Method for catalytically degrading VOCs (Volatile Organic Compounds) through cooperation of plasma and perovskite

Abstract

The invention discloses a method for catalytically degrading VOCs (Volatile Organic Compounds) through cooperation of plasma and perovskite, which comprises the following steps: step 1, preparing a catalyst based on perovskite, and loading the catalyst on a carrier; 2, arranging a plasma generator in a reactor to obtain a plasma synergistic reactor; 3, filling the plasma synergistic reactor obtained in the step 2 with the catalyst obtained in the step 1; 4, gas containing VOCs is pretreated and then introduced into the plasma synergistic reactor, and the VOCs are degraded through the synergistic effect of plasma and the catalyst. Compared with the prior art, the method has the advantage that the method for catalytically degrading the VOCs through cooperation of the plasma and the perovskite is used for constructing a synergistic system of the plasma and the perovskite catalyst.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, and in particular to a method for degrading VOCs by plasma-assisted perovskite catalysis. Background Art

[0002] Volatile organic compounds (VOCs) are one of the main sources of air pollution, causing serious harm to human health and the ecological environment.

[0003] In recent years, the combination of plasma technology and catalytic oxidation technology has been considered as an efficient and environmentally friendly method for VOCs treatment.

[0004] During the degradation of VOCs (Volatile Organic Compounds), high-energy electrons directly bombard the organic waste gas. High-energy electrons can not only directly break down large molecular pollutants into small molecular safe substances, but also produce active particles such as HO, O, HO2, O3, etc. that can further promote the decomposition of VOCs. Therefore, the degradation effect is relatively good.

[0005] However, during the degradation process, organic matter cannot be completely degraded into CO2 and H2O, but undegraded intermediates (organic alcohols, organic acids, organic ketones and other oxygen-containing organic small molecules) will be produced.

[0006] Perovskite catalysts show good application prospects in the catalytic oxidation of VOCs due to their excellent redox properties and stability.

[0007] However, single plasma technology or perovskite catalytic technology still has certain limitations in practical applications, such as low energy utilization of plasma technology and easy deactivation of catalysts. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the above technical defects and provide a method for constructing a synergistic system of plasma and perovskite catalysts to degrade VOCs by using plasma and perovskite catalysts.

[0009] In order to solve the above technical problems, the technical solution provided by the present invention is: a method for plasma-assisted perovskite catalytic degradation of VOCs, comprising the following steps:

[0010] Step 1: Prepare a catalyst based on perovskite and load it on a carrier;

[0011] Step 2: Arrange a plasma generator in the reactor to obtain a plasma co-reactor;

[0012] Step 3: Filling the catalyst obtained in step 1 into the plasma cooperative reactor obtained in step 2;

[0013] Step 4: The gas containing VOCs is pretreated and then introduced into a plasma co-reactor to degrade the VOCs through the synergistic effect of plasma and catalyst.

[0014] Preferably, the catalyst in step 1 is ABO 3 Type perovskite catalyst, wherein the A position is a rare earth element or an alkaline earth metal element, a rare earth element or an alkaline earth metal element.

[0015] Preferably, the A position is at least one of lanthanum, cerium and praseodymium, and the B position is at least two of manganese, cobalt and iron;

[0016] The A site and the B site are added with deionized water and mixed, and then heated and evaporated to obtain a dry gel. The dry gel is pre-burned at 300-500° C. and then calcined at 700-900° C. to obtain a perovskite crystal. The perovskite crystal is crushed, ground and sieved to obtain a perovskite catalyst.

[0017] Preferably, in step 1, the carrier is sepiolite, and the perovskite catalyst is mixed with the sepiolite and then ball-milled in a ball mill, and then calcined, so that the perovskite catalyst is loaded on the carrier.

[0018] Preferably, the plasma co-reactor in step 2 comprises a plasma generating zone, a catalytic reaction zone and a gas distribution zone, and the catalyst loaded on the carrier obtained in step 1 is filled into the catalytic reaction zone.

[0019] Preferably, the plasma generating zone includes any one of dielectric barrier discharge, corona discharge and microwave discharge.

[0020] Preferably, in step 4, the gas residence time is 1 to 3 seconds, the energy density is 50 to 150 J / L, and the active species generated by the plasma include OH, O 3 and high energy electrons.

[0021] Preferably, the gas pretreatment of VOCs in step 4 includes using a bag filter and a condensing dehumidifier;

[0022] The temperature of the condensation dehumidification device is 5-13°C, and the filtration accuracy of the bag dust collector is ≤1μm.

[0023] Preferably, the VOCs include at least one of benzene, toluene and xylene, and after degradation, CO 2 Selectivity ≥90%, by-product ozone concentration <10ppm.

[0024] Preferably, step 4 also includes tail gas treatment of the degraded VOCs gas, and the tail gas treatment includes any one of activated carbon adsorption, catalytic oxidation, and alkaline solution absorption.

[0025] The advantages of the present invention compared with the prior art are: by designing a synergistic system of a multi-metal perovskite catalyst and a dielectric barrier discharge reactor, efficient and low-temperature degradation of VOCs is achieved, the degradation efficiency and energy utilization rate of VOCs are significantly improved, and energy consumption and secondary pollution are reduced. The catalyst in the present invention adopts an acid-modified sepiolite carrier. Under the action of high-energy electrons and active oxygen species generated by plasma, the oxygen vacancy density of the catalyst is significantly improved, which is suitable for industrial organic waste gas treatment and has the advantages of low cost, high efficiency, and no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the implementation process of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0028] Combined with Figure 1 As shown, a method for plasma-assisted perovskite catalytic degradation of VOCs comprises the following steps:

[0029] Step 1: preparing a catalyst based on perovskite and loading it on a carrier, specifically comprising: preparing a perovskite catalyst by a sol-gel method-calcination method and loading it on a sepiolite carrier;

[0030] Step 2: Arrange a plasma generator in the reactor to obtain a plasma co-reactor, design the reactor structure, ensure the reasonable distribution of the plasma generation area, catalytic reaction area and gas distribution area, so as to optimize the degradation efficiency of VOCs;

[0031] Step 3: Filling the catalyst obtained in step 1 into the plasma cooperative reactor obtained in step 2, and uniformly filling the supported perovskite catalyst into the catalytic reaction zone to ensure sufficient contact between the gas and the catalyst;

[0032] Step 4: The gas containing VOCs is pretreated and then introduced into the plasma co-reactor. The VOCs are degraded through the synergistic effect of plasma and catalyst. The high-energy electrons, free radicals and active species (such as OH, O 3 ) and perovskite catalysts to degrade VOCs into CO 2 and H 2 O.

[0033] When the present invention is specifically applied:

[0034] In step 1:

[0035] The catalyst is ABO 3A type perovskite catalyst, wherein the A position is a rare earth element or an alkaline earth metal element, and the B position is a transition metal element, and the A-position element (such as La, Ce, Pr) can stabilize the perovskite structure and adjust the redox performance of the catalyst, and various combinations of the B-position element (such as Mn, Co, Fe) can form a composite oxide to enhance the synergistic effect of the catalyst; the A-position and B-position precursors (such as nitrates) are dissolved in deionized water according to a stoichiometric ratio, citric acid or ethylene glycol is added as a complexing agent, and stirred to form a transparent sol, and the sol is heated and evaporated at 80-100° C. to obtain a dry gel, and the dry gel is pre-calcined at 300-500° C. for 2-4 hours to remove organic matter and moisture, and the pre-calcined sample is calcined at 700-900° C. for 3-6 hours to obtain perovskite crystals, and the perovskite crystals are crushed, ground and sieved to obtain a perovskite catalyst with uniform particle size.

[0036] In step 1, the carrier is sepiolite. The perovskite catalyst is mixed with the sepiolite and then ball-milled in a ball mill. After ball-milling, calcination is performed to load the perovskite catalyst on the carrier. Specifically, the sepiolite needs to be treated with acid (such as 1 mol / L HCl) and dried pre-treated to remove impurities and improve its adsorption performance. The perovskite catalyst is mixed with the sepiolite in a mass ratio of 1:1 to 1:5, and ball-milled in a ball mill for 2 to 4 hours to uniformly disperse the catalyst on the surface of the carrier. The ball-milled mixture is calcined at 500 to 700° C. for 3 to 5 hours to firmly bond the catalyst to the carrier.

[0037] The plasma generating zone adopts dielectric barrier discharge (DBD), corona discharge or microwave discharge with a discharge power of 50 to 500 W and a discharge frequency of 1 to 100 kHz. The catalytic reaction zone is filled with a loaded perovskite catalyst with a filling height of 1 / 3 to 2 / 3 of the reactor height. A porous plate or distributor is used in the gas distribution zone to ensure that the VOCs gas passes through the catalytic reaction zone evenly.

[0038] When using:

[0039] Dielectric barrier discharge (DBD) is suitable for low-concentration VOCs treatment, and the discharge gap is 1 to 5 mm;

[0040] Corona discharge is suitable for high-concentration VOCs treatment, and the electrode spacing is 5 to 20 mm;

[0041] Microwave discharge is suitable for rapid degradation of VOCs, with a power density of 10 to 100 W / cm 3 ;

[0042] The gas residence time is 1 to 3 seconds, the energy density is 50 to 150 J / L, and the active species produced by the plasma include OH, O 3 and high energy electrons.

[0043] In order to ensure the treatment effect, the gas pretreatment of VOCs in step 4 includes the use of a bag filter and a condensation dehumidifier; the bag filter has a filtration accuracy of ≤1μm and is used to remove particulate matter in the gas, and the temperature of the condensation dehumidification device is 5-13°C, which is used to reduce the humidity of the gas and prevent the catalyst from deactivating;

[0044] VOCs include at least one of benzene, toluene and xylene. After degradation, CO 2 Selectivity ≥ 90%, byproduct ozone concentration < 10ppm, by optimizing plasma parameters and catalyst performance, ensure VOCs degradation efficiency ≥ 95%, CO 2 Selectivity ≥90%, by-product ozone concentration <10ppm.

[0045] Step 4 also includes treating the degraded VOCs gas with tail gas, wherein the tail gas treatment includes any one of activated carbon adsorption, catalytic oxidation, and alkaline solution absorption;

[0046] Specifically:

[0047] Activated carbon adsorption is used to remove incompletely degraded VOCs and byproducts (such as O 3 ), catalytic oxidation is used to further degrade residual VOCs, and the catalyst can be Pt / Al 2 O 3 or MnO 2 -Co 3 O 4 , alkali absorption is used to remove acidic gases (such as NO x 、SO 2 ) and ozone.

[0048] The present invention is specifically implemented:

[0049] Plasma generator settings: corona discharge, discharge power of 200W, discharge frequency of 50kHz;

[0050] Weigh Ce(NO 3 ) 3 6H 2 O, Fe(NO 3 ) 3 9H 2 O and Mn(NO 3 ) 2 ·4H 2 O was dissolved in deionized water, ethylene glycol was added as a complexing agent, and stirred to form a transparent sol. The sol was heated and evaporated at 90°C to obtain a dry gel. The dry gel was pre-calcined at 450°C for 4 hours and then calcined at 850°C for 6 hours to obtain CeFe 0.7 Mn 0.3 O 3Perovskite catalyst, the catalyst is crushed, ground and sieved to obtain a powder with uniform particle size, and CeFe 0.7 Mn 0.3 O 3 Catalyst and SiO 2 The mixture was mixed in a mass ratio of 1:3, ball-milled in a ball mill for 4 hours, and the ball-milled mixture was calcined at 700°C for 5 hours to obtain CeFe 0.7 Mn 0.3 O 3 / SiO 2 Supported Catalyst.

[0051] The catalytic reaction zone is filled with CeFe 0.7 Mn 0.3 O 3 / SiO 2 The catalyst is filled to 2 / 3 of the reactor height, and a distributor is used in the gas distribution area to ensure uniform gas distribution;

[0052] The gas containing xylene (initial concentration of 2000 ppm) was pretreated by a bag dust collector (filtration accuracy ≤ 1 μm) and a condensation dehumidifier (temperature of 8°C). The pretreated gas was passed into a plasma co-reactor with a gas flow rate of 2 L / min, a gas residence time of 3 seconds, and an energy density of 120 J / L. The pretreated gas was passed into a plasma co-reactor with a gas flow rate of 2 L / min, a gas residence time of 3 seconds, and an energy density of 120 J / L.

[0053] The degraded gas passes through an alkaline solution absorption device to remove residual VOCs and ozone.

[0054] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0055] =The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

[0056] The scope of the present invention is defined by the appended claims and their equivalents, and therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention as claimed but merely represents selected embodiments of the present invention.

[0057] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0058] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0059] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0060] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0061] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0062] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0063] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for degrading VOCs by plasma-assisted perovskite catalysis, characterized in that: The following steps are involved: Step 1: Prepare a catalyst based on perovskite and load it on a carrier; Step 2: Arrange a plasma generator in the reactor to obtain a plasma co-reactor; Step 3: Filling the catalyst obtained in step 1 into the plasma cooperative reactor obtained in step 2; Step 4: The gas containing VOCs is pretreated and then introduced into a plasma co-reactor to degrade the VOCs through the synergistic effect of plasma and catalyst.

2. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 1, characterized in that: The catalyst in step 1 is an ABO3 type perovskite catalyst, wherein the A position is a rare earth element or an alkaline earth metal element, a rare earth element or an alkaline earth metal element.

3. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 2, characterized in that: The A position is at least one of lanthanum, cerium, and praseodymium, and the B position is at least two of manganese, cobalt, and iron; The A site and the B site are added with deionized water and mixed, and then heated and evaporated to obtain a dry gel. The dry gel is pre-burned at 300-500° C. and then calcined at 700-900° C. to obtain a perovskite crystal. The perovskite crystal is crushed, ground and sieved to obtain a perovskite catalyst.

4. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 2 or 3, characterized in that: In step 1, the carrier is sepiolite, and the perovskite catalyst is mixed with the sepiolite and then ball-milled in a ball mill. After ball-milling, the mixture is calcined to load the perovskite catalyst on the carrier.

5. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 1, characterized in that: The plasma co-reactor in step 2 includes a plasma generating zone, a catalytic reaction zone and a gas distribution zone, and the catalyst loaded on the carrier obtained in step 1 is filled into the catalytic reaction zone.

6. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 5, characterized in that: The plasma generating area includes any one of dielectric barrier discharge, corona discharge and microwave discharge.

7. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 6, characterized in that: In step 4, the gas residence time is 1 to 3 seconds, the energy density is 50 to 150 J / L, and the active species generated by the plasma include ·OH, O3 and high-energy electrons.

8. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 1, characterized in that: The gas pretreatment of VOCs in step 4 includes using a bag filter and a condensing dehumidifier; The temperature of the condensation dehumidification device is 5-13°C, and the filtration accuracy of the bag dust collector is ≤1μm.

9. The method for degrading VOCs by plasma-assisted perovskite catalysis according to claim 7, characterized in that: The VOCs include at least one of benzene, toluene and xylene, and after degradation, the CO2 selectivity is ≥90%, and the byproduct ozone concentration is <10ppm.

10. A method for degrading VOCs by plasma-assisted perovskite catalysis according to any one of claims 1 to 9, characterized in that: The step 4 also includes tail gas treatment of the degraded VOCs gas, and the tail gas treatment includes any one of activated carbon adsorption, catalytic oxidation, and alkaline solution absorption.

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