A method for preparing refined oil from waste plastics

Abstract

The present invention belongs to the technical field of solid waste recycling and resource utilization, and specifically relates to a method for preparing refined oil from waste plastics, comprising the following steps: (1) performing a catalytic pyrolysis reaction on the waste plastics and a pyrolysis catalyst in an inert atmosphere; (2) condensing the pyrolysis gas obtained from the catalytic pyrolysis reaction to obtain pyrolysis oil, and further performing dehydration treatment; (3) mixing the dehydrated pyrolysis oil with a hydrogenation catalyst and then performing a hydrogenation reaction to obtain refined oil. The present invention uses waste plastics as raw materials for catalytic pyrolysis reaction, which can obtain a relatively high pyrolysis oil yield. Further, a low-temperature hydrogenation process is adopted to upgrade the quality of pyrolysis oil under relatively mild reaction conditions, remove unsaturated bonds, reduce energy consumption and the amount of hydrogen used, and obtain higher-quality refined oil.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste recycling and resource utilization, and particularly relates to a method for preparing refined oil from waste plastics. Background Art

[0002] Plastics are widely used due to their advantages such as low cost and high strength; the demand increases year by year, but the natural degradation rate of plastics is relatively low, resulting in an increasing number of waste plastics, and the problem of "white pollution" is becoming increasingly serious. The apparent consumption of polypropylene and polyethylene accounts for about half of plastic products, and their main components are carbon and hydrogen elements. Recycling their products can be used as refined oil, which can alleviate the increasingly shortage of fossil energy and environmental pollution problems to a certain extent.

[0003] Pyrolysis is the most studied chemical recycling method for waste plastics at present. It has low requirements for raw materials, a simple recycling process, low labor intensity, and can realize the high-value commercialization of products. Introducing a catalyst in the pyrolysis process can reduce the activation energy required for the reaction, improve the product distribution, and then greatly improve the quality of the liquid product, accelerating the conversion of plastic waste into high-value hydrocarbons.

[0004] Common catalysts for plastic pyrolysis include zeolite catalysts, metal oxide catalysts, fluid catalytic cracking (FCC) catalysts, biochar catalysts, etc. Metal oxides (such as calcium oxide, zirconium dioxide, cobalt oxide, etc.) can promote the conversion of oxygen-containing compounds from macromolecules to small molecules and reduce the oxygen content in pyrolysis oil; inorganic salts (such as potassium chloride, sodium carbonate, iron sulfate, etc.) can catalyze the decomposition of plastics by affecting the biomass structure or pyrolysis reaction pathway; molecular sieve catalysts (such as ZSM-5, HY, γ-Al2O3, etc.) are conducive to the formation of aromatic hydrocarbons due to their certain acidity and shape selectivity; biochar catalysts have the advantages of low cost, high chemical stability, easy adjustment of structure, good biocompatibility, strong tolerance to coke deposition, and can be recycled and reused, and have received extensive attention in the field of catalyst development. The introduction of a catalyst can reduce the activation energy of the pyrolysis reaction and reduce energy consumption; it can also improve the quality of pyrolysis oil while increasing the yield of pyrolysis oil, indirectly reducing the reaction temperature, reaction time, and hydrogen consumption in the subsequent hydrogenation process, and further improving the economy of preparing refined oil from waste plastics.

[0005] The olefin content in pyrolysis oil is relatively high and cannot be directly used as fuel. Therefore, it is necessary to upgrade the obtained liquid oil by hydrogenation to convert unsaturated olefins into saturated alkane compounds. The conditions required for the hydrogenation process are relatively harsh (300 - 400 °C, 8 - 30 MPa H2 pressure) and the production cost is relatively high, which seriously hinders the commercial promotion of the hydrogenation process. Therefore, it is of great practical significance to seek a method for the low-cost and high-value utilization of waste plastics. Summary of the Invention

[0006] In order to overcome the disadvantages of low yield and poor quality of the liquid products obtained by direct thermal cracking of waste plastics, the present invention proposes a method for preparing refined oil from waste plastics. A catalyst with low price and good catalytic performance is introduced for catalytic pyrolysis to obtain high-quality pyrolysis oil. Further, a low-temperature hydrogenation reaction is carried out in a high-temperature and high-pressure autoclave. By coupling the catalytic pyrolysis and low-temperature hydrogenation processes, the conversion of waste plastics into high-quality refined oil can be directly realized, truly providing a feasible and low-cost method for the recycling and reuse of waste plastics.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing refined oil from waste plastics, which can be partially referred to Figure 1 , includes the following steps:

[0009] (1) Carry out a catalytic pyrolysis reaction on waste plastics and a pyrolysis catalyst in an inert atmosphere;

[0010] (2) Condense the pyrolysis gas obtained from the catalytic pyrolysis reaction to obtain pyrolysis oil, and further carry out dehydration treatment;

[0011] (3) Mix the dehydrated pyrolysis oil with a hydrogenation catalyst and carry out a hydrogenation reaction to obtain refined oil.

[0012] Preferably, in step (1), the pyrolysis catalyst is a metal-loaded pyrolysis catalyst, wherein the carrier is selected from at least one of metal oxides, molecular sieves, and biochars, and the loaded metal is at least one of iron, cobalt, zinc, nickel, and copper, and the metal loading is 0-50 wt%. Further preferably, the biochar carrier is selected from at least one of cow dung biochar, municipal sludge biochar, and corn straw biochar; the loaded metal is at least one of zinc, iron, and nickel.

[0013] Preferably, in step (3), the hydrogenation catalyst is selected from at least one of Raney nickel, ruthenium carbon, and metal-loaded hydrogenation catalysts; further preferably, the metal-loaded hydrogenation catalyst is selected from at least one of Ni-HY, Fe-ZSM-5, Co-γ-Al2O3, and zinc-nickel bimetal-loaded corn straw biochar; more preferably, the silicon / aluminum ratio of the molecular sieve in Ni-HY is 5-120:1.

[0014] Preferably, in step (1), the waste plastics are at least one of lunch boxes (polypropylene), plastic bottles (polypropylene), agricultural films (polyethylene), and medical protective clothing (polypropylene and / or polyethylene); more preferably, they are dried and crushed into particles or flakes with a particle size of 1-10 mm before use.

[0015] Preferably, in step (1), the inert gas is at least one of nitrogen and argon.

[0016] Preferably, in step (1), the mass ratio of the waste plastic to the pyrolysis catalyst is 1:2 to 2:1; the temperature of the catalytic pyrolysis reaction is 400 to 600 °C, and the reaction time is 20 to 40 min.

[0017] Preferably, in step (1), the pyrolysis catalyst can be recycled and reused 6 to 7 times after recovery.

[0018] Preferably, in step (3), the dosage of the hydrogenation catalyst is 5 to 20 wt% of the mass of the pyrolysis oil.

[0019] Preferably, in step (3), the hydrogenation reaction is carried out in a hydrogen atmosphere, and the reaction temperature is 150 °C to 300 °C (low-temperature hydrogenation reaction); more preferably, the reaction pressure is 2 to 6 MPa, and the reaction time is 1 to 5 h.

[0020] Preferably, it further includes the following step: The non-condensable gas in the pyrolysis gas and the hydrogen obtained after purifying the effluent gas of the hydrogenation reaction are reused as the reaction atmosphere for the hydrogenation reaction.

[0021] The beneficial effects of the present invention are at least as follows:

[0022] (1) The method for preparing refined oil from waste plastics provided by the present invention uses waste plastics as raw materials to prepare high-quality refined oil, which can alleviate the increasingly shortage of fossil energy and the serious environmental pollution problems caused by the use of fossil energy;

[0023] (2) The method for preparing refined oil from waste plastics provided by the present invention introduces a pyrolysis catalyst with good catalytic performance, which can reduce the reaction temperature of the pyrolysis reaction, reduce energy consumption, and at the same time can improve the yield of pyrolysis oil and the quality of pyrolysis oil to a certain extent, and reduce the reaction conditions required for the subsequent hydrogenation reaction;

[0024] (3) The method for preparing refined oil from waste plastics provided by the present invention carries out low-temperature hydrogenation reaction on the obtained pyrolysis oil, upgrades the quality of the pyrolysis oil, eliminates the adverse effects of unsaturated bonds in the pyrolysis oil on subsequent applications, reduces energy consumption and reduces the amount of hydrogen used, providing a feasible new method for the resource utilization of waste plastics;

[0025] (4) The method for preparing refined oil from waste plastics provided by the present invention, the catalyst used in pyrolysis can be recycled and reused, and the combustible gas generated during catalytic pyrolysis and low-temperature hydrogenation can be purified and reused during low-temperature hydrogenation or used as civil gas. Description of the Drawings

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the prior art in the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the process flow diagram of the present invention for preparing high-quality refined oil from waste plastics. Detailed implementation manners

[0028] The present invention provides a method for preparing refined oil from waste plastics, including the following steps:

[0029] (1) Conduct a catalytic pyrolysis reaction on waste plastics and a pyrolysis catalyst in an inert atmosphere;

[0030] (2) Condense the pyrolysis gas obtained from the catalytic pyrolysis reaction to obtain pyrolysis oil, and further perform dehydration treatment;

[0031] (3) Mix the dehydrated pyrolysis oil with a hydrogenation catalyst and perform a low-temperature hydrogenation reaction to obtain refined oil.

[0032] In a preferred embodiment, the pyrolysis catalyst is a metal-loaded pyrolysis catalyst, wherein the carrier is selected from at least one of metal oxides, molecular sieves, and biochar, the loaded metal is at least one of iron, cobalt, zinc, nickel, and copper, and the metal loading is 0-50 wt%.

[0033] In a more preferred embodiment, the carrier of the metal-loaded pyrolysis catalyst is biochar, which is selected from one of cow dung biochar, municipal sludge biochar, and corn straw biochar, most preferably cow dung biochar; the loaded metal is one or more of zinc, iron, and nickel, preferably one or more of zinc and nickel, and further preferably zinc and nickel; the metal loading is 5-20 wt%, and further preferably 10 wt%.

[0034] In a preferred embodiment, the hydrogenation catalyst is selected from at least one of Raney nickel catalyst, ruthenium carbon, and metal-loaded hydrogenation catalyst; preferably one of Raney nickel or metal-loaded hydrogenation catalyst, and further preferably a metal-loaded hydrogenation catalyst selected from at least one of Ni-HY, Fe-ZSM-5, Co-γ-Al2O3, and zinc-nickel bimetal-loaded corn straw biochar, most preferably Ni-HY; the silicon / aluminum ratio of the molecular sieve in the Ni-HY is 5-120, preferably 5.2, and the loading of metal Ni is 0-20 wt%, preferably 20 wt%.

[0035] In a preferred embodiment, the waste plastic is one of lunch boxes (polypropylene), plastic bottles (polypropylene), agricultural films (polyethylene), and medical protective clothing (polypropylene and / or polyethylene), preferably plastic bottles (polypropylene) or medical protective clothing (polyethylene and / or polypropylene), and more preferably plastic bottles (polypropylene); after drying them respectively, they are crushed into particles or flakes with a particle size of 1 - 10 mm, preferably particles or flakes of 3 - 5 mm.

[0036] In a preferred embodiment, the inert gas is one of nitrogen or argon, preferably argon.

[0037] In a preferred embodiment, the mass ratio of the waste plastic to the pyrolysis catalyst is 1:2 - 2:1, preferably 1:1 - 2:1, and more preferably 1:1; the reaction temperature for the catalytic pyrolysis of the waste plastic is 400 - 600 °C, preferably 500 °C; the reaction time is 25 - 50 min, preferably 40 min.

[0038] In a preferred embodiment, the dosage of the hydrogenation catalyst is 5 - 20 wt% of the mass of the pyrolysis oil, more preferably 10 - 15 wt%, and further preferably 12.5 wt%.

[0039] In a preferred embodiment, the gas used in the low-temperature hydrogenation reaction is hydrogen, the reaction temperature is 150 - 300 °C, preferably 200 - 250 °C, and more preferably 200 °C; the pressure is 2 - 6 MPa, preferably 3 - 5 MPa, and more preferably 4 MPa; the reaction time is 1 - 5 h, preferably 2 - 3 h, and more preferably 3 h.

[0040] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0041] In the following examples, the preparation method of the metal-loaded biochar catalyst is as follows: The biomass raw material is washed with water, dried at 105 °C for 48 h, and crushed into particles with a mesh size of 40 - 100. Then, it is subjected to carbothermal reduction at 500 °C for 4 h to obtain biochar. The biochar is mixed with a quantitative metal salt solution and stirred at 500 rpm / min for 4 h; then, the mixture is placed in an oven at 105 °C and dried for 48 h to obtain a catalyst precursor; the catalyst precursor is subjected to carbothermal reduction at 800 °C for 4 h, cooled, and then washed successively with hydrochloric acid (0.1 mol / L), ethanol, and deionized water, and finally dried at 105 °C for 24 h to obtain the metal-loaded biochar catalyst.

[0042] The preparation method of the metal-loaded molecular sieve catalyst is as follows: A certain amount of metal salt is dissolved in anhydrous ethanol to obtain a metal salt solution. Then, a certain amount of calcined molecular sieve is mixed and stirred with the metal salt solution to make them fully mixed. After that, water bath heating is carried out at a temperature of 70 °C, and it is heated with stirring at a speed of 250 rpm / min for 4 h, then naturally dried for 24 h, and finally calcined at 550 °C for 4 h to obtain the metal-loaded molecular sieve catalyst.

[0043] The Raney nickel catalyst was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0044] Example 1

[0045] (1) 15 g of plastic bottles (polypropylene) were crushed into 3-mm particles and placed in a pyrolysis system. A biochar catalyst with a mass ratio of 1:1 was added for catalytic pyrolysis reaction. The precursor of the biochar catalyst was cow manure, and the loaded metals were zinc and nickel (mass ratio 1:1), with a metal loading of 10 wt%. The reaction temperature was 500 °C, the reaction time was 40 min, and argon was used as the carrier gas for the catalytic pyrolysis reaction.

[0046] (2) The condensable part of the pyrolysis vapor was condensed and collected as pyrolysis oil, and dehydration treatment was carried out. The non-condensable part was collected as combustible gas.

[0047] (3) 4 g of the dehydrated pyrolysis oil and 0.5 g of the Ni-HY molecular sieve catalyst were placed together in a high-temperature and high-pressure autoclave. The silicon / aluminum ratio of the HY molecular sieve was 5.2, and the loading of metal Ni was 20 wt%. A low-temperature hydrogenation reaction was carried out at a reaction temperature of 200 °C, a hydrogen pressure of 4 MPa, and a reaction time of 3 h. Finally, the refined oil could be obtained after cooling. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0048] (4) The biochar catalyst used in the pyrolysis process could be recycled, and the purified combustible gas was used for the low-temperature hydrogenation reaction.

[0049] Example 2

[0050] (1) 15 g of plastic bottles (polypropylene) were crushed into 3-mm particles and placed in a pyrolysis system. A biochar catalyst with a mass ratio of 1:1 was added for catalytic pyrolysis reaction. The precursor of the biochar catalyst was cow manure, and the loaded metal was zinc, with a metal loading of 5 wt%. The reaction temperature was 500 °C, the reaction time was 40 min, and argon was used as the carrier gas for the catalytic pyrolysis reaction.

[0051] (2) The condensable part of the pyrolysis vapor was condensed and collected as pyrolysis oil, and dehydration treatment was carried out. The non-condensable part was collected as combustible gas.

[0052] (3) Place 4 g of dehydrated pyrolysis oil and 0.5 g of Ni-HY zeolite catalyst in a high-temperature and high-pressure autoclave. The silicon / aluminum ratio of the HY zeolite is 5.2, and the loading of metal Ni is 20 wt%. Carry out low-temperature hydrogenation reaction under the conditions of a reaction temperature of 200 °C, a hydrogen pressure of 4 MPa, and a reaction time of 3 h. After final cooling, refined oil can be obtained. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0053] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0054] Example 3

[0055] (1) Crush 15 g of plastic bottles (polypropylene) into 3-mm particles and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1:1 to carry out catalytic pyrolysis reaction. The precursor of the biochar catalyst is cow manure, the loaded metal is nickel, the metal loading is 20 wt%, the reaction temperature is 500 °C, the reaction time is 40 min, and argon is used as the carrier gas for the catalytic pyrolysis reaction.

[0056] (2) Condense and collect the condensable part in the pyrolysis vapor as pyrolysis oil and carry out dehydration treatment, and collect the non-condensable part as combustible gas.

[0057] (3) Place 4 g of dehydrated pyrolysis oil and 0.5 g of Ni-HY zeolite catalyst in a high-temperature and high-pressure autoclave. The silicon / aluminum ratio of the HY zeolite is 5.2, and the loading of metal Ni is 20 wt%. Carry out low-temperature hydrogenation reaction under the conditions of a reaction temperature of 200 °C, a hydrogen pressure of 4 MPa, and a reaction time of 3 h. After final cooling, refined oil can be obtained. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0058] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0059] Example 4

[0060] (1) Crush 15 g of plastic bottles (polypropylene) into 3-mm particles and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1:1 to carry out catalytic pyrolysis reaction. The precursor of the biochar catalyst is cow manure, the metal loading is 0 wt%, the reaction temperature is 500 °C, the reaction time is 40 min, and argon is used as the carrier gas for the catalytic pyrolysis reaction.

[0061] (2) Condense and collect the condensable part of the pyrolysis vapor as pyrolysis oil, and conduct dehydration treatment. Collect the non-condensable part as combustible gas.

[0062] (3) Place 4 g of dehydrated pyrolysis oil and 0.5 g of Ni-HY zeolite catalyst in a high-temperature and high-pressure reactor. The silicon / aluminum ratio of the HY zeolite is 5.2, and the loading amount of metal Ni is 20 wt%. Conduct low-temperature hydrogenation reaction under the conditions of a reaction temperature of 200 °C, a hydrogen pressure of 4 MPa, and a reaction time of 2 h. After final cooling, refined oil can be obtained. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0063] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0064] Example 5

[0065] (1) Crush 15 g of plastic bottles (polypropylene) into particles of 3 mm and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1:1 for catalytic pyrolysis reaction. The precursor of the biochar catalyst is cow manure, and the metal loading amount is 0 wt%. The reaction temperature is 500 °C, the reaction time is 40 min, and argon is used as the carrier gas for catalytic pyrolysis reaction.

[0066] (2) Condense and collect the condensable part of the pyrolysis vapor as pyrolysis oil, and conduct dehydration treatment. Collect the non-condensable part as combustible gas.

[0067] (3) Place 4 g of dehydrated pyrolysis oil and 0.5 g of Ni-HY zeolite catalyst in a high-temperature and high-pressure reactor. The silicon / aluminum ratio of the HY zeolite is 5.2, and the loading amount of metal Ni is 20 wt%. Conduct low-temperature hydrogenation reaction under the conditions of a reaction temperature of 200 °C, a hydrogen pressure of 5 MPa, and a reaction time of 2 h. After final cooling, refined oil can be obtained. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0068] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0069] Example 6

[0070] (1) Crush 6 g of medical protective clothing (polypropylene and polyethylene) into flakes with a size of 5 mm and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1:1 for catalytic pyrolysis reaction. The precursor of the biochar catalyst is cow manure, the loaded metals are zinc and nickel (mass ratio 1:1), the metal loading is 10 wt%, the reaction temperature is 500 °C, the reaction time is 36 min, and argon is used as the carrier gas for the catalytic pyrolysis reaction.

[0071] (2) Condense and collect the condensable part of the pyrolysis vapor as pyrolysis oil and perform dehydration treatment. The non-condensable part is collected as combustible gas.

[0072] (3) Place 4 g of dehydrated pyrolysis oil and 0.4 g of Raney nickel catalyst together in a high-temperature and high-pressure reactor. Perform low-temperature hydrogenation reaction under the conditions of a reaction temperature of 200 °C, a hydrogen pressure of 3 MPa, and a reaction time of 2 h. After final cooling, refined oil can be obtained. The product distribution results obtained by GCMS detection of the high-quality refined oil are shown in Table 1.

[0073] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0074] Comparative Example 1

[0075] (1) Crush 15 g of plastic bottles (polypropylene) into particles with a size of 3 mm and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1:1 for catalytic pyrolysis reaction. The precursor of the biochar catalyst is cow manure, the metal loading is 0 wt%, the reaction temperature is 500 °C, the reaction time is 40 min, and argon is used as the carrier gas for the catalytic pyrolysis reaction.

[0076] (2) Condense and collect the condensable part of the pyrolysis vapor as pyrolysis oil and perform dehydration treatment. The non-condensable part is collected as combustible gas.

[0077] (3) The biochar catalyst used in the pyrolysis process can be recycled, and the purified combustible gas is used for low-temperature hydrogenation reaction.

[0078] Comparative Example 2

[0079] (1) Crush 6 g of plastic bottles (polypropylene) into particles with a size of 3 mm and place them in a pyrolysis system. Add a biochar catalyst with a mass ratio of 1.5:1 for catalytic pyrolysis reaction. The precursor of the biochar catalyst is corn straw, the loaded metals are zinc and nickel (mass ratio 1:1), the metal loading is 10 wt%, the reaction temperature is 500 °C, the reaction time is 25 min, and argon is used as the carrier gas for the catalytic pyrolysis reaction.

[0080] (2) Condense and collect the condensable part in the pyrolysis vapor as pyrolysis oil, and perform dehydration treatment. The non-condensable part is collected as combustible gas.

[0081] (3) Place 4 g of the dehydrated pyrolysis oil and 0.4 g of the metal-loaded corn straw biochar catalyst used in the above catalytic pyrolysis together in a high-temperature and high-pressure reactor, and carry out a low-temperature hydrogenation reaction under the conditions of a reaction temperature of 250 °C, a hydrogen pressure of 3 MPa, and a reaction time of 2 h. After final cooling, refined oil can be obtained. The product distribution results of the high-quality refined oil detected by GCMS are shown in Table 1.

[0082] (4) The biochar catalyst used in the pyrolysis process can be recycled, and the combustible gas is purified and used for the low-temperature hydrogenation reaction.

[0083] Table 1 Product distribution results in the refined oil obtained in Examples 1-6 and Comparative Example 1

[0084]

[0085] As can be seen from Table 1, in Comparative Example 1, without subsequent low-temperature hydrogenation reaction, the proportion of olefins in the liquid-phase product obtained by pyrolyzing plastic bottles (polypropylene) is as high as 66.07%, which is due to the unsaturated bonds inherent in polypropylene; similarly, in Comparative Example 2, when using bimetal-loaded corn straw biochar as the hydrogenation catalyst in the hydrogenation reaction, the proportion of olefins in the liquid-phase product is still as high as 68.91 wt%, which will seriously hinder the practical utilization of the liquid-phase product. Therefore, the selection of the catalyst is very important. In Examples 1-6, low-temperature hydrogenation reactions were carried out on the liquid-phase products obtained by catalytic pyrolysis. In Examples 1-3, different types and contents of metals were loaded on the cow manure biochar precursor, and it was found that the gasoline range (C5-C 12 ) and the aviation fuel range (C8-C 16 ) in the refined oil obtained by loading 5 wt% zinc and 5 wt% nickel had the highest proportions, which were 73.97% and 84.50% respectively. In Examples 4-5, different hydrogenation reaction times and hydrogen pressures were adopted. As the reaction time decreased, the proportions of the gasoline range (C5-C 12 ) and the aviation fuel range (C8-C 16 ) in the refined oil decreased, and the diesel range (C 10 -C 22)The proportion increases, while it shows the opposite trend with the increase of hydrogen pressure, indicating that to a certain extent, intensifying the reaction conditions is conducive to the conversion of more products to the gasoline and aviation fuel ranges. This may be because harsher reaction conditions promote certain thermal cracking reactions of pyrolysis oil. In Example 6, different waste plastics and different hydrogenation catalysts were selected, and the highest diesel proportion obtained was 61.00%, indicating that the use of medical protective clothing (polypropylene and polyethylene) and Raney nickel catalyst will promote the generation of products in the diesel range to a certain extent.

[0086] As can be seen from the above examples, the present invention provides a method for preparing refined oil from waste plastics. The waste plastics and pyrolysis catalyst are placed in a reaction system, and catalytic pyrolysis reaction is carried out with an inert gas as the carrier gas. The obtained pyrolysis oil is mixed with a hydrogenation catalyst and then hydrogenation reaction is carried out. Finally, high-quality refined oil can be obtained after cooling. The present invention proposes a brand-new method for the high-value utilization of waste plastics, which alleviates the increasingly shortage of fossil energy while reducing the serious environmental pollution problems caused by the use of fossil energy. The production process is simple, the production process is clean, and the production cost can be reduced to the greatest extent.

[0087] The above examples are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by those of ordinary engineering and technical personnel in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing refined oil from waste plastics, characterized in that, It includes the following steps: (1) Conduct a catalytic pyrolysis reaction on waste plastics and a pyrolysis catalyst in an inert atmosphere; the waste plastics are at least one of lunch boxes made of polypropylene, plastic bottles made of polypropylene, agricultural films made of polyethylene, and medical protective clothing made of polypropylene and / or polyethylene; the pyrolysis catalyst is a metal-loaded pyrolysis catalyst, wherein the carrier is biochar, and the loaded metal is at least one of zinc and nickel, and the metal loading is below 20 wt%; (2) Condense the pyrolysis gas obtained from the catalytic pyrolysis reaction to obtain pyrolysis oil, and further conduct dehydration treatment; the temperature of the catalytic pyrolysis reaction is 400 - 600 °C, and the reaction time is 20 - 40 min; (3) Mix the dehydrated pyrolysis oil with a hydrogenation catalyst and conduct a hydrogenation reaction to obtain refined oil; the hydrogenation reaction is conducted in a hydrogen atmosphere, and the reaction temperature is 150 °C - 300 °C; the hydrogenation catalyst is selected from at least one of Raney nickel catalyst and metal-loaded hydrogenation catalyst; the metal-loaded hydrogenation catalyst is selected from Ni-HY, and the silicon / aluminum ratio of the molecular sieve in Ni-HY is 5 - 120:

1.

2. The method for preparing refined oil from waste plastics according to claim 1, characterized in that, In step (1), the biochar carrier is selected from at least one of cow dung biochar, municipal sludge biochar, and corn straw biochar.

3. The method for preparing refined oil from waste plastics according to claim 1 or 2, characterized in that, In step (1), the inert gas is at least one of nitrogen and argon.

4. The method for preparing refined oil from waste plastics according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the waste plastics to the pyrolysis catalyst is 1:2 - 2:

1.

5. The method for preparing refined oil from waste plastics according to claim 3, wherein, In step (1), the mass ratio of the waste plastics to the pyrolysis catalyst is 1:2 - 2:

1.

6. The method for preparing refined oil from waste plastics according to claim 1, 2 or 5, characterized in that, In step (1), the pyrolysis catalyst is recycled and reused 6 - 7 times.

7. The method for preparing refined oil from waste plastics according to claim 1, 2 or 5, characterized in that In step (3), the dosage of the hydrogenation catalyst is 5 - 20 wt% of the mass of the pyrolysis oil.

8. The method for preparing refined oil from waste plastics according to claim 1, 2 or 5, characterized in that, In step (3), the reaction pressure is 2 - 6 MPa, and the reaction time is 1 - 5 h.

9. The method for preparing refined oil from waste plastics according to claim 7, wherein In step (3), the reaction pressure is 2 - 6 MPa, and the reaction time is 1 - 5 h.

10. The method for preparing refined oil from waste plastics according to claim 1, 2, 5 or 9, characterized in that, It also includes the following steps: Purify the non-condensable gas in the pyrolysis gas and the hydrogen gas obtained from the effluent gas of the hydrogenation reaction, and reuse it as the reaction atmosphere for the hydrogenation reaction.

11. The method for preparing refined oil from waste plastics according to claim 3, wherein It also includes the following steps: Purify the non-condensable gas in the pyrolysis gas and the hydrogen gas obtained from the effluent gas of the hydrogenation reaction, and reuse it as the reaction atmosphere for the hydrogenation reaction.

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