Preparation method of pseudo-boehmite catalyst carrier

Abstract

The invention discloses a preparation method of a pseudo-boehmite catalyst carrier, and relates to the technical field of preparation of catalyst carriers. The preparation method comprises the following steps: dissolving aluminum hydroxide in a sodium hydroxide solution to obtain a reaction solution; introducing compressed carbon dioxide into the reaction liquid to generate pseudo-boehmite slurry, and carrying out filter pressing to obtain a first pseudo-boehmite wet cake; mixing the first pseudo-boehmite wet cake with industrial nitric acid, and performing aging treatment to obtain alumina gel; adding a sodium metaaluminate solution into the alumina gel to adjust the pH value, adding a composite template agent, stirring, and carrying out filter pressing again to obtain a second pseudo-boehmite wet cake; and washing, calcining and crushing the second pseudo-boehmite wet cake to obtain the pseudo-boehmite catalyst carrier. According to the preparation method provided by the invention, the structural performance of the pseudo-boehmite catalyst carrier is improved, the pseudo-boehmite catalyst carrier is of a double-pore distribution structure, and the pseudo-boehmite catalyst carrier can be suitable for various catalytic reactions related to environmental governance and repair and has the advantages of simple preparation process, low cost, excellent product structural performance and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of catalyst carrier preparation, in particular to a preparation method of pseudo-boehmite catalyst carrier. BACKGROUND

[0002] At present, as an important catalyst carrier material, pseudo-boehmite is particularly widely used in environmental governance and remediation, can be efficiently adapted to water heavy metal removal, industrial waste gas purification, soil degradation of refractory pollutants and other scenes, is the core supporting material for improving environmental governance efficiency and optimizing remediation effect, and the product performance directly affects the standard rate and long-term effectiveness of environmental governance and remediation.

[0003] The common methods for preparing pseudo-boehmite in industry mainly include nitric acid method, aluminum sulfate method and alcohol aluminum method. Due to the differences in reaction principles and raw material characteristics, the performance and production cost of the products prepared by different production methods are significantly different, and such differences are directly related to the treatment effect, governance cost and scalability of environmental governance and remediation projects. In actual environmental governance and remediation applications, the corresponding preparation method needs to be selected according to the specific governance scene (such as basic waste gas treatment, high-end refractory pollutant purification, etc.) and performance requirements, but the existing common production methods always have the core contradiction of being difficult to balance product performance and production cost, thereby limiting the upgrading of environmental governance and remediation effect and the scalability of application.

[0004] Specifically, some preparation methods (such as nitric acid method and aluminum sulfate method) have the advantages of easy availability of raw materials and simple reaction process, and the production cost is relatively low, which can meet the basic requirements of catalyst carrier specific surface area, pore volume and other basic requirements in basic environmental governance and remediation scenes (such as low-concentration waste gas pretreatment, ordinary water suspended matter removal, etc.), but due to the difficulty in completely removing impurities in the reaction process, the product purity is insufficient, which cannot meet the strict requirements of catalytic activity and stability in high-end environmental governance and remediation scenes (such as high-concentration heavy metal wastewater deep treatment, refractory VOCs purification, soil complex pollution remediation, etc.); and another part of the method (such as alcohol aluminum method) can prepare pseudo-boehmite products with qualified purity, excellent specific surface area and pore volume, which can efficiently support the smooth development of high-end environmental governance and remediation reactions and significantly improve the governance and remediation effect, but due to the high cost of raw materials and the difficulty in controlling the reaction conditions, the product price is expensive, which greatly limits its popularization and application in large-scale environmental governance and remediation projects (such as industrial park centralized governance, large-area soil remediation, etc.), and it is difficult to meet the current development needs of large-scale, efficient and low-cost environmental governance and remediation. SUMMARY

[0005] To address the shortcomings of existing technologies, this application provides a method for preparing a pseudoboehmite catalyst support, which improves the structural performance of the pseudoboehmite catalyst support, giving it a dual-pore structure that is suitable for various catalytic reactions. It has the advantages of simple preparation process, low cost, and controllable product structure.

[0006] To achieve the above objectives, the method for preparing the pseudoboehmite catalyst support provided in this application includes the following steps:

[0007] S1. Add aluminum hydroxide to sodium hydroxide solution, and after dissolving, obtain the reaction solution;

[0008] S2. Then, compressed carbon dioxide is introduced into the reaction solution to adjust the pH and obtain pseudoboehmite slurry. The pseudoboehmite slurry is then filtered to obtain the first wet cake of pseudoboehmite.

[0009] S3. The first wet cake of boehmite was put into the reactor, industrial nitric acid was added, and after aging treatment, aluminum glue was obtained.

[0010] S4. Add sodium aluminate solution to the aluminum glue, adjust the pH, add composite template agent, stir and filter again to obtain the second wet cake of pseudoboehmite.

[0011] S5. The second wet cake of pseudoboehmite is washed with water, and then subjected to vacuum calcination and pulverization to obtain the pseudoboehmite catalyst support.

[0012] In one feasible implementation, the composite template agent is obtained by compounding polyethylene glycol with polyvinyl alcohol or by compounding polyethylene glycol with sodium stearate.

[0013] In one feasible implementation, the pseudoboehmite catalyst support has an average particle size D50 of 20-50 μm and a specific surface area ≥250 m². 2 / g, pore volume ≥0.5cm 3 / g.

[0014] This application provides a simple, efficient, and low-cost process for preparing pseudoboehmite catalyst supports, which enables precise control over the particle size, specific surface area, and pore volume of the prepared pseudoboehmite catalyst supports, and the final product meets the core requirements of the catalysis field.

[0015] Specifically, this application first generates a sodium aluminate solution by reacting aluminum hydroxide with sodium hydroxide, providing a uniform aluminum source for subsequent carbonization. Then, carbon dioxide is introduced into the solution to achieve the carbonization reaction, generating a pseudoboehmite first wet cake containing amorphous aluminum hydroxide. The pseudoboehmite first wet cake is further acidified and aged to form an aluminum glue, which is essentially a mixture of aluminum nitrate and amorphous aluminum hydroxide. This promotes further stabilization of its structure, increases the adhesion between particles, and improves its strength, resulting in a narrower pore distribution during its growth. Further addition of sodium aluminate solution to the aluminum glue and adjusting the pH to alkaline promotes the reaction of aluminum nitrate in the aluminum glue to generate amorphous aluminum hydroxide. After the addition of the composite template agent, the composite template agent disperses in the system and creates space occupancy, thereby forcing the generated amorphous aluminum hydroxide to further grow and produce different pore structures. During the subsequent calcination process, the composite template agent that creates space occupancy is completely decomposed by high temperature, resulting in a pseudoboehmite catalyst support with a biporous structure. Its unique pore structure and high specific surface area can increase the loading sites of active components, and the large pore volume can reduce the diffusion resistance of reactants and products, thus jointly improving the catalytic performance of the active components it supports.

[0016] In one feasible implementation, in S1, the average particle size of the aluminum hydroxide is 50-100 μm; and the mass concentration of the sodium hydroxide solution is 12-18%.

[0017] In this application, during the reaction of aluminum hydroxide with sodium hydroxide solution, controlling the particle size of aluminum hydroxide to 50-100 μm increases the solid-liquid contact area and prevents excessively fine aluminum hydroxide from agglomerating, which would hinder the reaction. Simultaneously, when the concentration of the sodium hydroxide solution is controlled at 12-18%, the concentration of hydroxide ions in the solution is sufficient to drive the reaction forward, and excessively high sodium hydroxide concentration will not lead to the subsequent carbonization process requiring more carbon dioxide, thus avoiding an increase in overall cost.

[0018] In one feasible implementation, in S1, the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:(6-10); the dissolution process parameters include: dissolution temperature 70-85℃, stirring speed 200-400rpm, and stirring time 1-3h.

[0019] During the reaction of aluminum hydroxide with sodium hydroxide solution, the mass of the sodium hydroxide solution is controlled to be 6-10 times that of the aluminum hydroxide to ensure that the aluminum hydroxide is fully dispersed and the reaction is complete. Control of temperature, stirring speed, and stirring time further guarantees a complete reaction.

[0020] In one feasible implementation, in S2, the temperature of the reaction solution is reduced to 30-50°C; the rate of introduction of compressed carbon dioxide is 0.8-1.5 L / min; and the pH is adjusted to 6.5-7.5.

[0021] In this application, the control of the reaction liquid temperature can ensure that the solubility of carbon dioxide is not too low, thereby promoting the carbonization process in conjunction with the carbon dioxide introduction rate.

[0022] In one feasible implementation, in S2, the process parameters of the pressure filtration include: pressure 0.4-0.7 MPa, temperature 25-35℃; and the moisture content of the first wet cake of the pseudo-boehmite is 55-65%.

[0023] When the moisture content of the first wet cake of boehmite is 55-65%, the subsequent addition of industrial nitric acid and aging treatment can quickly disperse and undergo an acidification reaction to form a more uniform aluminum paste.

[0024] In one feasible implementation, in S3, the mass fraction of the industrial nitric acid is 55-65%; the amount of industrial nitric acid added is 5-15% of the mass of the first wet cake of boehmite.

[0025] Controlling the mass fraction and amount of industrial nitric acid can further promote aging, transforming the first wet cake of boehmite into aluminum gel.

[0026] In one feasible implementation, the process parameters for the aging treatment in S3 include: temperature 50-60℃, stirring speed 200-300rpm, and aging time 2-3h.

[0027] Alumina gel is prepared through an aging process. Specifically, after the first wet cake of boehmite is acidified with industrial nitric acid, the particles cross-link through hydrogen bonds and van der Waals forces to form a gel. A temperature of 50-60℃ can accelerate the cross-linking reaction, thereby increasing the strength of the resulting aluminum gel, while preventing excessive temperature from causing dehydration and shrinkage, which would lead to the collapse of the pores. A stirring speed of 200-300 rpm can prevent the aluminum gel from agglomerating and ensure a uniform structure; an aging time of 2-3 hours ensures that the gelled aluminum gel is fully formed. If the aging time is too short, the strength of the aluminum gel may be insufficient; if the aging time is too long, the aluminum gel may harden easily, making subsequent dispersion difficult.

[0028] In one feasible implementation, in S4, the mass concentration of the sodium aluminate solution is 6-12%; the amount of sodium aluminate solution added is 5-10% of the mass of the aluminum glue; the pH is adjusted to 8-9; in the composite template agent, the mass ratio of polyethylene glycol to polyvinyl alcohol is (1-3):1, and the mass ratio of polyethylene glycol to sodium stearate is (2-4):1; the amount of the composite template agent added is 0.5-3% of the mass of the aluminum glue.

[0029] In this application, sodium aluminate solution is further added to the aluminum colloid, and the pH is adjusted to alkaline, which promotes the reaction of aluminum nitrate in the aluminum colloid to form amorphous aluminum hydroxide. Further addition of a composite template agent disperses in the system and creates vacant sites, thereby forcing the generated amorphous aluminum hydroxide to further grow and produce different pore structures. During the subsequent calcination process, the composite template agent that creates vacant sites is completely decomposed at high temperature, resulting in a biporous structure in the final boehmite catalyst support. The composite template agent used in this application neither reacts with substances in the system nor affects the generated boehmite crystal phase, and can be completely removed at high temperature during subsequent processing.

[0030] In one feasible implementation, in S4, the stirring process parameters include: stirring speed 300-500 rpm, stirring time 1-2 h, and stirring temperature 60-70℃; the re-press filtration process parameters include: pressure 0.8-1.5 MPa and temperature 30-40℃.

[0031] In a feasible implementation scenario, in S5, the number of times water is added for washing is 2-3 times.

[0032] In one feasible implementation, the process parameters for vacuum calcination in S5 include: absolute pressure 0.02-0.08 MPa, calcination temperature 450-550℃, and calcination time 5-8 h.

[0033] Beneficial technical effects:

[0034] This application first generates a sodium aluminate solution by reacting aluminum hydroxide with sodium hydroxide, providing a uniform aluminum source for subsequent carbonization. Then, carbon dioxide is introduced into the solution to achieve the carbonization reaction, generating a pseudoboehmite first wet cake containing amorphous aluminum hydroxide. The pseudoboehmite first wet cake is further acidified and aged to form an aluminum glue, which is essentially a mixture of aluminum nitrate and amorphous aluminum hydroxide. This promotes further stabilization of its structure, increases the adhesion between particles, and improves its strength, resulting in a narrower pore distribution during its growth. Further addition of sodium aluminate solution to the aluminum glue and adjusting the pH to alkaline promotes the reaction of aluminum nitrate in the aluminum glue to generate amorphous aluminum hydroxide. After the addition of the composite template agent, the composite template agent disperses in the system and creates space occupancy, thereby forcing the generated amorphous aluminum hydroxide to further grow and produce different pore structures. During the subsequent calcination process, the composite template agent that creates space occupancy is completely decomposed by high temperature, resulting in a pseudoboehmite catalyst support with a biporous structure. Its unique pore structure and high specific surface area can increase the loading sites of active components, while the large pore volume can reduce the diffusion resistance of reactants and products, thus jointly enhancing the catalytic performance of the supported active components. The preparation method of the pseudoboehmite catalyst support provided in this application also has the advantages of simple process, low cost, and excellent product structure and performance. Attached Figure Description

[0035] Figure 1 This is a physical image of the pseudoboehmite obtained in Example 1 of this application.

[0036] Figure 2 This is a schematic diagram of the preparation method of pseudoboehmite provided in this application. Detailed Implementation

[0037] To facilitate understanding of the content described in this application, the technical solutions described herein are further explained below with reference to specific embodiments; however, this application is not limited thereto. All equivalent transformations or simple substitutions made based on the substantive content of this application should fall within the protection scope of this application.

[0038] The singular forms “for,” “or,” “a,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] The following describes in detail, with reference to different embodiments, a method for preparing a pseudoboehmite catalyst support provided in this application.

[0040] Example 1

[0041] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0042] S1. Add aluminum hydroxide with an average particle size of 50 μm to a sodium hydroxide solution with a mass concentration of 12% and stir at 200 rpm for 1 hour at 70°C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:6.

[0043] S2. Reduce the temperature of the reaction solution to 30℃, then introduce compressed carbon dioxide into it at a rate of 0.8L / min, adjust the pH to 6.5, and obtain a pseudoboehmite slurry. Then filter the pseudoboehmite slurry under pressure of 0.4MPa and temperature of 25℃ to obtain a pseudoboehmite first wet cake with a water content of 55%.

[0044] S3. The first wet cake of boehmite was added to a reactor, and 55% industrial nitric acid was added. The mixture was aged at 50°C and 200 rpm for 2 hours to obtain aluminum gel. The amount of industrial nitric acid added was 5% of the mass of the first wet cake of boehmite.

[0045] S4. Add a 6% sodium aluminate solution (10% of the mass of aluminum glue) to the aluminum glue, adjust the pH to 8, then add the composite template agent, and stir at 300 rpm for 1 hour at 60°C. Then filter again under pressure of 0.8 MPa and temperature of 30°C to obtain the second wet cake of pseudoboehmite.

[0046] The composite template agent is added at 3% of the mass of the aluminum glue, and includes polyethylene glycol and polyvinyl alcohol, wherein the mass ratio of polyethylene glycol and polyvinyl alcohol is 1:1.

[0047] S5. The second wet cake of pseudoboehmite is washed twice with water, then calcined for 5 hours under an absolute pressure of 0.02 MPa and a temperature of 550℃, followed by pulverization to obtain the pseudoboehmite catalyst support. The actual product is shown in the figure. Figure 1 As shown.

[0048] Example 2

[0049] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0050] S1. Add aluminum hydroxide with an average particle size of 100 μm to a sodium hydroxide solution with a mass concentration of 18% and stir at 400 rpm for 3 hours at 85°C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:10.

[0051] S2. Reduce the temperature of the reaction solution to 50℃, then introduce compressed carbon dioxide into it at a rate of 1.5L / min, adjust the pH to 7.5, and obtain a pseudoboehmite slurry. Then filter the pseudoboehmite slurry under pressure of 0.7MPa and temperature of 35℃ to obtain a pseudoboehmite first wet cake with a water content of 65%.

[0052] S3. The first wet cake of boehmite was added to a reactor, and 65% industrial nitric acid was added. The mixture was aged at 60°C and 300 rpm for 3 hours to obtain aluminum gel. The amount of industrial nitric acid added was 15% of the mass of the first wet cake of boehmite.

[0053] S4. Add a 12% sodium aluminate solution (5% of the mass of aluminum glue) to the aluminum glue, adjust the pH to 9, then add the composite template agent, and stir at 500 rpm for 2 hours at 70℃. Then filter again under pressure of 1.5 MPa and temperature of 40℃ to obtain the second wet cake of pseudoboehmite.

[0054] The composite template agent is added at 2% of the mass of the aluminum glue, and includes polyethylene glycol and sodium stearate, wherein the mass ratio of polyethylene glycol to sodium stearate is 2:1.

[0055] S5. The second wet cake of pseudoboehmite is washed with water three times, then calcined for 8 hours under an absolute pressure of 0.08 MPa and a temperature of 450℃, and then pulverized to obtain the pseudoboehmite catalyst support.

[0056] Example 3

[0057] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0058] S1. Add aluminum hydroxide with an average particle size of 60 μm to a sodium hydroxide solution with a mass concentration of 14% and stir at 250 rpm for 1.5 h at 75 °C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:7.

[0059] S2. Reduce the temperature of the reaction solution to 35℃, then introduce compressed carbon dioxide into it at a rate of 1.0L / min, adjust the pH to 6.8, and obtain a pseudoboehmite slurry. Then filter the pseudoboehmite slurry under pressure of 0.5MPa and temperature of 28℃ to obtain a pseudoboehmite first wet cake with a water content of 58%.

[0060] S3. The first wet cake of boehmite was added to a reactor, and 58% industrial nitric acid was added. The mixture was aged at 52°C and 220 rpm for 2.2 hours to obtain aluminum gel. The amount of industrial nitric acid added was 8% of the mass of the first wet cake of boehmite.

[0061] S4. Add an 8% sodium aluminate solution (10% of the mass of the aluminum glue) to the aluminum glue, adjust the pH to 8.2, then add the composite template agent, and stir at 350 rpm for 1.2 h at 63℃. Then filter again under pressure of 1.0 MPa and temperature of 32℃ to obtain the second wet cake of pseudoboehmite.

[0062] The composite template agent is added at 1% of the mass of the aluminum glue, and includes polyethylene glycol and polyvinyl alcohol, wherein the mass ratio of polyethylene glycol to polyvinyl alcohol is 2:1.

[0063] S5. The second wet cake of pseudoboehmite is washed twice with water, then calcined for 6 hours under an absolute pressure of 0.04 MPa and a temperature of 500℃, and then pulverized to obtain the pseudoboehmite catalyst support.

[0064] Example 4

[0065] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0066] S1. Add aluminum hydroxide with an average particle size of 80 μm to a sodium hydroxide solution with a mass concentration of 16% and stir at 350 rpm for 2.5 h at 80 °C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:9.

[0067] S2. The temperature of the reaction solution is reduced to 45℃, and then compressed carbon dioxide is introduced into it at a rate of 1.3L / min to adjust the pH to 7.2, so as to obtain a pseudoboehmite slurry. The pseudoboehmite slurry is then filtered under pressure of 0.6MPa and temperature of 32℃ to obtain a pseudoboehmite first wet cake with a water content of 62%.

[0068] S3. The first wet cake of boehmite was added to a reactor, and industrial nitric acid with a mass fraction of 62% was added. The mixture was aged at 58°C and a stirring speed of 280 rpm for 2.8 hours to obtain aluminum gel. The amount of industrial nitric acid added was 12% of the mass of the first wet cake of boehmite.

[0069] S4. Add a 10% sodium aluminate solution (6% of the mass of aluminum glue) to the aluminum glue, adjust the pH to 8.8, then add the composite template agent, and stir at 450 rpm for 1.8 h at 68℃. Then filter again under pressure of 1.3 MPa and temperature of 38℃ to obtain the second wet cake of pseudoboehmite.

[0070] The composite template agent is added at 0.5% of the mass of the aluminum glue, and includes polyethylene glycol and sodium stearate, wherein the mass ratio of polyethylene glycol to sodium stearate is 4:1.

[0071] S5. The second wet cake of pseudoboehmite is washed with water three times, then calcined for 7 hours under an absolute pressure of 0.06 MPa and a temperature of 520℃, and then pulverized to obtain the pseudoboehmite catalyst support.

[0072] Example 5

[0073] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0074] S1. Add aluminum hydroxide with an average particle size of 70 μm to a sodium hydroxide solution with a mass concentration of 15% and stir at 300 rpm for 2 hours at 78°C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:8.

[0075] S2. Reduce the temperature of the reaction solution to 40℃, then introduce compressed carbon dioxide into it at a rate of 1.2L / min, adjust the pH to 7.0, and obtain a pseudoboehmite slurry. Then filter the pseudoboehmite slurry under pressure of 0.55MPa and temperature of 30℃ to obtain a pseudoboehmite first wet cake with a water content of 60%.

[0076] S3. The first wet cake of boehmite was added to a reactor, and 60% industrial nitric acid was added. The mixture was aged at 55°C and 250 rpm for 2.5 hours to obtain aluminum gel. The amount of industrial nitric acid added was 10% of the mass of the first wet cake of boehmite.

[0077] S4. Add a 9% sodium aluminate solution (9% of the mass of aluminum glue) to the aluminum glue, adjust the pH to 8.5, then add the composite template agent, and stir at 400 rpm for 1.5 h at 65℃. Then filter again under pressure of 1.2 MPa and temperature of 35℃ to obtain the second wet cake of pseudoboehmite.

[0078] The composite template agent is added at 2.5% of the mass of the aluminum glue, and includes polyethylene glycol and polyvinyl alcohol, wherein the mass ratio of polyethylene glycol to polyvinyl alcohol is 1:1.

[0079] S5. The second wet cake of pseudoboehmite is washed twice with water, then calcined for 6.5 h under an absolute pressure of 0.05 MPa and a temperature of 510 °C, and then pulverized to obtain the pseudoboehmite catalyst support.

[0080] Example 6

[0081] like Figure 2 As shown, a method for preparing a pseudo-boehmite catalyst support includes the following steps:

[0082] S1. Add aluminum hydroxide with an average particle size of 90 μm to a sodium hydroxide solution with a mass concentration of 13% and stir at 280 rpm for 1.8 h at 72 °C to obtain a reaction solution; wherein the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:6.5.

[0083] S2. The temperature of the reaction solution is reduced to 38℃, and then compressed carbon dioxide is introduced into it at a rate of 0.9L / min to adjust the pH to 6.9, thereby obtaining a pseudoboehmite slurry. The pseudoboehmite slurry is then filtered under pressure of 0.45MPa and temperature of 27℃ to obtain a pseudoboehmite first wet cake with a water content of 56%.

[0084] S3. The first wet cake of boehmite was added to a reactor, and 56% industrial nitric acid was added. The mixture was aged at 53°C and 230 rpm for 2.1 hours to obtain aluminum gel. The amount of industrial nitric acid added was 6% of the mass of the first wet cake of boehmite.

[0085] S4. Add a 7% sodium aluminate solution (8% of the mass of aluminum glue) to the aluminum glue, adjust the pH to 8.3, then add the composite template agent, and stir at 320 rpm for 1.3 h at 62℃. Then filter again under pressure of 0.9 MPa and temperature of 31℃ to obtain the second wet cake of pseudoboehmite.

[0086] The composite template agent is added at 1.5% of the mass of the aluminum glue, and includes polyethylene glycol and sodium stearate, wherein the mass ratio of polyethylene glycol to sodium stearate is 3:1.

[0087] S5. The second wet cake of pseudoboehmite is washed with water three times, then calcined for 5.5 hours under an absolute pressure of 0.03 MPa and a temperature of 480℃, and then pulverized to obtain the pseudoboehmite catalyst support.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a pseudo-boehmite catalyst support. The difference between this comparative example and Example 1 is that this comparative example omits steps S1 and S2, directly adding aluminum hydroxide into the reactor and then adding industrial nitric acid. Other process parameters and operating steps are exactly the same as in Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a method for preparing a pseudo-boehmite catalyst support. The difference between this comparative example and Example 1 is that this comparative example does not involve the processing of industrial nitric acid followed by aging. Other process parameters and operating steps are exactly the same as in Example 1.

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing a pseudo-boehmite catalyst support. The difference between this comparative example and Example 1 is that no composite template agent is added. Other process parameters and operating steps are exactly the same as in Example 1.

[0094] The specific surface area, pore volume, and average particle size D50 of the pseudoboehmite prepared in each embodiment and comparative example were tested to collectively demonstrate its structural properties. The test results are shown in Table 1.

[0095] Table 1. Statistical table of test results for pseudoboehmite prepared in the examples and comparative examples.

[0096]

[0097] As shown in Table 1, the specific surface area and pore volume of the pseudoboehmite prepared in Examples 1 to 6 are generally higher than those in Comparative Examples 1 to 3; while the average particle size D50 is generally lower than that in Comparative Examples 1 to 3.

[0098] The main reason is that this application first generates sodium aluminate solution by reacting aluminum hydroxide with sodium hydroxide, providing a uniform aluminum source for subsequent carbonization; then carbon dioxide is introduced into it to achieve the carbonization reaction, generating a pseudoboehmite first wet cake containing amorphous aluminum hydroxide; further, the pseudoboehmite first wet cake is acidified and aged to form an aluminum glue that is essentially a mixture of aluminum nitrate and amorphous aluminum hydroxide, which promotes further stability of its structure, increases the adhesion between particles and improves strength, and narrows the pore distribution of the structure during its growth; further, sodium aluminate solution is added to the aluminum glue and the pH is adjusted to alkaline, which can promote the aluminum nitrate in the aluminum glue to also react to generate amorphous aluminum hydroxide, so that after the addition of the composite template agent, the composite template agent is dispersed in the system and generates space occupancy, thereby forcing the generated amorphous aluminum hydroxide to further grow and generate different pore structures, and in the subsequent calcination process, the composite template agent that generates space occupancy is completely decomposed by high temperature, so that the final pseudoboehmite catalyst support has a dual-pore distribution structure. Its unique pore structure and high specific surface area can increase the loading sites of active components, and the large pore volume can reduce the diffusion resistance of reactants and products, thus jointly improving the catalytic performance of the active components it supports.

[0099] In contrast, Comparative Example 1 did not first prepare a pseudoboehmite wet cake before acidification and aging. Instead, it directly reacted aluminum hydroxide with nitric acid, lacking the alkaline dissolution in step S1 and the carbonization process in step S2. As a result, there were problems such as uneven dispersion of aluminum source, and it was impossible to form aluminum gel, which is essentially a mixture of aluminum nitrate and amorphous aluminum hydroxide. The specific surface area and pore volume of the final pseudoboehmite catalyst support were significantly lower than those of Example 1, while the average particle size D50 was significantly higher than that of Example 1.

[0100] Comparative Example 2 lacked the nitric acid processing and aging process, so the final boehmite catalyst support had a lower specific surface area and pore volume, and a larger average particle size. However, due to the alkaline dissolution and carbonization process, the aluminum source dispersion was more uniform than that of Comparative Example 1, and the subsequent process remained unchanged. Therefore, although its specific surface area and pore volume were lower than those of Example 1, and its average particle size D50 was higher than that of Example 1, it was still better than Comparative Example 1.

[0101] No composite template agent was added in Comparative Example 3, so no space was occupied and the generated amorphous aluminum hydroxide was not forced to grow further to produce different pore structures. The final boehmite catalyst support did not have a dual-pore distribution structure. Its specific surface area and pore volume were not only significantly lower than those of Example 1, but its average particle size D50 was also significantly higher than that of Example 1, and it was also worse than other comparative examples.

[0102] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0103] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A method for preparing a pseudo-boehmite catalyst support, characterized in that, Includes the following steps: S1. Add aluminum hydroxide to sodium hydroxide solution, and after dissolving, obtain the reaction solution; S2. Then, compressed carbon dioxide is introduced into the reaction solution to adjust the pH and obtain pseudoboehmite slurry. The pseudoboehmite slurry is then filtered to obtain the first wet cake of pseudoboehmite. S3. The first wet cake of boehmite was put into the reactor, industrial nitric acid was added, and after aging treatment, aluminum glue was obtained. S4. Add sodium aluminate solution to the aluminum glue, adjust the pH, then add the composite template agent, stir and filter again to obtain the second wet cake of pseudoboehmite; the composite template agent is obtained by compounding polyethylene glycol with polyvinyl alcohol or by compounding polyethylene glycol with sodium stearate; S5. The second wet cake of pseudoboehmite is washed with water, and then subjected to vacuum calcination and pulverization to obtain the pseudoboehmite catalyst support.

2. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, The pseudoboehmite catalyst support has an average particle size D50 of 20-50 μm and a specific surface area ≥250 m². 2 / g, pore volume ≥0.5cm 3 / g; In S1, the average particle size of the aluminum hydroxide is 50-100μm; the mass concentration of the sodium hydroxide solution is 12-18%.

3. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S1, the mass ratio of aluminum hydroxide to sodium hydroxide solution is 1:(6-10); the dissolution process parameters include: dissolution temperature 70-85℃, stirring speed 200-400rpm, and stirring time 1-3h.

4. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S2, the temperature of the reaction solution is reduced to 30-50℃; the rate of introduction of compressed carbon dioxide is 0.8-1.5L / min; and the pH is adjusted to 6.5-7.

5.

5. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S2, the process parameters for pressure filtration include: pressure 0.4-0.7 MPa, temperature 25-35℃; and the moisture content of the first wet cake of the pseudo-boehmite is 55-65%.

6. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S3, the mass fraction of the industrial nitric acid is 55-65%; the amount of industrial nitric acid added is 5-15% of the mass of the first wet cake of boehmite.

7. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S3, the process parameters for the aging treatment include: temperature 50-60℃, stirring speed 200-300rpm, and aging time 2-3h.

8. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S4, the mass concentration of the sodium aluminate solution is 6-12%; the amount of sodium aluminate solution added is 5-10% of the mass of the aluminum glue; the pH is adjusted to 8-9; in the composite template agent, the mass ratio of polyethylene glycol to polyvinyl alcohol is (1-3):1, and the mass ratio of polyethylene glycol to sodium stearate is (2-4):1; the amount of the composite template agent added is 0.5-3% of the mass of the aluminum glue.

9. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, The stirring process parameters in S4 include: stirring speed 300-500 rpm, stirring time 1-2 h, and stirring temperature 60-70℃; the re-pressing process parameters include: pressure 0.8-1.5 MPa and temperature 30-40℃.

10. The method for preparing a pseudoboehmite catalyst support according to claim 1, characterized in that, In S5, the process parameters for vacuum calcination include: absolute pressure 0.02-0.08 MPa, calcination temperature 450-550℃, and calcination time 5-8 h.

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