Silica gel adsorbent for hexane refining as well as preparation method and application of silica gel adsorbent

Abstract

The invention relates to the technical field of adsorbent preparation, and particularly discloses a silica gel adsorbent for hexane refining as well as a preparation method and application of the silica gel adsorbent for hexane refining. A boron-tin dual-modified skeleton and a surface grafted polymer layer form a multi-stage synergistic purification system, a tin coordination center realizes selective strong adsorption on oxygen-containing compounds and water, a long-chain alkyl side chain of the surface grafted polymer layer has excellent adsorption capacity on low-molecular-weight wax, surface capture is carried out on water and polar impurities through hydroxyl, and efficient and synchronous removal of the low-molecular-weight wax, the oxygen-containing compounds and the water in cyclic cyclohexane is realized. The technical defects that an existing adsorbent cannot simultaneously remove multiple impurities and is poor in water resistance and difficult to regenerate are overcome, long-period stable operation of a polyethylene device is guaranteed, and the industrial application value is remarkable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorbent preparation, and particularly relates to a silica gel adsorbent for hexane refining and a preparation method and application thereof. BACKGROUND

[0002] In a polyethylene production device, hexane is a widely used solvent, especially in a slurry method polyethylene process and an ultra-high molecular weight polyethylene device as a key circulating medium, and a high density polyethylene (HDPE) device of a Basell Hostalen process and a Mitsui CX process device are typical application representatives. Taking a low-pressure slurry polymerization process as an example, the process produces a unimodal, bimodal and multimodal HDPE product through copolymerization of ethylene and butene-1 under the action of a Ziegler-Natta catalyst with hexane as a dispersion medium. In the polymerization process, circulating hexane gradually accumulates low molecular wax (ethylene oligomer), oxygen-containing compounds (alcohols, ethers and the like) and moisture and the like impurities, which seriously affect catalyst activity, polymerization reaction stability and product quality, and may also cause heat exchangers and evaporators to be blocked, threatening long-period operation of the device.

[0003] Existing adsorbents for hexane refining mainly include ordinary silica gel, alumina and molecular sieve and the like, but obvious technical defects exist: ordinary silica gel can dehydrate, but has small specific surface area, narrow pore size distribution, cannot effectively accommodate macromolecular low molecular wax, and has poor water resistance and is easy to pulverize during regeneration; the alumina adsorbent has good lipophilic performance, has a certain adsorption capacity for oxygen-containing compounds, but has limited dehydration effect, and has high regeneration temperature and large energy consumption; the molecular sieve has strong adsorption selectivity, but has too small pore size, is difficult to remove macromolecular low molecular wax, and is easy to cause adsorbate polymerization reaction in the regeneration process.

[0004] In order to solve the above problems, relevant research attempts to develop composite adsorbents, such as silico-aluminate adsorbents, which improve adsorption performance by regulating the silicon-aluminum ratio, but mainly target the field of gas drying and cannot meet the needs of simultaneous removal of multiple impurities in the hexane system; although aluminum-modified silica gel improves mechanical strength and adsorption capacity, there are still deficiencies in the selectivity of multiple impurity removal and regeneration stability. Therefore, it is of great significance for efficient operation of a polyethylene device to develop a special silica gel adsorbent with large specific surface area, suitable mesoporous structure, hydrophilic and hydrophobic synergistic characteristics, good water resistance and simple regeneration. SUMMARY

[0005] In view of the defects that the existing adsorbents cannot simultaneously remove multiple impurities, have poor water resistance and are difficult to regenerate in the hexane refining of a slurry method polyethylene and an ultra-high molecular weight polyethylene process, the present application provides a silica gel adsorbent for hexane refining with reasonable preparation process and excellent performance, realizes efficient simultaneous removal of low molecular wax, oxygen-containing compounds and moisture in circulating hexane, and ensures long-period stable use of the adsorbent.

[0006] The technical scheme of the present application is implemented as follows: the present application provides a preparation method of silica gel adsorbent for hexane refining, comprising the following steps: S1, dissolving a silicon source in an ethanol aqueous solution, then adding an aluminum source and a boron source thereto, mixing uniformly, then adding a composite polycondensation agent thereto, heating and stirring to react, to obtain a sol; S2, sequentially adding a special template agent and a pore-expanding agent to the sol, ultrasonic dispersion to be uniform, then adding a tin salt, stirring to be uniform, using the obtained sol to be formed by extrusion or spray drying, then drying the formed particles and calcining, to obtain composite particles; S3, dispersing the composite particles in an ethanol aqueous solution, then adding a vinyl silane coupling agent thereto, stirring to treat, then filtering, washing and drying, to obtain double bond modified composite particles; S4, dispersing the double bond modified composite particles in a toluene solvent, then adding octadecyl acrylate and hydroxyethyl methacrylate thereto, stirring to be uniform, then adding azobisisobutyronitrile to heat to react, after the reaction is completed, filtering, washing and drying, to obtain the silica gel adsorbent for hexane refining.

[0007] In the technical scheme disclosed in the present application, the silicon source is 8-12 parts by weight, the aluminum source is 1-3 parts by weight, the boron source is 0.3-0.6 parts by weight, the composite polycondensation agent is 0.2-0.6 parts by weight, the special template agent is 0.04-0.12 parts by weight, the pore-expanding agent is 0.1-0.5 parts by weight, and the tin salt is 0.05-0.1 parts by weight.

[0008] In the technical scheme disclosed in the present application, the silicon source is selected from tetraethyl orthosilicate, silica sol or water glass.

[0009] In the technical scheme disclosed in the present application, the aluminum source is selected from aluminum sulfate, aluminum nitrate or aluminum chloride.

[0010] In the technical scheme disclosed in the present application, the boron source is selected from boric acid or triisopropyl borate.

[0011] In the technical scheme disclosed in the present application, the composite polycondensation agent is selected from tetraethylammonium hydroxide.

[0012] In the technical scheme disclosed in the present application, the special template agent is selected from cetyltrimethylammonium bromide.

[0013] In the technical scheme disclosed in the present application, the pore-expanding agent is selected from polyethylene glycol.

[0014] In the technical scheme disclosed in the present application, the tin salt is selected from tin chloride or stannous sulfate.

[0015] In the technical solution disclosed in the present application, in step S1, the temperature of the heating and stirring reaction is 60-70℃, for example, it can be selected as 60℃, 62℃, 65℃, 68℃, 80℃; the time of the heating and stirring reaction is 2-4h, for example, it can be selected as 2h, 2.5h, 3h, 3.5h, 4h; but it is not limited to the listed values, and other values not listed in the value range are also applicable.

[0016] In step S1, the basic silicon-oxygen skeleton is constructed by the hydrolysis and condensation reaction of the silicon source in the aqueous ethanol solution, and the introduction of the composite condensation agent can control the balance of the hydrolysis and condensation rate; the addition of the aluminum source makes the aluminum atoms partially replace the silicon atom positions in the silicon-oxygen tetrahedron, thereby enhancing the mechanical strength and thermal stability of the material; the doping of boron can locally produce skeleton distortion and defects, and these defect sites are converted into weak acid centers after calcination, which have a certain adsorption effect on low molecular waxes and oxygen-containing compounds.

[0017] In the technical solution disclosed in the present application, in step S2, the time of ultrasonic dispersion is 30-60min.

[0018] In step S2, the special template agent self-assembles into micellar structures in the sol system, and after calcination and removal, regular mesoporous channels are left, and these mesopores act as mass transfer channels to reduce the diffusion resistance of the adsorbate. The pore expanding agent molecules are inserted into the template micelles to make the micelles swell, and finally larger pore channels are formed. This double-template strategy constructs a hierarchical pore system with mesopores-macropores, which not only ensures the specific surface area, but also can accommodate low molecular waxes with larger molecular size.

[0019] By adding tin salt, tin is combined with the silicon-aluminum-boron skeleton through covalent bond or strong coordination, and is converted into tin oxide particles after calcination. Tin, as a soft acid metal, has a certain coordination affinity for oxygen-containing compounds. At the same time, the surface of tin oxide has moderate Lewis acidity, which can produce weak interaction with the weak polar groups (such as the methylene group) in the low molecular wax molecules, thereby enhancing the retention capacity of low molecular wax.

[0020] In the technical solution disclosed in the present application, in step S3, the mass ratio of the composite particles and the vinyl silane coupling agent is 10-15:0.5-1, for example, it can be selected as 10:0.5, 10:0.8, 10:1, 12:0.5, 12:0.8, 12:1, 15:0.5, 15:0.8, 15:1, but it is not limited to the listed values, and other values not listed in the value range are also applicable.

[0021] In the technical solution disclosed in the present application, the vinyl silane coupling agent is selected from KH570, vinyl trimethylsilane or vinyl triethoxysilane.

[0022] In the technical scheme disclosed in the present application, 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.

[0023] In the technical scheme disclosed in the present application, in step S4, the temperature of the heating reaction is 65-75℃, for example, 65℃, 70℃ or 75℃ can be selected; the time of the heating reaction is 4-8h, for example, 4h, 5h, 6h, 7h or 8h can be selected, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0024] In step S4, the ethylene groups on the surface of the double bond modified composite particles are subjected to a free radical copolymerization reaction with octadecyl acrylate and hydroxyethyl methacrylate under the initiation of azobisisobutyronitrile, and the polymer chains are grafted and grown on the particle surface in the form of chemical bonds, and the octadecyl acrylate contributes long-chain alkyl side chains, and these hydrophobic carbon chains significantly improve the hydrophobicity of the material and the adsorption capacity of the material for low molecular waxes; the hydroxyethyl methacrylate introduces hydroxyl groups into the polymer chains, and these hydroxyl groups act as hydrogen bond donors and acceptors to form hydrogen bond adsorption with water molecules and oxygen-containing compounds, thereby enhancing the capture capacity for such polar impurities.

[0025] The present application provides a silica gel adsorbent prepared by the above preparation method.

[0026] In the technical scheme disclosed in the present application, the specific surface area of the silica gel adsorbent prepared by the present application is 500-700m 2 / g, the mesopore size distribution is 2-50nm, the pore volume is 0.2-1.0cm 3 / g, the compressive strength is ≥90N, and the abrasion rate is ≤1%.

[0027] The present application also provides the application of the above silica gel adsorbent in hexane refining.

[0028] Specifically, the application of the silica gel adsorbent prepared by the present application in hexane refining in the Basel Hostalen ACP low-pressure slurry polymerization process HDPE device.

[0029] Specifically, the application step comprises: filling the adsorbent in a fixed bed adsorption tower, and circulating hexane through the adsorption tower under the conditions of a space velocity of 1-5h -1 , a temperature of 0-50℃ and a pressure of 0.1-4.0MPa to remove low molecular waxes, oxygen-containing compounds and water from the hexane.

[0030] After the adsorbent provided by the present application is saturated, it is regenerated by water vapor, and the regeneration conditions are: water vapor temperature 120-150℃, pressure 0.2-0.4MPa, and the adsorbent can be recycled for ≥30 times.

[0031] The present application has the following advantages over the prior art: (1) The present application constructs a basic silica skeleton through hydrolysis and condensation of silicon source in aqueous ethanol solution, and the introduction of complex condensation agent can control the balance of hydrolysis and condensation rate; the addition of aluminum source makes aluminum atoms partially replace silicon atoms in the silicon-oxygen tetrahedron, enhancing the mechanical strength and thermal stability of the material; the doping of boron can produce local skeleton distortion and defects, and these defect sites are converted into weak acid centers after calcination, which have certain adsorption effect on low molecular wax and oxygen-containing compounds.

[0032] (2) The present application adds tin salt, and tin is combined with the silicon-aluminum-boron skeleton through covalent bond or strong coordination, which is converted into tin oxide particles after calcination. Tin, as a soft acid metal, has certain coordination affinity for oxygen-containing compounds. At the same time, the surface of tin oxide has moderate Lewis acidity, which can produce weak interaction with the weakly polar groups (such as the methylene group) in the low molecular wax molecules, enhancing the interception capacity of low molecular wax.

[0033] (3) The present application modifies the surface of the double bond composite particles with vinyl and octadecyl acrylate, hydroxyethyl methacrylate, which undergoes free radical copolymerization under the initiation of azobisisobutyronitrile. The polymer chains grow on the surface of the particles in the form of chemical bonds. Octadecyl acrylate contributes long-chain alkyl side chains, which significantly improve the hydrophobicity of the material and enhance its adsorption capacity for low molecular wax. Hydroxyethyl methacrylate introduces hydroxyl groups into the polymer chain, which act as hydrogen bond donors and acceptors, forming hydrogen bond adsorption with water molecules and oxygen-containing compounds, and enhancing the capture capacity of these polar impurities.

[0034] (4) The present application provides a boron-tin double-modified skeleton and a surface grafted polymer layer to form a multi-level synergistic purification system: boron regulates the acidity and alkalinity of the skeleton to provide primary adsorption sites for low molecular wax and polar molecules, tin coordination centers achieve selective 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 wax, and the hydroxyl groups capture water and polar impurities on the surface, achieving efficient simultaneous removal of low molecular wax, oxygen-containing compounds and water in the circulating hexane. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0036] Figure 1This is a physical image of the silica gel adsorbent provided in Embodiment 1 of the present invention; Figure 2 The graph shows the BET test results of the silica gel adsorbent provided in Example 1 of the present invention. Detailed Implementation

[0037] 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.

[0038] Example 1 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0039] Example 2 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0040] Example 3 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0041] Comparative Example 1 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0042] Compared to Comparative Example 1 and Example 1, no boric acid was added.

[0043] Comparative Example 2 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0044] Compared to Example 1, no tin chloride was added in Comparative Example 2.

[0045] Comparative Example 3 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0046] Compared with Example 1, tin chloride was replaced with zirconium nitrate in Comparative Example 3.

[0047] Comparative Example 4 A method for preparing a silica gel adsorbent for hexane purification includes the following steps: 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. 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. 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. 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.

[0048] Compared to Example 1, Comparative Example 4 did not contain hydroxyethyl methacrylate.

[0049] 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: 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.

[0050] Table 1 Adsorption performance test results for different groups 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.

[0051] Mechanical strength: The average value of 10 particles was taken using a particle compressive strength tester. The wear rate was determined using the tumbling wear method, with a tumbling time of 30 minutes.

[0052] The test results are shown in Tables 2 and 3.

[0053] Table 2. Physical performance test results for different groups Table 3. BET test results of the silica gel adsorbent provided in Example 1 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.

[0054] 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 boron source to it, mix well, then add the composite polycondensation agent, heat and stir to react, and obtain a sol. 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. 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. 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.

2. The preparation method according to claim 1, characterized in that, By weight, the composition is as follows: 8-12 parts silicon source, 1-3 parts aluminum source, 0.3-0.6 parts boron source, 0.2-0.6 parts composite polycondensation agent, 0.04-0.12 parts special template agent, 0.1-0.5 parts pore expander, and 0.05-0.1 parts tin salt.

3. 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 composite polycondensation agent is selected from tetraethylammonium hydroxide; the special 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.

4. 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.

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

6. 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.

7. 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.

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

9. The silica gel adsorbent as described in claim 8, 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%.

10. The application of the silica gel adsorbent as described in claim 8 in the purification of hexane.

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