Dual-functional encapsulated molecular sieve catalyst for denitration and CVOCs removal, preparation method and application thereof

Abstract

The application provides a denitration and CVOCs removal encapsulated bifunctional molecular sieve catalyst and a preparation method and application thereof. y The composite nanoparticle is a core, and the hierarchical porous molecular sieve is a shell layer x -BO y The hierarchical porous-zeolite bifunctional molecular sieve catalyst is prepared by coupling two methods of reverse microemulsion and one-pot two-step dry gel conversion. The catalyst exhibits excellent NO x / CVOCs cooperative catalytic removal activity and stability in a medium-low temperature range (180-520 DEG C), and is suitable for simultaneous purification and removal of NO x and CVOCs in flue gas of waste incineration power generation and hazardous waste incineration pyrolysis industries. The catalyst preparation method is simple, can improve the flue gas pollutant purification efficiency, reduce the industry operation energy consumption and save the production cost.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, specifically to a denitrification and CVOCs-removing encapsulated bifunctional molecular sieve catalyst, its preparation method, and its application. Background Technology

[0002] China produces approximately 400 million tons of municipal solid waste annually. Faced with this massive volume, incineration pyrolysis is one of the main methods of waste treatment. Incineration can reduce the volume of waste by 80% to 90% and its mass by about 75%. Furthermore, the heat generated during incineration can be recovered and reused. Incineration has become the mainstream method for treating municipal solid waste both domestically and internationally, accounting for 35% of the total waste collected. While achieving solid waste reduction and resource utilization, waste incineration also generates a large amount of waste (5000~7000 m³). 3 / t of waste contains acidic gases (HCl, SO2, HF, HBr, NO). x Waste gas containing pollutants such as PCDDs and PCDFs.

[0003] The emission standards for waste incineration flue gas are gradually transitioning from the national standard (GB18485-2014) to the EU standard (EU2000 / 76 / EC). Some provinces and cities (such as Fujian, Hebei, and Shenzhen) have even proposed stricter emission standards than the EU standards, requiring that NO in flue gas be... x The 24-hour average emission of dioxins should not exceed 100 mg / m³. 3 and 0.1 ng TEQ / m 3 To meet increasingly stringent pollutant emission standards, most waste-to-energy plants' flue gas purification systems typically consist of a waste heat boiler, rapid cooling, semi-dry acid removal, activated carbon injection, bag filter dust collection, reheating, NH3-SCR denitrification, and a chimney, connected in series. Such flue gas purification systems have large footprints, high investment costs, complex purification processes, and huge energy consumption.

[0004] Activated carbon adsorption cannot achieve the transformation of organic pollutants into their forms, requiring further treatment of fly ash. Furthermore, this process is constrained by activated carbon quality, mixing uniformity, residence time, and flue gas temperature, resulting in low efficiency and high operating costs. The incineration flue gas entering the denitrification unit after acid removal treatment is characterized by low temperature (< 200 ℃), high humidity, and complex composition. Considering that both NH3-SCR denitrification and catalytic oxidation for CVOCs treatment require catalysts with abundant acidic sites and high redox performance, a low-temperature, high-efficiency denitrification and CVOCs removal encapsulated molecular sieve bifunctional catalyst is developed. This allows for the realization of NO removal on the same catalyst surface. x Synergistic catalytic removal with CVOCs meets increasingly stringent pollutant emission standards, reduces energy consumption in waste incineration flue gas purification operations, and promotes technological upgrading and healthy development of the industry.

[0005] The rearrangement of CVOC precursors such as chlorobenzene and dichloromethane in the gas phase of waste-to-energy plant flue gas at temperatures of 500-800 °C is a significant result. Therefore, efficient catalytic removal of CVOCs from flue gas is of great importance for controlling dioxin emissions from flue gas.

[0006] The activity of CVOCs catalytic combustion catalysts depends on their efficient activation and oxidative removal of various CVOCs, while the activity of NH3-SCR denitrification catalysts typically depends on the performance of the activated pollutant NOx and the reducing agent NH3, as well as the NO... x Reduction removal rate. Therefore, it is necessary to develop pollutant control catalysts with high redox performance.

[0007] On the other hand, after semi-dry desulfurization, the flue gas temperature drops to around 220 °C, while the operating range of commercial VW / Ti catalysts is 300–400 °C, requiring reheating of the flue gas, which inevitably leads to energy waste. Therefore, simplifying the flue gas purification process, reducing operating energy consumption, and efficiently and synergistically removing multiple pollutants (CVOCs, NOx) from the flue gas are crucial. x The development of integrated technologies has become a good idea.

[0008] For example, Chinese Patent 201910767360.7 discloses a method for preparing a VOCs catalyst using iron-containing solid waste. The catalyst uses a mixture of iron-containing solid waste and organic matter as a catalyst support material, loads a metal (one of Mn, Fe, Ni, Ce, and V) as the oxide active component, and does not contain an auxiliary agent (one of Fe, Co, Ce nitrates, and CaCO3). It maintains high activity against various VOCs such as benzene, toluene, xylene, and o-dichlorobenzene. However, it can be observed that the catalyst's catalytic removal effect on chemically stable VOCs is not ideal, reaching only 85.3% (less than 90%) at a high temperature of 350 °C. The purified exhaust gas may not meet emission standards. Increasing the temperature to improve purification efficiency would inevitably increase energy consumption and cost. Furthermore, there is no report on the catalyst's effectiveness against CVOCs and NO. x The function of synergistic removal. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing a bifunctional molecular sieve catalyst for denitrification and CVOCs removal, its preparation method, and its application. This catalyst has a wide activity temperature window, good NOx / CVOCs removal activity, and high N2 / CO2 selectivity.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A bifunctional molecular sieve catalyst encapsulated for denitration and CVOC removal, wherein the catalyst is composed of highly dispersed noble metal A and metal oxide BO. y A. Composite nanoparticles as the core and hierarchical porous molecular sieves as the shell x -BO y The @Hierarchical porous-Zeolite bifunctional molecular sieve catalyst has an activity temperature range of 180~520℃, with the highest catalytic activity observed in the low-temperature range of 200~500℃.

[0012] Specifically, the highly dispersed noble metal A is one or more of Ru, Pt, and Pd, and the metal oxide BO y CeO y SbO y NiO y WO y One or more of the following;

[0013] The A x -BO y In the @Hierarchical porous-Zeolite bifunctional catalyst, the atomic percentage of noble metal A in the support is x%, where x = 0.1~3.0;

[0014] The A x -BO y @Hierarchical porous-Zeolite bifunctional catalysts in metal oxide BO y The percentage of carrier atoms is y%, y = 0.1~3.0;

[0015] The A x -BO y @Hierarchical porous-Zeolite bifunctional catalysts containing noble metal A and metal oxide BO y The mass ratio is x:y = 0.1~3.0: 0.1~3.0.

[0016] A method for preparing the above-mentioned denitrification and CVOCs-removing encapsulated bifunctional molecular sieve catalyst, wherein A x -BO y The @Hierarchical porous-Zeolite bifunctional catalyst was prepared by coupling two methods: reverse microemulsion and a one-pot two-step dry gel conversion method. The specific preparation steps are as follows:

[0017] Synthesis of A without a single microporous structure by reverse microemulsion method x -BO y @SiO2 catalyst:

[0018] Step 1: Weigh 500-1500 mL of cyclohexane and 20-60 g of emulsifier according to the required loading amount and add them to a 2000 mL round-bottom flask. Stir the mixture under constant temperature and magnetic seal for 2-6 hours.

[0019] Step 2: Weigh a certain amount of metal salt B solution according to the loading requirements and add it to the well-stirred solution obtained in Step 1. Stir the solution under constant temperature and magnetic sealing at 20~50 ℃ for 5~20 h.

[0020] Step 3: Weigh a certain amount of ammonia solution according to the loading requirements and add it to the well-stirred solution obtained in Step 2. Stir the solution under constant temperature and magnetic sealing at 20~50 ℃ for 2~10 h.

[0021] Step 4: Weigh a certain amount of metal salt A solution according to the loading requirements and add it to the well-stirred solution obtained in Step 3. Stir the solution under constant temperature and magnetic sealing at 20~50 ℃ for 2~10 h.

[0022] Step 5: Weigh a certain amount of tetraethyl orthosilicate (TEOS) solution according to the loading requirements and add it to the solution obtained in Step 4. Stir the solution under constant temperature and magnetic sealing at 20-50 °C for 20-60 h.

[0023] Step 6: Weigh a certain amount of methanol solution according to the loading requirements and add it to the well-stirred solution obtained in Step 5 to break the emulsion, and let it stand for 8~24 h;

[0024] Step 7: Take the turbid liquid obtained after standing in step 6 and centrifuge it at 5000~8000 rpm for 5~20 min to achieve solid-liquid separation;

[0025] Step 8: Wash the solid obtained in step 7 2-8 times with a mixed solution of acetone and cyclohexane;

[0026] Step 9: Take the solid washed in Step 8 and dry it in a forced-air drying oven at 60~120 ℃ for 4~16 h to obtain uncalcined A. x -BO y @SiO2 catalyst sample;

[0027] The blocky solid sample cleaned in step 9 was ground into powder and calcined in a tube furnace at 200-800 ℃ in air atmosphere for 2-8 h to obtain A. x -BO y @SiO2 catalyst sample;

[0028] Using a one-pot, two-step dry glue conversion method, A x -BO y The SiO2 shell in the SiO2 catalyst is transformed into a highly crystalline hierarchical porous HP-Zeolite shell to obtain A x-BO y HP-Zeolite catalyst sample;

[0029] Step 10: Take the unbaked A from step 9. x -BO y @0.2 g of SiO2 catalyst sample powder was placed in a mortar, and 0.1~0.5 g of tetrapropylammonium hydroxide (TPAOH) was added to the mortar. The mixture was then ground under infrared lamp irradiation for 0.5~1.5 h to obtain catalyst powder with a smaller particle size.

[0030] Step 11, the smaller particle size of A obtained in step 10 x -BO y @The SiO2 catalyst sample powder was placed in a mortar, and 0.1~0.5 g of TPAOH was added to the mortar. The mixture was ground under infrared lamp irradiation for 0.5~1.5 h. The powder was then transferred to a 10 mL polytetrafluoroethylene inner liner. The 10 mL inner liner was then placed in a 100 mL polytetrafluoroethylene large inner liner. 10~40 mL of deionized water and 0.1~0.5 g of TPAOH were added to the large inner liner. The mixture was then loaded into a reaction vessel.

[0031] Step 12: Place the reaction vessel described in Step 11 into an oven and crystallize at 60~120 ℃ for 30~60 h, then raise the temperature to 80~140 ℃ and continue crystallizing for 20~40 h, then raise the temperature to 100~160 ℃ and continue crystallizing for 20~40 h.

[0032] Step 13: Take out the crystallized sample from Step 12 and dry it in an oven at 60~120 ℃ for 10~20 h until completely dry. Finally, after grinding, place it in a tube furnace and calcine at 300~800 ℃ for 2~8 h to obtain A. x -BO y @Hierarchical porous-Zeolite catalyst sample.

[0033] Specifically, the emulsifier is nonylphenol polyoxyethylene ether NP-5; the concentration of the ammonia solution is 28 wt%, and the concentration of the tetrapropylammonium hydroxide TPAOH is 25 wt%.

[0034] An application of a catalyst prepared using the above method:

[0035] (1) The catalyst is prepared and shaped and then placed after the flue gas bag filter to make full use of the waste heat of the flue gas, while avoiding the loss of catalyst service life by dust and other harmful substances.

[0036] (2) After the catalyst is prepared and shaped, it is coupled and integrated with dust removal devices such as dust removal filter material and ceramic fiber tube. After being directly arranged in the waste heat boiler, the main body of the airflow is in direct contact with the integrated process to achieve integrated purification of flue gas and tail gas.

[0037] (3) The catalyst, after being prepared and shaped, is applied to the control and removal of CVOCs and NOx pollutants in the tail gas of stationary sources such as waste incineration power plants and hazardous waste pyrolysis furnaces.

[0038] Specifically, the catalyst, after being prepared and shaped, is in the form of a honeycomb, granules, or corrugated plates.

[0039] Furthermore, this invention also provides catalysts for typical CVOCs and NO. x Pollution purification efficiency is measured by CVOCs removal rate and NO... x Evaluation indicators include removal rate, N2 selectivity, and CO2 selectivity:

[0040] (1);

[0041] (2);

[0042] (3);

[0043] (4);

[0044] In the above formula, , , and Representing CVOC removal rate and NO respectively x Removal rate, N2 selectivity, and CO2 selectivity; , , and They represent CVOC, CO2, NH3, and NO, respectively. x Imported gas concentration; while , , , , and Representing CVOC and NO respectively x The concentrations of NH3, CO, N2O and CO2 in the outlet gases.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. The denitrification and CVOCs-removing encapsulated molecular sieve bifunctional catalyst proposed in this invention can achieve the removal of CVOCs and NO. xThe catalyst exhibits synergistic removal of various CVOCs and NO, and possesses excellent catalytic performance. x To achieve efficient catalytic conversion, this catalyst has a low activation energy.

[0047] 2. The present invention proposes a method for preparing a bifunctional molecular sieve catalyst for denitrification and CVOC removal. This catalyst is constructed with highly dispersed noble metal A (A = Ru, Pt, and Pd, etc.) and oxide BO. x (B = CeO) y SbO y NiO y and WO y A composite nanoparticle core and hierarchical porous (microporous-mesoporous) molecular sieve shell x -BO y @Hierarchical porous-Zeolite (A x -BO y HP-Zeolite bifunctional catalyst is used in flue gas NO2 emissions from waste-to-energy incineration and hazardous waste incineration pyrolysis industries. x Highly efficient and stable synergistic catalytic removal of CVOCs. Composed of highly dispersed noble metal A (A = Ru, Pt, and Pd, etc.) and metal oxide BO. y (B = CeO) y SbO y NiO y and WO y It is composed of (etc.), with active component A x -BO y The molecular sieve is encapsulated and dispersed uniformly with good loading within a multi-level porous molecular sieve shell.

[0048] 3. The method for preparing a bifunctional molecular sieve catalyst for denitrification and CVOCs removal proposed in this invention involves drying the prepared catalyst sample and then calcining it at a suitable temperature. This makes the catalyst more stable and ensures close charge interaction between the cores of the active components and between the cores of the active components and the molecular sieve shell during the reaction. A noble metal component A with excellent CVOCs catalytic degradation performance is selected and combined with a metal oxide BO with strong redox properties. y The active components, such as A, are used to enhance their interfacial interaction with the noble metal A, thereby increasing the surface acidity of the catalyst and improving the dispersion, stability, and catalytic activity of the active component A. x -BO yUsing composite nanoparticles as the core can effectively improve the dispersion of noble metal A, thereby reducing its usage. The design of hierarchical (microporous-mesoporous) molecular sieves as the shell can not only effectively avoid competitive adsorption of gas molecules on the catalyst surface and within the pores, but also efficiently adsorb and capture gaseous pollutant molecules in flue gas, and facilitate their diffusion performance in the adsorption-reaction process, thereby improving the pollutant removal rate and the selectivity of the target product. It can also prevent the active components from agglomerating and sintering during the synergistic thermocatalytic removal of pollutants, thus increasing their stability.

[0049] 4. The denitrification and CVOCs removal encapsulated molecular sieve bifunctional catalyst of this invention has a very wide temperature window, exhibiting good catalytic activity in the temperature range of 180~520 °C, and can achieve more than 95% CVOCs and NO removal. x It boasts high conversion rates with minimal byproduct formation and high selectivity for CO2 and N2. Furthermore, it significantly reduces reaction temperature and energy consumption, thereby lowering production costs to some extent. It is highly suitable for applications involving CVOCs and NOx. x Purification and removal of pollutants from stationary sources such as waste incineration power plants and hazardous waste pyrolysis furnaces, including CVOCs and NOx. x The synergistic catalytic removal effect is significant. Attached Figure Description

[0050] Figure 1 Pd1-NiO 0.8 @HP-Zeolite catalyst (ab, dh) HADDF-TEM and EDX-mapping; (c, i) Particle size and pore size distribution maps;

[0051] Figure 2 The Pd1-NiO prepared in Example 1 of this invention 0.8 @HP-Zeolite catalyst catalytic oxidation efficiency of CB(a) and CO2 selectivity(b);

[0052] Figure 3 The Pd1-NiO prepared in Example 2 of this invention 0.8 @HP-Zeolite catalyst for NO x (a) Catalytic removal and N2 selectivity plots;

[0053] Figure 4 The Pd1-NiO prepared in Example 3 of this invention 0.8 Stability test results of synergistic catalytic removal of the HP-Zeolite catalyst under two operating conditions. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] This invention discloses a denitrification and CVOCs-removing encapsulated bifunctional molecular sieve catalyst, its preparation method, and its application. The preparation method employs a reverse microemulsion + one-pot two-step dry gel conversion method to synthesize the Pd1-NiO0.8@Hierarchicalporous-Zeolite catalyst. The specific preparation method is as follows: 2

[0056] Add 960 mL of cyclohexane to a 2000 mL round-bottom flask, then add 40.32 g of NP-5, stir well, and then add a certain amount of Ni(NO3)3·6H2O solution. After stirring at room temperature for 15 h, 4.32 mL of ammonia solution was added. After stirring at room temperature for 6 h, 2.16 mL of pre-prepared Pd(NO3)3 solution was added. After stirring for 2 h, 5 mL of TEOS was added. After stirring for 48 h, an appropriate amount of methanol was added to demulsify. After standing overnight, the mixture was centrifuged and washed 2-3 times with a 1:1 mixture of acetone and cyclohexane. Then, it was dried overnight in an oven at 80 °C. Finally, the solid block sample was ground into powder. 0.2 g of the synthesized uncalcined Pt-Ni@SiO2 sample was placed in a mortar, and 0.2666 g of TPAOH (25 wt.%) was added. The mixture was ground for 30 min under infrared lamp irradiation. The solid powder was then transferred into a 10 mL polytetrafluoroethylene (PTFE) inner liner. The 10 mL inner liner was placed in a 100 mL PTFE inner liner, and an appropriate amount of water and 0.1333 g of TPAOH (25 wt.%) were added to the inner liner. The mixture was then placed in an oven at 80 °C. The sample was crystallized at ℃ for 48 h, then heated to 100 ℃ for 24 h, and then heated to 120 ℃ for 24 h. The sample was then removed and dried overnight in an oven at 80 ℃. Finally, after grinding, it was calcined in a tube furnace at 500 ℃ for 4 h to obtain Pd1-NiO. 0.8 @Hierarchicalporous-Zeolite catalyst sample.

[0057] A microporous-mesoporous molecular sieve-encapsulated Pd1-NiO0.8@Hierarchical porous-Zeolite catalyst with Pd as the single core active component was initially synthesized using a reverse microemulsion method and a one-pot two-step dry gel conversion method. Figure 1(ab, dh) The morphology, structure, and dispersion state of the active component were characterized and analyzed using HADDF-TEM and EDX-mapping. The results showed that the active component Pd was well encapsulated and uniformly distributed, and the molecular sieve possessed a mesoporous structure. Simultaneously, BET-BJH pore size analysis indicated that the particle size and pore size distribution of the Pd1-NiO0.8@Hierarchical porous-Zeolite catalyst were approximately 30.0 nm and 5.2 nm, respectively (c, i). These characterization results demonstrate the successful preparation of a hierarchically encapsulated Pd1-NiO0.8@Hierarchical porous-Zeolite catalyst.

[0058] Example 1

[0059] The obtained sample was ground and sieved, and 40-60 mesh Pd1-NiO was taken. 0.8 The @Hierarchical porous-Zeolite catalyst particles were experimentally tested. The obtained catalyst powder was placed in a quartz tube, and 600 ppm CB + 10 vol.% O2 was introduced. N2 was used as the carrier gas, with N2 used to carry out chlorobenzene (CB) in a bubble flask, and another N2 was used as the balance gas. The gas flow rate was 100 mL / min. The catalytic oxidation efficiency of the catalyst for CB and the selectivity for CO2 were tested. The inlet and outlet CB contents were determined by gas chromatography, and the CO2 concentration was determined by a flue gas analyzer.

[0060] Pd1-NiO 0.8 The test results of the CB catalytic oxidation activity and CO2 selectivity of the @Hierarchical porous-Zeolite catalyst are as follows: Figure 2 As shown, the CB removal rate of the Pd1-NiO0.8@Hierarchical porous-Zeolite catalyst increases with increasing temperature, reaching almost 100% in the test temperature range of 200~400 °C, while its selectivity for CO2 is also close to 100% across the entire temperature range. This indicates that, compared to CO, the C atoms in the catalytically removed CB molecules are more likely to be converted into CO2.

[0061] Example 2

[0062] The obtained sample was ground and sieved, and 40-60 mesh Pd1-NiO was taken. 0.8 @Hierarchical porous-Zeolite catalyst particles were experimentally tested. The obtained catalyst powder was placed in a quartz tube, and 600 ppm NH3 + 600 ppm NO + 10 vol.% O2 was introduced at a gas flow rate of 100 mL / min. Pd1-NiO was then tested.0.8 @Hierarchical porous-Zeolite catalyst for NO x The catalytic removal efficiency and N2 selectivity. Inlet and outlet NO x The concentration was determined by a high-precision infrared flue gas analyzer.

[0063] Pd1-NiO 0.8 @Hierarchical porous-Zeolite catalyst for NO x Removal rate, such as Figure 3 As shown. Within the temperature range of 100~250 °C, Pd1-NiO 0.8 The CB conversion of the @Hierarchical porous-Zeolite catalyst increased from approximately 20% to 99.8%, and the Pd1-NiO 0.8 The @Hierarchical porous-Zeolite catalyst exhibited excellent denitrification performance (>90%) in the subsequent test temperature range (200~400 °C). In addition, the catalyst also showed excellent N2 selectivity in the test temperature range.

[0064] Example 3

[0065] The obtained sample was ground and sieved, and 40-60 mesh Pd1-NiO was taken. 0.8 @Hierarchical porous-Zeolite catalyst particles were used for combined removal experiments. The obtained Pd1-NiO 0.8 @Hierarchical porous-Zeolite catalyst powder was placed in a quartz tube, and 600 ppm CB + 600 ppm NO + 600 ppm NH3 + 600 ppm SO2 + 10 vol.% O2 and 600 ppm CB + 600 ppm NO + 600 ppm NH3 + 600 ppm SO2 + 10 vol.% O2 + 10 vol.% H2O were passed through it, with N2 as the carrier gas. The catalyst's effect on NO was tested. x The catalytic removal efficiency and N2 selectivity. Inlet and outlet NO x The content, SO2 concentration, and oxygen content were measured by a high-precision infrared flue gas analyzer.

[0066] like Figure 4As shown, the Pd1-NiO2 was further investigated under two conditions: (a, b) 600 ppm CB + 600 ppm NO + 600 ppm NH3 + 600 ppm SO2 + 10 vol.% O2 and (c, d) 600 ppm CB + 600 ppm NO + 600 ppm NH3 + 600 ppm SO2 + 10 vol.% O2 + 10 vol.% H2O. 0.8 The catalytic removal performance of the @Hierarchical porous-Zeolite catalyst for NO at 300 and 400 °C was observed. It can be seen that Pd1-NiO... 0.8 The @Hierarchical porous-Zeolite catalyst exhibits excellent resistance to SO2 and H2O poisoning. At test temperatures of 300 and 400 °C, Pd1-NiO... 0.8 The @Hierarchical porous-Zeolite catalyst maintained stable NO levels throughout the 24-hour reaction period. x The catalyst did not exhibit significant SO2 and H2O poisoning, despite its high conversion rate and N2 selectivity.

[0067] Although the above embodiments only select some transition metal oxides as the active components of the catalyst, they can actually be widely used in various stationary source exhaust gas emission and control fields. Besides waste-to-energy plants, the Pd1-NiO prepared in this invention... 0.8 @Hierarchical porous-Zeolite catalysts can also be used in the control and treatment of exhaust gases from hazardous waste incinerators and organic pyrolysis furnaces.

[0068] The following describes the Pd1-NiO prepared according to the present invention. 0.8 Specific uses of @Hierarchical porous-Zeolite catalysts:

[0069] In practical applications, Pd1-NiO 0.8 The @Hierarchical porous-Zeolite catalyst is placed in the flue gas duct. A reducing agent is injected upstream of the catalyst assembly and mixed with the exhaust gas. The reducing agent is either ammonia or urea, and the amount of reducing agent is equal to the NO content in the exhaust gas. x The stoichiometric ratio is 0.8 to 1.2 times, but it is also necessary to pay attention to the NH3 escape from the exhaust outlet and to maintain the flue gas under oxygen-rich conditions. Air can be introduced as an oxidizing agent during the test. The catalyst can react NO within a wide temperature window (~200℃). xHighly efficient reduction and catalytic oxidation of CVOCs, while also exhibiting excellent CO2 generation selectivity. The exhaust gas is preferably containing NO. x And stationary sources of CVOCs, such as industrial incinerators, pyrolysis furnaces, and waste-to-energy plants.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The use of a denitration and CVOCs removal encapsulated bifunctional molecular sieve catalyst in tail gas treatment, characterized in that, The catalyst is arranged in the tail gas pipeline after being shaped, and is used for purifying and removing NO x and CVOCs in the tail gas, the catalyst is a composite nanoparticle with noble metal A and metal oxide BO y as core and hierarchical porous molecular sieve as shell x -BO y @Hierarchical porous-Zeolite dual functional molecular sieve catalyst, the activity temperature range of the catalyst is 180~520℃; The high-dispersible noble metal A is one or more of Ru, Pt, Pd, the metal oxide BO y is one or more of CeO y , SbO y , NiO y , WO y . The A x -BO y @The percentage of noble metal A in the hierarchical porous-zeolite bifunctional molecular sieve catalyst with respect to the carrier atoms is x %, x = 0.1~3.0; The A x -BO y @Hierarchical porous-Zeolite bifunctional molecular sieve catalysts in metal oxide BO y The percentage of carrier atoms is y%, y = 0.1~3.0; The A x -BO y @Hierarchical porous-Zeolite dual functional molecular sieve catalyst of noble metal A and metal oxide BO y The mass ratio of A and BO is x:y=0.1~3.0: 0.1~3.

0. The A x -BO y @Hierarchical porous-Zeolite bifunctional molecular sieve catalysts were prepared by coupling two methods of reverse microemulsion + one-pot two-step dry gel conversion.

2. The use of the denitration and CVOCs removal encapsulated bifunctional molecular sieve catalyst according to claim 1 in tail gas treatment, characterized in that, The A x -BO y @The specific preparation process steps of the hierarchical porous-zeolite bifunctional molecular sieve catalyst are as follows: Synthesis of single-microporous-free A x -BO y @SiO2catalyst: Step 1, according to the load requirements, 500-1500 mL cyclohexane and 20-60 g emulsifier were weighed into a 2000 mL round-bottom flask, and constant temperature magnetic sealed stirring was carried out for 2-6 h; Step 2, according to the load requirements, a certain amount of B metal salt solution was weighed into the stirring uniform solution obtained in step 1, and constant temperature magnetic sealed stirring was carried out at 20-50 ℃ for 5-20 h; Step 3, according to the load requirements, a certain amount of ammonia solution was weighed into the stirring uniform solution obtained in step 2, and constant temperature magnetic sealed stirring was carried out at 20-50 ℃ for 2-10 h; Step 4, according to the load requirements, a certain amount of A metal salt solution was weighed into the stirring uniform solution obtained in step 3, and constant temperature magnetic sealed stirring was carried out at 20-50 ℃ for 2-10 h; Step 5, according to the load requirements, a certain amount of ethyl silicate TEOS solution was weighed into the stirring uniform solution obtained in step 4, and constant temperature magnetic sealed stirring was carried out at 20-50 ℃ for 20-60 h; Step 6, according to the load requirements, a certain amount of methanol solution was weighed into the stirring uniform solution obtained in step 5 to break the emulsion, and was placed for 8-24 h; Step 7, the turbid liquid obtained after standing in step 6 was centrifuged at 5000-8000 rpm for 5-20 min in a centrifuge to achieve solid-liquid separation; Step 8, the solid obtained in step 7 was washed 2-8 times with a mixed solution of acetone and cyclohexane in a ratio of 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 and 2:1; Step 9, dry the solid washed in step 8 in a forced air drying oven at 60-120 °C for 4-16 h to obtain uncalcined A x -BO y @SiO2catalyst sample; A x -BO y @SiO2catalyst the SiO2shell is converted into a high crystallinity Hierarchical porous-Zeolite shell to obtain A x -BO y @Hierarchical porous-Zeolite catalyst sample: Step 10, take the uncalcined A of step 9 x -BO y @SiO2catalyst sample powder 0.2 g was placed in a mortar, 0.1-0.5 g of tetrapropylammonium hydroxide TPAOH was added to the mortar, and grinding was carried out under infrared lamp irradiation for 0.5-1.5 h to obtain catalyst powder with smaller particle size; Step 11, the A with smaller particle size obtained in step 10 x -BO y @The SiO2catalyst sample powder was placed in a mortar, 0.1-0.5 g of TPAOH was further added to the mortar, and grinding was performed under infrared lamp irradiation for 0.5-1.5 h, and then the mortar was moved into a 10 mL polytetrafluoroethylene inner container, and the 10 mL inner container was placed in a 100 mL polytetrafluoroethylene large inner container, and 10-40 mL of deionized water and 0.1-0.5 g of TPAOH were added to the large inner container, and then the reaction kettle was loaded; Step 12, the reaction kettle in step 11 was placed in an oven at 60-120 ℃ for crystallization for 30-60 h, then the temperature was increased to 80-140 ℃ for continued crystallization for 20-40 h, and then the temperature was increased to 100-160 ℃ for continued crystallization for 20-40 h; Step 13, the sample crystallized in step 12 is taken out and dried in an oven at 60-120 °C for 10-20 h until completely dried, and finally ground and placed in a tube furnace for calcination at 300-800 °C for 2-8 h to obtain A x -BO y @Hierarchical porous-Zeolite catalyst samples.

3. The use of the denitration and CVOCs removal encapsulated bifunctional molecular sieve catalyst according to claim 2 in tail gas treatment, characterized in that, The emulsifier is nonylphenol polyoxyethylene ether NP-5; the concentration of the ammonia solution is 28 wt%, and the concentration of the tetrapropylammonium hydroxide TPAOH is 25 wt%.

4. The use of the denitration and CVOCs removal encapsulated bifunctional molecular sieve catalyst according to claim 1 in tail gas treatment, characterized in that, The prepared catalyst is in the form of honeycomb or granules or corrugated plate.

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