Preparation method of modified 10X molecular sieve, obtained molecular sieve and application

Abstract

The invention discloses a preparation method of a modified 10X molecular sieve, the obtained molecular sieve and application, and belongs to the technical field of porous adsorption materials. The method comprises the following steps: compounding an amino coupling agent and a nonionic surfactant into a composite modified component according to a mass ratio of 1: 1, preparing modifier solutions with different mass concentrations in an alcohol-water system, and sequentially carrying out grafting reaction at 70-75 DEG C by adopting a concentration gradient step-by-step grafting process from low to high, so as to obtain a modified component; and washing, drying and activating to obtain the composite modified 10X molecular sieve. Through the synergistic effect of composite modification and gradient grafting, uniform and controllable grafting of amino functional groups on the surface of the molecular sieve and in pore channels is achieved, the adsorption capacity and selectivity of the molecular sieve to carbonyl compounds in Fischer-Tropsch synthetic oil are remarkably improved, meanwhile, the good pore channel structure and stability are kept, and the molecular sieve has good application prospects. The method is suitable for efficient removal of carbonyl compounds.

Description

Technical Field

[0001] This invention belongs to the field of porous adsorption materials technology, specifically relating to a method for preparing modified 10X molecular sieve, the resulting molecular sieve, and its applications. Background Technology

[0002] Fischer-Tropsch synthesis oils are core intermediates in coal-to-olefins and coal-to-chemicals processes. C12 olefins (dodecenes) are key raw materials for the preparation of surfactants and lubricating oil bases, and their purity directly determines the quality of downstream products. Industrial Fischer-Tropsch oils commonly contain 0.5-3 wt% carbonyl compounds (such as n-butyraldehyde and acetone). These impurities severely affect the subsequent processing and use of dodecenes, thus requiring deep removal.

[0003] 10X molecular sieves, due to their good matching of pore size (8.8-9.2 Å) with dodecene (molecular diameter approximately 5.5 Å) and carbonyl compounds (molecular diameter 4-8 Å), have become potential adsorbents in this system. However, unmodified 10X molecular sieves have two major drawbacks: First, the surface is mainly composed of silanol groups (-Si-OH), and the adsorption of carbonyl compounds relies solely on weak van der Waals forces (adsorption energy ≤8 kJ / mol), resulting in low adsorption capacity and susceptibility to interference from the oil phase, making deep removal impossible; second, the adsorption selectivity for dodecene and carbonyl compounds is poor, easily leading to the simultaneous adsorption of dodecene along with carbonyl compounds, resulting in the loss of the target product.

[0004] To address the aforementioned problems, several modification schemes have been proposed in the prior art: one is by introducing Zn 2+ Ni 2+ While cations enhance the coordination adsorption of carbonyl compounds, metal salts are expensive (2-4 times the price of amino modifiers), and the ion exchange process requires multiple washings, generating large amounts of saline wastewater, which puts significant environmental pressure on the system. Furthermore, their adsorption specificity for aldehydes is weaker than for ketones, making them unsuitable for Fischer-Tropsch oil systems with high aldehyde content. Secondly, the targeted adsorption of amino groups (-NH2) can be used to modify 10X molecular sieves. For example, Chinese patent CN112969661A discloses an amino modification method for molecular sieves in an aqueous system. However, this technology uses deionized water as a solvent, which leads to excessive hydrolysis of silanol groups on the molecular sieve surface, causing non-specific aggregation of the modifier and clogging of the molecular sieve micropores. Moreover, the hydrolysis rate of aminosilanes in the aqueous system is difficult to control, making it impossible to guarantee the stability of adsorption performance in mass production. The modifier is also prone to detachment, making it difficult to meet the long-term operational requirements of continuous industrial separation.

[0005] Furthermore, while single-amino modification can improve the adsorption capacity for carbonyl compounds to some extent, there is still room for optimization of adsorption selectivity. Insufficient uniformity of the modifier's dispersion on the molecular sieve surface can easily lead to local adsorption site saturation, limiting overall adsorption efficiency and preventing true gradient grafting. Therefore, there is an urgent need to develop an effective modification process to further improve the uniformity of modifier grafting, the structural stability of the molecular sieve, and its adsorption performance. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by proposing a method for modifying 10X molecular sieves based on gradient amino functionalization. The aim is to synergistically regulate the surface chemical properties and pore structure of the molecular sieve through stepwise gradient grafting of composite modifying components, thereby solving problems such as low adsorption capacity, poor selectivity, uneven grafting of modifiers, and insufficient structural stability in traditional modification methods. This results in modified 10X molecular sieves exhibiting high adsorption capacity, high selectivity, and excellent cycling stability for carbonyl compounds in Fischer-Tropsch synthesis oils. This method innovatively combines amino coupling agents and nonionic surfactants in a specific ratio to form composite modifying components. By precisely controlling the mixed solvent system of anhydrous ethanol and deionized water, solutions of composite modifiers with different mass concentrations are prepared. Crucially, the stepwise gradient grafting strategy from low to high concentrations enables the composite modifying components to achieve a uniform and efficient grafting reaction from the surface to the interior of the activated 10X molecular sieve, avoiding the surface agglomeration and pore blockage problems that can occur with direct reaction of a single high-concentration modifier. Meanwhile, by strictly controlling the process parameters of each step, such as activation temperature and time, heating and stirring conditions of the modifier solution, reaction temperature and time of gradient grafting, and subsequent washing and drying activation procedures, the controllability and repeatability of the modification process are ensured. Ultimately, the modified molecular sieve is endowed with ideal surface functional group loading, optimized pore size distribution, and enhanced interaction with carbonyl compounds (such as hydrogen bonding and electrostatic attraction), providing an efficient and environmentally friendly technical approach for the deep removal of carbonyl compounds from Fischer-Tropsch synthetic oils.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 0.5-1h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 0.5-1h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 0.5-1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0008] Furthermore, in step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 360-450 min.

[0009] Furthermore, in step (2), the stirring temperature is 28-30℃, the stirring speed is 200-300r / min, and the stirring time is 30-40min.

[0010] Furthermore, in step (2), the amino coupling agent is one of KH-602 (N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane), KH-550 (γ-aminopropyltriethoxysilane), or A-1100 (γ-aminopropyltrimethoxysilane); the nonionic surfactant is OP-10 (alkylphenol polyoxyethylene ether) or Tween-80 (sorbitan monooleate polyoxyethylene ether).

[0011] Furthermore, the amino coupling agent is KH-550, and the nonionic surfactant is OP-10.

[0012] Furthermore, in step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0013] Furthermore, in step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0014] Furthermore, in step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0015] Furthermore, the heating program of the muffle furnace in step (5) is as follows: the temperature is raised to 120°C at a heating rate of 5°C / min and held for 3 hours, and then raised to 180°C at a heating rate of 5°C / min and held for 2 hours.

[0016] A molecular sieve prepared as described above, used for adsorbing carbonyl compounds in Fischer-Tropsch synthetic oil.

[0017] Compared with the prior art, the modified 10X molecular sieve preparation method and the obtained product provided by the present invention have the following significant advantages: 1. Achieved uniform, deep, and controllable surface functionalization: By compounding amino-based coupling agents with nonionic surfactants in a 1:1 ratio, the dispersion and template effects of the surfactants effectively inhibited the self-aggregation of modifier molecules, ensuring high dispersion in the alcohol-water system. Combined with a three-step gradient grafting method from low to high (1-2%→5-6%→9-10%), uniform grafting of the composite modified components onto the surface and within the pores of the molecular sieve was achieved, progressing layer by layer. This avoids rapid pore blockage caused by a single contact with high-concentration modifiers, ensuring a reasonable distribution of active amino functional groups in the depth of the pores, thus significantly increasing effective adsorption sites while maximizing pore patency.

[0018] 2. Significantly Enhanced Adsorption Performance and Selectivity: The composite modified 10X molecular sieve prepared in this invention exhibits strong hydrogen bonding between uniformly distributed amino groups (-NH2) on its surface and carbonyl groups (C=O) in carbonyl compounds (aldehydes, ketones), greatly enhancing its specific adsorption capacity. The ordered functional layer formed by gradient grafting optimizes the pore size distribution, minimizing molecular mass transfer obstacles to the target product, dodecene, while efficiently adsorbing carbonyl compounds. Experiments show that this material significantly improves the adsorption capacity of carbonyl compounds in Fischer-Tropsch oil compared to unmodified 10X molecular sieves and traditional one-step amino-modified products, while further reducing the co-adsorption rate of dodecene, achieving a balance between high capacity and high selectivity.

[0019] 3. Enhanced structural stability and recyclability of the material: The introduction of nonionic surfactants and gradient grafting process promotes the formation of more stable and uniform chemical bonds (Si-O-Si) between the modifier and the silanol groups on the molecular sieve surface. This ordered grafting structure effectively reduces the risk of modifier detachment in highly polar or fluid systems, meeting the long-term operational requirements of industrial continuous separation devices.

[0020] 4. Excellent process controllability, environmentally friendly, and easy to scale up for production: All parameters in this method are clearly defined and controllable, especially the gradient concentration and reaction time, which can be precisely adjusted to ensure batch-to-batch stability of product performance. The entire process uses an ethanol-water mixed solvent, avoiding the large-scale use of strong acids, strong alkalis, or metal salts. Post-treatment is simple, and washing wastewater pollution is minimal, aligning with the development direction of green chemistry. The rational design of parameters such as the solid-liquid ratio also facilitates reactor selection and process scale-up, demonstrating promising prospects for industrial application. Attached Figure Description

[0021] Figure 1 The adsorption effect of the 10x molecular sieve sample obtained in Example 5 on carbonyl groups; Figure 2 The adsorption effect of the 10x molecular sieve samples obtained in Comparative Examples 1-6 on carbonyl groups is shown. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0023] Example 1 A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 0.5h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 0.5h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 0.5h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain a composite modified 10X molecular sieve, denoted as NH2-10X-1.

[0024] In step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 360 min.

[0025] Step (2) The stirring temperature is 28-30℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0026] In step (2), the amino coupling agent is A-1100; the nonionic surfactant is Tween-80 (sorbitan monooleate polyoxyethylene ether).

[0027] In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0028] In step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0029] In step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0030] The heating program of the muffle furnace in step (5) is as follows: heat up to 120°C at a heating rate of 5°C / min, hold for 3 hours, then heat up to 180°C at a heating rate of 5°C / min, and hold for 2 hours.

[0031] Example 2 A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 0.5h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 0.5h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 0.5h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain a composite modified 10X molecular sieve, denoted as NH2-10X-2.

[0032] In step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 400 min.

[0033] Step (2) The stirring temperature is 28-30℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0034] In step (2), the amino coupling agent is KH-550 (γ-aminopropyltriethoxysilane); the nonionic surfactant is OP-10 (alkylphenol polyoxyethylene ether).

[0035] In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0036] In step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0037] In step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0038] The heating program of the muffle furnace in step (5) is as follows: heat up to 120°C at a heating rate of 5°C / min, hold for 3 hours, then heat up to 180°C at a heating rate of 5°C / min, and hold for 2 hours.

[0039] Example 3 A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 0.5h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 0.5h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 0.5h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and processed by setting a heating program to obtain a composite modified 10X molecular sieve, denoted as NH2-10X-3.

[0040] In step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 450 min.

[0041] Step (2) The stirring temperature is 28-30℃, the stirring speed is 300r / min, and the stirring time is 30min.

[0042] In step (2), the amino coupling agent is KH-602 (N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane); the nonionic surfactant is OP-10 (alkylphenol polyoxyethylene ether).

[0043] In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0044] In step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0045] In step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0046] The heating program of the muffle furnace in step (5) is as follows: heat up to 120°C at a heating rate of 5°C / min, hold for 3 hours, then heat up to 180°C at a heating rate of 5°C / min, and hold for 2 hours.

[0047] Example 4 A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 1h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 1h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain a composite modified 10X molecular sieve, denoted as NH2-10X-4.

[0048] In step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 360 min.

[0049] Step (2) The stirring temperature is 28-30℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0050] In step (2), the amino coupling agent is A-1100 (γ-aminopropyltrimethoxysilane); the nonionic surfactant is Tween-80 (sorbitan monooleate polyoxyethylene ether).

[0051] In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0052] In step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0053] In step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0054] The heating program of the muffle furnace in step (5) is as follows: heat up to 120°C at a heating rate of 5°C / min, hold for 3 hours, then heat up to 180°C at a heating rate of 5°C / min, and hold for 2 hours.

[0055] Example 5 A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 1h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 1h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and processed by setting a heating program to obtain a composite modified 10X molecular sieve, denoted as NH2-10X-5.

[0056] In step (1), the activation temperature of the muffle furnace is set to rise to 300°C in 180 min and then maintained at a constant temperature for 450 min.

[0057] Step (2) The stirring temperature is 28-30℃, the stirring speed is 300r / min, and the stirring time is 40min.

[0058] The amino-based coupling agent is KH-550, and the nonionic surfactant is OP-10.

[0059] In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:16.

[0060] In step (3), the solid-liquid ratio of the 10X molecular sieve to the composite modified liquid of all concentrations is 10g:100mL.

[0061] In step (4), the filter membrane of the Buchner funnel has a pore size of 0.45 μm, and the amount of ethanol used for each wash is 3 times the wet basis mass of the solid product.

[0062] The heating program of the muffle furnace in step (5) is as follows: heat up to 120°C at a heating rate of 5°C / min, hold for 3 hours, then heat up to 180°C at a heating rate of 5°C / min, and hold for 2 hours.

[0063] Comparative Example 1 The preparation steps for this comparative example are exactly the same as in Example 5, except that a nonionic surfactant is not used in the modified component. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Amino coupling agent is used as the modifier component; anhydrous ethanol and deionized water are measured and placed in a container, and under heating and stirring conditions, the modifier component is slowly added and stirring is continued until the solution is completely transparent, so as to obtain modifier solutions with a mass concentration of 1-2%, 5-6% and 9-10% respectively. (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 1h; after the reaction is completed, the solid product is separated by filtration, and the solid product is transferred to the modifier solution with the next concentration gradient of 5-6%, and the above reflux and stirring reaction operation is repeated for 1h. Finally, the product after the second reaction is separated by filtration again, transferred to the modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the grafting intermediate. (5) Drying and activation: The grafted intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0064] The amino-based coupling agent is KH-550.

[0065] Comparative Example 2 This comparative example is identical to Example 5 except that the ratio of amino-based coupling agent to nonionic surfactant in the composite modified component is changed to 2:1. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 2:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 1h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 1h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0066] The amino-based coupling agent is KH-550, and the nonionic surfactant is OP-10.

[0067] Comparative Example 3 This comparative example is identical to Example 5 except that the ratio of amino-based coupling agent to nonionic surfactant in the composite modified component is changed to 1:2. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:2 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add composite modifier component, continue stirring until the solution is completely transparent, and obtain composite modifier solutions with mass concentrations of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: The activated 10X molecular sieve in step (1) is added to the composite modifier solution with the lowest concentration of 1-2% in step (2), placed in a constant temperature water bath, heated to 70-75℃, refluxed and condensed, and stirred for 1h; after the reaction is completed, the solid product is separated by filtration and transferred to the next concentration gradient of 5-6% composite modifier solution, and the above reflux and stirring reaction operation is repeated for 1h. Finally, the product after the second reaction is separated by filtration again and transferred to the composite modifier solution with the highest concentration of 9-10%, and refluxed and stirred for 1h at 70-75℃. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0068] The amino-based coupling agent is KH-550, and the nonionic surfactant is OP-10.

[0069] Comparative Example 4 In this comparative example, except for the use of a single concentration of the composite modified component (mass concentration of 1-2%) for grafting treatment, the other preparation steps are exactly the same as in Example 5. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water and place them in a container, and slowly add composite modifier component under heating and stirring conditions, and continue stirring until the solution is completely transparent to obtain composite modifier solution with a mass concentration of 1-2% of modifier component; (3) Grafting reaction: Add the activated 10X molecular sieve in step (1) to the 1-2% composite modifier solution in step (2), place it in a constant temperature water bath, heat it to 70-75℃, reflux and condense it, and stir the reaction for 3h. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0070] Comparative Example 5 This comparative example, except for using only a single concentration of the composite modifier (mass concentration of 5-6%) for grafting treatment, follows the same preparation steps as Example 5. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water and place them in a container, and slowly add composite modifier component under heating and stirring conditions, and continue stirring until the solution is completely transparent to obtain composite modifier solution with a mass concentration of 5-6% of modifier component; (3) Grafting reaction: Add the activated 10X molecular sieve in step (1) to the 5-6% composite modifier solution in step (2), place it in a constant temperature water bath, heat it to 70-75℃, reflux and condense it, and stir the reaction for 3h. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0071] Comparative Example 6 In this comparative example, except for the use of a single-concentration composite modified component (mass concentration of 8-9%) for grafting treatment, the other preparation steps are exactly the same as in Example 5. That is: A method for preparing modified 10X molecular sieve, comprising the following preparation steps: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain the activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and nonionic surfactant at a mass ratio of 1:1 and mix them to obtain composite modifier component; measure anhydrous ethanol and deionized water and place them in a container, and slowly add composite modifier component under heating and stirring conditions, and continue stirring until the solution is completely transparent to obtain composite modifier solution with a mass concentration of 8-9% of modifier component; (3) Grafting reaction: Add the activated 10X molecular sieve in step (1) to the 8-9% composite modifier solution in step (2), place it in a constant temperature water bath, heat it to 70-75℃, reflux and condense it, and stir the reaction for 3h. (4) Collection and processing: The reaction mixture from step (3) was filtered using a Buchner funnel to collect the solid product, and the solid product was washed with anhydrous ethanol 3-5 times to obtain the composite grafting intermediate. (5) Drying and activation: The composite graft intermediate obtained in step (4) is transferred to a corundum crucible, placed in a muffle furnace, and a heating program is set to process it to obtain composite modified 10X molecular sieve.

[0072] Molecular sieves were prepared and their performance tested according to the methods of the examples and comparative examples. Each experiment was repeated five times and the average value was taken.

[0073] The testing method is as follows: In this invention, infrared spectroscopy is used to measure the amino grafting status, and nitrogen adsorption-desorption is used to measure the pore parameters.

[0074] Fourier transform infrared spectroscopy (FTIR) utilizes the absorption of infrared spectra to identify the structure of substances based on the vibrational and rotational energy levels of molecules, particularly for the qualitative analysis of organic groups and the structural analysis of organic molecules. To a certain extent, it can also determine the presence of heteroatoms. A Spectrum 100 infrared spectrometer was used to analyze the sample. Since the synthesized sample consisted of microspheres with macroscopic morphology, it needed to be crushed and ground into powder before testing.

[0075] Nitrogen adsorption-desorption test: N2 adsorption-desorption utilizes the numerous pores distributed within porous materials to detect the adsorption of nitrogen and the desorption under certain conditions, generating adsorption-desorption curves. The adsorption-desorption curves of mesoporous materials do not coincide, exhibiting a hysteresis loop; therefore, N2 adsorption-desorption can be used to test the pore structure and size of porous materials. A Micromeritics Gemini VII2390 N2 adsorption-desorption instrument was used.

[0076] Table 1. Pore size, specific surface area, and amino grafting amount for each embodiment and comparative experimental group. The olefin adsorption content and carbonyl content of the adsorbents in each experimental group were tested. The competitive adsorption behavior and carbonyl content of the modified molecular sieves for dodecene in Fischer-Tropsch synthetic oil were determined using a fixed-bed dynamic adsorption method. The specific steps are as follows: Adsorption experimental apparatus (1) Adsorption column: made of stainless steel, with an inner diameter of 10mm and a length of 300mm, and 200-mesh stainless steel screens at both ends; constant temperature system: circulating water bath with outer jacket, temperature control accuracy ±0.5℃; (2) Sample introduction system: high-pressure constant flow pump, flow rate range 0.1-10 mL / min; (3) Detection system: online gas chromatograph (GC-FID) and spectrophotometer for determination and analysis.

[0077] Adsorption experiment: 1. Pack the 10X molecular sieve into the adsorption column and set the temperature to 50℃; 2. The C12 fraction of the coal-based Fischer-Tropsch oil was distilled and pumped into the adsorption column at a constant flow rate of 2.0 mL / min; 3. Collect oil samples from the outlet every 10 minutes, analyze the dodecene content by GC-FID, and determine the carbonyl content by spectrophotometry.

[0078] Table 2. Olefin adsorption capacity of each embodiment and comparative experimental group As shown in Table 1-2, the composite modified 10X molecular sieves (NH2-10X-1 to NH2-10X-5) prepared in Examples 1-5 exhibit excellent performance in terms of pore size, specific surface area, and amino grafting amount, and their olefin adsorption content is generally lower than that of the comparative examples. This indicates that by adjusting the ratio of amino coupling agent to nonionic surfactant, the pore structure and surface chemical properties of the molecular sieve can be controlled. Appropriately increasing the proportion of amino coupling agent helps to increase the amino grafting amount, which may be due to more amino coupling agent molecules participating in the reaction with the silanol groups on the surface of the molecular sieve. Correspondingly, in terms of olefin adsorption content, the olefin adsorption content of Example 1 is 2.7%, while that of Example 5 decreases to 2.2%, which is consistent with the increasing trend of amino grafting amount. This indicates that the increase in amino grafting amount enhances the selective adsorption capacity of the molecular sieve for carbonyl compounds in C12 Fischer-Tropsch oil, thereby reducing the competitive adsorption of olefins.

[0079] Compared to Example 5, Comparative Example 1 used only an amino-based coupling agent (KH-550) for single modification without adding a nonionic surfactant. The results showed that the amino grafting amount in Comparative Example 1 was only 0.65 mmol / g, far lower than the 1.16 mmol / g in Example 5, while its olefin adsorption content was as high as 5.2%. This indicates that the introduction of a nonionic surfactant plays an important role in the composite modification process, possibly by improving the dispersibility of the amino-based coupling agent in the solvent and promoting its contact and reaction with the molecular sieve surface, thereby significantly improving the amino grafting efficiency and amount, and effectively reducing olefin adsorption.

[0080] Comparative Examples 2 and 3 varied the ratio of amino coupling agent to nonionic surfactant in the composite modified components, to 2:1 and 1:2, respectively. The amino grafting amount in Comparative Example 2 (2:1) was 0.92 mmol / g, slightly lower than the 1.16 mmol / g in Example 5 (1:1), and the olefin adsorption content was 3.8%, higher than the 2.2% in Example 5. This may be because when the proportion of amino coupling agent is too high, its dispersion effect in the modifier solution decreases, and some coupling agent molecules may self-aggregate, which is detrimental to uniform grafting and sufficient reaction on the molecular sieve surface. Comparative Example 3 (1:2) showed a significantly reduced pore size to 5.46 Å, a specific surface area of ​​535 m² / g, an amino grafting amount of 0.83 mmol / g, and an olefin adsorption content of 3.5%. This indicates that when the proportion of nonionic surfactant is too high, it may occupy too much of the pore structure of the molecular sieve, resulting in a reduction in pore size. Although the specific surface area is relatively preserved compared to Comparative Example 2, the amount of amino grafting is not effectively improved, and the overall adsorption selectivity is still not as good as the 1:1 ratio in Example 5. This further proves that when amino coupling agents and nonionic surfactants are mixed in equal proportions, the synergistic effect can be maximized to achieve the best modification effect.

[0081] Comparative Examples 4, 5, and 6 used a single concentration of composite modifier solution for grafting treatment, instead of the stepwise gradient grafting of Example 5. Comparative Example 4, reacting for 3 hours with the lowest concentration (1-2%) modifier solution, achieved an amino grafting amount of only 0.52 mmol / g and an olefin adsorption content of 4.5%. Comparative Example 5, reacting for 3 hours with a medium concentration (5-6%) modifier solution, achieved an amino grafting amount of 0.72 mmol / g and an olefin adsorption content of 3.9%. Comparative Example 6, reacting for 3 hours with a higher concentration (8-9%) modifier solution, achieved an amino grafting amount of 0.82 mmol / g and an olefin adsorption content of 5.1%. Although the amino grafting amount of Comparative Example 6 was higher than the other single-concentration groups, it was still lower than the 1.16 mmol / g of Example 5, and its olefin adsorption content was the highest. This clearly shows that the stepwise gradient grafting method, compared to a single-concentration long-term reaction, can more effectively increase the amino grafting amount and optimize adsorption performance. Stepwise gradient grafting can achieve higher grafting density and more uniform distribution by first allowing modifier molecules to slowly and uniformly diffuse and graft onto readily reactive sites on the molecular sieve surface at a low concentration, and then increasing the concentration to promote the binding of more modifier molecules to the remaining active sites. This avoids the problems of excessively rapid aggregation or pore blockage of modifier molecules on the molecular sieve surface at a single high concentration, as well as insufficient reaction driving force and limited grafting amount at a single low concentration.

[0082] From carbonyl breakthrough time ( Figure 1-2 It can also be seen that the modified 10X molecular sieve prepared using the composite modified component (amino coupling agent and nonionic surfactant in a 1:1 mass ratio) and a stepwise gradient grafting process described in this invention exhibits a longer breakthrough time and higher adsorption capacity during carbonyl adsorption, significantly outperforming the single-component or non-gradient grafted comparative samples. This indicates that this invention not only achieves efficient grafting of amino groups but also optimizes the distribution of amino groups on the molecular sieve surface through a gradient grafting strategy, thereby improving its specific adsorption capacity and adsorption kinetics performance for carbonyl compounds while maintaining unobstructed pores.

[0083] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified 10X molecular sieve, characterized in that, The preparation steps include: (1) Activation treatment: Take the raw material 10X molecular sieve, place it in a muffle furnace, and activate it at a constant temperature to obtain activated 10X molecular sieve; (2) Preparation of modifier solution: Select amino coupling agent and non-ionic surfactant in a mass ratio of 1:1 to obtain a composite modification component; Measure anhydrous ethanol and deionized water into a container, heat and stir, slowly add the composite modification component, continue to stir until the solution is completely transparent, and obtain a composite modifier solution with a mass concentration of 1-2%, 5-6% and 9-10% respectively; (3) Stepwise gradient grafting reaction: Add the activated 10X molecular sieve in step (1) to the composite modifier solution with the lowest concentration of 1-2% in step (2), place it in a constant temperature water bath device, heat to 70-75°C, reflux condense, and stir for 0.5-1h; After the reaction is completed, separate by suction filtration, transfer the solid product to the composite modifier solution with the next concentration gradient of 5-6%, and repeat the above reflux stirring reaction operation for 0.5-1h; Finally, the product after the second reaction is separated by suction filtration again, and transferred to the composite modifier solution with the highest concentration of 9-10%, and continue to reflux and stir at 70-75°C for 0.5-1h; (4) Collection and treatment: Collect the solid product of the reaction mixture in step (3) by Buchner funnel suction filtration, and wash the solid product with anhydrous ethanol for 3-5 times to obtain a composite grafting intermediate; (5) Drying and activation: Transfer the composite grafting intermediate obtained in step (4) to a corundum crucible, place it in a muffle furnace, set the temperature program for treatment, and obtain a composite modified 10X molecular sieve.

2. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, In step (1), the muffle furnace activation temperature is set to 180min to 300°C, and the constant temperature is maintained for 360-450min.

3. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, The stirring temperature in step (2) is 28-30°C, the stirring speed is 200-300r / min, and the stirring time is 30-40min.

4. The method of claim 1, wherein the modified 10X molecular sieve is prepared by the steps of: In step (2), the amino coupling agent is one of N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane KH-602, γ-aminopropyltriethoxysilane KH-550, and γ-aminopropyltrimethoxysilane A-1100; The non-ionic surfactant is alkylphenol polyoxyethylene ether OP-10 or sorbitan monooleate polyoxyethylene ether Tween-80.

5. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, In step (2), the mass ratio of anhydrous ethanol to deionized water is 144:

16.

6. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, In step (3), the solid-liquid ratio of 10X molecular sieve to all concentrations of composite modification liquid is 10g:100mL.

7. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, In step (4), the pore size of the filter membrane of the Buchner funnel is 0.45μm, and the amount of ethanol used for each washing is 3 times the wet basis mass of the solid product.

8. The method for preparing the modified 10X molecular sieve according to claim 1, characterized in that, In step (5), the temperature program of the muffle furnace is: increase the temperature to 120°C at a rate of 5°C / min, maintain the temperature for 3h, then increase the temperature to 180°C at a rate of 5°C / min, and maintain the temperature for 2h.

9. A molecular sieve prepared according to any one of claims 1-8.

10. Use of the molecular sieve of claim 9, characterized in that, For adsorbing carbonyl compounds in Fischer-Tropsch synthesis oil.

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