Deep cracking and regeneration purification method of waste lubricating oil

Abstract

The invention relates to the technical field of petrochemical engineering, in particular to a deep cracking and regeneration purification method of waste lubricating oil. The invention discloses a deep cracking and regeneration purification method of waste lubricating oil, which comprises the following steps: firstly, carrying out magnetic filtration on the waste lubricating oil to separate iron-based impurities, carrying out vacuum dehydration, adsorbing acidic substances by using modified diatomite and the like; secondly, cracking with a magnetic catalyst in a magnetically stabilized fluidized bed; then, carrying out counter-current extraction by using a gamma-valerolactone solution after magnetic separation; and finally, carrying out vacuum fractionation to obtain regenerated base oil. According to the method, impurities are thoroughly removed, the catalyst can be recycled, the solvent is easy to recover, solid waste can be utilized in a high-valued manner, and the yield of the base oil is high.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, and in particular to a method for deep cracking, regeneration and purification of waste lubricating oil. Background Art

[0002] With the rapid development of industry and the widespread use of mechanical equipment, the use of lubricants has increased, and with it, the amount of waste lubricants generated has also skyrocketed. Waste lubricants are lubricants that, during use, have become oxidized, aged, deteriorated, and mixed with fuel oil components, impurities, and water, resulting in significant differences in quality from new lubricants. Improper disposal of waste lubricants, such as incineration, landfill, or discharge into rivers and streams, can cause serious pollution to soil, water sources, and the atmosphere. Because it contains a variety of toxic substances, dumping it into the soil can kill plants and eliminate microorganisms within the contaminated soil. Even small amounts of waste lubricants entering drinking water sources can cause significant water pollution, posing a significant threat to both humans and the environment.

[0003] However, waste lubricating oil is not completely worthless. Aside from a small amount of deteriorated material, the majority of the remaining material consists of lubricating base oil components and light oil products, offering high recycling value. By using appropriate processing techniques to remove deteriorated impurities and impurities, waste lubricating oil can be converted into a base oil that meets quality requirements. Further processing and the blending of various additives can produce high-quality finished lubricating oil. This is a suitable option from the perspectives of technology, environmental protection, resource recovery, and economy.

[0004] Chinese patent publication number CN101070507A discloses a method for regenerating waste lubricating oil, which involves sequentially performing impurity sedimentation, coarse filtration through heating, vacuum dehydration, and secondary heating. Finally, molecular-level membrane separation and purification using a high-temperature, oil-corrosion-resistant hollow fiber membrane is performed to produce the regenerated oil. While the viscosity of the regenerated oil is significantly reduced in the patent, key indicators such as acid value and oxidation resistance are not mentioned. This method may not be directly applicable to high-demand lubrication scenarios and requires further refinement. While the hollow fiber membranes used are oil-corrosion-resistant, their average pore size of 0.01–0.5 μm is susceptible to clogging by colloidal impurities or tiny particles in the waste oil, resulting in decreased membrane flux and the need for regular backwashing and maintenance, increasing operational complexity and cost. Furthermore, the membrane assembly has a temperature resistance of only 80–90°C. If the waste oil contains high-boiling-point impurities, these impurities may not be effectively separated due to temperature limitations, affecting the purity of the regenerated oil.

[0005] A Chinese patent with publication number CN106753742B discloses a method for regenerating waste lubricating oil, which involves sequentially performing flocculation, demulsification, and sedimentation. The separated sedimented oil is mixed with a solvent and stirred with an additive. After centrifugation to remove the residue, the solvent is recovered by distillation and then extracted with an extractant. Activated clay is added for stirring and refining, and finally filtered to obtain the regenerated base oil. The patent uses a variety of reagents, including polyaluminum chloride, polyacrylamide, and polyoxypropylene polyoxyethylene glycol ether, in the flocculation and demulsification stages. These polymer flocculants and block polyether demulsifiers are relatively expensive, and some reagents, such as quaternary ammonium salts and polyphosphates, are difficult to fully biodegrade. If the waste residue is not handled properly, residual chemicals may cause secondary pollution. The waste clay residue produced after activated clay adsorption contains a large amount of colloid, asphaltene, and metal impurities. The subsequent treatment is not specified. If directly discarded or incinerated, it will cause soil and air pollution. If it is recycled, additional calcination equipment is required, increasing costs.

[0006] Chinese patent publication number CN110484345A discloses a method for regenerating waste lubricating oil. The method involves mixing the waste lubricating oil with a flocculating alkaline wash solution, allowing it to settle and dehydrate. The raw oil is then heated and distilled in a vacuum tower. Products at different temperature ranges are collected, reacted with an extraction solvent, and extracted and separated to produce a base oil. The patent describes a pretreatment method using a 10% sodium hydroxide-25% calcined soda ash solution, a strongly alkaline system. While it can neutralize organic acids and flocculated impurities, the waste residues produced after the reaction, such as magnesium hydroxide and calcium carbonate, are alkaline solid wastes. The patent only states that the waste residues are collected in barrels, and further details subsequent treatment. Direct discharge would contaminate soil and water bodies. Furthermore, the mass ratio of the alkaline wash solution to the waste oil is 50:1, resulting in high reagent costs and the need for additional environmental protection facilities for subsequent waste residue treatment.

[0007] Chinese patent publication number CN118085952B discloses a method for regenerating waste lubricating oil. The method involves mixing anhydrous ethanol and deionized water and adjusting the pH. A specific reagent is added for hydrolysis, followed by mixing with attapulgite, wet grinding, filtration, and drying to obtain pretreated attapulgite. The pretreated attapulgite is then dispersed, treated with alkali, and ultrasonically reacted. The pH is adjusted, filtered, and centrifuged to obtain modified attapulgite. The waste lubricating oil is then settled to remove impurities, added to the modified attapulgite, stirred, and filtered. Finally, nitrogen is introduced for pretreatment, where the waste lubricating oil and nitrogen are sprayed relative to each other. A catalyst is added, hydrogen is introduced to increase the temperature, and hydrogenation is performed under a certain pressure to obtain a base oil fraction. The patent requires multiple steps, including wet grinding, ultrasonic treatment, and carboxymethylation. These steps require controlled grinding rate, temperature, and time. The process also involves ultrasonic treatment with sodium hydroxide solution and modification with chloroacetic acid. The process requires multiple reagents and a long preparation cycle. Industrial production requires multiple grinding equipment and ultrasonic devices, increasing equipment investment costs. Furthermore, improper handling of highly corrosive reagents like chloroacetic acid and sodium hydroxide can easily produce wastewater containing phosphorus and chlorine, requiring additional treatment facilities and increasing costs. Although adsorbents can be regenerated by acid washing, the adsorption capacity of regenerated attapulgite decreases after acid washing. After its ineffectiveness, it contains large amounts of heavy metals, requiring special disposal and increasing costs.

[0008] In summary, existing waste lubricating oil recovery technologies have not completely addressed the removal of impurities, such as metals, from waste lubricating oil, nor have they proposed ideal, environmentally friendly recovery technologies, nor have they significantly improved the yield of lubricating oil base oils. Therefore, developing a method that can deeply crack waste lubricating oil, efficiently remove impurities, and achieve regeneration and purification to increase base oil yield, reduce environmental pollution, and enhance process applicability is an urgent challenge in the waste lubricating oil regeneration field. Summary of the Invention

[0009] In order to solve the above problems, the object of the present invention is to provide a method for deep cracking and regeneration purification of waste lubricating oil, which specifically comprises the following steps: S001, taking waste lubricating oil, heating it and then performing magnetic filtration to recover iron-based metal debris and collect oil samples, centrifuging the oil samples after cooling them to room temperature, and collecting the supernatant; S002, dehydrating the clear liquid, adding modified diatomaceous earth for adsorption and filtration, and collecting the pretreated oil; S003, the pretreated oil is preheated and then introduced into a reactor, mixed with a magnetic catalyst, subjected to a cracking reaction, and the cracked products are collected and subjected to magnetic separation to obtain cracked oil; S004, mixing the cracked oil with γ-valerolactone, performing countercurrent extraction, and collecting the upper refined oil after standing and stratification; S005, subjecting the refined oil to vacuum fractionation treatment, collecting the base oil fraction, and obtaining the regenerated base oil.

[0010] The magnetic catalyst is a magnetic iron-based-biomass carbon-supported HZSM-5 catalyst prepared by activating iron-based metal scraps, phosphorus-doped modified biomass carbon, co-impregnating pyrolysis synthesis supported HZSM-5 molecular sieve, and co-precipitating into an iron-cerium alloy phase, specifically comprising the following steps: S101, crushing, acid-leaching, washing, and calcining the recovered iron-based metal scraps to obtain active iron elemental powder; S102, mixing, drying, and pyrolyzing the biochar with a diammonium hydrogen phosphate solution to obtain phosphorus-doped biochar; S103, mixing active iron elemental powder with phosphorus-doped biochar, adding HZSM-5 molecular sieve suspension and cerium nitrate solution, ultrasonically treating, then evaporating and calcining to obtain a magnetic iron-based-biochar-supported HZSM-5 catalyst, recorded as a magnetic catalyst.

[0011] The conditions for the heating treatment in step S001 are 50°C, 200 rpm / min, and 30 min. The magnetic filtration treatment is to use a neodymium iron boron magnetic filter for 3 cycles of filtration, wherein each residence time is 5 min, the pore size is 50 μm, the magnetic field strength is 0.5 T, and the centrifugal treatment conditions are 15000 r / min and 15 min.

[0012] The dehydration treatment in step S002 is to transfer the clear liquid into a vacuum drying oven under the conditions of -0.09 MPa, 80°C, and 2 hours. The condensed water is collected and then adsorbed on activated carbon for reuse. The modified diatomaceous earth is surface-loaded with nano-silica with a pore size of 20-50 nm. The mass fraction of the modified diatomaceous earth added is 5%. The adsorption conditions are 300 rpm / min and 30 min. The acid residue diatomaceous earth after adsorption treatment is collected.

[0013] In step S003, before the pretreated oil is passed into the reactor, the magnetic catalyst is pre-loaded into the fixed bed reactor, and a neodymium iron boron permanent magnet with a magnetic field strength of 0.5 T is laid on the bottom to form a magnetically stable fluidized bed environment. The pretreated oil is preheated to 200°C, and the mass ratio of the pretreated oil to the magnetic catalyst is 10:1. The cracking reaction treatment conditions are 400°C and 2 hours, wherein the reactor is connected to a -10°C condenser, and the cracked gas is collected through the condenser to collect liquid light hydrocarbons and non-condensable gases. The magnetic separation treatment is to pass the collected cracked products through an external pipeline-type magnetic separator with a magnetic field strength of 0.8 T, and the separation time is 3 minutes. After the reaction, the catalyst bed is passed through water vapor at 150°C, a flow rate of 0.5 L / min, and purged for 30 minutes before being reused.

[0014] In step S004, the volume ratio of cracked oil to γ-valerolactone is 1:2, and the countercurrent extraction treatment is performed by countercurrent extraction at 60° C. for 45 minutes in an extraction tower, and after standing and separating the layers, the upper layer of refined oil is collected.

[0015] In step S005, the vacuum fractionation treatment is performed by collecting a light fraction below 280°C and a base oil fraction with a kinematic viscosity of 32 to 68 mm² / s at 280 to 330°C and 40°C in a vacuum distillation tower at -0.01 MPa and a temperature increase of 5°C / min to 200°C, and then collecting the tower bottom residue. After cooling, the residue is mixed with acid-containing diatomaceous earth after adsorption treatment at a mass ratio of 1:1.5 and molded to obtain the oil-resistant storage barrel lining material.

[0016] In step S101, the powder is crushed to 100 mesh, soaked in 3 mol / L hydrochloric acid for 30 min, washed with distilled water until neutral, and calcined under nitrogen at 300° C. for 1 h.

[0017] In step S102, the biochar is obtained by carbonizing corn cobs, the mass ratio of the biochar to the diammonium hydrogen phosphate solution is 1:1, the mixing treatment conditions are 80°C, 500 rpm / min, and 2 h, the drying treatment conditions are 60°C and 12 h, and the pyrolysis treatment conditions are nitrogen, 600°C, and 2 h.

[0018] In step S103, the mass ratio of activated iron elemental powder to phosphorus-doped biochar is 1:2, the HZSM-5 molecular sieve suspension is a 50wt% HZSM-5 molecular sieve ethanol suspension, the HZSM-5 molecular sieve suspension is added at a solid-liquid ratio of 1:5, the concentration of the cerium nitrate solution is 0.05 mol / L, wherein the molar ratio of cerium to iron is 1:10, the ultrasonic treatment conditions are 40 kHz, 300 W, 30 min, the evaporation treatment conditions are 60 ° C, 80 rpm / min, -0.08 MPa, 2 h, and the calcination treatment conditions are nitrogen, heating to 600 ° C at 5 ° C / min, and 3 h.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention pre-treats waste lubricating oil by sequentially performing magnetic filtration to separate iron-based impurities, vacuum dehydration, and acidic adsorption, thereby separating impurities in a targeted manner. First, the waste lubricating oil is heated and then circulated through a magnetic filter to separate the iron-based metal debris in the waste lubricating oil. This is based on the paramagnetic properties of iron-based substances and the construction of a neodymium iron boron magnetic field separation system. When the waste lubricating oil passes through the neodymium iron boron magnetic filter, the high-intensity magnetic field drives magnetic particles such as iron filings, driven by the Lorentz force, overcoming their own gravity and fluid resistance, rapidly migrating along the magnetic lines of force and adsorbing on the surface of the magnetic filter, thereby recovering the iron-based metal debris. For non-magnetic impurities such as copper filings and dust, the principle of centrifugal force is utilized. When the centrifuge rotates at high speed, substances of different densities in the oil sample are subjected to centrifugal forces of varying magnitudes. The density of non-magnetic impurities is usually greater than that of lubricating oil. Under the action of centrifugal force, they will settle to the wall of the centrifuge, while the lubricating oil will gather in the upper layer to form a clear liquid due to its lower density, thus achieving efficient separation of the lubricating oil and impurities. Finally, after the clear liquid is vacuum dehydrated, modified diatomaceous earth is added to adsorb organic acids. The vacuum environment is used to lower the boiling point of water, allowing water to evaporate quickly at a lower temperature to achieve efficient dehydration. The condensed water is collected and adsorbed by activated carbon and reused for equipment cooling. Activated carbon has a rich pore structure and a large specific surface area, which can adsorb impurities in the condensed water, achieving the recycling of water resources and reducing energy consumption and costs. The nano-scale pore size of the modified diatomaceous earth and the surface-loaded nano-silica work synergistically to greatly increase the specific surface area and adsorption activity. Through physical adsorption and surface chemical reactions, the organic acid molecules in the waste lubricating oil are captured in the pores and surface, and the diatomaceous earth containing acid residues is filtered and separated, achieving the recycling of metal debris, green impurity removal and dehydration. The present invention compounds activated iron-based metal scraps, phosphorus-doped modified biochar, loaded HZSM-5 molecular sieve and iron-cerium alloy phase to prepare a magnetic iron-based-biochar loaded HZSM-5 catalyst. First, the oxide layer on the surface of the iron scraps is removed by acid to expose the highly active surface of the iron element so that the metal sites can participate in subsequent catalytic reactions. Calcination is carried out under nitrogen to eliminate residual acid ions on the one hand and promote the refinement of the iron element grains on the other hand, increase surface defect sites, and provide anchor points for subsequent interfacial bonding with biochar. Secondly, corn cob biochar is pyrolyzed with diammonium hydrogen phosphate solution, and phosphorus is embedded in the carbon lattice in the form of phosphorus-oxygen-carbon bonds to form a phosphorus-doped conjugated π electron system to enhance the electron-donating ability of the biochar and promote electron transfer between it and the iron element. During the pyrolysis process, ammonia and water molecules escape, forming mesopores in the carbon matrix, providing spatial support for the loading of the HZSM-5 molecular sieve. Phosphorus doping introduces polar functional groups, enhancing the hydrophilicity of the biochar surface, improving interfacial compatibility with HZSM-5 molecular sieve and preventing agglomeration during loading. Finally, a co-impregnation-pyrolysis synthesis and alloy formation process are performed. The activated iron reacts with cerium ions during coprecipitation to form an iron-cerium alloy phase. The magnetic moment coupling between the cerium 4f electron layer and the iron 3d electron layer enhances the material's ferromagnetism, laying the foundation for magnetic separation. The HZSM-5 molecular sieve forms colloidal particles in ethanol, which hydrogen-bond to the hydroxyl groups on the phosphorus-doped biochar surface. Simultaneously, the iron particles are adsorbed within the carbon pores via van der Waals forces, forming a catalyst structure consisting of a magnetic iron core, a phosphorus-doped biochar shell, and an HZSM-5 outer layer. During calcination, the magnetic iron groups react with the phosphorus-oxygen-carbon bonds of the phosphorus-doped biochar to form a magnetic iron-phosphorus-oxygen-carbon interface layer, enhancing the metal-support interaction and inhibiting aggregation of the magnetic iron groups. The acidic sites of the HZSM-5 molecular sieve and the redox sites of the magnetic iron-based material form synergistic catalytic centers, promoting the cracking of long-chain hydrocarbons in waste lubricating oils. The magnetic and catalytic activity of the iron-based material, the carrier effect of the biochar, and the acidic catalytic function of the HZSM-5 are organically integrated through the material preparation process to form an integrated system of magnetic separation, catalytic cracking, and interfacial synergy, achieving a synergistic improvement in catalytic efficiency and separation performance in waste lubricating oil regeneration. This invention produces cracked oil, a base oil precursor, through a catalytic cracking reaction and magnetically stabilized fluidization. First, the pretreated oil enters the reaction system and comes into contact with a specially formulated composite catalyst at a critical temperature of 400°C. The acidic active centers of the HZSM-5 molecular sieve serve as the core of the reaction, protonating long-chain hydrocarbon molecules to form carbonium ion intermediates. These high-energy intermediates undergo β-scission at high temperatures, cracking the base oil precursor. Simultaneously, the iron-based active phase in the catalyst exerts a synergistic effect, converting the unstable olefins produced during the cracking process into saturated hydrocarbons through catalytic hydrogen transfer reactions. This reaction system achieves both improved cracking efficiency and product quality through a clever balance of acid and base functions. Furthermore, magnetically stabilized fluidization is employed. An array of NdFeB permanent magnets deployed at the bottom of the reactor creates a stable magnetic confinement space through a gradient magnetic field design. The combined effects of the magnetic field and fluid drag force maintain a uniformly suspended fluidized state for the catalyst particles, forming a magnetically stabilized fluidized bed with liquid-like properties. This special flow pattern increases the contact area between the gas, liquid, and solid phases, improving their mass transfer coefficient. At the same time, the magnetic field-induced micro-scale particle motion effectively inhibits catalyst agglomeration, ensuring continuous exposure of active sites, thereby significantly improving the waste oil cracking reaction rate and conversion rate. Finally, the magnetic catalyst can be removed through a simple magnetic separation process, and after the reaction, the catalyst bed is purged with water vapor to achieve in-situ catalyst regeneration. The present invention uses γ-valerolactone solvent and countercurrent extraction technology to refine cracked oil to separate the refined oil from the impurity-rich phase. First, based on the principle of like dissolves like, the polar ester group in the γ-valerolactone molecule can undergo specific dipole-π interactions with the π electron cloud in polar impurity molecules such as aromatic hydrocarbons and colloids. This intermolecular force enables γ-valerolactone to selectively and preferentially dissolve polar impurity components in waste lubricating oil. In sharp contrast, non-polar alkanes, which are the main components of base oil, have extremely low mutual solubility with γ-valerolactone due to the significant difference in the type of intermolecular force. On this basis, the significant density difference between the two phases in the solution system is utilized to achieve efficient separation of the polar impurity phase and the non-polar base oil phase by static stratification. The impurity-rich phase can be efficiently separated by vacuum distillation, making full use of the significant boiling point difference between γ-valerolactone and the impurities. Since the boiling point of γ-valerolactone is lower than that of high-boiling-point impurities such as asphaltene and polycyclic aromatic hydrocarbons remaining in waste lubricating oil, and by reducing the system pressure, the boiling point of γ-valerolactone is further reduced, and the solvent is evaporated at a lower temperature, effectively avoiding the problem of impurity coking caused by high temperature. γ-valerolactone can be recovered through vacuum distillation and condensation recovery devices. γ-valerolactone is also biodegradable, and the residual asphalt-based material can adsorb volatile organic compounds, reducing waste gas emissions. After cooling, it is formed into asphalt-based adsorption blocks for the treatment of some harmful exhaust gases, promoting low solid waste emissions in the waste lubricating oil treatment process, reducing production costs, and realizing solvent recycling, which meets the requirements of green chemical processes. The present invention obtains base oil through segmented collection by vacuum distillation. By utilizing vacuum, the boiling point of the oil is lowered, the risk of cracking or oxidation of the base oil that may occur under high temperature of conventional distillation is avoided, and the properties of the raw materials are ensured to be stable. First, light fractions below 280°C are collected, which can be used as fuel or blending oil; second, the base oil fractions are collected according to viscosity through real-time monitoring by an online viscometer; finally, the bottom residue produced by vacuum distillation is collected, cooled, and mixed with diatomaceous earth containing acid residue, and molded into an oil-resistant storage barrel lining material to achieve high-value utilization of solid waste. At the microscopic level, the aromatic rings in the asphaltene molecular chain and the silanol groups on the surface of the diatomaceous earth form a physical cross-linking network through hydrogen bonds and van der Waals forces. After hot pressing, the oil swelling rate of the composite material will be improved; The present invention achieves significant improvements in resource utilization, energy consumption and cost, environmental protection, etc., increases the yield of regenerated base oil, reduces waste oil treatment costs, reduces harmful solvent emissions, and recycles waste resources, providing a green, environmentally friendly and sustainable path. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments.

[0021] Example 1: A method for treating iron-based impurities in waste lubricating oil by magnetic filtration and centrifugation, comprising the following steps: Add 10 g of iron powder to 1 L of base oil ISO VG32 to obtain lubricating oil containing 1% iron-based impurities, which is recorded as simulated waste lubricating oil; 1 L of simulated waste lubricating oil was poured into a 2 L three-necked flask. After heating at 50 °C and 200 rpm / min for 30 min, the oil was filtered through a NdFeB magnetic filter three times, with each filter holding for 5 min. The residual oil on the filter surface was wiped with filter paper, and the iron chips adsorbed on the filter surface were scraped off with a scraper and placed in a weighing bottle to recover the iron-based metal debris. The oil sample after magnetic filtration was cooled to room temperature, centrifuged at 15000 r / min for 15 min, and the supernatant was collected to obtain the test sample 1.

[0022] Example 2: A method for treating waste lubricating oil by vacuum dehydration and modified diatomaceous earth adsorption of organic acid, specifically comprising the following steps: 250 mL of the clear liquid prepared in Example 1 was transferred to an evaporating dish, and the evaporating dish was placed in a vacuum drying oven and dehydrated at -0.09 MPa and 80°C for 2 hours to obtain the dehydrated waste lubricating oil. Add 5% modified diatomaceous earth and adsorb at 300 rpm / min for 30 min. Collect the acid residue diatomaceous earth and the adsorbed oil. Use medium-speed quantitative filter paper to filter the adsorbed oil and collect the pretreated oil to obtain sample 2.

[0023] Example 3: A method for treating waste lubricating oil by magnetic catalyst cracking and magnetic field separation, specifically comprising the following steps: The recovered iron-based metal scraps were crushed to 100 mesh, acid-soaked for 30 min, washed until neutral, and calcined at 300 °C for 1 h under nitrogen to obtain active iron elemental powder. Weigh 2 g of corncob biochar and diammonium hydrogen phosphate solution in a 1:1 mass ratio, mix them at 80 °C and 500 rpm / min for 2 h, dry them at 60 °C for 12 h, and pyrolyze them at 600 °C under nitrogen for 2 h to obtain phosphorus-doped biochar. 1 g of active iron powder was weighed and mixed with phosphorus-doped biochar in a mass ratio of 1:2. A 50 wt% HZSM-5 molecular sieve ethanol suspension and a 0.05 mol / L cerium nitrate solution were added at a solid-liquid ratio of 1:5. The mixture was ultrasonically treated at 40 kHz and 300 W for 30 min, evaporated at 60 °C, 80 rpm / min, and -0.08 MPa for 2 h, and calcined at 600 °C in nitrogen at a rate of 5 °C / min for 3 h to obtain a magnetic iron-based biochar-supported HZSM-5 catalyst, which was recorded as a magnetic catalyst. 100 mL of the pretreated oil prepared in Example 2 was preheated to 200°C and then introduced into a reactor loaded with a magnetic catalyst. The mixture was mixed with the magnetic catalyst at a mass ratio of 10:1 and cracked at 400°C for 2 hours. The cracked products were collected and magnetically separated at a magnetic field strength of 0.8 T to obtain cracked oil, which was recorded as Sample 3.

[0024] Example 4: A method for treating cracked oil by countercurrent extraction, comprising the following steps: 200 mL of the cracked oil obtained in Example 3 was transferred and mixed with 400 mL of γ-valerolactone, and subjected to countercurrent extraction at 60°C for 45 min in an extraction tower. After standing and separating the layers, the upper layer of refined oil was collected; The upper refined oil was passed through a vacuum distillation tower at -0.01 MPa and heated to 200 °C at 5 °C / min. The light fraction below 280 °C was collected, and the base oil fraction with a kinematic viscosity of 32-68 mm² / s at 280-330 °C and 40 °C was collected. The base oil fraction and the bottom residue were collected. The base oil fraction was the regenerated base oil and was recorded as sample 4.

[0025] Example 5: A method for preparing an oil-resistant storage barrel lining material, comprising the following steps: Weigh 5 g of the cooled tower bottom residue collected in Example 4 and 7.5 g of the acid-containing slag diatomaceous earth collected in Example 2, pour them into a high-speed mixer, mix at 800 rpm for 10 min, put them into a 10 cm × 10 cm mold, and press them at 20 MPa pressure for 3 min using a hydraulic press. After demolding, place the sample in a desiccator and let it stand for 24 h to obtain Sample 5.

[0026] Comparative Example 1: A method for treating iron-based impurities in waste lubricating oil by centrifugation alone, comprising the following steps: Add 10 g of iron powder to 1 L of base oil ISO VG32 to obtain lubricating oil containing 1% iron-based impurities, which is recorded as simulated waste lubricating oil; Take 1 L of simulated waste lubricating oil, centrifuge at 15000 r / min for 15 min, and collect the supernatant to obtain reference substance 1.

[0027] Comparative Example 2: A method for treating waste lubricating oil by atmospheric pressure dehydration and unmodified diatomaceous earth adsorption of organic acid. The difference from Example 2 is that atmospheric pressure dehydration at 80°C for 2 hours and 5% unmodified diatomaceous earth adsorption treatment are used to finally prepare Reference Product 2.

[0028] Comparative Example 3: A method for treating waste lubricating oil by cracking treatment with a non-phosphorus-doped magnetic catalyst and magnetic field separation. The difference from Example 3 is that the activated iron elemental powder is directly mixed with the biochar to finally prepare the reference product 3.

[0029] Comparative Example 4: A method for treating waste lubricating oil by cracking using an HZSM-5 catalyst, comprising the following steps: The HZSM-5 catalyst was calcined at 550 °C for 4 h to obtain the activated HZSM-5 catalyst. The pretreated oil obtained in Example 2 was preheated to 200°C and then introduced into a reactor containing an activated HZSM-5 catalyst. The oil was mixed with the activated HZSM-5 catalyst at a mass ratio of 10:1 and cracked at 400°C for 2 hours. The cracked product collected was obtained as Reference Sample 4.

[0030] Comparative Example 5: A method for treating cracked oil by extraction with stirring at room temperature. The difference from Example 4 is that the extraction is carried out in an extraction tower with stirring at room temperature for 45 minutes, and the base oil fraction collected at the end is obtained as Reference Product 5.

[0031] Experimental Example 1: This experimental example performs magnetic filtration and centrifugal separation efficiency tests on Example 1 and Comparative Example 1, specifically comprising the following steps: Magnetic filtration test: The mass of the iron-based metal scraps recovered in Example 1 was weighed three times, and the iron removal rate after magnetic filtration was calculated. The results are shown in Table 1.

[0032] Centrifugal separation efficiency test: Take 10 mL of test sample 1 and reference sample 1 respectively into a digestion tank, add 5 mL of aqua regia, and microwave digest at 180 °C for 30 min; After cooling, transfer to a 50 mL volumetric flask, dilute to volume with ultrapure water, and filter through a 0.45 μm filter membrane to obtain the sample to be tested.

[0033] Accurately weigh 0.1429 g of ferric oxide into a 250 mL beaker, slowly add 10 mL of 65% nitric acid, and stir until completely dissolved. Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with ultrapure water, and shake well to obtain the standard stock solution. Pipette 1 mL, 2 mL, 5 mL, 10 mL, 20 mL, and 50 mL of the standard stock solution into a 100 mL volumetric flask, and dilute to the mark with ultrapure water to obtain the standard working solution.

[0034] The RF power was 1550 W, the carrier gas flow rate was 0.85 L / min, the KED mode was adopted, the sampling depth was 1.93 mm, and the measurement time was 1 to 6 s.

[0035] Each sample was run in parallel for three times. The standard working concentration was used as the horizontal axis and the corresponding signal intensity was used as the vertical axis to draw a standard curve. A linear regression equation was obtained. The iron removal rate was calculated based on the volume of the supernatant, the measured iron concentration in the sample to be tested, and the residual iron mass. The results are shown in Table 1.

[0036] Table 1 Iron removal rate after magnetic filtration, iron removal rate of test sample 1 and reference sample 1

[0037] As can be seen in Table 1, the iron removal rate after magnetic filtration reached 98.2±0.1%, indicating that magnetic filtration can effectively remove iron in the initial stage. The NdFeB magnetic filter has a strong adsorption capacity for iron-based impurities, laying the foundation for subsequent treatment. The iron removal rate of Sample 1, prepared by magnetic filtration and centrifugation, was 98.9±0.1%, which is a further improvement compared to magnetic filtration alone. This shows that centrifugation can enhance the removal of residual trace iron-based impurities on the basis of magnetic filtration. The synergistic effect of the two processes results in better iron removal. The iron removal rate of Reference Sample 1, which was centrifuged alone, was only 1.1±0.1%, highlighting the difficulty of effective separation of iron-based impurities by centrifugation alone due to the dispersed nature of iron-based impurities in the lubricating oil. This indicates that centrifugation alone has a very weak effect on the removal of iron-based impurities in this system.

[0038] Magnetic filtration provides efficient initial iron removal, and Sample 1, produced by combining it with centrifugation, achieves even better iron removal. Reference Sample 1, produced by centrifugation alone, has minimal effect on removing iron-based impurities. This indicates that the combined magnetic filtration and centrifugation process offers significant advantages in removing iron-based impurities from waste lubricating oils, making it an effective treatment solution and a technical reference for waste lubricating oil purification and recovery. Further research is needed to optimize process parameters and explore its applicability to different types of iron-based impurities and lubricating oil systems.

[0039] Experimental Example 2: This experimental example tests the dehydration and organic acid adsorption effects of Example 2 and Comparative Example 2, specifically comprising the following steps: Moisture content detection: Pipette 10 μL of ultrapure water into the titration cell and stir, then inject Karl Fischer reagent until the endpoint, and record the calibration consumption volume; Take 10 mL of test sample 2 and reference sample 2 respectively into the titration cell, stir, inject Karl Fischer reagent until the endpoint, and record the sample consumption volume; Rinse the pycnometer three times with distilled water, dry it to constant weight, and then weigh the empty bottle and record the mass of the empty bottle; Take 5 mL of test sample 2 and reference sample 2 respectively and slowly inject them into the pycnometer to the scale line. Weigh the pycnometer filled with samples and record the total mass. The density of the corresponding sample was calculated based on the difference between the total mass and the mass of the empty bottle and the sample volume. The titer was calculated based on the calibration consumption volume and the mass of ultrapure water. The water content in the sample was then calculated based on the sample consumption volume. The results are shown in Table 2.

[0040] Acid value determination: Weigh 5 g of the dehydrated waste lubricating oil in Example 2, Test Sample 2, the dehydrated waste lubricating oil in Comparative Example 2, and Reference Sample 2 respectively into a 250 mL conical flask, add 50 mL of neutral ethanol containing 2 drops of phenolphthalein, and add 0.1 mol / L potassium hydroxide ethanol standard titrant until the solution turns slightly red and does not fade for 30 seconds. Record the volume of the standard titrant consumed. The dehydrated waste lubricating oil in Example 2 and Comparative Example 2 are used as the initial values ​​of Test Sample 2 and Reference Sample 2, respectively; Each sample was run in parallel for three times. The acid value was calculated based on the concentration of the potassium hydroxide ethanol standard titrant, the consumed volume, and the sample weight. The organic acid removal rate was then calculated based on the ratio of the difference between the initial acid value and the acid value after adsorption to the initial acid value. The results are shown in Table 2.

[0041] Table 2 Moisture content and organic acid removal rate

[0042] As shown in Table 2, Sample 2, prepared by vacuum dehydration and treatment with modified diatomaceous earth, had a moisture content of 0.03 ± 0.01 wt%, demonstrating that vacuum dehydration efficiently removes moisture. Combined with adsorption by the modified diatomaceous earth, the treated oil sample has an extremely low moisture content, meeting the requirements for deep dehydration. Reference Sample 2, prepared by atmospheric pressure dehydration and treatment with unmodified diatomaceous earth, had a moisture content of 9.66 ± 0.30 wt%, significantly higher than that of Sample 2. This indicates that atmospheric pressure dehydration is difficult to effectively remove moisture, and that unmodified diatomaceous earth has a weak water adsorption capacity. This highlights that a vacuum environment facilitates water evaporation and separation, and that modified diatomaceous earth also plays a positive role in the synergistic dehydration process. The organic acid removal rate for Sample 2 reached 99.4 ± 0.2%, demonstrating that after vacuum dehydration, the modified diatomaceous earth has excellent adsorption of organic acids. The modification may have increased the specific surface area and surface active sites of the diatomaceous earth, enhancing its adsorption capacity for organic acids. The organic acid removal rate of reference sample 2 reached 95.1±0.6%, which was somewhat effective, but lower than that of test sample 2. Because atmospheric pressure dehydration may affect the adsorption of some components in the oil, the adsorption performance of unmodified diatomaceous earth is limited, resulting in an organic acid removal rate lower than that of test sample 2.

[0043] The vacuum dehydration and modified diatomaceous earth adsorption processes of Sample 2 outperformed the atmospheric pressure dehydration and unmodified diatomaceous earth adsorption processes of Reference 2 in both water removal and organic acid removal. Vacuum dehydration effectively reduces moisture, while modified diatomaceous earth enhances organic acid adsorption. These two processes synergistically enhance waste lubricating oil purification, providing a more optimized technical approach for waste lubricating oil dehydration and acid removal. Further research is needed to further enhance treatment efficiency by investigating modified diatomaceous earth preparation parameters and optimizing the dehydration and adsorption processes.

[0044] Experimental Example 3: This experimental example conducted a catalytic cracking activity test on Example 3 and Comparative Examples 3-4, specifically comprising the following steps: Internal standard working solution: Weigh 10 mg of deuterated tetradecane into a beaker, dissolve it with a small amount of n-hexane, transfer it to a 100 mL volumetric flask, and dilute to the mark with n-hexane to obtain the internal standard working solution.

[0045] Sample pretreatment: Transfer 10 mL of the initial sample, test sample 3, reference sample 3, and reference sample 4 to a 100 mL volumetric flask, adjust the volume to the mark with the internal standard working solution, and filter to obtain the sample to be tested, wherein the initial sample is the pretreated oil prepared in Example 2.

[0046] Standard working solution: Pipette 10 mL, 5 mL, 1 mL, 0.5 mL, and 0.1 mL of the normal alkane mixed standard sample and adjust the volume to 10 mL with the internal standard working solution. The mixed standard contains 1000 μg / mL of n-decane, n-hexadecane, n-octadecane, and n-eicosane to obtain the standard working solution.

[0047] Determination: The chromatographic column was a DB-5MS, 30 m × 0.25 mm × 0.25 μm; the column temperature was 50 °C for 2 min, then 10 °C / min to 300 °C for 10 min; the injection port temperature was 280 °C; the EI source was used; the mass-to-charge ratios (m / z) of n-decane, n-hexadecane, n-octadecane, and n-eicosane were 142 / 85, 226 / 85, 254 / 71, and 282 / 57, respectively; the split ratio for split injection was 20:1; and the injection volume was 10 μL. A standard curve was drawn with the ratio of the concentration of the standard working solution to the internal standard concentration as the abscissa and the ratio of the peak area of ​​the standard working solution to the peak area of ​​the internal standard as the ordinate to obtain the concentration of the target compound. The conversion rate of long-chain hydrocarbons was calculated based on the total concentration of n-octadecane and n-eicosane and the ratio of the difference between the initial sample and the corresponding cracking reaction to the initial sample. The base oil selectivity was calculated based on the ratio of the total concentration of n-decane and n-hexadecane to the total concentration of total alkanes. The results are shown in Table 3.

[0048] Table 3 Long-chain hydrocarbon conversion and base oil selectivity

[0049] As shown in Table 3, Sample 3, prepared using a magnetic iron-based / phosphorus-doped biochar-supported HZSM-5 catalyst, achieved a long-chain hydrocarbon conversion of 91.4%. This indicates that the magnetic catalyst prepared using phosphorus-doped biochar exhibits high activity for cracking long-chain hydrocarbons from waste lubricating oil and effectively promotes their conversion. Reference Sample 3, prepared using a non-phosphorus-doped magnetic catalyst, achieved a conversion of 61.6%, significantly lower than Sample 3. This suggests that phosphorus doping significantly enhances catalytic activity, likely due to phosphorus doping altering the electronic structure of the biochar, increasing active sites, and enhancing the cracking of long-chain hydrocarbons. Reference Sample 4, prepared using a single HZSM-5 catalyst, achieved a conversion of 71.1%, lower than that of Sample 3. This highlights the synergistic advantages of the magnetic iron-based / phosphorus-doped biochar-supported HZSM-5 catalyst. The combination of active iron, phosphorus-doped biochar, and HZSM-5 molecular sieve is more conducive to the cracking of long-chain hydrocarbons than the HZSM-5 catalyst alone.

[0050] The base oil selectivity of Sample 3 was 76.5%, indicating that the magnetic catalyst can promote the cracking of long-chain hydrocarbons while also generating more base oil components, including short-chain high-quality base oil components such as n-decane and n-hexadecane, reflecting the catalyst's good controllability over product distribution. The selectivity of Reference 3 was 29.6%, far lower than that of Sample 3. This is because the absence of phosphorus doping reduces the activity and selectivity of the catalyst, making it difficult to generate base oil from the cracking products, reflecting the key role of phosphorus doping in improving base oil selectivity. The selectivity of Reference 4 was 44.6%, lower than that of Sample 3, indicating that the composite system of magnetic iron-phosphorus-doped biochar-supported HZSM-5 catalysts has greater advantages in regulating product selectivity. The activated iron, biochar, and molecular sieves work together to optimize the cracking pathway and promote base oil production.

[0051] The magnetic iron-based, phosphorus-doped biochar-supported HZSM-5 catalyst and magnetic field separation process of Example 3 outperformed the phosphorus-free magnetic catalyst of Comparative Example 3 and the single HZSM-5 catalyst of Comparative Example 4 in terms of long-chain hydrocarbon conversion and base oil selectivity. Phosphorus doping significantly enhances catalyst activity and selectivity. The synergistic effect of the magnetic composite catalyst enables efficient cracking of long-chain hydrocarbons and targeted production of base oil, providing a highly effective technical solution for the catalytic cracking of waste lubricating oils to produce base oils. Future research is underway to explore the optimization of catalyst preparation parameters and the impact of magnetic field separation on catalyst recovery and process continuity to further refine the process.

[0052] Experimental Example 4: This experimental example tests the regeneration performance of the magnetic catalyst in Example 3, specifically comprising the following steps: The first cracking reaction was carried out according to the operating steps of Example 3. After the reaction was completed, the first cracking products were collected and the used catalyst was separated by a magnetic separation device. Place the used catalyst into a fixed-bed reactor, set the bottom temperature of the reactor to 150°C, and introduce water vapor into the reactor at a flow rate of 0.5 L / min. After purging for 30 minutes, stop introducing water vapor, keep the reactor airtight, introduce nitrogen, and cool to room temperature. The cracking reaction was repeated three times, and steam purging was performed after each recording of the mass of the magnetic catalyst. The magnetic separation efficiency was calculated based on the ratio of the recovered mass of the magnetic catalyst to the added mass of the magnetic catalyst. At the same time, the long-chain hydrocarbon conversion rate was calculated each time using the determination method of Experimental Example 3. The results are shown in Table 4.

[0053] Table 4 Magnetic separation efficiency and long-chain hydrocarbon conversion rate

[0054] As can be seen from Table 4, the magnetic separation efficiency of the magnetic catalyst after one repetition is 98.1%, indicating that after the first regeneration, the magnetic catalyst can be efficiently separated and recovered from the cracking products due to its own magnetism and the action of the magnetic separation device, with little catalyst loss. The efficiency dropped to 95.1% after two repetitions, indicating that as the number of regenerations increases, carbon deposits, impurities, etc. may be adsorbed on the catalyst surface, or some magnetic components may be lost or agglomerated due to repeated treatment, making magnetic separation slightly more difficult, but still maintaining a high separation efficiency. The efficiency dropped further to 90.6% after three repetitions, reflecting that after multiple regenerations, the performance and structural changes of the catalyst accumulate, which have a continuous impact on the magnetic separation, but the overall magnetic separation effect is still acceptable, indicating that the magnetic catalyst has a certain degree of regeneration separation stability.

[0055] The conversion rate of long-chain hydrocarbons gradually decreased with the number of times the catalyst was reused. The conversion rate reached 91.0% after one recycle, 90.4% after two recycles, and dropped to 89.1% after three recycles. This suggests that after multiple regenerations, the catalyst's active sites may be damaged by carbon deposits and structural changes caused by sintering of active components, leading to a weakening of its ability to crack long-chain hydrocarbons. However, the decline in conversion rate was relatively gradual over the three recycle cycles, indicating that the catalyst has a certain degree of regeneration stability.

[0056] This magnetic iron-based, phosphorus-doped biochar-supported HZSM-5 catalyst can be reused for waste lubricating oil cracking through steam purge regeneration and magnetic separation recovery. Although both the magnetic separation efficiency and long-chain hydrocarbon conversion rate decrease with increasing use, the regeneration process may need to be optimized to reduce catalyst performance degradation and improve its recycling efficiency. Further research on the catalyst deactivation mechanism will be conducted to improve the regeneration method and enhance the catalyst's stability and cost-effectiveness.

[0057] Experimental Example 5: This experimental example is to determine the aromatic hydrocarbon content in the test sample 4 of Example 4 and the reference sample 5 of Comparative Example 5, specifically comprising the following steps: Standard solution: Weigh 0.01 g of n-hexadecane and 0.01 g of octadecylbenzene into a beaker, dissolve them with an appropriate amount of n-heptane, transfer them to a 10 mL volumetric flask, and dilute to the mark with n-heptane to obtain standard solution A. Weigh 0.1 g of n-hexadecane and 0.1 g of octadecylbenzene into a beaker, dissolve them with an appropriate amount of n-heptane, transfer them to a 10 mL volumetric flask, and dilute to the mark with n-heptane to obtain standard solution B. Weigh 1 g of n-hexadecane and 0.5 g of octadecylbenzene into a beaker, dissolve them with an appropriate amount of n-heptane, transfer them to a 10 mL volumetric flask, and dilute to the mark with n-heptane to obtain standard solution C. Weigh 2 g of n-hexadecane and 1 g of octadecylbenzene into a beaker, dissolve them with an appropriate amount of n-heptane, transfer them to a 10 mL volumetric flask, and dilute to the mark with n-heptane to obtain standard solution D. Weigh 5 g of n-hexadecane and 3 g of octadecylbenzene into a beaker, dissolve them with an appropriate amount of n-heptane, transfer them to a 10 mL volumetric flask, and dilute to the mark with n-heptane to obtain standard solution E.

[0058] Sample to be tested: 1 mL of the cracked oil used in Example 4, test sample 4, and reference sample 5 were respectively transferred to 10 mL volumetric flasks and dilute to the mark with n-heptane to obtain the test samples. The cracked oil used in Example 4 was the initial oil.

[0059] Determination: The silica gel column was YMC-Pack SIL-06, 250 mm × 10 mm × 5 μm; the cyano column was YMC-Pack CN, 150 mm × 10 mm × 5 μm; the differential refractive index detector had a resolution of 13.1 and a refractive index detection range of 1.3–1.6; the wavelength was 254 nm; the n-heptane flow rate was 3 mL / min; and the injection volume was 10 μL.

[0060] A standard curve was drawn with the concentration of the standard solution as the abscissa and the peak area of ​​the standard solution as the ordinate. The response factor was calculated by the ratio of the slope of the octadecylbenzene curve to the slope of the n-hexadecane curve. The total peak area was calculated based on the sum of the ratio of the saturated hydrocarbon peak area to the chromatographic peak area and the response factor of the aromatic hydrocarbons. The aromatic hydrocarbon content was calculated based on the ratio of the chromatographic peak area and the response factor of the aromatic hydrocarbons to the total peak area. The aromatic hydrocarbon removal rate was calculated based on the ratio of the difference between the aromatic hydrocarbon content in the initial oil and the aromatic hydrocarbon content in the regenerated base oil to the aromatic hydrocarbon content in the initial oil. After γ-valerolactone extraction, the delamination times were recorded respectively. The results are shown in Table 5.

[0061] Table 5 Aromatic hydrocarbon removal rate and stratification time

[0062] As shown in Table 5, Sample 4, prepared by countercurrent extraction at 60°C, achieved an aromatics removal rate of 94.0%. This indicates that countercurrent extraction of γ-valerolactone at 60°C in the extraction column is highly effective in removing aromatics from cracked oil. The temperature and countercurrent operation facilitated mass transfer between the extractant and the oil phase, enhancing aromatic separation. Reference Sample 5, prepared by extraction at room temperature with stirring, achieved a removal rate of 62.7%, significantly lower than that of Sample 4. This suggests that the room temperature and stirring extraction method are not conducive to the full interaction between γ-valerolactone and aromatics, resulting in low mass transfer efficiency. This highlights the key influence of temperature and extraction method on aromatics removal, with 60°C countercurrent extraction showing a significant advantage.

[0063] The separation time for Sample 4 was only 8 minutes, demonstrating that after 60°C countercurrent extraction, the oil and extract phases separated rapidly due to temperature-assisted and countercurrent-enhanced mass transfer, facilitating subsequent refined oil collection and improving process efficiency. Reference Sample 5, with a separation time of 43 minutes, was delayed due to poor mass transfer during room-temperature stirring extraction, making it difficult to quickly separate the two phases after mixing. This prolonged separation and increased process cycle time further demonstrates the positive role of 60°C countercurrent extraction in promoting separation and optimizing the process.

[0064] The 60°C countercurrent extraction and vacuum distillation process of Example 4 demonstrated significant advantages in aromatics removal and demixing efficiency compared to the room-temperature stirring extraction of Comparative Example 5. 60°C countercurrent extraction enhanced the aromatics extraction capacity of γ-valerolactone, increasing the aromatics removal rate while accelerating two-phase demixing and shortening the process time. This process provides an efficient solution for cracked oil refining dearomatization. Future research is underway to optimize parameters such as extraction temperature, time, and agent-to-oil ratio to further enhance dearomatization effectiveness and process economics. This process can also expand the compatibility of different extractants and improve the cracked oil refining technology system.

[0065] Experimental Example 6: This experimental example performs swelling rate and compressive strength tests on the sample 5 of Example 5, specifically comprising the following steps: Swelling rate test: Weigh the initial mass of the test sample 5, completely immerse it in the base oil, seal the container, and after immersion for 72 hours, take out the sample, gently wipe the base oil attached to the surface with filter paper, and immediately weigh its mass after immersion.

[0066] The swelling ratio was calculated based on the ratio of the difference between the mass after immersion and the initial mass to the initial mass. The results are shown in Table 6.

[0067] Compressive strength test: Specimen 5 was placed on the test platform of a universal material testing machine. The loading rate was 2 mm / min. Vertical pressure was continuously applied to specimen 5 until it ruptured. The maximum pressure value at rupture was recorded. The compressive strength was calculated based on the ratio of the maximum pressure value to the compressed area. The results are shown in Table 6.

[0068] Table 6 Swelling rate and compressive strength

[0069] As shown in Table 6, the swelling rate of Sample 5 is 3.4%, indicating that after 72 hours of immersion in the base oil, the lining material exhibits minimal volume expansion. This suggests a weak interaction between the material and the base oil, allowing it to maintain its shape well in an oil-resistant environment and demonstrate a certain degree of oil-swelling resistance. The compressive strength reaches 14 MPa, demonstrating that the material can withstand a certain amount of vertical pressure and possesses a certain mechanical strength, capable of resisting external forces during use and ensuring structural stability.

[0070] The oil-resistant storage barrel lining material prepared by Example 5 is prepared by combining the bottom residue of the tower and the acid-containing slag diatomaceous earth. It has good performance in oil swelling resistance and mechanical properties, and realizes the resource utilization of residues and acid slag in the process of waste lubricating oil treatment. It provides a reference for the preparation of environmentally friendly, high-performance lining materials and the resource utilization of solid waste. In the future, the performance test of the material can be expanded under different oil products and complex environments, and the preparation process can be optimized to improve the overall performance.

[0071] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any modifications and changes made to the technical solution of the present invention by ordinary persons in the art shall still fall within the scope of the present invention as long as they do not depart from the overall concept of the present invention.

Claims

1. A method for deep cracking and regeneration purification of waste lubricating oil, characterized by: The method for deep cracking and regeneration purification of waste lubricating oil specifically comprises the following steps: S001, taking waste lubricating oil, heating it and then performing magnetic filtration to recover iron-based metal debris and collect oil samples, centrifuging the oil samples after cooling them to room temperature, and collecting the supernatant; S002, dehydrating the clear liquid, adding modified diatomaceous earth for adsorption and filtration, and collecting the pretreated oil; S003, the pretreated oil is preheated and then introduced into a reactor, mixed with a magnetic catalyst, subjected to a cracking reaction, and the cracked products are collected and subjected to magnetic separation to obtain cracked oil; S004, mixing the cracked oil with γ-valerolactone, performing countercurrent extraction, and collecting the upper refined oil after standing and stratification; S005, subjecting the refined oil to vacuum fractionation treatment, collecting the base oil fraction, and obtaining the regenerated base oil.

2. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: The magnetic catalyst is a magnetic iron-based-biomass carbon-supported HZSM-5 catalyst prepared by activating iron-based metal scraps, phosphorus-doped modified biomass carbon, co-impregnating pyrolysis synthesis supported HZSM-5 molecular sieve, and co-precipitating into an iron-cerium alloy phase, specifically comprising the following steps: S101, crushing, acid-leaching, washing, and calcining the recovered iron-based metal scraps to obtain active iron elemental powder; S102, mixing, drying, and pyrolyzing the biochar with a diammonium hydrogen phosphate solution to obtain phosphorus-doped biochar; S103, mixing active iron elemental powder with phosphorus-doped biochar, adding HZSM-5 molecular sieve suspension and cerium nitrate solution, ultrasonically treating, then evaporating and calcining to obtain a magnetic iron-based-biochar-supported HZSM-5 catalyst, recorded as a magnetic catalyst.

3. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: In step S001, the magnetic filtration treatment is performed by circulating filtration three times through a neodymium iron boron magnetic filter, wherein each residence time is 5 minutes, the pore size is 50 μm, and the magnetic field strength is 0.5 T.

4. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: In step S002, the dehydration treatment is to transfer the clear liquid into a vacuum drying oven, the modified diatomaceous earth is surface-loaded with nano-silica, the mass fraction of the modified diatomaceous earth added is 5%, and the acid residue diatomaceous earth after adsorption treatment is collected.

5. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: In step S003, before the pretreated oil is passed into the reactor, the magnetic catalyst is pre-loaded into the fixed bed reactor, and a neodymium iron boron permanent magnet with a magnetic field strength of 0.5 T is laid on the bottom to form a magnetically stable fluidized bed environment. The pretreated oil is preheated to 200°C, and the mass ratio of the pretreated oil to the magnetic catalyst is 10:

1. The cracking reaction treatment conditions are 400°C and 2 hours. The magnetic separation treatment is to collect the cracking products and flow them through an external pipeline-type magnetic separator with a magnetic field strength of 0.8 T. After the reaction, the catalyst bed is reused after passing water vapor at 150°C, a flow rate of 0.5 L / min, and a purge for 30 minutes.

6. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: In step S004, the volume ratio of cracked oil to γ-valerolactone is 1:2, and the countercurrent extraction treatment is performed by countercurrent extraction at 60° C. in an extraction tower for 45 minutes. After standing and separating the layers, the upper layer of refined oil is collected.

7. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 1, characterized in that: In step S005, the vacuum fractionation treatment is carried out by collecting light fractions less than 280°C and base oil fractions with a kinematic viscosity of 32 to 68 mm² / s at 280 to 330°C and 40°C in a vacuum distillation tower at -0.01 MPa and a temperature increase of 5°C / min to 200°C, and then collecting the bottom residue. After cooling, the mixture is mixed with acid-containing diatomaceous earth after adsorption treatment at a mass ratio of 1:1.5 and molded to obtain the oil-resistant storage barrel lining material.

8. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 2, characterized in that: In step S102 , the biochar is obtained by carbonizing corn cobs, and the mass ratio of the biochar to the diammonium hydrogen phosphate solution is 1:

1.

9. The method for deep cracking and regeneration purification of waste lubricating oil according to claim 2, characterized in that: In step S103, the mass ratio of active iron elemental powder to phosphorus-doped biochar is 1:2, the HZSM-5 molecular sieve suspension is a 50wt% HZSM-5 molecular sieve ethanol suspension, and the HZSM-5 molecular sieve suspension is added at a solid-liquid ratio of 1:

5. The concentration of the cerium nitrate solution is 0.05 mol / L, and the molar ratio of cerium to iron is 1:10.

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