Silver-based dearsenical agent for ethylene plant and preparation method thereof

Abstract

The application discloses a silver-based arsenic removal agent for an ethylene device and a preparation method thereof. The arsenic removal agent comprises the following components in the total mass of the arsenic removal agent being 100%: 0.3-0.8 wt% of an active component silver; 5.0-8.0 wt% of a bimetallic promoter (consisting of 3.0-5.0 wt% of indium oxide and 2.0-3.0 wt% of tin oxide); 1.2-2.0 wt% of a modifier (consisting of 0.8-1.2 wt% of cerium oxide and 0.4-0.8 wt% of a polydopamine carbon skeleton); and the balance of modified alumina; the arsenic removal agent has low cost, high activity and high safety; through carrier surface regulation and multi-component synergy, the arsenic removal agent realizes synchronous deep removal of arsenic, mercury and sulfur under ultra-low silver loading (<1%), effectively inhibits the generation of silver acetylide and carbon deposition, the agent does not need to add an additional mercury / sulfur removal bed, significantly reduces investment, and guarantees long-period stable operation of the ethylene device.

Description

Technical Field

[0001] This invention relates to the field of arsenic removal agent technology, specifically to a silver-based arsenic removal agent for ethylene plants and its preparation method. Background Technology

[0002] Ethylene is a basic raw material for petrochemicals, and its output and technological level are important indicators of a country's petrochemical development level. In the ethylene production process, the C2 fraction (mainly composed of ethylene and acetylene) obtained after the cracked gas is compressed and separated usually contains trace amounts of impurities such as arsine, phosphine, hydrogen sulfide, and mercury.

[0003] Although these impurities are typically present in ppb levels, their hazards are immense. Arsine, in particular, is a highly toxic substance and a "permanent poison" for downstream acetylene selective hydrogenation catalysts (usually palladium- or silver-based catalysts). Arsenic reacts with active sites on the catalyst surface to form stable metal arsenides, leading to rapid loss of catalyst activity, severely shortening catalyst life, and even causing unplanned plant shutdowns. Furthermore, if mercury in the feedstock is not removed, it will not only poison the hydrogenation catalyst but also undergo amalgamation reactions with aluminum equipment (such as the cold boxes in cryogenic systems), causing severe intergranular corrosion, equipment leaks, and even explosions. Therefore, deep arsenic and mercury removal treatment is essential before the C2 fraction enters the hydrogenation reactor.

[0004] Currently, commonly used industrial arsenic removal agents mainly include copper oxide-zinc oxide series, lead oxide series, and silver-loaded series. Among them, copper oxide-based arsenic removal agents have low arsenic removal accuracy at room temperature and are prone to runaway temperature accidents caused by exothermic reduction; although lead oxide-based agents have better activity, they pose a serious risk of heavy metal pollution and are gradually being phased out. In contrast, silver-based arsenic removal agents are considered the most effective purification materials for protecting downstream precious metal catalysts due to their extremely high reactivity and removal accuracy at low temperatures.

[0005] However, existing silver-based arsenic removal agents still face the following pressing technical challenges in practical applications:

[0006] High raw material costs: Due to limitations in carrier surface properties and preparation processes, existing commercial silver arsenic removal agents typically require extremely high silver loadings to ensure sufficient active sites and service life. This results in extremely high manufacturing costs for the adsorbent, significantly increasing the operating expenses of ethylene plants.

[0007] There is a serious safety hazard: In an environment with high concentrations of acetylene (typically 1.0%–2.0%) in the C2 fraction, high levels of active silver readily react with acetylene to form silver acetylenide. Silver acetylenide is an extremely sensitive explosive compound that is highly susceptible to decomposition and explosion upon heating or friction, posing a significant safety risk to the loading and unloading of the adsorbent and the operation of the equipment.

[0008] The alumina support is prone to coking and side reactions: Commonly used alumina supports typically have numerous strongly acidic sites on their surface. Under reaction conditions, these acidic sites can catalyze the polymerization of acetylene and ethylene (i.e., the formation of "green oil") and the formation of coke and carbon deposits. These carbon deposits not only cover the active centers, leading to a decrease in arsenic capacity, but also clog pores, increasing bed pressure drop.

[0009] Limited functionality and lengthy process: Existing silver-based arsenic removal agents typically only have a good removal effect on arsine, with extremely weak capture capabilities for impurities such as mercury and hydrogen sulfide. To meet purification requirements, ethylene plants usually need to be equipped with dedicated mercury removal beds (such as sulfur-loaded activated carbon) in series, which not only increases equipment investment and floor space but also makes the process more complex.

[0010] Therefore, developing a novel multifunctional integrated arsenic removal agent with ultra-low silver content (low cost), the ability to inhibit the formation of silver in acetylene (high safety), strong anti-coking ability, and the ability to simultaneously achieve deep arsenic removal, mercury removal and desulfurization is a key technical challenge that urgently needs to be overcome in the current field of ethylene purification. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the present invention aims to provide a silver-based arsenic removal agent for ethylene plants and its preparation method. This arsenic removal agent combines low cost, high activity, and high safety. Through carrier surface regulation and multi-component synergy, simultaneous deep removal of arsenic, mercury, and sulfur is achieved at ultra-low silver loading (<1%), while effectively inhibiting the formation of silver acetylene and carbon deposition.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A silver-based arsenic removal agent for ethylene plants, comprising 100% by total mass of the arsenic removal agent, includes the following components: 0.3-0.8 wt% active component silver; 5.0-8.0 wt% bimetallic additive, wherein the bimetallic additive is composed of 3.0-5.0 wt% indium oxide and 2.0-3.0 wt% tin oxide; 1.2-2.0 wt% modifier, wherein the modifier is composed of 0.8-1.2 wt% cerium oxide and 0.4-0.8 wt% polydopamine carbon skeleton; and the balance being modified alumina.

[0014] Preferably, the modified alumina has a specific surface area of ​​280~320m² / g, a pore volume of 0.7~0.9mL / g, and an average pore size of 18~22nm.

[0015] Preferably, the modified alumina is prepared by the following method steps:

[0016] (1) Mix boehmite with boron source, add acid binder, knead and shape, calcine and then perform hydrothermal treatment to obtain pretreated alumina;

[0017] Preferably, in step (1), the boron source is one or more of boric acid, boron oxide, sodium borate, potassium borate, and ammonium borate; the amount of boron source added, calculated as B2O3, is 0.5~1.0 wt% of the mass of boehmite; the acidic binder is a 3~10 wt% aqueous solution of nitric acid; the calcination conditions are calcination at 550~600℃ for 3~4h; and the hydrothermal treatment conditions are treatment at 180~220℃ and 0.8~1.2 MPa in a steam atmosphere for 2~3h.

[0018] (2) Disperse the pretreated alumina into an ethanol / water mixture, add KH560, reflux the reaction, centrifuge, wash and dry the product to obtain functionalized alumina;

[0019] Silanization Grafting: The methoxy groups in the KH-560 silane coupling agent first undergo hydrolysis in an ethanol / water system, generating highly reactive silanol groups. These silanol groups are physically adsorbed onto the hydroxyl sites on the alumina surface via hydrogen bonds. Subsequently, during heating and reflux and drying dehydration, the silanols undergo dehydration condensation reactions with the hydroxyl groups on the alumina surface, forming thermally stable Al-O-Si covalent bonds. Simultaneously, silane molecules also undergo self-condensation to form a Si-O-Si network. This process "anchors" organosilane molecules to the inorganic surface, thereby introducing reactive epoxy groups into the outer layer of alumina.

[0020] Preferably, in step (2), the ratio of the amount of pretreated alumina, ethanol / water mixture and KH560 is 5g: 80~160mL: 2~5mL; the volume ratio of ethanol and deionized water in the ethanol / water mixture is 90~95: 5~10.

[0021] Preferably, in step (2), the reflux reaction conditions are: stirring and refluxing at 66~78℃ for 4~7h; the product is washed with anhydrous ethanol 2~5 times, and then placed in an oven at 105~115℃ for heat treatment for 1~2h to solidify the silane bonds.

[0022] (3) Disperse the functionalized alumina into ethanol, then add triethylamine and cystamine dihydrochloride, seal and stir the reaction, filter, wash and dry the product to obtain modified alumina.

[0023] Amine-epoxy addition: Triethylamine (TEA) first acts as an acid-binding agent, combining with HCl in cystamine dihydrochloride to convert the protonated ammonium ion into a nucleophilic free primary amino group. Subsequently, the lone pair of electrons at the terminal nitrogen atom of the cystamine molecule acts as a nucleophile, attacking the carbon atom with lower electron cloud density on the epoxy ring of the pretreated alumina surface, causing the epoxy ring to open. The resulting oxygen anion captures a proton to form a side hydroxyl group, while the amino group is converted into a secondary amine structure. Finally, cystamine is firmly grafted onto the alumina surface through a stable CN covalent bond, retaining the characteristic disulfide bond structure of the cystamine molecule.

[0024] Preferably, in step (3), the ratio of functionalized alumina, ethanol, triethylamine, and cystamine dihydrochloride is 5g:60~120mL:2~5mL:1~3g; the stirring reaction conditions are 50~65℃ for 12~24h; and the product is ultrasonically washed three times with anhydrous ethanol and deionized water alternately.

[0025] This invention also claims a method for preparing the silver-based arsenic removal agent, comprising the following steps:

[0026] (a) The silver precursor was prepared into a silver solution, which was then vacuum impregnated with modified alumina. After drying, the solution was subjected to reduction treatment under a reducing atmosphere to obtain a silver-containing carrier.

[0027] Preferably, in step (a), the silver precursor is silver nitrate; the reducing atmosphere is a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 5-15%, the reduction temperature is 200-220°C, and the reduction time is 2-4 hours.

[0028] (b) Prepare a mixed solution of indium salt and tin salt, impregnate it with a silver-containing carrier, dry it and then calcine it to obtain an intermediate loaded with silver, indium oxide and tin oxide;

[0029] Preferably, in step (b), the indium salt is indium nitrate, the tin salt is tin chloride, and the molar ratio of indium nitrate to tin chloride is 1~3:1; the calcination conditions are calcination at 380~420℃ for 2~4h.

[0030] (c) Cerium oxide sol is coated onto the intermediate, calcined, modified with dopamine solution, and finally dried under vacuum to obtain the silver-based arsenic removal agent for the ethylene plant.

[0031] Preferably, in step (c), cerium(III) acetate hydrate is added to anhydrous methanol, dissolved, and then propionic acid catalyst is added. After sealing, the mixture is stirred for 2-10 hours and allowed to stand for aging for 24 hours to obtain cerium oxide sol. The concentration of the cerium oxide sol is 0.1-1 mol / L, and the molar ratio of cerium(III) acetate hydrate to propionic acid is 1:3.

[0032] Preferably, in step (c), the calcination conditions are calcination at 350~400℃ for 2~4h; the concentration of the dopamine solution is 2~8g / L, and the pH value is 8~9; the temperature of the vacuum drying is 100~110℃.

[0033] This invention also claims the application of a silver-based arsenic removal agent in the C2 hydrogenation protective bed of an ethylene cracking unit, characterized in that it is used to simultaneously remove arsenic, mercury, and hydrogen sulfide impurities from the C2 feedstock; the operating conditions of the arsenic removal agent include: an operating temperature of 0~100℃, an operating pressure of 2.0~3.0MPa, and a volume hourly space velocity of less than 7000h⁻¹. -1 .

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The silver-based arsenic removal agent provided by this invention combines the advantages of low cost, high safety, and multifunctional integration through the synergistic effect of multiple components. First, this invention controls the content of the active component, silver, at 0.3~0.8wt%, far lower than that of traditional arsenic removal agents, significantly reducing raw material costs. Combined with bimetallic additives, especially the regulation of the electronic structure of silver by tin oxide, it not only improves the stability of silver but also effectively blocks the continuous sites for the formation of silver acetylene (an explosive compound) from silver and acetylene, eliminating safety hazards in equipment operation. The interaction between indium oxide and silver further enhances metal dispersion. Cerium oxide in the modifier utilizes its excellent oxygen storage and release capacity to promote the oxidative activation of arsine, while the polydopamine carbon skeleton acts as a robust interface layer to firmly anchor the active component. The organic combination of these components enables this arsenic removal agent to achieve simultaneous and deep removal of arsenic, mercury, and hydrogen sulfide from ethylene cracking C2 materials, achieving the required purification precision without the need for additional independent mercury or sulfur removal protective beds, thus significantly reducing equipment investment and process complexity.

[0036] 2. The modified alumina support of this invention solves the problems of easy coking and difficult dispersion of active components through multi-level structural regulation. First, boron source doping effectively regulates the acidity distribution on the alumina surface, reduces strong acid sites, thereby significantly inhibiting the polymerization and coking of olefins on the support surface and constructing a mesoporous framework with high hydrothermal stability. More importantly, through KH560 coupling and cystamine grafting, abundant disulfide bonds (-SS-) are successfully introduced on the support surface. This functional group plays a decisive role in the loading of silver ions: using the soft and hard acid-base theory, there is a very strong coordination complexation between sulfur atoms and silver. The disulfide bonds act as "molecular anchors" to firmly fix the silver species, forcing silver to be in an atomically highly dispersed state in the form of single atoms or nanoclusters, effectively preventing the migration and aggregation of silver microcrystals during reduction and reaction processes. It is this unique "sulfur-silver anchoring effect" that enables the present invention to expose more active sites than traditional high-silver carriers even with extremely low silver content (<1%), thereby achieving excellent arsenic removal activity; at the same time, the disulfide bond and the introduced amino group also endow the carrier itself with a strong ability to capture mercury and hydrogen sulfide. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is the silver-based arsenic removal agent product prepared in Example 1 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0040] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0041] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0042] (1) Boehmite is mixed with a boron source (the boron source is selected from one or more of boric acid, boron oxide, sodium borate, potassium borate, and ammonium borate, and the amount of boron source added is 0.5~1.0 wt% of the mass of boehmite, calculated as B2O3), and a nitric acid aqueous solution with a concentration of 3~10 wt% is added as an acidic binder for kneading and molding. The shaped material is calcined at 550~600℃ for 3~4h, and then treated at 180~220℃, 0.8~1.2 MPa, and water vapor atmosphere for 2~3h to obtain pretreated alumina;

[0043] (2) Disperse the pretreated alumina into an ethanol / water mixture, and then add silane coupling agent KH560; the volume ratio of ethanol to deionized water in the ethanol / water mixture is 90~95: 5~10, and the amount of ethanol / water mixture used is 80~160mL and the amount of silane coupling agent KH560 used is 2~5mL per 5g of pretreated alumina; stir and reflux at 66~78℃ for 4~7h, after the reaction is completed, centrifuge the product, wash it with anhydrous ethanol 2~5 times, and finally place it in an oven at 105~115℃ for heat treatment for 1~2h to obtain functionalized alumina;

[0044] (3) Disperse functionalized alumina in ethanol, add triethylamine and cystamine dihydrochloride; relative to 5g of functionalized alumina, the amount of ethanol is 60~120mL, the amount of triethylamine is 2~5mL, and the amount of cystamine dihydrochloride is 1~3g; seal and stir the reaction at 50~65℃ for 12~24h, filter the reaction product, wash it with anhydrous ethanol and deionized water alternately by ultrasonic washing 3 times, and dry it to obtain modified alumina;

[0045] (4) Prepare silver nitrate aqueous solution, vacuum impregnate the modified alumina for 0.5~2h, dry it at 100~120℃, and reduce it at 200~220℃ for 2~4h in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 5~15%) to obtain silver-containing carrier.

[0046] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 1~3:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 100~120℃, and then calcined at 380~420℃ for 2~4h to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0047] (6) Coat the intermediate with 0.1~1 mol / L cerium oxide sol and calcine it at 350~400℃ for 2~4 h. After cooling, modify it with a dopamine solution with a concentration of 2~8 g / L and a pH of 8~9. The amount of dopamine solution used is 50~150 mL relative to 5 g of intermediate. Finally, vacuum dry it at 100~110℃. Dopamine self-polymerizes on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for ethylene plants.

[0048] The final composition of the arsenic removal agent (by total mass) is: 0.3-0.8 wt% active component silver; 5.0-8.0 wt% bimetallic additive (composed of 3.0-5.0 wt% indium oxide and 2.0-3.0 wt% tin oxide); 1.2-2.0 wt% modifier (composed of 0.8-1.2 wt% cerium oxide and 0.4-0.8 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0049] The present invention will be further described below through specific embodiments.

[0050] Example 1

[0051] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0052] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 1.0% of the mass of boehmite, calculated as B2O3), and 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 600℃ for 3h, and then treated at 220℃, 1.2 MPa and water vapor atmosphere for 2h to obtain pretreated alumina.

[0053] (2) Disperse 5g of pretreated alumina into 160mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 5mL of silane coupling agent KH560, stir and reflux at 78℃ for 4h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 115℃ for 1h to obtain functionalized alumina.

[0054] (3) Disperse 5g of functionalized alumina into 120mL of ethanol, add 5mL of triethylamine and 3g of cystamine dihydrochloride, seal and stir at 65℃ for 12h. After filtering the reaction product, wash it with anhydrous ethanol and deionized water three times by alternating ultrasonication, and dry it to obtain modified alumina.

[0055] (4) Prepare an aqueous solution of silver nitrate, vacuum impregnate the modified alumina for 2 hours, dry it at 120°C, and then reduce it at 220°C for 2 hours in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain a silver-containing carrier.

[0056] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 120°C, and then calcined at 420°C for 2 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0057] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 400°C for 2 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0058] The final composition of the arsenic removal agent (by total mass) is: 0.8 wt% active component silver; 8.0 wt% bimetallic additive (composed of 5.0 wt% indium oxide and 3.0 wt% tin oxide); 2.0 wt% modifier (composed of 1.2 wt% cerium oxide and 0.8 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0059] Example 2

[0060] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0061] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 0.8% of the mass of boehmite, calculated as B2O3), and 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 580℃ for 3h, and then treated at 210℃, 1.1MPa and water vapor atmosphere for 2h to obtain pretreated alumina.

[0062] (2) Disperse 5g of pretreated alumina into 160mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 4mL of silane coupling agent KH560, stir and reflux at 74℃ for 5h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 110℃ for 1h to obtain functionalized alumina.

[0063] (3) Disperse 5g of functionalized alumina into 100mL of ethanol, add 4mL of triethylamine and 2g of cystamine dihydrochloride, seal and stir at 60℃ for 16h. After filtering the reaction product, wash it three times with anhydrous ethanol and deionized water by alternating ultrasonication, and dry it to obtain modified alumina.

[0064] (4) Prepare silver nitrate aqueous solution, vacuum impregnate the modified alumina for 1.5 h, dry it at 115 °C, and then reduce it at 215 °C for 3 h in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain silver-containing carrier.

[0065] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 115°C, and then calcined at 410°C for 3 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0066] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 380°C for 3 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0067] The final composition of the arsenic removal agent (by total mass) is: 0.6 wt% active component silver; 7.0 wt% bimetallic additive (composed of 4.5 wt% indium oxide and 2.5 wt% tin oxide); 1.8 wt% modifier (composed of 1.1 wt% cerium oxide and 0.7 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0068] Example 3

[0069] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0070] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 0.7% of the mass of boehmite, calculated as B2O3), and 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 560℃ for 4h, and then treated at 200℃, 1.0 MPa and water vapor atmosphere for 3h to obtain pretreated alumina.

[0071] (2) Disperse 5g of pretreated alumina into 120mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 3mL of silane coupling agent KH560, stir and reflux at 70℃ for 6h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 110℃ for 1.5h to obtain functionalized alumina;

[0072] (3) Disperse 5g of functionalized alumina into 100mL of ethanol, add 3mL of triethylamine and 2g of cystamine dihydrochloride, seal and stir at 55℃ for 20h. After filtering the reaction product, wash it with anhydrous ethanol and deionized water three times by alternating ultrasonication, and dry it to obtain modified alumina.

[0073] (4) Prepare silver nitrate aqueous solution, vacuum impregnate the modified alumina for 1 hour, dry it at 105°C, and then reduce it at 205°C for 3 hours in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain silver-containing carrier.

[0074] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 105°C, and then calcined at 390°C for 3 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0075] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 360°C for 3 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0076] The final composition of the arsenic removal agent (by total mass) is: 0.5 wt% active component silver; 6.0 wt% bimetallic additive (composed of 3.5 wt% indium oxide and 2.5 wt% tin oxide); 1.5 wt% modifier (composed of 1.0 wt% cerium oxide and 0.5 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0077] Example 4

[0078] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0079] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 0.5% of the mass of boehmite, calculated as B2O3), and a 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 550℃ for 4h, and then treated at 180℃, 0.8MPa and water vapor atmosphere for 3h to obtain pretreated alumina.

[0080] (2) Disperse 5g of pretreated alumina into 120mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 2mL of silane coupling agent KH560, stir and reflux at 66℃ for 7h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 105℃ for 2h to obtain functionalized alumina;

[0081] (3) Disperse 5g of functionalized alumina into 100mL of ethanol, add 2mL of triethylamine and 1g of cystamine dihydrochloride, seal and stir at 50℃ for 24h. After filtering the reaction product, wash it with anhydrous ethanol and deionized water three times by alternating ultrasonication, and dry it to obtain modified alumina.

[0082] (4) Prepare silver nitrate aqueous solution, vacuum impregnate the modified alumina for 0.5 h, dry it at 100 °C, and then reduce it at 200 °C for 4 h in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain silver-containing carrier.

[0083] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 100°C, and then calcined at 380°C for 4 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0084] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 350°C for 4 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0085] The final composition of the arsenic removal agent (by total mass) is: 0.3 wt% active component silver; 5.0 wt% bimetallic additive (composed of 3.0 wt% indium oxide and 2.0 wt% tin oxide); 1.2 wt% modifier (composed of 0.8 wt% cerium oxide and 0.4 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0086] Comparative Example 1

[0087] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0088] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 1.0% of the mass of boehmite, calculated as B2O3), and 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 600℃ for 3h, and then treated at 220℃, 1.2 MPa and water vapor atmosphere for 2h to obtain pretreated alumina.

[0089] (2) Disperse 5g of pretreated alumina into 160mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 5mL of silane coupling agent KH560, stir and reflux at 78℃ for 4h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 115℃ for 1h to obtain functionalized alumina.

[0090] (3) Disperse 5g of functionalized alumina into 120mL of ethanol, add 3g of cystamine dihydrochloride, soak for 2h, filter and dry the product to obtain modified alumina;

[0091] (4) Prepare an aqueous solution of silver nitrate, vacuum impregnate the modified alumina for 2 hours, dry it at 120°C, and then reduce it at 220°C for 2 hours in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain a silver-containing carrier.

[0092] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 120°C, and then calcined at 420°C for 2 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0093] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 400°C for 2 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0094] The final composition of the arsenic removal agent (by total mass) is: 0.8 wt% active component silver; 8.0 wt% bimetallic additive (composed of 5.0 wt% indium oxide and 3.0 wt% tin oxide); 2.0 wt% modifier (composed of 1.2 wt% cerium oxide and 0.8 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0095] Comparative Example 2

[0096] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0097] (1) Add boehmite to a 6wt% nitric acid aqueous solution for kneading and molding. The shaped material is calcined at 600℃ for 3h, and then treated at 220℃, 1.2 MPa and water vapor atmosphere for 2h to obtain pretreated alumina.

[0098] (2) Disperse 5g of pretreated alumina into 160mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 5mL of silane coupling agent KH560, stir and reflux at 78℃ for 4h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 115℃ for 1h to obtain functionalized alumina.

[0099] (3) Disperse 5g of functionalized alumina into 120mL of ethanol, add 5mL of triethylamine and 3g of cystamine dihydrochloride, seal and stir at 65℃ for 12h. After filtering the reaction product, wash it with anhydrous ethanol and deionized water three times by alternating ultrasonication, and dry it to obtain modified alumina.

[0100] (4) Prepare an aqueous solution of silver nitrate, vacuum impregnate the modified alumina for 2 hours, dry it at 120°C, and then reduce it at 220°C for 2 hours in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain a silver-containing carrier.

[0101] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 120°C, and then calcined at 420°C for 2 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0102] (6) 0.5 mol / L cerium oxide sol was coated on the intermediate and calcined at 400°C for 2 h. After cooling, it was modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5. The amount of dopamine solution used was 100 mL relative to 5 g of intermediate. Finally, it was vacuum dried at 105°C. Dopamine self-polymerized on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0103] The final composition of the arsenic removal agent (by total mass) is: 0.8 wt% active component silver; 8.0 wt% bimetallic additive (composed of 5.0 wt% indium oxide and 3.0 wt% tin oxide); 2.0 wt% modifier (composed of 1.2 wt% cerium oxide and 0.8 wt% polydopamine carbon skeleton); and the balance modified alumina.

[0104] Comparative Example 3

[0105] A method for preparing a silver-based arsenic removal agent for ethylene plants includes the following steps:

[0106] (1) Boehmite was mixed with boric acid (the amount of boric acid added was 1.0% of the mass of boehmite, calculated as B2O3), and 6wt% nitric acid aqueous solution was added as an acidic binder for kneading and molding. The shaped material was calcined at 600℃ for 3h, and then treated at 220℃, 1.2 MPa and water vapor atmosphere for 2h to obtain pretreated alumina.

[0107] (2) Disperse 5g of pretreated alumina into 160mL of ethanol / water mixture (the volume ratio of ethanol to deionized water is 95:5), then add 5mL of silane coupling agent KH560, stir and reflux at 78℃ for 4h, after the reaction is completed, centrifuge the product, wash it 3 times with anhydrous ethanol, and finally heat treat it in an oven at 115℃ for 1h to obtain functionalized alumina.

[0108] (3) Disperse 5g of functionalized alumina into 120mL of ethanol, add 5mL of triethylamine and 3g of cystamine dihydrochloride, seal and stir at 65℃ for 12h. After filtering the reaction product, wash it with anhydrous ethanol and deionized water three times by alternating ultrasonication, and dry it to obtain modified alumina.

[0109] (4) Prepare an aqueous solution of silver nitrate, vacuum impregnate the modified alumina for 2 hours, dry it at 120°C, and then reduce it at 220°C for 2 hours in a mixed gas atmosphere of hydrogen and nitrogen (hydrogen volume percentage of 10%) to obtain a silver-containing carrier.

[0110] (5) Using indium nitrate as the indium source and tin chloride as the tin source, a mixed solution was prepared with an indium nitrate to tin chloride molar ratio of 2:1 (the volume of which matched the pore volume of the silver-containing carrier). The silver-containing carrier was impregnated, dried at 120°C, and then calcined at 420°C for 2 hours to obtain an intermediate loaded with silver, indium oxide and tin oxide.

[0111] (6) The intermediate is modified with a dopamine solution with a concentration of 5 g / L and a pH of 8.5; the amount of dopamine solution used is 100 mL relative to 5 g of intermediate; finally, it is vacuum dried at 105 °C, and the dopamine self-polymerizes on the surface to form a polydopamine carbon skeleton, thus obtaining the silver-based arsenic removal agent for the ethylene plant.

[0112] The final composition of the arsenic removal agent (by total mass) is: 0.8 wt% active component silver; 8.0 wt% bimetallic additive (composed of 5.0 wt% indium oxide and 3.0 wt% tin oxide); 0.8 wt% polydopamine carbon skeleton; and the balance modified alumina.

[0113] The arsenic removal agents prepared in Examples 1-4 and Comparative Examples 1-3 were evaluated using a micro fixed-bed reactor.

[0114] Simulated feed gas: vinyl gas containing 2000 ppb arsine, 50 ppb mercury, and 1000 ppb hydrogen sulfide.

[0115] Reaction conditions: reaction temperature 50℃, system pressure 2.0MPa, gas hourly space velocity 3000h⁻¹ -1 .

[0116] Test metric definition:

[0117] Arsenic penetration capacity: The cumulative amount of arsenic adsorbed (mg / g) when the arsenic content at the reactor outlet first exceeds 10 ppb.

[0118] Arsenic content at the outlet: The average arsenic concentration (ppb) at the outlet after 48 hours of stable operation of the reaction, which characterizes the purification accuracy.

[0119] Mercury removal / desulfurization rate: (inlet concentration - outlet concentration) / inlet concentration × 100%.

[0120] Carbon deposit amount: The percentage of carbon deposit mass determined by thermogravimetric analysis (TGA) of the sample taken after 200 hours of reaction.

[0121] Lateral pressure strength: The average crushing force was measured by taking 20 shaped particles.

[0122] See Table 1 for specific data.

[0123] Table 1. Performance test results of arsenic removal agent

[0124]

[0125] Examples 1-4 demonstrate the performance changes as the silver content decreases from 0.8 wt% to 0.3 wt%. The results show that even under extreme conditions with a silver content of only 0.3 wt% (Example 4), the arsenic removal agent maintains a high penetration arsenic capacity of 21.5 mg / g and an outlet arsenic content of less than 5 ppb. This strongly demonstrates that the unique anchoring structure of "modified alumina-disulfide bond-silver" constructed in this invention successfully achieves atomic-level high dispersion of silver. Compared to traditional technologies that typically require 5-10% silver content, this invention significantly reduces the cost of precious metals (by more than 90%) while maintaining excellent performance for industrial applications.

[0126] Although cystamine was added during the preparation of Comparative Example 1, the reflux and triethylamine catalytic process were not used, resulting in the failure of grafting KH560 with cystamine and the failure to form effective disulfide bonds (-SS-). The results showed that the arsenic penetration capacity decreased from 28.5 mg / g to 10.2 mg / g, indicating the lack of sulfur atom coordination anchoring, silver aggregation, and a sharp reduction in active sites; the mercury removal rate plummeted from 99.8% to 18.5%, proving that the disulfide bonds and amino groups on the support surface are the key active centers for mercury capture. This confirms that the organic functional groups introduced through grafting in this invention are the core of achieving "simultaneous removal of arsenic, mercury, and sulfur."

[0127] Comparative Example 2, without the introduction of a boron source, exhibited a carbon deposition of 5.8 wt% after 200 hours of operation, nearly 10 times that of Example 1 (0.6 wt%); and its lateral pressure strength was significantly reduced. This indicates that the introduction of boron effectively modulates the acidity distribution on the alumina surface, suppresses the side reaction of olefin polymerization and coking, and enhances the hydrothermal stability of the framework, thus solving the problem of easy coking and powdering of traditional alumina supports.

[0128] Comparative Example 3, without cerium oxide coating, although its arsenic capacity was acceptable, had an export arsenic content as high as 28 ppb, failing to meet the deep removal standard of <10 ppb. This is because the removal of AsH3 relies on the "oxidation-adsorption" mechanism. Without cerium oxide, an oxidizing agent with oxygen storage and release functions, AsH3 cannot be rapidly oxidized into non-volatile arsenic oxides, resulting in the phenomenon of "fast penetration but poor precision".

[0129] In summary, the arsenic removal agent provided by this invention, through multi-component and multi-scale synergistic regulation, combines the advantages of low cost (low silver), high activity (high dispersion), high precision (Ce-assisted), multi-functionality (mercury removal and desulfurization), and high stability (anti-coking), and has extremely high industrial application value.

[0130] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A silver-based arsenic removal agent for ethylene plants, characterized in that, Based on the total mass of the arsenic removal agent as 100%, the arsenic removal agent contains the following components: 0.3~0.8% active component silver; 5.0~8.0% bimetallic additive, wherein the bimetallic additive is composed of 3.0~5.0% indium oxide and 2.0~3.0% tin oxide; 1.2~2.0% modifier, wherein the modifier is composed of 0.8~1.2% cerium oxide and 0.4~0.8% polydopamine; and the balance being modified alumina; The modified alumina was prepared by the following steps: (1) Mix boehmite with boron source, add acid binder, knead and shape, calcine and then perform hydrothermal treatment to obtain pretreated alumina; (2) Disperse the pretreated alumina into an ethanol / water mixture, add KH560, reflux the reaction, centrifuge, wash and dry the product to obtain functionalized alumina; (3) Disperse the functionalized alumina in ethanol, then add triethylamine and cystamine dihydrochloride, seal and stir the reaction, filter, wash and dry the product to obtain modified alumina; The preparation method of the silver-based arsenic removal agent includes the following steps: (a) The silver precursor was prepared into a silver solution, which was then vacuum impregnated with modified alumina. After drying, the solution was subjected to reduction treatment under a reducing atmosphere to obtain a silver-containing carrier. (b) Prepare a mixed solution of indium salt and tin salt, impregnate it with a silver-containing carrier, dry it and then calcine it to obtain an intermediate loaded with silver, indium oxide and tin oxide; (c) Cerium oxide sol is coated onto the intermediate, calcined, modified with dopamine solution, and finally dried under vacuum to obtain the silver-based arsenic removal agent for the ethylene plant.

2. The silver-based arsenic removal agent according to claim 1, characterized in that, In step (1), the boron source is one or more of boric acid, boron oxide, sodium borate, potassium borate, and ammonium borate; the amount of boron source added, calculated as B2O3, is 0.5~1.0 wt% of the mass of boehmite; the acidic binder is a 3~10 wt% aqueous solution of nitric acid; the calcination conditions are calcination at 550~600℃ for 3~4h; the hydrothermal treatment conditions are treatment at 180~220℃ and 0.8~1.2 MPa in a steam atmosphere for 2~3h.

3. The silver-based arsenic removal agent according to claim 1, characterized in that, In step (2), the ratio of pretreated alumina, ethanol / water mixture, and KH560 is 5g:80~160mL:2~5mL; the volume ratio of ethanol and deionized water in the ethanol / water mixture is 90~95:5~10.

4. The silver-based arsenic removal agent according to claim 1, characterized in that, In step (2), the reflux reaction conditions are: stirring and refluxing at 66~78℃ for 4~7h; the product is washed 2~5 times with anhydrous ethanol, and then placed in an oven at 105~115℃ for 1~2h for heat treatment.

5. The silver-based arsenic removal agent according to claim 1, characterized in that, In step (3), the ratio of functionalized alumina, ethanol, triethylamine, and cystamine dihydrochloride is 5g:60~120mL:2~5mL:1~3g; the stirring reaction conditions are 50~65℃ for 12~24h; the product is then ultrasonically washed three times with anhydrous ethanol and deionized water alternately.

6. A method for preparing the silver-based arsenic removal agent as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (a) The silver precursor was prepared into a silver solution, which was then vacuum impregnated with modified alumina. After drying, the solution was subjected to reduction treatment under a reducing atmosphere to obtain a silver-containing carrier. (b) Prepare a mixed solution of indium salt and tin salt, impregnate it with a silver-containing carrier, dry it and then calcine it to obtain an intermediate loaded with silver, indium oxide and tin oxide; (c) Cerium oxide sol is coated onto the intermediate, calcined, modified with dopamine solution, and finally dried under vacuum to obtain the silver-based arsenic removal agent for the ethylene plant.

7. The preparation method according to claim 6, characterized in that, In step (a), the silver precursor is silver nitrate; the reducing atmosphere is a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 5-15%, the reduction temperature is 200-220℃, and the reduction time is 2-4h.

8. The preparation method according to claim 6, characterized in that, In step (b), the indium salt is indium nitrate, the tin salt is tin chloride, and the molar ratio of indium nitrate to tin chloride is 1~3:1; the calcination conditions are calcination at 380~420℃ for 2~4h.

9. The preparation method according to claim 6, characterized in that, In step (c), the calcination conditions are calcination at 350~400℃ for 2~4h; the concentration of the dopamine solution is 2~8g / L, and the pH value is 8~9; the vacuum drying temperature is 100~110℃.

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