A polyionic liquid-modified nanomaterial, its preparation method and application

Abstract

The present invention provides a polyionic liquid-modified nanomaterial, belonging to the technical field of industrial catalytic ester-based base oils. In the present invention, acidic vinyl ionic liquid is polymerized onto nanoparticles, which can synergistically combine the high interfacial property of the nanoparticles and the high catalytic activity of the polyionic liquid, giving full play to the excellent properties of the polyionic liquid-functionalized nanoparticle composite material. At the same time, the surface of the nanoparticles provides attachment sites for the catalytic active centers of the polyionic liquid, thereby effectively inhibiting the aggregation of the active centers and solving the defect problem of the high viscosity of the polyionic liquid. In addition, the combination of the polyionic liquid and the nanomaterial can achieve a synergistic catalytic effect and reduce the dosage of the catalyst. The combination of the polyionic liquid and the nanomaterial can simplify the separation of the catalyst from the reaction system.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial catalytic ester-based base oils, and particularly relates to a polyionic liquid-modified nanomaterial, a preparation method thereof, and an application thereof. Background Art

[0002] Ester synthetic lubricating oils are prepared by esterifying and dehydrating organic acids and alcohols under the action of a catalyst. According to the ester group content of the reaction product, the ester compounds used for synthesizing lubricating oils are divided into: diesters, polyol esters, and complex esters. Among them, polyol esters are obtained by the esterification reaction of polyols (such as neopentyl glycol, trimethylolpropane, pentaerythritol, etc.) and fatty acids. The esterification reaction is a type of reversible reaction, which is simple in itself. The reactants generate esterified products and water, and in the process, water is removed by a water-carrying agent to promote the forward reaction. Usually, in actual industrial practice, a certain amount of catalyst is added to improve the reaction conversion rate. In the production of ester oils, traditional catalysts mostly use sulfuric acid, which has high catalytic efficiency. However, a series of problems such as many by-products, difficult separation, equipment corrosion, environmental pollution, and difficult recovery and reuse occur during use. Therefore, finding a catalyst to replace sulfuric acid has become an urgent problem to be solved in ester synthesis.

[0003] As a new type of environmentally friendly liquid acid catalyst, acidic ionic liquids have both the high-density reactive sites of liquid acids and the non-volatility of solid acids. Their molecular structure and acidity are adjustable, they are easy to separate from the products, and they have high thermal stability. Polymeric ionic liquids are new polyelectrolytes formed by polymerizing ionic liquid monomers, which greatly change the application scope of traditional ion polymers and polyelectrolytes. Therefore, polymeric ionic liquids have the common advantages of polymers and ionic liquids. Acid-functionalized polyionic liquids have abundant catalytic active center structures in catalytic applications, which can effectively reduce the reaction activation energy and accelerate the reaction rate. However, polyionic liquids have the defect of too high viscosity, which will lead to the aggregation of active catalysts and reduce the catalytic efficiency. In addition, since polyionic liquids are liquid-phase polymers, it is difficult to separate them from the reaction system after the catalytic reaction. Summary of the Invention

[0004] The purpose of the present invention is to provide a polyionic liquid-modified nanomaterial, a preparation method thereof, and an application thereof. The polyionic liquid-modified nanomaterial of the present invention has high catalytic activity for catalyzing the esterification of polyols and fatty acids to prepare polyol esters, and can avoid the aggregation of active centers and is easy to separate from the reaction system.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a polyionic liquid-modified nanomaterial, which comprises nanoparticles and polyionic liquids grafted onto the nanoparticles through a coupling agent; the polyionic liquids are obtained by polymerizing acidic vinyl ionic liquids; the acidic vinyl ionic liquids include 1-vinyl-3-(sulfobutyl) hydrogen sulfate, 1-vinyl-3-(sulfobutyl) dihydrogen phosphate, or 1-vinyl-3-(sulfobutyl) p-toluenesulfonate.

[0007] Preferably, the nanoparticles include silica or graphene oxide.

[0008] Preferably, the mass content of the polyionic liquids in the nanomaterial is 10-50%.

[0009] The present invention provides a preparation method of the polyionic liquid-modified nanomaterial described in the above scheme, which comprises the following steps:

[0010] Performing a coupling treatment on the nanoparticles with a bromosilane coupling agent to obtain pretreated nanoparticles;

[0011] Mixing the pretreated nanoparticles, acidic vinyl ionic liquids, cuprous halide catalyst, N,N-dimethylformamide, and organic ligand, and performing atom transfer radical polymerization to obtain the polyionic liquid-modified nanomaterial.

[0012] Preferably, the cuprous halide catalyst is cuprous chloride or cuprous bromide.

[0013] Preferably, the organic ligand is 2,2'-bipyridine, tetramethylethylenediamine, or pentamethyldiethylenetriamine.

[0014] Preferably, the mass ratio of the pretreated nanoparticles to the acidic vinyl ionic liquids is 1:(3-10); the molar ratio of the cuprous halide catalyst to the organic ligand is 1:1; the mass ratio of the acidic vinyl ionic liquids to the cuprous halide catalyst is (100-150):1.

[0015] Preferably, the temperature of the atom transfer radical polymerization is 110 °C, and the time is 24-48 h.

[0016] Preferably, the coupling treatment includes: dispersing the nanoparticles in toluene, and then adding a bromosilane coupling agent to the obtained dispersion for a coupling reaction; the temperature of the coupling reaction is 60 °C, and the time is 24 h; the mass ratio of the nanoparticles to the bromosilane coupling agent is 1:10.

[0017] The present invention provides the application of the polyionic liquid-modified nanomaterial described in the above scheme or the polyionic liquid-modified nanomaterial prepared by the preparation method described in the above scheme as a catalyst in the esterification reaction of polyols and fatty acids to prepare polyol esters.

[0018] The present invention provides a poly(ionic liquid)-modified nanomaterial, comprising nanoparticles and poly(ionic liquid) grafted onto the nanoparticles through a coupling agent; the poly(ionic liquid) is obtained by polymerizing acidic vinyl ionic liquid; the acidic vinyl ionic liquid includes 1-vinyl-3-(sulfobutyl) hydrogen sulfate, 1-vinyl-3-(sulfobutyl) dihydrogen phosphate or 1-vinyl-3-(sulfobutyl) p-toluenesulfonate.

[0019] In the present invention, the acidic vinyl ionic liquid is polymerized onto the nanoparticles, which can synergistically combine the high interfacial property of the nanoparticles and the high catalytic activity of the poly(ionic liquid), and fully exert the excellent properties of the poly(ionic liquid)-functionalized nanoparticle composite material. At the same time, the surface of the nanoparticles provides attachment sites for the catalytic active centers of the poly(ionic liquid), thereby effectively inhibiting the aggregation of the active centers and solving the defect problem of the high viscosity of the poly(ionic liquid). In addition, the combination of the poly(ionic liquid) and the nanomaterial can achieve a synergistic catalytic effect and reduce the dosage of the catalyst. The combination of the poly(ionic liquid) and the nanomaterial can also simplify the separation of the catalyst from the reaction system.

[0020] Compared with homogeneous catalysts, in the present invention, by polymerizing and modifying the acidic vinyl ionic liquid onto the nanoparticles, while ensuring the catalytic activity, the catalyst also has the advantages of separation, regeneration and low corrosion.

[0021] As a catalyst, ionic liquid can play the advantages of homogeneous catalysts and heterogeneous catalysts such as a wide liquid range, uniform acidity and low corrosion in the esterification reaction. Poly(ionic liquid) inherits the advantages of ionic liquid and effectively increases the unit molar concentration of ionic liquid.

[0022] Furthermore, the present invention uses silica and graphene oxide as the nanoparticles. The unique structures and nanoscale of silica and graphene oxide have certain advantages in aspects such as wear resistance and catalysis. At the same time, in the preparation of nanocomposite materials, the two are favored due to their low cost and simple preparation.

[0023] The preparation process of the present invention is simple, the raw material cost is low, and it can meet the needs of industrial production. The catalytic performance of the poly(ionic liquid)-modified nanomaterial prepared by the present invention is significantly improved, and it has great application value in the catalytic synthesis of high-performance synthetic ester base oils. Description of the Drawings

[0024] Figure 1 It is a thermogravimetric analysis curve graph of silica nanoparticles, pretreated silica and the poly(ionic liquid)-modified nanomaterial prepared in Example 1;

[0025] Figure 2Infrared spectra of silica nanoparticles, pretreated silica, and the poly(ionic liquid)-modified nanomaterials prepared in Example 1. Detailed implementation mode

[0026] The present invention provides a poly(ionic liquid)-modified nanomaterial, comprising nanoparticles and a poly(ionic liquid) grafted onto the nanoparticles via a coupling agent; the poly(ionic liquid) is obtained by polymerizing an acidic vinyl ionic liquid; the acidic vinyl ionic liquid includes 1-vinyl-3-(sulfobutyl) hydrogen sulfate, 1-vinyl-3-(sulfobutyl) dihydrogen phosphate, or 1-vinyl-3-(sulfobutyl) p-toluenesulfonate.

[0027] In the present invention, the nanoparticles preferably include silica or graphene oxide.

[0028] In the present invention, the mass content of the poly(ionic liquid) in the nanomaterial is preferably 10 - 50%, more preferably 15 - 40%, and further preferably 25 - 40%.

[0029] In the present invention, polymerizing the acidic vinyl ionic liquid onto the nanoparticles can synergistically combine the high interfacial property of the nanoparticles and the high catalytic activity of the poly(ionic liquid), giving full play to the excellent properties of the poly(ionic liquid)-functionalized nanoparticle composite. At the same time, the surface of the nanoparticles provides attachment sites for the catalytic active centers of the poly(ionic liquid), thus effectively inhibiting the aggregation of the active centers and solving the problem of the high viscosity of the poly(ionic liquid). In addition, the combination of the poly(ionic liquid) and the nanomaterial can achieve a synergistic catalytic effect and reduce the dosage of the catalyst. Most importantly, the combination of the poly(ionic liquid) and the nanomaterial can simplify the separation of the catalyst from the reaction system.

[0030] The present invention provides a preparation method of the poly(ionic liquid)-modified nanomaterial as described in the above scheme, comprising the following steps:

[0031] Performing a coupling treatment on the nanoparticles with a bromo-silane coupling agent to obtain pretreated nanoparticles;

[0032] Mixing the pretreated nanoparticles, the acidic vinyl ionic liquid, a cuprous halide catalyst, N,N-dimethylformamide, and an organic ligand, and performing atom transfer radical polymerization to obtain the poly(ionic liquid)-modified nanomaterial.

[0033] In the present invention, unless otherwise specified, all raw materials used are commercially available products well-known in the art.

[0034] The present invention performs a coupling treatment on the nanoparticles with a bromo-silane coupling agent to obtain pretreated nanoparticles. In the present invention, the bromo-silane coupling agent is preferably 2-bromo-2-methylpropionic acid (3-trimethoxysilyl) propyl ester.

[0035] In the present invention, the coupling treatment preferably includes: dispersing nanoparticles into toluene, and then adding a bromo-silane coupling agent to the resulting dispersion for a coupling reaction.

[0036] In the present invention, the particle size of the nanoparticles is preferably 10 - 100 nm. The present invention has no special requirements for the dosage of the toluene, as long as the nanoparticles can be evenly dispersed. In the present invention, the dispersion is preferably ultrasonic dispersion. The present invention has no special requirements for the conditions of the ultrasonic dispersion, as long as the nanoparticles can be evenly dispersed. In the examples of the present invention, specifically, the nanoparticles and toluene are mixed and ultrasonically dispersed for 30 min. In the present invention, the mass ratio of the nanoparticles to the bromo-silane coupling agent is preferably 1:10. In the present invention, the temperature of the coupling reaction is preferably 60 °C, and the time is preferably 24 h; the coupling reaction is preferably carried out under stirring conditions. During the coupling reaction in the present invention, the bromo-silane coupling agent reacts with the hydroxyl groups on the nanoparticles to form siloxane bonds, thereby grafting the bromo-silane coupling agent onto the nanoparticles.

[0037] After completing the coupling reaction, the present invention preferably centrifugally washes the reaction product with toluene three times and dries it under vacuum at 70 °C for 12 h to obtain pretreated nanoparticles.

[0038] After obtaining the pretreated nanoparticles, the present invention mixes the pretreated nanoparticles, an acidic vinyl ionic liquid, a copper halide catalyst, N,N-dimethylformamide, and an organic ligand for atom transfer radical polymerization to obtain a polyionic liquid-modified nanomaterial.

[0039] In the present invention, the acidic vinyl ionic liquid is preferably obtained by acidifying 1-vinyl-3-(sulfobutyl) ammonium salt.

[0040] In the present invention, the preparation of the 1-vinyl-3-(sulfobutyl) ammonium salt preferably includes the following steps: mixing 1-vinylimidazole, 1,4-butane sultone, and toluene, and reacting to obtain 1-vinyl-3-(sulfobutyl) ammonium salt.

[0041] In the present invention, the mixing of 1-vinylimidazole, 1,4-butane sultone, and toluene preferably includes: placing 1-vinylimidazole and 1,4-butane sultone in a container, and then dropwise adding butane sultone under magnetic stirring conditions. The present invention has no special requirements for the dropping rate of the butane sultone, and it can be added drop by drop.

[0042] In the present invention, the molar ratio of 1-vinylimidazole to 1,4-butanesultone is preferably 1:1; the present invention has no special requirements for the dosage of toluene, and the toluene as a solvent can ensure the smooth progress of the reaction. In the present invention, the temperature of the reaction is preferably 60 °C and the time is preferably 24 h.

[0043] After the reaction is completed, the reaction system is cooled to room temperature in the present invention, filtered by suction, washed 3 times with toluene, and dried under vacuum at 70 °C for 12 h to obtain 1-vinyl-3-(sulfobutyl)onium salt.

[0044] In the present invention, the structure of the 1-vinyl-3-(sulfobutyl)onium salt is shown in Formula 1:

[0045]

[0046] In the present invention, the acidification preferably includes the following steps: Under ice bath conditions, anhydrous ethanol is added to the 1-vinyl-3-(sulfobutyl)onium salt and stirred evenly, and an acid solution is added dropwise. The liquid product is rotary evaporated to remove ethanol and water to obtain a colorless viscous liquid, which is the acidic vinyl ionic liquid.

[0047] In the present invention, when the acidic vinyl ionic liquid is 1-vinyl-3-(sulfobutyl) hydrogen sulfate, the acid used for acidification is preferably concentrated sulfuric acid, and the mass concentration of the concentrated sulfuric acid is preferably 98%; when the acidic vinyl ionic liquid is 1-vinyl-3-(sulfobutyl) dihydrogen phosphate, the acid used for acidification is preferably concentrated phosphoric acid, and the mass concentration of the concentrated phosphoric acid is preferably 85%; when the acidic vinyl ionic liquid is 1-vinyl-3-(sulfobutyl) p-toluenesulfonate, the acid used for acidification is preferably p-toluenesulfonic acid.

[0048] In the present invention, the dosage ratio of anhydrous ethanol to 1-vinyl-3-(sulfobutyl)onium salt is preferably 200 mL:1 mol; the molar ratio of 1-vinyl-3-(sulfobutyl)onium salt to the acid solution is preferably 1:(1 - 1.2).

[0049] In the present invention, the structural formula of 1-vinyl-3-(sulfobutyl) hydrogen sulfate is shown in Formula 2; the structural formula of 1-vinyl-3-(sulfobutyl) dihydrogen phosphate is shown in Formula 3; the structural formula of 1-vinyl-3-(sulfobutyl) p-toluenesulfonate is shown in Formula 4:

[0050]

[0051] After obtaining the acidic vinyl ionic liquid and the pretreated nanoparticles, the present invention mixes the pretreated nanoparticles, the acidic vinyl ionic liquid, a cuprous halide catalyst, N,N-dimethylformamide, and an organic ligand, and performs atom transfer radical polymerization to obtain a polyionic liquid-modified nanomaterial.

[0052] In the present invention, the cuprous halide catalyst is preferably cuprous chloride or cuprous bromide; the organic ligand is preferably 2,2'-bipyridine, tetramethylethylenediamine, or pentamethyldiethylenetriamine; the N,N-dimethylformamide is preferably methanol. In the present invention, the function of the organic ligand is to coordinate with the bromine on the pretreated nanoparticles to form a complex, and convert the pretreated nanoparticles into an initiator for atom transfer radical polymerization.

[0053] In the present invention, the mass ratio of the pretreated nanoparticles to the acidic vinyl ionic liquid is preferably 1:(3 - 10), more preferably 1:10; the molar ratio of the cuprous halide catalyst to the organic ligand is preferably 1:1; the mass ratio of the acidic vinyl ionic liquid to the cuprous halide catalyst is preferably (100 - 150):1; the dosage ratio of the pretreated nanoparticles to N,N-dimethylformamide is preferably 1 g:(20 - 30) mL.

[0054] In the present invention, mixing the pretreated nanoparticles, the acidic vinyl ionic liquid, the cuprous halide catalyst, N,N-dimethylformamide, and the organic ligand preferably includes: dispersing the pretreated nanoparticles into N,N-dimethylformamide, freezing, evacuating, filling with nitrogen and thawing to remove oxygen in the reaction vessel, adding the cuprous halide catalyst under the protection of a nitrogen stream, freezing, evacuating, filling with nitrogen and thawing, then adding the acidic vinyl ionic liquid and the organic ligand under the protection of a nitrogen stream, freezing, evacuating, filling with nitrogen and thawing, heating to the temperature of atom transfer radical polymerization, and performing atom transfer radical polymerization.

[0055] In the present invention, the temperature of the atom transfer radical polymerization is preferably 110 °C, and the time is preferably 24 - 48 h, more preferably 30 - 40 h. In the atom transfer radical polymerization process of the present invention, the acidic vinyl ionic liquid polymerizes onto the surface of the nanoparticles and is connected to the nanoparticles through a coupling agent.

[0056] The present invention preferably terminates the polymerization by exposing the reaction mixture to air.

[0057] After completing the atom transfer radical polymerization, the present invention cools the reaction mixture to room temperature, centrifugally washes it 3 times with deionized water and methanol respectively, and dries it under vacuum at 70 °C for 12 h to obtain a polyionic liquid-modified nanomaterial.

[0058] The present invention provides the use of the polyionic liquid-modified nanomaterial described in the above solution or the polyionic liquid-modified nanomaterial prepared by the preparation method described in the above solution as a catalyst in the esterification reaction of polyols and fatty acids to prepare polyol esters.

[0059] In the present invention, the polyol preferably includes neopentyl glycol, trimethylolpropane or pentaerythritol; the fatty acid is preferably a C6-C10 fatty acid.

[0060] In the present invention, the addition amount of the catalyst is preferably 1-10% of the total mass of the polyol and the fatty acid, more preferably 3-7%, and most preferably 5%.

[0061] In the present invention, the esterification reaction of the polyol and the fatty acid to prepare the polyol ester preferably includes the following steps: adding the polyol, the fatty acid, the catalyst and the water-carrying agent to a reaction vessel, heating to the temperature of the esterification reaction, and carrying out the esterification reaction under stirring and reflux conditions; after the reaction is completed, rotating evaporation is carried out to remove water to obtain the polyol ester.

[0062] In the present invention, the water-carrying agent is preferably toluene.

[0063] The present invention has no special requirements for the conditions of the esterification reaction, and the well-known esterification conditions in the art can be adopted. In the present invention, when the polyol is trimethylolpropane or pentaerythritol and the fatty acid is n-caproic acid, the temperature of the esterification reaction is 160 °C and the time is 10 h. The present invention has no special requirements for the amounts of the polyol, the fatty acid and the water-carrying agent, and the well-known amounts in the art can be adopted.

[0064] The following is a detailed description of a polyionic liquid-modified nanomaterial provided by the present invention, its preparation method and application in conjunction with examples, but they cannot be construed as limiting the protection scope of the present invention.

[0065] Raw material preparation example 1

[0066] Synthesis of 1-vinyl-3-(sulfobutyl)imidazolium hydrogen sulfate

[0067]

[0068] Step 1: Place 0.1 mol (9.4 g) of 1-vinylimidazole and 50 mL of toluene in a three-necked flask, and dropwise add 0.1 mol (14.6 g) of 1,4-butanesultone under magnetic stirring. The addition is completed in 1 h, and the reaction is carried out at 60 °C for 24 h. A white solid is formed. Cool to room temperature, filter by suction, wash with toluene 3 times, and vacuum dry at 70 °C for 12 h to obtain the 1-vinyl-3-(sulfobutyl)onium salt monomer.

[0069]

[0070] Step 2: Under ice bath conditions, add 20 mL of absolute ethanol as a solvent to 0.1 mol of 1-vinyl-3-(sulfobutyl)onium salt monomer, stir evenly, slowly dropwise add 0.105 mol of concentrated sulfuric acid (98%), and rotate the resulting liquid product to remove ethanol and water to obtain a colorless viscous liquid, which is 1-vinyl-3-(sulfobutyl)imidazolium hydrogen sulfate.

[0071] Raw material preparation example 2

[0072] Synthesis of 1-vinyl-3-(sulfobutyl)imidazolium dihydrogen phosphate

[0073] The preparation of 1-vinyl-3-(sulfobutyl)onium salt monomer is the same as that in Raw material preparation example 1;

[0074] Under ice bath conditions, add 20 mL of absolute ethanol to 0.1 mol of 1-vinyl-3-(sulfobutyl)onium salt monomer, stir evenly, slowly dropwise add 0.12 mol of concentrated phosphoric acid (85%), and perform rotary evaporation on the resulting liquid product to remove absolute ethanol and water to obtain a colorless viscous liquid, which is 1-vinyl-3-(sulfobutyl)imidazolium dihydrogen phosphate.

[0075] Raw material preparation example 3

[0076] Synthesis of 1-vinyl-3-(sulfobutyl)imidazolium p-toluenesulfonate

[0077] The preparation of 1-vinyl-3-(sulfobutyl)onium salt monomer is the same as that in Raw material preparation example 1;

[0078] Under ice bath conditions, add 20 mL of absolute ethanol to 0.1 mol of 1-vinyl-3-(sulfobutyl)onium salt monomer, stir evenly, slowly dropwise add 0.105 mol of p-toluenesulfonic acid (99%), and perform rotary evaporation on the resulting liquid product to remove absolute ethanol and water to obtain a colorless viscous liquid.

[0079] Raw material preparation example 4

[0080] Synthesis of pretreated silica nanoparticles

[0081] Take 2 g of SBA-15 and 50 mL of toluene as a solvent and place them in a three-necked flask for ultrasonic dispersion for 30 min. Add 20 g of bromo-silane coupling agent and stir and react at 60 °C for 24 h. Centrifuge and wash with toluene 3 times and vacuum dry at 70 °C for 12 h to obtain pretreated silica.

[0082] Raw material preparation example 5

[0083] Take 2 g of graphene oxide and 50 mL of toluene and place them in a three-necked flask. Ultrasonically disperse for 30 min, add 20 g of bromo-silane coupling agent, and stir and react at 60 °C for 24 h. Centrifuge and wash with toluene three times, and vacuum dry at 70 °C for 12 h to obtain pretreated graphene oxide.

[0084] Example 1

[0085] Take 1 g of pretreated silica (Raw material preparation example 4) and 25 mL of DMF as the solvent and place them in a two-necked flask. Ultrasonically disperse for 30 min, freeze, evacuate, and fill with nitrogen to thaw to remove all oxygen in the flask. Under the protection of a nitrogen stream, add (80 mg, 0.56 mmol) CuBr, freeze, evacuate, and fill with nitrogen to thaw. Take 10 g of 1-butylsulfonic acid-3-vinylimidazole hydrogensulfate (Raw material preparation example 1) and add it to the reaction solution under the protection of a nitrogen stream. Add (0.117 mL, 0.56 mmol) pentamethyldiethylenetriamine, freeze again, evacuate, and fill with nitrogen to thaw. Stir and polymerize at 110 °C for 24 h. Expose the reaction mixture to air to terminate the polymerization. Cool to room temperature and centrifuge and wash with deionized water and methanol three times each. Vacuum dry at 70 °C for 12 h to obtain a polyionic liquid-modified nanomaterial, where the mass content of the polyionic liquid is 35%.

[0086] Example 2

[0087] The difference from Example 1 is only that 1-butylsulfonic acid-3-vinylimidazole hydrogensulfate is replaced with vinyl-3-(sulfobutyl)imidazole dihydrogen phosphate of Raw material preparation example 2, and the mass content of the polyionic liquid in the obtained polyionic liquid-modified nanomaterial is 33%.

[0088] Example 3

[0089] The difference from Example 1 is only that 1-butylsulfonic acid-3-vinylimidazole hydrogensulfate is replaced with 1-vinyl-3-(sulfobutyl)imidazole p-toluenesulfonate of Raw material preparation example 3, and the mass content of the polyionic liquid in the obtained polyionic liquid-modified nanomaterial is 32%.

[0090] Structure characterization:

[0091] Perform thermogravimetric analysis on silica nanoparticles (SBA15), pretreated silica (SBA15-Br), and the polyionic liquid-modified nanomaterial (SBA15-PVIMBs-HSO4) prepared in Example 1. The results are as Figure 1 shown. It can be seen from Figure 1 this that the polyionic liquid has been successfully grafted onto the nanoparticles.

[0092] The infrared spectra of silica nanoparticles (SBA15), pretreated silica (SBA15-Br), and the poly(ionic liquid)-modified nanomaterials (SBA15-PVIMBs-HSO4) prepared in Example 1 were observed, and the results are as Figure 2 shown. As can be seen from Figure 2 , the modified nanoparticles have an ionic liquid functional group structure, indicating that the poly(ionic liquid) has been grafted onto the nanocarrier.

[0093] Application Example 1

[0094] 6.7 g (0.05 mol) of trimethylolpropane, 17.4 g (0.15 mol) of n-hexanoic acid, and 1.2 g (5% of the total mass of the raw materials) of the poly(ionic liquid)-modified nanomaterials prepared in Example 1 as a catalyst were added to a 100 mL three-necked flask. 5 mL of toluene was used as a dehydrating agent. The mixture was stirred and refluxed for dehydration reaction at 160 °C for 10 h. After the reaction, the solution was concentrated by rotary evaporation to obtain an ester, and the unreacted substrates and by-product water were removed. The acid value of the product was measured with reference to GB / T 4945-2002, and the esterification degree of the product was analyzed through the acid value. The calculation formula for the esterification rate is shown in Formula (1):

[0095] Esterification rate (%) = [(1 - acid value of the product / initial acid value) × acid-alcohol molar ratio ÷ 3] × 100% Formula (1)

[0096] The measured acid value after the reaction was: 3.6 mg KOH / g, and the reaction conversion rate was 99.6%.

[0097] Application Example 2

[0098] 6.8 g (0.05 mol) of pentaerythritol, 23.2 g (0.20 mol) of n-hexanoic acid, and 1.5 g (5% of the total mass of the raw materials) of the poly(ionic liquid)-modified nanomaterials prepared in Example 1 as a catalyst were added to a 100 mL three-necked flask. 5 mL of toluene was used as a dehydrating agent. The mixture was stirred and refluxed for dehydration reaction at 160 °C for 10 h. After the reaction, the solution was concentrated by rotary evaporation to obtain an ester, and the unreacted substrates and by-product water were removed. The acid value of the product was measured with reference to GB / T 4945-2002, and the esterification degree of the product was analyzed through the acid value. The calculation formula for the esterification rate is shown in Formula (2):

[0099] Esterification rate (%) = [(1 - acid value of the product / initial acid value) × acid-alcohol molar ratio ÷ 4] × 100% Formula (2)

[0100] The measured acid value after the reaction was: 15.2 mg KOH / g, and the reaction conversion rate was 96.8%.

[0101] Application Example 3

[0102] The difference from Application Example 1 is only that the catalyst is replaced by the poly(ionic liquid)-modified nanomaterial prepared in Example 2.

[0103] Application Example 4

[0104] The difference from Application Example 1 is only that the catalyst is replaced by the poly(ionic liquid)-modified nanomaterial prepared in Example 3.

[0105] Comparative Application Example 1

[0106] The difference from Application Example 1 is only that the catalyst is replaced by SBA-15.

[0107] Blank group

[0108] The difference from Application Example 2 is only that no catalyst is added.

[0109] The catalytic performance results of Application Examples 2 to 4, Comparative Application Example 1, and the blank group are shown in Table 1.

[0110] Table 1 Catalytic activity test results of different catalysts and blank group

[0111]

[0112] As can be seen from Table 1, when SBA-15 is modified with acidic poly(ionic liquid) and applied to the esterification reaction of trimethylolpropane and n-hexanoic acid, the esterification reaction rate is significantly increased. There are slight differences in the catalytic activities of different acidic ionic liquids, among which the sulfated ionic liquid has the highest activity.

[0113] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Application of poly(ionic liquid)-modified nanomaterials as catalysts in the preparation of polyol esters by esterification of polyols and fatty acids; the poly(ionic liquid)-modified nanomaterials include nanoparticles and poly(ionic liquids) grafted onto the nanoparticles through a coupling agent; the poly(ionic liquids) are obtained by polymerization of acidic vinyl ionic liquids, and the acidic vinyl ionic liquids are 1-vinyl-3-(sulfobutyl) hydrogen sulfate; the nanoparticles are silica or graphene oxide; The preparation method of the poly(ionic liquid)-modified nanomaterials comprises the following steps: Carrying out coupling treatment on the nanoparticles with a bromoalkylsilane coupling agent to obtain pretreated nanoparticles; Mixing the pretreated nanoparticles, acidic vinyl ionic liquid, cuprous halide catalyst, N,N-dimethylformamide and organic ligand, and carrying out atom transfer radical polymerization to obtain poly(ionic liquid)-modified nanomaterials; The mass content of the poly(ionic liquid) in the nanomaterials is 25-50%.

2. The application according to claim 1, wherein The cuprous halide catalyst is cuprous chloride or cuprous bromide.

3. The application according to claim 1, wherein The organic ligand is 2,2'-bipyridine, tetramethylethylenediamine or pentamethyldiethylenetriamine.

4. The application according to claim 1, wherein The mass ratio of the pretreated nanoparticles to the acidic vinyl ionic liquid is 1:(3-10); the molar ratio of the cuprous halide catalyst to the organic ligand is 1:1; the mass ratio of the acidic vinyl ionic liquid to the cuprous halide catalyst is (100-150):

1.

5. The application according to claim 1, wherein The temperature of the atom transfer radical polymerization is 110 °C, and the time is 24-48 h.

6. The application according to claim 1, characterized in that The coupling treatment includes: dispersing the nanoparticles in toluene, and then adding a bromoalkylsilane coupling agent to the obtained dispersion for coupling reaction; the temperature of the coupling reaction is 60 °C, and the time is 24 h; the mass ratio of the nanoparticles to the bromoalkylsilane coupling agent is 1:10.

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