Micron fiber low-temperature rare earth-based denitration catalyst and preparation method thereof

Abstract

The application discloses a kind of micron fiber low-temperature rare-earth-based denitration catalyst and preparation method thereof, the preparation method of the micron fiber low-temperature rare-earth-based denitration catalyst includes: preparation modified sisal fiber, preparation alumina micron fiber carrier and preparation the micron fiber low-temperature rare-earth-based denitration catalyst.According to the preparation method of the micron fiber low-temperature rare-earth-based denitration catalyst of the embodiment of the application, the modified sisal silk in the preparation method can promote the growth of aluminum salt to alumina micron fiber carrier, both can increase the specific surface area of alumina micron fiber carrier, promote active component and promoter component on the surface of alumina micron fiber carrier uniform loading, also can be converted into carbon fiber after calcination, enhance catalyst mechanical strength;By drying calcination, oxidation of active component, so that micron fiber low-temperature rare-earth-based denitration catalyst has excellent redox performance and oxygen storage and release performance, when carrying out low-temperature denitration, with good catalytic activity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection catalysis, and particularly relates to a micron fiber low-temperature rare earth-based denitration catalyst and a preparation method thereof. BACKGROUND

[0002] Coal-fired power plants, as one of the main energy production and consumption units in the world, are one of the main sources of atmospheric pollutants such as nitrogen oxides. Nitrogen oxides are not only one of the main components of air pollution, but also can cause a series of environmental problems, such as acid rain, photochemical smog and harm to human health. Traditional denitration technologies, such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR), have been widely used in the removal of NO x x under high-temperature conditions. However, these technologies usually operate at relatively high temperatures (e.g., above 300℃). With increasingly stringent emission standards and higher requirements for energy saving and emission reduction, denitration technologies under low-temperature conditions have gradually become a research hotspot. However, under low-temperature conditions, the catalytic activity of the catalyst is poor, and the denitration efficiency is often severely affected, and the mechanical strength of the catalyst is also low, and when water vapor adheres to the surface of the catalyst, the mechanical strength of the catalyst is further reduced, which leads to the collapse of the catalyst during long-term application. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present application is to propose a preparation method of a micron fiber low-temperature rare earth-based denitration catalyst, which has high mechanical strength, is not easy to collapse when water vapor adheres to the surface of the micron fiber low-temperature rare earth-based denitration catalyst under low-temperature conditions, and has good catalytic activity during low-temperature denitration.

[0004] The present application also proposes a micron fiber low-temperature rare earth-based denitration catalyst prepared by the above preparation method.

[0005] The preparation method of the microfiber low-temperature rare earth-based denitration catalyst according to the first aspect of the present application comprises the following steps: preparing modified sisal fibers, which comprises the following steps: soaking sisal leaves in a sodium chloride solution, removing the outer leaf skin and stripping to extract the sisal fibers, placing the sisal fibers in a citric acid solution, performing ultrasonic and constant-temperature oscillation to obtain fine sisal fibers, washing the fine sisal fibers with deionized water and drying, placing the dried fine sisal fibers in a plasma surface treatment instrument, vacuumizing the plasma surface treatment instrument, then filling oxygen, and then performing surface treatment on the fine sisal fibers to obtain the modified sisal fibers; preparing an alumina microfiber carrier, which comprises the following steps: immersing the modified sisal fibers in an aluminum salt solution to obtain modified sisal fibers adsorbing aluminum salt, reacting ammonia gas volatilized from an ammonia solution with the aluminum salt adsorbed on the modified sisal fibers to obtain modified sisal fibers adsorbing aluminum hydroxide, mixing the modified sisal fibers adsorbing aluminum hydroxide, aluminum salt and deionized water in a hydrothermal reaction kettle to perform reaction, filtering and drying after hydrothermal reaction, and then placing in a tube furnace to pass nitrogen gas for high-temperature calcination to grow the alumina microfiber carrier on the modified sisal fibers; and preparing the microfiber low-temperature rare earth-based denitration catalyst, which comprises the following steps: placing the modified sisal fibers with the alumina microfiber carrier attached thereon in a precursor mixed solution, drying and then calcining to obtain the microfiber low-temperature rare earth-based denitration catalyst, wherein the precursor mixed solution is obtained by uniformly mixing manganese salt, cerium salt, nickel salt and deionized water.

[0006] The preparation method of the microfiber low-temperature rare earth-based denitration catalyst according to the present application can promote the growth of aluminum salt into the alumina microfiber carrier by using the modified sisal fibers in the preparation method, which can not only increase the specific surface area of the alumina microfiber carrier and promote the uniform loading of active components and catalyst component on the surface of the alumina microfiber carrier, but also can be converted into carbon fibers in the later stage to enhance the mechanical strength of the catalyst; the manganese salt, cerium salt and nickel salt are oxidized into manganese oxide, cerium oxide and nickel oxide by drying and calcination, so that the microfiber low-temperature rare earth-based denitration catalyst has excellent redox performance and oxygen storage and release performance, and has good catalytic activity in low-temperature denitration.

[0007] According to some embodiments of the present application, in the step of preparing the modified sisal fibers, the sodium chloride solution has a mass fraction of 5% to 10%, the mass ratio of the sisal leaves to the sodium chloride solution is 1:(30 to 50), the citric acid solution is monohydrate citric acid solution with a mass fraction of 10% to 20%, and the mass ratio of the sisal fibers to the citric acid solution is 1:(40 to 60).

[0008] According to some embodiments of the present application, the process parameters of placing the fine filamentary sisal fibers in a citric acid solution, ultrasonic and constant temperature oscillation include: the power of ultrasonic is 200W-400W, the time of ultrasonic is 30min-60min, the rate of constant temperature oscillation is 100r / min-200r / min, and the time of constant temperature oscillation is 2h-4h.

[0009] According to some embodiments of the present application, the process parameters of drying the cleaned fine filamentary sisal fibers include: the temperature of drying is 30℃-50℃, and the time of drying is 24h-48h.

[0010] According to some embodiments of the present application, the process parameters of placing the dried fine filamentary sisal fibers in a plasma surface treatment instrument for surface treatment include: the mass-volume ratio of the fine filamentary sisal fibers and oxygen is 1g:(20-40)mL, the input voltage during surface treatment is 220V, the working distance is 5mm-10mm, and the scanning rate of plasma flame is 20mm / s-40mm / s.

[0011] According to some embodiments of the present application, in the step of preparing the alumina micron fiber carrier, the aluminum salt is aluminum nitrate or aluminum chloride, the mass fraction of the aluminum salt in the aluminum salt solution is 20%-40%, and the mass ratio of the modified sisal fibers to the aluminum salt solution is 1:(0.5-1).

[0012] According to some embodiments of the present application, the ammonia gas volatilized from the ammonia solution reacts with the adsorbed aluminum salt on the modified sisal fibers, including: placing the modified sisal fibers adsorbing aluminum salt in a beaker mouth, placing the ammonia solution in the beaker, and placing the beaker in a water bath heater for water bath heating, so that the volatilized ammonia gas reacts with the adsorbed aluminum salt on the modified sisal fibers.

[0013] According to some embodiments of the present application, the ammonia solution is an ammonia solution with a mass fraction of 20%-25%, and the mass ratio of the modified sisal fibers adsorbing aluminum salt to the ammonia solution is 1:(30-50).

[0014] According to some embodiments of the present application, the temperature of the water bath heating is 80℃-90℃, and the time of the water bath heating is 6h-8h.

[0015] According to some embodiments of the present application, the mass ratio of the modified sisal fibers adsorbing aluminum hydroxide, aluminum salt and deionized water is 1:(5-10):(40-60), the temperature of the hydrothermal reaction is 140℃-160℃, the time of the hydrothermal reaction is 4h-8h, and the drying process parameters of filtering and drying after the hydrothermal reaction include: the temperature of drying is 80℃-100℃, and the time of drying is 12h-24h.

[0016] According to some embodiments of the present application, in the step of preparing the alumina micrometer fiber carrier, the rate of nitrogen gas flowing into the tubular furnace is 20 mL / min-40 mL / min, the temperature of high-temperature calcination is 500 DEG C-600 DEG C, and the time of high-temperature calcination is 2 h-4 h.

[0017] According to some embodiments of the present application, the manganese salt is manganese chloride or manganese nitrate hexahydrate, the cerium salt is cerium chloride or cerium nitrate hexahydrate, and the nickel salt is nickel nitrate hexahydrate or nickel chloride hexahydrate, and the mass ratio of the manganese salt to deionized water is 1:(20-30).

[0018] According to some embodiments of the present application, in the step of preparing the micrometer fiber low-temperature rare earth-based denitration catalyst, the temperature of drying is 80 DEG C-100 DEG C, the time of drying is 12 h-24 h, the temperature of calcination is 500 DEG C-600 DEG C, and the time of calcination is 2 h-4 h.

[0019] The micrometer fiber low-temperature rare earth-based denitration catalyst according to the second aspect of the embodiments of the present application is prepared by the above-mentioned method for preparing a micrometer fiber low-temperature rare earth-based denitration catalyst, the mass percentage of the active component in the micrometer fiber low-temperature rare earth-based denitration catalyst is 3%-5%, the mass percentage of the cocatalyst component in the micrometer fiber low-temperature rare earth-based denitration catalyst is 1%-3%, and the mass ratio of manganese oxide to cerium oxide in the active component is 1:(0.5-1).

[0020] The micrometer fiber low-temperature rare earth-based denitration catalyst according to the embodiments of the present application has high mechanical strength, and is not easy to collapse when water vapor adheres to the surface of the micrometer fiber low-temperature rare earth-based denitration catalyst during low-temperature denitration, and has good catalytic activity.

[0021] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0023] Figure 1 is a flowchart of a method for preparing a micrometer fiber low-temperature rare earth-based denitration catalyst according to some embodiments of the present application;

[0024] Figure 2is a field emission scanning electron microscope (FE-SEM) image of the microfiber low-temperature rare earth-based denitration catalyst in Example 1 of the present application. DETAILED DESCRIPTION

[0025] Embodiments of the present application are described in detail below with reference to examples illustrated in the accompanying drawings, in which the same or similar components are denoted by the same or similar reference numerals throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are for the purpose of explanation only and are not to be understood as limiting the present application.

[0026] The preparation method of the microfiber low-temperature rare earth-based denitration catalyst according to the first embodiment of the first aspect of the present application comprises:

[0027] The modified sisal fibers are prepared by immersing sisal leaves in a sodium chloride solution, removing the outer leaf skin and peeling to extract the sisal fibers, placing the sisal fibers in a citric acid solution, performing ultrasonic and constant temperature oscillation to obtain fine sisal fibers, washing the fine sisal fibers with deionized water and drying, placing the dried fine sisal fibers in a plasma surface treatment instrument, vacuumizing the plasma surface treatment instrument, then filling oxygen, and then performing surface treatment on the fine sisal fibers to obtain the modified sisal fibers;

[0028] The alumina microfiber carrier is prepared by immersing the modified sisal fibers in an aluminum salt solution to obtain modified sisal fibers adsorbing aluminum salt, reacting ammonia gas volatilized from an ammonia solution with the aluminum salt adsorbed on the modified sisal fibers to obtain modified sisal fibers adsorbing aluminum hydroxide, mixing the modified sisal fibers adsorbing aluminum hydroxide, aluminum salt and deionized water in a hydrothermal reaction kettle for reaction, filtering and drying after hydrothermal reaction, and then placing in a tube furnace and passing nitrogen gas for high-temperature calcination to grow alumina microfiber carriers on the modified sisal fibers;

[0029] The microfiber low-temperature rare earth-based denitration catalyst is prepared by placing the modified sisal fibers with the alumina microfiber carriers attached thereon in a precursor mixed solution, drying and then calcining to obtain the microfiber low-temperature rare earth-based denitration catalyst, wherein the precursor mixed solution is obtained by uniformly mixing manganese salt, cerium salt, nickel salt and deionized water, wherein the manganese salt and the cerium salt act as active components and the nickel salt acts as a cocatalyst component to play a catalytic role.

[0030] The micron fiber low-temperature rare earth-based denitration catalyst uses modified sisal fibers as a template agent, which can not only convert aluminum salt into alumina fiber to increase the specific surface area of the alumina micron fiber carrier, but also convert the modified sisal fiber into carbon fiber to further improve the mechanical strength of the carrier by using the toughness and mechanical strength of the carbon fiber itself; meanwhile, the excellent redox performance and oxygen storage and release performance of manganese oxide, cerium oxide and nickel oxide can improve the low-temperature catalytic activity of the micron fiber low-temperature rare earth-based denitration catalyst; and the active component and the catalyst component are uniformly loaded on the surface of the alumina micron fiber carrier to improve the exposure ratio of the active sites, thereby effectively ensuring the low-temperature activity and mechanical strength of the micron fiber low-temperature rare earth-based denitration catalyst.

[0031] In the preparation process of the micron fiber low-temperature rare earth-based denitration catalyst, the sisal fiber with excellent mechanical strength and toughness is first selected and extracted, then the fine filament-like sisal fiber with high cleanliness is obtained by using weak acid washing, ultrasonic and constant temperature oscillation, and then the fiber hydroxyl concentration is increased by using plasma surface treatment, so as to facilitate the adsorption of aluminum salt on the surface of the modified sisal fiber, and then the aluminum salt adsorbed on the surface of the modified sisal fiber is converted into aluminum hydroxide by using ammonia water, which can promote the growth of aluminum salt on the surface of the modified sisal fiber in the solution during the hydrothermal reaction process, and ensure that the aluminum salt can finally form an alumina micron fiber carrier under hydrothermal conditions, and finally the active component and the catalyst component are loaded on the surface of the alumina micron fiber carrier by using the impregnation calcination method. In this process, the nitrogen tube furnace calcination can not only ensure that the aluminum salt is completely converted into alumina, but also promote the conversion of the modified sisal fiber into carbon fiber.

[0032] The carbon fiber converted from the modified sisal fiber has high mechanical strength, and water vapor is easy to condense on the surface of the micron fiber low-temperature rare earth-based denitration catalyst in a low-temperature environment, but the micron fiber low-temperature rare earth-based denitration catalyst is not easy to collapse due to its high mechanical strength.

[0033] According to the preparation method of the micron fiber low-temperature rare earth-based denitration catalyst, the fine filament-like modified sisal fiber can promote the growth of aluminum salt into an alumina micron fiber carrier, which can not only increase the specific surface area of the alumina micron fiber carrier, promote the uniform loading of the active component and the catalyst component on the surface of the alumina micron fiber carrier, but also convert into carbon fiber in the later stage to enhance the mechanical strength of the catalyst, and water vapor is not easy to cause the micron fiber low-temperature rare earth-based denitration catalyst to collapse when adhering to the surface of the micron fiber low-temperature rare earth-based denitration catalyst in a low-temperature environment; the activation components such as manganese salt, cerium salt and nickel salt are oxidized into manganese oxide, cerium oxide and nickel oxide by drying and calcination, so that the micron fiber low-temperature rare earth-based denitration catalyst has excellent redox performance and oxygen storage and release performance, and has good catalytic activity during low-temperature denitration.

[0034] According to some embodiments of the present application, in the step of preparing the modified sisal fiber, the sodium chloride solution is a sodium chloride solution with a mass fraction of 5% to 10%, the mass ratio of the sisal leaves to the sodium chloride solution is 1:(30 to 50), the citric acid solution is a monohydrate citric acid solution with a mass fraction of 10% to 20%, and the mass ratio of the sisal fiber to the citric acid solution is 1:(40 to 60).

[0035] The sodium chloride solution can create an environment conducive to extracting the sisal fiber, and the citric acid solution can play a role in weak acid washing, thereby improving the dry breaking strength and dry breaking elongation of the sisal fiber and enhancing the mechanical properties of the sisal fiber. For example, the mass fraction of the sodium chloride solution can be 5%, 6%, 7%, 8%, 9%, 10%, etc.; the mass ratio of the sisal leaves to the sodium chloride solution can be 1:30, 1:35, 1:40, 1:45, 1:50, etc.; the mass fraction of the monohydrate citric acid solution can be 10%, 12%, 14%, 16%, 18%, 20%, etc.; and the mass ratio of the sisal fiber to the citric acid solution can be 1:40, 1:45, 1:50, 1:55, 1:60, etc. If the mass fraction of the sodium chloride solution and the monohydrate citric acid solution is too high, the structure of the sisal fiber can be easily damaged; if the mass fraction of the sodium chloride solution and the monohydrate citric acid solution is too low, the washing effect can not be good.

[0036] According to some embodiments of the present application, the process parameters of placing the sisal fiber in the citric acid solution and performing ultrasonic and constant-temperature oscillation include: the power of the ultrasonic is 200 W to 400 W, the time of the ultrasonic is 30 min to 60 min, the rate of the constant-temperature oscillation is 100 r / min to 200 r / min, and the time of the constant-temperature oscillation is 2 h to 4 h.

[0037] The ultrasonic and constant-temperature oscillation can effectively promote the uniform and rapid penetration of the citric acid solution into the fiber. For example, the power of the ultrasonic can be 200 W, 250 W, 300 W, 350 W, 400 W, etc.; the time of the ultrasonic can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.; the rate of the constant-temperature oscillation can be 100 r / min, 120 r / min, 140 r / min, 160 r / min, 180 r / min, 200 r / min, etc.; and the time of the constant-temperature oscillation can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc. If the power of the ultrasonic is too fast, the time is too long, or the speed of the constant-temperature oscillation is too fast, the time is too long, the structure of the modified sisal fiber can be easily damaged; if the power of the ultrasonic is too slow, the time is too short, or the speed of the constant-temperature oscillation is too slow, the time is too short, it can be difficult to obtain fine filamentous sisal fiber with high enough cleanliness.

[0038] According to some embodiments of the present application, the process parameters for drying the cleaned fine sisal fibers include a drying temperature of 30-50 DEG C and a drying time of 24-48 hours.

[0039] For example, the drying temperature can be 30 DEG C, 35 DEG C, 40 DEG C, 45 DEG C, 50 DEG C, etc. and the drying time can be 24 hours, 30 hours, 36 hours, 42 hours, 48 hours, etc. If the drying temperature is too high or the drying time is too long, the fiber structure of the fine sisal fibers can be damaged. If the drying temperature is too high or the drying time is too short, the drying effect is not good.

[0040] According to some embodiments of the present application, the process parameters for surface treatment of the dried fine sisal fibers in the plasma surface treatment instrument include a mass-volume ratio of the fine sisal fibers to oxygen of 1 g:(20-40) mL, an input voltage of 220 V during surface treatment, a working distance of 5-10 mm, and a plasma flame scanning rate of 20-40 mm / s.

[0041] For example, the mass-volume ratio of the fine sisal fibers to oxygen can be 1 g:20 mL, 1 g:25 mL, 1 g:30 mL, 1 g:35 mL, 1 g:40 mL, etc. and the plasma flame scanning rate can be 20 mm / s, 25 mm / s, 30 mm / s, 35 mm / s, 40 mm / s, etc. The oxygen treatment of the fine sisal fibers in the plasma surface treatment instrument improves the hydroxyl concentration of the fine sisal fibers, which is conducive to the adsorption of aluminum salt on the surface of the modified sisal fibers.

[0042] According to some embodiments of the present application, in the step of preparing the alumina micron fiber carrier, the aluminum salt is aluminum nitrate or aluminum chloride, the mass fraction of the aluminum salt in the aluminum salt solution is 20-40%, and the mass ratio of the modified sisal fibers to the aluminum salt solution is 1:(0.5-1).

[0043] For example, the aluminum salt can be aluminum nitrate, the mass fraction of the aluminum salt in the aluminum salt solution can be 20%, 25%, 30%, 35%, 40%, etc. and the mass ratio of the modified sisal fibers to the aluminum salt solution can be 2:1, 3:2, 1:1, etc.

[0044] According to some embodiments of the present application, the ammonia gas volatilized from the ammonia solution reacts with the aluminum salt adsorbed on the modified sisal fibers, which includes placing the modified sisal fibers adsorbing the aluminum salt in the mouth of a beaker, placing an ammonia solution in the beaker, and placing the beaker in a water bath to heat, so that the volatilized ammonia gas reacts with the aluminum salt adsorbed on the modified sisal fibers.

[0045] The water bath heating can promote the ammonia water solution to volatilize into ammonia gas, and the ammonia gas volatilized reacts with the aluminum salt adsorbed on the modified sisal fibers to convert the aluminum salt adsorbed on the surface of the modified sisal fibers into aluminum hydroxide.

[0046] According to some embodiments of the present application, the ammonia water solution is an ammonia water solution with a mass fraction of 20% to 25%, and the mass ratio of the modified sisal fibers adsorbing aluminum salt to the ammonia water solution is 1:(30 to 50).

[0047] For example, the mass fraction of the ammonia water solution can be 20%, 21%, 22%, 23%, 24%, 25%, etc., and the mass ratio of the modified sisal fibers adsorbing aluminum salt to the ammonia water solution can be 1:30, 1:35, 1:40, 1:45, 1:50, etc. By adjusting the mass fraction of the ammonia water solution and the mass ratio of the modified sisal fibers to the ammonia water solution, the volatilization rate of the ammonia water and the reaction rate of the aluminum salt adsorbed on the modified sisal fibers can be adjusted, so that the aluminum salt adsorbed on the surface of the modified sisal fibers is converted into an appropriate amount of aluminum hydroxide, which is conducive to the subsequent hydrothermal reaction to make the aluminum salt continue to grow on the surface of the modified sisal fibers.

[0048] According to some embodiments of the present application, the temperature of the water bath heating is 80℃ to 90℃, and the time of the water bath heating is 6h to 8h.

[0049] For example, the temperature of the water bath heating can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, etc., and the time of the water bath heating can be 6h, 6.5h, 7h, 7.5h, 8h, etc. By adjusting the temperature and time of the water bath heating, the volatilization rate of the ammonia water and the reaction rate of the aluminum salt adsorbed on the modified sisal fibers can be adjusted, so that the aluminum salt adsorbed on the surface of the modified sisal fibers is converted into an appropriate amount of aluminum hydroxide, which is conducive to the subsequent hydrothermal reaction to make the aluminum salt continue to grow on the surface of the modified sisal fibers.

[0050] According to some embodiments of the present application, the mass ratio of the modified sisal fibers adsorbing aluminum hydroxide to the aluminum salt to the deionized water is 1:(5 to 10):(40 to 60), the temperature of the hydrothermal reaction is 140℃ to 160℃, the time of the hydrothermal reaction is 4h to 8h, and the drying process parameters after the filtration and drying include that the temperature of the drying is 80℃ to 100℃ and the time of the drying is 12h to 24h.

[0051] For example, the mass ratio of modified sisal fibers, aluminum salt and deionized water can be 1:5:40, 1:5:50, 1:5:60, 1:10:40, 1:10:50, 1:10:60, etc.; the temperature of the hydrothermal reaction can be 140℃, 145℃, 150℃, 155℃, 160℃, etc.; the time of the hydrothermal reaction can be 4h, 5h, 6h, 7h, 8h, etc.; the temperature of the filtration and drying after the hydrothermal reaction can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the time of the filtration and drying after the hydrothermal reaction can be 12h, 16h, 20h, 24h, etc. By adjusting the temperature and time of the hydrothermal reaction at the same time, the aluminum salt in the solution can continue to grow on the surface of the modified sisal fibers during the hydrothermal reaction process, and it is ensured that the aluminum salt can finally form an alumina micro-fiber carrier under the hydrothermal condition.

[0052] According to some embodiments of the present application, in the step of preparing the alumina micro-fiber carrier, the rate of nitrogen gas flowing into the tube furnace is 20mL / min-40mL / min, the temperature of high-temperature calcination is 500℃-600℃, and the time of high-temperature calcination is 2h-4h.

[0053] For example, the rate of nitrogen gas flowing into the tube furnace can be 20mL / min, 25mL / min, 30mL / min, 35mL / min, 40mL / min, etc.; the temperature of high-temperature calcination can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc.; and the time of high-temperature calcination can be 2h, 2.5h, 3h, 3.5h, 4h, etc. By adjusting the appropriate temperature and time of high-temperature calcination, the aluminum salt can be completely converted into alumina, and by flowing nitrogen gas into the tube furnace at an appropriate rate, the modified sisal fibers can be prevented from being oxidized.

[0054] According to some embodiments of the present application, the manganese salt is manganese chloride or manganese nitrate hexahydrate, the cerium salt is cerium chloride or cerium nitrate hexahydrate, and the nickel salt is nickel nitrate hexahydrate or nickel chloride hexahydrate, and the mass ratio of the manganese salt and deionized water is 1:(20-30).

[0055] For example, the manganese salt can be manganese chloride or manganese nitrate hexahydrate, the cerium salt can be cerium chloride or cerium nitrate hexahydrate, and the nickel salt can be nickel nitrate hexahydrate or nickel chloride hexahydrate, and the mass ratio of the manganese salt and deionized water can be 1:20, 1:22, 1:24, 1:26, 1:28, 1:30, etc.

[0056] According to some embodiments of the present application, in the step of preparing the micro-fiber low-temperature rare earth-based denitration catalyst, the temperature of drying is 80℃-100℃, the time of drying is 12h-24h, the temperature of calcination is 500℃-600℃, and the time of calcination is 2h-4h.

[0057] For example, the drying temperature can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the drying time can be 12h, 16h, 20h, 24h, etc.; the calcination temperature can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc.; and the calcination time can be 2h, 2.5h, 3h, 3.5h, 4h, etc. High-temperature calcination makes the active component and the promoter component uniformly loaded on the surface of the alumina fiber, improves the exposure ratio of the active sites, and also promotes the conversion of the modified sisal fibers into carbon fibers, thereby making the micron fiber low-temperature rare earth-based denitration catalyst have good low-temperature activity and mechanical strength.

[0058] According to the micron fiber low-temperature rare earth-based denitration catalyst prepared by the preparation method of the micron fiber low-temperature rare earth-based denitration catalyst, the mass percentage of the active component in the micron fiber low-temperature rare earth-based denitration catalyst is 3% to 5%, the mass percentage of the promoter component in the micron fiber low-temperature rare earth-based denitration catalyst is 1% to 3%, and the mass ratio of manganese oxide to cerium oxide in the active component is 1:(0.5 to 1).

[0059] For example, the mass percentage of the active component in the micron fiber low-temperature rare earth-based denitration catalyst can be 3%, 3.5%, 4%, 4.5%, 5%, etc.; the mass percentage of the promoter component in the micron fiber low-temperature rare earth-based denitration catalyst can be 1%, 1.5%, 2%, 2.5%, 3%, etc.; and the mass ratio of manganese oxide to cerium oxide in the active component can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, etc.

[0060] The modified sisal fiber in the preparation method can promote the growth of aluminum salt into an alumina micron fiber carrier, increase the specific surface area of the carrier, promote the uniform loading of the active component and the promoter component on the surface of the carrier, and also convert into carbon fiber in the later stage to enhance the mechanical strength of the catalyst. The active component in the micron fiber low-temperature rare earth-based denitration catalyst is manganese oxide and cerium oxide, and the promoter component is nickel oxide. The active component and the promoter component in the micron fiber low-temperature rare earth-based denitration catalyst have good redox performance and oxygen storage and release performance, and the active component and the promoter component are uniformly distributed on the surface of the alumina micron fiber carrier under the micro interface, which is beneficial to the maximization of the utilization of active sites and makes the micron fiber low-temperature rare earth-based denitration catalyst maintain good catalytic activity at low temperature.

[0061] The micro-fiber low-temperature rare earth-based denitration catalyst has high mechanical strength, and is not prone to collapse when water vapor adheres to the surface of the micro-fiber low-temperature rare earth-based denitration catalyst in a low-temperature environment. The micro-fiber low-temperature rare earth-based denitration catalyst has good catalytic activity in low-temperature denitration.

[0062] Example 1,

[0063] The preparation method of the micro-fiber low-temperature rare earth-based denitration catalyst of Example 1 is as follows:

[0064] (1) Preparation of modified sisal fiber template

[0065] 100 g of sisal leaves are weighed and soaked in 3000 g of a 5% sodium chloride solution. After soaking for 7 days, the outer leaf skin is removed and the sisal fibers are extracted. Then, 20 g of the sisal fibers are weighed and placed in 800 g of a 10% citric acid solution. After being ultrasonically treated for 60 min at a power of 200 W, the fine sisal fibers are placed in a constant-temperature oscillator and oscillated at 30°C and 100 r / min for 4 h. The fine sisal fibers are then cleaned with deionized water and dried in an oven at 30°C for 48 h. Finally, 2 g of the dried fine sisal fibers are placed in a plasma surface treatment instrument, which is vacuumed and then filled with 40 mL of oxygen. Surface treatment is then performed (input voltage: 220 V, working distance: 5 mm, and plasma flame scanning rate: 20 mm / s) to increase the concentration of hydroxyl groups on the surface of the fine sisal fibers, thereby obtaining modified sisal fibers. The cycle of plasma surface modification is repeated until the fine sisal fibers are completely treated.

[0066] (2) Preparation of alumina micro-fiber carrier

[0067] 5 g of the modified sisal fibers obtained in step (1) are weighed and immersed in 2.5 g of a 20% aluminum nitrate solution. The modified sisal fibers adsorbed with aluminum nitrate are then placed in the mouth of a beaker, 165 g of an ammonia water solution with a mass fraction of 20% is placed in the beaker, and the beaker is placed in a water bath at 80°C for 8 h of water bath heating, so that ammonia gas is volatilized and reacts with aluminum nitrate. Finally, the modified sisal fibers adsorbed with aluminum hydroxide are obtained. 5 g of the modified sisal fibers adsorbed with aluminum hydroxide, 25 g of aluminum nitrate, and 200 g of deionized water are mixed and placed in a hydrothermal reaction kettle. After 8 h of hydrothermal reaction at 140°C, the mixture is filtered, dried in an oven at 80°C for 24 h, and then placed in a tube furnace. Nitrogen gas is introduced into the tube furnace at a rate of 20 mL / min, and the mixture is calcined at 500°C for 4 h to obtain an alumina micro-fiber carrier.

[0068] (3) Preparation of micro-fiber low-temperature rare earth-based denitration catalyst

[0069] Take 0.289 g of manganese chloride, 0.143 g of cerium chloride, 0.318 g of nickel chloride hexahydrate, 5.780 g of deionized water, mix them well to obtain a precursor mixed solution, then take 10.000 g of the alumina microfiber carrier prepared in step (2) and put it into the precursor mixed solution, dry it at 80℃ for 24 h, then place it in a muffle furnace and calcine it at 500℃ for 4 h to obtain a microfiber low-temperature rare earth-based denitration catalyst (the mass percentage of the active component is 3% and the mass percentage of the catalyst component is 1% based on the mass of the carrier; the mass ratio of manganese oxide and cerium oxide in the active component is 1:0.5; the FE-SEM image of the microfiber low-temperature rare earth-based denitration catalyst is shown in Figure 1 Fig. 1, the alumina microfiber carrier presents a microfiber shape, and the active component and the catalyst component present a nanoparticle shape and are evenly distributed on the surface of the carrier);

[0070] (4) Catalytic activity test

[0071] Take 20-40 mesh catalyst 1 mL, pour it into a quartz tube with an inner diameter of 6 mm, fix it with quartz wool and cerium wire, place the quartz tube in a tube furnace, adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace, the inlet gas components are: NO (500 ppm), NH3(500 ppm), O2(10 vol.%), and the rest is N2, the total gas flow is 500 mL / min, the temperature is set to 150℃, the flue gas analyzer measures the NO inlet and outlet concentrations, and the NO removal efficiency of the catalyst is 95.4% at 150℃ for 3 min.

[0072] Example 2,

[0073] The preparation method of the microfiber low-temperature rare earth-based denitration catalyst of Example 2 is as follows:

[0074] (1) Preparation of modified sisal fiber template agent

[0075] Take 100 g of sisal leaf and soak it in 5000 g of a 10% by mass sodium chloride solution. After 7 days of soaking, remove the outer leaf skin and peel off the sisal fibers. Then take 20 g of the sisal fibers and place them in 1200 g of a 20% by mass citric acid solution. After ultrasonic treatment for 30 min at a power of 400 W, place the fibers in a constant-temperature oscillator at 30°C and 200 r / min for 2 h to obtain fine sisal fibers. Then clean the fine sisal fibers with deionized water, and then place them in an oven at 50°C for drying for 24 h. Finally, take 2 g of the dried fine sisal fibers and place them in a plasma surface treatment instrument. Vacuumize the instrument, then fill it with 80 mL of oxygen, and then perform surface treatment (input voltage: 220 V, working distance: 10 mm, plasma flame scanning rate: 40 mm / s) to increase the concentration of hydroxyl groups on the surface of the fine sisal fibers, thereby obtaining modified sisal fibers. Repeat the step of plasma surface modification until the fine sisal fibers are treated.

[0076] (2) Preparation of alumina microfiber carrier

[0077] Take 5 g of the modified sisal fibers obtained in step (1) and immerse them in 5 g of a 40% by mass aluminum chloride solution. Then place the modified sisal fibers adsorbed with aluminum nitrate in a beaker, and place 350 g of a 25% by mass ammonia water solution in the beaker. Place the beaker in a water bath at 90°C and heat for 6 h to make ammonia gas volatilize and react with aluminum nitrate, thereby obtaining modified sisal fibers adsorbed with aluminum hydroxide. Take 5 g of the modified sisal fibers adsorbed with aluminum hydroxide, 50 g of aluminum chloride, and 300 g of deionized water, and mix them in an autoclave. After hydrothermal reaction at 160°C for 4 h, filter and then place the mixture in an oven at 100°C for drying for 12 h. Then place the mixture in a tube furnace and pass nitrogen gas into the furnace at a rate of 40 mL / min, and then perform high-temperature calcination at 600°C for 2 h to obtain an alumina microfiber carrier.

[0078] (3) Preparation of microfiber low-temperature rare earth-based denitration catalyst

[0079] Take 0.825 g of manganese nitrate hexahydrate, 0.631 g of cerium nitrate hexahydrate, 1.168 g of nickel nitrate hexahydrate, and 24.750 g of deionized water, and mix them uniformly to obtain a precursor mixed solution. Then take 10.000 g of the alumina microfiber carrier prepared in step (2) and place it in the precursor mixed solution. After drying at 100°C for 12 h, place the mixture in a muffle furnace and perform calcination at 600°C for 2 h to obtain a microfiber low-temperature rare earth-based denitration catalyst (the mass percentage content of the active component is 5% and the mass percentage content of the catalyst component is 3% based on the mass of the carrier, and the mass ratio of manganese oxide to cerium oxide in the active component is 1:1).

[0080] (4) Catalytic activity test

[0081] Take 20-40 mesh catalyst 1 mL, pour into the inner diameter of 6 mm quartz tube, with quartz wool and cerium 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 inlet gas composition: NO (500 ppm), NH3(500 ppm), O2(10 vol.%), the rest is N2, the total gas flow is 500 mL / min, the temperature is set to 150℃, the flue gas analyzer measures the NO inlet and outlet concentration, the NO removal efficiency of the catalyst is 99.6% at 150℃ for 3 min.

[0082] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0083] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for preparing a micron-fiber low-temperature rare-earth-based denitration catalyst, characterized in that, include: The preparation of modified sisal fiber includes: soaking sisal leaves in sodium chloride solution, removing the outer leaf bark and peeling to extract sisal fiber, placing the sisal fiber in citric acid solution, subjecting it to ultrasonic and constant temperature oscillation to obtain fine filamentous sisal fiber, washing the fine filamentous sisal fiber with deionized water and drying it, placing the dried fine filamentous sisal fiber in a plasma surface treatment instrument, evacuating the plasma surface treatment instrument, then filling it with oxygen, and then performing surface treatment on the fine filamentous sisal fiber to obtain the modified sisal fiber; The preparation of alumina microfiber carriers includes: impregnating the modified sisal fiber in an aluminum salt solution to obtain modified sisal fiber adsorbed with aluminum salt; reacting the aluminum salt adsorbed on the modified sisal fiber with ammonia gas volatilized from the ammonia solution to obtain modified sisal fiber adsorbed with aluminum hydroxide; mixing the modified sisal fiber adsorbed with aluminum hydroxide, aluminum salt, and deionized water in a hydrothermal reactor for reaction; filtering and drying after hydrothermal reaction; and then placing the mixture in a tube furnace and calcining it at high temperature with nitrogen gas to grow the alumina microfiber carrier on the modified sisal fiber. To prepare the microfiber low-temperature rare earth-based denitration catalyst, modified sisal fibers with the alumina microfiber carrier attached are placed in a precursor mixed solution, dried, and then calcined to obtain the microfiber low-temperature rare earth-based denitration catalyst. The precursor mixed solution is obtained by uniformly mixing manganese salt, cerium salt, nickel salt, and deionized water.

2. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, In the step of preparing the modified sisal fiber, the sodium chloride solution is a sodium chloride solution with a mass fraction of 5% to 10%, the mass ratio of the sisal leaf to the sodium chloride solution is 1:(30 to 50), the citric acid solution is a citric acid monohydrate solution with a mass fraction of 10% to 20%, and the mass ratio of the sisal fiber to the citric acid solution is 1:(40 to 60).

3. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, The process parameters for placing the sisal fiber in a citric acid solution and subjecting it to ultrasonic and isothermal oscillation include: ultrasonic power of 200W~400W, ultrasonic time of 30min~60min, isothermal oscillation rate of 100r / min~200r / min, and isothermal oscillation time of 2h~4h. The process parameters for drying the cleaned fine sisal fibers include: drying temperature of 30℃~50℃ and drying time of 24h~48h.

4. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, The process parameters for surface treatment of dried sisal fibers in a plasma surface treatment instrument include: the mass-to-volume ratio of the sisal fibers to oxygen is 1g:(20~40)mL, the input voltage during surface treatment is 220V, the working distance is 5mm~10mm, and the plasma flame scanning rate is 20mm / s~40mm / s.

5. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, In the step of preparing alumina microfiber carrier, the aluminum salt is aluminum nitrate or aluminum chloride, and the mass fraction of aluminum salt in the aluminum salt solution is 20%~40%; the mass ratio of the modified sisal fiber to the aluminum salt solution is 1:(0.5~1).

6. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, The reaction of ammonia gas volatilized from the ammonia solution with aluminum salts adsorbed on the modified sisal fiber includes: placing the modified sisal fiber with adsorbed aluminum salts at the mouth of a beaker, placing the ammonia solution in the beaker, and placing the beaker in a water bath for heating, so that the volatilized ammonia gas reacts with the aluminum salts adsorbed on the modified sisal fiber.

7. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 6, characterized in that, The ammonia solution is an ammonia solution with a mass fraction of 20%~25%, and the mass ratio of the modified sisal fiber that adsorbs aluminum salt to the ammonia solution is 1:(30~50). And / or, the water bath heating temperature is 80℃~90℃, and the water bath heating time is 6h~8h.

8. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, The mass ratio of the modified sisal fiber, aluminum salt, and deionized water used to adsorb aluminum hydroxide is 1:(5~10):(40~60), the hydrothermal reaction temperature is 140℃~160℃, the hydrothermal reaction time is 4h~8h, and the drying process parameters for filtration and drying after hydrothermal reaction include: drying temperature is 80℃~100℃, and drying time is 12h~24h. And / or, in the step of preparing alumina microfiber carrier, the rate of nitrogen gas introduced into the tube furnace is 20 mL / min to 40 mL / min, the temperature of the high-temperature calcination is 500℃ to 600℃, and the time of the high-temperature calcination is 2h to 4h.

9. The preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst according to claim 1, characterized in that, The manganese salt is manganese chloride or manganese nitrate hexahydrate, the cerium salt is cerium chloride or cerium nitrate hexahydrate, the nickel salt is nickel nitrate hexahydrate or nickel chloride hexahydrate, and the mass ratio of the manganese salt to deionized water is 1:(20~30). And / or, in the step of preparing the micron fiber low-temperature rare earth-based denitration catalyst, the drying temperature is 80℃~100℃, the drying time is 12h~24h, the calcination temperature is 500℃~600℃, and the calcination time is 2h~4h.

10. A micron-fiber low-temperature rare-earth-based denitration catalyst, characterized in that, The micron-fiber low-temperature rare earth-based denitration catalyst is prepared by the preparation method according to any one of claims 1-9. The micron-fiber low-temperature rare earth-based denitration catalyst contains an active component and a co-catalyst component. The active component is manganese oxide and cerium oxide, and the co-catalyst component is nickel oxide. The mass percentage of the active component in the micron-fiber low-temperature rare earth-based denitration catalyst is 3%~5%, and the mass percentage of the co-catalyst component in the micron-fiber low-temperature rare earth-based denitration catalyst is 1%~3%. The mass ratio of manganese oxide to cerium oxide in the active component is 1:(0.5~1).

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