Low-temperature plasma catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of low-temperature plasma catalysts, and discloses a low-temperature plasma catalyst and a preparation method and application thereof. The low-temperature plasma catalyst comprises a carrier and an active component loaded on the carrier; the active component contains manganese oxide, and the carrier is spherical theta-Al2O3. The low-temperature plasma catalyst has a rich pore channel structure, the specific surface area of the catalyst is greatly increased, the catalytic degradation efficiency of VOCs and intermediate product organic small molecules is further improved, meanwhile, by-products can be avoided, and secondary pollution is avoided.

Description

Technical Field

[0001] The present invention relates to the field of low-temperature plasma catalysts, and in particular to a low-temperature plasma catalyst and a preparation method and application thereof. Background Art

[0002] Low-temperature plasma technology is widely used in the treatment of volatile organic waste gases (VOCs) in the fields of petrochemical, spraying, aquaculture and municipal sewage treatment due to its advantages of simple process, instant start and stop, and low operating cost. The main reaction principle of this technology is that by applying high voltage to the positive and negative electrodes, the outer electrons in the gas molecules can undergo inelastic collisions with VOCs molecules and background gas molecules (such as nitrogen, oxygen and water vapor) under the action of the electric field formed by the air gap between the electrodes, generating active groups such as N radicals, O radicals and OH radicals that continue to react with VOCs molecules, and eventually mineralize VOCs into CO2 and H2O. However, when using low-temperature plasma alone to degrade VOCs, many toxic intermediate organic small molecules and reaction byproducts such as NOx and O3 will be produced, causing secondary pollution.

[0003] Studies have shown that combining catalysts with low-temperature plasma technology can effectively inhibit the generation of intermediate organic small molecules and reaction by-products (such as NOx and O3), and improve the energy efficiency of VOCs degradation. According to the placement area of ​​the catalyst, plasma-coupled catalytic technology is divided into two types: plasma built-in catalysis and plasma post-catalysis. Plasma built-in catalysis effectively inhibits the generation of intermediate organic small molecules by increasing the local electric field strength and prolonging the reaction time between VOCs molecules and active particles, thereby improving the mineralization efficiency of VOCs. However, the decomposition efficiency of by-products NOx and O3 is lower than that of plasma post-catalysis. In order to achieve the optimal comprehensive control of organic intermediates and reaction by-products, most plasma industrial waste gas treatment devices adopt a post-catalysis coupling method. However, the mineralization efficiency of intermediate organic small molecules by plasma post-catalysis technology is low, and the emission of by-products cannot be completely avoided, resulting in the difficulty in improving the degradation effect of VOCs. Moreover, the current low-temperature plasma catalyst cannot simultaneously take into account the catalytic degradation of VOCs, the intermediate organic small molecules, and the control of the emission of by-products NOx and O3 in the plasma post-catalytic coupling method. It is impossible to avoid the emission of by-products while improving the catalytic degradation efficiency of VOCs, and the catalytic degradation efficiency of VOCs needs to be improved urgently. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of low degradation efficiency of VOCs and easy secondary pollution in the process of plasma and catalyst synergistic treatment of VOCs in the prior art, and to provide a low-temperature plasma catalyst and its preparation method and application. The low-temperature plasma catalyst has a rich pore structure, which greatly improves 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 production of by-products and secondary pollution.

[0005] In order to achieve the above object, the present invention provides a low-temperature plasma catalyst, which includes a carrier and an active component supported on the carrier;

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

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

[0008] Preferably, the manganese oxide comprises α-MnO2 and optionally 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 60-90wt%, and the content of the manganese oxide is 10-40wt%.

[0010] Preferably, based on the total weight of 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%.

[0011] The second aspect of the present invention provides a method for preparing a low-temperature plasma catalyst, the preparation method comprising: mixing a manganese salt, spherical θ-Al2O3, an optional second active component precursor and water, spraying and granulating the obtained mixed solution, and then calcining.

[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 80-600nm;

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

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

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

[0017] The molar amounts of the manganese salt and the second active component precursor are calculated based on the metal element.

[0018] Preferably, the conditions of the 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° C. and a time of 4-12 hours.

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

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

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

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

[0025] The low-temperature plasma catalyst of the present invention has a rich pore structure and multiple types of holes, which are helpful for passing a large amount of gas and having a larger contact area with the reactants. In addition, the low-temperature plasma catalyst of the present invention uses spherical θ-Al2O3 as a catalyst carrier. The stability and large specific surface of the carrier can make the active components uniformly loaded, thereby further making the low-temperature plasma catalyst have a more excellent catalytic activity. In addition, the low-temperature plasma catalyst can effectively improve the decomposition efficiency of ozone and NOx on its surface through the mutual cooperation between the active component manganese oxide and the carrier spherical θ-Al2O3, while reducing the thermodynamic energy barrier required for the generation of hydroxyl radicals, greatly increasing the amount of hydroxyl radicals produced, and reducing the speed of self-decomposition of hydroxyl radicals, improving the utilization efficiency of hydroxyl radicals, thereby improving the degradation rate of VOCs and the decomposition rate of by-products, greatly reducing the emission of ozone and NOx, and avoiding secondary pollution while degrading VOCs.

[0026] In addition, in the method described in the present invention, the preparation process of the low-temperature plasma catalyst is further simplified by adopting spray granulation molding, and the prepared catalyst has a rich pore structure, which is convenient for loading more active components and has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 This is a SEM image of the low-temperature plasma catalyst prepared in Example 1;

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

[0030] Figure 4 It is the XRD spectra of the low-temperature plasma catalysts prepared in Examples 1-3 and Example 9. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0032] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0033] In the present invention, the low-temperature plasma catalyst includes a carrier and an active component loaded on the carrier; the active component contains manganese oxide, and the carrier is spherical θ-Al2O3. The low-temperature plasma catalyst of the present invention is coupled with plasma technology in the form of plasma post-coupling catalysis, that is, the placement area of ​​the low-temperature plasma catalyst is outside the plasma electric field area. The low-temperature plasma catalyst of the present invention can effectively improve the decomposition efficiency of ozone, while reducing the thermodynamic energy barrier required for the generation of hydroxyl radicals, increasing the amount of hydroxyl radicals produced by ozone decomposition, and reducing the speed of self-decomposition of hydroxyl radicals, improving the utilization efficiency of hydroxyl radicals, thereby improving the degradation rate of pollutants and the decomposition rate of by-products. Hydroxyl radicals are strongly oxidizing species. The low-temperature plasma catalyst of the present invention decomposes by catalyzing ozone, and further uses the hydroxyl radicals obtained by ozone decomposition to degrade the intermediate products produced by plasma zone degradation, thereby achieving the process of efficient degradation of VOCs and avoiding secondary pollution, while reducing the emission of ozone and NOx in the process of plasma degradation of VOCs.

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

[0035] In the present invention, the manganese oxide may be a common type of manganese oxide in the art, for example, one or more of MnO, Mn2O3 and MnO2. By combining the carrier spherical θ-Al2O3 with the manganese oxide, the low-temperature plasma catalyst can have high activity, high selectivity and excellent stability.

[0036] In a preferred embodiment, in order to make the catalytic activity of the low-temperature plasma catalyst more excellent and the removal effect of ozone and NOx in the by-products more excellent, the manganese oxide contains 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 manganese oxide, and the manganese oxide can also contain one or more of MnO, Mn3O4 and Mn2O3. For example, the components of the manganese oxide can be ɑ-MnO2, ɑ-MnO2 and MnO or ɑ-MnO2, MnO and Mn3O4. In the present invention, the ɑ-MnO2 contained in the manganese oxide has excellent activity and mainly plays a role in decomposing ozone. 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 degradation of VOCs and the control of by-products can be further achieved.

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

[0038] In the present invention, through the synergistic cooperation between the carrier θ-Al2O3, the active component manganese oxide and the second active component, the low-temperature plasma catalyst can quickly further treat the by-products ozone and NOx produced by plasma degradation, and can also improve the degradation rate of VOCs. While realizing the degradation of VOCs by plasma technology, the emission of by-products can be avoided, which gives full play to the advantages of low-temperature plasma technology and catalytic technology and realizes green treatment of VOCs.

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

[0040] In the present invention, when the active component of the low-temperature plasma catalyst also contains 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 40-90wt%, preferably 60-80wt%; the content of the manganese oxide is 5-40wt%, preferably 10-30wt%; the content of the second active component is 2.5-20wt%, preferably 5-18wt%. By limiting the content of each component in the low-temperature plasma catalyst, the low-temperature plasma post-coupling catalyst can exert a more excellent activity. Specifically, the content of the spherical θ-Al2O3 may be 40wt%, 50wt%, 60wt%, 65wt%, 68wt%, 70wt%, 75wt%, 80wt% or 90wt%; the content of the manganese oxide may be 10wt%, 15wt%, 18wt%, 20wt%, 25wt%, 28wt%, 30wt% or 40wt%; the content of the second active component may be 2.5wt%, 5wt%, 10wt%, 15wt% or 20wt%.

[0041] According to some embodiments of the present invention, the catalyst includes a carrier and an active component supported on the carrier; the active component contains manganese oxide, and the carrier is spherical θ-Al2O3. The manganese oxide contains 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 60-90wt%, and the content of the manganese oxide is 10-40wt%.

[0042] According to some other embodiments of the present invention, the catalyst includes a carrier and an active component supported on the carrier; the active component contains manganese oxide, and the carrier is spherical θ-Al2O3. The active component also contains a second active component, and the second active component is selected from one or more of the oxides of Ti, Ce, Co and Cu. The manganese oxide contains 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 40-90wt%, the content of the manganese oxide is 5-40wt%, and the content of the second active component is 2.5-20wt%.

[0043] The present invention also provides a method for preparing a low-temperature plasma catalyst, which comprises: mixing a manganese salt, spherical θ-Al2O3, an optional second active component precursor and water, spraying and granulating the obtained mixed solution, and then calcining.

[0044] In a specific embodiment, in order to further dissolve the manganese salt and the optional second active component precursor in water better, and to disperse the spherical θ-Al2O3 in water better, they can be dissolved and dispersed by ultrasound.

[0045] In a specific embodiment, the spherical θ-Al2O3 can be obtained through commercial purchase, or can be prepared according to conventional methods in the art, for example, it can be prepared according to 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 50-800nm, preferably 80-600nm.

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

[0048] In the present invention, the surface charge of the spherical θ-Al2O3 is a positive charge. Preferably, the surface charge of the spherical θ-Al2O3 is ≥30mV, for example, it can be 32-43mV. In the prior art, the surface charge of common spherical Al2O3 is usually negative, and it is easy to agglomerate and settle in aqueous solution. In the method described in the present invention, by selecting spherical θ-Al2O3 with a positive surface charge as a catalyst carrier, on the basis of increasing the specific surface area and pore volume of the prepared low-temperature plasma post-coupled catalyst, the dispersibility of the prepared low-temperature plasma post-coupled catalyst in aqueous solution is further increased, and it can be achieved that there is no agglomeration and sedimentation for a long time, which is beneficial to the uniformity of the active component loading, providing more sites for the active component to be responsible, preventing the agglomeration of the active component from causing a decrease in catalytic activity, and further improving the catalytic activity of the prepared low-temperature plasma catalyst.

[0049] In the present invention, the manganese salt is a water-soluble manganese salt, for example, it may be MnCl2 and / or Mn(NO3)2.

[0050] In the present 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, wherein the Ti salts, Ce salts, Co salts and Cu salts are all soluble metal salts.

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

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

[0053] In a specific embodiment, in order to ensure that the particle size of the prepared low-temperature plasma catalyst is more uniform and the morphology is more regular, the obtained mixed solution can be sieved to remove the precipitate obtained by agglomeration in the mixed solution before spray granulation, and then the sieve under the sieve is mechanically stirred, and then the dispersion obtained by stirring is spray granulated. Preferably, the speed of the mechanical stirring is 200-500rpm, and the time is 4-8h.

[0054] In the present invention, the low-temperature plasma catalyst is prepared by spray granulation. Compared with the commonly used solvent thermal method in the prior art, the spray granulation used in the present invention does not require high temperature and high pressure, and the particle size of the prepared low-temperature plasma catalyst is relatively uniform, the morphology is regular and has a rich pore structure, which greatly increases the specific surface area of ​​the isothermal plasma catalyst obtained, and the constructed porous channels are conducive to the passage of airflow, thereby improving the catalytic efficiency. In addition, spray granulation can complete the configuration and drying of particles in a very short time to form a spherical composite oxide catalyst precursor, which greatly shortens the preparation time.

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

[0056] In a preferred embodiment, the feed rate of the spray granulation is 10-30 mL / min, preferably 10-20 mL / min. The feed rate of the spray granulation refers to the rate at which the dispersion is fed 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 the present invention, the apparatus for performing the spray granulation in the method is not limited, and for example, it can be a common spray granulator 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°C, preferably 110-115°C; the drying time can be 4-12h, preferably 6-10h.

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

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

[0062] In a preferred embodiment, the heating rate of the calcination process is further limited to 1-5°C / min. Specifically, the heating rate of the calcination process refers to the heating rate when the ambient temperature is increased from room temperature to the calcination temperature during the calcination process.

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

[0064] In the present invention, the low-temperature plasma catalyst obtained by the above-mentioned preparation method includes a carrier and an active component loaded on the carrier; the active component contains manganese oxide, and the carrier is spherical θ-Al2O3. By selecting spherical θ-Al2O3 as a catalyst carrier, the active component is more evenly distributed on the carrier due to its large specific surface area and other advantages. Furthermore, through the mutual synergy between the spherical θ-Al2O3 and the manganese oxide, the energy required for the generation of hydroxyl radicals is further reduced, and ozone is accelerated to decompose into reactive hydroxyl radicals, so that the emission of byproducts such as ozone and NOx can be reduced as much as possible while using plasma to degrade VOCs, and the harmless treatment of VOCs through the coupling of plasma and catalyst is truly realized.

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

[0066] In the present invention, the low-temperature plasma catalyst can efficiently degrade acetone and / or pentane in VOCs after post-coupling with the plasma technology, and has efficient selectivity for acetone and pentane. More importantly, by post-coupling the low-temperature plasma catalyst with the low-temperature plasma technology, the tail gas after treating acetone and / or pentane can be secondary treated at the rear end of the low-temperature plasma reactor, greatly improving the degradation rate of acetone and pentane and the total hydrocarbon mineralization rate. At the same time, the byproducts O3 and NOx in the tail gas can also be synchronously degraded. The final O3 concentration in the tail gas emission is less than 1ppm, and the NOx concentration is less than 5ppm, achieving dual effective control of the intermediate organic small molecules and reaction byproducts generated in the plasma discharge zone, and achieving 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 examples, but the protection scope of the present invention is not limited thereto. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0070] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0071] The spherical θ-Al2O3 used in the following examples and comparative examples is 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) and water, mix by ultrasonication for 30 min to make the mixture uniform, pass the obtained mixture through a 500-mesh sieve, take the sieve under mechanical stirring, the mechanical stirring speed is 200 rpm, the time is 4 h, and a dispersion is obtained;

[0074] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 220° C., the outlet temperature to 110° C., the cyclone volume to 95%, and the feed rate to 10 mL / min; then placing the product obtained by spray granulation in an oven and drying it at 115° C. for 8 h; then heating the dried material to 600° C. at a rate of 5° C. / min and calcining it for 6 h to obtain a low-temperature plasma catalyst;

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

[0076] Example 2

[0077] (1) Spherical θ-Al2O3 (particle size 100-500nm, Zeta potential ≥30mV), manganese nitrate, cerium nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Ce :n Co =12:4:1:2) and water, mix by ultrasonic for 30 min to make it uniform, pass the obtained mixed solution through a 500-mesh sieve, take the sieve under mechanical stirring, the mechanical stirring speed is 150 rpm, the time is 4 h, and a dispersion is obtained;

[0078] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 220° C., the outlet temperature to 110° C., the cyclone volume to 95%, and the feed rate to 10 mL / min; then placing the product obtained by spray granulation in an oven and drying it at 110° C. for 8 h; then heating the dried material to 600° C. at a rate of 5° C. / min and calcining it for 6 h to obtain a low-temperature plasma catalyst;

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

[0080] Example 3

[0081] (1) Spherical θ-Al2O3 (particle size 200-500nm, Zeta potential ≥35mV), manganese nitrate, cerium nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Ce :n Co=10:2:1:1) and water, mix by ultrasonic for 30 min to make it uniform, pass the obtained mixed solution through a 500-mesh sieve, take the sieve under mechanical stirring, the mechanical stirring speed is 200 rpm, the time is 6 h, and a dispersion is obtained;

[0082] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 215° C., the outlet temperature to 115° C., the cyclone volume to 98%, and the feed rate to 10 ml / min; then placing the product obtained by spray granulation in an oven and drying it at 120° C. for 6 h; then heating the dried material to 650° C. at a rate of 10° C. / min and calcining it for 4 h to obtain a low-temperature plasma catalyst;

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

[0084] Example 4

[0085] (1) Spherical θ-Al2O3 (particle size 200-500nm, Zeta potential ≥35mV), manganese nitrate, copper nitrate, cobalt nitrate (n θ-Al2O3 :n Mn :n Cu :n Co =10:4:2:1) and water, mix by ultrasonication for 30 min to make the mixture uniform, pass the obtained mixture through a 500-mesh sieve, take the sieve under mechanical stirring, the mechanical stirring speed is 300 rpm, the time is 6 h, and a dispersion is obtained;

[0086] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 215° C., the outlet temperature to 115° C., the cyclone volume to 95%, and the feed rate to 15 ml / min; then placing the product obtained by spray granulation in an oven and drying it at 110° C. for 4 h; then heating the dried material to 600° C. at a rate of 2° C. / min and calcining it for 5 h to obtain a low-temperature plasma post-coupling catalyst;

[0087] XRF testing shows that the content of spherical θ-Al2O3 in the low-temperature plasma catalyst is 66.8wt%, the content of manganese oxide is 22.8wt%, the content of copper oxide is 5.2wt%, and the content of cobalt oxide is 5.2wt%.

[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, mix by ultrasonication for 30 min to make the mixture uniform, pass the obtained mixture through a 500-mesh sieve, take the sieve under mechanical stirring, the mechanical stirring speed is 300 rpm, the time is 5 h, and a dispersion is obtained;

[0090] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 220° C., the outlet temperature to 110° C., the cyclone volume to 98%, and the feed rate to 10 ml / min; then placing the product obtained by spray granulation in an oven and drying it at 110° C. for 4 h; then heating the dried material to 600° C. at a rate of 2° C. / min and calcining it for 5 h to obtain a low-temperature plasma catalyst;

[0091] XRF testing shows that the content of spherical θ-Al2O3 in the low-temperature plasma catalyst is 66wt%, the content of manganese oxide is 26wt%, the content of copper oxide is 4wt%, and the content of cobalt oxide is 4wt%.

[0092] Example 6

[0093] (1) Spherical θ-Al2O3 (particle size 100-800nm, Zeta potential ≥35mV), manganese nitrate (n θ-Al2O3 :n Mn =10:3) and water, and mix them by ultrasonication for 30 min to make them uniform. The obtained mixed solution was passed through a 500-mesh sieve, and the material under the sieve was mechanically stirred at a speed of 300 rpm for 5 h to obtain a dispersion;

[0094] (2) using a centrifugal nozzle, spray-drying the dispersion obtained in step (1) in a spray granulator, setting the inlet temperature to 220° C., the outlet temperature to 110° C., the cyclone volume to 98%, and the feed rate to 10 ml / min; then placing the product obtained by spray granulation in an oven and drying it at 110° C. for 4 h; then heating the dried material to 600° C. at a rate of 2° C. / min and calcining it for 5 h to obtain a low-temperature plasma catalyst;

[0095] XRF testing shows that the content of spherical θ-Al2O3 in the low-temperature plasma catalyst is 79.6wt%, and the content of manganese oxide is 20.4wt%.

[0096] Example 7

[0097] The method of Example 1 is followed, except that in step (2), the inlet temperature of the spray granulation is 170° C., to prepare a low-temperature plasma catalyst;

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

[0099] Example 8

[0100] The method of Example 1 is used, except that the particle size of the spherical θ-Al2O3 used is 1-10 μm and the Zeta potential is -15 mV;

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

[0102] Example 9

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

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

[0105] Example 10

[0106] The method of Example 1 was followed, except that cerium nitrate was replaced with an equal amount of iron nitrate for preparation;

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

[0108] Embodiment 11

[0109] The method of Example 1 is followed, except that the molar ratio of θ-Al2O3, manganese nitrate, cerium nitrate and cobalt nitrate is 10:10:10:3;

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

[0111] Example 12

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

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

[0114] Comparative Example 1

[0115] The method of Example 1 is used, except that the spherical θ-Al2O3 is replaced with γ-Al2O3 of equal weight for preparation;

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

[0117] Comparative Example 2

[0118] The method of Example 1 was followed, except that no manganese nitrate was added for preparation;

[0119] XRF testing shows that the content of spherical θ-Al2O3 in the low-temperature plasma catalyst is 80.2wt%, the content of cerium oxide is 13.5wt%, and the content of cobalt oxide is 6.3wt%.

[0120] Test Case

[0121] Test Example 1

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

[0123] The surface morphology of the low-temperature plasma catalyst prepared in Example 1 was tested by SEM. Figure 2 As shown, the low-temperature plasma catalyst is spherical, and the active component and the second active component are loaded on the surface of the carrier θ-Al2O3, and the structure is regular.

[0124] Test Example 2

[0125] XRD was used to detect the crystal form of spherical θ-Al2O3 in the raw material. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the carrier alumina used in the present invention is θ-Al2O3;

[0126] The low temperature plasma catalysts prepared in Examples 1-3 and 9 were tested by XRD. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that in the low-temperature plasma catalysts prepared in Examples 1-3 of the present invention, the active component manganese oxide contains ɑ-MnO2, and the crystal form of the carrier alumina is θ-Al2O3. In the low-temperature plasma catalyst prepared in Example 9, due to the low calcination temperature, the active component does not contain ɑ-MnO2 or the content of ɑ-MnO2 is too low, which affects the effect of the low-temperature plasma catalyst on the degradation of by-products to a certain extent.

[0127] Test Example 3

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

[0129] Test method: The simulated gas (pentane concentration is 300ppm) is passed into the plasma device for treatment, and the pentane content in the treated pollutants is measured using an Agilent 8890B gas chromatograph equipped with a dual hydrogen 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 ×100%, calculate the degradation rate of pentane, 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 106-M ozone analyzer from the American 2B company was used to detect the change in O3 concentration in the treated exhaust gas. The results are shown in Table 1.

[0132] Table 1

[0133] Example No. Pentane degradation rate <![CDATA[Concentration of O3 in tail 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 Embodiment 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] It can be seen from the results in Table 1 that after the low-temperature plasma post-coupled catalyst described in the present invention is coupled with the plasma technology, the pentane degradation rate and mineralization rate can be greatly improved without increasing the discharge power. The pentane degradation rate can reach about 98.5%. At the same time, the emission of by-products such as O3 and NOx is greatly reduced, and the harmless treatment of VOCs is achieved.

[0135] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A low-temperature plasma catalyst, characterized in that: The catalyst comprises a carrier and an active component supported on the carrier; The active component contains manganese oxide, and the carrier is spherical θ-Al2O3.

2. The low-temperature plasma post-coupled catalyst according to claim 1, characterized in that: The active component further contains a second active component, and the second active component is selected from one or more oxides of Ti, Ce, Co and Cu.

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

4. The low-temperature plasma catalyst according to claim 1 or 3, characterized in that Based on the total weight of the low-temperature plasma catalyst, 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 Based on the total weight of 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. A method for preparing a low-temperature plasma catalyst, characterized in that: The preparation method comprises: mixing manganese salt, spherical θ-Al2O3, an optional second active component precursor and water, spraying and granulating the obtained mixed solution, and then calcining.

7. The method for preparing a low-temperature plasma catalyst according to claim 6, characterized in that: The second active component precursor is selected from one or more of Ti salt, Ce salt, Co salt and Cu salt.

8. The method for preparing a low-temperature plasma catalyst according to claim 6, characterized in that: The particle size of the spherical θ-Al2O3 is 50-800nm; Preferably, the specific surface area of ​​the spherical θ-Al2O3 is 5-50m 2 / g; Preferably, the surface Zeta potential of the spherical θ-Al2O3 is ≥30mV.

9. The method for preparing a low-temperature plasma catalyst according to any one of claims 6 to 8, characterized in that: The molar ratio of the manganese salt, the second active component precursor and the spherical θ-Al2O3 is 0.2-32:1:1.6-61; The molar amounts of the manganese salt and the second active component precursor are calculated based on the metal element.

10. The method for preparing a low-temperature plasma catalyst according to claim 6, characterized in that: The spray granulation conditions include: inlet temperature of 200-250°C, outlet temperature of 100-130°C; Preferably, the feed rate of the spray granulation is 10-30 mL / min.

11. The method for preparing a low-temperature plasma catalyst according to claim 6, characterized in that: The calcination conditions include: a temperature of 500-1000° C. and a time of 4-12 hours.

12. A low-temperature plasma catalyst prepared by the method for preparing a low-temperature plasma catalyst according to any one of claims 6 to 11.

13. Use of the low-temperature plasma catalyst according to any one of claims 1 to 5 or the low-temperature plasma catalyst according to claim 12 in low-temperature plasma degradation of acetone and / or pentane.

14. The use according to claim 13, characterized in that The concentration of the acetone is 50-2000ppm; Preferably, the concentration of pentane is 50-2000 ppm.

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