Pentaerythritol ester as well as preparation method and application thereof

Abstract

The invention provides pentaerythritol ester as well as a preparation method and application thereof. The pentaerythritol ester disclosed by the invention comprises the following components in percentage by mass: 5.0%-50% of pentaerythritol ester as shown in a formula (I) and 50%-95% of pentaerythritol ester as shown in a formula (II): # imgabs0, wherein an R group in the # imgabs0 is a straight chain or branched chain alkylene of C1-C14; and each R'group is independently selected from C3-C9 linear chain or branched chain alkyl. The pentaerythritol ester synthesized by the invention has high viscosity index (greater than 130), low pour point (less than-60 DEG C), lower kinematic viscosity (less than 10000 mm < 2 > / s) at-40 DEG C and good high-temperature oxidation stability, and can meet the use requirements of MIL-PRF-23699G aviation turbine engine lubricating oil.

Description

Technical Field

[0001] The invention relates to a polyol ester base oil and a preparation method thereof, in particular to a pentaerythritol ester base oil meeting the MIL-PRF-23699G performance specification of synthetic lubricating oil for aviation turbine engines. Background Art

[0002] The aviation turbine engine lubricant specifications widely used around the world mainly include MIL-PRF-23699G "Performance Specification for Aviation Turbine Engine Synthetic Lubricants" (2014) and SAE AS 5780D "Specification for Aviation Gas Turbine Engine Lubricants" (2018), including three product specifications: MIL-PRF-23699G STD standard type / HTS high thermal stability type and SAE AS 5780D HPC high performance type. The kinematic viscosity at 100°C is 4.90~5.40mm 2 / s, 40℃ kinematic viscosity ≥23.0mm 2 / s, -40℃ kinematic viscosity ≤13000mm 2 / s, pour point ≤-57℃, and the lubricant base oil is required to use polyol ester. The operating temperature of STD aircraft engine lubricant is about -40~200℃, the long-term operating temperature is about 200℃, and the upper limit of high temperature use is about 220℃; the operating temperature of HTS high thermal stability and HPC high performance aircraft engine lubricant is about -40~220℃, the long-term operating temperature is about 220℃, and the upper limit of high temperature use is about 230℃.

[0003] Currently available on the market or in the literature, the 5mm 2 / s polyol ester aviation engine lubricant base oil is mainly trimethylolpropane, monopentaerythritol, dipentaerythritol or one or more thereof with C 2～10 Esterification products of saturated monobasic fatty acids.

[0004] US 5503761 uses a mixture of 88% to 90% monopentaerythritol and 10% to 12% dipentaerythritol and C 5～10 The monobasic mixed fatty acid is esterified to synthesize the ester base oil, wherein the mixed acid includes 5 to 20 mol% C 8～10 Acid, 50~65mol%C 5～7 Acid, at least 15 mol% C 6～10 Acid, esterification synthetic base oil 100 ℃ kinematic viscosity ≥ 4.6mm 2 / s, -40℃ kinematic viscosity<12000mm 2 / s, pour point <-54℃.

[0005] US 2004092411 discloses a method for preparing a base oil having high temperature stability, which is prepared by mixing pentaerythritol and C2～10 Obtained by esterification of fatty acids, including 95-80 mol% C 5～10 Acid, 5-20 mol% C 2～4 Acid. This method uses C 2～4 The viscosity index of acid-synthesized base oil is less than 130, which reduces the viscosity-temperature performance of the base oil.

[0006] CN114044740A discloses a method for preparing an ultra-high viscosity base oil. The method uses one of neopentyl glycol, trimethylolpropane, pentaerythritol, ditrihydroxypropane and dipentaerythritol and monohydric alcohol with n-hexanoic acid, n-heptanoic acid and 2-ethylhexanoic acid to obtain a high-viscosity mixed ester base oil through a step-by-step esterification reaction. Due to the presence of too much branched alcohol or branched acid or a single type of monobasic acid in the raw materials, the kinematic viscosity and pour point of the synthesized base oil are high, and the low-temperature fluidity is poor, which cannot meet the use requirements of MIL-PRF-23699G.

[0007] 5mm in the prior art 2 / s Polyol ester base oil has the defects of insufficient oxidation stability and poor viscosity-temperature performance, and it is difficult to take into account high viscosity index (>130), low pour point (<-60℃), low kinematic viscosity at -40℃ (<10000mm 2 / s) and good high temperature oxidation stability requirements still need further improvement. Summary of the invention

[0008] The invention provides a pentaerythritol ester and a preparation method and application thereof.

[0009] The pentaerythritol ester of the present invention comprises, by mass, 5.0% to 50% of the pentaerythritol ester represented by formula (I) and 50% to 95% of the pentaerythritol ester represented by formula (II):

[0010]

[0011] The R group is C1~C 14 Each R' group is independently selected from a C3 to C9 straight chain or branched chain alkyl group.

[0012] According to the present invention, the R group is preferably a C2-C8 straight chain or branched alkylene group; each R' group is preferably selected from two or more (e.g., three or four) of a C3 straight chain or branched alkyl group, a C4 straight chain or branched alkyl group, a C5 straight chain or branched alkyl group, a C6 straight chain or branched alkyl group, a C7 straight chain or branched alkyl group, a C8 straight chain or branched alkyl group, and a C9 straight chain or branched alkyl group, more preferably selected from a C3 straight chain alkyl group, a C4 straight chain alkyl group, a C5 straight chain alkyl group, a C6 straight chain alkyl group, a C7 straight chain alkyl group, a C8 straight chain alkyl group. Preferably, each R' group may include 0-10.0 mol% of C3 straight-chain alkyl, 0-35.0 mol% of C4 straight-chain alkyl, 30.0 mol%-75.0 mol% of C5 straight-chain alkyl, 5.0 mol%-45.0 mol% of C6 straight-chain alkyl, 0-30.0 mol% of C7 straight-chain alkyl, 0-15.0 mol% of C8 straight-chain alkyl, and 0-10.0 mol% of C9 straight-chain alkyl.

[0013] According to the present invention, the pentaerythritol ester preferably comprises, by mass, 5.0% to 25% of the pentaerythritol ester represented by formula (I) and 75% to 95% of the pentaerythritol ester represented by formula (II).

[0014] The preparation method of pentaerythritol ester of the present invention comprises the following steps:

[0015] (1) Excess monopentaerythritol and C 3～16 The dibasic fatty acid undergoes esterification reaction to obtain esterification product A1;

[0016] (2) The esterification product A1 is reacted with excess C 4～10 The monobasic fatty acids undergo esterification and the products are collected.

[0017] According to the present invention, in step (1), the monopentaerythritol and C 3～16 The molar ratio of the dibasic fatty acid can be (2.05-100):1, preferably (3-60):1, and more preferably (3-30):1; in step (2), the hydroxyl group and C in the esterification product A1 4～10 The molar ratio of the carboxyl groups in the monobasic fatty acid may be 1:(1.05-1.30), preferably 1:(1.10-1.20).

[0018] According to the present invention, the reaction temperature of step (1) is 50-180°C, preferably 80-150°C, and the reaction time is 1-20h, preferably 2-10h; the reaction temperature of step (2) is 50-250°C, preferably 100-220°C, and the reaction time is until no more water is produced, which can generally be 1-20h, or 5-10h.

[0019] According to the present invention, the dibasic fatty acid can be one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid.

[0020] According to the present invention, the monobasic fatty acid is preferably selected from two or more (for example, three or four) of n-butyric acid, isobutyric acid, n-pentanoic acid, isovaleric acid, n-hexanoic acid, isohexanoic acid, n-heptanoic acid, isoheptanoic acid, n-octanoic acid, isooctanoic acid, n-nonanoic acid, isononanoic acid, n-decanoic acid, and isodecanoic acid, and is more preferably selected from two or more (for example, three or four) of n-butyric acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. Further preferably, the monobasic fatty acid may include 0-10.0 mol% of n-butyric acid, 0-35.0 mol% of n-pentanoic acid, 30.0 mol%-75.0 mol% of n-hexanoic acid, 5.0 mol%-45.0 mol% of n-heptanoic acid, 0-30.0 mol% of n-octanoic acid, 0-15.0 mol% of n-nonanoic acid, and 0-10.0 mol% of n-decanoic acid.

[0021] According to the present invention, a catalyst may be added to the esterification reaction of step (1) and / or step (2), and the catalyst includes one or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, zinc oxide, cation exchange resin, ionic liquid, stannous oxide, titanate and activated carbon. The amount of the catalyst added may comply with the amount used in the esterification reaction in the prior art and is not particularly limited. The catalyst may be removed by methods known in the art such as alkali washing, water washing and filtering after the esterification reaction is completed and is not particularly limited.

[0022] According to the present invention, a solvent may be added to the esterification reaction of step (1) and / or step (2), and the solvent may be one or more of xylene, toluene, and cyclohexane. The amount of the solvent added may comply with the amount used in the esterification reaction in the prior art, and is not particularly limited. The solvent may be removed by a method known in the art such as distillation after the esterification reaction is completed, and is not particularly limited.

[0023] According to the present invention, the esterification reaction in step (1) and / or step (2) can be carried out under nitrogen protection.

[0024] According to the present invention, preferably, in step (2), the esterification product A1 is reacted with an excess of C 4～10 The product of the esterification reaction of the monobasic fatty acid is purified, and the purification method includes one or more of reduced pressure distillation, alkali washing, water washing, dehydration, decolorization, and filtering. After the purification treatment, a mixture of pentaerythritol esters as shown in formula (I) and pentaerythritol esters as shown in formula (II) with higher purity can be obtained.

[0025] The pentaerythritol ester of the present invention is suitable for use as a base oil or additive in a lubricating oil composition.

[0026] The pentaerythritol ester synthesized by the present invention has a high viscosity index (>130), a low pour point (<-60°C), a relatively low kinematic viscosity at -40°C (<10000mm 2 / s) and good high temperature oxidation stability, which can meet the use requirements of MIL-PRF-23699G aviation turbine engine lubricating oil.

[0027] The present invention also proposes a lubricating oil composition, comprising an antioxidant, an extreme pressure anti-wear agent, a rust inhibitor and the aforementioned pentaerythritol ester, wherein the antioxidant accounts for 0.5% to 10% of the lubricating oil composition, the extreme pressure anti-wear agent accounts for 0.1% to 5% of the lubricating oil composition, the rust inhibitor accounts for 0.01% to 1% of the lubricating oil composition, and the pentaerythritol ester accounts for 85% to 98% of the lubricating oil composition.

[0028] According to the present invention, the antioxidant can be selected from one or more of phenyl-α-naphthylamine, alkylated diphenylamine, alkylated phenyl-α-naphthylamine, and aromatic amine oligomers, for example, the trade names that can be selected include T531, Vanderbilt V81, T534, BASF L06, Vanderbilt 9317, etc.; the extreme pressure anti-wear agent can be selected from phosphate esters and phosphate amine salts, for example, the trade names that can be selected include TCP, BASF 349, AW6110, etc.; the rust inhibitor can be selected from benzotriazole derivatives, for example, 5-methylbenzotriazole, T551, etc.

[0029] The lubricating oil composition of the present invention has excellent high temperature oxidation resistance, corrosion resistance and anti-deposit formation ability, and its performance is better than that of commercially available 5mm 2 / s polyol ester base oil products can meet the use requirements of MIL-PRF-23699G aviation turbine engine lubricants and can significantly improve the high-temperature oxidation resistance of aviation engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the infrared spectrum of monopentaerythritol raw material.

[0031] Figure 2 This is the infrared spectrum of the pentaerythritol ester product obtained in Example 1.

[0032] Figure 3 This is the Fourier transform ion cyclotron resonance spectrum of the pentaerythritol ester product prepared in Example 1. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below by examples, but the present invention is not limited thereto.

[0034] The present invention relates to the monopentaerythritol, C 4～10 Monobasic fatty acids, C 3～16 The source of the dibasic fatty acid is not particularly limited, and any commercially available product or homemade product of the above raw materials known to those skilled in the art may be used.

[0035] The comparison base oils and raw materials used are as follows:

[0036] Mixed pentaerythritol ester MIXPE1, commercially available, Zhejiang Quzhou Chemical Co., Ltd., kinematic viscosity at 100℃ 5.02mm 2 / s

[0037] Mixed pentaerythritol ester HPC-51 is a mixture of monopentaerythritol and dipentaerythritol with excess C 5～10 The esterification product of saturated monobasic fatty acid has a kinematic viscosity of 4.85 mm at 100°C. 2 / s, and the synthesis method is as follows: in a 1L four-necked flask equipped with a stirring rod, a thermometer, a condenser and a water separator, 80g of monopentaerythritol, 20g of dipentaerythritol, 150g of n-pentanoic acid, 30g of n-hexanoic acid, 80g of n-heptanoic acid, 40g of n-octanoic acid, 40g of 3,5,5-trimethylhexanoic acid and 5g of tetrabutyl titanate catalyst are added; under nitrogen protection, the reaction temperature is heated to 100°C, and then the temperature is raised to 220°C at a rate of 10°C / h, and the reaction is carried out until no water is produced to obtain a crude esterification product, which is cooled to room temperature, and subjected to reduced pressure distillation, alkali washing, water washing, dehydration, decolorization and filtration to obtain a pentaerythritol mixed ester.

[0038] Monopentaerythritol PEMX5 is a monopentaerythritol ester with excess C 5～10 The esterification product of saturated monobasic fatty acid has a kinematic viscosity of 4.75 mm at 100 °C. 2 / s, and the synthesis method is as follows: in a 1L four-necked flask equipped with a stirring rod, a thermometer, a condenser and a water separator, 100g of monopentaerythritol, 100g of n-pentanoic acid, 60g of n-hexanoic acid, 180g of n-heptanoic acid, 40g of n-octanoic acid, 10g of n-nonanoic acid, 50g of 3,5,5-trimethylhexanoic acid and 10g of tetrabutyl titanate catalyst are added; under nitrogen protection, the reaction temperature is heated to 150°C, and then the temperature is raised to 220°C at a rate of 10°C / h, and the reaction is carried out until no water is produced to obtain a crude esterification product, which is cooled to room temperature, and subjected to reduced pressure distillation, alkali washing, water washing, dehydration, decolorization and filtration to obtain monopentaerythritol ester.

[0039] Antioxidant Vanderbilt V81, 4,4'-diisooctyl-diphenylamine, Vanderbilt Corporation, USA

[0040] Rust inhibitor 5-methylbenzotriazole, Shanghai Chemical Plant, chemically pure

[0041] Extreme pressure anti-wear agent Tritolyl phosphate TCP, Zibo Huihua Chemical Co., Ltd.

[0042] Example 1

[0043] In a 1L four-necked flask equipped with a stirring rod, a thermometer, a condenser and a water separator, 50.0g of monopentaerythritol (0.367mol), 4.3g of adipic acid (0.027mol), 80ml of xylene and 1.5g of tetrabutyl titanate catalyst were added, and the mixture was reacted at 150°C for 4h under nitrogen protection to obtain an esterification product A1, and the mixture was cooled to room temperature; then 36.0g of n-pentanoic acid, 110.0g of n-hexanoic acid, 58.0g of n-heptanoic acid and 2.0g of tetrabutyl titanate catalyst were added, and the reaction temperature was heated to 150°C under nitrogen protection, and then the temperature was raised to 220°C at a rate of 10°C / h, and the mixture was reacted until no water was produced to obtain an esterification crude product B1, which was cooled to room temperature, and the pentaerythritol ester of the present invention was obtained after vacuum distillation, alkali washing, water washing, dehydration, decolorization and filtration.

[0044] The monopentaerythritol raw material and the pentaerythritol ester product prepared in Example 1 were respectively subjected to infrared spectroscopy tests. The infrared spectrum of the monopentaerythritol raw material was shown in FIG. Figure 1 The infrared spectrum of the pentaerythritol ester product obtained in Example 1 is shown in Figure 2 By comparison, in the infrared spectrum of monopentaerythritol, 3200-3400cm -1 is the absorption peak of the alcoholic hydroxyl group in monopentaerythritol; there is no 3200-3400cm in the infrared spectrum of the pentaerythritol ester product obtained in Example 1. -1 The absorption peaks include 1744cm -1It is the stretching vibration peak of the C=O bond in the pentaerythritol ester product obtained in Example 1, indicating that the excess monobasic fatty acid in step (2) causes the excess monopentaerythritol in step (1) to react completely, and there is no alcoholic hydroxyl group in the product.

[0045] Example 2

[0046] In a 1L four-necked flask equipped with a stirring rod, a thermometer, a condenser and a water separator, 50.0g of monopentaerythritol (0.367mol), 2.2g of adipic acid (0.015mol), 80ml of xylene and 1.5g of tetrabutyl titanate catalyst were added, and the mixture was reacted at 150°C for 3h under nitrogen protection to obtain an esterification product A1, and then cooled to room temperature; then 5.0g of n-butyric acid, 28.5g of n-pentanoic acid, 82.0g of n-hexanoic acid, 92.0g of n-heptanoic acid and 2.0g of p-toluenesulfonic acid catalyst were added, and the reaction temperature was heated to 150°C under nitrogen protection, and then the temperature was raised to 220°C by a program of 10°C / h, and the reaction was carried out until no water was produced to obtain an esterification crude product B1, which was cooled to room temperature, and the pentaerythritol ester of the present invention was obtained after vacuum distillation, alkali washing, water washing, dehydration, decolorization and filtration.

[0047] Example 3

[0048] In a 1L four-necked flask equipped with a stirring rod, a thermometer, a condenser and a water separator, 50.0g of monopentaerythritol (0.367mol), 8.6g of adipic acid (0.06mol), 100ml of xylene and 2.0g of p-toluenesulfonic acid catalyst were added, and the mixture was reacted at 150°C for 7h under nitrogen protection to obtain an esterification product A1, and then cooled to room temperature; then 56.0g of n-pentanoic acid, 92.0g of n-hexanoic acid, 23.0g of n-heptanoic acid, 25.5g of n-octanoic acid and 2.0g of p-toluenesulfonic acid catalyst were added, and the reaction temperature was heated to 150°C under nitrogen protection, and then the temperature was raised to 220°C by a program of 10°C / h, and the reaction was carried out until no water was produced to obtain an esterification crude product B1, which was cooled to room temperature, and the pentaerythritol ester of the present invention was obtained after vacuum distillation, alkali washing, water washing, dehydration, decolorization and filtration.

[0049] Example 4

[0050] In a 1L four-necked flask provided with a stirring rod, a thermometer, a condenser and a water separator, 50.0g of monopentaerythritol (0.367mol), 7.6g of malonic acid (0.073mol), 4.0g of suberic acid (0.023mol), 100ml of xylene and 1.5g of tetrabutyl titanate catalyst were added, and the mixture was reacted at 150°C for 7h under nitrogen protection to obtain an esterification product A1, and then cooled to room temperature; then 36.0g of n-pentanoic acid, 98.5g of n-hexanoic acid, 46.0g of n-heptanoic acid, 12.7g of n-octanoic acid and 2.0g of tetrabutyl titanate catalyst were added, and the reaction temperature was heated to 150°C under nitrogen protection, and then the temperature was raised to 220°C by a program of 10°C / h, and the reaction was carried out until no water was produced to obtain an esterification crude product B1, which was cooled to room temperature, and the pentaerythritol ester of the present invention was obtained after vacuum distillation, alkali washing, water washing, dehydration, decolorization and filtration.

[0051] Mixed pentaerythritol esters MIXPE1, HPC-51 and monopentaerythritol ester PEMX5 were used as comparative examples 1 to 3, respectively.

[0052] The physical and chemical properties of the pentaerythritol esters of Examples 1-4 and Comparative Examples 1-3 were evaluated. The results are shown in Table 1.

[0053] The pentaerythritol ester prepared in Example 1 was subjected to Fourier transform ion cyclotron resonance test using an electrospray ionization source (ESI+) in positive ion mode. The test conditions were: ion transmission capillary temperature of 350°C, spray voltage of 2.8KV, m / z scanning range of 100-1500, and mass resolution of 70000. The measured spectrum is shown in Figure 3 .from Figure 3 It can be seen that C 26 H 46 O8~C 36 H 36 O8 represents the ester formed by monopentaerythritol and monobasic fatty acid (hereinafter referred to as monobasic acid ester), C 51 H 88 O 16 ~C 59 H 104 O 16 With C 73 H 124 O 24 ~C 79 H 136 O 24 It represents the ester formed by the esterification product of adipic acid and monopentaerythritol and then reacting with a monobasic fatty acid (hereinafter abbreviated as dibasic acid ester).

[0054] The content distribution of the pentaerythritol esters prepared in Examples 1 to 4 and the pentaerythritol esters in Comparative Examples 1 to 3 was determined according to the method for determining the boiling range distribution of petroleum fractions (NB / SH / T 0829), that is, the content of the monoacid ester and the diacid ester in Examples 1 to 4 or the content of the monopentaerythritol ester and the dipentaerythritol ester in Comparative Examples 1 to 3 was determined. The determination results are shown in Table 1. For example, the determination results of the product of Example 1 show that the content of the ester (i.e., the monoacid ester) generated by the reaction of the esterification product of adipic acid and monopentaerythritol with the monoacid is 88.2% (the boiling range is 350 to 500°C), and the content of the ester (i.e., the diacid ester) generated by the reaction of the esterification product of adipic acid and monopentaerythritol with the monoacid is 11.8% (the boiling range is > 500°C).

[0055] Table 1 Physical and chemical indicators of pentaerythritol esters of Examples 1-4 and pentaerythritol esters of Comparative Examples 1-3

[0056]

[0057] As can be seen from Table 1, compared with the comparative pentaerythritol esters MIXPE1, HPC-51 and PEMX5, the pentaerythritol ester synthesized in the present invention has a lower pour point (≤-66°C) and a higher viscosity index (≥135), indicating that the pentaerythritol ester base oil synthesized in the present invention has better low-temperature fluidity and viscosity-temperature properties.

[0058] Lubricating oil compositions 1 to 4 and comparative lubricating oil compositions 1 to 3 were prepared according to the formulations in Table 2 to evaluate the anti-oxidation and anti-corrosion properties of the lubricating oil compositions prepared from the pentaerythritol ester of the present invention and other additives.

[0059] Table 2 Formula composition of lubricating oil compositions 1 to 4 and comparative lubricating oil compositions 1 to 3

[0060]

[0061] The lubricating oil compositions 1 to 4 and the comparative lubricating oil compositions 1 to 3 were subjected to oxidation induction period determination, 218°C corrosion and oxidation stability assessment tests, respectively. The test comparison results are shown in Table 3. The oxidation induction period was determined by Pressure Differential Scanning Calorimetry (PDSC), and the test method standard was SH / T0719-2002 Lubricating Oil Oxidation Induction Period Determination Method (Pressure Differential Scanning Calorimetry). The test method used in the corrosion and oxidation stability assessment test was the method FED STD-791-5308 specified by MIL-PRF-23699G, and the experimental conditions were: dry air was introduced at a constant temperature of 218°C for oxidation for 72 hours, the oxygen flow rate was 50 to 83 mL / min, and the metal test pieces were steel, silver, titanium, aluminum, and titanium of specific specifications. The evaluation index was the change in the total acid value of the lubricating oil before and after oxidation (△TAN / mgKOH·g -1 )、40℃ kinematic viscosity change rate (△Viscosity%)、100mL oil deposit formation amount (Deposit / mg·(100mL) -1 ) and the mass change per unit area of ​​metal test pieces such as metal steel, silver, aluminum, titanium, etc. The present invention uses the mass change data of the steel sheet to evaluate the experimental results.

[0062] It can be seen from Table 3 that the pentaerythritol ester synthesized in the present invention has better corrosion resistance, high temperature oxidation stability and anti-deposit formation ability, and its performance is better than that of the commercially available 5mm 2 / s polyol ester base oil products can meet the use requirements of MIL-PRF-23699G aviation turbine engine lubricants.

[0063] Table 3 Oxidation induction period and 218℃ corrosion and oxidation stability test results

[0064]

Claims

1. Pentaerythritol ester, comprising, by mass, 5.0% to 50% of a pentaerythritol ester of formula (I) and 50% to 95% of a pentaerythritol ester of formula (II): The R group is C1~C 14 Each R' group is independently selected from a C3 to C9 straight chain or branched chain alkyl group.

2. The pentaerythritol ester according to claim 1, characterized in that The R group is a straight chain or branched alkylene group of C2 to C8; each R' group is selected from two or more of a straight chain or branched alkyl group of C3, a straight chain or branched alkyl group of C4, a straight chain or branched alkyl group of C5, a straight chain or branched alkyl group of C6, a straight chain or branched alkyl group of C7, a straight chain or branched alkyl group of C8, and a straight chain or branched alkyl group of C9.

3. The pentaerythritol ester according to claim 1, characterized in that The pentaerythritol ester comprises, by mass, 5.0% to 25% of the pentaerythritol ester represented by formula (I) and 75% to 95% of the pentaerythritol ester represented by formula (II).

4. The preparation method of pentaerythritol ester comprises the following steps: (1) Excess monopentaerythritol and C 3～16 The dibasic fatty acid undergoes esterification reaction to obtain esterification product A1; (2) The esterification product A1 is reacted with excess C 4～10 The monobasic fatty acids undergo esterification and the products are collected.

5. The preparation method according to claim 4, characterized in that: In step (1), the monopentaerythritol and C 3～16 The molar ratio of the dibasic fatty acid is (2.05-100):1; in step (2), the hydroxyl group and C in the esterification product A1 4～10 The molar ratio of the carboxyl group in the monobasic fatty acid is 1: (1.05～1.30)。 6. The preparation method according to claim 4, characterized in that: The reaction temperature of step (1) is 50-180° C., and the reaction time is 1-20 hours; the reaction temperature of step (2) is 50-250° C., and the reaction time is until no more water is produced.

7. The preparation method according to claim 4, characterized in that: The dibasic fatty acid is one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid; the monobasic fatty acid is selected from two or more of n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, n-hexanoic acid, isohexanoic acid, n-heptanoic acid, isoheptanoic acid, n-octanoic acid, isooctanoic acid, n-nonanoic acid, isononanoic acid, n-decanoic acid, and isodecanoic acid.

8. The preparation method according to claim 4, characterized in that: Adding a catalyst to the esterification reaction of step (1) and / or step (2), wherein the catalyst is selected from one or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, zinc oxide, cation exchange resin, ionic liquid, stannous oxide, titanate and activated carbon; and / or, The esterification reaction in step (1) and / or step (2) is carried out under nitrogen protection.

9. Use of the pentaerythritol ester according to any one of claims 1 to 3 or the pentaerythritol ester prepared by the preparation method according to any one of claims 4 to 8 as a base oil or additive in a lubricating oil composition.

10. A lubricating oil composition comprising an antioxidant, an extreme pressure anti-wear agent, a rust inhibitor, and the pentaerythritol ester according to any one of claims 1 to 3 or the pentaerythritol ester prepared according to the preparation method of any one of claims 4 to 8, wherein the antioxidant accounts for 0.5% to 10% of the lubricating oil composition, the extreme pressure anti-wear agent accounts for 0.1% to 5% of the lubricating oil composition, the rust inhibitor accounts for 0.01% to 1% of the lubricating oil composition, and the pentaerythritol ester accounts for 85% to 98% of the lubricating oil composition.

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