Hydrofining method of waste lubricating oil

Abstract

The invention relates to a hydrofining method of waste lubricating oil, and belongs to the technical field of petrochemical engineering. The method comprises the following steps: heating and stirring the waste lubricating oil, then standing and settling, adding a flocculating agent into the filtered lubricating oil, stirring and reacting, adding a demulsifier for demulsification after the reaction is finished, standing and settling, filtering filtrate by using a filter screen, carrying out reduced pressure distillation on the filtrate, and retaining a base oil part with the boiling point of 330-535 DEG C; and carrying out refining treatment by using a hydrogenation catalyst, carrying out reduced pressure distillation on the filtrate, and carrying out fraction cutting according to the distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products. The method realizes recycling of the waste lubricating oil, and has huge social benefits and economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical industry, in particular to a method for hydrogenating and refining waste lubricating oil. Background Art

[0002] During the use of lubricating oil, oxidation, thermal decomposition and polymerization are inevitable, resulting in performance degradation and becoming waste lubricating oil. Waste lubricating oil often contains non-ideal components such as water, light hydrocarbons, metal particles, carbon particles, dust, sludge, additives, residual asphalt and mechanical impurities. In fact, waste lubricating oil is not waste oil. The deteriorated components in the oil only account for 5% to 10%, and the remaining majority of hydrocarbon components are still the effective ingredients and main viscosity carriers of lubricating oil. Whether from the perspective of resource utilization, environmental protection or economy, the recovery and reuse of waste lubricating oil has economic value.

[0003] CN115820333A relates to a method for recycling waste lubricating oil sludge, comprising the following steps: (1) reacting the waste lubricating oil sludge in a water-gas atmosphere, and performing solid-liquid separation after the reaction is completed; (2) subjecting the obtained liquid phase to distillation to obtain regenerated lubricating oil base oil, and drying the obtained solid phase product to obtain iron powder particles.

[0004] CN109652197B discloses a method for recovering and filtering lubricating oil, which includes pre-deposition and filtering stages, wherein the filter aid in the pre-deposition stage is diatomaceous earth or a mixture of diatomaceous earth and cellulose, and the concentration of the filter aid is 7-16%, and the filter aid in the filtering stage is a mixture of diatomaceous earth and cellulose or a mixture of diatomaceous earth, cellulose and activated clay, and the concentration of the filter aid is 1-2%.

[0005] CN114225452A discloses a four-stage evaporation recovery method for waste lubricating oil, the steps comprising: the first stage: introducing the waste lubricating oil into an evaporation tower for atmospheric flash evaporation to remove water and paraffin oil; the second stage: introducing the waste lubricating oil obtained after the first stage treatment into a distillation tower for reduced pressure distillation to remove gas oil; the third stage: introducing the waste lubricating oil obtained after the second stage treatment into a molten salt heat exchanger for heating to convert the waste lubricating oil into a gas-liquid mixture, then introducing the gas-liquid mixture into a distillation tower for gas-liquid separation and equilibrium flash evaporation, evaporating and refluxing to obtain 100# or 150# base oil fraction, and the residual oil falls to the bottom of the tower; the fourth stage: introducing the bottom residual oil of the tower obtained by the third stage treatment into a scraped film evaporator for scraped film evaporation, then introducing the evaporated gas into the distillation tower, evaporating and refluxing to obtain 250# or 350# base oil fraction, and discharging the bottom residual oil.

[0006] CN114231316A provides a waste lubricating oil recycling process, which is characterized in that the waste lubricating oil is subjected to demulsification, dehydration, demetallization, hydrogenation refining, gas-liquid separation, deacidification, atmospheric and vacuum distillation and other process processes to obtain refined gasoline, refined diesel and base oil that meet standard requirements.

[0007] The sources of waste lubricating oil are complex. The existing methods for recycling lubricating oil mainly face problems such as high recovery cost, environmentally friendly technology, low waste oil recovery rate, and poor quality of recycled oil. Summary of the invention

[0008] In order to solve at least one of the technical problems existing in the prior art, the present invention provides a method for hydrofining waste lubricating oil.

[0009] The technical solution of the present invention to solve the above technical problems is as follows: A method for hydrofining of waste lubricating oil mainly comprises the following steps: Step 1: Sedimentation Filtration Heat the waste lubricating oil to 50-70°C, stir for 30-60 minutes, let it stand for 6-18 hours, and filter it through a filter screen 2-4 times; Step 2: Flocculation centrifugation Add 200-600 parts of flocculant to 100-300 parts of the filtered lubricating oil and stir. The reaction temperature is 60-80°C and the reaction time is 30-90 minutes. After the reaction is completed, add 5-10 parts of demulsifier and stir for 30-90 minutes. Let it stand and settle for 6-18 hours and then centrifuge. The centrifugal speed is 2000-16000r / min and the time is 1-5 minutes. Use a filter to filter the filtrate.

[0010] Step 3: Distillation The filtrate of step 2 is subjected to reduced pressure distillation, the reduced pressure distillation temperature is 160°C to 200°C, the vacuum degree is 1kPa to 90kPa, and the distillation time is 1h to 1.5h; the normal pressure insulation temperature is 290°C to 360°C, the insulation time is 4h to 6h, and the base oil part with a boiling point of 330-535°C is retained.

[0011] Step 4: Hydrotreating The waste lubricating oil treated in step 3 is refined with a hydrogenation catalyst. The hydrogenation refining reaction temperature is 280-360°C, the reaction pressure is 5.0-8.0 MPa, the hydrogen-oil volume ratio is 300-800:1, and the liquid volume space velocity is 0.2-1.2 h -1 .

[0012] Step 5: Membrane filtration and vacuum distillation The lubricating oil treated in step 4 is cooled to 60-80°C and then subjected to membrane filtration. The process parameters are set as filtration pressure -0.06~-0.04MPa and filtration temperature 40-60°C. The filtrate is subjected to reduced pressure distillation at a temperature of 300~370°C and a vacuum degree of -0.05~-0.098Mpa. Fractions are cut according to the distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products.

[0013] Furthermore, the filter screen in step 1 is 300-600 mesh.

[0014] Furthermore, the stirring speed in step one is 200300 / min.

[0015] Furthermore, the flocculant in step 2 is a composite flocculant, which is a composite alkaline flocculant formed by mixing one of sodium hydroxide, potassium hydroxide, sodium silicate and one of triethylenetetramine, oxalic acid, diethylenetriamine, and polyimide.

[0016] Furthermore, the demulsifier in step 2 is polyoxypropylene polyoxyethylene propylene glycol ether, polyoxypropylene polyoxyethylene propylene glycol ether, polyoxyethylene polyoxypropylene alkylphenol formaldehyde resin, alkylphenol formaldehyde resin block polyether, phenolamine formaldehyde resin block polyether or polyphosphate.

[0017] Furthermore, the filter screen in step 2 is 60-100 mesh.

[0018] Furthermore, the amount of hydrogenation catalyst used in step 4 is 0.005-0.2% of the weight of the waste lubricating oil.

[0019] Furthermore, the preparation method of the hydrogenation catalyst in step 4 is: B1: Add 2-5 parts of palladium nitrate, 0.002-0.02 parts of molybdenum nitrate, 0.002-0.04 parts of cerium nitrate, 100-200 parts of water, and 4-8 parts of 2,5-dihydroxyterephthalic acid to reactor 1 by weight, react at 30-40° C. for 30-50 minutes, and then distill to remove water to obtain a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex; B2: In reactor 2, 100-150 parts of isocyanate-based X-type molecular sieve, 2-5 parts of 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, 0.2-0.5 parts of stannous octoate, and 1000-1200 parts of toluene are added by weight, and the reaction is carried out at a temperature of 50-60°C for 10-20 minutes, and then 0.02-0.6 parts of tetraaminoporphyrin are added, and the reaction is carried out at 70-80°C for 100-140 minutes. The mixture is filtered and dried to obtain a hydrogenation catalyst for waste lubricating oil.

[0020] Furthermore, the preparation method of the isocyanate-based X-type molecular sieve described in B2 is: According to weight, 100-150 parts of X molecular sieve, 1000-1700 parts of water, and 4-7 parts of 3-isocyanate propyltrioxysilane are added into the reactor, reacted at 30-40°C for 30-50 minutes, filtered, and dried to obtain isocyanate X type molecular sieve.

[0021] The reaction mechanism of the hydrogenation catalyst is as follows: an isocyanate-based X-type molecular sieve undergoes a condensation reaction with the hydroxyl group of a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, and then undergoes a condensation reaction with the amino group of tetraaminoporphyrin to obtain an X-type molecular sieve loaded with porphyrin-based palladium / molybdenum / cerium complex, which is a hydrogenation catalyst.

[0022] Compared with the prior art, the method for hydrofining of waste lubricating oil of the present invention has the following significant effects: The waste lubricating oil is first subjected to sedimentation to remove most of the large mechanical impurities, and then filtered to remove small mechanical impurities. The flocculant is added and stirred so that the colloids and fine particles in the waste lubricating oil are collected by the flocculant to form flocs and then removed, effectively reducing the occurrence of coking during the hydrogenation process.

[0023] Through hydrorefining treatment, compounds containing S, O, N, Cl and other elements in the waste oil are converted into H2S, H2O, NH4, HCl and the like for removal, and the aromatics are partially hydrogenated and saturated, and the dienes and olefins are hydrogenated, thereby improving the oil quality and enabling the recycling of waste lubricating oil, which has huge social and economic benefits. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] Example 1 Step 1: Sedimentation Filtration The waste lubricating oil was heated to 50°C and stirred at a speed of 200 rpm. After 30 minutes, it was allowed to settle for 6 hours and filtered twice through a 600-mesh filter.

[0026] Step 2: Flocculation centrifugation Add 200 kg of sodium hydroxide-triethylenetetramine composite flocculant to 100 kg of filtered lubricating oil and stir. The reaction temperature is 60°C and the reaction time is 30 min. After the reaction, add 5 kg of polyoxypropylene polyoxyethylene propylene glycol ether demulsifier and stir for 30 min. Let it stand and settle for 6 hours and then centrifuge. The centrifugal speed is 2000 r / min and the time is 1 min. Use a 100-mesh filter to filter the filtrate.

[0027] Step 3: Distillation The filtrate of step 2 is subjected to reduced pressure distillation at a temperature of 160°C, a vacuum degree of 1 kPa, a distillation time of 1 hour, a normal pressure insulation temperature of 290°C, an insulation time of 4 hours, and the base oil portion with a boiling point of 330°C is retained.

[0028] Step 4: Hydrotreating The waste lubricating oil treated in step 3 is refined with a hydrogenation catalyst. The hydrogenation refining reaction temperature is 2800°C, the reaction pressure is 5.0 MPa, the hydrogen-oil volume ratio is 300:1, and the liquid volume space velocity is 0.2 h -1 .

[0029] Step 5: Membrane filtration and vacuum distillation The lubricating oil treated in step 4 is cooled to 6°C and then subjected to membrane filtration. The process parameters are set as filtration pressure -0.06MPa and filtration temperature 40°C. The filtrate is subjected to reduced pressure distillation at 300°C and vacuum degree -0.05Mpa. Fractions are cut according to distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products.

[0030] The amount of hydrogenation catalyst used in step 4 is 0.005% of the weight of the waste lubricating oil.

[0031] The preparation method of the hydrogenation catalyst is: B1: Add 2 g of palladium nitrate, 0.002 g of molybdenum nitrate, 0.002 g of cerium nitrate, 100 g of water, and 4 g of 2,5-dihydroxyterephthalic acid into reactor 1, and react at 30° C. for 30 minutes. After the reaction, remove the water by distillation to obtain a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex; B2: Add 100 g of isocyanate-based X-type molecular sieve, 2 g of 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, 0.2 g of stannous octoate, and 1000 g of toluene into reactor 2, react at 50° C. for 10 min, then add 0.02 g of tetraaminoporphyrin, react at 70° C. for 100 min, filter, and dry to obtain a hydrogenation catalyst for waste lubricating oil; The preparation method of the isocyanate-based X-type molecular sieve described in B2 is: 100 g of X molecular sieve, 1000 g of water and 4 g of 3-isocyanate propyltrioxysilane were added into the reactor, reacted at 30° C. for 30 minutes, filtered and dried to obtain isocyanate X-type molecular sieve.

[0032] Example 2 Step 1: Sedimentation Filtration The waste lubricating oil was heated to 60°C and stirred at a speed of 250 rpm. After 45 minutes, it was allowed to settle for 12 hours and filtered three times through a 450-mesh filter.

[0033] Step 2: Flocculation centrifugation Add 400 kg of potassium hydroxide-diethylenetriamine composite flocculant to 200 kg of filtered lubricating oil and stir. The reaction temperature is 70°C and the reaction time is 60 min. After the reaction, add 8 kg of polyoxyethylene polyoxypropylene alkylphenol formaldehyde resin demulsifier and stir for 60 min. Let it stand and settle for 12 hours and then centrifuge. The centrifugal speed is 9000 r / min for 3 min. The filtrate is filtered using an 80-mesh filter.

[0034] Step 3: Distillation The filtrate of step 2 is subjected to reduced pressure distillation at a temperature of 180°C, a vacuum degree of 45 kPa, and a distillation time of 1.2 h; the atmospheric pressure insulation temperature is 320°C, the insulation time is 5 h, and the base oil part with a boiling point of 425°C is retained.

[0035] Step 4: Hydrotreating The waste lubricating oil treated in step 3 is refined with a hydrogenation catalyst. The hydrogenation refining reaction temperature is 320°C, the reaction pressure is 7MPa, the hydrogen-oil volume ratio is 600:1, and the liquid volume space velocity is 0.7h -1 .

[0036] Step 5: Membrane filtration and vacuum distillation The lubricating oil treated in step 4 is cooled to 70°C and then subjected to membrane filtration. The process parameters are set to a filtration pressure of -0.05MPa and a filtration temperature of 50°C. The filtrate is subjected to reduced pressure distillation at a temperature of 335°C and a vacuum degree of -0.25Mpa. The fractions are cut according to the distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products.

[0037] The amount of hydrogenation catalyst used in step 4 is 0.1% of the weight of the waste lubricating oil.

[0038] The preparation method of the hydrogenation catalyst is: B1: Add 4 g of palladium nitrate, 0.01 g of molybdenum nitrate, 0.02 g of cerium nitrate, 150 g of water, and 6 g of 2,5-dihydroxyterephthalic acid into reactor 1, and react at 35° C. for 40 minutes. After the reaction, remove the water by distillation to obtain a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex; B2: Add 125 g of isocyanate-based X-type molecular sieve, 4 g of 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, 0.4 g of stannous octoate, and 1100 g of toluene into reactor 2, react at 55° C. for 15 min, then add 0.3 g of tetraaminoporphyrin, react at 75° C. for 120 min, filter, and dry to obtain a hydrogenation catalyst for waste lubricating oil; The preparation method of the isocyanate-based X-type molecular sieve described in B2 is: 125 g of X molecular sieve, 1350 g of water and 6 g of 3-isocyanate propyltrioxysilane were added into the reactor, reacted at 35° C. for 40 minutes, filtered and dried to obtain isocyanate X type molecular sieve.

[0039] Example 3 Step 1: Sedimentation Filtration The waste lubricating oil was heated to 70°C and stirred at a stirring speed of 300 / min. After 60 minutes, it was allowed to settle for 18 hours and filtered through a 300-mesh filter four times.

[0040] Step 2: Flocculation centrifugation To 300 kg of filtered lubricating oil, add 600 kg of sodium hydroxide-polyimide composite flocculant and stir. The reaction temperature is 80°C and the reaction time is 90 min. After the reaction, add 10 kg of alkyl phenolic resin block polyether demulsifier and stir for 90 min. Let it stand and settle for 18 hours and then centrifuge. The centrifugal speed is 6000 r / min and the time is 5 min. The filtrate is filtered through a 60-mesh sieve.

[0041] Step 3: Distillation The filtrate of step 2 is subjected to reduced pressure distillation at a temperature of 200°C, a vacuum degree of 90 kPa, and a distillation time of 1.5 h; the normal pressure insulation temperature is 360°C, the insulation time is 6 h, and the base oil part with a boiling point of 535°C is retained.

[0042] Step 4: Hydrotreating The waste lubricating oil treated in step 3 is refined with a hydrogenation catalyst. The hydrogenation refining reaction temperature is 360°C, the reaction pressure is 8.0 MPa, the hydrogen-oil volume ratio is 800:1, and the liquid volume space velocity is 1.2 h -1 .

[0043] Step 5: Membrane filtration and vacuum distillation The lubricating oil treated in step 4 is cooled to 80°C and then subjected to membrane filtration. The process parameters are set to a filtration pressure of -0.04MPa and a filtration temperature of 60°C. The filtrate is subjected to reduced pressure distillation at a temperature of 370°C and a vacuum degree of 0.098Mpa. The fractions are cut according to the distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products.

[0044] The amount of hydrogenation catalyst used in step 4 is 0.2% of the weight of the waste lubricating oil.

[0045] The preparation method of the hydrogenation catalyst described in step 4 is: B1: Add 2 g of palladium nitrate, 0.02 g of molybdenum nitrate, 0.04 g of cerium nitrate, 200 g of water, and 8 g of 2,5-dihydroxyterephthalic acid into reactor 1, and react at 40° C. for 50 minutes. After the reaction, remove the water by distillation to obtain a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex; B2: Add 150g of isocyanate-based X-type molecular sieve, 5g of 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, 0.5g of stannous octoate, and 1200g of toluene into reactor 2, and react at 60°C for 20min, then add 0.6g of tetraaminoporphyrin, react at 80°C for 140min, filter, and dry to obtain a hydrogenation catalyst for waste lubricating oil; The preparation method of the isocyanate-based X-type molecular sieve described in B2 is: 50 g of X molecular sieve, 1700 g of water and 7 g of 3-isocyanate propyltrioxysilane were added into the reactor, reacted at 40° C. for 50 minutes, filtered and dried to obtain isocyanate X type molecular sieve.

[0046] Comparative Example 1 No hydrogenation catalyst was added, and the rest of the technical scheme was the same as in Example 1.

[0047] Test items raw material Example 1 Example 2 Example 3 Comparative Example 1 Appearance black transparent transparent transparent transparent Viscosity Index 92 121 128 134 114 Flash point (open), ℃ 153 224 226 230 197 Pour point, ℃ -6 -17 -24 -35 -12 Acid value, mg(KOH) / g 3.48 0.013 0.005 0.007 0.25 Saturated hydrocarbons (mass fraction), % 66.78 96.9 97.3 98.6 84.3 Carbon residue (mass fraction), % 4.89 0.02 0.01 0.01 0.02 Sulfur content, ppm 6508 1 0.7 0.5 12.5 Nitrogen content, ppm 947 0.7 0.6 0.2 1.5 Chlorine content, ppm 578 1.3 0.8 0.5 2.9 Oxidation stability, min 302 314 326 285 From the above table, it can be clearly seen that the regenerated lubricating oils obtained in Examples 1 to 3 have a viscosity index of 100, a flash point of more than 220°C, an improved pour point, and various impurities are effectively removed. The overall properties of the regenerated lubricating oils finally prepared are good; In Example 1 and Comparative Example 1 where other conditions are the same, the process of Comparative Example 1 without adding a hydrogenation catalyst has lower indicators than Example 1. This is due to the fact that the hydrorefining catalyst can saturate part of the olefins while removing sulfur and nitrogen, thereby increasing the content of saturated hydrocarbons in the lubricating base oil, improving product quality, and improving product grade. The rare earth component contained in the catalyst has a moderate cracking ability, and the yield of high-quality gasoline and diesel components can be adjusted according to market needs, thereby improving the flexibility of device operation and increasing efficiency.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for hydrofining waste lubricating oil, characterized in that: The steps include: Step 1: Sedimentation Filtration Heat the waste lubricating oil to 50-70°C, stir at 200-300 rpm for 30-60 min, let it settle for 6-18 h, and filter it through a filter screen for 2-4 times; Step 2: Flocculation centrifugation Add 200-600 parts of flocculant to 100-300 parts of the filtered lubricating oil and stir, the reaction temperature is 60-80°C, the reaction time is 30-90 minutes, after the reaction is completed, add 5-10 parts of demulsifier and stir for 30-90 minutes, let it stand for 6-18 hours and centrifuge, the centrifugal speed is 2000-16000r / min, the time is 1-5 minutes, and the filtrate is filtered through a filter; Step 3: Distillation The filtrate of step 2 is subjected to vacuum distillation, the vacuum distillation temperature is 160°C to 200°C, the vacuum degree is 1kPa to 90kPa, and the distillation time is 1h to 1.5h; the normal pressure insulation temperature is 290°C to 360°C, the insulation time is 4h to 6h, and the base oil part with a boiling point of 330-535°C is retained; Step 4: Hydrotreating The waste lubricating oil treated in step 3 is refined with a hydrogenation catalyst. The hydrogenation refining reaction temperature is 280-360°C, the reaction pressure is 5.0-8.0 MPa, the hydrogen-oil volume ratio is 300-800:1, and the liquid volume space velocity is 0.2-1.2 h -1 ; Step 5: Membrane filtration and vacuum distillation The lubricating oil treated in step 4 is cooled to 60-80°C and then subjected to membrane filtration. The process parameters are set to a filtration pressure of -0.06~-0.04MPa and a filtration temperature of 40-60°C. The filtrate is subjected to reduced pressure distillation at a temperature of 300~370°C and a vacuum degree of -0.05~-0.098Mpa. Fractions are cut according to the distillation range and viscosity to obtain different grades of hydrogenated regenerated oil products. The hydrogenation catalyst described in step 4 is prepared by reacting 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, isocyanate-based X-type molecular sieve, and tetraaminoporphyrin.

2. The method for hydrofining of waste lubricating oil according to claim 1, characterized in that: The filter in step 1 is 300-600 mesh.

3. The method for hydrofining of waste lubricating oil according to claim 1, characterized in that: The flocculant in step 2 is a composite flocculant, which is a composite alkaline flocculant formed by mixing one of sodium hydroxide, potassium hydroxide, sodium silicate and one of triethylenetetramine, oxalic acid, diethylenetriamine, and polyimide.

4. The method for hydrotreating waste lubricating oil according to claim 1, characterized in that: The demulsifier in step 2 is polyoxypropylene polyoxyethylene propylene glycol ether, polyoxypropylene polyoxyethylene propylene glycol ether, polyoxyethylene polyoxypropylene alkylphenol formaldehyde resin, alkylphenol formaldehyde resin block polyether, phenolamine formaldehyde resin block polyether or polyphosphate.

5. The method for hydrotreating waste lubricating oil according to claim 1, characterized in that: The filter in step 2 is 60-100 mesh.

6. The method for hydrofining of waste lubricating oil according to claim 1, characterized in that: The amount of hydrogenation catalyst used in step 4 is 0.005-0.2% of the weight of the waste lubricating oil.

7. The method for hydrotreating waste lubricating oil according to claim 1, characterized in that: The preparation method of the hydrogenation catalyst described in step 4 is: B1: Add 2-5 parts of palladium nitrate, 0.002-0.02 parts of molybdenum nitrate, 0.002-0.04 parts of cerium nitrate, 100-200 parts of water, and 4-8 parts of 2,5-dihydroxyterephthalic acid to reactor 1 by weight, react at 30-40° C. for 30-50 minutes, and then distill to remove water to obtain a 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex; B2: In reactor 2, 100-150 parts of isocyanate-based X-type molecular sieve, 2-5 parts of 2,5-dihydroxyterephthalic acid / palladium / molybdenum / cerium complex, 0.2-0.5 parts of stannous octoate, and 1000-1200 parts of toluene are added by weight, and the reaction is carried out at a temperature of 50-60°C for 10-20 minutes, and then 0.02-0.6 parts of tetraaminoporphyrin are added, and the reaction is carried out at 70-80°C for 100-140 minutes. The mixture is filtered and dried to obtain a hydrogenation catalyst for waste lubricating oil.

8. The method for hydrotreating waste lubricating oil according to claim 7, characterized in that: The preparation method of the isocyanate-based X-type molecular sieve described in B2 is: According to weight, 100-150 parts of X molecular sieve, 1000-1700 parts of water, and 4-7 parts of 3-isocyanate propyltrioxysilane are added into the reactor, reacted at 30-40°C for 30-50 minutes, filtered, and dried to obtain isocyanate X type molecular sieve.