CN115945198B - Preparation method and application of low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst - Google Patents

Abstract

The invention discloses a preparation method and application of a low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst, and belongs to the field of air pollution control. The preparation method of the catalyst comprises the following steps: adding ammonium metavanadate into deionized water, dissolving under the conditions of magnetic stirring and heating, dripping ferric nitrate nonahydrate or a mixed solution of ferric nitrate and nitric acid into the ammonium metavanadate solution, maintaining the stirring and heating state until the reaction is finished, and performing centrifugation, washing, drying and calcination treatment to obtain the layered iron-vanadium composite oxide denitration catalyst. The catalyst obtained by the invention is applied to ammonia selective catalytic reduction (NH) ₃ SCR) denitration reaction shows better medium-low temperature catalytic activity and high N ₂ The selectivity and the high low-temperature ammonium bisulfate resistance are high.

Description

Preparation of a low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst Methods and applications

Technical field

The invention relates to a preparation method and application of a low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitrification catalyst, and belongs to the field of air pollution control.

Background technique

Nitrogen oxide (NO _x ) is one of the main pollutants in the atmosphere and the main precursor of air pollutants such as haze and photochemical smog. It can cause serious harm to the ecological environment and human health. At present, ammonia selective catalytic reduction (NH ₃ -SCR) technology is the mainstream denitrification technology for mobile and fixed sources. The traditional commercial V ₂ O ₅ -WO ₃ /TiO ₂ catalyst has a high operating temperature window (300-300- 400 ℃), mainly suitable for coal-fired power plants. However, the proportion of non-electrical industries such as steel, cement, coking, glass and ceramics in China is increasing day by day, and their flue gas temperatures are relatively low, mainly between 150-300°C. At this time, the traditional high-temperature V ₂ O ₅ -WO ₃ /TiO ₂ catalyst has low denitrification efficiency. In addition, flue gas contains a certain amount of SO ₂ and H ₂ O. SO ₂ can be oxidized to SO ₃ by the catalyst, which inevitably reacts with H ₂ O and NH ₃ in the flue gas to form ammonium bisulfate (NH ₄ HSO ₄ ), which has a certain viscosity at low temperatures and can cover the surface of the catalyst to deactivate the catalyst. If the flue gas is reheated to meet the use conditions of the catalyst, additional energy consumption will be generated. Therefore, the development of high-efficiency low-temperature resistant ammonium bisulfate catalysts can effectively save unnecessary energy consumption and is of great significance for flue gas denitration in non-electricity industries.

Among the common active components of denitration catalysts, iron oxide and vanadium oxide are less likely to chemically adsorb with sulfur dioxide or form metal sulfates than other metal oxides (such as manganese oxide, copper oxide, and cerium oxide). Relatively low, thus effectively avoiding deactivation caused by metal sulfate formation. In recent years, iron-vanadium composite oxide denitration catalysts have gradually attracted the attention of researchers due to their certain low-temperature denitration potential. Yonglong Li et al. (WLYonglong Li, Ran Yan, Jian Liang, Tao Dong, Yangyang Mi, Peng Wu, Zheng Wang, Honggen Peng, Taicheng An, Applied Catalysis B: Environmental 268 (2020).) found that 3DOM-Fe _9.0 V _1.0 The catalyst has a wide activity temperature window and exhibits excellent NH ₃ -SCR performance. The NO _x conversion rate can reach more than 80% in the temperature range of 220−412°C. Jincheng Mu et al. (XL Jincheng Mu, XinyangWang, Shiying Fan, Zhifan Yin, Zeyu Li, Moses O. Tadé, Shaomin Liu, The Journal of Physical Chemistry C 124 (2020) 21396-21406.) used a homogeneous precipitation method to synthesize a A series of vanadium-doped Fe ₂ O ₃ catalysts were studied and found that the Fe0 _.75 V _0.25 O _δ catalyst achieved 100% NO _x conversion rate at 200 ℃. However, iron-vanadium composite oxide denitration catalysts are susceptible to low-temperature deposition and poisoning by ammonium bisulfate, and improving its low-temperature resistance to ammonium bisulfate deserves further study.

Contents of the invention

In view of the shortcomings of the low-temperature resistance to ammonium bisulfate of existing denitration catalysts, the present invention provides a preparation method and application of a low-temperature resistance to ammonium bisulfate layered iron-vanadium composite oxide denitration catalyst.

The invention is based on the inhibitory effect of iron oxide and vanadium oxide on the adsorption of sulfur dioxide, and constructs a layered iron-vanadium metal oxide denitration catalyst. With the help of a large number of proton acceptor oxygen in the layered oxide, hydrogen bonds are formed with ammonium ions in ammonium bisulfate. , can promote the dissociation of ammonium bisulfate. At the same time, the layered structure oxide catalyst can provide transmission channels and storage space for dissociated ammonium ions, which can avoid the continuous accumulation of dissociated ammonium ions on the catalyst surface, accelerate the realization of the kinetic balance between ammonium bisulfate generation and decomposition, and then achieve Improve its low-temperature resistance to ammonium bisulfate.

The invention provides a method for preparing a low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst, which uses iron nitrate nonahydrate, ammonium metavanadate, and nitric acid as raw materials, and deionized water as a solvent. After preparing a solution, Hydrothermal treatment, centrifugation, washing and drying steps are used to prepare layered iron vanadate precursor material, and then the precursor is calcined to obtain layered Fe _x V _1-x O _y (x=0.20~0.33, y=2.10~ 2.30) Denitrification catalyst.

The above method specifically includes the following steps:

(1) Prepare ammonium metavanadate solution

Add deionized water to the round-bottomed flask and raise the temperature to 85~95°C. Add ammonium metavanadate powder into the flask and stir magnetically for 5~15 minutes to completely dissolve it to form an ammonium metavanadate solution.

(2) Prepare a mixed solution of ferric nitrate and nitric acid

Weigh the solid iron nitrate nonahydrate into a beaker, add deionized water and stir with a magnetic stirrer for 15 to 20 minutes to completely dissolve it and set aside;

Use a pipette to transfer concentrated nitric acid into a beaker, add deionized water to dilute it to form dilute nitric acid (0.16 mol/L~0.20 mol/L), mix dilute nitric acid and ferric nitrate solution to form a mixed solution, and set aside;

(3) Preparation of layered iron vanadate precursor

Add the prepared mixture of ferric nitrate and nitric acid to the above prepared ammonium metavanadate solution, and continue stirring at 85~95°C for 0.5~7 h until the reaction is complete;

(4) Centrifugal washing

Cool the reaction suspension to room temperature. After the precipitate settles to the bottom of the flask, use a pipette to remove most of the supernatant. Move the remaining solution and precipitate to a centrifuge tube for centrifugation at 3000~5000 rpm. Keep for 5 to 15 minutes, centrifuge and remove the upper liquid of the centrifuge tube; then add ethanol for ultrasonic washing for 5 to 15 minutes, centrifuge and separate again, and repeat the ethanol washing, centrifugation, and separation process 1 to 3 times;

(5) Drying

Keep the precipitate after centrifugation and washing in the centrifuge tube, and transfer it to an oven at 60~80°C for drying. The drying time is 12 h to obtain the layered iron vanadate precursor, which is ready for use;

(6) Roasting

Put the iron vanadate precursor obtained in step (5) into a muffle furnace and raise it to 350°C at a heating rate of 1 to 5 ℃ min ^-1 and keep it for 2 to 8 hours to prepare layered iron vanadium composite oxide flue gas. Denitrification catalyst.

In the above method, in step (1), the concentration of ammonium metavanadate in the mixed solution is controlled at 0.01~0.09 mol L ^-1 .

In the above method, in the step (2), the concentration of iron nitrate in the mixed solution of iron nitrate and nitric acid is controlled at 0.05~0.3 mol L ^-1 , and the pH value of the solution is controlled between 0.5-2.5.

In the above method, in step (3), c (V ⁵⁺ ) : c (Fe ³⁺ ) is controlled at 1:1~5:1, where c (V ⁵⁺ ) refers to the vanadium in the ammonium metavanadate solution The amount concentration of ionic substances, c (Fe ³⁺ ), refers to the amount concentration of iron ion substances in the mixture of ferric nitrate and nitric acid.

The invention provides a layered iron-vanadium composite oxide denitration catalyst prepared by the above preparation method.

The invention provides the application of the layered iron-vanadium composite oxide denitration catalyst in the NH ₃ -SCR reaction.

For _the above application _, when _the layered _Fe In a mortar, grind for 1 to 5 minutes, then take it out and sieve it through a 40 to 60 mesh sieve to obtain 40 to 60 mesh particles.

The present invention uses a fixed bed reactor to conduct NH ₃ -SCR reaction activity testing. The specific application process is: the catalytic reaction test is carried out in a fixed-bed continuous flow quartz reactor. The reaction gas composition is: [NO]=500 ppm, [NH ₃ ]=500ppm, 5 vol% O ₂ , [SO ₂ ]=200 ppm (when used), 10 vol% H ₂ O (when used), N ₂ As a balance gas, the total gas flow is 120 mL min ^-1 . The catalyst volume used was 0.2 mL, the volume space velocity was 36,000 h ^-1 , and the test temperature range was 90 to 360 ℃. The activity data was collected after the reaction reached equilibrium, and the product was detected by a Fourier transform infrared flue gas analyzer (MKS-6030E). analyze. _NOx conversion and _N2 selectivity are calculated by the following formula:

[NO _x ] represents the NO _x concentration, [NO] represents the NO concentration, [N ₂ O] represents the N ₂ O concentration, [NH ₃ ] represents the NH ₃ concentration, in represents the reactor inlet concentration, and out represents the reactor outlet concentration.

Beneficial effects of the present invention:

(1) The present invention is based on the research of dual active components of iron and vanadium. Based on the weak chemical adsorption of sulfur dioxide by iron oxide and vanadium oxide, a layered iron and vanadium composite oxide denitrification catalyst is constructed. The prepared layered iron and vanadium composite oxide The denitrification catalyst has a _NOx removal rate of more than 80% in the range of 210-330°C while maintaining high _N2 selectivity.

(2) The catalyst designed in the present invention has a layered structure, which can promote the formation of hydrogen bonds between the ammonium ions in the ammonium bisulfate and the proton acceptor oxygen in the catalyst to weaken the ionic bonds in the ammonium bisulfate and help promote the formation of ammonium bisulfate. break down.

(3) Conduct an in-situ ABS resistance test on each ratio of denitrification catalysts prepared in the present invention at 200°C. In the SCR test atmosphere, 10 vol% H ₂ O and 200 ppm SO ₂ are simultaneously introduced. The catalyst is tested within the 24 h test time range. It exhibits good internal stability and good in-situ anti-ABS performance.

Description of the drawings

Figure 1 is the X-ray diffraction pattern of the iron vanadate precursor, iron-vanadium composite oxide catalyst and commercial VWTi catalyst prepared in Examples 1, 2 and 3 of the present invention. (Ⅰ) is iron vanadate precursor (a) Fe _0.33 V _0.67 O _2.17 -P, (b) Fe _0.25 V _0.75 O _2.25 -P, (c) Fe _0.2 V _0.8 O _2.3 -P; (Ⅱ) is iron Vanadium composite oxide catalyst and commercial VWTi catalyst (a) Fe _0.33 V _0.67 O _2.17 -C, (b) Fe _0.25 V _0.75 O _2.25 -C, (c) Fe _0.2 V _0.8 O _2.3 -C, (d) VWTi ;

Figure 2 is a scanning electron microscope (SEM) image of the iron-vanadium composite oxide catalyst and the commercial VWTi catalyst prepared in Examples 1, 2, and 3 of the present invention, wherein (a) (b) Fe _0.33 V _0.67 O _2.17 -C, (c) ( d) Fe _0.25 V _0.75 O _2.25 -C, (e) (f) Fe _0.2 V _0.8 O _2.3 -C, (g) (h) VWTi. (a) (c) (e) are SEM images magnified 50,000 times, (b) (d) (f) are SEM images magnified 100,000 times, (g) and (h) are 1,000 and 10,000 times respectively. Magnified SEM image;

Figure 3 is the N ₂ adsorption/desorption isotherm of the iron-vanadium composite oxide catalyst prepared in Examples 1, 2, and 3 of the present invention. (Ⅰ) Nitrogen adsorption/desorption curve, (Ⅱ) Pore size distribution diagram; where (a) Fe _0.33 V _0.67 O _2.17 -C, (b) Fe _0.25 V _0.75 O _2.25 -C, (c) Fe _0.2 V _0.8 O _2.3 -C, (d) VWTi;

Figure 4 is a graph showing the performance evaluation (I) NO _x conversion rate and (II) N ₂ selectivity of the iron-vanadium composite oxide catalyst prepared in Examples 1, 2 and 3 and the commercial VWTi catalyst NH ₃ -SCR. Among them (a) Fe _0.33 V _0.67 O _2.17 -C, (b) Fe _0.25 V _0.75 O _2.25 -C, (c) Fe _0.2 V _0.8 O _2.3 -C, (d) VWTi (test condition [NH ₃ ]=[ NO]=500 ppm, 5 vol%O ₂ , N ₂ balance gas, GHSV=36,000 h ^-1 );

Figure 5 is a graph showing the in-situ resistance to NH ₄ HSO ₄ performance of the iron-vanadium composite oxide catalyst prepared in Examples 1, 2, and 3 and the commercial VWTi catalyst. Among them (a) Fe _0.33 V _0.67 O _2.17 -C, (b) Fe _0.25 V _0.75 O _2.25 -C, (c) Fe _0.2 V _0.8 O _2.3 -C, (d) VWTi (test conditions: [NH ₃ ]= [NO]=500 ppm, [SO ₂ ]=200 ppm, 5vol% O ₂ , 10 vol% H ₂ O, N ₂ balance gas, GHSV=36,000 h ^-1 , 200 ℃).

Implementation

The present invention is further described below through examples, but is not limited to the following examples.

Example 1

(1) Weigh 0.234 g of ammonium metavanadate into a beaker, add 100.0 mL of deionized water to the beaker, place it in a water bath at a constant temperature of 90°C, and stir it with a magnetic stirrer for 10 minutes to completely dissolve it, and set it aside for use ;

(2) Weigh 0.808 g of ferric nitrate nonahydrate into a beaker, add dilute nitric acid solution to the beaker to make the concentration of ferric nitrate 0.2 mol L ^-1 , control the pH value of the solution at around 1, and set aside;

(3) Add the above-prepared mixture of ferric nitrate and dilute nitric acid to the above-prepared ammonium metavanadate solution, continue the reaction for 1 hour under stirring at 90°C and 500 r/min, and then remove the resulting suspension. The liquid was left to settle for 1 h, the supernatant was removed, and the remaining sediment was centrifuged and washed (twice with deionized water and once with ethanol), and the washed precipitate was dried in a 60°C oven for 12 h. Grind to obtain the iron vanadate precursor (labeled Fe _0.33 V _0.67 O _2.17 -P), which is ready for use;

(4) Put the material obtained in step (3) into a muffle furnace and program the temperature from room temperature to 350 °C for 5 h at a heating rate of 2 °C min ^-1 . Wait until the temperature naturally drops to room temperature to obtain catalyst powder (labeled Fe _0.33 V _0.67 O _2.17 -C), after tableting and screening, 40~60 mesh catalyst particles are obtained and are ready for use.

Example 2

(1) Weigh 0.351 g of ammonium metavanadate into a beaker, add 100.0 mL of deionized water to the beaker, place it in a water bath at a constant temperature of 90°C, and stir it with a magnetic stirrer for 10 minutes to completely dissolve it, and set it aside for use ;

(2) Weigh 0.404 g of iron nitrate nonahydrate into a beaker, add 10.0 mL of deionized water to the beaker to prepare an iron nitrate solution with a concentration of 0.1 mol L ^-1 , and set aside;

(3) Add the above-prepared ferric nitrate solution to the above-prepared ammonium metavanadate solution, continue to react for 1 hour under stirring at 90°C and 500 r/min, and then let the resulting suspension settle. 1 hour, remove the supernatant, centrifuge and wash the remaining precipitate (wash twice with deionized water and once with ethanol), dry the washed precipitate in a 60°C oven for 12 hours, and then grind to obtain vanadate. Iron precursor (labeled Fe _0.25 V _0.75 O _2.25 -P), set aside;

(4) Put the material obtained in step (3) into a muffle furnace and program the temperature from room temperature to 350°C for 5 h at a heating rate of 2°C min ^-1 . Wait until the temperature naturally drops to room temperature to obtain catalyst powder (labeled Fe _0.25 V _0.75 O _2.25 -C), after tableting and screening, 40~60 mesh catalyst particles are obtained and are ready for use.

Example 3

(1) Weigh 0.936 g of ammonium metavanadate into a beaker, add 100.0 mL of deionized water to the beaker, place it in a water bath at a constant temperature of 95°C, and stir it with a magnetic stirrer for 10 minutes to completely dissolve it, and set aside ;

(2) Weigh 0.808 g of iron nitrate nonahydrate into a beaker, add 10.0 mL of deionized water to the beaker to prepare an iron nitrate solution with a concentration of 0.1 mol L ^-1 , and set aside;

(3) Add the above-prepared ferric nitrate solution to the above-prepared ammonium metavanadate solution, continue the reaction for 6 hours under stirring at 95°C and 500 r/min, and then let the resulting suspension settle. 1 hour, remove the supernatant, centrifuge and wash the remaining precipitate (wash twice with deionized water and once with ethanol), dry the washed precipitate in a 60°C oven for 12 hours, and then grind to obtain vanadate. Iron precursor (labeled Fe _0.2 V _0.8 O _2.3 -P), set aside;

(4) Put the material obtained in step (3) into a muffle furnace and program the temperature from room temperature to 350 °C for 5 h at a heating rate of 2 °C min ^-1 . Wait until the temperature naturally drops to room temperature to obtain catalyst powder (labeled Fe _0.2 V _0.8 O _2.3 -C), after tableting and screening, 40~60 mesh catalyst particles are obtained and are ready for use.

The iron vanadate precursor, iron-vanadium composite oxide catalyst and commercial V ₂ O ₅ -WO ₃ /TiO ₂ catalyst (labeled VWTi) prepared in steps (3) and (4) in Examples 1, 2 and 3 were used. Cormetech Co., Ltd.) conducted X-ray diffraction analysis, and the diffraction spectra are shown in Figure 1. Attached Figure 1 (I) The diffraction peaks of iron vanadate precursor shown in curves (a), (b) and (c) and the pure phase Fe ₅ V ₁₅ O ₃₉ (OH) ₉ ∙ 9H ₂ O (JCPDS Card No. 46–1334) is a good match and has a monoclinic structure. A strong diffraction peak appears near 8.3 ^o , corresponding to the (002) crystal plane, indicating that the iron vanadate precursor material has layered structure characteristics. After calcination at 350°C, as shown in curves (a), (b), and (c) in Figure 1 (II), its monoclinic structure remains unchanged, but the intensity of the (002) crystal plane diffraction peak near 8.3 ^o decreases and shifts to a high angle direction to around 10.4 ^° , indicating that the interlayer spacing in the c-axis direction shrinks. This is mainly due to the loss of structural water during the calcination process, but the calcined iron-vanadium composite oxide catalyst The layered structure can still be preserved to a certain extent. The VWTi catalyst is shown in curve (d) of Figure 1 (II). The catalyst exhibits a typical anatase TiO ₂ crystal phase, and no characteristic peaks of layered structure are observed.

The iron-vanadium composite oxide catalyst prepared in step (4) in Examples 1, 2, and 3 and the commercial VWTi catalyst were observed under a scanning electron microscope, and the results are shown in Figure 2. It can be seen from Figure 2 (a, c, e) under a magnification of 50,000 times that the prepared iron-vanadium composite oxide catalyst has a lamellar structure macroscopically, and the lamellae are interlaced with each other, and the lamellae thickness is Nanoscale, lamellar width is micron scale. Figure 2 (b, d, f) is a scanning electron micrograph after further magnification of 100,000 times. The layered structural characteristics of the catalyst can be seen more clearly. Figure 2 (g, h) are scanning electron micrographs of commercial VWTi catalysts magnified at 1,000 and 10,000 times. The micron rods in Figure 2 (g) are glass fibers added to increase the strength of the commercial catalyst. Figure 2 (h) The block material without obvious structural features shown is a composite composed of V ₂ O ₅ -WO ₃ /TiO ₂ catalyst powder and other additives. It can be seen that the catalyst has no obvious layered structure.

The iron-vanadium composite oxide catalyst prepared in step (4) of Examples 1, 2, and 3 and the commercial VWTi catalyst were subjected to nitrogen adsorption/desorption tests. The specific test process: first prepare 0.2 g of the sample to be tested in a degassing workstation. Pretreatment, specific test method: Degas the sample for 4 hours under vacuum at 200°C to remove weakly adsorbed impurities and water on the surface of the sample; then perform N ₂ adsorption and desorption tests in liquid nitrogen at -196°C environment. The Brunauer-Emmett-Teller (BET) method was used to calculate the specific surface area of each catalyst, while the Barrett-Joyner-Halenda (BJH) method was used to analyze the pore volume and pore size of the catalyst. Its nitrogen adsorption/desorption isotherm and pore size distribution are shown in Figure 3. Its nitrogen adsorption/desorption isotherm is a type IV isotherm accompanied by an H3 type hysteresis loop, indicating that the catalyst has mesoporous structural characteristics. Curves (a), (b), and (c) correspond to the BET specific surface of the Fe _0.33 V _0.67 O _2.17 -C, Fe _0.25 V _0.75 O _2.25 -C, and Fe _0.2 V _0.8 O _2.3 -C catalysts, which are 55 m ² respectively. g ^-1 , 36 m ² g ^-1 , 35 m ² g ^-1 , the average pore sizes are 14 nm, 16 nm, and 15 nm respectively. The BET specific surface of the commercial VWTi catalyst corresponding to curve (d) is 83 m ² g ^-1 and the average pore size is 12 nm.

Application Example 1: NH ₃ -SCR performance evaluation of catalyst

The iron-vanadium composite oxide catalysts prepared in Examples 1, 2, and 3 were tested for NH ₃ -SCR denitration performance, and compared with commercial VWTi catalysts. Before the experiment, the catalyst was pelletized, ground and sieved to 40-60 mesh. Take 0.20 mL of sieved catalyst particles and place them in the groove in the middle of the quartz reaction tube, and fill an appropriate amount of quartz wool above and below it. The temperature test range of layered iron-vanadium composite oxide catalysts with different Fe/V ratios is 90-330 ℃, the temperature test range of VWTi is 90-480 ℃, and the heating rate is 3 ℃ min ^-1 . The results are shown in Figure 4. The activation temperature (T ₅₀ ) of the layered iron-vanadium composite oxide catalyst is as low as 161 ℃, and the denitrification efficiency can reach more than 80% in the temperature range of 213~330 ℃. In the entire test interval temperature range ( 90-330 ℃), its N ₂ selectivity remains above 85%, showing good medium and low temperature denitrification catalytic activity and good N ₂ selectivity. In comparison, the commercial VWTi catalyst exhibits good _N selectivity within the test temperature range (90-480 ℃) and exhibits high denitrification activity above 300 ℃, but the denitrification activity below 300 ℃ is lower than that of iron vanadium Composite oxide catalyst has poor medium and low temperature denitration catalytic performance.

Application Example 2: Evaluation of catalyst in-situ resistance to NH ₄ HSO ₄

The iron-vanadium composite oxide catalysts prepared in Examples 1, 2, and 3 were tested for in-situ resistance to NH ₄ HSO ₄ by additionally passing 10 vol% H ₂ O and 200 ppm SO ₂ into the SCR test atmosphere at 200°C. , simulate the impact of in-situ generation of NH ₄ HSO ₄ on catalyst stability under actual operating conditions, and compare it with commercial VWTi catalysts. As shown in Figure 5, the Fe _0.33 V _0.67 O _2.17 -C, Fe _0.25 V _0.75 O _2.25 -C, Fe _0.2 V _0.8 O _2.3 -C catalyst corresponding to the curves (a), (b), and (c) is in the pass After adding 10 vol% H ₂ O and 200 ppm SO ₂ for one hour, the denitrification activity showed a relatively obvious attenuation, but slowly decayed in the subsequent 23 hours. After the test was completed, the activity retention rates were 71% and 79% respectively. and 71%, showing good catalytic stability under this test condition. In addition, the activity of the catalysts can be recovered to varying degrees after regeneration treatment. Among them, the denitrification activity of the Fe _0.2 V _0.8 O _2.3 -C catalyst with lower iron content can almost be restored to the initial state, while the denitrification activity of the other two Fe _0.33 V _0.67 O catalysts can be recovered to varying degrees. In _{the 2.17} -C and Fe _0.25 V _0.75 O _2.25 -C samples, as the iron content gradually increases, the recovery ability of the activity after regeneration decreases, indicating the occurrence of irreversible deactivation, which is mainly related to the chemistry between iron oxide and sulfur dioxide. related to adsorption. In contrast, the commercial VWTi catalyst had no obvious activity decay during the test (~6%), but its denitrification activity was at a low level (~35%) under this test condition. Therefore, it can be seen that the iron-vanadium composite oxide catalyst has better in-situ resistance to NH ₄ HSO ₄ and practical application potential under this test condition.

Claims (7)

1. A method for preparing a low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst, which is characterized in that iron nitrate nonahydrate, ammonium metavanadate, and nitric acid are used as raw materials, and deionized water is used as the solvent. Solution, hydrothermal treatment, centrifugation, washing, and drying steps to prepare a layered iron vanadate precursor material, which is then roasted to obtain a layered iron-vanadium composite oxide denitration catalyst. The general formula of the catalyst is Fe _x V _{1 -x} O _y , x=0.20~0.33, y=2.10~2.30; The preparation method of the low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst includes the following steps: (1) Prepare ammonium metavanadate solution Add deionized water to the round-bottomed flask and raise the temperature to 85~95°C. Add the ammonium metavanadate powder into the flask and stir it with magnetic force for 5~15 minutes to completely dissolve it to form an ammonium metavanadate solution; (2) Prepare a mixed solution of ferric nitrate and nitric acid Weigh the solid iron nitrate nonahydrate into a beaker, add deionized water and stir with a magnetic stirrer for 15 to 20 minutes to completely dissolve it and set aside; Use a pipette to transfer concentrated nitric acid into a beaker, add deionized water to dilute it to form 0.16 mol/L~0.20 mol/L dilute nitric acid, mix dilute nitric acid and ferric nitrate solution to form a mixed solution, set aside; (3) Preparation of layered iron vanadate precursor Add the prepared mixture of ferric nitrate and dilute nitric acid to the above prepared ammonium metavanadate solution, and continue stirring at 85~95°C for 0.5~7 h until the reaction is complete; (4) Centrifugal washing Cool the reaction suspension to room temperature. After the precipitate settles to the bottom of the flask, use a pipette to remove most of the supernatant. Move the remaining solution and precipitate to a centrifuge tube for centrifugation at 3000~5000 rpm. Keep for 5 to 15 minutes, centrifuge and remove the upper liquid of the centrifuge tube; then add ethanol for ultrasonic washing for 5 to 15 minutes, centrifuge and separate again, and repeat the ethanol washing, centrifugation, and separation process 1 to 3 times; (5) Drying Keep the precipitate after centrifugal washing in the centrifuge tube and transfer it to an oven at 60~80°C for drying. The drying time is 12 h to obtain the layered iron vanadate precursor, which is ready for use; (6) Roasting Put the iron vanadate precursor obtained in step (5) into a muffle furnace and raise it to 350°C at a heating rate of 1~5 ℃ min ^-1 and keep it for 2~8 hours to prepare a layered iron vanadium composite oxide denitration catalyst. . 2. The preparation method of the low-temperature ammonium bisulfate-resistant layered iron-vanadium composite oxide denitration catalyst according to claim 1, characterized in that: in step (1), the amount of ammonium metavanadate material in the ammonium metavanadate solution The concentration is controlled at 0.01~0.09 molL ^-1 ; in step (2), the concentration of iron nitrate in the mixed solution of iron nitrate and dilute nitric acid is controlled at 0.05~0.3 mol L ^-1 , and the pH value of the solution is controlled between 0.5-2.5. 3. The preparation method of low-temperature resistant ammonium bisulfate layered iron-vanadium composite oxide denitration catalyst according to claim 1, characterized in that: in the step (3), c (V ⁵⁺ ): c (Fe ³⁺ ) is controlled at 1:1~5:1, where c (V ⁵⁺ ) refers to the concentration of vanadium ion species in the ammonium metavanadate solution, c (Fe ³⁺ ) refers to iron nitrate or its mixture with nitric acid The concentration of iron ions in the liquid. 4. A low-temperature resistant ammonium bisulfate layered iron-vanadium composite oxide denitration catalyst prepared by the preparation method according to any one of claims 1 to 3. 5. Application of a low-temperature resistant ammonium bisulfate layered iron-vanadium composite oxide denitrification catalyst in NH ₃ -SCR reaction according to claim 4. 6. The application according to claim 5, characterized in that: during application, the layered iron-vanadium composite oxide denitrification catalyst is first pressed into tablets, ground and placed in a 40~60 mesh sieve for sieving, to obtain 40~ 60 mesh denitration catalyst particles. 7. Application according to claim 5, characterized in that: reaction conditions are as follows: [NO]=500 ppm, [NH ₃ ]=500 ppm, 5 vol% O ₂ , [SO ₂ ]=200 ppm, 10 vol% H ₂ O and N ₂ are used as balance gas, the total gas flow is 120 mL min ^-1 , the catalyst particle volume of 40 to 60 mesh is 0.2 mL, the volume space velocity is 36,000 h ^-1 , and the test temperature range is 90 to 360°C; Gas concentration data are collected after the reaction reaches equilibrium, and the _NOx conversion rate and _N2 selectivity are calculated by the following formula: ; ; [NO _x ] represents the NO _x concentration, [NO] represents the NO concentration, [N ₂ O] represents the N ₂ O concentration, [NH ₃ ] represents the NH ₃ concentration, in represents the reactor inlet concentration, and out represents the reactor outlet concentration.