Extreme pressure Anti-wear additive, and preparation method thereof and use thereof in lubricating oil

Abstract

Provided are an extreme pressure anti-wear additive, a preparation method thereof and use thereof in a lubricating oil. The preparation method of the extreme pressure anti-wear additive includes: step 1: mixing a cerium dioxide dispersion with a 2-methylimidazole aqueous solution, and conducting a first stirring and a first filtering in sequence to obtain a first solid powder; step 2: mixing the first solid powder with a soluble cobalt salt solution, and conducting s second stirring and a second filtering in sequence to obtain a second solid powder; and step 3: repeating the step 1 and the step 2 for the second solid powder to obtain the extreme pressure anti-wear additive.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This patent application claims the benefit and priority of Chinese Patent Application No. 202411950933.7 filed with the China National Intellectual Property Administration on Dec. 27, 2024, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of lubrication, and in particular to an extreme pressure anti-wear additive, a preparation method thereof and use thereof in a lubricating oil.BACKGROUND

[0003] In industrial production, friction leads to significant energy loss and component wear, affecting the stable operation of equipment. The introduction of lubricating greases could effectively reduce interface friction and extend the service life of equipment, and thus the lubricating greases have been widely used in industrial production. However, a base lubricating oil tends to fail due to poor stability under extreme operating conditions such as high temperature and high load, thereby affecting equipment operation. Owing to their surface effect, small-size effect, and quantum-size effect, nanomaterials, as a lubricant additive, could effectively improve the tribological performance and stability of lubricating oils, attracting researchers'attention.

[0004] Rare earth nanomaterials possess excellent anti-wear and anti-oxidation properties, and could effectively enhance the tribological performance of lubricating oils, preventing lubricant failure under extreme conditions. Therefore, they have been widely applied in the field of lubrication. In addition, rare earth materials facilitate the occurrence of chemical reactions during the friction process due to the special 4f orbital of the rare earth materials, thereby forming a friction protective layer at the interface. This avoids direct contact between interfaces and is conducive to further reducing wear. However, due to their high density, the rare earth materials exhibit poor dispersion stability in lubricating oil and are prone to agglomeration during the friction process, thus adversely affecting their tribological performance. Metal-organic frameworks (MOFs) are a class of porous crystalline materials formed by the coordination reaction between metal ions and organic ligands. They offer advantages such as a highly ordered framework structure, tunable pore structure, large specific surface area, and desirable chemical stability. Consequently, MOFs have found extensive applications in the fields such as gas storage, catalytic reactions, electrochemistry, and sensors. Furthermore, due to the introduction of the organic framework, MOFs could exhibit better dispersion stability in lubricating oils compared to inorganic nanoscale lubricant additives, thereby further enhancing the tribological performance of lubricating oils. Zeolitic imidazolate framework (ZIF)-structured MOFs, due to their high thermal and chemical stability, have found extensive applications in the field of lubricating oil additives. However, MOFs are prone to deformation under mechanical action, which may lead to lubrication failure under extreme conditions.SUMMARY

[0005] In view of this, an object of the present disclosure is to provide an extreme pressure anti-wear additive, a preparation method thereof and use thereof in a lubricating oil. The extreme pressure anti-wear additive prepared by the preparation method exhibits desirable dispersion stability in lubricating oil and could still maintain excellent lubricating performance under extreme pressure conditions.

[0006] To achieve the above object, the present disclosure provides the following technical solutions:

[0007] The present disclosure provides a method for preparing an extreme pressure anti-wear additive, including:

[0008] step 1: mixing a cerium dioxide dispersion with a 2-methylimidazole aqueous solution, and conducting a first stirring and a first filtering in sequence to obtain a first solid powder;

[0009] step 2: mixing the first solid powder with a soluble cobalt salt solution, and conducting a second stirring and a second filtering in sequence to obtain a second solid powder; and

[0010] step 3: repeating the step 1 and the step 2 for the second solid powder to obtain the extreme pressure anti-wear additive.

[0011] In some embodiments, the cerium dioxide dispersion includes cerium dioxide and water; and

[0012] a mass ratio of the cerium dioxide to the water is in a range of 1:50-100.

[0013] In some embodiments, a mass ratio of 2-methylimidazole to water in the 2-methylimidazole aqueous solution is in a range of 1:20-50.

[0014] In some embodiments, a mass ratio of a soluble cobalt salt to water in the soluble cobalt salt solution is in a range of 1:20-100.

[0015] In some embodiments, a molar ratio of the cerium dioxide in the cerium dioxide dispersion to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10.

[0016] In some embodiments, a molar ratio of the soluble cobalt salt in the soluble cobalt salt solution to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:2-10.

[0017] In some embodiments, the first stirring is conducted at a rotational speed of 300 rpm to 800 rpm for 10 min to 30 min;

[0018] the second stirring is conducted at a rotational speed of 300 rpm to 800 rpm for 10 min to 30 min; and

[0019] the step 1 and the step 2 are repeated 3 times to 10 times.

[0020] The present disclosure further provides an extreme pressure anti-wear additive prepared by the method as described in the above technical solutions, including: cerium dioxide nanoparticles and a zeolitic imidazolate framework-67 (ZIF-67) coated on a surface of each of the cerium dioxide nanoparticles.

[0021] The present disclosure further provides use of the extreme pressure anti-wear additive in a lubricating oil.

[0022] The present disclosure further provides a lubricating oil, including: a base oil and an extreme pressure anti-wear additive; where

[0023] the extreme pressure anti-wear additive accounts for 0.1% to 1% by mass of the lubricating oil; and

[0024] the extreme pressure anti-wear additive is the extreme pressure anti-wear additive described above.

[0025] The method for preparing the extreme pressure anti-wear additive includes the following steps: step 1: mixing a cerium dioxide dispersion with a 2-methylimidazole aqueous solution, and conducting a first stirring and a first filtering in sequence to obtain a first solid powder; step 2: mixing the first solid powder with a soluble cobalt salt solution, and conducting a second stirring and a second filtering in sequence to obtain a second solid powder; and repeating the step 1 and the step 2 for the second solid powder to obtain the extreme pressure anti-wear additive. In the present disclosure, the method is straightforward, primarily involving adsorbing 2-methylimidazole onto the surface of cerium dioxide nanoparticles by adsorption, and then adding cobalt nitrate, thereby forming ZIF-67 through the coordination between the cobalt nitrate and the 2-methylimidazole. The thickness of the outer ZIF-67 shell is controlled by controlling the times for sequential addition of 2-methylimidazole and cobalt nitrate. In addition, the extreme pressure anti-wear additive prepared by the method exhibits excellent dispersion stability in base oil: organic ligands in the MOF structure are lipophilic, which alters the surface hydrophilicity of the cerium dioxide nanoparticles, thereby effectively addressing the poor dispersion stability of cerium dioxide nanoparticles in lubricating oil. The rolling effect and self-repairing effect of the nano-additive (cerium dioxide nanoparticles), combined with the tribochemical reaction that generates a tribo-protective layer, reduce friction and wear between mechanical components, and maintain excellent lubricating performance even under extreme conditions of high temperature and high load.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1A shows a scanning electron microscope (SEM) image of the extreme pressure anti-wear additive in Example 1, and FIG. 1B shows a transmission electron microscope (TEM) image of the extreme pressure anti-wear additive in Example 1;

[0027] FIG. 2A and FIG. 2B show schematic diagrams of the dispersion stability of the lubricating oil in Use Example 1;

[0028] FIG. 3 shows friction coefficients of the lubricating oils in Comparative Example 1 and Use Examples 2 to 5;

[0029] FIG. 4 shows wear rates of the lubricating oils in Comparative Example 1 and Use Examples 2 to 5;

[0030] FIG. 5 shows friction coefficient curves of the lubricating oils in Comparative Example 1 and Use Example 5 under a variable load test; and

[0031] FIG. 6 shows friction coefficient curves of the lubricating oils in Comparative Example 1 and Use Example 5 under a variable temperature test.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present disclosure provides a method for preparing an extreme pressure anti-wear additive, including the following steps:

[0033] step 1: mixing a cerium dioxide dispersion with a 2-methylimidazole aqueous solution, and conducting a first stirring and a first filtering in sequence to obtain a first solid powder;

[0034] step 2: mixing the first solid powder with a soluble cobalt salt solution, and conducting a second stirring and a second filtering in sequence to obtain a second solid powder; and

[0035] step 3: repeating the step 1 and the step 2 for the second solid powder to obtain the extreme pressure anti-wear additive.

[0036] In the present disclosure, unless otherwise specified, all raw materials for preparation are commercially available products well known to those skilled in the art.

[0037] In the present disclosure, a cerium dioxide dispersion is mixed with a 2-methylimidazole aqueous solution, and a first stirring and a first filtering are conducted in sequence to obtain a first solid powder.

[0038] In some embodiments of the present disclosure, the mixing is conducted by adding the 2-methylimidazole aqueous solution to the cerium dioxide dispersion.

[0039] In some embodiments of the present disclosure, a mass ratio of 2-methylimidazole to water in the 2-methylimidazole aqueous solution is in a range of 1:20-50. In some embodiments, the mass ratio of the 2-methylimidazole to the water in the 2-methylimidazole aqueous solution is in a range of 1:30-40. In some embodiments, the water is deionized water. In some embodiments, the mass ratio of the 2-methylimidazole to the water is 1.15:30.

[0040] In some embodiments of the present disclosure, the 2-methylimidazole aqueous solution is prepared by mixing the 2-methylimidazole and the water. There is no specific limitation on the mixing, and a process well-known to those skilled in the art may be used.

[0041] In some embodiments of the present disclosure, the cerium dioxide dispersion includes cerium dioxide and water. In some embodiments, the water is deionized water. In some embodiments, the cerium dioxide is in the form of cerium dioxide nanoparticles. In some embodiments, a particle size of each of the cerium dioxide nanoparticles is in a range of 10 nm to 50 nm. In some embodiments, the particle size of each of the cerium dioxide nanoparticles is in a range of 20 nm to 30 nm. In some embodiments, a mass ratio of the cerium dioxide to the water is in a range of 1:50-100. In some embodiments, the mass ratio of the cerium dioxide to the water is in a range of 1:60-90. In some embodiments, the mass ratio of the cerium dioxide to the water is in a range of 1:70-80. In some embodiments, the mass ratio of the cerium dioxide to the water is 0.3:30.

[0042] In some embodiments of the present disclosure, the cerium dioxide dispersion is prepared by subjecting cerium dioxide and deionized water to ultrasonic treatment. There is no specific limitation on the ultrasonic treatment, and a process well-known to those skilled in the art may be used.

[0043] In some embodiments of the present disclosure, a molar ratio of the cerium dioxide in the cerium dioxide dispersion to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10. In some embodiments, the molar ratio of the cerium dioxide in the cerium dioxide dispersion to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:6-8. In some embodiments of the present disclosure, the molar ratio of the cerium dioxide in the cerium dioxide dispersion to the 2-methylimidazole in the 2-methylimidazole aqueous solution is 1:8.235.

[0044] In the present disclosure, there is no specific limitation on a process of adding the 2-methylimidazole aqueous solution, and a process well-known to those skilled in the art may be used.

[0045] In some embodiments of the present disclosure, the first stirring is conducted at a rotational speed of 300 rpm to 800 rpm. In some embodiments, the first stirring is conducted at a rotational speed of 500 rpm to 600 rpm. In some embodiments, the first stirring is conducted for 10 min to 30 min. In some embodiments, the first stirring is conducted for 15 min to 20 min. In some embodiments, the first stirring is conducted at a temperature of 20° C. to 40° C. In some embodiments, the first stirring is conducted at a rotational speed of 600 rpm. In some embodiments, the first stirring is conducted for 15 min. In some embodiments, the first stirring is conducted at 25° C.

[0046] In the present disclosure, the first stirring functions to adsorb 2-methylimidazole onto the surface of the cerium dioxide nanoparticles via electrostatic adsorption.

[0047] In the present disclosure, there is no specific limitation on the first filtering, and a process well-known to those skilled in the art may be used.

[0048] In the present disclosure, the first solid powder is mixed with a soluble cobalt salt solution, and the second stirring and the second filtering are conducted in sequence to obtain the second solid powder.

[0049] In some embodiments of the present disclosure, the soluble cobalt salt solution includes a soluble cobalt salt and water. In some embodiments, the water is deionized water. In some embodiments, the soluble cobalt salt includes cobalt nitrate hexahydrate and / or cobalt acetate tetrahydrate. In some embodiments, the soluble cobalt salt includes cobalt nitrate hexahydrate. When the soluble cobalt salt includes two of the aforementioned specific selections, there is no specific limitation on the ratio of these specific substances, and they may be mixed in any proportion. In some embodiments, the soluble cobalt salt is cobalt nitrate hexahydrate.

[0050] In some embodiments of the present disclosure, a mass ratio of the soluble cobalt salt to the water in the soluble cobalt salt solution is in a range of 1:20-100. In some embodiments, the mass ratio of the soluble cobalt salt to the water in the soluble cobalt salt solution is in a range of 1:30-80. In some embodiments, the mass ratio of the soluble cobalt salt to the water in the soluble cobalt salt solution is in a range of 1:40-60. In some embodiments, the mass ratio of the soluble cobalt salt to the water is 0.62:30.

[0051] In some embodiments of the present disclosure, the soluble cobalt salt solution is prepared by mixing a soluble cobalt salt and water. There is no specific limitation on the mixing, and a process well-known to those skilled in the art may be used.

[0052] In some embodiments of the present disclosure, the mixing is conducted by adding the soluble cobalt salt solution to the first solid powder. In some embodiments, the soluble cobalt salt solution is added under stirring conditions. There is no specific limitation on the stirring conditions, and conditions well-known to those skilled in the art may be used.

[0053] In some embodiments of the present disclosure, a molar ratio of the 2-methylimidazole in the 2-methylimidazole aqueous solution to the soluble cobalt salt in the soluble cobalt salt solution is in a range of 1:2-5. In some embodiments, the molar ratio of the 2-methylimidazole in the 2-methylimidazole aqueous solution to the soluble cobalt salt in the soluble cobalt salt solution is in a range of 1:3-4.

[0054] In some embodiments of the present disclosure, there is no specific limitation on the method and adding process of the soluble cobalt salt solution, and methods and processes well-known to those skilled in the art may be used.

[0055] In some embodiments of the present disclosure, the second stirring is conducted at a rotational speed of 300 rpm to 800 rpm. In some embodiments, the second stirring is conducted at a rotational speed of 500 rpm to 600 rpm. In some embodiments, the second stirring is conducted for 10 min to 30 min. In some embodiments, the second stirring is conducted for 10 min to 20 min. In some embodiments, the second stirring is conducted at a temperature of 20° C. to 40° C. In some embodiments, the second stirring is conducted at a rotational speed of 600 rpm. In some embodiments, the second stirring is conducted for 15 min. In some embodiments, the second stirring is conducted at a temperature of 25° C.

[0056] In some embodiments of the present disclosure, the repeating is conducted 3 to 10 times. In some embodiments, the repeating is conducted 4 to 8 times. In some embodiments, the repeating is conducted 5 times. Steps 1 and 2 are repeated to control the thickness of the ZIF-67 shell.

[0057] In some embodiments of the present disclosure, after the process of repeatedly preparing the first solid powder and adding the soluble cobalt salt solution for the second stirring is completed, the method further includes filtering, and sequentially conducting washing and drying. There is no specific limitation on the filtering and washing, and processes well-known to those skilled in the art may be used. In some embodiments, the drying is vacuum drying. In some embodiments, the drying is conducted at 40° C. In some embodiments, the drying is conducted for 12 h. In some embodiments, the washing is conducted three times using anhydrous ethanol.

[0058] The present disclosure further provides an extreme pressure anti-wear additive prepared by the method as described in the above technical solutions, including: cerium dioxide nanoparticles and a ZIF-67 coated on a surface of each of the cerium dioxide nanoparticles.

[0059] The present disclosure further provides use of the extreme pressure anti-wear additive as described in the above technical solutions in a lubricating oil.

[0060] The present disclosure further provides a lubricating oil, including: a base oil and an extreme pressure anti-wear additive; where

[0061] the extreme pressure anti-wear additive accounts for 0.1% to 1% by mass of the lubricating oil; and

[0062] the extreme pressure anti-wear additive is the aforementioned extreme pressure anti-wear additive.

[0063] In some embodiments of the present disclosure, the base oil includes at least one selected from the group consisting of 500SN, 500N, PAO4, PAO6, and PAO10.

[0064] In the present disclosure, the extreme pressure anti-wear additive accounts for 0.1% to 1% by mass of the lubricating oil. In some embodiments, the extreme pressure anti-wear additive accounts for 0.3% to 0.8% by mass of the lubricating oil.

[0065] In some embodiments of the present disclosure, a process for preparing the lubricating oil includes the following steps: mixing the base oil and the extreme pressure anti-wear additive, subjecting a resulting mixture to ultrasonic dispersion to obtain the lubricating oil. There is no specific limitation on the ultrasonic dispersion, and a process well-known to those skilled in the art may be used. In some embodiments, the ultrasonic dispersion is conducted at room temperature for 1 h.

[0066] The technical solutions of the present disclosure will be clearly and completely described below with reference to the examples of the present disclosure. Apparently, the described examples are merely a part rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.Example 1

[0067] 0.3 g (172 g / mol, 0.0017 mol) of cerium dioxide nanoparticles were ultrasonically dispersed in 30 g of deionized water to obtain a cerium dioxide dispersion.

[0068] 1.15 g (82 g / mol, 0.014 mol) of 2-methylimidazole was dissolved in 30 g of deionized water to obtain a 2-methylimidazole aqueous solution.

[0069] 0.62 g (291 g / mol, 0.0021 mol) of cobalt nitrate hexahydrate was dissolved in 30 g of deionized water to obtain a cobalt nitrate solution.

[0070] The 2-methylimidazole aqueous solution was added to the cerium dioxide dispersion, a resulting mixture was subjected to a first stirring for 15 min (at 25° C. and a rotational speed of 600 rpm), and then filtering to obtain a mixing solution.

[0071] The cobalt nitrate solution was added to the mixing solution. An obtained mixture was subjected to a second stirring for 15 min (at 25° C. and a rotational speed of 600 rpm). A process of preparing the mixing solution, and adding the cobalt nitrate solution to the mixing solution for the second stirring was repeated 5 times. A resulting product was then filtered, washed three times with anhydrous ethanol, and vacuum-dried at 40° C. for 12 h to obtain the extreme pressure anti-wear additive (denoted as ZIF-67@CeO2).

[0072] FIG. 1A shows an SEM image of the extreme pressure anti-wear additive, and FIG. 1B shows a TEM image of the extreme pressure anti-wear additive. It can be seen from FIG. 1A and FIG. 1B that a clear boundary exists between ZIF-67 and the CeO2 nanoparticles, exhibiting a core-shell structure. The ZIF-67 has very smooth surface and is coated onto the surface of the cerium dioxide nanoparticles in the form of nanosheets.Use Example 1

[0073] 0.005 g of the extreme pressure anti-wear additive in Example 1 was mixed with 4.995 g of 500SN base oil. A resulting mixture was subjected to ultrasonic dispersion to obtain a lubricating oil.

[0074] The lubricating oil was subjected to standing at room temperature for 1 day to 4 days, and an absorbance of the dispersion after different standing periods was tested by ultraviolet-visible spectroscopy.

[0075] FIG. 2A and FIG. 2B show schematic diagrams of the dispersion stability of the lubricating oil. It can be seen from FIG. 2 A and FIG. 2B that after standing for 96 h, the relative absorbance of the lubricating oil decreases to 0.7, indicating that the extreme pressure anti-wear additive exhibits relatively excellent dispersion stability.Use Example 2

[0076] 9.99 g of 500SN base oil was mixed with 0.01 g of the extreme pressure anti-wear additive in Example 1. A resulting mixture was ultrasonically dispersed at room temperature for 1 h to obtain a lubricating oil (with a mass percentage concentration of the extreme pressure anti-wear additive being 0.1%).Use Example 3

[0077] 9.97 g of 500SN base oil was mixed with 0.03 g of the extreme pressure anti-wear additive in Example 1. A resulting mixture was ultrasonically dispersed at room temperature for 1 h to obtain a lubricating oil (with a mass percentage concentration of the extreme pressure anti-wear additive being 0.3%).Use Example 4

[0078] 9.95 g of 500SN base oil was mixed with 0.05 g of the extreme pressure anti-wear additive in Example 1. A resulting mixture was ultrasonically dispersed at room temperature for 1 h to obtain a lubricating oil (with a mass percentage concentration of the extreme pressure anti-wear additive being 0.5%).Use Example 5

[0079] 9.9 g of 500SN base oil was mixed with 0.1 g of the extreme pressure anti-wear additive in Example 1. A resulting mixture was ultrasonically dispersed at room temperature for 1 h to obtain a lubricating oil (with a mass percentage concentration of the extreme pressure anti-wear additive being 1%).Comparative Example 1

[0080] 500SN base oil was used as the lubricating oil.Test Example

[0081] The friction performance of the lubricating oils in Use Examples 2 to 5 was tested under friction conditions with a load of 150 N, a speed of 0.05 m / s, and a temperature of 40° C. FIG. 3 shows friction coefficients of the lubricating oils according to Comparative Example 1 and Use Examples 2 to 5, and FIG. 4 shows wear rates of the lubricating oils according to Comparative Example 1 and Use Examples 2 to 5. It can be seen from FIG. 3 and FIG. 4 that the introduction of the extreme pressure anti-wear additive at different addition ratios could reduce both the friction coefficient and the wear rate of the 500SN base lubricating oil. The average friction coefficient of the 500SN base oil is 0.207. When 0.1 wt %, 0.3 wt %, 0.5 wt %, and 1 wt % of the ZIF-67@CeO2 additives are added, the average interfacial friction coefficients are 0.125, 0.124, 0.127, and 0.121, respectively. When the 500SN base oil is used as the lubricating medium, the interfacial wear volume is 22.344±1.656×104 μm3. As the addition content of the extreme pressure anti-wear additive increases, the interfacial wear volume gradually decreases. When the addition amounts of the extreme pressure anti-wear additive are 0.1 wt %, 0.3 wt %, 0.5 wt %, and 1 wt %, the interfacial wear volumes are 13.55±1.85×104 μm3, 7.044±0.352×104 μm3, 5.43±0.5×104 μm3, and 4.075±0.185×10μm3, respectively. When the additive content is 1 wt %, the interface exhibits the most excellent tribological performance, with its friction coefficient decreasing by 41.54% and its wear rate decreasing by 81.76% compared to the 500SN base oil of Comparative Example 1.

[0082] The friction performance of the lubricating oil in Use Example 5 was tested under friction conditions with a speed of 0.05 m / s, a temperature of 40° C., and a load increasing from 50 N to 700 N at a rate of 50 N / 3 min. FIG. 5 shows the friction coefficient curves of the lubricating oils according to Comparative Example 1 and Use Example 5 under the variable load test. It can be seen from FIG. 5 that the introduction of the 1 wt % extreme pressure anti-wear additive effectively increases the extreme load of the 500SN base oil. When the load increases to 200 N, the 500SN base oil experiences lubrication failure. However, after the introduction of the extreme pressure anti-wear additive, the lubricating oil does not fail until the load reaches 700 N, indicating that the introduction of the extreme pressure anti-wear additive enables the lubricating oil to maintain its lubricating performance even under high loads.

[0083] The friction performance of the lubricating oil described in Use Example 5 was tested under friction conditions with a load of 150 N, a speed of 0.05 m / s, and a temperature increasing from 30° C. to 130° C. at a rate of 10 ° C. / 3 min. FIG. 6 shows the friction coefficient curves of the lubricating oils according to Comparative Example 1 and Use Example 5 under the variable temperature test. It can be seen from FIG. 6 that the introduction of the 1 wt % extreme pressure anti-wear additive effectively improves the stability of the 500SN base oil at high temperatures and prevented lubrication failure. When the temperature increases to 60° C., the 500SN base oil experiences lubrication failure. However, after the introduction of the extreme pressure anti-wear additive, the lubricating oil could still maintain stable lubrication even at 130° C., indicating that the introduction of the extreme pressure anti-wear additive enables the lubricating oil to maintain its lubricating performance at high temperatures.

[0084] In summary, the extreme pressure anti-wear additive of the present disclosure exhibits excellent lubricating performance, making it particularly suitable for lubrication under extreme conditions such as high temperature and high load.

[0085] The above described are merely preferred embodiments of the present disclosure rather than limitations to the present disclosure in any form. It should be noted that those of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should be deemed as falling within the scope of the present disclosure.

Claims

1-13. (canceled)14. A method for preparing an extreme pressure anti-wear additive, comprising:step 1: mixing a cerium dioxide dispersion with a 2-methylimidazole aqueous solution, and conducting a first stirring and a first filtering in sequence to obtain a first solid powder;step 2: mixing the first solid powder with a soluble cobalt salt solution, and conducting a second stirring and a second filtering in sequence to obtain a second solid powder; andrepeating the step 1 and the step 2 for the second solid powder to obtain the extreme pressure anti-wear additive.

15. The method of claim 14, wherein the cerium dioxide dispersion comprises cerium dioxide and water; anda mass ratio of the cerium dioxide to the water is in a range of 1:50-100.

16. The method of claim 14, wherein a mass ratio of 2-methylimidazole to water in the 2-methylimidazole aqueous solution is in a range of 1:20-50.

17. The method of claim 14, wherein a mass ratio of a soluble cobalt salt to water in the soluble cobalt salt solution is in a range of 1:20-100.

18. The method of claim 14, wherein a molar ratio of cerium dioxide in the cerium dioxide dispersion to 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10.

19. The method of claim 18, wherein a molar ratio of a soluble cobalt salt in the soluble cobalt salt solution to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:2-10.

20. The method of claim 14, wherein the first stirring is conducted at a rotational speed of 300 revolutions per minute (rpm) to 800 rpm for 10 minutes (min) to 30 min;the second stirring is conducted at a rotational speed of 300 rpm to 800 rpm for 10 min to 30 min; andthe step 1 and the step 2 are repeated 3 times to 10 times.

21. An extreme pressure anti-wear additive prepared by the method of claim 14, comprising: cerium dioxide nanoparticles and a zeolitic imidazolate framework-67 (ZIF-67) coated on a surface of each of the cerium dioxide nanoparticles.

22. A lubricating oil, comprising: a base oil and an extreme pressure anti-wear additive; whereinthe extreme pressure anti-wear additive accounts for 0.1% to 1% by mass of the lubricating oil; andthe extreme pressure anti-wear additive is the extreme pressure anti-wear additive of claim 21.

23. The method of claim 15, wherein a molar ratio of the cerium dioxide in the cerium dioxide dispersion to 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10.

24. The method of claim 16, wherein a molar ratio of cerium dioxide in the cerium dioxide dispersion to the 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10.

25. The method of claim 17, wherein the molar ratio of cerium dioxide in the cerium dioxide dispersion to 2-methylimidazole in the 2-methylimidazole aqueous solution is in a range of 1:5-10.

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