A method for liquefying polyethylene to produce oil using low-temperature solvent hydrogen donation
By using a low-temperature solvent hydrogen supply method and mixing Ni/CeO2 catalyst with solvent, the high cost and low safety issues of high-temperature and high-pressure catalytic hydrogenation conversion of polyethylene waste plastics were solved, achieving low-cost and high-efficiency oil preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2023-05-23
- Publication Date
- 2026-07-17
AI Technical Summary
In existing technologies, the catalytic hydrogenation conversion process of polyethylene waste plastics is costly and has low safety. Precious metal catalysts are expensive, and the increased hydrogen pressure at high temperatures leads to harsh reaction conditions.
The process involves mixing a Ni/CeO2 catalyst with a solvent at low temperature and then using a batch reactor to liquefy polyethylene waste plastics into oil. The relatively inexpensive Ni-based metal catalyst is used, and hydrogen is supplied through the solvent to avoid high-pressure hydrogen. Solid-liquid separation and catalyst recovery are achieved in conjunction with an extractant.
It achieves efficient conversion of waste polyethylene plastics at low temperatures into oil products that meet the standards for gasoline, aviation fuel, diesel, and lubricating oil, reduces catalyst costs, improves reaction safety and economy, and allows the catalyst to be recycled.
Smart Images
Figure CN116606668B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyethylene waste plastic resource utilization technology, and in particular to a method for liquefying polyethylene to produce oil using low-temperature solvent hydrogen supply. Background Technology
[0002] The rapid development of the plastics industry, while bringing convenience to human life, has also generated a large amount of waste plastics, causing serious damage to the ecological environment. Therefore, waste plastic recycling methods have been actively explored both domestically and internationally. Polyolefins constitute the majority of waste plastics, primarily polyethylene. Currently, chemical conversion of polyethylene waste plastics to produce oil products is one of the most widely studied methods for the resource recovery of waste plastics. Chemical recycling methods for waste plastics include pyrolysis and catalytic hydrogenation. Pyrolysis suffers from drawbacks such as high temperatures, easy catalyst deactivation, and harsh reaction conditions, while catalytic hydrogenation is relatively milder. Catalytic hydrogenation of waste plastics generally involves heating the plastics under conditions of noble metal catalysts, such as Ru and Pt-based catalysts, and a certain amount of hydrogen pressure. This method offers advantages such as low temperature, good catalytic effect, and high selectivity. However, noble metals are expensive, and the significant increase in hydrogen pressure at high temperatures makes the catalytic hydrogenation process costly and unsafe. Therefore, developing a method for liquefying waste plastics with hydrogen using a low-temperature solvent to produce oil products is of great significance for the resource recovery of waste plastics. Summary of the Invention
[0003] The purpose of this invention is to address the problems existing in the background technology by proposing a method for liquefying polyethylene into oil using low-temperature solvent hydrogen supply, with the aim of converting waste polyethylene plastics into oil products under low-temperature solvent hydrogen supply conditions.
[0004] The technical solution of the present invention is a method for liquefying polyethylene to produce oil using a low-temperature solvent-donated hydrogen source, characterized by comprising the following specific steps:
[0005] S1: A certain amount of solvent, polyethylene waste plastic with a mass ratio of 2:1 and Ni / CeO2 catalyst are placed in an intermittent batch reactor, mixed evenly, sealed, and the air in the reactor is replaced three times with Ar gas at room temperature. Then, the reactor is placed in a sand bath at 330-350℃ and reacted for 12-24 hours.
[0006] S2: After the reactor is cooled, the reaction mixture in the vessel is taken out and a certain amount of extractant is added and extracted at room temperature for 30 minutes. Then, solid-liquid separation is carried out. The obtained liquid is recovered by rotary evaporation to recover the extractant and solvent, and the remainder is the liquefied oil.
[0007] S3: The solid consists of Ni / CeO2 catalyst and unreacted polyethylene waste plastic. The Ni / CeO2 catalyst is recovered by calcination in air and reduction with 5% H2 / Ar.
[0008] A further technical solution is as follows: the Ni / CeO2 catalyst is prepared by initial wet impregnation method. The Ni / CeO2 catalyst is in particulate form, and the Ni loading is 0-10 wt%. Ni exists in elemental form, and the Ni / CeO2 catalyst has weak acid and moderate acid sites.
[0009] Preferably, the reaction is hydrogen-supplied by a solvent.
[0010] Preferably, the product remaining after rotary evaporation of the liquid obtained in the solid-liquid separation step S3 is a n-alkanes.
[0011] Preferably, the reaction solvent is one of alcohols, alkanes or acids, and more preferably methanol, isopropanol, formic acid, n-hexane or cyclohexane.
[0012] Preferably, the extractant is a n-alkane, an aromatic hydrocarbon, or a polar solvent.
[0013] Compared with the prior art, the present invention has the following beneficial technical effects:
[0014] This invention proposes a method for producing oil from waste polyethylene plastics through low-temperature solvent hydrogen liquefaction. This method offers the advantages of lower reaction temperature and the elimination of the need for hydrogen. The lower reaction temperature helps to extend the catalyst's lifespan while improving the economic efficiency of the reaction process. Solvent hydrogen supply avoids the use of hydrogen gas, thus enhancing the safety of the reaction. The main product is a multi-component oil product, primarily composed of n-alkanes, conforming to standards for gasoline, jet fuel, diesel, and lubricating oil. The catalyst used is a relatively inexpensive Ni-based metal catalyst, resulting in lower catalyst costs. Both the catalyst and the solvent used for extraction can be recycled, improving raw material utilization and reducing operating costs. Attached Figure Description
[0015] Figure 1 This is a schematic flowchart of a method for producing oil from polyethylene waste plastic by low-temperature solvent hydrogen liquefaction according to the present invention.
[0016] Figure 2 This is a schematic diagram of the reaction results table for an embodiment of the low-temperature solvent hydrogen liquefaction of polyethylene waste plastics to produce oil according to the present invention. Detailed Implementation
[0017] See Figure 1 This application provides a method for producing oil from polyethylene waste plastic through low-temperature solvent hydrogen liquefaction, the specific steps of which are as follows:
[0018] A certain amount of solvent, polyethylene waste plastic (mass ratio 2:1), and Ni / CeO2 catalyst were mixed evenly in a batch reactor, sealed, and the air inside the reactor was replaced three times with Ar gas at room temperature. The reactor was then placed in a sand bath at 330-350℃ and reacted for 12-24 hours. After cooling, the reaction mixture was removed, and a certain amount of extractant was added and extracted at room temperature for 30 minutes. Solid-liquid separation was then performed. The obtained liquid was used to recover the extractant and solvent through rotary evaporation, and the remainder was liquefied into an oil product. The solid consisted of Ni / CeO2 catalyst and unreacted polyethylene waste plastic, which was recovered by calcination in air and reduction with 5% H2 / Ar.
[0019] The Ni / CeO2 proposed in this invention is prepared by initial wet impregnation and has the following properties: the catalyst is granular, the Ni loading is (0-10wt%) and mainly exists in the form of element, and the catalyst has certain weak acid and moderate acid sites.
[0020] Example 1
[0021] 1g of polyethylene waste plastic with a particle size of 2-3mm, 0.5g of Ni / CeO2 (Ni loading of 10wt%), and 2.5mL of solvent (one of alcohols, alkanes, or acids) were added to a batch reactor and sealed. The mixture was thoroughly mixed, and the air inside the reactor was replaced three times with Ar. Once the sand bath temperature reached 330℃, the reactor was placed in the sand bath, and timing began after 5 minutes. Heating was stopped after 24 hours of reaction. The reactor was removed and quenched in an ice-water bath. The vent valve was opened to release all gas from the reactor. The solid and liquid mixture inside the reactor was collected in a beaker. 10mL of extractant (one of n-alkanes, aromatics, or polar solvents) was added to the beaker, and ultrasonic extraction was performed for 30 minutes. The solid and liquid were separated by a vacuum filtration device. The liquid was separated into reaction solvent, extractant, and oil by rotary evaporation. The solid was recovered by air combustion and reduction in a tube furnace to obtain Ni / CeO2. Component analysis of the oils obtained from the reaction revealed the following yields: gasoline (C7-C12) 4.5%; aviation fuel (C8-C16) 14%; diesel (C9-C22) 67%; and lubricating oil (C20-C40) 42%.
[0022] Example 2
[0023] 1g of polyethylene waste plastic with a particle size of 2-3mm, 0.5g of Ni / CeO2 (Ni loading of 5wt%), and 2.5mL of solvent (one of alcohols, alkanes, or acids) were added to a batch reactor and sealed. The mixture was thoroughly mixed, and the air inside the reactor was replaced three times with Ar. After the sand bath temperature reached 330℃, the reactor was placed in the sand bath, and timing began after 5 minutes. Heating was stopped after 24 hours of reaction. The remaining steps were the same as in Example 1. Component analysis of the resulting oils showed the following yields: gasoline (C7-C12) 3%; aviation fuel (C8-C16) 10%; diesel (C9-C22) 43%; and lubricating oil (C20-C40) 70%.
[0024] Example 3
[0025] 1g of polyethylene waste plastic with a particle size of 2-3mm, 0.5g of CeO2, and 2.5mL of solvent (one of alcohols, alkanes, or acids) were added to a batch reactor and sealed. The mixture was thoroughly mixed, and the air inside the reactor was replaced three times with Ar. Once the sand bath temperature reached 330℃, the reactor was placed in the sand bath, and timing began after 5 minutes. Heating was stopped after 24 hours of reaction. The remaining steps were the same as in Example 1. Component analysis of the resulting oils showed the following yields: gasoline (C7-C12) 3%; aviation fuel (C8-C16) 0%; diesel (C9-C22) 0%; and lubricating oil (C20-C40) 0%.
[0026] Example 4
[0027] 1g of polyethylene waste plastic with a particle size of 2-3mm, 0.5g of Ni / CeO2 (Ni loading of 10wt%), and 2.5mL of solvent (one of alcohols, alkanes, or acids) were added to a batch reactor and sealed. The mixture was thoroughly mixed, and the air inside the reactor was replaced three times with Ar. After the sand bath temperature reached 350℃, the reactor was placed in the sand bath, and timing began after 5 minutes. Heating was stopped after 24 hours of reaction. The remaining steps were the same as in Example 1. Component analysis of the resulting oils showed the following yields: gasoline (C7-C12) 8%; aviation fuel (C8-C16) 20%; diesel (C9-C22) 33%; and lubricating oil (C20-C40) 60%.
[0028] Example 5
[0029] 1g of polyethylene waste plastic with a particle size of 2-3mm, 0.5g of Ni / CeO2 (Ni loading of 10wt%), and 2.5mL of solvent (one of alcohols, alkanes, or acids) were added to a batch reactor and sealed. The mixture was thoroughly mixed, and the air inside the reactor was replaced three times with Ar. After the sand bath temperature reached 330℃, the reactor was placed in the sand bath, and timing began after 5 minutes. Heating was stopped after 12 hours of reaction. The remaining steps were the same as in Example 1. Component analysis of the resulting oils showed the following yields: gasoline (C7-C12) 2%; aviation fuel (C8-C16) 9%; diesel (C9-C22) 40%; and lubricating oil (C20-C40) 65%.
[0030] like Figure 2 As shown, Example 1 demonstrates a high yield of diesel components under relatively mild reaction conditions without the use of high-pressure hydrogen; Example 2 shows a high yield of lubricating oil components under lower reaction temperatures and lower Ni loadings without the use of high-pressure hydrogen; Example 3 serves as a control, indicating that the conversion of PE cannot be achieved using CeO2 as a catalyst alone, indirectly illustrating the importance of the synergistic effect of Ni and CeO2 in the liquefaction of PE into petroleum products; Example 4 demonstrates that excessively high temperatures tend to convert PE into high-molecular-weight lubricating oils and low-molecular-weight gasoline; Example 5, in contrast to Example 1, shows that increasing the reaction time is beneficial for the conversion of PE into diesel and gasoline components. In summary, by reasonably controlling the reaction conditions, this system holds promise for achieving highly selective conversion of PE into a certain petroleum product under mild conditions with solvent-based hydrogen supply rather than the use of high-pressure pure hydrogen.
[0031] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.
Claims
1. A method for liquefying polyethylene to produce oil using low-temperature solvent hydrogen donation, characterized in that, The specific steps include the following: S1: Mix 2-5 mL of solvent, polyethylene waste plastic (mass ratio 2:1), and Ni / CeO2 catalyst in a batch reactor until homogeneous. Seal the reactor and purge the air inside with Ar gas three times at room temperature. Then place the reactor at 330-350°C. o The reaction of C in a sand bath lasted 12-24 h; the Ni / CeO2 catalyst was prepared by initial wet impregnation; the reaction solvent was an alcohol. S2: After the reactor is cooled, the reaction mixture in the vessel is removed and 10 mL of extractant is added. Extraction is carried out at room temperature for 30 min. Then, solid-liquid separation is performed. The obtained liquid is recovered by rotary evaporation to recover the extractant and solvent. The remainder is the liquefied oil. S3: The solid is Ni / CeO2 catalyst and unreacted polyethylene waste plastic. The Ni / CeO2 catalyst is recovered by calcination in air and reduction with 5% H2 / Ar. Hydrogen is supplied to the reaction via a solvent. The Ni / CeO2 catalyst is granular with a Ni loading of 10 wt%; Ni exists in elemental form and has weakly acidic and moderately acidic sites.
2. The method for producing oil from polyethylene by low-temperature solvent hydrogen supply according to claim 1, characterized in that, The liquid obtained from the solid-liquid separation step in S3, after rotary evaporation, yields n-alkanes as the remaining product.
3. The method for producing oil from polyethylene by low-temperature solvent hydrogen donation according to claim 1, characterized in that, The extractant is one of n-alkanes, aromatics, or polar solvents.