped oxide catalyst. The device mainly includes an ultrasonic atomization unit, a carrier gas unit, a heating unit, a water absorption unit, and a delivery unit. The ultrasonic atomization unit consists of a glass container with a built-in ultrasonic atomizer, which is used to atomize the catalyst precursor solution in the glass container. The carrier gas unit is equipped with a rotor flowmeter to deliver carrier gas at a preset flow rate. The heating unit consists of a tubular furnace and an electric furnace temperature controller to control the reaction temperature of catalyst decomposition. The water absorption unit contains an absorption bottle filled with deionized water, which is used to absorb the catalyst products carried by the carrier gas. The delivery unit includes an insulation tube, an insulation thermostat, a high-temperature decomposition tube, and an exhaust pipe, which is responsible for delivering the carrier gas and atomized droplets to the reaction zone and introducing the products into the water absorption bottle after the reaction. The insulation thermostat is used to maintain the temperature of the insulation tube to ensure temperature stability throughout the entire process. Finally, solid catalyst powder is obtained through high-speed centrifugation and drying. The device is designed to achieve efficient and precise preparation of Mn-CeO2-doped oxide catalysts.

[0038] Based on the above device, see Figure 1 The present invention provides a method for preparing a Mn-CeO2 doped oxide catalyst.

[0039] S1: An aqueous solution of manganese nitrate and cerium nitrate is atomized using an ultrasonic atomizer. The resulting mist is transported to an insulated pipe via an inert gas (e.g., nitrogen). At a temperature of 60-70°C, the water in the mist evaporates to form a particulate aerosol containing manganese nitrate and cerium nitrate.

[0040] S2: The above aerosol enters a high-temperature decomposition tube at 500-800°C along with nitrogen gas. The aerosol decomposes at high temperature and converts into manganese and cerium oxide. The manganese element is doped into the lattice structure of cerium oxide to form a partially or fully doped Mn-CeO2 doped oxide solid product.

[0041] S3: The obtained Mn-CeO2 doped oxide solid product enters the water absorption bottle along with the nitrogen flow. After the solid product is absorbed by water, it is separated by high-speed centrifugation and then dried in a drying oven to finally obtain a Mn-CeO2 doped oxide catalyst.

[0042] The beneficial effects of the present invention are:

[0043] The present invention adopts doping, high temperature, nano-engineering and interface to realize the catalyst-cooperated low-temperature plasma through the low-temperature gasification of carbonate on the catalyst surface, releasing active sites, and achieving 100% conversion of n-pentane under the conditions of temperature ≥30°C and energy density 10-150J / L, CO xThe selectivity is as high as 97%, while reducing the generation of by-products of n-pentane degradation and significantly reducing the generation of ozone.

[0044] Catalyst preparation: Prepare a precursor solution with an atomic ratio of Mn / Ce = 0, weigh 1g of a 50% mass concentration of manganese nitrate (Mn(NO3)2) aqueous solution and 2g of cerium nitrate (Ce(NO3)3) hexahydrate, add deionized water to 50mL, stir evenly, and place in an atomizer bottle. Use an ultrasonic atomizer to atomize the precursor solutions of manganese nitrate and cerium nitrate. The resulting mist is transported to an insulated pipe via nitrogen. At a temperature of 60-70°C, the water in the mist evaporates, forming a particulate aerosol containing manganese nitrate and cerium nitrate. This aerosol enters a 600°C pyrolysis tube along with the nitrogen gas. The aerosol decomposes at high temperature and converts into manganese and cerium oxide. The manganese element is doped into the lattice structure of the cerium oxide, forming a partially or fully doped Mn-CeO2-doped oxide solid product. The obtained Mn-CeO2 doped oxide solid product enters the water absorption bottle with the nitrogen flow. After the solid product is absorbed by water, it is separated by high-speed centrifugation and then dried in a drying oven to finally obtain a Mn-CeO2 doped oxide catalyst.

[0045] Performance test: Take 0.15g of the catalyst obtained in the example (catalyst particle size is 40-60 mesh) and place it in the discharge space of a flow-through dielectric barrier discharge (DBD) fixed bed reactor; the carrier gas flow rate is maintained at 100mL / min, and the gas volume space velocity (WHSV) per unit catalyst mass is 40000mL / (gh); n-pentane liquid is injected into the vaporization chamber through a micro-injector, and nitrogen and oxygen are introduced into the vaporization chamber at a ratio of 8:2 and mixed with n-pentane gas before flowing into the DBD reactor. The micro-injector adjusts the n-pentane liquid injection flow rate to adjust the required n-pentane concentration (30-330mg / m 3 ) mixed gas, the concentration of n-pentane in the embodiment is 330 mg / m 3 . The temperature of the DBD reactor is controlled by an electric furnace. It is 30°C. The discharge in the DBD discharge space is achieved by applying pulsed high voltage electricity to the DBD reactor. The mixed gas containing n-pentane is catalytically degraded by the Mn-CeO2 doped oxide catalyst and low-temperature plasma in the catalyst bed passing through the DBD reactor. The concentrations of n-pentane, CO2, CO and ozone in the gas at the outlet of the DBD reactor are continuously detected. By calculating the concentrations before and after the degradation of n-pentane, the conversion rate of n-pentane by the catalyst in collaboration with low-temperature plasma and the conversion of CO, CO2, CO x Selectivity. By applying different pulse voltages to adjust the discharge energy density (discharge energy applied per unit volume of gas), different degradation effects can be obtained, and the graph of n-pentane conversion rate versus energy density as well as the CO, CO2, CO x Selective graph.

[0046] Example 1

[0047] The method is the same as the above-mentioned "catalyst preparation", wherein a precursor solution with an atomic ratio of Mn / Ce=0 is prepared, 0g of 50% manganese nitrate aqueous solution and 10g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0048] Example 2

[0049] The process is the same as that in Example 1, wherein a precursor solution having an atomic ratio of Mn / Ce=0.25 is prepared, 1.87 g of a 50% manganese nitrate aqueous solution and 9.07 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0050] Example 3

[0051] The process was the same as that in Example 1, except that a precursor solution with a Mn / Ce ratio of 0.5 was prepared, 3.42 g of a 50% manganese nitrate aqueous solution and 8.29 g of cerium nitrate hexahydrate were weighed, and the remaining steps remained unchanged.

[0052] Example 4

[0053] The process is the same as that in Example 1, wherein a precursor solution having an atomic ratio of Mn / Ce=0.75 is prepared, 4.74 g of a 50% manganese nitrate aqueous solution and 7.64 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0054] Example 5

[0055] The process is the same as that in Example 1, except that a precursor solution having an atomic ratio of Mn / Ce=1 is prepared, 5.84 g of a 50% manganese nitrate aqueous solution and 7.08 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0056] Example 6

[0057] The process is the same as that in Example 1, except that a precursor solution having an atomic ratio of Mn / Ce=1.5 is prepared, 7.64 g of a 50% manganese nitrate aqueous solution and 6.18 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0058] Example 7

[0059] The process was the same as that in Example 1, except that a precursor solution with an atomic ratio of Mn / Ce=2 was prepared, 9.04 g of a 50% manganese nitrate aqueous solution and 5.48 g of cerium nitrate hexahydrate were weighed, and the remaining steps remained unchanged.

[0060] Example 8

[0061] The process is the same as that in Example 1, except that a precursor solution having an atomic ratio of Mn / Ce=3 is prepared, 11.06 g of a 50% manganese nitrate aqueous solution and 4.47 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0062] Example 9

[0063] The process is the same as that in Example 1, wherein a precursor solution having an atomic ratio of Mn / Ce=4 is prepared, 12.45 g of a 50% manganese nitrate aqueous solution and 3.78 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0064] Example 10

[0065] The process is the same as that in Example 1, except that a precursor solution without cerium nitrate is prepared, 10 g of 50% manganese nitrate aqueous solution and 0 g of cerium nitrate hexahydrate are weighed, and the remaining steps remain unchanged.

[0066] like Figure 2 As shown, the Mn-CeO2 doped oxide catalyst preparation device of the present invention consists of an ultrasonic atomization component, a carrier gas component, a heating component, a water absorption bottle and a conveying component. The ultrasonic atomization component includes a glass bottle 11 and an ultrasonic atomizer installed in the bottle, which is used to atomize the liquid. The carrier gas component is equipped with a rotor flowmeter to control the carrier gas flow rate. The heating component consists of a tubular furnace 21 and an electric furnace temperature controller to maintain a suitable reaction temperature. The water absorption bottle is used to collect the Mn-CeO2 doped oxide solid product after the reaction. The conveying component includes an insulation tube, a quartz tube as a high-temperature decomposition tube, an insulation controller and a discharge pipe, which work together to transport the atomized liquid and carrier gas to the reaction area, and introduce the product into the water absorption bottle after the reaction is completed. The design of the entire device is intended to achieve efficient preparation of Mn-CeO2 doped oxide catalysts while ensuring the accuracy of operation and the collection efficiency of products.

[0067] The experimental parameters are: N2 flow rate: 0.8 L / min; precursor solution: 50 mL; pipeline temperature: 70°C; electric furnace temperature: 600°C; centrifugal separation: 100,000 rpm, 3 minutes; drying temperature: 80°C for 12 hours.

[0068] The morphology and composition of the 1.5Mn-CeO2 doped oxide catalyst prepared in Example 6 were characterized.

[0069] 1. The image of Mn-CeO2 doped oxide catalyst with Mn / Ce=1.5 was taken by scanning electron microscope. Figure 3 .

[0070] Result analysis:

[0071] The catalyst consists of open and closed hollow spheres ranging in size from 10 nanometers to 5 microns. The sphere walls are composed of solid spheres ranging from a few nanometers to tens of nanometers, with burr-like structures growing on the surface of the spheres. This burr structure on the spherical shell increases the catalyst's specific surface area and surface defects, a key factor in the efficient purification of n-pentane using low-temperature plasma.

[0072] 2. The image of Mn-CeO2 doped oxide catalyst with Mn / Ce=1.5 was taken by transmission electron microscopy. Figure 4 .

[0073] Result analysis:

[0074] from Figure 4 The crystal striations of CeO2 (yellow frame) and Mn3O4 (blue frame) are clearly visible. However, there are areas where the crystal striations are blurred through the electron microscope image, indicating the presence of lattice defects.

[0075] 3. XRD analysis of Mn-CeO2 doped oxide catalyst when Mn / Ce=1.5 Figure 5 .

[0076] Result analysis:

[0077] When Mn / Ce=1.5, cerium oxide appeared as the main peak on the catalyst, indicating that manganese, which is smaller than cerium atoms, was doped into the cerium oxide skeleton.

[0078] These results indicate that when the manganese / cerium ratio (Mn / Ce) is 1.5, the Mn-CeO2-doped oxide catalyst is a mixture of Mn3O4, CeO2, and Mn-doped CeO2, with lattice defects. This mixture forms nanoparticles into hollow spheres ranging from tens of nanometers to 5 microns, with burr-like structures growing on the spherical shells. This burr structure on the spherical shell increases the catalyst's specific surface area and surface defects, and is believed to be a key factor in the efficient purification of n-pentane by low-temperature plasma.

[0079] Effect Examples

[0080] The performance of the catalysts prepared in Examples 1-10 in purifying n-pentane in conjunction with low-temperature plasma was evaluated using a flow-through dielectric barrier discharge (DBD) fixed-bed reactor. The test results at a temperature of 30°C and a plasma energy density of 100 J / L are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] The relationship between the conversion of n-pentane and the energy density of the Mn-CeO2 doped oxide catalysts with different Mn / Ce atomic ratios is shown in Figure 1. Figure 6 .

[0085] Result analysis: The conversion of n-pentane of the Mn-CeO2 doped oxide catalysts with Mn / Ce atomic ratios from 0.75 to 4 is 100% when the energy density is in the range of 100-150 J / L.

[0086] The curve of the conversion of n-pentane of the Mn-CeO2 doped oxide catalysts prepared in Example 1-10 with different Mn / Ce atomic ratios at 30°C and an energy density of 150 J / L is shown in Figure 2. Figure 7 .

[0087] Result analysis: The energy density for the degradation of n-pentane can be significantly reduced when the Mn / Ce atomic ratio is 1.5, thereby reducing the energy input. The n-pentane can be completely converted when the Mn / Ce atomic ratio is in the range of 0.75-4 at 30°C and an energy density of 150 J / L.

[0088] The curve of the generation of ozone of the 1.5Mn-CeO2 doped oxide catalyst prepared in Example 6 at 30°C and an energy density of 10-100 J / L compared with the case without catalyst is shown in Figure 3. Figure 8 .

[0089] Result analysis: The concentration of ozone generated by the low-temperature plasma can be significantly reduced when the Mn / Ce atomic ratio is 1.5. The ozone generated by the degradation of n-pentane by the low-temperature plasma alone at 30°C and an energy density of 100 J / L is 1860 ppm, while the ozone generated by the 1.5Mn-CeO2 catalyst in cooperation with the low-temperature plasma is only 670 ppm, which greatly reduces the generation of ozone by-products.

[0090] The curve of the conversion of n-pentane of the 1.5Mn-CeO2 doped oxide catalyst prepared in Example 6 at 30°C and an energy density of 0-150 J / L compared with the case without catalyst is shown in Figure 4. Figure 9 .

[0091] Result analysis: The degradation of n-pentane by the low-temperature plasma in cooperation with the 1.5Mn-CeO2 catalyst is better than the degradation of n-pentane by the low-temperature plasma alone. It is found by detection that the n-pentane cannot be completely degraded by the low-temperature plasma alone at 30°C and an energy density of 150 J / L, and the CO xThe low selectivity indicates that a large amount of intermediate products are produced, which may cause secondary pollution and are not conducive to environmental protection and life safety. The 1.5Mn-CeO2 catalyst can not only achieve 100% degradation of n-pentane at a lower energy density (100 J / L) and temperature (30 ° C), but also CO x The selectivity is as high as 97%, which means that the production of intermediate products is greatly reduced and the generation of secondary pollution is effectively avoided.

[0092] Since the 1.5Mn-CeO2-doped oxide catalyst provided by the present invention catalyzes the efficient oxidation of n-pentane to CO2 in the presence of oxygen with an energy density in the range of 10-150 J / L, the present invention provides an application of the Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma in the purification of n-pentane, particularly in the following aspects:

[0093] (1) Purify air containing n-pentane by synergistic low-temperature plasma at room temperature (30°C) or above. By treating n-pentane gas emitted from refinery storage tanks with low-temperature plasma and catalysis, the toxic and harmful n-pentane is converted into non-toxic and harmless CO2.

[0094] (2) Degradation of n-pentane in the exhaust gas from the combustion of fossil fuels (such as gasoline engines, diesel engines, etc.).

[0095] The use of Mn-CeO2 doped oxide catalyst in conjunction with low temperature plasma catalysis can achieve 100% conversion of n-pentane under different conditions with Mn / Ce atomic ratios of 0.75-4. When there is no water in the gas and the energy density is 10-150 J / L, 100% conversion of n-pentane can be achieved, and CO x Selectivity up to 97%

[0096] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma, characterized in that: The method comprises the following steps: placing a Mn-CeO2 doped oxide catalyst into a reactor, introducing a gas containing n-pentane, and catalytically oxidizing and degrading n-pentane at a plasma energy density of 10-150 J / L and a temperature of ≥30°C; The preparation method of the Mn-CeO2 doped oxide catalyst comprises the following steps: S1: A compound containing a manganese source and a cerium source is dissolved in water to form a solution, which is then atomized using atomization technology to form fine droplets. These droplets are then carried by an inert gas into an insulated pipe, where the water in the droplets evaporates, leaving behind solid particles containing manganese and cerium to form an aerosol. S2: The aerosol is then transported to a pyrolysis tube by an inert gas, where the solid particles in the aerosol decompose to form Mn-CeO2-doped oxides; S3: The generated Mn-CeO2 doped oxide flows into a water absorption bottle along with the inert gas, where it is captured by water. The captured solid product is subjected to high-speed centrifugation and drying to obtain a Mn-CeO2 doped oxide catalyst; the Mn / Ce atomic ratio of the Mn-CeO2 doped oxide catalyst is 0.75-4.

2. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The n-pentane concentration is 30-330 mg / m 3 , the gas volume space velocity per unit catalyst mass is 5000-50000 mL / (gh).

3. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The Mn-CeO2 doped oxide catalyst is an open or non-open hollow sphere composed of a mixture of Mn3O4, CeO2 and Mn-doped CeO2, with a burr-like structure on the surface of the sphere shell. The mixture is nanoparticles.

4. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The Mn / Ce atomic ratio in the Mn-CeO2 doped oxide catalyst is 1-2.

5. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The reactor is a flow-through dielectric barrier discharge fixed bed reactor.

6. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The temperature of the heat-insulated pipe is 60-70°C.

7. The method for degrading n-pentane using a Mn-CeO2-doped oxide catalyst in conjunction with low-temperature plasma as claimed in claim 1, characterized in that: The temperature of the high-temperature decomposition tube is 500-800°C.

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