Low-temperature rare-earth-based denitration catalyst as well as preparation method and application thereof

Abstract

The invention discloses a low-temperature rare earth based denitration catalyst as well as a preparation method and application thereof. The catalyst takes a TiO2-ZrO2 nanocage as a carrier and Ce-Sm-La rare earth oxide as an active component; by taking the mass of the carrier as a reference, the mass percentage of the active component is 5-10%. The method comprises the following steps: synthesizing a TiO2-ZrO2 nanocage catalyst carrier by a microfluidic gas jet spinning method, then growing rare earth metal oxide on the surface of the carrier in situ by a hydrothermal method to serve as a catalytic active component by taking polyvinylpyrrolidone as a crystal face regulator, and finally drying and roasting to obtain the low-temperature rare earth-based denitration catalyst. The catalyst synthesized by the method has a confinement structure, is large in specific surface area, is environment-friendly, and can efficiently and stably realize the denitration target of low-temperature flue gas working conditions in various non-electric industries.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method and application of a low-temperature rare earth-based denitration catalyst, and belongs to the field of industrial flue gas purification. BACKGROUND

[0002] SCR is the most commonly used NO x removal method at present, and the core technology of SCR mainly focuses on the research and development of new denitration catalysts. At present, the commercial catalysts for fixed source flue gas denitration mainly include vanadium-based catalysts and rare earth-based catalysts. However, the commercial vanadium-based catalysts still have some unavoidable defects, such as poor low-temperature activity, easy volatility and biological toxicity of V2O5, which seriously hinder the further development of the catalyst in practical applications. Therefore, it is very important to prepare an environmentally friendly catalyst that overcomes the above-mentioned shortcomings. The denitration catalyst with Ce, La and other rare earth elements as active components can not only effectively reduce the pollution of NO x to the atmosphere, but also avoid the secondary pollution of toxic element V to the environment. However, the rare earth-based catalyst still faces the problem of insufficient activity at low temperature.

[0003] Among the existing low-temperature denitration patents, patent CN201510488728.8 uses Cr2O3 and V2O5 as active components, NiSO4 as an additive, and TiO2 as a carrier to prepare a low-temperature denitration catalyst, which improves the chemical adsorption capacity of NH3 at low temperature, thereby improving the catalyst activity, reducing the conversion rate of SO2 / SO3, and prolonging the service life of the low-temperature denitration catalyst. Patent CN201811654451.1 prepares a ruthenium-based ultra-low-temperature denitration catalyst by subsection impregnation and calcination, which achieves good denitration effect at ultra-low temperature, has significantly improved anti-poisoning performance, and has a long service life. Patent CN201710773182.X obtains a low-temperature denitration catalyst by loading metal oxides on nitrogen-doped graphene, which has good denitration effect at low temperature and can effectively resist sulfur dioxide. Although the above-mentioned catalysts achieve low-temperature high-catalytic activity, they are expensive due to the presence of V or noble metals, which is not suitable for large-scale industrial applications. CN201910883380.0 mixes dozens of salt types such as nano-titanium dioxide, nano-zirconium dioxide, tantalum pentoxide, antimony trioxide, ammonium metatungstate, ammonium heptamolybdate, ammonium metavanadate, cerium salt, samarium salt, neodymium salt, and chromium salt, and then calcines them to prepare a high-low-temperature denitration catalyst. Although the denitration catalyst is long-term efficient at 150-430℃, has excellent sulfur resistance and anti-poisoning ability, and has high strength, the preparation of the catalyst is difficult due to the complexity of the raw materials. CN201910083480.5 prepares a copper-doped phosphomolybdic acid low-temperature denitration catalyst, which can enhance the ability of the catalyst to resist SO2 and water vapor. However, the catalytic efficiency of the catalyst is insufficient at less than 200℃, which makes it difficult to meet the needs of some low-temperature industrial application scenarios. SUMMARY

[0004] The application aims at the insufficient catalytic activity of the existing industrial flue gas low-temperature denitration catalyst and the existing problems, and provides a preparation method and application of a low-temperature rare earth-based denitration catalyst.

[0005] A low-temperature rare earth-based denitration catalyst, which takes TiO2-ZrO2 nanocage as a carrier and Ce-Sm-La rare earth composite oxide as an active component; the method first synthesizes the TiO2-ZrO2 nanocage catalyst carrier by microfluidic gas jet spinning method, then grows the rare earth metal oxide on the surface of the carrier in situ as the catalytic active component by hydrothermal method with polyvinylpyrrolidone as a crystal face regulator, and finally dries and calcines to obtain the low-temperature rare earth-based denitration catalyst; the mass percentage of the active component is 5-10% based on the mass of the carrier.

[0006] In the technical scheme of the application, the mass ratio of titanium oxide to zirconium oxide in the TiO2-ZrO2 nanocage carrier is 1:(0.6-1.5).

[0007] In the technical scheme of the application, the mass ratio of cerium oxide to samarium oxide to lanthanum oxide in the Ce-Sm-La composite oxide is 1:(0.2-0.5):(0.3-0.5) in turn.

[0008] A preparation method of a low-temperature rare earth-based denitration catalyst, the preparation method of the catalyst is as follows:

[0009] (1) Preparation of spinning solution

[0010] Dissolve tetrabutyl titanate, zirconium oxychloride and polyacrylonitrile in N,N-dimethylformamide and stir uniformly at room temperature to obtain a spinning solution;

[0011] (2) Preparation of carrier

[0012] Inject the spinning solution into the micro-pore channel of the microfluidic control chip through a micro-injection pump, then perform gas jet spinning molding through high-speed airflow of a microfluidic gas jet spinning machine, transfer the fiber to a muffle furnace after the fiber molding is completed, and calcine to obtain the TiO2-ZrO2 nanocage carrier;

[0013] (3) Preparation of catalytic active component precursor solution

[0014] Weigh cerium salt, samarium salt, lanthanum salt and polyvinylpyrrolidone, add deionized water and stir uniformly to obtain an active component precursor solution;

[0015] (4) Preparation of catalyst

[0016] The TiO2-ZrO2 nanocage carrier prepared in step (2) is transferred into a polytetrafluoroethylene hydrothermal reactor with the active component precursor ion solution prepared in step (3) to perform hydrothermal reaction, and after the hydrothermal reaction is completed, the mixture is taken out and placed in a blast drying oven for heat preservation and drying, and then is placed into a muffle furnace for calcination to prepare a low-temperature rare earth-based denitration catalyst.

[0017] In the technical scheme of the present application, the mass ratio of tetrabutyl titanate, zirconium oxychloride, polyacrylonitrile and N,N-dimethylformamide in step (1) is 1:(0.5-1):(2-5):(20-50).

[0018] In the technical scheme of the present application, the molecular weight of polyacrylonitrile in step (1) is 80000-150000.

[0019] In the technical scheme of the present application, the injection rate of the micro-injection pump in step (2) is 5-15 ml / h.

[0020] In the technical scheme of the present application, the air pressure of the microfluidic air jet spinning machine in step (2) is 0.02-0.1 Mpa.

[0021] In the technical scheme of the present application, the calcination temperature in step (2) is 600-800 DEG C, and the calcination time is 4-6 h.

[0022] In the technical scheme of the present application, the cerium salt in step (3) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the samarium salt is samarium nitrate hexahydrate; and the lanthanum salt is lanthanum nitrate hexahydrate.

[0023] In the technical scheme of the present application, the mass ratio of the total amount of cerium salt, samarium salt and lanthanum salt, polyvinylpyrrolidone and deionized water in step (2) is 1:(0.02-0.05):(80-150) in turn.

[0024] In the technical scheme of the present application, the hydrothermal temperature in step (4) is 120-200 DEG C, and the hydrothermal time is 6-12 h.

[0025] In the technical scheme of the present application, the heat preservation and drying temperature in step (4) is 100-120 DEG C, and the drying time is 4-8 h.

[0026] In the technical scheme of the present application, the calcination temperature in step (4) is 400-600 DEG C, and the calcination time is 2-4 h.

[0027] In the technical scheme of the present application, the above-mentioned catalyst preparation method is applied to low-temperature flue gas denitration.

[0028] The catalyst activity evaluation experiment condition of the application: 40-60 mesh catalyst 1 mL is poured into a quartz tube with an inner diameter of 8 mm, fixed with quartz wool and iron wire, the quartz tube is placed in a tube furnace, the actual temperature of the catalytic reaction is adjusted by controlling the heating temperature of the tube furnace. The gas composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), the rest is N2, the total gas flow is 500 mL / min, the temperature is controlled at 90-210 DEG C, each 30 DEG C stays stable for 30 min, and the NO concentration is tested by Laoying 3021 type portable carbon emission monitor. The denitration efficiency of the catalyst is higher than 90% in the temperature range of 90-210 DEG C.

[0029] In the technical scheme of the application: the pressure is gauge pressure unless otherwise specified.

[0030] Beneficial effects:

[0031] (1) The rare earth elements Ce, Sm and La have oxygen affinity, and the composite oxide formed has high purity. Ce has a unique 4f electron layer structure, and after being combined with Sm and La oxides, it shows strong synergistic effect, effectively improving the catalytic activity of the composite oxide;

[0032] (2) The catalyst carrier is prepared by a microfluidic gas jet spinning device. According to Bernoulli's principle, when the high-pressure gas is ejected from the nozzle, the change of gas pressure will cause the change of gas flow rate or kinetic energy. The high-pressure gas is converted into kinetic energy to form the driving force of the solution jet. At the same time, the high-pressure gas flow will generate shear force on the gas-liquid surface. The polymer solution forms a liquid cone at the outlet. When the shear force overcomes the surface tension, the TiO2-ZrO2 precursor and the polyacrylonitrile solution jet are continuously and staggered ejected from the end of the liquid cone, and finally the TiO2-ZrO2 precursor and the polyacrylonitrile staggered coexisting fiber is formed. The nanofiber also prevents the agglomeration of the TiO2-ZrO2 precursor. The polyacrylonitrile part in the fiber is removed by calcination, thereby obtaining a nanocage TiO2-ZrO2 carrier. When the calcined polyacrylonitrile is converted into a gas substance, the nanocage TiO2-ZrO2 carrier has more pore structures, effectively increasing the specific surface area of the carrier and strengthening the bonding with the active component. The composite fiber prepared by traditional electrospinning shows an ordered component long fiber shape, which still maintains the long fiber morphology after calcination and other technologies, and it is difficult to provide complex structures such as nanocage;

[0033] (3) Polyvinylpyrrolidone as a crystal face regulator can direct the regulation of CeO2 to expose more (100) high-energy crystal faces during the hydrothermal process. The adsorption capacity of CeO2 (100) high-energy crystal face to NO and NH3 gas is stronger, which is beneficial to improve the low-temperature adsorption activation process of the catalyst;

[0034] (4) the nanocage structure of the catalyst provides nanoscale confined space for the denitration reaction, including nanoscale channels, pores and cavities, and the physicochemical properties of the guest substance (i.e. the reactant) in the nanoscale space will change, so that the reactant has stronger catalytic stability in the nanoscale space, and the adsorption and activation capacity of the catalyst nanoscale confined structure to the reactant will also be greatly improved;

[0035] Therefore, the catalyst prepared in the present application not only has excellent low-temperature flue gas denitration performance, but also effectively promotes the high-value and efficient use of rare earth elements in the environmental protection field, and the catalyst components are environmentally friendly, the preparation process is simple, the cost is low, the cost performance is high, and the catalyst has strong application promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 SEM image of the catalyst prepared in Example 1;

[0037] Figure 2 SEM image of the catalyst prepared in Comparative Example 1;

[0038] Figure 3 TEM image of the catalyst prepared in Example 2;

[0039] Figure 4 TEM image of the catalyst prepared in Comparative Example 2;

[0040] Figure 5 NO removal performance diagram of the catalyst prepared in Examples 1-3 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0041] The present application will be further described below in conjunction with examples, which are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0042] Example 1

[0043] (1) Preparation of spinning dope

[0044] 10.0000 g of tetrabutyl titanate, 10.0000 g of zirconium oxychloride and 50.0000 g of polyacrylonitrile (molecular weight 150000) were dissolved in 500.0000 g of N,N-dimethylformamide at room temperature and stirred for 8 h to obtain a spinning solution, wherein the mass ratio of tetrabutyl titanate, zirconium oxychloride, polyacrylonitrile and N,N-dimethylformamide is 1:1:5:50;

[0045] (2) Preparation of carrier

[0046] The 10 mL syringe is used to suck the spinning dope and is placed in a micro-injection pump. The micro-injection pump injects the spinning solution into the micro-fluid control chip, and the high-speed airflow of the air-jet spinning machine (Nanjing Bell Times Technology Co., Ltd.) is used for air-jet spinning. The injection rate of the micro-injection pump is 15 ml / h, and the air pressure is 0.1 Mpa. After the fiber is formed, it is transferred to a muffle furnace and calcined at 800℃ for 3h to obtain a TiO2-ZrO2 nanocage carrier, wherein the mass ratio of titanium oxide to zirconium oxide is 1:0.61;

[0047] (3) Preparation of a catalytically active component precursor solution

[0048] 2.1647g of cerium chloride heptahydrate, 1.0197g of samarium nitrate hexahydrate, 1.0632g of lanthanum nitrate hexahydrate, and 0.1699g of polyvinylpyrrolidone are weighed into 509.7115g of deionized water and stirred for 2h to obtain an active component precursor solution, wherein the mass ratio of the total amount of cerium salt, samarium salt, and lanthanum salt, polyvinylpyrrolidone, and deionized water is 1:0.05:150, respectively;

[0049] (4) Preparation of a catalyst

[0050] Based on the mass of the carrier, 1.0000g of the TiO2-ZrO2 nanocage carrier prepared in step (2) and 14.1587g of the active component precursor ion solution prepared in step (3) are weighed, and the mixture is transferred to a polytetrafluoroethylene hydrothermal reactor, and hydrothermal treatment is carried out at 180℃ for 5h. After the hydrothermal treatment is completed, the mixture is taken out and placed in a forced air drying oven for drying at 120℃ for 4h, and then it is placed in a muffle furnace and calcined at 600℃ for 2h to obtain a low-temperature rare earth-based denitration catalyst, wherein the mass ratio of cerium oxide, samarium oxide, and lanthanum oxide is 1:0.5:0.5. (For example Figure 1 )

[0051] (5) Catalytic activity test

[0052] 40-60 mesh of the catalyst 1mL is taken and poured into a quartz tube with an inner diameter of 8mm, and quartz wool and iron wire are used to fix it. The quartz tube is placed in a tube furnace, and the actual temperature of the catalytic reaction is adjusted by controlling the heating temperature of the tube furnace. The gas composition is: NO (500ppm), NH3 (500ppm), O2 (11vol.%), and the rest is N2. The total gas flow is 500mL / min, and the control temperature is 90-210℃. Each temperature stays for 30min, and the NO concentration is tested by Laoying 3021 portable carbon emission monitor. The denitration activity of the catalyst at 90℃ reaches 92.5% in 5min, and the denitration efficiency in the range of 120-210℃ is 100% in 5min.

[0053] Example 2

[0054] (1) Spinning dope preparation

[0055] 10.0000 g of tetrabutyl titanate, 5.0000 g of zirconium oxychloride and 20.0000 g of polyacrylonitrile (molecular weight 150000) were weighed and dissolved in 200.0000 g of N, N-dimethylformamide at room temperature with stirring for 6 h to obtain a spinning solution, wherein the mass ratio of tetrabutyl titanate, zirconium oxychloride, polyacrylonitrile and N, N-dimethylformamide was 1:0.5:2:20;

[0056] (2) Preparation of the carrier

[0057] A 10 mL syringe was used to suck the spinning dope and placed in a micro-injection pump. The micro-injection pump injected the spinning solution into the microfluidic control chip, and the high-speed airflow of the air-jet spinning machine (Nanjing Bell Times Technology Co., Ltd.) was used for air-jet spinning to form fibers. The injection rate of the micro-injection pump was 10 ml / h, and the air pressure was 0.05 Mpa. After the fiber formation was completed, it was transferred to a muffle furnace and calcined at 600℃ for 6 h to obtain a TiO2-ZrO2 nanocage carrier, wherein the mass ratio of titanium oxide to zirconium oxide was 1:1.23;

[0058] (3) Preparation of the catalytically active component precursor solution

[0059] 2.5228 g of cerium nitrate hexahydrate, 0.5098 g of samarium nitrate hexahydrate, 0.7974 g of lanthanum nitrate hexahydrate and 0.0766 g of polyvinylpyrrolidone were weighed and added to 306.4076 g of deionized water and stirred for 1 h to obtain an active component precursor solution, wherein the mass ratio of the total of cerium salt, samarium salt and lanthanum salt, polyvinylpyrrolidone and deionized water was 1:0.02:80, respectively;

[0060] (4) Preparation of the catalyst

[0061] Based on the mass of the carrier, 1.5000 g of the TiO2-ZrO2 nanocage carrier prepared in step (2) and 30.6408 g of the active component precursor ion solution prepared in step (3) were weighed and transferred to a polytetrafluoroethylene hydrothermal reactor, and hydrothermal treatment was carried out at 120℃ for 12 h. After the hydrothermal treatment was completed, the mixture was taken out and placed in a forced air drying oven for drying at 100℃ for 8 h, and then placed in a muffle furnace for calcination at 400℃ for 4 h to obtain a low-temperature rare earth-based denitration catalyst (such as Figure 3 ), wherein the mass ratio of cerium oxide, samarium oxide and lanthanum oxide was 1:0.2:0.3;

[0062] (5) Catalytic activity test

[0063] Take 40-60 mesh catalyst 1 mL, pour into the inner diameter of 8 mm quartz tube, with quartz wool and iron wire fixed, the quartz tube is placed in the tube furnace, by controlling the heating temperature of the tube furnace to adjust the actual temperature of the catalytic reaction. The gas composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), the rest is N2, the total gas flow is 500 mL / min, the control temperature is 90-210℃, each 30℃ stays stable for 30 min, the NO concentration is tested by Laoying 3021 type portable carbon emission monitor. The denitration activity of the catalyst at 90℃ reaches 90.7% in 5 min, and the denitration efficiency in the interval of 120-210℃ is 100% in 5 min.

[0064] Example 3

[0065] (1) Spinning dope preparation

[0066] Take 10.0000 g of tetrabutyl titanate, 8.0000 g of zirconium oxychloride and 40.0000 g of polyacrylonitrile (molecular weight 80000) and dissolve in 400.0000 g of N, N-dimethylformamide at room temperature for 6 h to obtain a spinning solution, wherein the mass ratio of tetrabutyl titanate, zirconium oxychloride, polyacrylonitrile and N, N-dimethylformamide is 1:0.8:4:40;

[0067] (2) Preparation of carrier

[0068] A 10 mL syringe is used to suck the spinning dope and placed in a microsyringe pump, the microsyringe pump injects the spinning solution into a microfluidic control chip, and a gas jet spinning machine (Nanjing Bell Times Technology Co., Ltd.) is used for high-speed gas jet spinning molding, the injection rate of the microsyringe pump is 5 ml / h, and the gas pressure is 0.02 Mpa. After the fiber molding is completed, it is transferred to a muffle furnace for calcination at 800℃ for 4 h to obtain a TiO2-ZrO2 nanocage carrier, wherein the mass ratio of titanium oxide to zirconium oxide is 1:0.77;

[0069] (3) Preparation of catalytically active component precursor solution

[0070] Take 2.5228 g of cerium nitrate hexahydrate, 1.2746 g of samarium nitrate hexahydrate, 1.3290 g of lanthanum nitrate hexahydrate and 0.2563 g of polyvinylpyrrolidone, add 768.9673 g of deionized water and stir for 1 h to obtain an active component precursor solution, wherein the mass ratio of the total amount of cerium salt, samarium salt and lanthanum salt, polyvinylpyrrolidone and deionized water is 1:0.04:120, respectively;

[0071] (4) Preparation of catalyst

[0072] With the carrier quality as the basis, 2.0000 g of the TiO2-ZrO2 nanocage carrier prepared in step (2) and 76.8967 g of the active component precursor ion solution prepared in step (3) were weighed according to the active component accounting for 5% of the carrier quality, and were transferred into a polytetrafluoroethylene hydrothermal reactor. Hydrothermal treatment was carried out at 200 ℃ for 10 h. After the hydrothermal treatment, the mixture was taken out and placed in a blast drying oven for heat preservation and drying at 120 ℃ for 2 h. Then, the mixture was placed into a muffle furnace for calcination at 500 ℃ for 3 h to prepare a low-temperature rare earth-based denitration catalyst. The mass ratio of cerium oxide, samarium oxide, and lanthanum oxide in the catalyst was 1:0.4:0.4.

[0073] (5) Catalyst activity test

[0074] 1 mL of the catalyst with a particle size of 40-60 mesh was poured into a quartz tube with an inner diameter of 8 mm, and quartz wool and iron wire were used for fixation. The quartz tube was placed in a tube furnace, and the actual temperature of the catalytic reaction was adjusted by controlling the heating temperature of the tube furnace. The gas components were: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), and the rest was N2. The total gas flow was 500 mL / min, and the temperature was controlled at 90-210 ℃. Each temperature was kept stable for 30 min. The NO concentration was tested by using a Laoying 3021 type portable carbon emission monitor. The denitration activity of the catalyst at 90 ℃ reached 91.2% in 5 min, and the denitration efficiency at 120-210 ℃ was 100% in 5 min.

[0075] Comparative Example 1

[0076] (1) Preparation of the carrier

[0077] Except that the microfluidic gas jet spinning method was not used for the preparation of the catalyst carrier, but the blending method was used for the preparation, and the other conditions were the same as in Example 1.

[0078] (2) Catalyst activity test

[0079] 1 mL of the catalyst with a particle size of 40-60 mesh was poured into a quartz tube with an inner diameter of 8 mm, and quartz wool and iron wire were used for fixation. The quartz tube was placed in a tube furnace, and the actual temperature of the catalytic reaction was adjusted by controlling the heating temperature of the tube furnace. The gas components were: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), and the rest was N2. The total gas flow was 500 mL / min, and the temperature was controlled at 90-210 ℃. Each temperature was kept stable for 30 min. The NO concentration was tested by using a Laoying 3021 type portable carbon emission monitor. The denitration activity of the catalyst at 90 ℃ reached 91.2% in 5 min, and the denitration efficiency at 120-210 ℃ was 100% in 5 min.

[0080] (3) Comparison effect

[0081] Compared with Example 1, the catalyst is not prepared by microfluidic gas-jet spinning method, but is prepared by electrospinning method, as shown in Figure 2 The catalyst carrier prepared has long fiber shape and does not have nanocage structure, loses the effect of limited structure, has poor combination with catalytically active components, and has low low-temperature catalytic activity of the catalyst.

[0082] Comparative Example 2

[0083] (1) Preparation of catalyst

[0084] Except that polyvinylpyrrolidone is not used as a crystal face regulator during preparation of the catalyst, other conditions are the same as in Example 2.

[0085] (2) Catalytic activity test

[0086] 40-60 mesh catalyst 1 mL is taken and poured into a quartz tube with an inner diameter of 8 mm, and quartz wool and iron wire mesh are used for fixation, and the quartz tube is placed in a tube furnace, and the actual temperature of the catalytic reaction is adjusted by controlling the heating temperature of the tube furnace. The gas components are: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), and the rest is N2, and the total flow rate of the gas is 500 mL / min, and the control temperature is 90-210℃, and each 30℃ stays stable for 30 min, and the NO concentration is tested by using Laoyang 3021 type portable carbon emission monitor. The denitration activity of the catalyst at 90℃ is 71.3% in 5 min, and the denitration efficiency is 85.6% in 5 min at 180℃;

[0087] (3) Comparison effect

[0088] Compared with Example 2( Figure 3 ), polyvinylpyrrolidone is not used as a crystal face regulator during preparation of the catalyst, Figure 4 The exposure of the CeO2(100) crystal face of the shaped catalyst active component is reduced, the adsorption capacity of the catalyst for NO and NH3 gas is weakened, which is not conducive to the low-temperature adsorption and activation process of the catalyst, thereby causing a significant decrease in catalytic activity.

[0089] Comparative Example 3

[0090] (1) Preparation of catalyst

[0091] Except that the hydrothermal synthesis method is not used during preparation of the catalyst, but the impregnation method is used, other conditions are the same as in Example 3.

[0092] (2) Catalytic activity test

[0093] Take 40-60 mesh catalyst 1 mL, pour into the inner diameter of 8 mm quartz tube, with quartz wool and iron wire fixed, the quartz tube is placed in the tube furnace, by controlling the heating temperature of the tube furnace to adjust the actual temperature of the catalytic reaction. The gas composition: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), the rest is N2, the total gas flow is 500 mL / min, the control temperature is 90-210℃, every 30℃ stop for 30 min, using Laoying 3021 type portable carbon emission monitor to test the concentration of NO. The denitration activity of the catalyst at 90℃ is 62.4% in 5 min, and the denitration efficiency at 210℃ is 76.3% in 5 min;

[0094] (3) Comparative effect

[0095] Compared with Example 3, the hydrothermal synthesis method is not used in the preparation of the catalyst, but the ordinary impregnation method is used instead. The active component of the catalyst prepared by impregnation method is not uniformly distributed on the surface of the carrier, and is prone to agglomeration. The number of active sites of the catalyst is reduced, resulting in a significant decrease in catalytic activity.

Claims

1. A low-temperature rare earth-based denitration catalyst, characterized by: The catalyst takes TiO2-ZrO2 nanocage as a carrier and Ce-Sm-La rare earth composite oxide as an active component; the TiO2-ZrO2 nanocage catalyst carrier is synthesized by a micro-fluidic gas-jet spinning method, polyvinylpyrrolidone is used as a crystal face regulator, the rare earth metal oxide is in-situ grown on the surface of the carrier by a hydrothermal method as the catalytic active component, and the low-temperature rare earth-based denitration catalyst is obtained by drying and calcination; wherein, the mass percentage of the active component is 5-10% based on the mass of the carrier.

2. The low-temperature rare earth-based de-NOx catalyst according to claim 1, characterized by: The mass ratio of titanium oxide to zirconium oxide in the TiO2-ZrO2 nanocage carrier is 1:(0.6-1.5). 3.The low-temperature rare earth-based de-NOx catalyst according to claim 1, characterized by: The mass ratio of cerium oxide, samarium oxide and lanthanum oxide in the Ce-Sm-La composite oxide is 1:(0.2-0.5):(0.3-0.5) in turn.

4. A process for the preparation of the catalyst of claim 1, characterized in that: The catalyst is prepared by the following method: (1) Preparation of the spinning solution Tetrabutyl titanate, zirconium oxychloride and polyacrylonitrile are dissolved in N,N-dimethylformamide to obtain a spinning solution by stirring uniformly at room temperature; (2) Preparation of the carrier The spinning solution is injected into the micro-pore channel of the micro-fluid control chip by a micro-injection pump, and then is formed by gas-jet spinning through the high-speed airflow of the micro-fluid gas-jet spinning machine; after the fiber formation, the carrier is transferred to a muffle furnace for calcination to obtain the TiO2-ZrO2 nanocage carrier; (3) Preparation of the active component precursor solution Cerium salt, samarium salt, lanthanum salt and polyvinylpyrrolidone are weighed and added to deionized water to obtain the active component precursor solution by stirring uniformly; (4) Preparation of the catalyst The TiO2-ZrO2 nanocage carrier prepared in step (2) and the active component precursor solution prepared in step (3) are transferred to a polytetrafluoroethylene hydrothermal reactor for hydrothermal reaction; after the hydrothermal reaction, the mixture is taken out and placed in a forced air drying oven for drying, and then is placed in a muffle furnace for calcination to obtain the low-temperature rare earth-based denitration catalyst.

5. The method of claim 4, wherein: The mass ratio of tetrabutyl titanate, zirconium oxychloride, polyacrylonitrile and N,N-dimethylformamide in step (1) is 1:(0.5-1):(2-5):(20-50); the molecular weight of the polyacrylonitrile in step (1) is 80000-150000.

6. The method of claim 4, wherein: The injection rate of the micro-injection pump in step (2) is 5-15 ml / h; the air pressure of the micro-fluid gas-jet spinning machine is 0.02-0.1 Mpa; the calcination temperature is 600-800℃, and the calcination time is 4-6 h.

7. The method of claim 4, wherein: The cerium salt in step (3) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the samarium salt is samarium nitrate hexahydrate; and the lanthanum salt is lanthanum nitrate hexahydrate.

8. The preparation method according to claim 4, characterized in that: The hydrothermal temperature in step (4) is 120-200℃, and the hydrothermal time is 5-12 h; the drying temperature in step (4) is 100-120℃, and the drying time is 2-8 h; the calcination temperature in step (4) is 400-600℃, and the calcination time is 2-4 h.

9. The use of the catalyst in claim 1 in low-temperature flue gas denitration.

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