High-temperature denitration catalyst as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature denitration catalyst and a preparation method and application thereof.The catalyst takes a waste manganese-based denitration catalyst, rare earth slag and a waste rare earth-based denitration catalyst as active component raw materials, NaOH as a crystal face regulating agent, urea as a reducing agent, polyvinyl alcohol as an inner-layer protective agent and rosin as an outer-layer protective agent; by adopting a secondary hydrothermal method, active raw materials in the waste manganese-based denitration catalyst and the rare earth slag are extracted, and crystal faces of active components are regulated and controlled at the same time. According to the method disclosed by the invention, high-added-value resource reutilization of the waste manganese-based denitration catalyst, the rare earth slag and the waste rare earth-based denitration catalyst is realized, and meanwhile, the high-temperature denitration catalyst with excellent activity is synthesized.

Description

Technical Field

[0001] The present invention relates to a high-temperature denitration catalyst and a preparation method thereof, belonging to the fields of air pollution control and waste treatment. Background Art

[0002] Cement, as the main basic building material, plays a key role in the world economic development and is an important cornerstone of the world's material civilization. The cement industry has played an important role in China's industrialization, urbanization, and modernization drive.

[0003] However, with the rapid development of the cement industry, a series of environmental protection problems have also emerged. At present, 80% of the main equipment for air pollution control in China is dust removal equipment, namely electrostatic precipitators or bag filters. With the industrial restructuring and technological upgrading of the entire industry, dry-process cement production technology has been widely applied. However, for the cement industry, the emissions of air pollutants such as SO2, NO x and so on are still very large.

[0004] Currently, the main environmental protection problems in the cement industry are that it is relatively difficult to complete denitration under the condition of relatively high particulate matter emissions. At present, the national standards for air pollutant emissions from cement production still implement GB4915-2013. The control indicators involved in the vast majority of enterprises are "particulate matter, sulfur dioxide, nitrogen oxides, ammonia". In fact, the national standard is the minimum standard and is not strict enough. It can be said that by the end of 2019, all existing cement production enterprises in China have been able to achieve it. Moreover, with the country's emphasis on environmental protection governance in the cement industry, since 2013, the emissions of nitrogen oxides in the cement industry have been steadily decreasing. However, overall, the emissions of air pollutants in the cement industry are still at a relatively high level. The environmental pollution problems and environmental protection pressure brought by the large emissions of pollutants in the cement industry are still huge. The cement manufacturing process and technological transformation level need to be further improved. The treatment levels and process levels of pollutants are uneven. There are many links where pollutants are generated and the emissions of pollutants are large. It is still necessary to adopt processes to improve the pollutant treatment level to meet higher-level environmental protection requirements.

[0005] With the rapid development of the cement industry, the environmental protection problems and environmental protection pressure derived therefrom are slowly increasing. At present, the emissions of pollutants in China's cement industry are large, and there are also significant differences in the treatment levels and processes among different production enterprises in various places. Most domestic cement production enterprises need to implement a more refined production model and further improve the pollutant emission treatment process. With the increasingly strict environmental protection governance standards in China, the cement industry still has a large room for improvement in solving environmental protection problems and achieving up-to-standard emissions.

[0006] Considering the situation of the integral denitration catalyst being prone to particulate matter blockage and easy sulfur and chlorine poisoning, using waste manganese-based denitration catalyst, rare earth slag, and waste rare earth-based denitration catalyst as the raw materials of the active components, the high-temperature denitration catalyst synthesized by a special process can not only solve the high emission problem of NO x in the cement industry, but also reuse the waste catalyst to improve the economic value. Summary of the Invention

[0007] The purpose of the present invention is to provide a reuse method for waste manganese-based denitration catalyst, rare earth slag, and waste rare earth-based denitration catalyst in view of the single reuse method and low economic benefits of current waste manganese-based denitration catalyst, rare earth slag, and waste rare earth-based denitration catalyst; another purpose of the present invention is to provide a preparation method and application of a high-temperature denitration catalyst in view of the current status of pollutant emissions in the cement industry.

[0008] A high-temperature denitration catalyst, which uses waste manganese-based denitration catalyst, rare earth slag, and waste rare earth-based denitration catalyst as the raw materials of the active components, NaOH as the crystal plane regulator, urea as the reducing agent, polyvinyl alcohol as the inner protective agent, and rosin as the outer protective agent, and is prepared by the secondary hydrothermal method.

[0009] In the technical solution of the present invention, the dosage of each component is as follows:

[0010]

[0011]

[0012] Preferably:

[0013]

[0014] A preparation method of the above-mentioned high-temperature denitration catalyst, and the steps of the method are as follows:

[0015] (1) Extraction of the active component precursor: Mix the waste manganese-based denitration catalyst, rare earth slag, and dilute hydrochloric acid solution and carry out hydrothermal reaction. After the hydrothermal reaction, filter to obtain the supernatant;

[0016] (2) Crystal plane regulation of the active component: After crushing the waste rare earth-based denitration catalyst into powder, place it in the supernatant obtained in step (1), let it stand for 4-6 h, then add NaOH and deionized water and carry out hydrothermal reaction again. After the reaction, filter to obtain the slurry, and dry it to obtain the catalyst powder;

[0017] (3) Preparation of catalyst: Dissolve urea in deionized water to obtain a urea solution, then place the catalyst powder obtained in step (2) into the urea solution, filter and dry it after impregnation for 2 - 3 h; Weigh polyvinyl alcohol and dissolve it in deionized water and heat to form a polyvinyl alcohol solution, then add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powdered catalyst. Finally, place the small particle powdered catalyst into the melted rosin liquid, filter again to obtain the small particle powdered catalyst wrapped by rosin liquid, and cool to obtain the high-temperature denitration catalyst.

[0018] In the above preparation method: In step (1), the waste manganese-based denitration catalyst uses TiO2 as the carrier, MnO2 and Fe2O3 as the active components, and the rest are additives; among them, the TiO2 carrier accounts for 70% - 85% of the content of the waste manganese-based denitration catalyst, and the active components MnO2 and Fe2O3 are respectively 5% - 10% and 1% - 3% of the content of the waste manganese-based denitration catalyst;

[0019] In step (1), the rare earth slag is the west tailings of Bayan Obo, and the mass fraction of CeO2 is 0.6 - 0.8%;

[0020] In step (1), the mass ratio of the rare earth slag to the dilute hydrochloric acid solution is 1:(10 - 15), and the mass fraction of the dilute hydrochloric acid solution is 10 - 15%.

[0021] In the above preparation method: In step (1), the temperature of the hydrothermal reaction is 140 - 160 °C, and the time of the hydrothermal reaction is 4 - 6 h.

[0022] In the above preparation method: In step (2), the waste rare earth-based denitration catalyst uses TiO2 as the carrier, WO3 and CeO2 as the active components, and the rest are additives; among them, the TiO2 carrier accounts for 70% - 85% of the content of the waste rare earth-based denitration catalyst, and the active components WO3 and CeO2 are respectively 3% - 7% and 1% - 3% of the content of the waste rare earth-based denitration catalyst;

[0023] In step (2), the particle size of the powder obtained by crushing the waste rare earth-based denitration catalyst into powder is 0.090 - 0.125 mm;

[0024] In step (2), the mass ratio of NaOH to deionized water is 1:(10 - 20);

[0025] The temperature of the hydrothermal reaction is 160 - 180 °C, the time of the hydrothermal reaction is 6 - 8 h, the drying temperature is 100 - 120 °C, and the drying time is 2 - 4 h.

[0026] In the above preparation method: In step (3), the mass ratio of urea to deionized water is 1:(10 - 15), the drying temperature is 100 - 120 °C, and the drying time is 2 - 4 h.

[0027] In the above preparation method: in step (3), the particle size of the small particle powdered catalyst is 0.150 - 0.212 mm.

[0028] In the technical solution of the present invention, the application of the catalyst in high-temperature denitrification of cement is described. Further, the temperature for cement denitrification is 700 - 1200 °C.

[0029] Beneficial effects:

[0030] (1) In the present invention, the catalyst uses waste manganese-based denitrification catalyst, rare earth slag, and waste rare earth-based denitrification catalyst as active component raw materials, NaOH as a crystal plane regulator, urea as a reducing agent, polyvinyl alcohol as an inner protective agent, and rosin as an outer protective agent to achieve high-value resource recycling of waste manganese-based denitrification catalyst, rare earth slag, and waste rare earth-based denitrification catalyst.

[0031] (2) The waste manganese-based denitrification catalyst contains a large amount of Mn and Fe elements, while the rare earth slag is rich in Ce elements. Extracting Mn, Fe, and Ce elements from the waste manganese-based denitrification catalyst and rare earth slag can not only effectively utilize the waste manganese-based denitrification catalyst and slag, but also greatly reduce the catalyst preparation cost. At the same time, using NaOH as a crystal plane regulator enables Mn and Fe, as well as Ce and Mn, to form solid solutions and expose their high-energy crystal planes, improving the catalyst activity.

[0032] (3) Using urea as a reducing agent, ammonia will be decomposed when urea is heated, and ammonia can be used as a reducing gas to react with nitrogen oxides. Using polyvinyl alcohol with a granulation effect to turn the catalyst powder into powdered small particle catalysts can improve the pore structure inside the catalyst and increase the adsorption efficiency of NO x and NH3, thereby improving the catalytic activity.

[0033] (4) Using polyvinyl alcohol as an inner protective agent and rosin as an outer protective agent, after the catalyst enters the actual flue gas, the flue gas will first contact with rosin and polyvinyl alcohol. The heat of the flue gas will cause rosin and polyvinyl alcohol to melt and decompose, which will delay the decomposition process of urea, thereby achieving the effect of sufficient contact between the internal powdered high-temperature denitrification catalyst and the flue gas and improving the catalytic activity. At the same time, during the thermal decomposition process of rosin and polyvinyl alcohol, some reduction gases will be formed. The powdered high-temperature denitrification catalyst of the present invention can catalyze CO, C x H y to reduce NO x , that is, three-way catalysis, thereby further improving the catalytic activity. Description of the drawings

[0034] Figure 1 Denitrification catalyst activity diagrams of Examples 1 - 6 in the temperature range of 700 - 1200 °C.

[0035] Figure 2 Activity diagrams of the denitration catalysts of Comparative Examples 1 to 4 in the temperature range of 700 to 1200 °C. Specific embodiments

[0036] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0037] In the activity test of the present invention, the flue gas components are simulated according to the NO concentration in the actual flue gas of cement.

[0038] Some raw materials used in the embodiments of the present invention are as follows:

[0039] Waste manganese-based denitration catalyst: with a TiO2 carrier, with MnO2 and Fe2O3 as active components, and the rest as additives; wherein, the TiO2 carrier is 85% of the content of the waste manganese-based denitration catalyst, and the active components MnO2 and Fe2O3 are 5% and 3% of the content of the waste manganese-based denitration catalyst respectively;

[0040] Rare earth slag: West tailings of Bayan Obo, wherein the mass fraction of CeO2 is 0.7%;

[0041] Waste rare earth-based denitration catalyst: The waste rare earth-based denitration catalyst has a TiO2 carrier, with WO3 and CeO2 as active components, and the rest as additives; wherein, the TiO2 carrier is 78% of the content of the waste rare earth-based denitration catalyst, and the active components WO3 and CeO2 are 7% and 2% of the content of the waste rare earth-based denitration catalyst respectively.

[0042] Example 1

[0043] (1) Extraction of active component precursors: Mix 3.0 g of waste manganese-based denitration catalyst, 4.0 g of rare earth slag, and 40 g of a 10% by mass dilute hydrochloric acid solution in a hydrothermal reaction kettle, and filter to obtain the supernatant after hydrothermal reaction at 140 °C for 6 h;

[0044] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and select 9.0 g of powder with a particle size range of 100 to 140 mesh using a sieve, place it in the supernatant obtained in step (1), let it stand for 4 to 6 h, add 0.1 g of NaOH and 1.0 g of deionized water, and place the mixed solution in a hydrothermal reaction kettle. Filter to obtain a slurry after hydrothermal reaction at 160 °C for 6 h, and then dry at 100 °C for 2 h to obtain catalyst powder;

[0045] (3) Catalyst preparation: Dissolve 0.5 g of urea in 5.0 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, impregnate for 2 - 3 h, filter, and dry at 100 °C for 2 h. Weigh 2.0 g of polyvinyl alcohol, dissolve it in 20 g of deionized water, and heat it to dissolve at 80 °C to form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powder catalysts (particle size: 0.150 - 0.212 mm). Finally, place the small particle powder catalysts into 4.0 g of rosin liquid melted by heating at 180 °C, filter again to obtain small particle powder catalysts wrapped with rosin liquid, and cool to obtain a high-temperature denitration catalyst.

[0046] (4) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity: 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. Wait for the tubular furnace to heat up to 700 - 1200 °C, place the metal reaction tube in a vertical tubular furnace, keep it at a constant temperature for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0047] Example 2

[0048] (1) Extraction of active component precursor: Mix 2.8 g of waste manganese-based denitration catalyst, 4.4 g of rare earth slag, and 66 g of 15% (mass concentration) dilute hydrochloric acid solution, place them in a hydrothermal reaction kettle, carry out hydrothermal reaction at 150 °C for 5 h, and then filter to obtain the supernatant;

[0049] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and use a sieve to select 9.2 g of powder with a particle size range of 100 - 140 mesh, place it in the supernatant obtained in step (1), let it stand for 4 - 6 h, add 0.2 g of NaOH and 4.0 g of deionized water, place the mixed solution in a hydrothermal reaction kettle, carry out secondary hydrothermal reaction at 170 °C for 7 h, filter to obtain a slurry, and then dry at 110 °C for 3 h to obtain catalyst powder;

[0050] (3) Catalyst preparation: Dissolve 0.6 g of urea in 9.0 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, impregnate for 2 - 3 h, filter, and dry at 110 °C for 3 h. Weigh 1.8 g of polyvinyl alcohol, dissolve it in 18 g of deionized water, and heat it to 80 °C to dissolve and form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powdered catalyst (particle size is 0.150 - 0.212 mm). Finally, place the small particle powdered catalyst into 4.4 g of molten rosin liquid heated to 190 °C, filter again to obtain small particle powdered catalyst wrapped with rosin liquid, and after cooling, obtain the high-temperature denitration catalyst.

[0051] (4) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, and the space velocity is 30000 h -1 ) from the bottom to the top into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. When the tube furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, keep it warm for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0052] Example 3

[0053] (1) Extraction of active component precursor: Mix 2.6 g of waste manganese-based denitration catalyst, 4.8 g of rare earth slag, and 48 g of 12% mass concentration dilute hydrochloric acid solution, place them in a hydrothermal reaction kettle, perform a one-time hydrothermal reaction at 140 °C for 4 h, and then filter to obtain the supernatant;

[0054] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and use a sieve to select 9.4 g of powder with a particle size range of 100 - 140 mesh, place it in the supernatant obtained in step (1), let it stand for 4 - 6 h, add 0.3 g of NaOH and 4.5 g of deionized water, and place the mixed solution in a hydrothermal reaction kettle. Perform a secondary hydrothermal reaction at 180 °C for 6 h, filter to obtain a slurry, and then dry at 120 °C for 4 h to obtain the catalyst powder;

[0055] (3) Catalyst preparation: Dissolve 0.7 g of urea in 90 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, filter it after impregnation for 2 - 3 h, and dry it at 120 °C for 4 h. Weigh 1.6 g of polyvinyl alcohol, dissolve it in 16 g of deionized water, and heat it to dissolve at 80 °C to form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powdered catalyst (particle size is 0.150 - 0.212 mm). Finally, place the small particle powdered catalyst into 4.8 g of rosin liquid melted by heating at 190 °C, filter it again to obtain small particle powdered catalyst wrapped by rosin liquid, and obtain powdered high-temperature denitration catalyst after cooling.

[0056] (4) Activity test: Weigh 2 g of powdered denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity is 30000 h -1 ) from the bottom to the top into the metal reaction tube to suspend the powdered high-temperature denitration catalyst in the metal reaction tube. When the tube furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, and measure the denitration efficiency at the reaction temperature points after holding for 5 min. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0057] Example 4

[0058] (1) Extraction of active component precursor: Mix 2.4 g of waste manganese-based denitration catalyst, 5.2 g of rare earth slag, and 52 g of dilute hydrochloric acid solution with a mass concentration of 11% in a hydrothermal reaction kettle, conduct a hydrothermal reaction at 140 °C for 4 h once, and filter to obtain the supernatant;

[0059] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and select 9.6 g of powder with a particle size range of 100 - 140 mesh using a sieve, place it in the supernatant obtained in step (1), after standing for 4 - 6 h, add 0.4 g of NaOH and 4.0 g of deionized water, and place the mixed solution in a hydrothermal reaction kettle. Conduct a hydrothermal reaction at 180 °C for 8 h twice, filter to obtain a slurry, and then dry it at 120 °C for 4 h to obtain catalyst powder;

[0060] (3) Catalyst preparation: Dissolve 0.8 g of urea in 9.0 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, impregnate for 2 - 3 h, filter, and dry at 120 °C for 4 h. Weigh 1.4 g of polyvinyl alcohol, dissolve it in 14 g of deionized water, and heat it at 80 °C to dissolve and form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powder catalysts (particle size 0.150 - 0.212 mm). Finally, place the small particle powder catalysts into 5.2 g of molten rosin liquid heated to 190 °C, filter again to obtain small particle powder catalysts wrapped with rosin liquid, and obtain powder high-temperature denitration catalysts after cooling.

[0061] (4) Activity test: Weigh 2 g of the powder high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the powder high-temperature denitration catalyst in the metal reaction tube. When the tube furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, keep it warm for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0062] Example 5

[0063] (1) Extraction of active component precursor: Mix 2.2 g of waste manganese-based denitration catalyst, 5.6 g of rare earth slag, and 56 g of dilute hydrochloric acid solution with a mass concentration of 14% in a hydrothermal reaction kettle, conduct a hydrothermal reaction at 140 °C for 4 h once, and filter to obtain the supernatant;

[0064] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and use a sieve to select 9.8 g of powder with a particle size range of 100 - 140 mesh, place it in the supernatant obtained in step (1), let it stand for 4 - 6 h, add 0.5 g of NaOH and 6.0 g of deionized water, and place the mixed solution in a hydrothermal reaction kettle. Conduct a hydrothermal reaction at 180 °C for 8 h twice, filter to obtain a slurry, and then dry at 120 °C for 4 h to obtain catalyst powder;

[0065] (3) Catalyst preparation: Dissolve 0.9 g of urea in 9.0 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, impregnate for 2 - 3 h, filter, and dry at 120 °C for 4 h. Weigh 1.2 g of polyvinyl alcohol, dissolve it in 12 g of deionized water, and heat it to 80 °C to dissolve and form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powder catalysts (particle size 0.150 - 0.212 mm). Finally, place the small particle powder catalysts into 5.6 g of rosin liquid melted by heating at 180 °C, filter again to obtain small particle powder catalysts wrapped with rosin liquid, and obtain powder high-temperature denitration catalysts after cooling.

[0066] (4) Activity test: Weigh 2 g of the powder high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the powder high-temperature denitration catalyst in the metal reaction tube. Wait until the tube furnace heats up to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, keep it warm for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0067] Example 6

[0068] (1) Extraction of active component precursor: Mix 2.0 g of waste manganese-based denitration catalyst, 6.0 g of rare earth slag, and 80 g of 15% by mass concentration of dilute hydrochloric acid solution, place them in a hydrothermal reaction kettle, conduct a one-time hydrothermal reaction at 140 °C for 4 h, and then filter to obtain the supernatant.

[0069] (2) Crystal plane regulation of active components: Crush the waste rare earth-based denitration catalyst and use a sieve to select 10.0 g of powder with a particle size range of 100 - 140 mesh, place it in the supernatant obtained in step (1), let it stand for 4 - 6 h, add 0.5 g of NaOH and 6.0 g of deionized water, and place the mixed solution in a hydrothermal reaction kettle. Conduct a secondary hydrothermal reaction at 180 °C for 8 h, filter to obtain a slurry, and then dry at 120 °C for 4 h to obtain catalyst powder.

[0070] (3) Catalyst preparation: Dissolve 1.0 g of urea in 15 g of deionized water to obtain a urea solution. Then, place the catalyst powder obtained in step (2) into the urea solution, impregnate for 2 - 3 h, and then filter and dry at 120 °C for 4 h. Weigh 1.0 g of polyvinyl alcohol and dissolve it in 10 g of deionized water and heat it to dissolve at 80 °C to form a polyvinyl alcohol solution. Then, add the polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powder catalysts (particle size 0.150 - 0.212 mm). Finally, place the small particle powder catalysts into 6.0 g of rosin liquid melted by heating at 200 °C, filter again to obtain small particle powder catalysts wrapped with rosin liquid, and cool to obtain powder high-temperature denitration catalysts.

[0071] (4) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the powder high-temperature denitration catalyst in the metal reaction tube. When the tube furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, keep it warm for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 1 .

[0072] Comparative example 1

[0073] (1) Catalyst preparation: When preparing the catalyst, except that no NaOH solution is added in step (2), other conditions are the same as in Example 1;

[0074] (2) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, space velocity 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. When the tube furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, keep it warm for 5 min, and then measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 2 .

[0075] (3) Comparative effect: Without using NaOH solution as the crystal plane regulator, the high-energy crystal planes of CeO2 and MnO2 are exposed. Its NO removal efficiency at 700 - 1200 °C is only 67% at most. The main reason is that the conventional crystal plane is the main exposed crystal plane, and the electron energy provided by the active component for the reaction is reduced, resulting in a decrease in the catalyst activity. x

[0076] Comparative example 2

[0077] (1) Catalyst preparation: When preparing the catalyst, except that urea is replaced by ammonia water in step (3), other conditions are the same as in Example 2;

[0078] (2) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, and the space velocity is 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. Wait until the tube furnace heats up to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, and after holding for 5 minutes, measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 2 .

[0079] (3) Comparison effect: When urea is replaced by ammonia water during the catalyst preparation process, its NO x removal efficiency at 700 - 1200 °C is only 13% at most. The main reason is that ammonia water volatilizes continuously during the preparation process, resulting in the lack of a reducing agent. Only relying on the reducing agent formed by the decomposition of polyvinyl alcohol and rosin leads to a significant decrease in activity.

[0080] Comparative Example 3

[0081] (1) Catalyst preparation: When preparing the catalyst, except that polyvinyl alcohol is not added in step (3), other conditions are the same as in Example 3;

[0082] (2) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, and the space velocity is 30000 h -1 ) from the bottom up into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. Wait until the tube furnace heats up to 700 - 1200 °C, place the metal reaction tube in a vertical tube furnace, and after holding for 5 minutes, measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst denitration performance is shown in Figure 2 .

[0083] (3) Comparison effect: When polyvinyl alcohol is not added during the catalyst preparation process, its NO x removal efficiency at 700 - 1200 °C is only 72% at most. The main reason is that polyvinyl alcohol does not modify the catalyst to form a porous structure, resulting in a decrease in catalytic activity.

[0084] Comparative Example 4

[0085] (1) Catalyst preparation: When preparing the catalyst, except that rosin is not added in step (3), other conditions are the same as in Example 4;

[0086] (2) Activity test: Weigh 2 g of the high-temperature denitration catalyst and place it in a metal reaction tube. Then, introduce a mixed gas (NO 1000 ppm, O2 10%, NH3 1000 ppm, N2 as the carrier gas, and the space velocity is 30000 h -1 ) from the bottom to the top into the metal reaction tube to suspend the high-temperature denitration catalyst in the metal reaction tube. After the tubular furnace is heated to 700 - 1200 °C, place the metal reaction tube in a vertical tubular furnace. After keeping it warm for 5 minutes, measure the denitration efficiency at the reaction temperature points respectively. The evaluation of the catalyst's denitration performance can be seen in Figure 2 .

[0087] (3) Comparison effect: During the preparation of the catalyst, no rosin is added. Its NO x removal efficiency at 700 - 1200 °C is only 49% at most. The main reason is that without rosin as the outer protective agent, when urea decomposes by heat, it is quickly diluted by the flue gas and carried out of the reaction tube, and the contact time between the catalyst and the reducing agent is relatively short, resulting in a significant decrease in catalytic activity.

Claims

1. A high-temperature denitrification catalyst, characterized in that: The catalyst is prepared by a secondary hydrothermal method using waste manganese-based denitration catalyst, rare earth slag, and waste rare earth-based denitration catalyst as raw materials for active components, NaOH as a crystal plane regulator, urea as a reducing agent, polyvinyl alcohol as an inner protective agent, and rosin as an outer protective agent.

2. The high-temperature denitration catalyst according to claim 1, wherein: The dosages of the components in the catalyst are as follows: Preferably:

3. A method for preparing the high-temperature denitration catalyst according to claim 1, characterized in that: The method steps are as follows: (1) Extraction of active component precursors: Mix waste manganese-based denitration catalyst, rare earth slag, and dilute hydrochloric acid solution and carry out hydrothermal reaction. After the hydrothermal reaction, filter to obtain the supernatant. (2) Crystal plane regulation of active components: After crushing the waste rare earth-based denitration catalyst into powder, place it in the supernatant obtained in step (1). After standing for 4 - 6 h, add NaOH and deionized water and carry out hydrothermal reaction again. After the reaction, filter to obtain a slurry, and dry it to obtain catalyst powder. (3) Catalyst preparation: Then place the catalyst powder obtained in step (2) in a urea solution, impregnate for 2 - 3 h and then filter and dry; then add a polyvinyl alcohol solution to the dried catalyst powder, stir and granulate to obtain small particle powder catalysts. Finally, place the small particle powder catalysts in melted rosin liquid, and then filter to obtain small particle powder catalysts wrapped with rosin liquid. After cooling, a high-temperature denitration catalyst is obtained.

4. The preparation method according to claim 2, characterized in that: In step (1), the waste manganese-based denitration catalyst uses TiO2 as a carrier, MnO2 and Fe2O3 as active components, and the rest as additives; among them, the TiO2 carrier accounts for 70% - 85% of the content of the waste manganese-based denitration catalyst, and the active components MnO2 and Fe2O3 are respectively 5% - 10% and 1% - 3% of the content of the waste manganese-based denitration catalyst. In step (1), the rare earth slag is the west tailings of Bayan Obo, and the mass fraction of CeO2 is 0.6 - 0.8%. In step (1), the mass ratio of rare earth slag to dilute hydrochloric acid solution is 1:(10 - 15), and the mass fraction of the dilute hydrochloric acid solution is 10 - 15%.

5. The preparation method according to claim 2, characterized in that: In step (1), the temperature of the hydrothermal reaction is 140 - 160 °C, and the time of the hydrothermal reaction is 4 - 6 h.

6. The preparation method according to claim 2, wherein: In step (2), the waste rare earth-based denitration catalyst uses TiO2 as a carrier, WO3 and CeO2 as active components, and the rest as additives; among them, the TiO2 carrier accounts for 70% - 85% of the content of the waste rare earth-based denitration catalyst, and the active components WO3 and CeO2 are respectively 3% - 7% and 1% - 3% of the content of the waste rare earth-based denitration catalyst. In step (2), the particle size of the powder obtained by crushing the waste rare earth-based denitration catalyst into powder is 100 - 140 mesh. In step (2), the mass ratio of NaOH to deionized water is 1:(10 - 20). The temperature of the hydrothermal reaction is 160 - 180 °C, the time of the hydrothermal reaction is 6 - 8 h, the drying temperature is 100 - 120 °C, and the drying time is 2 - 4 h.

7. The preparation method according to claim 2, characterized in that: In step (3), the drying temperature is 100 - 120 °C, and the drying time is 2 - 4 h.

8. The preparation method according to claim 2, characterized in that: In step (3), the particle size of the small particle powder catalyst is 0.150 - 0.212 mm.

9. Application of the catalyst according to claim 1 in high-temperature denitration of cement.

10. The application according to claim 9, wherein: The temperature of cement denitration is 700 - 1200 °C.

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