Desulfurization adsorbent and preparation method therefor

Abstract

Provided in the present invention are a desulfurization adsorbent and a preparation method therefor. The preparation method comprises: dissolving a complexing agent in water, and adjusting the pH value thereof, so as to obtain a treatment solution, wherein the complexing agent comprises one or a combination of two or more of polyethylene glycol, cetyltrimethyl ammonium bromide, and ethylenediaminetetraacetic acid; dispersing activated alumina in the treatment solution, and heating same until reflux, so as to obtain modified alumina; and dispersing the modified alumina in a solution containing an alkaline substance, then mixing same with a solution containing an active metal, and then performing hydrothermal crystallization and calcination, so as to obtain the desulfurization adsorbent. In the solid desulfurization adsorbent for medium- and low-temperature flue gas provided in the present invention, metal ions form bonds with aluminum species in the activated alumina and are uniformly distributed on the surface of the activated alumina, thereby providing relatively high stability and sulfur capacity.

Description

A desulfurization adsorbent and its preparation method Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, specifically to a desulfurization adsorbent and its preparation method. Background Technology

[0002] Flue gas desulfurization technology utilizes methods such as flue gas desulfurization, fuel desulfurization, and high-chimney emissions to effectively control SO2 in industrial waste gas. x Pollution. Flue gas desulfurization (FGD) technologies are mainly divided into three categories: pre-combustion desulfurization, in-combustion desulfurization, and post-combustion desulfurization. Post-combustion desulfurization is the most common method, including wet, dry, and semi-dry FGD technologies. Among these, regenerable dry FGD technology utilizes powdered or granular adsorbents, absorbents, or catalysts to remove SO2 from flue gas in a dry state, featuring a simple overall process and no wastewater generation.

[0003] Activated alumina is a common solid desulfurizing agent with a large specific surface area, abundant pore structure, and good hydrothermal stability. It can remove sulfur dioxide from the gas by reacting with sulfur dioxide molecules through hydrogen bonds and aluminum-oxygen bonds on the surface of activated alumina crystals to form sulfate ions. However, single activated alumina solid desulfurizers have low sulfur capacity, and the sulfate adsorbed on the surface is highly stable, making regeneration difficult and resulting in poor regeneration activity. Using activated alumina as a carrier and coupling it with a certain amount of metal oxides can effectively enhance its desulfurization performance through catalytic desulfurization. Traditional impregnation techniques have limited capacity for loading metal oxides onto the activated alumina surface, and the active components are prone to agglomeration at higher temperatures. Furthermore, differences in the radius and electronegativity of metal ions in the impregnation solution lead to low loading and poor dispersion of active components, resulting in decreased material porosity and significantly affecting the catalytic effect.

[0004] CN115739101B discloses a controllable preparation method for a bimetallic supported ozone catalyst, including surface modification of an activated alumina support with a complex and coating with an active metal, which can effectively improve the dispersion of the active metal. CN107486211B discloses a flue gas desulfurization catalyst, comprising rare earth oxides, copper oxide, and titanium dioxide as active components, and porous silica beads and activated alumina as a composite support, which reduces the interaction force between the active components and the alumina support. Both modification methods yield desulfurization catalysts that exhibit high desulfurization efficiency, but the active metal loading is limited.

[0005] CN112569953B discloses a desulfurization catalyst and its preparation method, which includes selecting a macroporous alumina support with specific pore volume and specific surface area, and loading group IVB, group VIII and lanthanide metal oxide additives. It can effectively remove sulfur-containing compounds from coke oven gas and exhibits high desulfurization efficiency. However, the large pore size of the alumina support will lead to a certain degree of decrease in catalyst strength.

[0006] CN111195520B discloses a highly dispersed adsorption desulfurization catalyst and its preparation and application. The desulfurization catalyst is composed of at least one +2 valent metal oxide, one +3 valent metal oxide, one group IIA metal oxide, at least one group IVB metal oxide, and at least one group VIII metal oxide. It has a high degree of dispersion of active components and exhibits high desulfurization activity and sulfur adsorption capacity in the adsorption desulfurization process of treating sulfur-containing gases or liquids. However, the preparation of the modified metal additive composite material by multiple precipitation methods and then the preparation of the desulfurization catalyst by molding is a complex process with high cost. Summary of the Invention

[0007] To solve at least one of the above-mentioned technical problems, the present invention aims to provide a desulfurization adsorbent and a method for preparing the same.

[0008] To achieve the above objectives, the present invention provides a method for preparing a desulfurization adsorbent, comprising:

[0009] S1: Dissolve the complexing agent in water and adjust its pH value to obtain a treatment solution; wherein the complexing agent includes one or more of polyethylene glycol, hexadecyltrimethylammonium bromide (CTAB), and ethylenediaminetetraacetic acid (EDTA);

[0010] S2: Disperse activated alumina in the treatment solution and heat under reflux to obtain modified alumina;

[0011] S3: The modified alumina is dispersed in a solution containing an alkaline substance, then mixed with a solution containing an active metal, and hydrothermally crystallized to obtain a solid product; calcined to obtain the desulfurization adsorbent.

[0012] Activated alumina possesses a large surface area, uniform pore structure, good stability and mechanical properties, and adjustable surface chemistry, making it suitable for various catalytic reactions. It is a promising type of desulfurization adsorbent for future development and application. Increasing the quantity and dispersion of active metal coatings on the surface can fully leverage the catalytic effect of the active metals and enhance the desulfurization reaction activity.

[0013] This invention employs a complexing agent to modify the surface of activated alumina, reducing interparticle interactions and effectively improving its dispersibility and stability in alkaline solutions. The modification of activated alumina in this invention primarily utilizes reflux heating to promote the interaction of the complexing agent with Al on the activated alumina surface. 3+ The reaction occurs and a stable complex is formed.

[0014] In this invention, aluminum in activated alumina reacts with added active metals under alkaline conditions via hydrothermal crystallization to form hydrotalcite compounds (precursors to metal oxides). Since the trivalent aluminum in the hydrotalcite compounds originates from alumina, the formed hydrotalcite compounds can grow in situ on the surface of activated alumina. The high dispersibility of the activated alumina modified with a complexing agent in the reaction solution effectively reduces the formation of uncoupled hydrotalcite compounds, fully utilizing the role of the activated alumina as a carrier. After high-temperature calcination, a medium- and low-temperature regenerable nanoscale solid desulfurization adsorbent with high active metal dispersibility and thermal stability is obtained. This avoids the agglomeration of active metal oxide particles caused by high-temperature calcination in traditional impregnation methods, effectively increasing the specific surface area of ​​the adsorbent and improving the content and dispersion of surface-active metal oxides, resulting in highly efficient desulfurization reactivity.

[0015] The preparation method of the desulfurization adsorbent of the present invention can effectively solve the problems of low loading of active components, poor dispersion and decreased porosity of materials in traditional impregnation processes.

[0016] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the mass ratio of the active alumina to the complexing agent is 1:0.087-0.44.

[0017] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the molar content of the complexing agent in the treatment liquid is 0.015-0.045 mmol / L.

[0018] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the polyethylene glycol is polyethylene glycol 400.

[0019] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the pH value of the treatment solution is 4.5-8; the reagent used to adjust the pH value is a pH buffer solution.

[0020] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, when the complexing agent is polyethylene glycol, the pH value of the treatment solution is 6-7.

[0021] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, when the complexing agent is hexadecyltrimethylammonium bromide, the pH value of the treatment solution is 7.5-8.

[0022] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, when the complexing agent is ethylenediaminetetraacetic acid, the pH value of the treatment solution is 4.5-6.

[0023] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the pH buffer solution is an acetic acid-ammonium acetate buffer solution.

[0024] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in S1, the pH value of the acetic acid-ammonium acetate buffer is 4-7, and the concentration of ammonium acetate in the acetic acid-ammonium acetate buffer is 0.8-4.4 mol / L.

[0025] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S2, the reflux temperature is 60-90℃ and the time is 6-12h.

[0026] In the above-mentioned method for preparing the desulfurization adsorbent, preferably, in step S2, the specific surface area of ​​the activated alumina is 250-300 m². 2 / g, pore volume 0.67-0.75cm³ 3 / g.

[0027] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S2, the activated alumina is further pretreated, and the pretreatment process of activated alumina includes washing, drying and calcination; the calcination temperature is 400-500℃ and the calcination time is 2-5h.

[0028] In the above-mentioned method for preparing the desulfurization adsorbent, preferably, the drying in the pretreatment of activated alumina includes natural air drying for 12-24 hours and drying at 60-100℃ for 2-6 hours. More preferably, the washing is performed with deionized water to remove impurities generated or remaining during the preparation process, followed by centrifugation and repeated operations.

[0029] In this invention, the pretreatment process of activated alumina can remove impurities and unnecessary substances from the surface of activated alumina, ensuring the subsequent modification effect.

[0030] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the solution containing alkaline substances includes one or more of the following: sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, urea solution, and ammonia water.

[0031] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the mass ratio of the modified alumina to the alkaline substance is 1:0.68-3.6.

[0032] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the molar content of the alkaline substance in the solution containing the alkaline substance is 2-10 mol / L.

[0033] In the above-mentioned method for preparing the desulfurization adsorbent, preferably, in step S3, the active metal provided by the solution containing the active metal includes divalent active metal cations, and may also selectively include trivalent active metal cations. More preferably, the active metal provided by the solution containing the active metal includes one or more of magnesium, copper, cobalt, manganese, zinc, nickel, iron, cerium, and lanthanum.

[0034] In the above-mentioned method for preparing the desulfurization adsorbent, preferably, in step S3, the solution containing the active metal is a solution containing an active metal salt. More preferably, the active metal salt in the solution containing the active metal salt can be a nitrate and / or a sulfate.

[0035] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the mass ratio of the active metal (calculated as oxide) to the active alumina is 0.51-0.84:1.

[0036] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the total molar content of active metal in the solution containing active metal is 1.0-1.5 mol / L.

[0037] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the hydrothermal crystallization temperature is 80-120℃ and the hydrothermal crystallization time is 12-24h.

[0038] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the calcination temperature is 450-550℃ and the calcination time is 3-9h.

[0039] In the above-mentioned method for preparing desulfurization adsorbent, preferably, in step S3, the heating rate to the calcination temperature is 2-10℃ / min.

[0040] In the above-mentioned method for preparing desulfurization adsorbent, preferably, step S3 further includes: washing and drying the solid product before calcination; the drying temperature is 90-120℃ and the drying time is 12-24h.

[0041] In the above-mentioned method for preparing the desulfurization adsorbent, preferably, the method further includes: pressing and pulverizing the calcined solid into tablets, and pulverizing it into 20-40 mesh particles to obtain the desulfurization adsorbent.

[0042] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned desulfurization adsorbent includes the following steps:

[0043] (1) Pretreatment: Wash the activated alumina with water to remove impurities and unnecessary substances from the surface to ensure the subsequent modification effect. This includes washing, drying and calcination.

[0044] (2) A complexing agent, including one or more of polyethylene glycol 400, hexadecyltrimethylammonium bromide (CTAB) and ethylenediaminetetraacetic acid (EDTA), is used to modify the surface of the pretreated active alumina to reduce the interparticle interaction force and effectively improve its dispersibility and stability in alkaline solution.

[0045] (3) Disperse the above-modified active alumina into a solution containing alkaline substances to form a mixture A, and prepare a solution B containing a specific active metal salt.

[0046] (4) Mix the mixture A and solution B at room temperature and transfer them to a polytetrafluoroethylene reactor. After hydrothermal crystallization at a certain temperature for a period of time, centrifuge and wash with deionized water until neutral. Then dry and calcine to obtain active metal alumina coated with metal oxide.

[0047] (5) The active metal alumina coated with metal oxide is pressed into tablets on a powder tablet press. After being pulverized into 20-40 mesh particles, a medium-low temperature renewable solid desulfurization adsorbent is obtained.

[0048] The present invention also provides a desulfurization adsorbent, which is prepared by the above-described method for preparing the desulfurization adsorbent.

[0049] Preferably, the specific surface area of ​​the above-mentioned desulfurization adsorbent is 250-300 m². 2 / g. More preferably, the pore volume of the desulfurization adsorbent is 0.40-0.55 cm³. 3 / g.

[0050] Preferably, the desulfurization adsorbent comprises an alumina support and an active metal, wherein the active metal, calculated as oxide, has a mass content of 33-54% in the desulfurization adsorbent, more preferably 33-45%.

[0051] The present invention also provides an application of the above-mentioned desulfurization adsorbent in treating low-temperature flue gas at 300-400℃.

[0052] The technical solution provided by this invention has the following beneficial effects:

[0053] This invention provides a medium- and low-temperature flue gas solid desulfurization adsorbent for active alumina coated with composite metal oxides. Through high-temperature hydrothermal crystallization, divalent active metal cations (or a combination of divalent and trivalent active metal cations) are bonded to trivalent aluminum in the active alumina to form a hydrotalcite-like compound coupled to the alumina surface via in-situ growth. A complexing agent is used to improve the alumina dispersion, effectively increasing both the dispersion and content of the active metals, thus exhibiting high stability and sulfur capacity. Furthermore, by changing the type of active metal, a series of metal-modified active alumina desulfurization catalysts can be obtained. The preparation process is simple and can significantly improve desulfurization activity. Detailed Implementation

[0054] 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.

[0055] The preparation method of the acetic acid-ammonium acetate buffer solution in this embodiment of the invention is as follows:

[0056] Preparation of acetic acid-ammonium acetate buffer solution:

[0057] First, take a 100mL volumetric flask, then add 7.708g of ammonium acetate and dissolve it in 40mL of deionized water. Then, add 6mL of acetic acid and dilute the solution to the 100mL mark with deionized water. Shake well to obtain an acetate-ammonium acetate buffer solution with a pH of 4.5.

[0058] Take a 100mL volumetric flask, add 33.333g of ammonium acetate and dissolve it in 40mL of deionized water. Then add 0.7mL of acetic acid and dilute the solution to the 100mL mark with deionized water. Shake well to obtain an acetate-ammonium acetate buffer solution with a pH of 7.

[0059] Example 1

[0060] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0061] (1) Pretreatment of activated alumina:

[0062] First, weigh out 10g of activated alumina (specific surface area 300m²). 2 / g, pore volume 0.75cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 450℃ for 5h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 2℃ / min;

[0063] (2) Modification with activated alumina:

[0064] Prepare 200 mL of 0.015 mol / L ethylenediaminetetraacetic acid (EDTA) solution, and adjust the pH of the EDTA solution to 4.5 using an acetate-ammonium acetate buffer solution with a pH of 7 to obtain the treatment solution; then add 10 g of pretreated activated alumina to the treatment solution, stir and reflux at 60 °C for 12 h, centrifuge and wash with deionized water to remove unreacted EDTA on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0065] (3) Coating active metals:

[0066] Prepare 60 mL of 10 mol / L urea solution and add 10 g of the above modified activated alumina. Stir and mix evenly at room temperature to obtain mixture A; then prepare 45 mL of aqueous solution of 1.2 mol / L nickel nitrate and 0.3 mol / L ferric nitrate, and denote it as mixture B.

[0067] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 120 °C and stirred under reflux for 12 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0068] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0069] The powder was then transferred to a muffle furnace and calcined at 450°C for 9 hours in air (heating rate of 2°C / min) to obtain alumina coated with active metal.

[0070] (3) Granulation and molding:

[0071] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S1 is obtained.

[0072] Example 2

[0073] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0074] (1) Pretreatment of activated alumina:

[0075] First, weigh out 10g of activated alumina (specific surface area 250m²). 2 / g, pore volume 0.67cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 400℃ for 5h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 10℃ / min;

[0076] (2) Modification with activated alumina:

[0077] Prepare 200 mL of 0.045 mol / L ethylenediaminetetraacetic acid (EDTA) solution, and adjust the pH of the EDTA solution to 6 using an acetate-ammonium acetate buffer solution with a pH of 7 to obtain the treatment solution; then add 10 g of pretreated activated alumina to the treatment solution, stir and reflux at 90 °C for 6 h, centrifuge, wash with deionized water to remove unreacted EDTA on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0078] (3) Coating active metals:

[0079] Prepare 50 mL of 8 mol / L ammonia solution and add 10 g of the above modified activated alumina. Stir and mix evenly at room temperature to obtain mixture A; then prepare 50 mL of 1.0 mol / L copper nitrate and 0.4 mol / L cerium nitrate aqueous solution, and denote it as mixture B.

[0080] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 80 °C and stirred under reflux for 24 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0081] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0082] The powder was then transferred to a muffle furnace and calcined at 550°C for 3 hours in air (heating rate of 10°C / min) to obtain alumina coated with active metal.

[0083] (3) Granulation and molding:

[0084] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S2 is obtained.

[0085] Example 3

[0086] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0087] (1) Pretreatment of activated alumina:

[0088] First, weigh out 10g of activated alumina (specific surface area 286m²). 2 / g, pore volume 0.72cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 450℃ for 3h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 5℃ / min;

[0089] (2) Modification with activated alumina:

[0090] Prepare 200 mL of 0.03 mol / L hexadecyltrimethylammonium bromide solution, and adjust the pH of the above hexadecyltrimethylammonium bromide solution to 8 using an acetate-ammonium acetate buffer solution with a pH of 4.5 to obtain the treatment solution; then add 10 g of pretreated activated alumina to the treatment solution, stir and reflux at 80 °C for 12 h, centrifuge and wash with deionized water to remove unreacted hexadecyltrimethylammonium bromide on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0091] (3) Coating active metals:

[0092] Prepare 60 mL of a 1 mol / L sodium hydroxide and 1 mol / L sodium carbonate solution, add 10 g of the above modified activated alumina, and stir and mix evenly at room temperature to obtain mixture A; then prepare 80 mL of an aqueous solution of 0.8 mol / L manganese nitrate and 0.3 mol / L lanthanum nitrate, and denote it as mixture B;

[0093] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 90 °C and stirred under reflux for 15 h to carry out hydrothermal crystallization, yielding a solid product.

[0094] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0095] The powder was then transferred to a muffle furnace and calcined at 450°C for 6 hours in air (heating rate of 2°C / min) to obtain alumina coated with active metal.

[0096] (3) Granulation and molding:

[0097] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S3 is obtained.

[0098] Example 4

[0099] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0100] (1) Pretreatment of activated alumina:

[0101] First, weigh out 10g of activated alumina (specific surface area 300m²). 2 / g, pore volume 0.75cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 500℃ for 2h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 10℃ / min;

[0102] (2) Modification with activated alumina:

[0103] Prepare 400 mL of 0.045 mol / L hexadecyltrimethylammonium bromide solution, and adjust the pH of the above hexadecyltrimethylammonium bromide solution to 7.5 using an acetate-ammonium acetate buffer solution with a pH of 4.5 to obtain the treatment solution; then add 15 g of pretreated activated alumina to the treatment solution, stir and reflux at 90 °C for 10 h, centrifuge and wash with deionized water to remove unreacted hexadecyltrimethylammonium bromide on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0104] (3) Coating active metals:

[0105] Prepare 80 mL of 10 mol / L urea solution and add 15 g of the above modified activated alumina. Stir and mix evenly at room temperature to obtain mixture A; then prepare 80 mL of aqueous solution of 0.9 mol / L copper nitrate and 0.4 mol / L ferric nitrate, and denote it as mixture B.

[0106] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 40 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 110 °C and stirred under reflux for 24 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0107] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0108] The powder was then transferred to a muffle furnace and calcined at 500°C for 3 hours in air (heating rate of 5°C / min) to obtain alumina coated with active metal.

[0109] (3) Granulation and molding:

[0110] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S4 is obtained.

[0111] Example 5

[0112] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0113] (1) Pretreatment of activated alumina:

[0114] First, weigh out 10g of activated alumina (specific surface area 286m²). 2 / g, pore volume 0.72cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 450℃ for 4h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 5℃ / min;

[0115] (2) Modification with activated alumina:

[0116] Prepare 200 mL of 0.03 mol / L polyethylene glycol 400 solution, and adjust the pH of the polyethylene glycol 400 solution to 6 using an acetate-ammonium acetate buffer solution with a pH of 4.5 to obtain a treatment solution; then add 10 g of pretreated activated alumina to the treatment solution, stir and reflux at 80 °C for 8 h, centrifuge, wash with deionized water to remove unreacted polyethylene glycol 400 on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0117] (3) Coating active metals:

[0118] Prepare 60 mL of 1.5 mol / L potassium hydroxide solution and 1.0 mol / L potassium carbonate solution, and add 10 g of the above modified active alumina. Stir and mix evenly at room temperature to obtain mixture A; then prepare 80 mL of aqueous solution of 0.4 mol / L magnesium nitrate and 0.8 mol / L cobalt nitrate, and denot it as mixture B.

[0119] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 90 °C and stirred under reflux for 18 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0120] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0121] The powder was then transferred to a muffle furnace and calcined at 500°C for 5 hours in air (heating rate of 10°C / min) to obtain alumina coated with active metal.

[0122] (3) Granulation and molding:

[0123] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S5 is obtained.

[0124] Example 6

[0125] This embodiment provides a desulfurization adsorbent, the preparation method of which includes the following steps:

[0126] (1) Pretreatment of activated alumina:

[0127] First, weigh out 10g of activated alumina (specific surface area 300m²). 2 / g, pore volume 0.75cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 450℃ for 4h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 5℃ / min;

[0128] (2) Modification with activated alumina:

[0129] Prepare 200 mL of 0.045 mol / L polyethylene glycol 400 solution, and adjust the pH of the polyethylene glycol 400 solution to 7 using an acetate-ammonium acetate buffer solution with a pH of 4.5 to obtain the treatment solution; then add 15 g of pretreated activated alumina to the treatment solution, stir and reflux at 80 °C for 10 h, centrifuge and wash with deionized water to remove unreacted polyethylene glycol 400 on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0130] (3) Coating active metals:

[0131] Prepare 60 mL of 1.5 mol / L sodium hydroxide solution and 0.8 mol / L potassium carbonate solution, and add 10 g of the above modified activated alumina. After stirring and mixing evenly at room temperature, obtain mixture A; then prepare 80 mL of aqueous solution of 0.2 mol / L zinc nitrate and 0.8 mol / L ferric nitrate, and denote it as mixture B;

[0132] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 90 °C and stirred under reflux for 18 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0133] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0134] The powder was then transferred to a muffle furnace and calcined at 450°C for 5 hours in air (heating rate of 5°C / min) to obtain alumina coated with active metal.

[0135] (3) Granulation and molding:

[0136] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S6 is obtained.

[0137] Example 7

[0138] This embodiment is basically the same as Embodiment 1, except that ferric nitrate is replaced with an equimolar amount of nickel nitrate.

[0139] A desulfurization adsorbent, the preparation method of which includes the following steps:

[0140] (1) Pretreatment of activated alumina:

[0141] First, weigh out 10g of activated alumina (specific surface area 300m²). 2 / g, pore volume 0.75cm³ 3 / g), and add 100mL of deionized water, stir at room temperature for 5min, and then centrifuge (5000rpm); repeat the operation 3 times, and place the final centrifuged solid product in a 100℃ constant temperature forced air drying oven to dry for 6h; grind the dried solid product into powder, and transfer it to a muffle furnace to calcine at 450℃ for 5h to obtain pretreated activated alumina, wherein the heating rate of calcination is controlled at 2℃ / min;

[0142] (2) Modification with activated alumina:

[0143] Prepare 200 mL of 0.015 mol / L ethylenediaminetetraacetic acid (EDTA) solution, and adjust the pH of the EDTA solution to 4.5 using an acetate-ammonium acetate buffer solution with a pH of 7 to obtain the treatment solution; then add 10 g of pretreated activated alumina to the treatment solution, stir and reflux at 60 °C for 12 h, centrifuge and wash with deionized water to remove unreacted EDTA on the surface, and dry in a constant temperature drying oven at 80 °C to obtain modified activated alumina;

[0144] (3) Coating active metals:

[0145] Prepare 60 mL of 10 mol / L urea solution and add 10 g of the above modified activated alumina. Stir and mix evenly at room temperature to obtain mixture A; then prepare 50 mL of 1.5 mol / L nickel nitrate aqueous solution, which is denoted as mixture B.

[0146] Mixture A and mixture B were simultaneously added to a round-bottom flask containing 20 ml of deionized water. After stirring at 60 °C for 0.5 h, the temperature was raised to 120 °C and stirred under reflux for 12 h to carry out hydrothermal crystallization, and a solid product was obtained.

[0147] The synthesized solid product was centrifuged and washed with deionized water until neutral. Finally, it was washed once with ethanol. The resulting solid was dried in a constant temperature drying oven at 90°C for 12 hours and then ground into powder.

[0148] The powder was then transferred to a muffle furnace and calcined at 450°C for 9 hours in air (heating rate of 2°C / min) to obtain alumina coated with active metal.

[0149] (3) Granulation and molding:

[0150] Alumina coated with active metal is pressed into tablets using a powder tableting machine. After being pulverized into 20-40 mesh particles, desulfurization adsorbent S7 is obtained.

[0151] Comparative Example 1

[0152] This comparative example provides a desulfurization adsorbent, which is prepared in the same way as in Example 1, except that the alumina modification step (2) is not performed.

[0153] Comparative Example 2

[0154] This comparative example provides a desulfurization adsorbent, which is prepared in the same way as in Example 1, except that the pH value of the treatment liquid (EDTA solution) is not adjusted in step (2).

[0155] Comparative Example 3

[0156] This comparative example provides a desulfurization adsorbent, the preparation method of which is the same as that of Example 1, except that the pH value of the treatment liquid in step (2) is adjusted to 6.5.

[0157] Comparative Example 4

[0158] This comparative example provides a desulfurization adsorbent, which is prepared in the same way as in Example 4, except that the pH value of the treatment liquid is adjusted to 6.5 in step (2).

[0159] Comparative Example 5

[0160] This comparative example provides a desulfurization adsorbent, the preparation method of which is the same as that of Example 4, except that the pH value of the treatment liquid in step (2) is adjusted to 5.5.

[0161] Comparative Example 6

[0162] This comparative example provides a desulfurization adsorbent, the preparation method of which is the same as that of Example 1, except that the heating and stirring (hydrothermal crystallization) in step (3) is replaced by room temperature impregnation.

[0163] Comparative Example 7

[0164] This comparative example provides a desulfurization adsorbent, the preparation method of which is the same as that of Example 1, except that the heating and stirring (hydrothermal crystallization) temperature in step (3) is 60°C.

[0165] Experimental Example

[0166] This experimental example is used to evaluate the desulfurization performance of the desulfurization adsorbents in the above embodiments and comparative examples.

[0167] Evaluation method: First, weigh 1.0 g of the desulfurization adsorbent prepared above and fill it into a quartz tube with an inner diameter of 1.5 mm. Then, introduce a feed gas containing SO2 (the composition of which is shown in Table 2) and control the reaction volume hourly space velocity at 500 h⁻¹. -1When the SO2 concentration at the outlet of the quartz tube is higher than 150 ppm, nitrogen gas is introduced to purge the adsorbent bed and the bed temperature is raised to 400℃. After the temperature stabilizes, 10% H2 is switched to regenerate the desulfurization adsorbent. After complete regeneration, SO2-containing raw gas is introduced for adsorption and regeneration again. After 6 cycles, the breakthrough sulfur capacity of the desulfurization adsorbent is calculated. The results are shown in Table 1.

[0168] In addition, a fully automated nitrogen adsorption surface area analyzer was used to analyze and detect the specific surface area and pore volume of the desulfurization adsorbents in the above examples and comparative examples; ICP analysis was used to analyze the elemental composition of the desulfurization adsorbents and calculate the loading of active metal oxides; H2 pulsed chemisorption was used to analyze the dispersion of active metal oxides, where dispersion (%) = (number of adsorbed metal atoms / total number of active metal atoms) × 100%. In the specific calculation, the number of adsorbed metal atoms was determined by integrating the peak area of ​​pulsed chemisorption and combining it with the calibration curve; the total number of active metal atoms was converted from the metal loading and molecular weight in the catalyst. The results are shown in Table 1.

[0169] Table 1. Specific surface area and sulfur penetration capacity of desulfurization adsorbents

[0170] Table 2 Composition of SO2-containing feed gas

[0171] The desulfurization adsorbents of this invention exhibit high active component loading and dispersion, as well as large pore volume. The sulfur capacity of the desulfurization adsorbents in these embodiments reaches 0.17 g SO2 / gcat. or higher, demonstrating excellent desulfurization activity for medium- and low-temperature flue gas. In contrast, the highest sulfur capacity of the desulfurization adsorbent in the comparative example is 0.14 g SO2 / gcat. Furthermore, after six cycles, the breakthrough sulfur capacity of the desulfurization adsorbents in these embodiments remains high, indicating high stability of the adsorbent.

[0172] Furthermore, comparing Example 1 and Comparative Example 1, it was found that the sulfur capacity of the desulfurization adsorbent prepared with modified activated alumina was significantly improved. This was mainly because the complexing agent modified the activated alumina, which could significantly improve its dispersibility and stability in alkaline solution, allowing more metal oxides to couple and grow on the alumina surface.

[0173] Comparing Example 1 with Comparative Examples 2 and 3, and Example 4 with Comparative Examples 4 and 5, it can be found that the pH value of the complexing agent-modified solution directly affects the sulfur capacity of the desulfurization adsorbent. This is mainly because pH value affects the interaction between the complexing agent and the Al on the alumina surface. 3+ The stability of the complex formed by the reaction is affected by pH values ​​that are too high or too low, as these can both affect the complexation reaction.

[0174] Compared with Example 1 and Comparative Example 6, the sulfur capacity of the desulfurization adsorbent prepared by coupling activated alumina with metal oxides is significantly higher than that of the desulfurization adsorbent prepared by the ordinary impregnation method. This is mainly because the ordinary impregnation method loads active metals onto the surface of activated alumina, resulting in relatively poor dispersion of the metal oxides and a limited loading amount.

[0175] Compared with Example 1 and Comparative Example 7, the desulfurization adsorbent prepared at a lower stirring reflux heating reaction temperature has a significantly lower sulfur capacity. This indicates that the coupled growth of metal oxides on the surface of activated alumina needs to be carried out within a certain temperature range. This is mainly because changes in reaction temperature directly affect the ion movement rate in the hydrotalcite crystallization, thus affecting the speed and quality of hydrotalcite crystallization. Specifically, at lower temperatures, the crystal growth rate is slower, and there are relatively more structural defects. Furthermore, when urea is used as the alkali source, the lower reaction temperature results in a higher OH content in the reaction system. - The concentration is insufficient to meet the requirements for crystal growth.

[0176] The active metal loading in Examples 1-7 is mainly affected by the metal concentration and the volume of the metal salt. Additionally, the amount of metal grown also affects the dispersion of hydrotalcite on the surface of activated alumina. Excessive metal addition increases the nucleation site density, promoting two-dimensional growth or three-dimensional aggregation, thereby reducing dispersion. Furthermore, in adsorbent preparation, a highly dispersed alumina support can promote uniform anchoring of metal species, reduce agglomeration, and improve metal dispersion and loading. Therefore, the dispersion in Comparative Examples 1-5 is significantly lower than that in the corresponding examples.

Claims

1. A method for preparing a desulfurization adsorbent, comprising: S1: Dissolve the complexing agent in water and adjust its pH value to obtain a treatment solution; wherein the complexing agent includes one or more of polyethylene glycol, hexadecyltrimethylammonium bromide, and ethylenediaminetetraacetic acid; S2: Disperse activated alumina in the treatment solution and heat under reflux to obtain modified alumina; S3: The modified alumina is dispersed in a solution containing an alkaline substance, then mixed with a solution containing an active metal, and hydrothermally crystallized to obtain a solid product; calcined to obtain the desulfurization adsorbent.

2. The method for preparing the desulfurization adsorbent according to claim 1, wherein, The mass ratio of the activated alumina to the complexing agent is 1:0.087-0.44; And / or, the molar concentration of the complexing agent in the treatment solution is 0.015-0.045 mmol / L.

3. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S1, the pH value of the treatment solution is 4.5-8; the reagent used to adjust the pH value is a pH buffer solution.

4. The method for preparing the desulfurization adsorbent according to claim 3, wherein, In S1, when the complexing agent is polyethylene glycol, the pH value of the treatment solution is 6-7.

5. The method for preparing the desulfurization adsorbent according to claim 3, wherein, In S1, when the complexing agent is hexadecyltrimethylammonium bromide, the pH value of the treatment solution is 7.5-8.

6. The method for preparing the desulfurization adsorbent according to claim 3, wherein, In S1, when the complexing agent is ethylenediaminetetraacetic acid, the pH value of the treatment solution is 4.5-6.

7. The method for preparing the desulfurization adsorbent according to claim 3, wherein, In S1, the pH buffer is an acetic acid-ammonium acetate buffer.

8. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S2, the temperature of the heating reflux is 60-90℃, and the time is 6-12h.

9. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S2, the specific surface area of ​​the activated alumina is 250-300 m². 2 / g, pore volume 0.67-0.75cm³ 3 / g.

10. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S2, the activated alumina is further pretreated. The pretreatment process of activated alumina includes washing, drying and calcination. The calcination temperature is 400-500℃ and the calcination time is 2-5 hours.

11. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the solution containing alkaline substances includes one or more of the following: sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, urea solution, and ammonia water.

12. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the mass ratio of the modified alumina to the alkaline substance is 1:0.68-3.

6.

13. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the molar content of the alkaline substance in the solution containing the alkaline substance is 2-10 mol / L.

14. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the active metal provided by the solution containing the active metal includes one or more of magnesium, copper, cobalt, manganese, zinc, nickel, iron, cerium, and lanthanum.

15. The method for preparing the desulfurization adsorbent according to claim 1, wherein, The mass ratio of the active metal (calculated as oxide) to the active alumina is 0.51-0.84:

1.

16. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the total molar content of the active metal in the solution containing the active metal is 1.0-1.5 mol / L.

17. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the hydrothermal crystallization temperature is 80-120℃, and the hydrothermal crystallization time is 12-24h.

18. The method for preparing the desulfurization adsorbent according to claim 1, wherein, In S3, the calcination temperature is 450-550℃ and the calcination time is 3-9h; And / or, in S3, the heating rate to the calcination temperature is 2-10 °C / min.

19. The method for preparing the desulfurization adsorbent according to claim 1, wherein, S3 further includes: washing and drying the solid product before calcination; the drying temperature is 90-120℃ and the drying time is 12-24h; And / or, the preparation method of the desulfurization adsorbent further includes: pressing and pulverizing the calcined solid into tablets, pulverizing it to 20-40 mesh particles to obtain the desulfurization adsorbent.

20. A desulfurization adsorbent, which is prepared by the method for preparing the desulfurization adsorbent according to any one of claims 1-19.

21. The desulfurization adsorbent according to claim 20, wherein, The specific surface area of ​​the desulfurization adsorbent is 250-300 m². 2 / g.

22. The desulfurization adsorbent according to claim 20, wherein, The desulfurization adsorbent comprises an alumina carrier and an active metal, wherein the active metal, calculated as oxide, comprises 33-45% by mass in the desulfurization adsorbent.

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