Resource regeneration method of waste lubricating oil

Abstract

The invention discloses a resource regeneration method of waste lubricating oil, relates to the technical field of petrochemical engineering, and belongs to the patent classification number C10M175 / 06. The preparation method comprises the following steps: adding a composite flocculant into the waste lubricating oil, heating and stirring, and then carrying out magnetic separation to obtain pretreated waste lubricating oil; uniformly mixing the pretreated waste lubricating oil, glycerol and a Ni / Al2O3 catalyst, then heating and reacting under pressure, and cooling to room temperature to obtain a catalytic hydrogenation product; and carrying out reduced pressure distillation on the catalytic hydrogenation product, recovering the lubricant base oil fraction, adding methanol and concentrated sulfuric acid into the distillation residual liquid, heating for esterification reaction, and separating the liquid to obtain the biodiesel. In the pretreatment process, the composite flocculant is used for removing acid and particle impurities in the lubricating oil, a traditional alkali adding neutralization precipitation process is replaced, the method is environmentally friendly, and the recovery cost of enterprises is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical engineering, belonging to the patent classification number C10M175 / 06, and specifically relates to a method for resource regeneration of waste lubricating oil. Background Art

[0002] In current industrial production and mechanical operation, lubricating oil plays a crucial role. It can effectively reduce the friction between mechanical components, reduce wear, and ensure the stable operation of equipment. However, during the use of lubricating oil, due to factors such as metal chips generated by mechanical wear, impurities mixed in the environment, high temperature, and air oxidation, it will gradually age and deteriorate. When the degree of deterioration reaches a certain proportion, the lubricating oil can no longer meet the usage requirements and thus becomes waste lubricating oil. According to incomplete statistics, the amount of waste lubricating oil generated globally each year is quite substantial. If these waste lubricating oils are not properly treated, it will not only cause a great waste of resources but also cause serious pollution to the environment, such as polluting soil, water sources, etc., and destroying the ecological balance.

[0003] Currently, in the field of waste lubricating oil resource regeneration, the method of using catalytic hydrorefining to recover lubricating oil is a relatively common means. This method can effectively remove impurities in waste lubricating oil to a certain extent, restore some of its properties, and make it reach the standard for reuse. During the pretreatment process of lubricating oil, the commonly used process is alkali neutralization precipitation filtration. By adding a strong base for neutralization reaction, the acidic substances in the waste lubricating oil are neutralized, and then through precipitation and filtration steps, the solid impurities and water are removed to provide a relatively pure raw material for subsequent hydrorefining.

[0004] However, this traditional alkali neutralization precipitation filtration process has many drawbacks. The waste alkali liquid generated after using a strong base contains a large amount of harmful substances. If not properly treated, it will cause serious pollution to the environment. Treating these waste alkali liquids harmlessly often requires a high cost, including special treatment equipment, chemical reagents, and professional treatment processes, etc. This undoubtedly increases the economic burden of the entire waste lubricating oil regeneration process and limits the wide application and promotion of waste lubricating oil regeneration technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for resource regeneration of waste lubricating oil to solve the technical problems proposed in the above background art. In the pretreatment process of the present invention, a composite flocculant is used to remove acids and particulate impurities in the lubricating oil, replacing the traditional alkali neutralization precipitation process, which is environmentally friendly and reduces the recycling cost of enterprises.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A method for resource regeneration of waste lubricating oil, comprising the following steps: S1. Add a composite flocculant to the waste lubricating oil, heat and stir, and then obtain the pretreated waste lubricating oil through magnetic separation; S2. Mix the pretreated waste lubricating oil, glycerol, and Ni / Al2O3 catalyst evenly, and then heat and react under pressure, and cool to room temperature to obtain the catalytic hydrogenation product; S3. Subject the catalytic hydrogenation product to vacuum distillation to recover the lubricating oil base oil fraction, add methanol and concentrated sulfuric acid to the distillation residue, heat for an esterification reaction, and separate to obtain biodiesel.

[0007] In the technical solution of the present invention, through the composite flocculant and combined with the magnetic separation technology, the particulate impurities and acids in the waste lubricating oil are adsorbed and removed. Compared with the traditional alkali neutralization process, the magnetic separation process does not need to introduce chemical waste liquid, reducing the environmental pollution and wastewater treatment cost in the traditional pretreatment stage. A mixed system of glycerol and Ni / Al2O3 catalyst is used to carry out the catalytic hydrogenation reaction under pressure heating conditions. Glycerol, as a green solvent, can improve the solubility of polar substances in waste oil and promote the uniform progress of the hydrogenation reaction. It can not only effectively remove impurities such as sulfur and nitrogen, but also retain the effective components of the base oil, improving the quality of the regenerated oil. The lubricating oil base oil is separated by vacuum distillation, and the distillation residue is subjected to an esterification reaction to prepare biodiesel, realizing the co-recovery of the base oil and biodiesel, significantly improving the resource utilization rate. In addition, no waste alkali liquor is generated in the whole process chain, avoiding the environmental pollution problems of the traditional process.

[0008] Preferably, in step S1, the addition amount of the composite flocculant is 0.5-3.0% of the mass of the waste lubricating oil.

[0009] Preferably, in step S2, the mass ratio of the pretreated waste lubricating oil, glycerol, and Ni / Al2O3 catalyst is 10:1.5:0.3.

[0010] Preferably, in step S2, the heating reaction temperature is 220-230 °C, and the heating reaction time is 3-4 h.

[0011] Preferably, in step S3, the vacuum distillation temperature is 280 °C, and the pressure is 5 kPa.

[0012] Preferably, in step S3, the mass ratio of the distillation residue to methanol is 2:1.

[0013] Preferably, in step S1, the preparation method of the composite flocculant includes the following steps: S11. Dissolve ferric chloride and ferrous chloride in deionized water, heat to 70-80 °C under nitrogen protection, add ammonia water, stir and react, and obtain Fe3O4 nanocrystals through magnetic separation and water washing; S12. Disperse Fe3O4 nanocrystals in a mixed solution of ethanol and water, add tetraethyl orthosilicate and ammonia water, stir and react at room temperature, and obtain Fe3O4@SiO2 composite particles after magnetic separation and drying; S13. Disperse Fe3O4@SiO2 composite particles in an aqueous solution of cetyltrimethylammonium bromide, then add tetraethyl orthosilicate, heat and stir to react, and perform calcination to remove the template agent after magnetic separation to obtain mesoporous Fe3O4@SiO2 composite particles; S14. Add silane coupling agent KH560 to a mixed solution of ethanol and water, heat and stir for hydrolysis, then add mesoporous Fe3O4@SiO2 composite particles, heat and stir to react, and obtain epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles; S15. Dissolve chitosan in an acetic acid solution, then add glycidyl methacrylate, and heat to react to obtain double-bond modified chitosan; S16. Dissolve double-bond modified chitosan in an acetic acid solution, then add epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles, heat and stir to react, and obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles; S17. Disperse grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in deionized water, then add acrylamide and ammonium persulfate, and heat to react under nitrogen protection to obtain a composite flocculant.

[0014] In the technical solution of the present invention, the reaction principle for preparing the composite flocculant is as follows: First, under nitrogen protection, ferric chloride and ferrous chloride react in ammonia water to generate Fe3O4 nanocrystals, then SiO2 is coated on the surface of the Fe3O4 nanocrystals to form a core-shell structure, and a cetyltrimethylammonium bromide template agent is used to guide the secondary deposition of SiO2 and calcination to form a mesoporous layer. Then, epoxy groups are grafted onto the mesoporous SiO2 through the silane coupling agent KH560, and an amine-epoxy ring-opening reaction occurs with chitosan modified by glycidyl methacrylate. Finally, free radical copolymerization occurs with acrylamide under the initiation of ammonium persulfate to form a composite structure of Fe3O4@mesoporous SiO2-grafted chitosan-polyacrylamide. When this flocculant is used for pretreatment, the mesoporous size of the mesoporous SiO2 matches with small molecule acids to provide selective adsorption sites for small molecule acids, and at the same time, organic acids are synergistically removed through the chemical neutralization of the amino groups of chitosan. In addition, the electro-neutralization and bridging flocculation effects of the polyacrylamide chain segments (long chains adsorb particles to form flocs) are used to remove solid impurities, and the Fe3O4 nanocrystal core provides magnetic response and can be rapidly separated under the action of an electric field, thereby efficiently purifying waste lubricating oil.

[0015] Preferably, in the step S11, the reaction time is 30 - 50 min.

[0016] Preferably, in the step S13, the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is 10:1 - 3.

[0017] In the technical solution of the present invention, as described above, cetyltrimethylammonium bromide templating agent is used to guide the secondary deposition of SiO2 and calcined to form a mesoporous layer. The pore structure of the mesoporous layer provides selective adsorption sites for small molecule acids, and cooperates to remove acidic substances in waste lubricating oil. To achieve a good removal rate of acidic substances, a sufficient amount of cetyltrimethylammonium bromide templating agent must be added. Therefore, the present invention controls the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide to be less than 10 / 1. As the amount of cetyltrimethylammonium bromide continues to increase, the research team of the present invention unexpectedly finds that when the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is less than 10 / 3, the flocculation effect of the prepared composite flocculant on solid particles suddenly decreases significantly. After research, it is found that this is because after excessive cetyltrimethylammonium bromide is carbonized, it occupies the surface reaction sites, resulting in a decrease in the grafting amount of subsequent polyacrylamide, and further leading to a decrease in the flocculation effect on solid particles. Therefore, in order to comprehensively balance the removal effect of acid and the flocculation effect of solid particles, the present invention strictly controls the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide in the range of 10:1 - 3.

[0018] Preferably, in the step S16, the mass ratio of epoxy group mesoporous Fe3O4@SiO2 composite particles to double bond modified chitosan is 7:2 - 4.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. In the pretreatment stage of recovering lubricating oil by the catalyst hydrorefining method, the composite flocculant is combined with the magnetic separation technology, without introducing chemical waste liquid through the traditional alkali neutralization process, significantly reducing the environmental pollution and wastewater treatment cost in the pretreatment stage.

[0020] 2. The lubricating oil base oil is separated by vacuum distillation, and the distillation residue is subjected to an esterification reaction to prepare biodiesel, realizing the co - recovery of the base oil and biodiesel, and significantly improving the resource utilization rate.

[0021] 3. The composite flocculant can simultaneously remove acidic substances and solid particles in waste lubricating oil. The Fe3O4 nanocrystal core provides magnetic response and can be rapidly separated under the action of an electric field, thus efficiently purifying waste lubricating oil.

[0022] 4. Control the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide within the specified range to comprehensively balance the removal effect of acid and the flocculation effect of solid particles. Specific embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Example 1 A method for preparing a composite flocculant, comprising the following steps: Step S11: Take a three-necked flask, add 16.2 g of ferric chloride (FeCl3 6H2O, analytical pure, purity ≥ 99%) and 6.0 g of ferrous chloride (FeCl2 4H2O, analytical pure, purity ≥ 99%), pour into 100 mL of deionized water, and stir magnetically until completely dissolved. Pass high-purity nitrogen (purity ≥ 99.99%) for protection, heat in an oil bath to 75 °C, stir at a rate of 300 rpm, and slowly dropwise add 20 mL of ammonia water (NH3 H2O, analytical pure, 25%). Maintain the pH of the reaction system ≥ 10, and continuously stir and react for 45 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device, separate for 10 min under a magnetic field strength of 1.2 T, collect the black precipitate, and wash it 3 times with deionized water until the pH of the washing solution is close to neutral to obtain Fe3O4 nanocrystals.

[0025] Step S12: Disperse 5 g of the above-mentioned Fe3O4 nanocrystals in a mixed solution of 150 mL of ethanol (analytical pure, 95%) and 50 mL of deionized water, add 2 mL of ammonia water (25%), and stir at a rate of 200 rpm at room temperature for 30 min. Slowly dropwise add 5 mL of tetraethyl orthosilicate (TEOS, analytical pure, purity ≥ 98%), and continue to stir and react for 24 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, place it in a vacuum drying oven, and dry at 60 °C for 12 h to obtain Fe3O4@SiO2 composite particles.

[0026] Step S13: Dissolve 0.013 mol of cetyltrimethylammonium bromide (CTAB, analytical pure, purity ≥ 99%) in 500 mL of deionized water, add 5 g of Fe3O4@SiO2 composite particles, heat in a water bath at 60 °C, and stir at a rate of 300 rpm for 30 min. Dropwise add 0.05 mol of tetraethyl orthosilicate, raise the temperature to 80 °C, and continuously stir and react for 12 h. After the reaction solution is separated by a 1.2 T magnetic field for 10 min, transfer the solid product to a muffle furnace, raise the temperature to 550 °C at a heating rate of 1 °C / min, and calcine for 6 h to remove the CTAB template agent to obtain mesoporous Fe3O4@SiO2 composite particles.

[0027] Step S14: In a round-bottom flask, add 2 mL of silane coupling agent KH560 (analytical pure, purity ≥ 98%), 50 mL of ethanol and 10 mL of deionized water, heat in an oil bath at 70 °C, with a stirring rate of 200 rpm, and carry out hydrolysis reaction for 2 h. Add 5 g of mesoporous Fe3O4@SiO2 composite particles, raise the temperature to 80 °C, and carry out reflux reaction for 6 h. After the reaction is completed, collect the solid by magnetic separation (1.2 T, 10 min), and dry overnight at 60 °C to obtain epoxy group-containing mesoporous Fe3O4@SiO2 composite particles.

[0028] Step S15: Dissolve 2 g of chitosan (degree of deacetylation ≥ 90%, analytical pure) in 50 mL of 1% acetic acid solution (v / v), heat in a water bath at 40 °C, and stir until completely dissolved to form a transparent solution. Add 1.5 mL of glycidyl methacrylate (GMA, analytical pure, purity ≥ 98%), raise the temperature to 60 °C, and carry out reflux reaction for 8 h. Dialyze the reaction solution through a dialysis bag for 48 h to remove unreacted monomers, and freeze-dry for 48 h to obtain double-bond modified chitosan solid.

[0029] Step S16: Dissolve 3.5 g of double-bond modified chitosan in 100 mL of 1% acetic acid solution, add 7 g of epoxy group-containing mesoporous Fe3O4@SiO2 composite particles, heat in an oil bath at 80 °C, and stir and react at a rate of 300 rpm for 12 h. After the reaction is completed, separate for 10 min through a 1.2 T magnetic field, collect the solid product, and vacuum-dry at 60 °C for 12 h to obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles.

[0030] Step S17: Disperse 5 g of grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in 50 mL of deionized water, add 2.5 g of acrylamide (AM, analytical pure, purity ≥ 98%) and 0.1 g of ammonium persulfate (APS, analytical pure, purity ≥ 98%), and introduce nitrogen for protection for 30 min. Heat in an oil bath at 60 °C, and stir and react at a rate of 200 rpm for 4 h to form a black suspension, which is the composite flocculant.

[0031] A method for resource regeneration of waste lubricating oil, comprising the following steps: S1: Take 100 g of waste lubricating oil (acid value 1.55 mgKOH / g, particulate impurities 0.896%) in a beaker, heat in an oil bath to 50 °C, add 2.5 g of the composite flocculant, and stir at a rate of 300 rpm for 20 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device, and separate for 15 min under a magnetic field intensity of 1.2 T. The upper clear liquid is the pretreated waste lubricating oil.

[0032] S2: Add 100 g of pretreated waste lubricating oil, 15 g of glycerol (analytical pure, purity ≥ 99.5%), and 3 g of Ni / Al2O3 catalyst (Ni loading of 15%) into a 500 mL high-pressure reactor. Replace the air with nitrogen three times (each time with a pressure of 0.5 MPa and a pressure holding time of 5 min). Turn on the heating and stirring, raise the temperature to 225 °C, maintain the reaction pressure at 3 MPa (providing hydrogen source through glycerol decomposition), with a stirring rate of 500 rpm, and react for 3.5 h. After the reaction, cool it naturally to room temperature to obtain the catalytic hydrogenation product.

[0033] S3: Recover the base oil by vacuum distillation. Transfer the catalytic hydrogenation product to a 500 mL vacuum distillation device, install a 30 cm packing column, control the distillation temperature at 280 °C, and the system pressure at 5 kPa. Collect the fraction at 180 - 320 °C to obtain the lubricating oil base oil, and retain the distillation residue for the esterification reaction.

[0034] Place it in a round-bottom flask, add 15 g of the distillation residue, 7.5 g of methanol (analytical pure, purity ≥ 99.5%), and 0.15 g of concentrated sulfuric acid (analytical pure, 98%, 1% of the residue mass). Heat it in an oil bath at 65 °C and stir the reaction at a rate of 300 rpm for 2 h. After the reaction solution cools, transfer it to a separatory funnel, let it stand for layering, separate the upper layer of biodiesel, and wash it with deionized water until it is neutral to obtain biodiesel.

[0035] Example 2 The preparation method of the composite flocculant includes the following steps: Step S11: Place it in a three-necked flask, add 16.2 g of ferric chloride (FeCl3 ·6H2O, analytical pure, purity ≥ 99%) and 6.0 g of ferrous chloride (FeCl2 ·4H2O, analytical pure, purity ≥ 99%), pour into 100 mL of deionized water, and stir magnetically until completely dissolved. Pass in high-purity nitrogen (purity ≥ 99.99%) for protection, heat it in an oil bath to 75 °C, stir at a rate of 300 rpm, and slowly dropwise add 20 mL of ammonia water (NH3 ·H2O, analytical pure, 25%). Maintain the pH of the reaction system ≥ 10, and continuously stir and react for 40 min. After the reaction, transfer the mixed solution to a magnetic separation device, separate it at a magnetic field intensity of 1.2 T for 10 min, collect the black precipitate, and wash it with deionized water three times until the pH of the washing solution is close to neutral to obtain Fe3O4 nanocrystals.

[0036] Step S12: Disperse 5 g of the above Fe3O4 nanocrystals in a mixed solution of 150 mL of ethanol (analytical grade, 95%) and 50 mL of deionized water. Add 2 mL of ammonia water (25%) and stir at a rate of 200 rpm for 30 min at room temperature. Slowly add dropwise 5 mL of tetraethyl orthosilicate (TEOS, analytical grade, purity ≥ 98%) and continue stirring and reacting for 24 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, place it in a vacuum drying oven, and dry at 60 °C for 12 h to obtain Fe3O4@SiO2 composite particles.

[0037] Step S13: Dissolve 0.008 mol of cetyltrimethylammonium bromide (CTAB, analytical grade, purity ≥ 99%) in 500 mL of deionized water, add 5 g of Fe3O4@SiO2 composite particles, heat in a water bath at 60 °C, and stir at a rate of 300 rpm for 30 min. Add dropwise 0.05 mol of tetraethyl orthosilicate, raise the temperature to 80 °C, and continuously stir and react for 12 h. After the reaction solution is separated by a 1.2 T magnetic field for 10 min, transfer the solid product to a muffle furnace, raise the temperature to 550 °C at a heating rate of 1 °C / min, and calcine for 6 h to remove the CTAB template agent to obtain mesoporous Fe3O4@SiO2 composite particles.

[0038] Step S14: In a round-bottom flask, add 2 mL of silane coupling agent KH560 (analytical grade, purity ≥ 98%), 50 mL of ethanol, and 10 mL of deionized water, heat in an oil bath at 70 °C, stir at a rate of 200 rpm, and carry out a hydrolysis reaction for 2 h. Add 5 g of mesoporous Fe3O4@SiO2 composite particles, raise the temperature to 80 °C, and carry out a reflux reaction for 6 h. After the reaction is completed, collect the solid by magnetic separation (1.2 T, 10 min) and dry at 60 °C overnight to obtain epoxy group-containing mesoporous Fe3O4@SiO2 composite particles.

[0039] Step S15: Dissolve 2 g of chitosan (degree of deacetylation ≥ 90%, analytical grade) in 50 mL of 1% acetic acid solution (v / v), heat in a water bath at 40 °C, and stir until completely dissolved to form a transparent solution. Add 1.5 mL of glycidyl methacrylate (GMA, analytical grade, purity ≥ 98%), raise the temperature to 60 °C, and carry out a reflux reaction for 8 h. Dialyze the reaction solution through a dialysis bag for 48 h to remove unreacted monomers, and freeze-dry for 48 h to obtain a double-bond modified chitosan solid.

[0040] Step S16: Dissolve 2.5 g of double-bond modified chitosan in 100 mL of 1% acetic acid solution, add 7 g of epoxy group-containing mesoporous Fe3O4@SiO2 composite particles, heat in an oil bath at 80 °C, and stir at a rate of 300 rpm for 12 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, and dry in vacuum at 60 °C for 12 h to obtain mesoporous Fe3O4@SiO2 composite particles grafted with double-bond modified chitosan.

[0041] Step S17: Disperse 5 g of grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in 50 mL of deionized water, add 2.5 g of acrylamide (AM, analytical pure, purity ≥ 98%) and 0.1 g of ammonium persulfate (APS, analytical pure, purity ≥ 98%), and introduce nitrogen for protection for 30 min. Heat in an oil bath at 60 °C and stir the reaction at a rate of 200 rpm for 4 h to form a black suspension, which is the composite flocculant.

[0042] A method for resource regeneration of waste lubricating oil, comprising the following steps: S1: Take 100 g of waste lubricating oil (acid value 1.55 mgKOH / g, particulate impurities 0.896%) in a beaker, heat it in an oil bath to 50 °C, add 1.0 g of the composite flocculant, and stir at a rate of 300 rpm for 20 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device and separate it for 15 min under a magnetic field strength of 1.2 T. The upper clear liquid is the pretreated waste lubricating oil.

[0043] S2: Add 100 g of pretreated waste lubricating oil, 15 g of glycerol (analytical pure, purity ≥ 99.5%) and 3 g of Ni / Al2O3 catalyst (Ni loading 15%) to a 500 mL high-pressure reactor, and displace it with nitrogen three times (each time the pressure is 0.5 MPa and the pressure is maintained for 5 min). Turn on heating and stirring, raise the temperature to 225 °C, maintain the reaction pressure at 3 MPa (providing a hydrogen source through glycerol decomposition), the stirring rate is 500 rpm, and react for 3.5 h. After the reaction is completed, naturally cool to room temperature to obtain the catalytic hydrogenation product.

[0044] S3: Recover the base oil by vacuum distillation. Transfer the catalytic hydrogenation product to a 500 mL vacuum distillation device, install a 30 cm packing column, control the distillation temperature at 280 °C, and the system pressure at 5 kPa. Collect the fraction at 180 - 320 °C to obtain the lubricating oil base oil, and retain the distillation residue for the esterification reaction.

[0045] Take a round-bottom flask, add 15 g of the distillation residue, 7.5 g of methanol (analytical pure, purity ≥ 99.5%) and 0.15 g of concentrated sulfuric acid (analytical pure, 98%, 1% of the residue mass), heat in an oil bath at 65 °C, and stir the reaction at a rate of 300 rpm for 2 h. After the reaction solution is cooled, transfer it to a separatory funnel, let it stand for stratification, separate the upper layer of biodiesel, and wash it with deionized water until neutral to obtain biodiesel.

[0046] Example 3 A method for preparing a composite flocculant, comprising the following steps: Step S11: Take a three-necked flask and add 16.2 g of ferric chloride (FeCl3 6H2O, analytical pure, purity ≥ 99%) and 6.0 g of ferrous chloride (FeCl2 4H2O, analytical reagent grade, purity ≥ 99%), pour it into 100 mL of deionized water, and stir magnetically until completely dissolved. Protect by introducing high-purity nitrogen (purity ≥ 99.99%), heat it in an oil bath to 75 °C, stir at a rate of 300 rpm, and slowly add 20 mL of ammonia water (NH3 H2O, analytical reagent grade, 25%), maintain the pH of the reaction system ≥ 10, and continuously stir and react for 40 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device, separate it for 10 min under a magnetic field intensity of 1.2 T, collect the black precipitate, and wash it 3 times with deionized water until the pH of the washing solution is close to neutral to obtain Fe3O4 nanocrystals.

[0047] Step S12: Disperse 5 g of the above-mentioned Fe3O4 nanocrystals in a mixed solution of 150 mL of ethanol (analytical reagent grade, 95%) and 50 mL of deionized water, add 2 mL of ammonia water (25%), and stir at a rate of 200 rpm at room temperature for 30 min. Slowly add 5 mL of tetraethyl orthosilicate (TEOS, analytical reagent grade, purity ≥ 98%), and continue to stir and react for 24 h. After the reaction is completed, separate it by a 1.2 T magnetic field for 10 min, collect the solid product, place it in a vacuum drying oven, and dry it at 60 °C for 12 h to obtain Fe3O4@SiO2 composite particles.

[0048] Step S13: Dissolve 0.01 mol of cetyltrimethylammonium bromide (CTAB, analytical reagent grade, purity ≥ 99%) in 500 mL of deionized water, add 5 g of Fe3O4@SiO2 composite particles, heat it in a water bath at 60 °C, and stir at a rate of 300 rpm for 30 min. Add 0.05 mol of tetraethyl orthosilicate, raise the temperature to 80 °C, and continuously stir and react for 12 h. After the reaction solution is separated by a 1.2 T magnetic field for 10 min, transfer the solid product to a muffle furnace, raise the temperature to 550 °C at a heating rate of 1 °C / min, and calcine it for 6 h to remove the CTAB template agent to obtain mesoporous Fe3O4@SiO2 composite particles.

[0049] Step S14: In a round-bottom flask, add 2 mL of silane coupling agent KH560 (analytical reagent grade, purity ≥ 98%), 50 mL of ethanol, and 10 mL of deionized water, heat it in an oil bath at 70 °C, stir at a rate of 200 rpm, and carry out a hydrolysis reaction for 2 h. Add 5 g of mesoporous Fe3O4@SiO2 composite particles, raise the temperature to 80 °C, and carry out a reflux reaction for 6 h. After the reaction is completed, collect the solid by magnetic separation (1.2 T, 10 min), and dry it at 60 °C overnight to obtain epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles.

[0050] Step S15: Dissolve 2 g of chitosan (degree of deacetylation ≥ 90%, analytical pure) in 50 mL of 1% acetic acid solution (v / v), heat it in a water bath at 40 °C, and stir until it is completely dissolved to form a transparent solution. Add 1.5 mL of glycidyl methacrylate (GMA, analytical pure, purity ≥ 98%), raise the temperature to 60 °C, and reflux for 8 h. Dialyze the reaction solution through a dialysis bag for 48 h to remove unreacted monomers, and freeze-dry for 48 h to obtain double-bond modified chitosan solid.

[0051] Step S16: Dissolve 3 g of double-bond modified chitosan in 100 mL of 1% acetic acid solution, add 7 g of epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles, heat in an oil bath at 80 °C, and stir at a rate of 300 rpm for 12 h. After the reaction is completed, separate for 10 min through a 1.2 T magnetic field, collect the solid product, and vacuum dry at 60 °C for 12 h to obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles.

[0052] Step S17: Disperse 5 g of grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in 50 mL of deionized water, add 2.5 g of acrylamide (AM, analytical pure, purity ≥ 98%) and 0.1 g of ammonium persulfate (APS, analytical pure, purity ≥ 98%), and introduce nitrogen for protection for 30 min. Heat in an oil bath at 60 °C and stir at a rate of 200 rpm for 4 h to form a black suspension, which is the composite flocculant.

[0053] A method for resource regeneration of waste lubricating oil, comprising the following steps: S1: Take 100 g of waste lubricating oil (acid value 1.55 mgKOH / g, particulate impurities 0.896%) in a beaker, heat it in an oil bath to 50 °C, add 2 g of the composite flocculant, and stir at a rate of 300 rpm for 20 min. After the reaction is completed, transfer the mixture to a magnetic separation device and separate for 15 min at a magnetic field strength of 1.2 T. The upper clear liquid is the pretreated waste lubricating oil.

[0054] S2: Add 100 g of pretreated waste lubricating oil, 15 g of glycerol (analytical pure, purity ≥ 99.5%) and 3 g of Ni / Al2O3 catalyst (Ni loading 15%) to a 500 mL high-pressure reactor, displace with nitrogen 3 times (each time the pressure is 0.5 MPa and the pressure is maintained for 5 min). Turn on heating and stirring, raise the temperature to 225 °C, maintain the reaction pressure at 3 MPa (providing hydrogen source through glycerol decomposition), the stirring rate is 500 rpm, and react for 3.5 h. After the reaction is completed, naturally cool to room temperature to obtain the catalytic hydrogenation product.

[0055] S3: Recover the base oil by vacuum distillation. Transfer the catalytic hydrogenation product to a 500 mL vacuum distillation apparatus, install a 30 cm packed column, control the distillation temperature at 280 °C, and the system pressure at 5 kPa. Collect the fraction at 180 - 320 °C to obtain the lubricating oil base oil, and retain the distillation residue for the esterification reaction.

[0056] In a round-bottom flask, add 15 g of the distillation residue, 7.5 g of methanol (analytical grade, purity ≥ 99.5%), and 0.15 g of concentrated sulfuric acid (analytical grade, 98%, 1% of the residue mass). Heat in an oil bath at 65 °C and stir the reaction at a rate of 300 rpm for 2 h. After the reaction solution cools, transfer it to a separatory funnel, let it stand for stratification, separate the upper layer of biodiesel, and wash it with deionized water until neutral to obtain biodiesel.

[0057] Example 4 Preparation method of a composite flocculant, comprising the following steps: Step S11: In a three-necked flask, add 16.2 g of ferric chloride (FeCl3 ·6H2O, analytical grade, purity ≥ 99%) and 6.0 g of ferrous chloride (FeCl2 ·4H2O, analytical grade, purity ≥ 99%), pour into 100 mL of deionized water, and stir magnetically until completely dissolved. Pass high-purity nitrogen (purity ≥ 99.99%) for protection, heat in an oil bath to 80 °C, stir at a rate of 300 rpm, and slowly add 20 mL of ammonia water (NH3 ·H2O, analytical grade, 25%). Maintain the pH of the reaction system ≥ 10 and continuously stir the reaction for 50 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device, separate for 10 min at a magnetic field intensity of 1.2 T, collect the black precipitate, and wash it 3 times with deionized water until the pH of the washing solution is close to neutral to obtain Fe3O4 nanocrystals.

[0058] Step S12: Disperse 5 g of the above Fe3O4 nanocrystals in a mixed solution of 150 mL of ethanol (analytical grade, 95%) and 50 mL of deionized water, add 2 mL of ammonia water (25%), and stir at a rate of 200 rpm at room temperature for 30 min. Slowly add 5 mL of tetraethyl orthosilicate (TEOS, analytical grade, purity ≥ 98%), and continue to stir the reaction for 24 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, place it in a vacuum drying oven, and dry at 60 °C for 12 h to obtain Fe3O4@SiO2 composite particles.

[0059] Step S13: Dissolve 0.015 mol of cetyltrimethylammonium bromide (CTAB, analytical pure, purity ≥ 99%) in 500 mL of deionized water, add 5 g of Fe3O4@SiO2 composite particles, heat in a water bath at 60 °C, and stir at a rate of 300 rpm for 30 min. Dropwise add 0.05 mol of tetraethyl orthosilicate, raise the temperature to 80 °C, and continuously stir and react for 12 h. After the reaction solution is separated by a 1.2 T magnetic field for 10 min, transfer the solid product to a muffle furnace, raise the temperature to 550 °C at a heating rate of 1 °C / min, and calcine for 6 h to remove the CTAB template agent to obtain mesoporous Fe3O4@SiO2 composite particles.

[0060] Step S14: In a round-bottom flask, add 2 mL of silane coupling agent KH560 (analytical pure, purity ≥ 98%), 50 mL of ethanol, and 10 mL of deionized water, heat in an oil bath at 70 °C, stir at a rate of 200 rpm, and carry out a hydrolysis reaction for 2 h. Add 5 g of mesoporous Fe3O4@SiO2 composite particles, raise the temperature to 80 °C, and carry out a reflux reaction for 6 h. After the reaction is completed, collect the solid by magnetic separation (1.2 T, 10 min), and dry overnight at 60 °C to obtain epoxy group-containing mesoporous Fe3O4@SiO2 composite particles.

[0061] Step S15: Dissolve 2 g of chitosan (degree of deacetylation ≥ 90%, analytical pure) in 50 mL of 1% acetic acid solution (v / v), heat in a water bath at 40 °C, and stir until completely dissolved to form a transparent solution. Add 1.5 mL of glycidyl methacrylate (GMA, analytical pure, purity ≥ 98%), raise the temperature to 60 °C, and carry out a reflux reaction for 8 h. Dialyze the reaction solution through a dialysis bag for 48 h to remove unreacted monomers, and freeze-dry for 48 h to obtain a double-bond modified chitosan solid.

[0062] Step S16: Dissolve 4 g of double-bond modified chitosan in 100 mL of 1% acetic acid solution, add 7 g of epoxy group-containing mesoporous Fe3O4@SiO2 composite particles, heat in an oil bath at 80 °C, and stir and react at a rate of 300 rpm for 12 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, and vacuum dry at 60 °C for 12 h to obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles.

[0063] Step S17: Disperse 5 g of grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in 50 mL of deionized water, add 2.5 g of acrylamide (AM, analytical pure, purity ≥ 98%) and 0.1 g of ammonium persulfate (APS, analytical pure, purity ≥ 98%), and introduce nitrogen for protection for 30 min. Heat in an oil bath at 60 °C, and stir and react at a rate of 200 rpm for 4 h to form a black suspension, which is the composite flocculant.

[0064] A method for resource regeneration of waste lubricating oil, comprising the following steps: S1: Take 100 g of waste lubricating oil (acid value 1.55 mgKOH / g, particulate impurities 0.896%) in a beaker, heat it in an oil bath to 50 °C, add 3 g of composite flocculant, and stir at a rate of 300 rpm for 20 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device and separate it for 15 min under a magnetic field intensity of 1.2 T. The upper clear liquid is the pretreated waste lubricating oil.

[0065] S2: Add 100 g of pretreated waste lubricating oil, 15 g of glycerol (analytical pure, purity ≥ 99.5%), and 3 g of Ni / Al2O3 catalyst (Ni loading 15%) to a 500 mL high-pressure reactor, and displace it with nitrogen three times (each time the pressure is 0.5 MPa and the pressure is maintained for 5 min). Turn on heating and stirring, raise the temperature to 230 °C, maintain the reaction pressure at 3 MPa (providing a hydrogen source through glycerol decomposition), the stirring rate is 500 rpm, and react for 4 h. After the reaction is completed, naturally cool to room temperature to obtain the catalytic hydrogenation product.

[0066] S3: Recover the base oil by vacuum distillation. Transfer the catalytic hydrogenation product to a 500 mL vacuum distillation device, install a 30 cm packing column, control the distillation temperature at 280 °C, and the system pressure at 5 kPa. Collect the fraction at 180 - 320 °C to obtain the lubricating oil base oil, and retain the distillation residue for the esterification reaction.

[0067] Take it in a round-bottom flask, add 15 g of distillation residue, 7.5 g of methanol (analytical pure, purity ≥ 99.5%), and 0.15 g of concentrated sulfuric acid (analytical pure, 98%, 1% of the residue mass), heat it in an oil bath at 65 °C, and stir and react at a rate of 300 rpm for 2 h. After the reaction solution is cooled, transfer it to a separatory funnel, let it stand for stratification, separate the upper layer of biodiesel, and wash it with deionized water until it is neutral to obtain biodiesel.

[0068] Example 5 Preparation method of composite flocculant, including the following steps: Step S11: Take it in a three-necked flask, add 16.2 g of ferric chloride (FeCl3 6H2O, analytical pure, purity ≥ 99%) and 6.0 g of ferrous chloride (FeCl2 4H2O, analytical pure, purity ≥ 99%), pour it into 100 mL of deionized water, and stir magnetically until completely dissolved. Protect it by introducing high-purity nitrogen (purity ≥ 99.99%), heat it in an oil bath to 70 °C, stir at a rate of 300 rpm, and slowly add 20 mL of ammonia water (NH3 H2O, analytical grade, 25%), maintain the pH of the reaction system ≥10, and continuously stir the reaction for 30 min. After the reaction is completed, transfer the mixed solution to a magnetic separation device, separate it at a magnetic field strength of 1.2 T for 10 min, collect the black precipitate, and wash it 3 times with deionized water until the pH of the washing solution is close to neutral to obtain Fe3O4 nanocrystals.

[0069] Step S12: Disperse 5 g of the above-mentioned Fe3O4 nanocrystals in a mixed solution of 150 mL of ethanol (analytical grade, 95%) and 50 mL of deionized water, add 2 mL of ammonia water (25%), and stir at a rate of 200 rpm at room temperature for 30 min. Slowly add dropwise 5 mL of tetraethyl orthosilicate (TEOS, analytical grade, purity ≥98%), and continue to stir and react for 24 h. After the reaction is completed, separate it by a 1.2 T magnetic field for 10 min, collect the solid product, place it in a vacuum drying oven, and dry it at 60 °C for 12 h to obtain Fe3O4@SiO2 composite particles.

[0070] Step S13: Dissolve 0.005 mol of cetyltrimethylammonium bromide (CTAB, analytical grade, purity ≥99%) in 500 mL of deionized water, add 5 g of Fe3O4@SiO2 composite particles, heat it in a water bath at 60 °C, and stir at a rate of 300 rpm for 30 min. Add dropwise 0.05 mol of tetraethyl orthosilicate, raise the temperature to 80 °C, and continuously stir and react for 12 h. After the reaction solution is separated by a 1.2 T magnetic field for 10 min, transfer the solid product to a muffle furnace, raise the temperature to 550 °C at a heating rate of 1 °C / min, and calcine it for 6 h to remove the CTAB template agent to obtain mesoporous Fe3O4@SiO2 composite particles.

[0071] Step S14: In a round-bottom flask, add 2 mL of silane coupling agent KH560 (analytical grade, purity ≥98%), 50 mL of ethanol, and 10 mL of deionized water, heat it in an oil bath at 70 °C, stir at a rate of 200 rpm, and carry out a hydrolysis reaction for 2 h. Add 5 g of mesoporous Fe3O4@SiO2 composite particles, raise the temperature to 80 °C, and carry out a reflux reaction for 6 h. After the reaction is completed, collect the solid by magnetic separation (1.2 T, 10 min), and dry it at 60 °C overnight to obtain epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles.

[0072] Step S15: Dissolve 2 g of chitosan (degree of deacetylation ≥90%, analytical grade) in 50 mL of 1% acetic acid solution (v / v), heat it in a water bath at 40 °C, and stir until it is completely dissolved to form a transparent solution. Add 1.5 mL of glycidyl methacrylate (GMA, analytical grade, purity ≥98%), raise the temperature to 60 °C, and carry out a reflux reaction for 8 h. Dialyze the reaction solution through a dialysis bag for 48 h to remove unreacted monomers, and freeze-dry it for 48 h to obtain a double-bond modified chitosan solid.

[0073] Step S16: Dissolve 2 g of double-bond modified chitosan in 100 mL of 1% acetic acid solution, add 7 g of epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles, heat in an oil bath at 80 °C, and stir at a rate of 300 rpm for 12 h. After the reaction is completed, separate by a 1.2 T magnetic field for 10 min, collect the solid product, and dry in vacuum at 60 °C for 12 h to obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles.

[0074] Step S17: Disperse 5 g of grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in 50 mL of deionized water, add 2.5 g of acrylamide (AM, analytical grade, purity ≥98%) and 0.1 g of ammonium persulfate (APS, analytical grade, purity ≥98%), and purify with nitrogen for 30 min. Heat in an oil bath at 60 °C and stir at a rate of 200 rpm for 4 h to form a black suspension, which is the composite flocculant.

[0075] A method for resource regeneration of waste lubricating oil, comprising the following steps: S1: Take 100 g of waste lubricating oil (acid value 1.55 mgKOH / g, particulate impurities 0.896%) in a beaker, heat in an oil bath to 50 °C, add 0.5 g of the composite flocculant, and stir at a rate of 300 rpm for 20 min. After the reaction is completed, transfer the mixture to a magnetic separation device and separate at a magnetic field intensity of 1.2 T for 15 min. The upper clear liquid is the pretreated waste lubricating oil.

[0076] S2: Add 100 g of pretreated waste lubricating oil, 15 g of glycerol (analytical grade, purity ≥99.5%), and 3 g of Ni / Al2O3 catalyst (Ni loading 15%) to a 500 mL high-pressure reactor, and displace with nitrogen three times (each time the pressure is 0.5 MPa and the pressure is maintained for 5 min). Turn on heating and stirring, raise the temperature to 220 °C, maintain the reaction pressure at 3 MPa (hydrogen source provided by glycerol decomposition), the stirring rate is 500 rpm, and react for 3 h. After the reaction is completed, naturally cool to room temperature to obtain the catalytic hydrogenation product.

[0077] S3: Recover the base oil by vacuum distillation. Transfer the catalytic hydrogenation product to a 500 mL vacuum distillation device, install a 30 cm packing column, control the distillation temperature at 280 °C, and the system pressure at 5 kPa. Collect the fraction at 180 - 320 °C to obtain the lubricating oil base oil, and retain the distillation residue for the esterification reaction.

[0078] In a round-bottom flask, add 15 g of distillation residue, 7.5 g of methanol (analytical grade, purity ≥ 99.5%), and 0.15 g of concentrated sulfuric acid (analytical grade, 98%, 1% of the residue mass). Heat it in an oil bath at 65 °C and stir the reaction at a rate of 300 rpm for 2 h. After the reaction solution is cooled, transfer it to a separatory funnel, let it stand for layering, separate the upper layer of biodiesel, and wash it with deionized water until it is neutral to obtain biodiesel.

[0079] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in the resource regeneration process of waste lubricating oil, the composite flocculant is replaced with Fe3O4@SiO2 composite particles, and the other steps are the same.

[0080] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in the resource regeneration process of waste lubricating oil, the composite flocculant is replaced with mesoporous Fe3O4@SiO2 composite particles, and the other steps are the same.

[0081] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in the resource regeneration process of waste lubricating oil, the composite flocculant is replaced with grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles, and the other steps are the same.

[0082] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is 10:4.

[0083] Comparative Example 5 The difference between Comparative Example 5 and Example 4 is that the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is 10:5.

[0084] Performance Test: 1.1 Yield Test of Lubricating Oil Base Oil and Biodiesel: First, weigh the mass of the pretreated waste lubricating oil. Collect the distillate by vacuum distillation, and after cooling, weigh the mass of the base oil. Calculate the yield of the lubricating oil base oil according to the formula: mass of recovered base oil / mass of pretreated waste lubricating oil × 100%. The biodiesel yield is then measured by weighing the mass of the distillation residue after vacuum distillation, and calculating the biodiesel yield according to the formula: mass of biodiesel / mass of distillation residue × 100%. The test results are shown in Table 1.

[0085] 1.2 Acid Value Test of Lubricating Oil Base Oil and Biodiesel: Using the acid-base titration method, for lubricating oil base oil or biodiesel, take 10 mL of the sample, add 50 mL of an ethanol-ether mixed solvent with a volume ratio of 1:1, add 2 drops of phenolphthalein indicator, and titrate with 0.1 mol / L potassium hydroxide ethanol solution until the solution turns slightly pink and does not fade within 30 seconds. According to the volume, concentration of the potassium hydroxide solution consumed in the titration, the mass of the sample, and the molar mass of potassium hydroxide, calculate the acid value = (volume of potassium hydroxide solution consumed in the titration × concentration of potassium hydroxide solution × 56.1) / mass of the sample. The test results are shown in Table 1.

[0086] Table 1: 2.1 Testing the acid removal rate of the composite flocculant: The acid value of waste lubricating oil was determined by the acid-base titration method. Take 10 mL of the waste lubricating oil before and after pretreatment, respectively add 50 mL of an ethanol-ether mixed solvent with a volume ratio of 1:1, add 2 drops of phenolphthalein indicator, and titrate with 0.1 mol / L potassium hydroxide ethanol solution until the solution turns slightly pink and does not fade within 30 seconds. The calculation method of the acid value is: acid value = volume of potassium hydroxide solution consumed in the titration × concentration of potassium hydroxide solution × 56.1 / mass of the sample. The calculation method of the acid value removal rate is (initial acid value - acid value after treatment) / initial acid value × 100%. The calculation results are shown in Table 2.

[0087] 2.2 Testing the solid particle removal rate of the composite flocculant: The content of solid particles was determined by the gravimetric method. Take 100 mL of waste lubricating oil, perform vacuum filtration with a 0.45-micron microporous filter membrane that has been weighed to a constant weight, collect the filter residue, and dry it to a constant weight at 105 °C. The calculation method of the solid particle content is calculated according to (total mass of the filter membrane and filter residue - mass of the filter membrane) / mass of the sample and then multiplied by 100%. The calculation of the particle removal rate is calculated according to (initial particle content - particle content after treatment) / initial particle content × 100%. The calculation results are shown in Table 2.

[0088] Table 2: Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for resource regeneration of waste lubricating oil, characterized in that, It includes the following steps: S1. Add a composite flocculant to waste lubricating oil, heat and stir, and then perform magnetic separation to obtain pretreated waste lubricating oil; S2. Mix the pretreated waste lubricating oil, glycerol and Ni / Al2O3 catalyst evenly, and then heat and react under pressure, and cool to room temperature to obtain a catalytic hydrogenation product; S3. Subject the catalytic hydrogenation product to vacuum distillation to recover the lubricating oil base oil fraction, add methanol and concentrated sulfuric acid to the distillation residue, heat for an esterification reaction, and separate by liquid separation to obtain biodiesel.

2. The resource regeneration method of waste lubricating oil according to claim 1, characterized in that In the step S1, the addition amount of the composite flocculant is 0.5-3.0% of the mass of the waste lubricating oil.

3. A method for resource regeneration of waste lubricating oil according to claim 1, characterized in that, In the step S2, the mass ratio of the pretreated waste lubricating oil, glycerol and Ni / Al2O3 catalyst is 10:1.5:0.

3.

4. The resource regeneration method of waste lubricating oil according to claim 1, characterized in that, In the step S2, the heating reaction temperature is 220-230 °C, and the heating reaction time is 3-4 h.

5. A method for resource regeneration of waste lubricating oil according to claim 1, characterized in that, In the step S3, the vacuum distillation temperature is 280 °C, and the pressure is 5 kPa.

6. A method for resource regeneration of waste lubricating oil according to claim 1, characterized in that, In the step S3, the mass ratio of the distillation residue to methanol is 2:

1.

7. A method for resource regeneration of waste lubricating oil according to claim 1, characterized in that, In the step S1, the preparation method of the composite flocculant includes the following steps: S11. Dissolve ferric chloride and ferrous chloride in deionized water, heat to 70-80 °C under nitrogen protection, add ammonia water, stir and react, and perform magnetic separation and water washing to obtain Fe3O4 nanocrystals; S12. Disperse the Fe3O4 nanocrystals in a mixed solution of ethanol and water, add tetraethyl orthosilicate and ammonia water, stir and react at room temperature, and perform magnetic separation and drying to obtain Fe3O4@SiO2 composite particles; S13. Disperse the Fe3O4@SiO2 composite particles in an aqueous solution of cetyltrimethylammonium bromide, then add tetraethyl orthosilicate, heat and stir to react, perform magnetic separation and then calcine to remove the template agent to obtain mesoporous Fe3O4@SiO2 composite particles; S14. Add the silane coupling agent KH560 to a mixed solution of ethanol and water, heat and stir for hydrolysis, then add the mesoporous Fe3O4@SiO2 composite particles, heat and stir to react to obtain epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles; S15. Dissolve chitosan in an acetic acid solution, then add glycidyl methacrylate, heat and react to obtain double-bond modified chitosan; S16. Dissolve the double-bond modified chitosan in an acetic acid solution, then add the epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles, heat and stir to react to obtain grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles; S17. Disperse the grafted double-bond modified chitosan mesoporous Fe3O4@SiO2 composite particles in deionized water, then add acrylamide and ammonium persulfate, heat and react under nitrogen protection to obtain a composite flocculant.

8. A method for resource regeneration of waste lubricating oil according to claim 7, characterized in that, In the step S11, the reaction time is 30-50 min.

9. A method for resource regeneration of waste lubricating oil according to claim 7, characterized in that, In the step S13, the molar ratio of tetraethyl orthosilicate to cetyltrimethylammonium bromide is 10:1-3.

10. A method for resource regeneration of waste lubricating oil according to claim 7, characterized in that, In the step S16, the mass ratio of the epoxy-functionalized mesoporous Fe3O4@SiO2 composite particles to the double-bond modified chitosan is 7:2-4.

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