Alumina-type adsorbent and preparation method thereof

Abstract

The present application relates to the technical field of adsorbents, and specifically discloses an alumina-type adsorbent and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing a lanthanum salt, a cerium salt and a polyethylene glycol aqueous solution, and then uniformly mixing the mixture with γ-Al2O3, adjusting the pH, allowing the mixture to stand, performing solid-liquid separation, drying, and calcining to obtain a dual-doped carrier; dispersing the dual-doped carrier in a mixed solution containing 2-methylimidazole, an iron salt and a zinc salt, adjusting the pH, heating the solution under an inert atmosphere, performing solid-liquid separation, drying, and grinding the solution to obtain a powder, which is then molded to obtain a composite carrier; uniformly mixing an Ag-modified molecular sieve and a silica sol, coating the mixture on the surface of the composite carrier, and drying to obtain an adsorbent precursor; immersing the adsorbent precursor in a dispersion, immersing the mixture, performing solid-liquid separation, drying, and then reactivating the mixture to obtain an alumina-type adsorbent; the adsorbent prepared in the present application can synergistically and efficiently remove multiple impurities and has excellent corrosion resistance.

Description

Technical Field

[0001] The present application relates to the technical field of adsorbents, and more specifically, to an alumina-type adsorbent and a preparation method thereof. Background Art

[0002] In the propane dehydrogenation process to produce propylene, impurities such as sulfides (H2S, thiophene), acidic gases (such as HCl), and moisture in the feed gas can severely impact the activity, selectivity, and stability of the catalyst, and can even lead to catalyst poisoning, equipment corrosion, and coking. Traditional purification processes often utilize aluminum chloride-based adsorbents. Their acidic sites have a certain adsorption capacity for acidic gases like HCl, but they have significant inherent drawbacks: aluminum chloride readily sublimates and decomposes at high temperatures (sublimation at 178°C), leading to the loss of active components and the release of corrosive HCl. It is highly hygroscopic and easily hydrolyzes to produce hydrochloric acid, exacerbating equipment corrosion. Furthermore, its adsorption selectivity for organic sulfur compounds (such as thiophene) is insufficient, making it difficult to meet modern industry's requirements for adsorbents with high-temperature resistance, corrosion resistance, and deep desulfurization.

[0003] With advances in catalytic technology (for example, Pt-Sn / Al2O3 dehydrogenation catalysts require a total sulfur content of less than 0.1 ppm), developing new, highly selective adsorbents has become crucial. Alumina-based adsorbents have become a research focus due to their low cost and ease of modification. Patent application publication number CN112619590A discloses a regenerable hydrogen sulfide adsorbent consisting of an active component and a support: a metaaluminate active component and an activated alumina support. The active component is bonded to the support by solution impregnation, spraying, or solid mixing.

[0004] Although the aluminate / alumina composite adsorbent produced by this technical solution has made progress in H2S removal, industrial gases also contain multiple impurities such as hydrogen chloride, organic sulfur (such as thiophene) and water. Due to competitive adsorption, the dynamic adsorption capacity of H2S will be significantly reduced, and the penetration rate of organic sulfur such as thiophene will increase simultaneously. In addition, the adsorbent lacks a chloride ion fixation mechanism, and the continuous reaction of HCl gas with the Al2O3 carrier triggers chlorination corrosion, resulting in the collapse of the pore structure. Summary of the Invention

[0005] In order to solve the technical problems of existing adsorbents in industrial gas purification, such as competitive adsorption of multiple impurities leading to a decrease in H2S dynamic adsorption capacity, an increase in organic sulfur penetration rate, and HCl-induced chlorination corrosion causing collapse of the pore structure, the present application provides an alumina-type adsorbent and a preparation method thereof.

[0006] In a first aspect, the present application provides a method for preparing an alumina-type adsorbent, which adopts the following technical solution:

[0007] A method for preparing an alumina-type adsorbent comprises the following steps:

[0008] (1) The lanthanum salt, the cerium salt and the polyethylene glycol aqueous solution are mixed evenly, and then mixed evenly with γ-Al2O3, and the pH is adjusted to 5-6. The mixture is allowed to stand, solid-liquid separation is performed, dried, and calcined to obtain a dual-doped carrier; the dual-doped carrier is dispersed in a mixed solution containing 2-methylimidazole, iron salt and zinc salt, and the pH is adjusted to 8-9. The mixture is heated to 60-80°C under an inert atmosphere, reacted for 12-24 hours, solid-liquid separation is performed, dried, and ground to obtain a powder. The powder is then shaped to obtain a composite carrier;

[0009] (2) Evenly mixing the Ag-modified molecular sieve and silica sol, coating the mixture on the surface of the composite support, and drying the mixture to obtain an adsorbent precursor;

[0010] (3) Immersing the adsorbent precursor in a dispersion containing perfluoropolyether and silanized nano-silica for 10 to 20 minutes, separating the solid and liquid, drying, and then reactivating to obtain an alumina-type adsorbent;

[0011] The molar ratio of the γ-Al2O3, lanthanum salt, cerium salt, 2-methylimidazole, iron salt and zinc salt is 50: (3-5): (1-2): (8-12): (0.5-0.7): (0.3-0.5).

[0012] In this technical solution, firstly, lanthanum and cerium are doped into γ-Al2O3 to construct an alkaline adsorption substrate. The alkaline sites and redox properties of rare earth elements are used to capture gaseous H2S, gaseous HCl and other gases in a targeted manner and form stable compounds. At the same time, the carrier's resistance to chloride corrosion is enhanced by lattice doping. Then, a transition metal (Fe 2+ / Zn 2+ ) and 2-methylimidazole to form a porous coordination layer, Fe 2+ / Zn 2+ As Lewis acid centers, they achieve targeted and efficient adsorption of organic sulfur through coordination with thiophene sulfur atoms and the molecular sieving effect of nanopores, reducing competitive adsorption with acidic gases. The synergistic design of these two creates a layered adsorption mechanism where the inner alkaline sites capture acidic gases while the outer coordination structure enriches organic sulfur. This not only reduces competitive adsorption of H2S, HCl, and thiophene, but also enhances the carrier's impact resistance and mass transfer efficiency through the complementary effects of the rigid rare earth skeleton and the flexible pores of the transition metal.

[0013] Then, through the microporous physical adsorption and silver ion chemical precipitation effects of Ag-modified molecular sieves, deep removal of H2S and microporous physical adsorption to intercept water are achieved, reducing the concentration of gas-phase impurities and alleviating the burden on the subsequent adsorption layer; finally, a low surface energy hydrophobic barrier is constructed by perfluoropolyether impregnation. On the one hand, it reduces the penetration of liquid HCl into the interior of the carrier and reduces the corrosion path of Al2O3→AlCl3. On the other hand, through surface polarity regulation, acidic gases are quickly captured by the alkaline sites in the inner layer of the composite carrier, and organic sulfur is directionally enriched in the outer layer of the composite carrier, thereby forming a progressive purification mechanism, and ultimately achieving the synergistic and efficient removal of multiple impurities and long-term stability of the adsorbent structure.

[0014] Preferably, the mass ratio of the Ag-modified molecular sieve to the composite carrier is 1:(3-5).

[0015] Preferably, the polyethylene glycol aqueous solution comprises polyethylene glycol 400 and water, and the mass concentration of the polyethylene glycol aqueous solution is 5% to 8%.

[0016] Preferably, the lanthanum salt is lanthanum nitrate hexahydrate.

[0017] Preferably, the cerium salt is cerium nitrate hexahydrate.

[0018] Preferably, the iron salt is ferric nitrate nonahydrate, and the zinc salt is zinc nitrate hexahydrate.

[0019] Preferably, in step (1), the standing temperature is 20-25° C., and the standing time is 12-18 h.

[0020] Preferably, in step (1), the calcination conditions are: a temperature of 500-600°C, calcination for 2-4 hours, during which a mixed gas of oxygen and nitrogen is continuously introduced, the volume ratio of oxygen to nitrogen is (5-10): (90-95), and the flow rate of the mixed gas is 50-100 mL / min.

[0021] Preferably, in step (1), the solvent used in the mixed solution includes N,N-dimethylformamide, ethanol and water.

[0022] Preferably, the volume ratio of N,N-dimethylformamide, ethanol and water is (4-6): (2-4): (1-3).

[0023] Preferably, in step (1), the molding process comprises: adding silica sol, camphor and ethyl orthosilicate to the powder, mixing, molding, drying, and then performing a staged calcination process.

[0024] Preferably, in step (1), the molding process is as follows: adding 3% to 5% of silica sol by weight of the powder, 2% to 4% of camphor by weight of the powder, and 0.5% to 1.5% of ethyl orthosilicate by weight of the powder, mixing them evenly, pressing them into tablets (diameter 1 to 2 mm), drying them, calcining them at 165 to 175° C. for 90 to 120 min, heating them to 245 to 265° C., calcining them for 150 to 210 min, and cooling them to obtain the product.

[0025] During the molding process of this technical solution, camphor volatilizes during low-temperature roasting to form a porous structure, providing channels for gas diffusion; ethyl orthosilicate enhances the interfacial bonding strength of each component through chemical cross-linking, constructs a strong skeleton and forms an anti-corrosion barrier. The two synergistically optimize the mass transfer efficiency and structural stability of the adsorbent, solving the problems of pore blockage and interface peeling in traditional processes, and enabling the adsorbent to have both high-efficiency adsorption and industrial durability.

[0026] Preferably, in step (2), the preparation method of the Ag-modified molecular sieve comprises the following steps:

[0027] The MCM-41 molecular sieve was immersed in a mixed solution containing 0.05-0.2 mol / L silver nitrate and 0.1-0.2 mol / L citric acid, heated to 40-60°C, reacted for 6-10 hours, solid-liquid separation, dried, and calcined at 300-400°C for 2-4 hours under an inert atmosphere to obtain the Ag-modified molecular sieve.

[0028] In this technical solution, the MCM-41 molecular sieve is immersed in a mixed solution of silver nitrate and citric acid, and the Ag is chelated by the citric acid. + Evenly dispersed in the mesoporous channels of the molecular sieve, after mild reaction and calcination, highly dispersed Ag is formed. + active sites and firmly anchored on the pore surface.

[0029] Preferably, in step (2), the amount of the silica sol used is 3% to 8% of the mass of the Ag-modified molecular sieve.

[0030] Preferably, the mass concentration of the silica sol is 20% to 40%.

[0031] Preferably, in step (3), in the dispersion, the mass concentration of perfluoropolyether is 5% to 10%, and the mass concentration of silanized nano-silica is 2% to 3%.

[0032] Preferably, the dispersion further comprises sodium lauryl sulfate at a mass concentration of 0.5% to 1%.

[0033] In this technical solution, perfluoropolyether forms a chemically inert hydrophobic barrier on the surface of the composite carrier. Its low surface energy characteristics not only reduce the penetration of liquid HCl, but also reduce the residence of acidic gases on the adsorbent surface, allowing it to diffuse faster into the interior and be captured by alkaline sites. Silanized nano-silica enhances the mechanical strength of the barrier layer through physical inlay and chemical bonding. The nano-scale protrusion structure on its surface not only increases the hydrophobic contact area but also provides anchoring points for perfluoropolyether, preventing the coating from falling off under high-temperature regeneration or high-speed airflow impact. The two together construct a dual protection mechanism to solve the problems of traditional hydrophobic coatings that are easy to peel off and have poor corrosion resistance and durability, ensuring that the adsorbent maintains structural integrity and adsorption activity for a long time under complex working conditions.

[0034] Preferably, the mass ratio of the composite carrier to the dispersion is (0.4-0.5):1.

[0035] Preferably, in step (3), the solvent used in the dispersion is N,N-dimethylformamide.

[0036] Preferably, the preparation method of the silanized nano-silicon dioxide comprises the following steps:

[0037] Disperse nano-silica in ethanol aqueous solution, add 3-aminopropyltriethoxysilane accounting for 5% to 10% of the mass of nano-silica, adjust the pH to 4 to 5, raise the temperature to 50 to 70°C, react for 4 to 8 hours, separate the solid and liquid, and dry to obtain the product.

[0038] Preferably, the activation in step (3) is as follows: heating to 230-250° C. under an inert atmosphere and activating for 40-60 min.

[0039] Preferably, in step (3), after drying, the step of vapor deposition of fluorosilane is also included.

[0040] Preferably, the step of vapor depositing fluorosilane is: introducing fluorosilane at a flow rate of 40-60 mL / min for 25-30 min under the conditions of 180-200° C. and a nitrogen flow rate of 300-350 mL / min.

[0041] Preferably, the fluorosilane is heptadecafluorodecyltrimethoxysilane.

[0042] In this technical solution, on the basis of the hydrophobic barrier constructed by perfluoropolyether and silanized nano-silica, heptadecafluorodecyltrimethoxysilane is further used for vapor deposition modification. The long-chain fluoroalkyl group in its molecular structure, with its lower surface energy characteristics, undergoes condensation reaction with the hydroxyl group on the carrier surface through the trimethoxy group to form a covalently bonded molecular-level dense hydrophobic layer. This layer synergistically enhances the hydrophobicity, chemical inertness and mechanical strength of the previous coating, thereby achieving corrosion resistance and optimization of adsorption selectivity.

[0043] In a second aspect, the present application provides an alumina adsorbent prepared by the above preparation method.

[0044] In summary, this application has the following beneficial effects:

[0045] 1. This application constructs an alkaline substrate by rare earth dual-doped alumina, and cooperates with a bimetallic coordination layer, Ag-modified molecular sieve and perfluoropolyether hydrophobic layer to form a layered adsorption and anti-corrosion mechanism, thereby achieving efficient removal of multiple impurities and long-term stability of the carrier structure.

[0046] 2. After further deposition of fluorosilane, the hydrophobicity and chemical inertness of the adsorbent surface are significantly enhanced, which can effectively block water vapor penetration and inhibit acidic liquid phase corrosion; at the same time, the adsorption selectivity of organic sulfur is optimized by regulating the surface polarity, and the removal ability of gaseous H2S, gaseous HCl, etc. is enhanced, which significantly prolongs the adsorption saturation time and increases the adsorption capacity. The performance is better maintained after regeneration, thereby enhancing the long-term stability of the adsorbent under complex working conditions such as high temperature, high humidity, and strong acidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the XRD spectrum of the alumina-type adsorbent prepared in Example 2. DETAILED DESCRIPTION

[0048] The present application is further described in detail below with reference to the embodiments.

[0049] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0050] The molecular weight of perfluoropolyether is 2000~5000, and the fluorine content is ≥70%.

[0051] Preparation Examples 1-3 Silanized Nanosilica

[0052] Preparation Example 1

[0053] Add 10 g of nano-silica to 100 mL of ethanol-water solution, ultrasonically disperse for 30 min, add 0.75 g of 3-aminopropyltriethoxysilane, adjust the pH to 4.5 with 10% dilute nitric acid, heat to 60°C, react for 6 h, filter, wash twice with anhydrous ethanol, and dry at 80°C to constant weight.

[0054] Among them, the particle size distribution of nano-silica is 15~30nm.

[0055] Preparation Example 2

[0056] Add 10 g of nano-silica to 100 mL of ethanol-water solution, ultrasonically disperse for 30 min, add 0.5 g of 3-aminopropyltriethoxysilane, adjust the pH to 5 with 10% dilute nitric acid, heat to 50°C, react for 8 h, filter, wash twice with anhydrous ethanol, and dry at 80°C to constant weight to obtain the product.

[0057] Among them, the particle size distribution of nano-silica is 15~30nm.

[0058] Preparation Example 3

[0059] Add 10 g of nano-silica to 100 mL of ethanol-water solution, ultrasonically disperse for 30 min, add 1 g of 3-aminopropyltriethoxysilane, adjust the pH to 4 with 10% dilute nitric acid, heat to 70°C, react for 4 h, filter, wash twice with anhydrous ethanol, and dry at 80°C to constant weight.

[0060] Among them, the particle size distribution of nano-silica is 15~30nm.

[0061] Example 1

[0062] The preparation method of the alumina-type adsorbent of this embodiment includes the following steps:

[0063] (1) Add 0.04 mol of lanthanum nitrate hexahydrate and 0.015 mol of cerium nitrate hexahydrate to 40 mL of a 6% polyethylene glycol 400 aqueous solution, and heat slightly to 50°C to obtain an impregnation solution;

[0064] 0.5 mol γ-Al2O3 was added to a rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 5.5, and the mixture was stirred for 1 h. The mixture was allowed to stand at 20°C for 16 h, and then filtered and separated. The filter cake was washed three times with 0.05 mol / L dilute ammonia water, dried at 80°C in a vacuum oven to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 8:92 was introduced at a flow rate of 80 mL / min, and the temperature was increased to 550°C at a rate of 5°C / min. The mixture was calcined for 3 h and naturally cooled to room temperature to obtain a dual-doped carrier.

[0065] 0.1 mol 2-methylimidazole, 0.006 mol ferric nitrate nine hydrate, 0.004 mol zinc nitrate hexahydrate and 300 mL mixed solvent were mixed evenly, and the pH was adjusted to 8.5 with triethylamine. After stirring and mixing evenly, the dual-doped carrier was added and transferred to a high-pressure reactor. Under a nitrogen atmosphere, the temperature was raised to 70 ° C. and the reaction was carried out for 18 hours. After cooling to room temperature, the mixture was separated by suction filtration. The filter cake was washed 3 times with N, N-dimethylformamide, dried in a vacuum at 80 ° C. to constant weight, and ground until it was completely After passing through a 100-mesh sieve, 50 g of the sieve residue was taken, and then 1.5 g of camphor, 2 g of 30% silica sol, and 0.5 g of ethyl orthosilicate were added and mixed evenly. The mixture was then pressed into tablets (1.5 mm in diameter) using a tablet press under a pressure of 10 MPa. The tablets were then transferred to a muffle furnace and heated to 170°C at a rate of 2°C / min under a nitrogen atmosphere. The tablets were calcined for 110 min, then continued to be heated to 255°C, calcined for 180 min, and naturally cooled to room temperature to obtain a composite carrier.

[0066] (2) 12 g of MCM-41 molecular sieve was immersed in 50 mL of an aqueous solution containing 0.1 mol / L silver nitrate and 0.15 mol / L citric acid, stirred and mixed evenly, heated to 50 ° C, reacted for 8 h, cooled to room temperature, filtered and separated, the filter cake was rinsed once with deionized water, dried at 120 ° C to constant weight, and then calcined at 350 ° C for 3 h to obtain Ag-modified molecular sieve;

[0067] 10 g of Ag-modified molecular sieve was mixed evenly with 0.5 g of 40% silica sol, and 40 mL of deionized water was added to make a uniform slurry. The slurry was then coated on the surface of 40 g of a composite support by an impregnation method and dried in vacuum at 80°C to a constant weight to obtain an adsorbent precursor.

[0068] (3) 8 g of perfluoropolyether, 2.5 g of silanized nano-silica and 0.5 g of sodium dodecyl sulfate were added to 89 g of N,N-dimethylformamide, and ultrasonically dispersed for 30 min. Then, the adsorbent precursor was added and stirred and immersed for 15 min. After being taken out and drained, the mixture was dried at 120 °C to constant weight. The mixture was then transferred to a tube furnace and heated to 240 °C (heating rate 2 °C / min). The mixture was activated for 50 min and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0069] Wherein, the mixed solvent in step (1) comprises N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 5:3:2;

[0070] The silanized nano-silica was obtained from Preparation Example 1.

[0071] Example 2

[0072] The preparation method of the alumina-type adsorbent of this embodiment includes the following steps:

[0073] (1) Add 0.03 mol of lanthanum nitrate hexahydrate and 0.01 mol of cerium nitrate hexahydrate to 40 mL of 8% polyethylene glycol 400 aqueous solution, and heat slightly to 50°C to obtain an impregnation solution;

[0074] 0.5 mol of γ-Al2O3 was added to a rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 6, and the mixture was stirred for 1 hour. The mixture was allowed to stand at 25°C for 12 hours, and filtered to separate. The filter cake was washed three times with 0.05 mol / L dilute ammonia water, dried under vacuum at 80°C to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 5:95 was introduced at a flow rate of 50 mL / min, and the temperature was increased to 500°C at 5°C / min. The mixture was calcined for 4 hours and naturally cooled to room temperature to obtain a dual-doped carrier.

[0075] 0.08 mol 2-methylimidazole, 0.005 mol ferric nitrate nonahydrate, 0.003 mol zinc nitrate hexahydrate and 300 mL of mixed solvent were mixed evenly, and the pH was adjusted to 8 with triethylamine. After stirring and mixing evenly, the dual-doped carrier was added and transferred to a high-pressure reactor. Under a nitrogen atmosphere, the temperature was raised to 60 ° C. and the reaction was carried out for 24 hours. After cooling to room temperature, the mixture was separated by filtration. The filter cake was washed 3 times with N, N-dimethylformamide, dried in a vacuum at 80 ° C. to constant weight, and ground until it was completely filtered. After passing through a 00-mesh sieve, 50 g of the sieve under-sieve was taken, and then 1 g of camphor, 1.5 g of silica sol with a mass concentration of 30%, and 0.25 g of ethyl orthosilicate were added and mixed evenly. The mixture was pressed into tablets (with a diameter of 1.5 mm) under a pressure of 10 MPa using a tablet press. The tablets were then transferred to a muffle furnace and heated to 165 ° C at a rate of 2 ° C / min under a nitrogen atmosphere. The tablets were calcined for 120 min, and then continued to be heated to 245 ° C, calcined for 210 min, and naturally cooled to room temperature to obtain a composite carrier.

[0076] (2) 15 g of MCM-41 molecular sieve was immersed in 75 mL of a mixed solution containing 0.05 mol / L silver nitrate and 0.1 mol / L citric acid, stirred and mixed evenly, heated to 40 ° C, reacted for 10 h, cooled to room temperature, filtered and separated, the filter cake was rinsed once with deionized water, dried at 120 ° C to constant weight, and then calcined at 300 ° C for 4 h, and naturally cooled to room temperature to obtain Ag-modified molecular sieve;

[0077] 15 g of Ag-modified molecular sieve was mixed evenly with 0.45 g of 40% silica sol, and 60 mL of deionized water was added to make a uniform slurry. The slurry was then coated on the surface of 45 g of a composite support by an impregnation method and dried in a vacuum at 80°C to a constant weight to obtain an adsorbent precursor.

[0078] (3) Add 5 g of perfluoropolyether, 2 g of silanized nano-silica and 0.5 g of sodium dodecyl sulfate to 92.5 g of N,N-dimethylformamide, and ultrasonically disperse for 30 min. Then add the adsorbent precursor, stir and immerse for 10 min, take out and drain, dry at 120 °C to constant weight, then transfer to a tube furnace, heat to 230 °C (heating rate 2 °C / min), activate for 60 min, and cool naturally to room temperature to obtain an alumina-type adsorbent.

[0079] Wherein, the mixed solvent in step (1) comprises N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 4:2:1;

[0080] The silanized nano-silica comes from Preparation Example 2.

[0081] Example 3

[0082] The preparation method of the alumina-type adsorbent of this embodiment includes the following steps:

[0083] (1) Add 0.05 mol of lanthanum nitrate hexahydrate and 0.02 mol of cerium nitrate hexahydrate to 40 mL of a 5% polyethylene glycol 400 aqueous solution, and heat slightly to 50°C to obtain an impregnation solution;

[0084] 0.5 mol γ-Al2O3 was added to a rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 5, and the mixture was stirred for 1 hour. The mixture was allowed to stand at 20°C for 18 hours, and filtered to separate. The filter cake was washed three times with 0.05 mol / L dilute ammonia water, dried under vacuum at 80°C to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 10:90 was introduced at a flow rate of 100 mL / min, and the temperature was increased to 600°C at 5°C / min. The mixture was calcined for 2 hours and naturally cooled to room temperature to obtain a dual-doped carrier.

[0085] 0.12 mol 2-methylimidazole, 0.007 mol ferric nitrate nine hydrate, 0.005 mol zinc nitrate hexahydrate and 300 mL mixed solvent were mixed evenly, and the pH was adjusted to 9 with triethylamine. After stirring and mixing evenly, the dual-doped carrier was added and transferred to a high-pressure reactor. Under a nitrogen atmosphere, the temperature was raised to 80 ° C. and the reaction was carried out for 12 hours. After cooling to room temperature, the mixture was separated by suction filtration. The filter cake was washed 3 times with N, N-dimethylformamide, dried in a vacuum at 80 ° C. to constant weight, and ground until it was completely After passing through a 100-mesh sieve, 50 g of the sieve residue was taken, and then 2 g of camphor, 2.5 g of 30% silica sol, and 0.75 g of ethyl orthosilicate were added and mixed evenly. The mixture was then pressed into tablets (2 mm in diameter) using a tablet press under a pressure of 10 MPa. The tablets were then transferred to a muffle furnace and heated to 175°C at a rate of 2°C / min under a nitrogen atmosphere, calcined for 90 min, and then further heated to 265°C, calcined for 150 min, and naturally cooled to room temperature to obtain a composite carrier.

[0086] (2) Immerse 10 g of MCM-41 molecular sieve in 30 mL of a mixed solution containing 0.2 mol / L silver nitrate and 0.2 mol / L citric acid, stir and mix evenly, heat to 60 ° C, react for 6 h, cool to room temperature, filter and separate, rinse the filter cake with deionized water once, dry at 120 ° C to constant weight, and then calcine at 400 ° C for 2 h to obtain Ag-modified molecular sieve;

[0087] 10 g of Ag-modified molecular sieve was mixed evenly with 0.8 g of 40% silica sol, and 40 mL of deionized water was added to make a uniform slurry. The slurry was then coated on the surface of a 50 g composite support by an impregnation method and dried in vacuum at 80°C to a constant weight to obtain an adsorbent precursor.

[0088] (3) 10 g of perfluoropolyether, 3 g of silanized nano-silica and 1 g of sodium dodecyl sulfate were added to 86 g of N,N-dimethylformamide, and ultrasonically dispersed for 40 min. Then, the adsorbent precursor was added and stirred and immersed for 20 min. After being taken out and drained, the mixture was dried at 120 °C to constant weight. The mixture was then transferred to a tube furnace and heated to 250 °C (heating rate 2 °C / min). The mixture was activated for 40 min and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0089] Wherein, the mixed solvent in step (1) comprises N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 6:4:3;

[0090] The silanized nano-silica comes from Preparation Example 3.

[0091] Example 4

[0092] The difference between this embodiment and embodiment 3 is that:

[0093] Step (3) is as follows: 10 g of perfluoropolyether, 3 g of silanized nano-silica and 1 g of sodium dodecyl sulfate are added to 86 g of N,N-dimethylformamide, ultrasonically dispersed for 40 min, then the adsorbent precursor is added, stirred and immersed for 20 min, taken out and drained, dried at 120 ° C to constant weight, and heptafluorodecyltrimethoxysilane is introduced at a flow rate of 40 mL / min for 30 min under the conditions of nitrogen flow rate of 300 mL / min and temperature of 180 ° C, and then the temperature is continuously raised to 250 ° C (heating rate of 2 ° C / min), activated for 50 min, and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0094] Other details are the same as in Example 3.

[0095] Example 5

[0096] The difference between this embodiment and embodiment 4 is that:

[0097] Step (3) is as follows: 10 g of perfluoropolyether, 3 g of silanized nano-silica and 1 g of sodium dodecyl sulfate are added to 86 g of N,N-dimethylformamide, ultrasonically dispersed for 40 min, then the adsorbent precursor is added, stirred and immersed for 20 min, taken out and drained, dried at 120 ° C to constant weight, and heptafluorodecyltrimethoxysilane is introduced at a flow rate of 60 mL / min for 25 min under the conditions of nitrogen flow rate of 350 mL / min and temperature of 200 ° C, and then the temperature is continuously raised to 250 ° C (heating rate of 2 ° C / min), activated for 60 min, and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0098] Other details are the same as in Example 4.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 1 is:

[0101] Step (1) is: placing 0.5 mol of γ-Al2O3 in a tube furnace, heating to 550°C at 5°C / min, calcining for 3 hours, and naturally cooling to room temperature to obtain a carrier;

[0102] 0.1 mol 2-methylimidazole, 0.006 mol ferric nitrate nonahydrate, 0.004 mol zinc nitrate hexahydrate and 300 mL of mixed solvent were mixed evenly, and the pH was adjusted to 8.5 with triethylamine. After stirring and mixing evenly, the carrier was added and the mixture was transferred to a high-pressure reactor. Under a nitrogen atmosphere, the temperature was raised to 70°C and the reaction was carried out for 18 hours. After cooling to room temperature, the mixture was separated by suction filtration. The filter cake was washed 3 times with N,N-dimethylformamide, dried in a vacuum at 80°C to constant weight, and ground until it was completely filtered. After passing through a 00-mesh sieve, 50 g of the sieve under-sieve was taken, and then 1.5 g of camphor, 2 g of silica sol with a mass concentration of 30%, and 0.5 g of ethyl orthosilicate were added and mixed evenly. The mixture was pressed into tablets (with a diameter of 1.5 mm) under a pressure of 10 MPa using a tablet press. The tablets were then transferred to a muffle furnace and heated to 170 ° C at a rate of 2 ° C / min under a nitrogen atmosphere. The tablets were calcined for 110 min, and then continued to be heated to 255 ° C, calcined for 180 min, and naturally cooled to room temperature to obtain a composite carrier.

[0103] Other details are the same as in Example 1.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is:

[0106] Step (1) is: adding 0.04 mol of lanthanum nitrate hexahydrate and 0.015 mol of cerium nitrate hexahydrate to 40 mL of a 6% polyethylene glycol 400 aqueous solution, and slightly heating to 50° C. to obtain an impregnation solution;

[0107] 0.5 mol γ-Al2O3 was added to the rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 5.5, and the mixture was stirred for 1 hour. The mixture was allowed to stand at 20 ° C for 16 hours, and then filtered and separated. The filter cake was washed 3 times with 0.05 mol / L dilute ammonia water, dried at 80 ° C in vacuum to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 8:92 was introduced at a flow rate of 80 mL / min, and the temperature was raised to 550 ° C at 5 ° C / min, and calcined for 3 hours. , naturally cooled to room temperature, ground until it completely passed through a 100-mesh sieve, took 50 g of the sieve, then added 1.5 g of camphor, 2 g of 30% silica sol and 0.5 g of ethyl orthosilicate and mixed evenly, and then pressed into tablets (1.5 mm in diameter) using a tablet press under a pressure of 10 MPa. Then, the tablets were transferred to a muffle furnace and heated to 170 ° C at a rate of 2 ° C / min under a nitrogen atmosphere. The tablets were calcined for 110 min, and then continued to be heated to 255 ° C, calcined for 180 min, and naturally cooled to room temperature to obtain a composite carrier;

[0108] Other details are the same as in Example 1.

[0109] Comparative Example 3

[0110] The preparation method of the alumina-type adsorbent of this comparative example comprises the following steps:

[0111] (1) Add 0.04 mol of lanthanum nitrate hexahydrate and 0.015 mol of cerium nitrate hexahydrate to 40 mL of a 6% polyethylene glycol 400 aqueous solution, and heat slightly to 50°C to obtain an impregnation solution;

[0112] 0.5 mol γ-Al2O3 was added to a rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 5.5, and the mixture was stirred for 1 h. The mixture was allowed to stand at 20°C for 16 h, and then filtered and separated. The filter cake was washed three times with 0.05 mol / L dilute ammonia water, dried at 80°C in a vacuum oven to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 8:92 was introduced at a flow rate of 80 mL / min, and the temperature was increased to 550°C at a rate of 5°C / min. The mixture was calcined for 3 h and naturally cooled to room temperature to obtain a dual-doped carrier.

[0113] 0.1 mol 2-methylimidazole, 0.006 mol ferric nitrate nine hydrate, 0.004 mol zinc nitrate hexahydrate and 300 mL mixed solvent were mixed evenly, and the pH was adjusted to 8.5 with triethylamine. After stirring and mixing evenly, the dual-doped carrier was added and transferred to a high-pressure reactor. Under a nitrogen atmosphere, the temperature was raised to 70 ° C. and the reaction was carried out for 18 hours. After cooling to room temperature, the mixture was separated by suction filtration. The filter cake was washed 3 times with N, N-dimethylformamide, dried in a vacuum at 80 ° C. to constant weight, and ground until it was completely After passing through a 100-mesh sieve, 50 g of the sieve residue was taken, and then 1.5 g of camphor, 2 g of 30% silica sol, and 0.5 g of ethyl orthosilicate were added and mixed evenly. The mixture was then pressed into tablets (1.5 mm in diameter) using a tablet press under a pressure of 10 MPa. The tablets were then transferred to a muffle furnace and heated to 170°C at a rate of 2°C / min under a nitrogen atmosphere. The tablets were calcined for 110 min, then continued to be heated to 255°C, calcined for 180 min, and naturally cooled to room temperature to obtain a composite carrier.

[0114] (2) 12 g of MCM-41 molecular sieve was immersed in 50 mL of an aqueous solution containing 0.1 mol / L silver nitrate and 0.15 mol / L citric acid, stirred and mixed evenly, heated to 50 ° C, reacted for 8 h, cooled to room temperature, filtered and separated, the filter cake was rinsed once with deionized water, dried at 120 ° C to constant weight, and then calcined at 350 ° C for 3 h to obtain Ag-modified molecular sieve;

[0115] 10 g of Ag-modified molecular sieve was evenly mixed with 0.5 g of silica sol with a mass concentration of 40%, and 40 mL of deionized water was added to make a uniform slurry. The slurry was coated on the surface of 40 g of the composite support by an impregnation method, and then vacuum-dried at 80 ° C to constant weight. The slurry was then transferred to a tube furnace, heated to 240 ° C (heating rate 2 ° C / min), activated for 50 min, and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0116] Wherein, the mixed solvent in step (1) comprises N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 5:3:2.

[0117] Comparative Example 4

[0118] The preparation method of the alumina-type adsorbent of this comparative example comprises the following steps:

[0119] (1) Add 0.04 mol of lanthanum nitrate hexahydrate and 0.015 mol of cerium nitrate hexahydrate to 40 mL of a 6% polyethylene glycol 400 aqueous solution, and heat slightly to 50°C to obtain an impregnation solution;

[0120] 0.5 mol γ-Al2O3 was added to a rotary evaporator, and the impregnation solution was slowly added dropwise while stirring at a speed of 100 r / min. After the addition was completed, the pH was adjusted to 5.5, and the mixture was stirred for 1 h. The mixture was allowed to stand at 20°C for 16 h, and then filtered and separated. The filter cake was washed three times with 0.05 mol / L dilute ammonia water, dried at 80°C in a vacuum oven to constant weight, and then transferred to a tube furnace. A mixture of oxygen and nitrogen with a volume ratio of 8:92 was introduced at a flow rate of 80 mL / min, and the temperature was increased to 550°C at a rate of 5°C / min. The mixture was calcined for 3 h and naturally cooled to room temperature to obtain a dual-doped carrier.

[0121] 0.1 mol 2-methylimidazole, 0.01 mol ferric nitrate nonahydrate and 300 mL of a mixed solvent were mixed uniformly, the pH was adjusted to 8.5 with triethylamine, and the mixture was stirred and mixed uniformly. The dual-doped carrier was added and the mixture was transferred to a high-pressure reactor. The mixture was heated to 70°C under a nitrogen atmosphere and reacted for 18 hours. After cooling to room temperature, the mixture was filtered and separated. The filter cake was washed three times with N,N-dimethylformamide, dried in a vacuum at 80°C to constant weight, ground until it completely passed a 100-mesh sieve, and 50 g of the sieve was taken. 1.5 g of camphor, 2 g of 30% silica sol and 0.5 g of ethyl orthosilicate were added and mixed uniformly. The mixture was pressed into tablets (1.5 mm in diameter) under a pressure of 10 MPa using a tablet press. The mixture was then transferred to a muffle furnace and heated to 170°C at a rate of 2°C / min under a nitrogen atmosphere. The mixture was calcined for 110 minutes, then heated to 255°C and calcined for 180 minutes. The mixture was naturally cooled to room temperature to obtain a composite carrier.

[0122] (2) 12 g of MCM-41 molecular sieve was immersed in 50 mL of an aqueous solution containing 0.1 mol / L silver nitrate and 0.15 mol / L citric acid, stirred and mixed evenly, heated to 50 ° C, reacted for 8 h, cooled to room temperature, filtered and separated, the filter cake was rinsed once with deionized water, dried at 120 ° C to constant weight, and then calcined at 350 ° C for 3 h to obtain Ag-modified molecular sieve;

[0123] 10 g of Ag-modified molecular sieve was mixed evenly with 0.5 g of 40% silica sol, and 40 mL of deionized water was added to make a uniform slurry. The slurry was then coated on the surface of 40 g of a composite support by an impregnation method and dried in vacuum at 80°C to a constant weight to obtain an adsorbent precursor.

[0124] (3) 8 g of perfluoropolyether, 2.5 g of silanized nano-silica and 0.5 g of sodium dodecyl sulfate were added to 89 g of N,N-dimethylformamide, and ultrasonically dispersed for 30 min. Then, the adsorbent precursor was added and stirred and immersed for 15 min. After being taken out and drained, the mixture was dried at 120 °C to constant weight. The mixture was then transferred to a tube furnace and heated to 240 °C (heating rate 2 °C / min). The mixture was activated for 50 min and naturally cooled to room temperature to obtain an alumina-type adsorbent.

[0125] Wherein, the mixed solvent in step (1) comprises N,N-dimethylformamide, ethanol and water, and the volume ratio of N,N-dimethylformamide, ethanol and water is 5:3:2;

[0126] The silanized nano-silica was obtained from Preparation Example 1.

[0127] Performance testing

[0128] The alumina-based adsorbents (50 g loading) prepared in Examples 1-5 and Comparative Examples 1-4 were loaded into a fixed-bed reactor to test the adsorption-regeneration performance of propane gas with multiple impurities. The gas composition was: propane gas containing 100 ppm hydrogen sulfide, 50 ppm hydrogen chloride, 50 ppm thiophene, and water vapor (dew point -10°C). The adsorption was carried out at 25°C, 0.5 MPa, and 3000 h. -1 The volumetric space velocity (corresponding to a gas flow rate of 3.125 L / min) was passed into the reactor, and the breakthrough endpoint was taken when the thiophene outlet concentration was ≥1 ppm. The breakthrough time t was recorded. p After adsorption saturation, switch to nitrogen (space velocity 1000h -1 ), regenerated at 200℃ for 8h, and after 3 cycles, the adsorption capacity q was calculated. s , the calculation formula is: s =C0×10 6 ×Q×t p ×M×P std / (P×T std ×22.4×m)=0.053×tp , where C0=50ppm, Q=3.125L / min, M=84.14g / mol, m=50g, P std =1atm, T std =273K, P=0.5MPa=5atm, T=25℃=298K and regeneration retention rate, the specific structure is shown in Table 1.

[0129] Regeneration retention rate (%): the ratio of the adsorption capacity after the third regeneration to the initial adsorption capacity.

[0130] Table 1 Performance test results of the alumina-type adsorbents prepared in Examples 1 to 5 and Comparative Examples 1 to 4

[0131]

[0132] From Table 1 we can see that:

[0133] Examples 1-5 all utilize rare earth element (lanthanum / cerium) doping of alumina supports to create alkaline active centers, forming strong chemical adsorption sites for capturing acidic gases (H2S / HCl). The Fe / Zn bimetallic coordination layer targets thiophene for adsorption. A perfluoropolyether-based superhydrophobic barrier, leveraging low surface energy and nanostructured interface, blocks water vapor penetration and reduces acidic liquid-phase corrosion. Comparative Example 1, in contrast, lacks rare earth element doping and primarily relies on physical adsorption of acidic gases via alumina, resulting in lower acid gas removal accuracy. Furthermore, acidic gases easily corrode alumina pores, causing structural collapse and reduced regeneration retention.

[0134] Although comparative example 2 contains rare earth element doping, it lacks the Fe / Zn bimetallic coordination layer, resulting in insufficient thiophene adsorption sites and direct exposure of basic sites. As a result, carbon deposits cover the active centers during the regeneration process.

[0135] In Comparative Example 3, the lack of a hydrophobic layer results in the Ag-modified molecular sieve adsorbing water vapor and forming a water film covering the Ag. + active sites, inhibiting H2S chemical precipitation; at the same time, water vapor causes the ionization of silanols in the Ag-modified molecular sieve to produce H + Accelerated chlorine corrosion, H3O + With Cl - Combined to form HCl, which corrodes the alumina framework.

[0136] In Comparative Example 4, a single iron salt was used, which lacked the synergistic effect of zinc element and insufficient coordination ability, resulting in decreased adsorption selectivity and stability for thiophene.

[0137] Combined analysis Figure 1The broadening of the main γ-Al₂O₃ peak (37.1°) indicates the formation of a nanocrystalline structure after low-temperature calcination, retaining a relatively high specific surface area. The secondary peak (34.3°) is attributed to the ZnO crystal planes, representing functional components decomposed during calcination. Lanthanum and cerium ions, due to their larger ionic radius than aluminum ions, replace lattice sites in the γ-Al₂O₃, resulting in a lower-angle shift of the 37.1° peak relative to the standard peak, indicating successful incorporation of lanthanum and cerium ions into the lattice. Ag-doped molecular sieve coating shifts the characteristic γ-Al₂O₃ peak negatively to 63.1°, suggesting that the coating inhibits excessive grain growth. This peak shift is related to compressive stress generated by the difference in thermal expansion coefficients, demonstrating the mesoporous coating's ability to regulate crystal plane strain. The slight shift in the ZnO characteristic peak (31.9°) is attributed to the difference in radius between iron and zinc ions, which triggers a localized contraction of the crystal lattice upon solid solution formation. The broadening of the peak base correlates with the refinement of the ZnO nanocrystal size. In addition, the peaks at 33° and 35.3° may correspond to trace independent phases of iron-based oxides, indicating that a small amount of segregation or lattice distortion occurred when iron was dissolved in zinc. The peaks at 16.4° and 35°~40° showed broad peaks with relatively low intensity, reflecting that the alumina adsorbent has an "amorphous phase-nanocrystalline" mixed structure, which, to a certain extent, provides a structural basis for the full exposure of the adsorption sites.

[0138] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing an alumina-type adsorbent, characterized in that: The steps include: (1) The lanthanum salt, the cerium salt and the polyethylene glycol aqueous solution are mixed evenly, and then mixed evenly with γ-Al2O3, and the pH is adjusted to 5-6, and the mixture is allowed to stand, solid-liquid separation is performed, dried, and calcined to obtain a dual-doped carrier; the dual-doped carrier is dispersed in a mixed solution containing 2-methylimidazole, iron salt and zinc salt, and the pH is adjusted to 8-9. Under an inert atmosphere, the mixture is heated to 60-80°C, reacted for 12-24 hours, solid-liquid separation is performed, dried, and ground to obtain a powder, which is then formed into a composite carrier; (2) Mixing Ag-modified molecular sieve MCM-41 and silica sol evenly, coating the mixture on the surface of the composite support, and drying the mixture to obtain an adsorbent precursor; (3) Immersing the adsorbent precursor in a dispersion containing perfluoropolyether and silanized nano-silica for 10 to 20 minutes, separating the solid and liquid, drying, and then reactivating to obtain an alumina-type adsorbent; the silanization agent is 3-aminopropyltriethoxysilane; The molar ratio of the γ-Al2O3, lanthanum salt, cerium salt, 2-methylimidazole, iron salt and zinc salt is 50: (3-5): (1-2): (8-12): (0.5-0.7): (0.3-0.5).

2. The method for preparing an alumina-type adsorbent according to claim 1, wherein: The mass ratio of the Ag-modified molecular sieve to the composite carrier is 1:(3-5).

3. The method for preparing an alumina-type adsorbent according to claim 1, wherein: In step (1), the molding process includes: adding silica sol, camphor and ethyl orthosilicate to the powder, mixing and molding, drying, and then performing a staged roasting process.

4. The method for preparing an alumina-type adsorbent according to claim 1, wherein: The preparation method of the Ag-modified molecular sieve comprises the following steps: The MCM-41 molecular sieve was immersed in a mixed solution containing 0.05-0.2 mol / L silver nitrate and 0.1-0.2 mol / L citric acid, heated to 40-60°C, reacted for 6-10 hours, solid-liquid separation, dried, and calcined at 300-400°C for 2-4 hours under an inert atmosphere to obtain the Ag-modified molecular sieve.

5. The method for preparing an alumina-type adsorbent according to claim 1, wherein: In step (3), in the dispersion, the mass concentration of perfluoropolyether is 5% to 10%, and the mass concentration of silanized nano-silica is 2% to 3%.

6. The method for preparing an alumina-based adsorbent according to claim 1, wherein: The preparation method of the silanized nano-silicon dioxide comprises the following steps: Disperse nano-silica in ethanol aqueous solution, add 3-aminopropyltriethoxysilane accounting for 5% to 10% of the mass of nano-silica, adjust the pH to 4 to 5, raise the temperature to 50 to 70°C, react for 4 to 8 hours, separate the solid and liquid, and dry to obtain the product.

7. The method for preparing an alumina-based adsorbent according to claim 1, wherein: The activation in step (3) is as follows: in an inert atmosphere, the temperature is raised to 230-250°C and the activation is carried out for 40-60 minutes.

8. The method for preparing an alumina-based adsorbent according to claim 1, wherein: In step (3), after drying, the process also includes the step of vapor deposition of fluorosilane.

9. The method for preparing an alumina-based adsorbent according to claim 8, wherein: The step of vapor-depositing fluorosilane is as follows: introducing fluorosilane at a flow rate of 40-60 mL / min for 25-30 minutes under the conditions of 180-200° C. and a nitrogen flow rate of 300-350 mL / min.

10. An alumina adsorbent obtained by the method for preparing an alumina-type adsorbent according to any one of claims 1 to 9.

Images