Synthesis methods of polyol ester emulsifiers

Abstract

This invention discloses a method for synthesizing polyol ester emulsifiers, relating to the field of chemical technology. The method comprises the following steps: adding a polyol to a reaction vessel, then sequentially adding an emulsifier, fatty acid, and catalyst, and circulating the mixed solution between the reaction vessel and a static mixer until the reaction is complete; the emulsifier is composed of triethanolamine oleate and polyglycerol-3-methylglucose distearate. This invention solves the problems in existing synthesis processes, such as large density differences in raw materials, uneven mixing, resulting in small contact area and imbalanced ratio between the two phases, leading to low reaction efficiency and irregular products.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method for synthesizing polyol ester emulsifiers. Background Technology

[0002] Currently, the synthesis of long-chain fatty acid esters of polyols mainly adopts the traditional esterification reaction process, which usually involves esterifying polyols and long-chain fatty acids under the action of a catalyst.

[0003] In actual production, due to the significant difference in polarity between alcohols and long-chain fatty acids, they are in a stratified state in the reactor. Even under vigorous stirring, they cannot be fully mixed, resulting in incomplete reaction and the formation of a mixture of monoesters, diesters, and trimers, along with a large amount of unreacted polyols. To ensure that all polyols participate in the reaction, an excess of fatty acids is usually added in actual production. This method inevitably reduces the content of monoesters in the product, failing to achieve optimal performance. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for synthesizing polyol ester emulsifiers, which solves the problems of large density difference of raw materials and uneven mixing in the existing synthesis process, resulting in small contact area and imbalance of the two phases, and thus low reaction efficiency and irregular products.

[0005] The present invention proposes a method for synthesizing a polyol ester emulsifier, the method steps of which are as follows: adding a polyol to a reaction vessel, adding an emulsifier, a fatty acid and a catalyst in sequence, and circulating the mixed solution in the reaction vessel and a static mixer until the reaction is completed.

[0006] Preferably, the molar ratio of the polyol and fatty acid is 1:1-1.1.

[0007] Preferably, the polyol is one or more of glycerol, pentaerythritol, xylitol, sorbitol, and dehydrated sorbitol.

[0008] Preferably, the fatty acid is one or more of dodecanoic acid, tetradecanoic acid, hexadecanoic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

[0009] Preferably, the emulsifier is composed of triethanolamine oleate and polyglycerol-3-methylglucose distearate in a mass ratio of 2:1-4; the amount of emulsifier added is 0.1-1% of the total mass of polyol and fatty acid.

[0010] Preferably, the catalyst is a solid acid catalyst; the amount of catalyst added is 0.2-0.6% of the total mass of polyols and fatty acids.

[0011] Preferably, the solid acid catalyst is prepared by the following method:

[0012] S1: Tetraethyl orthosilicate and aluminum nitrate are dissolved in anhydrous ethanol, then the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide is added and mixed evenly. The pH is then adjusted to 9-9.5, the temperature is raised to 50-70℃ and aged for 6-18 hours, and then dried and calcined to obtain a mesoporous SiO2-γ-Al2O3 composite support.

[0013] S2: The mesoporous SiO2-γ-Al2O3 composite support was impregnated in zirconium sulfate solution and then dried to obtain a composite support loaded with zirconium precursor;

[0014] S3: The composite support loaded with zirconium precursor is impregnated in sulfuric acid solution, then filtered and calcined to obtain a composite solid acid support;

[0015] S4: The composite solid acid support is impregnated in a phosphotungstic acid solution, allowed to stand, dried, and activated at low temperature to obtain a solid acid catalyst.

[0016] Preferably, in S1, the mass ratio of tetraethyl orthosilicate, aluminum nitrate, and triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide is 2-4:1:0.2-0.4; the calcination temperature is 500-600℃, the time is 4-8h, and the heating rate is 4-6℃ / min.

[0017] Preferably, the concentration of the zirconium sulfate solution in S2 is 0.1-0.3 mol / L; the mass-to-volume ratio of the mesoporous SiO2-γ-Al2O3 composite support to the zirconium sulfate solution is 1 g: 5-10 ml; the impregnation temperature is 20-30℃, and the time is 6-12 h.

[0018] Preferably, the concentration of sulfuric acid solution in S3 is 0.4-0.6 mol / L, the mass-to-volume ratio of the composite support for the zirconium precursor to the sulfuric acid solution is 1 g: 5-15 ml; the impregnation temperature is 20-30℃, the time is 1-3 h; the calcination temperature is 400-500℃, the time is 2-6 h, and the heating rate is 4-6℃ / min.

[0019] Preferably, the concentration of the phosphotungstic acid solution in S4 is 0.1-0.5 mol / L, and the mass-to-volume ratio of the composite solid acid carrier to the phosphotungstic acid solution is 1 g: 0.5-1 ml; the low-temperature activation conditions are 300-350℃ and 2-3 h.

[0020] Preferably, the reaction conditions are: temperature 120-240℃, time 2-6h, and vacuum degree -0.1~0.07MPa.

[0021] Beneficial technical effects of the present invention:

[0022] (1) In the emulsifier of the present invention, triethanolamine oleate has strong lipophilicity and interfacial charge softening ability, and can preferentially accumulate in the fatty acid phase and form a dynamic complex layer with polyol; polyglycerol-3-methylglucose distearate contains polyglycerol segments, which have strong hydrogen bond association with polyol, and can capture trace amounts of unconverted polyol at the oil phase-liquid film interface. After the two are combined, a bilayer adsorption structure is formed, which transforms the fatty acid phase and the polyol phase from a "macroscopically immiscible system" to a "dynamically mixed system of interfacial microstructure", reducing the effective activation energy per unit reaction time and increasing the probability of ester bond formation. By having the two emulsifiers respectively dominate the hydrophobic extension and hydrophilic capture of the interface, the coupling effect of "oil phase loading-cross-interfacial directional aggregation-local concentration reaction" is realized, which significantly increases the local active substance concentration in the reaction system.

[0023] (2) This invention employs a mesoporous SiO2-γ-Al2O3 solid acid catalyst supported on phosphotungstic acid, which forms an interfacial catalytic synergistic effect with the above-mentioned emulsifier system. The catalyst surface has a composite structure of strong Brønsted acid sites and weak Lewis acid sites, forming high-intensity proton donation sites through phosphotungstic acid, while the mesoporous structure of the support provides diffusion channels, allowing the polyol-fatty acid-half-ester intermediate to be continuously adsorbed-reacted-desorbed on the surface. The dynamic film layer formed by the emulsifier can be stably adsorbed on the catalyst surface, and its polar groups undergo weak complexation with the catalytic center, enabling unreacted fatty acids to achieve "secondary localization enrichment" on the catalytic surface. This forms a "ternary synergistic interface of emulsifier dynamic film-acid center-substrate", transforming the esterification reaction pathway into an interfacial active-directional reaction mode, significantly improving the esterification rate and increasing the product yield. Detailed Implementation

[0024] The present invention will be further explained below with reference to specific embodiments.

[0025] In the various embodiments of the present invention, the polyols were purchased from BASF; the fatty acids were purchased from Jiangsu Jiaxian Chemical Co., Ltd.; the triethanolamine oleate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; the polyglycerol-3-methylglucose distearate was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; the tetraethyl orthosilicate and aluminum nitrate were purchased from Huainan Kedi Chemical Technology Co., Ltd.; the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide was purchased from BASF; the zirconium sulfate was purchased from Anhui Kangda Zirconium Industry Co., Ltd.; the sulfuric acid was purchased from Wanhua Chemical Group Co., Ltd.; and the phosphotungstic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0026] Example 1

[0027] 1 mol of glycerol was added to a reaction vessel and heated to melt. Then, 1.659 g of emulsifier was added, and after stirring, 1.05 mol of preheated myristic acid and 1.328 g of solid acid catalyst were added. Stirring continued to allow the glycerol and myristic acid to initially emulsify. The temperature was then raised to the esterification reaction temperature, and the screw pump at the bottom of the reaction vessel was turned on, allowing the pre-emulsified material in the reaction vessel to enter the screw pump. The material was then transported to an SV-type static mixer downstream of the screw pump for vigorous emulsification (refining). The refined emulsified material was then pumped back into the reaction vessel through a pipeline. This process was repeated continuously until the reaction was complete. During the reaction, water generated in the reaction was promptly removed from the reaction system using a reflux device to promote the forward reaction. After the reaction, the reaction product was filtered to remove the solid catalyst. The filtrate was then separated and purified using vacuum distillation, and fractions with different boiling points were collected to obtain high-purity polyol ester products.

[0028] The esterification reaction conditions were: temperature 180℃, time 4h, and vacuum degree 0.03MPa.

[0029] The emulsifier is composed of triethanolamine oleate and polyglycerol-3-methylglucose distearate in a 1:1 mass ratio.

[0030] The preparation method of solid acid catalysts is as follows:

[0031] S1: Tetraethyl orthosilicate and aluminum nitrate were dissolved in anhydrous ethanol, and then the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide was added and mixed evenly. The pH was then adjusted to 9.2, the temperature was raised to 60℃ and aged for 12 hours, and then dried and calcined to obtain a mesoporous SiO2-γ-Al2O3 composite support.

[0032] S2: The mesoporous SiO2-γ-Al2O3 composite support was impregnated in zirconium sulfate solution and then dried to obtain a composite support loaded with zirconium precursor;

[0033] S3: The composite support loaded with zirconium precursor is impregnated in sulfuric acid solution, then filtered and calcined to obtain a composite solid acid support;

[0034] S4: The composite solid acid support is impregnated in a phosphotungstic acid solution, allowed to stand, dried, and activated at low temperature to obtain a solid acid catalyst.

[0035] In S1, the mass ratio of tetraethyl orthosilicate, aluminum nitrate, and triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) is 3:1:0.3; the calcination temperature is 550℃, the time is 6h, and the heating rate is 5℃ / min.

[0036] The concentration of zirconium sulfate solution in S2 is 0.2 mol / L; the mass-to-volume ratio of mesoporous SiO2-γ-Al2O3 composite support to zirconium sulfate solution is 1 g: 8 ml; the impregnation temperature is 25℃ and the time is 9 h.

[0037] The concentration of sulfuric acid solution in S3 is 0.5 mol / L, the mass-to-volume ratio of the composite support for the zirconium precursor to the sulfuric acid solution is 1 g: 10 ml; the impregnation temperature is 25℃ and the time is 2 h; the calcination temperature is 450℃ and the time is 4 h, with a heating rate of 5℃ / min.

[0038] The concentration of phosphotungstic acid solution in S4 is 0.3 mol / L, and the mass-to-volume ratio of composite solid acid support to phosphotungstic acid solution is 1 g: 0.7 ml; the low-temperature activation conditions are 320℃ and 2 h.

[0039] Example 2

[0040] 1 mol of pentaerythritol was added to a reactor and heated to melt. Then, 0.340 g of emulsifier was added, and after stirring, 1.02 mol of preheated dodecanoic acid and 0.681 g of solid acid catalyst were added. Stirring continued to allow the pentaerythritol and dodecanoic acid to initially emulsify. The temperature was then raised to the esterification reaction temperature, and the screw pump at the bottom of the reactor was turned on, allowing the pre-emulsified material in the reactor to enter the screw pump. The material was then transported to an SV-type static mixer downstream of the screw pump for vigorous emulsification (refining). The refined emulsified material was then pumped back into the reactor through pipelines. This process was repeated continuously until the esterification reaction was complete. During the reaction, water generated in the reaction was promptly removed from the reaction system using a reflux device to promote the forward reaction. After the reaction, the reaction product was filtered to remove the solid catalyst. The filtrate was then separated and purified using vacuum distillation, and fractions with different boiling points were collected to obtain high-purity polyol ester products.

[0041] The esterification reaction conditions were: temperature 120℃, time 6h, and vacuum degree -0.1MPa.

[0042] The emulsifier is composed of triethanolamine oleate and polyglycerol-3-methylglucose distearate in a 2:1 mass ratio.

[0043] The preparation method of solid acid catalysts is as follows:

[0044] S1: Tetraethyl orthosilicate and aluminum nitrate were dissolved in anhydrous ethanol, and then the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide was added and mixed evenly. The pH was then adjusted to 9, the temperature was raised to 50°C and aged for 18 hours, and then dried and calcined to obtain a mesoporous SiO2-γ-Al2O3 composite support.

[0045] S2: The mesoporous SiO2-γ-Al2O3 composite support was impregnated in zirconium sulfate solution and then dried to obtain a composite support loaded with zirconium precursor;

[0046] S3: The composite support loaded with zirconium precursor is impregnated in sulfuric acid solution, then filtered and calcined to obtain a composite solid acid support;

[0047] S4: The composite solid acid support is impregnated in a phosphotungstic acid solution, allowed to stand, dried, and activated at low temperature to obtain a solid acid catalyst.

[0048] In S1, the mass ratio of tetraethyl orthosilicate, aluminum nitrate, and triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) is 2:1:0.2; the calcination temperature is 500℃, the time is 8h, and the heating rate is 4℃ / min.

[0049] The concentration of zirconium sulfate solution in S2 is 0.1 mol / L; the mass-to-volume ratio of mesoporous SiO2-γ-Al2O3 composite support to zirconium sulfate solution is 1 g: 5 ml; the impregnation temperature is 20℃ and the time is 12 h.

[0050] The concentration of sulfuric acid solution in S3 is 0.4 mol / L, the mass-to-volume ratio of the composite support for the zirconium precursor to the sulfuric acid solution is 1 g: 5 ml; the impregnation temperature is 20℃ and the time is 3 h; the calcination temperature is 400℃ and the time is 6 h, with a heating rate of 4℃ / min.

[0051] The concentration of phosphotungstic acid solution in S4 is 0.1 mol / L, and the mass-to-volume ratio of composite solid acid support to phosphotungstic acid solution is 1 g: 0.5 ml; the low-temperature activation conditions are 300℃ and 3 h.

[0052] Example 3

[0053] 1 mol of sorbitol was added to a reactor and heated to melt. Then, 4.951 g of emulsifier was added, and after stirring, 1.1 mol of preheated stearic acid and 2.971 g of solid acid catalyst were added. Stirring continued to allow initial emulsification of sorbitol and stearic acid. The temperature was then raised to the esterification reaction temperature, and the screw pump at the bottom of the reactor was turned on, allowing the pre-emulsified material in the reactor to enter the screw pump. The material was then transported to an SV-type static mixer downstream of the screw pump for vigorous emulsification (refining). The refined emulsified material was then pumped back into the reactor through pipelines. This process was repeated continuously until the esterification reaction was complete. During the reaction, water generated was promptly removed from the reaction system using a reflux device to promote the forward reaction. After the reaction, the reaction product was filtered to remove the solid catalyst. The filtrate was then purified by vacuum distillation, and fractions with different boiling points were collected to obtain high-purity polyol ester products.

[0054] The esterification reaction conditions were: temperature 240℃, time 2h, and vacuum degree 0.07MPa.

[0055] The molar ratio of polyol to fatty acid is 1:1.1; the polyol content is [missing value]; the fatty acid content is [missing value].

[0056] The emulsifier is composed of triethanolamine oleate and polyglycerol-3-methylglucose distearate in a mass ratio of 1:2; the amount of emulsifier added is 1% of the total mass of polyol and fatty acid.

[0057] The catalyst is a solid acid catalyst, and the amount added is 0.6% of the total mass of polyols and fatty acids.

[0058] The preparation method of solid acid catalysts is as follows:

[0059] S1: Tetraethyl orthosilicate and aluminum nitrate were dissolved in anhydrous ethanol, and then the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide was added and mixed evenly. The pH was then adjusted to 9.5, the temperature was raised to 70℃ and aged for 6 hours, and then dried and calcined to obtain a mesoporous SiO2-γ-Al2O3 composite support.

[0060] S2: The mesoporous SiO2-γ-Al2O3 composite support was impregnated in zirconium sulfate solution and then dried to obtain a composite support loaded with zirconium precursor;

[0061] S3: The composite support loaded with zirconium precursor is impregnated in sulfuric acid solution, then filtered and calcined to obtain a composite solid acid support;

[0062] S4: The composite solid acid support is impregnated in a phosphotungstic acid solution, allowed to stand, dried, and activated at low temperature to obtain a solid acid catalyst.

[0063] In S1, the mass ratio of tetraethyl orthosilicate, aluminum nitrate, and triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) is 4:1:0.4; the calcination temperature is 600℃, the time is 4h, and the heating rate is 6℃ / min.

[0064] The concentration of zirconium sulfate solution in S2 is 0.3 mol / L; the mass-to-volume ratio of mesoporous SiO2-γ-Al2O3 composite support to zirconium sulfate solution is 1 g:10 ml; the impregnation temperature is 30℃ and the time is 6 h.

[0065] The concentration of sulfuric acid solution in S3 is 0.6 mol / L, the mass-to-volume ratio of the composite support for the zirconium precursor to the sulfuric acid solution is 1 g: 15 ml, the impregnation temperature is 30 ℃, the time is 1 h, the calcination temperature is 500 ℃, the time is 2 h, and the heating rate is 6 ℃ / min.

[0066] The concentration of phosphotungstic acid solution in S4 is 0.5 mol / L, and the mass-to-volume ratio of the composite solid acid support to the phosphotungstic acid solution is 1 g: 1 ml; the low-temperature activation conditions are 350℃ and 2 h.

[0067] Comparative Example 1

[0068] The emulsifier in this scheme is triethanolamine oleate, and all other conditions are the same as in Example 1.

[0069] Comparative Example 2

[0070] The emulsifier in this scheme is polyglycerol-3-methylglucose distearate, and all other conditions are the same as in Example 1.

[0071] Comparative Example 3

[0072] The catalyst in this scheme is concentrated sulfuric acid, and all other conditions are the same as in Scheme 1.

[0073] The yields of polyol esters synthesized in Examples 1 and Comparative Examples 1-2 were determined, and the results are shown in Table 1. Wherein:

[0074] The saponification value test method is as follows:

[0075] 1) Weigh approximately 2 g of polyol ester emulsifier (weighing accuracy 0.0001 g) into a 250 ml conical flask;

[0076] 2) Accurately pipette 25 ml of NaOH ethanol solution into an Erlenmeyer flask;

[0077] 3) Install the spherical condenser; heat in a water bath to a gentle boil, then reflux for 30 minutes (shaking intermittently to dissolve).

[0078] 4) Rinse the inner wall of the condenser and the lower part of the stopper with 20 ml of anhydrous ethanol;

[0079] 5) Add 3-5 drops of phenolphthalein;

[0080] 6) Titrate with standard hydrochloric acid solution while hot until the red color just disappears;

[0081] 7) Reheat to boiling. If a red color appears, titrate until the red color just disappears.

[0082] 8) Simultaneously perform a blank test. Blank test: Repeat steps 2, 6, 7, and 8.

[0083]

[0084] Where: X—Saponification value of the sample, mgKOH•g -1V0—Volume of hydrochloric acid standard solution consumed in blank test, ml; V1—Volume of hydrochloric acid standard solution consumed in sample, ml; C—Molar concentration of hydrochloric acid standard solution, mol / L; m—Mass of sample, g.

[0085] The yield is calculated as follows:

[0086] Yield = (Target product quality / Input raw material quality) × 100%

[0087] Table 1 Results of polyol ester yield test

[0088]

[0089] As can be seen from the experimental results of Example 1 in Table 1, the method of the present invention can significantly improve the yield of polyol esters. The experimental results of Example 1 and Comparative Examples 1-2 show that the emulsifier of the present invention has a synergistic promoting effect on improving the yield of polyol esters. This is because triethanolamine oleate in the emulsifier of the present invention has strong lipophilicity and interfacial charge softening ability, and can preferentially accumulate in the fatty acid phase and form a dynamic complex layer with the polyol; polyglycerol-3-methylglucose distearate contains polyglycerol segments, which have strong hydrogen bonding association with the polyol, and can capture trace amounts of unconverted polyol at the oil phase-liquid film interface. The combination of the two forms a bilayer adsorption structure, transforming the fatty acid phase and polyol phase from a "macroscopically immiscible system" to a "dynamically mixed system of interfacial microstructures," reducing the effective activation energy per unit reaction time and increasing the probability of ester bond formation. By having the two emulsifiers respectively dominate the hydrophobic extension and hydrophilic capture at the interface, a coupling effect of "oil phase loading - cross-interfacial directional aggregation - local concentration reaction" is achieved, significantly increasing the local concentration of active substances in the reaction system.

[0090] The experimental results of Example 1 and Comparative Example 3 show that the solid acid catalyst of the present invention can further improve the yield of polyol esters. This is because the present invention uses a mesoporous SiO2-γ-Al2O3 solid acid catalyst supported on phosphotungstic acid, which forms an interfacial catalytic synergistic effect with the above-mentioned emulsifier system. The catalyst surface has a composite structure of strong Brønsted acid sites and weak Lewis acid sites. The phosphotungstic acid forms a high-strength proton donation site, while the mesoporous structure of the support provides diffusion channels, allowing the polyol-fatty acid-half-ester intermediate to be continuously adsorbed-reacted-desorbed on the surface. The dynamic film layer formed by the emulsifier can be stably adsorbed on the catalyst surface, and its polar groups undergo weak complexation with the catalytic center, enabling unreacted fatty acids to achieve "secondary localization enrichment" on the catalytic surface. This forms a "ternary synergistic interface of emulsifier dynamic film-acid center-substrate", transforming the esterification reaction pathway into an interfacial active-directional reaction mode, significantly improving the esterification rate and resulting in a higher product yield.

[0091] To further investigate the reusability of the solid acid catalyst prepared in this application, the solid acid catalyst prepared in Example 1 was used as an example. After each reaction, the catalyst was recovered by filtration, washed and dried, and reused. The yield of polyol esters of the solid acid catalyst was measured, and the results are shown in Table 2.

[0092] Table 2 Results of Solid Acid Catalyst Recycling Performance Test

[0093]

[0094] As can be seen from the results in Table 2, the solid acid catalyst prepared in this application has good reusability. After being recycled 5 times, the yield of polyol ester can still reach more than 85%.

[0095] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A method for the synthesis of polyol ester emulsifiers, characterized in that, The method steps are as follows: the polyol is added into a reaction kettle, the emulsifier, the fatty acid and the catalyst are sequentially added, and the mixed solution is circulated and transported in the reaction kettle and a static mixer until the reaction is completed; The emulsifier is composed of triethanolamine oleate and polyglycerol-3 methyl glucose distearate in a mass ratio of 2:1-4; The catalyst is a solid acid catalyst, and the preparation method is as follows: S1: tetraethyl orthosilicate and aluminum nitrate are dissolved in anhydrous ethanol, then triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide is added and uniformly mixed, the pH is adjusted to 9-9.5, the temperature is raised to 50-70℃, and the mixture is aged for 6-18h, and then dried and calcined to obtain a mesoporous SiO2-γ-Al2O3 composite carrier; S2: the mesoporous SiO2-γ-Al2O3 composite carrier is immersed in a zirconium sulfate solution, and then dried to obtain a composite carrier loaded with a zirconium precursor; S3: the composite carrier loaded with the zirconium precursor is immersed in a sulfuric acid solution, and then filtered and calcined to obtain a composite solid acid carrier; S4: the composite solid acid carrier is immersed in a phosphotungstic acid solution, and then dried and activated at low temperature to obtain the solid acid catalyst; The low-temperature activation conditions in S4 are a temperature of 300-350℃ and a time of 2-3h.

2. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, The molar ratio of the polyol to the fatty acid is 1:1-1.1; The polyol is one or more of glycerol, pentaerythritol, xylitol, sorbitol and sorbitan; The fatty acid is one or more of dodecanoic acid, tetradecanoic acid, hexadecanoic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

3. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, The addition amount of the emulsifier is 0.1-1% of the total mass of the polyol and the fatty acid.

4. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, The addition amount of the catalyst is 0.2-0.6% of the total mass of the polyol and the fatty acid.

5. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, In S1, the mass ratio of tetraethyl orthosilicate, aluminum nitrate and triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide is 2-4:1:0.2-0.4; the calcination temperature is 500-600℃, the time is 4-8h, and the temperature rising rate is 4-6℃ / min.

6. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, In S2, the concentration of the zirconium sulfate solution is 0.1-0.3mol / L; the mass-volume ratio of the mesoporous SiO2-γ-Al2O3 composite carrier to the zirconium sulfate solution is 1g:5-10ml; the immersion temperature is 20-30℃, and the time is 6-12h.

7. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, In S3, the concentration of the sulfuric acid solution is 0.4-0.6mol / L, the mass-volume ratio of the composite carrier loaded with the zirconium precursor to the sulfuric acid solution is 1g:5-15ml; the immersion temperature is 20-30℃, the time is 1-3h; the calcination temperature is 400-500℃, the time is 2-6h, and the temperature rising rate is 4-6℃ / min.

8. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, In S4, the concentration of the phosphotungstic acid solution is 0.1-0.5mol / L, and the mass-volume ratio of the composite solid acid carrier to the phosphotungstic acid solution is 1g:0.5-1ml.

9. The method of synthesis of polyol ester emulsifier according to claim 1, wherein, The reaction conditions are as follows: a temperature of 120-240℃, a time of 2-6h, and a vacuum degree of-0.1~0.07MPa.

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