A method for preparing amorphous alumina and its application

Abstract

This invention discloses a method for preparing amorphous alumina and its applications. The method uses aluminum nitrate as the aluminum source, utilizing the complexing effect of citric acid, the slow-release properties of urea, and the polarity difference between water and ethanol. In a sealed thermal environment, aluminum nitrate reacts with multi-component reactants to transform into a nearly ellipsoidal aluminum ammonium carbonate precursor with a surface full of wrinkles and a diameter of approximately 200 nm. Calcination then yields amorphous alumina with a high specific surface area, well-developed mesoporous and macroporous structures, and numerous weakly to moderately alkaline sites. This amorphous alumina exhibits superior activity and stability in catalyzing the hydrolysis of COS. The amorphous alumina catalyst of this invention uses inexpensive raw materials, is environmentally friendly, and exhibits excellent performance. It is suitable not only for typical blast furnace gas systems containing 30-130 ppm COS, but also for COS enrichment and efficiency improvement treatment of blast furnace gas (COS concentration higher than 200 ppm), and possesses strong antioxidant capacity, showing great promise for industrial applications.

Description

Technical Field

[0001] This invention relates to the fields of material preparation and environmental catalysis technology, specifically to a method for preparing amorphous alumina and its application. Background Technology

[0002] my country's energy structure has long been characterized by a resource endowment of "abundant coal, scarce oil, and limited natural gas." Coal still accounts for a high proportion of primary energy consumption and is a crucial energy and raw material base for industries such as steel, coal chemicals, and coking. Within the coal-based industrial system, the steel industry is not only a major consumer of coal but also a primary source of industrial by-product gas emissions. Blast furnace gas, produced during ironmaking, is rich in combustible components such as CO and H2, possessing high resource utilization value. However, when blast furnace gas is used directly as fuel, its sulfur-containing components are easily converted into SO2 during combustion, causing not only air pollution but also equipment and pipeline corrosion, limiting its high-value utilization. The sulfur-containing components in blast furnace gas mainly include carbonyl sulfide (COS) and hydrogen sulfide (H2S). Mature industrial technologies exist for H2S removal, such as the Claus process, selective H2S oxidation, and wet desulfurization. In contrast, traditional desulfurization methods have limited effectiveness in removing COS. Therefore, developing removal technologies suitable for blast furnace gas operating conditions and capable of achieving efficient and stable COS conversion has become a key issue that urgently needs to be addressed in the clean utilization of coal-based industrial gases.

[0003] Currently, COS removal methods mainly include adsorption, hydrogenation conversion, oxidation, and hydrolysis. Among these, catalytic hydrolysis is considered a promising COS removal pathway due to its relatively mild reaction conditions, simple process flow, low energy consumption, and lack of reliance on an additional hydrogen source. The COS hydrolysis reaction essentially involves the adsorption and activation of COS and H2O on the catalyst surface; therefore, the specific surface area, pore structure, and surface acidity / base properties of the catalyst have a significant impact on reaction performance. In particular, surface alkaline sites are generally considered closely related to the adsorption and activation of COS molecules and are one of the key factors affecting catalytic hydrolysis performance.

[0004] Alumina, due to its wide availability, low cost, good thermal stability, and tunable surface properties, has become an ideal candidate material for COS hydrolysis catalytic systems. However, alumina catalysts prepared by traditional methods still have significant shortcomings: their specific surface area, pore structure, and distribution of surface alkaline sites are difficult to synergistically control, often resulting in a trade-off between catalyst activity and stability. Especially under complex operating conditions such as oxygen- and water-containing environments, the surface properties of the catalyst are prone to change, leading to catalytic performance degradation. On the other hand, to improve the efficiency of blast furnace gas treatment, the strategy of enriching COS and then removing it by hydrolysis is receiving increasing attention. This process places higher demands on the number of active sites on the catalyst. Therefore, developing an alumina catalyst with a simple preparation method, tunable texture and surface alkalinity characteristics, and good stability is of great significance for improving COS hydrolysis efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the problem that the stability of existing COS hydrolysis catalysts in the COS enrichment and efficiency improvement treatment of blast furnace gas needs to be improved, and to provide a method for preparing an amorphous alumina catalyst with high surface area, hierarchical porous structure and a large number of weak to medium alkaline sites and its application in COS hydrolysis.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing an amorphous alumina catalyst includes the following steps: aluminum nitrate, citric acid, urea, water, and ethanol are taken in a certain proportion, placed in a closed reaction vessel, and heated to react. After the reaction is completed, the mixture is cooled to room temperature, and after separation, washing, and drying, an ammonium aluminum carbonate precursor is obtained. The precursor is then calcined to obtain the amorphous alumina catalyst. The molar ratio of aluminum nitrate, citric acid, urea, water, and ethanol is (2.5~3.5):1:(15~21):120:(10-15).

[0007] Preferably, the molar ratio of aluminum nitrate, citric acid, urea, water, and ethanol is 3:1:18:120:12.

[0008] Preferably, the reaction temperature is 120 °C and the reaction time is 18 h.

[0009] Preferably, the calcination conditions are: heating to 500 °C at a heating rate of 2 °C / min and holding at that temperature for 4 h.

[0010] The present invention also provides an application of the amorphous alumina catalyst prepared by the above method in COS hydrolysis.

[0011] Based on the above technical solution, preferably, the amorphous alumina catalyst can be used in an atmospheric pressure COS hydrolysis reaction, wherein the COS volume concentration in the reaction feed gas is 200~10000 ppm, the O2 volume concentration is 100~5000 ppm, and the space velocity is 5000~12000 mL·g. -1 ·h -1 The reaction temperature is 70-110 ℃, and the water vapor volume concentration is 6%~13%.

[0012] Compared with existing technologies, this invention has the following advantages: Utilizing the complexing effect of citric acid, the sustained-release properties of urea, and the polarity difference between water and ethanol, this invention transforms aluminum nitrate into a nearly ellipsoidal aluminum ammonium carbonate precursor with a surface texture and a diameter of approximately 200 nm through the reaction of aluminum nitrate with multi-component reactants in a sealed thermal environment. This precursor is then calcined to obtain amorphous alumina with a well-developed hierarchical porous structure and numerous weak and moderately strong basicity sites. This method is simple, the preparation conditions are easy to control, and the resulting catalyst structure is tunable. Further research shows that within the scope of this invention, a molar ratio of aluminum nitrate, citric acid, urea, water, and ethanol of 3:1:18:120:12 yields a sample with a specific surface area of ​​up to 334 m². 2 With a concentration of 821 μmol / g of weakly and moderately basic sites, the catalyst maintained a conversion rate of over 80% even under harsh conditions, including a COS concentration as high as 1% and an O2 to COS volume ratio of 1:2, after a stability test lasting 1440 min, demonstrating excellent catalytic stability. This indicates that the alumina catalyst obtained by the method of this invention possesses strong antioxidant properties and adaptability to high COS concentrations, meeting the requirements of high-oxygen COS environments and COS enrichment and efficiency improvement treatment in blast furnace gas, and has great potential for industrial application. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 The XRD patterns of the precursors of Examples 1-3 and Comparative Example 1 of this invention are shown below. Figure 2 The XRD patterns of Al2O3 obtained in Examples 1-3 and Comparative Example 1 of this invention are shown below. Figure 3 The XRD patterns of Al2O3 obtained in Comparative Examples 2-4 of this invention are shown below. Figure 4 SEM images of the precursors and Al2O3 obtained in Examples 1-3 and Comparative Example 1; Figure 5 The N2 adsorption isotherms of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention are shown below. Figure 6 The pore size distribution diagrams of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention are shown. Figure 7 The CO2-TPD spectra of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention are shown. Figure 8 The figures show the stability evaluation results of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention under the conditions of reaction temperature 110 °C, COS volume concentration of 10000 ppm, O2 volume concentration of 5000 ppm, and water vapor volume concentration of 12%; the illustration shows the results of the stability evaluation of Al2O3 obtained in Example 2 and Comparative Example 1 extended to 1440 min. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the embodiments and accompanying drawings. The examples described are further illustrations of this invention and are not intended to limit the scope of this invention. Example 1

[0016] Preparation of near-ellipsoidal ammonium aluminum carbonate precursor: Weigh out 0.5 mol aluminum nitrate nonahydrate, 0.2 mol citric acid, 3.0 mol urea, 24 mol water, and 2.0 mol ethanol sequentially, and stir at room temperature for 1 hour until homogeneous. Transfer the resulting system to a 1 L sealed reaction vessel and incubate at 5 °C·min. -1 The temperature was increased to 120 °C and held at that temperature for 18 h. After the reaction was complete, the mixture was cooled to room temperature. The resulting product was collected by centrifugation and washed alternately with deionized water and ethanol. The washed solid was dried overnight at 120 °C to obtain the dried precursor, which was designated Al2O3-P1.

[0017] Preparation of amorphous alumina: The dried precursor Al2O3-P1 was placed in a muffle furnace and heated to 2 °C·min. -1 The temperature was increased to 500 °C at a certain rate and held for 4 h to obtain the calcined product—amorphous alumina, which was denoted as Al2O3-1. Example 2

[0018] Preparation of near-ellipsoidal ammonium aluminum carbonate precursor: Weigh out 0.6 mol aluminum nitrate nonahydrate, 0.2 mol citric acid, 3.6 mol urea, 24 mol water, and 2.4 mol ethanol sequentially, and stir at room temperature for 1 hour until homogeneous. Transfer the resulting system to a 1 L sealed reaction vessel and incubate at 5 °C·min. -1 The temperature was increased to 120 °C and held at that temperature for 18 h. After the reaction was complete, the mixture was cooled to room temperature. The resulting product was collected by centrifugation and washed alternately with deionized water and ethanol. The washed solid was dried overnight at 120 °C to obtain the dried precursor, which was designated Al2O3-P2.

[0019] Preparation of amorphous alumina: The dried precursor Al2O3-P2 was placed in a muffle furnace and heated to 2 °C·min. -1 The temperature was increased to 500 °C at a certain rate and held for 4 h to obtain the calcined product—amorphous alumina, which was denoted as Al2O3-2. Example 3

[0020] Preparation of near-ellipsoidal ammonium aluminum carbonate precursor: Weigh out 0.7 mol aluminum nitrate nonahydrate, 0.2 mol citric acid, 4.2 mol urea, 2.4 mol water, and 3.0 mol ethanol sequentially, and stir at room temperature for 1 hour until homogeneous. Transfer the resulting system to a 1 L sealed reaction vessel and incubate at 5 °C·min. -1 The temperature was increased to 120 °C and held at that temperature for 18 h. After the reaction was complete, the mixture was cooled to room temperature. The resulting product was collected by centrifugation and washed alternately with deionized water and ethanol. The washed solid was dried overnight at 120 °C to obtain the dried precursor, which was designated Al2O3-P3.

[0021] Preparation of amorphous alumina: The dried precursor Al2O3-P3 was placed in a muffle furnace and heated to 2 °C·min. -1 The temperature was increased to 500 °C and held for 4 h to obtain the calcined product—amorphous alumina, which was denoted as Al2O3-3.

[0022] Comparative Example 1

[0023] Preparation of ammonium aluminum carbonate precursor: Weigh 45.02 g of aluminum nitrate nonahydrate, dissolve it in deionized water and bring the volume to 100 mL to prepare a 1.2 mol·L⁻¹ solution. -1 A solution of aluminum nitrate precursor was prepared; separately, 19.22 g of ammonium carbonate was weighed, dissolved in deionized water, and diluted to 100 mL to prepare a 2.0 mol·L⁻¹ solution. -1An ammonium carbonate solution (prepared fresh) was used. 150 mL of deionized water was added to a 1 L three-necked flask and preheated with magnetic stirring at 60 °C. Then, 35.7 mL of the aluminum nitrate solution and 64.3 mL of the ammonium carbonate solution were simultaneously added dropwise to the reaction system over 30 min using a dual-path synchronous addition method, maintaining the system temperature at 60 °C and ensuring thorough stirring during the addition. After the addition was complete, stirring was continued at 60 °C for 1 h to mature the mixture. The resulting suspension was filtered, rapidly washed with approximately 125 mL of 60 °C hot water, dried under vacuum, and placed in a 120 °C oven to dry overnight. The collected suspension was then ground to obtain the precursor AACH.

[0024] Preparation of alumina derived from ammonium aluminum carbonate precursor: The dried precursor AACH was heated at 2 °C·min. -1 The temperature was increased to 500 °C at a certain heating rate and held for 4 h to obtain the calcined product, which was designated as AACH-500.

[0025] Comparative Example 2

[0026] Preparation of γ-Al2O3: A certain amount of commercial pseudo-water pseudo-stone (AlOOH) was taken as raw material and placed in a muffle furnace, and heated at 2℃·min under air atmosphere. -1 The temperature was increased to 550 °C and held for 4 h. After natural cooling, the calcined product was obtained and designated as γ-Al2O3.

[0027] Comparative Example 3

[0028] Preparation of δ-Al2O3: A certain amount of commercial pseudo-water pseudo-stone (AlOOH) was taken as raw material and placed in a muffle furnace, and heated at 2℃·min under air atmosphere. -1 The temperature was increased to 900 °C at a heating rate and held for 4 h. After natural cooling, the calcined product was obtained and denoted as δ-Al2O3.

[0029] Comparative Example 4

[0030] Preparation of θ-Al2O3: A certain amount of commercial pseudo-water pseudo-stone (AlOOH) was taken as raw material and placed in a muffle furnace, and heated at 2℃·min under air atmosphere. -1 The temperature was increased to 1000 °C at a heating rate and held for 4 h. After natural cooling, the calcined product was obtained and denoted as θ-Al2O3.

[0031] X-ray powder diffraction (XRD): The phase characterization of the samples was performed using an X'pert pro powder diffractometer from Panalytical, with a PIXcel1 detector, a copper target (Cu Kα, λ = 0.154 nm) as the excitation source, an operating voltage of 45 kV, and an operating current of 40 mA.

[0032] N2 physical adsorption: The specific surface area and pore size of the samples were determined using an ASAP2020 analyzer from Micrometric (USA) at liquid nitrogen temperature (77 K). Test conditions were: 0.20 g of sample was weighed, and the sample was subjected to a pressure of less than 10 kJ / kg at 573 K. -5 Degassing under torr for 4 h, the specific surface area of ​​the sample was calculated using the BET (Brunauer-Emmett-Teller) method, and the pore size distribution was obtained from the adsorption branch data analyzed by the BJH (Barrett-Joyner-Halenda) method.

[0033] Temperature-Programmed Carbon Dioxide Desorption (CO2-TPD): The properties of basic sites on the sample surface were characterized using the CO2-TPD method. The instrument used was an AMI-300 chemisorption analyzer manufactured by Beijing Jingwei Gaobo Scientific Technology Co., Ltd. During the test, 0.05 g of sample was weighed and heated to 300 °C under a high-purity helium atmosphere and maintained for 1 h to remove surface adsorbed impurities. Subsequently, the temperature was lowered to 50 °C, and a 10% CO2 / He mixed gas was introduced for adsorption for 60 min. After adsorption, the sample was purged with high-purity helium for 10 min to remove physically adsorbed CO2. Finally, the temperature was increased to 800 °C at a rate of 10 °C / min under a high-purity helium atmosphere. The CO2 signal released during desorption was detected using a TCD to obtain information on the basic sites on the sample surface.

[0034] Scanning electron microscopy (SEM): The catalyst morphology was annotated using a Regulus 8100 high-resolution field emission scanning electron microscope. The vacuum level in the analysis chamber was less than 2.7 × 10⁻⁶. -6 Pa, scanning voltage and current were 5 kV and 7 μA, respectively. The sample powder was adhered to conductive adhesive and sputtered with gold before observation.

[0035] Figure 1 The XRD patterns of the precursors of Examples 1-3 and Comparative Example 1 are shown. The diffraction peak positions of the precursors of Examples 1-3 and Comparative Example 1 are relatively well matched with the characteristic diffraction peak positions of the standard diffraction card of aluminum ammonium carbonate (NH4)Al(OH)2CO3 (PDF 96-52-4598). However, the diffraction peaks of the examples are sharper and have higher crystallinity.

[0036] Figure 2The XRD spectra of Al2O3 obtained in Examples 1-3 and Comparative Example 1 show that all examples exhibit broad and diffuse peaks, indicating that the obtained products are mainly amorphous alumina. However, Comparative Example 1, with a lower degree of precursor crystallization, exhibits characteristic peaks that clearly match those of γ-Al2O3.

[0037] Figure 3 The XRD spectra of Al2O3 obtained in Comparative Examples 2-4 were confirmed to match γ-Al2O3, δ-Al2O3, and θ-Al2O3 by searching the standard spectral library.

[0038] Figure 4 The images show SEM images of the precursors and Al2O3 obtained in Examples 1-3 and Comparative Example 1. The precursors obtained in Examples 1-3 are all nearly ellipsoidal, with their major axes between 200 nm and 300 nm. Their surfaces exhibit obvious nanoparticle self-assembly fragment stacking characteristics. The alumina obtained after calcination retains its original morphology, but the surface becomes rougher, with more pronounced grooves and wrinkles between the particles. The precursor in Comparative Example 1 is smaller, and the morphology of the calcined alumina resembles that of a corncob.

[0039] Figure 5 The N2 adsorption isotherms of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 all belong to Type IV isotherms. Table 1 shows the specific surface area and pore volume of the catalysts obtained in Examples 1-3 and Comparative Examples 1-4 of this invention. As can be seen from Table 1, the samples of this invention generally exhibit higher specific surface area and larger pore volume. Although the precursor crystal phase structure of Comparative Example 1 is the same as that of the examples (ammonium aluminum carbonate), and its specific surface area is slightly higher than that of Examples 1-3, subsequent catalytic evaluation results show that the catalyst performance does not simply depend on the absolute size of the specific surface area, but is closely related to the synergistic optimization of pore structure characteristics and surface properties. This indicates that the method of this invention can effectively control the texture properties of alumina, providing favorable conditions for reactant mass transfer and exposure of surface active sites.

[0040] Table 1. Specific surface area and pore volume of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0041] Figure 6 The images show the pore size distribution of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4. It can be seen that Examples 1-3 all have abundant mesopores and macropores, exhibiting a clear bimodal characteristic; the former has pores in the range of 2-10 nm, while the latter has pores in the range of 20-100 nm, even exceeding the 100 nm testing range. In contrast, the pores in Comparative Example 1 are mainly distributed between 2-25 nm, while those in Comparative Examples 2-4 are mainly distributed between 5-100 nm. Compared to the examples, Comparative Example 1 lacks pores larger than 30 nm, and Comparative Examples 2-4 have significantly fewer pores around 4 nm.

[0042] Figure 7 The CO2-TPD spectra of the catalysts obtained in Examples 1-3 and Comparative Examples 1-4 are shown. The desorption temperature of CO2 reflects the strength of the surface basic sites, while the peak area is related to the number of corresponding basic sites. Quantitative analysis was performed on the desorption peaks corresponding to weakly basic and moderately basic sites below 450 °C, and the results are listed in Table 2. As can be seen from Table 2, the CO2 adsorption capacity of the weakly and moderately basic sites in the samples of the present invention is generally higher than that in the comparative samples, indicating that the method of the present invention is beneficial to increasing the number of weakly and moderately basic sites on the alumina surface. Further analysis of the performance results shows that the catalyst stability is not simply positively correlated with the total number of weakly and moderately basic sites, but is related to the comprehensive regulation of specific surface area, pore structure, and surface basic site distribution. Although the total number of weakly and moderately basic sites in Example 2 is not the highest, it has a higher specific surface area, a suitable distribution of weakly and moderately strong basic centers on the surface, and a pore structure, thus exhibiting better COS hydrolysis stability.

[0043] Table 2. CO2 adsorption capacity of weak and moderately strong basic sites of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of the present invention.

[0044] COS hydrolysis stability test of catalyst: The catalytic hydrolysis activity of COS was tested in a fixed-bed reactor at a space velocity of 6000 mL·g⁻¹. -1 ·h -1 The reaction temperature was 110 ℃, the COS volume concentration in the reaction system was 10000 ppm, the O2 volume concentration was 5000 ppm, and the water vapor volume concentration was 12%, with a COS to O2 volume concentration ratio of 2:1. The COS concentration at the reactor inlet and outlet was analyzed by online chromatography. Stability was expressed as a percentage of COS conversion, and the activity was calculated using the following formula: (1) in, and These are the COS concentrations at the reactor inlet and outlet, respectively.

[0045] Figure 8 The results show the stability evaluation of Al2O3 obtained in Examples 1-3 and Comparative Examples 1-4 of this invention at a reaction temperature of 110 °C. Figure 8It can be seen that the stability of different samples varies significantly, with the Al2O3 obtained in Example 2 exhibiting the best stability. It maintained a conversion rate of over 95% throughout the 660-minute test. In contrast, the conversion rates of Comparative Examples 1-4 decreased rapidly. Comparative Example 1, which had the best performance, maintained a conversion rate of over 95% for less than 200 minutes, and when the stability evaluation was extended to 1440 minutes, the conversion rate was only 47% (see...). Figure 8 (Illustration); In contrast, in Example 2, the Al2O3 obtained by the present invention maintained a conversion rate of over 80% after a stability test of up to 1440 min, demonstrating excellent catalytic stability.

[0046] In summary, this invention constructs a self-assembled morphology structure of an aluminum ammonium carbonate precursor based on a multi-element thermal reaction of aluminum nitrate, citric acid, urea, water, and ethanol, thereby obtaining amorphous alumina with high specific surface area, hierarchical porous structure, and abundant weakly and moderately alkaline sites. Within the scope of this invention, when the molar ratio of aluminum nitrate, citric acid, and urea is 3:1:18, the resulting sample exhibits excellent catalytic stability, adapting not only to typical blast furnace gas systems containing 30–130 ppm COS, but also to COS enrichment and efficiency enhancement treatment conditions in blast furnace gas (COS concentration higher than 200 ppm), and demonstrating strong antioxidant capacity. This method is simple, uses readily available raw materials, and has promising application prospects.

[0047] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing amorphous alumina, characterized in that, Includes the following steps: (1) A homogeneous multi-component solution is obtained by stirring and mixing a certain amount of aluminum nitrate, citric acid, urea, water and ethanol. (2) The multi-component solution obtained in step (1) is transferred to a closed reaction vessel for solvothermal reaction. After the reaction is completed, it is cooled to room temperature and then separated, washed and dried to obtain the aluminum ammonium carbonate precursor. (3) The precursor obtained in step (2) is calcined to obtain amorphous alumina.

2. The preparation method according to claim 1, characterized in that: The molar ratio of aluminum nitrate, citric acid, urea, water and ethanol in step (1) is (2.5~3.5):1:(18~21):120:

12.

3. The preparation method according to claim 1, characterized in that: The molar ratio of aluminum nitrate, citric acid, urea, water and ethanol in step (1) is 3:1:18:120:

12.

4. The preparation method according to claim 1, characterized in that: In step (2), the solvothermal reaction temperature is 120 °C and the reaction time is 18 h.

5. The preparation method according to claim 1, characterized in that: In step (3), the calcination conditions are: heating rate of 2 ℃ / min, calcination temperature of 500 ℃, and holding time of 4 h.

6. The preparation method according to claim 1, characterized in that: The morphology of the aluminum ammonium carbonate precursor is a nearly ellipsoidal particle with a diameter of 200 nm and a wrinkled surface.

7. The amorphous alumina prepared by the method according to any one of claims 1-6, characterized in that: It has a high specific surface area, a multi-level porous structure, and abundant weak to moderately strong basic sites.

8. The application of amorphous alumina according to claim 7, characterized in that: The amorphous alumina is used as a catalyst for the COS hydrolysis reaction under the COS enrichment and efficiency improvement treatment conditions of blast furnace gas.

9. The application of amorphous alumina according to claim 8, characterized in that: This reaction is used for COS hydrolysis at atmospheric pressure. The COS volume concentration in the feed gas is 200–10000 ppm, the O2 volume concentration is 100–5000 ppm, and the space velocity is 5000–12000 mL·g. -1 ·h -1 The reaction temperature is 70-110 ℃, and the water vapor volume concentration is 6%~13%.

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