Preparation method of denitration catalyst and denitration catalyst

Abstract

The application belongs to the field of environmental catalytic materials and air pollution control, and provides a preparation method of a denitration catalyst and the denitration catalyst, comprising the following steps: step one: adding cerium iron tungsten oxide precursor into distilled water, heating and stirring until completely dissolved to obtain solution A; step two: adding a template agent into distilled water, stirring uniformly to obtain dispersion liquid B; step three: adding the solution A into the dispersion liquid B, drying to obtain solid C; step four: soaking the solid C in a dilute sulfuric acid solution for a specified time, calcining to obtain SO4 2‑ supported cerium iron tungsten composite oxide, and the denitration catalyst. According to the method, the denitration catalyst can have stable water and sulfur poisoning resistance and good denitration capacity at medium and low temperatures.

Description

Technical Field

[0001] This application belongs to the field of environmental catalytic materials and air pollution control, and relates to a method for preparing a denitrification catalyst and the denitrification catalyst itself. Background Technology

[0002] Nitrogen oxides (NOx) damage the ozone layer, cause photochemical smog and acid rain, severely impacting people's production and lives. Among the many NOx elimination technologies currently available, NH3 selective catalytic reduction (NH3-SCR) is considered the most effective method. The denitrification catalyst is crucial to its success.

[0003] Traditional VWT (V₂O₅-WO₃ / TiO₂) catalysts have been widely used in the power industry, with an activity temperature of 300-400℃. However, the emission temperature of flue gas from industrial boilers in non-power industries (glass ceramics, cement, steel metallurgy, etc.) is typically 150-300℃, making it difficult to directly use this catalyst to control NOx emissions. Furthermore, the flue gas contains large amounts of moisture and SO₂, which can easily poison and clog the catalyst; additionally, vanadium has a certain degree of biotoxicity. Therefore, developing non-vanadium-based low-temperature NH₃-SCR catalysts with excellent catalytic performance is of great significance.

[0004] Among NH3-SCR catalysts, manganese-based, iron-based, and cerium-based oxides are currently the most promising medium- and low-temperature catalysts. Cerium-based catalysts, in particular, have been extensively studied due to their excellent low-temperature activity. However, pure CeO2 catalysts suffer from a narrow operating temperature window and poor resistance to poisoning, limiting their practical applications. Therefore, improving cerium-based catalysts to enhance their low-temperature activity, broaden their temperature window, increase denitrification efficiency, and improve resistance to water and SO2 poisoning, thereby meeting the application requirements in non-power industries, is a crucial research focus.

[0005] Therefore, in existing technologies, how to improve the denitrification activity and resistance to water and sulfur poisoning of denitrification catalysts at medium and low temperatures has become a technical challenge. Summary of the Invention

[0006] The purpose of this application is to provide a denitrification catalyst that can improve denitrification activity and resistance to water and sulfur poisoning at medium and low temperatures. To achieve the above objective, one aspect of this application is a method for preparing a denitrification catalyst, comprising the following steps: Step 1: Adding a cerium iron tungsten oxide precursor to distilled water, heating and stirring until completely dissolved to obtain solution A; Step 2: Adding a template agent to distilled water, stirring evenly to obtain dispersion B; Step 3: Adding solution A to dispersion B, drying to obtain solid C; Step 4: Soaking solid C in dilute sulfuric acid solution for a specified time, calcining to obtain SO4. 2-The supported cerium-iron-tungsten composite oxide is used as the denitration catalyst; wherein the cerium-iron-tungsten oxide precursor comprises cerium nitrate, ferric nitrate, and ammonium metatungstate; the molar ratio of cerium, iron, and tungsten in the cerium-iron-tungsten oxide precursor is 1:(0.8-1.2):(0.01-0.05); the template agent is polyvinylpyrrolidone; the mass ratio of polyvinylpyrrolidone to the cerium-iron-tungsten oxide precursor is (0.03-0.08):1; the concentration range of the dilute sulfuric acid is 0.05-0.15 mol / L; in step four, the solid C is soaked in the dilute sulfuric acid solution for 3-4 hours.

[0007] In a preferred embodiment, the heating temperature in step one is 50-70°C.

[0008] In a preferred embodiment, in step three, the drying temperature is 80-120°C and the drying time is 6-8 hours.

[0009] In a preferred embodiment, in step four, the calcination temperature is 300-500°C and the calcination time is 2-4 hours.

[0010] In addition, another aspect of this application is a denitrification catalyst prepared by the aforementioned method for preparing a denitrification catalyst, wherein polyvinylpyrrolidone is used as a template agent and iron oxide, tungsten oxide, and cerium oxide are used as active components.

[0011] According to the aforementioned technical solution, the denitrification catalyst of the above embodiments of this application has a wider applicable temperature window and exhibits excellent denitrification activity and anti-poisoning stability in environments where water and sulfur coexist. Attached Figure Description

[0012] To more clearly illustrate this application, the accompanying drawings will be described and explained below. Obviously, the drawings described below only illustrate certain aspects of some exemplary embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0013] Figure 1 These are schematic diagrams illustrating the denitrification performance of each embodiment and comparative example.

[0014] Figure 2 This is a schematic diagram of the water and sulfur resistance stability of Example 1, Comparative Example 1, and Comparative Example 2.

[0015] Figure 3 This is a transmission electron microscope (TEM) image of the denitrification catalyst from Example 1.

[0016] Figure 4 This is the XPS spectrum of sulfur content in the denitrification catalyst in Example 1. Detailed Implementation

[0017] Various exemplary embodiments of this application are described in detail below with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are in no way intended to limit the application or its application or use. This application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the application thorough and complete, and to fully express the scope of the application to those skilled in the art. It should be noted that, unless otherwise stated, the relative arrangement of components and steps, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0018] As used in this application, the words “including” or “comprising” or similar terms mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility that it may also cover other elements.

[0019] All terms used in this application (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this application pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as being interpreted with idealized or highly formalized meanings, unless explicitly defined herein.

[0020] For components, specific model numbers and other parameters of components not described in detail in this section, the interrelationships between components and control circuits, these may be considered as techniques, methods and devices known to those skilled in the art, but where appropriate, such techniques, methods and devices should be considered part of the specification.

[0021] It should be noted that although the operations of the method described in this application are given a specific order, this does not require or imply that these operations must be performed in that specific order, or that all of the operations shown must be performed to achieve the desired result. On the contrary, the steps described in this application may be performed in a different order. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0022] The following provides a detailed description of the denitrification catalyst and its preparation method.

[0023] Preferably, this application uses iron oxide, tungsten oxide, and cerium oxide as the main active components, and dilute sulfuric acid as SO4. 2- Supported liquid. The preparation method of the denitration catalyst of this application includes the following steps:

[0024] Step 1: Add the cerium iron tungsten oxide precursor to distilled water, heat and stir until completely dissolved to obtain solution A;

[0025] Step 2: Add the template agent to distilled water and stir well to obtain dispersion B;

[0026] Step 3: Add the solution A to the dispersion B and dry to obtain solid C; preferably, after adding solution A to dispersion B, sonicate to homogenize and then place in an oven to dry;

[0027] Step 4: Immerse the solid C in a dilute sulfuric acid solution for a specified time, then calcine to obtain SO4. 2- The supported cerium-iron-tungsten composite oxide is used as the denitrification catalyst. Preferably, solid C is soaked in dilute sulfuric acid solution, filtered, dried in an oven, and finally calcined in a muffle furnace to obtain SO4. 2- Supported cerium-iron-tungsten composite oxide.

[0028] Preferably, in step two, polyvinylpyrrolidone (PVP) is used as a template agent. Due to its unique structure (polar groups, adjustable molecular chain length) and properties (thermal decomposition, dispersibility), polyvinylpyrrolidone can not only act as a template agent to regulate the morphology and size of the material, but also act as a pore-forming agent to introduce pores. Here, it is used as a multifunctional additive, which is simple to operate and highly controllable.

[0029] Furthermore, the core advantage of dilute sulfuric acid acidification in the field of denitrification lies in enhancing oxidant activity, promoting nitrogen oxide conversion, suppressing side reactions, and improving process stability by controlling the acidic environment of the reaction system. It is simple to operate, low in cost, and adaptable to various denitrification processes, making it a key auxiliary means to improve efficiency and reduce pollution.

[0030] Preferably, the cerium iron tungsten oxide precursor comprises cerium nitrate, iron nitrate, and ammonium metatungstate.

[0031] Preferably, in step one, the heating temperature is 50-70℃.

[0032] Preferably, in step three, the drying temperature is 80-120℃ and the drying time is 6-8 hours.

[0033] Preferably, in step four, the drying temperature is 120-150℃, and the drying time is 2-4 hours. The calcination temperature is 300-500℃, and the calcination time is 2-4 hours, using a programmed temperature rise at a rate of 2-5℃ / min.

[0034] To select a suitable ratio, the following experimental data were collected:

[0035] Experimental Data 1: Adjusting the ratios of different components (Ce, Fe, W) in the cerium-iron-tungsten oxide precursor, using cerium (Ce) as a baseline, and varying the molar ratio of Fe to W:

[0036]

[0037] The T column in the right column of the table above and the table below 90 This represents the temperature range corresponding to a denitrification activity greater than 90%. It can be seen that when Ce:Fe:W = 1:(0.8-1.2):(0.01-0.05), a denitrification activity greater than 90% can be achieved at 200℃, and the corresponding temperature range is relatively wide. Especially when Ce:Fe:W = 1:1:0.01, 1:1:0.05, and 1:0.8:0.05, the temperature range corresponding to a denitrification activity greater than 90% is 200-370℃, with the widest range.

[0038] Other ratios correspond to relatively narrower temperature ranges. For example, when Ce:Fe:W=1:1:0.08, the temperature range corresponding to a denitrification activity greater than 90% is 215-360℃.

[0039] Experimental Data 2: Only the proportion of polyvinylpyrrolidone (PVP) was adjusted (based on the cerium-iron-tungsten composite oxide precursor, the mass ratio of PVP to the cerium-iron-tungsten composite oxide precursor).

[0040]

[0041] The experimental conditions were: NO and NH3, both at inlet concentrations of 1000 ppm; O2 content of 10%; SO2 concentration of 250 ppm; H2O content of 5 vol.%; catalyst dosage of 1.2 ml; and space velocity of 40,000 h⁻¹. - ¹, Soaking time in dilute sulfuric acid is 4 hours.

[0042] As shown in the table above, when the mass ratio of polyvinylpyrrolidone (PVP) to cerium-iron-tungsten composite oxide precursor is (0.03-0.08):1, a denitrification efficiency greater than 90% can be achieved over a wide temperature range. The widest temperature window (160-390℃) is observed at a mass ratio of 0.05 due to the optimized porous structure and sufficient active sites. Conversely, the activity decreases at a mass ratio of 0.1:1. This is because the higher proportion of PVP leads to uneven dispersion, aggregation, and the formation of localized macropores.

[0043] Experimental Data 3: After determining the optimal mass ratio of polyvinylpyrrolidone (PVP) to the cerium-iron-tungsten composite oxide precursor, the molar concentration of dilute sulfuric acid was adjusted.

[0044]

[0045] The experimental conditions were the same as above, with a soaking time of 4 hours. As can be seen from the table above, when the concentration of dilute sulfuric acid is 0.05-0.15 mol / L, the temperature range where the denitrification efficiency is greater than 90% is relatively wide. When the concentration of dilute sulfuric acid is 0.1 mol / L, it covers a temperature range of 150-400℃, because SO4... 2- With a moderate loading, the acidic environment and active sites work synergistically. Both excessively high and low concentrations of dilute sulfuric acid narrow the temperature range window.

[0046] Experimental Data 4: After determining the optimal mass ratio of polyvinylpyrrolidone (PVP) to the cerium-iron-tungsten composite oxide precursor and the optimal molar concentration of dilute sulfuric acid, the soaking time in the dilute sulfuric acid solution in step 4 above was determined.

[0047]

[0048] The experimental conditions were the same as above. As can be seen from the table above, the widest temperature range for denitrification efficiency (greater than 90%) was achieved when soaking in dilute sulfuric acid solution for 3-4 hours, with the 4-hour soaking temperature covering 150-400℃, due to SO4... 2- Uniform loading and appropriate amount; too short a soaking time will result in insufficient loading, while too long a soaking time will result in excessive coverage of active sites, both of which will lead to a narrowing of the temperature range window.

[0049] The denitrification effect of the present invention will be further illustrated below with reference to embodiments and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0050] The denitrification performance evaluation method of the catalyst of this invention is as follows: Simulating the composition of exhaust gas, the inlet NO concentration is 1000 ppm, the inlet NH3 concentration is 1000 ppm, the O2 content is 10%, the SO2 concentration is 250 ppm (added during use), the H2O content is 5 vol.% (added during use), and N2 is used as the carrier gas. The catalyst dosage is set to 1.2 ml, and the reaction space velocity (GHSV) is set to 40000 h⁻¹. -¹ The reaction temperature range was set to 120-450℃, and the NO concentration change before and after the reaction was monitored online using a flue gas analyzer.

[0051] Example 1

[0052] 0.1 mol cerium nitrate, 0.1 mol ferric nitrate, and 0.001 mol ammonium metatungstate were added to distilled water and heated at 70°C with stirring until completely dissolved to form solution A. 1 g of polyvinylpyrrolidone was added to distilled water and stirred until homogeneous, yielding dispersion B. Solution A was added to dispersion B and sonicated until homogeneous. The mixture was then dried in an oven at 100°C for 6 hours to obtain solid C. Solid C was soaked in a 0.1 mol / L dilute sulfuric acid solution for 4 hours, filtered, dried in an oven at 120°C for 2 hours, and finally calcined in a muffle furnace at 450°C for 2 hours with a heating rate of 3°C / min.

[0053] Example 2

[0054] 0.1 mol cerium nitrate, 0.2 mol ferric nitrate, and 0.005 mol ammonium metatungstate were added to distilled water and heated at 50°C with stirring until completely dissolved to form solution A. 2 g of polyvinylpyrrolidone was added to distilled water and stirred until homogeneous, yielding dispersion B. Solution A was added to dispersion B and sonicated until homogeneous. The mixture was then dried in an oven at 120°C for 8 hours to obtain solid C. Solid C was soaked in a 0.2 mol / L dilute sulfuric acid solution for 5 hours, filtered, dried in an oven at 150°C for 3 hours, and finally calcined in a muffle furnace at 500°C for 3 hours with a heating rate of 5°C / min.

[0055] Comparative Example 1

[0056] 0.1 mol cerium nitrate, 0.1 mol ferric nitrate, and 0.001 mol ammonium metatungstate were added to distilled water and heated at 70°C with stirring until completely dissolved to form solution A. 1 g of polyvinylpyrrolidone was added to distilled water and stirred until homogeneous, yielding dispersion B. Solution A was added to dispersion B and sonicated until homogeneous. The mixture was then dried in an oven at 100°C for 6 hours to obtain solid C. Solid C was transferred to a muffle furnace and calcined at 450°C for 2 hours with a heating rate of 3°C / min.

[0057] Comparative Example 2

[0058] 0.1 mol cerium nitrate, 0.1 mol ferric nitrate, and 0.001 mol ammonium metatungstate were added to distilled water and heated at 70°C with stirring until completely dissolved to form solution A. The solution was then dried in an oven at 100°C for 6 hours to obtain solid C. C was soaked in a 0.1 mol / L dilute sulfuric acid solution for 4 hours, filtered, dried in an oven at 120°C for 2 hours, and finally transferred to a muffle furnace and calcined at 450°C for 2 hours at a heating rate of 3°C / min.

[0059] Figure 1 These are schematic diagrams illustrating the denitrification performance of each embodiment and comparative example. Figure 2 This is a schematic diagram of the water and sulfur resistance stability of Example 1, Comparative Example 1, and Comparative Example 2. Figure 3 This is a transmission electron microscope (TEM) image of the denitrification catalyst from Example 1. Figure 4 This is the XPS spectrum of sulfur content in the denitrification catalyst in Example 1.

[0060] The main difference between Example 1 and Comparative Example 1 is that Comparative Example 1 omits the step of soaking solid C in dilute sulfuric acid solution. The main difference between Example 1 and Comparative Example 2 is that Comparative Example 2 omits the step of adding polyvinylpyrrolidone to obtain dispersion B. In Example 2, the molar ratio of cerium, iron, and tungsten is 1:2:0.5, and the concentration of the dilute sulfuric acid solution is 0.2 mol / L, both of which are outside the optimal range. Figure 1It can be seen that the denitrification performance gradually decreases from Example 1 and Example 2 to Comparative Example 1 and Comparative Example 2, with Example 1 showing the best denitrification performance and the widest applicable temperature range.

[0061] like Figure 2 As shown, in Example 1, under conditions of 200°C and continuous 48-hour passage of 5 vol.% H2O and 250 ppm SO2, the denitrification efficiency remained stable at over 95%, demonstrating good water and sulfur resistance and denitrification activity. Figure 3 It can be seen that the denitrification catalyst of this application has a good pore structure, indicating that polyvinylpyrrolidone plays a good role as a template agent and pore-forming agent, which is more conducive to improving catalytic efficiency. From Figure 4 It can be seen that after being soaked in dilute sulfuric acid solution, the denitrification catalyst of this application contains a certain amount of sulfur, which is beneficial to enhancing the sulfur resistance performance.

[0062] In summary, this application uses polyvinylpyrrolidone as a template and pore-forming agent to increase the number of surface active sites. Cerium oxide, iron oxide, and tungsten oxide are used as the main active components, and the final process involves soaking the surface in a dilute sulfuric acid solution to load SO4. 2- Among these methods, acidification with dilute sulfuric acid regulates the acidic environment of the reaction system, enhances the activity of the oxidant, promotes the conversion of nitrogen oxides, inhibits side reactions, and improves process stability and resistance to water and sulfur.

[0063] The preparation method described in this application is simple, low-cost, and requires minimal synthesis equipment. The prepared cerium-based denitrification catalyst exhibits a wide denitrification temperature window, high denitrification efficiency, and excellent resistance to water and sulfur poisoning. This catalyst is particularly suitable for the stable and efficient purification of NOx in complex flue gas from non-power industries, and can significantly extend the catalyst's service life in flue gas denitrification.

[0064] It should be understood that the specific embodiments described above are only used to explain this application, and the scope of protection of this application is not limited thereto. Any changes, substitutions, or combinations made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be covered within the scope of protection of this application.

Claims

1. A method for preparing a denitrification catalyst, characterized in that, It includes the following steps: Step 1: Add the cerium iron tungsten oxide precursor to distilled water, heat and stir until completely dissolved to obtain solution A; Step 2: Add the template agent to distilled water and stir well to obtain dispersion B; Step 3: Add the solution A to the dispersion B and dry to obtain solid C; Step 4: Immerse the solid C in a dilute sulfuric acid solution for a specified time, then calcine to obtain SO4. 2- Supported cerium-iron-tungsten composite oxide is used as the denitration catalyst; The cerium iron tungsten oxide precursor includes cerium nitrate, iron nitrate, and ammonium metatungstate; The molar ratio of cerium, iron, and tungsten in the cerium-iron-tungsten oxide precursor is 1:(0.8-1.2):(0.01-0.05); The template agent is polyvinylpyrrolidone; the mass ratio of the polyvinylpyrrolidone to the cerium iron tungsten oxide precursor is (0.03-0.08):1; The concentration range of the dilute sulfuric acid is 0.05-0.15 mol / L; In step four, the solid C is soaked in the dilute sulfuric acid solution for 3-4 hours.

2. The method for preparing the denitrification catalyst according to claim 1, characterized in that: In step one, the heating temperature is 50-70℃.

3. The method for preparing the denitrification catalyst according to claim 1, characterized in that: In step three, the drying temperature is 80-120℃ and the drying time is 6-8 hours.

4. The method for preparing the denitrification catalyst according to claim 1, characterized in that: In step four, the calcination temperature is 300-500℃ and the calcination time is 2-4 hours.

5. A denitrification catalyst, characterized in that: Prepared by the method for preparing the denitrification catalyst according to any one of claims 1-4; Polyvinylpyrrolidone is used as a template agent, and iron oxide, tungsten oxide, and cerium oxide are used as active components.

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