An ammonia fuel engine lubricating oil and a method of making the same

Abstract

The application provides an ammonia fuel engine lubricating oil and a preparation method thereof, and belongs to the technical field of lubricating oils.The ammonia fuel engine lubricating oil comprises the following components in percentage by mass: an oiliness agent 1.5-15%, a lubricant 1-5%, a cleaning dispersant 1-5%, an antioxidant 0.5-5%, a friction modifier 0.1-5%, and a balance of base oil; wherein the friction modifier is selected from one or more of the compounds shown in formula I.The lubricating oil provided by the application has good ammonia decomposition resistance, is not prone to emulsification after contacting ammonia gas or ammonia water, can maintain good lubricating performance in an ammonia-containing environment, and is suitable for use in ammonia fuel engines.

Description

Technical Field

[0001] This invention belongs to the field of lubricating oil technology, specifically relating to an ammonia fuel engine lubricating oil and its preparation method. Background Technology

[0002] Traditional internal combustion engines primarily utilize the heat energy from the combustion of fuels such as gasoline, diesel, and natural gas to convert into kinetic energy, thereby outputting power. With the industry's emphasis on green and low-carbon goals, the decarbonization and zero-carbonization of internal combustion engines are imperative. Ammonia, as a zero-carbon fuel, has naturally become a popular choice among new energy sources.

[0003] Ammonia fuel has the following characteristics: (1) It does not emit CO2 and is a zero-carbon fuel. Compared with traditional fuels, the most significant advantage of ammonia is that it does not emit CO2 after combustion. Even if the ignition fuel is included (about 5%), the emission reduction of ammonia can be achieved by more than 95% compared with traditional energy sources; (2) Ammonia has a high energy density and is easy to store. Compared with hydrogen, ammonia can be stored at 20°C, while hydrogen can be stored at -253°C. The flammability limit of ammonia is lower than that of hydrogen, and the combustion process is safer than that of hydrogen; (3) Ammonia is very hygroscopic and can easily cause engine oil emulsification in the engine, reducing the lubricity of the engine oil.

[0004] Engine oil plays a vital role in engine operation, providing lubrication and reducing friction, assisting in cooling, sealing against leaks, preventing rust and corrosion, and damping shocks. It is often referred to as the engine's "blood." However, traditional engine oils are prone to emulsification or ammonolysis upon contact with ammonia, making them unsuitable for direct use in ammonia-fueled engines.

[0005] Therefore, there is a need to develop a lubricant suitable for ammonia fuel engines. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a lubricating oil for ammonia fuel engines and its preparation method. This lubricating oil exhibits excellent resistance to ammonia decomposition and is not easily emulsified upon contact with ammonia gas or ammonia water, maintaining good lubrication performance in ammonia-containing environments, making it suitable for use in ammonia fuel engines.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an ammonia fuel engine lubricating oil, the lubricating oil comprising the following components by mass percentage:

[0009] Oiliness agent 1.5-15%, lubricant 1-5%, detergent-dispersant 1-5%, antioxidant 0.5-5%, friction modifier 0.1-5%, and balance base oil;

[0010] The friction modifier is selected from one or more compounds shown in Formula I below;

[0011]

[0012] R1 is C8-C 22 alkyl.

[0013] The aforementioned friction modifiers have good resistance to ammonia degradation and can improve the ammonia resistance of lubricating oils.

[0014] In this invention, the mass percentage of the oiling agent can be any value within the range of 1.5%-15%, for example, it can be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 13%, 14%, or 15%, etc. Preferably, it is 5-12%.

[0015] The mass percentage of the lubricant can be any value between 1% and 5%, for example, it can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, or 5%, etc.

[0016] The mass percentage of the cleaning and dispersing agent can be any value within the range of 1-5%, for example, it can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, or 5%, etc.

[0017] The mass percentage of the antioxidant can be any value within the range of 0.5% to 5%, for example, it can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, or 5%, etc.

[0018] The mass percentage of the friction modifier can be any value within the range of 0.1% to 5%, for example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, or 5%, etc. Preferably, it is 1% to 5%.

[0019] R1 is any straight-chain or branched alkyl group with 8-22 carbon atoms (e.g., 8, 9, 10, 12, 13, 15, 16, 18, 20 or 22).

[0020] Oily agent

[0021] Oiliness agents are additives in lubricating oils that enhance lubricity and prevent wear and scratches under boundary lubrication conditions.

[0022] In some embodiments of the present invention, the oiliness agent is selected from one or more of oleyl alcohol, pentaerythritol fatty acid ester, trimethylolpropane saturated fatty acid ester, and benzotriazole fatty acid amine salt, preferably trimethylolpropane C6-C18 saturated fatty acid ester. The above-mentioned oiliness agent has stable properties and can exert a certain repulsive effect on ammonia, thereby improving the ammonia resistance of the lubricating oil.

[0023] lubricant

[0024] Lubricants are a collective term for anti-wear additives and extreme pressure additives. Their main function is to improve the lubricity of lubricating oil, reduce the frictional resistance of friction pairs, and slow down wear.

[0025] In some embodiments of the present invention, the lubricant is selected from one or more of nitrogen-containing derivatives of thiophosphate, tricresyl phosphate, amine salts of phosphate esters, amine salts of thiophosphate esters, triphenyl thiophosphate, and aminothiophosphate esters, preferably amine salts of phosphate esters and / or triphenyl thiophosphate. The above-mentioned lubricants have good lubrication performance and a certain resistance to ammonolysis, which can improve the anti-ammonia performance of lubricating oils.

[0026] Detergent dispersant

[0027] Most detergent dispersants contain both lipophilic and hydrophilic groups in their structure. Differences in structure lead to variations in their performance. The primary function of detergent dispersants is to keep the engine interior clean and prevent the formation of oil-insoluble substances such as carbon deposits, varnish, or sludge. Their mechanism of action mainly involves acid neutralization, solubilization, adsorption, and washing to inhibit the formation and accumulation of insoluble substances and clean the engine's internal surfaces.

[0028] In some embodiments of the present invention, the detergent-dispersant is selected from one or more of high-base-value calcium sulfonate, high-base-value magnesium sulfonate, alkyl salicylate calcium, alkylphenol sulfide calcium, and alkenyl succinimide, preferably high-base-value calcium sulfonate and alkenyl succinimide. The above-mentioned detergent-dispersant can exert a certain repulsive effect on ammonia, thereby improving the ammonia resistance of the lubricating oil.

[0029] It should be noted that "high alkalinity" in the high alkalinity calcium sulfonate and high alkalinity magnesium sulfonate refers to an alkalinity value ≥300mgKOH / g.

[0030] antioxidants

[0031] Antioxidants are additives that prevent aging and extend the life of organic matter by delaying or inhibiting its oxidation. A small amount of effective antioxidant is essential to prevent some easily oxidized substances in lubricating oil from being oxidized over long periods at high temperatures.

[0032] In some embodiments of the present invention, the antioxidant is selected from one or more of 2,6-di-tert-butyl-p-cresol, mixed di-tert-butyl esters, N-phenyl-α-naphthylamine, octyl diphenylamine, hindered phenolic ester antioxidants and thioether antioxidants, preferably 2,6-di-tert-butyl-p-cresol and / or octyl diphenylamine.

[0033] corrosion inhibitor

[0034] Since engine materials contain materials such as iron, copper, aluminum and their alloys, and some components of lubricating oil may cause rust and corrosion, the lubricating oil described in this invention preferably also includes corrosion inhibitors in order to inhibit such rust and corrosion.

[0035] In some embodiments of the present invention, the mass percentage of the corrosion inhibitor can be 0.01-1 wt%; for example, it can be 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, etc. Preferably, it is 0.05-0.5 wt%.

[0036] In some embodiments of the present invention, the corrosion inhibitor is selected from one or more of thiadiazole derivatives, benzotriazole derivatives, benzotriazole, methylbenzotriazole and sodium methylbenzotriazole, preferably thiadiazole derivatives.

[0037] Defoamer

[0038] Defoamers are substances that reduce the surface tension of water, solutions, suspensions, etc., preventing foam formation or reducing or eliminating existing foam. To prevent air bubbles from affecting the lubricating performance of lubricating oil during use, the lubricating oil described in this invention preferably also contains a defoamer.

[0039] In some embodiments of the present invention, the mass percentage of the defoamer can be 0.01-0.1 wt%, for example, it can be 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, or 0.1 wt%.

[0040] In some embodiments of the present invention, the defoamer is selected from one or more of methyl silicone oil, modified polyacrylate defoamer and polyether modified organosilicon defoamer, preferably methyl silicone oil.

[0041] In some embodiments of the present invention, the base oil is selected from one or more of polyalphaolefin (PAO), hydrotreated Group III base oil and hydrotreated Group II base oil, preferably polyalphaolefin.

[0042] In some embodiments of the present invention, the kinematic viscosity of the polyalphaolefin at 100°C is 5-15 mm. 2 / s; for example, it could be 5mm 2 / s, 6mm 2 / s, 7mm 2 / s, 8mm 2 / s, 9mm 2 / s, 10mm 2 / s, 11mm 2 / s, 12mm 2 / s, 13mm 2 / s, 14mm 2 / s or 15mm 2 / s etc.

[0043] In some embodiments of the present invention, the lubricating oil comprises the following components by mass percentage:

[0044] Oiliness agent 5-12%, lubricant 1-5%, detergent-dispersant 1-5%, antioxidant 0.5-5%, friction modifier 1-5%, corrosion inhibitor 0.05-0.5%, defoamer 0.01-0.1%, and balance base oil.

[0045] In a second aspect, the present invention provides a method for preparing a lubricating oil as described in the first aspect, the method comprising the following steps:

[0046] The components are mixed in the specified proportions until the mixture is clear and transparent to obtain the lubricating oil.

[0047] In some embodiments of the present invention, the preparation method includes the following steps:

[0048] (1) Heat the base oil to 50-55℃, add oiliness agent, lubricant, antioxidant and friction modifier, and stir until the solution is clear and transparent;

[0049] (2) Add a cleaning and dispersing agent, optionally a corrosion inhibitor, and optionally a defoamer to the mixed solution obtained in step (1), and stir until the solution is clear and transparent to obtain the lubricating oil.

[0050] It should be noted that "optionally" in step (2) above means adding or not adding, and whether or not to add depends on whether the lubricating oil mentioned in the first aspect contains the component.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] In this invention, by selecting appropriate oiliness agents, lubricants, detergents, dispersants and friction modifiers to work together, the resistance of lubricating oil to ammonia decomposition and its ability to resist emulsification after contact with ammonia gas or ammonia water are improved, so that the resulting lubricating oil can maintain good lubrication performance in an ammonia-containing environment, and is therefore suitable for use in ammonia fuel engines. Attached Figure Description

[0053] Figure 1 This is a photograph of the lubricating oil after amination, as provided in Embodiment 1 of the present invention.

[0054] Figure 2 This is a photograph of the lubricating oil after amination, provided in Comparative Example 1 of this invention.

[0055] Figure 3 The friction coefficient diagram of the lubricating oil before and after amination is provided in Embodiment 1 of the present invention;

[0056] Figure 4 The friction coefficient diagram of the lubricating oil before and after amination provided in Embodiment 7 of the present invention.

[0057] Figure 5 This is a graph showing the friction coefficients of the lubricating oil before and after amination, as provided in Example 8 of the present invention.

[0058] Figure 6 The friction coefficient diagram of the lubricating oil before and after amination is provided in Embodiment 9 of the present invention;

[0059] Figure 7 For commercially available CF-4 + Friction coefficient diagram of 10W40 diesel engine oil before and after ammoniaation;

[0060] Figure 8 The friction coefficient diagram of commercially available CF-4 10w40 diesel engine oil before and after ammonia treatment;

[0061] Figure 9 The friction coefficient diagram of commercially available CI-4 5w40 diesel engine oil before and after ammoniaation;

[0062] Figure 10 The graph shows the coefficient of friction of commercially available CK-4 10w40 diesel engine oil before and after ammonia treatment. Detailed Implementation

[0063] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the specific embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0064] The sources of the raw materials used in the embodiments of the present invention are as follows:

[0065] PAO 10 (Polyalphadecene): Mobil, kinematic viscosity 9-11 mmHg at 100°C. 2 / s;

[0066] Hydroisolated Group II base oils: 150BS from PetroChina Karamay Petrochemical Company and 500N from Panjin Northern Asphalt Fuel Co., Ltd.

[0067] Trimethylolpropane octyl caprylate: Priolube 3970 from CRODA;

[0068] Oil alcohol: Shanghai Maclean Biochemical Technology Co., Ltd.;

[0069] Triphenyl thiophosphate: BASF's TPPT;

[0070] Nitrogen-containing derivatives of thiophosphate: BASF's IRGALUBE 353;

[0071] Phosphate ester amine salt: T-308 from Shenyang Hualun Lubricating Oil Additives Co., Ltd.;

[0072] Zinc dialkyl dithiophosphate (ZDDP): RF2202 from Xinxiang Ruifeng New Materials Co., Ltd.;

[0073] High-alkalinity calcium sulfonate: RF1106 from Xinxiang Ruifeng New Materials Co., Ltd.;

[0074] Medium-alkali value synthetic calcium sulfonate: RF1105 from Xinxiang Ruifeng New Materials Co., Ltd.;

[0075] Alkylphenol calcium sulfide: RF1122 from Xinxiang Ruifeng New Materials Co., Ltd.;

[0076] Alkenyl succinimide: RF1161H from Xinxiang Ruifeng New Materials Co., Ltd.;

[0077] Octyl diphenylamine: T-557 from Jinzhou Xinxing Petroleum Additives Co., Ltd.;

[0078] Thiadiazole derivative: T-551 from Jinzhou Xinxing Petroleum Additives Co., Ltd.;

[0079] Methyl silicone oil: T901 from Guangzhou Ruishengyan Chemical Technology Co., Ltd.;

[0080] Molybdenum dialkyl dithiocarbamate: POUPC 1001 from Pacific United (Beijing) Petrochemical Co., Ltd.;

[0081] CF-4 + 10W40 diesel engine oil: China Petroleum & Chemical Corporation;

[0082] CF-4 10w40 diesel engine oil: Shanghai Strait Peak Lubricating Oil Development Co., Ltd.;

[0083] CI-4 5w40 diesel engine oil: Ningbo Huada Petrochemical Co., Ltd.;

[0084] CK-4 10w40 diesel engine oil: Shanghai Yinsheng Network Technology Co., Ltd.

[0085] The synthesis method of compound I is as follows:

[0086] Weigh 93g of palmitoleic acid (a mixed fatty acid of C8-C22) and 24.2g of hydroxyethyl ethylenediamine into a 500mL three-necked flask. Add 0.3g of polyethylene glycol 400 catalyst, followed by 250.0mL of xylene as solvent. Reflux under mechanical stirring, then add 55g of ammonium molybdate into the three-necked flask. Separate the generated water using a water separator. React for 6 hours until no more water evaporates. Filter to obtain a dark green solution. Remove the solvent by rotary evaporation and dry under vacuum to obtain a brown liquid, which is compound I.

[0087] In this embodiment of the invention, the preparation method of the ammonia fuel engine lubricating oil is as follows:

[0088] (1) Heat the base oil to 50°C and start stirring; add oiliness agent, lubricant, antioxidant and friction modifier, and stir until the solution is clear and transparent;

[0089] (2) Add detergent, dispersant, corrosion inhibitor and defoamer to the mixed solution obtained in step (1) and stir until the solution is clear and transparent to obtain ammonia fuel engine lubricating oil.

[0090] Examples 1-9

[0091] Examples 1 to 9 each provide an ammonia fuel engine lubricating oil, the composition and content (wt%) of which are shown in Tables 1 and 2 below.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096]

[0097] Comparative Example 1

[0098] This comparative example provides a lubricant that differs from Example 1 only in that the friction modifier is replaced with molybdenum dialkyldithiocarbamate.

[0099] Comparative Example 2

[0100] This comparative example provides a lubricating oil, which differs from Example 1 only in that the lubricant triphenyl thiophosphate is replaced with zinc dialkyl dithiophosphate.

[0101] Comparative Example 3

[0102] This comparative example provides a lubricating oil that differs from Example 1 only in that the oiliness agent trimethylolpropane octyl decanoate is replaced with oleic acid.

[0103] Performance testing

[0104] The lubricating oils provided in the above embodiments and comparative examples, as well as commercially available CF-4... + The lubrication performance of 10W40 diesel engine oil, CF-4 10W40 diesel engine oil, CI-4 5W40 diesel engine oil, and CK-4 10W40 diesel engine oil, as well as their lubrication performance after ammoniation, were tested. The test methods are as follows:

[0105] (1) Ammoniation method: In a petri dish (φ=16cm), add 10g of ammonia water (26wt%) to 100g of oil, stir evenly, and then dry at 105℃;

[0106] (2) Test method for friction coefficient: The test was conducted using a four-ball friction tester; the test pressure was 200N, the rotation speed was 1500r / min, the temperature was 90℃, and the time was 30min; the tester model was Xiamen Tianji MS-10A.

[0107] (3) Test method for wear rate: The test was conducted using a micro-motion friction and wear tester; the test pressure was 200N, the temperature was 90℃, the time was 30min, the wear rate was 2mm, and the frequency was 50Hz; the tester model was SRV-5.

[0108] The actual image of the ammoniated lubricating oil provided in Example 1 is shown below. Figure 1 As shown, a photograph of the ammoniated lubricating oil provided in Comparative Example 1 is shown below. Figure 2 As shown. From Figure 1 and Figure 2 It can be seen that the lubricating oil provided in Example 1 remains transparent after ammonia treatment, indicating that it has a certain resistance to ammonia; while the lubricating oil provided in Comparative Example 1 emulsifies after ammonia treatment, and its resistance to ammonia is poor.

[0109] The lubricating oils provided in Examples 1, 7, 8, and 9 and commercially available CF-4+ The coefficients of friction for 10W40 diesel engine oil, CF-4 10W40 diesel engine oil, CI-4 5W40 diesel engine oil, and CK-4 10W40 diesel engine oil are as follows: Figures 3 to 10 As shown in the figure, the friction coefficient of the lubricating oil provided in this embodiment of the invention decreases or becomes similar to that before ammonia treatment after ammonia treatment, while the friction coefficient of commercially available diesel engine oil increases significantly after ammonia treatment, indicating that the lubricating oil provided by this invention has good resistance to ammonia.

[0110] The wear rate test results for the examples and comparative examples are shown in Table 3 below.

[0111] Table 3

[0112]

[0113]

[0114] As can be seen from the test data in Table 3, the wear rate of the lubricating oil provided in the embodiments of the present invention decreases or remains similar to that before ammonia treatment after ammonia treatment, while the wear rate of the lubricating oil provided in the comparative example and the commercially available diesel engine oil increases significantly after ammonia treatment. This indicates that the lubricating oil provided in the present invention has better ammonia resistance and can be used in ammonia fuel engines.

[0115] Compared with Example 1, the base oils, oiliness agents, lubricants or detergents and dispersants used in Examples 2-6 were not preferred, and the reduction rate of wear rate of the resulting lubricating oils after ammonia treatment was lower.

[0116] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lubricating oil for an ammonia fuel engine, characterized in that, The lubricating oil comprises the following components by mass percentage: Oiliness agent 1.5-15%, lubricant 1-5%, detergent-dispersant 1-5%, antioxidant 0.5-5%, friction modifier 0.1-5%, and the balance base oil; The friction modifier is selected from one or more compounds shown in Formula I below; Formula I; R1 is C8-C 22 alkyl; The oiling agent is selected from one or more of oleyl alcohol, pentaerythritol fatty acid ester, and trimethylolpropane saturated fatty acid ester; The lubricant is selected from one or more of nitrogen-containing derivatives of thiophosphate, amine salts of phosphate esters, and triphenyl thiophosphate. The cleaning and dispersing agent is selected from one or more of high-alkalinity calcium sulfonate, calcium sulfide alkylphenol, and alkenyl succinimide.

2. The lubricating oil according to claim 1, characterized in that, The oiliness agent has a mass percentage of 5-12%.

3. The lubricating oil according to claim 1, characterized in that, The oiliness agent is a trimethylolpropane C6-C18 saturated fatty acid ester.

4. The lubricating oil according to claim 1, characterized in that, The lubricant is an amine phosphate salt and / or triphenyl thiophosphate.

5. The lubricating oil according to claim 1, characterized in that, The cleaning and dispersing agents are high-alkalinity calcium sulfonate and alkenyl succinimide.

6. The lubricating oil according to claim 1, characterized in that, The antioxidant is selected from one or more of di-tert-butyl-p-cresol, di-tert-butyl mixed ester, N-phenyl-α-naphthylamine, octyl diphenylamine, sterically hindered phenolic ester type antioxidants, and thioether type antioxidants.

7. The lubricating oil according to claim 6, characterized in that, The antioxidant is 2,6-di-tert-butyl-p-cresol and / or octyldiphenylamine.

8. The lubricating oil according to claim 1, characterized in that, The friction modifier has a mass percentage of 1-5%.

9. The lubricating oil according to claim 1, characterized in that, The base oil is selected from one or more of polyalphaolefins, hydrotreated Group III base oils, and hydrotreated Group II base oils.

10. The lubricating oil according to claim 9, characterized in that, The base oil is a polyalphaolefin.

11. The lubricating oil according to claim 9 or 10, characterized in that, The kinematic viscosity of the polyalphaolefin at 100°C is 5-15 mm. 2 / s.

12. The lubricating oil according to claim 1, characterized in that, The lubricating oil also includes 0.01-1 wt% corrosion inhibitor.

13. The lubricating oil according to claim 1, characterized in that, The lubricating oil also includes 0.05-0.5 wt% corrosion inhibitor.

14. The lubricating oil according to claim 12 or 13, characterized in that, The corrosion inhibitor is selected from one or more of thiadiazole derivatives, benzotriazole derivatives, and benzotriazole.

15. The lubricating oil according to claim 12 or 13, characterized in that, The corrosion inhibitor is selected from one or more of methylbenzotriazole and sodium methylbenzotriazole.

16. The lubricating oil according to claim 14, characterized in that, The corrosion inhibitor is a thiadiazole derivative.

17. The lubricating oil according to claim 1, characterized in that, The lubricating oil also includes 0.01-0.1 wt% of defoamer.

18. The lubricating oil according to claim 17, characterized in that, The defoamer is selected from one or more of methyl silicone oil, modified polyacrylate defoamer, and polyether modified silicone defoamer.

19. The lubricating oil according to claim 18, characterized in that, The defoamer is methyl silicone oil.

20. The lubricating oil according to claim 1, characterized in that, The lubricating oil comprises the following components by mass percentage: Oiliness agent 5-12%, lubricant 1-5%, detergent-dispersant 1-5%, antioxidant 0.5-5%, friction modifier 1-5%, corrosion inhibitor 0.05-0.5%, defoamer 0.01-0.1%, and balance base oil.

21. A method for preparing a lubricating oil according to any one of claims 1-20, characterized in that, The preparation method includes the following steps: The components are mixed in the specified proportions until the mixture is clear and transparent to obtain the lubricating oil.

22. The preparation method according to claim 21, characterized in that, The preparation method includes the following steps: (1) Heat the base oil to 50-55℃, add oiliness agent, lubricant, antioxidant and friction modifier, and stir until the solution is clear and transparent; (2) Add a cleaning and dispersing agent, optionally a corrosion inhibitor, and optionally a defoamer to the mixed solution obtained in step (1), and stir until the solution is clear and transparent to obtain the lubricating oil.

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