Catalytic denitration agent and preparation method thereof

Abstract

The application provides a catalytic denitration agent and a preparation method thereof, and comprises the following components: a reducing base: urea 30-60 parts, ammonium carbamate 10-25 parts, ammonium carbonate 5-15 parts, ammonium bicarbonate 5-15 parts; a phase change catalytic component: ammonium dihydrogen phosphate 2-6 parts, di-ammonium hydrogen phosphate 1-5 parts, molybdate 0.05-0.5 parts, tungstate 0.1-0.8 parts, organic acid metal salt 0.1-0.8 parts, modified zeolite 1-8 parts; a functional additive: dispersant 0.2-1.0 parts, surfactant 0.1-0.6 parts, corrosion inhibitor 0.05-0.2 parts. The application constructs a multi-component complex catalytic system, and the prepared high-molecular catalytic denitration agent can realize the unity of wide-temperature high-efficiency denitration, low corrosion, low ammonia escape and high operation stability while significantly reducing the phase change temperature and energy consumption, and effectively solves the multiple problems of harsh reaction conditions, unstable efficiency and equipment corrosion in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification technology in air pollution control, specifically relating to a catalytic denitrification agent and its preparation method. Background Technology

[0002] Nitrogen oxides in industrial flue gas are among the major air pollutants, posing a serious threat to the environment and human health. To cope with increasingly stringent environmental emission standards, various denitrification technologies have been developed and applied in practice, mainly including selective catalytic reduction (SCR), selective non-catalytic reduction (SNR), and the denitrification technology based on reducing agents that has emerged in recent years.

[0003] Selective catalytic reduction (SCR) technology offers high denitrification efficiency, but suffers from drawbacks such as catalyst poisoning, high investment and operating costs, the need for specific temperature windows, and poor adaptability to boiler load changes. Selective non-catalytic reduction (SNR), while catalyst-free, requires even higher reaction temperature windows and exhibits relatively lower denitrification efficiency, with significant ammonia slip. While using urea or ammonia water hydrolysis as a reducing agent avoids some of the safety risks associated with directly using liquid ammonia, it still faces numerous challenges: the urea hydrolysis reaction is slow, especially during frequent boiler load fluctuations, making it difficult for ammonia supply to quickly respond to demand changes, leading to unstable denitrification efficiency; the hydrolysis reaction requires high temperature and pressure, resulting in high energy consumption; reaction intermediates such as ammonium carbamate are highly corrosive, demanding high-quality reactor and piping materials, increasing equipment maintenance costs; furthermore, ammonia, carbon dioxide, and water vapor in the product gas are prone to condensation and ammonium salt crystallization during transport if temperature control is inadequate, causing pipe blockage and affecting the continuous and stable operation of the system.

[0004] To address the aforementioned issues, some explorations have been undertaken in existing technologies. For example, metal compounds are used as catalysts to lower the urea hydrolysis temperature and increase the reaction rate. However, metal catalysts are prone to leaching, potentially causing secondary pollution, and may deactivate under prolonged high-temperature conditions. Other technologies attempt to prepare solid powder denitrification agents by combining melamine metal complexes with peroxy acid salts. While this avoids some drawbacks of liquid systems, it still suffers from complex preparation processes, high costs, insufficient stability of the metal components in high-temperature flue gas, a limited denitrification temperature window, and poor adaptability to complex flue gas compositions. More importantly, existing technologies primarily focus on improving single functions, failing to systematically address the synergistic issues of multiple stages such as hydrolysis, catalysis, corrosion prevention, and stable transport. In particular, there is a lack of in-depth design and material support for the efficient coupling of phase change and catalytic reduction processes in the PTCR phase change catalytic reduction process.

[0005] Therefore, there is an urgent need in this field to develop a novel catalytic denitrification agent and its preparation method, which can fully leverage the advantages of PTCR (Phase Transition Catalytic Reduction) technology, improve catalytic reduction efficiency through precise control of the phase change process, and simultaneously solve problems such as corrosion, clogging, and poor stability in existing technologies, providing a more efficient and reliable solution for industrial flue gas denitrification. This novel denitrification agent needs to possess excellent phase change characteristics, enabling efficient catalytic reduction reactions under PTCR process conditions while ensuring long-term stable operation of the system. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, a catalytic denitrification agent and its preparation method are provided.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A catalytic denitrification agent, comprising, by weight, the following components:

[0009] Reducing base material: 30-60 parts urea, 10-25 parts ammonium carbamate, 5-15 parts ammonium carbonate, 5-15 parts ammonium bicarbonate;

[0010] Phase change catalyst components: 2-6 parts of ammonium dihydrogen phosphate, 1-5 parts of diammonium hydrogen phosphate, 0.05-0.5 parts of molybdate, 0.1-0.8 parts of tungstate, 0.1-0.8 parts of organic acid metal salt, and 1-8 parts of modified zeolite;

[0011] Functional additives: 0.2-1.0 parts dispersant, 0.1-0.6 parts surfactant, and 0.05-0.2 parts corrosion inhibitor.

[0012] The molybdate is selected from at least one of sodium molybdate and ammonium molybdate; the tungstate is selected from at least one of sodium tungstate and ammonium tungstate.

[0013] The organic acid metal salt is at least one of citrate, tartrate, and EDTA metal complex, wherein the metal element is zinc, copper, manganese, or iron.

[0014] In the organic acid metal salt, the mass ratio of different metal elements is zinc:copper:manganese:iron = 1:(0.5-2):(0.3-1.5):(0.2-1).

[0015] The modified zeolite is prepared by the following method: natural zeolite is acid-treated and washed until neutral, then calcined at 350-650℃ for 1.5-5 hours; then the calcined zeolite is immersed in a solution containing multiple metal salts for 3-10 hours, and finally activated at 250-550℃ for 1.5-4 hours.

[0016] The specific steps of the acid treatment are as follows: natural zeolite is treated with hydrochloric acid at 50-90℃ for 1-5 hours, and the concentration of the hydrochloric acid is 0.3-2.0 mol / L.

[0017] The solution containing multiple metal salts includes copper salt, zinc salt, manganese salt and iron salt, wherein the concentration of copper ions is 0.05-0.5 mol / L, the concentration of zinc ions is 0.1-0.6 mol / L, the concentration of manganese ions is 0.05-0.4 mol / L and the concentration of iron ions is 0.03-0.3 mol / L.

[0018] The dispersant is a compound of polyacrylamide, polyvinylpyrrolidone, and sodium polyacrylate, with a mass ratio of 1:(0.3-2):(0.2-1.5).

[0019] The surfactant is a compound of polyoxyethylene ether, alkyl polysaccharide glycoside, and sulfonate surfactants, with a mass ratio of 1:(0.5-2):(0.3-1.8).

[0020] The corrosion inhibitor is a compound of hydroquinone, benzotriazole, mercaptobenzothiazole, and organophosphonate, with a mass ratio of 1:(0.5-3):(0.3-2):(0.2-1.5).

[0021] A method for preparing a catalytic denitrification agent, the method comprising the following steps:

[0022] (1) Pretreatment of reducing base material: Mix urea, ammonium carbamate, ammonium carbonate and ammonium bicarbonate at 40-70℃ for 15-50 minutes;

[0023] (2) Preparation of phase change catalytic components: Ammonium dihydrogen phosphate, diammonium hydrogen phosphate, molybdate, tungstate, organic acid metal salt and modified zeolite are mixed and ground until the particle size is less than 100 μm;

[0024] (3) Preparation of functional additives: Mix the dispersant, surfactant and corrosion inhibitor, and add deionized water to prepare a 5-40% solution;

[0025] (4) Mixing and granulation: Mix the pretreated reducing base material, phase change catalyst component and functional additive solution at a speed of 500-1500 r / min for 5-30 minutes, and then granulate by extrusion granulator to obtain wet granules;

[0026] (5) Drying and sieving: Dry the wet particles at 70-110℃ for 1.5-5 hours, and sieve out the particles with a particle size of 0.3-3.0mm, which is the finished product of the catalytic denitrification agent.

[0027] The grinding in step (2) is carried out using an air jet mill or a ball mill; the sieving in step (5) is carried out using a vibrating screen with a mesh size of 8-30.

[0028] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0029] 1. This invention uses a composite formula of urea, ammonium carbamate, ammonium carbonate and ammonium bicarbonate as the reducing base material. This multi-component combination can produce a synergistic effect, effectively reduce the activation energy required for the hydrolysis reaction, and make the release of ammonia more stable and rapid. In particular, it can maintain a stable denitrification efficiency when the boiler load fluctuates.

[0030] 2. In the phase change catalytic component of this invention, the combined use of ammonium dihydrogen phosphate and diammonium hydrogen phosphate not only provides an acidic catalytic environment but also maintains the stability of the reaction system through the buffering effect of phosphate ions. The introduction of molybdate and tungstate significantly enhances the redox performance of the catalyst, while the synergistic effect of multiple organic acid metal salts further broadens the temperature range of the catalytic reaction.

[0031] 3. In the preparation process of the modified zeolite of the present invention, the specific surface area and pore volume of the zeolite are improved through dual modification of acid treatment and metal loading, while introducing a variety of active metal sites. This modified zeolite not only serves as an excellent catalyst support, but also promotes the diffusion and mass transfer of reactants through its special pore structure, thereby increasing the overall reaction rate.

[0032] 4. Regarding functional additives, this invention designs a compound system of dispersants, surfactants, and corrosion inhibitors. The dispersant effectively prevents the aggregation and sedimentation of the components, the surfactant improves the wettability and permeability of the material, and the corrosion inhibitor significantly inhibits the formation of corrosive intermediates such as ammonium carbamate by forming a protective film on the metal surface.

[0033] 5. The catalytic denitrification agent of the present invention exhibits good phase change characteristics in the PTCR process and can achieve efficient catalytic reduction reaction within the phase change temperature range. Its unique porous structure and surface characteristics are conducive to the adsorption and activation of reactants, and also promote the timely desorption of reaction products, avoiding the blockage of active sites. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows:

[0036] Urea: Purchased from Hubei Xingfa Chemical Group Co., Ltd., industrial grade.

[0037] Ammonium carbamate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., purity 99%.

[0038] Ammonium carbonate: purchased from Sinopharm Chemical Reagent Co., Ltd., analytical grade.

[0039] Ammonium bicarbonate: purchased from Tianjin Bodi Chemical Co., Ltd., industrial grade.

[0040] Ammonium dihydrogen phosphate: Purchased from Sichuan Lanjian Chemical Technology Co., Ltd., industrial grade.

[0041] Diammonium hydrogen phosphate: Purchased from Yunnan Chengjiang Phosphate Chemical Co., Ltd., industrial grade.

[0042] Sodium molybdate: purchased from Changsha Yongxin Chemical Co., Ltd., industrial grade.

[0043] Sodium tungstate: purchased from Zigong Cemented Carbide Co., Ltd., industrial grade.

[0044] Zinc citrate: purchased from Zhejiang Xin'an Chemical Group Co., Ltd., industrial grade.

[0045] Ammonium molybdate: Purchased from Jinduicheng Molybdenum Co., Ltd., industrial grade.

[0046] Ammonium tungstate: Purchased from Ganzhou Qiandong Rare Earth Group Co., Ltd., industrial grade.

[0047] Copper tartrate: Purchased from Shanghai Maclean Biochemical Technology Co., Ltd., 98% purity.

[0048] EDTA iron-manganese complex: purchased from Nanjing Chemical Reagent Co., Ltd., industrial grade.

[0049] Polyacrylamide: Purchased from Aisen (China) Flocculant Co., Ltd., anionic type.

[0050] Polyvinylpyrrolidone: Purchased from BASF (China) Co., Ltd., type K30

[0051] Sodium polyacrylate: Purchased from Shandong Baomo Biochemical Co., Ltd., industrial grade.

[0052] Polyoxyethylene ethers: Purchased from Jiangsu Haian Petrochemical Plant, type O-20

[0053] Alkyl polysaccharide glycosides: purchased from Shanghai Fakai Chemical Co., Ltd., type APG0814

[0054] Sulfonate surfactants: purchased from China National Light Industry Chemical Co., Ltd., MES type.

[0055] Hydroquinone: Purchased from Hubei Jusheng Technology Co., Ltd., industrial grade.

[0056] Benzotriazole: Purchased from Nanjing Runsheng Petrochemical Co., Ltd., industrial grade

[0057] Mercaptobenzothiazole: Purchased from Tianjin Kemei Chemical Reagent Co., Ltd., industrial grade.

[0058] Organophosphonates: purchased from Shandong Taihe Water Treatment Technology Co., Ltd., DTPMPA type

[0059] Natural zeolite: purchased from Nanjing Chenshao Building Materials Co., Ltd.

[0060] Hydrochloric acid: purchased from Zhejiang Juhua Co., Ltd., chemically pure.

[0061] Copper salt: Purchased from Jinan Xiangfa Chemical Technology Co., Ltd., copper sulfate

[0062] Zinc salt: Purchased from Tianjin Dingshengxin Chemical Co., Ltd., zinc sulfate heptahydrate

[0063] Manganese salts: Purchased from Xinke Chemical Technology Co., Ltd., manganese sulfate monohydrate

[0064] Iron salts: purchased from Guangzhou Cancheng Chemical Technology Co., Ltd., ferrous sulfate.

[0065] The technical solution of this application is as follows:

[0066] A catalytic denitrification agent, comprising, by weight, the following components:

[0067] Reducing base material: 30-60 parts urea, 10-25 parts ammonium carbamate, 5-15 parts ammonium carbonate, 5-15 parts ammonium bicarbonate;

[0068] Phase change catalyst components: 2-6 parts of ammonium dihydrogen phosphate, 1-5 parts of diammonium hydrogen phosphate, 0.05-0.5 parts of molybdate, 0.1-0.8 parts of tungstate, 0.1-0.8 parts of organic acid metal salt, and 1-8 parts of modified zeolite;

[0069] Functional additives: 0.2-1.0 parts dispersant, 0.1-0.6 parts surfactant, and 0.05-0.2 parts corrosion inhibitor.

[0070] The molybdate is selected from at least one of sodium molybdate and ammonium molybdate; the tungstate is selected from at least one of sodium tungstate and ammonium tungstate.

[0071] The organic acid metal salt is at least one of citrate, tartrate, and EDTA metal complex, wherein the metal element is zinc, copper, manganese, or iron.

[0072] In the organic acid metal salt, the mass ratio of different metal elements is zinc:copper:manganese:iron = 1:(0.5-2):(0.3-1.5):(0.2-1).

[0073] The modified zeolite is prepared by the following method: natural zeolite is acid-treated and washed until neutral, then calcined at 350-650℃ for 1.5-5 hours; then the calcined zeolite is immersed in a solution containing multiple metal salts for 3-10 hours, and finally activated at 250-550℃ for 1.5-4 hours.

[0074] The specific steps of the acid treatment are as follows: natural zeolite is treated with hydrochloric acid at 50-90℃ for 1-5 hours, and the concentration of the hydrochloric acid is 0.3-2.0 mol / L.

[0075] The solution containing multiple metal salts includes copper salt, zinc salt, manganese salt and iron salt, wherein the concentration of copper ions is 0.05-0.5 mol / L, the concentration of zinc ions is 0.1-0.6 mol / L, the concentration of manganese ions is 0.05-0.4 mol / L and the concentration of iron ions is 0.03-0.3 mol / L.

[0076] The dispersant is a compound of polyacrylamide, polyvinylpyrrolidone, and sodium polyacrylate, with a mass ratio of 1:(0.3-2):(0.2-1.5).

[0077] The surfactant is a compound of polyoxyethylene ether, alkyl polysaccharide glycoside, and sulfonate surfactants, with a mass ratio of 1:(0.5-2):(0.3-1.8).

[0078] The corrosion inhibitor is a compound of hydroquinone, benzotriazole, mercaptobenzothiazole, and organophosphonate, with a mass ratio of 1:(0.5-3):(0.3-2):(0.2-1.5).

[0079] A method for preparing a catalytic denitrification agent, the method comprising the following steps:

[0080] (1) Pretreatment of reducing base material: Mix urea, ammonium carbamate, ammonium carbonate and ammonium bicarbonate at 40-70℃ for 15-50 minutes;

[0081] (2) Preparation of phase change catalytic components: Ammonium dihydrogen phosphate, diammonium hydrogen phosphate, molybdate, tungstate, organic acid metal salt and modified zeolite are mixed and ground until the particle size is less than 100 μm;

[0082] (3) Preparation of functional additives: Mix the dispersant, surfactant and corrosion inhibitor, and add deionized water to prepare a 5-40% solution;

[0083] (4) Mixing and granulation: Mix the pretreated reducing base material, phase change catalyst component and functional additive solution at a speed of 500-1500 r / min for 5-30 minutes, and then granulate by extrusion granulator to obtain wet granules;

[0084] (5) Drying and sieving: Dry the wet particles at 70-110℃ for 1.5-5 hours, and sieve out the particles with a particle size of 0.3-3.0mm, which is the finished product of the catalytic denitrification agent.

[0085] The grinding in step (2) is carried out using an air jet mill or a ball mill; the sieving in step (5) is carried out using a vibrating screen with a mesh size of 8-30.

[0086] This invention constructs a multi-component compound catalytic system, which significantly reduces phase change temperature and energy consumption while achieving a balance between wide-temperature high-efficiency denitrification, low corrosion, low ammonia escape, and high operational stability. It effectively solves multiple problems in existing technologies, such as harsh reaction conditions, unstable efficiency, and equipment corrosion.

[0087] The technical solutions of the present invention are further illustrated below through examples and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0088] Example 1

[0089] This embodiment provides a catalytic denitrification agent, the composition of which, by weight, is: 60 parts urea, 17.5 parts ammonium carbamate, 5 parts ammonium carbonate, 15 parts ammonium bicarbonate, 6 parts ammonium dihydrogen phosphate, 1 part diammonium hydrogen phosphate, 0.5 parts sodium molybdate, 0.1 parts sodium tungstate, 0.8 parts zinc citrate, 1 part modified zeolite, 0.5 parts polyacrylamide, 0.3 parts polyvinylpyrrolidone, 0.15 parts sodium polyacrylate, 0.2 parts polyoxyethylene ethers, 0.2 parts alkyl polysaccharide glycosides, 0.15 parts sulfonate surfactants, 0.05 parts hydroquinone, 0.075 parts benzotriazole, 0.04 parts mercaptobenzothiazole, and 0.025 parts organophosphonates.

[0090] The modified zeolite was prepared using the following process: Natural zeolite was treated with 2.0 mol / L hydrochloric acid at 50°C for 5 hours, washed until neutral, and then calcined at 350°C for 5 hours. Subsequently, the calcined zeolite was impregnated in a specific metal salt solution containing 0.05 mol / L copper ions, 0.6 mol / L zinc ions, 0.05 mol / L manganese ions, and 0.3 mol / L iron ions for 3 hours. Finally, it was activated at 550°C for 1.5 hours.

[0091] The preparation process includes the following steps: First, urea, ammonium carbamate, ammonium carbonate, and ammonium bicarbonate are mixed and stirred at 40°C for 50 minutes to obtain a pretreated base material. Then, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium molybdate, sodium tungstate, zinc citrate, and modified zeolite are mixed and ground using an air jet mill until the particle size is less than 100 μm to obtain a phase change catalyst component. Next, various functional additives weighed strictly according to the above proportions are mixed and added to deionized water to prepare a 5% solution. Finally, the pretreated base material, phase change catalyst component, and functional additive solution are mixed and stirred at 500 r / min for 30 minutes, and granulated by an extrusion granulator to obtain wet granules. The wet granules are dried at 70°C for 5 hours and sieved through an 8-mesh vibrating screen to obtain the final granular product with a particle size of 0.3-3.0 mm.

[0092] Example 2

[0093] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0094] This embodiment provides another catalytic denitrification agent, the composition of which, by weight, is: 30 parts urea, 25 parts ammonium carbamate, 15 parts ammonium carbonate, 5 parts ammonium bicarbonate, 2 parts ammonium dihydrogen phosphate, 5 parts diammonium hydrogen phosphate, 0.05 parts ammonium molybdate, 0.8 parts ammonium tungstate, 0.1 parts copper tartrate, 8 parts modified zeolite, 0.15 parts polyacrylamide, 0.1 parts polyvinylpyrrolidone, 0.05 parts sodium polyacrylate, 0.06 parts polyoxyethylene ethers, 0.09 parts alkyl polysaccharide glycosides, 0.03 parts sulfonate surfactants, 0.015 parts hydroquinone, 0.015 parts benzotriazole, 0.012 parts mercaptobenzothiazole, and 0.008 parts organophosphonates.

[0095] The modified zeolite preparation process is as follows: Natural zeolite is treated with 0.3 mol / L hydrochloric acid at 90℃ for 1 hour, washed, and then calcined at 650℃ for 1.5 hours. The zeolite is then impregnated in a solution containing 0.5 mol / L copper ions, 0.1 mol / L zinc ions, 0.4 mol / L manganese ions, and 0.03 mol / L iron ions for 10 hours, and finally activated at 250℃ for 4 hours.

[0096] The preparation process includes: mixing and stirring the basic raw materials at 70°C for 15 minutes to obtain a pretreated base material. The catalytic components are mixed and then ground to the required fineness using a ball mill. The functional additives are prepared into a 40% solution according to the above proportions and mixed with the aforementioned components. The mixture is then stirred at 1500 r / min for 5 minutes, granulated, dried at 110°C for 1.5 hours, and sieved through a 30-mesh sieve to obtain the finished product.

[0097] Example 3

[0098] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0099] This embodiment provides another catalytic denitrification agent, the composition of which, by weight, is: 45 parts urea, 10 parts ammonium carbamate, 10 parts ammonium carbonate, 10 parts ammonium bicarbonate, 4 parts ammonium dihydrogen phosphate, 3 parts diammonium hydrogen phosphate, 0.275 parts sodium molybdate, 0.45 parts sodium tungstate, 0.45 parts EDTA iron-manganese complex, 4.5 parts modified zeolite, 0.3 parts polyacrylamide, 0.18 parts polyvinylpyrrolidone, 0.12 parts sodium polyacrylate, 0.1 parts polyoxyethylene ethers, 0.15 parts alkyl polysaccharide glycosides, 0.1 parts sulfonate surfactants, 0.03 parts hydroquinone, 0.045 parts benzotriazole, 0.03 parts mercaptobenzothiazole, and 0.02 parts organophosphonates.

[0100] The modified zeolite was prepared using a compromise parameter: treatment with 1.15 mol / L hydrochloric acid at 70℃ for 3 hours, followed by calcination at 500℃ for 3.25 hours. The impregnation solution contained 0.275 mol / L copper ions, 0.35 mol / L zinc ions, 0.225 mol / L manganese ions, and 0.165 mol / L iron ions. After impregnation for 6.5 hours, it was activated at 400℃ for 2.75 hours.

[0101] The preparation process parameters are as follows: mixing at 55℃ for 32.5 minutes, grinding with an air jet mill, preparing a 22.5% solution of functional additives according to the above ratio, mixing at 1000 r / min for 17.5 minutes, drying at 90℃ for 3.25 hours, and sieving through a 19-mesh sieve.

[0102] Comparative Example 1

[0103] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0104] It does not contain modified zeolite components.

[0105] Comparative Example 2

[0106] In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows:

[0107] Adjust the ratio of metal elements in the organic acid metal salt to zinc:copper:manganese:iron = 1:0.2:0.1:0.1.

[0108] Comparative Example 3

[0109] In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows:

[0110] Use unmodified natural zeolite.

[0111] Comparative Example 4

[0112] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0113] The dispersant used in the functional additives is only polyacrylamide (0.95 parts), and does not contain polyvinylpyrrolidone or sodium polyacrylate.

[0114] Comparative Example 5

[0115] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0116] The corrosion inhibitor uses only hydroquinone (0.05 parts) and does not contain benzotriazole, mercaptobenzothiazole, or organophosphonates.

[0117] Performance Test Results and Analysis

[0118] Catalytic denitrification agents were prepared according to the parameters of the examples and comparative examples, and all samples underwent systematic testing under conditions simulating the actual PTCR process environment. The ammonia conversion characteristics of the samples were investigated within the phase transition temperature range, with a test pressure of 0.5 MPa and a temperature gradient of 120-150 °C. Corrosion rate testing was performed using the gravimetric method in a simulated hydrolysis environment. Hygroscopicity and agglomeration rate tests were conducted in a constant temperature and humidity chamber at 40 °C and 80% relative humidity. Denitrification efficiency testing was performed in a custom-designed reaction apparatus, simulating flue gas composition, with the reaction temperature controlled within the optimal phase transition range.

[0119] Table 1 Analysis of Test Results

[0120]

[0121] As shown in Table 1, the products from the three examples prepared strictly according to the formulation and proportion requirements of this invention exhibited comprehensive and excellent performance in the PTCR phase change catalytic reduction process. Example 3 showed the best overall performance, with an ammonia conversion rate of 95.1% and a denitrification efficiency of 93.8%. This was attributed to the balanced setting of parameters for each component, especially the synergistic effect of the functional additive compound system, which made the phase change process more stable and efficient. Examples 1 and 2 also showed good PTCR phase change characteristics, with all core indicators significantly better than all comparative examples.

[0122] All the products in the examples exhibited a narrower window (122-145°C) within the phase transition temperature range, which is closer to the ideal reaction temperature. This indicates that their phase transition process is more concentrated and controllable, which is conducive to the stable release of ammonia and the efficient reduction of nitrogen oxides. This is also the key reason for their high denitrification efficiency and low ammonia slip. Regarding corrosion resistance, the corrosion rate of the products in the examples was significantly lower than that of the comparative examples. This directly proves the effectiveness of the corrosion inhibition system composed of hydroquinone, benzotriazole, mercaptobenzothiazole, and organophosphonates. This system can form a dense protective film on the metal surface, significantly inhibiting the erosion of corrosive intermediates such as ammonium carbamate.

[0123] Comparative Example 1, lacking acid-treated and metal-supported modified zeolite, exhibited a significantly higher and wider phase transition temperature range, resulting in a marked decrease in catalytic efficiency. This demonstrates the importance of modified zeolite as a catalyst support and in providing active sites. In Comparative Example 2, the imbalanced metal element ratio weakened the synergistic effect of the catalytic components, leading to a decline in redox performance. Comparative Example 3 used unmodified zeolite, whose pore structure and surface properties were not optimized, failing to provide effective support for phase change catalysis. Comparative Examples 4 and 5 demonstrated the significant advantages of using a compound system of functional additives (dispersants and corrosion inhibitors) compared to single components. The compound system exhibited synergistic effects in preventing component aggregation, improving material properties, and inhibiting corrosion; the absence of any one component led to a decline in performance.

[0124] In the actual operation of the PTCR process, the product in the examples also exhibited good physical stability. Low moisture absorption and low agglomeration rate ensured smooth operation during storage and pneumatic conveying, which is crucial for ensuring the long-term stable operation of the denitrification system. In summary, these experimental results fully demonstrate that this invention, through precise component selection, strict ratio control, and optimized preparation process, has successfully developed a high-performance catalytic denitrification agent highly suitable for the PTCR process, providing an effective technical solution to overcome the bottleneck problems in existing technologies.

[0125] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A catalytic denitrification agent, characterized in that, The catalytic denitrification agent comprises the following components in parts by weight: Reducing base material: 30-60 parts urea, 10-25 parts ammonium carbamate, 5-15 parts ammonium carbonate, 5-15 parts ammonium bicarbonate; Phase change catalyst components: 2-6 parts of ammonium dihydrogen phosphate, 1-5 parts of diammonium hydrogen phosphate, 0.05-0.5 parts of molybdate, 0.1-0.8 parts of tungstate, 0.1-0.8 parts of organic acid metal salt, and 1-8 parts of modified zeolite; Functional additives: 0.2-1.0 parts dispersant, 0.1-0.6 parts surfactant, and 0.05-0.2 parts corrosion inhibitor; The organic acid metal salt is at least one of citrate, tartrate, and EDTA metal complex, wherein the metal element is zinc, copper, manganese, or iron; In the organic acid metal salt, the mass ratio of different metal elements is zinc:copper:manganese:iron = 1:(0.5-2):(0.3-1.5):(0.2-1); The modified zeolite is prepared by the following method: natural zeolite is acid-treated and washed until neutral, then calcined at 350-650℃ for 1.5-5 hours; then the calcined zeolite is immersed in a solution containing multiple metal salts for 3-10 hours, and finally activated at 250-550℃ for 1.5-4 hours. The solution containing multiple metal salts includes copper salt, zinc salt, manganese salt, and iron salt, wherein the concentration of copper ions is 0.05-0.5 mol / L, the concentration of zinc ions is 0.1-0.6 mol / L, the concentration of manganese ions is 0.05-0.4 mol / L, and the concentration of iron ions is 0.03-0.3 mol / L; the dispersant is a compound of polyacrylamide, polyvinylpyrrolidone, and sodium polyacrylate, with a mass ratio of 1:(0.3-2):(0.2-1.5). The surfactant is a compound of polyoxyethylene ether, alkyl polysaccharide glycoside, and sulfonate surfactants, with a mass ratio of 1:(0.5-2):(0.3-1.8). The corrosion inhibitor is a compound of hydroquinone, benzotriazole, 2-mercaptobenzothiazole, and organophosphonate, with a mass ratio of 1:(0.5-3):(0.3-2):(0.2-1.5).

2. The catalytic denitrification agent according to claim 1, characterized in that, The molybdate is selected from at least one of sodium molybdate and ammonium molybdate; the tungstate is selected from at least one of sodium tungstate and ammonium tungstate.

3. The catalytic denitrification agent according to claim 1, characterized in that, The specific steps of the acid treatment are as follows: natural zeolite is treated with hydrochloric acid at 50-90℃ for 1-5 hours, and the concentration of the hydrochloric acid is 0.3-2.0 mol / L.

4. A method for preparing a catalytic denitrification agent as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Pretreatment of reducing base material: Mix urea, ammonium carbamate, ammonium carbonate and ammonium bicarbonate at 40-70℃ for 15-50 minutes; (2) Preparation of phase change catalytic components: Ammonium dihydrogen phosphate, diammonium hydrogen phosphate, molybdate, tungstate, organic acid metal salt and modified zeolite are mixed and ground until the particle size is less than 100 μm; (3) Preparation of functional additives: Mix the dispersant, surfactant and corrosion inhibitor, and add deionized water to prepare a 5-40% solution; (4) Mixing and granulation: Mix the pretreated reduced base material, phase change catalyst component and functional additive solution at a speed of 500-1500 r / min for 5-30 minutes, and then granulate by extrusion granulator to obtain wet granules; (5) Drying and sieving: Dry the wet particles at 70-110℃ for 1.5-5 hours, and sieve out the particles with a particle size of 0.3-3.0mm, which is the finished product of the catalytic denitrification agent.

5. The method for preparing the catalytic denitrification agent according to claim 4, characterized in that, The grinding in step (2) is carried out using an air jet mill or a ball mill; the sieving in step (5) is carried out using a vibrating screen with a mesh size of 8-30.

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