A method for reusing lubricating oil based on membrane separation and ultrafiltration

Abstract

This invention relates to the field of comprehensive utilization technology of waste mineral oil, and in particular to a method for reusing lubricating oil based on membrane separation and ultrafiltration. The invention discloses a method for reusing lubricating oil based on membrane separation and ultrafiltration. First, waste lubricating oil is preheated and then an adsorbent is added. After stirring, settling, and filtering, a preliminary purified oil is obtained. The adsorbent is composed of multiple components, including silanized basalt fibers. Second, the preliminary purified oil is separated by microfiltration and ultrafiltration membranes to obtain a refined base oil precursor. The microfiltration membrane contains basalt fibers, and the ultrafiltration membrane is a metal-organic framework-ionic liquid type. Next, a hydrogenation modifier is added to the refined base oil precursor to hydrogenate it, resulting in a hydrogenated base oil. The hydrogenation modifier is a cerium-doped nickel-molybdenum-phosphorus / zirconium-based metal-organic framework. Finally, the hydrogenated base oil is preheated, then an anti-wear agent is added and subjected to high-speed shearing. An antioxidant is then added, followed by stirring, distillation, and filtration to obtain the lubricating oil, achieving efficient regeneration.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of waste mineral oil, and in particular to a method for reusing lubricating oil based on the combined use of membrane separation and ultrafiltration. Background Technology

[0002] During use, waste lubricating oil can become contaminated with various impurities, such as carbon black, colloidal particles, metal shavings, sulfur, nitrogen, and aromatics. Furthermore, oxidation and other reactions can produce substances like aldehydes, ketones, and asphaltenes, leading to performance degradation. Since most components of waste lubricating oil have reuse value, regenerating it is of great significance as it conserves resources and reduces environmental pollution.

[0003] Traditional waste lubricating oil regeneration processes have many limitations, such as the use of strong acids and alkalis during the process, which can easily cause environmental pollution; high energy consumption and complex operation; difficulty in completely removing various impurities; unstable quality of regenerated oil; and difficulty in achieving key properties such as anti-wear and anti-oxidation, which cannot meet the needs of high-end equipment.

[0004] Membrane separation technology, with its high efficiency, energy saving, and pollution-free characteristics, has shown potential in the field of waste lubricating oil regeneration, and can effectively separate some impurities. However, single membrane separation technology may face problems such as oil adhesion and membrane fouling during the process, and it is difficult to completely separate impurities of different sizes, resulting in limited purification effects.

[0005] Chinese patent CN103289807A discloses an integrated membrane treatment process for the purification and regeneration of waste lubricating oil. In this process, waste lubricating oil undergoes natural sedimentation to remove impurities and water, followed by extraction with a polar organic solvent to separate a mixture, oil residue, and water. The mixture is then separated into oil and solvent in a separation tower, with the solvent being recovered and reused. The separated waste lubricating oil is heated to reduce viscosity, then subjected to coarse filtration with a metal filter, fine filtration with a metal membrane to remove impurities, adsorption with clay to remove contaminants, and plate and frame filtration to remove the clay. Finally, additives are added to produce the finished regenerated lubricating oil. This patent relies on clay adsorption, relying solely on the physical adsorption of impurities through a porous structure, which may result in significant oil loss and weak targeting for complex impurities. The use of only a single-stage metal membrane filtration may be insufficient in retaining small polar impurities, and the risk of membrane fouling is high. The absence of a hydrotreating step and the addition of only conventional performance additives may result in insufficient chemical stability and performance of the regenerated base oil.

[0006] Chinese Patent CN119591660A discloses a method and system for the continuous production of base oil from chlorosilicone-containing waste mineral oil. In this method, the waste mineral oil is first subjected to thermal sedimentation to remove impurities such as solid particles, sludge, and water. It then enters a flash evaporation unit to separate light component oil and heavy component oil. The heavy component oil is first dechlorinated with a heavy oil dechlorinating agent, then with a demetallizing agent to remove metallic impurities. After vacuum distillation, distillate oil, light fraction, and residue oil are obtained. The light component oil, after oil-water separation, is added together with the aforementioned light fraction to a light oil dechlorinating agent for dechlorination. The dechlorinated light oil is mixed with the residue oil and filtered through a ceramic nanofiltration membrane or a silicon carbide tubular membrane. The resulting clear liquid and distillate oil enter an adsorption desiliconization tank to remove silicon impurities. Finally, after a three-stage hydrogenation reaction and distillation, solvent oil, industrial white oil, and base oil are obtained. This patent primarily relies on thermal settling, dechlorination agents, demetallizing agents, and chelating resin adsorption for desilication. It shows good results in treating specific impurities such as chlorine, silicon, and metals, but lacks a multi-component synergistic design for adsorbing complex impurities in waste oil, such as gums, asphaltenes, and acidic substances. Using a single ceramic nanofiltration membrane or silicon carbide tubular membrane mainly removes large particulate impurities, with limited precision in removing small polar impurities, and anti-clogging relies on a backwashing system. After hydrogenation and distillation, base oils and other products are directly obtained without specific optimization for the anti-wear and anti-oxidation properties of the finished product, potentially resulting in insufficient lubrication performance under high load and high temperature environments.

[0007] In summary, combining membrane separation with ultrafiltration, along with adsorption, hydrotreating, and the addition of composite additives, to form a synergistic treatment system represents an important direction for the deep regeneration of waste lubricating oil. This combined approach leverages the advantages of each process, achieving gradient removal of different impurities, improving the purity and performance of the regenerated oil, while simultaneously reducing pollution and energy consumption, thus meeting the requirements of green environmental protection and efficient resource utilization. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for reusing lubricating oil based on a combination of membrane separation and ultrafiltration, specifically comprising the following steps:

[0009] S001, preheat the waste lubricating oil, add an adsorbent, and perform adsorption and filtration treatment to obtain the preliminary purified oil;

[0010] S002, the pre-purified oil is passed through a microfiltration membrane and an ultrafiltration membrane for separation treatment to obtain the refined base oil precursor;

[0011] S003, add a hydrotreating agent to the refined base oil precursor and perform hydrotreating to obtain the hydrotreated base oil;

[0012] S004 involves preheating the hydrotreated base oil, slowly adding an anti-wear agent, performing high-speed shearing, slowly adding an antioxidant, stirring, vacuum distilling, cooling to room temperature, and then filtering to obtain the lubricating oil.

[0013] In step S001, the waste lubricating oil is preheated to 60~80 ℃, and the adsorbent is added at 2% of the oil mass. The adsorption treatment is carried out by stirring at 300 rpm for 30 min and then letting it stand for 2 h. The filtration treatment is carried out by plate and frame filtration.

[0014] In step S002, the conditions for microfiltration membrane separation are 1.0 MPa pressure, 70 ℃, crossflow rate of 3.5 m / s, and backwashing cycle of 6 h. The conditions for ultrafiltration membrane separation are 0.6 MPa pressure and 100 ℃.

[0015] In step S003, the amount of hydrotreating agent added is 1.5% of the mass of the refined base oil precursor, and the hydrotreating conditions are 14.5 MPa pressure, 355 ℃, 10 L / h hydrogen flow rate, and 2 h.

[0016] In step S004, the preheating conditions are 65 ℃, 200 rpm for 10 min, the amount of anti-wear agent added is 2% of the hydrotreated base oil, the high-speed shearing conditions are 1000 rpm for 15 min, the stirring conditions are 300 rpm for 30 min, and the vacuum distillation conditions are 120 ℃, -0.09 MPa for 2 h.

[0017] The adsorbent is composed of basalt fibers with a silanized surface, a silica network derived from tetraethyl orthosilicate, a modified copolymer of acrylamide-maleic anhydride-N-isopropylacrylamide, sodium allyl sulfonate, and trimethylsiloxy group derived from hexamethyldisilazane, with a mass ratio of 5:85:9:0.3:0.1. The specific preparation method includes the following steps:

[0018] S101, basalt fibers are immersed in hydrochloric acid solution, shaken, washed and dried, then immersed in γ-aminopropyltriethoxysilane solution, refluxed, washed and dried to obtain pretreated basalt fibers.

[0019] S102 involves deoxygenating an ethanol solution containing acrylamide-maleic anhydride copolymer and N-isopropylacrylamide, adding potassium persulfate initiator, performing polymerization, cooling, dialysis, and freeze-drying to obtain the modified copolymer.

[0020] S103, the modified copolymer is added to an ethanol solution for mixing, sodium allyl sulfonate is slowly added, the mixture is stirred, pretreated basalt fiber is added for dispersion, and the pH is adjusted.

[0021] S104 is subjected to a catalyst dropwise with stirring, followed by the addition of formamide for gelation, the addition of hexamethyldisilazane solution for oleophobic treatment, and then washing, drying, and stabilization to obtain the adsorbent.

[0022] In step S101, the concentration of hydrochloric acid solution was 1 M, and the shaking treatment conditions were 60 ℃, 150 rpm, and 2 h. After washing with ultrapure water until neutral, the drying treatment conditions were 110 ℃ and 2 h. The γ-aminopropyltriethoxysilane solution was an ethanol solution of γ-aminopropyltriethoxysilane with a concentration of 2% and a pH of 4.5~5.5. The reflux treatment conditions were 70 ℃ and 4 h. Then, it was cooled to room temperature, washed three times with anhydrous ethanol, and the drying treatment conditions were 60 ℃, -0.09 MPa, and 1 h.

[0023] In step S102, the molar ratio of acrylamide-maleic anhydride copolymer to N-isopropylacrylamide is 10:1. The ethanol solution is a 70% aqueous ethanol solution with a pH of 8.0-9.0. The deoxygenation treatment conditions are 65 °C, nitrogen, for 30 min. The concentration of potassium persulfate initiator is 0.5%. The polymerization treatment conditions are 65 °C, nitrogen, for 3 h. After cooling to room temperature, the mixture is transferred to a dialysis bag with a molecular weight cutoff of 8000-14000 and dialyzed in ultrapure water for 72 h. The freeze-drying conditions are -50 °C for 24 h.

[0024] In step S103, the mass ratio of the modified copolymer, sodium allyl sulfonate, and pretreated basalt fiber is 9:0.3:5. The ethanol solution is an 80% aqueous ethanol solution with a pH of 8.5-9.5. The mixing conditions are 40 ℃ and 300 rpm until dissolved. The stirring conditions are 60 ℃, 300 rpm, and 30 min. The dispersion conditions are 0-2 ℃, 500 W, and 30 min, with a pH of 9-10.

[0025] In step S104, the catalyst is composed of tetraethyl orthosilicate-ethanol solution, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer, and formamide. The mass ratio of tetraethyl orthosilicate, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer, and formamide is 1:0.1:0.5, and the molar ratio of tetraethyl orthosilicate to ethanol is 1:4. The stirring conditions are 25 °C, 300 rpm, and 20 min. The gelation treatment involves first standing at 40 °C for 24 h, followed by aging in anhydrous ethanol for 24 h. The mass ratio of hexamethyldisilazane to pretreated basalt fiber is 1:50, and the hexamethyldisilazane solution concentration is 3.4 mg / mL. The oleophobic treatment conditions are 80 °C for 6 h, followed by cooling and washing five times with anhydrous ethanol. Before drying, the catalyst is first immersed in tert-butanol for 24 h, then pre-frozen at -40 °C for 6 h, and dried at -50 °C and 10 Pa for 24 h. The stabilization treatment is performed by placing the catalyst in a supercritical fluid at 40 °C. At ℃, 10 MPa, 2 h, then immersed in an ethanol-acetic acid solution with a volume ratio of 9:1, microwave irradiated at 60 ℃ and 300 W for 10 min, and then dried at 40 ℃ for 30 min.

[0026] The microfiltration membrane is a ceramic microfiltration membrane containing basalt fibers, cerium oxide, and surface-grafted sodium dodecylbenzenesulfonate hydrophobic segments. The specific preparation method includes the following steps:

[0027] S201 involves adding pretreated basalt fibers, cerium oxide, and alumina to anhydrous ethanol and a dispersant, followed by homogenization, molding, and sintering to obtain a sintered membrane.

[0028] S202, the sintered membrane is immersed in the modification solution for modification treatment, and the microfiltration membrane is obtained.

[0029] In step S201, the pretreated basalt fiber is first soaked in 5% dilute hydrochloric acid for 30 min, then rinsed with ultrapure water until neutral, and then dried at 120 ℃. The mass ratio of the pretreated basalt fiber, cerium oxide, and alumina is 3:1:96. Anhydrous ethanol is added at a solid-liquid mass-volume ratio of 1:3. The dispersant is 0.5% polyacrylic acid. Homogenization is performed by ball milling at 300 rpm for 24 h. The molding process involves drying at 60 ℃ for 24 h, followed by drying at 80 ℃ for 12 h. The sintering process involves heating at 5 ℃ / min to 600 ℃ for 1 h, then heating at 3 ℃ / min to 1200 ℃ for 2 h, and finally cooling to room temperature.

[0030] In step S202, the modification solution is a 5% sodium dodecylbenzenesulfonate ethanol solution. The modification treatment involves first reacting at 80 °C for 4 h, then washing three times with anhydrous ethanol, and finally drying at 80 °C.

[0031] The ultrafiltration membrane is a metal-organic framework-ionic liquid ultrafiltration membrane, and the specific preparation method includes the following steps:

[0032] S301, chromium-based MIL-101 is immersed in lithium-based ionic liquid, loaded and vacuum dried to obtain the filler;

[0033] S302, add N-methylpyrrolidone to the filler and sonicate, then add polyethersulfone for dispersion treatment to obtain the casting solution;

[0034] S303 involves scraping and solidifying the casting solution to obtain an ultrafiltration membrane.

[0035] The loading conditions in step S301 are 60 ℃, 300 rpm, 24 h, and the vacuum drying conditions are -0.09 MPa, 120 ℃, 24 h.

[0036] In step S302, the ultrasonic treatment conditions are 500 W for 30 min, and the dispersion treatment is to first pass through 60 ℃, 300 rpm for 12 h, and then let it stand for 6 h. The mass ratio of filler, N-methylpyrrolidone, and polyethersulfone is 12:73:15.

[0037] In step S303, the film coating process involves coating the casting solution onto a polyester nonwoven fabric substrate to form a liquid film. The curing process involves first immersing the substrate in a 30% N-methylpyrrolidone aqueous solution at 25 °C, then immersing it in ultrapure water at 60 °C for 48 h, and finally air-drying it at room temperature for 24 h.

[0038] The hydrogenation modifier is a cerium-doped nickel-molybdenum-phosphorus / zirconium-based metal-organic framework, and the specific preparation method includes the following steps:

[0039] S401, the zirconium-based UiO-66 metal-organic framework is immersed in the active component solution for adsorption treatment;

[0040] S402, cerium oxide is added, and the mixture is stirred. A complexing agent is added, and the mixture is aged, dried, calcined, and reduced to obtain a cerium-doped nickel-molybdenum-phosphorus / zirconium-based metal-organic framework, which is referred to as a hydrogenation modifier.

[0041] In step S401, the active component solution is composed of nickel sulfate, ammonium heptamolybdate, and ammonium hydrogen phosphate in a molar ratio of 1:0.8:0.5, the carrier loading is 15%, and the adsorption treatment conditions are 60 ℃, 300 rpm, and 4 h.

[0042] In step S402, the amount of cerium oxide used is 0.2% of the carrier mass, the stirring conditions are 60 ℃, 300 rpm, 2 h, the complexing agent is 0.5 M citric acid, the volume is 10% of the total solution volume, the aging conditions are 80 ℃, 12 h, the drying conditions are 120 ℃, -0.09 MPa, 8 h, the calcination conditions are 400 ℃ under nitrogen, 3 h, and the reduction conditions are 350 ℃ under a mixed protective gas, which is a mixture of 70% nitrogen and 30% hydrogen.

[0043] The anti-wear agent is composed of zinc dialkyl dithiophosphate, titanium dioxide-coated antimony-doped tin oxide, and polyisobutylene succinimide. The mass ratio of zinc dialkyl dithiophosphate to titanium dioxide-coated antimony-doped tin oxide is 5:1. The amount of polyisobutylene succinimide added is 0.5% of the hydrotreated base oil. The anti-wear agent is obtained by adding zinc dialkyl dithiophosphate and titanium dioxide-coated antimony-doped tin oxide to polyisobutylene succinimide and stirring at -20 ℃ and 500 rpm for 30 min.

[0044] The antioxidant is composed of 2,6-di-tert-butyl-p-cresol and diphenylamine, with the addition amounts being 0.2% and 0.1% of the hydrogenated base oil, respectively. The antioxidant is obtained by mixing 2,6-di-tert-butyl-p-cresol and diphenylamine and stirring at 60 °C and 200 rpm for 20 min.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. The adsorbent of this invention achieves highly efficient and selective adsorption through the synergistic effect of multiple components. Basalt fibers on the silanized surface provide a rigid framework; γ-aminopropyltriethoxysilane modification introduces amino groups that can adsorb polar impurities via hydrogen bonding; the tetraethyl orthosilicate-derived silica network forms a porous structure, providing numerous adsorption sites; the acrylamide-maleic anhydride-N-isopropylacrylamide modified copolymer contains polar groups, enabling selective adsorption of polar impurities; the sulfonic acid groups introduced by sodium allyl sulfonate enhance hydrophilicity, further strengthening the adsorption of polar impurities; the oleophobic treatment of hexamethyldisilazane reduces the adsorption of lubricating oil, minimizing oil loss. This adsorbent can efficiently remove harmful impurities such as coagulated n-pentane insolubles, coagulated toluene insolubles, and acidic substances from waste lubricating oil, and maintains relatively stable adsorption performance even after multiple cycles, demonstrating good durability.

[0047] 2. This invention achieves deep purification through gradient membrane material design and combined processes. Using a basalt fiber-reinforced ceramic membrane as the matrix enhances impact resistance; cerium oxide doping decomposes some organic impurities; and surface grafting of hydrophobic sodium dodecylbenzenesulfonate segments reduces oil adhesion to the membrane surface, lowering contamination. The metal-organic framework of the ultrafiltration membrane provides high porosity, while lithium-based ionic liquids enhance selective retention of polar small molecule impurities. Microfiltration pretreatment removes large particles to reduce the ultrafiltration membrane load, while ultrafiltration depth retains small molecule impurities. The two work synergistically to achieve gradient separation of coarse and fine purification, effectively improving oil purity and resulting in a high-purity, highly transparent base oil precursor. Simultaneously, the microfiltration membrane exhibits strong anti-clogging capabilities and extends backwashing intervals; the ultrafiltration membrane maintains stable filtration performance over a long period, ensuring a long service life. The temperature setting is integrated with the waste oil preheating process, avoiding energy waste from repeated heating and aligning with green environmental protection principles.

[0048] 3. The hydrotreating agent of this invention synergistically enhances performance through the support, active components, and dopants. The zirconium-based UiO-66 metal-organic framework serves as the support, possessing a high specific surface area and uniform pore size, enabling uniform dispersion of the active components. The active components, nickel, molybdenum, and phosphorus, act as hydrotreating active centers, desulfurization active centers, and components that promote the dispersion of active components, respectively, and can specifically remove sulfur, nitrogen, and aromatics. The dopant, cerium, enhances the reducing power of nickel through electron transfer effects, improving hydrotreating activity, and can adsorb hydrogen molecules and dissociate them into active hydrogen atoms. This hydrotreating agent effectively removes impurities such as sulfur, nitrogen, and aromatics from lubricating oil, increasing the depth of hydrotreating; it improves base oil performance, increases the viscosity index to enhance viscosity-temperature stability, and lowers the pour point to improve low-temperature fluidity; it also exhibits good stability, with slow activity decay after prolonged continuous use, reducing catalyst replacement frequency and lowering costs.

[0049] 4. This invention solves the problem of simultaneously achieving both wear resistance and antioxidant properties through the synergistic effect of composite anti-wear and antioxidant additives. The anti-wear agent, composed of polyisobutylene succinimide, zinc dialkyl dithiophosphate, and titanium dioxide-coated antimony-doped tin oxide, synergistically forms a dual anti-wear mechanism of chemical film and physical filling. Specifically, zinc dialkyl dithiophosphate forms a chemical adsorption film to enhance wear resistance, while titanium dioxide-coated antimony-doped tin oxide nanoparticles fill the friction surface for physical reinforcement. Polyisobutylene succinimide disperses the nanoparticles, preventing their aggregation. In the antioxidant, the combination of 2,6-di-tert-butyl-p-cresol and diphenylamine enhances antioxidant efficiency through a synergistic effect. 2,6-di-tert-butyl-p-cresol captures free radicals to inhibit oxidation chain reactions, while diphenylamine decomposes peroxides to terminate oxidation. High-speed shearing is used to ensure uniform dispersion of the anti-wear agent, and vacuum distillation is used to remove low-boiling-point impurities to avoid additive failure. This gives the regenerated waste lubricating oil good anti-wear ability and anti-oxidation properties. Even when used for a long time in a high-temperature environment, it can still maintain relatively stable performance, with little viscosity change, and can provide reliable lubrication for equipment.

[0050] 5. This invention achieves efficient regeneration through matching and complementary functions across the entire process. Matching the adsorption pretreatment temperature with the microfiltration membrane operating temperature avoids viscosity increases caused by oil cooling, reducing membrane separation energy consumption. Membrane separation removes colloidal / macromolecular impurities, reducing the load on hydrotreating agents and preventing impurities from covering active sites. The hydrotreated base oil provides a stable matrix for additives, ensuring the full effectiveness of anti-wear agents and antioxidants. Filtration / washing processes in each step prevent secondary contamination by impurities. This process effectively improves the conversion rate of waste lubricating oil and uses recyclable adsorption materials and a high-efficiency membrane separation system, avoiding the use of highly polluting treatment methods such as strong acids and alkalis. This reduces pollutant generation at the source, minimizing the impact on the ecological environment and aligning with green process principles. Detailed Implementation

[0051] The present invention will be further described below with reference to specific embodiments.

[0052] Example 1: A lubricating oil treated with the adsorbent of the present invention, specifically including the following steps:

[0053] 1. Preparation of the adsorbent of this invention:

[0054] 10 g of basalt fiber was immersed in 500 mL of hydrochloric acid solution and shaken at 60 ℃ and 150 rpm for 2 h. It was then washed with ultrapure water until neutral, dried at 110 ℃ for 2 h, immersed in 500 mL of 2% γ-aminopropyltriethoxysilane ethanol solution with pH 5, refluxed at 70 ℃ for 4 h, cooled to room temperature, washed 3 times with anhydrous ethanol, and dried at 60 ℃ and -0.09 MPa for 1 h to obtain pretreated basalt fiber.

[0055] 17.8 g of acrylamide-maleic anhydride copolymer and 1.13 g of N-isopropylacrylamide were added to 200 mL of 70% ethanol aqueous solution with pH 8.5, and treated with nitrogen at 65 ℃ for 30 min. Then, 0.1 g of potassium persulfate initiator was added, and polymerization was carried out at 65 ℃ with nitrogen for 3 h. After cooling to room temperature, the copolymer was transferred to a dialysis bag and dialyzed in ultrapure water for 72 h. Finally, it was dried at -50 ℃ for 24 h to obtain the modified copolymer.

[0056] 15.2 g of the modified copolymer was added to 250 mL of 80% ethanol aqueous solution with pH 9.0 and stirred at 40 ℃ and 300 rpm until dissolved. 0.51 g of sodium allyl sulfonate was slowly added and stirred at 60 ℃ and 300 rpm for 30 min. 8.5 g of pretreated basalt fiber was slowly added and ultrasonically dispersed at 0~2 ℃ and 500 W for 30 min. The pH was then adjusted to 9.5.

[0057] The catalyst is obtained by mixing 2.5 g of tetraethyl orthosilicate, 2.2 g of anhydrous ethanol and 0.25 g of polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0058] Add the catalyst dropwise, stir at 25 °C and 300 rpm for 20 min, add 1.25 g of formamide, first gel at 40 °C for 24 h, then age in anhydrous ethanol for 24 h, add 50 mL of 3.4 mg / mL hexamethyldisilazane ethanol solution, treat with oleophobicity at 80 °C for 6 h, cool and wash 5 times with anhydrous ethanol, immerse in tert-butanol for 24 h, pre-freeze at -40 °C for 6 h, dry at -50 °C and 10 Pa for 24 h, supercritical treatment at 40 °C and 10 MPa for 2 h, immerse in ethanol-acetic acid solution with a volume ratio of 9:1, microwave irradiate at 60 °C and 300 W for 10 min, and dry at 40 °C for 30 min to obtain the adsorbent of the present invention.

[0059] 2. Methods for treating lubricating oil:

[0060] 500 g of waste lubricating oil was preheated to 70 °C, 10 g of the adsorbent of this invention was added, stirred at 300 rpm for 30 min, allowed to stand for 2 h, and filtered by plate and frame filtration to obtain the preliminarily purified oil, which is recorded as test sample 1.

[0061] Example 2: A lubricating oil treated by the combined microfiltration and ultrafiltration membranes of the present invention, specifically comprising the following steps:

[0062] 1. Preparation of the microfiltration membrane of the present invention:

[0063] Basalt fibers were soaked in 5% dilute hydrochloric acid for 30 minutes, rinsed with ultrapure water until neutral, and dried at 120 ℃.

[0064] 3 g of pretreated basalt fiber, 1 g of cerium oxide and 96 g of alumina were added to 300 mL of anhydrous ethanol and 0.5 g of 0.5% polyacrylic acid dispersant. The mixture was ball-milled at 300 rpm for 24 h, dried at 60 ℃ for 24 h, and then dried at 80 ℃ for 12 h to form a sintered film. The film was then heated to 600 ℃ at 5 ℃ / min for 1 h, and then heated to 1200 ℃ at 3 ℃ / min for 2 h. Finally, it was cooled to room temperature to obtain the sintered film.

[0065] The sintered membrane was immersed in a 5% sodium dodecylbenzenesulfonate ethanol solution for modification, reacted at 80 °C for 4 h, rinsed three times with anhydrous ethanol, and then dried at 80 °C to obtain the microfiltration membrane.

[0066] 2. Preparation of the ultrafiltration membrane of the present invention:

[0067] 12 g of chromium-based MIL-101 was immersed in a lithium-based ionic liquid, loaded at 60 ℃ and 300 rpm for 24 h, and dried at -0.09 MPa and 120 ℃ for 24 h to obtain the filler.

[0068] S302: Add 12 g of filler to 73 g of N-methylpyrrolidone, sonicate at 500 W for 30 min, add 15 g of polyethersulfone, disperse at 60 ℃ and 300 rpm for 12 h, and let stand for 6 h to obtain the casting solution.

[0069] S303 involves coating a casting solution onto a polyester nonwoven fabric substrate to form a liquid film, immersing it in a 30% N-methylpyrrolidone aqueous solution at 25 ℃, immersing it in ultrapure water at 60 ℃ for 48 h, and then air-drying it at room temperature for 24 h to obtain an ultrafiltration membrane.

[0070] 3. Methods for treating lubricating oil:

[0071] Sample 1 was introduced into a microfiltration membrane at a pressure of 1.0 MPa, a temperature of 70 ℃, and a crossflow rate of 3.5 m / s. After a backwashing cycle of 6 h, it was introduced into an ultrafiltration membrane at a pressure of 0.6 MPa and a temperature of 100 ℃ to obtain the refined base oil precursor, which was designated as sample 2.

[0072] Example 3: A lubricating oil treated with the hydrogenation modifier of the present invention, specifically including the following steps:

[0073] 1. Preparation of the hydrogenation modifier of this invention:

[0074] Add 0.43 g nickel sulfate, 2.41 g ammonium heptamolybdate, and 0.18 g ammonium hydrogen phosphate to 100 mL of ultrapure water to obtain the active component solution;

[0075] 20 g of zirconium-based UiO-66 metal-organic framework was immersed in the above active component solution and adsorbed at 60 °C and 300 rpm for 4 h.

[0076] Add 0.04 g of cerium oxide, stir at 60 °C and 300 rpm for 2 h, add 10 mL of 0.5 M citric acid complexing agent, age at 80 °C for 12 h, dry at 120 °C and -0.09 MPa for 8 h, calcine at 400 °C under nitrogen for 3 h, and reduce at 350 °C for 4 h under a mixed protective atmosphere of 70% nitrogen and 30% hydrogen to obtain cerium-doped nickel-molybdenum-phosphorus / zirconium-based metal-organic framework, denoted as hydrogenation modifier.

[0077] 2. Methods for treating lubricating oil:

[0078] Add 3 g of hydrotreating agent to 200 g of sample 2, and hydrotreat for 2 h at 14.5 MPa pressure, 355 ℃ and 10 L / h hydrogen flow rate to obtain the hydrotreated base oil, which is designated as sample 3.

[0079] Example 4: A lubricating oil treated with the anti-wear agent and antioxidant of the present invention, specifically comprising the following steps:

[0080] 1. Preparation of the anti-wear agent of the present invention:

[0081] Add 5 g of polyisobutylene succinimide, 12.5 g of zinc dialkyl dithiophosphate and 2.5 g of titanium dioxide-coated antimony-doped tin oxide to a 50 mL beaker and stir at -20 ℃ and 500 rpm for 30 min to obtain the anti-wear agent.

[0082] 2. Preparation of the antioxidant of the present invention:

[0083] Mix 2 g of 2,6-di-tert-butyl-p-cresol with 1 g of diphenylamine and stir at 60 °C and 200 rpm for 20 min to obtain the antioxidant.

[0084] 3. Methods for treating lubricating oil:

[0085] Preheat sample 3 to 65 ℃, maintain at 200 rpm for 10 min, slowly add anti-wear agent, perform high-speed shearing at 1000 rpm for 15 min, slowly add antioxidant, stir at 300 rpm for 30 min, distill under reduced pressure at 120 ℃ and -0.09 MPa for 2 h, cool to room temperature and filter to obtain lubricating oil, which is designated as sample 4.

[0086] Comparative Example 1

[0087] A lubricating oil treated with activated carbon specifically includes the following steps:

[0088] The difference from Example 1 is that 800-mesh activated carbon is used instead of the adsorbent of the present invention, and the remaining steps are carried out according to the lubricating oil treatment method in Example 1, thus obtaining control product 1.

[0089] Comparative Example 2

[0090] A lubricating oil treated with diatomaceous earth specifically includes the following steps:

[0091] The difference from Example 1 is that 500-mesh diatomaceous earth is used instead of the adsorbent of the present invention, and the remaining steps are carried out according to the lubricating oil treatment method in Example 1, thus obtaining control product 2.

[0092] Comparative Example 3

[0093] A lubricating oil treated with a single ceramic microfiltration membrane and a single organic ultrafiltration membrane specifically includes the following steps:

[0094] The difference from Example 2 is that a single ceramic microfiltration membrane with a pore size of 0.2 μm is used instead of the microfiltration membrane of the present invention, and a single organic ultrafiltration membrane with a molecular weight cutoff of 1000 Da is used instead of the ultrafiltration membrane of the present invention. The remaining steps are carried out according to the lubricating oil treatment method in Example 2, thus obtaining control product 3.

[0095] Comparative Example 4

[0096] A lubricating oil treated with a nickel-molybdenum-phosphorus catalyst / alumina hydrogenation catalyst specifically includes the following steps:

[0097] The difference from Example 3 is that a nickel-molybdenum-phosphorus catalyst / alumina hydrogenation catalyst is used instead of the hydrogenation modifier of the present invention, and the remaining steps are carried out according to the lubricating oil treatment method in Example 3, thus obtaining control product 4.

[0098] Comparative Example 5

[0099] A lubricating oil treated with the addition of a single anti-wear agent and a single antioxidant specifically includes the following steps:

[0100] The difference from Example 4 is that zinc dialkyl dithiophosphate is used instead of the anti-wear agent of the present invention, and 2,6-di-tert-butyl-p-cresol is used instead of the antioxidant of the present invention. The remaining steps are carried out according to the lubricating oil treatment method in Example 4, thus obtaining control product 5.

[0101] Experimental Example 1

[0102] This experimental example tests the high-efficiency selective adsorption performance of the test sample from Example 1 and the control samples from Comparative Examples 1 and 2, specifically including the following steps:

[0103] 1. Comparative experiment on adsorption efficiency:

[0104] Determination of n-pentane insolubles after condensation:

[0105] Add 50 mL of n-butyldiethanolamine and 50 mL of isopropanol to 1 L of n-pentane solvent and mix to obtain n-pentane-coagulant solution;

[0106] Place a clean centrifuge tube in an oven at 105 ℃±3 ℃ for 30 min, cool it in a desiccator, and weigh the centrifuge tube. Record the weight as m0.

[0107] Add 10.0 g of the waste lubricating oil from Example 1, test sample 1, reference sample 1, and reference sample 2 to the centrifuge tubes mentioned above. Add n-pentane-coagulant solution to the 100 mL mark, stopper the tubes, shake to mix, centrifuge at 1500 r / min for 20 min, and pour off the supernatant to make the remaining liquid less than 3 mL. Add 10 mL of n-pentane, stir to disperse the precipitate, add n-pentane to the 50 mL mark, shake to mix, centrifuge at 1500 r / min for 20 min, and pour off the supernatant to complete one washing cycle. Repeat the washing cycle once more.

[0108] Centrifuge tubes were dried in an oven at 105 ℃ ± 3 ℃ for 30 min, cooled in a desiccator, and weighed. The weight was recorded as m1. Each sample was tested in triplicate.

[0109] The mass fraction of n-pentane insolubles after condensation is calculated based on the ratio of the difference between m1 and m0 to the sample weight.

[0110] Determination of toluene-insoluble matter after coagulation:

[0111] Mix 50 mL of toluene and 50 mL of 95% ethanol to obtain a toluene-ethanol solution;

[0112] Place a clean centrifuge tube in an oven at 105 ℃±3 ℃ for 30 min, cool it in a desiccator, and weigh the centrifuge tube. Record the weight as m2.

[0113] Add 10.0 g of the waste lubricating oil from Example 1, test sample 1, reference sample 1, and reference sample 2 to the centrifuge tubes mentioned above. Add n-pentane-coagulant solution to the 100 mL mark, stopper the tubes, shake to mix, centrifuge at 1500 r / min for 20 min, and pour off the supernatant to make the remaining liquid less than 3 mL. Add 10 mL of n-pentane, stir to disperse the precipitate, add n-pentane to the 50 mL mark, shake to mix, centrifuge at 1500 r / min for 20 min, and pour off the supernatant to complete one washing cycle. Repeat the washing cycle once more.

[0114] Add 10 mL of toluene-ethanol solution, stir to disperse the precipitate, add toluene-ethanol solution to the 50 mL mark, shake to mix, centrifuge at 1500 r / min for 20 min, decant the supernatant, add 10 mL of toluene, stir to disperse the precipitate, add toluene to the 50 mL mark, shake to mix, centrifuge at 1500 r / min for 20 min, and decant the supernatant.

[0115] Centrifuge tubes were dried in an oven at 105 ℃ ± 3 ℃ for 1 h, cooled in a desiccator, and weighed. The weight was recorded as m3. Each sample was tested in triplicate.

[0116] The mass fraction of toluene-insoluble matter after coagulation was calculated based on the ratio of the sample weight difference between m3 and m1. The results are shown in Table 1.

[0117] The mass fraction of insoluble colloids after coagulation was calculated based on the difference between the mass fraction of n-pentane insoluble matter and the mass fraction of toluene insoluble matter after coagulation. The results are shown in Table 1.

[0118] Determination of acidic substance content:

[0119] Mix 100 mL of toluene and 100 mL of isopropanol to obtain a toluene-isopropanol mixed solvent;

[0120] 10 g of waste lubricating oil from Example 1, test sample 1, reference sample 1, and reference sample 2 were placed in 250 mL beakers, and 125 mL of toluene-isopropanol mixed solvent was added. The mixture was stirred until the samples were completely dissolved. Each sample was in triplicate.

[0121] Place the beaker on an electromagnetic stirrer, insert the glass electrode and calomel electrode, connect the potentiometric titrator, and titrate with a 0.1 mol / L potassium hydroxide-isopropanol standard solution. Record the potential change during the titration process, determine the titration endpoint, and read the volume of potassium hydroxide-isopropanol standard solution consumed.

[0122] The content of acidic substances was calculated by the ratio of the product of the volume of potassium hydroxide-isopropanol standard solution consumed, the concentration of potassium hydroxide-isopropanol standard solution, and the molar mass of potassium hydroxide to the sample mass. The results are shown in Table 1.

[0123] Using the waste lubricating oil from Example 1 as the initial sample, the total mass fraction of toluene insoluble matter after coagulation, the mass fraction of insoluble colloids after coagulation, and the content of acidic substances were used to calculate the impurity content. The impurity removal rate was calculated based on the ratio of the difference between the initial impurity content and the treated impurity content to the initial impurity content. The results are shown in Table 1.

[0124] 2. Stability Cyclic Experiment:

[0125] The adsorbent obtained from the comparative adsorption efficiency experiment was collected, washed three times with anhydrous ethanol, and then dried at 60 °C. The dried adsorbent was then used again to adsorb waste lubricating oil, and the adsorption experiment was repeated five times.

[0126] Following the comparative experimental method for adsorption efficiency, the impurity removal rate was measured for the fifth time. The attenuation rate was calculated based on the ratio of the difference between the first and fifth impurity removal rates to the first removal rate. The results are shown in Table 1.

[0127] Table 1 Comparative experimental results of adsorption efficiency

[0128]

[0129] As shown in Table 1, the mass fraction of toluene-insoluble matter after coagulation in Example 1 was 0.12%, and the mass fraction of insoluble colloids was 0.18%, which is much lower than that in Comparative Examples 1 and 2. This indicates that the adsorbent of the present invention has a stronger adsorption capacity for these two types of substances and can effectively reduce such impurities in lubricating oil. The content of acidic substances in Example 1 was only 0.1%, compared to 1.4% in Comparative Example 1 and 1.7% in Comparative Example 2, demonstrating that the adsorbent of the present invention has a good removal effect on acidic substances and can optimize the acid value of lubricating oil. The impurity removal rate of Example 1 was as high as 97.3%, which is much lower than that in Comparative Examples 1 and 2, indicating that the adsorbent of the present invention can remove impurities in lubricating oil more efficiently and improve oil purity. The attenuation rate of Example 1 was 6.9%, which is much lower than that in Comparative Examples 1 and 2, indicating that the adsorbent of the present invention has good stability, and the adsorption performance decreases only slightly after multiple cycles, demonstrating good durability.

[0130] In summary, when treating lubricating oil, the adsorbent of this invention is significantly superior to activated carbon and diatomaceous earth in reducing the content of various insoluble and acidic substances after coagulation, improving the impurity removal rate, and maintaining the stability of the adsorbent. It can effectively optimize the quality of lubricating oil and has good application potential.

[0131] Experimental Example 2

[0132] This experimental example demonstrates gradient membrane separation testing of the combined microfiltration and ultrafiltration membranes of the present invention on the test sample of Example 2 and the control sample of Comparative Example 3. The specific steps include:

[0133] 1. Impurity content determination:

[0134] Place a 100 mL G4 glass frit funnel in an oven at 105±2 ℃ and dry until constant weight. Weigh the sample and record the weight as m4. Each sample is tested in triplicate.

[0135] 100 g of test sample 2 and reference sample 3 were placed in 250 mL beakers, 60 mL of toluene was added, the mixture was heated to 80 °C in a water bath and stirred until completely dissolved, then transferred to a G4 glass frit funnel, filtered under reduced pressure while hot, and washed 5 times with toluene at 80 °C. The G4 glass frit funnel containing impurities was placed in an oven at 105 ± 2 °C and dried for 50 min. After cooling to room temperature, it was weighed and the weight was recorded as m5. Each sample 3 was tested in parallel.

[0136] The mechanical impurity content was calculated based on the ratio of the difference between m5 and m4 to the sample mass, and the results are shown in Table 2.

[0137] 2. Transmittance measurement:

[0138] Sample 2 and reference 3 were placed in cuvettes and measured at a wavelength of 600 nm using a UV-Vis spectrophotometer. Each sample 3 was measured in parallel, with sample 1 as the reference. The transmittance of the samples was recorded, and the results are shown in Table 2.

[0139] Table 2. Results of Impurity Content and Transmittance Measurement

[0140]

[0141] As shown in Table 2, Example 2 uses a combination of microfiltration and ultrafiltration membranes of the present invention to treat lubricating oil, while Comparative Example 3 uses a single ceramic microfiltration membrane and a single organic ultrafiltration membrane. Regarding the mechanical impurity content, Example 2 is significantly lower than Comparative Example 3, indicating that the combined membrane of the present invention can more efficiently retain mechanical impurities and improve oil cleanliness. In terms of light transmittance, Example 2 is significantly higher than Comparative Example 3, reflecting that after treatment with the combined membrane of the present invention, there are fewer impurities affecting light transmittance in the lubricating oil, resulting in better light transmittance. This further demonstrates that the combined use of microfiltration and ultrafiltration membranes of the present invention is superior to conventional single-membrane combinations in optimizing lubricating oil quality, showcasing the advantages of gradient membrane separation.

[0142] Experimental Example 3

[0143] This experimental example tests the performance of the hydrogenation modifier on the test sample of Example 3 and the control sample of Comparative Example 4, specifically including the following steps:

[0144] 1. Comparison experiment on hydrogenation efficiency:

[0145] Sulfur content determination:

[0146] Weigh 0.2 g of test sample 2, test sample 3, and reference sample 4 into a porcelain boat. Cover the oil sample in the porcelain boat with fine sand. Place the porcelain boat into the high-temperature zone of the porcelain tube of a tube furnace, quickly stopper it, connect the air source and flow meter, set the air flow rate to 500 mL / min, and burn the tube furnace at 900~950 ℃ for 35 min. Remove the receiver, rinse the glass bend with distilled water, add bromocresol green-methyl red mixed indicator, and titrate with 0.02 mol / L sodium hydroxide standard solution until the solution changes from purple-red to dark green. Record the volume of sodium hydroxide standard solution consumed. Perform three replicates for each sample.

[0147] The sulfur content is calculated based on the ratio of the product of the concentration of the sodium hydroxide standard solution, the volume of sodium hydroxide standard solution consumed, and the molar mass of sulfur to the sample mass. The sulfur content of test sample 2 is taken as the sulfur content before hydrogenation.

[0148] Nitrogen content determination:

[0149] Add 10 mg of 8-hydroxyquinoline to a 100 mL volumetric flask and dilute to the mark with xylene to obtain the nitrogen standard stock solution.

[0150] Take 10 mL, 1 mL, 0.1 mL, 0.01 mL, and 0.005 mL of nitrogen standard stock solution respectively into 100 mL volumetric flasks, and dilute to the mark with xylene to obtain nitrogen standard working solutions;

[0151] Dissolve 1 g of test sample 2, test sample 3, and reference standard 4 in 5 g of xylene to obtain the test sample;

[0152] 5 μL of the sample to be tested and nitrogen standard working solution were injected into the boat-injected chemiluminescence analyzer. The oxygen was pyrolyzed at 360±36 mL / min, the inlet oxygen was 60±6 mL / min, the carrier gas was 155±15 mL / min, the boat injection speed was 150±10 mm / min, and the chemiluminescence response value was detected. Each sample was repeated in triplicate, with xylene as a blank.

[0153] A standard curve was plotted with the concentration of the nitrogen standard working solution on the x-axis and the response value on the y-axis. The concentration of the sample was calculated based on the response value, and the nitrogen content was calculated based on the dilution factor and sample mass. The nitrogen content of sample 2 was taken as the nitrogen content before hydrogenation.

[0154] Aromatic hydrocarbon content determination:

[0155] Fill the adsorption column with activated silica gel to half the height of the separation section, add a 3-5 mm thick layer of dyed silica gel, continue filling with silica gel to 75 mm of the feeding section, and compact by vibrating at 100 Hz for 4 min.

[0156] 0.75 mL of test sample 2, test sample 3, and reference sample 4 were injected into the feed section 30 mm below the silica gel surface. After complete adsorption, isopropanol was added to the spherical connector.

[0157] Connect the gas supply system and maintain a pressure of 14 kPa for 2.5 minutes, then maintain a pressure of 34 kPa for 2.5 minutes, and finally adjust to 28~69 kPa.

[0158] When the red alcohol-aromatic interface enters the analytical section 350 mm, the upper end of the aromatic region, i.e. the upper end of the first red-brown ring, is marked under UV light at 365 nm. After the hydrocarbons descend 50 mm, the marking is reversed and marked a second time. The adsorption column is placed horizontally, and the length of the aromatic region marked twice is measured. The length from the upper end of the first red-brown ring to the front of the clear liquid sample is measured, and the total length of the hydrocarbon region is recorded. Three parallel samples are used for each sample.

[0159] The aromatic content is calculated by the ratio of the length of the aromatic hydrocarbon to the total length of the hydrocarbon region, and the aromatic content of sample 2 is taken as the aromatic content before hydrogenation.

[0160] The impurity content after hydrogenation was calculated by summing the sulfur content, nitrogen content, and aromatic hydrocarbon content. The impurity removal rate after hydrogenation was calculated by the ratio of the difference between the impurity content before hydrogenation and the impurity content after hydrogenation to the impurity content before hydrogenation. The results are shown in Table 3.

[0161] 2. Base oil performance testing:

[0162] Viscosity index determination:

[0163] Add 10 mL of test sample 3 and reference sample 4 to test tubes respectively, place them in a 40 ℃ water bath for 30 min, and measure the kinematic viscosity of the samples at 40 ℃ using a kinematic viscosity meter. Each sample 3 is in duplicate.

[0164] Add 10 mL of test sample 3 and reference sample 4 to test tubes respectively, place them in a water bath at 100 ℃ for 30 min, and measure the kinematic viscosity of the samples at 100 ℃ using a kinematic viscosity meter. Each sample 3 is in duplicate.

[0165] Based on the kinematic viscosity of the sample at 40 ℃, the kinematic viscosity of the sample at 100 ℃, and Method B in GB / T 1995-1998 Calculation Method for Viscosity Index of Petroleum Products, the viscosity index was calculated, and the results are shown in Table 3.

[0166] Pour point determination:

[0167] Add 10 mL of test sample 3 and reference sample 4 to test tubes respectively, insert a cloud point and pour point thermometer, heat to 50℃, maintain for 5 min, and cool to room temperature in a 25℃ water bath;

[0168] Place the test tube containing the sample into the cold bath sleeve, so that the liquid level in the test tube is level with the liquid level in the cold bath. Cool at a rate of about 3 °C / min. Every 3 °C, remove the test tube from the sleeve, tilt it at 45° and hold it for 5 seconds. Repeat this process three times for each sample.

[0169] Record the lowest temperature at which the observed sample can flow, i.e., the pour point. The results are shown in Table 3.

[0170] 3. Stability test of hydrogenation modifier

[0171] The hydrogenation modifiers used in the first experiments of Example 3 and Comparative Example 4 were collected, washed three times with anhydrous ethanol, and dried at 60°C for 2 h. They were then used again in the experiments of Example 3 and Comparative Example 4, respectively, meaning the hydrogenation modifiers were used twice. The test samples and control samples were collected after the 100th use. The impurity removal rate after hydrogenation of the hydrogenation modifiers after the 100th use was determined according to the method in the hydrogenation efficiency comparison experiment. Each sample was in triplicate.

[0172] The activity decay rate was calculated based on the ratio of the difference between the impurity removal rate after the first hydrogenation and the impurity removal rate after the 100th hydrogenation to the impurity removal rate after the first hydrogenation. The results are shown in Table 3.

[0173] Table 3 Comparison of Adsorption Efficiency Experimental Results

[0174]

[0175] As shown in Table 3, Example 3, using the hydrotreating agent of this invention, achieved an impurity removal rate of up to 97.2% after hydrotreating; while Comparative Example 4, using a nickel-molybdenum-phosphorus catalyst / alumina hydrotreating catalyst, only achieved a removal rate of 53.2%. This indicates that the hydrotreating agent of this invention is significantly more effective in removing impurities such as sulfur, nitrogen, and aromatics from lubricating oil, greatly reducing the impurity content after hydrotreating and increasing the depth of oil hydrotreating. The viscosity index of Example 3 was 140.8±1.3, higher than that of Comparative Example 4, indicating that the viscosity of the lubricating oil changes less with temperature. After treatment with the hydrotreating agent of this invention, the lubricating oil exhibits better viscosity-temperature stability, which is beneficial for use in a wide temperature range. The pour point of Example 3 reached -25.3±0.6 ℃, lower than that of Comparative Example 4, indicating good low-temperature fluidity of the lubricating oil. The hydrotreating agent of this invention can effectively improve the low-temperature performance of lubricating oil, showing significant advantages in cold environments and other scenarios. Example 3 showed an activity decay rate of 3.6%, which was lower than that of Comparative Example 4. This indicates that the hydrogenation modifier of the present invention exhibits a small decrease in hydrogenation activity after 100 cycles of use, and its stability and durability are far superior to conventional nickel-molybdenum-phosphorus / alumina hydrogenation catalysts. It can reduce the cost of frequent catalyst replacement and is suitable for industrial continuous production applications.

[0176] In summary, the hydrotreating agent of this invention exhibits significant advantages in improving the hydrotreating efficiency of lubricating oil, optimizing the performance of base oil, and ensuring its own stability. It can effectively help upgrade the hydrotreating process of lubricating oil and improve product quality and production economy.

[0177] Experiment Example 4

[0178] This experimental example verifies the synergistic effect of the anti-wear and anti-oxidation composite additive system on the test samples of Examples 3-4 and the control sample of Comparative Example 5, specifically including the following steps:

[0179] 1. Wear resistance test:

[0180] The test was conducted using a four-ball extreme pressure testing machine. Three steel balls were placed in the oil box recess and fixed with a clamping ring. Test sample 3, test sample 4, and control sample 5 were poured in until they submerged the steel balls and reached the joint between the clamping ring and the nut. The upper ball was installed in the chuck and fixed to the spindle. The spindle speed was 1450±50 r / min, the load was 392 N, and the test time was 10 s. The test phenomena were recorded to see if there was jamming, noise, or smoke.

[0181] Remove the steel balls, clean them with petroleum ether, and measure the diameter of the wear scar on each steel ball. The results are shown in Table 4.

[0182] 2. Antioxidant performance test:

[0183] Take 5 mL of test sample 3, test sample 4 and reference sample 5 respectively, and pour them into a clean glass sample cup. Place a polished copper sheet in the sample cup. Each sample 3 is parallel.

[0184] Add 50 mL of ultrapure water to the oxygen bomb, fix the sample cup to the sample holder inside the oxygen bomb, tighten the oxygen bomb cover, fill with oxygen to 690 kPa, close the air inlet valve, let stand for 5 min, place the oxygen bomb in a constant temperature water bath at 150 ℃, rotate the oxygen bomb at a speed of 100±5 r / min, and record the time when the pressure drop rate reaches 0.2 MPa / min, which is the oxidation induction period. The results are shown in Table 4.

[0185] 3. High-temperature stability test:

[0186] Place 100 mL of test sample 3, test sample 4 and reference sample 5 into a clean beaker, cover the mouth of the beaker with breathable plastic wrap, and age in an oven at 150 ℃ for 100 h to obtain aged samples.

[0187] Immediately load 100 mL of each of the following samples into a viscometer: sample 3, sample 4, reference sample 5, and aging sample. Fix the viscometer in a 40 ℃ constant temperature water bath for 15 min. Adjust the viscometer to be vertical and release it. Record the sample flow time. Each sample 3 is parallel.

[0188] The kinematic viscosity was calculated by multiplying the viscometer constant and the flow time. The viscosity change rate was calculated by the ratio of the difference between the kinematic viscosity after aging and the kinematic viscosity before aging to the kinematic viscosity before aging. The results are shown in Table 4.

[0189] Table 4. Results of the synergistic effect verification of the anti-wear and anti-oxidation composite additive system.

[0190]

[0191] As shown in Table 4, Example 3 exhibited brief jamming, noticeable noise, and slight smoke; Example 4 showed no abnormalities; and Comparative Example 5 exhibited brief jamming and slight noise. This indicates that the anti-wear agent and antioxidant in Example 4 worked synergistically, resulting in superior anti-wear performance of the lubricating oil. The composite additive of this invention can improve the stability of the anti-wear process. The diameter of the steel ball wear scar in Example 4 was 0.3±0.1 mm, smaller than that in Example 3 and Comparative Example 5, indicating good anti-wear effect. The anti-wear agent and antioxidant of this invention work synergistically to effectively reduce steel ball wear, resulting in superior anti-wear performance. The oxidation induction period in Example 4 reached 380.7±4.5 min, much longer than that in Example 3 and Comparative Example 5, indicating strong antioxidant capacity of the lubricating oil. The anti-wear agent and antioxidant of this invention work synergistically to significantly improve the antioxidant stability of the lubricating oil and delay oxidative deterioration. The viscosity change rate of Example 4 was 4.7 ± 0.6%, which was lower than that of Example 3 and Comparative Example 5, indicating that the viscosity of the lubricating oil remained stable after high-temperature aging. The composite additives of the present invention worked synergistically to enhance the high-temperature stability of the lubricating oil, reduce abnormal viscosity changes caused by high temperature, and help maintain good lubrication performance under high-temperature conditions.

[0192] In summary, the anti-wear agent and antioxidant of this invention synergistically treat lubricating oil, which has significant advantages in anti-wear, anti-oxidation and high-temperature stability. Compared with lubricating oil with single additives and only hydrogenation modification, it can comprehensively optimize lubrication performance and demonstrate the good effect of the composite additive synergistic system.

[0193] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for reusing lubricating oil based on membrane separation and ultrafiltration, characterized in that: The lubricating oil reuse method based on membrane separation and ultrafiltration specifically includes the following steps: S001, waste lubricating oil is preheated, an adsorbent is added, and adsorption and filtration are performed to obtain pre-purified oil. The adsorbent is composed of basalt fibers with silanized surfaces, a silica network derived from tetraethyl orthosilicate, a modified copolymer of acrylamide-maleic anhydride-N-isopropylacrylamide, sodium allyl sulfonate, and trimethylsiloxy group derived from hexamethyldisilazane, with a mass ratio of 5:85:9:0.3:0.

1. S002, the pre-purified oil is passed through a microfiltration membrane and an ultrafiltration membrane for separation treatment to obtain the refined base oil precursor; S003, add a hydrotreating agent to the refined base oil precursor and perform hydrotreating to obtain the hydrotreated base oil; S004 involves preheating the hydrotreated base oil, slowly adding an anti-wear agent, performing high-speed shearing, slowly adding an antioxidant, stirring, vacuum distilling, cooling to room temperature, and then filtering to obtain the lubricating oil.

2. The lubricating oil reuse method based on membrane separation and ultrafiltration according to claim 1, characterized in that: In step S001, the adsorbent is added at 2% of the oil mass. The adsorption treatment is carried out by stirring at 300 rpm for 30 min and then letting it stand for 2 h. The filtration treatment is carried out by plate and frame filtration. In step S003, the amount of hydromodifier added is 1.5% of the mass of the refined base oil precursor. In step S004, the amount of anti-wear agent added is 2% of the hydrotreated base oil.

3. The lubricating oil reuse method based on membrane separation and ultrafiltration according to claim 1, characterized in that: The microfiltration membrane is a ceramic microfiltration membrane containing basalt fiber, cerium oxide, and surface-grafted sodium dodecylbenzenesulfonate hydrophobic segments. The ultrafiltration membrane is a metal-organic framework-ionic liquid ultrafiltration membrane. The hydrogenation modifier is a cerium-doped nickel-molybdenum-phosphorus / zirconium-based metal-organic framework.

4. The lubricating oil reuse method based on membrane separation and ultrafiltration according to claim 1, characterized in that: The anti-wear agent is composed of zinc dialkyl dithiophosphate, titanium dioxide-coated antimony-doped tin oxide, and polyisobutylene succinimide. The mass ratio of zinc dialkyl dithiophosphate to titanium dioxide-coated antimony-doped tin oxide is 5:1, and the amount of polyisobutylene succinimide added is 0.5% of the hydrogenated base oil.

5. The lubricating oil reuse method based on membrane separation and ultrafiltration according to claim 1, characterized in that: The antioxidant is composed of 2,6-di-tert-butyl-p-cresol and diphenylamine, with addition amounts of 0.2% and 0.1% of the hydrogenated base oil, respectively.

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