Method for improving the friction-reducing, wear-resisting and self-repairing performance of lubricating oil by adding attapulgite / nano cerium oxide composite

Abstract

The application discloses a method for improving the friction-reducing, wear-resisting and self-repairing performance of lubricating oil by adding attapulgite / nano cerium oxide composite material, first synthesizes the attapulgite / nano cerium oxide composite material under the mediation of plants, then uniformly mixes the attapulgite / nano cerium oxide composite material, an ester modifier and lubricating oil base oil, and carries out wet sanding to obtain a solid-liquid composite lubricating oil product. The application fully utilizes the synergistic stabilization of attapulgite and plant active ingredients on cerium oxide nanoparticles, green and controllable synthesis of attapulgite / nano cerium oxide composite material, further realizes the modification and efficient dispersion of the composite material in the lubricating oil phase through sanding, and the obtained solid-liquid composite lubricating oil can construct a high-strength, high-toughness and soft-hard adaptive friction reaction film on the friction surface, greatly improving the friction-reducing, wear-resisting and self-repairing performance of the composite lubricating oil.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fine chemical industry, and relates to a solid-liquid composite lubricating oil and a preparation process of a lubricating oil additive, in particular to a method for improving the friction-reducing, wear-resisting and self-repairing performance of lubricating oil by adding attapulgite / nano cerium oxide composite materials. BACKGROUND

[0002] It is well known that the phenomenon of friction and wear is ubiquitous, and the loss caused by friction and wear is self-evident, especially in the field of mechanical engineering. Friction consumes about 1 / 3 of the primary energy in the world, and wear causes about 60% of mechanical component failures, and solid thin film lubrication and liquid lubrication are considered to be effective means to reduce friction and wear. However, hard solid thin film lubrication is difficult to meet the performance requirements of high wear resistance and long service life when facing complex and harsh working conditions, and liquid lubrication is prone to oil starvation under high-speed heavy-load lubrication system, which causes excessive wear, and the traditional lubricating oil additive (such as extreme pressure agent ZDDP) cannot repair the damage of wear marks, and has certain corrosion, environmental toxicity and is not easy to be decomposed, which leads to the development and application of traditional single solid / liquid lubrication and related additives being limited to a certain extent. Therefore, developing new type of lubricating oil additive and constructing solid-liquid composite lubrication system is the only way to realize the synergistic lubrication effect and improve the comprehensive friction performance of the system.

[0003] Clay minerals, as a kind of natural and green lubricating oil additive, have the characteristics of wide sources, large specific surface area, high chemical activity and low cost. They are easy to be adsorbed on the surface of the friction pair metal materials, and the bond breaking reaction releases a large number of high reactivity groups, which can form a protective film on the surface of the friction pair. The hard particles such as silicon oxide and aluminum oxide can also fill the worn parts. Among them, the layered silicate minerals (such as serpentine and talc) have shown great development and application potential in the field of solid lubricating materials or lubricating oil additives. Attapulgite is a magnesium-aluminum silicate clay mineral with regular nanochannels and one-dimensional rod crystal morphology. Its unique crystal structure and excellent adsorption, carrier, colloid and reinforcing properties make it play an important role in many fields of the national economy. Mixed attapulgite clay is a nano-structured mineral material mainly composed of one-dimensional rod-shaped attapulgite and two-dimensional sheet-shaped illite, accompanied by a variety of minerals such as montmorillonite, chlorite and quartz, and has the comprehensive characteristics of one-dimensional and two-dimensional clay minerals. However, there are few reports on the application of attapulgite and mixed attapulgite clay as lubricating oil additives, and the poor dispersion and suspension stability of inorganic clay minerals in lubricating oil have always been a problem, which has become a key factor limiting their large-scale application in the field of lubricating oil additives. In addition, compared with sulfides, elemental metals and rare earth compounds such as cerium oxide, as lubricating oil additives, they can activate and purify the surface of workpieces and form a soft film layer on the friction surface, exhibiting similar lubrication behavior to high viscosity fluids. For example, patents such as "Silicon-coated cerium oxide nanopowder material, its preparation method and application (CN101875873B)", "Environment-friendly friction material modified by rare earth oxides and its preparation method (CN102516942B)", "Low-viscosity energy-saving diesel engine oil based on cerium oxide nano-additive and its preparation method (CN115011402B)", and "Metal organic friction repair agent and its preparation method (CN104004566B)" are all related to this content. However, the cost of synthesizing nano-sized cerium oxide is high, and nano-cerium oxide is prone to agglomeration into irregular agglomerates, which may cause abrasive wear and other adverse conditions when entering the lubricating oil system. With the rapid development of nanotechnology, as described in "Research progress of plant-mediated synthesis of metal nanoparticles", "Green synthesis of silver nanoparticles using plant extracts and their toxicity to Formosan subterranean termite", and "Green synthesis of nano-iron from two plant leaf extracts and its removal of U(Ⅵ)", plant mediation has been proven to be beneficial to the synthesis and particle size control of nanomaterials.

[0004] Based on this, the application is based on the system cognition of the structural characteristics of attapulgite-based mineral materials, the plant-mediated green synthesis process, and the solid-liquid composite lubrication advantage, the plant-mediated synthesized nano cerium oxide is uniformly loaded on the surface of attapulgite to obtain a composite material, and after the composite material is mixed with lubricating oil base oil and ester modifier and subjected to sanding treatment, a solid-liquid composite lubricating oil with excellent suspension stability, friction reduction and wear resistance, and self-repairing performance is obtained. This technology or process can be used as one of the important ways for the high-value utilization of attapulgite, other clay minerals and rare earth compounds in the field of lubricating oil, and there is no related research report and no related industrial application precedent. SUMMARY

[0005] The purpose of the application is to solve the problems of the application of clay minerals (attapulgite) and rare earth compounds (nano cerium oxide) as lubricating oil additives in solid-liquid composite lubricating systems, and to provide a method for improving the friction reduction, wear resistance and self-repairing performance of lubricating oil by adding attapulgite / nano cerium oxide composite material. The preparation method of solid-liquid composite lubricating oil mainly includes the following steps:

[0006] (1) Ultrasonic-assisted extraction of plant active ingredients: first, wash and dry (75-85℃, ≥48h) olive leaves, crush (700W, 28000rpm, 5-10min) to obtain 200-300 mesh olive leaf powder, uniformly disperse the olive leaf powder in a 25-30% ethanol aqueous solution to form a suspension with a solid content of 2.5-5.0%, and ultrasonically treat for 1h, then reflux the suspension at 60-70℃ for 2-4h, after cooling, separate the solid and liquid, filter and collect the supernatant to obtain a plant extract rich in active ingredients. The ultrasonic treatment is carried out at low frequency and high power (frequency 20-30kHz, power density 50-100W / L), and the solid-liquid separation is carried out by centrifuging the suspension at 6000-10000rpm for 10min, preferably passing the supernatant obtained by centrifugation through a 0.22μm filter membrane to further remove particulate matter. The plant extract obtained contains various active ingredients such as oleuropein, hydroxytyrosol, rutin, amino acids, proteins, plant polysaccharides, etc., which can form stable metal complexes in subsequent plant-mediated synthesis, and play multiple roles such as complexation, synergistic regulation of cerium oxide size, etc.

[0007] (2) Plant-mediated synthesis of attapulgite / nano ceria composite material: first, the sand removal treatment is carried out on the attapulgite, specifically, the attapulgite crushed to more than 200 meshes is subjected to cyclone separation and grading treatment, or the crushed attapulgite is uniformly dispersed in an acidic aqueous solution with a pH value of 3-4 for activation for 4 h, and then subjected to three-stage hydrocyclone treatment, solid-liquid separation and drying treatment in sequence to obtain sand-removed attapulgite; the sand removal treatment can effectively avoid the introduction of hard and irregularly shaped quartz sand into the composite lubricating oil system and increase the wear on the surface of the friction pair. Then, the sand-removed attapulgite powder is uniformly dispersed in a cerium nitrate aqueous solution and ultrasonically treated for 1 h, and then the above plant extract is added to obtain a suspension, the pH value of the suspension is adjusted to 9, heated to 60-70°C and continuously stirred for 3-6 h, after cooling and solid-liquid separation, the obtained precipitate is washed, dried, sieved and calcined at 400-500°C for 2 h to obtain an attapulgite / nano ceria composite material, wherein the loading amount of nano ceria is 10-30%. Preferably, the sand-removed attapulgite is first subjected to rod crystal bundle dissociation pretreatment to improve the dispersibility, and then dispersed in the cerium nitrate aqueous solution, which is beneficial to improve the loading efficiency and uniformity; specifically, the attapulgite slurry with a solid content of 10-20% is subjected to ultrasonic or high-pressure homogenization treatment to realize attapulgite rod crystal bundle dissociation, the ultrasonic treatment conditions are 20-50 kHz in frequency and 30-50 W / L in power density for 10-15 min, or high-pressure homogenization treatment is carried out at 30 MPa. The sand-removed attapulgite is dispersed in the suspension, the mass fraction of the attapulgite powder is 5-10%, and the mass ratio of the cerium nitrate aqueous solution to the plant extract in the suspension is 3:7; 2M sodium hydroxide or 1.5M ammonia water solution is used to adjust the pH value.

[0008] By controlling the addition amount of attapulgite and cerium nitrate, introducing various plant active ingredients and adjusting the pH value of the mixed solution, the size of the generated nano ceria is limited and the uniform loading of ceria on the surface of attapulgite is promoted. Specifically, the limited amount of plant active ingredients and cerium ions in the mixed solution will form small particle size cerium complexes and be uniformly loaded on the mineral surface, which is beneficial to control the size of the nanoparticles and improve their dispersibility, and the introduction of attapulgite also effectively inhibits the soft agglomeration between the nanoparticles, limiting their further formation of cluster structure. The subsequent calcination treatment makes the cerium complexes uniformly loaded on the attapulgite in situ generate nano ceria. In the entire synthesis process of nano ceria, no other chemical stabilizer or template agent is needed, and the attapulgite / nano ceria composite material can be successfully prepared only under the mediation of plant active ingredients.

[0009] (3) High-efficiency preparation of solid-liquid composite lubricating oil using sand milling process: The above-mentioned attapulgite / nano-cerium oxide composite material, lubricating oil base oil and ester modifier are uniformly mixed at a mass ratio of 0.5-2.0:100:1-8, and then sand milled at 2000-3000 rpm for 6-12 hours to obtain lubricating oil with added attapulgite / nano-cerium oxide composite material. Preferably, the attapulgite / nano-cerium oxide composite material, lubricating oil base oil and ester modifier are homogenized by stirring at 6000-12000 rpm for 10-20 minutes, and then sand milled. The ester modifier is at least one of phosphate ester, oleate ester, borate ester, glycerol ester and polyol ester. The aforementioned sand milling process involves adding the above-mentioned uniform mixture into a sand mill and processing it for 6 to 12 hours at a frequency of 50 Hz and a grinding speed of 2000 to 3000 rpm, with the grinding balls having a diameter of 0.5 to 2 mm. Throughout the sand milling process, the outlet temperature of the circulating material is controlled to be below 40°C, and the pore size of the material filter membrane is 500 nm to 1 μm.

[0010] During the wet sand milling process, the attapulgite / nano-cerium oxide composite material is continuously subjected to strong axial and longitudinal rolling shearing and grinding, further achieving nano-sizing. Simultaneously, it enhances the modification efficiency of the ester on the attapulgite / nano-cerium oxide composite material, transforming it into oleophilic nanoparticles uniformly dispersed in the lubricating oil phase. This effectively avoids nanoparticle agglomeration, contributing to the long-term maintenance of excellent dispersibility and suspension stability. Compared to dry or semi-dry ball milling, the wet sand milling process can simultaneously achieve nano-sizing, modification, and efficient dispersion of inorganic composite materials in the lubricating oil system. It also effectively avoids the secondary agglomeration problem of nanoparticles in dry ball milling, directly yielding a solid-liquid composite lubricating oil product. The entire process combination is more efficient and convenient.

[0011] According to the attapulgite clay classification standard (DB32 / T 3668-2016), the sand content of attapulgite and fibrous attapulgite clay before and after sand removal was determined. After hydrocyclone or cyclone separation and classification, the sand content of attapulgite or fibrous attapulgite clay was significantly reduced from 5.5-32.3% in the original ore to below 0.85%; the sand content of attapulgite / nano-cerium oxide composite material was analyzed from the infrared spectrum (…). Figure 1 (Right) Si-O-Si stretching vibration peaks of quartz sand (792 and 1030 cm⁻¹) -1 The significant reduction in strength also confirms this; moreover, the subsequent nano-grinding process will further reduce the particle size of the remaining quartz sand or transform it into lamellar / spherical shapes, without negatively affecting the tribological properties of the composite lubrication system.

[0012] XRD patterns of attapulgite / nano-cerium oxide composites ( Figure 1The main phases in the composite material are attapulgite (2Q = 20.35°, 27.59°, 28.04°, 34.34°), cerium oxide (2Q = 28.55°, 33.08°, 47.48°, 56.34°), quartz (2Q = 20.86°, 26.64°, 36.51°, 50.63°, 59.95° and 68.14°) and illite (2Q = 8.80°), which confirms that the attapulgite / nano cerium oxide composite material is successfully prepared under the mediation of plants. Figure 1 The infrared spectrum of the attapulgite / nano cerium oxide composite material is shown on the right. It can be seen that the characteristic absorption peaks of Si, Al bonding region and -OH functional group specific to attapulgite do not shift, which indicates that the layer chain crystal structure of attapulgite is not damaged, and the crystal framework of clay minerals is completely retained. The absorption peaks (3550 and 1638 cm -1 ) of crystal water and zeolite water in the composite material are weakened or even disappeared due to calcination treatment; the characteristic peaks (1195 and 513 cm -1 ) of Si-O-Si group and the characteristic peaks (985 cm -1 ) of Si-O-Mg group in attapulgite are weakened, which also confirms that the active groups in attapulgite and cerium complexes are bonded, and a limited number of cerium ions in the solution are uniformly and strongly loaded on the surface of attapulgite, effectively inhibiting the soft agglomeration between nanoparticles.

[0013] Figure 2 The TEM image of the attapulgite / nano cerium oxide composite material is shown. Under the microscope, it can be observed that the rod crystal surface of Mingguang and Xuyi attapulgite (MPal and BPal) is relatively smooth and flat; due to the geological origin of lacustrine deposition and the presence of various minerals and other reasons, the rod crystal surface of mixed attapulgite clay (MDPal) is slightly rough, but no obvious granular material is observed on the rod crystal surface. After loading nano cerium oxide through plant mediation, it can be observed that nano-sized spherical particles are almost uniformly distributed on the surface of attapulgite, and only a small amount of small aggregates are observed; from the high-magnification electron micrograph (Fig. 4), it can be observed that the spherical particles are evenly distributed on the surface of attapulgite, and the size of the spherical particles is about 20 nm, which is consistent with the size of the nano cerium oxide particles. Figure 3) and the interplanar spacing of the synthesized cerium oxide is 0.26 nm, which is almost consistent with the interplanar spacing of the (2 0 0) crystal plane of the synthesized cerium oxide (0.27 nm); it can be known from the TEM image and the estimation of the particle size by using Nano Measure 1.2 software that the particle size of the cerium oxide loaded on the attapulgite surface is 1.7-7.1 nm, and the particle size of 1.7-3.8 nm accounts for more than 60%, and the average particle size is 3.5 nm. After a small amount of nano cerium oxide is loaded on the attapulgite or mixed attapulgite clay, it is still inclined to be hydrophilic, and even after high-speed stirring and dispersion, the suspension stability of the solid-liquid composite lubricating oil is poor (see Figure 4 left 1), which does not meet the suspension requirements of the lubricating oil additive. However, after the nano sanding & modification treatment with the lubricating oil base oil and the ester modifier, the attapulgite-based friction-reducing and anti-wear additive has good suspension stability in the lubricating oil after standing for 30 days (see Figure 4 right).

[0014] It can be found from the thermogravimetric curves (Fig. 2 Figure 5 ) of the attapulgite and the sanding modified treatment powder that the weight loss rates of the attapulgite and the sanding modified treatment powder are 16.11% and 51.35% respectively, and the weight loss of the attapulgite is mainly caused by the removal of the surface adsorbed water, the pore zeolite water, the crystal water and the structural water, while the high weight loss rate of the sanding modified treatment powder is mainly caused by the volatilization or decomposition of the ester modifier combined with the attapulgite and the pore resident lubricating oil, which also proves the close combination between the composite material and the organic phase. It can be known from the comparison of the water contact angles (Fig. 3 Figure 5 ) of the two that the attapulgite exhibits excellent hydrophilicity, and the water droplets will spread and penetrate instantly, while the water contact angle of the sanding modified treatment powder is as high as 126°, which is much greater than 90°, indicating that it is in a hydrophobic state, which indicates that the sanding treatment improves the ester modification efficiency and the affinity between the lubricating oil. It can be seen from the friction coefficient change curve (Fig. 4 Figure 6 ) of the solid-liquid composite lubricating oil that the average friction coefficient of the pure lubricating oil base oil system under 200 N is 0.3375, and the addition of the attapulgite / nano cerium oxide composite material can reduce the friction coefficient of the composite lubricating oil to 0.0997, and the friction coefficient is reduced by 70.46%; compared with the low friction system (MPal-Lub-1, the average friction coefficient is 0.1356), after the addition of the attapulgite / nano cerium oxide composite material, the wear cross-sectional area and the wear rate are reduced from 583.7 μm 2 , 6.75 μm 3 ×N -1 m -1 to 254.2 μm2 2.42 μm 3 x N -1 m -1 (see Figure 7 ), which also proves that the attapulgite and nano cerium oxide exhibit excellent friction-reducing and anti-wear performance in cooperation.

[0015] In summary, compared with the prior art, the lubricating oil added with the attapulgite / nano cerium oxide composite material and the preparation process thereof have the following advantages:

[0016] 1. On the basis of systematically understanding the chain crystal structure, porous characteristics and clay mineral lubrication mechanism of the attapulgite layer, the present application successfully constructs the lubricating oil system added with the attapulgite / nano cerium oxide composite material by taking attapulgite, olive leaves and lubricating oil base oil as raw materials and through a combination process of ultrasonic extraction, plant-mediated synthesis and sand grinding, so that the solid-phase friction-reducing and anti-wear additive has excellent dispersibility and suspension stability in the lubricating oil phase, and the attapulgite / nano cerium oxide composite material greatly improves the tribological performance and self-repairing effect of the lubricating oil, and exhibits good application prospect.

[0017] 2. The present application fully utilizes the synergistic stabilizing effect of the active ingredients in the plant extract and the attapulgite, uniformly loads the cerium complex with small particle size on the surface of the attapulgite, and then generates the attapulgite / nano cerium oxide composite material in situ through calcination, so as to synthesize the nano composite material with high dispersibility by a green and efficient preparation method, and the double solid phases of the mineral and the rare earth oxide help to construct the friction reaction film with high strength, high toughness and soft and hard adaptation, effectively prevent the direct contact of the friction pair surfaces, and realize the efficient repair of the worn surfaces.

[0018] 3. The present application takes the natural nano-structured mineral material (attapulgite) with huge reserves and low price as a base material, optimally utilizes the structural advantages of the attapulgite-like micro-reactor and the plant-mediated green synthesis process to prepare the composite material, and further adopts the wet sand grinding treatment process to simultaneously improve the affinity and dispersibility of the composite material in the lubricating oil through rolling shear and efficient dispersion, so that the solid-liquid composite lubricating oil product can be directly obtained, the preparation process flow of the composite lubricating oil is efficient, convenient, low in energy consumption and free of three wastes, and has the advantages of controllable cost and green efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD pattern (left, a-MPal / CeO 2， b-BPal / CeO 2， c-MDPal / CeO2) and infrared spectrum (right) of the attapulgite / nano cerium oxide composite material prepared in the present application;

[0020] Figure 2TEM image of the attapulgite / nano cerium oxide composite material prepared in the present application;

[0021] Figure 3 Lattice fringes and interplanar spacing of the attapulgite / nano cerium oxide composite material prepared in the present application;

[0022] Figure 4 Suspension stability of the solid-liquid composite lubricating oil sample prepared in the present application after standing for 30 days (from left to right: MPal-Lub-1, DMPal / CeO2-Lub-2, MPal / CeO2-Lub-3 and BPal / CeO2-Lub-4);

[0023] Figure 5 Thermogravimetric curve and water contact angle (inset) of the powder of attapulgite and attapulgite / nano cerium oxide composite material after sanding treatment.

[0024] Figure 6 Friction coefficient change curve of the solid-liquid composite lubricating oil prepared in the present application and added with attapulgite / nano cerium oxide composite material.

[0025] Figure 7 Wear cross-sectional area and wear rate comparison of the solid-liquid composite lubricating oil prepared in the present application and added with attapulgite / nano cerium oxide composite material. DETAILED DESCRIPTION

[0026] The preparation process of the solid-liquid composite lubricating oil of the present application and the tribological and self-repairing properties of the attapulgite / nano cerium oxide composite material will be further described below through specific examples. The friction experiment is tested by a reciprocating friction and wear tester, the frequency is 20 Hz, the load is 200 N, the stroke is 1 mm, and the lubrication mode is drop oil lubrication. The wear rate (W) is calculated using the following formula: W

[0027]

[0028] In the above formula, V is the wear volume loss (in μm 3 ), P is the applied normal load (in N), L is the sliding distance (in m).

[0029] Comparative Example 1

[0030] ​First, the raw palygorskite taken from Mingguang, Anhui province, was weathered and crushed to 100 mesh, then uniformly dispersed in a pH = 4 aqueous solution of phosphoric acid at a solid-liquid ratio of 1:15, stirred and activated for 4 hours, then treated by three-stage hydrocyclone, pressure filtration and drying, to obtain Mingguang palygorskite with a sand content of 0.59%; finally, the lubricating oil base oil PAO6, Mingguang palygorskite and triethanolamine borate were mixed at a mass ratio of 100:1:2, and after stirring at 12000 rpm for 20 min, a Mingguang palygorskite-added composite lubricating oil was obtained, which was marked as MPal-Lub-1.

[0031] Example 1

[0032] (1) The washed and dried at 80℃ for 72h olive leaves were crushed (700W, 28000rpm, 5min) to obtain olive leaf powder, which was uniformly dispersed in 25% ethanol aqueous solution to form a suspension with a solid content of 2.5% and treated by ultrasonic (20KHz, 50W / L) for 1h, then the suspension was refluxed at 70℃ for 2h, after cooling, centrifuged at 10000rpm for 10min, the supernatant was collected and filtered through a 0.22μm filter membrane, to obtain a plant extract rich in active ingredients;

[0033] (2) The Linze mixed palygorskite clay was crushed to 200 mesh, then treated by cyclone separation and classification to obtain mixed palygorskite clay with a sand content of 0.55%, and the mixed palygorskite clay was further slurried, then treated by ultrasonic at a frequency of 20KHz and a power density of 50w / L for 10min to realize the dissociation and exfoliation of the palygorskite crystal bundles, then treated by solid-liquid separation and drying to obtain dissociated mixed palygorskite clay; the dissociated mixed palygorskite clay was uniformly dispersed in cerium nitrate aqueous solution and treated by ultrasonic for 1h, then the plant extract was added to obtain a suspension, wherein the mass fraction of palygorskite in the suspension was 10%, and the mass ratio of cerium nitrate aqueous solution to plant extract in the suspension was 3:7; then the pH value of the suspension was adjusted to 9 with 2M sodium hydroxide solution, heated to 70℃ and continuously stirred for 6h, after cooling, the solid-liquid separation was carried out, the obtained precipitate was washed, dried, sieved and calcined at 400℃ for 2h, to obtain a palygorskite / nano cerium oxide composite material (marked as MDPal / CeO2), wherein the loading amount of cerium oxide was 20%;

[0034] (3) The palygorskite / nano cerium oxide composite material, lubricating oil base oil PAO6 and tributyl borate were uniformly mixed at a mass ratio of 2:100:8, then sand milling treatment was carried out at 2200rpm for 12h, to obtain a lubricating oil added with palygorskite / nano cerium oxide composite material, which was marked as MDPal / CeO2-Lub-2.

[0035] Example 2

[0036] (1) The washed and dried at 85°C for 48h olive leaves were crushed (700W, 28000rpm, 10min) to obtain olive leaf powder, which was uniformly dispersed in 30% ethanol aqueous solution to form a suspension with a solid content of 5%, and then treated by ultrasonic (20KHz, 100W / L) for 1h. The suspension was refluxed at 70°C for 2h. After cooling, the supernatant was collected by centrifugation at 6000rpm for 10min, and then filtered through a 0.22μm filter to obtain a plant extract rich in active ingredients;

[0037] (2) The Mingguattabias were crushed to 100 mesh and uniformly dispersed in a sulfuric acid aqueous solution with a pH value of 3 and stirred for 4h. The attabias were then treated by three-stage hydrocyclone, washing, solid-liquid separation and drying to obtain attabias with a sand content of 0.58%. The attabias were uniformly dispersed in a cerium nitrate aqueous solution and treated by ultrasonic for 1h. The plant extract was added to obtain a suspension, in which the mass fraction of attabias in the suspension was 10%, and the mass ratio of cerium nitrate aqueous solution to plant extract in the suspension was 3:7. The pH value of the suspension was adjusted to 9 by using 1.5M ammonia water solution, and then the suspension was heated to 70°C and continuously stirred for 6h. After cooling, the precipitate was obtained by solid-liquid separation, washed, dried, sieved and calcined at 400°C for 2h to obtain attabia / nano ceria composite material (labeled as MPal / CeO2), in which the loading amount of ceria was 10%;

[0038] (3) The attabia / nano ceria composite material, lubricating oil base oil PAO6 and triethanolamine borate were uniformly mixed according to a mass ratio of 0.5:100:2, and then sand milling treatment was carried out at 2000rpm for 12h to obtain a lubricating oil added with attabia / nano ceria composite material, which was labeled as MPal / CeO2-Lub-3.

[0039] Example 3

[0040] (1) The washed and dried at 75°C for 72h olive leaves were crushed (700W, 28000rpm, 10min) to obtain olive leaf powder, which was uniformly dispersed in 30% ethanol aqueous solution to form a suspension with a solid content of 2.5%, and then treated by ultrasonic (30KHz, 100W / L) for 1h. The suspension was refluxed at 60°C for 4h. After cooling, the supernatant was collected by centrifugation at 10000rpm for 10min, and then filtered through a 0.22μm filter to obtain a plant extract rich in active ingredients;

[0041] (2) The Xuyi attapulgite is crushed to 200 mesh and uniformly dispersed in a sulfuric acid aqueous solution with a pH value of 4 and stirred for activation for 4 h, and then sequentially subjected to three-stage hydrocyclone treatment, washing, solid-liquid separation, and drying treatment to obtain attapulgite with a sand content of 0.87%; the above attapulgite powder is uniformly dispersed in a cerium nitrate aqueous solution and subjected to ultrasonic treatment for 1 h, and then the above plant extract is added to obtain a suspension, wherein the mass fraction of attapulgite in the suspension is 5%, and the mass ratio of the cerium nitrate aqueous solution to the plant extract in the suspension is 3:7; then 2M sodium hydroxide solution is used to adjust the pH value of the above suspension to 9, and the suspension is heated to 60°C and continuously stirred for reaction for 3 h, and after cooling, the solid-liquid separation is performed, and the obtained precipitate is washed, dried, sieved, calcined at 500°C for 2 h to obtain an attapulgite / nano ceria composite material (labeled as BPal / CeO2), wherein the loading amount of ceria is 30%;

[0042] (3) The above attapulgite / nano ceria composite material, lubricating oil base oil PAO6, and glycerol monooleate are uniformly mixed at a mass ratio of 1:100:4, and then subjected to sand milling treatment at 3000 rpm for 6 h to obtain a lubricating oil added with the attapulgite / nano ceria composite material, which is labeled as BPal / CeO2-Lub-4.

Claims

1. A method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material, mainly comprising the following steps: (1) Ultrasonic-assisted extraction of plant active ingredients: First, the washed, dried and crushed olive leaf powder is evenly dispersed in an ethanol aqueous solution to form a suspension and ultrasonically treated. Then, the above suspension is refluxed at 60-70℃ for 2-4 hours. After cooling, the solid and liquid are separated, filtered and the supernatant is collected to obtain a plant extract rich in active ingredients. (2) Plant-mediated synthesis of attapulgite / nano-cerium oxide composite material: Attapulgite with a quartz sand content of <1% was uniformly dispersed in a cerium nitrate aqueous solution and ultrasonically treated. The above-mentioned plant extract was added to obtain a suspension. The pH of the suspension was adjusted to 9, and the mixture was heated to 60-70℃ and stirred for 3-6 hours. After cooling, the solid and liquid were separated, and the resulting precipitate was washed, dried, sieved, and calcined at 400-500℃ to obtain the attapulgite / nano-cerium oxide composite material, wherein the cerium oxide loading was 10-30%. (3) Preparation of solid-liquid composite lubricating oil by sand milling process: The above-mentioned attapulgite / nano-cerium oxide composite material, lubricating oil base oil and ester modifier are mixed evenly at a mass ratio of 0.5-2.0:100:1-8, and then sand milled at 2000-3000 rpm for 6-12 hours to obtain lubricating oil with added attapulgite / nano-cerium oxide composite material.

2. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The drying process described in step (1) involves drying the olive leaves at 75-85°C for at least 48 hours, and the pulverizing process involves pulverizing the leaves for 5-10 minutes at a motor power of 700W and a rotation speed of 28000rpm.

3. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The mass fraction of olive leaf powder in the suspension in step (1) is 2.5-5.0%.

4. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The concentration of the ethanol-water solution in step (1) is 25-30%; the solid-liquid separation is performed by centrifugation at 6000-10000 rpm for 10 min.

5. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The sand-removing attapulgite mentioned in step (2) is made by cyclone separation, grading or pulping of attapulgite crushed to 200 mesh or above, followed by at least two stages of hydraulic cyclone treatment.

6. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: In step (2), the sand-removing attapulgite is first pretreated by dissociation of bar crystal bundles and then uniformly dispersed in a cerium nitrate aqueous solution.

7. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: In step (2), the mass fraction of the sand-removing attapulgite in the suspension is 5-10%; the mass ratio of cerium nitrate aqueous solution to plant extract is 3:7; and the pH of the solution is adjusted with 2M sodium hydroxide or 1.5M ammonia aqueous solution.

8. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The ester modifier mentioned in step (3) is at least one of phosphate ester, oleate ester, borate ester, and polyol ester.

9. The method for improving the friction-reducing, wear-resistant, and self-repairing properties of lubricating oil by adding attapulgite / nano-cerium oxide composite material as described in claim 1, characterized in that: The frequency of the sand milling process in step (3) is 30~50Hz, and the diameter of the grinding balls is 0.5~2.0 mm.

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