Process for the preparation of a hydrorefined lubricating oil
By combining physical separation, adsorption purification and catalytic hydrogenation steps, the problems of catalyst poisoning and incomplete removal of sulfur and nitrogen impurities in waste lubricating oil regeneration are solved, achieving the preparation of high-quality regenerated base oil and extending the operation cycle of the unit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-21
- Publication Date
- 2026-06-05
AI Technical Summary
In existing waste lubricating oil hydrogenation regeneration technologies, the catalyst is prone to poisoning and deactivation, the equipment has a short operating cycle, sulfur and nitrogen impurities are not completely removed, and the viscosity index is low, which cannot meet the standards for high-end lubricating oils.
A combination of specific physical separation, adsorption purification and catalytic hydrogenation steps is employed, including gravity sedimentation, vacuum distillation, protective agent adsorption and hydrogenation purification, pretreatment with amorphous silica or silica protective agents, and deep hydrogenation treatment with palladium-cobalt catalyst supported on Y-type molecular sieves.
It significantly improves the viscosity index and oxidation stability of the recycled base oil, extends the stable operating cycle of the catalyst, improves product yield and quality, and meets high-end lubricant standards.
Abstract
Description
Technical Field
[0001] This application relates to the fields of waste oil resource utilization and petrochemical technology, and in particular to a method for preparing waste lubricating oil through hydrogenation regeneration. Background Technology
[0002] Waste lubricating oil contains impurities such as oxides, sulfides, nitrides, carbon deposits, and metal shavings. Direct discharge or simple regeneration without treatment will cause serious environmental pollution and resource waste. Traditional regeneration processes, such as the acid-clay method and distillation-refining method, suffer from complex processes, low product yields, severe secondary pollution, and difficulty in deeply removing polar impurities. The quality of regenerated oil is usually poor and cannot meet the standards of high-end lubricating oils.
[0003] Hydrorefining is an effective way to deeply purify waste lubricating oil. It removes impurities such as sulfur, nitrogen, and oxygen as H2S, NH3, and H2O through hydrogenation, and saturates olefins and some aromatics, thereby restoring the performance of the base oil. However, waste lubricating oil has a complex composition, and direct hydrogenation easily leads to rapid catalyst deactivation due to metal deposition and carbon buildup. Furthermore, it requires extremely high catalyst activity and selectivity. Existing hydrogenation processes often suffer from short catalyst life, harsh operating conditions (high temperature and high pressure), high hydrogen consumption, and poor adaptability to feedstocks, limiting their industrial application.
[0004] Therefore, developing a waste lubricating oil regeneration process that can effectively protect the catalyst, achieve deep hydrogenation, and operate stably for a long time has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention
[0005] The purpose of this application is to provide a method for preparing waste lubricating oil through hydrogenation regeneration, which aims to improve the existing waste lubricating oil hydrogenation regeneration technology, which suffers from problems such as easy poisoning and deactivation of hydrogenation catalysts due to metal and colloidal impurities in the raw materials, short equipment operation cycles, and incomplete removal of sulfur and nitrogen impurities and low viscosity index of the regenerated base oil.
[0006] By adopting the above technical solutions, the present invention is achieved through the following technical solution: The first aspect of the present invention provides a method for preparing waste lubricating oil through hydrogenation regeneration. This method, through a combination of specific physical separation, adsorption purification, and catalytic hydrogenation steps, achieves the removal of impurities and the structural restoration of hydrocarbon components in waste lubricating oil. The method includes the following steps:
[0007] S1. Pretreatment: The waste lubricating oil is placed in a settling device for gravity settling to separate the sludge and free water at the bottom; the upper oil phase is taken and filtered through a filter medium to remove suspended solid particles; the filtrate is sent to a dehydration unit for flash dehydration under an absolute pressure of 80 kPa to 95 kPa and a temperature of 110°C to 130°C until the water content in the oil phase is reduced to below 0.1 wt%, thus obtaining dehydrated waste oil.
[0008] S2. Vacuum Distillation: The dehydrated waste oil is fed into a vacuum distillation tower for fractionation. The absolute pressure of the distillation system is controlled at 5 kPa to 15 kPa, and the bottom heating temperature is 320°C to 360°C. During the fractionation process, the lubricating oil fraction with a normal boiling point range of 300°C to 450°C corresponding to the gas phase temperature is collected as intermediate feedstock.
[0009] S3. Protective Agent Adsorption Treatment: The intermediate feedstock oil obtained in step S2 is introduced into a fixed-bed reactor filled with a solid protective agent. The treatment temperature is controlled at 250℃ to 300℃, and the amount of protective agent is set to 0.5% to 2.0% of the mass of the intermediate feedstock oil. The protective agent is selected as amorphous aluminosilicate or amorphous silica, with a specific surface area of 200m² / g to 400m² / g and a pore volume of 0.5cm³ / g to 0.9cm³ / g. In this process, the porous structure and surface properties of the protective agent are utilized to adsorb and remove residual gums, asphaltenes, and some metal ions from the feedstock oil.
[0010] S4. Hydrorefining Reaction: The oil treated with a protective agent is mixed with hydrogen and fed into a high-pressure hydrorefining fixed-bed reactor packed with a hydrorefining catalyst. The reaction process parameters are controlled as follows: reaction pressure 2.0 MPa to 8.0 MPa, reaction temperature 300℃ to 360℃, and liquid hourly space velocity 0.5 h⁻¹. -1 Up to 2.0h -1 The hydrogen-to-oil volume ratio is 500:1 to 1000:1.
[0011] The hydrorefining catalyst uses a Y-type molecular sieve as a support, loading active components palladium and cobalt. The molar ratio of SiO2 to Al2O3 in the Y-type molecular sieve support is 5 to 15, and the specific surface area is 500 m² / g to 700 m² / g. The loading of the active components, based on elemental composition, is 0.1 wt% to 0.5 wt% of the total catalyst mass for Pd and 0.5 wt% to 1.5 wt% of the total catalyst mass for Co. Under these reaction conditions, the palladium component provides active hydrogenation centers, promoting the hydrogenation saturation of polycyclic aromatic hydrocarbons; the cobalt component acts as an auxiliary agent, synergistically with the palladium component in hydrodesulfurization and hydrodenitrogenation reactions; and the Y-type molecular sieve support provides acidic centers, improving the low-temperature fluidity of the oil through ring-opening or isomerization reactions.
[0012] S5. Post-treatment and product separation: The hydrorefining reaction effluent is sent to a high-pressure gas-liquid separator for gas-liquid separation. The separated liquid product is cooled to 40°C to 60°C and then passed through a precision filter with an accuracy of 5μm to 10μm to remove solid particles. The filtrate is then sent to a vacuum drying tower, where dissolved gases and trace amounts of moisture are stripped at a temperature of 100°C to 120°C and an absolute pressure of 5kPa to 10kPa to obtain regenerated lubricating oil base oil.
[0013] A second aspect of the present invention provides a method for preparing a hydrorefining catalyst for the above-described method. The method includes the following steps:
[0014] Prepare a mixed aqueous solution containing palladium nitrate and cobalt nitrate, the volume of which is equal to the total pore volume of the carrier to be impregnated;
[0015] An equal volume of the mixed aqueous solution was impregnated onto the pretreated Y-type molecular sieve support, with the loading of active components controlled at 0.1wt% to 0.5wt% Pd and 0.5wt% to 1.5wt% Co.
[0016] The impregnated samples were left to age at room temperature and then dried at 100°C to 120°C.
[0017] The dried precursor is heated to 500°C to 550°C in air and calcined at a constant temperature for 4 to 6 hours to obtain the oxidized precursor catalyst.
[0018] Before participating in the hydrogenation reaction, the oxidized precursor catalyst is reduced for 2 to 4 hours in a hydrogen atmosphere at a temperature range of 300°C to 400°C.
[0019] A third aspect of the present invention provides a regenerated lubricating oil base oil prepared by the above method. This regenerated base oil, through the above process, has a sulfur content reduced to below 50 ppm, a nitrogen content reduced to below 10 ppm, and a viscosity index greater than 105.
[0020] In the technical solution provided by this invention, the protective agent treatment unit is located between the vacuum distillation unit and the hydrorefining unit. Even after distillation, waste lubricating oil may still carry trace amounts of metal shavings and thermally unstable colloids. If these substances directly contact the noble metal hydrorefining catalyst, they will cover the active sites or deposit at the catalyst pore openings. By setting an amorphous silica-alumina or silica protective agent bed at 250°C to 300°C, the aforementioned impurities are retained through physical adsorption and weak chemical adsorption, thereby maintaining the active surface area and pore openness of the subsequent Pd-Co / Y type molecular sieve catalyst.
[0021] In summary, this application includes at least one of the following beneficial technical effects:
[0022] 1. This application utilizes a Y-type molecular sieve supported on palladium and cobalt as a hydrorefining catalyst. By leveraging the high hydrogenation activity of Pd and the auxiliary effect of Co, combined with the strong acidic center and shape-selective pore structure of the Y-type molecular sieve support, deep saturation of polycyclic aromatic hydrocarbons and bond breaking and removal of sulfur and nitrogen heteroatoms are achieved under a reaction pressure of 2.0-8.0 MPa, thereby significantly improving the viscosity index and oxidation stability of the recycled base oil.
[0023] 2. This application sets up a protective agent adsorption treatment step before the hydrorefining unit. Utilizing the porous characteristics of amorphous silica or silica, trace metal ions and easily coking colloidal precursors remaining in the feed oil are pre-adsorbed at 250-300℃. This blocks the direct contact between the above impurities and the active sites of the subsequent precious metal catalyst, delays the deactivation of the catalyst due to poisoning or carbon deposition, and prolongs the stable operation cycle of the unit.
[0024] 3. This application effectively separates the target lubricating oil components from light fuel oil components and heavy asphalt residues by precisely controlling the cutting temperature and system pressure of vacuum distillation. This ensures that the distillation range of the hydrotreating feedstock meets the base oil standards and removes heavy components that may cause high-temperature coking to the maximum extent, thereby improving the conversion efficiency and product yield of the subsequent hydrotreating process. Detailed Implementation
[0025] Example:
[0026] Example 1
[0027] This embodiment provides a method for preparing waste lubricating oil through hydrogenation regeneration, the specific steps of which are as follows:
[0028] S1. Pretreatment: Place the waste lubricating oil in a settling tank and let it stand for 48 hours to separate the bottom sludge and water. The upper layer of oil is filtered with a precision of 20μm and then enters a dehydration tower for flash dehydration under an absolute pressure of 90kPa and a temperature of 120℃ until the water content is reduced to 0.05wt%.
[0029] S2. Vacuum Distillation: The dehydrated waste oil is fed into a vacuum distillation column. The system absolute pressure is set to 10 kPa, and the bottom heating temperature is set to 340℃. The lubricating oil fraction with an atmospheric boiling point in the range of 340℃ to 420℃ corresponding to the vapor phase temperature is collected as intermediate feedstock.
[0030] S3. Protective Agent Adsorption Treatment: The intermediate feedstock oil obtained in step S2 is fed into a fixed-bed reactor filled with an amorphous silica-alumina protective agent. The amount of protective agent is set at 1.25% of the mass of the intermediate feedstock oil. The treatment temperature is controlled at 275°C, and the operating pressure is consistent with that of the subsequent hydrogenation unit.
[0031] S4. Catalyst preparation and hydrorefining:
[0032] Catalyst preparation: An equal-volume impregnation method was used. Y-type molecular sieve support was weighed, and a mixed solution containing palladium nitrate and cobalt nitrate was prepared, with a loading of 0.3 wt% Pd and 1.0 wt% Co. After impregnation, the catalyst was dried at 110 °C for 10 hours, followed by calcination at 525 °C for 5 hours in air. Before use, it was reduced at 350 °C for 3 hours in hydrogen atmosphere.
[0033] Hydrogenation reaction: The oil treated with the protective agent is mixed with hydrogen and fed into the hydrogenation reactor. The reaction conditions are set as follows: reaction pressure 5.0 MPa, reaction temperature 330℃, liquid hourly space velocity 1.0 h⁻¹, and hydrogen-to-oil volume ratio 750:1.
[0034] S5. Post-processing: After high-pressure gas-liquid separation and low-pressure gas-liquid separation, the liquid phase product is cooled to 50°C, filtered through a 5μm precision filter, and finally vacuum dried at 110°C and 8kPa absolute pressure to obtain the regenerated lubricating oil base oil.
[0035] Example 2
[0036] This embodiment provides a method for preparing waste lubricating oil through hydrogenation regeneration, the specific steps of which are as follows:
[0037] S1. Pretreatment: The operation is the same as in Example 1. The dehydration conditions are set as follows: absolute pressure 95 kPa, temperature 110°C, and dehydration is carried out until the water content is less than 0.1 wt%.
[0038] S2. Vacuum Distillation: The dehydrated waste oil is fed into a vacuum distillation tower. The system absolute pressure is set to 5 kPa, and the bottom heating temperature is set to 320℃. The lubricating oil fraction with an atmospheric boiling point in the range of 300℃ to 400℃ corresponding to the vapor phase temperature is collected as intermediate feedstock.
[0039] S3. Protective agent adsorption treatment: The intermediate feedstock oil obtained in step S2 is fed into a fixed-bed reactor filled with amorphous silica protective agent. The amount of protective agent is set to 0.5% of the mass of the intermediate feedstock oil. The treatment temperature is controlled at 250℃.
[0040] S4. Catalyst preparation and hydrorefining:
[0041] Catalyst preparation: Y-type molecular sieve was selected as the support. An impregnation solution was prepared with a loading of 0.1 wt% Pd and 0.5 wt% Co. After impregnation, the catalyst was dried at 100°C for 12 hours and calcined at 500°C for 6 hours in air. Before use, it was reduced at 300°C for 4 hours in hydrogen atmosphere.
[0042] Hydrogenation reaction: The reaction conditions were set as follows: reaction pressure 2.0 MPa, reaction temperature 300℃, and liquid hourly space velocity 0.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500:1.
[0043] S5. Post-processing: The liquid product is cooled to 40°C, filtered through a 10μm precision filter, and finally vacuum dried at 100°C and 10kPa absolute pressure to obtain the regenerated lubricating oil base oil.
[0044] Example 3
[0045] This embodiment provides a method for preparing waste lubricating oil through hydrogenation regeneration, the specific steps of which are as follows:
[0046] S1. Pretreatment: The operation is the same as in Example 1. The dehydration conditions are set as follows: absolute pressure 80 kPa, temperature 130°C, and dehydration is carried out until the water content is less than 0.1 wt%.
[0047] S2. Vacuum Distillation: The dehydrated waste oil is fed into a vacuum distillation tower. The system absolute pressure is set to 15 kPa, and the bottom heating temperature is set to 360°C. The lubricating oil fraction with an atmospheric boiling point in the range of 350°C to 450°C corresponding to the vapor phase temperature is collected as intermediate feedstock.
[0048] S3. Protective agent adsorption treatment: The intermediate feedstock oil obtained in step S2 is fed into a fixed-bed reactor filled with an amorphous silica-alumina protective agent. The amount of protective agent is set to 2.0% of the mass of the intermediate feedstock oil. The treatment temperature is controlled at 300℃.
[0049] S4. Catalyst preparation and hydrorefining:
[0050] Catalyst preparation: Y-type molecular sieve was selected as the support. An impregnation solution was prepared with a loading of 0.5 wt% Pd and 1.5 wt% Co. After impregnation, the catalyst was dried at 120 °C for 8 hours and calcined at 550 °C for 4 hours in air. Before use, it was reduced at 400 °C for 2 hours in hydrogen atmosphere.
[0051] Hydrogenation reaction: The reaction conditions were set as follows: reaction pressure 8.0 MPa, reaction temperature 360℃, and liquid hourly space velocity 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 1000:1.
[0052] S5. Post-processing: The liquid product is cooled to 60°C, filtered through a 5μm precision filter, and finally vacuum dried at 120°C and 5kPa absolute pressure to obtain the regenerated lubricating oil base oil.
[0053] Comparative Example 1
[0054] Compared with Example 1, the difference is that step S3, the protective agent adsorption treatment, is omitted, and the intermediate feedstock oil obtained in step S2 is directly sent to the hydrorefining reactor in step S4 to contact with the catalyst. The remaining steps and parameters are the same.
[0055] Comparative Example 2
[0056] Compared with Example 1, the difference is that the hydrorefining catalyst in step S4 is replaced with a conventional industrial-grade Ni-Mo / Al2O3 catalyst, wherein the Ni loading is 4.0 wt%, the Mo loading is 15.0 wt%, and the support is alumina. The rest of the preparation methods and reaction parameters are the same.
[0057] Comparative Example 3
[0058] Compared with Example 1, the difference is that the hydrorefining catalyst prepared in step S4 is not loaded with the active component cobalt, but only with 0.3 wt% palladium, that is, the catalyst is a Pd / Y type molecular sieve. The rest of the preparation steps and reaction parameters are the same.
[0059] Compared with Example 1, Comparative Example 4 differs in that the catalyst support in step S4 is replaced with amorphous alumina, i.e., the catalyst is Pd-Co / Al2O3, the loading of the active component remains unchanged, and the remaining preparation steps and reaction parameters are the same.
[0060] Compared with Example 1, Comparative Example 5 omits step S2 vacuum distillation and directly sends the full fraction of waste oil after dehydration in step S1 to step S3 for protective agent treatment and subsequent hydrogenation reaction. The remaining steps and parameters are the same.
[0061] Test Example 1: Physical and Chemical Properties Testing of Regenerated Base Oil
[0062] Experimental steps
[0063] This experiment determined the physicochemical properties of the recycled base oil samples prepared in Examples 1 to 3 and Comparative Examples 1 to 5. The experimental procedure is as follows:
[0064] After each preparation process unit has been running continuously and stably for 48 hours, 500 mL of oil sample is collected from the liquid phase outlet at the bottom of the gas-liquid separator. After collection, the sample is sealed and stored in the dark, and cooled to room temperature.
[0065] The samples were then analyzed using the following standard methods:
[0066] Yield determination: The mass percentage is calculated by weighing the mass of liquid base oil collected per unit time and the mass of raw waste oil entering the system.
[0067] Kinematic viscosity determination: According to GB / T265 standard, the kinematic viscosity of the oil was determined using a capillary viscometer in a constant temperature bath at 40℃ and 100℃ respectively.
[0068] Viscosity index calculation: The viscosity index is calculated according to the GB / T1995 standard using the measured kinematic viscosity values at 40℃ and 100℃.
[0069] Sulfur content determination: The total sulfur content in the oil was determined using an ultraviolet fluorescence sulfur analyzer in accordance with the SH / T0689 standard.
[0070] Nitrogen content determination: The total nitrogen content in the oil was determined using a chemiluminescence nitrogen analyzer in accordance with the SH / T0657 standard.
[0071] Color determination: The color number of the oil is determined using a standard colorimeter in accordance with ASTM D1500 standard.
[0072] Experimental data
[0073] The test results for each sample are shown in Table 1 below.
[0074] Table 1. Physicochemical property test data of recycled base oil under different process conditions
[0075] Sample number Liquid yield (wt%) Kinematic viscosity (100℃, mm² / s) Viscosity Index (VI) Sulfur content (ppm) Nitrogen content (ppm) Colorimetry (ASTM) Example 1 73.4 9.05 109 32.5 6.8 <0.5 Example 2 74.8 9.12 105 48.2 9.4 0.5 Example 3 70.9 8.85 112 18.6 2.5 <0.5 Comparative Example 1 73.1 9.08 107 75.4 18.2 1 Comparative Example 2 72.5 9.35 96 168 45.3 2 Comparative Example 3 73.2 9.15 106 92.1 29.7 1 Comparative Example 4 73 9.42 94 115.6 36.8 1.5 Comparative Example 5 52.6 11.2 88 235 84.1 >4.0
[0076] Results Analysis
[0077] Data from Examples 1 to 3 show that, using a Y-type molecular sieve catalyst system supported on palladium and cobalt, the sulfur content of the recycled oil can be controlled below 50 ppm, the nitrogen content below 10 ppm, and the viscosity index maintained above 105, within the set reaction temperature and pressure range. Compared with samples using Pd / Y or Ni-Mo / Al2O3 catalysts, the example samples exhibited lower heteroatom content. This indicates that the palladium and cobalt components have an electronic synergistic effect in the hydrodesulfurization and denitrification reactions, enhancing the ability to break CS and CN bonds. Furthermore, compared to Comparative Example 4 using an alumina support, the Y-type molecular sieve support used in the examples resulted in a higher viscosity index for the final product. This corresponds to the acidic centers of the Y-type molecular sieve promoting alkane isomerization and aromatic ring-opening reactions, thereby improving the viscosity-temperature properties of the oil.
[0078] Comparative Example 1 omitted the protective agent treatment step, and its product had higher sulfur and nitrogen content than Example 1. This indicates that trace amounts of gum precursors or polar impurities present in the feedstock were not effectively retained before entering the main hydrotreating reactor. These substances compete for adsorption or deposition on the surface of the hydrotreating catalyst, resulting in the covering of some active sites and thus reducing the depth of hydrorefining. The protective agent layer, through physical adsorption and weak chemisorption, removes impurities that interfere with the hydrotreating reaction at the front end of the reaction, ensuring the hydrotreating efficiency of the subsequent catalyst.
[0079] Comparative Example 5 omitted the vacuum distillation step, resulting in a significantly reduced yield of the final product, along with a darker color and higher impurity content. The uncut whole-fraction waste oil contains heavy asphaltenes and easily coking components. These components undergo thermal condensation reactions under the high-temperature environment of the hydrogenation reaction, generating large-molecule coking precursors. These precursors not only fail to convert into the target lubricating oil fraction but also adsorb onto the catalyst surface, inhibiting the reaction. The vacuum distillation step, through physical separation, limits the molecular weight distribution entering the reaction system, ensuring that the substrate for the hydrogenation reaction is primarily a renewable lubricating oil fraction, thereby improving the yield and purity of the target product.
[0080] Test Example 2: Long-term operational stability and catalyst lifetime test of the unit
[0081] Experimental steps
[0082] This experiment aimed to investigate the stability of the process systems of Examples 1 to 3 and Comparative Examples 1 to 5 under long-term continuous operation conditions. The experiment was conducted on the same fixed-bed hydrogenation apparatus as the preparation examples.
[0083] The specific operating procedure is as follows:
[0084] The catalysts and protective agents corresponding to each embodiment and comparative example were loaded into the reactor. The device was started according to the process parameters set in each example and adjusted to a stable state. After 48 hours of stable operation, the pressure difference between the reactor inlet and outlet was recorded as the initial bed pressure drop, and the sulfur content was sampled and measured as the initial sulfur content.
[0085] Subsequently, with all input parameters kept constant, the unit was continuously operated for 1000 hours. During operation, changes in the pressure difference between the reactor inlet and outlet were monitored. At the 1000-hour mark, the final bed pressure drop was recorded, and the liquid phase oil from the reaction effluent after gas-liquid separation was collected and its sulfur content was determined as the final sulfur content.
[0086] The increase in pressure drop characterizes the change in bed porosity and the degree of carbon buildup and blockage; the increase in sulfur content characterizes the degree of decline in catalyst hydrogenation activity.
[0087] The test data of each process system after 1000 hours of continuous operation are recorded in Table 2.
[0088] Table 2. Stability test data during long-term operation (1000 hours)
[0089] Experimental group Initial bed pressure drop (MPa) Final bed pressure drop (MPa) Pressure reduction growth rate (%) Initial sulfur content (ppm) Final sulfur content (ppm) Sulfur content drift (ppm) Example 1 0.021 0.026 23.8 32.5 38.1 5.6 Example 2 0.018 0.024 33.3 48.2 55.4 7.2 Example 3 0.025 0.032 28 18.6 23.9 5.3 Comparative Example 1 0.021 0.185 780.9 75.4 142.3 66.9 Comparative Example 2 0.022 0.045 104.5 168 215.6 47.6 Comparative Example 3 0.021 0.038 80.9 92.1 128.4 36.3 Comparative Example 4 0.02 0.052 160 115.6 158.2 42.6 Comparative Example 5 0.023 0.88 3726.1 235 480.5 245.5
[0090] Results Analysis
[0091] Table 2 shows that in Examples 1 to 3, the bed pressure drop remained below 0.035 MPa and the sulfur content drift was less than 8 ppm during a 1000-hour operating cycle, indicating that the system maintained hydrodynamic stability and catalytic activity. In contrast, the pressure drop growth rate of Comparative Example 1 was significantly higher than that of the Examples, and the final sulfur content increased sharply. This result confirms that setting up a protective agent adsorption unit before the hydrogenation reactor can retain colloidal precursors and metallic impurities in the feedstock. Without this step, these impurities directly enter the hydrogenation reactor, where they rapidly undergo thermal condensation or deposition under high temperature and pressure, leading to catalyst pore blockage and active site coverage, resulting in a sharp increase in bed pressure drop and a rapid decrease in desulfurization efficiency.
[0092] Data from Comparative Example 5 shows that the undistilled full-fraction waste oil resulted in extremely high pressure drop increases during long-term operation, approaching the unit's operating limits at the end of the experiment. Heavy components and asphaltenes present in the full fraction are highly susceptible to coking at reaction temperatures above 300°C, with the generated coke rapidly filling the voids between catalyst particles. The example used vacuum distillation to cut the feedstock into fractions at 300-450°C, physically eliminating easily coking macromolecular components and controlling the rate of coke formation in the reactor from the source, ensuring the unit's continuous operation capability.
[0093] Comparing the sulfur content drift data of Example 1 with Comparative Examples 2, 3, and 4, it can be seen that the catalyst system using Pd-Co bimetal supported on a Y-type molecular sieve exhibits superior activity stability. The sulfur content of Comparative Examples 2 and 4 increased significantly at the end of operation, indicating that conventional alumina supports are more prone to failure due to carbon buildup or impurity adsorption when treating complex raw materials such as waste lubricating oil, as their pore structure and surface acidic sites are more susceptible to degradation. In contrast, the Y-type molecular sieve support combined with the Pd-Co active component in these examples not only provides a suitable pore size distribution to accommodate reactant molecules, but also the electronic interactions between Pd and Co, as well as the interactions between the metal and the support, inhibit the sintering and agglomeration of active metal particles, thus maintaining high hydrodesulfurization activity even after long-term operation.
Claims
1. A method for preparing waste lubricating oil through hydrogenation regeneration, characterized in that, Includes the following steps: S1. The waste lubricating oil is settled, filtered and dehydrated to remove the sludge, free water and suspended solid particles at the bottom, and the dehydrated waste oil is obtained. S2. The dehydrated waste oil obtained in step S1 is sent to a vacuum distillation tower and fractionated under a system absolute pressure of 5-15 kPa. The lubricating oil fraction with a normal boiling point of 300-450℃ corresponding to the gas phase temperature is collected as intermediate feed oil. S3. The intermediate feedstock oil obtained in step S2 is passed through a fixed-bed reactor filled with a protective agent and subjected to adsorption treatment at a processing temperature of 250-300℃. The protective agent is amorphous aluminum silica or amorphous silica, and the amount of protective agent used is 0.5%-2.0% of the mass of the intermediate feedstock oil; S4. The oil processed in step S3 is mixed with hydrogen and then fed into a high-pressure hydrotreating fixed-bed reactor containing a hydrotreating catalyst for reaction. The hydrorefining catalyst was prepared by an equal-volume impregnation method, using a Y-type molecular sieve as a support to load active components palladium and cobalt, wherein the loading of palladium was 0.1-0.5 wt% and the loading of cobalt was 0.5-1.5 wt%. The reaction conditions were: reaction pressure 2.0-8.0 MPa, reaction temperature 300-360℃, and liquid hourly space velocity 0.5-2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500:1-1000:
1. S5. Post-processing and product separation: The reaction effluent from step S4 is subjected to gas-liquid separation. The separated liquid product is cooled, finely filtered and vacuum dried to obtain the recycled base oil product.
2. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The dehydration described in step S1 is carried out in a dehydration tower, and the process conditions are as follows: The absolute pressure is 80-95 kPa and the temperature is 110-130℃, until the water content in the waste oil is less than 0.1 wt%.
3. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The bottom heating temperature of the vacuum distillation column in step S2 is 320-360℃.
4. The preparation method of waste lubricating oil by hydrogenation regeneration according to claim 1, characterized in that, The protective agent described in step S3 has a specific surface area of 200-400 m² / g and a pore volume of 0.5-0.9 cm³ / g.
5. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The SiO2 / Al2O3 molar ratio of the Y-type molecular sieve support for the hydrorefining catalyst described in step S4 is 5-15, and the specific surface area is 500-700 m² / g.
6. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The preparation process of the hydrorefining catalyst in step S4 includes: The mixed impregnation solution was loaded onto a Y-type molecular sieve support and dried at 100-120℃. Then, it was heated to 500-550℃ in air and calcined for 4-6 hours to obtain the oxidized precursor catalyst.
7. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 6, characterized in that, Before use, the oxidized precursor catalyst needs to be reduced at 300-400℃ for 2-4 hours in a hydrogen atmosphere.
8. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The reaction conditions described in step S4 are as follows: The reaction pressure is 3.0-5.0 MPa, the reaction temperature is 320-350℃, and the liquid hourly space velocity is 0.8-1.5 h⁻¹. -1 .
9. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The precision filtration in step S5 has a filtration accuracy of 5-10 μm, and the cooling temperature of the liquid product before entering the precision filtration is 40-60℃.
10. The method for preparing waste lubricating oil through hydrogenation regeneration according to claim 1, characterized in that, The vacuum drying described in step S5 is carried out in a vacuum drying tower, with the following process conditions: temperature 100-120℃ and absolute pressure 5-10kPa.