Hydrodechlorination method for waste plastic pyrolytic oil
By using a two-stage hydrogenation process and a metal sulfide catalyst, the problem of removing organochlorides from waste plastic pyrolysis oil was solved, improving oil quality, protecting equipment, and reducing energy consumption.
Patent Information
- Application Number
- CN202511996420.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-02-27
AI Technical Summary
Existing methods for hydrodechlorination of waste plastic pyrolysis oil are inefficient at removing organochlorides, resulting in poor oil quality and easy corrosion of equipment.
A two-stage hydrogenation strategy was adopted, using a metal sulfide catalyst, and hydrogenation was carried out in a first fixed-bed reactor and a second fixed-bed reactor to remove dienes, monoolefins and organochlorides. The reaction conditions were optimized by controlling parameters such as temperature, pressure and hydrogen-to-oil volume ratio.
It improves the quality of waste plastic pyrolysis oil, avoids equipment corrosion, reduces energy consumption, and achieves efficient impurity removal.
Smart Images
Figure CN121574748A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of waste plastic pyrolysis oil treatment technology, and more specifically, to a method for hydrogenation dechlorination of waste plastic pyrolysis oil. Background Technology
[0002] Currently, catalytic pyrolysis technology for waste plastics has attracted widespread attention as an emerging approach to waste plastic treatment. This technology converts waste plastics into high-value-added plastic oil under the action of a catalyst, which not only improves economic efficiency but also helps reduce carbon dioxide emissions.
[0003] However, in practical applications, waste plastics are usually mixtures, often containing chlorinated plastics such as polyvinyl chloride (PVC), resulting in a high concentration of organochlorines in the pyrolysis product, plastic oil (i.e., waste plastic pyrolysis oil, or simply plastic oil). These organochlorines can easily cause equipment corrosion during subsequent processing and utilization, severely affecting the stable operation and service life of production equipment, and potentially adversely impacting the quality of the final product. In the process of catalytic pyrolysis of waste plastics to produce oil, existing technologies still have shortcomings in treating waste plastic pyrolysis oil containing organochlorines. For example, there are problems such as low dechlorination efficiency, generation of secondary pollutants, and the increased fixed asset investment and energy consumption due to the need for three, four, or even more fixed-bed reactors for hydrodechlorination. All of these factors limit the further promotion and application of waste plastic pyrolysis oil.
[0004] Therefore, in order to solve the technical problem that the existing hydrodechlorination method for waste plastic pyrolysis oil is difficult to remove organochlorides in waste plastic pyrolysis oil in a low cost and with high efficiency, resulting in poor oil quality and easy corrosion of downstream equipment, it is urgent to develop a low-cost hydrodechlorination method for waste plastic pyrolysis oil. Summary of the Invention
[0005] The purpose of this application is to provide a method for hydrodechlorination of waste plastic pyrolysis oil. Using a metal sulfide catalyst and a two-stage hydrotreating strategy, it removes dienes, monoolefins, and organochlorides from the waste plastic pyrolysis oil. This solves the problem that existing methods for hydrodechlorination of waste plastic pyrolysis oil are inefficient in removing organochlorides, leading to poor oil quality and potential corrosion of downstream equipment. The two-stage hydrotreating process achieves targeted removal of different types of impurities in the waste plastic pyrolysis oil, improving its quality while avoiding excessive energy consumption.
[0006] In a first aspect, this application provides a method for hydrodechlorination of waste plastic pyrolysis oil, comprising the following steps: The first fixed-bed reactor and the second fixed-bed reactor are connected in series, and the first metal oxide catalyst and the second metal oxide catalyst are respectively loaded into the first fixed-bed reactor and the second fixed-bed reactor. The first metal oxide catalyst and the second metal oxide catalyst were respectively subjected to presulfurization treatment to obtain a first metal sulfide catalyst and a second metal sulfide catalyst; Waste plastic pyrolysis oil is fed into the first fixed-bed reactor. Based on the first metal sulfide catalyst, a first-stage hydrogenation treatment is carried out under the process parameters of a preset first hydrogenation temperature, a preset hydrogenation pressure, a preset space velocity, and a preset hydrogen-to-oil volume ratio to remove easily polymerizable dienes and monoolefins, thereby obtaining waste plastic pyrolysis oil after the first-stage hydrogenation treatment. The waste plastic pyrolysis oil after the first stage of hydrogenation is introduced into the second fixed-bed reactor. Based on the second metal sulfide catalyst, a second stage of hydrogenation is carried out under the preset process parameters of the second hydrogenation temperature, the preset hydrogenation pressure, the preset space velocity, and the preset hydrogen-oil volume ratio to remove organochlorides and hydrogenate olefins into alkanes, thereby obtaining dechlorinated waste plastic pyrolysis oil.
[0007] The hydrodechlorination method for waste plastic pyrolysis oil provided in this application can achieve hydrodechlorination of waste plastic pyrolysis oil. By using a metal sulfide catalyst and a staged hydrotreating strategy, it removes dienes, monoolefins, and organochlorides from the waste plastic pyrolysis oil. This solves the problem that existing hydrodechlorination methods for waste plastic pyrolysis oil are difficult to efficiently remove organochlorides, resulting in poor oil quality and easy corrosion of downstream equipment. The staged hydrotreating process achieves targeted removal of different types of impurities in the waste plastic pyrolysis oil, thereby improving the quality of the waste plastic pyrolysis oil.
[0008] Optionally, the preset first hydrogenation temperature is lower than the preset second hydrogenation temperature.
[0009] The hydrodechlorination method for waste plastic pyrolysis oil provided in this application can achieve hydrodechlorination of waste plastic pyrolysis oil. By controlling the first hydrogenation temperature to be lower than the second hydrogenation temperature, it can effectively avoid catalyst deactivation or side reactions caused by excessively high temperature during the first hydrogenation process. At the same time, it ensures that the second hydrogenation can efficiently remove organochlorides and convert olefins at a higher temperature, thereby optimizing the reaction conditions and improving the dechlorination efficiency and product quality.
[0010] Optionally, the preset first hydrogenation temperature is 120~250℃; the preset hydrogenation pressure is 3~8MPa; the preset space velocity is 0.2~2.5h-1; and the preset hydrogen-to-oil volume ratio is 200~2000:1.
[0011] Optionally, the preset second hydrogenation temperature is 220~350℃.
[0012] Preferably, the preset first hydrogenation temperature is 170~190℃; the preset hydrogenation pressure is 5~7MPa; the preset space velocity is 0.8~1.2h-1; and the preset hydrogen-to-oil volume ratio is 600~1000:1.
[0013] Preferably, the preset second hydrogenation temperature is 260~320℃.
[0014] Optionally, the pre-sulfurization treatment is performed by using a liquid sulfurizing agent at 250°C to pre-sulfurize the first metal oxide catalyst and the second metal oxide catalyst.
[0015] Optionally, the specific value of the preset first hydrogenation temperature can be adjusted according to the content information of dienes and alkynes in the waste plastic pyrolysis oil.
[0016] The hydrodechlorination method for waste plastic pyrolysis oil provided in this application enables hydrodechlorination of waste plastic pyrolysis oil. By introducing a strategy of dynamically adjusting the first-stage reaction temperature based on the composition of the feed oil, intelligent optimization of process parameters is achieved, allowing for flexible adjustment according to actual conditions, further improving olefin removal efficiency and process adaptability. Optionally, the specific value of the preset second hydrogenation temperature can be adjusted based on the content information of organochlorides and olefins in the waste plastic pyrolysis oil after a first stage of hydrogenation treatment.
[0017] Optionally, the method for hydrodechlorination of waste plastic pyrolysis oil is used in a waste plastic recycling system.
[0018] Beneficial effects: The hydrodechlorination method for waste plastic pyrolysis oil provided in this application uses a metal sulfide catalyst and a segmented hydrotreating strategy to remove dienes, monoolefins, and organochlorides from the waste plastic pyrolysis oil. This solves the problem that existing hydrodechlorination methods for waste plastic pyrolysis oil are unable to efficiently remove organochlorides, resulting in poor oil quality and easy corrosion of subsequent equipment. The segmented hydrotreating process achieves targeted removal of different types of impurities in the waste plastic pyrolysis oil, thereby improving the quality of the waste plastic pyrolysis oil. Attached Figure Description
[0019] Figure 1 A flowchart of a method for hydrodechlorination of waste plastic pyrolysis oil provided in an embodiment of this application. Detailed Implementation
[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0021] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0022] Please refer to Figure 1 , Figure 1 This application discloses a method for hydrodechlorination of waste plastic pyrolysis oil, as described in some embodiments, which includes: Step S1: Connect the first fixed-bed reactor and the second fixed-bed reactor in series, and fill the first metal oxide catalyst and the second metal oxide catalyst into the first fixed-bed reactor and the second fixed-bed reactor respectively. Step S2: The first metal oxide catalyst and the second metal oxide catalyst are pre-sulfurized to obtain the first metal sulfide catalyst and the second metal sulfide catalyst. Step S3: Waste plastic pyrolysis oil is introduced into the first fixed-bed reactor. Based on the first metal sulfide catalyst, a first-stage hydrogenation treatment is carried out under the process parameters of preset first hydrogenation temperature, preset hydrogenation pressure, preset space velocity and preset hydrogen-oil volume ratio to remove easily polymerizable dienes and monoolefins, and to obtain waste plastic pyrolysis oil after the first-stage hydrogenation treatment. Step S4: The waste plastic pyrolysis oil after the first stage of hydrogenation treatment is introduced into the second fixed-bed reactor. Based on the second metal sulfide catalyst, a second stage of hydrogenation treatment is carried out under the preset process parameters of the second hydrogenation temperature, preset hydrogenation pressure, preset space velocity and preset hydrogen-oil volume ratio to remove organochlorides and hydrogenate olefins into alkanes, thereby obtaining dechlorinated waste plastic pyrolysis oil.
[0023] This method for hydrodechlorination of waste plastic pyrolysis oil utilizes a metal sulfide catalyst and a segmented hydrotreating strategy to remove dienes, monoolefins, and organochlorides from the waste plastic pyrolysis oil. It addresses the problem of existing methods failing to efficiently remove organochlorides from waste plastic pyrolysis oil, resulting in poor oil quality and potential corrosion of downstream equipment. The segmented hydrotreating process achieves targeted removal of different types of impurities in the waste plastic pyrolysis oil, thus improving its overall quality.
[0024] Specifically, in step S1, the first fixed-bed reactor and the second fixed-bed reactor are connected in series. This series connection can be a physical pipe connection, allowing the material to flow through the two reactors sequentially. For example, the outlet of the first fixed-bed reactor can be directly connected to the inlet of the second fixed-bed reactor. Simultaneously, the first metal oxide catalyst and the second metal oxide catalyst are respectively loaded into the first and second fixed-bed reactors. This can be done manually by pouring the catalyst particles into the reactors or by automated equipment. For example, gravity loading or pneumatic conveying can be used to uniformly fill the catalyst beds inside the corresponding reactors with the metal oxide catalysts (first metal oxide catalyst and second metal oxide catalyst). Metal oxide catalysts refer to a class of catalysts with metal oxides as the main active component or support. They can be single metal oxides (such as alumina Al2O3) or mixtures or complexes of multiple metal oxides (such as vanadium-molybdenum oxide V2O5-MoO3). Their core characteristic is the use of a crystal lattice composed of metal ions and oxygen ions to catalyze reactions through the participation of surface acidic sites, basic sites, redox sites, and lattice oxygen.
[0025] Specifically, in step S2, the first and second metal oxide catalysts are pre-sulfurized at 250°C using a liquid sulfiding agent. This pre-sulfurization aims to ensure that the active components of the metal oxide catalysts are effectively converted into the corresponding sulfides. The purpose of pre-sulfurization is to convert the metal oxides in the catalysts into sulfides, such as converting molybdenum oxide into molybdenum disulfide and cobalt oxide into cobalt sulfide, thereby improving the hydrogenation activity and stability of the catalysts. These sulfides typically have higher hydrogenation activity and stability, and are better resistant to potential poisoning during the reaction process. Especially for olefins and organochlorides present in waste plastic pyrolysis oil, the pre-sulfurized catalysts (first and second metal sulfide catalysts) can more effectively perform hydroremoval while reducing coke formation and extending catalyst lifespan. By controlling the pre-sulfurization temperature and pressure, the degree of sulfidation can be optimized to avoid over-sulfidation or under-sulfidation, thus achieving optimal catalytic performance.
[0026] Specifically, in step S3, waste plastic pyrolysis oil is introduced into the first fixed-bed reactor. Based on the first metal sulfide catalyst, a first-stage hydrogenation treatment is carried out under preset process parameters of a first hydrogenation temperature, preset hydrogenation pressure, preset space velocity, and preset hydrogen-to-oil volume ratio. The main purpose of the first-stage hydrogenation treatment is to remove easily polymerizable dienes and monoolefins from the waste plastic pyrolysis oil. These unsaturated hydrocarbons are prone to polymerization at high temperatures, forming gums or coke, clogging the equipment, and affecting subsequent reactions. Through the first-stage hydrogenation treatment, these unsaturated hydrocarbons can be converted into saturated hydrocarbons, thereby reducing their polymerization tendency. In the first stage of hydrogenation, a lower temperature is beneficial for selectively hydrogenating highly reactive dienes and alkynes in the waste plastic pyrolysis oil, thereby maximally suppressing side reactions such as polymerization and coking of these easily polymerizable components at high temperatures, protecting catalyst activity, and reducing the risk of reactor blockage. Furthermore, since the hydrogenation reaction is exothermic, excessively high temperatures are detrimental to hydrogenation, while excessively low temperatures will reduce the efficiency of the hydrogenation process. Therefore, the first hydrogenation temperature should not be too high or too low, and the preset first hydrogenation temperature is set to 120℃~250℃.
[0027] In the process of hydrodechlorination of waste plastic pyrolysis oil, the preset hydrogenation pressure, preset space velocity, and preset hydrogen-to-oil volume ratio are important operating parameters that affect the hydrogenation reaction effect. They work synergistically with the preset first hydrogenation temperature and preset second hydrogenation temperature to ensure the effective removal of dienes, alkynes, and monoolefins.
[0028] In an optional embodiment, the preset hydrogenation pressure is set within the range of 3–8 MPa. This is to provide sufficient hydrogen partial pressure to promote the hydrogenation reaction and inhibit coking. This pressure range ensures reaction efficiency while also considering the economics of equipment investment and operating costs. The preset space velocity is set between 0.2 and 2.5 h⁻¹. -1 Within this range, the aim is to ensure sufficient contact time between the waste plastic pyrolysis oil and the catalyst to achieve the desired reaction conversion rate. Excessive space velocity may lead to incomplete reaction, while insufficient space velocity will reduce production efficiency. The preset hydrogen-to-oil volume ratio is set within the range of 200~2000:1. This is to provide sufficient hydrogen to maintain catalyst activity and effectively remove sulfides and chlorides generated during the reaction, while inhibiting coke formation. Too low a hydrogen-to-oil volume ratio may cause rapid catalyst deactivation, while too high a ratio will increase hydrogen consumption and recycling costs.
[0029] Preferably, in another optional embodiment, the preset first hydrogenation temperature can be set to 170~190°C, the preset hydrogenation pressure can be set to 5~7 MPa, and the preset space velocity can be set to 0.8~1.2 h⁻¹. -1The preset hydrogen-to-oil volume ratio can be set to 600~1000:1, thus providing a narrower range of optimized process parameters, which can further improve the efficiency and stability of the first-stage hydrogenation treatment and lay a good foundation for subsequent deep dechlorination.
[0030] Specifically, in step S3, the preset first hydrogenation temperature is adjusted based on the content information of dienes and alkynes in the waste plastic pyrolysis oil. This content information can be obtained through online or offline analysis of the waste plastic pyrolysis oil before it enters the first fixed-bed reactor, using methods such as gas chromatography-mass spectrometry (GC-MS), infrared spectroscopy, or chemical titration to accurately determine the total amount of dienes and alkynes or the content of specific components. Based on this content information, an adjustment model can be established or a preset process parameter table can be consulted to dynamically determine the optimal first hydrogenation temperature. For example, when the content of dienes and alkynes in the waste plastic pyrolysis oil is high, the first hydrogenation temperature can be appropriately increased to enhance the hydrogenation reaction activity and ensure the complete removal of these easily polymerizable components; conversely, when the content is low, the temperature can be appropriately decreased to avoid unnecessary energy consumption and side reactions.
[0031] In summary, by introducing real-time or near-real-time monitoring of the diene and alkyne content in waste plastic pyrolysis oil, and dynamically adjusting the first hydrogenation temperature based on this information, precise control of the hydrogenation process is achieved.
[0032] Specifically, in step S4, the waste plastic pyrolysis oil after a first-stage hydrotreating is introduced into the second fixed-bed reactor. Based on the second metal sulfide catalyst, a second-stage hydrotreating process is carried out under preset process parameters: a second hydrotreating temperature, a preset hydrotreating pressure, a preset space velocity, and a preset hydrogen-to-oil volume ratio. The main purpose of the second-stage hydrotreating is to remove organochlorides and hydrogenate the remaining olefins into alkanes. In the second-stage hydrotreating, the catalyst converts organochlorides into inorganic chlorides (such as hydrogen chloride), which are then removed by washing and other methods. Simultaneously, the olefins are further hydrogenated into alkanes, thereby obtaining dechlorinated waste plastic pyrolysis oil. In the second-stage hydrotreating, a higher temperature provides sufficient activation energy to ensure efficient removal of organochlorides and complete conversion of olefins to alkanes, thus obtaining high-quality dechlorinated waste plastic pyrolysis oil. Therefore, the preset second hydrotreating temperature is set to 220℃~350℃.
[0033] In some alternative embodiments, the preset second hydrogenation temperature can be set to a narrower range of 260°C to 320°C. A narrower range of second hydrogenation temperature can significantly improve the dechlorination efficiency and olefin hydrogenation conversion rate of waste plastic pyrolysis oil, resulting in a final oil product with lower chlorine content and higher saturated hydrocarbon content.
[0034] Specifically, in step S4, before or during the second stage of hydrogenation, samples of the waste plastic pyrolysis oil after the first stage of hydrogenation, flowing from the first fixed-bed reactor into the second fixed-bed reactor, are taken for analysis to obtain real-time or near-real-time content data of organochlorides and olefins. This content information can serve as a feedback signal to dynamically adjust the preset second hydrogenation temperature in the second fixed-bed reactor. For example, when a high content of organochlorides or olefins is detected in the waste plastic pyrolysis oil after the first stage of hydrogenation, the second hydrogenation temperature can be appropriately increased to enhance the reaction rate and depth of dechlorination and olefin hydrogenation conversion; conversely, when the content is low, the second hydrogenation temperature can be appropriately decreased to avoid over-reaction and energy waste. The content information can be obtained through online analyzers, periodic laboratory sampling and analysis, etc.
[0035] In summary, by introducing a dynamic adjustment mechanism for the second hydrogenation temperature, the second-stage hydrogenation process can be better adapted to the actual composition of the intermediate products.
[0036] For example, the dechlorination method of waste plastic pyrolysis oil described in this application was used for dechlorination, and the results are shown in Table 1 below.
[0037] Table 1 Comparison of Waste Plastic Pyrolysis Oil Before and After Hydrochlorination
[0038] As shown in Table 1, after dechlorination using the hydrodechlorination method for waste plastic pyrolysis oil of this application, the contents of dienes, bromine, and organochlorines in the waste plastic pyrolysis oil are significantly reduced. Therefore, the hydrodechlorination method for waste plastic pyrolysis oil of this application achieves efficient removal of organochlorines and improves the quality of waste plastic pyrolysis oil.
[0039] Specifically, the waste plastic recycling system is a complete industrial chain encompassing waste plastics from collection, pretreatment, pyrolysis, hydrodechlorination to final product utilization. In this system, the aforementioned hydrodechlorination method for waste plastic pyrolysis oil is configured as a key intermediate processing step. Its purpose is to deeply purify the waste plastic pyrolysis oil obtained from pyrolysis, making it meet the quality requirements for subsequent utilization, such as as a chemical feedstock or fuel. In practical applications, this waste plastic recycling system typically includes a waste plastic collection unit, a sorting and cleaning unit, a pyrolysis unit, a hydrodechlorination unit, and a product storage and transportation unit. The aforementioned hydrodechlorination method for waste plastic pyrolysis oil is applied in the hydrodechlorination unit. By applying the hydrodechlorination method to waste plastic pyrolysis oil in the waste plastic recycling system, a closed-loop management system covering the entire chain from waste to high-value products is achieved. This allows the crude oil produced by pyrolysis to be efficiently and thoroughly purified, overcoming the limitation of traditional pyrolysis oil, which is difficult to use directly due to its high impurity content. This systematic integration ensures the maximum utilization of waste plastic resources and provides a stable and high-quality source of raw materials for downstream industries.
[0040] As can be seen from the above, the method for hydrodechlorination of waste plastic pyrolysis oil involves connecting a first fixed-bed reactor and a second fixed-bed reactor in series, and loading a first metal oxide catalyst and a second metal oxide catalyst into the first and second fixed-bed reactors respectively. The first and second metal oxide catalysts are pre-sulfurized to obtain a first metal sulfide catalyst and a second metal sulfide catalyst. Waste plastic pyrolysis oil is then introduced into the first fixed-bed reactor. Based on the first metal sulfide catalyst, a first-stage hydrotreating process is performed under preset process parameters of a first hydrotreating temperature, preset hydrotreating pressure, preset space velocity, and preset hydrogen-to-oil volume ratio to remove easily polymerizable dienes and monoolefins, yielding first-stage hydrotreated waste plastic pyrolysis oil, which is then introduced into the second fixed-bed reactor. Waste plastic pyrolysis oil after primary hydrotreating undergoes secondary hydrotreating based on a second metal sulfide catalyst, under preset process parameters of secondary hydrotreating reaction temperature, preset hydrotreating pressure, preset space velocity, and preset hydrogen-to-oil volume ratio. This secondary hydrotreating removes organochlorides and hydrogenates olefins to alkanes, resulting in dechlorinated waste plastic pyrolysis oil. Thus, by employing a staged hydrotreating strategy using a metal sulfide catalyst, dienes, monoolefins, and organochlorides are removed from the waste plastic pyrolysis oil. This addresses the problem of existing hydrogenation dechlorination methods for waste plastic pyrolysis oil being unable to efficiently remove organochlorides, leading to poor oil quality and potential corrosion of downstream equipment. Staged hydrotreating achieves targeted removal of different types of impurities in the waste plastic pyrolysis oil, improving its quality.
[0041] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.
[0042] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A method for hydrodechlorination of waste plastic pyrolysis oil, characterized in that, Includes the following steps: The first fixed-bed reactor and the second fixed-bed reactor are connected in series, and the first metal oxide catalyst and the second metal oxide catalyst are respectively loaded into the first fixed-bed reactor and the second fixed-bed reactor. The first metal oxide catalyst and the second metal oxide catalyst were respectively subjected to presulfurization treatment to obtain a first metal sulfide catalyst and a second metal sulfide catalyst; Waste plastic pyrolysis oil is fed into the first fixed-bed reactor. Based on the first metal sulfide catalyst, a first-stage hydrogenation treatment is carried out under the process parameters of a preset first hydrogenation temperature, a preset hydrogenation pressure, a preset space velocity, and a preset hydrogen-to-oil volume ratio to remove easily polymerizable dienes and monoolefins, thereby obtaining waste plastic pyrolysis oil after the first-stage hydrogenation treatment. The waste plastic pyrolysis oil after the first stage of hydrogenation is introduced into the second fixed-bed reactor. Based on the second metal sulfide catalyst, a second stage of hydrogenation is carried out under the preset process parameters of the second hydrogenation temperature, the preset hydrogenation pressure, the preset space velocity, and the preset hydrogen-oil volume ratio to remove organochlorides and hydrogenate olefins into alkanes, thereby obtaining dechlorinated waste plastic pyrolysis oil.
2. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, The preset first hydrogenation temperature is lower than the preset second hydrogenation temperature.
3. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 2, characterized in that, The preset first hydrogenation temperature is 120-250 DEG C; the preset hydrogenation pressure is 3-8 MPa; the preset space velocity is 0.2-2.5 h -1 -1; and the preset hydrogen / oil volume ratio is 200-2000:
1.
4. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 3, characterized in that, The preset second hydrogenation temperature is 220~350℃.
5. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 2, characterized in that, The preset first hydrogenation temperature is 170~190℃; the preset hydrogenation pressure is 5~7MPa; and the preset space velocity is 0.8~1.2h. -1 The preset hydrogen-to-oil volume ratio is 600-1000:
1.
6. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 5, characterized in that, The preset second hydrogenation temperature is 260~320℃.
7. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 4 or 6, characterized in that, The pre-sulfurization treatment is performed by using a liquid sulfurizing agent at 250°C to pre-sulfurize the first metal oxide catalyst and the second metal oxide catalyst.
8. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 7, characterized in that, The specific value of the preset first hydrogenation temperature is adjusted based on the content information of dienes and alkynes in the waste plastic pyrolysis oil.
9. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 8, characterized in that, The specific value of the preset second hydrogenation temperature is adjusted based on the content information of organochlorides and olefins in the waste plastic pyrolysis oil after a first stage of hydrogenation treatment.
10. The method for hydrodechlorination of waste plastic pyrolysis oil according to claim 9, characterized in that, Used in waste plastic recycling systems.