Desulfurizing agents, their preparation methods, and their applications in flue gas desulfurization.

Abstract

This invention provides a desulfurizing agent, its preparation method, and its application in flue gas desulfurization. The preparation method includes: mixing a mixture A containing magnesium salts, aluminum salts, and a precipitant with a mixture B containing a gemini-type anionic surfactant at a molar concentration of 0.1–0.5 mol / L, followed by a hydrothermal reaction; then, the precipitate obtained from the hydrothermal reaction is sequentially washed, dried, ground, calcined once, shaped, and calcined a second time to obtain the desulfurizing agent. This invention utilizes the high crystallinity and easily controllable morphology of the hydrotalcite-like compound prepared using the gemini-type anionic surfactant, thereby effectively controlling the microstructure and performance of the desulfurizing agent, improving the dispersion of active metals, and significantly enhancing the desulfurization activity of the desulfurizing agent.

Description

Technical Field

[0001] This invention belongs to the field of chemical environmental protection technology, and relates to a desulfurizing agent, its preparation method and its application in flue gas desulfurization. Background Technology

[0002] SO2 is a colorless acidic gas with a strong, pungent odor. Large-scale emissions of SO2 cause serious harm to humans and the environment. As a common air pollutant, SO2 mainly originates from flue gas produced by the combustion of fossil fuels. To reduce SO2 emissions, various flue gas treatment technologies have been proposed, which can be categorized into wet, dry, and semi-dry flue gas desulfurization (FGD) processes based on their characteristics. Wet FGD technology is mature and widely used, but its systems are complex, equipment is large, investment and operating costs are high, and it generates secondary pollution. Compared to wet FGD technology, dry FGD has advantages such as smaller footprint, simpler equipment operation, and lower cost, and has received widespread attention since its inception. Dry FGD refers to the catalytic conversion of SO2 in flue gas into metal sulfates or sulfites, which are then fixed by a desulfurizing agent, thereby effectively reducing the concentration of sulfur oxides in the exhaust gas. Desulfurizing agents are generally classified into renewable and non-renewable types. Among them, regenerable desulfurizers refer to those that, under the action of reducing gases, catalytically convert sulfur in metal sulfates or sulfites into SO2, H2S, or elemental S, thereby restoring the initial reactivity of the desulfurizer.

[0003] Available renewable desulfurizing agents mainly include metal oxides, spinels, and composite metal oxides derived from hydrotalcite compounds. Metal-based catalysts, including transition metals, noble metals, and non-noble metals, possess good structural tunability, abundant Lewis acid active sites, and high activity stability, thus exhibiting excellent catalytic reduction activity. However, these adsorbents are difficult to reduce and have low sulfur capacity. Spinel-based desulfurizing agents have simple preparation processes, good desulfurization effects, and mature processes, making them the main type of desulfurization adsorbent currently used in commercial applications. However, these desulfurizing agents have low Mg content, and bulk sulfates are difficult to regenerate and reduce, resulting in unstable activity. Summary of the Invention

[0004] To improve the above-mentioned problems, according to one aspect of the present invention, a method for preparing a desulfurizing agent is provided, comprising: mixing a mixture A containing magnesium salt, aluminum salt, and a precipitant with a mixture B containing a gemini anionic surfactant at a molar concentration of 0.1–0.5 mol / L, and then subjecting the mixture to a hydrothermal reaction; and sequentially washing, drying, grinding, primary calcination, molding, and secondary calcination of the precipitate obtained from the hydrothermal reaction to obtain the desulfurizing agent; wherein the gemini anionic surfactant has the structure shown in Formula I:

[0005]

[0006] In Equation I, 10≤n≤16, 2≤m≤6, and n and m are both integers.

[0007] Hydrotalcite compounds (LDHs) belong to the hexagonal crystal system, with two-dimensional layers arranged in a three-dimensional manner. The desulfurization performance of composite metal oxide desulfurizers is closely related to the structure and morphology of the LDH crystals before calcination. This invention utilizes the geminal anionic surfactant shown in the above structure to effectively control crystal growth during the crystallization process of LDHs. After calcination, composite metal oxide crystals with a 3D spherical morphology (formed by the aggregation of hexagonal nanosheets), high crystallinity, and large specific surface area are obtained. This improves the dispersion of active metals in the desulfurizer, fully utilizes the synergistic catalytic effect between metals, enhances the sulfur capacity and reduction reaction activity of the adsorbent, and achieves the beneficial effect of significantly improving desulfurization catalytic activity.

[0008] In the initial reaction system of hydrotalcite compounds, when the concentration of the gemini anionic surfactant exceeds the critical micelle concentration, the surfactant in the solution aggregates to form spherical micelles, with the hydrophobic tail group facing inward and the hydrophilic head group facing outward. Due to the strong electrostatic attraction between the anionic surfactant and the hydrotalcite layers, it can embed itself between the hydrotalcite layers through anion exchange, resulting in a significant increase in interlayer spacing. Simultaneously, this invention also effectively controls the increase in interlayer spacing by controlling the number of carbon atoms in the hydrophobic alkyl chain. The negatively charged anion at the head generates a strong attraction with the metal cation in the solution, causing crystals to grow along the interface of the spherical micelles and aggregate to form a 3D spherical morphology.

[0009] Furthermore, this invention utilizes the gemini-type anionic surfactant shown in the above structure to modify hydrotalcite-like compounds, enabling the one-step preparation of hydrotalcite-like compound crystals without the need for organic solvents. This method is simple, environmentally friendly, and has better prospects for industrial application. Simultaneously, the resulting desulfurizer can be easily regenerated through simple subsequent treatment, improving its usability.

[0010] Furthermore, the aforementioned geminal anionic surfactants described in this application are commercially available or can be prepared independently by referring to existing literature. The synthetic route is shown below:

[0011]

[0012] In one optional implementation, the specific synthesis steps are as follows: Take H2NC m H 2mNH2 is dissolved in ethanol, and then the mixture is vigorously stirred while adding the corresponding bromo-n-alkane. The reaction is carried out at 70–90 °C for 45–50 h. After the reaction is complete, the solvent is removed by vacuum rotary evaporation to obtain a pale yellow powder. Subsequently, the mixture is washed with diethyl ether until white, and recrystallized 2–3 times with a methanol-chloroform mixture (volume ratio 2:1) to obtain a white needle-like solid. The above white needle-like solid, 1,3-propanesulfonyl lactone, and sodium hydroxide are dissolved in methanol and refluxed at 60–65 °C for 20–30 h under a nitrogen atmosphere. The mixture is then evaporated to dryness in a vacuum rotary evaporator to obtain a white solid. Column chromatography is performed using a mixture of chloroform and petroleum ether as eluent. The solution containing the desired components is collected and evaporated to dryness in a vacuum rotary evaporator to obtain a white solid powder. Recrystallization 2–3 times with methanol-chloroform yields a white powder product, which is the corresponding geminal anionic surfactant.

[0013] In some alternative embodiments, the solvents for mixture A and mixture B may each be water independently. Gemini anionic surfactants include, but are not limited to, one or more compounds selected from the following:

[0014]

[0015] Furthermore, the precipitant is selected from one or more of urea, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. In mixture A, the molar concentration of the precipitant is 8–12 mol / L.

[0016] Furthermore, the raw materials forming mixture A also include cerium salt; in mixture A, the total molar concentration of magnesium, aluminum, and cerium is 0.8–1.2 mol / L; in mixture A, the molar ratio of magnesium, aluminum, and cerium is 2:0.5–1:0.1–0.5. In some optional embodiments, the magnesium salt, aluminum salt, and cerium salt include, but are not limited to, one or more of the corresponding metal element's sulfate, chloride, nitrate, and acetate salts.

[0017] In a preferred embodiment, after primary calcination and before molding, the preparation method further includes the step of mixing the primary calcination product with a binder and a pore-expanding agent to form a mixed system C. The binder is selected from one or more of alumina sol, high-temperature resistant cement, and boehmite. In the mixed system C, the weight content of the pore-expanding agent is 1–5 wt%. The pore-expanding agent is selected from one or more of guar gum powder, carboxymethyl cellulose, starch, and cetyltrimethylammonium bromide. The weight ratio of the binder to the primary calcination product is 1:1–3. In some optional embodiments, molding includes, but is not limited to, extrusion molding.

[0018] Preferably, the hydrothermal reaction temperature is 140–180°C and the time is 8–16 h. Preferably, the primary and secondary calcination temperatures are each 450–600°C and the times are each 5–12 h. Preferably, the drying temperature is 60–90°C. Preferably, the particle size of the ground material is 300–500 mesh.

[0019] According to another aspect of the present invention, a desulfurizing agent is provided, which is prepared by the aforementioned method for preparing a desulfurizing agent. For the reasons stated above, the desulfurizing agent of the present invention exhibits excellent desulfurization catalytic activity.

[0020] According to another aspect of the present invention, an application of the aforementioned desulfurizing agent in flue gas desulfurization is provided. For the reasons stated above, the desulfurizing agent of the present invention exhibits excellent catalytic reduction activity when applied in flue gas desulfurization, and has high sulfur capacity, making it easy to reduce and regenerate.

[0021] In one optional embodiment, the volume concentration of SO2 in the flue gas to be treated is 0.1-2%, and the temperature during flue gas treatment is 400-600°C. After flue gas desulfurization, the desulfurizing agent can be reduced and regenerated using H2 / N2 at a temperature of 400-600°C. Detailed Implementation

[0022] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0023] Raw material source:

[0024] Synthesize a series of gemini-type anionic surfactants based on existing literature:

[0025] C n H 2n+1 NC2H4NC n H 2n+1 Synthesis and purification of (n is an integer, and 10≤n≤16): 0.1 mol of ethylenediamine was dissolved in 200 mL of ethanol, then stirred vigorously and 0.25 mol of the corresponding alkane (bromo-n-alkane) was added dropwise. The reaction was carried out at 80 °C for 48 h. After the reaction was complete, the solvent was removed by rotary evaporation under vacuum to obtain a pale yellow powder. Subsequently, the powder was washed with diethyl ether until white, and recrystallized 2-3 times with a methanol-chloroform mixture (volume ratio 2:1) to obtain a white needle-like solid.

[0026] Accordingly, by replacing ethylenediamine with equimolar amounts of propylenediamine and hexamethylenediamine, while keeping the other steps unchanged, C can be synthesized. n H 2n+1 NC3H6NC n H 2n+1C n H 2n+1 NC6H 12 NC n H 2n+1 , 10≤n≤16, and n is an integer.

[0027] Synthesis and purification of gemini anionic surfactants: 0.02 mol of the above-synthesized intermediate product C... n H 2n+ 1NC2H4NC n H 2n+1 (n is an integer, and 10≤n≤16) and 0.11 mol of 1,3-propanesulfonyl lactone and 0.11 mol of sodium hydroxide were dissolved in 250 mL of methanol and refluxed at 333 K under a nitrogen atmosphere for 24 h. The mixture was then evaporated to dryness in a vacuum rotary evaporator to obtain a white solid. The solid was subjected to column chromatography using chloroform-petroleum ether as eluent. The solution containing the desired components was collected and evaporated to dryness in a vacuum rotary evaporator to obtain a white solid powder. The powder was recrystallized 2-3 times with methanol and chloroform to obtain a white powder product.

[0028] C n H 2n+1 NC3H6NC n H 2n+1 C n H 2n+1 NC6H 12 NC n H 2n+1 The intermediates are processed accordingly, and the following compounds are synthesized sequentially based on the different intermediate products:

[0029]

[0030] The solvent for both mixture A and mixture B is deionized water.

[0031] Example 1

[0032] This embodiment provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0033] (1) Preparation of hydrotalcite compounds

[0034] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0035] Prepare 250 mL of an aqueous solution of the gemini anionic surfactant M, denoted as mixture B. The concentration of the gemini anionic surfactant M is 0.2 mol / L.

[0036] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0037] (2) Preparation of composite metal oxide desulfurizing agent

[0038] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0039] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S1.

[0040] Example 2

[0041] This embodiment provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0042] (1) Preparation of hydrotalcite compounds

[0043] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate and urea, denoted as Mixture A. The concentration of magnesium nitrate is 0.65 mol / L, the concentration of aluminum nitrate is 0.31 mol / L, the concentration of cerium nitrate is 0.04 mol / L, and the concentration of urea is 10 mol / L.

[0044] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant K, denoted as Mixture B, in which the concentration of Gemini anionic surfactant K is 0.2 mol / L.

[0045] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0046] (2) Preparation of composite metal oxide desulfurizing agent

[0047] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0048] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S2.

[0049] Example 3

[0050] This embodiment provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0051] (1) Preparation of hydrotalcite compounds

[0052] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0053] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.2 mol / L.

[0054] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0055] (2) Preparation of composite metal oxide desulfurizing agent

[0056] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0057] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S3.

[0058] Example 4

[0059] (1) Preparation of hydrotalcite compounds

[0060] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0061] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.1 mol / L.

[0062] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0063] (2) Preparation of composite metal oxide desulfurizing agent

[0064] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0065] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S4.

[0066] Example 5

[0067] (1) Preparation of hydrotalcite compounds

[0068] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0069] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.5 mol / L.

[0070] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0071] (2) Preparation of composite metal oxide desulfurizing agent

[0072] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0073] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S5.

[0074] Example 6

[0075] (1) Preparation of hydrotalcite compounds

[0076] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0077] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.2 mol / L.

[0078] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0079] (2) Preparation of composite metal oxide desulfurizing agent

[0080] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 450°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0081] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S6.

[0082] Example 7

[0083] (1) Preparation of hydrotalcite compounds

[0084] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0085] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.2 mol / L.

[0086] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0087] (2) Preparation of composite metal oxide desulfurizing agent

[0088] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 600°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0089] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S7.

[0090] Example 8

[0091] (1) Preparation of hydrotalcite compounds

[0092] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0093] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.2 mol / L.

[0094] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 140 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0095] (2) Preparation of composite metal oxide desulfurizing agent

[0096] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0097] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S8.

[0098] Example 9

[0099] (1) Preparation of hydrotalcite compounds

[0100] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0101] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.2 mol / L.

[0102] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 180 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0103] (2) Preparation of composite metal oxide desulfurizer

[0104] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0105] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S9.

[0106] Example 10

[0107] (1) Preparation of hydrotalcite compounds

[0108] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 8 mol / L.

[0109] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.1 mol / L.

[0110] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0111] (2) Preparation of composite metal oxide desulfurizer

[0112] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0113] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S10.

[0114] Example 11

[0115] (1) Preparation of hydrotalcite compounds

[0116] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 12 mol / L.

[0117] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.5 mol / L.

[0118] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0119] (2) Preparation of composite metal oxide desulfurizing agent

[0120] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0121] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S1.

[0122] Example 12

[0123] (1) Preparation of hydrotalcite compounds

[0124] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0125] Prepare 250 mL of an aqueous solution of the gemini anionic surfactant Q, denoted as mixture B, wherein the concentration of the gemini anionic surfactant Q is 0.2 mol / L.

[0126] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0127] (2) Preparation of composite metal oxide desulfurizing agent

[0128] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0129] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S12.

[0130] Comparative Example 1

[0131] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0132] (1) Preparation of hydrotalcite compounds

[0133] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0134] Mixture A and 250 mL of deionized water were transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0135] (2) Preparation of composite metal oxide desulfurizing agent

[0136] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0137] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent D1.

[0138] Comparative Example 2

[0139] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0140] (1) Preparation of hydrotalcite compounds

[0141] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0142] Prepare 250 mL of a mixture of dodecyl sulfonate anionic surfactant, denoted as mixture B, in which the concentration of the anionic surfactant is 0.2 mol / L.

[0143] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0144] (2) Preparation of composite metal oxide desulfurizing agent

[0145] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0146] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent D2.

[0147] Comparative Example 3

[0148] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0149] (1) Preparation of hydrotalcite compounds

[0150] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0151] Prepare 250 mL of an aqueous solution of the gemini sulfonate anionic surfactant, denoted as mixture B, wherein the structural formula of the gemini sulfonate anionic surfactant is: The concentration is 0.2 mol / L.

[0152] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (greater than 300 mesh), yielding a hydrotalcite compound powder.

[0153] (2) Preparation of composite metal oxide desulfurizing agent

[0154] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0155] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent D3.

[0156] Comparative Example 4

[0157] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0158] (1) Preparation of hydrotalcite compounds

[0159] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0160] Prepare 250 mL of an aqueous solution of the gemini sulfonate anionic surfactant, denoted as mixture B, wherein the structural formula of the gemini sulfonate anionic surfactant is: The concentration is 0.2 mol / L.

[0161] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (greater than 300 mesh), yielding a hydrotalcite compound powder.

[0162] (2) Preparation of composite metal oxide desulfurizing agent

[0163] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0164] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent D4.

[0165] Comparative Example 5

[0166] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0167] (1) Preparation of hydrotalcite compounds

[0168] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0169] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.05 mol / L.

[0170] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0171] (2) Preparation of composite metal oxide desulfurizing agent

[0172] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0173] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S13.

[0174] Comparative Example 6

[0175] This comparative example provides a method for preparing a composite metal oxide desulfurizing agent, the specific steps of which include:

[0176] (1) Preparation of hydrotalcite compounds

[0177] Prepare 500 mL of a mixed solution of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea, denoted as Mixture A. The concentrations of magnesium nitrate, aluminum nitrate, cerium nitrate, and urea are 0.65 mol / L, 0.31 mol / L, 0.04 mol / L, and 10 mol / L.

[0178] Prepare 250 mL of an aqueous solution of Gemini anionic surfactant J, denoted as Mixture B, wherein the concentration of Gemini anionic surfactant J is 0.8 mol / L.

[0179] Mixtures A and B were stirred at room temperature for 0.5 h, then transferred to a 1000 mL polytetrafluoroethylene high-pressure reactor and reacted at 160 °C for 12 h under a nitrogen atmosphere. The mixture was then centrifuged, washed with deionized water until neutral, and finally washed once with ethanol. The resulting solid was dried overnight in a 90 °C oven and then ground into a powder (300–500 mesh), which is a hydrotalcite compound powder.

[0180] (2) Preparation of composite metal oxide desulfurizing agent

[0181] The hydrotalcite compound powder obtained in step (1) was transferred to a muffle furnace and calcined at 500°C for 6 hours in an air atmosphere to obtain the corresponding composite metal oxide powder, wherein the heating rate was 2°C / min.

[0182] Weigh 50g of composite metal oxide powder, add 40g of aluminum sol, 2.7g of guar gum powder and 50g of deionized water, mix thoroughly and extrude into shape, then place at room temperature for 48h, dry at 100℃ for 12h, and calcine at 500℃ for 4h to obtain the corresponding desulfurizing agent S14.

[0183] Activity evaluation: The composition of the inlet feed gas in this experiment is shown in Table 1, and the desulfurization reaction space velocity is 500 h⁻¹. -1 The desulfurization activity was evaluated at a reaction temperature of 500℃.

[0184] Table 1

[0185] gas composition <![CDATA[SO2]]> <![CDATA[O2]]> <![CDATA[CO2]]> <![CDATA[N2]]> Volume percentage (%) 0.5 4 20 75.5

[0186] The evaluation experiment began by weighing 3g of the molded desulfurizing agent (in the examples and comparative examples) and filling it into a fixed-bed microreactor, with the upper and lower layers fixed with quartz wool. During the reaction, when the SO2 content in the outlet gas exceeded 140ppm, the gas flow was switched to a reducing flow. After regeneration, the next desulfurization reaction cycle was initiated, and the sulfur capacity of the desulfurizing agent at this point was calculated. The results are shown in Table 2.

[0187] Table 2

[0188] desulfurizer <![CDATA[Sulfur capacity (gSO2 / gcat.)]]> Example 1 0.22 Example 2 0.21 Example 3 0.24 Example 4 0.20 Example 5 0.21 Example 6 0.20 Example 7 0.24 Example 8 0.20 Example 9 0.24 Example 10 0.20 Example 11 0.21 Example 12 0.20 Comparative Example 1 0.17 Comparative Example 2 0.18 Comparative Example 3 0.18 Comparative Example 4 0.16 Comparative Example 5 0.18 Comparative Example 6 0.19

[0189] Note: cat. refers to desulfurizing agent.

[0190] The sulfur capacity of the desulfurizing agents described above in this invention (e.g., Examples 1-12) can all reach 0.20 g SO2 / gcat. or higher, while the sulfur capacity of the desulfurizing agents in Comparative Examples 1-6 is less than 0.20 g SO2 / gcat. Further:

[0191] When the hydrophobic chains are the same but the linking groups are different, the hydrophobicity of the surfactant does not increase with the increase of the carbon number of the linking group. Instead, it is a balanced result where the hydrophobicity of the linking group and the hydrophilicity of the hydrophilic group are mutually inversely related. Specifically, when... The addition of only one carbon atom to the linker group of the molecule does not significantly increase hydrophobicity; the overall result is an increase in the molecule's hydrophilicity. The stability of the emulsion formed during the hydrothermal reaction is slightly reduced, therefore Example 1 is slightly superior to Example 2. When the linker group length is further increased, the hydrophobicity of the linker group is stronger than the hydrophilicity of the hydrophilic group, leading to an increase in the molecule's hydrophobicity and a decrease in its solubility in water. Therefore, Example 3 is slightly superior to Example 12.

[0192] When the linker is the same but the hydrophobic chain length is different, as the carbon chain length increases, the hydrophilicity of the activator decreases and the lipophilicity increases, and the interfacial tension gradually decreases. This results in a more stable emulsion formed during the hydrothermal reaction, a more uniform morphology of the hydrotalcite crystals, and higher reactivity of the desulfurizer. Therefore, Example 3 is slightly better than Example 1.

[0193] Too little surfactant will make it difficult for droplets to disperse and form, resulting in an unstable emulsion; while too much surfactant may lead to over-emulsification, causing droplets to become too small and affecting the stability of the emulsion. Therefore, Example 3 is slightly better than Examples 4 and 5.

[0194] The concentration of the precipitant affects the crystallinity of hydrotalcite compounds. Both excessive and insufficient precipitant dosage can affect the OH- concentration in the reaction system, leading to the formation of other impurity phases in the hydrothermal reaction and affecting the dispersion of the active metal. Therefore, Example 3 is slightly better than Examples 10 and 11.

[0195] The hydrothermal reaction temperature affects the crystallinity of the crystals. The crystallinity gradually increases with increasing temperature and then gradually remains constant. Therefore, Examples 3 and 9 are slightly better than Example 8.

[0196] The calcination temperature affects the final crystal structure, thus influencing the activity of the desulfurizer. Hydrotalcite compounds decompose at certain temperatures, a process involving the removal of interlayer water, carbonate ions, and dehydration of hydroxyl groups in the layers. Below 200℃, only interlayer water is lost, with no impact on the structure. At 250–450℃, more water is lost, and CO2 is generated. At 450–500℃, CO3 is produced. 2- The LDHs disappear completely, transforming into CO2 and forming a bimetallic composite oxide. During heating, the ordered layered structure of the LDHs is disrupted, increasing the surface area and pore volume. When the heating temperature exceeds 600°C, the metal oxides formed after decomposition begin to sinter, resulting in a decrease in surface area and pore volume, forming a spinel phase. Therefore, Example 3 is slightly superior to Examples 6 and 7.

Claims

1. A method for preparing a desulfurizing agent, characterized in that, include: A mixture A containing magnesium salt, aluminum salt, and precipitant is mixed with a mixture B containing a gemini anionic surfactant at a molar concentration of 0.1~0.5 mol / L and subjected to a hydrothermal reaction. The precipitate obtained from the hydrothermal reaction is then washed, dried, ground, calcined once, shaped, and calcined a second time to obtain the desulfurizing agent. The gemini anionic surfactant has the structure shown in Formula I: Formula I In Equation I, 10≤n≤16, 2≤m≤6, and n and m are both integers.

2. The method for preparing the desulfurizing agent according to claim 1, characterized in that, The raw materials for forming the mixture A also include cerium salt.

3. The method for preparing the desulfurizing agent according to claim 1 or 2, characterized in that, The precipitant is selected from one or more of urea, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

4. The method for preparing the desulfurizing agent according to claim 1 or 2, characterized in that, In the mixture A, the molar concentration of the precipitant is 8~12 mol / L.

5. The method for preparing the desulfurizing agent according to claim 2, characterized in that, In the mixture A, the total molar concentration of magnesium, aluminum and cerium is 0.8~1.2 mol / L.

6. The method for preparing the desulfurizing agent according to claim 2, characterized in that, In the mixture A, the molar ratio of magnesium, aluminum and cerium is 2:0.5~1:0.1~0.

5.

7. The method for preparing the desulfurizing agent according to claim 1, characterized in that, After the first calcination and before the shaping, the preparation method further includes the step of mixing the first calcination product with a binder and a pore-expanding agent to form a mixed system C.

8. The method for preparing the desulfurizing agent according to claim 7, characterized in that, The binder is selected from one or more of aluminosilicate, high-temperature resistant cement, or pseudoboehmite.

9. The method for preparing the desulfurizing agent according to claim 7, characterized in that, The pore-expanding agent is selected from one or more of guar gum powder, carboxymethyl cellulose, starch, and hexadecyltrimethylammonium bromide.

10. The method for preparing the desulfurizing agent according to claim 7, characterized in that, In the mixture C, the weight content of the pore-expanding agent is 1~5wt%.

11. The method for preparing the desulfurizing agent according to claim 7, characterized in that, The weight ratio of the binder to the first-calcined product is 1:1 to 3.

12. The method for preparing the desulfurizing agent according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 140~180℃ for a time of 8~16h.

13. The method for preparing the desulfurizing agent according to claim 1, characterized in that, The temperature of the first roasting and the second roasting are each independently 450~600℃ and the time is each independently 5~12h.

14. A desulfurizing agent, characterized in that, The desulfurizing agent is prepared by the method described in any one of claims 1 to 13.

15. The application of the desulfurizing agent according to claim 14 in flue gas desulfurization.

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