Silica gel adsorbent for refining hexane and preparation method and application thereof

Abstract

The present application relates to the technical field of adsorbent preparation, and specifically discloses a silica gel adsorbent for hexane refining and a preparation method and application thereof, and provides a multi-stage synergistic purification system composed of a boron-tin double-modified framework and a surface grafted polymer layer: the boron regulates the acid-base property of the framework to provide primary adsorption sites for low molecular waxes and polar molecules, the tin coordination center selectively strongly adsorbs oxygen-containing compounds and water, and the long-chain alkyl side chain of the surface grafted polymer layer has excellent adsorption capacity for low molecular waxes, and also captures water and polar impurities on the surface through the hydroxyl group, thereby realizing efficient and simultaneous removal of low molecular waxes, oxygen-containing compounds and water in circulating hexane. The present application solves the technical defects that the existing adsorbent cannot simultaneously remove multiple impurities, has poor water resistance and is difficult to regenerate, guarantees long-period stable operation of a polyethylene device, and has significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of adsorbent preparation technology, and in particular to a silica gel adsorbent for hexane purification, its preparation method, and its application. Background Technology

[0002] Hexane is a widely used solvent in polyethylene production plants, especially in slurry polyethylene processes and ultra-high molecular weight polyethylene (UHMWPE) plants, where it serves as a key circulating medium. The Hostalen process in Basel and the Mitsui CX process are typical examples. Taking low-pressure slurry polymerization as an example, this process uses hexane as the dispersion medium and, under the action of a Ziegler-Natta catalyst, produces monophasic, biphasic, and multiphasic HDPE products through the copolymerization of ethylene and butene-1. During polymerization, the recycled hexane gradually accumulates impurities such as low-molecular-weight waxes (ethylene oligomers), oxygen-containing compounds (alcohols, ethers, etc.), and moisture. These impurities severely affect catalyst activity, polymerization reaction stability, and product quality, and may also cause blockages in heat exchangers and evaporators, threatening the long-term operation of the plant.

[0003] Existing adsorbents for hexane refining mainly include ordinary silica gel, alumina, and molecular sieves, but they have obvious technical defects: although ordinary silica gel can dehydrate, its specific surface area is small and its pore size distribution is narrow, making it unable to effectively accommodate large and low molecular weight waxes, and it has poor water resistance and is prone to pulverization during regeneration; alumina adsorbents have good lipophilic properties and a certain adsorption capacity for oxygen-containing compounds, but its dehydration effect is limited, and it has high regeneration temperature and high energy consumption; although molecular sieves have strong adsorption selectivity, their pore size is too small, making it difficult to remove large and low molecular weight waxes, and the regeneration process is prone to initiating adsorbate polymerization reactions.

[0004] To address these issues, related research has attempted to develop composite adsorbents, such as aluminosilicate adsorbents, which improve adsorption performance by adjusting the silica-alumina ratio. However, these are primarily targeted at gas drying applications and cannot simultaneously meet the synergistic removal requirements of multiple impurities in hexane systems. While aluminum-modified silica gel improves mechanical strength and adsorption capacity, it still falls short in terms of selectivity for removing multiple impurities and regeneration stability. Therefore, developing a special silica gel adsorbent that combines a large specific surface area, suitable mesoporous structure, synergistic hydrophilic and hydrophobic properties, good water resistance, and easy regeneration is of great significance for the efficient operation of polyethylene plants. Summary of the Invention

[0005] To address the shortcomings of existing adsorbents in hexane refining processes using slurry polyethylene and ultra-high molecular weight polyethylene, such as inability to simultaneously remove multiple impurities, poor water resistance, and difficulty in regeneration, this invention provides a silica gel adsorbent for hexane refining with a reasonable preparation process and excellent performance. This adsorbent achieves efficient and simultaneous removal of low molecular weight waxes, oxygen-containing compounds, and moisture from recycled hexane, while ensuring long-term stable use over a long period.

[0006] The technical solution of this invention is achieved as follows: This invention provides a method for preparing a silica gel adsorbent for hexane purification, comprising the following steps:

[0007] S1. Dissolve the silicon source in an aqueous ethanol solution, then add the aluminum source and the boron source to it, mix them evenly, then add the composite polycondensation agent, heat and stir to react, and obtain a sol.

[0008] S2. Add special template agent and pore expander to the sol in sequence, disperse evenly by ultrasonication, then add tin salt, stir evenly, and shape the obtained sol by extrusion molding or spray drying. Then dry the shaped particles and calcine to obtain composite particles.

[0009] S3. Disperse the composite particles in an ethanol aqueous solution, then add a vinyl silane coupling agent, stir, filter, wash, and dry to obtain double bond modified composite particles.

[0010] S4. Disperse the double bond modified composite particles in toluene solvent, then add octadecyl acrylate and hydroxyethyl methacrylate, stir evenly, then add azobisisobutyronitrile and heat to react. After the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0011] In the technical solution disclosed in this invention, by weight, there are 8-12 parts of silicon source, 1-3 parts of aluminum source, 0.3-0.6 parts of boron source, 0.2-0.6 parts of composite polycondensation agent, 0.04-0.12 parts of special template agent, 0.1-0.5 parts of pore-expanding agent, and 0.05-0.1 parts of tin salt.

[0012] In the technical solution disclosed in this invention, the silicon source is selected from tetraethyl orthosilicate, silica sol, or water glass.

[0013] In the technical solution disclosed in this invention, the aluminum source is selected from aluminum sulfate, aluminum nitrate or aluminum chloride.

[0014] In the technical solution disclosed in this invention, the boron source is selected from boric acid or triisopropyl borate.

[0015] In the technical solution disclosed in this invention, the composite polycondensation agent is selected from tetraethylammonium hydroxide.

[0016] In the technical solution disclosed in this invention, the special template agent is selected from hexadecyltrimethylammonium bromide.

[0017] In the technical solution disclosed in this invention, the pore-expanding agent is selected from polyethylene glycol.

[0018] In the technical solution disclosed in this invention, the tin salt is selected from tin chloride or stannous sulfate.

[0019] In the technical solution disclosed in this invention, in step S1, the temperature of the heating and stirring reaction is 60-70℃, for example, 60℃, 62℃, 65℃, 68℃, or 80℃ can be selected; the heating and stirring reaction time is 2-4h, for example, 2h, 2.5h, 3h, 3.5h, or 4h can be selected; but it is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0020] In step S1, a basic silicon-oxygen framework is constructed through the hydrolysis-condensation reaction of a silicon source in an ethanol-water solution. The introduction of a composite polycondensation agent can regulate the balance between hydrolysis and polycondensation rates. The addition of an aluminum source causes aluminum atoms to partially replace silicon atom positions in the silicon-oxygen tetrahedron, enhancing the mechanical strength and thermal stability of the material. Boron doping will produce local framework distortion and defects. These defect sites are transformed into weakly acidic centers after calcination, which have a certain adsorption effect on low-molecular-weight waxes and oxygen-containing compounds.

[0021] In the technical solution disclosed in this invention, the ultrasonic dispersion time in step S2 is 30-60 min.

[0022] In step S2, the special template agent self-assembles into a micelle structure in the sol system. After calcination and removal, it leaves behind regular mesoporous channels. These mesopores act as mass transfer channels, reducing the diffusion resistance of the adsorbate. Pore expander molecules insert into the template agent micelles, causing the micelles to expand in volume and ultimately forming channels with larger pore sizes. This dual-template strategy constructs a multi-level porous system of mesoporous-macroporous composites, which ensures both specific surface area and the ability to accommodate low-molecular-weight waxes with larger molecular sizes.

[0023] By adding tin salts, tin combines with the silicon-aluminum-boron framework through covalent bonds or strong coordination, and is transformed into tin oxide particles after calcination. As a soft acid metal, tin has a certain coordination affinity for oxygen-containing compounds. At the same time, the surface of tin oxide has moderate Lewis acidity, which can generate weak interactions with the weak polar groups (such as the methylene groups at the branched chain) in low molecular weight wax molecules, thereby enhancing the retention capacity of low molecular weight wax.

[0024] In the technical solution disclosed in this invention, in step S3, the mass ratio of the composite particles to the vinyl silane coupling agent is 10-15:0.5-1. For example, 10:0.5, 10:0.8, 10:1, 12:0.5, 12:0.8, 12:1, 15:0.5, 15:0.8, and 15:1 can be selected, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In the technical solution disclosed in this invention, the vinyl silane coupling agent is selected from KH570, vinyltrimethylsilane, or vinyltriethoxysilane.

[0026] In the technical solution disclosed in this invention, in step S4, the mass ratio of double bond modified composite particles, octadecyl acrylate, hydroxyethyl methacrylate and azobisisobutyronitrile is 10-15:3-6:3-6:0.5-1.

[0027] In the technical solution disclosed in this invention, in step S4, the temperature of the heating reaction is 65-75℃, for example, 65℃, 70℃, or 75℃ can be selected; the heating reaction time is 4-8h, for example, 4h, 5h, 6h, 7h, or 8h can be selected, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] In step S4, the vinyl groups on the surface of the double-bond modified composite particles undergo a free radical copolymerization reaction with octadecyl acrylate and hydroxyethyl methacrylate under the initiation of azobisisobutyronitrile. The polymer chains are grafted onto the particle surface in the form of chemical bonds. Octadecyl acrylate contributes long-chain alkyl side chains, and these hydrophobic carbon chains significantly improve the hydrophobicity of the material and enhance its adsorption capacity for low-molecular-weight waxes. Hydroxyethyl methacrylate introduces hydroxyl groups into the polymer chains. These hydroxyl groups act as hydrogen bond donors and acceptors, forming hydrogen bond adsorption on water molecules and oxygen-containing compounds, thereby enhancing the capture capacity for such polar impurities.

[0029] The present invention provides a silica gel adsorbent prepared by the above preparation method.

[0030] In the technical solution disclosed in this invention, the specific surface area of ​​the silica gel adsorbent prepared by this invention is 500-700 m². 2 / g, with a mesopore size distribution of 2-50nm and a pore volume of 0.2-1.0cm³. 3 / g, compressive strength ≥90N, wear rate ≤1%.

[0031] The present invention also provides the application of the above-mentioned silica gel adsorbent in the purification of hexane.

[0032] Specifically, the silica gel adsorbent prepared in this invention is used in the hexane purification process of the HDPE unit in the Hostalen ACP low-pressure slurry polymerization process in Basel.

[0033] Specifically, the application steps include: filling the adsorbent into a fixed-bed adsorption tower, and circulating hexane at a space velocity of 1-5 h⁻¹. -1 The adsorption tower removes low-molecular-weight waxes, oxygen-containing compounds, and moisture under conditions of 0-50℃ and 0.1-4.0MPa.

[0034] The adsorbent provided by this invention is regenerated by steam after adsorption saturation. The regeneration conditions are: steam temperature 120-150℃, pressure 0.2-0.4MPa, and it can be recycled ≥30 times.

[0035] The present invention has the following advantages over the prior art:

[0036] (1) The present invention constructs a basic silicon-oxygen framework through the hydrolysis and condensation reaction of silicon source in ethanol aqueous solution. The introduction of composite polycondensation agent can regulate the balance of hydrolysis and polycondensation rate. The addition of aluminum source causes aluminum atoms to partially replace silicon atom positions in silicon-oxygen tetrahedra, which enhances the mechanical strength and thermal stability of the material. Boron doping will produce local framework distortion and defects. These defect sites are transformed into weak acid centers after calcination, which have a certain adsorption effect on low molecular weight wax and oxygen-containing compounds.

[0037] (2) By adding tin salt, tin is combined with the silicon-aluminum-boron skeleton through covalent bonds or strong coordination. After calcination, it is transformed into tin oxide particles. As a soft acid metal, tin has a certain coordination affinity for oxygen-containing compounds. At the same time, the surface of tin oxide has moderate Lewis acidity, which can generate weak interactions with the weak polar groups (such as the methylene group at the branch) in low molecular weight wax molecules, thereby enhancing the retention capacity of low molecular weight wax.

[0038] (3) In this invention, the vinyl groups on the surface of the composite particles modified by double bonds undergo free radical copolymerization with octadecyl acrylate and hydroxyethyl methacrylate under the initiation of azobisisobutyronitrile. The polymer chains are grafted onto the particle surface in the form of chemical bonds. Octadecyl acrylate contributes long-chain alkyl side chains. These hydrophobic carbon chains significantly improve the hydrophobicity of the material and enhance the material's adsorption capacity for low molecular weight waxes. Hydroxyethyl methacrylate introduces hydroxyl groups into the polymer chains. These hydroxyl groups act as hydrogen bond donors and acceptors, forming hydrogen bond adsorption on water molecules and oxygen-containing compounds, thereby enhancing the capture capacity of such polar impurities.

[0039] (4) The present invention provides a multi-level synergistic purification system consisting of a boron-tin dual-modified framework and a surface-grafted polymer layer: the boron regulates the acidity and alkalinity of the framework to provide primary adsorption sites for low molecular weight waxes and polar molecules, the tin coordination center achieves selective and strong adsorption of oxygen-containing compounds and water, and the long-chain alkyl side chains of the surface-grafted polymer layer have excellent adsorption capacity for low molecular weight waxes, and also capture water and polar impurities on the surface through hydroxyl groups, thereby achieving efficient and simultaneous removal of low molecular weight waxes, oxygen-containing compounds and water from recycled hexane. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1This is a physical image of the silica gel adsorbent provided in Embodiment 1 of the present invention;

[0042] Figure 2 The graph shows the BET test results of the silica gel adsorbent provided in Example 1 of the present invention. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0046] S1. Dissolve 10g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 2g of aluminum nitrate and 0.5g of boric acid, mix well, then add 0.4g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0047] S2. Add 0.08g hexadecyltrimethylammonium bromide and 0.3g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.08g tin chloride and stir evenly. Spray dry the resulting sol to form particles, then dry the particles and calcine them at 600℃ for 3 hours. After calcine, allow them to cool naturally to room temperature to obtain composite particles.

[0048] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.5g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0049] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 3g of octadecyl acrylate and 3g of hydroxyethyl methacrylate, stir evenly, then add 0.5g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0050] Example 2

[0051] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0052] S1. Dissolve 8g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 1g of aluminum nitrate and 0.3g of triisopropyl borate, mix well, then add 0.2g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0053] S2. Add 0.04g hexadecyltrimethylammonium bromide and 0.2g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.05g tin chloride and stir evenly. Spray dry the resulting sol to form particles, then dry the particles and calcine them at 600℃ for 3 hours. After calcine, allow them to cool naturally to room temperature to obtain composite particles.

[0054] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.8g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0055] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 5g of octadecyl acrylate and 4g of hydroxyethyl methacrylate, stir evenly, then add 0.8g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0056] Example 3

[0057] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0058] S1. Dissolve 12g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 3g of aluminum nitrate and 0.6g of boric acid, mix well, then add 0.6g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0059] S2. Add 0.12g hexadecyltrimethylammonium bromide and 0.5g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.1g tin chloride and stir evenly. Spray dry the resulting sol to form a granule, then dry the granule and calcine it at 600℃ for 3 hours. After calcine, allow it to cool naturally to room temperature to obtain composite granules.

[0060] S3. Disperse 15g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 1g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0061] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 5g of octadecyl acrylate and 5g of hydroxyethyl methacrylate, stir evenly, then add 1g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0062] Comparative Example 1

[0063] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0064] S1. Dissolve 10g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 2g of aluminum nitrate, mix well, then add 0.4g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0065] S2. Add 0.08g hexadecyltrimethylammonium bromide and 0.3g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.08g tin chloride and stir evenly. Spray dry the resulting sol to form particles, then dry the particles and calcine them at 600℃ for 3 hours. After calcine, allow them to cool naturally to room temperature to obtain composite particles.

[0066] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.5g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0067] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 3g of octadecyl acrylate and 3g of hydroxyethyl methacrylate, stir evenly, then add 0.5g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0068] Compared to Comparative Example 1 and Example 1, no boric acid was added.

[0069] Comparative Example 2

[0070] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0071] S1. Dissolve 10g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 2g of aluminum nitrate and 0.5g of boric acid, mix well, then add 0.4g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0072] S2. Add 0.08g hexadecyltrimethylammonium bromide and 0.3g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, spray dry the resulting sol to form a granule, then dry the granule and calcine it at 600℃ for 3h. After calcine, allow it to cool naturally to room temperature to obtain composite granules.

[0073] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.5g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0074] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 3g of octadecyl acrylate and 3g of hydroxyethyl methacrylate, stir evenly, then add 0.5g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0075] Compared to Example 1, no tin chloride was added in Comparative Example 2.

[0076] Comparative Example 3

[0077] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0078] S1. Dissolve 10g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 2g of aluminum nitrate and 0.5g of boric acid, mix well, then add 0.4g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0079] S2. Add 0.08g hexadecyltrimethylammonium bromide and 0.3g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.08g zirconium nitrate, stir evenly, spray dry the resulting sol to form a granule, then dry the granule and calcine it at 600℃ for 3h. After calcine, allow it to cool naturally to room temperature to obtain composite granules.

[0080] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.5g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0081] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 3g of octadecyl acrylate and 3g of hydroxyethyl methacrylate, stir evenly, then add 0.5g of azobisisobutyronitrile, heat at 70℃ for 6h, and after the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0082] Compared with Example 1, tin chloride was replaced with zirconium nitrate in Comparative Example 3.

[0083] Comparative Example 4

[0084] A method for preparing a silica gel adsorbent for hexane purification includes the following steps:

[0085] S1. Dissolve 10g of tetraethyl orthosilicate in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 2g of aluminum nitrate and 0.5g of boric acid, mix well, then add 0.4g of tetraethylammonium hydroxide, heat and stir at 65℃ for 3h to obtain sol.

[0086] S2. Add 0.08g hexadecyltrimethylammonium bromide and 0.3g pore expander polyethylene glycol 400 to the sol in sequence, disperse evenly by ultrasonication, then add 0.08g tin chloride and stir evenly. Spray dry the resulting sol to form particles, then dry the particles and calcine them at 600℃ for 3 hours. After calcine, allow them to cool naturally to room temperature to obtain composite particles.

[0087] S3. Disperse 10g of composite particles in 100mL of ethanol-water solution (ethanol to water volume ratio of 4:1), then add 0.5g of silane coupling agent KH570, stir at room temperature for 2h, filter, wash and dry to obtain double bond modified composite particles.

[0088] S4. Disperse 10g of double bond modified composite particles in 100mL of toluene solvent, then add 3g of octadecyl acrylate and stir evenly. Then add 0.5g of azobisisobutyronitrile and heat at 70℃ for 6h. After the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification.

[0089] Compared to Example 1, Comparative Example 4 did not contain hydroxyethyl methacrylate.

[0090] The silica gel adsorbents prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to adsorption performance tests, and the specific steps are as follows:

[0091] In a high-pressure adsorption evaluation device, simulating a Basel slurry HDPE process, the following conditions were met: 50 ppm water, 30 ppm oxygenated compounds (mainly methanol, ethanol, dimethyl ether, and acetone), and 500 ppm low-molecular-weight waxes. The adsorption was carried out at a space velocity of 3 h⁻¹. -1 Dynamic adsorption experiments were conducted under the conditions of 30℃ temperature and 0.5MPa pressure. The amount of adsorbent was 30mL. Samples were taken periodically to detect the impurity content. The test results are shown in Table 1.

[0092] Table 1 Adsorption performance test results for different groups

[0093]

[0094] The silica gel adsorbents prepared in Examples 1-3 of this invention were subjected to physical property tests. Specific surface area: determined using liquid nitrogen adsorption-desorption (BET) under degassing conditions of 150℃ for 3 hours; pore volume: calculated based on the total pore volume of single-point adsorption according to the BET adsorption isotherm; wherein... Figure 2 The graph shows the BET test results of the silica gel adsorbent provided in Example 1 of the present invention.

[0095] Mechanical strength: The average value of 10 particles was taken using a particle compressive strength tester.

[0096] The wear rate was determined using the tumbling wear method, with a tumbling time of 30 minutes.

[0097] The test results are shown in Tables 2 and 3.

[0098] Table 2. Physical performance test results for different groups

[0099]

[0100] Table 3. BET test results of the silica gel adsorbent provided in Example 1

[0101]

[0102] After the silica gel adsorbent sample prepared in Example 1 was saturated with adsorption, it was regenerated with steam. The specific steps are as follows: steam at 152°C and 0.5 MPa was introduced into the adsorption tower for 3 hours. The desorbed impurities were separated and treated after condensation with the steam. After regeneration, the adsorption experiment was repeated and the product was recycled 30 times. The impurity content in the recycled hexane after 6 hours of adsorption was tested. The moisture content was found to be <1 ppm, the oxygen content was <1 ppm, and the low molecular weight wax content was <10 ppm. It can be seen that the silica gel adsorbent provided by the present invention has a good regeneration effect.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a silica gel adsorbent for hexane purification, characterized in that, Includes the following steps: S1. Dissolve the silicon source in an aqueous ethanol solution, then add the aluminum source and the boron source to it, mix well, then add the polycondensation agent, heat and stir to react, and obtain a sol. S2. Add template agent and pore expander to sol in sequence, disperse evenly by ultrasonication, then add tin salt, stir evenly, and shape the resulting sol by extrusion molding or spray drying. Then dry the shaped particles and calcine to obtain composite particles. S3. Disperse the composite particles in an ethanol aqueous solution, then add silane coupling agent KH570, stir, filter, wash and dry to obtain double bond modified composite particles. S4. Disperse the double bond modified composite particles in toluene solvent, then add octadecyl acrylate and hydroxyethyl methacrylate, stir evenly, then add azobisisobutyronitrile and heat to react. After the reaction is completed, filter, wash and dry to obtain silica gel adsorbent for hexane purification. The composition, by weight, includes 8-12 parts silicon source, 1-3 parts aluminum source, 0.3-0.6 parts boron source, 0.2-0.6 parts polycondensation agent, 0.04-0.12 parts template agent, 0.1-0.5 parts pore expander agent, and 0.05-0.1 parts tin salt.

2. The preparation method according to claim 1, characterized in that, The silicon source is selected from tetraethyl orthosilicate, silica sol, or water glass; the aluminum source is selected from aluminum sulfate, aluminum nitrate, or aluminum chloride; the boron source is selected from boric acid or triisopropyl borate; the polycondensation agent is selected from tetraethylammonium hydroxide; the template agent is selected from hexadecyltrimethylammonium bromide; the pore-expanding agent is selected from polyethylene glycol; and the tin salt is selected from tin chloride or stannous sulfate.

3. The preparation method according to claim 1, characterized in that, In step S1, the temperature for heating and stirring the reaction is 60-70℃, and the reaction time is 2-4 hours.

4. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of the composite particles to the silane coupling agent KH570 is 10-15:0.5-1.

5. The preparation method according to claim 1, characterized in that, In step S4, the mass ratio of the double bond modified composite particles, octadecyl acrylate, hydroxyethyl methacrylate, and azobisisobutyronitrile is 10-15:3-6:3-6:0.5-1.

6. The preparation method according to claim 1, characterized in that, In step S4, the temperature of the heating reaction is 65-75℃, and the heating reaction time is 4-8h.

7. The silica gel adsorbent prepared by the preparation method according to any one of claims 1-6.

8. The silica gel adsorbent as described in claim 7, characterized in that, The specific surface area of ​​the silica gel adsorbent is 500-700 m². 2 / g, with a mesopore size distribution of 2-50nm and a pore volume of 0.2-1.0cm³. 3 / g, compressive strength ≥90N, wear rate ≤1%.

9. The application of the silica gel adsorbent as described in claim 7 in the purification of hexane.

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