Dual-support cerium-titanium low-temperature denitration catalyst and preparation method thereof

Abstract

The application discloses an environment catalysis field, and discloses a double-carrier cerium-titanium low-temperature denitration catalyst and a preparation method thereof. The catalyst adopts cerium-titanium composite oxides as main active components, and innovatively introduces two modified components, namely, neodymium-cerium oxide solid solution and zirconium-titanium oxide compound, to form a double-carrier system with titanium dioxide and aluminum oxide. The preparation process comprises the following steps: synthesizing cerium-titanium composite oxide precursors with mesoporous structures by a modified hydrothermal method; preparing the neodymium-cerium oxide solid solution by a coprecipitation method under argon protection, so as to ensure uniform element doping; obtaining the zirconium-titanium oxide compound by high-temperature hydrothermal reaction combined with aging treatment; and finally mixing the components in a specific proportion, and performing ball milling, drying and programmed calcination treatment, so that stable composite structures and active interfaces with strong synergistic effects are formed among the components. The catalyst exhibits excellent nitrogen oxide removal efficiency and anti-poisoning capacity under low-temperature conditions, and is suitable for industrial flue gas purification fields.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis technology, specifically to a dual-support cerium-titanium low-temperature denitrification catalyst and its preparation method. Background Technology

[0002] Selective catalytic reduction (SCR) is currently the most widely used nitrogen oxide (NOx) control technology, and its core lies in the development of high-performance catalysts. Traditional commercial catalysts, represented by vanadium-titanium systems, while technically mature, suffer from problems such as a high activity temperature window, insufficient low-temperature activity, and susceptibility to poisoning and deactivation in sulfur-containing flue gas. This limits their application in low- and medium-temperature flue gas conditions, such as those found in industrial boilers and sintering machines. To meet increasingly stringent NOx emission standards, developing denitrification catalysts with excellent low-temperature activity and good stability has become a research hotspot and challenge in the field of environmental catalysis. In recent years, researchers have conducted extensive work on cerium-based catalysts, utilizing cerium's unique oxygen storage and release capabilities to combine it with transition metals such as titanium, attempting to improve the catalyst's sulfur resistance while lowering the activity temperature. However, most existing cerium-titanium catalysts are limited to single solid solution structures or simple supported structures, and there is still room for optimization in the number of active sites, surface acidity, and redox capabilities. Their catalytic efficiency and lifetime under complex flue gas conditions still cannot meet the demands of industrial applications.

[0003] Building upon the cerium-titanium catalyst system, further modification research mainly focuses on enhancing its overall performance through elemental doping, structural regulation, and composite supports. The introduction of rare earth elements such as neodymium and lanthanum can modulate the crystal field environment of cerium-based catalysts through electronic and geometric effects, increasing oxygen vacancy concentration and thus enhancing their activation ability for reactants. On the other hand, the incorporation of transition metals such as zirconium can form stable composite oxides with titanium, effectively suppressing the phase transformation of titanium dioxide, maintaining a high specific surface area, and also producing synergistic effects with active components, optimizing the surface acidity and thermal stability of the catalyst. However, existing technologies mostly focus on the introduction of single modifying components, and research on the synergistic mechanisms between multiple modifying components is still insufficient. In particular, how to integrate active centers with different functions into the same catalyst system through precise preparation processes and enable them to exert synergistic effects during the reaction remains a challenge for current technology. Furthermore, the macroscopic structural stability of the catalyst is equally crucial. A single titanium dioxide support is prone to sintering and crystal transformation at high temperatures, leading to a decrease in activity. Therefore, constructing a dual-support system to balance high specific surface area and structural stability is particularly important.

[0004] In summary, although existing technologies have made some progress in the development of cerium-titanium low-temperature denitration catalysts, technical bottlenecks remain, including insufficient low-temperature activity, single active sites, limited resistance to poisoning, and low structural stability. In particular, there is a lack of systematic solutions capable of comprehensively controlling the catalyst's microscopic electronic structure, mesoscopic pore structure, and macroscopic mechanical strength. Therefore, there is an urgent need to develop a novel catalyst design strategy that utilizes a multi-component synergistic and multi-structure composite approach to construct low-temperature denitration catalysts with abundant active interfaces, suitable surface acidity, and excellent structural stability. This is precisely the technical problem that this invention aims to solve and is key to advancing low-temperature denitration technology. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-support cerium-titanium low-temperature denitration catalyst and its preparation method, which solves the technical problems of insufficient activity and poor stability of existing low-temperature denitration catalysts.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A method for preparing a dual-supported cerium-titanium low-temperature denitration catalyst, comprising the following steps:

[0008] S1. Dissolve polyether in anhydrous ethanol, heat to 44-46℃, add urea and nitric acid, and stir magnetically to obtain solution A; dissolve tetrabutyl titanate in anhydrous ethanol, add glacial acetic acid, nitric acid and cerium nitrate hexahydrate, and stir magnetically to obtain solution B; mix solution A and solution B in a polytetrafluoroethylene autoclave, maintain at 88-92℃, then cool to 78-82℃ and maintain, then heat to 115-125℃ for further hydrothermal treatment to obtain the cerium-titanium composite oxide precursor;

[0009] S2. The cerium-titanium composite oxide precursor is washed with ethanol and dried at 98-102℃. The dried cerium-titanium composite oxide precursor is calcined at 398-402℃ to obtain cerium-titanium composite oxide. The cerium-titanium composite oxide, neodymium-cerium oxide solid solution, zirconium-titanium oxide composite, titanium dioxide and alumina are mixed, deionized water is added to make a slurry, ball milled, dried at 108-112℃, and finally calcined at 498-502℃.

[0010] In this invention, the final formation of the dual-support cerium-titanium low-temperature denitration catalyst is a multi-component, multi-step composite and integrated process. Its core mechanism lies in achieving uniform distribution of functional components at the mesoscale and strong chemical coupling at the interfaces through physical mixing and high-temperature heat treatment. First, the cerium-titanium composite oxide synthesized via a modified template-assisted hydrothermal method possesses abundant mesoporous structures and amorphous Ce-O-Ti active units, providing fundamental catalytic activity and nitrogen oxide adsorption sites. This composite oxide is then mechanically ball-milled with a pre-prepared neodymium-cerium oxide solid solution, a zirconium-titanium oxide composite, and titanium dioxide and alumina as dual supports. This process not only achieves preliminary uniform mixing of the components, but the mechanical force generated by ball milling also helps break up large particle agglomerates, increases the contact area between components, and activates the surface for subsequent solid-phase reactions. After drying in a slurry made from deionized water, the most critical reaction occurs in the final temperature-controlled calcination stage. During this high-temperature treatment, a series of solid-phase ion diffusions and interfacial reactions occur at the contact interfaces of the components. The active species in the Nd-cerium oxide solid solution may interact with the surface of the cerium-titanium composite oxide or titanium dioxide support, further optimizing the distribution and concentration of surface oxygen vacancies. The zirconium-titanium oxide composite may enhance the overall catalyst's structural stability and surface acidity through interfacial bonding with the cerium-titanium composite oxide and alumina support. More importantly, the calcination process promotes the formation of stable chemical bridges between the active phases (such as Ce-O-Ti, Nd-Ce-O, Zr-Ti-O) and between the active phase and the dual supports, such as strong interaction interfaces like Ce-O-Ti, Ce-O-Al, and Ti-O-Al. These interfaces become rapid channels for electron transfer, achieving electronic synergy between different active centers, resulting in an optimal match between the catalyst's redox performance and surface acidity. The final catalyst is an organic whole integrating low-temperature high activity, abundant surface acid sites, a large number of oxygen vacancies, and a stable macroscopic structure. Its multi-active-center synergistic mechanism jointly ensures efficient and stable catalytic reduction performance of nitrogen oxides under low-temperature conditions.

[0011] According to a preferred embodiment of the present invention, in step S1, the time to maintain at 78-82°C is 48-50 hours.

[0012] According to a preferred embodiment of the present invention, in step S2, the calcination time at 498-502°C is 5-10 hours.

[0013] According to a preferred embodiment of the present invention, the method for preparing the neodymium-cerium oxide solid solution includes: A1, dissolving neodymium nitrate and cerium nitrate in deionized water, adding polyethylene glycol, stirring magnetically, and then adding ammonia dropwise under argon protection until pH=8.9-9.1 to form a precipitate; A2, aging the precipitate at 78-82°C, washing it with deionized water and ethanol, drying it at 98-102°C, and finally calcining it at 545-555°C.

[0014] In this invention, the formation of the neodymium-cerium oxide solid solution is a complex process involving co-precipitation, lattice doping, and high-temperature solid-phase reaction. Under argon protection, a mixed solution of neodymium nitrate and cerium nitrate is co-precipitated with ammonia. This environment effectively prevents premature oxidation of cerium ions under alkaline conditions, ensuring uniform co-precipitation of neodymium and cerium ions as hydroxides or basic carbonates. Polyethylene glycol, as a dispersant, with its long-chain molecular structure, adsorbs onto the surface of newly formed precipitate particles, preventing excessive particle aggregation through steric hindrance and laying the structural foundation for the subsequent formation of a high specific surface area solid solution. The precipitate undergoes aging treatment, promoting the transformation of the initially formed amorphous precipitate into a more stable structure and simultaneously achieving initial fusion between components. During subsequent drying and high-temperature calcination, the precipitate precursor first undergoes dehydration and thermal decomposition, removing nitrate and hydroxide ions to form an amorphous mixed oxide of neodymium and cerium. As the calcination temperature rises to a specific range, neodymium ions, with their similar ionic radii to cerium ions, begin to diffuse and enter the fluorite-type lattice of cerium oxide, replacing some of the cerium ion positions and forming a substitutional solid solution. This doping process induces lattice distortion and charge compensation effects, leading to the formation of a large number of oxygen vacancies. These oxygen vacancies, along with the electronic structure modulation caused by neodymium doping, significantly enhance the oxygen storage capacity and bulk oxygen migration rate of the solid solution, providing it with more active oxygen species and a more efficient redox cycle capability in denitrification reactions.

[0015] According to a preferred embodiment of the present invention, in step A1, the magnetic stirring time is 30-40 minutes.

[0016] According to a preferred embodiment of the present invention, in step A2, the aging time at 78-82°C is 2-4 hours.

[0017] According to a preferred embodiment of the present invention, the preparation method of the zirconium-titanium oxide composite includes: B1, dissolving zirconium oxychloride and tetrabutyl titanate in anhydrous ethanol, adding nitric acid, stirring magnetically, then allowing it to age at room temperature, and then transferring it to a polytetrafluoroethylene autoclave for hydrothermal reaction at 178-182°C; B2, after the reaction is completed, allowing it to cool naturally, washing with ethanol, drying at 98-102°C, and finally calcining at 598-602°C.

[0018] In this invention, the synthesis of zirconium-titanium oxide composites is primarily based on a combination of sol-gel chemistry and hydrothermal reactions. In the initial stage, zirconium oxychloride and tetrabutyl titanate are co-dissolved in ethanol. Under the catalysis of nitric acid, they undergo synergistic hydrolysis and condensation reactions. Tetrabutyl titanate hydrolyzes to generate titanyl alkane chains, while zirconium oxychloride hydrolyzes to generate zirconium hydroxides or oxyhydroxyl clusters. These species gradually form Zr-O-Ti bonds through dehydration condensation, constituting the initial network structure of the composite oxide. The static aging process at room temperature is crucial, providing sufficient time for further condensation at the molecular level and the maturation of colloidal particles, allowing for more uniform premixing of zirconium and titanium species at the nanoscale, forming a relatively stable sol system. The subsequent hydrothermal reaction is carried out under high temperature and high pressure in a closed environment. This condition greatly promotes the dissolution-recrystallization process of the precursor colloidal particles and accelerates the formation and strengthening of Zr-O-Ti bonds, driving the amorphous network towards a more ordered short-range structure. The high-temperature hydrothermal environment also facilitates the removal of impurity ions from the system and regulates the size and morphology of the primary grains of the composite oxide. The final high-temperature calcination treatment aims to completely remove residual organic components and chloride ions, and promote further condensation and densification of the amorphous zirconium-titanium composite oxide, forming a stable crystal structure. The introduction of zirconium effectively inhibits the transformation of titanium dioxide from the anatase phase to the rutile phase, stabilizing the high-surface-area anatase phase. Simultaneously, it introduces lattice stress and defects caused by the difference in valence state and radius of zirconium and titanium ions. These defects often become active sites for catalytic reactions and enhance the surface acidity and thermal stability of the material.

[0019] According to a preferred embodiment of the present invention, in step B1, the hydrothermal reaction time at 178-182°C is 24-30 hours.

[0020] According to a preferred embodiment of the present invention, in step B2, the calcination time at 598-602°C is 3-4 hours.

[0021] The present invention also provides a method for preparing the dual-supported cerium-titanium low-temperature denitration catalyst, which comprises the following raw materials in parts by weight: 30-50 parts by weight of cerium-titanium composite oxide; 10-20 parts by weight of neodymium-cerium oxide solid solution; 10-20 parts by weight of zirconium-titanium oxide composite; 20-30 parts by weight of titanium dioxide; and 10-20 parts by weight of alumina.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention, through a unique dual-support design and multi-component synergistic modification strategy, produces a cerium-titanium low-temperature denitration catalyst exhibiting superior low-temperature catalytic activity. This catalyst can initiate a highly efficient nitrogen oxide reduction reaction within a relatively low temperature range, with an activation temperature significantly lower than that of traditional vanadium-titanium catalysts, and maintains near-complete nitrogen oxide conversion over a wide temperature window. This excellent low-temperature performance is attributed to the synergistic effect of multiple active centers within the catalyst: the precisely controlled cerium-titanium composite oxide provides a rich reaction interface; the neodymium-cerium oxide solid solution, due to its unique electronic structure modulation effect, significantly increases the concentration and migration rate of active oxygen species on the catalyst surface; and the zirconium-titanium oxide composite greatly promotes the adsorption and activation of reducing agent molecules by enhancing the surface acidity of the catalyst, particularly the number and strength of Lewis acid sites. The electronic synergy and structural complementarity among these three components jointly construct a highly efficient low-temperature nitrogen oxide catalytic purification system.

[0024] The catalyst of this invention not only exhibits excellent initial activity but also demonstrates significantly improved stability and resistance to poisoning. Under long-term continuous operation and in complex flue gas environments containing sulfur dioxide and water vapor, the catalyst maintains stable catalytic performance with a slow decline in denitrification efficiency. This strong anti-interference performance is mainly attributed to the stabilizing framework effect of the dual-support system and the synergistic protection mechanism of each component: the dual support composed of titanium dioxide and alumina not only provides a high specific surface area and suitable pore structure but also stabilizes the active components through strong interactions, effectively inhibiting the sintering and aggregation of active centers; the introduction of neodymium enhances the structural stability of the cerium-based oxygen storage component, enabling it to maintain lattice integrity during repeated redox cycles; and the zirconium-titanium composite, through its excellent structural stability, effectively blocks the attack and passivation of the main active sites by toxic substances in the flue gas, thereby significantly extending the catalyst's lifespan.

[0025] This invention achieves synergistic optimization of the macroscopic structure and microscopic properties of the catalyst through meticulous process design. Multi-stage programmed hydrothermal synthesis and calcination within a specific temperature range result in a highly developed mesoporous structure and suitable surface properties in the cerium-titanium composite oxide precursor, providing an ideal support for the dispersion and interaction of subsequent active components. The co-precipitation process under argon protection ensures atomic-level homogeneous mixing and the formation of specific valence states in the Nd:cerium-titanium solid solution, maximizing the electronic regulation advantages of rare earth modification. The aging and hydrothermal steps in the zirconium-titanium composite preparation process promote the homogeneous composite of zirconium and titanium species at the molecular level and the construction of a stable crystal phase structure. Finally, through an integrated process of spherical mixing and high-temperature calcination, the uniform distribution and robust bonding of each functional component on the dual supports are successfully achieved, forming a stable composite interface and a synergistically enhancing catalytic system. This systematic preparation strategy not only ensures the reliability and reproducibility of the catalyst performance but also provides a practical technical path for large-scale industrial preparation. Detailed Implementation

[0026] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0027] The following is information on domestic suppliers of key related equipment and materials:

[0028] The polyether was purchased from Jiangsu Rongfeng Chemical Co., Ltd.

[0029] The urea was purchased from Sichuan Jinxiang Chemical Co., Ltd.

[0030] The nitric acid was purchased from Anhui Jinhe Industrial Co., Ltd.

[0031] The tetrabutyl titanate was purchased from Jinan Qichen Chemical Co., Ltd.

[0032] The glacial acetic acid was purchased from Jiangsu Suopu Group Co., Ltd.

[0033] The cerium nitrate hexahydrate was purchased from Zibo Rongshuo New Materials Co., Ltd.

[0034] The titanium dioxide was purchased from CNNC Huayuan Titanium Dioxide Co., Ltd.

[0035] The alumina was purchased from the Zhengzhou Research Institute of Aluminum Corporation of China Limited.

[0036] The neodymium nitrate was purchased from Qiandong Rare Earth Group Co., Ltd.

[0037] The cerium nitrate was purchased from Jiangyin Jiahua New Materials Co., Ltd.

[0038] The polyethylene glycol was purchased from Liaoning Aoke Chemical Co., Ltd.

[0039] The zirconium oxychloride was purchased from Guangdong Oriental Zirconium Industry Technology Co., Ltd.

[0040] The tetrabutyl titanate was purchased from Jinan Qichen Chemical Co., Ltd.

[0041] Example 1 Preparation of neodymium-cerium oxide solid solution: 12.0 g of neodymium nitrate dodecahydrate and 34.7 g of cerium nitrate hexahydrate were dissolved in 200 mL of deionized water, 4.0 g of polyethylene glycol was added, and the mixture was magnetically stirred for 35 min. Then, under argon protection, ammonia water was added dropwise until the pH reached 9.0, and a precipitate was formed. The precipitate was aged at 80 °C for 3 h, washed three times each with deionized water and ethanol, dried at 100 °C for 12 h, and finally calcined at 550 °C for 4 h to obtain neodymium-cerium oxide solid solution.

[0042] Preparation of zirconium-titanium oxide composite: 8.1 g of zirconium oxychloride octahydrate and 13.6 g of tetrabutyl titanate were dissolved in 60 mL of anhydrous ethanol, and 0.5 mL of 65% nitric acid was added. The mixture was magnetically stirred for 60 min, and then allowed to stand at room temperature for 12 h for aging. Subsequently, it was transferred to a 100 mL polytetrafluoroethylene autoclave and hydrothermally reacted at 180 °C for 28 h. After the reaction was completed, it was naturally cooled to room temperature, washed three times with ethanol, dried at 100 °C for 12 h, and finally calcined at 600 °C for 3.5 h to obtain the zirconium-titanium oxide composite.

[0043] Preparation of a dual-supported cerium-titanium low-temperature denitration catalyst: 2.6 g of polyether F127 was dissolved in 40 mL of anhydrous ethanol, heated to 45 °C, and 4.8 g of urea and 0.41 mL of 65% nitric acid were added. The mixture was magnetically stirred for 30 min to obtain solution A. 11.34 g of tetrabutyl titanate was dissolved in 40 mL of anhydrous ethanol, and 0.5 mL of glacial acetic acid was added, followed by 0.41 mL of 65% nitric acid and 2.89 g of nitric acid hexahydrate. Cerium was magnetically stirred for 30 min to obtain solution B. Solutions A and B were mixed in a 250 mL PTFE autoclave and maintained at 90 °C for 3 h, then cooled to 80 °C and maintained for 49 h, followed by hydrothermal treatment at 120 °C for 5 h to obtain a cerium-titanium composite oxide precursor. This precursor was washed three times with ethanol, dried at 100 °C for 12 h, and calcined at 400 °C for 4 h to obtain a cerium-titanium composite oxide. 40 g of the cerium-titanium composite oxide, 15 g of neodymium-cerium oxide solid solution, 15 g of zirconium-titanium oxide composite, 25 g of titanium dioxide, and 15 g of alumina were mixed and 50 mL of deionized water was added to form a slurry. The slurry was ball-milled for 4 h, dried at 110 °C for 12 h, and finally calcined at 500 °C for 8 h to obtain a dual-support cerium-titanium low-temperature denitration catalyst.

[0044] Example 2 was prepared in the same way as Example 1, except that the neodymium-cerium oxide solid solution was prepared as follows: 2.4 g of neodymium nitrate dodecahydrate and 31.3 g of cerium nitrate hexahydrate were dissolved in 180 mL of deionized water, 3.5 g of polyethylene glycol was added, and the mixture was magnetically stirred for 30 min. Then, under argon protection, ammonia water was added dropwise until the pH reached 8.9, and a precipitate was formed. The precipitate was aged at 78 °C for 4 h, washed three times each with deionized water and ethanol, dried at 98 °C for 12 h, and finally calcined at 545 °C for 4 h to obtain the neodymium-cerium oxide solid solution.

[0045] Preparation of zirconium-titanium oxide composite: 6.8 g of zirconium oxychloride octahydrate and 11.9 g of tetrabutyl titanate were dissolved in 50 mL of anhydrous ethanol, and 0.4 mL of 65% nitric acid was added. The mixture was magnetically stirred for 50 min, and then allowed to stand at room temperature for 10 h for aging. Subsequently, it was transferred to a 100 mL polytetrafluoroethylene autoclave and hydrothermally reacted at 178 °C for 30 h. After the reaction was completed, the mixture was naturally cooled to room temperature, washed three times with ethanol, dried at 98 °C for 12 h, and finally calcined at 598 °C for 4 h to obtain the zirconium-titanium oxide composite.

[0046] Preparation of a dual-supported cerium-titanium low-temperature denitration catalyst: Cerium-titanium composite oxide was prepared according to the method in Example 1. 30g of cerium-titanium composite oxide, 10g of neodymium-cerium oxide solid solution, 10g of zirconium-titanium oxide composite, 20g of titanium dioxide, and 10g of alumina were mixed and 40mL of deionized water was added to form a slurry. The slurry was ball-milled for 4 hours, dried at 108℃ for 12 hours, and finally calcined at 498℃ for 10 hours to obtain the dual-supported cerium-titanium low-temperature denitration catalyst.

[0047] Example 3 was prepared in the same way as Example 1, except that the neodymium-cerium oxide solid solution was prepared as follows: 4.8 g of neodymium nitrate dodecahydrate and 38.1 g of cerium nitrate hexahydrate were dissolved in 220 mL of deionized water, 4.5 g of polyethylene glycol was added, and the mixture was magnetically stirred for 40 min. Then, under argon protection, ammonia water was added dropwise until the pH reached 9.1, and a precipitate was formed. The precipitate was aged at 82 °C for 2 h, washed three times each with deionized water and ethanol, dried at 102 °C for 12 h, and finally calcined at 555 °C for 4 h to obtain the neodymium-cerium oxide solid solution.

[0048] Preparation of zirconium-titanium oxide composite: 9.4 g of zirconium oxychloride octahydrate and 15.3 g of tetrabutyl titanate were dissolved in 70 mL of anhydrous ethanol, and 0.6 mL of 65% nitric acid was added. The mixture was magnetically stirred for 70 min, and then allowed to stand at room temperature for 14 h for aging. Subsequently, it was transferred to a 100 mL polytetrafluoroethylene autoclave and hydrothermally reacted at 182 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed three times with ethanol, dried at 102 °C for 12 h, and finally calcined at 602 °C for 3 h to obtain the zirconium-titanium oxide composite.

[0049] Preparation of a dual-supported cerium-titanium low-temperature denitration catalyst: Cerium-titanium composite oxide was prepared according to the method in Example 1. 50g of cerium-titanium composite oxide, 20g of neodymium-cerium oxide solid solution, 20g of zirconium-titanium oxide composite, 30g of titanium dioxide, and 20g of alumina were mixed and 60mL of deionized water was added to form a slurry. The slurry was ball-milled for 4 hours, dried at 112℃ for 12 hours, and finally calcined at 502℃ for 5 hours to obtain the dual-supported cerium-titanium low-temperature denitration catalyst.

[0050] Comparative Example 1

[0051] The preparation method is the same as in Example 1, except that a dual-support cerium-titanium low-temperature denitration catalyst is prepared: cerium-titanium composite oxide is prepared according to the method in Example 1. 40g of cerium-titanium composite oxide, 25g of titanium dioxide, and 15g of alumina are mixed, and 50mL of deionized water is added to form a slurry. The slurry is ball-milled for 4 hours, dried at 110℃ for 12 hours, and finally calcined at 500℃ for 8 hours to obtain the comparative catalyst.

[0052] Comparative Example 2

[0053] The preparation method is the same as in Example 1, except that the neodymium-cerium oxide solid solution is prepared according to the method in Example 1. The dual-support cerium-titanium low-temperature denitration catalyst is prepared according to the method in Example 1. 40g of cerium-titanium composite oxide, 15g of neodymium-cerium oxide solid solution, 25g of titanium dioxide, and 15g of alumina are mixed, and 50mL of deionized water is added to form a slurry. The slurry is ball-milled for 4 hours, dried at 110℃ for 12 hours, and finally calcined at 500℃ for 8 hours to obtain the comparative catalyst.

[0054] Comparative Example 3

[0055] The preparation method is the same as in Example 1, except that the traditional vanadium-titanium catalyst preparation method is used: 1.5g of vanadium pentoxide, 4.5g of tungsten trioxide and 35g of titanium dioxide are mixed, 40mL of deionized water is added to make a slurry, ball milled for 4h, dried at 110℃ for 12h, and finally calcined at 500℃ for 5h to obtain the traditional vanadium-titanium denitration catalyst.

[0056] According to existing national and industry standards, the performance of the dual-support cerium-titanium low-temperature denitrification catalysts prepared in Examples 1-3 and Comparative Examples 1-3 was tested using the following methods: The denitrification performance of the catalysts was tested in a fixed-bed reactor with an inner diameter of 8 mm. 1.0 mL of a catalyst sample with a particle size of 40-60 mesh was placed in the constant-temperature zone of the reactor. The simulated flue gas composition was 500 ppm nitric oxide, 500 ppm ammonia, 5% oxygen, 100 ppm sulfur dioxide (introduced when testing sulfur resistance), and 10% water vapor (introduced when testing water resistance), with the remainder being nitrogen as a balance gas. The total gas flow rate was 500 mL / min, corresponding to a space velocity of 30,000 h⁻¹. -1 The test temperature range was 150-350℃. After maintaining a stable temperature for 30 minutes at each point, the inlet and outlet nitrogen oxide concentrations were measured using a flue gas analyzer. The nitrogen oxide conversion rate was calculated using the formula (inlet nitrogen oxide concentration - outlet nitrogen oxide concentration) / inlet nitrogen oxide concentration × 100%. Nitrogen selectivity was calculated by measuring the amount of nitrous oxide generated in the tail gas. The stability test was conducted continuously at 250℃ for 100 hours. The sulfur resistance test was conducted by introducing 100 ppm sulfur dioxide at 250℃ for 24 hours. The water resistance test was conducted by introducing 10% water vapor at 250℃ for 24 hours. All tests were repeated three times and the average value was taken.

[0057] Table 1: Performance test results of each embodiment and comparative example

[0058]

[0059] As shown in Table 1, the test data fully demonstrate that Examples 1-3 successfully solved the technical problems of insufficient activity and poor stability of low-temperature denitrification catalysts by introducing neodymium-cerium oxide solid solutions and zirconium-titanium oxide composites. At a low temperature of 150℃, the nitrogen oxide conversion rate of Examples 1-3 reached 88.3-92.5%, while that of Comparative Examples 1 and 3 was only 52.4% and 45.2%, respectively, indicating that the synergistic effect of the two modified compounds significantly improved the low-temperature activity of the catalyst. At the optimal activity temperature of 250℃, the nitrogen oxide conversion rate of Examples 1-3 remained at a high level of 98.6-99.2%, while the nitrogen selectivity reached 97.9-98.5%, significantly better than the 85.3% and 92.1% of Comparative Example 1. Regarding anti-poisoning performance, Examples 1-3 maintained an activity retention rate of 93.7-95.3% and 96.5-97.8% in sulfur dioxide and water vapor environments, respectively, while Comparative Example 1 only maintained 72.6% and 85.4%, respectively. Of particular note is that Comparative Example 2, which only added neodymium-cerium oxide solid solution without adding zirconium-titanium oxide composite, showed better performance indicators than Comparative Example 1 but significantly lower than Examples 1-3, demonstrating the indispensable synergistic effect of the two modified compounds. Regarding long-term stability, Examples 1-3 showed an activity decay of only 2.1-2.8% after 100 hours of continuous operation, far lower than the 8.7% of Comparative Example 1 and 12.5% ​​of Comparative Example 3. These results fully confirm that through dual-support design and the synergistic effect of the two modified compounds, this invention successfully constructed a catalytic system with abundant active sites, excellent anti-poisoning ability, and long-term stability, effectively solving the key technical bottlenecks of existing low-temperature denitrification catalysts.

[0060] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-support cerium-titanium low-temperature denitration catalyst, characterized in that the steps include... include: S1. Dissolve the polyether in anhydrous ethanol, heat to 44-46℃, add urea and nitric acid, and stir magnetically to obtain solution A. Tetrabutyl titanate was dissolved in anhydrous ethanol, glacial acetic acid was added, nitric acid and cerium nitrate hexahydrate were added, and the mixture was magnetically stirred to obtain solution B. Solution A and solution B were mixed in a polytetrafluoroethylene autoclave and kept at 88-92℃. Then the temperature was lowered to 78-82℃ and kept there. Then the temperature was raised to 115-125℃ and hydrothermally heated to obtain the cerium-titanium composite oxide precursor. S2. The cerium-titanium composite oxide precursor is washed with ethanol, dried at 98-102℃, and calcined at 398-402℃ to obtain the cerium-titanium composite oxide. The cerium-titanium composite oxide, neodymium-cerium oxide solid solution, zirconium-titanium oxide composite, titanium dioxide, and alumina are mixed, deionized water is added to form a slurry, ball-milled, dried at 108-112℃, and finally calcined at 498-502℃. The dual carrier is composed of titanium dioxide and alumina.

2. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 1, characterized in that, In step S1, the temperature is maintained at 78-82℃ for 48-50 hours.

3. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 1, characterized in that, In step S2, the calcination time at 498-502℃ is 5-10 hours.

4. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 1, characterized in that, The preparation method of the neodymium-cerium oxide solid solution includes: A1, dissolving neodymium nitrate and cerium nitrate in deionized water, adding polyethylene glycol, stirring magnetically, and then adding ammonia dropwise under argon protection until pH=8.9-9.1 to form a precipitate; A2, aging the precipitate at 78-82℃, washing it with deionized water and ethanol, drying it at 98-102℃, and finally calcining it at 545-555℃.

5. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 4, characterized in that, In step A1, the magnetic stirring time is 30-40 minutes.

6. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 4, characterized in that, In step A2, the aging time is 2-4 hours at 78-82℃.

7. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 1, characterized in that, The preparation method of the zirconium-titanium oxide composite includes: B1, dissolving zirconium oxychloride and tetrabutyl titanate in anhydrous ethanol, adding nitric acid, stirring magnetically, then aging at room temperature, and then transferring to a polytetrafluoroethylene autoclave for hydrothermal reaction at 178-182℃; B2, after the reaction is completed, naturally cooling, washing with ethanol, drying at 98-102℃, and finally calcining at 598-602℃.

8. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 7, characterized in that, In step B1, the hydrothermal reaction time at 178-182℃ is 24-30 hours.

9. The preparation method of the dual-support cerium-titanium low-temperature denitration catalyst according to claim 7, characterized in that, In step B2, the calcination time is 3-4 hours at 598-602℃.

10. A method for preparing a dual-supported cerium-titanium low-temperature denitration catalyst according to any one of claims 1-9, characterized in that, The raw materials include the following parts by weight: 30-50 parts by weight of cerium-titanium composite oxide; 10-20 parts by weight of neodymium-cerium oxide solid solution; 10-20 parts by weight of zirconium-titanium oxide composite; 20-30 parts by weight of titanium dioxide; and 10-20 parts by weight of aluminum oxide.

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