Three-dimensional hierarchical structure composite dechlorination agent, preparation method and application thereof

Abstract

The present application belongs to the technical field of environmental protection adsorption material, and particularly relates to a three-dimensional hierarchical structure composite dechlorination agent, a preparation method and application thereof. The method comprises the following steps: hydrothermal reaction of a water solution containing a carbohydrate under a closed condition to obtain a carbon microsphere sacrifice template; dispersing the carbon microsphere sacrifice template in a solution containing a soluble alkali earth metal salt and urea, performing a first step of hydrothermal reaction, and depositing alkali earth metal hydroxide nuclei on the surface of the carbon microsphere sacrifice template; then mixing with a soluble aluminum salt, performing a second step of hydrothermal reaction, and forming a precursor; calcining the precursor to obtain a dechlorination agent semi-finished product; and performing surface functionalization through an impregnation method to obtain the three-dimensional hierarchical structure composite dechlorination agent. Through a self-assembly method from inside to outside, a micron-level spherical morphology and a nanometer-level sheet structure are constructed, an unobstructed diffusion path is provided for gas molecules, internal diffusion resistance is greatly reduced, and the mass transfer efficiency is maximized.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly adsorption materials technology, specifically relating to a three-dimensional hierarchical composite dechlorination agent, its preparation method, and its application. Background Technology

[0002] Chlorine-containing waste gases, especially those containing hydrogen chloride, emitted during industrial production processes are a major source of equipment corrosion, environmental acidification, and catalyst poisoning. Dry dechlorination technology has attracted much attention due to its advantages such as simple process and no secondary pollution. Its core lies in efficient, stable, and inexpensive solid-phase dechlorination agents.

[0003] Currently, dechlorinating agents using activated alumina as a carrier or main component are widely used. To improve their performance, research focuses primarily on increasing their specific surface area and loading of active components through modification. However, traditional dechlorinating agents generally face several mutually restrictive challenges in industrial applications. Firstly, there is a contradiction between mass transfer efficiency and bed pressure drop. To increase the reaction rate, smaller particle sizes are generally desired to increase the external specific surface area and shorten the internal diffusion path. However, this leads to a significant increase in gas flow resistance in fixed-bed reactors, resulting in excessively high bed pressure drop, significantly increasing fan energy consumption, and even causing gas path blockage. Conversely, while using larger particles can reduce pressure drop, severe internal diffusion limitations prevent the effective utilization of numerous active sites within the particles. Secondly, there is a contradiction between high activity and mechanical strength. High specific surface area materials prepared through methods such as pore formation often have a loose and porous structure with poor mechanical strength. Long-term exposure to high-temperature airflow and inter-particle collisions and friction in industrial reactors easily leads to pulverization and wear, causing not only loss of active components and shortened service life, but also contaminating downstream equipment and products with the detached dust. Finally, there is the problem of a narrow active temperature window. Conventional dechlorinating agents often only show good activity in specific medium and high temperature ranges. They are difficult to start at low temperatures or rapidly deactivated at high temperatures due to the sintering of active components, making it difficult to adapt to the wide and fluctuating operating temperatures in actual industry.

[0004] Patent CN112892580A discloses a room-temperature gas-phase dechlorination agent composed of transition metal oxides, light metal oxides, molecular sieves, and a support. This technical solution achieves multi-component synergistic dechlorination to a certain extent by physically mixing powders with different functions. However, this dechlorination agent is composed of multiple independent powder particles through physical blending or simple bonding, lacking strong chemical bonds between the components. In industrial applications, long-term airflow scouring and inter-particle friction easily lead to the peeling of different components and pulverization of the overall structure, resulting in loss of active material and decreased bed stability. Although its components include micron-sized molecular sieves and supports, the active components and supports are simply physically mixed, failing to form a highly open and interconnected internal mass transfer network. Gas molecules need to pass through tortuous inter-particle packing channels to contact the active sites; internal diffusion resistance remains a bottleneck limiting its reaction rate and chlorine capacity. Physical mixing makes it difficult to achieve uniform dispersion of active components at the atomic or nanometer level, easily leading to agglomeration, causing most of the active material to be encapsulated internally and unable to participate in the reaction, resulting in an actual chlorine capacity far lower than the theoretical value. This patent is mainly for dechlorination at room temperature. Its formula and structure have not been optimized to adapt to high-temperature conditions. In practical applications with large temperature fluctuations, its high-temperature stability and activity are difficult to guarantee.

[0005] Therefore, developing a novel dechlorinating agent that can maintain a suitable particle size on a macroscopic level to ensure low bed pressure drop, has a highly open structure on a microscopic level to achieve extremely low mass transfer resistance, and at the same time possesses high mechanical strength and high dechlorination activity over a wide temperature range is a key technical problem that urgently needs to be solved in this field, and has significant industrial value for promoting the advancement of dry dechlorination technology. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a three-dimensional hierarchical composite dechlorinating agent, which consists of micron-sized spherical particles. The particles are constructed by self-assembling two-dimensional nanomaterials to form a continuous, robust, and hierarchically porous three-dimensional framework. The active components are in situ composited within this framework in the form of nanocrystals.

[0007] The present invention also provides a preparation method that is simple, easy to implement, and suitable for large-scale production.

[0008] The preparation method of the three-dimensional hierarchical composite dechlorination agent of the present invention includes the following steps:

[0009] (a) Preparation of sacrificial template: A water solution containing carbohydrates was subjected to a hydrothermal reaction under closed conditions at 170~220℃ to obtain carbon microsphere sacrificial template;

[0010] (b) Deposition of active crystal nuclei: The carbon microsphere sacrificial template is dispersed in a solution containing soluble alkaline earth metal salts and urea, and a first-step hydrothermal reaction is carried out at 100~150°C to deposit alkaline earth metal hydroxide crystal nuclei on the surface of the carbon microsphere sacrificial template.

[0011] (c) Self-assembly growth of the main framework: The product treated in step (b) is mixed with soluble aluminum salt and subjected to a second hydrothermal reaction at 170~220℃, so that the aluminum-containing compound grows in situ under the induction of the crystal nucleus to form a precursor with a three-dimensional structure.

[0012] (d) Calcination and molding: The precursor obtained in step (c) is calcined at 580~650℃ to remove the carbon microsphere sacrificial template and to convert the aluminum-containing compound and alkaline earth metal hydroxide into the corresponding metal oxides to obtain the dechlorination agent semi-finished product.

[0013] (e) Surface functionalization: The dechlorination agent semi-finished product is contacted with a precursor solution containing at least one metal salt selected from copper, iron, and cerium, and then dried and calcined to obtain the three-dimensional hierarchical composite dechlorination agent.

[0014] In step (a), the carbohydrate is glucose or sucrose, and its aqueous solution concentration is 0.8~1.4 mol / L.

[0015] In step (b), the soluble alkaline earth metal salt is calcium chloride or magnesium chloride; the molar ratio of urea to the soluble alkaline earth metal salt is (2~5):1.

[0016] In step (c), the soluble aluminum salt is aluminum nitrate or aluminum chloride; the mass ratio of aluminum in the soluble aluminum salt to the carbon microsphere sacrificial template is (1.3~4):1.

[0017] The roasting temperature in step (e) is 400~500℃.

[0018] The three-dimensional hierarchical composite dechlorinating agent of the present invention is composed of a number of microspheres with a particle size of 30~80μm.

[0019] The aforementioned three-dimensional hierarchical composite dechlorination agent is composed of the following components by mass percentage:

[0020] γ-Al2O3: 55%~68%;

[0021] Selected from one or two of CaO and MgO: 20%~30%;

[0022] Selected from at least one of CuO, Fe2O3, and CeO2: 12%~15%.

[0023] The three-dimensional hierarchical composite dechlorinating agent described in this invention is applied to the removal of hydrogen chloride from the gas phase.

[0024] The carbon microsphere sacrificial template obtained by hydrothermal reaction has a dual role of induction and sacrifice. First, it provides a monodisperse, micron-sized spherical mold, directly determining the macroscopic morphology of the product, which is a physical prerequisite for achieving low bed pressure drop. The abundant oxygen-containing functional groups on the surface of the carbon microspheres can electrostatically adsorb metal cations, providing "anchor points" for subsequent heterogeneous nucleation. During growth, it acts as a temporary support, ensuring that nanosheets grow around it, initially forming a spherical prototype. Then, during calcination, the carbon microspheres are oxidized and removed, and the freed-up space is directly transformed into the core macropores inside the microspheres, becoming the main channels of the hierarchical pore network. This is the key to achieving "through-channel" pores in this method.

[0025] This invention achieves precise assembly of the structure through a two-step hydrothermal reaction. First, it utilizes the slow-release OH from urea hydrolysis. - The principle is that the initial hydrothermal reaction forces alkaline earth metal ions M to precipitate as M(OH)2 nanocrystal nuclei only at anchor sites near the carbon sphere surface. This achieves monolayer-level, highly dispersed pre-fixation of the active component on the template surface, avoiding subsequent disordered bulk growth. Then, an aluminum source is added, and under high-temperature hydrothermal conditions again, boehmite (AlOOH) tends to undergo heterogeneous nucleation on the existing M(OH)2 nuclei with matching crystal structures. Due to the anisotropy of boehmite itself, it preferentially grows into two-dimensional nanosheets along specific crystal planes. This process is in-situ self-assembly: with the pre-fixed nuclei as growth base points, the nanosheets grow radially outward, naturally forming an interlocking and interdependent structure due to steric hindrance and hydrogen bonding interactions, rather than parallel stacking. This two-step method couples the localization of the active component M(OH)2 with the growth of the framework material (AlOOH), allowing the active component to be embedded in the nodes of the growing framework network, achieving atomic-level composite of active sites and structural framework.

[0026] The calcination process causes the carbon microspheres to burn as a sacrificial template, creating macropores; boehmite undergoes dehydration and transforms into γ-Al₂O₃, forming a robust ceramic framework; and M(OH)₂ decomposes into MO, forming highly reactive oxides. This process, while removing the temporary template, also utilizes high-temperature sintering to create stronger Al-O-Al or Al-OM chemical bonds at the junctions of the contacting nanosheets. This "interlocking" of the nanosheets welds them into a rigid, integrated three-dimensional network. Under stress, this rigid network distributes stress throughout the entire microsphere, rather than concentrating it at a few weak points, effectively resisting the erosion caused by airflow and particle wear under industrial conditions.

[0027] Traditional pores are formed by the stacking of particles, and are mostly tortuous and discontinuous, resulting in high diffusion resistance. The pores of this invention are formed by the interconnectedness of stacked pores between nanosheets and large pores left by template sacrifice, creating a hierarchical, straight-through network. The diffusion paths of gas molecules are short and have low tortuosity, reducing internal diffusion resistance to a minimum and achieving intrinsically efficient mass transfer.

[0028] The precursor of the active component (MO) serves as a seed crystal for nanosheet growth, ultimately chemically embedded in the nodes and substrate of the γ-Al₂O₃ nanosheet framework in nanocrystal form. This achieves atomic-level dispersion, avoiding high-temperature agglomeration; it also provides strong anchoring, resisting airflow erosion and stripping; and it offers extremely high site accessibility, as it directly faces the interconnected channels. The surface-loaded catalytic components CuO, Fe₂O₃, and CeO₂ further modify the chemical environment of this framework.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) This invention constructs micron-sized spherical morphology and nano-sized sheet structure through a self-assembly method from the inside out. The micron-sized spherical shape ensures high porosity and low bed pressure drop in a fixed bed. The open three-dimensional hierarchical channels formed by the interlocking of nanosheets provide unobstructed diffusion paths for gas molecules, greatly reducing internal diffusion resistance and maximizing mass transfer efficiency.

[0031] (2) The interlocking nanosheets form a stable self-supporting framework, enabling individual microspheres to maintain a high degree of porosity while possessing mechanical strength that is difficult to achieve with traditional porous materials. This effectively resists the erosion of airflow and particle wear under industrial conditions, significantly extending the service life of the dechlorinating agent.

[0032] (3) The huge and highly accessible specific surface area allows the loaded active components to be fully exposed. The composite low-temperature active components on the surface and the high-temperature active components in the bulk ensure that the dechlorinating agent can exhibit excellent dechlorination activity and extremely high chlorine capacity over a wide temperature range from low to high. Attached Figure Description

[0033] Figure 1 The system described in this invention is used to test the dechlorination performance of both the embodiment and the comparative example. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. All raw materials used in the embodiments, unless otherwise specified, are commercially available.

[0035] Example 1

[0036] The preparation method of the three-dimensional hierarchical composite dechlorination agent includes the following steps:

[0037] (a) Preparation of sacrificial template: A 1.2 mol / L glucose aqueous solution was pumped into a 10 L hydrothermal reactor, sealed, and heated to 180 °C. The reactor was kept at this temperature for 16 hours. After cooling, the slurry was collected by centrifugation, washed three times alternately with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 80 °C for 12 hours to obtain carbon microsphere sacrificial templates with an average particle size of approximately 50 μm.

[0038] (b) Deposition of active crystal nuclei: Weigh 100g of carbon microspheres prepared in step (a) and disperse them in 5L of deionized water containing 300g CaCl2 and 330g urea. Transfer the mixed slurry to a 10L hydrothermal reactor and heat it to 120°C with stirring. React at a constant temperature for 6 hours.

[0039] (c) Self-assembly growth of the main framework: After the reactor is cooled to room temperature, 5L of deionized water solution containing 2800g of Al(NO3)3·9H2O is added to the reactor, and after sealing, the temperature is raised to 180℃ again and the reaction is carried out at a constant temperature for 12 hours.

[0040] (d) Calcination and Shaping: The product obtained in step (c) is filtered, washed with a large amount of deionized water until the filtrate is neutral, and dried in an oven at 120°C. The dried powder is then placed in a rotary kiln and heated to 600°C at a rate of 10°C / min under air atmosphere, and held at this temperature for 4 hours to obtain a dechlorination agent semi-finished product. Calculations show that the mass ratio of CaO to Al2O3 in this semi-finished product is approximately 1:2.5, with CaO weighing 151.4 g and Al2O3 weighing 380.8 g.

[0041] (e) Surface functionalization:

[0042] Pore ​​volume determination: Take 10.0 g of the dried semi-finished product obtained in step (d) and place it in a beaker. Slowly add deionized water dropwise using a burette while continuously stirring with a glass rod until the powder surface just shows a moist luster but can still flow freely. Record the water consumption as 5.0 mL. The saturated adsorption volume (pore volume) of the semi-finished product is calculated to be 0.50 mL / g.

[0043] Preparation of impregnation solution: Weigh 147.0g Cu(NO3)2·3H2O and 61.1g Ce(NO3)3·6H2O, dissolve them in a beaker, dilute with deionized water and accurately bring the volume to 266.1mL (based on the total mass of the semi-finished product 532.2g × 0.50mL / g).

[0044] Impregnation process: Place 532.2g of the semi-finished product in a planetary mixer. While stirring, use a peristaltic pump to evenly spray 266.1mL of the prepared impregnation solution onto the powder within 30 minutes. Continue stirring for 1 hour for aging.

[0045] Secondary roasting: The impregnated material is dried at 120℃ for 4 hours, then placed in a muffle furnace and roasted at 400℃ for 2 hours. After natural cooling, the final product is obtained. The final composition of the obtained three-dimensional hierarchical composite dechlorinating agent is (mass percentage): CaO: 25.0%, γ-Al2O3: 63.0%, CuO: 8.0%, CeO2: 4.0%.

[0046] Example 2

[0047] The preparation method of the three-dimensional hierarchical composite dechlorination agent includes the following steps:

[0048] (a) Preparation of sacrificial template: 0.8 mol / L sucrose aqueous solution was hydrothermally reacted at 170 °C for 20 hours, and the subsequent treatment was the same as in Example 1, to obtain carbon microspheres with an average particle size of about 80 μm.

[0049] (b) Deposition of active crystal nuclei: Weigh 100g of carbon microspheres and disperse them in a solution containing 400g of MgCl2·6H2O and 250g of urea. The mixture is then subjected to a hydrothermal reaction at 100°C for 8 hours.

[0050] (c) Self-assembly growth of the main framework: A solution containing AlCl3 (corresponding to a mass ratio of Al element to carbon spheres of 1.43:1) was added to the reactor, and the reaction was carried out hydrothermally at 170°C for 15 hours.

[0051] (d) Calcination and molding: The product obtained in step (c) is filtered, washed with a large amount of deionized water until the filtrate is neutral, and dried in an oven at 120°C. Then the dried powder is placed in a rotary kiln and calcined at 580°C at a rate of 10°C / min for 4 hours in an air atmosphere to obtain a dechlorination agent semi-finished product.

[0052] (e) Surface functionalization: Using the same volumetric impregnation method as in Example 1, Fe(NO3)3·9H2O and Ce(NO3)3·6H2O were loaded, so that the theoretical mass fraction of Fe2O3 in the final product was 4.0% and the theoretical mass fraction of CeO2 was 8.0%. After drying, it was calcined at 420℃ for 2 hours; the final composition of the obtained three-dimensional hierarchical composite dechlorinating agent was (mass percentage): MgO: 20.0%, γ-Al2O3: 68.0%, Fe2O3: 4.0%, CeO2: 8.0%.

[0053] Example 3

[0054] The preparation method of the three-dimensional hierarchical composite dechlorination agent includes the following steps:

[0055] (a) Preparation of sacrificial template: A 1.4 mol / L glucose aqueous solution was hydrothermally reacted at 220 °C for 15 hours, and the subsequent treatment was the same as in Example 1, to obtain carbon microspheres with an average particle size of about 30 μm.

[0056] (b) Deposition of active crystal nuclei: Weigh 100g of carbon microspheres and disperse them in a solution containing 800g of CaCl2 and 900g of urea. Perform hydrothermal reaction at 150°C for 4 hours.

[0057] (c) Self-assembly growth of the main framework: Al(NO3)3·9H2O solution was added to the reactor to make the mass ratio of Al element to carbon spheres 3.91:1, and the hydrothermal reaction was carried out at 220℃ for 6 hours.

[0058] (d) Calcination and shaping: The product obtained in step (c) is filtered, washed with a large amount of deionized water until the filtrate is neutral, and dried in an oven at 120°C. Then the dried powder is placed in a rotary kiln and calcined at 650°C for 2 hours under air atmosphere at a rate of 10°C / min.

[0059] (e) Surface functionalization: Using the same volume impregnation method as in Example 1, Cu(NO3)2·3H2O was loaded to make the theoretical mass fraction of CuO in the final product 15.0%. After drying, it was calcined at 500℃ for 1 hour; the final composition of the obtained three-dimensional hierarchical composite dechlorinating agent was (mass percentage): CaO: 30.0%, γ-Al2O3: 55.0%, CuO: 15.0%.

[0060] Comparative Example 1

[0061] Commercial γ-Al₂O₃ microspheres were purchased from Hangzhou Jikang New Materials Co., Ltd., with an average particle size of 50 μm (300 mesh). 630 g of these commercial microspheres were weighed as a carrier. To prepare a sample with the same composition as in Example 1, 250 g of CaO, 80 g of CuO, and 40 g of CeO₂ were loaded. Using an equal-volume co-impregnation method, the corresponding molar amounts of Ca(NO₃)₂·4H₂O, Cu(NO₃)₂·3H₂O, and Ce(NO₃)₃·6H₂O were dissolved in 327.6 mL (630 g × 0.52 mL / g) of deionized water to prepare a mixed impregnation solution. The impregnation, drying, and calcination conditions were exactly the same as in step (e) of Example 1, yielding the Comparative Example 1 sample.

[0062] Comparative Example 2

[0063] The preparation steps of Example 1 were basically repeated, except that step (b) of depositing active crystal nuclei was omitted. Instead, step (c) was carried out directly in the 100g carbon microsphere dispersion obtained in step (a), with the addition of 2800g Al(NO3)3·9H2O for hydrothermal reaction. The subsequent calcination and surface functionalization steps were exactly the same as in Example 1, resulting in Comparative Example 2 sample.

[0064] Comparative Example 3

[0065] Repeat steps (a) to (d) of Example 1 to obtain the dechlorination agent semi-finished product, and then skip the surface functionalization step (e). This semi-finished product was directly used as the sample for Comparative Example 3 for testing.

[0066] Comparative Example 4

[0067] The preparation method is the same as that of Comparative Example 1, except that γ-Al2O3 powder with an average particle size of 100 nm is used, and it is referred to as Comparative Example 4 sample.

[0068] Performance Testing and Analysis

[0069] Test 1: Dechlorination Performance Evaluation

[0070] Test conditions: The system used to test dechlorination performance is as follows: Figure 1 As shown, 10.0 g of the sample to be tested was packed into a quartz tube fixed-bed reactor with an inner diameter of 25 mm. Nitrogen gas entered the HCl saturator through a glass rotor flowmeter, carrying HCl gas into the reactor. The HCl concentration in the mixed gas at the reactor inlet was 1000 ppm, nitrogen was used as the balance gas, and the total flow rate was 1.0 L / min. Tests were conducted at room temperature (25℃) and high temperature (450℃). The outlet HCl concentration was monitored using an online Fourier transform infrared spectrometer. The breakthrough point was defined as the point at which the outlet concentration reached 5% of the inlet concentration (i.e., 50 ppm). The breakthrough time was recorded, and the breakthrough chlorine capacity (unit: mgHCl / g dechlorinating agent) was calculated accordingly. The test results are shown in Table 1 below.

[0071] Table 1 Dechlorination performance results

[0072] Dechlorination performance analysis:

[0073] Examples 1-3 of this invention all exhibited dechlorination performance far exceeding that of Comparative Example 1 prepared by the traditional impregnation method at both room temperature and high temperature, proving that the three-dimensional hierarchical structure constructed by the unique preparation method of this invention can greatly improve the utilization rate of active components and effectively overcome the limitation of mass transfer and diffusion inside the particles.

[0074] Compared with Comparative Example 2, the chlorine capacity of Comparative Example 2 decreased significantly, especially at room temperature, which almost failed. This shows that the crystal nucleus deposition in step (b) is not only the key to forming a high-capacity host active component, but also a prerequisite for constructing an efficient mass transfer structure.

[0075] Compared with Comparative Example 3, the performance of Comparative Example 3 deteriorated sharply at room temperature, proving that the CuO and other components loaded in step (e) are the core to achieve excellent low-temperature dechlorination performance.

[0076] The performance of the micron-sized spheres prepared by this invention is numerically close to or even surpasses that of the nano-sized comparative example 4, indicating that this invention has successfully achieved nano-level reaction efficiency on micron-sized materials.

[0077] Test 2: Evaluation of Fluid Dynamics and Mechanical Stability

[0078] Bed pressure drop test: Each sample was filled to a height of 30cm in a glass tube with an inner diameter of 25mm. N2 was introduced at 25℃, and the bed pressure drop (kPa / m) was measured using a differential pressure gauge at a flow rate of 1.0L / min.

[0079] Accelerated airflow erosion-anti-pulverization performance test: 20.0g of the sample was placed in a small fluidized bed reactor, and N2 was introduced at 450℃. The airflow velocity was controlled at three times the pre-determined minimum fluidization velocity of the sample, and erosion was carried out continuously for 24 hours. After the test, all remaining particles were collected and weighed, and the mass loss rate was calculated. The test results are shown in Table 2 below:

[0080] Table 2 Results of mechanical properties and mechanical stability of the body

[0081]

[0082] Fluid mechanics and stability analysis:

[0083] (1) The bed pressure drop test results show that the micron-sized spherical dechlorinating agent prepared in the embodiments of the present invention and the dechlorinating agents prepared in comparative examples 1 to 3 both have low bed pressure drops, which meet the requirements of industrial applications. However, the nano-sized powder in comparative example 4 has an excessively large pressure drop due to its small particle size, making it difficult to use in engineering.

[0084] (2) The anti-pulverization performance test results demonstrate the core advantage of this invention. Samples from Examples 1-3 and the semi-finished product Comparative Example 3 all exhibited extremely low mass loss rates (≤0.5%), proving that their self-assembled internal interlocking structure possesses excellent mechanical strength and wear resistance. In contrast, Comparative Example 1, which underwent traditional impregnation, suffered severe pulverization due to weak bonding force caused by the active component's mere physical adhesion. While Comparative Example 2, which did not undergo nucleation-induced growth, exhibited integrated growth, its disordered structure resulted in significantly lower strength compared to this invention. This powerfully demonstrates that this invention fundamentally resolves the contradiction between high activity and high strength in traditional dechlorination agents.

[0085] This invention successfully prepared a three-dimensional hierarchical composite dechlorinating agent with excellent dechlorination performance, low bed pressure drop, and high mechanical strength through a "sacrificial template-induced two-step hydrothermal synthesis" method. The overall performance of this material is significantly superior to existing technologies, solving a key technical problem that has long plagued this field and demonstrating great promise for industrial applications.

Claims

1. A method for preparing a three-dimensional hierarchical composite dechlorinating agent, characterized in that, Includes the following steps: (a) Preparation of sacrificial template: A carbohydrate-containing aqueous solution was subjected to a hydrothermal reaction under closed conditions to obtain carbon microsphere sacrificial template; (b) Deposition of active crystal nuclei: The carbon microsphere sacrificial template is dispersed in a solution containing soluble alkaline earth metal salts and urea, and a first-step hydrothermal reaction is carried out to deposit alkaline earth metal hydroxide crystal nuclei on the surface of the carbon microsphere sacrificial template. (c) Self-assembly growth of the main framework: The product treated in step (b) is mixed with soluble aluminum salt and subjected to a second hydrothermal reaction, so that the aluminum-containing compound grows in situ under the induction of the crystal nucleus to form a precursor with a three-dimensional structure. (d) Calcination and molding: The precursor obtained in step (c) is calcined to remove the carbon microsphere sacrificial template and to convert the aluminum-containing compound and alkaline earth metal hydroxide into the corresponding metal oxides to obtain the dechlorination agent semi-finished product. (e) Surface functionalization: The dechlorination agent semi-finished product is contacted with a precursor solution containing at least one metal salt selected from copper, iron, and cerium, and then dried and calcined to obtain the three-dimensional hierarchical composite dechlorination agent.

2. The preparation method of the three-dimensional hierarchical composite dechlorinating agent according to claim 1, characterized in that, In step (a), the carbohydrate is glucose or sucrose, and its aqueous solution concentration is 0.8~1.4 mol / L.

3. The preparation method of the three-dimensional hierarchical composite dechlorinating agent according to claim 1, characterized in that, In step (b), the soluble alkaline earth metal salt is calcium chloride or magnesium chloride.

4. The preparation method of the three-dimensional hierarchical composite dechlorinating agent according to claim 1, characterized in that, In step (c), the soluble aluminum salt is aluminum nitrate or aluminum chloride; the mass ratio of aluminum in the soluble aluminum salt to the carbon microsphere sacrificial template is (1.3~4):

1.

5. The preparation method of the three-dimensional hierarchical composite dechlorinating agent according to claim 1, characterized in that, The roasting temperature in step (e) is 400~500℃.

6. A three-dimensional hierarchical composite dechlorinating agent, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

7. The three-dimensional hierarchical composite dechlorinating agent according to claim 6, characterized in that, The dechlorination agent is composed of several microspheres with a particle size of 30~80μm.

8. The three-dimensional hierarchical composite dechlorinating agent according to claim 6, characterized in that, Components by mass percentage composition: γ-Al2O3: 55%~68%; Selected from one or two of CaO and MgO: 20%~30%; Selected from at least one of CuO, Fe2O3, and CeO2: 12%~15%.

9. The application of the three-dimensional hierarchical composite dechlorinating agent according to any one of claims 6 to 8, characterized in that, It is used for the removal of hydrogen chloride from the gas phase.

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