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

Abstract

The invention discloses a micron fiber low-temperature rare-earth-based denitration catalyst and a preparation method thereof. The preparation method of the micron fiber low-temperature rare-earth-based denitration catalyst comprises the following steps: preparing modified sisal fibers, preparing an aluminum oxide micron fiber carrier and preparing 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, the modified sisal silk in the preparation method can promote aluminum salt to grow into an aluminum oxide micron fiber carrier, so that the specific surface area of the aluminum oxide micron fiber carrier can be increased; uniform loading of the active component and the cocatalyst component on the surface of the alumina micron fiber carrier is promoted, the active component and the cocatalyst component can be converted into carbon fibers after roasting, and the mechanical strength of the catalyst is enhanced; the activated components are oxidized through drying and roasting, so that the micron fiber low-temperature rare earth-based denitration catalyst has excellent oxidation-reduction performance and oxygen storage and release performance, and has good catalytic activity during low-temperature denitration.

Description

Technical Field

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

[0002] As one of the world's major energy production and consumption units, coal-fired power plants are one of the main sources of emissions of air pollutants such as nitrogen oxides. Nitrogen oxides are not only one of the main components of air pollution but also 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 for NO x removal at high temperatures. However, these technologies usually operate at relatively high temperatures (e.g., above 300 °C). With the increasingly strict emission standards and higher requirements for energy conservation 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, the denitration efficiency is often severely affected, and the mechanical strength of the catalyst is also low. When water vapor adheres to the surface of the catalyst, the mechanical strength of the catalyst is further reduced, and the catalyst is prone to collapse during long-term application. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a preparation method of a micron fiber low-temperature rare earth-based denitration catalyst. The micron fiber low-temperature rare earth-based denitration catalyst prepared by this preparation method has high mechanical strength and is not prone to collapse when water vapor adheres to its surface under low-temperature conditions. When performing low-temperature denitration, the micron fiber low-temperature rare earth-based denitration catalyst has good catalytic activity.

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

[0005] The preparation method of the micron fiber low-temperature rare earth-based denitration catalyst according to the embodiment of the first aspect of the present invention includes: preparing modified sisal fibers, including: soaking sisal leaves in a sodium chloride solution, removing the outer leaf skin and stripping to extract sisal fibers, placing the sisal fibers in a citric acid solution, performing ultrasonic and constant-temperature oscillation to obtain filamentous sisal fibers, then washing the filamentous sisal fibers with deionized water and drying, placing the dried filamentous sisal fibers in a plasma surface treatment instrument, evacuating the plasma surface treatment instrument, then filling it with oxygen, and then performing surface treatment on the filamentous sisal fibers to obtain the modified sisal fibers; preparing an alumina micron fiber carrier, including: impregnating the modified sisal fibers in an aluminum salt solution to obtain modified sisal fibers adsorbed with aluminum salts, reacting the ammonia gas volatilized from the ammonia water solution with the aluminum salts adsorbed on the modified sisal fibers to obtain modified sisal fibers adsorbed with aluminum hydroxide, mixing the modified sisal fibers adsorbed with aluminum hydroxide, aluminum salts, and deionized water and placing them in a hydrothermal reaction kettle for reaction, filtering and drying after hydrothermal reaction, and then placing them in a tubular furnace and introducing nitrogen for high-temperature roasting to grow the alumina micron fiber carrier on the modified sisal fibers; preparing the micron fiber low-temperature rare earth-based denitration catalyst, placing the modified sisal fibers with the alumina micron fiber carrier attached in a precursor mixed solution, drying and roasting to obtain the micron fiber low-temperature rare earth-based denitration catalyst, wherein the precursor mixed solution is obtained by mixing manganese salts, cerium salts, nickel salts, and deionized water evenly.

[0006] According to the preparation method of the micron fiber low-temperature rare earth-based denitration catalyst of the embodiment of the present invention, the modified sisal filaments in this preparation method can promote the growth of aluminum salts 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 active components and promoter components on the surface of the alumina micron fiber carrier, but also be converted into carbon fibers in the later stage to enhance the mechanical strength of the catalyst; through drying and roasting, activation components such as manganese salts, cerium salts, and nickel salts are oxidized to manganese oxide, cerium oxide, and nickel oxide, 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.

[0007] According to some embodiments of the present invention, in the step of preparing the modified sisal fibers, 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 fibers to the citric acid solution is 1:(40 to 60).

[0008] According to some embodiments of the present invention, the process parameters for placing the sisal fiber in a citric acid solution and performing 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 invention, the process parameters for drying the cleaned filamentous sisal fiber include: the drying temperature is 30°C - 50°C, and the drying time is 24h - 48h.

[0010] According to some embodiments of the present invention, the process parameters for surface treatment of the dried filamentous sisal fiber in a plasma surface treatment instrument include: the mass-volume ratio of the filamentous sisal fiber 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.

[0011] According to some embodiments of the present invention, in the step of preparing the alumina microfiber carrier, the aluminum salt is aluminum nitrate or aluminum chloride, and the mass fraction of the 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).

[0012] According to some embodiments of the present invention, the reaction of ammonia gas volatilized from an ammonia water solution with the aluminum salt adsorbed on the modified sisal fiber includes: placing the modified sisal fiber adsorbed with the aluminum salt at the mouth of a beaker, placing the ammonia water solution in the beaker, and placing the beaker in a water bath for water bath heating to make the volatilized ammonia gas react with the aluminum salt adsorbed on the modified sisal fiber.

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

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

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

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

[0017] According to some embodiments of the present invention, 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).

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

[0019] The microfiber low-temperature rare-earth-based denitration catalyst according to the embodiments of the second aspect of the present invention is prepared by the preparation method of the above-mentioned microfiber low-temperature rare-earth-based denitration catalyst. The mass percentage content of the active component in the microfiber low-temperature rare-earth-based denitration catalyst is 3% to 5%, the mass percentage content of the promoter component in the microfiber 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 - 1).

[0020] The microfiber low-temperature rare-earth-based denitration catalyst according to the embodiments of the present invention has high mechanical strength. When performing low-temperature denitration, when water vapor adheres to the surface of the microfiber low-temperature rare-earth-based denitration catalyst, it is not easy to cause it to collapse, and the microfiber low-temperature rare-earth-based denitration catalyst has good catalytic activity.

[0021] The additional aspects and advantages of the present invention will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0023] Figure 1 is a schematic flow chart of the preparation method of the microfiber low-temperature rare-earth-based denitration catalyst according to some embodiments of the present invention;

[0024] Figure 2It is the field emission scanning electron microscope (FE-SEM) image of the micron fiber low-temperature rare earth-based denitration catalyst in Embodiment 1 of the present invention. Detailed implementation manners

[0025] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0026] The preparation method of the micron fiber low-temperature rare earth-based denitration catalyst according to the first aspect embodiment of the present invention includes:

[0027] Preparing modified sisal fibers, including: soaking sisal leaves in a sodium chloride solution, removing the outer leaf skin and stripping to extract sisal fibers, placing the sisal fibers in a citric acid solution, performing ultrasonic and constant temperature oscillation to obtain filamentous sisal fibers, then washing the filamentous sisal fibers with deionized water and drying, placing the dried filamentous sisal fibers in a plasma surface treatment instrument, evacuating the plasma surface treatment instrument, then filling it with oxygen, and then performing surface treatment on the filamentous sisal fibers to obtain modified sisal fibers;

[0028] Preparing an alumina micron fiber carrier, including: impregnating the modified sisal fibers in an aluminum salt solution to obtain modified sisal fibers adsorbed with aluminum salts, reacting the ammonia gas volatilized from the ammonia water solution with the aluminum salts adsorbed on the modified sisal fibers to obtain modified sisal fibers adsorbed with aluminum hydroxide, mixing the modified sisal fibers adsorbed with aluminum hydroxide, aluminum salts, and deionized water and placing them in a hydrothermal reaction kettle for reaction, filtering and drying after hydrothermal reaction, and then placing them in a tubular furnace and introducing nitrogen for high-temperature calcination to grow an alumina micron fiber carrier on the modified sisal fibers;

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

[0030] Among them, the micron-fiber low-temperature rare-earth-based denitration catalyst uses modified sisal fiber as a template agent, which can not only hydrothermally convert aluminum salt into alumina fiber, increasing the specific surface area of the alumina micron-fiber carrier, but also convert the modified sisal fiber into carbon fiber, and further improve the mechanical strength of the carrier by using the toughness and mechanical strength of the carbon fiber itself; at the same time, by utilizing the excellent redox performance and oxygen storage and release performance of manganese oxide, cerium oxide, and nickel oxide, the low-temperature catalytic activity of the micron-fiber low-temperature rare-earth-based denitration catalyst is improved; and the active components and promoter components are also evenly loaded on the surface of the alumina micron-fiber, increasing the exposure ratio of active sites, thereby effectively ensuring the low-temperature activity and mechanical strength of the micron-fiber low-temperature rare-earth-based denitration catalyst.

[0031] During the preparation process of the micron-fiber low-temperature rare-earth-based denitration catalyst, first, sisal fibers with excellent mechanical strength and toughness are screened and extracted, then the sisal fibers in the form of thin filaments with high cleanliness are obtained by weak acid washing, ultrasonic treatment, and constant-temperature oscillation, and then the hydroxyl concentration of the fibers is increased by plasma surface treatment, which is beneficial to the adsorption of aluminum salt on the surface of the modified sisal fiber. Then, the aluminum salt adsorbed on the surface of the modified sisal fiber is converted into aluminum hydroxide by ammonia water, which can promote the continuous growth of the aluminum salt in the solution on the surface of the modified sisal fiber during the hydrothermal reaction process, ensuring that the aluminum salt can finally form an alumina micron-fiber carrier under hydrothermal conditions. Finally, the active components and promoter components are loaded on the surface of the alumina micron-fiber carrier by the impregnation roasting method. During this process, the nitrogen tube furnace roasting can, on the one hand, ensure the complete conversion of the aluminum salt into alumina, and on the other hand, also promote the conversion of the modified sisal fiber into carbon fiber.

[0032] Among them, the carbon fiber converted from the modified sisal fiber has high mechanical strength. In a low-temperature environment, water vapor is likely to adhere to the surface of the micron-fiber low-temperature rare-earth-based denitration catalyst to form condensation. At this time, due to the high mechanical strength of the micron-fiber low-temperature rare-earth-based denitration catalyst, it is not easy to cause collapse.

[0033] According to the preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst of the embodiment of the present invention, the thin-filament modified sisal fiber in this preparation method 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 components and promoter components on the surface of the alumina micron-fiber carrier, but also be converted into carbon fiber in the later stage, enhancing the mechanical strength of the catalyst. In a low-temperature environment, when water vapor adheres to the surface of the micron-fiber low-temperature rare-earth-based denitration catalyst, it is not easy to cause its collapse; through drying and roasting, activation components such as manganese salt, cerium salt, and nickel salt are oxidized to manganese oxide, cerium oxide, and nickel oxide, making the micron-fiber low-temperature rare-earth-based denitration catalyst have excellent redox performance and oxygen storage and release performance. When performing low-temperature denitration, the micron-fiber low-temperature rare-earth-based denitration catalyst has good catalytic activity.

[0034] According to some embodiments of the present invention, 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 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 sisal fiber to the citric acid solution is 1:(40 to 60).

[0035] Among them, the sodium chloride solution can create an environment conducive to the extraction of sisal fiber, and the citric acid solution plays a role in weak acid washing, which can improve the dry breaking strength and dry breaking elongation of sisal fiber and is used to enhance the mechanical properties of 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 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.; the mass ratio of sisal fiber to the citric acid solution can be 1:40, 1:45, 1:50, 1:55, 1:60, etc. If the mass fractions of the sodium chloride solution and the monohydrate citric acid solution are too high, it is easy to damage the structure of sisal fiber; if the mass fractions of the sodium chloride solution and the monohydrate citric acid solution are too low, a good washing effect cannot be achieved.

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

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

[0038] According to some embodiments of the present invention, the process parameters for drying the washed filamentary sisal fibers include: the drying temperature is 30°C to 50°C, and the drying time is 24h to 48h.

[0039] For example, the drying temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, etc.; the drying time can be 24h, 30h, 36h, 42h, 48h, etc. If the drying temperature is too high or the drying time is too long, it is easy to damage the fiber structure of the filamentary sisal fibers; if the drying temperature is too high or the drying time is too short, a good drying effect cannot be achieved.

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

[0041] For example, the mass-volume ratio of the filamentary sisal fibers to oxygen can be 1g:20mL, 1g:25mL, 1g:30mL, 1g:35mL, 1g:40mL, etc.; the plasma flame scanning rate is 20mm / s, 25mm / s, 30mm / s, 35mm / s, 40mm / s, etc. By treating the filamentary sisal fibers with oxygen in a plasma surface treatment instrument, the hydroxyl concentration of the filamentary sisal fibers is increased, which is beneficial to the adsorption of aluminum salts on the surface of the modified sisal fibers.

[0042] According to some embodiments of the present invention, in the step of preparing the alumina microfiber carrier, the aluminum salt is aluminum nitrate or aluminum chloride, and the mass fraction of the aluminum salt in the aluminum salt solution is 20% - 40%; 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, and the mass fraction of the aluminum salt in the aluminum salt solution can be 20%, 25%, 30%, 35%, 40%, etc.; 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 invention, the reaction of ammonia gas volatilized from the ammonia water solution with the aluminum salt adsorbed on the modified sisal fibers includes: placing the modified sisal fibers adsorbed with the aluminum salt at the mouth of a beaker, placing the ammonia water solution in the beaker, and placing the beaker in a water bath for water bath heating to make the volatilized ammonia gas react with the aluminum salt adsorbed on the modified sisal fibers.

[0045] Among them, water bath heating can promote the volatilization of ammonia water solution into ammonia gas. The volatilized ammonia gas reacts with the aluminum salt adsorbed on the modified sisal fiber, converting the aluminum salt adsorbed on the surface of the modified sisal fiber into aluminum hydroxide.

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

[0047] For example, the mass fraction of the ammonia water solution can be 20%, 21%, 22%, 23%, 24%, 25%, etc.; the mass ratio of the modified sisal fiber adsorbed with 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 fiber adsorbed with aluminum salt to the ammonia water solution, the volatilization rate of ammonia water and the reaction rate of the aluminum salt adsorbed on the modified sisal fiber can be adjusted, so that the aluminum salt adsorbed on the surface of the modified sisal fiber is converted into an appropriate amount of aluminum hydroxide, which is beneficial to the subsequent hydrothermal reaction for the continuous growth of aluminum salt on the surface of the modified sisal fiber.

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

[0049] For example, the temperature of the water bath heating can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, etc.; the time of the water bath heating can be 6h, 6.5h, 7h, 7.5h, 8h, etc. By the temperature and time of the water bath heating, the volatilization rate of ammonia water and the reaction rate of the aluminum salt adsorbed on the modified sisal fiber can be adjusted, so that the aluminum salt adsorbed on the surface of the modified sisal fiber is converted into an appropriate amount of aluminum hydroxide, which is beneficial to the subsequent hydrothermal reaction for the continuous growth of aluminum salt on the surface of the modified sisal fiber.

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

[0051] For example, the mass ratio of the modified sisal fiber, 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°C, 145°C, 150°C, 155°C, 160°C, etc.; the time of the hydrothermal reaction can be 4 h, 5 h, 6 h, 7 h, 8 h, etc.; the temperature of filtration and drying after the hydrothermal reaction can be 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the time of filtration and drying after the hydrothermal reaction can be 12 h, 16 h, 20 h, 24 h, etc. By adjusting the temperature and time of the hydrothermal reaction while performing the hydrothermal reaction, it is possible to promote the continuous growth of the aluminum salt in the solution on the surface of the modified sisal fiber during the hydrothermal reaction process, ensuring that the aluminum salt can finally form an alumina microfiber support under hydrothermal conditions.

[0052] According to some embodiments of the present invention, in the step of preparing the alumina microfiber support, the rate of nitrogen gas introduced into the tubular furnace is 20 mL / min to 40 mL / min, the temperature of high-temperature calcination is 500°C to 600°C, and the time of high-temperature calcination is 2 h to 4 h.

[0053] For example, the rate of nitrogen gas introduced into the tubular furnace can be 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, 40 mL / min, etc.; the temperature of high-temperature calcination can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, etc.; the time of high-temperature calcination can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc. By adjusting the appropriate temperature and time of high-temperature calcination, it is possible to completely convert the aluminum salt into alumina, and by introducing nitrogen gas at an appropriate rate into the tubular furnace, the modified sisal fiber is prevented from being oxidized.

[0054] According to some embodiments of the present invention, 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 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; the nickel salt can be nickel nitrate hexahydrate or nickel chloride hexahydrate; 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 invention, in the step of preparing the microfiber low-temperature rare earth-based denitration catalyst, the drying temperature is 80°C to 100°C, the drying time is 12 h to 24 h, the calcination temperature is 500°C to 600°C, and the calcination time is 2 h to 4 h.

[0057] For example, the drying temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the drying time can be 12 h, 16 h, 20 h, 24 h, etc.; the calcination temperature can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, etc.; the calcination time can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc. Through high-temperature calcination, the active components and the promoter components are uniformly loaded on the surface of the alumina fiber, the exposure ratio of the active sites is increased, and the conversion of the modified sisal fiber into carbon fiber can also be promoted, so that the micron-fiber low-temperature rare-earth-based denitration catalyst has good low-temperature activity and mechanical strength.

[0058] According to the micron-fiber low-temperature rare-earth-based denitration catalyst of the second aspect embodiment of the present invention, the micron-fiber low-temperature rare-earth-based denitration catalyst is prepared by the above-mentioned preparation method of the micron-fiber low-temperature rare-earth-based denitration catalyst. The mass percentage content of the active components in the micron-fiber low-temperature rare-earth-based denitration catalyst is 3% to 5%, and the mass percentage content of the promoter components in the micron-fiber low-temperature rare-earth-based denitration catalyst is 1% to 3%. The mass ratio of manganese oxide to cerium oxide in the active components is 1:(0.5 - 1).

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

[0060] Among them, the modified sisal fibers in the preparation method can promote the growth of aluminum salts into alumina microfiber carriers, which can not only increase the specific surface area of the carrier, promote the uniform loading of the active components and the promoter components on the surface of the carrier, but also be converted into carbon fibers in the later stage to enhance the mechanical strength of the catalyst. The active components in the micron-fiber low-temperature rare-earth-based denitration catalyst are manganese oxide and cerium oxide, and the promoter component is nickel oxide. The active components and the promoter components in the micron-fiber low-temperature rare-earth-based denitration catalyst have good redox performance and oxygen storage and release performance. The active components and the promoter components are evenly distributed on the surface of the alumina microfiber carrier under the microscopic interface, which is beneficial to the maximization of the utilization of active sites and enables the micron-fiber low-temperature rare-earth-based denitration catalyst to maintain good catalytic activity at low temperatures.

[0061] According to the micron fiber low-temperature rare earth-based denitration catalyst of the embodiment of the present invention, the micron fiber low-temperature rare earth-based denitration catalyst has high mechanical strength. When water vapor adheres to the surface of the micron fiber low-temperature rare earth-based denitration catalyst in a low-temperature environment, it is not easy to cause it to collapse. When performing low-temperature denitration, the micron fiber low-temperature rare earth-based denitration catalyst has good catalytic activity.

[0062] Example 1

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

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

[0065] Weigh 100 g of sisal leaves and soak them in 3000 g of a 5% sodium chloride solution by mass. After soaking for 7 days, remove the outer leaf skin and strip and extract the sisal fiber. Then weigh 20 g of sisal fiber and place it in 800 g of a 10% citric acid solution by mass. Ultrasonic it for 60 min at a power of 200 W and then place it in a constant temperature oscillator and keep it oscillating at a constant temperature under the conditions of 30 °C and 100 r / min for 4 h to obtain filamentous sisal fiber. Then wash the filamentous sisal fiber with deionized water, and then place it in an oven and dry it at 30 °C for 48 h. Finally, weigh 2 g of the dried filamentous sisal fiber and place it in a plasma surface treatment instrument. Vacuumize the plasma surface treatment instrument, then fill it with 40 mL of oxygen, and then perform surface treatment (input voltage is 220 V, working distance is 5 mm, and the plasma flame scanning rate is 20 mm / s) to increase the hydroxyl concentration on the surface of the filamentous sisal fiber and obtain modified sisal fiber. Cycle the plasma surface modification step until the filamentous sisal fiber is processed;

[0066] (2) Preparation of alumina micron fiber carrier

[0067] Weigh 5 g of the modified sisal fiber obtained in step (1) and impregnate it in 2.5 g of a 20% aluminum nitrate solution by mass. Then place the modified sisal fiber adsorbed with aluminum nitrate at the mouth of a beaker. Place 165 g of a 20% ammonia water solution by mass in the beaker and place the beaker in a water bath at 80 °C and heat it in the water bath for 8 h to volatilize ammonia and react with aluminum nitrate. Finally, obtain the modified sisal fiber adsorbed with aluminum hydroxide. Weigh 5 g of the modified sisal fiber adsorbed with aluminum hydroxide, 25 g of aluminum nitrate, and 200 g of deionized water, mix them and place them in a hydrothermal reaction kettle. After hydrothermal reaction at 140 °C for 8 h, filter and then place it in an oven and dry it at 80 °C for 24 h. Then place it in a tubular furnace and pass nitrogen (the rate of passing nitrogen is 20 mL / min) and calcine it at a high temperature of 500 °C for 4 h to obtain an alumina micron fiber carrier;

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

[0069] 0.289 g of manganese chloride, 0.143 g of cerium chloride, 0.318 g of nickel chloride hexahydrate, and 5.780 g of deionized water were weighed and mixed uniformly to obtain a precursor mixed solution, and then 10.000 g of the alumina micron fiber carrier obtained in step (2) was weighed and placed in the precursor mixed solution, dried at 80° C. for 24 h, and then placed in a muffle furnace and calcined at 500° C. for 4 h to obtain a micron fiber low-temperature rare earth-based denitration catalyst (based on the mass of the carrier, the mass percentage of the active component is 3%, the mass percentage of the co-catalyst component is 1%, and the mass ratio of manganese oxide to cerium oxide in the active component is 1:0.5; the FE-SEM image of the micron fiber low-temperature rare earth-based denitration catalyst is as shown in FIG. Figure 1 As shown, the alumina micron fiber carrier is in the form of micron fibers, and the active component and the co-catalyst component are in the form of nanoparticles and are dispersed on the carrier surface);

[0070] (4) Catalytic activity test

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

[0072] Embodiment 2,

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

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

[0075] Weigh 100 g of sisal leaves and soak them in 5000 g of sodium chloride solution with a mass fraction of 10%. After soaking for 7 days, remove the outer leaf skin and strip to extract sisal fibers. Then, weigh 20 g of sisal fibers and place them in 1200 g of citric acid solution with a mass fraction of 20%. Use a power of 400 W to ultrasonicate for 30 min, and then place them in a constant temperature oscillator and oscillate at a constant temperature of 30 °C and 200 r / min for 2 h to obtain filamentous sisal fibers. Then, wash the filamentous sisal fibers with deionized water, and then place them in an oven and dry at 50 °C for 24 h. Finally, weigh 2 g of the dried filamentous sisal fibers and place them in a plasma surface treatment instrument. Vacuum the plasma surface treatment instrument, then fill it with 80 mL of oxygen, and then perform surface treatment (input voltage is 220 V, working distance is 10 mm, plasma flame scanning rate is 40 mm / s) to increase the surface hydroxyl concentration of the filamentous sisal fibers and obtain modified sisal fibers. Repeat the plasma surface modification step until all the filamentous sisal fibers are processed;

[0076] (2) Preparation of alumina microfiber support

[0077] Weigh 5 g of the modified sisal fibers obtained in step (1) and immerse them in 5 g of aluminum chloride solution with a mass fraction of 40%. Then, place the modified sisal fibers adsorbed with aluminum nitrate at the mouth of the beaker. Place 350 g of ammonia water solution with a mass fraction of 25% in the beaker, and place the beaker in a water bath at 90 °C and heat for 6 h to volatilize ammonia and react with aluminum nitrate, finally obtaining modified sisal fibers adsorbed with aluminum hydroxide. Weigh 5 g of the modified sisal fibers adsorbed with aluminum hydroxide, 50 g of aluminum chloride, and 300 g of deionized water, mix them and place them in a hydrothermal reaction kettle. After hydrothermal reaction at 160 °C for 4 h, filter and then place them in an oven and dry at 100 °C for 12 h. Then, place them in a tubular furnace, introduce nitrogen (the rate of introducing nitrogen is 40 mL / min), and calcine at 600 °C for 2 h to obtain an alumina microfiber support;

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

[0079] Weigh 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, mix them evenly to obtain a precursor mixed solution. Then, weigh 10.000 g of the alumina microfiber support prepared in step (2) and place it in the precursor mixed solution. After drying at 100 °C for 12 h, place it in a muffle furnace and calcine at 600 °C for 2 h to obtain a microfiber low-temperature rare earth-based denitration catalyst (based on the mass of the support, the mass percentage content of the active component is 5%, the mass percentage content of the promoter component is 3%, and the mass ratio of manganese oxide to cerium oxide in the active component is 1:1);

[0080] (4) Catalytic activity test

[0081] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh and pour it into a quartz tube with an inner diameter of 6 mm. Fix it with quartz wool and cerium wire mesh. Place the quartz tube in a tube furnace and 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 rate is 500 mL / min. Set the temperature to 150 °C. Measure the NO inlet and outlet concentrations with a flue gas analyzer. The NO removal efficiency of the catalyst at 150 °C for 3 minutes is 99.6%.

[0082] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean 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 invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

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

Claims

1. A preparation method of a micron fiber low-temperature rare earth-based denitration catalyst, characterized in that, Including: Preparing modified sisal fibers, including: soaking sisal leaves in a sodium chloride solution, removing the outer leaf skin and stripping to extract sisal fibers, placing the sisal fibers in a citric acid solution, performing ultrasonic and constant temperature oscillation to obtain filamentous sisal fibers, then washing the filamentous sisal fibers with deionized water and drying, placing the dried filamentous sisal fibers in a plasma surface treatment instrument, evacuating the plasma surface treatment instrument, then filling it with oxygen, and then performing surface treatment on the filamentous sisal fibers to obtain the modified sisal fibers; Preparing an alumina microfiber carrier, including: impregnating the modified sisal fibers in an aluminum salt solution to obtain modified sisal fibers adsorbed with aluminum salts, reacting the ammonia gas volatilized from an ammonia water solution with the aluminum salts adsorbed on the modified sisal fibers to obtain modified sisal fibers adsorbed with aluminum hydroxide, mixing the modified sisal fibers adsorbed with aluminum hydroxide, aluminum salts, and deionized water and placing them in a hydrothermal reaction kettle for reaction, filtering and drying after hydrothermal reaction, and then placing them in a tubular furnace and introducing nitrogen for high-temperature roasting to grow the alumina microfiber carrier on the modified sisal fibers; Preparing the microfiber low-temperature rare earth-based denitration catalyst, placing the modified sisal fibers with the alumina microfiber carrier attached in a precursor mixed solution, drying and then roasting to obtain the microfiber low-temperature rare earth-based denitration catalyst, wherein the precursor mixed solution is obtained by mixing manganese salts, cerium salts, nickel salts, and deionized water evenly.

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 fibers, the sodium chloride solution is a sodium chloride solution with a mass fraction of 5% - 10%, the mass ratio of the sisal leaves to the sodium chloride solution is 1:(30 - 50), the citric acid solution is a monohydrate citric acid solution with a mass fraction of 10% - 20%, and the mass ratio of the sisal fibers to the citric acid solution is 1:(40 - 60).

3. The preparation method of the micron fiber low-temperature rare earth-based denitration catalyst according to claim 1, characterized in that, The technological parameters for placing the sisal fibers in the citric acid solution and performing 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; The technological parameters for drying the washed filamentous sisal fibers include: the drying temperature is 30°C - 50°C, and the drying time is 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 technological parameters for placing the dried filamentous sisal fibers in a plasma surface treatment instrument for surface treatment include: the mass-volume ratio of the filamentous 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 the alumina microfiber 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%; the mass ratio of the modified sisal fibers 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 ammonia gas volatilized from the ammonia aqueous solution reacts with the aluminum salt adsorbed on the modified sisal fiber, including: placing the modified sisal fiber adsorbed with aluminum salt at the mouth of a beaker, placing the ammonia aqueous solution in the beaker, and placing the beaker in a water bath for heating, so that the volatilized ammonia gas reacts with the aluminum salt 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 aqueous solution is an ammonia aqueous solution with a mass fraction of 20% to 25%, and the mass ratio of the modified sisal fiber adsorbed with aluminum salt to the ammonia aqueous solution is 1:(30 to 50); and / or, the temperature of the water bath heating is 80°C to 90°C, and the time of the water bath heating is 6h to 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 adsorbed with aluminum hydroxide, aluminum salt, and deionized water is 1:(5 to 10):(40 to 60), the temperature of the hydrothermal reaction is 140°C to 160°C, the time of the hydrothermal reaction is 4h to 8h, and the drying process parameters after filtration and drying in the hydrothermal reaction include: the drying temperature is 80°C to 100°C, and the drying time is 12h to 24h; and / or, in the step of preparing the alumina micron fiber carrier, the rate of nitrogen gas introduced into the tubular furnace is 20 mL / min to 40 mL / min, the temperature of the high-temperature roasting is 500°C to 600°C, and the time of the high-temperature roasting 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 to 30); and / or, in the step of preparing the micron fiber low-temperature rare earth-based denitration catalyst, the drying temperature is 80°C to 100°C, the drying time is 12h to 24h, the roasting temperature is 500°C to 600°C, and the roasting time is 2h to 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 mass percentage content of the active component in the micron fiber low-temperature rare earth-based denitration catalyst is 3% to 5%, the mass percentage content 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).

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