A method for producing fuel oil from waste plastics

Abstract

The application discloses a method for producing fuel oil from waste plastics. The method comprises the following steps: mixing waste plastics with solvent oil and heating to melt, filtering the insoluble substances, and then flash evaporating and recovering the solvent oil to obtain molten plastics; mixing the molten plastics with vacuum gas oil to obtain blended oil; under a hydrogen atmosphere, the blended oil is subjected to hydrofining and hydrocracking reactions in sequence under the action of catalysts to generate fuel oil, and through a fractionation system, naphtha, kerosene and diesel are obtained. In the application, the pretreatment process effectively removes inorganic additives in the waste plastics, reduces pollution and blockage of subsequent devices, reduces the generation yield of gas products in the waste plastic treatment process, and maximizes the production of naphtha, kerosene and diesel products.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, and more specifically to a method for producing fuel oil from waste plastics. Background Technology

[0002] Waste plastics degrade slowly, putting significant pressure on society to manage them. They are globally recognized as white pollutants. Incineration produces toxic pollutants and greenhouse gases, while landfilling consumes more land resources. Their degradation rate underground is extremely slow, and the heavy metals they contain also cause soil and groundwater pollution during the degradation process. The generation of waste plastics poses a huge threat to the environment and human health.

[0003] Currently, waste plastics are treated through power generation and pyrolysis. Power generation requires incineration, which releases toxic substances and greenhouse gases. Pyrolysis produces oil with high impurity content and poor quality.

[0004] Hydrogenation technology has become the mainstream technology for producing clean fuel oil due to its green and environmentally friendly technical solutions. As a petroleum derivative, plastics can be degraded using hydrogenation technology to produce fuel oil. The process does not generate pollutants and has become a potential environmentally friendly technology for treating waste plastics.

[0005] Existing technologies for treating waste plastics using hydrogenation have the following problems: some processes in the overall process route lack pretreatment processes for waste plastics, and some processes are combined with pyrolysis processes, resulting in a large amount of gaseous products generated, making subsequent recycling of gaseous products difficult.

[0006] CN111363580A discloses a method for treating waste plastics using a liquid-phase hydrogenation process. The waste plastics are subjected to hydrogenation cracking in a liquid-phase hydrogenation reactor. The cracking products are then subjected to a liquid-phase hydrogenation isomerization reaction with at least one of paraffinic distillate oil and Fischer-Tropsch wax to obtain lubricating oil base oil, diesel oil, and hydrocarbon gas. The waste plastics contain a certain amount of inorganic additives, but the method lacks pretreatment of the waste plastics.

[0007] CN106520168A discloses a method for treating waste plastics, in which inferior oil and waste plastics are mixed and subjected to thermal cracking reaction. The resulting cracked gas comes into contact with a catalyst to undergo a catalytic reaction, forming gaseous products and liquid oil products. The liquid oil products are then hydrogenated to form naphtha and diesel. This process produces a relatively large amount of gaseous products, and additional processes are required to treat the gaseous products, resulting in high processing costs.

[0008] CN101896582A discloses a method for recycling waste plastics, which involves pyrolyzing a combination of biomass, waste plastics, and Fischer-Tropsch wax to obtain pyrolysis oil, which is then fractionated. At least one fraction is hydrogenated, and at least one intermediate after hydrogenation is catalytically isomerized to obtain isomerized products. However, since the waste plastics are not pretreated, a large amount of solid residue is generated in the pyrolysis device, which can easily cause blockage of the device. At the same time, the amount of gas generated is large, and gas recovery and utilization are difficult. Summary of the Invention

[0009] The purpose of this invention is to provide a method for producing fuel oil from waste plastics, wherein the pretreatment process effectively removes inorganic additives from the waste plastics, reducing pollution and blockage to subsequent equipment; at the same time, it reduces the generation rate of gaseous products during the waste plastics treatment process, maximizing the production of naphtha, kerosene and diesel products.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] This invention provides a method for producing fuel oil from waste plastics, the method comprising the following steps:

[0012] Waste plastic is mixed with solvent oil and heated to melt. The insoluble matter is filtered out and the solvent oil is then flash-evaporated to recover the molten plastic.

[0013] The molten plastic is mixed with vacuum wax oil to obtain a blended oil;

[0014] Under a hydrogen atmosphere, the blended oil undergoes hydrorefining and hydrocracking reactions in sequence under the action of a catalyst to produce fuel oil, which is then distilled to obtain naphtha, kerosene and diesel.

[0015] Waste plastics contain a large proportion of inorganic additives. In the recycling of waste plastics, inorganic additives are effectively removed to reduce pollution and blockage of subsequent equipment, while also reducing the gas yield during the treatment process.

[0016] According to the method of the present invention, the waste plastic is decomposed by thermogravimetric analysis, and the initial decomposition temperature and the decomposition termination temperature range are in the range of 200-500°C. Preferably, the waste plastic is a hydrocarbon plastic, selected from, but not limited to, at least one of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-cycloolefin copolymer, polydicyclopentadiene, and polystyrene.

[0017] According to the method of the present invention, preferably, the solvent oil is selected from at least one of pentane, cyclopentane, hexane, cyclohexane, heptane, toluene, xylene, and naphtha. The solvent oil and waste plastic are heated to 140–200°C in a reaction vessel or container to dissolve. Insoluble substances in the waste plastic are filtered out, and the solvent oil is flash-evaporated. The recovered solvent oil is recycled. There are no special requirements for the reaction vessel or container; it only needs to be able to heat to the temperature required for plastic dissolution and meet the flash-evaporation conditions.

[0018] According to the method of the present invention, preferably, the waste plastic is mixed with solvent oil and heated to 100-200°C to dissolve. Since the plastic contains some insoluble inorganic additives, the insoluble matter is filtered off after dissolution, and then the solvent oil is flash-evaporated for recycling.

[0019] According to the method of the present invention, the vacuum-pressed wax oil is a hydrotreated oil; preferably, the vacuum-pressed wax oil is at least one of vacuum-pressed first-line wax oil, vacuum-pressed second-line wax oil, vacuum-pressed third-line wax oil, and vacuum-pressed fourth-line wax oil. The boiling range of the vacuum-pressed wax oil is 300–580°C.

[0020] According to the method of the present invention, preferably, the sulfur content of the vacuum-reducing wax oil is ≤50μg / g and the nitrogen content is ≤20μg / g.

[0021] According to the method of the present invention, preferably, the mass ratio of the molten plastic to the vacuum wax oil is 1:10 to 4:1, more preferably 1:5 to 2:1.

[0022] According to the method of the present invention, preferably, the hydrorefining and hydrocracking reactions are carried out in a fixed-bed reactor, the hydrorefining is carried out in a hydrotreatment section, and the hydrocracking is carried out in a hydrocracking section.

[0023] According to the method of the present invention, preferably, the hydrotreating section is filled with a hydrotreating catalyst, and the hydrocracking section is filled with a hydrocracking catalyst; the volume ratio of the hydrotreating catalyst to the hydrocracking catalyst is 0.5:1 to 2:1.

[0024] The hydrogenation catalyst can be a conventional hydrogenation catalyst in the art, such as catalyst PHT-01 (purchased from the Petrochemical Research Institute of China National Petroleum Corporation).

[0025] The hydrocracking catalyst is a molecular sieve-type catalyst, whose main components include oxides of at least one element selected from Ni, Mo, W, Co, Al, and Si. The catalyst contains 30-60% molecular sieve and 10-30% metal element. Preferably, the main components of the catalyst are a combination of at least one molecular sieve selected from Y, Beta, ZSM-23, and ZSM-22 and at least one metal element selected from Ni, Mo, W, and Co. The catalyst also includes at least one element selected from P, B, F, Ce, and K as an auxiliary agent.

[0026] According to the method of the present invention, preferably, the blended oil undergoes hydrorefining and hydrocracking reactions under the action of a catalyst in a hydrogen atmosphere, wherein the hydrogen partial pressure of the reaction is 12-18 MPa, the reaction temperature is 340-400°C, the volume hourly space velocity is 1.0-3.0, and the hydrogen-to-oil volume ratio is 200-800:1.

[0027] According to the method of the present invention, preferably, the naphtha has a BMCI value ≤10 (preferably 4-8), which is a high-quality ethylene cracking feedstock.

[0028] According to the method of the present invention, preferably, the yield of naphtha is ≥45% (preferably 45% to 55%), and the total yield of naphtha, kerosene and diesel oil is ≥80%.

[0029] The pretreatment process of this invention involves mixing waste plastics with solvent oil, dissolving the plastics at a certain temperature to convert them into a liquid phase, and removing inorganic additives and other solid impurities from the waste plastics through high-temperature filtration. This reduces the risk of catalyst blockage and deactivation caused by directly feeding the waste plastics into the hydrotreating section. After removing inorganic additives and other solid impurities, the solvent is flash-evaporated and recovered, and the solvent oil is reused. The molten plastics are directly blended with vacuum wax oil and then fed into the post-hydrotreating process, followed by hydrocracking. This process can produce naphtha, kerosene, and diesel oil with high conversion rates. Naphtha, as an important basic raw material for chemical products, has a yield of not less than 40% and a BMCI value of not more than 10, making it a high-quality feedstock for ethylene cracking. The total yield of naphtha, kerosene, and diesel oil is ≥80%. The method for producing fuel oil from waste plastics in this invention has a high overall fuel oil yield, a low gas yield, and is environmentally friendly, producing no greenhouse gases. Detailed Implementation

[0030] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0031] This invention provides a method for producing fuel oil from waste plastics. The waste plastics are mixed with solvent oil and heated to melt. The insoluble matter is filtered out and the solvent oil is flash-evaporated to recover the plastics. Molten plastics are then mixed with vacuum wax oil to obtain blended oil. Under a hydrogen atmosphere, the blended oil and a catalyst are subjected to hydrorefining and hydrocracking reactions in the hydrotreating and hydrocracking sections of a fixed-bed reactor, respectively, to produce a small amount of low-carbon hydrocarbon gas, with the remainder mainly consisting of naphtha, kerosene, and diesel oil.

[0032] The waste plastics were analyzed by thermogravimetric analysis, and the initial decomposition temperature and the decomposition termination temperature ranged from 200 to 500°C. The waste plastics were preferably one or more of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-cycloolefin copolymer, polydicyclopentadiene, and polystyrene, but were not limited to these waste plastics.

[0033] The vacuum-treated wax oil is a hydrotreated oil, preferably one or a mixture of vacuum-treated first-line wax oil, vacuum-treated second-line wax oil, vacuum-treated third-line wax oil, and vacuum-treated fourth-line wax oil, with a distillation range of 300–580°C.

[0034] Preferably, the mass ratio of the molten plastic to the decompression wax oil is 1:10 to 4:1, and more preferably, it is 1:5 to 2:1.

[0035] During the solvent dissolution process, the solvent oil used is preferably one or more of pentane, cyclopentane, hexane, cyclohexane, heptane, toluene, xylene, and naphtha. The solvent oil and waste plastic are heated to 140-200°C in a reaction vessel or container to dissolve. The insoluble matter in the waste plastic is filtered out, and the solvent oil is flash-evaporated. The recovered solvent oil can be reused next time. There are no special requirements for the reaction vessel or container, as long as it can be heated to the temperature required for plastic dissolution and the flash evaporation conditions can be met.

[0036] The hydrotreating catalyst used in the hydrotreating section can be the commercially available catalyst PHT-01, purchased from the Petrochemical Research Institute of China National Petroleum Corporation.

[0037] The hydrocracking catalyst used in the hydrocracking section is a molecular sieve type catalyst, whose main components include oxides of at least one element selected from Ni, Mo, W, Co, Al, and Si. The catalyst contains 30-60% molecular sieve and 10-30% metal element. Preferably, the main components of the catalyst are a combination of at least one molecular sieve selected from Y, Beta, ZSM-23, and ZSM-22 and at least one metal element selected from Ni, Mo, W, and Co. The catalyst also includes at least one element selected from P, B, F, Ce, and K as an auxiliary agent.

[0038] Under hydrogen-rich conditions, blended oil undergoes hydrocracking with a catalyst at a hydrogen partial pressure of 12–18 MPa, a reaction temperature of 340–400 °C, a volume hourly space velocity of 1.0–3.0, and a hydrogen-to-oil volume ratio of 200–800:1. The resulting fuel oils include naphtha, kerosene, and diesel. The naphtha produced has a BMCI value of no more than 10, making it a high-quality feedstock for ethylene cracking. The naphtha yield is no less than 45%, and the total yield of naphtha, kerosene, and diesel is no less than 80%.

[0039] The technical solution of the present invention will be further described below through specific embodiments.

[0040] Example 1

[0041] This embodiment prepares a blended oil 1, including the following steps:

[0042] Taking polyethylene waste plastic as an example, thermogravimetric analysis showed that the initial decomposition temperature was 203℃, the 50% decomposition temperature was 336℃, the decomposition termination temperature was 402℃, and the melting range of the waste plastic was 93~125℃.

[0043] Take 5 kg of polyethylene waste plastic granules, which are granulated by a granulator and have a size of 1-3 mm. Add the waste plastic granules to a reactor equipped with flash evaporation and stirring functions. Then add 7 kg of cyclohexane as solvent oil to the reactor. Seal the reactor and turn on the stirring function. Heat to 105℃ and maintain the temperature for 30 minutes. After filtering out the insoluble matter from the molten waste plastic, flash evaporate the solvent oil and collect it in a container for reuse in dissolving plastic. After recovering the solvent oil, weigh the molten waste plastic and collect 4.75 kg of waste plastic, with a waste plastic recovery rate of 97.5%. Filter out 2.5% of inorganic insoluble matter. Mix the filtered molten waste plastic with a non-reducing wax oil at a mass ratio of 2:1 to obtain blended oil 1. The properties of the non-reducing wax oil are shown in Table 1.

[0044] Table 1 Properties of First-Line Wax Oil

[0045]

[0046] Example 2

[0047] This embodiment prepares a blended oil 2, including the following steps:

[0048] Taking polypropylene waste plastic as an example, thermogravimetric analysis showed that the initial decomposition temperature was 235℃, the 50% decomposition temperature was 346℃, the decomposition termination temperature was 491℃, and the melting range of the waste plastic was 109~145℃.

[0049] Take 5 kg of polypropylene waste plastic granules, which are granulated by a granulator and have a size of 1-3 mm. Add the waste plastic granules to a container (reactor) equipped with flash evaporation and stirring functions. Add 8 kg of n-heptane as solvent oil to the container, seal the container, turn on the stirring function, heat to 150℃, and maintain the temperature for 60 minutes. After filtering out the insoluble matter from the molten waste plastic, flash evaporate the solvent and recover it in the container for future use in dissolving plastic. After removing the solvent, weigh the molten waste plastic and collect 4.52 kg of waste plastic, with a waste plastic recovery rate of 90.4%. Filter out 9.6% of inorganic insoluble matter. Mix the molten waste plastic with non-reduced tert-cream wax oil at a mass ratio of 1:5 to obtain blended oil 2. The properties of non-reduced tert-cream wax oil are shown in Table 2.

[0050] Table 2 Properties of Reducing Four-Line Wax Oil

[0051]

[0052] Example 3

[0053] This embodiment prepares a blended oil 3, including the following steps:

[0054] Taking waste plastics mixed with polyethylene and polypropylene (the mass ratio of polyethylene to polypropylene is 1:1) as an example, through thermogravimetric analysis, the initial decomposition temperature is 209℃, the 50% decomposition temperature is 351℃, the decomposition termination temperature is 487℃, and the melting range of the waste plastics is 95~142℃.

[0055] Take 5 kg of mixed polyethylene and polypropylene waste plastic granules. These granules are produced by a granulator and have a size of 1-3 mm. Add the waste plastic granules to a container (reactor) equipped with flash evaporation and stirring functions. Add 8 kg of naphtha as solvent oil to the container, seal the container, and turn on the stirring function. Heat to 140℃ and maintain the temperature for 40 minutes. After filtering out the insoluble matter from the molten waste plastic, flash evaporate the solvent and recover it in the container for future use in dissolving plastic. After removing the solvent, weigh the molten waste plastic and collect 4.63 kg of waste plastic, with a waste plastic recovery rate of 92.6%. Filter out 7.4% of inorganic insoluble matter. Mix the molten waste plastic with triple-cured wax oil at a mass ratio of 1:1 to obtain blended oil 3. The properties of triple-cured wax oil are shown in Table 3.

[0056] Table 3 Properties of Reducing Three-Line Wax Oil

[0057]

[0058] Comparative Example 1

[0059] The difference from Example 3 is that the polyethylene and polypropylene mixed plastic is not melted with naphtha as a solvent to remove impurities. Instead, the polyethylene and polypropylene mixed plastic is directly mixed with the reduced-density wax oil at a mass ratio of 1:1 and heated to melt and mix evenly to obtain blended oil 4.

[0060] Example 4

[0061] This embodiment prepares a hydrocracking catalyst precursor QA-1, including the following steps:

[0062] Take 60g of Y molecular sieve (Y silicon-aluminum ratio SiO2 / Al2O3 is 5.9), 20g of ASA amorphous silicon-aluminum (SiO2 content is 40%), 10g of alumina, 8g of citric acid and 5g of guar gum powder, mix them evenly, add 72mL of solution containing 3% nitric acid dropwise to the above mixed powder, extrude into strips, dry at 120℃ for 3h, and calcine at 550℃ for 5h to obtain ZT-1.

[0063] A mixed solution of 60 mL of tungsten salt (ammonium metatungstate) and nickel salt (nickel nitrate) (tungsten concentration of 90 mg / mL and nickel concentration of 67 mg / mL) was mixed with 20 mL of auxiliary agent solution (phosphate concentration of 30 mg / mL and ethylenediaminetetraacetic acid concentration of 15 mg / mL) to obtain an impregnation solution. The impregnation solution was added dropwise to ZT-1 and dried at 80 °C for 5 h to obtain hydrocracking catalyst precursor QA-1.

[0064] Example 5

[0065] This embodiment prepares a hydrocracking catalyst precursor QA-2, including the following steps:

[0066] Take 30g of Beta molecular sieve (Beta SiO2 / Al2O3 ratio of 15.2), 25g of ASA amorphous silica-alumina (SiO2 content of 40%), 15g of alumina, 10g of citric acid and 6g of guar gum powder, mix them evenly, add 60mL of a solution containing 4% nitric acid dropwise to the above mixed powder, extrude into strips, dry at 120℃ for 3h, and calcine at 550℃ for 5h to obtain ZT-2.

[0067] A mixed solution of 50 mL of nickel salt (nickel nitrate) and molybdenum salt (ammonium molybdate) (nickel element concentration of 450 mg / mL and molybdenum element concentration of 150 mg / mL) was mixed with 30 mL of auxiliary agent solution (phosphoric acid concentration of 20 mg / mL and polyethylene glycol concentration of 35 mg / mL) to obtain an impregnation solution. The impregnation solution was added dropwise to ZT-2 and dried at 80 °C for 5 h to obtain hydrocracking catalyst precursor QA-2.

[0068] Example 6

[0069] This embodiment prepares a hydrocracking catalyst precursor QA-3, including the following steps:

[0070] Take 30g of Y molecular sieve (Y silicon-to-aluminum ratio SiO2 / Al2O3 is 5.9), 20g of ZSM-22 molecular sieve (ZSM-22 silicon-to-aluminum ratio SiO2 / Al2O3 is 55), 25g of ASA amorphous silicon-aluminum (SiO2 content is 40%), 5g of alumina, 6g of citric acid and 5g of guar gum powder, mix them evenly, add 65mL of solution containing 4% nitric acid dropwise to the above mixed powder, extrude into strips, dry at 120℃ for 3h, and calcine at 550℃ for 5h to obtain ZT-3.

[0071] A mixed solution of 70 mL of cobalt salt (cobalt nitrate) and molybdenum salt (ammonium molybdate) (cobalt element concentration of 150 mg / mL and molybdenum element concentration of 140 mg / mL) was mixed with 10 mL of auxiliary agent solution (boric acid concentration of 35 mg / mL and KCl concentration of 20 mg / mL) to obtain an impregnation solution. The impregnation solution was added dropwise to ZT-2 and dried at 80 °C for 5 h to obtain hydrocracking catalyst precursor QA-3.

[0072] Example 7

[0073] This embodiment prepares a hydrocracking catalyst precursor QA-4, including the following steps:

[0074] Take 20g of Y molecular sieve (Y silicon-to-aluminum ratio SiO2 / Al2O3 is 5.9), 40g of ZSM-23 molecular sieve (ZSM-23 silicon-to-aluminum ratio SiO2 / Al2O3 is 65), 15g of ASA amorphous silicon-aluminum (SiO2 content is 30%), 5g of alumina, 6g of citric acid and 5g of guar gum powder, mix them evenly, add 65mL of solution containing 4% nitric acid dropwise to the above mixed powder, extrude into strips, dry at 120℃ for 3h, and calcine at 550℃ for 5h to obtain ZT-4.

[0075] A mixed solution of 60 mL of nickel salt (nickel nitrate) and molybdenum salt (ammonium molybdate) (nickel element concentration of 180 mg / mL and molybdenum element concentration of 153 mg / mL) was mixed with 20 mL of auxiliary agent solution (hydrofluoric acid concentration of 25 mg / mL and cerium nitrate concentration of 25 mg / mL) to obtain an impregnation solution. The impregnation solution was added dropwise to ZT-4 and dried at 100 °C for 2 h to obtain the hydrocracking catalyst precursor QA-4.

[0076] Example 8

[0077] A catalyst was loaded into a fixed-bed reactor using a combination of hydrotreating and hydrocracking processes. The hydrotreating section was loaded with a commercially available PHT-01 catalyst, while the hydrocracking section was loaded with the hydrocracking catalyst prepared according to this invention. The volume ratio of the hydrotreating catalyst to the hydrocracking catalyst was 1.5:1. The PHT-01 catalyst was combined with the hydrocracking catalyst precursor prepared in Examples 4 to 7 and loaded into the fixed-bed reactor for sulfidation activation at 370°C for 10 hours, yielding combined catalysts A, B, C, and D.

[0078] Example 9

[0079] Hydrogenation performance was evaluated using the combined catalyst prepared in Example 8. Four catalyst combinations were selected for hydrogenation performance evaluation. A fixed-bed reactor was used, and the catalyst loading volume was 100 mL. The hydrogenation evaluation process conditions are shown in Table 4.

[0080] Table 4 Hydrogenation Evaluation Process Conditions

[0081] Hydrogenation treatment section Hydrocracking section Reaction temperature, °C 350 370 Hydrogen partial pressure, MPa 12 15 Liquid hourly space velocity, h⁻¹ 1 1.5 Hydrogen-to-oil volume ratio 400 600

[0082] The raw material used for evaluation was blended oil 3 obtained in Example 3, and the specific properties of the raw material are shown in Table 5.

[0083] Table 5 Properties of Crude Oil

[0084]

[0085] The product properties evaluated by hydrogenation are shown in Table 6.

[0086] Table 6. Evaluation Results of Hydrogenation

[0087]

[0088] Comparative Example 2

[0089] The difference from Example 9 is that blended oil 4 is used as the raw material oil, and the properties of the raw material oil are shown in Table 7.

[0090] Table 7 Properties of Crude Oil

[0091]

[0092] The product properties evaluated by hydrogenation are shown in Table 8.

[0093] Table 8. Evaluation Results of Hydrogenation

[0094]

[0095] As can be seen from the data in Tables 4, 6, 7, and 8 above, the method of this invention removes inorganic insoluble substances from waste plastics through a pretreatment process, preventing these insoluble substances from entering subsequent processes and causing blockages in the subsequent processes (hydrotreating catalyst and hydrocracking catalyst). This ensures that the waste plastics are converted into naphtha, kerosene, and diesel oil through hydrotreating and hydrocracking processes. The naphtha yield is not less than 50%, and the naphtha BMCI value is not greater than 10. This type of naphtha is a high-quality feedstock for ethylene cracking. The total yield of naphtha, kerosene, and diesel oil is not less than 80%, and the gas yield is not greater than 3.5%, achieving a high conversion rate of plastic resources into fuel oil. However, without solvent melting to remove impurities from the waste plastics, the activity of the catalysts (hydrotreating catalyst and hydrocracking catalyst) is lost, resulting in low naphtha, kerosene, and diesel oil yields and feedstock conversion rates. At the same time, the method of this invention does not generate greenhouse gases, making the process environmentally friendly and producing no pollutants.

[0096] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for producing fuel oil from waste plastics, characterized in that, The method includes the following steps: Waste plastic is mixed with solvent oil and heated to melt it. Insoluble matter is removed by high-temperature filtration, and the solvent oil is then flash-evaporated to recover the molten plastic. The solvent oil is selected from at least one of pentane, cyclopentane, hexane, cyclohexane, heptane, and naphtha. The molten plastic is mixed with vacuum-reducing wax oil to obtain a blended oil; the mass ratio of the molten plastic to the vacuum-reducing wax oil is 1:5 to 2:

1. Under a hydrogen atmosphere, the blended oil undergoes hydrorefining and hydrocracking reactions in sequence under the action of a catalyst to produce fuel oil, which is then distilled to obtain naphtha, kerosene and diesel oil. The hydrorefining and hydrocracking reactions are carried out in a fixed-bed reactor, with the hydrorefining taking place in a hydrotreatment section and the hydrocracking in a hydrocracking section. The hydrotreating section is filled with a hydrotreating catalyst, and the hydrocracking section is filled with a hydrocracking catalyst; the volume ratio of the hydrotreating catalyst to the hydrocracking catalyst is 0.5:1 to 2:

1. The hydrotreating catalyst is catalyst PHT-01; the hydrocracking catalyst contains 30-60% molecular sieve and 10-30% metal element, wherein the molecular sieve is selected from at least one of Y, Beta, ZSM-23, and ZSM-22, and the metal element is selected from at least one of Ni, Mo, W, and Co. The hydrocracking catalyst also includes at least one of the promoters P, B, F, Ce, and K.

2. The method according to claim 1, characterized in that, The waste plastic was analyzed by thermogravimetric analysis, and the initial decomposition temperature and the decomposition termination temperature range were found to be 200~500℃.

3. The method according to claim 2, characterized in that, The waste plastics are selected from at least one of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-cycloolefin copolymer, polydicyclopentadiene, and polystyrene.

4. The method according to claim 1, characterized in that, The waste plastic is mixed with solvent oil and heated to 100~200℃ to melt.

5. The method according to claim 1, characterized in that, The pressure-reducing wax oil is selected from at least one of the following: pressure-reducing first-line wax oil, pressure-reducing second-line wax oil, pressure-reducing third-line wax oil, and pressure-reducing fourth-line wax oil.

6. The method according to claim 5, characterized in that, The sulfur content of the vacuum-reducing wax oil is ≤50 μg / g, and the nitrogen content is ≤20 μg / g.

7. The method according to claim 1, characterized in that, Under a hydrogen atmosphere, the blended oil undergoes hydrorefining and hydrocracking reactions in the presence of a catalyst. The hydrogen partial pressure of the reaction is 12-18 MPa, the reaction temperature is 340-400℃, the volume hourly space velocity is 1.0-3.0, and the hydrogen-to-oil volume ratio is 200-800:

1.

8. The method according to claim 1, characterized in that, The BMCI value of the naphtha is ≤10.

9. The method according to claim 1, characterized in that, The BMCI value of the naphtha is 4-8.

10. The method according to claim 1, characterized in that, The yield of naphtha is ≥45%, and the total yield of naphtha, kerosene and diesel is ≥80%.

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