Aero-engine lubricating oil composition and preparation method thereof

Abstract

The invention discloses an aero-engine lubricating oil composition and a preparation method thereof, and relates to the field of lubricating oil. The composition comprises a composite base oil system, an antioxidant, an anti-wear reagent at extreme pressure, a corrosion inhibitor, an anti-foaming agent and an optional viscosity index improver, the composite base oil system is composed of high-purity pentaerythritol ester, poly-alpha-olefin and dipentaerythritol ester, wherein the high-purity pentaerythritol ester is synthesized by two-step esterification of pentaerythritol, binary fatty acid and monobasic fatty acid; according to the preparation method, a staged fine blending process is adopted, and vacuum dehydration and degassing, nitrogen protection and multi-stage filtration are combined. Through base oil structure innovation, additive purity control, function cooperation and process optimization, the high-temperature oxidation stability, extreme pressure wear resistance, corrosion resistance and rubber compatibility of the lubricating oil are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of lubricating oils, and particularly to an aircraft engine lubricating oil composition and its preparation method. Background Technology

[0002] Aviation turbine engine lubricants must operate under high temperature, high speed, high load, and wide temperature range conditions, requiring excellent high-temperature oxidation stability, extreme pressure anti-wear properties, corrosion resistance, material compatibility, and long-term stability. Current technologies for aviation lubricants often use polyol esters as base oils, compounded with various functional additives. For example, pentaerythritol esters are used as base oils, compounded with various additives to improve thermal stability. However, using traditional pentaerythritol esters as base oil systems fails to address the electrochemical corrosion problems caused by additive impurities (such as chlorine and sulfur), and the one-time mixing process may affect the full utilization of some additive functions. Another example is lubricants compounded with synthetic ester base oils and polyether base oils, with the addition of phosphorus-containing anti-wear extreme pressure agents, benzotriazole derivatives, aniline and aromatic amine dimer antioxidants. While these lubricants achieve high viscosity and excellent viscosity-temperature properties through base oil blending, they do not address the long-term compatibility issues between polyether and ester oils, the potential deposition problems caused by additive decomposition at high temperatures, or the control of key additive impurities to inhibit corrosion. In addition, chlorine and sulfur impurities in commonly used additives such as tricresyl phosphate (TCP) and benzotriazole (T706) are important factors that cause electrochemical corrosion and pitting of metals. Conventional single corrosion inhibitors (such as T706) may exacerbate corrosion at high temperatures due to their own acidity or impurities.

[0003] Therefore, the existing technology has the following shortcomings: the base oil system has limited synergistic improvement on high-temperature oxidation stability and high load-carrying capacity; there is a lack of systematic solutions to corrosion problems caused by additive impurities; and the existing blending process cannot ensure that all additives, especially solid or highly active components, are uniformly and stably dispersed in the system and fully exert their effectiveness.

[0004] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an aero-engine lubricating oil composition and its preparation method. This composition, through an innovatively designed base oil system and a high-purity, synergistic composite additive formulation, combined with a staged refined preparation process, achieves a comprehensive improvement in high-temperature oxidation stability, extreme pressure anti-wear properties, corrosion resistance (especially resistance to electrochemical pitting), rubber compatibility, and long-term storage stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An aircraft engine lubricating oil composition, by weight, comprises the following components: 88-97.5 parts of complex base oil, 1-4 parts of antioxidant, 1-2.5 parts of extreme pressure anti-wear agent, 0.5-1.8 parts of corrosion inhibitor, and 0.002-0.01 parts of antifoaming agent; by weight, the complex base oil comprises the following components: 50-70 parts of pentaerythritol ester base oil, 15-25 parts of polyalphaolefin, and 5-15 parts of dipentaerythritol ester.

[0007] The aforementioned aircraft engine lubricating oil composition, wherein the pentaerythritol ester base oil is formed by esterification of pentaerythritol, dicarboxylic acid and monocarboxylic acid.

[0008] The aforementioned aero-engine lubricating oil composition, wherein the preparation process of the pentaerythritol ester base oil includes the following steps: adding pentaerythritol, dicarboxylic acid, catalyst, and organic solvent to a container, heating the container under a protective gas to carry out the first esterification reaction; cooling the container and adding monocarboxylic acid and catalyst, heating again to carry out the second esterification reaction to obtain a crude product; after the reaction is completed, the crude product is post-treated to obtain a pentaerythritol ester base oil that is a light yellow transparent liquid.

[0009] The aforementioned aero-engine lubricating oil composition, wherein the prepared pentaerythritol ester base oil has a kinematic viscosity of 4.8–5.2 mm at 100°C. 2 / s, viscosity index ≥135, pour point ≤-60℃.

[0010] The aforementioned aircraft engine lubricating oil composition, wherein the dicarboxylic acid is adipic acid, glutaric acid, or pimelic acid; the monocarboxylic acid is a C5-C9 monocarboxylic acid; and the catalyst is tetrabutyl titanate.

[0011] The aforementioned aircraft engine lubricating oil composition, wherein the antioxidant is an oligomer solution of alkylated diphenylamine and N-phenyl-α-naphthylamine; the mass ratio of the alkylated diphenylamine to N-phenyl-α-naphthylamine is (1-2):1.

[0012] The aforementioned aero-engine lubricating oil composition, wherein the extreme pressure anti-wear agent is tricresyl phosphate with an impurity chlorine content of less than 8 µg / g and an ortho-isomer content of less than 0.5%; and the antifoaming agent is a polyacrylate copolymer-based non-silicone antifoaming agent.

[0013] The aforementioned aircraft engine lubricating oil composition, wherein the corrosion inhibitor is composed of 0.3 to 1 part of benzotriazole, 0.1 to 0.5 parts of urea, and 0.1 to 0.3 parts of organoboroate.

[0014] The aforementioned aircraft engine lubricating oil composition further includes 0 to 1 part of a viscosity index improver, wherein the viscosity index improver is polymethyl methacrylate or hydrogenated styrene-diene copolymer.

[0015] A method for preparing an aircraft engine lubricating oil composition includes the following steps: Pretreatment and mixing of composite base oils: Pentaerythritol ester base oil and dipentaerythritol ester are heated, dehydrated and degassed respectively; the two pretreated ester base oils are added into a primary blending tank in proportion, stirred under a protective gas and heated to 80-90°C; polyα-olefins are added during stirring and mixed with ester base oils to form a homogeneous composite base oil. The first stage of additive blending: maintaining the conditions of the primary blending vessel, first add the antioxidant and stir thoroughly; then add the urea from the corrosion inhibitor and stir thoroughly; finally add the organoboroate from the corrosion inhibitor and stir thoroughly; after the addition is complete, continue stirring and reacting at 80-90℃ under a protective gas to form the functionalized base oil phase; The second stage of additive blending: the temperature in the reactor is controlled at 70-80℃, and the vacuum degree is maintained above -0.090MPa; first, benzotriazole in the corrosion inhibitor is added and stirred thoroughly; then, extreme pressure anti-wear agent is added and stirred thoroughly; finally, antifoaming agent and optional viscosity index improver are added and stirred until the oil is completely homogeneous and transparent; after cooling and filtration, the above-mentioned aero-engine lubricating oil composition is obtained.

[0016] Beneficial effects: This invention provides an aero-engine lubricating oil composition and its preparation method. It employs a composite base oil system of high-purity pentaerythritol ester, poly-α-olefin, and dipentaerythritol ester. A specific ester molecular structure is constructed through a two-step esterification synthesis process. Compared to traditional base oil systems, this not only synergistically improves high-temperature oxidation stability and high load-carrying capacity but also optimizes low-temperature fluidity and viscosity-temperature properties, ensuring stable lubrication performance under wide temperature range and high load conditions. This invention reduces the inducing factors of electrochemical corrosion at the source by strictly controlling the impurity content of key additives. Simultaneously, it creatively constructs a composite corrosion inhibition system of high-purity corrosion inhibitor, urea, and organoboroester ester, achieving a synergistic improvement in corrosion resistance and pitting resistance. Furthermore, the combination of composite antioxidants and high-purity extreme pressure anti-wear agents not only enhances the high-temperature oxidation resistance of the lubricating oil and inhibits oil aging and deterioration but also significantly improves extreme pressure load-carrying capacity and anti-wear protection. This invention employs a phased, refined preparation process, combining vacuum dehydration and degassing, nitrogen protection, and stepwise feeding and stirring to ensure that various additives are uniformly and stably dispersed in the base oil, fully leveraging the functional efficacy of each component, and avoiding problems such as uneven additive dispersion and functional interference caused by traditional one-time mixing processes. Detailed Implementation

[0017] This invention provides an aircraft engine lubricating oil composition and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0018] This invention provides an aircraft engine lubricating oil composition, which, by weight, comprises the following components: 88-97.5 parts of composite base oil, 1-4 parts of antioxidant, 1-2.5 parts of extreme pressure anti-wear agent, 0.5-1.8 parts of corrosion inhibitor, 0.002-0.01 parts of antifoaming agent, and 0-1 parts of viscosity index improver.

[0019] Specifically, the composite base oil provided by this invention is composed of the following three base oils: (1) High-purity pentaerythritol ester base oil: accounting for 50-70 parts of the complex base oil. This base oil is a specific structure ester synthesized by two-step catalytic esterification of pentaerythritol, di-fatty acids, and mono-fatty acids. This pentaerythritol ester differs from traditional mono / di-pentaerythritol esters. The dicarboxylic acid segment of the di-fatty acid in the ester molecule increases molecular rigidity and reduces oxidative degradation at high temperatures. Combined with complex antioxidants, it reduces the viscosity change rate of the oil after high-temperature oxidation, thus improving the high-temperature oxidation stability of the oil. In addition, the kinematic viscosity of this base oil at 100℃ is 4.8-5.2 mm. 2 The viscosity index is ≥135, and the pour point is ≤-60℃. These properties ensure that the oil forms a stable oil film at high temperatures. Combined with extreme pressure anti-wear agents (high-purity tricresyl phosphate TCP), the oil's high load-carrying capacity is enhanced.

[0020] (2) Polyalphaolefin (PAO): accounting for 15 to 25 parts of the composite base oil, with a viscosity grade of PAO6 or PAO8. PAO works synergistically with ester base oil to compensate for the problem of insufficient low-temperature fluidity of traditional ester oil, making the pour point of the base oil ≤ -60℃, while improving anti-foaming properties and avoiding the impact of foaming on lubrication performance at high speeds.

[0021] (3) Dipentaerythritol ester (DPE): accounting for 5 to 15 parts of the composite base oil, its fatty acid chain is C5 to C7, used to help improve viscosity-temperature performance and high-temperature oil film strength. DPE, PAO, and pentaerythritol ester form a synergistic effect of low-temperature flow, high-temperature stability and high load-bearing capacity, solving the problem that traditional base oil cannot take into account multiple properties.

[0022] More specifically, the preparation process of the high-purity pentaerythritol ester base oil includes the following steps: (1) Add pentaerythritol, dicarboxylic acid, catalyst, and organic solvent to the container, and heat the container under a protective gas to carry out the first esterification reaction. The reaction of dicarboxylic acid with pentaerythritol forms a carboxyl-containing intermediate, which provides an active site for subsequent esterification with monocarboxylic acid. At the same time, the introduction of dicarboxylic acid segments improves the high-temperature stability and molecular rigidity of the final ester.

[0023] (2) After cooling the container, add monobasic fatty acids and catalyst, and then heat it up again to carry out the second esterification reaction to obtain crude product. The C5 to C9 carbon chains of monobasic fatty acids are esterified with intermediates to regulate the carbon chain length and branching degree of ester molecules, ensuring that the final base oil meets the indicators of kinematic viscosity and pour point at 100℃, while taking into account both low-temperature fluidity and high-temperature oil film strength.

[0024] (3) After the reaction is completed, the organic solvent is recovered by vacuum distillation (to avoid residual solvent from affecting the performance of the oil film) and excess unreacted monobasic fatty acids (to reduce the base oleic acid value).

[0025] (4) The crude product undergoes post-treatment steps such as alkali washing, water washing, drying, decolorization, and filtration to obtain a light yellow transparent liquid. Alkali washing neutralizes residual trace amounts of organic acids and catalyst residues, while water washing removes water-soluble impurities such as salts, further reducing the acid value and preventing the base oil from undergoing oxidative degradation or corrosion at high temperatures due to acidic impurities. Drying deeply removes residual trace amounts of water after water washing, preventing water from causing ester hydrolysis or affecting the compatibility of subsequent additives, thus ensuring the long-term storage stability of the base oil. Through the adsorption effect of, for example, activated clay, trace amounts of colored impurities generated during the esterification reaction are removed, resulting in a light yellow transparent product; at the same time, filtration removes clay particles and other solid impurities, improving the purity and cleanliness of the base oil and preventing impurities from affecting the lubricating performance of the lubricating oil.

[0026] In this embodiment, the dicarboxylic acid is adipic acid, glutaric acid, or pimelic acid.

[0027] The monobasic fatty acids are C5 to C9 monobasic fatty acids. For example, straight-chain valeric acid, hexanoic acid, heptanoic acid, octanoic acid, and nonanoic acid, and branched-chain isovaleric acid, isohexanoic acid, isohexanoic acid, isohexanoic acid, isooctanoic acid, and isononanoic acid. A mixed acid system of straight-chain and branched-chain structures is selected.

[0028] The catalyst is tetrabutyl titanate.

[0029] In this embodiment, the antioxidant is an oligomer solution of alkylated diphenylamine (such as diisooctyl diphenylamine, DODPA) and N-phenyl-α-naphthylamine (PAN) (molecular weight 600-1000), with a mass ratio of (1-2):1. The antioxidant formulated as described above can synergistically inhibit the oxidative degradation of the composite base oil and additives, reduce the formation of acidic oxidation products, lower the acid value, and reduce the risk of corrosion from the source.

[0030] In one embodiment, the extreme pressure anti-wear agent is tricresyl phosphate (TCP) with an impurity chlorine content of less than 8 µg / g and an ortho-isomer content of less than 0.5%. These limitations allow high-purity TCP to eliminate corrosion-causing chlorine impurities found in traditional TCP, while also reducing the thermal instability caused by ortho-isomers and preventing decomposition at high temperatures that could generate corrosive substances.

[0031] In one embodiment, the corrosion inhibitor comprises 0.3–1 part of high-purity benzotriazole (T706) (with impurity chlorine content less than 25 µg / g and sulfur content less than 15 µg / g); 0.1–0.5 parts of urea; and 0.1–0.3 parts of an organoboroester (such as stearic acid diethanolamide borate). The high-purity T706 in the corrosion inhibitor helps reduce the risk of corrosion from impurities within the inhibitor itself, resolving the contradiction that conventional T706, due to impurities, both inhibits and exacerbates corrosion. As the main component of the corrosion inhibitor, high-purity T706 can adsorb onto the metal surface to form a protective film, inhibiting electrochemical corrosion. The auxiliary corrosion inhibitor innovatively introduced in this invention works synergistically with T706 to neutralize trace amounts of acidic substances produced by the decomposition of additives at high temperatures, while simultaneously enhancing the density of the protective film and preventing pitting corrosion. The organoboroester further strengthens the corrosion-inhibiting film, improving the corrosion resistance to copper, steel, aluminum, iron, and other metals.

[0032] In one embodiment, the antifoaming agent is a polyacrylate copolymer-based non-silicone antifoaming agent. Oils are prone to foaming under high temperature and high speed conditions due to mixing of the composite base oil and additives, airflow agitation, etc. The polyacrylate copolymer-based non-silicone antifoaming agent selected in this invention inhibits foam generation by reducing the oil-air interfacial tension, quickly eliminating existing foam and ensuring that the lubricating oil maintains a low-foaming state under high temperature and high speed conditions. This antifoaming agent is non-silicone, avoiding the incompatibility and impurity precipitation problems that silicone-based antifoaming agents may have with other additives (such as high-purity TCP, composite corrosion inhibitors). Simultaneously, it has good compatibility with the composite base oil system, does not affect the homogeneity and long-term storage stability of the oil, and does not negatively impact rubber compatibility.

[0033] In one embodiment, the viscosity index improver is polymethyl methacrylate (PMA) or hydrogenated styrene-diene copolymer (HSD). The composite base oil system already possesses basic viscosity-temperature properties (viscosity index ≥ 135), but for some scenarios requiring higher viscosity at high temperatures, it is necessary to further optimize the viscosity-temperature properties of the lubricating oil using a viscosity index improver to compensate for the viscosity shortcomings of the base oil system at extreme temperatures and ensure the stability of lubrication performance over a wide temperature range.

[0034] The present invention also provides a method for preparing an aircraft engine lubricating oil composition, comprising the following steps: (1) Pretreatment and mixing of composite base oils: Pentaerythritol ester base oil and dipentaerythritol ester were heated (70-80℃) and dehydrated and degassed under vacuum (-0.092 to -0.098 MPa) for 1 hour to remove moisture and low-boiling substances, thus avoiding affecting the solubility of additives. The two pretreated ester base oils were added to the primary blending vessel in proportion, stirred under a protective gas and heated to 80-90℃; during the stirring process, poly-α-olefin was added and mixed with the ester base oil to form a homogeneous composite base oil, and the conditions were maintained and stirring continued for 30 minutes. Mixing the ester base oil first and then mixing PAO can avoid the phase separation problem caused by direct and rapid mixing of PAO and ester base oil.

[0035] (2) Blending of additives in the first stage: Maintaining the conditions of the primary blending vessel, first add the antioxidant and stir thoroughly (at least 45 min); then add the urea from the corrosion inhibitor and stir thoroughly (at least 45 min); finally add the organoboroate from the corrosion inhibitor and stir thoroughly (at least 45 min); after the addition is complete, continue stirring and reacting for 2 h at 80-90℃ under a protective gas atmosphere to form the functionalized base oil phase. This blending step ensures that the water-soluble / oil-soluble additives are fully dissolved, avoiding excessively high or low local concentrations.

[0036] (3) Second stage of additive blending: The temperature in the reactor is controlled at 70-80℃, and the vacuum degree is maintained above -0.090MPa (the functionalized base oil phase can be transferred to the secondary blending reactor (or carried out in the same reactor)); first, add benzotriazole from the corrosion inhibitor and stir thoroughly; then add the extreme pressure anti-wear agent and stir thoroughly; finally, add the antifoaming agent and optional viscosity index improver, and stir until the oil is completely homogeneous and transparent. This stage of blending utilizes the vacuum environment to remove the trace bubbles generated when the additives are dissolved, while avoiding premature reaction between highly active components (such as TCP) and other additives, which would affect the performance of the oil.

[0037] (4) Cooling and post-treatment: The oil is cooled and filtered to remove possible impurity particles and undissolved trace components, ensuring that the oil is uniform and transparent, and the above-mentioned aircraft engine lubricating oil composition is obtained.

[0038] The above preparation method, through steps such as segmented addition, mild process, full-process protective gas protection, and fine filtration, ensures that each additive is uniformly dispersed in the system and performs its function independently, thereby improving the oxidation stability, corrosion resistance, wear resistance and long-term stability of the oil.

[0039] To further illustrate the aero-engine lubricating oil composition and its preparation method provided by the present invention, the following examples and comparative examples are provided.

[0040] Example 1 Synthesis of high-purity pentaerythritol ester base oil: In a reactor equipped with a stirrer, thermometer, water separator, and nitrogen inlet pipe, 1 mol of pentaerythritol, 0.2 mol of adipic acid, 0.4 wt% tetrabutyl titanate catalyst, and 200 mL of xylene were added. Under nitrogen protection, the temperature was raised to 175°C, and the reaction continued until no water was formed in the water separator (approximately 4 hours). The temperature was lowered to 80°C, and 3.8 mol of a mixed acid consisting of valeric acid and isohexanoic acid, along with an additional 0.1 wt% catalyst, were added. The temperature was raised to 185°C, and the reaction continued until no water was formed (approximately 7 hours). After the reaction was complete, the solvent and excess acid were recovered by vacuum distillation. The crude product was washed with 5% NaOH solution, followed by water until neutral, dried over anhydrous magnesium sulfate, and then decolorized with activated clay at 90°C for 30 minutes before filtration to obtain a light yellow transparent liquid. Its kinematic viscosity at 100°C was measured to be 5.05 mm⁻¹. 2 It has a viscosity index of 138, a pour point of -62℃, and an acid value of 0.06 mgKOH / g.

[0041] Example 2 Preparation of lubricating oil composition: (1) Pretreatment and initial mixing of compound base oils: The high-purity pentaerythritol ester base oil and dipentaerythritol ester (DPE) were heated to 75°C and dehydrated and degassed under a vacuum of -0.095 MPa for 1 hour. The two dehydrated ester base oils were then added to a primary blending vessel in a specific ratio and stirred at 70 rpm under nitrogen protection, while the temperature was raised to 85°C. While continuing to stir, PAO base oil was slowly pumped into the primary blending vessel to mix with the ester base oils, forming a homogeneous base oil composite phase. The temperature was then maintained and stirring continued for another 30 minutes.

[0042] (2) Blending of additives in the first stage (antioxidant and corrosion inhibitor): While maintaining the conditions of the primary mixing vessel, add urea and organic borate esters from the composite antioxidant and composite corrosion inhibitor in sequence.

[0043] After each additive is added, continue stirring for 45 minutes to ensure complete dissolution and dispersion.

[0044] After the feed is added, the mixture is stirred and reacted for 2 hours at 85°C under nitrogen protection to form a functionalized base oil phase.

[0045] (3) Second-stage additive blending (extreme pressure and antifoaming) and final blending: The functionalized base oil phase was transferred to a secondary blending reactor, with the temperature controlled at 75°C and the vacuum maintained above -0.090 MPa. First, high-purity benzotriazole (T706) was added and stirred for 60 minutes to dissolve. Then, high-purity tricresyl phosphate (TCP) was added and stirred for 60 minutes to dissolve. Finally, an antifoaming agent and, optionally, a viscosity index improver were added, and the mixture was stirred for 90 minutes until the system was completely homogeneous and transparent.

[0046] (4) Cooling and post-treatment: The blended oil is slowly cooled to below 40°C while stirring. It is then filtered sequentially through a 10µm bag filter and a 3µm absolute precision filter. The final product is obtained by filling under nitrogen protection.

[0047] Examples 3-5: The composition of the lubricating oil composition is shown in Table 1, and it is prepared in accordance with the method of Example 2.

[0048] Table 1 Formulations (by weight) of the lubricating oil compositions in Examples 3-5

[0049] Comparative Example 1 The composition of the lubricating oil is as follows: 93.399% conventional pentaerythritol base oil, 1% N,N'-disubstituted 2,4-diaminodiphenyl ester, 2.5% composite antioxidant (DODPA:PAN oligomer = 1.5:1), 2% TCP, 0.8% T706, 0.3% stearic acid diethanolamide borate, and 0.001% antifoaming agent (polyacrylate).

[0050] Fill the blending vessel with nitrogen, pump the pentaerythritol ester base oil into the blending vessel, and heat the pentaerythritol ester base oil to 85°C while stirring. Then, pump the additives into the blending vessel, mix and stir thoroughly for 1 hour, let stand and cool to room temperature, and filter to obtain the finished product.

[0051] Comparative Example 2 The composition of the lubricating oil is as follows: 70 parts of synthetic ester base oil (ESTEREX A51), 30 parts of polyether base oil (SDNO6A), 2 parts of aromatic amine dimer antioxidant (NYCOPERF A0337 from Nicol), 1 part of aniline antioxidant (diisooctyl diphenylamine), 3 parts of phosphorus-containing anti-wear extreme pressure agent (tricresol phosphate), and 0.01 parts of benzotriazole derivative anti-corrosion agent (benzotriazole).

[0052] Performance testing Key performance tests were conducted on the oils obtained in Examples 3-5 and Comparative Examples 1-2, and the results are shown in Table 2.

[0053] Table 2 Performance Test Results

[0054] Results Analysis: Table 2 shows that Examples 3-5 of this invention are significantly superior to Comparative Examples 1 and 2 in terms of high-temperature oxidation stability, extreme pressure anti-wear properties, corrosion resistance (especially pitting corrosion resistance), and anti-foaming properties. Specifically, this invention uses pentaerythritol ester base oil, which is esterified from pentaerythritol, di-fatty acids, and mono-fatty acids, and is compounded with PAO and dipentaerythritol ester, supplemented by the synergistic effect of DODPA and PAN oligomer antioxidants, which can inhibit high-temperature oxidative degradation. The compatibility of high-purity TCP with the composite base oil and the staged blending process ensure uniform dispersion of anti-wear components, thereby improving extreme pressure anti-wear capability. This invention not only limits the content of key impurities in TCP and T706, eliminating electrochemical corrosion from the source through impurity control, but also creatively introduces urea, a small molecule compound, as an auxiliary corrosion inhibitor, forming a highly efficient corrosion inhibition system. In addition, the combination of PAO base oil and non-silicone antifoaming agent solves the foaming problem under high temperature and high speed, and improves the swelling effect of the composite system on the seals.

[0055] Comparative Example 1 used conventional pentaerythritol ester base oil, which lacks the synergistic structure of dicarboxylic and monocarboxylic acids, affecting the oil's high-temperature stability and load-carrying capacity. Furthermore, the lack of control over chlorine and sulfur impurities in TCP and T706 led to electrochemical corrosion caused by these additive impurities. Moreover, Comparative Example 1 employed a one-time mixing process, resulting in uneven dispersion of highly active components, mutual interference between the functions of some additives, and poor anti-foaming properties and rubber compatibility.

[0056] Comparative Example 2 used a mixture of ester and polyether base oils, without controlling TCP / T706 impurities and without urea. Due to the poor long-term compatibility of ester-polyether base oils, phase separation easily occurs at high temperatures, affecting oxidation stability; the lack of control over TCP and T706 impurity content, and the absence of urea-assisted corrosion inhibition, prevents the formation of a dense corrosion protective film, affecting corrosion resistance; the poor compatibility between polyether base oils and antifoaming agents leads to a surge in foaming at high temperatures, and also a more pronounced swelling effect on rubber.

[0057] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. An aircraft engine lubricating oil composition, characterized in that, The compound base oil comprises, by weight, 88-97.5 parts of complex base oil, 1-4 parts of antioxidant, 1-2.5 parts of extreme pressure anti-wear agent, 0.5-1.8 parts of corrosion inhibitor, and 0.002-0.01 parts of antifoaming agent; and by weight, the complex base oil comprises, by weight, 50-70 parts of pentaerythritol ester base oil, 15-25 parts of polyalphaolefin, and 5-15 parts of dipentaerythritol ester.

2. The aircraft engine lubricating oil composition according to claim 1, characterized in that, The pentaerythritol ester base oil is formed by esterification of pentaerythritol, dicarboxylic acid and monocarboxylic acid.

3. The aircraft engine lubricating oil composition according to claim 2, characterized in that, The preparation process of the pentaerythritol ester base oil includes the following steps: adding pentaerythritol, dicarboxylic acid, catalyst and organic solvent to a container, heating the container under a protective gas to carry out the first esterification reaction; cooling the container and adding monocarboxylic acid and catalyst, heating again to carry out the second esterification reaction to obtain a crude product; after the reaction is completed, the crude product is post-treated to obtain a pentaerythritol ester base oil that is a light yellow transparent liquid.

4. The aircraft engine lubricating oil composition according to claim 3, characterized in that, The prepared pentaerythritol ester base oil has a kinematic viscosity of 4.8–5.2 mm at 100°C. 2 / s, viscosity index ≥135, pour point ≤-60℃.

5. The aircraft engine lubricating oil composition according to claim 3, characterized in that, The dicarboxylic acid is adipic acid, glutaric acid, or pimelic acid; the monocarboxylic acid is a C5-C9 monocarboxylic acid; and the catalyst is tetrabutyl titanate.

6. The aircraft engine lubricating oil composition according to claim 1, characterized in that, The antioxidant is an oligomer solution of alkylated diphenylamine and N-phenyl-α-naphthylamine; the mass ratio of alkylated diphenylamine to N-phenyl-α-naphthylamine is (1-2):

1.

7. The aircraft engine lubricating oil composition according to claim 1, characterized in that, The extreme pressure anti-wear agent is tricresyl phosphate with an impurity chlorine content of less than 8 µg / g and an ortho-isomer content of less than 0.5%; the antifoaming agent is a polyacrylate copolymer non-silicone antifoaming agent.

8. The aircraft engine lubricating oil composition according to claim 1, characterized in that, The corrosion inhibitor is composed of 0.3 to 1 part of benzotriazole, 0.1 to 0.5 parts of urea, and 0.1 to 0.3 parts of organoboroate.

9. The aircraft engine lubricating oil composition according to claim 1, characterized in that, The aero-engine lubricating oil composition further includes 0 to 1 part of a viscosity index improver, wherein the viscosity index improver is polymethyl methacrylate or hydrogenated styrene-diene copolymer.

10. A method for preparing an aircraft engine lubricating oil composition, characterized in that, Includes the following steps: Pretreatment and mixing of composite base oils: Pentaerythritol ester base oil and dipentaerythritol ester are heated, dehydrated and degassed respectively; the two pretreated ester base oils are added into a primary blending tank in proportion, stirred under a protective gas and heated to 80-90°C; polyα-olefins are added during stirring and mixed with ester base oils to form a homogeneous composite base oil. The first stage of additive blending: maintaining the conditions of the primary blending vessel, first add the antioxidant and stir thoroughly; then add the urea from the corrosion inhibitor and stir thoroughly; finally add the organoboroate from the corrosion inhibitor and stir thoroughly; after the addition is complete, continue stirring and reacting at 80-90℃ under a protective gas to form the functionalized base oil phase; The second stage of additive blending: the temperature in the reactor is controlled at 70-80°C and the vacuum degree is maintained above -0.090MPa; first, benzotriazole in the corrosion inhibitor is added and stirred thoroughly; then, extreme pressure anti-wear agent is added and stirred thoroughly; finally, antifoaming agent and optional viscosity index improver are added and stirred until the oil is completely homogeneous and transparent; after cooling and filtration, the oil composition of the aero-engine lubricating oil as described in any one of claims 1-9 is obtained.

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