Catalytic adsorption material capable of capturing low-concentration SO2, preparation method and application

Abstract

The present invention discloses a catalytic adsorption material capable of efficiently capturing low-concentration SO2, a preparation method, and an application thereof, and relates to the field of environmental technology. The preparation method comprises the following steps: (1) adding gelatin to deionized water, stirring under heating conditions until completely dissolved, then adding zinc oxide nanoparticles thereto, and ultrasonically dispersing the solution to uniformly mix the solution; (2) adding citric acid and ammonium chloride to the solution of step (1), stirring under heating conditions, evaporating excess liquid, and obtaining a dried sample; (3) carbonizing the dried sample in step (2), and then immersing the carbonized sample in an acidic solution at room temperature, magnetically stirring, washing away excess zinc oxide, and washing with deionized water until neutral; (4) drying and grinding the sample obtained in step (3) under vacuum heating conditions to obtain the adsorption material. The adsorption material of the present invention can have high chemical adsorption performance for SO2 at low concentrations.

Description

Technical Field

[0001] The present invention relates to the field of environmental technology, and in particular to a catalytic adsorption material capable of efficiently capturing low-concentration SO2, a preparation method and an application thereof. Background Art

[0002] The continuous advancement of industrial production technology and the increasing concentration of atmospheric pollutants have led to stricter control requirements for molecular contaminants in cleanrooms. SO₂ is a large and widespread gaseous pollutant, produced in large quantities during fuel combustion, ore smelting, refinery production processes, and chemical solvent volatilization. Even at low concentrations, prolonged exposure to SO₂ can irritate the eye membranes, damage skin and tissue, harm the respiratory system, and corrode equipment, thus endangering production. Therefore, designing materials that exhibit excellent capture capabilities for low-concentration SO₂ at room temperature is of great practical significance.

[0003] Current technologies for removing toxic substances primarily include incineration, membrane separation, and absorption. Incineration not only requires a large amount of energy due to its high temperatures, but also produces other harmful substances. Membrane separation is widely used for liquid purification due to its low maintenance and low energy consumption, but it is inherently susceptible to contamination. Absorption technologies typically use metal complexes or ionic liquids to absorb pollutant gases, but these methods suffer from low efficiency, secondary contamination, and a small gas-liquid interface, limiting their widespread application. In practical applications, adsorption using porous materials is often utilized, as this method requires no additional equipment and facilitates adsorption. Consequently, adsorption materials based on solid-gas reactions have gained wider application in various environments. To date, a variety of materials have been used to remove and retain pollutant gases, including zeolites, metal-organic frameworks, porous alumina, resins, and activated carbon. Activated carbon remains the predominant adsorbent in air purification due to its excellent specific surface area, low price, wide pore size range, and tunable chemical properties.

[0004] In clean rooms or atmospheric environments, the concentration of sulfur dioxide is usually very low, making it difficult to capture. Although activated carbon has a large specific surface area, the efficiency of capturing sulfur dioxide by physical adsorption alone is still very low. The traditional modification method is to impregnate the activated carbon and introduce active sites through modifiers to enhance the chemical adsorption of sulfur dioxide. However, the introduction of modifiers reduces the specific surface area of ​​the activated carbon and limits the effective contact between the adsorbent and the adsorbate. Secondly, the introduction of modifiers through impregnation will block the gas channels in the activated carbon, thereby changing the pore structure of the material, which is not conducive to the contact between the gas in the adsorbent and the active sites and cannot meet the requirements of practical applications.

[0005] Therefore, it is of great practical significance for technicians in this field to devote themselves to developing a new adsorption material that has high chemical adsorption performance for SO2 at low concentrations. Summary of the Invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a new adsorption material that has high chemical adsorption performance for SO2 at low concentrations.

[0007] To achieve the above object, the present invention provides a method for preparing a catalytic adsorption material capable of efficiently capturing low-concentration SO2, comprising the following steps:

[0008] (1) Gelatin was added to deionized water and stirred under heating conditions until completely dissolved. Then zinc oxide nanoparticles were added thereto and ultrasonic dispersion was performed to mix the solution uniformly.

[0009] (2) adding citric acid and ammonium chloride to the solution of step (1), stirring under heating conditions, evaporating excess liquid to obtain a dry sample;

[0010] (3) Carbonizing the sample dried in step (2), and then immersing the carbonized sample in an acidic solution at room temperature, stirring it magnetically to wash away excess zinc oxide, and then washing it with deionized water until it is neutral;

[0011] (4) Drying and grinding the sample obtained in step (3) under vacuum heating conditions to obtain the adsorption material.

[0012] In a preferred embodiment of the present invention, in step (1), 0.8 g of gelatin is added to 120 ml of deionized water and stirred at 60° C. until completely dissolved.

[0013] In another preferred embodiment of the present invention, in step (1), the diameter of the zinc oxide nanoparticles is 30 nm, and the weight of the zinc oxide nanoparticles is 10-50 g.

[0014] In another preferred embodiment of the present invention, in step (2), the amount of citric acid and ammonium chloride added is 10 g each, and the mixture is stirred at 80°C.

[0015] In another preferred embodiment of the present invention, in step (3), the carbonization method is: heating the sample dried in step (2) to 800°C at 5°C / min under an inert atmosphere and keeping the temperature for 90 minutes to carbonize the sample.

[0016] In another preferred embodiment of the present invention, in step (3), the acidic solution is a 1M hydrochloric acid solution.

[0017] In another preferred embodiment of the present invention, in step (4), vacuum drying and grinding are performed at 80°C.

[0018] The present invention also provides a catalytic adsorption material prepared by the above method, which can efficiently capture low-concentration SO2.

[0019] The present invention also provides a use of the catalytic adsorption material described above in adsorbing SO2.

[0020] Furthermore, the catalytic adsorption material adsorbs and oxidizes SO2 into SO3.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The adsorption material of the present invention introduces a Zn-NC structure, which enhances the material activity and improves the SO2 affinity. The four carbon atoms play a chelating role and successfully fix the metal atoms. At the same time, due to the difference in electronegativity, electrons are easily transferred from Zn to the adjacent N, thereby enhancing the activity of Zn.

[0023] (2) The present invention adopts an in-situ template method to prepare Zn-N doped hierarchical porous carbon, changing the two-step method of traditional adsorption materials to a one-step method. Active elements are added to the raw materials, and ZnO is used as a template agent to directly carbonize to obtain the adsorbent. Compared with the adsorption materials prepared by traditional methods, the adsorption materials have a larger specific surface area and a larger pore volume, which can load more active sites and facilitate the entry of gas into the pores.

[0024] (3) Sulfur dioxide, as a small molecule gas, is more easily adsorbed in micropores, while traditional modification methods can cause micropore clogging. The present invention uses citric acid as a carbon source and etchant to etch ZnO. The carbon source can wrap the template during the stirring process. After carbonization, the template is washed away with hydrochloric acid, thereby forming a porous structure. By adjusting the ratio of citric acid and zinc oxide nanoparticles, the size of the ZnO template can be controlled, and the pore size distribution of the adsorption material can be adjusted. This can overcome the disadvantage of traditional modification methods that cause micropore clogging, thereby providing sulfur dioxide gas with more adsorption sites and enhancing its adsorption effect.

[0025] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of a method for preparing an adsorption material provided by a preferred embodiment of the present invention;

[0027] Figure 2 : These are the relevant spectra of the Zn / AC-2 adsorption material provided by the present invention, wherein a is the XPS spectrum of Zn / AC-2, b is the high-resolution C1s spectrum of Zn / AC-2, c is the high-resolution N1s spectrum, and d is the high-resolution O1s spectrum;

[0028] Figure 3 This is a comparison chart of the SO2 adsorption effects of various adsorption materials provided by the present invention;

[0029] Figure 4 isothermal adsorption-desorption curves of various adsorption materials provided by the present invention;

[0030] Figure 5 These are the XPS graph and high-resolution S2p spectrum of the Zn / AC-2 adsorption material provided by the present invention after adsorbing sulfur dioxide, wherein a is the XPS graph after Zn / AC-2 adsorption, and b is the high-resolution S2p spectrum after Zn / AC-2 adsorption. DETAILED DESCRIPTION

[0031] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0032] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0033] Example 1 Preparation of adsorption material

[0034] Figure 1 The following is a flow chart for the preparation of the adsorbent material. First, 0.8 g of gelatin was added to 120 ml of deionized water and magnetically stirred at 60°C until completely dissolved. Then, 20 g of zinc oxide nanoparticles (30 nm diameter) were added and the solution was homogenized by ultrasonic dispersion for 30 minutes. To this solution, 10 g of citric acid and 10 g of ammonium chloride were added, and the excess liquid was evaporated under mechanical stirring at 80°C. The dried preform was then heated to 800°C at a rate of 5°C / min under an argon atmosphere and held at that temperature for 90 minutes to carbonize the material. The carbonized sample was then immersed in a 1 M HCl solution at room temperature with magnetic stirring for 12 hours. Excess zinc oxide was then washed off and washed with deionized water until neutral. Finally, the resulting material was vacuum-dried at 80°C and ground. The resulting sample was designated Zn / AC-2.

[0035] In the present invention, for comparison, under the same conditions and steps, only the weight of zinc oxide nanoparticles was changed to 10g, 30g, 40g and 50g respectively, and the obtained samples were named Zn / AC-1, Zn / AC-3, Zn / AC-4 and Zn / AC-5, respectively.

[0036] In the present invention, gelatin is used as a stabilizer and is dissolved in water at 60°C to prevent agglomeration between the raw materials. Citric acid is used as a carbon source and an etchant to dissociate hydrogen ions in water, which etch the zinc oxide particles added later, thereby changing the size of the zinc oxide particles. At the same time, citric acid acts as a carbon source, wrapping the zinc oxide particles during the stirring and drying process to form a precursor. Ammonium chloride is used as a nitrogen source to provide nitrogen to the material. Zinc oxide is used as a template in a granular form. After being etched by citric acid, the particle size can be changed, thereby changing the final pore size of the material. After carbonization, hydrochloric acid is used for pickling to clean out the remaining zinc oxide particles and release the pore volume.

[0037] Among them, the various spectra of the prepared adsorption material Zn / AC-2 are as follows Figure 2 shown. Figure 2 a in the figure is the Zn / AC-2XPS spectrum. Figure 2 As shown in Figure b, the high-resolution C1s spectrum of Zn / AC-2 can be divided into five peaks at 284.8eV, 285.6eV, 286.6eV, 287.7eV and 289.1eV, corresponding to CC bond, CN bond, OCO, C=O bond and OC=O bond respectively. Figure 2 As shown in Figure c, there are five peaks at 398.34eV, 399.3eV, 400.1eV, 401.1eV and 402.3eV, corresponding to pyridinic N, Zn-N, pyrrolic N, graphitic N and oxide N, respectively. Figure 2 In the d, the two peaks in the O1s high-resolution spectrum correspond to C=O (531.7 eV) and CO (533.3 eV), respectively. Therefore, the XPS results indicate that the zinc atoms are fixed in the carbon skeleton by the non-metallic element N, forming a Zn-NC structure.

[0038] Test Example 1: Investigating the adsorption effect of various adsorption materials on SO2

[0039] Under the same humid environment, specifically 50%RH, upstream sulfur dioxide concentration of 90ppm±5%, air flow of 3L / min, and cut-off concentration of 45ppm, the ability of each adsorbent material to adsorb sulfur dioxide was tested. The upstream concentration is the airflow concentration before the adsorbent, that is, the original airflow concentration. In contrast, the downstream concentration is the sulfur dioxide concentration in the airflow after purification by the adsorbent. The cut-off concentration is the downstream concentration when the test is stopped. The results are as follows: Figure 3 shown.

[0040] Depend on Figure 3It can be observed that all five adsorption materials exhibit relatively high adsorption capacities, with Zn / AC-2 reaching 3.37 mmol / g. According to the BET data, an appropriate hierarchical porous structure is beneficial to improving the adsorption capacity. Among them, the mesopores mainly provide diffusion channels for pollutant gases, while adsorption mainly occurs in the micropores. Therefore, although Zn / AC-5 has a large specific surface area, the larger average pore size leads to a significant decrease in adsorption capacity, while other materials with mainly micropores exhibit better adsorption capacity. In the adsorption process, chemical adsorption plays a major role. The mesopores help small SO2 molecules enter the interior of the material, while the micropores are the main place for chemical adsorption due to their similar kinetic diameter to SO2 molecules.

[0041] Test Example 2: BET test results of various adsorption material samples

[0042] Isothermal adsorption-desorption curves were drawn for the five adsorption material samples Zn / AC-1, Zn / AC-2, Zn / AC-3, Zn / AC-4 and Zn / AC-5 prepared in Example 1 of the present invention. The results are as follows: Figure 4 shown.

[0043] Depend on Figure 4 It can be seen that the adsorption curves of different materials show significant differences. The adsorption-desorption curve of Zn / AC-1 rises rapidly at low P / P0 values ​​and reaches saturation at a certain pressure, indicating that there is a well-developed microporous structure in the material. Zn / AC-2, Zn / AC-3, Zn-AC-4 and Zn / AC-5 materials show obvious hysteresis loops when P / P0>0.4, indicating the presence of a mesoporous structure. Zn / AC-2 shows an H4 hysteresis loop, indicating a mixed structure of micropores and mesopores. Zn / AC-4 and Zn / AC-5 show an H3 hysteresis loop, indicating an irregular pore structure with some large pores. Zn / AC-3 is between the two. The pore size distribution of this material is as follows Figure 4 As shown in Figure d, the pore size is mainly concentrated below 2nm. The pore size increases with the addition of zinc oxide, and the average pore size is as follows Figure 4 This is because citric acid, as an etchant, can react with zinc oxide particles to produce templates of different particle sizes. The carbon precursor encapsulates templates of different sizes, forming different pore sizes during the carbonization process. Therefore, as the amount of zinc oxide increases, the template size increases, resulting in an increase in the pores in the material. The specific surface area and pore volume of the material are shown in Figure 2. Figure 4 As shown in Figure c, Zn / AC-5 has a high specific surface area of ​​1528.93 m2 / g and a pore volume of 2.18 cm3 / g.

[0044] Test Example 3: Investigation of the effect of Zn / AC-2 adsorption material on sulfur dioxide adsorption

[0045] By observing the XPS graph and high-resolution S2p spectrum of sulfur dioxide adsorbed by Zn / AC-2 adsorbent material, the results are as follows Figure 5 As shown. Figure 5 It can be seen that the S2p characteristic peak appears in the sample, indicating that SO2 is successfully adsorbed on the surface of the material. Further analysis of the existence form of the S element was conducted. In the high-resolution S2p spectrum of Zn / AC-2-s ( Figure 5 In (b), there are only two characteristic peaks at 168.4 eV and 169.6 eV, demonstrating that sulfur is almost always present in a higher valence state, and that SO2 is efficiently oxidized to a higher valence state through chemical adsorption on the material surface.

[0046] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a catalytic adsorption material capable of capturing low-concentration SO2, characterized in that: The steps include: (1) Gelatin was added to deionized water and stirred under heating conditions until completely dissolved. Then zinc oxide nanoparticles were added thereto and ultrasonic dispersion was performed to mix the solution uniformly. (2) adding citric acid and ammonium chloride to the solution of step (1), stirring under heating conditions, evaporating excess liquid to obtain a dry sample; (3) Carbonizing the sample dried in step (2), and then immersing the carbonized sample in an acidic solution at room temperature, stirring it magnetically to wash away excess zinc oxide, and then washing it with deionized water until it is neutral; (4) Drying and grinding the sample obtained in step (3) under vacuum heating conditions to obtain the adsorption material.

2. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (1), 0.8 g of gelatin was added to 120 ml of deionized water and stirred at 60°C until completely dissolved.

3. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (1), the diameter of the zinc oxide nanoparticles is 30 nm, and the weight of the zinc oxide nanoparticles is 10-50 g.

4. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (2), the amount of citric acid and ammonium chloride added is 10 g each, and the mixture is stirred at 80°C.

5. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (3), the carbonization method is as follows: the sample dried in step (2) is heated to 800°C at 5°C / min under an inert atmosphere and kept at this temperature for 90 minutes to carbonize the sample.

6. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (3), the acidic solution is a 1M hydrochloric acid solution.

7. The method for preparing a catalytic adsorption material capable of capturing low-concentration SO2 according to claim 1, characterized in that: In step (4), vacuum drying and grinding are performed at 80°C.

8. A catalytic adsorption material capable of capturing low-concentration SO2 prepared by the method according to any one of claims 1 to 7.

9. Use of the catalytic adsorption material according to claim 8 in adsorbing SO2.

10. The use according to claim 9, characterized in that: The catalytic adsorption material adsorbs and oxidizes SO2 into SO3.

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