Composite catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of low-temperature plasma catalyst preparation, and discloses a composite catalyst as well as a preparation method and application thereof. The composite catalyst comprises a carrier as well as manganese oxide, an auxiliary active component and a heat stabilizer which are loaded on the carrier, the auxiliary active component is transition metal oxide, and transition metal is selected from at least one of Cu, Co and Ce; the carrier is selected from one or two of alpha-Al2O3, gamma-Al2O3, eta-Al2O3, a high-silicon Y type molecular sieve, a ZSM-5 type molecular sieve and an MCM-41 type molecular sieve; and the heat stabilizer is selected from one or more than two of La oxide, Nd oxide and Pr oxide. The composite catalyst is coupled with a low-temperature plasma technology, dual control over VOCs and by-products NOx and ozone can be achieved, the degradation efficiency of the VOCs can be improved, meanwhile, emission of the by-products can be reduced, and green treatment of the VOCs is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature plasma catalyst preparation, in particular to a composite catalyst and its preparation method and application. BACKGROUND

[0002] Low-temperature plasma technology is widely used in the treatment of volatile organic waste gas (VOCs) in petrochemical, spraying, breeding and municipal sewage treatment fields due to its simple process, on-off operation and low running cost. The main reaction principle of this technology is that under the action of the electric field formed in the gap between the positive and negative electrodes, the outer electrons in the gas molecules can not only have non-elastic collision with VOCs molecules, but also have non-elastic collision with background gas molecules (such as nitrogen, oxygen and water vapor, etc.), generating active groups such as N free radicals, O free radicals and OH free radicals to continue to react with VOCs molecules, and finally mineralize VOCs into CO2 and H2O. However, when low-temperature plasma is used alone to degrade VOCs, many organic intermediate products, NO x and O3 reaction by-products with certain toxicity are generated, which can easily cause secondary pollution to the environment.

[0003] Studies have shown that the combination of catalysts and low-temperature plasma technology can effectively inhibit the generation of organic intermediate products and reaction by-products (NO x and O3, etc.), and improve the efficiency of VOCs degradation. According to the placement area of the catalyst, plasma coupling catalysis technology is divided into two types, plasma built-in catalysis and plasma post-catalysis. Plasma built-in catalysis refers to the placement of catalysts in the discharge area of plasma, which can effectively inhibit the generation of organic intermediate products by increasing the local electric field strength and prolonging the reaction time of VOCs molecules and active particles, and improve the mineralization efficiency of VOCs. However, the emission of by-products NO x and O3 is large, which can easily cause secondary pollution; plasma post-catalysis refers to the placement of catalysts outside the plasma electric field area, which can decompose NO x and O3, but the degradation efficiency of organic intermediate products generated by the degradation of VOCs in the plasma area is low, which further leads to low VOCs degradation efficiency.

[0004] Therefore, at present, in the coupling of low-temperature plasma technology and catalysts to degrade VOCs, it is temporarily impossible to improve the catalytic degradation efficiency of VOCs while avoiding the emission of by-products NO x and O3, and the catalytic degradation efficiency of VOCs needs to be improved. SUMMARY

[0005] The present application aims to overcome the problems of low degradation efficiency of VOCs and high concentration of by-product emissions in the catalytic degradation of VOCs by plasma technology, and to provide a composite catalyst, a preparation method and application thereof. x The composite catalyst is coupled with low-temperature plasma technology to achieve dual control of VOCs and by-products NO

[0006] To achieve the above-mentioned purpose, the present application provides a composite catalyst, which comprises a carrier and manganese oxide, an active component and a thermal stabilizer supported on the carrier.

[0007] The active component is a transition metal oxide, and the transition metal is selected from at least one of Cu, Co and Ce.

[0008] The carrier is selected from one or two of α-Al2O3, γ-Al2O3, η-Al2O3, high-silicon Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve.

[0009] The thermal stabilizer is selected from one or two or more of La oxide, Nd oxide and Pr oxide.

[0010] Preferably, the manganese oxide comprises α-MnO2 and optionally one or more of MnO, Mn3O4 and Mn2O3.

[0011] Preferably, the content of α-MnO2 in the manganese oxide is 10wt%-40wt%.

[0012] Preferably, based on the total weight of the composite catalyst, the content of the manganese oxide is 10wt%-40wt%, the content of the active component is 5wt%-20wt%, the content of the thermal stabilizer is 0.1wt%-2wt%, and the content of the carrier is 38wt%-84.9wt%.

[0013] The present application provides a method for preparing a composite catalyst, which comprises: placing a pretreated carrier in a solution containing a manganese salt, an active component precursor and a thermal stabilizer precursor for several times of impregnation-drying, and then performing calcination.

[0014] The active component precursor is selected from at least one of Cu salt, Co salt and Ce salt.

[0015] The carrier is selected from one or two of α-Al2O3, γ-Al2O3, η-Al2O3, high silicon Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve;

[0016] The thermal stabilizer precursor is selected from at least one of La(NO3)3, Nd(NO3)3 and Pr(NO3)3.

[0017] Preferably, the pretreatment process comprises: subjecting the carrier to heat treatment;

[0018] Preferably, the heat treatment temperature is 400°C-800°C, and the heat treatment time is 2-5.5h;

[0019] Preferably, the atmosphere of the heat treatment is air, nitrogen, argon or vacuum atmosphere;

[0020] Preferably, the heating rate of the heat treatment is 1-10°C / min.

[0021] Preferably, the impregnation method in the impregnation-drying is excessive impregnation;

[0022] Preferably, the dipping-drying is repeated 2-4 times.

[0023] Preferably, the calcination conditions include: a temperature of 500-800° C. and a time of 2-8 hours.

[0024] Preferably, the weight ratio of the manganese source, the co-active component precursor, the thermal stabilizer precursor and the carrier is 3.7-300:2.3-190:1:22-1000, wherein the weights of the manganese source, the co-active component precursor and the thermal stabilizer precursor are calculated as metal elements.

[0025] The third aspect of the present invention provides a composite catalyst prepared by the above preparation method.

[0026] A fourth aspect of the present invention provides a method for degrading VOCs, the method comprising: loading the composite catalyst into a plasma reactor, and then introducing VOCs to react.

[0027] Preferably, the VOCs are C2-C5 hydrocarbon compounds;

[0028] Preferably, the concentration of the VOCs is 50-2000 ppm;

[0029] Preferably, the catalytic temperature of the composite catalyst is 20-200°C.

[0030] The composite catalyst described in the present invention contains manganese oxide, a co-active component and a thermal stabilizer. The co-active component contains multiple metal oxides. Through the mutual cooperation between various active components, the generation of hydroxyl radicals in the process of degrading VOCs by low-temperature plasma coupled catalytic technology can be increased, and the generated hydroxyl radicals can be further utilized to improve the degradation rate of VOCs and by-products. While improving the degradation rate of VOCs, the emission of by-products can be controlled, thereby reducing secondary pollution.

[0031] Furthermore, the method described in the present invention prepares a composite catalyst by a multiple impregnation method, which can accurately control the amount of active components and thermal stabilizers in the composite catalyst. The preparation method is simple, and the prepared composite catalyst can degrade VOCs at room temperature and pressure, further saving the degradation cost of VOCs and realizing a low-cost, green and harmless VOCs treatment process. DETAILED DESCRIPTION

[0032] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0033] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0034] The composite catalyst of the present invention comprises a carrier and manganese oxide, a co-active component and a heat stabilizer loaded on the carrier.

[0035] In the present invention, the manganese oxide serves as the primary active component, while the co-active component further enhances the catalytic performance of the composite catalyst. The synergistic effect between the manganese oxide and the co-active component results in the composite catalyst possessing excellent catalytic performance and catalytic stability. The thermal stabilizer further enhances the stability of the composite catalyst, contributing to its efficiency in degrading VOCs using plasma-coupled catalysis technology.

[0036] In the present invention, the co-active component is a transition metal oxide, and the transition metal is selected from at least one of Cu, Co, and Ce. In the present invention, the number of metal elements in the co-active component is not limited. The co-active component can also provide catalytic activity to the composite catalyst, synergizing with the manganese oxide to further enhance the catalytic performance of the composite catalyst.

[0037] In the present application, the thermal stabilizer is selected from one or more of La oxide, Nd oxide and Pr oxide, preferably La oxide. The thermal stabilizer can further improve the stability of the composite catalyst, ensuring long-term stability of the catalytic activity of the composite catalyst.

[0038] In the present application, the carrier is one or more of α-Al2O3, γ-Al2O3, η-Al2O3, high-silica Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve. The carrier has a large specific surface area, which can further improve the loading of the active component, and the loading of the active component is more uniform, which helps to improve the catalytic performance of the composite catalyst.

[0039] In the present application, the composite catalyst can significantly reduce the energy required to generate hydroxyl radicals through the synergistic cooperation between the components, accelerate the decomposition of the byproduct ozone, increase the amount of hydroxyl radicals generated, and further utilize the hydroxyl radicals generated by the decomposition of ozone to improve the degradation efficiency of VOCs. The composite catalyst can also significantly improve the decomposition efficiency of the byproduct NO x , truly realizing the dual control of VOCs degradation and toxic byproduct emission, and realizing the harmless degradation treatment of VOCs.

[0040] In a specific embodiment, the coupling mode of the composite catalyst with low-temperature plasma technology is not limited, i.e., it can be plasma-in-catalyst or plasma-after-catalyst. The composite catalyst can be placed in the discharge area of the plasma reactor to be coupled with the low-temperature plasma technology, or placed outside the discharge area of the plasma reactor to be coupled with the low-temperature plasma technology.

[0041] In a preferred embodiment, in order to further improve the degradation rate of VOCs, the manganese oxide comprises ɑ-MnO2 and optionally one or more of MnO, Mn3O4 and Mn2O3. It can be understood that the ɑ-MnO2 is a necessary component of the manganese oxide, and the manganese oxide can also contain one or more of MnO, Mn3O4 and Mn2O3, for example, the composition of the manganese oxide can be ɑ-MnO2, ɑ-MnO2 and MnO, or ɑ-MnO2, MnO and Mn3O4. In the present application, the ɑ-MnO2 contained in the manganese oxide has excellent activity, further improving the decomposition efficiency of ozone, thereby generating more active hydroxyl radicals in the reaction. In this preferred embodiment, by further limiting 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, and the harmless degradation of VOCs can be further realized.

[0042] In a preferred embodiment, in order to further improve the catalytic performance of the composite catalyst, the content of α-MnO2 in the manganese oxide is 15wt%-30wt%. Specifically, the content of α-MnO2 can be 15wt%, 20wt%, 25wt% or 30wt%.

[0043] In a preferred embodiment, in order to further ensure the catalytic performance of the composite catalyst and improve the degradation efficiency of VOCs, based on the total weight of the composite catalyst, the content of the manganese oxide is 10wt%-40wt%, preferably 15wt%-30wt%; the content of the co-active component is 5wt%-20wt%, preferably 5wt%-18wt%; the content of the thermal stabilizer is 0.1wt%-2wt%, preferably 0.5wt%-2wt%; and the content of the carrier is 38wt%-84.9wt%, preferably 53.5wt%-79.5wt%.

[0044] The present invention further provides a method for preparing a composite catalyst, which comprises: placing a pretreated carrier in a solution containing a manganese salt, a co-active component precursor and a thermal stabilizer component precursor, performing several immersion-drying steps, and then calcining.

[0045] In the present invention, the carrier is one or more of α-Al2O3, γ-Al2O3, η-Al2O3, high-silicon Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve.

[0046] In a specific embodiment, pre-treating the carrier can remove impurities attached to the surface and pores of the carrier, thereby exposing more active sites on the carrier, thereby facilitating the loading of active components, increasing the loading amount of active components and the uniformity of loading, thereby improving the activity of the prepared composite catalyst.

[0047] In a preferred embodiment, the pretreatment process includes: subjecting the carrier to a heat treatment, which can better remove impurities on the surface and in the pores of the carrier.

[0048] In a preferred embodiment, during the heat treatment of the carrier, the temperature of the heat treatment is 400-800℃, and the time of the heat treatment is 2-5.5h. Specifically, the temperature of the heat treatment can be 600℃, 700℃ or 800℃; and the time of the heat treatment can be 4h, 4.5h, 5h or 5.5h. Further preferably, the heating rate of the heat treatment process is 1.5-3℃ / min. The heating rate of the heat treatment process refers to the heating rate when the ambient temperature is raised to the heat treatment temperature during the heat treatment.

[0049] In a preferred embodiment, during the heat treatment of the carrier, the atmosphere of the heat treatment is air.

[0050] In the present application, the co-active component precursor is selected from one or more of Cu salt, Co salt and Ce salt. Specifically, the Cu salt, Co salt and Ce salt are all soluble metal salts. Specifically, the Cu salt can be Cu(NO3)2 or CuCl2, the Co salt can be Co(NO3)2 or CoCl2; and the Ce salt can be Ce(NO3)3 or Ce2Cl3.

[0051] In the present application, the heat stabilizer precursor is selected from at least one of La(NO3)3, Nd(NO3)3 and Pr(NO3)3. Specifically, in the method of the present application, the heat stabilizer precursor can only be prepared by selecting the nitrate salt of the corresponding metal, and selecting the chloride salt or the sulfate salt of the corresponding metal will result in the preparation of the composite catalyst by the substance.

[0052] In a specific embodiment, by repeatedly immersing the pretreated carrier in a solution containing a manganese salt, a co-active component precursor and a heat stabilizer precursor, the loading amount of manganese oxide, co-active component and heat stabilizer on the carrier can be further improved, and the loading amount of the active component can also be accurately controlled, so that the performance of the prepared composite catalyst is more excellent.

[0053] In a preferred embodiment, the impregnation-drying refers to immersing the solid phase material in the impregnation solution, followed by solid-liquid separation, and drying the obtained solid phase material. Specifically, the process of impregnation-drying includes immersing the pretreated carrier in a solution containing a manganese salt, a co-active component precursor and a heat stabilizer precursor, followed by solid-liquid separation, and drying the obtained solid phase material. Preferably, the impregnation in the impregnation-drying is over-impregnation.

[0054] In a specific embodiment, the specific process of impregnation in the impregnation-drying process comprises: mixing the solution containing the manganese salt, the promoter precursor and the thermal stabilizer precursor with the pretreated carrier by spraying, then impregnating, and continuously stirring to mix the impregnation solution uniformly.

[0055] In a specific embodiment, in the impregnation-drying process, the loading amount of the active component in the composite catalyst can be significantly increased by drying the material after each impregnation before the next impregnation, thereby improving the catalytic performance of the composite catalyst.

[0056] In a preferred embodiment, the temperature for drying the impregnated material is 100-120℃, and the drying time is 8-12h.

[0057] In a preferred embodiment, the impregnation-drying process is performed 2-4 times.

[0058] In a preferred embodiment, the calcination conditions include a temperature of 500-800℃, preferably 550-750℃, and a time of 2-8h. Specifically, the calcination temperature can be 550℃, 650℃, 750℃ or 800℃, and the calcination time can be 3.5h, 4h, 4.5h, 5h, 6h, 7h or 8h.

[0059] In the present application, the weight ratio of the manganese source, the promoter precursor, the thermal stabilizer precursor and the carrier is 3.7-300:2.3-190:1:22-1000, preferably 5-44:2-49:1:30-186, wherein the weight of the manganese source, the promoter precursor and the thermal stabilizer precursor is calculated based on the metal elements.

[0060] The composite catalyst described in the present application can be used in the field of degrading VOCs as a low-temperature plasma catalyst coupled with low-temperature plasma technology.

[0061] The present application also provides a method for degrading VOCs, which comprises: loading the composite catalyst into a plasma reactor, and then introducing VOCs for reaction.

[0062] In a preferred embodiment, the VOCs are C2-C5 hydrocarbon compounds. Specifically, the C2-C5 hydrocarbon compounds can be one or more than two of ethane, propane, butane, pentane and isopentane.

[0063] In a preferred embodiment, the concentration of the VOCs is 50-2000ppm.

[0064] In the present application, the composite catalyst has a low catalytic temperature in the process of catalytic degradation of VOCs, and can realize its catalytic function at normal temperature, further saving the energy consumption of degradation of VOCs. The catalytic temperature of the composite catalyst is 20-200℃, specifically, the catalytic temperature of the composite catalyst can be 20℃, 80℃ or 180℃. In the present application, the catalytic temperature of the composite catalyst refers to the working temperature when the low-temperature plasma catalyst exerts its catalytic function.

[0065] The composite catalyst described in the present application can significantly reduce the energy consumption of active hydroxyl radical generation in the degradation process, and further reduce the consumption of hydroxyl radicals, thereby increasing the generation amount of hydroxyl radicals, and improving the degradation rate of C2-C5 small molecular hydrocarbon compounds without increasing the discharge power. More importantly, the composite catalyst described in the present application can greatly reduce the amount of NOx and ozone emitted in the VOCs degradation process, avoid the generation of secondary pollution, and realize the double effective control of organic intermediate products and reaction by-products generated in the plasma discharge area. x and ozone, avoid the generation of secondary pollution, and realize the double effective control of organic intermediate products and reaction by-products generated in the plasma discharge area.

[0066] The present application will be described in detail by the following examples, but the protection scope of the present application is not limited thereto.

[0067] The examples are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0068] The experimental methods in the following examples are all conventional methods in the art, unless otherwise specified. The experimental materials used in the following examples are all commercially available, unless otherwise specified.

[0069] Example 1

[0070] (1) γ-Al2O3 was placed in a muffle furnace, and heat-treated at 700℃ under air atmosphere at a temperature rising rate of 2℃ / min for 1h, to obtain pretreated γ-Al2O3;

[0071] (2) Mn(NO3)2, Ce(NO3)3and Nd(NO3)3were mixed with water to obtain an impregnation solution, and then the obtained impregnation solution was sprayed onto the pretreated γ-Al2O3(Mn(NO3)2, Ce(NO3)3, Nd(NO3)3and γ-Al2O3were used in a weight ratio of 15:11.7:1:47, and the weight of Mn(NO3)2, Ce(NO3)3and Nd(NO3)3was calculated based on metal elements), followed by 3 times of impregnation-drying; wherein the impregnation-drying included: placing the pretreated γ-Al2O3in the impregnation solution for over-impregnation, then performing solid-liquid separation after impregnation saturation, and then drying the obtained solid material at 110°C for 10h;

[0072] (3) The material after drying in step (2) was calcined at a temperature of 600°C, the temperature rising rate during calcination was 2°C / min, and the calcination time was 6h, to obtain a composite catalyst;

[0073] XRF test showed that the content of Al2O3 in the composite catalyst was 54.4wt%, the content of manganese oxide was 27.4wt%, the content of cerium oxide was 16.7wt%, and the content of Nd oxide was 1.5wt%;

[0074] (4) The composite catalyst was loaded outside the discharge area of the plasma reactor, and then the simulated gas (the sum of the concentrations of isopentane and butane was 300ppm, the volume ratio of isopentane to butane was 1:1, and the carrier gas was air) was introduced for treatment, the flow rate of the simulated gas was 0.5L / min (space velocity SV = 1200L / m 3 h), and the catalytic temperature was 45°C.

[0075] Example 2

[0076] (1) α-Al2O3was placed in a muffle furnace, and heat-treated at a temperature rising rate of 2°C / min to 750°C under an air atmosphere, for 5h, to obtain pretreated α-Al2O3;

[0077] (2) Mn(NO3)2, Ce(NO3)3and Nd(NO3)3were mixed with water to obtain an impregnation solution, and then the obtained impregnation solution was sprayed onto the pretreated α-Al2O3(Mn(NO3)2, Ce(NO3)3, Nd(NO3)3and α-Al2O3were used in a weight ratio of 15:11.7:1:47, and the weight of Mn(NO3)2, Ce(NO3)3and Nd(NO3)3was calculated based on metal elements), followed by 3 times of impregnation-drying; wherein the impregnation-drying included: placing the pretreated α-Al2O3in the impregnation solution for over-impregnation, then performing solid-liquid separation after impregnation saturation, and then drying the obtained solid material at 110°C for 10h;

[0078] (3) The material dried in step (2) is calcined at a temperature of 750°C, a temperature rising rate of 1°C / min, and a calcination time of 4h to obtain a composite catalyst;

[0079] XRF test shows that the content of Al2O3 in the composite catalyst is 54.4wt%, the content of manganese oxide is 27.4wt%, the content of cerium oxide is 16.7wt%, and the content of Nd oxide is 1.5wt%;

[0080] (4) The composite catalyst is loaded outside the discharge area of the plasma reactor, and then the simulated gas (the sum of the concentrations of isopentane and butane is 300ppm, the volume ratio of isopentane to butane is 1:1, and the carrier gas is air) is introduced for treatment, the flow rate of the simulated gas is 0.5L / min (space velocity SV = 1200L / m 3 h), and the catalytic temperature is 45°C.

[0081] Example 3

[0082] (1) γ-Al2O3 is placed in a muffle furnace and heat treated at 700°C under an air atmosphere at a temperature rising rate of 2°C / min for 5h to obtain pretreated γ-Al2O3;

[0083] (2) Mn(NO3)2, Ce(NO3)3, Co(NO3)2, Cu(NO3)2, and Nd(NO3)3 are mixed with water to obtain an impregnation solution, which is then sprayed onto the pretreated γ-Al2O3 (the weight ratio of the use amounts of Mn(NO3)2, Ce(NO3)3, Co(NO3)2, Cu(NO3)2, and Nd(NO3)3 to γ-Al2O3 is 7.5:3.9:7.8:0.8:1:35, and the weight of Mn(NO3)2, Ce(NO3)3, Co(NO3)2, Cu(NO3)2, and Nd(NO3)3 is calculated based on metal elements), followed by 3 times of impregnation-drying; wherein, the impregnation-drying comprises: placing the pretreated γ-Al2O3 in the impregnation solution for excessive impregnation, performing solid-liquid separation after saturation, and then drying the obtained solid material at 120°C for 10h;

[0084] (3) The material dried in step (2) is calcined at a temperature of 800°C, a temperature rising rate of 5°C / min, and a calcination time of 3h to obtain a composite catalyst;

[0085] The XRF test shows that the content of Al2O3 in the composite catalyst is 62.1wt%, the content of manganese oxide is 19.3wt%, the content of cerium oxide is 7.8wt%, the content of copper oxide is 1.8wt%, the content of cobalt oxide is 7wt%, and the content of Nd oxide is 2wt%;

[0086] (4) The composite catalyst is loaded outside the discharge area of the plasma reactor, and then the simulated gas (the concentration of butane is 400ppm, and the carrier gas is air) is introduced for treatment, the flow rate of the simulated gas is 0.5L / min (space velocity SV = 1200L / m 3 h), and the catalytic temperature is 55℃.

[0087] Example 4

[0088] The method of Example 3 is followed, except that the composition of the simulated gas introduced is a mixture of butane and pentane, the sum of the concentrations of butane and pentane is 600ppm, and the catalytic temperature is 65℃.

[0089] Example 5

[0090] (1) η-Al2O3 is placed in a muffle furnace, and heat-treated at a temperature rising rate of 2℃ / min to 700℃ under an air atmosphere for 5h to obtain pretreated η-Al2O3;

[0091] (2) Mn(NO3)2, Ce(NO3)2, Co(NO3)2 and La(NO3)2 are mixed with water to obtain an impregnation solution, and then the obtained impregnation solution is sprayed onto the pretreated η-Al2O3 (the weight ratio of the dosages of Mn(NO3)2, Ce(NO3)3, Co(NO3)2 and La(NO3)3 to η-Al2O3 is 15:5:20:1:83.7, and the weight of Mn(NO3)2, Ce(NO3)3, Co(NO3)2 and La(NO3)3 is calculated based on the metal elements), and then impregnation-drying is carried out for 3 times; wherein, the impregnation-drying comprises: placing the pretreated γ-Al2O3 in the impregnation solution for excessive impregnation, carrying out solid-liquid separation after saturation, and then drying the obtained solid material at 110℃ for 10h;

[0092] (3) The material after drying in step (2) is calcined, the calcination temperature is 750℃, the temperature rising rate during calcination is 4℃ / min, and the calcination time is 4h to obtain the composite catalyst;

[0093] XRF test shows that the content of η-Al2O3 in the composite catalyst is 62.7wt%, the content of manganese oxide is 17.8wt%, the content of cerium oxide is 4.6wt%, the content of cobalt oxide is 13wt%, and the content of La oxide is 1.9wt%;

[0094] (4) The composite catalyst is loaded outside the discharge area of the plasma reactor, and then the simulated gas (the concentration of butane is 400 ppm, and the carrier gas is air) is introduced for treatment, the flow rate of the simulated gas is 1 L / min (space velocity SV = 1200 L / m 3 h), and the catalytic temperature is 35℃.

[0095] Example 6

[0096] (1) η-Al2O3 is placed in a muffle furnace, and heat treated at 2℃ / min to 600℃ under air atmosphere for 5h to obtain pretreated η-Al2O3;

[0097] (2) Mn(NO3)2, Ce(NO3)2, Cu(NO3)2 and La(NO3)2 are mixed with water to obtain an impregnation solution, and then the obtained impregnation solution is sprayed onto the pretreated η-Al2O3 (the weight ratio of Mn(NO3)2, Ce(NO3)3, Cu(NO3)2 and La(NO3)3 to η-Al2O3 is 9.2:2.4:4.6:1:34, and the weight of Mn(NO3)2, Ce(NO3)3, Cu(NO3)2 and La(NO3)2 is calculated based on metal elements), and then impregnation-drying is carried out for 3 times; wherein, the impregnation-drying comprises: placing the pretreated η-Al2O3 in the impregnation solution for excessive impregnation, and after saturation, carrying out solid-liquid separation, and then drying the obtained solid material at 110℃ for 10h;

[0098] (3) The dried material of step (2) is calcined, the calcination temperature is 750℃, the temperature rising rate during calcination is 2℃ / min, and the calcination time is 4h to obtain a composite catalyst;

[0099] XRF test shows that the content of η-Al2O3 in the composite catalyst is 57.9wt%, the content of manganese oxide is 25wt%, the content of cerium oxide is 5.1wt%, the content of copper oxide is 10wt%, and the content of La oxide is 2wt%;

[0100] (4) The composite catalyst is loaded outside the discharge area of the plasma reactor, and then the simulated gas (the concentration of butane is 800 ppm, and the carrier gas is air) is introduced for treatment, the flow rate of the simulated gas is 1 L / min (space velocity SV = 1200 L / m 3h), the catalytic temperature is 35℃.

[0101] Example 7

[0102] (1) The ZSM-5 type molecular sieve was placed in a muffle furnace and heat treated under an air atmosphere at a temperature of 700℃ with a temperature increase of 2℃ / min, for a time of 5h, to obtain a pretreated ZSM-5 type molecular sieve;

[0103] (2) Mn(NO3)2, Cu(NO3)2, Co(NO3)2and La(NO3)3were mixed with water to obtain an impregnation solution, the impregnation solution was then sprayed onto the pretreated ZSM-5 type molecular sieve (the weight ratio of Mn(NO3)2, Cu(NO3)2, Co(NO3)2, La(NO3)2and ZSM-5 was 15:5.5:4.9:1:43.4, the weight of Mn(NO3)2, Cu(NO3)2, Co(NO3)2, La(NO3)2was calculated based on the metal element), followed by 3 times of impregnation-drying; wherein, the impregnation-drying included: the pretreated ZSM-5 type molecular sieve was placed in the impregnation solution for excess impregnation, after saturation, solid-liquid separation was performed, and then the obtained solid phase material was dried at 110℃ for 10h;

[0104] (3) The material after drying in step (2) was calcined, the calcination temperature was 800℃, the temperature increase rate during calcination was 2℃ / min, and the calcination time was 5h, to obtain a composite catalyst;

[0105] XRF test showed that the content of the ZSM-5 type molecular sieve in the composite catalyst was 54.3wt%, the content of manganese oxide was 30.2wt%, the content of copper oxide was 8.7wt%, the content of cobalt oxide was 5.2wt%, and the content of La oxide was 1.6wt%;

[0106] (4) The composite catalyst was loaded outside the discharge area of the plasma reactor, and then the simulated gas (the concentration of isopentane was 300ppm, and the carrier gas was air) was introduced for treatment, the flow rate of the simulated gas was 500mL / min (space velocity SV = 1200L / m 3 h), the catalytic temperature is 30℃.

[0107] Example 8

[0108] (1) The ZSM-5 type molecular sieve was placed in a muffle furnace and heat treated under an air atmosphere at a temperature of 700℃ with a temperature increase of 2℃ / min, for a time of 5h, to obtain a pretreated ZSM-5 type molecular sieve;

[0109] (2) Mn(NO3)2, Cu(NO3)2, Co(NO3)2and La(NO3)2were mixed with water to obtain an impregnation solution, then the obtained impregnation solution was sprayed onto the pretreated ZSM-5 molecular sieve (the weight ratio of the amount of Mn(NO3)2, Cu(NO3)2, Co(NO3)2, La(NO3)2and ZSM-5 molecular sieve was 15:5.5:4.9:1:43.4, and the weight of Mn(NO3)2, Cu(NO3)2, Co(NO3)2, La(NO3)3was calculated based on the metal element), then impregnation-drying was carried out for 3 times; wherein, the impregnation-drying included: the pretreated ZSM-5 was placed in the impregnation solution for excessive impregnation, then solid-liquid separation was carried out after saturation, and then the obtained solid material was dried at 110℃ for 10h;

[0110] (3) the material after drying in step (2) was calcined, the calcination temperature was 500℃, the temperature rising rate during calcination was 2℃ / min, the calcination time was 5h, and a composite catalyst was obtained;

[0111] XRF test showed that the content of ZSM-5 molecular sieve in the composite catalyst was 54.3wt%, the content of manganese oxide was 30.2wt%, the content of copper oxide was 8.7wt%, the content of cobalt oxide was 5.2wt%, and the content of La oxide was 1.6wt%;

[0112] (4) the composite catalyst was loaded outside the discharge area of the plasma reactor, then simulated gas (the concentration of isopentane was 300ppm, and the carrier gas was air) was introduced for treatment, the flow rate of the simulated gas was 500mL / min (space velocity SV = 1200L / m 3 h), and the catalytic temperature was 30℃.

[0113] Example 9

[0114] (1) MCM-41 molecular sieve was placed in a muffle furnace, and heat treatment was carried out under air atmosphere at a temperature rising rate of 2℃ / min to 600℃ for 2h, and pretreated MCM-41 was obtained;

[0115] (2) Mn(NO3)2, Ce(NO3)3, Co(NO3)2, and Pr(NO3)3are mixed with water to obtain an impregnation solution, then the obtained impregnation solution is sprayed onto the pretreated MCM-41 type molecular sieve (the weight ratio of the amounts of Mn(NO3)2, Ce(NO3)3, Co(NO3)2, Pr(NO3)3and MCM-41 type molecular sieve is 15:8:16:1:56.7, the weight of Mn(NO3)2, Ce(NO3)3, Co(NO3)2, Pr(NO3)3is calculated based on the metal elements), then impregnation-drying is carried out for 3 times; wherein, the impregnation-drying comprises: placing the pretreated MCM-41 type molecular sieve in the impregnation solution for over-impregnation, carrying out solid-liquid separation after impregnation saturation, then drying the obtained solid phase material at 110℃ for 10h;

[0116] (3) the material after drying in step (2) is calcined, the calcination temperature is 650℃, the temperature rising rate during calcination is 5℃ / min, the calcination time is 6h, and a composite catalyst is obtained;

[0117] It can be known through XRF test that the content of the MCM-41 type molecular sieve in the composite catalyst is 58.1wt%, the content of manganese oxide is 22.4wt%, the content of cerium oxide is 9.3wt%, the content of cobalt oxide is 9wt%, and the content of Pr oxide is 1.2wt%;

[0118] (4) the composite catalyst is loaded outside the discharge area of the plasma reactor, then the simulated gas (the sum of the concentrations of isopentane and butane is 300ppm, the volume ratio of isopentane and butane is 1:1, and the carrier gas is air) is introduced for treatment, the flow rate of the simulated gas is 1L / min (space velocity SV = 1200L / m 3 h), and the catalytic temperature is 35℃.

[0119] Comparative Example 1

[0120] The preparation is carried out according to the method of Example 1, except that Nd(NO3)3is not added.

[0121] Comparative Example 2

[0122] The preparation is carried out according to the method of Example 1, except that Ce(NO3)3is not added.

[0123] Comparative Example 3

[0124] The preparation is carried out according to the method of Example 1, except that Nd(NO3)3is replaced by an equal weight of NdCl3.

[0125] XRF testing showed that the content of Al2O3 in the composite catalyst was 54.1 wt%, the content of manganese oxide was 27.3 wt%, the content of cerium oxide was 16.5 wt%, and the content of Nd oxide was 2.1 wt%.

[0126] Test Example 1

[0127] The low-temperature plasma catalysts prepared in Examples 1-9 and Comparative Examples 1-3 were tested for the degradation rate of VOCs, and the O3 and NO in the exhaust gas were also tested. x concentration.

[0128] Test method: Agilent 8890B gas chromatograph was used to measure the VOCs content in the treated gas, equipped with a double hydrogen flame ionization detector, according to the formula: (M 模拟气体中vocs的浓度 -M 降解后气体中vocs的浓度 )÷M 模拟气体中vocs的浓度 ×100%, calculate the degradation rate of VOCs, and the results are shown in Table 1;

[0129] The NO in the exhaust gas was analyzed online using a gas analyzer (Antaris IGS) x The concentrations are shown in Table 1.

[0130] The 106-M ozone analyzer from the American 2B company was used to detect the changes in the O3 concentration of the treated exhaust gas. The results are shown in Table 1.

[0131] Table 1

[0132] Example No. Degradation rate of VOCs / % Ozone concentration in off-gas / ppm NOx concentration in exhaust gas x Concentration / ppm Example 1 99.1 0.01 0.19 Example 2 98.9 0.01 0.23 Example 3 98.7 0.01 0.21 Example 4 99.2 0.05 0.28 Example 5 98.5 0.06 0.36 Example 6 96.7 0.04 0.39 Example 7 99.4 0.06 0.41 Example 8 97.6 0.07 0.45 Example 9 99.5 0.05 0.51 Comparative Example 1 90.1 0.78 3.54 Comparative Example 2 90.6 6.76 26.81 Comparative Example 3 82.5 12.15 4.92

[0133] The results in Table 1 show that the low-temperature plasma catalyst of the present invention can significantly improve the removal rate of isopentane and significantly reduce the ozone and NO in the tail gas. x concentration, reducing the toxic byproducts ozone and NO x emissions, achieving harmless treatment of VOCs.

[0134] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite catalyst, characterized in that The composite catalyst comprises a carrier and manganese oxide, a co-active component and a thermal stabilizer supported on the carrier; The co-active component is a transition metal oxide, and the transition metal is selected from at least one of Cu, Co and Ce; The carrier is selected from one or two of α-Al2O3, γ-Al2O3, η-Al2O3, high silicon Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve; The thermal stabilizer is selected from one or more of La oxide, Nd oxide and Pr oxide.

2. The composite catalyst according to claim 1, characterized in that The manganese oxide comprises α-MnO2 and optionally one or more of MnO, Mn3O4 and Mn2O3; Preferably, the content of α-MnO2 in the manganese oxide is 10wt%-40wt%.

3. The composite catalyst according to claim 1, characterized in that Based on the total weight of the composite catalyst, the content of the manganese oxide is 10wt%-40wt%, the content of the co-active component is 5wt%-20wt%, the content of the heat stabilizer is 0.1wt%-2wt%, and the content of the carrier is 38wt%-84.9wt%.

4. A method for preparing a composite catalyst, characterized in that: The method comprises: placing the pretreated support in a solution containing a manganese salt, a precursor of a co-active component and a precursor of a thermal stabilizer, performing several immersion-drying steps, and then calcining; The co-active component precursor is selected from at least one of Cu salt, Co salt and Ce salt; The carrier is selected from one or two of α-Al2O3, γ-Al2O3, η-Al2O3, high silicon Y-type molecular sieve, ZSM-5 type molecular sieve and MCM-41 type molecular sieve; The thermal stabilizer precursor is selected from at least one of La(NO3)3, Nd(NO3)3 and Pr(NO3)3.

5. The method for preparing a composite catalyst according to claim 4, wherein The pretreatment process includes: heat treating the carrier; Preferably, the heat treatment temperature is 400°C-800°C, and the heat treatment time is 2-5.5h; Preferably, the atmosphere of the heat treatment is air, nitrogen, argon or vacuum atmosphere; Preferably, the heating rate of the heat treatment is 1-10°C / min.

6. The method for preparing a composite catalyst according to claim 4, wherein The impregnation method in the impregnation-drying is excessive impregnation; Preferably, the dipping-drying is repeated 2-4 times.

7. The method for preparing a composite catalyst according to claim 4, wherein The calcination conditions include: a temperature of 500-800° C. and a time of 2-8 hours.

8. The method for preparing a composite catalyst according to claim 4, wherein The weight ratio of the manganese source, the co-active component precursor, the thermal stabilizer precursor and the carrier is 3.7-300:2.3-190:1:22-1000, wherein the weight of the manganese source, the co-active component precursor and the thermal stabilizer precursor is calculated as metal elements.

9. The composite catalyst prepared by the method for preparing a composite catalyst according to any one of claims 4 to 8.

10. A method for degrading VOCs, characterized in that: The method comprises: loading a composite catalyst into a plasma reactor, and then introducing VOCs to react; The composite catalyst is the composite catalyst according to any one of claims 1 to 4 or 9.

11. The method for degrading VOCs according to claim 10, characterized in that: The VOCs are C2-C5 hydrocarbon compounds; Preferably, the concentration of the VOCs is 50-2000 ppm; Preferably, the catalytic temperature of the composite catalyst is 20-200°C.