A bio-based polyol base oil and a method of making the same

Abstract

This invention belongs to the field of base oil preparation technology and provides a bio-based polyol base oil and its preparation method. Firstly, through Lewis acid catalysis, epoxidized soybean oil is used to modify polypropylene glycol to obtain an epoxidized soybean oil-modified polyether component. Simultaneously, bio-based azelaic acid and branched alcohol undergo a high-temperature esterification reaction under a catalyst to obtain a diester component with excellent low-temperature performance. Furthermore, using citric acid as the core framework, it first reacts with oleyl alcohol to form an oil-soluble matrix, then grafts benzoyl groups onto the central hydroxyl sites, and finally introduces anti-wear metal passivation functional groups containing sulfur-nitrogen heterocycles into the side chains through a thiol-ene reaction. The above-mentioned epoxidized soybean oil-modified polyether, diester, and multifunctional additives are compounded with polyalphaolefin base oil, and after homogenization and blending, the target product is obtained. The prepared base oil combines the advantages of bio-based sources and high-performance synthetic oils, exhibiting good lubricity and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of base oil preparation technology, and relates to a bio-based polyol base oil and its preparation method. Background Technology

[0002] With the rapid development of modern industrial technology, synthetic base oils, represented by polyalphaolefins, polyethers, and esters, play a vital role in the lubrication field. However, the vast majority of these traditional synthetic base oils are derived from non-renewable petrochemical resources. Utilizing renewable biomass resources to produce bio-based lubricants has become an important development direction for the industry.

[0003] Currently, while using natural biomass such as vegetable oils directly as lubricants aligns with environmental protection principles, their inherent molecular structure leads to poor thermal oxidation stability. Under actual operating conditions, they are highly susceptible to oxidation, polymerization, and other deteriorating reactions, thus limiting their application in high-performance fields. Even simple bio-based esters prepared through conventional chemical modification often fail to achieve the long-term thermal stability comparable to high-end synthetic oils. Furthermore, the final performance of traditional mineral oils, synthetic oils, and bio-based oils generally relies on traditional physical blending techniques using additives. This technique physically dissolves or disperses various independent functional additives such as anti-wear agents, antioxidants, and metal passivators in the base oil. This approach has inherent technical limitations: additive molecules with different chemical structures may exhibit poor solubility or antagonistic interactions, affecting overall efficacy. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a bio-based polyol base oil and its preparation method. The bio-based raw materials are converted into stable modified polyethers and diesters through chemical modification. Through multi-step synthesis, functional groups such as anti-wear and antioxidant are covalently integrated into the same molecule. Finally, the above-mentioned self-synthesized components are compounded with polyalphaolefins to meet the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a bio-based polyol base oil, the method comprising:

[0007] S1, PPG-2000 and xylene are mixed to obtain reaction solution A. Epoxidized soybean oil and boron trifluoride ether solution are simultaneously added dropwise to reaction solution A for reaction. Magnesium oxide powder is added to obtain epoxidized soybean oil modified polyether.

[0008] S2, react bio-based azelaic acid with 2-ethylhexanol, then add tetrabutyl titanate, distill under reduced pressure and add activated clay to obtain di(2-ethylhexyl) azelaic acid.

[0009] S3, anhydrous citric acid, xylene, oleyl alcohol and p-toluenesulfonic acid are mixed and reacted to obtain trioleyl citrate. Trioleyl citrate, dichloromethane and 3,5-di-tert-butyl-4-hydroxybenzoic acid are mixed and 4-dimethylaminopyridine and dicyclohexylcarbodiimide are added to react to obtain (3,5-di-tert-butyl-4-hydroxybenzoylated) trioleyl citrate. (3,5-di-tert-butyl-4-hydroxybenzoylated) trioleyl citrate, 2,5-dimercapto-1,3,4-thiadiazole, azobisisobutyronitrile and toluene are mixed and reacted to obtain thiadiazole-benzoyl citrate.

[0010] S4, an epoxidized soybean oil modified polyether, di(2-ethylhexyl) azelate, thiadiazole-benzoyl citrate and polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0011] Specifically, it includes:

[0012] S1, PPG-2000 and xylene are mixed to obtain reaction solution A. Under nitrogen atmosphere, the temperature is adjusted to the first temperature. Epoxidized soybean oil and boron trifluoride ether solution are simultaneously added dropwise to reaction solution A. The reaction is carried out at the first temperature. Magnesium oxide powder is added and stirring is continued. The mixture is filtered under reduced pressure and rotary evaporated to obtain epoxidized soybean oil modified polyether.

[0013] S2, bio-based azelaic acid is mixed with 2-ethylhexanol, reacted under a nitrogen atmosphere at a second temperature, then tetrabutyl titanate is added, the temperature is adjusted to a third temperature, cooled to 90°C, vacuum distilled and activated clay is added, and filtered to obtain di(2-ethylhexyl) azelaic acid.

[0014] S3, anhydrous citric acid, xylene, oleyl alcohol, and p-toluenesulfonic acid are mixed and heated to a fourth temperature under reflux. The mixture is washed, dried, and rotary evaporated to obtain trioleyl citrate. Trioleyl citrate, dichloromethane, and 3,5-di-tert-butyl-4-hydroxybenzoic acid are mixed and placed under a nitrogen atmosphere in an ice-water bath. 4-Dimethylaminopyridine and dicyclohexylcarbodiimide are added. The ice bath is removed, and the mixture is stirred at room temperature. The mixture is filtered and rotary evaporated to obtain an oily substance. This oily substance is added to sufficient methanol and allowed to stand at -10°C. The supernatant methanol is removed, and the remaining product is added again... Add pre-cooled methanol at -10℃, stir and wash, remove the methanol layer, and dry to obtain (3,5-di-tert-butyl-4-hydroxybenzoyl)triolein citrate. Mix (3,5-di-tert-butyl-4-hydroxybenzoyl)triolein citrate, 2,5-dimercapto-1,3,4-thiadiazole, azobisisobutyronitrile and toluene, and perform three "freezing-vacuuming-nitrogen purging" operations on the system under nitrogen atmosphere, adjust the temperature to the first temperature for reaction, rotary evaporation, filtration, concentration and column chromatography purification to obtain thiadiazole-benzoyl citrate.

[0015] S4, an epoxidized soybean oil modified polyether, di(2-ethylhexyl) azelate, thiadiazole-benzoyl citrate and polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0016] The first step involves the preparation of epoxidized soybean oil modified polyether. The boron atom in the boron trifluoride molecule has an empty p orbital, exhibiting strong electron deficiency. This orbital coordinates with the oxygen atom of the epoxy group in the epoxidized soybean oil molecule. This coordination polarizes the carbon-oxygen bond of the epoxy group, giving the carbon atom on the epoxy ring a significant positive charge and activating its electrophilicity. At this point, the hydroxyl group at the end of the polypropylene glycol chain acts as a nucleophile, its lone pair of electrons attacking the electrophilic activated epoxidized carbon atom, causing a ring-opening reaction to form a new ether bond. This grafts the long-chain fatty acid structure of the epoxidized soybean oil onto the polypropylene glycol chain. This process consumes one hydroxyl group and simultaneously generates a new secondary hydroxyl group at the ring-opening position of the epoxy ring. Magnesium oxide, added after the reaction, acts as a basic oxide. Its role is to neutralize the residual acidic catalyst, forming a salt insoluble in the organic phase, thereby terminating the catalyst's activity and preventing undesirable degradation of the product during storage or subsequent use.

[0017] Next, the preparation of di(2-ethylhexyl)azelate was carried out. The titanium central atom in the tetrabutyl titanate molecule coordinates with the carbonyl oxygen of one of the two carboxyl groups in the bio-based azelate, enhancing the electrophilicity of the carbonyl carbon. Subsequently, the hydroxyl oxygen atom of 2-ethylhexanol, acting as a nucleophile, attacks the activated carbonyl carbon, forming a tetrahedral intermediate. In this intermediate, through proton transfer, one hydroxyl group is converted into a water molecule, becoming a leaving group. With the rearrangement of the tetrahedral intermediate, the water molecule is removed, forming an ester bond. After both carboxyl groups have completed esterification, excess 2-ethylhexanol is removed by vacuum distillation, while activated clay, through its porous structure and surface active sites, adsorbs residual catalyst and colored impurities.

[0018] The subsequent preparation involves thiadiazole-benzoyl citrate. First, p-toluenesulfonic acid, acting as a protonic acid catalyst, protonates the carbonyl oxygen of one of the three carboxyl groups in anhydrous citric acid, enhancing the electrophilicity of that carbonyl carbon. The hydroxyl group of oleyl alcohol attacks this carbon atom as a nucleophile, resulting in the formation and rearrangement of a tetrahedral intermediate, and the removal of a water molecule to form an ester bond. The three carboxyl groups of citric acid are more reactive than their central tertiary hydroxyl group, thus preferentially undergoing esterification. Next, a substituted benzoyl group is attached to the central tertiary hydroxyl group of trioleyl citrate, using dicyclohexylcarbodiimide as a dehydration coupling agent. First, the carboxyl group of 3,5-di-tert-butyl-4-hydroxybenzoic acid undergoes nucleophilic addition to a carbon-nitrogen double bond in dicyclohexylcarbodiimide, forming a highly reactive O-acylisourea intermediate. Subsequently, 4-dimethylaminopyridine, acting as a nucleophilic catalyst, attacks the intermediate, displacing the dicyclohexylurea moiety and forming a more reactive N-acylpyridinium salt cation. Due to the steric hindrance and weak nucleophilicity of the tertiary alcohol hydroxyl group, conventional esterification methods are difficult to perform. However, the N-acylpyridinium salt cation possesses sufficiently high reactivity to be effectively attacked by the tertiary alcohol hydroxyl group of triolein citrate. Following the attack, an ester bond is formed, releasing the 4-dimethylaminopyridine catalyst. Finally, the initiator azobisisobutyronitrile decomposes to generate a primary radical. This radical abstracts a hydrogen atom from a thiol group of 2,5-dimercapto-1,3,4-thiadiazole to generate a thio radical. This thio radical rapidly adds to the carbon-carbon double bond on the oleyl alcohol chain, forming a carbon-centered radical. This carbon-centered radical then abstracts a hydrogen atom from a thiol group of another thiadiazole molecule, forming the final product.

[0019] As a preferred embodiment of the present invention, in S1, the mass ratio of PPG-2000 (polypropylene glycol 2000), xylene, epoxidized soybean oil, boron trifluoride ether solution, and magnesium oxide powder is (100-110):(45-50):(24-25):5.2:2, for example, it can be (100, 101, 102, 103, 104, 105, 106, 107, 108, ...). 109 or 110: (45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5 or 50): (24, 24.1, 24.2, 24.3, 24.4, 24.5, 24.6, 24.7, 24.8, 24.9 or 25): 5.2:2, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0020] In some optional embodiments, the boron trifluoride diethyl ether solution has a mass fraction of 4 wt.% and the solvent is anhydrous xylene.

[0021] In some optional embodiments, the synchronous dripping time is no more than 1.5 hours.

[0022] In some alternative embodiments, the first temperature is 80-85°C, for example, it can be 80°C, 80.5°C, 81°C, 81.5°C, 82°C, 82.5°C, 83°C, 83.5°C, 84°C, 84.5°C or 85°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some alternative embodiments, the reaction time at the first temperature is 4-5 hours, for example, 4.0 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the continued stirring time is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] As a preferred technical solution of the present invention, in S2, the mass ratio of the bio-based azelaic acid, 2-ethylhexanol, tetrabutyl titanate and activated clay is (47-50):(67-70):0.3:0.5, for example, it can be (47, 47.3, 47.6, 47.9, 48.2, 48.5, 48.8, 49.1, 49.4, 49.7 or 50):(67, 67.3, 67.6, 67.9, 68.2, 68.5, 68.8, 69.1, 69.4, 69.7 or 70):0.3:0.5, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] In some alternative embodiments, the second temperature is 140-160°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C or 160°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some alternative embodiments, the reaction time at the second temperature is 1-2 hours, for example, 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some alternative embodiments, the third temperature is 200-220°C, for example, it can be 200°C, 202°C, 204°C, 206°C, 208°C, 210°C, 212°C, 214°C, 216°C, 218°C or 220°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some alternative embodiments, the reaction time at the third temperature is 6-7 hours, for example, 6.0 hours, 6.1 hours, 6.2 hours, 6.3 hours, 6.4 hours, 6.5 hours, 6.6 hours, 6.7 hours, 6.8 hours, 6.9 hours, or 7.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] As a preferred technical solution of the present invention, in S3, the fourth temperature is 135-140℃, for example, it can be 135℃, 135.5℃, 136℃, 136.5℃, 137℃, 137.5℃, 138℃, 138.5℃, 139℃, 139.5℃ or 140℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the fourth temperature reflux reaction time is 8-9 hours, for example, 8.0 hours, 8.1 hours, 8.2 hours, 8.3 hours, 8.4 hours, 8.5 hours, 8.6 hours, 8.7 hours, 8.8 hours, 8.9 hours, or 9.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the mass ratio of triolein citrate, dichloromethane, 3,5-di-tert-butyl-4-hydroxybenzoic acid, 4-dimethylaminopyridine, and dicyclohexylcarbodiimide is (75-78):250:(22-25):(0.22-0.25):(18-20), for example, it can be (75, 75.3, 75.6, 75.9, 76.2, 76.5, 76.8, 77.1, 77.4, 77.7, or 78):250:(22, 22.3, 22.6, 2...). 2.9, 23.2, 23.5, 23.8, 24.1, 24.4, 24.7 or 25: (0.22, 0.223, 0.226, 0.229, 0.232, 0.235, 0.238, 0.241, 0.244, 0.247 or 0.25): (18, 18.2, 18.4, 18.6, 18.8, 19.0, 19.2, 19.4, 19.6, 19.8 or 20), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0033] In some optional embodiments, the stirring time at room temperature is 24-25 hours, for example, 24.0 hours, 24.1 hours, 24.2 hours, 24.3 hours, 24.4 hours, 24.5 hours, 24.6 hours, 24.7 hours, 24.8 hours, 24.9 hours, or 25.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] In some alternative embodiments, the settling time is 1-2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the mass ratio of (3,5-di-tert-butyl-4-hydroxybenzoyl) triolein citrate, 2,5-dimercapto-1,3,4-thiadiazole, azobisisobutyronitrile, and toluene is (58-60):(7-8):0.16:100, for example, it can be (58, 58.2, 58.4, 58.6, 58.8, 59.0, 59.2, 59.4, 59.6, 59.8, or 60):(7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, or 8.0):0.16:100, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] In some alternative embodiments, the reaction time at the first temperature is 12-13 hours, for example, 12.0 hours, 12.1 hours, 12.2 hours, 12.3 hours, 12.4 hours, 12.5 hours, 12.6 hours, 12.7 hours, 12.8 hours, 12.9 hours, or 13.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] As a preferred embodiment of the present invention, in S4, the mass ratio of the epoxidized soybean oil modified polyether, di(2-ethylhexyl) azelate, thiadiazole-benzoyl citrate, and polyalphaolefin is (130-150):(600-650):(17-20):(250-270), for example, it can be (130, 132, 134, 136, 138, 140, 142, 144, 146, 148, or 150):(600, 605, 610). 615, 620, 625, 630, 635, 640, 645 or 650: (17.0, 17.3, 17.6, 17.9, 18.2, 18.5, 18.8, 19.1, 19.4, 19.7 or 20.0): (250, 252, 254, 256, 258, 260, 262, 264, 266, 268 or 270), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0038] Secondly, the present invention provides a bio-based polyol base oil prepared by the preparation method described in the first aspect.

[0039] Compared with the prior art, the beneficial effects of this invention are as follows: This invention prepares epoxidized soybean oil modified polyether and di(2-ethylhexyl) azelaic acid ester, respectively, transforming chemically unstable natural bio-based raw materials into structurally well-defined base oil components, thus solving the inherent defect of poor thermal oxidation stability of natural bio-oils; secondly, this invention prepares thiadiazole-benzoyl citrate, integrating thiadiazole groups providing anti-wear and metal passivation functions, benzoyl groups providing antioxidant functions, and long-chain groups providing oil solubility onto a single citric acid skeleton through covalent bonds, avoiding the performance instability problems caused by poor solubility in traditional physical blending additives; finally, thiadiazole-benzoyl citrate containing thiadiazole groups reacts with the metal surface to generate an anti-wear protective film. After local wear of the film layer, the residual active components continuously replenish the film, and with the polar adsorption and dispersion effect of the epoxy modified polyether, the film layer regeneration is accelerated, maintaining low friction and stable wear, and achieving interface self-repair. Attached Figure Description

[0040] Figure 1 The structural formula of (3,5-di-tert-butyl-4-hydroxybenzoyl) triolein citrate provided in Example 1 of this invention is as follows:

[0041] Figure 2 The structural formula of thiadiazole-benzoyl citrate provided in Example 1 of the present invention is shown. Detailed Implementation

[0042] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0043] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0044] Example 1

[0045] This embodiment provides a bio-based polyol base oil and its preparation method, the preparation method specifically including the following steps:

[0046] S1, 100g PPG-2000 and 50g xylene were mixed to obtain reaction solution A. Under nitrogen atmosphere, the temperature was adjusted to 80℃. 25g epoxidized soybean oil and 5.2g boron trifluoride ether solution were simultaneously added dropwise to reaction solution A within 1.5h and reacted for 4h. 2g magnesium oxide powder was added and stirring was continued for 2h. The mixture was then filtered under reduced pressure and rotary evaporated to obtain epoxidized soybean oil modified polyether.

[0047] S2, 50g of bio-based azelaic acid and 67g of 2-ethylhexanol were mixed and reacted at 160℃ for 1h under a nitrogen atmosphere. Then 0.3g of tetrabutyl titanate was added, the temperature was adjusted to 200℃ and reacted for 7h. The temperature was then lowered to 90℃, the mixture was distilled under reduced pressure and 0.5g of activated clay was added. The mixture was then filtered to obtain di(2-ethylhexyl) azelaic acid.

[0048] S3, 20g anhydrous citric acid, 130g xylene, 90g oleyl alcohol, and 1g p-toluenesulfonic acid were mixed and refluxed at 140℃ for 8 hours. The mixture was washed, dried, and rotary evaporated to obtain trioleyl citrate. 78g of trioleyl citrate was mixed with 250g dichloromethane and 22g 3,5-di-tert-butyl-4-hydroxybenzoic acid. Under a nitrogen atmosphere and in an ice-water bath, 0.25g of... 4-Dimethylaminopyridine and 18g dicyclohexylcarbodiimide were mixed, the ice bath was removed, and the mixture was stirred at room temperature for 25 hours. After filtration and rotary evaporation, an oily substance was obtained. The oily substance was added to sufficient methanol and allowed to stand at -10℃ for 2 hours. The supernatant methanol was removed, and pre-cooled methanol at -10℃ was added to the remaining product. After stirring and washing, the methanol layer was removed and dried to obtain (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate. 60g of (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate and 7g... 2,5-dimercapto-1,3,4-thiadiazole, 0.16 g azobisisobutyronitrile and 100 g toluene were mixed and subjected to three "freezing-vacuuming-nitrogen purging" operations. Under nitrogen atmosphere, the temperature was adjusted to 85℃ and the reaction was carried out for 12 h. Thiadiazole-benzoyl citrate was obtained by rotary evaporation, filtration, concentration and column chromatography purification.

[0049] S4, 150g of epoxidized soybean oil modified polyether, 600g of di(2-ethylhexyl) azelate, 20g of thiadiazole-benzoyl citrate and 270g of polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0050] Figure 1 The structural formula of (3,5-di-tert-butyl-4-hydroxybenzoyl) triolein citrate provided in this embodiment is as follows: Figure 2 The structural formula of thiadiazole-benzoyl citrate provided in this embodiment is shown.

[0051] Example 2

[0052] This embodiment provides a bio-based polyol base oil and its preparation method, the preparation method specifically including the following steps:

[0053] S1, 110g PPG-2000 and 45g xylene were mixed to obtain reaction solution A. Under nitrogen atmosphere, the temperature was adjusted to 85℃. 24g epoxidized soybean oil and 5.2g boron trifluoride ether solution were simultaneously added dropwise to reaction solution A within 1.2h and reacted for 5h. 2g magnesium oxide powder was added and stirring was continued for 1h. The mixture was filtered under reduced pressure and rotary evaporated to obtain epoxidized soybean oil modified polyether.

[0054] S2, 47g of bio-based azelaic acid and 70g of 2-ethylhexanol were mixed and reacted at 140℃ for 2h under a nitrogen atmosphere. Then 0.3g of tetrabutyl titanate was added, the temperature was adjusted to 220℃ and reacted for 6h. The temperature was then lowered to 90℃, the mixture was distilled under reduced pressure and 0.5g of activated clay was added. The mixture was then filtered to obtain di(2-ethylhexyl) azelaic acid.

[0055] S3, 22g anhydrous citric acid, 130g xylene, 88g oleyl alcohol, and 2g p-toluenesulfonic acid were mixed and refluxed at 135℃ for 9 hours. The mixture was washed, dried, and rotary evaporated to obtain trioleyl citrate. 75g of trioleyl citrate was mixed with 250g dichloromethane and 25g 3,5-di-tert-butyl-4-hydroxybenzoic acid. Under a nitrogen atmosphere and in an ice-water bath, 0.22g of... 4-Dimethylaminopyridine and 20g dicyclohexylcarbodiimide were mixed, and the mixture was stirred at room temperature for 24h after removing the ice bath. The mixture was filtered and rotary evaporated to obtain an oily substance. The oily substance was added to sufficient methanol and allowed to stand at -10℃ for 1h. The supernatant methanol was removed, and pre-cooled methanol at -10℃ was added to the remaining product. After stirring and washing, the methanol layer was removed and dried to obtain (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate. 58g of (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate, 8g of 2,5-dimercapto-1,3,4-thiadiazole, 0.16g of azobisisobutyronitrile and 100g of toluene were mixed, and the system was subjected to three "freezing-vacuuming-nitrogen purging" operations under a nitrogen atmosphere. The temperature was adjusted to 80℃ and the reaction was carried out for 13h. The mixture was rotary evaporated, filtered, concentrated, and purified by column chromatography to obtain thiadiazole-benzoyl citrate.

[0056] S4, 130g of epoxidized soybean oil modified polyether, 650g of di(2-ethylhexyl) azelate, 17g of thiadiazole-benzoyl citrate and 250g of polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0057] Example 3

[0058] This embodiment provides a bio-based polyol base oil and its preparation method, the preparation method specifically including the following steps:

[0059] S1, 105g PPG-2000 and 48g xylene were mixed to obtain reaction solution A. Under a nitrogen atmosphere, the temperature was adjusted to 82℃. 24.5g epoxidized soybean oil and 5.2g boron trifluoride ether solution were simultaneously added dropwise to reaction solution A within 1.0h and reacted for 4.5h. 2g magnesium oxide powder was added and stirring was continued for 1.5h. The mixture was then filtered under reduced pressure and rotary evaporated to obtain epoxidized soybean oil modified polyether.

[0060] S2, 48g of bio-based azelaic acid and 68g of 2-ethylhexanol were mixed and reacted at 150℃ for 1.5h under a nitrogen atmosphere. Then 0.3g of tetrabutyl titanate was added, the temperature was adjusted to 210℃ and reacted for 6.5h. The temperature was then lowered to 90℃, the mixture was distilled under reduced pressure and 0.5g of activated clay was added. The mixture was then filtered to obtain di(2-ethylhexyl) azelaic acid.

[0061] S3, 21g anhydrous citric acid, 130g xylene, 89g oleyl alcohol, and 1.5g p-toluenesulfonic acid were mixed and refluxed at 138℃ for 8.5h. After washing, drying, and rotary evaporation, trioleyl citrate was obtained. 76g trioleyl citrate was mixed with 250g dichloromethane and 23g 3,5-di-tert-butyl-4-hydroxybenzoic acid. Under a nitrogen atmosphere and in an ice-water bath, 0.23g of... 4-Dimethylaminopyridine and 19g of dicyclohexylcarbodiimide were mixed, the ice bath was removed, and the mixture was stirred at room temperature for 24.5h. After filtration and rotary evaporation, an oily substance was obtained. The oily substance was added to sufficient methanol and allowed to stand at -10℃ for 1.5h. The supernatant methanol liquid was removed, and pre-cooled methanol at -10℃ was added to the remaining product again. After stirring and washing, the methanol layer was removed, and the product was dried to obtain (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate. 59g of (3,5-di-tert-butyl-4-hydroxybenzoyl)trioleyl citrate and 7.5g of... 2,5-dimercapto-1,3,4-thiadiazole, 0.16 g azobisisobutyronitrile, and 100 g toluene were mixed, and the system was subjected to three "freezing-vacuuming-nitrogen purging" operations under a nitrogen atmosphere. The temperature was adjusted to 82 °C and the reaction was carried out for 12.5 h. The mixture was then purified by rotary evaporation, filtration, concentration, and column chromatography to obtain thiadiazole-benzoyl citrate.

[0062] S4, 140g of epoxidized soybean oil modified polyether, 620g of di(2-ethylhexyl) azelate, 18g of thiadiazole-benzoyl citrate and 260g of polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0063] Example 4

[0064] This embodiment provides a bio-based polyol base oil and its preparation method, the preparation method specifically including the following steps:

[0065] S1, 102g PPG-2000 and 47g xylene were mixed to obtain reaction solution A. Under a nitrogen atmosphere, the temperature was adjusted to 84℃. 24.2g epoxidized soybean oil and 5.2g boron trifluoride ether solution were simultaneously added dropwise to reaction solution A over 1.4h and reacted for 4.2h. 2g magnesium oxide powder was added and stirring was continued for 1.2h. The mixture was then filtered under reduced pressure and rotary evaporated to obtain epoxidized soybean oil modified polyether.

[0066] S2, 49g of bio-based azelaic acid and 69g of 2-ethylhexanol were mixed and reacted at 155℃ for 1.8h under a nitrogen atmosphere. Then 0.3g of tetrabutyl titanate was added, the temperature was adjusted to 215℃ and reacted for 6.2h. The temperature was then lowered to 90℃, the mixture was distilled under reduced pressure and 0.5g of activated clay was added. The mixture was then filtered to obtain di(2-ethylhexyl) azelaic acid.

[0067] S3, 21.5 g anhydrous citric acid, 130 g xylene, 88.5 g oleyl alcohol, and 1.8 g p-toluenesulfonic acid were mixed and refluxed at 136 °C for 8.2 h. After washing, drying, and rotary evaporation, trioleyl citrate was obtained. 77 g trioleyl citrate was mixed with 250 g dichloromethane and 24 g 3,5-di-tert-butyl-4-hydroxybenzoic acid. Under a nitrogen atmosphere and in an ice-water bath, 0.24 g 4-dimethylaminopyridine and 19.5 g dicyclohexylcarbodiimide were added. The ice bath was removed, and the mixture was stirred at room temperature for 24.2 h. After filtration and rotary evaporation, an oily substance was obtained. The oily substance was added to sufficient methanol and allowed to stand at -10 °C for 1.2 h. The supernatant methanol was removed, and pre-cooled methanol at -10 °C was added to the remaining product. After stirring and washing, the methanol layer was removed, and the product was dried to obtain (3,5-di-tert-butyl-4-hydroxybenzoyl) trioleyl citrate. 58.5 g of (3,5-di-tert-butyl-4-hydroxybenzoylated) triolein citrate, 7.2 g of 2,5-dimercapto-1,3,4-thiadiazole, 0.16 g of azobisisobutyronitrile, and 100 g of toluene were mixed. The system was subjected to three "freezing-vacuuming-nitrogen purging" operations under a nitrogen atmosphere, and the temperature was adjusted to 84 °C for 12.8 h. The mixture was then purified by rotary evaporation, filtration, concentration, and column chromatography to obtain thiadiazole-benzoyl citrate.

[0068] S4, 135g of epoxidized soybean oil modified polyether, 630g of di(2-ethylhexyl) azelate, 19g of thiadiazole-benzoyl citrate and 255g of polyalphaolefin are mixed to obtain a bio-based polyol base oil.

[0069] Comparative Example 1

[0070] This comparative example provides a bio-based polyol base oil and its preparation method. The difference between this example and Example 1 is that boron trifluoride ether grafting is not performed in S1, and the epoxidized soybean oil modified polyether in S4 is replaced by physical blending of PPG-2000 with epoxidized soybean oil at an equivalent hydroxyl value. Other process parameters and operating conditions are exactly the same as in Example 1.

[0071] Comparative Example 2

[0072] This comparative example provides a bio-based polyol base oil and its preparation method. The difference between this example and Example 1 is that 4-dimethylaminopyridine and dicyclohexylcarbodiimide are not added in S3, and thiadiazole-benzoyl citrate is replaced by an equimolar physical blend of (3,5-di-tert-butyl-4-hydroxybenzoyl) triolein citrate and 2,5-dimercapto-1,3,4-thiadiazole in S4. Other process parameters and operating conditions are exactly the same as in Example 1.

[0073] Comparative Example 3

[0074] This comparative example provides a bio-based polyol base oil and its preparation method. The difference between this example and Example 1 is that the mass of di(2-ethylhexyl) azelate in S4 is 0, and it is replaced by an equal mass of bio-based di(2-ethylhexyl) adipate. Other process parameters and operating conditions are exactly the same as in Example 1.

[0075] The performance of the bio-based polyol base oils prepared in Examples 1-4 and Comparative Examples 1-3 was tested using the following methods:

[0076] The thermal oxidation stability test method is ASTM D2272, and the result is recorded as RPVOT life.

[0077] Thermal storage stability test method: Approximately 50 mL of the bio-based polyol base oil sample to be tested was injected into a clean, transparent, stoppered 100 mL glass sample bottle that had been pre-dried in a 105℃ oven for 4 hours and cooled before weighing, ensuring a uniform liquid level. The sample bottle was weighed on an analytical balance, and the initial total mass was recorded. The sample bottle (with the stopper slightly loosened to balance internal and external pressure) was placed vertically in a 100℃ constant temperature oven for static thermal storage. After 168 hours (7 days), the sample bottle was removed and cooled to 25℃ at room temperature. The clarity of the sample and the presence of any turbidity, precipitation, layering, or adhesion were carefully observed and recorded under strong light. The test results are shown in Table 1.

[0078] Table 1. Test results of bio-based polyol base oils from Examples 1-4 and Comparative Examples 1-3

[0079]

[0080] As shown in Table 1, compared to Example 1, Comparative Example 1 showed a decrease in RPVOT lifetime and thermal storage stability; Comparative Example 2 showed a decrease in RPVOT lifetime and thermal storage stability; and Comparative Example 3 showed a decrease in RPVOT lifetime. This is because the physically blended PPG-2000 and epoxidized soybean oil in Comparative Example 1 contained free low-molecular-weight compounds and unreacted epoxide / secondary alcohol terminals, resulting in decreased thermal oxidation stability and thermal stability. Comparative Example 2 did not add 4-dimethylaminopyridine and dicyclohexylcarbodiimide, leading to decreased free radical capture and chain transfer efficiency, thus decreasing thermal oxidation stability and thermal stability. Comparative Example 3 used an equal mass of bio-based di(2-ethylhexyl) adipate to replace di(2-ethylhexyl) azelaate. Di(2-ethylhexyl) adipate has a lower molecular weight and higher α / β-hydrogen activity, thus resulting in decreased thermal oxidation stability.

[0081] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for the preparation of a bio-based polyol base oil, characterized by, The preparation method comprises: S1, mixing PPG-2000 and xylene to obtain a reaction solution A, synchronously adding epoxy soybean oil and boron trifluoride ether solution to the reaction solution A to react, adding magnesium oxide powder to obtain epoxy soybean oil modified polyether; S2, mixing bio-based azelaic acid and 2-ethylhexanol to react, then adding tetrabutyl titanate to react, vacuum distillation and adding activated clay to obtain azelaic acid di(2-ethylhexyl) ester; S3, mixing anhydrous citric acid, xylene, oleyl alcohol and p-toluenesulfonic acid to react to obtain trioleyl citrate, mixing trioleyl citrate, dichloromethane and 3,5-di-tert-butyl-4-hydroxybenzoic acid, adding 4-dimethylaminopyridine and dicyclohexyl carbodiimide to react to obtain (3,5-di-tert-butyl-4-hydroxybenzoylated) trioleyl citrate, mixing (3,5-di-tert-butyl-4-hydroxybenzoylated) trioleyl citrate, 2,5-dimercapto-1,3,4-thiadiazole, azobisisobutyronitrile and toluene to react to obtain thiazole-benzoyl citrate; S4, mixing epoxy soybean oil modified polyether, azelaic acid di(2-ethylhexyl) ester, thiazole-benzoyl citrate and polyalphaolefin to obtain a bio-based polyol base oil.

2. The method for preparing a bio-based polyol base oil according to claim 1, characterized in that, In S1: The mass ratio of the PPG-2000, xylene, epoxy soybean oil, boron trifluoride ether solution and magnesium oxide powder is (100-110):(45-50):(24-25):5.2:

2.

3. The method of making a bio-based polyol base oil of claim 1, wherein, In S1: The mass fraction of the boron trifluoride ether solution is 4wt.%, and the solvent is anhydrous xylene.

4. The method of making a bio-based polyol base oil of claim 1, wherein, In S1: The time of the synchronous dropping is not more than 1.5h.

5. The method of making a bio-based polyol base oil of claim 1, wherein, In S2: The mass ratio of the bio-based azelaic acid, 2-ethylhexanol, tetrabutyl titanate and activated clay is (47-50):(67-70):0.3:0.

5.

6. The method of making a bio-based polyol base oil of claim 1, wherein, In S3: The mass ratio of the anhydrous citric acid, xylene, oleyl alcohol and p-toluenesulfonic acid is (20-22):130:(88-90):(1-2).

7. The method of making a bio-based polyol base oil of claim 1, wherein, In S3: The mass ratio of the trioleyl citrate, dichloromethane, 3,5-di-tert-butyl-4-hydroxybenzoic acid, 4-dimethylaminopyridine and dicyclohexyl carbodiimide is (75-78):250:(22-25):(0.22-0.25):(18-20).

8. The method of making a bio-based polyol base oil of claim 1, wherein, In S3: The mass ratio of the (3,5-di-tert-butyl-4-hydroxybenzoylated) trioleyl citrate, 2,5-dimercapto-1,3,4-thiadiazole, azobisisobutyronitrile and toluene is (58-60):(7-8):0.16:

100.

9. The method of making a bio-based polyol base oil of claim 1, wherein, In S4: The mass ratio of the epoxy soybean oil modified polyether, azelaic acid di(2-ethylhexyl) ester, thiazole-benzoyl citrate and polyalphaolefin is (130-150):(600-650):(17-20):(250-270).

10. The bio-based polyol base oil obtained by the preparation method according to any one of claims 1-9.

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