Corrugated SCR catalyst and preparation method thereof
The preparation of corrugated SCR catalysts by combining electrodeposition and hydrothermal heat solves the problem of numerous materials used in the prior art and difficult to control the coating amount, and achieves efficient and controllable catalyst preparation and improves denitrification efficiency.
Patent Information
- Application Number
- CN202311210153.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-19
- Publication Date
- 2025-03-21
AI Technical Summary
The existing corrugated catalyst preparation process uses a wide variety of materials, and the coating amount is difficult to control, resulting in low yield, strict substrate size restrictions and poor applicability.
The preparation method of corrugated catalysts with main electrodeposition and auxiliary hydrothermal heat is adopted to optimize the material types, improve the yield and reduce the impact of substrate size on production by electrochemical in-situ deposition of active components.
The process route is optimized, and the operation is at room temperature and pressure, which avoids interlayer heat diffusion, fast deposition speed, precise control of the amount of active components, and improves the denitrification efficiency of the catalyst.
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Figure CN119657113A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of denitration, and in particular relates to a corrugated SCR catalyst and a preparation method thereof. Background Art
[0002] At present, the preparation process of corrugated catalysts is basically to prepare slurry first, then coat, dry and calcine. The whole process uses a variety of materials, and it is easy to have too much or too little coating during the preparation process. The amount of active components deposited in electrochemical in-situ is controllable, which reduces the interference of human factors on the coating quality. In addition, electrochemical deposition has the advantages of less restrictions on substrate size and simple operation, and can be applied to the preparation of corrugated denitrification catalysts.
[0003] In view of this, the present invention is proposed. Summary of the invention
[0004] The purpose of the present invention is to provide a corrugated SCR catalyst and a preparation method thereof to solve the above problems. Specifically, it is a preparation method of a corrugated catalyst using electrodeposition as the main method and hydrothermal as the auxiliary method, which can optimize the types of materials used, improve the yield rate, reduce the adverse effects of substrate size on production, and facilitate practical engineering applications.
[0005] In order to achieve the above objectives, the present invention particularly adopts the following technical solutions:
[0006] A method for preparing a corrugated SCR catalyst comprises the following steps:
[0007] S1: adding nitric acid to a mixed solution of sodium tungstate dihydrate solution and hydrogen peroxide to obtain an electrolyte;
[0008] Furthermore, the concentration of the sodium tungstate dihydrate solution in step S1 is 0.05-0.15 mol / L;
[0009] Further, the concentration of hydrogen peroxide is 0.05-0.15 mol / L;
[0010] Further, the concentration of the nitric acid is 0.2-0.4 mol / L;
[0011] Further, the pH value of the nitric acid is 1.5-1.6;
[0012] Furthermore, the pH value of the mixed solution is 10.5-11.5.
[0013] S2: using the electrolyte obtained in S1 to perform a first electrodeposition treatment on the substrate, and performing a first drying on the product.
[0014] Further, in step S2, the reference electrode of the first electrodeposition is silver or silver chloride / potassium chloride;
[0015] Further, the first electrodeposited counter electrode is a platinum mesh;
[0016] Further, the size of the first electrodeposited counter electrode is twice the size of the substrate;
[0017] Further, the electrochemical workstation for the first electrodeposition is CHI660e;
[0018] Further, the constant voltage of the first electrodeposition is -0.7V;
[0019] Further, the electrodeposition time of the first electrodeposition is 15-30 min;
[0020] Furthermore, the first drying includes drying at room temperature for 1 hour.
[0021] Before step S2, the substrate is pretreated;
[0022] Furthermore, the pretreatment includes: using hydrochloric acid, anhydrous ethanol and water to perform ultrasonic treatment on the substrate respectively, followed by dehydration for standby use.
[0023] Preferably, the substrate comprises glass fiber paper or high silica fiber paper;
[0024] Preferably, the ultrasonic treatment time is 10-20 min;
[0025] Preferably, the dehydration temperature is 100-120°C and the time is 1-3h.
[0026] S3: Prepare a homogeneous mixed system of sodium tungstate dihydrate aqueous solution, hydrochloric acid aqueous solution, oxalic acid and ammonium sulfate, then add the first electrodeposition product of S2, carry out hydrothermal reaction, wash the obtained product, perform a second drying, and cool to obtain a single-component WO3 catalyst.
[0027] Further, the molar ratio of sodium tungstate dihydrate, oxalic acid and ammonium sulfate is 1-8:15-20:30-60;
[0028] Further, the concentration of the hydrochloric acid aqueous solution is 1-4 mol / L;
[0029] Further, the hydrothermal reaction temperature is 150-200°C;
[0030] Furthermore, the hydrothermal reaction time is 10-20 hours.
[0031] S4: CeO2 is loaded on the single-component WO3 catalyst through a second electrodeposition treatment, and then a third drying and calcination is performed to obtain a finished composite metal oxide catalyst.
[0032] Further, the electrolyte of the second electrodeposition is a mixture of cerium nitrate hexahydrate and sodium nitrate;
[0033] Preferably, the concentration ratio of the cerium nitrate hexahydrate solution to the sodium nitrate solution is 1:1-5;
[0034] Preferably, before the second electrodeposition, O2 is introduced into the electrolyte to saturate the electrolyte;
[0035] Further, the reference electrode of the second electrodeposition is a saturated calomel electrode;
[0036] Further, the second electrodeposited counter electrode is a platinum mesh;
[0037] Further, the constant voltage of the second electrodeposition is -0.8V;
[0038] Furthermore, the electrodeposition time of the second electrodeposition is 10-30 min.
[0039] The present invention also provides a corrugated SCR catalyst obtained by the preparation method of the corrugated SCR catalyst.
[0040] Beneficial effects of the present invention:
[0041] (1) The process route is optimized, and it is easy to operate at room temperature and pressure, which can avoid interlayer thermal diffusion, and the deposition speed is fast. The amount of in-situ deposited active components can be precisely controlled by adjusting the electrodeposition time, and the coating composition is single;
[0042] (2) Optimize the types of materials used, improve the yield rate, reduce the adverse effects of substrate size on production, and facilitate practical engineering applications;
[0043] (3) The denitrification efficiency of the catalyst is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0045] Figure 1 It is a comparison chart of the denitrification efficiency of the sample of the embodiment of the present invention and the sample of the comparative example. DETAILED DESCRIPTION
[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0047] First, the present invention is explained as a whole, as follows:
[0048] An embodiment of the present invention provides a preparation method of a corrugated SCR catalyst, wherein the preparation method is as follows: S1: adding nitric acid to a mixed solution of a sodium tungstate dihydrate solution and hydrogen peroxide to obtain an electrolyte; S2: using the electrolyte obtained in S1 to perform a first electrodeposition treatment on a substrate, and performing a first drying on the product; S3: preparing a homogeneous mixed system of a sodium tungstate dihydrate aqueous solution, a hydrochloric acid aqueous solution, oxalic acid and ammonium sulfate, then adding the first electrodeposition product of S2, performing a hydrothermal reaction, washing the obtained product, performing a second drying, and cooling to obtain a single-component WO3 catalyst; S4: loading CeO2 on the single-component WO3 catalyst through a second electrodeposition treatment, and then performing a third drying and calcining to obtain a finished corrugated catalyst.
[0049] In an optional embodiment, the substrate needs to be ultrasonically treated with hydrochloric acid, anhydrous ethanol, and water before use, and then dehydrated for standby use. The ultrasonic treatment time is 10-20 minutes, the dehydration temperature is 100-120° C., and the dehydration time is 1-3 hours. In the embodiment of the present invention, the selected substrate is glass fiber paper or high silica fiber paper.
[0050] The purpose of hydrochloric acid pickling of the substrate is, first, surface acidification so that the substrate can adapt to the acidic environment of electrodeposition, and second, to remove surface impurities and micro-etch the substrate to enhance the adhesion of the substrate; the purpose of subsequent cleaning with anhydrous ethanol and water is because it is miscible with hydrochloric acid, which can remove excess hydrochloric acid on the surface of the substrate and eliminate its interference with the electrolyte composition; the main purpose of pretreatment is to remove surface impurities and improve substrate adhesion. At the same time, new impurities cannot be introduced during the pretreatment process. On this basis, three types of substances that can be arbitrarily soluble in each other are selected, namely hydrochloric acid, anhydrous ethanol, and water, and the order of addition cannot be changed.
[0051] In an optional embodiment, in the step S1, the concentration of the sodium tungstate dihydrate solution in the electrolyte is 0.05-0.15 mol / L; the concentration of the hydrogen peroxide is 0.05-0.15 mol / L; the concentration of the nitric acid is 0.2-0.4 mol / L; the pH value of the nitric acid is 1.5-1.6; the pH value of the mixed solution is 10.5-11.5. In an optional embodiment, in the step S2, the reference electrode of the first electrodeposition is silver, silver chloride / potassium chloride, the counter electrode is a platinum mesh, and the size of the counter electrode is twice the size of the substrate; the electrochemical workstation of the first electrodeposition is CHI660e, the constant voltage is -0.7V, and the electrodeposition time is 15-30min; the first drying includes drying at room temperature for 1h.
[0052] In an optional embodiment, in step S3, the molar ratio of sodium tungstate dihydrate, oxalic acid and ammonium sulfate is 1-8:15-20:30-60; the concentration of the hydrochloric acid aqueous solution is 1-4 mol / L; the hydrothermal reaction temperature is 150-200°C, and the hydrothermal reaction time is 10-20h.
[0053] In an optional embodiment, in step S4, the electrolyte for the second electrodeposition is a mixture of cerium nitrate hexahydrate and sodium nitrate, the concentration ratio of the two is 1:1-5, the reference electrode for the second electrodeposition is a saturated calomel electrode, the counter electrode is a platinum mesh, the constant voltage is -0.8V, and the electrodeposition time is 10-30min. Before the second electrodeposition, O2 is introduced into the electrolyte to saturate the electrolyte.
[0054] The reason for selecting the above-mentioned concentration of electrolyte, hydrothermal solution composition, hydrothermal temperature time and pH value during the electrodeposition and hydrothermal process is that the morphology of the sediment and the difficulty of deposition are affected by the concentration of electrolyte, the concentration of hydrothermal solution, the hydrothermal temperature time and pH value. Under the same conditions, the sample deposited with this concentration and pH value has the best denitrification performance.
[0055] The embodiment of the present invention adopts an electrochemical combined with hydrothermal in-situ deposition method at room temperature and pressure, which can avoid interlayer heat diffusion and has a fast deposition speed. At the same time, the amount of active components deposited in situ can be precisely controlled by adjusting the electrodeposition time. Since its principle is the electrochemical reaction of metal complex ions in the interface layer, only active components are deposited on the carrier surface. Compared with the direct coating method, the influence of other impurities such as unburned dispersant on the denitrification performance of the catalyst is eliminated.
[0056] The embodiment of the present invention further provides a corrugated SCR catalyst obtained by the preparation method of the corrugated SCR catalyst.
[0057] Example 1
[0058] This embodiment provides a method for preparing a corrugated SCR catalyst and a corrugated catalyst, and the specific steps are as follows:
[0059] S1: Process the glass fiber paper into a square of 1×1 cm, and treat it with 2 mol / L hydrochloric acid, anhydrous ethanol, and deionized water for 15 min respectively, and then put it in an oven to dry at 110°C for 2 h for later use;
[0060] S2: 0.1 mol / L sodium tungstate dihydrate solution and 0.1 mol / L hydrogen peroxide are fully mixed until the pH of the mixed solution is 11, and then 0.3 mol / L nitric acid (pH=1.56) is added to the mixed solution to obtain an electrolyte;
[0061] S3: silver / silver chloride was used as the reference electrode, a platinum mesh (2×2 cm) was used as the counter electrode, the electrolyte obtained in S2 was used as the electrolyte, and the treated glass fiber paper obtained in S1 was electrodeposited at a constant -0.7 V for 20 min, and then dried at room temperature for 1 h for use;
[0062] S4: Weigh 6.25 mmol of sodium tungstate dihydrate and dissolve it in deionized water, add 2 mol / L hydrochloric acid aqueous solution, then weigh 17.5 mmol of oxalic acid and 47.7 mmol of ammonium sulfate and add them to the mixed solution;
[0063] S5: The mixed solution obtained in S4 was diluted to 125 mL, stirred for 30 minutes, and then transferred to a hydrothermal reactor, and the product obtained in S3 was added to perform a hydrothermal reaction at 180°C for 16 hours. After the reaction was completed, the hydrothermal reaction product was rinsed three times with deionized water, dried, and cooled to room temperature to obtain a single-component WO3 catalyst;
[0064] S6: Use 0.05 mol / L cerium nitrate and 0.1 mol / L sodium nitrate to prepare the electrolyte for the second electrodeposition treatment. First, saturate the electrolyte with O2 (6 mL / min) for 30 minutes, then use a saturated calomel electrode as a reference electrode, a platinum mesh as a counter electrode, a deposition voltage of -0.8 V, and an electrodeposition time of 10 min. Load CeO2 on the single-component WO3 catalyst obtained in S5 to obtain the corrugated SCR catalyst provided by the present invention, which is recorded as implementation-1.
[0065] Example 2
[0066] This embodiment provides a method for preparing a corrugated SCR catalyst and a corrugated catalyst, and the specific steps are as follows:
[0067] S1: Process the glass fiber paper into a square of 1×1 cm, and treat it with 2 mol / L hydrochloric acid, anhydrous ethanol, and deionized water for 15 min respectively, and then put it in an oven to dry at 110°C for 2 h for later use;
[0068] S2: 0.1 mol / L sodium tungstate dihydrate solution and 0.1 mol / L hydrogen peroxide are fully mixed until the pH of the mixed solution is 11, and then 0.3 mol / L nitric acid (pH=1.56) is added to the mixed solution to obtain an electrolyte;
[0069] S3: silver / silver chloride was used as the reference electrode, a platinum mesh (2×2 cm) was used as the counter electrode, the electrolyte obtained in S2 was used as the electrolyte, and the treated glass fiber paper obtained in S1 was electrodeposited at a constant -0.7 V for 20 min, and then dried at room temperature for 1 h for use;
[0070] S4: Weigh 6.25 mmol of sodium tungstate dihydrate and dissolve it in deionized water, add 2 mol / L hydrochloric acid aqueous solution, then weigh 17.5 mmol of oxalic acid and 47.7 mmol of ammonium sulfate and add them to the mixed solution;
[0071] S5: The mixed solution obtained in S4 was diluted to 125 mL, stirred for 30 minutes, and then transferred to a hydrothermal reactor, and the product obtained in S3 was added to perform a hydrothermal reaction at 180°C for 16 hours. After the reaction was completed, the hydrothermal reaction product was rinsed three times with deionized water, dried, and cooled to room temperature to obtain a single-component WO3 catalyst;
[0072] S6: Use 0.05mol / L cerium nitrate and 0.1mol / L sodium nitrate to prepare the electrolyte for the second electrodeposition treatment. First, saturate the electrolyte with O2 (6mL / min) for 30 minutes, then use a saturated calomel electrode as a reference electrode, a platinum mesh as a counter electrode, a deposition voltage of -0.8V, and an electrodeposition time of 20min. CeO2 is loaded on the single-component WO3 catalyst obtained in S5 to obtain the corrugated SCR catalyst provided by the present invention, which is recorded as Implementation-2.
[0073] Example 3
[0074] This embodiment provides a method for preparing a corrugated SCR catalyst and a corrugated catalyst, and the specific steps are as follows:
[0075] S1: Process the glass fiber paper into a square of 1×1 cm, and treat it with 2 mol / L hydrochloric acid, anhydrous ethanol, and deionized water for 15 min respectively, and then put it in an oven to dry at 110°C for 2 h for later use;
[0076] S2: 0.1 mol / L sodium tungstate dihydrate solution and 0.1 mol / L hydrogen peroxide are fully mixed until the pH of the mixed solution is 11, and then 0.3 mol / L nitric acid (pH=1.56) is added to the mixed solution to obtain an electrolyte;
[0077] S3: silver / silver chloride was used as the reference electrode, a platinum mesh (2×2 cm) was used as the counter electrode, the electrolyte obtained in S2 was used as the electrolyte, and the treated glass fiber paper obtained in S1 was electrodeposited at a constant -0.7 V for 20 min, and then dried at room temperature for 1 h for use;
[0078] S4: Weigh 6.25 mmol of sodium tungstate dihydrate and dissolve it in deionized water, add 2 mol / L hydrochloric acid aqueous solution, then weigh 17.5 mmol of oxalic acid and 47.7 mmol of ammonium sulfate and add them to the mixed solution;
[0079] S5: The mixed solution obtained in S4 was diluted to 125 mL, stirred for 30 minutes, and then transferred to a hydrothermal reactor, and the product obtained in S3 was added to perform a hydrothermal reaction at 200°C for 20 hours. After the reaction was completed, the hydrothermal reaction product was rinsed three times with deionized water, dried, and cooled to room temperature to obtain a single-component WO3 catalyst;
[0080] S6: Use 0.05 mol / L cerium nitrate and 0.1 mol / L sodium nitrate to prepare the electrolyte for the second electrodeposition treatment. First, saturate the electrolyte with O2 (6 mL / min) for 30 minutes, then use a saturated calomel electrode as a reference electrode, a platinum mesh as a counter electrode, a deposition voltage of -0.8 V, and an electrodeposition time of 20 min. Load CeO2 on the single-component WO3 catalyst obtained in S5 to obtain the corrugated SCR catalyst provided by the present invention, which is recorded as implementation-3.
[0081] Example 4
[0082] This embodiment provides a method for preparing a corrugated SCR catalyst and a corrugated catalyst, and the specific steps are as follows:
[0083] S1: Process the glass fiber paper into a square of 1×1 cm, and treat it with 2 mol / L hydrochloric acid, anhydrous ethanol, and deionized water for 15 min respectively, and then put it in an oven to dry at 110°C for 2 h for later use;
[0084] S2: 0.15 mol / L sodium tungstate dihydrate solution and 0.15 mol / L hydrogen peroxide are fully mixed until the pH of the mixed solution is 11.5, and then 0.4 mol / L nitric acid (pH=1.6) is added to the mixed solution to obtain an electrolyte;
[0085] S3: silver / silver chloride was used as the reference electrode, a platinum mesh (2×2 cm) was used as the counter electrode, the electrolyte obtained in S2 was used as the electrolyte, and the treated glass fiber paper obtained in S1 was electrodeposited at a constant -0.7 V for 20 min, and then dried at room temperature for 1 h for use;
[0086] S4: Weigh 6.25 mmol of sodium tungstate dihydrate and dissolve it in deionized water, add 2 mol / L hydrochloric acid aqueous solution, then weigh 17.5 mmol of oxalic acid and 47.7 mmol of ammonium sulfate and add them to the mixed solution;
[0087] S5: The mixed solution obtained in S4 was diluted to 125 mL, stirred for 30 minutes, and then transferred to a hydrothermal reactor, and the product obtained in S3 was added to perform a hydrothermal reaction at 180°C for 16 hours. After the reaction was completed, the hydrothermal reaction product was rinsed three times with deionized water, dried, and cooled to room temperature to obtain a single-component WO3 catalyst;
[0088] S6: Use 0.05 mol / L cerium nitrate and 0.25 mol / L sodium nitrate to prepare the electrolyte for the second electrodeposition treatment. First, saturate the electrolyte with O2 (6 mL / min) for 30 minutes, then use a saturated calomel electrode as a reference electrode, a platinum mesh as a counter electrode, a deposition voltage of -0.8 V, and an electrodeposition time of 10 min. CeO2 is loaded on the single-component WO3 catalyst obtained in S5 to obtain the corrugated SCR catalyst provided by the present invention, which is recorded as implementation-4.
[0089] Example 5
[0090] This embodiment provides a method for preparing a corrugated SCR catalyst and a corrugated catalyst, and the specific steps are as follows:
[0091] S1: 0.1 mol / L sodium tungstate dihydrate solution and 0.1 mol / L hydrogen peroxide are fully mixed until the pH of the mixed solution is 11, and then 0.3 mol / L nitric acid (pH=1.56) is added to the mixed solution to obtain an electrolyte;
[0092] S2: silver / silver chloride was used as the reference electrode, a platinum mesh (2×2 cm) was used as the counter electrode, the electrolyte obtained in S2 was used as the electrolyte, the glass fiber paper was electrodeposited at a constant -0.7 V for 20 min, and then dried at room temperature for 1 h for use;
[0093] S3: Weigh 6.25 mmol of sodium tungstate dihydrate and dissolve it in deionized water, add 2 mol / L hydrochloric acid aqueous solution, then weigh 17.5 mmol of oxalic acid and 47.7 mmol of ammonium sulfate and add them to the mixed solution;
[0094] S4: The mixed solution obtained from S4 was diluted to 125 mL, stirred for 30 minutes, and then transferred to a hydrothermal reactor, and the product obtained from S3 was added to perform a hydrothermal reaction at 180°C for 16 hours. After the reaction was completed, the hydrothermal reaction product was rinsed three times with deionized water, dried, and cooled to room temperature to obtain a single-component WO3 catalyst;
[0095] S5: Use 0.05 mol / L cerium nitrate and 0.1 mol / L sodium nitrate to prepare the electrolyte for the second electrodeposition treatment. First, saturate the electrolyte with O2 (6 mL / min) for 30 minutes, then use a saturated calomel electrode as a reference electrode, a platinum mesh as a counter electrode, a deposition voltage of -0.8 V, and an electrodeposition time of 10 min. Load CeO2 on the single-component WO3 catalyst obtained in S5 to obtain the corrugated SCR catalyst provided by the present invention, which is recorded as implementation-5.
[0096] Comparative Example 1
[0097] (1) Processing glass fiber paper into a square (1×1 cm), impregnating the glass fiber paper with an alkaline silica sol solution (glue: water = 2:1), then drying at 110°C, and calcining at 500°C for 2 h for later use;
[0098] (2) Weigh 250 g of deionized water, add 46.6 g of vanadyl oxalate, 8 g of sodium tungstate dihydrate, and 150 g of titanium dioxide in sequence, and stir ultrasonically for 1.5 h;
[0099] (3) 90 g alkaline silica sol, 10.5 g ammonia water, 3 g monoethanolamine, 0.75 g emulsified silicone oil, 1.5 g water glass, 1.5 g polyacrylamide, and 57 g water were added to the mixed solution after ultrasonic treatment. The prepared mixed solution was ball milled in a ball mill for 0.5 h;
[0100] (4) The glass fiber paper sample was immersed in the above mixed solution and coated twice, dried at 110° C. and then calcined at 500° C. for 4 h. The coating amount after calcination was 125 g / L to obtain a comparative catalyst, which was recorded as Comparative-1.
[0101] Comparative Example 2
[0102] (1) Processing glass fiber paper into a square (1×1 cm), impregnating the glass fiber paper with an alkaline silica sol solution (gel: water = 1:1), then drying at 110°C, and calcining at 500°C for 2 h for later use;
[0103] (2) Weigh 250 g of deionized water, add 56.6 g of vanadyl oxalate, 10 g of sodium tungstate dihydrate, and 150 g of titanium dioxide in sequence, and stir ultrasonically for 1.5 h;
[0104] (3) 70 g alkaline silica sol, 10.5 g ammonia water, 3 g monoethanolamine, 0.75 g emulsified silicone oil, 1.5 g water glass, 1.5 g polyacrylamide, and 60 g water were added to the mixed solution after ultrasound treatment. The prepared mixed solution was ball milled in a ball mill for 0.5 h;
[0105] (4) The glass fiber paper sample was immersed in the above mixed solution and coated twice, dried at 110° C. and then calcined at 500° C. for 4 h. The coating amount after calcination was 125 g / L to obtain a comparative catalyst, recorded as Comparative-2.
[0106] The samples obtained in the above Examples 1-5 and Comparative Examples 1-2 were analyzed and tested, and the results are as follows:
[0107] The catalyst inlet and outlet concentrations before and after the reaction were measured using a flue gas analyzer. The test conditions were: total flue gas flow rate of 100 mL / min, hourly space velocity (GHSV) of 70,000 h -1 The flue gas composition is: NO accounts for 0.05%, NH3 accounts for 0.05%, O2 accounts for 3%, SO2 accounts for 0.02%, H2O accounts for 5%, and N2 is the balance gas. The SCR reaction test temperature range is 200-450℃.
[0108] The comparison of denitration efficiency between the samples of the present invention and the comparative examples is shown in Figure 1 The denitrification efficiency of the sample with CeO2 electrodeposition time of 10 min at 200 °C is close to that of the single-component sample, and rapidly increases to 93.24% after 250 °C, reaching a maximum value of 100% at 350 °C, but the denitrification efficiency gradually decreases as the temperature increases further, and drops to 61.48% at 450 °C.
[0109] The electrodeposition time of CeO2 was increased to 20min, and the implementation-2 sample showed the best denitration performance of the two-component catalyst. The denitration efficiency was significantly improved to 91.89% at 200℃, reaching a peak of 100% at 250℃ and maintaining it to 350℃, after which the denitration efficiency gradually decreased, and finally dropped to 70.27% at 450℃. The sample has a wider activity window of 200-400℃, and the denitration efficiency is significantly improved.
[0110] Depend on Figure 1It can be seen from the data that the electrolyte concentration, pH value, hydrothermal temperature and time, and pretreatment of the substrate were subsequently modified, and Implementations 3-5 all showed a significant decrease in denitrification efficiency. Since Implementation-5 did not pretreat the glass fiber paper, when other preparation conditions were the same as those in Example 1, the denitrification efficiency of Implementation-5 was significantly reduced compared with Example 1. Because the main purpose of pretreatment is to remove surface impurities and improve substrate adhesion, the performance of the glass fiber paper in Example 1 was significantly improved after pretreatment, which in turn helped to improve the catalytic activity of the catalyst. Compared with implementation-2, implementation-3 has a lower denitration efficiency. When other preparation conditions are the same as implementation-2, the hydrothermal reaction temperature of implementation-3 is higher and the hydrothermal reaction time is prolonged, because the temperature and time of the hydrothermal reaction will affect the morphology of the deposit and the ease of deposition, which will eventually affect the denitration efficiency of the catalyst. It can be seen that the denitration efficiency does not increase with the increase of temperature and the extension of reaction time, and there is no linear relationship between the two. Similarly, compared with implementation-1, implementation-4 has a lower denitration efficiency. When other preparation conditions are the same as implementation-1, what is changed is the concentration of the electrolyte. The difference in electrolyte concentration will also affect the morphology of the deposit and the ease of electrodeposition, which will lead to a decrease in denitration efficiency. Examples 1-2 all have a significant improvement in denitration efficiency compared to the comparative sample (comparison 1-2), among which the sample with an electrodeposition time of 20 min in implementation-2 is the best.
[0111] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.
Claims
1. A method for preparing a corrugated SCR catalyst, characterized in that: The following steps are involved: S1: adding nitric acid to a mixed solution of sodium tungstate dihydrate solution and hydrogen peroxide to obtain an electrolyte; S2: using the electrolyte obtained in S1 to perform a first electrodeposition treatment on the substrate, and performing a first drying on the product; S3: preparing a homogeneous mixed system of sodium tungstate dihydrate aqueous solution, hydrochloric acid aqueous solution, oxalic acid and ammonium sulfate, then adding the first electrodeposition product of S2, carrying out a hydrothermal reaction, washing the obtained product, second drying, and cooling, to obtain a single-component WO3 catalyst; S4: CeO2 is loaded on the single-component WO3 catalyst by a second electrodeposition treatment, and then a third drying and calcination is performed to obtain the catalyst.
2. The preparation method according to claim 1, characterized in that: The preparation method further comprises, before step S2, pre-treating the substrate; The pretreatment comprises: using hydrochloric acid, anhydrous ethanol and water to perform ultrasonic treatment on the substrate respectively, followed by dehydration for standby use; Preferably, the ultrasonic treatment time is 10-20 min; Preferably, the dehydration temperature is 100-120°C and the time is 1-3h.
3. The preparation method according to claim 1, characterized in that: The step S1 satisfies one or more of the following conditions: a. The concentration of the sodium tungstate dihydrate solution is 0.05-0.15 mol / L; b. The concentration of hydrogen peroxide is 0.05-0.15 mol / L; c. The concentration of the nitric acid is 0.2-0.4 mol / L; d. the pH value of the nitric acid is 1.5-1.6; e. The pH value of the mixed solution is 10.5-11.
5.
4. The preparation method according to claim 1, characterized in that: The step S2 satisfies one or more of the following conditions: f. The reference electrode of the first electrodeposition is silver, silver chloride / potassium chloride; g. The first electrodeposited counter electrode is a platinum mesh; h. The size of the first electrodeposited counter electrode is twice the size of the substrate; i. The electrochemical workstation for the first electrodeposition is CHI660e; j. The constant voltage of the first electrodeposition is -0.7V; k. The electrodeposition time of the first electrodeposition is 15-30min; 1. The first drying comprises drying at room temperature for 1 hour.
5. The preparation method according to claim 1 or 2, characterized in that: The substrate comprises glass fiber paper or high silica fiber paper.
6. The preparation method according to claim 1, characterized in that: The step S3 satisfies one or more of the following conditions: m. The molar ratio of sodium tungstate dihydrate, oxalic acid and ammonium sulfate is 1-8:15-20:30-60; n. The concentration of the aqueous hydrochloric acid solution is 1-4 mol / L; o. The hydrothermal reaction temperature is 150-200°C; p. The hydrothermal reaction time is 10-20h.
7. The preparation method according to claim 1, characterized in that: The step S4 satisfies one or more of the following conditions: q. The second electrodeposition electrolyte is a mixture of cerium nitrate hexahydrate and sodium nitrate; r. The reference electrode of the second electrodeposition is a saturated calomel electrode; s: the counter electrode of the second electrodeposition is a platinum mesh; t: the constant voltage of the second electrodeposition is -0.8V; u: The electrodeposition time of the second electrodeposition is 10-30 min.
8. The preparation method according to claim 7, characterized in that: The concentration ratio of the cerium nitrate hexahydrate solution to the sodium nitrate solution is 1:1-5.
9. The preparation method according to claim 7, characterized in that: Before performing the second electrodeposition in step S4, O2 is introduced into the electrolyte to saturate the electrolyte.
10. A corrugated SCR catalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.