Novel VOCs circulating purification method with adsorption storage and plasma catalytic oxidation double-zone coupling

Abstract

The invention relates to a novel adsorption storage and plasma catalytic oxidation double-zone coupled VOCs (Volatile Organic Compounds) circulating purification method, which at least comprises the following steps of: filling a first catalyst into a non-discharge zone of a reaction tube as an adsorption bed layer, and filling a second catalyst into a plasma discharge zone of the reaction tube as an oxidation bed layer; 2, introducing mixed gas containing volatile organic compound molecules into the reaction tube filled with the adsorption bed layer and the oxidation bed layer in the step 1, and adsorbing to obtain the adsorption bed layer with saturated storage; and switching the mixed gas into mixed gas without volatile organic compound molecules, accurately matching the desorption temperature of the target molecules by utilizing a localized temperature field generated by the plasma, and carrying out oxidation regeneration under the action of the plasma and a second catalyst. According to the method, an energy coupling mechanism between dynamic adsorption and plasma concerted catalytic oxidation is established through sequential control, effective removal of gaseous organic pollutants is guaranteed, and 100% carbon circulation can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas pollutant purification, and particularly relates to a new VOCs recycling purification method of a double-zone coupling of "adsorption storage and plasma catalytic oxidation". BACKGROUND

[0002] Volatile organic compounds (VOCs) refer to various organic compounds with boiling points between 50 DEG C and 260 DEG C at normal temperature and pressure. Most of the emitted VOCs are important precursors of secondary pollutants such as fine particulate matter (PM2.5) and ozone (O3), which in turn cause atmospheric environmental problems such as haze and photochemical smog. Among them, benzene series molecules (including benzene, toluene, xylene, etc.) are representative VOC molecules, which not only damage the liver and kidney functions when a small amount exists, but also damage the nervous system of the human body, and can even endanger human life when the damage is serious. N-hexane is commonly used as a solvent and widely used in various fields of chemical production due to its high volatility and high fat solubility. It is a relatively common VOC, and its toxicity, irritability, carcinogenicity and special odor not only affect the skin and mucous membrane, but also cause acute damage to the human body, and can even endanger life in severe cases. Therefore, it is very important to develop low-cost and high-efficiency VOCs treatment technology.

[0003] At present, the commonly used VOC removal technologies are adsorption method and catalytic oxidation method. The adsorption method is to use the physical and chemical action between the adsorbent and the volatile organic molecules for enrichment and separation, and usually selects adsorbents with large specific surface area, such as activated carbon, molecular sieve, metal organic framework material (MOFs) and the like. MOFs have excellent performance such as super-high specific surface area, excellent thermal stability and rich pore structure, and show great advantages in adsorbing and removing VOCs. However, the structural stability of MOF material is weak, and the structure may collapse due to changes in temperature or humidity during regeneration, resulting in escape of pollutant molecules, causing secondary pollution, and significantly reducing the adsorption capacity. The oxidation temperature of catalytic oxidation method for chemically stable alkane molecules is 300-500 DEG C, which limits its practical application due to high energy consumption. Traditional thermal catalytic oxidation usually requires high temperature to ensure complete oxidation, which has high energy consumption and high requirements for equipment materials. The plasma technology can generate high-energy electrons, free radicals and other active species at room temperature or low temperature, which can quickly oxidize and decompose VOCs. There are a large number of high-energy particles and strong oxidizing free radicals in the plasma environment, and the adsorbent with poor thermal stability is easy to collapse or have unexpected side reactions during discharge, so the catalytic efficiency is low and the service life of the material is short. With the increasing requirements for VOCs emission control in industry and daily life, how to realize efficient removal of VOCs under low energy consumption and mild operating conditions has become a research hotspot.

[0004] CN113825294A discloses a waste gas treatment method using a composite plasma discharge device. By combining or using alone the two discharge forms of surface discharge and dielectric barrier discharge, different discharge modes are obtained to meet the energy needs of different types of waste gas degradation. This method uses different discharge modes to remove toluene, benzene, and formaldehyde, respectively. Although the removal efficiency can reach more than 90%, this method has the problem of secondary pollution caused by toxic substances in the product. This method requires continuous and long-term use of plasma, which has the problems of high energy consumption and low safety.

[0005] To solve the problem that a single method cannot solve, researchers have proposed a "storage-oxidation" cycle method. This method simultaneously achieves adsorption and in-situ oxidation on a catalyst and regenerates the catalyst for the next cycle, thereby comprehensively treating air pollutants. The principle of this method is as follows: in the room temperature stage, low-concentration VOCs are first enriched and stored on the catalyst. After saturation, the oxidation and regeneration stage is entered. In the regeneration stage, different energy input methods (thermal catalytic oxidation, plasma-assisted oxidation, ozone-assisted oxidation, etc.) can be selected to rapidly oxidize the desorbed species into CO2 and H2O, while the catalyst is regenerated in-situ. Then the next cycle continues.

[0006] CN104226241A discloses a catalyst for removing low-concentration benzene series from gas at room temperature and its application. This catalyst is mainly used in the storage and discharge stages which are alternately operated. In the storage stage, low-concentration benzene series in the gas are first adsorbed and stored on the catalyst. In the discharge stage, the benzene series adsorbed and stored on the catalyst are catalytically oxidized into carbon dioxide and water by plasma. This method can remove low-concentration benzene series from gas at room temperature and solve the problems of high energy consumption and toxic by-products in existing plasma methods for removing low-concentration benzene series. However, in actual application, molecular sieves with good thermal stability are often used as catalysts, and the storage capacity is low. Moreover, for some VOC molecules with low desorption temperature, the regeneration process may cause secondary pollution due to desorption. When used to treat n-hexane and other long-chain alkanes, the catalyst has weak adsorption strength for alkane molecules due to their excellent property stability, and the desorption temperature is low (less than 100°C). In addition, long-chain alkanes are easily cracked under the action of plasma, producing small-molecule alkanes that are difficult to degrade, and complete degradation cannot be achieved.

[0007] Because most organic pollutant molecules have stable properties and are difficult to form strong interactions with adsorbent materials, the adsorption strength is weak. Therefore, the desorption rate during the regeneration process is much higher than the oxidation rate, and complete regeneration cannot be achieved. Even if plasma-assisted regeneration is used, the problem of desorption cannot be completely solved, and there are problems of poor structural stability of the adsorbent material and the production of toxic by-products under high-energy electric fields. It is difficult to achieve complete removal of VOCs using existing technologies.

[0008] At present, there are problems in the removal method of volatile organic compounds, such as the desorption rate in the regeneration process is much higher than the oxidation rate, which leads to the inability to achieve complete regeneration, the plasma method causes the structure of the adsorbed material to be easy to collapse under heat, and long-chain alkane molecules are easy to crack to produce difficult-to-degrade products. A new VOCs cyclic purification method of "adsorption storage and plasma catalytic oxidation" dual-zone coupling is proposed. SUMMARY

[0009] To solve the above technical problems, the present application provides a new VOCs cyclic purification method of "adsorption storage and plasma catalytic oxidation" dual-zone coupling. By constructing a two-stage cascade reaction system of adsorption storage zone and plasma catalytic oxidation zone, the dynamic adsorption enrichment and in-situ catalytic oxidation of volatile organic compounds are realized, breaking through the technical limitation of the structure instability of conventional adsorbents (such as MOF, AC, etc.) in the plasma discharge field, and effectively solving the problems of desorption escape and secondary pollution caused by physical adsorption (weak force). In addition, by optimizing the discharge parameters, the localized temperature field generated by the plasma heat effect accurately matches the desorption temperature of the target molecules, which reduces the system energy consumption and inhibits the generation of by-products, significantly improving the catalytic oxidation efficiency and cyclic regeneration stability.

[0010] According to one aspect of the present application, a new VOCs cyclic purification method of "adsorption storage and plasma catalytic oxidation" dual-zone coupling is provided, which comprises the following steps: Catalyst filling, step 1: filling the first catalyst into the non-discharge zone of the reaction tube as an adsorption bed, and filling the second catalyst into the plasma discharge zone of the reaction tube as an oxidation bed, to obtain a reaction tube filled with an adsorption bed and an oxidation bed; Gas storage, step 2: passing a mixed gas containing volatile organic compound molecules into the reaction tube filled with the adsorption bed and the oxidation bed in step 1 for adsorption, to obtain a saturated adsorption bed; Regeneration, step 3: switching the mixed gas in step 2 to a mixed gas not containing volatile organic compound molecules, and regenerating the saturated adsorption bed in step 2 under the action of plasma discharge and the second catalyst, to obtain a regenerated adsorption bed and an oxidation bed.

[0011] Optionally, the first catalyst in step 1 is selected from at least one of MIL catalyst, UiO-66 catalyst, MOF catalyst, Beta molecular sieve, HZ molecular sieve, and TS-1 molecular sieve.

[0012] Optionally, the first catalyst is selected from at least one of MIL catalyst, HZ molecular sieve, and TS-1 molecular sieve; The pore size of the first catalyst is 0.38-1 nm. The second catalyst in step 1 is a non-noble metal oxide catalyst; The non-noble metal oxide catalyst is at least one selected from cobalt-manganese oxide, cobalt-cerium oxide, and manganese-cerium oxide.

[0013] Optionally, the non-noble metal oxide catalyst is a cobalt-manganese catalyst. The mass ratio of the first catalyst to the second catalyst used in the packing in step 1 is 1:1-2. The discharge zone and the non-discharge zone in step 1 are separated by quartz wool.

[0014] Optionally, the concentration of the volatile organic compound molecules in the mixed gas containing the volatile organic compound molecules in step 2 is 1-550 ppm. The volatile organic compound molecules are at least one selected from toluene, n-hexane, benzene, and propane. The flow rate of the mixed gas containing the volatile organic compound molecules in step 2 is 100-200 mL / min. The mixed gas containing the volatile organic compound molecules in step 2 further comprises 21 vol% O2 and the balance N2.

[0015] Optionally, the adsorption in step 2 is under the following conditions: The relative humidity of the adsorption is 0-100%. The temperature of the adsorption is 0-25°C. The time of the adsorption is 0-1 h. The content of the volatile organic compound molecules in the outlet gas of the storage saturated reaction tube in step 2 is 10% of the content of the volatile organic compound molecules in the inlet gas of the reaction tube.

[0016] Optionally, the relative humidity of the adsorption is independently selected from any value or a range between any two values of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%.

[0017] Optionally, the storage amount of the volatile organic compound molecules in the storage saturated adsorption bed in step 2 is 0-1.5 mmol / g.

[0018] Optionally, the storage amount of volatile organic compound molecules in the saturated adsorption bed in step 2 is independently selected from any value or range between any two values of 0 mmol / g, 0.1 mmol / g, 0.2 mmol / g, 0.3 mmol / g, 0.4 mmol / g, 0.5 mmol / g, 0.6 mmol / g, 0.7 mmol / g, 0.8 mmol / g, 0.9 mmol / g, 1.0 mmol / g, 1.1 mmol / g, 1.2 mmol / g, 1.3 mmol / g, 1.4 mmol / g, 1.5 mmol / g.

[0019] Optionally, the mixed gas without volatile organic compound molecules in step 3 is 21 vol% O2 and the balance N2. The flow rate of the mixed gas without volatile organic compound molecules in step 3 is 21 vol% O2 and the balance N2 is 100-200 mL / min.

[0020] Optionally, the flow rate of the mixed gas without volatile organic compound molecules in step 3 is 21 vol% O2 and the balance N2 is 100 mL / min.

[0021] Optionally, the discharge type of the plasma in step 3 is dielectric barrier discharge. The power of the dielectric barrier discharge is 20-30 W. The time of the dielectric barrier discharge is 0-30 min.

[0022] Optionally, the bottom temperature of the adsorption bed in step 3 is 90-200°C. Optionally, the bottom temperature of the adsorption bed in step 3 is generated by plasma discharge and / or plasma discharge and the action of a second catalyst.

[0023] Optionally, the relative humidity of the regeneration in step 3 is 0-100%.

[0024] Optionally, the relative humidity of the regeneration in step 3 is independently selected from any value or range between any two values of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%.

[0025] Compared with the prior art, the present application has the following advantages: (1) The technical scheme provided by the present application has a wide application range, and is particularly suitable for the treatment of structural sensitive adsorbents and weakly adsorbed pollutant molecules. Compared with traditional thermal regeneration technology (whole heating by a tubular furnace) and radiation regeneration technology (infrared rapid heating), the present application places the adsorbent (i.e. the first catalyst) in the non-discharge area (i.e. upstream of the plasma) of the reaction tube, and uses the heat effect generated by downstream plasma discharge to rapidly desorb gaseous volatile organic compound molecules; the addition of a catalyst (i.e. an oxidation bed) in the downstream plasma area rapidly oxidizes the desorbed volatile organic compound molecules, avoids high-temperature heating or high-energy bombardment of the entire adsorption bed, reduces the damage to the structure of the adsorbent, and can effectively prolong the service life of the catalyst.

[0026] (2) The technical scheme adopted by the present application can break the limitations of easy production of by-products and high energy consumption of plasma technology. Traditional plasma technology often has problems such as high energy consumption and easy generation of toxic by-products when decomposing pollutant molecules. The present application provides a "adsorption storage and plasma catalytic oxidation" dual-zone coupled recycling purification method, i.e. a strategy of first storage and then plasma catalytic coupling rapid oxidation: VOCs are first stored by high-capacity adsorbent at ambient temperature, and then regenerated by in-situ plasma catalytic oxidation after saturation. By shortening the residence time of VOC molecules and strengthening the oxidation capacity of the catalyst, the generation of excessive cracking and intermediate toxic by-products is reduced, and there is no need for continuous high-temperature operation, greatly improving the energy use efficiency.

[0027] (3) The technical scheme disclosed by the application utilizes a "adsorption storage-plasma catalytic oxidation" double-zone coupling system, which can realize storage of gaseous volatile organic compound molecules under room temperature conditions by using a material with high adsorption capacity, and no pollutant molecules escape during the storage process; after saturation of storage, a localized temperature field generated by plasma heat effect is precisely matched with the desorption temperature of target molecules by regulating discharge parameters, and when the control input power is in the range of 20-30 W, an axial gradient temperature field (90-200 DEG C at the bottom of the adsorption bed) can be successfully constructed, which is matched with the desorption activation temperature of typical VOCs on the surface of a catalyst (for example, the desorption peak temperature of n-hexane on an MFI molecular sieve is about 90-130 DEG C). Meanwhile, the temperature is lower than the critical temperature of MOFs skeleton phase change, so that the structural stability of the MOFs material can be fully maintained. By using the above precise matching, desorption of target molecules is promoted, and the desorbed molecules are oxidized to carbon dioxide and water in situ in the plasma zone, avoiding escape of pollutant molecules in the regeneration process, and realizing cyclic purification of VOCs. The whole process is basically operated at room temperature, which can effectively solve the problems of high energy consumption of existing volatile organic compound removal catalytic oxidation, low storage capacity of single material "storage-oxidation", side reactions of part of molecules on the storage material, and easy collapse of MOFs and other materials exposed directly to plasma, and the like, and the energy coupling mechanism between dynamic adsorption and plasma synergistic catalytic oxidation is established by time sequence control, so that the purification efficiency is ensured while the energy consumption is significantly reduced, and the generation of by-products is effectively inhibited, and the in-situ "storage-oxidation" cyclic purification of VOCs is realized. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The specific packing mode diagram of the catalyst described in the present application embodiment 1 and comparative examples 1-2 is shown in the figure; Figure 2 The carbon cycle result diagram of the catalyst obtained by using different packing modes in the present application embodiment 1 and comparative examples 1-2 is shown in the figure; Figure 3 The cycle curve diagram of the "storage-plasma oxidation" cycle removal of n-hexane of the TS-1‖CoMnOx-R series catalyst described in the present application embodiment 1 is shown in the figure; Figure 4 The cycle curve diagram of the "storage-plasma oxidation" cycle removal of n-hexane of the HZ-500‖CoMnOx-R series catalyst described in the present application embodiment 2 is shown in the figure; Figure 5 The cycle curve diagram of the "storage-plasma oxidation" cycle removal of n-hexane of the TS-1‖CoMnOx-R series catalyst regenerated under dry gas atmosphere described in the present application embodiment 3 is shown in the figure; Figure 6Cycle curve of MIL-53‖CoMnOx-R tandem catalyst for "storage-plasma oxidation" cycle removal of toluene according to the present application embodiment 4; Figure 7 Cycle curve of MIL-53‖CoMnOx-R tandem catalyst for "storage-plasma oxidation" cycle removal of toluene according to the present application embodiment 5 under dry gas atmosphere; Figure 8 Cycle curve of TS-1 for "storage-oxidation" thermal cycle removal of n-hexane according to the present application comparative example 1; Figure 9 Cycle curve of TS-1 for "storage-discharge" cycle removal of n-hexane according to the present application comparative example 2. DETAILED DESCRIPTION

[0029] The present application is further described in conjunction with specific examples, but in no way limited to the present application. If no explicit description, the reagents and raw materials used in the method are purchased.

[0030] TS-1 (titanium silical molecular sieve, wherein the mass ratio of silicon and titanium is 37) used in the embodiment is purchased from Zhongcui New Material Co., Ltd.; The concentration of pollutant molecules (n-hexane) in the reaction tube during the gas storage process according to the present application embodiment and comparative example is calculated by formula 1:

[0031] Formula 1; In formula 1, C co2 and C co represent the CO x concentration detected by S710 carbon oxide gas analyzer of Sikemaheike (Beijing) Instrument Co., Ltd. λ represents the number of carbon atoms in a molecule of gas pollutant molecules; The storage amount of volatile organic compound molecules of the catalyst according to the present application embodiment and comparative example is calculated by formula 2

[0032] Formula 2; In formula 2, N VOC represents the storage capacity, mmol / g cat ; C represents the concentration of pollutant molecules in the reaction tube, ppm; F1 represents the total flow rate, mL / min; t 1 represents the time of storage saturation, min; m represents the mass of the first catalyst, g; The formula for calculating the carbon balance (i.e., the regeneration ratio) in the regeneration process according to the embodiments and comparative examples of the present application is shown in Equation 3:

[0033] Equation 3 In Equation 3, λ represents the number of carbon atoms in one molecule of the gaseous pollutant molecule; represents the amount of the pollutant molecule stored during the gas storage process, mol; represents the amount of CO generated during the regeneration process, mol; represents the amount of CO2 generated during the regeneration process, mol.

[0034] Example 1 Preparation of the first catalyst: 2 g of a commercial TS-1 catalyst (titanium silicalite, in which the mass ratio of silicon to titanium is 37) was weighed into a 100 mL crucible, and the crucible was placed in a muffle furnace and heated at a rate of 2°C / min from 25°C to 550°C for 4 h, ground, and the activated TS-1 catalyst (i.e., the first catalyst, with a pore size of 0.56 nm) was obtained.

[0035] Preparation of the second catalyst: A cobalt acetate solution was prepared by dissolving 3.74 g of cobalt acetate in 100 ml of water to form a solution with a concentration of 1.5 mol / L, and a potassium permanganate solution was prepared by dissolving 0.79 g of potassium permanganate in 50 ml of water to form a solution with a concentration of 0.1 mol / L. The cobalt acetate solution was added dropwise to the potassium permanganate solution under stirring to form a mixed solution, and the pH of the mixed solution was adjusted to 12 using a 1 mol / L KOH solution. After stirring vigorously for 5 min, the mixture was filtered, and the filter cake was dried in a vacuum drying oven at 60°C for 12 h. The dried product was ground into a powder, which was then placed in a muffle furnace and heated at a rate of 5°C / min to 350°C for 3 h, ground, and the second catalyst was obtained.

[0036] Catalyst packing: The first catalyst and the second catalyst powders obtained were tabletted and sieved to obtain granules with a size of 20-40 mesh, and then 50 mg of the first catalyst and 100 mg of the second catalyst were mixed according to the weight ratio of 1:2 to obtain a catalyst mixture. Figure 1The method of in-series coupling plasma regeneration is filled in the reaction tube (wherein the white ball represents the first catalyst, the blue ball represents the second catalyst, and the tooth shape represents the plasma), i.e. the first catalyst is filled in the adsorption bed layer in the non-discharge area of the reaction tube, and the second catalyst is filled in the oxidation bed layer in the discharge area of the reaction tube, the non-discharge area and the discharge area are separated by quartz wool, and the reaction tube filled with the adsorption bed layer and the oxidation bed layer (i.e. TS-1‖CoMnOx-R series catalyst, the mass ratio of the adsorption bed layer to the oxidation bed layer in the series catalyst is 1:2).

[0037] Gas storage: under the condition of 25℃ 101.325kPa, a mixed gas containing 550 ppm n-hexane / 21 vol% O2 / remainder N2 (containing contaminant gas molecules) is introduced into the gas inlet (i.e. the upper opening of the reaction tube, see Figure 1 ) of the reaction tube filled with the adsorption bed layer and the oxidation bed layer at a total flow rate of 100 mL / min for adsorption, the relative humidity RH is 50%, and the adsorption temperature is 25℃, when the concentration of n-hexane in the mixed gas at the gas outlet (i.e. the lower opening of the reaction tube, see Figure 1 ) of the reaction tube is 10% of the concentration of n-hexane in the mixed gas at the gas inlet of the reaction tube, i.e. the concentration of n-hexane in the mixed gas at the gas outlet of the reaction tube is 55 ppm, and the concentration of n-hexane in the mixed gas at the gas inlet of the reaction tube is 550 ppm, the storage saturation is reached, the storage saturation time is 10 min, and the storage amount of n-hexane in the adsorption bed layer is 0.72 mmol / g.

[0038] Regeneration: after the gas storage saturation, the reaction gas is switched to an atmosphere containing 21 vol% O2 / remainder N2, the relative humidity is 50%, the input power of the plasma discharge area in the reaction tube is 30 W, and the discharge is performed for 20 min, and the temperature at the bottom of the adsorption bed layer rapidly rises from 30℃ to 200℃ as the oxidation reaction proceeds, which promotes the desorption of the adsorbed contaminant molecules (n-hexane) and the complete oxidation of the contaminant molecules into CO2 and H2O under the synergistic action of the plasma and the second catalyst. The number of carbon atoms in one molecule of the gas contaminant molecule is 6, the amount of the stored contaminant molecules in the gas storage process is 0.72 mol, and the selectivity of CO2 in the regeneration process is 94.4%. The carbon balance result is shown in Figure 2 (i.e. in-series coupling plasma regeneration), the carbon balance is 100%, indicating that all the n-hexane molecules stored on the catalyst can be completely oxidized and removed in the regeneration process, and no contaminant molecules overflow. The cycle curve of the TS-1‖CoMnOx-R series catalyst for the removal of n-hexane by "storage-plasma oxidation" cycle is shown in Figure 3As shown in FIG. 2, the results show that under the condition of regeneration at a relative humidity RH of 50%, the storage amount of n-hexane is 0.72 mmol / g, the selectivity of CO2 is 94.4%, and the regeneration ratio is 100%, indicating that the enriched n-hexane stored on the TS-1 molecular sieve can be completely removed by oxidation.

[0039] Comparative Example 1 Different from Example 1, only the first catalyst was prepared, the catalyst was filled in different ways, and no plasma was used. The first catalyst was filled in the following way: Figure 1 The thermal regeneration method was the same as in the middle of FIG. 1 (wherein the white ball represents the first catalyst), that is, 100 mg of the first catalyst was filled in the reaction tube to obtain an adsorption bed; the gas storage process was consistent with that in Example 1, and the storage amount was as shown in FIG. 2. Figure 8 As shown in FIG. 2, the storage amount was 0.79 mmol / g; then the thermal regeneration method was used for regeneration, that is, after the gas storage was saturated, the reaction tube after the gas storage was saturated was placed in a tube furnace, and at the same time, the reaction gas was switched to an atmosphere containing 21%vol O2 / remaining N2, the relative humidity RH was 50%, and the temperature was increased from 25°C to 500°C at a rate of 10°C / min, and the catalyst was regenerated for 0.5 h to remove the gas pollutant molecules (n-hexane). The carbon cycle results of this comparative example are shown in FIG. 2 (thermal regeneration). Figure 2 As shown in FIG. 2 (thermal regeneration), the carbon cycle was 5.61%; the cycle curve of TS-1 “storage-oxidation” thermal cycle for removing n-hexane is shown in FIG. 3. Figure 8 As shown in FIG. 2, the results show that under the condition of regeneration at a relative humidity RH of 50% in 21%vol O2 / remaining N2, the storage amount of n-hexane is 0.79 mmol / g, the selectivity of CO2 is 76.7%, and the regeneration ratio is 5.61%, indicating that most of the stored n-hexane is desorbed near the boiling point rather than being oxidized, and the desorption rate is much higher than the oxidation rate, so the carbon balance is low, and complete removal of n-hexane cannot be achieved.

[0040] Comparative Example 2 Different from Comparative Example 1, the prepared first catalyst was filled into the plasma, and no second catalyst was used. The filling method is as shown in FIG. 4. Figure 1 The plasma regeneration method was the same as in the middle of FIG. 4 (wherein the white ball represents the first catalyst, and the tooth-shaped object represents the plasma); the gas storage process was consistent with that in Comparative Example 1; then the plasma regeneration method was used for regeneration, that is, the reaction gas was switched to an atmosphere containing 21%vol O2 / remaining N2, the relative humidity for regeneration was 50%, and the catalyst was removed in the plasma discharge area of the reaction tube at an input power of 30 W for 20 min to obtain a catalyst for removing gas pollutant molecules (n-hexane). The carbon cycle results of this comparative example are shown in FIG. 4 (plasma regeneration), and the carbon cycle was 46.2%; the cycle curve of TS-1 “storage-discharge” cycle for removing n-hexane is shown in FIG. 5. Figure 9As shown in FIG. 6, the results show that under the condition of regeneration at 21% vol O2 / remainder N2with a relative humidity RH of 50%, the storage amount of n-hexane is 0.79 mmol / g, the selectivity of CO2is 55.8%, and the regeneration ratio is 46.2%, indicating that although the carbon balance of plasma regeneration is improved compared with that of thermal regeneration, the bed temperature rapidly rises during the discharge process, and part of the n-hexane still escapes, the oxidation rate and the desorption rate are not matched, and thus the regeneration ratio is low, and complete regeneration of n-hexane cannot be achieved.

[0041] Example 2 Different from Example 1, the type of the first catalyst is different (i.e., HZ-500‖CoMnOx-R series catalyst, the mass ratio of the adsorption bed to the oxidation bed in the series catalyst is 1:2), that is, 2 g of commercial HZ-500 molecular sieve catalyst (the mass ratio of SiO2 / Al2O3 is 500) is weighed into a 100 ml crucible and placed in a muffle furnace, and the temperature is increased from 30°C to 550°C at a rate of 2°C / min, and calcination is performed for 4 h, and grinding is performed to obtain the activated catalyst of HZ-500 (i.e., the first catalyst, the pore size is 0.56 nm); the rest of the process is consistent with Example 1, and the carbon balance of this embodiment can also reach 100%, indicating that the n-hexane molecules stored on the catalyst at room temperature can be completely oxidized and removed during the regeneration process, and no pollutant molecules overflow, and the cycle curve of the HZ-500‖CoMnOx-R series catalyst for cyclic removal of n-hexane by “storage-plasma oxidation” is as shown in FIG. 7. Figure 4 As shown in FIG. 7, the results show that under the condition of regeneration at a relative humidity RH of 50%, the storage amount of n-hexane is 0.58 mmol / g, the selectivity of CO2is 95.2%, and the regeneration ratio reaches 100%, indicating that the n-hexane stored on the HZ-500 molecular sieve can be completely oxidized and removed, but the storage amount of n-hexane is lower than that of the TS-1‖CoMnOx-R series catalyst.

[0042] Example 3 Different from Example 1, the regeneration is performed in a dry gas atmosphere of 21% vol O2 / remainder N2(i.e., the relative humidity RH is 0), and the rest of the process is consistent with Example 1, and the cycle curve of the TS-1‖CoMnOx-R series catalyst for cyclic removal of n-hexane by “storage-plasma oxidation” under the condition of regeneration in a dry gas atmosphere is as shown in FIG. 8. Figure 5 As shown in FIG. 8, the results show that under the condition of regeneration in a dry gas atmosphere, the storage amount of n-hexane is 0.79 mmol / g, the selectivity of CO2is 94.6%, and the regeneration ratio reaches 100%, indicating that the n-hexane stored on the TS-1 molecular sieve can be completely oxidized and removed under the condition of a dry gas atmosphere.

[0043] Example 4 The difference between Example 1 is that the first catalyst is different, and the gas pollutant molecule is toluene, that is, 6.645 g of terephthalic acid (H2BDC, 40 mmol), 1.6 g of sodium hydroxide (NaOH, 40 mmol), 30 g of aluminum nitrate (Al(NO3)3·9H2O, 80 mmol) are dissolved in 57.6 g of water, stirred at room temperature for 24 h, filtered, calcined at 330°C for 12 h under air atmosphere, ground to obtain MIL-53(Al) catalyst (i.e. the first catalyst, the pore size is 0.76 nm), and the second catalyst is combined to obtain the MIL-53‖CoMnOx-R series catalyst (i.e. the adsorption bed is the MIL-53 catalyst, and the mass ratio of the adsorption bed to the oxidation bed in the series catalyst is 1:2); Gas storage: under the condition of 25°C 101.325kPa, a mixed gas containing 200 ppm toluene / 21 vol% O2 / remainder N2 (containing pollutant gas molecules) is introduced into the inlet of the reaction tube containing the catalyst at a total flow rate of 100 mL / min, and the mixed gas introduced into the reaction tube in sequence passes through the adsorption bed and the oxidation bed in the reaction tube, the adsorption relative humidity RH is 50%, and the adsorption temperature is 25°C; when the concentration of toluene in the mixed gas at the outlet of the reaction tube is 10% of the concentration of toluene in the mixed gas at the inlet, that is, the concentration of toluene in the mixed gas at the outlet is 20 ppm, and the concentration of toluene in the mixed gas at the inlet is 200 ppm, the storage saturation is reached, the storage saturation time is 20 min, and the storage capacity of toluene is 0.53 mmol / g; the regeneration process is consistent with Example 1, and the cycle curve of the MIL-53‖CoMnOx-R series catalyst for "storage-plasma oxidation" cycle removal of toluene is shown in Figure 6 The results show that under the condition of regeneration at a relative humidity RH of 50%, the storage capacity of toluene is 0.53 mmol / g, the selectivity of CO2 is 94.6%, and the regeneration ratio reaches 100%, indicating that the toluene stored on the MIL-53 catalyst can be completely oxidized and removed without pollutant molecules overflowing.

[0044] Example 5 The difference between Example 4 is that the regeneration atmosphere is a dry gas atmosphere of 21%vol O2 / remainder N2, and the rest of the process is consistent with Example 4; under the dry gas atmosphere, the cycle curve of the MIL-53‖CoMnOx-R series catalyst for "storage-plasma oxidation" cycle removal of toluene is shown in Figure 7 The results show that under the condition of regeneration at a dry gas atmosphere of 21%vol O2 / remainder N2, the storage capacity of toluene is 1.37 mmol / g, the selectivity of CO2 is 89.6%, and the regeneration ratio reaches 100%, indicating that the toluene stored on the MIL-53 catalyst can be completely oxidized and removed without pollutant molecules overflowing.

[0045] The above merely describes several embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with the above preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the technical solutions of the present application, and such changes or modifications are equivalent to equivalent embodiments, and all of them are within the scope of the technical solutions.

Claims

1. A new VOCs recycling purification method with dual-zone coupling of "adsorption storage and plasma catalytic oxidation", characterized by: The method comprises at least the following steps: Catalyst filling, step 1: filling the first catalyst into the non-discharge zone of the reaction tube as an adsorption bed, and filling the second catalyst into the plasma discharge zone of the reaction tube as an oxidation bed, to obtain a reaction tube filled with the adsorption bed and the oxidation bed; Gas storage, step 2: passing the mixed gas containing volatile organic compound molecules into the reaction tube filled with the adsorption bed and the oxidation bed as described in step 1 for adsorption, thereby obtaining a saturated adsorption bed; Regeneration, step 3: switching the mixed gas described in step 2 to a mixed gas that does not contain volatile organic compound molecules, and oxidizing and regenerating the saturated adsorption bed described in step 2 under the synergistic action of plasma discharge and the second catalyst to obtain a regenerated adsorption bed and oxidation bed.

2. The novel VOCs recycling purification method according to claim 1, characterized in that: In step 1, the first catalyst is selected from at least one of a MIL-based catalyst, a UiO-66-based catalyst, a MOF-based catalyst, a Beta molecular sieve, a HZ molecular sieve, and a TS-1 molecular sieve; Preferably, the first catalyst is selected from at least one of a MIL series catalyst, a HZ molecular sieve, and a TS-1 molecular sieve; The pore size of the first catalyst is 0.38-1.0 nm; In step 1, the second catalyst is a non-noble metal oxide catalyst; The non-noble metal oxide catalyst is selected from at least one of cobalt manganese oxide, cobalt cerium oxide, and manganese cerium oxide; Preferably, the non-noble metal oxide catalyst is a cobalt-manganese catalyst; The mass ratio of the first catalyst to the second catalyst in the reaction tube filled with the adsorption bed and the oxidation bed in step 1 is 1:1-2; The discharge area and the non-discharge area in step 1 are separated by quartz wool.

3. The novel VOCs recycling purification method according to claim 1, characterized in that: The concentration of the volatile organic compound molecules in the mixed gas containing volatile organic compound molecules in step 2 is 1 to 550 ppm; The volatile organic compound molecules are selected from at least one of toluene, n-hexane, benzene, and propane; The flow rate of the mixed gas containing volatile organic compound molecules in step 2 is 100-200 mL / min; The mixed gas containing volatile organic compound molecules in step 2 also includes 21 vol% O2 and the balance N2.

4. The novel VOCs recycling purification method according to claim 1, characterized in that: The adsorption conditions in step 2 are as follows: The relative humidity of the adsorption is 0-100%; The adsorption temperature is 0~25℃; The adsorption time is 0~1 h; The storage saturation in step 2 means that the content of the volatile organic compound molecules at the air outlet of the reaction tube is 10% of the content of the volatile organic compound molecules at the air inlet of the reaction tube.

5. The novel VOCs recycling purification method according to claim 1, characterized in that: The storage capacity of the saturated adsorption bed in step 2 for volatile organic compound molecules is 0-1.5 mmol / g.

6. The novel VOCs recycling purification method according to claim 1, characterized in that: The mixed gas without volatile organic compound molecules in step 3 is 21 vol% O2 and the balance N2; In step 3, the mixed gas containing no volatile organic compound molecules is 21 vol% O2 and the balance N2, and the flow rate is 100-200 mL / min.

7. The novel VOCs recycling purification method according to claim 1, characterized in that: The plasma discharge type in step 3 is dielectric barrier discharge; The power of the dielectric barrier discharge is 20~30W; The dielectric barrier discharge time is 0 to 30 minutes.

8. The novel VOCs recycling purification method according to claim 1, characterized in that: The bottom temperature of the adsorption bed during regeneration in step 3 is 90-200°C; The relative humidity of the regeneration in step 3 is 0-100%.

Images