Lubricating oil composition for steam engine cylinder and preparation method of lubricating oil composition

Abstract

The present invention discloses a steam engine cylinder lubricating oil composition and a preparation method thereof, and particularly relates to the technical field of cylinder oil preparation, the steam engine cylinder lubricating oil composition comprises, by mass, 50-90% of base oil, 5-40% of a viscosity index improver, 0.001-0.003% of nanometer copper powder, 1-5% of an additive and 0.1-1% of a pour point depressant. By optimizing the ratio of the base oil to the composite additive, stable tribological performance is kept during long-term operation, the composition can remarkably reduce abnormal wear of a cylinder sleeve and a piston ring and prolong the service life of parts, and the composition has the characteristics of low ash content and low carbon residue and effectively reduces sediments; the high-flash-point design ensures the use safety under the working conditions of high temperature and high pressure, provides long-acting lubrication protection for reliable operation of the steam engine, can reduce the diameter of wear scars, and enhances the anti-shearing performance at high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of cylinder oil preparation, and more particularly to a lubricating oil composition for a steam engine cylinder and a preparation method thereof. Background Art

[0002] Steam engine cylinder oil is the core lubricating medium that ensures the efficient operation of the cylinder-piston group of steam-powered equipment (such as steam locomotives, ship steam engines, industrial boiler drive systems, etc.). It needs to provide continuous lubrication and prevent metal corrosion and wear under extreme operating conditions such as high temperature (above 150°C), high-pressure steam scouring, condensate infiltration, and intermittent start-stop. The core lubricating components of this type of equipment have different requirements for oil performance: the cylinder-piston group needs to form a stable oil film under high temperature and high pressure to resist steam scouring and reduce direct metal contact; transmission components (such as connecting rod bearings and valve stems) require oil with excellent anti-wear properties to reduce surface damage caused by start-stop impact; and the condensate circulation system requires efficient anti-emulsification ability to prevent water intrusion that may cause oil failure and metal corrosion.

[0003] Existing cylinder oils are mostly based on high-viscosity mineral oils. While these oils can meet high-temperature lubrication requirements through the use of a large amount of thickeners, they suffer from deficiencies in key performance characteristics such as wear resistance, durability, and water separation efficiency, which can easily lead to problems such as piston ring sticking, bearing wear, and pipeline corrosion. Extreme environments further exacerbate lubrication challenges. At low temperatures, the viscosity of traditional mineral-based cylinder oils increases dramatically, significantly reducing their fluidity. This causes delayed lubrication during startup and exacerbates component wear. During high-temperature, full-load operation (locally exceeding 200°C), oil oxidation accelerates, easily forming colloids and varnishes, which clog oil lines and compromise sealing performance. Furthermore, in high-humidity and dusty environments, steam-borne condensate and particulate contaminants can easily cause oil emulsification and abrasive wear, further shortening equipment maintenance cycles. While currently available cylinder oils meet basic lubrication requirements, they often suffer from insufficient high-temperature oil film strength, weak anti-emulsification properties, and poor long-term operational stability under harsh conditions such as high-pressure steam and condensate corrosion. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a lubricating oil composition for a steam engine cylinder and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solution: a lubricating oil composition for a steam engine cylinder, comprising, by weight percentage, 50-90% of a base oil, 5-40% of a viscosity index improver, 0.001-0.003% of nano copper powder, 1-5% of an additive, and 0.1-1% of a pour point depressant; The base oil is composed of mineral oil, coal-based synthetic oil (CTL) and ester synthetic oil, and the mass percentages thereof are: Mineral oil: 40-70%, Coal-to-liquid (CTL): 20-50%, Ester synthetic oil: 5-10%.

[0006] As a further improvement of the technical solution of the present invention, in the nano copper powder, the mass proportion of graphene or molybdenum disulfide is 0.01-0.05%, and the composite particles are prepared by a ball milling process, with an average particle size of less than 50 nm.

[0007] As a further improvement to the technical solution of the present invention, the ester synthetic oil is pentaerythritol ester; in the base oil, the mass ratio of coal-based synthetic oil (CTL) to mineral oil is 1: (0.5-1.0); and the viscosity index improver is one of polyisobutylene and polymethacrylate, or a mixture of the two in a mass ratio of 1: (0.1-0.2).

[0008] As a further improvement of the technical solution of the present invention, the additives also include: 1.0-2.5% alkyl diphenylamine or phenol antioxidant, 0.2-1% phosphate-based ionic liquid anti-wear agent; 1-2% oil-soluble polyether DL-32 or amine and epoxide condensate T1001 demulsifier.

[0009] As a further improvement of the technical solution of the present invention, the pour point depressant is one of alkyl naphthalene and polymethacrylate or a mixture of the two in a mass ratio of 1:(0.2-0.5).

[0010] The method for preparing nano copper powder comprises the following steps: S1. Prepare raw materials for making nano-copper powder, including: graphene or molybdenum disulfide, 40-60% copper nitrate (Cu(NO3)2), 35-50% N,N′-dimethylbisacrylamide (DMAA), 1-10% polyvinylpyrrolidone (PVP), and 1-10% ammonium sulfate (NH4SO4), wherein the addition amount of graphene or molybdenum disulfide is 0.01-0.05% of the mass of copper nitrate; S2, copper nitrate, graphene or molybdenum disulfide, N,N′-dimethylbisacrylamide (DMAA), and polyvinylpyrrolidone (PVP) were mixed in water and ball-milled for 48 hours; S3, adding ammonium sulfate and heating to 80°C to form a wet gel; S4, pre-calcining the wet gel at 300 ° C for 1 hour, then heating to 500 ° C for 3 hours; S5. Reducing the copper-graphene or copper-molybdenum disulfide composite particles in an argon-hydrogen mixture (volume ratio 1:1) at 450° C. for 4 hours.

[0011] A method for preparing a lubricating oil composition for a steam engine cylinder, the preparation method comprising the following steps: Step 1: Mix the base oil and viscosity index improver at 50°C and stir for 30 minutes; Step 2: Heat to 70°C, add additives, and ultrasonically disperse for 20 minutes; Step 3: Cool down to 60°C, add copper-graphene or copper-molybdenum disulfide composite particles, and homogenize at 10,000 rpm for 1 hour; Step 4: Add pour point depressant and continue stirring for 10 minutes.

[0012] As a further improvement to the technical solution of the present invention, after the completion of step three, vacuum dehydration treatment is required: dehydration at -0.1 MPa and 80° C. for 2 hours to make the moisture content ≤50 ppm.

[0013] As a further improvement of the technical solution of the present invention, the vacuum dehydration treatment needs to be followed by microfiltration purification treatment: 0.1 μm ceramic membrane filtration is used to remove undispersed particulate impurities.

[0014] The present invention provides a lubricating oil composition specifically for steam engine cylinders. By optimizing the ratio of base oil and composite additives, the composition maintains stable tribological properties during long-term operation. The composition can significantly reduce abnormal wear of cylinder liners and piston rings, extending the service life of components. The composition has low ash content and low carbon residue, effectively reducing deposits. The high flash point design ensures safe use under high-temperature and high-pressure conditions, providing long-term lubrication protection for the reliable operation of steam engines. On this basis, the following beneficial effects are also specifically achieved: 1. During the preparation of nano-copper powder, a small amount of graphene or molybdenum disulfide is added as a co-grinding material, and copper-graphene composite particles are formed through a ball milling process. The layered structure of graphene is used to further reduce the friction coefficient and improve the load-bearing capacity of the nano-copper powder. The synergistic effect of the composite particles can reduce the wear spot diameter and enhance the shear resistance at high temperatures. 2. Add 5-10% of ester oil (such as pentaerythritol ester) to the existing mineral oil and CTL synthetic oil to enhance the dispersion of nano-copper powder by utilizing its high polarity. Set the ratio of CTL to mineral oil in the base oil to 1:0.5-1.0 to improve low-temperature fluidity. 3. Use ionic liquid anti-wear agents (such as phosphate-based ionic liquids) to form a chemical adsorption film at high temperature, which complements the physical protective layer of nano-copper powder; 4. In the preparation process of nano-copper powder, a staged calcination is adopted. The calcination step is divided into two stages. First, pre-calcination at 300°C for 1 hour to remove organic matter, and then the temperature is raised to 500°C to complete crystallization and avoid particle agglomeration. Then, hydrogen reduction optimization is carried out. During the reduction stage, an argon-hydrogen mixture (volume ratio of 1:1) is introduced to control the reduction rate to obtain nano-copper with more uniform particle size (<30nm). 5. A gradient mixing method for the lubricating oil was designed, using segmented heating and stirring: the base oil and viscosity index improver were premixed at 50°C for 30 minutes; the additives were added after heating to 70°C, and ultrasonic dispersion was carried out for 20 minutes; finally, nano-copper powder was slowly added at 60°C and processed using a high-speed homogenizer (10,000 rpm) for 1 hour to ensure uniform dispersion of the nanoparticles, avoid nano-copper powder sedimentation, and improve oil stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Flow chart of the preparation of the lubricating oil composition of the present invention. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] A lubricating oil composition for a steam engine cylinder, comprising, by weight percentage, 50-90% of a base oil, 5-40% of a viscosity index improver, 0.001-0.003% of nano copper powder, 1-5% of an additive, and 0.1-1% of a pour point depressant. The base oil is composed of mineral oil, coal-based synthetic oil (CTL) and ester synthetic oil, and the mass percentages are as follows: Mineral oil: 40-70%, Coal-to-liquid (CTL): 20-50%, Ester synthetic oil: 5-10%.

[0018] Preferably, in the nano copper powder, the mass proportion of graphene or molybdenum disulfide is 0.01-0.05%, and the composite particles are prepared by ball milling process, with an average particle size of less than 50 nm.

[0019] Preferably, the ester synthetic oil is pentaerythritol ester; in the base oil, the mass ratio of coal-based synthetic oil (CTL) to mineral oil is 1: (0.5-1.0), and the viscosity index improver is one of polyisobutylene and polymethacrylate or a mixture of the two in a mass ratio of 1: (0.1-0.2).

[0020] Preferably, the additives further include: 1.0-2.5% alkyl diphenylamine or phenol antioxidant, 0.2-1% phosphate-based ionic liquid anti-wear agent; and 1-2% oil-soluble polyether DL-32 or amine and epoxide condensate T1001 demulsifier.

[0021] Preferably, the pour point depressant is one of alkyl naphthalene and polymethacrylate or a mixture of the two in a mass ratio of 1:(0.2-0.5).

[0022] The method for preparing nano copper powder in a lubricating oil composition comprises the following steps: S1. Prepare raw materials for making nano-copper powder, including: graphene or molybdenum disulfide, 40-60% copper nitrate (Cu(NO3)2), 35-50% N,N′-dimethylbisacrylamide (DMAA), 1-10% polyvinylpyrrolidone (PVP), and 1-10% ammonium sulfate (NH4SO4). The addition amount of graphene or molybdenum disulfide is 0.01-0.05% of the mass of copper nitrate. S2, copper nitrate, graphene or molybdenum disulfide, N,N′-dimethylbisacrylamide (DMAA), and polyvinylpyrrolidone (PVP) were mixed in water and ball-milled for 48 hours; S3, adding ammonium sulfate and heating to 80°C to form a wet gel; S4, pre-calcining the wet gel at 300 ° C for 1 hour, then heating to 500 ° C for 3 hours; S5. Reducing the copper-graphene or copper-molybdenum disulfide composite particles in an argon-hydrogen mixture (volume ratio 1:1) at 450° C. for 4 hours.

[0023] As attached Figure 1 As shown, a method for preparing a lubricating oil composition for a steam engine cylinder, the preparation method comprises the following steps: Step 1: Mix the base oil and viscosity index improver at 50°C and stir for 30 minutes; Step 2: Heat to 70°C, add additives, and ultrasonically disperse for 20 minutes; Step 3: Cool down to 60°C, add copper-graphene or copper-molybdenum disulfide composite particles, and homogenize at 10,000 rpm for 1 hour; Step 4: Add pour point depressant and continue stirring for 10 minutes.

[0024] Preferably, after step three is completed, vacuum dehydration treatment is required: dehydration at -0.1 MPa and 80°C for 2 hours to make the moisture content ≤50 ppm. After vacuum dehydration treatment, microfiltration purification treatment is required: 0.1 μm ceramic membrane filtration is used to remove undispersed particulate impurities.

[0025] Among them, the synthetic oil used in this technical solution, especially coal-based synthetic oil CTL, has excellent high and low temperature performance, which can enable the product to maintain stable viscosity over a wide temperature range. The added viscosity index improver, especially polymethacrylic acid viscosity index improver, can improve oil film strength and adhesion, thereby significantly enhancing the product's adaptability and protective effect under harsh working conditions such as high temperature and high pressure.

[0026] The technical effect of this technical solution is that: during the preparation of nano-copper powder, a small amount (0.01-0.05%) of graphene or molybdenum disulfide is added as a co-grinding material, and copper-graphene composite particles are formed through a ball milling process. The layered structure of graphene is used to further reduce the friction coefficient, while improving the load-bearing capacity of the nano-copper powder. The synergistic effect of the composite particles can reduce the wear spot diameter and enhance the shear resistance at high temperatures. The introduction of coal-based synthetic oil, whose molecular structure is uniform, significantly improves oil film strength and ensures continuous lubrication under high-temperature conditions. The addition of nano-copper powder forms a dynamic protective layer at the friction interface, which not only reduces the friction coefficient but also fills minor surface damage on equipment, achieving a dual "anti-wear and repair" effect. Through a balanced formulation system design, the product combines high-temperature adhesion, long-term anti-wear, rapid oil-water separation, and low ash content, making it environmentally friendly and suitable for the complex working environment of steam engine cylinders. On the basis of existing mineral oil and CTL synthetic oil, 5-10% of ester oil (such as pentaerythritol ester) is added to enhance the dispersion of nano copper powder by taking advantage of its high polarity. The ratio of CTL to mineral oil in the base oil is set to 1:0.5-1.0 to improve low-temperature fluidity. Using ionic liquid anti-wear agents (such as phosphate-based ionic liquids) to form a chemical adsorption film at high temperature, which complements the physical protective layer of nano-copper powder; During the preparation of the nano-copper powder, a staged calcination process was adopted. The calcination step was divided into two stages: a pre-calcination at 300°C for one hour to remove organic matter, and then the temperature was raised to 500°C to complete crystallization and prevent particle agglomeration. Then, a hydrogen reduction optimization was carried out. During the reduction stage, an argon-hydrogen mixture (1:1 by volume) was introduced to control the reduction rate to obtain nano-copper with a more uniform particle size (<30nm). A gradient mixing method for the lubricant was designed, using segmented heating and stirring: the base oil and viscosity index improver were premixed at 50°C for 30 minutes; the additives were added after heating to 70°C, and ultrasonic dispersion was performed for 20 minutes; finally, nano-copper powder was slowly added at 60°C and treated with a high-speed homogenizer (10,000 rpm) for 1 hour to ensure uniform dispersion of the nanoparticles, prevent nano-copper powder sedimentation, and improve oil stability (no stratification after 6 months of storage). After the lubricating oil is prepared, it is vacuum dehydrated (-0.1MPa, 80℃, 2h) to reduce the moisture content to below 50ppm and enhance its demulsibility. It is then filtered through a 0.1μm ceramic membrane to remove undispersed nanoparticle impurities and reduce the risk of abrasive wear.

[0027] The following examples further illustrate the present application in detail.

[0028] Preparation example of nano copper powder Table 1 Preparation Example 1: The raw materials and amounts are shown in Table 1; The method for preparing the nano copper powder comprises the following steps: S1. Prepare copper nitrate solution according to the component ratio in Table 1, then add N,N′-dimethylbisacrylamide, stir at 200 rpm for 30 minutes, then add polyvinylpyrrolidone and stir for 30 minutes; S2. The mixture was treated with a ball mill for 48 h, and ammonium sulfate was added thereto, and the mixture was slowly heated to 80° C. to form a wet gel; S3. The wet gel is heated to 120° C. to evaporate the water therein, and calcined at 500° C. in a muffle furnace for 3 h. Finally, the gel is reduced at 450° C. in a hydrogen atmosphere for 4 h.

[0029] Preparation Example 2: The difference between the nano copper powder and the preparation example 1 is that the raw materials and amounts are shown in Table 1; The method for preparing the nano copper powder comprises the following steps: S1. Prepare copper nitrate solution according to the component ratio in Table 1, then add N,N′-dimethylbisacrylamide, stir at 200 rpm for 30 minutes, then add polyvinylpyrrolidone and stir for 30 minutes; S2. The mixture was treated with a ball mill for 48 h, and ammonium sulfate was added thereto, and the mixture was slowly heated to 85° C. to form a wet gel; S3. The wet gel is heated to 120° C. to evaporate the water therein, and calcined at 600° C. in a muffle furnace for 3 h. Finally, the gel is reduced at 450° C. for 4 h in a hydrogen atmosphere.

[0030] Preparation Example 3: The difference between the nano copper powder and the preparation example 1 is that the raw materials and amounts are shown in Table 1; The method for preparing the nano copper powder comprises the following steps: S1. Prepare copper nitrate solution according to the component ratio in Table 1, then add N,N′-dimethylbisacrylamide and ultrasonicate for 10 minutes, then add polyvinylpyrrolidone and ultrasonicate for 10 minutes; S2. The mixture was treated with a ball mill for 48 h, and ammonium sulfate was added thereto, and the mixture was slowly heated to 80° C. to form a wet gel; S3. The wet gel is heated to 120° C. to evaporate the water therein, and calcined at 550° C. in a muffle furnace for 3 h. Finally, the gel is reduced at 450° C. for 4 h in a hydrogen atmosphere to obtain the obtained product.

[0031] Preparation Example 4: The difference between the nano copper powder and the preparation example 1 is that the raw materials and amounts are shown in Table 1; The method for preparing the nano copper powder comprises the following steps: S1. Mix copper nitrate and graphene in 100 g of water and disperse them ultrasonically for 30 min (power 600 W). S2, add DMAA and PVP, and ball mill for 48 h (ball-to-material ratio 10:1, speed 300 rpm); S3, add ammonium sulfate, and form a wet gel at 80℃; S4, pre-calcining at 300℃ for 1h to remove organic matter, then calcining at 500℃ for 3h; S5. Reduce the sample at 450 °C for 4 h (heating rate 5 °C / min) in an Ar / H2 mixture (1:1 volume ratio) to obtain composite particles with an average particle size of 35 nm.

[0032] Preparation Example 5: The difference between the nano copper powder and the preparation example 1 is that the raw materials and amounts are shown in Table 1; The method for preparing the nano copper powder comprises the following steps: S1. Mix copper nitrate and molybdenum disulfide in 100 g of water and disperse them by ultrasonication for 30 min (power 600 W). S2, add DMAA and PVP, and ball mill for 48 h (ball-to-material ratio 10:1, speed 300 rpm); S3, add ammonium sulfate, and form a wet gel at 80℃; S4, pre-calcining at 300℃ for 1h to remove organic matter, then calcining at 500℃ for 3h; S5, reduced at 450℃ for 4h (heating rate 5℃ / min) in Ar / H2 mixed gas (1:1 volume ratio), to obtain composite particles with an average particle size of 38nm Example 1: A lubricating oil composition for steam engine cylinders, wherein the raw materials and amounts are shown in Table 2, wherein the base oil is mineral oil and CTL synthetic oil in a ratio of 1:0.2; the thickener comprises polyisobutylene PIB1300 and PIB2400 in a mass ratio of 1:2; the nano copper powder is obtained according to Preparation Example 1; and the pour point depressant is alkyl naphthalene. The preparation method of the lubricating oil composition comprises the following steps: The viscosity index improver, pour point depressant and additives were added to the base oil, mixed and heated to 60°C to uniformly disperse them, and blend A was obtained after 1 hour; Then, nano copper powder was added to blend A, and the mixture was heated at 60° C. with stirring for 1 h.

[0033] Table 2 Example 2: A lubricating oil composition for a steam engine cylinder, which differs from Example 1 in that the raw materials and amounts are as shown in Table 2, wherein the base oil comprises mineral oil and poly-α-olefin synthetic oil in a mass ratio of 1:0.3, the thickener comprises polyisobutylene PIB1300 and polymethacrylate V0-120 in a mass ratio of 1:1, the nano-copper powder is obtained according to Preparation Example 2, and the pour point depressant is alkyl naphthalene. The preparation method of the lubricating oil composition comprises the following steps: Step 1: Add the viscosity index improver, pour point depressant and additives to the base oil, mix and heat to 70°C to make them uniformly dispersed, and obtain blend A after 1 hour; Step 2: Add nano copper powder to blend A, and heat with stirring at 60° C. for 1 h to obtain the mixture.

[0034] Example 3: A lubricating oil composition for a steam engine cylinder, which differs from Example 1 in that the raw materials and amounts are as shown in Table 2, wherein the base oil comprises mineral oil and CTL synthetic oil in a mass ratio of 1:0.5, the thickener comprises polyisobutylene PIB1300 and polymethacrylate V0-120 in a mass ratio of 1:0.4, the nano-copper powder is obtained according to Preparation Example 1, and the pour point depressant is alkyl naphthalene. The preparation method of the lubricating oil composition comprises the following steps: Step 1: Add the viscosity index improver, pour point depressant and additives to the base oil, mix and heat to 70°C to make them uniformly dispersed, and obtain blend A after 1 hour; Step 2: Add nano copper powder to blend A, and heat with stirring at 70° C. for 1 h to obtain the mixture.

[0035] Example 4: A lubricating oil composition for a steam engine cylinder, which differs from Example 1 in that the raw materials and amounts are as shown in Table 2, wherein the base oil is a mineral oil and a poly-α-olefin synthetic oil in a mass ratio of 1:0.1, the thickener is polyisobutylene PIB2400, the nano-copper powder is obtained in Preparation Example 1, and the pour point depressant is alkyl naphthalene; The preparation method of the lubricating oil composition comprises the following steps: Step 1: Add the viscosity index improver, pour point depressant and additives to the base oil, mix and heat to 60°C to make them uniformly dispersed, and obtain blend A after 1 hour; Step 2: Add nano copper powder to blend A, and heat with stirring at 60° C. for 1 h to obtain the mixture.

[0036] Example 5: A lubricating oil composition for steam engine cylinders, which differs from Example 1 in that the raw materials and amounts are as shown in Table 2, wherein the base oil is specifically composed of: 40% mineral oil, 35% CTL synthetic oil, and 8% pentaerythritol ester (acid value 0.05 mgKOH / g); the additives are: 1.5% alkyldiphenylamine or phenol, 0.8% phosphate-based ionic liquid, and 0.68% oil-soluble polyether DL-32 or amine and epoxide condensate T1001 (1:0.5); and the nanoparticles are: the copper-graphene composite particles obtained in Preparation Example; The preparation method of the lubricating oil composition comprises the following steps: Step 1: Stir the base oil and viscosity improver at 50°C for 30 minutes; Step 2: Heat to 70°C, add additives, and ultrasonically disperse (800W, 40kHz) for 20 minutes; Step 3: Cool to 60°C, add nanoparticles, and homogenize at 10,000 rpm for 1 hour*; Step 4: Add pour point depressant and stir for 10 minutes; Step 5: Vacuum dehydration (-0.1MPa, 80℃, 2h) → Microfiltration (0.1μm ceramic membrane) Example 6: A lubricating oil composition for a steam engine cylinder, which differs from Example 5 in that the base oil is replaced with: 45% mineral oil, 35% CTL synthetic oil, and 10% pentaerythritol ester, and the nanoparticles are the copper-molybdenum disulfide composite particles obtained in Preparation 5; The preparation method of the lubricating oil composition is the same as that in Example 5: Comparative Example Comparative Example 1, a lubricating oil composition for a steam engine cylinder, differs from Example 1 in that the nano copper powder in the raw material is replaced with a base oil of equal mass, and the other steps are the same as Example 1.

[0037] Comparative Example 2 is a lubricating oil composition for steam engine cylinders. The difference from Example 1 is that the base oil in the raw material is pure mineral oil and does not contain synthetic oil. The other steps are the same as Example 1.

[0038] Comparative Example 3, a lubricating oil composition for a steam engine cylinder, differs from Example 5 in that the nanoparticles are replaced with ordinary nano-copper powder (without graphene / molybdenum disulfide, Preparation Example 1), and the vacuum dehydration and microfiltration steps are omitted.

[0039] Comparative Example 4, a lubricating oil composition for steam engine cylinders, wherein the base oil is 50% mineral oil + 35% CTL (without pentaerythritol ester); preparation process: all components are stirred at 80°C for 2 hours at once (without ultrasonication, homogenization, or post-treatment).

[0040] Performance Testing The lubricating oil composition for a steam engine cylinder obtained in Examples 1-4 and Comparative Examples 1-2 was subjected to the following relevant performance tests.

[0041] 1. Viscosity index: refer to the method specified in GB / T 1995-1998; 2. Flash point (open cup): refer to the method specified in GB / T 3536-2008; 3. Pour point: refer to the method specified in GB / T 3535-2006; 4. Carbon residue: refer to the method specified in GB / T 268-1987; 5. Ash content: refer to the method specified in GB / T 508-1985; 6. Demulsification: Demulsification of the lubricating oil composition at 54°C was determined according to the method specified in GB / T 8022-2019. 7. Wear spot diameter: Measure the wear spot diameter of the lubricating oil composition at 392 N, 60 min, 75°C, and 1200 r / min, referring to the method specified in NB / SH / T 0189-2017. Table 3 According to the performance test results in Table 3, it can be seen that the lubricating oil composition for steam engine cylinders of the present application has excellent viscosity-temperature characteristics. In a low-temperature environment, the composition can maintain good fluidity, and in a high-temperature environment, it can maintain stable adhesion, providing long-lasting and efficient lubrication protection for the cylinder. Compared with the disadvantages of traditional solutions that are difficult to balance high and low temperature performance, the lubricating oil composition of the present application successfully achieves good adaptability to different temperature conditions. In addition, the lubricating oil composition also has excellent properties such as anti-wear and durability, high-efficiency anti-emulsification and low ash content. From the perspective of lubricating oil, these characteristics significantly improve the reliability of steam power equipment and effectively extend the service life of the equipment.

[0042] The performance test results of Examples 1-4 and Comparative Example 1 demonstrate that the introduction of nano-copper powder into lubricating oil effectively enhances its anti-wear properties. The addition of nano-copper powder effectively reduces friction and wear between friction pairs, significantly reducing the occurrence of dry friction. Furthermore, nano-copper powder significantly enhances the demulsification properties of lubricating oils, providing a crucial contribution to extending their service life and possessing significant value in optimizing lubricating oil performance.

[0043] The addition of synthetic oils, particularly coal-based synthetic oils, significantly improves the viscosity-temperature characteristics of the oil. Compared to pure mineral oil solutions, the pour point and viscosity index of the oils containing synthetic oils are significantly higher. Furthermore, due to the low impurity content of synthetic oils, the resulting formulations exhibit excellent demulsification properties, far surpassing existing solutions and demonstrating significant advantages in this regard.

[0044] Table 4 Performance comparison of Examples 5-6 and Comparative Examples 3-4 From Table 4 we can see that: 1. Synergistic effect of composite nanoparticles + gradient process (Examples 5-6): a. Wear spot diameter ≤ 0.23mm (30%+ lower than traditional nano-copper) due to the enhanced shear resistance of the graphene / molybdenum disulfide layered structure; b. Oil film retention rate at 200℃>90%, thanks to the polar adsorption of ester oil and the surface film-forming property of composite particles; 2. Necessity of post-processing process: a. Vacuum dehydration reduces moisture to ≤35ppm (Comparative Example 4: 120ppm), significantly improving demulsibility; b. After microfiltration purification, the D90 particle size is ≤75nm (laser scattering method), avoiding the risk of abrasive wear; 3. High temperature advantages of ionic liquids: a. Phosphate-based ionic liquid forms a chemical adsorption film at 250°C, which complements the nano-physical protective layer and reduces the friction coefficient to below 0.08.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lubricating oil composition for a steam engine cylinder, characterized in that: Calculated by mass percentage, the components include: 50-90% base oil, 5-40% viscosity index improver, 0.001-0.003% nano copper powder, 1-5% additives and 0.1-1% pour point depressant; The base oil is composed of mineral oil, coal-based synthetic oil (CTL) and ester synthetic oil, and the mass percentages thereof are: Mineral oil: 40-70%, Coal-to-liquid (CTL): 20-50%, Ester synthetic oil: 5-10%.

2. The lubricating oil composition for a steam engine cylinder according to claim 1, characterized in that: In the nano copper powder, the mass proportion of graphene or molybdenum disulfide is 0.01-0.05%, and the composite particles are prepared by a ball milling process, with an average particle size of less than 50 nm.

3. The lubricating oil composition for a steam engine cylinder according to claim 1, characterized in that: The ester synthetic oil is pentaerythritol ester; in the base oil, the mass ratio of coal-based synthetic oil (CTL) to mineral oil is 1: (0.5-1.0); the viscosity index improver is one of polyisobutylene and polymethacrylate or a mixture of the two in a mass ratio of 1: (0.1-0.2).

4. The lubricating oil composition for a steam engine cylinder according to claim 1, characterized in that: The additives further include: 1.0-2.5% of alkyl diphenylamine or phenol antioxidants, 0.2-1% of phosphate-based ionic liquid anti-wear agent; and 1-2% of oil-soluble polyether DL-32 or amine and epoxide condensate T1001 demulsifier.

5. The lubricating oil composition for a steam engine cylinder according to claim 1, characterized in that: The pour point depressant is one of alkyl naphthalene and polymethacrylate or a mixture of the two in a mass ratio of 1:(0.2-0.5).

6. The lubricating oil composition for a steam engine cylinder according to claim 1, characterized in that: The preparation steps of the nano copper powder are as follows: S1. Prepare raw materials for making nano-copper powder, including: graphene or molybdenum disulfide, 40-60% copper nitrate (Cu(NO3)2), 35-50% N,N′-dimethylbisacrylamide (DMAA), 1-10% polyvinylpyrrolidone (PVP), and 1-10% ammonium sulfate (NH4SO4), wherein the addition amount of graphene or molybdenum disulfide is 0.01-0.05% of the mass of copper nitrate; S2, copper nitrate, graphene or molybdenum disulfide, N,N′-dimethylbisacrylamide (DMAA), and polyvinylpyrrolidone (PVP) were mixed in water and ball-milled for 48 hours; S3, adding ammonium sulfate and heating to 80°C to form a wet gel; S4, pre-calcining the wet gel at 300 ° C for 1 hour, then heating to 500 ° C for 3 hours; S5. Reducing the copper-graphene or copper-molybdenum disulfide composite particles in an argon-hydrogen mixture (volume ratio 1:1) at 450° C. for 4 hours to obtain the finished nano-copper powder.

7. A method for preparing the lubricating oil composition according to any one of claims 1 to 6, characterized in that: The preparation method steps are as follows: Step 1: Mix the base oil and viscosity index improver at 50°C and stir for 30 minutes; Step 2: Heat to 70°C, add additives, and ultrasonically disperse for 20 minutes; Step 3: Cool down to 60°C, add copper-graphene or copper-molybdenum disulfide composite particles, and homogenize at 10,000 rpm for 1 hour; Step 4: Add pour point depressant and continue stirring for 10 minutes.

8. The method for preparing the lubricating oil composition according to claim 7, wherein: After step 3 is completed, vacuum dehydration treatment is required: dehydration is performed at -0.1 MPa and 80°C for 2 hours to reduce the moisture content to ≤50 ppm.

9. The method for preparing the lubricating oil composition according to claim 8, wherein: After the vacuum dehydration treatment, microfiltration purification treatment is required: 0.1 μm ceramic membrane filtration is used to remove undispersed particulate impurities.

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