Preparation method and application of aluminum oxide rich in penta-coordinated aluminum ions
Alumina rich in five-coordinate aluminum ions was prepared by heat-treating boehmite in a flowing reducing atmosphere, which solved the problems of high synthesis cost and complexity in the prior art and achieved efficient and low-cost synthesis of five-coordinate aluminum ions and excellent catalytic performance.
Patent Information
- Application Number
- CN202510939002.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-11-14
AI Technical Summary
Existing technologies make it difficult to stably synthesize alumina rich in pentacoordinate aluminum ions without using different aluminum source precursors or complex synthesis processes. Furthermore, traditional methods are costly and have a significant environmental impact.
Alumina rich in pentacoa ions is prepared by heat treatment of alumina in a flowing reducing atmosphere, using a mixture of reducing gases such as H2, CO, and CH4 with an inert gas to treat boehmite, thus simplifying the production process and reducing costs.
It significantly increased the content of five-coordinate aluminum ions, simplified the production process, reduced costs, and improved the catalytic activity and stability of alumina as a catalyst support, especially showing excellent conversion rate in the CO2 hydrogenation catalytic reaction.
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Abstract
Description
Technical Field
[0001] This invention belongs to the fields of materials science and chemical engineering technology, and specifically relates to a method for preparing alumina rich in pentacoordinate aluminum ions and its application. Background Technology
[0002] In the field of materials science, γ-Al₂O₃ has attracted much attention due to its unique physicochemical properties and broad application prospects. γ-Al₂O₃ is a nanomaterial obtained by high-temperature calcination of aluminum hydroxide between 550-800℃, and is also known industrially as activated alumina. This material possesses advantages such as porosity, high specific surface area, good thermal stability, moderate surface acidity / alkalinity, and low cost, and is often used as a support for hydrogenation catalysts. The structure of γ-Al₂O₃ is generally considered to be spinel, with tetrahedral (Al) and octahedral (Al) crystals in the lattice. o The coordination environment contains Al 3+ Ions. In addition, γ-Al2O3 can also be obtained by calcining boehmite between 400-700 °C.
[0003] However, traditional air calcination makes it difficult for pentacoordinate aluminum to exist stably due to high temperature and oxidizing properties. An oxygen-rich environment will accelerate the oxidation of aluminum species and promote crystallization, further reducing surface defects and making it difficult to obtain pentacoordinate-rich alumina.
[0004] It is worth noting that the non-reducible oxide γ-Al₂O₃ has very few electronic defects and is essentially free of unsaturated five-coordinate Al. 3+ (Al) p ). Targeting the five-coordinated Al of γ-Al₂O₃ 3+ The current main approaches to address this issue are using different aluminum sources as precursors or employing complex synthesis processes. For example, Professor Zheng Nanfeng of the College of Chemistry and Chemical Engineering at Xiamen University proposed a method for calcining aluminum acetate hydroxide [Al(Ac)2OH] precursors in an argon atmosphere, resulting in F-Al2O3 rich in oxygen vacancies and five-coordinated aluminum ions (J. Am. Chem. Soc. 2024, 146, 47, 32263–32268). Professor Yan Ning of the National University of Singapore reported a method for preparing catalysts via a modified sol-gel solvent vaporization self-assembly method, using aluminum isopropoxide as the aluminum source, and the synthesized m-Al2O3 was also rich in oxygen vacancies and five-coordinated aluminum ions (Nat. Commun. 2017, 8, 16100).
[0005] Although these methods can effectively synthesize pentacoordinate-rich alumina, they require the use of different aluminum source precursors or complex synthesis processes. Therefore, developing processes for synthesizing pentacoordinate-rich alumina remains an important research direction. Summary of the Invention
[0006] This invention addresses the issue that synthesizing alumina rich in five-coordinate aluminum ions requires different aluminum source precursors or complex synthesis processes. It provides a method for reducing alumina in a flowing reducing atmosphere. This method not only significantly increases the content of five-coordinate aluminum ions but also simplifies the production process, reduces production costs, and significantly reduces environmental impact. When used as a support in catalytic reactions, for example, loading Ni for use in CO2 hydrogenation catalysts can approximately double the CO2 conversion rate compared to existing five-coordinate alumina synthesis methods. The method provided by this invention does not require expensive organometallic precursor reagents or stringent synthesis conditions, has significantly lower production costs, and achieves a similar five-coordinate aluminum content.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows: One aspect of this invention provides a method for preparing alumina rich in pentacoordinate aluminum ions, wherein boehmite is heat-treated at 400-800℃ for 2-4 hours in a flowing reducing atmosphere to obtain alumina rich in pentacoordinate aluminum ions.
[0008] In the above technical solution, the reducing atmosphere is further defined as a reducing gas or a mixture of a reducing gas and an inert gas; the reducing gas includes one or more of H2, CO, and CH4; and the inert gas includes N2 or Ar.
[0009] In the above technical solution, further, in the mixture of reducing gas and inert gas, the volume percentage of reducing gas is not less than 5%.
[0010] Another aspect of the present invention provides an alumina rich in pentacoordinate aluminum ions prepared by the above-described method, wherein the alumina has a specific surface area of 200-300 m². 2 / g.
[0011] The present invention also provides an application of the above-mentioned alumina rich in pentacoordinate aluminum ions as a catalyst support, wherein a catalyst is obtained by loading a metal on the alumina as a support, wherein the metal is one or more of Ni, Co, Cu and Fe; and the metal content in the catalyst is 10-80 wt%.
[0012] In the above technical solution, the catalyst is further prepared by adding an aqueous ethanol solution to the alumina rich in pentacoordinate aluminum ions, adding impregnated metal salt, stirring, evaporating the water in a water bath, drying overnight, grinding, and then calcining.
[0013] The beneficial effects of this invention are as follows: 1. The method of the present invention utilizes a flowing reducing atmosphere to prepare alumina rich in pentacoordinate aluminum ions. The prepared alumina is rich in oxygen vacancies and pentacoordinate aluminum ions, and the specific surface area does not change much, which gives it good stability. Under TEM, the particle size of impregnated metal Ni is reduced, which significantly improves the dispersion of the metal.
[0014] 2. Regarding the synthesis process, this invention provides a method for reducing pseudoboehmite in a flowing reducing atmosphere, which directly utilizes alumina to prepare the material, avoiding the addition of other substances and effectively simplifying the production process.
[0015] 3. Besides its applications in the field of catalysts, this alumina rich in pentacoordinate aluminum ions can also be used in liquid reactions and macromolecular reactions, facilitating reaction and product transfer, which is of great significance for improving the conversion of reactants into target products. It has shown broad application prospects in multiple fields such as catalytic materials, drug carriers, and sensors. Attached Figure Description
[0016] Figure 1 The N2 adsorption-desorption isotherms and pore size distribution diagrams for samples of Comparative Example 1, Example 1, Example 2 and Example 3 are shown. a is the N2 adsorption-desorption isotherm diagram and b is the pore size distribution diagram. Figure 2 Electron paramagnetic resonance (EPR) spectra of the samples from Comparative Example 1 and Example 1; Figure 3 To compare the SEM images of the samples in Application Example 1 and Application Example 2, a is the comparison of Application Example 1, and b is Application Example 1; Figure 4 To compare the TEM and particle size distribution of the sample in Application Example 1, a is the TEM image and b is the particle size distribution. Figure 5 The TEM and particle size distribution of the sample in Application Example 1 are shown in Figure a, where a is the TEM image and b is the particle size distribution. Figure 6 To compare the CO2 conversion rate and CH4 selectivity test results of the catalytic CO2 hydrogenation to CH4 reaction of the samples of Application Example 1, Application Example 2 and Application Example 3, a is CO2 conversion rate and b is CH4 selectivity; Figure 7 The results of CO2 conversion rate tests during the catalytic hydrogenation of CO2 to CH4 at different reaction temperatures; Figure 8 The results show the CO2 conversion rate during the catalytic hydrogenation of CO2 to CH4 reaction under different metal loading conditions. Detailed Implementation
[0017] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.
[0018] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.
[0019] The pseudoboehmite used in the following examples was produced by Yangzhou Zhongtianli New Material Co., Ltd., model ZTL-CAH-4.
[0020] Comparative Example 1 2.0 g of pseudoboehmite was placed in a quartz tube and treated at 600 °C for 2 h with air flowing through it at a rate of 40 mL / min and a heating rate of 5 °C / min. The sample was then cooled to room temperature and removed to obtain alumina, which was denoted as PB-Air, where Air represents air treatment.
[0021] Example 1 2.0 g of pseudoboehmite was placed in a quartz tube and heat-treated in a flowing hydrogen atmosphere at a flow rate of 40 mL / min, a heat treatment temperature of 600℃, a heat treatment time of 2 h, and a heating rate of 5℃ / min. After cooling to room temperature, the sample was removed, and alumina rich in pentacoordinate aluminum ions was obtained, denoted as PB-H2, where H2 represents hydrogen treatment.
[0022] Example 2 2.0 g of pseudoboehmite was placed in a quartz tube and heat-treated in a flowing atmosphere of carbon monoxide and argon (with a carbon monoxide volume concentration of 5%). The mixed gas flow rate was 40 mL / min, the heat treatment temperature was 600 ℃, the heat treatment time was 2 h, and the heating rate was 5 ℃ / min. After cooling to room temperature, the sample was removed, and alumina rich in pentacoordinate aluminum ions was obtained, denoted as PB-CO, where CO represents carbon monoxide gas treatment.
[0023] Example 3 2.0 g of pseudoboehmite was placed in a quartz tube and heat-treated in a flowing atmosphere of a mixture of methane and hydrogen (methane volume concentration of 20%). The flow rate of the mixture was 40 mL / min, the heat treatment temperature was 600 ℃, the heat treatment time was 2 h, and the heating rate was 5 ℃ / min. After cooling to room temperature, the sample was removed, and alumina rich in pentacoordinate aluminum ions was obtained, denoted as PB-CH4, where CH4 represents methane gas treatment.
[0024] The specific surface area, pore volume, and average pore diameter of the samples in Comparative Example 1 and Examples 1-3 are shown in Table 1.
[0025] Table 1. Specific surface area, pore volume, and average pore size of samples from Comparative Example 1 and Examples 1-3
[0026] Comparative Application Example 1 Take 0.80 g of PB-Air prepared in Comparative Example 1 and 1.0 g of nickel nitrate hexahydrate in a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4 h, then stir in a water bath at 60 °C to evaporate the water, and place in a 105 °C forced-air drying oven to dry overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500 °C for 2 h under air conditions with a heating rate of 5 °C / min. After cooling to room temperature, a catalyst with PB-Air as the support and supported on metallic Ni is obtained, wherein the mass fraction of metallic Ni is 20 wt%. This sample is denoted as 20Ni-PB-Air.
[0027] Comparative Application Example 2 Take 0.80 g of PB-Air prepared in Comparative Example 1 and 1.0 g of cobalt nitrate hexahydrate in a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4 h, then stir in a water bath at 60 °C to evaporate the water, and dry in a 105 °C forced-air drying oven overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500 °C for 2 h under air conditions with a heating rate of 5 °C / min. After cooling to room temperature, a catalyst with PB-Air as the support and supported on metallic Co is obtained, wherein the mass fraction of metallic Co is 20 wt%. This sample is denoted as 20Co-PB-Air.
[0028] Comparative Application Example 3 Take 0.80g of PB-Air prepared in Comparative Example 1 and 1.5g of ferric nitrate nonahydrate into a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4h, then stir and evaporate the water in a 60℃ water bath, and dry in a 105℃ forced-air drying oven overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500℃ for 2h under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-Air as the support and supporting metallic Fe is obtained, wherein the mass fraction of metallic Fe is 20wt%. This sample is denoted as 20Fe-PB-Air.
[0029] Comparative Application Example 4 Take 0.80 g of PB-Air prepared in Comparative Example 1 and 0.38 g of copper nitrate trihydrate in a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4 h, then stir in a water bath at 60 °C to evaporate the water, and place in a 105 °C forced-air drying oven to dry overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500 °C for 2 h under air conditions with a heating rate of 5 °C / min. After cooling to room temperature, a catalyst with PB-Air as the support and supported on metal Cu is obtained, wherein the mass fraction of metal Cu is 10 wt%. This sample is denoted as 10Cu-PB-Air.
[0030] Application Example 1 Preparation of 20Ni-PB-H2: 0.80g of PB-H2 prepared in Example 1 and 1.0g of nickel nitrate hexahydrate were placed in a beaker, and 25 mL of anhydrous ethanol solution was added. After stirring at room temperature for 4 hours, the water was evaporated by stirring in a water bath at 60℃. The sample was then dried overnight in a 105℃ forced-air drying oven. The next day, the sample was taken out, ground in a mortar, and calcined in a tube furnace at 500℃ for 2 hours under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-H2 as the support and supported on metallic Ni was obtained, wherein the mass fraction of metallic Ni was 20wt%. This sample was designated as 20Ni-PB-H2.
[0031] Application Example 2 Preparation of 20Ni-PB-CO: 0.80g of PB-CO prepared in Example 2 and 1.0g of nickel nitrate hexahydrate were placed in a beaker, and 25 mL of anhydrous ethanol solution was added. After stirring at room temperature for 4 hours, the water was evaporated by stirring in a water bath at 60℃. The sample was then dried overnight in a 105℃ forced-air drying oven. The next day, the sample was taken out, ground in a mortar, and calcined in a tube furnace at 500℃ for 2 hours under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-CO as the support and supported on metallic Ni was obtained, wherein the mass fraction of metallic Ni was 20wt%. This sample was designated as 20Ni-PB-CO.
[0032] Application Example 3 Preparation of 20Ni-PB-CH4: 0.80g of PB-CH4 prepared in Example 3 and 1.0g of nickel nitrate hexahydrate were placed in a beaker, and 25 mL of anhydrous ethanol solution was added. After stirring at room temperature for 4 hours, the water was evaporated by stirring in a water bath at 60℃. The sample was then dried overnight in a 105℃ forced-air drying oven. The next day, the sample was taken out, ground in a mortar, and calcined in a tube furnace at 500℃ for 2 hours under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-CH4 as the support and supported on metallic Ni was obtained, wherein the mass fraction of metallic Ni was 20wt%. This sample was designated as 20Ni-PB-CH4.
[0033] Application Example 4 Preparation of 20Co-PB-H2: Take 0.80g of PB-H2 prepared in Example 1 and 1.0g of cobalt nitrate hexahydrate into a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4h, then stir and evaporate the water in a water bath at 60℃, and dry in a 105℃ forced-air drying oven overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500℃ for 2h under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-H2 as the support and supported on metallic Co is obtained, wherein the mass fraction of metallic Co is 20wt%. This sample is denoted as 20Co-PB-H2.
[0034] Application Example 5 Preparation of 20Fe-PB-H2: Take 0.80g of PB-H2 prepared in Example 1 and 1.5g of ferric nitrate nonahydrate into a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4h, then stir and evaporate the water in a water bath at 60℃, and dry in a 105℃ forced-air drying oven overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500℃ for 2h under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-H2 as the support and supporting metallic Fe is obtained, wherein the mass fraction of metallic Fe is 20wt%. This sample is denoted as 20Fe-PB-H2.
[0035] Application Example 6 Preparation of 20Fe-PB-H2: Take 0.80g of PB-H2 prepared in Example 1 and 0.38g of copper nitrate trihydrate into a beaker, add 25 mL of anhydrous ethanol solution, stir at room temperature for 4h, then stir and evaporate the water in a water bath at 60℃, and dry in a 105℃ forced-air drying oven overnight. The next day, take out the sample, grind it in a mortar, and calcine it in a tube furnace at 500℃ for 2h under air conditions with a heating rate of 5℃ / min. After cooling to room temperature, a catalyst with PB-H2 as the support and supporting metal Cu is obtained, wherein the mass fraction of metal Cu is 10wt%. This sample is denoted as 10Cu-PB-H2.
[0036] Test Example 1 The CO2 hydrogenation performance of the samples was tested using a micro fixed-bed reactor. 100 mg of each of the following samples (20Ni-PB-Air, 20Ni-PB-H2, 20Ni-PB-CO, and 20Ni-PB-CH4) was mixed with 1.00 g of quartz sand and packed into a quartz tube with an outer diameter of 10 mm and an inner diameter of 8 mm. The mixture was then installed on a CO2 hydrogenation reactor. The samples were treated with H2 at 400 °C for 2 h, then cooled to 300 °C. A reaction gas mixture of 10 mL / min CO2 + 40 mL / min H2 + 5 mL / min N2 was introduced into the reactor. The CO2 hydrogenation activity of the catalyst was tested, and the resulting gas was analyzed by gas chromatography. The results are shown in Table 2.
[0037] The carbon dioxide conversion rate and methane selectivity of carbon dioxide hydrogenation at 300℃ for the 20Ni-PB-Air, 20Ni-PB-H2, 20Ni-PB-CO, and 20Ni-PB-CH4 samples are shown in Table 2.
[0038] Table 2. Carbon dioxide conversion rate and methane selectivity of carbon dioxide hydrogenation
[0039] Test Example 2 100 mg of each of the 20Ni-PB-Air and 20Ni-PB-H2 samples from Comparative Application Example 1 were mixed with 1.00 g of quartz sand and packed into quartz tubes with an outer diameter of 10 mm and an inner diameter of 8 mm. These tubes were then installed on a CO2 hydrogenation reactor. The samples were treated with H2 at 400 °C for 2 h, then cooled to 240-360 °C. A reaction gas mixture of 10 mL / min CO2 + 40 mL / min H2 + 5 mL / min N2 was introduced into the reactor. The CO2 hydrogenation activity of the catalyst was tested at different reaction temperatures. The resulting gas was analyzed by gas chromatography. The results are shown below. Figure 6 As shown.
[0040] Test Example 3 The CO2 hydrogenation performance of the samples was tested using a micro fixed-bed reactor. 100 mg of 10Co-PB-H2, 10Fe-PB-H2, and 10Cu-PB-H2 samples were mixed with 1.00 g of quartz sand and packed into quartz tubes with an outer diameter of 10 mm and an inner diameter of 8 mm. These tubes were then installed on a CO2 hydrogenation reactor. The samples were treated with H2 at 400 °C for 2 h, then cooled to 350 °C. A reaction gas mixture of 10 mL / min CO2 + 30 mL / min H2 + 5 mL / min N2 was introduced into the reactor. The CO2 hydrogenation activity of the catalyst was tested. The resulting gas was analyzed by gas chromatography. The results are shown below. Figure 8 As shown.
[0041] Table 1 shows the test results of specific surface area, pore volume and average pore size of the samples in Comparative Example 1 and Examples 1-3. As can be seen from Table 1, the physical properties of the samples in Examples 1-3 are not significantly different from those of the sample in Comparative Example 1. Figure 1 The figures show the N2 adsorption-desorption isotherms and pore size distribution of PB-Air, PB-H2, PB-CO and PB-CH4 samples from Comparative Example 1 and Examples 1-3. It can be seen from the figures that the pore size and pore structure of alumina remained basically unchanged after treatment in a reducing atmosphere, while the pore volume increased slightly.
[0042] Figure 2 Electron paramagnetic resonance (EPR) spectra of PB-Air (Comparative Example 1) and PB-H2 (Example 1). 10 mg samples were taken and subjected to EPR testing on a Bruker A300-10 spectrometer to determine the oxygen vacancy content, indicating that alumina rich in pentacoordinate aluminum ions was obtained. The figure shows that, compared to PB-Air, the oxygen vacancy content of PB-H2 was significantly increased, indicating that reducing atmosphere treatment can significantly increase the content of pentacoordinate aluminum ions in alumina.
[0043] Figure 3The SEM images of Ni-PB-Air and Ni-PB-H2 in Application Example 1 are shown in the figure. It can be seen from the figure that there is no significant difference in the structure of the sample after reduction treatment.
[0044] Figure 4 , 5 To compare the TEM and particle size distribution of Ni-PB-Air and Ni-PB-H2 in Application Example 1, it can be seen from the figure that the five-coordinate aluminum ion-rich alumina obtained after reduction treatment can reduce the particle size of impregnated metallic Ni and significantly improve the dispersion of metallic Ni.
[0045] Figure 6 The figures show the CO2 conversion rate and CH4 selectivity of the catalytic CO2 hydrogenation to CH4 reaction of the 20Ni-PB-Air, 20Ni-PB-H2, 20Ni-PB-CO, and 20Ni-PB-CH4 samples. As can be seen from the figures, at 300 °C, the CO2 hydrogenation conversion rate increased from 30.3% to 56.6%, and the CH4 selectivity increased from 97.5% to nearly 100%. This is because the alumina treated in a reducing atmosphere is rich in pentacoordinate aluminum ions. Alumina rich in pentacoordinate aluminum ions can significantly improve the metal dispersion and anti-sintering properties, thereby significantly improving its catalytic activity and CH4 selectivity when used as a support for impregnated metals for CO2 hydrogenation.
[0046] like Figure 7 As shown, the CO2 conversion rate of 20Ni-PB-H2 at various temperature points was significantly improved, indicating that the reducing atmosphere treatment can significantly increase the content of five-coordinate aluminum ions in alumina, which is very beneficial for the activation and conversion of CO2.
[0047] Figure 8 The figure shows the application of PB-Air and PB-H2 as supports for impregnation of Co, Fe and Cu in the CO2 hydrogenation to CH4 and RWGS reactions. The figure shows that PB-H2 as a support can significantly improve the catalytic activity after impregnation with metals, indicating that it can be well applied as a support in different reactions.
[0048] The above embodiments are merely preferred examples of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.
Claims
1. A method for preparing alumina rich in pentacoordinate aluminum ions, characterized in that, Boehmite was heat-treated at 400-800℃ for 2-4 hours in a flowing reducing atmosphere to obtain alumina rich in pentacoordinate aluminum ions.
2. The method according to claim 1, characterized in that, The reducing atmosphere is a reducing gas or a mixture of a reducing gas and an inert gas; the reducing gas includes one or more of H2, CO, and CH4; the inert gas includes N2 or Ar.
3. The method according to claim 2, characterized in that, In the mixture of reducing gas and inert gas, the volume percentage of reducing gas is not less than 5%.
4. An alumina rich in pentacoordinate aluminum ions prepared by the method according to any one of claims 1-3, characterized in that, The specific surface area of the alumina is 200-300 m². 2 / g.
5. The application of the alumina rich in pentacoordinate aluminum ions as described in claim 4 as a catalyst support, characterized in that, Using the alumina as a support, a catalyst is obtained by loading a metal, wherein the metal is one or more of Ni, Co, Cu and Fe; the metal content in the catalyst is 10-80 wt%.
6. The application according to claim 5, characterized in that, The catalyst is prepared by adding an aqueous ethanol solution to the alumina rich in pentacoordinate aluminum ions, adding impregnated metal salt, stirring, evaporating in a water bath, drying overnight, grinding, and then calcining.