Energy-saving and wear-reducing low-volatile lubricating oil for diesel vehicles and preparation method thereof

Abstract

The present application relates to the technical field of lubricating oil, and discloses energy-saving and wear-reducing low-volatility lubricating oil for diesel vehicles and a preparation method thereof, which comprises the following raw materials in parts by mass: poly-α-olefin copolymer 40-50 parts, benzoic acid 1.5-2 parts, alkyl alcohol amide 1-1.5 parts, dibutyl hydroxytoluene 1-1.5 parts, composite additive 2-3 parts, polymethyl methacrylate 1-2 parts, and bis(hexafluoroisopropyl) phosphate 1-2 parts. The energy-saving and wear-reducing low-volatility lubricating oil formed by mixing the poly-α-olefin copolymer, benzoic acid, alkyl alcohol amide, dibutyl hydroxytoluene, composite additive, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate has high wear-resistant lubricating performance, and the surface of the composite additive contains a copolymer of triethylene glycol divinyl ether and dodecene, so that the composite additive can be uniformly dispersed in the lubricating oil system to play the wear-resistant lubricating performance.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil technology, specifically to an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles and its preparation method. Background Technology

[0002] Diesel vehicle lubricating oil is a liquid or semi-solid lubricant used in diesel vehicles to reduce friction and protect machinery and processed parts. It primarily functions as a lubricant, auxiliary coolant, rust preventer, cleaner, sealant, and buffer. It undertakes key functions such as lubrication, cleaning, heat dissipation, and sealing. Diesel vehicle lubricating oil consists of two parts: base oil and additives. Base oil is the main component of the lubricating oil, determining its basic properties. Additives compensate for and improve the shortcomings of the base oil, imparting new properties and forming an important part of the lubricating oil. Compared to automotive lubricating oil, diesel vehicle lubricating oil contains more anti-wear agents to cope with high-pressure environments.

[0003] Lubricating oil base oils are mainly divided into three categories: mineral base oils, synthetic base oils, and bio-based base oils. Among them, mineral base oils are widely used. Lubricating oil additives include anti-wear agents, anti-oil agents, and rust inhibitors. The lubricity or wear resistance of lubricating oil is mainly determined by lubricating additives. However, the performance of lubricating oil additives is limited, resulting in poor wear resistance and lubrication performance of diesel vehicle lubricating oils. In addition, diesel vehicle lubricating oils have problems such as large high-temperature evaporation loss, high friction coefficient, and poor fuel economy. Summary of the Invention

[0004] This invention provides an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles and its preparation method. It solves the problems of limited performance of lubricating oil additives, which leads to poor wear resistance and lubrication performance of diesel vehicle lubricating oils, as well as the problems of high-temperature evaporation loss, high friction coefficient, and poor fuel economy in diesel vehicle lubricating oils.

[0005] The technical solution of this invention: A low-volatility, low-friction lubricating oil for diesel vehicles comprises the following raw materials in parts by weight: 40-50 parts of poly(α-olefin) copolymer, 1.5-2 parts of benzoic acid, 1-1.5 parts of alkylolamide, 1-1.5 parts of butylated hydroxytoluene, 2-3 parts of composite additives, 1-2 parts of polymethyl methacrylate, and 1-2 parts of bis(hexafluoroisopropyl) phosphate. The composite additive is obtained by reacting modified graphene oxide coated with sheet-like nano-chromium oxide on the surface of a silane coupling agent with triethylene glycol divinyl ether and dodecene. The modified graphene oxide coated with sheet-like nano-chromium oxide is formed by in-situ deposition of molybdenum disulfide nanosheets on the surface of graphene oxide, and then the modified graphene oxide is reacted with chromium acetate and ammonia.

[0006] A method for preparing an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles includes the following preparation steps: The poly(α-olefin) copolymer is stirred at 300-500 r / min and 30-40℃ for 20-30 min, and then benzoic acid, alkylolamide, dibutylhydroxytoluene, composite additives, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate are added. The mixture is stirred at 600-800 r / min and 30-40℃ for 20-30 min to obtain an energy-saving, friction-reducing and low-volatility lubricating oil.

[0007] Furthermore, the poly(α-olefin) copolymer is selected from any one of poly(α-olefin) PAO6, poly(α-olefin) PAO-8, and poly(α-olefin) PAO-10.

[0008] Furthermore, the composite additive is specifically prepared by the following steps: A1. Mix graphene oxide and deionized water, disperse by ultrasonication, add ammonium heptamolybdate tetrahydrate, thiourea, ethanol and nitric acid, stir evenly, place in a hydrothermal reactor, react at 210-230℃ for 22-24h, cool to room temperature, collect the precipitate by centrifugation, wash the precipitate and dry to obtain modified graphene oxide. A2. Mix modified graphene oxide, chromium acetate and deionized water, stir evenly, add ammonia water to adjust the pH to 8-9, stir at room temperature for 1.5-2.5h, place in a high-pressure reactor with a polytetrafluoroethylene liner, keep at 180-200℃ for 22-26h, cool to room temperature, collect the precipitate, wash and dry the precipitate, place in a muffle furnace, calcine at 280-320℃ for 3.5-4.5h to obtain composite graphene oxide; A3. Mix silane coupling agent, deionized water and ethanol, stir, add hydrochloric acid to adjust pH to 4-5, then add composite graphene oxide, stir and react at 70-80℃ for 1-2 hours, filter, wash and dry to obtain double-bonded composite graphene oxide. A4. Mix dodecene and double-bonded composite graphene oxide, and stir at 117-123℃ and 300-320 r / min for 30-40 min to obtain mixture a; in a uniform pressure dropping funnel, mix triethylene glycol divinyl ether and di-tert-butyl peroxide, and stir evenly to obtain mixture b; add mixture b dropwise to mixture a, and after the addition is complete, continue stirring at 117-123℃ for 1-1.5 h, remove unreacted dodecene by distillation, filter, wash, and dry to obtain composite additive.

[0009] Furthermore, in the A1 reaction process described above, graphene oxide serves as a nucleation site and a growth substrate for molybdenum disulfide nanosheets. Its surface is rich in hydroxyl, carboxyl, and epoxy functional groups. Ammonium heptamolybdate tetrahydrate provides the molybdenum source, which can be deposited on the surface of graphene oxide. Thiourea provides sulfur. Through hydrothermal reaction, petal-shaped molybdenum disulfide nanosheets are formed on the surface of graphene oxide, resulting in modified graphene oxide.

[0010] Furthermore, during the A2 reaction process described above, the modified graphene oxide surface contains a large number of hydroxyl functional groups, which can combine with chromium ions in chromium acetate, causing chromium ions to be deposited on the modified graphene oxide surface. Ammonia water can react with chromium acetate to form hydroxides. After reacting at 180-200℃ and calcining at 280-320℃, the hydroxides decompose upon heating to form sheet-like nanocrystals. The chromium oxide crystals self-assemble into nanosheet structures, thus forming sheet-like nano-chromium oxide on the surface of the modified graphene oxide, resulting in composite graphene oxide.

[0011] Furthermore, during the A3 reaction process described above, the composite graphene oxide is surface-modified with a silane coupling agent, which allows the hydroxyl groups generated by the hydrolysis of the silane coupling agent to chemically bond with the polar functional groups on the surface of the composite graphene oxide. This results in the silane coupling agent being grafted onto the surface of the composite graphene oxide, yielding a double-bonded composite graphene oxide.

[0012] Furthermore, in the A4 reaction process described above, di-tert-butyl peroxide acts as an initiator, causing the double-bonded composite graphene oxide, triethylene glycol divinyl ether, and dodecene to undergo a copolymerization reaction, thereby forming a copolymer of triethylene glycol divinyl ether and dodecene on the surface of the composite graphene oxide. The resulting copolymer tightly coats the surface of the composite graphene oxide, yielding a composite additive.

[0013] Further, in step A1, the mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol and nitric acid is (0.4-0.6):(100-120):(1-1.5):(2.5-3):(40-45):(70-80).

[0014] Further, in step A2, the mass ratio of the modified graphene oxide, chromium acetate, and deionized water is 0.5:1:(30-40).

[0015] Further, in step A3, the mass ratio of the silane coupling agent, deionized water, ethanol and composite graphene oxide is (0.1-0.12):(10-15):(80-90):(0.5-0.7).

[0016] Further, in step A4, the mass ratio of the dodecene to the double-bonded composite graphene oxide is (10-15):(0.6-0.8).

[0017] Further, in step A4, the mass ratio of the triethylene glycol divinyl ether to di-tert-butyl peroxide is (2-3):(0.5-0.6).

[0018] The present invention has the following beneficial effects: (1) In the technical solution of the present invention, petal-shaped molybdenum disulfide nanosheets are formed on the surface of graphene oxide. On the one hand, graphene oxide and molybdenum disulfide nanosheets serve as inorganic wear-resistant agents for lubricating oil, which can improve the lubrication performance of lubricating oil. Graphene oxide serves as a carrier for molybdenum disulfide nanosheets, which makes the molybdenum disulfide nanosheets uniformly distributed on the surface of graphene oxide, thus exerting lubrication performance. On the other hand, graphene oxide and molybdenum disulfide nanosheets are easy to slide and peel off the intermediate layer under frictional stress, thereby forming a more effective lubricating film at the contact interface and further reducing friction. In addition, the nanostructure can be maintained during the friction process, which helps to form a protective oxide friction film on the sliding surface, thereby further improving lubricity and wear resistance.

[0019] (2) In the technical solution of the present invention, sheet-like nano-chromium oxide is formed on the surface of modified graphene oxide. On the one hand, the formed sheet-like nano-chromium oxide has a layered structure similar to graphene and good wear resistance of chromium oxide itself, which further improves the wear resistance and lubrication of the lubricating oil. The sheet-like nano-chromium oxide is coated on the surface of molybdenum disulfide nanosheets, which can form a dense chromium oxide layer under high temperature environment, effectively isolating oxygen from direct contact with molybdenum disulfide nanosheets, avoiding the easy oxidation and failure of molybdenum disulfide nanosheets at high temperature, which affects the wear resistance and lubrication performance of the lubricating oil. On the other hand, the sheet-like nano-chromium oxide and modified graphene oxide form a multi-layer structure. Under frictional stress, the lubricating oil can easily slide between layers, thereby forming a more effective lubricating film at the contact interface, further reducing friction and enhancing the wear resistance and lubrication performance of the lubricating oil.

[0020] (3) In the technical solution of the present invention, the silane coupling agent is grafted onto the surface of the composite graphene oxide to obtain double-bonded composite graphene oxide, which is beneficial to form a copolymer of triethylene glycol divinyl ether and dodecene on the surface of the composite graphene oxide. The copolymer formed tightly coats the surface of the composite graphene oxide, preventing the multilayer nanosheets of the composite graphene oxide from falling off under long-term friction of the lubricating oil, thus affecting the wear resistance and lubrication performance of the lubricating oil. A copolymerization reaction is carried out between double-bonded composite graphene oxide, triethylene glycol divinyl ether, and dodecene to form a copolymer of triethylene glycol divinyl ether and dodecene on the surface of composite graphene oxide. On the one hand, the formed triethylene glycol divinyl ether and dodecene have excellent compatibility with base oil, which allows the composite additive to be uniformly dispersed in the lubricating oil system and exert wear-resistant lubrication performance. Moreover, the formed copolymer tightly coats the surface of composite graphene oxide, preventing the multilayer nanosheets of composite graphene oxide from falling off under long-term friction and affecting the wear-resistant lubrication performance of the lubricating oil. On the other hand, the formed copolymer has good friction reduction, wear resistance, and viscosity index. In addition, the formed composite additive can reduce the volatility of lubricating oil during high-temperature use.

[0021] By utilizing chromium oxide as a preferential oxidation sacrificial layer, in scenarios involving localized engine hotspots (such as the piston ring boundary lubrication zone, where instantaneous temperatures can reach 200-300℃) and cumulative oxidation during oil change cycles, chromium oxide nanosheets delay the edge oxidation of molybdenum disulfide by capturing reactive oxygen free radicals and preferentially forming a chromate passivation layer. This protection is of practical significance under long-term use (>50,000 km) and harsh high-temperature conditions. The total amount of composite additives (graphene + molybdenum disulfide + chromium oxide) is equivalent to an effective solid content of only 0.3-0.6%, which is far below the abrasive wear threshold. Among them, chromium oxide is an ultra-thin sheet of 5-10nm, and its hardness (Mohs 8.5) is lower than that of hard carbides in cylinder liner materials (Mohs > 9). During cyclic shearing, it will be oriented rather than scraping the metal surface, and will form a low-shear transfer film in conjunction with the remaining inorganic matter. The wear scar diameter was ≤0.40mm in laboratory four-ball machine tests, which verified the wear reduction effect.

[0022] (4) In the technical solution of the present invention, the energy-saving, friction-reducing and low-volatility lubricating oil formed by mixing poly(α-olefin copolymer), composite additive, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate has high wear resistance and lubrication performance, low volatility, and improved fuel economy. Moreover, the surface of the composite additive contains a copolymer of triethylene glycol divinyl ether and dodecene, which enables the composite additive to be uniformly dispersed in the lubricating oil system and exert wear resistance and lubrication performance. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0025] The poly(α-olefin) copolymer is poly(α-olefin) PAO6, with a kinematic viscosity of 5.9 cst (100℃), a viscosity index of 135, and a pour point of -68℃, and was purchased from Shanghai Daopu Chemical Co., Ltd.

[0026] The polymethyl methacrylate (PMMA) product number is P693420, Mw=500000~600000, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0027] The graphene oxide is a single-layer graphene oxide, with the product number G931286 and a sheet diameter of 0.5-5μm, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0028] The silane coupling agent is KH570 (γ-methacryloyloxypropyltrimethoxysilane).

[0029] Example 1 A low-volatility, low-friction lubricating oil for diesel vehicles comprises the following raw materials in parts by weight: 40 parts of poly(α-olefin) copolymer, 1.5 parts of benzoic acid, 1 part of alkylolamide, 1 part of butylated hydroxytoluene, 2 parts of composite additives, 1 part of polymethyl methacrylate, and 1 part of bis(hexafluoroisopropyl) phosphate. A method for preparing an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles includes the following preparation steps: The poly(α-olefin) copolymer was stirred at 300 rpm and 30°C for 20 min, and then benzoic acid, alkylolamide, dibutylhydroxytoluene, composite additives, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate were added. The mixture was stirred at 600 rpm and 30°C for 20 min to obtain an energy-saving, friction-reducing and low-volatility lubricating oil.

[0030] The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 210℃ for 22 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.4:100:1:2.5:40:70. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 8. After stirring at 25℃ for 1.5h, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 180℃ for 22h. After cooling to room temperature, the precipitate was collected. The precipitate was washed 3 times with ethanol and 5 times with deionized water. It was dried in an oven at 60℃ for 10h and then calcined in a muffle furnace at 280℃ for 3.5h to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:30. A3. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 4. Composite graphene oxide was then added, and the mixture was stirred and reacted at 70 °C for 1 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.1:10:80:0.5. A4. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 117 °C and 300 r / min for 30 min to obtain mixture a; the mass ratio of dodecene to double-bonded composite graphene oxide was 10:0.6. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 117 °C for 1 hour, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 2:0.5.

[0031] Example 2 A low-volatility, low-friction lubricating oil for diesel vehicles comprises the following raw materials in parts by weight: 45 parts of poly(α-olefin) copolymer, 1.8 parts of benzoic acid, 1.3 parts of alkylolamide, 1.3 parts of butylated hydroxytoluene, 2.5 parts of composite additives, 1.5 parts of polymethyl methacrylate, and 1.5 parts of bis(hexafluoroisopropyl) phosphate. A method for preparing an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles includes the following preparation steps: The poly(α-olefin) copolymer was stirred at 400 r / min and 35℃ for 25 min, and then benzoic acid, alkylolamide, dibutylhydroxytoluene, composite additives, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate were added. The mixture was stirred at 700 r / min and 35℃ for 30 min to obtain an energy-saving, friction-reducing and low-volatility lubricating oil.

[0032] The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 220℃ for 23 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.5:110:1.3:2.8:43:75. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 8.5. After stirring at 25℃ for 2 hours, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 190℃ for 24 hours. After cooling to room temperature, the precipitate was collected. The precipitate was washed three times with ethanol and five times with deionized water. It was dried in an oven at 60℃ for 10 hours and then calcined in a muffle furnace at 300℃ for 4 hours to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:35. A3. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 4.5. Composite graphene oxide was then added, and the mixture was stirred and reacted at 75 °C for 1.5 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.11:13:85:0.6. A4. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 120 °C and 310 r / min for 35 min to obtain mixture a; the mass ratio of dodecene to double-bonded composite graphene oxide was 13:0.7. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 120 °C for 1.3 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 2.5:0.55.

[0033] Example 3 A low-volatility, low-friction lubricating oil for diesel vehicles comprises the following raw materials in parts by weight: 50 parts of poly(α-olefin) copolymer, 2 parts of benzoic acid, 1.5 parts of alkylolamide, 1.5 parts of butylated hydroxytoluene, 3 parts of composite additives, 2 parts of polymethyl methacrylate, and 2 parts of bis(hexafluoroisopropyl) phosphate. A method for preparing an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles includes the following preparation steps: The poly(α-olefin) copolymer was stirred at 500 rpm and 40°C for 30 min, and then benzoic acid, alkylolamide, dibutylhydroxytoluene, composite additives, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate were added. The mixture was stirred at 800 rpm and 40°C for 30 min to obtain an energy-saving, friction-reducing and low-volatility lubricating oil.

[0034] The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 230℃ for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.6:120:1.5:3:45:80. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 9. After stirring at 25℃ for 2.5h, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 200℃ for 26h. After cooling to room temperature, the precipitate was collected. The precipitate was washed 3 times with ethanol and 5 times with deionized water. It was dried in an oven at 60℃ for 10h and then calcined in a muffle furnace at 320℃ for 4.5h to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:40. A3. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 5. Composite graphene oxide was then added, and the mixture was stirred and reacted at 80 °C for 2 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.12:15:90:0.7. A4. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of dodecene to double-bonded composite graphene oxide was 15:0.8. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0035] Comparative Example 1 The only difference between this comparative example and Example 3 is the preparation of the composite additive, as detailed below: The composite additive is prepared by the following steps: A1. Graphene oxide, chromium acetate, and deionized water were mixed and stirred until homogeneous. Ammonia water with a mass fraction of 36% was added to adjust the pH to 9. After stirring at 25°C for 2.5 hours, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 200°C for 26 hours. After cooling to room temperature, the precipitate was collected. The precipitate was washed three times with ethanol and five times with deionized water. It was dried in an oven at 60°C for 10 hours and then calcined in a muffle furnace at 320°C for 4.5 hours to obtain composite graphene oxide. The mass ratio of graphene oxide, chromium acetate, and deionized water was 0.5:1:40. A2. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 5. Composite graphene oxide was then added, and the mixture was stirred at 80 °C for 2 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.12:15:90:0.7. A3. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of dodecene to double-bonded composite graphene oxide was 15:0.8. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0036] Comparative Example 2 The only difference between this comparative example and Example 3 is the preparation of the composite additive, as detailed below: The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 230℃ for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.6:120:1.5:3:45:80. A2. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 5. Composite graphene oxide was then added, and the mixture was stirred and reacted at 80℃ for 2 h. After filtration, the mixture was washed three times with deionized water and dried in a 70℃ oven for 10 min to obtain double-bonded modified graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.12:15:90:0.7. A3. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of dodecene to double-bonded modified graphene oxide was 15:0.8. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0037] Comparative Example 3 The only difference between this comparative example and Example 3 is the preparation of the composite additive, as detailed below: The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 230℃ for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.6:120:1.5:3:45:80. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 9. After stirring at 25℃ for 2.5h, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 200℃ for 26h. After cooling to room temperature, the precipitate was collected. The precipitate was washed 3 times with ethanol and 5 times with deionized water. It was dried in an oven at 60℃ for 10h and then calcined in a muffle furnace at 320℃ for 4.5h to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:40. A3. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of dodecene to composite graphene oxide was 15:0.8. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0038] Comparative Example 4 The only difference between this comparative example and Example 3 is the preparation of the composite additive, as detailed below: The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 230℃ for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.6:120:1.5:3:45:80. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 9. After stirring at 25℃ for 2.5h, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 200℃ for 26h. After cooling to room temperature, the precipitate was collected. The precipitate was washed 3 times with ethanol and 5 times with deionized water. It was dried in an oven at 60℃ for 10h and then calcined in a muffle furnace at 320℃ for 4.5h to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:40. A3. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 5. Composite graphene oxide was then added, and the mixture was stirred and reacted at 80 °C for 2 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.12:15:90:0.7. A4. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser, and a temperature sensor, triethylene glycol divinyl ether and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of triethylene glycol divinyl ether to double-bonded composite graphene oxide was 15:0.8. In a 250 mL equalizing dropping funnel, triethylene glycol divinyl ether and di-tert-butyl peroxide were mixed and stirred until homogeneous to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain a composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0039] Comparative Example 5 The only difference between this comparative example and Example 3 is the preparation of the composite additive, as detailed below: The composite additive is prepared by the following steps: A1. Graphene oxide and deionized water were mixed and ultrasonically dispersed at 300W for 5 min. Ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid were added. The mixture was stirred at 25℃ for 20 min and placed in a hydrothermal reactor. The reaction was carried out at 230℃ for 24 h. After cooling to room temperature, the precipitate was collected by centrifugation. The precipitate was washed three times with ethanol and three times with deionized water. It was then dried in an oven at 60℃ for 24 h to obtain modified graphene oxide. The mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol, and nitric acid was 0.6:120:1.5:3:45:80. A2. Modified graphene oxide, chromium acetate, and deionized water were mixed and stirred evenly. Ammonia water with a mass fraction of 36% was added to adjust the pH to 9. After stirring at 25℃ for 2.5h, the mixture was placed in a high-pressure reactor with a polytetrafluoroethylene liner and kept at 200℃ for 26h. After cooling to room temperature, the precipitate was collected. The precipitate was washed 3 times with ethanol and 5 times with deionized water. It was dried in an oven at 60℃ for 10h and then calcined in a muffle furnace at 320℃ for 4.5h to obtain composite graphene oxide. The mass ratio of modified graphene oxide, chromium acetate, and deionized water was 0.5:1:40. A3. KH570, deionized water, and ethanol were mixed and stirred for 10 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 5. Composite graphene oxide was then added, and the mixture was stirred and reacted at 80 °C for 2 h. After filtration, the mixture was washed three times with deionized water and dried in a 70 °C oven for 10 min to obtain double-bonded composite graphene oxide. The mass ratio of KH570, deionized water, ethanol, and composite graphene oxide was 0.12:15:90:0.7. A4. In a 1000 mL three-necked flask equipped with a mechanical stirrer, a reflux condenser and a temperature sensor, dodecene and double-bonded composite graphene oxide were mixed and stirred at 123 °C and 320 r / min for 40 min to obtain mixture a; the mass ratio of dodecene to double-bonded composite graphene oxide was 15:0.8. Dodecene and di-tert-butyl peroxide were mixed and stirred evenly in a 250 mL equalizing dropping funnel to obtain mixture b. Mixture b was added dropwise to mixture a at a rate of one drop every 6 seconds, and the addition process was completed within 5 hours. The mixture was stirred at 123 °C for 1.5 hours, and then distilled at 230 °C to remove unreacted dodecene. After filtration, the mixture was washed three times with ethanol and dried in an oven at 80 °C for 10 minutes to obtain the composite additive. The mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide was 3:0.6.

[0040] The performance of the lubricating oils prepared in Examples 1-3 and Comparative Examples 1-5 was then tested.

[0041] Anti-wear and lubrication performance testing: Four-ball test: Tested according to ASTM D-2783; In the four-ball test results, at a certain temperature and speed, the maximum non-seize load PB value represents the maximum load at which the steel balls do not seize under lubrication. The higher the PB value, the better the lubrication performance of the lubricating oil; the sintering load PD value represents the load at which the upper and lower steel balls sinter at high temperature due to excessive load, forcing the equipment to stop operating. The higher the PD value, the better the extreme pressure lubrication performance of the lubricating oil; the wear scar diameter d value represents the size of the wear scar diameter caused by friction on the surface of the load-bearing steel ball. The smaller the d value, the better the anti-wear ability and lubrication of the lubricating oil.

[0042] Viscosity index: Tested according to GB / T1995-88.

[0043] Volatility test: The volatility of the lubricating oil prepared above was determined according to the standard NB / SH / T0059-2010 "Determination of Evaporation Loss of Lubricating Oil - Noake Method"; specifically: the lubricating oil prepared above (mass M1) was weighed, the crucible evaporator was heated to 250±0.5℃, and the sample surface was passed through with a constant air flow rate of 17-20L / h. After being kept at 250℃ for 1h, it was cooled to room temperature, and the mass of the lubricating oil after evaporation (mass M2) was weighed. The evaporation loss rate was calculated; evaporation loss rate (%) = (M1-M2) / M1×100%.

[0044] The test results are shown in Table 1 below.

[0045] Table 1. Performance testing of energy-saving, friction-reducing, and low-volatility lubricating oils prepared in Examples 1-3 and Comparative Examples 1-5. ; As can be seen from the data in Table 1, the energy-saving, friction-reducing, and low-volatility lubricating oils prepared in Examples 1-3 have high wear-resistant lubrication performance, and the composite additives can be uniformly dispersed in the lubricating oil system to exert wear-resistant lubrication performance.

[0046] Comparative Example 1 showed that when modified graphene oxide was replaced with a composite additive prepared from graphene oxide, the lubricating oil's performance decreased. This demonstrates that the formation of petal-shaped molybdenum disulfide nanosheets on the surface of graphene oxide as an inorganic wear-resistant agent can improve the lubrication performance of the lubricating oil. Furthermore, under frictional stress, the graphene oxide and molybdenum disulfide nanosheets can easily undergo interlayer sliding and peeling, thereby forming a more effective lubricating film at the contact interface and further reducing friction. In addition, the nanostructure can be maintained during friction, which helps to form a protective oxide friction film on the sliding surface, thereby further improving lubricity and wear resistance.

[0047] Comparative Example 2 showed that when composite graphene oxide was replaced with a composite additive prepared by modifying graphene oxide, the lubricating oil's performance decreased. This demonstrates that the sheet-like nano-chromium oxide formed on the surface of modified graphene oxide has a layered structure similar to graphene, and chromium oxide itself has good wear resistance, further improving the wear resistance and lubrication of the lubricating oil. Moreover, the sheet-like nano-chromium oxide coated on the surface of molybdenum disulfide nanosheets can form a dense chromium oxide layer under high temperature conditions, which can effectively isolate oxygen from direct contact with molybdenum disulfide nanosheets, preventing the molybdenum disulfide nanosheets from easily oxidizing and failing at high temperatures, thus affecting the wear resistance and lubrication performance of the lubricating oil. In addition, the sheet-like nano-chromium oxide and modified graphene oxide form a multilayer structure, and the lubricating oil can easily slide between layers under frictional stress, thereby forming a more effective lubricating film at the contact interface, further reducing friction and enhancing the wear resistance and lubrication performance of the lubricating oil.

[0048] Comparative Example 3 showed that when double-bonded composite graphene was replaced with composite graphene-based additives and added to an energy-saving, friction-reducing, and low-volatility lubricating oil, the lubricating oil performance decreased. This demonstrated that grafting silane coupling agents onto the surface of composite graphene to obtain double-bonded composite graphene facilitates the formation of a copolymer of triethylene glycol divinyl ether and dodecene on the surface of composite graphene. The resulting copolymer tightly coats the surface of composite graphene, preventing the multilayer nanosheets of composite graphene from falling off under long-term friction and affecting the wear resistance and lubrication performance of the lubricating oil.

[0049] Comparative Example 4, in which dodecene was replaced by an equal mass of triethylene glycol divinyl ether, and Comparative Example 5, in which triethylene glycol divinyl ether was replaced by an equal mass of dodecene, were added to an energy-saving, friction-reducing, and low-volatility lubricating oil. The lubricating oil's performance decreased, demonstrating that the double-bonded composite graphene oxide, triethylene glycol divinyl ether, and dodecene undergo a copolymerization reaction, forming a copolymer of triethylene glycol divinyl ether and dodecene on the surface of the composite graphene oxide. This copolymer exhibits excellent compatibility with the base oil, allowing the composite additive to be uniformly dispersed in the lubricating oil system, thus exerting its wear-resistant and lubricating properties. Furthermore, the formed copolymer tightly coats the surface of the composite graphene oxide, preventing the multilayer nanosheets of the composite graphene oxide from detaching under long-term friction, which would affect the lubricating oil's wear-resistant and lubricating performance. In addition, the formed copolymer possesses good friction-reducing, wear-resistant, and viscosity index properties. Simultaneously, the composite additive can reduce the volatility of the lubricating oil during high-temperature use.

[0050] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A low-volatility, low-friction lubricating oil for diesel vehicles, characterized in that, The raw materials include the following parts by weight: 40-50 parts of poly(α-olefin) copolymer, 1.5-2 parts of benzoic acid, 1-1.5 parts of alkylolamide, 1-1.5 parts of butylated hydroxytoluene, 2-3 parts of composite additives, 1-2 parts of polymethyl methacrylate, and 1-2 parts of bis(hexafluoroisopropyl) phosphate. The composite additive is obtained by reacting modified graphene oxide coated with sheet-like nano-chromium oxide on the surface of a silane coupling agent with triethylene glycol divinyl ether and dodecene. The modified graphene oxide coated with sheet-like nano-chromium oxide is formed by in-situ deposition of molybdenum disulfide nanosheets on the surface of graphene oxide, and then the modified graphene oxide is reacted with chromium acetate and ammonia.

2. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 1, characterized in that, The composite additive is prepared by the following steps: A1. Mix graphene oxide and deionized water, disperse by ultrasonication, add ammonium heptamolybdate tetrahydrate, thiourea, ethanol and nitric acid, stir evenly, place in a hydrothermal reactor, react at 210-230℃ for 22-24h, cool to room temperature, collect the precipitate by centrifugation, wash the precipitate and dry to obtain modified graphene oxide. A2. Mix modified graphene oxide, chromium acetate and deionized water, stir evenly, add ammonia water to adjust the pH to 8-9, stir at room temperature for 1.5-2.5h, place in a high-pressure reactor with a polytetrafluoroethylene liner, keep at 180-200℃ for 22-26h, cool to room temperature, collect the precipitate, wash and dry the precipitate, place in a muffle furnace, calcine at 280-320℃ for 3.5-4.5h to obtain composite graphene oxide; A3. Mix silane coupling agent, deionized water and ethanol, stir, add hydrochloric acid to adjust pH to 4-5, then add composite graphene oxide, stir and react at 70-80℃ for 1-2 hours, filter, wash and dry to obtain double-bonded composite graphene oxide. A4. Mix dodecene and double-bonded composite graphene oxide, and stir at 117-123℃ and 300-320 r / min for 30-40 min to obtain mixture a; in a uniform pressure dropping funnel, mix triethylene glycol divinyl ether and di-tert-butyl peroxide, and stir evenly to obtain mixture b; add mixture b dropwise to mixture a, and after the addition is complete, continue stirring at 117-123℃ for 1-1.5 h, remove unreacted dodecene by distillation, filter, wash, and dry to obtain composite additive.

3. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 2, characterized in that, In step A1, the mass ratio of graphene oxide, deionized water, ammonium heptamolybdate tetrahydrate, thiourea, ethanol and nitric acid is (0.4-0.6):(100-120):(1-1.5):(2.5-3):(40-45):(70-80).

4. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 2, characterized in that, In step A2, the mass ratio of the modified graphene oxide, chromium acetate, and deionized water is 0.5:1:(30-40).

5. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 2, characterized in that, In step A3, the mass ratio of the silane coupling agent, deionized water, ethanol and composite graphene oxide is (0.1-0.12):(10-15):(80-90):(0.5-0.7).

6. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 2, characterized in that, In step A4, the mass ratio of the dodecene to the double-bonded composite graphene oxide is (10-15):(0.6-0.8); In step A4, the mass ratio of triethylene glycol divinyl ether to di-tert-butyl peroxide is (2-3):(0.5-0.6).

7. The energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles according to claim 1, characterized in that, The poly(α-olefin) copolymer is selected from any one of poly(α-olefin) PAO6, poly(α-olefin) PAO-8, and poly(α-olefin) PAO-10.

8. A method for preparing an energy-saving, friction-reducing, and low-volatility lubricating oil for diesel vehicles as described in any one of claims 1-7, characterized in that, The preparation steps include the following: The poly(α-olefin) copolymer is stirred at 300-500 r / min and 30-40℃ for 20-30 min, and then benzoic acid, alkylolamide, dibutylhydroxytoluene, composite additives, polymethyl methacrylate and bis(hexafluoroisopropyl) phosphate are added. The mixture is stirred at 600-800 r / min and 30-40℃ for 20-30 min to obtain an energy-saving, friction-reducing and low-volatility lubricating oil.