A phosphine-containing ligand modified silica gel chromatographic packing and a preparation method thereof

Abstract

The present application relates to the technical field of chromatographic packing, in particular to a kind of phosphine ligand modified silica gel chromatographic packing and preparation method thereof, the present application first designs and synthesizes the porous silsesquioxane microspheres containing diphenyl phosphine ligand as functional unit, and the modified bridged silane containing phenyl ether structure as alkali-resistant reinforcing unit, then by sol-gel method, the above unit is copolymerized with tetraethyl orthosilicate, constructs organic-inorganic hybrid silica gel skeleton, finally, the pore structure of packing is optimized by two-step hole expansion process;The method makes phosphine ligand firmly embedded in the interior of silica gel skeleton in the form of covalent bond, and the modified bridged silane containing phenyl ether structure provides hydrophobic protection and space stabilization effect as part of the skeleton, so as to realize the long-term stability of packing in strong alkaline environment and high capacity, high selectivity adsorption of metal ions.

Description

Technical Field

[0001] This invention relates to the field of chromatographic packing technology, and in particular to a silica gel chromatographic packing material modified with phosphine ligands and its preparation method. Background Technology

[0002] Silica-based chromatographic packing materials are widely used in analytical detection and separation and purification due to their high specific surface area and good mechanical strength. However, traditional silica packing materials have poor chemical stability under alkaline conditions. The silicon-oxygen bonds on their surface are easily attacked by hydroxide ions and hydrolyzed, leading to the collapse of the packing structure and the loss of functional groups. This severely limits their application in the chelation and separation of specific metal ions under alkaline conditions.

[0003] To address the alkali resistance issue of silica gel, existing technologies primarily employ the following solutions: first, coating the silica gel surface with an alkali-resistant material, such as a zirconium oxide or titanium oxide film; second, using high-purity silica gel to reduce impurities from catalytic hydrolysis. These solutions improve the alkali resistance of silica gel to some extent. However, the surface coating may cover some functional groups or block pores, affecting adsorption capacity and mass transfer efficiency. Increasing silica gel purity is costly and has limited impact on improving alkali resistance. Furthermore, it is crucial to ensure the long-term stability of functional ligands on the silica gel packing surface while achieving high alkali resistance. Therefore, a silica gel chromatographic packing material is needed that maintains its performance temperature under strongly alkaline conditions and provides stable functional ligands to achieve efficient and durable selective separation of metal ions. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a phosphine-ligand-modified silica gel chromatography packing material and its preparation method. This invention first designs and synthesizes porous silsesquioxane microspheres containing diphenylphosphine ligands as functional units, and modified bridging silanes containing phenyl ether structures as alkali-resistant reinforcing units. Then, the above units are co-condensed with tetraethyl orthosilicate via a sol-gel method to construct an organic-inorganic hybrid silica gel framework. Finally, the pore structure of the packing material is optimized through a two-step pore-expansion process. This method allows the phosphine ligands to be firmly embedded in the silica gel framework via covalent bonds, while the modified bridging silanes containing phenyl ether structures provide hydrophobic protection and steric stabilization as part of the framework, thereby synergistically achieving long-term stability of the packing material in strongly alkaline environments and high-capacity, high-selectivity adsorption of metal ions.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a silica gel chromatography packing material modified with phosphine ligands, comprising the following steps:

[0006] Step S1: Preparation of hybrid silica gel: Mix dodecylamine, hexadecylammonium bromide, ethanol and deionized water, stir and add ammonia solution, then add a mixture of tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres, react, let stand, filter, wash with deionized water / methanol, dry, and obtain hybrid silica gel.

[0007] Step S2: First-stage pore expansion of silica gel: N,N-dimethyldecylamine, dodecylamine, hybrid silica gel and deionized water are mixed and ultrasonically dispersed, transferred to a reaction vessel, reacted, filtered, washed with deionized water / methanol / ethanol to obtain the washing material, then the washing material is added to a mixture of hydrochloric acid / ethanol, reacted, filtered, washed with deionized water / methanol / ethanol, and dried to obtain expanded silica gel;

[0008] Step S3: Secondary pore expansion of silica gel: Mix and ultrasonically disperse the pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water, transfer to a reaction vessel, react, wash with deionized water / methanol, and dry to obtain silica gel chromatographic packing material modified with phosphine ligands.

[0009] Furthermore, in step S1: during the preparation of hybrid silica gel: the temperature is room temperature, the reaction time is 30 min, and the standing time is 12 h; the ratio of the amount of dodecylamine, hexadecylammonium bromide, ammonia solution, tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is 6 g: 1.5 g: 1 mL: 6-10 mL: 5-6 g: 2 g.

[0010] Furthermore, in step 2: during the preparation of the expanded silica gel, the reaction temperature in the reactor is 135℃ and the reaction time is 24h, while the reaction temperature in the hydrochloric acid / ethanol mixture is 80℃ and the reaction time is 12h. The volume ratio of hydrochloric acid solution to ethanol in the hydrochloric acid / ethanol mixture is 5:95, and the mass fraction of hydrochloric acid solution is 37%. The ratio of N,N-dimethyldecylamine, dodecylamine, hybrid silica gel, and deionized water is 4g:0.5g:4g:50mL.

[0011] Furthermore, in step S3: the reaction temperature in the reactor is 160°C and the reaction time is 24h; the ratio of pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water is 3g:0.5g:20mL.

[0012] The modified bridged silane is prepared by the following steps:

[0013] Tetraethyl orthosilicate, magnesium powder and tetrahydrofuran were mixed and stirred at 300 rpm at room temperature for 15 min. Iodine crystals were then added and the temperature was raised to 65 °C. The mixture was reacted for 2 h. The mixture of 4,4'-dibromodiphenyl ether and tetrahydrofuran was added and the temperature was raised to 75 °C. The mixture was reacted for 10-12 h. After cooling, the petroleum ether precipitate was filtered, rotary evaporated, and distilled under reduced pressure to obtain the modified bridged silane.

[0014] Furthermore, in the preparation process of the modified bridged silane, the ratio of tetraethyl orthosilicate, magnesium powder, iodine crystals, 4,4'-dibromodiphenyl ether and tetrahydrofuran is 34-35g:3g:0.5g:3.5-4g:100mL, wherein the ratio of the first addition of tetrahydrofuran to the second addition of tetrahydrofuran is 1:1.

[0015] Furthermore, in the reaction process for preparing modified bridged silanes, under the conditions of iodine as an activator and magnesium as a catalyst, tetraethyl orthosilicate reacts with 4,4'-dibromodiphenyl ether via a Grignard reaction to form silicon-carbon bonds, thus obtaining the modified bridged silane. See attached diagram for a schematic representation of the reaction. Figure 1 .

[0016] The phosphorus ligand porous microspheres were prepared by the following steps:

[0017] Step A1: Mix methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane and deionized water, stir at 300 rpm at room temperature for 30 min, then add hydrochloric acid solution, continue stirring for 4-6 h, then add ammonia solution, let stand for 6 h, filter, wash and dry to obtain silsesquioxane microspheres; mix silsesquioxane microspheres and ethanol solution, stir at 500 rpm at 70 °C and add ammonia solution, react for 10-12 h, filter, wash and dry to obtain thiol-functionalized microspheres;

[0018] Furthermore, in step A1, during the preparation of sesquioxane microspheres, the ratio of methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane, deionized water, hydrochloric acid solution, and ammonia solution is 18-20g: 4-6g: 150mL: 0.8mL: 0.01mL, wherein the molar concentration of hydrochloric acid solution is 0.1mol / L, and the molar concentration of ammonia solution is 0.1mol / L.

[0019] In the preparation of thiol-functionalized microspheres: the ratio of sesquioxane microspheres, ethanol solution and ammonia solution is 5-6g:100mL:15mL, wherein the volume fraction of ethanol solution is 80% and the mass fraction of ammonia solution is 27%.

[0020] Step A2: Mix the thiol-functionalized microspheres and ethanol and ultrasonically disperse for 20 min. Under nitrogen protection, with a stirring rate of 300 rpm and at room temperature, stir and add allylamine and azobisisobutyronitrile. Then heat to 70℃ and react for 10-12 h. Centrifuge, filter, wash, and dry to obtain amino-functionalized microspheres.

[0021] Furthermore, in step A2, the ratio of the amount of thiol-functionalized microspheres, ethanol, allylamine, and azobisisobutyronitrile is 4-5g:100mL:0.8-1g:0.1g.

[0022] Step A3: Mix paraformaldehyde, diphenylphosphine and methanol, stir at 300 rpm for 20 min under nitrogen protection and at room temperature, then heat to 60 °C and add amino-functionalized microspheres, continue stirring for 30 min, then add toluene, continue heating to 100 °C, react for 24 h, filter, wash and dry to obtain phosphorus ligand porous microspheres;

[0023] Furthermore, in step A3, the ratio of paraformaldehyde, diphenylphosphine, methanol, and amino-functionalized microspheres is 0.6-0.8g: 3.5-4mL: 40mL: 3g.

[0024] Furthermore, in the preparation process of the phosphorus ligand porous microspheres, methyltrimethoxysiloxane and mercaptopropyltrimethoxysilane are first used as monomers. These monomers undergo hydrolysis and condensation to form silsesquioxane structures, yielding silsesquioxane microspheres. These silsesquioxane microspheres are then subjected to an alkaline-thermal reaction in an ammonia solution to form microspheres with a porous structure, thus obtaining thiol-functionalized microspheres. Using these thiol-functionalized microspheres as a substrate, under the condition of azobisisobutyronitrile as a catalyst, the surface thiol groups undergo a click reaction with allylamine, introducing amino groups to obtain amino-functionalized microspheres. The amino groups in these amino-functionalized microspheres then react with paraformaldehyde and diphenylphosphine to introduce diphenylphosphine structures, yielding phosphorus ligand porous microspheres. A schematic diagram of the reaction is attached. Figure 2 .

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention relates to a silica gel chromatography packing material modified with phosphine ligands and its preparation method. First, porous silsesquioxane microspheres containing diphenylphosphine ligands are designed and synthesized as functional units, and modified bridging silanes containing phenyl ether structures are used as alkali-resistant reinforcing units. Then, the above units are co-condensed with tetraethyl orthosilicate via a sol-gel method to construct an organic-inorganic hybrid silica gel framework. Finally, the pore structure of the packing material is optimized through a two-step pore-expansion process. This method allows the phosphine ligands to be firmly embedded in the silica gel framework in the form of covalent bonds, while the modified bridging silanes containing phenyl ether structures provide hydrophobic protection and steric stability as part of the framework, thereby synergistically achieving long-term stability of the packing material in a strongly alkaline environment and high-capacity, high-selectivity adsorption of metal ions.

[0026] This invention uses pre-synthesized phosphorus ligand porous microspheres as functional precursors, combined with modified bridging silanes containing phenyl ether structures, to solve the key problems of uneven distribution of functional groups and poor matrix alkali resistance in traditional post-modification methods. Specifically, the phosphorus ligand porous microspheres themselves possess a porous structure and a silsesquioxane framework. The abundant silanol groups on their surface enable them to co-condense with tetraethyl orthosilicate and modified bridging silanes during the sol-gel process, thereby firmly anchoring the diphenylphosphine ligand to the growth points of the silica matrix in a covalent manner, achieving in-situ embedding and uniform dispersion of functional units. At the same time, the phenyl ether structure in the modified bridging silane directly connects to the silicon-oxygen network through silicon-carbon bonds. The hydrophobic benzene ring can effectively prevent water molecules and hydroxide ions from eroding adjacent silicon-oxygen bonds, while the flexibility of the ether bond can alleviate internal stress in the material. The two work synergistically to enhance the stability of the silica matrix in alkaline environments at the molecular level.

[0027] This invention employs a mixed template agent of N,N-dimethyldecylamine and dodecylamine for hydrothermal primary pore expansion, followed by extraction with a hydrochloric acid / ethanol mixture, to achieve controllable formation and unblocking of mesoporous structures. Long-chain alkylamines interact with the silica gel framework under high-temperature hydrothermal conditions, guiding the formation of mesopores. Using two amines with different chain lengths allows for modulation of the pore size distribution. Subsequent acid-alcohol treatment effectively dissolves and removes organic template agent molecules embedded in the pores, opening the pores, providing accessible surface area for phosphine ligands, and preventing slow precipitation and contamination of the template agent during subsequent use. A secondary hydrothermal pore expansion using tris(hydroxymethyl)aminomethane achieves smoothing of the pore walls and a slight homogenization and expansion of the pore size. Due to the higher solubility in areas with greater curvature on the silica gel surface, silica dissolves and redeposits in areas with less curvature. This process eliminates the micropore bottleneck present after primary pore expansion, making the pores more unobstructed, reducing mass transfer resistance, and further increasing the diffusion rate of metal ions to the internal phosphine ligand active sites, thereby enhancing the dynamic adsorption capacity. Attached Figure Description

[0028] Appendix Figure 1 This is a process flow diagram of the present invention;

[0029] Appendix Figure 2 This is a schematic diagram of the reaction for preparing the modified bridged silane of the present invention;

[0030] Appendix Figure 3 This is a schematic diagram of the reaction for preparing the phosphorus ligand porous microspheres of the present invention. Detailed Implementation

[0031] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0032] Preparation Example 1: The modified bridged silane was prepared by the following steps:

[0033] Tetraethyl orthosilicate, magnesium powder and tetrahydrofuran were mixed and stirred at 300 rpm at room temperature for 15 min. Iodine crystals were then added and the temperature was raised to 65 °C. The mixture was reacted for 2 h. The mixture of 4,4'-dibromodiphenyl ether and tetrahydrofuran was added and the temperature was raised to 75 °C. The mixture was reacted for 10-12 h. After cooling, the petroleum ether precipitate was filtered, rotary evaporated, and distilled under reduced pressure to obtain the modified bridged silane.

[0034] Furthermore, in the preparation process of the modified bridged silane, the ratio of tetraethyl orthosilicate, magnesium powder, iodine crystals, 4,4'-dibromodiphenyl ether and tetrahydrofuran is 34g:3g:0.5g:3.5g:100mL, wherein the ratio of the first addition of tetrahydrofuran to the second addition of tetrahydrofuran is 1:1.

[0035] Preparation Example 2: Compared with Preparation Example 1, the ratio of tetraethyl orthosilicate to 4,4'-dibromodiphenyl ether in Preparation Example 2 was adjusted to 35g:4g.

[0036] Preparation Example 3: The phosphorus ligand porous microspheres were prepared by the following steps:

[0037] Step A1: Mix methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane and deionized water, stir at 300 rpm at room temperature for 30 min, then add hydrochloric acid solution, continue stirring for 4-6 h, then add ammonia solution, let stand for 6 h, filter, wash and dry to obtain silsesquioxane microspheres; mix silsesquioxane microspheres and ethanol solution, stir at 500 rpm at 70 °C and add ammonia solution, react for 10-12 h, filter, wash and dry to obtain thiol-functionalized microspheres;

[0038] Furthermore, in step A1: during the preparation of sesquioxane microspheres: the ratio of methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane, deionized water, hydrochloric acid solution, and ammonia solution is 18g:4g:150mL:0.8mL:0.01mL, wherein the molar concentration of hydrochloric acid solution is 0.1mol / L, and the molar concentration of ammonia solution is 0.1mol / L;

[0039] In the preparation of thiol-functionalized microspheres: the ratio of sesquioxane microspheres, ethanol solution and ammonia solution is 5g:100mL:15mL, wherein the volume fraction of ethanol solution is 80% and the mass fraction of ammonia solution is 27%.

[0040] Step A2: Mix the thiol-functionalized microspheres and ethanol and ultrasonically disperse for 20 min. Under nitrogen protection, with a stirring rate of 300 rpm and at room temperature, stir and add allylamine and azobisisobutyronitrile. Then heat to 70℃ and react for 10-12 h. Centrifuge, filter, wash, and dry to obtain amino-functionalized microspheres.

[0041] Furthermore, in step A2, the ratio of the amount of thiol-functionalized microspheres, ethanol, allylamine, and azobisisobutyronitrile is 4g:100mL:0.8g:0.1g.

[0042] Step A3: Mix paraformaldehyde, diphenylphosphine and methanol, stir at 300 rpm for 20 min under nitrogen protection and at room temperature, then heat to 60 °C and add amino-functionalized microspheres, continue stirring for 30 min, then add toluene, continue heating to 100 °C, react for 24 h, filter, wash and dry to obtain phosphorus ligand porous microspheres;

[0043] Furthermore, in step A3, the ratio of paraformaldehyde, diphenylphosphine, methanol, and amino-functionalized microspheres is 0.6g:3.5mL:40mL:3g.

[0044] Preparation Example 4: Compared to Preparation Example 3, Preparation Example 4 adjusts the following in step A1: the ratio of methyltrimethoxysiloxane to mercaptopropyltrimethoxysilane in the preparation of silsesquioxane microspheres to 20g:6g; the ratio of silsesquioxane microspheres to ammonia solution in the preparation of mercaptofunctionalized microspheres to 6g:15mL; the ratio of mercaptofunctionalized microspheres to allylamine in step A2 to 5g:1g; and the ratio of paraformaldehyde, diphenylphosphine, and aminofunctionalized microspheres in step A3 to 0.8g:4mL:3g; all other steps remain the same.

[0045] Preparation Example 5: Compared with Preparation Example 3, in Preparation Example 5, the ratio of thiol-functionalized microspheres to allylamine in step A2 is 5g:0.2g, and the other steps are the same.

[0046] Preparation Example 6: Compared with Preparation Example 3, in Preparation Example 6, the ratio of paraformaldehyde, diphenylphosphine and amino-functionalized microspheres in step A3 is 0.6g:3.5mL:5g, and the other steps are the same.

[0047] Example 1: A method for preparing a silica gel chromatography packing material modified with phosphine ligands, comprising the following steps:

[0048] Step S1: Preparation of hybrid silica gel: Dodecylamine, hexadecylammonium bromide, ethanol and deionized water are mixed, stirred and ammonia solution is added, then tetraethyl orthosilicate, the modified bridged silane of Preparation Example 2 and the phosphorus ligand porous microspheres of Preparation Example 4 are added, reacted, allowed to stand, filtered, washed with deionized water / methanol, and dried to obtain hybrid silica gel.

[0049] Step S2: First-stage pore expansion of silica gel: N,N-dimethyldecylamine, dodecylamine, hybrid silica gel and deionized water are mixed and ultrasonically dispersed, transferred to a reaction vessel, reacted, filtered, washed with deionized water / methanol / ethanol to obtain the washing material, then the washing material is added to a mixture of hydrochloric acid / ethanol, reacted, filtered, washed with deionized water / methanol / ethanol, and dried to obtain expanded silica gel;

[0050] Step S3: Secondary pore expansion of silica gel: Mix and ultrasonically disperse the pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water, transfer to a reaction vessel, react, wash with deionized water / methanol, and dry to obtain silica gel chromatographic packing material modified with phosphine ligands.

[0051] Furthermore, in step S1: the preparation of hybrid silica gel: the temperature is room temperature, the reaction time is 30 min, and the standing time is 12 h; the ratio of the amount of dodecylamine, hexadecylammonium bromide, ammonia solution, tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is 6 g: 1.5 g: 1 mL: 10 mL: 6 g: 2 g.

[0052] Furthermore, in step 2: during the preparation of the expanded silica gel, the reaction temperature in the reactor is 135℃ and the reaction time is 24h, while the reaction temperature in the hydrochloric acid / ethanol mixture is 80℃ and the reaction time is 12h. The volume ratio of hydrochloric acid solution to ethanol in the hydrochloric acid / ethanol mixture is 5:95, and the mass fraction of hydrochloric acid solution is 37%. The ratio of N,N-dimethyldecylamine, dodecylamine, hybrid silica gel, and deionized water is 4g:0.5g:4g:50mL.

[0053] Furthermore, in step S3: the reaction temperature in the reactor is 160°C and the reaction time is 24h; the ratio of pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water is 3g:0.5g:20mL.

[0054] Example 2: Compared with Example 1, in Example 2, the ratio of the following in step S1 is 6g:1.5g:1mL:6mL:5g:2g.

[0055] Example 3: Compared with Example 1, Example 3 uses the same steps as Example 1 for the modified bridged silane and the phosphorus ligand porous microspheres in step S1: modified bridged silane and phosphorus ligand porous microspheres in Example 3.

[0056] Example 4: Compared with Example 1, Example 4 changes step S1: phosphorus ligand porous microspheres to prepare phosphorus ligand porous microspheres as in Example 5, while the other steps are the same.

[0057] Example 5: Compared with Example 1, Example 5 changes step S1: phosphorus ligand porous microspheres to prepare phosphorus ligand porous microspheres as in Example 6, while the other steps are the same.

[0058] Example 6: Compared with Example 1, Example 6 uses the following method in step S1: the ratio of dodecylamine, hexadecylammonium bromide, ammonia solution, tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is 6g:1.5g:1mL:3mL:6g:2g, and the other steps are the same.

[0059] Example 7: Compared with Example 1, Example 7 uses the following method in step S1: the ratio of dodecylamine, hexadecylammonium bromide, ammonia solution, tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is 6g:1.5g:1mL:3mL:6g:2g, and the other steps are the same.

[0060] Example 8: Compared with Example 1, in step S2 of Example 8, the ratio of N,N-dimethyldecylamine, dodecylamine, hybrid silica gel and deionized water is 2g:0.5g:4g:50mL, and the other steps are the same.

[0061] Example 9: Compared with Example 1, in step S3 of Example 9, the ratio of pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water is 3g:0.2g:20mL, and the other steps are the same.

[0062] Comparative Example 1: Compared with Example 1, Comparative Example 1 does not add modified bridged silane in step S1, while the other steps are the same.

[0063] Comparative Example 2: Compared with Example 1, the phosphorus ligand porous microspheres in step S1 were changed to the prepared sesquioxane microspheres of Example 4, while the other steps were the same.

[0064] Comparative Example 3: Compared with Example 1, step S3 is omitted in Comparative Example 3, while the other steps are the same.

[0065] The silica gel chromatographic packing materials prepared in Examples 1-9 and Comparative Examples 1-3 were used as samples for the following tests:

[0066] Referring to GB / T 19587-2017, the specific surface area and pore size were determined using a specific surface area and pore size analyzer. Before measurement, the sample was dried at 200℃ for 5 hours, and nitrogen was used as the gas to calculate its specific surface area and pore size. 1 g of sample was placed in 10 mL of sodium hydroxide solution with pH 12, and shaken at 150 rpm for 72 hours at 80℃. After filtration, washing with deionized water, and drying, the specific surface area was measured, and the specific surface area retention rate was calculated. Specific surface area retention rate = (initial specific surface area - specific surface area after alkaline washing) / initial specific surface area × 100%. The test results are shown in Table 1 below.

[0067] Table 1 Material Testing Results

[0068] ;

[0069] Solutions of indium nitrate, ytterbium nitrate, erbium nitrate, and neodymium nitrate with a concentration of 100 mg / L were prepared, and the pH was adjusted with sodium hydroxide. 20 mg of silica gel chromatography packing material was placed in an Erlenmeyer flask, and 20 mL of each solution was added. The mixture was shaken at 200 rpm for 24 h at 25 °C, filtered, and the ion concentrations in the remaining filtrate were determined. The adsorption capacity was calculated, and the results are shown in Table 2 below.

[0070] Table 2 Adsorption capacity test results

[0071] ;

[0072] The results of the test, as shown in the table, indicate that:

[0073] Example 1 shows that its specific surface area and pore size are in the excellent range, indicating that the two-step pore expansion process effectively constructs a mesoporous structure that is conducive to mass transfer. The specific surface area retention rate of up to 96.0% proves that the phenyl ether bridging structure endows the framework with excellent alkali resistance. It shows the highest adsorption capacity for all four rare earth ions, indicating that the high density of phosphine ligands and the unobstructed pore structure synergistically achieve efficient metal chelation.

[0074] Example 2 reduced the amount of tetraethyl orthosilicate and modified bridged silane, resulting in a slight decrease in specific surface area and pore size. This led to a slight decrease in the adsorption capacity for the four rare earth ions compared to Example 1, while the alkali resistance remained excellent. This was because the total amount of tetraethyl orthosilicate and bridged silane was reduced, resulting in a relative shortage of building material for the silica gel skeleton. This affected the structural integrity and pore development of the final material, which in turn had a slight negative impact on the adsorption capacity.

[0075] Example 3 used the raw materials of Preparation Example 1 and Preparation Example 3. Its performance was slightly lower than that of Example 1, but significantly better than other non-optimal examples. This is because the molar ratio of phenyl ether structure to silicon in the bridged silane of Preparation Example 1 was slightly lower, which may have a slightly weaker effect on the reinforcement and protection of the skeleton. At the same time, the loading density of amino and phosphine ligands in the phosphorus ligand microspheres of Preparation Example 3 was slightly lower than that of Preparation Example 4, which resulted in a slight decrease in the density of active sites, which together caused a slight decrease in performance.

[0076] Example 4 used the phosphorus ligand porous microspheres prepared in Example 5. The key change was that the amount of allylamine used in step A2 was greatly reduced. Its physical properties were similar to those in Example 1, but the adsorption capacity was significantly reduced. This was because the amount of allylamine used in the microsphere preparation was sharply reduced, and the amino group density grafted onto the surface of the microsphere through the click reaction was significantly reduced. This directly led to a reduction in the number of diphenylphosphine ligands that could be introduced in the subsequent reaction, that is, the density of effective chelating sites per unit area of ​​the material was insufficient, which in turn led to a decrease in adsorption capacity. This illustrates the decisive influence of the precursor amino group density in the functional microspheres on the final material performance.

[0077] Example 5 used the phosphorus ligand porous microspheres prepared in Example 6. The key change was that the amount of amino-functionalized microspheres added in step A3 was increased, while the amount of phosphine reagent remained unchanged. Its specific surface area and pore size were even slightly higher than those in Example 1, but its adsorption capacity was the lowest among all examples. This is because in the phosphine reaction stage, the amount of amino microspheres added was increased while the amount of paraformaldehyde and diphenylphosphine remained unchanged. The change was that the ratio of amino to phosphine reagent in the reaction system was unbalanced, which caused some amino groups to fail to participate in the reaction and not be converted into phosphine ligands. At the same time, the amino groups that participated in the reaction may also form incomplete ligand structures due to insufficient reagents. The absolute content of effective phosphine ligands per unit mass of the final product was diluted. Therefore, although the framework structure was good, the concentration of effective active sites was too low, resulting in the worst adsorption performance.

[0078] Both Examples 6 and 7 significantly reduced the amount of tetraethyl orthosilicate compared to Example 1, while the proportion of bridging silane in Example 7 was also relatively high. The specific surface area and pore size of both examples were significantly reduced, and the adsorption capacity was also significantly reduced. However, the alkali resistance was still good. This is because the amount of tetraethyl orthosilicate, which is the main framework building unit, was insufficient. The change is that a sufficiently developed and stable silicon-oxygen network cannot be formed. The significant reduction in pore size greatly increased the mass transfer resistance of rare earth ions to diffuse into the material, which made it impossible to effectively utilize a large number of phosphine ligand sites located deep in the pores, thus leading to a significant decrease in adsorption capacity. This illustrates the importance of a sufficient main silicon source in the formation of the silica skeleton.

[0079] Example 8 reduced the amount of N,N-dimethyldecylamine, the primary pore-expanding template agent in step S2. Its specific surface area increased, but the average pore size decreased, and the adsorption capacity was slightly lower than that of Example 1. This is because the amount of the long-chain template agent N,N-dimethyldecylamine was reduced, which weakened its guiding effect on the formation of larger-sized mesopores during the high-temperature hydrothermal process. The system tended to form more pores but smaller pores, which was manifested as an increase in specific surface area and a decrease in average pore size. The smaller pore size also introduced a certain mass transfer limitation, resulting in the adsorption capacity not reaching the optimal level.

[0080] Example 9 reduced the amount of the secondary pore-expanding reagent, tris(hydroxymethyl)aminomethane, in step S3. Its specific surface area and pore size were lower than those in Example 1, and the adsorption capacity was also slightly reduced. This was because the reduced amount of secondary pore-expanding reagent resulted in insufficient alkaline hydrothermal environment intensity, leading to incomplete reaction process. The rough surface and micro-bottleneck structure in the pores could not be effectively smoothed and eliminated, and the pore size expansion and homogenization effects were limited, resulting in the mass transfer efficiency not reaching the optimal level, which in turn affected the adsorption performance. This demonstrates the key role of the amount of secondary pore-expanding reagent in the final pore optimization.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a silica gel chromatographic packing material modified with phosphine ligands, characterized in that: The process includes the following steps: Step S1: Preparation of hybrid silica gel: Dodecylamine, hexadecylammonium bromide, ethanol and deionized water are mixed, stirred and ammonia solution is added, then a mixture of tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is added, the mixture is reacted, allowed to stand, filtered, washed with deionized water / methanol, and dried to obtain hybrid silica gel. Step S2: First-stage pore expansion of silica gel: N,N-dimethyldecylamine, dodecylamine, hybrid silica gel and deionized water are mixed and ultrasonically dispersed, transferred to a reaction vessel, reacted, filtered, washed with deionized water / methanol / ethanol to obtain the washing material, then the washing material is added to a mixture of hydrochloric acid / ethanol, reacted, filtered, washed with deionized water / methanol / ethanol, and dried to obtain expanded silica gel; Step S3: Secondary pore expansion of silica gel: Mix and ultrasonically disperse the pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water, transfer to a reaction vessel, react, wash with deionized water / methanol, dry, and obtain silica gel chromatographic packing material modified with phosphine ligands. The modified bridged silane is prepared by the following steps: Tetraethyl orthosilicate, magnesium powder and tetrahydrofuran were mixed and stirred at 300 rpm at room temperature for 15 min. Iodine crystals were then added and the temperature was raised to 65 °C. The mixture was reacted for 2 h. The mixture of 4,4'-dibromodiphenyl ether and tetrahydrofuran was added and the temperature was raised to 75 °C. The mixture was reacted for 10-12 h. After cooling, the petroleum ether precipitate was filtered, rotary evaporated, and distilled under reduced pressure to obtain the modified bridged silane. The phosphorus ligand porous microspheres were prepared by the following steps: Step A1: Mix methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane and deionized water, stir at 300 rpm at room temperature for 30 min, then add hydrochloric acid solution, continue stirring for 4-6 h, then add ammonia solution, let stand for 6 h, filter, wash and dry to obtain silsesquioxane microspheres; mix silsesquioxane microspheres and ethanol solution, stir at 500 rpm at 70 °C and add ammonia solution, react for 10-12 h, filter, wash and dry to obtain thiol-functionalized microspheres; Step A2: Mix the thiol-functionalized microspheres and ethanol and ultrasonically disperse for 20 min. Under nitrogen protection, with a stirring rate of 300 rpm and at room temperature, stir and add allylamine and azobisisobutyronitrile. Then heat to 70℃ and react for 10-12 h. Centrifuge, filter, wash, and dry to obtain amino-functionalized microspheres. Step A3: Mix paraformaldehyde, diphenylphosphine and methanol, stir at 300 rpm for 20 min under nitrogen protection and at room temperature, then heat to 60 °C and add amino-functionalized microspheres, continue stirring for 30 min, then add toluene, continue heating to 100 °C, react for 24 h, filter, wash and dry to obtain phosphorus ligand porous microspheres.

2. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step S1: In the preparation of hybrid silica gel: the temperature is room temperature, the reaction time is 30 min, and the standing time is 12 h; the ratio of the amount of dodecylamine, hexadecylammonium bromide, ammonia solution, tetraethyl orthosilicate, modified bridged silane and phosphorus ligand porous microspheres is 6 g: 1.5 g: 1 mL: 6-10 mL: 5-6 g: 2 g.

3. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step 2: during the preparation of the expanded silica gel, the reaction temperature in the reactor was 135℃ and the reaction time was 24h. The reaction temperature in the hydrochloric acid / ethanol mixture was 80℃ and the reaction time was 12h. The volume ratio of hydrochloric acid solution to ethanol in the hydrochloric acid / ethanol mixture was 5:95, and the mass fraction of hydrochloric acid solution was 37%. The ratio of N,N-dimethyldecylamine, dodecylamine, hybrid silica gel and deionized water was 4g:0.5g:4g:50mL.

4. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step S3: the reaction temperature in the reactor is 160℃ and the reaction time is 24h; the ratio of pore-expanding silica gel, tris(hydroxymethyl)aminomethane and deionized water is 3g:0.5g:20mL.

5. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In the preparation process of the modified bridged silane: the ratio of tetraethyl orthosilicate, magnesium powder, iodine crystals, 4,4'-dibromodiphenyl ether and tetrahydrofuran is 34-35g. 3g:0.5g:3.5-4g:100mL, wherein the ratio of the amount of tetrahydrofuran added in the first addition to the amount of tetrahydrofuran added in the second addition is 1:

1.

6. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step A1: During the preparation of sesquioxane microspheres: the ratio of methyltrimethoxysiloxane, mercaptopropyltrimethoxysilane, deionized water, hydrochloric acid solution, and ammonia solution is 18-20g: 4-6g: 150mL: 0.8mL: 0.01mL, wherein the molar concentration of hydrochloric acid solution is 0.1mol / L, and the molar concentration of ammonia solution is 0.1mol / L; In the preparation of thiol-functionalized microspheres: the ratio of sesquioxane microspheres, ethanol solution and ammonia solution is 5-6g:100mL:15mL, wherein the volume fraction of ethanol solution is 80% and the mass fraction of ammonia solution is 27%.

7. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step A2: the ratio of thiol-functionalized microspheres, ethanol, allylamine and azobisisobutyronitrile is 4-5g:100mL:0.8-1g:0.1g.

8. The method for preparing a phosphine-ligand-modified silica gel chromatography packing material according to claim 1, characterized in that: In step A3, the ratio of paraformaldehyde, diphenylphosphine, methanol, and amino-functionalized microspheres is 0.6-0.8g: 3.5-4mL: 40mL: 3g.

9. A silica gel chromatography packing material modified with phosphine ligands, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.

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