CN115253665B - Method for degrading VOCs and NOx by K modified OMS-2 in cooperation with low-temperature plasma catalysis - Google Patents

Method for degrading VOCs and NOx by K modified OMS-2 in cooperation with low-temperature plasma catalysis Download PDF

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CN115253665B
CN115253665B CN202210780404.1A CN202210780404A CN115253665B CN 115253665 B CN115253665 B CN 115253665B CN 202210780404 A CN202210780404 A CN 202210780404A CN 115253665 B CN115253665 B CN 115253665B
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vocs
oms
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molecular sieve
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赵松建
吴樊彬
叶招莲
邱超
周全法
孙慧慧
李贞�
郑纯智
梁国斌
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Jiangsu University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/32—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
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    • B01D2259/818—Employing electrical discharges or the generation of a plasma
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Abstract

The invention provides a method for catalyzing and degrading VOCs and NO by coupling a potassium modified manganese molecular sieve with low-temperature plasma x Is a method of (2). The prepared potassium modified manganese molecular sieve has good synergistic effect with low-temperature plasmas by adopting double Dielectric Barrier Discharge (DBD) low-temperature plasmas. The K/OMS-2 one-stage DBD catalytic reaction of the invention can degrade VOCs and NO simultaneously x At an input power of 65W, the O in the exhaust gas is simulated 2 Concentration 4%, toluene initial concentration 2000mg/m 3 Initial concentration of NO 250mg/m 3 When the method is used, the toluene removal rate reaches 68.5%, the NO removal rate reaches 77%, and the toluene degradation rate and the NO degradation rate are respectively improved by 23% and 40% compared with the single DBD degradation rate. In addition, the DBD coupling of the catalyst of the invention improves the carbon balance by 8% compared with the independent DBD, O 3 About 80% drop. The method provided by the invention realizes the synergistic degradation of high-performance VOCs and NO, low energy consumption and effective inhibition of the formation of byproducts. The catalyst and the method provided by the invention are used for removing VOCs and NO in industrial kiln, chemical waste gas, nitric acid waste gas, coal-fired flue gas and the like x Opens up a new idea.

Description

Method for degrading VOCs and NOx by K modified OMS-2 in cooperation with low-temperature plasma catalysis
Technical Field
The invention relates to a method for catalyzing and degrading VOCs and NOx by using K modified OMS-2 and low-temperature plasma, belonging to the technical field of material preparation and environmental protection.
Background
NO x And VOCs are used as common pollutants, so that the physical health and the ecological environment of people are seriously affected. In addition, VOCs and NO in the atmosphere x As PM2.5 and O 3 Plays an important role in the formation of atmospheric recombination pollution, and has attracted considerable attention. NO (NO) x The emission of VOCs is mainly derived from the chemical industry of industrial kiln flue gas (coal-fired flue gas, sintering flue gas, garbage incineration flue gas and the like), including the kiln production and processing processes of coating, oil refining, metallurgy, medicine, petrochemical industry and the like, nitric acid industrial sites and the like. For NO x And VOCs are combined with polluted gas, and the polluted gas is treated by adopting a combined process, so that the investment and the operation cost are obviously increased; more importantly, when both are present, NO x Interactions with VOCs can have an impact on the respective degradation process. In order to better realize the up-to-standard emission of various polluted gases and obtain the optimal investment and operation cost, the development of a cooperative control technology has become the development trend of multi-pollutant control of the flue gas, and the multi-pollutant control is realized on the same equipment and the same catalyst, so that the method is a difficult problem commonly faced by the current academic and industrial circles, and has important scientific significance and application value.
At present with respect to NO x The research on the synergistic treatment of the combined pollution of VOCs is still in a preliminary exploration stage, and the prior art mainly adopts a Selective Catalytic Reduction (SCR) system to carry out NO x And removal of VOCs, but this technique presents considerable challenges for the synergistic degradation of both: the SCR catalyst adopted at present contains noble metal and catalystHigh cost and NO removal x And the VOCs have over high operable temperature, so that the degradation effect needs to be improved. The low-temperature plasma technology can overcome thermodynamic reaction barriers at normal temperature and normal pressure, realizes the conversion of atmospheric pollutants under mild conditions, has strong reaction activity and high reaction speed, is valued by more and more researchers at home and abroad, and has good development prospect. However, the use of the low temperature plasma technique alone has a problem of low energy efficiency of the reaction process, and the like.
Disclosure of Invention
Technical problems:
provides a method for synchronously degrading low-concentration VOCs and NO (the concentration of the VOCs is 2000 mg/m) at normal temperature and normal pressure 3 NO concentration of 250mg/m 3 ) The method has the removal rate of toluene and NO of 68 percent and 77 percent respectively at the input power of the plasma of 65W, 5%H 2 O or 200ppm SO 2 In the presence of the interfering component, the removal rate of toluene and NO is above 63% when the input power of the plasma is 65W, and the cost of the used catalyst is low.
The technical scheme is as follows:
the invention provides a preparation method of a potassium-doped modified manganese molecular sieve and a waste gas treatment process for degrading VOCs and NOx by cooperation of the potassium-doped modified manganese molecular sieve and plasma.
The first aim of the invention is to provide a method for catalyzing and degrading VOCs and NO by low-temperature plasma in cooperation with a non-noble metal catalyst x The method comprises the steps of adopting a coaxial double-medium DBD catalytic reactor, and placing a non-noble metal catalyst in a plasma discharge area; VOCs and NO x Comprises a mixed gas containing VOCs and NO, wherein the concentration of the VOCs in the mixed gas is 50-2000mg/m 3 The concentration of NO is 50-1000mg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The input power of the plasma is 65-130W; the removal rates of VOCs and NO are respectively above 68% and above 77%;
the non-noble metal catalyst is a potassium modified manganese molecular sieve; the preparation method of the potassium modified manganese molecular sieve comprises the following steps:
s1, preparation of a solution: will 0.01mol Mn 2+ Source, 0.01mol (NH) 4 ) 2 S 2 O 8 And 0.01mol (NH) 4 ) 2 SO 4 Adding the suspension into ultrapure water, and stirring to form a suspension; subsequently, the suspension is reacted at 150 ℃;
s2, filtering and washing: centrifuging the system obtained after the reaction in the step S1, collecting precipitate, washing the precipitate with ultrapure water, and then drying to obtain a manganese molecular sieve;
s3, doping K + : placing the manganese molecular sieve obtained in the step S2 in KNO 3 In the solution, ultrasonic dissolving, stirring and drying to obtain potassium modified manganese molecular sieve, controlling K + The doping amount of (2) was 5%.
As a preferred embodiment of the present invention, the initial concentration of VOCs in the mixed gas is 2000mg/m 3 Initial concentration of NO 250mg/m 3 ，O 2 The content is 4%, and the flow rate of the mixed gas is 1L/min.
As a preferred embodiment of the invention, 5%H is also added to the mixed gas 2 And the removal rate of VOCs and NO is above 63% when the input power of the plasma is 65W.
As a preferred embodiment of the invention, 200ppm SO is also added to the mixed gas 2 The removal rate of VOCs and NO is above 63% when the plasma input power is 65W.
As a preferred embodiment of the present invention, the plasma input power is 65W.
As a preferred embodiment of the present invention, mn 2+ The source is MnSO 4 Or a hydrate thereof.
As a preferred embodiment of the present invention, the reaction time of step S1 is 12h.
As a preferred embodiment of the present invention, the drying conditions in step S2 and step S3: drying at 105 deg.c for 10-12 hr.
As a preferred embodiment of the present invention, VOCs are at least one of toluene, ethyl acetate, formaldehyde and acetone.
A second object of the present invention is to provide the method as described above in the presence of VOCs and NO x Is used in industrial waste gas.
The beneficial effects are that:
(1) The invention optimizes the preparation method of the potassium modified manganese molecular sieve (K/OMS-2), particularly sets the reaction temperature in the preparation process of the OMS-2 catalyst to 150 ℃ and controls K + The doping amount of the potassium modified manganese molecular sieve (K/OMS-2) is 5 percent, and the prepared potassium modified manganese molecular sieve has excellent adsorption and catalysis of VOCs and NO x Is provided). The invention degrades VOCs and NO by combining the potassium modified manganese molecular sieve (K/OMS-2) with low-temperature plasma catalysis x The method adopts a one-stage reactor, and is applied to the treatment of VOCs concentration in the mixed gas of 50-2000mg/m 3 The concentration of NO is 50-1000mg/m 3 The mixed gas is researched, and the input power of the plasma is 65-130W; the removal rates of VOCs and NO are respectively above 68% and above 77%. K-doped modified OMS-2 prepared by other methods reported in the literature, and changing the reaction temperature during OMS-2 catalyst preparation to 100℃or changing K, compared to other catalysts under the same conditions (unmodified OMS-2) + The doping amount of the catalyst is 2% or 10% of the prepared potassium modified manganese molecular sieve), and the degradation efficiency of the DBD coupling catalyst for treating toluene and NO is obviously improved under the same energy density.
(2) The K/OMS-2 one-stage DBD catalytic reaction of the invention can degrade VOCs and NO simultaneously x At an input power of 65W, the O in the exhaust gas is simulated 2 Concentration 4%, toluene initial concentration 2000mg/m 3 Initial concentration of NO 250mg/m 3 When the method is used, the toluene removal rate reaches 68.5%, the NO removal rate reaches 77%, and the toluene degradation rate and the NO degradation rate are respectively improved by 23% and 40% compared with the single DBD degradation rate. In addition, the DBD coupling of the catalyst of the invention improves the carbon balance by 8% compared with the independent DBD, O 3 About 80% drop. The method provided by the invention realizes the synergistic degradation of high-performance VOCs and NO, low energy consumption and effective inhibition of the formation of byproducts. The catalyst and the method provided by the invention open up a new idea for removing VOCs and NOx in industrial kilns, chemical waste gas, nitric acid waste gas, coal-fired flue gas and the like.
(3) The potassium modified manganese molecular sieve (K/OMS-2) prepared by the invention not only has a porous structure as the manganese molecular sieve, but also has added K + Into manganese molecular sievesIn the pore canal, OMS-2 can have more oxygen vacancies, and the electron conduction capacity of the catalyst is enhanced; added K + Can also adjust the average valence state of Mn ions, thereby enhancing VOCs and NO x Is used for the adsorption capacity of the catalyst. Therefore, the potassium modified manganese molecular sieve (K/OMS-2) prepared by the invention has porous structure morphology, mn ions in mixed valence state, mild surface acidity and alkalinity and excellent ion exchange property, and is beneficial to efficiently adsorbing VOCs and NO x And (3) a pollutant.
(4) The invention synthesizes the OMS-2 catalyst by a hydrothermal method, and then prepares K by a simple impregnation method + Doping into OMS-2 catalyst, and finally obtaining potassium modified manganese molecular sieve (K/OMS-2) with high specific surface area (-80 m) 2 Per g), kong Rong 0.4.4 cm 3 And/g. In the prior art, K is generally introduced in the OMS-2 catalyst synthesis process + Of, K + The doping amount of (c) is difficult to control. The invention can be prepared by setting KNO through an immersion method 3 The parameters such as concentration, impregnation condition and the like can better regulate and control K compared with the prior art + And selects the optimal K through experiments + Is added to the substrate. The method for preparing the potassium modified manganese molecular sieve (K/OMS-2) has the advantages of simple process, low cost, good reaction stability and low energy consumption, and is suitable for industrial application.
(5) The potassium modified manganese molecular sieve (K/OMS-2) prepared by the invention has a synergistic effect with DBD, specifically, a one-stage reactor is adopted, the discharge type and electron energy distribution of plasma can be changed by introducing the potassium modified manganese molecular sieve (K/OMS-2) prepared by the invention into plasma discharge, so that new active substances (such as atomic oxygen, super-oxygen species, hydroxyl free radicals and the like) are generated, and the degradation efficiency of pollutants is improved; the free radical, ion and electron generated by the induction of the plasma can directly attack the adsorbed reaction product to promote the desorption process of the reaction product, so that the problem that the catalyst is easy to poison is relieved to a certain extent, and the long-term use stability of the potassium modified manganese molecular sieve (K/OMS-2) is improved; ion wind generated in the plasma discharge process can improve VOCs and NO x Adsorption capacity on the surface of the potassium modified manganese molecular sieve (K/OMS-2) so as to improve pollutant degradation efficiency; plasma can also be modifiedChanging oxidation state of potassium modified manganese molecular sieve (K/OMS-2), improving adsorption capacity of pollutants and desorption capacity of products, and enhancing adsorption capacity of potassium modified manganese molecular sieve (K/OMS-2) on VOCs and NO x Degradation rate, stability and anti-interference and anti-poisoning capabilities.
(6) The invention provides a method and a process for cooperatively controlling VOCs and NO, which can solve the problems of overhigh operable temperature, large cost investment and the like in the prior art, and in addition, compared with the existing common catalyst, the potassium modified manganese molecular sieve (K/OMS-2) can be better coupled with low-temperature plasmas, thereby improving the coupling of the VOCs and the NO x Degradation rate, stability and anti-interference and anti-poisoning capabilities. The potassium modified manganese molecular sieve (K/OMS-2) can be used as a cheap substitute of a noble metal catalyst to effectively degrade NO in flue gas by combining with a plasma technology x And VOCs.
Drawings
FIG. 1 is XRD patterns of OMS-2 and K/OMS-2 prepared in example 1;
FIG. 2 is a Scanning Electron Microscope (SEM) image (a) and element distribution (Mapping) images (b) to (d) of K/OMS-2 prepared in example 1;
FIG. 3 is the N of OMS-2 and K/OMS-2 prepared in example 1 2 Adsorption and desorption curves;
FIG. 4 is a comparison of the effects of DBD+K/OMS-2 catalyzed toluene degradation alone for example 3;
FIG. 5 is a graph comparing carbon balance under catalysis of DBD+K/OMS-2 alone for example 3;
FIG. 6 is a DBD alone, DBD+K/OMS-2 catalyzed by-product O of example 3 3 A generated comparison graph;
FIG. 7 is a comparison of NO degradation effects under DBD+K/OMS-2 alone for example 4;
FIG. 8 is a graph showing the degradation effect of DBD+K/OMS-2 on toluene and NO in the presence and coexistence of toluene and NO in example 5 alone, at a comparative power of 65W;
FIG. 9 is a graph comparing the effects of DBD coupled K/OMS-2 and DBD coupled OMS-2 in comparative example 1 on the catalytic degradation of toluene or NO;
FIG. 10 is a graph comparing the degradation effect of DBD coupled K/OMS-2 of comparative example 2 with that of K-doped modified OMS-2 coupled DBD prepared in literature report in toluene or NO degradation;
FIG. 11 is a graph showing the comparison of the properties of the K-doped OMS-2 plasma-coupled DBD catalytic degradation of VOCs and NO prepared under different preparation parameters in example 6;
FIG. 12 is the effect of smoke interfering components on the catalytic degradation of VOCs and NO by K-doped OMS-2 plasma coupled DBD in example 7.
Detailed Description
EXAMPLE 1 preparation of Potassium modified manganese molecular sieves (K/OMS-2)
The invention provides a preparation method of a potassium modified manganese molecular sieve (K/OMS-2), which is characterized by comprising the following steps:
(1) Preparation of the solution: 0.01mol of MnSO 4 ·H 2 O，0.01mol(NH 4 ) 2 S 2 O 8 And 0.01mol (NH) 4 ) 2 SO 4 Adding into 100mL of ultrapure water, and stirring for 30min to form a suspension; subsequently, the suspension was reacted at 150 ℃ for 12h;
(2) Filtering and washing: centrifuging the system obtained after the reaction in the step (1), collecting precipitate, washing the precipitate with ultrapure water, and then drying at 105 ℃ for 10 hours to obtain a manganese molecular sieve (OMS-2);
(3) Doping K + : taking 1.0g of OMS-2 obtained in the step (2) to 100mL of KNO with the concentration of 1.3g/L 3 Dissolving in solution by ultrasonic wave and stirring for 30min; finally drying at 105 ℃ for 12 hours to obtain the potassium modified manganese molecular sieve (K/OMS-2), wherein K + Mass ratio to OMS-2 (K) + The doping level of (c) is about 5%.
Physical and chemical characteristics of OMS-2 and K/OMS-2 catalysts are characterized by XRD, SEM and adsorption and desorption tests, and the results are shown in figures 1-3, the specific surface area of the catalyst is calculated by combining with BET theory, and the pore diameter D of the catalyst is calculated by combining with BJH theory pore And pore volume V pore 。
As a result, the invention has been found to synthesize a high specific surface area (-80 m) by a hydrothermal method 2 Per g), kong Rong 0.4.4 cm 3 K/OMS-2 catalyst/g. The specific surface area and pore size of the K/OMS-2 catalyst are compared to OMS-2 catalysisThe agent is improved, and is favorable for adsorption and catalytic degradation. Contrast XRD characterization pattern found, K + The crystal structure of the OMS-2 catalyst is not changed after doping, and the OMS-2 catalyst has good stability.
Example 2
The plasma reactor adopted by the invention is a laboratory self-made coaxial double-medium DBD catalytic reactor. The reactor main body is made of a quartz glass tube with the length of 20cm and the outer diameter of 26mm, and a copper sheet or an aluminum sheet is wrapped outside the quartz tube to be used as a grounding electrode; metal powder (stainless steel powder, copper powder, aluminum powder and the like) with the length of 25cm and the outer diameter of 9mm is placed in a quartz medium to be used as a high-voltage electrode, a catalyst is filled between the inner quartz tube and the outer quartz tube, and the catalyst is placed on a sand core or a support piece with a sieve hole. The power supply adopts CTP-2000KP modulated pulse power supply provided by Nanjing Su Man plasma technology Co. The alternating current with the input of 220V and 50Hz is matched with a contact voltage regulator, the output voltage regulating range is 0-30k V, the output frequency regulating range is about 5-25 Hz, and the frequency point of the maximum output power is about 9.7 Hz.
The invention can be divided into a one-stage type (in-situ plasma catalysis) and a two-stage type (post-plasma catalysis) reactor according to the cooperative mode of the catalyst and the plasma. One-stage catalyst is set in the plasma discharge area to produce synergistic effect to strengthen NO x And VOCs degradation processes; the two-stage catalyst is placed at the rear end of the plasma discharge zone, i.e. downstream. In the two-stage reactor, two systems of plasma and catalyst are independent, the plasma firstly pretreats pollutants, and long-life species O generated in the plasma 3 The catalytic layer can be decomposed and utilized.
VOCs and NO in the present invention x The mixed gas is prepared by controlling certain flow rate of nitrogen gas from a compression steel cylinder by a Mass Flow Controller (MFC), introducing into a stainless steel tank filled with liquid VOCs as carrier gas or balance gas by a polytetrafluoroethylene tube with an outer diameter of 3mm, carrying out VOCs vapor, fully mixing with other two paths of nitrogen gas and oxygen gas controlled by a mass flow controller in a mixer to form stable concentration of VOCs gas, and introducing into a DBD discharge reactionIn the apparatus, a plasma VOCs degradation experiment was performed. NO is supplied from an 8L compressed gas cylinder containing 1% NO concentration, and a certain flow rate is controlled by an MFC to enter the mixer so as to form mixed gas containing VOCs and NO.
When the synergistic experiment of VOCs and NO is carried out, the concentration of the VOCs in the mixed gas is 50-2000mg/m 3 The concentration of NO is 50-1000mg/m 3 The energy density of the plasma discharge is 100-1000J/L, and the airspeed is 10000-60000h -1 。
The stainless steel tank for containing VOCs is placed in the low-temperature constant-temperature tank, so that the concentration of VOCs can be adjusted, and the stability of the concentration of VOCs can be ensured.
The invention is mainly aimed at low concentration of VOCs and NO x The concentration is selected to be as close as possible to the actual industrial exhaust gas concentration. The VOCs treated include toluene, ethyl acetate, formaldehyde, acetone or other organics.
Example 3: potassium modified manganese molecular sieve (K/OMS-2) plasma catalysis and single plasma toluene degradation comparison
The experiment was developed on the basis of example 2.
The experimental conditions are as follows: at normal temperature and pressure, introducing simulated waste gas with the gas flow rate of 1L/min into a one-stage reactor, wherein O 2 The content is 4%, and the initial concentration of toluene is 2000mg/m 3 And adjusting the input power of the plasmas to 40W,65W,78W,91W and 130W, and comparing the degradation effects of toluene under the catalysis conditions of DBD and DBD+K/OMS-2 under different powers.
As shown in fig. 4, the experimental results show that the efficiency of the plasma (DBD) in cooperation with the K/OMS-2 catalyst for degrading toluene is higher than that of the plasma (DBD) alone at different powers. Under the condition of 65W of power, the DBD+K/OMS-2 synergistic catalysis improves the toluene degradation efficiency by 23% compared with the DBD alone; at the power of 91W and 130W, the toluene degradation rate of the independent DBD is over 90 percent, so that the coupling catalysis lifting effect is not obvious.
The results of FIGS. 5 and 6 also show that the carbon balance of the plasma (DBD) synergistic K/OMS-2 catalyst is significantly higher than that of the DBD catalytic system alone, and the corresponding by-product O 3 Is of the concentration of (1)Significantly reduced, indicating that the introduction of K/OMS-2 can activate O 3 Thereby oxidizing the plasma intermediate product.
Example 4 comparison of Potassium modified manganese molecular sieves (K/OMS-2) plasma catalysis with Single plasma degradation of NO
Introducing simulated waste gas with the gas flow rate of 1L/min into a one-stage reactor at normal temperature and normal pressure, wherein O 2 The content is 4%, the initial concentration of NO is 250mg/m 3 The plasma input power is adjusted to 40W,65W,78W,91W and 130W, and the NO removal effect under the catalysis condition of DBD and DBD+K/OMS-2 under different powers is compared.
As shown in fig. 7, the experimental results show that the efficiency of the plasma (DBD) in cooperation with the K/OMS-2 catalyst to degrade NO is higher than that in the presence of DBD alone at different powers. Under the conditions of 65W and 78W, the degradation efficiency of the DBD+K/OMS-2 on NO is improved by 40% and 32% respectively compared with that of the DBD alone; when the power is 91W and 130W, the NO degradation rate of the DBD alone reaches more than 90%, so that the coupling catalysis lifting effect is not obvious.
EXAMPLE 5 plasma-catalyzed degradation of toluene and NO by Potassium modified manganese molecular sieves (K/OMS-2)
Introducing mixed gas containing toluene and NO into a one-stage reactor at normal temperature and normal pressure, wherein the initial concentration of toluene is 2000mg/m 3 Initial concentration of NO 250mg/m 3 ，O 2 The content was 4%, and the gas flow rate was 1L/min. The degradation efficiency of DBD+K/OMS-2 in the presence of toluene and NO alone and in the presence of both was 65W for the comparative power.
As shown in fig. 8, the removal rates of toluene and NO were 70.2% and 72.3%, respectively, when toluene and NO were present alone; the removal rates of toluene and NO were 68.5% and 77%, respectively, when toluene and NO were coexisted. Indicating that the presence of toluene in the system of the present invention promotes the degradation of NO; the presence of NO has slight inhibition effect on the degradation of toluene, but still has high catalytic efficiency (about 70%).
Comparative example 1: unmodified OMS-2 plasma catalyzed degradation of toluene and NO
Toluene was catalytically degraded at normal temperature and pressure by using unmodified OMS-2 and potassium modified manganese molecular sieve (OMS-2) of example 1, the method of example 3 was used, and NO was catalytically degraded at normal temperature and pressure by using the method of example 4, wherein the plasma input power was 65W.
As shown in fig. 9, the result found that: the efficiency of degrading toluene and NO by the cooperation of the plasma (DBD) and the K/OMS-2 catalyst is higher than the degradation efficiency of treating toluene and NO by the DBD coupled with the OMS-2 catalyst under the same energy density.
Comparative example 2: k-doped modified OMS-2 plasma catalytic degradation of toluene and NO reported in the prior art
K-doped modified OMS-2 catalysts prepared using literature Hou et al ("Hou J, ni C, ren L, et al Simultaneous introduction of K) + and Rb + into OMS-2 tunnels as an available strategy for substantially increasing the catalytic activity for benzene elimination[J]Environmental Research,2020,191:110146 "). The method of reference example 3 catalytically degraded toluene at normal temperature and pressure and the method of reference example 4 catalytically degraded NO at normal temperature and pressure, with a plasma input power of 65W, except that the catalyst was replaced with a K-doped modified OMS-2 prepared in the literature Hou et al, designated dbd+k/OMS-2 (literature).
As shown in FIG. 10, the results show that the efficiency of degrading toluene and NO by using the K/OMS-2 catalyst prepared by the invention through plasma (DBD) coupling is higher than the degradation efficiency of treating toluene and NO by using the K/OMS-2 catalyst reported in DBD coupling literature under the same energy density.
Example 6: performance comparison of K-doped modified OMS-2 prepared under different preparation parameters
Example 6-1: influence of reaction temperature on toluene and NO degradation performance in OMS-2 catalyst preparation process
The potassium modified manganese molecular sieve (K/OMS-2) of reference example 1 was different only in that the reaction temperature during the preparation of the OMS-2 catalyst was changed to 100 ℃, the catalyst was labeled K/OMS-2 (100 ℃), toluene was catalytically degraded at normal temperature and pressure by the method of reference example 3, and NO was catalytically degraded at normal temperature and pressure by the method of reference example 4, wherein the plasma input power was 65W, and the difference was only in that the catalyst was replaced with K/OMS-2 (100 ℃).
As shown in FIG. 11, the efficiency of the plasma (DBD) coupling K/OMS-2 (100 ℃) for degrading toluene and NO is lower than that of the plasma (DBD) coupling K/OMS-2 catalyst prepared by the invention for treating toluene and NO under the same energy density.
Example 6-2: k (K) + Effect of the doping amount on toluene and NO degradation Properties
Reference example 1, potassium modified manganese molecular Screen (K/OMS-2), differs only in that K was changed + The doping amounts of (a) were 2% and 10% (labeled as 2K/OMS-2, 10K/OMS-2), toluene was catalytically degraded at normal temperature and pressure by the method of reference example 3, NO was catalytically degraded at normal temperature and pressure by the method of reference example 4, wherein the plasma input power was 65W, except that the catalyst was replaced with 2K/OMS-2 or 10K/OMS-2.
As shown in FIG. 11, the plasma (DBD) coupled with 2K/OMS-2 or 10K/OMS-2 was found to degrade toluene and NO with less efficiency than plasma (DBD) coupled with the K/OMS-2 catalyst prepared according to the present invention when treating toluene and NO with the same energy density. Indicating too high or too low K + The doping amount of the catalyst is not beneficial to the improvement of the toluene and NO removal efficiency.
Example 7: influence of interfering Components on the catalytic degradation of VOCs and NO by K-doped OMS-2 plasma coupling
The potassium-modified manganese molecular sieve (K/OMS-2) of example 1 was used to catalyze the degradation of toluene and NO at normal temperature and pressure in accordance with the method of comparative example 1, except that 5%H was added to the mixed gas 2 O and 200ppm SO 2 The gas was examined for its effect on the reaction process, degradation efficiency and byproducts.
As shown in FIG. 12, it was found that H 2 O or SO 2 Can generate a certain inhibition effect on the degradation performance of DBD coupled K/OMS-2 to toluene and NO, but the removal efficiency of pollutants is reduced slightly as a whole, and the catalytic system still has higher performance and stability.

Claims (10)

1. Low-temperature plasma synergistic non-noble metal catalyst catalysisDegradation of VOCs and NO x Is characterized in that:
the method adopts a coaxial double-medium DBD catalytic reactor, and places a non-noble metal catalyst in a plasma discharge area; VOCs and NO x Comprises a mixed gas containing VOCs and NO, wherein the concentration of the VOCs in the mixed gas is 50-2000mg/m 3 NO concentration of 50-1000mg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The input power of the plasma is 65-130W; the removal rates of VOCs and NO are respectively above 68% and above 77%;
the non-noble metal catalyst is a potassium modified manganese molecular sieve; the preparation method of the potassium modified manganese molecular sieve comprises the following steps:
s1, preparation of a solution: will 0.01mol Mn 2+ Source, 0.01mol (NH) 4 ) 2 S 2 O 8 And 0.01mol (NH) 4 ) 2 SO 4 Adding the suspension into ultrapure water, and stirring to form a suspension; subsequently, the suspension is reacted at 150 ℃;
s2, filtering and washing: centrifuging the system obtained after the reaction in the step S1, collecting precipitate, washing the precipitate with ultrapure water, and then drying to obtain a manganese molecular sieve;
s3, doping K + : placing the manganese molecular sieve obtained in the step S2 in KNO 3 In the solution, ultrasonic dissolving, stirring and drying to obtain potassium modified manganese molecular sieve, controlling K + The doping amount of (2) was 5%.
2. The method according to claim 1, characterized in that: the initial concentration of VOCs in the mixed gas is 2000mg/m 3 Initial concentration of NO 250mg/m 3 ，O 2 The content is 4%, and the flow rate of the mixed gas is 1L/min.
3. The method according to claim 1, characterized in that: the mixed gas is also added with 5 percent of H 2 The removal rate of VOCs and NO is above 63% when the input power of the plasma is 65W.
4. The method according to claim 1, characterized in that: 200ppm SO is also added into the mixed gas 2 In the followingThe removal rate of VOCs and NO is above 63% when the input power of the plasma is 65W.
5. The method according to claim 1, characterized in that: the plasma input power was 65W.
6. The method according to claim 1, characterized in that: mn (Mn) 2+ The source is MnSO 4 Or a hydrate thereof.
7. The method according to claim 1, characterized in that: the reaction time in step S1 was 12h.
8. The method according to claim 1, characterized in that: drying conditions in step S2 and step S3: 105. drying at the temperature of 10-12 h.
9. The method according to any one of claims 1-8, wherein: VOCs are at least one of toluene, ethyl acetate, formaldehyde and acetone.
10. The method of any one of claims 1-9 comprising VOCs and NO x Is used in industrial waste gas.
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