Preparation method and application of hydrotalcite-like derived magnesium-aluminum composite oxide with coral spherical structure

Abstract

The invention discloses a preparation method and application of a hydrotalcite-like compound derivative magnesium-aluminum composite oxide with a coral spherical structure, magnesium nitrate is taken as a magnesium source, aluminum nitrate is taken as an aluminum source, a proper amount of citric acid and urea are introduced, and under the thermal action of an alcohol-water mixed solvent, a citric acid intercalated hydrotalcite-like compound is obtained in one pot; and further roasting to obtain the derived magnesium-aluminum composite oxide. The magnesium-aluminum composite oxide has a unique coral spherical structure, is endowed with a large specific surface area and a developed pore structure, contains rich alkalescence and moderately strong alkaline sites and oxygen vacancies, shows excellent activity and stability in a high-concentration COS system, and is suitable for being used as a catalyst for a COS hydrolysis reaction.

Description

Technical Field

[0001] The invention relates to the technical field of material preparation and environmental catalysis, and in particular to a preparation method and application of a hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure. Background Art

[0002] Blast furnace gas is often produced in the process of smelting pig iron in the steel industry. It is an important secondary energy source for processes such as hot blast furnaces, sintering, steel rolling and waste pressure power generation. Blast furnace gas contains hydrogen sulfide (H 2 S) and carbonyl sulfide (COS), the H 2 S content is about 50~100 mg / Nm 3 、COS content is about 200~300 mg / Nm 3 Some industrial tail gases, such as calcium carbide furnace tail gas, coke oven tail gas, and yellow phosphorus tail gas, also contain a large amount of COS. 2 The removal of S also has a relatively mature process, which can remove the discharged H 2 The S concentration was reduced to 1 mg / Nm 3 The following: For example, Claus technology, H 2 S selective oxidation technology, iron-based solid desulfurization and Lo-Cat wet desulfurization, etc. Therefore, the current treatment of industrial tail gas sulfide is mainly to solve the removal of COS.

[0003] Organic sulfides such as COS exist in different concentrations in industrial raw gas and domestic gas. They are extremely toxic to industrial catalysts and can also corrode equipment.

[0004] As a relatively economical and feasible method for removing COS, COS hydrolysis has the advantages of wide operating temperature range, low energy consumption, and no consumption of hydrogen source compared with COS catalytic hydrogenation, and has become an effective way to solve the deep removal of COS from blast furnace gas. 2 The activation of O is closely related to alkaline sites. At present, catalysts such as alumina, titanium dioxide, transition metal oxides (Fe, Co, Ni and Zn) and activated carbon as carriers and loaded with alkali metals and alkaline earth metals as active components are often used for the catalytic hydrolysis of COS. However, these catalysts are complex in composition (blast furnace gas contains H 2 O, CO, CO 2 , O 2 Under actual working conditions (such as gases such as hydrocarbons and trace sulfides), the loaded active components are easy to be lost, resulting in catalyst deactivation, and it is easy to corrode the pipeline. Summary of the invention

[0005] The COS hydrolysis reaction is the reaction between COS and H 2 O reacts to form CO2 and H 2 S's process: Hydrotalcite-derived magnesium-aluminum composite oxides are a type of catalyst with structured alkaline centers. However, the catalysts obtained by the traditional coprecipitation method have a small specific surface area and a low oxygen vacancy concentration, which cannot meet the requirements of high-performance COS hydrolysis catalysts for high specific surface area to achieve sufficient exposure of basic sites and cannot provide abundant oxygen vacancies for synergistically promoting H 2 Therefore, if a magnesium-aluminum composite catalyst with controllable morphology and structure, high specific surface area and abundant oxygen vacancies can be designed and developed, it will be beneficial to improve its COS hydrolysis performance and enhance the application potential of magnesium-aluminum composite oxide materials.

[0006] The purpose of the present invention is to provide a preparation method and application of a magnesium-aluminum composite oxide with controllable morphology and structure, high specific surface area and abundant oxygen vacancies, so as to provide a new solution for high-performance COS hydrolysis catalyst.

[0007] To achieve the above objectives, the present invention is designed to synthesize a hydrotalcite precursor intercalated with citric acid in a one-step method by a mixed solvent thermal method of ethanol and water. In the one-step synthesis process, citric acid and metal complexation are used, and slowly hydrolyzed in a certain amount of urea and alcohol-water ratio solvent thermal environment, self-assembled to form a unique coral ball structure in two equilibrium reaction processes, and the reduction characteristics of citric acid and ethanol are used to form oxygen vacancies, and the roasting conditions are controlled so that the obtained derivative maintains its morphology and structure, thereby giving it a high specific surface area, a developed pore structure, and containing abundant weak alkaline and medium-strong alkaline sites and abundant oxygen vacancies, so that it exhibits excellent catalytic performance in a high-concentration COS system. The specific technical scheme is as follows: A method for preparing hydrotalcite-like magnesium aluminum oxide derived from a coral spherical structure comprises the following steps: S1. Preparation of a hydrotalcite precursor with a coral spherical structure: a certain amount of magnesium nitrate, aluminum nitrate, urea and citric acid were added to a mixed solvent of deionized water and ethanol, and a clear solution was obtained after vigorous stirring for 1 h. The obtained solution was transferred to a high-pressure reactor for solvent thermal treatment, and after natural cooling at room temperature, the hydrotalcite precursor with a coral spherical structure was obtained by filtering, washing and drying; S2. Preparation of hydrotalcite-derived magnesium-aluminum composite oxide with coral spherical structure: First, the hydrotalcite-like precursor prepared in step S1 is finely ground and placed in a muffle furnace, and calcined in a static air atmosphere to obtain a hydrotalcite-derived magnesium-aluminum composite oxide with coral spherical structure.

[0008] The temperature of the solvent thermal treatment in step S1 is 150-170° C. and the time is 6-18 h.

[0009] The molar ratio of magnesium nitrate, aluminum nitrate, urea and citric acid in step S1 is (1-3):(1-2):(1-12):(1-2), and the volume ratio of deionized water and ethanol in the mixed solvent is 3:1.

[0010] In step S2, the precursor is calcined at a heating rate of 2-4°C / min, a calcination temperature of 400-600°C, and a calcination time of 4-6 h.

[0011] Furthermore, the hydrotalcite-derived magnesium-aluminum composite oxide with a coral spherical structure prepared by the above method is used for the hydrolysis reaction of COS. The specific reaction conditions are: the space velocity is 2000~12000 mL·g -1 ·h -1 , the reaction temperature is 70~110 ℃, the COS volume concentration of the reaction system is 100~10000 ppm, and the water vapor volume concentration is 3~12%.

[0012] The technical solution of the present invention has the following advantages: (1) The coral spherical structure of the hydrotalcite-derived magnesium aluminum oxide provided by the present invention utilizes the reducing properties of citric acid and ethanol to form oxygen vacancies, and controls the calcination conditions so that the obtained derivative maintains its morphology and structure, thereby giving it a high specific surface area, a developed pore structure, and containing abundant weak alkaline and medium-strong alkaline sites and abundant oxygen vacancies, which is beneficial to improving its COS hydrolysis performance and enhancing the application potential of magnesium aluminum composite oxide materials.

[0013] (2) The present invention provides a method for preparing a hydrotalcite-derived magnesium aluminum oxide with a coral spherical structure, wherein a hydrotalcite-derived citric acid intercalated hydrotalcite is obtained in one pot, and a derived magnesium aluminum composite oxide is obtained after further roasting. The advantages of the present invention are that the synthesis process of the prepared catalyst is simple, it is not easy to agglomerate, the raw material price is low, and it is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 The XRD spectra of the catalysts obtained in Example 1 and Comparative Example 1 of the present invention are shown in FIG. Figure 2 This is the XRD spectrum of the precursor of Example 1 of the present invention; Figure 3 This is a SEM image of the precursor and the derived composite oxide of Example 1 of the present invention; Figure 4 The SEM images of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Example 1 are shown; Figure 5 The nitrogen isothermal adsorption-desorption curves of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Example 1; Figure 6 CO of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Example 1 2 -TPD spectrum; Figure 7 The EPR spectra of the catalysts obtained in Example 1 and Comparative Examples 1 to 4 of the present invention are shown in FIG. Figure 8 The stability of the catalysts obtained in Example 1 and Comparative Example 4 of the present invention at a reaction temperature of 90°C; Fig. 9 The stability of the catalysts obtained in Example 1 and Comparative Examples 1 to 3 of the present invention at a reaction temperature of 70°C. DETAILED DESCRIPTION

[0016] The present invention provides a method for preparing a hydrotalcite-like magnesium aluminum oxide having a coral spherical structure, comprising the following steps: S1. Preparation of a hydrotalcite precursor with a coral spherical structure: Magnesium nitrate, aluminum nitrate, urea and citric acid in a molar ratio of (1-3):(1-2):(1-12):(1-2) are added to a mixed solvent of deionized water and ethanol in a volume ratio of 3:1, and the solution is vigorously stirred for 1 h to obtain a clear solution. The solution is transferred to a high-pressure reactor for solvent thermal treatment at a temperature of 150-170°C for 6-18 h. After natural cooling at room temperature, the solution is filtered, washed and dried to obtain a hydrotalcite precursor with a coral spherical structure. S2. Preparation of hydrotalcite-like magnesium-aluminum composite oxides with coral spherical structures: First, the hydrotalcite-like precursor prepared in step S1 is finely ground and placed in a muffle furnace, and calcined in a static air atmosphere at a heating rate of 2-4 °C / min, a calcination temperature of 400-600 °C, and a calcination time of 4-6 h to obtain coral spherical hydrotalcite-like magnesium-aluminum composite oxides.

[0017] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0018] Example 1 Preparation of a coral spherical structured hydrotalcite-derived magnesium aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, 108 g of urea, and 40.3 g of citric acid were weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol were added, and stirred at 500 r / min for 1 h. The mixture was transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 h, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 min; the washed sample was dried at 120 °C overnight to obtain a precursor (named MgAl-LDH-CA). The precursor MgAl-LDH-CA was heated to 500 ℃ at a heating rate of 120 ℃ / h in a muffle furnace and kept at 500 ℃ for 4 h. After natural cooling, a coral-spherical hydrotalcite-derived magnesium-aluminum composite oxide was obtained and named MgAl-LDO-CA.

[0019] Example 2 Preparation of a hydrotalcite-derived magnesium-aluminum composite oxide with a coral spherical structure: 115.4 g of magnesium nitrate hexahydrate, 28.2 g of aluminum nitrate nonahydrate, 108 g of urea, and 40.3 g of citric acid were weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol were added, and stirred at 500 r / min for 1 hour, transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 hours, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents for a total of 4 times, each time for 5 min; the washed sample was dried at 120 °C overnight to obtain a precursor (named MgAl 0.5 -LDH-CA). 0.5 -LDH-CA was heated to 500 °C at a heating rate of 120 °C / h in a muffle furnace and kept at 500 °C for 4 h. After natural cooling, a hydrotalcite-derived magnesium-aluminum composite oxide with a coral spherical structure was obtained and named MgAl 0.5 -LDO-CA.

[0020] Example 3 Preparation of a coral spherical structured hydrotalcite-derived magnesium aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, 108 g of urea, and 20.2 g of citric acid were weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol were added, stirred at 500 r / min for 1 h, transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 h, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 min; the washed sample was dried at 120 °C overnight to obtain a precursor (named MgAl-LDH-CA 0.5 ). The precursor MgAl-LDH-CA 0.5 The temperature was raised to 500 °C at a heating rate of 120 °C / h in a muffle furnace and kept at 500 °C for 4 h. After natural cooling, a hydrotalcite-derived magnesium-aluminum composite oxide with a coral spherical structure was obtained and named MgAl-LDO-CA. 0.5 .

[0021] Example 4 Preparation of a coral spherical structured hydrotalcite-derived magnesium aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, 108 g of urea, and 80.6 g of citric acid were weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol were added, stirred at 500 r / min for 1 h, transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 h, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 min; the washed sample was dried at 120 °C overnight to obtain a precursor (named MgAl-LDH-CA 2 ). The precursor MgAl-LDH-CA 2 The temperature was raised to 500 °C at a heating rate of 120 °C / h in a muffle furnace and kept at 500 °C for 4 h. After natural cooling, a hydrotalcite-derived magnesium-aluminum composite oxide with a coral spherical structure was obtained and named MgAl-LDO-CA. 2 .

[0022] Comparative Example 1 Preparation of a magnesium-aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, and 108 g of urea are weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol are added, stirred at 500 r / min for 1 hour, transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 hours, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 minutes; the washed sample is dried at 120 °C overnight to obtain a precursor MgAl-LDH. The precursor MgAl-LDH was heated to 500 ℃ at a heating rate of 120 ℃ / h in a muffle furnace and kept at 500 ℃ for 4 h. After natural cooling, a magnesium-aluminum composite oxide was obtained and named MgAl-LDO.

[0023] Comparative Example 2 Preparation of a magnesium-aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, 108 g of urea, and 60.5 g of sodium dodecyl sulfate (SDS) are weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol are added, stirred at 500 r / min for 1 hour, transferred to a hydrothermal autoclave, heated to 170 ° C at a heating rate of 5 ° C / min, kept warm for 12 hours, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 minutes; the washed sample is dried at 120 ° C overnight to obtain a precursor MgAl-LDH-SDS. The precursor MgAl-LDH-SDS was heated to 500 ℃ at a heating rate of 120 ℃ / h in a muffle furnace and kept at 500 ℃ for 4 h. After natural cooling, a magnesium-aluminum composite oxide was obtained and named MgAl-LDO-SDS.

[0024] Comparative Example 3 Preparation of a magnesium-aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate, 56.3 g of aluminum nitrate nonahydrate, 108 g of urea, and 76.5 g of hexadecyltrimethylammonium bromide (CTAB) are weighed in sequence, placed in a 1000 mL beaker, 450 mL of deionized water and 150 mL of anhydrous ethanol are added, stirred at 500 r / min for 1 hour, transferred to a hydrothermal autoclave, heated to 170 °C at a heating rate of 5 °C / min, kept warm for 12 hours, then cooled to room temperature, filtered, and washed alternately by centrifugation at a speed of 4000 r / min, using deionized water and 95wt% ethanol as detergents, for a total of 4 times, each time for 5 minutes; the washed sample is dried at 120 °C overnight to obtain a precursor MgAl-LDH-CTAB. The precursor MgAl-LDH-CTAB was heated to 500 ℃ at a heating rate of 120 ℃ / h in a muffle furnace and kept at 500 ℃ for 4 h. After natural cooling, a magnesium-aluminum composite oxide was obtained and named MgAl-LDO-CTAB.

[0025] Comparative Example 4 Preparation of a magnesium-aluminum composite oxide: 115.4 g of magnesium nitrate hexahydrate and 56.3 g of aluminum nitrate nonahydrate were weighed in sequence and dissolved in 2 L of deionized water to obtain solution A. 43.2 g of sodium hydroxide was dissolved in 3 L of deionized water to obtain solution B. 5.3 g of sodium carbonate was dissolved in 1 L of deionized water and placed in a 10 L three-necked flask, heated in an oil bath at 75 °C, and solution A and solution B were simultaneously added dropwise to the three-necked flask through a peristaltic pump. During the titration process, the pH was controlled to be 10. After continuous stirring for 4 h, stirring was stopped and the solution was allowed to stand and age for 12 h. After aging, the product was washed by vacuum filtration, and the filter cake was dried in a 90 °C oven for 12 h, heated to 500 °C in a muffle furnace at a heating rate of 120 °C / h, and then calcined at 500 °C for 4 h. After natural cooling, a magnesium-aluminum composite oxide was obtained and named MgAlO.

[0026] X-ray powder diffraction (XRD): The phase characterization of the samples was measured using Panalytical's X'pert pro powder diffractometer, with a PIXcel1 detector, a copper target (Cu Kα, λ = 0.154 nm) as the excitation radiation source, an operating voltage of 45 KV, and an operating current of 40 mA.

[0027] Field emission scanning electron microscopy (SEM): The SEM images of the samples were observed on a S-4800 scanning electron microscope with a test current and voltage of 7 μA and 5 kV, respectively.

[0028] N 2Physical adsorption: The specific surface area and pore size of the samples were measured at liquid nitrogen temperature (77 K) using an ASAP2020 analyzer from Micrometric, USA. The samples were first vacuum pretreated at 573 K and then heated to a pressure of less than 10 -5 The samples were degassed at 400 torr for 3 h, and the specific surface area was calculated by the BET (Brunauer-Emmett-Teller) method, and the pore size distribution curve was obtained according to the BJH (Barrett-Joyner-Halenda) method.

[0029] Temperature programmed carbon dioxide desorption (CO 2 -TPD): The characteristics of the base centers on the sample surface are determined by CO 2 -TPD determination was carried out on an Auto Chem Ⅱ 2920 chemical adsorption instrument from Micrometric, USA. Test conditions: Weigh 0.2 g of sample, first purge with high-purity helium and raise the temperature to 450 °C for 1 h to remove impurities adsorbed on the surface, then switch to high-purity CO after dropping the temperature to 50 °C. 2 Adsorb for 60 min, then switch to high-purity helium and continue purging for 30 min to eliminate the CO physically adsorbed on the surface. 2 Finally, the temperature was raised to 500 °C at a rate of 10 °C / min under high-purity helium purge, and CO was detected by TCD. 2 Desorption signal.

[0030] Electron paramagnetic resonance (EPR): The oxygen vacancies of the samples were analyzed using the EPR200M electron paramagnetic resonance spectrometer from Quantum Instruments. The test power was 0.5011 mW, the test was performed at room temperature, and the magnetic field scanning range was 3330-3390 Gauss.

[0031] Figure 1 The XRD spectra of the catalysts obtained in Example 1 and Comparative Example 1 show that both of them have characteristic diffraction peaks at around 42.9° and 62.2° corresponding to the (200) and (220) crystal planes of the cubic periclase structure.

[0032] Figure 2 : This is the XRD spectrum of the precursor of Example 1. The spectrum shows that the characteristic diffraction peak of hydrotalcite-like particles shifts to a low angle, which indicates that the distance between its anion layers is enlarged, indicating that citric acid is intercalated between the anion layers of hydrotalcite-like particles.

[0033] Figure 3 The SEM spectra of the precursor and the derived composite oxide of Example 1 show that there is no obvious difference in morphology between the precursor and the derived composite oxide obtained after calcination, indicating that the derived composite oxide can maintain the coral spherical structure of the precursor through the design of the present invention.

[0034] Figure 4 The SEM spectra of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 show that the catalysts obtained in Examples 1 to 4 are all composed of two-dimensional nanosheets self-assembled into three-dimensional coral ball structures, which are different from the round sheet structure of the catalyst obtained in Comparative Example 1.

[0035] Figure 5 Table 1 is the nitrogen isothermal adsorption-desorption curve of the catalysts obtained in Examples 1 to 4 and Comparative Example 1, and Table 1 is the specific surface area and pore volume of the catalysts obtained in Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention. It can be seen from Table 1 that the specific surface area and pore volume of the catalysts obtained in Examples 1 to 4 are higher than those obtained in Comparative Examples 1 to 3. Although the pore volume of the catalyst obtained in Examples 1 to 2 is slightly lower than that in Comparative Example 4, the specific surface area is significantly higher than that in Comparative Example 4. This shows that the magnesium-aluminum composite oxide obtained in the present invention has a large specific surface area and a developed pore structure, which is beneficial to mass transfer in the reaction process and provides more adsorption sites.

[0036] Table 1 Specific surface area and pore volume of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 Figure 6 CO of the catalysts obtained in Examples 1 to 4 and Comparative Example 1 2 -TPD spectrum, acid gas CO 2 The desorption temperature represents the strength of the basic site, and the size of the peak area corresponds to the number of basic sites. The desorption peaks belonging to weak alkalinity and medium-strong alkalinity sites below 350 ° C were quantitatively analyzed, and the results are listed in Table 2. It can be seen that the weak alkalinity and medium-strong alkalinity sites on the surface of the catalysts obtained in Examples 1 to 4 are significantly increased compared with Comparative Example 1. It is confirmed that the present invention is beneficial to increase the number of weak alkalinity and medium-strong alkalinity sites of the magnesium-aluminum composite oxide, so that it exhibits higher catalytic activity.

[0037] Table 2 Weakly basic and medium-strong basic site CO of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Example 1 2 Adsorption Figure 7 The EPR spectra of the catalysts obtained in Example 1 and Comparative Examples 1 to 4 are shown in FIG. From the figure, it can be seen that Example 1 obtained by intercalating the precursor with citric acid has more abundant oxygen vacancies. It is confirmed that the present invention is beneficial to increase the oxygen vacancy concentration of the magnesium-aluminum composite oxide, so that it exhibits higher catalytic activity.

[0038] Catalytic hydrolysis activity test: The catalytic hydrolysis activity of COS was tested in a fixed bed reactor with a reaction tube diameter of 5 mm, a catalyst loading of 0.3 g, and a reaction space velocity of 4000 mL g -1 ·h-1 The reaction temperature was 60-110 °C, the COS volume concentration of the reaction system was 10000 ppm, and the water vapor volume concentration was 7.28% H 2 O. The concentration of COS at the reactor inlet and outlet was analyzed by online chromatography, and the activity was expressed as the percentage of COS conversion. The activity calculation formula is as follows: (1) in, and are the COS concentrations at the reactor inlet and outlet, respectively.

[0039] Table 3 shows the catalytic activities of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 at different reaction temperatures. As shown in Table 3, the catalysts prepared in Examples 1 to 4 show higher COS conversion rates at any temperature within the temperature range of 60°C-110°C than Comparative Example 1 in which the precursor is not intercalated with citric acid, Comparative Examples 2 to 3 synthesized using surfactants, and Comparative Example 4 prepared using a coprecipitation method, wherein the COS hydrolysis conversion rate of Example 1 in the temperature range of 70°C-110°C is close to 100%. This indicates that the catalyst obtained in the present invention has better COS hydrolysis activity.

[0040] Table 3 Catalytic activity of the catalysts obtained in Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 at different temperatures Catalyst COS hydrolysis stability test: The stability test of COS catalytic hydrolysis of the catalyst was carried out in a fixed bed reactor for activity evaluation. The reaction system contained 10000 ppm COS and 7.28% H 2 In addition to O, it also contains 0.5% by volume of O 2 The catalyst loading was 0.6 g and the reaction space velocity was 2000 mL·g -1 ·h -1 The changes in the concentration of COS at the outlet of the reaction process were analyzed by online chromatography, and the COS catalytic hydrolysis stability of the catalyst was evaluated by the changes in COS conversion rate.

[0041] Figure 8 The results are the evaluation results of the COS catalytic hydrolysis stability of the catalysts obtained in Example 1 and Comparative Example 4 at a reaction temperature of 90°C. Figure 8 It can be seen that the catalyst obtained in Example 1 has better stability than the magnesium-aluminum composite oxide prepared by coprecipitation method in Comparative Example 4. The catalyst obtained in Example 1 can maintain a conversion rate higher than 80% for more than 180 min, while the conversion rate of the latter drops below 80% in less than 100 min.

[0042] Fig. 9 The results are the evaluation results of the COS catalytic hydrolysis stability of the catalysts obtained in Example 1 and Comparative Examples 1 to 3 of the present invention at a reaction temperature of 70°C. Fig. 9 It can be observed that the catalyst obtained in Example 1 has a more superior COS hydrolysis activity stability, and can maintain a conversion rate above 80% for more than 200 min, which is significantly better than Comparative Example 1, in which the conversion rate drops below 80% in less than 50 min.

[0043] In summary, the hydrotalcite-derived magnesium aluminum oxide with a coral spherical structure provided by the present invention has a high specific surface area, a developed pore structure, and abundant oxygen vacancies, wherein the preferred molar ratio of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, urea addition, and citric acid is 3:1:12:1.4, and the corresponding magnesium aluminum composite oxide has better hydrolysis activity and stability, which can enhance the application potential of magnesium aluminum composite oxide materials. At the same time, the hydrotalcite-derived magnesium aluminum composite oxide is obtained by one pot, and the citric acid intercalated hydrotalcite is further calcined to obtain the derived magnesium aluminum composite oxide. The preparation method has a simple synthesis process, is not easy to agglomerate, has low raw material prices, and is easier to achieve industrial production.

[0044] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure, characterized in that: The following steps are involved: (1) A certain amount of magnesium nitrate, aluminum nitrate, urea, and citric acid were added to a mixed solvent of deionized water and ethanol, and a clear solution was obtained after vigorous stirring for 1 h. (2) transferring the solution obtained in step (1) to a high-pressure reactor for solvent thermal treatment, cooling naturally at room temperature, filtering, washing, and drying to obtain a hydrotalcite-like substance having a coral spherical structure; (3) Grinding the coral spherical hydrotalcite obtained in step (2) into fine powder, placing it in a muffle furnace, and calcining it in a static air atmosphere to obtain a coral spherical hydrotalcite-derived magnesium aluminum composite oxide.

2. The method for preparing the hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure according to claim 1, characterized in that: The molar ratio of magnesium nitrate, aluminum nitrate, urea and citric acid in step (1) is (1-3):(1-2):(1-12):(1-2), and the volume ratio of deionized water and ethanol is 3:

1.

3. The method for preparing the hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure according to claim 1, characterized in that: The temperature of the solvent heat treatment in step (2) is 150-170°C and the time is 6-18 hours.

4. The method for preparing the hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure according to claim 1, characterized in that: In step (3), the calcination heating rate is 2-4 °C / min, the calcination temperature is 400-600 °C, and the calcination time is 4-6 h.

5. A hydrotalcite-like magnesium-aluminum composite oxide with a coral spherical structure obtained by the method according to any one of claims 1 to 4.

6. The use of the hydrotalcite-like derived magnesium-aluminum composite oxide according to claim 5, characterized in that: The hydrotalcite-like derived magnesium-aluminum composite oxide is used as a catalyst for the hydrolysis reaction of COS.

7. The use according to claim 6, characterized in that: The reaction conditions for COS hydrolysis are as follows: space velocity of 2000-12000 mL·g -1 ·h -1 The reaction temperature is 70~110 ℃, the COS volume concentration of the reaction system is 100~10000ppm, and the water vapor volume concentration is 3~12%.

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