Preparation method of high porosity adsorption silica gel

Abstract

The application relates to the technical field of adsorbing silica gel, and discloses a preparation method of high-porosity adsorbing silica gel. In the application, styrene, acrylic acid and a modified crosslinking agent are polymerized to obtain modified polystyrene microspheres; the silicon hydroxyl generated by hydrolysis of triethoxysilyl in a silane coupling agent type quaternary phosphonium salt and the carboxyl on the surface of the modified polystyrene microspheres are subjected to a dehydration condensation reaction to obtain quaternary phosphonium salt grafted modified polystyrene microspheres; the quaternary phosphonium salt grafted modified polystyrene microspheres are used as sacrificial space-occupying templates; and a sol-gel process is combined to synchronously construct a double-stage hierarchical pore structure, so that the porosity of the adsorbing silica gel is improved.

Description

Technical Field

[0001] This invention relates to the field of silica gel adsorption technology, specifically a method for preparing high-porosity silica gel adsorption. Background Technology

[0002] Silica gel is a core porous material in wastewater heavy metal treatment, VOC exhaust gas treatment, and biomolecule separation. Porosity is a key indicator determining its adsorption capacity and mass transfer efficiency. Currently, the mainstream method in the industry is to prepare hierarchical porous silica gel using polystyrene microsphere templates. However, due to the hydrophobic surface properties of ordinary polystyrene microspheres, the microspheres are prone to irreversible aggregation in the silica sol system, resulting in ineffective closed pores in the finished product. Conventional products have low porosity, making it difficult to meet the requirements of high-load adsorption scenarios. Existing optimization solutions in the industry mostly use carboxyl and hydroxyl groups to perform simple hydrophilic modification on the surface of microspheres. Although this can reduce the aggregation effect to some extent, the interfacial bonding between the modified microspheres and silica sol is still weak. During calcination, pore wall collapse and mesopore blockage are prone to occur, becoming a core technical bottleneck restricting the large-scale application of high-capacity adsorbent silica gel. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for preparing high-porosity adsorbent silica gel. The adsorbent silica gel prepared by this invention has high porosity.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-porosity adsorbent silica gel, comprising the following steps: Step 1: Add 9-11g of tetraethyl orthosilicate, 15-25mL of anhydrous ethanol, and 8-12mL of ultrapure water to the reaction flask, stir and mix, add 0.1-0.12mol / L hydrochloric acid solution dropwise to adjust the pH to 2.5-3, heat to 38-42℃ and stir for 1-1.5h to obtain silica sol; Step 2: Add 0.4-0.6 g of quaternary phosphonium salt-grafted modified polystyrene microspheres to the silica sol, ultrasonically disperse for 10-20 min, stir at 36-44℃ for 1-1.5 h, add 0.1-0.12 mol / L ammonia solution dropwise to adjust the pH to 6.9-7.1, heat to 60-65℃ and allow to stand for 3.5-4.5 h to solidify, obtaining a wet gel. Place the wet gel at 62-68℃ and 8% relative humidity. The silica gel is aged in a constant temperature and humidity chamber at 5%-95% for 20-24 hours. After aging, it is freeze-dried at -55--45℃ for 18-22 hours to obtain a dry gel. The dry gel is placed in a muffle furnace and heated from room temperature to 300-310℃ at a rate of 1-2℃ / min, held for 2-3 hours, and then heated to 542-555℃ at a rate of 2-3℃ / min, held for 3-4 hours, and cooled to room temperature to obtain high-porosity adsorbent silica gel.

[0005] Preferably, the quaternary phosphonium salt-grafted modified polystyrene microspheres are prepared by the following steps: (1) Under a nitrogen atmosphere, add 2.6-2.74 g of 4-((4-hydroxyphenyl)azo)benzaldehyde to 40-60 mL of anhydrous ethanol solvent, stir to dissolve, add 0.4-0.6 mL of acetic acid catalyst, continue stirring for 5-10 min, add 2.5-2.66 g of 2-(diphenylphosphine)ethylamine dropwise, after the addition is complete, heat to 75-83℃ and react for 9-12 h. After the reaction is complete, cool to room temperature, filter under reduced pressure, wash and dry under vacuum to obtain intermediate 1; (2) Add 4.6-4.7g of intermediate 1 to 80-100mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 74-78℃, add 3.2-3.36g of 11-chloroundecyltriethoxysilane dropwise, after the addition is complete, continue the reaction for 8-10h, after the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 40-60mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain silane coupling agent type quaternary phosphonium salt; (3) Add 7-8g of styrene, 1.2-1.8g of acrylic acid, 0.7-1.2g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.08-0.12g of azobisisobutyronitrile initiator to 60-90mL of anhydrous ethanol solvent, stir to dissolve, purge with nitrogen gas for protection, heat to 65-75℃, and react for 11-14h. After the reaction is completed, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (4) Add 1.5-2.5g of modified polystyrene microspheres to 20-30mL of toluene solvent, disperse ultrasonically for 20-30min, add 0.1-0.2g of silane coupling agent type quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 4-5 with acetic acid, heat to 58-64℃ and react for 4-7h. After the reaction is completed, cool to room temperature, collect the microspheres by centrifugation, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres.

[0006] Preferably, the dropping time of 11-chloroundecyltriethoxysilane in step (2) is 25-35 min.

[0007] Preferably, the mass of hydroquinone polymerization inhibitor in step (3) is 0.08%-0.12% of the total mass of styrene, acrylic acid, and modified crosslinking agent.

[0008] Preferably, the modified crosslinking agent in step (3) is prepared by the following steps: Under a nitrogen atmosphere, 2-2.4g of N-vinylpyrrolidone, 1.8-1.9g of 3-aminopropanol vinyl ether, and 0.004-0.008g of hydroquinone polymerization inhibitor are added to 30-50mL of anhydrous ethanol solvent, stirred and dissolved, and the pH value is adjusted to 3-4 with acetic acid. 1.7-1.84g of formaldehyde solution with a mass fraction of 37%-38% is added dropwise. After the addition is completed, the temperature is raised to 70-75℃ and reacted for 4.5-6h. After the reaction is completed, the temperature is cooled to room temperature, and the pH value is adjusted to 6.8-7.2 with a mass fraction of 9%-10% sodium hydroxide solution. The solvent is removed by rotary evaporation, and the modified crosslinking agent is obtained by vacuum distillation.

[0009] Preferably, the temperature is controlled at 20-30℃ during the formaldehyde solution dropwise addition process.

[0010] In summary, this application includes at least one of the following beneficial technical effects: This invention polymerizes styrene, acrylic acid, and a modified crosslinking agent to obtain modified polystyrene microspheres. The silanol groups generated by the hydrolysis of the triethoxysilyl group in the silane coupling agent quaternary phosphonium salt undergo a dehydration condensation reaction with the carboxyl groups on the surface of the modified polystyrene microspheres to obtain quaternary phosphonium salt-grafted modified polystyrene microspheres. Using the quaternary phosphonium salt-grafted modified polystyrene microspheres as sacrificial site templates, combined with a sol-gel process, the microspheres completely decompose during calcination to form macropores, while the interstitial gaps between the silicon nanoparticles formed by the hydrolysis and condensation of tetraethyl orthosilicate form mesopores, simultaneously constructing a bilevel hierarchical pore structure.

[0011] In the modified crosslinking agent, the nitrogen atom in the pyrrole group forms hydrogen bonds with the silanol group of the silica sol, which enhances the hydrophilicity of the microspheres, prevents hydrophobic aggregation of the microspheres, reduces ineffective closed pores caused by macropore stacking, and directly increases the effective proportion of macropores. The secondary amino group in the Mannich base structure has both hydrogen bond donor and acceptor properties. On the one hand, it anchors the silica sol to avoid interfacial gaps and reduces pore wall collapse during calcination. On the other hand, it buffers the condensation rate of silica sol, prevents silica particles from agglomerating and blocking mesopores, and improves the mesopore retention rate. In the silane coupling agent type quaternary phosphonium salt, the azo group decomposes and releases gas when the microsphere template is removed during calcination, forming additional through-pores in the silica gel, thereby improving the open porosity. The strong positive charge of the quaternary phosphonium salt can adsorb the negatively charged silica sol under weakly acidic conditions through electrostatic adsorption, forming a uniform silica sol coating layer on the surface of the microspheres, avoiding mesopore blockage caused by local aggregation of silica particles. Attached Figure Description

[0012] Figure 1 It is the synthetic reaction formula for quaternary phosphonium salts in the form of silane coupling agents.

[0013] Figure 2 It is the synthesis reaction formula of the modified crosslinking agent. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0016] Example 1 (1) Under a nitrogen atmosphere, 2g of N-vinylpyrrolidone, 1.8g of 3-aminopropanol vinyl ether, and 0.004g of hydroquinone polymerization inhibitor were added to 30mL of anhydrous ethanol solvent. The mixture was stirred and dissolved. The pH was adjusted to 3 with acetic acid. 1.7g of 37% formaldehyde solution was added dropwise, with the temperature controlled at 20℃ during the addition. After the addition was complete, the temperature was raised to 70℃ and the reaction was allowed to proceed for 4.5h. After the reaction was completed, the mixture was cooled to room temperature. The pH was adjusted to 6.8 with 9% sodium hydroxide solution. The solvent was removed by rotary evaporation, and the mixture was distilled under reduced pressure to obtain the modified crosslinking agent. The synthesis reaction formula is as follows: Figure 2 As shown; (2) Under a nitrogen atmosphere, 2.6 g of 4-((4-hydroxyphenyl)azo)benzaldehyde was added to 40 mL of anhydrous ethanol solvent and stirred to dissolve. 0.4 mL of acetic acid catalyst was added and stirred for 5 min. 2.5 g of 2-(diphenylphosphine)ethylamine was added dropwise. After the addition was complete, the temperature was raised to 75 °C and reacted for 9 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, washed and dried under vacuum to obtain intermediate 1. (3) Add 4.6 g of intermediate 1 to 80 mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 74 °C, and add 3.2 g of 11-chloroundecyltriethoxysilane dropwise over 25 min. After the addition is complete, continue the reaction for 8 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 40 mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain a silane coupling agent type quaternary phosphonium salt; the synthesis reaction formula is as follows. Figure 1 As shown; (4) Add 7g of styrene, 1.2g of acrylic acid, 0.7g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.08g of azobisisobutyronitrile initiator to 60mL of anhydrous ethanol solvent. The mass of hydroquinone polymerization inhibitor is 0.08% of the total mass of styrene, acrylic acid, and modified crosslinking agent. Stir to dissolve, purge with nitrogen for protection, heat to 65℃, and react for 11h. After the reaction is complete, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (5) Add 1.5g of modified polystyrene microspheres to 20mL of toluene solvent, sonicate for 20min, add 0.1g of silane coupling agent quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 4 with acetic acid, heat to 58℃ and react for 4h. After the reaction is completed, cool to room temperature, centrifuge to collect the microspheres, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres. (6) Add 9g of tetraethyl orthosilicate, 15mL of anhydrous ethanol and 8mL of ultrapure water to the reaction flask, stir and mix, add 0.1mol / L hydrochloric acid solution dropwise to adjust the pH value to 2.5, heat to 38℃ and stir for 1h to obtain silica sol. (7) Add 0.4 g of quaternary phosphonium salt-grafted modified polystyrene microspheres to silica sol, ultrasonically disperse for 10 min, stir at 36 °C for 1 h, add 0.1 mol / L ammonia solution dropwise to adjust the pH value to 6.9, heat to 60 °C and let stand for 3.5 h to obtain wet gel, place the wet gel in a constant temperature and humidity chamber at 62 °C and 85% relative humidity for 20 h to age, after aging, freeze dry at -55 °C for 18 h to obtain dry gel, place the dry gel in a muffle furnace, heat from room temperature to 300 °C at a rate of 1 °C / min, keep at 300 °C for 2 h, then heat to 542 °C at a rate of 2 °C / min, keep at 3 h, cool to room temperature to obtain high porosity adsorbed silica gel.

[0017] Example 2 (1) Under a nitrogen atmosphere, 2.4 g of N-vinylpyrrolidone, 1.9 g of 3-aminopropanol vinyl ether, and 0.008 g of hydroquinone polymerization inhibitor were added to 50 mL of anhydrous ethanol solvent. The mixture was stirred and dissolved. The pH was adjusted to 4 with acetic acid. 1.84 g of 38% formaldehyde solution was added dropwise, with the temperature controlled at 30 °C during the addition. After the addition was complete, the temperature was raised to 75 °C and reacted for 6 h. After the reaction was completed, the mixture was cooled to room temperature, and the pH was adjusted to 7.2 with 10% sodium hydroxide solution. The solvent was removed by rotary evaporation, and the mixture was distilled under reduced pressure to obtain the modified crosslinking agent. The synthesis reaction formula is as follows: Figure 2 As shown; (2) Under a nitrogen atmosphere, 2.74 g of 4-((4-hydroxyphenyl)azo)benzaldehyde was added to 60 mL of anhydrous ethanol solvent and stirred to dissolve. 0.6 mL of acetic acid catalyst was added and stirred for 10 min. 2.66 g of 2-(diphenylphosphine)ethylamine was added dropwise. After the addition was complete, the temperature was raised to 83 °C and the reaction was carried out for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, washed and dried under vacuum to obtain intermediate 1. (3) Add 4.7 g of intermediate 1 to 100 mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 78 °C, and add 3.36 g of 11-chloroundecyltriethoxysilane dropwise over 35 min. After the addition is complete, continue the reaction for 10 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 60 mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain a silane coupling agent type quaternary phosphonium salt; the synthesis reaction formula is as follows. Figure 1 As shown; (4) Add 8g of styrene, 1.8g of acrylic acid, 1.2g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.12g of azobisisobutyronitrile initiator to 90mL of anhydrous ethanol solvent. The mass of hydroquinone polymerization inhibitor is 0.12% of the total mass of styrene, acrylic acid, and modified crosslinking agent. Stir to dissolve, purge with nitrogen for protection, heat to 75℃, and react for 14h. After the reaction is complete, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (5) Add 2.5g of modified polystyrene microspheres to 30mL of toluene solvent, sonicate for 30min, add 0.2g of silane coupling agent quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 5 with acetic acid, heat to 64℃ and react for 7h. After the reaction is completed, cool to room temperature, centrifuge to collect microspheres, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres. (6) Add 11g of tetraethyl orthosilicate, 25mL of anhydrous ethanol and 12mL of ultrapure water to the reaction flask, stir and mix, add 0.12mol / L hydrochloric acid solution dropwise to adjust the pH value to 3, heat to 42℃ and stir for 1.5h to obtain silica sol. (7) Add 0.6 g of quaternary phosphonium salt-grafted modified polystyrene microspheres to silica sol, ultrasonically disperse for 20 min, stir at 44 °C for 1.5 h, add 0.12 mol / L ammonia solution dropwise to adjust the pH value to 7.1, heat to 65 °C and let stand for 4.5 h to obtain wet gel, place the wet gel in a constant temperature and humidity chamber at 68 °C and 95% relative humidity for 24 h to age, after aging, freeze dry at -45 °C for 22 h to obtain dry gel, place the dry gel in a muffle furnace, heat from room temperature to 310 °C at a rate of 2 °C / min, keep at 3 h, then heat to 555 °C at a rate of 3 °C / min, keep at 4 h, cool to room temperature to obtain high porosity adsorbed silica gel.

[0018] Example 3 (1) Under a nitrogen atmosphere, 2.2 g of N-vinylpyrrolidone, 1.85 g of 3-aminopropanol vinyl ether, and 0.006 g of hydroquinone polymerization inhibitor were added to 40 mL of anhydrous ethanol solvent. The mixture was stirred and dissolved. The pH was adjusted to 3.5 with acetic acid. 1.77 g of 37.5% formaldehyde solution was added dropwise. The temperature was controlled at 25 °C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 72 °C and the reaction was allowed to proceed for 5.2 h. After the reaction was completed, the mixture was cooled to room temperature. The pH was adjusted to 7 with 9.5% sodium hydroxide solution. The solvent was removed by rotary evaporation, and the mixture was distilled under reduced pressure to obtain the modified crosslinking agent. The synthesis reaction formula is as follows: Figure 2 As shown; (2) Under a nitrogen atmosphere, 2.67 g of 4-((4-hydroxyphenyl)azo)benzaldehyde was added to 50 mL of anhydrous ethanol solvent and stirred to dissolve. 0.5 mL of acetic acid catalyst was added and stirred for 8 min. 2.58 g of 2-(diphenylphosphine)ethylamine was added dropwise. After the addition was complete, the temperature was raised to 79 °C and the reaction was carried out for 10.5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, washed and dried under vacuum to obtain intermediate 1. (3) Add 4.65 g of intermediate 1 to 90 mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 76 °C, and add 3.28 g of 11-chloroundecyltriethoxysilane dropwise over 30 min. After the addition is complete, continue the reaction for 9 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 50 mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain a silane coupling agent type quaternary phosphonium salt; the synthesis reaction formula is as follows. Figure 1 As shown; (4) Add 7.5g of styrene, 1.5g of acrylic acid, 0.95g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.1g of azobisisobutyronitrile initiator to 75mL of anhydrous ethanol solvent. The mass of hydroquinone polymerization inhibitor is 0.1% of the total mass of styrene, acrylic acid, and modified crosslinking agent. Stir to dissolve, purge with nitrogen for protection, heat to 70℃, and react for 12.5h. After the reaction is complete, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (5) Add 2g of modified polystyrene microspheres to 25mL of toluene solvent, sonicate for 25min, add 0.15g of silane coupling agent quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 4.5 with acetic acid, heat to 61℃ and react for 5.5h. After the reaction is completed, cool to room temperature, centrifuge to collect the microspheres, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres; (6) Add 10g of tetraethyl orthosilicate, 20mL of anhydrous ethanol and 10mL of ultrapure water to the reaction flask, stir and mix, add 0.11mol / L hydrochloric acid solution dropwise to adjust the pH value to 2.8, heat to 40℃ and stir for 1.2h to obtain silica sol; (7) Add 0.5g of quaternary phosphonium salt-grafted modified polystyrene microspheres to silica sol, ultrasonically disperse for 15min, stir at 40℃ for 1.2h, add 0.11mol / L ammonia solution dropwise to adjust the pH value to 7, heat to 62℃ and let stand for 4h to solidify to obtain wet gel. Place the wet gel in a constant temperature and humidity chamber at 65℃ and 90% relative humidity for 22h to age. After aging, freeze dry at -50℃ for 20h to obtain dry gel. Place the dry gel in a muffle furnace and heat from room temperature to 305℃ at a rate of 1℃ / min, hold for 2.5h, then heat to 549℃ at a rate of 3℃ / min, hold for 3.5h, and cool to room temperature to obtain high porosity adsorbed silica gel.

[0019] Example 4 (1) Under a nitrogen atmosphere, 2g of N-vinylpyrrolidone, 1.8g of 3-aminopropanol vinyl ether, and 0.004g of hydroquinone polymerization inhibitor were added to 30mL of anhydrous ethanol solvent. The mixture was stirred and dissolved. The pH was adjusted to 3 with acetic acid. 1.7g of 37% formaldehyde solution was added dropwise, with the temperature controlled at 20℃ during the addition. After the addition was complete, the temperature was raised to 70℃ and the reaction was allowed to proceed for 4.5h. After the reaction was completed, the mixture was cooled to room temperature. The pH was adjusted to 6.8 with 9% sodium hydroxide solution. The solvent was removed by rotary evaporation, and the mixture was distilled under reduced pressure to obtain the modified crosslinking agent. The synthesis reaction formula is as follows: Figure 2 As shown; (2) Under a nitrogen atmosphere, 2.6 g of 4-((4-hydroxyphenyl)azo)benzaldehyde was added to 40 mL of anhydrous ethanol solvent and stirred to dissolve. 0.4 mL of acetic acid catalyst was added and stirred for 5 min. 2.5 g of 2-(diphenylphosphine)ethylamine was added dropwise. After the addition was complete, the temperature was raised to 75 °C and reacted for 9 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, washed and dried under vacuum to obtain intermediate 1. (3) Add 4.7 g of intermediate 1 to 100 mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 78 °C, and add 3.36 g of 11-chloroundecyltriethoxysilane dropwise over 35 min. After the addition is complete, continue the reaction for 10 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 60 mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain a silane coupling agent type quaternary phosphonium salt; the synthesis reaction formula is as follows. Figure 1 As shown; (4) Add 8g of styrene, 1.8g of acrylic acid, 1.2g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.12g of azobisisobutyronitrile initiator to 90mL of anhydrous ethanol solvent. The mass of hydroquinone polymerization inhibitor is 0.12% of the total mass of styrene, acrylic acid, and modified crosslinking agent. Stir to dissolve, purge with nitrogen for protection, heat to 75℃, and react for 14h. After the reaction is complete, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (5) Add 2g of modified polystyrene microspheres to 25mL of toluene solvent, sonicate for 25min, add 0.15g of silane coupling agent quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 4.5 with acetic acid, heat to 61℃ and react for 5.5h. After the reaction is completed, cool to room temperature, centrifuge to collect the microspheres, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres; (6) Add 10g of tetraethyl orthosilicate, 20mL of anhydrous ethanol and 10mL of ultrapure water to the reaction flask, stir and mix, add 0.11mol / L hydrochloric acid solution dropwise to adjust the pH value to 2.8, heat to 40℃ and stir for 1.2h to obtain silica sol; (7) Add 0.5g of quaternary phosphonium salt-grafted modified polystyrene microspheres to silica sol, ultrasonically disperse for 15min, stir at 40℃ for 1.2h, add 0.11mol / L ammonia solution dropwise to adjust the pH value to 7, heat to 62℃ and let stand for 4h to solidify to obtain wet gel. Place the wet gel in a constant temperature and humidity chamber at 65℃ and 90% relative humidity for 22h to age. After aging, freeze dry at -50℃ for 20h to obtain dry gel. Place the dry gel in a muffle furnace and heat from room temperature to 305℃ at a rate of 1℃ / min, hold for 2.5h, then heat to 549℃ at a rate of 3℃ / min, hold for 3.5h, and cool to room temperature to obtain high porosity adsorbed silica gel.

[0020] Example 5 (1) Under a nitrogen atmosphere, 2.2 g of N-vinylpyrrolidone, 1.85 g of 3-aminopropanol vinyl ether, and 0.006 g of hydroquinone polymerization inhibitor were added to 40 mL of anhydrous ethanol solvent. The mixture was stirred and dissolved. The pH was adjusted to 3.5 with acetic acid. 1.77 g of 37.5% formaldehyde solution was added dropwise. The temperature was controlled at 25 °C during the dropwise addition. After the dropwise addition was completed, the temperature was raised to 72 °C and the reaction was allowed to proceed for 5.2 h. After the reaction was completed, the mixture was cooled to room temperature. The pH was adjusted to 7 with 9.5% sodium hydroxide solution. The solvent was removed by rotary evaporation, and the mixture was distilled under reduced pressure to obtain the modified crosslinking agent. The synthesis reaction formula is as follows: Figure 2 As shown; (2) Under a nitrogen atmosphere, 2.67 g of 4-((4-hydroxyphenyl)azo)benzaldehyde was added to 50 mL of anhydrous ethanol solvent and stirred to dissolve. 0.5 mL of acetic acid catalyst was added and stirred for 8 min. 2.58 g of 2-(diphenylphosphine)ethylamine was added dropwise. After the addition was complete, the temperature was raised to 79 °C and the reaction was carried out for 10.5 h. After the reaction was completed, the mixture was cooled to room temperature, filtered under reduced pressure, washed and dried under vacuum to obtain intermediate 1. (3) Add 4.6 g of intermediate 1 to 80 mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 74 °C, and add 3.2 g of 11-chloroundecyltriethoxysilane dropwise over 25 min. After the addition is complete, continue the reaction for 8 h. After the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 40 mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain a silane coupling agent type quaternary phosphonium salt; the synthesis reaction formula is as follows. Figure 1 As shown; (4) Add 7g of styrene, 1.2g of acrylic acid, 0.7g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.08g of azobisisobutyronitrile initiator to 60mL of anhydrous ethanol solvent. The mass of hydroquinone polymerization inhibitor is 0.08% of the total mass of styrene, acrylic acid, and modified crosslinking agent. Stir to dissolve, purge with nitrogen for protection, heat to 65℃, and react for 11h. After the reaction is complete, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (5) Add 2.5g of modified polystyrene microspheres to 30mL of toluene solvent, sonicate for 30min, add 0.2g of silane coupling agent quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 5 with acetic acid, heat to 64℃ and react for 7h. After the reaction is completed, cool to room temperature, centrifuge to collect microspheres, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres. (6) Add 11g of tetraethyl orthosilicate, 25mL of anhydrous ethanol and 12mL of ultrapure water to the reaction flask, stir and mix, add 0.12mol / L hydrochloric acid solution dropwise to adjust the pH value to 3, heat to 42℃ and stir for 1.5h to obtain silica sol. (7) Add 0.6 g of quaternary phosphonium salt-grafted modified polystyrene microspheres to silica sol, ultrasonically disperse for 20 min, stir at 44 °C for 1.5 h, add 0.12 mol / L ammonia solution dropwise to adjust the pH value to 7.1, heat to 65 °C and let stand for 4.5 h to obtain wet gel, place the wet gel in a constant temperature and humidity chamber at 68 °C and 95% relative humidity for 24 h to age, after aging, freeze dry at -45 °C for 22 h to obtain dry gel, place the dry gel in a muffle furnace, heat from room temperature to 310 °C at a rate of 2 °C / min, keep at 3 h, then heat to 555 °C at a rate of 3 °C / min, keep at 4 h, cool to room temperature to obtain high porosity adsorbed silica gel.

[0021] Comparative Example 1 The difference between this comparative example and Example 5 is that it does not include step (1), and in step (4) the modified crosslinking agent is replaced with divinylbenzene.

[0022] Comparative Example 2 The difference between this comparative example and Example 5 is that it does not include steps (2), (3), and (5), and in step (7) the modified polystyrene microspheres are replaced with quaternary phosphonium salt grafted modified polystyrene microspheres.

[0023] The porosity of the adsorbed silica gel in Examples 1-5 and Comparative Examples 1-2 was tested according to GB / T34709-2017 "General Test Methods for Silica Gel". The test results are shown in Table 1.

[0024] Table 1: Porosity Test

[0025] As shown in Table 1, the adsorbed silica gel in Examples 1-5 of the present invention has a higher porosity than the adsorbed silica gel in Comparative Examples 1-2.

[0026] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0028] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing high-porosity adsorbent silica gel, characterized in that, Includes the following steps: Step 1: Add 9-11g of tetraethyl orthosilicate, 15-25mL of anhydrous ethanol, and 8-12mL of ultrapure water to the reaction flask, stir and mix, add 0.1-0.12mol / L hydrochloric acid solution dropwise to adjust the pH to 2.5-3, heat to 38-42℃ and stir for 1-1.5h to obtain silica sol; Step 2: Add 0.4-0.6 g of quaternary phosphonium salt-grafted modified polystyrene microspheres to the silica sol, ultrasonically disperse for 10-20 min, stir at 36-44℃ for 1-1.5 h, add 0.1-0.12 mol / L ammonia solution dropwise to adjust the pH to 6.9-7.1, heat to 60-65℃ and allow to stand for 3.5-4.5 h to solidify, obtaining a wet gel. Place the wet gel at 62-68℃ and 8% relative humidity. The silica gel is aged in a constant temperature and humidity chamber at 5%-95% for 20-24 hours. After aging, it is freeze-dried at -55--45℃ for 18-22 hours to obtain a dry gel. The dry gel is placed in a muffle furnace and heated from room temperature to 300-310℃ at a rate of 1-2℃ / min, held for 2-3 hours, and then heated to 542-555℃ at a rate of 2-3℃ / min, held for 3-4 hours, and cooled to room temperature to obtain high-porosity adsorbent silica gel.

2. The method for preparing high-porosity adsorbent silica gel according to claim 1, characterized in that, The quaternary phosphonium salt-grafted modified polystyrene microspheres were prepared through the following steps: (1) Under a nitrogen atmosphere, add 2.6-2.74 g of 4-((4-hydroxyphenyl)azo)benzaldehyde to 40-60 mL of anhydrous ethanol solvent, stir to dissolve, add 0.4-0.6 mL of acetic acid catalyst, continue stirring for 5-10 min, add 2.5-2.66 g of 2-(diphenylphosphine)ethylamine dropwise, after the addition is complete, heat to 75-83℃ and react for 9-12 h. After the reaction is complete, cool to room temperature, filter under reduced pressure, wash and dry under vacuum to obtain intermediate 1; (2) Add 4.6-4.7g of intermediate 1 to 80-100mL of anhydrous acetonitrile solvent, stir to dissolve, heat to 74-78℃, add 3.2-3.36g of 11-chloroundecyltriethoxysilane dropwise, after the addition is complete, continue the reaction for 8-10h, after the reaction is complete, cool to room temperature, remove the solvent by rotary evaporation, add 40-60mL of pre-cooled anhydrous diethyl ether for recrystallization, filter, wash, and vacuum dry to obtain silane coupling agent type quaternary phosphonium salt; (3) Add 7-8g of styrene, 1.2-1.8g of acrylic acid, 0.7-1.2g of modified crosslinking agent, hydroquinone polymerization inhibitor, and 0.08-0.12g of azobisisobutyronitrile initiator to 60-90mL of anhydrous ethanol solvent, stir to dissolve, purge with nitrogen gas for protection, heat to 65-75℃, and react for 11-14h. After the reaction is completed, a microsphere suspension is obtained. Centrifuge the microsphere suspension, discard the supernatant, wash and vacuum dry to obtain modified polystyrene microspheres. (4) Add 1.5-2.5g of modified polystyrene microspheres to 20-30mL of toluene solvent, disperse ultrasonically for 20-30min, add 0.1-0.2g of silane coupling agent type quaternary phosphonium salt, purge with nitrogen for protection, adjust the pH to 4-5 with acetic acid, heat to 58-64℃ and react for 4-7h. After the reaction is completed, cool to room temperature, collect the microspheres by centrifugation, wash and vacuum dry to obtain quaternary phosphonium salt grafted modified polystyrene microspheres.

3. The method for preparing high-porosity adsorbent silica gel according to claim 2, characterized in that, In step (2), the dropping time of 11-chloroundecyltriethoxysilane is 25-35 min.

4. The method for preparing high-porosity adsorbent silica gel according to claim 2, characterized in that, In step (3), the mass of hydroquinone polymerization inhibitor is 0.08%-0.12% of the total mass of styrene, acrylic acid, and modified crosslinking agent.

5. The method for preparing high-porosity adsorbent silica gel according to claim 2, characterized in that, The modified crosslinking agent in step (3) is prepared by the following steps: Under a nitrogen atmosphere, 2-2.4g of N-vinylpyrrolidone, 1.8-1.9g of 3-aminopropanol vinyl ether, and 0.004-0.008g of hydroquinone polymerization inhibitor are added to 30-50mL of anhydrous ethanol solvent, stirred and dissolved, and the pH value is adjusted to 3-4 with acetic acid. 1.7-1.84g of formaldehyde solution with a mass fraction of 37%-38% is added dropwise. After the addition is complete, the temperature is raised to 70-75℃ and reacted for 4.5-6h. After the reaction is completed, the temperature is cooled to room temperature, and the pH value is adjusted to 6.8-7.2 with a mass fraction of 9%-10% sodium hydroxide solution. The solvent is removed by rotary evaporation, and the modified crosslinking agent is obtained by vacuum distillation.

6. The method for preparing high-porosity adsorbent silica gel according to claim 5, characterized in that, The temperature is controlled at 20-30℃ during the formaldehyde solution dropwise addition process.

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