Preparation method of denitration catalyst and denitration catalyst

Abstract

The invention belongs to the field of environmental catalytic materials and air pollution abatement, and provides a preparation method of a denitration catalyst and the denitration catalyst.The preparation method comprises the following steps that firstly, a cerium-iron-tungsten oxide precursor is added into distilled water, and heating and stirring are conducted till the cerium-iron-tungsten oxide precursor is completely dissolved to obtain a solution A; 2, adding a template agent into distilled water, and uniformly stirring to obtain dispersion liquid B; 3, adding the solution A into the dispersion liquid B, and drying to obtain a solid C; and 4, soaking the solid C in a dilute sulfuric acid solution for a specified time, and calcining to obtain an SO4 < 2->-loaded cerium-iron-tungsten composite oxide which is used as the denitration catalyst. Therefore, the denitration catalyst has stable water and sulfur poisoning resistance and good denitration capacity at medium and low temperatures.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental catalytic materials and air pollution control, and relates to a preparation method of a denitration catalyst and the denitration catalyst. BACKGROUND

[0002] Nitrogen oxides (NOx) can destroy the ozone layer, cause photochemical smog and acid rain, and seriously affect people's production and life. Among the current numerous nitrogen oxide elimination technologies, NH3 selective catalytic reduction (NH3-SCR) is considered to be the most effective means. The denitration catalyst is the key to the success or failure.

[0003] The traditional VWT (V2O5-WO3 / TiO2) catalyst has been widely used in the power industry, and its active temperature is 300-400℃. However, the emission temperature of the flue gas of industrial boiler equipment in non-power industries (glass ceramics, cement, steel smelting, etc.) is usually 150-300℃, which is difficult to directly use the catalyst to control the NOx emission. In addition, the flue gas contains a large amount of water and SO2, which can easily poison and block the catalyst. At the same time, vanadium has certain biological toxicity. Therefore, it is of great significance to develop a non-vanadium-based low-temperature NH3-SCR catalyst with excellent catalytic performance.

[0004] Among the NH3-SCR catalysts, manganese-based, iron-based and cerium-based oxides are the most concerned medium and low temperature catalysts. The cerium-based catalyst is widely studied due to its excellent low-temperature activity. However, the pure CeO2 catalyst has a narrow working temperature window and poor resistance to poisoning, which limits its practical application. Therefore, it is an important research content to improve the cerium-based catalyst, improve its low-temperature activity, broaden the temperature window, improve the denitration efficiency and resistance to water and SO2 poisoning, and meet the application requirements in non-power industries.

[0005] Therefore, in the prior art, how to improve the denitration activity and resistance to water and sulfur poisoning of the denitration catalyst at medium and low temperatures has become a technical problem. SUMMARY

[0006] The purpose of the present application is to provide a denitration catalyst capable of improving the denitration activity and resistance to water and sulfur poisoning at medium and low temperatures. In order to achieve the above purpose, one scheme of the present application is a preparation method of a denitration catalyst, comprising the following steps: step one: adding a cerium-iron-tungsten oxide precursor into distilled water, heating and stirring until completely dissolved to obtain a solution A; step two: adding a template agent into distilled water, stirring uniformly to obtain a dispersion liquid B; step three: adding the solution A into the dispersion liquid B, drying to obtain a solid C; step four: soaking the solid C in a dilute sulfuric acid solution for a specified time, calcining to obtain a SO4 2- loaded cerium-iron-tungsten composite oxide, which is the denitration catalyst. The cerium iron tungsten oxide precursor comprises 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).

[0007] In a preferred mode, the template agent is polyvinylpyrrolidone.

[0008] In a preferred mode, the mass ratio of the polyvinylpyrrolidone to the cerium iron tungsten oxide precursor is (0.03-0.08):1.

[0009] In a preferred mode, the concentration of the dilute sulfuric acid ranges from 0.05 to 0.15 mol / L.

[0010] In a preferred mode, in the step four, the solid C is soaked in the dilute sulfuric acid solution for 3-4 hours.

[0011] In a preferred mode, in the step one, the heating temperature is 50-70℃.

[0012] In a preferred mode, in the step three, the drying temperature is 80-120℃, and the drying time is 6-8 hours.

[0013] In a preferred mode, in the step four, the calcination temperature is 300-500℃, and the calcination time is 2-4 hours.

[0014] In addition, another aspect of the present application is a denitration catalyst prepared by the aforementioned method for preparing a denitration catalyst; wherein polyvinylpyrrolidone is used as a template agent, and iron oxide, tungsten oxide and cerium oxide are used as active components.

[0015] According to the aforementioned technical solution, the denitration catalyst of the above-mentioned embodiments of the present application has a wider temperature window, and has excellent denitration activity and anti-poisoning stability in the environment where water and sulfur coexist. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the present application, the drawings of the specification of the present application will be described and explained below. Obviously, the drawings in the following description only illustrate certain aspects of some exemplary embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0017] Figure 1 is a schematic diagram of the denitration performance of each embodiment and comparative example.

[0018] Figure 2is a graph showing the water resistance and sulfur stability of the denitration catalyst of Example 1 and Comparative Example 1 and Comparative Example 2.

[0019] Figure 3 is a transmission electron microscope image of the denitration catalyst of Example 1.

[0020] Figure 4 is an XPS spectrum of the sulfur element contained in the denitration catalyst of Example 1. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present application are described in detail below with reference to the attached drawings. The description of exemplary embodiments is merely illustrative and does not in any way limit the scope of the application. The application can be implemented in any of numerous forms, as will be apparent to those skilled in the art. The embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. It should be noted that the relative arrangement of components and steps, numerical expressions, and numerical values set forth in these embodiments are to be interpreted as merely exemplary, and not as a limitation unless otherwise specified.

[0022] The terms "include" or "comprise" and similar terms as used in this application are meant to encompass the elements listed thereafter, not to exclude any other elements. The terms "include" or "comprise" and similar terms as used in this application are meant to encompass the elements listed thereafter, not to exclude any other elements.

[0023] All terms used in this application, including technical or scientific terms, have the same meanings as those understood by those skilled in the art to which the present application pertains, unless otherwise defined. It should also be understood that the terms defined by a general dictionary should be interpreted to have meanings consistent with those in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense unless expressly so defined herein.

[0024] For components not described in detail in this section, specific models of components, parameters of components, and the mutual relationship between components, and control circuits, can be considered as technology, methods, and devices known to those skilled in the art, but in appropriate cases, the technology, methods, and devices should be considered as part of the specification.

[0025] It should be noted that although the operations of the method of the present application are described in a particular order, this does not require or imply that the operations must be performed in that particular order, or that all of the illustrated operations must be performed to achieve the desired result. On the contrary, the steps depicted in the present application can be changed in the order of execution. Additionally or alternatively, certain steps can be omitted, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps.

[0026] The denitration catalyst of the present application and the method for preparing the same are described in detail below.

[0027] Preferably, the application takes iron oxide, tungsten oxide, and cerium oxide as the main active components, and dilute sulfuric acid as SO4 2- The preparation method of the denitration catalyst of the application comprises the following steps: Step one: add cerium iron tungsten oxide precursor into distilled water, heat and stir until completely dissolved to obtain solution A; Step two: add a template agent into distilled water, stir until uniform to obtain dispersion liquid B; Step three: add the solution A into the dispersion liquid B, dry to obtain solid C; preferably, after adding the solution A into the dispersion liquid B, ultrasonic is used for uniformity, and then put into an oven for drying; Step four: soak the solid C in a dilute sulfuric acid solution for a specified time, calcine to obtain SO4 2- The cerium iron tungsten composite oxide loaded, which is the denitration catalyst. Preferably, after soaking the solid C in a dilute sulfuric acid solution, filter, put into an oven for drying, and finally transfer to a muffle furnace for calcination to obtain SO4 2- The cerium iron tungsten composite oxide loaded.

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

[0029] In addition, the dilute sulfuric acid acidification has the core advantages in the field of denitration, that is, by adjusting the acidic environment of the reaction system, the activity of the oxidizing agent is enhanced, the conversion of nitrogen oxides is promoted, the side reactions are inhibited, and the process stability is improved. It is simple to operate, low in cost, and suitable for various denitration processes, which is 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℃, the drying time is 2-4h, the calcination temperature is 300-500℃, the calcination time is 2-4 hours, and the temperature is raised at a rate of 2-5℃ / min.

[0034] To select the appropriate ratio, the following experimental data are collected: Experimental data one: adjust the ratio of different components in cerium iron tungsten oxide precursor, take cerium Ce as the reference, change the molar ratio of iron Fe and tungsten W:

[0035] T in the right column of the above table and the table described below 90 represents the temperature interval corresponding to denitration activity greater than 90%. It can be seen that when Ce: Fe: W = 1: (0.8-1.2): (0.01-0.05), the denitration activity greater than 90% can be achieved at 200℃, and the corresponding temperature interval is relatively wide, especially when Ce: Fe: W = 1: 1: 0.01 and 1: 1: 0.05 and 1: 0.8: 0.05, the temperature interval corresponding to denitration activity greater than 90% is 200-370℃, and the interval width is the largest.

[0036] While the temperature interval corresponding to other ratios is relatively narrow, for example, when Ce: Fe: W = 1: 1: 0.08, the temperature interval corresponding to denitration activity greater than 90% is 215-360℃.

[0037] Experimental data two: only adjust the ratio of polyvinylpyrrolidone (PVP) (take the mass ratio of PVP to cerium iron tungsten composite oxide precursor as the reference, PVP to cerium iron tungsten composite oxide precursor).

[0038]

[0039] The experimental conditions are NO and NH3, the inlet concentration is 1000ppm, the O2 content is 10%, the SO2 concentration is 250ppm, the H2O content is 5vol.%, the catalyst dosage is 1.2ml, and the space velocity is 40000h -1 , the dilute sulfuric acid immersion time is 4h.

[0040] As can be seen from the above table, when the mass ratio of polyvinylpyrrolidone (PVP) to cerium iron tungsten composite oxide precursor is (0.03-0.08): 1, the denitration efficiency can be greater than 90% in a relatively wide temperature interval, among which the temperature window is the widest (160-390℃) when the mass ratio is 0.05, because the porous structure is optimized and the active sites are sufficient. In addition, when the mass ratio is 0.1:1, the activity decreases, which is due to the high proportion of polyvinylpyrrolidone (PVP), resulting in uneven dispersion, aggregation and local large pores.

[0041] Experimental data three: after determining the optimal mass ratio of polyvinylpyrrolidone (PVP) to cerium iron tungsten composite oxide precursor, adjust the molar concentration of dilute sulfuric acid.

[0042]

[0043] The experimental conditions are the same as above, and the soaking time is 4h. From the above table, it can be seen that when the concentration of dilute sulfuric acid is 0.05-0.15 mol / L, the temperature range with denitration efficiency greater than 90% is wide, and when the concentration of dilute sulfuric acid is 0.1 mol / L, the temperature range with denitration efficiency greater than 90% covers 150-400℃, because SO4 2- The loading is moderate, and the acid environment and active sites are synergistically best. Too high or too low concentration of dilute sulfuric acid will result in a narrow temperature range window.

[0044] Experimental data four: after determining the optimal mass ratio of polyvinylpyrrolidone (PVP) to cerium-iron-tungsten composite oxide precursor and the optimal molar concentration of dilute sulfuric acid, the soaking time of the dilute sulfuric acid solution in the above step four is determined.

[0045]

[0046] The experimental conditions are the same as above. From the above table, it can be seen that when the soaking time in the dilute sulfuric acid solution is 3-4h, the temperature range with denitration efficiency greater than 90% is the widest, and when the soaking time is 4h, the temperature range with denitration efficiency greater than 90% covers 150-400℃, because SO4 2- The loading is moderate, and the acid environment and active sites are synergistically best. Too high or too low concentration of dilute sulfuric acid will result in a narrow temperature range window.

[0047] The denitration effect of the present application will be further described in combination with examples and comparative examples, but the protection scope of the present application is not limited thereto.

[0048] The denitration performance evaluation method of the catalyst of the present application is as follows: the composition of simulated fuel gas tail gas is simulated, the NO inlet concentration is 1000ppm, the NH3 inlet concentration is 1000ppm, the O2 content is 10%, the SO2 concentration is 250ppm (added when used), the H2O content is 5vol.% (added when used), and N2 is the carrier gas. The catalyst dosage is set to 1.2ml, the reaction space velocity (GHSV) is set to 40000h -1 , the reaction temperature range is set to 120-450℃, and a flue gas analyzer is used to monitor the change of NO concentration before and after reaction.

[0049] Example 1

[0050] 0.1mol cerium nitrate, 0.1mol iron nitrate and 0.001mol ammonium metatungstate were added to distilled water heated and stirred at 70℃ until completely dissolved to form solution A. 1g polyvinylpyrrolidone was added to distilled water and stirred uniformly to obtain dispersion B. Solution A was added to dispersion B and ultrasonically uniformly, and then placed in an oven at 100℃ for drying for 6h to form solid C. Solid C was soaked in 0.1mol / L dilute sulfuric acid solution for 4h, filtered, placed in a 120℃ oven for drying for 2h, and finally transferred to a muffle furnace at a temperature rising rate of 3℃ / min at 450℃ for calcination for 2h.

[0051] Example 2 0.1 mol cerium nitrate, 0.2 mol iron nitrate and 0.005 mol ammonium metatungstate were added to distilled water, heated and stirred at 50°C until completely dissolved to form solution A. 2 g of polyvinylpyrrolidone was added to distilled water, stirred until uniform to obtain dispersion B. Solution A was added to dispersion B, ultrasonically stirred until uniform, then placed in an oven and dried at 120°C for 8 h to form solid C. Solid C was soaked in a 0.2 mol / L dilute sulfuric acid solution for 5 h, filtered, placed in an oven and dried at 150°C for 3 h, and finally transferred to a muffle furnace and calcined at 500°C at a temperature increase rate of 5°C / min for 3 h.

[0052] Comparative Example 1 0.1 mol cerium nitrate, 0.1 mol iron nitrate and 0.001 mol ammonium metatungstate were added to distilled water, heated and stirred at 70°C until completely dissolved to form solution A. 1 g of polyvinylpyrrolidone was added to distilled water, stirred until uniform to obtain dispersion B. Solution A was added to dispersion B, ultrasonically stirred until uniform, then placed in an oven and dried at 100°C for 6 h to form solid C. C was transferred to a muffle furnace and calcined at 450°C at a temperature increase rate of 3°C / min for 2 h.

[0053] Comparative Example 2 0.1 mol cerium nitrate, 0.1 mol iron nitrate and 0.001 mol ammonium metatungstate were added to distilled water, heated and stirred at 70°C until completely dissolved to form solution A, and placed in an oven and dried at 100°C for 6 h to form solid C. C was soaked in a 0.1 mol / L dilute sulfuric acid solution for 4 h, filtered, placed in an oven and dried at 120°C for 2 h, and finally transferred to a muffle furnace and calcined at 450°C at a temperature increase rate of 3°C / min for 2 h.

[0054] Figure 1 is a schematic diagram of the denitration performance of each example and comparative example. Figure 2 is a schematic diagram of the water resistance and sulfur stability of Example 1 and Comparative Examples 1 and 2. Figure 3 is a transmission electron microscope image of the denitration catalyst of Example 1. Figure 4 is an XPS spectrum of the sulfur element contained in the denitration catalyst of Example 1.

[0055] The main difference between Example 1 and Comparative Example 1 is that the step of soaking solid C in a dilute sulfuric acid solution is missing in Comparative Example 1. The main difference between Example 1 and Comparative Example 2 is that the step of adding polyvinylpyrrolidone to obtain dispersion B is missing in Comparative Example 2. 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, neither of which is within the optimal range. From Figure 1 It can be seen that the denitration performance gradually decreases from Example 1, Example 2 to Comparative Example 1 and Comparative Example 2, and the denitration performance of Example 1 is the best and the temperature range is the widest.

[0056] As shown in Figure 2 Example 1, under the condition of 5vol.% H2O, 250ppm SO2 at 200℃ for 48 hours, the denitration efficiency is stable at more than 95%, with good water and sulfur resistance and denitration activity. Figure 3 It can be seen that the denitration catalyst of the present application has a good pore structure, indicating that polyvinylpyrrolidone plays a good template and pore-forming function, which is more conducive to improving the catalytic performance. Figure 4 As can be seen, after soaking in dilute sulfuric acid solution, the denitration catalyst of the present application contains a certain amount of sulfur element, which is beneficial to enhance the sulfur resistance.

[0057] In summary, the present application uses polyvinylpyrrolidone as a template and pore-forming agent, and prepares an ordered porous structure by co-precipitation-soft template method to increase the surface active site. Cerium oxide, iron oxide and tungsten oxide are used as the main active components, and finally SO4 2- is loaded by soaking in dilute sulfuric acid solution. Among them, the dilute sulfuric acid acidification 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 the process stability and water and sulfur resistance.

[0058] The preparation method of the present application is simple, low in cost and low in requirement for synthesis equipment. The cerium-based denitration catalyst prepared has a wide denitration temperature window, high denitration efficiency and excellent water and sulfur poisoning resistance. The catalyst is particularly suitable for stable and efficient purification of NOx in complex flue gas in non-electricity industry, and can greatly prolong the service life of the catalyst in flue gas denitration.

[0059] It should be understood that the specific embodiments described above are only for the purpose of explaining the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application, according to the technical scheme and inventive concept of the present application, can make changes, substitutions and combinations, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a denitration catalyst, characterized in that: The following steps are included: 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 into distilled water and stir evenly to obtain dispersion B; Step 3: adding the solution A to the dispersion B and drying to obtain solid C; Step 4: Soak the solid C in a dilute sulfuric acid solution for a specified time and calcine to obtain SO4 2- Supported cerium-iron-tungsten composite oxide, used as the denitration catalyst; Wherein, the cerium-iron-tungsten oxide precursor comprises 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).

2. The method for preparing a denitration catalyst according to claim 1, wherein: The template agent is polyvinyl pyrrolidone.

3. The method for preparing a denitration catalyst according to claim 2, wherein: The mass ratio of the polyvinyl pyrrolidone to the cerium iron tungsten oxide precursor is (0.03-0.08):

1.

4. The method for preparing a denitration catalyst according to claim 3, wherein: The concentration range of the dilute sulfuric acid is 0.05-0.15 mol / L.

5. The method for preparing a denitration catalyst according to claim 4, wherein: In the step 4, the solid C is immersed in the dilute sulfuric acid solution for 3-4 hours.

6. The method for preparing a denitration catalyst according to claim 1, wherein: In the step 1, the heating temperature is 50-70°C.

7. The method for preparing a denitration catalyst according to claim 1, wherein: In the step 3, the drying temperature is 80-120° C., and the drying time is 6-8 hours.

8. The method for preparing a denitration catalyst according to claim 1, wherein: In the step 4, the calcination temperature is 300-500° C., and the calcination time is 2-4 hours.

9. A denitration catalyst, characterized in that: Prepared by the preparation method of the denitration catalyst according to any one of claims 1 to 8; Polyvinyl pyrrolidone is used as a template, and iron oxide, tungsten oxide and cerium oxide are used as active components.

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