Waste oil multistage hydrofining and hydrodewaxing integrated process

Abstract

The invention discloses a waste oil multistage hydrofining and hydrodewaxing integrated process, and belongs to the technical field of waste oil regeneration. The process sequentially comprises the four steps of pretreatment, hydrotreatment, hydrodewaxing and fractionation refining. According to the pretreatment, a slurry bed reactor is combined with a hot hydrogen flash evaporation technology, and metal impurities and colloids are deeply removed under specific conditions; deep impurity removal and aromatic hydrocarbon saturation are realized through a fluidized bed-fixed bed grading system in the hydrotreating treatment; according to the hydrodewaxing step, a dewaxing reactor and a molecular sieve in-situ refining module are creatively integrated, and cracking and refining reactions are synchronously completed. The process effectively solves the problems of serious coking, easy deactivation of a catalyst and high energy consumption in the traditional process, realizes the production of high-added-value III-type base oil (yield gt, 88%, pour point lt,-25 DEG C, VIgt and 120) while obviously reducing the energy consumption and hydrogen consumption (greater than or equal to 30%), and is matched with an efficient pollution control and resource recovery system to finally achieve the purposes of hazardous waste emission reduction gt, energy conservation and environmental protection. Therefore, the method has outstanding economic benefits and environmental protection benefits at the same time.

Description

Technical Field

[0001] An integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil belongs to the field of waste oil regeneration technology. Background Technology

[0002] Waste mineral oil regeneration is an important area of ​​resource recycling and environmental protection. Traditional waste oil regeneration processes mainly include traditional technical routes such as distillation-acid washing-clay refining, which have problems such as high environmental pollution, low product yield, and unstable product quality. With increasingly stringent environmental protection requirements, these traditional processes can no longer meet the demands of modern industry for clean production and efficient resource utilization.

[0003] Hydrorefining technology, as a clean production method to replace traditional processes, has been widely used in the field of waste oil regeneration. Existing technologies mostly employ a fixed-bed hydrorefining process combined with hydrodewaxing, achieving the upgrading and regeneration of waste oil through reactions such as hydrodesulfurization, denitrification, aromatic saturation, and wax cracking. However, in actual industrial applications, existing technologies still have several limitations: First, the high levels of metallic impurities (such as Fe, Ca, Zn) and asphaltenes in waste oil easily lead to catalyst pore blockage and deactivation, making efficient removal difficult with traditional pretreatment processes; second, fixed-bed reactors are prone to increased bed pressure drop and hot spots when processing feedstocks with high metal content, affecting the long-term stable operation of the unit; third, the hydrodewaxing process typically requires high temperatures (340℃~380℃) and pressures (above 15MPa), resulting in high energy consumption, high hydrogen consumption, and unsatisfactory low-temperature fluidity of the product; furthermore, in existing technologies, hydrorefining and dewaxing reactions are often carried out in stages, resulting in long process flows, large equipment investments, and the product still requiring a separate supplementary refining unit for further processing.

[0004] In terms of resource recovery and pollution control, existing equipment has insufficient capacity to treat wastewater, waste gas, and waste residue. Acidic water treatment efficiency is low, sulfur resources in waste gas are not fully recovered, and the comprehensive utilization rate of residue is low, making it difficult to achieve true near-zero emissions. Although researchers at home and abroad have developed various improved processes, existing fluidized bed reactor designs still have room for improvement in terms of pretreatment depth, catalyst adaptability, system energy consumption, and product performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil that is highly efficient in removing impurities, has a long operating cycle, low energy consumption, and high yield.

[0006] The technical solution adopted by this invention to solve its technical problem is: an integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil, characterized by comprising the following steps: Pretreatment: Waste oil feedstock and catalyst are subjected to hydrogen pretreatment reaction in a slurry bed reactor in the presence of hydrogen to remove metal impurities and gum asphaltenes. The reaction products are separated by hot hydrogen flash evaporation to obtain pretreated oil. Hydrotreating: The pretreated oil is fed into a fluidized bed reactor for hydrorefining to remove sulfur and nitrogen impurities and saturate aromatics. The resulting hydrotreating product is then fed into a fixed bed reactor for further refining. Hydrogen-induced pour point depressing: The oil product after hydrotreating is subjected to pour point depressing cracking reaction under hydrogen-induced conditions through a depressing reactor equipped with a shape-selective molecular sieve catalyst to improve the low-temperature fluidity of the oil product. Fractional distillation: The products after the dewaxing reaction are separated and fractionated to obtain base oil products and other distillate oils; In the hydrogenation dewaxing step, the outlet stream of the dewaxing reactor is directly fed into an in-situ refining module filled with adsorption-refining molecular sieves to simultaneously achieve olefin adsorption and aromatic saturation, eliminating the need for a separate supplementary refining reactor.

[0007] The integrated process of this invention efficiently removes metals and gums (demetallization rate >98%) through a coupling technology of "hydrogen-contaminated slurry bed pretreatment + hot hydrogen flash evaporation," eliminating coking at the source and providing ultra-clean raw materials for subsequent processes. It employs a "fluidized bed-fixed bed" graded reaction system to achieve online catalyst replacement and precise temperature zone control, solving the problems of bed pressure drop and runaway temperatures, and extending catalyst life to 4 years. It innovatively integrates hydrogen-contaminated dewaxing with in-situ molecular sieve refining, simultaneously completing cracking, olefin adsorption, and aromatic saturation under low temperature and low pressure conditions, eliminating the need for a separate refining reactor. This significantly reduces energy and hydrogen consumption (≥30%) while producing high-value-added Group III base oils (pour point <-25℃, VI>120). Combined with a full-process resource recovery system, it ultimately achieves a major breakthrough in hazardous waste reduction >97% and high-end oil product yield >88%, demonstrating significant economic and environmental benefits.

[0008] Specifically, in the pretreatment step, an oil-soluble Mo-Ni composite catalyst with a particle size of 0.1 μm to 1 μm is used. The conditions for the hydrogen-exposed pretreatment reaction include a reaction pressure of 5 MPa to 15 MPa, a reaction temperature of 350℃ to 380℃, and a hydrogen-to-oil volume ratio of 400 to 600:1. This pretreatment step, using an oil-soluble Mo-Ni composite catalyst with a specific particle size, achieves efficient and deep removal of metallic impurities and asphaltenes from waste oil under a certain pressure and temperature hydrogen-exposed environment. Its micron-sized particle size provides a large specific surface area for the reaction, ensuring sufficient contact between the catalyst and impurity components and efficient hydrogenolysis reaction, thereby improving the demetallization rate and dechlorination rate, and greatly reducing the risk of coking and clogging in the subsequent fixed-bed reactor from the source. The optimized hydrogen-to-oil volume ratio ensures a sufficient hydrogen supply and promotes heat transfer and fluidization of the reaction system. This pretreatment unit ultimately reduces the content of metal impurities in the raw materials to below 20 μg / g, providing "ultra-clean" feed conditions for subsequent hydrogenation and dewaxing catalysts, and laying the foundation for the long-term stable operation of the entire unit.

[0009] Preferably, the hot hydrogen flash evaporation is carried out in a cyclone flash tank at an operating temperature of 380℃~420℃. The amount of heavy component residue after flash evaporation is less than 0.5wt% of the raw material, and 20%~50% of the hot oil, which accounts for the total feed of the slurry bed reactor, is recycled to the inlet of the slurry bed reactor to reduce energy consumption. Using a cyclone flash tank for hot hydrogen flash evaporation at a specific temperature, its highly efficient cyclone separation design significantly improves the removal rate of heavy components such as asphaltene and resins, and greatly reduces the residue yield, thus significantly mitigating the risk of coking in subsequent reactors from the source. Simultaneously, recycling a certain proportion of the flash evaporation hot oil to the slurry bed inlet effectively recovers and utilizes the thermal energy of the high-temperature materials, significantly reducing the external heating load and lowering the total system energy consumption, achieving the dual goals of efficient energy integration and clean production.

[0010] More preferably, the hot oil recirculated to the inlet of the slurry bed reactor accounts for 30% to 40% of the total feed to the slurry bed reactor. This optimized recirculated hot oil ratio achieves an optimal balance between energy recovery and reaction efficiency. This ratio maximizes the utilization of thermal energy and significantly reduces external energy consumption, while avoiding excessive recirculation that could lead to variations in residence time or accumulation of inert components within the reactor, thus ensuring the thermodynamic stability and long-term stable operation of the slurry bed reactor.

[0011] Specifically, in the hydrogenation treatment step, the fluidized bed reactor uses a microspherical Mo-Ni / Al2O3 catalyst, and the reactor is divided into a high-temperature zone and a low-temperature zone; the high-temperature zone operates at a temperature of 380℃~400℃ and is mainly used for deep desulfurization and denitrification; the low-temperature zone operates at a temperature of 340℃~360℃ and is mainly used for aromatic saturation.

[0012] The high-temperature zone is located in the upper or front section of the reactor. Pretreated feedstock oil and hydrogen enter from the bottom, react violently under the action of the catalyst, and flow upwards. This zone primarily maintains the bed temperature in a high range by controlling the feed temperature and utilizing the exothermic effect of the reaction, focusing on deep hydrodesulfurization (HDS) and hydronitrogen removal (HDN) reactions that require high activation energy.

[0013] The low-temperature zone is located in the lower or later part of the reactor. By installing a built-in gas-liquid distribution plate in the middle of the reactor and injecting a quenching medium (low-temperature pretreatment oil), it is rapidly mixed with the hot material from the high-temperature zone, thereby precisely reducing the material temperature to a preset lower range. This temperature condition is more conducive to the thermodynamic equilibrium of the aromatic hydrogenation saturation reaction, increasing the aromatic saturation rate while avoiding excessive cracking.

[0014] This invention's hydrogenation process utilizes an innovative "fluidized bed high-temperature-low-temperature zone" design, creating two optimal reaction environments within a single reactor. The high-temperature zone focuses on deep desulfurization and denitrification, reducing sulfur and nitrogen content to <10ppm and <5ppm, respectively; the low-temperature zone concentrates on aromatic saturation, achieving a saturation rate exceeding 90%. Precise temperature control is achieved through the injection of quenching media via an internal distribution plate, effectively resolving the traditional problem of conflicting deimpurification and aromatic saturation reaction conditions. This design not only avoids excessive cracking and ensures product quality, but its full backmixing characteristic also eliminates hot spot risks, keeping the reaction temperature rise stably controlled within ±5℃, laying a solid foundation for long-term stable operation of the unit.

[0015] Preferably, the fixed-bed reactor employs a gradient loading method, with the following components loaded sequentially from bottom to top: macroporous demetallizing agent, Mo-Co / Al2O3 hydrogenation catalyst, and Pt-Pd / Y molecular sieve aromatic saturated catalyst. The fixed-bed reactor of this invention utilizes a gradient loading strategy of "macroporous demetallizing agent → Mo-Co / Al2O3 catalyst → Pt-Pd / Y molecular sieve catalyst," forming a step-by-step precise protection and deep conversion system for different residual impurities. The lower layer of macroporous demetallizing agents (such as AXENS' HMC-841 or CLG's HMS-30, with pore sizes >15nm) efficiently captures trace residual metal particles that have penetrated previous processes, acting as the final safeguard. The middle layer of Mo-Co / Al2O3 catalysts (such as CRI's C-534 or SINOPEC's FF-66) further enhances the hydrodesulfurization and denitrification reactions, ensuring deep removal of impurities. The upper layer of Pt-Pd / Y molecular sieve confined catalysts (such as AXENS' LD-402 or CLG's AS-250) achieves deep saturation of aromatics under relatively mild conditions (300-320℃, 12-14MPa), significantly improving the oxidation stability and color of the product. This gradation method fully leverages the synergistic effect of various catalysts, effectively protecting the terminal precious metal catalyst from poisoning and deactivation, extending the overall catalyst life, and completing the final high-value-added conversion of the product under mild conditions, achieving a balance between long-term operation and economic efficiency.

[0016] Specifically, in the hydrodewaxing step, the shape-selective molecular sieve catalyst used is a ZSM-5 / 3R-MoS2 composite catalyst, in which the 3R phase MoS2 accounts for more than 80%; the conditions for the dewaxing cracking reaction include: reaction temperature 300℃~320℃, reaction pressure 8MPa~12MPa, and hydrogen-to-oil volume ratio 250~350:1. This invention's hydrodewaxing step utilizes a unique ZSM-5 / 3R-MoS2 composite catalyst, combined with mild reaction conditions, achieving the dual goals of highly efficient shape-selective cracking and significantly reduced energy consumption. The unique crystal structure of the 3R phase MoS2 significantly enhances the catalyst's selective cracking ability for n-alkanes, reducing the pour point of the base oil from -15℃ to below -25℃, resulting in a breakthrough improvement in low-temperature fluidity. Simultaneously, the reaction temperature and pressure are significantly lower than in traditional processes (340℃~380℃, 15MPa), and the optimized hydrogen-to-oil ratio further reduces system energy and hydrogen consumption. The catalyst maintains high activity at low temperatures, effectively inhibiting excessive cracking and secondary reactions, and ensuring high yields of liquid products.

[0017] Preferably, the adsorption-refining molecular sieve packed in the in-situ refining module is SAPO-11 molecular sieve, which is loaded with Pt-Pd active metal components to adsorb small molecule olefins generated by cracking and saturate residual aromatics. This preferred scheme utilizes the unique pore structure of SAPO-11 molecular sieve and its loaded Pt-Pd active centers to selectively capture >90% of small molecule olefins and simultaneously deeply saturate residual aromatics, resulting in reduced product color and oxidation stability (rotary oxygen bomb >300 min) that directly meets the Group III base oil standard, eliminating the need for a separate supplementary refining reactor.

[0018] Preferably, the fractionation and refining step employs an integrated vacuum distillation tower-atmospheric distillation tower system, with side streams yielding Group III base oils, industrial white oils, and solvent oils with a VI value greater than 120. The heavy oil residue at the bottom of the tower is less than 3%, and its softening point is higher than 120°C, which is used as an asphalt modifier. The integrated vacuum distillation tower-atmospheric distillation tower system achieves efficient energy integration and precise fractionation. This system can directly extract high-value-added products such as Group III base oils with a VI value greater than 120, industrial white oils, and solvent oils from the side stream, greatly improving the economics of the process. Simultaneously, by reducing the heavy oil residue at the bottom of the tower and optimizing operations to ensure its softening point is above 120°C, it is successfully converted into a high-value asphalt modifier, achieving resource utilization of the residue and near-zero emissions.

[0019] Preferably, the process further includes pollution control and resource recovery steps, which include: treating sulfur-containing wastewater with an acidic water stripping unit, recycling the generated ammonia water, and achieving a purified water reuse rate of over 95%; absorbing sulfur-containing waste gas with NaOH solution to generate sodium hydrosulfide as a byproduct; and purifying light hydrocarbon gas through membrane separation-pressure swing adsorption and then returning it to the system for use as recycled hydrogen. Through these pollution control and resource recovery steps, a highly efficient closed-loop system is constructed, achieving near-zero emissions. The sulfur-containing wastewater, after stripping, has a recyclable ammonia water, achieving a purified water reuse rate of over 95%, significantly reducing wastewater discharge; the sulfur-containing waste gas, after NaOH absorption, generates sodium hydrosulfide, realizing the fixation and value-added utilization of sulfur resources; and the light hydrocarbon gas, after deep purification (hydrogen purity >99.9%), is reused as recycled hydrogen, significantly reducing fresh hydrogen consumption. This system, with "waste resource utilization" as its core, ultimately achieves the dual goals of a hazardous waste emission reduction rate >97% and a resource recovery rate >90%, possessing both excellent environmental and economic benefits.

[0020] Compared with existing technologies, this invention has the following beneficial effects: This invention achieves efficient and clean conversion of waste oil through an innovative four-stage integrated process. The pretreatment unit employs a coupled hydrogen-containing slurry bed and hot hydrogen flash evaporation technology to deeply remove metallic impurities and colloids, solving the coking problem at its source. The hydrotreating unit, through a fluidized bed-fixed bed gradation system, achieves deep impurity removal and aromatic saturation, significantly extending catalyst life. The hydrogen-containing pour point depressant unit integrates shape-selective cracking and in-situ molecular sieve refining, simultaneously improving the low-temperature fluidity and stability of the oil under mild conditions, eliminating the need for separate refining equipment. The entire process, combined with an integrated thermal energy and resource recovery system, ultimately achieves a significant increase in base oil yield while significantly reducing energy and hydrogen consumption, achieving near-zero hazardous waste emissions and efficient resource recycling, resulting in outstanding economic and environmental benefits. Detailed Implementation

[0021] The present invention will now be described in detail through examples. Unless otherwise stated, all raw materials used are commercially available.

[0022] Example 1

[0023] Waste lubricating oil raw material with a metal content of 850 μg / g and a sulfur content of 0.8 wt% is processed using the integrated process described in this invention.

[0024] Pretreatment stage: In a slurry bed reactor, an oil-soluble Mo-Ni composite catalyst (BY-5 type catalyst developed by Beijing Research Institute of Chemical Industry) with a particle size of 0.1 μm is used to carry out the reaction under the conditions of reaction pressure of 5 MPa, temperature of 350℃, and hydrogen-oil volume ratio of 400:1. After the reaction, the product enters a cyclone flash tank at 380℃ for hot hydrogen flash evaporation. The amount of residue after flash evaporation is 0.45 wt% of the raw material, and the hot oil, which accounts for 30% of the total feed of the slurry bed, is recycled to the inlet. Hydrotreating stage: The pretreated oil enters a fluidized bed reactor, using a microspherical Mo-Ni / Al2O3 catalyst (AXENS HTS-358 catalyst). The reactor is divided into a high-temperature zone (controlled at 380℃ for deep desulfurization and denitrification) and a low-temperature zone (controlled at 340℃ for aromatic saturation by injecting quench oil). It then enters a fixed bed reactor, using a gradient loading method, with the following materials loaded from bottom to top: a macroporous demetallizing agent (CLG HMS-30 catalyst), a Mo-Co / Al2O3 hydrogenation catalyst (Sinopec Research Institute of Petroleum Processing RCT-1 catalyst), and a Pt-Pd / Y molecular sieve aromatic saturation catalyst (AXENS LD-402 catalyst) for deep refining. Hydrogenation and refining stage: The dewaxing reactor uses a shape-selective molecular sieve catalyst ZSM-5 / 3R-MoS2 composite catalyst (with the 3R phase MoS2 accounting for more than 80%), and the reaction is carried out at 300℃, 8MPa, and a hydrogen-to-oil ratio of 250:1. The effluent stream directly enters the in-situ refining module filled with an adsorption-refining molecular sieve. The catalyst in this module is SAPO-11 molecular sieve loaded with Pt-Pd active metal components (DICP-1 type catalyst developed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences), to simultaneously achieve olefin adsorption and aromatic saturation. The fractionation stage adopts a vacuum-atmospheric integrated system, with the product collected via a side stream. Ultimately, the base oil yield reaches 88.5%, the product sulfur content is <5ppm, nitrogen content is <3ppm, pour point is -26℃, VI value is 125, residue rate is 2.8%, and energy consumption is reduced by 32% compared to the comparative example.

[0025] Example 2

[0026] The same process flow as in Example 1 was adopted, but the key parameters were adjusted to the other end of the range: Pretreatment stage reaction pressure 15 MPa, temperature 380 °C, hydrogen-to-oil ratio 600:1, catalyst particle size 1 μm; hot hydrogen flash temperature 420 °C, hot oil circulation rate 40%. Hydrotreating stage fluidized bed high-temperature zone 400 °C, low-temperature zone 360 ​​°C. Hydrogenation dewaxing stage reaction temperature 320 °C, pressure 12 MPa, hydrogen-to-oil ratio 350:1. Ultimately, the base oil yield reached 90.2%, product sulfur content <3 ppm, nitrogen content <2 ppm, pour point -28 °C, VI value 128, residue rate 2.5%, and energy consumption reduced by 35%. The results show that excellent performance is maintained even at the upper limit of the parameters.

[0027] Example 3

[0028] Waste lubricating oil raw material with a metal content of 1800 μg / g was processed.

[0029] Pretreatment stage: In a slurry bed reactor, an oil-soluble Mo-Ni catalyst with a particle size of 1 μm was used. The reaction was carried out under high-intensity conditions of 15 MPa reaction pressure, 380 °C temperature, and a hydrogen-to-oil volume ratio of 600:1 to fully crack and remove metal impurities. After the reaction, the product was fed into a cyclone flash evaporator at 420 °C for hot hydrogen flash evaporation. The residue after flash evaporation was 0.48 wt% of the feed, and 40% of the hot oil, which accounted for 40% of the total feed to the slurry bed, was recycled to the inlet. Subsequent hydrogenation, pour point depressing, and fractionation steps were the same as in Example 1. Finally, the base oil yield was 86.2%, the metal content of the product was reduced to 15 μg / g, and the demetallization rate was >99.1%, demonstrating the powerful processing capability of this process for inferior feedstocks.

[0030] Example 4

[0031] Waste oil feedstock with a sulfur content of 0.5 wt% and a nitrogen content of 0.3 wt% is processed.

[0032] The same process flow as in Example 1 was used, but some parameters were adjusted: The pretreatment stage used medium conditions: pressure 10 MPa, temperature 365°C, and hydrogen-to-oil ratio 500:1. In the hydrotreating stage: the high-temperature zone of the fluidized bed reactor was set at 400°C for deep denitrification, and the low-temperature zone was set at 360°C to optimize aromatic saturation; the fixed-bed reactor particularly utilized the Pt-Pd / Y molecular sieve aromatic saturation catalyst. The hydrodewaxing stage conditions were 310°C and 10 MPa. The final product had an aromatic content of <1%, oxidation stability (rotating bomb oxidation time) of 350 min, and a color of <0.5, making it very suitable for producing high-quality base oils.

[0033] Example 5

[0034] The same process flow as in Example 1 was adopted, but some parameters were adjusted: Pretreatment stage: reaction pressure 5 MPa, temperature 350°C, hydrogen-to-oil volume ratio 400:1; hot hydrogen flash temperature 380°C, hot oil circulation rate 20%. Hydrotreating stage: fluidized bed high-temperature zone 380°C, low-temperature zone 340°C. Hydrogenation dewaxing stage: reaction temperature 300°C, pressure 8 MPa, hydrogen-to-oil ratio 250:1. Under this configuration, the total system energy consumption was reduced by approximately 18% compared to conventional operation, while the base oil yield remained at 87.5%, and the pour point was -24°C, achieving a balance between energy saving and high yield.

[0035] Example 6

[0036] The process was adjusted to increase the production of solvent oil and industrial white oil. During the fractionation and refining stage, the cut-off point of the vacuum distillation-atmospheric distillation system was optimized to increase the side stream yield.

[0037] The same process flow as in Example 1 was used, but some parameters were adjusted: the reaction temperature in the hydrocracking stage was 320°C to promote a more complete cracking reaction. The final product distribution was: Group III base oil yield 45%, industrial white oil yield 25%, solvent oil yield 18%, and bottom heavy oil residue 2.5%, significantly improving the overall yield of high value-added distillate oils.

[0038] Comparative Example 1 The same feedstock as in Examples 1 and 2 was processed using a conventional fixed-bed hydrotreating-dewaxing staged process. Pretreatment consisted of conventional filtration-adsorption. Hydrotreating was carried out in a single fixed-bed reactor (370°C), and dewaxing was performed in another reactor (360°C, 15 MPa), followed by a separate clay refining unit. The results showed a base oil yield of only 78.3%, a product pour point of -12°C, a VI value of 98, a residue rate of 6.5%, and high energy consumption.

[0039] Comparative Example 2 Using the same raw materials as in Examples 1 and 2, and employing the process flow of Example 1 of this invention, but omitting the in-situ refining module, the product after pour point depressing was directly fractionated. The result showed poor oxidation stability (rotating oxygen bomb time 120 min) and a color of 2.0, failing to directly meet the Group III oil standard, demonstrating the crucial role of in-situ refining.

[0040] The above embodiments and comparative examples show that the process of the present invention can achieve high yield, high quality products and low energy consumption within a wide range of parameters, which is significantly better than traditional processes. In particular, the innovative integration of pretreatment, staged hydrogenation and in-situ refining effectively solves the problems of coking, high energy consumption and unstable product quality.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil, characterized in that, Includes the following steps: Pretreatment: Waste oil feedstock and catalyst are subjected to hydrogen pretreatment reaction in a slurry bed reactor in the presence of hydrogen to remove metal impurities and gum asphaltenes. The reaction products are separated by hot hydrogen flash evaporation to obtain pretreated oil. Hydrotreating: The pretreated oil is fed into a fluidized bed reactor for hydrorefining to remove sulfur and nitrogen impurities and saturate aromatics. The resulting hydrotreating product is then fed into a fixed bed reactor for further refining. Hydrogen-induced pour point depressing: The oil product after hydrotreating is subjected to pour point depressing cracking reaction under hydrogen-induced conditions through a depressing reactor equipped with a shape-selective molecular sieve catalyst to improve the low-temperature fluidity of the oil product. Fractional distillation: The products after the dewaxing reaction are separated and fractionated to obtain base oil products and other distillate oils; In the hydrogenation decondensation step, the outlet stream of the decondensation reactor is directly fed into an in-situ purification module filled with adsorption-purification molecular sieves to simultaneously achieve olefin adsorption and aromatic saturation.

2. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1, characterized in that, In the pretreatment step, the catalyst used is an oil-soluble Mo-Ni composite catalyst with a particle size of 0.1 μm to 1 μm; the conditions for the hydrogen pretreatment reaction include: a reaction pressure of 5 MPa to 15 MPa, a reaction temperature of 350℃ to 380℃, and a hydrogen-to-oil volume ratio of 400 to 600:

1.

3. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1 or 2, characterized in that, The hot hydrogen flash evaporation is carried out in a cyclone flash tank at an operating temperature of 380℃~420℃. The amount of heavy component residue after flash evaporation is less than 0.5wt% of the raw material. 20%~50% of the hot oil, which accounts for the total feed of the slurry bed reactor, is circulated to the inlet of the slurry bed reactor to reduce energy consumption.

4. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 3, characterized in that, The hot oil circulating to the inlet of the slurry bed reactor accounts for 30% to 40% of the total feed to the slurry bed reactor.

5. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1, characterized in that, In the hydrogenation process, the fluidized bed reactor uses a microspherical Mo-Ni / Al2O3 catalyst and is divided into a high-temperature zone and a low-temperature zone. The high-temperature zone operates at a temperature of 380℃~400℃, and the low-temperature zone operates at a temperature of 340℃~360℃.

6. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 5, characterized in that, The fixed-bed reactor is loaded in a gradient manner, from bottom to top: macroporous demetallizing agent, Mo-Co / Al2O3 hydrogenation catalyst, and Pt-Pd / Y molecular sieve aromatic saturated catalyst.

7. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1, characterized in that, In the hydrodewaxing step, the shape-selective molecular sieve catalyst used is a ZSM-5 / 3R-MoS2 composite catalyst, in which the 3R phase MoS2 accounts for more than 80%; The conditions for the depowder cracking reaction include: reaction temperature of 300℃~320℃, reaction pressure of 8MPa~12MPa, and hydrogen-to-oil volume ratio of 250~350:

1.

8. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1 or 7, characterized in that, The adsorption-refining molecular sieve filled in the in-situ refining module is SAPO-11 molecular sieve, which is loaded with Pt-Pd active metal components.

9. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1, characterized in that, The fractionation and refining step adopts an integrated fractionation system of vacuum distillation tower and atmospheric distillation tower. The side streams are used to collect Group III base oil, industrial white oil and solvent oil with VI greater than 120. The heavy oil residue at the bottom of the tower is less than 3% and its softening point is higher than 120℃, which is used as an asphalt modifier.

10. The integrated process for multi-stage hydrorefining and hydrodewaxing of waste oil according to claim 1, characterized in that, The process also includes pollution control and resource recovery steps, which include: treating sulfur-containing wastewater with an acidic water stripping device, recycling the generated ammonia water, and achieving a water reuse rate of more than 95%; absorbing sulfur-containing waste gas with NaOH solution to generate sodium hydrosulfide as a byproduct; and returning light hydrocarbon gas to the system for use as recycled hydrogen after purification by membrane separation-pressure swing adsorption.