A catalyst for ethylene oxide ring-opening polymerization and preparation method thereof

Abstract

The invention relates to a catalyst for ring-opening polymerization of ethylene oxide and a preparation method thereof, and belongs to the technical field of polymer material synthesis. The catalyst is a composite structure based on silicon dioxide nanoparticles loaded with bimetallic organic complexes. The invention adopts a special method to prepare a modified nitrogen-containing multidentate ligand, and coordinates with metal ions through covalent bonds to load the ligand on silicon dioxide nanoparticles. The high dispersibility and stability of silicon dioxide nanoparticles and the synergistic catalytic effect of bimetallic organic complexes are utilized to effectively improve the catalytic effect, accelerate the polymerization process, enhance the polymerization stability, increase the polymerization molecular weight, and narrow the distribution.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis, and particularly relates to a catalyst for ethylene oxide ring-opening polymerization and a preparation method thereof. Background Art

[0002] In the field of materials science, polyethylene oxide (PEO), as a high molecular polymer with unique properties, has extremely wide applications. From personal care products in daily life to complex biomedicine fields and high-end industrial production, PEO plays an indispensable role with its excellent water solubility, lubricity, dispersibility and biocompatibility. The ring-opening polymerization of ethylene oxide is the key way to prepare PEO. In this process, the catalyst plays a core role. Its performance directly determines the efficiency of the polymerization reaction, the quality and performance of the product. Therefore, the development of high-performance ethylene oxide ring-opening polymerization catalysts has always been the focus of scientific research and industry.

[0003] There are many types of traditional ethylene oxide ring-opening polymerization catalysts, each with its own characteristics and limitations. Although anionic catalysts such as alkali metal hydroxides and alcohol salts can initiate ethylene oxide ring-opening polymerization, chain transfer and side reactions are prone to occur during the reaction, resulting in a wide molecular weight distribution of the product, making it difficult to accurately control the structure and properties of the polymer. This greatly limits the application of such catalysts in fields that have strict requirements on polymer quality, such as the preparation of drug sustained-release carriers. This is because drug sustained-release carriers require polymers to have precise molecular weights and narrow distributions to ensure the stability and controllability of drug release.

[0004] Cationic catalysts also have problems. Although cationic catalysts such as boron trifluoride and its complexes can accelerate the reaction rate to a certain extent, the high activity of the cationic active center makes the reaction difficult to control, and chain termination and branching reactions are prone to occur, which not only affects the molecular weight of the polymer, but also changes its molecular structure and reduces the performance uniformity of the polymer. In fields such as electronic materials that have extremely high requirements for polymer purity and structural regularity, these shortcomings of cationic catalysts seriously restrict their application.

[0005] To address the shortcomings of traditional catalysts, metal-organic complex catalysts have emerged. This type of catalyst has a unique structure and catalytic active center, which can achieve controlled polymerization of ethylene oxide under mild reaction conditions. For example, some rare earth metal complex catalysts have shown good catalytic activity and selectivity, and can effectively regulate the molecular weight and distribution of polymers. However, the synthesis process of rare earth metal complex catalysts is often complicated and the raw material cost is high.

[0006] The research on ethylene oxide ring-opening polymerization catalysts is an evolving process. Although many achievements have been made, there are still many shortcomings. Therefore, it is necessary to develop environmentally friendly, efficient and low-cost ethylene oxide ring-opening polymerization catalysts and improve the synthesis quality of polyethylene oxide (PEO). Summary of the invention

[0007] In view of the problems of the existing ethylene oxide ring-opening polymerization catalyst, such as the wide molecular weight distribution of the product, the difficulty in controlling the reaction, the complex synthesis process of the rare earth metal complex catalyst, and the high cost of raw materials, the present invention provides a catalyst for ethylene oxide ring-opening polymerization and a preparation method thereof. The present invention adopts a special method to prepare the ligand L, and the ligand L forms a composite structure by covalent bond coordination with the metal ion, which is loaded on the silicon dioxide nanoparticles; the high dispersibility and stability of the silicon dioxide nanoparticles and the synergistic catalytic effect of the bimetallic organic complex are utilized to effectively improve the catalytic effect, accelerate the polymerization process, enhance the polymerization stability, increase the polymerization molecular weight, and narrow the distribution. The specific technical scheme is as follows:

[0008] A catalyst for the ring-opening polymerization of ethylene oxide, the catalyst is based on a composite structure of silicon dioxide nanoparticles loaded with bimetallic organic complexes, named SiO 2 -M 1 M 2 -L catalyst; M 1 is zinc, M 2 The ligand L is a modified nitrogen-containing multidentate ligand; the ligand L coordinates with the metal ion through a covalent bond to form a metal organic complex, which is then loaded on the surface of the silica nanoparticles.

[0009] The above-mentioned method for preparing a catalyst for ethylene oxide ring-opening polymerization comprises the following steps:

[0010] S1, Synthesis of ligand L:

[0011] S1.1, Preliminary inclusion of cyclodextrin and halogenated alkane:

[0012] According to the mass ratio, deionized water: β-cyclodextrin: 1-bromododecane = (30-35): (1.5-2): (4.8-5.2), add β-cyclodextrin to deionized water, stir and heat to dissolve, then add 1-bromododecane dropwise, stirring continuously during the addition process, and continue stirring and reacting for 2h-2.5h after the addition is completed, so that 1-bromododecane is included in the hydrophobic cavity of β-cyclodextrin to form a stable inclusion complex, which is named mixed solution A;

[0013] S1.2, Preparation of cellulose derivative solution:

[0014] According to the mass ratio, deionized water: hydroxypropyl methylcellulose = (45-50): (0.8-1); add hydroxypropyl methylcellulose into deionized water, stir and dissolve at room temperature to form a uniform cellulose derivative solution, named mixed solution B;

[0015] S1.3, ligand synthesis reaction:

[0016] According to the mass ratio, mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = (30-35): (45-50): (4.5-5.5): (1.2-1.8): (0.3-0.5); add 2,2'-bipyridine to mixed solution B, stir and mix evenly, add potassium tert-butoxide under nitrogen protection, continue to stir and dissolve evenly, then add mixed solution A and L-alanine, continue to stir and mix evenly, heat to reflux for reaction for 12h-14h, cool to room temperature, and obtain ligand L reaction solution;

[0017] S1.4, product separation and purification:

[0018] According to the mass ratio, the reaction liquid of ligand L: deionized water = (1-2): (2-3); the reaction liquid of ligand L is mixed with deionized water, and extracted with dichloromethane for 3-4 times, each time using dichloromethane of the same mass as the reaction liquid of ligand L; the dichloromethane phases are combined, dried with anhydrous sodium sulfate, filtered, and the filtrate is distilled under reduced pressure at 30°C-40°C to 20%-30% of the volume, the sample is passed through a 200-mesh to 300-mesh silica gel column chromatography, eluted with 2-3 silica gel column volumes of eluent, the eluent is collected, the eluent is distilled under reduced pressure at 60°C-70°C to remove the eluent, and dried in a vacuum drying oven to constant weight to obtain ligand L;

[0019] S2, Synthesis of bimetallic organic complexes:

[0020] By mass ratio, anhydrous methanol: Zn(NO 3 ) 2 6H 2 O:Mg(NO 3 ) 2 6H 2 O: Ligand L solution = (15-20): (0.12-0.15): (0.20-0.25): (10-15); Zn(NO 3 ) 2 6H 2 O and Mg(NO 3 ) 2 6H 2O was added into anhydrous methanol, mixed and dissolved evenly, and the ligand L solution was added dropwise under stirring at room temperature, and the dropping speed was controlled at 1ml / min~1.5ml / min. After the dropping was completed, the pH value was adjusted to 7~8 with triethylamine solution, and the stirring reaction was continued for 6h~8h. After the reaction was completed, the solvent was removed by reduced pressure distillation at 50℃~60℃ to obtain a precipitate, which was washed with anhydrous ether for 3~4 times, and finally the precipitate was placed in a vacuum drying oven and dried to obtain a bimetallic organic complex named M 1 M 2 -L;

[0021] S3, catalyst loading:

[0022] According to mass ratio, cyclohexane: M 1 M 2 -L: silica nanoparticles = (25-30): (0.3-0.5): (1-2); M 1 M 2 -L was added to cyclohexane, ultrasonicated at 30kHz to 40kHz for 10min to 15min, then silica nanoparticles were added, ultrasonicated at 40kHz to 60kHz for 40min to 60min; then stirred at room temperature for 24h to 30h to make M 1 M 2 -L is loaded on the surface of silica nanoparticles by physical adsorption and chemical bonding, centrifuged, the supernatant is discarded, and the precipitate is washed with cyclohexane 3 to 4 times; the precipitate is placed in a vacuum drying oven and dried to obtain SiO 2 -M 1 M 2 -L catalyst.

[0023] In S1.1 of the above preparation method, the stirring speed is 150 r / min to 200 r / min, the heating temperature is 60° C. to 65° C., and the dropping speed is 1 drop every 5 to 8 seconds.

[0024] In S1.2 of the above preparation method, the stirring speed is 100 r / min to 200 r / min.

[0025] In S1.3 of the above preparation method, the stirring speed is 150 r / min to 200 r / min; and the heating temperature is 110° C. to 115° C.

[0026] In S1.4 of the above preparation method, the amount of anhydrous sodium sulfate is 5g to 10g of anhydrous sodium sulfate per 100mL of dichloromethane phase, and the drying time is 1h to 2h; the eluent is petroleum ether and ethyl acetate, and the volume ratio is petroleum ether:ethyl acetate = (8 to 10): (1 to 2); the temperature of the vacuum drying oven is 40°C to 50°C.

[0027] In S2 of the above preparation method, the mass ratio of the components of the ligand L solution is anhydrous methanol: ligand L = (10-15): (0.08-0.12); the triethylamine solution is a triethylamine methanol solution with a concentration of 0.6 mol / L-1 mol / L; the stirring speed is 150 r / min-200 r / min; the drying temperature is 45°C-50°C, and the drying time is 10h-12h.

[0028] In S3 of the above preparation method, the stirring speed is 100r / min~150r / min; the centrifugal speed is 8000r / min~10000r / min, and the centrifugal time is 20min~30min; the drying temperature is 45℃~50℃, and the drying time is 12h~15h.

[0029] In S3 of the above preparation method, the preparation method of the silica nanoparticles comprises the following steps: by volume ratio, anhydrous ethanol: ammonia water: tetraethyl orthosilicate = 100: (10-14): (16-20); under stirring conditions, first add ammonia water to anhydrous ethanol, and then add tetraethyl orthosilicate dropwise at 23°C to 26°C, and control the dropping speed to add 1 drop every 3s to 5s. After the dropwise addition is completed, continue stirring the reaction at 40°C to 45°C for 6h to 8h to obtain a silica reaction solution; centrifuge the silica reaction solution, discard the supernatant, and wash the precipitate with anhydrous ethanol for 3 to 4 times; finally, place the precipitate in a vacuum drying oven to dry to obtain pure silica nanoparticles with a particle size range of 50nm to 100nm.

[0030] In the above-mentioned method for preparing silica nanoparticles, the stirring speed is 200r / min~300r / min; the mass concentration of the ammonia water is 20%~25%; the centrifugal speed is 10000r / min~12000r / min, and the centrifugal time is 20min~25min; the drying temperature is 60℃~70℃, and the drying time is 10h~12h.

[0031] The present invention provides a catalyst for ethylene oxide ring-opening polymerization and a preparation method thereof, and the beneficial effects are as follows:

[0032] 1. The present invention utilizes the high dispersibility and stability of silicon dioxide nanoparticles and the synergistic catalytic effect of bimetallic organic complexes to effectively improve the catalytic effect, accelerate the polymerization process, enhance the polymerization stability, increase the polymerization molecular weight, and narrow the distribution.

[0033] 2. The present invention uses β-cyclodextrin as the main molecule in S1.1, and uses its hydrophobic cavity to enclose 1-bromodecane to form a stable inclusion complex, which provides a specific spatial environment and reaction site for subsequent reactions, making 1-bromodecane more inclined to undergo a substitution reaction with 2,2'-bipyridine, introducing specific hydrophobicity and steric hindrance to the final ligand, and generating a modified ligand L. Hydroxypropyl methylcellulose is dissolved in S1.2 to form a solution, which provides a medium for subsequent reactions, helps to stabilize the reaction system and promote the mixing of various substances, and improves the quality of ligand L. 2,2'-Bipyridine is used as an important raw material for ligand synthesis in S1.3, reacts with other substances to form a part of a nitrogen-containing multidentate ligand, and provides a coordination site. Potassium tert-butoxide is used as a strong base in S1.3 to promote related chemical reactions and trigger reactions such as nucleophilic substitution. L-alanine participates in the ligand synthesis reaction, reacts with other substances through its amino and carboxyl functional groups, and introduces specific structures and functions into the ligand; the amino and carboxyl groups in L-alanine can interact weakly with metal ions and other reactants, regulate the activity and selectivity of the reaction, and induce the generation of ligands with specific chirality. Zn(NO3)2·6H2O and Mg(NO3)2·6H2O provide zinc ions and magnesium ions in S2 to form bimetallic organic complexes with ligand L. The metal ions can activate the substrate in the catalytic process. Triethylamine solution is used in S2 to adjust the pH value and create a suitable reaction environment so that the coordination reaction between metal ions and ligands can proceed smoothly. Silica nanoparticles are used as carriers in S3 to provide loading sites for bimetallic organic complexes, increase the specific surface area of ​​the catalyst, and improve the stability and dispersibility of the catalyst.

[0034] 3. In S1.1, an inclusion complex of a specific structure is formed through an inclusion reaction, and a specific structural unit and spatial configuration are introduced for the subsequent ligand synthesis. In S1.2, a uniform cellulose derivative solution is prepared to provide a good reaction medium and environment for the ligand synthesis. In S1.3, the raw materials react under specific conditions to form a nitrogen-containing multidentate ligand L, which lays the foundation for coordination with metal ions. In S1.4, impurities are removed through a series of operations to obtain a pure ligand L to ensure the purity and performance of the subsequently synthesized bimetallic organic complex. In S2, the metal salt and the ligand L are coordinated under suitable conditions to form a bimetallic organic complex M1M2-L with a specific structure and activity. In S3, the bimetallic organic complex is loaded onto the surface of silica nanoparticles to form a catalyst with a composite structure, so that the catalyst has both the catalytic activity of the bimetallic organic complex and the carrier advantages of silica nanoparticles.

[0035] 4. The catalyst prepared by the present invention has high activity: the synergistic effect of zinc and magnesium in the bimetallic organic complex and the structural characteristics of the nitrogen-containing multidentate ligand make the catalyst have high catalytic activity for the ring-opening polymerization of ethylene oxide, which can effectively reduce the activation energy of the reaction and accelerate the reaction rate.

[0036] 5. The catalyst prepared by the present invention has high selectivity: the specific ligand structure and metal ion combination endow the catalyst with high selectivity for the ring-opening polymerization of ethylene oxide, reduce the occurrence of side reactions, and improve the purity and quality of the product.

[0037] 6. The catalyst prepared by the present invention has good stability: the catalyst is loaded on the surface of the silica nanoparticles, which increases the stability of the catalyst. The silica nanoparticles can protect the bimetallic organic complex, prevent it from agglomerating or decomposing during the reaction, and extend the service life of the catalyst. The silica nanoparticles have a large specific surface area, so that the bimetallic organic complex loaded on the surface can be fully exposed, increase the contact area with the reactants, and improve the catalytic efficiency.

[0038] 7. The catalyst is recyclable: Due to the presence of silica nanoparticles, the catalyst can be easily separated from the reaction system by centrifugation and other methods after the reaction is completed, so as to achieve recycling and reuse, reduce costs and reduce pollution to the environment. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0040] Example 1: A catalyst for the ring-opening polymerization of ethylene oxide, the catalyst is based on a composite structure of silicon dioxide nanoparticles loaded with a bimetallic organic complex, named SiO 2 -M 1 M 2 -L catalyst; M 1 is zinc, M 2 The ligand L is a modified nitrogen-containing multidentate ligand; the ligand L coordinates with the metal ion through a covalent bond to form a metal organic complex, which is then loaded on the surface of the silica nanoparticles.

[0041] The above-mentioned method for preparing a catalyst for ethylene oxide ring-opening polymerization comprises the following steps:

[0042] S1, Synthesis of ligand L:

[0043] S1.1, Preliminary inclusion of cyclodextrin and halogenated alkane:

[0044] According to the mass ratio, deionized water: β-cyclodextrin: 1-bromododecane = 32:1.8:5.0, β-cyclodextrin was added to deionized water, stirred at 180 r / min and heated to 62°C for dissolution, and then 1-bromododecane was added dropwise at a rate of 1 drop every 6 seconds. Stirring was continued at 180 r / min during the addition process. After the addition was completed, stirring was continued at 180 r / min for 2 hours to allow 1-bromododecane to be included in the hydrophobic cavity of β-cyclodextrin to form a stable inclusion complex, which was named mixed solution A;

[0045] S1.2, Preparation of cellulose derivative solution:

[0046] According to the mass ratio, deionized water: hydroxypropyl methylcellulose = 48:0.9; hydroxypropyl methylcellulose was added into deionized water, and stirred at room temperature at a speed of 150r / min to dissolve to form a uniform cellulose derivative solution, which was named mixed solution B;

[0047] S1.3, ligand synthesis reaction:

[0048] According to the mass ratio, the mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = 33:48:5.0:1.5:0.4; 2,2'-bipyridine was added to the mixed solution B, and the mixture was stirred at 180 r / min to be uniformly mixed. Under the protection of nitrogen, potassium tert-butoxide was added, and the mixture was stirred at 180 r / min to be uniformly dissolved. Then, the mixed solution A and L-alanine were added, and the mixture was stirred at 180 r / min to be uniformly mixed. The mixture was heated at 113°C for 13 hours and then cooled to room temperature to obtain a ligand L reaction solution;

[0049] S1.4, product separation and purification:

[0050] According to the mass ratio, the reaction solution of ligand L: deionized water = 1.5:2.5; the reaction solution of ligand L was mixed with deionized water, and extracted with dichloromethane for 3 times, each time using dichloromethane of the same mass as the reaction solution of ligand L; the dichloromethane phases were combined, dried with anhydrous sodium sulfate, 8g of anhydrous sodium sulfate was added to every 100mL of dichloromethane phase, and dried for 1.5h to remove the residual water in the dichloromethane phase, filtered, and the filtrate was distilled at 35°C under reduced pressure to 25% of the volume, and the sample was passed through a 250-mesh silica gel column chromatography, eluted with 2.5 silica gel column volumes of eluent, and the eluent was collected, and the eluent was distilled at 65°C under reduced pressure to remove the eluent, and dried at 45°C in a vacuum drying oven for 1.5h to constant weight to obtain ligand L;

[0051] The eluents are petroleum ether and ethyl acetate, and the volume ratio is petroleum ether:ethyl acetate = 9:2;

[0052] S2, Synthesis of bimetallic organic complexes:

[0053] By mass ratio, anhydrous methanol: Zn(NO 3 ) 2 6H 2 O:Mg(NO 3 ) 2 6H 2 O: ligand L solution = 18:0.13:0.23:12; Zn(NO 3 ) 2 6H 2 O and Mg(NO 3 ) 2 6H 2 O was added into anhydrous methanol, mixed and dissolved evenly, and the ligand L solution was added dropwise at room temperature with stirring at 180 r / min, and the dropping speed was controlled at 1.2 ml / min. After the addition was completed, the pH value was adjusted to 7.5 with triethylamine solution, and the stirring reaction was continued at 180 r / min for 7 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation at 55°C to obtain a precipitate, which was washed with anhydrous ether for 3 times, and finally the precipitate was placed in a vacuum drying oven and dried at 48°C for 11 hours to obtain a bimetallic organic complex named M 1 M 2 -L;

[0054] The mass ratio of the components of the ligand L solution is anhydrous methanol: ligand L = 12:0.1; the triethylamine solution is a triethylamine methanol solution with a concentration of 0.8 mol / L;

[0055] S3, catalyst loading:

[0056] According to mass ratio, cyclohexane: M 1 M 2 -L:silicon dioxide nanoparticles = 28:0.4:1.5; M 1 M 2 -L was added to cyclohexane and ultrasonicated at 35kHz for 12min, then silica nanoparticles were added and ultrasonicated at 50kHz for 50min; then stirred at room temperature at 120r / min for 26h to make M 1 M 2 -L was loaded on the surface of silica nanoparticles by physical adsorption and chemical bonding, centrifuged at 9000r / min for 25min, the supernatant was discarded, and the precipitate was washed with cyclohexane three times; the precipitate was placed in a vacuum drying oven and dried at 48°C for 14h to obtain SiO 2 -M 1 M 2 -L catalyst.

[0057] In this embodiment, the preparation method of silicon dioxide nanoparticles includes the following steps: by volume ratio, anhydrous ethanol: ammonia water: tetraethyl orthosilicate = 100:12:18; under the condition of stirring at a speed of 250 r / min, first adding ammonia water with a mass concentration of 22% to anhydrous ethanol, and then dripping tetraethyl orthosilicate at 25°C, the dripping speed is controlled to drip 1 drop every 4 seconds, after the dripping is completed, stirring and reacting at 250 r / min for 7 hours at 42°C to obtain a silicon dioxide reaction liquid; centrifuging the silicon dioxide reaction liquid at a speed of 11000 r / min for 22 minutes, discarding the supernatant, and washing the precipitate with anhydrous ethanol for 3 times; finally, placing the precipitate in a vacuum drying oven at 65°C and drying it for 11 hours to obtain pure silicon dioxide nanoparticles with a particle size range of 50nm to 100nm.

[0058] Example 2: A catalyst for the ring-opening polymerization of ethylene oxide, the catalyst is based on a composite structure of silicon dioxide nanoparticles loaded with a bimetallic organic complex, named SiO 2 -M 1 M 2 -L catalyst; M 1 is zinc, M 2 The ligand L is a modified nitrogen-containing multidentate ligand; the ligand L coordinates with the metal ion through a covalent bond to form a metal organic complex, which is then loaded on the surface of the silica nanoparticles.

[0059] The above-mentioned method for preparing a catalyst for ethylene oxide ring-opening polymerization comprises the following steps:

[0060] S1, Synthesis of ligand L:

[0061] S1.1, Preliminary inclusion of cyclodextrin and halogenated alkane:

[0062] According to the mass ratio of deionized water: β-cyclodextrin: 1-bromododecane=30:1.5:4.8, β-cyclodextrin was added to deionized water, stirred at 150r / min and heated to 60°C for dissolution, and then 1-bromododecane was added dropwise at a rate of 1 drop every 5s. Stirring was continued at 150r / min during the addition process. After the addition was completed, stirring was continued at 150r / min for 2h to allow 1-bromododecane to be included in the hydrophobic cavity of β-cyclodextrin to form a stable inclusion complex, which was named mixed solution A;

[0063] S1.2, Preparation of cellulose derivative solution:

[0064] According to the mass ratio, deionized water: hydroxypropyl methylcellulose = 45:0.8; hydroxypropyl methylcellulose was added into deionized water, and stirred at room temperature at a speed of 100 r / min to dissolve to form a uniform cellulose derivative solution, which was named mixed solution B;

[0065] S1.3, ligand synthesis reaction:

[0066] According to the mass ratio, the mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = 30:45:4.5:1.2:0.3; 2,2'-bipyridine was added to the mixed solution B, and the mixture was stirred at 150 r / min to be uniformly mixed. Under the protection of nitrogen, potassium tert-butoxide was added, and the mixture was stirred at 150 r / min to be uniformly dissolved. Then, the mixed solution A and L-alanine were added, and the mixture was stirred at 150 r / min to be uniformly mixed. The mixture was heated at 110°C for 12 hours and then cooled to room temperature to obtain a ligand L reaction solution;

[0067] S1.4, product separation and purification:

[0068] According to the mass ratio, the reaction solution of ligand L: deionized water = 1:2; the reaction solution of ligand L was mixed with deionized water, and extracted with dichloromethane for 3 times, each time using dichloromethane of the same mass as the reaction solution of ligand L; the dichloromethane phases were combined, dried with anhydrous sodium sulfate, 5g of anhydrous sodium sulfate was added to every 100mL of dichloromethane phase, dried for 1h, residual water in the dichloromethane phase was removed, filtered, and the filtrate was distilled under reduced pressure at 30°C to 20% of the volume, the sample was passed through a 200-mesh silica gel column chromatography, eluted with 2 silica gel column volumes of eluent, the eluent was collected, the eluent was distilled under reduced pressure at 60°C to remove the eluent, and a vacuum drying oven was used to dry at 40°C for 1h to constant weight to obtain ligand L;

[0069] The eluent is petroleum ether and ethyl acetate, and the volume ratio is petroleum ether:ethyl acetate = 8:1;

[0070] S2, Synthesis of bimetallic organic complexes:

[0071] By mass ratio, anhydrous methanol: Zn(NO 3 ) 2 6H 2 O:Mg(NO 3 ) 2 6H 2 O: ligand L solution = 15:0.12:0.20:10; Zn(NO 3 ) 2 6H 2 O and Mg(NO 3 ) 2 6H 2O was added into anhydrous methanol, mixed and dissolved evenly, and the ligand L solution was added dropwise at room temperature with stirring at 150 r / min, and the dropping speed was controlled at 1 ml / min. After the addition was completed, the pH value was adjusted to 7 with triethylamine solution, and the stirring was continued at 150 r / min for 6 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation at 50°C to obtain a precipitate, which was washed with anhydrous ether for 3 times, and finally the precipitate was placed in a vacuum drying oven and dried at 45°C for 10 hours to obtain a bimetallic organic complex named M 1 M 2 -L;

[0072] The mass ratio of the components of the ligand L solution is anhydrous methanol: ligand L = 10: 0.08; the triethylamine solution is a 0.6 mol / L triethylamine methanol solution;

[0073] S3, catalyst loading:

[0074] According to mass ratio, cyclohexane: M 1 M 2 -L:silicon dioxide nanoparticles = 25:0.3:1; M 1 M 2 -L was added to cyclohexane and ultrasonicated at 30kHz for 10min, then silica nanoparticles were added and ultrasonicated at 40kHz for 40min; then stirred at room temperature at 100r / min for 24h to make M 1 M 2 -L was loaded on the surface of silica nanoparticles by physical adsorption and chemical bonding, centrifuged at 8000r / min for 20min, the supernatant was discarded, and the precipitate was washed with cyclohexane three times; the precipitate was placed in a vacuum drying oven and dried at 45°C for 12h to obtain SiO 2 -M 1 M 2 -L catalyst.

[0075] In this embodiment, the preparation method of silicon dioxide nanoparticles includes the following steps: by volume ratio, anhydrous ethanol: ammonia water: tetraethyl orthosilicate = 100:10:16; under the stirring condition of 200 r / min, first adding ammonia water with a mass concentration of 20% to anhydrous ethanol, and then dripping tetraethyl orthosilicate at 23°C, the dripping speed is controlled to drip 1 drop every 3 seconds, after the dripping is completed, stirring and reacting at 40°C for 6 hours at 200 r / min to obtain a silicon dioxide reaction solution; centrifuging the silicon dioxide reaction solution at 10000 r / min for 20 minutes, discarding the supernatant, and washing the precipitate with anhydrous ethanol for 3 times; finally, placing the precipitate in a vacuum drying oven at 60°C and drying it for 10 hours to obtain pure silicon dioxide nanoparticles with a particle size range of 50nm to 100nm.

[0076] Example 3: A catalyst for the ring-opening polymerization of ethylene oxide, the catalyst is based on a composite structure of silicon dioxide nanoparticles loaded with a bimetallic organic complex, named SiO 2 -M 1 M 2 -L catalyst; M 1 is zinc, M 2 The ligand L is a modified nitrogen-containing multidentate ligand; the ligand L coordinates with the metal ion through a covalent bond to form a metal organic complex, which is then loaded on the surface of the silica nanoparticles.

[0077] The above-mentioned method for preparing a catalyst for ethylene oxide ring-opening polymerization comprises the following steps:

[0078] S1, Synthesis of ligand L:

[0079] S1.1, Preliminary inclusion of cyclodextrin and halogenated alkane:

[0080] According to the mass ratio of deionized water: β-cyclodextrin: 1-bromododecane = 35:2:5.2, β-cyclodextrin was added to deionized water, stirred at 200 r / min and heated to 65°C for dissolution, and then 1-bromododecane was added dropwise at a rate of 1 drop every 8 seconds. Stirring was continued at 200 r / min during the addition process. After the addition was completed, stirring was continued at 200 r / min for 2.5 hours to allow 1-bromododecane to be included in the hydrophobic cavity of β-cyclodextrin to form a stable inclusion complex, which was named mixed solution A;

[0081] S1.2, Preparation of cellulose derivative solution:

[0082] The mass ratio of deionized water to hydroxypropyl methylcellulose is 50:1. Hydroxypropyl methylcellulose is added into deionized water and stirred at 200 r / min at room temperature to dissolve to form a uniform cellulose derivative solution, which is named mixed solution B.

[0083] S1.3, ligand synthesis reaction:

[0084] According to the mass ratio, the mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = 35:50:5.5:1.8:0.5; 2,2'-bipyridine was added to the mixed solution B, and the mixture was stirred at 200 r / min to be uniformly mixed. Under the protection of nitrogen, potassium tert-butoxide was added, and the mixture was stirred at 200 r / min to be uniformly dissolved. Then, the mixed solution A and L-alanine were added, and the mixture was stirred at 200 r / min to be uniformly mixed. The mixture was heated at 115°C for 14 hours and cooled to room temperature to obtain a ligand L reaction solution;

[0085] S1.4, product separation and purification:

[0086] According to the mass ratio, the reaction solution of ligand L: deionized water = 2:3; the reaction solution of ligand L was mixed with deionized water, and extracted with dichloromethane for 4 times, each time using dichloromethane of the same mass as the reaction solution of ligand L; the dichloromethane phases were combined, dried with anhydrous sodium sulfate, 10 g of anhydrous sodium sulfate was added to every 100 mL of dichloromethane phase, and dried for 2 h to remove the residual water in the dichloromethane phase, filtered, and the filtrate was distilled under reduced pressure at 40°C to 30% of the volume, and the sample was passed through a 300-mesh silica gel column chromatography, eluted with 3 silica gel column volumes of eluent, and the eluent was collected, and the eluent was distilled under reduced pressure at 70°C to remove the eluent, and dried at 50°C for 2 h in a vacuum drying oven to constant weight to obtain ligand L;

[0087] The eluents are petroleum ether and ethyl acetate, and the volume ratio is petroleum ether:ethyl acetate = 10:1.5;

[0088] S2, Synthesis of bimetallic organic complexes:

[0089] By mass ratio, anhydrous methanol: Zn(NO 3 ) 2 6H 2 O:Mg(NO 3 ) 2 6H 2 O: ligand L solution = 20: 0.15: 0.25: 15; Zn(NO 3 ) 2 6H 2 O and Mg(NO 3 ) 2 6H 2 O was added into anhydrous methanol, mixed and dissolved uniformly, and the ligand L solution was added dropwise at room temperature with stirring at 200 r / min, and the dropping speed was controlled at 1.5 ml / min. After the addition was completed, the pH value was adjusted to 8 with triethylamine solution, and the stirring reaction was continued at 200 r / min for 8 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation at 60°C to obtain a precipitate, which was washed with anhydrous ether for 4 times. Finally, the precipitate was placed in a vacuum drying oven and dried at 50°C for 12 hours to obtain a bimetallic organic complex named M 1 M 2 -L;

[0090] The mass ratio of the components of the ligand L solution is anhydrous methanol: ligand L = 15:0.12; the triethylamine solution is a 1 mol / L triethylamine methanol solution;

[0091] S3, catalyst loading:

[0092] According to mass ratio, cyclohexane: M 1 M 2 -L:silicon dioxide nanoparticles = 30:0.5:2; M1 M 2 -L was added to cyclohexane and ultrasonicated at 40kHz for 15min, then silica nanoparticles were added and ultrasonicated at 60kHz for 60min; then stirred at room temperature at 150r / min for 30h to make M 1 M 2 -L was loaded on the surface of silica nanoparticles by physical adsorption and chemical bonding, centrifuged at 10000r / min for 30min, the supernatant was discarded, and the precipitate was washed with cyclohexane for 4 times; the precipitate was placed in a vacuum drying oven and dried at 50℃ for 15h to obtain SiO 2 -M 1 M 2 -L catalyst.

[0093] In this embodiment, the preparation method of silicon dioxide nanoparticles includes the following steps: by volume ratio, anhydrous ethanol: ammonia water: tetraethyl orthosilicate = 100:14:20; under the condition of stirring at a speed of 300 r / min, first adding ammonia water with a mass concentration of 25% to anhydrous ethanol, and then dripping tetraethyl orthosilicate at 26°C, and the dripping speed is controlled to drip 1 drop every 5 seconds. After the dripping is completed, stirring and reacting at 300 r / min for 8 hours at 45°C to obtain a silicon dioxide reaction liquid; centrifuging the silicon dioxide reaction liquid at a speed of 12000 r / min for 25 minutes, discarding the supernatant, and washing the precipitate with anhydrous ethanol 4 times; finally, placing the precipitate in a vacuum drying oven at 70°C and drying it for 12 hours to obtain pure silicon dioxide nanoparticles with a particle size range of 50nm to 100nm.

[0094] The hydroxypropyl methylcellulose used in the above examples is from Shandong Maifei Chemical Co., Ltd., with a density of 1.2 g / cm 3 .

[0095] Comparative Example 1

[0096] In S1.1, β-cyclodextrin is not added, and 1-bromododecane is not included by β-cyclodextrin; other methods and parameters are the same as those in Example 1.

[0097] Comparative Example 2

[0098] S1.2 is omitted, mixed solution B (cellulose derivative solution) is not prepared, and mixed solution B is not added to S1.3; other methods and parameters are the same as those in Example 1.

[0099] Comparative Example 3

[0100] In S1.3, potassium tert-butoxide was not added; other methods and parameters were the same as in Example 1.

[0101] Comparative Example 4

[0102] In S1.3, L-alanine was not added; other methods and parameters were the same as in Example 1.

[0103] Comparative Example 5

[0104] No ligand L was prepared, no ligand L solution was added to S2, and the silica nanoparticles in S3 were directly loaded with M. 1 M 2 ; Other methods and parameters are the same as in Example 1.

[0105] The catalytic effects of the catalysts prepared in the above-mentioned embodiments and comparative examples were tested.

[0106] 1. Carry out catalytic reaction test:

[0107] 1. Reaction materials: ethylene oxide (purity ≥ 99%), catalyst (prepared in each example and comparative example).

[0108] 2. Reaction apparatus: A 250 mL three-necked flask equipped with a mechanical stirring device, a high-precision thermometer and a high-efficiency condenser, connected to a high-vacuum vacuum pump and a high-purity nitrogen cylinder through a vacuum pipeline, is used for deoxygenation and inert gas protection of the reaction system.

[0109] 3. Reaction steps:

[0110] Place the three-necked flask in an oil bath with precise temperature control, first evacuate to a pressure of 6Pa, then fill with high-purity nitrogen to normal pressure, repeat this operation 3 times to completely exclude the air. Use a high-precision electronic balance to accurately weigh 50g of ethylene oxide, slowly add it to the three-necked flask, and then add 0.5g of accurately weighed catalyst. Turn on the mechanical stirring device and set the stirring speed to 300r / min to ensure full contact between the reactants and the catalyst. Slowly heat the oil bath to 80°C and continue the reaction at this temperature for 5h.

[0111] 2. Product testing:

[0112] 1. Ethylene oxide conversion rate: Agilent gas chromatograph equipped with a high-sensitivity hydrogen flame ionization detector (FID) and a 30m×0.32mm×0.25μm capillary column was used to ensure efficient separation of ethylene oxide and related products. Take 0.1g of the sample after the reaction, place it in a 10mL volumetric flask, dilute it to the scale with anhydrous ethanol, shake it thoroughly, and use a micro-injector to take 1μL for injection. The injection port temperature is set to 250℃ to ensure instantaneous vaporization of the sample; the detector temperature is set to 300℃ to ensure the stability and accuracy of the detection signal; the column temperature is programmed to rise, with an initial temperature of 50℃, maintained for 3min, to fully separate low-boiling impurities, and then raised to 200℃ at a rate of 10℃ / min, maintained for 5min, to ensure full separation of ethylene oxide and polymers. Calculation: Ethylene oxide conversion rate (%) = (initial amount of ethylene oxide substance - amount of remaining ethylene oxide substance) / initial amount of ethylene oxide substance × 100%. The content of remaining ethylene oxide was calculated based on the sample peak area. The results are shown in Table 1 below.

[0113] 2. Polymer molecular weight: A Waters GPC instrument equipped with a differential refractive index detector was used, and the chromatographic column was three PLgel 5μm MIXED-C (300×7.5mm) gel columns in series to ensure the effective separation of polymers with different molecular weights. Tetrahydrofuran was used as the mobile phase, filtered through a 0.22μm filter membrane and ultrasonically degassed, the flow rate was set to 1.0mL / min, and the column temperature was maintained at 35°C to ensure the stability of the mobile phase and the optimal performance of the chromatographic column. Take 0.1g of the polymer after the reaction, place it in a 10mL volumetric flask, add tetrahydrofuran to dissolve, ultrasonically vibrate for 30min to fully dissolve the polymer, and then filter with a 0.45μm filter membrane to remove insoluble impurities, and then take an appropriate amount of filtrate and inject it into the GPC instrument injection bottle for testing. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer are calculated according to the retention time of the sample, accurate to the hundredth place. The results are shown in Table 1 below.

[0114] 3. Polymer Dispersity Index (PDI): Calculated from GPC data, PDI = Mw / Mn. The results are shown in Table 1 below.

[0115] Table 1 Test results

[0116]

[0117] From the above results, it can be seen that, by optimizing the preparation conditions, the complete synthesis path of Examples 1 to 3 makes the catalyst structure complete and rich in active sites, and can effectively catalyze the ring-opening polymerization of ethylene oxide, with a high conversion rate and a narrower distribution of polymer molecular weight. Among them, Example 3 has the best catalytic effect, the highest ethylene oxide conversion rate, and a higher polymer molecular weight and a narrower distribution due to more reasonable optimization of the parameters in each step.

[0118] Comparative Example 1 did not use β-cyclodextrin to include 1-bromododecane, which affected the ligand structure, reduced the catalyst activity and selectivity, and resulted in low conversion rate, low molecular weight and wide distribution. Because β-cyclodextrin inclusion can change the reactivity and spatial position of 1-bromododecane, it is helpful for the orderly synthesis of the ligand. Without this step, the ligand structure is disordered and the catalyst performance is greatly reduced.

[0119] In comparative example 2, mixed solution B was not added, which affected the ligand synthesis and catalyst structure, and reduced the catalytic performance. Hydroxypropyl methylcellulose in mixed solution B participates in the formation of a specific spatial structure and provides a reaction microenvironment, which has an important influence on the synthesis of the ligand and the distribution of active sites of the subsequent catalyst. Its absence leads to poor catalytic performance.

[0120] Comparative Example 3 did not add potassium tert-butoxide, which affected the reaction process and resulted in reduced catalytic activity. Potassium tert-butoxide plays the role of catalyst and promoter in the ligand synthesis reaction, participates in acid-base balance and specific chemical reaction steps, and its absence will slow down the reaction rate and hinder the formation of catalyst active centers.

[0121] Comparative Example 4 did not add L-alanine, which affected the ligand modification and catalyst performance, and reduced the conversion rate and molecular weight. L-alanine participates in the ligand modification process, affects the coordination mode between the ligand and the metal ion and the spatial structure of the catalyst, and further affects the catalytic activity and the formation of the polymer.

[0122] In Comparative Example 5, no ligand L was prepared, the metal ions could not be effectively coordinated, the catalyst activity was low, and the polymerization effect was poor. Ligand L is the key to the formation of metal organic complexes. Without ligand L, the metal ions could not form a structure with specific catalytic activity, resulting in extremely low catalytic activity, low ethylene oxide conversion rate, low polymer molecular weight and wide distribution.

Claims

1. A catalyst for the ring-opening polymerization of ethylene oxide, characterized in that: The catalyst is a composite structure based on silica nanoparticles loaded with bimetallic organic complexes, named SiO2-M1M2-L catalyst; M1 is zinc, M2 is magnesium, and ligand L is a modified nitrogen-containing multidentate ligand; ligand L coordinates with metal ions through covalent bonds to form a metal organic complex, which is then loaded on the surface of silica nanoparticles; The preparation method of the catalyst comprises the following steps: S1.1: According to the mass ratio, deionized water: β-cyclodextrin: 1-bromododecane = (30-35): (1.5-2): (4.8-5.2), β-cyclodextrin is dissolved in deionized water, 1-bromododecane is added dropwise, stirred and reacted to form an inclusion complex, which is named mixed solution A; S1.2: According to the mass ratio, deionized water: hydroxypropyl methylcellulose = (45-50): (0.8-1); hydroxypropyl methylcellulose is dissolved in deionized water to form a cellulose derivative solution, which is named mixed solution B; S1.3: According to the mass ratio, mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = (30-35): (45-50): (4.5-5.5): (1.2-1.8): (0.3-0.5); 2,2'-bipyridine is added to mixed solution B and mixed evenly. Under nitrogen protection, potassium tert-butoxide is added to dissolve evenly. Mixed solution A and L-alanine are added to mix evenly. Heat to reflux for reaction for 12h-14h, cool, and obtain ligand L reaction solution; S1.4: According to the mass ratio, the reaction solution of ligand L: deionized water = (1-2): (2-3); the reaction solution of ligand L is mixed with deionized water, extracted with dichloromethane, the dichloromethane phase is taken, dried over anhydrous sodium sulfate, filtered, and the filtrate is distilled under reduced pressure to 20%-30% of the volume, the sample is passed through a 200-300 mesh silica gel column chromatography, eluted with 2-3 silica gel column volumes of eluent, the eluate is collected, distilled under reduced pressure, and dried to obtain ligand L; S2: According to the mass ratio, anhydrous methanol: Zn(NO3)2·6H2O: Mg(NO3)2·6H2O: ligand L solution = (15-20): (0.12-0.15): (0.20-0.25): (10-15); Zn(NO3)2·6H2O and Mg(NO3)2·6H2O were added to anhydrous methanol to dissolve, and the ligand L solution was added dropwise under stirring. The pH value was adjusted to 7-8 with triethylamine solution, and the reaction was stirred for 6h-8h; vacuum distillation was carried out, the precipitate was washed with anhydrous ether, and dried to obtain a bimetallic organic complex named M1M2-L; S3: By mass ratio, cyclohexane: M1M2-L: silica nanoparticles = (25-30): (0.3-0.5): (1-2); add M1M2-L to cyclohexane and sonicate, add silica nanoparticles and sonicate; stir at room temperature to allow M1M2-L to be loaded on the surface of silica nanoparticles through physical adsorption and chemical bonding, centrifuge, wash the precipitate with cyclohexane, and dry to obtain SiO2-M1M2-L catalyst.

2. A method for preparing a catalyst for ethylene oxide ring-opening polymerization, for preparing the catalyst for ethylene oxide ring-opening polymerization according to claim 1, characterized in that: The steps include: S1, Synthesis of ligand L: S1.1, Preliminary inclusion of cyclodextrin and halogenated alkane: According to the mass ratio, deionized water: β-cyclodextrin: 1-bromododecane = (30-35): (1.5-2): (4.8-5.2), add β-cyclodextrin to deionized water, stir and heat to dissolve, then add 1-bromododecane dropwise, stirring continuously during the addition process, and continue stirring and reacting for 2h-2.5h after the addition is completed, so that 1-bromododecane is included in the hydrophobic cavity of β-cyclodextrin to form a stable inclusion complex, which is named mixed solution A; S1.2, Preparation of cellulose derivative solution: According to the mass ratio, deionized water: hydroxypropyl methylcellulose = (45-50): (0.8-1); add hydroxypropyl methylcellulose into deionized water, stir and dissolve at room temperature to form a uniform cellulose derivative solution, named mixed solution B; S1.3, ligand synthesis reaction: According to the mass ratio, mixed solution A: mixed solution B: 2,2'-bipyridine: potassium tert-butoxide: L-alanine = (30-35): (45-50): (4.5-5.5): (1.2-1.8): (0.3-0.5); add 2,2'-bipyridine to mixed solution B, stir and mix evenly, add potassium tert-butoxide under nitrogen protection, continue to stir and dissolve evenly, then add mixed solution A and L-alanine, continue to stir and mix evenly, heat to reflux for reaction for 12h-14h, cool to room temperature, and obtain ligand L reaction solution; S1.4, product separation and purification: According to the mass ratio, the reaction liquid of ligand L: deionized water = (1-2): (2-3); the reaction liquid of ligand L is mixed with deionized water, and extracted with dichloromethane for 3-4 times, each time using dichloromethane of the same mass as the reaction liquid of ligand L; the dichloromethane phases are combined, dried with anhydrous sodium sulfate, filtered, and the filtrate is distilled under reduced pressure at 30°C-40°C to 20%-30% of the volume, the sample is passed through a 200-mesh to 300-mesh silica gel column chromatography, eluted with 2-3 silica gel column volumes of eluent, the eluent is collected, the eluent is distilled under reduced pressure at 60°C-70°C to remove the eluent, and dried in a vacuum drying oven to constant weight to obtain ligand L; S2, Synthesis of bimetallic organic complexes: According to the mass ratio, anhydrous methanol: Zn(NO3)2·6H2O: Mg(NO3)2·6H2O: ligand L solution = (15-20): (0.12-0.15): (0.20-0.25): (10-15); Zn(NO3)2·6H2O and Mg(NO3)2·6H2O were added to anhydrous methanol, mixed and dissolved evenly, and the ligand L solution was added dropwise under stirring at room temperature, and the dropping speed was controlled at 1ml / min-1.5ml / min. After the addition was completed, the pH value was adjusted to 7-8 with triethylamine solution, and the stirring reaction was continued for 6h-8h; after the reaction was completed, the solvent was removed by reduced pressure distillation at 50℃-60℃ to obtain a precipitate, and the precipitate was washed with anhydrous ether for 3-4 times, and finally the precipitate was placed in a vacuum drying oven and dried to obtain a bimetallic organic complex, named M1M2-L; S3, catalyst loading: According to the mass ratio, cyclohexane:M1M2-L:silica nanoparticles = (25-30): (0.3-0.5): (1-2); add M1M2-L into cyclohexane, ultrasonicate at 30kHz-40kHz for 10min-15min, then add silica nanoparticles, ultrasonicate at 40kHz-60kHz for 40min-60min; then stir at room temperature for 24h-30h to load M1M2-L on the surface of silica nanoparticles through physical adsorption and chemical bonding, centrifuge, discard the supernatant, wash the precipitate with cyclohexane for 3-4 times; place the precipitate in a vacuum drying oven and dry it to obtain SiO2-M1M2-L catalyst.

3. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S1.1, the stirring speed is 150 r / min to 200 r / min, the heating temperature is 60° C. to 65° C., and the dropping speed is 1 drop every 5 to 8 seconds.

4. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S1.2, the stirring speed is 100 r / min to 200 r / min.

5. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S1.3, the stirring speed is 150 r / min to 200 r / min; the heating temperature is 110° C. to 115° C.

6. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S1.4, the amount of anhydrous sodium sulfate is 5g to 10g per 100mL of dichloromethane phase, and the drying time is 1h to 2h; the eluent is petroleum ether and ethyl acetate, and the volume ratio is petroleum ether:ethyl acetate = (8 to 10): (1 to 2); the temperature of the vacuum drying oven is 40°C to 50°C.

7. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S2, the mass ratio of the components of the ligand L solution is anhydrous methanol: ligand L = (10-15): (0.08-0.12); the triethylamine solution is a triethylamine methanol solution with a concentration of 0.6 mol / L-1 mol / L; the stirring speed is 150 r / min-200 r / min; the drying temperature is 45°C-50°C, and the drying time is 10h-12h.

8. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S3, the stirring speed is 100r / min~150r / min; the centrifugal speed is 8000r / min~10000r / min, and the centrifugal time is 20min~30min; the drying temperature is 45℃~50℃, and the drying time is 12h~15h.

9. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 2, characterized in that: In S3, the preparation method of the silica nanoparticles comprises the following steps: by volume ratio, anhydrous ethanol: ammonia water: tetraethyl orthosilicate = 100: (10-14): (16-20); under stirring conditions, first adding ammonia water to anhydrous ethanol, and then dripping tetraethyl orthosilicate at 23°C-26°C, and controlling the dripping speed to drip 1 drop every 3s-5s. After the dripping is completed, continuously stirring the reaction at 40°C-45°C for 6h-8h to obtain a silica reaction liquid; centrifuging the silica reaction liquid, discarding the supernatant, and washing the precipitate with anhydrous ethanol for 3-4 times; finally, placing the precipitate in a vacuum drying oven to dry to obtain pure silica nanoparticles with a particle size range of 50nm-100nm.

10. The method for preparing a catalyst for ethylene oxide ring-opening polymerization according to claim 9, characterized in that: In the preparation method of silicon dioxide nanoparticles, the stirring speed is 200r / min~300r / min; the mass concentration of the ammonia water is 20%~25%; the centrifugal speed is 10000r / min~12000r / min, and the centrifugal time is 20min~25min; the drying temperature is 60℃~70℃, and the drying time is 10h~12h.

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