A method for the preparation of an alumina support

Abstract

This invention discloses a method for preparing an alumina support, belonging to the field of catalyst support technology. Addressing the shortcomings of existing alumina supports, such as difficulty in synergistically improving pore volume and strength, and poor hydrothermal stability, this invention uses boehmite as raw material and silk fibroin as a biomimetic template. The process involves solution preparation, sol-gel, template addition, molding, drying, and segmented calcination to obtain the product. The core innovation lies in utilizing the dual-structure characteristics of β-sheet crystalline and amorphous regions of silk fibroin, combined with the synergistic effect of selective β-sheet induction treatment and segmented calcination, to construct a hierarchical pore structure and strengthen the support framework. The resulting support has a pore volume of 1.2-1.8 mL / g, a lateral compressive strength of 220-350 N / cm, and after aging in steam at 800℃ for 12 h, a specific surface area and pore volume retention rate of ≥80% and ≥85%, respectively, overcoming the limitations of traditional techniques. This method is simple, compatible with existing production lines, and the product is suitable for harsh conditions such as heavy oil hydrogenation, showing broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials and catalyst support technology, specifically relating to a method for preparing a high-strength hierarchical porous alumina support using boehmite as raw material and silk fibroin as a biomimetic template agent. Background Technology

[0002] Alumina supports are one of the most widely used support types in catalytic reactions in the petrochemical industry, playing a crucial role in key processes such as hydrorefining, hydrocracking, and catalytic cracking. In existing technologies, alumina supports are mostly prepared from boehmite using conventional processes such as sol-gel, molding, and calcination. The products are mostly γ-alumina phases with a certain specific surface area, which can meet the basic requirements of ordinary catalytic reactions. However, as petroleum processing feedstocks become heavier and of lower quality, existing alumina supports have gradually revealed many insurmountable defects: pore volume is small and pore size distribution is narrow, mainly concentrated in the mesopore range. For large molecular impurities in heavy oil and residual oil, the diffusion resistance is extremely high, easily leading to a rapid increase in catalyst bed pressure drop, accelerated coking and deactivation, and significantly shortening catalyst lifespan. To increase pore volume, the industry often uses conventional pore-forming agents such as carbon black, starch, and polyvinyl alcohol. However, while these pore-forming agents can form some macropores after pyrolysis, they disrupt the continuity of the support skeleton, resulting in a significant decrease in mechanical strength. This fails to meet the stringent requirements of industrial extrusion molding and high-pressure reactor loading, leading to a long-standing technical prejudice that "increased pore volume inevitably leads to decreased strength." Furthermore, the pyrolysis process of conventional pore-forming agents is violent, easily causing pore collapse or uneven distribution, resulting in poor hydrothermal stability of the support and difficulty in long-term stable operation under harsh conditions such as heavy oil hydrotreating. In recent years, although there have been attempts to prepare porous alumina using polymer templates or surfactants, these templates are mostly derived from chemical synthesis. Not only is it difficult to achieve a truly hierarchical pore structure, but the synergistic effect on strength and pore volume improvement is also limited, resulting in low feasibility for industrial-scale application. Therefore, the field has long lacked alumina support preparation technology capable of simultaneously achieving large pore volume, high strength, hierarchical pore structure, and excellent hydrothermal stability, failing to meet the urgent industrial demand for efficient catalyst supports. Summary of the Invention

[0003] In view of this, the present invention proposes a method for preparing an alumina support, aiming to overcome the technical biases and performance bottlenecks of the prior art, and provide an alumina support that takes into account high pore volume, high strength, hierarchical pore structure and excellent hydrothermal stability, while ensuring that the preparation process is simple, cost controllable and easy to scale up industrially.

[0004] The technical solution of this invention is achieved as follows: This invention provides a method for preparing an alumina support, comprising the following steps: (1) Preparation of silk fibroin solution: Take regenerated silk fibroin powder and dissolve it in deionized water to prepare a silk fibroin aqueous solution; (2) Sol-gel: Take the dry powder of boehmite, add deionized water and acidic adhesive solvent, and stir to form sol A; (3) Adding biomimetic template additive: Add the silk fibroin solution prepared in step (1) to the sol A, stir and knead for 1-6 hours to obtain plastic paste B; the amount of silk fibroin added is 0.5-10 wt% of the dry weight of Al2O3; (4) Molding: Mold the plastic paste B, and then age the wet blank at room temperature or 40-80°C for 6-48 hours; (5) Drying: Dry the aged wet blank at 80-150℃ for 4-12 hours to obtain the dried carrier green blank; (6) Segmented calcination: Three or four-stage temperature rise calcination is adopted, the calcination atmosphere is air or oxygen atmosphere, and the alumina carrier is obtained after natural cooling.

[0005] In some embodiments, the molecular weight of the regenerated silk fibroin powder in step (1) is 10-300 kDa, and the concentration of the silk fibroin aqueous solution is 5-30 wt%.

[0006] As a natural biomacromolecule, the molecular weight and concentration of silk fibroin directly affect its self-assembly behavior in aqueous solution. Limiting the molecular weight range can ensure that silk fibroin can form a stable nanofiber network structure, while a specific concentration range can ensure the full play of the template effect and avoid abnormal solution viscosity caused by excessive concentration. This ensures uniform mixing with boehmite sol and lays the foundation for the construction of hierarchical pore structure.

[0007] In some embodiments, step (1) further includes β-sheet induction treatment of the silk fibroin aqueous solution, wherein the β-sheet induction treatment is: adding methanol to the silk fibroin aqueous solution, wherein the mass ratio of methanol to silk fibroin is 0.1-1.0:1; or heating to 50-80°C and holding for 0.5-4 hours.

[0008] Silk fibroin naturally possesses a dual structural feature of β-sheet crystalline regions and amorphous regions. The β-sheet crystalline regions endow it with excellent mechanical strength, while the amorphous regions provide self-assembly capabilities. β-sheet induction through methanol or heat treatment can significantly improve the rigidity and thermal stability of silk fibroin, preventing it from collapsing due to structural instability in the early stages of subsequent calcination. This ensures that the template structure can be accurately replicated as a channel structure, while also enhancing its interaction with pseudoboehmite particles.

[0009] The selection of silk fibroin as a carrier in alumina preparation is not a conventional approach for those skilled in the art. The difference in compatibility between silk fibroin and similar biological templates (such as cellulose) in the alumina system stems from fundamental differences in molecular structure, interaction modes, and pyrolysis behavior. The specific mechanisms are as follows: Differences in molecular structure: Silk fibroin has a dual structure of β-sheet crystalline region and amorphous region. The β-sheet crystalline region (containing a large number of amide bonds and hydrogen bonds) gives it rigidity and thermal stability, while the amorphous region (flexible molecular chain) provides self-assembly capability. In contrast, cellulose is a linear glucose unit polymer, which only has a single rigid structure formed by intermolecular hydrogen bonds. It has no flexible self-assembly segments and cannot form a nanofiber network.

[0010] Differences in interaction with the alumina colloidal system: Silk fibroin can form double hydrogen bonds with Al-OH on the surface of boehmite through amide bonds (NH) and hydroxyl groups in the amorphous region, while the charged groups (-COO) in the β-folded crystal region... - ) and Al 3+ It generates a weak electrostatic effect, forming a "coating-crosslinking" composite structure, which significantly improves the plasticity of the colloid; while cellulose can only form a single hydrogen bond with Al-OH through the hydroxyl groups of glucose units, and the linear structure leads to severe intermolecular entanglement, resulting in weak binding force with boehmite particles, easy agglomeration and precipitation, and inability to form a stable plastic paste.

[0011] Differences in pyrolysis behavior: After β-sheet induction, silk fibroin undergoes an orderly and controllable pyrolysis process (slow weight loss in two stages), and the residual carbon skeleton is in a continuous network, which can strengthen the connection of alumina grains; while the pyrolysis process of cellulose is violent, with rapid weight loss in the range of 280-350℃, no obvious segmentation characteristics, and the gas generated by pyrolysis is prone to cause pore collapse, and the residual carbon content is only 5-8%, which is discretely distributed and cannot play a role in skeleton reinforcement.

[0012] The aforementioned differences in mechanism directly lead to performance gaps: after cellulose replaces silk fibroin, the pore volume is only 1.12 mL / g, the lateral compressive strength is 183 N / cm, and there is no hierarchical pore structure.

[0013] In some embodiments, the dry basis content of the pseudoboehmite dry adhesive powder in step (2) is ≥65wt%; the acidic adhesive solvent is nitric acid, and the molar ratio of the nitric acid to the dry basis Al2O3 is 0.03-0.20; the solid content of the sol A is 25-50wt%.

[0014] The dry basis content of boehmite directly affects the final purity and structural compactness of the carrier. A higher dry basis content can reduce impurity interference. Nitric acid, as an acidic colloidal solvent, can precisely control the degree of colloidal solubility of boehmite by limiting its molar ratio with Al2O3, avoiding particle agglomeration due to insufficient colloidal solubility or damage to the carrier skeleton due to excessive colloidal solubility. Sol A with a specific solid content range can balance fluidity and plasticity, providing a good reaction environment for subsequent molding and template coating.

[0015] In some embodiments, the amount of silk fibroin added in step (3) is 2-6 wt% of the dry weight of Al2O3.

[0016] The amount of silk fibroin added is key to balancing pore volume and strength. If it is too low, a complete nanofiber network cannot be formed, the template effect is insufficient, and it is difficult to achieve a significant increase in pore volume. If it is too high, it may lead to excessive carbon residue, affecting the phase purity and catalytic activity of the alumina support. This optimal range can achieve the best synergistic effect of pore-forming and strengthening effects of silk fibroin.

[0017] In some embodiments, the molding method in step (4) is extrusion molding or oil-ammonia column / oil-drop ball forming; the carrier diameter of extrusion molding is 1.0-3.0 mm, and the carrier diameter of ball forming is 2-8 mm.

[0018] Different molding methods are suitable for the filling requirements of different reactors. Extrusion molding is a mature and low-cost process, suitable for fixed-bed reactors, while spherical molding has better fluidity and bed permeability, suitable for moving-bed or fluidized-bed reactors. Limiting the carrier diameter range can ensure that the carrier has sufficient mechanical strength while providing a reasonable specific surface area and pore mass transfer path, avoiding the increase in internal diffusion resistance due to excessive diameter or the excessive bed pressure drop due to excessive diameter.

[0019] In some embodiments, the drying temperature in step (5) is 100-130°C and the drying time is 6-8 hours.

[0020] The core of the drying process is to slowly remove moisture from the wet blank, avoiding rapid evaporation of moisture which could lead to pore collapse or carrier cracking. This temperature and time range can achieve stable moisture removal while preserving the stability of the composite structure formed by silk fibroin and boehmite, thus ensuring the construction of pores in the subsequent calcination process.

[0021] In some embodiments, the parameters for the three-stage roasting process in step (6) are as follows: increase the temperature to 300-320℃ at 2℃ / min and hold for 3-4 hours; then increase the temperature to 450-480℃ at 3℃ / min and hold for 2 hours; finally increase the temperature to 600-620℃ at 4℃ / min and hold for 4 hours.

[0022] The three-stage calcination process is precisely matched with the pyrolysis characteristics of silk fibroin. In the low-temperature stage, the amorphous regions of silk fibroin are slowly decomposed to form a micro-mesoporous structure. In the medium-temperature stage, the β-sheet region is decomposed to construct a macroporous structure and the residual carbon skeleton is used to strengthen the intergranular connections of alumina. In the high-temperature stage, the γ-Al2O3 phase is fully activated. The heating rate and holding time of each stage are limited to avoid pore collapse and ensure the integrity of the hierarchical pore structure and the compactness of the carrier skeleton.

[0023] In some embodiments, the parameters for the four-stage roasting process in step (6) are as follows: increase the temperature to 320°C at 2°C / min and hold for 4 hours; then increase the temperature to 480°C at 3°C / min and hold for 2 hours; then increase the temperature to 620°C at 4°C / min and hold for 4 hours; finally increase the temperature to 800°C at 3-5°C / min and hold for 1 hour.

[0024] Adding a high-temperature post-treatment stage to the three-stage calcination process can further optimize the connectivity of the macroporous structure, promote the sintering and fusion between alumina grains, improve the hydrothermal stability of the carrier, enable it to withstand the high-temperature steam environment under harsh conditions such as heavy oil hydrogenation, and extend its service life.

[0025] The present invention has the following advantages over the prior art: This invention overcomes the technical bias in existing technologies that increasing pore volume inevitably leads to a decrease in strength. By selecting natural silk fibroin as a biomimetic template agent, utilizing its unique dual-structure characteristics and self-assembly capabilities, combined with targeted β-sheet induction treatment and segmented calcination processes, a synergistic improvement in pore structure, mechanical strength, and hydrothermal stability is achieved. Compared with conventional alumina support preparation technologies, this invention does not rely on chemically synthesized templates or traditional pore-forming agents. It constructs hierarchical pores through the ordered pyrolysis of silk fibroin, while simultaneously strengthening the support skeleton using residual carbon framework. This solves the problem of macromolecular diffusion and ensures the mechanical strength and stability of the support. The preparation process is fully compatible with existing boehmite production lines, requiring no additional specialized equipment. It is simple to operate, cost-controllable, and easy to scale up industrially. The resulting alumina support can adapt to the catalytic reaction requirements under harsh conditions such as heavy oil hydrogenation, effectively alleviating the problem of catalyst coking and deactivation, extending the catalyst's operating cycle, and providing technical support for efficient production in the petrochemical industry. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 1. Preparation of silk fibroin solution: Take 20g of regenerated silk fibroin powder with a molecular weight of 50kDa, dissolve it in 80g of deionized water, stir evenly, and prepare a 20wt% silk fibroin aqueous solution without β-sheet induction treatment.

[0028] 2. Sol formation: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1500g of deionized water and 50g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.08), stir for 30min to form sol A with a solid content of 35wt%.

[0029] 3. Add biomimetic template additive: Add all the above-mentioned silk fibroin aqueous solution to sol A. The dry basis weight of silk fibroin is 4wt% of the dry basis weight of Al2O3. Continue stirring and kneading for 3 hours to obtain a uniform plastic paste B.

[0030] 4. Molding: The plastic paste B is extruded into shape using an extruder with a carrier diameter of 1.6 mm. After molding, the wet blank is aged at room temperature for 24 hours.

[0031] 5. Drying: Place the aged wet blank in a 120℃ oven and dry for 6 hours to obtain the dried carrier green blank.

[0032] 6. Segmented calcination: A three-stage temperature-increasing calcination process is adopted, with air as the calcination atmosphere; the temperature is increased to 300℃ at a rate of 2℃ / min and held for 3 hours; then the temperature is increased to 450℃ at a rate of 3℃ / min and held for 2 hours; finally, the temperature is increased to 600℃ at a rate of 4℃ / min and held for 4 hours; after natural cooling, alumina carrier is obtained.

[0033] Example 2 1. Preparation of silk fibroin solution and β-sheet induction: Take 30g of regenerated silk fibroin powder with a molecular weight of 100kDa, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% silk fibroin aqueous solution; add 15g of methanol (methanol to silk fibroin mass ratio 0.5:1), stir at room temperature for 2 hours to complete the β-sheet induction treatment.

[0034] 2. Sol formation: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1500g of deionized water and 50g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.08), stir for 30min to form sol A with a solid content of 35wt%.

[0035] 3. Add biomimetic template additive: Add all the above-mentioned silk fibroin aqueous solution to sol A. The dry basis weight of silk fibroin is 5wt% of the dry basis weight of Al2O3. Continue stirring and kneading for 3 hours to obtain a uniform plastic paste B.

[0036] 4. Molding: The plastic paste B is extruded into shape using an extruder with a carrier diameter of 1.6 mm. After molding, the wet preform is aged at 60°C for 12 hours.

[0037] 5. Drying: Place the aged wet blank in a 120℃ oven and dry for 6 hours to obtain the dried carrier green blank.

[0038] 6. Segmented calcination: A four-stage temperature-increasing calcination process was adopted, with air as the calcination atmosphere. The temperature was increased to 320℃ at a rate of 2℃ / min and held for 4 hours; then increased to 480℃ at a rate of 3℃ / min and held for 2 hours; next, the temperature was increased to 620℃ at a rate of 4℃ / min and held for 4 hours; finally, the temperature was increased to 800℃ at a rate of 4℃ / min and held for 1 hour; after natural cooling, the alumina carrier was obtained.

[0039] Example 3 1. Preparation of silk fibroin solution and β-sheet induction: 3.75g of regenerated silk fibroin powder with a molecular weight of 10kDa was dissolved in 71.25g of deionized water and stirred evenly to prepare a 5wt% silk fibroin aqueous solution; the solution was heated to 50℃ and kept at that temperature for 4 hours to complete the β-sheet induction treatment.

[0040] 2. Sol-gel: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1800g of deionized water and 30g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.03), stir for 30min to form sol A with a solid content of 25wt%.

[0041] 3. Add biomimetic template additive: Add all the above-mentioned silk fibroin aqueous solution to sol A. The dry basis weight of silk fibroin is 0.5wt% of the dry basis Al2O3 mass. Continue stirring and kneading for 6 hours to obtain a uniform plastic paste B.

[0042] 4. Molding: The plastic paste B is spherically shaped using the oil-ammonia column method with a carrier diameter of 2mm. After molding, the wet blank is aged at 40℃ for 48 hours.

[0043] 5. Drying: Place the aged wet blank in an 80℃ oven and dry for 12 hours to obtain the dried carrier green blank.

[0044] 6. Segmented calcination: A three-stage temperature-increasing calcination process is adopted, with oxygen as the calcination atmosphere; the temperature is increased to 250℃ at a rate of 1℃ / min and held for 4 hours; then the temperature is increased to 400℃ at a rate of 2℃ / min and held for 3 hours; finally, the temperature is increased to 550℃ at a rate of 3℃ / min and held for 6 hours; after natural cooling, alumina carrier is obtained.

[0045] Example 4 1. Preparation of silk fibroin solution and β-sheet induction: Take 80g of regenerated silk fibroin powder with a molecular weight of 300kDa, dissolve it in 120g of deionized water, stir evenly to prepare a 32wt% silk fibroin aqueous solution; add 80g of methanol (methanol to silk fibroin mass ratio 1.0:1), stir at room temperature for 1 hour to complete the β-sheet induction treatment.

[0046] 2. Sol formation: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1000g of deionized water and 120g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.20), stir for 30min to form sol A with a solid content of 50wt%.

[0047] 3. Add biomimetic template additive: Add all the above-mentioned silk fibroin aqueous solution to sol A. The dry basis weight of silk fibroin is 10wt% of the dry basis weight of Al2O3. Continue stirring and kneading for 1 hour to obtain a uniform plastic paste B.

[0048] 4. Molding: The plastic paste B is spherically shaped using the oil-ammonia column method with a carrier diameter of 8mm. After molding, the wet blank is aged at 80℃ for 6 hours.

[0049] 5. Drying: Place the aged wet blank in an oven at 150℃ and dry for 4 hours to obtain the dried carrier green blank.

[0050] 6. Segmented calcination: A four-stage temperature-increasing calcination process was adopted, with air as the calcination atmosphere. The temperature was increased to 350℃ at a rate of 3℃ / min and held for 1 hour; then increased to 500℃ at a rate of 4℃ / min and held for 1 hour; next, the temperature was increased to 650℃ at a rate of 5℃ / min and held for 2 hours; finally, the temperature was increased to 950℃ at a rate of 5℃ / min and held for 0.5 hours; after natural cooling, the alumina carrier was obtained.

[0051] Example 5 1. Preparation of silk fibroin solution and β-sheet induction: Take 45g of regenerated silk fibroin powder with a molecular weight of 150kDa, dissolve it in 105g of deionized water, stir evenly to prepare a 30wt% silk fibroin aqueous solution; add 22.5g of methanol (methanol to silk fibroin mass ratio 0.5:1), stir at room temperature for 2 hours to complete the β-sheet induction treatment.

[0052] 2. Sol formation: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1600g of deionized water and 60g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.10), stir for 30min to form sol A with a solid content of 35wt%.

[0053] 3. Add biomimetic template additive: Add all the above-mentioned silk fibroin aqueous solution to sol A. The dry basis weight of silk fibroin is 6wt% of the dry basis weight of Al2O3. Continue stirring and kneading for 4 hours to obtain a uniform plastic paste B.

[0054] 4. Molding: The plastic paste B is extruded into shape using an extruder with a carrier diameter of 2.0 mm. After molding, the wet blank is aged at 50°C for 24 hours.

[0055] 5. Drying: Place the aged wet blank in an oven at 110℃ and dry for 7 hours to obtain the dried carrier green blank.

[0056] 6. Segmented calcination: A three-stage temperature-increasing calcination process is adopted, with air as the calcination atmosphere; the temperature is increased to 310℃ at a rate of 2℃ / min and held for 3.5 hours; then the temperature is increased to 460℃ at a rate of 3℃ / min and held for 2.5 hours; finally, the temperature is increased to 610℃ at a rate of 4℃ / min and held for 5 hours; after natural cooling, alumina carrier is obtained.

[0057] Comparative Example 1 1. Sol-gel: Take 1000g of pseudoboehmite dry adhesive powder (dry basis content 75wt%), add 1500g of deionized water and 50g of concentrated nitric acid (nitric acid to dry basis Al2O3 molar ratio 0.08), stir for 30min to form sol A with a solid content of 35wt%.

[0058] 2. Mixing and molding: Directly stir and knead sol A for 3 hours to obtain a uniform plastic paste; extrude it through an extruder to form a carrier with a diameter of 1.6 mm. After molding, the wet blank is aged at room temperature for 24 hours.

[0059] 3. Drying: Place the aged wet blank in a 120℃ oven and dry for 6 hours to obtain the dried carrier green blank.

[0060] 4. Segmented calcination: The same three-stage heating and calcination process as in Example 1 was used, and the alumina carrier was obtained after natural cooling.

[0061] Comparative Example 2 1. Preparation and treatment of PVP solution: Take 30g of PVP with a molecular weight of 30000, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% PVP aqueous solution; add 15g of methanol (methanol to PVP mass ratio 0.5:1), stir at room temperature for 2 hours, and the treatment method is the same as the β-sheet induction in Example 2.

[0062] 2. Plugging, adding additives, molding, drying, and calcination: The remaining steps (plastic parameters, PVP addition amount of 5wt%, molding method, aging and drying conditions, and four-stage calcination parameters) are exactly the same as in Example 2.

[0063] Comparative Example 3 1. Preparation and treatment of cellulose solution: Take 30g of industrial grade cellulose, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% cellulose aqueous solution; add 15g of methanol (methanol to cellulose mass ratio 0.5:1), stir at room temperature for 2 hours, and the treatment method is the same as the β-sheet induction in Example 2.

[0064] 2. Plugging, adding additives, molding, drying, and calcination: The remaining steps (plumping parameters, cellulose addition amount of 5wt%, molding method, aging and drying conditions, and four-stage calcination parameters) are exactly the same as in Example 2.

[0065] Comparative Example 4 1. Preparation and treatment of chitosan solution: Take 30g of chitosan with a degree of deacetylation ≥90%, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% chitosan aqueous solution; add 15g of methanol (methanol to chitosan mass ratio 0.5:1), stir at room temperature for 2 hours, and the treatment method is the same as the β-sheet induction in Example 2.

[0066] 2. Gel sol, addition of additives, molding, drying, and calcination: The remaining steps (gel sol parameters, chitosan addition amount of 5wt%, molding method, aging and drying conditions, and four-stage calcination parameters) are exactly the same as in Example 2.

[0067] Comparative Example 5 1. Preparation of silk fibroin solution: Take 30g of regenerated silk fibroin powder with a molecular weight of 100kDa, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% silk fibroin aqueous solution, without any β-sheet induction treatment.

[0068] 2. Gel formation, addition of additives, molding, drying, and calcination: The remaining steps (gel formation parameters, silk fibroin addition amount of 5wt%, molding method, aging and drying conditions, and four-stage calcination parameters) are exactly the same as in Example 2.

[0069] Comparative Example 6 1. Preparation of silk fibroin solution and β-sheet induction: exactly the same as in Example 2.

[0070] 2. Gel formation, addition of additives, molding, and drying: The remaining steps (gel formation parameters, silk fibroin addition amount of 5wt%, molding method, and aging and drying conditions) are exactly the same as in Example 2.

[0071] 3. Conventional single-stage calcination: Conventional single-stage calcination is adopted, with air as the calcination atmosphere; the temperature is directly increased to 620℃ at a rate of 5℃ / min and held for 8 hours; after natural cooling, alumina carrier is obtained.

[0072] Comparative Example 7 1. Preparation and treatment of PVP solution: Take 30g of PVP with a molecular weight of 30000, dissolve it in 70g of deionized water, stir evenly to prepare a 30wt% PVP aqueous solution; add 15g of methanol (methanol to PVP mass ratio 0.5:1), stir at room temperature for 2 hours.

[0073] 2. Plugging, adding additives, molding, drying, and calcination: The remaining steps (plastic parameters, PVP addition amount of 5wt%, molding method, aging and drying conditions, and four-stage calcination parameters) are exactly the same as in Example 2.

[0074] Comparative Example 8 1. Preparation of cellulose solution: Take 20g of industrial grade cellulose, dissolve it in 80g of deionized water, and stir evenly to prepare a 20wt% cellulose aqueous solution.

[0075] 2. Plugging, adding additives, molding, drying, and calcination: The remaining steps (plumping parameters, cellulose addition amount of 4wt%, molding method, aging and drying conditions, and three-stage calcination parameters) are exactly the same as in Example 1.

[0076] Comparative Example 9 1. Preparation and conventional modification of silk fibroin solution: 20g of regenerated silk fibroin powder with a molecular weight of 50kDa was dissolved in 80g of deionized water to prepare a 20wt% silk fibroin aqueous solution; conventional modification was performed by irradiation with a UV lamp (wavelength 254nm) for 1 hour, replacing β-sheet induction.

[0077] 2. Gel sol, addition of additives, molding, drying and calcination: The remaining steps (gel sol parameters, silk fibroin addition amount of 4wt%, molding method, aging and drying conditions) are the same as in Example 1; calcination is carried out by conventional single-stage calcination (600℃ for 6 hours).

[0078] Performance verification 1. Pore volume test: Liquid nitrogen adsorption-desorption method was used (according to GB / T19587-2004). Before the test, the sample was degassed in vacuum at 150℃ for 4 hours. The total pore volume was calculated by Brunauer-Emmett-Teller (BET) model, and the proportion of mesopore volume was verified by Barrett-Joyner-Halenda (BJH) model.

[0079] 2. Lateral compressive strength test: Using an intelligent particle strength tester (according to GB / T31590-2015), take 10 molded carriers (extruded carriers with a length of 5mm, spherical carriers are tested directly), apply pressure in the radial direction until fracture, and take the average value as the final lateral compressive strength.

[0080] 3. Hydrothermal stability test: The sample was placed in a high-pressure reactor and aged for 12 hours at 800℃ and 100% water vapor. After aging, the pore volume and lateral pressure strength were tested again according to the above test methods. The specific surface area retention rate (specific surface area after aging / specific surface area before aging × 100%) and pore volume retention rate (pore volume after aging / pore volume before aging × 100%) were calculated.

[0081] Performance verification results

[0082] As can be seen from the comparison results of the above embodiments and comparative examples, the present invention, through the core feature combination of silk fibroin and optional β-sheet induction combined with segmented calcination, successfully overcomes the technical bias in the prior art that the increase in macropore volume inevitably leads to a decrease in strength. Examples 1-5, regardless of whether they are at the upper or lower limit of parameters or in the preferred combination, all achieve a synergistic improvement in pore volume, lateral pressure strength, and hydrothermal stability, with core performance far exceeding that of various comparative examples. Comparative Example 1 (without template) confirms that silk fibroin is a necessary condition for performance breakthrough; Comparative Examples 2-4 (conventional template or other biological template replacement) show that only the dual structure of the β-sheet crystalline region and amorphous region of silk fibroin can adapt to the process of the present invention, and other templates cannot achieve the same synergistic effect; Comparative Examples 5-6 (lacking β-sheet induction or using conventional calcination) verify the indispensability of key dependent features for performance optimization; Comparative Examples 7-9 (combined with prior art) prove that any combination of prior art cannot replicate the technical effect of the present invention. In summary, the technical solution of the present invention has significant inventiveness and industrial feasibility, and the resulting carrier has excellent performance and can meet the demanding requirements of petrochemical operating conditions.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an alumina carrier, characterized in that, Includes the following steps: (1) Preparation of silk fibroin solution: Take regenerated silk fibroin powder and dissolve it in deionized water to prepare a silk fibroin aqueous solution; (2) Sol-gel: Take the dry powder of boehmite, add deionized water and acidic adhesive solvent, and stir to form sol A; (3) Adding biomimetic template additive: Add the silk fibroin solution prepared in step (1) to the sol A, stir and knead for 1-6 hours to obtain plastic paste B; the amount of silk fibroin added is 0.5-10 wt% of the dry weight of Al2O3; (4) Molding: Mold the plastic paste B, and then age the wet blank at room temperature or 40-80°C for 6-48 hours; (5) Drying: Dry the aged wet blank at 80-150℃ for 4-12 hours to obtain the dried carrier green blank; (6) Segmented calcination: Three or four-stage temperature rise calcination is adopted, the calcination atmosphere is air or oxygen atmosphere, and the alumina carrier is obtained after natural cooling. The three-stage roasting process is as follows: heating to 250-350℃ at a rate of 1-3℃ / min, and holding at that temperature for 1-4 hours; Then raise the temperature to 400-500℃ at a rate of 2-4℃ / min and hold for 1-3 hours; finally, raise the temperature to 550-650℃ at a rate of 3-5℃ / min and hold for 2-6 hours. The four-stage roasting process is as follows: after the three-stage roasting process, the temperature is increased to 800-950℃ at a rate of 3-5℃ / min, and held for 0.5-3 hours.

2. The preparation method according to claim 1, characterized in that, In step (1), the molecular weight of the regenerated silk fibroin powder is 10-300 kDa, and the concentration of the silk fibroin aqueous solution is 5-30 wt%.

3. The preparation method according to claim 1 or 2, characterized in that, Step (1) also includes β-sheet induction treatment of the silk fibroin aqueous solution, wherein the β-sheet induction treatment is: adding methanol to the silk fibroin aqueous solution, wherein the mass ratio of methanol to silk fibroin is 0.1-1.0:1; or heating to 50-80℃ and holding for 0.5-4 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the dry basis content of the pseudoboehmite dry adhesive powder is ≥65wt%; the acidic adhesive solvent is nitric acid, and the molar ratio of nitric acid to dry basis Al2O3 is 0.03-0.20; the solid content of sol A is 25-50wt%.

5. The preparation method according to claim 1, characterized in that, In step (3), the amount of silk fibroin added is 2-6 wt% of the dry weight of Al2O3.

6. The preparation method according to claim 1, characterized in that, In step (4), the molding method is extrusion molding or oil-ammonia column / oil-drop ball forming; the carrier diameter of extrusion molding is 1.0-3.0 mm, and the carrier diameter of ball forming is 2-8 mm.

7. The preparation method according to claim 1, characterized in that, In step (5), the drying temperature is 100-130℃ and the drying time is 6-8 hours.

8. The preparation method according to claim 1, characterized in that, In step (6), the parameters for the three-stage roasting process are as follows: increase the temperature to 300-320℃ at 2℃ / min and hold for 3-4 hours; then increase the temperature to 450-480℃ at 3℃ / min and hold for 2 hours; finally increase the temperature to 600-620℃ at 4℃ / min and hold for 4 hours.

9. The preparation method according to claim 1, characterized in that, In step (6), the parameters for the four-stage roasting process are as follows: increase the temperature to 320°C at 2°C / min and hold for 4 hours; then increase the temperature to 480°C at 3°C / min and hold for 2 hours; then increase the temperature to 620°C at 4°C / min and hold for 4 hours; finally increase the temperature to 800°C at 3-5°C / min and hold for 1 hour.

10. The alumina carrier prepared by any one of claims 1-9, characterized in that, The alumina support is mainly composed of γ-Al₂O₃ with a specific surface area of ​​250-450 m². 2 / g, pore volume is 1.2-1.8mL / g, average pore size is 8-20nm, lateral pressure strength is 220-350N / cm; after aging at 800℃ and 100% water vapor for 12h, the specific surface area retention rate is ≥80%, and the pore volume retention rate is ≥85%.

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