A method for preparing a vanadium-titanium catalyst repair agent and a method for repairing vanadium-titanium catalysts using the agent.

Abstract

This invention provides a method for preparing a vanadium-titanium catalyst repair agent and a method for repairing vanadium-titanium catalysts using the agent. The preparation method of the repair agent is as follows: A seed mother liquor from the Bayer process for alumina production is added to lime slurry and stirred to obtain a filter cake and filtrate; the filter cake is added to a mixed solution of organic acid and ammonium salt and stirred to obtain an active component replenishment solution; aluminum hydroxide slurry from the Bayer process for alumina production is added to a citric acid solution and stirred to obtain an aluminum sol strength repair solution; the active component replenishment solution and the aluminum sol strength repair solution are then mixed to obtain the final product. The repair method is as follows: the vanadium-titanium catalyst to be repaired is immersed in the repair agent, dried, and calcined to obtain the final product. This invention cleverly incorporates the Bayer process to obtain the key materials required for the repair process, thereby achieving the repair of vanadium-titanium catalysts; after repair, the radial and axial compressive strength, wear resistance, and catalytic activity of the catalyst are all significantly improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a vanadium-titanium catalyst repair agent and a method for repairing vanadium-titanium catalysts using the agent, and more particularly to a method for preparing a vanadium-titanium catalyst repair agent using an intermediate product of the Bayer process for alumina production and a method for repairing vanadium-titanium catalysts using the agent. Background Technology

[0002] Vanadium-titanium catalysts, as broad-spectrum catalysts, are widely used in SCR denitrification, catalytic oxidation of VOCs, catalytic oxidation to phthalic anhydride, and catalytic oxidation of methanol, with their application being most extensive in SCR denitrification. However, the large-scale use of vanadium-titanium catalysts has also brought new problems, with the annual generation of spent catalysts exceeding 300,000 m³. 3 Vanadium-titanium spent catalysts are classified as hazardous waste. Therefore, maximizing the repair, regeneration, and reuse of these catalysts has significant economic and environmental value and is a crucial focus for the upgrading and development of related industries. Decreased mechanical strength and loss of active components are key factors leading to catalyst decommissioning.

[0003] Mechanical and thermal shocks can damage the physical structure of catalysts, causing internal cracks or even pulverization, leading to reduced mechanical strength and making them unusable. Mechanical wear, on the other hand, reduces both the mechanical strength and the loss of active components, resulting in decreased catalytic activity. The key to catalyst repair lies in healing internal cracks and replenishing active components.

[0004] Finding a simple and efficient way to repair vanadium-titanium catalysts is an urgent problem to be solved and a very meaningful task.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a vanadium-titanium catalyst repair agent and a method for repairing vanadium-titanium catalysts using the agent, so as to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a vanadium-titanium based catalyst repair agent includes the following steps:

[0009] S1: Take the vanadium-enriched mother liquor from the Bayer process for alumina production (hereinafter referred to as the Bayer process), maintain the temperature of the mother liquor at 85-100℃, and add lime slurry at a uniform rate while stirring to obtain a filter cake and filtrate. Return the filtrate to the mother liquor for recycling. The filter cake is calcium vanadate, an active component extract, which contains calcium carbonate impurities, but this does not affect subsequent use.

[0010] The following typical reaction occurs in this step:

[0011] Ca(OH)2+2NaVO3=Ca(VO3)2+2NaOH,

[0012] Ca(OH)2+2Na2CO3=CaCO3+2NaOH.

[0013] The Bayer process for producing alumina refers to the traditional or modified chemical process widely used in industry to produce alumina from bauxite. Its principle is to first dissolve the aluminum with concentrated sodium hydroxide and then precipitate it, with the sodium hydroxide being reused.

[0014] In the production and purification of Bayer process alumina, vanadium, a widely present associated element in bauxite, is both an impurity element that must be treated during alumina purification and an active component that needs to be replenished to repair vanadium-titanium catalysts. Therefore, this invention extracts vanadium from vanadium through a corresponding technical solution for the preparation of vanadium-titanium catalyst repair agents.

[0015] Preferably, the temperature of the seed mother liquor is maintained at 90-95°C.

[0016] Preferably, the amount of lime slurry added is 7.5–30 kg / m³ based on the dry weight of calcium hydroxide. 3 Mother liquor.

[0017] More preferably, the amount of lime slurry added is 15-18.5 kg / m³ based on the dry weight of calcium hydroxide. 3 Mother liquor.

[0018] Preferably, a trace amount of calcium vanadate is also added during the stirring reaction with lime slurry to promote the crystallization and precipitation of vanadate ions in the seed mother liquor in the form of calcium vanadate. Further, the dosage of calcium vanadate is 0.05-0.15 kg / m³. 3 Mother liquor.

[0019] S2: The filter cake is added at a uniform rate to a mixed solution of organic acid and ammonium salt at 60-85℃, stirred and reacted, cooled, allowed to stand, and filtered to obtain a replenishment solution of active components. Generally, the preferred feeding time is 0.5-1.5 hours, and stirring and reaction are continued for another 0.5-1 hour after feeding.

[0020] Preferably, the organic acid includes oxalic acid; the ammonium salt includes ammonium oxalate. Calcium vanadate first dissolves slowly, and then is reduced by oxalic acid to form vanadium oxalate oxycarboxylate complex. The purpose of adding the ammonium salt is to promote the dissolution of vanadium. In addition, calcium in the feed is precipitated as calcium oxalate and then removed by filtration.

[0021] The following typical reaction occurs in this step:

[0022] Ca(VO3)2+4H2C2O4=2CO2+CaC2O4+2VOC2O4+4H2O,

[0023] CaCO3+H2C2O4=CO2+CaC2O4+H2O.

[0024] Preferably, the concentration of the organic acid is 8.5-25.5 kg / m³. 3 The mixed solution; the concentration of the ammonium salt is 11.5-13 kg / m³. 3 The mixed solution.

[0025] More preferably, the concentration of the organic acid is 17 kg / m³. 3 The mixed solution.

[0026] Preferably, the amount of filter cake added is 15-17 kg / m³, calculated as calcium vanadate. 3 The mixed solution.

[0027] Preferably, the temperature of the mixed solution is maintained at 70-75°C.

[0028] S3: Prepare a citric acid solution, keep the liquid temperature at 30-65℃, add the aluminum hydroxide slurry from the Bayer process for producing alumina at a uniform rate to the citric acid solution, stir to react, cool, and obtain an aluminum sol strength repair solution.

[0029] The aluminum hydroxide slurry is obtained by separating and washing aluminum hydroxide, an intermediate product of the Bayer process.

[0030] The resulting aluminum sol exhibits excellent adhesion, heat resistance, and film-forming properties, making it suitable as a heat-resistant inorganic binder raw material and also a good catalyst carrier precursor. Using aluminum sol as a repair material can not only repair internal cracks in the catalyst to restore its mechanical strength but also compensate for the loss of carrier components caused by mechanical wear.

[0031] Preferably, the concentration of citric acid in the system is 100-270 kg / m³. 3 More preferably, the concentration of citric acid in the system is 188-213 kg / m³. 3 .

[0032] Preferably, the liquid temperature is maintained at 40-45°C. Higher temperatures can accelerate the sol-gel process, but excessively high temperatures will accelerate the gelation of the sol.

[0033] Preferably, the concentration of aluminum hydroxide in the system is 40-110 kg / m³. 3 More preferably, the concentration of aluminum hydroxide in the system is 75-85 kg / m³. 3 .

[0034] Preferably, to improve the stability of the aluminum sol strength repair solution, the pH value of the reaction system is controlled at 2.2-4.5; more preferably, the pH value is controlled at 2.8-3.5.

[0035] Optionally, the pH value of the reaction system is adjusted by adding oxalic acid and ammonium carbonate.

[0036] Further preferably, to further improve the stability of the aluminum sol strength repair solution and enhance the uniform distribution of the system, a sol stabilizer is also added to the reaction system.

[0037] Optionally, the sol stabilizer includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfonate, sodium lignosulfonate, or hexadecyltrimethylammonium bromide.

[0038] Furthermore, the amount of the sol stabilizer added accounts for 0.02-0.1 wt% of the total mass of the citric acid solution and the aluminum hydroxide slurry.

[0039] S4: The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:3-1:8 to obtain the vanadium-titanium catalyst repair agent.

[0040] Preferably, the active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:4 to 1:6.

[0041] Thus, by cleverly incorporating the Bayer process, we obtained the key materials required for the remediation process, and thereby achieved the remediation of vanadium-titanium catalysts.

[0042] The present invention also provides a method for repairing vanadium-titanium catalysts using a repair agent prepared by the above-described method: the vanadium-titanium catalyst to be repaired is soaked in the repair agent for 0.5-3 hours, then removed, dried, and calcined.

[0043] The vanadium-titanium catalyst to be repaired can be a used catalyst, a fresh catalyst whose performance needs to be improved, or a repaired catalyst. Preferably, before soaking, the vanadium-titanium catalyst to be repaired is pretreated by blowing off soot, cleaning, and drying.

[0044] Preferably, the soaking is carried out under alternating negative pressure and normal pressure to improve the soaking effect.

[0045] Preferably, the drying process involves heating the air to 90-150°C and holding the temperature for 1-5 hours.

[0046] Preferably, the calcination is carried out in an air atmosphere by heating to 350-420°C at a rate of 0.5-5.0°C / min and holding for 1-20 hours.

[0047] More preferably, the calcination is carried out in an air atmosphere at a rate of 1.0-2.5℃ / min to 380-400℃, and held for 4-6 hours.

[0048] During the drying and calcination process, the aluminum sol portion of the repair agent adheres to the catalyst surface in the form of γAl₂O₃, replenishing the lost support components. Some of the aluminum sol enters the catalyst support cracks and bonds with the titanium in the support to form Al-O-Ti bonds, thus healing and repairing the cracks and restoring the catalyst strength. The vanadium component of the repair agent oxidizes on the catalyst surface to form V₂O₅, replenishing the catalyst with new catalytic active sites.

[0049] Compared with the prior art, the present invention has the following beneficial effects;

[0050] (1) Traditional repair methods focus more on restoring catalytic activity, but are difficult to repair simultaneously the strength reduction caused by mechanical impact, thermal shock, mechanical wear, etc. This invention achieves the simultaneous and efficient restoration of catalyst mechanical strength and catalytic activity by formulating a composite repair agent.

[0051] (2) Vanadium is an impurity component that continuously accumulates in the seed liquor of the Bayer process and must be removed. This invention employs a method embedded in an existing mature production line, shortening the vanadium extraction process and eliminating processes such as repeated dissolution, sodium removal, ammonia removal, and calcination. This improves the vanadium extraction efficiency of the seed liquor and provides a new high-value utilization pathway for vanadium in the Bayer process seed liquor, namely, as a supplementary active component necessary for catalyst remediation. Based on the same idea, this invention uses aluminum hydroxide slurry, an intermediate product of the Bayer process, as a raw material to formulate a strength remediation solution, shortening the high-value utilization process of alumina.

[0052] (3) The axial and radial crush strength, wear resistance, and catalytic activity of the vanadium-titanium catalyst repaired by the method described in this invention are significantly improved, making it particularly suitable for catalytic scenarios with severe mechanical and thermal shocks. This is because the Al-O-Ti structure unique to the repaired catalyst has a lower coefficient of thermal expansion and higher resistance to thermal shock.

[0053] Apart from the above, the process flow of this invention has the advantages of being simple, mild, easy to control, and requiring minimal equipment. The auxiliary raw materials used are inexpensive and readily available, and the processing does not produce harmful substances. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Where the proportions of substances in the embodiments are not specified, it should be understood that they can be matched in any proportion. Where the units of proportion of substances are not specified, it should be understood as mass ratios.

[0056] Example 1

[0057] A method for preparing a vanadium-titanium catalyst repair agent:

[0058] (1)Remove 1m 3 The vanadium-enriched Bayer process seed mother liquor was kept at 100°C, and 30 kg of lime milk (dry weight) was added at a uniform rate. After stirring and reacting for 3 hours, 0.1 kg of calcium vanadate was added, precipitated, filtered, and washed to obtain a filter cake (active component extract). The filtrate was returned to the seed mother liquor for recycling.

[0059] (2) Prepare an oxalic acid solution with a concentration of 25.5 kg / m 3 The concentration of ammonium oxalate is 12.5 kg / m³. 3 1m of mixed solution 3 Maintain the liquid temperature at 85℃, add the active component extract obtained in step (1) to the mixed solution at a uniform rate and stir thoroughly. The dosage is 16 kg / m³ based on the effective component calcium vanadate. 3 The feeding time was 1.5 hours, and the reaction was stirred for another hour after feeding. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand for 12 hours. After filtration, the active component replenishment solution was obtained.

[0060] (3) Prepare a citric acid solution, maintaining the liquid temperature at 65℃. Add the Bayer process aluminum hydroxide slurry to the citric acid solution at a uniform rate to achieve a citric acid concentration of 270 kg / m³ in the system. 3 The aluminum hydroxide concentration is 110 kg / m³. 3 After stirring thoroughly for 3 hours, the mixture was cooled to room temperature. The pH of the liquid was controlled to 4.5 by adding oxalic acid and ammonium carbonate. A stabilizing agent with a mass fraction of 0.1 wt% was then added to the liquid to obtain the aluminum sol strength repair solution. The stabilizing agent consisted of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate in a 1:1 mass ratio.

[0061] (4) The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:3 to obtain the vanadium-titanium catalyst repair agent.

[0062] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0063] (1) Take the old vanadium-titanium SCR catalyst to be repaired, clean it, dry it, soak it in the vanadium-titanium catalyst repair agent for 3 hours, and then take it out and drain it.

[0064] (2) The product obtained in step (1) was heated to 150°C in air and held for 5 hours. Then, the temperature was increased to 420°C at a rate of 5.0°C / min and held for 20 hours. After that, it was cooled and removed to obtain the repaired catalyst. The performance test results of the catalyst before and after repair are shown in Table 1.

[0065] Example 2

[0066] A method for preparing a vanadium-titanium catalyst repair agent:

[0067] (1)Remove 1m 3 The vanadium-enriched Bayer process seed mother liquor was kept at 85°C, and 7.5 kg of lime milk (dry weight) was added at a uniform rate. After stirring and reacting for 1 hour, 0.15 kg of calcium vanadate was added, precipitated, filtered, and washed to obtain a filter cake (active component extract). The filtrate was returned to the seed mother liquor for recycling.

[0068] (2) Prepare an oxalic acid solution with a concentration of 8.5 kg / m 3 The concentration of ammonium oxalate is 12.5 kg / m³. 3 1m of mixed solution 3 Maintain the liquid temperature at 60℃, add the active component extract obtained in step (1) to the mixed solution at a uniform rate and stir thoroughly. The dosage is 15 kg / m³ based on the effective component calcium vanadate. 3 The feeding time was 0.5 hours, and the reaction was continued for another 0.5 hours after feeding. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand for 2 hours. After filtration, the active component replenishment solution was obtained.

[0069] (3) Prepare a citric acid solution, keeping the liquid temperature at 30℃. Add the Bayer process aluminum hydroxide slurry to the citric acid solution at a uniform rate to make the citric acid concentration in the system 100 kg / m³. 3 The aluminum hydroxide concentration is 40 kg / m³. 3 After stirring thoroughly for 0.5 hours, the mixture was cooled to room temperature. The pH of the liquid was controlled to 2.2 by adding oxalic acid and ammonium carbonate. Sodium lignosulfonate (0.02 wt%) was then added to the liquid to obtain the aluminum sol strength repair solution.

[0070] (4) The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:8 to obtain the vanadium-titanium catalyst repair agent.

[0071] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0072] (1) Take the old vanadium-titanium methanol catalytic oxidation catalyst to be repaired, and after blowing off the soot, cleaning and drying, place it in the vanadium-titanium catalyst repair agent, and soak it in the negative pressure-normal pressure alternating environment for 0.5h, and then take it out and drain it.

[0073] (2) The product obtained in step (1) was heated to 90°C in air and held for 1 hour. Then the temperature was increased to 350°C at a rate of 0.5°C / min and held for 1 hour. After that, it was cooled and removed to obtain the repaired catalyst.

[0074] Example 3

[0075] A method for preparing a vanadium-titanium catalyst repair agent:

[0076] (1)Remove 1m 3 The vanadium-enriched Bayer process seed mother liquor was kept at 95°C, and 18.5 kg of lime slurry (dry weight) was added at a uniform rate. After stirring and reacting for 2.5 h, 0.05 kg of calcium vanadate was added, precipitated, filtered, and washed to obtain a filter cake (active component extract). The filtrate was returned to the seed mother liquor for recycling.

[0077] (2) Prepare an oxalic acid solution with a concentration of 17 kg / m 3 The concentration of ammonium oxalate is 12.5 kg / m³. 3 1m of mixed solution 3 Maintain the liquid temperature at 75℃, add the active component extract obtained in step (1) to the mixed solution at a uniform rate and stir thoroughly. The dosage is 17 kg / m³ based on the effective component calcium vanadate. 3 The feeding time was 1.2 hours, and the reaction was stirred for another 1.2 hours after feeding. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand for 10 hours. After filtration, the active component replenishment solution was obtained.

[0078] (3) Prepare a citric acid solution, maintaining the liquid temperature at 45℃. Add the Bayer process aluminum hydroxide slurry to the citric acid solution at a uniform rate to make the citric acid concentration in the system 231 kg / m³. 3 The aluminum hydroxide concentration is 85 kg / m³. 3 After stirring thoroughly for 2 hours, the mixture was cooled to room temperature. The pH of the liquid was controlled to 3.5 by adding oxalic acid and ammonium carbonate. A stabilizing agent with a mass fraction of 0.08 wt% was then added to the liquid to obtain the aluminum sol strength repair solution. The stabilizing agent consisted of sodium hexadecyl sulfonate, sodium lignosulfonate, and hexadecyltrimethylammonium bromide in a mass ratio of 1:2:3.

[0079] (4) The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:4 to obtain the vanadium-titanium catalyst repair agent.

[0080] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0081] (1) Take the old vanadium-titanium VOCs catalytic oxidation catalyst to be repaired, and after blowing off the soot, cleaning and drying, place it in the vanadium-titanium catalyst repair agent, and soak it for 1.5 hours under the alternating negative pressure and normal pressure environment, and then take it out and drain it.

[0082] (2) The product obtained in step (1) was heated to 120°C in air and held for 3 hours. Then, the temperature was increased to 400°C at a rate of 2.5°C / min and held for 6 hours. After that, it was cooled and removed to obtain the repaired catalyst.

[0083] Example 4

[0084] A method for preparing a vanadium-titanium catalyst repair agent:

[0085] (1)Remove 1m 3 The vanadium-enriched Bayer process seed mother liquor was kept at 90°C, and 15 kg of lime milk (dry weight) was added at a uniform rate. After stirring and reacting for 2 hours, 0.1 kg of calcium vanadate was added, precipitated, filtered, and washed to obtain a filter cake (active component extract). The filtrate was returned to the seed mother liquor for recycling.

[0086] (2) Prepare an oxalic acid solution with a concentration of 17 kg / m 3 The concentration of ammonium oxalate is 12.5 kg / m³. 3 1m of mixed solution 3 Maintain the liquid temperature at 70℃, add the active component extract obtained in step (1) to the mixed solution at a uniform rate and stir thoroughly. The dosage is 16 kg / m³ based on the effective component calcium vanadate. 3 The feeding time was 0.8 hours, and the reaction was continued with stirring for another 0.5 hours after feeding. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand for 6 hours. After filtration, the active component replenishment solution was obtained.

[0087] (3) Prepare a citric acid solution, keeping the liquid temperature at 40℃. Add the Bayer process aluminum hydroxide slurry to the citric acid solution at a uniform rate to make the citric acid concentration in the system 188 kg / m³. 3 The aluminum hydroxide concentration is 75 kg / m³. 3 After stirring thoroughly for 1.5 hours, the mixture was cooled to room temperature. The pH of the liquid was controlled to 2.8 by adding oxalic acid and ammonium carbonate. A stabilizing agent with a mass fraction of 0.06 wt% was then added to the liquid to obtain the aluminum sol strength repair solution. The stabilizing agent consisted of sodium dodecyl sulfate, sodium hexadecyl sulfonate, sodium lignosulfonate, and hexadecyltrimethylammonium bromide in a mass ratio of 1:1:1:4.

[0088] (4) The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:6 to obtain the vanadium-titanium catalyst repair agent.

[0089] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0090] (1) Take the old vanadium-titanium SCR catalyst to be repaired, clean it, dry it, place it in the vanadium-titanium catalyst repair agent, soak it in the negative pressure-normal pressure alternating environment for 1 hour, and then take it out and drain it.

[0091] (2) The product obtained in step (1) was heated to 110°C in air and held for 2 hours. Then, the temperature was increased to 380°C at a rate of 1.0°C / min and held for 4 hours. After that, it was cooled and removed to obtain the repaired catalyst. The performance test results of the catalyst before and after repair are shown in Table 1.

[0092] Example 5

[0093] A method for preparing a vanadium-titanium catalyst repair agent:

[0094] (1)Remove 1m 3 The vanadium-enriched Bayer process seed mother liquor was kept at 92°C, and 16 kg of lime milk (dry weight) was added at a uniform rate. After stirring and reacting for 2.5 h, 0.1 kg of calcium vanadate was added, precipitated, filtered, and washed to obtain a filter cake (active component extract). The filtrate was returned to the seed mother liquor for recycling.

[0095] (2) Prepare an oxalic acid solution with a concentration of 17 kg / m 3 The concentration of ammonium oxalate is 12.5 kg / m³. 3 1m of mixed solution 3 Maintain the liquid temperature at 72℃, add the active component extract obtained in step (1) to the mixed solution at a uniform rate and stir thoroughly. The dosage is 16 kg / m³ based on the effective component calcium vanadate. 3 The feeding time was 1 hour, followed by stirring and reaction for another 0.8 hours. After the reaction was completed, the mixture was cooled to room temperature and allowed to stand for 8 hours. After filtration, the active component replenishment solution was obtained.

[0096] (3) Prepare a citric acid solution, maintaining the liquid temperature at 42℃. Add the Bayer process aluminum hydroxide slurry to the citric acid solution at a uniform rate to make the citric acid concentration in the system 205 kg / m³. 3 The aluminum hydroxide concentration is 80 kg / m³. 3After stirring thoroughly for 1.8 hours, the mixture was cooled to room temperature. The pH of the liquid was controlled to 3.1 by adding oxalic acid and ammonium carbonate. A stabilizing agent with a mass fraction of 0.07 wt% was then added to the liquid to obtain the aluminum sol strength repair solution. The stabilizing agent consisted of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfonate, sodium lignosulfonate, and hexadecyltrimethylammonium bromide in a mass ratio of 1:2:3:2:1.

[0097] (4) The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:5 to obtain the vanadium-titanium catalyst repair agent.

[0098] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0099] (1) Take the same vanadium-titanium SCR old catalyst to be repaired as in Example 4, and after blowing off the soot, cleaning and drying, place it in the vanadium-titanium catalyst repair agent, soak it in the negative pressure-normal pressure alternating environment for 1 hour, and then take it out and drain it.

[0100] (2) The product obtained in step (1) was heated to 115°C in air and held for 3 hours. Then, the temperature was increased to 390°C at a rate of 2.0°C / min and held for 5 hours. After that, it was cooled and removed to obtain the repaired catalyst. The performance test results of the repaired catalyst are shown in Table 1.

[0101] Example 6

[0102] A method for preparing a vanadium-titanium catalyst repair agent differs from Example 5 in that:

[0103] In step (3), the concentration of citric acid in the system is made to be 200 kg / m³. 3 The stabilizer has a mass fraction of 0.06 wt%. The stabilizer is composed of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfonate, sodium lignosulfonate, and hexadecyltrimethylammonium bromide in a mass ratio of 1:2:1:2:1.

[0104] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0105] (1) Take fresh vanadium-titanium SCR catalyst, clean it, dry it, place it in the vanadium-titanium catalyst repair agent, soak it in the negative pressure-normal pressure alternating environment for 1.2 hours, and then take it out and drain it.

[0106] (2) The product obtained in step (1) was heated to 118°C in air and held for 3 hours. Then, the temperature was increased to 395°C at a rate of 2.0°C / min and held for 5 hours. After that, it was cooled and removed to obtain the repaired catalyst. The performance test results of the catalyst before and after repair are shown in Table 1.

[0107] Example 7

[0108] The preparation method of the vanadium-titanium catalyst repair agent is the same as in the examples.

[0109] A method for repairing vanadium-titanium catalysts using a repair agent prepared by the above method:

[0110] (1) The vanadium-titanium SCR catalyst repaired in Example 4 was placed in the vanadium-titanium catalyst repair agent and repaired using the method in Example 6 to obtain the repaired catalyst. The performance test results of the catalyst after the second repair are shown in Table 1.

[0111] Comparative Example 1

[0112] The vanadium-titanium SCR catalyst to be repaired as described in Example 4 was scavenged, cleaned, and dried, then placed in the aluminosilicate strength repair solution obtained in step (3) of Example 5. After immersion in an alternating negative and normal pressure environment for 1.2 hours, it was removed and drained. The resulting product was heated to 115°C in air and held for 3 hours. Then, the temperature was increased to 390°C at a rate of 2.0°C / min and held for 5 hours. Afterward, it was cooled and removed to obtain the repaired catalyst. The performance test results of the repaired catalyst are shown in Table 1.

[0113] Comparative Example 2

[0114] The vanadium-titanium SCR catalyst to be repaired as described in Example 4 was scavenged, cleaned, and dried, then placed in the active component replenishment solution obtained in steps (1) and (2) of Example 5. After soaking in an alternating negative and normal pressure environment for 1.2 hours, it was removed and drained. The resulting product was heated to 115°C in air and held for 3 hours. Then, the temperature was increased to 390°C at a rate of 2.0°C / min and held for 5 hours. Afterward, it was cooled and removed to obtain the repaired catalyst. The performance test results of the repaired catalyst are shown in Table 1.

[0115] Comparative Example 3

[0116] The preparation method of the vanadium-titanium catalyst repair agent differs from that of Example 5 in that step (3) did not involve pH adjustment or the addition of a stabilizer. The catalyst to be repaired and the repair method are the same as in Example 5. The performance test results of the repaired catalyst are shown in Table 1.

[0117] The test items and methods are as follows:

[0118] Test methods for catalyst wear resistance before and after repair in Examples 1, 4-7 and Comparative Examples 1-3: The wear rate of honeycomb flue gas denitrification catalysts was determined according to the method for determining the wear rate (GB / T 31587—2015). The gas flow velocity in the catalyst channels was 14.5 m / s (standard conditions), and the concentration of abrasive (dry 0.300–0.425 mm high-hardness quartz sand) was 50 g / m³. 3 The flushing time was 2 hours. The test results are shown in Table 1.

[0119] The catalytic activity of the SCR catalysts in Examples 1, 4-7, and Comparative Examples 1-3 before and after remediation was tested under simulated flue gas conditions in a fixed-bed reactor. Test conditions: reaction temperature 350℃, catalyst loading height 2100mm, catalyst cross-sectional area 25cm². 2 The flue gas flow rate was 350 L / min, NO concentration was 300 ppm, ammonia-nitrogen molar ratio was 1.0, SO2 concentration was 500 ppm, oxygen concentration was 4.0%, water content was 10.0%, and nitrogen was used as a balance gas. The test results are shown in Table 1.

[0120] Table 1 Catalyst performance of Examples 1, 4-7 and Comparative Examples 1-3

[0121]

[0122]

[0123] As can be seen from Table 1, the performance test results of the catalysts before and after the repair in Examples 4 and 5 show that the radial compressive strength, axial compressive strength, wear resistance, and catalytic activity of the catalysts after repair are significantly improved.

[0124] Example 6 shows that the performance test results of the catalyst before and after repair indicate that the strength and activity of the fresh catalyst can be further improved after repair treatment.

[0125] The performance test results of the catalyst after repair in Example 7 show that the performance of the catalyst was restored after a single treatment, and repeated treatment can further improve the repair effect.

[0126] The performance test results of the catalysts after repair in Example 5 and Comparative Examples 1 and 2 show that the active component replenishment solution and the aluminum sol strength repair solution both have clear effects and are indispensable.

[0127] The performance test results of the catalysts after repair in Example 5 and Comparative Example 3 show that, without pH adjustment or the addition of a stabilizing agent, the aluminum sol strength repair solution partially gelled after being left for a long time, resulting in a poor strength repair effect.

[0128] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a vanadium-titanium based catalyst repair agent, characterized in that, Includes the following steps: S1: Take the vanadium-enriched seed mother liquor from the Bayer process for alumina production, maintain the temperature of the seed mother liquor at 85-100℃, add lime slurry and a trace amount of calcium vanadate, and stir to obtain filter cake and filtrate; the dosage of calcium vanadate is 0.05-0.15 kg / m³. 3 Seed mother liquor; S2: Add the filter cake to a mixed solution of organic acid and ammonium salt at 60-85℃, stir and react, cool, let stand, filter, and obtain an active component replenishment solution; The organic acid includes oxalic acid; the ammonium salt includes ammonium oxalate. The concentration of the organic acid is 8.5-25.5 kg / m³. 3 The mixed solution; the concentration of the ammonium salt is 11.5-13 kg / m³. 3 The mixed solution; The amount of filter cake added, calculated based on calcium vanadate, is 15-17 kg / m³. 3 The mixed solution; S3: Prepare a citric acid solution, keep the liquid temperature at 30-65℃, add the aluminum hydroxide slurry from the Bayer process for producing alumina to the citric acid solution, stir to react, cool, and obtain an aluminum sol strength repair solution. In step S3, the pH value of the reaction system is controlled to be 2.2-4.5; In step S3, a sol stabilizer is also added to the reaction system; the sol stabilizer includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfonate, sodium lignosulfonate, or hexadecyltrimethylammonium bromide. S4: The active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:3-1:8 to obtain the vanadium-titanium catalyst repair agent.

2. The preparation method according to claim 1, characterized in that, Step S1 satisfies one or more of the following conditions: a. Maintain the temperature of the seed mother liquor at 90-95℃; b. The amount of lime slurry added is 7.5~30 kg / m³ based on the dry weight of calcium hydroxide. 3 Mother liquor.

3. The preparation method according to claim 2, characterized in that, The amount of lime slurry added is 15-18.5 kg / m³ based on the dry weight of calcium hydroxide. 3 Mother liquor.

4. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the organic acid is 17 kg / m³. 3 The mixed solution.

5. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the mixed solution is maintained at 70-75°C.

6. The preparation method according to claim 1, characterized in that, Step S3 satisfies one or more of the following conditions: c. The concentration of citric acid in the system is 100-270 kg / m³. 3 ; d. Maintain the liquid temperature at 40-45℃; e. The concentration of aluminum hydroxide in the system is 40-110 kg / m³. 3 .

7. The preparation method according to claim 6, characterized in that, The concentration of citric acid in the system is 188-213 kg / m³. 3 .

8. The preparation method according to claim 6, characterized in that, The concentration of aluminum hydroxide in the system is 75-85 kg / m³. 3 .

9. The preparation method according to claim 1 or 6, characterized in that, In step S3, the pH value of the reaction system is controlled at 2.8-3.

5.

10. The preparation method according to claim 9, characterized in that, In step S3, the pH value of the reaction system is adjusted by adding oxalic acid and ammonium carbonate.

11. The preparation method according to claim 1, characterized in that, The amount of the sol stabilizer added is 0.02-0.1 wt% of the total mass of the citric acid solution and aluminum hydroxide slurry.

12. The preparation method according to claim 1, characterized in that, In step S4, the active component replenishment solution and the aluminum sol strength repair solution are mixed at a volume ratio of 1:4 to 1:

6.

13. A method for repairing vanadium-titanium catalysts using a repair agent prepared by any one of claims 1-12, characterized in that, The vanadium-titanium catalyst to be repaired is immersed in the repair agent for 0.5-3 hours, then removed, dried, and calcined.

14. The method according to claim 13, characterized in that, The soaking was carried out under alternating negative pressure and normal pressure; And / or, the drying is carried out by heating to 90-150°C in an air atmosphere and holding for 1-5 hours; And / or, the calcination is carried out in an air atmosphere by heating to 350-420°C at a rate of 0.5-5.0°C / min and holding for 1-20 hours.

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