A composite catalyst for denitration and removal of VOC and its preparation and use method

Abstract

The present invention provides a denitration and de-VOC composite catalyst and a preparation and use method thereof, belonging to the technical field of catalysts, wherein the particle structure of the catalyst of the present invention comprises a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and a VOCs oxide; the ZrO2-TiO2@CeO2 composite carrier loads the denitration active substance and the VOCs oxide; the ZrO2-TiO2@CeO2 composite carrier comprises a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance comprises a Mn-Co diatomic cluster and a Ce-W-O nanosheet; and the VOCs oxide comprises a Fe-Cu-La modified porous carbon. The present invention prepares a ZrO2-TiO2@CeO2 composite carrier, adopts a special method to load the denitration active substance and the VOCs oxide, and forms a multifunctional catalyst with a stable structure, which has a wide temperature window activity, good anti-poisoning performance, high stability and environmental friendliness.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a denitration and de-VOC composite catalyst and a preparation and use method thereof. Background Art

[0002] In the process of industrial development, the environmental problems caused by waste gas emissions are becoming increasingly serious. Nitrogen oxides (NOx) and volatile organic compounds (VOCs) in industrial waste gas are major pollutants, posing a serious threat to the ecological environment and human health. NOx can cause a series of environmental problems such as acid rain and photochemical smog, and can also damage the human respiratory system and reduce atmospheric visibility. VOCs not only have a pungent odor, but also react with nitrogen oxides under light conditions to form secondary pollutants such as ozone, aggravating photochemical smog pollution. Some VOCs are also carcinogenic, teratogenic, and mutagenic, seriously endangering human health.

[0003] Traditional denitrification technologies mainly include selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). SNCR does not require a catalyst, but the reaction temperature is high (850-1100℃), the denitrification efficiency is relatively low, generally 30%-80%, and the ammonia escape is large, which will cause secondary pollution. SCR technology relies on catalysts. At relatively low temperatures (300-400℃), ammonia is used as a reducing agent to reduce NOx to nitrogen and water, and the denitrification efficiency can be as high as 90% or more. The core component of the SCR catalyst is the active component, such as V2O5, etc. The carrier is usually TiO2, etc., and additives such as WO3, MoO3, etc. can improve the performance of the catalyst. However, traditional SCR catalysts have some limitations, such as strict requirements on the temperature window, reduced activity at low temperatures, insufficient sulfur and water resistance, and easy to be deactivated by SO2 and water vapor in the exhaust gas. In addition, the active component V2O5 has certain toxicity, and improper treatment of waste catalysts will cause environmental pollution.

[0004] In terms of VOCs treatment, common methods include adsorption, combustion, biological and catalytic oxidation. The adsorption method is suitable for low-concentration VOCs treatment, but there are problems of adsorbent saturation and secondary pollution; the combustion method requires a higher temperature and consumes a lot of energy; the efficiency of the biological method is restricted by factors such as microbial activity, and its scope of application is limited. The catalytic oxidation method reduces the activation energy of the reaction through a catalyst, so that VOCs are oxidized and decomposed into carbon dioxide and water at a lower temperature, which has the advantages of high efficiency and energy saving. VOCs catalytic oxidation catalysts mainly include precious metal catalysts (such as Pt, Pd, etc.) and non-precious metal catalysts (such as transition metal oxides). Precious metal catalysts have high activity and low ignition temperature, but they are expensive, scarce resources, and are easily affected by poisons such as sulfur and chlorine; non-precious metal catalysts have low cost, but the activity and stability need to be further improved. The development of high-performance, low-cost, and anti-poisoning VOCs catalysts has become a research hotspot.

[0005] With the continuous improvement of environmental protection requirements, the development of multifunctional catalysts that can both efficiently denitrate and effectively remove VOCs has become a development trend. Such catalysts must have wide temperature window activity, good anti-poisoning performance, high stability and environmental friendliness to adapt to the complex and changing industrial waste gas composition and working conditions, and provide better solutions for the comprehensive treatment of industrial waste gas. Summary of the invention

[0006] Aiming at developing a multifunctional catalyst that can both efficiently denitrate and effectively remove VOCs, with wide temperature window activity, good anti-poisoning performance, high stability and environmental friendliness, the present invention provides a denitrate and de-VOC composite catalyst and its preparation and use method, prepares a ZrO2-TiO2@CeO2 composite carrier, and then uses a special preparation method to load the denitrate active substance and VOCs oxides to form a multifunctional catalyst with a stable structure, with wide temperature window activity, good anti-poisoning performance, high stability and environmental friendliness. Its specific technical scheme is as follows:

[0007] A denitration and de-VOC composite catalyst, the particle structure of the catalyst comprises a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier loads the denitration active substance and the VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier comprises a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance comprises a Mn-Co diatomic cluster and a Ce-WO nanosheet; the VOCs oxide comprises Fe-Cu-La modified porous carbon.

[0008] In the above catalyst, the preparation method of the ZrO2-TiO2@CeO2 composite carrier comprises the following steps:

[0009] N1: According to the mass ratio, zirconium oxychloride: tetrabutyl titanate: non-ionic surfactant: deionized water = (0.4-0.5): (1-1.5): (0.04-0.08): (8-10), zirconium oxychloride and tetrabutyl titanate are mixed, and the gas is exhausted by vacuum to obtain a mixture A, and the non-ionic surfactant is dissolved in deionized water to obtain a solution B; then, under stirring, according to the volume ratio of mixture A: solution B = (1-2): (3-5), the mixture A is added to the solution B, and the stirring is continued for 1h-2h, and the pH value is adjusted to 2-3 with hydrochloric acid; then, the mixture is reacted at 150℃-180℃ for 12h-24h, and then centrifuged to discard the upper liquid, the solid is washed with deionized water, and dried to constant weight to obtain the ZrO2-TiO2 mesoporous core;

[0010] N2: Place the ZrO2-TiO2 mesoporous core into the reaction chamber of the atomic layer deposition equipment, set the temperature of the reaction chamber to 200℃~250℃, and then control the gas pulse time and flow rate to allow cerium nitrate carrier gas and oxygen to alternately enter the reaction chamber; each cycle must go through four steps: cerium nitrate carrier gas pulse, blow away excess cerium nitrate with nitrogen, oxygen pulse, and then blow away excess oxygen with nitrogen. The cycle is repeated 40 to 60 times; a CeO2 shell is deposited on the surface of the ZrO2-TiO2 mesoporous core to obtain a ZrO2-TiO2@CeO2 composite carrier.

[0011] In N1 of the preparation method of the above-mentioned ZrO2-TiO2@CeO2 composite carrier, the stirring speed is 200r / min~300r / min; the centrifugal speed is 8000r / min~10000r / min, and the centrifugal time is 10min~20min; the number of deionized water washings is 2 times~4 times; the median particle size of the zirconium oxychloride is 1μm~5μm; and the non-ionic surfactant is Pluronic F127.

[0012] In the N2 of the preparation method of the ZrO2-TiO2@CeO2 composite carrier, the cerium nitrate carrier gas is a carrier gas loaded with cerium nitrate, and the carrier gas is nitrogen; the pulse time of the cerium nitrate carrier gas is 2s to 2.5s; the flow rate of the cerium nitrate carrier gas is 150sccm to 180sccm; the cerium nitrate concentration of the cerium nitrate carrier gas is 48g / L to 52g / L; the pulse time of the oxygen is 1.5s to 2s; the flow rate of the oxygen is 100sccm to 120sccm; the median particle size of the cerium nitrate is 1μm to 5μm; the thickness of the CeO2 shell is 2nm to 5nm. The CeO2 shell can store and release oxygen through its own oxygen vacancies, so that the ZrO2-TiO2@CeO2 composite carrier is not afraid of the attack of sulfur and water in the exhaust gas, and enhances the stability of the catalyst in a complex environment.

[0013] The above-mentioned method for preparing a denitration and de-VOC composite catalyst comprises the following steps:

[0014] S1, denitrification active material load:

[0015] S1.1: According to the mass ratio, manganese nitrate: cobalt nitrate: oxalic acid: deionized water = (2-2.5): (1-1.2): (0.2-0.5): (30-40), add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio, ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = (1-1.5): (3-5), immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, place it in a reaction vessel with electrodes, and use a DC power supply that can adjust the voltage and frequency to apply a pulse electric field to the reaction vessel, and the voltage is set to 0.50 V~0.55V, and the frequency is set to 100Hz~120Hz; under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier. After the deposition reaction time is 2h~4h, centrifuge, take the solid, dry to constant weight, grind and break up, and obtain the ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I; Mn-Co atomic clusters are like small nails, firmly fixed on the surface of the carrier, and can provide active sites for low-temperature SCR reaction, that is, in the relatively low temperature range of 150℃~400℃, the denitrification reaction can be carried out quickly and efficiently, and the nitrogen oxides in the exhaust gas can be converted into harmless nitrogen and water.

[0016] S1.2: Place carrier I into the quartz tube of a tubular furnace, first introduce hydrogen to expel the air in the quartz tube; introduce a mixture of hot tungsten hexachloride vapor and hydrogen into the tubular furnace to react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, which will be inserted into the small holes of carrier I; after reacting at 280℃~320℃ for 3h~5h, naturally cool the tubular furnace to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II; Ce-WO nanosheets will be inserted into the small holes of the carrier like small blades, which can not only allow the denitrification reaction to proceed in a wider temperature range, but also block the sulfur dioxide in the exhaust gas and prevent it from being adsorbed on the catalyst, thereby reducing the damage of sulfur dioxide to the catalyst.

[0017] S2, VOCs oxide construction:

[0018] According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = (1-1.5): (10-12); the Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 20mL / min-50mL / min is introduced as the plasma gas, the power is set to 500W-550W, the temperature is 50℃-100℃, and the processing time is 2min-5min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst. Fe-Cu-La modified porous carbon can make electrons run faster inside, increase the speed of the catalytic reaction, and resist carbon deposition, so that the catalyst can work stably for a long time without frequent replacement.

[0019] In S1.1 of the above preparation method, the centrifugal speed is 5000 r / min to 8000 r / min, the centrifugal time is 10 min to 20 min; and the grinding is performed until the particle size passes through a 100-mesh sieve.

[0020] In S1.2 of the above preparation method, the hydrogen is used as a carrier gas and a reducing agent, and the flow rate of the mixed gas is 50 mL / min to 100 mL / min; in the mixed gas, the volume ratio of hydrogen to tungsten hexachloride hot vapor is (20 to 25): (1 to 3).

[0021] In S2 of the above preparation method, the preparation method of the Fe-Cu-La-MOF precursor comprises the following steps: dissolving ferric nitrate, copper nitrate and lanthanum nitrate in DMF according to the mass ratio of DMF: ferric nitrate: copper nitrate: lanthanum nitrate = (100-120): (5-15): (3-10): (2-8) to prepare a metal salt mixed solution; dissolving the organic ligand and sodium hyaluronate in DMF according to the mass ratio of DMF: organic ligand: sodium hyaluronate = (100-120): (8-15): (0.3-1) to form an organic ligand solution; stirring under stirring conditions The organic ligand solution is added dropwise to the metal salt mixed solution in a volume ratio of metal salt mixed solution: organic ligand solution = (1-1.5): (2-3). After the addition is completed, stirring is continued to allow the metal ions and organic ligands to be fully mixed and undergo coordination reaction. Stirring is stopped after 1.5h-3h. Crystallization reaction is carried out at 80°C-150°C for 24h-72h. The suspension is then naturally cooled to room temperature to obtain a suspension containing a Fe-Cu-La-MOF precursor. The suspension is centrifuged, the liquid is discarded, the solid is washed with DMF, and vacuum dried to obtain a Fe-Cu-La-MOF precursor.

[0022] In the above-mentioned preparation method of Fe-Cu-La-MOF precursor, the stirring speed is 300r / min~500r / min; the centrifugal speed is 5000r / min~8000r / min; the time is 5min~10min; the number of washing times is 3 times~5 times; the vacuum drying temperature is 60℃~80℃; the vacuum drying time is 12h~24h; the organic ligand is terephthalic acid or trimesic acid; the DMF is N,N-dimethylformamide.

[0023] The method for using the above-mentioned denitration and de-VOC composite catalyst comprises:

[0024] The temperature of industrial waste gas denitrification and de-VOC reaction is controlled between 160℃ and 380℃, which can make the two reactions of denitrification and VOCs oxidation proceed efficiently together; the flow rate of industrial waste gas is set at 20000h -1 ~40000h -1 , that is, the speed at which industrial waste gas passes through the catalyst; a solution of urea and anhydrous ethanol mixed in a molar ratio of (1-1.5): (2-2.5) is used as a reducing agent, and the reducing agent is sprayed into the reaction system in the form of a spray using a metering pump. The reducing agent can not only reduce the pollution caused by ammonia escaping into the air, but also help the VOCs in the exhaust gas to be adsorbed onto the catalyst in advance, allowing the catalytic reaction to proceed faster and better.

[0025] The catalyst undergoes periodic pulse regeneration every 8 to 10 hours of operation: a nitrogen-hydrogen mixed gas containing 5% hydrogen by volume is introduced into the reaction system, and the temperature of the reaction system is adjusted to 300°C to 320°C and maintained for 10 to 15 minutes. In this process, the sulfates and nitrates formed by the adsorption of sulfur and nitrogen oxides in industrial waste gas on the catalyst surface are cleaned up, allowing the catalyst to regain its vitality.

[0026] When the reaction is in progress, industrial waste gas itself contains carbon dioxide. By using Fe-Cu-La to modify the active sites of porous carbon, carbon dioxide is catalyzed into activated carbon. The activated carbon can react with the carbon deposits produced by the reaction on the surface of the oxide layer, clean up the carbon deposits, and repair the problem of decreased catalyst activity caused by carbon deposits. The catalyst can work stably without frequent replacement, saving costs.

[0027] The present invention provides a denitration and de-VOC composite catalyst and a preparation and use method thereof, and the beneficial effects are as follows:

[0028] 1. During the preparation of the ZrO2-TiO2 mesoporous core, zirconium oxychloride and tetrabutyl titanate are mixed and vacuumed to remove the gas, because the presence of gas will interfere with the subsequent chemical reaction. Excluding the gas can ensure the purity of the reaction system and create conditions for the subsequent uniform hydrolysis-condensation reaction. Non-ionic surfactants are dissolved in deionized water and act as templates. Surfactant molecules will form specific micelle structures in the solution. These micelles can guide zirconium and titanium ions to gather around them. As the subsequent reaction proceeds, the position of the micelles eventually forms a mesoporous structure, so that the prepared ZrO2-TiO2 has a large specific surface area and an ordered mesoporous structure, which is conducive to the subsequent loading of active substances and the diffusion of reaction gases.

[0029] 2. During the deposition of the CeO2 shell, the temperature setting can ensure that the cerium nitrate carrier gas and oxygen in the reaction chamber have sufficient activity to participate in the reaction, and will not destroy the structure of the ZrO2-TiO2 mesoporous core. The CeO2 shell obtained by cyclic deposition has a unique oxygen vacancy structure. In the industrial waste gas environment, when encountering sulfur and water, the oxygen vacancies can store oxygen atoms in the waste gas and prevent sulfur and water from reacting with the internal structure of the catalyst, thereby enhancing the stability of the catalyst in a complex environment. At the same time, oxygen vacancies can also participate in electron transfer during the reaction process and promote the catalytic reaction.

[0030] 3. During the loading process of denitrification active substances, a specific proportion of oxalic acid acts as a chelating agent, forming a stable complex with manganese and cobalt ions, controlling the release rate of ions, avoiding rapid precipitation in the solution, and facilitating subsequent uniform deposition on the surface of the carrier. Under the action of the electric field, the positively charged Mn-Co complex ions will move directionally to the surface defects of the negatively charged carrier to achieve directional deposition. This directional deposition method can make the Mn-Co atomic clusters more evenly and firmly fixed on the surface of the carrier, like small nails, providing a large number of active sites for low-temperature SCR reactions. In the low temperature range of 150℃ to 400℃, these active sites can effectively adsorb nitrogen oxides and ammonia in the exhaust gas, reduce the activation energy of the reaction, make the denitrification reaction proceed quickly and efficiently, and convert nitrogen oxides into harmless nitrogen and water.

[0031] 4. During the formation of Ce-WO nanosheets, tungsten hexachloride vapor reacts with CeO2 on the surface of the carrier, and forms Ce-WO nanosheets on the surface of the carrier through redox and chemical reactions. These nanosheets will penetrate into the small holes of carrier I, which increases the specific surface area of ​​the catalyst and provides more active sites. On the other hand, it changes the electronic structure and chemical properties of the catalyst, allowing the denitrification reaction to proceed in a wider temperature range. At the same time, Ce-WO nanosheets have a strong adsorption and fixation ability for sulfur dioxide in the exhaust gas, which can intercept sulfur dioxide and prevent it from being adsorbed on other active sites of the catalyst, reduce the poisoning effect of sulfur dioxide on the catalyst, and extend the service life of the catalyst.

[0032] 5. During the construction of VOCs oxides, Fe-Cu-La modified porous carbon is formed on the surface of carrier II. This porous carbon structure has good conductivity, which allows electrons to be quickly transmitted, speeding up the electron transfer rate during the catalytic reaction, thereby increasing the speed of the catalytic reaction. At the same time, its special structure and composition can effectively resist the formation of carbon deposits, so that the catalyst maintains a high activity during long-term use, does not need to be replaced frequently, and reduces the cost of industrial applications.

[0033] 6. In the preparation process of Fe-Cu-La-MOF precursor, sodium hyaluronate is added to help metal ions and organic ligands to mix better and fully and undergo coordination reactions, making the entire reaction system more stable and orderly, and helping to form a MOF precursor with good structure and performance. Sodium hyaluronate participates in regulating the structure and performance of the final Fe-Cu-La-MOF precursor, which in turn affects the performance of Fe-Cu-La modified porous carbon, including electron transport, catalyst structural compactness, and resistance to carbon deposition. Under the special environment of microwave plasma, combined with temperature conditions, the polymer chain of sodium hyaluronate undergoes degradation, cross-linking, carbonization and other reactions, further helping to improve the performance of the catalyst.

[0034] 7. The catalyst of the present invention has wide temperature window activity: Mn-Co atomic clusters, as active sites for low-temperature SCR reactions, can effectively promote the reaction of nitrogen oxides and ammonia in the low temperature range of 150°C to 400°C. The optimum catalytic temperature is 160°C to 380°C, which can quickly catalyze and improve the efficiency of denitration and VOC removal. Its special atomic structure and electron cloud distribution make it have a strong adsorption capacity for nitrogen oxides and ammonia, reduce the activation energy of the reaction, and thus achieve efficient denitration at low temperatures without significantly reducing its activity at low temperatures. The presence of Ce-WO nanosheets not only increases the active sites of the catalyst, but also changes the electronic structure of the catalyst, so that the catalyst can maintain good activity at high temperatures, broadening the active temperature range of the entire catalyst. The composite catalyst of the present invention can work efficiently in a wider temperature range.

[0035] 8. The catalyst of the present invention has good anti-poisoning performance: the CeO2 shell can effectively resist the attack of sulfur and water in the exhaust gas by storing and releasing oxygen through its own oxygen vacancies. When the sulfur and water in the exhaust gas come into contact with the catalyst, the oxygen vacancies preferentially adsorb the oxygen atoms in the sulfur and water, preventing them from reacting with the active components inside the catalyst and avoiding catalyst deactivation. At the same time, the Ce-WO nanosheets can intercept sulfur dioxide in the exhaust gas, further enhancing the sulfur resistance of the catalyst. Fe-Cu-La modified porous carbon has a special structure and electronic properties, which can effectively resist the formation of carbon deposits; in the process of catalytic oxidation of VOCs, it can inhibit the deposition of carbon species generated during the reaction on the catalyst surface, keep the catalyst surface clean and the accessibility of active sites, so that the catalyst maintains stable catalytic performance during long-term use, while traditional VOCs catalysts, especially non-precious metal catalysts, perform poorly in terms of anti-carbon deposition.

[0036] 9. The catalyst of the present invention has high stability: the composite carrier ZrO2-TiO2@CeO2 itself has good structural stability. The ZrO2-TiO2 mesoporous core provides a stable skeleton structure. The CeO2 shell not only enhances the anti-poisoning performance, but also further stabilizes the entire carrier structure. The Mn-Co atomic clusters loaded thereon are firmly fixed on the carrier surface by directional deposition, the Ce-WO nanosheets are interspersed in the carrier pores, and the Fe-Cu-La modified porous carbon is evenly distributed on the carrier surface. These structures cooperate with each other, so that the catalyst can maintain a stable physical and chemical structure in a complex industrial waste gas environment and under different temperature conditions. The active ingredients form a stable chemical structure through chemical bonding and electronic interaction. During the reaction process, the components can cooperate with each other to jointly maintain the chemical stability of the catalyst, reduce the loss of active ingredients and structural changes, and ensure the long-term stable operation of the catalyst, which has obvious advantages.

[0037] 10. The catalyst of the present invention is environmentally friendly: the active component V2O5 in the traditional SCR catalyst has certain toxicity, and improper disposal of the waste catalyst will cause environmental pollution. However, the composite catalyst of the present invention does not contain toxic components such as V2O5, and is less harmful to the environment during use and disposal.

[0038] 11. The catalyst of the present invention has the potential for recyclability: its special structure and composition make it easier to recover and reuse through physical or chemical methods after being discarded, further reducing the impact on the environment. It has greater advantages in waste treatment than traditional catalysts. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0040] Example 1

[0041] A denitration and de-VOC composite catalyst, wherein the particle structure of the catalyst comprises a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier loads the denitration active substance and the VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier comprises a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance comprises a Mn-Co diatomic cluster and a Ce-WO nanosheet; and the VOCs oxide comprises a Fe-Cu-La modified porous carbon.

[0042] The preparation method of the ZrO2-TiO2@CeO2 composite carrier comprises the following steps:

[0043] N1: According to the mass ratio, zirconium oxychloride: tetrabutyl titanate: non-ionic surfactant (Pluronic F127): deionized water = 0.45:1.2:0.06:9, zirconium oxychloride with a median particle size of 3μm and tetrabutyl titanate were mixed, and the gas was exhausted by vacuum to obtain a mixture A, and the non-ionic surfactant (Pluronic F127) was dissolved in deionized water to obtain a solution B; then, under stirring at 250r / min, according to the volume ratio, mixture A: solution B = 1.5:4, mixture A was added to solution B, and stirred at 250r / min for 1.5h, and the pH value was adjusted to 2.5 with hydrochloric acid; then, the mixture was reacted at 165℃ for 18h, and then centrifuged at 9000r / min for 15min, the upper liquid was discarded, the solid was washed 3 times with deionized water, and dried to constant weight to obtain a ZrO2-TiO2 mesoporous core;

[0044] N2: Put the ZrO2-TiO2 mesoporous core into the reaction chamber of the atomic layer deposition equipment, set the temperature of the reaction chamber to 220℃, and then control the gas pulse time and flow rate to allow cerium nitrate carrier gas and oxygen to enter the reaction chamber alternately. The cerium nitrate carrier gas is the carrier gas loaded with cerium nitrate, and the carrier gas is nitrogen. The cerium nitrate concentration of the cerium nitrate carrier gas is 50g / L, and the median particle size of cerium nitrate is 2μm; each cycle must go through four steps: 160sccm cerium nitrate carrier gas pulse for 2s, blow away the excess cerium nitrate with nitrogen, 110sccm oxygen pulse for 2s, and then blow away the excess oxygen with nitrogen. The cycle is repeated 50 times; a 4nm CeO2 shell is deposited on the surface of the ZrO2-TiO2 mesoporous core to obtain a ZrO2-TiO2@CeO2 composite carrier. The CeO2 shell can store and release oxygen through its own oxygen vacancies, making the ZrO2-TiO2@CeO2 composite carrier resistant to attacks by sulfur and water in the exhaust gas, thereby enhancing the stability of the catalyst in complex environments.

[0045] The above-mentioned method for preparing a denitration and de-VOC composite catalyst comprises the following steps:

[0046] S1, denitrification active material load:

[0047] S1.1: According to the mass ratio of manganese nitrate: cobalt nitrate: oxalic acid: deionized water = 2.3:1.1:0.3:35, add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio of ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = 1.3:4, immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, place it in a reaction vessel with electrodes, and use a A DC power supply with voltage and frequency is used to apply a pulse electric field to the reaction container. The voltage is set to 0.52V and the frequency is set to 110Hz. Under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier. After the deposition reaction time is 3h, the solid is centrifuged at 6000r / min for 15min, and the solid is taken, dried to constant weight, ground and broken up, and passed through a 100-mesh sieve. The sieve-less material is taken to obtain the ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I. The Mn-Co atomic clusters are like small nails, firmly fixed on the surface of the carrier, and can provide active sites for low-temperature SCR reactions, that is, in the relatively low temperature range of 150℃ to 400℃, the denitrification reaction is carried out quickly and efficiently, and the nitrogen oxides in the exhaust gas are converted into harmless nitrogen and water.

[0048] S1.2: Place carrier I in the quartz tube of the tube furnace, use hydrogen as carrier gas and reducing agent, first introduce hydrogen to exhaust the air in the quartz tube; introduce the mixed gas of tungsten hexachloride hot steam and hydrogen into the tube furnace, the flow rate of the mixed gas is 80mL / min, the volume ratio of hydrogen to tungsten hexachloride hot steam is 23:2, react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, these Ce-WO nanosheets will be inserted into the small holes of carrier I; after reacting at 300℃ for 4h, the tube furnace is naturally cooled to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II. Ce-WO nanosheets will be inserted into the small holes of the carrier like a small blade, which can not only allow the denitration reaction to proceed in a wider temperature range, but also intercept the sulfur dioxide in the exhaust gas and prevent it from being adsorbed on the catalyst, thus reducing the damage of sulfur dioxide to the catalyst.

[0049] S2, VOCs oxide construction:

[0050] According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = 1.2:11; the Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 30mL / min is introduced as the plasma gas. The power is set to 520W, the temperature is 80℃, and the processing time is 3min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst. Fe-Cu-La modified porous carbon can make electrons run faster inside, increase the speed of catalytic reaction, and resist carbon deposition, so that the catalyst can work stably for a long time without frequent replacement.

[0051] The preparation method of the Fe-Cu-La-MOF precursor comprises the following steps: dissolving ferric nitrate, copper nitrate and lanthanum nitrate in DMF (N,N-dimethylformamide) at a mass ratio of DMF: ferric nitrate: copper nitrate: lanthanum nitrate = 110:10:6:5 to prepare a metal salt mixed solution; using terephthalic acid as an organic ligand, dissolving the organic ligand and sodium hyaluronate in DMF at a mass ratio of DMF: organic ligand: sodium hyaluronate = 110:12:0.6 to form an organic ligand solution; stirring at 400 r / min, dissolving the metal salt by volume ratio Mixed solution: organic ligand solution = 1.2:2.5, the organic ligand solution is added dropwise to the metal salt mixed solution, after the addition is completed, stirring is continued at 400r / min to allow the metal ions and the organic ligands to be fully mixed and a coordination reaction to occur, stirring is stopped after 2h, and a crystallization reaction is carried out at 120°C for 48h, and then naturally cooled to room temperature to obtain a suspension containing a Fe-Cu-La-MOF precursor; centrifuged at 6000r / min for 8min, the liquid is discarded, the solid is washed 4 times with DMF, and vacuum dried at 70°C for 18h to obtain a Fe-Cu-La-MOF precursor.

[0052] Example 2

[0053] A denitration and de-VOC composite catalyst, wherein the particle structure of the catalyst comprises a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier loads the denitration active substance and the VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier comprises a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance comprises a Mn-Co diatomic cluster and a Ce-WO nanosheet; and the VOCs oxide comprises a Fe-Cu-La modified porous carbon.

[0054] The preparation method of the ZrO2-TiO2@CeO2 composite carrier comprises the following steps:

[0055] N1: According to the mass ratio, zirconium oxychloride: tetrabutyl titanate: non-ionic surfactant (Pluronic F127): deionized water = 0.4:1:0.04:8, zirconium oxychloride with a median particle size of 1μm and tetrabutyl titanate were mixed, and the gas was exhausted by vacuum to obtain a mixture A, and the non-ionic surfactant (Pluronic F127) was dissolved in deionized water to obtain a solution B; then, under stirring at 200r / min, according to the volume ratio, mixture A: solution B = 1:3, mixture A was added to solution B, and stirred at 200r / min for 1h, and the pH value was adjusted to 2 with hydrochloric acid; then, the mixture was reacted at 150℃ for 12h, and then centrifuged at 8000r / min for 10min, the upper liquid was discarded, the solid was washed twice with deionized water, and dried to constant weight to obtain a ZrO2-TiO2 mesoporous core;

[0056] N2: Put the ZrO2-TiO2 mesoporous core into the reaction chamber of the atomic layer deposition equipment, set the temperature of the reaction chamber to 200℃, and then control the gas pulse time and flow rate to allow cerium nitrate carrier gas and oxygen to alternately enter the reaction chamber. The cerium nitrate carrier gas is a carrier gas loaded with cerium nitrate, and the carrier gas is nitrogen. The cerium nitrate concentration of the cerium nitrate carrier gas is 48g / L, and the median particle size of cerium nitrate is 1μm. Each cycle must go through four steps: a cerium nitrate carrier gas pulse with a flow rate of 150sccm for 2s, blowing away excess cerium nitrate with nitrogen, an oxygen pulse with a flow rate of 100sccm for 1.5s, and then blowing away excess oxygen with nitrogen. The cycle is repeated 40 times. A 2nm CeO2 shell is deposited on the surface of the ZrO2-TiO2 mesoporous core to obtain a ZrO2-TiO2@CeO2 composite carrier. The CeO2 shell can store and release oxygen through its own oxygen vacancies, making the ZrO2-TiO2@CeO2 composite carrier resistant to attacks by sulfur and water in the exhaust gas, thereby enhancing the stability of the catalyst in complex environments.

[0057] The above-mentioned method for preparing a denitration and de-VOC composite catalyst comprises the following steps:

[0058] S1, denitrification active material load:

[0059] S1.1: According to the mass ratio of manganese nitrate: cobalt nitrate: oxalic acid: deionized water = 2:1:0.2:30, add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio of ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = 1:3, immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, place it in a reaction vessel with electrodes, and use a device that can adjust the voltage and A DC power supply with a high frequency is used to apply a pulse electric field to the reaction container, with the voltage set to 0.50V and the frequency set to 100Hz; under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier. After the deposition reaction time is 2h, the solid is centrifuged at 5000r / min for 10min, and the solid is taken, dried to constant weight, ground and broken up, and passed through a 100-mesh sieve. The sieve-less material is taken to obtain the ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I. The Mn-Co atomic clusters are like small nails, firmly fixed on the surface of the carrier, and can provide active sites for low-temperature SCR reactions, that is, in the relatively low temperature range of 150℃ to 400℃, the denitrification reaction is carried out quickly and efficiently, and the nitrogen oxides in the exhaust gas are converted into harmless nitrogen and water.

[0060] S1.2: Place carrier I in the quartz tube of the tube furnace, use hydrogen as carrier gas and reducing agent, first introduce hydrogen to exhaust the air in the quartz tube; introduce a mixed gas of tungsten hexachloride hot steam and hydrogen into the tube furnace, the flow rate of the mixed gas is 50mL / min, the volume ratio of hydrogen to tungsten hexachloride hot steam is 20:1, react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, these Ce-WO nanosheets will be inserted into the small holes of carrier I; after reacting at 280℃ for 3h, the tube furnace is naturally cooled to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II. Ce-WO nanosheets will be inserted into the small holes of the carrier like a small blade, which can not only allow the denitration reaction to proceed in a wider temperature range, but also intercept the sulfur dioxide in the exhaust gas and prevent it from being adsorbed on the catalyst, thus reducing the damage of sulfur dioxide to the catalyst.

[0061] S2, VOCs oxide construction:

[0062] According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = 1:10; Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 20mL / min is introduced as plasma gas. The power is set to 500W, the temperature is 50℃, and the processing time is 2min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst. Fe-Cu-La modified porous carbon can make electrons run faster inside, increase the speed of catalytic reaction, and resist carbon deposition, so that the catalyst can work stably for a long time without frequent replacement.

[0063] The preparation method of the Fe-Cu-La-MOF precursor includes the following steps: dissolving ferric nitrate, copper nitrate and lanthanum nitrate in DMF (N,N-dimethylformamide) at a mass ratio of DMF: ferric nitrate: copper nitrate: lanthanum nitrate = 100:5:3:2 to prepare a metal salt mixed solution; using terephthalic acid as an organic ligand, dissolving the organic ligand and sodium hyaluronate in DMF at a mass ratio of DMF: organic ligand: sodium hyaluronate = 100:8:0.3 to form an organic ligand solution; stirring at 300r / min, dissolving the metal salt by volume ratio Mixed solution: organic ligand solution = 1:2, the organic ligand solution is added dropwise to the metal salt mixed solution, after the addition is completed, stirring is continued at 300 r / min to allow the metal ions and organic ligands to be fully mixed and undergo coordination reaction, stirring is stopped after 1.5 hours, and crystallization reaction is carried out at 80°C for 24 hours, and then naturally cooled to room temperature to obtain a suspension containing Fe-Cu-La-MOF precursor; centrifuged at 5000 r / min for 5 minutes, the liquid is discarded, the solid is washed 3 times with DMF, and vacuum dried at 60°C for 12 hours to obtain Fe-Cu-La-MOF precursor.

[0064] Example 3

[0065] A denitration and de-VOC composite catalyst, wherein the particle structure of the catalyst comprises a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier loads the denitration active substance and the VOCs oxides; the ZrO2-TiO2@CeO2 composite carrier comprises a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance comprises a Mn-Co diatomic cluster and a Ce-WO nanosheet; and the VOCs oxide comprises a Fe-Cu-La modified porous carbon.

[0066] The preparation method of the ZrO2-TiO2@CeO2 composite carrier comprises the following steps:

[0067] N1: According to the mass ratio, zirconium oxychloride: tetrabutyl titanate: non-ionic surfactant (Pluronic F127): deionized water = 0.5:1.5:0.08:10, zirconium oxychloride with a median particle size of 5μm and tetrabutyl titanate are mixed, and the gas is exhausted by vacuum to obtain a mixture A, and the non-ionic surfactant (Pluronic F127) is dissolved in deionized water to obtain a solution B; then, under stirring at 300r / min, according to the volume ratio, mixture A: solution B = 2:5, mixture A is added to solution B, and stirring is continued at 300r / min for 2h, and the pH value is adjusted to 3 with hydrochloric acid; then, react at 180℃ for 24h, and then centrifuge at 10000r / min for 20min, the upper liquid is discarded, the solid is washed 4 times with deionized water, and dried to constant weight to obtain a ZrO2-TiO2 mesoporous core;

[0068] N2: Put the ZrO2-TiO2 mesoporous core into the reaction chamber of the atomic layer deposition equipment, set the temperature of the reaction chamber to 250℃, and then control the gas pulse time and flow rate to allow cerium nitrate carrier gas and oxygen to enter the reaction chamber alternately. The cerium nitrate carrier gas is a carrier gas loaded with cerium nitrate, and the carrier gas is nitrogen. The cerium nitrate concentration of the cerium nitrate carrier gas is 52g / L, and the median particle size of cerium nitrate is 5μm; each cycle must go through four steps: a cerium nitrate carrier gas pulse with a flow rate of 180sccm for 2.5s, blowing away excess cerium nitrate with nitrogen, an oxygen pulse with a flow rate of 120sccm for 2s, and then blowing away excess oxygen with nitrogen. The cycle is repeated 60 times; a 5nm CeO2 shell is deposited on the surface of the ZrO2-TiO2 mesoporous core to obtain a ZrO2-TiO2@CeO2 composite carrier. The CeO2 shell can store and release oxygen through its own oxygen vacancies, making the ZrO2-TiO2@CeO2 composite carrier resistant to attacks by sulfur and water in the exhaust gas, thereby enhancing the stability of the catalyst in complex environments.

[0069] The above-mentioned method for preparing a denitration and de-VOC composite catalyst comprises the following steps:

[0070] S1, denitrification active material load:

[0071] S1.1: According to the mass ratio of manganese nitrate: cobalt nitrate: oxalic acid: deionized water = 2.5:1.2:0.5:40, add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio of ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = 1.5:5, immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, place it in a reaction vessel with electrodes, and use a A DC power supply with voltage and frequency is used to apply a pulse electric field to the reaction container, with the voltage set to 0.55V and the frequency set to 120Hz; under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier. After the deposition reaction time is 4h, the solid is centrifuged at 8000r / min for 20min, and the solid is taken, dried to constant weight, ground and broken up, and passed through a 100-mesh sieve. The sieve-less material is taken to obtain the ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I. The Mn-Co atomic clusters are like small nails, firmly fixed on the surface of the carrier, and can provide active sites for low-temperature SCR reactions, that is, in the relatively low temperature range of 150℃ to 400℃, the denitrification reaction is carried out quickly and efficiently, and the nitrogen oxides in the exhaust gas are converted into harmless nitrogen and water.

[0072] S1.2: Place carrier I in the quartz tube of the tube furnace, use hydrogen as carrier gas and reducing agent, first introduce hydrogen to exhaust the air in the quartz tube; introduce a mixed gas of tungsten hexachloride hot steam and hydrogen into the tube furnace, the flow rate of the mixed gas is 100mL / min, the volume ratio of hydrogen to tungsten hexachloride hot steam is 25:3, react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, these Ce-WO nanosheets will be inserted into the small holes of carrier I; after reacting at 320℃ for 5h, the tube furnace is naturally cooled to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II. Ce-WO nanosheets will be inserted into the small holes of the carrier like a small blade, which can not only allow the denitration reaction to proceed in a wider temperature range, but also intercept the sulfur dioxide in the exhaust gas and prevent it from being adsorbed on the catalyst, thus reducing the damage of sulfur dioxide to the catalyst.

[0073] S2, VOCs oxide construction:

[0074] According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = 1.5:12; Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 50mL / min is introduced as plasma gas. The power is set to 550W, the temperature is 100℃, and the processing time is 5min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst. Fe-Cu-La modified porous carbon can make electrons run faster inside, increase the speed of catalytic reaction, and resist carbon deposition, so that the catalyst can work stably for a long time without frequent replacement.

[0075] The preparation method of the Fe-Cu-La-MOF precursor includes the following steps: dissolving ferric nitrate, copper nitrate and lanthanum nitrate in DMF (N,N-dimethylformamide) at a mass ratio of DMF: ferric nitrate: copper nitrate: lanthanum nitrate = 120:15:10:8 to prepare a metal salt mixed solution; using trimesic acid as an organic ligand, dissolving the organic ligand and sodium hyaluronate in DMF at a mass ratio of DMF: organic ligand: sodium hyaluronate = 120:15:1 to form an organic ligand solution; stirring at 500r / min, the metal salts are stirred at a volume ratio of 1:1. Mixed solution: organic ligand solution = 1.5:3, the organic ligand solution is added dropwise to the metal salt mixed solution, after the addition is completed, stirring is continued at 500r / min to allow the metal ions and the organic ligands to be fully mixed and a coordination reaction to occur, stirring is stopped after 3 hours, and a crystallization reaction is carried out at 150°C for 72 hours, and then naturally cooled to room temperature to obtain a suspension containing a Fe-Cu-La-MOF precursor; centrifuged at 8000r / min for 10 minutes, the liquid is discarded, the solid is washed 5 times with DMF, and vacuum dried at 80°C for 24 hours to obtain a Fe-Cu-La-MOF precursor.

[0076] In the above embodiments, the nonionic surfactant is Pluronic F127 from BASF; sodium hyaluronate is from Shandong Runxin Biotechnology Co., Ltd., and has a molecular weight range of 800,000 to 1.5 million.

[0077] When the catalysts prepared in the above embodiments are used, the parameter ranges are controlled as follows:

[0078] The temperature of industrial waste gas denitrification and de-VOC reaction is controlled between 160℃ and 380℃, which can make the two reactions of denitrification and VOCs oxidation proceed efficiently together; the flow rate of industrial waste gas is set at 20000h -1 ~40000h -1, that is, the speed at which industrial waste gas passes through the catalyst; a solution of urea and anhydrous ethanol mixed in a molar ratio of (1-1.5): (2-2.5) is used as a reducing agent, and the reducing agent is sprayed into the reaction system in the form of a spray using a metering pump. The reducing agent can not only reduce the pollution caused by ammonia escaping into the air, but also help the VOCs in the exhaust gas to be adsorbed onto the catalyst in advance, allowing the catalytic reaction to proceed faster and better.

[0079] The catalyst undergoes periodic pulse regeneration every 8 to 10 hours of operation: a nitrogen-hydrogen mixed gas containing 5% hydrogen by volume is introduced into the reaction system, and the temperature of the reaction system is adjusted to 300°C to 320°C and maintained for 10 to 15 minutes. In this process, the sulfates and nitrates formed by the adsorption of sulfur and nitrogen oxides in industrial waste gas on the catalyst surface are cleaned up, allowing the catalyst to regain its vitality.

[0080] When the reaction is in progress, industrial waste gas itself contains carbon dioxide. By using Fe-Cu-La to modify the active sites of porous carbon, carbon dioxide is catalyzed into activated carbon. The activated carbon can react with the carbon deposits produced by the reaction on the surface of the oxide layer, clean up the carbon deposits, and repair the problem of decreased catalyst activity caused by carbon deposits. The catalyst can work stably without frequent replacement, saving costs.

[0081] Comparative Example 1

[0082] The ZrO2-TiO2@CeO2 composite carrier does not prepare the CeO2 shell layer (the N2 step is omitted); the Ce-WO nanosheets are not prepared (the S1.2 step is omitted); the other parameters and methods are the same as in Example 1.

[0083] Comparative Example 2

[0084] Ce-WO nanosheets were not prepared (step S1.2 was omitted); other parameters and methods were the same as in Example 1.

[0085] Comparative Example 3

[0086] No Mn-Co diatomic clusters were prepared (step S1.1 was omitted); other parameters and methods were the same as in Example 1.

[0087] Comparative Example 4

[0088] In the preparation method of Fe-Cu-La-MOF precursor, the ratio of Fe-Cu-La-MOF precursor to carrier II is 0.5:11; other parameters and methods are the same as in Example 1.

[0089] Comparative Example 5

[0090] In the preparation method of Fe-Cu-La-MOF precursor, the ratio of Fe-Cu-La-MOF precursor to carrier II is 5:11; other parameters and methods are the same as in Example 1.

[0091] Comparative Example 6

[0092] In the preparation method of the Fe-Cu-La-MOF precursor, lanthanum nitrate is not added, that is, the Fe-Cu-MOF precursor is used in S2 to replace the Fe-Cu-La-MOF precursor; other parameters and methods are the same as in Example 1.

[0093] Comparative Example 7

[0094] In the preparation method of the Fe-Cu-La-MOF precursor, iron nitrate and copper nitrate are not added, that is, La-MOF precursor is used in S2 to replace Fe-Cu-La-MOF precursor; other parameters and methods are the same as in Example 1.

[0095] Comparative Example 8

[0096] In the preparation method of the Fe-Cu-La-MOF precursor, sodium hyaluronate is not added; other parameters and methods are the same as in Example 1.

[0097] Experimental tests were performed on the catalysts prepared in the above examples and the catalysts prepared in the comparative examples.

[0098] 1 Experiment:

[0099] For the comparability of experimental detection, the parameters of the catalysts were uniformly selected when used in experiments:

[0100] 1.1 Catalyst loading: A stainless steel fixed bed reactor with an inner diameter of 50 mm was selected. A layer of quartz sand with a thickness of 10 mm and a particle size range of 3 mm-5 mm was evenly laid on the bottom of the reactor. Then the prepared catalyst was evenly loaded on top of the quartz sand with a loading height of 100 mm. A layer of quartz sand with a thickness of 10 mm was covered on top of the catalyst to ensure uniform distribution of the airflow and prevent the catalyst from being carried out by the airflow.

[0101] 1.2 Reaction gas configuration: To simulate industrial waste gas, cylinder gas is used to configure the reaction gas. Among them, NOx is a mixture of NO and N2, with a NO volume fraction of 0.1%; VOCs uses toluene as a representative substance, with a volume fraction of 0.1%; SO2 has a volume fraction of 0.03%; the rest is balance gas N2. At the same time, 5% (volume fraction) of water vapor is mixed in to simulate the water vapor content in actual industrial waste gas. The mass flow controller is used to accurately control the flow of each gas so that the total flow reaches the set value to meet different air velocity requirements.

[0102] 1.3 Reaction start-up and condition control: Before the reaction starts, nitrogen is introduced to purge the reaction system for 30 minutes to remove the air in the system. Then the reaction temperature is slowly raised to the set value of 200°C, and the heating rate is controlled at 5°C / min. When the temperature reaches the set value, it is stabilized for 30 minutes, and then the configured reaction gas is introduced. By adjusting the gas flow rate, the flow rate of industrial waste gas is controlled at 30,000 h -1 The reducing agent is a solution of urea and anhydrous ethanol mixed in a molar ratio of 1:2, which is sprayed into the reaction system using a metering pump at a spray pressure of 0.5 MPa and a spray particle size of 50 μm. The spray frequency is 10 times per minute, and each spray lasts for 3 seconds.

[0103] 1.4 After the reaction has been running stably for 1 hour, data collection begins.

[0104] 2 Project Testing:

[0105] 2.1 Denitrification efficiency test: At the reactor outlet, a gas sample is collected through a stainless steel sampling tube with an inner diameter of 6 mm. A ceramic filter is installed at the front end of the sampling tube to prevent particulate matter from entering the analyzer. The sample is transported to the flue gas analyzer for detection at a flow rate of 1L / min through a sampling pump. The sample is sampled three times in a row, and the average value is taken as the test result. The formula for calculating the denitrification efficiency is: Denitrification efficiency (%) = (inlet NOx concentration-outlet NOx concentration) / inlet NOx concentration × 100%. The results are shown in Table 1 below.

[0106] 2.2 VOCs oxidation rate detection:

[0107] A Tenax-TA adsorption tube was used to collect gas samples at the outlet of the reactor, with a sampling flow rate of 0.5L / min and a sampling time of 30 minutes. After sampling, the adsorption tube was sealed and stored, and sent to a gas chromatograph-mass spectrometer for analysis. The gas chromatographic column used a DB-5MS capillary column (30m×0.25mm×0.25μm), the inlet temperature was 250℃, and the split ratio was 10:1. The program temperature conditions were: initial temperature 40℃, maintained for 3min, heated to 280℃ at a rate of 10℃ / min, and maintained for 5min. The mass spectrometry ion source was an electron impact source (EI), the ion source temperature was 230℃, and the scanning range was m / z35-400. The concentration of toluene in the sample was calculated based on the standard curve of toluene, and the VOCs oxidation rate was calculated as follows: VOCs oxidation rate (%) = (inlet toluene concentration-outlet toluene concentration) / inlet toluene concentration × 100%. The results are shown in Table 1 below.

[0108] 2.3 Catalyst stability test:

[0109] 2.31 Regeneration conditions: After the catalyst has worked for 10 hours, pulse regeneration is performed. A nitrogen-hydrogen mixed gas containing 5% hydrogen by volume is introduced into the reaction system at a flow rate of 500 mL / min, and the temperature of the reaction system is raised to 300°C at a rate of 10°C / min and maintained for 10 minutes. The temperature is then lowered to the reaction temperature of 200°C, and the reaction gas is introduced again to continue the reaction.

[0110] 2.32 Testing frequency: After the catalyst was pulse regenerated 3 times, 6 times, and 9 times, the catalyst was tested according to the above-mentioned testing methods for denitrification efficiency and VOCs oxidation rate to evaluate the stability of the catalyst. The results are shown in Table 1 below.

[0111] Table 1 Denitrification, deVOC and stability test results

[0112]

[0113] It can be seen from the above results that the catalysts prepared in Examples 1 to 3 have better catalytic effects, high stability and long service life.

[0114] From the results of Comparative Examples 1 and 2, it can be seen that without the preparation of the CeO2 shell, the ZrO2-TiO2 mesoporous core loses the ability of the CeO2 shell to store and release oxygen through oxygen vacancies, and cannot effectively resist the attack of sulfur and water in the exhaust gas. In the exhaust gas containing sulfur and water, the active sites on the catalyst surface are easily covered by sulfur and water or chemically react, resulting in decreased activity. At the same time, the CeO2 shell lacks the synergistic effect on the active components, making it impossible for the denitrification active substances and VOCs oxides to fully exert their catalytic performance, resulting in reduced denitrification efficiency and VOCs oxidation rate, and poor stability.

[0115] Without Ce-WO nanosheets, the catalyst cannot widen the temperature window, that is, the catalytic energy is reduced at a low temperature of 200°C. In addition, Ce-WO nanosheets can intercept sulfur dioxide in the exhaust gas and prevent it from adsorbing on the catalyst. Without Ce-WO nanosheets, sulfur dioxide will be adsorbed on the catalyst surface, occupying active sites, causing catalyst poisoning, thereby reducing denitration efficiency and VOCs oxidation rate, and reducing stability.

[0116] From the results of Comparative Example 3, it can be seen that the lack of Mn-Co diatomic clusters greatly reduces the active sites of low-temperature SCR reactions. At a low temperature of 200°C, Mn-Co diatomic clusters are a key factor in promoting the rapid denitration reaction. Without it, nitrogen oxides are difficult to be effectively reduced to nitrogen and water at low temperatures, resulting in a significant decrease in denitration efficiency. At the same time, due to the reduction of denitration active sites, a chain reaction occurs on the electron transport and catalytic activity of the entire catalyst, affecting the catalytic performance of VOCs oxides, reducing the VOCs oxidation rate, and deteriorating stability.

[0117] From the results of Comparative Example 4, it can be seen that the ratio of Fe-Cu-La-MOF precursor to carrier II has changed, and the loading amount of Fe-Cu-La modified porous carbon on the carrier surface is insufficient. Fe-Cu-La modified porous carbon can accelerate electron transfer, increase the catalytic reaction rate and resist carbon deposition. When the loading amount is insufficient, the electron transfer efficiency decreases, the catalytic reaction rate slows down, and the VOCs oxidation rate decreases. At the same time, the anti-carbon deposition ability is weakened, making the catalyst more susceptible to carbon deposition and deactivation during the reaction process, thereby affecting the stability and having a certain negative impact on the denitrification efficiency.

[0118] From the results of Comparative Example 5, it can be seen that there are too many Fe-Cu-La-MOF precursors and they are unevenly dispersed on the surface of carrier II. Too many precursors agglomerated on the surface of the carrier and could not form a uniform modified porous carbon structure, resulting in uneven distribution of active sites, and some active sites were covered or could not function effectively. This not only reduces the catalytic oxidation ability of the catalyst for VOCs, but also affects the performance stability of the entire catalyst, resulting in a decrease in the denitration efficiency and VOCs oxidation rate.

[0119] From the results of Comparative Example 6, it can be seen that without the addition of lanthanum nitrate, the Fe-Cu-La modified porous carbon structure is incomplete. Lanthanum plays an important role in structural support and electronic regulation in Fe-Cu-La modified porous carbon. The lack of lanthanum will change the structure and electronic properties of porous carbon, affect its adsorption and activation ability of reactants, thereby reducing the catalytic activity and anti-carbon deposition performance of the catalyst, resulting in a decrease in denitration efficiency and VOCs oxidation rate, and poor stability.

[0120] It can be seen from the results of Comparative Example 7 that only La-MOF precursor is used, and Fe and Cu elements are missing. Fe and Cu elements are key components for forming effective catalytic active sites. They work synergistically with La elements to promote denitration and VOCs oxidation reactions. Without Fe and Cu elements, complete active sites cannot be formed, and the catalyst's adsorption and catalytic conversion capabilities for NOx and VOCs are greatly reduced, resulting in a serious reduction in denitration efficiency and VOCs oxidation rate, and a sharp deterioration in stability.

[0121] It can be seen from the results of Comparative Example 8 that in the preparation process of Fe-Cu-La-MOF precursor, sodium hyaluronate helps metal ions and organic ligands to be better fully mixed and undergo coordination reactions, making the entire reaction system more stable and orderly, and helping to form a MOF precursor with good structure and performance. Sodium hyaluronate is involved in regulating the structure and performance of the Fe-Cu-La-MOF precursor finally formed, thereby affecting the performance of Fe-Cu-La modified porous carbon, including affecting electron transmission, catalyst structural tightness, resistance to carbon deposition and other properties. Under the special environment of microwave plasma, combined with temperature conditions, the polymer chain of sodium hyaluronate undergoes reactions such as degradation, cross-linking, and carbonization, further assisting in improving the performance of the catalyst. The lack of sodium hyaluronate affects the crystallinity, purity and performance of the Fe-Cu-La-MOF precursor, thereby affecting the performance of Fe-Cu-La modified porous carbon and the catalyst.

Claims

1. A composite catalyst for denitration and de-VOC, characterized in that: The particle structure of the catalyst includes a ZrO2-TiO2@CeO2 composite carrier, a denitration active substance and a VOCs oxide; the ZrO2-TiO2@CeO2 composite carrier carries a denitration active substance and a VOCs oxide; the ZrO2-TiO2@CeO2 composite carrier includes a ZrO2-TiO2 mesoporous core and a CeO2 shell; the denitration active substance includes a Mn-Co diatomic cluster and a Ce-WO nanosheet; the VOCs oxide includes a Fe-Cu-La modified porous carbon; The preparation method of the catalyst comprises the following steps: S1, denitrification active material load: S1.1: According to the mass ratio of manganese nitrate: cobalt nitrate: oxalic acid: deionized water = (2-2.5): (1-1.2): (0.2-0.5): (30-40), add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio of ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = (1-1.5): (3-5), immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, and place The ZrO2-TiO2@CeO2 composite carrier is placed in a reaction container with electrodes, and a pulse electric field is applied to the reaction container using a DC power supply capable of adjusting voltage and frequency, with the voltage set to 0.50V-0.55V and the frequency set to 100Hz-120Hz; under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier, and after the deposition reaction time is 2h-4h, the solid is centrifuged, dried to constant weight, and ground to obtain a ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I; S1.2: Place carrier I in a quartz tube of a tube furnace, first introduce hydrogen to expel the air in the quartz tube; introduce a mixture of hot steam of tungsten hexachloride and hydrogen into the tube furnace to react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, which will be inserted into the small holes of carrier I; after reacting at 280℃~320℃ for 3h~5h, cool the tube furnace naturally to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II; S2, VOCs oxide construction: According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = (1~1.5): (10~12); the Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 20mL / min~50mL / min is introduced as the plasma gas, the power is set to 500W~550W, the temperature is 50℃~100℃, and the processing time is 2min~5min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst.

2. A denitration and deVOC composite catalyst according to claim 1, characterized in that: The preparation method of the ZrO2-TiO2@CeO2 composite carrier comprises the following steps: N1: According to the mass ratio, zirconium oxychloride: tetrabutyl titanate: non-ionic surfactant: deionized water = (0.4-0.5): (1-1.5): (0.04-0.08): (8-10), zirconium oxychloride and tetrabutyl titanate are mixed, and the gas is exhausted by vacuum to obtain a mixture A, and the non-ionic surfactant is dissolved in deionized water to obtain a solution B; then, under stirring, according to the volume ratio of mixture A: solution B = (1-2): (3-5), the mixture A is added to the solution B, and the stirring is continued for 1h-2h, and the pH value is adjusted to 2-3 with hydrochloric acid; then, the mixture is reacted at 150℃-180℃ for 12h-24h, and then centrifuged to discard the upper liquid, the solid is washed with deionized water, and dried to constant weight to obtain the ZrO2-TiO2 mesoporous core; N2: Place the ZrO2-TiO2 mesoporous core into the reaction chamber of the atomic layer deposition equipment, set the temperature of the reaction chamber to 200℃~250℃, and then control the gas pulse time and flow rate to allow cerium nitrate carrier gas and oxygen to alternately enter the reaction chamber; each cycle must go through four steps: cerium nitrate carrier gas pulse, blow away excess cerium nitrate with nitrogen, oxygen pulse, and then blow away excess oxygen with nitrogen. The cycle is repeated 40 to 60 times; a CeO2 shell is deposited on the surface of the ZrO2-TiO2 mesoporous core to obtain a ZrO2-TiO2@CeO2 composite carrier.

3. A denitration and deVOC composite catalyst according to claim 2, characterized in that: In N1, the stirring speed is 200 r / min to 300 r / min; the centrifugal speed is 8000 r / min to 10000 r / min, and the centrifugal time is 10 min to 20 min; the number of deionized water washings is 2 to 4 times; the median particle size of the zirconium oxychloride is 1 μm to 5 μm; and the non-ionic surfactant is Pluronic F127.

4. A denitration and deVOC composite catalyst according to claim 2, characterized in that: In N2, the cerium nitrate carrier gas is a carrier gas loaded with cerium nitrate, and the carrier gas is nitrogen; the pulse time of the cerium nitrate carrier gas is 2s to 2.5s; the flow rate of the cerium nitrate carrier gas is 150sccm to 180sccm; the cerium nitrate concentration of the cerium nitrate carrier gas is 48g / L to 52g / L; the pulse time of the oxygen gas is 1.5s to 2s; the flow rate of the oxygen gas is 100sccm to 120sccm; the median particle size of the cerium nitrate is 1μm to 5μm; the thickness of the CeO2 shell is 2nm to 5nm.

5. A method for preparing a denitration and de-VOC composite catalyst, used for preparing a denitration and de-VOC composite catalyst according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: S1, denitrification active material load: S1.1: According to the mass ratio of manganese nitrate: cobalt nitrate: oxalic acid: deionized water = (2-2.5): (1-1.2): (0.2-0.5): (30-40), add manganese nitrate, cobalt nitrate and oxalic acid into deionized water to prepare a Mn-Co nitrate-oxalic acid mixture; according to the mass ratio of ZrO2-TiO2@CeO2 composite carrier: Mn-Co nitrate-oxalic acid mixture = (1-1.5): (3-5), immerse the ZrO2-TiO2@CeO2 composite carrier in the Mn-Co nitrate-oxalic acid mixture, and place The ZrO2-TiO2@CeO2 composite carrier is placed in a reaction container with electrodes, and a pulse electric field is applied to the reaction container using a DC power supply capable of adjusting voltage and frequency, with the voltage set to 0.50V-0.55V and the frequency set to 100Hz-120Hz; under the action of the electric field, Mn-Co atomic clusters are directionally deposited in the surface defects of the ZrO2-TiO2@CeO2 composite carrier, and after the deposition reaction time is 2h-4h, the solid is centrifuged, dried to constant weight, and ground to obtain a ZrO2-TiO2@CeO2 composite carrier with deposited Mn-Co atomic clusters, referred to as carrier I; S1.2: Place carrier I in a quartz tube of a tube furnace, first introduce hydrogen to expel the air in the quartz tube; introduce a mixture of hot steam of tungsten hexachloride and hydrogen into the tube furnace to react with CeO2 on the surface of the carrier to form Ce-WO nanosheets, which will be inserted into the small holes of carrier I; after reacting at 280℃~320℃ for 3h~5h, cool the tube furnace naturally to room temperature to obtain a carrier loaded with Ce-WO nanosheets, referred to as carrier II; S2, VOCs oxide construction: According to the mass ratio, Fe-Cu-La-MOF precursor: carrier II = (1~1.5): (10~12); the Fe-Cu-La-MOF precursor and carrier II are mixed evenly, and then put into the reaction chamber of the microwave plasma generator, and ammonia gas with a flow rate of 20mL / min~50mL / min is introduced as the plasma gas, the power is set to 500W~550W, the temperature is 50℃~100℃, and the processing time is 2min~5min. Under the action of microwave plasma, the Fe-Cu-La-MOF precursor will decompose and carbonize, and Fe-Cu-La modified porous carbon will be formed on the surface of carrier II to obtain a catalyst.

6. The method for preparing a denitration and de-VOC composite catalyst according to claim 5, characterized in that: In S1.1, the centrifugal speed is 5000 r / min to 8000 r / min, the centrifugal time is 10 min to 20 min; and the grinding is performed until the particle size passes through a 100-mesh sieve.

7. The method for preparing a denitration and de-VOC composite catalyst according to claim 5, characterized in that: In S1.2, the hydrogen is used as a carrier gas and a reducing agent, and the flow rate of the mixed gas is 50 mL / min to 100 mL / min; in the mixed gas, the volume ratio of hydrogen to tungsten hexachloride hot vapor is (20 to 25): (1 to 3).

8. The method for preparing a denitration and de-VOC composite catalyst according to claim 5, characterized in that: In S2, the preparation method of the Fe-Cu-La-MOF precursor comprises the following steps: dissolving ferric nitrate, copper nitrate and lanthanum nitrate in DMF according to the mass ratio of DMF: ferric nitrate: copper nitrate: lanthanum nitrate = (100-120): (5-15): (3-10): (2-8) to prepare a metal salt mixed solution; dissolving the organic ligand and sodium hyaluronate in DMF according to the mass ratio of DMF: organic ligand: sodium hyaluronate = (100-120): (8-15): (0.3-1) to form an organic ligand solution; and stirring the mixture at a mass ratio of 1:1 to 1. The volume ratio is metal salt mixed solution: organic ligand solution = (1-1.5): (2-3). The organic ligand solution is added dropwise to the metal salt mixed solution. After the addition is completed, stirring is continued to allow the metal ions and the organic ligands to be fully mixed and undergo coordination reaction. Stirring is stopped after 1.5h-3h. The crystallization reaction is carried out at 80°C-150°C for 24h-72h. The mixture is then naturally cooled to room temperature to obtain a suspension containing a Fe-Cu-La-MOF precursor. The suspension is centrifuged, the liquid is discarded, the solid is washed with DMF, and vacuum dried to obtain a Fe-Cu-La-MOF precursor.

9. The method for preparing a composite catalyst for denitration and de-VOC according to claim 8, characterized in that: The stirring speed is 300r / min~500r / min; the centrifugal speed is 5000r / min~8000r / min; the time is 5min~10min; the number of washings is 3 times~5 times; the vacuum drying temperature is 60℃~80℃; the vacuum drying time is 12h~24h; the organic ligand is terephthalic acid or trimesic acid; the DMF is N,N-dimethylformamide.

10. A method for using a denitration and VOC removal composite catalyst, using the denitration and VOC removal composite catalyst according to claim 1 or 2, characterized in that: Usage methods include: The temperature of industrial waste gas denitrification and VOC removal reaction is controlled between 160℃ and 380℃; the flow rate of industrial waste gas is set at 20000h -1 ~40000h -1 ; A solution of urea and anhydrous ethanol mixed in a molar ratio of (1-1.5): (2-2.5) is used as a reducing agent, and the reducing agent is sprayed into the reaction system using a metering pump; The catalyst is subjected to periodic pulse regeneration every 8 to 10 hours of operation: a nitrogen-hydrogen mixed gas containing 5% by volume of hydrogen is introduced into the reaction system, and the temperature of the reaction system is adjusted to 300°C to 320°C and maintained for 10 to 15 minutes.

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