Pentaerythritol esters and process for their preparation
The preparation of pentaerythritol esters via a two-step method combined with a metal catalyst solves the problems of low hydroxyl value and insufficient high-temperature stability in existing technologies, providing a high-performance lubricant for high-temperature environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-18
- Publication Date
- 2026-06-19
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lubricating oils, and more specifically to a pentaerythritol ester and its preparation method. Background Technology
[0002] Pentaerythritol esters are high-performance base oils for synthetic ester lubricants, exhibiting excellent high-temperature stability, low-temperature fluidity, and good lubricity. They are widely used in demanding fields such as aviation, aerospace, and automotive. However, with industrial and technological advancements, the demand for high-performance lubricants is constantly increasing, especially in high-temperature environments where conventional synthetic ester lubricants often fall short. Therefore, developing a pentaerythritol ester base oil with high-temperature stability has significant practical value. In existing technologies, the preparation methods for pentaerythritol esters mainly include esterification reactions and post-treatment processes. The commonly used esterification reaction involves the reaction of pentaerythritol with fatty acids or their derivatives under the action of a catalyst to generate ester products.
[0003] Most existing esterification methods cannot directly obtain pentaerythritol esters with low hydroxyl values. They often require long-term esterification (about 5 hours) combined with ultra-high temperature (>220℃) or post-processing, such as adsorption or distillation, to ensure that the hydroxyl value meets the requirements. This not only increases the product cost but also reduces the conversion rate and performance of the target product. Summary of the Invention
[0004] The purpose of this invention is to overcome the problems of existing pentaerythritol esters, such as insufficient high-temperature stability and difficulty in directly obtaining pentaerythritol esters with low hydroxyl values, and to provide a pentaerythritol ester and its preparation method. The pentaerythritol ester prepared using the method provided by this invention requires no post-processing, has high purity, a hydroxyl value not exceeding 0.2 mg KOH / g, good high-temperature stability, and excellent antioxidant properties.
[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing pentaerythritol ester, wherein the method comprises: carrying out a first reaction of pentaerythritol and a first fatty acid in the presence of a first catalyst, and then adding a second fatty acid in the presence of a second catalyst to carry out a second reaction to obtain pentaerythritol ester, wherein the first fatty acid and the second fatty acid each have ≤9 carbon atoms independently, and the second catalyst is a metal catalyst.
[0006] A second aspect of the present invention provides a pentaerythritol ester, wherein the pentaerythritol ester is prepared by the preparation method described in the first aspect of the present invention.
[0007] This invention employs a two-step method to prepare pentaerythritol esters. In the first step, pentaerythritol reacts with a first fatty acid to obtain an esterification product. Then, under the action of a metal catalyst, the esterification product is reacted with a second fatty acid to obtain pentaerythritol esters. By combining the two-step method with a metal catalyst, pentaerythritol esters with a hydroxyl value not exceeding 0.2 mg KOH / g can be directly obtained without the need for post-processing. Tested using the SH / T0192 method, after 10 hours of oxidative corrosion at 150°C, the steel sheet showed no corrosion, the viscosity increase was less than or equal to 40%, the acid value increase was less than 3 mg KOH / g, and the high-temperature stability and antioxidant properties were excellent. Detailed Implementation
[0008] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0009] The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as “first” or “second” may explicitly or implicitly include one or more of that feature.
[0010] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0011] The first aspect of the present invention provides a method for preparing pentaerythritol ester, wherein the method comprises: reacting pentaerythritol and a first fatty acid in the presence of a first catalyst, and then adding a second fatty acid in the presence of a second catalyst to conduct a second reaction to obtain pentaerythritol ester, wherein the first fatty acid and the second fatty acid each have ≤9 carbon atoms, and the second catalyst is a metal catalyst.
[0012] This invention employs a two-step method to prepare pentaerythritol esters. In the first step, pentaerythritol reacts with a first fatty acid to obtain an esterification product. Then, under the action of a metal catalyst, the esterification product is reacted with a second fatty acid to obtain pentaerythritol esters. By combining the two-step method with a metal catalyst, pentaerythritol esters with a hydroxyl value not exceeding 0.2 mg KOH / g can be directly obtained without the need for post-processing. Tested using the SH / T0192 method, after 10 hours of oxidative corrosion at 150°C, the steel sheet showed no corrosion, the viscosity increase was less than or equal to 40%, the acid value increase was less than 3 mg KOH / g, and the high-temperature stability and antioxidant properties were excellent.
[0013] The number of carbon atoms in the primary and secondary fatty acids can be arbitrarily selected from 1, 2, 3, 4, 5, 6, 7, 8, and 9, depending on the need.
[0014] In some embodiments, preferably, the pentaerythritol includes monopentaerythritol, dipentaerythritol, and tripentaerythritol.
[0015] In some embodiments, preferably, the first fatty acid and the second fatty acid are each independently a monobasic fatty acid having 5-9 carbon atoms.
[0016] In some embodiments, preferably, the first fatty acid includes valeric acid, hexanoic acid, heptanoic acid, and caprylic acid.
[0017] In some embodiments, preferably, the second fatty acid includes isooctanoic acid and nonanoic acid.
[0018] The choice of raw materials has a significant impact on the high-temperature stability of the obtained esters. This invention, through its unique alcohol-acid composition structure, can further improve the high-temperature stability and antioxidant properties of the obtained pentaerythritol esters.
[0019] In some embodiments, preferably, the molar ratio of the total amount of the first fatty acid and the second fatty acid to the pentaerythritol is 5.2-6:1. The total amount of all fatty acids and the molar ratio of pentaerythritol affect the antioxidant properties and low-temperature stability of the obtained pentaerythritol ester. The molar ratio of the total amount of fatty acids and pentaerythritol selected in this invention is beneficial for further improving the antioxidant properties and low-temperature stability of the obtained pentaerythritol ester. Specifically, the molar ratio of the total amount of the first fatty acid and the second fatty acid to pentaerythritol can be any value between any two of the following: 5.2:1, 5.4:1, 5.6:1, 5.8:1, 5.9:1, and 6:1.
[0020] In some embodiments, preferably, based on the total amount of the first fatty acid and the second fatty acid, the amount of the first fatty acid is 70-85 wt%, and the amount of the second fatty acid is 15-30 wt%. The proportion of fatty acid feed in the two-step reaction affects the antioxidant properties and low-temperature stability of the obtained pentaerythritol ester. The proportion of fatty acid feed selected in this invention is beneficial to further improve the above-mentioned properties of the obtained pentaerythritol ester. Specifically, based on the total amount of the first fatty acid and the second fatty acid, the amount of the first fatty acid is any value between any two of the following: 70 wt%, 72 wt%, 75 wt%, 77 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 85%. The amount of the second fatty acid can be any value between any two of the following: 15 wt%, 16 wt%, 17 wt%, 20 wt%, 22 wt%, 24 wt%, 25 wt%, 27 wt%, 30 wt%.
[0021] In some embodiments, preferably, the temperature of the first reaction is 140-190°C, and the reaction time is 5-7 hours. The temperature and time of the first reaction affect the overall properties of the obtained pentaerythritol ester, including antioxidant properties, low-temperature stability, yield, and hydroxyl value. The reaction temperature and time selected in this invention are beneficial to further improve the above properties. The temperature of the first reaction can be any value between any two of 140°C, 150°C, 160°C, 170°C, 180°C, and 190°C; the reaction time can be any value between any two of 5 hours, 5.5 hours, 6 hours, 6.5 hours, and 7 hours.
[0022] In some embodiments, preferably, the temperature of the second reaction is 210-230°C, and the reaction time is 0.5-1.5 h. In this invention, by optimizing the preparation method and catalyst, the reaction time at higher temperatures is significantly shortened. Shortening the reaction time at higher temperatures helps reduce the occurrence of side reactions and reverse reactions. The temperature of the second reaction can be any value between any two of 210°C, 215°C, 220°C, 225°C, and 230°C; the reaction time can be any value between any two of 0.5 h, 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, and 1.5 h.
[0023] In some embodiments, preferably, the temperature of the second reaction is 220-230°C and the reaction time is 1 hour. The high-temperature stage of the present invention can be shortened to as little as 1 hour, which helps to reduce the occurrence of side reactions and reverse reactions, further improves the yield of the target product, and saves costs.
[0024] In some embodiments, preferably, the first catalyst is sodium bisulfate.
[0025] In some embodiments, the metal catalyst preferably includes titanate catalysts and / or tin-based catalysts.
[0026] In some embodiments, preferably, the titanate catalyst includes tetrabutyl titanate, and the tin catalyst includes stannous oxalate.
[0027] In some embodiments, preferably, the amount of the first catalyst is 0.1-0.2 wt% based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid. Based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid, the amount of the first catalyst can be any value between any two of 0.1 wt%, 0.15 wt%, and 0.2 wt%.
[0028] In some embodiments, preferably, the amount of the second catalyst is 0.05-0.2 wt% based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid. Based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid, the amount of the second catalyst can be any value between any two of the following: 0.05 wt%, 0.1 wt%, 0.15 wt%, and 0.2 wt%.
[0029] In some embodiments, preferably, the first reaction is carried out at atmospheric pressure in a nitrogen atmosphere.
[0030] In some embodiments, preferably, the second reaction is carried out at atmospheric pressure in a nitrogen atmosphere.
[0031] The method provided by this invention does not require additional pressure, and the nitrogen atmosphere helps to reduce the occurrence of oxidation side reactions. At the same time, it can also remove the generated water, thereby increasing the reaction rate and yield.
[0032] A second aspect of the present invention provides a pentaerythritol ester, wherein the pentaerythritol ester is prepared by the preparation method described in the first aspect of the present invention.
[0033] The pentaerythritol ester obtained by this invention has a hydroxyl value ≤ 0.2 mg KOH / g. The hydroxyl value reflects the purity of the product; a low hydroxyl value indicates high product purity. The pentaerythritol ester obtained by this invention has a hydroxyl value not exceeding 0.2 mg KOH / g, 0.1 mg KOH / g, 0.05 mg KOH / g, 0.02 mg KOH / g, and may even be less than 0.01 mg KOH / g.
[0034] In some embodiments, preferably, the acid value of the pentaerythritol ester does not exceed 0.1 mg KOH / g.
[0035] In some embodiments, preferably, the pentaerythritol ester has a kinematic viscosity of 20-25 mmHg at 40°C.2 / s.
[0036] In some embodiments, preferably, after the pentaerythritol ester is oxidized and corroded at 150°C for 10 h according to the SH / T0192 method, the increase in kinematic viscosity is ≤40%, and the increase in acid value is ≤3 mg KOH / g. No corrosion was observed in the steel sheets after the oxidation operation, fully demonstrating that the pentaerythritol ester prepared by this invention has excellent oxidation resistance and high-temperature stability. Furthermore, the kinematic viscosity of the pentaerythritol ester prepared by this invention at -40°C is 10000-11000 mmHg. 2 After a 72-hour low-temperature stability test, the change rate of its kinematic viscosity does not exceed 3%, and in particular, it does not exceed 1.8%, indicating that the pentaerythritol ester provided by the present invention also unexpectedly has excellent low-temperature performance.
[0037] This invention employs a two-step method to prepare pentaerythritol esters. In the first step, pentaerythritol reacts with a first fatty acid to obtain an esterification product. Then, under the action of a metal catalyst, the esterification product reacts with a second fatty acid to obtain pentaerythritol esters. By combining this two-step method with a metal catalyst, pentaerythritol esters with a hydroxyl value not exceeding 0.2 mg KOH / g can be directly obtained without subsequent processing. The product exhibits good stability and a yield of not less than 92%, making it suitable for industrial production. Furthermore, the preparation method provided by this invention significantly shortens the reaction time at higher temperatures, resulting in pentaerythritol esters with high purity and excellent high-temperature performance. It is particularly suitable for the lubrication of equipment such as supercritical gas turbines and aero engines that require long-term high-temperature operation.
[0038] In addition, the pentaerythritol esters prepared by the method provided in this invention exhibit excellent stability between different batches.
[0039] According to a particularly preferred embodiment of the present invention, the preparation method includes: carrying out a first reaction of pentaerythritol and a first fatty acid in the presence of a first catalyst, and then adding a second fatty acid in the presence of a second catalyst to carry out a second reaction to obtain pentaerythritol ester, wherein the first fatty acid and the second fatty acid each have ≤9 carbon atoms, and the second catalyst is a metal catalyst; The molar ratio of the total amount of the first fatty acid and the second fatty acid to the pentaerythritol is 5.3-5.5:1, and the pentaerythritol includes monopentaerythritol, dipentaerythritol and tripentaerythritol. Based on the total amount of the first fatty acid and the second fatty acid, the first fatty acid is 75-80 wt%, the second fatty acid is 20-25 wt%, the first fatty acid includes valeric acid, hexanoic acid, heptanoic acid and octanoic acid, and the mass ratio of the four is 0.29-0.3:0.04-0.06:0.26-0.28:0.14-0.15, the second fatty acid includes isooctanoic acid and nonanoic acid, and the mass ratio of the two is 0.08-0.09:0.14-0.15, the first catalyst is sodium bisulfate, and the second catalyst is tetrabutyl titanate; The temperature of the first reaction is 170-190℃ and the reaction time is 5-7h, while the temperature of the second reaction is 220-230℃ and the reaction time is 1h.
[0040] The present invention will be described in detail below through embodiments.
[0041] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available.
[0042] In the following examples, the acid value was tested using the GB / T 7304 method; the kinematic viscosity was tested using the GB / T 265 method; the oxidation corrosion test was conducted using the SH / T 0192 method, with test conditions of 150℃ for 10 hours. The measured performance included changes in kinematic viscosity, acid value, and steel sheet mass; the low-temperature performance was tested using the GJB1264 method (-40℃, 72 hours); and the hydroxyl value was determined using the acetylation method at room temperature. For specific procedures, please refer to "Discussion on Factors Affecting the Determination of Hydroxyl Value of Polyol Esters" (Zhang Qin, Synthetic Lubricating Materials, April 2014).
[0043] The yield calculation formula is as follows: Yield =
[0044] Example 1 Weigh out 250 g (1.836 mol) of monopentaerythritol, 90 g (0.354 mol) of dipentaerythritol, 50 g (0.134 mol) of tripentaerythritol, and 1584 g (12.65 mol) of fatty acids (the molar ratio of pentaerythritol to fatty acids is 1:5.44). The fatty acids include 1221 g of primary fatty acids (accounting for 77.08 wt% of total fatty acids) and 363 g of secondary fatty acids (accounting for 22.92 wt% of total fatty acids). The primary fatty acids include valeric acid, hexanoic acid, heptanoic acid, and octanoic acid, with a mass ratio of 0.295:0.050:0.278:0.148. The secondary fatty acids include isooctanoic acid and nonanoic acid, with a mass ratio of 0.083:0.147.
[0045] Pentaerythritol and the primary fatty acid were reacted at 170°C for 6 h under normal pressure and nitrogen protection in the presence of 2.96 g sodium bisulfate (0.15 wt% of the total amount of pentaerythritol and fatty acid) to obtain the esterified product. Then, the temperature was lowered to 150°C, and a second fatty acid was added to the esterification product in the presence of 2.96 g tetrabutyl titanate (0.15 wt% of the total amount of pentaerythritol and fatty acids). The reaction was carried out at 220°C for 1.0 h under normal pressure and nitrogen protection. Finally, the unreacted fatty acids were removed by distillation under reduced pressure (pressure -0.096 MPa) at 200°C for 1 h to obtain pentaerythritol ester.
[0046] Example 2 and Example 3 Following the method of Example 1, the products prepared using the same methods in Examples 1, 2, and 3 were subjected to performance tests to verify the stability of different batches of products.
[0047] Example 4 Weigh out 250 g (1.836 mol) pentaerythritol, 90 g (0.354 mol) dipentaerythritol, and 50 g (0.134 mol) tripentaerythritol, and 1708.84 g (14.05 mol) fatty acids (molar ratio of the two is 1:6). The fatty acids include 1442.26 g of primary fatty acid (accounting for 84.4 wt% of the total fatty acids) and 266.58 g of secondary fatty acid (accounting for 15.6 wt% of the total fatty acids). The primary fatty acids include valeric acid, hexanoic acid, heptanoic acid, and octanoic acid, with a mass ratio of 0.37:0.047:0.27:0.15. The secondary fatty acids include isooctanoic acid and nonanoic acid, with a mass ratio of 0.058:0.098.
[0048] Pentaerythritol and the primary fatty acid were reacted at 140°C for 7 h under normal pressure and nitrogen protection in the presence of 3.14 g sodium bisulfate (0.15 wt% of the total amount of pentaerythritol and fatty acid) to obtain the esterified product. Then, the temperature was lowered to 120°C, and a second fatty acid was added to the esterification product. In the presence of 2.09 g tetrabutyl titanate (0.1 wt% of the total amount of pentaerythritol and fatty acids), the reaction was carried out at 210°C for 0.8 h under normal pressure and nitrogen protection. Finally, the unreacted fatty acids were removed by distillation under reduced pressure (pressure -0.096 MPa) at 200°C for 1 h to obtain pentaerythritol ester.
[0049] Example 5 The method of Example 1 is followed, except that the pentaerythritol includes monopentaerythritol and dipentaerythritol, and the molar ratio of pentaerythritol to fatty acid is 6:1.
[0050] Example 6 The method is the same as in Example 1, with the only difference being: Weigh out 390 g (2.324 mol) pentaerythritol and 1601.24 g (11.62 mol) fatty acids (the molar ratio of the two is 1:5).
[0051] Example 7 The method is the same as in Example 1, with the only difference being: Weigh out 390 g (2.324 mol) pentaerythritol and 1745.975 g (14.409 mol) fatty acids (the molar ratio of the two is 1:6.2).
[0052] Example 8 The procedure was carried out as described in Example 1, with the only difference being: 250 g (1.836 mol) of monopentaerythritol, 90 g (0.354 mol) of dipentaerythritol, and 50 g (0.134 mol) of tripentaerythritol, along with 1826 g (14.88 mol) of fatty acids (the molar ratio of pentaerythritol to fatty acids was 1:6.4), comprising 1473.58 g of primary fatty acid (80.7 wt% of total fatty acids) and 352.42 g of secondary fatty acid (19.3 wt% of total fatty acids). The primary fatty acid comprised valerate, hexanoic acid, heptanoic acid, and octanoic acid in a mass ratio of 0.35:0.05:0.27:0.14, and the secondary fatty acid comprised isooctanoic acid and nonanoic acid in a mass ratio of 0.08:0.11.
[0053] Pentaerythritol and the primary fatty acid were reacted at 190°C for 5 h under normal pressure and nitrogen protection in the presence of 3.32 g sodium bisulfate (0.15 wt% of the total amount of pentaerythritol and fatty acid) to obtain the esterified product. Then, the temperature was lowered to 170°C, and a second fatty acid was added to the esterification product. The reaction was carried out at 230°C for 1 h under normal pressure and nitrogen protection in the presence of 3.32 g of stannous oxalate (0.15 wt% of the total amount of pentaerythritol and fatty acids). Finally, the unreacted fatty acids were removed by distillation under reduced pressure (pressure -0.096 MPa) at 200°C for 1 h to obtain pentaerythritol ester.
[0054] Example 9 The procedure was carried out according to Example 1, except that tetrabutyl titanate was replaced with diisopropyl titanate.
[0055] Comparative Example 1 The procedure was carried out according to Example 1, except that tetrabutyl titanate was replaced with sodium bisulfate.
[0056] Comparative Example 2 The method of Example 1 was followed, except that a one-step preparation method was used, as follows: pentaerythritol and fatty acids were reacted at 170°C for 6 h under atmospheric pressure and nitrogen protection in the presence of 2.96 g sodium bisulfate (0.15 wt% of the total amount of pentaerythritol and fatty acids), followed by reaction at 220°C for 1 h under atmospheric pressure and nitrogen protection. Finally, unreacted fatty acids were removed by distillation at 200°C under reduced pressure (pressure -0.096 MPa) for 1 h to obtain pentaerythritol ester.
[0057] Comparative Example 3 Follow the method in Comparison 2, except that sodium bisulfate is replaced with stannous oxalate.
[0058] The yields of pentaerythritol esters prepared in Examples 1-9 and Comparative Examples 1-3 were calculated, and their acid value, kinematic viscosity at 40°C, oxidative corrosion, kinematic viscosity change at -40°C, and hydroxyl value were tested. The results are shown in Table 1.
[0059] Table 1 Test Results
[0060] Table 1 (Continued)
[0061] Table 1 (Continued)
[0062] As can be seen from Examples 1-3, the pentaerythritol ester prepared by the present invention exhibits excellent product performance stability between different batches.
[0063] Compared with Example 1, Example 5 has fewer types of pentaerythritol. The pentaerythritol ester prepared in this way showed an increase in kinematic viscosity and acid value after an oxidation corrosion test at 150°C for 10 hours, which is higher than that of Example 1. This indicates that using a combination of multiple pentaerythritols as raw materials can yield pentaerythritol esters with better performance.
[0064] Compared with Example 1, Examples 6 and 7 differ only in the molar ratio of pentaerythritol and fatty acid. The pentaerythritol esters obtained thus showed increased kinematic viscosity after testing at 150°C for 10 hours and at -40°C for 72 hours, indicating that pentaerythritol esters with better low-temperature and high-temperature performance can be obtained when the molar ratio of fatty acid to pentaerythritol is between 5.2 and 6:1.
[0065] Compared with Example 1, Example 9 differs only in the catalyst used in the second reaction. When diisopropyl titanate is used as the second catalyst, the hydroxyl value of the prepared pentaerythritol ester and the rate of change of kinematic viscosity after low-temperature testing both increase, indicating that using tetrabutyl titanate as the second catalyst can yield pentaerythritol ester with better purity and better low-temperature performance.
[0066] As can be seen from Comparative Examples 1-3, when the second catalyst is replaced with other types of catalysts or when the traditional one-step preparation method is used, the hydroxyl value of the product is large, the product purity is low, and its low-temperature and high-temperature performance is poor.
[0067] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing pentaerythritol ester, characterized in that, The preparation method includes: reacting pentaerythritol and a first fatty acid in the presence of a first catalyst, then adding a second fatty acid in the presence of a second catalyst to carry out a second reaction to obtain pentaerythritol ester, wherein the first fatty acid and the second fatty acid each have ≤9 carbon atoms, and the second catalyst is a metal catalyst.
2. The preparation method according to claim 1, wherein, The pentaerythritol includes monopentaerythritol, dipentaerythritol, and tripentaerythritol; And / or, the first catalyst is sodium bisulfate.
3. The preparation method according to claim 1 or 2, wherein, The first fatty acid and the second fatty acid are each independently a monobasic fatty acid with 5-9 carbon atoms; Preferably, the first fatty acid includes valeric acid, hexanoic acid, heptanoic acid, and octanoic acid; Preferably, the second fatty acid includes isooctanoic acid and nonanoic acid.
4. The preparation method according to any one of claims 1-3, wherein, The total amount of the first fatty acid and the second fatty acid, in molar ratio to the pentaerythritol, is 5.2-6:1; Preferably, based on the total amount of the first fatty acid and the second fatty acid, the amount of the first fatty acid is 70-85 wt%, and the amount of the second fatty acid is 15-30 wt%.
5. The preparation method according to any one of claims 1-4, wherein, The temperature of the first reaction is 140-190℃, and the reaction time is 5-7h.
6. The preparation method according to any one of claims 1-5, wherein, The temperature of the second reaction is 210-230℃, and the reaction time is 0.5-1.5h; Preferably, the temperature of the second reaction is 220-230℃, and the reaction time is 1 hour.
7. The preparation method according to any one of claims 1-6, wherein, The metal catalyst includes titanate catalysts and / or tin-based catalysts; Preferably, the titanate catalyst includes tetrabutyl titanate, and the tin catalyst includes stannous oxalate.
8. The preparation method according to any one of claims 1-7, wherein, Based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid, the amount of the first catalyst is 0.1-0.2 wt%. And / or, based on the total amount of the pentaerythritol, the first fatty acid, and the second fatty acid, the amount of the second catalyst is 0.05-0.2 wt%.
9. The preparation method according to any one of claims 1-8, wherein, The first reaction was carried out at atmospheric pressure in a nitrogen atmosphere; And / or, the second reaction is carried out at atmospheric pressure in a nitrogen atmosphere.
10. A pentaerythritol ester, characterized in that, The pentaerythritol ester is prepared by the preparation method described in any one of claims 1-9.